Pervious pavement effectively treats, detains, and infiltrates stormwater runoff where landscape-based strategies are restricted or less desired. Pervious pavements have multiple applications, including sidewalks, street furniture zones, and entire roadways (or just their parking lane or gutter strip portions). Treatments should be tailored to their specific climate and available maintenance capacities.
Critical
Pervious pavements must be designed to account for the native subsoil infiltration rate. The depth of the pervious layer, void space, and the infiltration rate of the underlying soils result in the desired storage volume and intended drain time of the facility.
1Prior to installation, verify that underlying native soils are not contaminated. A full geotechnical evaluation is required to determine the permeability, height of the water table, and depth to bedrock. Many urban areas have significant swaths of unclassified urban fill that may cause issues if not remediated.
Based on the potential vehicle usage and loading, verify the structural stability of the sub-grade materials. For example, some decorative pavers may be more susceptible to shifting than others, and are thus more appropriate for use in pedestrian- and bike-only areas.
In cold climates, use biodegradable, non-corrosive de-icing agents, such as BX36, GEN3, and BetaFrost.
The drain rock layer must be clean and wrapped in filter fabric.
Protect the adjacent subsurface infrastructure by maintaining minimum clearances, installing waterproof liners as separation barriers, or constructing a deep curb to separate the roadbed subgrade or parallel utility line from the facility.
In cold climates, salt should be applied in moderation to reduce contamination of the subsoil. Plowing should be done carefully, and abrasives, such as sand or cinders, should be avoided to preserve the integrity of the pavement system.
Recommended
2Utilize an underdrain system to treat overflow, or if partial infiltration is preferred, to convey remaining runoff to the municipal sewer system.
Pervious pavement should drain within 48 hours.
Pervious pavements often require ongoing cleaning (vacuuming or power washing) to remove silt from the void spaces to maintain infiltration performance.
Optional
3Selection of pavements, such as permeable pavers, permeable concrete, permeable asphalt, or other materials, should be based on engineering constraints and the surrounding street context.1
- “Permeable Pavement Systems,” Draft District of Columbia Stormwater Management Guidebook (Washington, D.C.: District Department of the Environment, 2012). ↩︎
Urban Street Stormwater Guide
Learn more about stormwater in NACTO’s Urban Street Stormwater Guide