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Groundwater Lowering in Construction: A Practical Guide to Dewatering

SECTION I. PRINCIPLES I. Groundwater Lowering: A Personal View and Introduction by Pat M. Cashman The History of Groundwater Theory and Practice INTRODUCTION FROM THE EARLIEST TIMES TO THE SIXTEENTH CENTURY FROM THE RENAISSANCE PERIOD TO THE NINETEENTH CENTURY PROGRESS FROM A QUALITATIVE TO A QUANTITATIVE SCIENCE Seepage towards Wells Land Drainage in the Eighteenth and Nineteenth Centuries Kilsby Tunnel, London to Birmingham Railway Early Theory - Darcy and Dupuit LATER THEORETICAL DEVELOPMENTS Verifications and Modification of Darcy Non-Steady-State Flow GROUNDWATER MODELLING EARLY DEWATERING TECHNOLOGY IN BRITAIN PRACTICAL PUBLICATIONS Principles of Groundwater Flow INTRODUCTION HYDROLOGY AND HYDROGEOLOGY The Hydrological Cycle Geology and Soil Mechanics PERMEABILITY, HYDRAULIC CONDUCTIVITY AND GROUNDWATER FLOW Drivers for Groundwater Flow Darcy’s Law Darcian and Non-Darcian Flow Groundwater Velocities Effect of Groundwater on Soil and Rock Properties AQUIFERS, AQUITARDS AND AQUICLUDES Unconfined Aquifers Confined Aquifers Aquicludes Aquitards and Leaky Aquifers Aquifer Parameters AQUIFERS AND GEOLOGICAL STRUCTURE Multiple Aquifers beneath London Water Pressures Trapped beneath a Trench Excavation AQUIFER BOUNDARIES Interaction between Aquifers and Surface Water Interaction between Aquifers Tidal Groundwater Conditions Recharge Boundaries Barrier Boundaries Discharge Boundaries GROUNDWATER CHEMISTRY Chemical Composition of Groundwater Field Monitoring of Groundwater Chemistry GROUNDWATER TEMPERATURES EFFECT OF CLIMATE AND WEATHER Permeability of Soils and Rocks INTRODUCTION WHAT IS PERMEABILITY?Intrinsic Permeability Hydraulic Conductivity Electro-Osmotic Permeability PERMEABILITY IN SOILS PERMEABILITY IN ROCK PROBLEMS WITH ASSESSING PERMEABILITY WORKING WITH PERMEABILITY IN THE REAL WORLD Permeability at Different Scales Karstic Flow in Rocks METHODS OF DETERMINING PERMEABILITY Non-Quantitative Assessment Methods Quantitative Assessment Methods Groundwater Models INTRODUCTION GROUNDWATER MODELLING COMPLEXITY IN MODELLING Relevance of Models Typical Simplifications Used in Modelling CONCEPTUAL MODELS ANALYTICAL MODELS Empirical Models Mathematical Models Using Closed-Form Solutions Numerical Models OTHER TYPES OF MODELS THE ROLE OF GEOLOGICAL STRUCTURE IN MODELS FLOW TO WELLS AND SLOTS Planar Flow to Slots Radial Flow to Wells Zone of Influence Well Losses Effect of Diameter of Well Equivalent Wells and Lines of Wells MODELLING GROUNDWATER CONTROL TECHNOLOGY SELECTING AND APPLYING AN APPROPRIATE MODEL Objectives of Groundwater Control INTRODUCTION GROUNDWATER CONTROL - THE OBJECTIVES GROUNDWATER CONTROL AS PART OF TEMPORARY WORKS GROUNDWATER MANAGEMENT IN EXCAVATIONS GROUNDWATER, EFFECTIVE STRESS AND INSTABILITY GROUNDWATER BEHAVIOUR IN HIGH- AND LOW-PERMEABILITY SOILS AND ROCKS Drained and Undrained Conditions Drained Pore Water Pressure Responses during Excavation Undrained Pore Water Pressure Responses during Excavation Intermediate Conditions between Drained and Undrained Response Relevance of Drained and Undrained Conditions to Groundwater Control Problems POSSIBLE APPROACHES TO GROUNDWATER CONTROL SURFACE WATER PROBLEMS