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

Runoff Reduction Control Measure Fact SheetPorous PavementPorous Gravel PavementPorous gravel pavement (Figure PP-5) consists of a loose gravel surface installed with or withoutadditional stabilization depending on anticipated loads and traffic. This type of pavement must be placedover a sufficient aggregate base to allow for storage and infiltration. Where drainage is slow, anunderdrain may be required. It is ideal for temporary use areas where permanent pavement would be toocostly, as well as rural and park settings, overflow parking lots, maintenance roads, fire access lanes, andmaterials storage areas. However, check with the local permitting agency, since some agencies in theSacramento area don’t allow gravel except for certain types of storage yards. Refer to Table PP-1 fordesign criteria for this type of porous pavement.Note: Wrap all geotextileor impervious liners upat edges and flow barrierto within 1-in of topof gravel layer.Secure firmly in place.Woven geotextile fabric meeting:ASTM D4751-AOS of 50-70ASTM D4633 min. trapezoidal tear strength 100 x 60lbs.Minimum COE specified open area of 4%.When Type C soils are present and when infiltration isallowed, unless permeability shows otherwise,eliminate the bottom sand layer, use underdrains andgeotextile liner instead of an impermeable one underthe gravel.When the underlying soils are Type D or expansive,use underdrains and 16 mil minimum thicknessimpermeable liner under and on sides of the pavementsand and gravel media.Figure PP-5.Porous GravelPavement,TypicalSections*(source: adapted fromDenver)*Installationspecifications may varyby site; check with localpermitting agencyWoven geotextile fabric meeting:ASTM D4751-AOS of 50-70ASTM D4633 min. trapezoidal tear strength 100 x 60 lbs,Minimum COE specified open area of 4%.Stormwater Quality Design Manual for the Sacramento and South Placer RegionsPP-10 May 2007