Porous Pavements

The rain showers that nourish lawns and flower beds come at a price. The water pouring down driveways and across patios and other hardscape surfaces can not only lead to flooding, but it also transports pollutants like oil, fertilizers and other impurities into sewers that eventually empty into open bodies of water.

To deal with the problem, many towns on Long Island now require storm water management systems for all new construction. Municipalities want water that falls on a home’s property to stay put. One of the most popular solutions is building walkways, driveways and patios with permeable pavers. Instead of letting water run off, these specially designed concrete pavers allow it to percolate through. It’s all in the smart design and base layers.

Like standard concrete pavers, those used in permeable systems are available in a number of shapes and colors. Standard pavers are set 1/8- to 1/4-inches apart on a bed of sand and gravel. After the installation, the joints between the pavers are filled with fine, uniform masonry sand, which locks them together. With a permeable system, tabs on the side of pavers provide wider joints, about 1/4- to 1/2-inches. The larger joints are filled with rounded gravel, which, unlike uniform sand, can’t compact. The voids between the stones allow surface water to percolate down.

Once it bypasses the paver, the water travels through different filtering levels of rock and gravel, giving the surrounding soil time to soak it up. “Permeable pavers not only reduce runoff and prevent flooding, they also provide an attractive pavement for driveways, walkways and patios,” said Reo Tallini, owner of Island Block and Masonry Supply in Wyandanch. “It’s really a win situation for everybody.”

“Before, homeowners would have to store runoff water in a dry well,” said Doug Connell, owner of Island Associates in Massapequa, referring to a system that often requires digging up a manicured lawn. “But the permeable system is almost two feet of different size gravel so the water stays on the property.” The result is a design that, according to the Interlocking Concrete Pavement Institute, can drain four to nine inches of water per hour, which should handle most rainstorms. “The service life is about 25 to 30 years,” said Tallini. “There’s no maintenance involved and there are no special requirements for plowing during the winter. It’s basically the same as a regular concrete paver.”

While building departments make the upgrade standard for new homes, the remodeling market is slower to adopt the change. “I’ve done some remodels of existing driveways and patios,” said Connell. “But not many. Homeowners really have to want to do something that is environmentally friendly to have a permeable system installed.” It’s a matter of price. Standard pavers are about $12 to $14 per square foot installed, permeable pavement ranges from $20 to $25 per square foot. There is more excavation involved and the gravel and stone used as the base are more expensive than the crushed recycled concrete under standard pavers, but permeable systems do away with the need for dry wells. And because water drains through them so quickly, they help control ice formation during the winter while contributing to the long-term health of the environment.

Rainwater runoff is a serious fact: The 5 inches of rain Merrick received during a storm last April produced over 3,100 gallons of water for every 1,000 square feet of pavement.