CHANGING GROUNDWATER CONDITIONS Groundwater Problems for Excavations in Soils INTRODUCTION GROUNDWATER MANAGEMENT PROBLEMS IN SOILS LARGE-SCALE AND SMALL-SCALE INSTABILITY CAUSED BY GROUNDWATER SLOPE INSTABILITY BASE INSTABILITY Base Instability by Buoyancy Uplift Base Instability by Fluidization Due to Upward Seepage Gradients Base Instability by Internal Erosion Base Instability by Piping LOCALIZED GROUNDWATER PROBLEMS Drainage of Slopes and Formation Perched Water Table High-Permeability Zones Spring Sapping and Internal Erosion GROUNDWATER PROBLEMS WHEN TUNNELLING IN SOILS Groundwater Instability Effects in Tunnel Faces Buoyancy Uplift in Tunnels Groundwater Instability Effects on Shaft Construction Groundwater Instability Effects on Other Underground Works Groundwater Problems for Excavations in Rock INTRODUCTION GROUNDWATER MANAGEMENT PROBLEMS IN ROCK GROUNDWATER EFFECTS ON EXCAVATIONS IN ROCK Groundwater and Small-Scale Fractures Effect of Isolated Highly Permeable Fractures Groundwater and Larger-Scale Geological Structure Weathered Rocks Soluble Rock and Karst Groundwater Conditions GROUNDWATER-INDUCED INSTABILITY IN ROCK SLOPE INSTABILITY BASE INSTABILITY Base Instability by Buoyancy Uplift Enlargement/Erosion of Water Pathways LOCALIZED GROUNDWATER PROBLEMS Localized Erosion Due to High Groundwater Velocities Erosion or Collapse of Weak or Weathered Zones Perched Water Conditions Localized Concentration of Water Inflow Water Trapped by Rock Structure GROUNDWATER PROBLEMS WHEN TUNNELLING IN ROCK Groundwater Management during Tunnel Construction Sudden Inflows Groundwater Problems during Shaft Sinking in Rock Groundwater Problems during Other Underground Works SECTION 2. DESIGN Methods for Control of Surface Water and Groundwater INTRODUCTION CONTROL OF SURFACE WATER Collection and Control of Surface Water Run-Off Treatment of Surface Water Run-Off METHODS OF GROUNDWATER CONTROL EXCLUSION METHODS DEWATERING METHODS Open Pumping and Pre-Drainage Methods Passive Drainage Methods Comparison of Different Pumped Groundwater Control Methods Pore Water Pressure Control Systems in Fine-Grained Soils Some Deep Well and Ejector Projects Deeper Than 20 m USE OF PUMPING AND EXCLUSION METHODS IN COMBINATION Exclusion Methods to Reduce Pumped Flows in High-Permeability Soils Exclusion Methods to Reduce External Groundwater Impacts Groundwater Pumping within Areas Enclosed by Cut-Off Walls Groundwater Lowering Used to Reduce Loading on Cut-Off Structures Example of Optioneering of Groundwater Pumping and Exclusion Scheme GROUNDWATER CONTROL FOR SURFACE MINES Groundwater Control for Tunnelling Projects INTRODUCTION TYPES OF TUNNELLING WORKS Tunnels Shafts Cross Passages Other Tunnel Applications Recovery Works WATER MANAGEMENT IN TUNNELLING WORKS GROUNDWATER CONTROL METHODS FOR TUNNELS Open Face Tunnelling Using Compressed Air Working Closed Face Tunnel Boring Machines (TBMs)Tunnel Exclusion Methods Using Ground Treatment Ground Treatment from the Surface Ground Treatment from within the Tunnel Pumping Methods in Tunnelling Direct Pumping from within the Tunnel Dewatering Wells from the Surface In-Tunnel Dewatering Wells GROUNDWATER CONTROL METHODS FOR SHAFTS Shaft Exclusion Methods Using Physical Cut-Off Walls Shaft Exclusion Methods Using Ground Treatment