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TABLE 5-5 RUNOFF CURYE NUMBERS FOR HYOROLOGIC SOIL-COYER COMPLEXES uRBAN ANO SUBURBAN CONDITIONS II (For Antecedent Moisture Condition Il) (From: U.S. Department of Agriculture, Soil Conservation Service, 1977) Land Use Open spaces, lawns, parks, golf courses, cemeteries, etc. Good condition: grass cover on 75% or more of the area Fair cond iton: grass cover on 50% to 75% of the area Corrmercial and business areas (85% impervious) Industrial districts 72% impervious) Residential:Y Acres per Dwelling Unit 1/8 acre or less 1/4 acre 1/3 acre 1/2 acre 1 ac re Average % imperviou~~/ 65 38 30 ;15 ;10 Paved parking lots, roofs, driveways, etc. Streets and roads: paved with curbs and storm sewers gravel dirt NOTE: THIS TABLE TO 'BrUSED FOR 24..HOUR STORM ONLY. Hydrologic Soi l_GrOL~. ABC 0 39* 61 711 80 49* 69 92 88 79 84 95 93 89* 94 91 81* 77* 85 90 92 61* 75 83 137 57* 72 81 86 54* 70 80 135 51* 68 79 134 98 98 98 98 98 98 98 98 76* 85 89 91 72* 82 87 89 .Y For a more detailed description of agricultural land use curve numbers, refer to in the National Engineering H,~ndbook (U.S. Dept. of Agriculture, Soil Conservation Service, 1972). ?:l Curve numbers are computed assuming the runof~ from the house and driveway is directed towards the street with a minimum of roof water d'irected to lawns where additional infiltration could occur. 3L The remaining pervious areas (lawn) are considered to be in good pasture condition for these curve numbers. * Not to be used wherever over lot grad i ng or fill i ng is to occur. Ii ~, 5-29 ",",~__c:..v.,. .