2013-05-01_REVISION - M1978116 ‎(9)‎

• Permit No: M1978116
• IBM Index Class Name: REVISION
• Doc Date: 5/1/2013
• Doc Name: RESPONSE TO SECOND ADEQUACY REVIEW
• From: COTTER
• To: DRMS
• Type & Sequence: AM2
• Email Name: THM
• Email Name: TC1
• Email Name: GRM
• Media Type: D
• Archive: No

M
2 -5
_ Table 2- 2.-- Runoff curve numbers ror selected agricultural, suburban, and
urban land use. (Antecedent moisture condition II, and Ia = 0.25)
For a more detailed description or agrinatural ;and use carve numbers refer to
National EbSineering Handbook, Section 4, Hydrology, Chapter 9, Aug. 1972.
V Good cover is protected from grazing and litter and brush cover soil.
Oirve numbers are computed assuming the runoff from the house and drivewapr
is directed towards the street with a mining= of root vat--r directed to lwns
where additiaael infiltration could occur.
The relmH.ining pervious areas Us n) arc considered to be in good pasture condition
for these curve nambcra.
s( In some varmr climates of the country a curve comber or 95 mar yr. used.
HYDROLOGIC SOIL GROUP
LARD USX DESCRIPTION
A
B
C
I D
Cultivated landl /: without conservation treatment
T2
Bi
88
91
with conservation treatment
62
71
78
8a
Pasture or range land: poor condition
G8
79
86
89
good condition
39
61
741
80
14tadov: good condition
30
58
71
78
Wood or Forest fund: thin ato d, poor cover, no mulch
45
66
77
83
good cover?/
25
55
70
77
Open Spaces, lawns, parks, golf courses. cemeteries, etc.
good condition:-grass cover on 75% or more of the area
49
61
T4
80
fair condition: grass cover on 50% to 75% of tht area
49
69
T9
914
Commercial and business areas (85% imtperviou3)
89
92
94
95
Industrial districts (72% impervious).
81
88
91
93
Residential:;/
Average lot size Average % Impervious =/
1/8 acre or less 65
T7
85
90
92
1/4 acre 38
61
T5
83
87
1/3 acre 30
57
72
81
86
1/2 nave 25
54
70
80
85
1 acYe 20
51
68
79
84
Paved parking lots, roofs, drivevags, etc.s/
98
98
98
98
EtrcrOs and roads:
Paved with curbs and stozm severs/
98
98
98
98
gravel
76
85
89
91
dirt
72
82
87
89
For a more detailed description or agrinatural ;and use carve numbers refer to
National EbSineering Handbook, Section 4, Hydrology, Chapter 9, Aug. 1972.
V Good cover is protected from grazing and litter and brush cover soil.
Oirve numbers are computed assuming the runoff from the house and drivewapr
is directed towards the street with a mining= of root vat--r directed to lwns
where additiaael infiltration could occur.
The relmH.ining pervious areas Us n) arc considered to be in good pasture condition
for these curve nambcra.
s( In some varmr climates of the country a curve comber or 95 mar yr. used.