Permeable Pavements

Types | Design Considerations | Permeable Pavements on Commercial Sites | Local Examples

A variety of product alternatives to traditional paving exist that allow for the infiltration of stormwater. Certain products are more applicable in certain settings; therefore, each paving type contains information regarding the best use of the product. Limitations are also highlighted.

Types of Permeable Pavements

Concrete Block Pavers | Concrete Grid Pavers | Plastic Grid Pavers | Pervious Asphalt | Pervious Concrete

Concrete Block Pavers

Concrete block pavers have been around since the 1960s. They add anywhere from 20% to 50% of open surface that would not have been there had an impermeable surface been used. They can also add aesthetic value to any area. Research on concrete pavers in Washington has been ongoing for several years.

These pavers are recommended for use in driveways, parking areas, shoulders along airstrips and highways, ditch liners, embankment stabilization, roadway medians, boat launching ramps, emergency access roads, fire lanes, sidewalks, grassed rooftops, pool decks and patios.

Specific Design Considerations

Some provision should be made for edging material to hold to blocks in place, and to prevent grass from creeping into the pavement.

The type of sub-base and filler used will determine the amount of infiltration the pavers provide.

Best used in: Driveways, parking areas, highway shoulders, ditch liners, embankment stabilization, roadway medians, boat launching ramps, emergency access roads, fire lanes, sidewalks, grassed rooftops, pool decks and patios.

Limitations: Winter sanding should be kept to a minimum to avoid clogging the infiltrating surface.

Concrete Grid Pavers

Concrete grid pavers are similar in composition to concrete block pavers, but the structure and pattern is different. The construction of the permeable base is the same. Research on concrete pavers in Washington has been ongoing for several years.

Specific Design Considerations

The type of sub-base and filler used will determine the amount of infiltration the pavers provide.

Limitations: Winter plowing needs to be done with care to reduce the chance of damage. Winter sanding should also be kept to a minimum to avoid clogging the infiltrating surface.

Plastic Grid Pavers

Plastic grid pavers are made mainly out of recycled plastic materials that provide a high porous surface using grass or gravel to make the area more attractive. These pavers are also flexible, allowing them to be used on uneven sites. This system is environmentally friendly, it uses recycled plastic, reduces the imperviousness of the area, and therefore the volume of stormwater runoff.

They do not require curbs, catch basins, detention or retention ponds or any other associated drainage facility. Plastic grid pavers are competitively priced to asphalt and concrete paving, when their required drainage costs are factored in.

These pavers are recommended for use as sidewalks, parking areas, golf cart paths, residential driveways, fire lanes, emergency access roads and others that are product specific.

Specific Design Considerations

The type of sub-base used will determine the amount of infiltration the pavers provide.

Best used in: Overflow parking lots, sidewalks, shoulder parking, or other low-traffic areas.

Limitations: Winter plowing needs to be done with care to reduce the chance of damage. Winter sanding should also be kept to a minimum to avoid clogging the infiltrating surface.

Pervious Asphalt

Pervious asphalt is fundamentally the same as regular asphalt, but it does not contain the fine particles that asphalt does. This creates porosity in the matrix, which allows water to flow through and infiltrate into the ground. As would be expected, the volume of stormwater runoff that flows off the pavement is greatly reduced, and the need for curbing, catch basins, and large detention facilities is reduced. Research on porous asphalt is currently being performed at the University of New Hampshire and the University of Rhode Island.

Specific Design Considerations

The type of sub-base used will determine the amount of infiltration the surface provides.

Best used in: With a proper base, porous asphalt can be used in the same settings as regular asphalt. Research on plowing and sanding in cold climates in ongoing (see left).

Limitations: Can become clogged and have reduced infiltration rates if installed in areas with high sediment loading.

Pervious Concrete

Pervious Concrete is a variation of traditional concrete. Similar to pervious asphalt, pervious concrete does not have the fine particles in the mix. The installation of this type of concrete is quite different from the traditional method, and requires experienced installers. Research on pervious concrete in Pennsylvania has been ongoing for several years.

This surface is recommended for use in driveways, parking areas, shoulders along airstrips and highways, ditch liners, roadway medians, boat launching ramps, emergency access roads, fire lanes, sidewalks, and patios.

Specific Design Considerations

Installation must be performed by experienced installers.

The type of sub-base used will determine the amount of infiltration the surface provides.

Best used in: With a proper base, porous concrete can be used in the same settings as regular concrete. Research on plowing and sanding in cold climates in ongoing (see left).

Limitations: Can become clogged and have reduced infiltration rates if installed in areas with high sediment loading.

Design Considerations

Permeable pavements can be used in a wide variety of land use settings. However, areas that have high potential for contamination such as transfer stations, gas stations, or highly industrial areas may not be suitable for permeable pavements due to the increased risk of groundwater contamination. Research has shown that in most urban, suburban, and commercial areas, the use of permeable pavements will not increase the risk of groundwater contamination.
Native soils on the site should be conducive to infiltration, with an infiltration rate at least 0.3 inches/hour.
A properly designed and installed base is critical to a successful permeable pavement application. Most product manufacturers will provide specifications for the base and installation.
Pervious pavements should not be used in areas with a slope > 15%, as erosion of the fill material may occur.
The seasonal high water table should be at least 3 feet below grade.
Pervious pavements should be installed at least 75 feet from drinking water wells.

For more information, visit the following sections of the CT Stormwater Quality Manual: Chapter 11, Section S-6