Nelson Dam project as of Nov. 10, 2022. Photo courtesy Yakima County

Work continues on Nelson Dam removal and replacement project. Current work includes pouring concrete for a new fish screen structure and rip-rap installation.

The project reached a milestone with the removal of a fish ladder August 10th-12th. This marked the conclusion of demolition on the project.

Going forward, the remainder of the project will focus on concrete work to divert water for fish passage.

The diversion structure, known as a roughened channel, will not only aid fish but also help with flood mitigation. “It will make a much bigger pathway so all that sediment trapped up above will start moving, lowering the flood risk,” said Assistant Public Works Director Dave Brown.  

As always, the schedule for this type of project is subject to change daily dependent on weather, equipment failure, and emergencies.

Work on the Nelson Dam removal and replacement project began in August 2021. The project will improve fish passage and sediment continuity to improve habitat, increase flow conveyance to decrease flooding risks for nearby landowners, and improve water supply reliability.

Nelson Dam, on the Naches tributary of the Yakima River, was built in the 1920s to divert irrigation water for Yakima and the Naches-Cowiche Irrigation Association. The original design did not allow any fish passage. The dam has held back tons of sediment and silt over the years, raising the river bed and causing the Naches River to overflow its banks and move into the surrounding community during even minor flooding.

The Washington Dept. of Fish and Wildlife detailed how fish are being saved even as water levels are lowered to allow workers to carry out the project.

The City of Yakima and Yakima County have been collaborating on the design and implementation of this project. The dam removal and replacement is one of several major public works projects initiated by the Yakima Basin Integrated Plan.

The City of Yakima is investing $10.8 million in the $26 million multi-agency collaboration — part of the Yakima Basin Integrated Plan — over the next four to five years.

The City of Yakima plans to invest $10.8 million in the $26 million, multi-agency collaboration over the next four to five years. To help pay for the project, the City of Yakima received $4.4 million from Washington State’s Floodplain by Design program, $4.134 million from Washington State’s Brian Abbott Fish Barrier Removal Board, $1.325 million from the state’s Capital Budget and $500,000 from both the Resource Legacy Fund and the Bureau of Reclamation.

The Nelson Dam removal/replacement project began July 2021 and scheduled for completion April 2023.

For more about the project, contact City of Yakima Assistant Public Works Director Dave Brown by phone at 509-575-6154 or by email at David.Brown@yakimawa.gov

Photos from the project’s start in Summer 2021. More available at Nelson Dam Project Progress | Snapshots (yakimawa.gov)