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Phase 1 of the Swale on Yale project was completed in 2013.
SPU constructed a stormwater treatment system on four blocks on Yale Avenue North and Pontius Avenue North. The project consists of four biofiltration swales, a pre-treatment swirl concentrator, and a diversion structure. The project will greatly improve the quality of stormwater runoff entering South Lake Union.
The last phase of the “Swale on Yale” Capitol Hill Water Quality project moved into construction in April 2018. In this phase, Exxel Pacific constructed bioswales on the 300 blocks of Yale Avenue North and Pontius Avenue North (between Thomas and Harrison streets). This work was performed in conjunction with Vulcan Real Estate’s construction of the Sitka building.
In mid-December, we anticipate planting the newest bioswales and wrapping up construction. Planting is weather-dependent. At the end of this work, four city blocks will have stormwater treatment swales that remove pollutants before the water enters Lake Union.
This project will treat an average of 190 million gallons of stormwater annually flowing from Capitol Hill into Lake Union, greatly reducing the amount of pollution flowing into the lake. It does this by diverting the stormwater into a series of extra-wide planting areas between the sidewalk and the roadway. These naturalistic, biofiltration “swales” are designed to slow the stormwater flow and remove pollutants before they reach the lake.
This project includes: