ForConstructionPros.com

Thomas says MAPA created an 11-page draft specification for porous asphalt. "An agency can put that spec right into a contract," says Thomas. "It covers everything from the geotextile to the mix design to the stone recharge bed."

Porous asphalt is catching on in Minnesota - with 15 to 20 projects constructed since 2005 - in part because groundwater infiltration is being promoted by environmental agencies.

Thomas says watershed districts limit the impervious area that a new building can create. But if, for example, a new Target store can build a porous parking lot, it helps offset the amount of impervious area that would have been included in the project. Plus, the porous parking lot eliminates the need for a retention basin - and the space it would occupy.

Not difficult

"Paving with porous asphalt is no different from paving dense-graded asphalt," says Huddleston. "You mix it in the same plant, haul it with the same trucks, and pave it with the same pavers. There are some minor differences, but they're not huge. I tell our members to develop good porous mix designs, and to make sure they avoid poorly designed jobs.

"Don't skimp on quality in any way," adds Huddleston. "Porous pavement is like going to a new restaurant. You'll try it once, and if the food is bad, you won't go back. You have to make sure the project works so that the technology will promote itself."