2014-04-22_REPORT - M1990057

• Permit No: M1990057
• IBM Index Class Name: REPORT
• Doc Date: 4/22/2014
• Doc Name: Drainage report
• From: Union Milling Company, LLC
• To: DRMS
• Email Name: TC1
• Media Type: D
• Archive: No

Chapter 2 Estimating Runoff Technical Release 56
Urban hydrology for Small Watersheds
Table 2 -2c Runoff curve numbers for other agricultural lands ]/
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Curve numbers for
Cover description
hydrologic
soil group
Hydrologic
Cover type
condition
A
B
C
D
Pasture, grassland, or range -- continuous
Poor
68
79
86
89
forage for grazing. v
Fair
49
69
79
84
Good
39
61
74
80
Meadow — continuous grass, protected from
—
30
8
71
78
grazing and generally mowed for hay.
Brush—brush-weed-grass mixture with brush
Poor
48
67
77
83
the major element. &
Fair
35
66
70
77
Good
301,
48
65
73
Woods —grass combination (orchard
Poor
57
73
82
86
or tree farm). V
Fair
43
66
76
82
Good
32
8
72
9
Woods. a'
Poor
45
66
77
83
Fair
36
60
73
79
Good
30!V
55
70
77
Farmsteads — buildings, lanes, driveways,
—
59
74
82
86
and surrounding lots.
1 Average runoff condition, and & = 0.2S.
8 Poor: <50%) ground cover or heavily grazed with no mulch
Fair. 50 to 7696 ground cover and not heavily grazed.
Good. > 7696 ground cover and lightly or only occasionally grazed.
a Poor. <50% ground cover.
Fair: 50 to 75% ground cover.
Good: >76% ground cover.
4 Actual curve number is less than 30; use CN = 30 for runoff computations.
a CN's shown were computed for areas with 50% woods and 60% grass (pasture) cover. Other combinations of conditions may be computed
from the CN's for woods and pasture.
e Poor. Forest litter, small trees, and brush are destroyed by heavy grazing or regular burning.
Fair. Woods are grazed but not burned, and some forest litter covers the soil.
Good: Woods are protected from grazing, and litter and brush adequately cover the soil.
(2IM- TR-66, Second Ed., June 1986) 2-7