Environmental Protection: Ship Canal Water Quality Project Updates

SUMMARY: The Ship Canal Water Quality Project is a “mega project” planned over many years due to the state and federal governments requiring the city and county governments to prevent harmful stormwater and wastewater from polluting our local waterways. With a cost estimated at more than $600 million (shared with King County), this environmental protection project includes a new tunnel-boring machine starting its work in 2021. This ambitious 2.7-mile long, 19-foot diameter stormwater storage tunnel should be completed by 2025.

In some parts of Seattle, sewage and stormwater (rain) share a set of pipes underneath our city streets; this is called a “combined sewer.” During heavy rains, the untreated water often exceeds the pipes’ capacity (known as a combined sewer overflow), which then dumps portions of the untreated sewage and stormwater into our natural waterways. These polluted overflows can harm our environment, including fish and wildlife. This environmental protection project will enable us to store 29 million gallons of untreated sewage and stormwater during large storm events, until the treatment plant it ready to process it over time. Because every year has multiple storm surges with combined sewer overflows, the storage capacity translates into preventing approximately 75 million gallons annually from contaminating our precious waterways — from Salmon Bay to Lake Union.

Because this is one of the most expensive projects ever undertaken by the City of Seattle and it involves multiple layers of government, additional scrutiny is warranted to ensure the project is on time and on budget. Like most large capital projects, the Ship Canal Water Quality Control Project is on the City’s “Watch List” so that it receives extra attention.

Illustration from Seattle Times


During a meeting of our Transportation & Seattle Public Utilities committee, SPU reported on several issues likely to result in a longer schedule and higher costs for this mega environmental project. SPU increased the previous estimate of $570 million to a higher $615 to $650 million. Fortunately, the City of Seattle shares the costs with King County and SPU confirmed the increase will NOT increase utility bills and will NOT require support from the City’s General Fund.

  • For SPU’s 12/12/2022 PowerPoint presentation, CLICK HERE.

JULY 19, 2022 UPDATE:

During a meeting of our Transportation & Seattle Public Utilities committee, SPU provided an update:

  • For SPU’s 7/19/2022 PowerPoint presentation, CLICK HERE.

APRIL 12, 2021 UPDATE:

The winner is Mudhoney, with potential new band member Mami Hara 🙂 (photo from Seattle Public Utilities, April 9, 2021)

Astonishingly, over 30,000 people voted to name the tunnel-boring machine for the environmental protection project. The winner is: Mudhoney!

The rock-blasting Mudhoney band was the tip of the spear for Seattle’s grunge music and their namesake on this drilling machine will be the tip of the spear to carve this mega project so important for protecting our city’s waterways,” said Councilmember Alex Pedersen who chairs Seattle’s Transportation & Utilities Committee. “Thanks to tens of thousands of people who participated in the contest to name the massive new drill needed for this massive environmental protection project.”

As chair of the Transportation & Utilities Committee, I joined on April 9 several officials from Seattle Public Utilities (SPU), King County government, and the workers constructing the project to see the massive drill up close (it’s certainly not boring :). The new drill (which creates a diameter that is similar in size to the successful Sound Transit tunnels) will be lowered into its starting point in Ballard and drill the new water storage tunnel all the way to Wallingford in District 4.


Tim Barker, left, and Keith Ward discuss the assembly of the tunnel boring machine being prepared in Ballard. (Alan Berner / The Seattle Times)
What’s in a name? The tunnel-boring machine ready for assembly.
(photo by the Seattle Times)

To vote on the name of the new 19-inch boring machine, CLICK HERE before April 1, 2021. The five finalists offered by area residents are Boris the Plunger, Daphne, Molly the Mole, Mudhoney, and Sir Digs-A-Lot.

Currently During Storm Surges (before project is completed):

During heavy rain, sewage and stormwater can overflow into a nearby body of water.

After project is completed:

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.

More Info:

  • For the official Seattle Public Utilities site on the project, CLICK HERE.
  • For the official website detailing activity in each neighborhood (Wallingford, Fremont, East Ballard, Ballard, and Queen Anne), CLICK HERE.
  • For the Seattle Times article published March 27, 2021, CLICK HERE. Here’s an excerpt: “Currently, drainage basins in Queen Anne, Ballard, Fremont and Wallingford, overflow an average of about 144 times a year — basically any time there’s heavy or prolonged rain, the city said. Once the project — which is mandated by a federal consent decree that requires the county to reduce storm and wastewater pollution — is completed in 2025 (hopefully), overflows should drop to fewer than six per year, the city said.”
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