Ship Canal Water Quality Project update 3/30/2023

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Tunnel boring machines, boulder detection systems, locomotives, and... hand tools?

Crew members building the adit in East Ballard.

Crew members building the adit in East Ballard.

With modern technology, this project must practically build itself, right? Right? Tunnel boring machines like MudHoney are a dramatic example of technological innovation, but some parts of this project must be built using hand tools, a construction method as old as humanity.

Take our diversion structures, for example. If you’re new here, diversion structures are underground structures that will divert excess untreated sewage and stormwater from the existing pipes to the storage tunnel during heavy rains. We're almost done building one of these structures in East Ballard, but an important last step remains: connecting the diversion structure to the tunnel MudHoney built.

The smaller tunnels that connect diversion structures to the main Ship Canal tunnel are called adits. To build the adit in East Ballard, crews descended a drop shaft and excavated the soil between the bottom of the drop shaft and the tunnel. Crews used hand tools and a remotely operated small excavator to dig a path to the main tunnel. As crews moved toward the tunnel, they sprayed concrete at an extremely high velocity on the newly exposed earth around them to stabilize the soil.

With the help of radar (and no fear of small, underground spaces), crews eventually exposed the side of the 18-ft diameter tunnel. Next, crews will sawcut into the tunnel and complete the adit that will connect the East Ballard diversion structure to the Ship Canal tunnel with in-situ concrete.

To learn more about the project, visit our project website. We also continue to update our Flickr albums with construction photos, including some new photos of the Seattle Fire Department tunnel rescue drills, which we highlighted in our last email.

MudHoney graphic


Our 18-ft diameter TBM has tunneled over 11,800 feet! Follow along with our tunneling tracker on our project website.

Ground monitoring is ongoing along the tunnel alignment and is done from both inside MudHoney and on the surface.


Our Ballard shaft site near Shilshole Ave NW will continue to be busy with tunneling activities until MudHoney reaches Wallingford this year.

During regular tunneling activities, you should anticipate:

  • Truck deliveries of concrete segments and MudHoney equipment
  • Nighttime segment deliveries and both nighttime/daytime tunnel spoils being hauled off
  • Noise and vibrations typical of a construction site

Crews are working 24 hours a day, six days a week.

East Ballard

Crews continue building the mechanical and electrical vault on NW 45th St and the diversion structure walls on 11th Ave NW. Crews are also constructing a horizontal tunnel at the bottom of the drop shaft to connect the conveyance pipe that will extend from the diversion structure to the storage tunnel.

Local closures and detours:

  • There continues to be a one-lane traffic configuration on 11th Ave NW at NW 45th St. Traffic signals and flaggers will direct traffic at the intersection during single lane closures.
  • NW 45th St remains closed to traffic between 11th Ave NW and 9th Ave NW; vehicles must detour onto NW 46th St
  • Burke-Gilman Trail remains detoured to the north side of NW 45th St through the project area. For safety, bicyclists should either dismount or cross train tracks at a 90-degree angle. Please use extra caution in wet weather as ramps may be slippery.

You should anticipate:

  • Heavy equipment in the area
  • Noise and vibrations typical of a construction site

Regular work hours will be Monday through Friday, from 7 am to 5 pm. Night and weekend work may occur.


Crews are working on the pipes that will run between the diversion structure and the tunnel. Before crews place the conveyance pipes, they are installing a shoring system to keep soil out of underground work areas. After the shoring system is in place, crews will use this area to install the conveyance pipes.

Local closures and detours:

  • Our contractor will be working in the southernmost eastbound lane of Leary Way NW during working hours for the next several weeks.
  • On 2nd Ave NW, between Leary Way NW and NW Canal St, the street remains closed to vehicle and pedestrian traffic through mid-2023. NW Canal St is open to two-way traffic to allow access during this closure.
  • NW 36th St, between Leary Way NW and 3rd Ave NW, remains closed through 2023
  • Pedestrian detours are in place on Leary Way NW; please follow all detour guidance

You should anticipate:

  • Truck traffic on Leary Way NW as trucks bring materials and equipment to and from the site
  • Fans running during work hours to provide fresh air to crews working in the shaft

Regular work hours will be Monday through Friday, from 7 am to 6 pm; and some Saturdays from 9 am to 6 pm.


Crews continue working on the electrical building and gate structure at the Wallingford site on Interlake Ave N and N 35th St.

Wallingford Conveyance project crews continue working within Stone Way N, between N 34th St and N 35th St, and on the north half of N 34th St to install conveyance pipes, a diversion structure, and perform utility work. Crews have completed installation of a temporary sewer bypass pipe down the center of Stone Way N and will begin installing shoring and excavating for construction of the diversion structure.

In the coming weeks, crews will reopen westbound N 34th St. In the coming month, crews will move operations into N 35th St and the intersection between Stone Way N and Interlake Ave N. We’ll share more details about the upcoming detour and traffic impacts as they become available.

Vehicle detour:

  • Stone Way N between N 34th St and N 35th St is closed to vehicles
  • Improvements are being made at the all-way stop traffic revision at the intersection of N 35th St and Woodland Park Ave N
  • Westbound N 34th St is closed to through traffic between Wallingford Ave N and Woodland Park Ave N
  • Local access to Densmore Ave N, Woodlawn Ave N, private driveways, businesses, and to the North Transfer Station from N 34th St will continue to be maintained. Local Access Only signs were added at both N 34th St and N 35th St (for each way) to discourage through-traffic.
  • Westbound traffic on N Pacific St/N 34th St can access the detour route at Wallingford Ave N
  • Left turns are not permitted at the intersection of N 34th St where N Northlake Way turns into Stone Way N
  • Westbound traffic further east on N Northlake Way can access the detour route using the N 36th St cutoff or Densmore Ave N
  • Please adhere to the Road Closed and Traffic Revision Ahead signage and follow the detour route signs

Bicycle detour: No bike lane through one block project area

Please use the bike detour route on N 35th St and on Woodland Park Ave N. Please dismount and walk if you use the sidewalk.

You should anticipate:

  • Trucks coming in and out of the site
  • Noise and vibrations typical of a construction site

Regular work hours will be Monday through Friday, from 7 am to 5:30 pm.

Queen Anne

Crews are preparing to install the piping and an air duct inside the 8-ft diameter tunnel casing.

Local closures and detours:

  • Localized Ship Canal Trail detour at least through summer 2023 (see map). Please continue to remain alert when moving through this area.
  • West Ewing Mini Park parking closure through mid-2023

You should anticipate:

  • Trucks coming in and out of the site
  • Noise and vibrations typical of a construction site

Regular work hours will be Monday through Friday, from 7 am to 5 pm. Night and weekend work may occur.

Contact Us

Please email with questions or comments or call our hotline at (206) 701-0233. You can also find information online at To support the community during active tunneling, we have changed our hotline hours to 24 hours a day, Monday through Friday.

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