Dewatering and construction dewatering are terms used to describe the action of removing groundwater or surface water from a construction site through deep wells or wellpointing. Normally the dewatering process is done by pumping or evaporation and is usually done before excavation for footings or to lower the water table that might be causing problems during excavations. The most common dewatering methods used frequently involves the use of submersible dewatering pumps, centrifugal trash pumps, eductors, or application of vacuum to well points. Deep wells can be installed in a ring around an excavation to lower the water level and maintain a safe, dry site.
Wellpoints are small-diameter (about 50 mm) tubes with slots near the bottom that are inserted into the ground from which water is drawn by a vacuum generated by a dewatering pump. Wellpoints are typically installed at close centers in a line along or around the edge of an excavation.