work underway on a water-discharge structure we designed for poor soil conditions
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stormwater infiltration retrofit of suburban mall

stormwater infiltration retrofit of suburban mall

runoff reduced and filtered naturally

Maplewood Mall is an aging shopping facility in the Twin Cities metropolitan area with 35 acres of impervious parking and road surfaces. Working with the Ramsey-Washington Metro Watershed District, the City of Maplewood, Ramsey County, and mall owner Simon Property Group, Barr designed a stormwater management system that reduces polluted runoff, while meeting regulatory, technical, and aesthetic challenges.

The final design incorporated above- and below-ground treatment facilities and storage for stormwater reuse while maximizing available parking space. Engineered soils and subsurface irrigation allow plantings to thrive in the challenging parking lot conditions, and the system features more than a mile of rock trenches planted with 200 trees—a technique adapted from one used in Sweden—that will remove up to 50 pounds of phosphorus and five tons of sediment annually. We added public art and educational components that explain the need for and the benefits of treating stormwater.

The large-scale retrofit will capture and treat 90 percent of the lot’s stormwater runoff. By intercepting, filtering, and/or infiltrating the first inch of runoff, the system will remove over 60 percent of the phosphorus from the site that would otherwise flow into impaired Kohlman Lake.

planting trees in a parking lot

entrance features