Acid Mine Drainage

ACID MINE DRAINAGE

ABSTRACT

The decommissioning and closure of mining operations within the Witwatersrand Gold Basins and the subsequent cessation of the dewatering of the mines has led to an increase in the levels of acid mine water within the basins. The potential decant of this acid mine water has significant environmental and economic concerns, as was witnessed following the decanting of water in the Western Basin in 2002. The reality is not that basements and homes will become flooded, but rather that the local rivers and flora and fauna will suffer as acid water mixes into the surrounding catchments and ground water. This article looks at the potential macro concerns and the wished-for clarifications thus far.

INTRODUCTION

Topical South African media attention has stressed the issue of the potential decant of underground mine water into the urban areas of Johannesburg from the Western, Eastern and Central Gold Mining Basins of the Witwatersrand. This mass of underground water is acidic in nature as it has reacted chemically with the remaining earth within the mining basins through a process of oxidation and has been tested at a pH of between 2 and 4 depending on geographic location. Not only is the chemical nature of the water a concern, so is the amount of water that is due to decant into the local rivers and the cities’ wastewater management system. Local media excitement increased public awareness of the issue, known internationally and in the mining community as acid mine drainage. Government, together with private sector mining companies, academics, engineering firms and environmental impact assessment consultants have initiated an investigation to curtail the problem within the short term, whilst searching for longer-term solutions.

The South African market for essential goods such as energy, water, and municipal services is currently weakened by a shortage in supply relative to desired capacity demand. As can be witnessed in the case of Eskom in Figure 1, the state