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• <br /> Note: Prior to construction of Units 1-4,undeveloped site contained SFR(-1,610 sf.), gravel <br />• driveway(-2,825 sf.)pool (-313 sf.) and concrete patios (806 sf.). Only existing garage now <br /> remains. Total impervious area prior to duplex construction totaled approximately 6,192 sf. Due <br /> to removal of all existing impervious areas on-site,undeveloped site to be analyzed as forested. <br /> =>Undeveloped Impervious Area= 0 sf. <br />• Pervious Area: 20,059 sf. (total)—0 sf. (Imp.) =20,059 sf. (0.460 Ac.) <br /> DEVELOPED: <br /> Impervious Area(on-site): <br /> Unit 1/2 = 1,600 sf. <br />• Unit 3/4 = 1,600 sf. <br /> Unit 5/6 = 1,600 sf <br /> Unit 7/8 = 1,600 sf <br /> Drive Aisle Area = 5,397 sf. <br /> Covered Car Wash Area = 160 sf. <br />• Total = 11,957 sf. (0.274 Ac.) <br /> Note: Due to the roof drains for units 5-8 being designed with roof drains to splash blocks <br /> meeting minimum requirements of downspout dispersion BMP 12.50 (per section 12.3.5 of <br /> Volume III of the 2010 City of Everett Stormwater Design Manual) roof areas for units 5-8 to be <br />• analyzed as pervious lawn area for detention system sizing. <br /> Pervious Area(on-site): <br /> Area=20,059 sf. (total)—11,957 sf. (imp.) = 8,757 sf. (0.259 Ac.) <br />• <br /> Impervious Area(R/W): <br /> Drive Aisle Area = 130 sf. <br /> 5' S/W& Curb = 660 sf. <br /> New Asphalt Area = 812 sf. <br />• Total = 1,602 sf. (0.037 Ac.) <br /> Note: Frontage Improvements drain to different drainage basin than the on-site improvements. <br /> Drainage from the existing and developed frontage improvements will continue to drain to the <br /> north and then west into a neighboring stream and wetland system. <br />• <br />• <br /> E: /2011 / 111103A/Drainage Report.doc <br />• <br />