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Protecting Seattle’s Waters

CS0 tour1Nothing beats a field trip for understanding how this city’s infrastructure works. Thus, even though it was spitting rain under cloudy overcast skies last Thursday, my staff and I eagerly took a tour of a unique and amazing stormwater project.

On paper, it’s known as the Windermere Basin project.

In practice, it’s a super-sized undertaking, a 2.05 million gallon underground storage tank that’s under construction near Magnuson Park. The tank sinks several stories into the glacial till and is, literally, the size of a football field. When finished it will have state-of-the-art technology to keep heavy rainfall from flushing stormwater and wastewater into Lake Washington.

CSO tour3Previously, the basin area was protected by a storage tank known as Windy Junior that is hidden beneath a private park in Windermere. However, in recent years that tank has been inadequate during heavy downpours. Consequently, storm and wastewater stream into Lake Washington several times a year.

The remedy is a key element of the new CSO (Combined Sewer Overflow) system. A well-versed crew of men and women are constructing a giant new tank, one that boasts self-cleaning equipment as well as technology designed to handle odor and pumping. The design calls for the storage tank to empty stored contents back into the existing system once rainfall subsides.

The project now underway also calls for construction of a pipeline from the existing tank to the new facility. The 2,000 feet of new sewer main will run along N.E. 65th and then under Sand Point Way NE, using advanced drilling technology. Turns out Big Bertha isn’t the only boring machine at work in Seattle. Seattle Public Utilities plans to use a combination of open-cut and trenchless methods to install the new pipeline that leads to the new storage tank. The idea is to keep impacts to a minimum.

CSO tour2Once crews install the giant tank and pipeline, they will restore the sections of street and surfaces, enhancing the streetscape and making use of green infrastructure elements wherever possible. Infrastructure may not be the showiest addition to the city. But it’s easily one of the most valuable when it’s engineered to protect our waters for generations to come.

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