Nelson Dam Progress

A drone photo, courtesy of Yakima County, shows progress on the Nelson Dam removal/replacement project as of Jan. 6, 2023.

photo courtesy Yakima County

The project reached a milestone on Dec. 2, 2022 with removal of a temporary sheet pile wall that had been at the work site for about a year.

Current focus on the project is 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 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.