Methods for construction dewatering and groundwater control

1. www.preene.com
CONTROLLING GROUNDWATER ON
CONSTRUCTION SITES
Dr Martin Preene
Preene Groundwater Consulting
June 2014

2. www.preene.com
SYNOPSIS
• Good and bad examples of water management
• Surface water management
• Groundwater control
• Environmental impacts from water management
• Conclusion

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. www.preene.com
GOOD CONTROL OF GROUNDWATER

5. www.preene.com
POOR CONTROL OF GROUNDWATER

6. www.preene.com
SURFACE WATER CONTROL
Groundwater control alone cannot keep an excavation dry. Surface water
must also be controlled

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. www.preene.com
GROUNDWATER CONTROL BY EXCLUSION
Cut-off walls
penetrate into
underlying low
permeability stratum

9. www.preene.com
GROUNDWATER CONTROL BY PUMPING
Common Techniques
• Sump Pumping
• Wellpoints
• Deepwells
• Ejector wells

10. www.preene.com
SUMP PUMPING

11. www.preene.com
WELLPOINTS
From CIRIA Report
C515 (2000):
Groundwater Control:
Design and Practice

12. www.preene.com
DEEPWELLS
From CIRIA Report
C515 (2000):
Groundwater Control:
Design and Practice

13. www.preene.com
EJECTOR WELLS
From CIRIA Report
C515 (2000):
Groundwater Control:
Design and Practice

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. 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. 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. www.preene.com
Distortion of structure in
uniform soil conditions
IMPACTS FROM ABSTRACTION – SETTLEMENT
Distortion of structure due
to change in soil
conditions

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. www.preene.com
CONTROLLING WATER ON
CONSTRUCTION SITES
Dr Martin Preene
Preene Groundwater Consulting
June 2014