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Contractors and homeowners alike are becoming more aware of their environmental footprint and seeking out solutions to decrease their impact. Whether for a commercial or residential project, careful storm water planning helps to account for Mother Nature’s needs while still developing land for our use.
Previous urban sprawl and the proliferation of impervious surfaces over the land and the transportation of rain water via urban infrastructure have had grave consequences over the natural hydrological cycle.
This rising impermeability of surfaces has limited the recharging of soil water reserves, thus drying out the soils from which plant roots draw their nutrients. Dry soils also become more prone to erosion. Unable to leech down through the surface, rain water gathers sediments and ground pollutants as they dramatically increase surface runoffs through urban infrastructure, flowing down to receiving waters.
This has affected humans at the expense of the environment around which we live, as well as economically, raising costs of development and maintenance of infrastructures.
Permeable pavements answer both qualitative and quantitative needs for storm water management. As water rains on the pavement, it seeps through to the ground, reducing surface flows, often even eliminating the need for sewers and manholes.
The key to understanding permeable pavers is to perceive the pavement and the base aggregates as a system, instead of separate products. As water rains down on the pavement, it begins its journey by seeping through the pavement, and then through the base aggregates, which naturally filter the pollutants. As it travels down, the water is stored in the base, until it reaches the natural underlying soils and recharges the ground aquifers. Thus, permeable pavement serves as an underground storage basin that filters the water while allowing pedestrian and vehicular traffic on the surface.
Depending on site conditions and owner preferences, permeable pavement can be designed to obtain full, partial or zero exfiltration. Full exfiltration is the most often desired and used application, which sees all the rain water stored in the base leeching down to the underlying subgrade. When natural soils are not permeable enough, or storms too heavy, perforated pipes are added to alleviate the excess water. Thirdly, an impermeable geo-membrane can be installed above the natural soils to prevent exfiltration of contaminated flows when the pavement is installed in industrial sites.
According to the Interlocking Concrete Pavement Institute (ICPI), when choosing permeable pavement technology, the designer or owner will benefit from:
• Conservation of space on the site and reduction of impervious cover
• Reduction of runoff
• Reduced peak discharge and stress on sewers
• Reduction of downstream erosion
• Improved water quality
• Reduction of water temperature
• Increased recharge of groundwater
• Promote tree survival by providing air and water to the roots
• Reduction of total development costs
• Reduction of infrastructure construction
• Decrease in retention basins and other unsellable land
• Reduction in risk of accidents/injuries
• Elimination of puddling and flooding on parking lots
• Faster snow melt drainage
• Urban heat island reduction
• Eligibility for LEED® credits
To learn more about improving storm water management, click here.