Open Cast Mining

An open-cast mine is the extraction of mineral resources on the earth's surface. The soil and a top layer may have to be removed beforehand. If the raw material is exposed, it can be mined by excavators and transported from the open-cast mine by truck or conveyor belt. When rock is mined, the rock must first be released from the composite. If it is needed in blocks, it is split or sawn. If simply the material is needed, it is shoveled, possibly blasted beforehand for shredding.

An open-cast mine is mostly used for raw materials deposited flat and close to the surface It can cover a huge area, but can also reach a depth of several hundred meters. Opencast mining is cheaper than underground mining, so it is often worthwhile for ores with a very low content of the sought mineral.

An open-cast mine is exposed to the weather. Rainwater and groundwater often lead to the formation of a lake in the hollow. As a rule, the water must be continuously pumped out during the operation.

At the end of mining, a huge depression remains, partially filled with groundwater. Due to the very high landscape consumption, many countries have requirements that the area must be renaturalized after mining. This is particularly important if the degraded substance is harmful to health. Opencast mines of uranium, asbestos or heavy metals must then be covered with a waterproof layer to prevent the toxins from being released into the environment. Unfortunately, this was often neglected in historical opencast mines.

Depending on the location of the mining, it can be worthwhile to use the former open-cast mine as a landfill, for example for household waste, industrial waste or building materials. The depression is usually first sealed with a thick layer of water-impermeable clay to prevent the release of toxins from the garbage into the groundwater. After the garbage has been stored, it is sealed again to prevent meteoric water from entering the garbage. A layer of rubble protects the waterproofing and the landscape can be planted on top. Because mining companies traditionally go bankrupt with the exhaustion of the deposits and leave the cleaning up to the taxpayer, the creation of a financial reserve during mining is now often required by law.