The Elizabeth Mine is an abandoned copper mine located on Mine Road in the Village of South Strafford within the Town of Strafford, Orange County, Vermont. The Elizabeth Mine site is situated in a rural setting, on the east side of Copperas Hill.
Based upon the results of recent geotechnical studies performed by EPA’s Remedial Program, a potential for a failure of the tailing dam referred to as tailing pile 1 (TP-1) has been identified. Should the tailing dam be breached, there would be significant human health and ecological consequences. Potential failure modes for the tailing dam include overtopping, a slope failure resulting from an increase in pore pressure due to watertable rise within the tailing pile, and internal dam erosion (piping). Possible consequences of a tailing dam failure include a large release (possibly 500,000 to 1,000,000 cubic yards) of tailing into Copperas Brook, flowing into the West Branch of the Ompompanoosuc River (WBOR), the Ompompanoosuc River, and eventually the Connecticut River. Preliminary modeling has calculated an initial flood wave with a depth of 8 to 10 feet, traveling at velocities ranging from 10 - 15 feet per second (7 to 10 miles per hour). The environmental impacts are expected to be significant with the potential for a major fish kill and high metal/low pH conditions in the impacted water bodies for an extended period of time, possibly decades. All of the tailing are acid generating and contain metals (copper, cadmium, iron, aluminum, zinc). If the dam failure were to occur, residences near Gove Hill Road could possibly be impacted too.
EPA has initiated a time-critical removal action to stabilize the tailing pile. Response actions include: 1) mobilization of high-capacity pumps during the spring of 2003; 2) placement of graded filters on active piping (internal dam erosion) areas; 3) placement of a surface water diversion pipe to replace existing decant system; and, 4) construction of a soil buttress along the slope of the tailing pile.