Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

SUSTAINABLE WELLS Maintenance, Problem Prevention, and Rehabilitation

SUSTAINABLE WELLS Maintenance, Problem Prevention, and Rehabilitation Stuart A. Smith Allen E. Comeskey

Boca Raton London New York

CRC Press is an imprint of the Taylor & Francis Group, an informa business

CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2010 by Taylor and Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Printed in the United States of America on acid-free paper 10 9 8 7 6 5 4 3 2 1 International Standard Book Number: 978-0-8493-7576-7 (Hardback) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www.copyright. com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data Smith, Stuart A. Sustainable wells : maintenance, problem prevention, and rehabilitation / Stuart A. Smith and Allen E. Comeskey. p. cm. Includes bibliographical references and index. ISBN 978-0-8493-7576-7 1. Wells--Maintenance and repair. I. Comeskey, Allen E. II. Title. TD407.S663 2010 628.1’14--dc22 Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com

2009019275

Contents List of Tables and Figures....................................................................................... xiii Disclaimer................................................................................................................xxi Preface.................................................................................................................. xxiii Authors..................................................................................................................xxvii Acknowledgments..................................................................................................xxix Chapter 1. A Brief Colorful History of Well Maintenance and Rehabilitation and Their Milestones.....................................................1 1.1 1.2 1.3 1.4 1.5

Some History..............................................................................1 The Role of the “Environmental” Sector in Shaping Well Rehabilitation and Maintenance........................................5 The Impact of Biology on Hydrogeology and GroundWater Technology.......................................................................6 Economics, Human Skills, Personalities, Demographics, and Other Issues.........................................................................8 A Word about Terminology...................................................... 11

Chapter 2. Causes and Effects of Well Deterioration........................................... 13 2.1 2.2 2.3 2.4 2.5 2.6 2.7

Summary: Causes of Poor Performance.................................. 13 True Grit—Sand and Silt.......................................................... 13 Yield and Drawdown Problems................................................ 17 Chemical Incrustation..............................................................20 Corrosion.................................................................................. 22 Plastic Deterioration.................................................................26 Biofouling—A Hitchhiker’s Guide to How Life Takes Over................................................................................26 2.7.1 Biofilm and Biofouling Basics..................................... 27 2.7.1.1 Biofilms and Microbial Survival................. 29 2.7.1.2 Biofilm Function and Ecological Function....................................................... 30 2.7.1.3 Biofilms and Biofouling in Ground Water............................................................ 30 2.7.2 Water Quality Degradation: Monitoring and Remediation Problems................................................ 33 2.7.3 Microbially Mediated Metallic Corrosion.................. 37 2.7.4 Iron, Manganese, and Sulfur Biofouling..................... 39 2.7.4.1 Fe, Mn, and S Biofouling: What’s Happening.................................................... 39 2.7.4.2 How Fe, Mn, and S Biofouling Occurs.......40 2.7.4.3 The Redox Fringe........................................ 42 v

vi

Contents

2.7.5

Effects on Performance of Well Systems: A Summary..................................................................... 43 2.7.5.1 Hydraulic Impacts........................................46 2.7.5.2 Sample Quality in Monitoring Wells........... 47 2.7.5.3 ASR Well Systems....................................... 47 2.7.6 Health Concerns Relating to Biofouling..................... 48 2.7.6.1 Pathogens..................................................... 48 2.7.6.2 Toxic Accumulation..................................... 49 2.7.6.3 Chlorination of Organic Chemicals............. 49 2.8 Impacts on Treatment Plants.................................................... 49 2.9 Engineering and Construction Aggravation of Clogging and Corrosion........................................................................... 50 2.10 Well Structural Deformation and Failure: Natural and Human Caused......................................................................... 51 2.10.1 Natural......................................................................... 51 2.10.1.1 Earthquakes................................................. 51 2.10.1.2 Mass Wasting............................................... 53 2.10.2 Human Induced........................................................... 55 2.10.2.1 Mining......................................................... 55 2.10.2.2 Mine Blasting.............................................. 56 2.10.2.3 Grouting....................................................... 57 2.10.2.4 Casing Weight/Quality/Integrity/ Engineering Issues....................................... 59 2.10.2.5 Improper Rehabilitation and Development Methods, and Other Abuses of Wells........................................... 61 2.10.2.6 Electrochemical Corrosion from Stray Potentials..................................................... 62 2.10.2.7 And Other Factors ….................................. 63 2.11 Disaster-Related Flooding........................................................64 2.12 Management and Operational Overview.................................. 65 Chapter 3. Economic Impacts of Well Deterioration............................................ 67 3.1

3.2 3.3

3.4

Identifying Costs of Well Deterioration................................... 67 3.1.1 Defining Economic Parameters.................................. 67 3.1.2 Types and Dimensions of Costs of Well Operation and Service................................................. 69 Asset Management and Life Cycle Cost.................................. 73 3.2.1 Asset Management Features of Well Systems............ 74 3.2.2 Life Cycle Costs.......................................................... 75 Assigning Economic Value...................................................... 76 3.3.1 Water Supply EV......................................................... 77 3.3.2 Other Environmental EV............................................ 77 3.3.3 Government Accounting Valuation of Assets............. 78 A Costly Example..................................................................... 78

vii

Contents

Chapter 4. Prevention Practices for Sustainable Wells......................................... 81 4.1 4.2 4.3

Prevention—Its Place in the Well Life Cycle........................... 81 Interlude: Teeth and Motor Vehicles........................................ 82 Prevention: Design and Construction Considerations..............84 4.3.1 Planning Considerations..............................................84 4.3.2 Role of Well Purpose.................................................. 86 4.3.3 Well Design................................................................. 86 4.3.4 Casing for Well Completion........................................ 87 4.3.5 Well Hydraulics and Efficiency—General Considerations............................................................. 89 4.3.6 Well Screens and Intakes............................................90 4.3.6.1 Screen Design.............................................. 91 4.3.6.2 Screen and Filter Pack Material Selection....................................................... 91 4.3.7 Grouting and Well Sealing.......................................... 93 4.4 Well Development....................................................................94 4.4.1 Reasons for Development............................................94 4.4.2 Development Method Descriptions............................. 95 4.4.2.1 Overpumping...............................................96 4.4.2.2 Surging and Pumping or Bailing (Utilizing Surge Block)................................96 4.4.2.3 Airlift Development.....................................99 4.4.2.4 Jetting......................................................... 100 4.4.3 “Conventional” Development Choices...................... 102 4.4.4 Fluid-Pulse Development.......................................... 104 4.4.5 Other Care Issues in Development and Redevelopment.......................................................... 105 4.5 Preventing Contamination during Drilling, Well Construction, and Development............................................. 105 4.6 Preventative Pump Choices and Actions................................ 106 4.6.1 Pump Selection.......................................................... 107 4.6.1.1 Pumps in Water Supply and Other Extraction (or Abstraction) Wells.............. 107 4.6.1.2 Pumps in Monitoring Wells....................... 108 4.6.2 Pump Protection........................................................ 110 4.7 Design Aspects: The “Cliff Notes” Version........................... 113 4.8 A Note about Well Houses..................................................... 114 4.9 Well Array Design Recommendations................................... 115 4.10 A Developing World Note...................................................... 116 Chapter 5. Maintenance Monitoring Programs for Wells.................................. 119 5.1 5.2

Maintenance Monitoring: Rationale for Instituting a Monitoring Program............................................................... 119 Maintenance Procedures Overview....................................... 122

viii

Contents

5.3 5.4 5.5

5.6

5.7

Implementing a Maintenance Program—It’s Institutional, Not Personal...................................................... 122 Maintenance Is Personal (and Personnel), Too....................... 122 Maintenance Basics................................................................ 123 5.5.1 Well System Maintenance Records........................... 123 5.5.2 Maintenance Monitoring for Performance and Water Quality............................................................ 124 5.5.3 Maintenance Actions and Treatments....................... 125 A Maintenance Monitoring Protocol for Wells...................... 126 5.6.1 Purposes of Maintenance Monitoring....................... 127 5.6.2 Background for Current Monitoring Recommendations..................................................... 127 5.6.3 Deciding How to Monitor......................................... 128 5.6.3.1 Incorporating PM Data Collection into the Facility Data Collection Effort............ 130 Recommended Testing and Information Monitoring Methods.................................................................................. 130 5.7.1 Visual and Other Sensory Examination.................... 130 5.7.2 Well and Pump Performance.................................... 131 5.7.2.1 Benchmarking........................................... 132 5.7.2.2 Compare Apples with Apples.................... 136 5.7.2.3 Monitoring Pump and Pump Motor Performance............................................... 137 5.7.2.4 Tracking Well Performance....................... 137 5.7.2.5 Water Level Measurement Recommendations..................................... 139 5.7.2.6 Well Discharge Measurement.................... 139 5.7.2.7 Pressure Measurement............................... 141 5.7.2.8 Electrical (Power)...................................... 141 5.7.3 Water Sampling......................................................... 142 5.7.4 Physicochemical Analyses........................................ 142 5.7.5 Biological Monitoring: Decision Making................. 143 5.7.5.1 Whether to Monitor for Biofouling............ 144 5.7.5.2 Biofouling Monitoring: What Methods to Choose................................................... 144 5.7.5.3 A Note about the Current State of the Art in Well Maintenance Monitoring Methods.................................. 144 5.7.6 Biofouling Monitoring Methods: Analysis............... 145 5.7.6.1 Microscopic Examination and Analysis.... 145 5.7.6.2 Culturing Methods.................................... 146 5.7.6.3 How Minimal Can Testing Be?................. 149 5.7.7 Biofouling Monitoring Methods: Sampling Methods..................................................................... 151

Contents

ix

5.7.7.1 Pumped Sampling...................................... 151 5.7.7.2 Surface Collection on Slides or Coupons..................................................... 152 5.7.7.3 Representativeness of Collection Sampling.................................................... 153 5.7.8 Electrochemical In-line Sensors............................... 155 5.8 Summary of Recommendations for Maintenance Monitoring in Routine Practice.............................................. 156 5.8.1 Summary of Data Collection Requirements............. 156 5.8.2 Well Data File Features............................................. 156 5.8.3 Pumping Rates.......................................................... 157 5.8.4 System Pressure......................................................... 157 5.8.5 Water Level Data....................................................... 157 5.8.6 Electrical (Power) Data............................................. 158 5.8.7 Video for Historical Comparison.............................. 158 5.8.8 Hydrogeologic Information That Should Be on File............................................................................. 158 5.8.8.1 Piezometric Data....................................... 158 5.8.8.2 Piezometric Maps...................................... 159 5.8.8.3 Geologic Regime....................................... 159 5.8.9 Development Data..................................................... 159 5.8.10 Maintenance Logs for Individual Wells.................... 161 5.8.10.1 Where Records Should Be Kept................ 161 5.8.10.2 Downtime History..................................... 161 5.8.10.3 File Records Purpose and Format Issues.......................................................... 162 5.9 Schedule of Maintenance Monitoring Actions for Wells....... 163 5.9.1 Minimum Regular Schedule for First Year............... 163 5.9.2 Schedule for Reducing Maintenance Monitoring after First Year.......................................................... 163 5.9.3 Rationale and Commentary...................................... 165 5.10 Institutional and Funding Issues in Maintenance Planning, Analysis, and Execution......................................... 165 5.10.1 Background and Barriers to Effective Maintenance Implementation.................................... 165 5.10.2 Institutional Needs for Effective Implementations........................................................ 167 5.10.3 Quarterly Review of Facility Performance Data....... 168 5.10.4 Baseline and Historical Data for Wells/Site.............. 168 5.10.5 Operator/Working Crew Leader Qualifications and Training.............................................................. 169 5.10.6 Determination of Operational Maintenance Responsibilities......................................................... 170

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Contents

Chapter 6. Preventive Treatments and Actions................................................... 171 6.1 6.2 6.3 6.4 6.5

Sand/Sediment Pumping........................................................ 171 What Do We Do if We Have Corrosion?................................ 172 Biofouling (General)............................................................... 174 Inorganic Encrustations (General)......................................... 174 Preventive Chemical Treatments............................................ 174 6.5.1 General: Cost-Effectiveness, Professionalism........... 174 6.5.1.1 Cost-Effectiveness..................................... 175 6.5.1.2 Professionalism.......................................... 176 6.5.2 Chemical Classes and Properties.............................. 176 6.5.2.1 Acids for Maintenance Treatment............. 176 6.5.2.2 Biocides and Oxidizing Compounds......... 176 6.5.2.3 Penetrating, Sequestering, and Dispersing Agents...................................... 181 6.5.2.4 Blended Method Treatments...................... 181 6.5.3 Use and Interpretation of MSDSs............................. 182 6.5.4 Compatibility with Well Cleaning Chemicals.......... 183 6.6 Mechanical Agitation and Augmentation.............................. 183 6.7 Chemical Emplacement.......................................................... 184 6.8 Chemical Removal and Recovery.......................................... 184 6.9 In Situ Maintenance Treatment Techniques........................... 185 6.9.1 Chemical Feeders in Wells........................................ 185 6.9.2 Radiation—That Gentle Glow................................... 185 6.9.3 Application of Electromagnetically Charged Surfaces..................................................................... 186 6.9.4 CO2 Well Environment Adjustment—Making the Environment Inhospitable for Biofouling....................................... 186 6.10 Further Procedural Requirements.......................................... 187 6.10.1 Regulatory Aspects................................................... 187 6.10.2 Biofouling Recurrence.............................................. 187 6.11 Health and Safety Concerns................................................... 187 6.11.1 Health and Safety Plan.............................................. 187 6.11.2 Level of Protection for Mixing and Well Application................................................................ 188 6.11.3 Chemical Handling Hazards..................................... 188 6.11.4 Mixing Chemicals—Personal Safety Aspects.......... 188 6.12 Costs and Time of Routine Preventive Measurements........... 189 6.12.1 Maintenance Cost-Benefit Analysis.......................... 189 6.12.1.1 Cost-Benefit Analysis: A Spreadsheet Approach.................................................... 189 6.12.1.2 The Heartbreak of Well Failure: An Overriding Weighting Factor..................... 190 6.12.2 Costs of Maintenance Activities............................... 192

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Contents

6.12.2.1 Maintenance Monitoring Costs— Typical....................................................... 192 6.12.2.2 Preventive Treatment Costs....................... 194 6.12.3 Improving Cost-Effectiveness in Maintenance......... 194 Chapter 7. Rehabilitation and Reconstruction Planning..................................... 197 7.1 7.2

7.3

7.4

7.5

7.6

Decisions on Rehabilitation Methods: After Things Go Wrong..................................................................................... 197 Management and Safety in Well Rehabilitation..................... 198 7.2.1 Facility Management Considerations........................ 198 7.2.1.1 Responsibility for the Work....................... 199 7.2.1.2 Getting the Job Done.................................200 7.2.2 Safety and Productivity in Well Rehabilitation Work.......................................................................... 201 7.2.2.1 Safety Assurance....................................... 201 7.2.2.2 Facilitating Productivity............................202 7.2.3 Rehabilitation Contractor Considerations.................203 7.2.3.1 Safety: What the Contractor Needs to Have and Know......................................... 203 7.2.3.2 Practical Stuff: Access and Response.......205 Contractors and Consultants: Avoiding Trouble in Working Together...................................................................208 7.3.1 Mutual Respect in Rehabilitation Work....................208 7.3.2 Specifications: Business and Bidding Considerations...........................................................208 7.3.2.1 Specification Pitfalls..................................208 7.3.2.2 Overcoming Pitfalls...................................209 7.3.2.3 Effluent Waste Water Containment........................... 210 Well Rehabilitation: Decision Making on Methods............... 210 7.4.1 To Rehab or Not to Rehab? That Is the Question...... 210 7.4.2 The Costs of Well Rehabilitation.............................. 213 7.4.2.1 The Cost of Doing Nothing....................... 213 7.4.2.2 Costs for Serious Rehabilitation Work...... 214 7.4.2.3 Contractor Pricing of Rehabilitation Work.......................................................... 215 7.4.3 Choosing Rehabilitation Methods............................. 216 7.4.4 Damage...................................................................... 217 7.4.5 Issues in Rehabilitation Chemical Selection............. 218 7.4.6 Reconstruction........................................................... 220 Specifications for Rehabilitation............................................ 221 7.5.1 Specification Deficiencies......................................... 221 7.5.2 What Well Rehabilitation Specifications Should Have........................................................................... 225 7.5.3 Selecting Well Rehabilitation Bids............................ 226 The Role of Consultant Specifier-Observer............................ 227

xii

Contents

Chapter 8. Rehabilitation Methods..................................................................... 229 Chapter Technical Descriptions............................................................................ 229 8.1

8.2

8.3 8.4 8.5 8.6

Physical Agitation................................................................... 229 8.1.1 Basic Principles......................................................... 229 8.1.2 “Conventional” Redevelopment................................ 229 8.1.3 Other or Advanced Physical Redevelopment Methods..................................................................... 231 8.1.3.1 Cold CO2 Treatment................................... 231 8.1.3.2 Sonic/Vibratory Disruption—“Use the Force, Luke!”............................................. 233 8.1.3.3 Fluid-Pulse Tools....................................... 236 The Pharmacopoeia: Chemical Use in Rehabilitation...........240 8.2.1 Overview...................................................................240 8.2.2 Acidizing................................................................... 243 8.2.2.1 Types of Acid Compounds........................ 243 8.2.2.2 Using Acidizing in Well Treatment........... 245 8.2.3 Sequestering and Other PSDD Functions................. 247 8.2.4 Antibacterial (Antimicrobial) Agents.......................248 8.2.4.1 Chlorination...............................................248 8.2.4.2 Alternatives to Chlorine as Oxidants for Biofouling............................................. 252 Blended Method Treatments.................................................. 254 Application of Rehabilitation Methods Summary................. 256 Posttreatment after Well Rehabilitation................................. 257 Some Follow-up “Truisms”.................................................... 257

Chapter 9. Learning and Going Forward............................................................ 263 9.1 9.2

Learning from the Past........................................................... 263 Where Do We Go from Here?................................................264 9.2.1 Wish List................................................................... 265 9.2.2 Education, Communication, and Mutual Respect: Human Issues in Well Maintenance...........266

Recommended Reading List................................................................................ 269 Recommended Reading List............................................................. 269 Selected References........................................................................... 272 Selected Relevant Standards.............................................................. 277 ANSI/ASTM Standards (a selection)..................................... 278 Index....................................................................................................................... 279

List of Tables and Figures List of Tables Table 2.1

Categories of Well Problems and Related Causes.......................... 14

Table 3.1

Costs of Pumping (Per Year and Per Unit Volume)........................ 71

Table 4.1

General Well Design and Placement Guidelines............................ 85

Table 4.2

Casing Types and Choices...............................................................90

Table 4.3

Cathodic-Anodic Series of Metal Alloys........................................ 93

Table 5.1

Troubleshooting Summary Guide for Well Maintenance............. 125

Table 5.2

Parameters Useful in Well Maintenance Monitoring................... 126

Table 5.3

Features of Water Level Measurement Methods........................... 140

Table 5.4

 ummary of Physicochemical Methods Relevant to Well S Maintenance.................................................................................. 143

Table 5.5

First-Year PM Monitoring Schedule............................................. 164

Table 5.6

Long-Term PM Monitoring Schedule........................................... 166

Table 6.1

 cid Effectiveness, Safety and Handling—Recommended A Compounds.................................................................................... 177

Table 6.2

 ommon Well Cleaning Chemicals in Use—Not C Recommended (USACE).............................................................. 178

Table 6.3

Well Treatment Chemical Incompatibility.................................... 182

List of Figures Figure 1.1

 lephant digging for water in sand. (Tarangire National Park, E Tanzania)...........................................................................................2

Figure 1.2

 ump impellers clogged by oxidized iron deposition. P Extraction well, DOE Fernald Preserve (Ohio).................................6

Figure 2.1

Impellers destroyed by pumping sand and gravel (Mexico)........... 15

Figure 2.2 Precleaning flow from a clogged well............................................. 17 Figure 2.3 W  ell screen clogged by iron biofouling (North Dakota State University Extension, Scherer, 2005, Circular AE 97)................... 18 xiii

xiv

List of Tables and Figures

Figure 2.4 Pumping well yield and drawdown components............................. 18 Figure 2.5 O  xidation and reduction and ecology changes around pumping wells................................................................................. 19 Figure 2.6 P  ipe clogged by iron mineral (U.S. Environmental Protection Agency)............................................................................................20 Figure 2.7 Schematic of well with gas pressure release................................... 21 Figure 2.8 M  ineral-clogged drain—mostly calcite (photograph courtesy of Chuck Cooper, Bureau of Reclamation)..................................... 22 Figure 2.9

Corroded submersible pump end (southern Colorado).................... 23

Figure 2.10 Diagram of a corrosion tubercle in steel pipe.................................24 Figure 2.11 C  ross section of steel pipe corrosion tubercles (Lytle, Gerken, and Maynard, 2004, U.S. EPA).......................................................25 Figure 2.12 M  ixed biofilm from water well samples (normal light photomicrograph)............................................................................28 Figure 2.13 Examples of manifestations of biofouling....................................... 29 Figure 2.14 Z  ebra mussel fouling in pipe (Gemma Grace, Ontario, Canada)............................................................................................ 29 Figure 2.15 B  acterial size, movement, and attachment in relation to pore size in aquifer materials (U.S. Geological Survey)......................... 31 Figure 2.16 I ron-related biofilm from well water samples (normal light photomicrograph)............................................................................ 31 Figure 2.17 Soil-water-oil-biofilm interface....................................................... 32 Figure 2.18 Microbial ecology schematic of a remediation system................... 33 Figure 2.19 P  assage of a contaminant plume in an alluvial aquifer. This is a simulation based on observed phenomena, usually indications of microbial activity are detected months or years later in response to some observed problem...................................34 Figure 2.20 F  e, Mn, and S transformations and mobility in aquifers—a schematic of typical occurrences in a biologically active mixed reducing-oxidizing aquifer system....................................... 35 Figure 2.21 F  e transformation and plugging zone around an affected well—a schematic of the many activities and results of activity in the busy environment of a pumping well....................... 35 Figure 2.22 M  icrobial corrosion processes schematic—illustrating the range of bio-electrical activity around a corrosion tubercle on a steel surface (some features also apply to crevice corrosion of stainless steel alloys)................................................................... 37

List of Tables and Figures

xv

Figure 2.23 E  xample of mild steel well pump discharge pipe tuberculation.................................................................................... 38 Figure 2.24 M  icrobially influenced corrosion of Type 316 stainless steel monitoring well casing. Section at left has begun anodic attack under biofilm associated with bentonite grout, while in the section on the right, corrosion is associated with metal fatigue..... 38 Figure 2.25 G  allionella-dominated water well biofilm (normal light photomicrograph)............................................................................40 Figure 2.26 M  ixed filamentous biofilm featuring MnIV oxide mineralogy (normal light photomicrograph (PMG)).......................................... 41 Figure 2.27 F  ilamentous Mn-precipitating bacteria reemerging when MnIV oxide particles (black) are rehydrated (Bureau of Reclamation–Stuart Smith PMG, annotated by SAS)— minutes after adding water.............................................................. 42 Figure 2.28 S  ulfur oxidizing biofouling in well pump discharge pipe, South Africa (Courtesy of Hose Solutions Inc.).............................. 42 Figure 2.29 T  hothrix-dominated sulfur-oxidizing biofouling of geotechnical drains (Bureau of Reclamation–Stuart Smith photographs).................................................................................... 43 Figure 2.30 W  hite sulfur biomass associated with artesian spring (in actuality, an uncontrolled well) in western Ohio............................ 45 Figure 2.31 S  chematic presentation of the initiation and development of a biofilm (P. Dirckx, Montana State University Center for Biofilm Engineering)....................................................................... 45 Figure 2.32 E  xtensively tuberculated pipe interior (Argentina: photo by Miguel A. Gariboglio).....................................................................46 Figure 2.33 Some causes of well structural failure............................................ 52 Figure 2.34 S  lope and rail line affected by soil creep (Courtesy U.S. Geological Survey).......................................................................... 53 Figure 2.35 Slope affected by slump (Courtesy U.S. Geological Survey).......... 54 Figure 2.36 Shoreline erosion processes, Ashtabula County, Ohio.................... 54 Figure 2.37 H  ouse foundation undermined by collapse of mining cavities (Pennsylvania Dept. of Environmental Protection photo)............... 55 Figure 2.38 L  ong-wall mining effects diagram (Pennsylvania Dept. of Environmental Protection).............................................................. 55 Figure 2.39 P  VC casing distorted by heat due to improper cement grouting (photo by Gary L. Hix). The casing is pushed in and cracked at the visible joint and the foreground surface is blistered.............. 58

xvi

List of Tables and Figures

Figure 2.40 Monitoring well casing bent due to vehicle collision...................... 62 Figure 2.41 P  VC water well casing broken due to vehicle strike in parking lot. There was an attempt to fix it with a rubber boot coupling and protect it with a tire. This was a public water supply (bowling alley, now closed) in Ohio.................................... 62 Figure 2.42 F  looding in the St. Mary’s River watershed (Ohio) (NOAA photo)...............................................................................................64 Figure 3.1

The meter is running....................................................................... 68

Figure 4.1

The well life cycle continuum......................................................... 82

Figure 4.2 S  ome types of connections used in well casing and pump discharge pipe. (a) bell-end PVC casing pipe and (b) splinelock coupling (Certain Teed CertaLok™)...................................... 88 Figure 4.3 The necessary in-and-out motion of proper well development.......96 Figure 4.4

Example surge blocks (both double surge block tools)...................97

Figure 4.5 E  xample well cleaning brush (manufactured by Cotey Chemical Corp., figure courtesy of Kevin McGuiness).................. 98 Figure 4.6

 chematic of airlift development and pumping apparatus S (North Dakota State University, Scherer, 2005)..............................99

Figure 4.7

J etting system schematic (North Dakota State University Extension, Scherer, 2005).............................................................. 101

Figure 4.8 J etting heads (North Dakota State University Extension, Scherer, 2005)................................................................................ 101 Figure 4.9

 irlift testing and development, test drilling in carbonate A aquifer (Ohio). The illustrated system is set up to permit periodic flow testing by measuring tank fill volume over a set period of time................................................................................ 103

Figure 4.10 T  esting for field parameters during test drilling. pH, conductivity, temperature, and several key chemical parameters were measured in nonfiltered and filtered samples.... 103 Figure 4.11 Well pump electrical system protection (photo by Gary L. Hix)...... 110 Figure 4.12 S  chematic of suction flow control device (Eucastream SFCD design, Kabelwerk Eupen AG product literature, Eufor S.A., Eupen, Belgium)............................................................................ 111 Figure 4.13 S  and separator for submersible pump installation (illustration courtesy of LAKOS Separators and Filtration Systems)............... 112 Figure 4.14 B  low-off hydrant examples (photos courtesy of Kupferle Foundry Company, illustration modified)..................................... 115

List of Tables and Figures

xvii

Figure 4.15 Example easy-to-service well house............................................. 116 Figure 5.1

Well decision-making flowchart................................................... 120

Figure 5.2

 ome indications that you may have biocorrosion problems in S the well (Ohio). Corrosion hole (middle section, top), above pump was losing several 100 gpm................................................. 131

Figure 5.3

 own- and side-view borehole video camera system operated D by Geoscope Inc., Mansfield, Ohio............................................... 132

Figure 5.4

 xample pump performance curve (Scherer, 1993, AE-1057, E North Dakota State University Extension). Note: HP and head are per stage.................................................................................. 133

Figure 5.5 A plot of step-drawdown test data................................................. 134 Figure 5.6 A  nalysis of step-drawdown test using Hantush-Bierschenk straight-line method, B established by intercept and C from slope of plot................................................................................... 134 Figure 5.7

 raph of efficiency vs. pumping rate from analysis of step G test plot, aquifer loss and well loss illustrated............................... 135

Figure 5.8

 lot of percent well efficiency vs. pumping rate. Derived from P analysis illustrated in Figures 5.5 and 5.6, with extrapolations to gpm above and below the tested flow rates (Figure 5.5)........... 136

Figure 5.9

 ART method tube schematic. (Courtesy Droycon B Bioconcepts Inc.)........................................................................... 147

Figure 5.10 A selection of BART reactions from an alluvial aquifer well....... 148 Figure 5.11 I noculated BRS-MAG tubes and syringe applicator. Sample is injected into vial........................................................................ 149 Figure 5.12 W  ellhead flow cell collector: (a) element and (b) as installed on a wellhead................................................................................. 153 Figure 5.13 E  lectron micrographs (EMGs) of filamentous biofilms (Bureau of Reclama­tion project—scanning EMGs by L. Tuhela-Reuning, Ohio Wesleyan University)................................ 154 Figure 5.14 F  ield analysis of drive cores for physicochemical and biochemical parameters (Iowa)..................................................... 155 Figure 6.1

Well maintenance decision tree..................................................... 172

Figure 6.2

 rojections of annual and cumulative costs over time using P Sutherland et al. method. “Discounted annual costs” illustrates annual-cost profile, “Cumulative discounted costs” shows difference between “with” and “without” maintenance monitoring in this simulation............................................................191

xviii

List of Tables and Figures

Figure 7.1

 ell rehabilitation work in motion. Cleaning carbonate W aquifer wells in western Ohio........................................................ 198

Figure 7.2

 ometimes there are access challenges (photo courtesy of S Ohio EPA Southeast District staff)...............................................206

Figure 7.3

 ood well site access is important. Note room for crane and G service vehicles on pad within fence, personnel access at the crane side to the interior and access through the roof...................207

Figure 7.4

 ellhead in East Africa where site security is paramount. W Well service will require removing a portion of the “castle” wall................................................................................................207

Figure 7.5

 ining a well, sealing off undersirable zones using a Griffitts L well packer (illustration courtesy Griffitts Drilling and Seals)..... 221

Figure 7.6

 etting a liner in place using an inflatable swaging system S (illustration courtesy of Inflatable Packers International Pty Ltd).......................................................................................... 222

Figure 7.7

 ireline or “riserless” pump installation schematic W (illustration courtesy of Inflatable Packers International Pty Ltd). A riserless pump uses the casing as the discharge line........ 223

Figure 7.8

 FCD retrofit in well changes hydraulic profile (Eucastream S SFCD design, Kabelwerk Eupen AG product literature, Eufor S.A., Eupen, Belgium)...................................................................224

Figure 8.1

 etting a well shooting charge (eastern Ohio sandstone-shale S well)............................................................................................... 234

Figure 8.2 S  onar-Jet treatment sequence (Michigan). (a) The string is assembled and connected, (b) the assembled 5-ft string to be lowered to the screen interal, (c) the returning string after firing, (d) seeing what has been retrieved in the basket................ 235 Figure 8.3 A  irShock air impulse gun. (Courtesy ProWell Technolgoies, Ltd.)............................................................................................... 237 Figure 8.4 A  irburst AIG well assembly—bolt air gun mounted on bail (foreground), compressor and winches background...................... 238 Figure 8.5 A  irburst treatment sequence (carbonate aquifer, northern Ohio). (a) Hooking up and deploying the tool, (b) checking water level, (c) inserting the tool, (d) visible results at the surface...........................................................................................240 Figure 8.6 p H influence on relative occurrence of hypochlorite ion species plotted from calculated data. Note that actual values may vary due to water quality and temperature variables............ 250

List of Tables and Figures

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Figure 8.7 I llustration of features of flexible well pump discharge pipe. (a) Coil of 6-in. pipe with fittings, (b) top connection at flanged well head, (c) pump connection, same installation, (d) full installation view, (e) installation of Wellmaster in an angled well (UK). Note that the pumps illustrated are not small. (Photos (b) and (c) courtesy of Boreline (Hose Solutions Inc., www.allhoses.com). Photos (a), (d), and (e) courtesy of Angus Flexible Pipelines.).......................................... 259

Disclaimer This work provides insight and understanding on the problems of wells and their prevention and cures and is presented as a reference work. It is not a detailed specification or substitute for experience. Any conclusions and recommendations provided are based on the informed professional opinion of the authors, and these are based on their experience and research. People just reading this or any combination of books and manuals should not consider themselves fully qualified to perform, specify, or supervise well maintenance and monitoring programs without the necessary knowledge base and experience with specific situations. Generally this knowledge and experience is concentrated in consultants and contractors, but there is no reason that it cannot be developed “in house” within a facility’s operations and maintenance staff. This book is based on a body of knowledge. How you apply it is up to you. The construction of wells is so individual and the geological environment so variable that we cannot guarantee the applicability or outcome in your particular situation. Also keep in mind that some of the procedures and technology mentioned are protected by patent. If you are a consumer of professional services in well rehabilitation, this book will help you to get the most from your professional help. A major point in this work is the need for operational data collection and maintenance. This is important. If you will not do this, we cannot help you with this book. If you are a provider, this book is a source of information intended to help you do your job better and more safely. With that in mind, and understanding that we all have a lot to learn, read on. Stuart A. Smith, CGWP Allen E. Comeskey, CPG

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Preface This book is intended to be a guide in keeping well systems operating to their best capacity. These include pumping water supply and plume control, pressure relief and dewatering wells, barrier and other recharge wells—horizontal, angled, and vertical. To a certain degree, the scope covers monitoring wells and drains, and even wells for hydrocarbon withdrawal and fluid injection. It is written for those people who have to wrestle with these problems: well and overall facility managers, their operators, consultants and regulators, and contractors who may perform well and pump repair and rehabilitation services. The problems you may be experiencing with your wells are not new or unique. They may be more intense for some wells than others. Each category of wells has its particular issues, for example: • Public water supply (PWS) and hydrocarbon wells are perhaps best covered by well maintenance and rehabilitation experience (since some are willing to spend money on it). • Private or farm water supply, small facility PWS, and some irrigation wells are also similar to other PWS wells, but often smaller in dimension and rarely maintained properly. • Monitoring and recovery wells are only specialized wells, but often installed where no reasonable person would put a water supply well unless they were desperate. • Recovery and treatment systems are also nothing more than specialized ground-water-source water treatment systems. What sets them apart from a maintenance standpoint is that they are routinely exposed to harsh environments and operated in such a way that maximizes the potential for performance and water quality deterioration. • Even where ground water is considered to be uncontaminated but monitored due to potential hazards, monitoring wells are subject to greater deterioration effects than active pumped water supply wells, since they sit for long periods, unused. • Aquifer storage and recovery (ASR) wells are increasingly being installed and used as utilities and regions attempt to better manage water resources. These systems are basically injection wells that can then be reversed to pumping wells. Injection wells have known maintenance problems. Can such wells be relied upon in the long run? • Increasing numbers of nontraditional nonvertical wells, like drains, have their own maintenance issues, exacerbated by the environments in which they are developed and by construction and development methods that leave them vulnerable to clogging mechanisms. xxiii

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The process of operating any engineered system should include active maintenance. The alternative (in this case, the neglect of well and pump problems) leads to continued performance deficiencies, or even additional problems. For a variety of reasons, wells have traditionally not been maintained like the active, valuable facility assets they are. However, an attitude of maintenance is catching on in all sectors. This current work is an update and expansion of the 1995 work, Monitoring and Remediation Wells: Problem Prevention, Maintenance and Rehabilitation, by Stuart Smith (CRC Press). That work was intended to accompany reports coauthored by Smith and published by the AWWA Research Foundation, Methods for Monitoring Iron and Manganese Biofouling in Water Supply Wells (1992) and Evaluation and Restoration of Water Supply Wells (1993), which were oriented toward water supply wells. These have now been out of print for several years (although they are still quite relevant). This present work reflects those changes and positive improvements in the state of the art that have occurred in the last decade or so. It builds upon and complements other titles in the Sustainable Well Series that have documented improvements in the last twenty years. This book, rather than focusing on one sector of well use as the 1995 book did, is intended to serve as a comprehensive yet readable state-of-the-art summary of performance maintenance, problem prevention, and rehabilitation or restoration practice for wells for the purpose of sustaining optimal performance over the long term. The current understanding of processes that impair performance and shorten well component life, practices designed to sustain performance during operations, and feasible rehabilitation and restoration methods will be considered. It will address design features to maximize sustainability and issues of cost-effectiveness in planning sustainable well efforts. Emphasis will be on operational practicality. It is a guidebook to the causes of well deterioration, methods of well maintenance, and well restoration or well rehabilitation methods. Like a useful travel guidebook, this work is not a one-stop encyclopedia, but, where useful, it points you to further sources of more information. In this case, the information for this work is built on the experience of the authors and numerous other people, and a good chunk of that information is published and should be on the bookshelf of—and read by—anyone responsible for well systems. We supply a recommended reading list. You know, as soon as you stop and go to print with a book, that a good story will come your way or a new technology will emerge that may sweep the industry. So consider this book as a snapshot. By all means, keep up with new developments. Even with new technology, most of the principles expressed herein will apply. Seek all the good advice you can find, and respect it when you get it. The coauthors offer a website for up-to-date information, and they link it to other good sources. We plan to offer a discussion blog or some such vehicle for those who purchase the book in order to update the reader on new findings and ideas and to access additional resources.

Preface

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A Comment on the “Voice” of This Book The authors have devoted much time in front of groups of operators, municipal boards, etc., informing them of the mysterious goings-on in their wells. We have found that a relaxed discussion results in more understanding than a formal lecture. While the material is intended to be entirely serious and authoritative, we have applied the same style to this book. We envision ourselves sitting on our stools, talking with you. As with instruction, we repeat ourselves at times for emphasis, in case your attention drifts.

Authors Stuart A. Smith has been managing partner of Smith-Comeskey Ground Water Science LLC (Ground Water Science) since 1996. He is certified (CGWP) and licensed as a hydrogeologist and is a highly applied environmental microbiologist focusing on the biofouling and biocorrosion issues of wells and geotechnical drains. Prior to forming the predecessor of Ground Water Science in 1986, Mr. Smith served as a technical editor for Battelle Memorial Institute, as an adjunct associate professor in ground-water technology for Wright State University (Ohio), and as education program coordinator and research associate for the National Ground Water Association (NGWA, then known as the National Water Well Association), where he joined the staff in 1979 after a short stint as a secondary school teacher in Ohio. He also served as a lecturer in biology at Ohio Northern University in the 1990s. He holds BA and MS degrees from Wittenberg University (Ohio) and The Ohio State University, respectively. He is the author or coauthor of numerous publications, such as Methods for Monitoring Iron and Manganese Biofouling in Water Supply Wells and Evaluation and Restoration of Water Supply Wells (AWWA Research Foundation), Monitoring and Remediation Wells: Problem Prevention, Maintenance and Rehabilitation (CRC Lewis Publishers), and Operation and Maintenance of Extraction and Injection Wells at HTRW Sites (U.S. Army Corps of Engineers), and the first manual on the subject in Spanish (with the late Dr. Miguel Gariboglio), Corrosión e incrustación microbiológia en sistemas de captación y conducción de agua: aspectos teóricos y aplicados. He is also a contributor to AWWA’s Water Quality & Treatment, 5th edition and ASCE’s upcoming International Manual of Well Hydraulics (ASCE). He is a coauthor of both the 1992 Australian Drilling Manual and its 1997 successor, Drilling, published by CRC Press, and principal author-editor of NGWA’s 2nd edition of the Manual of Water Well Construction Processes. Since 1980, he has contributed to the general understanding of causes and cures for well problems through talks and seminars across North America and in Argentina and Australia, and through industry publications, such as the Water Well Journal and National Drillers Buyers Guide/National Driller, and web content. He is active with the NGWA (including being active in the development of the new water well standard, ANSI/NGWA-01) and the AWWA’s Ohio Section. He is currently chair of the Standard Methods for the Examination of Water and Wastewater joint technical group for Section 9240 (iron and sulfur bacteria). He is also active locally with the Sandusky River (Ohio) Watershed Coalition and involved in some water supply development planning in East Africa. Allen E. Comeskey has been a member and partner in Ground Water Science since 1996. He is a certified professional geologist (CPG) and registered geologist in several states. He has been involved in water supply hydrogeology and exploration since 1979. With Ground Water Science, he focuses on well construction planning and xxvii

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execution, and the performance and analysis of logging and well hydraulic and aquifer tests. He is also an experienced ground-water modeler and hydrologic analyst with extensive experience in both fractured rock and glacial-alluvial hydrology. Prior to forming Ground Water Science, he worked for 10 years with the North Dakota State Water Commission, and also with Earth Data and LBG, Inc. on projects in Maryland, New York, Pennsylvania, and New England. While in North Dakota, he conducted community and county water resources exploration and delineations (often logging more than 50,000 ft of borehole each year), and worked with wetlands water budgets. While in the eastern United States, he worked on complex wellhead protection and contaminant delineation studies and continued detailed modeling, well testing, and well rehabilitation project work with Smith-Comeskey. He holds BS and MS degrees in geology from Bowling Green State University and the University of North Dakota, respectively, and has completed advanced study in fractured rock hydrology and modeling at the University of Wisconsin–Madison and GIS at BGSU.

Acknowledgments Thanks to the past support of AWWARF (Water Research Foundation) at that crucial time in the early 1990s when good information was being compiled again. They can fund future needed research proposals we send if they want to. Thanks also to the U.S. Army Corps of Engineers (USACE), the U.S. Department of Interior’s Bureau of Reclamation (BOR), and the National Ground Water Association for past and present support and confidence. “Up north,” Canada Agriculture’s Prairie Farm Rehabilitation Administration (PFRA) and the private company Droycon Bioconcepts, Inc. have provided vision, leadership, and crucial support to the art, and those witty Canadians coined the catchy concept of a “sustainable well.” We also acknowledge other working experts and authors in the field, who help one another learn and improve “as iron sharpens iron” (even in those instances when we do not agree). The input of George Alford, Olli Tuovinen, Roy Cullimore, Bill Frazier, Gennady Carmi, Miguel Gariboglio, Jay Lehr, Ross Carruthers, Rob McLaughlan, Peter Howsam, John Schneiders, Denise Hosler, and many others over the years is particularly appreciated. We most gratefully thank our clients who had the problems that have served as our classroom and laboratory (we benefit from the troubles of others), as well as our working colleagues on the service side, who move the iron and the water. Nothing gets done without them. Karen Ward helped with art carried over from the 1995 predecessor to this work. We slavishly acknowledge the support of our wives, who mostly humor us as we pursue our star. Crack librarian Rebecca Quintus, who finds things we seek, also contributed materially to this work.

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Colorful History 1 AofBrief Well Maintenance and Rehabilitation and Their Milestones 1.1 Some History No one recorded when well digging started, but surely humans imitated elephants in digging holes in the sand to access cooler water that did not make the children sick so quickly (Figure 1.1). People dig such “wells” to this day. Well construction is an ancient craft: Genesis, the book of the Judeo-Christian scriptures that provides an account of the primordial history of human interaction with God, recounts the exploits of Abraham, leader of a large and successful nomadic pastoral clan and claimed as patriarch by many, living about four thousand years ago. Operating in a semiarid country, Abraham’s company (like their neighbors) dug wells, a skill they learned from other people in the Levant who had already been constructing wells for several thousand years. Excavated wells in Europe, Syria, Israel (including a site now 10 m deep in the sea), and South Asia have been dated to before 6300 BCE. As for the subsea well, people presumably constructed wells on land to access fresh water, so the well was constructed before the sea level rebound at the end of the last Pleistocene ice advance. Since such wells were valuable (Genesis reports squabbling among the tribes over Abraham’s wells), there presumably has been well maintenance and rehabilitation since that time—and before—if you count all that sand, silt, and debris removal from all those countless wells in dry riverbeds back to the dawn of humanity. Maintenance must have been at least selectively successful. In Jesus’ encounter with a woman at a well in Samaria (early first century CE), she attributes the source of the well to the patriarch Abraham’s son Jacob (who lived over seventeen hundred years before). That’s some long well life. Naturally, maintenance of dug wells was not always performed, or performed well. Excavated wells are excellent sources of archaeological information from old settlements such as colonial sites in Virginia, Jamestown or Williamsburg. Objects in wells mean that people were throwing undesirable objects into wells back then, just as they do today. One of us (Comeskey) observed in North Dakota in the early 1980s (a process since stopped) that wherever a platform over an old dug well rotted away, the hole was soon filled with pesticide jugs and oil cans. As we see everywhere, if there is a hole in the ground, someone throws something in it. 1

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Figure 1.1  Elephant digging for water in sand. (Tarangire National Park, Tanzania)

Objects Found in a 400-Year-Old Well at Jamestown, Virginia Plants, wild and domestic seeds, pollen, parasites, insects, paper, leather, pewter, wood, ceramics, beads, fabric and other materials and food remains (a great quantity of butchered animal bones, oyster shells, and other marine life, including clam, mussel, and scallop shells, fish bones, dorsal plates from huge Atlantic sturgeon, crab claws, and barnacles). historicjamestowne.org Likewise, spoiling wells is an ancient tactic in warfare that was applied as recently as the Balkan wars and Rwandan civil strife of the 1990s, when human remains were dumped in wells. With less intention, spoiled wells can change history. Black rat remains found in Roman wells in Britain suggest that Romans may have lost their grip on northern Europe due to bubonic plague. When such wells required attention, there was no simple option to “move over and drill new,” especially in rock country. Establishing a new well would involve an incredible investment of labor, since the engine-powered drill would not appear until the nineteenth century. Cleaning the existing well would be the more cost-effective strategy in terms of time and labor, even if it were risky.

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Georg Houben and Christoph Treskatis, in their excellent McGraw-Hill book (see the recommended reading list), recount examples of well maintenance and reconstruction dating back to Neolithic times. One notable example of premodern well maintenance comes from Germany. By the sixteenth century, regular well maintenance on two- or three-year intervals was established in the city of Duderstadt. This took the form of a “well-cleaning feast.” Sadly, they report that the practice was abolished by 1724 “because the amounts of beer (5 barrels) served—free of charge—during this festivity caused ‘… on the one hand much exuberance, fighting and desecration of the holy days, on the other hand also the ruin of citizens and neighbours….’” Maybe this is why we have industrial safety regulations today, but it must have been more fun then. Well maintenance and rehabilitation through the history of dug-masonry wells was largely limited to cleaning out debris and silt, cleaning off what we would now call biofouling, and necessary deepening and reconstruction. The use of chlorine (chlorinated lime) as a disinfectant began in the nineteenth century in response to disease outbreaks associated with wells. One widely reported account is that of Dr. John Snow’s attempt to disinfect the Broad Street Pump in London in 1850 during the cholera outbreak, which Snow pinned on that infamous well. That it would occur to anyone to disinfect a well, of course, required an understanding of germ theory, which also did not emerge until the nineteenth century, and the industrial extraction of chlorine, also an innovation of the 1800s. The face of well construction changed dramatically in the nineteenth century in Europe and the Americas with the advent of the steam engine and engine-­powered reciprocating drilling machines. Although Chinese drillers reportedly drilled 1,000 m salt wells four thousand years ago with spring pole drilling systems, these took generations to complete (as one can imagine) and were therefore rare and valuable. The appearance of the steam engine attached to a drilling machine (dated to the 1830s in the United States) provided a reasonable means to drill deep wells into aquifers rarely tapped before. These were better protected from contamination and tapped water with more abundant reduced iron, manganese, and sulfur. Although more sanitary and easier to protect, their inefficient water intakes were more vulnerable to clogging by what we would come to know as iron, manganese, and sulfur biofouling. Thus, we came to an approximation of the modern drilled (tube) well maintenance situation:

1. A productive and valuable well that was (to varying degrees) prone to performance, sanitation, and structural issues. 2. The well is now deep—often quite deep—but no longer accessible for direct action by masons or youth with brushes and buckets. 3. Yet on the other hand, it could be built using engineering, process, and chemical capabilities also unavailable in previous millennia. For example, it can be pumped using a wind- or engine-powered piston pump.

The early decades of the twentieth century brought these notable advances in water well science, engineering, and technology:

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

1. The emergence of the cable tool drilling machine and associated tools and methods in their modern form provided a viable, powerful, and versatile well construction and service system 2. Modern well screen designs and other inventions with familiar names attached to them, such as Johnson, Layne, Moss, and (not to be forgotten) Cook 3. Modern metallurgy, giving us high-strength and corrosion-resistant alloys, precision machining, welding, and other fabrication methods 4. Development of technical procedures such as well grouting and filter packing 5. Development and adoption of the vertical turbine pump 6. Electric line power (often of high quality) becomes widely available 7. Development of well testing and analytical methods that are still in use today

As such drilled wells accumulated some age, performance decline and a need for rehabilitation, and of course pump service, became inevitable. As long as there have been well development tools and procedures, mechanical redevelopment has been used to clean wells that had filled with sediment or declined in performance. For many purposes, redevelopment worked well. However, it was not long before people tried various means to enhance the experience. While talking with a retired driller, Hubert Keith, in the early 1980s, he related to one of us (Smith) that Layne Mishiwaka crews in the 1930s pumped hot water and steam generated by their steam-powered cable tool rigs into wells to dislodge “iron bacteria” deposits. They would let the wells work and pass the time reforging drilling bits. This is the kind of patience (rarely expressed today) that Depression-era men, glad to have good jobs, possessed. Houben and Treskatis report that a Heinrich Böttcher filed a 1905 patent in Germany (no. 181,578) that dealt with the “cleaning of tube wells by means of hot steam.” So the concept had widespread application. The post–World War II period brought more revolution. The first was the spread of the truck-mounted rotary drilling rig. While they were used before the war, especially in the petroleum field, they were slow to be adopted by the water well industry due to cost and their complicated nature. However, once they became economical to deploy (and there was a suburban housing market), rotaries became common. Wells could be installed very quickly and less expensively. There was much less investment in time and emotion compared to installing them with cable tool rigs or by digging. Consequently, wells became consumables, to be used and discarded. Why maintain something you are going to use up and replace? In 1955, we had cheap land, cheap drilling, and limited regulatory environment. A second revolution was in the flowering of industrial chemistry, which made a wide range of cleaning and disinfecting compound chemicals available for use in well cleaning, and the ingenious experimented with a lot of them. Mineral acids such as hydrochloric acid were used for removing deposits. Chlorinated lime, chlorine gas, and liquid sodium hypochlorite were used for disinfection and odor removal. The use of chemicals became more prevalent after World War II, with the final passing of steam engines and the universal use of internal combustion engines to power drilling equipment. The proliferation of designer organic chemicals after World War II brought us the age of detergents, beginning in the 1950s. Paging through water well industry

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journals of the time, one finds wide-eyed articles and advertisements for compounds from familiar manufacturers. These phosphate-containing detergents were a major part of the well-cleaning toolkit for decades. Starting in the 1980s, more sophisticated chemistry that presented fewer side effect problems came into wider use. The period since the early 1980s brought a modern flowering of research, conferences, and publications (especially since the early 1990s) on well rehabilitation and maintenance. There was much experimentation in types of processes. That same period brought some of the first systematic experimentation and training in what constitutes effective well cleaning and maintenance. It also brought the era of well cleaning mass marketing, in which companies (including some of the major suppliers in the ground-water industry) provide us with designer compounds intended to be better and safer than what we select a la carte off the chemical supplier’s dock. Many of these products have names with letters and numbers. The innovation, testing, and exuberant marketing continue to the present day.

1.2 The Role of the “Environmental” Sector in Shaping Well Rehabilitation and Maintenance Millions of wells have been constructed in the industrialized world, mostly since the early 1980s, for a purpose other than the traditional ones: ground-water supply, recharge, or dewatering. Among these other purposes are monitoring ground-water quality and pumping to control or clean up contaminated ground water—the other side of the effect of the industrial chemical era on the industry. At the same time that construction of such environmental wells was accelerating, the environmental industry (consultants, government, drillers, and service users such as waste management firms), one challenge was to make remediation systems work in an environment far more challenging than that of a potable ground-water system. The development of several important consensus standards, including ASTM standards for construction and development and maintenance of monitoring wells, helped the process. An entire training and continuing education industry sprang up to service the needs of professionals in the environmental industry so that monitoring and recovery systems could be competently designed and installed. Manuals on monitoring well construction and design were written. Improved methods, tools and equipment, and personnel skills were developed and became part of the maturing of the industry. The results are not uniform—poorly designed systems are not disappearing. Unfortunately, with the gutting of funding for ground-water clean up, much of the training and continuing education sector has withered, but the publications and concepts remain. The remediation side of the business has been transformed since the mid-1990s with the phasing out of many pump-and-treat systems due to their high operational failure rate. It is not that such systems could not be maintained, but resources and plans to do so were rarely included in project plans. The entire budget went to design and construction. In their place, in situ remediation has been a more prevalent tactic. Of course, the whole pace of ground-water cleanup slowed in recent years with the loss of funding.

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

Figure 1.2  (See color insert following page 66.) Pump impellers clogged by oxidized iron deposition. Extraction well, DOE Fernald Preserve (Ohio).

In recovery and pump-and-treat systems, the chief problems are reduced flow and increased drawdown in the well systems and clogging of downstream piping and treatment apparatus. Pumps are a particularly hard-hit component of the system (Figure 1.2). Environmental well problems are fundamentally the same as those that cause water supply wells to provide poor performance. Poor design and poor construction and development also can contribute. However, inherent environmental causes of deterioration may occur even if design, installation, and development are adequate. Note:  We use numerous technical terms such as drawdown throughout this work. We are assuming an audience generally familiar with wells and their processes. If you are entirely new to well construction, testing, etc., we suggest reviewing primers on the subject (and do not forget to read the disclaimer and other warnings in this text). Monitoring wells may have less obvious performance symptoms since they are not always stressed by pumping. Symptoms of well deterioration experienced in monitoring wells are most likely to include changes in physicochemical water quality and increased turbidity. Such changes can interfere with the quality of samples from wells, as well as their performance, for example, interfering with the recovery of organic constituents of ground water such as trichlorethylene (TCE) results in erratic sample results over time. Results become more consistent after wells are rehabilitated. Aquifer storage and recovery (ASR) wells represent a new development in terms of their being in mainstream use. Injection wells for management of coastal salt water intrusion and barrier wells are known to be prone to particulate and biological clogging (Chapter 2). Such wells and associated infrastructure are large investments based on rather meager research into longevity issues.

1.3 The Impact of Biology on Hydrogeology and Ground-Water Technology Much to the bafflement and annoyance of many people with pure physical science and engineering backgrounds (not everyone certainly), the concept that biological

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occurrence, activity, and functions have significant impact on or dominance over the behavior of water and water constituents in the subsurface and the performance and service life of our engineered structures in the subsurface has become more and more difficult to ignore. Everything about planet Earth, from the stratosphere of the atmosphere down to the base of the crust, is affected by life, and has been profoundly transformed since life appeared on Earth. Microflora are ubiquitous. If there is a niche, they exploit it. If there is a pore space, they occupy it. If there is a surface, they coat it. The world as we know it is a product of the actions of living things. This revolution in understanding is hardly new. A very good conceptual understanding of the role of microflora in what we now call geomicrobiology (a term coined by 1954, according to Ehrlich (see Ehrlich and Newman in our recommended reading list)) developed in the late nineteenth century, but went quiet for several decades for historical-political reasons. “Geomicrobiology” pioneers were Russians, and the Soviet revolution came along in 1917. By the 1950s, a revival of interest was developing in some academic circles. H. L. Ehrlich’s first edition of Geomicrobiology appeared in the 1960s. The field gained traction by the 1970s in various research groups and at the U.S. Geological Survey. A lot of good work continued to be published in Russian (largely inaccessible to Americans). Finnish geochemists and environmental microbiologists (who read Russian and German and communicated well across the Iron Curtain) were among the leaders in the “breakout” in the 1970s and 1980s. Diffusion of these concepts to the practical ground-water field was rather slow. One of us (Smith) was the only individual on the staff of what was then the National Water Well Association (now National Ground Water Association) with a biology degree in the early 1980s. So he fielded all the inquiries about biological things and started on his “life of slime.” He met a lot of resistance and doubt when speaking about microbial corrosion and clogging. By the publishing of this work’s predecessor, Monitoring and Remediation Wells: Problem Prevention, Maintenance and Rehabilitation (CRC Press) in 1995, the role of microbial activity in well problems and the remediation of contaminated ground water were well on their way to being accepted in ground-water development and environmental remediation circles. By then, the now well-known Biological Activity Reaction Test (BART) tests were in the market and tested, a lot of work had been done in cleaning biofouled wells, the U.S. Department of Energy supported landmark work in deep subsurface microbiology that was very revealing, and D. R. Cullimore’s first edition of Practical Manual of Groundwater Microbiology was published by CRC Press. This growth and development (and intellectual acceptance) of the role of life in the ground-water engineering world has continued. Such a paradigm shift in thinking is consistent with the growing acceptance of the idea of an integrated, interactive universe and intedisciplinary study of phenomena. Although geomicrobiology has been experiencing another academic revival due to interest in global climate change and the possibility of life on Mars, the academic activity is not translating well into applied practice. It seems like a lot of people still are not paying attention. Ground-water remediation systems, especially those for commercial properties, are designed as if biological clogging will not occur— even if the system is designed to foster bioremediation. Then folks are stunned

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

when clogging does occur, but they remain unwilling to take the necessary steps in response, expecting it to simply go away or to be treated cheaply. A more subtle issue is that of the influence of developed biomass on well and aquifer hydrology. Actually, the physics and math are what they are. If a biomass clog is present, it lowers the hydraulic conductivity and alters flow paths, so the effects of biomass development can be analyzed and modeled with available tools. The weakness in hydrologic practice is the persistant assumption that the water level response of pumping and monitoring wells (regardless of age and condition) during tests transparently reflects the surrounding aquifer. Experience shows that is not the case. We even have math for that: analysis of “skin effect.” The problem with taking well biomass development into consideration is that to do so requires an initial step of well reconnaisance to assess conditions and then factoring those conditions into the analysis in a meaningful way. This requires a budget for such work, and suddenly, everyone likes simplifying assumptions. Myths like “isotropic and of infinite areal extent” are popular in the effort to do ground-water protection modeling on the cheap, for example.

1.4 Economics, Human Skills, Personalities, Demographics, and Other Issues As will be discussed further in this work, the economics of energy, land availability, water, and scarcity are driving a renewed interest in the economic benefits of well cleaning and maintenance in the commercial and municipal sectors. Practice is beginning to catch up with ideals, theory and persistent preaching. More of the water well industry has embraced rehabilitation, along with drilling, especially as the economic attractiveness of service has become evident. There is a beginning of a sense of economic value for ground water that was lacking before. Also, there is a sense that sustainable choices must be made: we cannot just run down a wellfield through neglect, then move over and establish another. There may be no other place available. Nontechnical human choices heavily influence the acceptance of ideas and technologies. The Enlightenment movement in Western thought led to a flowering of robust science, but the Enlightenment’s model of a mechanistic, clockwork universe results in resistance to ideas such as complex, literally organic interaction of formation materials, hydrology, biology, and operations. Interestingly enough, the “mechanic” side of the ground-water field, the water well contracting sector, embraced the biological clogging and corrosion model faster than their colleagues with academic and engineering credentials. This organic view of the situation fits their experience in life. Life is an integrated whole of earth, biology, machines, people, institutions, and various intangibles such as matters of faith. The modern story of water well construction, maintenance, and rehabilitation is also a social history, and heavily influenced by personalities.

1. It is impossible to envision the development of modern (meaning nineteenth century to present) water well and environmental technology without (a) free enterprise, (b) the American view of patent and intellectual rights

A Brief History of Well Maintenance, Rehabilitation and Their Milestones

(inventors should benefit from their work, and this is something to shoot for), and (c) the development of oil and gas. People had incentive to invent, try new methods, and take risks because they could benefit materially. Otherwise, we stay in the feudal system. The water well and rehabilitation fields are rich with invention. This continues today. Oil required invention to make serious progress and money. Oil and gas were the drivers for the cable tool rig’s development, the blowout preventer, and the tricone drilling bit, among so much more. Oil is valuable and people have strong incentive to invent and engineer to get it. Face it—people will get water from a creek. It required an economic incentive (irrigation, settling on prairie land, raising living standards) and social imperative (improve the lives of the poor and women) to drive improvement in water. 2. We have to make note of the “farm boy” phenomenon of North American society (which includes “farm girls” by the way). University engineering departments recognize that farm kids make the best mechanical engineers. Whether or not they have an engineering degree, people with this rural, machine-rich background know how to figure out how things work and how to do things like making field innovations and repairs. Are we losing this capacity-building ability in our society? 3. The story is full of colorful and interesting individuals. The 2007 movie There Will Be Blood, based loosely on Upton Sinclair’s 1927 novel Oil!, follows one such character, an inventive sociopath. That example is rather extreme. The pioneers and current drivers of the ground-water industry, especially the water well sector, are not likely to commit child abandonment and brutal acts of murder, but they tend to be individualistic, creative, technically focused inventors. They are not organization people. The drivers of recent improvements in well cleaning practice include the pioneers and visionaries typical of new or newly flowered technologies. It is impossible for us to imagine the current state of well diagnosis, maintenance, and cleaning without several people who demonstrated laserlike focus on these subjects—personal mission, actually, that resembles some kind of apostolic calling more than personal choice. Two that come to mind are the late George Alford on the cleaning side and his collaborator, Roy Cullimore (and his longtime devoted staff of associates). Then there is the skill of tent preaching that brings the sinners to repentance and salvation: Where would we be without Dave Hanson in that regard (setting aside for the moment some details of doctrine)? One person who labored in relative obscurity, and who should not be forgotten, is the late Miguel Gariboglio of Argentina. Since most of the publication in our field is done in North America and Europe, and much of it in English or its technical cousins German and French, this Spanish-speaking Argentine labored off on stage right. Besides, during the height of his work, Argentina was economically and politically isolated. Still, he and a number of his compatriot colleagues labored on developing and practicing practical biofouling and biocorrosion diagnosis in a very difficult situation, adding materially to our knowledge.

9

10



Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

4. However, despite how we lift up and remember the colorful personalities and the pioneers, the full mainstreaming of well cleaning required the influence of our “mud” and “screen” company colleagues. These businesses put the “soap” in jugs on the shelf with the appropriate instructions and certification labels, print the literature, staff the booths, and generally have brought well cleaning to the back roads of North America. Likewise, our laboratory supply mass marketers, with their catalogs and websites, and using our relentlessly organized package transport system, put the new biological tests in the hands of the operators who need them. Together, these businesses generally brought the combination of mass marketing and relentlessly efficient distribution that has come to be known as “walmarting” to well maintenance and cleaning tasks. 5. The occurrence of a maintenance mindset: The worldview that it is virtuous and valuable to maintain valuable systems is one that is culturally dependent and somewhat dependent on economics and other intangibles. Indoctrination is important (as we will discuss). One also finds that the maintenance ethic is most evident in societies (and segments of those societies) that have the most experience with machines and complex engineered structures (e.g., agriculture). This ethic is magnified when one owns or has fiduciary responsibility for the object of maintenance. Maintenance vision can be selective. This is well exemplified by the experience of water wells. People are most likely to maintain what they see or can otherwise readily detect. Operators will maintain a pump (especially a lineshaft turbine) but neglect the well structure. A maintenance ethic is less evident in societies (such as in the developing world) where machines have been dropped in by outsiders rather recently without transition from a previous condition. A state of lack of maintenance is amplified when the local people do not own the asset. Then the donor gets the message, “Dear friend, YOUR [fill in the blank—tractor, well pump, etc.] is broken. Please send money.” When frustrated by such a situation, understand that experience and comfort with (even love of) machines and systems comes through generations of acclimation and familiarity. Remember that the current state of ground-water technology had evolved over close to two centuries by the time this work was written. Such lapses of maintenance vision and planning occur in the United States. Here, funding for maintenance (as we discuss later) is not universally provided. Under some urban areas, subways were constructed, and in some cases, operated for some time but left to deteriorate due to lack of maintenance, and then abandoned. Highways and other infrastructure are often built, funded by grants, without maintenance funding and requirements. The political system can generate the will and momentum to build it, but no long-term commitment to maintain it. The rise of the “asset management” culture from roughly the turn of the twenty-first century is an attempt to systematize asset maintenance and financial responsibility. This is a system and ethic that can be readily (and rightly) applied to the specific assets known as wells and associated systems.

A Brief History of Well Maintenance, Rehabilitation and Their Milestones



11

6. The deep training, indoctrination, and knowledge needed to do these properly are yet to be mainstreamed. There is much evidence that many in charge of operating or advising operators of ground-water assets have paid no attention to the last twenty years’ progress. We (the authors) provide training where we can, as do some others. This book is one attempt to extend our reach. Fortunately, well cleaning methods now being lifted up (as described within) are relatively effective and much less hazardous than older methods, even if applied inefficiently. Just when improved well cleaning technologies are being mainstreamed, we now are experiencing a relative shortage of the service personnel necessary to perform well service work. As in the water and wastewater operations sector, the skilled and available ground-water industry workforce in the United States is aging. It remains predominantly rural, white, and male, while the United States is increasingly urban and pluralistic. Language and (sometimes ridiculous) immigration barriers impede the recruitment of other willing, skilled workers, and many women with the right skills and temperment find better pay and working conditions in other sectors, such as medical trades. Many other good people for this work are also occupied with being in the military—indefinitely it seems. How this will work out will await future works.

1.5 A Word about Terminology Our English language (the only one either of us uses with any confidence) allows for subtle subdivisions of meaning and easy word creation. In the current context, the process of cleaning and repairing a well to improve or restore performance has been referred to as rehabilitation, remediation, restoration, and simply as well cleaning. Each has merit. Remediation is a term often reserved for cleaning up contaminated ground water. That is how we will use the term here. Restoration was used in Evaluation and Restoration of Water Supply Wells, the 1993 manual that one of us (Smith) coauthored. That is a good term, but it may be too optimistic. Cleaning is a straightforward concept, and we use it herein for the process of clearing out debris, biofouling, and so forth. It implies, but does not promise, restoration. Roy Cullimore, in the new edition of Practical Manual of Groundwater Microbiology, favors regeneration for excellent reasons, including facility manager distaste for rehabilitation, which reminds them of the process of bringing injured workers back to health—an uncertain process with hidden costs and legal minefields, as he points out. We choose to stay with rehabilitation because it is a widely understood and used term for what we are discussing, and the process does have those features: risk, uncertainty, and hidden costs. Thus, we promote preventive maintenance as a lower-risk and more sure policy alternative. Besides, we would have to conduct a word search and change a lot of text, and we are acquiring age-related attention-deficit disorder as we look ahead to more important struggles in life than word choices. As you read Cullimore’s work (and you should not fail to do so—order it now if you do not have it), you will find some other differences in terminology. We stay with biofilm and biofouling where we use them and use biomass less often, although

12

Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

he is entirely correct in his choices. We tend to stay with a much simplified and mainstream choice of terminology. As you applaud our choice, remember that his terminology (consortia, biomass, no iron bacteria, etc.) pushes into mainstream literature and teaching, displacing the “mainstream.” It will continue to do so as long as he is writing and people pay attention to what he says, for he is the prophet of biology in the underground and we are apostles, applying and proclaiming what is revealed to us. And finally, following decades of U.S. Geological Survey usage (through March 2009) and the preference of the National Ground Water Association, ground water is two words as a modified noun and hyphenated ground-water as an adjective. Either that or we go with surface­water, drinkingwater, or potablewater in the German style. Enough pontificating, on with the meat of the discussion …

and Effects 2 Causes of Well Deterioration Well deterioration is a serious concern in the operation of ground-water systems. Causes include formation, water quality, and biofouling, as well as operational, factors. In order to understand and deal with well performance problems, it is necessary to understand causes of well deterioration and how they affect the performance of the well. Even if you now already have deteriorated wells and are looking for solutions, take some time to absorb this information.

2.1 Summary: Causes of Poor Performance There are numerous causes of poor and deteriorating well performance. Causes may include inherent characteristics of the formations that supply water to the well, well design and construction, and the ground-water quality. Operation of the well comes into play as well. Table 2.1 is a list of several categories of poor well performance or malfunction and likely causes. Chances are that several interacting factors are involved in your well’s problems. Think of these as interactive.

2.2 True Grit—Sand and Silt The infiltration of sand and other particulate fines remains one of the most common problems faced by well operators. Pumping sand and silt in the product water wears pump impellers and other components and clogs the downstream system (Figure 2.1). “Sanding” has a number of causes, including inadequate filtration design (large nonengineered slots and other engineering deficiencies, mobilization of fines in rock fractures, and breaks in sealing system components such as grout or casing). In some cases, high entrance velocities through engineered screens and gravel packs can cause sand pumping, usually when the filter pack fails to stabilize the aquifer and sand enters the well. These issues are exhaustively discussed in a wide array of available industry literature (see our recommended reading list) and do not need to be detailed here for the diligent student of well performance, although we taken them up as a topic of prevention in Chapter 4. Much of the same information is available online for the less motivated, and those who do not or cannot access the better references. Proper screen and filter pack design are adequately considered in the above-mentioned well construction publications and will not be detailed here, except to note that proper design practices, such as those spelled out in the National Ground Water Association’s (NGWA) new Water Well Construction Standard (ANSI NGWA-01), should be followed. 13

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

Table 2.1 Categories of Well Problems and Related Causes Problems

Causes

Sand/silt pumping: Pump and equipment wear and plugging

Inadequate screen and filter pack selection or installation; incomplete development; screen corrosion; collapse of filter pack due to washout resulting from excessive filter pack vertical velocity; presence of sand or silt in fractures intercepted by well completed open-hole; incomplete casing bottom seat (casingscreen break) or casing-screen break due to settlement, ground movement, or poor installation; pumping in excess of gravel pack and system capacity (oversized pump, pipe breakage— lowering pumping head, etc.)

Silt/clay infiltration: Filter clogging; sample turbidity

Inadequate well casing seals; infiltration through filter pack or “mud seams” in rock; inadequate development; casing-screen break due to settlement, ground movement, or poor installation; formation material may be so fine that engineered solutions are inadequate

Pumping water level decline: Reduced yields; impaired pump performance; increased oxidation; well interference

Area or regional water level declines; pumping in excess of sustainable aquifer capacity; well interference; well plugging or encrustation; sometimes a regional decline will be exaggerated at a well due to plugging

Lower (or insufficient) yield: Unsatisfactory system performance

Dewatering or caving in of a major water-bearing zone; pump wear or malfunction; encrustation; plugging; corrosion and perforation of discharge lines; increased total dynamic head (TDH) in water delivery or treatment system

Complete loss of production: Failure of system

Most typically pump failure; also loss of well production due to dewatering, plugging, or collapse

Chemical encrustation: Increased drawdown; reduced output; reduced injection acceptance rate

Deposition of saturated dissolved solids, usually high Ca, Mg carbonate, and sulfate salts, or iron oxides or FeII sulfides; may occur at chemical feed points, e.g., feeding caustic soda to raise pH into a Ca-rich water

Biofouling plugging: Increased drawdown or reduced injection acceptance rate; reduced output; alteration of samples; clogging of filters and lines

Microbial oxidation and precipitation of Fe, Mn, and S (sometimes other redox-changing metals that are low solubility when oxidized) with associated growth and slime production; often associated with simultaneous chemical encrustation and corrosion; associated problem: well “filter effect”—samples and pumped water are not necessarily representative of the aquifer; often works simultaneously with other problems, such as silting

Pump/well corrosion: Loss of performance; sanding or turbidity

Natural aggressive water quality, including H2S, NaCl type waters, biofouling, and electrolysis due to stray currents; aggravated by poor engineered material selection

Well structural failure: Well loss and abandonment

Tectonic ground shifting; ground subsidence; failure of unsupported casing in caves or unstable rock due to poor grout support; casing or screen corrosion and collapse; casing insufficient; construction and service work and other local site operations

Causes and Effects of Well Deterioration

15

Figure 2.1  Impellers destroyed by pumping sand and gravel (Mexico).

Recommendations on what is “proper design practice” vary somewhat (see also Chapter 4). Simplifying for conceptual purposes, the Western (U.S.) design school centered around the long gravel-packed louver screen accepts much higher slot entrance velocities than the wire-wound screen (e.g., Johnson Screens) design school. These differences in design follow differences in the hydrogeology-well-construction interactive system that they are designed around. This is important and proper: hydrogeologic parameters should drive well design, with parameters derived by thorough hydrogeologic testing and analysis. Some well design practices seem to assume that the earth can be forced to submit to the will of the engineer or regulatory authority. One trend in our experience is that of moving toward conservative slot selection to avoid sand infiltration. No one wants sand infiltration, but conservative slot selection can sacrifice efficiency and long-term performance to achieve that goal. The smaller the slot in any particular geochemical environment (see following), the sooner it will plug. If fines are going to be a problem, we advocate using a well-designed filter pack (following well-researched design practice) and budgeting for extended development. In the glacial-fluvial outwash valleys that are part of the experience in the Great Lakes region of the United States, we often encounter a wide and even bimodal distribution of particles in immature sediments: That is, the sieve analysis (including those obtained from Rotasonic cores) yields (1) boulders and (2) fine sand. Such a distribution is extraordinarily difficult to screen and prone to migration of fines toward the well, so designed filter packs are necessary. When an otherwise sensibly designed filter pack becomes partially or entirely plugged with fine-grained material, oxidation products, or biofouling (see follow­ing), the hydraulic conductivity of the filter pack is locally reduced, resulting in increased velocity and head losses through the filter pack, which increases the well loss component of total drawdown and can induce sand pumping. When near-screen velocities are too high in a well tapping a formation containing abundant fines (e.g., glaciofluvial aquifers), sand sealing by fines occurs. Sand sealing also occurs when too fine

16

Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

a screen slot is used, which prevents the normal passage of fine-grained materials during development of the well. To repeat, rather than using a too fine slot size distribution, filter pack and development should be optimized for maximum efficiency, while retaining fines. This requires informed engineering, skill, and some significant work time, and thus investment in the well development work. In rock wells, silting may result from an incomplete casing seat, which fails to seal off unconsolidated material. Also, water-bearing fractures themselves may contain fines. These are mobilized by pumping, and may stabilize at a new energy equilibrium after a period of time, or continue pumping fines indefinitely, requiring an engineering response. One poor practice, often employed in developing country economies (and in environmental settings elsewhere—is there a connection?), is the use of filter cloth in well screen to make up for the operational limitations of locally saw-slotted screen. Such filter cloth or geotextile can keep out fines, but fines can also be retained on the cloth (causing sand sealing), or they can bridge with biofouling to rapidly seal off the well, ending the usefulness of a promising water source that brought new hope to a community or of an important monitoring point. Monitoring Wells: Monitoring, dewatering, and recovery wells represent a special case in design and rehabilitation response. Water wells would be completed in favorable sand aquifer zones, and thus avoid many of the problems that wells completed for environmental tasks have with clay, silt, and sand. The mission of such wells, however, is to be completed in discrete horizons to provide samples or contaminant recovery or just a dry trench. For that reason, they are often completed in unfavorable zones, often at the top of the first water-bearing zone or aquifer (broadly defined) encountered. Sometimes screens are designed to straddle the water table. Taken all together, you have the worst possible scenario for well service life. Standard practice in monitoring wells is to complete screened wells with filter packs. These packs usually consist of uniform, rounded quartz sand of an average particle diameter suitable for holding out the more coarse material in a formation. However, selection of pack material and screen involves compromises. The pallet of filter sand that happens to be on the site is one size, not a range of sizes customized for the various wells. The result is that the well screen and pack may not be suitable for retaining the finest material present in a screened interval. Monitored formations are typically highly biologically active (see following), and biological activity can rapidly alter a monitoring well’s performance. Filter Packing Issues: It is also often difficult to properly place the filter pack material in the screen for optimal performance. Well annular spaces are usually small and not smooth. Bridging is highly likely. If the well is more than 40 ft (13 m) or so deep (not very deep), only the tremie methods can ensure that pack material actually reaches the screen. Alternatively, a prepacked screen approach may be considered. Bottom line: Plan adequate annular space for grout and filter pack work. Plan for proper placement. Beyond the inherent technical difficulties are the realities of field conditions. Numerous factors may interfere with exacting well installation. Drillers may be in a hurry because the customer or consultants are pressing to meet a deadline or looking

Causes and Effects of Well Deterioration

17

at a budget overrun. Supervisors of both drillers and field consultant personnel may want them to press the schedule because they have a backlog to work down. Site conditions may be poor, drilling equipment inadequate for the task (not uncommon), etc. For example, as is typically the case, drilling has commenced in the winter after the planning and approval cycle has been completed (having started after the beginning of the fiscal year). Everyone is cold, it is soggy, and work just does not go as well. The chances for a poor pack are enhanced. The fact that so much good work does get done under the project conditions imposed is a credit to the real professionals of the industry. A typical result, however, from a maintenance standpoint is that many wells have less than optimal screens, packs, and development. Under certain circumstances, especially in pumping wells, well clogging is likely and will have to be controlled so that the wells perform properly. Monitoring wells will produce turbid water that will have to be filtered for analysis, with unknown amounts of contaminants left adsorbed onto the suspended solids, thus affecting sample quality. Unless these are analyzed separately, sample fractions may be lost.

2.3 Yield and Drawdown Problems Lower (or insufficient) yield may result from either hydrogeologic or mechanical causes. Is it the pump or the well, or both (Figures 1.2, 2.1–2.3)? Figure 2.4 illustrates components of the water level system in a well (static water level, pumping water level, and drawdown and its components). Keep this figure in mind as we discuss well performance issues and components throughout the text. Pumping water level decline may be symptoms of zone dewatering or outside influences, such as area or regional water level declines or well interference, or of reduced hydraulic efficiency in the well, resulting from plugging or encrustation of

Figure 2.2  (See color insert following page 66.) Precleaning flow from a clogged well.

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

Figure 2.3  Well screen clogged by iron biofouling (North Dakota State University Extension, Scherer, 2005, Circular AE 97).

Static water level

Total drawdown

Aquifer loss

Cone of depression Aquifer pumping water level

Well loss Well pumping water level

Figure 2.4  Pumping well yield and drawdown components.

the borehole, screen, or filter pack. Typical causes of plugging are silt retained in filter packs or biofouling (Section 2.7), and are usually both. Dewatering of an aquifer zone can radically change the local biogeochemistry. Formerly reduced zones become oxidized, changing the nature of chemical constituents and the microbial ecology (Figure 2.5). Such changes affect pumped water quality since constituents may change. Contaminants may increasingly become attenuated. Dewatering or caving in of a major fracture or other water-bearing zone, or loss of connection to water-bearing zones, can be especially dramatic examples of dewatering phenomena.

19

Causes and Effects of Well Deterioration

Fe III Mn IV & S precip.

Fe III & Mn IV precip.

Fe III precip.

Reduction Ground water flow Increasing Eh

Figure 2.5  Schematic of oxidation and reduction and ecology changes around pumping wells.

