Wildwood Commons

Two townhome buildings with nine units in all, on a 30,000 sq ft infill lot in Willernie, Minnesota. They were built in 2006 with EPIC in every green area as the site's only stormwater management system, collecting, treating and storing the runoff from the whole development.

The lot was once a gas station and an engine repair shop. It sits on the boundary between two cities, in a watershed that drains toward White Bear Lake, and a large wetland wraps around its north-east corner. Opposition focused on stormwater and the wetland, including concern that infiltration would carry pollutants into the water. Contamination was found during the works and cleaned up by TetraTech, Inc. with the MPCA. The site was below the Rice Creek Watershed District's one-acre permit threshold, but the developer met the standard anyway.

Stormwater from the roofs, roads and rear driveways is filtered and treated through the sand and reused for irrigation. Any excess drains through 4-inch PVC storm lines to an existing street catch basin. Irrigation works by gravity, with no pumps and nothing to prepare for winter or summer. At its normal water level the system holds up to three weeks of irrigation water. On this site the EPDM liner deliberately prevents infiltration, sealing the cleaned-up soil so contaminants cannot leach toward the wetland or groundwater.

Site performance was published as a modelled baseline compared with the system's actual outflow. From 16 June to 24 September 2007, with 13.55 in of rain, modelled runoff was 32,181 cubic feet and actual outflow was 14,172, a 56% reduction. For total phosphorus from 11 August to 20 September, the paper gives a modelled load of 0.2 lbs and an outflow of 0.019 lbs, and states an 85% reduction.