REVISITING GEOCHEMISTRY OF WATER IN PINE FOREST TREATMENT SYSTEM IN ST. CLAIR (SCHYULKILL COUNTY), PA

On November 2, 2018, we conducted an assessment of the Pine Forest AMD Treatment System (an anoxic limestone drain, or ALD) to analyze the chemistry of the water going through the system as well as the water in the adjacent Little Wolfe Creek that receives the treated AMD. In situ determinations of dissolved oxygen, pH, conductivity and temperature were collected at a total of 11 sites, along with large water samples at all sites and sediment cores and cattail roots at select sites (subject of a concurrent study). Samples were transported to the laboratory and filtered and analyzed for acidity and alkalinity within 6 hours. Triplicate subsamples were bottled and preserved for later analysis of metals by ICP-OES and simple cations and anions by IC. The ALD was successful in raising pH and alkalinity and reducing the concentrations of iron and manganese, as well as aluminum to a lesser degree. Aluminum is reduced somewhat in the ALD, then stabilizes, but its concentration in the mine drainage is much lower than aluminum concentrations in Little Wolfe Creek. Iron is reduced coming out of the ALD (contrary to design specs for an ALD) but then continues a stepwise reduction as would be expected in sequential oxidation ponds. Manganese, above 4 ppm coming out of the mine, is reduced by half NOT in the ALD effluent but in the seepage water coming up through the top of the ALD and the many cattails that have grown up there. Previous work has noted that although the system is adjusting water chemistry as hoped, there is an overwhelming abundance of iron precipitate collecting in the ALD, a probable consequence of an oxygen leak in the system. The resultant requisite frequent flushing is causing premature filling of the first oxidation pond. We should note that due to the very heavy precipitation in the summer, the mine pool had been partially drained, reducing the head of pressure forcing water into the treatment system and thus greatly reducing the amount of water going through the system compared to that in previous studies.