Adit all up: Building connections inside the tunnel
 Crew members building a mock-up for placing concrete for the adits on left. Crew members make a precut inside the tunnel at East Ballard in preparation for the installation of the adit on right.
In the coming months, crews will be building adits at two of the project sites that will connect to our storage tunnel. What are adits, you ask? Adits are short, horizontal underground tunnel segments that connect vertical shafts to a tunnel. Our adits will bring the combined sewer flows into the storage tunnel. Building these underground tunnels required getting the ground ready first. Prior to the tunnel boring machine reaching the two sites, workers used a technique called "jet grouting" to make the ground strong before they start constructing the adits.
Crews will use the “Sequential Excavation Method (SEM)” to build the adits. SEM uses small digging machines (think of a gopher tunneling) to make short parts of the tunnel. These parts are about 12 feet wide and 3 feet long. After they dig, they cover the ground initially with a special layer called shotcrete. It's like a protective coating made of a concrete mix combined with water at a nozzle and a steel mesh to temporarily support the ground while the tunnel is excavated. After the adit is excavated to its full length, a second layer of shotcrete and reinforced steel is sprayed onto the walls of the adit for the final wall. Even though the tunnels are short, they're important because they connect to the storage tunnel. The two connections are different, so they are being built in different ways. One of the adits will be built from inside the tunnel toward the shaft and the other one will be built from inside the shaft toward the tunnel. Making everything fit together just right is like solving a puzzle and needs careful planning and work sequencing.
Updated Wallingford detour maps
In our last update, we informed you that our contractor would be moving work areas from N 34th St to N 35th St., which would entail new detours. At that time, we expected to open N 34th St and detour N 35th St between Stone Way N and Interlake Ave N starting August 21. The work in N 34th St has taken longer than expected, so we have postponed the detour of N 35th St until September 5. We hope to open N 34th St by September 2, and start the closure of N 35th St on the Tuesday after Labor Day. We have updated detour maps for upcoming changes in Wallingford. Please follow all detour signage and safety directions when traveling through the work area.
We continue to work directly with adjacent neighbors to maintain access to all businesses and will continue to provide updates by email and on our website. Check out our Flickr albums for the latest construction photos.
Ballard
Crews continue to dismantle, clean, and remove the equipment that was needed to build the tunnel.
You should anticipate:
- Nighttime truck movements may be necessary to remove the particularly large equipment over the next few months
- Noise and vibrations typical of a construction site
Crews are working 20 hours a day, six days a week. Some work may occur on Sundays.
East Ballard
Crews continue to work inside the adit, the drop shaft, and conveyance piping on NW 45th St, and the isolation maintenance hole in 11th Ave NW.
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 (BGT) 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 take 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 6 pm. Night and weekend work may occur.
Fremont
Crews continue to build the permanent structure inside the shaft as well as the adit which will connect the 8-ft diameter conveyance tunnel to the storage tunnel. They also continue to work on the large underground mechanical and electrical vault.
As of August 14, crews began work on the vent shaft which connects to the top of our new 18-ft diameter tunnel underneath Leary Way NW at N 36th St. This work should take approximately three more weeks.
Local closures and detours:
- The two southernmost lanes of Leary Way NW are closed. One lane of traffic in each direction is being maintained. This configuration should remain in place 24/7 for approximately three more weeks. After that, the two southernmost lanes will be closed between 9 am and 3 pm, Monday through Friday for continued utility work. One lane of traffic in each direction will be maintained.
- In October, there will be short-term overnight work to connect the new watermain to the existing system. We will share more when we have details on this work.
- On 2nd Ave NW, between Leary Way NW and NW Canal St, the street remains closed to vehicle and pedestrian traffic through 2023
- NW Canal St is open to two-way traffic 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
- Concrete trucks entering and leaving the site
- Fans running during work hours to provide fresh air to crews working in the shaft
- 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 6 pm; and some Saturdays from 9 am to 6 pm.
Wallingford
Crews have dismantled and removed MudHoney from the Wallingford site.
Wallingford Conveyance crews continue to install pipes and maintenance holes in the north portion of the intersection at N 34th St and Stone Way N.
The left turn lane from Northlake Way onto westbound N 34th St is planned to be reopened by September 2 to allow for the N 35th St closure to start after Labor Day. See our new detour routes for cyclists and pedestrians in our detour maps.
As of Tuesday, September 5, N 35th St between Stone Way N and Interlake Ave N and the intersection of N 35th St and Stone Way N will be closed. N 34th St will be opened to two-way traffic prior to the closure of N 35th St.
Metro bus routes 31, 32, and 62 will be detoured. Please view service advisories on King County Metro’s website.
Vehicle detour:
- Check out the vehicle detour map
- Traffic will be detoured to N 34th St via Woodland Park Ave N and Wallingford Ave N
- A new all-way stop was installed at N 34th St and Woodland Park Ave N
- The all-way stops remain in place at Woodland Park Ave N and N 35th St and also at Wallingford Ave and N 35th St
- Stone Way N between N 34th St and N 35th St remains closed to vehicles and bicycles
- Please adhere to the Road Closed, Local Access Only, and Traffic Revision Ahead signage and follow marked detour routes
Bicycle detour
- Check out the bicycle and pedestrian detour map
- Bicyclists are detoured to the west on N 35th St and to the south on Woodland Park Ave N
- Access to the Burke Gilman Trail is on N 34th St at Stone Way N and at Troll Ave N
- Please dismount and walk if you use the sidewalk
You should anticipate:
- Trucks coming in and out of the site
- Heavy equipment in the area
- Vibrations typical of a construction site
- Road and periodic sidewalk closures
Crews will resume working a single day shift, Monday through Friday. Night and weekend work may occur periodically.
Queen Anne
Crews continue to work inside the shaft.
Local closures and detours:
- Localized Ship Canal Trail detour at least through 2023 (see map). Please continue to remain alert when moving through this area.
- West Ewing Mini Park parking closure through 2023
You should anticipate:
- Trucks coming in and out of the site
- 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 6 pm. Night and weekend work may occur.
Construction Safety is Everyone’s Job
Check out some top safety tips at
www.seattle.gov/utilities/constructionsafety
Contact Us
Please email SPU_ShipCanalProject@seattle.gov with questions or comments or call our hotline at (206) 701-0233. You can also find information online at spushipcanal.participate.online.
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