Mine Hydrology  
  Karst Hydrology  
  Project Reports  
  Research Papers  

Project WV 173: Water Chemistry

The formation of acidic water from coal is not dependent on mining; it is a natural process resulting from oxidation of iron pyrite found in coal. Acid water is created in any exposed outcropping of coal, but becomes particularly problematic with the exposure of a large amount of acid forming substances, which are comonly found in coal mines. (Casner,1994)
      When exposed to air and water, pyrite found in and near coal is transformed into minerals that create sulfuric acid when combined with water. In water, further oxidation may take place and produceing orange staining commonly refered to as “yellow boy.” The Pittsburgh coal has a moderate to high sulfur content and therefore can produce enormous acid loads. Acid production does not depend on fresh exposures; abandoned mines and mine refues piles will produce AMD for decades.

It is estimated that over 17 billion gallons of mine water discharges annually from the Pittsburgh coal basin, 50% of which is not currently treated. Mined area in the Pittsburgh basin in PA and WV is now about 84,262 acres; about 26,687 acres are known or believed to be flooded, containing 340 billion gallons of mine water. Additional flooded mines are still being identified within the basin. Water quality from underground coal mines in the Pittsburgh seam is known to vary broadly. While the water quality of newly flooded mines can be very poor – high in iron, low in pH it is known that this quality will improve over time as the acid laden water is removed from the system, either by treatment or discharge, and is replaced net alkaline ground water (Donovan et al., 2003, in preparation). Long closed mines in the basin have much improved water qualities.