For years, Lake Union has been getting a most unwelcome gift from Capitol Hill.

Capitol Hill’s old system wasn’t built to filter its stormwater, which means filthy runoff flows right on down the hill, through the streets of Cascade, and into the water. Each year, Lake Union winds up on the receiving end of millions of gallons of gunk-laden stormwater.

“Because Capitol Hill is so densely settled, it’s among the most polluted stormwater in the City,” said Rachel Ben-Shmuel, Senior Project Manager at Vulcan Real Estate. “It has become critical to find a creative way to clean some of this stormwater before it hits the lake.”

Vulcan Real Estate teamed up with the City of Seattle Public Utilities Department to find a fix. The plan? An eco-friendly little wonder called a swale.

A swale is a channel packed with plants and special soil that slow and clean stormwater. When dirty stormwater flows through the swales, the plants help filter out the crud, and the cleaned water is released.

The in-the-works project will build four swales on Yale and Pontius Avenues, making it the country’s first large-scale biofiltration swale in an urban streetscape.

Swales are cheaper to build than a traditional stormwater facility, more sustainable, incredibly efficient, and – as if it couldn’t get any better – they blend in like they’re part of the landscaping.

Located between the sidewalk and the street, the planned swales will look like low concrete planter boxes with nice greenery inside.

“It won’t be obvious to the passerby that these swales are actually a filtration system,” said Ben-Shmuel. “In addition to cleaning up the stormwater, the swales will actually enhance the curb appeal on these streets.”

The first two swales will be up and running in 2013, while the last two are slated to be finished by 2015. Once completed, the swales will treat up to 200 million gallons of stormwater a year.

Although the “Swale on Yale” isn’t built yet, the project is so impressive the Seattle Design Commission named it a Design Excellence Award winner this month.

“This project benefits the community on several levels,” said Ben-Shmuel. “It’s proof that creative thinking goes a long way in solving problems.”

Posted by DiscoverSLU on Jan. 25
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