Permeable pavements are specifically designed to allow percolation or infiltration of storm water through the pavement surface. Storm water runoff filters through surface voids into an underlying stone aggregate reservoir layer, optional underdrains, and geotextile over uncompacted soil subgrade for temporary storage and/or infiltration.
The depth of the base course is dependent on the runoff volume and must be of sufficient to prevent cracking of the asphalt or concrete during freeze-thaw cycles. The most commonly used permeable pavement surfaces are permeable concrete, porous asphalt, and permeable interlocking concrete pavers.
Permeable pavement is typically designed to manage rainfall landing directly on the pavement surface. Permeable pavement surfaces may accept runoff contributed by adjacent impervious areas such as driving lanes or rooftops if the capacity of the underlying reservoir is designed for it. Adjacent vegetated areas must be stabilized so that runoff containing sediment does not accelerate the clogging of the intentional voids in the permeable pavement surfaces.
Permeable pavements have been used for areas with light traffic at commercial and residential sites to replace traditional impervious surfaces of low-speed roads, alleys, parking lots, driveways, sidewalks, plazas, and patios. While permeable pavements can withstand truck loads, their structural performance and surface stability have not yet been consistently demonstrated in areas receiving high-volume use by trucks or in high-speed areas.
This treatment may have some application on PWA sites in highly urbanized areas where regular maintenance can be assured and the appropriate equipment is available.
Regular maintenance of permeable pavements is necessary to ensure long-term effectiveness. Regular vacuum sweeping of surface debris (litter, sediment, etc.) is recommended for pavement or pavers. If clogging occurs, the filtration media below the surface may need to be replaced. Manufacturers should be consulted for specific maintenance requirements.