Ship Canal Water Quality Project

King County and Seattle Public Utilities

Detail map of Seattle from Ballard to Wallingford along Lake Washington Ship Canal.
Project area sites in Ballard, East Ballard, Fremont, Queen Anne and Wallingford, with route of storage tunnel along the north side of the West Ship Canal from Lake Union to Salmon Bay.

Project Description

Investing in the Health of the Sound and the Future of Our Region

Seattle Public Utilities and King County Wastewater Treatment Division are building the Ship Canal Water Quality Project (SCWQP) to significantly reduce the amount of polluted stormwater (from rain) and sewage that flows into the Lake Washington Ship Canal, Salmon Bay, and Lake Union from our sewer system.

Jump to the project sites and more information:
Tunnel | Ballard | E Ballard | Fremont | Queen Anne | Wallingford | About the project | Public Art | Project Library

What’s Happening Now?

Ballard

Crews at the Ballard Pump Station continue placing rebar and concrete for the concrete tower walls.

The Ballard Conveyance contractor continues work along 24th Ave NW, NW 56th St, and 28th Ave NW. 

Crews are setting up a work area at the intersection of 24th Ave NW and NW 56th St to support upcoming tunneling operations. This work area will be in place through spring 2027. One northbound and one southbound lane on 24th Ave NW will always remain open to maintain traffic flow during this phase.  

Map of Traffic Control Plan on 24th Ave NW and NW 56th St

Aerial view of the intersection of NW 56th St and 24th Ave NW.
Map of traffic control plan showing one northbound and one southbound lane open in each direction on 24th Ave NW at the intersection of NW 56th St. Also showing work zone and shaft construction area at the intersection of 24th Ave NW and NW 56th St in place until spring 2027.

You should anticipate:

  • Parking restrictions, intermittent road closures, and local access only along 24th Ave NW, NW 56th St, and 28th Ave NW
  • Increased truck traffic bringing materials on- and off-site
  • Noise, dust, and vibration typical of a large construction site
  • Vehicle, pedestrian, and bicycle detours in the area
  • Heavier traffic volumes as residents and commuters adjust to detour routes

Community Benefits

  • Reduces the amount of polluted stormwater and sewage flowing into local waterways, protecting fish, wildlife, and the overall ecosystem
  • Helps keep Lake Union, Salmon Bay, and the Lake Washington Ship Canal cleaner and safer for recreation like boating and kayaking
  • Improves water quality for neighborhoods across Seattle, supporting a healthier Puget Sound region
  • Reduces sewage overflows during storms, making infrastructure more resilient in the face of climate change and extreme weather
  • Supports long-term public health
  • Invests in public infrastructure that benefits both current residents and future generations 

Tunnel & project sites

The Ship Canal Water Quality Project includes a 2.7-mile, 18-ft and 10-in internal-diameter tunnel that extends from Ballard to Wallingford. Tunneling operations started in Ballard with the vertical access shaft construction in 2020 and tunneling completion in 2023.

Learn more about the tunnel

Since the 1800s, 150 tunnels spanning over 70 miles have been constructed in Seattle for sewers, utility corridors, and transportation needs. The Ship Canal Water Quality Project includes a 2.7-mile, 18-ft and 10-in internal-diameter tunnel that extends from Ballard to Wallingford.

The purpose of the tunnel is to collect and hold stormwater and sewage flows which would normally overflow into the Ship Canal. Along the tunnel path, there are five vertical shafts (in Ballard, East Ballard, Fremont, Queen Anne, and Wallingford). They will collect stormwater and sewage flows from each basin and send them approximately 40 – 80 ft below ground into the new storage tunnel. In order to bring flows from Queen Anne into the storage tunnel, SPU built an 8-ft diameter conveyance tunnel underneath the Ship Canal connecting the vertical shafts in Queen Anne and Fremont. For the final piece of the SCWQP, SPU will install new pipes to connect the existing sewer systems to the new shafts.

Diagram of storage tunnel operation.
How the new Ship Canal Storage Tunnel works: flows from Queen Anne, Wallingford, Fremont, East Ballard, and Ballard neighborhoods will flow into the storage tunnel which is pumped to the Westpoint Treatment Plant and then clean water is pumped into Puget Sound.

