Site Description
Chicago Mercury Mine, Sonoma Co., California
The Chicago Mine is situated in the Mayacmas Mining District near the headwaters of Dry Creek. The mine is the northernmost working of three mercury mines in the area. According to historical records the mine was located about 1865 and was intermittently active up to 1956. Development at the lower level included over 1500 feet of drifts, crosscuts and shafts. Above the main site at least four other short adits have been identified. The site contributes mercury-laden sediments to the Upper Dry Creek watershed, which is already impacted from mercury loads discharging from historic mercury mine properties downstream.. The main adit, although not readily accessible to the public, poses a minor safety hazard.
Site Characterization
A GPS survey of the mine features were was undertaken during FY2000. Sampling of storm water flows of the mine effluent, stream water and sediment downstream occurred during FY2001-2. Biota mercury sampling occurred during FY2003. Elevated levels of total and methyl mercury were detected in the calcine mine waste dumps. adjacent to the mine portal.
CERCLA Actions
CERLCA cleanup actions are proposed during the FY2006-13 period, depending upon the BLM AML statewide CERCLA remediation schedule and available funding for priority, impaired watersheds.
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