Of the mechanical/engineering difficulties, pump problems are much more common. They include pump wear or malfunction, encrustation, plugging (Figure 1.2), or corrosion and perforation of the column pipe, and any increased total dynamic head (TDH) in the water delivery or treatment system. A common situation is the pump that gradually clogs or wears unnoticed, to the point where it can deliver its water discharge rate at just the head in the system. If a nearby well starts pumping, lowering the dynamic water level a foot or meter, the well stops pumping, because the pump simply cannot work against the new head regime. Complete loss of production most typically results from pump mechanical or electrical (mechanical, controls, or supply) failure. However, well mechanical causes may include catastrophic loss of well production due to dewatering, plugging, or collapse. Unless it is a pump mechanical or power failure, usually there is some warning in the form of a noticeable well performance decline. Except for pump mechanical failure, complete well failure usually indicates some lapse or negligence in design, construction, or operation. For example, as reported in Water Well Sustainability in Ontario, a very useful 2006 report produced by the Ontario (Canada) Ministry of Environment, available (at the time of writing) from http://www.wellwise.ca/, a survey of rural well infrastructure by the PFRA in the municipal district of Kneehill, Alberta, concluded that abrupt well failures during times of drought were mostly due to well clogging, not depleted aquifers per se. During these relatively short droughts, the historical range of aquifer water levels was essentially unchanged. Rather, the cause of well failure was felt to be due to the added effect of an increased but unnoticed loss in well efficiency beginning from the time the well was first constructed. In an impaired state, the well cannot function during the low point of the natural range of water level cycles.

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

2.4 Chemical Incrustation Figures  2.3 and 2.6 illustrate examples of essentially chemical incrustration. Ground waters typically maintain dissolved solids and gases in solution, even when supersaturated. The types and concentrations of dissolved minerals and gases in the ground water determine whether precipitates will form and how much will be deposited. Slow-moving ground water has ample time to dissolve large amounts of the minerals that it contacts. In most cases, a delicate equilibrium is achieved in native ground water, but pumping a well can upset this equilibrium. Actually, ground water can often be supersaturated with respect to major constituents such as calcite. These changes can result in dissolution from solids and subsequent precipitation and incrustation. In some cases, physicochemical transformations can alter aquifer hydraulic properties, especially when pumping begins (lowering pressure) or changes. Such mineral precipitates can be hard and brittle or can form a soft material like sludge or toothpaste. A commonly found deposit in potable ground water is calcium carbonate (CaCO3). Ground waters contain varying amounts of calcium bicarbonate (Ca(HCO3)2) and carbon dioxide (CO2) in solution. When a well is pumped, drawdown and head loss result. The head or pressure loss near the well bore hole can upset the fine balance that keeps CO2 in solution and it can be released. CO2 is over fifty times as soluble in water as other common air gases, so it does not degas easily. CO2 degassing would be most likely if the pumping water level is significantly deeper than the static water level. Otherwise, it will remain in solution and come on through into the engineered water system unless other mechanisms intervene (Figure 2.7). Still, carbonate clogging of extended hydraulic structures is known from antiquity. A notable example was the circumstances of carbonate clogging in the Roman aqueduct system. The source water for the aqueduct that served the Roman colony at the present city of Nîmes in southern France is high in calcium, low in manganese,

Figure 2.6  Pipe clogged by iron mineral (U.S. Environmental Protection Agency).

Causes and Effects of Well Deterioration

21

Gas relieved through vent

Gas comes out of solution

Figure 2.7  Schematic of well with gas pressure release.

hard, and alkaline, with most of the hardness being bicarbonate. Extensive deposition due to H+ loss from biocarbonate in a manganese-undersaturated environment resulted in bulky carbonate deposition. Much the same phenomena occur in geotechnical drains (Figure 2.8). As the CO2 comes out of solution, the soluble Ca(HCO3)2 becomes more insoluble CaCO3, which can precipitate within the formation and on the well screen. Magnesium carbonate (MgCO3) can form in a similar manner from magnesium bicarbonate. It is marginally more soluble than CaCO3 in water (which means it is still poorly soluble). Ground water with shifting carbonate species will be revealed by shifts in Ca:Mg ratio compared to surrounding wells in the same aquifer unit. Redox and pH shifts toward oxidation and alkalinity, respectively, may result in the deposition of iron and manganese oxides and carbonates. These shifts, which occur in engineered water treatment aerators, for example, drive oxidation of dissolved iron (Fe) and (under some circumstances) manganese (Mn) to their respective oxidized (and poorly soluble) forms. The resulting oxidized precipitates can form reddish brown or black sludge. Microorganisms accelerate the formation of such deposits, however. In particular, dissolved MnII resists chemical oxidation in ground water of a pH suitable for potable use and requires a microbial mediator for Mn oxides to form (see the following discussion).

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

Figure 2.8  Mineral-clogged drain—mostly calcite (Photograph courtesy of Chuck Cooper, Bureau of Reclamation).

Where methane is present and being oxidized to CO2, or CO2 naturally occurs in water due to metabolism or other oxidation of biological material, abundant carbonate deposits may also form when biocarbonates oxidize to poorly soluble carbonates. Oxidation and changes in pH may be aggravated by high near-well turbulence and velocity, oxygen entrainment due to excessive drawdown, and microbial oxidation. Chemical encrustation is also typically a secondary effect of biofouling oxidation or corrosion (Section 2.5 and Section 2.7). Encrustation causes reduced specific capacity and well efficiency and interference with product water quality. Chemical incrustation cannot be eliminated because it is a property of the existing water quality. Geochemistry can, however, be modeled if there is sufficient information, and changes such as precipitation can be predicted (as long as the role of biology—see following—is understood). If proper water quality analyses have been performed prior to construction, the screen can be designed with somewhat larger openings to allow for incrustation or the well system design and operating plan can be modified to slow the changes in equilibrium. Also, a screen material resistant to corrosion, such as high-quality stainless steel, can be selected to allow rehabilitation to remove the incrustation. Plans can also be implemented for periodic treatments to maintain the well’s efficiency.

2.5 Corrosion Pump and well structural corrosion is a very complex phenomenon (Figure  2.9). Corrosion as a term is generally associated with metals, and involves the removal of metal ions from metallic solids in contact with aqueous solutions. As with well and screen design, corrosion is adequately described in the print literature and online. So we summarize here. Causes of abiotic corrosion include naturally aggressive water quality, including waters containing sulfides (H2S or S2–) and chlorides (Cl–), and electrolysis due to stray electrical currents. However, most corrosion has a biological component as well.

Causes and Effects of Well Deterioration

23

Figure 2.9  (See color insert following page 66.) Corroded submersible pump end (southern Colorado).

Any corrosive situation is aggravated by inappropriate material selection in the design of pump or column pipe, casing, and screen components. Corrosion has secondary effects, such as sand pumping, alteration in water quality (especially elevated metals), secondary system clogging with corrosion products, and structural collapse. Metal corrosion in both fresh and saline water is always the result of an electrochemical reaction. Pure water is a weak electrolyte and is a fair insulator or very poor conductor of electricity. However, it is “hungry” for ions and can be severely corrosive. Sea water and other high total dissolved solids (TDS) waters are strong electrolytes. As an electrical current starts, iron begins to corrode:

Feo = Fe2+ + 2e –

Positively charged ions (Na+, Ca2+, etc.) flow to the cathode (the more noble metallic surface) while the negative ions (Cl–, SO4 –, etc.) flow to the anode. One commonly described manifestation of electrochemical corrosion is the galvanic cell system. A galvanic cell results when two metal surfaces with dissimilar electromotive properties are in contact in an electrolyte. These may be two pieces of metal or places on the same piece of metal that have differing electrical potentials. While useful for conceptual explanation, the galvanic cell is responsible for only a small fraction of corrosion that occurs in potable waters. The principal cause of corrosion in such fresh water is the oxygen concentration cell (or concentration cell corrosion) (Figure 2.10). Carbon steel and stainless steel both develop a coating of corrosion once exposed to oxygen in the presence of water. The chromium in the stainless steel produces a significantly stable coating that electrochemically passifies the surface and inhibits further corrosion. The coating is less effective and stable on carbon steel. The oxygen concentration cell may be initiated by anything that will shield a small area from the dissolved oxygen in the water, such as a grain of sand or a biofilm patch (see Section 2.7.1).

24

Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation 2Fe++ + ½ O2 + 4OH–

2H2O +

4e–

Fe2O3 + H2O

e–

2Fe++ + 4e–

2Fe

4OH– e–

e–

e–

e–

e–

(mild steel)

Figure 2.10  Diagram of a corrosion tubercle in steel pipe.

Concentration cell corrosion can begin at any breach, and often occurs at pipe joints, under gaskets at flanges, threads, and other points of metal stress. Once the coating is breached, either physically by abrasion or by being destabilized (e.g., by Cl–), the point becomes an anode of an electrolytic cell. The surrounding area, which still retains its passifying coating, becomes the cathode of an electrolytic cell. The dissolved oxygen (DO) in the water is in the molecular form as O2. Where the O2 is in contact with the pipe the potential is there to strip electrons from the Fe, even if the surface is uniformly coated with metal oxide. Thus, an electron potential is established between the areas in contact with O2 and where it is excluded. The potential of the cell is dependent on the concentration of dissolved oxygen in the water. The gross potential that is produced may be very small, but the cathode area is large relative to the anode point, which results in a high charge density at the anode. The charge density alone is what provides the energy to the system to strip electrons from the iron and oxidize it to the Fe2+ (ferrous) state:

Feo = Fe2+ + 2e –

The electron stripped from the iron moves through the pipe as an electric current. Fe2+ is soluble under the eH-pH conditions of most ground waters and therefore diffuses away from the anode site. Once started, the cell becomes self-perpetuating and a pit forms. The ferrous (Fe2+) ions produced encounter oxygenated water and are oxidized to ferric (FeIII) hydroxide:

4Fe2+ + O2 + 10H2O = 4Fe(OH)3 + 8H+

The incipient pit becomes covered or surrounded with a crust of insoluble metal oxide or biofilm (Section 2.7), preventing or limiting diffusion of oxygen to the anode. The structure formed is a corrosion tubercle. By ensuring that there will be no oxygen under the tubercle, the electron potential is maintained and the exposed metal cannot reoxidize and repassify, thus perpetuating the process. As indicated above, the further oxidation of ferrous iron to ferric iron liberates hydrogen ions, H+. These migrate to the cathodic areas and form a hydrogen film. Figure 2.11 illustrates some tubercle formations. See also the biological corrosion discussion (Section 2.7.3).

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Causes and Effects of Well Deterioration

Outer layer

Shell-like layers Porous interior

1 mm 1 mm

Figure 2.11  Cross section of steel pipe corrosion tubercles (Lytle, Gerken, and Maynard, 2004, U.S. EPA).

Note:  In referring to mineral charge states, we will use a superscript numeral (e.g., Fe2+) for an ionic state, as in solution, and Roman numerals (FeIII) in a mineral form. For some minerals (e.g., As for arsenic and U for uranium, we will use parentheses also—As(IV)). Except as it may affect calculation of the Langelier index, pH has little effect on corrosion over the ranges normally found in well waters. However, when the pH of water is below 7, the rate of formation of Fe3+ from Fe2+ and O2 is very much slower than at higher pH values (except when iron-precipitating microflora are involved). Values of pH less than 7 are usually encountered in waters of low alkalinity and low TDS (e.g., water in granite aquifers or representing fresh recharge). Under these conditions, uniform corrosion is more likely to occur (unless iron biofouling is active). Corrosion may be severe in terms of total loss of metal, but in the absence of pitting, perforation will not be rapid and facilities often have reasonably long life. It is the pitting type corrosion that is most often implicated in premature decline in water quality and equipment failure. Perforation of casing by pitting corrosion that results in a coliform-bacteria positive test result can doom the entire well. Corrosion of steel under nonpitting circumstances is inhibited by the formation of calcite layers on metal surfaces. CaCO3 saturation is governed by pH, temperature, and the water’s ionic strength. The values of solubility constants depend upon the temperature and the degree of mineralization (ionic strength) of the water. Simplifying: At 25°C and moderate mineralization (400+ mg/L total dissolved solids) the situation can be described by

pHs = 11.85 – log [Ca] – log [HCO3]

(2.1)

In wells, the portions of the casing and column above the water level are usually covered with condensate saturated with air. Since air contains CO2, the condensate water may contain carbonic acid and locally have a pH of less than 7, and TDS will be very low. Nonpitting sheet corrosion may be expected to occur.

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

One problem with extrapolating from empirical observation to concept is that water quality data reported from corrosion incidents are seldom complete. Hardness may be reported, but not alkalinity, or hardness (as what?) is tested, but no bicarbonate data collected. DO and other dissolved gases such as CO2 are seldom reported, and they are major drivers for corrosivity. Note: Corrosion potentials and symptoms are different in sea water (for which much of the corrosion literature is written) and fresh water. Specifically of interest for wells is that corrosion between dissimilar metals is confined to a few millimeters in distance, and is more likely to occur at welds, fastenings, threads, or other alterations.

2.6 Plastic Deterioration Plastics are routinely used in well and pumping equipment due to their resistance to corrosion, smoothness, light weight, and flexibility. Polyvinyl chloride (PVC), fluoro­ carbon (e.g., Teflon), and polystyrene formulations used in casing and pump com­ ponents are indeed recalcitrant, that is, not susceptible to corrosion, by themselves. PVC becomes subject to deterioration if it contains a significant percentage of plasticizers; however, PVC specified for water use (designated NSF-pw) forms a rigid product that contains a low level of mobile plasticizers. Hydrocarbons are known to penetrate PVC pipe, however, and may serve as a means of softening PVC bonds and making its polymer components available for biodegradation in some circumstances. Where solvent welding of casing sections is practiced, transient detections of solvent components occur, usually only early in the well’s life. Casing plastic cement bonds are softened and broken when certain organic compounds are present in ground water.

2.7 Biofouling—A Hitchhiker’s Guide to How Life Takes Over Who Are Those Guys?: In the movie Butch Cassidy and the Sundance Kid, the main characters (likable criminals) are tracked after a botched robbery for a long time by determined and skillful trackers. They repeatedly ask, “Who are those guys?” as they desperately try one trick after another to shake the posse. Wells and associated systems are usually designed by well drillers, sometimes engineers, and (if the planner is prudent) geologists. Naturally, plugging by sediment (sand, silt, clay) has traditionally been the most often recognized cause of well plugging and reduced performance. Water sample quality is affected by what are described as colloids. However, experience with a wide range of well types (water supply, dewatering, recovery, recharge, and monitoring) around the world suggests that the number one contributor to reduced well performance in most regions across the globe is biofouling, which can be defined as the impairment or degradation of something (well, ship’s hull, catheter) as a result of the growth or activity of living organisms. It occurs in a broad range of systems.

Causes and Effects of Well Deterioration

27

Who are those guys? As in the movie, knowing what you are dealing with is important when trying to develop a solution. The key words here are experienced, adaptable, and survivors. In the case of microbial actions, good evidence indicates that cellular microbial life was present over 3.4 billion years ago. By that time, microbes were forming biofilms and complex structures (stromatolites) and interacting with their environments under more lethal conditions than exist today (higher UV influx, for example). They survived young Earth conditions that very nearly wiped out life more than once. Over the intervening thousands of millions of years, microbes have reached the deep terrestrial subsurface and the deepest ocean. They use a wide range of processes for respiration. Their genetic systems allow for borrowing genes from the environment. They can survive brutal conditions on present-day Earth. Other organisms, especially fungi and plants, have thrown up ingenious and complex antibiotic defenses against bacteria. The microbes have seen it all. Keep that in mind as you consider preventive and treatment measures. Other Causes Contribute, but … Where silting is indicated as a cause of well plugging, it is most likely working in tandem with biofouling plugging at or near the intake surface and the portion of the aquifer matrix subject to partial oxidation. Likewise, many alterations of chemistry and formations of physical properties can occur due to biological action depending on the circumstances: carbonate deposition, gas formation, oxidation, and reduction. So who are these guys? Biofouling involves the biological formation and deposition of fouling materials, which usually include mineral and metal precipitates (e.g., Fe oxides and sulfides, Mn, S oxides, and CaCO3). Because of its importance, biofouling and its adjunct—biocorrosion—will be discussed here at length. We also specifically refer you to Microbiology of Well Biofouling and Practical Manual of Groundwater Microbiology by D. R. Cullimore (see our recommended reading list) to get a more in-depth and poetic assessment of the subject of biofouling.

2.7.1 Biofilm and Biofouling Basics Biofouling and other biomass-driven effects of living things can take many forms in engineered systems, from zebra mussel clogging of surface water intakes or irrigation gates to fairly benign coatings in all sorts of industrial systems, both on the surface and underground, and everywhere in between. Biofouling is also a medically important phenomenon: coating catheters, aiding antiobiotic resistance, and more. Figure 2.12 illustrates a typical mixed biofilm. Biofouling begins with the development of biofilms. These biofilms are complex biological coatings. Bacteria that form biofilms are considered to be ubiquitous in terrestrial and aquatic environments. The impulse to form biofilms is also ubiquitous and ancient in nature. Fossil evidence shows that marine microbes formed biofilms at least 3.4 billion years ago. Naturally, biofilm-forming microbes adapt to novel

28

Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

Figure 2.12  (See color insert following page 66.) Mixed biofilm from water well samples (normal light photomicrograph).

environments. Biofilms and biofouling also occur on medical appliances, in laboratory systems, and even in our own bodies (complications of cystic fibrosis being the most extreme example in humans), in addition to aquatic or marine environments. Biofilms are typically formed by bacteria (and cyanobacteria), but they typically include diatoms and other algae, protists, and small multicellular animals such as rotifers, where conditions permit. In wells, biofilms are almost entirely bacterial. However, protists (usually ciliates) are common. Figure 2.13 illustrates some macroscopic manifestations of biofilm formation. Figure 2.14 illustrates some really chunky biofouling. Zebra mussel and quagga mussel and similar biofouling that involves macroorganisms can cause severe metal corrosion and iron deposition, as these aggregations attract and support bacterial biofouling by providing abundant organic material and growth surfaces. Mussel verligers (some as small as 2 μm) can find their way down fractures out of reservoirs and Rant Speaking of zebra mussels, here in North America and elsewhere, we pay a constant, undefined tax—dealing with the costly side effects of greed in world trade in the form of exotic species introduced into our ecosystems. The shipping industry says it is too costly to manage ship ballast water with the least bit of responsibility, so our cities and power stations and fisheries are expected to pay for cleaning off their mussels. Sports fisheries people in their careless ignorance have now spread these to the waters of the U.S. West. Our foreign trade partners cannot be bothered to inspect and disinfect pallets. So we get Dutch elm disease and ash borers. We Americans nearly destroyed the European wine industry with vine root parasites. No wonder some people are socialist and protectionist. This is the thanks we get for supporting globalization?

Causes and Effects of Well Deterioration

29

Biofilms Forming

Seep in tunnel (above L), Fe biofouled pipe (above R) and trickling water treatment (right)

Figure 2.13  Examples of manifestations of biofouling.

Figure 2.14  Zebra mussel fouling in pipe (Gemma Grace, Ontario, Canada).

into pressure relief drains, for example, so they can on occasion become a ground water issue. They are certainly a utility and facility maintenance issue. 2.7.1.1 Biofilms and Microbial Survival Biofilms have a survival function for microorganisms in aquatic and soil environments. One is to provide, on a microscopic scale, multiple environments within the biofilm, allowing for the survival of a variety of microorganisms (collectively referred to as a consortium), transport of nutrients, and physicochemical gradients. Multicellularity is an advantage to the community or consortium. Some members are good protectors, others best at recycling the dead, and so forth. An important factor to remember is the complexity and adaptability of biofilm communities—in economic terms, these are diverse, innovative economies, not “company towns.” Biofilms also serve to protect living cells within them from external stress, such as disinfectants or designer biocides. Fe-, S-, and Mn-precipitating bacteria in these

30

Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

biofilms precipitate metallic oxides and extracellular polymers (ECPs). Anaerobic bacteria associated with biofilms produce reducing agents (e.g., sulfides and methane). All of these can react with and effectively neutralize oxidants such as chlorine, oxygen, and hydrogen peroxide. Buffers generated by the bacteria and their biofilm matrices likewise can dampen the effects of acids or caustics used in well treatments. Plus, the biofilm matrix itself can take a “burn” while cells inside retract and adapt to the toxic conditions. Together, what you have is an example of a complex adaptive system (CAS): a system that is complex (having multiple resources—in this case, multiple, flexible genomes and enzymatic systems) and can adapt (brings these resources to bear to meet challenges). Societies, economies, and ecosystems are other examples of CAS. 2.7.1.2 Biofilm Function and Ecological Function Many of you with ecological or agricultural experience understand the value of plants in anchoring unstable slopes. Recent University of Colorado research in Peru has documented the role of microorganisms in stabilizing talus and unstable soil in extreme conditions immediately after glacier retreat at high altitude. At their research site at the Puca Glacier, microbes stabilized the soil and prevented erosion on the slope by using their filament-like structure to weave soil particles together in a matrix. The CU-Boulder researchers also found the microbes excrete a glue-like sugar compound to further bond soil particles. Does that sound a little like what happens in a pumping well over time (see following)? In addition, the University of Colorado researchers discovered that nitrogen fixation rates—the process in which nitrogen gas is converted by the bacteria into compounds in the soil like ammonia and nitrate—increased by about a hundred-fold in the first five years after exposure of the soil. It should not be overlooked that microorganisms in the environment (working in consortia as complex adaptive systems) have adaptive functions or behaviors that can find expression in our engineered systems. 2.7.1.3 Biofilms and Biofouling in Ground Water It should hardly be surprising that aquifers often contain large, active, microbial populations. Aquifers are (1) formed from sediments or (2) fractured rocks (also sedimentary in most cases) with interconnected fractures. Fracture or pore apertures greater than 1–2 μm permit migration of microbial particles (Figure  2.15). In ground-water source systems, microbial biofilms are the predominant habitat for aquifer microflora (Figure 2.16). From a microbial standpoint, aquifers are ideal environments in many cases, especially if suitable organic substrates are present. There is tremendous surface area for colonization, moderate temperatures, nutrient flux, and overall very little disturbance. Because the surface areas of the interstitial spaces in an aquifer are very large, the total mass of biofilms around a well can be likewise large given the right conditions. As these biofilms accumulate cell material and debris over time, they accumulate biomass. Such biomass is the basis for biologically mediated encrustation in water wells and is implicated in associated corrosion. Where significant amounts of hydrocarbons and other assimilable organic compounds (AOCs) are mixed with water, large populations of the many microorganisms

31

Causes and Effects of Well Deterioration

Re-entrainment: Size preference unknown

Earth matrix Dispersion

Sorptive filtration: Preferential attachment of smaller bacteria

Pore spaces vs. microbe size – conditions affect bacteria size, types, attachment

Advection

USGS

Figure 2.15  Bacterial size, movement, and attachment in relation to pore size in aquifer materials (U.S. Geological Survey).

Figure 2.16  Iron-related biofilm from well water samples (normal light photomicrographs).

that can utilize these compounds also occur. This is particularly the case where in situ bioremediation is encouraged by the addition of microbial nutrients, cometabolites, and electron acceptors (PO4, NO3, O2, etc.). A widely observed phenomenon in ecology is that community diversity and total live biomass are greatest where there are gradients, such as forest edges. In the microbial realm, these gradients are primarily physicochemical in nature, and can occur over microscopic to centimeter distances.

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

A variety of environmental gradients can be expected to be formed by biogeochemical processes in aquifers. Such processes are enhanced in aquifers with notable AOC concentrations. AOC concentrations may be sufficient to encourage microbial growth and sharp changes in redox potential. Add pumping wells and you have especially rich environmental diversity. These gradients facilitate (and are the product of) a variety of microbial activities. This variety is reflected in a high overall microbial diversity in relatively rich ground water, although single species may dominate locally or transiently in time. Fermentation, chemoheterotrophic oxidation of organics, and both oxidation and reduction of minerals and metals are practiced by microorganisms all living in close proximity. Case History Example: Organics Contamination of Iowa Wellfield—Species Diversity Apparently as a result of leaking organics-laden carbon dioxide from a pipeline, a large wellfield was affected by an intense increase in bioavailable organic material in the aquifer. In a study that sampled formation material and analyzed microbial diversity, the biodiversity of aquifer sediment cores was greatest right at the alledged point of release, decreasing away from the release point.

More hydrophobic organics (e.g., hydrocarbons) may adhere to particles where the biofilms form, so that the bacteria present have an especially favorable situation for mass growth. Hydrocarbon-water interfaces provide a favorable growth situation as well. On a soil particle coated with dilute product, both situations occur (solid and oilwater interfaces), providing more variety in growth conditions (Figure 2.17). Clogging deposits coating particles rapidly fill pore spaces, throttling hydraulic conductivity. The microbial ecology of a near-well system of a ground-water remediation system (such as one that incorporates pumping and venting) may be quite complex (Figure 2.18), with molds and other microbes that form elaborate three-dimensional Product

Interface biofilm

Mixing zone Organic coating and biofilm Water

Figure 2.17  Soil-water-oil-biofilm interface.

33

Causes and Effects of Well Deterioration Mold spores aerosol-borne bacteria

Well

Soil ventilation

Biodegradation & organic acid formation

Molds

Smeared product

Vapors

Molds

Product

FeIII, MnIV, S0/SO4 reduction Fe, Mn, S biofouling

Redox fringe Fe, Mn, S biofouling, clogging and corrosion

Figure 2.18  Microbial ecology schematic of a remediation system.

structures occupying the unsaturated zone above the water table, anaerobic dissimilatory metal reducers occupying the anaerobic ground water, and metal oxidizers and hydrocarbon utilizers found mostly at the interface between the aerobic and anaerobic zones. One can expect that microorganisms will function in such constructed environments as if the system were a disturbed environment, expressing filamentous and adhesive and other system-modifying functions, such as nitrogen fixation and nutrient hoarding.

2.7.2 Water Quality Degradation: Monitoring and Remediation Problems Typically, the earliest noticeable manifestation of biofouling in any well is the water quality change that accompanies mass bacterial growth and associated Fe, Mn, and S transformations. Fe and Mn occurrence and concentrations in ground water are affected by several complex mechanisms with microbial and physical-chemical components, including feedback controls over rates of activity. Turbidity increases, filters are clogged, or filtration of samples becomes necessary. Odors may change or form. Supersaturation of CO2 and CH4 and subsequent off-gassing can occur. This can be alarming, or at the very least troublesome operationally (and occasionally lethal to animals). These are further symptoms of microbial processes, either in the wells involved or in the source water. Biological interaction with transient pulses of organics reflects passages of spill components. Figure  2.19 depicts a hypothetical relationship of this type.

34

Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

35

Organic Chemical and Bacterial Data, Affected Water Well 2 million cells/mL

30

ug/L

25 500,000 cells/mL

20 15 10

1000 cells/mL

0

May-89 Jun-89 Sep-89 Nov-89 Jan-90 Mar-90 May-90 Jul-90 Sep-90 Nov-90 Jan-91 Mar-91 May-91 Jul-91 Sep-91 Nov-91 Jan-92 Mar-92 May-92 Jul-92 Sep-92 Nov-92 Jan-93 Mar-93 May-93 Jul-93 Sep-93 Nov-93 Jan-94 Mar-94 May-94 Jul-94 Sep-94 Nov-94 Jan-95 Mar-95 May-95 Jul-95 Sep-95 Nov-95

5

Dates

TCE ug/L

Vinyl chloride ug/L

Vinyl chloride MCL ug/L

ds-1, 2-dichloroethene ug/L

TCE MCL ug/L

Figure 2.19  Passage of a contaminant plume in an alluvial aquifer. This is a simulation based on observed phenomena. Usually indications of microbial activity are detected months or years later in response to some observed problem.

Discoloration, high bacterial counts, high turbidity (excluding sediment), and odor are symptomatic of active, established biofilms present in and around the pumping well. Portions of biofilms will intermittently slough off into the water being pumped through the collection-distribution system to the treatment plant or distribution system. Transient, elevated Fe, Mn, and H2S concentrations in pumped ground water, and increases in levels at the leading edge of a contaminant plume, are typically the result of stimulated bacterial activities in the aquifer. The bacteria metabolically reduce FeIII, MnIV, and SO42–, thus mobilizing soluble Fe, Mn, and S species. Subsequent sloughing of FeIII and MnIV biofilms containing sulfide products adds to total metal contents. Figures 2.5, 2.20, and 2.21 are summary representations of Fe, Mn, and S transformations in aquifers, especially around wells. Metallic oxides (predominantly Fe hydroxides) produced by corrosion and FeIII precipitation due to biofouling are important reactive surfaces. They interact with charged species such as H+ (thus affecting pH), Cd2+ and other metallic cations, and anions such as SO42, as well as organic compounds. MnIV and FeIII oxides can thus scavenge heavy metals such as Co, Ni, Cu, Zn, and Sn, for example. Fe sulfides and hydroxides are also involved in the immobilization of soluble U(VI). With changes in drinking water arsenic (As) regulations, control of As has become an important ground-water quality issue. Soluble As is readily scavenged and held by FeIII oxihydroxide surfaces. Where soluble Mn is present in ground water, it is also complexed with the FeIII oxides. Where ground-water redox potential is reducing, low-solubility As(V) can be reduced to mobile As(III). In heavily biofouled wells, this transformation can occur in the reducing conditions of sediment-filled sumps, or where low-Eh ground water encounters As-containing sediment.

35

Causes and Effects of Well Deterioration

Free Fe2+, Mn2+, S2–

FeIII, S, MnIV oxides on matrix Sulfide/sulfate & carbonate minerals

Methane and CO2

Biofilm oxidation retention

Sulfide/sulfate/carbonate minerals interspersed

FeIII, S, MnIV oxides carbonate Biofilm

Microbial reduction & mobilization

Figure 2.20  Fe, Mn, and S transformations and mobility in aquifers—a schematic of typical occurrences in a biologically active mixed reducing-oxidizing aquifer system.

Sh m ed s et lu al gs se o tc f .

Pipe surface

Detail

Typical: FeIII oxide outside, FeII sulfides inside

Uptake heavy metals etc. Biofilm

Perforation from MIC

Plugging at oxic-anoxic interface

Plugging at oxic-anoxic interface

Clogging intake & impellers sulfides & oxides

Screen and filter pack FeIII oxides, carbonates, FeII sulfides (clogging)

Figure 2.21  Fe transformation and plugging zone around an affected well—a schematic of the many activities and results of activity in the busy environment of a pumping well.

Many types of microorganisms can selectively precipitate minerals. Microbial reduction results in forming insoluble U(IV) from soluble U(VI), potentially immobilizing uranium in the subsurface. In a similar case, a variety of bacterial and archaean species have been identified as facilitating the capture and reduction of gold chloride to elemental gold in soils. Both can result in minable ore deposits.

36

Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

Levels of organic constituents detected in monitoring well samples may become erratic over time. This may be the result of partial attenuation on soil particles, followed by release in sloughing events, but biofilms also may cause partial attenuation and sloughing. FeIII hydroxide minerals associated with biofilms are highly reactive with reduced organic compounds. The cycle of adsorption, partial utilization, and slug release results in sample interference and data that indicate irregular concentrations, or show breakdown products and “unknowns” in organic analyses. Microbially mediated FeIII and MnIV reduction and FeII and MnII mobilization result in dissolved Fe2+ and Mn2+ in ground water, with pronounced differences along flow paths from recharge to discharge areas. Crystalline FeIII is reduced by bacteria in aquifer materials, with the rate of reduction and dissolution controlled by FeII in solution. Mn and Fe complexed with ECP may occur in suspension, and can be detected in high levels in analytical results from unfiltered samples. This is a process that is analogous to Fe sequestration treatments used to control Fe and Mn precipitation in water distribution systems. Conversely, biofilms may also act as metal filters, removing Fe and possibly Mn from solution. Once the well biofilm has been removed or inactivated during rehabilitation treatment, Fe and Mn levels may increase in the produced water due to the lack of a sequestering effect previously provided by the biofilm. The result is that biofouled wells (both production and monitoring wells) typically exhibit fluctuating raw water constituent (e.g., Fe and Mn) levels (both soluble or colloidal). And you may think you are collecting representative water samples from the aquifer from your monitoring well; however, such samples may actually be products of microbial and other well-associated redox modifications. If you drive a probe into the aquifer several meters away, you may get out of this bioactive zone and thus encounter unmodified aquifer water (maybe). Intermittently high Fe and Mn levels can have a considerable effect on the operation of water treatment plants. These effects include increased chemical oxidant demand, bleed-through of filters, increased system hydraulic head, and more frequent filter backwash and aeration tower cleaning intervals. These biologically mediated water quality changes can be particularly troubling when FeIII oxide or S-slime deposits clog pipelines (typically not very large in diameter in remediation systems) and coat carbon filters or aeration tower media. It is clear that microbial effects can be very important influences on monitoring and recovery wells, just as they are for water wells, and dealing with these effects needs to be a part of design and operation (Chapters 4 through 6). This discussion of microbial transformations of elements and compounds is brief and intended to provide the reader with an introduction to causes. The reader should realize that after probably 3.5 billion years of cellular life history, the range and complexity of microbial systems and actions is vast. Readers interested in a detailed review of geomicrobiological transformations are referred to Geomicrobiology, fifth edition, by H. L. Ehrlich and Dianne K. Newman (recommended reading list).

37

Causes and Effects of Well Deterioration

2.7.3 Microbially Mediated Metallic Corrosion Microorganisms accelerate corrosion of well and water treatment system metallic components in a variety of ways. The microbial enhancement of corrosion is related to the production of corrosive metabolites such as nitric and other mineral and organic acids (which act as metal scavenging anions) and sulfides (S2–), as well as the establishment of differential oxidation cells in the form of colonies or biofilms. The formation of these cells creates conditions for anodic dissolution of metals, particularly iron. Likewise, FeIII-reducing bacteria have been demonstrated to reduce Fe oxide coatings on steel, stimulating corrosion. Fe biofouling is typically not uniform, and areas of differing electron potentials result on biofouled surfaces, providing local environments conducive to corrosion. When differential oxidation cells form, electrochemical corrosion occurs at areas (anodes) of lowest oxygen concentration, for example, under a biofilm. In addition to providing a diffusion barrier to oxygen mass transfer, the microorganisms present in biofilms consume available oxygen by aerobic respiration. Figure 2.22 is a schematic of microbial corrosion processes. When oxygen depletion occurs, anaerobes such as sulfate (SO4)-reducing bac­ teria (SRB) can proliferate if suitable organic carbon sources are present. They seem to be virtually ubiquitous in aquifers, even those with overall high bulk Eh. SRB can utilize molecular hydrogen and produce S2–, both of which are important in electrochemical corrosion. In addition, biofilms shelter other heterotrophic bacteria that produce acidic metabolites that are corrosive or serve to promote or maintain reducing environments that benefit the SRB. One example is the production

Biofilm surface

Biofilm

Hardened tubercle

Organic acids: Metal corrosion

n tio tra ne Pe

Metal surface

Metallic sulfides magnetite

Re

x do

t ien ad r g

Biofilm

Redox gra dients: Electron movemen t

nt

die

ra xg edo

R

Metal oxides

Crevice

Figure 2.22  Microbial corrosion processes schematic—illustrating the range of bioelectrical activity around a corrosion tubercle on a steel surface (some features also apply to crevice corrosion of stainless steel alloys).

38

Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

Figure 2.23  (See color insert following page 66.) Example of mild steel well pump discharge pipe tuberculation. Biocorroded stainless steel monitoring well casing

Hole at 10 ft 4 in Start of anode development only (left)

Figure 2.24  Microbially influenced corrosion of Type 316 stainless steel monitoring well casing. Section at left has begun anodic attack under biofilm associated with bentonite grout, while in the section on the right, corrosion is associated with metal fatigue.

of short-chain organic acids during incomplete anaerobic oxidation of long-chain aliphatic hydrocarbons. Microbially induced corrosion (MIC) of ground-water well components is widely recognized and associated with degradation of mild steel (Figure  2.23) and even Type 304 stainless steel, but sometimes also more resistant classes of stainless (Figure 2.24). Corrosion of stainless steel components of monitoring wells has been implicated in the alteration of sample water quality. Such metal corrosion processes are accelerated in recovery well systems controlling organic plumes, due to both the presence of organics that are degraded to organic acids, and the overall intensity of microbial activity. This microflora may additionally include a wide range of fungal growth and functions where wells and

Causes and Effects of Well Deterioration

39

sediments are frequently unsaturated. Thus, there is a complex overall biochemical situation that encourages multiple electron potential cells and corrosion. A common expression of metallic corrosion in monitoring and pumping wells is intergranular corrosion cracking. Corrosion initiates in heat-affected zones such as weld areas of wire-wound screens at features called nodes, and spreads. Nodes may have small external openings, but large subsurface expression. Heated austenitic steel is sensitized at 950–1,450°C, with chromium depletion at intergranular boundaries. Biofilms interfere with the oxidation at the metallic surface necessary for repassivation of the stainless steel by forming differential oxidation cells. Biofouling proceeds as in mild steel.

2.7.4 Iron, Manganese, and Sulfur Biofouling Fe, Mn, and S biofouling can be considered together as a particular case in the biofouling topic, primarily because of its prevalence and impact on the performance of well systems and downstream piping and treatment. Such biofouling is complex, and is a factor in the water quality and corrosion effects just discussed. 2.7.4.1 Fe, Mn, and S Biofouling: What’s Happening Microbiological activities are now regarded as the most important factor in the oxidation-reduction reactions that take place in ground water for both inorganics and many organics, even under anaerobic conditions. Bacteria are able to utilize substrates such as hydrocarbons as carbon sources in the absence of oxygen by using other electron acceptors, such as Fe3+, SO4, and NO3, in respiration. Microbially mediated redox reactions can be complex and add greatly to the problem of fully understanding the geochemical environment in an aquifer setting (Figures 2.5, 2.20, and 2.21). Shallow aquifers rarely have such low redox potentials that organic-oxidation reactions are not favorable, unless the organic content and microbial activity are quite high and oxygen entirely depleted. This, of course, is likely to be the case when hydrocarbon contamination occurs. In ground-water-source (GWS) systems, biofouling usually involves the oxidation of Fe, Mn, and S compounds by bacteria. These compounds become part of biofilm complexes, including the Fe, Mn, and S compounds, ECP, and the bacterial cells themselves. Fe and Mn biofouling can vary from being a minor nuisance to a cause of major maintenance problems, even resulting in complete abandonment of wells and wellfields. Fe- and Mn-biofouling problems are well documented, with numerous reports published in a variety of water supply and ground-water industry literature based on experience from North America and around the world. S-slime biofouling is much less well documented, but typical of wells operating in sulfide-containing ground waters (including those recovering hydrocarbons), where oxidizing conditions exist in pumping wells. Problems include clogging of pumps, drop (discharge) pipes, screens, and filters by slimes (Figures 1.2, 2.3, and 2.13) and subsequent precipitates, such as Ca sulfate, and associated corrosion of metal pump components.

40

Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

Microbially mediated Fe, Mn, and S transformations also play an integral role in fouling attached water collection and treatment systems. As in wells, corrosion and the formation of encrustation and slimes, and changes in Fe, Mn, and S content and form in pumped water, occur downstream. 2.7.4.2 How Fe, Mn, and S Biofouling Occurs Fe and Mn biofouling may take many forms and may be caused by both direct and indirect or passive microbial processes. FeII compounds (ferrous Fe) or ions (Fe2+) can also be oxidized to the FeIII (ferric) state by nonbiological (abiotic) oxidants such as chlorine or oxygen. However, kinetic estimates for conditions relevant to ground-water conditions indicate that abiotic rates of Fe oxidation are not sufficient to account for the relatively rapid clogging problems experienced in ground-water extraction systems. Autooxidation of MnII to MnIV rarely occurs abiotically under ambient conditions, requiring a redox potential of 600–800 mV at pH 7. In aquifers with typical >0.1 mg/L total organic carbon levels and bulk Eh-pH conditions in the stability range for dissolved species of Fe and Mn, abiotic processes are unlikely to be the immediate cause of FeIII and MnIV oxide precipitation. Some bacterial strains associated with iron biofouling have been demonstrated experimentally to actively (enzymatically) oxidize Fe and Mn for various purposes, and others are suspected, especially the common neutrophilic (prefers neutral pH) iron bacterium, Gallionella ferruginea (Figure  2.25). Besides direct enzymatic

Figure 2.25  (See color insert following page 66.) Gallionella-dominated water well biofilm (normal light photomicrograph).

Causes and Effects of Well Deterioration

41

Figure 2.26  (See color insert following page 66.) Mixed filamentous biofilm featuring MnIV oxide mineralogy (normal light photomicrograph (PMG)).

oxidation, FeIII and sometimes MnIV oxidation is also favorably mediated by microbial structures and reaction with ECP under common ground-water conditions (Figures 2.26 and 2.27). Iron oxidation can also be driven anaerobically by reduction of nitrate. CO2 generated by microbial respiration drives carbonate equilibrium toward bicarbonate saturation, and microbial cells cause precipitation of various carbonate minerals near or on their cell surfaces. These and other microbial effects (descriptions of which occupy entire chapters in Geomicrobiology) tend to complicate geochemical estimating. Microbial oxidation of sulfides results in the familiar white slime phenomenon of wells and sulfur springs. Sulfur-oxidizing bacteria (SOB) have been found to be relatively common in aquifer sediments and also in wells developed in S2–-containing ground waters (Figure 2.28) and in relief drains in dams (Figure 2.29). S0 has a narrow stability range (Eh approximately 200–400 mV vs. pH 4–2) under the very specific environmental conditions of Eh-pH stability diagrams published by the U.S. Geological Survey (see recommended reading). Bacteria precipitating S0 apparently provide this environmental condition in their biofilms for as yet unknown reasons. The expression of S biofouling resembles Fe and Mn biofouling in that soluble S2– is oxidized and precipitated as S0 in biofilms at some point where the O2 reaches some (as yet unknown) threshold. S-biofouling (white slime) occurs when Fe2– is typically absent or present in very low levels or otherwise the S2– is taken up as FeS minerals.

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Rehydrated biogenic MnIV oxide particle

Emerging bacterial cells in biofilm matrix

Emerging filament

Figure 2.27  Filamentous Mn-precipitating bacteria reemerging when MnIV oxide particles (black) are rehydrated (Bureau of Reclamation–Stuart Smith PMG, annotated by SAS)— minutes after adding water.

Figure 2.28  Sulfur oxidizing biofouling in well pump discharge pipe, South Africa (Courtesy of Hose Solutions Inc.).

2.7.4.3 The Redox Fringe Redox zonation is a feature of aquifers, both those in close contact with the surface and those without such oxygen influence. Boundaries may be abrupt, especially in aquifers containing high levels of reduced ions and organic compounds. The boundary zone between zones containing and depleted of free dissolved oxygen appears to be an important environment for the mass occurrence of

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Figure 2.29  (See color insert following page 66.) Thothrix-dominated sulfur-oxidizing biofouling of geotechnical drains (Bureau of Reclamation–Stuart Smith photographs).

FeIII-precipitating biofouling organisms. D. R. Cullimore coined the term redox fringe (redox front is also used) to describe this oxygen depletion boundary in ground water, where dissolved FeII species are oxidized to FeIII (see Figures 2.5, 2.20, and 2.21). The precise Eh values in which Fe, Mn, and S transformations occur, of course, also depend upon pH and other physical parameters. Valid Eh determinations are notoriously difficult to make in natural and contaminated ground water due to the variety of redox-active compounds present, as well as complicating microbial influences such as providing catalytic surfaces. Hydrolysis of FeIII leads to formation of complexes of FeIII oxides with bacterial ECP. MnIV oxide formation, complexation, and precipitation occurs in much the same way. Microbially facilitated FeII, MnII, and S2– oxidation occurs, followed by deposition of FeIII and Mn(III and IV) oxides and elemental S.

2.7.5 Effects on Performance of Well Systems: A Summary The extent and effect of Fe, Mn, and S oxidation and precipitation and associated biofouling in any particular situation depends on a variety of environmental, hydraulic, and use factors in the well or the downstream receiver of its production, such as a treatment system. These effects may be dramatic or hardly noticeable in the short term. Probably the most adverse effect of Fe and (theoretically) Mn oxidation and biofouling is systemic plugging of near-well-aquifer pore volume through an entire aquifer unit.

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Previous studies of core samples obtained adjacent to clogging wells have shown significant biofilm presence and plugging around wells. Filling of the interstitial space and resulting permeability reduction by 65–99% may locally occur. However, in the limited studies available, Fe and Mn biofouling, like S biofouling, is rare in aquifer samples away from the near vicinity of wells unless oxidation is deliberately induced (e.g., with in situ aeration installations designed to remove Fe and Mn in situ or aeration for in situ bioremediation). However, widespread porosity clogging by FeIII oxides is certainly possible based on the example of massive, low-permeability FeIII oxide ores deposited in sandstones and formerly unconsolidated deposits that typically serve as aquifers, known locally as bog ores. Such ore deposition is considered to have a microbiological origin. Europeans have used such deposits since ancient times (including Norse settlers and explorers in Iceland and coastal North America). Americans have “iron bacteria” to thank for these locally important ore deposits that were used for making cannons and other ordinance during our wars of independence from the British empire. Processes occurring in unconsolidated aquifers treated with in situ aeration to remove Fe and Mn are likely also to occur in aquifers aerated for in situ bioremediation, and probably in any drawdown cone around a well. Likewise, the Eh-pH and filtration conditions of a biological iron filter plant are favorably recreated in the redox fringe around filter packed wells and subsequently in downstream treatment systems. Of course, this is happening without the efficient backwash systems designed in engineered filters to keep the filter media clear. Do you want some free engineering advice from the ground-water science people? Do not treat your water for Fe and Mn in the aquifer. Treat it aboveground in an engineered water treatment plant, where it belongs. Or at least trickle it down a slope instead. The more typical case is that aquifers with waters that exhibit relatively low Eh levels overall contain an indigenous microbial community capable of reducing FeIII, SO4 and possibly MnIV. The Fe-, Mn-, and S-oxidizing and -precipitating biofouling itself, associated with aerobic metabolism, occurs at the oxidation-reduction interface (redox fringe). The redox fringe (Figures 2.5, 2.20, and 2.21) occurs near the water table, wells and springs, and along organic contaminant plume fronts, as described. In well systems, S slimes that impede flow seem to occur (1) when there is both significant dissolved S2– and O2 available in the pumped ground water and (2) in boreholes or downstream at meters, particulate filters, or other restrictions. Such well systems provide conditions similar to those at spring outfalls where sulfur slimes are found naturally. Figure 2.30 is a white sulfur spring, but not actually natural. In the well itself, biofouling phenomena may encrust or loosely plug well borehole intake areas and screens, pumps, and other equipment (Figures 1.2, 2.3, and 2.21). The initial process is the formation of a biofilm on surfaces in the well (casing, screen, etc.) and the aquifer matrix in the vicinity of the well. Figure 2.31 illustrates the process of biofilm attachment and development on a surface (whatever the surface may be). View 1 illustrates initial adherence and attachment. View 2 represents the maturation of the biofilm structure, including the formation of complex threedimensional structures. View 3 represents some of the ways that biofilms spread.

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Figure 2.30  (See color insert following page 66.) White sulfur biomass associated with artesian spring (in actuality, an uncontrolled well) in western Ohio.

Figure 2.31  Schematic presentation of the initiation and development of a biofilm (P. Dirckx, Montana State University Center for Biofilm Engineering).

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In a relatively oxygenated well environment, typical of pumping wells, Fe-, Mn-, and S-depositing biofilms may form within weeks and biofouling within weeks or months. The time course of this process, resulting in water quality or pumping problems, may vary considerably. 2.7.5.1 Hydraulic Impacts Hydrogeologic conditions affect the impact of Fe, Mn, and S biofouling on the well. For example, wells in highly transmissive gravels or rock aquifers do not tend to plug at the borehole wall even if they may be experiencing significant biofouling. Fractures and solution channels intercepted in these formations typically have such a large volume (and volume-to-surface ratio) that hydraulically noticeable plugging is improbable in most cases. On the other hand, poorly or moderately transmissive porous-media aquifers and filter packs have lower volume-to-surface ratios and are more vulnerable to plugging. Zones in which FeIII oxyhydroxides are precipitated may be quite narrow, resulting in bands of Fe oxides forming locally around wells. These form microartesian conditions (tiny confined zones) in our experience. Biofouling effects on pumps and discharge pipes, as well as downstream water collection and treatment system components, can be dramatic. Fe, Mn, S, and combination deposits break loose and enter the pump, leading to clogging problems (Figures  1.2 and 2.3). Biofilms on interior pipe walls become increasingly hard or thick over time. Corrosion tubercles or iron buildup at nodes on steel pipe (Figures  2.22 to 2.24) increase hydraulic resistance by reducing diameter and by increasing roughness of the interior surface of the pipe, dramatically increasing the energy cost to pump (Figures 2.6 and 2.32). Some well screen effects can be dramatic (Figure 2.3). In other cases, these effects may not be apparent until they are well advanced unless regular monitoring of system water quality and performance is carried out (Chapter 5). Modern turbine pumps and other pump types, such as gas-driven models, used in monitoring sampling, are robust and may not exhibit the symptoms of deterioration for long periods.

Figure 2.32  Extensively tuberculated pipe interior (Argentina: photo by Miguel A. Gariboglio).

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Likewise, significant aquifer clogging can progress before changes in well performance are noticed, such as during step-test analysis. 2.7.5.2 Sample Quality in Monitoring Wells Well deterioration can result in sample quality degradation in a number of ways. Solid material entrained in sampled water can adsorb dissolved compounds or interfere with analytical quality. Chemical encrustation reflects shifts in redox potential and pH (and sometimes pressure) that may alter the solubility of compounds in ground water. Pump and screen corrosion add metals such as Ni and Cr to ground water, where they might not occur otherwise. Corrosion also results in excessive metallic oxides in suspension. Zinc sulfides readily attach themselves to Fe sulfides. Due to the reactivity of metallic oxides such as FeIII and Mn(III-IV) hydroxides (particularly the ferrihydrite and birnassite forms), their principal effect when present is to act as chemical sieves, adsorbing reactive inorganic species and organic compounds. Pumped samples from Fe-biofouled wells and aquifers then do not provide analytical results representative of the aquifer beyond the well’s area of influence. 2.7.5.3 ASR Well Systems Most studies of aquifer storage and recovery (ASR) systems, that special class of injection wells with reversing valves so they can be transformed into pumping wells, have focused on water quality and recovery aspects. The performance of ASR wells is also potentially affected by the quality of injected water. Significant (80%) loss of specific capacity can occur within months and even weeks in aquifer formations that have limited hydraulic conductivity. Clogging of injection wells by suspended solids is a long and well-known phenomenon. Published research indicates that suspended solids tend to be the primary clogging agents in ASR systems, resulting in physical clogging. Reversing of flow (a feature of ASR wells) can cause the remobilization and deposition of fines. Likewise, incompatible water reactions (chemical reactions between injected and formation water or surfaces) can cause trouble. Some constituents can cause formation clays to swell, for example. Biological clogging is considered secondary, but (as discussed here) it is probably interactive with suspended solids in injection well clogging, and the secondary status may change with increased experience. Unless sterilized (unlikely), pretreated water will always contain microorganisms, and these will form biofilms and develop biomass in wells, regardless of the nutrient loading. Even when the injectant is chlorinated or otherwise treated with biocides, pauses between injection and pumping (as is typical with wet-season injection and dry-season pumping) result in recovery of microflora, including total coliform (TC) bacteria. So water quality alteration and injection and repumping efficiency loss are likely to be matters of ongoing concern in ASR operations. Where environmental monitoring and ASR projects are designed by personnel (environmental engineers and hydrogeologists) who usually have limited background

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in microbiology, the importance of these effects can be missed (or maybe people don’t want to know). Sometimes they have no alternatives and have to accept what happens. It is important to understand the purposes for the emphasis on bioassay in maintenance monitoring (Chapter 5) for it to be taken seriously.

2.7.6 Health Concerns Relating to Biofouling Biofouling has traditionally been considered primarily an engineering or operational concern, and not a high-priority health concern. Likewise, bioremediation is encouraged in contaminated ground water and soils, with only the use of genetically engineered microorganisms actively discouraged at present. Wherever mass growth of microorganisms is encouraged or tolerated, operators of ground-water remediation treatment systems need to consider the health aspects. 2.7.6.1 Pathogens There has been a tendency in bioremediation potential studies (although this has been changing) to pass over identification of microbial types as “too expensive.” However, if potential pathogens are present, especially in concentrated slugs in pumped ground water or aerosols from aeration towers, there is a potential hazard to personnel directly exposed. For example, Fe-precipitating and -reducing bacteria frequently found in mass microbial development include genera that are better known as including potentially enteric and respiratory pathogenic types (e.g., Escherichia, Clostridium, Klebsiella, Pseudomonas, and Serratia spp.). Mixed microbial populations in which the components produce mutually beneficial products or conditions are common in the environment. Such mutualistic consortia may contribute to the survival of other virulent or opportunistic pathogens traced to well water supplies. For example, besides the Fe-manipulating potential pathogens just discussed, Legionella pneumophila (a respiratory pathogen) is assisted by association with other bacteria. Legionella is common in soils and many other environments, including cooling tower systems that are analogous to the commonly used volatile organic carbon compound (VOC) stripping aeration towers on environmental sites. Other common sources of possible human contact are wet soils and poorly maintained water systems with dead ends and biofouling. Legionella bacteria may also be found encysted within their predators: larger bacteria and protozoa in soil and biofilms. Enhancement of natural L. pneumophila populations in natural soils undergoing aerobic bioremediation would also be expected. Wet, organically laden soils with high microbial densities are favorable habitats for their mass growth. The presence of such Legionella in airborne dust and aerosols around such remediation facilities has to be considered a potential inhalation hazard, primarily to people with impaired immune responses, including smokers, who typically lack nose and throat defenses against airborne bacterial infection.

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2.7.6.2 Toxic Accumulation Biofilms and their associated reactive metallic oxides can accumulate toxic metals and other toxics at levels higher than in the bulk ground water itself. The reason may be for some nutrient bioaccumulation purpose or as an antipredatory effect, or simply due to the reactions with the charged surfaces of metallic oxides, as previously described. The benefits of binding toxic U and Au to cell membranes and sheaths are not at all clear at this time. There have been occasions where Fe-biofouled wells were found to have become point sources of arsenic, heavy metals, and radionuclide contamination through accumulation over time. These metallic elements can originate from weathered granitic or metamorphic rocks and sedimentary rocks derived from them (such as shales), ore bodies or subeconomic roll-front deposits, or anthropogenic sources, such as buried sources of metallic or radioactive waste. Both the biofilm slug effect and microbial mobilization can result in intermittent high metal or radionuclide concentrations in the treated water. This can result in a declaration of nonperformance by the remediation site’s regulatory agency that probably would not have occurred if the biofouling were not present. 2.7.6.3 Chlorination of Organic Chemicals Chlorine and chlorine-based disinfectants (see Chapters 4 to 8) can react with components of the biofilm or hydrocarbons in the ground water to produce halogenated organic compounds. Chlorine substitutions of hydrogen make the organics more resistant to safe degradation and also more toxic. For this reason, chlorination is routinely excluded as a well treatment method for monitoring and extraction pumping wells in ground-water contamination control schemes. Chlorinated organics, forming disinfection by-products, are also an issue in public water supply.

2.8 Impacts on Treatment Plants The scope of this work does not extend to treatment plant operations and maintenance (O&M); however, it has become evident that bio-physical-chemical activity in wells (pumping and injection) has a direct influence on plant and project mission performance. Briefly, direct, adverse treatment plant effects expected should include: • Plant excessive organic loading (BOD, COD, etc.). • Sediment production and geochemical alteration of constituents so that they are not as well addressed by the treatment system. Clogging slugs of biofilm and solids (sand, silt, clay) developed out of wells may be particularly destructive to membrane and resin bed treatment systems. • Fouling of piping, sensors, air strippers, granular activated carbon columns, ultraviolet emission lamps, etc. • Alteration of geochemistry: When wells are cleaned, rapid flip-flopping of pH can be expected during treatments. Plants adapted to established reductive water may have to transiently adapt to a more oxidative Eh. Erratic

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detects or spikes of compounds whose solubility is redox or pH sensitive may occur. • Metal oxide breakthrough from filters into the rest of the treatment train: Acidic waters may flush attached iron and other metal oxides from filter particle surfaces, and breakthrough may occur, resulting in coating of downstream media and membranes. • Enhanced cost of operation due to lowered efficiencies and frequent cleaning, backwashing, or replacement of media. • Pumping well and system or aquifer clogging restricts system performance so that cleanup of calculated plume volume is slowed or stopped, or contaminated ground water bypasses the installed system while wells are replaced or rehabilitated.

2.9 Engineering and Construction Aggravation of Clogging and Corrosion Where biofouling and MIC are likely to occur, system engineering and construction can aggravate the problems they cause. For these reasons, knowledge of the potential transformations that can occur in the well-aquifer system is essential. Some aggravating human choices include: • If well development or optimal screen design is not practiced, premature clogging can be expected. Biofouling alters and clogs pore and screen slot spaces. • If corrodible metals are used, clogging with corrosion products and breakdown of the well structure can be expected. • While possibly unavoidable, the bigger the oxygenated “wash zone,” the more likely it is that problems may occur. • Pump, pressure, and valving systems can aggravate clogging within the water moving system itself. Noncompatible metals corrode, and these convoluted systems offer much surface area and small pressure changes that encourage biofouling. The design and construction of wells is not the primary focus of this book, but proper well design, construction, and development are important in prevention and planning for maintenance, as described in Chapter 4. These are areas in which engineering knowledge, skill, and application have an impact. Briefly, good well design has several interlocking aspects. Wells designed to resist corrosion, and permit reasonably free but laminar flow to the well, usually provide water with the least possible drawdown (good well efficiency), lower intake velocity at the screen, and oxidation at the intake. These are less likely to plug quickly. Good screen and filter pack selection and installation minimize potential sanding problems. The construction process can defeat a good design if packs, screens, or casings are installed in a hasty fashion or development is inadequate. Adequate development may be neglected because it takes more time and skill than may be available (or than the crews or their bosses want to spend). Project supervisors may fail to demand

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adequate development because of apparent time pressures, or they want to avoid disturbing the monitored formation. If they do not have experience with the installation of pumping wells, field supervisors may not have a grasp of the time required to fully develop a well: the scale is hours and days, not minutes. Crews in a hurry can be persuasive. Supervisors or inspectors have to stand their ground and say “keep developing!”

2.10 Well Structural Deformation and Failure: Natural and Human Caused For our purposes, our discussion of well structural failure will be confined to the casing, screen, open bedrock hole, and grout envelope. Pump and pump riser failure will be dealt with separately. We will deal with well failure based on two sources, natural and human induced. Catastrophic structural failure is relatively rare in water supply wells, where “catastrophic” infers a scenario in which the components and materials that comprise the well cease to function over a relatively short period of time (virtually instantaneously), perhaps even dramatically. Catastrophic structural failure is apparently not so rare on remediation sites. A well in which the components and materials that comprise it cease to function far earlier than the expected life span can be considered to have failed structurally, if not catastrophically. And a well that has served for decades, perhaps a century, will eventually fail structurally as the effects of time and entropy take a toll. Let’s be realistic. Total structural failure results in many of the same symptoms as in pump and casing or screen corrosion: Turbidity or sand pumping may rather suddenly increase. Yield may dramatically decline (if the pump remains functional). Related problems include pump and system wear and pump corrosion. Figure  2.33 diagramatically illustrates some examples of structural failure.

2.10.1 Natural Causes include regional forces such as tectonic (earthquakes), mass wasting (landslides and soil creep), and ground subsidence (usually resulting from overpumping). 2.10.1.1 Earthquakes Earthquakes produce complex movements in three dimensions from transverse and longitudinal (compressional) waves, as well as displacement along slippage zones. Depending on the local geology, and construction and condition of the well, effects could conceivably range from none to complete loss of the well. A well in good condition with no construction flaws would probably survive the shaking movements (vertical and horizontal accelerations) of an earthquake with no discernable structural damage, just transient turbidity. It is possible that portland cement grout would fracture due to its lack of flexibility, thus compromising the sanitary seal of

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Casing

Unstable borehole collapse

Casing collapsed due to rock fall in cavern Casing

Casing

Fault

Casing Differential force on casing from subsidence

Failure due to ground shift

Figure 2.33  Some causes of well structural failure—these are schematic representations of possible scenarios.

the well. When the well condition is not optimal, construction failures (from vertical and horizontal accelerations) may result from: • Unsupported casing in caves or due to inadequate grout support • Casing or screen corrosion and collapse—casing insufficiently strong for in-ground conditions, screen collapse due to prolonged sand pumping, and the collapse of unstable rock boreholes Open boreholes could experience temporary turbidity due to sloughing of loose or less competent lithologies (or accumulated coatings such as biofouling) from the sides. Complete loss of the well would likely result if the well intersects fractures, faults, or planes of weakness that experience physical displacement. That big reservoir of knowledge that translates to the ground-water side—the wisdom of the oil patch—gives us the example of damage to oil well casing from horizontal displacement along shale slippage planes. Casings were offset many inches with attendant plastic deformation and failure from high shock waves (rather than slow bending). It is not possible to construct well casings to withstand such forces, and the methods employed in the oil field to shield a well from displacement may not be appropriate for a potable water well. If the displacement occurred within an open borehole, the well may or may not retain its original capacity, depending on whether

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the borehole is completely occluded, and sufficient available drawdown remains visà-vis the aquifer chracteristics and required withdrawal rate. If the pump was set within or below the zone of displacement, it may be completely lost. 2.10.1.2 Mass Wasting Mass wasting is the process by which large masses of earth are moved downslope by gravity, either slowly or rapidly. Wells constructed on slopes or at the bases of slopes would be vulnerable to these processes. A slow process that may be pertinent is soil creep (Figure  2.34). Soil creep is the unsaturated downslope movement of soil, which does affect vegetation such as trees, and man-made structures such as power poles, by tilting or displacing them. It is conceivable that a well casing could at least be pushed out of plumb. Also, the sanitary grout seal may be compromised by the downslope movement of the material that surrounds it. The rapid processes include earthflows and mudflows, landslides, slump (Figure 2.35), and rockslides. Earthflows and mudflows require a degree of saturation of the materials involved. Mudflows have a higher degree of saturation and are confined within defined channels. Slump involves the displacement of a mass that rotates backwards as it moves downslope. A debris slide is the movement of a mass downslope by either sliding or rolling without backward rotation. Rockslides are masses of rock that move downslope along bedding planes, joints, or faults that are oriented (tilted) in the downslope direction. Figure 2.36 illustrates several mechanisms on a shoreline along Lake Erie that is subject to wave action erosion, slumping in the clay till, and water transport in and collapse of the overlying sand. Such forces take down trees and structures, so you can expect that a well located within the areas undergoing displacement will most likely have its casing bent out of

Figure 2.34  Slope and rail line affected by soil creep (Courtesy U.S. Geological Survey).

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

Figure 2.35  Slope affected by slump (Courtesy U.S. Geological Survey).

Figure 2.36  Shoreline erosion processes, Ashtabula County, Ohio.

plumb or be displaced (Figure 2.33) or be entirely carried along with the mass. Wells located at the base of a slope that experiences one of these events have a chance of having the casing damaged or displaced by the force of impact, or to be buried. Obviously, the amount of damage that results will be event specific and may range from no damage to complete loss of the well. The authors consider it unlikely that a well could be recovered if impacted by one of these events. It would be wise not to locate wells in areas regularly subject to these processes unless no other options exist. If a well does have wet, unstable soil upslope, consider a crash revegetation program.

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2.10.2 Human Induced There is a range of structural problems that are caused by human activities. 2.10.2.1 Mining Mining, in the form of either surficial quarrying or underground pillar-and-room and long-wall extraction, can have effects on structures, including wells (Figure 2.37). More on mine blasting is found in the next section. Underground mining can have the effect of (literally) undermining overlying strata. As mass (coal, for example) is extracted, overlying strata can collapse if not supported. The practice of long-wall mining results in deliberate collapse of strata in the wake of the extraction system. Strata bend and then collapse behind the extraction face (Figure 2.38).

Figure 2.37  House foundation undermined by collapse of mining cavities (Pennsylvania Dept. of Environmental Protection photo).

Mine water breakout Coal outcrop

Sinkhole Overburden subsidence

Sandstone Underclay Through roof subsidence Coal workings

Collapse stopped Coal by strong stratum outcrop

Figure 2.38  Long-wall mining effects diagram (Pennsylvania Dept. of Environmental Protection).

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Curvature rather than vertical drop puts tensile strain on strata and structures. This is a transient effect. When vertical subsidence is approximately half of the maximum subsidence, i.e., as the face passes under the surface point, the ground reaches its maximum horizontal displacement and the strain reduces to zero again. As the long-wall face moves farther away from the surface point, the settlement continues, horizontal displacement reduces, and the ground is subjected to compressive strains. When the subsidence is complete, the ground is commonly left with no horizontal displacement and little residual tilt or strain. Most of the points on the surface will thus be subjected to three-dimensional movements, with tilt, curvature, and strain in both the transverse and longitudinal directions. The impact of subsidence on surface infrastructure is therefore dependent upon its position within the trough. The severity and duration of these impacts will depend upon the position of the point (such as a well structure) relative to each portion of the stress-strain curve. Mountaintop removal has the dual unpleasant effects of (1) literally removing aquifer rock and (2) covering and obliterating valley sediments and structures. From a hydrogeologic point of view, this is devastating on local well water sources. 2.10.2.2 Mine Blasting Significant research has been conducted into the effects of surface mine blasting on water wells (see our reading list). The impetus behind the research is the claims by domestic well owners that their wells were damaged by blasting in the vicinity of their wells. The authors themselves have received anecdotal accounts of damage to domestic wells by quarry blasting and the occasional home propane tank explosion in Ohio and oil exploration seismic shots in North Dakota, with little insight into what was experienced by the homeowner. Controlled, systematic observation of the phenomenon was needed but did not occur. No one wants to invest in it despite the benefits that could accrue. Similar to earthquakes, the forces experienced by a well during such shots appear to be vertical accelerations. Also, as with earthquakes, the severity of the impacts may be a function of the condition and construction of the well. The studies focused generally on new domestic-style wells with open-hole construction in the bedrock. In the authors’ experience, domestic wells are often of marginal integrity when new, and of very tenuous integrity to completely degraded when aged. The studies mentioned above observed no damage to casing as a result of measured accelerations of up to 2 ft/s. Counter to expectations, well performance/capacity increased as the mine wall approached the well due to stress relief increasing the porosity and permeability of the rock fracture system. Two undesirable effects were observed: temporary turbidity of the water and temporary decline in static water levels. Turbidity was attributed to drill cutting remaining in the well from incomplete development and natural deposition (Fe sulfides or oxides). Water level declines were attributed to the increase in porosity, which required some adjustment in the local flow system to reestablish static water levels. Only as the cone of depression from mine dewatering operations intersected the wells did water levels permanently decline. Municipal potable water supply wells are generally constructed to high standards and are physically robust for both sanitary integrity and long life, and most likely

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would be unaffected by blasting. Any wells with corroded, damaged, or substandard materials may expect more severe effects from blasting. The authors have observed severely corroded casing revealed in downhole television surveys. Paper-thin iron oxide remains of a well casing probably will not sustain the acceleration from blasting. The anticipated results would be the oxidized material sloughing into the well and causing significant turbidity, and the casing being open to undesirable zones in terms of both overall water quality and sanitary quality. Also possible is the fracturing of portland cement grout, compromising the sanitary seal. 2.10.2.3 Grouting The most common cause of well casing failure in the authors’ experience is related to poor or improper grouting. Well grouting is the filling of the annular space with low permeability materials that are of higher quality than those removed by the drilling process and is exhaustively described in the pertinent publications and standards that should be available to the reader who is involved in any kind of decision making about wells. Two general materials are used to grout well casing: bentonite-based grouts and neat portland cement (or portland with 2 to 6% bentonite added). Which methods for proper grout emplacement and which material to use are dependant on the specific conditions of construction and geologic conditions, and are discussed in well construction manuals, such as those listed in our suggested reading, and in ANSI NGWA-01. During construction, the well casing is grouted in place and the annular space filled (or should be filled) completely to accomplish four things: (1) provide a sanitary seal to prevent contamination from surface water, (2) prevent communication between aquifer zones, (3) provide structural support of well components, and (4) provide corrosion protection. Failure of the grout to accomplish these goals can be grouped into two issues: (1) failure to successfully emplace the grout and provide a complete grout envelope surrounding the casing and (2) choice of grout material for the specific situation. Roscoe Moss Company’s classic text (see reading list) summed up the first issue succinctly as a failure of the grouting process to completely displace the drilling fluid from the annulus, leaving channels of drilling fluid within the grout. This generalization can also include bridging in the borehole (lack of sufficient annular space) and the casing being in contact with the borehole surface (need for casing centralizers). A common mistake is drilling casing boreholes with a diameter that is too small for grout (or filter pack) to be emplaced properly around the casing. Bentonite-based grouts utilize the property of bentonite (montmorillinite) clays to swell in volume when properly hydrated. They form a somewhat firm, plastic seal around the casing as the mixture hydrates in the annular space. The swelling property ensures that the grout fills the annular space completely. Also, bentonite grout is less dense and more viscous than neat portland cement; therefore, there is less loss to the surrounding formation as a result of the high hydraulic heads at the bottom of the hole. However, bentonite grouts must remain hydrated to remain in their plastic, expanded state. Otherwise, they will shrink and crack, providing no seal around the casing. Therefore, bentonite grouts are not appropriate at sites with deep unsaturated zones. Bentonite grouts provide little to no structural support compared to neat

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portland cement. They will not support long or heavy casing strings. In the authors’ experience, bentonite grout is used in shallow constructions not much over 200 ft (60 m). It is used extensively to grout casings through unconsolidated materials overlying bedrock in open-hole bedrock wells. In this case, the weight of the casing is supported completely or partially by being seated in the bedrock prior to drilling the open-hole portion of the well. Bentonite-based grouts are vulnerable to vigorous well development and rehabilitation procedures. The authors have witnessed a pressure-acid rehabilitation job in an open-hole limestone well where the acid solution channeled to land surface through the grout, and then the pressure lifted the casing out of the hole, requiring the casing to be reseated and regrouted. Neat portland cement exhibits significant structural strength and is used in situations where heavy casing needs to be supported, formation pressures (as in artesian wells) may be encountered, vigorous physical/mechanical development may be employed, etc. It has been demonstrated to increase the collapse strength of casing after it cures in certain circumstances. It is important to choose the correct cement for the conditions and to mix it with the correct proportions of water to attain the correct strength and reduce shrinkage. It must be allowed to cure to achieve proper strength before continuing operations. Portland cement is significantly more dense than bentonite and will generate high hydrostatic pressures in deep applications. Therefore, one must be mindful of the collapse pressure of casing during grout emplacement. It can also quickly “escape” into shallow rock bedding planes or cavities, resulting in the loss of significant volumes of expensive cement. Also, the heat of hydration can be problematic, especially with plastic casing, which will soften, melt, and deform (Figure 2.39). Pure portland does shrink as it cures, which may compromise the grout’s sealing properties. Bentonite can be added to the mixture to mitigate the effects of shrinkage. Voids in the cement, as discussed above (incomplete grout envelope), will result in no enhancement of collapse strength of the casing. The purposes of using bentonite-cement grouts are a matter of controversy. We

Figure 2.39  (See color insert following page 66.) PVC casing distorted by heat due to improper cement grouting (photo by Gary L. Hix). The casing is pushed in and cracked at the visible joint and the foreground surface is blistered.

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refer you to the outside literature and ANSI NGWA-01 for more detail on this crucial aspect of well construction. 2.10.2.4 Casing Weight/Quality/Integrity/Engineering Issues Well casing performs four functions: (1) prevent collapse of borehole walls, (2) prevent the introduction of contaminants into the water source, (3) convey the water from the aquifer to the surface, and (4) provide a housing for the pump (if used). Failure of the casing to perform these functions can be grouped into two categories: (1) incorrect choice of materials/poor engineering for conditions and (2) damage to casing during handling and construction. A complete quantitative discussion of casing materials and engineering is beyond the scope of this work (and unnecessary). As with screen and filter pack design and grouting, our reading list is packed with excellent references to literature that describe casing selection and installation. In particular, the authors recommend publications by the Australian Drilling Industry Training Committee, National Ground Water Association, American Society for Civil Engineering (ASCE), and Roscoe Moss Co. In short, casing is expected to withstand the effects of corrosion, axial extension and compression, bending forces, collapse forces, and bursting forces; and it is also expected to provide a reasonable service life. Well casing is manufactured specifically for enhanced collapse and tensile strength, rather than burst strength as with line pipe. Much to the authors’ frustration, this distinction is often missed in the minds of those who write state regulations and engineering specifications. The casing must meet the rigors of rough handling during installation and years of service in the subsurface. The more extreme the subsurface conditions, the more preconstruction engineering planning should be performed to choose materials that can withstand those conditions. Angled and Horizontal Casing: Angled and horizontal or directionally installed casings have somewhat different stress, joining, and other specification issues. Neither is suspended in tension, as is the case with screened casings installed using rotary methods. Laterals of caisson-collector (e.g., Ranney collector) wells are jacked or pressed out from the caisson, and are naturally in compression. They are not hammered, as is the case with cable tool casings, but screened segments must be designed to withstand the installation process. Angled straight wells (such as those that are sometimes installed under rivers) can be subject to slight deflection depending on the straightness of the borehole and the presence of lithology with diverse compressibility. Casings in directionally drilled wells must be able to “make the turns.” Plastic (e.g., high-density polyethylene (HDPE)) is rather ideally suited for such applications; however, steel is used, as pioneered in the oil and gas industry. Such steel casing is angled in without exceeding the angular stress limits of the pipe type, wall thickness, and diameter. However, it should be recognized that the stresses imposed could be a factor in corrosion at joints. This is a specialized kind of construction that should be conducted under the supervision of engineers specializing in such applications. In the authors’ experience, the most common failures resulting from casing engineering are (1) corrosion and (2) underdesign (price trumps attention to service life).

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

Premature corrosion damage is a consequence of underdesign, but it also includes the situation of the common house well, often built too fragile to clean effectively. Predominantly, casing has corroded through sooner than expected as a result of utilizing casing with too little wall thickness. No well is expected to last indefinitely, but one strives to have well replacement coincide with other changed operating conditions in the future that may require/include constructing new wells. Under the most chemically harsh conditions, alternative casing materials such as the appropriate grade of stainless steel, PVC, or composite such as fiberglass-resin would be a better choice. As states have adopted minimum casing standards (and grouting standards), this may become less of a problem. ANSI NGWA Standard 01 provides a guide. The authors have also obtained anecdotal data that some observed casing corrosion incidents are the result of periods of time when only poor-quality casing materials were available to the water well contractors. Conversely, some anecdotal observations by drilling firms with institutional memory back to the turn of the twentieth century suggest that casing steel was actually better prior to World War II in the United States. For some time, galvanized casing was sold in the marketplace, which allowed poor-quality alloys to replace better mild steel alloys. Galvanized casing is frankly a ridiculous idea, as the success of a galvanized coating depends on its uniformity. Maintaining uniformity is impossible with a pipe hammered or shoved into earth and rock, especially when threaded. Alloy choice and wall thickness (as well as a good external grout seal) are the keys to extended corrosion resistance. Good grout seals present what is effectively a single electrical grounding (earthing) potential to the casing exterior. Poor engineering for greater depths is the next cause. States adopt construction standards that normally can be expected to be appropriate for the geologic conditions and well construction practices common within their jurisdictions. As well depth increases, engineering for collapse resistance and tensile strength becomes an issue. The authors assume that collapsing or pulling apart a casing during construction is a catastrophic failure that would be immediately obvious to all involved. Scenarios in which these occur while the well is in service seem to be low-probability events and not likely to be a problem requiring diagnosis later on. However, it is conceivable that a reduction in well specific capacity with time could result in an unplanned-for pumping water level sufficiently deep to collapse the casing under some hydrogeologic and well construction scenarios. And certainly one can imagine all manner of well maintenance or repair jobs gone bad in which the casing is pulled apart and recovering tools stuck in the well. Rough handling during transportation and construction appears to increase the potential for casing failure. Surface imperfections (scratches and pits—analogous to those blemishes in galvanizing coatings) become the focus of anodic corrosion. Casing that is distorted out of round is far more susceptible to collapse. Even if correctly engineered for the expected operating conditions, postconstruction damage can occur. Development often involves violent turbulence and upward hammering by airlifted water discharge. Performance testing (a process in which we intentionally stress the capacity of the well) may result in deeper than expected pumping water levels and resultant pressure difference on the casing, resulting in casing collapse.

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Pumping at too high a pressure during displacement grouting through the casing can either balloon or burst the casing. Any procedure that requires pressurization of the casing can potentially burst the casing, and therefore must be thought out ahead of time. For example, when considering pressure acidization for well rehabilitation, gas pressure rehabilitation, fluid-pulse, or explosive performance enhancement (Chapter 8), one should consider effects on the casing, and take into consideration its weaknesses. Conversely, casing installation should be designed with such treatments in mind in the future. Most likely, casing damage from redevelopment would manifest itself as a sudden-onset water quality or turbidity/sediment problem. Among commonly used casing types, PVC casing is particularly susceptible to damage from rough handling during construction. The damage may not be apparent until it is time to install the pump or water quality degrades while in use. If portland cement grout is used, care must be taken to circulate water in and cool the casing during hydration (Figure 2.39). Heat reduces the collapse strength and the weight of the cement collapses the casing. Tripping tools in and out of the casing and rotating drilling tools could crack or puncture the casing, allowing poor quality water in. Gluing bell-end casing joints must be done with care to ensure that they are sealed properly and allowed sufficient time to set. However, if specified using National Ground Water Association guidelines and standards (and some state regulations), and installed properly, PVC casings provide a corrosion-resistant and durable installation for many purposes. Given the available experience and range of materials, the most important asset in preventing premature failure during the construction phase is knowledge. The design engineering and hydrogeology team must work together to estimate pumping water levels, exterior heads (for collapse-strength calculation) and installation and development stresses, anticipate future stresses, and estimate water quality effects. 2.10.2.5 Improper Rehabilitation and Development Methods, and Other Abuses of Wells Another category of human-induced failure is damage during development and rehabilitation. This usually involves an improper procedure for the conditions or a mistake in its application. It is closely related to damage during construction and transportation. Generally these operations involve working screen, casing, and openhole intervals with brushes, surge blocks, swabs, high-pressure jetting, and (at times) aggressive chemicals. Problems usually occur due to lack of information, application of the wrong methods (often deliberately by ignoring well cleaning specifications carefully developed by consultants), or lack of communication. Some human-induced well problems include:

1. Poor record keeping (no one knows what happened, dimensions, etc.). 2. Tools and pumps and various parts dropped into the screen or well bottom. Junk in the hole induces clogging and impairs both function and service. 3. Tools stuck and left (whistling heard from the truck window leaving the site).

We will consider this issue more completely in Chapters 7 and 8.

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Figure 2.40  Monitoring well casing bent due to vehicle collision.

Figure 2.41  PVC water well casing broken due to vehicle strike in parking lot. There was an attempt to fix it with a rubber boot coupling and protect it with a tire. This was a public water supply (bowling alley, now closed) in Ohio.

