Crews prep boring machine for new sewage tunnel from Ballard to Wallingford
“Sir Digs-A-Lot” is one of five finalists out of 1,200 community suggestions for the name of Seattle’s next big underground tunnel boring machine.
The soon-to-be-named machine will be used to dig a 2.7-mile long, underground storage tunnel from Ballard to Wallingford.
As the project page explains: “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.”
In some areas of Seattle, sewage and stormwater share a set of pipes called a combined sewer. The problem is that when it rains, the water can exceed the pipes’ capacity, “sending untreated sewage (yep, that means poop) and stormwater into the Ship Canal,” as Seattle Public Utilities so eloquently states.
According to Seattle Public Utilities, 84% of the city’s overflows in 2018 came from the combined sewers in Crown Hill, Ballard, Fremont, Wallingford, Queen Anne, Downtown, and Capitol Hill.
The new tunnel will be able to capture and store more than 29 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,” Seattle Public Utilities explains.
Currently under construction, the tunnel is one of several projects that make up the Ship Canal Water Quality Project. Tunneling operations are set to start in Ballard where the team is assembling the tunnel boring machine on site, before it begins its journey in summer 2021.
Additionally, the troubled West Point Treatment Plant at Discovery Park is getting a $65 million makeover, thanks to a unanimous King County Council vote. The upgrades will help prevent future sewage overflows into the Puget Sound during storms by providing better on-site power at the plant.
The KIRO Radio Newsdesk contributed to this report.