Groundwater Lowering in Construction: A Practical Guide to Dewatering

SECTION I. PRINCIPLESI. Groundwater Lowering: A Personal View and Introduction by Pat M. CashmanThe History of Groundwater Theory and PracticeINTRODUCTIONFROM THE EARLIEST TIMES TO THE SIXTEENTH CENTURYFROM THE RENAISSANCE PERIOD TO THE NINETEENTH CENTURYPROGRESS FROM A QUALITATIVE TO A QUANTITATIVE SCIENCESeepage towards WellsLand Drainage in the Eighteenth and Nineteenth CenturiesKilsby Tunnel, London to Birmingham RailwayEarly Theory - Darcy and DupuitLATER THEORETICAL DEVELOPMENTSVerifications and Modification of DarcyNon-Steady-State FlowGROUNDWATER MODELLINGEARLY DEWATERING TECHNOLOGY IN BRITAINPRACTICAL PUBLICATIONSPrinciples of Groundwater FlowINTRODUCTIONHYDROLOGY AND HYDROGEOLOGYThe Hydrological CycleGeology and Soil MechanicsPERMEABILITY, HYDRAULIC CONDUCTIVITY AND GROUNDWATER FLOWDrivers for Groundwater FlowDarcy’s LawDarcian and Non-Darcian FlowGroundwater VelocitiesEffect of Groundwater on Soil and Rock PropertiesAQUIFERS, AQUITARDS AND AQUICLUDESUnconfined AquifersConfined AquifersAquicludesAquitards and Leaky AquifersAquifer ParametersAQUIFERS AND GEOLOGICAL STRUCTUREMultiple Aquifers beneath LondonWater Pressures Trapped beneath a Trench ExcavationAQUIFER BOUNDARIESInteraction between Aquifers and Surface WaterInteraction between AquifersTidal Groundwater ConditionsRecharge BoundariesBarrier BoundariesDischarge BoundariesGROUNDWATER CHEMISTRYChemical Composition of GroundwaterField Monitoring of Groundwater ChemistryGROUNDWATER TEMPERATURESEFFECT OF CLIMATE AND WEATHERPermeability of Soils and RocksINTRODUCTIONWHAT IS PERMEABILITY?Intrinsic PermeabilityHydraulic ConductivityElectro-Osmotic PermeabilityPERMEABILITY IN SOILSPERMEABILITY IN ROCKPROBLEMS WITH ASSESSING PERMEABILITYWORKING WITH PERMEABILITY IN THE REAL WORLDPermeability at Different ScalesKarstic Flow in RocksMETHODS OF DETERMINING PERMEABILITYNon-Quantitative Assessment MethodsQuantitative Assessment MethodsGroundwater ModelsINTRODUCTIONGROUNDWATER MODELLINGCOMPLEXITY IN MODELLINGRelevance of ModelsTypical Simplifications Used in ModellingCONCEPTUAL MODELSANALYTICAL MODELSEmpirical ModelsMathematical Models Using Closed-Form SolutionsNumerical ModelsOTHER TYPES OF MODELSTHE ROLE OF GEOLOGICAL STRUCTURE IN MODELSFLOW TO WELLS AND SLOTSPlanar Flow to SlotsRadial Flow to WellsZone of InfluenceWell LossesEffect of Diameter of WellEquivalent Wells and Lines of WellsMODELLING GROUNDWATER CONTROL TECHNOLOGYSELECTING AND APPLYING AN APPROPRIATE MODELObjectives of Groundwater ControlINTRODUCTIONGROUNDWATER CONTROL - THE OBJECTIVESGROUNDWATER CONTROL AS PART OF TEMPORARY WORKSGROUNDWATER MANAGEMENT IN EXCAVATIONSGROUNDWATER, EFFECTIVE STRESS AND INSTABILITYGROUNDWATER BEHAVIOUR IN HIGH- AND LOW-PERMEABILITY SOILS AND ROCKSDrained and Undrained ConditionsDrained Pore Water Pressure Responses during ExcavationUndrained Pore Water Pressure Responses during ExcavationIntermediate Conditions between Drained and Undrained ResponseRelevance of Drained and Undrained Conditions to Groundwater Control ProblemsPOSSIBLE APPROACHES TO GROUNDWATER CONTROLSURFACE WATER PROBLEMSCHANGING GROUNDWATER CONDITIONSGroundwater Problems