Meet our Tunnel Boring Machines (TBMs) 

In addition to MudHoney, our roughly 18-ft diameter tunnel boring machine that constructed the storage tunnel, did you know that our project is also building a couple of other, smaller tunnels? We are using smaller tunneling machines for two conveyance tunnels, one went under the Ship Canal between Fremont and Queen Anne, and the other one will be used in Ballard. Both of these smaller conveyance tunnels will be used to carry flows to the storage tunnel. The Ballard tunnel began construction in 2025.

See the following table to learn more about the differences between these TBMs and check out our storage tunnel TBM factsheet for more information!

MudHoney, on display after arrival and before use.
MudHoney, our 18-ft storage TBM.
The smaller TBM before use in a staging area.
Our smaller 8-ft conveyance TBM.
Tunnel Boring Machine Comparison
Features MudHoney, 18-ft Storage Tunnel TBM 8-ft Conveyance Tunnel TBM*
Type of Machine Earth Pressure Balance Pressurized face TBM Slurry pressurized face TBM
Manufacturer Germany Germany
Age Newly manufactured in 2020 Manufactured in 2014 and refurbished from King County's Fremont Siphon Project
Length 14,256-ft 646-ft
Length of TBM shield
(This is the part of the machine that isolates the TBM equipment from the surrounding ground.)		 31-ft 2-in 22-ft 7-in
Number of cutterhead tools 18 double-disc cutters
48 scrapers
16 bucket cutters		 12 double-disc cutters
16 scrapers
14 chisels
How do we operate the TBM? Operated by crews in a control room inside the front of the TBM Operated remotely by crews above ground
Number of staff needed to operate 10-15 people 6-10 people
Diameter of TBM
(The TBM has to drill a hole larger than the final tunnel size to have space to build the concrete tunnel liner.)		 21-ft 8-in 9-ft 10-in
Finished tunnel diameter 18-ft 10-in 8-ft 0-in
Tunnel construction 6 concrete segments combined to form a ring Concrete reinforced pipe

*Note that we do not yet have information about the Ballard TBM

Learn more about ground monitoring: 

 While no significant ground movement is anticipated, as a precaution, crews will be monitoring hundreds of structures along the tunnel path before, during, and after tunnel construction. Learn more from our ground monitoring fact sheet.

Learn more about the Ballard site

Map of Ballard project area.
Map showing construction area in Ballard. Jan 2025 - May 2027: parking restrictions and road closures on 28th Ave NW, where there is a fenced work area and two maintenance structures/vertical shafts. Mar 2025 - Feb 2027: parking restrictions and road closures on NW 56th St, with two maintenance structures/vertical shafts between 24th Ave NW and 28th Ave NW. April 2025 - Mar 2027: lane closures throughout the duration of the project on 24th Ave NW. One lane is always maintained in north/south direction. July 2025 - April 2026: parking restrictions and lane closures at Pump Station work area on Shilshole Ave NW.

Ballard is home to the western end of the tunnel and above-ground facilities supporting the tunnel. Tunnel boring started at this site before it made its way to Wallingford.

We started work at our site near 24th Ave NW and Shilshole Ave NW in 2018 to prepare for tunneling. This work included soil remediation, utility relocation, 24th Ave Pier replacement, and replacing a sewer outfall pipe. 

Project elements in Ballard include:

  • A new pipe in Ballard that will convey polluted stormwater and sewage from the Ballard neighborhood into the storage tunnel. This pipe will run along 24th Ave NW, NW 56th St, and 28th Ave NW.
  • A new 80-ft tall pump station at the 107-ft deep, 80-ft diameter vertical shaft that was used for tunneling. The pump station will take flows from the tunnel to the West Point Treatment Plant.
  • A new 24th Ave NW Pier containing art inlays by artist Christian French (This pier is completed, publicly accessible, and managed by Seattle Department of Transportation.)

After construction is completed at the Ballard site, you can expect to see:

  • Ballard Pump Station (not publicly accessible):
    • 80-ft illuminated tower with above- and below-ground mechanical equipment and odor control
    • Maintenance yard with vehicle access
    • Landscaping
    • Fencing
  • 24th Ave NW Restoration
    • Green stormwater infrastructure
    • Pedestrian improvements, including seating and bike racks
    • Parking improvements
    • Street-end improvements
    • Public art by artist Jeffrey Veregge

About the Ballard Pump Station concept

Our designers have been inspired both by our underground infrastructure and the Ballard community. The cylindrical shape mirrors the pump station and below-ground equipment space. The frame around the building echoes the industrial feel and scaffolding of Ballard's shipyards. Near the tower will be smaller buildings for equipment as well as parking for our amazing maintenance crews.

