<P> In response to negative land effects of coal mining and the abundance of abandoned mines in the US the federal government enacted the Surface Mining Control and Reclamation Act of 1977, which requires reclamation plans for future coal mining sites . These plans must be approved by federal or state authorities before mining begins . </P> <P> Surface mining may impair groundwater in numerous ways: by drainage of usable water from shallow aquifers; lowering of water levels in adjacent areas and changes in flow direction within aquifers; contamination of usable aquifers below mining operations due to infiltration (percolation) of poor - quality mine water; and increased infiltration of precipitation on spoil piles . Where coal or carbonaceous shale is present, increased infiltration may result in: increased runoff of poor - quality water and erosion from spoil piles, recharge of poor - quality water to shallow groundwater aquifers and poor - quality water flow to nearby streams . </P> <P> The contamination of both groundwater and nearby streams may be for long periods of time . Deterioration of stream quality results from acid mine drainage, toxic trace elements, high content of dissolved solids in mine drainage water, and increased sediment loads discharged to streams . When coal surfaces are exposed, pyrite comes in contact with water and air and forms sulfuric acid . As water drains from the mine, the acid moves into the waterways; as long as rain falls on the mine tailings the sulfuric - acid production continues, whether the mine is still operating or not . Also waste piles and coal storage piles can yield sediment to streams . Surface waters may be rendered unfit for agriculture, human consumption, bathing, or other household uses . </P> <P> To anticipate these problems, water is monitored at coal mines . The five principal technologies used to control water flow at mine sites are: diversion systems, containment ponds, groundwater pumping systems, subsurface drainage systems and subsurface barriers . </P>

State two environmental problems resulting from coal mining in south africa