Success! SWIZY the tunneling machine finished digging two 465-foot tunnels under the Ship Canal on Tuesday, July 12. Check out the video below to see King County's contractor lifting SWIZY out of the 80-foot deep shaft on the Queen Anne side of the project. View July 11 news release.
King County’s contractor will now install new pipes in each of the tunnels to carry wastewater from north Seattle and beyond to King County's treatment plant in Magnolia. These pipes replace the existing siphon, which is more than 100 years old. The new pipes will be installed by this fall. The project is on track to finish in 2017.
Did you know?
The Fremont Siphon Replacement Project was SWIZY’s first project.
SWIZY is 7 feet in diameter.
SWIZY dug two tunnels 20 feet below the bottom of the Ship Canal, about 100 feet underground.
SWIZY removed about 650 cubic yards of dirt for each tunnel - enough to fill 65 dump trucks!
Queen Anne Project site: W Ewing Alley closed between 3rd Avenue W and 6th Avenue W until fall
In late March, King County’s contractor for the Fremont Siphon Replacement project began building the structure to connect the new siphons to the existing sewer under the W Ewing Alley. W Ewing Alley is closed to through traffic between 3rd Ave W and 6th Ave W until the fall.
Vehicle traffic will be detoured off of W Ewing Alley onto W Ewing St or W Nickerson St. The Ship Canal Trail will remain open. Along with the closure, this work will increase noise and activity around the project site. The contractor will begin by installing shoring for excavation of the new connecting structure.
Fremont Project Site: Intersection of 2nd Ave. N.W. and N.W. Canal St. closed until fall
The corner of 2nd Ave. NW and NW Canal St. will remain closed through the fall while crews install the 9-foot diameter pipe connecting the new siphons to the existing sewer system. Burke-Gilman Trail users should follow the trail detour just south of the normal trail to get around the Fremont Canal Park work area safely.
Have a comment or question? Need more information about the project?
Click here to contact the project team.
King County will replace 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.
Why do we need this project?
The Fremont Siphon has provided safe, reliable sewer service to north Seattle and other cities in north King County for decades. Sewage and stormwater from more than 100 square miles of King and Snohomish Counties pass through the Fremont Siphon every year to be cleaned and safely discharged at the County’s treatment plant in Magnolia. During storms, the pipe carries up to 220 million gallons per day, making it one of the most heavily used pipes in the regional sewer system.
The existing Siphon is nearly 100 years old and has reached the end of its of service life. The new pipes will ensure north Seattle and northern King County continue to enjoy safe, reliable sewer service for decades.
How King County works with the community during construction
King County recognizes that its construction projects can disrupt the daily lives of those near them. During construction, the County’s project team update the community and local jurisdictions on the project’s progress and any unforeseen developments.
The County project team will also work directly with the community to minimize construction impacts to those living or working nearby. Information from the community helps to shape the County’s decisions about ways to address community disruptions, private property impacts attributable to the project and promote public safety around the work site.
Interested community members will have a number of ways to interact with the project, including:
Community meetings with the contractor prior to construction
Community briefings on project progress during construction
Advance written notice of major construction activities
Project status reports available via email and flyer
Prompt response to all community inquiries
24/7 construction hotline
What is a siphon and how does it work?
The Fremont Siphon is an inverted siphon. Inverted siphons use gravity to push liquids downhill. In this case, sewage and stormwater from north Seattle and elsewhere is pushed through the Fremont Siphon by having sewage and stormwater enter the pipe in Fremont Canal Park at a higher elevation than where it exits the pipe in Queen Anne.
To help keep the sewage and stormwater moving, inverted siphons in the sewer system are a smaller diameter pipe than those connecting to it on either side. The smaller diameter speeds up the passage of sewage and stormwater pass through the pipe to keep solids moving and avoid clogs.
Project updates / news
Project updates and news releases are located on the library page.