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Controlling Water On Construction Sites

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Methods for construction dewatering and groundwater control

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Controlling Water On Construction Sites

  1. 1. www.preene.com CONTROLLING GROUNDWATER ON CONSTRUCTION SITES Dr Martin Preene Preene Groundwater Consulting June 2014
  2. 2. www.preene.com SYNOPSIS • Good and bad examples of water management • Surface water management • Groundwater control • Environmental impacts from water management • Conclusion
  3. 3. www.preene.com PRACTICE PROFILE Preene 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)
  4. 4. www.preene.com GOOD CONTROL OF GROUNDWATER
  5. 5. www.preene.com POOR CONTROL OF GROUNDWATER
  6. 6. www.preene.com SURFACE WATER CONTROL Groundwater control alone cannot keep an excavation dry. Surface water must also be controlled
  7. 7. www.preene.com SURFACE WATER CONTROL • Source 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)
  8. 8. www.preene.com GROUNDWATER CONTROL BY EXCLUSION Cut-off walls penetrate into underlying low permeability stratum
  9. 9. www.preene.com GROUNDWATER CONTROL BY PUMPING Common Techniques • Sump Pumping • Wellpoints • Deepwells • Ejector wells
  10. 10. www.preene.com SUMP PUMPING
  11. 11. www.preene.com WELLPOINTS From CIRIA Report C515 (2000): Groundwater Control: Design and Practice
  12. 12. www.preene.com DEEPWELLS From CIRIA Report C515 (2000): Groundwater Control: Design and Practice
  13. 13. www.preene.com EJECTOR WELLS From CIRIA Report C515 (2000): Groundwater Control: Design and Practice
  14. 14. www.preene.com RANGE OF APPLICATION OF PUMPING METHODS Amount of lowering of groundwater level Low permeability (silts) High permeability (gravels) From CIRIA Report C515 (2000): Groundwater Control: Design and Practice
  15. 15. www.preene.com Water 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 waters ENVIRONMENTAL IMPACTS
  16. 16. www.preene.com IMPACTS FROM ABSTRACTION Effect on groundwater quality • Pumping from dewatering systems changes natural hydraulic gradients and velocities • This can cause the migration of plumes of polluted water associated with contaminated sites
  17. 17. www.preene.com Distortion of structure in uniform soil conditions IMPACTS FROM ABSTRACTION – SETTLEMENT Distortion of structure due to change in soil conditions
  18. 18. www.preene.com CONCLUSION • Effective management of surface water and groundwater can be crucial for construction projects • Groundwater can be controlled by pumping methods and exclusion methods • Technology needs to be carefully selected • Environmental impacts including ground settlement and movement of contaminated groundwater • With suitable planning and design these challenges can be overcome
  19. 19. www.preene.com CONTROLLING WATER ON CONSTRUCTION SITES Dr Martin Preene Preene Groundwater Consulting June 2014

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