2015-09-09_PERMIT FILE - C1981019A ‎(16)‎

• Permit No: C1981019A
• IBM Index Class Name: Permit File
• Doc Date: 9/9/2015
• Section_Exhibit Name: Exhibit 07 Methodologies & Assumptions for Sedimentation Pond Design Evaluations
• Media Type: D
• Archive: Yes

The curve number (CN) of an area indicates the runoff poten-
tial of the area. Table 2.20 gives the CN's for various land use and
Table 2 20 Runoff Curve Numbers for Selected Agricultural, Suburban, and Urban
Land Use. (Antecedent Moisture Condition II).
i/ For s more detailed description'cf agricultural lend use curve number. refer to
Hetionel Engineering Handbook, Section 4, ltvdrology, Chapter 91 Aug. 1972,
3/ Good cover is protected from grazing and litter end brush cover soil.
3/ Curve numbers — computed g,noing the raaoff from the house and driveway
is directed tovards the street with • minia za of roof water directed to lawns
vhere additional infiltration Could occur.
Tae remsiaing pervious areas (lnvn) are considered tc be in good pasture condition
for the_. curve n Lers.
In some vernier climates of the country a curve nuobar or 95 nay be used.
Table 7 Scanned image of Table 2.20 from "Applied Hydrology and Sedimentology for Disturbed
Areas ", Barfield, B.J., Warner, R. C., and Haan, C. T., Oklahoma Technical Press, Fourth
Printing, 1987.
Exhibit 7 Page 11 Revision Date: 3/18/13
Revision No.: TR -95
HYDROLOGIC 60IL GROUP
LAND USE DESCRInIDN
A
B
C
D
Cultivated 1en411: vithout conservation treatment
72
81
68
91
. vith conservation treatment
62
T1
TS
81
pasture or range land, poor condition
68
T9
86
89
good condition
39
61
74
80
3C
56
71
78
Meadow. good condition
Mood or Forest land: thin stand, peor cow r, no mulch
45
66
T7
83
cover?/
25
55
TO
T7
goad
Open spaces, lawns, parka, golf courses, emeteriea, etc.
good condition: grass cover on 75% or, mar of the area
39
61
74
80
fair condition: grass cover on 50% to 75 %eof the area
4g
69
79
84
Commerei•1 and busimea. arena (85% Impervious)
89
92
94
95
Industrial districts (T2% impervious)-
81
88
91
93
Reaidenti•1: �/
Average lot size Average % Impervious!/
1/8 sere or 1— 65
T7
85
90
92
1/4 acre 38
61
75
83
87
113 sere 30
5T
72
61
86
112 acre 25
54
To
8o
85
20
51
68
79
84
1 acre
etc. -e/
98
98
98
98
Paved parking lots, roofs, driveway.,
streets and reeds:
severe:/
9B
98
98
98
paved vith curbs and storm
16
85
89
91
gravel
T2
82
67
89
dirt
i/ For s more detailed description'cf agricultural lend use curve number. refer to
Hetionel Engineering Handbook, Section 4, ltvdrology, Chapter 91 Aug. 1972,
3/ Good cover is protected from grazing and litter end brush cover soil.
3/ Curve numbers — computed g,noing the raaoff from the house and driveway
is directed tovards the street with • minia za of roof water directed to lawns
vhere additional infiltration Could occur.
Tae remsiaing pervious areas (lnvn) are considered tc be in good pasture condition
for the_. curve n Lers.
In some vernier climates of the country a curve nuobar or 95 nay be used.
Table 7 Scanned image of Table 2.20 from "Applied Hydrology and Sedimentology for Disturbed
Areas ", Barfield, B.J., Warner, R. C., and Haan, C. T., Oklahoma Technical Press, Fourth
Printing, 1987.
Exhibit 7 Page 11 Revision Date: 3/18/13
Revision No.: TR -95