Blessed by grunge rockers Mudhoney, a TBM grinds its way under Seattle

It was in the spirit of Mudhoney, a feisty local grunge band, that the machine excavating a tunnel alongside a canal in Seattle, Washington, managed to grind through a massive boulder that had blocked its path early this spring.

It took five weeks, but the tunnel-boring machine (TBM) named MudHoney, reinvigorated by the change of a significant number of tools to its cutterhead, overcame the obstacle to reach its first milestone in August: East Ballard, one of two sites along the TBM’s 4.2-kilometre (2.7 miles) journey that will end at Wallingford, a neighbourhood in north-central Seattle.

The TBM made a brief stop at the site to undergo maintenance, some 1.5 kilometres from where it started last year boring under the city with the blessing of members of Mudhoney, whose hits include “Touch Me I’m Sick”. “It is a beautiful honour,” band leader Mark Arm told King 5, a local NBC affiliate, after the TBM’s baptism. “I don’t know any other band that (is) on the side of a tunnel-boring machine… We are an underground band, and we have an underground tunnel-boring machine.”

At a diameter of 5.5 metres (18.1 feet), the tunnel being created by the TBM is part of the Ship Canal Water Quality Project that is being developed by Webuild and its U.S. subsidiary Lane Construction. It aims to reduce the amount of storm water and raw sewage that flows into the Lake Washington Ship Canal – and Salmon Bay and Lake Union on either end of it – during heavy rainstorms. The sewage enters these bodies of water when the city’s sewer system is overwhelmed and unable to treat it. Pollution in waterways isn’t good for anyone, including fish, wildlife and people. “It is an increasing problem because of climate change and the bigger storms we are having – as well as just the increase in population and demand on the system,” Dow Constantine, a county executive, said in a video produced by Seattle Public Utilities, who is primary client for the project.

With an annual storage capacity of more than 280 million litres (75 million gallons), the tunnel will help make this happen less frequently. According to a June report by the U.S. Environmental Protection Agency (EPA), it ought to reduce what is known as combined sewer overflows (CSOs) by an average 84 percent a year. After the passing of a storm, the stormwater and sewage stored inside the tunnel will be pumped to a treatment plant before being released into the Washington state’s Puget Sound.

Cities in other parts of the United States are doing the same thing as they seek to upgrade their infrastructure to meet the challenges posed by extreme weather events, which are occurring more frequently as a result of climate change.

In Washington, D.C., the recently completed Northeast Boundary Tunnel (NEBT) will increase the capacity of the city’s sewer system, reducing the frequency, force and impact of floods during heavy rains. It is one of four tunnels including the Anacostia River Tunnel – 3.8 kilometres (2.3-mile) long and 30 metres (98 feet) deep – that belong to the Clean Rivers Project to reduce by 96% wastewater in nearby rivers by 2025. In Cleveland, there is the Dugway Storage Tunnel, which stretches for 4.5 kilometres to the east of the city. It will store up to 58 million gallons of water and sewage and hold them until the rains subside and a treatment plant has the capacity to treat them. Then there is the Three Rivers Protection & Overflow Reduction Tunnel in Fort Wayne, Indiana, a project designed to reduce the number of CSOs into the rivers by 90%―or more than 850 billion gallons on average each year.