Vacuum deep wells are used for dewatering and site decontamination in regions with low subsoil permeability and low-lying aquifers Vacuum deep wells are operated effectively in aquifers with permeability [kf] coefficients ranging from 1x10-5 m/s to 1x10-7 m/s. They are installed by drilling a 324 mm / 700 mm diameter borehole up to a depth of 50 m. Depending on the diameter, the site geology and the intended depth, the borehole can be sunk by casing drilling or rotary drilling.
The borehole is drilled and fitted with a filter pipe. The annular void around the filter is backfilled with gravel. In addition the annular void is sealed at the top with a clay compound.
Groundwater pumping is realized by a multi-stage submersible pump installed in the completed well. The pump conveys the groundwater to a runoff ditch at the surface, therefore lowering the water table to the desired depth.
The groundwater removal is also assisted by a partial vacuum drawn by a vacuum pump aggregate at the upper edge of the well. The partial vacuum achieved can range up to -0.9 bar.The vacuum provides quick and more extensive drainage even in soils with low permeability, therefore stabilizing the surrounding soil layers.