2013-04-25_PERMIT FILE - C1981019A

• Permit No: C1981019A
• IBM Index Class Name: Permit File
• Doc Date: 4/25/2013
• 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, 1985), Continued
Runoff Curve Numbers for Other Aaricultural Lands
Cover Type Hydrologic Condition A B C
D
Pasture, grassland, or range - continuous Poor 68 79 86
89
forage for grazing Fair 49 69 79
84
Good 39 61 74
80
Meadow — continuous grass, protected from 30 58 71
78
grazing and generally mowed for ha
Brush — brush- weed -grass mixture, with Poor 48 67 77
83
brush the major element Fair 35 56 70
77
Good 30 48 65
73
Woods — grass combination (orchard or tree Poor 57 73 82
86
farm) Fair 43 65 76
82
Good 32 58 72
79
Woods Poor 45 66 77
83
Fair 36 60 73
79
Good 30 55 70
77
Farmsteads — buildings, lanes, driveways, 59 74 82
86
and surrounding lots
Notes: Values are for average runoff condition, and la = 0.2S.
Pasture: Poor is < 50% ground cover or heavily grazed with no mulch, Fair is 50% to 75%
ground cover and not heavily grazed, and Good is >75% ground cover and lightly or only
occasionally grazed.
Meadow: Poor is <50% ground cover, Fair is 50% to 75% ground cover, Good is >75%
ground cover.
Woods/grass: RCNs shown were computed for areas with 50 percent grass (pasture) cover.
Other combinations of conditions may be computed from RCNs for woods and pasture.
Woods: Poor is forest I fitter, small trees, and brush destroyed by heavy grazing or regular
burning. Fair is woods grazed but not burned and with some forest litter covering the soil.
Good is woods protected from grazing and with litter and brush adequately covering soil.
Exhibit 7 Page 14 Revision Date: 3/18/13
Revision No.: TR -95