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Tunnel construction underway in Seattle
Construction is underway to dig out a 3 mile long tunnel from Ballard to Wallingford to store excess water as part of the Ship Canal Water Quality Project.
SEATTLE - A massive infrastructure project with a price tag topping more than half a billion dollars is underway in the city of Seattle and the investment is happening right under our feet.
For generations heavy rainstorms would overwhelm the city’s ability to process the run off. That meant debris and oil washed from roadways joined untreated sewage. The mess flowed freely into what makes our region so special – Puget Sound.
Seattle Public Utilities and King County Wastewater Treatment Division are poised to begin tunneling a pollution solution. The Ship Canal Water Quality Project has been years in the making.
Construction workers have done this kind of work before in the city, but most of the action will not be happening at the street level. To see what is really going on, you’ll have to look down. A 122-foot deep vertical shaft is being prepared to launch yet another tunnel boring machine designed to tackle one of our region’s biggest infrastructure projects.
Tunnel inspector Tim Barker’s office has been subterranean for decades.
"It’s no different to me than working up here," he said.
The dig will excavate a nearly 3-mile long tunnel underneath Ballard, Fremont, Wallingford and Queen Anne neighborhoods. It’s not a freeway or light rail station. The tunnel is designed to catch 75 million gallons of pollution that usually flows into Seattle’s waterways and beyond..
"It goes back 100 years ago," said SPU’s Keith Ward. "There were no treatment plants."
During heavy storms, the 2.7-mile long tunnel will store the excess runoff. The pollution will be pumped to King County’s West Point Treatment Plant after storms pass.
More giant storage tanks along Lake Washington were constructed back in 2013. This year’s project is only another step for local governments to achieve federal compliance by reducing water pollution.
Seattle and King County are shouldering the $570 million price tag. Ward says the goal is to change how people see and use Puget Sound.
"We want people swimming in these water bodies," he said. "We want to protect the environment and fish and species as well."
The tunnel boring machine doesn’t look small when standing next to it, but its size is nowhere near what was used to dig tunnels for light rail or when Bertha carved out a new SR99. That size difference and a plan to only dig under city streets leads engineers to believe businesses will not suffer damage to structures during Bertha’s reign. Monitors were installed across the construction projects, but SPU insists no plan is 100% perfect.
"If we see a problem, we’ll stop," said Ward. "We’re actually in the machine every minute they are tunneling."
When this machine begins cutting through soil crews will aim to chew through 60-feet per day. Construction on the project might be completed by 2025.
While Barker says he has worked in some capacity for almost all recent tunneling projects in Seattle, the latest endeavor could leave Seattle’s future and waters cleaner than ever before.
"I love it," he said. "It’s always exciting, every project is a new start every time."
Sound Transit utilized tunnel boring machines to construct light rail stations. Another major infrastructure project that used similar machines buried SR99 under Seattle. That TBM was nicknamed Bertha. Now, SPU is seeking public input to name the latest TBM being used for this latest project.
Submissions can be made via an online survey, or by sharing the #NameThatTBM hashtag on Twitter. Crew members will get pick finalists from submissions. In order for your suggestion to be considered, submissions must be shared by Friday March 12.