Are Pitlakes an Environmentally Sustainable Closure Option for South African Coal Mines
Johnstone, Andrew Clifford
GCS (Pty) Ltd, South Africa
There are over 120 pitlakes in South Africa because of over two centuries of historical coal mining. The aim of the study is to determine if pitlakes are a sustainable coal mine closure option in South Africa. The study investigated the water balance, chemistry, limnology and bacteria of three selected pit lakes. The pitlake occur in the three major coal basins of South Africa and are associated with different mining methods. The major factors driving the water balance of the pitlakes are rainfall, runoff, inflow from historical mine workings and groundwater inflow with the major losses being evaporation or discharge on surface. The study proved that pitlakes could be designed to be terminal sinks and as a result a sustainable closure option in terms of the water balance. The groundwater chemistry showed the pitlakes to be stable with alkaline pH, mostly a sodium sulphate water with total dissolved solid content of less than 3000mg/l. The phytoplankton and microbiological data showed that the pitlake supported aquatic life. The study proved that with the correct design, coal mine pitlakes are an environmentally sustainable closure option for South Africa coal mines.