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The curve number (CN) of an area indicates the runoff poterl- <br />tial of the area. Table 2.20 gives the CN's for various land use and <br />Table 2.20 Runoff Curve Numbers for Selected Agricultural, Suburban, and Urban <br />Land Use. (Antecedent Moisture Condition In• <br /> a7pa0u101C sou. OEM <br />I= 114 MCarPfl0s A H c D <br />Cultivated 3wnclit vitbout conservation treatment T2 81 8a 91 <br />: with conservation treatment 62 T1 TH 81 <br />Pasture or range land: poor condition 68 T9 as 89 <br />good condition 39 61 Th 80 <br />IDaadovr good condition 30 58 71 T8 <br />Wood or Forest land: thin stand. poor cover. an -1. b 45 66 T7 83 <br />good eoverE/ 25 55 TO TT <br />Open spates. loans, parks. golf courses, eamteriss, att. <br />good condition: grew cover on 75% or morn of the aav a 39 61 Th 80 <br />fair mndttion: grass sov.r on 50% to 75% of the area h9 69 T9 ah <br />Con-lal and busineea anew (85% impervious) 09 92 9h 95 <br />Indtetrial districts (r2% impervious)- 81 as 91 93 <br />awideatial:l/ <br />Average lot size Average % Imperviowl/ <br />1/8 scro or law 65 TT a5 90 92 <br />1/4 acre 35 61 TS 83 87 <br />1/3 acre 30 5T T2 81 86 <br />1/2 acre 25 54 To so 85 <br />1 am :.20 51 68 T9 ah <br />paved parting lots, roofs. drivanra, ato.v 98 98 99 9H <br />street. and and.: <br />aved with curbs and storm see-ell 98 98 9H 98 <br />p <br />gravel 76 85 89 91 <br />dirt T2 a2 8T 89 <br />refer to <br />It wre detailed section h?t Hydrology, chapter . Aug. 19T2. <br />National Engineering <br />E/ good cover is protected from grazing and litter and brush cover sail. <br />Pave nvemers an computed --d- the runoff from the hooza and drivem <br />is directed swards the strut with a ainin m of roof water directed to ]mras <br />share additional infiltration could oaMS. <br />the remaining pervious drew (lawn) are considered to be In good pasture condition <br />for the... - n-tars. <br />it In a= varme, climates of tb. ccuntr7 a curve number of 95 may be used. <br />Table 7 Scanned image of Table 2.20 from "Applied Hydrology and Sedimentology for Disturbed <br />Areas", Barfield, B.J., Warner, R. C., and Haan, C. T., Oklahoma Technical Press, Fourth <br />Printing, 1987. <br />Exhibit 7 Page 10 Revision Date: 6/19/09 <br />Revision No.: TR-73