Paper No. 4
Presentation Time: 9:00 AM
CURRENT PERFORMANCE OF A PASSIVE WETLAND TREATING ACID MINE DRAINAGE AT MORAINE STATE PARK, BUTLER COUNTY, PENNSYLVANIA
Coal mining was conducted in the area of Moraine State Park prior to the establishment of the park and associated Lake Arthur. A total of 69 underground mine entries were sealed during the 1960s and early 1970s along the proposed northern shore of Lake Arthur. Seals were constructed using a fly ash/cement mixture along with grout injected into the adjacent strata. During 1979 and 1980, a study was performed by Maksimovic and Maynard (1983) for the United States Department of the Interior, Bureau of Mines, to determine the long term effectiveness of the underground mine sealing and reclamation work. Not all seals were successful as evidenced by leakage emanating from one of these sealed mines that resulted in the deposition of iron hydroxides on the shoreline of Lake Arthur. During 1995 and 1996, a passive wetlands treatment system was designed and constructed to treat this acid mine drainage (AMD). The design life of the three pond passive wetlands treatment system was estimated at twelve years, after which time it was believed the precipitate in the ponds would need to be removed and the system rehabilitated to continue treating the AMD discharge. This study evaluated the performance of the passive wetlands treatment system to determine if the system continues to function adequately.
Hypothesized that the passive wetlands treatment system was treating the water adequately based on visual observations. Water quality samples were collected and analyzed for standard AMD parameters at the treatment wetlands, an untreated discharge, and a control stream unaffected by mining. Precipitate thickness was measured in Pond 1 yielding an average deposition rate of approximately 1 inch per year. Based on this deposition rate, Pond 1 can continue to function an estimated 25 to 30 years before it would require precipitate/sludge removal. Current studies are being performed to determine where water is flowing into Pond 1, if Pond 2 needs to be cleaned out, and if Pond 3 water quality is meeting discharge standards. The passive wetlands treatment system is performing adequately, continues to ameliorate the AMD discharge, and the affect on overall lake water quality is minimal.