Combie Reservoir Sediment & Mercury Removal Project

The purpose of the Combie Reservoir Sediment and Mercury Removal Project is to remove elemental mercury from the accumulated sediment and to restore reservoir capacity for drinking water use and recreational opportunities in the upper portion of Combie Reservoir.   This Project will combine emergent technologies for a unique application of safe elemental mercury removal from dredged sediments, thereby returning high-quality water back to the reservoir.  Combie Reservoir is located on the Bear River, which lies along the Nevada-Placer County border. The sediment that flows into Combie Reservoir contains elevated mercury concentrations that are remnants of gold processing practices used over a century ago.

The sediment removal process consists of three components. The first involves the dredging of upper Combie Reservoir using a wet dredge. The second involves the mercury removal and separation process using a Knelson Concentrator and dewatering of the dredge material using on-shore equipment. The third involves the transport of sand and aggregate byproducts to a third party for further processing and/or sale. The maximum sediment removal would be 80,000 cubic yards for the first three to five years, and would decrease thereafter to the amount needed to maintain storage capacity. The proposed Project change would affect only the first component, and would allow the District to supplement the wet removal process with dry removal during the low water season, using earthmoving equipment, including tracked excavators, bulldozers, front loaders, and dump trucks.

The Project was approved and the Mitigated Negative Declaration was adopted in September 2009. The Notice of Determination filed on September 25, 2009. An addendum to the Mitigated Negative Declaration was submitted in May 2018.

The video below and documents in the sidebar provide further information and description of the project.