The design of the future lighting structure to be built around the Ballard Pump Station has been updated to reduce construction, operations, and maintenance costs without sacrificing design integrity. 

Artwork developed by Jeffrey Veregge, from the Port Gamble S'Kallam Tribe, celebrates the Coast Salish heritage and historical use of the area. 

Learn more from our Ballard site fact sheet or check out our introductory video. To see renderings of future site improvements, take a look at our Ballard Pump Station Flickr album.

Pump station and artwork lit up at night.
Rendering of future Ballard Pump Station.
Landscaped shore line access with pump station in the background.
Design concept for the Ballard Pump Station and improvements on the 24th Ave NW street-end.

Learn more about Ballard Conveyance

Now that the new storage tunnel has been built, crews are installing a 2,000-ft long, 60-in diameter pipeline in Ballard along 24th Ave NW, NW 56th St, and 28th Ave NW to convey polluted stormwater and sewage from the Ballard neighborhood into the storage tunnel.

Work has started in this area, and you can expect single-lane and full-street closures, intersection closures, and parking restrictions on impacted blocks. Sign up to receive more specific updates about these impacts by emailing us at spu_shipcanalproject@seattle.gov. 

What to expect during construction 

Timeline chart of schedule.
Construction schedule: 2020, site preparation. 2020 - 2021, shaft construction. 2021 - 2023, tunneling. 2023 - 2024, tunneling clean up. 2024 - 2027, conveyance pipe installation and pump station construction. 2027, site restoration and storage tunnel operational.

Ballard construction schedule

  • Crews will generally work Monday through Friday from 7 am to 5 pm
    • Possible weekend and nightwork to maintain progress
  • Parking restrictions along the east side of 24th Ave NW, NW 56th St, and 28th Ave NW so construction trucks can exit the work site
  • Trucks and large equipment moving in and out of the work zone
  • Short interruptions on Shilshole Ave NW for trucks entering the work zone, and on 24th Ave NW for trucks exiting the site; please pay attention to flaggers
  • Noise typical of a large construction site
  • Access to all buildings and businesses will be maintained

Learn about the East Ballard site

East Ballard project area.
Map showing construction area in E Ballard with construction area on NW 45th St, extending from 9th Ave NW to 11th Ave NW. The Burke-Gilman Trail is noted as well as the path of the tunnel following below NW 45th St.

Most work in this area is complete. Project elements in East Ballard included:

  • A new 55-ft deep, 10-ft diameter vertical shaft, also called a drop shaft, near the intersection of 11th Ave NW and NW 45th St to carry sewage to the new storage tunnel
  • A new below-grade structure to house mechanical, electrical, and odor control equipment
  • A new diversion structure, gate vault, and conveyance pipes to connect the existing sewer and stormwater overflow pipe to the storage tunnel

Learn more from our East Ballard fact sheet.

Learn about the Fremont site

Fremont project area.
Map showing construction area in Fremont bounded by the Burke-Gilman Trail, NW 36th St, and 2nd Ave NW. The path of the storage tunnel running under NW 36th St is shown, as wellas the 8-ft tunnel that runs under the ship canal and connecting with the storage tunnel. The King County Fremont Siphon is located in the center of the construction area on NW 36th St., and there is a new traffic signal at the intersection of NW 36th St and 1st Ave NW, just east of the construction area.

Project elements in Fremont include:

  • A new 85-ft deep, 32-ft diameter vertical shaft, also called a drop shaft, to carry sewage and stormwater into the new storage tunnel
  • A new diversion structure and conveyance pipe to connect the existing sewer and stormwater overflow pipes to the storage tunnel
  • A new 8-ft diameter conveyance tunnel under the Ship Canal to carry flows from Queen Anne to the storage tunnel
  • A new underground structure to house mechanical, electrical, and odor control equipment
The conveyance pipe and components.
Cross section diagram of the 8-ft conveyance tunnel:

Artists Preston Singletary and David Franklin collaborated on artwork installed at the Fremont and Queen Anne sites.

Learn more from our Fremont site fact sheet.

