2.2.3 Pervious Surfaces
Make use of pervious surfaces (ground cover that allows rainwater to infiltrate and flow through to subsurface layers) in order to prevent storm water run-off and flow of pollutants off site and to mitigate the heat island effect.
Surfaces include exterior horizontal or sloped areas intended for pedestrian or vehicular use or components that are part of a building envelope. Tactics include plastic grid systems (light-weight traffic and emergency access paths), porous block pavement systems (all load conditions, typically used as sidewalks or driveways), porous or open-graded asphalt paving (roads and parking lots) and porous Portland cement concrete (roads and parking lots). The latter two options are not recommended where wind-blown (or vehicle-blown) sediment is expected.
Evaluate maximum surface load capacity with respect to anticipated vehicle loads. Verify the slopes on site, as most pervious surfaces with vehicular access are not recommended for slopes greater than 5 percent.
Lowers storm water utility rates and reduces solar radiation loads due to lower exterior ambient temperature by virtue of evaporative cooling.
Pervious surfaces reduce the loads on storm water and/or sewage systems. The heat island effect is mitigated due to water retention and associated evaporative cooling.
Minimum soil depth of 4 feet (1.2 meters) to bedrock or highest water table is recommended. Bioswales and retention ponds can be used at larger scale developments to reduce run-off utility loads, creating biotope and natural habitat (see 2.1.1 rainwater storage and use). Stabilizing materials on sloped surfaces allow for pervious surfaces, preventing erosion and stabilizing soils.
1.4.9 Green Roof
4.6.1 Heat island effect