CHANGES IN AMD DISCHARGE CHEMISTRY FROM THE ALTON, WV SURFACE MINE SITE, 1993-2010

A surface mine near Alton, WV, has been producing acidic mine drainage continuously since the mid 1980’s. In summer 2010, groundwater was resampled at 4 springs and 30 wells in a portion of the mine, previously sampled in 1993 and 1998-99, to determine temporal and spatial changes in water chemistry. In addition to attenuation of acidic weathering products due to natural depletion of pyritic material in the spoil by weathering, it is hypothesized that there may be additional effects from (a) continued leakage of alkaline sludge from a central disposal pond, and (b) introduction of alkaline waste-lime slurry into a 4-m deep trench in 2000-2001 as an experimental attempt at in-situ neutralization. Results show enlargement since 1993 of the zone of metal neutralization around the sludge pond, from which pond leakage induces radial groundwater movement, and the development of a new zone of neutralization downgradient from the alkaline slurry trench. Sulfate, iron, and calcium concentrations have all substantially declined from 1993 in all but a small number of wells. There are multiple possible interpretations for this decline, including natural attenuation of acid-forming reactions, man-induced alkaline recharge, depletion of gypsum and/or jarosite formed early in the spoil history as reaction products, and reduction in the rate of overburden carbonate dissolution. Additional research will attempt to address the question of the relative dominance of these mechanisms.