Permeable pavements are alternative paving surfaces that allow stormwater runoff to filter through voids in the pavement surface into an underlying stone reservoir, where it is temporarily stored and/or infiltrated. Traditionally paved surfaces are impermeable, converting rainfall to runoff. Permeable pavement slows and captures rainwater, allowing it to infiltrate, promoting a high degree of runoff volume reduction and nutrient removal, and reducing the amount of impervious cover of a developed site. A variety of permeable pavement surfaces are available, including pervious gird pavers, porous asphalt/concrete, and permeable interlocking pavers. While the specific design may vary, all permeable pavement systems have a similar structure, consisting of a surface permeable pavement layer, an underlying stone aggregate reservoir layer, and a filter layer or fabric installed underneath.
Previous Grid Pavers typically consist of a plastic or wire mesh grid filled with amended soil or sandy gravel on top of a 4-12 inch clean stone aggregate. These are typically used for low traffic areas.
Porous Asphalt and Concrete consist of a pavement mix with few fines that create pores in the surface. The Asphalt/Concrete is placed on top of a filter layer of clean pea gravel above a 12-24 inch clean stone aggregate reservoir.
Permeable Interlocking Pavers have previous seams around the paver filled with sandy gravel or pea gravel. The pavers are placed on top of a filter layer of clean pea gravel above a 12-24 inch clean stone aggregate reservoir.
Permeable pavement is typically designed with an underdrain and treats stormwater that falls on the actual pavement surface area, but it may also be used to accept run-off from small adjacent impervious areas, such as driving lanes or rooftops.