Deep well dewatering

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Deep filter well - dewatering

Whenever the water collection capacity of well-points is not enough to dewater an area, due to its highly permeable soil and significant water recharge, deep well dewatering is used.

Application

  • In case of high-permeability
    • sand
    • coarse sand
    • sandy gravel
    • soils, soil layers with boulders, or
  • any combination of these soils, sandwich structure, or
  • if water has to be drained from greater depths, or
  • if a high amount of water enters the area.

Structural buildup of deep wells

They are deep filter wells, with a diameter of 400-600 mm, surrounded by classified fine gravel filtering in the proper length. The outside diameter of the borehole is 600-1400 mm, depending on soil properties and structure. The space between the borehole wall and the well casing is filled with a gravel filter pack. The wells can be constructed 5-25 metersapart from each other.

Heavy-duty submersible pumps with an automatic device to control the pressure head are installed to the deep wells. These are connected to a collector pipe, leading the excess groundwater away from the area. As a result of pumping, a parabolic depression curve is formed in the soil mass between the deep wells, the highest point of which is the maximum of the lowered groundwater level.