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MERCURY SOURCES IN CALIFORNIA
Since the early 1800s, residual mercury from mining has been transported with sediment downstream into the Sacramento/San Francisco Bay estuary, where it is believed to have contributed to elevated mercury contents in fish, resulting in consumption advisories. Most of the mercury pollution in this area was from placer gold mines, which used mercury to extract gold through hydraulic, drift, and dredging methods. In addition, mercury mines in the Cache Creek watershed have contributed extensive amounts of mercury pollution and raised subsequent water-quality, fish-tissue, and human-health issues.
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Mercury contamination from legacy mines and atmospheric deposition lead to human and wildlife health issues and concerns in Central California (San Francisco Bay RWQCB, 1998).
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Location of past-producing gold and mercury mines in California. (Alpers and Hunerlach, 2000). Box shows location of Sacramento River watershed below.
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Gold and mercury mines in the Sacramento River Basin Study Unit of the National Water Quality Assessment Program (Domagalski et al., 2000)
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Monitors (water cannons) were used to break down the gold-bearing gravel deposits with tremendous volumes of water under high pressure. Some mine operated several monitors in the same pit. North Bloomfield Mine, circa 1860, Malakoff Diggings, Nevada County (California Department of Conservation, Division of Mines and Geology Library, used with permission. DMG CD 98-001 California Gold Mines—A Sesquicentennial Photograph Collection).
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