Initial situation

The long-term effects of mining on the hydrologic balance and the surface have sometimes caused permanent damage as the hydrologic balance begins to be restored after mining has ended. It is particularly housing, and other forms of land use that are permanently affected. LMBV has wide experience in this area. The reference project is the Hoyerswerda urban area, where since 1958 buildings were constructed without taking account of rising ground water levels. After financing had been agreed by the Free State of Saxony in 1997, LMBV was requested, as project sponsor, to draw up a drainage system.

Approach

One option for active protection of the buildings is to take technical measures that maintain a low ground water level. The technical solution to the problem of maintaining a permanent low ground water level in the Hoyerswerda urban area was found by planning and installing a system of horizontal filtering wells and collector shafts, part of which is connected to underground drains. The water that is thus raised is led into the purpose-built western boundary dike. The filtering wells, each with eight 70-metre filter trains, produce 60 to 340 m³ an hour.

Result

In the meantime, the system which consists of three horizontal filtering wells and the above-ground drainage element of the 3.3.km long, and up to seven metres deep western boundary dike has been operated successfully, whereby it is essential to ensure that the amounts pumped out correspond to the ground water level that will not result in damage to the endangered residential areas.