Permeable Paving Helps Solve Runoff From April Showers
Permeable paving can help solve storm water runoff and erosion problems and is a valuable upgrade, according to the Partnership for Advancing Housing Technology's (PATH) Tip of the Month for April.
Permeable pavement mixtures and grid systems minimize water runoff problems, recharge the groundwater, help filter out pollutants and improve the aesthetics of the home, PATH says.
Installing porous pavers is easier in some ways than installing impermeable pavers, PATH says, with the biggest difference the substrate materials below the paving, which must be designed to handle the water.
Several options are available:
- Porous Asphalt. The advantage provided by this material is that it uses the same mixing and application equipment used for impervious asphalt. The formula for the paving material is different, and the amount of asphalt binder required is about 6% of weight, which is somewhat higher than for standard impermeable asphalt.
- Plastic Grid Systems. These high-strength grids are often made from recycled materials and 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 allows 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 be absorbed into the water below.
- Block Pavers. This material can be used to create a porous surface with the aesthetic appeal of brick, stone or other interlocking paving materials. Sand is used in the joints instead of mortar. The pavers are most often used for driveways, entryways or terraces to provide a more traditional, formal appearance.
- Gravel. Certain types of plain old gravel can look beautiful and some just do the job, but less labor is needed for the entire process, including manufacturing, making gravel the greenest choice.
Permeable paving is most appropriate for sidewalks, patios, driveways or alleys, and even parking lots, but it should not be used for heavy or high-speed traffic because it has lower load-bearing capacity than conventional pavement.
Information resources include: the Center for Watershed Protection, the National Pavement Contractor’s Association, the Pennsylvania Stormwater Management Manual Porous pavement specification, the Portland Cement Association and the U.S. Environmental Protection Agency.
For information on green home building resources available from NAHB, e-mail Calli Schmidt, or call her at 800-368-5242 x8132.
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