Range of application of dewatering techniques
(based on CIRIA C515, London 2000)
Groundwater control/dewatering
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Groundwater control or dewatering is the temporary reduction of pore pressures or groundwater levels to provide dry, stable and safe soil conditions in excavations below groundwater level. Dewatering is used to facilitate the construction of the deep excavations that are required for basements, tunnels and other underground structures.
WJ designs, installs and operates the deepwell, ejector or wellpoint systems that provide groundwater control. Recharge systems can be deployed to protect structures and environmentally sensitive areas that may be adversely affected by off-site drawdowns.
The choice of dewatering system depends on ground conditions, as shown in the diagram left. Ground conditions are assessed by the analysis of site investigation information, which may be supported by specialist pumping tests.