Stormwater Quality Design Manual (May 2007) - City of Sacramento ...

Runoff Reduction Control Measure Fact SheetPorous PavementHow does Porous Pavement work?Porous pavements include a variety of stabilized surfaces with void spaces designed to infiltratestormwater runoff into the ground or slowly release the water into a subsurface drainage system. Usingporous pavement minimizes impervious areas, thereby reducing the amount of site runoff requiringtreatment.Planning and Siting ConsiderationsDevelopment type/land useIn developments where it is difficult to provide stormwater treatment (such as small or redeveloping sitesor high-density residential developments), porous pavement may provide the best or only opportunity toreduce site imperviousness.All land uses contain potentially suitable locations for porous pavement. Consider porous pavement for:• Residential driveways, patios, and walkways (also see Alternative Driveway Fact Sheetelsewhere in this chapter)• Commercial plazas and courtyards, overflow parking areas, parking stalls, some types of storageareas, walkways, and entryway features• Employee parking and entryway features at industrial sites• Fire lanes, maintenance access roads and other roadways where infrequent or low traffic loadsand volume are expected (check with fire department for minimum specifications)• Within parks and open space for parking areas, sports courts, playgrounds, and pedestrian/biketrails.Porous pavement is not suitable for commercial drive aisles, loading and waste management areas andother heavy traffic areas. It is also not appropriate where spills may occur, due to the potential for soil andgroundwater contamination. Such areas include retail gas outlets, auto maintenance businesses,processing/manufacturing areas, food-handling businesses, and chemical handling/storage areas.Other Siting Considerations• Consult a geotechnical engineer to determine what types of porous pavement are suitable for theexpected traffic load and volume.• Consult a geotechnical engineer to determine set back from building foundation, or use 10 feet.• Determine site soil type and permeability before selecting porous pavement as a runoff reductionstrategy; a soil permeability of 0.6-2.0 in/hr is required. The local permitting agencies will requirea permeability soils test to verify infiltration capacity of native soils. May be used over soils withlower permeability in selected situations if underdrain is provided (check with permitting agencyto verify).• Address seasonal shrink/swell in sites with expansive subgrade. Use the expansion index test(ASTM D4828) to provide insight as to degree of surface deformation in choosing pavingsections.• Consider opportunities for directing runoff from impervious surfaces across porous pavement toachieve runoff reduction credits. See the Disconnected Pavement Fact Sheet located elsewhere inthis chapter.• Select the porous pavement type based on the type of anticipated pedestrian traffic; most types ofporous pavement can be designed to be Americans with Disabilities Act (ADA) compliant.• A water barrier or interceptor drain will be required where porous material abuts regularasphalt/concrete pavement and there is concern about water infiltrating the regular pavementsubbase. The water barrier should be 24 inch wide thick visqueen run down the 12 inch deepStormwater Quality Design Manual for the Sacramento and South Placer RegionsPP-2 May 2007