Experiences with mine closure in the European coal mining industry: an overview of the situation in Germany and adjacent regions

摘要

In recent decades, the mining industry in Europe has been characterised by a very high rate of mine closure. One of the affected branches is the underground hard coal mining industry. There is substantial demand for environmentally compatible mine closure programs, especially in light of the implementation of the new EU Water Framework Directive. Hence, acid mine drainage is a specific challenge.By 2018, the last remaining active coal mines in Germany's largest hard coal mining area, the Ruhr industrial region, will be closed. With a maximum population density of 2,800 people per km2, the Ruhr district is the largest urban agglomeration in Germany and one of the most densely populated coal mining areas worldwide. Early coal mining activities date back to the twelfth century. Since then, a total of about 10 billion t tonnesof coal has been produced. The maximum depth of the mining process is 1,500 m below the surface, and the maximum subsidence ranges up to 25 m. It is necessary to sustain the drainage system to prevent built-up areas from being flooded or impacted by mine water. Hence, water management measures will continue in perpetuity after coal mining has ceased: about 70 million m~3/a of mine water and an additional 900 million m~3/a of water in the polder areas have to be pumped permanently. Numerous shafts, deep cavities and shallow openings call for remedial activities in order to prevent damage, stabilise new structures or restore former geomorphology. For these reasons, risk management was established a couple of years ago. A special challenge will be the protection of subsurface groundwater horizons, especially drinking water horizons, against infiltration of mine water.The paper also summarises the results of a study that compiles numerous European hard coal mining areas' experiences with mine closures. In particular, the investigation compares the effects of rising mine water level, impacts on the ground surface resulting from mine subsidence/uplift and effects of the mine water hydrochemistry at the different sites. On this basis, advice is given to reduce closure risks and optimise closure operations. The purpose is to achieve lasting safety for the ground surface, the population and the water bodies at a reasonable cost.