Water Wells and Boreholes

Bruce Misstear teaches hydrogeology at Trinity College Dublin, where he is a Fellow of the College. He previously worked for an international firm of consulting engineers, carrying out groundwater development projects in many countries in Europe, Africa, the Middle East and Asia. His current research interests include groundwater pollution, aquifer recharge and groundwater engineering.David Banks is a consulting hydrogeologist with Holymoor Consultancy Ltd in the UK and is a Research Fellow at the University of Glasgow. His particular interests include mine water, hydrochemistry and ground source heat. He has worked extensively internationally in Scandinavia, Eastern Europe, Russia, Central Asia, South America and Africa.The late Lewis Clark worked for many years with the Water Research Centre in the UK before setting up his own consultancy. He was involved in many groundwater projects internationally, especially in Europe, Africa and Asia. He was also a Visiting Professor in Hydrogeology at University College London.

"This book is important. There are now many books on hydrogeology and groundwater, but there are very few that deal with the most essential fundamental part of hydrogeology. Whether you work in the field, lab or office, you need to know how to get into the subsurface, and how to make observations and take measurements that enable an understanding of the characteristics of the groundwater flow and bio-chemical system in the rocks and soils." (David Ball, Irish Groundwater Newsletter, Issue 55, May 2017)"An excellent resource for the geologist-in-training as well as the seasoned groundwater professional." (Michael Schnieders, Groundwater, April 2018)

• Preface to Second Edition xPreface to First Edition xiLewis Clark (1937–2004): An Appreciation xiiiAcknowledgements xiv1 Introduction 11.1 Wells and boreholes 11.2 Groundwater occurrence 51.2.1 Aquifers, aquicludes and aquitards 51.2.2 Porosity and aquifer storage 121.3 Groundwater flow 171.3.1 Darcy’s equation 171.3.2 General equations of groundwater flow 211.3.3 Radial flow to wells 252 Groundwater Investigations for Locating Well Sites 282.1 Desk studies 312.2 Field reconnaissance 352.3 Well survey 362.4 Geophysical surveys 412.4.1 Electrical resistivity 422.4.2 Electromagnetics 492.5 Drilling investigations 522.6 Groundwater resources assessment 592.6.1 Inflow estimation: direct recharge 612.6.2 Inflow estimation: indirect recharge 642.6.3 Aquifer response analysis 652.6.4 Outflow estimation 662.6.5 Catchment water balance and modelling 662.7 Groundwater quality 692.7.1 Introduction 692.7.2 Chemical composition of groundwater 692.7.3 Groundwater for potable supply 722.7.4 Groundwater for irrigation 772.8 Pollution risk assessment and prevention 782.8.1 Groundwater vulnerability 792.8.2 Wellhead protection areas 812.8.3 Estimating the pollution risk for a new well site 852.9 Planning the well scheme 873 An Introduction to Well and Borehole Design 913.1 Drilled wells 913.1.1 General design principles 913.1.2 Wells in crystalline aquifers 963.1.3 Wells in consolidated aquifers 1003.1.4 Wells in unconsolidated aquifers 1043.1.5 Economic considerations in well design 1073.2 Hand‐dug wells 1093.2.1 Design for yield 1133.2.2 Design for health 1143.3 Infiltration galleries 1163.4 Radial collector wells 1203.5 Observation boreholes 1203.6 Exploration boreholes 1253.7 Pump selection 1253.7.1 Vertical turbine pumps 1283.7.2 Electrical submersible pumps 1293.7.3 Motorized suction pumps 1333.7.4 Helical rotor pumps 1343.7.5 Hand pumps 1354 Issues in Well Design and