PowerPoint Presentation

Controlling groundwater on construction sitesDr Martin PreenePreene Groundwater ConsultingJune 2014

www.preene.comSynopsisGood and bad examples of water management

Surface water management

Groundwater control

Environmental impacts from water management

Conclusionwww.preene.com2PRACTICE PROFILEPreene Groundwater Consulting is the Professional Practice of Dr Martin Preene and provides specialist advice and design services in the fields of dewatering, groundwater engineering and hydrogeology to clients worldwide

Dr Martin Preene has more than 25 years experience on projects worldwide in the investigation, design, installation and operation of groundwater control and dewatering systems. He is widely published on dewatering and groundwater control and is the author of the UK industry guidance on dewatering (CIRIA Report C515 Groundwater Control Design and Practice) as well as a dewatering text book (Groundwater Lowering in Construction: A Practical Guide to Dewatering)www.preene.comGood control of groundwater

www.preene.com4Poor control of groundwater

www.preene.com5Surface water controlGroundwater control alone cannot keep an excavation dry. Surface water must also be controlled

www.preene.com6Surface water controlSource control- intercept run-off before it reaches the excavation- prevent unnecessary generation of water in the excavation- collect water as soon as it reaches the work area (or before!)

Water collection - French drains to intercept run off- collector drains and sumps- pumping systems (keep it simple!)

Water treatment- solids removal (settlement tanks, Siltbusters)

www.preene.com7Groundwater control by exclusion

Cut-off walls penetrate into underlying low permeability stratumwww.preene.com8Groundwater control by pumping

Common Techniques

Sump Pumping

Wellpoints

Deepwells

Ejector wells

www.preene.com9Sump pumping

www.preene.com10Wellpoints

From CIRIA Report C515 (2000): Groundwater Control: Design and Practicewww.preene.com11Deepwells

From CIRIA Report C515 (2000): Groundwater Control: Design and Practicewww.preene.com12Ejector wells

From CIRIA Report C515 (2000): Groundwater Control: Design and Practicewww.preene.com13Range of application of pumping methodsAmount of lowering of groundwater level

Low permeability (silts)High permeability (gravels)From CIRIA Report C515 (2000): Groundwater Control: Design and Practicewww.preene.com14Water management on construction sites can have a range of impacts:Impact 1: Abstraction- e.g. settlement, impact on water sources and water quality

Impact 2: Pathways for groundwater flow- e.g. increased risk of aquifer pollution

Impact 3: Barriers to groundwater flow- e.g. changes in groundwater level

Impact 4: Discharges to groundwater- e.g. risk of fuel spills, etc

Impact 5: Discharge to surface water- e.g. risk of pollution of surface watersEnvironmental impactswww.preene.com15Impacts from abstractionEffect on groundwater qualityPumping from dewatering systems changes natural hydraulic gradients and velocitiesThis can cause the migration of plumes of polluted water associated with contaminated sites

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Distortion of structure in uniform soil conditionsImpacts from abstraction settlement

Distortion of structure due to change in soil conditionswww.preene.com17ConclusionEffective management of surface water and groundwater can be crucial for construction projectsGroundwater can be controlled by pumping methods and exclusion methodsTechnology needs to be carefully selectedEnvironmental impacts including ground settlement and movement of contaminated groundwaterWith suitable planning and design these challenges can be overcome

www.preene.com18Controlling water on construction sitesDr Martin PreenePreene Groundwater ConsultingJune 2014

www.preene.com