Perhaps as a final insult added to injury is vehicle damage. Vehicles are a major cause of monitoring well damage and of damage to water wells in high-traffic areas. Collisions cause casing breaks and dislocation (Figures 2.40 and 2.41). 2.10.2.6 Electrochemical Corrosion from Stray Potentials Anode corrosion is a process of which engineers and physical scientists are aware, but which really goes unaddressed when designing and constructing wells. The

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degradation of the well components starts at the anodes that are created on the surfaces of the well and spreads as cancer from there. Electromagnetic induction from high-voltage power transmission lines is a significant source of corrosion and other problems for buried pipelines. In a paper in the 2006 IEEE Transactions on Power Line Delivery, L. Bortels and coauthors reported that induced currents can be on the order of hundreds of amperes (see reading list). Pipelines are generally protected by cathodic corrosion protection systems, but in 2002, Osella and coauthors reported that the system can be overwhelmed during days of high magnetic activity. The corrosion results from pipe-to-soil potentials, with the pipe acting as an anode in the system. Wells with steel casing can be expected to be subject to the same process as pipelines if the wells are in electrical continuity with a metal waterline. As a rule, there is no electrically insulating coupling between the well and steel, copper, or ductile iron pipeline, so any induced potentials in the pipeline would also be transmitted through the well. Since both the well casing and the pump components may be in electrical continuity with the pipeline, both can be expected to be subject to the enhanced corrosion. These effects are exacerbated if the well casing pipe and screen are already damaged during handling and construction: during transport to the site, if dropped, welded, nicked during installation, etc. The most egregious damage to casing is crude slotting or perforation for water yield. Such saw- or torch-cut perforation is damaging to the structural strength of both thermoplastic and steel casing. It also provides corrosion starting points, typically anodes, in metal. This practice is the “poster child” for cheap in our field. Vertical well screens must be supported in tension during installation and never forced into place. Angled and directional well screens may be slipped in, and telescoping used for either vertical or nonvertical installations. However, excessive force and torque should be avoided. Generally, if installations follow the new ANSI/NGWA well construction standards (or even the AWWA A-100 standard) and relevant ASTM standards for materials, and proper care is observed, installations should have a chance for reasonable service life. 2.10.2.7 And Other Factors … It has sometimes been puzzling why two similar wells, both with well deterioration problems (and especially in the case of biofouling development), experience very different symptoms. The explanation may be in well design, construction, and operation in many cases, combined with subtly different in-ground conditions, such as local differences in hydraulic conductivity. These may result due to formation conditions or development differences. Such design and operational aspects are primarily in the realm that human activity affects directly, i.e., people can influence them. Toxicity and pathogenicity are also human concerns, especially for the workers operating ground-water remediation systems and people exposed to their effluents.

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Water head

Willshire, Ohio 2003 floods limestone bedrock

National Weather Service

Figure 2.42  Flooding in the St. Mary’s River watershed (Ohio) (NOAA photo).

2.11 Disaster-Related Flooding A number of catastrophic events were discussed under structural failure (Section 2.10). One that combines hydrologic and water quality effects—and is widespread— is inundation during flooding (Figure 2.42). Flooding of wells is a widespread issue in the United States, Mexico, Central America, Caribbean islands, and Bangladesh (a nation that is basically a river delta and an estuary), with the heavily populated coastal areas (and whole island nations) subject to hurricanes. A similar threat exists in the western Pacific and Indian Oceans, subject to typhoons and tropical cyclones. Much of the eastern and southern United States coastline is a flat-lying sandy landscape where wells are often very shallow and relatively unprotected from the surface. Hurricanes and intense tropical storms come ashore with large storm surges of sometimes 6 to 10 m, and generate torrential rains in short periods, causing inland as well as coastal flooding. Heavy rain events can cause river valley flooding anywhere, such as regularly occurs in the massive river basins of central North America and Europe. In North America in recent decades, major flooding events have occurred in the watersheds of the Red River of the North, and the Mississippi, Missouri, Ohio, and their tributaries. Another source of flooding in coastal areas is tsunamis. The great Indian Ocean tsunami of December 2004 (caused by plate shifting in western Indonesia) resulted in incredible devastation as far as Sri Lanka, and drownings as far as Dar es Salaam, Tanzania. This event also flooded wells with debris-laden sea water. Such flooding can inundate wells with dirty, bacteria-laden water. Of course, this is not just the occasional well, but wells over entire river basins or coastal villages, resulting in a lack of potable water for many people, and potential public health emergencies. Reflecting the structural problem discussion, inundation of wells has natural and human-generated components. The “natural” is natural meteorological and

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h­ ydrologic phenomena. The “human” part is the human tendency to locate dwellings and important infrastructure in areas prone to flooding. A further complication is that electric power and fuel may be unavailable, and surface infrastructure ruined (including surface-mounted pump motors, solar ­panels, and windmills), Thus, one of the best tools to restore a well—simply pumping off the well—is difficult to do until the capacity to pump is restored. When wells are inundated, the impact can largely be predicted using Darcy variables: hydraulic conductivity (k) and head. The head would be the height of inundation, and the k that of the shallow receiving aquifer. For the most part, debris and microbial contamination do not penetrate far into the aquifer in the well intake zone. For example, in a project the authors and Mike Vaught conducted for the NGWA and their client, it was found that extensive hurricane-related flooding in eastern North Carolina resulted in relatively little residual total coliform (TC) occurrence, even in wells one would suspect would be vulnerable to TC under normal conditions. Most of these wells were quickly pumped off after flooding when the power was restored. A larger problem in that regard is the areal impact of flushing organic carbon and contaminants into the subsurface where permeable materials extend to the surface. This can present an opportunity for enhanced microbial growth over many years.

2.12 Management and Operational Overview In addition to the construction and planning issues described above, well operation impacts biofouling in particular by providing conditions that enhance or discourage biofilm formation and buildup. Cyclical pumping or long periods of idleness, resulting in stagnation, promote biofilm formation and associated problems. Pumping beyond design capacity introduces more oxygen into the system, increasing the rate of FeII-FeIII oxidation (both abiotic and microbial) and encouraging S and Mn oxide biofouling. Such operating profiles are, of course, the operational descriptions of typical monitoring and recovery or plume control well systems and many water wells. System operational design is also a factor. In multiwell systems with automatic pump controls, stronger producing wells may produce more water to compensate for other wells with falling production. The result (in a remediation well system) may be that strong pumping occurs around productive wells, while the plume quietly bypasses clogged wells, or pumps may run, burning power for no result. There has been virtually no systemic research into these phenomena, so we just don’t know for sure. However, active facility management can make adjustments to compensate for these changes. Proactive management makes use of performance and water quality monitoring to detect such situations, and prescribes a maintenance strategy to deal with them. These topics are the subject of much of the rest of this publication.

Impacts of 3 Economic Well Deterioration 3.1 Identifying Costs of Well Deterioration We are not accountants or economists, but we are business people as well as ground-water professionals. This also is not a treatise on ground-water economics. For more on that, we refer you to the emerging body of work on that subject. Entire shelves of books have been written on this subject. A good place to start is some of the discussion in the much-anticipated International Manual of Well Hydraulics, to be published by ASCE (www.asce.org). However, we refer you to several recommended sources in the following sections (cited in our recommended reading list). We are presenting enough material here to support a discussion of the economic value of a sustainable management (maintenance and rehabilitation) of well systems (Figure 3.1).

3.1.1 Defining Economic Parameters We know that the valuation of wells and difficulties with wells are normally made in currency, although access to usable water can at times be priceless. How these valuations are calculated, and decisions about investing in prevention, maintenance, and rehabilitation depend on the questions being asked. The primary focus of our economic discussion is with the wells themselves, rather than considering resource depletion or overexploitation or similar concepts. However, as with any attempt to put a fence around parameters, the reader must realize that resource depletion does impose costs and affects well management decision making. The direct immediate costs of resource depletion at the well itself include:



1. The need to extend discharge pipe and change or modify pumps to provide service under the new conditions. 2. Depletion of aquifer thickness (reducing aquifer transmissivity), resulting in permanent decline in specific capacity. This decline can be exacerbated as shallower aquifer zones with more favorable characteristics (transmissivity, water quality) are depleted. Under certain conditions, formations may actually collapse as they are dewatered (subsidence may occur, inducing structural damage, and aquifer capacity permanently lost). 3. Increased power costs due to increased pumping lift. 4. Potentially the need to drill and construct deeper wells (land, regulatory issues and water rights, construction, etc.). 67

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

Figure 3.1  The meter is running.





5. Probable decline in water quality as more recently recharged fresh water becomes less available or other change in water quality as different aquifer zones supply water to the well. 6. Related to item 5: If nitrate-rich water is drawn down to the well intake or the nitrate-reducing zone eliminated as the drawdown zone is oxidized, nitrate treatment or loss of the well as a drinking water source may become an issue. 7. Legal issues associated with depletion (neighboring water rights—however defined legally—including surface water impacts, ecological impacts, etc.). 8. Long-term economic and social uncertainty (no water, no one can live there and people move or must be relocated elsewhere, or the costs to import water are incurred).

The costs of aquifer depletion are not in the least bit theoretical, and living sustainably within the limits of local hydrologic resources obviously has economic, ecological, and social benefits. In analyzing the causes of water level decline during a wellfield performance evaluation, the degree of regional decline must be considered. If you really want to become conversant on regional water value, sustainable water extraction, and related topics, we refer you to our recommended reading list. One paper in particular is that by Emilio Custodio (2002). If you have a general interest in ground-water resources and their value, you should read more by Custodio. Our assumption is that (1) the wells in question are exploiting a renewable resource, i.e., the water pumped is being replaced by recharge, or (2) the decision maker considers depletion of a finite resource to be irrelevant, an acceptable tradeoff to achieve a goal, or beyond control. For the sake of discussion, our assumption will be that an undersirable pumping water level is due to a reversible condition such as clogging, and that investment in a solution has some probability of providing a measurable benefit (i.e., the situation is not hopeless).

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Costs of well deterioration can be divided into three realms:



1. The direct well impacts of reduced performance of the well and well equipment, such as pumps, through clogging and corrosion, including increased costs of operation through reduced efficiency 2. Increased systemwide (e.g., water utility) capital and operational costs due to corrosion, clogging, or encrustation, coating and fouling of resins, shortened filter cycles, additional chemical costs, or other need for additional treatment (e.g., for nitrates) 3. The cost of well function lost to the community or facility

The most costly result is of course the failure of the system to perform its design function, such as produce water or provide adequate monitoring of indicators of ground-water quality, plume control, or remediation. The economic valuation of wells is relatively well described technically (see our recommended reading list) but not necessarily well used in practice.

3.1.2 Types and Dimensions of Costs of Well Operation and Service As with any asset, the cost of operating a well (to be factored into cost-benefit analysis, see following) has a number of components. There is the fixed cost of the installation (construction plus planning (engineering, hydrogeology, inspection, tests, etc.) amortized over time) and operating costs (inputs of personal time, power, and other consumables). Some component of the installation cost is going to be determined by the overall degree of difficulty of the installation. How deep is the desirable water? What screen (if any) and casing diameter are needed to allow water to enter the well and be pumped away in sufficient quantity? What materials are needed? A large percentage of the direct costs of well deterioration are due to side effects of biofouling and corrosion (biological or not), such as clogging or corrosion of pumps, screens, discharge pipe, and pipelines. Costs may take the form of well rehabilitation and pump and column pipe repair or the abandonment of old wells and drilling new wells. Pumps can be particularly expensive to fix or replace, especially in developing countries. Well reconstruction after corrosion is an uncertain and costly venture to be approached cautiously. At this point in the damage assessment and decision-making process, a decision may be made on actions to deal with the deterioration. Will the well or system be operated in its impaired state? Or will it be decommissioned and replaced, or rehabilitated? Decommissioning as an option may be chosen if the system is deemed uneconomical (or otherwise not feasible) to rehabilitate. Rehabilitation may be chosen if it is technically feasible and desirable. As with the grim practice of battlefield triage, increased probability to achieve success (and confidence in success) drives the rehabilitate-or-replace equation toward rehabilitation. Rehabilitation (see Chapters 7 and 8) is usually attempted for deteriorated wells once a performance problem is recognized. Usually rehabilitation takes the form of cleaning and refurbishing pumps and mechanically/chemically cleaning the clogging and encrusting material from the well. In the case of biofouling, rehabilitation

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is often only partially successful. Relief may occasionally last for years, but more typically it lasts a few months on environmental projects. Rehabilitation of high-capacity public water supply wells, for example, is relatively costly: typically $3,500 to over $10,000 to refurbish a pump, and $500 to well over $50,000 to completely rehabilitate a high-capacity well. The cost is similar ($8,000 to $20,000 per well, regardless of the yield value) for hazardous and toxic waste recovery projects due to the usually advanced state of fouling in such wells, the extra time and care involved in the cleaning process and control of fluids, and site health and safety requirements. Purge fluids often must be handled as liquid hazardous waste and may not be suitable for treatment with the on-site process. Workers may be required to work in protective gear, and there is of course the time cost of suiting up, decontaminating people and tools, and the other well-known rituals of contamination containment. However, the alternative is an even costlier compromise or loss of well system performance or degraded water quality. An estimate of the costs of neglecting to detect and control well deterioration is warranted, even though current information is sparse. Based on a variety of available technical and economic data, one of the authors (Smith) in 1990 estimated that the direct (physical plant) cost of well deterioration for U.S. water supply utilities and irrigators is conservatively in the range of $200–285 million (1990 dollars) annually (in 2007 dollars: $314–447 million), and close to $1,000 million ($1.6 billion in 2007) when private water supply wells were included. The total economic cost to environmental control projects is not yet calculated, but easily could approach these figures, although many such pumping projects are now abandoned (see following discussion on economic valuation). Beyond the cost of replacement and rehabilitation is the cost in terms of reduced performance. For comparison, Peter Howsam and Sean Tyrrel (then of Cranfield University) estimated in 1990 that 40% of water supply wells worldwide are operating inefficiently or are out of commission due to well deterioration. Contractors performing environmental well rehabilitations are aware that the large numbers of environmental pumping wells rather quickly degrade to a less than desirable operational state. Efficiency is a large factor in pumping and other well operating costs. Helweg et al. (1983) have provided an empirical formula for calculating annual power costs.

C=

(Q)(s + SWL + h)(0.746)(T )( K ) 3956 × e

(3.1)

where C = cost in dollars per period of time (e.g., one year), Q = discharge in gallons per minute (L/s × 15.85 = gpm), s = drawdown (in feet from a static water level, SWL; m × 0.348 = ft), SWL = static water level in feet from the surface (not altitude; m × 0.348 = ft), h = system head or pressure in ft of head (m × 0.348 = ft), T = time pumped (hours), K = cost of electricity in dollars per kilowatt-hour, e = oval efficiency (wire to water) of pump and motor, 0.746 is a conversion factor for horsepower to kilowatts, and 3,956 is a conversion factor (gpm × ft) to horsepower.

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Table 3.1 Costs of Pumping (Per Year and Per Unit Volume) Cost per Year (pumping 175.2 million gal) KWh ($/kWh) $0.05 $0.09 $0.13

s=

Cost per 1,000 gal

20

45

70

KWh ($/kWh)

$10,564 $19,015 $27,467

$12,531 $22,556 $32,580

$14,497 $26,095 $37,693

$0.05 $0.09 $0.13

s=

20

45

70

$0.06 $0.10 $0.16

$0.07 $0.13 $0.19

$0.08 $0.15 $0.22

In this equation, efficiency (being in a single-variable denominator) strongly affects C. However, power cost, specific capacity, and system pressure are all important variables that can be controlled to some degree. The numerator components s + SWL + h can be simplified as total dynamic head (TDH). Table 3.1 illustrates outputs (C = $ per year and C = $ per 1,000 gal) from an example pumping 800 gpm for 10 h per day (480,000 gal/day) with SWL = 45 ft, system pressure head = 138.6 ft (60 psi*2.31), overall system efficiency = 70%, and pumping 365 days/year. Under this calculation, the single best operational action is to pick up the telephone and work power supply rates with the utility. If you can pump off-peak (e.g., at night) to shave kWh costs, you can save money (and at times, enjoy better power quality). Other critical issues include:



1. As with motor vehicle fuel efficiency, incentive to boost efficiency increases with per-kWh or per-volume-pumped cost. At 70% efficiency and $0.05/ kWh, the reduction in specific capacity (Q/s) from 40 gpm/ft (s = 20 ft) to 11.4 gpm/ft (s = 70 ft) costs $3,933/year or $0.02/1,000 gal. At $0.13/kWh, the difference is $10,226 or $0.06/1,000 gal (3.785 m3). 2. An increase in wire-to-water efficiency to 80% at $0.13/kWh and same system head saves $4,711. So buying the high-efficiency pump pays for itself rather quickly. 3. An increase in system head to 80 lb/in.2 (185 ft) at $0.13/kWh and 70% efficiency costs an additional $4,725/year, so preventing buildup in the raw water lines or filters saves money.

Note:  There is an upper limit on well efficiency. This is a function of local geology; therefore, preventing efficiency decline (rather than improving efficiency)—or manipulating other variables (e.g., TDH, kWh cost)—may be the management goal. Q, s, SWL, and PWL are ultimately controlled by aquifer characteristics as the well efficiency approaches 100%. There is a limit to how much one can improve these variables, and they are specific to local aquifer parameters. Other calculations one can make using these variables can answer questions such as, “What happens if we switch pumping to well X, boosting hours pumped?” For

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation

example, if the companion to the example well above pumps 750 gpm and is 65% efficient, a savings could be realized if the more efficient and more productive example well is pumped for more hours, assuming that you do not incur peak-hour power rates. As we repeatedly say in our courses, “Do the math, then make a decision.” This example illustrates that relatively simple calculations of cost can be used for planning and justifying well cleaning and maintenance in pumping well applications. Such analysis is relatively theoretical. One needs to run the numbers locally. Actual savings can be higher or lower due to unexamined parameters. One example was that of the City of Madison, Wisconsin. Madison determined that its overall power usage (energy intensity) for water production was about 1.98 kWh/1,000 gal compared to 1.7 kWh/1,000 gal for comparably sized utilities, according to a University of Wisconsin study. Based on a daily average pumping rate of 33.5 million gallons, this implies about $182,000 in annual savings if the average rate could be attained. The authors of that study believed the savings potential could be significantly larger and achieved with relatively simple, proven technologies. In their case, a review of performance data revealed several key savings opportunities: (1) deep-well rehabilitation, (2) adding variable frequency drives (VFDs) and controls to distribution pumps, and (3) energy-efficient motors. If the three measures are applied across the utility, annual savings may reach 4.7 million kWh, or $256,000. In the case of well rehabilitation, percent energy efficiency improved on a ratio of 1.4:1 for each percent reduction in head. However, cost savings were even better, as pumps were also removed and refurbished to replace worn impellers. Thus, evaluation must include multiple factors. Direct economic impacts are more difficult to judge for monitoring wells. As discussed previously, monitoring wells are widely assumed to provide water quality altered by the well environment (e.g., biochemical filters). The costs come in the form of the consequences of having monitoring points providing erroneous information:

1. Questions about the validity of data in public hearings, legal proceedings, or regulatory actions, and subsequent costs of confirming data, or providing new monitoring points 2. Worse, actual arrival of a plume at a water supply well or ecological treasure because monitoring wells failed to provide the necessary early warning

It might be worthwhile to mention that now widely accepted micropurging protocols do not seem to take near-well chemical alteration into consideration, and may delay identification of monitoring well deterioration. For recovery and remediation wells, reductions in efficiency are relatively rapid and steep. Recurrence of renewed deterioration after rehabilitation is also rapid since well cleaning rarely is very effective in removing clogging precipitates. This situation puts managers of remediation wells in the position of dealing with rapid and repeated declines, with well rehabilitation in each case being relatively expensive. Although highly useful, the above operating costs equation—focused on power costs—and other equations and nomagraphs like it are relatively simple and do not address additional “downstream” factors. Examples of these include (1) increased chemical costs due to removing precipitated Fe or Mn, (2) a need for additional

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treatment (e.g., for nitrates), (3) labor and equipment costs involved in renewing biofouled water treatment systems, water treatment equipment, or encrusted pipelines, (4) excess consultant or contractor time devoted to fixing problems, and (5) business losses. Business losses to remediation or environmental engineering companies may result from reduced client or regulator confidence. Business losses for facilities may occur if regulatory officials order a shutdown if ground-water contamination is not contained. These factors have to be calculated on a site-by-site basis, using normal accounting methods (see Section 3.3). Among the important cost considerations, human time and well-being (at least ideally) stand above and beyond anything else in Western (higher-wage) economies and value systems. The costs of well materials, pumps, chemicals, etc., are relatively minor by comparison.

3.2 Asset Management and Life Cycle Cost What we are really working around here is the application of broader principles to the matter of wells and wellfields. These are assets and should rightly be considered as a part of comprehensive facility asset management and treated much as an institution would treat a fleet of vehicles or a water treatment plant. A concise and useful definition of asset management (USEPA) is that it is “a process for maintaining a desired level of customer service at the best appropriate cost.” The operating components of the definition are: • • • •

Process: Not a single action or event, that is, it is systematic. Maintaining: Not permitted to deteriorate. Desired level of … service: There is a standard of acceptable service defined. Best appropriate cost: There is a cost-benefit analysis, and cost is generally defined as a life cycle cost or per-unit cost.

Another way to look at it is that asset management is a planning process to reduce cost, and increase efficiency and reliability (finding the “best appropriate cost”) while achieving service performance and business goals. A process of asset management involves several stages or tasks:

1. Information collection: Finding out what the assets are and what condition they are in. 2. Analysis: Understanding what is critical to achieving an appropriate level of service (LOS). In conducting this analysis, it is important to ask: a. What is the facility’s or organization’s (e.g., utility) required sustained LOS? b. Which assets are critical to sustained performance? 3. Planning prioritization: This may start with prioritizing what to fix first, and may include the priority of other planned tasks. Often this process involves understanding the consequences of the failure, malfunction, or impairment of a component or system.

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4. Ongoing capital asset management: Evaluate and plan fixes and improvements that will have the best minimum life cycle cost. Ask the following questions: a. What are the facility’s best minimum life cycle cost (see Section 3.2.2), capital improvement, and operations and maintenance (O&M) strategies? b. What is the facility’s long-term financing strategy?

This process is interactive, with multiple feedback loops. Ideally, it is conducted by a team of people with multiple skill sets, and not dominated by one particular set. For example, the capital-financial management people are listening to the hydro­ geologists and vice versa.

3.2.1 Asset Management Features of Well Systems

1. Wells and their components have individual characteristics and likely were put into service at various times, not simultaneously. 2. They are, therefore, not going to degrade at the same rate, and they have their own features. 3. They are expensive and expected to last a long time, and they can be maintained. 4. Ideally, in any one year, maintenance is performed, with occasional replacement of major components or whole systems. 5. However, such systems (like water or wastewater treatment plants) have often been built without adequate provision for maintenance. 6. Maintenance and financial forecasting benefit from information acquisition and record keeping (budgeting is optimized). 7. There is a desirable LOS (and lack of malfunction) that requires a certain level of diagnostic and preventive maintenance action, rehabilitation and replacement, and reactive maintenance.

For ground-water systems, (1) knowing assets well, (2) understanding risks (Chapter 2), and (3) monitoring (Chapter 5) are keys to effective asset management. The budgeting (now optimized by improved data collection) for such asset management should allocate resources for the following to provide the desired LOS:

1. Diagnostics and preventive maintenance 2. Rehabilitation and replacement 3. Reactive maintenance

This desired LOS will have some quantifiable or semiquantifiable value. Experience shows that when such maintenance investment is cut, the cost is transferred elsewhere, to either tolerance of a lower level of performance, or more costly and risky incidents of more drastic rehabilitation. Defining the balance point of service value vs. inputs for maintenance requires a valuation for that desired LOS. What is the value of abundant, reliable, quality water?

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For too long, public infrastructure has been built without regard for the costs and difficulty of operations and maintenance (O&M). This is because funding and program responsibilities have been fragmented between capital and maintenance functions. Daniel Dornan, Asset Management and GASB 34—Challenge or Opportunity? Government Accounting Standards Board What is the cost of tolerating a lesser standard in your situation? If the pharmaceutical plant will leave because of the cost of self-treating deteriorating water quality, is that an acceptable cost for scrimping on maintenance costs? Can your facility obtain funding for upgrades or rehabilitation now that you collect better information? Thus is the calculus of valuing water and actions.

3.2.2 Life Cycle Costs According to the Hydraulics Institute (www1.eere.energy.gov/), the life cycle cost (LCC) of any piece of equipment is the total lifetime cost to purchase, install, operate, maintain, and dispose of that equipment. Determining LCC involves following a methodology to identify and quantify all of the components of the LCC equation. When used as a comparison tool between possible design and overhaul alternatives, the LCC process will show the most cost-effective solution within the limits of the available data. The components of a life cycle cost analysis typically include initial costs, installation and commissioning costs, energy costs, operation costs, maintenance and repair costs, downtime costs, environmental costs, and decommissioning and disposal costs. Rather than simply repeating what is written there, we direct you to the Hydraulics Institute’s publication, Pump Life Cycle Costs: LCC Analysis for Pumping Systems, available on the web. Go for it, power up the spreadsheet, and do the math. To help with the calculations, at the time of publication, there are a number of sources of present-value and LCC calculations. For example, an Excel worksheet for LCC is available from the Barringer & Associates website (http://www.barringer1. com/). Other fill-in-the-blank calculators are available. Remember that you need good data to make these efforts worthwhile. If you are the person typically likely to buy a book like ours (admittedly, not likely to become a movie script), you have a technical bent. When reading Dilbert, you identify with Dilbert or Alice, not the Pointy-Haired Boss (PHB). You think facts, argued rationally, should drive decision making (you naïve soul). You may like to sit down with a cup of coffee and develop a spreadsheet (or worksheet, if you prefer) to derive answers to questions such as “What is an LCC for this asset?” Remember that you probably have to make it understandable to those who hold your purse strings. These people are likely to be dedicated and thorough managers, but not well specialists.

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3.3 Assigning Economic Value Assigning value to ground water is notoriously subjective and often practiced in an atmosphere of misinformation. Assigning value is subjective, and representative of what a person is (subjectively) willing to pay for a good or service. It is not related to need or benefit. People pay large sums for grams of diamonds (and producers risk their lives to mine and distribute them), and diamonds are generally a useless substance in everyday use (unless you are core drilling or grinding). People buy bottled water costing up to a thousand times more than the per-liter cost of safe tap water. The health value of the bottled water is not a thousand times better (sometimes worse), plus there is an economic cost to bottle disposal and a carbon footprint issue due to transport. On the other hand, people complain about water bills when fractions of a penny per gallon bring safe water to their tap 24/7. Closer to the subject, in defining the economic value (EV) of the water in an aquifer, or an aquifer’s EV as an environmental asset, what is the appropriate value system to employ? Generally, EV is associated with water use. The EV may vary depending on how the water is used: as (among the consumptive uses) cooling water, for bottled water (as a product), as drinking water, or for irrigation (improving crop value). Quality is an issue in assigning EV. Generally, water utilities do not really charge for water itself (an extractive cost is seldom factored in) but for providing quality water (safe, palatable) in a convenient way. The customer pays for personnel time, treatment, pipes, maintenance, etc. Often these costs are undervalued in the price charged. On the other hand, affordable water is a social good: In our society (North America and the developed West generally), cheap, safe water is generally available even to the poor. In developing countries, in both urban and rural areas, water is often very expensive. In terms of labor and energy expended (hours hauling, calories expended in fuel or muscle), the per-volume cost of (sometimes unsafe, seldom treated) water in a rural village is much higher than the delivered cost of treated water in an American city. The ground water may support wetlands or other watery environmental assets that have an environmental EV (EEV) or recreational EV (REV; a subset of EEV). Such an EV is an amenity, a service function that may not be a survival function per se but improves the quality of life, for example, by providing a pleasing landscape for leisure pursuits. This definition is paraphrased from the Organisation for Economic Cooperation and Development (OECD) Glossary of Statistical Terms (www.oecd. org/). Now, there is abundant evidence that ecosystem equilibria can collapse suddenly under stress, so we have to be careful in accepting such definitions of value. Human modifications of the environment can be deadly and costly, especially in the long run. The REV of nonconsumptive in-stream flows for a single river can be tens of millions of dollars per year (e.g., recreational boating, fishing, bird watching, etc.). Additional value comes in support of endangered species (e.g., here in Ohio’s Sandusky River basin, sturgeon and bald eagles) and in making wastewater disposal relatively cheap. Thus, ground water (the source of baseflow and water in wetlands that serve as wildlife refugia) can be characterized as having an EEV.

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3.3.1 Water Supply EV In a study to define the EV of the Assiniboine Delta Aquifer in the province of Manitoba in Canada, S. N. Kulshreshtha (see recommended reading list) of the University of Saskatchewan employed a method that disaggregated the total water use into its major types, rather than picking one (e.g., irrigation) and forcing all EV analysis under that category. These categories are:



1. Municipal drinking water: Cost-of-service principle (what would be the cost of alternatives to using this water for water supply?) based on the fuzzy concept of consumer surplus—basically understanding what such a commodity is worth to people, e.g., what is the perceived worth of having abundant, good-quality water? From this valuation, a maximum cost can be established. This study further disaggregated “municipal” into residential, commercial, industrial, and other categories. 2. Rural residential drinking water: A miniature version of municipal. 3. Agricultural: Valuation compared to the water being absent for agricultural production in terms of net income change (value of irrigated crops and watersupplied livestock production vs. dryland alternatives or not producing). Such a valuation depends on crop/livestock prices, and therefore fluctuates.

The Kulshreshtha study is a valuable and replicable case history, providing a conceptual basis, the mathematics, and example calculations. Understanding the EV of the function of a well or wellfield permits the establishment of a benefit (B) to be expected from the cost (C) of a process or action (e.g., establishing a maintenance monitoring program or conducting rehabilitation). Run the numbers. Do the math.

3.3.2 Other Environmental EV While we may focus on water supply, ground water has other EEV; for example, there is a basis for EEV for:

1. Impairment of a sensitive receptor 2. Impairment as a carrier of residue

These two concepts may not seem to apply to well maintenance and rehabilitation planning. However, impairment of a sensitive receptor (e.g., a valued water asset such as a lake or a drinking water wellfield) is an inherent EV component to the benefit of maintaining monitoring and remediation well arrays. Such an impairment EV can serve as a rational valuation for defining a B to the cost of maintaining environmental well arrays. That is, the EV of the system is the EV of what would happen if it were not there and not functioning. This EV may include the cost of replacing a wellfield (land, engineering, regulatory issues, etc.) but also may include legal costs (the cost of being sued for the impairment of the asset).

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Also, some wellfields have the sole purpose of pumping water into surface water bodies. For example, the hundred-plus wells of Closed Basin wellfield maintained by the Bureau of Reclamation in southern Colorado serve to pump water into the Rio Grande in support of the multistate Rio Grande Compact. Establishing an EEV for this asset has been somewhat difficult; however, a combination of the Kulshreshtha method (summing multivariate water EV) and establishing EV for impairment as a receiver of wastewater and cooling water would seem reasonable.

3.3.3 Government Accounting Valuation of Assets In matters of diplomacy, the 1975 Helsinki Accords seemed to entrench the Cold War status quo in Europe, recognizing recognition of post–World War II borders (including Soviet claims on Baltic states). The Soviets received the recognition that they desired, while they in turn agreed to respect human rights, and acknowledge that the issue of human rights was an international concern. Soon, what became known as Helsinki Watch Groups were established throughout the Soviet Union. They became beacons that kept opposition alive in the Soviet Union. “Within 16 years, the Baltics would become independent of the Soviet Union, and full human rights would be instituted [at least for a few years] in a new Russian Federation” (HistoryCentral.com). A similar hidden asset for water and environmental infrastructure is GASB Statement 34, Basic Financial Statements—and Management’s Discussion and Analysis—for State and Local Governments, issued by the Government Accounting Standards Board (see our recommended reading list, www.gasb.org/). Again, we are not accountants, but this looks like a Helsinki Accords type instrument to sweep out the old system of paying for capital assets while neglecting maintenance funding and replacing it with an assets management valuation system. GASB 34 requires reporting the valuation of infrastructure assets and the cost of deferred maintenance. Documents referring to GASB 34 implementation seem to stall out by 2002–2003, but look for this process and imperative to be picked up again.

3.4 A Costly Example Let’s consider a fairly simple but costly example. Readers can plug in relevant costs in their own situations, and extrapolate outward for complex systems. Problem: A set of four remediation wells feeding a filter and stripper unit lose performance and clog the treatment system and piping with iron precipitation. Rehabilitation becomes necessary as abandonment is not possible. The resulting effort required: Time (never mind related direct and indirect costs): 1. A week for two people (site personnel) to take down and clean the filter/ stripper system (clogged and coated by iron precipitation), with supervision and health monitoring 2. Two days each to clean four wells plus one day each for mobilization and demobilization (contractor)



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3. Consultant time to draw up remediation plan for state approval (two days) and to confirm system and filter performance (two days) 4. Approval process triggers an OSHA site inspection, resulting in two days of managerial time, plus citations that have to be addressed Chemical/material costs: 1. Discard and replace filter media and aeration tower packing (secure disposal due to chemical residues) 2. Discard and replace accessible piping (secure disposal due to chemical residues) 3. Mechanical/acid cleaning of supply lines from wells (20 L of glycolic acid), line brush, and rods or cables (clean and test for residues) 4. Containerize and discard acid-sludge waste from lines 5. Mechanical/acid cleaning of wells, 1,000 L of glycolic acid solution, including use of a jetting rig (rig and lines to be decontaminated after well cleaning) 6. Containment and secure disposal of 3,000 L of purged pH 6.5 but turbid water containing the VOC contaminant

The goal of the following chapters is to introduce means of limiting these considerable and oftentimes unplanned operational costs. These sections include methods to compare maintenance costs vs. the costs of well deterioration.

Practices 4 Prevention for Sustainable Wells Poor performance and failure of well systems can be controlled or prevented. This can be accomplished via prevention in design and construction, recognition of well deterioration factors, monitoring for problems, and preventive actions when problems are detected. If well systems do deteriorate, a limited number of rehabilitative options are available. Monitoring and preventive design and maintenance are preferable on both cost and operational bases. Chapters 4 through 6 will consider prevention and control of well deteriorating condition, including detailed information on preventive maintenance monitoring. Rehabilitative strategies are discussed after that. If you skip ahead to “cures” (Chapters 7 and 8), come back to learn about ways to avoid a crisis the next time.

4.1 Prevention—Its Place in the Well Life Cycle There is an extensive literature and body of unpublished and uncelebrated practical experience with prevention and removal of clogging conditions in water supply wells. There is a large parallel body of experience in corrosion prevention in oil field and marine engineering systems. There is also a largely unpublished body of reports on the design, operation, and maintenance of monitoring and pumping wells on environmental sites. The quality of existing information varies greatly, and facility consultants or managers should not proceed based on armchair research alone. They should also take into account the experience now being gained by the companies and organizations that are actively performing well rehabilitation and maintenance. Based on this experience, there are several “ground truths” of well system operation and maintenance:





1. The best defense is to know about and acknowledge the presence of factors in the well and aquifer system that will cause clogging and corrosion (see Chapter 2). Knowledge can lead to either action or despair, but it will preferably lead to preventive action to the degree possible. 2. Preventive design, operation, maintenance, and rehabilitation strategies are site specific and require fine-tuning as operators gain experience with deteriorating conditions on-site. 3. Maintenance is one area where much is possible, but it requires a commitment to doing what needs to be done (Chapters 5 and 6). Maintenance is best implemented from the beginning, but can be implemented after deteriorated wells have been rehabilitated to slow or prevent recurrence of the problem. 4. Rehabilitation itself (Chapters 7 and 8) should be the last phase and last resort (before decommissioning or reconstruction) in the life cycle of a well system (Figure 4.1). It is never a permanent solution and has to be followed 81

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Well Lifecycle Continuum

Design Construct Operate Maintain Rehabilitate Jump on somewhere on the life cycle

Figure 4.1  The well life cycle continuum.



up by maintenance to be effective. Rehabilitation is frequently limited by environmental protection and safety factors when chemicals are present in the ground water. It is also limited by the typically small size and relative delicacy of some wells—including the typical domestic water well, which is usually constructed to be just robust enough so that it will not collapse. 5. In the case of environmental monitoring and treatment wells of various descriptions, prevention, rehabilitation, and maintenance possibilities are all more limited than those possible for water supply wells, and certainly those used in oil and gas production and reservoir flooding wells. The tools available for water well cleaning are receiving significant scrutiny in regulatory quarters (sometimes for good reason!). The virtuous role of prevention is limited to a degree by the need to construct wells in aquifer zones that may consist of fine sediments that are rich in microbes and diverse biogeochemical environments (see Chapter 2). Such situations can sometimes be avoided in water well design, whereas they can’t always be avoided in environmental well planning. However, performing the preventive well design at least helps to some degree in delaying performance decline and the need for rehabilitation.

4.2 Interlude: Teeth and Motor Vehicles The most instructive illustrations are those from other industries where prevention and maintenance are employed. In this regard, much of the ground-water industry remains fairly primitive in practice by comparison. Let’s look at two sectors: automobiles and dentistry. These two industries have successfully (1) cultivated a maintenance ethic in their market bases and (2) employed preventive material and design choices. If you are any older than “Boomer prime” or talk with your elders, both dentistry and automobiles are associated with much pain and inconvenience. Why most people (including your authors) remember old cars

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with fondness is something of a mystery, and probably associated with the emotional connection we were taught to accept as children. If you are old enough (or poor enough) and remember your pre-1980s automobile (wherever it was built), you remember that it rusted. Whatever other positive characteristics it had, the holes started over the headlights, along the wheel wells, in the heater channels, etc. In my (Smith) experience, there is the neighbor’s sharplooking red 1965 Chevrolet Impala that ended life sagging in the driveway as it rotted in two (those Impala frames collected and held salty water), my 1971 Ford Pinto (seemed like a good idea!) and its four fenders in seven years, cold feet and pop-riveting plates in the 1973 Superbeetle, and the dealer driving his screwdriver through the wheel well of my 1987 Subaru wagon (I liked that car!) when I was trading it (then of course, there was its iron and copper radiator that turned to dust). You get the idea. Of course, these are all vehicles that had the misfortune of operating in Ohio. For those of you who live in warm climates, Ohio roads are salted during the winter because driving on ice and snow is hazardous. By the late 1990s, I was running steel-body vehicles for well over 120,000 mi without rust damage. Materials and design have improved. Complaints about modern vehicles are usually associated with something complex, like the automatic transmissions one cannot seem to avoid in the United States anymore. Motor vehicles really have improved (no ring jobs at 50,000 mi either). The auto industry (largely due to self-interest) also promoted preventive maintenance. We are convinced we should change oil and filters at 3,000 mi (5,000 km) intervals (even if the manual says 7,500 mi). Except for the rare individual who would rather change engines than oil (they exist), we go along gladly. This habit of maintenance preserves a major asset (a motor vehicle) and benefits the service vendor (regular service fees). If you service the vehicle at an establishment that sells vehicles, eventually the sales agent will be at the desk to convince you to trade in Old Betsy on something shiny and new. The cycle then continues. In the automotive world, the maintenance cycle involves (1) engineering to improve the product, (2) enlightened self-interest of both the vendor and customer, (3) profitability for the service provider, and (4) willing cooperation of the customer base. The history of preventive dentistry probably is more directly comparable to preventive maintenance in ground-water supply and protection. However, the ground-water industry lags about thirty years behind dentistry in this regard in North America. • Both dental and water system equipment are deteriorated by biofouling/ biocorrosion. • The mechanisms of deterioration were known in both dentistry and civil engineering by the turn of the twentieth century. Actually, the use of the toothbrush goes back centuries. • The benefits of oral hygiene were described by the end of the First World War (1918) in the United States. However, a description of the history of dentistry in North Carolina (where the first U.S. oral public health program was initiated) states that in 1934, more than half of people examined had never seen a dentist (something like what you would find now in developing countries).

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• Efforts at oral hygiene and education continued through the decades. However, toothbrushing was not practiced widely among Americans until U.S. troops brought the habit (enforced while on duty) home with them after World War II (mid-1940s). • By the 1980s, sealing children’s teeth was widely practiced, reducing the initial onset of dental decay. You get the idea. The ground-water industry was generally aware of many forms of well deterioration by the 1950s, but preventive design and treatments were limited. Stainless steel and other corrosion-resistant metals in well screens were common by the 1950s, and plastics and stainless steel were used in other critical components, especially pumps, by the 1980s. Preventive design already existed—practicing what was already recommended in the industry for well hydraulic efficiency. A resurgence of preaching the maintenance ethic in wells resumed in the early 1980s. Today, it is still viewed as a novel idea in parts of the well-using population, early in the twenty-first century. We are still at the “let them decay, then pull them and install dentures” stage in this industry (and it will stay that way as far as some are concerned), with some notable exceptions.

4.3 Prevention: Design and Construction Considerations Prevention is the fundamental step in avoiding costly and project-threatening well deterioration and plugging. As just described in reference to oral health, the best protection against deterioration in wells and water systems of any kind is prevention. Prevention involves a combination of good design and construction practices, followed by preventive maintenance monitoring and treatment. Practicing prevention requires a team effort among well managers and operators, drillers, equipment suppliers, and consultants.

4.3.1 Planning Considerations Prevention needs to start at the very beginning. Unfortunately, the usual situation at the present time is that facility operators are considering improvements in well performance after wells have deteriorated in performance or water quality. Even when reacting too late, it is useful to review good design and construction practices to assess (1) what went wrong or (2) what improvements can be made. Some problems (Table 4.1) are preventable from the beginning. A crucial part of prevention planning is proper well design and construction. There has always been a temptation on many projects to attempt to save money by asking too much of limited and undersized wells, using standard pack and screen sizes and inexpensive pumps, and shaving on development time. Considering that a well—like a set of teeth—operates bathed in a wet, biologically active, environmentally heterogeneous, and corrosive environment, good design and material choice are going to result in an optimal performance life.

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Table 4.1 General Well Design and Placement Guidelines What

Why

Room for personnel to operate and manipulate equipment around the wellhead; reasonably accessible; dry and stable wellhead area; avoid confined-space-entry conditions

Improves accuracy, and reduces the potential for accidental injury or equipment damage or loss; minimizes personnel needs for routine tasks; reduces time and equipment required for maintenance events

Locks, caps, or security apparatus are corrosion and weather resistant

Personnel do not waste time and risk injury or equipment damage attempting to perform maintenance; instrumentation is not easily damaged by heat, cold, vandalism

Water level measurement access and pumping rate readings are easily obtained

Personnel can perform these tasks efficiently and willingly

Wellhead structures and fittings permit easy removal of pumps and downhole equipment

Pumps can be removed quickly, saving money

Piping and valving designed to limit pressure drops and permit convenient flow diversion and pipe maintenance

Clogging is minimized and maintenance flushing and pigging can be accomplished to minimize total system head

Water quality taps accessible and protected from weather and corrosion

Samples can be readily obtained and taps maintained

Monitoring and recovery/control wells are no different than water wells in that quality well design and construction contribute to long and trouble-free service. For monitoring wells, quality is absolutely essential since so few effective options exist for rehabilitation. Water well, remediation well, and dewatering well system design is ably described for a variety of environments and purposes by numerous publications in our recommended reading list. The ASCE International Manual of Well Hydraulics will be an especially modern source on the subject (date of publication unknown at this point). Standards/standard practices in all these well use categories have been published by American Society for Testing and Materials (ASTM), American Water Works Association (AWWA), and National Ground Water Association (NGWA) in the United States, and by others internationally. These standards reflect modern practice in well construction and development, and many features of standards specific to certain well categories (e.g., monitoring wells) can also be transferred to other well categories. These standards are not intended to be encyclopedic, or even always highly specific. The recently developed ANSI NGWA Standard 01 is more comprehensive and detailed than the more familiar ANSI AWWA Standard A100. Combined with the specific ASTM standard guides, 01 probably should be the design framework for the ground-water industry. However, A100 is on the shelf at our regulators and referenced in their guidelines, so pay attention.

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Standards aside, design, construction, and development, of course, should be based on site-specific information—as the standards recommend. For example, even when casings, pumps, and gravel packs have been lovingly selected for material compatibility and corrosion resistance based on the literature and developing standards (using good water quality data), poor performance may still occur. For example, if biofouling is going to coat everything (blanking off a reactive casing, or alternatively, accelerating corrosion), this should be known up front.

4.3.2 Role of Well Purpose The purpose of water well construction is to provide a water supply well that will efficiently provide good-quality water over a long service life—on the order of decades. Monitoring wells, like water wells, are usually intended to have a long service life— on the order of decades. Trends in ground-water quality at a location, such as saline water infiltration, aquifer zone oxidation, or rates of plume degradation, can often only be ascertained based on long study of data from consistent monitoring points. Some monitoring wells must be ready, long after their designers are dead, to provide advanced warning of approaching problems, such as those serving as sentinels for leaking radionuclides around high-level waste repositories. Recovery and plume control wells, both examples of extraction pumping wells, have divergent lifestyles. Recovery wells, for example, are optimistically expected to have short design lives. However, current experience indicates that both recovery/ remediation and plume control are long-term processes for most sites. In any case, they must be as productive as the formation permits and do their job as long as needed. So such wells (like water supply wells) should be designed with the expectation of sustained operational life. Another difference from water supply wells for all classes of environmental wells is that they have to be in specific (often undesirable) places for the job requirement. This particular zone or aquifer has to be sampled or pumped down regardless of the longterm impact on the well. A water well (ideally) is planned and sited to abstract water from optimal aquifer zones (offering optimal yield at minimal operational risk). Quality well design and construction assists in the prevention of encrustation and corrosion problems during the life of wells. By using quality materials, care in construction, and proper sealing and disinfection, the designer and driller can help to ensure a long and less troublesome life for the well and can potentially reduce life cycle costs.

4.3.3 Well Design Proper well design, in addition to determining the depth and diameter for the purpose of the well, includes casing selection, appropriate intake section design, grouting to prevent infiltration around the casing and between sampled intervals, and procedures for well development, testing, and removal of other introduced materials (drilling fluid, surface soil, etc.). Unlike water wells, disinfection is not likely to be a necessary step in environmental wells. All of these tasks are necessary to achieve the optimal performance. Neglecting any of them is false economy.

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While monitoring and many recovery/control wells are often not great producers or efficient in a water well sense, they should still be designed with optimal efficiency in mind, within the constraints imposed by the situation (such as the need to sample specific intervals with minimum oxidation). The main reason is that designing for maximum efficiency helps to minimize biofouling and encrustation, as well as oxidation, effects to the extent possible. In monitoring well doctrine, materials selection is made so that materials do not interfere with analyses. A plus from a maintenance standpoint is that noncorrodible and nondegradable materials are also those that provide resistance to biofouling and corrosion. Table 4.1 summarizes general well design and placement guidelines.

4.3.4 Casing for Well Completion Casing is used in wells to (1) provide a stable hole and (2) seal the walls of the hole to exclude undesirable water. In a pumped well, the casing must also house and protect the pumping equipment. Casing for both monitoring and pumping wells must have (1) a sufficient diameter to accommodate pumping equipment and instruments, (2) strength to withstand forces during emplacement and use, and (3) ability to resist corrosion, heat, abrasion, and other causes of well deterioration that affect service life and mission factors, such as product or sample quality. In monitoring wells, casing diameter is often restricted to limit the amount of well purging necessary and, in some cases, to minimize the drill cuttings that have to be drummed and landfilled during well construction. In other wells, diameter is restricted due to economic considerations or limits of available well construction equipment. From a maintenance standpoint, diameter, strength, and corrosion resistance are important as well. Casings that have sufficient tensile and compressive strength and corrosion resistance are unlikely to fail catastrophically. Diameter is a factor in limiting which redevelopment tools may be used, as well as determining the volume of purge water that may need to be handled after a treatment. Casing material should be selected on a site-specific basis, taking into consideration water quality and hydrogeologic conditions. All water-well-grade casing thermoplastics have almost total corrosion resistance. However, they may be subject to attack and softening by certain organic solvents, just as if they were being solvent joined. Tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexane, for example, if present in parts per thousand or percentage concentrations, may solvate thermoplastics. On the other hand, PVC is highly resistant to other nonpolar solvents such as gasoline components. In the typical parts per million and billion ranges of concentration, such casing degradation has not been reported. On the other hand, dissolution of cement bonds has been reported, so solvent joining should be avoided in lieu of threaded or spline-lock joints where such shallow ground-water contamination is suspected or known. Figure 4.2 illustrates bell-end and example spline-lock (CertainTeed Certa-Lok™) connectors. Numerous other types are in use. Heat is a consideration for wells on projects using heat-amended remediation, requiring cement grouting, or intended for hot-water environments. Plastics chosen (if

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(a) 

OD

(b)  T1 T2 L1

D

15°

BOD

L2

Figure 4.2  Some types of connections used in well casing and pump discharge pipe. (a) bell-end PVC casing pipe and (b) spline-lock coupling (Certain Teed CertaLok™).

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stainless steel is not an option) may have to be thermally stable: not likely to become reactive or to physically deform. PVC, for example, is not thermally stable above certain temperatures, depending on the composition. Thermal stability data provided by a manufacturer should be for the expected life span of the well. Short-term temperature resistance data provided may not be relevant for long-term exposure. PVC casing is at a disadvantage when mechanical cleaning is contemplated. Generally, such well casing will stand up to development forces; however, if airlifting pushes high volumes of water into the lower end of a less than optimal casing, it can break. Stainless steels have good corrosion resistance in general, but most especially if oxygen is present. The way that stainless steel corrosion resistance works is that a layer of metallic oxide is deposited on the metal surface. Under reducing conditions, however, which prevail as biodegradation of organics occurs, stainless steel corrosion resistance may be impaired. For this reason, steels of all sorts (including stainless) should be considered susceptible to corrosion under ground-water conditions in which organics are present. In a case where Type 304 may be specified under uncontaminated conditions, a higher grade, such as Type 316, may be needed. Even then, microbial corrosion is known to severely affect joints and welds in Type 316 stainless steel casing. There are many specific grades of stainless alloys. Become acquainted with them. Alternatively, plastics, at sometimes a third or less of the cost (only in materials), should be used if ground-water quality conditions will promote corrosion. However, strength and thermal considerations may preclude the use of available thermoplastics. Thermal and collapse resistance depend on the plastic pipe material used. As with steel casing, the diameter and wall thickness of the casing pipe determine the hydraulic collapse resistance of plastic pipe. Tables for various plastic and steel casings are provided in standard industry references (see our recommended reading list). The NGWA’s Manual of Water Well Construction Practices, and the ANSI NGWA 01 Water Well Construction Standard derived from it, have detailed information on both plastic and steel casing and should be in your design arsenal. Standards and data are also provided in the relevant ASTM pipe standards (American Society for Testing and Materials, West Conshohocken, PA, www.astm.org). Weld or threaded joints? The strategy is to minimize corrosion attack. How to do that depends somewhat on the application. Table 4.2 compares some casing types and materials. High-quality, uniform cement grouting provides a uniform noncorrosive barrier between steel and external environments that have varied electrochemical potentials. Bentonite grouting can serve the same purpose, but remains wet and can transmit electrical potentials. Grout sealing tends to counteract the effects of metal alterations due to welding.

4.3.5 Well Hydraulics and Efficiency—General Considerations Good hydraulic flow characteristics at the well contribute to good efficiency and reduced maintenance problems. In particular, for wells that may experience biofouling, good hydraulic efficiency reduces the impact of clogging and allows time to begin a rehabilitation program.

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Table 4.2 Casing Types and Choices Application

Casing Type

Recommendation

Water well

Mild or stainless steel

Welded joints by qualified welders, meeting industry standards; cement grouting if deep and multiple aquifers, or deep water table, bentonite grouting beneficial otherwise; if filter pack and screen, put high-solids bentonite between cement seal and filter pack

Water well

PVC

Solvent jointed if sealing is ensured before lowering; spline-lock jointing also recommended, better for deep installations; high-solids bentonite grouting

Remediation pumping well

PVC

Spline-lock jointing; bentonite grouting

Stainless steel

In case of severe corrosive and PVC-degrading conditions; welded joints above small diameter (with appropriate heat and rod types); cement grouted, but if filter pack and screen, put high-solids bentonite between cement seal and filter pack

PVC

Or exotic plastic as needed; bentonite grouted; ASTM threaded

Stainless steel (Type 316)

Where ground-water quality indicates; bentonite grouted, unless severe biocorrosion conditions indicated, then cement and separate from the intake zone by bentonite; ASTM threaded

Monitoring well

It is beyond the scope of this book to discuss well hydraulics in detail, and it is well covered elsewhere. Did we mention that you should familiarize yourself with our recommended reading list? This industry and the science and technology that go with it are too complex and diverse to be understood by oneself or by reading one slim book. You need to have references on your shelf, bookmarks in your browser, and familiarity with practice installed in your brain. However, efficient screen selection, pumping rates appropriate for hydrogeologic conditions, and thorough well development contribute to optimal hydraulic efficiency, which in turn improves the reliability of monitoring, since a good formation-well contact is established. Good well hydraulic characteristics depend on some basic understandings of the aquifer.

4.3.6 Well Screens and Intakes Wells generally can be divided into two categories, based on the intake type: screened or unscreened. Aquifer formations that require screens are usually those that are unstable, and must be held back from the borehole. These include sands and gravels as well as unstable and weathered rock formations (e.g., volcanics and their weathering products). Filter-packed screens are considered to be assumed in monitoring well design (cf. ASTM Standard Guide D 5092). Recommendations for good monitoring well screen and pack design have been ably described elsewhere (see that reading list!).

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4.3.6.1 Screen Design The ASTM Standard Guide D 5092 and water well standards ANSI/AWWA A100 and ANSI/NGWA 01 (as well as a voluminous literature) offer definitions of good screen and pack design and selection for monitoring and water wells. However, even when standards apply, it must always be realized that well design has to be site specific in nature. Screened wells in environmental applications also can be divided into those that are (1) always submerged and (2) sometimes exposed to unsaturated conditions, such as product recovery wells. In standard water well design doctrine, dewatering of the screen is to be avoided. This ideal is often not possible in dewatering wells and product recovery wells. Dewatering wells constructed over impermeable sediments or rock may have to drawdown completely to produce the desired water level. Recovery wells also often have to provide contact with the top of the local water table to permit skimming of light hydrocarbons. In these cases, engineering involves “designing for failure” more than in any other case. Designers must realize that these wells will biofoul and plug over time, design them accordingly, and make plans from the beginning to perform regular maintenance. Within the constraints of the well purpose, designing for failure can take the form of expanded filter pack and associated larger borehole diameter to permit more complete rehabilitation. Screen materials should be chosen to resist the expected rehabilitation actions. Screen inflow modification may be employed to slow velocity and clogging (see well reconstruction discussion following). Well terminuses and hookups should be designed to permit access for rehabilitation. Quality manufactured water well screens can be relatively expensive. Regardless, they are preferred for long life since they have good hydraulic efficiency. Stainless steel, plastic, and even fiberglass models resist erosion and corrosion much better than slotted steel pipe or galvanized wire screens. In any case, the slot size should be small enough to contain most filter pack particles, but not too small. The slots should be uniform in width and free of shavings or weld spatter. Various texts in our recommended reading list sources show examples of screen designs. Slotted or louvered screens should be installed with a sand filter pack per ASTM D 5092 and other literature, while wedge-wire screens may also be naturally developed under certain conditions. Screens may be installed with the casing in rotaryor auger-drilled holes, or they can be slipped inside cable-tool-driven casings using the telescoping method. 4.3.6.2 Screen and Filter Pack Material Selection With their higher surface areas, screen material selection is more critical than that for casing material. Stainless steel screens are often the material of choice for wells due to the ability to very precisely define slot size, the strength of louvered and even wire-wound screens to resist development forces, and their long-term durability. PVC or fiberglass screen made from water well casing tubing is often superior to metals under chemically reducing redox conditions in which steel corrosion is accel-

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erated. On the other hand, some solvents present may attack these materials. Also, deeper (>120 m) and hotter conditions restrict plastic and fiberglass use. In the cases where plastic screens (thermo or composite) are unsuitable due to constituents, heat, or strength factors, stainless steel should be used. However, where reduction is possible (in the presence of hydrocarbons, especially) corrosion has to then be considered in maintenance planning. One lamentable situation at present is the highly variable quality of fiberglass casing and screen products worldwide. In many cases, fiberglass composites have very favorable characteristics, with strength and heat resistance superior to those of comparable thermoplastics. However, the finish of produced items leaving exposed, friable glass fibers makes them unusable for monitoring and extraction purposes, as well as water supply production. If fiberglass is an optimal option, the quality of the available products has to be determined before specifying. It is the authors’ opinion that the use of mill- or field-slotted and perforated steel casing should be avoided in all cases, as should mild- or galvanized-steel wirewound screens, even in short-lived product recovery wells. The reason is that biofouling and biodeterioration by-products can corrode these screens well within even the optimistic estimated short performance lives. Table 4.3 illustrates the galvanic series for metal alloys. Two lists are provided, one that is general (sea water or fresh) and one for fresh water. The positions of some alloys and metals in the listing change somewhat depending on water quality and temperature. For example, zinc and iron change place above certain temperatures. Also, relative passivity or activity depends on how the alloys are treated, and may also change (as described in Chapter 2) due to manufacturing (heating and bending) and handling stress. Factory-punched louvered and wirewound screens finished and coated to minimize corrosion attack buy time against the still likely corrosion attack. In projected life spans of wells, consider: Just when has a pump-and-treat or in situ remediation project been completed on the predetermined schedule? What happens when a two-month job extends to a year and you have a screen with a two-month life span? The costs of restoring such a well or dealing with corrosion products are certainly much higher than simply specifying corrosion-resistant materials in the first place. The sand or gravel used in filter packs should be clean: free from organic soil that may cause clogging and feed bacterial growth (the native soil will be lively enough). The filter material should be as uniform as possible, with a uniformity coefficient of 2.5 or less, preferably 1.0 (ASTM D 5092), rounded (to the extent possible), and consist almost entirely of quartz. Particle size should be selected to filter the formation without silt packing at the borehole-pack interface. ASTM D 5092 specifies that the filter pack material should be selected based on sieve analysis to pass the 30% fraction (retaining 70%), and the screen should retain 90 to 99% of the pack. Again, consult ANSI NGWA Standard 01. Unscreened, open-borehole completions should include a casing or liner to the pumping water level at the least, unless (in the case of recovery wells) low specific gravity product has to be recovered at the bedrock surface or interface. Small

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Table 4.3 Cathodic-Anodic Series of Metal Alloys Protected (Passive, Cathodic, Nobler) Fresh Water Carbon (graphite) Titanium Ni-Cr-Mo-based alloys Stainless steels Copper alloys

Carbon steel/cast iron Aluminum Zinc Magnesium

General (Sea Water and Fresh Water) Gold Graphite Inconel® alloy 825 Monel Nickel 200 (passivated) Type 316 stainless steel (passivated) Type 304 stainless steel (passivated) Copper alloy (30% Ni) Red brass (85% Cu) Yellow brass (65% Cu) Type 316 stainless steel (active) Type 304 stainless steel (active) Cast iron Low-carbon steel Galvanized steel Zinc Magnesium Active (Anodic)

water-bearing fractures or screened zones above the selected pumping zone should be monitored separately and not allowed to cascade. For water supply wells, there is a trade-off between the benefit of screening multiple zones, some above the pumping water level, to extract more water or to induce flow to the well in a rock aquifer, and the challenges to well performance that the resultant cascading poses in the long run. Besides adding to water to be treated or interfering with sample quality, the water cascading down from these small seeps encourages bacterial growth and fouling. An additional issue for potable water wells is that screening shallow zones above a local water table results in more casing-seal compromises.

4.3.7 Grouting and Well Sealing In addition to basic quality well construction considerations, grouting helps by preventing the flow of bacteria-laden shallow water down into the aquifer and intake area of the well. It also helps by limiting contact of such water with the metal well casing, and thus limiting corrosion. Again, this is not essentially a manual on well sealing, but several considerations should be mentioned. Grouts should be:

1. Of low permeability (lower than the surrounding earth materials) 2. Capable of bonding well with both the casing and earth materials

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3. Capable of setting up to strength quickly to permit well completion (including development) without excessive delay 4. Chemically nonreactive with formation materials, constituents, and well materials 5. Easily mixed and pumped in a reasonable time into the annulus 6. Unlikely to penetrate far into permeable formations 7. Easily cleaned and safe to handle

The reader should stay current with developments in optimal grouting, most recently reviewed in the NGWA’s Water Well Construction Standard. Both cement and bentonite grout mixtures should be properly mixed and placed in the well so that the space between the borehole and the casing is completely sealed per evolving recommendations and standards. Unused boreholes and wells should be promptly and properly decommissioned by sealing to control inflow of oxygen and nutrients to the aquifer, which may affect fouling at other nearby wells. Note about Diameters:  You need an annular space sufficiently large to permit adequate placement of grout and filter pack. Setting a casing in the next larger nominal borehole size (6 in. in 8 in.) does not allow enough room if one takes casing thickness into consideration.

4.4 Well Development Well development is the action of removing drilling damage and additives from the intake area of the well and the surrounding aquifer. We cannot emphasize enough the crucial importance of proper initial well development and redevelopment in well maintenance and rehabilitation (Chapters 6 to 8). Proper well development breaks down the compacted borehole wall, liquefies gelled mud, and moves both mud and formation fines into the well, from which they are removed by bailing or pumping. By doing so, development helps to restore the physical characteristics of the aquifer to the predrilling situation, provide a good hydraulic contact with the formation, remove fine cutting and formation material from the well vicinity, and improve stability around the well. In addition, development action in natural development situations sets up a gradation of particle sizes that tends to keep fines away from the well screen and improves permeability. Development in filter-packed wells helps to set up this gradation at the interface between the pack and the formation. Redevelopment, the process of applying physical development methods in a remedial fashion, is a crucial part of maintenance and rehabilitation treatments.

4.4.1 Reasons for Development The objective of well development for monitoring wells is to improve the ability of the well to provide representative, unbiased chemical and hydraulic data. As with pumping wells, development does this by helping to provide a suitable hydraulic con-

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nection between the well bore and the surrounding formation so that natural ground water can flow to the well, providing more accurate sample quality. Proper well development becomes more critical for wells in other ways. It minimizes the potential for damage to pumps, samplers, and sensors from abrasive particles. Those used in monitoring are often less resistant to damage than are water supply pumps. It also helps to at least initially minimize biofouling effects by removing bacteria-laden drilling mud and make-up water used in drilling, as well as contaminants such as compressor lubricating oil. By opening up the aquifer, development also helps to limit or delay the clogging impact of biofouling when it does occur. Well development methods are well described in other literature (see our reading list). These descriptions are oriented toward water wells, but most of the principles are the same as for any type of wells expected to produce some fluid. Some discussion of development of monitoring wells has taken place in the published literature. ASTM Standard D 5099 provides standard guidance for monitoring wells in granular aquifers. No such standard guidance should be considered limiting for methods used in environmental pumping wells. D 5099’s intent is to provide a minimum standard guidance for development, not to constrain methods that can be used. Standard ANSI NGWA 01 provides a state-of-the-art summary of methods and applications for pumping wells.

4.4.2 Development Method Descriptions There is a variety of development methods in use. In each case, the development of a fluid velocity in the near vicinity of the borehole is involved. Water is propelled out of the well bore and flows back in, breaking up films and mixing up the aquifer material and filter pack. There are many variations on basic approaches, and some methods are more effective than others. Preferably (and essentially in more delicate wells), the process starts gently, increases gradually in intensity, and continues as long as improvement results with a characteristic in-and-out fluid motion (Figure 4.3). One bit of information to remember is that proper well development for pumping wells takes time. It usually cannot be accomplished in half an hour, but takes some hours to fully break up drilling damage and to cause the desired sorting of formation particles. Developing just until visually clear is not enough. Another factor to remember is that not all formations can be satisfactorily developed. Wells in intervals consisting mostly of very fine particles may never develop properly, and further development may just increase turbidity. The following are descriptions of a number of conventional (pipe- and line-based) development methods that are widely employed. Monitoring and remediation well applications can employ a more limited tool kit than is available for water wells. Generally, overpumping with backflushing, surging (surge block), and jetting is employed. Application of these and other methods is discussed in Sections 4.4.3 and 4.4.4, as well as in Chapters 6 and 8.

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Reciprocating motion

Double surge block

Flow in and out of screen

Figure 4.3  The necessary in-and-out motion of proper well development.

4.4.2.1 Overpumping Overpumping (which can include bailing), a very common form of monitoring well development, brings material into the well for removal as the well is stressed by pumping. The well may be pumped at up to 1½ times the design pumping rate (if pump diameter permits), either continually or intermittently in an attempt to surge. A disadvantage of using this method alone is that overpumping and bailing, which lack the necessary in-and-out motion of optimal development actions, tend to pack formation fines against the filter pack. Conversely, backflushing packs fines against the borehole wall. These methods are not recommended for pumping well development or redevelopment. 4.4.2.2 Surging and Pumping or Bailing (Utilizing Surge Block) The surging development process is carried out by surging and bailing the well. The surging is done by a single or double solid (or valved) surge block with development water and sediment removed typically by airlift pumping. Surging should be conducted with tools capable of a 1 to 2 ft/s stroke and work the screen in 2–6 ft (1–2 m) sections, concentrating on known trouble spots. 4.4.2.2.1 Surging Mechanical surging forces water to flow into and out of the screen by operating a plunger-like surge block in an up-and-down motion in the casing (Figure 4.4). This is a highly effective method suitable for low-cost cable tool rigs. The device shown schematically in Figure 4.3 is a double surge block with capacity for pumping or

Prevention Practices for Sustainable Wells

(a)

(b) Figure 4.4  Example surge blocks (both double surge block tools).

97

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Figure 4.5  Example well cleaning brush (manufactured by Cotey Chemical Corp., figure courtesy of Kevin McGuiness).

airlift through the central tube (see following). This is the most efficient version of the tool. A variation on the surge block is the brush (Figure 4.5). This tool, also fitting on the cable tool line, works like a bottle brush to remove incrustation and biofouling on rock walls, casings, and screen surfaces. These tools are often combined. The brush illustrated here is a commercial model that features the use of street sweeper brushes, which clean deposits without ripping hunks from casing. Variations on this theme include the line swab, which incorporates a surge block and heavy bailer that is more tight fitting than a surge block, and slowly dragged upward, then downward to clean the screen interval and casing. The flapper valve of the bailer allows the tool to fall rapidly, enhancing the surge action in the formation outside the screen. 4.4.2.2.2 Surging and Pumping Pumping is conducted through the surge block, which incorporates a piece of the suction pipe in the fabrication of the block, at rates up to half of the design capacity. A variation of surging and pumping and overpumping, especially useful in smalldiameter wells, employs a well pump moved up and down with a reversible pump puller. Upon completion of the development work, the well is cleaned to the bottom.

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Where there is insufficient submergence for airlift pumping to work properly (see following), development can proceed using surging and pumping with a well pump. 4.4.2.3 Airlift Development Airlift development is perhaps the most widely used development method for surging and pumping, especially when rotary drilling is conducted. Additionally, it can be used wherever development is needed and an air compressor can be secured. Figure 4.6 is a schematic of an airlift apparatus. Air is applied in bursts at a controlled level to initiate a surging action in the well to loosen fines and deposits. In well redevelopment during maintenance (Chapter 6) and cleaning (Chapters 7 and 8), it is very useful for mixing chemicals. When it is desired to clear the well of deposits, sand, and debris, air is applied so that the solution is driven to the surface. As the water reaches the top of the casing or floods over into the receiving tank, the air supply is suddenly shut off and the water level allowed to drop. This action is repeated as long as necessary (or budget and patience permit). Care should be taken to ensure the free flow of ground water into the screen or intake zone. 4.4.2.3.1 General Air Development Procedure The process is performed either (1) by using a single pipe air pumping system using either the casing or the borehole itself as the eductor line (casing open) or with the casing closed to the atmosphere, or (2) with a dual-line air system employing an airintroducing pipe and an air and water eductor line. Compressors, airlines, hoses, fittings, etc., should be of adequate size to pump the well by the airlift method at 1½ to 2 times the design capacity of the well. Each case is specific in terms of depth, submergence, well diameter, and screen hydraulic

Air line Plug

Educator or pumping pipe Air pipe Well casing Well screen Air pipe in position to pump Air pipe in position to back-blow

Figure 4.6  Schematic of airlift development and pumping apparatus (North Dakota State University, Scherer, 2005).

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conductivity. For wells less than 300 ft in depth, with 60% submergence possible, approximately 0.75 cubic feet per minute (cfm) of air compressor capacity is needed per gpm of anticipated pumping rate. In practice, a 375 cfm compressor developing 100 psi can usually pump 400 to 500 gpm (approximately 44 to 67 cfm) of water with proper airline submergence. 4.4.2.3.2 Development Process 1. The first goal is to establish a piston effect (surging) and not to conduct airlift pumping. In surging, sufficient air is fed to raise the water level as high as possible, then released to let it drop. 2. Airlift pumping is then used to pump the well periodically to remove sediment from the screen or borehole. When the well yields clear debris-free water, the airline is lowered to a point below the bottom of the eductor line and air introduced until the water between the eductor pipe and the casing is raised to the surface. At this time the airline is raised back up into the eductor line, causing the water to be pumped from the well through the eductor line. The procedure of alternating the relative positions of the air and eductor line is repeated until the water yielded by the well remains clear when the well is surged and backwashed by this technique. Care must be taken to ensure that air does not enter the formation, but is only used to move the fluid, which carries the kinetic development force. Under some conditions, the aquifer may become air locked when a large burst of air is injected into the screen area of the well. Aquifers with good vertical hydraulic conductivity are generally not affected by air locking. 4.4.2.4 Jetting Jetting requires a high-pressure water pump to pump fluid into the well and through jets that turn water pressure into water velocity. Return pumping can be accomplished using either an air compressor for airlift or an installed water pump. A circulation can be set up once upward pumping is initiated. When working together, the jetting and pumping set up a circulation, with the jet pumping water under pressure into the formation material, and the water returning due to the suction pumping action. This removes the foreign water and fines and drilling debris. Figure 4.7 is a jetting system schematic. The jetting tool itself can be as simple as a sealed length of pipe with drilled holes of a proper diameter and orientation (for balance) to provide sufficient volume and velocity against the screen. Figure 4.8 shows examples. Tools can theoretically be of any diameter. Small monitoring well diameters provide an engineering challenge, however, and very large tools require quite large pumps. The outside diameter of the jetting tool must be 1 in. (about 25 mm) less in diameter than the screen inside diameter. The minimum exit velocity of the jetting fluid at the jet nozzle should be 150 ft/s (45 m/s). The tool is rotated at a speed less than 1 rpm and positioned at one level for not less than 2 min and then moved to the next level, which is no more than 6 in. (150 mm) vertically from the preceding jetting level. Pumping from the well should be at a rate of 5 to 15% more than the rate at

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Air pipe Well casing High pressure water Jetting tool Water jets Well screen

Figure 4.7  Jetting system schematic (North Dakota State University Extension, Scherer, 2005).

Figure 4.8  Jetting heads (Photo courtesy of Scott Deasy, Flatwater Fleet, Inc.).

which water is introduced through the jetting tool. Water to be used for jetting must contain less than 1 ppm suspended solids. Jetting alone without pumping will agitate formation material and dislodge fines, but tends to pack debris against the borehole wall and introduces chemically altered water to the formation. The simultaneous pumping, usually by airlift, alleviates this problem. Jetting is most effective in V-slot screens and less effective in machine-slotted or louvered screens due to jet deflection, a contention supported experimentally. Jetting is also really only effective in relatively permeable formation materials and filter packs due to the limited penetration of jetting flow into the formation material. It is less beneficial than surging (see following) in rock aquifer intervals where effective permeability is provided by relatively few, discrete fractures and bedding plane partings. Any fluids introduced must be of known and acceptable quality and developed out as soon as possible. Air used for airlift must be filtered to remove any residual compressor oil. If introduction of any air or altered fluid is unacceptable, jetting is usually precluded as an option.

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4.4.3 “Conventional” Development Choices Formations monitored in environmental studies and cleanups tend to contain a high percentage of fine material, and well screens may be correspondingly fine with very limited formation contact. Rock aquifers likewise often have discrete fracture and bedding plane permeability. Surging is more easily adapted for these low­permeability and high-percentage-fines formations than jetting, and does not require high-pressure pumping or the injection of foreign water. While jetting necessarily involves mechanical pumping, surging should also be done with power equipment, as hand surging is too hard to sustain to be effective, even with young weight-lifting graduate students on hand. The double surge-eductor pumping method version of surging helps to concentrate the surging action of the tool, and pumping brings loosened material out of the well instead of merely washing it back out on the downstroke. Such tools consist of a dual-wall pipe and double surge block (Figure 4.4). An eductor fitting is installed above the surge blocks in the pipe. Tools for this purpose are frequently driller fabricated, but commercially tools are available for small diameters (even for less than 2 in. I.D.). Prior to the use of this tool (if physically possible), material inside the casing should be vacuumed out using a suction tool. An airlift system with eductor pipe works very well. The development tool provides two actions: Gentle surging provides the agitation to remove fines in the formation-screen-pack area. A double surge block setup concentrates the surging action. The velocity of air pumped down the outer pipe and past the mouth of the eductor sets up a vacuum in the surge zone that removes water and solids (Figure 4.6). Variations on these methods are limited only by the creativity of the people employing them. Numerous tool developments combine elements of more than one method, as developers understand that multiple methods attack multiple clogging mechanisms. The best example in widespread use is the cable tool surge-eductor tool. Also, air tools have been adapted to provide a percussive force using pressure relief valves. One caution about surging or swabbing is that negative pressure should not exceed the collapse strength of the weakest well structure component (usually the screen or casing joints). For both jetting and surging with pumping, solids can be removed from effluent discharge water by settling (e.g., in a tank, which can also be used for flow rate estimation), and development water can be analyzed to monitor the well development progress. Figure 4.9 illustrates such a system in action during test drilling. This is the only objective way to evaluate well development effectiveness and to decide when to stop. Measure solids content and also check other indicative water quality parameters, such as pH, conductivity, and Eh for stabilization or evidence of changing water input (Figure 4.10), for example, new water-bearing zones encountered. Both surging and jetting should be done with considerable care, especially when developing typical monitoring, recovery, and domestic and smaller commercial wells since they are not often durably constructed (compared to many municipal water wells), are possibly deteriorated due to environmental attack, and may be more easily damaged.

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Diverter

Ope n di and scharge valv e

Tank for measuring flow rate

Figure 4.9  Airlift testing and development, test drilling in carbonate aquifer (Ohio). The illustrated system is set up to permit periodic flow testing by measuring tank fill volume over a set period of time.

Figure 4.10  Testing for field parameters during test drilling. pH, conductivity, temperature, and several key chemical parameters were measured in nonfiltered and filtered samples.

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Bailing and air surging without pumping are slow and do not permit good feedback on events downhole. Air surging alone, if overly vigorous, can also pack fines against the borehole wall and otherwise cause more damage than it solves in relatively delicate monitoring well environments. For typical monitoring and recovery well situations, two methods probably stand out as the most practical and safe for development: (1) jetting with airlift pumping and (2) double surge with airlift or eductor pumping. Both provide the in-and-out motion necessary to properly develop wells. When properly used, both provide sufficient agitation to clear fines from the formation material. Pumping clears fines from the well.

4.4.4 Fluid-Pulse Development A relatively hard-to-classify method was developed by several groups across the world, including Airburst (Frazier Industries), AirShock (ProWell Technologies, Arava, Israel), and hydropuls® (TLM GmbH, Markkleeberg, Germany). Layne Christensen’s Boreblast mark uses the AirShock system under license. These systems utilize a seismic air tool, originally developed for marine seismic signal generation. The tool releases a burst of air of a specific volume and pressure, rapidly displacing water (air displacement of 1 m in 1 ms) and generating a high-pressure percussive wave, then a negative pressure and a return flow as the air bubble collapses. The tool’s force characteristics can be calibrated infinitely over a large range by selecting tool and chamber size and air or gas pressure up to 3,000 psi. Force can rival shooting forces (up to 0.5 kg of dynamite), but the system can also be used selectively inside of well screens. More technical descriptions and illustrations are provided in Chapter 8. Hydrofracturing (injection of water and sometimes additives under high pressure) is mainly used in primary development and not redevelopment. This technique is used to open fractures and apertures, primarily in crystalline rock aquifers. A significant advantage of fluid-pulse methods is the capacity to be used in an iterative fashion, for example, “shooting” at foot or meter intervals (fired every 4–10 s) up and down a borehole interval, adjusting the tool’s characteristics in response to results (compared to shooting or other “force” methods of development, which offer a “one-shot” effort each time). Fluid-pulse methods may be used alone or in combination with chemicals and other tools. Using compressed gas or air alone is inherently low risk, and liability and legal aspects of explosives handling are avoided, as is hauling fluids. Thus, the system is highly portable as well. Cleaning projects can be relatively rapid (1–2 h). The full potential for water production can be realized only by the use of such development procedures. Water quality can be severely degraded by excessive amounts of sediment, and therefore causes unwarranted wear on pumps and increased pumping costs. Well development is not expensive in the long run, considering the improvement in yields and the elimination of sand pumping.

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4.4.5 Other Care Issues in Development and Redevelopment



1. Understand well structural limits: To avoid applying forces on the casing, screen, and grout that are beyond their capacity for resistance, care and attention to detail are required in development and redevelopment. Sufficient force, efficiently supplied, is needed to set formation particles in motion and to sheer off incrustation. However, this does not have to be a violent force that damages the well. For example, causing an excessive difference in hydrologic pressure between the outside and inside of a casing may result in casing distortion. Sharp shock loading or unloading of some well screens may cause distortion or collapse. And dislodged particles and rock fragments can break plastic casing. 2. Development typically should proceed in 3–6 ft (1–2 m) segments. 3. Tools should not impact sharply against casing joints or screen rods.

4.5 Preventing Contamination during Drilling, Well Construction, and Development Drilling and development, as well as other well intrusions such as pump service, will never be sterile or really contamination-free. On the other hand, shallow aquifers have such large microbial populations that bacteria introduced during drilling are inconsequential, anyway, in the development of well biofouling. Still, steps are available to minimize contamination from tools and limit drilling damage. One favorite tactic in water well construction in preventing microbial contamination is the liberal use of chlorination in preparing tools, treating the well during construction, and disinfecting gravel pack materials. Chlorination during monitoring and recovery well construction presents a host of problems, however, by drastically changing the aquifer environment locally and interfering with sample quality. In any case, good cleanliness practice should prevail, as a matter of quality assurance. Tools, cables, pipes, wires, etc., should be free of visible dirt, oil, grease, etc. It is a good practice to keep tools up off the soil surface and to decontaminate tools before introduction to the well. The most sure decontamination for drilling tools and components is steam cleaning. While it is not reliable for sterilization, steam cleaning at least gets the tools clean and relatively free of organic matter. These steps are normally taken in any case on monitoring and remediation well installations. There is just another reason to do so not only on environmental jobs, but on water well jobs also. Development tools, cable tool bailers, and drill tools should be handled in such a way at the surface as to minimize contamination. All equipment and material to be installed in a well that is not prewrapped and ensured clean (certainly a rare situation) must be decontaminated just prior to installation. These are not onerous procedures. This can be done by steam cleaning with an Alconox (or similar) wash and filtered water rinse, such as described sketchily in ASTM Standard Guide D 5088, followed by repeat steam cleaning to limit bacteria. However, it is important to realize that despite such measures (which will clean tools), there is no sterilization possible under any known procedure for drilling and well construction tools and equipment.

