LEAVENWORTH — A $4.56 million project on a 114-year-old dam is underway, but the fish keep swimming upstream.
Major repair work on Tumwater Dam began Sept. 5 and is expected to last possibly into January. Crews are repairing its apron, a section of concrete that sits just downstream of the dam, and installing grout at its leading edge on the west side, according to project manager Sam Dilly.
Water is getting diverted to the east side of the river during this period. The work will help prevent “undercutting of the structure,” according to a Chelan County PUD release. Deer Park-based Knight Construction was awarded the project.
The dam was constructed in 1909 for the Great Northern Railway to produce power for electric locomotives traveling through the old Cascade Tunnel on Stevens Pass. Puget Sound Power & Light leased the dam from 1924-1957 and power production ended in 1956. The PUD acquired the dam in 1957, and the Bonneville Power Administration funded rebuilding of the fishway in 1986.
The dam provides “adult fish collection at the fishway to fulfill hatchery mitigation obligations for the Rocky Reach and Rock Island Habitat Conservation Plans (HCPs),” Alene Underwood, PUD natural resources director, has said, and is important for other entities’ fish studies. The plans signed in 2002 committed Chelan and Douglas county PUDs to a 50-year program to ensure hydro projects have no net impact on mid-Columbia salmon and steelhead runs.
The work on the water release control and protective apron is required to meet state Department of Ecology regulations for dam stability, Underwood said last year.
The current work is the second part of a multiyear maintenance plan for Tumwater Dam. In 2020, the PUD reinforced the entrance of the fishway with concrete, according to a PUD release.
This year, a temporary bridge was placed over the Wenatchee River to move materials and equipment, while fish pass through the dam’s ladder undisturbed. The bridge will stay during construction.
“The fish ladder has remained open and operable during construction,” Underwood said. “Steelhead will continue to pass Tumwater Dam in single digits through the remainder of the year and the coho run will begin to taper off at the end of October/beginning of November.”
Between Jan. 1 and Oct. 17, 116 coho salmon have used the ladder, according to the University of Washington Columbia Basin Research’s Columbia River Data Access in Real Time website. The 10-year average is 489. For chinook, 3,588 have passed through the dam, according to the website. The 10-year average for chinook passage is 5,604, according to the site. The number of sockeye salmon has been 84,473 since Jan. 1, compared to the 10-year average of 48,580. Many other kinds of fish travel through the ladder, too, including coho salmon, lamprey and bull trout.
However, the PUD doesn’t look at comparing fish numbers year to year, according to Rachel Hansen, PUD spokesperson.
“There are a number of factors that can change the timing and number of fish that come through,” Hansen wrote in an email. “Some species have cyclical patterns with big/small runs, in addition to environmental differences year to year.”
Jersey barriers run with the fish along Highway 2, next to the river in that area, and the viewing area will remain closed during construction, likely through the end of the year. Trucks are entering and exiting the job site on a routine basis. Intermittent lane closures could interrupt traffic.