Pervious surfaces such as porous asphalt provide many benefits when designed, installed and maintained properly. According to the latest EPA estimates, porous asphalt can infiltrate up to 400 inches of water/hour. Furthermore, they can eliminate the need for expensive detention/retention ponds or underground storage systems thus preserving more open space. Porous asphalt works by storing excess storm water runoff inside of its aggregate base layer, which consists of various sized rocks and cobble below the asphalt.
This allows for reduction of traditional storm water infrastructure such as pipes and catch basins, and it is also suitable for applications in all climates as the asphalt is not subjected to the freeze/thaw cycle of more traditional materials. Porous asphalt reduces storm water runoff while simultaneously improving the water quality as the water filters through the aggregate. The application of porous asphalt does not require disturbing the land or tree removal. Porous asphalt can be installed up to the drip line of the trees and water, and air will filter through to the roots. Porous asphalt also meets most LEED requirements.
During the winter, snow melt also filters through the media thus reducing the need for applications of salt and sand. Black ice typically will not accumulate on the surface as precipitation is quickly infiltrated before the ice has the opportunity to form. While the cost of paving with porous asphalt is approximately 20-25% more than traditional materials, these costs can be offset by the savings from the elimination of the need for more traditional storm water infrastructure and the need to apply salt much less frequently. Porous asphalt works great when used in parking spots or other areas with low traffic volume but is generally not recommended for high traffic applications such as main thoroughfares.
The application of porous asphalt at St. Gregory’s Church in Parsippany NJ was made possible through the Troy Brook Phase II Grant received through the 319h section of the Clean Water Act, obtained through the New Jersey Department of Environmental Protection Bureau of Environmental Analysis, Restoration, and Standards.