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Hardscapes (Continued from page 14) 0!6%23s-!3/.29s",/#+3s2/#+3 Above, Right: This detail illustrates a common design for permeable pavers and the sub-base beneath them. The open graded aggregate receives, stores and infiltrates runoff before releasing it into the subgrade soil. Above, Left: Permeable pavers can reduce job costs by eliminating the need for other stormwater management systems, like swales and retention ponds. Left: Pavestone's Eco-Priora™ permeable pavers (pictured) meet or exceed ASTM C-936 requirements, with a compressive strength greater than 8,000 psi and a water absorption maximum of 5 percent. There are no structural load-bearing reductions using PICP, and the product does not need any time to cure at the job site. Bottom, Left: Research on permeable pavers has shown substantial reductions in total suspended solids (TSS), nutrients, metals, and can reduce surface runoff temperatures by four to six degrees compared to asphalt. compressed into a paver mold. A press is inserted into the concrete-filled mold and vibrated to cre- ate a strong bind between the aggregate particles and cement. These solid, high-strength concrete units support vehicle traffic, and are surrounded by small, highly permeable stone-filled joints that infiltrate stormwater. The angular aggregate in the joints also contributes to load transfer and inter- lock between units. PICP is produced in a variety of shapes and sizes, and generally have joints that vary between 3/16 and 1/2 inches. The joints should be filled with small-sized aggregate (ASTM No. 8, 9, or 89 stone) that provide high surface infiltration rates. Some sites have initial infiltration tests exceeding 500 inches-per-hour, well above the most intense of rainfalls, equaling or exceeding other perme- able surfaces. Meet Low Impact Development Objectives with PICP Low Impact Developments (LIDs) work within nature to manage stormwater as close to its source as possible. LID goals include preserving natural landscape features, minimizing effective imper- viousness, and creating functional and appealing site drainage that treats stormwater as a resource rather than a waste product. Permeable pavement has become an inte- gral component of LID design and regulations. Through low impact principles, water can be managed in a way that reduces the effect of built areas and promotes the natural movement of wa- 16 LC DBM ter within a watershed. LID has been characterized as a sustainable stormwater practice by the Water Environment Research Foundation and is increas- ingly being added to state and municipal storm- water design manuals. PICP Advantages In many cases, permeable pavers can eliminate runoff completely and prevent or greatly reduce any opportunity for pollutants to contaminate waterways. Permeable pavements rely on the abil- ity of open graded aggregate in their surfaces and base to receive, store and infiltrate runoff back into the subgrade soil. By capturing stormwater and al- lowing it to seep into the ground, PICP is instru- mental in recharging groundwater and reducing damage from runoff. In fact, by eliminating the need for other stormwater management devices, PICP gives contractors the ability to lower overall project costs on a first-cost basis. The EPA and many environmental manage- ment agencies recognize permeable pavements as a best management practice (BMP) for sustainable construction. As authorized by the Clean Water Act, the National Pollutant Discharge Elimination System also recognizes the use of permeable pave- ment as a BMP for stormwater control. Addition- ally, rating systems for sustainable construction such as Leadership in Energy and Environmental Design (LEED®) and Green Globes offer credit to site designs that use permeable pavement. For more PICP information, visit www.icpi.org/permeable. LC DBM