Contamination from Acid Mine Drainage

The process of extracting copperas from the "mother rock" left large piles of waste rock at the site of the Elizabeth Mine. The waste contains copper, zinc, aluminum, cadmium and other metals. Forty-seven acres of the site are currently covered with deep piles of this waste rock or tailings, the finely powdered rock that is a byproduct of the mining process. While some of the tailings are vegetated enough to absorb some rainfall, much of this land is exposed to the elements. When rain, snowmelt and groundwater flow through the tailings and waste rock, sulfuric acid is formed, making the runoff as acidic as vinegar. This acidic water dissolves metals and sediments from the tailings and waste rock and carries them into Copperas Brook and the West Branch of the Ompompanoosuc River. The contamination of waterways by metals and sediments is known as "Acid Mine Drainage", or "AMD" .

Concentrations of 15 heavy metals and other contaminants in Copperas Brook and a six-mile stretch of the West Branch of the Ompompanoosuc River are higher than standards for water quality set by the State of Vermont and the Environmental Protection Agency (EPA). Concentrations of metals in the "Mixing Zone" (the area just below the point where Copperas Brook flows into the West Branch) are many times higher than the maximum standard. In this area, aluminum is 200 times higher, copper is 63 times higher, iron is 50 times higher, manganese is 17 times higher and cobalt is nine times higher than the standards.

In the Draft Engineering Evaluation and Cost Analysis, issued in September, 2001, scientists reported that nearly all of the minnows and other aquatic creatures exposed to water from the West Branch "Mixing Zone" died. The Site Summary Report and the Engineering Evaluation and Cost Analysis contain more detailed information about the environmental issues related to the Elizabeth Mine Site, including a map that depicts Copperas Brook, and the West Branch of the Ompompanoosuc River.

Cleanup Strategy

A number of cleanup alternatives were considered to address acid mine drainage problems at the Elizabeth Mine. The primary goal of these alternatives is to stop the formation of highly acidic runoff, or Acid Mine Drainage (AMD), by preventing water from coming into contact with the tailings and waste rock where possible and by treating the water that does come into contact with tailings or waste rock. The Community Advisory Group worked closely with EPA and the Agency of Natural Resources to develop alternatives that significantly reduce mine-related contamination of the water and sediments of the West Branch, while preserving the historic resources at the site.

If you would like more information about the cleanup, please come to a Community Advisory Group meeting, or contact Cindy Cook.

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