Pumping Methods Used for Shaft Construction Sump Pumping from within the Shaft Dewatering Wells from the Surface S.3.3 In-Shaft Dewatering Wells Use of Fluid Pressure to Stabilize the Base of the Shaft Shaft Sinking by the Wet Caisson Method Shaft Boring Machines in Flooded Shafts Underwater Excavation within Cofferdams Shaft Sinking under Compressed Air Working GROUNDWATER CONTROL METHODS FOR CROSS PASSAGES General Principles of Groundwater Control for Cross Passages Investigation to Gather Information on Ground Conditions at Cross Passage Locations Drilling out from Existing Tunnels Compressed Air Methods Ground Treatment Used to Exclude Groundwater Groundwater Depressurization GROUNDWATER CONTROL METHODS FOR OTHER TUNNELLING APPLICATIONS GROUNDWATER CONTROL METHODS FOR RECOVERY WORKS Site Investigation for Groundwater Lowering INTRODUCTION THE OBJECTIVES OF SITE INVESTIGATION THE ROLE OF THE CONCEPTUAL MODEL PLANNING OF SITE INVESTIGATIONS STAGES OF SITE INVESTIGATION DESK STUDY AND SITE RECONNAISSANCE GROUND INVESTIGATION Boring, Drilling and Probing Boring Methods Used in Investigations Drilling Methods Used in Investigations Probing Methods Used in Investigations Trial Pitting In Situ Testing Geophysics Surface Geophysics Borehole Geophysics Laboratory Testing Installation of Monitoring Wells and Piezometers Standpipes Standpipe Piezometers Specialist Piezometer Installations REPORTING DETERMINATION OF GROUND PROFILE DETERMINATION OF GROUNDWATER CONDITIONS Groundwater Level Observations in Trial Pits and Boreholes Groundwater Levels Observed in Trial Pits Groundwater Levels Observed during Cable Percussion Boring Groundwater Levels Observed during Rotary Drilling Groundwater Level Observations in Monitoring Wells and Piezometers Groundwater Sampling and Testing DETERMINATION OF PERMEABILITY Assessment of Permeability INTRODUCTION THE ROLE OF PERMEABILITE IN GROUNDWATER CONTROL PROBLEMS SOME OF THE DIFFICULTIES OF ASSESSING PERMEABILITY METHODS OF ASSESSING PERMEABILITY ASSESSING PERMEABILITY BY NON- QUANTITATIVE METHODS Visual Assessment Drilling Records Geophysics QUANTITATIVE ASSESSMENT OF PERMEABILITY - EMPIRICAL METHODS Correlations with Particle Size Distribution (PSD) of Soil Background to Particle Size Correlations Hazen’s Method Kozeny-Carman Method Prugh Method Correlations with Descriptions of Rock Quality Inverse Numerical Modelling QUANTITATIVE ASSESSMENT OF PERMEABILITY - EX SITU TEST METHODS Laboratory Testing of Soil Samples Laboratory Testing of Rock Samples QUANTITATIVE ASSESSMENT OF PERMEABILITY - IN SITU TEST METHODS Rising, Falling and Constant Head Tests in Boreholes Rising, Falling and Constant Head Tests in Monitoring Wells Packer Permeability Testing in Boreholes in Rock Specialist In Situ Tests Pumping Tests Single Well Pumping Test Alternative Forms of Pumping Test Groundwater Control Trials Borehole Geophysics Borehole Magnetic Resonance (BMR)Borehole Flowmeter Logging COMPARISON OF PERMEABILITY ASSESSMENT METHODS Design of Groundwater Lowering Systems INTRODUCTION WHAT IS DESIGN?DESIGN APPROACH Pre-Defined Designs for Groundwater Lowering The Observational Method for Groundwater Lowering DEVELOPMENT OF CONCEPTUAL MODEL EXPECTATIONS OF ACCURACY SELECTION OF METHOD AND GEOMETRY Equivalent Wells and Slots Geological