2018-08-08_PERMIT FILE - C1982056 ‎(17)‎

• Permit No: C1982056
• IBM Index Class Name: Permit File
• Doc Date: 8/8/2018
• Section_Exhibit Name: EXHIBIT 08 TAB 1 SEDIMENT CONTROL PLAN
• Media Type: D
• Archive: No

REVISED
7/30/85
Table 2
SEDIMENTATION POND E DESIGN CALCULATIONS
WEIGHTED CURVE NUMBER: (AMC II)
Total Drainage area is 35 ac.
24 ac. roads & parking area - CN 87
11 ac. contoured range land - CN 70
Weighted CN = (87 x 24) + (70 x 11) = 82
35
DESIGN CRITERIA:
- 35 ac watershed area
- 24 ac disturbance
- AMC II Curve No. 82
- 10 -yr, 24 -hr design event of 1.8" rainfall
SEDIMENT VOLUME:
Total Runoff (Q): 10 -yr, 24 -hr precipitation event = 1.8 in.
1.8 in. rainfall @ curve number (82) = 0.52 in. runoff
0.52 (in) / 12(in/ft) x 35 ac. = 1.53 ac -ft
Peak Flow (gp): Type II storm, western Colorado, moderate slope, curve
number (82) = 32 cfs/in. runoff; 32 cfs/in. runoff x 0.52 in. runoff
= 16.6 cfs uncorrected
Basin Slope Factor (actual slope 60-) = 1.11
Basin Shape Factor (hydraulic length = 1,750 ft., equivalent area - 36.5
ac) 35/36.5 = 0.96
Corrected Peak Flow = 16.6 cfs x 1.11 x 0.96 = 17.7 cfs
Soil Erodibility Factor (K): Winnevada-splitro series = 0.2 (SCS)
Length -Slope Factor (LS):
LS = (L/72.6) '(430x2 + 30 x + 0.43) / 6.613)
= (1,750/72.6) 0'5((430(.06)2 + 30 (.06) + 0.43)/6.613)
= 2.80
Crop Management Factor (c): 1.0
Support Practice Factor (P): 1.0
10