Learn about the Queen Anne site

Map of project site area.
Map showing construction area in Queen Anne between the end of W Ewing St and the intersection of 3rd Ave W, alongside the South Ship Canal Trail. The path of the 8-ft tunnel that runs under the ship canal to the Fremont side is shown.

Project elements in Queen Anne include:

  • A new 8-ft diameter tunnel under the Ship Canal to carry stormwater and sewage from Queen Anne to the new storage tunnel
  • A new 74-ft deep, 20-ft diameter vertical shaft, also called a drop shaft, to direct flows into the new 8-ft diameter tunnel
  • New structures and conveyance pipes to connect the existing sewer and stormwater overflow pipe to the new vertical shaft 

Artists Preston Singletary and David Franklin collaborated on artwork installed at the Fremont and Queen Anne sites.

Learn more from our Queen Anne site fact sheet.

Learn about the Wallingford site

Map of project site area.
Map of the construction area in Wallingford, on the corner of N 35th St and Interlake Ave N. The storage tunnel path is shown extending from the construction area westward following and below N 35th St.

Wallingford marks the eastern end of the Ship Canal Water Quality Project and is where tunneling ended underneath N 35th St and Interlake Ave N in June 2023. 

Project elements in Wallingford include:

  • A new 56-ft deep, 32-ft diameter vertical shaft, also called a drop shaft, near Stone Way N and N 35th St to convey stormwater and sewage into the tunnel
  • New conveyance pipe installation along Stone Way N and N 35th St to connect the existing sewer and stormwater overflow pipe to the storage tunnel
  • A new small, above-ground electrical building near 3500 Interlake Ave N
  • New underground structures to house mechanical, electrical, and odor control equipment
  • Site and roadway restoration
  • Public art by Ryan! Feddersen

Once construction at the Wallingford site is complete, SPU will retain ownership of the southern portion of the site. The site will be mostly fenced to secure utility equipment. The fenced area will house an aboveground electrical building, and several large, underground structures attached to the storage tunnel.

Our landscape architects reviewed the planting schemes for the North Transfer Station and the Carr Place Play Area to create a site that is unique to the neighborhood but still complemented the aesthetic of nearby open spaces.

Artist Ryan! Feddersen designed and installed the artwork at the site.

Learn more from our Wallingford site fact sheet.

Metal fence with cut out design.
Art fence by artist RYAN! Feddersen at the Wallingford shaft site.

Community Engagement

We're committed to providing timely information and updates on project activities. Sign-up for our project mailing list to stay up to date.

Seattle Public Utilities and King County Wastewater Treatment Division are building an underground storage tunnel to significantly reduce the amount of polluted stormwater (from rain) and sewage that flows into the Lake Washington Ship Canal, Salmon Bay, and Lake Union from our sewer system.

Detail of Seattle map covering project areas across downtown and northwest portion of the city.
Map of storage tunnel alignment and the combined-sewer areas that will send flows to the new tunnel. Areas served by the Ship Canal Water Quality Project include Crown Hill, Ballard, Fremont, and parts of Wallingford, Queen Anne, downtown, and Capitol Hill. The path of the storage tunnel is shown running along the north side of the ship canal from Wallingford to Ballard, as wellas the existing transfer pipe to the West Point Treatment Plant in Magnolia.

In some parts of Seattle, sewage and stormwater (rain) share a set of pipes; this is called a combined sewer. During heavy rains (What? Rain? Here?) the water often exceeds the pipes’ capacity (known as an overflow to us sewer nerds), sending untreated sewage (yep, that means poop) and stormwater into the Ship Canal. These overflows can harm fish, wildlife, and the environment, and can contain pollution.

During a heavy storm, the new tunnel will capture and temporarily store more than 30 million gallons of untreated stormwater and sewage until the treatment plant is ready for it. The tunnel will improve water quality regionally by keeping more than 75 million gallons of polluted stormwater (from rain) and sewage on average each year from flowing into the Lake Washington Ship Canal, Salmon Bay, and Lake Union. Based on data from the last five years, the Ship Canal Water Quality Project would have removed about 70% of SPU’s total combined sewer overflow volume.

This storage tunnel (completed) and the conveyance pipes in Wallingford (completed) and Ballard (under construction) are three of several components that comprise the Ship Canal Water Quality Project. The total cost for the overall Ship Canal Water Quality Project is around $710 million dollars.  

For an overview of the project, check out this construction overview video (made in 2020).

