Dewatering is used on civil engineering and construction projects to enable excavations to go below the groundwater level. Dewatering involves the temporary lowering of groundwater level to below an excavation level or depressurisation of groundwater pressures to enable an excavation to be undertaken in stable and dry ground conditions.
Each deep well is borehole, which is then lined with a slotted screen, the annulus between the borehole and well screen is backfilled with filter media or formation stabilizer to form a filter pack. A deep well system has individual submersible pumps installed within the liner close to the base of the well and can be installed/recovered by the riser pipe. The wells are usually sited just outside the proposed area of excavation.
As water is pumped from a deep well, a hydraulic gradient is formed and water flows into the well, forming a cone of depression around the well in which there is little or no water remaining in the pore spaces of the surrounding soil. Installation of deep well boreholes is usually by Rotary Drilling techniques, depending on the geology we can utilise Biodegradable polymer mud flush, water flush, and simultaneous drilling casing systems.
Should conditions be favourable we can install dewatering wells to large diameters with our fleet of Cable percussive rigs. Danbar Drilling can install deep wells up to 400mm diameter. In competent ground, such as chalk or sandstone, wells may be installed with an open-hole drilling method. The borehole depths can range from 10-50 meters, on occasion wells can be drilled to greater depths. If your project requires deep well drilling then Danbar Drilling Services can help, we have completed a number of dewatering projects including Hinckley Point which involved drilling 70 No deep wells to around 70m, at a diameter of 300mm