Structure, Well Depth and Underdrainage ASSESSMENT OF BASE STABILITY Assessment of Risk of Buoyancy Uplift Assessment of Risk of Fluidization Due to Upward Seepage Gradients ESTIMATION OF STEADY-STATE DISCHARGE FLOW RATE Steady-State Well and Slot Formulae Cumulative Drawdown Analysis - Theoretical Method Cumulative Drawdown Analysis - Graphical Method Estimation of Flow Rates Where Cut-Off Walls Are Present Estimation of Flow Rates into Tunnels Storage Release and Uprating of Pumping Capacity Other Methods SPECIFICATION OF WELL YIELD AND SPACING Well Yield Depth of Wells Number of Wells and Well Spacing SPECIFICATION OF WELL SCREENS AND FILTERS Requirements for Well Screens and Filter Packs Design Rules for Artificial Filter Packs and Slot Size Design Rules for Natural Filter Packs and Slot Size Annular Seals for Wells Dewatering Wells in Rock OTHER CONSIDERATIONS Estimation of Drawdown Distribution around Well Estimation of Groundwater-Lowering- Induced Settlements Estimation of Potential Environmental Impacts NUMERICAL MODELLING Potential Applications of Numerical Modelling Potential Pitfalls of Numerical Modelling DESIGN EXAMPLES SECTION 3. CONSTRUCTION Sump Pumping INTRODUCTION APPLICATIONS AND LIMITATIONS OF SUMP PUMPING SUMPS FOR SURFACE WATER RUN-OFF SUMPS FOR GROUNDWATER PUMPING DRAINAGE OF SIDE SLOPES OF AN EXCAVATION SUMP PUMPING OF SMALL EXCAVATIONS SUMP PUMPING FROM WITHIN CUT-OFF WALLS SUMP PUMPING PROBLEMS DISPOSAL OF WATER FROM SUMP PUMPING OPERATIONS Wellpoint Systems INTRODUCTION WHICH SYSTEM: WELLPOINTS OR DEEP WELLS?WHAT IS A WELLPOINT SYSTEM?Types of Wellpoint WELLPOINT INSTALLATION TECHNIQUES Installation of Self-Jetting Wellpoints Installation of Disposable Wellpoints by Placing Tube Installation Using the Holepuncher and Heavy-Duty Placing Tube Installation by Rotary Jet Drilling Installation through Clay Strata The Merits of Jetted Hole Installations The Need for Filter Media Sanding-ln SPACING OF WELLPOINTS AND DRAWDOWN TIMES SEALED VACUUM WELLPOINT SYSTEMS WELLPOINT PUMPING EQUIPMENT Duty or Running Pumps Standby Pumps Operation of a Wellpoint System and ‘Trimming’WELLPOINT INSTALLATIONS FOR TRENCH EXCAVATIONS Single-Sided Wellpoint Installations Double-Sided Wellpoint Installations Progressive Installation for Trench Works WELLPOINTING FOR WIDE EXCAVATIONS WELLPOINTING FOR DEEPER EXCAVATIONS Long Risers and Lowered Header Mains Multi-Stage Wellpointing Deep Well Systems INTRODUCTION DEEP WELL INSTALLATIONS REQUIREMENTS FOR WELLS FOR GROUNDWATER LOWERING Depth of Well Diameter of Well Types of Well Screen Filter Media and Slot Size CONSTRUCTING DEEP WELLS DRILLING OF WELL BOREHOLES Cable Tool Percussion Drilling Wash Boring and/or Jet Drilling Rotary Drilling: Direct Circulation Rotary Drilling: Reverse Circulation Rota-Sonic Drilling INSTALLATION OF WELL MATERIALS WELL DEVELOPMENT Monitoring of Pumped Water for Suspended Solids Well Development by Acidization Re-Development of Wells during Long- Term Dewatering Pumping INSTALLATION AND OPERATION OF DEEP WELL PUMPS VACUUM DEEP WELL INSTALLATIONS SHALLOW SUCTION WELL INSTALLATIONS Other Dewatering Systems INTRODUCTION EJECTOR WELLS Merits of Ejector Well Systems Types of Ejectors Installation Techniques Ejector Pumping Equipment Operation of an Ejector Well System and Potential