Narrative:
The Oat Hill Extension mercury mine is small 25-acre parcel of BLM land surrounded by the larger Oat Hill Mine Complex, which represents the 5th largest mercury producing mine in California. The Oat Hill Mine operated during the 1860's-1920's by a Boston, Mass. based company.
Project Description:
Preliminary Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) actions to date at the Oat Hill Extension Mercury Mine in Lake County, California have focused on compilation of a Potentially Resounsible Party (PRP) search, Removal Site Investigation (RSI) and Engineering Evaluation/Cost Analysis (EE/CA) reports. Proposed CERCLA removal and disposal operations removal of +20,000 tons of mercury calcines and related mine wastes from the Oat Hill Extension Mine mercury retort mill and tailings disposal sites within the James Creek subwatershed, tributary to the Putah Creek watershed.
Benefits/Results:
The removal of mercury mine wastes from the mine and retort mill site will reduce the downstream transport of mercury into James and Putah Creeks and thence into Lake Berryessa and the San Francisco-Bay Delta watersheds. These water courses provide spawning habitat for sports and native fish species. The Lake Berryessa reservoir already has an existing fish consumption advisory for mercury.
Feasibility/Implementation:
A formal PRP search was compiled by a contractor in FY2006-7 to determine if a viable party exists. A Removal Site Investigation (RSI) document was also compiled by a contractor in FY2007. During FY2007-8 an EE/CA document was compiled by a contractor. Proposed CERCLA mercury cleanup actions are pending negotiations with an adjacent landowner .
External Support/Partners:
Developed partnerships include the CA Water Resources Board and USGS-Geologic Division. Local watershed stakeholder groups (Putah Creek Watershed Group) also support the project. The California Regional Water Quality Control Board (CRWQCB) is supportive of this project. There is no known opposition to the project.
Risks: Water Quality, Biota, and Human (fish consumption) mercury-related impacts
Location: Section 27, T10N, R6W, MDB&M, Oat Hill MD, Napa County, CA
Field Office : Ukiah Field Office
Congressional District: 01
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