IMPACT OF MINE DRAINAGE ON STREAM WATER QUALITY TWENTY YEARS AFTER RECLAIMATION

Acid Mine Drainage (AMD) is a problem that affects lakes and streams where mining exposes pyrite or other sulfide minerals to oxidation by weathering processes. Lake Harris is a man-made reservoir located in east-central Tuscaloosa County, Alabama. A coal strip mine operated in the watershed until 1976, located just a few hundred meters from Lake Harris. The mine was abandoned and the land left exposed for a decade. The site was reclaimed in 1986 by the Tuscaloosa County Soil and Water Conservation District, using remediation techniques such as retention ponds and limestone (rip-rap) in drainage channels. A second order stream, with its head located just above the mining activity, bisects the old strip mine area and discharges into Lake Harris. The pH at the mouth of the stream ranges from 3.30 to 3.50, while at the head of the stream the pH is 5.23. Stream water samples were taken periodically over a period of three years and analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES) for Al, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mo, K, Ni, Pb, Se, Sb, Ag, Sn, Sr, Na, Tl, Ti, V, Zn, and Si. Ion Chromatography (IC) was utilized for analysis of Cl-, F-, Br-, NO3-, and SO42-. The stream waters are enriched with respect to Ca, K, Fe, Mg, Na, and SO42- relative to Lake Harris and exhibited seasonal variability. The stream sulfate levels exceed the United States Environmental Protection Agency maximum contaminant level (MCL) recommendation of 250 mg/L by more than 300 percent. Remediation techniques utilized at the strip mine site seem successful in areas where the techniques have been applied; however, further treatment must be incorporated within additional areas surrounding the strip mine that contribute to acid mine drainage before the effects of these techniques can be accurately determined.