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Rant There is no technical reason why tools and pipe (casing and pump pipe) and wire cannot be kept out of the dirt on racks or on plastic, covered when not in use, and cleaned and disinfected prior to insertion. It just takes organization. Develop a site plan for a specific rig setup ahead of time. Lead driller leadership on the job site can enforce organization to make this happen. Warning: This may cut into the cell phone and cigarette time of driller helpers. If you are a contractor and routinely do this, and your competitors do not, educate your clientele to include these sanitation measures in specifications and site requirements. In spite of reservations about chlorination in environmental practice, prechlorinated water should be used for make-up water for cable tool drilling, circulation water for mud rotary, and in air injection. The water may be treated and stored in closed, disinfected tanks vented to allow chlorine to dissipate. Air used in drilling should be filtered to remove compressor oil. Simply keeping the solids contents of fluids to a minimum, minimizing the use of biodegradable polymers, and using mud tanks instead of dug pits are good practices to limit contamination. Drilling additives suppliers have made recommendations for mud control, tank designs, and chlorine levels for many years. Extensive discussion of fluids control is provided in industry publications (see our reading list— we especially recommend Drilling: The Manual of Methods, Applications, and Management). Biodegradable polymer circulating fluids and lubricating oils have some following in the monitoring well drilling field, especially for coring and directional wells, due to their capacity to break down, thus minimizing development and core interference. In the hands of experienced and skilled drillers, they have a place as long as it can be ensured that the by-products are all removed. It should be remembered, however, that the breakers used also interfere with ground-water quality, and that breakdown is seldom complete. Substrates remain that can be used by bacteria for food, and thus biofouling may be enhanced. Since biofouling interferes with sample quality, many of the advantages of polymers (relative to bentonite muds) in limiting formation interference may be negated. For any well construction method, especially those using added fluids, proper well development to remove the foreign water is both feasible and desirable. Proper development is therefore, for many reasons, a good place to start in the preventive maintenance treatment of a well.

4.6 Preventative Pump Choices and Actions Prevention should be considered in how the well is equipped and used after it is constructed. Preventative decision making begins with deliberate decisions to choose minimal-maintenance pumps and to protect them to the extent possible.

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4.6.1 Pump Selection Pump selection can be something of an afterthought for domestic water supply and remediation wells, although it is often well thought out for larger pumping wells and monitoring wells in most cases. Pump selection options have improved in recent years with the introduction of improved designs based on years of experience in the field. The pump’s service life is a definite consideration in well design and construction because of the high cost of pump repair and replacement, as well as the reliability of the installation. If a pump fails or works poorly, the well usually cannot do its job as a sampling point or means of managing a contamination plume. In general terms, pumps should be selected for good service life under the conditions that will be encountered in the wells. They should also be protected as well as possible from unnecessary environmental attack. For example, manufacturers and specifiers of well pumping equipment, as well as evolving consensus standards (most notably, the new NGWA Water Well Construction Standards), recommend that wells be thoroughly developed to limit abrasives in the pumped water (see above discussion). Screens on the pump intake may stop larger particles that may come through. Certain pump types are designed to perform under sand-pumping conditions. There is certainly a benefit to this, in that it provides a margin for error. However, sand or silt pumping is an indication of a well structural problem that should not be ignored. In extraction pumping wells in which silt intrusion cannot be fully controlled by the screen and pack, flow modification using suction flow control devices (SFCDs) or similarly engineered tail pipes has shown good results in halting or reducing it to less than 1% of the previous level. See Section 4.6.2, Ehrhardt and Pelzer (1992), and Chapters 2 and 3 in the upcoming International Manual of Well Hydraulics (ASCE, in press) in our recommended reading list. Evaluate wells individually for efficacy. Most pump types do not do well when pumping dry, especially submersible centrifugal types. In fact, submersible pumps are designed to operate within specific temperature, power quality, and intake head ranges. Output should be adjusted if necessary to avoid drawdown to the intake of the pump. Power supply and electrical protection are important considerations in keeping pumps operating. Selections in our recommended reading list describe power supply and protection considerations in detail. Also, pump manufacturer sales and specification literature should be consulted for specific pump requirements and recommendations. In any case, pump performance should be monitored and parts inspected on a regular basis. More on that is provided in the following and later sections on well maintenance and well reconstruction (Chapters 5 and 7–9). 4.6.1.1 Pumps in Water Supply and Other Extraction (or Abstraction) Wells In the past, remediation wells were simply equipped with off-the-shelf submersible well pumps designed for water wells, and this is still often the case. Such pumps are designed to pump essentially clean water at reasonable efficiency with ten- to twenty-year life cycles. Alternatively, dewatering type eductor pump systems may be employed in very shallow conditions, especially for plume control.

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Submersible well pumps have improved tremendously in service reliability in recent years. Corrodible materials have generally been replaced by noncorrodible plastics and stainless steel. Motors have improved service life, and most are directly water cooled. The general service submersible well pump is perhaps the most reliable device in the ground-water industry. Eductor pump systems have no moving parts at the pump end, relying on jet action to aspirate water upward. Water power is applied by surface-mounted centrifugal pumps. Such systems have a lengthy history of service in dewatering projects, and geotechnical engineers designing similar contamination control projects naturally employed this type of system. Still, not all such pumps do well in remediation wells. Silt, silica, carbonate scale, and excessive metallic oxides are abrasive, and quickly wear plastic impellers, seals, and bearings in centrifugal pumps. Corrosive conditions may exceed the designed limits of stainless steel components intended for use in circum-neutral pH well water. The small volute channels of submersible pumps (even those designed and priced for environmental applications) provide a flow restriction where fouling deposits tend to accumulate (sometimes in days to weeks). Until there is some design breakthrough, this will continue to be a maintenance consideration. Eductor pumps are vulnerable to clogging by metallic oxides and other solids. When water containing high levels of iron is exposed to the oxidation occurring as eductors pump air, clogging can occur rapidly. Iron biofouling can seal off eductors as well as the water circulation system very rapidly. This is a problem in shallow, organic-rich ground water even without human-caused organic contamination. Power systems are important considerations for extraction well pumps as well as those for monitoring wells. Power supply and control considerations relevant to environmental projects are discussed in detail in other literature (see the list). Power to dedicated pumps should be consistent and secure. The voltage, amperage, and phase balance should closely match the requirements of the pump. Connections should be secure and weatherproof. Control boxes should be sealed from moisture and shielded from excessive dust, sunlight, heat, and cold (not always easy on a remediation site). Cables running to wells should be routed away from heavy traffic or excavation and protected from crushing. Lines should be clearly marked and respected. On long-term projects, power systems and boxes should be vandal resistant. In potentially explosive atmosphere situations, controls should also be spark resistant, meeting relevant code standards for this purpose. 4.6.1.2 Pumps in Monitoring Wells Pumps used in monitoring may be either dedicated (installed permanently in a well and not moved) or portable (used repeatedly in different boreholes or wells). The choice is determined by the project requirements, and characteristics of these pumps are considered here from a maintenance point of view. The reader is recommended to industry literature and developing ASTM standard guides as they become available for pump selection from a sampling quality standpoint.

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4.6.1.2.1 Dedicated Monitoring Well Pumps Monitoring wells that are designed for long-term use are frequently equipped with dedicated pumping-sampling installations. These are intended to work in place for long periods, often in aggressive conditions, so their proper selection and maintenance is of interest for good service. Most of these dedicated pumps are at present of the bladder type design, with the pump at the designated pumping level, connected to the surface via discharge tubes and airlines used to transmit compressed gas to the bladder. Bladder pumps resist clogging, and the bladders generally are not subject to abrasive wear at the low flow rates used in ground-water sampling. Stainless steel submersible centrifugal pumps designed for monitoring well applications also are showing good service in silty water at least for short periods. Neither manufacturers of dedicated bladder pump units nor those manufacturing submersibles report significant maintenance problems with the pump ends in general use if abrasives are limited. However, if abrasives are present, check valves and tubing may experience scour. Most problems experienced with dedicated pumping units occur above the water level (static or pumping). Both discharge tubing and airlines, as well as their fittings, are prone to freezing in cold conditions unless protected. Provision for heaters can be made to keep the air in the well column above freezing. Wellhead fittings should be covered in any case, and can be heated also if necessary. Heated casing columns or wellheads should be vented to exhaust volatiles and humidity. Gas used for pump power in sampling pumps should be as dry as possible to limit condensation (and freezing in cold climates) in the airlines. 4.6.1.2.2 Portable Pumps and Bailers For the purposes of well maintenance planning, portable pumps transported from well to well pose different types of long-term maintenance questions. The pumps are more accessible and not exposed for long periods to corrosive water. The main maintenance concern here is service under difficult site conditions, including abusive or careless use and ease of repair and decontamination. The quality of the pumped water has to be a consideration since water containing abrasive solids can clog or wear pumps and can be difficult to clean out. Oily water may cling to pump and line surfaces and require frequent detergent washing. Mechanical matters also come into play. For pumps that are repeatedly inserted into and withdrawn from wells, it is important to pay attention to line abrasion and bending at cable or airline motor junctions. Field washing and decontamination can become a mechanical concern if deionized water freezes in the pump mechanism or lines (a problem below 20°F (–6.7°C) air temperature). In pump selection, if a particular pump type contemplated for project use is likely to become a maintenance problem, avoiding that type is step one in pump maintenance decision making. Care must also be taken with electrically powered pumps that the power supply matches the characteristics of the motor. Check connections and generator or inverter output to make sure the right volts and amps are consistently being supplied.

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Manufacturers supply detailed service and troubleshooting instructions should be read and not just filed. Besides being concerned with the pumps, it should be noted that pump insertion and extraction can also damage well casings and screens. If maintenance and reliable operation are major concerns in the project being planned, bailers dedicated to individual wells have many advantages. Bailers have no moving parts aside from balls and stopcock valves. They require no power transmission via airline or cable, and are not prone to clogging in routine use. Stopcocks and check valves may block open or closed with silt or sand. Problems then can be limited to the human operators. Difficult or slow purging, sample aeration, contamination, and other factors may weigh against bailers from a sampling viewpoint, but from a maintenance angle, they are simple and reliable in operation.

4.6.2 Pump Protection Once selected based on their characteristics and installed, steps need to be taken to protect pumps in operation (Figure 4.11). The two biggest problems are power supply and mechanical clogging and wear. Power protection involves isolation from power surges (line or lightning), including abnormal fluctuations in both voltage and amperage (which may be due to the utility supply’s weaknesses). Electrical motors should be securely grounded to an adequate, dead ground separate from the well to redirect line surges and stray currents.

Figure 4.11  Well pump electrical system protection (photo by Gary L. Hix).

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Prevention Practices for Sustainable Wells Suction flow control device (engineered tailpipe) function in a pumping well (Eucastream SFCD)

Pump jacket x x

Control element

Vh (x) + const

L??

Vh (X) = const Slots

Represents entrance velocity (proportionally to intale length)

dws db

dws db

Figure 4.12  Schematic of suction flow control device (Eucastream SFCD design, Kabelwerk Eupen AG product literature, Eufor S.A., Eupen, Belgium).

Submersible motors should be protected from running dry and all motors from running hot. If loss of submergence or flow along the submersible motor is likely, it should be equipped with sensors to cut off power if temperature or flow may vary from established norms. Use pump power protectors that cut off power if it is outside tolerances. A simple means of protecting submersible well pumps is the pump shroud, which is basically just a pipe that fits over the pump, forcing water to flow up along the motor to cool the motor as intended. Especially where screens cannot fully prevent inmigration of particles, pumps need to be protected against sand and silt pumping to limit wear. There are a number of approaches to take. Including an integral suction flow control device (SFCD) (Figure 4.12) or engineered pump intake is one option in the well intake design of pumping extraction wells that prevents sand and silt pumping, and also buys time before screen performance decline due to encrustation begins. The SFCD or engineered pump tail pipe is designed for both submersible and lineshaft turbine pumps. It extends down to the bottom of the screen, and all pumped flow is forced through it. The SFCD intake perforation profile makes it more hydraulically open at the bottom of the intake pipe than at the top. The upper part of the screen is where most flow tends to enter the screen in a conventional pumped borehole well, since the pressure is lower near the pump intake. The effect is to force a more cylindrical flow into the well (Figure 4.12).

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SFCDs have a demonstrated track record in reducing sand and turbidity, even under difficult conditions. SFCDs can also serve to reduce encrustation effects by making the entrance velocity more uniform. In some very shallow wells and in other situations where an SFCD may not be suitable (e.g., where the ratio screen length to screen diameter is less than approximately 30), available, or feasible to install, centrifugal sand separators can be mounted on the well pump to remove sand prior to entering the pump intake (Figure 4.13). How it Works

Pump enclosure shell

Submersible pump motor 1 Sandy water enters through tangential inlet slots and begins to swirl inside 2 Centrifugal action pushes sand to outer wall “Sand-free” water is drawn by the swirling vortex to the pump’s intake

4 Sand particles fall to the bottom and are purged through flexible “Flapper Valve” deep into well

Figure 4.13  Sand separator for submersible pump installation (illustration courtesy of LAKOS Separators and Filtration Systems).

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These discharge sand to the bottom of the well, but some field experience suggests that it ceases to pile up after a hydraulic equilibrium is reached. One drawback to discharging sand to the bottom in pumped wells that are monitored for quality is that particulates may hold and intermittently desorb constituents. Such accumulations can also harbor coliform bacteria and other undesirable microflora. Well design and selection is ideally the time when preventive material and process section and maintenance should start. Maintenance takes over as the operational issue once the system is constructed. This is considered next in Chapters 5 and 6.

4.7 Design Aspects: The “Cliff Notes” Version A variety of design considerations can serve to prevent or slow well system deterioration and facilitate maintenance and rehabilitation in the future. In many cases, the improvements cost little or no more than inferior designs and materials initially, and they save money in life cycle costs. Corrosion- and deterioration-resistant materials slow the deterioration of well components and limit recurrence of preventable problems, making the success of maintenance actions more likely. Specific to well equipment, PVC casing, for example, is corrosion resistant and suitable for most applications. Alternative metal casings are available where plastic or fiberglass casings are not suitable. Notable product developments that may seem new to some, but have actually been available for more than twenty years, include the widespread availability of all-stainless-steel and stainless-and-plastic pumps, high-quality rigid plastic pump discharge (drop) pipe with twist-on-twist-off or spline-lock connections (e.g., Certa-Lok), and flexible Wellmaster™ (Kidde Wellmaster) or Boreline (Hose Solutions) discharge hose (specifically designed for well pump use) composed of reliable, high-strength, corrosionresistant material that permits easy pump service. Relatively smooth pump interior surfaces and corrosion resistance increase intervals between pump service events. Pump motor and discharge-end product lines can seem to have a remarkable sameness in a competitive market. On the other hand, pumps may be marketed for environmental duty, which may not be superior to other products for aggressive ground-water pumping applications. Some considerations include:





1. Pump end material selection: a. A material designation of “stainless steel” includes a range of corrosion-resistant alloys. Some do well in anaerobic environments typical of high-organic-carbon water (e.g., Type 316 and better) and some do not (Type 304). b. Welding and stamping alters the corrosion-resistant characteristics of stainless steel alloys, so that the manufactured product may not match the resistance of the unaltered alloy. In some cases, a cast stainless bowl selection may be superior. c. While versatile, stainless steel may not suit every situation. In some high-chloride, biocorrosive environments, only high-silicon bronze or plastics may provide suitable service life.

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2. Pump end hydraulic efficiency: Higher-efficiency pump ends are recommended. Pump impeller-bowl designs and numbers of stages should be matched to the operating head conditions. 3. Achieving a balance of equipment features: Because exact matches to conditions and ideals may not be possible, pump choice may be a balance of features. In general, the highest-efficiency pump models should be used. Exceptions occur where service is so severe that short operating life spans can make more expensive, tunable pumps not cost-effective to operate. In these cases (particularly where efficiency differences are minor), low-priced but serviceable pumps that can be discarded and replaced or cleaned may be the better option.

Once selected, make provisions to protect the pump and to give it as favorable an environment as is possible, for example, installing an engineered tail pipe or SFCD, desander, or pump shroud (Sections 4.6.1 and 4.6.2). A maintenance-friendly wellhead design and completion are important to minimize the difficulty of performing maintenance. Issues include meeting limits to avoid confined space designation, making the well seal secure but removable, and making discharge head and instrument connections easy to detach. Table 4.1 provides recommendations for wellhead features to facilitate maintenance. Automated water level and pumping rate information facilitates data analysis and planning. Devices exist to provide real-time water level and discharge rate measurements without personnel being on site. SCADA (supervisory, control, and data acquisition) systems originally developed for process treatment can be adapted for well fields, permitting rapid, easy, and continuous monitoring of well and pump hydraulic performance, and even physical-chemical changes. Pump controllers help to maintain regular current flow of the proper characteristics and phase to pump motors, prolonging motor life and shielding motors from line surges. All pump motors should be equipped with automatic controllers. Two points should be kept in mind for wellhead chemical treatment:



1. Hydrants: A valved hydrant should be installed between the well pitless discharge and the well house flow meter–valve assembly for discharge to waste during treatment (Figure  4.14). Several suitable self-draining hydrant styles approved for potable water distribution are available on the market (adhering to standard ANSI/AWWA C503). During the well treatment process, a hose may be run from the blow-off hydrant to containment and treatment. 2. Systems have been developed to systematically redevelop with the pump in place, and they are designed to provide treatment chemicals to the screen where past pump-in-place designs were not effective. These should be considered as maintenance treatment options.

4.8 A Note about Well Houses Many wells (particularly in cold climates) for larger water systems feature well houses. Designs for these can be remarkably unfriendly for maintenance. At times,

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Prevention Practices for Sustainable Wells Frost-Free Blow-off Hydrant Examples (Kuperferle Foundry) Underground installation

Above ground installation

Shut off valve

Ground line

4" MJ inlet 4" FIP outlet & plug Specially depth of bury Install in meter box #7600

4" MJ inlet 4" Riser & plug Specially depth of bury #7500

Figure 4.14  Blow-off hydrant examples (photos courtesy of Kupferle Foundry Company, illustration modified).

their designs have contributed to serious injury. Besides that, they slow down work and make it awkward. Some recommendations include:

1. The roof should either (a) come off completely or (b) feature a hatch big enough to remove any well equipment (and other heavy objects in the well house). 2. There should be direct line-of-sight visibility between where a hoist crane can be set up and the top of the well casing. 3. There should be wide access into the building to permit removal of large objects. Roll-up doors are good for this. 4. If possible, make the entire structure removable. 5. The well itself can be located outside the well house, using a pitless adapter, so that pump removal and well cleaning do not involve the building at all.

Although housing another application (a wastewater plant pump station), Figure  4.15 illustrates a highly useful pump house design: big enough to house a lineshaft pump motor, valves, flow meter, and controls (and more). It can be unbolted from the pad and lifted off by the pump crane (note hoisting rings).

4.9 Well Array Design Recommendations

1. Have enough wells installed in a pumping or injection array to permit continued withdrawal operation or plume control while wells are out of service (being treated or pumps replaced).

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Figure 4.15  Example easy-to-service well house.





2. Install a ring of treatment wells around pumping or injection wells subject to clogging (where this is permitted by regulation). Example locations would be aging wellfields in which aquifer clogging is becoming significant or recovery well arrays operating in severely clogging conditions. Treatment wells can greatly improve treatment success in the near-well formation by providing a way to force treatment chemicals toward the pumping well screen from the outside, and also by providing more access for agitation of the near-well formation. One regulatory impediment in the United States is the classification by state regulators (e.g., in Ohio) of such wells as Class V injection wells. Such designation imposes licensing requirements, including fees that may make them uneconomical to install and use. 3. On sites with very deep wells, options 1 and 2 may be quite expensive. In these cases, where both replacement and rehabilitation may be very expensive and difficult, designing and planning for a rigorous maintenance defense of the existing pumping wells is especially important.

4.10 A Developing World Note As you read this, you may be sitting under a tree or near your vintage Toyota Land Cruiser, somewhere outside of North America (or maybe in your Ford F250 in a remote location on Native American land). You say, “All this is well and good for you there in the North, but we do not have all of these things. We do not even have

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well-rounded filter pack. We’re happy to have filter pack and PVC casing!” Some general principles still apply:



1. A suitable borehole diameter for grout and filter pack is more important than ever. 2. Install grout of correct proportions, mixed properly. You may need to improvise to develop a good grout using local materials, such as laterite clays that have good qualities, especially as cement is expensive in many places. 3. Choose those screen slots—regularly machine-slotted—carefully. 4. As in the old movie The Graduate, the answer is [sufficiently thick, potablewater-use, high-quality] “Plastics.” PVC and composite screens, casing, and pipe are a big help. They also can be made “in country” and are easier to transport. Maybe soon they will be made from polymers derived from materials common to the developing world. 5. Filter pack: When using a pile of pyroclastic quartzite, screen to a suitable size and wash thoroughly, then chlorinate. Bag in clean, washed agricultural bags such as used for maize or sim sim. 6. Develop more than recommended for those nice, rounded, glacially sorted quartz North American filter packs. Your hourly rate is low. 7. Use good pumps. Yes, they are expensive, but quality pays for itself. 8. Use power protection for both line power and generators. Pump off-peak for better quality. Choose three-phase pumps where possible. 9. Keep downhole components up off the ground where the cattle walk.

Monitoring 5 Maintenance Programs for Wells Once wells are designed and installed, and in operation, they must be maintained to prevent or slow deteriorating conditions. Again, if you need a cure, go ahead and make it happen, but come back here to see how to avoid a recurrence.

5.1 Maintenance Monitoring: Rationale for Instituting a Monitoring Program Once design, construction, and development are completed, well maintenance has to begin, based on a preconceived maintenance plan regularly modified to fit the installation conditions. Despite design and care in construction and development, well deterioration happens. Aquifer water quality problems on ground-water remediation projects are inevitably particularly difficult. Future problems with wells are likely to occur, and just have to be planned for and dealt with. There is a cost to preventive maintenance in operator time, contractor and consultant assistance, maintenance contracts, spare parts and equipment, analyses, and record keeping. The cost-benefit decisions on well maintenance depend on the local situation. However, studies and experience have shown the following general relationship for municipal water wells: over a twenty-year period, a program of preventive maintenance monitoring and treatment costs approximately 40% of the cost of a strategy of running a well to failure, then fixing problems. This essentially saves buying a new well. The cost of rehabilitation (the actions that bring an impaired well back to satisfactory performance) over twenty years can range from 10% to over 100% of new well construction (that is, the act of well construction alone). The high-end value can seem daunting. As discussed elsewhere (e.g., Chapters 3, 4, 7, and 8), some wells are valuable or irreplaceable where they are. Thus, investment in these tasks can be worth it. Such calculations obviously depend on the cost and difficulty of well construction in any one place, and the difficulty of the operational environment. There will be a wide range. Figure  5.1 illustrates a decision-making flowchart illustrating some of the factors involved in making rehabilitation vs. maintenance cost decisions. With smaller installations, including smaller water supply systems and monitoring and recovery well systems, the direct cost of preventive maintenance and rehabilitation is at first glance relatively more similar in cost to new construction. This is due to the relatively fixed costs of maintenance and rehabilitation that are, percentagewise, higher in relation to the cost of new construction for smaller installations.

119

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation < 85% target specific capacity

Conducts step-drawdown tests

Conduct rehabilitation Inspections: Video, tests

≥ 85% target specific capacity

Begin, continue maintenance program

With recovery comes the need to apply regular preventative maintenance with radical treatments when required

Figure 5.1  Well decision-making flowchart.

Note:  In case you are unfamiliar with “smaller” ground-water extraction systems, a ground-water cleanup recovery well and a smaller water supply well serving a house, farmstead, or mobile home park greatly resemble one another. You have a 5- or 6-in. PVC casing housing an inexpensive submersible pump. In other words, they are at the lower end of the construction cost scale—not as inherently valuable as a highcapacity well system. It is important to remember that considering direct costs of various options alone can provide a distorted picture. Considering direct, immediate costs alone tends to exclude some real operational expenses (e.g., impacts on water treatment costs, such as filter backwashing) and also the implications of future problems temporarily avoided. For example, rehabilitation and new construction involve the personnel expense of submitting rehabilitation plans or new designs to the authorities, the meetings, the questions, etc. Maintenance minimizes the need for such planning work, especially if the maintenance plan is part of the initial facilities plan. Maintenance flies under the regulatory radar, and evidence of it builds confidence in your credibility. New well construction may simply serve to temporarily avoid recurrence of a problem. Current experience is demonstrating that clogging, biofouling, and Fe/Mn/S transformations may extend several meters away from existing problem wells. Wellfields in operation for several decades likely have a subsurface environment prone to biofouling covering the entire area of the asset. The need to control or monitor plumes usually constrains where new wells can be placed. Of necessity, a replacement well must operate in the same challenging locations as the abandoned problem well, and subsequently fall rapidly to the same symptoms. Do not have any illusions about a new well installed near abandoned clogged wells. The symptoms will recur sooner or later—assume sooner. Well maintenance is therefore the better option than abandonment and new construction when existing well systems are well designed and constructed, because the old problem cannot be easily avoided. Where existing failing wells are not up to current standards and are tagged for abandonment, the performance problem of the former wells cannot be considered solved by installing new wells. Well deterioration that is no less aggressive than the old problem will recur with the new wells unless a maintenance program is implemented.

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Finally, regardless of comparative costs, you should consider the question, “What is the value of smooth operation (a reliable level of service (LOS)—Section 3.2) to your facility?” when making management decisions about maintenance. This is what is known as an externality— it has value, but this value can be subjective, although it can and should be quantified as discussed in Chapter 3. As in the operation of any engineered system (e.g., trucks or nuclear power plants), maintenance of monitoring and remediation well arrays and their attached systems preserves valuable assets and keeps them up and running. Preventive maintenance, even if the costs are high, are budgeted items and scheduled events. Well rehabilitation, by contrast, is conducted under emergency circumstances, is never convenient, and was probably not in the budget. The collective act of systematic tracking, assessment, and maintenance of systems is now lumped under the term asset management (Section 3.2). A choice in favor of intentional well maintenance is simply a decision to consider well systems to be genuine physical assets, just like a fleet of trucks or a water treatment plant, part of asset management rather than throwaway items or mere “holes in the ground.” They are extensions of your facility that happen to be underground. Management systems of engineering companies consider regular cost control and regular preventive maintenance as part of the cost of operating physical assets. In the case of a household or community water supply, that well is a drinking water source and who wants to tolerate a deteriorating, nasty water source? The principles are otherwise precisely the same for wells as for other mechanical assets that are expected to work without much attention in a hostile environment: none works well if it is neglected. Like vehicles and wastewater plants, well systems are more expensive to fix and replace than to maintain properly over their life cycles (Section 3.1.2). Strategies that result in premature replacement of wells and associated systems, such as pumps, drive up system life cycle cost (LCC). Unlike vehicles and wastewater plants (and more like underground storage tanks), problems with wells are not visibly apparent. Rational, systematic well maintenance is, however, entirely possible. Routine well maintenance as envisioned here has a short modern engineering history, but where systematic maintenance inspection, monitoring, and treatment have been employed, they have visibly reduced clogging and other impacts on well performance, piping, and filtration and treatment equipment.

Maintenance, Stewardship, Husbandry, and Other Value Judgments We get caught in our “silos” of various industries and disciplines, where we do not look at the examples of others. The asset management industry is productive to mine for techniques, and the maintenance ethic we are preaching here is analogous to land stewardship or husbandry in agriculture. If you take care of the land, it takes care of you. This is a sustainable system (sustainable is in the title of this book).

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5.2 Maintenance Procedures Overview Wells are best maintained by a preventive maintenance program that involves a combination of regular monitoring of their physical condition and well performance factors, and reconstructive maintenance and preventive treatments as necessary. Maintenance monitoring is monitoring of well physical, hydraulic, and water quality factors for the purpose of detecting deterioration conditions. Reconstructive maintenance is replacement of well and pump components on an as-needed or scheduled basis. Preventive treatments are redevelopment or chemical treatments applied before significant, irreversible performance decline occurs, often on a schedule once the rate of corrosion, biofouling, etc., is known. Rehabilitation is the next resort when a well’s performance is allowed to deteriorate too far. The last step is abandonment and starting over. If well failure and replacement has had to happen in the course of events, then the well system manager has a chance to “get religion,” implementing a maintenance program to prevent or delay a recurrence.

5.3 Implementing a Maintenance Program— It’s Institutional, Not Personal The primary task in a preventive maintenance program is first of all to make the institutional commitment to perform preventive maintenance on wells, assuming that well deterioration is a potentially serious and costly problem. It is hoped that the case for this assumption has been amply made here. The commitment has to be institutional and not the personal mission of one facilities manager, who may die, retire, storm off in disgust, divorce the boss, or otherwise move on next month, although it typically starts that way. One individual has a vision (based on possibly bitter experience) that a preventive maintenance program is needed. That person influences others with this worldview. If it remains the personal commitment of one person only, the momentum toward a maintenance program is lost in the transition until the next manager encounters a crisis.

5.4 Maintenance Is Personal (and Personnel), Too Experience shows that the combined sensory-analytical systems of animals (including humans) often outperform physical-electronic instruments. Humans working with critical systems (cavalry horse, steam engine, turbine, well pump) develop sensitivity to subtle behaviors and sounds of that system and are able to detect if there has been a change in the system. Most of us are familiar with being in tune with our motor vehicles. Is there a new squeak? Greater roll and sway during cornering? A rapid tick when accelerating uphill? We know these sounds are warnings. Engine tuning by ear used to be an important mechanic’s art, but is now less important due to the dominance of electronic controls on newer vehicles. Relative to wells, pump wear and line clogging result in changes in sound during pumping. Increased drawdown may be detected due to cascading or a change in the

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sound of recovery. Women at village wells know when the pump foot valve is worn: It takes longer and more strokes for water to come to the surface! The jugs and buckets line up longer and longer. The human mind can also make leaps of logic, often referred to as intuition, about conditions based on such sensory input. The trained operator will make such a deduction, follow it up with some confirmatory measurement, and document the issue. Such deductions are more likely to be valid if the person is better informed. Having a trained and equipped person around who is familiar with the wells operated by a facility makes use of these talents and capabilities. Such capability takes time, so nurturing and maintaining staff for long periods is important. Longevity alone is not sufficient. They person has to listen and feel, too. This means that the person has to care. What if we developed dogs trained to use their sensory capabilities to detect biofouling in its early stages? Resistance: The following is going to require some hands-on attention and effort. However, people (especially North American private well owners, who rely on the well water being a pure water source) resist doing maintenance testing, inspection, and record keeping. Then they are upset when deterioration happens. It is time for the ground-water industry, water supply, and health oversight sectors to insist maintenance efforts must be performed.

5.5 Maintenance Basics As in any kind of maintenance, well maintenance includes some simple asset-protecting activities. Among these are simply knowing where wells are, making sure they are accessible and visible, making sure records are kept and available (and not buried in a file cabinet at some off-site office), and checking on their surface equipment. Are the caps on? Are the locks working? Are the well tops visible and properly labeled? Are their well construction (as built) records available? Do pumps operate within nominal ranges?

5.5.1 Well System Maintenance Records Well records are among the most valuable tools in well maintenance because they provide the necessary dimensions and history to make maintenance and rehabilitation effective. Without records, maintenance and rehabilitation are much less certain of success, and more prone to failure. In addition to construction data, the maintenance system should have an accurate record of well operational information and data, such as water quality, recorded over time. These records should be organized in a logical fashion within the framework of the facility’s management system, and readily accessible to people in the organization concerned with well maintenance (but not to just anyone, for security reasons). Such a record system may consist solely of hard-copy paper files or may include a database spreadsheet system, such as is presumably available and familiar to the vast majority of managers of monitoring and remediation programs. Ideally, the computerized system speeds data retrieval and analysis (if designed and used properly).

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We are not living out a Dilbert cartoon, are we? Specific well system management software is available (but must be modified to exactly fit a certain facility’s needs). Business type spreadsheet database software may suffice (often combined with geographic information systems (GIS)), and can be adapted by a knowledgeable team of computer and water well people to fit the well maintenance needs of the facility. Computer systems should be securely backed up—preferably off-site—and augmented by hard-copy or image (e.g., pdf, jpg) files of existing hard-copy documents, such as well logs, invoices for services, and test results. In actuality, critical summary information (existing equipment, pump setting, discharge rates, capacities, water quality, water levels, etc.) should be kept in hard copy, printed on acid-free paper in a secure place in fireproof files. Copies of video tapes and disks should be made and stored securely as well. You know, even one hundred years is not a long time. It is important that maintenance records be available to all the relevant parties on a need-to-know basis. Facility managers and owners should have contractual access to records maintained by contractor management and well maintenance firms in case of changes in contracting firms (hardly an unusual occurrence). These files remain the property of the facility’s owners (not the contractor). In the case of environmental cleanup sites, the site’s responsible party also must have access.

5.5.2 Maintenance Monitoring for Performance and Water Quality Maintenance monitoring is the process of performing systematic monitoring to permit early detection of deterioration that may affect the well’s hydraulic performance and water quality. The ideal is to detect deteriorating effects in time to prevent problems or allow the easiest possible treatment. Without collecting quantitative data, symptoms of well deterioration may not be apparent until well performance is severely impaired. The results of system water and quality and performance monitoring are compared over time to establish trends. Such problems can be prevented and mitigated by effective O&M, but to do so requires valid information on the environment, hydrology, and material performance of the well system produced by information collection in the process known as maintenance monitoring. Table 5.1 is a testing summary guide and Table 5.2 summarizes factors of interest in maintenance monitoring. In general, maintenance monitoring approaches should be tried and reviewed over a period of time and adjusted based on experience. Systems and procedures must be implemented as part of a systematic maintenance program involving: • • • •

Institutional commitment A goal of deterioration prevention Systematic monitoring as part of site maintenance procedures A method evaluation of information to determine what maintenance actions are necessary

In any case, it has to be recognized that monitoring approaches and responses will be site specific, and likely will require adjustment during implementation.

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•

Silt/clay infiltration

•

•

•

•

•

•

•

Pumping water level decline

•

•

Lower (or insufficient) yield

•

•

Complete loss of production

•

•

•

•

•

•

•

•

•

•

•

•

•

•

•

Chemical encrustation

•

Biofouling plugging

•

Pump/well corrosion

•

•

•

Well structural failure

•

•

•

•

Check for Power Malfunction

•

Test Pump Mechanical Condition and Performance and Changes in Head Relationships

Conduct Step Tests and Review History

•

Test for Physical-Chemical Parameters and Review Records

Check SWL and PWL and Review Histories

•

Test for biofouling Parameters and Review Records

Conduct Downhole TV Inspection

Sand/silt pumping

Problem

Review Area-Regional Ground-Water Conditions

Review Design and Construction Records

Table 5.1 Troubleshooting Summary Guide for Well Maintenance

•

•

•

•

•

•

Source: Modified from Borch et al. (1993) and Smith (1995).

Timescale note: Over the eighty-year life span of a well, the first twenty years may reveal the trends and correlations/relationships that inform the next sixty years of maintenance activities. Think lifetime, not next fiscal cycle.

5.5.3 Maintenance Actions and Treatments Once maintenance or diagnostic testing has indicated that a deteriorating condition is likely to cause a problem, or has established a suitable maintenance interval, some action needs to be taken. This may be in the form of an inspection and repair of a component such as a pump, replacement or cleaning of a filter, or some treatment

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Table 5.2 Parameters Useful in Well Maintenance Monitoring Hydraulic testing

Pumping rate and drawdown for specific capacity (acceptance rate and WL rise in injection wells) Total amount of pumping time and quantity pumped per year Periodic step tests for well and pump efficiency Power and fuel consumption for pump efficiency

Physicochemical parameters (for changes due to deterioration)

Total and ferric iron, and total manganese (and other metals as indicated) Important anions as identified, including sulfides, sulfates, carbonates, and bicarbonates pH, conductivity, and redox potential (Eh) where possible (instrument readings may be replaced by checking ratios of Fe (total) to Fe2+ (soluble)) Turbidity or total suspended solids calculation of product water Calculation of corrosion/encrustation potential using a consistent method

Microbial

Total Fe/Mn-related bacteria (IRB), sulfur-reducing bacteria (SRB), slime-forming, and other microbial types of maintenance concern as indicated

Visual/physical

Pump and other equipment inspection for deterioration Borehole TV for casing and screen deterioration Electrical parameters: V, A, Ω data, and phase imbalance calculation Listening and feeling change in performance

Source: Modified from Alford et al. (2000).

such as redevelopment, designed to minimize or correct a problem condition. Some actions are considered in Chapter 6.

5.6 A Maintenance Monitoring Protocol for Wells Monitoring is a key part of preventive and proactive maintenance. This section describes decision making, considerations, and recommendations for practical preventive maintenance. Managers of well systems (like those of any engineered system) make operational decisions based on formal or informal cost-benefit analysis. Deciding how to maintain a system properly requires recognizing the risks to the system. Recognition requires knowing what to look for, such as those factors outlined in Chapter 2. Assuming that wells will experience a variety of problems, a variety of risks have to be evaluated, at least initially. It has been established that deteriorating conditions in wells can be complex, and best controlled if detected early. For these reasons, effective maintenance has to be based on regular monitoring, including electro­ mechanical, physical, chemical, and microbial factors, as well as pump and well service and record keeping. Because of its importance, monitoring is considered here in some detail. Who should do maintenance monitoring? Anyone can be trained to do it, but it requires diligence and attention to detail. As home-well and many other small-facility

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operators neglect such maintenance, perhaps well contractors should provide sevice agreements with well construction contracts, if they do not do so already.

5.6.1 Purposes of Maintenance Monitoring Effective maintenance of wells without monitoring of well parameters is no more possible than effective vehicle maintenance without analysis of engine operation and regular mechanical inspection. Maintenance monitoring of such parameters provides useful knowledge of the nature of problems, which permits reasonable countermeasures to be explored. Repair and replacement intervals and preventive maintenance treatments can then be chosen and fine-tuned accordingly. At a minimum, a preventive maintenance (PM) monitoring program should provide for regular analyses to determine: • Whether a deteriorating condition may be occurring • The reasons for changes in well and pump performance and water quality as soon as they can be detected The effects of chemical action and solids such as silt on well performance, and methods to monitor for them, are typically rather well known to managers of environmental site well arrays. Monitoring for these factors should be relatively easy to sell if there is any commitment to maintenance whatsoever. Biofouling monitoring for wells benefited from the development of rational sampling and suitable analytical methods in the 1990s. Unlike water level, withdrawal rate, and physicochemical and silt and turbidity analyses, biofouling diagnosis methods are still not really standardized (and may never be). For these and other reasons, biofouling monitoring is not as well appreciated. However, biofouling and changes in physical parameters, such as turbidity and sand content, among all the indicators of deteriorating effects, are the most amenable to preventive or early warning monitoring. To be treated effectively, all have to be detected as early as possible. Such monitoring permits making reasonable judgments, for example, of how quickly biofouling is occurring, its effects on the system, and how it can be controlled. (Why Fe, S, and Mn biofouling is a particularly vexing problem for well maintenance is discussed in Chapter 2.) The control of sanding and silting also benefits from early warning so that troubles can be tackled early on, before a pump is ruined or a screen collapses. The recommendations and rationale presented here are designed to be used in presenting a convincing argument to facilities management that well monitoring, including biofouling factors, should be budgeted as a part of a maintenance program designed to protect capital assets and provide the best possible system performance.

5.6.2 Background for Current Monitoring Recommendations The following recommendations are primarily based on the experience of consulting and research projects, including that which culminated in the venerable but now

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out-of-print AWWA Research Foundation publications Methods for Monitoring Iron and Manganese Biofouling in Water Supply Wells (addressing biofouling parameters) that one of us (Smith) completed in 1992 with the valuable assistance of Olli H. Tuovinen and Laura Tuhela-Reuning, then at The Ohio State University, and the more general Evaluation and Restoration of Water Supply Wells, written by Smith, Mary Ann Borch, and Luci Noble for the National Ground Water Association and AWWARF in 1993. We are also indebted to other published reports from colleagues around the world, written or updated in the 1990s. These include good works on performance monitoring. The field with regard to monitoring well deterioration parameters has been largely quiet post-2001 except for polishing, although significant work is being done in related fields such as bioremediation and geothermal energy. There seems to be a new pulse of activity, with the works by Schnieders (2003), Houben and Treskatis (2007), Cullimore (2008), and this one you are reading. A major part of this chapter borrows from (and in the form of its 1995 predecessor, contributes to—this is a feedback loop) Operation and Maintenance of Extraction and Injection Wells at HTRW Sites (EP-1110-1-27), written by Smith, George Alford, and Roy Leach for the U.S. Army Corps of Engineers. This “environmental pamphlet” is a very accessible summary background document (download it from the web) that applies to more situations than the target subject scope. Attempting to maintain systems without such monitoring is virtually pure guesswork, an exercise in gambling on short-term savings without much hope for any payoff in any currency but grief later. This discussion is updated from our year 2000 work. No monitoring program can prevent deteriorating conditions from occurring. However, with such a monitoring program, taking effective countermeasures is possible, resulting in long-term savings. To make use of its monitoring data over time, a maintenance system must have organized and accessible records as described.

5.6.3 Deciding How to Monitor The recommendations of this section should be considered guidance in making decisions about a PM monitoring program rather than a standard guidance of methods or detailed manual of action. Both the monitoring tools available and the methods of employing them have until recently been evolving too rapidly to be formalized into a definite standard procedure. They have, however, now been passing into revisions of standard methods, specifically Standard Methods for the Examination of Water and Wastewater, and some ASTM standard guides. Besides the recommendations here, there are alternative methodologies, essentially variations on a theme, for example, biofouling monitoring methods presented by D. R. Cullimore in Practical Manual of Groundwater Microbiology as part of our publisher’s Sustainable Well Series. If you do not have the second edition, make sure to order one. Selection of a monitoring program should proceed based on a thorough technical assessment of the wells of interest.

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At a minimum (Table 5.2), system operators should monitor:

1. Hydraulic performance, well performance, and pump and motor characteristics (voltage, amperage, vibration, and sound) 2. Physicochemical parameters relevant to the system 3. Indicators of growth or occurrence of biofouling microorganisms in wells

Methods chosen should be as consistent as possible over time, but allow for changes as appropriate. The maintenance monitoring recommendations presented are designed to detect a variety of conditions and symptoms, many of which are interactive. For example, consider a circular interaction situation in which silting is aggravating biofouling clogging, which is reducing the hydraulic efficiency of a well, resulting in initially increased drawdown, which then apparently recovers when the pump subsequently wears and clogs, thereby reducing yield. High motor amperage draw with reduced discharge signifies pump clogging, while low amperage draw and low output indicates a leak somewhere (perhaps indicating corrosion). We will provide some specific monitoring recommendations for the detection and monitoring of deteriorating conditions in wells. Recommendations are made for physicochemical, biological, and hydraulic performance monitoring methods. Selection of a level of monitoring effort should be based on an analysis of the information the methods can provide, as well as the technical needs and financial resources of the facility. The recommendation contains a heavy emphasis on biofouling analysis, since it is among the most troublesome and common problem in wells. Monitoring of hydraulic performance and solids such as sand are equally important in most systems. None of these factors in well deterioration can be profitably neglected. A Note about Cost-Benefit of This Approach: A separate budget analysis serves to determine the long-term cost-benefits of maintenance monitoring and preventive treatment vs. reactive rehabilitation. This should be based upon cost per unit water, and also be factored into LCC calculations (see Chapter 3). Although simple, costper-water calculations provide a useful basis to objectively evaluate cost-benefit for pumping wells. Another system (developed for water supply well systems) is also presented. This spreadsheet-based system can provide rational comparisons among a variety of alternatives, such as monitoring and maintenance (M&M) vs. doing nothing or among different levels of M&M. The cost analyses specific for monitoring well maintenance cannot be defined using a cost-per-unit water basis. The valuation system is a different one entirely. Here you are considering your business goals (Section 3.2). Either you are complying with your consent decree or you are not. Are your clients staying out of court or avoiding “findings and orders”? The cost when the facility is caught in a legal or regulatory web is in the need for repeated sampling events, hours of meetings with lawyers and regulatory people, legal fines and costs, client problems, and community confidence decline and fear. This is the “impairment” of environmental economic value (EEV) discussed in Section 3.3.2.

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5.6.3.1 Incorporating PM Data Collection into the Facility Data Collection Effort Too often the significance and central importance of data are overlooked in the ­context of the scope of an entire project. What may seem to be minor clerical details to those responsible for a project’s overall management can be important later in facility operations. The quality and completeness of boring logs, well completion diagrams, well testing, etc., are often left to contractors who do not appreciate the value of the data, or left to inexperienced, overworked, or unsupervised junior technical staff. Omissions in the data are often apparent only when it is too late to correct the deficiency. Data are easiest to obtain and more accurate if data collection is incorporated into the project plan at the onset. Compiling data at a later stage of a project’s operation is generally difficult and less successful. Why does this not happen? There is a tendency to omit maintenance planning, data gathering, and repair costs when bids are higher than budgeted, or to inadequately fund these tasks as costs are adjusted to available funds during project management. Budgets to fund remediation activities themselves can be unrealistic in this regard by not adequately considering the real costs of maintenance. Since facility managers and operators are likely to be inexperienced with both the causes of well deterioration and methods for its monitoring and control, seeking outside expert help in getting started is highly recommended. Fortunately, it so happens that there is a community of professionals who are well experienced with these specific methods, their benefits, and limitations. Among these are authors of many of the references cited. Ideally, once properly implemented with adequate training, well maintenance monitoring programs should proceed without outside help unless the facility managers wish to subcontract the M&M.

5.7 Recommended Testing and Information Monitoring Methods The following is a survey of existing monitoring methods and their uses in preventive maintenance and diagnosis of problems.

5.7.1 Visual and Other Sensory Examination Regular visual inspection of the well and pump components is the first line of defense and can reveal important signs of corrosion and encrustation. Problem areas can be observed and a rate of progression ascertained. For better or worse, pumps and pipe components in systems experiencing well deterioration serve as high-cost coupons or sacrificial indicators of corrosion and encrustation, such as those illustrated in Figure 5.2 (also Figures 1.2, 2.3, 2.6–2.8, etc.). Another form of visual inspection is by borehole video camera. Borehole video recording provides direct visual information on the well and can be used to record changes over time. High-resolution color reception is highly useful, and widely available with camera heads of less than 2 in. diameter. The most preferable equipment is that which provides a right-angle color view that permits direct observation of the

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Figure 5.2  (See color insert following page 66.) Some indications that you may have biocorrosion problems in the well (Ohio). Corrosion hole (middle section, top), above pump was losing several 100 gpm.

casing and screen. Figure 5.3 illustrates a typical borehole television system. More important than sophistication in equipment is a knowledgeable camera operator who knows what is likely to be interesting and an observer who can interpret accurately what the camera reveals. Sometimes this is the same person. If not, it helps if the knowledgeable observer is on site when the survey is conducted in order to guide the operator. Familiarity with well components and function is helpful, as the view from inside the well may not be intuitive at first. Although the purchase of a borehole video camera or the hire of its services represents a significant cost, the amount of information that can be obtained in a brief survey makes the survey a good value. Presumptive identification of borehole and casing wall fouling, encrustation, corrosion, and other structural damage can be made rapidly through downhole inspection by the experienced observer. These can be confirmed by direct testing of deposits or equipment retrieved. Sound and other vibratory signals are often crucial early indicators of problems. If the well sounds different when it is pumping, the pump or piping vibrates, valves shutting or opening sound different, there is a sizzling or crackling, or a bubbling, these are signs that some change has happened in the well.

5.7.2 Well and Pump Performance Well and pump performance changes are inevitable and occur as a function of time as a result of many processes. But to many operators or those responsible for wells, it appears that somewhat mysteriously the well just ceases to perform as needed, leaving everyone in a crisis. Worse yet, when the well ceases to function, it is not known whether it is a problem with the well, the pump, or both. However, one can monitor and track changes in well and pump performance, thus planning for and performing needed maintenance and avoiding a crisis. To do so, facilities need to establish a well

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Figure 5.3  Down- and side-view borehole video camera system operated by Geoscope Inc., Mansfield, Ohio.

and pump performance monitoring program to systematically collect data, analyze it, discern trends, and take action. Two priorities stand out in establishing a well and pump performance monitoring program: (1) benchmark the original performance, and (2) be sure to compare “apples with apples,” not “apples with oranges.” Common to both priorities is the need for consistency, which is maintained through set procedures for collecting and analyzing the data. This implies a need to train the responsible personnel in the set procedures and for someone to understand what the results of the analysis are telling them. 5.7.2.1 Benchmarking We benchmark the performance of both the well and the pump as a standard with which to compare and to discern trends in the future. It is preferable that the baseline performance be performance when new. In the case of the typical centrifugal well pump, establishing the baseline performance of the pump is relatively easy. This is provided by the pump manufacturer as a pump performance curve (Figure 5.4 is an example). The pump performance curve plots the relationship of the output from the pump (discharge rate, e.g., gal/min, gpm)

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Figure 5.4  Example pump performance curve (Scherer, 1993, AE-1057, North Dakota State University Extension). Note: HP and head are per stage.

as it pumps against a given total dynamic head (e.g., feet of water or lb/in.2, PSI). Ideally, using this information, the pump is sized for the specific conditions of the well, system, and intended pumping rate. Plotting the point of intended pumping rate vs. total dynamic head permits designing a system in which performance would fall on the performance curve in the range of maximum efficiency of the pump. Manufacturers of pump motors will provide information on the current requirements (amps) that the new motor will draw in an appropriate application. This current requirement is an indicator of the baseline performance of the pump motor. Establishing the baseline performance of the well can be accomplished with a step-drawdown test (well described by publications in our reading list). This method consists of pumping the well at steps of increasing discharge rates, with each step continuing until the pumping water level begins to stabilize (Figure 5.5). Throughout each step, water levels are regularly measured and recorded, and the discharge rate is accurately monitored and maintained. When the step-drawdown test data are analyzed (Figure 5.6), we can separate out the aquifer drawdown and well loss drawdown components of the total drawdown observed in the well during pumping (Figures 5.6 and 5.7). The function for aquifer and well loss parameters and total well drawdown in a screened sand and gravel well may be represented:

Total drawdown (ft or m) = BQ + CQ2

(5.1)

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation Village Well No. 5 Step-Drawdown Test Time-Drawdown Data

0 10

159 g.p.m 203 g.p.m

20 Drawdown (ft.)

30

298 g.p.m

40 50

401 g.p.m

60 70

464 g.p.m

80 90 100

0

20

40

60

80

100

120

140

160

180

200

Time (min.)

Figure 5.5  A plot of step-drawdown test data.

Village Well No. 5 Step Test Analysis

0.20 0.19 0.18 1/Specific Capacity

0.17 0.16 0.15 0.14

C = 1.71E-04

0.13 0.12 0.11 B = 0.082

0.10 0.09 0.08

0

50

100

150

200 250 300 Pumping Rate (g.p.m.)

350

400

450

500

Figure 5.6  Analysis of step-drawdown test using Hantush-Bierschenk straight-line method, B established by intercept and C from slope of plot.

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Aquifer Loss & Total Drawdown (ft.)

Village Well No. 5 Aquifer Loss & Total Drawdown 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160

Aquifer loss

Well loss Total drawdown

0

100

200 300 Pumping Rate (g.p.m.)

400

500

Figure 5.7  Graph of efficiency vs. pumping rate from analysis of step test plot, aquifer loss, and well loss illustrated.

where B = aquifer loss parameter, C = well loss parameter, and Q = pumping rate (gpm). The exponent in CQ2 may vary slightly from "2." Note: American engineering units (gpm and feet) or SI engineering units (L/s, m) (rather than consistent units) may be used in the analysis. The BQ factor represents the water level drawdown (that is, energy) required to move water through the aquifer toward the well when pumping. The CQ2 factor represents the water level drawdown (energy) to move water from the aquifer through the gravel pack and screen into the well. Several parameters of well performance can be derived from the step-drawdown test. First, we can establish a specific capacity of the well. This is a single value relationship of a given output (discharge rate, Q, e.g., gpm) at a given water level change (usually feet or meters of drawdown, s) expressed in the units of

Specific capacity (Q/s) = gpm/ft of drawdown

Specific capacity (Q/s) is only useful for comparison purposes if the value is derived from a consistent pumping rate. We generally state Q/s as

x gpm/ft of drawdown at y gpm

Second, we can establish the efficiency of the well. This is the ratio of the water level drawdown in the aquifer to the total water level drawdown in the well at a given pumping rate, expressed as a percent:

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Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation Village Well No. 5 Estimated Efficiency

100 90

% Efficiency

80 70 60 50 40

0

100

200

300 400 Pumping Rate (g.p.m.)

500

600

700

Figure 5.8  Plot of percent well efficiency vs. pumping rate. Derived from analysis illustrated in Figures 5.5 and 5.6, with extrapolations to gpm above and below the tested flow rates (Figure 5.5).



% Efficiency = (BQ/(BQ + CQ2))*100

(5.2)

Again, efficiency is only useful for comparison purposes if the value is derived from a consistent pumping rate. We generally state efficiency as

x% efficiency at y gpm

Third, we can use the results of the step-drawdown test and the functions presented above to produce useful curves documenting the performance of our individual well over a wide range of pumping rates. For example, we can plot the total drawdown (ft) vs. puming rate (gpm). Or we can plot percent efficiency vs. pumping rate (Figure 5.8). 5.7.2.2 Compare Apples with Apples Now that we have documented the baseline performance of our pump and well when new, we can track the performance changes over time with a performance monitoring program. We need to regularly obtain the same raw data and perform the same interpretations as the benchmarking process. Therefore, we need regular measurements of: • Total dynamic head (TDH) (e.g., ft H2O, or PSI), the pump is working against • Pumping rate (Q) (e.g., gpm) • Current draw on each leg of the pump motor (amps) • Water level measurements, both static and pumping (e.g., ft)

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From these data we will be able to derive the same performance parameters that were benchmarked. This is where consistency is an issue. For example, when water levels are measured, they should always be measured from the same reference point, called the measuring point. If each employee who collects a water level measurement does so from a different reference point, the data collected will be of little use. This is why explicit procedures and training are important. Ideally, the wellhead should be equipped to facilitate consistent manual measurements of these parameters or a SCADA (supervisory, control, and data acquisition) system installed to automatically monitor them (more on that below). The data and interpretations need to be entered into some sort of record system (more on that below). 5.7.2.3 Monitoring Pump and Pump Motor Performance Somewhere at the wellhead, a pressure gauge needs to be installed in the discharge line ahead of any valves used to regulate the discharge from the pump. From this gauge we obtain the head the pump is pumping against at the elevation of the gauge. We also measure a pumping water level, which needs either to be measured directly with the gauge as the reference point, or the depth to water corrected to indicate depth below the pressure gauge. For our purposes, the total dynamic head (TDH) will be the sum of the two:

TDH (e.g., ft H 2O) = depth to pumping water level (ft)   + gauge reading (ft H 2O)



(5.3)

Additional accuracy can be obtained by including velocity losses up the riser pipe, friction losses in the riser pipe accounting for pipe roughness (if significant), losses from pipe bends, etc. Your consulting engineer should be able to help provide values for these other losses. Also at the wellhead, we need an accurate measurement of the pumping rate. Flow meters of various designs are available for this. Now we can go back to the pump performance curve provided by the manufacturer (Figure 5.4 is an example) and compare the head generated by the pump (ft H 2O) against the pumping rate (gpm). If the point falls on the original performance curve, then the pump is performing as designed. If the point falls below the curve, then the pump is beginning to wear. As the pump’s performance begins to decline, the point moves away from the range of maximum efficiency, thus consuming more energy for the water pumped. Also check the current draw for each leg against the manufacturer’s data. If the current draw is increasing, it is an indicator of developing problems in either the pump or motor. A complete guide to troubleshooting pump and motor problems is beyond the scope of this work. The reader is referred to Butts (2006) and the Water Systems Council (2002) for more detailed information on this subject (see our recommended reading list). 5.7.2.4 Tracking Well Performance Utilizing the water level that has been measured, calculate the current water level drawdown (s). Use the drawdown value and current pumping rate (Q) data that have been collected (as described above) to calculate a current specific capacity (Q/s) for

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the well. Compare this to the benchmark specific capacity (assuming that both values were calculated at a consistent pumping rate). If the pumping rate is not a constant, then the values for drawdown and pumping rate can be compared to the benchmark curve prepared when the well was new. Well hydraulic performance monitoring should consist of regular (e.g., monthly or quarterly) measurements of pump operation and well hydraulic characteristics, as follows:

1. Pumping dynamic water level (DWL) (pumping water level, PWL) in pumping wells 2. Static DWL (“true” static water level (SWL) or static DWL at the well with the pump off but under the influence of nearby pumping wells) for all wells 3. Area water levels to keep track of seasonal, tidal, or other effects that may affect well DWL 4. Wellhead pumping rate and operating hours for regularly pumping wells 5. For regularly pumping wells, pump power consumption and power characteristics (voltage, amperage draw, occurrence of stray currents), especially noting how each varies from the manufacturer’s nominal specifications

The pumping rate should be determined against a consistent system head (if pumping into a collection system) and periodically against free discharge if feasible. Methods of hydraulic pump testing and motor characteristics tests are widely known and referenced (see our reading list). The Water Systems Handbook (Water Systems Council) and some motor references provide very useful troubleshooting (diagnostic) charts. For environmental monitoring wells, slug tests (see the reading list) also can be used to detect changes in hydraulic conductivity for low-production monitoring wells as long as there is a historical record. Their utility in well maintenance and rehabilitation is less direct than with step-drawdown tests, but data derived from these tests can be used in preliminary calculations of expected well hydraulic parameters. As with constant rate pumping test data, calculations of aquifer characteristics based on slug test data can be used for estimation of theoretical well mounding in injection wells. If changes in conductivity are noted and there are no other hydrologic reasons, fouling of the well may be occurring. Because of the small volumes of water involved and the short (or long) time span over which the test occurs, pressure transducers and digital data logging are generally employed. Pressure transducers are submerged in the well and register the pressure of the column of water overlying them. Water level changes are detected as changes in pressure as the height of the overlying water column either increases or decreases. The data logger can be programmed to sample and record data from the transducer at required time intervals. This feature of digital data logging is most useful when conducting slug tests in high-permeability sediments where many water level measurements will be required over a span of seconds as the water level rapidly recovers.

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In general, for arrays of monitoring and pumping wells, such as those used for plume control, automatic sensor-recorder methods make excellent sense in providing a lot of information with minimal operator labor or contact with contaminated fluids (if present). Special Conditions: Hazardous cleanup sites may impose restrictions on optimal step testing methodology. For example, a five-step test with pressure measurement is recommended to determine pump wear (as distinguished from well performance parameters). However, pumping contaminated ground water requires collection of the fluid. Perfecting the gathering of pump wear data from a three-step test, and learning to extrapolate from short steps, may be a necessary compromise in methodology. Site managers of environmental projects typically have access to database systems with graphical output. Drawdown data from water level monitor output files can be input to the program for the well array, and anomalies such as increased drawdown at particular wells can be displayed. 5.7.2.5 Water Level Measurement Recommendations • Water level data may be collected manually or the process automated. • For relatively small numbers of wells and conditions where personnel are not at health risk when water columns are exposed: Use electric water level probe and manual data entry. • For larger numbers of wells where personnel time would be inordinately devoted to water level measurements: Use automated water level recording via transducers. • For conditions where exposure to vapors off-gassing from well fluids poses an inhalation hazard: Use automated water level recording via transducers. Several approaches to water level measurement are possible, each with its advantages and disadvantages. Table 5.3 summarizes water level measurement methods and their features. Note: Airlines are a traditional method of water level measurement. However, they are very inaccurate and prone to clogging. We do not recommend their use. Note that all conventional water level measurement systems are fouled by nonaqueous-phase liquids and will yield inaccurate results. There are specialized instruments for dual-phase level detection. 5.7.2.6 Well Discharge Measurement Each pumping well and receiving well or discharge should be metered. Total system pumping production should match total discharge. Unbalances may indicate leaks or metering inaccuracies.

1. Flow meters should be sized to the expected well discharge rate. Instantaneous and totalized flow readings in commonly used volume-rate units (m3/h, gal/min, etc.) are necessary.

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Table 5.3 Features of Water Level Measurement Methods Type of Water Level Measurement

Advantages

Disadvantages

Electric sounder

Commonly available; reliable when maintained; accurate under most water-only conditions (±0.02 in.); not highly subject to downhole fouling; one sounder can be used on multiple wells

Requires wellhead access and unobstructed water surface access; probe will foul in floating material on water surface; mechanical aging of conductor wire must be considered; cross-contamination is possible; requires personnel to take levels and manually enter data

Airline (gauge measurement) or instrument measurement)

Inexpensive; no need for direct access to water level surface; each well has a dedicated airline

Relatively inaccurate (+1 in. or more); subject to fouling; requires personnel for taking levels and manual entry of data

Airline (instrument measurement)

Inexpensive; no need for direct access to water level surface; each well has a dedicated airline; with instrument, improves accuracy to electric water level sounder range; data recording possible

Subject to fouling; requires personnel for taking levels

Water level transducers

Relatively accurate when properly selected and maintained; permit automatic data querying in SCADAa system; dedicated to well; no personnel exposure to water; no direct water access needed

Relatively expensive per unit; requires regular maintenance to deter fouling; if maintenance not performed, automatic systems may record inaccurate (useless) data

Source: Modified from Alford et al. (2000). Supervisory, control, and data acquisition. Note that all these water level monitoring methods provide data that can be manually entered into SCADA databases.

a





2. Flow measurement method selections should take into consideration the quality of the fluid to be measured. Clogging fluids may foul turbine flow meters. Acoustic devices may have better service lives under some circumstances. Systems standard to industrial waste water treatment applications should suffice. 3. At a minimum, measurements should be taken manually daily to weekly, depending upon fluctuation. 4. Wherever possible, flow meters should have automatic readouts, either to a central SCADA system or readout device. Systems standard to industrial water supply should suffice.

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5.7.2.7 Pressure Measurement Either manually read or digital read-out meters may be used. With both, plugging of sensor orifices is to be expected. To detect pressure changes in the conveyance system, pressure should be measured as near as possible to the wellhead (immediately downstream of the pump discharge check valve. Measurements should be taken daily to weekly. Automation facilitates data collection. 5.7.2.8 Electrical (Power) Changes in pump motor amperage (A) draw and circuit voltage (V) and ohms (Ω) are used to detect problems on the power side.









1. V should be within ±10% of the motor nameplate voltage (or within stated manufacturer’s specification) when the motor is under load (running). Larger V variations may cause winding damage. These should be corrected in the power supply or the motor changed to match the supplied V characteristics if it remains constantly high or low. 2. Increases in amperage on start or run cycles over listed service factor amps indicate: • Loose terminals in the control box or possible cable defect • Too high or low service V • Motor windings are shorted • Mechanical resistance such as sand in bearings 3. A drop in typical “run” amperage indicates a loss of mechanical resistance against motor operation. This datum, in combination with reduced pump discharge rate or pressure data, can be used to confirm that a problem has developed in pump output, such as the development of a hole in the pump discharge pipe. 4. Deviations in circuit ohms indicate wiring problems. A low value on one or more line legs indicates a potential motor short. Greater than normal values indicate poor cable connections or joints or that windings or cables may be open. If some values are higher than normal and others lower than normal, drop leads may be mixed. 5. Megaohm (MΩ) detections outside the circuit indicate ground faults. For a motor installed in a well: If resistance between any wire lead and true ground is <0.5 MΩ, motor damage is likely to have occurred. 6. Voltage imbalance across legs in three-phase (3 ϕ) systems cause excessive motor aging and poor performance, and should also be checked routinely. 7. Total kilowatt-hour (kWh) use can be used to calculate changes in motor and system efficiency. 8. Electrical monitoring should be automatic if at all possible or, if manual, checked weekly. Several good references provide guidance in specifying apparatus for monitoring pump motor operation as well as the rate, pressure, temperature, and chemical-physical properties of the discharge. Particular attention should be paid to regularly monitoring wellhead V, A, Ω, and ϕ balance conditions of individual wells. Grounding should also be checked on a routine schedule.

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5.7.3 Water Sampling Strategically placed water sampling ports permit analysis of maintenance-related water quality parameters. Noncorrodible taps placed to permit sampling fluid at (1) well discharge and (2) other strategic points are necessary to detect indicators of chemical and biological clogging and corroding conditions. Where corrosion and biofouling are sampled directly using coupons, provision must be made for attachment of the necessary sampling devices and discharge of flow-through fluids. More on technique follows.

5.7.4 Physicochemical Analyses The purpose of physicochemical monitoring for maintenance is to detect changes in parameters that may indicate conditions that cause or reflect well deterioration. This monitoring is separate in purpose from regulatory monitoring and has a different agenda. The needs are for more immediate results, more data in a given length of time, and less need for rigidly certifiable, legally defensible analytical precision. The need is to detect change over time early enough to make decisions about maintenance. Basic water chemistry analysis should include, at a minimum, soluble (Fe2+) and total Fe, total Mn, total S2–, pH, Eh, and temperature. Sulfate and S0 or SO4 solids monitoring may also be important on certain systems. Redox potential is very important both to the make-up of the microflora in the well and aquifer and to the fate of Fe, S, and Mn at the well, such as the mineral forms of precipitates. Redox may be measured directly using appropriate electrode methods or estimated based on the redox-couple ratio Fe2+:Fe3+, which is the only relevant reversible ratio in ambient ground water. It is notoriously difficult to decide the meaning of a particular redox reading taken out of context, but charted over time, patterns can emerge. Parameters relevant to formation of encrustation (e.g., Ca2+ ion) should be determined. Standard Methods for the Examination of Water and Wastewater (current edition) provides guidance. Also, sediment content and type in bailed or pumped purge and sampling water (e.g., by ASTM standard method D 3977) are important gauges of screen and pack performance. These results can be charted over time. Total suspended solids can also be detected and measured using readily available turbidometers and particle counters. Turbidometers are the most widely used method for monitoring the particle removal efficiency of filters, and have wide commercial use. Standard Methods Section 2130 provides an instrument and method standard. Particle counters are the subject of significant recent research. Such particle counters and turbidometers can monitor particle density automatically to save on sampling and analysis time, and have a second purpose in monitoring the performance of filtration. Particle counters provide more information than turbidometers, in that they can both count and determine the size of particles. For surface water supply filtration, the size is important in detecting the possible presence of protozoan spores. In maintenance monitoring for wells, the emphasis again is on change in particle density over time. Important data are changes in particulate concentrations and characteristics such as mean diameter.

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Table 5.4 Summary of Physicochemical Methods Relevant to Well Maintenance Fe (total, Fe2+/Fe3+, Fe minerals and complexes)

Indications of clogging potential, presence of biofouling, and Eh shifts; Fe transformations are the most common among redox-sensitive metals in the environment

Mn (total, Mn4+/Mn2+, minerals and complexes)

Indications of clogging potential, presence of biofouling, and Eh shifts; less common but locally important

S (total, S2–/S0/SO42–, S minerals and complexes)

Indications of corrosion and clogging potential, presence of biofouling, and Eh shifts

Eh (redox potential)

Direct indication of probable metallic ion states, microbial activity; usually bulk Eh, which is a composite of microenvironments

pH

Indication of acidity/basicity and likelihood of corrosion or mineral encrustation; combined with Eh to determine likely metallic mineral states present

Conductivity

Indication of TDS content and a component of corrosivity assessment

Major ions

Carbonate minerals, F, Ca, Mg, Na, and Cl determine the types of encrusting minerals that may be present and are used in saturation indices; one surrogate for many cations is total hardness

Turbidity

Indication of suspended particles content; suitable for assessment of relative changes indicating changes in particle pumping or biofouling

Sand/silt content (v/v, w/v)

Indication of success of development/redevelopment; potential for abrasion and clogging

Source: Modified from Alford et al. (2000) and Smith-Comeskey Ground Water Science (2007).

As with microbiological methods (described in the following), particle counting and turbidometry are highly site specific in application. Particle counting results, for example, cannot be compared among differing sites. However, a history of readings can be built to provide a history of a particular well site, which can be interpreted. As with microbiological data, to build such a history requires good records. Table  5.4 is a summary of physicochemical methods relevant in well maintenance.

5.7.5 Biological Monitoring: Decision Making A system of monitoring biofouling should be chosen and implemented as part of the overall preventive maintenance monitoring program. Even when the problem is not obviously microbial in origin, microbial monitoring can often pinpoint root causes. An example is CaS04 plugging, a secondary effect of sulfide oxidation (which has a microbial component). As with other monitoring methods, biological monitoring methods chosen should be within the technical and fiscal capacities of the facility and expert technical support available.

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The methods chosen should be capable of detecting indicators of biofouling likely to cause difficulty for a well and water collection/treatment system at sufficiently low levels to permit treatment before performance or water quality impacts become serious. Biofouling monitoring should not be conducted in place of other monitoring, especially that for performance parameters. 5.7.5.1 Whether to Monitor for Biofouling Whether to consider biofouling monitoring is a relatively easy question, from a practical standpoint. The biological conditions that result in various forms of biofouling are pervasive in many aquifer settings, and there are no apparent constraints on biofouling in aquifers used for drinking water supply. Aquifers typically being monitored, or undergoing remediation, are also typically highly active biologically. These aquifers and wells in them are almost certainly a setting for well biofouling. In general, facility managers and their consultants should consider early-warning biofouling monitoring in just about any operational situation. 5.7.5.2 Biofouling Monitoring: What Methods to Choose For biofouling, constant surveillance and willingness to act in response to indications of occurrence are essential. How the monitoring is carried out is important, but secondary to the primary requirements to commit to implement a useful monitoring program and to continue it over time. The methods chosen should readily answer the following questions: • Is biofouling present? • What types of biofouling organisms are present? • Is the well more or less biofouled than before? The answer to this last question requires monitoring over time. Maintenance monitoring methods chosen should be task oriented: to detect those biological indicators or conditions that lead to reduced well system performance. For this reason, methods that provide rapid, general insight into biofouling and bio­ corrosive conditions are preferred over methods that characterize genetic make-up or metabolic capabilities. 5.7.5.3 A Note about the Current State of the Art in Well Maintenance Monitoring Methods Physicochemical water quality and hydraulic performance monitoring are relatively well developed, standardized, and even automated. They can be reasonably applied in a precise fashion, and results for the most part comparable from place to place. Field instruments (despite what our regulatory minders often think) offer reliable results when used properly and are relatively user-friendly even for novices. At present, biofouling monitoring always (not sometimes) involves some degree of subjective judgment, in both implementation and interpretation of the results of monitoring. Current biofouling monitoring methods do not provide results that are quantitatively directly comparable to other methods of analysis, or other locations, or

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even other wells in a wellfield, although experience is providing statistical data that may bring a situation of comparable data. This case-by-case situation must be clearly understood so that methods chosen are appropriate to the conditions in the wells in question and that each well is adequately monitored. Also, it must be understood so that those in charge of maintenance monitoring do not become frustrated with the methods. The factors resulting in a particular analytical result are complex and interrelated and not yet fully understood. Significant change over time (e.g., months, seasons, years, or through a pumping cycle) provides some of the best insight on deteriorating processes taking place in a well or wellfield. To do this effectively, good records of data are required.

5.7.6 Biofouling Monitoring Methods: Analysis 5.7.6.1 Microscopic Examination and Analysis Light microscopic examination has traditionally been the method of choice for confirming and identifying “iron bacteria.” Microscopic examination of water samples as well as fouling and encrustations can reveal stalk and sheath fragments of bacteria presumed to be involved in Fe, Mn, or S biofouling (for examples, see Figures 2.12, 2.16, 2.25–2.27). Standard Methods Section 9240 and ASTM procedure D 932 document the commonly used procedures for sampling and analyzing samples by light microscopy for such so-called iron bacteria. The optical resolutions necessary for observing bacterial structures are based on 400× to 1,000× magnification (such as provided by a 40× common or 100× common or oil immersion objective + 10× ocular) with a direct filtered electric light source. Most microscopes are routinely equipped with maneuverable stage calipers, micrometer readings on the focusing knobs, and a micrometer scale in the ocular, and they can be equipped with a camera attachment that permits the recording of observations. Note that such microscopes can be purchased rather inexpensively these days. Phase contrast and epifluorescent methods are useful enhancements for light microscopy, but not necessary for biofouling diagnosis, as most biofilm samples from wells provide good visual contrast. Electron microscopy provides ultrastructural details of specimens but is purely a research tool in the study of biofouling at the present time. Light microscopy is also a satisfying and elegant procedure to perform. One of us (Smith) puts on the music, sets everything up, and goes to work in a zen-like state. When the pictures turn out (e.g., figures referenced just above), it is very satisfying. However, as with the likewise satisfying tasks of performing a carburetor or distributor tune-up, it is also a little old-fashioned and incomplete. In many instances, biofouling as a cause of well problems may be difficult to diagnose via microscopy alone, even with very good tools and skills. Microscopy does not tell the complete story about the environment of biofouling deposition:

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1. The biofouling root cause of a symptom, such as the secondary precipitation of calcium sulfate mentioned earlier, may be overlooked. 2. Samples examined may not include the filamentous or stalked bacteria normally searched for in such analyses. Samples may also not include enough recognizable materials to provide the basis for a diagnosis of biofouling.

Enhancements for the existing ASTM and Standard Methods procedures provide better results and aid in diagnosis, making microscopy (which may at times be the only available analytical technique) more useful. For example, collecting biofouling samples on immersed surfaces (glass coverslips and slides) improves sample collection for analysis by light and electron microscopy. Other improvements in microscopic technique have been made to distinguish microbial components of biofilms from mineral components. It is also useful to note that examination of the particles of sulfides and oxides themselves is a useful part of defining the nature of fouling in a well and water treatment system. Seeing the mineral particles themselves (with some knowledge of mineral and rock particle examination) is illuminating. If you see the wear (such as with weathered limestone), you also see the effects of biofouling. 5.7.6.2 Culturing Methods Standard Methods: Standard Methods presents several formulations for nutrient media for heterotrophic Fe-precipitating bacteria, Mn-oxidizing organisms, and Gallionella and SRB enrichment. As this is written, the methods included are undergoing revision, so we will not go into detail here. In addition, numerous formulations are available in the microbiological literature. Media for Fe-precipitating bacteria have been used with mixed success. No effort has been made to standardize these media with reference cultures from well water, and thus the recovery efficiency of iron bacteria from ground-water samples remains unknown at the present time. As Roy Cullimore comments in Practical Manual for Groundwater Microbiology, ground-water microbiology is not at the center of policy and public interest (and thus funding for research). Given their inconclusiveness, combined with the mess and fuss, it is unlikely that a wellfield maintenance program would willingly devote the time, facilities, and effort required for these older types of cultural enrichments, except in the interests of research (and who does that anymore?). Fortunately, there has been some progress in making biological monitoring easier and more suitable for routine maintenance. 5.7.6.2.1 Prepared BART Methods The currently most promising culturing approach for routine monitoring purposes widely available in North America is that developed by Droycon Bioconcepts, Inc., Regina, Saskatchewan, in Canada based on research first conducted at the University of Regina. These BART™ method tubes contain dehydrated media formulations and a floating intercedent device (FID), which is a ball that floats on the hydrated medium of the sample. These devices and their proposed use are described in detail in Cullimore’s Practical Manual of Groundwater Microbiology, which you should

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Droycon Bioconcepts, Inc. Aerobic growth of the bacteria will occur at the surface of the medium between the BART-FID and the wall of the tube. 15 mls of sample are used to bring the BART-FID up to the correct level. Nutrients will gradually diffuse up the sample column to support the aerobic growth. Nutrient media for growth is provided as a sterile dried matrix on the floor of the tube.

Floating Intercedent Device (FID) used to create a barrier for oxygen diffusion.

Once the oxygen has been used by the aerobes, this zone becomes free of oxygen and anaerobic growth will dominate.

Figure 5.9  BART method tube schematic. (Courtesy Droycon Bioconcepts Inc.)

order and read if you have not yet done so. This method, which is gaining ever more acceptance as a means of detecting biofouling microorganisms, has been demonstrated independently by one of us (Smith) in field trials to provide useful qualitative information in well biofouling events. Figure 5.9 illustrates the BART tube system. The BART method tubes come with a variety of media mixtures. The IRBBART, for example, is designed to recover microaerophilic heterotrophic Fe- and Mn-precipitating microorganisms. The IRB-BART has been presented as a method of detecting growth to provide a presence-absence (P-A) or semiquantitative mostprobable number (MPN) result. The theory and recommended implementation of BART methods are elaborated in Practical Manual of Groundwater Microbiology, first in the 1993 edition and updated in a 2007 edition. In short, BARTs are interpreted based on:

1. Visual appearance of the inoculated tubes at initial reaction and as reactions change (Figure 5.10) 2. Days of delay (d.d.) or time (usually days) until a noticeable reaction occurs One of the best uses of BARTs is as a quick and easy indication of:



1. Existence of probable heterotrophic Fe and Mn biofouling and the presence of sulfide-forming SRBs 2. Presence of general heterotrophic microflora that indicate the state of well hygiene 3. Relative “aggressivity” or activity of the biofouling, hygienic, and SRB communities

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Figure 5.10  (See color insert following page 66.) A selection of BART reactions from an alluvial aquifer well.

They are, like the “custom” Standard Methods formulations, enrichment media, not necessarily precise research tools (although do not dismiss them for that purpose). However, they can be unpacked and used under on-site conditions. Above and beyond the other benefits of the BART system, this “test-ready-to-use” attribute is their foremost benefit as a monitoring tool. With enough repetitions of samples, standardized sampling, and time, statistically significant data can be collected using these methods, which are useful in making decisions about maintenance. For example, based on empirical field research by Cullimore and others, BART results can be compared to plate count values (if you really have to). A manufactured analysis system that is comparable to the BART system is that developed by the late M. A. Gariboglio and others and marketed by Laboratorio MAG, La Plata, Argentina (www.laboratoriomag.com.ar/). These MAG tests are liquid media provided in serum bottles that are inoculated by means of injection. Their range of products (for heterotrophic iron related, sulfate reducing, heterotrophic aerobic, etc.) is similar to that for DBI’s product line. A description of these tests and their use is provided in Gariboglio and Smith in our reading list (1993, in Spanish). Figure 5.11 shows the use of MAG tests in practice (they are inoculated using a sterile syringe). Additionally, other vendors provide culturing tubes for some of the BART types, specifically for SRBs. Some of these (e.g., Biosan) can be used as swabs. Some react more quickly than BARTs. However, there is usually more preparation involved. Readers serious about finding suitable microbiological analytical methods should research the alternatives. However, those mentioned here are known to work reliably and provide information suitable for maintenance monitoring. Use of Prepared Biofouling Semiquantitative Methods (e.g., BART Kits) Inoculated with Pumped Samples: Pumping should be conducted after a nonpumping period (not less than 2 h) and proceed for not less than 30 min (see sampling discussion following). BART tubes should be exposed over the pumping period. BARTs may be exposed on consecutive days to check for the effects of differential sloughing on reaction times (d.d. data).

