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Natural Resources and Parks
Public Affairs

Tour King County’s newly completed Fremont Siphon Project, June 18


Celebrate the completion of King County’s Fremont Siphon Project on Sunday, June 18, with facility tours and information about the facility’s public art and rain gardens. The event will take place from 11 a.m. to 3 p.m. at the Fremont Siphon Odor Control Facility, 215 N.W. 36th Street in Seattle’s Fremont neighborhood.


Fremont Fair patrons and fans of clean-water infrastructure are invited to celebrate the completion of King County’s Fremont Siphon Project on Sunday, June 18 from 11 a.m. to 3 p.m. The facility ribbon cutting ceremony begins at 11:30 a.m.

Take tours, snap a selfie by the community-inspired public art and rain gardens, and learn how King County used modern microtunnel technology to replace sewer lines beneath the Lake Washington Ship Canal that had been in service for over a century. 

Festivities will take place at the Fremont Siphon Odor Control Facility, located at 215 N.W. 36th Street in Seattle.

The Fremont Siphon is one of King County’s most heavily used sewer lines, pushing up to 220 million gallons of stormwater and sewage a day from north Seattle to Queen Anne, and eventually to the West Point Treatment Plant in Magnolia. King County invested nearly $46 million in the project, which will increase system capacity and also help control overflows of stormwater mixed with sewage that sometimes spilled from the old siphon on very rainy days. 

King County completed construction on two new 5-foot-diameter pipelines that now rest 20 feet beneath the floor of the Ship Canal in 2016. The project also entailed building a new odor control facility in Fremont, which will help ensure the new facilities are good neighbors to the surrounding community. 

The project was completed on schedule and under budget on May 19, 2017. Additional information about the project is available online.