for Excavations in SoilsINTRODUCTIONGROUNDWATER MANAGEMENT PROBLEMS IN SOILSLARGE-SCALE AND SMALL-SCALE INSTABILITY CAUSED BY GROUNDWATERSLOPE INSTABILITYBASE INSTABILITYBase Instability by Buoyancy UpliftBase Instability by Fluidization Due to Upward Seepage GradientsBase Instability by Internal ErosionBase Instability by PipingLOCALIZED GROUNDWATER PROBLEMSDrainage of Slopes and FormationPerched Water TableHigh-Permeability ZonesSpring Sapping and Internal ErosionGROUNDWATER PROBLEMS WHEN TUNNELLING IN SOILSGroundwater Instability Effects in Tunnel FacesBuoyancy Uplift in TunnelsGroundwater Instability Effects on Shaft ConstructionGroundwater Instability Effects on Other Underground WorksGroundwater Problems for Excavations in RockINTRODUCTIONGROUNDWATER MANAGEMENT PROBLEMS IN ROCKGROUNDWATER EFFECTS ON EXCAVATIONS IN ROCKGroundwater and Small-Scale FracturesEffect of Isolated Highly Permeable FracturesGroundwater and Larger-Scale Geological StructureWeathered RocksSoluble Rock and Karst Groundwater ConditionsGROUNDWATER-INDUCED INSTABILITY IN ROCKSLOPE INSTABILITYBASE INSTABILITYBase Instability by Buoyancy UpliftEnlargement/Erosion of Water PathwaysLOCALIZED GROUNDWATER PROBLEMSLocalized Erosion Due to High Groundwater VelocitiesErosion or Collapse of Weak or Weathered ZonesPerched Water ConditionsLocalized Concentration of Water InflowWater Trapped by Rock StructureGROUNDWATER PROBLEMS WHEN TUNNELLING IN ROCKGroundwater Management during Tunnel ConstructionSudden InflowsGroundwater Problems during Shaft Sinking in RockGroundwater Problems during Other Underground WorksSECTION 2. DESIGNMethods for Control of Surface Water and GroundwaterINTRODUCTIONCONTROL OF SURFACE WATERCollection and Control of Surface Water Run-OffTreatment of Surface Water Run-OffMETHODS OF GROUNDWATER CONTROLEXCLUSION METHODSDEWATERING METHODSOpen Pumping and Pre-Drainage MethodsPassive Drainage MethodsComparison of Different Pumped Groundwater Control MethodsPore Water Pressure Control Systems in Fine-Grained SoilsSome Deep Well and Ejector Projects Deeper Than 20 mUSE OF PUMPING AND EXCLUSION METHODS IN COMBINATIONExclusion Methods to Reduce Pumped Flows in High-Permeability SoilsExclusion Methods to Reduce External Groundwater ImpactsGroundwater Pumping within Areas Enclosed by Cut-Off WallsGroundwater Lowering Used to Reduce Loading on Cut-Off StructuresExample of Optioneering of Groundwater Pumping and Exclusion SchemeGROUNDWATER CONTROL FOR SURFACE MINESGroundwater Control for Tunnelling ProjectsINTRODUCTIONTYPES OF TUNNELLING WORKSTunnelsShaftsCross PassagesOther Tunnel ApplicationsRecovery WorksWATER MANAGEMENT IN TUNNELLING WORKSGROUNDWATER CONTROL METHODS FOR TUNNELSOpen Face Tunnelling Using Compressed Air WorkingClosed Face Tunnel Boring Machines (TBMs)Tunnel Exclusion Methods Using Ground TreatmentGround Treatment from the SurfaceGround Treatment from within the TunnelPumping Methods in TunnellingDirect Pumping from within the TunnelDewatering Wells from the SurfaceIn-Tunnel Dewatering WellsGROUNDWATER CONTROL METHODS FOR SHAFTSShaft Exclusion Methods Using Physical Cut-Off WallsShaft Exclusion Methods Using Ground TreatmentPumping Methods Used for Shaft