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Figure 5.11  (See color insert following page 66.) Inoculated BRS-MAG tubes and syringe applicator. Sample is injected into vial.

5.7.6.3 How Minimal Can Testing Be? An ideal in biological testing is to have one, simple, easy-to-use and interpret test of biological activity. Some argue that testing for total anaerobic heterotrophic population is that single trigger analysis, as an anaerobic condition with abundant growth can lead to heavy blockage with mineral accumulation, taste and odor problems, red water, and possible coliform or pathogen contamination. When the anaerobic bacterial community is abundant in the well, the well sanitation is in poor condition and in urgent need of cleaning. We advise that yes, this is a good simple test, but that aquifers can be naturally anaerobic, and thus favor anaerobic heterotrophs without other undesirable conditions being present. This is a place to start, but include the other testing. The role of total coliform (TC) testing, that old standby of water sanitation, is currently somewhat in flux. We do not plan to describe TC analysis here in detail. However, the current state of testing is that there is a very accurate test, the defined enzyme-substrate test (Colilert, IDEXX, Inc., etc.), that is available and widely used. The test is sensitive to 1 cell forming unit (CFU) per 100 ml. It is widely used and well understood statistically. False negatives are rare. Occasionally, there are false positives, as microflora within a biomass acquire enzyme capability that triggers the response in the MUG indicator identical to that triggered by the target β-galactosidase enzyme (remember the biofilm discussion in Section 2.7.1?). These false positives are rare but have been documented in Ohio by speciation testing of positive test vials. A TC positive in water (as low as 1 CFU/100 ml) is widely considered to be a standard of sanitation. Originally, in the United States, the <1 per 100 ml standard was applied in the U.S. Environmental Protection Agency’s (USEPA) Total Coliform Rule (TCR) for treated, distributed water. However, regulatory creep led to <1 per 100 ml being the sanitary standard for raw water from water wells. As TC are a

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Alternative for Biofouling Monitoring Step These alternatives should only be performed in labs with a competent graduate-level microbiologist (or determined, well-informed, self-taught amateur) familiar with the methods, equipped for preparation of and handling of cultures for microbiological testing (“Don’t try this at home, kids!”). See Smith (1992) in our reading list for most of these formulations.



1. R2A heterotrophic plate count medium may be used to replace SLYM-BART since it supports slime-forming pseudomonads pretty well. However, to enrich or isolate for pseudomonads or sulfur-oxidizing slime formers, consult formularies for nutrient and other media specifics. 2. W-R medium, or R2A+FAC (R2A amended with ferric ammonium citrate), provides organic-Fe complexes and serves something of the same function in a plate environment as IRB-BART. 3. Culture denitrifiers in C-free denitrifying media, in which disimilatory denitrifiers produce gas if present and metabolically active. 4. Culture SRB in Postgate type roll tubes.

Note: Agar plate methods such as heterotrophic plate count (HPC) media and generic broth media such as those for SRBs do not employ precisely the same media formulations or provide the same growth environments as the BART or MAG tubes, and potentially could recover a different array of microflora. Safety note: All cultures of microorganisms should be considered biohazards. Do not treat their handling lightly. Follow either manufacturer (e.g., BART or MAG) recommendations for treatment, handling, and disposal or general microbiological laboratory safety protocol (e.g., Standard Methods). Always handle with gloves and treat any spills as biologically hazardous, cleaning thoroughly with disinfectant.

functional class of bacterial types found in soil (not always enteric bacteria), this is a steep standard for water derived from the earth. Also, TC are routinely found even in pristine waters in the tropics. This problem is recognized and regulations are in debate. Both World Health Organization (WHO) and EPA standards require Escherichia coli (E. coli) to be <1 per 100 ml in drinking water. This is obviously a reasonable standard for raw water. The decision to designate an alternative to the TC test has not been made. So expect to continue to take coliform tests and to be held to the TC standard in the United States. Whatever opinion one may have of the importance of a TC+ test result, such a result should be considered a signal to look further at sanitary conditions. The H2S or septic test, intended to detect H2S-producing bacteria of sanitary interest (as opposed to SRBs that produce H2S as a result of dissimilatory reduction of sulfate as a form of respiration), was developed to provide a simple and low-cost

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indicator of the presence of microflora associated with fecal material. A wide range of bacteria of sanitary interest produce H2S as a result of decomposition of S-containing organic matter. Tests by Sobsey and Pfaender for the WHO (see recommended reading list) reviewed studies of comparisons between the H2S septic test and comparable methods (e.g., coliform testing) and concluded that the tests have value as an indicator test for fecal contamination, especially in warm-water climates. The test has also been recommended by some for general hygiene indication in water wells. However, in many aquifer settings, SRBs can also produce a positive result even when a well is not necessarily septic. Thus, like many tests, use of these simple tests has limits and qualifications. As a maintenance indicator test, the H2S test probably has considerable merit for well hygiene screening in oxic aquifers, especially in developing country settings. Biofouling monitoring analysis can also be done with only a light microscope and sufficient knowledge. One can see much in a good sample. Given the option to also use other methods, use them, but if all you have for analysis is the microscope at the village dispensary, use it.

5.7.7 Biofouling Monitoring Methods: Sampling Methods Grab samples can be collected by pumping, or biofilm material allowed to collect on in-well coupons or wellhead filtration devices. 5.7.7.1 Pumped Sampling Pumped (grab) sampling is the easiest way to obtain samples from wells for analysis, including for evidence of biofouling. This method assumes that biofilm bacteria and their characteristic structures are also present in the water column (planktonic phase). However, if pumping fails to detach and suspend biofilm particles, they will not be available for collection. The absence of bacteria in samples taken this way may simply mean that the bacteria remained attached, not that they are actually absent in the well. Pumped samples may be analyzed by microscopy or by bacterial enumeration with selective or general purpose nutrient media. Pumped water streams may also be evaluated using turbidometers or laser particle counters, both of which have use in automated monitoring, as previously described. A drawback to pumped sampling is the snapshot nature of the samples, representing the water quality only at the time that the sample was taken. Shedding events may provide slugs that transiently increase microbial counts or the concentration of Fe and Mn in ground water. Most bacteria in any single pumped water sample collected under these circumstances have been sloughed off the biomass and are likely to represent only a tiny fraction of the population and diversity of organisms that comprise the biomass. After a period of sustained pumping, biomass will yield very little of the turbid material usually necessary for microscopic examination. Analyses of samples taken after prolonged pumping may fail to detect the presence of chemical and microbiological parameters that would indicate the presence of biofilms near wells.

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In Practical Manual of Groundwater Microbiology, Cullimore (2008) describes a time-series pumped sampling program that attempts to overcome the “crap shoot” nature of such grab sampling. Cullimore’s procedures are based on understanding the occurrence and behavior of microflora in the underground (review Chapter 2). For example, when wells are shut off for several days (specifically seven), the flow of nutrients is shut off and bacteria “panic” and move out of the biomass and into the ground water, looking for the “promised land,” or at least greener pastures. If the well is then pumped and sampled, this greatly improves the ability to detect the broadest range of microflora types present and active in the biomass. If the seven-day shutoff is impractical, a lesser time still helps (hours to several days). Samples are taken on a schedule of minutes that correspond to the likely zone of occurrence around a well (10, 30, 60, 90, 120, 1,440, 2,880 min). For the numerically inclined that prefer a hydrologic basis, calculate (1) bore volumes and (2) drawdown cone volumes and adjust the sampling frequency accordingly. Of particular interest in the analysis is detection of changes in relative importance or the presence-absence of types of microflora that indicate the occurrence of zones. In particular, the position of the redox fringe (Chapter 2) can be determined by the reaction that occurs in the HAB-BART (or MAG-CHA) heterotrophic test. In the case of the HAB-BART, oxidative conditions are indicated by the UP (bleach up) reaction and anaerobic conditions by the DO (down) reaction. When the HAB results switch from UP to DO, there it is! This approach, including taking replicates of samples at each sample event, helps to overcome the limitations of pumped grab sampling as the sampling methods for cultural analysis. Do recognize that any sample taken during pumping is a composite of the intervals producing water and available to the pump. So each sample is likely to be a little statistical composite, centered around a certain focus. Your sample from 120 min that is pulling water from a radius of x according to your calculations is also bringing in bacteria from other distances. Grab samples remain unreliable for microscopic analysis. For this, some method is needed to provide enough sample to view or otherwise analyze mineralogically or chemically. 5.7.7.2 Surface Collection on Slides or Coupons Surface collection methods provide a different procedure for detecting bacteria involved in biofouling phenomena in the well bore and at the wellhead. These methods overcome some of the shortcomings of pumped grab methods in providing samples for microscopy or other analysis during regular well operation. While they also rely on the detachment and suspension of biofilm particles by pumping, collectors have a longer time to gather particles. The result is that samples from collection surfaces provide reasonable approximations of essentially intact biofilms downhole for analysis. This method is also adaptable for collection of samples of inorganic encrustations. Collection surfaces can be placed at various locations in the water system. For collection of well biofilm samples, collectors may be placed directly in the well bore or in the water pumped from the well. The primary considerations for choosing in-well or wellhead collectors are (1) need for representative collection of biofilm

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            (a)                 (b) Figure 5.12  (See color insert following page 66.) Wellhead flow cell collector: (a) element and (b) as installed on a wellhead.

samples, (2) access to the well for collection, and (3) influence of the collector on well performance. In-well biofilm collectors are practical only if there is access to the wellbore itself through the well cap or nearby water level monitoring wells (piezometers), and if it is acceptable to introduce such a device into a well. An in-well collector has to avoid hanging up on submersible pump wire or other obstacles. Wellhead devices allow collection even on wells that are permanently sealed at the surface. Figure 5.12 shows a collector type sampler used as a wellhead collector. Sample collection using this method is described in Standard Methods Section 9240. The flow cell system developed by Smith and O. H. Tuovinen (basically the device in Figure 5.12) has proven to have the additional advantages of being readily field serviceable, and adaptable for a variety of collection applications, as well as for use as a laboratory model. Such samplers can be very simple and do not need to be a sophisticated manufactured product. Something as simple as a clean microscope slide stuffed in a section of plastic tubing and disinfected is a useful sampler. 5.7.7.3 Representativeness of Collection Sampling Since biofilm communities are unevenly attached on immersed surfaces, there is a question of the representativeness of biofilm sampling. Glass and polycarbonate slides have been used for in-well collectors in a variety of work, all the way back to the 1920s. In addition, other materials, especially metals of interest, can be used for collection. This is an old technology in the collection of well samples for microscopy, and is also used to collect soil and surface water microflora, especially in streams.

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(a)

(b) Figure 5.13  Electron micrographs (EMGs) of filamentous biofilms (Bureau of Reclama­ tion project—scanning EMGs by L. Tuhela-Reuning, Ohio Wesleyan University).

One factor in collection-surface selection is the surface free energy of a surface, which influences bacterial attachment. Although their surface characteristics are somewhat different from those of stainless steel and other metal surfaces immersed in well water, glass slides are considered to be acceptable model surfaces because of the similarities of their surface free energy characteristics. In addition, slides are readily available, inexpensive, noncorrodible, and can be directly examined microscopically, or sampled for chemical analysis and for cultural recovery of microorganisms. However, collection of biofilm on materials used in the wells, analyzed by various means, including electron microscopy (Figure 5.13 shows scanning electron micrographs of biofilm samples), would provide information on actual biofouling effects on materials used in wells. The collectors chosen in any case will collect a biofilm sample typical of that existing in the near wellbore environment only. Wellhead collection (slide or filter) and pumped grab samples also will have been modified by the pressure and rotation

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Figure 5.14  (See color insert following page 66.) Field analysis of drive cores for physicochemical and biochemical parameters (Iowa).

changes exerted by the pump, resulting in samples that are likely to be somewhat more oxidized and physically disturbed than biofilms within the aquifer.



1. Examination of slides. Slides are exposed in the well or well discharge for a period of usually not less than one week (adjusted to meet local needs). They are then examined using light microscopy (400× to 1,000× magnification) for signs of filamentous or stalked bacteria associated with Fe precipitation. 2. Cores represent a type of surface collector. In this case, they are a sample of the formation. Your authors and their Canadian and German colleagues have collected direct push and drive core samples around affected wells, at various distance and depth, and from presumably unaffected aquifers. These have been analyzed for field physical-chemical parameters and microflora (in our case, using phospholipid fatty acid (PLFA) analysis). Figure  5.14 shows field processing of core in process. If subsampled properly from the cores, the analytical results should represent the microbial community or biomass of the sampled interval.

5.7.8 Electrochemical In-line Sensors Analysis by microscopy, culturing, and other laboratory type techniques is relatively awkward and time-consuming. There is certainly a place for a sensor that says “getting biofouled” before performance issues become evident. The key is to find a reliable sensor system that provides a valid signal in time to begin the response process. A number of devices have been developed and patented for the purpose of MIC or biofouling monitoring, as a cursory patent search will reveal. One such device is the BioGEORGE™, patented by the Electric Power Research Institute (Structural Integrity Associates, Inc., San Jose, California). This system consists of a stack of stainless steel disks comprising two identical electrodes. One electrode is polarized relative to the other for a short time, the effect being

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to encourage growth on the instrument as a precursor to fouling on plant components. Biofilm formation is detected as an increase in the applied current required for achieving the preset electrical potential. The variance from baseline is indicative of the biofilm formation. The electronic system of this device provides a wide range of useful output as well as a red, yellow, and green light system. So far, a less cumbersome and more simple device for mass use in wells has not entered the marketplace, although their function has been described conceptually in conference literature.

5.8 Summary of Recommendations for Maintenance Monitoring in Routine Practice Now let’s summarize what we have presented. Methods are further summarized in Table 5.2 and cross-referenced against well problems in Table 5.1. Selection of a monitoring program should only be attempted with the initial assistance of persons very familiar with current methods and their application because evolving methods may be refining those described in the literature. Even this book will become obsolete over time. Actions that should be taken as a result of detection of deteriorating conditions are discussed in Chapter 6.

5.8.1 Summary of Data Collection Requirements The primary purpose of routine maintenance monitoring data acquisition is to provide information to chart trends in historical well and system performance. These changes over time indicate performance change, and trends are used to schedule maintenance activities. The key factors in maintenance monitoring analyses are not really the absolute numerical values (e.g., total Fe = 2.6), but the changes over time (total Fe was 2.6, six months later it is 0.6). A significant change in parameters that represents a trend indicates that the well may be in need of attention. Do not forget information such as costs and time of service. The purpose of data collection and its use should be kept in front of personnel involved. To make use of the information collected, a data record system and analysis procedures are necessary.

5.8.2 Well Data File Features Each well requires a comprehensive file of all data pertaining to its ongoing maintenance and performance history as well as the initial data pertaining to its construction, well performance, pump performance, water chemistry, and biological environment described above. Establishing this record system for each well should be done at the onset of the project—or as soon as someone is motivated to do so. Since such data will periodically be manipulated and analyzed, establish a format for the records that is compatible with the methods used for analysis. Consistency will save time and frustration and improve accuracy.

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5.8.3 Pumping Rates The typical pumps used in water supply or remediation pumping wells are the widespread centrifugal type. In centrifugal pumps, the output discharge rate is in a dynamic relationship with the system head: As the system head is raised and lowered, the discharge rate lowers or rises in inverse proportion. Changes in pumping rates over time will result due to changes in pumping head: Internal pump changes. Clogging (increased resistance) and wear (reduced pressure) both result in lowered pump output, usually as a gradual declining trend. In submersible well pumps, an abrupt loss of output usually is due to a hole developing in discharge piping. Another cause may be an inadvertent valve closing or other obstruction. External head changes. If regional or pumping/injection head changes, this will affect the pump output of an otherwise properly functioning pump. While direct measurement of water level is a more sensitive parameter, increased drawdown may be reflected in reduced discharge. The size of this effect is specific to the pump. System demand changes. Operational changes may affect the output discharge rate and efficiency of a pump. Valving back the pump to restrict discharge rate (e.g., for plume management) may result in the pump operating inefficiently and having a shortened operating life.

5.8.4 System Pressure System pressure significantly affects pump discharge rate. If system head increases, a centrifugal pump cannot produce as much output. Reduced discharge then also may be a reflection of increased system head. This in turn is most typically a result of clogging activity. However, other causes, such as inadvertent valve closing or insufficient power, should also be investigated.

5.8.5 Water Level Data Water level data, combined with discharge data, can be used to chart changes in well Q/s (and when s is charted over several Q, aquifer and well loss) over time. The longer and more representative the water level history, the more reliable the trends that can be drawn from the data:



1. Pumping or injection dynamic level to filter pack piezometer comparisons: These are used to determine where clogging is in the screen and filter pack. Installation of in-screen and satellite rehabilitation wells facilitates this monitoring. 2. Pumping or injection dynamic level to area monitoring well: Is clogging occurring in the screen and filter pack vicinity, or does a change in pumping water reflect change at the regional scale?

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3. Geological-unit-specific piezometer levels: What changes are occurring in the contributions by multiple geologic units to a well? These changes can result in changes in inflow to and outflow from the well. Depending on hydrostatic head relationships between hydrostatic units, some water can actually flow out of the well screen during pumping of long-screen wells, as observed during borehole flow meter studies.

5.8.6 Electrical (Power) Data Historically, power problems may be the most common source of well operational problems. Power component (V, A, Ω,) data charted over time provide a history of motor and power system changes. Power supply consistency is sometimes suspect, especially with current voltage imbalance in three-phase systems, referred to as phase imbalance, which is calculated based on V readings taken on the three legs supplying a three-phase motor. A history of phase imbalance calculations can provide the evidence needed to take well system power source problems to the power supplier for correction or provide justification for installing protection systems. Within a pump circuit, changes in amperage draw can be used to spot worn motors, or pumping system problems such as a clogged or perforated discharge line. As with the hydrologic data, the longer and more complete the records, the more likely that valid trends can be charted. On generator- or solar-run systems, V and A changes reflect variability of the quality of power supplied and can provide ideas on what changes may be necessary.

5.8.7 Video for Historical Comparison Downhole video provides a direct view of conditions within wells, when properly used. Types of clogging conditions can be identified visually with some background. A progression of videos in any particular well, especially from the original construction condition, provides a direct way to watch changing conditions in the well (e.g., progressing screen corrosion or biofouling development). A video can also be used for comparison to file records where these are suspect or incomplete.

5.8.8 Hydrogeologic Information That Should Be on File 5.8.8.1 Piezometric Data Piezometric data provide water levels outside the immediate casing and pumping influence of a well. Piezometers (water level monitoring wells) offer information on the response of a producing or accepting unit to change induced by site activities in addition to larger-scale effects (e.g., changes in water table). You will use piezometric data to draw a hydrograph, which is a plot of water levels over time. A hydrograph for a well outside the influence of the pumping wellfield will reveal regional water level trends that affect wellfield operations.

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As with pumping and recharge wells, the reliability of water level response in monitoring wells depends on their original design, development, and maintenance. A standard guide to procedures for this purpose has been published by ASTM (D 5978). 5.8.8.2 Piezometric Maps Piezometric or water table maps provide information on regional head data that influence specific capacity, and help to illustrate anomalies around pumping wells. They are based on measured piezometric data (Section 5.8.8.1). Depths of water-bearing formation exposure and evidence of pumping centers can also provide insight into well-clogging oxidation occurrence in a wellfield. 5.8.8.3 Geologic Regime Geologic maps and cross sections provide information on the influence of stratification and particle and geochemical types on well performance and degradation, and also about how effective original well designs were. Trouble-causing situations such as long, large-particle-size filter packs in variable stratified aquifers can be identified. Expected well treatment problems, such as those that would be caused by screening across clay lenses, can be predicted. Good geology and geophysical data relevant to the well’s location are essential for proper well design. In addition, the seismic activity of the area should be understood for the purpose of planning preventive construction (Chapter 4) and contingency planning. Well systems are often designed based on too little geologic site information. Problems that crop up often have a basis in a well being designed for a generic site condition, sometimes based on single borings, instead of well-site-specific data. Files reveal when this is the case, when no geologic information is to be found, the hydrogeologist’s report is the county agricultural extension report, or multiple wells on a site will have identical depths, screen slot sizes, and filter packs. Results include screens and filter packs that are too fine or too coarse for the formation material and generally poor hydraulic efficiency. Because interpretations of geologic data over time may be distorted or simplified, it is recommended to preserve original field notes for reference. Good data collection and analysis save operational money in the long term by aiding good well design that improves the capability of facility operators to maintain well systems.

5.8.9 Development Data In well construction, development has three purposes:

1. Repair damage done to the aquifer during drilling 2. Set the filter pack 3. Increase the permeability of the aquifer in the vicinity of the well

Later, development activities may be a component of a maintenance program to further the original development effort, or applied as a component of a maintenance program to maintain or restore a well’s performance. In this use, the processes are

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termed redevelopment. Information from such work helps to understand well behavior and to diagnose well impairments. Descriptions of development and redevelopment processes can be found in Chapters 4 and 8. We also specifically recommend Drilling: The Manual of Methods, Application, and Management, the NGWA Manual of Water Well Construction Practices, and various industry standards. ASTM Standard Guide D 5521 is a good source in the context of monitoring wells. Development data should include descriptions of the tools and methods utilized. For example:





1. If air lifting was applied, what was the size and capacity of the air compressor (e.g., air compressor cubic feet per minute (cfm) capacity) and at what depth was the air line set? 2. If surging was applied, what was the configuration of the surge block assembly, does the diameter of the assembly match the casing and screen, through what intervals was it applied, and what was the length and speed of the stroke? 3. If jetting was applied, what was the configuration of the jetting tool, through what intervals was it applied, etc. (nozzle velocity and distance from screen)? 4. Time for each segment. 5. Description of material drawn into well: (a) Amount and type to determine its origin (need to know if it is aquifer or filter pack) and (b) if possible, quantify sediment content (e.g., Imhoff sediment cone or Rossum tester) and plot turbidity vs. time of development. 6. What predevelopment planning and decisions were made that would make development more or less likely to be successful?

Development information is merged with step-drawdown data, well construction data, and lithologic data to provide insight into how the aquifer material has been modified or is behaving through time in the vicinity of the well. This insight is crucial for assessing changes in well performance and the appropriateness and effectiveness of maintenance and rehabilitation efforts. The significance of development data gathered is:



1. Development time: The effectiveness of even an appropriate development method is related to the amount of time it is applied, and one must determine if the time of application was sufficient for the method to be effective. Development data should include the amount of time devoted to each of the tools and methods mentioned above. The construction log may provide the amount of time devoted to development, or the work crews’ time sheets or daily log may also provide the time devoted. 2. Development results: The data should include some form of documentation of the progress of the development. Some drillers estimate changes in the

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discharge from the well during air lifting or surging to indicate the progression of development. The driller may record a qualitative description of the sediment and material removed from the well. A semiquantitative record of the sediment concentration may be had from allowing samples to settle in a bucket, and a quantitative record may be available if water samples were collected using an Imhoff cone or Rossum sampler. 3. Finally, data from well acceptance tests, usually a step-drawdown test, are helpful to document the effectiveness of the development. As described in the discussion on step-drawdown testing (Section 5.7.2), the resulting efficiency of the well can be estimated from the analysis of the test.

5.8.10 Maintenance Logs for Individual Wells While general site information such as piezometric maps can be held centrally, files should be kept for individual wells to record their specific O&M histories. Make sure that information such as costs, dates, and who performed the work is preserved. 5.8.10.1 Where Records Should Be Kept As an on-site backup, brief basic information on the well should be kept within the casing or casing protection sleeve or structure. Include: • Dimensions of the entire well (depth), casing (length) and screen (length, location, type, and slot sizes), and filter pack (length, thickness, and particle sieve sizes) • Material construction of each • Pump and power information • Information on any inserts downhole • Last service date and information on how to obtain more detailed records Perhaps one day soon, detailed information may be kept on a well-site chip or flash drive. Files and video kept at the facility site should be duplicated at an off-site location that will continue to be available to site O&M personnel perpetually, regardless of changes in project management or service provider firms. 5.8.10.2 Downtime History Well files should include a brief comment section on history of the total (project site) system for use in pinpointing causes and effects. Service intervals, costs, details of persons and companies involved, and analyses of results (what works, what doesn’t, specific capacity changes) should be included for a history analysis, and for the sake of the next person (perhaps years in the future and unacquainted with the last service action). Also, it is sometimes most useful to know why and how long a well was out of operation. For example:

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1. It is commonly the case to construct wells and then to leave them sitting idle for long periods during project development. It is widely observed that this practice results in wells that must be rehabilitated before they can be used. 2. Facilities and individual wells may experience periods of hiatus in operations for various reasons. Again, equipped, developed wells, perhaps already with developing degrading conditions, sit idle. 3. Such information can help personnel in troubleshooting problems down the line to make sense of the condition they find.

The bottom line for collecting, analyzing, and tracking trends in collected data is that there may be multiple reasons why a well may experience diminished performance, and collected data are crucial for identifying causes. Also, once a pattern of well performance decline is established, collected data will enable the operators to plan maintenance and rehabilitation activities before a well is beyond recall. 5.8.10.3 File Records Purpose and Format Issues Accurate and relevant field data recording is essential for data to be of any use. How this is done can be project specific. The data management system in place for the project in question can be adapted to provide the same activities for maintenance planning. • Successful maintenance monitoring programs have been run using only physi­cal paper files in the water supply field—do not be mesmerized by technology. • Spreadsheet organization of data (e.g., Microsoft® Excel™) provides a tabular display of various data but also permits plugging data into formulas to perform routine calculations, such as those for specific capacity and motor efficiency, and rapid charting of data trends. Excel files are likely to be readable far into the future. • Database systems (e.g., Microsoft Access™, Lotus®, Approach™, opensource versions of the same, or even DOS flat-field systems) permit crosscomparison of parameters to ascertain cause-effect relationships (e.g., changes in hydrocarbon concentration vs. head loss in pumping systems). • Keep disk and hard copies on site at the wellfield in individual record books for each well. Another option is to use the increasingly capable handheld devices available for file storage. Also, old laptops with big disk drives can be purchased cheap (or rededicated from another purpose in your organization) and dedicated to the task. • Essential well data (depth, diameter, pump type and identification) should be marked in a durable way at the well. • There should be accessible inventories of physical file components such as video tapes or disks so that people reviewing files may know what is present. Note: TV records should be a permanent part of well records, labeled by date. Where videotape has been used as the recording medium, bulky tapes can pile up. Also, VHS and other analog video formats are rapidly disappearing and may become

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unreadable for future reviewers. Tapes can be edited onto summary tapes, CDs, or DVDs showing important features. Note that recent evidence suggests that many videotapes deteriorate in seven to ten years, so recopy them every five years for safe keeping or copy them to more stable high-quality DVDs and store according to vendor instructions. CDs and DVDs have the additional advantage of taking up less physical storage space. In some cases, it may be beneficial to store the videos on other, high-capacity storage media such as hard drives (dedicate an external hard drive to this purpose). All media have finite service lives, so keep that in mind (and storage requirements) when planning permanent archives. It is difficult to make the right choice in matters such as data formats. A software system designed specifically for well maintenance management (e.g., AllMax Software’s Atero) can be used without modification to record and display graphically at least most of the data helpful in well maintenance analysis. The major drawback is the financial investment. There are many upside points. General interactive database spreadsheet software has the disadvantage out of the box of not being designed for your purpose (the programmers never heard of well maintenance). It does have the elements you need: the ability to store data in formats you design, the permitting of analysis of data, and graphical displays of existing data, changes over time, and the ability to make projections. A qualified programmer who knows what you want can make the necessary modifications to provide the well recordkeeping and analysis system that meets your specific needs and system capacities. An example of when computer-aided analysis is especially useful is in making sense of BART reaction type and day-of-delay (d.d.) values. The trends they reveal are best analyzed graphically by looking at the microbial ecology “signatures” of well environments and changes in d.d. values over time. These analyses can be made using the commercial BARTSOFT™ software developed by the BART system developer or by database spreadsheet. If there is a change from the previous sampling period, repeat the test.

5.9 Schedule of Maintenance Monitoring Actions for Wells 5.9.1 Minimum Regular Schedule for First Year This and the following sections offer maintenance monitoring schedule recommendations based on the principle of establishing a data baseline and then settling into less frequent (or more intense) PM activity if conditions warrant. Table 5.5 is a summary recommendation for first-year maintenance activity frequency for a valuable well array.

5.9.2 Schedule for Reducing Maintenance Monitoring after First Year Maintenance (including monitoring) intervals can be reduced as trends are established. An exception is troublesome wells that may be on annual or more frequent

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Table 5.5 First-Year PM Monitoring Schedule Physical inspection

Borehole color video

Once each well, then annually or at pump service intervals

Surface facility inspection; inspect sampling points and clean as needed

Monthly or whenever visited

Examination of pulled components

As needed (at least test pump if not pulling it annually)

Well discharge (volume rate and pressure)

Weekly (recommend installation of automated data collection)

Drawdown: Taken concurrently with well discharge measurement

Weekly (recommend installation of automated data collection)

Conduct graphical analysis

Monthly

Specific capacity test (well hydraulic performance)

Annually or at recommended shorter intervals

Pump performance: Conduct five-step pump test of centrifugal pumps and similar wear analysis of positive displacement pumps; compare to “nominal” data

At least annually or at recommended shorter intervals in pump service if severe (Q/s and pump test can be a single operation)

Electrical (power)

System and motor V, A, Ω, phase imbalance

Weekly; check at various times of day and in various pumping configurations; recommend installation of current monitors with alarms

Physicochemistry

Inorganic parameters and pH, mV, Eh, and temperature

At well start-up and monthly using project on-site instruments (calibrated) or routine (laboratory)

Suspended particulate matter (sand, silt, clay)

At well testing,then quarterly

Turbidity (adds colloidal)

In-line monitors (continuous)

Biofouling microbial component

BART analyses: Wide suite (IRB, SRB, SLYM, HAB, DN)a

At well start-up for baseline, then monthly

Biofilm flow cell for microscopy

Quarterly for baseline, then annually

Treatments and serviceb

Well hydraulic improvement and pumping systems

As testing indicates, Q/s drops below 90%, or pumping system degrades

Instrumentation calibration

In accordance with documented procedures and manufacturer instructions

Hydraulic performance

Source: Modified from Alford et al. (2000). a Or viable alternative to BART methods. b See Chapter 6.

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treatment schedules based on first-year experience. Typically, on wells performing adequately, the frequency of physicochemical and biofouling parameter testing can drop to quarterly if little change in conditions is noticeable after one year. Table 5.6 summarizes a post-first-year PM schedule. After the first year, you may need to conduct maintenance treatment as needed per Chapter 6. Remember our timescale comment made earlier: Over the eighty-year life span of a well, the first twenty years may reveal the trends and correlations/relationships that inform the next sixty years of maintenance activities. Think lifetime, not next fiscal cycle. You are just beginning the generations-long process of maintaining a well at the end of year 1.

5.9.3 Rationale and Commentary While not ultimately conclusive or a precise step-by-step recipe for maintenance monitoring of well deteriorating conditions, methods such as those presented here can provide sufficiently early warning of deterioration to allow for effective control if employed properly and used faithfully. In actual practice, a customized monitoring program may employ methods at several levels of sophistication. At any sophistication level, there still is no direct correlation between microbiological data (such as BART, CFU/ml, or slide results) and particle/turbidity data to terms such as lightly biofouled or heavily biofouled. At the present time, judgments as to whether a well is more or less biofouled than before can only be made on the basis of monitoring over time, and some definition of what is biofouled, usually expressed in terms of performance loss that can or cannot be tolerated operationally. In general, maintenance monitoring approaches should be tried and reviewed over a period of time and adjusted based on experience. Experience will demonstrate where the action triggers will be, and this is specific to individual wells or wellfields. Such monitoring must be implemented as part of a systematic maintenance program involving:

1. Institutional commitment to a goal of deterioration prevention 2. Maintenance monitoring as part of an overall site and well system maintenance 3. A method to evaluate improvements in performance

5.10 Institutional and Funding Issues in Maintenance Planning, Analysis, and Execution 5.10.1 Background and Barriers to Effective Maintenance Implementation Successful O&M of any mechanical system such as a pumping well array requires an institutional structure and indoctrination that preventive maintenance is valuable and indeed essential in preventing future problems. This is well demonstrated for wells in a variety of operating settings (including water supply, dewatering, and hydraulic relief)

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Table 5.6 Long-Term PM Monitoring Schedule Physical inspection

Borehole color video

At pump service intervals; concentrate on screen and other stress points

Surface facility inspection; inspect sampling points and clean as needed

Quarterly or each visit

Examination of pulled components

As needed (at least test pump if not pulling it annually); wells should be equipped for easy pulling if at all possible

Well discharge (flow rate and pressure)

Weekly (recommend installation of automated data collection)

Drawdown: Taken concurrently with well discharge measurement

Weekly (recommend installation of automated data collection)

Conduct graphical analysis

Quarterly

Specific capacity test (well hydraulic performance)

Annually or at recommended shorter intervals

Pump performance: Conduct five-step pump test of centrifugal pumps and similar wear analysis of positive displacement pumps; compare to “nominal” data

At least annually or at recommended shorter intervals in pump service if severe (Q/s and pump test can be a single operation)

Electrical (power)

System and motor V, A, Ω, phase imbalance

Weekly; check at various times of day and in various pumping configurations; recommend installation of current monitors with alarms

Physicochemistry

Inorganic parameters

At least quarterly using project on-site instruments (calibrated) or laboratory instruments

Suspended particulate matter (sand, silt, clay)

Manually at well testing, then quarterly

Turbidity (adds colloidal)

In-line monitors (continuous)a

BART (or alternative) analyses: Wide suite (IRB, SRB, SLYM, HAB, DN)

Quarterly until patterns develop then drop to those that change

Biofilm flow cell for microscopy

Annually on selected wells

Instrumentation calibration

In accordance with good practice and manufacturer instructions

Hydraulic performance

Biofouling microbial component

Source: Modified from Alford et al. (2000).

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and particularly well demonstrated in ground-water remediation. However, despite the well-known vulnerability of monitoring and remediation wells to performance degradation, provisions for preventive design and maintenance are routinely shortchanged. A persistent problem in encouraging rational well maintenance planning and execution is the array of roadblocks that discourage the implementation of these logical behaviors in the utility and environmental remediation fields. Basically, these include (1) typical public funding processes in which capital costs can be financed but no O&M budget provided, or it is delegated without preparation to the local community, and (2) typical ground-water remediation cases, where the “potentially responsive party” (no fault established) pays to install a remediation system, but again there is no provision for O&M costs. This situation is analogous to a high school student finally scraping together the money to buy a used car, but forgetting the costs for fuel, insurance, routine maintenance, and repairs.

5.10.2 Institutional Needs for Effective Implementations It is imperative that well system O&M be explicitly incorporated into implementing public works planning or legislation and orders, scopes of work (SOW), and specifications, and included as an issue in design (designing for ease of maintenance). Likewise, contract administration needs to enforce the well system O&M imperatives of the SOW. Trotting out GASB 34 (Chapter 3) as a standard in funding or case resolution might do the trick. If a water supply or ground-water monitoring and remediation system is not working due to living things and the earth reclaiming their own, the mission of the system is not going to be completed. Typically, something must be done to rectify the situation. History and experience demonstrate the necessity of planning and adequately funding well system O&M oversight and professional review. • Such funding and O&M planning: • Should be an integral part of a ground-water system’s planning and funding activities at the outset of project development, and included in any specifications or scopes of work involving the monitoring and pumping of ground water • Should be part of the project’s review checklist • Should include maintenance monitoring data management as an integral part of facility data management • Once constructed and active, facilities, especially water supply and remediation projects, must have the funding budgeted and available to perform adequate routine well system maintenance monitoring, repair, replacement, and cleaning as part of the overall site and system O&M contract. It will be a cost, no doubt. Someone must be responsible for paying for it. • Funds should be protected to the extent possible contractually from transfer to other purposes.

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• Personnel are the most important and valuable asset in a maintenance system. With experience and training, they detect changes, especially as well symptoms can be subtle and incremental. They have a memory that supplements and corrects a paper history. The logical necessity of such planning takes the form of a typically remorseless “pay me now or pay me later” scenario: • Filter and other water treatment clogging occurs due to components pumped from wells that supply the treatment plants. Some of this is unavoidable, but others, such as biofouling buildup, can be minimized by preventive maintenance actions at the well source. • Hydraulic losses due to clogging can be prevented and mitigated in the same way by maintenance activities at the well source and by preventive engineering design that reduces choke points and permits line service. • Perhaps most costly of all is a situation where the project’s objectives (e.g., ground-water cleanup) are not achieved or delayed due to preventable wellfield problems. Remember those EEV costs (Chapter 3)? System not working? Let the lawyering begin.

5.10.3 Quarterly Review of Facility Performance Data At a minimum, facilities should regularly review performance and other maintenance monitoring data. Doing so quarterly is a common recommendation and fits into many routine review schedules. At this time the operational team reviews data and operational information to answer the questions “Where do we stand now?” and “What do we expect to happen?” A review of the range of information required for baseline wellfield maintenance monitoring shows that it is multidisciplinary. It is highly recommended that the facility should engage personnel experienced in wellfield maintenance for information review and interpretation. Such persons (or a team of persons) should be conversant with all of the material covered in the following sections.

5.10.4 Baseline and Historical Data for Wells/Site An essential element in this process is data management systems that permit the detailed tabulation, plotting, cross-reference, and statistical analysis of a broad range of information. A system that stores and permits the easy retrieval and cross-referencing of a variety of information without artificial topical boundaries helps human troubleshooters and planners to see patterns that may not be immediately obvious. This archive may be physical and the retrieval system may be a knowledgeable human or computer based. Project data systems should permit:

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• Charting of information (e.g., pumping water levels) back to the site’s characterization and development at flexible scales • Cross-referencing of various data to look for trends (e.g., Q/s vs. lithology or biofouling indicators) • Data access by or maintained by the department or firm responsible for O&M if these tasks are split from regulatory oversight As useful as data and other information are, they are most valuable when filtered through human operational experience. All systems have quirks or features that defy the kind of quantification possible in a computer database file.



1. Filing systems are imperfect and incomplete. Human experience provides the kind of anecdotal background that is often most useful in troubleshooting, for example, noting that problems began when there was a change in pumps, or changes in sounds and vibration. However, anecdotal “feelings” or intuition can be misleading. Such feelings or hunches should not be ignored, but tested using objective methods. It may be worth moving up a pumping test, for example, or scheduling an electrician’s visit. 2. Facility well system maintenance planning should make provision for: • Regular recording of maintenance actions and observations by operating personnel • Minimizing personnel changes to preserve memories • Ensuring that key operating personnel are well informed and trained in their tasks • Outside expert assistance on an as-needed basis—expertise that respects and listens to local operational experience

5.10.5 Operator/Working Crew Leader Qualifications and Training Well-trained and motivated on-site operating personnel are crucial in successful O&M management. Frequent turnover, poor training, and lack of positive motivation will defeat even the most well-crafted O&M plan. While requirements may vary, the following are essential: • Institutional continuity and ownership of the O&M plan and its execution are crucial in fulfilling any plans to properly maintain well arrays. Experience shows that if maintenance is the personal mission or vision quest of one person, but not adopted by the entire facility operator crew and management, the effort ends if the original enthusiast leaves. • The operators on site must understand the O&M plan, the purpose of its activities, and why they are important to the operation of the ground-water monitoring or pumping system. At a minimum, the operations supervisor

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should understand and be able to verify field data collection, manage and participate with field personnel in maintenance actions daily, and enforce commonsense issues during daily operation. • For these reasons, training is essential. All personnel responsible for well array O&M should be formally trained in the O&M plan, its components that pertain to the well system, and essential tasks.

5.10.6 Determination of Operational Maintenance Responsibilities An important consideration in well system O&M is defining the roles of plant management and operational personnel in scheduling, analyzing, reviewing, and revising various O&M activities. These can be divided into two primary levels: Plant manager—project level. This person or team operates at the level of the facility’s management and integrates O&M activities into the overall project goals and structure. Primary tasks related to well system O&M include: • Setting up maintenance action schedules • Following up to ensure actions are accomplished • Being responsible for data collection and evaluation • Preparing status report of evaluations • Seeking and working with outside expert help as needed Designated oversight personnel—operations level. This person operates at the wellfield or water plant level. If a separate O&M company oversees the regular function of the facility’s physical plant, then this group may consist of both the O&M company’s management and on-site personnel. Their work scope involves: • Assisting in maintenance schedules and making recommendations for modifications based on site-level experience with individual wells • Conducting necessary training of pertinent personnel (as necessary with outside expert assistance) • Being responsible for enforcing maintenance actions and reporting to the plant manager

Treatments 6 Preventive and Actions Maintenance monitoring does no good if no action is taken to control deteriorating effects once they are detected. Likewise, waiting until performance deteriorates markedly raises the odds that treatments are less than totally effective. Preventive treatments represent a proactive treatment approach, to borrow a term from current pop-psych lingo. A preventive treatment is that which is applied before performance (however defined) declines.

If well performance-degrading problems such as sand pumping, corrosion, or biofouling are detected by monitoring, then what? At this point, preventive maintenance repairs and treatment are implemented. Preventive treatments must be implemented upon detection of the indicator signs of a problem and before performance deteriorates. The nature of the response or treatment depends on the nature of the problem. The decision-making process might follow the decision flow paths illustrated in Figure  6.1. To make such plans effectively, well systems must be equipped for preventive monitoring and treatment (Chapters 4 and 5) and a maintenance program must be in place (Chapter 5 and 6).

6.1 Sand/Sediment Pumping Sedimentation in a monitoring or pumping well can possibly be controlled by redevelopment using methods described earlier. Methods chosen should be appropriate for the screen and aquifer. An attempt should be made to develop the well until it has a very low level of sediment in samples (< 50 mg/L). In some wells, especially monitoring wells in formations with layers of fine material, this may not be entirely possible. Water supply wells, when finished and developed, should produce water free of clay or particulates. Sediment may have to be minimized by purging during sampling events. Surging and jetting should only be performed by well rehabilitation contractors or crews experienced with these methods. In pumping wells, sediment production can be greatly limited by installing a suction flow control device (SFCD) or engineered tail pipe (see reading list), which seem to force a cylindrical well inflow pattern in many cases, as described earlier. This can serve to reduce or eliminate turbulent upflow through packs that are too open, and limits or eliminates selective channeling through the pack in the top 15% of the screen. The SFCD (Figure 4.12) can be installed as original equipment in a new well, or it can be retrofitted. Note that this is not a panacea. It does not have the desired effect in all well configurations and must be tested in individual wells to determine if this solution fits the circumstances. 171

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Action Completed: Resume Operations

Analysis No

Sign of Problem? Change? Yes Diagnose Choose Options

Performance Degraded

Performance Not Yet Degraded, Action Needed

Beyond Repair: Abandon Asset

Rehabilitate Reconstruct

Maintenance Action

Replacement

Figure 6.1  Well maintenance decision tree.

Chronically sand-pumping wells that cannot be repaired in any other way or replaced should be fitted with sand removal devices. Probably the most useful is the in-well centrifugal desander, such as the Lakos model. This desander fits over the pump intake (Figure 4.13), protecting both the pump and system. Sediment will be dropped to the bottom of the well, and this may have to be cleaned out on a regular basis. Some limited anecdotal experience indicates that a desander over time will force a new equilibrium in the well, eventually reducing or halting sand production. As a last temporary resort until something else can be done, sand-resistant pumps should be employed. Such pumps should not be considered a permanent solution to a sand-pumping problem. Sanding/sedimenting small pumping wells (<6 in. diameter) and monitoring wells are very difficult to fix because of their already restricted diameters, which precludes effective rescreening or SFCD installation. Desanders can be readily used. Redevelopment may work, or (as a last resort) overpumping can be tried. If not, purging should proceed before sampling until the water clears, or alternatively, samples should be filtered. The risk of relying on sample purging and filtration is that sorbed constituents may be lost to analysis or at least difficult to quantify. As the situation permits (budgets, time, permission), sanding monitoring wells that interfere with sample quality should be replaced with better-designed, betterconstructed, and better-developed wells.

6.2 What Do We Do if We Have Corrosion? The primary method of controlling corrosion is to design the well and treatment system properly to prevent corrosion (Chapter 4). As you recall from Chapter 4, water

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quality information should be used before design decisions are made. If corrosive conditions exist, proper casing and screen materials can be chosen. What about cathodic protection? Where external sources of corrosion induction, such as high-voltage power lines, are detected, cathodic protection of steel casings may be specified on certain systems. Experience has shown that where microbial activity is generally absent, protection of steel is achieved when the potential is depressed to –850 mV, but where microbial activity is intense (or likely to be, the most normal case), the potential has to be depressed to at least –1,000 mV. This voltage drop may be extremely difficult to achieve over the length of wells in many situations, and may affect water quality near the well. In any case, casings installed in most earth sequences encounter multiple electrical potentials (somewhat dampened by grout), rendering cathodic protection impractical. Maybe more practically for most installations:







1. Examine the system for dissimilar metals (Table 4.3) in contact or other corrosion-inducting conditions. “Contact” can be maintained by water flowing by two pieces of dissimilar metal. In fresh water, they generally have to be in close proximity. Corrosive conditions include various chemical injectors. We have also noted inner and outer casings of different metals in contact by way of wet bentonite that have electrical potentials across them, causing corrosion. When identified, try to install components and systems that are more electrochemically compatible. 2. Identify potential problems even if corrosion is not yet occurring, so you can plan ahead. Do you have a cast-iron-and-bronze pump operating in a sulfide or high-chloride water? 3. Alter the pumping scheme to reduce corroding conditions. For example, reduce pumping to reduce the oxidizing drawdown wash zone or reduce pressure and velocity in piping systems. 4. Look for design flaws that enhance corrosion potential: One particularly bad idea is to have unsealed annular space between inner (pumping conductor) and outer casing left open to the filter pack. The oxidation and wash zone provided can result in rapid penetration of the inner casing, and no way to treat the annulus effectively. 5. Look for grounding (earthing) shorts such as worn wires, bad splices, incomplete or incorrect system grounding, induced electrical currents, etc. 6. Well TV surveys result in “Wow (or #@&!), look at that!” moments, such as the lower end of casings corroded off, or the typical pattern of increased tuberculation in the lower reaches of a casing. When such situations are identified, it is time to plan to replace the system. 7. Reconsider pump and discharge pipe types and materials after visual inspection during pump pulling events. See item 2. Maybe now is the time to install the noncorroding pump discharge pipe or stainless steel pump. 8. If casing is rotted off and there is sufficient diameter, attempt a lining with noncorrodible casing that provides a sanitary installation. But if not, plan replacements.

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These are just some examples. Dealing with corrosion requires step-by-step detective investigation. Looking at cause and effect, and sometimes through trial and error, you build a more corrosion-resistant system. In the “what the …” department, we are aware of situations where regulatory authorities allow water utilities to operate wells with perforated casings, but do not let them install linings because the well does not have a sufficient sanitary radius from a property line. Is this some kind of upside-down reasoning?

6.3 Biofouling (General) In many cases real well plugging does not occur, only maddening and irregular poor-water-quality problems. For these situations, periodic treatment with a nonoxidizing chemical mixture based around an organic acid (e.g., acetic or glycolic acid and a penetrating, sequestering, detergent, and dispersing (PSDD) compound—see Chapter 8), combined with surging, can be beneficial in keeping biofouling below problem levels. It is common for such products to be available as commercial blends. These typically are listed as conforming with NSF Standard 60 (NSF International), which is convenient in documenting and justifying well treatment choices.

6.4 Inorganic Encrustations (General) Preventive chemical encrustant removal is specified in wells that have encrusting waters, where mineral salts tend to build up on slots. These can be removed by appropriate acidizing or by sonic vibratory or fluid-pulse treatments as described elsewhere (Chapter 8, reading list). Such encrustation often occurs along with biofouling, and must be removed to permit effective biofouling treatment.

6.5 Preventive Chemical Treatments Chemical treatment in a preventive mode is a major aspect of maintenance of well and fluid system performance.

6.5.1 General: Cost-Effectiveness, Professionalism Listings of chemicals and brief summaries of their uses are detailed in the following and in Chapter 8. Before we get into specific recipes, stay with the discussion here a little longer, as there are some underlying principles to consider.

1. Cost-effectiveness: Cost is frequently cited as an issue in choices made as to whether to use chemicals, and electing which ones and how much to use. 2. Professionalism: Touched on here briefly, but seeded throughout the discussion of the following sections and Chapters 7 to 9. 3. Reactivity with constituents of contaminated ground water is an issue in ground-water remediation and monitoring well maintenance. Section 6.5.4 discusses chemical constituent reactions and incompatabilities.

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6.5.1.1 Cost-Effectiveness Related to cost-effectiveness, three factors affect the market price of chemical products used in well cleaning:

1. Actual process and shipping costs (shipping becoming an increasing part of shipping typically heavy fluids and solid chemicals, many of which are also classified as hazardous) 2. Premiums for purity and standard certification (more on that follows) 3. Degree of commercial exclusivity (particularly with proprietary products) and similar commercial tack-ons (marketing, etc., such as for brandname medicines)

In terms of effectiveness, a more expensive chemical may be a better choice and therefore cost-effective. Among the following acids, for example, organic-based and more concentrated products are more expensive than inorganic acids, primarily due to process costs. However, their effectiveness against biofouling and relative handling safety may outweigh the actual material cost differential. Cost Note:  As you may have noticed, costs of chemical stocks have increased tremendously, especially since 2007 (with some retraction during the recession that blew in soon thereafter). The cost of petroleum- and crop-derived polymers and the cost of fuel to move product have, of course, increased, as we all know. Even with temporary retraction, you know the long-term trend (as with motor fuel) is upward. A second factor is the rapid development of China and South Asia, requiring massive quantities of materials and opening new markets for chemicals as new water and wastewater treatment plants go on line. The petroleum production industry itself uses large quantities of chemicals for extraction and refining. There is a real incentive to move toward effectiveness, prevention, and best use in cleaning. Is a “cheap” buy in chemicals really frugal? If a chemical is extraordinarily low cost, you may want to investigate why that is. You may be familiar with the great olive scandal, in which most “olive oil” sold is really not olive oil at all. Or you may have heard of cheap generic medicines being ineffective or adulterated. The same principles apply. Your “great buy” may be mislabeled, poor quality, or contaminated. Check it out. Taking a “long-view” approach to O&M cost-effectiveness calculations, i.e., to consider cost-effectiveness on a life cycle cost basis, is going to reduce life cycle cost. Available research (Sutherland et al. (1994) in our reading list) in water supply applications indicates that even aggressive preventative maintenance (PM) is cost-effective compared to losses in efficiency, equipment repair, and well failure. Ground-water plume management adds the factor of the project mission, i.e., the cost of failure to control contaminated ground water (see Chapter 3). Note: These chemicals are all reactive and pose risks to skin, mucous membranes and other soft tissues of humans, and potentially to the environment if handled improperly. They should only be used by trained personnel familiar with their safe

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use and equipped with proper respiratory and skin protection. Material safety data sheets (MSDSs) and other safety information must be reviewed by all personnel involved (make this mandatory). No facility should employ personnel or contractors in well cleaning who cannot clearly demonstrate competence in relevant chemical knowledge. 6.5.1.2 Professionalism Any treatment program must be initiated by professional specifiers and contractors highly familiar with these treatments. Facility personnel can be trained in the safe use and evaluation of the effectiveness of these methods by the contractor. More on that in the following discussion.

6.5.2 Chemical Classes and Properties The following are summaries of chemical purposes and effects, safety, handling, and effectiveness features. More on this discussion from the perspective of rehabilitation practice in Chapters 7 and 8. 6.5.2.1 Acids for Maintenance Treatment Acids are used to dissolve hard encrusting materials, including Fe and Mn oxides and carbonate deposits. Tables 6.1 and 6.2 list acids most commonly used in well rehabilitation. Table 6.1 lists recommended compounds. Table 6.2 lists commonly used well cleaning compounds not recommended by the U.S. Army Corps of Engineers (USACE) for hazardous, toxic, radioactive waste (HTRW)-site well PM treatment. Note that “not recommended” is specifically for the maintenance cleaning application. Long-Term Treatment Note: USACE documentation advises that some well cleaning compounds, including acetic and phosphoric acid, can cause intergranular corrosion in sensitized austenitic stainless steel. Additionally, frequent exposure of metal to HCl and chlorine can also result in erosion corrosion. 6.5.2.2 Biocides and Oxidizing Compounds These agents are used in the attempt to reduce bacterial populations. For both water supply and environmental well cleaning (maintenance or rehabilitation, Chapters 7 and 8), this is not a primary objective. The primary objective is reducing biomass and improving hydraulic efficiency. 6.5.2.2.1 Chlorine Chlorine disinfection is a fundamental tool in the toolbox of well maintenance and rehabilitation (and the water supply industry in general). Typically, chlorine disinfection is conducted using sodium or calcium hypochlorite (AWWA Standard B300). Na hypochlorite is liquid and more likely to retain solubility in high-TDS solutions. One procedure used to limit and remove biological encrustation is the

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Table 6.1 Acid Effectiveness, Safety and Handling—Recommended Compounds Acetic acid

Excellent biocide and biofilm dispersing acids; relatively safe to handle; often a major component of biofouling enhancers and brand-name mixtures specified for biofouling

Acidizing to pH < 2 with sulfamic acid recommended (rapidly loses acid power without); use food or good industrial grade > 85% acid

Safety: Use gloves, splash protection, and respirator at barrel enda,b

Handling: These solutions freeze at working ambient temperatures: glacial at 50–55°F, 84% at 40°F, 15% (working solution) ~ 32°F; make the dilution at an ambient above the stock solution freezing point

Glycolic acid (hydroxyacetic)

Very similar to acetic: More products with NSF listings, less odor, higher acid power than acetic

Handling and physical properties similar to acetic; can use about 1/2 to 2/3 as much as acetic

Sulfamic acid

Relatively effective against carbonate scales, and as an acid enhancer for acetic acid

Solid, less aggressive than HCl (Table 6.2); not effective alone against biofouling or metal oxides

Handling: Relatively safe to transport and handle (solid, dust inhalation should be avoided)

Safety: Use gloves, dust mask, and goggles; provide proper ventilation; circulate during mixing

For example, oxalic and citric acids

Useful as chelating agents; oxalic acid is also effective as a primary acidizer in low-Ca water

Handling depends on form (typically granular solids); safe to transport

Often form insoluble precipitates in high-Ca waters

Other organic acids

Source: Modified from Alford et al. (2000). a Refer to following discussion, Chapter 7, and health and safety references. b NSF International Standard 60 covers the safety of chemicals for human contact.

so-called shock chlorine treatment. Standard ANSI/AWWA C654, Disinfection of Wells and the disinfection section of Standard ANSI/NGWA-01 cover the procedures for preventive and shock chlorination and bacteriological testing for the disinfection of wells for potable water service. NGWA also offers best practice documents on well disinfection. The mode of action of chlorination is described in Section 8.2.4. As for chlorine use in well cleaning (maintenance and rehabilitation are not formally standardized but methods are generally prescribed), concentrations as high as 500 to 2,000 mg/L of chlorine have been recommended for years for this purpose. This is not recommended for maintenance treatment applications. Chlorine is a powerful oxidant that reacts with reductive organic compounds, causing chemical alteration to more difficult-to-treat forms or potentially explosive situations.

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Table 6.2 Common Well Cleaning Chemicals in Use—Not Recommended (USACE) Muriatic acid (HCl)

Powerful for removing mineral and inorganic metal oxide scale

Relatively ineffective against biofouling and deleterious to stainless steel

Warning: Extremely hazardous to handle

Volatile liquid: Requires respiratory and splash protection; do not mix with chlorine; use inhibitors for metal but note that some industrial inhibitors should not be used in potentially potable ground water, and gelatin (safe) provides nutrient and inoculum for regrowth

Steel industry pickling liquor by-product; quality is a problem, with cadmium and other impurities often present in industrial grades, although NSF 60 listed solutions are available; not recommended for maintenance treatments

Phosphoric acid

A strong food-grade quality acid; readily available, 75%; in 55 gal drums and 12–15 gal containers

Effective against metal and mineral hydroxides; somewhat effective against biofouling, but no more so than some other mixtures

Warning: Extremely hazardous to handle

Quite hazardous to handle; full breathing mask and splash protection required; adequate ventilation a must

Leaves phosphorus residue behind for bacteria; not recommended for maintenance treatments

Source: Modified from Alford et al. (2000).

The ideal now is to (1) get the well as clean as possible with the detergent step (mild acid and dispersants) and then (2) chlorinate to not more than 200 mg/L (typically less). Note about Chlorine Quality: Do not use products for domestic use that have additives (scents, “ultra” agents). It is best to use NSF 60-listed 12+% Na hypochlorite that is freshly delivered and intended for potable water disinfection. Its manufacturing date should be <60 days in the past so as to minimize the potential for perchlorate formation in the solution. If unavailable, in an emergency, buy the cheap, plain 5% Na hypochlorite bleach (no additives, but quality is uncertain) or generate on-site (see following). 6.5.2.2.1.1   Calcium Hypochlorite, the Remote, Emergency, Developing World Option  Na hypochlorite has a serious drawback in that it has a short effective shelf life, particularly when conditions are warm. It loses about 1% of strength per week in moderate climate conditions. That is, a 12% solution is 11% a week later. It is then necessary to adjust dosing calculations accordingly. Ca hypochlorite is easier to transport and store for long periods (up to one year is recommended). So it makes more sense where transport and storage are big factors. In these cases, use it, but mix at the surface before treatment.

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Pellet droppers for maintenance disinfection of well water columns are not recommended. Undesirable results include corrosion of metal components, stratification of chlorine in the lower part of the well, deposition of calcium solids, and whole pellets left untouched. Biofilms also become adapted to the level of chlorine, hardening in the well and retracting to form a clog farther out in the redox fringe. Batch chlorinate wells and use pellet chlorination in mixing systems for line disinfection. 6.5.2.2.1.2   The Gas Chlorine Alternative  If your facility is a water utility that uses Cl2 for distribution water disinfection, this same chlorine can be used for well disinfection if properly equipped and personnel are trained in correct and safe procedures. Replace the Na hypochlorite dosing step with gas meters and regulators, and employ the same concentrations. Cl2 is a very clean chlorine source that does not require acidification to provide hypochlorous acid in water and does not form insoluble solids, as is the case with Ca hypochlorite. Of course, it is now necessary to provide security to ensure that the chlorine cylinders are not diverted for criminal purposes. See further discussion in Section 8.2.4. Na hypochlorite and mixed chlorine-oxygen solutions can be generated on site from dilute solutions of NaCl using electrohydrolysis. Actually, that is how chlorine gas and Na hypochlorite solutions have been generated for more than a century (HOCl forming due to hydrolysis of Cl2), but they were delivered to the user in cylinders, jugs, barrels/carboys, or tank cars, as the generating equipment was industrial scale. Since the 1970s, site-scale and portable (even personal-sized) generators have been developed. In addition to chlorine, chlorine dioxide (ClO2) and mixed-oxidant solutions that include other chlor-oxygen compounds are generated along with the chlorine during electrolysis. The mix generated depends on how the generating system is configured. MIOX Corporation, which developed and markets electrolytic hypochlorite and mixed-oxidant generators, claims that studies show that mixed oxidants usually are several orders of magnitude more effective in microbial contaminant inactivation than conventional chlorine, “achieving up to 2 logs higher inactivation of even extremely resistant organisms,” and greater biofouling removal efficiency than hypochlorite disinfection. ClO2 also is understood to react better with sulfides, where those are present in anaerobic well environments. On-site generation may be the best solution for well disinfection (as well as potable water disinfection) for many remote locations, as long as electrical power is available. The generators use common salt, which has no shelf life issues (but should be kept dry). Electrolysis generates the more preferred Na hypochlorite, as well as mixed oxidants, and ClO2. Another practical effect is elimination of the need to transport powerful oxidant, a potential safety and security benefit. A suitcase-sized MIOX generator (which can use a 12 V battery and solar power as well as line AC) can supply enough solution to produce 300 gal of 200 mg/L solution in a day, so if the system is used, it is probably best to set it up running first (shortly before the job is to be completed—remember HOCl decay in solution) to build an inventory. Note that all these systems require training in dosing and application to be employed safely and effectively.

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Security in General All of these powerful oxidizing compounds have use in illegal lethal compound formulation, for example, in making explosives. Secure your stock under lock and key and keep exact inventory. Report missing stock to authorities.

6.5.2.2.2 Brominated Compounds Bromine has some advantages over chlorine in routine preventive well disinfection. Solids like the brand-name HaloSan have a longer effective shelf life than sodium hypochlorites and dissolve better than calcium hypochlorite in ground water that is typically alkaline and has significant calcium hardness. Br compounds react and dissipate rather quickly, and many combined Br compounds such as bromamines are also disinfecting. We still do not recommend continuous treatment of wells with halogens (including bromine) unless you have no other reasonable alternative to protect your system. Also, check with health officials regarding permission. 6.5.2.2.2.1   Ozone  Ozone (O3) is formed by exposure of oxygen (O2) to strong electrical charges. It has to be generated at the point of application due to its instability, which precludes storage under pressure or transport, making it largely impractical for rehabilitation. Ozone does not have a recognized practical application in well maintenance treatment, although it may be used in piping system treatment to repress biological activity. 6.5.2.2.2.2   Hydrogen Peroxide  Like ozone, aqueous hydrogen peroxide is a powerful disinfectant and oxidant. It has been used with some effectiveness in removing well biofouling in both water supply and environmental wells. There are a variety of sources of generic 50% peroxide mixtures available commercially. It should also be noted that H2O2 is aggressively attacked by bacterial enzymes. It breaks down to form H2O and O2, and the resultant oxygenation can actually enhance microbial growth away from the well and the lethal oxidant zone. Unless chlorine is specifically prohibited, it is probably still your first biocidal choice. Ozone may be used in piping system treatment to repress biological activity. 6.5.2.2.2.3   Potassium Permanganate  Potassium permanganate (AWWA Stand­ ard B303), another powerful oxidant used in maintaining industrial process systems and in water treatment for relatively uncontaminated water, is not used as a primary oxidant in well treatments. Dissolution of metals and biofilms is more effectively accomplished using acids. 6.5.2.2.2.4   Iodine  Iodine is not used as a well oxidizing or disinfecting compound, but it does have use in making controlled substances. We once had an inquiry in which someone caught with large quantities said it was for well cleaning—not recommended, due to solids formation. Lock them up for trial.

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6.5.2.2.3 Use of Heat In some cases, water heated to 54°C and recirculated over several days is sufficient without chemicals, at least in the short term. Note that heat propagates from the application source, but typically accumulates in the well structure due to the poor thermal conductivity of soil materials. Heat can actually enhance growth away from the thermal shock zone, as well as cause drying and shrinking clays such as bentonite grout. Using heat alone is also very inefficient in terms of fuel or power to generate thermal energy. In Practical Manual of Groundwater Microbiology, D. R. Cullimore relates experiences with situations where biomass was cooked and congealed, enhancing clogging. We envision a giant omelet. The best approach to using heat is in a process such as the blended chemical heat treatment method described below (and in Chapter 8) with a prudent selection of chemicals. This is most typically a rehabilitative treatment. 6.5.2.3 Penetrating, Sequestering, and Dispersing Agents In well treatment, penetrating, sequestering, dispersing, and detergent (PSDD) compounds are most properly used in low concentrations in chemical blends as aids in acidizing mixtures to retain biomass, metal oxide and sulfide components, clay, and other colloidal materials in solution/suspension for removal, once they are dissolved and dispersed in the water column. Examples are various polyphosphates, pyrophosphates, and polyacrylamide-based compounds. In addition, various organic acids and some proprietary acid formulations also have related chelating properties. Note that phosphorus-containing compounds (regardless of molecular structure) are not recommended for maintenance well treatment. Residuals of the compounds themselves (higher-molecular-weight (MW) polymers) and breakdown products (low-MW pyrophosphate and orthophosphate or P) remain behind in the formation (attached to clays, calcite minerals, and iron). The presence of an enhanced P resource can induce enhanced biomass development, often at the edge of development influence where redevelopment tools and well cleaning chemicals are not much use. Polyacrylamide and similar polyelectrolytes provide the desired effects of dispersing and suspending clogging deposits and clay/silt build up without being P sources. These compounds are not readily attacked by microorganisms. They should be handled, used, and ultimately disposed of according to manufacturer/supplier and MSDS instructions. Certain anionic polyacrylamides (e.g., CB-4, ARCC, Inc.) can be used alone for preventive maintenance treatment in low concentrations, as these compounds have properties that disrupt incipient biofouling and have some biocidal effect. Note various reactivity tables (e.g., Table  6.3) for problems with ground-water constituents and review available guidance on system material reactivity. 6.5.2.4 Blended Method Treatments Typically, no one chemical type will address all encrustation and biofouling removal, suspension, dispersal, and repression needs. Blending more than one approach or process can permit more effective removal of multiple problems or treat a single difficult problem more effectively. The exact blend of chemicals for a particular

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Table 6.3 Well Treatment Chemical Incompatibility Acetic acid

Chromic acid, ethylene glycol, nitric acid, hydroxyl compounds, perchloric acid, peroxides, permanganates, and other strong oxidizers

Acids (in general)

Sulfides, cyanide compounds, chlorates and perchlorates, ammonium nitrate, azides, alkali and alkaline earth metals, organic peroxides

Carbon dioxide

Dusts of aluminum, Mg, Ti, Cr, and Mn suspended in CO2 streams

Chlorine

Anhydrous ammonia, ammonia, acetylene, butadiene, hydrocarbons, hydrogen, sodium carbide, turpentine, benzene, finely divided metals, activated carbon, any strong reducing compounds

Chlorine dioxide

Organic materials, ammonia, methane, phosphine, hydrogen sulfide

Halogens in general (strong oxidants)

Fuels, any flammable liquid, or other organic compounds

Hydrofluoric acid

Aqueous or anhydrous ammonia, intensely corrosive to organics

Hydrogen peroxide (strong oxidant)

Copper, chromium, iron, most metals or their salts, alcohols, aniline, acetone, organic materials in general

Hypochlorites

Acids (specifically HCl), activated carbon, other concentrated organic compounds, anhydrous ammonia

Nitric acid (concentrated)

Acetic acid, acetone, aniline, chromic acid, hydrocyanic acid, hydrogen sulfide, flammable liquids, flammable gases

Organic acids

Aluminum, arsenic compounds, strong reducing compounds

Oxalic acid

Silver, mercury (forms low-solubility minerals in presence of Ca

Potassium permanganate (strong oxidant)

Glycerin, ethylene glycol, benzaldehyde, sulfuric acid, fuels, other organic compounds, flammable and explosive compounds

wellfield situation is determined based on an analysis of the needs for cleaning the clogging materials present and ground-water quality. More discussion is available in Chapter 8. ASTM Standard Guide D 5978, which addresses the maintenance of monitoring wells, does not recommend the use of chemicals, but redevelopment only. This restrictive guidance is not extended to pumping and injecting wells on HTRW sites, and the USACE recommends the responsible use of chemicals in PM redevelopment to improve its effectiveness. It is crucial that personnel engaged in the planning of well system O&M become well acquainted with the features of chemical choices, both for effectiveness and safety.

6.5.3 Use and Interpretation of MSDSs Having MSDS on hand is a central feature in safety plans involving chemical safety and a requirement of U.S. government agencies (including USACE and Bureau of Reclamation (BOR)) and many local jurisdictions, where chemical handling is part of a task. MSDSs provide guidance in personnel exposure problems,

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reactivity concerns, neutralization recommendations, and information on basic physical properties (e.g., the relatively high freezing temperature of organic acids). The MSDSs of proprietary chemical blends also permit interpretation of their contents and modes of operation in treatment. A MSDS is required by Occupational Safety and Health Administration (OSHA) to accompany each container of reactive chemical from point of origin to point of consumption or final disposal. Each person handling each chemical is to verify that he or she has read the MSDS or has had it read to him or her, and that he or she understands the precautions necessary.

6.5.4 Compatibility with Well Cleaning Chemicals Chemicals that may be used in maintenance and rehabilitative treatment of wells (Chapters 6–8) may react unfavorably with other chemicals or compounds present in the water to produce: • A hazardous personnel condition • Unexpected system damage Potential reactions should be worked out prior to chemical application. Table 6.3 provides representative incompatibility relationships with compounds used in well treatment. This table is not to be considered comprehensive or legally authoritative. If there is any question of problems with the water quality you will be working in, do your due diligence. Persons designing any treatment involving fluids that contain strongly reactive, oxidative, reductive, explosive, or volatile compounds should specifically review chemical reactivity databases for conflicts. USACE’s EM 385-1-1, Safety and Health Requirements Manual, is one reference that provides guidance in health and safety physical-chemical reporting requirements and guidelines for health and safety.

6.6 Mechanical Agitation and Augmentation Chemical application alone does not accomplish the cleaning task. Mechanical agitation is also required. Chemicals introduced should be mixed through the screen column, through either surging (see Chapter 4) or recirculation pumping. In fact, while most of the attention is often focused on well chemical choices, the discussion really should be couched in terms of what chemical mixture best complements well redevelopment (Chapters 4 and 7). You get more benefit from redevelopment with selective use of chemicals, and you certainly get more benefit from a good chemical mix by agitating it properly in the well. Various “surge in tank” procedures exist. One version (often called the “standard treatment” in parts of the Great Lakes region) involves hooking tanks to the lineshaft turbine pump discharge and removing the antibackspin feature on the motor. Chemicals are mixed and fed in through the pump. The pump is then turned on and off manually to agitate. Then the solution is pumped out to a tank. It may be checked for pH or chlorine strength, adjusted, and returned back down through the pump. The

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procedure is repeated as needed. The main drawbacks of this method are that (1) the solution drains into the well under very low head and against impeller resistance, and (2) solutions tend to work on the nearest clog material, near the pump intake, and not much anywhere else. This is strictly a maintenance treatment for use when there is no performance degradation measurable by step test or biofouling indicators. A somewhat better approach is to remove the pump and use a surge block-­airlift system in its place. Chemical solution can be drained in with greater force or pumped in. Airlift can develop more treatment agitation and is adjustable for depth. Fluid-pulse methods (see Chapter 8) can be especially effective for agitation of chemical solutions, as they are easy to deploy and produce a high-energy pulse in place. Heating (as described above) can be considered augmentation for chemical treatment or as a primary type of antimicrobial treatment. This is the principle behind the blended chemical heat treatment (BCHT) described in Chapter 8.

6.7 Chemical Emplacement Chemicals may be introduced into wells by gravity (tremie), pumping in against water column pressure, and high-pressure jetting. A feature of each is that chemical solutions are directed to the screen region or producing interval and not simply poured into the well. For maintenance treatments, simple pouring and pumping (vs. jetting or pressurizing) is usually sufficient. Jetting may be used for more completely developed clogging situations. Note that both redevelopment methods and chemicals used in maintenance (as well as rehabilitation) treatments can be: • Hazardous to personnel • Possibly damaging to well structures

6.8 Chemical Removal and Recovery Chemical solutions containing biomass, metal oxides, and other solid or semisolid debris must be removed from the well column. It is essential to note that neutralization should never be conducted in the well column itself. The reasons for this are that: • Clogging material will drop out of suspension or solution. • Explosive effervescence is possible when caustic solutions are introduced into solids-laden acid solutions. Containment and treatment such as neutralization are then necessary before release into the environment. Options include:

1. Pump into holding tanks: Most typically, development effluent wastes are best pumped to pretreatment tanks for settling and acid neutralization. Such tanks should be sufficiently large to hold three to six times the borehole volume so that development does not have to stop. Other options include neutralization “on the fly” in smaller tanks using a calculated feed rate of neutralizing chemical solution that results in the solution being

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nonhazardous upon exit. Such nonhazardous effluent wastes should not be noxious or incompatible with the property condition and use. So no, iron sludge-laden effluent should not be simply discharged in the wellfield (or storm drains). Get over it. 2. Divert to existing lagoons: On occasion, effluent wastes may be diverted to surface containment and permitted to lose acid or oxidant power. Solids may settle in place.

Any effluent waste fluids, slurries, or sludge should be disposed of properly in wastewater treatment or to surface spreading on soil. The definition of properly will depend on the chemical mixtures, their chemical properties (e.g., pH), and the sensitivity of the treatment or land system, as well as applicable law. Discharge to any surface waters must be avoided. Phosphate-loaded water discharged to surface waters causes algal blooms and oxygen depletion, resulting in suffocation of aquatic animals. Additionally, pH shock is toxic to aquatic life, and turbidity can cause suffocation. Where wastewater treatment (including ground-water remediation facility primary water treatment) is available, development effluent waste can be handled by this route. Typically pretreatment is necessary to adjust pH, settle solids, and remove compounds that are toxic to wastewater treatment processes. The tolerances and requirements of the treatment process should be known and not exceeded. Where there is a regulated wastewater treatment facility, the judgment and opinion of the operator-engineer in charge must be respected. Generally, pH > 6.5 is preferred with alkaline solutions welcome. Biocides must be deactivated to avoid killing activated sludge communities. For remediation systems where toxic levels of metals may occur in well clog deposits, pretreatment filtration is necessary.

6.9  In Situ Maintenance Treatment Techniques 6.9.1 Chemical Feeders in Wells A long-promoted practice is feeding chemicals such as chlorine and PSDD compounds in wells. Chlorine pellet feeders are not recommended for reasons mentioned above in Section 6.5.2.2. These are forbidden in some U.S. states, including Ohio and Michigan. We have seen very bad results from their use in Arizona. For the most part, other types of chemical feed in wells are ineffective.

6.9.2 Radiation—That Gentle Glow Radiation has also been successfully tested as a biofouling limiting agent. A U.S. patent exists (no. 4,958,683, William Rogers and George Alford) for an in-well cobalt-60 gamma-source tool that has been tested in practice. Gamma irradiation serves to generate hydrogen peroxide in situ, which serves as the biofouling degrading agent. Based on experience, interest in such a tool is likely to be limited despite its promise due to regulatory and personnel constraints. We must remember the Homer Simpsons and Timothy McVeys of the world.

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6.9.3 Application of Electromagnetically Charged Surfaces Work conducted by Droycon Bioconcepts and the Prairie Farm Rehabilitation Administration (PFRA) in western Canada has looked at the potential for using impressed currents for biofouling repression. Other electromagnetic devices for this purpose, for example, the Zeta Rod device, are used for the same purpose. Corrosion, where it is microbially induced, involves a number of stages. The early stages relate to the attachment of microbes to the surfaces and the generation of expanding biofilms that cover significant amounts of the surface. To understand corrosion, there is one golden rule: The microbes are all negatively charged on their surfaces and therefore gravitate toward positive poles of electrolytic cells. When cathodic protection is used to protect a surface from a microbial biofilm infestation, the surface contains an impressed negative charge that prevents successful attachment of microbial cells to the surfaces. At the same time an anodic (positively charged) surface is generated as a sacrificial point at which microbial attachment and subsequent growth and corrosion will occur at sites that have no consequence to the operation of the device. The art of cathodic protection is now widely practiced in industrial fluid handling applications such as refineries, underground storage tanks, and on many types of transmission pipelines, but not widely in the potable water treatment sector. It also has not been extended to wells because of high operating costs and uncertain benefits, as wells require very deep anodic voltage “wells” that may still be deficient, as wells are exposed to multiple electrical potentials in situ. Wells have been difficult to treat this way due to the multiple potentials present in the system. However, this use of cathodic and anodic charged surfaces and fields is now being subjected to investigation as a means of anodically focusing (AF) or cathodically disrupting (CD) a potential or actual site of biofouling locally within the well. These processes have potentially major implications for applications to wells as a means of manipulating the form, function, and position of biofouling events. It is expected that the CD process may be very suitable for application as a part, or the whole, of a preventative maintenance treatment. Stay tuned to the websites we mention for updates. This is a work in progress and to date the results are inconclusive. [New development since writing.]

6.9.4 CO2 Well Environment Adjustment—Making the Environment Inhospitable for Biofouling Subsurface Technologies (Rock Tavern, New York) markets a system (Aqua Gard™) that includes a permanent injection system running beside the installed well pump that permits periodic injection of carbon dioxide (gas and liquid) to disrupt incipient biofouling in the well. Disrupted debris is removed by the well pump. A diversion system is necessary to blow off purge water. The system uses no aggressive chemicals. Additionally, a CO2-dominated borehole water chemistry represses respiration and biological activity if CO2 bubbling is maintained.

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6.10 Further Procedural Requirements 6.10.1 Regulatory Aspects Environmental regulations and standards that apply must be followed. Project agreements with regulators and local regulations may need to be checked before discharging to existing treatment plants or lagoons if they were not originally intended to accept such waste. Ultimately solids may need to go to secure disposal per regulatory requirement.

6.10.2 Biofouling Recurrence Whatever the treatment, biofouling always grows back—the trick is to treat it again before it reaches a problem stage (however that is logically defined). Monitor to head off a comeback using the methods described (Chapter 5). If regrowth persists, look into regular or continuous chemical treatment. A maintenance contract between a competent well cleaning contractor (qualified for the site conditions in question) and the well system operator is a good idea.

6.11 Health and Safety Concerns Generally, water supply well system O&M has a number of critical health and safety issues related to general well and pump mechanical and electrical operation and control. Environmental cleanup and control projects also have specific concerns of handling potentially hazardous formation and treatment fluids. Both (but especially environmental systems in our experience) have related issues, such as confined space operation.

6.11.1 Health and Safety Plan O&M safety must be a component of overall facility safety. The development and implementation of a specific but flexible plan is needed, including personnel expertise and compliance, and training to make personnel thoroughly familiar with chemical and mechanical activities. Depending on the specific nature of the well system and the nature of contaminants (if any) and treatment chemicals, O&M activities will require worker hazard analyses and (in the United States) compliance with any applicable OSHA standard found in 29 CFR 1910 and 29 CFR 1926 (or your requirements outside the United States, if any), in addition to any applicable requirements of the responsible organizations and service companies. In all cases, O&M safety and health managers in the United States will be required to comply with 29 CFR 1910.132 through the performance of a site-specific hazard analysis, the selection of personal protective equipment (PPE) appropriate to protect workers from the hazards identified, a written hazard assessment certification, and worker training in the hazards and PPE to be used. The following is intended as guidance only to assist in that effort. We are not workplace safety experts. More in Chapter 7.

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6.11.2 Level of Protection for Mixing and Well Application Well maintenance treatments involve the use of reactive chemicals (see also Chapters 7 and 8). Once a chemical regime is selected, the appropriate use of chemical-resistant gloves, boots, and apparel, full-face splash shields, and other specific protection, such as for handling hot and super-cold solutions, should be specified. An excellent strategic policy for safety is to, as a rule, employ treatment mixtures that minimize hazard and the likelihood of personal injury due to error, while still being effective.

