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Lord Electric Company, Inc. <br />STORM WATER STORAGE CALCULATIONS <br />1. Runoff Coefficient <br />Existing site: <br />Wooded >5% 76,050 X .10 = 7605 <br />Light crass >5% 159000 X .20 =_3000 <br />Totals: 91,050 10,605 <br />C(exist)= 10,605/91,050= 0.116 <br />Developed Sites <br />Pavement & roofs <br />Parking lot 109240 <br />Warehouse 12,000 <br />Office bldg 4,800 <br />Driveway 1,500 <br />total: 28,540 X .90= 25.686 <br />Gravel yard 39,336 X .75= 29,502 <br />Landscaping 239174 X .20= 4,365 <br />Totals: 91.050 59.823 <br />C(dev)= 59,823/91,050= 0.657 <br />2. Time of Concentration <br />Assume average site drop of 4 feet over 220 feet, or l8%. <br />From Figure 1 the overland velocity is 1.2 feet per second. <br />Therefore: T(c)= (220/(1.2 X 6)) + 10 <br />T(c)= 13.05 minutes <br />3. Rainfall Intensity <br />Assume a 10 year frequent, storm. <br />From Figure 2: <br />i= 1.6 inches per hour. <br />