By Lynda Myer
While TBM assembly for the storm water tunnel is implemented on the Ballard site over the coming weeks by other works, the Seattle’s Ship Canal Water Quality Project (SCWQP) goes ahead with progress.
A US $255m contract has been awarded for SCWQP project, which includes the construction of a 4.32km-long storage tunnel with an interior diameter of 5.74m that is going to grab and temporarily reserve around 132bn liters (29m gallons) of composed sewer overflows.
The concrete lining for the 37.2m-deep, 27.4m diameter shaft for pulling down the Herrenknecht TBM will be installed at the Ballard site. The site, which is located at the western end of the tunnel, will also host the pumping station that will transmit water to the treatment plant. On the East Ballard site, soil fixation and ground improvement operations are continuing.
This project involves five shafts that one of them is located at the Fremont site, and will excavate with 26m-deep, 9.75m-diameter as a drop shaft and will be a location for launching a smaller TBM. The indicated TBM will dig the 2.43m diameter, 197m-long tunnel (beneath the existing Ship Canal) which will connect two vertical drop shafts at Queen Anne and Fremont.
It is estimated that the construction of the secant pile wall at Wallingford will last to mid-April. Although almost 10 out of 101 piles have been finished till now, at the Queen Anne site, shaft excavation continues and crews are expected to shed the concrete base over next weeks.
The Seattle Public Utilities and King County Wastewater Treatment Division, have the responsibility of the Ship Canal Water Quality Project. Decreasing the noticeable amount of composed sewage overflows into local water bodies, such as the Lake Washington Ship Canal, Salmon Bay and Lake Union, is the major purpose of this these works. The project will be done by Lane Construction Corp – the US subsidiary of Webuild Group and the date of tunneling commencement is expected to be the summer of 2021.
