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� Willows Aparunents <br /> Drainage Study <br /> � 09/16/2009 <br /> gI'I'E HYDRAULIC ANALYSIS (cant) <br /> 1 WATER QUALITY DESIGN CRITERIA <br /> � For a commercial with less than 10,000 SF of pmposed pavement, the City of Everett <br /> Water Quality BMP will be satisfied with a simple Storn►Filter solution. In ihis case, <br /> � The small amowt of potential polluting surface can easily be filtered with a Cartridge <br /> Storm Filter by Contec. The Stonn Filtet will catch the surface flows upstream of <br /> detention with the filter media most suited to the pazking lot conditions.Non-polluting <br /> roof drains will be diverted directly into detention,bypassing ihe filter and leaving the <br /> t, filter capacity for the polluting surfaces. <br /> Polluting Surfaces: Pazking Stalis&Driving Surface= 3,436 SF=0.079 AC <br /> � TABLE 2 <br /> � EXISTING PEAK STORM FLOWS FROM <br /> DEVELOPED PARKING TO <br /> � STORM FILTER AFTER DETENTION <br /> Event Existin¢Od(CFS) Desi¢n(CFS) <br /> � 1 0.016 480 255 CF 0.08 6-month(7.18 GPIv� <br /> 2 0.023 480 367 CF 0.08 2-yeaz(10.32 GPM) <br /> 3 0.035 480 56ti CF 0.08 10-yeaz <br /> 4 0.052 480 851 CF 0.08 100-y'eat <br /> �_ <br /> According to a Contec Mass Loading calculation, a CB aiagle storm filter <br /> ( cartridge manhole with a i cartridge (treating 7.5 gpm) will provided water <br /> quality improvement to the project and will comply with DOE reguladons. It is <br /> � anticipated that oil, grease and silt will be the primary tatgets az►d that the media <br /> will be Perlite. <br /> I_ <br /> 1. <br /> I <br /> ' <br /> I <br /> 9 PP olECT95112 <br /> � <br />