http://www.perviouscrete.com/watch_video/why_pervious_concrete/

 

Pervious concrete is a special type of concrete with a high porosity used for concrete flatwork applications that allows water from precipitation and other sources to pass directly through, thereby reducing the runoff from a site and allowing groundwater recharge. Pervious concrete pavement is a unique and effective means to address important environmental issues and support green, sustainable growth.  This pavement technology creates more efficient land use by eliminating the need for retention ponds, swales, and other stormwater management devices. In doing so, pervious concrete has the ability to lower overall project costs on a first-cost basis. The high porosity is attained by a highly interconnected void content. Typically pervious concrete has little or no fine aggregate and has just enough cementitious paste to coat the coarse aggregate particles while preserving the interconnectivity of the voids. Pervious concrete is traditionally used in parking areas, areas with light traffic, residential streets, pedestrian walkways, and greenhouses.[1] It is an important application for sustainable construction and is one of many low impact development techniques used by builders to protect water quality.  In fact, the use of pervious concrete is among the Best Management Practices (BMPs) recommended by the EPA– and by other agencies and geotechnical engineers across the country– for the management of stormwater runoff on a regional and local basis.