The Site contains areas affected by mining, including three principal areas that were directly affected by mining along with other areas, primarily downstream, where hazardous substances have come to be located. The three principal areas include the 1950s Mine and Mill Area, the 19th Century Operations Area and a Main Tailings Impoundment.
At the end of the tailings impoundment is a dam about 70 feet high and 700 feet wide. The dam has been subjected to severe erosion and water emanates from the dam in several places. The face of the dam is deeply incised and erodes directly into a creek. The creek, the Ore Knob Branch, is piped underneath the tailings impoundment through a 24 inch pipe that exits the bottom of the dam face. The pipe discharges into a sediment pond that is now full and no longer able to contain sediment and other precipitates from continuing down Ore Knob Branch. Tailings have slumped over the dam face and appear to have at least partially blocked the pipe, causing water to back up into the tailings impoundment and seep through the dam face. In addition, the upper end of the pipe is known to become blocked.
Seeps emanating from the face of the tailings dam have extremely high concentrations of several metals, acidity, sulfate, and total dissolved solids. All of the seeps on the dam face exceeded surface water quality criteria applicable to Ore Knob Branch by factors of five or more for aluminum, copper, iron, manganese, silver, zinc, and sulfate when sampled recently. Sampling has also shown impacts from the tailings impoundment to other downstream receiving waters. Surface water samples collected from ponds atop the tailings impoundment exceed water quality criteria for several metals and pH. Soil samples collected adjacent to the tailings impoundment also contain elevated concentrations of various metals.
