Mining at Middelburg Colliery in the Witbank Coalfield commenced at the turn of the last century. Initially, there was little environmental degradation associated with mining activities; however, in the late 1930s, a pillar-robbing programme commenced. This has had a marked effect on the environment. Some of the most notable primary effects include subsidence, the appearance of tension cracks a! the surface and crownhole development. Secondary effects include spontaneous combustion of the coal worked, as air has been provided with ready access to the mine, accelerated subsidence due to the strength of many pillars being reduced by burning, and a marl;ed deterioration of groundwater quality in the area due to the seepage of acid mine drainage from the mine. Spoil heaps also form blemishes on the landscape. These contain significant amounts of coal and have undergone spontaneous combustion. The deterioration in the duality of water has led to the decimation of vegetation in some areas and the eradication of aquatic flora and fauna in a nearby stream. (C) 2001 Elsevier Science B.V. All rights reserved.