2009-06-23_PERMIT FILE - C1981019A

• Permit No: C1981019A
• IBM Index Class Name: Permit File
• Doc Date: 6/23/2009
• Section_Exhibit Name: Exhibit 07 Methodologies & Assumptions for Sedimentation Pond Design Evaluations
• Media Type: D
• Archive: Yes

Table 8 Curve Numbers Provided in the SEDCAD model (from National Engineering
Handbook (NEH-4) (USDA-SCS, 1 985), Continued
Runoff Curve Numbers for Cultivated Agricultural Land'
Cover Type Treatment' Hydrologic A B C D
Cond ition3
Fallow Bare soil 77 86 91 94
Crop residue Poor 76 85 90 93
cover (CR) Good 74 83 88 90
Row Crops Straight row (S R) Poor 72 81 88 91
Good 67 78 85 89
SR+CR Poor 71 80 87 90
Good 64 75 82 85
Contoured (C) Poor 70 79 84 88
Good 65 75 82 86
C + CR Poor 69 78 83 87
Good 64 74 81 85
Contoured & terraced (C&T) Poor 66 74 80 82
Good 62 71 78 81
C&T + CR Poor 65 73 79 81
Good 61 70 77 80
Small grain SR Poor 65 76 84 88
Good 63 75 83 87
SR + CR Poor 64 75 83 86
Good 60 72 80 84
C Poor 63 74 82 85
Good 61 73 81 84
C + CR Poor 62 73 81 84
Good 60 72 80 83
C&T Poor 61 72 79 82
Good 59 70 78 81
C&T + C R Poor 60 71 78 81
Good 58 69 77 80
Close-seeded SR Poor 66 77 85 89
or broadcast Good 58 72 81 85
Legumes or C Poor 64 75 83 85
Rotation Good 55 69 78 83
Meadow C&T Poor 63 73 80 83
Good 51 67 76 80
Notes. ' Values are for average runoff condition, and 1, = 0.2S.
' Crop residue cover applies only if residue is on at least 5 percent of the surface throughout the year.
3 Hydrologic condition is based on a combination of factors affecting infiltration and runoff: density
and canopy of vegetative areas, amount of year-round cover, amount of grass or closed-seeded l egumes
in rotations, percent of residue cover on land surface (good > 20 percent), and degree of roughness.
Poor. Factors impair infiltration and tend to increase runoff.
Good. Factors encourage average and better infiltration and tend to decrease ru noff.
Exhibit 7 Page 12 Revision Date: 6/19/09
Revision No.: TR-73