ConstructionSump Pumping from within the ShaftDewatering Wells from the SurfaceS.3.3 In-Shaft Dewatering WellsUse of Fluid Pressure to Stabilize the Base of the ShaftShaft Sinking by the Wet Caisson MethodShaft Boring Machines in Flooded ShaftsUnderwater Excavation within CofferdamsShaft Sinking under Compressed Air WorkingGROUNDWATER CONTROL METHODS FOR CROSS PASSAGESGeneral Principles of Groundwater Control for Cross PassagesInvestigation to Gather Information on Ground Conditions at Cross Passage LocationsDrilling out from Existing TunnelsCompressed Air MethodsGround Treatment Used to Exclude GroundwaterGroundwater DepressurizationGROUNDWATER CONTROL METHODS FOR OTHER TUNNELLING APPLICATIONSGROUNDWATER CONTROL METHODS FOR RECOVERY WORKSSite Investigation for Groundwater LoweringINTRODUCTIONTHE OBJECTIVES OF SITE INVESTIGATIONTHE ROLE OF THE CONCEPTUAL MODELPLANNING OF SITE INVESTIGATIONSSTAGES OF SITE INVESTIGATIONDESK STUDY AND SITE RECONNAISSANCEGROUND INVESTIGATIONBoring, Drilling and ProbingBoring Methods Used in InvestigationsDrilling Methods Used in InvestigationsProbing Methods Used in InvestigationsTrial PittingIn Situ TestingGeophysicsSurface GeophysicsBorehole GeophysicsLaboratory TestingInstallation of Monitoring Wells and PiezometersStandpipesStandpipe PiezometersSpecialist Piezometer InstallationsREPORTINGDETERMINATION OF GROUND PROFILEDETERMINATION OF GROUNDWATER CONDITIONSGroundwater Level Observations in Trial Pits and BoreholesGroundwater Levels Observed in Trial PitsGroundwater Levels Observed during Cable Percussion BoringGroundwater Levels Observed during Rotary DrillingGroundwater Level Observations in Monitoring Wells and PiezometersGroundwater Sampling and TestingDETERMINATION OF PERMEABILITYAssessment of PermeabilityINTRODUCTIONTHE ROLE OF PERMEABILITE IN GROUNDWATER CONTROL PROBLEMSSOME OF THE DIFFICULTIES OF ASSESSING PERMEABILITYMETHODS OF ASSESSING PERMEABILITYASSESSING PERMEABILITY BY NON- QUANTITATIVE METHODSVisual AssessmentDrilling RecordsGeophysicsQUANTITATIVE ASSESSMENT OF PERMEABILITY - EMPIRICAL METHODSCorrelations with Particle Size Distribution (PSD) of SoilBackground to Particle Size CorrelationsHazen’s MethodKozeny-Carman MethodPrugh MethodCorrelations with Descriptions of Rock QualityInverse Numerical ModellingQUANTITATIVE ASSESSMENT OF PERMEABILITY - EX SITU TEST METHODSLaboratory Testing of Soil SamplesLaboratory Testing of Rock SamplesQUANTITATIVE ASSESSMENT OF PERMEABILITY - IN SITU TEST METHODSRising, Falling and Constant Head Tests in BoreholesRising, Falling and Constant Head Tests in Monitoring WellsPacker Permeability Testing in Boreholes in RockSpecialist In Situ TestsPumping TestsSingle Well Pumping TestAlternative Forms of Pumping TestGroundwater Control TrialsBorehole GeophysicsBorehole Magnetic Resonance (BMR)Borehole Flowmeter LoggingCOMPARISON OF PERMEABILITY ASSESSMENT METHODSDesign of Groundwater Lowering SystemsINTRODUCTIONWHAT IS DESIGN?DESIGN APPROACHPre-Defined Designs for Groundwater LoweringThe Observational Method for Groundwater LoweringDEVELOPMENT OF CONCEPTUAL MODELEXPECTATIONS OF ACCURACYSELECTION OF METHOD AND GEOMETRYEquivalent Wells and SlotsGeological Structure, Well Depth and