Villanova University Bio-Infiltration Garden

Executive Summary

Urban stormwater has the potential to deliver large pollutant loads and increased flows to receiving waters over short intervals. The increased runoff has been shown to accelerate stream bank erosion and reduce infiltration thereby increasing drought effects on the headwaters of streams. Best management practices are currently recommended by PaDEP to control stormwater runoff. Detailed information on their performance is still emerging as recognized by Pennsylvania’s Chesapeake Bay Nutrient Reduction Strategy (PaDEP 1996a) and the Pennsylvania Handbook of Best Management Practices for Developing Areas (PACD 1998).

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Rain Garden

An existing traffic island was retrofitted to become a bio-infiltration BMP. The facility intercepts flows that would normally be captured by inlets and delivered through culverts to a dry detention basin without a chance to cleanse or infiltrate the stormwater runoff. Designed for the smaller storms (0 – 1.5 inches), the runoff infiltrates thereby reducing downstream stormwater volumes, stream bank erosion, and non-point source pollution to the headwaters of the Darby Creek. The advantage of this type of facility is the capture and infiltration of over 90% of the yearly rainfall. This will significantly reduce stream bank erosion and protect low baseflows during times of drought. As all the stormwater for these rainfalls is infiltrated, there is NO pollutant input to the headwaters for smaller storms.

During larger storm events (2 – 100 year storms) a significant portion of the rainfall, as well as the first flush of pollutants is infiltrated. Flows over the capacity of the BMP go through the original culvert system to a dry detention pond.

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Complete Traffic Island

The bio-infiltration pond is incorporated within the “Best Management Practice Demonstration Park” on Villanova’s campus, and joins the retrofitted stormwater wetlands, infiltration trench, porous asphalt and porous concrete site. To validate the performance of the device, rainfall and groundwater depth are monitored. In addition to those displayed on this website, results are included in the final report to the PaDEP.

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