Lower Baker Dam repairs begin

Work will bring heavy equipment, helicopters to town. New grouting will control leakage in rock abutments.

(posted 4.6.15)

Puget Sound Energy will begin a series of three projects at Lower Baker Dam this month that will upgrade and improve operations at the hydroelectric facilities.

Improvements at the dam are scheduled to begin on Mon., April 6. For several months, there will be increased activity around the Lower Baker Dam site, which will include teams of workers, boats on the water, a crane positioned near the dam, and frequent flights by helicopters in the area.

PSE said in a release there are no concerns regarding the integrity of the dam. The first phase of the work will focus on drilling test holes in the dam’s rock abutments—the area between the concrete structure and the rock canyon walls—to investigate why leakage occurs and better understand the geology. Crews will then work on grouting in the dam’s abutments to address the leakage that historically happens about every 30 years. Grouting is a standard and necessary practice that’s widely used to maintain dams. The leakage at the dam occurs naturally through seams in the limestone rock of the canyon walls. The dam itself has a functioning internal drain system.

The grouting project will be completed in 2016. After that work ends, construction starts on floodwall upgrades designed to protect the abutments from the impacts of potential floodwaters. The final phase, starting in 2018 and lasting two years, will involve replacing and modernizing the areas above the water line, such as the dam crest, the piers, spillway gates, and all equipment needed to operate those gates at the dam.

The improvements planned with the Lower Baker Dam Capital Program will last for the 50-year life of the project license with the Federal Energy Regulatory Commission (FERC), which PSE received in 2008.

The Lower Baker Dam is a concrete arch dam that was constructed in 1924–25, with additional work done in 1927. It impounds the waters of the Baker River, creating Lake Shannon.

—J. K. M.

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