Ground Works
Construction Dewatering & Groundwater Control
Dewatering design, wellpoints, deep wells and sump pumping, standby pumps, temporary electrical supply, drawdown and settlement control, monitoring, shutdown and system removal.
v2.1Updated 9 Aug 2026ADOSH-SF v4.1 (February 2026)Learning Objectives
- Select an appropriate dewatering method for the ground and drawdown required.
- Set up pumps, standby pumps, hoses and pipe routes safely.
- Apply temporary electrical safety controls to dewatering plant.
- Monitor groundwater levels, drawdown and settlement against trigger levels.
- Plan safe shutdown, decommissioning and removal of the system.
Training Video
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1. Dewatering Design
Design is based on the geotechnical and permeability data: required drawdown, radius of influence, flow rate, recharge risk and the effect on adjacent structures and wells. The design defines pump duty, spacing, filter media and monitoring points, and is a temporary-works item subject to check.
2. Methods
Wellpoints for shallow drawdown in permeable soils; deep wells with submersible pumps for greater depth or higher flow; sump pumping and perimeter drainage for small inflows in stable ground; cut-off walls (including sheet piles) to reduce pumped volume.
3. Pumps & Standby
Standby pumps and an alternative power source are mandatory where an unplanned shutdown would flood a supported excavation or cause instability. Pump guards fitted, non-return valves used, fuel handling bunded, and alarms fitted for pump failure and high water level.
4. Hoses & Pipe Routing
Discharge lines routed clear of access routes or protected by ramps; secured against whipping; joints restrained; no trip hazards across walkways; routes kept clear of live traffic and of excavation edges where leakage could soften the ground.
5. Temporary Electrical Supply
Dewatering plant is a wet-environment electrical risk: RCD-protected supply, IP-rated enclosures, mechanical protection of cables, competent electrician installation, isolation and LOTO for pump maintenance, and earthing/bonding checks recorded.
6. Drawdown, Settlement & Monitoring
Piezometers and standpipes monitor groundwater levels; settlement markers monitor adjacent ground and structures. Trigger, action and alarm levels are defined, recorded daily, and escalated. Excessive drawdown can consolidate soils and settle neighbouring buildings and services.
7. Shutdown & Removal
Planned shutdown only after the permanent works can resist uplift and water pressure; buoyancy/flotation check completed. Wells are decommissioned and sealed, sumps backfilled, and the system removed with the excavation support still in place until the designed sequence allows removal.
Knowledge Assessment
1. Dewatering design is based on:
2. Deep wells with submersible pumps are used for:
3. Standby pumps and alternative power are required when:
4. Dewatering plant electrical supply must be:
5. Pump maintenance requires:
6. Groundwater levels are monitored using:
7. Excessive drawdown can cause:
8. Monitoring records should be:
9. Before permanent shutdown of dewatering:
10. Sheet-pile cut-off walls are used in dewatering to:
Certificate
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