UnderdrainageASSESSMENT OF BASE STABILITYAssessment of Risk of Buoyancy UpliftAssessment of Risk of Fluidization Due to Upward Seepage GradientsESTIMATION OF STEADY-STATE DISCHARGE FLOW RATESteady-State Well and Slot FormulaeCumulative Drawdown Analysis - Theoretical MethodCumulative Drawdown Analysis - Graphical MethodEstimation of Flow Rates Where Cut-Off Walls Are PresentEstimation of Flow Rates into TunnelsStorage Release and Uprating of Pumping CapacityOther MethodsSPECIFICATION OF WELL YIELD AND SPACINGWell YieldDepth of WellsNumber of Wells and Well SpacingSPECIFICATION OF WELL SCREENS AND FILTERSRequirements for Well Screens and Filter PacksDesign Rules for Artificial Filter Packs and Slot SizeDesign Rules for Natural Filter Packs and Slot SizeAnnular Seals for WellsDewatering Wells in RockOTHER CONSIDERATIONSEstimation of Drawdown Distribution around WellEstimation of Groundwater-Lowering- Induced SettlementsEstimation of Potential Environmental ImpactsNUMERICAL MODELLINGPotential Applications of Numerical ModellingPotential Pitfalls of Numerical ModellingDESIGN EXAMPLESSECTION 3. CONSTRUCTIONSump PumpingINTRODUCTIONAPPLICATIONS AND LIMITATIONS OF SUMP PUMPINGSUMPS FOR SURFACE WATER RUN-OFFSUMPS FOR GROUNDWATER PUMPINGDRAINAGE OF SIDE SLOPES OF AN EXCAVATIONSUMP PUMPING OF SMALL EXCAVATIONSSUMP PUMPING FROM WITHIN CUT-OFF WALLSSUMP PUMPING PROBLEMSDISPOSAL OF WATER FROM SUMP PUMPING OPERATIONSWellpoint SystemsINTRODUCTIONWHICH SYSTEM: WELLPOINTS OR DEEP WELLS?WHAT IS A WELLPOINT SYSTEM?Types of WellpointWELLPOINT INSTALLATION TECHNIQUESInstallation of Self-Jetting WellpointsInstallation of Disposable Wellpoints by Placing TubeInstallation Using the Holepuncher and Heavy-Duty Placing TubeInstallation by Rotary Jet DrillingInstallation through Clay StrataThe Merits of Jetted Hole InstallationsThe Need for Filter MediaSanding-lnSPACING OF WELLPOINTS AND DRAWDOWN TIMESSEALED VACUUM WELLPOINT SYSTEMSWELLPOINT PUMPING EQUIPMENTDuty or Running PumpsStandby PumpsOperation of a Wellpoint System and ‘Trimming’WELLPOINT INSTALLATIONS FOR TRENCH EXCAVATIONSSingle-Sided Wellpoint InstallationsDouble-Sided Wellpoint InstallationsProgressive Installation for Trench WorksWELLPOINTING FOR WIDE EXCAVATIONSWELLPOINTING FOR DEEPER EXCAVATIONSLong Risers and Lowered Header MainsMulti-Stage WellpointingDeep Well SystemsINTRODUCTIONDEEP WELL INSTALLATIONSREQUIREMENTS FOR WELLS FOR GROUNDWATER LOWERINGDepth of WellDiameter of WellTypes of Well ScreenFilter Media and Slot SizeCONSTRUCTING DEEP WELLSDRILLING OF WELL BOREHOLESCable Tool Percussion DrillingWash Boring and/or Jet DrillingRotary Drilling: Direct CirculationRotary Drilling: Reverse CirculationRota-Sonic DrillingINSTALLATION OF WELL MATERIALSWELL DEVELOPMENTMonitoring of Pumped Water for Suspended SolidsWell Development by AcidizationRe-Development of Wells during Long- Term Dewatering PumpingINSTALLATION AND OPERATION OF DEEP WELL PUMPSVACUUM DEEP WELL INSTALLATIONSSHALLOW SUCTION WELL INSTALLATIONSOther Dewatering SystemsINTRODUCTIONEJECTOR WELLSMerits of Ejector Well SystemsTypes of EjectorsInstallation TechniquesEjector Pumping EquipmentOperation of an Ejector Well System and Potential ImperfectionsHORIZONTAL