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Most King County offices will be closed on Monday, May 29, 2017, for Memorial Day.  
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Project update

May 25, 2017

Major construction activities complete – project art on the way!


King County is happy to announce that the Fremont Siphon Replacement Project contractor finished major construction activities on May 19 – right on schedule. View project update.

Community celebration and ribbon cutting
Sunday, June 18, 11:00 a.m. – 3:00 p.m.
Fremont Siphon Odor Control Facility
215 Northwest 36th Street

During the Fremont Fair, bring your friends and family by the north project site to: 

  • Take a tour of the building and rain gardens
  • See and learn about project art
  • Speak with project staff

Have a comment or question? Need more information about the project?
Click here to contact the project team.


Contact us

Contact Doug Marsano at:


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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  .