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

Runoff Reduction Control Measure Fact SheetPorous Pavementexcavation and 12 inch under the drain rock.Interceptor drains should tie into an openlandscape area or treatment control measure toquickly relieve the water pressure in the pavementsection and prolong the pavement life.• For manufactured products, check themanufacturer’s specifications for any additionalsiting considerations.Porous Pavement TypesSix types of porous pavement material are presented inthis fact sheet: 1) pervious concrete, 2) pervious asphalt(considered on case by case basis), 3) modular block, 4)reinforced grass, 5) cobblestone block and 6) gravel.Additional types may be allowed on a case-by-case basis;check with the local permitting agency for verification before proceeding with design.Pervious Concrete and AsphaltPervious concrete and pervious asphalt have a higher load bearing capacity than the other porouspavement options discussed in this chapter. Table PP-1 (presented later in this chapter) lists and comparesthe design criteria for all featured porous pavement types.Pervious concrete is poured like traditionalconcrete pavement, but is made from a speciallyformulatedmixture of Portland Cement and nosand; the result is 15% to 21% void space. SeeFigure PP-1 for a typical installation detail.Colorants can be added for aesthetic reasons, andsurfaces can be ground for smoothness. Owners,architects, and engineers are encouraged to visitlocal sites where pervious concrete has beeninstalled before deciding to use the material (seelist of selected local installations in Table PP-3 atthe end of this fact sheet).Pervious concrete parking lot; Bannister Park, Fair Oaks, CAPhoto: CNCPC and Fair Oaks Recreation and Parks DistrictPervious asphalt roadway. Photo: City of PortlandA water barrier or interceptor drain will be requiredbetween regular load-bearing pavement/streets andporous pavement materials. Photo: City of PortlandPervious asphalt consists of an open-graded coarseaggregate, bound together by asphalt cement into acoherent mass, with sufficient interconnected voidsto provide a high rate of permeability. As long asthe appropriate asphalt mix and designspecification is used, pervious asphalt may be asdurable as regular asphalt (Adams 2003). Perviousasphalt is less expensive than pervious concrete,but both types cost more than regular asphalt orconcrete.Most available pervious asphalt designspecifications include the use of a collection systemand underlying recharge bed, which at this time arenot being proposed. Pervious asphalt installationsare currently being examined, and it is anticipatedthat applicable design standards will soon beStormwater Quality Design Manual for the Sacramento and South Placer RegionsMay 2007PP-3