Imperfections HORIZONTAL WELLPOINTS Merits of Horizontal Wellpoint Systems Installation Techniques Pumping Equipment HORIZONTAL DIRECTIONALLY DRILLED (HDD) WELLS SUB-HORIZONTAL DRAINS COLLECTOR WELLS DRAINAGE TUNNELS AND ADITS RELIEF WELLS Merits of Relief Well Systems Installation Techniques Relief Wells - Are a Well Casing and Screen Needed?VERTICAL DRAINS SLOPE DRAINAGE Toe Drains Drainage Measures at the Crest of the Slope Drainage Measures within the Slope SIPHON DRAINS ELECTRO-OSMOSIS ARTIFICIAL RECHARGE SYSTEMS Applications of Artificial Recharge Systems What Is the Aim of Artificial Recharge?Recharge Trenches Recharge Wells Water Quality Problems and Clogging Operation of Recharge Systems DEWATERING AND GROUNDWATER CONTROL TECHNOLOGIES USED FOR THE CONTROL OR REMEDIATION OF CONTAMINATED GROUNDWATER Applications of Pumping Systems on Contaminated Sites Applications of Barrier Systems on Contaminated Sites Groundwater Treatment Technologies Methods for Exclusion of Groundwater INTRODUCTION PRINCIPAL METHODS FOR GROUNDWATER EXCLUSION GEOMETRIES OF EXCLUSION APPLICATIONS Basal Seals PERMEABLE WALLS Contiguous Concrete Bored Pile Walls Soldier Pile Walls STEEL SHEET-PILING AND COMBI-PILE WALLS VIBRATED BEAM WALLS SLURRY TRENCH WALLS CONCRETE DIAPHRAGM WALLS CONCRETE SECANT PILE WALLS GROUT BARRIERS Principles of Grouting Types of Grout Cement-Based Grouts Chemical Grouts Design of Grout Barriers Permeation Grouting Rock Grouting Jet Grouting MIX-IN-PLACE BARRIERS ARTIFICIAL GROUND FREEZING Brine Circulation Systems Liquid Nitrogen (LN) Systems Typical Applications for Artificial Ground Freezing Effect of Groundwater Flow on Artificial Ground Freezing Other Limitations of Artificial Ground Freezing LOW-PERMEABILITY SURFACE BARRIERS VERIFICATION OF GROUNDWATER EXCLUSION METHODS Prediction of Inflow to Groundwater Exclusion Schemes Methods to Determine Total Inflow to Groundwater Exclusion Schemes Assessment of Acceptable Performance Pumps for Groundwater Lowering Duties INTRODUCTION PRINCIPLES OF PUMPING What Is a Pump?Different Pumping Methods Mathematics of Pumping TYPES OF DEWATERING PUMPS UNITS FOR SUMP PUMPING Contractor’s Submersible Pump All-Purpose Self-Priming Centrifugal Suction Pump WELLPOINT DEWATERING PUMPS Double-Acting Piston Pump Vacuum-Assisted Self-Priming Centrifugal Pumpset Vacuum Tank Unit Comparison of Merits of Piston Pumps vs. Vacuum- Assisted Centrifugal Wellpoint Pumps Wellpoint Jetting Pumps PUMPS FOR DEEP WELLS Borehole Electro-Submersible Turbine Pumps Use of Oversized Pumps Encrustation and Corrosion Borehole Electro-Submersible Pumps - Operational Problems Vertical Lineshaft Turbine Pumps Lineshaft Pumps - Operational Problems Comparison of Merits of Lineshaft Pumps vs. Electro-Submersible Pumps PUMPS FOR EJECTOR WELL SYSTEMS Ejector Supply Pumps Ejectors Ejector Performance Curves OTHER PUMPING METHODS Airlift Pumping Bailing of Deep Shafts PUMP CONTROL SYSTEMS Electrical Control Systems Intermittent Operation of Pumps DISCHARGE PIPEWORK AND EQUIPMENT DESIGN OF PUMPING SYSTEMS Assessing the Pump Duty Estimating Friction Losses Sizing of Pumps Energy Used in Pumping Permanent Groundwater Control Systems INTRODUCTION TYPES OF PERMANENT GROUNDWATER CONTROL SYSTEMS Permanent Groundwater Pumping Systems Permanent