Porous Asphalt - part 2
Posted by Jesse Willoughby on Tue, May 19, 2009 @ 04:53 AM
How long do these pavements last, and how long do they remain porous?
Even after twenty years, porous pavements show little if any cracking or pothole problems. The surface wears well. Porous asphalt retains its ability to handle rain water for many years. One of the best-known porous parking lots, located at the Walden Pond State Reservation in Massachusetts, was constructed in 1977. While it has never been repaved, it is in good shape and still drains effectively.
In a study of a porous pavement system constructed at the Centre County/Pennsylvania State Visitor center, researchers found that the system had maintained a consistent infiltration rate. During a 25-year precipitation event, there was no surface discharge from the stone beds.
Do these pavements look "different?" Are they smooth?
While slightly coarser than standard asphalt, porous asphalt pavements are attractive and acceptable. Most people parking on a porous asphalt parking lot will not notice (or believe) that it is porous. The surface of a porous asphalt pavement is smooth enough to meet requirements of the Americans with Disabilities Act (ADA).
What special additives or construction techniques are needed?
An added advantage to porous asphalt is that it does not necessitate proprietary ingredients. It does not require the contractor to have special paving equipment or skills. With the proper information, most asphalt plants can easily prepare the mix and general paving contractors can install it.
How does porous asphalt affect water quality?
There has been limited sampling data on the porous pavement systems, although the available data indicate a very high removal rate for total suspended solids, metals, and oil and grease.
Are there other environmental benefits?
Because of the open structure of the pavement, porous asphalt offers a "cooler" pavement choice. By replenishing water tables and aquifers rather than forcing rainfall into storm sewers, porous asphalt also helps to reduce demands on storm sewer systems. In areas where storm-water impact fees are imposed by local governments, such fees may be reduced by using porous asphalt.
