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MURPHY BUILDING COMPANY <br />3426 Oakes Street <br />City of Everett <br />Storm Drainaie Calculations <br />Total parcel size: 6,000 S.F. 0.14 Acres <br />Existing Ground Cover: <br />Light ground cover over 85% of the area. Homes, shops and sidewalks occupy the <br />remaining 15:0. Existing ground slope =5% <br />Proposed Ground Cover: <br />Landscaping areas of 25% of the parcel with parking and apartments to be constructed <br />over the remaining 75%. Propose ground slope - 5% <br />Parcel is within the "combined sewer outside downtown" design basin <br />. calculations are for design storm as follows: (See Table 1) <br />Pre -development 10 year <br />Post -development 10 year <br />Pre -Development Calculations: <br />Impervious area = 0.140 acres x .15 = 0.020 Ac <br />Peak runoff (See Table 5) = 1.40 cfs/Ac <br />Peak rate of runoff = 0.020 x 1.40 = 0.028 cfs <br />Landscaped area = 0.14 Ac x 0.85 = 0.120 Ac <br />Peak runoff (see Table 3) = 0.41 cfs/Ac <br />Peak rate of runoff = 0.12 x 0.41 = 0.049 cfs <br />Total Pre -development Peak Rate of Runoff <br />0.028 cfs + 0.049 cfs = 0.077 cfs <br />