6.11.3 Chemical Handling Hazards Typically, the major exposure injury risk point during PM and rehabilitation (Chapter 8) treatment is at drums and containers containing concentrated acid, caustic, or oxidizing agent solutions. Spilling or transfer hose troubles may result in skin exposure. Vapors may cause mucous membrane and eye tissue irritation or damage. Persons handling concentrated chemicals should wear full-face splash guards and respirators, chemical-resistant clothing and gloves, and have an emergency washdown available. Persons handling dilute solutions may work with care in level D (general industrial site safety) gear. Note: People working frequently around these chemicals tend to get complacent about the risks, especially when nothing bad happens for a long time. They cut corners, using inappropriate transfer and safety equipment. This trend must be resisted by indoctrination and enforcement. Another hazard may be posed by solid-phase acid or caustic dust, or opportunistic pathogens in biofilms permitted to dry and blow. Review hazards posed by inhalation of vapor and chemical dust. Also review prevention and treatment of chemical and thermal burns, and review MSDSs for specific chemical reactions and storage requirements and physical changes. More on safety planning in Chapters 7 and 8.

6.11.4 Mixing Chemicals—Personal Safety Aspects Mixing of concentrated reactive solutions can result in personal hazards. For example, neutralization of acids poses a potential hazard if basic compounds are added too rapidly to strongly acid solutions (
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• Alkaline and caustic compounds should be added slowly to acidic compounds when neutralization is required, and never added to wells when acid solutions are still in the well. • Hoses, valves, and connections should be secured and not leaking. Spraying acid or oxidant chemicals can result in dermal burns and clothing damage. • All work should be conducted in unobstructed and well-ventilated areas. • Personnel must routinely review MSDSs and company recipe sheets before each treatment event. • Follow the work plan “by the numbers” and work at a deliberate pace, avoiding rush. Put the cell phone down. • Extra lime or soda ash should be kept on hand to treat spills, and eyewash packages and abundant clean water should be kept close at hand for dilution when personnel are splashed.

6.12 Costs and Time of Routine Preventive Measurements Costs of well deterioration impacts were discussed previously in Chapter 3. Maintenance measures have costs associated with them, too. However, the concept of maintenance is to incur the costs of operation as a regular investment in preserving the assets vs. the uncontrolled depreciation of facility (well) deterioration. The investment in maintenance monitoring and maintenance preventive treatment should be recouped through reduced operational problems, energy and treatment costs, and the reduction or elimination of rehabilitation and its interruptions and emergency costs. The Sutherland et al. (1994) method described in the following can be used for these analyses.

6.12.1 Maintenance Cost-Benefit Analysis This cost and time investment in maintenance activities should be compared to the available history of equipment renewal, increased pumping costs, well rehabilitation, and other maintenance costs, such as line flushing and chemical costs that are impacted by fouling and corrosion originating in the well. Valuable history may come from the past at this particular facility or from experience elsewhere that applies. Do not forget to keep the LOS, best available costs, and business goals in mind (Chapter 3). 6.12.1.1 Cost-Benefit Analysis: A Spreadsheet Approach The report to the British Overseas Development Agency by Sutherland et al. (1994, see reading list) provides a rational basis for cost-effectiveness comparisons of operating wells with and without monitoring and maintenance. While developed principally for water supply well projects, the methodology is directly applicable to environmental well system management. The Sutherland et al. system is based on a spreadsheet analysis (what if) approach that takes into consideration a variety of levels of:

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1. Maintenance monitoring (and associated costs) 2. Maintenance action levels 3. Well classifications based on historical assessment of well deterioration in a variety of hydrogeologic settings 4. Costs and intervals of rehabilitation with and without maintenance actions 5. Costs of operation with and without maintenance actions 6. Methods of factoring in costs, level of service (LOS), and other external factors (see Section 3.2) in making decisions about well maintenance, such as the existence of high LOS standards for product water quality, the need for uninterrupted water supply, and regulatory considerations (consequences of poor water quality or supply interruption) (Figure 6.1 illustrates a factor analysis decision process)

The system acts as a convenient means of encouraging a site manager to get and organize relevant well operational information, but also allows the maintenance analyst to guess about costs and intervals to some degree. Weighting factors are provided to quantify the relative importance (high-mediumlow) of:

1. Societal factors (levels of service or regulatory official trouble in the case of unreliable environmental wells) 2. Availability of alternative supplies (assume irreplaceable for environmental well arrays) 3. Environmental factors (see item 1, plus consider environmental impacts on well performance)

Figure 6.2 illustrates the type of projections (e.g., over twenty years) possible with this analysis. 6.12.1.2 The Heartbreak of Well Failure: An Overriding Weighting Factor The above discussion and Chapters 3 and 5 highlight some values judgments in addition to purely cost issues. Making decisions about high-maintenance systems that are also critical (certain water supply wells, mine dewatering wells) can trump the cost-benefit discussion laid out on a spreadsheet. Environmental well systems, especially those for remediation pumping, have historically been high maintenance since they are at risk for costly severe deterioration (see Chapters 1 and 2). They also have critical missions: keeping ground-water contamination where it cannot cause harm or removing it. However, costs are not insignificant. At present, a maintenance monitoring and treatment program can justifiably cost (1) 100% or more of projected rehabilitation and reconstruction costs or (2) the annual amortization of the well array over the project life. Consequently, for facility managers, if maintenance practices save money and keep the system working over the life of a facility (and this assertion can be quantified using methods such as that described above), maintenance is costeffective. As discussed in Chapter 5, PM has additional benefits, even if costly:

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Calculated Costs to Operate One Well: With and without Maintenance Monitoring (20 years) Discounted Annual Costs

Cost ($) Thousands

12 10 8

Without M&M

4 2 0

Cost ($) Thousands

With M&M

6

1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 Year

Cumulative Discounted Costs

120 100 80

With M&M

60

Without M&M

40 20 0

1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 Year

Figure 6.2  Projections of annual and cumulative costs over time using Sutherland et al. method. “Discounted annual costs” illustrates annual-cost profile, “Cumulative discounted costs” shows difference between “with” and “without” maintenance monitoring in this simulation.



1. The money is spent in a controlled manner (whatever the costs happen to be), not in an uncontrolled, episodic way. 2. The system remains operational and provides the required results (pretty much regardless of cost).

We realize that some people really do get a rush out of mitigating (we would not say “managing”) a crisis and appearing to be a hero. There is value in having to deal with a crisis. Your time is better spent elsewhere, and your mental health is preserved. The alternatives, such as continual well and system rehabilitation, loss of control of a plume, or surprise arrival of a plume at a water supply wellfield (lawyer up!), are by comparison infinitely more expensive, making conventional accounting costbenefit analyses virtually irrelevant. Certainly “cheaping out” on prevention and O&M seems unwise. In summary, maintenance planning and execution has the following projected results:

1. Buys time, more likely to work. Although monitoring and treatment cannot prevent all forms of well deterioration by themselves, early detection

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of problems permits effective regular preventive treatments (if needed). Preventive treatments limit the need for more extensive and less sure rehabilitation (Chapter 8) and lengthen the time until such treatments may be needed. 2. Budgeting and use of resources. The maintenance cost is spread evenly over time instead of in episodes of emergency expenditures. Figure 6.2 shows a simulation of the financial effect of maintenance monitoring over time— tending to provide a predictable annual cost. Such cost is also accounted for in the normal budget and therefore funded. When pumps have to be pulled for proactive maintenance repair, the required work is accomplished more quickly and the damage less severe. This reduces LCC and cumulative cost (Chapter 3, Figure 6.2). The figure also illustrates the alternative of history without maintenance monitoring—the typical haphazard, unpredictable costs one can expect. 3. Scheduling. Service interruptions are eliminated or less frequent and capable of being scheduled. Wells may be occasionally off-line for preventive treatment, but can be brought on-line quickly in case of need. 4. Better downstream results. Allied problems (biofouling and discoloration in distribution lines, water treatment costs, filter backwash intervals) are brought under greater control. 5. Longer facility service life. Any time added beyond normal depreciation is a financial plus in the life of such systems. In addition to accounting depreciation, time expenditures for design and approval of replacement systems are delayed, and construction of new systems is also delayed.

What are these costs then? They are highly variable and hard to compare among situations. Following are some example values, which readers should check for in their specific situation.

6.12.2 Costs of Maintenance Activities Costs of equipment and materials are quite subjective. The following costs are ballpark (approximations) for the United States. In many countries, costs are much higher. Equipment and instruments recommended can be purchased through laboratory and environmental supply sources, or can be fabricated under license or based on public domain designs. So do your own cost research. 6.12.2.1 Maintenance Monitoring Costs—Typical 6.12.2.1.1 Water Quality The total cost for the first year of monitoring pumping wells, assuming there is no laboratory equipment at all, quality field electronic instruments are purchased, BART kits are used, and a monthly sampling program under the Chapter 5 recommended protocols is implemented, would be about $3,000 for the first well and about $650 for additional BART tubes and other supplies and reagents for additional wells for the biofouling and physicochemical water quality monitoring.

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6.12.2.1.2 Hydraulic Performance Hydraulic performance monitoring is equipment-intensive but requires very little personnel time. Assessing changes in performance is not possible without both discharge rate and drawdown data, and both have to be measured in the wellfield. Good combination ammeter-voltmeter-ohmmeters such as Amprobes can be found anywhere for less than $300 and should be available to all well operation crews, who should know how to take control and lead readings. Turbine flow meter installations may cost up to several hundred dollars each and require wells to be taken out of service for installation. These require protective housings and certain installation requirements (e.g., mounted level and 4 ft of straight pipe before the meter). They can be equipped for automatic data collection. Venturi type flow meters (for wells pumping <50 gpm) cost somewhat less, have no moving parts, and can be a benefit on wells that produce some turbid water. They are basically manual-read only. Both types of meters themselves must be maintained to be reliable. Mag meters cost anywhere from $1,300 to over $3,000, but have much lower maintenance, can be installed in tight spaces and at any orientation, work over a wide flow rate range, and are very adaptable to automatic data collection. Such flow (discharge rate) monitoring is normally required in any case for control of the treatment stream, as well as regulatory records purposes. Discharge rate monitoring is also absolutely essential to allow the detection of very fine changes in performance before pumps clog or corrode. Alternatives to permanently installed flow meters include portable sonic flow meters. These cost over $1,000 each, but may be used on multiple wells and are quite practical for remediation pumping streams with their high particle counts. Water levels are conveniently measured by the ubiquitous electric water level sounder ($300–1,200), airline (capital expense plus air source <$200), transducerbased systems, or sonic water level sounder (each >$900). Sonic sounders and airlines allow water level measurements access in wells with limited or no casing access. Airlines and sonic sounders have an accuracy of approximately ±6 in. (152 mm) and ±1 in. (25 mm), respectively, vs. approximately ±0.03 in. (0.76 mm) for electric water level sounders. In addition, airlines clog under most well conditions and have to be properly maintained (if used at all—we suggest you retire them). Transducer-based water level sensors provide accuracy, low maintenance, and easy adaptability to automation and data recording. These are preferable for arrays of pumping wells for routine maintenance. A system with more than two wells can make a cost-effectiveness case for installing such automated data gathering systems on a labor basis alone. It frees operational people to be operators. Automated data gathering should be backed up by and calibrated to manual measurements occasionally. Adding flow meters and additional instrumentation (automatic water level recording, motor controls such as Franklin Subtrols) to pumping wells may boost well costs by several hundreds to over $4,000 per well, which is recouped in reduced future motor burnout, rehabilitation costs ($5,000 per well per incident instead of $4,000 once + time and minor equipment maintenance), and intangible costs of having critical wells performing badly.

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Actually, all or most of these devices are normally already present on the site for other testing needs and do not represent new costs dedicated to maintenance. Maintenance is just one more good reason to install, maintain, and faithfully use them. 6.12.2.1.3 Personnel Time One hour per well per month of operator time is a reasonable assumption using manual methods for the model Chapter 5 analyses (more if apparatus maintenance is required). This can be reduced and streamlined if hydraulic parameter and some other measurements are automated. Sampling intervals may be more or less frequent and perhaps focused on specific (troublesome) wells. SCADA (supervisory, control, and data acquisition) systems are now very flexible, customizable, and inexpensive for even small water supply systems. Cost is recovered in reduced personnel time or in gathering data that trigger a preventive maintenance action, instead of a problem being overlooked, leading to a costly failure. There may be an additional cost of professional assistance, and again, the costs are variable and subjective, but probably worthwhile in getting off to a good start. 6.12.2.2 Preventive Treatment Costs The treatment costs themselves, if an assessment of monitoring data calls for such treatment, are highly variable. They can probably be most closely correlated to personnel time involved. The chemicals (even though rising in cost) and other materials themselves are relatively inexpensive, on the order of $200–1,000 per well. What is expensive (in a Western economy) is the time of skilled well cleaning crews and their equipment, comparable to drilling crews (>$1,500 per day plus materials and mobilization) for maintenance work. These kinds of costs may mushroom, of course, when there are additional requirements, such as personal protection and highly contained handling of purge water. However, note that some companies are skilled and efficient at performing well service under difficult conditions. They may cost more per hour but be more effective to employ. It pays to know the capabilities of service companies and to put more weight on the effectiveness part of the equation. A goal in cost projection, as mentioned previously, should be to keep life cycle maintenance costs within projected rehabilitation costs, and annual costs within the ten-year amortization figure for the specific installation. This should be split between monitoring and treatment.

6.12.3 Improving Cost-Effectiveness in Maintenance While it may be justifiable to peg maintenance costs to some end-of-life-cycle replacement cost (e.g., ten years for a pump), it is not necessary to do so. There are ways to keep costs down without compromising the maintenance program.

1. Design for maintenance. The first step to make the best use of maintenance funds is to design well systems so that they are readily and easily treated as necessary (Chapter 4):

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a. A well-designed system resists deterioration and does not need as much maintenance. b. Wells and treatment systems should be designed for rapid and easy monitoring with automated hydrologic instruments and convenient sampling. c. There should be good access, easy hookups, readily available hauling service, and other steps taken to minimize the fuss and labor costs associated with maintenance and rehabilitation treatments. 2. Diligence in maintenance. Second, keep the well-designed equipment in good shape: a. Monitoring has to be diligent to detect problems while they are minor. Good design facilitates this. b. Have spare pumps and replacement parts readily available, and have personnel trained in the diagnosis and repair of pumps. If on-site personnel are the first called on for service, pump service contractors should be on call as backup. c. Apply preventive maintenance treatments as soon as is practical. Good design, access, and planning help to make this more likely. d. Check results and refine the monitoring and treatment based on experience, and incorporate new methods and information to fine-tune your system. 3. Negotiation. This is business, and the facility management is buying a service. There is competition, and the service and equipment providers in the business want the projects. Such maintenance work is regular work that a service company can count on for cash flow. If in checking around, the site manager finds that costs for maintenance services he or she is using are out of line, it is time to find out why and make adjustments as necessary.

It may be that the services being provided are indeed superior (usually a temporary situation), or that the conditions for maintenance on the site result in higher costs (fluid concentrations, rapid deterioration, and frequent maintenance). On the other hand, the facility manager may be getting soaked on chemical or instrument costs. If your service company does the “same old, same old” and does not seek to adapt to streamline and save money, look for alternatives. Do some testing and have an independent analysis of your process conducted by a knowledgeable expert. For example, using some analysis, we have put wellfield operators on systems that allow for automated self-cleaning, reducing the frequency of expensive pump pulling and refurbishing. Compare costs for comparable performance, but definitely compare. Can all the effort described in Chapters 5 and 6 be reduced to a single sensor and automated response? So far, the answer is no unless “neglect, ignore, abandon, rebuild (repeat)” really is a strategy for you. However, as we advise, keep watching available information sources for that Holy Grail of an effortless well maintenance system, should it appear. Then, no one would have any reason to get up off the couch. It should be remembered, though, that such a system would necessarily be sensor based, and sensors deteriorate, too. Wells require attention to function optimally and indefinitely. We do not see that situation changing anytime soon.

and 7 Rehabilitation Reconstruction Planning This is probably where you enter this discussion if you are a typical new and unwilling student of well maintenance and rehabilitation. Performance is already down at the well array: drawdowns are increasing, discharge lines are partially clogged, and filters are backwashing constantly. Now you have to save the system. Here are considerations for well rehabilitation and reconstruction. Once you get it under control, or if you start over, go back and review the chapters on prevention and maintenance.

7.1 Decisions on Rehabilitation Methods: After Things Go Wrong It’s very unpleasant for me, but it’s a lot more attractive than the alternative. We can spend a lot of time talking about how it happened and how we got here. But we have to get through the night first. U.S. Treasury Secretary Henry Paulson, after intervention to ward off the looming crash of 2008

Well rehabilitation (or restoration or regeneration) vs. well maintenance is analogous to war vs. diplomacy or heart surgery vs. heart-healthy lifestyle, respectively. Where the latter is neglected or half-hearted (as history amply testifies), the former often becomes inevitable. We might add “managing financial markets” to the pool of relevant analogy. Well rehabilitation ideally may never be necessary if effective preventive maintenance measures are implemented (Chapters 5 and 6), based on a clear understanding of the challenges faced by the well (Chapter 2), and supported by preventive measures (Chapter 4), or at least only necessary after a long time. However, the need for rehabilitation (an attempt to reverse or repair serious well malfunction or failure) is often the starting point of thinking about preventive design and maintenance for well systems. Rehabilitation choices depend on the problems encountered. Treatments per se are only used for biofouling and encrustation, where something is removed or suppressed. Preventing or rectifying sand or other solids pumping and corrosion usually requires some reconstruction strategy to keep the abrasives out and limit deterioration of the screen and casing, as well as the pump. Sand or silt pumping additionally can be addressed through redevelopment. In well rehabilitation, these are essentially preventive activities (materials selection, design, and development) that are applied reactively, but typically under less than ideal circumstances. This chapter covers the planning issues of rehabilitation. Chapter 8 reviews recommendations and techniques for well rehabilitation. Chapter 9 summarizes experience history and looks forward to what needs to be done to progress in a future that 197

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Figure 7.1  Well rehabilitation work in motion. Cleaning carbonate aquifer wells in western Ohio.

demands a sustainable worldview for all our water, environmental, and power assets and capacities. Figure 7.1 is a typical well rehabilitation scene.

7.2 Management and Safety in Well Rehabilitation Most of you probably want to skip to “the good stuff”—chemicals and tools in Chapter 8. However, management and safety considerations are mentioned first, because any well rehabilitation task has to be planned first before it is executed. The idea is that with planning, the procedures deployed are more effective. Using a martial analogy again, you can rush your enemy swinging sticks, or lay out a plan to gain maximum advantage with the least possible harm to you. In his Gallic Wars, Julius Caesar (Roman general and dictator) made this point over and over again as his rather small but disciplined force repeatedly defeated a series of Gauls on their own turf in Gaul (roughly today’s France and Belgium), then he successfully invaded Britain. Naked, tattooed Gauls screaming and swinging swords had to look impressive, but we both know that organization and division of labor wins in the end. Sometimes well rehabilitation jobs resemble Gallic battle tactics: a lot of screaming and flailing around without a good plan and unsatisfactory results. Considerations for site management or consultants contracting well rehabilitation services are somewhat different from those for the well rehabilitation contractors themselves. They will be considered here in sequence.

7.2.1 Facility Management Considerations Management’s first goal is to get the wells and associated systems up and running effectively in the least time possible. Cost should be a secondary (but obviously

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important) consideration. Ideally, the focus is on cost-effectiveness—that the intervention restores a level of function that meets the objectives set. The alternatives to performing the restorative work are often themselves costly and debilitating or disastrous—certainly not “business as usual” or you would not be considering well rehabilitation. Management also has to be concerned with safety and liability problems in well rehabilitation, which has the potential for being the least well-controlled activity on the site (except maybe for personal behavior of staff). Furthermore, management has to be concerned about regulatory aspects of any well treatment and reconstruction. 7.2.1.1 Responsibility for the Work One important consideration at this stage (the system has deteriorated until something had to be done) is responsibility for actions and costs. The need for rehabilitation of wells and systems may already have resulted from deficiencies in design, construction, and operation of the system. Such decisions may have occurred in the far past, or maybe you can still reach the responsible parties on speed dial. If there is desire to fix responsibility on someone on the design and planning side, finger pointing and acrimony may flare up among site management, operators, and consultants who may have designed and implemented the systems that are now failing or performing poorly. Regulatory personnel likely will want a review of the causes of the problems and plans for treatment. They may want to exercise review or veto power over potential treatment approaches. This can result in delays in implementing well rehabilitation while lines of responsibility are determined and requirements satisfied, or worse yet, legal proceedings are instituted. Meanwhile, the systems do not function properly and the purpose of the installation—water supply, plume control, recovery, monitoring, or whatever—is not fulfilled. This is a situation in which management considerations rather than technical constraints become paramount. Personality clashes come to the surface. Honor, reputation, and sometimes a sense of manhood or control are at stake. Obviously, who writes the checks becomes an issue. In such an atmosphere, it is important for facility management to keep their focus on fulfilling their mission: the management of a water supply, dewatering, monitoring, or remediation array to make sure it can perform its task. Therefore, the first objective in any management negotiations should be to safely and effectively restore the systems to acceptable performance and to prevent the problems from being so bad again. Then maybe you go after the consultant’s Mercedes or insurance company. Referring back to descriptions of causes in Chapter 2, people who are conversant with the interactions of all the variety of microbial, hydraulic, chemical, and operational impacts faced by wells are hard to find—despite the apparent presence of so many instant experts in the field today. Taking human limitations into consideration, it could be argued that the consequences of (at the time) reasonable decisions and actions may not have been foreseen. However, unlike the situation in 1995 when the precursor to this work was published, you out there in ground water, water supply, and environmental land have had access to:

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• About fifteen years’ worth of extensive publication on the maintenance and rehabilitation (M&R) of wells, more if you count the reasonably good body of literature scattered in journals. The predecessor to this work was published in 1995 as a companion to works we saw published in 1992 and 1993. Roy Cullimore’s first edition of Practical Manual of Groundwater Microbiology was also published in 1993. • Publications on the effects of iron biofouling and tuberculation and other corrosion problems that go back to the turn of the twentieth century, with key (accessible) papers extending from the 1940s in journals such as Journal AWWA (not obscure to water engineers). • Pretty much anything you needed to know about proper well design and construction to provide efficient, durable wells. • Quite a few short courses and seminars since about 1994—and extending back to at least 1981 in the case of several National Water Well Association contractor short courses. In 2008, several groups in North America were offering various forms of seminars and courses, as your authors have for several years. Going back to the NGWA’s Outdoor Action Conference, talks on well problems and solutions were common from 1991. • The authors’ website, with well maintenance and rehabilitation information, has been up since 1998. Ours is not the only one, but so far the most comprehensive. The principles of proper well design and construction are decades old, preceding the careers of most everyone not yet retired. A really good selection of materials for corrosion resistance extends back to the 1980s. All the principals of well problem diagnosis were available by the 1950s in the case of pumping tests and by the 1990s in the case of biological analysis as we now know it. Can we now claim with certainty that the time for excuses is over? Any objections? Thanks, meeting adjourned. Let’s get to work … 7.2.1.2 Getting the Job Done The pragmatic solution in any such situation is to avoid the laying of blame and get the job done (while learning a lesson for next time). Environmental site well and pumping service is usually included in the service contracts between site management and consultant engineers. They may choose to subcontract such work, and often do, except where consultant management philosophy is to provide all services from “in house.” Some companies, for management reasons, then attempt to have all necessary skills from botanists to pump technicians under the corporate roof. This may or may not be a worthy goal from a cost-effectiveness standpoint. Maintaining dedicated in-house well rehabilitation teams is a particularly unproductive strategy in planning for well rehabilitation services for most institutions. One reason is that highly experienced independent companies already exist that do such rehabilitation work frequently, and repetition breeds competence. These firms

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are qualified, know the necessary methods, and fully understand the safety considerations involved. When they are done, the work is done and the highly experienced and expensive crew is not on the facility management’s or consultant’s overhead. Keeping such crews on overhead would only make sense if the company (1) uses them frequently and (2) can market such a service to the outside. Assuming reasonably then that work is contracted out, a second consideration is writing specifications for well and pump rehabilitation and contracting to get the work done. Specifications need to be more goal and less process oriented, unless a specific process is known to be especially effective. They also need to be based on analysis of the actual problem and the actual operational challenges involved. Unfortunately, two counterproductive tendencies prevail in specification writing for well rehabilitation:



1. By the book: One tendency in well rehabilitation specification writing is to assemble boilerplate specifications based on a variety of historical documents developed in the water-well sector. Another tendency is for the control-freak specification writer to narrowly define the rehabilitation methods. These issues are discussed in more detail in the following material on specifications for rehabilitation. On the other hand, some specifications are so vague as to provide little guidance as to what the purpose and objectives of the work is to be. 2. Getting off the subject: Another specification problem is misalignment of the focus of the work. On environmental well rehabilitation projects, this usually takes the form of excessive attention devoted to chemical safety and hygiene considerations. Obviously with human life involved, under our prevailing value systems, these are paramount concerns, but specification writers have to have some faith in the experienced contractors they hire. If reputable experienced contractors are retained, they can be counted upon to work safely while being productive as well.

So what is the solution? Specifications should be written by people experienced with well rehabilitation (as applied in the particular situation) and the work performed by or under the supervision of experienced contractors or crews who can verify experience. An excellent tactic is to prequalify service providers—as long as qualifying is based on satisfying the objective safely, rather than nontechnical criteria.

7.2.2 Safety and Productivity in Well Rehabilitation Work 7.2.2.1 Safety Assurance Safety as a further consideration, and from a liability standpoint, is at the top of the importance list. All environmental and many other facility managers in the United States are, of course, required to have a site health and safety plan under Occupational Safety and Health Administration (OSHA) regulations (29 CFR Part

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1910), and similar requirements exist (or should exist) elsewhere. The site safety plan describes the hazards involved on the site (chemicals, noise, radiation, etc.), levels of personal protection and monitoring, traffic and site access control, and policies and methods available for decontamination, confined-space entry, and emergency response. This should be supplied to the potential contractors and can be specified as being confidential. Management should prequalify potential contractors both from their technical qualifications and their safety preparedness, relative to your facility requirements.





1. All personnel working on facilities with potential or actual environmental health and safety hazards in the United States should have completed the OSHA forty-hour training at the minimum, with necessary supervisory qualifications and proof of attending annual refresher courses. Elsewhere in the world, modify this sentence with your own jargon. 2. The potential contractor should also have a written general safety and hazards notification plan to protect their own workers, and it should include decontamination procedures (routine and emergency) for personnel and equipment. 3. The contractor should be prepared to verify that contractor personnel on site know about potential site hazards (if any) and how well rehabilitation activities may interact with these hazards.

Two main problems are personnel contact with potentially contaminated ground water and the interactions of ground-water constituents with chemicals that may be used in well rehabilitation. The contractor should be aware of chemical mixing problems, and be prepared to use methods that minimize the generation of hazardous effluent waste fluid or splash. At the same time, site operators or their consultants should have a plan for containment and disposition of any discharged material, as well as expendable equipment and supplies such as pipe. Management should make sure that contractor personnel actually have and know how to use personal protective equipment necessary for the facility (even if it is only level D), air monitoring instruments appropriate for the potential hazards (as needed, not as convenient), and means of communication used locally (ability to talk with site people). The facilities safety manager needs to actively work with the contractor to help integrate the contractor’s procedures into the overall facility site safety requirements, not just check to see if personnel have a certain specific piece of personal safety gear, then walk away. Personnel should be equipped with any special gear that the site specifies for visitors, such as neon orange vests with polka dots or special-issue radios. 7.2.2.2 Facilitating Productivity The well rehabilitation or pump service activities themselves have to be worked into the flow of facility operations. Personnel need to be briefed on the specifics of the current site hazards (if any) and operations. Contractor personnel need to know where they can safely go and where heavy equipment such as pump hoists are unusable. To the best of their ability, however, site management should work to remove

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obstacles to permit the contracting firm to do its work quickly and effectively, saving on billable hours and shortening the time until wells are back on line. Facilities management should keep regular contact with contractor supervisors on site to check on progress and to assist in any way possible to keep the work moving along. Rehabilitation work can be frustrating to watch, since there may be long periods of waiting during chemical contact times, mixing, and surging. If people are sitting around at the contractor’s vehicles, this is normal and not necessarily shirking, but it is a good time to make contact. Simple pump repair work is more straightforward and should proceed quickly. After the work is completed at any well, facility management or consultant personnel should verify the results and evaluate them in relation to the scope of work and specification goals for performance improvement. This is then a suitable time for a conference to determine if the performance has met the specification goals. Failing to meet goals, or making things worse, in many situations is nonperformance, but in well rehabilitation, it is often difficult to determine all the causes of well deterioration and foresee the problems that may occur. Success in predicting results depends upon data collection and experience.

7.2.3 Rehabilitation Contractor Considerations Rehabilitation or well service contractors have a different problem: making these difficult jobs profitable and worthwhile. Mirroring the “homework” tasks of the facility manager or consultant, the contractor should be fully prepared to safely and effectively take on the well rehabilitation tasks under sometimes difficult environmental site conditions. 7.2.3.1 Safety: What the Contractor Needs to Have and Know It should be obvious that at the top of the safety list is personnel competence around the machinery and systems used in well rehabilitation, and provision and use of safe equipment in good repair that is appropriate for the work planned. One does not send the summer help with a ½-ton pickup hoist to pull a 500-foot-deep lineshaft turbine pump, for example. Additional qualifications and preparations may be needed. If they are planning to tackle pump or well service work on potentially hazardous sites in the United States, contractors need to put workers and supervisors through OSHA forty-hour training, eight-hour supervisor training for any person that will supervise another, and eighthour refreshers. Such training can be expensive, but absolutely necessary to walk into many facilities. Contractors should be aware that (in the United States) OSHA will require more record keeping and state worker compensation, commercial insurance may go up, and that USEPA and state environmental agency personnel on site are deputized to report to OSHA as well, so scrutiny is possible at any time. (Readers outside the United States, translate this advice into your own regulatory environment.) Even without environmental hazards, well cleaning, mechanical redevelopment, and well reconstruction involve potential personnel hazards. Risks associated with rehabilitation of even small potable water wells should not be underestimated. Such work involves a number of physical and chemical risks. For example:

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• Handling contaminated ground water • Handling rehabilitation chemical solutions • Interactions between rehabilitation chemicals and ground-water constituents that involve additional inhalation and dermal contact risk (Chapter 6) • Potential for unfortunate interactions between human bodies and cables, sharp objects, and swinging or falling heavy objects • Potential for high-voltage, high-amperage electrical shock • Encountering unbreathable atmospheres or flammable gas In the water well industry, people die every year in the United States due to suffocation in hydrogen sulfide or carbon dioxide atmospheres, and others are burned or are killed in methane explosions. Others are electrocuted. Then there are the uncounted eyes and extremities lost or impaired that do not result in death, just misery! Contractors should have a general site safety and hazard communications plan written and on file, and be prepared to make it available to potential clients and insurers. In addition, a contractor should draw up a site-specific safety plan for environmental site jobs, which should also be available and verbally explained to all site personnel and site management (and review by OSHA inspectors). Contrary to some recommendations, most facility managers prefer that the sitespecific plans be relatively brief and clearly written. The general safety and hazard communication (hazcom) plans should be more lengthy and comprehensive. Employees must be informed, equipped, and well trained to deal with the site hazards. Regardless of the legal requirements, this is a trust obligation to valuable trained employees and their families. To do otherwise is medieval and stupid. Insulted? Send the book back. Drawing up general safety and hazcom plans is well covered in good OSHA site supervisor courses and in a variety of literature. A recently developed manual that provides good guidance is the Environmental Remediation Drilling Safety Guideline, which is being made available free of charge from the National Ground Water Association (www.ngwa.org) for download. Contractors contemplating work on environmental hazard sites should have this and at least the following literature on hand for ready reference (most supplied in OSHA supervisor training):



1. Occupational Safety and Health Guidance Manual for Hazardous Waste Site Activities (DHHS/NIOSH Publication 85-115), National Institute for Occupational Health and Safety (NIOSH), Cincinnati, Ohio (http://www. cdc.gov/NIOSH/85-115.html). This publication, or its successors, if any, along with your supervisor training, virtually guides you through the writing of your safety plans. Further publications are available at the NIOSH website (http://www.cdc.gov/niosh/). 2. NIOSH Pocket Guide to Chemical Hazards, National Institute for Occupational Health and Safety, Cincinnati, Ohio (http://www.cdc.gov/ niosh/npg/). This publication or its equivalent helps in assessing personnel exposure risk and problems with incompatible chemicals such as the strong oxidants used in well rehabilitation.

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3. Multiple copies of Protecting Health and Safety at Hazardous Waste Sites: An Overview (EPA/625/9-85-006), USEPA. This is a condensation of the guidance manual aimed at “nontechnical personnel” (whoever they are) that is good for handing out to employees. Sources include http://www.p2pays. org/ref/19/18737.pdf and the USEPA’s National Environmental Publications Internet Site (NEPIS) database (accessible via http://www.epa.gov/nscep). 4. 29 CFR 1910 and associated OSHA regulations with applicable amendments and corrections, as published in the Federal Register, available online. These contain all the applicable requirements and definitions for easy reference. 5. Material safety data sheets (MSDSs) and other documentation (such as NSF listings) for chemicals used in well treatment. These should be up to date and on file, and made available to site management along with your site safety plan. It is sometimes a pain to get useful MSDSs on some proprietary chemical mixtures, but you should insist that suppliers provide them or that you will buy materials from someone who will.

How are these health and safety plans written? If a contracting firm is typical, writing is not the first love of its key people, and writing a suitable plan may seem to be a tremendous task, ranking in preference well behind stripping and repainting a rig and just ahead of filing financial statements. If this is the case, the firm is well advised to hire a technical writer to perform the task. Such writers are available around the country, many of them with experience with environmental documentation. The Society for Technical Communication (www.stc.org) or industry professional associations such as the National Ground Water Association can provide references to suitable writers in a contractor’s area. STC and its various discussion groups and chapters have lists of professional communicators for hire. There may even be a few writers with both environmental safety and well rehabilitation experience. It pays to find out. Why not just borrow the consultant’s plan? There are some drawbacks:

1. Assuming they will share it, the contractor does not know whether the consultant’s plans are fully accurate, suitable, or in compliance with regulations. 2. Many aspects of the consultant’s plans are not applicable to the contractor and vice versa. 3. Finally, these plans may have to stand up to scrutiny by unfriendly people, and it is not a good idea to possibly be at the mercy of the engineer trainee (however diligent), who may have written the consultant’s plan.

A technical writer working directly for contractor management will do a better job at typically less cost. The writer’s work should be reviewed by an attorney competent in environmental health and safety regulations. 7.2.3.2 Practical Stuff: Access and Response Problems abound in well and pump rehabilitation and repair on both hazardous and nonhazardous job sites. Access is usually a problem for heavy equipment, and pumps

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Figure 7.2  Sometimes there are access challenges (photo courtesy of Ohio EPA Southeast District staff).

themselves may be hard to reach or retrieve thanks to engineering that never considered that eventuality. Some of these jobs best resemble undersea repair by divers. In fact, rehabilitation of caisson and lateral (e.g., Ranney) collector wells can require divers at critical stages. Especially on ground-water remediation projects, wells may be anywhere, depending on need, so contractors may find themselves rehabilitating a well down a bank in a wetland 100 ft from the road. Irrigation wells are sited to serve agricultural fields. Access at certain times of the year may be difficult or impossible due to permafrost thaw, wet ground, or outright flooding. Where there are distinct monsoonal rainy seasons, road access itself may be impossible (Figure 7.2). Facilities such as wellfields should be proactive in providing convenient access for service activities (Figure 7.3). Maintenance treatment (Chapter 6) and rehabilitation are work performed on existing systems, so access roads should be established, built to handle typical pump rigs and cranes. There should be space around wells for trucks, extra vehicles, tanks, and people, preferably in an area not prone to being a muddy, soupy mess in the rainy season. Fence gates should be large enough to pass service vehicles, although some facilities may have other priorities, such as making sure there is something at the well to service! (Figure 7.4). The otherwise simple act of going out for parts may be very difficult and waste hours if decontamination and unsuiting is necessary. Similar trouble is encountered by crews working in sparsely populated “developing world” areas. In these situations, contractors really have to plan ahead, or have people on the outside standing by who can be reached by telecommunications. It helps if contractors have on hand accurate equipment and configuration descriptions, equipment and part numbers, and well locations before they travel to the work site.

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Figure 7.3  Good well site access is important. Note room for crane and service vehicles on pad within fence, personnel access at the crane side to the interior and access through the roof.

Figure 7.4  Wellhead in East Africa where site security is paramount. Well service will require removing a portion of the “castle” wall.

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We note the phenomenon of the disconnect between the sales engineer leaving the job site with work order in hand, and what the crews show up with to do the job. Make sure the contractor’s sales agent fully understands the task and what is required, and communicates that to the field crew. Hold him or her responsible for wasted time and effort.

7.3 Contractors and Consultants: Avoiding Trouble in Working Together There are a number of considerations for consultants and contractors to ensure a harmonious relationship. Areas of friction occur most frequently in contract and specification language, specifically regarding environmental responsibility, costs and fees, and definitions of performance.

7.3.1 Mutual Respect in Rehabilitation Work Contractors should also avoid bypassing or duplicating the work of consultants working for the facilities in question. Environmental control (e.g., landfills) and ground-water remediation are usually managed by multidisciplinary environmental engineering or management firms, and any trespassing on their “turf” can result in a loss of good contract potentials. A better approach is to establish mutually beneficial relationships with such firms, allowing both to profit reasonably from their respective skills and assets. As in monitoring and other site contract work, well rehabilitation contractors should have a realistic view of the inflated costs of doing business in this environment that also go along with the higher profit potential in environmental work.

7.3.2 Specifications: Business and Bidding Considerations 7.3.2.1 Specification Pitfalls What jobs will competent contractors bid on or avoid with a 10 ft (or 10 m) pole? Well rehabilitation specifications that contain the following elements deserve to be avoided or modified in negotiation:

1. Specifies in detail the exact methods to rehabilitate, but … 2. Fails to provide sufficient information on the wells to be rehabilitated 3. Specifies what the contractor knows from experience will be inadequate or poorly fitting rehabilitation methods 4. Sets overly precise performance standards for acceptance of work (“401% increase in specific capacity”) 5. Sets unreasonable time limits 6. Specifies unreasonably low or rigid cost caps 7. Contractor liability for effluent waste material or anything else beyond the scope of work 8. Really bad idea: Specifying one commercially restricted kind of rehabilitation treatment without alternatives; other processes will do the job

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From the consultant or supervising engineer’s standpoint, this can be a very demanding list of caveats. Well rehabilitation work best resembles site drilling work in that it is (ideally) a service provided by highly skilled technical professionals in an atmosphere (usually) of uncertainty and limited information. It is different from drilling since facility supervisors probably have less experience with well rehabilitation than drilling, well construction, and environmental testing, and there are no established standard guides for performance. 7.3.2.2 Overcoming Pitfalls The typical facility supervisor’s personnel do not have enough experience with or knowledge of the technical issues in the rehabilitation task: chemical interactions, volumes, time, surging, equipment, etc. Facility management should hire a professional who does have this experience and knowledge to write the specifications and act as the facility’s advocate in ensuring that the work is completed properly. If they do not wish to take this wise advice, facility management should acknowledge its limitations, hire very experienced and capable contractors, and take advantage of the experience and knowledge the contractor provides. For example:







1. Let them take the lead or have significant input into the rehabilitation plan. Facility engineers may prefer precise control of such crisis projects, and thus prefer providing detailed instructions to contractors. However, the more specifically experienced contractor may have recommendations that boost effectiveness, save time or money, or improve safety. Even if you hire a consultant to specify and supervise, good contractor input should be entertained and incorporated as feasible. We ourselves learn something on each job. 2. Let the contractor have the information he or she wants to plan the job well. Information may be sensitive or may not be in a form easily transmitted in a specification. Make it available anyway! Good well rehabilitation contractors or consultants demand all the available information on the wells in question and all potential hazards to be encountered. They will be able to sift through what the site management has in order to make better decisions. 3. Give them flexibility in doing the job. No one wants costs or schedules to balloon out of control. However, it is very difficult to precisely define costs and time with the uncertainties of well rehabilitation. There has to be trust and communication to provide reasons and reassurance. 4. Avoid overly precise performance goals. There should be goals based on experience and testing. However, there are numerous factors that may prevent well rehabilitation from achieving desired improvements. These can include the effects of negligence on the part of the facility. If the well specific capacity is 20% of original, putting the responsibility of returning it to 100% on the contractor is not just or realistic. However, contractors must be prepared to give and defend good reasons why performance goals were not achieved.

Specifications and contracts for pump service work can be more narrowly specific in scope and price structure, since the engineers set the pump requirements. Hours and other contractor costs are also likely to be better defined, more like electrical

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and plumbing contracting. For more technical considerations, see Specifications for Well Rehabilitation.

7.3.2.3 Effluent Waste Water Containment Well rehabilitation usually generates various forms of effluent waste (solutions, slurries, and sludges). Some of that may be defined as hazardous wastewater. An issue is: Who should be responsible for control of this water? In the “outside world” (private wells, irrigation, and municipal), effluent waste water was often simply dumped on the grass or “around” or “away.” This is no longer acceptable. Effluent waste fluid should be contained, then treated as needed to make it nonhazardous to a receiving facility, such as a wastewater treatment plant or RV waste dump. Then it should be directed to the sewer or tanked and hauled. On environmental remediation facilities, if the facility is already involved in containing contaminated soil or water, or hazardous substances, on-site management has already made arrangements for secure disposal or treatment. However, if the contractor offers fully qualified hauling to secure disposal or on-site treatment (at a price), this is a good choice. The party responsible for the contaminated material (the agent of the property owner) should receive copies of chain-of-custody documents from the hauler.

7.4 Well Rehabilitation: Decision Making on Methods 7.4.1 To Rehab or Not to Rehab? That Is the Question The first issue to resolve: Rehabilitate these wells or not? Several questions can be answered: How intrinsically valuable is the well? Review Chapter 3. Water well value is readily defined in terms of cost-per-unit-water choices. Value for monitoring or remediation wells can be subjective and can be defined both in terms of replacement cost and whether the well can be easily replaced as a monitoring or pumping point. What has to be done administratively to replace the well? How much time does that take? The physical act of new construction of such wells is rarely expensive in itself. It is the consequences of the loss of the well’s function that are expensive. What is the local history of well problems? What are the history and structural condition of the well systems? Does the well system have a history of chronic clogging, corrosion, pump failure, sand pumping, etc.? Does a well produce noticeably less water than comparable wells in the area or site (was this sudden or gradual)? If low producers are common in the area, do they respond to redevelopment? Another consideration is whether the well meets current technical standards (e.g., D 5092, ANSI AWWA A100, ANSI NGWA 01, or state requirements): Is it well constructed, well located, and efficient? If it is not, is it so deteriorated as to be beyond reconstruction?

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Is well rehabilitation technically effective? • Is it possible to get long-term or permanent well improvement by relocating a well, or does the condition soon reappear in new wells? • Can the current well construction materials withstand the chemicals, heat, and physical shock of redevelopment? • Is there a chance that redevelopment tools will be hung up, lost, or severely contaminated during redevelopment? The answer to any of these determines the technical viability of rehabilitation (forget cost-effectiveness, regulatory constraints, or other practice issues for the moment). If conditions quickly reappear, preventive maintenance (Chapters 5 and 6) has to be practiced to protect the new wells. Rehabilitation alone won’t work. If the well will not stand up to proposed treatment, it may be necessary to: 1. Tone down the treatment 2. Look into alternatives that might work 3. Abandon the well and start over If tools can be lost, damaged, or contaminated so that they are difficult to decontaminate, the first question is does the contractor try to perform decontamination? And secondly, will the client buy the tools if they are lost or contaminated beyond reasonable recovery? How expensive will the well be to replace? In general, relatively shallow monitoring and recovery or plume control wells are not especially complicated or finely designed. However, administrative considerations (especially the costs associated with design time, design approval, etc.) can make each well worthy of saving if possible. Even relatively shallow highcapacity pumping wells can be expensive to replace, as are any wells in remote locations. Cost goes up as wells are deeper, drilled in difficult formations, have long, variable-slot screens, or are otherwise more complicated. Largerdiameter wells are of course more expensive per unit depth. The major problem in monitoring applications may be in nested and other multiple completion wells, where one well or interval is a problem, while others are not. To replace such a well may require replacement of an entire nest or disruption of multiple intervals. In this case, an attempt at rehabilitation is preferable. Will the well be difficult to relocate? Relocating water supply wells often involves a lot more than moving over and drilling another one. Production wells may be part of a wellfield, and new wells would require the various connections necessary to make them useful. Regulatory requirements must be fulfilled. Sometimes that involves buying new land and a whole cascade of new demands. Add engineering costs—you get the idea. Another monitoring well problem is with wells that are critical or hardto-replace data points, or those that have been monitored for a number of years. If such a well becomes unusable or its data unreliable, rehabilitation is a good option, even if water quality is disrupted briefly, because new

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well construction is also disruptive, and paperwork for new construction becomes a cost and administration issue in many places. However, if the well is substandard or irretrievably deteriorated, then it is preferable to attempt to replace the well in the same location. In doing so, it must be recognized that the deteriorating conditions may remain to affect the new well. Just how bad is the well? Can site management live with the well as it is or not? Historically, experience indicates that well owners and managers will live a remarkably long time with poor wells rather than make the investment in improving them (the curse of the well maintenance consultant and contractor). For pumping wells, what is the well’s working efficiency and what does it cost the well operator to operate at the poor efficiency vs. an improved efficiency? In terms of wire-to-water or well efficiency, using two useful equations from Helweg et al. (1983) provide some information to use in making decisions about changes in well efficiency (Equation 7.1) and pump efficiency (Equation 7.2): Well efficiency (Ew), defined as measured specific capacity in relation to a theoretical specific capacity:

Ew = SCact/SCmax (100)

(7.1)

where Ew = well efficiency in percent, SCact = current actual specific capacity (SC), and SCmax = calculated theoretical maximum SC. (Note that this is a restatement of the equation for efficiency used in Chapter 5. Also note that we elsewhere use Q/s for specific capacity, and Cs is also widely used.) Pump efficiency:

En = Eo/Emax (100)

(7.2)

where En = normalized pump efficiency in percent, Eo = measured pump efficiency in percent, Emax = maximum or new pump efficiency. (Note that Emax should have been tested at the well and not under ideal factory conditions.) Efficiencies should be compared (apples to apples) at the same total dynamic head (TDH) and discharge rate (e.g., gpm): for example, 100 ft TDH and 30 gpm, not Eo at 100 ft and 300 gpm and Emax at 50 ft and 250 gpm. En should not be used alone as an indicator of well efficiency, since it is only a pump efficiency value. Actual calculations of cost-effectiveness require knowledge of the costs of operation at a given efficiency. One cost consideration equation is provided in the following section. It is important to note that such equations do not directly factor diminished screen effectiveness or corrosion wear, but these will be reflected in reduced performance efficiency. Reduced pump service life or more frequent repair intervals are significant factors in operational costs. If a $2,000 pump lasts only two years (the warranty period) before replacement instead of five, the $2,000 pump is purchased 2½ times instead of once.

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Other matters to consider are the tangible and intangible costs of poor water quality, and fouling of water treatment and water system components. The Sutherland et al. (see reading list) or similar spreadsheet cost analysis approaches expand the scope of cost analysis beyond power costs.

7.4.2 The Costs of Well Rehabilitation Well rehabilitation decision-making processes fall into three categories:





1. The “well cleaner’s dream”: The well in question is irreplaceable, cannot be operated as it is, and new well construction or other options are not alternatives. In this case, cost-effectiveness will be no real factor in the decision to rehabilitate. 2. Looking at rehabilitation vs. doing nothing: The natural inclination of the well operating management is to do nothing until a crisis develops. It may be up to the seller of well rehabilitation services or the well system operator to convince higher management of the actual benefits of rehabilitating the well. 3. Rehabilitation vs. new construction: To drill or to analyze the problem and solve it? Assuming that the well will stand up to rehabilitation and cleaning, and it is otherwise feasible to rehabilitate, the cost of the rehab job determines the decision in most cases. If the cost approaches the cost of new drilling, the owner will be inclined to drill new unless there are other constraints. Make sure the cost estimate of the “drill new” option includes all the extras that go with siting and bringing a new well online.

7.4.2.1 The Cost of Doing Nothing As discussed in Chapter 3, this is usually expressed in the increased cost of pumping water, due to either increased well losses, expressed in increased drawdown, or reduced wire-to-water efficiency (e.g., Helweg et al., 1983): C=



Q (s + SWL + P) (0.746) (T) (K) 3,956 × E o

(7.3)

where C = total cost of operating over time, Q = discharge in gpm, s = drawdown in ft, SWL = static water level in ft, P = system pressure in ft of head, Eo = overall efficiency as a decimal, T = time pumped in hours, K = cost in dollars per kWh, 0.746 = conversion factor, hp to kW, and 3,956 = conversion factor, gpm*ft to hp. Example Q = 100 gpm, s = 30 ft, SWL = 100 ft, P = 115 ft, Eo = 0.60, T = 24 h, K = $0.07. (The expression (s + SWL + P) can be replaced by TDH.) C=

100 (30 + 100 + 115)(0.746)( 24)(0.07) 3, 956×0.60

C=

30,705.36 = $12.94 per 24 day to pu umpt that well 2, 373.6



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Change s to 50 ft, and C = $13.94 per day. Change Eo to 0.50, and C = $15.52 per day. For 24 h/day, 365 days/year pumping, $15.52/day = $5,664.80 per year, vs. $4,723.10 at $12.94/day. The nearly $942.00 difference on this one well could buy a lot of electricity.

The cost effect is more dramatic for steeper efficiency losses and larger, deeper wells, and multiple-well systems, and less dramatic for smaller, lower-flow wells and systems. The next step is to convince management that the cost of the rehabilitation (usually more than the $942.00 per well) is worth the effort. To do that, it is necessary to look at:

1. The long term: convincing management that, with regular maintenance, the well cleaning will pay for itself in power savings over a period of years. 2. Other factors beyond mere power costs: Such as sand pumping and bacterial fouling of filters and treatment tanks, which affect critical site remediation performance and increase the cost-benefit. This more dramatic expression of well problems is more common in environmental remediation extraction wells.

7.4.2.2 Costs for Serious Rehabilitation Work Historically this ranges from 10% to >100% of new construction. It is closer to 10% to 20% of new construction for municipal and irrigation water supply wells and closer to 100% for environmental site wells, excluding design, planning, and other associated permitting costs. The 20% figure is a psychological barrier for many in well-owning management (even if told that new construction is not a permanent solution). Above 20%, drilling new seems to be the more attractive option if feasible. Sometimes the options are limited. For irreplaceable wells, prices can be 100% of new drilling if the result is the same: an operational well providing the necessary capacity. The cost in any case is higher if the well is more deteriorated or plugged or if it is harder to clean for whatever reason than it is for a light-weight problem. The incentive here for management is then, of course, to make sure that wells do not become so radically deteriorated. Wells are like any other working machine or structure in this regard. The potential for abuse can be great in pricing (or slicing of service if there are price caps), since it is difficult to monitor well rehabilitation progress while the rig is over the hole. However, this is a business trust issue, not a technical one, or a reason not to rehabilitate. It simply means that there has to be trust, honor, and accountability in the relationship. Hiring a third-party inspector to watch the work and document results helps with the accountability part. Note:  Trust and confidence in well rehabilitation contractors have been a running theme here in (1) site safety, (2) participation in well M&R planning and flexibility in implementation, and now (3) costing and value for the money. How does a manager gauge the qualifications and trustworthiness of a contractor? Management should check into past experience and referrals from other clients in

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choosing appropriate contractors. If you engage a consultant to advise this work, he or she will narrow the potential contractor list based on his or her experience with them. They know who has been caught pouring water into drawdown tubes to make the specific capacity look better during testing and who ignores specifications. Hire consultants who know those things. In vetting contractors, ask for the bad as well as the good. Call up other clients of this contractor and check into problems with performance, billing, timeliness of service (keeping in mind that the person on the other end of the phone may not have a true sense of the time problems), follow-up, and general professionalism. If negatives come up, discuss these with the potential contractor. Do not just write them off without a chance to explain. The nature of the work means that there will be bad days. Examples Why were you four weeks late in completing that job? Answers: “Our chemical supplier was backordered on the necessary chemical and we could not find an alternative approved by the state DEP. Site conditions were too soft to risk bringing in our equipment.” Why did that job cost 150% of estimates? Answer: “Our chemical costs went up since that acid is no longer a process by-product, and have you priced chemicals lately? We had to make special wellhead modifications to permit us to maintain a positive head during chemical introduction, a change condition on that job,” the contractor adds. The project manager at XYZ says you left the job site a mess and were rude and disrespectful to him. Answer: “They insisted we start on that site in the Ohio Valley in March and we had to winch in and winch out. We’re sorry, but tank trucks and pump rigs are heavy! We’re sorry we were rude, but the pinhead watching us was always in the way telling us what to do … and he was a horse’s ass. Gary’s girlfriend has been running up his charge card and, OK, some jobs just do not go well, do they?”

If trust and confidence in current contractors is strained, problems should be resolved by discussion and changes made if problems are not resolved satisfactorily and trust cannot be reestablished. 7.4.2.3 Contractor Pricing of Rehabilitation Work The trick for the contractor is to provide a viable service at a cost feasible and salable to site management, while also making a living at it. Some factors include:

1. Costs: Capital equipment (spudder, compressor, jetting rig, tool strings with special development tools), chemicals, fuel and power for engines and boilers, most especially labor and overhead. Insurance, training, travel and mobilization-demobilization costs are very important expenses. There is no avoiding some significant expense, but costs can be kept down with some basic ingenuity and frugality. Some existing equipment

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lying idle can be recycled into rehabbing tools at little cost: spudders (cable tool rigs), low-pressure compressors, pump hoists, drilling pipe, etc. Chemical handling equipment is low cost. The chemicals themselves may be cheap to expensive depending on unit volume and type (but the trend is that they are getting more expensive). Packers and high-pressure pumps are relatively expensive, and there is not much to do about that but to take care of them. Training and protective gear to handle chemicals are expensive, but absolutely justified. 2. Pricing (in general): The typical costs (e.g., 16 man-days, 1,600 gal of chemicals, travel, equipment time, and overhead) can usually be accommodated within a fraction of the expected charge. Contractors may suggest a price structure in which the contractor charges that amount “for trying,” receiving a bonus for results. Just to illustrate contrasts, on some water well hydro­fracturing jobs, for example, the costs are so low that $1,500 will cover the attempt unless there is a lot of travel involved, and charges of $3,000 for good results are not unusual. On the other hand, cleaning a line of biofouled plume control wells or a single deep high-capacity well may run into the hundreds of thousands of dollars. 3. Pricing (on a particular job): Given what you have been told about the wells in question: Can the contractor afford to do the job? Is it too far away? Will it require extra effort? The contractor might have to decide: Are there times when you need a “loss leader” to demonstrate your techniques or to gain experience?

7.4.3 Choosing Rehabilitation Methods Before choosing a method, it is necessary to analyze the need. It is easy to overkill or underkill the job. Review the analysis part of this text (Chapter 2) for methods and applications for analyses to determine what the problems are that have to be treated. The rehabilitative methods themselves are really only variations on water well methods. All are undergoing some development and improvement over time. Several are described in Chapters 4 and 6. All active rehabilitative treatment strategies (i.e., excluding redesign and material selection) in practice involve some combination of removing encrustants, suppressing microbial growth, and clearing the material from the well. All such methods should be considered temporary measures. Maintenance followup is required to ensure continued improved performance. Maintenance follow-up should always be part of the project discussion. See Chapters 5 and 6. We wish to specifically call attention to one contractor tactic that does not have the best interests of the client at heart, the practice we call “creative obsolescence.” This strategy is that the contractor does not wish to clean the well so thoroughly that he does not come back for a long time. He wants to clean it just enough so he comes back again on a two-year cycle. The sales engineer then sells this cycle as normal, what you should expect. “Have a beer! How’s your wife? Here’s a new ball cap, dude.”

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7.4.4 Damage Overly aggressive swabbing is a frequent cause of damage to well components. The upstroke of a swab or surge block essentially pulls a vacuum on the well and under the right conditions has been known to exceed the casing collapse strength, therefore collapsing the casing. Working within the screen carries added risk. The authors have observed downhole television surveys of screen after rehabilitation in which damage was done. The surge block fit too tight and caught gravel protruding through the wire wrap screen. The gravel pried the screen open significantly beyond gage, thus allowing gravel pack and formation through the screen. Stainless steel is vulnerable to abrasive and chemical damage. High-pressure jetting can actually cut and enlarge the openings. And the authors have witnessed a rehabilitation job in which multiple barrels of hydrochloric acid were introduced directly into a stainless screen, allowed to sit, and then worked with a swab. The screen openings were significantly enlarged and the well produced sand beyond any hope of recovery. Poor record keeping can lead to well damage. The authors have observed drilling or rehabilitation tools stuck and abandoned in wells screens. It may likely be the result of a work crew being sent to the location with inaccurate information on the construction dimensions of the well, that is, depth and diameter of casing and screen. The crew runs their tools into the well, and then the tools become permanently jammed into the screen or impact the bottom of the screen. In another incident, a driller was short one casing section (joint) during construction; the well modification was not documented. So using the inaccurate record, a rehabilitation crew later slammed development tools into the bottom of the well, which drove the completed well 20 feet into the overdrilled section of the borehole. As related in Chapter 6 and the following, pressure acidization rehabilitation carries risks, as does any treatment that involves pressuring up the well and borehole (e.g., CO2). Pressure acidization is the practice of introducing hydrochloric acid into an open-hole limestone well through a wellhead that can be shut in. Once the acid is in contact with limestone, CO2 is generated. As the acid reacts with the mineral, the evolution of CO2 rapidly builds pressure in the shut-in well. The gas pressure depresses the water level in the well and forces the solution out into the fractures of the limestone. The authors have observed a case where the casing was grouted with bentonite, which could not contain the pressures generated within the well. The acid solution channeled to the land surface through the grout and then the pressure lifted the casing a few feet out of its seat in the bedrock. Also, fracture systems can extend to the land surface, and in the case of a thin overburden, the acid solution can channel to the land surface some distance from the well. This creates direct conduits for surface water to enter the aquifer in the immediate vicinity of the well, which compromises the sanitary integrity of the well and poses a sanitary risk. “Junk in the hole” is a frequent problem that is not necessarily the direct result of working on the well. In fact, it is often the result of not working on the well. Parts of

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both lineshaft turbine and submersible pumps are often found in the bottom of wells and in screens. Pump columns and drop pipes corrode off, and everything below the failure point goes to the bottom of the well. The pump parts can potentially damage a screen or wedge into it as with drilling tools. Regardless, the well needs to be put quickly back into service, and there is no time to recover the junk at the time it is discovered, so it is left in the well. After some turnover in personnel, knowledge of the junk in the well is lost and the junk stays there, accumulating sediment, blocking significant lengths of the producing interval of the well, and reducing the well capacity. By the time well maintenance is performed, the junk is seriously locked in by sediment, biofouling, or corrosion products, such that no attempt is even made to clean that interval of the well (and the task wasn’t included in the work specifications because no one knew it was there). Other hardware is also found in the well, such as tubing, cables, wiring, wood beams, pipe wrenches, etc. All can wedge in the well, enhance the accumulation of sediment and corrosion, snag tools, or punch a hole in the screen. Such are the nightmares not always accounted for in well cleaning specifications.

7.4.5 Issues in Rehabilitation Chemical Selection Rehabilitation chemical selection should involve choosing the most specifically useful blends that provide the best results and least damage, including damage to the environment and living things. Selection for environmental applications is more restrictive than for water well applications (at least so far). In water wells, the criteria are that the chemicals are (1) effective for the purpose, (2) have low toxicity at low residual concentrations (chlorine but not formaldehyde can be used, for example), and are (3) removable in the development process. In an increasing number of cases, NSF or some similar health and safety listing is required. Reactivity with the ground-water chemistry is also an issue, but only rarely technically restrictive (getting permission is another matter in some jurisdictions). In environmental applications, chemical reactivity is the prime concern. Acute or chronic toxicity is less important than in water supply or discharge, because the chemical mixture resulting from the mixing of treatment chemicals and ground water will be contained, and not usually handled by the well cleaning crew. Effectiveness in dissolving and dispersing fouling material has to come in third. For recovery wells, reactivity is an issue since the ground water is usually contaminated with a relatively significant concentration of some combination of chemicals. They did not put these wells and treatment system there for a design exercise, did they? In monitoring wells, the chemical treatment should not leave a long-term residual change in the native well environment. Actually, the existing ASTM standard for monitoring well maintenance is not to use chemicals at all. If this status quo continues to stand, chemicals will not be used in monitoring well rehabilitation. Reactivity is different from place to place, of course, depending on the contaminants present. Some compounds are explosively or thermally reactive with oxidants such as chlorine or hydrogen peroxide. See Table 6.3. If the contaminants are primarily organic compounds that do not react violently with oxidants, the issue is the fate of the altered product water. Using chlorine will

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result in chlorinated organics (disinfection by-products (DBPs)) that are more recalcitrant for bioremediation, for example. DBPs are also a problem for public water supply systems, since long-term exposure to such compounds is possibly carcinogenic for customers. Development effluent wastewater contaminated with chlorinated organics has to be contained and treated. Also, if a relatively pure contaminant such as toluene is being recovered from spent filters, then the presence of chlorine contaminates the product and the filtrate is less valuable or useless. However, such chlorinated organics should be removable in carbon filtration or air stripping, or by reductive dehalogenation. Assuming that reactivity and effluent wastewater handling are not problems, chemicals should be chosen based on effectiveness. Within the limited list available, once chemicals are eliminated for reactivity and toxicity, chemicals used in well rehabilitation are chosen according to the nature of the well problem, which has been determined by analysis, not guessing. There are no standard or stock procedures. Again, aside from safety issues, chemicals should primarily be chosen to assist in removal of clogging and encrusting materials, based on a diagnosis of the problem in the well. And, before selecting a chemical regime, it is prudent to be thoroughly familiar with modern well rehabilitation methods for these jobs. Some who are assigned the task of specifying chemical selections assume it is (1) simple or (2) can be made from an old spec, text, or with a phone call. This is really not the case, and one should not bet their job on oversimplification. Specification writing should not be attempted by anyone not familiar with:

1. The actual well problems (determined by analysis) 2. The effectiveness and reactivity of the chemicals 3. Practical considerations in application of chemicals

Well rehabilitation methods are in a period of change as new information improves on the knowledge of the effects of treatments on well-deteriorating problems. For example, heat augmentation may be used to boost the effectiveness of chemicals, and special proprietary blends and methods are increasingly marketed and employed by contractors in North America, Europe, and Australia. Beyond knowledge of the problem and applications, it is important to note that many of these chemicals are quite hazardous to handle if proper safety procedures are not followed. They should only be used by trained personnel familiar with their safe use, and equipped with proper personnel protection (respiratory and dermal). For people specifying treatment with chemicals, this is the ultimate issue (assuming human life is valuable to you). The project management should know:



1. Can the chemicals and their mixture with the treated ground water be safely handled by the personnel available? Do they have the training, experience, and equipment? If not, do not try to make “ninety-day wonders.” Hire experience. 2. Will the proposed treatment meet with regulatory approval? The mentality in well rehabilitation circles in the past was to “sock it” with strong,

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highly reactive compounds, primarily “hard” mineral acids and (secondarily) highly concentrated hypochlorites. “If some is good, more is better.” There was little regulatory oversight. In the past decade, regulatory agencies have begun to scrutinize what is being used in well rehabilitation, for both potable water supply and environmental wells. The State of Wisconsin has an approved chemicals list, and many states and jurisdictions require NSF 60 listing. There has now developed a tendency of extreme conservatism and reluctance to approve any chemical use in some circles. Keeping these issues in mind, Chapter 8 is a review of physical and chemical treatment applications in well rehabilitation and maintenance. Many of these are also discussed in Chapter 6, and in greater detail in some publications in our reading list, or in company literature in some cases.

7.4.6 Reconstruction The structure of the well sometimes has to be renewed or modified to solve a problem, usually a silt lens or silt-filled fracture or other source of fines, or to repair collapsed or corroded sections. Usually, for any of these problems, a suitable liner is installed and grouted into place where there is sufficient diameter. Installing liners can be complicated and not always effective, plus they are impractical in smaller wells typical of environmental applications. Relining does not replace good well design and material choice from the beginning, but it is often a choice that can be successfully used. One limitation is that well diameter is lost during the lining process, often more than 5 cm (2 in.). This can restrict pumps or provide complications in future pump service. Figure 7.5 illustrates a lining installation using a Griffitts packer (Griffitts Drilling and Seals, Maryville, Tennessee), used in securing a liner in place against a casing or borehole surface. Figure 7.6 illustrates a slim-line relining sequence in a rock well using an inflatable swage (Inflatable Packers International, Osborne Park, Washington). Whatever the limitations posed by relining, it is better than using a rotted-out well if relining and use “as is” are your alternatives. Wireline-installed or “riserless” pumps offer some relief for restricted-­diameter installations. In this case, a pump almost as big as the liner I.D. can be used (Figure 7.7). Another reconstruction technique to limit or eliminate sanding is the installation of suction flow control devices (SFCDs) or engineered tail pipe, as previously described briefly. The concept is to provide engineered resistance to inflow in the screen interval to counteract the typical V-shaped entry profile to force a cylindrical profile (Figures 4.12 and 7.8). These have been used with success in a number of countries to control sand pumping and encrustation problems in wells. A variation on this device is produced by Aquastream (Sand Control Technologies) in the United States. This device has a cemented-on filter pack on the outside of a pipe that is variably slotted. Strictly speaking, the filter pack is unnecessary to the SFCD function, which can be accomplished by slot pattern alone. As mentioned earlier, not all well configurations respond as predicted by the flow equalization equations. Wells

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Sealing off surface water and bad upper streams

Figure 7.5  Lining a well, sealing off undersirable zones using a Griffitts well packer (illustration courtesy Griffitts Drilling and Seals).

should be evaluated as candidates individually. Further reading on SFCD function and application can be found in our recommended reading.

7.5 Specifications for Rehabilitation 7.5.1 Specification Deficiencies Specification writing for well rehabilitation in general is frankly in a disreputable state in the United States. We cannot speak for elsewhere. Locally, there are surely pockets of excellence, but specifications coming across the desk of the author usually have some of the following deficiencies:

1. No provision for analysis of well performance or, especially, the qualitative nature of the fouling problem. The treatment method has been preordained by the engineer writer. The bidder therefore has no idea whether the problem has been properly diagnosed, the extent of the problem, or the well history.

222

Sustainable Wells: Maintenance, Problem Prevention, and Rehabilitation Inflatable Packers International Pty Ltd Re-lining with swaged Unit 1, 6 Pitino Court, Osbome Park WA 6017 Australia packer and liner Ph: +61 8 9204 2448 Fx: +61 8 9204 2449 Email: [email protected] P6638

Inflation line Drill string Existing casing New thin wall liner

HP Swaging packer “Swage” packer

Existing screen

Run in new casing after well cleaning & video inspection

Set swage packer

Continue swaging to surface

Figure 7.6  Setting a liner in place using an inflatable swaging system (illustration courtesy of Inflatable Packers International Pty Ltd).





2. There is insufficient information on the pump and well structure for the bidder to make intelligent judgments. The bidder has to have useful information to make a decision about the vulnerability of the well, chemical types and volumes recommended, or what has to be done to fix or refurbish the pump. Well screens and dimensions—especially odd ones, like a screen is bigger than the casing diameter or the presence of a restrictive ring at the top of the screen—must be clearly noted. These are all factors in chosen approach and cost analysis. 3. The specification writer has provided an exact procedure and chemical volume specification that the bidder is to follow in exact detail. The bidder has no idea, of course, if the specified well rehabilitation procedure is a good match without sufficient analysis information. At best, such procedures are often dated or insufficient. Now, we often specify an exact procedure in

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Figure 7.7  Wireline or “riserless” pump installation schematic (illustration courtesy of Inflatable Packers International Pty Ltd). A riserless pump uses the casing as the discharge line.





this way, but the specification is based on analysis, and we provide enough information to bidders to help them make their own alternative proposals. 4. There are no performance standards or provision for follow-up. The process specified is assumed to do the job, but there is no budgeted time and effort to find out through testing, and no common ground for agreement between contractor and client to determine effective performance. 5. There is too much irrelevant detail. Government RFPs sent out for general bid of course typically devote one hundred pages to equality in employment and maintaining a drug-free workplace and three pages to technical details on how to clean the well. The one hundred pages part cannot be helped, of course, due to regulations, but these RFPs could often be more user-friendly and informative about the technical issues. The same is true of specifications written for the private sector. Based on page count, fence design can seem to be way more important than a procedure to clean the well or conduct a step-drawdown test.

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vs : slot velocity As : slot area ∆p (x) = pi (x) – po (x) ≠ const vs (x) . As (x) = const vh = const vv = vv (x = 0) . [1 – Lx ] Pump jacket

Casing Gravel pack Well screen vh (x) = const

x vs (x)

Le

pi (x)

po (x) Control element

As (x)

dce

dws db

Figure 7.8  SFCD retrofit in well changes hydraulic profile (Eucastream SFCD design, Kabelwerk Eupen AG product literature, Eufor S.A., Eupen, Belgium).

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7.5.2 What Well Rehabilitation Specifications Should Have Specifications for well rehabilitation should have several features:

1. The cause of the well problem has been or will be properly analyzed (information available to the bidder), or analysis is part of the scope of work. 2. The treatment specified can be adapted to address the specific problem if necessary. 3. To be qualified, the treatment contractor has to be knowledgeable and adaptable (and should be able to demonstrate these qualities). 4. The well will be tested before and after for performance (always with a step-drawdown test, sometimes with camera and other procedures). 5. A report on the project and its results will be presented to the client.

In some cases (as we prefer, for example), a consultant conducts the testing and writes a report on the project. It may then be the case that the contractor may be engaged to properly maintain the well to prevent or mitigate recurrence of the problem (Chapters 5 and 6). Alternatively, the water or environmental facility institutes maintenance. Item 1: Problem analysis. Specifications for the whole project (if not the well cleaning contract itself) should require microbial, physicochemical, and performance analysis (as recommended in Chapter 5), and TV inspection (where possible), before and after treatment. Borehole geophysics (typically gamma, borehole flow meter, and caliper tools) may also be employed. Such tests should be diagnostic and practical in nature. Item 2: The treatment specification should be goal and not process oriented. The goal is increased performance, reduced fouling, etc. The exact treatment may be left to the knowledgeable contractor to propose as a request for proposal (RFP). Alternatively, a knowledgeable consultant, working for the well-operating facility, writes a specification for competitive bidding. If the format is RFP, the contractor should be required to submit a description of the proposed procedure for assessment by a knowledgeable project manager or consultant. Item 3: Limits to contractor freedom. The major exceptions to the freedom of item 2 are (a) the presence of contaminants that react poorly with major well cleaning compounds, (b) the consultant writes a well-conceived specification, and (c) the site and well history are so well known that the treatment can be narrowly defined based on past experience. Chlorine may be banned, for example, and a replacement recommended (based on experience and not on a company brochure). Other exceptions to item 2 are (a) an example treatment protocol to permit “level-field” bidding by all interested or (b) a protocol highly specific to a favored contractor who has provided excellent service with a specific approach. By “service,” what is meant is service at the wellhead, not the one with the best advertising visibility or most persuasive sales representatives.

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There can be “game changers” in these either-or decision analyses. The use of fluid-pulse tools, for example, can be one in that they can exert considerable development force using a rather small, portable device. See Chapter 8. Item 4: Performance testing. There should be some suitable testing procedure to determine the extent of difference between the condition before and after rehabilitation to rationally assess the effectiveness of the treatment. Generally, item 1 defines the before and similar methods are used to define after. This contributes to the knowledge base of the well or wellfield: “It worked—why? It didn’t work—why not? We achieved A but did not achieve B.” All this feeds back to the need for long-term, accessible records. Specifications should define standards for conducting tests. We observe that the state of the art for step-drawdown testing, for example, is degraded. This requires us to be very specific in what we require in such tests. Item 5: Posttreatment. The specification should have provisions for providing follow-up maintenance. The project may make this part of the well cleaning package, or it can be separate. The specification should ask for: 1. The contractor’s recommended approach and fees based accordingly, spelled out intelligently. Alternatively, bidders quote prices on a consultant-designed specification bid sheet. 2. Contractor company and personnel qualifications, experience, training, and references. 3. Assurance of contractor training, licensing, safety plan, insurance, bonding, etc.

7.5.3 Selecting Well Rehabilitation Bids Bid proposals should be accepted based on the qualifications and demonstrated competence and knowledge of the bidder, as well as price. Bids accepted should be “best.” Of course, price is important, but only if there is value for the price. Low bids that provide substandard service may cause greater life cycle cost in terms of (1) reduced pump life, (2) well damage, (3) too rapid return of the offending condition, and (4) higher pumping costs due to lower than necessary efficiency. Experience and reputation in this business are important. Bid reviewers should themselves be knowledgeable about the issues, and judge experience and reputation based on actual performance in the recent past. Companies can claim decades or centuries of experience; however, the legendary old experts from the golden age extolled may now be dead. Avoid being swayed by marketing atmosphere and sophistication. As is reiterated several times elsewhere in this work, well service contractors themselves need to be professional. Two annoying habits we have observed in the less professional are: • Sometimes very low bids are placed on rather complex jobs with the intention of not following the consultant’s specification, if at all possible. This works if the consultant is not on site, coffee mug, pen, and camera in hand (Section 7.6).

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• Especially on jobs in small communities, some contractors do not show up equipped and prepared, ready to go. On every job, there is always a Monday, and a fitting needing to be located locally or called in from the home shop, but excessive time spent (and billed) scrounging for parts and equipment from the customer should be avoided.

7.6 The Role of Consultant Specifier-Observer The above discussion is rather optimistic about contractor capabilities, interest in providing excellence and innovation in service, and businesslike process. This actually is the case with a select number of well service contractors in our experience and observation in the United States. On the other hand, we do experience a different kind of approach to the work: do the least possible, “do what we always do,” come on the job underequipped or not equipped to perform the specified task, unprepared to fulfill the specified scope of work, but fully prepared to argue or whine. Busy facility managers or operators who are not extensively experienced with well rehabilitation work often rely on these companies to provide the excellence they expect. However, they may be disappointed or underserved, and not even know it. In more remote, developing world type markets, contractor capability to perform the desired work may simply not exist. It may have to be assembled and trained. The well rehabilitation consultant (properly experienced and motivated) can drive the process toward excellence: conducting the necessary diagnostic testing, writing the specification that will plan out a successful scope of work, observing and enforcing during the site work, and testing afterwards to document the results—all on behalf of the well owner-operator. Employing such people can relieve the facility management of the burden of supervising work they are not well equipped to supervise. Consultants can also develop the follow-up maintenance plans and train facility personnel in their implementation. In the developing world situation, the versatile consultant may (MacGuyver-like) paper-clip together the capacity to clean wells from components found in the mine country and marketplace.

Methods 8 Rehabilitation Technical Descriptions Methods differ depending on the circumstances, but this is a description of methods for general information. For the most part, these are suitable for maintenance as well as rehabilitative treatments within limits.

8.1 Physical Agitation 8.1.1 Basic Principles



1. Physical agitation is essential for most rehabilitation and maintenance treatments for the same reason that it is essential when you wash a bottle, you scrub it out—agitation makes the washing more effective. Think of a Thermos bottle that held clam chowder. There is no way you will get the bottle clean without physical agitation. In many cases, the chemicals are relatively ineffective against entrenched deposits in the cold ground water. Agitation methods can take several forms. Agitation must be vigorous, and it usually takes a significant amount of time in rehabilitation tasks. 2. We also almost always recommend that some method (e.g., brushing and airlifting) be employed to take off surficial growth and other material mechanically to avoid wasting chemicals and effort on surface material, letting the chemicals and redevelopment work on more deep-seated clogging material obstructing aquifer porosity.

8.1.2 “Conventional” Redevelopment Redevelopment (already considered in Chapters 4 and 6) is usually required for most well cleaning—surging with surge block or air, or jetting for redevelopment. Brushing is an important and useful variation for removing encrustation from shutter screen and open-rock boreholes. See the discussion on well development methods in Chapter 4 (virtually the same procedures as used in rehabilitation) and also other relevant references in our reading list. As previously discussed, reciprocal surging and air tools are optimally combined to gain the benefits of both approaches, this works with brushing as well. The double surge block eductor tool (Figure 4.4), ideally run on a cable tool rig that provides a reciprocating stroke of 2 ft/s continuously, is a highly effective and economicalto-deploy redevelopment tool. The surging action induces a harmonic in-and-out movement in any well (screened or open borehole). The double surge block serves to concentrate effort. The airlift eductor removes dislodged materials, increasing the 229

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efficiency of the process. The tool can be deployed for long periods without awkward removal. As discussed in the following, the double block with an opening between (Figure 4.4) is useful in “spot dosing” with chemicals. Deployment is economical. Functional cable tool rigs can be purchased inexpensively, and are operated (for this purpose) using four-cylinder gasoline (petrol) or diesel engines on a few gallons of fuel per shift. The tools are widely available at discount these days as the drilling industry runs from this veteran, slow-drilling method, or can be fabricated with steel and rubber. Deployment is “low-tech”: anyone capable of maintaining an antique tractor can maintain a cable tool rig. Most of these rigs are not very large (the wheelbase of some American pickup trucks), and can be driven, hauled, pushed, or hoisted to locations inaccessible to many crane trucks. The cable tool rig is designed to perform the task of providing a reciprocal motion over a long period of time. For other types of equipment, this is a fringe application of the machine (e.g., pump hoist or crane). The surge block development or combination tool (that old geezer) is often charged with ineffectiveness. That sounds a lot like “toothlessness,” which is an “age-ist” charge. “The well was cleaned with surge block to no result, so we brought in the Gee Whiz™ tool and cleaned it right up!” Chances are (based on our experience), the blocks had poorly fitting or floppy disks (they were toothless), the tool was run too slowly on a crane hoist, or not long enough. It also may be that the surge tool started development and the Gee Whiz tool just finished it. Do not overlook the “slow” issue. Big crane reels are too slow for proper surge block movement. They are alright for swabs. Most pump hoists do not have the capacity to generate a sustained reciprocal motion. Some have hydraulic spudder beams. These are acceptable if the hydraulic system has sufficient cooling capacity in good repair. When the system overheats and blows, no more spudding. Cable tool rigs are best for providing the appropriate speed, stroke length, and longevity of surging. Face the facts, people. There is a reason that the oil patch uses them for work over rigs to this day. Airlift eductor surging without the reciprocation is certainly beneficial. In this case, most action is focused at the point of air injections and eductor suction. This approach lacks the focus effect, but can be quite effective. It also can be accomplished with air compressor and relatively simple, widely available components. There is certainly a benefit to using other redevelopment methods (as follows). Usually they then should be followed by airlift-eductor surging using some variation on this venerable, versatile system as a polishing step. One important difference between development or maintenance and rehabilitation is in handling development tools if they are being used with hot water, cryogenic carbon dioxide, or corrosive/caustic chemicals. Chemical-laden splash and discharge have to be tightly controlled. The development tools themselves have to stand up to the chemical or thermal environment. Personnel have to be knowledgeable and respectful about handling chemicals and hot (or supercold) water and tools, and equipped to do so safely.