WELLPOINTSMerits of Horizontal Wellpoint SystemsInstallation TechniquesPumping EquipmentHORIZONTAL DIRECTIONALLY DRILLED (HDD) WELLSSUB-HORIZONTAL DRAINSCOLLECTOR WELLSDRAINAGE TUNNELS AND ADITSRELIEF WELLSMerits of Relief Well SystemsInstallation TechniquesRelief Wells - Are a Well Casing and Screen Needed?VERTICAL DRAINSSLOPE DRAINAGEToe DrainsDrainage Measures at the Crest of the SlopeDrainage Measures within the SlopeSIPHON DRAINSELECTRO-OSMOSISARTIFICIAL RECHARGE SYSTEMSApplications of Artificial Recharge SystemsWhat Is the Aim of Artificial Recharge?Recharge TrenchesRecharge WellsWater Quality Problems and CloggingOperation of Recharge SystemsDEWATERING AND GROUNDWATER CONTROL TECHNOLOGIES USED FOR THE CONTROL OR REMEDIATION OF CONTAMINATED GROUNDWATERApplications of Pumping Systems on Contaminated SitesApplications of Barrier Systems on Contaminated SitesGroundwater Treatment TechnologiesMethods for Exclusion of GroundwaterINTRODUCTIONPRINCIPAL METHODS FOR GROUNDWATER EXCLUSIONGEOMETRIES OF EXCLUSION APPLICATIONSBasal SealsPERMEABLE WALLSContiguous Concrete Bored Pile WallsSoldier Pile WallsSTEEL SHEET-PILING AND COMBI-PILE WALLSVIBRATED BEAM WALLSSLURRY TRENCH WALLSCONCRETE DIAPHRAGM WALLSCONCRETE SECANT PILE WALLSGROUT BARRIERSPrinciples of GroutingTypes of GroutCement-Based GroutsChemical GroutsDesign of Grout BarriersPermeation GroutingRock GroutingJet GroutingMIX-IN-PLACE BARRIERSARTIFICIAL GROUND FREEZINGBrine Circulation SystemsLiquid Nitrogen (LN) SystemsTypical Applications for Artificial Ground FreezingEffect of Groundwater Flow on Artificial Ground FreezingOther Limitations of Artificial Ground FreezingLOW-PERMEABILITY SURFACE BARRIERSVERIFICATION OF GROUNDWATER EXCLUSION METHODSPrediction of Inflow to Groundwater Exclusion SchemesMethods to Determine Total Inflow to Groundwater Exclusion SchemesAssessment of Acceptable PerformancePumps for Groundwater Lowering DutiesINTRODUCTIONPRINCIPLES OF PUMPINGWhat Is a Pump?Different Pumping MethodsMathematics of PumpingTYPES OF DEWATERING PUMPSUNITS FOR SUMP PUMPINGContractor’s Submersible PumpAll-Purpose Self-Priming Centrifugal Suction PumpWELLPOINT DEWATERING PUMPSDouble-Acting Piston PumpVacuum-Assisted Self-Priming Centrifugal PumpsetVacuum Tank UnitComparison of Merits of Piston Pumps vs. Vacuum- Assisted Centrifugal Wellpoint PumpsWellpoint Jetting PumpsPUMPS FOR DEEP WELLSBorehole Electro-Submersible Turbine PumpsUse of Oversized PumpsEncrustation and CorrosionBorehole Electro-Submersible Pumps - Operational ProblemsVertical Lineshaft Turbine PumpsLineshaft Pumps - Operational ProblemsComparison of Merits of Lineshaft Pumps vs. Electro-Submersible PumpsPUMPS FOR EJECTOR WELL SYSTEMSEjector Supply PumpsEjectorsEjector Performance CurvesOTHER PUMPING METHODSAirlift PumpingBailing of Deep ShaftsPUMP CONTROL SYSTEMSElectrical Control SystemsIntermittent Operation of PumpsDISCHARGE PIPEWORK AND EQUIPMENTDESIGN OF PUMPING SYSTEMSAssessing the Pump DutyEstimating Friction LossesSizing of PumpsEnergy Used in PumpingPermanent Groundwater Control SystemsINTRODUCTIONTYPES OF PERMANENT GROUNDWATER CONTROL SYSTEMSPermanent Groundwater Pumping SystemsPermanent Groundwater Barrier SystemsOBJECTIVES OF