Hölscher Wasserbau GmbH

Vacuum Deep Wells

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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.

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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.

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