Virginia Asphalt Association : Serving the needs of Virginia's asphalt community

Storm Water Pollution - Porous Asphalt Pavements - The Green Solution

The Problem
Rainfall runoff from these surfaces greatly increase the volume of flows in small streams and ditches in a short period of time and can result in the erosion of bank and stream bed material which then becomes suspended in the water column and is harmful to aquatic life. Additional water quality problems occur from contaminants deposited on pavement surfaces such as oil and grease from vehicles that get washed off into receiving streams during storm water events. Rainwater is also denied access to ground water aquifers when it runs off quickly into surface waters and can have a deleterious effect on local well water levels.

The Remedy
Porous asphalt pavement can be constructed to take water from rainfall events down into and through the pavement into a storage reservoir located beneath the pavement where the water is filtered through stones to help remove pollutants and allowed to slowly be released to ground water or surface water. The water quality benefits are significant and porous asphalt pavements can be of great benefit to solving tough water quality problems such as trying to clean up the Chesapeake Bay. The Virginia Asphalt Association has developed a pavement design for porous pavements that can be constructed by its member companies at surprisingly reasonable costs. Porous Asphalt Pavement Designs provide the information necessary on how to construct these "green" storm water control systems. Most of the association's Member Companies located throughout the state have the equipment, materials and know-how to build long-lasting asphalt porous pavements. The location of the nearest asphalt plant can be found at the Plants link on this web site. Some maintenance of the asphalt porous pavement is required to help keep the surface free-draining. Research has been done to evaluate the most effective methods of prolonging the porosity of the pavement by keeping pavement voids from becoming clogged. This information can be found at the porous asphalt cleaning link. Contact the VAA office or asphalt producer members for additional information on porous asphalt pavements.

The Competition
The concrete industry is heavily marketing their version of porous pavements. One of their pavements was placed at the parking lot of the offices of Wetland Studies and Solutions, Inc. located near Gainesville, Virginia last fall. Earlier this year an asphalt porous pavement was placed adjacent to the concrete so that the performance could be observed over time for comparative purposes. One of the myths being circulated by some in the concrete industry is that porous asphalt pavements contain toxic components that leach out in run off and pollute receiving streams. Asphalt has been safely used as a paving material for many years with over 95% of the pavements in Virginia surfaced with asphalt. There is absolutely no toxicity issue with asphalt pavements. The myth apparently stems from some studies conducted by the USGS which found that higher levels of some contaminates were leaching off of pavements sealed with coal tar based sealants. These sealers are not widely used and do not contain asphalt. The VAA as well as Wetlands Studies and Solutions, Inc. will be monitoring the performance and costs of the two pavement types over time.

For more information on Porous Asphalt Pavement see these links: