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Dewatering - Excavation & Ground Water Control

Dewatering - Excavation & Ground Water Control

Dewatering is the process of removing groundwater. It ensures construction work can occur without trenches collapsing.

When groundwater is present, dewatering costs are charged to the customer. If the costs are more than the final invoice, the extra charges are not passed on to the customer. If the work required to remove the groundwater is less, we will refund any unused part of the invoice.

Refunds will be confirmed after SA Water receives the contractor's invoice.

There are many systems that can control groundwater. The method used will be determined by the level, size and depth of excavation. Geological conditions and characteristics of the soil are also considered.

The simplest and most cost effective form of dewatering is a trench pump. Groundwater entering the excavation can be collected in a sump and pumped away. This system is only effective where the excavation is on or just below the groundwater level.

A trench pump cannot always control groundwater inflow. In this case we use a vacuum truck or well point dewatering system.  This requires specialist contractors and equipment to extract, pump and dispose of the groundwater. This also increases the cost of dewatering significantly.

A vacuum truck uses a heavy duty vacuum to load solids, liquids, sludge or slurry through a suction line. This may require more than one truck. Disposal of the collected material and groundwater must be in compliance with environmental regulations.

Well point dewatering systems need a series of suction spears. These are installed near the excavation site.

The suction spears are driven into the ground below the groundwater level. These suction spears are connected to larger header pipes which are also connected to a pump. The pump draws the groundwater into the suction spears and through the header pipe. The water is discharged via an approved environmental treatment system.

Dewatering systems require installation before the planned excavation.  They may need to run continuously for several days. This lowers the groundwater level so excavation can begin.

The following areas may be subject to groundwater conditions:

Albert ParkClearviewGlenelg EastLockleysRoyal Park
AlbertonCowandillaGlenelg NorthMansfield ParkSeaton
Allenby GardensDry CreekGlenelg SouthMawson LakesSemaphore
Angle ParkEdinburghGlengowrieMorphettvilleSemaphore Park
Athol ParkEdinburgh NorthGlobe Derby ParkNorth HavenSemaphore South
BeverleyEtheltonGrangeNorthfieldSt Kilda
BirkenheadExeterGreenacresNovar GardensSt Clair
BolivarFerryden ParkGreenfieldsOsborneTaperoo
BrightonFindonHendonOttowayTennyson
Brighton SouthFlinders ParkHenley BeachOuter HarborWest Beach
BroadviewFulhamHenley Beach SouthPenningtonWest Lakes
Brooklyn ParkFulham GardensHovePeterhead

West Lakes Shore

Buckland ParkGepps CrossKidman ParkPlympton ParkWingfield
Camden ParkGillmanKilburnPlympton SouthWoodville Gardens
CavanGlanvilleLargs BayPort AdelaideWoodville West

  • Major faults

  • Reported

  • Various suburbs
  • 24/02/2017
  • Water Quality
  • Some Adelaide Hills customers may notice changes in the taste and/or smell of their tap water, as we work hard to reduce the impact of an algal bloom in the Summit Reservoir.
    The algal bloom is causing a naturally occurring compound called geosmin, which can affect water taste and odour, but is harmless to health. The water remains safe to drink.
    We expect customers in the following areas may notice this change: Mount Barker, Balhannah, Oakbank, Verdun, Hahndorf, Heathfield, Stirling, Crafers, Lenswood, Lobethal, Woodside, Brukunga, Mount Torrens, Birdwood, Gumeracha, Kersbrook, Cudlee Creek, Wistow, Nairne, Littlehampton, Strathalbyn, Clayton, Milang, Langhorne Creek and Bridgewater.
    We have made changes to our treatment processes at the Summit Water Treatment Plant to reduce the level of geosmin in the water.   
    Our testing shows no algae has been detected in the network and it has been completely removed as part of our normal treatment process.
    If our customers have any questions or concerns, please contact us on 1300 SA WATER.
  • See all major faults

  • Scheduled works

  • Underway
  • Filsell Tce
  • Gawler South
  • 25/02/2017
  • Supply Interruption
  • Estimated start time (water off): 28/02/2017 09:00 AM
    Estimated restore time (water back on): 28/02/2017 03:00 PM

    We’re committed to improving your services and are undertaking maintenance work in Gawler South. Water supply in the surrounding area may be impacted during the above times. Traffic restrictions may also apply.


  • See all scheduled works