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Project update

June 2017

Thank you to all the folks who came out on Sunday, June 18 to see the site and celebrate the completion of the Fremont Siphon Replacement Project. King County deeply appreciates the community’s patience and understanding during this important project.

Thanks again for your time and consideration throughout the project.  


operations phase

Contact us

Contact Doug Marsano at:


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See how public art at KCWTD facilities connects community to our system and the environment.

In July 2016, a remote-controlled microtunnel boring machine completed two tunnels underneath the Lake Washington Ship Canal as part of a King County Fremont Siphon Replacement Project. Watch as the 26-foot-long, 7-foot-wide machine is hoisted from its exit pit in Fremont.

Project description

King County is replacing the Fremont Siphon, a major sewer pipe running under the Ship Canal between Fremont and Queen Anne. The new siphon will be located west of the existing siphon to reduce project risks and impacts to the community. Construction begins in early 2015 and will continue until early 2017. The old siphon will be decommissioned.

Project schedule

Project schedule

Project location

Fremont Siphon

Back to the capital projects overview map .

Fremont Siphon service area

Building the Fremont Siphon Tunnel, 1913. Photo provided by Seattle Municipal Archives  .