PERMANENT GROUNDWATER CONTROL SYSTEMSReduction of Groundwater Uplift Loads on StructuresControl of Anticipated Rises in Groundwater LevelsReduction in Leakage into Below-Ground StructuresStabilization of Slopes and Earth StructuresRemediation and Containment of Contaminated GroundwaterDESIGN ISSUES FOR PERMANENT GROUNDWATER CONTROL SYSTEMSLongevity of Permanent Groundwater Control SystemsReliability of Permanent Groundwater Control SystemsEfficiency of Permanent Groundwater Control SystemsEnvironmental Impacts of Permanent Groundwater Control SystemsLegacy Issues for Permanent Groundwater Control SystemsPRACTICAL ISSUES FOR PERMANENT GROUNDWATER CONTROL SYSTEMSOPPORTUNITIES ASSOCIATED WITH PERMANENT GROUNDWATER CONTROL SYSTEMSEnvironmental Impacts from Groundwater ControlINTRODUCTIONWHY ARE IMPACTS FROM GROUNDWATER CONTROL OF CONCERN?POTENTIAL ENVIRONMENTAL IMPACTS FROM GROUNDWATER CONTROLIMPACTS FROM GROUNDWATER ABSTRACTIONSettlement Due to Groundwater LoweringSettlement Due to Poorly Controlled GroundwaterSettlement Due to Loss of FinesSettlement Due to Increases in Effective StressSettlement Damage to StructuresRisk Assessment of Settlement Damage from Groundwater LoweringMitigation and Avoidance of SettlementImpact on Groundwater-Dependent FeaturesEffect on Groundwater QualityMovement of Contaminated GroundwaterSaline IntrusionEffect on Groundwater Borehole or Spring SuppliesOther EffectsIMPACTS FROM RECOVERY OF GROUNDWATER LEVELSIMPACTS FROM GROUNDWATER PATHWAYSVertical Pathways via Boreholes and WellsVertical Pathways via Excavations and StructuresHorizontal PathwaysIMPACTS FROM GROUNDWATER BARRIERSIMPACTS FROM DISCHARGE FLOWS TO THE GROUNDWATER ENVIRONMENTIMPACTS FROM DISCHARGE FLOWS TO THE SURFACE WATER ENVIRONMENTErosion Caused by Discharge FlowsSuspended SolidsDischarge Water Chemistry and TemperatureOil and Petroleum ProductsContaminated GroundwaterASSESSMENT OF POTENTIAL ENVIRONMENTAL IMPACTSIdentification of Potential Environmental ImpactsPrediction of Potential Environmental ImpactsMitigation of Potential Environmental ImpactsMonitoring of Potential Environmental ImpactsMonitoring of Groundwater Control SystemsINTRODUCTIONTHE NEED FOR MONITORINGManual Monitoring or Automated Monitoring?PHASES OF MONITORINGUsing the DataDATALOGGING SYSTEMSDATA MANAGEMENT AND DISSEMINATIONMONITORING OF GROUNDWATER LEVELSDatums Used for Groundwater Level MonitoringManual Monitoring of Groundwater LevelsMonitoring Groundwater Levels Using Pressure TransducersMonitoring of Artesian Groundwater LevelsValidating Groundwater Level DataMONITORING OF DISCHARGE FLOW RATEMonitoring Total Flow Rate or Flow from Individual WellsProprietary FlowmetersWeir TanksTimed Volumetric MethodsOther MethodsValidating Flow Rate Measurement DataMONITORING OF DISCHARGE WATER QUALITYMONITORING OF SURFACE SETTLEMENTSConventional Surveying TechniquesRemote Sensing TechniquesMONITORING OF SURFACE WATER BODIESOTHER PARAMETERS THAT MAY BE MONITOREDMaintenance of Groundwater Lowering SystemsINTRODUCTIONTHE NEED FOR MAINTENANCEPRINCIPAL MAINTENANCE REQUIREMENTSSTANDBY PUMPS AND AUTOMATIONStandby PumpsStandby Electrical Power SuppliesAlarm Systems and AutomationENCRUSTATION, BIOFOULING AND