Case Study as part of a Web-based Technical and Regulatory Guidance

American Tunnel Mine
San Juan County, Colorado

1. Site Information
1.1 Contacts
Vance Weems
Telephone: 775-321-8101

Timothy Tsukamoto, Ph.D.
Telephone: 775-321-8101

1.2 Name, Location, and Description
The American Tunnel Mine is located in central San Juan County in southwestern Colorado (Lat. 37.817407N, Long. 107.636689W). The American Tunnel Mine was an underground silver mine. Affected media include soil, sediment, surface water (e.g., stream, rivers, runoff, and drainage), surface pool water (e.g., lakes, ponds, and pools), and groundwater.

2. Remedial Action and Technologies
At the American Tunnel Mine, the primary impacts are from acidity, sulfate, and metals (aluminum, arsenic, cadmium, copper, iron, lead, manganese, nickel, and zinc). Reclamation of the site falls under the provisions of the Clean Water Act (CWA) and the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). The primary treatment technology in place at the American Tunnel Mine is chemical precipitation.

Chemical precipitation at the American Tunnel Mine includes lime neutralization and aeration and oxidation of reducing metals with the rotating-cylinder treatment system (RCTS) system. Chemical precipitation has been operating as a pilot-scale demonstration for a period of three days using varying flow rates. The quantity of affected water being remediated is up to 100 gallons per minute.

Site cleanup goals are based on the mitigation of human health risk and mitigation of ecological risk.

3. Performance
Performance applicable standards include CERCLA and CWA. Performance criteria include measuring the contaminant concentrations in water, the amount of lime consumption, and sludge production. The RCTS demonstration showed the ability to be quickly mobilized and operated on the entire flow of up to 100 gallons per minute of water contaminated with high concentrations of reduced iron. The system was tested at varying flow rates of 30, 60, and 100 gallons per minute (total flow). As of October 2008, confirmation laboratory results were pending. On-site testing was positive including lime efficiency calculations and sludge production.

4. Costs
Cost of activities at these site are reported as a total:

• Capital: Unable to report since project is in pilot-scale testing phase.
• Operation and maintenance: Cost figures not provided.

5. Regulatory Challenges
None encountered.

6. Stakeholder Challenges
No information available.

7. Other Challenges and Lessons Learned
No information available

8. References
No information available.