Old Redmond Road Bioretention Swale
In the summer of 2007, the City built improvements to Old Redmond Road between 132nd Ave NE and 140th Ave NE. Those improvements feature a planted median.
At the east end of the project, that planted median was configured as a stormwater bioretention swale. Stormwater from the roadway flows through the median where pollutants are removed before the water continues on its way toward Peters Creek and the Sammamish River.
What is a Bioretention Swale?
Bioretention systems are stormwater best management practices (BMP's) that use filtration to treat stormwater runoff. Bioretention systems are modeled after the biological and physical characteristics of an upland terrestrial forest or meadow ecosystem. These systems use vegetation, such as trees, shrubs, and grasses, to remove pollutants from stormwater runoff.
Sources of runoff are diverted into bioretention systems directly as overland flow or through a stormwater drainage system. Alternatively, a bioretention system can be constructed directly in a drainage channel or swale.
But where is it?
If you look closely, you can see the plants growing in the median!
When City Hall was constructed, a number of "green" techniques were used in the site design and construction. A bioinfiltration swale was constructed so stormwater from the roof and other areas filters through this swale that has been incorporated into the landscaping The best view of the "swirl" bioinfiltration swale is from the fourth floor balcony of City Hall.