A study of the Stony Fork basin in southern Fayette County, Pennsylvania, from 1977 through 1980 determined the impacts of surface coal mining on surface-water quality. Stony Fork was sampled at six sites, during which time the area of surface mines increased from 0.5 to 5.5 percent of the study area. Streamflow, suspended-sediment, and water quality data were collected at gaging stations upstream and downstream of mining. The total runoff between the upstream and downstream stations differed by one percent; this small difference could not be attributed to the effects of mining. The suspended-sediment yield increased during storms due to erosion from the mining sites. The suspended-sediment yield doubled at the downstream site following mining. Specific conductance was highly variable during storm runoff but generally varied inversely with flow and increased slightly during the study period. The pH ranged between 4.8 and 7.9 with values below 6.0 usually occurring during storm runoff. Concentrations of dissolved zinc and sulfate increased between the upstream and downstream sampling sites. Laboratory analysis of a precipitation sample indicates that acid precipitation may be partly responsible for pH depressions during storm runoff periods. (USGS)
