Impact of residual coal extraction from hard coal mining waste dumps on groundwater salinity

Re-mining of existing dumping sites for the extraction of coal residues (around 10% wt.) with subsequent reuse of a secondary waste in engineering constructions or its re-disposal in the environmentally safe way is an attractive and economically viable way of coal protection as a valuable natural resource and of adequate reduction of dumped waste volume. These methods of bulk waste re-use may though cause also negative consequences, if not properly controlled. In this article, the adverse environmental impacts of technological processes of coal extraction are exemplified in a coal mining waste dump in the Upper Silesia coal basin (USCB) in Poland, where coal waste has been reprocessed since 1998. Both the disturbance of original waste layers in the dump and altered exposure of the processed rock material to the atmospheric conditions during residual coal extraction, and secondary wastes re-disposal/re-use appeared to result in significant increase of groundwater salinity. Therefore, adverse effects of was...