Open pit mine

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" The Big Hole ", the open pit of the Kimberley diamond mine in South Africa

An open pit is a deepening in the surface of the earth as a result of the extraction of mineral raw materials ( lignite , ore , sand , gravel ) in open-cast mining . The volume theoretically comprises the mass deficit from raw production and usable production after the open pit mine has been filled with the unusable material ( overburden ).

From Tagebaurestsee is called only when the remaining hole becomes full by the end of degradation. In many quarry ponds , however, they are dredged from the lake: Although gravel mining is opencast mining, one does not speak of a residual open pit. The same applies to brick ponds (clay holes).


Opencast mines that have been permanently shut down must be recultivated . As a post-mining landscape , the open pit can either:

  • Filled completely with foreign material (e.g. tunnel excavation, power plant ash, rubble),
  • expanded to a landfill or
  • be flooded.

In Germany, after the open pit mine has been closed, flooding of the remaining hole is the predominant option because:

  • in the often flat opencast mining areas there are mostly high groundwater levels ,
  • Due to strict environmental regulations, foreign material can often only be brought in to a small extent.

Most of the remaining open pit holes are flooded with ground or surface water. With a corresponding recultivation of the riparian zones (flattening and consolidation of the riparian zones to prevent landslides, planting) high quality recreational landscapes can arise. In this way, for example, parts of the local recreation area Naturpark Rheinland west of Cologne , the Leipziger Neuseenland or the Blausteinsee north of Eschweiler were created . The remaining holes in Garzweiler , Hambach and Inden in the Rhineland are also to be flooded.

The LMBV is responsible for this in central Germany and Lausitz .

Acid wastewater

One of the main environmental problems of residual lakes, especially after the mining of ores, is acidic mine water . During the weathering of sulfide-containing ores such as pyrite , sulfur is oxidized to sulfuric acid. Post-weathering and complex chemical processes often cause the pH value in residual lakes to drop to values ​​of 2–4.

Flooding of the remaining open pit at Klinge ( Niederlausitz )

Web links

Wiktionary: Remnants of open pit mining  - explanations of meanings, word origins, synonyms, translations


  • Heiko Geitner: Contributions to the environmental impact study, flooding of the remaining open-cast mine hole in Müuellen / Geiseltalsee . Diploma thesis agency, Hamburg 1998, ISBN 978-3-8386-0976-8 .