Bear-Yuba Watersheds
Interagency Abandoned Mine Lands Project

SUMMARY OF INTERAGENCY STUDY OF MERCURY CONTAMINATION ASSOCIATED WITH ABANDONED MINE LANDS

WHO: An interagency group of scientists is conducting the study. The U.S. Geological Survey (USGS) is taking the technical lead, and is working in close cooperation with the U.S.D.A. Forest Service (Regional Office and Tahoe National Forest), the Bureau of Land Management (State Office and Folsom Resource Area), the State Water Resources Control Board, and the Nevada County Resource Conservation District. (See list of Agency Contacts.)

WHAT: A major focus of the interagency study is to determine the distribution, transport, and fate of mercury and methylmercury in the vicinity of historic hydraulic placer-gold mines. The overall purpose of the study is to provide unbiased scientific information on potential impacts of mercury and arsenic from abandoned and inactive mine sites, as a sound basis for effective resource management.

WHEN: The project began in April 1999 and will continue into at least 2002. The USGS fact sheet "Mercury Contamination from Historic Gold Mining in California," which describes the historical context of mercury use in gold mining and the rationale for the project, was released in May 2000. A report with data on mercury concentrations in sport fish from reservoirs and stream habitats in the Bear River, Deer Creek, and South Yuba River watersheds (USGS Open-File Report 00-367) was released in September 2000. A series of reports with data on mercury in water, sediments, and other biota is planned for publication in late 2001 or early 2002. Some preliminary information may be released sooner on the World Wide Web. Check the web site http://ca.water.usgs.gov/mercury/bear-yuba/ for project updates.

WHERE: The study area includes the Bear River watershed and the southern Yuba River watershed, including the South Yuba River and Deer Creek drainages.

WHY: Elemental mercury (quicksilver) was used extensively for gold processing during historic mining in the Sierra Nevada. Despite the knowledge that mercury is a substance of potentially high toxicity, to date there has been no comprehensive survey of the potential risks to human health and ecosystems from residual mercury in Sierran watersheds. The interagency abandoned mine lands (AML) study is focused on the Bear and southern Yuba watersheds because these areas are the most heavily impacted by historic hydraulic mining, and some areas are heavily recreated. An earlier study by the University of California at Davis, in cooperation with Larry Walker Associates and the Sacramento Regional County Sanitation District, used samples collected in 1994-95 to document elevated mercury levels in fish and invertebrates in these watersheds. Those researchers concluded that the mercury bioaccumulation is most likely associated with the use of mercury in gold processing at historic mine sites.

HOW: Sampling will consist of water, sediment, and biological specimens, including bird eggs, amphibians, invertebrates, and fish. A limited number of fish were collected from the following water bodies in the Bear and Yuba river watersheds: Englebright Lake, Scotts Flat Reservoir, the Dutch Flat Afterbay, Combie Lake, Rollins Lake, and Camp Far West Reservoir.

The goal of preliminary site characterization efforts will be to identify a small number of sites on federal lands that may be suitable for remediation on a pilot scale basis. Depending on the results of the present study and the availability of additional funding to the federal agencies, follow-up activities may include investigations of the feasibility, costs, and benefits of remediation in areas impacted by mercury use in hydraulic mining. The present study will result in collection of baseline data at various sites prior to any remediation, so that the benefits of later remediation may be quantified in terms of improvements in water quality and/or reductions in mercury bioaccumulation in various species.

Bear-Yuba Index

Last modified: Tuesday, Oct 10, 2000