Diagram of combined sewer operation in dry weather.
During dry weather conditions, sewage flows directly to a treatment plant.
Operation of combined sewer in heavy rains.
During heavy rain, sewage and stormwater can overflow into a nearby body of water.
Operation of combined sewer system during heavy rains, with storage tunnel.
During heavy rain, sewage and stormwater overflows will be held in the new storage tunnel to be sent to the treatment plant at a later time.

Seattle Public Utilities, in partnership with the Office of Arts & Culture, has commissioned a suite of artworks, both temporary and permanent, that will help tell the story of the underground storage tunnel. Aligned with the goals outlined in the Ship Canal Water Quality Project and the SPU Drainage and Wastewater Art Master Plan, the artworks seek to make the invisible visible and to provide visitors with an understanding of the flow of water on site and through the surrounding neighborhoods.

The City of Seattle's Public Art program integrates artworks and the ideas of artists into a variety of public settings, advancing Seattle's reputation as a cultural center for innovation and creativity. The program specifies that 1% of eligible city capital improvement project funds be set aside for the commission, purchase, and installation of artworks in a variety of settings. For more information about the Public Art program visit, the Office of Arts & Culture’s Public Art webpageor email the Office of Arts & Culture at arts.culture@seattle.gov.

Audio tour: Saltwater Soundwalk

Saltwater Soundwalk

Saltwater Soundwalk is a site-specific audio experience, created by artists Jenny Asarnow and Rachel Lam (Anigiduwagi enrolled Cherokee Nation), about our relationships and responsibilities towards the Salish Sea and connecting waters, centering Indigenous Coast Salish voices and language. Listen on site in Seattle’s Fremont, Wallingford and Ballard neighborhoods or anywhere you listen to podcasts.

Permanent artwork

As a part of the Ship Canal Water Quality Project, five new permanent artworks will be developed and displayed. Explore below for more information about each artist and their inspiration or take a look at our public art fact sheet.

Meet our artists!

Vaughn Bell – Tunnel alignment
Vaughn Bell creates interactive projects and immersive environments that deal with how we relate to our environment. Bell created and installed a Connective Thread artwork that ties all the art themes together and runs the length of the new tunnel. Bell was an Artist-in-Residence at Seattle Public Utilities and created the SPU Drainage and Wastewater Art Master Plan.

Jeffrey Veregge - Ballard
Jeffrey Veregge is an award-winning Native American comic book artist from the Port Gamble S’Klallam Tribe in Kingston, Washington. His work uses Coastal Salish and contemporary graphic design techniques. He is dubbed “Salish Geek” by his fans and peers. Veregge has recently installed murals at the Smithsonian, The Burke Museum, Snoqualmie Casino, and the Citizen M Hotel.

Christian French – 24th Ave NW Pier
Christian French’s, Sing, Calypso, embedded images and a poem into the new 24th Ave NW Pier. The artwork tells the simple tale of a fisherman who was saved from drowning by a magical fish he had spared out of compassion. The artwork can be seen while visiting the pier.

Preston Singletary (Tlingit) and David Franklin – Fremont and Queen Anne
Artist team Preston Singletary and David Franklin have been commissioned for the Fremont and Queen Anne locations. Their artwork tells the traditional native story of Petrel Guards the Water and Raven Steals the Water Paddle through two large-scale canoe paddle sculptures constructed of glass and steel that flank each side of the ship canal waterway.

RYAN! Feddersen - Wallingford
RYAN! Feddersen is a mixed-media installation artist who specializes in interactive and immersive artworks that invite audience engagement. She was born and raised in Wenatchee, WA. She was inspired to create interactive and temporary artworks as a way to honor an indigenous perspective on the relationship between artist and community. Her approach emphasizes humor, play, and creative engagement to create opportunities for personal introspection and discovery.

The artwork, Overflow, is a waterjet-cut art fence which illustrates connections between our water usage, city planning, hardscapes, waterways, and underground systems. By reflecting on the many ways we need water to live healthy and happy lives, we acknowledge that we all personally benefit from access to clean water. 

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Public Utilities

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Address: 700 5th Avenue, Suite 4900, Seattle, WA, 98104
Mailing Address: PO Box 34018, Seattle, WA, 98124-5177
Phone: (206) 684-3000
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Seattle Public Utilities (SPU) is comprised of three major direct-service providing utilities: the Water Utility, the Drainage and Wastewater Utility, and the Solid Waste Utility.