ENVIRONMENTAL CONSEQUENCES OF ACIDIC DRAINAGE FROM DAVIS PYRITE MINE, ROWE, MASSACHUSETTS

Davis Mine in Rowe, MA, which operated from 1882 until 1911, was a source of pyrite from a massive sulfide deposit in the Ordovician Hawley Formation. This unit is in the Berkshire Mountains of western Massachusetts, and consists of gneiss, schist, and amphibolite, all metamorphosed to lower amphibolite grade. The ore body contains granular pyrite, with associated chalcopyrite, pyrrhotite, sphalerite, and galena. Since the time of the mine collapse in 1911, acidic drainage has been transporting sulfate, iron, and trace metals from the exposed tailings piles in surface runoff and groundwater. Previous research and historical data indicate that the environment has remained stable for decades. Acidity, sulfate and metal concentrations increase in the mine effluent as it traverses the tailings piles. Shallow groundwater shows a similar trend, even greater in magnitude, suggesting that slower groundwater flow permits enhanced dissolution of sulfides in the tailings. Mineralogical studies of the tailings piles document intense weathering, typified by destruction of secondary aluminosilicates and the formation of soluble acidic sulfates such as jarosite and hydrobasaluminite.

New data from multi-level wells installed in April, 2003 define a lens of impacted groundwater with pH < 3, Fe > 100 mg/l and sulfate > 500 mg/l that moves rapidly through the mine tailings and shallow bedrock fractures, but is restricted by ambient groundwater from uncontaminated recharge areas. The mine effluent flows into Davis Mine Brook, which maintains elevated sulfate, acidity, and aluminum 300 meters from the confluence with the effluent. Fish and megafauna are absent from the entire length of Davis Mine Brook, 1 km downstream from the mine. In areas peripheral to the site of acid mine-drainage generation, there is evidence of an active microbial community that reduces the dissolved sulfate, and possibly Fe(III), to remediate the acidic drainage.