Mercury contamination from mining practices 150 years ago is a widespread problem affecting many Sierra foothill lakes and rivers, and it poses a health danger to humans who enjoy eating wild caught fish.
Environmental groups, water and government agencies and tribal leaders are looking at mercury and ways to deal with it in the future.
In the latest step toward clean-up, Nevada Irrigation District's board of directors agreed to submit an application with other groups for a $1 million grant to remove mercury from Combie Reservoir.
Mercury extraction on Combie and the Bear River that feeds it could serve as a pilot project for others, including the removal of toxic mercury buildup behind Englebright dam on the South Yuba River, said Jason Rainey, executive director of the South Yuba River Citizens League.
"We need to be thinking long term. This region needs ambitious clean-up efforts," Rainey said.
The Bureau of Land Management and the U.S. Forest Service has been working to clean up abandoned mine sites on a small scale throughout the county, including the Boston Mine project in the Greenhorn area.
A project facilitated by Friends of Deer Creek and funded by the Environmental Protection Agency is underway to clean up five abandoned mine sites along Deer Creek within Nevada City limits.
This Saturday, the Tsi-Akim Maidu tribe will meet with environmental groups and tribes from California and Nevada to address the issue through ongoing discussions entitled, "Mercury in our water, our fish, our people."
"We're educating people. We want to clean it up," said Don Ryberg, director of the Tsi-Akim.
Miners used mercury to extract gold from mined materials. The waste was then discharged into streams where it accumulated in the sediment.
Mercury contamination builds up behind dams and does not decompose over time. Many reservoirs in Nevada County have issued restrictions and do-not-eat advisories, including Combie Reservoir and Lake Englebright, especially for predatory feeders such as large mouth bass.
Though elemental mercury poses little risk to humans, excessive exposure to the organic form called methylmercury found in fish, can cause damage to the nervous system of developing children, according to health experts. Subtle decreases in learning ability, language skills, attention and memory can result.
In general, public land agencies responsible for cleaning up toxins remain under-funded, said eco- hydrologist Carrie Monohan, a consultant for NID and Friends of Deer Creek, Monohan said.
Ryberg said the state and federal governments have a responsibility to clean up the problem.
"They are our leaders. Aren't they supposed to keep us from getting poisoned? They have an obligation to all the people to do something about it, whatever the cost," Ryberg said.
If NID and other groups win a grant for Proposition 50 funding, the water agency could apply new mercury-extraction technology from Canada to clean up Combie Reservoir. The grant is being submitted by CABY (Cosumnes, American, Bear and Yuba regional watershed alliance).
"What we're doing is a type of cleanup that hasn't been done before," said Tim Crough, assistant manager for NID.
Monohan, Charlie Alpers from the U.S. Geological Survey, Chevreaux Aggregates, Nevada County Resource District and the NID are working together on the project.
Chevreaux Aggregates has agreed to dredge the sediment.
"As they remove the sediments, we'll remove the mercury," Crough said.
A centrifuge would spin and force the sediment and mercury to separate. The remaining sand and clay could be sold to Idaho-Maryland Mine's offshoot company, Golden Bear Ceramics, to make ceramic tiles, Crough said.
"It's a win-win for the environment, the water district and the customer. We just need a little help from the feds to get it started," Crough said.
To contact Staff Writer Laura Brown, e-mail lbrown@the union.com or call 477-4231.