April showers may bring May flowers, but they also bring rainwater that rushes down driveways and sidewalks and into streets, picking up contaminants along the way.
Traditional paving prevents rainwater from being filtered by the earth and may contribute to erosion caused by improper drainage.
However, permeable pavement, uses special materials designed to handle water. And it is definitely more environmentally friendly!
Several types of permeable pavement systems exist, including:
Pervious Concrete Walkway
Porous asphalt and porous concrete, which both use the same mixing and application equipment as their impervious counterparts:
Porous Asphalt: A great advantage to porous asphalt is that the same mixing and application equipment is used as for impervious asphalt. Only the formula for the paving material changes. The amount of asphalt binder required is about 6 percent of weight, which is somewhat higher than required for standard impermeable asphalt.
Porous Concrete: Once again, porous concrete uses the same equipment and process as common concrete. The difference is larger pea gravel and a lower water-to-cement ratio to achieve a pebbled, open surface that is roller compacted.
Plastic grid with soil can grow grass within the driveway!
Plastic grid systems, which use high-strength plastic grids for supporting vehicles and preventing erosion: High-strength plastic grids-often made from recycled materials-are placed in traffic areas. Some are designed to be filled with gravel on top of an engineered aggregate material, while others are filled with a sand/soil mixture on top of an aggregate/topsoil mix that allow grass to be planted on the surface. The grids provide a support structure for heavy vehicles, and prevent erosion. After heavy rains, the grids act as mini holding-ponds, and allow water to gradually absorb into the soil below. 
Block pavers make a beautiful driveway!
Block pavers, which can create porous surfaces with the appearance of brick, stone, or interlocking paving materials: This material can be used to create a porous surface with the aesthetic appeal of brick, stone, or other interlocking paving materials. Just use sand in the joints instead of mortar. They are most often used for driveways, entryways, walkways, or terraces to achieve a more traditional, formal appearance. 
An attractive gravel driveway
Plain gravel: Yes, that's right, plain old, or not so plain gravel. Lots of driveways used to be surfaced with it. Some types look beautifully elegant. Some just do the job. But talk about pervious. . .and less labor goes into the whole process, including the manufacturing part. So in the right application gravel is the greenest choice.
All of these can be done very easily and attractively, while helping your neighborhood environment, as well as that of the planet!
Permeable paving is most appropriate for sidewalks, patio, driveways or alleys. You know, around your house. Parking lots, too. It is not for high traffic/high speed areas because it has lower load-bearing capacity than conventional pavement.
As for initial costs, permeable paving is competitive with conventional materials; sometimes lower, sometimes higher. Definitely better for the environment.
For your household project, you should run the numbers, look for the one that appeals to you, and decide what's best for you.
Click on these Resources fo rmore information:
Center for Watershed Protection
National Pavement Contractor’s Association
Pennsylvania Stormwater Management Manual Porous pavement specification
United States Environmental Protection Agency
Copyright 2008 Ronald Sauve All Rights Reserved
This page was last modified on March 28, 2008
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