CORROSIONChemical EncrustationBacterial Growth and BiofoulingMaintenance Strategies to Manage Clogging and EncrustationCorrosionFAULT FINDING AND PROBLEM SOLVINGDecommissioning of Groundwater Control SystemsINTRODUCTIONTHE NEED FOR DECOMMISSIONINGHazards from Dewatering WellsHazards from Cut-Off WallsDECOMMISSIONING OF WELLS EXTERNAL TO STRUCTURESDECOMMISSIONING OF WELLS AND SUMPS LOCATED WITHIN STRUCTURESBREACHING OF CUT-OFF WALLSSafety, Contracts and Environmental RegulationINTRODUCTIONHEALTH AND SAFETYCDM RegulationsWorking with Hazardous SubstancesUse of Electricity on SiteLifting OperationsWorking at HeightWork Equipment and Drilling RigsSafety of ExcavationsNoiseWorking with Wells and BoreholesInteraction with Third-Party Services, Tunnels and InfrastructureRisk from Unexploded Ordnance (UXO)CONTRACTS FOR GROUNDWATER CONTROL WORKSThe Need for ContractsTraditional Contract ArrangementsAlternative Forms of ContractDewatering CostsENVIRONMENTAL REGULATION OF GROUNDWATER CONTROLGroundwater ProtectionAbstraction of GroundwaterDischarge of GroundwaterSettlement Resulting from the Abstraction of GroundwaterEnvironmental Regulation of Major ProjectsLocal RegulationsOptimization of Groundwater Control SystemsINTRODUCTIONWHY OPTIMIZE?DIFFERENT OPTIMIZATION METHODSEmpirical OptimizationNumerical Modelling or Analytical OptimizationObservational OptimizationOptimization in the Field (Troubleshooting)PROBLEMS WITH OPTIMIZATIONLack of Clarity in Objectives of OptimizationInsufficient Data Quality and QuantityErrors in Conceptual ModelInappropriate Groundwater Control TechniquePOSSIBLE PRIORITIES FOR OPTIMIZATIONCase HistoriesINTRODUCTIONCASE HISTORY: SUMP PUMPING OF LARGE EXCAVATION, ABERDEEN, UKCASE HISTORY: WELLPOINTING AT DERWENT OUTLET CHANNEL, NORTHUMBERLAND, UKCASE HISTORY: DEEP WELLS AND RELIEF WELLS AT TEES BARRAGE, STOCKTON-ON-TEES, UKCASE HISTORY: EJECTOR WELLS FOR SHAFT DEWATERING, WITH HIGH-PERMEABILITY FEATURE PRESENT, UKCASE HISTORY: HYDRAULIC FAILURE OF BASE OF SHAFT, UKCASE HISTORY: GROUNDWATER CONTROL BY SUMP PUMPING AND DEEP WELLS FOR SHAFT, UKCASE HISTORY: ARTIFICIAL RECHARGE TO CONTROL SETTLEMENT: MISR BANK, CAIRO, EGYPTCASE HISTORY: ARTIFICIAL RECHARGE TO PROTECT DRINKING WATER SOURCE, UKCASE HISTORY: LOW-PERMEABILITY CUT-OFF WALL AT SIZEWELL В POWER STATION, UKCASE HISTORY: CONTAMINATION REMEDIATION USING CUT-OFF WALLS AND GROUNDWATER ABSTRACTION AT DERBY PRIDE PARK, UKCASE HISTORY: PERMANENT GROUNDWATER CONTROL SYSTEM AT GOVAN UNDERGROUND TUNNEL, GLASGOW, UKThe FutureINTRODUCTIONREGULATION AND LEGISLATIONTECHNOLOGY AND THE INTERNET OF THINGSDESIGN AND NUMERICAL MODELLINGAPPLICATIONS AND TECHNIQUESWHERE DO WE GO FROM HERE?THE NEXT GENERATION OF DEWATERING PRACTITIONERSAppendix I: Estimation of Permeability by Correlations with Particle Size Distribution (PSD) of SoilAppendix 2: Execution and Analysis of Variable Head Permeability Tests in BoreholesAppendix 3: Execution and Analysis of Packer Permeability Tests in Boreholes in RockAppendix 4: Execution of Well Pumping TestsAppendix 5: Design ExamplesAppendix 6: Estimation of Flow Rate Using V-Notch WeirsNotationConversion factorsGlossary
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