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Ship Canal Water Quality Project: Year-End Update  

In the closing weeks of 2022, we want to highlight some Ship Canal Water Quality Project milestones, successes and challenges from recent years and begin to look at how they may impact the overall project. While we are still a few years away from completion, it is exciting to see the progress we’ve made to build a system that will improve water quality regionally by keeping some 75 million gallons of polluted stormwater and sewage from entering our waters each year. 

Despite an ongoing pandemic, Seattle Public Utilities (SPU), project partner King County Wastewater Treatment Division, and the contractor team have continued active construction. With strict safety protocols in place, tunneling from Ballard to Wallingford is moving right along. As of December 5, MudHoney, our 18-foot-plus diameter tunnel boring machine, has tunneled past the halfway point—7,750 of 13,946 feet to be exact. That’s higher than the Space Needle! 

Fullow MudHoney, the 18-foot tunnel boring machine, on its journey! A map depicts MudHoney's progress and current position as it has tunneled from Ballard past East Ballard and is nearing Fremont as it tunnels toward the final destination in Wallingford.
MudHoney has passed the halfway point as it tunnels from Ballard to Wallingford! Follow MudHoney’s progress on the Ship Canal Water Quality Project website:

Work is also progressing on the smaller, 8-foot diameter conveyance tunnel under the Ship Canal to carry flows from North Queen Anne to the storage tunnel. Additionally, we have made significant progress on many large underground structures in East Ballard, Fremont, and North Queen Anne.  By 2023, the project will have contractors working on or lined up for all parts of project construction.  

In any construction project, escalation, uncertainties, and potential risks are carefully considered and incorporated into cost estimates and related risk evaluations. This provides funding for anticipated escalation and reserves or contingencies that can absorb many risk-related cost increases. Escalation in material prices and risks from underground obstructions (like boulders!) are standard in big, underground construction projects, but no one could have predicted some of the challenges we faced: pandemic-related staffing challenges, supply chain issues, and inflation. And let’s not forget the MegaBoulder. 

Last spring, our tunneling crew struck a boulder about the size of a small car—thought to be the largest boulder ever encountered on a North American tunneling project. Most obstructions are less than 3 feet, or about a quarter the size of the 12-foot diameter boulder we encountered. 

We only briefly paused tunneling to get more information on the boulder size and strength and to repair some cutterhead tools on MudHoney. By the end of May, we successfully broke through the boulder and tunneling resumed at its original pace. 

Workers in hard hats repair the cutting head of the MudHoney tunnel boring machine.
Members of the tunneling crew repair MudHoney’s cutterhead after it struck a boulder the size of a small car.

We’re also looking ahead to the second quarter of 2023, when we receive bids for our final construction package of the project. We know that current trends in escalation, supply chain, and labor availability will influence bids.  

SPU’s project team is currently assessing the impact of these recent challenges, but we anticipate the cost of the project, which is shared with King County, to increase by as much as 14%. We also expect to extend the schedule. While we won’t know specifics until we finish our assessment and receive bids for our Ballard pump station and conveyance pipe, we do not expect these challenges to affect our projected rate path through 2026. 

SPU is proud of its investments in the health of Puget Sound and the future of our region, which are reflected in our designation as a sustainable infrastructure project. We remain dedicated to designing, building and delivering community infrastructure with integrity and transparency.