Impact of the method of managing opencast excavations by filling with mining waste on the quality of leachate entering the surface water

For years, environmental protection has been struggling with the problem of water contamination in Poland, especially salinity in surface water. The main source of water salinity in Poland is mining, so the problem of water salinity most affects the region of Silesia, which is characterized by a large number of hard coal mines and industrial plants. The hard coal mines located in Upper Silesia, during mining operations, pump large quantities of highly saline waters from the drainage of mine workings to the surface. Therefore, the problem of environmental protection is nowhere else on such a large scale. However, due to the fact that hard coal mines in our country constitute the main source of energy resources, solving the problem of saline water is difficult. The first part of the article presents the negative impact of salinity on water quality and resources in Poland and and it also indicates the economic effects associated with excessive salinity of rivers, which mainly include corrosive effects. The second part of the article will indicate the method of reclamation of the minefilling sand excavation, from which the leachate is discharged into surface water. As the reclamation takes place by filling the excavation with post-mining waste, there is a risk that saltwater may enter the surface water. This article also presents the example how to properly reclaim areas with post-mining waste and maintain good water status, to which leachate from the reclaimed area is discharged. The article specifies how much water from post-mining waste can be safely discharged into surface water, without creating the risk of excessive salinity. In the event of an imminent threat, there is an obligation to immediately take preventive measures, including immediate control, containment, removal or reduction of pollution or other harmful factors e.g. by controlling leachate effluent flows.