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Flood Control District project to provide better protection to Tolt water supply pipeline


A major project on the Snoqualmie River beginning in June will rebuild a damaged flood-protection facility that protects a pipeline that delivers water to Seattle, Bellevue, Redmond, Issaquah and several other cities.


King County will begin rebuilding a damaged section of bank armoring along the Snoqualmie River, protecting a major pipeline that provides nearly a third of the water to several cities and communities across the county.

The Tolt Pipeline Protection Project, funded by the King County Flood Control District, will rebuild and improve 1,200 feet of damaged rock armoring – or revetment – along the Snoqualmie River south of Duvall. Construction crews, expected to begin work in late June, will use rock-and-wood engineered structures to protect the bank.

The revetment protects the Tolt pipeline from the Snoqualmie River, which could otherwise migrate across the floodplain and damage the pipeline. The pipeline brings water from the South Fork Tolt River Reservoir to people in several cities and water districts, including Seattle, Bellevue, Redmond, Issaquah, Bothell, Kirkland, the Sammamish Plateau, Woodinville, Northshore, Lake Forest Park and Duvall.

The project will also replace a damaged culvert on Deer Creek and regrade the creek channel to improve drainage on nearby farms, improve fish habitat and provide better fish passage. Native trees and shrubs will be planted along the riverbank for additional bank stability.

“This is a critical project for our region, protecting the drinking water for tens of thousands of people,” said King County Flood Control District Chairman Reagan Dunn. “It underscores the value of a countywide flood district that can work to address countywide needs.”

“I’m pleased to be able to serve constituents in my district, as well as residents throughout the county, with this important protection project,” said Flood Control District Supervisor Kathy Lambert. “This project is a win-win for the region.”

City of Seattle leaders and regional water districts are also pleased to see the project get underway. The pipeline is owned and operated by Seattle Public Utilities (SPU).

“This project provides long-term protection to our critical Tolt Water Supply System and benefits Seattle Public Utilities’ drinking water customers throughout King County,” said Mami Hara, SPU general manager. “Delivery of essential utility services is a top priority for the City of Seattle. SPU and King County have had a very positive working relationship during design of this project and look forward to this summer’s construction phase.”

“Over the last two decades, our engineers have been monitoring as the river gradually moved closer to the regional water pipelines operated by Seattle and benefiting the whole region,” said Seattle City Councilmember Lisa Herbold. “We very much appreciate the Flood District’s help with this project to protect a critical water supply line.”

“It is reassuring to see the King County Flood Control District’s proactive effort to protect critical infrastructure serving our region,” said Alan G. Nelson, Northshore Utility District’s general manager. “The Tolt Pipeline system is extremely valuable in the delivery of potable water to our customers and communities. Northshore Utility District greatly appreciates the measures they are taking to enhance the river system and safeguard our water supply.” 

The project, including planning, design and construction, will cost approximately $10.2 million; all funding is from the Flood Control District. Construction is expected to be substantially completed in October. Tree and shrub installation will occur from October through February 2019.

More information about the Tolt Pipeline Protection Project can be found at

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The King County Flood Control District is a special purpose government created to provide funding and policy oversight for flood protection projects and programs in King County. The Flood Control District’s Board is composed of the members of the King County Council. The Water and Land Resources Division of the King County Department of Natural Resources and Parks develops and implements the approved flood protection projects and programs. Information is available at