The tunnel boring machine constructing a new sewer line for the Ship Canal Water Quality Project has passed NW Market St and continues moving north beneath 24th Ave NW, according to the project’s July construction update.
The 7-foot-diameter machine is installing a new sewer conveyance pipe beneath 24th Ave NW, NW 56th St and 28th Ave NW that will connect the neighborhood to the project’s storage tunnel and pump station. Tunneling is expected to continue through late 2026.
The machine is traveling north beneath 24th Ave NW toward Northwest 56th Street, where it will be removed from the ground, rotated and sent west beneath NW 56th St to its final destination at 28th Ave NW.
As tunneling continues, crews have returned to the intersection of 24th Ave NW and NW 56th St to prepare for the machine’s arrival. According to the update, contractors are building a support wall that will help push the tunneling equipment forward and constructing the walls the machine will pass through when it reaches the site.
Most of that work is taking place inside the underground shaft, with little visible construction at street level beyond cranes and construction trucks moving materials and equipment. Traffic control measures remain in place, with one northbound and one southbound lane open on 24th Avenue Northwest.
At 26th Ave NW and NW 56th St, crews continue excavating a shaft for a maintenance hole. A temporary cover is expected to be installed by mid-July.
Construction is also continuing at 28th Ave NW and NW 56th St, where contractors have completed installation of above-ground piping and pumps for a temporary combined sewer bypass that will remain in place until later this year. Crews are continuing excavation of the diversion structure after installing supports for existing underground electrical utilities.
On Shilshole Ave NW, crews have completed the first phase of utility work needed to build the pump station discharge maintenance hole at the southeast corner of 24th Ave NW and Shilshole Ave NW. The work area has reopened to traffic through July 8 to comply with the FIFA World Cup construction pause. After the pause ends, crews will begin preparing to install the discharge pipe connecting the pump station to the new maintenance hole.
At the Ballard Pump Station site, crews are continuing utility work while concrete floors are poured inside the structure. Once the floors are complete, construction will move on to building the pump station’s concrete walls.
Project officials say residents can continue to expect construction trucks, equipment noise, vibration, vehicle, pedestrian and bicycle detours, and increased traffic as drivers adjust to changing routes. Tunneling operations are scheduled from 6 a.m. to 6 p.m., Monday through Saturday, with most above-ground work taking place at the pump station site near 24th Ave NW and Shilshole Ave NW.
The Ship Canal Water Quality Project is a partnership between Seattle Public Utilities and the King County Wastewater Treatment Division. The project is designed to reduce the amount of polluted stormwater and sewage that overflows into the Lake Washington Ship Canal, Salmon Bay and Lake Union during heavy rainfall.