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8.1.3 Other or Advanced Physical Redevelopment Methods There is a variety of additional physical development methods used for water supply, oil, recharge, and other wells, including shooting, hydrofracturing, fluid percussion tools, and similar or hybridized methods. Using a martial analogy again, improved well rehabilitation methods are simply the bigger, faster cannon: they make a bigger impression, but are still a poor substitute for preventive maintenance actions (Chapters 4 to 6).  And of course, “shock and awe” (the powerful tool) is usually followed by rifle-toting boots on the ground (the finishing surge procedure). Maintenance is “winning hearts and minds” (and paying off bad guys). Some of these methods are too vigorous and not sufficiently controlled for well redevelopment of smaller pumping and monitoring wells, especially where contaminated water can be encountered. However, existing hydrofracturing equipment can be used for supplying pressure (scaled down to be nondestructive) to jetting tools. Fluid percussion tools can also be adjusted to provide a pulse force and duration that cleans nondestructively. The surge block procedure (Chapters 4 and 6) is widely applicable and can be scaled down to the small monitoring well, even using tiny cable tool rigs or grad students with bailers. The available tools can be divided into three categories that generally encompass variations on each: cold CO2 “fracking,” sonic/vibratory disruption, and fluid-pulse methods. Shooting with explosives is the original sonic/vibratory method and considered with other similar methods. Fluid-pulse tools also develop a percussive force. A feature of most of these methods is that they have brand names, a certain proprietary and patented nature, and some exclusivity in use (e.g., through licensees). However, they are all derivative from previously available methods that are in the public domain. In most cases, however, the “new” method is a more refined and systematic application of the underlying principle. As mentioned in Chapter 1, the hope of reward coming from patenting an improved system continues to be an important driver promoting innovation. Innovation keeps economies vibrant. 8.1.3.1 Cold CO2 Treatment The use of dry ice (solid CO2) has a long history as a well development tool in North America; however, control of dose and application has been a problem. If metered in slowly, capped, allowed to release, and repeated, the generic system works in many cases. CO2 also represses microbial activity where it saturates ground water (Chapter 2). Dry ice development is a highly portable force method. Dry ice blocks or pellets in a cooler can be hauled up trails where no rig or hoist can go, and provide a potent development force at modest cost. When CO2 liquid is injected, the temperature drops to freezing. Forming ice crystals “pop” and disrupt biofouling and encrustation. Carbonic acid formed as CO2 is dissolved in water which inhibits respiration and causes a localized microbial kill. Safety Note:  CO2 must be used in the open in fresh air, as the CO2 can displace oxygenated air as the solid blocks sublimate and the gas evolves out of water. If fed too quickly or too much is used, the explosive force of the escaping gas is very powerful. Well equipment can burst, resulting in flying shrapnel. Also, freezing may disrupt

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casing seals downhole, and this can take a while to be noticed. Supercold tools and piping or escaped cryogenic liquid or gas can freeze flesh. The Aqua Freed procedure (Aqua Freed, a subsidiary of Subsurface Technologies, Inc., Rock Tavern, New York) is described by Neil Mansuy in his book that is part of our publisher’s Sustaining Well Series. Aqua Freed was developed as a way to provide the redevelopment effects of cryogenic CO2 in a controlled manner. A variation on the method, Aqua Gard, is provided as a maintenance treatment (Chapter 6) that has considerable merit. The Aqua Freed process is described by its developers as acting on the formation and encrustants in the wells through gas expansion and freezing and thawing, which dislodges deposits, and also through the formation of carbonic acid, acting under pressure. The carbonic acid solution is relatively high in concentration and acts as a mild acid, which can attack deposits. The thermal shock on bacteria and their biofilm networks probably has some benefit in dislodging biofouling. The action steps of this process are:

1. Injection of gaseous CO2 to begin forming carbonic acid 2. Injection of cryogenic liquid CO2, starting agitation and freezing 3. Allowing time for penetration into the formation and reaction 4. After application, remove packer and thaw, venting and depressurization 5. Mechanical redevelopment (e.g., with surging tools as described above)— this is crucial, as noted in descriptions of the process)

As with any cleaning procedure, these steps should be sandwiched between precleaning and postcleaning well testing and borehole TV inspection (Chapter 5). The Aqua Freed process has some other attractive features:

1. The injectant is chemically reduced and not reactive with organic molecules. 2. Although pressurizing, it does not work under “fracking” pressures, so fracture opening is minimized. 3. The material, compressed CO2, is relatively safe to handle (suspending dusts of aluminum, Mg, Ti, Cr, and Mn in CO2 streams should be avoided). 4. No other chemicals are absolutely necessary. So there are no effluent residual chemicals to contain and discard. Some Aqua Freed service providers will add a chemical rehabilitation step and additional redevelopment after the freezing step as needed. Doing so can be beneficial, as in general terms, combining methods can attack multiple clogging phenomena. Problems identified are (at present):



1. Commercial restriction (exclusive territories), and not cost of the action itself, may result in a lack of optimal price (Subsurface Technologies does not agree with this assessment—“we report, you decide”). Some price differential between an Aqua Freed quote and a standard chemical rehabilitation quote may be due to shortcomings in the conventional quote, such

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as inadequate chemical application or handling and disposal. Some contractors will low-ball chemical treatment bids, betting on change orders later. This is something you should definitely be aware of (as discussed in Chapter 7). In other words, compare apples to apples in proposal review. 2. CO2 seems to find a weak spot going to the surface. 3. The cold thermal shock is not nearly as effective as can be applied by heating the water. 4. Kinetic force generated is readily dissipated in high hydraulic conductivity aquifers, and is most likely confined to discrete channels. 5. The poor thermal conductivity of lithologic materials also will limit cold transmission to the immediate area of the well, based on studies of glacially influenced materials. 6. In our clientele’s experience, competence in application was not always consistently of high quality in the past. If packers are not set properly and the CO2 blows out up the casing, the effort and money are wasted.

Its best use is probably in situations with significant encrustation immediately at the screen or borehole wall vicinity, removal of which will provide significant relief in many instances. The system will be more effective in fractured rock, as water access comes through discrete fracture, and CO2 can contact most of the effective radius of and biomass associated with the well. Also, it can be used where use of chemicals is forbidden as a rehabilitation choice. Casings must be firmly sealed into the formation with cement, unless the packer is used to isolate the casing. In its current form, it is probably best to be very cautious with bentonite-grouted wells, especially structurally weak monitoring wells (although with time, use with these wells should be possible). One additional problem for us at present in recommending the process is a lack of detailed, objective, documented case histories of its effectiveness (short testimonies are available at the Subsurface Technologies website). The recently published (2007) AWWA Research Foundation report on well cleaning comparisons (originally scheduled for release in 2000) includes a number of Aqua Freed case history evaluations. In this report, the documented Aqua Freed cases included additional cleaning steps (chemical and mechanical). So, unfortunately, based on the facts we have, it is still not objectively possible to separate the effect of the Aqua Freed treatment from that of the additional treatment steps. So the question of Aqua Freed effectiveness is still open. 8.1.3.2 Sonic/Vibratory Disruption—“Use the Force, Luke!” It has long been well understood from mining experience that applying explosives to rock opens up fractures. This observation led to using nitroglycerin, dynamite, and other solid explosives to open and clean out wells. Dynamite and similar solids that are stable, and can be handled safely, then lit with a cap fired by electrical impulse, are capable of opening fractures in wells and cleaning out solid encrustations (Figure 8.1). Note that shooting wells with conventional explosives is a specialized skill that should only be performed by people with specific knowledge of the craft.

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Figure 8.1  Setting a well shooting charge (eastern Ohio sandstone-shale well).

The need for a method to provide a cleaning shot resulted in the development of lower-force gas shock tools. Such refinements are better for providing controlled shock treatments for wells. Among these are treatments based around detonating a shaped or charged wire, cord, or device in wells. This cleaning approach has been in common use in the water and oil industry for several decades. These methods take advantage of the different elastic properties of the materials (filter pipes, gravel backfill and surroundings, deposits on rock or between the gravel particles) to loosen deposits from well and aquifer/filter pack surfaces. The force effect is affected by the detonation of small charges at differential frequencies. Possibly the best known in the United States is the Sonar-Jet™ treatment (Water Well Redevelopers, Inc., Anaheim, California), in development for over fifty years. This process employs two controlled physical actions working simultaneously:

1. A mild harmonic (kinetic) frequency of shock waves designed to gently loosen hardened mineral, bacterial, or other type deposits, even heavy gypsum deposits that are almost impossible to attack chemically. 2. Pulsating, horizontally directed, gas pressure jets cause fluid to oscillate at high velocity back and forth through the perforations to clean out openings.

The EnerJet (Welenco, Bakersfield, California) and Shockblasting (Berliner Wasserbetriebe, BWB, Berlin, Germany) tools are similar devices for cleaning wells (explosive/implosive type of cleaning method) that use detonating cord and blasting caps attached to a wire carrier. The Shockblasting system (as well as some others we will mention) illustrates the worldwide nature of well rehabilitation innovation and practice. As with good basketball, North Americans do not have a headlock on this sector that they pioneered. In shock treatments, the shock waves loosen crust-like deposits and the gas jets repetitively surge the well’s own fluid back and forth through the perforations to reach the surrounding aquifer. Figure 8.2 illustrates a Sonar-Jet treatment sequence.

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  (a)                 (b)

  (c)                (d) Figure 8.2  Sonar-Jet treatment sequence (Michigan). (a) The string is assembled and connected, (b) the assembled 5-ft string to be lowered to the screen interval, (c) the returning string after firing, (d) seeing what has been retrieved in the basket.

Such treatments are particularly useful for removing hard deposits on and around louvered gravel pack screens and borehole walls. These are also more safe and more controlled than blasting. One problem currently is that this technology may not be available everywhere, although it is more widely available than before. Sonic methods to date have little effect on soft deposits. However, sometimes problems identified as biofouling actually have a hydraulic impact through deposition of hard solids in pore spaces, often behind the soft, chewy outer coating visible to the well camera. Such deposits typically form around persistently dewatered screens and filter packs. We have had very good results using the Sonar-Jet treatment in such wells, and in rock wells with hardened ferrous sulfide encrustation. For all three systems, different force strengths or grain sizes of detonating cord are used depending on the well diameter, condition, and amount of encrustation on the casing. The EnerJet tool has a centralizer at the top and bottom of the string, and both products deploy a basket at the bottom to catch a sample of the encrustation and formation material (or damage!) (see Figure 8.2) that may enter the well during the cleaning process.

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These types of treatments have often been paired with downhole TV inspection services. The same cable used to run in and operate a borehole camera can be used to run in and actuate a sonic shock treatment. A treatment protocol that we recommend for a treatment process (see following on chemical applications) involving a sonic step is:

1. Conduct pretreatment well testing (step test preferred) and downhole TV inspection. 2. Brush and airlift surficial encrustation and biofouling. 3. Treat with vibratory method. 4. Pump to waste (usually airlifting). 5. Shock disruptive chemical step/agitation/pump off. 6. Redevelop with surge tools or airlift. 7. Posttest for effectiveness and repeat TV survey. 8. Repeat as necessary.

A further use is described by BWB. Wells that have screens made of brittle or worn-out materials (i.e., vitreous clay, plastic and similar materials, as well as badly corroded steel) can be rehabilitated by shattering the old screen and replacing it. For this, a suitable explosive charge is used, thus loosening and regenerating the surrounding filter gravel. A new coiled wire screen and filter pack are then installed. The redevelopment is carried out afterwards in order to improve the results. We recommend that only operators with very specific experience with this procedure should be engaged. There are a number of risks, and the risk of failure is high. In our experience, we think the best use of sonic/vibratory methods is in the combined approach as delineated in the steps just above. Conventional redevelopment remains essential. 8.1.3.3 Fluid-Pulse Tools After a lot of experience with military sonar, and noticing that compressed air can be used to produce signals detectable by seismic geophone, seismic air guns have been used in geophysical exploration on land and sea since the beginning of the 1950s. Specific gases, such a nitrogen, and water can also be used in addition to compressed air. The tools generate a pulse through the abrupt and rapid expansion of a highly compressed gas or liquid. By the beginning of the 1990s (possibly earlier), people had noticed that the effect can clean wells, and the process was tried as a well rehabilitation process. ARCC, Inc. and the University of Mississippi experimented with it in the early to mid-1990s in the United States, and groups in Germany, Israel, and the United States developed parented systems in the same time frame. These include the Airburst method (Frazier Industries, Muskego, Wisconsin); TLM GmbH, Markkleeburg, Germany (commercializing the Steinbrecher Engineering hydropuls® technology); and ProWell Technologies, Arava, Israel (AirShock Method). See also Chapter 4. The AirShock tool (Figure  8.3) is licensed to one of the major interstate U.S. water services firms, but is also available in some other market sectors in the water well industry in North America. Frazier Industries licenses Airburst (borehole tool

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Figure 8.3  AirShock air impulse gun. (Courtesy ProWell Technolgoies, Ltd.)

illustrated in Figure 8.4) to a variety of well service firms in the United States and internationally, and the hydropuls system is licensed to partners, mostly in Europe at present. All this commercial news can change as this book ages. Look them up in your “real time.” All have websites. In each case, the mode of action is that pressure pulse sequences are created by pulsing inputs of gas or water portions under high pressure using a pulse generator that is inserted in the well attached to the pressure hose. The pulse generator is provided with a valve system that is able to rapidly release the energy that is accumulated in the generator in the form of highly compressed gas (or in the case of the hydropuls tool in certain cases, water) within a very short time (milliseconds). The fluid vents from the tool (air displacement of about 1 m in 1 ms). This action creates hydraulic shock waves moving outward, and then a cavitation and negative-pressure effect is caused as the expanding bubble collapses suddenly. The alternating effect of the pressure load and the pressure relief loosens fines, encrustation, etc., on the screen, borehole face, and in filter pack. The return flow transports loosened material into the well, where it can be pumped off. The tools employed by the various vendors use the same baseline principles, but differ slightly. Airburst uses the Bolt Technologies air gun. ProWell markets its own air impulse gun (AIG) tool that has a steerable vent. TLM likewise deploys its own pulse generators.

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Figure 8.4  Airburst AIG well assembly—bolt air gun mounted on bail (foreground), compressor and winches background.

A significant advantage of fluid-pulse tools is that the tool’s force characteristics can be calibrated infinitely over a large range by selecting tool and chamber size and air or gas pressure up to 3,000 lb/in.2 (PSI) or 21 MPa in the case of the Airburst tool. Force can rival shooting forces (up to 0.5 kg of dynamite), but the system can also be used selectively inside of well screens. Each of the vendors provides tools in various sizes, depending on the application. Safety Note: These systems involve high-pressure gas generation. High pressures can cause injury and property damage. Use with care and secure hoses. A second significant advantage of the system is the capacity to be used in an iterative fashion, for example, “shooting” at foot or meter intervals (fired every 4–10 s) up and down a borehole interval, adjusting the tool’s characteristics in response to results (compared to shooting or sonic/vibratory strings, which are “one-shot” efforts each time). Summarizing, fluid-pulse tools provide:

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1. Highly efficient action of shock wave and strong surging without utilizing explosives. The device can be fired in rapid succession, e.g., 1 ft intervals up and down a screen, and the pressure waveform and amplitude adjusted by managing the pressure and gas volume. 2. Effective well development, redevelopment, and posttreatment well surging or airlifting. 3. A tool that may be used instead of or in conjunction with any chemical well operations and maintenance (O&M) technique in some cases, and, like CO2 and sonic tools, they are possibly the only practical solution in “no chemicals” situations. 4. The ability to develop concussive force is an improvement over air surging. The force is on the order of that developed by explosives type tools such as Sonar-Jet, but is (a) dialable and (b) repeatable in the same application. These are major advantages.

From safety and practicality standpoints, the fluid-pulse approach also has advantages. Using compressed gas or air alone is rather low (but not zero) risk, and liability and legal aspects of explosives handling are avoided, as is hauling cleaning fluids. Where introducing air (containing oxygen) is not a good idea, nitrogen can be used. Otherwise, air can be compressed on site, so that there is no need to transport extra gas canisters. Thus, the system is highly portable, as well. Cleaning projects can be relatively rapid (one to two hours in duration). Fluid-pulse tools, like sonic/vibratory tools, are a natural match with a borehole TV camera system in a van or trailer. The TV can be used in diagnosis and selecting treatment intervals, and the tools provide cleaning. In this case, the TV camera and the AIG tool are run on separate winches, but both can be handled by one person or a small crew and run from a single console. Figure 8.5 illustrates an Airburst treatment sequence. An effective combination procedure is:



1. Conduct pretreatment testing (step test) and borehole TV sequence. 2. Brush or swab to remove surface debris. 3. Deploy fluid-pulse tool and conduct treatment. The tool tends to provide its own air surging effect. 4. Follow with surging and airlift to remove debris. 5. Possibly add a chemical finishing step and redevelop—chemicals can be placed in the well and then treated with the tool, which effectively surges them into the formation and filter pack (if present). 6. Surge and pump off solutions if used and handle as otherwise recommended. 7. Conduct postcleaning step-drawdown test and downhole TV inspection.

Note that we do have some testing results for these methods that meet our standard for testing to determine efficacy.

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(a)

(b) Figure 8.5  Airburst treatment sequence (carbonate aquifer, northern Ohio). (a) Hooking up and deploying the tool, (b) checking water level, (c) inserting the tool, (d) visible results at the surface.

8.2 The Pharmacopoeia: Chemical Use in Rehabilitation The chemicals mentioned here represent many of the available options. They will be summarized in terms of both effectiveness against various well problems, their environmental reactivity and other such practical problems.

8.2.1 Overview Chemical treatments may be classified in a number of ways, but may be broadly considered as (1) acids, used in dissolving and disruption of deposits; (2) antibacterial agents (used for disinfection and control of biofouling—there is some overlap with acidizers as well as polymer aids); and (3) penetrating, sequestering, detergent, and dispersing (PSDD) agents, used to aid acid and disinfectant penetration, clean surfaces, and remove waste deposits.

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(c)

(d) Figure 8.5  (continued).

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Within these classifications, particular agents can be further classified as: Generics: These are the chemical mixtures as available industrially without special blends and suitable for well cleaning. Alphabet brews: Numerous proprietary chemical products are marketed for well cleaning. They include enhanced mixtures of common acid compounds or PSDD standing alone, but whatever their purpose or class, these should be evaluated based on the information provided by the supplier (although this is often sketchy) and recommendations of an informed well maintenance consultant (who does not have commercial ties to a product) and other users. Where possible, proprietary compounds will be discussed here based on their method of action (acids, etc.). Where we mention name brands, this is for comparison purposes only. Safety Note: Remember at all times that many of the compounds described in the following are highly reactive. They react with other compounds and can cause dermal and inhalation injury. They can harm living things if spilled or misdirected. Some can damage well equipment. Do not forget that redevelopment and application procedures involve heavy equipment, cables, winches, cranes, and various spinning and reciprocating devices, and expanding gases. These can crush, amputate, and otherwise maim and kill. Tools can damage well components. Be careful out there. Plan and use common sense. Make sure crews are informed, trained, level-headed, awake, and sober. Security Note: Reminder of the warning in Chapter 6: Many of these compounds are highly reactive and have criminal and military-terrorist applications as components of explosives and chemical weapons. In this fallen world, keep such chemicals secured and inventories of stock well counted. As much as possible, have on hand only what you need to use and leave security and inventory to the suppliers, who are probably better equipped for those tasks. Objectivity Note: No one is perfectly objective. However, your authors do not have any commercial ties to chemical vendors. Favorable or unfavorable mentions are based on project experience. The well rehabilitation sector is, however, a small community. For example, we have consulted for a number of physical redevelopment, equipment, and contracting companies because of our specific “life of slime” experience. We are picky about who we work for in this capacity, so if we recommend it here, we are confident in the efficacy of it. Applicability Note: In monitoring wells or elsewhere in which chemical introduction is excluded by regulatory or project managers, the following information is useless. While chemicals may be completely removed in such cases and the subsurface environment returned to normal, management often considers the risk too great to gamble on. If this is the case, although surging, CO2, or fluid-pulse methods may be

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used alone for rehabilitation, the monitoring well array manager had better have a good maintenance program in action to maintain well reliability.

8.2.2 Acidizing Acids are used to remove blockage in carbonate rock aquifers and to dissolve iron/­ manganese oxides and carbonate encrustation, they also have some antibacterial effect by providing an ionic shock to aquifer microflora typically adapted to circumneutral pH. Not all acids are equally desirable for the purpose. In wells and water systems, the acids historically most commonly used in rehabilitation are muriatic (­industrial-grade hydrochloric acid, HCl), sulfamic (H3NO3S), and the organic acetic or hydroxyacetic (C2H4O3) acids. Also, phosphoric acid is widely specified. 8.2.2.1 Types of Acid Compounds Muriatic acid is one of the most powerful acids used for removing mineral scale, and comes in liquid form. It can be purchased with inhibitors that minimize the acid’s corrosive effect on metal well screens, casing, and pump components. A limited selection of NSF 60-listed products is available. Although it is often an effective well cleaner, muriatic is not especially effective against iron biofouling (the premier problem in many water supply and almost all monitoring and extraction wells) and is hazardous to handle. Respirator and fullbody splash protection are required and washdown treatment facilities should be immediately available. Once placed in the well, toxic fumes are expelled from the borehole within moments. Inhalation of these fumes can cause death, and contact of the liquid with human tissue can result in serious injury. For environmental projects in particular, which are already difficult (the need to suit up, decontaminate, etc.), the hassle of dealing with muriatic acid is an unnecessary additional worry. Muriatic acid presents effluent waste handling problems as well. There is a tendency to overdose based on common tables, so that much acid is wasted, and these doses depress pH of well bore water to <1. If it is not extensively buffered or neutralized by substances in the well, the effluent wastewater is highly corrosive and difficult to dispose of properly and safely. Muriatic as generally available commercially (with the exception of listed products—assuming that NSF is doing its job) also has a reputation of containing contaminants. For these reasons also, the resultant effluent wastewater brew may be unacceptable to wastewater treatment or disposal. Sulfamic acid is a dry granular or pelleted material that produces a strong acid when mixed with water. Sulfamic acid should not be confused with sulfuric acid (a yellow liquid), which should never be used in well cleaning, due to the formation of insoluble products. Sulfamic is typically more expensive than muriatic acid (per volume acidified H2O solution) and is slightly less aggressive. Sulfamic acid, as a solid, is relatively much more safe to handle and easily transported. It is readily available in NSF 60-listed formulations with various useful additives. The dry material does not give off fumes and will

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not irritate dry skin on brief contact. If a spill of solid occurs, it can be easily and safely cleaned up. For all these reasons, sulfamic is often preferred as an acidizing agent. Under certain circumstances, sulfamic can be effectively placed dry into the water column in carefully measured doses, but it is usually better (as is the case with all solids) to premix precise doses of granular acid with water in a tank at the surface before introducing it into the well. During in-well treatment or surface mixing, the slowly dissolving acid releases dangerous fumes at a relatively slow rate, so proper ventilation should be always provided. Less corrosion of pumps, screens, and casing will occur when an inhibitor is added to the acid (some readily available brands have a premixed inhibitor). Less corrosion results when stainless steel well screens are treated repeatedly with inhibited sulfamic acid, as opposed to using HCl. Sulfamic acid is highly effective on carbonates. It has limitations in dealing with certain sulfate compounds. It does not dissolve them well alone, and can be very slow with iron and manganese scale. It should be replaced in these situations with other acids more appropriate for the mineral to be dissolved. Sulfamic is an excellent acidifying agent in organic acid blends. As a commercial-grade material, sulfamic also has impurities in small concentrations. There is a reported tendency to produce ammonia upon mixing with water under certain circumstances. So again, ventilation is essential. Sulfamic stock currently all originates in East Asia, and there are only feeble impurity standards in force there. In the case of sulfamic generally, buying or specifying the NSF 60 formulations is a must to ensure safety. As with muriatic, pH is greatly depressed at typically recommended mix concentrations. Overdosage is a common problem, and effluent waste may have to be neutralized prior to treatment or disposal. Phosphoric acid or blends containing it are widely specified, especially as vendors promoting their use have deep and strong penetration in the ground-water industry in North America. As mentioned earlier, phosphoric acid has some useful applications, but it has the disadvantage of leaving behind P that can become oxidized to phosphate, the active component in ATP, the cellular compound that transfers energy in respiration and metabolism. As one observer noted, you clean out the biofilm, then lay down a bed for the establishment of replacement biomass. Hydroxyacetic acid, also known as glycolic acid, is a liquid organic acid and available commercially in 70% to 95% concentrations. It is chemically similar to acetic acid (vinegar) but with a higher pK, and more effective against basic salts, specifically carbonates. Its use has achieved excellent results in well treatment for iron and other types of biofouling and has good features for cleaning environmental wells. It is relatively safe to use because it is relatively noncorrosive, nonoxidative (it is an acid, a net H+ generator), produces few toxic fumes, and is spent quickly. Still, it is a powerful liquid acid, so caution and splash protection are necessary. It also must be labeled to be transported like other liquid acids. Hydroxyacetic acid is a major active ingredient in certain commercial antibiofouling acid mixtures. Several brand name mixtures are NSF listed under Standard 60.

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Due to its bactericidal and metal chelating properties, hydroxyacetic acid is often very effective in treating wells with biofouling problems. Since hydroxyacetic acid is weaker than hydrochloric and sulfamic acid, its effective pH in solution is higher (pH 2–3), so a longer contact time, or admixture with sulfamic to reduce pH, is required to achieve the same amount of scale removal. On the other hand, effluent waste fluid problems are less severe, since the pH of spent effluent wastewater is higher even if overdosing occurs. Other organic acids have found use as chelating agents in dispersing encrustants in well cleaning. One acid, oxalic acid, is also effective as a primary acidizer in low-Ca water. It has also been used in wells to attack biofouling, a situation in which the Ca2+ ion concentration problem is less of an issue. Impurities in oxalic acid (all originating in the People’s Republic of China) may also be an issue that should be explored. General Note about “Alphabet Brews”: As mentioned in Chapter 1, industrial suppliers of products to the ground-water and water treatment sectors have noticed the potential in the well rehabilitation market and responded. Several firms provide blends with various brand names that usually contain an acid (or caustic) and additives, usually inhibitors and PSDD compounds. The blends are usually NSF 60 listed. A significant benefit of these products is their step-by-step dosing and application instructions and convenient packaging. The best of these companies offer useful technical support, both on the web and by people. These make the work of dosing rather more safe and sure. This ABC approach can be replicated using generics and appropriate knowledge. We will not provide specific recommendations on products here, as they change and we have incomplete knowledge of composition of these blends in some cases. A general recommendation is that blends based on glycolic acid, blended with other acids and the appropriate PSDD compounds, are a good choice for acidizing. We do not recommend blends or products containing phosphoric acid due to the issue of leaving P behind on surfaces, which become foci for regrowth—biofilms following basic microbial ecology principles (Chapter 2). 8.2.2.2 Using Acidizing in Well Treatment Acid dosages need to be introduced into the well and forced out into the near-well environment to be effective. The acid mixture may be agitated by surging with a surge block, jetting, or compressed air (conventionally or by using a fluid-pulse tool). Displacement or pressure injection may also be used. See method descriptions elsewhere in this chapter. Displacement: Generally, in screened wells, two bore volumes are dosed in, sometimes less in rock wells. After an acid solution is placed in the well, a volume of water equal to that standing in the well screen is poured into the well to force the acid solution through the screen-slot openings into the formation if possible. The displacement water should be introduced slowly to make sure the strong acid mixture does not flow out over the top.

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Spot dosing: In wells with discrete water-producing zones such as those with multiple screen sections or rock wells with discrete zones, chemicals can be introduced discretely (spot dosing). One way to do this is to use the double surge block, position the tool at the zone (identified by borehole TV, caliper, borehole flow meter, etc.) and introduce the chemical, then surge in place. Where beneficial, straddle packers or other tools may be used. Pressure injection: Injection through a packer is an alternative for relying on head for force. It provides a controllable force and may force the chemical farther into the formation. It should be used with caution on bentonitegrouted wells, those that are structurally suspect, and smaller wells in general. Acid migration should also be as tightly controlled as possible. Jetting: Jetting is another means of controlled injection in which the acid can be directed at specific screen sections. The crew doing the jetting should be skilled and very careful to make sure that there is no splash. In both pressure injection and jetting application, crews should very carefully connect and inspect hoses and all fittings, replace suspect hoses and fittings, and securely restrain all pressurized hoses to prevent disconnection, hose breaks, and resulting hazardous acid spray. Inhibitors are often recommended to limit attack by strong acids on metal in the well. Several types are available, including Rochell’s salts and gelatin. Most of the inorganic inhibitors are toxic and must be completely removed after treatment. Gelatin has the unpleasant side effect of sticking to formation materials and providing food for bacterial growth (including coliforms originating in the gelatin). It also must be completely removed, or avoided if this cannot be ensured. A number of proprietary inhibitors (composition?) are included in NSF 60-listed blends. 8.2.2.2.1 Penetrating, Suspending and Dispersing Agents A range of chemicals, mostly polymers, are in use as aids to cleaning. Common dishwashing detergents, such as Proctor & Gamble’s Dawn product line, are good examples. These are some form of PSDD as previously introduced. The purpose of these agents is to provide some combination of penetration into biofouling or other hydrophobic clog (such as lineshaft oil in water), cleaning surfaces (surfactants), and dispersing and suspending the “lifted” material, keeping it from resettling in place and improving removal. Such compounds tend to be proprietary mixtures and difficult to classify chemically. They may be cationic, anionic, or neutral in charge, and alkaline, acidic, or neutral. So again, opinion is based mostly on empirical experience, not an evaluation of the chemistry. One generalization your authors make is that phosphorus-containing compounds (whatever their form) should be avoided in PSDD use, as they leave P residue on iron oxides (common clogging components), regardless of efforts to remove it. P (necessary to respiration and deficient in ground water) tends to promote biomass regrowth. Some PSDD compounds can be stand-alone disinfectants, or can be used as cleaners in maintenance treatment (Chapter 6). For example, the anionic polymer

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detergent CB-4 (ARCC, Inc.) is reportedly bacteriocidal at a 0.5% concentration (see also Section 8.2.4.2). 8.2.2.2.2 Posttreatment for Acids After mechanical agitation, the solution is left in the well to react with the encrustants until a pH of 6.0–6.5 has been reached, if possible, then agitated again and pumped to waste. The time for the reaction to occur varies from a few hours to more than fifteen hours, depending on the type of acids used and the solution concentration, temperature, and type and amount of encrustants. The chemicals and materials removed during treatment should be developed out and pumped off until the product water is clear and consistently close to former quality. Treatment effluent fluid should be disposed of in an environmentally safe manner, as discussed in Chapter 7. Acidic effluent waste fluid can be neutralized in a lime-filter basin or tank and pumped to wastewater treatment or containment as permitted or required. If conditions indicate (e.g., rapid acid consumption), the chemical treatment may be repeated.

8.2.3 Sequestering and Other PSDD Functions Sequestrants act to lower surface tension, solubilize, and wet affected compounds such as metal oxides. Similar functions are penetration and suspension, as previously discussed. In wells, this may be accomplished by application of long-chain polyphosphates, and polyacrylamides and polyelectrolyte mixtures (e.g., CB-4), which help to remove clays and loosen slime and encrustation. Hydroxyacetic acid, citric acid, and some proprietary acid formulations also have related chelating properties. PSDD compounds should be an integral part of acidifying treatments to keep loosened debris in suspension, aiding removal. Polyphosphates (including brand name formulations used in water treatment) are losing favor quickly for dispersing biofilms in wells since the chemicals themselves are difficult to remove, remaining behind in the formation (usually attached to clays or feldspars, calcite, or Fe oxides) to enhance growth, usually at the edge of development influence where they are difficult to remove effectively. Phosphate is essential to all cells (microbial or the reader’s) since it is used in making ATP, the “energy currency” of cells. P is usually a limiting nutrient in ground water for microbial growth, since it is typically naturally available only in very low levels or absent (having been siphoned off long ago by surficial soil communities). Adding P-containing compounds can trigger a microbial bloom. It has to be apparent that adding phosphates (or nonoxidized P forms such as phosphoric or phosphonic acid) improves the chances of aggravating a condition of persistent biofouling over time. The typical initial reaction of well performance to introducing phosphates is a rapid removal of clogging material and improvement of performance. This increases confidence and casts doubts on naysaying such as ours. The problem is that loss of performance then can return quickly as the now P-fortified residual microflora left after well cleaning can now rebound and reform their biofilms (“doing what comes naturally”). These tend to be slimy and gelatinous, and very good at agglomerating particles. Virtually solid low-conductivity cylinders can be formed at the edge of

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redevelopment force influence in the aquifer around polyphosphate-treated wells. If chlorinated, these gel-like clogs “carmelize” and harden. These warnings are not aimed at the proper use of polyphosphates or pyrophosphates in water supply system treatment. In a controlled water system setting (usually chlorinated), long-chain pyrophosphates keep Fe and Mn ions in suspension. Maybe the water system managers should be planning for a filtration plant, but these compounds have a legitimate function, as an interim solution. The problem with the use of such chemicals in wells is that they are uncontrolled and microflora-rich environments. Polyphosphates or pyrophosphates may also have a place in keeping nonchlorinated remediation treatment system pipelines from closing up with Fe precipitation as long as the lines are monitored for growth and appropriate measures can be taken to control secondary biofouling. Polyelectrolytes (among the PSDD compounds) provide the desired effects of dispersing clogging deposits and clay/silt buildup without being P sources. These compounds are recalcitrant and are not readily attacked by microorganisms. They can be used in biofouled wells that are part of a rehabilitative treatment program, but should be developed out and not left in place. Mostly, such compounds are present in <1% solution in blends. Posttreatment, all polyphosphates (if they are used regardless of what we advise) and polyelectrolytes should be removed from the well, and thus should be confirmed by chemical analysis (total P for polyphosphates and specific indicators for polyelectrolytes). After they are removed, the well should be surged and pumped several bore volumes again to remove any traces of product. Effluent waste fluid should be disposed of properly in wastewater treatment, containment, or to controlled surface spreading on soil. Phosphate-loaded water discharged to surface waters causes algal or cyanobacterial blooms and oxygen depletion, resulting in suffocation of aquatic animals. Unannounced discharge into wastewater treatment is likely to disrupt the balance in engineered activated sludge. All treatments should be concluded with follow-up testing for residual chemicals, contaminant and biofouling bacteria, and changes in chemistry. If results show inadequate treatment results, treatments should be repeated. If adverse effects are observed, alter the treatment.

8.2.4 Antibacterial (Antimicrobial) Agents Treating biofouling and microbial contamination of wells and chlorination used to be synonymous, but in recent years, alternatives to chlorination have become more prominent. The following are options in use. There has also been a revolution in application of chemistry, specifically chlorine, for the purposes of disinfection. 8.2.4.1 Chlorination Generally, in well rehabilitation, this is shock chlorination intended as a well treatment, which serves to rapidly kill planktonic bacteria and disperse slimes somewhat, breaking down organic polymers. It should only be used where chlorination of water constituents is not a safety or disposal problem. Otherwise, alternative oxidants

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(e.g., hydrogen peroxide) or nonoxidizing antibacterial chemicals (e.g., hydroxyacetic acid blends with PSDD) should be used (see also Chapter 6). Another function is preventive chlorination of filter pack, other well components, and tools to be installed or used in the well, or as a polishing disinfectant step. Procedures for this are available as standards (ANSI/AWWA C654, and part of ANSI/ NGWA 01). Generally, concentrations are in the 50–100 mg/L range. Similar solutions can be used for tool and component washdown or pressure washing (e.g., casing). Because of its importance in well maintenance (Chapter 6) and rehabilitation, we will take the time to describe in some detail the mode of action of chlorine as a disinfectant. Chlorine is fundamentally a strong oxidizer. Elemental chlorine (Cl2(gas)) exhibits a high positive standard electrode potential of 1.36 V in a reduction half-cell reaction, as follows:

Cl2(gas) + 2e – → 2Cl–(aqueous)

A species with such a strong reduction potential functions as a strong oxidizer (see also Section 8.2.4.2) as it grabs e – from any available source to reduce itself. In other words, Cl will nearly spontaneously (and often violently) be reduced to chloride (Cl–) by grabbing e –’s from anything unfortunate enough to come in contact with it (metals, fuels, people—you get the picture). This is why chlorine gas is so dangerous. In the water industry we are dealing with aqueous solutions. The forms of available chlorine therefore are the hypochlorite ion (OCl–) and hypochlorous acid (HOCl). These provide disinfection action by oxidizing proteins, lipids, and carbohydrates. The predominant action appears to be against proteins, both structural and functional. Recent studies have shown that hypochlorites cause essential cell proteins to lose their essential structures and to clump, much like the effect of heat (think eggs cooking). At pH between 4 and 7, there is increased penetration through the outer cell layers. Also affected (by oxidation) are metabolic enzymes, respiratory coenzymes, and DNA synthesis. All this tends to be lethal to cells. HOCl has been observed to be, and is considered to be, significantly more effective at bacterial inactivation due to this ability to penetrate cell walls and membranes. OCl– and HOCl work as follows:

OCl– + 2e – + 2H+ → Cl– + H2O



HOCl + 2e – + H+ → Cl– + H2O

There are various sources of OCl– and HOCl in the water supply industry. One source of HOCl (as previously discussed) is directly from Cl2(gas) by the following:

Cl2(aqueous) + H2O → H+ + HOCl + Cl–

For most applications, the most safe and preferred sources of chlorine are calcium hypochlorite (CaOCl) and sodium hypochlorite (NaOCl). Chlorine gas can be used, but presents significant safety and security issues, and is probably better kept inside

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a properly equipped and secured water treatment plant. Both forms of hypochlorites are salts that dissociate to provide OCl– by the following:

Ca(OCl)2 → Ca+ + 2OCl–



NaOCl → Na+ + OCl–

But then, these provide OCl–, and we would prefer to use HOCl, which is more strongly biocidal. This is where the pH of our solutions is manipulated to our advantage. HOCl dissociates by the following equilibrium reaction:

HOCl = H+ + OCl–

Concentrations will be controlled by the following relationship: K=



[H + ] + [OCl − ] [HOCl]

Therefore, if we start with OCl– provided by NaOCl, we can decrease the pH of our solution (increase [H+]) and force the equilibrium to the left side of the equation, thus creating HOCl in the well. The relative concentrations as a function of pH are indicated in Figure 8.6. Adjusting the pH in the range of 5.5 to 6.5 will maximize the HOCl concentration. Where available, hypochlorite used should be the liquid Na hypochlorite form, and most appropriately an NSF 60 listed product intended for potable water use— not off-the-shelf bleach, which should never be used if it has additives (scents, silica). NaOCl should be freshly made (<60 days) and delivered to ensure low (1 μg/L) Percent HOCl and OCl– by pH

100 Percent HOCl and OCl–

90 80 70 60 50

Percent HOCl

Percent OCl–

40 30 20 10 0

5

5.5

5

6.5

7

7.5 8 pH @ 25 C

8.5

9

9.5

10

Figure 8.6  pH influence on relative occurrence of hypochlorite ion species plotted from calculated data. Note that actual values may vary due to water quality and temperature variables.

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perchlorate concentration. Solid Ca hypochlorite can be used in acidic, low-total dissolved solids (TDS) well water, or blended at the surface. Ca hypochlorite stores well and transports easily, so it should be part of the tool kit, especially for emergency response and for use in remote areas, particularly in warm climates. Another alternative is to use a process that generates HOCl or mixed chlorine solutions on site from NaCl (see Section 6.5.2.2). Adjusting the pH of such a normally alkaline solution means gently adjusting pH downward using gentle acid to about pH 5.5 to 6.5 (not lower, as chlorine gas evolves). A good choice for acid is 5% white vinegar. Do not add concentrated acid products (high percentage acid) as Cl gas evolves on contact. Dilute to 5% first. Alternatively, there are commercially formulated buffers designed to set the solution pH of a certain chlorine concentration in the desirable zone. Such pH adjustment is generally not necessary where Cl2 is used. Other chlorinated disinfectants are not recommended for this purpose. Chlorine concentration recommendations have changed. It used to be “if a little is good, more is better—the stuff is cheap.” Now it is understood that the high concentrations are counterproductive. Such solutions often do not disinfect properly (pH is too high) and they harden metal-containing biofilms. Solutions of 100–200 mg/L, pH adjusted to favor hypochlorous acid, are ideal. These solutions can be used after organic acid treatment is used to clear the clogging material and provide a “clean” well to disinfect. Typically 1½ to 2 or more bore volumes are used in treatments to make sure that enough solution is available to contact filter pack volume, extended fractures, etc. Also consider demand in estimating the chlorine necessary to add to provide a free residual of 100 to 200 mg/L. Iron, manganese, and total sulfide are the most common demand agents. Add 2 mg/L (each) per mg/L of manganese and total sulfide and 1 mg/L per mg/L of iron. In one recent case, we worked with a well that had 200 mg/L total sulfide, so we had to double the chlorine dosage. High-pH chlorine solutions can also be used in a flip-flop treatment alternating acid (low-pH) and basic (caustic) steps to disrupt serious biological growth in wells. In some lithologic settings, a caustic approach is preferred over the acid approach to solids removal to avoid swelling and mobilizing certain clays. Preparation is important for improving the effectiveness of chlorination. Brushing is very effective as a first step before chlorination to help in dislodging material from the casing, screen, and borehole interior, but should be done with or prior to the acid cleaning step. After the chlorine solution has been introduced into the well, it should be forced through the screen-slot openings into the water-bearing formation by adding water to the well or agitating with development methods. Then, as with acid treatment, mechanical agitation should be used to enhance the treatment. As the chlorine penetrates the remaining organic slime, the mechanical agitation helps dislodge what is loosened, and moves it from the formation into the well, where it can be removed by pumping. Effluent wastewater with any chlorine residual should be pumped to an open retention tank and the chlorine allowed to dissipate or be neutralized chemically, e.g., with sodium thiosulfate. Chlorine in high concentration can disrupt waste­

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water treatment and kill aquatic life. Certain buffers and detergents may also harm wastewater-system-activated sludge microflora. Once it is harmless to the process, the effluent wastewater can be discharged to wastewater sewers, RV tank waste collection, or a similar safe endpoint. Time always favors chlorine effectiveness, but effectiveness diminishes after a certain point. For disinfection purposes, chlorine solutions should be allowed to work for twelve to twenty-four hours using the above protocol before being pumped off. If the well is clean before disinfection, the shorter end of the time frame can be chosen. If conditions indicate, repeat the procedure. Although wells can be treated for biological encrustation or biofouling, the bacteria are difficult to eliminate and most problems recur. Prevention and secondarily preventive treatment is the rule for biofouling problems (Chapters 5 and 6). 8.2.4.2 Alternatives to Chlorine as Oxidants for Biofouling The use of chlorination (using gas chlorine and hypochlorites) in wells is becoming more restrictive in parts of North America and Europe (not entirely a bad thing). Both because of this and because shock chlorination alone is seldom the most effective treatment, several other treatments are being used for biofouling control in a rehabilitative manner (see Chapter 6 for use in a preventive mode). 8.2.4.2.1 Chlorine Dioxide Chlorine dioxide (ClO2) is a synthetic, green-yellowish gas that is generated on site, and commonly used to bleach paper. Chlorine dioxide is a highly soluble, pH-neutral chlorine compound, and a powerful oxidant, with more than 2½ times the oxidation capacity of chlorine, yet it is selectively reactive. Being an oxidizing halogen, it reacts with reducing agents, as do other halogens, but typically only at high concentration. At dilute concentrations, it is safe to use in hydrocarbon-contaminated water. ClO2 readily dissociates into Cl2 and O2 in an endothermic reaction (generating heat). The process has been used in oil and gas well rehabilitation, and has potential application in degrading Fe sulfide-dominated clogs. The end products of chlorine dioxide reactions are chloride (Cl–), chlorite (ClO –), and chlorate (ClO3–). Each of these is a potential water quality problem. See also the mixed oxide (e.g., MIOX) generation discussion in Section 6.5.2.2. 8.2.4.2.2 Ozone As a powerful oxidant, ozone aggressively reacts with organic compounds, reducing its availability for biocidal action and making it dangerous with compounds that are unstable in the presence of oxidants. It does not form halogenated organics, however—a real advantage, although bromate forms in the presence of Br. Its best application is probably as a preoxidation step in enclosed water system treatment and in combination with other treatments to tackle suspended (planktonic) microflora and remove sulfide in water. Ozone and hydrogen peroxide (discussed next) are used together in commercially available processes (e.g., the PEROXONE process).

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8.2.4.2.3 Hydrogen Peroxide Like ozone and other halogens, aqueous hydrogen peroxide is a powerful disinfectant and oxidant. It has been used with some effectiveness in removing well biofouling in both water supply and environmental wells. On the other hand, H2O2 can enhance microbial growth away from the well as it breaks down to form H2O and O2. It is after all used as a means of providing oxygen in this way for in situ bioremediation of ground water. H2O2 is also strongly reactive with combustible mixtures. Good uses of H2O2 include (1) forcing the redox fringe out away from a well in reducing ground water and (2) removing H2S that builds up under hydrostatic pressure while HCl is dissolving iron sulfide clogs in deep wells (don’t use chlorine for that purpose). Liquid peroxide solutions are volatile and should be handled with the respect given to corrosive chlorine and acid solutions, because they can be dangerous to skin and mucus membranes. An alternative to handling aqueous H2O2 is to form H2O2 in situ. Sodium perboric (DuPont) can be used for this purpose, but the use of this approach likewise will depend on whether this compound is safe to introduce into the system in question. Other H2O2 alternatives are: Calcium peroxide: Calcium peroxide (CaO2) is a solid compound that is considered safe and convenient to handle, especially when compared with other solid oxidants. It reacts with water to form oxidizing and disinfecting H2O2 and calcium hydroxide. CaO2 is used in aquaculture and for environmental applications like solid waste remediation, wastewater treatment, and soil decontamination. Peracetic acid: A powerful disinfectant formed from a mixture of H2O2 and acetic acid. It is used mainly in the food industry as a cleanser-disinfectant, for the disinfection of medical supplies, biofilm prevention in applications such as cooling towers and the pulp industries, and plumbing disinfection. It effectively represses Legionella bacteria and deactivates viruses. Peracetic acid, which has a stronger oxidation potential than chlorine or chlorine dioxide, oxidizes the outer cell membranes of microorganisms, deactivating them rapidly. At a pH around 2.8, it is an effective nonfoaming cleaner. Unlike aqueous solutions of H2O2, peracetic acid activity is hardly influenced by organic compounds that are present in the water, but it has a narrow pH range where it is effective. Also, it is relatively ineffective at a typical North American ground-water temperature of 15°C, with pathogen deactivation requiring five times more peracetic acid than is required for deactivation at 35°C. It would be worth a look for tropical-water or geothermal applications. 8.2.4.2.4 Designer Biocidal Compounds Note that there is a wide range of biocidal compounds on the market for various applications, including cooling system and food processing system disinfection.

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These do not have wide application in ground-water well disinfection due to the availability and generally good effectiveness of hypochlorite compounds. However, they should be evaluated for use if they are available, cost-effective, meet potable water criteria, and have some benefit, such as shelf life. Peracetic acid (CH3COOH) is one such example. It is also an example of an organic acid (see following)—and thus an example of how classification systems become complicated. 8.2.4.2.5 Organic Acids Contractors who perform well maintenance (as well as your authors) are abandoning the use of chlorine compounds in favor of certain organic acids (as described above) for use in preventive maintenance (Chapter 6) and biofouling control treatments (as distinct from disinfection). We are finding that the biofouling bacteria become accustomed to the chlorine and actually make more oxidized iron and organic byproducts in response to this stress (remember Chapter 2). No total bacterial kill is achieved with chlorine. The clogging zone also simply reestablishes itself farther out in the formation, beyond the reach of the treatment process. In addition, frequent use results in the formation of chlorinated organic compounds (those famous disinfection by-products (DBPs)). Chelating organic acids such as acetic or glycolic acid have antibacterial effects and serve to remove oxidized iron products, especially when combined with the right PSDD compounds. The microflora are not extensively disrupted, but their clogging products are removed. 8.2.4.2.6 Use of Heat Heat is sometimes favored as a biofouling removal method where chemicals cannot be used for environmental reasons. However, heat is cumulative around the well structure when applied (due to lithologic resistance to heat transfer—same problem as with cold) and can actually enhance growth away from the thermal shock zone— it can actually cause the “omelet effect” of congealed biomass that enhances clogging. It is also very inefficient in terms of fuel or power to generate thermal energy, and can also deteriorate grout, plastic casings, and other bore features. The general consensus is that the best approach to using heat is as a part of the blended chemical heat treatment method described in the following. Safety Note: Remember that heating at these temperatures causes burns, and should be used with caution where brush or grass fires can be ignited.

8.3 Blended Method Treatments One trouble in considering chemical treatment types individually is that individual chemicals seldom do the job alone. Agitation is necessary for chemical treatments to have maximal effect, and it is the most common augmentation method. Chemicals can be otherwise augmented by mixtures and temperature increase. For example, PSDD compounds improve the contact between disinfectants and bacteria in biofilms, acids provide ionic shock, and such mixtures can be heated to increase molecular activity. Contact time additionally improves effectiveness of biocidal action.

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The patented blended chemical heat treatment (BCHT) process (U.S. Patent 4,765,410, ARCC, Inc., Port Orange, Florida), developed by George Alford, Roy Cullimore, and Bill Rogers, is one good example of the blended method approaches. The BCHT process involves three phases of application to shock, disrupt, and disperse biofouling. The process is otherwise described in Practical Manual of Groundwater Microbiology and by Alford and Cullimore in our publisher’s Sustainable Well Series (see the reading list). It also is relatively unique among available well rehabilitation methods in that its effectiveness and results have been studied and documented extensively by unbiased observers (U.S. Army Engineers) on a large scale over more than fifteen years of work. There has not been a similar degree of documentation of other unique processes, including the above-mentioned AWWA Research Foundation study dominated by Aqua Freed projects. The following is one typical scenario. The exact blend of chemicals for a particular wellfield situation is determined based on an analysis of the needs and chemical reactivity among the range of chemicals useful for cleaning the materials, the microorganisms and encrustants present, and ground-water constituents. In the shock phase, a solution such as chlorine amended with nonphosphate polyelectrolyte surfactant is jetted into the production zone. The result is (1) a reduction of chemical demand in the disruption phase, (2) softening of biofouling and encrustants, and (3) increasing microbial trauma. The disruption phase involves more customization (based on analysis of the well conditions), but revolves around jetting in blends of acid (recently dominated by hydroxyacetic acid) and specific PSDD compounds (usually CB-4), or alternatively, chlorine or other biocides blended with stabilized acid. Sometimes only CB-4 is used, depending on the formation characteristics and nature of the clog. The solutions to be jetted in are heated to between 60 and 95°C (prior to injection) and allowed a contact time as long as possible. The pH shift is down to as low as pH 1. Heating increases metabolic rates at the fringe of the heat influence zone, increasing assimilation of toxic disinfectants. There is further dissipation of fouling material in the well. The dispersion phase involves the physical removal of the disrupted fouling material from the affected well surfaces. Standard surging methods are typically employed. An advanced method such as a fluid-pulse tool may be employed. This method employs all the aforementioned recommendations of rehabilitative treatment:

1. Analysis of the nature of the problems. 2. Physical agitation in combination with chemicals. 3. Augmentation of chemicals (in this case, using heat). 4. Appropriate mixtures of chemicals customized (based on analyses) for the situation. Different acids and PSDD may be used, and chlorine is often omitted. 5. Staged treatment to produce various effects.

The treatment is preceded and followed by typical testing and analyses of results. Treatment is repeated and modified as necessary.

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BCHT can have wide application. It has been employed on everything from municipal water wells to redwood-stave pressure-relief wells to pumping remediation wells on hazardous sites. A limiting feature is that application of the process requires very specific knowledge of chemicals, their application, and their effects on fouling, wells, and ground-water quality, and access to the process is limited at the present time. This is not all bad, because it means that such treatments must be applied in a tightly controlled fashion by knowledgeable well rehabilitation crews. The specified heating equipment (stainless steel coil boiler) is expensive to purchase and requires significant maintenance.

8.4 Application of Rehabilitation Methods Summary









1. Preliminaries: a. A specific capacity (step-drawdown if possible) test of the well should be performed before rehabilitation is attempted to benchmark well performance. b. Bacterial, chemical analyses and physical well inspection using TV or other methods should be used to determine the cause and nature of the problem. 2. Redevelopment: Sometimes all that is required is to finish the job that the original driller did not complete in the first place. Surging or jetting to remove remaining drilling damage or mud wall, or to finish mixing sediment particles, sometimes provides dramatic improvement alone; however, more in-depth rehabilitation is usually required. Incrustations and biofouling combinations may, in some cases, be cleaned out using vibratory and fluid-pulse redevelopment methods alone. These may also be quick ways of improving performance if it has to be done in a hurry. 3. A general well rehabilitation procedure: While no single procedure is suitable for all problems, a procedure such as this (selected in conjunction with analyses of performance deteriorating problems) will provide some improvement for biofouling and encrustation. This sample procedure is provided as an example for illustration only. a. Test pump the well and record performance, physicochemical, and microbiological data. Remove well pump and set aside, refurbish, clean, or replace. Conduct TV surveys (recommended) and additional logging as desired. Sometimes perform TV and logging before removing the pump where having the pump out of service for some time is a hardship (or provide water). b. Use this information to design the treatment plan, start preparations. c. Start the redevelopment process to gain hydraulic connection (brushing, gentle surging). d. Shock, disrupt, and disperse in some fashion using a chemical mixture (chosen based on analysis) providing osmotic shock (disinfectant or acids) with mechanical surging, e.g., for four hours, or a fluid-pulse method, followed by an eighteen- to twenty-four-hour soaking period (may be preceded by a P-free PSDD wash with pump running). e. Jetting or surging with chelating acid solution or further disinfectant with acid for four hours with pumping. Brushing is often preferable for

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f.



g.



h.



i.



j. k.



l.

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soft iron buildup on borehole walls. Fluid-pulse methods may also be used for agitation. Pump off discharge fluids to waste or containment until well is free of chemicals (use pH and chemical testing methods on site) and discolored fluid clears. Initiate final shock disinfection for water supply wells, methods depending on the volume of solids removed. If using chlorination, follow the modern protocol—light and pH appropriate. Inspect for corrosion and wear of well and pump parts, replace defective parts, wash down pump, pipe, wire, etc., with chlorine solution (flush with treated water) or steam decontaminate and reset. Test pump well to determine what (if any) improvement in specific capacity and well hydraulic characteristics has occurred. Take the water quality samples required to be passed to return to potable water supply use (typically a coliform test). TV and log to document postcleaning status. Repeat some or all steps a to i as necessary. After some time (two to six weeks), check physicochemistry and indicators of biofouling and biocorrosion. Implement maintenance program (Chapters 5 and 6).

This is one example of a procedure and is not specifically recommended for all purposes.

8.5 Posttreatment after Well Rehabilitation The natural reaction after a well rehabilitation episode is a feeling of “mission accomplished.” We all know how that smug feeling can come back to bite you in an uncomfortable place. However, at least in the case of a chronically biofouled well that has been rehabilitated, the best comparison is to a human patient who has had extensive open-heart surgery. The major problems (blockage, encrustation, poor circulation) may be solved for now, but a strict treatment program—the maintenance program—is now necessary to prevent or slow recurrence. Review Chapters 4 to 6, recalling the need to know causes and rates (Chapter 2) and to understand the economics (Chapter 3).

8.6 Some Follow-up “Truisms”



1. There is no completely effective well rehabilitation treatment known for biofouling and encrustation. In time, all biofouling and encrustation returns. The purpose of rehabilitation is to restore or improve performance to buy time before the problem comes back. On the other hand, redevelopment and reconstruction to control sand or silt pumping often are virtually 100% effective for indefinite periods (for those problems alone, of course). 2. Maintenance monitoring and treatment as previously described (Chapters 5 and 6) are collectively (along with a dose of prevention—Chapter 4) the only rational strategy that may prevent or delay a need for further rehabilitation.

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They can certainly lengthen the time until full-scale rehabilitation is necessary. The only difference between a general “shotgun” monitoring approach such as described in Chapter 5 may be that the testing method and treatments may be more narrowly focused on the problem attacked in rehabilitation. With biofouling, it is critically important to remember that water quality changes (caused by developing biomass) precede measurable loss of hydraulic performance. However, the changes in aquifer and well loss detectable by the step-drawdown test are the most useful for defining the location of clog problems. When testing indicates that biofouling growth is again becoming troublesome, a staged antibiofouling maintenance treatment should be employed at the first opportunity. When the treatment is completed, more analyses should be made to test effectiveness, and tests should be repeated as necessary. Remember to delay biofouling testing until the system “settles down.” This will result in delays in decision making, but the delay is necessitated by available method limitations. Chemical encrustation can be limited using preventive treatments at intervals determined based on testing and experience. 3. After sufficient experience, a regular treatment interval without much testing is possible, and treatments can become preventive instead of reactive. A good idea during this maintenance phase is to take steps to reduce the impact of well biofouling, encrustation, or corrosion on the operation of the well and its attached water system. Possible steps include: a. When pump replacement becomes necessary, choose designs that make rehabilitation easier. b. Where feasible, use noncorrodible components, such as plastic-stainless or stainless pumps and pump discharge pipe, in pumping wells prone to clogging. Always use the most resistant possible metal and metalplastic pumps in water wells. Yes, they are more expensive at times, but they last for many years. Flexible riser hoses such as Wellmaster™ (Kidde Angus Flexible Pipelines, Exton, Pennsylvania) or Boreline (Hose Solutions, Scottsdale, Arizona) permit easy removal of pumps for cleaning (Figure 8.7). Wellmaster and Boreline are both popular for mine dewatering wells because of this advantage. c. Check for and eliminate stray electrical currents as in metallic pipe networks as much as possible. Cathodic protection may be called for in some industrial settings in the remediation system pipeline network if it is metal. Use plastic pipes as much as possible. d. Consider the installation of suction flow control device (SFCD) (engineered tail pipe) in wells, as possible, to control sand/silt pumping and to reduce biofouling impact. This requires an individual evaluation of the well as a candidate. If it works, a successful SFCD installation buys time until rehabilitation becomes necessary. e. Install backwashable filters between the well and the distribution system or before the critical part of the treatment system (such as an aera-

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(a)

(b) Figure 8.7  (See color insert following page 66.) Illustration of features of flexible well pump discharge pipe. (a) Coil of 6-in. pipe with fittings, (b) top connection at flanged well head, (c) pump connection, same installation, (d) full installation view, (e) installation of Wellmaster in an angled well (UK). Note that the pumps illustrated are not small. (Photos (b) and (c) courtesy of Boreline (Hose Solutions Inc., www.allhoses.com). Photos (a), (d), and (e) courtesy of Angus Flexible Pipelines.)

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(c) Figure 8.7  (continued).



tion tower) to limit or prevent the migration of biofouling microbes into hard-to-clean sections. This is better than sequestering feeds. f. Make the distribution system easy to inspect and clean, for example, by running poly-pigs through the lines. g. Learn from the experience and record results and findings for future reference by current or future management and operational staff.

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(d)

(e) Figure 8.7  (continued)

and 9 Learning Going Forward 9.1 Learning from the Past In the 1995 predecessor of this work, there are a number of case histories presented. All throughout our publisher’s Sustainable Well Series, you find additional case histories. There are more to be found in the works in our reading list. We have more on our website, and any web search and perusal of water supply and ground-water industry literature will reveal even more. We decided not to add more case histories in this work. One reason is that each of the problem causes and response actions described in this work is indeed based on numerous practical experiences. The science and practice have moved beyond proving concepts and techniques by illustrative cases. If you can bear to do so, take our word for it: “We have been there and done that.” A second reason is that some of our best stories must remain either entirely or to some degree confidential. The specific learning experiences of our clients and colleagues should not be permanently displayed in a book. Chances are that learning experiences are lurking in your wellfield. We recommend that you make the effort to explore the case histories in the referenced literature. However, you should above all else take the principles promoted in this book and apply them to your specific situation(s). Those principles are:



1. Take the long view of fostering sustainability in well system construction and operation. 2. Know your well-wellfield-hydrogeologic-environmental-operation system. 3. Take the position that a well is “more than a hole in the ground.” Apply preventive design and construction principles as long understood. 4. Maintain the wells in your care as if you owned them and needed them to function properly for decades or centuries. 5. As part of that maintenance, do your best to track water quality and performance over time, looking for trends. 6. If potentially deteriorating processes are in action, take preemptive action before performance and water quality are impaired. 7. If you are handed a degraded, poorly performing situation, do the forensics necessary to design a reasonable and effective rehabilitation program, design it accordingly, and do what it takes to make sure that the work is done properly. 8. Conduct the logging and testing that are beneficial for documenting before and after conditions; then do them regularly as part of PM. 263

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9. Know your cost-benefits and the value of water in your context. Fight for the budgets, personnel, and technical resources to keep systems maintained properly. 10. Communicate: Communicate with budget people, regulators, field and operational people, and customers. 11. Learn: Keep up, keep learning. We do not know it all. Neither do you. When we get caught up, something new comes along. We were adding material right up to the submittal date for this work. 12. Contribute: What you learn, share with others so they can learn. It is interesting to reflect on what has changed since the 1995 work. The World Wide Web, more or less as we know it, was brand new, and few of us outside of academia were on it. Our company Ground Water Science website went online in 1998 in glorious HTML. We were among the early American independent ground-water firms to have a full-blown website. It was wordy, and then we figured out pictures. Before long, quite a few consultant and contractor firms had sites. The web really helped in the quest to research what people can do and make connections. We could put aside some of our paper files. Back then, you needed to know a URL to find a website. When search engines (“search” in industry parlance) came along, the rules changed and the key was presence and connection. Another change was in content. In 1998, content was important. You went to a website to learn something. Over the years, we have had many people express their appreciation for the information we posted there, and it led to some good professional relationships. We still try to keep this up in our “new look” website. The most recent advance on the World Wide Web is the availability of specialized technical literature (journals) databases that provide for sophisticated subject searches beyond “word occurrences,” and may provide immediate download of the full text material. These databases are likely available at most college and university libraries, as they are generally expensive subscription services. However, the librarians will be glad to assist you with an interesting search for information, as universities usually have a policy of providing some services to the local community, and even librarians tire of constantly directing students to the locations of the restrooms. In general, the web has permitted people to be better informed about aspects of well maintenance and rehabilitation. At least you know who to ask and have some information on chemicals, other materials and tools, and processes. The web can also be used to obscure and mislead. You need to look for pseudotechnical discussions that sound authoritative but are actually advertising. Anyway, keep learning with this resource. However, also buy and read the books and subscribe to the journals, and go to the courses, and invest in what it takes to do what you need to do.

9.2 Where Do We Go from Here? There is still a lot to be learned on the practical level. The root causes of the types of well problems occurring are probably well enough understood, in a theoretical way, and the methods available, at this moment in history, to develop and execute useful

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preventive maintenance and well rehabilitation action plans. You can do this, and it is beneficial to do so. The intrinsic value of prevention and maintenance is also well demonstrated, at least in a semiquantitative conceptual way, but the gospel message has yet to be well spread through the environmental engineering empire. There is still a lot of denial, flailing around, guessing, and grasping at straws going on—and way too much surprise about and lack of preparation for the problems of well-based systems.

9.2.1 Wish List There are a number of definite needs and wants in the ongoing quest to keep wells operating in a sustainable way:









1. The useful maintenance monitoring methods available now need to be used systematically. We know how to do maintenance monitoring, and it is practical to adopt these practices. There is still entirely too much guessing, relying on hunches, and working in the dark going on. Although new methods should be aggressively researched and implemented, using the methods we have now will provide useful early-warning maintenance monitoring. Now, if we could only get wellfield operators, and especially small systems, to adopt these practices. 2. Controlled research into more effective, and at the same time environmentally benign, preventive and restorative treatments. There are a lot of candidate methods and continual refinement, but controlled and really unbiased research into their efficacy is needed. Remarkably, this has never been done successfully, and an entire sector of the ground-water supply and protection industry is making decisions based on anecdotal information, massaged by very effective communicators. Such study (with methods that cancel out the effects of bias—ours or anyone’s) is needed so that methods proposed for specific jobs can be objectively evaluated. It will be difficult, expensive, and will take years to do. 3. The economics of well maintenance have to be updated in general and specifically for environmental projects. No industrywide information is available, only case histories. There is nothing in modern literature comparable to studies published in 1960 and 1961 by L. Koenig (summarized in Borch et al. (1993)) for water supply wells (in an economy that is now ancient history). We are working on this, but the numbers remain fuzzy. 4. Our regulator colleagues need to get on board. Well maintenance is more than keeping the well house free of herbicide. Regulators of private and other smaller water supply wells need to help to start the push that results in these wells being properly maintained at many facilities. Well maintenance should be a required part of water supply system operations. However, we expect that they will work with the industry to get their regulatory requirements right. 5. Stated slightly differently, well maintenance needs to finally become a feature of small, private potable water supplies, including household private well operations in the United States and their critical close kin in public

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water supply, such as wells serving schools. Our experience is that the designers of and maintenance people caring for these systems do not know very much about well maintenance. 6. Well maintenance and rehabilitation needs to be adapted for the developing world. It is a sad sight when you pull up in the vehicle and there is a priest standing there waiting for you with a dead submersible pump motor. A once vitally important well is now out of service. The small children at the school and the clinic once again do not have safe water, and the older girls are hauling buckets from the creek, as they would have a thousand years ago. The priest (a good faithful man, called to care for his flock) knows nothing about pumps and motors. “Who will help us?” he asks. The developing world is littered with abandoned wells. Most of these can be readily returned to service after cleaning, disinfection, and new pump installation. Such wells can be returned to service relatively inexpensively, but we need to continue to adapt systems and knowledge for use in remote areas for people who have little money and expertise. And when relief organizations provide a water system, they need to provide the effective training and guidance to the locals so that they can maintain it. 7. A more extensive documented body of experience with well maintenance on environmental monitoring and remediation wells is badly needed. Right now what is out there is limited in value because the case histories available involve work that is patchy, short in duration, and hampered by the need for client confidentiality (our own included). 8. Above all, what is needed is an appreciation for a preventive maintenance ethos, the complexity of the causes of well deterioration, and how it can be prevented and tackled in a targeted way. All wells, regardless of purpose, need to be maintained the way that other expensive, long-life-cycle structures are maintained. People need to appreciate that well maintenance is most comparable to medicine (and maybe modern auto service) at the present time: a. Maintenance is less costly than rehabilitation. b. Lack of maintenance will kill you over the long haul. c. The causes of deterioration are complex. d. Such maintenance cannot be planned without some expert involvement and adjustment over time.

People in facility management have to be practical and open-minded about this, with a view to the long-term, not the immediate. We also need a range of (we hope) ever-improving maintenance options available.

9.2.2 Education, Communication, and Mutual Respect: Human Issues in Well Maintenance Experience shows that people in the trenches of both water supply and environmental remediation work find well maintenance and rehabilitation to be frustrating and unglamorous, and the solutions intimidating. There are no quick and easy solutions

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sometimes, but with some communication, perhaps the frustration and intimidation can be alleviated. There are two somewhat opposing tendencies determining the number of options available for well maintenance and rehabilitation in the water supply and environmental industries:

1. On the one hand we have the increasing number of products, services, and techniques available and the continued inventiveness of well rehabilitation practitioners. 2. On the other hand, there is regulatory pressure to disapprove any and all chemical use in the maintenance of ground-water pumping and monitoring systems, a trend in both potable and environmental applications alike. This is like washing when you are really dirty, without soap and detergent. Sure, scrubbing helps, but a little soap is a good thing. Just no phosphorous in that soap, please.

No reasonable person wants to contaminate the biosphere. People in responsible charge should have a firm understanding of the consequences of their actions. Level heads and education are needed to keep a reasonable arsenal of treatments available to keep wells operating. If they cannot operate, they will be incapable of reliably providing water or samples to detect contaminants, or of extracting water to clean it up or keep contamination away from sensitive environments. Achieving this balance takes broad training, communication, mutual respect and team approach among regulators, site management, hydrogeologists, engineers, and drilling and pump technicians, each valuing the skills, experience, and advice of the other. All of this is necessary: the scientific and engineering principles, the empirical applied experience that knows how pumps and wells work and fail, and what to do about it (and when to quit). Facilities management and consultants can start by keeping a healthy humility in the face of and respect for the value of experience and specialized technical training in all aspects of well M&R. Saying this as delicately as possible, sometimes such humility and respect does not seem to be natural to educated people these days and has to be learned by example in a company culture, since it has not been taught in higher education environments in recent years. It seems that many emerging educated professionals are coming from an already self-defined elite class, not the farm (see Chapter 1), and the wisdom of the “mechanic” is no longer as well valued as it used to be. Through continuing education, the message has to be heard through the symposia and short course circuit, online, and in company and agency training throughout the industrial world:

1. Operating water supply wells over the long haul requires a maintenance, even an asset management, mentality. It is possible to maintain these systems, and it is worth doing, but it requires proactive thinking, planning, and budgeting.

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2. Operating monitoring and remediation recovery wells is a high-maintenance practice. The potential for problems is great, but manageable if planned for. 3. Design both water supply and environmental wells to prevent problems and for the long term, not quick and cheap regardless of the pressures. 4. Plan rationally for long-term maintenance and rehabilitation (apply asset management principles). 5. Base both the well design and the maintenance plan on adequate diagnosis of potential problems (which may be numerous and interactive). 6. If you have a problem, get help and fix it properly as quickly as possible— do not wait or apply half-baked solutions.

There have to be lines of communication among all the payers and players in the ground-water, water supply, and environmental remediation industries. Project management and facility supervision needs to be listening to the people who have made the study of well deterioration problems and solutions their specialties. Doing so will save a lot of grief and expense. We all need to talk to one another and share our experiences as much as possible. Echoing Roy Cullimore’s sentiments, it is hoped that this work should also only be part of the continuing dialog on the maintenance of water supply, ground-water monitoring, remediation, recovery, and plume control wells. Indeed, we expect it to become obsolete in time as new methods and experience change what we know and recommend. If we talk these problems out, write up our successes and failures, conduct and fund the needed research, share our experiences and expertise, while keeping specialists in this field gainfully employed doing what they do best (instead of selling water filters or something), we can keep these projects operating and serving their purpose: providing us with the best water there is (ground water) and preventing and controlling ground-water contamination. Quoting Edward R. Murrow, one of the founders of modern broadcast journalism: Goodbye and good luck. —Allen and Stuart

Recommended Reading List Our reference section includes a recommended reading list and a selected references list. We have used both sets in preparing this work. The recommended reading selection is more that which makes a good bookshelf or reference file selection for the serious student of planning and carrying out the practice of developing sustainable wells. The second list contains literature that we used that has been published since preparing the predecessor to this work (Smith, 1995). It also includes selected “oldies but goodies,” some specifically mentioned in the text.

Recommended Reading List Alford, G., R. Leach, and S. A. Smith. 2000. Operation and maintenance of extraction and injection wells at HTRW sites. EP 1110-1-27, U.S. Army Corps of Engineers, St. Louis, MO. Available for download from http://140.194.76.129/publications/. Follow the link for “engineer pamphlets.” Note about web links: The web is an incredible resource and often very easy to access and use. However, website administrators do not think like librarians, who prefer permanent identifications. They move page addresses for a host of (usually) benign and logical reasons. For example, the above-referenced link changed shortly before manuscript submittal. Sometimes it is best to use a search tool, searching for entire title/document number. Amy, P. S., and D. L. Haldeman. 1997. The microbiology of the terrestrial deep subsurface. Boca Raton, FL: CRC Press, LLC. Note: A good review of the state of the art (not much changed in the intervening years, unfortunately). APHA, AWWA, WEF. 2005. Section 9240: Iron and sulfur bacteria. In Standard methods for the examination of water and wastewater. 21st ed. Washington, DC: American Public Health Association. Current edition in print is dated 2005; some newer online, www. standardmethods.org/. Subscription required for online lookup. ASCE. In press. International manual of well hydraulics. Reston, VA: ASCE. Note: Material from this work reviewed in preparation of our work is in draft form. Atlas, R. M., and R. Bartha. 1998. Microbial ecology: Fundamentals and applications. 4th ed. Menlo Park, CA: Benjamin/Cummings Publishing Co. Australian Drilling Industry Training Committee Ltd. 1997. Drilling, the manual of methods, applications, and management. 4th ed. Boca Raton, FL: CRC Lewis Publishers, Taylor & Francis Group. AWWA Groundwater Committee. 2003. Groundwater. Manual 21, 3rd ed. Denver: American Water Works Association. Block, S. S., ed. 2002. Disinfection, sterilization, and preservation. 5th ed. Philadelphia: Lippincott Williams & Wilkins. Additional chlorine dioxide material from Sabre Energy Services (www.sabreenergyservices.com/). Borch, M. A., S. A. Smith, and L. N. Noble. 1993. Evaluation, maintenance, and restoration of water supply wells. Denver: American Water Works Association Research Foundation. Note: Out of print. Can be found by library search, as a used book, or contact the AWWARF (Water Research Foundation). Brikké, F., and M. Bredero. 2003. Linking technology choice with operation and maintenance in the context of community water supply and sanitation: A reference document for planners and project staff. Geneva, Switzerland: World Health Organization and IRC Water and Sanitation Centre. www.who.int/water_sanitation_health/hygiene/om/wsh9241562153/en/. 269

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Bureau of Reclamation. 1995. Ground water manual. 2nd ed. Highlands Ranch, CO: Water Resources Publications, LLC. This is a very good general reference free of product endorsement bias. Some well “sterilization” advice is outdated. Chapelle, F. H. 2000. Ground-water microbiology and geochemistry. New York: John Wiley & Sons. Clarke, F. E., and I. Barnes. 1969. Evaluation and control of corrosion and encrustation in tube wells of the Indus Plains, West Pakistan. Water-Supply Paper 1608-L, U.S. Geological Survey, Washington, DC. Note: Worthwhile to find a copy somewhere. Cullimore, D. R. 2007. Microbiology of well biofouling. Regina, SK, Canada: Droycon Bioconcepts, Inc. www.dbi.ca/. Cullimore, D. R. 2008. Practical manual of groundwater microbiology. 2nd ed. Boca Raton, FL: CRC Press, Taylor & Francis Group. Custodio, E. 2002. Aquifer overexploitation: What does it mean? Hydrogeology Journal 10:254–77. Dornan, D. 2001. Asset management and GASB 34—Challenge or opportunity? Government Accounting Standards Board. Norwalk, CT. www.gasb.org/. Driscoll, F. 1986. Groundwater and wells. 2nd ed. St. Paul, MN: Johnson Well Screens. Note: This is superseded by the third edition (see Sterrett, 2007), but they are really two different works, and Sterrett lacks a lot of the reference resources in Driscoll. Don’t recycle the old one. Ehrlich, H. L., and D. K. Newman. 2009. Geomicrobiology. 5th ed. Boca Raton, FL: CRC Press, Taylor & Francis Group, LLC. ERDSG Collective. 2005. Environmental drilling remediation safety guidelines. Prepared by AniEntropics, Inc., available from the National Ground Water Association. GASB. 1999. Basic financial statements—and management’s discussion and analysis—for state and local governments. GASB 34, Government Accounting Standards Board, Norwalk, CT. www.gasb.org. Hardisty, P. E., and E. Özdemiroˇglu. 2005. The Economics of Groundwater Remediation and Protection, Boca Raton, FL: CRC Press. Helweg, O. J., V. H. Scott, and W. C. Scalmanini. 1983. Improving well and pump efficiency. Denver: American Water Works Association. Note: This work is now out of print. It may be obtained from libraries or used-book sources. Although its computer/calculator information is now dated, the cost-benefit and analytical discussion remains highly relevant. Hem, J. D. 1985. Study and interpretation of the chemical characteristics of natural water. 3rd ed. Water Supply Paper 2254, U.S. Geological Survey, Reston, VA. This work by the late great Dr. Hem (d. 1994) is available as a PDF from http://pubs.usgs.gov/wsp/ wsp2254/ at the time of publication. Houben, G., and C. Treskatis. 2007. Water well rehabilitation and reconstruction. New York: McGraw-Hill. Howsam, P., ed. 1990a. Microbiology in civil engineering. FEMS Symposium 59, E&FN Spon, London. Howsam, P., ed. 1990b. Water wells monitoring, maintenance, and rehabilitation. Proceedings of the International Groundwater Engineering Conference, Cranfield Institute of Tech­ nol­ogy, London. These two references contain a large number of relevant and still-timely papers, including some devoted to developing world well maintenance. Jordan, J. K. 2000. Maintenance management for water utilities. 2nd ed. Denver: American Water Works Association. Kissane, J. A., and R. E. Leach. 1993. Redevelopment of relief wells, Upper Wood River Drainage and Levee District, Madison County, Illinois. Technical Report REMR-GT-16, U.S. Army Corps of Engineers Waterways Experiment Station, Vicksburg, MS.