Groundwater Barrier Systems OBJECTIVES OF PERMANENT GROUNDWATER CONTROL SYSTEMS Reduction of Groundwater Uplift Loads on Structures Control of Anticipated Rises in Groundwater Levels Reduction in Leakage into Below-Ground Structures Stabilization of Slopes and Earth Structures Remediation and Containment of Contaminated Groundwater DESIGN ISSUES FOR PERMANENT GROUNDWATER CONTROL SYSTEMS Longevity of Permanent Groundwater Control Systems Reliability of Permanent Groundwater Control Systems Efficiency of Permanent Groundwater Control Systems Environmental Impacts of Permanent Groundwater Control Systems Legacy Issues for Permanent Groundwater Control Systems PRACTICAL ISSUES FOR PERMANENT GROUNDWATER CONTROL SYSTEMS OPPORTUNITIES ASSOCIATED WITH PERMANENT GROUNDWATER CONTROL SYSTEMS Environmental Impacts from Groundwater Control INTRODUCTION WHY ARE IMPACTS FROM GROUNDWATER CONTROL OF CONCERN?POTENTIAL ENVIRONMENTAL IMPACTS FROM GROUNDWATER CONTROL IMPACTS FROM GROUNDWATER ABSTRACTION Settlement Due to Groundwater Lowering Settlement Due to Poorly Controlled Groundwater Settlement Due to Loss of Fines Settlement Due to Increases in Effective Stress Settlement Damage to Structures Risk Assessment of Settlement Damage from Groundwater Lowering Mitigation and Avoidance of Settlement Impact on Groundwater-Dependent Features Effect on Groundwater Quality Movement of Contaminated Groundwater Saline Intrusion Effect on Groundwater Borehole or Spring Supplies Other Effects IMPACTS FROM RECOVERY OF GROUNDWATER LEVELS IMPACTS FROM GROUNDWATER PATHWAYS Vertical Pathways via Boreholes and Wells Vertical Pathways via Excavations and Structures Horizontal Pathways IMPACTS FROM GROUNDWATER BARRIERS IMPACTS FROM DISCHARGE FLOWS TO THE GROUNDWATER ENVIRONMENT IMPACTS FROM DISCHARGE FLOWS TO THE SURFACE WATER ENVIRONMENT Erosion Caused by Discharge Flows Suspended Solids Discharge Water Chemistry and Temperature Oil and Petroleum Products Contaminated Groundwater ASSESSMENT OF POTENTIAL ENVIRONMENTAL IMPACTS Identification of Potential Environmental Impacts Prediction of Potential Environmental Impacts Mitigation of Potential Environmental Impacts Monitoring of Potential Environmental Impacts Monitoring of Groundwater Control Systems INTRODUCTION THE NEED FOR MONITORING Manual Monitoring or Automated Monitoring?PHASES OF MONITORING Using the Data DATALOGGING SYSTEMS DATA MANAGEMENT AND DISSEMINATION MONITORING OF GROUNDWATER LEVELS Datums Used for Groundwater Level Monitoring Manual Monitoring of Groundwater Levels Monitoring Groundwater Levels Using Pressure Transducers Monitoring of Artesian Groundwater Levels Validating Groundwater Level Data MONITORING OF DISCHARGE FLOW RATE Monitoring Total Flow Rate or Flow from Individual Wells Proprietary Flowmeters Weir Tanks Timed Volumetric Methods Other Methods Validating Flow Rate Measurement Data MONITORING OF DISCHARGE WATER QUALITY MONITORING OF SURFACE SETTLEMENTS Conventional Surveying Techniques Remote Sensing Techniques MONITORING OF SURFACE WATER BODIES OTHER PARAMETERS THAT MAY BE MONITORED Maintenance of Groundwater Lowering Systems INTRODUCTION THE NEED FOR MAINTENANCE PRINCIPAL MAINTENANCE REQUIREMENTS STANDBY PUMPS AND AUTOMATION Standby Pumps Standby Electrical Power Supplies Alarm Systems and Automation