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— _ <br /> 08L <br /> An area of . 112 of the site will be impervious. This amount <br /> falls below the alloted 122 maximum allowable impervious ratio <br /> for R-1 with public water/sewer unavailable, (Pg. 19, Table B of <br /> the Subdivision Regual.tions Amendment) . <br /> _:S <br /> In addition to the relatively low ratio of impervious material to <br /> vegetation on this site, it must be noted that the natural <br /> terrain of this site, along with swales, will allow all of the <br /> runoff to either pass through natural vegetation or be detained <br /> in erosion control devices. <br /> The stormwater runoff from the roads will be carried by means of <br /> a grassed swale. The grassed swale will slow the runoff down and <br /> allow some pollutants to settle within the swale. - <br /> Runoff from a 5.42 acre area located near the center of the site <br /> and South of Highland Dr. will be draining across a naturally <br /> vegetated area in a. northly direction to the south side of <br /> Highland Drive, and along the south side of Highland Drive <br /> through a grass swain to an 24" RCP at which point: <br /> Q = CIA <br /> A = 5.42 Acres Q = 21.3 CFS <br /> 1 = 6.-V <br /> C = 0.6 <br /> Velocity dissapator needed at outlet of pipe is 10 ft. X 6 ft. s <br /> 4.5 sq.., yards of Class 1 Riprap. <br /> The stormwater runoff from Highland Dr. flowing Easterly will be <br /> passing through grassed swales along the road. The grass swains <br /> will slow the runoff allowing some pollutants to settle within <br /> the swales. The runoff flowing in the direction of Terry Rd. <br /> - along Highland Dr. flowing westerly will also be passing through <br /> grassed swains, allowing pollutants. to be filtered out. At the <br /> 1 -• point where Highland Dr. intersects with Terry Road, the grade is <br /> almost flat; therefore, any stormwater runoff would be easily <br /> disbursed by the 18" min. pipe required by NC DOT at driveway <br /> turnouts. <br />