Work will begin soon to restore a barrier that protects a crucial water pipeline near Duvall.
The Tolt Pipeline Protection project will rebuild and improve some 1,200 feet of rock barriers along the Snoqualmie River south of the city. The pipeline is a crucial one for the area’s water supply as it pumps water to cities, including Bellevue, Bothell, Redmond and Seattle from the South Fork Tolt River Reservoir.
The barrier sits between a curve in the Snoqualmie River and the pipelines and was installed in the 1960s. Since then, erosion and river migration has severely damaged the barrier. The river is moving toward the pipeline, and if the barrier is not repaired, continued migration will eventually damage the pipeline.
The restoration project will include placing 760 large boulders and log structures near the river to reinforce the barrier. A small, collapsed culvert at Deer Creek will be removed and replaced some 600 feet upstream from its current location on the banks of the Snoqualmie River. The new culvert will be equipped with a floodgate and will not impede fish passage.
The project will cost roughly $10.2 million and is funded through the King County Flood Control District. Construction is expected to be completed in October.
Kathy Lambert, a King County council member who sits on the district’s board of directors, said the project is one of a slew that the flood district is working on. The district was formed in 2007 and identifies and completes projects to help reduce flooding and damages in the county.
Lambert said that due to regulations surrounding permitting, many projects have been in the works for years and are just now moving to construction. Many areas in the Snoqualmie valley are being studied for future projects, including roadway repairs, levee improvements and additional river bank repairs.
One large potential project could be the clearing out of a collection of rocks, known as an alluvial fan, near North Bend in the Snoqualmie River. These rocks build up near the three forks section of the river and slow water, which can lead to backups and flooding. However, Lambert said if they take action to clear it they would ensure the increased flow didn’t create more problems downstream.
“Those need to be cleaned on a regular basis,” she said.
County residents can sign up for flood alerts at the King County flood services website.