New Sierra Water Bodies Listed as Impaired for Mercury

23 November 2010 – The California Regional Water Quality Board recently released an updated 303(d) list designating even more Sierra Nevada streams and reservoirs as being impaired for mercury.

The vast majority of mercury contamination in the Sierra results from the large scale use of mercury in historic gold mining operations. Contaminated sediment from the Sierra is a major source of mercury to the San Francisco Bay-Delta.

When a water body is placed on the Clean Water Act Section 303(d) List, it is the beginning of regulatory process designed to address the problem. A TMDL (“Total Maximum Daily Load” – The regulatory tool used to reduce contaminate loading into streams and rivers) will be developed for each one of the 303(d) listed water bodies by a certain deadline.

The following water bodies are now listed:



Bear River Watershed

Rollins Reservoir


Combie Reservoir


Lower Bear River (below Camp Far West Reservoir)

Camp Far West Reservoir

Upper Bear River (from Combie  to Camp Far West Reservoir)


Deer Creek Watershed


Scotts Flat Reservoir


Deer Creek (Scotts Flat Reservoir to Lake Wildwood)


Little Deer Creek


Gold Run


Lake Wildwood


Yuba River Watershed

North Fork of the Yuba


New Bullards Bar Reservoir


Middle Fork of the Yuba River


Humbug Creek


South Fork of the Yuba River (Spauding Reservoir to Englebright)


Englebright Lake


Lower Yuba River


Feather River Watershed

North Fork Feather River (below Lake Almanor)


Lower Feather River (Lake Oroville Dam to Confluence with Sacramento River)


Thermalito Afterbay


Oroville, Lake


American River Watershed

Hell Hole Reservoir


Oxbow Reservoir (Ralston Afterbay)


South Fork of the American River (Slab Creek Reservoir to Folsom Lake)


Slab Creek Reservoir


North Fork of the American River (North Fork Dam to Folsom Lake)


Folsom Lake


Lake Natoma


Lower American River (Nimbus Dam to Sacramento River)


This official government order and 303(d) listing to reduce the amount of mercury in water bodies will require unique and innovative remediation techniques to remove mercury from Sierra streams and rivers.   The TMDL sets limits on the amount of contaminant allowable and if the dischargers were operating under waste discharge permits, the regional board would update those permits and require that effluents containing mercury be reduced. In the case of mercury in the Gold County, the source of mercury contamination is largely river gravels that were washed into the streams and rivers during hydraulic mining and which cannot be regulated by plan upgrades or permit changes.  The Regional Board is currently working on the American River Watershed TMDL process and expects to be completed by Spring of 2011.

The State Water Board approved the 2010 Integrated Report on August 4, 2010. The 2010 Integrated Report includes changes to the 2006 Clean Water Act Section 303(d) list of impaired water bodies and Clean Water Act Section 305(b) report on the quality of waters in California. The 2010 Integrated Report and supporting documents were submitted to the USEPA for final approval on October 13, 2010. For more information or copies of these documents, go here: