The water quality consequences of mountaintop removal - valley fill coal mining

Background/Question/Methods The Mountaintop Mining Environmental Impact Statement found that in 2002 more than 1200 miles of stream channels had already been buried by valley fills or directly harmed by mining.  Later studies by the Office of Surface Mining found that from October of 2001 to June of 2005, mining permits impacted yet another 535 miles of streams nationwide and approximately 2/3 of those impacts were from valley fills. Some watersheds have been particularly hard hit by mining activities. For example, more than 10% of the total land area within the watershed of the Coal and Guyandotte rivers of southern West Virginia are impacted by surface mines.  In addition to the localized destruction of individual stream reaches, many thousands of miles of downstream reaches have been impacted by the resulting hydrologic alteration and accompanying sediment and chemical pollutants that are transmitted throughout the river network. 
Results/Conclusions Stream water chemistry is shaped by processes that occur as rainwater infiltrates the ground and moves through pore spaces and soil on its way to streams.  The streams and rivers below valley fills receive alkaline mine drainage that include highly elevated concentrations of sulfate, bicarbonate, calcium and magnesium ions and which often include elevated concentrations of multiple trace metals.  The combined toxicity of multiple constituents results in significant increases in conductivity and total suspended solids below valley fills.  This decline in water quality leads to a loss of sensitive aquatic organisms even when downstream habitats are intact.  The resulting high conductivity and high sulfates can persist long after mining activities cease and scientists have found no empirical evidence documenting recovery of macroinvertebrate communities in the streams impacted by alkaline mine drainage.  The water quality impacts of MTMVF activities are more severe and more persistent than other land use changes within the southern Appalachians.  Pollutants added to ephemeral and intermittent stream channels will be transported downstream to larger rivers.  The more surface mining and valley fill activity within a large watershed, the greater the cumulative transport of alkaline mine drainage pollutants to major rivers will be.