Aaron Leclerc/Staff photographer Considered the mastermind behind pervious concrete, Dale Fisher of Woodstock, Georgian-based, PCI, maneuvers a 200 pound, hydraulic-driven, roller screed, which levels the mixture immediately after being poured. For more information on his company, visit pervious.com and e-mail him at dalefisher@pervious.com.

DURHAM — On a cloudy, gray Tuesday morning, the University of New Hampshire campus got a little greener with the installation of a pervious concrete parking lot that can treat polluted storm water.

The school began refitting a lot adjacent to Williamson Hall with the eco-friendly paving material on Tuesday morning, and construction will last through Thursday afternoon.

Pervious concrete is a porous road material that allows water to drain through its surface. The water is then filtered through several inches of rock and a 14-inch layer of sand that strips away pollutants.

In a demonstration of the pavement's capabilities, Robert Roseen, director of the UNH Storm water Center, held a hose to the newly laid parking lot. The steady stream of water passed through the pavement instantly, as did five gallons of water dumped from a large bucket.

The 21,000-square-foot project cost $200,000 and was funded by a partnership between the University and the Northern New England Concrete Promotion Association, the Northeast Cement Shippers Association, and PCI Systems, which contributed materials and installation costs.

"This is a big deal," Roseen said of the project. He added that the school has committed to installing further pervious parking lots in the future.

Although retrofitting an existing parking lot with pervious concrete is more expensive than using conventional concrete to repave the surface, Roseen says that pervious concrete lots last twice as long as conventional concrete lots, approximately 30 years, and that pricing can be competitive for new lots.

The UNH parking site, which is one of the first major pervious concrete installations in New England, will be studied by researchers at the Storm water Center, who will analyze the amount of water that the system captures, salt levels, and chemical contaminants in the water, among other things. The Center has been working with pervious materials since 2004. According to Roseen, storm water runoff is the largest source of contamination in ground water.

Roseen says that the "green" parking lot will provide valuable protection to the Oyster River, which runs along a steep bank next to the lot. UNH has faced criticism from Durham residents in the past for overburdening the drainage of the river with development projects in the town.

In addition to providing treatment for polluted storm water, Roseen says that the lot will perform better than conventional concrete during the winter months. Because of its design, the lot will not crack apart during the transition from winter to spring, and Roseen says that the lot will require zero to 25 percent the amount of salt because water will not pool on its surface and form sheets of ice.

In addition, the pavement maintains the same friction whether wet or dry. The open-graded road mix looks a little bumpier on the surface, but according to Roseen, the pervious concrete has passed the "eggs in a shopping cart" test, in which a tester pushes an open carton of eggs across the lot in a shopping cart.

Another benefit of the material is that it is lighter in color than traditional concrete, cutting down on the amount of heat that is drawn in from the sun during the day and the number of street lights needed to illuminate it at night.