April 29, 2019 – Nevada Irrigation District’s (NID) Combie Reservoir Sediment and Mercury Removal Project team members were honored during an April 24 banquet as winners of the prestigious 2018 Small Project of the Year award, presented by the American Society of Civil Engineers, Sacramento Section.
The goal of the three-year pilot project is to remove sediment from Combie Reservoir while introducing an innovative mercury recovery process. Benefits include restoring water storage capacity in an existing surface water reservoir, removing mercury from the Bear River watershed, and creating long-term benefits to downstream aquatic habitat.
From Oct. 1 to Nov. 19, 2018, about 40,000 cubic yards of sediment were removed from the dry Combie Reservoir lakebed using an excavator / front loader. The next phase – which will continue through August of this year – will focus on removing sediment in wet conditions using a suction dredge. Once the material is out of the reservoir, a centrifuge technology will be used to remove elemental mercury.
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Mercury was introduced to the Sierra Nevada during the Gold Rush period of the 1800s and used to process mining ore for gold. That mercury has remained and led to contamination of sediments throughout Sierra watersheds.
Findings from this project will become valuable to state regulators and help water managers address mercury in the aquatic food chain. When complete, this project can act as a replicate process, applied at other impacted reservoirs.
NID is working with partners, including the Sierra Fund, US Geological Society, the Department of Water Resources, the Cosumnes-American-Bear-Yuba Integrated Regional Water Management Group (CABY), NV5 Global, Inc., Great Lakes Environmental and Teichert Aggregates.
ASCE honored the Combie project and others during its annual awards banquet, held April 24 in Sacramento.