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Table 1-5.6 SCS Runoff Curve Numbers <br /> LAND USE DESCRIPTION CURVE NUMBERS BY <br /> HYDROLOGIC SOIL GROUP <br /> A B CD <br /> Cultivated Land winter condition 86 91 94 95 <br /> Mountain open area low growing brush&grasslands 74 82 89 92 <br /> Meadow or pasture 65 78 85 89 <br /> Wood or forest land undisturbed 42 64 76 81 <br /> young second growth or brush 55 72 81 86 <br /> Orchard with cover crop 81 88 92 94 <br /> Open spaces(lawns,parks, <br /> golf courses,landscaping,etc.) <br /> Good condition grass cover on>75%of area 68 80 Lti 90 <br /> Fair condition grass cover on 50-75%of area 77 85 90 92 <br /> Gravel roads and parking lots 76 85 89 91 <br /> Dirt roads and parking lots 72 82 87 89 <br /> Impervious surfaces pavement,roofs,etc. 98 98 ;1 98 <br /> Open water bodies lakes,wetlands,ponds,etc. 100 100 100 100 <br /> Single family residential(1) <br /> Dwelling Unit/Gross Acre %Impervious <br /> 1.0 15 Separate curve <br /> 1.5 20 numbers must <br /> 2.0 25 be selected for <br /> 2.5 30 pervious and <br /> 3.0 34 impervious <br /> 3.5 38 portions of the <br /> 4.0 42 site or basin <br /> 4.5 46 <br /> 5.0 48 <br /> 5.5 50 <br /> 6.0 52 <br /> 6.5 54 <br /> 7.0 56 <br /> PRD's,multi-family, <br /> commercial,industrial - <br /> (1) The%impervious values assume that roof and driveway runoff is directed into the street/storm system <br /> 1-5-33 <br />