First stage of Combie Reservoir mercury project removes 40,000 cubic yards of sediment | TheUnion.com

First stage of Combie Reservoir mercury project removes 40,000 cubic yards of sediment

On Wednesday, the Nevada Irrigation District board of directors heard an update on the Combie Reservoir Sediment and Mercury Removal Project, a multi-year, multi-million-dollar pilot project.

The project got underway in July 2017 and will remove sediment from the reservoir, while extracting mercury using an innovative centrifuge technology.

The water district has been testing the new technology, suctioning sediment from waterways and funneling it into a centrifuge machine, which spins and cleans the sediment and removes 98 percent of mercury.

If the project demonstrates mercury can be effectively removed from river sediments, the process can be applied at other reservoirs throughout the Sierra Nevada, according to the water district.

The district is collaborating with The Sierra Fund to conduct education, outreach and expert technical review for the project. The Sierra Fund will conduct an annual meeting that addresses the role reservoir management activities play in the fate and transport of mercury, will conduct outreach and education through fish advisory postings and angler surveys, and develop a Gold Rush Curriculum and Activity Guide for teachers in Nevada and Placer counties on the history of mercury in the Sierra during the Gold Rush days.

In June 2018, the water district signed off on $6.6 million in contracts for the project, which is expected to cost $7.67 million. The bulk of that — $5.5 million — is coming from the Department of Water Resources’ Riverine Stewardship Program, with $2.17 million from the water district’s Capital Reserves.

Last year, the district was told the sediment was not marketable because it was not in demand currently. Staff now has identified a location on Teichert Aggregates property near the project processing area that can serve as short-term (three-year) storage until either a buyer is found, or the district identifies a different permanent location for the material.

Between Oct. 1 and Nov. 19, Great Lakes Environmental moved approximately 40,000 cubic yards of sediment from the dry lakebed and moved it to the sediment stockpile area. None of the material has been processed through the centrifuge, Assistant General Manager Greg Jones told the directors during the presentation Wednesday.

The water district sent out a Request for Proposals in January for the purchase and removal of the sediment and got one response, at $1 per cubic yard.

The next stage of the project is expected to run from April through August and will remove sediment using a dredge and then clean it with the centrifuge, Jones said.

Contact reporter Liz Kellar at 530-477-4236 or by email at lizk@theunion.com.


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