It all started back in ancient Rome. Sometime after 273 B.C., Roman architects perfected a new type of concrete that many consider their most relevant contribution to the modern world. Indeed, the engineering marvel of the Roman Aqueducts wouldn’t have been possible without concrete.
With the advent of concrete, in addition to building structures and aqueducts, square pavers were developed. They were used for walkways; in fact, there are estates in Italy that were built hundreds of years ago that use these pavers as walkways, but with an added benefit: underneath them lie cisterns, to capture rainwater for reuse during drier times.
Jumping forward to the present day, pavers similar to those that were used hundreds of years ago are again being utilized; today, we refer to them as ‘permeable pavers’. These pavers are laid side by side, but with some space in between, allowing water to leach into the ground, instead of running off and ending up in stormwater drains.
Today, there is widespread concern about what is pouring into our storm drains—not only because otherwise useful rainwater is being literally flushed out to sea, but because on its way there, it gathers petroleum products, animal wastes, fertilizers and pesticides. These contaminates end up in our streams, lakes and oceans, where they are harmful to wildlife and people alike. Permeable pavements direct that stormwater back into the ground, and in doing so, many of the pollutants are filtered out.
In addition to environmental benefits, there are economic advantages to using permeable pavers. Brian Crooks, president of B.C. Pavers, Inc., in Sarasota, Florida, explains one of them: “The biggest reason for choosing permeable pavers is to avoid installing a lot of drainage systems. If a contractor has to run storm drains all the way around a house, that’s more expensive than putting in a permeable system.”
Crooks also makes clear possibly the most pragmatic reason for using permeable pavers: “A lot of municipalities are requiring it by imposing an impervious surface limit. For this reason alone, these pavers will continue to become increasingly commonplace.” Permeable pavers are an efficient way to meet these regulations.
Traditionally, landscape contractors have outsourced the paving elements of their jobs, giving up a potentially flush revenue source.
With a growing emphasis on hardscapes, businesses that keep this work in-house can enjoy lucrative benefits. “There’s real money to be made in the paver business,” maintains Rich Goldstein, president and founder of Green Meadows Landscaping in Oakland, New Jersey, and a board member of the New Jersey Landscape Contractors Association.
There’s a push these days among business owners, commercial and residential property developers, and homeowners to become more ecologically responsible. Consequently, designers and contractors with these types of systems in their portfolios will be sought after. Permeable pavers have already been used in impressive and marketable ways. By adding a few design features, such systems can be used for water harvesting. The water can then be used for irrigation or, for residential clients, chores around the house.
Permeable pavers can also help with existing drainage issues, eliminating the need for surface grates or areas of standing water. They are often used as a way to control stormwater on developed sites. Any rain falling on these paved patios, walkways or driveways simply percolates down between the pavers, rather than accumulating or needing to be piped away.
According to Bruce K. Ferguson, Fellow of the American Society of Landscape Architects, when installed and maintained correctly, these surfaces’ infiltration rates are higher than almost any natural soil, and several times greater than the maximum possible rainfall intensity nationwide. “So, a surface of this type must be given complete credit for ‘100 percent perviousness,’ as would a meadow or forest. Giving it any credit less than 100 percent pervious would fly in the face of scientific evidence.”
Costs for permeable paver projects will vary widely, depending on the application selected, the size of the area chosen, and the condition of the soil. Typically, a surface done with permeable pavers costs approximately 20 percent more than traditional pavers. But because the installation of these pavers dramatically improves drainage, reducing stormwater contribution from driveways, walkways and patios, these projects end up being cost-effective. Replacing impermeable surfaces with permeables often in- creases property values as well.
The pavers infiltrate, filter and decrease stormwater runoff rates and reduces Total Maximum Daily Loads. By incorporating permeable pavers into hardscapes, builders become potentially qualified for LEED credits for sustainable sites, water efficiency, materials and resources, and/or innovative design. They can also garner ‘green globe’ points.
Homeowners can become eligible to receive rebates when they convert a minimum of 100 square feet of hard surface to permeable, while the minimum conversion for multi-family, commercial or institutional properties is 350 square feet.
When choosing a site, consider nearby surfaces, soil type and drainage issues, as they can affect the stability of the surface and rainwater infiltration. Because clay soils can be impermeable, an underdrain or storage media would be necessary to prevent ponding, while sand and loam would allow rapid infiltration. Installing permeable pavers on a slope of five percent or greater will negatively affect their strength and efficiency. And pavers shouldn’t be installed at the base of a slope, because soil, sand or mulch would constantly interfere with the functionality of the system by clogging the pores.