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NPL Site Narrative for Sulphur Bank Mercury Mine
SULPHUR BANK MERCURY MINE
Clear Lake, California
Federal Register Notice: August 30, 1990Conditions at proposal (June 24, 1988): The Sulphur Bank Mercury (SBM) Mine is on the east shore of the Oaks Arm of Clear Lake, in Clear Lake, Lake County, California. The area was initially mined for sulfur during 1865-68. Mercury ore was mined by underground methods during 1899-1902 and 1915-18. The majority of the mercury ore was mined using open pit methods during 1922-47 and 1955-57. The mine, once one of the largest producers of mercury in California, has been inactive since 1957 and is presently owned by Bradley Mining Co. (BMC) of San Francisco.
Approximately 120 acres of tailings and an open, unlined mine pit (called the Herman Pit) are on the property. The mine tailings extend into the Oaks Arm of Clear Lake along 1,320 feet of shoreline. The Herman Pit covers approximately 23 acres and is 750 feet upgradient of the lake. The pit is filled with water to a depth of 150 feet.
The California Regional Water Quality Control Board (CRWQCB) is coordinating an ongoing investigation of SBM. Department of Health Services, Department of Fish and Game, and CRWQCB analyses indicate that mercury is present in the tailings and in the biota and bottom sediments in the Oaks Arm of Clear Lake. The levels of mercury in fish from Clear Lake led the State to issue an advisory on May 14, 1986 against consumption of the fish. The lake is a major recreational area.
On March 13, 1987, CRWQCB informed BMC that the Herman Pit is regulated under the Toxic Pits Cleanup Act (TPCA). Under the act, BMC is required to submit a Hydrogeologic Assessment Report (HAR). The property owners are conducting a waste characterization study of the site prior to submitting a HAR to determine if the site may be exempt from the TPCA.
On November 4, 1987, CRWQCB awarded a contract for a pollution abatement study of the Oaks Arm of Clear Lake and the adjacent mine site. The study is scheduled to be completed in early 1989.
An estimated 4,700 people obtain drinking water from Clear Lake Oaks Water District wells about 1 mile from the site.
Status (August 30, 1990): The property owners submitted their HAR to CRWQCB in July 1988. CRWQCB exempted the Herman Pit from TPCA in April 1990.
CRWQCB's study of Clear Lake was completed in late 1989. It indicated that the largest continued input of mercury to Clear Lake is probably from erosion of waste rock and tailings into the lake.
For more information about the hazardous substances identified in this narrative summary, including general information regarding the effects of exposure to these substances on human health, please see the Agency for Toxic Substances and Disease Registry (ATSDR) ToxFAQs. ATSDR ToxFAQs can be found on the Internet at http://www.atsdr.cdc.gov/toxfaq.html or by telephone at 1-888-42-ATSDR or 1-888-422-8737.