DEFINITION
Porous pavements are a paving system that allows water to infiltrate through the pavement in order to more accurately reflect the pre-development hydrologic cycle
In the realm of stormwater management, porous pavement is considered a structural measure.
Specifically, it is a generic term that includes porous asphalt, porous concrete and modular pavers.
Like a conventional surface, porous pavement consists of a pervious surface course that is typically underlain by washed, uniformly graded coarse aggregate, followed by a a layer of geotextile and finally the un-compacted sub-grade.
The idea is that stormwater enters through the pores in the pavement and is stored in the voids that exist in the layer of aggregate until it can percolate through the natural ground.
Porous pavement has been used for parking lots, walkways, playgrounds, alleys, and other areas where low speeds apply.
The latest product that has been introduced to this portion of the market is Plastisoil. Plastisoil was developed by Naji Khoury, an assistant professor of civil & environmental engineering at Temple University. Plastsoil, created from a mixture of aggregate and used drinking water bottles (polyethylene terephtahlate plastic) can be used to form sidewalks and other hardscapes. It is estimated that it takes approximately 30,000 bottles to manufacture 1 ton of Plastisoil..
A variation of the product has been developed for roadways. Superpave (to put simply, conventional asphalt minus the fines) is used to hasten water runoff from roadways.

AKA
Porous Concrete, Porous Asphalt, Porous Pavers, Open-jointed Paving blocks, Open cell paving blocks (gravel, grass etc), Pervious Pavement

PERFORMANCE CRITERIA
the primary measurement for performance is the infiltrative capacity of the pavement. this can be effected over time by the build up of sediment and dirt within the pores of the pavement, but this can be remedied with regular maintenance

ILLUSTRATION



In the parking lot for Nextel at Tecnoparque in Mexico City




Two examples in Germany, open pavers and filter strips under the car

CASE STUDIES
High Point, Seattle
Kitsap Homebuilders LID Demonstration Project, Bremerton
Williamsburg Prime Outlets, Hampton Roads, Virginia
Arkadien AspergHousing Development, Stuttgart, Germany
Grass Lawn Park, Redmond, Washington
Queen city eco-village, Shoreline, Washington
Decatur Street LID Project, Olympia, WA
Woonerf - Terry Avenue, Seattle

ADDITIONAL RESOURCES
Porous Pavement Powerpoint(as PDF) for Seattle's Stormwater Seminar Series
case study of an eastern North Carolina permeable pavement:http://www.box.net/shared/al1h2z7tod
Toronto Guidelines for Greening Parking Lots
City of Seattle Guide for Green Parking Lots
Portland Cement Pervious Concrete Pavement: Field Performance Investigation on Parking Lot and Roadway Pavements
Curtis Hinman of WSU's survey of porous pavement performance research
Mutual Materials'Eco-Stone Performance Study