Abstract: Surface water enters the Haile Gold Mine, Lancaster County, South Carolina by means of a small stream and is ponded behind a dam and in an abandoned pit. This water is affected by acidic drainage. In spite of the large exposures of potentially acid producing pyritic rock, the flux of acid to the water is relatively low. Nevertheless, the resulting pH values of the mine water are low (around 3.5) due to negligible buffering capacity. In view of the observed low release of acidity, the potential for acid drainage abatement by limestone ameliorants appears feasible. This study investigated the effects of limestone treatment on acid generation rates of the Haile mine pyritic rocks through a series of leaching experiments. Below a critical alkalinity threshold value, solutions of dissolved limestone were found consistently to accelerate the rate of pyrite oxidation by varying degrees. The oxidation rates were further accelerated by admixing solid limestone with the pyritic rock. However, after a period of about a month, the pyrite oxidation rate of the admixed samples declined to a level lower than that of untreated pyrite. Leachates produced by the pyrite and limestone mixtures contained little if any iron. Further, in the mixtures, an alteration of the pyrite surface was apparent. The observed behaviour of the treated pyrite appears to be related to the immersion of the pyrite grains within a high alkalinity/high pH environment. The high pH increases the rate of oxidation of ferrous iron which results in a higher concentration of ferric iron at the pyrite surface. This, in turn, increases the rate of pyrite oxidation. Above a threshold alkalinity value, the precipitation of hydrous iron oxides at the pyrite surface eventually outpaces acid generation and coats the pyrite surface, retarding the rate of pyrite oxidation.

Abstract: Beth Energy's Mine 105W is located in Barbour County, West Virginia, near Buckhannon. The mine was opened by drifts updip into the Pittsburgh Seam in 1971 and operated until June, 1982. Most of the water which enters Mine 105W percolates down from previously mined areas in the Redstone Seam, Mine 101, which generally lies 38 feet above the Pittsburgh Seam. The quality of this water is good as it enters Mine 105W. While operating, the Mine 105W water was segregated by pumping. The bulk of the water was collected in sumps near the main area of infiltration from the Redstone Seam and was pumped to Gnatty Creek Portal where, because of the quality, it was minimally treated and discharged. The remainder of the water flowed to the original West Portal where it was occasionally treated with lime.