Dewatering is the process of removing groundwater, which ensures construction work can occur without trenches collapsing.
When groundwater is present, dewatering costs are charged to you. If the costs are more than the final invoice, the extra charges are not passed on to our customer. If the work required to remove the groundwater is less we will refund any unused part of the invoice to you.
You will be invoiced for the estimated dewatering cost. Once we’ve received your full payment, site works will commence.
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 significantly increases the cost of dewatering.
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 comply 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.
Is your suburb likely to need dewatering
The suburbs below may be subject to groundwater costs. Recent costs for well point dewatering work in these suburbs have averaged $16,500. However additional fees may be payable depending on the specific job requirements, to be confirmed when assessing the application.
Globe Derby Park
Henley Beach South
West Lakes Shore
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