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

Runoff Reduction Control Measure Fact SheetPorous PavementConstruction Considerations• Proper installation is important for all porous pavement types, but it is especially critical forpervious concrete and asphalt, which must be installed by certified or otherwise qualifiedcontractors. Certification programs are now offered by various National and State associations(contact National Ready Mixed Concrete Association for more information).• The designer should define compaction criteria to protect infiltration capacity of perviousmaterials and satisfy roadway loading requirements.• Weather conditions can affect the final product. Avoid extremely high or low temperatures duringinstallation. The bottom of the crushed rock reservoir below the pavement should be flat so thatrunoff will be able to infiltrate across the entire sub surface area (unless subsurface drain required).• Additional information must be incorporated into construction specifications depending on thetype of porous pavement proposed and addressing site-specific pavement design. Manufacturer’srecommendations could be incorporated into the project specifications.• After installation, and as construction continues elsewhere on the site, prevent fine sediment fromclogging the material by covering the surface with plastic, using staked straw wattles around theperimeter, etc.• As soon as possible, stabilize the entire tributary area to keep sediment-laden runoff fromcontacting the new pavement.Long-term Maintenance RecommendationsTable PP-2 presents inspection and maintenance recommendations for porous pavement. The localpermitting agencies will require that the property owner be responsible for maintaining the features toensure continued, long-term performance. The pervious features should not be removed or replaced withimpervious surfaces in the future, or all water quality benefits will be lost. Check with your localpermitting agency to determine if and when a maintenance agreement will be required for your project.Table PP-2. Inspection and Maintenance Recommendations for Porous PavementSurface MaintenanceCare of VegetationVector ControlMaintenance ofReinforcement ProductsManufacturer’sRecommendationsReplacement• Keep the surface clean and free of leaves, debris, and sediment, and do not replace orcover it with an impermeable paving surface.• Regularly sweep or vacuum pervious concrete and asphalt, modular block pavementor cobblestone Block Pavement (typically three to four times per year).• Do not store loose material such as bark or sand on porous pavement.• Mow, irrigate, fertilize, and—when necessary—reseed grasses planted in pavement.Keep grasses healthy and dense enough to provide filtering while protectingunderlying soils from erosion.• Mow grass to less than four inches and remove grass clippings.• Avoid planting trees and shrubs near non-flexible porous pavement types becauseroots may crack pavement and excessive leaves may clog the surface. Use ofstructural soil material may alleviate this concern.• Eliminate any standing water, since that provides an environment for insect larvae.• If sprays are considered, then use a licensed pest controller to apply an approvedmosquito larvicide.• Where reinforcement products are used to stabilize grass or gravel, replace individualgrid sections when they become damaged.• For manufactured products, follow manufacturer’s maintenance recommendations.• Reconstruct or replace when it is no longer functioning properly (see projected lifespanin Appendix B for informational purposes).Stormwater Quality Design Manual for the Sacramento and South Placer RegionsPP-12 May 2007