Specialist Applications 1404.1 Choice of construction materials 1404.1.1 Strength 1414.1.2 Jointing system 1414.1.3 Durability 1434.1.4 Chemical inertness 1434.1.5 Standards 1444.2 Casing 1454.2.1 Steel casing 1454.2.2 Plastic and fibreglass casing 1464.3 Screen 1474.3.1 Slot design and open area 1474.3.2 Slot width 1494.4 Gravel pack design 1504.4.1 Natural gravel pack 1504.4.2 Artificial gravel pack 1514.5 Hydraulic design 1544.5.1 Partial penetration effects 1564.5.2 The damage zone and well bore skin 1584.5.3 Gravel pack loss 1594.5.4 Screen entrance loss 1594.5.5 Well upflow losses 1624.6 Economic optimization of well design 1674.6.1 General principles 1674.6.2 Example 1684.7 Groundwater and wells for heating and cooling 1714.7.1 Groundwater for cooling 1724.7.2 Heating with groundwater: geothermal fluids 1734.7.3 Heating with groundwater: heat pumps 1744.7.4 Well configurations 1754.8 Well doublets 1774.8.1 Hydraulic equations 1784.8.2 Feedback and breakthrough 1784.8.3 Water chemistry 1794.9 Recharge wells 1804.9.1 Purpose 1804.9.2 Construction of injection wells 1824.9.3 Installations 1834.9.4 Testing and operation 1844.9.5 Clogging of recharge wells 1844.9.6 Seismic risk from water injection 1884.10 Aquifer storage and recovery 1885 Well and Borehole Construction 1915.1 Percussion (cable‐tool) drilling 1935.1.1 Drilling in hard‐rock formations 1965.1.2 Drilling in soft, unstable formations 1985.1.3 Light‐percussion drilling 2015.2 Rotary drilling 2025.2.1 Direct circulation rotary 2025.2.2 Fluids used in direct circulation rotary drilling 2085.2.3 Reverse circulation 2125.2.4 Top‐hole and down‐the‐hole hammer drilling 2155.2.5 Dual rotary 2175.2.6 Borehole testing during drilling 2185.2.7 Methods of casing and screen installation 2205.3 Sonic drilling 2215.4 Auger drilling 2225.5 Jetting 2235.6 Direct push and drive sampling 2245.7 Driving of well‐points 2265.8 Manual construction 2265.9 Well development 2285.9.1 Well and aquifer damage 2295.9.2 Developing the well 2295.9.3 Developing the aquifer around the well 2295.9.4 Methods of development 2315.9.5 Disinfecting the well 2405.10 Wellhead completion 2406 Formation Sampling and Identification 2446.1 Observing the drilling process 2446.1.1 Observing the drilling process in hard‐rock aquifers 2476.2 Collecting formation samples 2486.2.1 Disturbed formation sampling 2486.2.2 Undisturbed formation sampling 2566.3 Description and analysis of drilling samples 2606.3.1 Characterizing disturbed samples 2616.3.2 Characterization of representative samples 2616.3.3 Characterization of undisturbed samples 2676.4 Downhole geophysical logging 2696.4.1 The geophysical logging package 2706.4.2 Organizing a geophysical logging mission 2756.4.3 On arriving on site 2756.4.4 Formation logs 2766.4.5 Fluid logs 2836.4.6 Well construction logs 2876.5 Downhole geophysical imaging 2876.6 Distributed (fibre‐optic) temperature sensing (DTS) 2906.7 Preparing a composite well log 2927 Well and Borehole Testing 2957.1 Objectives of test pumping 2957.1.1 Well performance 2957.1.2 Water quality 2967.1.3 Sustainability 2967.1.4 Environmental impacts 2987.1.5 Aquifer properties 2987.2 Planning a well pumping test 2987.2.1 Before starting 2987.2.2 When to test pump 3017.2.3 Consents and permissions 3017.2.4 Equipment 3027.2.5 The observation network 3087.2.6 Recording of data 3137.3 Types of pumping test 3157.3.1 Dimension pumping 3157.3.2 The step test 3157.3.3 Medium to long‐term (constant rate) test 3167.3.4 Recovery test 3177.4 Analysis of test pumping data from single wells 3177.4.1 Fundamentals 3177.4.2 The misuse of test