Deep Well Dewatering

Very effective where you have large volumes of groundwater to be removed or reduced and where soil permeability is moderate to high. A deep well system is typically installed over a wide area beneath excavations, shafts, tunnels or basements by pumping water from a ring or array of individually drilled wells. Below 6 meters deep (boreholes typically 200mm to 300mm in diameter). Consisting of several wells enabling lower groundwater levels. A series of boreholes is installed inside or outside the excavation area, lined with slotted screens and granular filter packs, through the target geological strata.

Pumped using electrical submersible pumps at the base of each well, connected to the surface by a riser pipe through which water is pumped into a common header main, before being discharged. As water is pumped from each well, the groundwater is lowered, creating a cone of depression (or drawdown cone) around itself. A cone of depression is a V-shaped or inverted conical drop in the local water table or piezometric surface (known also as a potentiometric surface), an imaginary or hypothetical surface that represents the level to which water will rise in a well or tube (a piezometer) due to hydrostatic pressure in a confined or semi-confined aquifer (an underground layer of water-bearing permeable rock, gravel, sand or silt able to store and transmit usable amounts of groundwater, of which there are different types), centered around a pumping well.