Argonaut Heights Residential Development Environmental Assessment

Project Profile
Argonaut Heights Residential Development Environmental Assessment
Location: Jackson, California
Owner: Argonaut Heights, LLC
Total Project Value: Estimate $20,000,000
Consultant/Engr. Cost: $40,000
Square Footage/Area: 13 acres
Completion Date: 2004

The project site for the 13-acre residential development containing 40 homes was on a portion of the former Argonaut Mine property that included the mine stamp mill. Arsenic in soil was determined to be the chemical of concern. The client required complete environmental sampling, assessment, as well as negotiations with Amador County and the DTSC for approval to allow development.

Project Challenges

Arsenic concentrations in surface and near-surface soil samples were detected at extremely high concentrations. Seventeen samples from throughout the site exceeded the EPA arsenic hazard preliminary remediation goal. Based upon the arsenic soil concentrations, regulatory agencies required site mitigation.

Stratus personnel used a protocol developed by the U.S. Navy’s Naval Facilities Engineering Command in testing for human risk assessment.

Stratus Solutions

While completing the site investigation and preparing a work plan, Stratus personnel submitted the results to county and state agencies. Meetings with the client, City, county, and State were held to discuss results and alternatives for arsenic in the site soil.

In some cases, research had identified that only a portion of a chemical in a soil or mining waste contributes a potential health risk. Stratus personnel used a protocol developed by the U.S. Navy Naval Facilities Engineering Command in testing for human risk assessment. The bioavailability percentage was then used in the US EPA and DTSC risk and hazard equations using arsenic cancer slope and oral reference dose factors for acceptable risk.

Since the maximum soil arsenic concentration detected on the site was below the protocol standard, no additional site mitigation measures, beyond the import of clean fill in a limited area, were recommended.

DTSC and Amador County Department of Environmental Health approved the cleanup goals.