2011-11-30_PERMIT FILE - C1981008 ‎(2)‎

• Permit No: C1981008
• IBM Index Class Name: Permit File
• Doc Date: 11/30/2011
• Doc Name: Pond 013 As Built Sedcad & SurvCad Hydrology Calculations for 10yr-24hr & 25yr-24hr Events
• Section_Exhibit Name: Section 2.05.3‎(3)‎ Attachment 2.05.3‎(3)‎-21
• Media Type: D
• Archive: No

TOW 3.16 Runoff Curve Numbers for Selected Land Uses (Soil Conservation Service, 1986) t
Hydrologic soil group
Land use description
A
B
C
D
Cultivated land'
Without conservation treatment
72
81
88
91
With conservation treatment
62
71
78
81
Pasture or range land
Poor condition
68
79
86
89
Good condition
39
61
74
8o
Meadow
Good condition
30
58
71
78
Wood or forest land
Thin stand, poor cover, no mulch
45
66
77
83
Good covert
25
55
70
77
Open Spacer, lawns, parks, golf courses, cemeteries, etc.
Good condition (grass cover on 75% or more of the area)
39
61
74
80
Fair condition (grass cover on 50 to 75% of the area)
49
69
79
84
Commercial and business areas (85% impervious)
89
92
94
95
Industrial districts (72% impervious)
81
88
91
93
Resideruiar
Average lot size Average percentage imperviousd
acre or ku 65
77
85
90
92
acre 38
61
75
83
87
( acre 30
57
72
81
86
} acre 25
54
70
80
85
1 acre 20
51
68
79
84
Paved parking lots, roofs, driveways, etc.'
98
98
98
98
Streets and roads
Paved with curbs and storm sewers'
98
98
98
98
Gravel
76
85
89
91
Dirt
72
82
87
89
"For a more detailed description of agricultural and land use curve numbers refer to "National
Engineering Handbook;' Sect. 4, "Hydrology" Chap. 9, 1972.
°Good cover is protected from grazing, litter, and brush cover soil.
Curve number are computed assuming the runoff from the house and driveway is directed toward the
street with a minimum of roof water directed to lawns where additional infiltrations could occur.
*lie remaining pervious areas (lawn) are considered to be in good pasture condition for these curve
numbers.
M some wanner climates of the country a curve number of 95 may be used.
Attachment 2.05.3(3) -21 -39