Lake Combie mercury removal project crosses another hurdle

By: Gus Thomson, Journal Staff Writer
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With a key state approval in place, a dredging project on Combie Reservoir to remove a toxic legacy of mercury from the area’s gold-mining past could be in position to start this spring.

Plans call for a $6.9 million program over two years to siphon off an estimated 50 to 150 pounds of mercury from Combie Reservoir in Meadow Vista.

The quicksilver is left over from the Gold Rush era, when it was used in the process to extract gold from gravel but dumped rather than retained.

The Nevada Irrigation District  is working with the Sierra Nevada Conservancy and other partners on a project to dredge an area on the upstream side of Combie Reservoir and extract some of the mercury during the process.

Tim Crough, district assistant general manager, said that the state Water Resources Control Board approved the proposed dredging program this month.

If funding is in place, work could start in April, Crough said.

The Sierra Nevada Conservancy has been a supporter of the mercury removal effort, initially providing $100,000 for some of the initial work.

Pete Dufour, conservancy spokesman, said the state agency applauds both the Nevada  Irrigation District and Teichert, which has a license for extracting sand and gravel from the site, for looking after their watershed, putting together environmental approvals and obtaining  permits.

The irrigation district will be working with Canadian-based Pegasus Earth Sensing Corp. to use suction dredging equipment to help remove mercury from sand and gravel.

“The ability to effectively remove mercury from sediments that have built up in our water-storage facilities is a major accomplishment that can be replicated at many other sites around the state,” Dufour said.

Three years ago, a demonstration project at the Teichert property by Pegasus indicated that five pounds of mercury could be removed for every five tons of gravel that could be cleaned.

Mercury, a byproduct of the gold-extraction process in California from the 1840s into the early 20th century, rests at the bottoms of rivers and streams throughout Gold Country. A report from the irrigation district states that when the river is swollen by snowmelt and winter rains, the riverbed is stirred up and mercury released to flow downstream.

Eating fish from mercury-laden streams has been proven to cause developmental delays in fetuses, infants and children.