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 suburbs listed below may be subject to groundwater costs. Recent costs for well point dewatering work in the listed suburbs have averaged $16,500. However additional fees may be payable depending on the specific job requirements, to be confirmed when assessing the application.

Albert ParkClearviewGlenelg EastLargs NorthPort AdelaideWoodville West
AlbertonCowandillaGlenelg NorthLockleysRoyal Park 
Allenby GardensDry CreekGlenelg SouthMansfield ParkSeaton 
Angle ParkEdinburghGlengowrieMawson LakesSemaphore 
Athol ParkEdinburgh NorthGlobe Derby ParkMorphettvilleSemaphore Park 
BeverleyEtheltonGrangeNorth HavenSemaphore South 
BirkenheadExeterGreenacresNorthfieldSt Kilda 
BolivarFerryden ParkGreenfieldsNovar GardensSt Clair 
Brighton SouthFlinders ParkHenley BeachOttowayTennyson 
BroadviewFulhamHenley Beach SouthOuter HarborWest Beach 
Brooklyn ParkFulham GardensHovePenningtonWest Lakes
Buckland ParkGepps CrossKidman ParkPeterheadWest Lakes Shore 
Camden ParkGillmanKilburnPlympton ParkWingfield 
CavanGlanvilleLargs BayPlympton SouthWoodville Gardens

Example photography of dewatering work being undertaken

Well point dewatering system in place with associated road closure and temporary fencing

Close up of the suction spears for the wellpoint dewatering system

Close up of the suction spears for the wellpoint dewatering system

Well point dewatering system in place with associated road closure and temporary fencing

Example of an approved environmental treatment system

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