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Pervious Pavements: New findings about their functionality and performance in cold climates

By Jeff Gunderson, StormCon Sept. 2008 online issue

Widespread misconception exists in the industry about pervious pavement systems, specifically about their functionality in cold-weather environments. The prevalent belief is that pervious pavements are not an effective stormwater management option for cold-weather climates because of concerns related to diminished permeability during freezing and that the material is not durable enough to withstand freeze-thaw conditions. Cold climates are typically very hard on constructed systems, and naturally, questions should arise about the effectiveness of pervious pavements in these environments—especially due to concerns about freezing of the filter media.

However, according to Dr. Robert Roseen, director of the University of New Hampshire Stormwater Center (UNHSC), stormwater management systems using infiltration and filtration mechanisms, if properly designed, can work well in cold-weather environments. He has been leading a four-year research effort focused on monitoring the year-round performance of a porous asphalt placement that was installed on the UNH campus. In addition, the UNHSC is hoping to shed light on the functionality of pervious concrete by testing a large placement that was also installed on the university campus in August 2007—the first major pervious concrete parking facility in New England. The purpose and function of the UNHSC is to evaluate the range of stormwater treatments systems available to designers, including proprietary and nonproprietary systems. The UNHSC is funded by the Cooperative Institute for Coastal and Estuarine Environmental Technology and the National Oceanic and Atmospheric Administration.

Findings from the porous asphalt study have demonstrated functionality that exceeds conventional practices by measures of both water quality and hydraulics.

Porous Asphalt Study
Design and Durability. The principal cause of parking lot pavement breakdown in northern climates is freeze-thaw cycling. Parking lots in these regions typically have a lifespan of about 15 years. By design, an open-graded, well-drained porous pavement system incorporating significant depth will have a longer life cycle from reduced freeze-thaw susceptibility and greater load-bearing capacity than conventional parking lot pavements. “Design guidelines for freeze-thaw consideration reflect frost depth ranges from 48 to 52 inches from coast to inland,” says Roseen. “For porous pavements, greater depth of frost is not the concern, but rather, the increase in the rate of cycling between freeze and thaw. This rate is highest near the coast.”

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