An estimated 96 percent of all U.S. roads are paved, most using impervious materials like asphalt. All of those surfaces contribute to runoff, erosion, water pollution, water shortages and even adverse human health effects. Add parking lots, sidewalks, common areas and other large covered land areas to the mix and the negative impact grows even more.
When used correctly, permeable pavers create areas usable for auto and foot traffic where water soaks directly into the ground instead of running off the surface into drainage systems, retention basins or another outlet.
Typically, when it rains, runoff is guided into underground drainage systems. Once in the system, the water is directed to a drainage basin where it is held until it can soak back into the ground and replenish the nearest underground aquifer (water table). Or, it is discharged into natural bodies of open water, such as streams, rivers and bays.
Problems occur when storm water systems are inadequate, for which flooding occurs. Problems also occur when there are no measures in place to prevent pollution from trash, fertilizers and other man-made materials from reaching open waters.
The Heat Island Effect
In urban areas, the heat island effect has become a grave problem. It occurs when large expanses of impervious pavement and other man-made structures (such as buildings) retain or even emit heat. The heat is trapped by surrounding buildings because they limit air movement. Impervious surfaces (asphalt, concrete) contribute by absorbing heat from the sun, which then heat up and release it onto the surrounding area. The scenario is made worse by vehicle exhaust, air conditioning exhaust and the like. All these combined create an urban area where the temperature is several degrees warmer than other surrounding areas.
Research and Benefits of Paver Systems
Within the past 15 years, according to the Interlocking Concrete Paving Institute (ICPI), permeable pavers have been found to reduce the environmental impact by lowering surrounding temperatures, creating faster aquifer replenishment, reducing runoff and pollution and even lowering water usage for lawn and garden areas. Other Studies completed in the U.S. and Europe show that permeable concrete paving systems result in "significant runoff reductions, as well as lower levels of suspended soils, nutrients and metals" in water.
It is clear that interlocking permeable paver systems are an environmentally friendly alternative to asphalt and concrete surfaces.
The use of permeable pavers, according to ICPI, can help businesses and developers meet LEED credit requirements under the Sustainable Sites Initiative (guidelines and standards for landscape sustainability).
How Do Paver Systems Work?
Pavers are different and better than porous concrete or asphalt because pavers are manufactures as interlocking components. When installed, they create a pattern of pavers separated by joints that are filled with joint stabilizers such as sand. When water hits those joints, it percolates down through the material into the subsurface. Those layers create storage areas for water, holding it until it can flow into the soil sub-grade and eventually the nearest underground aquifer (water table).