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Some people think the hydrocarbons will leach out of asphalt and into the groundwater. Not true, says Huddleston; asphalt does not leach hydrocarbons. In fact, porous asphalt pavements, with stone recharge beds, have been found to be very effective at removing hydrocarbons and other pollutants that are deposited or washed onto the pavement.

No added cost

On a yard-by-yard basis, the cost of the open-graded asphalt mix is little more than conventional dense-graded asphalt. The underlying stone bed is usually more expensive than a dense-graded aggregate base, but that difference in cost is offset by the significant reduction in stormwater pipes and inlets.

Because porous pavement is designed to fit into the topography of a site, there is generally less earthwork and there are no deep excavations. Hansen says Cahill has compared the cost of porous pavements to other stormwater management options - and generally the porous pavement turns out to be the less expensive option.

"What we're promoting is that porous pavements are beneficial, and asphalt is the best way to build a porous pavement," says Huddleston. "When properly designed and built, porous asphalt pavements will out perform the competition in all areas. Asphalt is faster to construct, it is lower cost, and it has a proven performance history with jobs that are over 30 years old still performing well today."

Resources

The definitive technical guidance document is NAPA's Porous Asphalt Pavements for Stormwater Management (order number IS-131). New last fall, the publication is lavishly illustrated in full color. An accompanying executive summary brochure, Porous Asphalt Pavements (PS-33), is useful as a trade-show or seminar giveaway. Both are available from the NAPA online store at http://store.hotmix.org.

Also, check www.hotmix.org for information about NAPA's porous asphalt webinar series.