Are Pitlakes an Environmentally Sustainable Closure Option for South African Coal Mines?

摘要

There are over 200 pitlakes in South Africa due to over two centuries of coal mining. The aim of this 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 pitlakes occur in the three major coal basins of South Africa and are as a result of different mining methods. The major factors driving the water balance of the pitlakes are rainfall, runoff, groundwater and inflow from historical mine workings. The major losses from the pitlakes are evaporation or discharge of water on surface. The study proved that pitlakes can 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 type water with total dissolved solid content of less than 3 000mg/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. A suggested design manual was developed to aid mine planners, owners and regulators to develop sustainable coal mines pitlakes as a closure tool.