Written by: Samantha Justice, P.E.

Green infrastructure incentive programs have become commonplace for new construction and redevelopment regulations. Five of the most common incentives include:

• Development incentives such as expedited permitting, decreased fees, zoning upgrades, and stormwater requirement reductions.
• Grants.
• Rebates and installation financing.
• Awards and recognition programs.
• Stormwater fee discounts.

A subset of green infrastructure, stormwater management usually includes the consideration of pervious/porous pavements. Traditional asphalt and concrete parking lot surfaces create significant stormwater runoff, and many municipalities do not allow them in expansion or new build situations.

When the entire parking area is constructed using a porous pavement system, stormwater concerns are greatly reduced. Depending on the type chosen, pavements that return rainwater to the aquifer nearly eliminate stormwater runoff and reduce sheet flow and point load erosion problems at the pavement edges. They also reduce the need for additional stormwater infrastructure to convey the water away from the area. Integrating porous pavement systems with asphalt and concrete surfaces can reduce such failures and reduce or eliminate the need for stormwater conveyance channels, pipes, and swales. As a result, downstream stormwater pipe systems see less silt and water, which requires less maintenance and less capital expenditure for upsizing stormwater pipes.

Increase Parking Capacity

Expanding parking areas with porous pavement can have a neutral effect on the existing stormwater loading or, in some cases, can even decrease existing loading.

• In cases where existing parking areas drain to internal inlets, additions self drain but seldom offer any benefit to existing hard surfaces.
• In cases where parking areas sheet drains in the direction of the parking capacity addition, the new porous surface can go beyond self-draining and can cut off sheet flow and absorb hard-surface runoff. Of course, you must be careful not to overload the new porous system with sediment.

Integrating Permeable with Impervious Pavements

Not all new-build parking lots need to be 100% porous. A combination of pervious and impervious surfaces can solve stormwater concerns and heavy traffic loading expectations. Using asphalt or concrete surfaces in the drive lanes of parking lots alleviates stresses on the system from repetitive passes from vehicles and ensures that all types of vehicles can use the lot. Joined to these drive lanes can be adjacent porous parking stalls, controlling stormwater runoff and eliminating the need for inlets and conveyance systems. While permeable infill promotes fast infiltration, the base depth may be designed to suit the stormwater needs of the site, allowing for storage and natural percolation.

Semi-rigid resin-based porous pavement units may be filled with either aggregate or topsoil, allowing for customization of parking lots for aesthetic appeal while considering intensity and frequency of use. The permeable paver units are easily cut to seamlessly align with hard-surface pavements (permeable pavers, asphalt, concrete), even along curved lines. Impervious surfaces can be painted for centerlines and turning lanes. Porous pavement units offer delineators, allowing parking stall lines and other separation markers. Parking stops and signs can be easily installed over porous pavement units, so there are no limitations when it comes to fully outfitting parking areas for a project’s needs.

The Benefits of Porous Pavements in Pavement Design

Whether porous pavements are included in all or part of a green infrastructure pavement project, the benefits they offer for reducing runoff and stormwater infrastructure size/need, protecting watersheds, and reducing cost are significant.

Presto Geosystems offers the GEOBLOCK® grass and GEOPAVE® gravel porous pavement systems to help control stormwater, meet load requirements and suit landscape plans.

See our Myth Busters Blog Series for how the units eliminate typical concerns about using porous pavements.

For more information on porous pavements, visit our web page: Porous Pavements.