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Bio-Retention Swales at Grange Avenue - Greendale, Wisconsin

Bio-Retention Swales at Grange Avenue - Greendale, WisconsinTo the casual observer, a median covered with wildflowers adds an aesthetic touch to any roadway. But there’s a bigger story to tell about the median along a portion of the newly constructed Grange Avenue in Greendale, Wisconsin.

Lying beneath the median on Grange Avenue is a system for collecting and treating stormwater runoff that yields a significant water quality benefit. This green infrastructure will remove about 700 pounds of pollutants each year from a little more than a one-quarter mile stretch of Grange Avenue.

R.A. Smith National’s Len Roecker, Greendale Village Engineer, recently participated in an MMSD (Milwaukee Metropolitan Sewerage District ) video project with the Village of Greendale Director of Public Works Carl Tisonik to demonstrate the project’s water quality benefits.

How Does it Work?
Sections of the new pavement on the Grange Avenue project have been shaped to direct stormwater toward the median and into the bio-retention swales. A series of 41 openings in the curb-line equally distributes the water in the filtering area via concrete flumes.

After being collected in the swale, the water then percolates through large nativewildflower-covered beds comprised of layers of engineered soils, crushed stone and sand. Thefiltered water collects at the bottom of the swale and flows through a series of distribution pipes into Dale Creek. 

This bio-filtration device is designed to remove silt and other pollutants from stormwater runoff. It is an excavated area that is backfilled with crushed stone (for storage) and an engineered soil mix (consisting of sand, topsoil and compost) that is covered with a mulch layer and then planted with wildflowers.

Stormwater percolates through the mulch and engineered soil, where it is treated by a variety of physical, chemical and biological processes that trap pollutants and silt before infiltrating back into the native soil or overflowing into the storm sewer system.

More Information
For more information, contact Len Roecker, Greendale Village Engineer, at 262-317-3383 or Robbie Mc Faul, Greendale Director of Public Works, at 414-423-2133.

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