INFLUENCE OF THE ONEIDA #3 ACID MINE DRAINAGE AND PASSIVE LIMESTONE TREATMENT SYSTEM ON LITTLE TOMHICKEN CREEK NEAR ONEIDA (LUZERNE COUNTY), PA

Discharge from the Oneida #3 abandoned coal mine drainage tunnel enters Little Tomhicken Creek near Oneida, PA. This study is part of an ongoing effort to assess the efficacy of a passive limestone treatment system installed in December of 2009, and designed to raise the pH and alkalinity and reduce dissolved aluminum in the treated mine effluent. Due to funding constraints, the present treatment system is designed to treat only about half of the mine discharge. Samples were collected at two sites in the mine drainage tunnel, two sites across Little Tomhicken Creek upstream of the confluence, three sites across the confluence of the mine drainage water and creek water, two sites across the stream between the confluence and the entry point of the treated drainage into the stream, and two sites across the stream below the treatment system effluent. In addition, we sampled the treatment system itself: one site at the exit of the limestone holding pond, one site at the exit of the first settling pond, and one site at the exit of the second settling pond prior to its discharge into Little Tomhicken Creek. Dissolved oxygen, pH, and conductivity were measured in situ. A four liter sample was collected at each site; turbidity analyses were performed on the non-filtered samples, alkalinity and acidity analyses were promptly performed on filtered samples. Triplicate subsamples of both non-filtered and filtered were preserved for later ion and metal analyses in the laboratory. We found that the metal concentrations for both iron and aluminum in the filtered samples from the outflow of the treatment system were higher than the concentrations of those metals from the creek itself, indicating that the creek mitigated these metals more efficiently than the treatment system. As observed in past studies, the treatment system is effective in raising both pH and alkalinity. We have suspected from those studies that the settled aluminum floc could be a potential source of aluminum back to the stream, and it appears that on this occasion, at least, it was.