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<br />Table 4.4.1.3-3 <br /> <br />R1..~off Curve Numbers <br />for Hydro10"ic SOU-C(cverC~'mple}es <br />Urban and Suburban ConditionslT <br />(From: U. S. Dept~:-of Agricc;ltllre, <br />Soil Conservation Service, 197/) <br /> <br />Land Use <br /> <br />Hydro~~ic So:~J Group <br />ABC D <br /> <br />Open spaces, lai-.rns, parks, golf courses, <br />cemeteries, etc. <br /> <br />Good condition: grass cover on 7.5% or <br />more of the area <br /> <br />Fair condition: grass cover on 50% to <br />75% of the area <br /> <br />Commercial and business areas (85% imlervious) <br /> <br />Industrial districts (72% impervious) <br />Residential:],.! <br /> <br />Average lot size <br /> <br />1/8 acre or less <br /> <br />1/4 acre <br /> <br /> <br />1/3 acre <br /> <br /> <br />1/2 acre <br /> <br /> <br />1 acre <br /> <br />Average % imperviousll <br /> <br />65 <br />38 <br />30 <br />25 <br />20 <br /> <br />Paved parking lots, roofs, driveways, etc. <br /> <br />Streets and roads: <br />paved with curbs and storm sewers <br />grave 1 <br />dirt <br /> <br />;19 <br /> <br />49 <br /> <br />89 <br /> <br />81 <br /> <br />77 <br />61 <br /> <br />57 <br />54 <br /> <br />51 <br /> <br />98 <br /> <br />98 <br />76 <br />72 <br /> <br />61 <br /> <br />69 <br /> <br />92 <br /> <br />88 <br /> <br />85 <br />75 <br /> <br />72 <br /> <br />70 <br />68 <br /> <br />98 <br /> <br />98 <br />85 <br />82 <br /> <br />71, <br /> <br />80 <br /> <br />79 <br /> <br />84 <br /> <br />91, <br /> <br />95 <br /> <br />91 <br /> <br />93 <br /> <br />90 <br />83 <br /> <br />81 <br /> <br />80 <br /> <br />79 <br /> <br />92 <br />87 <br /> <br />86 <br /> <br />85 <br /> <br />84 <br /> <br />98 <br /> <br />98 <br /> <br />98 <br />89 <br />87 <br /> <br />98 <br />91 <br />89 <br /> <br />'!/For a more detailed description of agricultural land use curve <br />numbers, refer to in the National Engineering. Handbook (U. S. <br />Dept. of Agriculture, Soil Conservation Service, 1972). ~ <br /> <br />2:..1 Curve numbers are computed ass\l",ing the runoff from the house and <br />driveway is directed towards thE' st:.eet with a minimum of roof water <br />directed to lawns where additional infiltration could occur. <br /> <br />11 The rem..ining pervious areas (la\ol11) are considEred to be in good <br />pasture condition for these curve numbers. <br /> <br />LCS-;.'M Manual <br /> <br />1,.4--.,10 <br /> <br />April 1979 <br />