Geohydrological impact of co-disposed coal material into an opencast pit

Abstract

Investigations have shown that receiving water bodies, which mainly include rivers, streams and the more complicated geohydrological system, are part of the primary end receivers of harmful contaminants from identified coal mining waste bodies. Some of these potential dangers include acid drainage (AD) and saline drainage (SD), which have dire effects on the surroundings. In the compilation of this dissertation the characteristics of the Northern KwaZulu Natal (KZN) coal fields and waste disposal methods are explored. A logical approach to dealing with some of the problems and risks associated with conventional disposal methods of coal wastes at a coal mine are considered and assessed. Various disposal methods implemented at a typical coal mine are assessed and simple co-disposal technique, whereby the various waste product are mixed before and after deposition are explored. The geological attributes of the KZN coal fields and the geochemical research results indicates that on its own, coal discard has great potential to produce long term SD and that coal tailings have a lower SD potential. Co-disposed results are promising and the buffering against long term chemical changes are noted. The end result is a waste product which is less reactive to the environment as well as easier to manage when it comes to mine closure. Geochemical laboratory testing results as well as long term monitoring data of the study area were integrated into a groundwater numerical model to illustrate the potential of co-disposed techniques versus that of conventional disposal methods. By exploring this alternative waste disposal method, gave more clarity on aspects relating to sustainable coal mine closure. Furthermore, the information gained from thus study sets the foundation for further research to accurately define and understand the co-disposal principle, as well as the better understand the environmental and management risks associated with it.