Characterisation of gold tailings dams of the Witwatersrand Basin with reference to their acid mine drainage potential,Johannesburg, South Africa

Factors which play a role in acid mine drainage (AMD) formation were investigated over a period of 12 months. These include climatic, mineralogical, hydrological and oxygen diffusion parameters. The oxygen diffusion data reveal that the flow of oxygen in the Witwatersrand tailings dams is controlled by secondary porosity (i.e. cracks caused by roots on the dam surface). The age of the dam does not have a significant bearing on the extent to which the oxidised zone development and subsequently AMD can progress. Most of these processes take place within the first 3 m of the dams. The amount of rainfall plays a crucial role in determining the extent to which an oxidised zone progresses. The average oxidised zone in the 5 sites is 2.4 m ranging from 2.2 to 3.5 m. Water SA Vol.32 (4) 2006: pp.499-50