Mono Steel Building Structures for Seattle Ship Canal Water Quality Project

Mono Steel designs qualified steel structures for major projects all over the world, and now has been hired for the Seattle Ship Canal Water Quality Project. The firm will produce the steel structures necessary for the huge tunnels that will encircle the city underground.

The project planned with an investment of $570 million. An environmental sustainability project that aims to prevent untreated rainwater and sewage from leaking into major water bodies in the region.

In some parts of Seattle, sewage and stormwater share a set of pipes; called a combined sewer. During heavy rains the water often exceeds the pipes’ capacity sending untreated sewage and stormwater into the Ship Canal. These overflows can harm fish, wildlife, and the environment, and can contain pollution.

During a heavy storm, the new tunnel will capture and temporarily 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. Based on data from the last five years, the Ship Canal Water Quality Project would have removed about 70% of Seattle Public Utilities’s total combined sewer overflow volume.

The purpose of the tunnel is to collect and hold stormwater and sewage flows which would normally overflow into the Ship Canal. Along the tunnel path, there will be five vertical shafts (in Ballard, East Ballard, Fremont, Queen Anne, and Wallingford). They will collect stormwater and sewage flows from each basin and send them approximately 40 – 80 ft below ground into the new storage tunnel. This storage tunnel (currently under construction) is one of several projects that comprise the Ship Canal Water Quality Project. The Storage Tunnel construction contract value is $255 million. The total cost for the overall Ship Canal Water Quality Project is $570 million.

Since 1800, 150 tunnels have been built in Seattle with a total length of 70 miles. The Ship Canal Water Quality Project includes a 2.7-mile, 18-ft and 10-in internal-diameter tunnel that will extend from Ballard to Wallingford. The construction of the project, whose foundations were laid in 2020, started in September from Ballard, the western end of the tunnel. Later this year, it will head towards Fremont and Queen Anne. The last stop of the project, which is planned to be completed in 2025, is Wallingford.

“We were very excited when we learned the outline of the project because this is also a sustainability project,” said Mustafa Toprakçeken, CEO of Mono Steel. “We will spend this time producing the qualified steel structures required for the construction of tunnels and storage areas.”

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