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Better Site Desiqn Table 8.1: Perceived Impedimen'!:s To Reduced PaJddi1Jg lo'!: Im~eMOi.llSi"ieSs Perception Facts, Case S'i:l!.lclies, aJli"illO'J (!1Ja[[elriges 1. Existing stall sizes are CHALLENGE: There is an increasing trend towards larger sport utility vehicles already too small for the (SUVs). largest cars. FACT: Many SUVs are actually small cars (e.g., Jeep Wranglers, Suzuki Sidekick, Toyota Rav4). FACT: Stall width requirements in most local parking codes are much Larger than the widest SUVs.1 2. Alternative paVlng is FACT: Yes, but long term costs savings may be achieved. Less expensive. imperviousness may reduce the need for stormwater management or eliminate the need for curb and gutter. 3. Alternative paving may not FACT: Alternative paving materials that do not conflict with the ADA are comply with ADA. available. FACT: Alternative paving is recommended for spillover parking only. ADA compliant parking spaces typically will be placed near the building in the permanent parking area paved with traditional materials. 4. Alternative p a Vl n 9 CHALLENGE: The performance of alternative pavements (other than porous performance is uncertain. pavement) is not well documented. lOne of the largest SUVs, the Ford Expedition, is 6'7" wide; most local codes set parking stall width as high as 9.5' Site Conditions The most successful installations of alternative pavements are found in coastal aJreas where slopes are fI.at, sandy soils are present, and winter sanding and salting are minimal (BASMAA, 1997). However, in coastal areas with very coarse sands, infiltration through the pavement may be too rapid to allow adequate water quality treatment. In these cases, the pavement may need to be augmented with a peat liner to enhance water quality treatment (Cahill, 1994). On the other hand, pervious pavement will not work if existing soil conditions do not allow for minimum necessary rates of infiltration (0.5 inches per hour or more). Pervious pavement has been successfully applied in cold climates but is only recommended for spillover parking. In addition, sand causes dogging and should be completely eliminated as a method for handling snow or ice. Performance The performance of alternative paving materials is dependent upon proper installation and maintenance. For example, tests by the Florida Concrete and Products Association show the permeability of new pervioQJs concrete surfaces as high as 56'!/hr with proper installation. With improper installation, permeability is reduced to 12"/hr (BASMAA, 1997). Some ,common causes of pavement failure include: o Lack of erosion and sediment control during construction; e Compaction of the subsoils during construction; o Clogging due to sand used to deice in the winter; '- ,j - 76 - ----