Ship Canal Water Quality Project update 08/11/22

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Ship Canal LogoCrews in MudHoney send replacement cutterhead tools into the pressurized chamber

Crews in MudHoney send replacement cutterhead tools into the pressurized chamber where workers service the cutterhead during planned and unplanned TBM pauses.

MudHoney has arrived in East Ballard! It’s time for a little TBM TLC

It’s an exciting moment in the world of the Ship Canal Water Quality Project: MudHoney, our 18-ft diameter tunnel boring machine (TBM), has officially arrived at the East Ballard project site! MudHoney has been grinding along for a while now, and this is one of several planned maintenance stops to check MudHoney’s cutterhead along the route.

Crews need to work in front of MudHoney’s cutterhead to inspect it for wear and damage. To do this, compressed air is delivered in front of MudHoney (kind of like a bubble), which creates a soil-free pocket where our crews can work. Crews need to be quick: because of the compressed air environment, they can only spend 120 minutes per shift in front of the cutterhead.

Before inspections can happen, crews clean up the cutterhead so they can see what might need to be replaced. From there, they inspect all the parts and replace anything that doesn’t meet standards.

This compressed air environment requires crews to acclimatize by spending time in an air chamber housed inside MudHoney that slowly raises the air pressure to prepare them for the pressure levels in front of MudHoney’s cutterhead. The crews reverse this process after the inspection and stay in the air chamber for a few hours as atmospheric air pressure levels return. It’s very similar to recreational diving – these crew members are even referred to as divers – except underground instead of underwater!

At two locations – East Ballard and Fremont – we carried out jet grouting ground improvement works which we hoped would allow us to enter the cutterhead in free air (no diving). We are very happy to report that at the East Ballard site we have now entered the cutterhead chamber in free air, and there is no water inflow! MudHoney will be paused for the next several weeks while this inspection and maintenance takes place.

Perhaps you’d like to do some coloring while you wait? Check out Flickr for the latest project photos, including from this intervention!


Inside a MudHoney pressure chamber

Inside a MudHoney pressure chamber where crews will adjust to changes in pressure as they transition in and out of the cutting face. These hyperbaric interventions affect the body the same way as scuba diving 60 to 100 feet.

MudHoney graphic


MudHoney, our 18-ft diameter tunnel boring machine, is paused for maintenance after reaching East Ballard this week. Once tunneling resumes in several weeks, 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 continues to bustle with activity. Crews use the Ballard shaft site to access the tunnel, deliver supplies to MudHoney, and haul spoils out of the tunnel.

During regular tunneling activities, you should anticipate:

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

Crews are working 24 hours a day, six days a week and will continue until MudHoney reaches Wallingford in 2023. Sunday work may also occur. The Ballard shaft site is also the site of the future pump station.

East Ballard

Crews are building the diversion structure on 11th Ave NW, requiring the road to be reduced to a single lane. This allows for work to occur on the eastern area of 11th Ave NW, near NW 45th St.

Local closures and detours:

  • One-lane closure on 11th Ave NW through November 2022. During daytime working hours, traffic signals with assistance of flaggers will direct northbound and southbound traffic as well as bicyclists and other trail users, and traffic signals will direct traffic during non-working hours. Directional signage is also in place. 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.
  • 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 detour to the north side of NW 45th St through the project area

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 have built a sewer bypass and will be starting the construction of the diversion structure in 2nd Ave NW with the installation of shoring later this month. Preparations also continue for conveyance tunneling within the Fremont site’s east end near 2nd Ave NW.

Local closures and detours:

  • 2nd Ave NW, between Leary Way NW and NW Canal St, closed to vehicle and pedestrian traffic through the end of 2022. 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, closed through the remainder of the project
  • Pedestrian detours on Leary Way NW; please follow all detour guidance on site

You should anticipate:

  • Truck traffic on Leary Way NW as trucks bring materials and equipment to and from the site
  • Generators running during work hours to power pumps and equipment
  • Noise and vibrations typical of a construction site

Regular work hours will be Monday through Friday, from 7 am to 5 pm. Crews also continue to work on large eight-foot conveyance tunnel pipes underneath white tents within the site from 7 am to 10 pm on weekdays, and possibly 9 am to 10 pm on weekends, over the next few months.


Crews continue working on the Wallingford shaft walls, including concrete pours for the upper portion of the shaft wall.

You should anticipate:

  • Concrete 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.

Queen Anne

Crews continue constructing underground vaults through the summer. The South Ship Canal Trail has been temporarily adjusted for construction of the third below-grade vault through summer 2022 and will revert back to the detour shown in the linked map below this fall. Our contractor will be working on both sides of the trail so please continue to remain alert when moving through this area.

Local closures and detours:

  • Localized Ship Canal Trail detour at least through summer 2023 (see map)
  • 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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