Compared with traditional solid surfaces that allow rainwater to “run off,” picking up pollutants and carrying them into stormwater systems and waterways, permeable paver systems filter water through layers of aggregate and then into soil or through pipes into rain gardens or retention ponds. Walkways, patios, golf course paths, driveways and streets can be made of permeable pavements. Ted Corvey, paver business director for Pine Hall Brick, says two forces are driving increased interest in permeable paver systems: government regulations and consumer desire to use environment-friendly products.
The U.S. EPA began implementing phase two of its stormwater program, which requires small municipalities to manage stormwater runoff in 2003, and the regulations went into effect fully in July 2007. (Phase one, developed in 1990, applied to municipalities with populations of 100,000 or more.) To comply with the federal mandates, local governments enacted a variety of laws associated with stormwater runoff. Corvey says interest in permeable pavement systems increased dramatically after phase two of the EPA program took effect.
Tal Shuford, president of Cobble Systems and EuroGrout, says architects and engineers specified permeable paver systems three times as often this year compared with last year in projects which used his company’s products. Meeting evolving regulations was the primary motivation.
New laws most likely to affect your residential clients are those setting “impervious cover limits.” These ordinances apply to new construction and remodeling projects, and state impervious surfaces such as the footprint of the home, driveway, patio, etc., can’t take up more than a certain percentage of the lot. Corvey says impervious cover limits often come into play in established, affluent neighborhoods where property owners are discovering they’ll have to decrease the size of their driveways – or replace them with permeable/pervious systems – in order to increase their home’s footprint through a remodeling project.
Permeable paver systems offer your commercial clients benefits and increased options as well. When installed properly, most systems qualify for LEED credits – a big plus since many corporations and universities are striving for LEED certification. Owners of commercial properties with large buildings have the opportunity to satisfy new ordinances with permeable parking lots rather than retention ponds, Corvey says. Products such as EP Henry’s Turf Pavers, which permit grass to grow through gravel-filled cells, allow cities and companies to retain green space in areas that have to stand up to occasional vehicle traffic. Turf Pavers often are used around shore homes as well, to help control erosion and water pollution and maximize green space on small lots, says Lance Malesh, chief operating officer, EP Henry.
Municipalities that use permeable pavement systems for streets, alleyways and sidewalks can reduce their reliance on or eliminate the need for complex storm water systems. For example, Rosemary Beach, Florida, a planned community founded in 1995, has no stormwater system and installed a permeable paver system for its main street and town square in October. The ability of the town’s original pervious concrete roads to stand up to heavy traffic and absorb water was poor, due largely to inconsistent batches, says Jim Bagby, town manager of Rosemary Beach. Retrofitting the 107-acre development with a stormwater system in order to use traditional paving methods would have been cost prohibitive, Bagby says. In September 2007, the town installed a 5,000-square-foot test pattern comprising Cobble Systems’ concrete pavers and permeable EuroGrout. When five inches of rain fell in two hours, “it handled it marvelously,” Bagby says. The look is aesthetically pleasing as well. “The town has a West Indies, European feel and the cobblestones just add to it,” he says. Town leaders plan to use the permeable paver system throughout Rosemary Beach.
How it works
The oft-used phrase “permeable pavers” is a bit misleading. In most cases, the pavers themselves, whether brick or concrete, are not permeable. The only difference between permeable pavers and traditional pavers is the spacing between them. Most permeable pavers have spacers on their sides that create larger gaps – typically / inch to 1/2 inch – than the joints between traditional pavers. Cobble Systems’ pavers are attached to 5-foot-square nylon grids, with similar spacing between stones.
The key to making the systems permeable is site preparation. It usually involves excavating to a depth of 12 to 24 inches and installing layers of progressively smaller, open-graded aggregates. (See cross-section drawing below). You use the top-layer aggregate instead of sand to fill voids between pavers or you can use permeable grout. Because the market for permeable pavement is growing and few landscape contractors are trained to install it, learning these skills now could benefit your business. “You can differentiate yourself,” Malesh says. “It also gives you another way of selling a paving system. A lot of people want to make sure they’re doing their part to preserve the environment.”
Installing a permeable paver system
Proper installation is site and paver specific (www.icpi.org for guidelines), but this drawing shows a typical permeable paver system. Aggregate layers below pavers create a reservoir for rainwater. Soil and aggregate compaction and appropriate edge restraints differ from traditional paver installation.
Drawing courtesy EP Henry.