Park and drain

Case Studies
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The new Visitor Center for the Pennsylvania State University has been designed as a “sustainable” building. In keeping with the concepts of sustainability, Cahill Associates Environmental Consultants of West Chester, Pa., designed a stormwater system that incorporates a variety of innovative infiltration technologies including porous asphalt parking areas.

The key to the success of the porous asphalt parking areas is that they provide the water with a place to go, in the form of an underlying, open-graded stone bed. As the water drains through the porous asphalt and into the stone bed, it slowly infiltrates into the soil.


The stone bed size and depth are designed so that the water level never rises into the asphalt. This stone bed provides a tremendous sub-base for the asphalt paving. The surface wears well, and while slightly coarser than standard asphalt, it is attractive and acceptable—people parking on the lot will not notice that it is porous.

In addition to the porous asphalt parking lots, the stormwater system at Penn State includes a vegetated infiltration bed that receives runoff from an existing building and parking lot, bioretention basins—small depressions carefully planted to improve water quality—and a shallow infiltration trench that receives roof runoff.

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