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Kruseman, G. P., and Ridder, N. A. de. 1994. Analysis and evaluation of pumping test data. ILRI Publication 47, International Institute for Land Reclamation and Improvement, Wageningen, The Netherlands. Kulshreshtha, S. N. 1994. Economic value of groundwater in the Assiniboine Delta Aquifer in Manitoba. Social Science Series 29. Ottawa: Environmental Conservation Service, Environment Canada. Available to download: http://www.wca-infonet.org/id/714 (or search by author and title). Lennox, J. B. 2007. Application of well condition assessment and rehabilitation techniques application of well condition assessment and rehabilitation techniques. Denver: AWWA and AWWA Research Foundation. With CD-ROM. Note: See if you can get this one from your friend the research librarian. The cost-benefit ratio is rather high. Mathews, W. H., III, and Boyer, R. E., eds. 1976. Dictionary of geological terms. Garden City, NY: American Geological Institute, Anchor Press/Doubleday. Matichich, M., R. Booth, J. Rogers, E. Rothstein, E. Speranza, C. Stanger, E. Wagner, and P. Gruenwald. 2006. Asset management planning and reporting options for water utilities. Denver: AWWA and AWWA Research Foundation. McLaughlan, R. G. 2002. Managing water well deterioration. International Contribution to Hydrogeology, Vol. 22. International Association of Hydrogeologists, A.A. Balkema Publishers. McNamee, P., D. Dornan, D. Bajadek, and E. Chait. 1999. Understanding GASB 34’s infrastructure reporting requirements. Government Accounting Standards Board. Norwalk, CT. www.gasb.org/. Michigan Department of Environmental Quality. 2003. Water well disinfection manual. Lansing, MI: Michigan DEQ. Available as a PDF download from the DEQ off the www.michigan.gov website. Note: The architecture of this site does not allow for concise, meaningful URL reference. Use a search engine to find it. Misstear, B., D. Banks, and L. Clarke, eds. 2006. Water wells and boreholes. Hoboken, NJ: John Wiley & Sons, Ltd. National Ground Water Association. 1998. Manual of water well construction practices. 2nd ed. Westerville, OH. Note: This is the foundational work for standard ANSI/NGWA 01, edited by S. A. Smith. National Ground Water Association. 2002. Field evaluation of emergency well disinfection for contamination events. NGWA for U.S. Federal Emergency Management Agency, Washington, DC, National Ground Water Association, Westerville, OH. Note: Written by S. A. Smith. Includes field work by Mike Vaught. To our knowledge, FEMA (now a part of the Homeland Security Administration) lost this work (are we surprised?). Although accepted by project management after peer review, we have not seen it made public. The work is available (at the time of publication) for free download from www.groundwaterscience.com. National Ground Water Association. 2008. Residential well cleaning, best suggested practice. Westerville, OH. Available as member-available download from www.ngwa.org. National Research Council Committee on Valuing Ground Water. 1997. Valuing ground water: Economic concepts and approach. Washington, DC: National Academy Press. Nielsen, D. M., ed. 1991. Practical handbook of ground-water monitoring. Chelsea, MI: Lewis Publishers. Novakowski, K., B. Betty, M. J. Conboy, and J. Lebedin. 2006. Water well sustainability in Ontario. Expert panel report, Sustainable Water Well Initiative, Ontario Ministry of Environment, Orono, Ontario, Canada. www.wellwise.ca/ Powers, J. P. 1992. Construction dewatering. New York: Wiley-Interscience. Pryfogle, P. A. 2005. Monitoring biological activity at geothermal power plants. INLEXT-05-00803, Idaho National Laboratory, U.S. Department of Energy, Idaho Falls.

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Pyne, R. D. G. 1995. Groundwater recharge and wells: A guide to aquifer storage recovery. Boca Raton, FL: CRC Press Lewis Publishers. Note: A second edition (date uncertain) is available from ASR System, Gainesville, Florida (www.asrforum.com/). Roscoe Moss Company. 1992. Water well development. New York: Wiley-Interscience. Note: This work sets out what we call the Western school of well design and includes excellent resources on well structural calculation, well corrosion, and well hydraulics and testing. Scherer, T. 2005. Care and maintenance of irrigation wells. AE-97, North Dakota State University Extension, Fargo. Schnieders, J. H. 2003. Chemical cleaning, disinfection & decontamination of water wells. St. Paul, MN: Johnson Screens, Inc. This has a good discussion of the “reformed chlorination” approach and the reasoning behind it. Note that not all chemical choice advice in this work matches that found in the work you are currently reading. Smith, S. A. 1992. Methods for monitoring iron and manganese biofouling in water supply wells. Denver: AWWA Research Foundation. Note: Out of print. Can be found by library search, as a used book, or contact the AWWARF (Water Research Foundation). Smith-Comeskey Ground Water Science. 2007. Wellfield operations and maintenance water quality testing manual. Smith-Comeskey Ground Water Science, LLC. Upper Sandusky, OH. www.groundwaterscience.com (downloadable). Sterrett, R. 2007. Groundwater and wells. 3rd ed. New Brighton, MN: Johnson Screens. Note: See also Driscoll, 1986. In some respects, Sterrett and Driscoll are very different books, and Driscoll has some resources in it that were not included in the newer edition. Sterrett is filled with excellent material, but has a remarkably stunted and incomplete discussion of open-borehole development (to be expected in a screen company book) and a well rehabilitation chapter based on their company philosophy, which deviates from ours. Don’t throw away Driscoll, and look further for your complete well cleaning approach. Definitely make use of much of the rest of the 812 pages. Sutherland, D. C., P. Howsam, and J. Morris. 1994. The cost-effectiveness of monitoring and maintenance strategies associated with groundwater abstraction—A methodology for evaluation. ODA Project Report 5478A, Silsoe College, Silsoe, Bedford, UK. USACE. 1992. Design, construction, and maintenance of relief wells. Engineering Manual 1110-2-1914, U.S. Army Corps of Engineers, Washington, DC. Note: Some obsolete advice in this one, but worth reviewing. Available for download from http://140.194.76.129/publications/. Follow the link for “engineering manuals.” USACE. 1999. Groundwater hydrology. Engineer Manual 1110-2-1421, U.S. Army Corps of Engineers, Washington, DC. Available for download from http://140.194.76.129/ publications/. Follow link “engineering manuals.” Videla, H. A. 1996. Manual of biocorrosion. Boca Raton, FL: CRC Press. Water Systems Council. 2002a. Large submersible water pump manual. 4th ed. Washington, DC; Water Systems Council. Water Systems Council. 2002b. Water systems handbook. 12th ed. Washington, DC: Water Systems Council. Young, R. A. 2005. Determining the economic value of water: Concepts and methods. Washington, DC: Resources for the Future. www.rffpress.org/.

Selected References Note that many older citations to references that were used in developing the 1995 edition are cited in that work and in Borch et al. (1993). Those listed here are sources for updated and expanded material, are specifically noted in the text, or are especially notable.

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Alford, G., and D. R. Cullimore. 1999. The application of heat and chemicals in the control of biofouling events in wells. Boca Raton, FL: CRC Press Lewis Publishers. Alford, G., N. Mansuy, and D. R. Cullimore. 1989. The utilization of the blended chemical heat treatment (BCHT) process to restore production capacities to biofouled water wells. In Proceedings of the Third Annual Outdoor Action Conference, Las Vegas, 229–37. Dublin, OH: National Water Well Association. Aller, L., et al. 1990. Handbook of suggested practices for the design and installation of ground-water monitoring wells. Dublin, OH: National Water Well Association. Barbic, F. F., O. Krajcic, and I. Savic. 1990. Complexity of causes of well yield decrease. In Microbiology in civil engineering, ed. P. Howsam, 198–208. FEMS Symposium 59. London: E&FN Spon. Bortels, L., J. Deconinck, C. Munteau, and V. Topa. 2006. A general applicable model for AC predictive and mitigation techniques for pipeline networks influenced by HV power lines. IEEE Transactions on Power Line Delivery 21:210–17. Brown, P. 2007. Asset management for groundwater systems. Seminar presentation notes for Golder Associates for Arizona Hydrological Society Well Performance Symposium, Tucson, AZ. August. Butts, E. 2006a. Troubleshooting those pumps—Part 1. Water Well Journal 60:26–29. Butts, E. 2006b. Troubleshooting those pumps—Part 2. Water Well Journal 60:30–33. Butts, E. 2006c. Troubleshooting those pumps—Part 3. Water Well Journal 60:46–51. Butts, E. 2006d. Troubleshooting those pumps—Part 4. Water Well Journal 60:42–48. Butts, E. 2006e. Troubleshooting those pumps—Part 5. Water Well Journal 60:42–48. Butts, E. 2006f. Troubleshooting those pumps—Part 6. Water Well Journal 60:32–33. Cromwell, J. E., III, and E. Speranza. 2007. Asset management too complicated? Just think about your car. Journal American Water Works Association 99:46–51. Culver, G., and K. Rafferty. 1998. Well pumps. In Geothermal direct use engineering and design guidebook, chap. 9. 3rd ed. Klamath Falls, OR: Geo-Heat Center, Oregon Institute of Technology. Available as download at http://geoheat.oit.edu/pdf/tp56.pdf. Droycon Bioconcepts, Inc. Undated. Rehabilitation of injection and extraction wells. Regina, SK, Canada: Droycon Bioconcepts, Inc. www.dbi.ca/. Note: Developed as an “engineer pamphlet” for the U.S. Army Corps of Engineers. Ehrhardt, G., and R. Pelzer. 1992. Wirkung von Saugstromsteuerungen in Brunnen. bbr 43:452–458. (English translation, “Effect of Suction Flow Control Devices in Wells,” available from the author of this text.) Environmental Programs—Water Stewardship Project. 2006. Well rehabilitation pilot study execution plan. LA-UR-06-3874, Los Alamos National Laboratory, Los Alamos, NM. ESTCP. 2005. A review of biofouling controls for enhanced in situ bioremediation of groundwater. Environmental Security Technology Certification Program. www.estcp.org/. Fahey, W., and M. Yarlott. 2008. The importance of data in asset management. Underground Infrastructure Management, November 3. www.uimonline.com/. Fiedler, W. 2001. Drainage for dams and associated structures [draft]. Denver: Civil Engineer­ ing and Geotechnical Services, Technical Services Center, Bureau of Reclamation. Fountain, J., and P. Howsam. 1990. The use of high-pressure water jetting as a rehabilitation technique. In Water wells monitoring, maintenance, and rehabilitation, ed. P. Howsam, 180–94. London: E&FN Spon. Froedge, D. T. 1983. Blasting effects on water wells. In Proceedings of the 9th Conference on Explosives and Blasting Technique, 83–96. Society of Explosives. Galili, E., and Y. Nir. 1993. The submerged pre-pottery Neolithic water well at Atlit-Yam, northern Israel, and its paleoenvironmental implications. The Holocene 3:265–70. Gariboglio, M. A., and S. A. Smith. 1993. Corrosión e incrustación microbiológia en sistemas de captación y conducción de agua: aspectos teóricos y aplicados. Serie Investigaciones Aplicadas, Buenos Aires, Argentina, Consejo Federal de Inversiones.

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Geibel, N. M. 2004. Technical note: Rehabilitation of a biofouled pressure-relief well network, Garrison Dam, North Dakota. Environmental & Engineering Geoscience X:175–83. Gilson, J. A., J. Heinrichs, and B. Zollinger. 2001. The economic value of an acre foot of water. In The value of Ogallala aquifer water in southwest Kansas, chap. 4. Prepared for Southwest Kansas Groundwater Management District, Docking Institute of Public Affairs, Hayes, KS. www.fhsu.edu/docking/. Globa, R., J. R. Lawrence, and H. Rohde. 2004. Observations on impressed current systems to mitigate water well biofouling. Paper presented at the 57th Canadian Geotechnical Conference, Canadian Geotechnical Society, Richmond, BC. http://www.cgs.ca/. Globa, R., and H. Rohde. 2003. Application of impressed current systems to mitigate water well biofouling. Paper presented at the 56th Canadian Geotechnical Conference, Canadian Geotechnical Society, Richmond, BC. http://www.cgs.ca/. Hajra, M. G., L. N. Reddi, G. L. Marchin, and J. Mutyala. 2000. Biological clogging in porous media. In Geo-Denver 2000: Environmental geotechnics: Proceedings of sessions of Geo-Denver 2000, Denver, 151–65. Geo-Institute of the American Society of Civil Engineers. Helweg, O. J., F. Von Hofe, and P. T. Quek. 1991. Improving well hydraulics. In Proceedings of the Irrigation and Drainage Specialty Conference, Honolulu, HI, 423–34. Hydraulics Institute and Europump. 2001. Pump life cycle costs: A guide to LCC analysis for pumping systems. DOE/GO-102001-1 190, U.S. Department of Energy. www.eere.energy.gov/. Note: A version with calculation resources is available from www.pumpsystemsmatter.org/. King, A. J., A. F. Meyer, and S. K. Schmidt. 2008. High levels of microbial biomass and activity in unvegetated tropical and temperate alpine soils. Soil Biology and Biochemistry 40:2605–10. Krumholz, L. R. 2000. Microbial communities in the deep subsurface. Hydrogeology Journal 8:4–10. Kunigk, L., J. R. Schramm, and C. K. Kunigk. 2008. Hypochlorous acid loss from neutral electrolyzed water and sodium hypochlorite solutions upon storage. Brazilian Journal of Food Technology 11:153–58. Leach, R., A. Mikell, C. Richardson, and G. Alford. 1991. Rehabilitation of monitoring, production, and recharge wells [report]. Vicksburg, MS: U.S. Army Engineer Waterways Experiment Station. Lytle, D. A., T. L. Gerke, and J. B. Maynard. 2004. Geochemistry of sulfur in iron scales found in DW DS. Slides presented at the AWWA Water Quality Technology Conference, San Antonio, TX. Cincinnati, OH: U.S. Environmental Protection Agency and University of Cincinnati Geology Department. Mansur, C. I., G. Postel, and R. L. Salley. 2000. Performance of relief well systems along Mississippi River levees. Journal of Geotechnical and Geoenvironmental Engineering 126:727–36. McDonnell, G. E. 2007. Antisepsis, disinfection, and sterilization: Types, action, and resistance. Washington, DC: ASM Press. Mollica, A. 2000. Simple electrochemical sensors for biofilm and MIC monitoring. In Biofilm and MIC monitoring: State of the art, Meeting of Task 5, Venezia, Italy, April 13. Segrate (Milano), Italy Centro Elettrotecnico Sperimentale Italiano. Nemergut, D., S. Anderson, C. Cleveland, A. Martin, A. Miller, A. Seimon, and S. Schmidt. 2007. Microbial community succession in an unvegetated, recently deglaciated soil. Microbial Ecology 53:110–22. Norton, G. 1992. Pump service at hazardous sites. Ground Water Age 26:14–15. Nuckols, T. E. 1990. Development of small diameter wells. In Proceedings of the Fourth National Outdoor Action Conference on Aquifer Restoration, Ground Water Monitoring and Geophysical Methods, 193–207. Dublin, OH: National Water Well Association.

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Nuzman, C. E., and R. C. Jackson. 1990. Aquastream suction flow control device. In Proceedings of Conserv 90, the National Conference and Exposition, Phoenix, AZ, August 12–16, pp. 1275–76. Dublin, OH: National Water Well Association. Olsen, S., and A. Larson. 2007. Opportunities and barriers in Madison, Wisconsin: Understanding process energy use in a large municipal water utility. Boston: Consortium for Energy Efficiency, Inc. www.cee1.org/ind/mot-sys/ww/mge2.pdf. Osella, A., P. Martinelli, A. B. Favetto, and E. Lopez. 2002. Induction effects of 2-D structures on buried pipelines. IEEE Transactions on Geoscience and Remote Sensing 40:197–205. Pavelic, P., P. Dillon, K. Barry, D. Armstrong, A. Hodson, J. Callaghan, and N. Gerges. 2008. Lessons drawn from attempts to unclog an ASR well in an unconsolidated sand aquifer. Glen Osmond, SA, Australia: CSIRO Land and Water. Pelzer, R., and S. A. Smith. 1990. Eucastream suction flow control device: An element for optimization of flow conditions in wells. In Water wells monitoring, maintenance, and rehabilitation, ed. P. Howsam, 209–16. London: E&FN Spon. Powrie, W., T. O. L. Roberts, and S. A. Jefferis. 1990. Biofouling of site dewatering systems. In Microbiology in civil engineering, ed. P. Howsam, 341–52. FEMS Symposium 59. London: E&FN Spon. Prairie Farm Rehabilitation Administration. 1999a. City of North Battleford well 15 1997 field test of UAB™ water well treatment technology. Technical Service Earth Sciences Unit, Regina, Saskatchewan, Canada. Prairie Farm Rehabilitation Administration. 1999b. City of North Battleford well rehabilitation project, phase 2: Well treatment evaluation. Regina, SK, Canada: Technical Service Earth Sciences Unit. Raucher, B. 2005. The value of water: What it means, why it’s important, and how water utility managers can use it. Journal American Water Works Association 97:90–98. Reith, F. 2003. Evidence for a microbially mediated biogeochemical cycle of gold—A literature review. In Advances in Regolith 2003, 336–41. Kensington, W.A., Australia: Cooperative Research Centre for Landscape Environments and Mineral Exploration. Riss, A., and R. Schweisfurth. 1985. Basic investigation about denitification and nitrateammonification during the degradation of organic pollutions in the underground. Water Supply 3:27–34. Roberts, D. L. 1951. Anti-earthquake damage operations. World Oil 132:83–86. Robertson, D. A. 1988. Should blasting take the blame for “damaged” wells? Pit & Quarry 81:24–26. Roerick, R. 2006. The big picture: Downhole cameras and a few tricks help in rehabilitating wells. Water Well Journal 60:18, 20. Rose, R., B. Bowles, and W. L. Bender. 1991. Results of blasting in close proximity to water wells at the Sleeper Mine, Montville, Ohio. In Proceedings of the 17th Conference on Explosives and Blasting Technique, 103. Society of Explosives, Ryan, K. K., D. I. Morris, and J. K. Meisenheimer. 1991. Evaluation and rehabilitation of clogged drains at concrete gravity drains. In Waterpower ’91, Proceedings of the International Conference on Hydropower, Denver, Colorado, July 24­–26, pp. 1894–903. New York: American Society of Civil Engineers. Saripalli, K. P., P. D. Meyer, D. H. Bacon, and V. L. Freedman. 2001. Changes in hydrologic properties of aquifer media due to chemical reactions: A review. Critical Reviews in Environmental Science and Technology 31:311–49. Scherer, T. F. 1993. Irrigation water pumps. AE-1057, North Dakota State University Extension, Fargo. http://www.ag.ndsu.edu/pubs/ageng/irrigate/ae1057w.htm. Sevee, J. E., and P. M. Maher. 1990. Monitoring well rehabilitation using the surge block technique. In Ground water and vadose zone monitoring, ed. D. M. Nielsen and A. I. Johnson, 91–97. STP 1053. Philadelphia: American Society for Testing and Materials.

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Siskind, D. E., and J. W. Kopp. 1987, Blasting effects on Appalachian water wells. Paper presented at Surface Mine Blasting, Proceedings: Bureau of Mines Technology Transfer Seminar, April 1987, Information Circular 9135. Bureau of Mines. Sloan, G. B., M. McLaughlin, and J. Troutt. 2007. New technology injects new life into municipal well. Journal AWWA 99:100­–3. Smith, S. A. 1995. Monitoring and remediation wells: Problem prevention, maintenance and rehabilitation. Boca Raton, FL: CRC Lewis Publishers. Smith, S. A. 1996. Monitoring biofouling in source and treated waters: Status of available methods and recommendation for standard guide. In Sampling environmental media, ASTM STP 1282, 158–75. West Conshohocken, PA: American Society for Testing and Materials. Smith, S. A. 2006. In an imperfect world of well cleaning: Information, time, and motion matter. Water Well Journal 60:26, 28. Smith, S. A., and A. E. Comeskey. 2006. Performance testing and reference manual. Upper Sandusky, OH: Ground Water Science. Available from www.groundwaterscience.com. Smith, S. A., and D. M. Hosler. 2001. Report of investigations with recommendations, biological fouling of the pressure relief drainage system, Pablo Canyon Dam, Montana. Denver: Bureau of Reclamation, U.S. Department of Interior. Smith, S. A., and D. M. Hosler. 2006. Current Research in Dam drain clogging and its prevention. Paper presented at Dam Safety ’06, 23rd Annual Conference, Association of State Dam Safety Officials, Lexington, KY. www.damsafety.org. Smith-Comeskey Ground Water Science. 2000. Evaluation of problems with closed basin division salvage wells, rehabilitation method tests, methods for monitoring well deterioration, and recommendations for preventive maintenance and rehabilitation: A comprehensive report. Delivery Order 116, Alamosa Field Office Closed Basin Division, Bureau of Reclamation, U.S. Department of Interior, Denver. Sobolev, D., and E. E. Roden. 2004. Characterization of a neutrophilic, chemolithotrophic, Fe(II)-oxidizing b-proteobacterium from freshwater wetlands sediments. Geomicrobiology Journal 21:1–10. Sobsey, M. D., and F. K. Pfaender. 2002. Evaluation of the H2S method for detection of fecal contamination of drinking water. WHO/SDE/WSH/02.08, World Health Organization, Geneva, Switzerland. www.who.int/water_sanitation_health/dwq/wsh0208/en/index.html. Strawn, J. 2005. More powerful than dynamite. Water Well Journal 59:26. Stuyfzand, P. J., and A. Doomen. 2004. The Dutch experience with MARS (Managed Aquifer Recharge and Storage); A review of facilities, techniques, and tools. KWR 05.001, Kiwa N.V. Water Research, Nieuwgein, The Netherlands. Thullner, M., L. Mauclaire, M. H. Schroth, W. Kinzelbach, and J. Zeyer. 2002. Interaction between water flow and spatial distribution of microbial growth in a two-dimensional flow field in saturated porous media. Journal of Contaminant Hydrology 58:169–89. Tuhela, L., L. Carlson, and O. H. Tuovinen. 1997. Biogeochemical transformations of Fe and Mn in oxic groundwater and well environments. Journal of Environmental Science and Health A 32:407–26. Tuhela, L., S. A. Smith, and O. H. Tuovinen. 1993. Flow-cell apparatus for monitoring iron biofouling in water wells. Ground Water 31:982–88. USACE. 1998. Inspection, monitoring and maintenance of relief wells. ER 1110-2-1942, U.S. Army Corps of Engineers. USEPA. 2003. Asset management: A handbook for small water systems. EPA-816-R-03-016, Office of Water, U.S. Environmental Protection Agency. http://www.epa.gov/safewater/ smallsystems/. USEPA. 2008. Asset management: A best practices guide. EPA-816-F08-014, Office of Water, U.S. Environmental Protection Agency. http://www.epa.gov/safewater/smallsystems/.

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Von Hofe, F. P., and O. J. Helweg. 1998. Modeling well hydrodynamics. Journal of Hydraulic Engineering 124:1198–202. Vuorinen, A., and L. Carlson. 1985. Scavenging of heavy metals by hydrous Fe and Mn oxides precipitating from groundwater in Finland. In Proceedings of the International Conference on Heavy Metals in the Environment, Athens, Greece, September 10–13, pp. 266–68. Vol. 1. Helsinki, Finland: University of Helsinki. Waite, T. D., and T. E. Payne. 1993. Uranium transport in the subsurface environment, Koongarra—A case study. In Metals in groundwater, ed. H. E. Allen et al., 349–410. Chelsea, MI: Lewis Publishers. Walter, D. A. 1997a. Geochemistry and microbiology of iron-related well screen encrustation and aquifer biofouling in Suffolk County, Long Island, New York. Water Resources Investigations Report 97-4032, U.S. Geological Survey, Coram, NY. Walter, D. A. 1997b. Effects and distribution of iron-related well screen encrustation and aquifer biofouling in Suffolk County, Long Island, New York. Water Resources Investigations Report 97-4217, U.S. Geological Survey, Coram, NY. Watson, S. C., and G. R. Benson. 1984. Liquid propellant stimulation of shallow Appalachian basin wells, Richardson, Texas. Paper presented at the Society of Petroleum Engineers of AIME, SPE Eastern Regional Meeting, Charleston, WV. Wilhelms, A., E. Rein, C. Zwach, and A. S. Steen. 2001. Application and implication of horizontal well geochemistry. Petroleum Geoscience 7:75–79. Winegardner, D. L. 1990. Monitoring wells: Maintenance, rehabilitation, and abandonment. In Ground water and vadose zone monitoring, ed. D. M. Nielsen and A. I. Johnson, 98–107. STP 1053. Philadelphia: American Society for Testing and Materials. Woodhouse, J. 2001. Asset management. Newbury, UK: Woodhouse Partnership, Ltd. Available at Asset Management Resource Center, New England Water Environment Association, www.newea.org/AMRC/.

Selected Relevant Standards ANSI/AWWA 100: Water wells. American Water Works Association. ANSI/AWWA B300: Hypochlorite. ANSI/AWWA C654: Well disinfection. ANSI/NGWA 01: Water well construction standard. Note: May still be in development at publication. ANSI/NSF Standard 60: Drinking water treatment chemicals—Health effects. NSF International. ANSI/NSF Standard 61: Drinking water system components—Health effects. NSF International. PAS-97(04): WSC performance standards and recommended installation procedures for sanitary water well pitless adapters, pitless units, and well caps. Water Systems Council. Standard Methods Section 9240: Iron and sulfur bacteria. Note: Standard Methods (referenced above) contains practices for the range of physical, chemical, and microbiological analyses conducted in the laboratory in support of water quality investigations (www. standardmethods.org/). Refer to the most recent version—a major update was in progress in 2009 and may appear in the 22nd edition, but at least it will be available online. WHO. 1997. Guidelines for drinking water quality: Surveillance and control of community supplies. 2nd ed., Vol. 3. Geneva, Switzerland: World Health Organization. www.who. int/water_sanitation_health/dwq/2edvol3a.pdf. WHO. 2006. Microbial aspects. In Guidelines for drinking-water quality, chap. 7. Geneva, Switzerland: World Health Organization. www.who.int/water_sanitation_health/dwq/ gdwq0506_7.pdf

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ANSI/ASTM Standards (a selection) Note that these are revised periodically. Refer to the most recent version (www. astm.org/). D 932: Iron bacteria. D 3977: Suspended sediment in water samples. D 4050: Standard test method (field procedure) for withdrawal and injection well tests for determining hydraulic properties of aquifer systems. D 4412: Test methods for sulfide reducing bacteria in water and water-formed deposits. D 4750: Test method for determining subsurface liquid levels in a borehole or monitoring well (observation well). D 5088: Practice for decontamination of field equipment used at nonradioactive waste sites. D 5092: Practice for design and installation of ground water monitoring wells in aquifers. D 5099: Standard guide for development of ground-water monitoring wells in granular aquifers. D 5521: Guide for development of ground water monitoring wells in granular aquifers. D 5716: Standard test method for measuring the rate of well discharge by circular orifice weir. D 5753: Standard guide for planning and conducting borehole geophysical logging. D 5787: Standard practice for monitoring well protection. D 5978: Standard guide for maintenance and rehabilitation of ground-water monitoring wells. D 6034: Standard test method (analytical procedure) for determining the efficiency of a production well in a confined aquifer from a constant rate pumping test. D 6634: Standard guide for the selection of purging and sampling devices for ground-water monitoring wells. A589/A589M: Standard specification for seamless and welded carbon steel water-well pipe. Note: Other types of steel pipe are covered by ASTM and other standards, but this deals specifically with casing pipe. ASTM F480: Standard specification for thermoplastic well casing pipe and couplings made in standard dimension ratios (SDR), SCH 40 and SCH 80.

There are too many international standards to list here. We recommend that readers also be conversant in sanitary and environmental standards and regulations relevant to ground water and well construction and operation where you are working. In some cases, relevant regulations and standards may not exist in a certain nation, for example. Well construction regulations are frequently absent in developing nations. In that case, it may be useful to adopt a suitable set of standards for your project or general use.

Index A Abiotic corrosion, 22 Abstraction wells, 107–108 Acceptance tests, 161 Access, 205–207 Acetic acid, 183 Acidizing, 243–247 Acids chemical incompatibility, 183 chemical treatments, 176, 177 compound types, 243–246 posttreatment for, 247 Actions, maintenance monitoring programs, 125 Adaptability, biofilms, 30 Advanced redevelopment methods, 231–242 Agitation and augmentation, mechanical, 182–184 Agriculture water, EV, 77 AIG, see Air impulse gun (AIG) Airburst method, 104, 237, 240 Air impulse gun (AIG), 237 Airlift eductor surging, 230 Airlift systems, 99–100, 102–104 Airlines, 193 AirShock, 104, 237 Air surging, 104 Alford, George, 9, 255 Alford, Rogers and, studies, 185 Alkalinity, 21 Alphabet brew, chemicals, 242, 245–246 Alternatives, 149, 190 Amenity, 76 American Society for Testing and Materials (ASTM), see also specific standard environmental sector, role in shaping, 5 installations, 63 pipe standards, 89 standards, 85 American Society of Civil Engineers (ASCE), 59, 85 American Water Works Association (AWWA), 85, 255, see also specific standard Amprobes, 192 Analysis, 73, 144–150 Angled casing, 59–61 ANSI/ASTM standards, 277–278, see also specific standard Antibacterial (antimicrobial) agents, 249–255

AOCs, see Assimilable organic compounds (AOCs) Application summary example, 25–257 Appropriate cost, best, 73, see also Costs Aqua Freed, 232–233, 255 Aqua Gard, 186 Aqueducts, Roman colony (France), 20–21 Aquifers biofouling, 39, 44 clogging and corrosion, 81 conventional development, 102 cost of depletion, 68 ground water biofouling, 30–31 monitoring, 143 redox zonation, 43 screens, 90–91 sulfur-oxidizing bacteria, 41 treating for iron or manganese, 44 water supply economic value, 77 Aquifer storage and recovery (ASR) systems current developments, 6 issues, xxi performance effects, 47–48 ARCC, Inc., 237 Array design recommendations, 115–116 Arsenic (As), 36 As, see Arsenic (As) ASCE, see American Society of Civil Engineers (ASCE) ASR, see Aquifer storage and recovery (ASR) systems Asset management continuing education, 267 defined, 121 life cycle cost, 73–75 Assimilable organic compounds (AOCs), 32 Assiniboine Delta Aquifer, 77 ASTM, see American Society for Testing and Materials (ASTM) Atero software, 163 Au, see Gold (Au) Augmentation and agitation, mechanical, 182–184, 256 Australian Drilling Industry Training Committee, 59 Automobile industry, 82–84 Autooxidation, 41 AWWA, see American Water Works Association (AWWA)

279

280 B Backwashable filters installation, 260 Bacteria biofilms, 28 disaster-related flooding, 64 no iron, 12 symptoms, 34 Bailing, 96–99, 104 Balkan wars, 2 BARTSOFT, 163 BART tests computer-aided analysis, 163 costs of maintenance activities, 192 historical developments, 7 prepared methods, 146–148 Baseline data, 168–169 BCHT, see Blended chemical heat treatment (BCHT) Bell-end casing joints, 61 Benchmarking, 132–136 Bentonite grouting, 57–58, 89 Berliner Wasserbetriebe, 234 Best appropriate cost, 73, see also Costs Biblical references, 1 Bids, 208–210, 226–227 Biocides, chemical treatments, 176–181 Biofilms biofouling, 28 case example, 32 defined, 28 ecological function, 30 ground water biofouling, 30–32 in-well collectors, 152 microbes, 26–27, 30 terminology, 11 Biofouling alternative monitoring, 149 aquifers, 44 aquifer storage and recovery systems, 47–48 biofilms, 28–32 case example, 32 chlorination, organic chemicals, 49 defined, 27 ecological function, 30 fundamentals, 26–28 ground water biofouling, 30–32 health concerns, 48–49 hydraulic impacts, 46–47 iron, 39–43 manganese, 39–43 metallic corrosion, 37–39 microbes, 26–27, 30, 37–39 monitoring recommendations, 143–144 pathogens, 48 performance effects, 43–44, 46–48 preventive treatments and actions, 174

Index quality degradation, monitoring and remediation problems, 34–37 recurrence, prevention, 187 redox fringe, 43 sample quality, monitoring wells, 47 silting, 27 sulfur, 39–43 terminology, 11 toxic accumulation, 49 BioGEORGE, 155 Biohazards, 149 Biological monitoring alternative, 149 analysis, 144–150 collection sampling representativeness, 152–154 culturing methods, 145–148 current state of the art, 144 electrochemical in-line sensors, 154–155 fundamentals, 142–143 method selection, 143–144 microscopic analysis, 144–145 minimalism, 148–150 pumped sampling, 151–152 recommendations, maintenance monitoring programs, 149 sampling methods, 150–154 surface collections, slides or coupons, 152 Biology impact, 6–8 Biomass ground water biofouling, 32 influence, 8 terminology, 11–12 Black rat remains, 2 Blended chemical heat treatment (BCHT), 255–256 Blended method treatments, 181–182, 255–256 Bolt Technologies, 237 Borch studies, 128 Boreblast, 104 Boreline, 113, 259 Bortels studies, 63 Böttcher, Heinrich, 4 Boundary zones, 43 British Overseas Development Agency, 189 Broad Street Pump (London), 3 Brominated compounds, 179–180 Budgets, 17, 267, see also Costs; Funding Bureau of Reclamation (BOR), 78, 182 Business considerations, 208–210 Business goals, 129 Butch Cassidy and the Sundance Kid, 26 Butts studies, 137

C Cable cleanliness, 105 Cable tool bailers, 105–106

Index CaCO3, see Calcium carbonate (CaCO3) Cadmium (Cd), 35 Ca(HCO3)2, see Calcium bicarbonate (Ca(HCO3)2) Calcium bicarbonate (Ca(HCO3)2), 20–21 Calcium carbonate (CaCO3), 20–21 Calcium hypochlorite, 178–179 Calcium peroxide, 253 Capacity, establishing specific, 134 Capital asset management, 74 Carbon dioxide (CO2) adjustment, 186 chemical incompatibility, 183 chemical incrustation, 20–21 cold CO2 fracking, 231 Carriers of residue economic value, 77–78 Case example, see Examples Casing cold CO2 treatment, 233 design and construction considerations, 87–89 deterioration, 59–61 grouting, 57 perforated without lining, 174 Catastrophic structural failure, 51, see also Structural deformation and failure Categories, deterioration, 14 Cathodic protection, 173, 186, 259 Caustic dust, 188 Cd, see Cadmium (Cd) Cell phones, 105, 189 Cement, see Portland cement CertainTeed Certa-Lok connectors, 87, 113 Cheap, “poster child” for, 63 Cheaping out, 191 Chemical encrustation, 47 Chemical incompatibility, 183 Chemical incrustation, 20–22 Chemicals alphabet brews, 242, 245–246 conventional redevelopment, 230 costs, 174–176 emplacement, 184 generic, 242 handling hazards, 188 mixing, 188–189 removal and recovery, 184–185 selection, 217–219 Chemicals, treatments acids, 176, 177 biocides, 176–181 blended method treatments, 181–182 classes and properties, 176–182 cost effectiveness, 174–176 dispersing agents, 181 MSDSs, 182 oxidizing compounds, 176–181

281 penetrating agents, 181 potential reactions, 182 professionalism, 174, 176 security, 180 sequestering agents, 181 Chlorinated lime, 4 Chlorination, 49, 249–252 Chlorine chemical feeders in wells, 185 chemical incompatibility, 183 classes and properties, 176–179 historical developments, 3 Chlorine dioxide, 183, 252–253 Chlorine gas, 4 Christensen, Layne, 104 Chromium (Cr), 47 Citric acid, 247 Classes, chemicals, 176–182 Cleaning, see Well cleaning Cliff Notes version, 113–115 Clogging, 50–51, 81 Closed Basin wellfield, 78 Clostridium sp., 48 Co, see Cobalt (Co) CO2, see Carbon dioxide (CO2) Coating breach, 23 Cobalt (Co), 36, 185 Code of Federal Regulations, 187, 201 Cold CO2 treatment, 231–233 Colilert, IDEXX, 149 Collection sampling representativeness, 152–154 Commitment, 122, 124 Communication, 266–268 Comparisons, 132, 136 Complacency about risks, 188 Completeness, 129–130 Complexity, biofilms, 30 Consortia, 12 Construction casing failure, 60–61 deterioration, 50–51 role of well purpose, 86 Construction and design considerations casing, 87–89 efficiency, 90 fundamentals, 84 grouting, 93–94 hydraulics, 90 intakes, 90–93 planning considerations, 84–86 role of well purpose, 86 screens, 90–93 sealing, 93–94 well design, 86–87 Consultant specifier/observer role, 227 Consultants relationship, 205–207 Contamination prevention, 105–106

282 Continuing education, 5 Contractor considerations bidding considerations, 208–210 business considerations, 208–210 consultants relationship, 205–207 effluent waste water containment, 209–210 facilitating productivity, 202 fundamentals, 202–203 information needed, 209 input, 209 performance goals, 209 pitfalls, 208–209 pricing of rehabilitation work, 215–216 productivity, 203–205 safety, 203–205 specifications, 208–210 written safety assurance, 201–202 Conventional choices, 102–104, 229–230 Copper (Cu), 36 Corrosion aquifers, 81 deterioration, causes and effects, 22–26 engineering and construction aggravation, 50–51 preventive treatments and actions, 172–174 Cost-benefit analysis, 129, 189–192 Cost effectiveness, 174–176, 194–195 Costs, see also Budgets; Funding aquifer depletion, 68 chemicals, 174–176 contractor pricing, 215–216 deterioration, 69 direct, 69 doing nothing, 112, 113 example, 78–79 identifying, 67–73 preventive treatments and actions, 189–195 public water supply wells, 70 reconstruction planning, 212–216 rehabilitation, 69–70, 212–216 replacing well, 211 resource depletion, 67–68 system failure, 69 well failure, 191 Cr, see Chromium (Cr) Crash vegetation program, 54 Creativity, 102 Cu, see Copper (Cu) Cullimore, D.R. blended chemical heat treatment, 255–256 continuing dialog, 268 leader in field, 9 monitoring recommendations background, 128 redox fringe, 43 Cullimore, D.R. (Practical Manual of Groundwater Microbiology)

Index biofouling, 27 blended chemical heat treatment, 255 culturing methods, 146 heat as preventative treatment, 181 historical developments, 7 monitoring, decision-making, 128 prepared BART methods, 146–148 pumped sampling, 151 Culturing methods, 145–148 Current state of the art, 144 Curvature, mining, 56 Custodio, Emilio, 68 Cyanobacteria, biofilms, 28

D Damage, 216–217 Dams, 41 Darcy variables, 65 Data collection asset management, 73 maintenance monitoring programs, 129–130 requirements, 156 Dawn product line (P&G), 247 DBP, see Disinfection by-products (DBPs) Deadlines, impact on installation, 17 Decision making decision tree, 172 flowchart, 119–120 maintenance monitoring programs, 128–130 rehabilitation and reconstruction planning, 197 upside-down reasoning, 174 Decommissioning, 69 Dedicated monitoring well pumps, 108–109 Deficiencies of specifications, 221–223, see also Specifications Deformation, structural casing issues, 59–61 earthquakes, 51–53 electrochemical corrosion, stray potentials, 62–63 fundamentals, 51 grouting, 57–58 human causes, 55–63 improper procedures and mistakes, 61–62 mass wasting, 53–54 mine blasting, 56–57 mining, 55–56 natural causes, 51–54 Demographics, 8–11 Dentistry sector, 82–84 Design, Cliff Notes version, 113–115 Design and construction considerations casing, 87–89 efficiency, 90 fundamentals, 84

Index grouting, 93–94 hydraulics, 90 intakes, 90–93 planning considerations, 84–86 role of well purpose, 86 screens, 90–93 sealing, 93–94 well design, 86–87 Designer compounds, 5, 254 Detergents, 4–5, see also Penetrating, sequestering, detergent, and dispersing (PSDD) compounds Deterioration biofilm, 28–32 biofouling, 26–49 case example, 32 casing issues, 59–61 categories, 14 chemical incrustation, 20–22 chlorination, organic chemicals, 49 clogging, 50–51 construction aggravation, 50–51 corrosion, 22–26 costs, 69 disaster-related flooding, 63–65 drawdown problems, 17–19 earthquakes, 51–53 ecological function, 30 electrochemical corrosion, stray potentials, 62–63 engineering aggravation, 50–51 fundamentals, 13 grit, 13, 15–17 ground water biofouling, 30–32 grouting, 57–58 health concerns, 48–49 human causes, 55–63 hydraulic impacts, 46–47 improper procedures and mistakes, 61–62 iron, 39–43 management overview, 65 manganese, 39–43 mass wasting, 53–54 metallic corrosion, 37–39 microbes, 26–27, 30 mine blasting, 56–57 mining, 55–56 natural causes, 51–54 operational overview, 65 pathogens, 48 performance effects, 43–44, 46–48 plastic deterioration, 26 poor performance, 13 quality degradation, monitoring and remediation problems, 34–37 redox fringe, 43 sample quality, monitoring wells, 47

283 sand, 13, 15–17 silt, 13, 15–17 silting, 27 structural deformation and failure, 51–63 sulfur, 39–43 toxic accumulation, 49 treatment plant impact, 49–50 zebra mussel, 29 Deterioration, economic impacts asset management, 73–75 assigning economic value, 76–78 carriers of residue economic value, 77–78 costs, 69 dimensions, 69–73 environmental economic value, 77–78 example, 78–79 government accounting valuation of assets, 78 identifying costs, 67–73 life cycle cost, 73–75 parameters, defining, 67–69 sensitive receptor economic value, 77–78 types, 69–73 water supply economic value, 77 Developing world locations calcium hypochlorite, 178–179 MacGuyver-like versatility, 227 prevention practices, 116–117 Development, 61–62, 159–161 Development, prevention practices airlift development, 99–100 bailing, 96–99 conventional choices, 102–104 fluid-pulse development, 104 fundamentals, 94 jetting, 100–101 method descriptions, 95–101 overpumping, 96 reasons for, 94–95 segment lengths, 105 structural limits, 104–105 surging and pumping, 96–99 tools, 105 utilizing surge block, 96–99 Dewatering wells, 16 Dewatering zone, 17–18 Diameter, 94 Dilbert, 75, 124 Dimensions, 69–73 Direct costs, 69 Disaster-related flooding, 63–65 Discoloration, 34 Disinfection by-products (DBPs), 218, 254 Dispersing agents, 181, see also Penetrating, sequestering, detergent, and dispersing (PSDD) compounds Dispersion phase, 256 Displacement, acidizing, 246

284 Doing nothing, cost of, 212, 213 Dornan, Daniel, 75 Double surge-eductor pumping method, 102 Downstream results, 192 Downtime history, 161–162 Drawdown, 17–19, 133 Drillers, 16–17 Drilling: The Manual of Methods, Applications, and Management, 106, 160 Drill tool cleanliness, 105–106 Drinkingwater, 12 Drinking water treatment chemicals-Health effects (ANSI/NSF Standard 60), 174 Droycon Bioconcepts, Inc., 146, 185 Dry ice, 231 Duderstadt, Germany, 3 DWL, see Dynamic water level (DWL) Dynamic water level (DWL), 137

E Earthflows, see Mass wasting Earthquakes, 51–53, see also Seismic activity Ecological function, biofilms, 30 Economics, 8–11 Economic value (EV), assigning, 76–78 Education, 266–268 Eductor pump systems, 108 Efficiency conservative slot selection, 15 costs, 70–72 design and construction considerations, 90 establishing, 135 rehabilitation, 211–212 Effluent wastes chemical removal and recovery, 184–185, 218 chlorine, 252 containment, contractor considerations, 209–210 proper disposal, 248–249 Eh, see Redox (Eh) Ehrlich and Newman studies, 37 Electric Power Research Institute (EPRI), 155 Electric water level sounder, 193 Electrical power power costs, formula, 70–72 power supply, 107–108 recommendations, 140–141, 158 stray, 62–63, 259 Electrical protection, 107, 110–112 Electrochemical corrosion, 37, 62–63 Electrochemical in-line sensors, 154–155 Electrochemical reactions, 23 Electromagnetically charged surfaces, 185–186 Emplacement, chemicals, 184 Encrustations, inorganic, 174 EnerJet, 234, 235

Index Engineering business losses, 73 casing, 60 deterioration, 50–51 Engine-powered reciprocating drilling machines, 3 Enlightenment movement, 8 Environmental concerns, 218 Environmental economic value (EEV), 76–78 Environmental factors, 190 Environmental monitoring, 82 Environmental Remediation Drilling Safety Guideline, 204 Environmental sector, 5–6 Epifluorescent, 145 EPRI, see Electric Power Research Institute (EPRI) Equipment, 17 Escherichia sp., 48, 150 Evaluation and Restoration of Water Supply Wells monitoring recommendations background, 128 restoration terminology, 11 water supply orientation, xxii Examples deterioration, 78–79 organics contamination, 32 Sustainable Well Series, 263 External pump changes, 157 Extraction wells, 86, 107–108 Extrapolation, empirical observation, 26

F Facilities maintenance planning and execution, 192 management, 198–201 performance data review, 168 well system management, 169 Failure bell-end casing joints, 61 casing, 59–61 catastrophic structural, 51 construction, 60–61 earthquakes, 51–53 electrochemical corrosion, stray potentials, 62–63 engineering for, 91 fundamentals, 51 grouting, 57–58 human causes, 55–63 improper procedures and mistakes, 61–62 mass wasting, 53–54 mine blasting, 56–57 mining, 55–56 natural causes, 51–54

285

Index preventive treatments and actions, 191–192 structural deformation and, 51–63 system, costs, 69 False positives and negatives, 149–150 Farm boy/girl phenomenon, 9 Farm water supply, xxi Fe, see Iron (Fe) Feeders in wells, 185 Fiberglass screen, 92 Field-slotted/perforated steel casing, 92 Figures, list of, xv–xix File format issues and purpose, 162–163, see also Records Filter cloths, 16 Filter pack design, 13, 15–16 Finnish research, 7 First year scheduled maintenance, 163, 164 Fiscal year timescale, 166 Flexibility, 209 Flooding, deterioration from, 63–65 Fluid-pulse tools and methods blended method treatments, 256 mechanical agitation and augmentation, 184 physical agitation, 237–240, 242 prevention practices, 104 redevelopment methods, 231, 238 Fluorocarbons, 26 Follow-up truisms, 258–260 Formulas, annual power costs, 70–72 Fracking, 231 Franklin Subtrols, 193 Frazier Industries, 237 Fresh water, corrosion in, 23 Funding, 10, 166–170, see also Budgets; Costs Future outlook, 264–268

G Gallionella ferruginea, 41, 145–146 Galvanic cell system, 23 Garbage, see Junk in wells Gariboglio, Miguel A., 9, 148 Gas chlorine, 179 Gee Whiz tool, 230 Geochemistry, 22 Geological Survey, see U.S. Geological Survey (USGS) Geologic regime, 159 Geomicrobiology, 7 Geomicrobiology, 37, 41 Germany, 3 Glacial-fluvial outwash valleys, 15 Globalization, 29 Glossary of Statistical Terms, 76 Gold (Au), 49 Government Accounting Standards Board (GASB), 75, 78

Government accounting valuation of assets, 78 Graduate, The (movie), 116 Great Lakes region (U.S.), 15 Griffitts Drilling and Seals, 220 Grit, 13, 15–17, see also Sand Ground water, 12 Ground-water, 12 Ground water biofouling, 30–32 Ground-water-source (GWS) systems, 39 Ground-water systems, 74 Ground-water technology, 6–8 Grouting construction, 89 deterioration, 57–58 well sealing, 93–94 Guide for development of ground water monitoring wells in granular aquifers (D 5521), 160 GWS, see Ground-water-source (GWS) systems

H H, see Hydrogen (H) HAB-BART heterotrophic test, 151 Halogens, 183 HaloSan, 179–180 Handling hazards, chemicals, 188 Hard-copy files, see Records Hazard communications (hazcom) plans, 203 Hazardous waste recover projects, 700 Health concerns chlorination, organic chemicals, 49 fundamentals, 48 handling chemicals, 188 pathogens, 48 preventive treatments and actions, 187–189 toxic accumulation, 49 Heat and heating blended method treatments, 255–256 chemicals used in rehabilitation, 254–255 construction, 87–89 material selection, 92 mechanical agitation and augmentation, 184 preventative treatment with, 180–181 Helsinki Accords, 78 Historical developments data, maintenance monitoring programs, 168–169 learning from, 263–264 perspectives, 1–5 History of well, 210 Holding tanks, 184 Horizontal casing, 59–61 Hose Solutions, 259 Houben and Treskatis studies, 3–4, 128 Houses, well, 115 H2S test, 150

286 Human aspects anecdotal background, 169 asset, importance as, 167, 169 casing issues, 59–61 changes noticed, 122–123 disaster-related flooding, 63–65 electrochemical corrosion, stray potentials, 62–63 grouting, 57–58 improper procedures and mistakes, 61–62 maintenance monitoring programs, 122–123 mine blasting, 56–57 mining, 55–56 skills, 8–11 sound changes, 122–123, 132 Hurricanes, 64 Hydrants, 114 Hydraulics design and construction considerations, 90 impacts, 46–47 performance costs, 192–193 Hydraulics Institute, 75 Hydrochloric acid, 4 Hydrofluoric acid, 183 Hydrogen (H), 35 Hydrogen peroxide, 180, 183, 253–254 Hydrogeological information, 15, 158–159 Hydrogeology, 6–8 Hydrographs, 159 Hydrolysis, iron, 43 Hydroxyacetic acid, 245, 247 Hypochlorites, 183

I IDEXX Colilert, 149 Implementation, 122, 166–168 Improper procedures and mistakes, 61–62 Indoctrination, 10–11 Influence, political system, 10 Information collection, 73 Inhibitors, acidizing, 246 Injection wells, 6, 47 Inorganic encrustations, 174 in situ techniques, 185–186 Inspection resistance, 123 Institutional issues, 166–170 Intakes, design and construction, 90–93 Internal pump changes, 157 International Manual of Well Hydraulics, 67, 85 Internet, 264 Intrinsic value, 210 In-well biofilm collectors, 152 In-well centrifugal desander, 172 Iodine, 180

Index IRB-BART, 149 Iron bacteria (D 932), 144–145 Iron (Fe) biofouling, 39–43, 44 costs to remove, 72 culturing, 145–146 hydraulic impacts, 46 microscopic analysis, 144 monitoring and remediation problems, 34–37 performance effects, 43–44, 46–48 pumped sampling, 151 redox fringe, 43 toxic accumulation, 49 Irrigation wells, xxi “Isotropic and of infinite areal extent” myth, 8 Issues, xxi

J Jamestown (VA), objects in well, 2 Jetting acidizing, 246 blended method treatments, 255 conventional development, 102–104 prevention practices, 100–101 Junk in wells, 1–2, 217

K Keith, Hubert, 4 Kidde Angus Flexible Pipelines, 259 Kinetic development force, 100 Klebsiella sp., 48 Knowledge, 10–11 Kulshreshtha studies, 77–78

L Laboratorio MAG, 148 Lagoons, 184–185 Landslides, see Mass wasting Langelier index, 25 Laval model, 172 Layne Mishiwaka crews, 4 LCC, see Life cycle cost (LCC) Legionella sp., 48, 254 Level of service (LOS), 73 Life cycle, prevention practices, 81–82 Life cycle cost (LCC), 73–75 Lifetime timescale, 166 Liquid sodium hypochlorite, 4 Long-term maintenance schedule, 163, 165, 166 Long-wall extraction mining, see Mining LOS, see Level of service (LOS) Louvered screens, 101

Index M MacGuyver-like versatility, 227 Machine-slotted screens, 101 Madison, Wisconsin, 72 MAG-CHA test, 151 Mag meters, 193 Magnesium carbonate (MgCO3), 21 MAG tests, 148 Maintenance active, xxii defined, 73 funding, 10 ground truths, 81 historical developments, 3 human issues, 266–268 mindset, 10 monitoring, 122 Maintenance logs, 161–163 Maintenance monitoring programs actions, 125 analysis, 144–150 baseline data, 168–169 benchmarking, 132–136 biofouling monitoring, 143–144 biological monitoring, 149 collection sampling representativeness, 152–154 culturing methods, 145–148 current state of the art, 144 data collection, 129–130, 156 decision making, 128–130 development data, 159–161 downtime history, 161–162 electrical power, 140–141, 158 electrochemical in-line sensors, 154–155 facility performance data review, 168 file format issues and purpose, 162–163 first year schedule, 163, 164 fundamentals, 119 funding issues, 166–170 geologic regime, 159 historical data, 168–169 human aspect, 122–123 hydrogeological information, 158–159 implementation, 122, 166–168 institutional issues, 166–170 long-term schedule, 163, 165, 166 maintenance logs, individual wells, 161–163 method selection, 143–144 microscopic analysis, 144–145 minimalism, 148–150 parameters, 124, 126 performance, 124–125 physiochemical analysis, 141–142 piezometric data, 158–159

287 piezometric maps, 159 pressure measurements, 139–140 procedures overview, 122 protocol, 126–130 pumped sampling, 151–152 pumping rates, 157 pump performance, 132–141 purpose, 127 qualifications and training, personnel, 169 rationale, 119–121, 166 recommendations, 127–130 records, 123–124 responsibilities, 170 sampling methods, 150–154 schedules, 163–166 sensory examination, 130, 132 summary, 156–163 surface collections, slides or coupons, 152 system pressure, 157 testing, 130–155 tracking well performance, 137–138 treatments, 125 video, historical comparison, 158 visual inspection, 130, 132 water level, 139, 140, 157–158 water quality, 124–125 water sampling, 141 well data file features, 156–157 well discharge measurements, 139 well performance, 132–141 Maintenance testing, resistance, 123 Management facilities, 198–201 fundamentals, 198 responsibility for work, 50–51, 198–200 solutions, 200–201 Management overview, 65 Manganese (Mn) autooxidation, 41 biofouling, 39–43, 44 costs to remove, 72 culturing, 145–146 hydraulic impacts, 46 microscopic analysis, 144 monitoring and remediation problems, 34–37 performance effects, 43–44, 46–48 physiochemical analysis, 142 pumped sampling, 151 redox fringe, 43 Mansuy studies, 232 Manual of Water Well Construction Practices, 89, 160 Mass wasting, 53–54 Material Safety Data Sheets (MSDS), 182, 188, 204 Material selection, 22–23

288 Mechanical agitation and augmentation, 182–184 Metal filters, biofilms acting as, 36 Metallic corrosion, 37–39 Metallic oxides, 35–36 Methane, 22 Methods biological monitoring, 143–144 chemical selection, 217–219 choosing, 216 damage, 216–217 descriptions, 95–101 questions to ask, 210–212 recommendations, 143–144 reconstruction, 219–221 selection, 143–144 Methods for Monitoring Iron and Manganese Biofouling in Water Supply Wells, xxii, 127 (MgCO3), see Magnesium carbonate (MgCO3) Microbes fundamentals, 26–27 metallic corrosion, 37–39 survival, biofilms, 30 Microbiology of Well Biofouling, 27 Microorganisms, chemical incrustation, 21 Microscopic analysis, 144–145 Mill-slotted/perforated steel casing, 92 Mine blasting, 56–57 Mineral acids, 4 Minimal testing, 148–150 Mining, 55–56 MIOX Corporation, 179 Mishiwaka (Layne) crews, 4 Mistakes and improper procedures, 61–62 Mixing, chemicals, 188–189 Mn, see Manganese (Mn) Monitoring and Remediation Wells: Problem Prevention, Maintenance and Rehabilitation, xxii Monitoring problems, biofouling, 34–37 Monitoring wells conventional development, 103 dedicated pumps, 108–109 direct economic impacts, 72 issues, xxi performance symptoms, 6 pump choices and actions, 108–110 reactivity, chemical treatments, 218 sand and silt, 16 Moss Company, Roscoe, 57, 59 Mountaintop removal, 56 MSDS, see Material Safety Data Sheets (MSDS) Mudflows, see Mass wasting Multicellularity, 30 Municipal potable water supply wells, 56–57, 77 Muriatic acid (HCl), 178, 243–244 Murrow, Edward R., 268

Index N National Environmental Publications Internet Site (NEPIS), 204 National Ground Water Association (NGWA), see also specific standard casing, 59, 61 construction standards, 89 historical developments, 7 hurricane-related flooding, 65 safety and hazcom plans, 204 sand and silt deterioration, 13 standards, 85 technical writers, 205 terminology, 12 National Institute for Occupational Health and Safety (NIOSH), 204 National Well Water Association (NWWA), 7, see also National Ground Water Association (NGWA) Natural causes, deterioration disaster-related flooding, 63–65 earthquakes, 51–53 mass wasting, 53–54 Near-well systems, 32 Negotiation, 195 NEPIS, see National Environmental Publications Internet Site (NEPIS) Newman, Ehrlich and, studies, 37 New wells, 2, 120 Nickel (Ni), 36, 47 NIOSH Pocket Guide to Chemical Hazards, 204 Nitric acid, 183 No iron bacteria, 12 Noble studies, 128 Nontraditional, nonvertical wells, xxi

O O, see Oxygen (O) Occupational Safety and Health Administration (OSHA) contractor safety, 203 MSDSs, 182 safety and hazcom plans, 204 safety assurance, 201 Occupational Safety and Health Guidance Manual for Hazardous Waste Site Activities, 204 Odors, 34 OECD, see Organisation for Economic Cooperation and Development (OECD) Ohio State University, 128 Oil! (novel), 9 O&M, see Operations and maintenance (O&M) Omissions in data, 130 Operational overview, 65

Index Operation and Maintenance of Extraction and Injection Wells at HTRW Sites, 128 Operations and maintenance (O&M) blended method treatments, 182 chemical handling hazards, 188 crew leader qualifications and training, 169 health and safety plan, 187 maintenance implementation barriers, 166–167 public infrastructure, 75 responsibilities, 170 statement of work, 167 treatment plants, 49 Opportunistic pathogens, 188 Organic acids, 183, 254 Organisation for Economic Cooperation and Development (OECD), 76 OSHA, see Occupational Safety and Health Administration (OSHA) Overpumping, 96 Oversight personnel, 170 Oxalic acid, 183 Oxidation, 21–22 Oxidizing compounds, 176–181 Oxygen (O), 37 Ozone, 180, 253

P Paradigm shift, 7 Parameters, 67–69, 126 Pathogens, 48 Paulson, Henry, 197 “Pay me now or pay me later” scenario, 168 Pellet droppers and feeders, 178, 185 Penetrating, sequestering, detergent, and dispersing (PSDD) compounds blended method treatments, 255–256 chemicals used in rehabilitation, 245–249 chlorination, 249 organic acids, 254 Penetrating agents, 181 Peracetic acid, 253–254 Performance aquifer storage and recovery systems, 47–48 conservative slot selection, 15 fundamentals, 43–44, 46 hydraulic impacts, 46–47 maintenance monitoring programs, 124–125 poor, 13 precise goals, 209 sample quality, monitoring wells, 47 Personal injury protection, 187, 188–189 Personalities, 8–11, see also Human aspects Personal protective equipment (PPE), 187 Personnel, 167, 193–194, see also Human aspects Pfaender studies, 150

289 PFRA, see Prairie Farm Rehabilitation Administration (PFRA) Pharmacopoeia, see also Chemicals acid compound types, 243–246 acidizing, 243–247 antibacterial (antimicrobial) agents, 249–255 chlorination, 249–252 chlorine dioxide, 252–253 designer biocidal compounds, 254 fundamentals, 242–243 heat, 254 hydrogen peroxide, 253–254 organic acids, 254 ozone, 253 PSDD functions, 247–249 sequestering, 247–249 well treatments, 246–247 Phase contrast, 145 pH factor blended method treatments, 255 chemical incrustation, 21–22 chlorine, 249–250 corrosion, 25 hydroxyacetic acid, 245 metallic oxides, 35 physiochemical analysis, 142 Phosphoric acid, 178, 245 Phosphorus-containing compounds, 181 Physical agitation advanced redevelopment methods, 231–242 blended method treatments, 256 cold carbon dioxide, 231–233 conventional redevelopment, 229–230 fluid-pulse tools, 237–240, 242 principles, 229 sonic disruption, 233–237 vibratory disruption, 233–237 Physiochemical analysis, 141–142, 143 Piezometric data, 158–159 Piezometric maps, 159 Pipes, cleanliness, 105 Pitting corrosion frequency, 25 Planning considerations, 73, 84–86 Plant manager, 170 Plastic deterioration, 26 developing world circumstances, 116 usage, 88 Plume control wells, 86 Political system, 10 Polyacrylamides, 181, 247 Polyelectrolytes, 181, 247, 248 Polyphosphates, 247, 248 Poly-pigs, 260 Polystyrene, 26

290 Polyvinyl chloride (PVC) casing, 61, 89 material selection, 92 plastic deterioration, 26 Porosity clogging, iron oxides, 44 Portable pumps and bailers, 109–110 Portable sonic flow meters, 193 Portland cement, 58, 61 “Poster child” for cheap, 63 Posttreatment, rehabilitation methods, 257–258 Post-World War II period, 4 Potablewater, 12 Potassium permanganate, 180, 183 Potential reactions, 182 Potentials and electrical currents, stray, 62–63, 259 Power costs, formula, 70–72 Power Line Delivery, 63 Power supply, 107–108 PPE, see Personal protective equipment (PPE) Practical Manual of Groundwater Microbiology (D.R. Cullimore) biofouling, 27 blended chemical heat treatment, 255 culturing methods, 146 heat as preventative treatment, 181 historical developments, 7 monitoring, decision-making, 128 prepared BART methods, 146 pumped sampling, 151 Practice for decontamination of field equipment used at nonradioactive waste sites (D 5088), 106 Practice for design and installation of ground water monitoring wells in aquifers (D 5092), 91–92 Prairie Farm Rehabilitation Administration (PFRA), 185 Pressure acidization rehabilitation, 217 measurement recommendations, 139–140 safety, 238 Pressure injection, 246 Prevention practices abstraction wells, 107–108 airlift development, 99–100 array design recommendations, 115–116 automobile industry, 82–84 bailing, 96–99 casing, 87–89 Cliff Notes version of design aspects, 113–115 contamination prevention, 105–106 conventional choices, 102–104 costs, 119, 121, 194 dentistry sector, 82–84 design and construction considerations, 84–94 developing world locations, 116–117

Index development, 94–105 efficiency, 90 extraction wells, 107–108 fluid-pulse development, 104 fundamentals, 81 ground truths, 81 grouting, 93–94 hydraulics, 90 intakes, 90–93 jetting, 100–101 life cycle, 81–82 method descriptions, 95–101 monitoring wells, 108–110 overpumping, 96 overview, 122 planning considerations, 84–86 protection, 110–112 pump choices and actions, 106–112 reasons for, 94–95 role of well purpose, 86 screens, 90–93 sealing, 93–94 segment lengths, 105 selection, 106–110 structural limits, 104–105 surging and pumping, 96–99 tools, 105 utilizing surge block, 96–99 water supply wells, 107–108 well design, 86–87 well houses, 115 Preventive treatments and actions acids, 176, 177 and/sediment pumping, 171–172 biocides, 176–181 biofouling, 174, 187 blended method treatments, 181–182 carbon dioxide adjustment, 186 chemical emplacement, 184 chemical handling hazards, 188 chemical mixing, 188–189 chemical removal and recovery, 184–185 chemical treatments, 174–182 classes and properties, 176–182 corrosion, 172–174 cost-benefit analysis, 189–192 cost effectiveness, 174–176, 194–195 costs, 189–195 dispersing agents, 181 electromagnetically charged surfaces, 185–186 feeders in wells, 185 fundamentals, 171 health and safety concerns, 187–189 inorganic encrustations, 174 mechanical agitation and augmentation, 182–184

291

Index mixing chemicals, 188–189 MSDSs, 182 oxidizing compounds, 176–181 penetrating agents, 181 potential reactions, 182 professionalism, 174, 176 protection against personal injury, 187, 188–189 radiation, 185 regulatory aspects, 186 security, 180 sequestering agents, 181 in situ techniques, 185–186 time, 189–195 well failure, 191–192 Pricing, rehabilitation work, 215–216, see also Costs Private water supply, xxi Proactive treatment approach, see Prevention practices Problems, categories of, 14 Procedures overview, 122 Processes, 73 Proctor & Gamble, 247 Productivity, 202 Professionalism, 174, 176 Properties, chemicals, 176–182 Protecting Health and Safety at Hazardous Waste Sites: An Overview, 204 Protection, 110–112, 187, 188–189 Protocol, 126–130 ProWell Technologies, 237 PSDD, see Penetrating, sequestering, detergent, and dispersing (PSDD) compounds Pseudomonas sp., 48 Pseudotechnical discussions, 264 Public water supply (PWS) wells, xxi, 70 Puca Glacier, 30 Pump-and-treat systems, 5–6 Pump choices and actions abstraction wells, 107–108 “Cliff Notes” version, 113–115 extraction wells, 107–108 monitoring wells, 108–110 protection, 110–113 selection, 107–110 water supply wells, 107–108 Pump Life Cycle Costs: LCC Analysis for Pumping Systems, 75 Pumped sampling, 151–152 Pumping casing failure, 61 rates, 157 surging and, 98–99 Pumps, 19, 132–141 PVC, see Polyvinyl chloride (PVC) PWS, see Public water supply (PWS) wells

Q Quagga mussel, 28 Qualifications, personnel, 169 Quality assigning economic value, 76 data collection, 129–130 degradation, 34–37 role of well purpose, 86 sample, monitoring wells, 47 water, 124–125, 192 Quarrying, see Mining Questions, 210–212

R Radiation, 185 Rants, 29, 106 Rationale, 119–121, 166 Reactivity, chemical treatments, 174, 217–219 Reasons, prevention practices, 94–95 Recommendations analysis, 144–150 benchmarking, 132–136 biofouling monitoring, 143–144 biological monitoring, 149 collection sampling representativeness, 152–154 culturing methods, 145–148 current state of the art, 144 data collection requirements, 156 development data, 159–161 downtime history, 161–162 electrical power, 140–141, 158 electrochemical in-line sensors, 154–155 file format issues and purpose, 162–163 geologic regime, 159 hydrogeological information, 158–159 maintenance logs, 161–163 maintenance monitoring programs, 127–130 method selection, 143–144 microscopic analysis, 144–145 minimalism, 148–150 physiochemical analysis, 141–142 piezometric data, 158–159 piezometric maps, 159 pressure measurements, 139–140 pumped sampling, 151–152 pumping rates, 157 pump performance, 132–141 reading list, 269–272 sampling methods, 150–154 sensory examination, 130, 132 summary, 156–163 surface collections, slides or coupons, 152 system pressure, 157 tracking well performance, 137–138

292 video, historical comparison, 158 visual inspection, 130, 132 water level, 139, 140, 157–158 water sampling, 141 well data file features, 156–157 well discharge measurements, 139 well performance, 132–141 Recommended reading list, xxii Reconstruction, 122, 219–221 Records damage from poor, 216–217 future reference, 260 human aspects, 169 improper rehabilitation and development, 61–62 maintenance monitoring programs, 123–124 resistance, 123 storage location, 161 TV records, 162–163 video comparison, 158 Recovery and removal, 184–185 Recovery and treatment systems, xxi Recovery wells conventional development, 103 efficiency reductions, 72 issues, xxi reactivity, chemical treatments, 218 role of well purpose, 86 sand and silt, 16 Recreational economic value (REV), 76 Redox (Eh) biofouling, 39, 43 chemical incrustation, 21 fringe (front), 43 physiochemical analysis, 142 References, 272–277 Regulatory aspects, 186, 267 Rehabilitation costs, 69–70, 119, 121 example, 78–79 ground truths, 81–82 historical developments, 3 improper, 61–62 overview, 122 planning before executing, 198 pressure acidization type, 217 technical effectiveness, 210–211 terminology, 11 Rehabilitation and reconstruction planning access, 205–207 bids, 208–210, 226–227 business considerations, 208–210 chemical selection, 217–219 choosing, 216 consultant specifier/observer role, 227 consultants relationship, 205–207 contractors, 202–207

Index costs, 212–216 damage, 216–217 decisions after problems, 197 deficiencies of specifications, 221–223 effluent waste water containment, 209–210 facilities, 198–201 fundamentals, 197 management, 198–207 methods, decision making on, 210–221 pricing of rehabilitation work, 215–216 productivity, 201–202 questions to ask, 210–212 reconstruction, 219–221 response, 205–207 responsibility for work, 198–200 safety, 201–205 solutions, 200–201 specification requirements, 208–210, 221–227 Rehabilitation methods acid compound types, 243–246 acidizing, 243–247 advanced redevelopment methods, 231–242 antibacterial (antimicrobial) agents, 249–255 application summary example, 25–257 blended method treatments, 255–256 chemicals used in rehabilitation, 242–255 chlorination, 249–252 chlorine dioxide, 252–253 cold carbon dioxide, 231–233 conventional redevelopment, 229–230 designer biocidal compounds, 254 fluid-pulse tools, 237–240, 242 follow-up truisms, 258–260 fundamentals, 229, 242–243 heat, 254 hydrogen peroxide, 253–254 organic acids, 254 ozone, 253 physical agitation, 229–242 posttreatment, 257–258 principles, 229 PSDD functions, 247–249 sequestering, 247–249 sonic disruption, 233–237 vibratory disruption, 233–237 well treatments, 246–247 Relocation, wells, 211 Remediation business losses, 73 problems, 34–37 terminology, 11 Remediation wells, 72 Removal and recovery, 184–185 Requirements, specifications, 225–226 Resource depletion costs, 67–68 Resources, 191–192 Respect, human issues, 266–268

Index Responsibilities, 170, 198–200 Restoration, 11 REV, see Recreational economic value (REV) Rio Grande Compact, 78 Risks, complacency, 188 Rock aquifers, 102 Rockslides, see Mass wasting Rogers, (William) Bill, 185, 255 Role, well purpose, 86 Roscoe Moss Company, 57, 59 Rural residential drinking water, 77 Russian research, 7 Rwandan civil strife, 2

S S, see Sulfur (S) Safety assurance, 201–202 contractor considerations, 203–205 preventive treatments and actions, 187–189 productivity, 202 safety assurance, 201–202 Safety and Health Requirements Manual, 182 Saline water, 23 Samples, 47, 150–154 Sand deterioration, causes and effects, 13, 15–17 filter packs, 92 infiltration, 15 preventive treatments and actions, 171–172 sealing, 15–16 SCADA (supervisory, control, and data acquisition), 136, 193–194 Schedules first year, 163, 164 interference with exacting installation, 17 long-term, 163, 165, 166 maintenance planning and execution, 192 rationale, 166 Schnieders studies, 128 Screens damage, 216 design and construction considerations, 90–93 sand deterioration, 13 Sealing, 93–94 Security, 180 Segment lengths, 105 Seismic activity, 159, see also Earthquakes Sensitive receptor economic value, 77–78 Sensory examination, 130, 132 Septic test, 150 Sequestrants, 181, 247–249, see also Penetrating, sequestering, detergent, and dispersing (PSDD) compounds Serratia sp., 48

293 SFCDs, see Suction flow control devices (SFCDs) Shockblasting, 234 Shock treatment, 233–237 Silt, see also Sand bifouling, 27 deterioration, 13, 15–17 Sinclair, Upton, 9 Site conditions, 17 Skin effect, 8 Sludge, 185 Slump, see Mass wasting Slurries, 185 Small facility public water supply, xxi Smith and Tuovinen system, 152, 153 Sn, see Tin (Sn) Snow, John, 3 SO, see Sulfates (SO) SOB, see Sulfur-oxidizing bacteria (SOB) Sobsey studies, 150 Societal factors, 190 Society for Technical Communication (STC), 205 Soil creep, see Mass wasting Solutions, 200–201 Sonar-Jet treatment, 234, 239 Sonic-based tools, 193, 231, 233–237 Sound changes, 122–123, 132, see also Human aspects Specifications contractor considerations, 208–210 deficiencies of specifications, 221–223 requirements, 225–226 writing, 200–201, 219, 221 Spills, hazardous, 188 Spoiling wells, 2 Spot dosing, 246 Spreadsheet approach, 189–190 SRB, see Sulfate-reducing bacteria (SRB) Stainless steel corrosion, 37–39, 89 damage, 216 submersible centrifugal pumps, 109 Standard guide for development of ground-water monitoring wells in granular aquifers (D 5099), 95 Standard guide for maintenance and rehabilitation of ground-water monitoring wells (D 5978), 181 Standard Methods for the Examination of Water and Wastewater, 128, 142 Standard Methods Section 9240: Iron and sulfur bacteria, 144–145, 147, 152 Standards, see also specific standard ANSI/ASTM, 277–278 environmental sector, role in shaping, 5 planning, 85–86 relevant, 277 Statement of work (SOW), 167

294 Static water levels (SWLs), 56, 137 Steam engines, 3 Steinbrecher Engineering hydropuls technology, 237 Step-drawndown test, 161 Stray potentials and electrical currents, 62–63, 259 Structural deformation and failure casing issues, 59–61 earthquakes, 51–53 electrochemical corrosion, stray potentials, 62–63 fundamentals, 51 grouting, 57–58 human causes, 55–63 improper procedures and mistakes, 61–62 mass wasting, 53–54 mine blasting, 56–57 mining, 55–56 natural causes, 51–54 Structural limits, 105 Subjective judgment, 144 Submersible centrifugal pumps, 109 Submersible motors, 110 Submersible well pumps, 107–108, 110 Subsurface Technologies, 186, 233 Suction flow control devices (SFCDs) installation, 260 pump protection, 111 pump selection, 107 reconstruction using, 220 sand/sediment pumping, 171–172 Sulfamic acid, 244 Sulfate-reducing bacteria (SRB) culturing methods, 145–146, 148 metallic corrosion, 37 Sulfates (SO) metallic corrosion, 37 monitoring and remediation problems, 34–35 physiochemical analysis, 142 Sulfur-oxidizing bacteria (SOB), 41 Sulfur (S) biofouling, 39–43, 44 hydraulic impacts, 46 microscopic analysis, 144 monitoring and remediation problems, 34–37 performance effects, 43–44, 46–48 physiochemical analysis, 142 redox fringe, 43 stability range, 42 Sulfur springs, 41, 44, 45 Summary, recommendations, 156–163 Surface collections, slides or coupons, 152 Surface water, 12 Surficial quarrying, see Mining Surge block-airlift system, 183

Index Surge block development, 230 “Surge in tank” procedures, 183 Surging and pumping, 96–99, 102 Suspended sediment in water samples (D 3977), 142 Sustainable system, 121 Sustainable Well Series Aqua Freed, 232 blended chemical heat treatment, 255 case histories, 263 documented improvements, xxii monitoring, decision-making, 128 Sutherland system, 189 Swabbing, 216 System demand changes, 157 System failure, 69 System pressure, 157

T Tables, list of, xv TC, see Total coliform (TC) bacteria Technical writers chemical selection specifications, 219 counterproductive tendencies, 200–201 health and safety plans, 204–205 well rehabilitation specifications, 221 Televisions, see Video cameras Temperature, 142, see also Heat and heating Terminology, 11–12 Testing, 130–155 The Graduate (movie), 116 There Will Be Blood (movie), 9 Third world countries, see Developing world locations Threaded casing, 60 Threaded joints, 89 Time, 189–195 Timescale, 166 Tin (Sn), 36 TLM GmbH, 237 Tools care issues, 105 cleanliness, 105–106 improper rehabilitation and development, 61–62 prevention practices, 105 Total coliform (TC) bacteria, 47 Total dynamic head (TDH), 19, 137 Toxic accumulation, 49, 700 Tracking well performance, 137–138 Training, 5, 10–11 Transducer-based systems, 193 Transfer hose troubles, 188 Transportation, 60 Trash, see Junk in wells

295

Index Treatment plants, 49–50 Treatments acidizing, 246–247 ground truths, 82 maintenance monitoring programs, 125 overview, 122 Treskatis, Houben and, studies, 3–4, 128 Tropical storms, 64 Troubleshooting summary guide, 125 Truisms, 258–260 Tuhela-Reuning, Touvinen and, studies, 127–128 Tuovinen, Smith and, system, 152, 153 Tuovinen and Tuhela-Reuning studies, 127–128 Turbidity, 34, 56 Turbine flow meter installations, 192

U U, see Uranium (U) Underground pillow-and-room mining, see Mining Uniformity, casing, 60 University of Colorado, 30 University of Mississippi, 237 Unscreened, open-boreholed completions, 93 Upside-down reasoning, 174 Uranium (U), 49 U.S. Army Corps of Engineers (USACE) acids for maintenance treatment, 176 blended method treatments, 182, 255 monitoring recommendations background, 128 MSDSs, 182 U.S. Environmental Protection Agency (USEPA), 203 U.S. Geological Survey (USGS), 12 Utilizing surge block, 96–99

V Vapors, hazardous, 188 Vaught, Mike, 65 Vegetation program (crash-type), 54 Vehicles, 62, 121 Venturi type flow meters, 193 Versatility, 227 Vertical well screens, 63 Vibration, see also Human aspects changes in, 132 disruption, redevelopment methods, 233–237 redevelopment methods, 231 Video cameras damage, 216 historical comparison, 158 records purpose and format, 162–163 shock treatments, 236

storage location, 161 visual inspection, 130, 132 “Voice” of book, xxii–xxiii V-slot screens, 101

W “Walmarting,” 10 Wastewater plants, 121 Water level data, 157–158 Water level measurements, 139, 140 Water quality, 124–125, 192 Water sampling, 141 Water supply economic value, 77 Water supply wells, 93, 107–108 Water Systems Council, 137 Water Systems Handbook, 138 Water table maps, 159 Water well construction standard (ANSI/NGWA 01) casing, 60 chlorine, 177, 249 construction, 89 filter pack materials selection, 92 grouting, 57, 59 installations, 63 pump selection, 107 reasons for development, 95 sand and silt deterioration, 13 screen design, 91 Water Well Developers, 234 Water wells (ANSI/AWWA 100), 63, 91 Water Well Sustainability in Ontario, 19 Welded joints, 89 Welenco, 234 Well cleaning, 11 “Well-cleaning feast,” 3 Well data file features, 156–157, see also Records Well design, 86–87, see also Design and construction considerations Well discharge measurements, 139 Well disinfection (ANSI/AWWA C654), 177, 249 Well houses, 115 Wellmaster, 113, 258–259 Well performance, 132–141, see also Performance Well sealing, 93–94 Well treatments, 246–247, see also Treatments “What the ...” department, 174 White slim phenomenon, 41, 4445 Wires, cleanliness, 105 Wish list, 265–266 World Wide Web, 264 Writers chemical selection specifications, 219 counterproductive tendencies, 200–201

296 health and safety plans, 204–205 well rehabilitation specifications, 221

Y Yield, 17–19

Index Z Zebra mussels, 28–29 Zeta Rod device, 185 Zinc (Zn), 36, 47, 92 Zn, see Zinc (Zn)

Color Figure 1.2  Pump impellers clogged by oxidized iron deposition. Extraction well, DOE Fernald Preserve (Ohio).

Color Figure 2.2  Precleaning flow from a clogged well.

Color Figure 2.9  Corroded submersible pump end (southern Colorado).

Color Figure 2.12  Mixed biofilm from water well samples (normal light photomicrograph).

Color Figure 2.23  Example of mild steel well pump discharge pipe tuberculation.

Color Figure 2.25  Gallionella-dominated water well biofilm (normal light photomicrograph).

Color Figure 2.26  Mixed filamentous biofilm featuring MnIV oxide mineralogy (normal light photomicrograph (PMG)).

Color Figure 2.29  Thothrix-dominated sulfur-oxidizing biofouling of geotechnical drains (Bureau of Reclamation–Stuart Smith photographs).

Color Figure 2.30  White sulfur biomass associated with artesian spring (in actuality, an uncontrolled well) in western Ohio.

Color Figure 2.39  PVC casing distorted by heat due to improper cement grouting (photo by Gary L. Hix). The casing is pushed in and cracked at the visible joint and the foreground surface is blistered.

Color Figure 5.2  Some indications that you may have biocorrosion problems in the well (Ohio). Corrosion hole (middle section, top), above pump was losing several 100 gpm.

Color Figure 5.10  A selection of BART reactions from an alluvial aquifer well.

Color Figure 5.11  Inoculated BRS-MAG tubes and syringe applicator. Sample is injected into vial.

            (a)                 (b) Color Figure 5.12  Wellhead flow cell collector: (a) element and (b) as installed on a wellhead.

Color Figure 5.14  Field analysis of drive cores for physicochemical and biochemical parameters (Iowa).

(d) Color Figure 8.7  Illustration of features of flexible well pump discharge pipe. (d) full installation view.