A tunnel-boring machine (TBM) machine, ‘MudHoney’, is carrying out the work on the project, which is designed to prevent untreated stormwater and sewage from flowing into local bodies of water. The combined sewer overflow (CSO) tunnel will prevent up to 276 million litres a year of wastewater from entering Lake Washington Ship Canal, Salmon Bay and Lake Union. The tunnel will capture and temporarily hold more than 100 million litres of stormwater and sewage during heavy rainfall.
The TBM has started from Ballard - the western end of the planned 5.5m-diameter tunnel - and will head towards Fremont and Wallingford.
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