Lake Sacajawea Flushing Facilities Upgrade

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ELS worked on behalf of the City of Longview Public Works to complete environmental permitting for the Lake Sacajawea Flushing Facilities Upgrade project, which consisted of modifying the existing water-intake structure located on the Cowlitz River for use as a pump station to supply raw river water to the lake.  Annual lake flushing with Cowlitz River water started in the early 1980s and continues today.  Water from the Cowlitz River is pumped under existing recreational and municipal water rights to provide flushing water for Lake Sacajawea.  Without routine flushing in the summer months with water from the Cowlitz River, oxygen levels in Lake Sacajawea are reduced, and the lake becomes eutrophic.  With the only natural sources of water to Lake Sacajawea being rainfall and groundwater, water quality drastically declines from May through October without the introduction of clean water from the Cowlitz River.  Maintenance dredging in the Cowlitz River is necessary periodically to keep the intake area free from sediment.  The facility upgrade will help the City of Longview provide long-term management of water quality in Lake Sacajawea, and will be beneficial for fish, as the intake screens will now meet WDFW requirements for fish exclusion.  The amount of water pumped out of the Cowlitz River will be minimized with the new automated system while water quality in the lake will be better maintained, and maintenance of the water-intake structure will no longer require dewatering an area where juvenile salmonids could be present.  ELS prepared a biological assessment, JARPA, and SEPA for the project.  ELS is conducting a new monitoring protocol project at the intake structure to determine the potential presence of smelt eggs and larvae that meets new NOAA Fisheries requirements.

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