pumping analysis 3187.4.3 Well performance – the step test 3207.4.4 Steady-state analyses 3237.4.5 Time‐variant analysis 3267.4.6 Analysis of recovery tests 3317.5 Multiple wells 3347.5.1 Steady-state analysis of multiple pumping wells 3347.5.2 Time‐variant analysis of multiple wells 3347.5.3 Application of the Cooper‐ Jacob approximation to multiple wells 3347.6 The shape of the yield‐drawdown curve: Deviations from the ideal response 3357.6.1 A non‐infinite aquifer: Presence of an impermeable barrier 3367.6.2 Recharge during a pumping test 3367.6.3 Unconfined aquifers: Delayed yield 3397.6.4 Poroelasticity, subsidence and the ‘Noordbergum Effect’ 3417.6.5 Large diameter wells 3417.6.6 Diagnostic plots 3427.7 Interpretation of pumping and recovery test data in hard‐rock aquifers 3447.7.1 High yielding hard‐rock wells 3457.7.2 Low‐yielding hard‐rock wells 3467.7.3 Sustainable yield of hardrock wells 3487.8 Single borehole tests: slug tests 3507.8.1 Slug tests 3507.8.2 Packer testing 3527.9 Tracer tests 3537.10 Geophysical logging during pumping tests 3557.11 Test pumping a major well field: the Gatehampton case study 3567.12 Record‐keeping 3598 Groundwater Sampling and Analysis 3618.1 Water quality parameters and sampling objectives 3638.1.1 Master variables 3638.1.2 Main physicochemical parameters 3638.1.3 Major ions 3648.1.4 Drinking water 3658.1.5 Water for agricultural and industrial purposes 3678.1.6 Pollution‐related parameters 3678.1.7 Indicator parameters 3698.1.8 Microbiological quality and indicator parameters 3708.2 Field determinations 3738.2.1 The purpose of field determinations 3738.2.2 Downhole sondes and throughflow cells 3748.2.3 Field kits for other parameters 3758.2.4 Emergency water supply 3778.3 Collecting water samples from production wells 3808.3.1 The sample line 3808.3.2 When to sample: well testing 3808.3.3 When to sample: production wells 3828.4 Collecting water samples from observation boreholes 3838.4.1 Preparation for sampling 3838.4.2 Bailers and depth samplers 3848.4.3 Simple pumps 3868.4.4 Submersible pumps 3868.4.5 Other pumps 3878.4.6 Sampling at specific depths 3898.4.7 Sampling for non‐aqueous phase liquids 3918.5 Sample filtration, preservation and packaging 3928.5.1 Sampling order 3948.5.2 Physicochemical parameters 3948.5.3 Microbial parameters 3968.5.4 Inorganic parameters: acidification and filtration 3978.5.5 Inorganic parameters: sampling 4008.5.6 Organic parameters 4008.5.7 Stable isotopes 4038.5.8 Dissolved gases 4048.6 Packing and labelling samples 4068.7 Quality control and record keeping 4078.8 Sample chemical analysis 4088.9 Hydrochemical databases 4129 Well Monitoring and Maintenance 4149.1 Factors affecting well system performance 4159.1.1 Physical processes 4159.1.2 Chemical processes 4169.1.3 Microbiological processes 4219.1.4 Well design and construction 4239.1.5 Well system operation 4239.2 Monitoring well system performance 4249.2.1 Monitoring well performance 4259.2.2 Well inspection tools 4339.2.3 Pump performance 4349.2.4 Water quality monitoring 4369.2.5 Monitoring microbial processes 4369.3 Well maintenance and rehabilitation measures 4379.4 Well decommissioning 44310 Well and Borehole Records 44610.1 Well archives 44610.2 Operational well databases 44710.3 An example of a hydrogeological database ‐ Afghanistan 454Appendix 1 Units and Conversion Tables 458Appendix 2 Hydraulic Equations forGroundwater Engineers 460Appendix 3 Health and Safety Plans 464Appendix 4 World Health OrganizationDrinking Water Guidelines 467Appendix 5 FAO Irrigation WaterQuality Guidelines 473References 475Index 506