Mine Discharge - Passive Treatment: Abandoned/Inactive Mine
San Juan County, Colorado
Western Water & Land prepared an Engineering Evaluation/Cost Analysis (EE/CA) for the Elk Tunnel abandoned mine site located in the Cement Creek drainage near Silverton Colorado. The EE/CA, developed in accordance with EPA’s Guidance on Conducting Non-Time Critical Removal Action Under CERCLA, focused on the treatment of acid mine drainage from a collapsed adit at an elevation of approximately 10,000 feet above mean sea level. The Elk Tunnel discharge averages approximately 0.45 cubic feet per second flow and contains high concentrations of iron, manganese, zinc, and aluminum. Specific criteria were established for the project, including passive operation and low maintenance, implementation constrained to the mine site area, and construction costs within our client’s projected budget. An initial screening-level evaluation was conducted to define potential passive water treatment alternatives. A detailed comparative analysis was conducted on up to four alternatives based on effectiveness, implementability, and cost. Alternatives considered included anoxic and oxic limestone treatment, and/or anoxic and oxic biomass (bioreactor) treatment. An increase in retention time of mine discharge was a critical factor necessary to maximize treatment effectiveness. The selected alternative involved installation of an open limestone channel, containing shallow drop structures to promote aeration of the water and production of metals precipitates, which discharges to a series of three settling ponds designed to retain precipitates before discharging to Cement Creek. The site is readily visible from a public road, and care was taken to ensure the design would complement the natural conditions in the area.
Following completion of the EE/CA, WWL prepared reclamation design drawings and technical specifications to control the products, execution, and workmanship for the selected removal action alternative at the mine sites. The reclamation action was implemented in 2004, resulting in a significant reduction in the acidity of the mine drainage and in the amount of minerals discharging to Cement Creek and the Animas River.
San Juan County, Colorado
Western Water & Land prepared an Engineering Evaluation/Cost Analysis (EE/CA) for the Elk Tunnel abandoned mine site located in the Cement Creek drainage near Silverton Colorado. The EE/CA, developed in accordance with EPA’s Guidance on Conducting Non-Time Critical Removal Action Under CERCLA, focused on the treatment of acid mine drainage from a collapsed adit at an elevation of approximately 10,000 feet above mean sea level. The Elk Tunnel discharge averages approximately 0.45 cubic feet per second flow and contains high concentrations of iron, manganese, zinc, and aluminum. Specific criteria were established for the project, including passive operation and low maintenance, implementation constrained to the mine site area, and construction costs within our client’s projected budget. An initial screening-level evaluation was conducted to define potential passive water treatment alternatives. A detailed comparative analysis was conducted on up to four alternatives based on effectiveness, implementability, and cost. Alternatives considered included anoxic and oxic limestone treatment, and/or anoxic and oxic biomass (bioreactor) treatment. An increase in retention time of mine discharge was a critical factor necessary to maximize treatment effectiveness. The selected alternative involved installation of an open limestone channel, containing shallow drop structures to promote aeration of the water and production of metals precipitates, which discharges to a series of three settling ponds designed to retain precipitates before discharging to Cement Creek. The site is readily visible from a public road, and care was taken to ensure the design would complement the natural conditions in the area.
Following completion of the EE/CA, WWL prepared reclamation design drawings and technical specifications to control the products, execution, and workmanship for the selected removal action alternative at the mine sites. The reclamation action was implemented in 2004, resulting in a significant reduction in the acidity of the mine drainage and in the amount of minerals discharging to Cement Creek and the Animas River.