REASSESSING PENNSYLVANIA ABANDONED COAL MINE DISCHARGES

Two centuries of coal mining in Pennsylvania have left a legacy of impaired waterways. In contrast to present mining operations that must meet land reclamation and water quality criteria for environmental protection, historic mining was conducted without forethought to environmental degradation. Consequently, abandoned mines have been left to drain acid, iron, and other metals leached from the remaining rock into nearby waterways, and produce what is known as coal-mine discharge (CMD). Abandoned CMDs are responsible for the degradation of more than 5,000 km of streams in Pennsylvania. Environmental degradation by CMDs includes the death of plant and animal species, food chain disruption, and the destruction of the buffering capacity of water bodies through high concentrations of metals and in many cases, low pH. Dissolved metals in water can also make it unfit for human consumption.

A study of 143 CMD sites in the Anthracite and Bituminous Coalfields of Pennsylvania was performed by the USGS in 1999 to determine the hydrologic and geochemical behavior of mine discharges (Cravotta, 2008). Complete hydrologic and inorganic aqueous geochemical data was compiled and reported with measurements of trace element concentrations and loading. Water samples and water quality data were collected in the summer of 2012 from these same CMDs. Unfiltered water samples were used to determine alkalinity, filtered and unfiltered samples were used for cation analysis, and filtered samples were used for anion analysis. Hydrologic data collection included measurements of flow, dissolved oxygen (DO), temperature, pH, eH, and specific conductance. Correlations were identified between the contaminant loading, flow, and water quality data, and were used to analyze changes in the contaminant loading and acidity over the past thirteen years.