Interagency Team Studying Mercury

Contamination in California Watersheds

Notes from meeting held May 2000 at BLM State Office in Sacramento, as edited by Erin Klaesius, Communications Coordinator, California Biodiversity Council

Scientists from a variety of federal, state, and local agencies have formed a study team to investigate the extent of mercury contamination from historic gold mining in the Bear River and South Yuba River watersheds. The U.S. Geological Survey (USGS) has taken the technical lead for the team. USGS has funding support from Bureau of Land Management (BLM), U.S.Forest Service (USFS), California State Water Resources Control Board (SWRCB), and Nevada County Resource Conservation District (NCRCD). Other organizations, like the U.S. Environmental Protection Agency (USEPA), the California Department of Parks and Recreation, and the Nevada Irrigation District, have joined in the effort by providing in-kind services and access to lands. A previous study by the University of California at Davis indicated that the highest mercury levels in organisms correspond to watersheds heavily impacted by hydraulic mining. This conclusion provided the impetus for the selection of the Bear and South Yuba River watersheds.

In early 1999, the study team began its analysis by sampling water, sediment, and biota. A major focus of the sampling effort is the characterization of mine sites, which will most likely identify several contaminated "hot spots." This investigation will also characterize mercury contamination at the large watershed scale. The watershed-scale monitoring includes monthly measurements of mercury and methyl-mercury concentrations and a reconnaissance of mercury levels in tissues of sport fish from several reservoirs in the Bear and Yuba watersheds. Available data indicate that mercury concentrations in some fish species compare to concentrations that have prompted fish consumption advisories in other areas.

Depending on the results of the USGS fish samples, this study may prompt fish consumption mercury advisories in the sampled reservoirs. The Office of Environmental Health Hazard Assessment (OEHHA) has the statutory authority and the expertise to determine fish consumption advisories in California. Currently, there are 12 mercury advisories for sport fish in the state. The document, Advisories on Sport Fish Consumption in California, provides information on current fish consumption advisories for mercury and other contaminants (available on OEHHA’s website: www.oehha.ca.gov/fish/general/index.html). The California Department of Fish and Game provides information on fish consumption advisories in the brochure they distribute with their fishing licenses. While OEHHA performs analyses of fish data, individual counties may choose to make local, interim fish consumption advisories. (See OEHHA’s Special Reports and Notices www.oehha.ca.gov/fish/special_reports/index.html).

Drinking water appears generally unaffected by mercury contamination in the Sierra Nevada. All municipal water supplies regularly test mercury concentrations in their water and no problems have been reported. Although the drainage from some mine tunnels and ground sluices may have mercury concentrations in excess of the drinking water standard (2 parts per billion), these waters are generally not used for human consumption.

The information collected in the interagency study of mercury contamination in the Bear and Yuba watersheds will be used to inform the public of potential human health risks. Additionally, this study will determine if these isolated "hot spots" can be restored. In May, the USEPA began a pilot remediation project at the Polar Star mine in the Bear River drainage. Mercury-contaminated sediments were removed from a 480-foot-long drain tunnel that still contained a partially intact sluice box. The experience from this removal action will be useful to the land management agencies, like the BLM and the USFS, in their evaluation of the costs and benefits of cleaning other mercury and methyl-mercury "hot spots."