Designing and developing a stormwater solution is a constant challenge due to the two major variables: municipal code and site variability.
Know Which Way the Wind is Blowing
Fresh potable water is a vital resource that in the future may be as limited as oil, if steps aren’t taken to preserve it now. Using non-potable water or gray water collected via PICP water harvesting for gray water needs like irrigation or toilet flushing, preserves potable water for human consumption. PICP systems may be employed to capture, treat, and store this water in concrete tanks or other materials and recycle when needed.
Local regulations will vary but all typically are mandated to comply with the water quality and quantity requirements of the Federal Clean Water Act and meet the NPDES Phase II rule (National Pollutant Discharge Elimination System) for capturing and treating the first flush from storms. Stormwater management objectives generally include:
- Water Quantity
- Retain/infiltrate runoff volumes and peak flows
- Imitate pre-development conditions
- Control amount of impervious cover
- Reduce stormwater utility fees
- Capture percentage of storms
- Control specific nutrients, metals
Overall it’s important to make sure you have the right stormwater management strategy based on the specific details of your project.
Take Advantage of LEED Opportunity
USGBC’s LEED (Leadership in Energy and Environmental Design) green building certification program is the nationally accepted benchmark for the design, construction, and operation of green buildings. LEED covers the performance of materials in aggregate, not that of individual products or brands, so that products that meet the LEED performance criteria can only contribute toward earning points needed for LEED certification; they cannot earn points individually. PICP systems may contribute to numerous LEED rating system credits.
- SS Credits: 6.1 and 6.2 Stormwater Design: Quantity Control and Credit 7.1 Heat Island Effect: Non-Roof
- WE Credit: 1.0 Water Efficient Landscaping
- MR Credits: 2 Construction Waste Management, 3 Materials Reuse, 4 Recycled Content and 5 Regional Materials.
Dark, non-reflective hardscape surfaces absorb and radiate the sun’s heat and contribute to the heat island effect. Heat island effect can raise urban temperatures by 2ºF to 10ºF. The use of light colored pavers or pavers with a high Solar Reflectance Index (SRI) will reduce this effect. The SRI is a measure of the paver surface’s ability to reflect solar heat, as shown by a small temperature rise. LEED Credit 7.1 requires the paver to have an SRI of at least 29. Higher SRI values for pavers may be achieved and used on ballast type roofs or in conjunction with green roof systems.
High SRI pavers also provide enhanced night illumination because of their high reflectivity, reducing the need for larger and higher wattage light fixtures, a result witnessed by the Chicago DOT during implementation of its Green Alley program, where lower wattage exterior lights used in conjunction with high SRI pavers lowered electricity consumption.
Create a Sustainable Solutions
Though development has a deleterious effect on the hydrologic cycle, creating low impact development scenarios and best management practices can mitigate impacts. As an engineered ecological system that captures, treats, and stores stormwater, PICP plays a major part in the mitigation efforts, and has proven its ability to capture and treat first flush pollutants. Embraced as a first design strategy by engineers and design professionals, the full potential of permeable pavement systems in restoring a watershed’s hydrologic functions can be realized.
A special thanks to Oldcastle APG Masonry and Architectural Record for supplying us with this article.