ENCRUSTATION, BIOFOULING AND CORROSION Chemical Encrustation Bacterial Growth and Biofouling Maintenance Strategies to Manage Clogging and Encrustation Corrosion FAULT FINDING AND PROBLEM SOLVING Decommissioning of Groundwater Control Systems INTRODUCTION THE NEED FOR DECOMMISSIONING Hazards from Dewatering Wells Hazards from Cut-Off Walls DECOMMISSIONING OF WELLS EXTERNAL TO STRUCTURES DECOMMISSIONING OF WELLS AND SUMPS LOCATED WITHIN STRUCTURES BREACHING OF CUT-OFF WALLS Safety, Contracts and Environmental Regulation INTRODUCTION HEALTH AND SAFETY CDM Regulations Working with Hazardous Substances Use of Electricity on Site Lifting Operations Working at Height Work Equipment and Drilling Rigs Safety of Excavations Noise Working with Wells and Boreholes Interaction with Third-Party Services, Tunnels and Infrastructure Risk from Unexploded Ordnance (UXO)CONTRACTS FOR GROUNDWATER CONTROL WORKS The Need for Contracts Traditional Contract Arrangements Alternative Forms of Contract Dewatering Costs ENVIRONMENTAL REGULATION OF GROUNDWATER CONTROL Groundwater Protection Abstraction of Groundwater Discharge of Groundwater Settlement Resulting from the Abstraction of Groundwater Environmental Regulation of Major Projects Local Regulations Optimization of Groundwater Control Systems INTRODUCTION WHY OPTIMIZE?DIFFERENT OPTIMIZATION METHODS Empirical Optimization Numerical Modelling or Analytical Optimization Observational Optimization Optimization in the Field (Troubleshooting)PROBLEMS WITH OPTIMIZATION Lack of Clarity in Objectives of Optimization Insufficient Data Quality and Quantity Errors in Conceptual Model Inappropriate Groundwater Control Technique POSSIBLE PRIORITIES FOR OPTIMIZATION Case Histories INTRODUCTION CASE HISTORY: SUMP PUMPING OF LARGE EXCAVATION, ABERDEEN, UK CASE HISTORY: WELLPOINTING AT DERWENT OUTLET CHANNEL, NORTHUMBERLAND, UK CASE HISTORY: DEEP WELLS AND RELIEF WELLS AT TEES BARRAGE, STOCKTON-ON-TEES, UK CASE HISTORY: EJECTOR WELLS FOR SHAFT DEWATERING, WITH HIGH-PERMEABILITY FEATURE PRESENT, UK CASE HISTORY: HYDRAULIC FAILURE OF BASE OF SHAFT, UK CASE HISTORY: GROUNDWATER CONTROL BY SUMP PUMPING AND DEEP WELLS FOR SHAFT, UK CASE HISTORY: ARTIFICIAL RECHARGE TO CONTROL SETTLEMENT: MISR BANK, CAIRO, EGYPT CASE HISTORY: ARTIFICIAL RECHARGE TO PROTECT DRINKING WATER SOURCE, UK CASE HISTORY: LOW-PERMEABILITY CUT-OFF WALL AT SIZEWELL В POWER STATION, UK CASE HISTORY: CONTAMINATION REMEDIATION USING CUT-OFF WALLS AND GROUNDWATER ABSTRACTION AT DERBY PRIDE PARK, UK CASE HISTORY: PERMANENT GROUNDWATER CONTROL SYSTEM AT GOVAN UNDERGROUND TUNNEL, GLASGOW, UK The Future INTRODUCTION REGULATION AND LEGISLATION TECHNOLOGY AND THE INTERNET OF THINGS DESIGN AND NUMERICAL MODELLING APPLICATIONS AND TECHNIQUES WHERE DO WE GO FROM HERE?THE NEXT GENERATION OF DEWATERING PRACTITIONERS Appendix I: Estimation of Permeability by Correlations with Particle Size Distribution (PSD) of Soil Appendix 2: Execution and Analysis of Variable Head Permeability Tests in Boreholes Appendix 3: Execution and Analysis of Packer Permeability Tests in Boreholes in Rock Appendix 4: Execution of Well Pumping Tests Appendix 5: Design Examples Appendix 6: Estimation of Flow Rate Using V-Notch Weirs Notation Conversion factors Glossary

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