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MERCURY FATE AND TRANSPORT IN GROUND WATER AT AN ABANDONED MINE
Citation:
Jewett*, D G., M. A. Engle, G. J. Reller, J. B. Bauman, AND E. Manges. MERCURY FATE AND TRANSPORT IN GROUND WATER AT AN ABANDONED MINE. Presented at 4th Int'l. Conf. Remediation of Chlorinated & Racalcitrant Compounds, Monterey, CA, May 24 - 27, 2004.
Impact/Purpose:
To inform the public.
Description:
Clear Lake, one of California's largest freshwater lakes located approximately 150 km north of San Francisco, is an important natural, economic, and cultural resource for the surrounding community. Elevated mercury levels in fish, first identified in the late 1970s, have been a major issue impacting the use of this important resource. Naturally occurring mercury deposits are common in the Coast Ranges, but the Sulphur Bank Mercury Mine (SBMM) Superfund Site, an abandoned mine located on the Oaks Arm of Clear Lake, is an obvious "smoking gun" as far as potential sources of mercury contamination. The Sulphur Bank hot springs mineral deposit was discovered in 1857 and the hydrothermal system responsible for depositing the sulfur and mercury ores remains active. Underground mining and open-pit mining produced an estimated 4.7 x 106 kg of mercury and created the Herman Pit (a 9.3 ha, 30 m deep, open pit) surrounded by over 1.1 x 109 kg of waste rock, tailings, and overburden. Mining ceased in 1957 and the open pit has since filled with water. Remedial actions (runoff and erosion control) reduced mercury loading to the lake from the SBMM, but preliminary data suggested that the local ground-water flow system might also be an important migration pathway. In order to estimate the mercury load in ground water discharging to Clear Lake, the U.S. EPA initiated an extensive field investigation characterizing ground-water flow and water-rock interactions influencing mercury fate and transport.