Pervious concrete allows rain to soak into the ground instead of running off. This helps break the flood and drought cycles that plague so many areas these days. Water that seeps into the ground slowly runs out into streams and springs slowly, which provides much more consistent moisture for plants and animals.
Pervious concrete pavement systems provide a valuable stormwater management tool under the requirements of the EPA Storm Water Phase II Final Rule. Phase II regulations provide programs and practices to help control the amount of contaminants in our waterways. Impervious pavements– particularly parking lots– collect oil, anti-freeze, and other automobile fluids that can be washed into streams, lakes, and oceans when it rains.
By capturing the first flush of rainfall and allowing it to percolate into the ground, soil chemistry and biology can then “treat” the polluted water naturally. Thus, stormwater retention areas may be reduced or eliminated, allowing increased land use. Furthermore, by collecting rainfall and allowing it to infiltrate, groundwater and aquifer recharge is increased, peak water flow through drainage channels is reduced, and flooding is minimized. In fact, the EPA named pervious pavements as a BMP for stormwater pollution prevention because they allow fluids to percolate into the soil.
Another important factor leading to renewed interest in pervious concrete is an increasing emphasis on sustainable construction. Because of its benefits in controlling stormwater runoff and pollution prevention, pervious concrete has the potential to help earn a credit point in the U.S. Green Building Council’s Leadership in Energy & Environmental Design (LEED) Green Building Rating System (Sustainable Sites Credit 6.1), increasing the chance to obtain LEED project certification.
The light color of concrete pavements absorbs less heat from solar radiation than darker pavements, and the relatively open pore structure of pervious concrete stores less heat, helping to lower heat island effects in urban areas.
Trees planted in parking lots and city sidewalks offer shade and produce a cooling effect in the area, further reducing heat island effects. Pervious concrete pavement is ideal for protecting trees in a paved environment (many plants have difficulty growing in areas covered by impervious pavements, sidewalks and landscaping, because air and water have difficulty getting to the roots). Pervious concrete pavements or sidewalks allow adjacent trees to receive more air and water and still permit full use of the pavement (see Figure 2b). Pervious concrete provides a solution for landscapers and architects who wish to use greenery in parking lots and paved urban areas.
Although high-traffic pavements are not a typical use for pervious concrete, concrete surfaces can also improve safety during rainstorms by eliminating ponding (and glare at night), spraying, and the risk of hydroplaning.