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Navajo Elementary Navajo Elementary BEFORE Top, Left: The contractor chose Grasscrete as the product to meet their needs, due to the historically poor performance of traditional no-fines or pervious concrete in the region. Bottom, Left: The original parking lot at the Navajo Elementary school flooded fairly regularly, with up to six inches of standing water present for extended periods of time. Bottom, Middle: The company installed more than 472 square feet of Xeripave for this installation. Right: Beneath the pavers, workers laid in a ¼-inch layer of compacted rock. The pavers were then laid and secured in place. St. Paul's Church Navajo Elementary Green Pervious Systems This Green Pervious Systems project solved a major flooding problem for Navajo Elementary in Albuquerque, New Mexico (see photos above). Us- ing more than 62,000 square feet of Void Structured Concrete, this project is an example of a parking lot application requiring a pervious concrete sur- face that could with stand the New Mexico climate, while dealing with exceptional water volume and providing the necessary structural capacity. The Navajo Elementary School is located on a flood plain just west of the Rio Grande not far from downtown Albuquerque. The area is subject to periodic flooding due to a combination of its topography, localized heavy rain and poor draining soils. The utilization of storm- water retention chambers under 20,000 square feet of the lot, combined with the clear stone bed, achieved the necessary capacity to handle the heavy rains. With a conventional stone filled void Grasscrete application capable of storing three inches of rain, this revised system was capable of several times this volume. This not only solved the parking lot 26 LC DBM St. Paul's Church flooding problem but gained additional capacity to pump water from areas surrounding the school when required. The school and the parking lot were renovated at the same time, so construction vehicles such as large delivery trucks, forklifts and waste disposal trucks had to gain access to the parking lot shortly after placement. This was achieved through the use of a concrete mix that had an average compressive strength of 4,200 PSI at seven days and an ultimate strength in excess of 6,000 PSI while still utilizing the desired 26-percent fly ash replacement of Portland cement. According to the contractor, "This type of com- posite system is both cost effective and practical, providing smooth, uninterrupted access where nec- essary, but still achieving the required amount of pervious surface." As the contractor stated, "Grasscrete offers sig- nificant structural advantages, including load bear- ing up to 40 tons gross vehicle weight, resists differ- ential settlement and purportedly reduces sub-base depths. It has been tested to flow rates in excess of eight meters per second." LC DBM