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 5
FISH CREEK TIPPLE
DIVERSION DITCH DESIGN CALCULATIONS (Continued)
Ditch E-4
Tributary area = 12.6 ac. watershed
Weighted CN = 70
Total runoff @ CN(70) = 0.17 (in)/12 (in/ft) x 12.6 (ac.) = 0.18 ac -ft
Peak flow (steep slope) 17.7 (cfs/in. runoff) x 0.17 (in. runoff)
= 1.6 cfs uncorrected
Basin slope factor (actual slope 26'0 = 1.07
Basin shape factor (hydraulic length 760 ft., equivalent area 8.5 ac.)
= 12.6/8.5 = 1.48
Corrected peak flow = 3.0 cfs x 1.07 x 1.48 = 4.75 cfs
Design: trapezoidal ditch, 1.5 ft. deep, bottom width = 1.0 ft.,
side slopes = 2:1, gradient = 0.04 ft/ft, n = 0.03
Flow conditions: depth = 0.5 ft., velocity = 4.6 fps, area
= 1.04 sq. ft.
Check calculation: Q = VA = 4.6 x 1.04 = 4.78 cfs
Ditch F-1
Tributary area = 140 ac. undisturbed
Weighted CN = 70
Total runoff @ CN(70) = 0.17 (in) / 12 (in/ft) x 140 (ac.) = 1.98 ac -ft
Peak flow (steep slope) 225 (cfs/in. runoff) x 0.17 (in. runoff)
= 38.3 cfs uncorrected
Basin slope factor (actual slope 1001:) = 0.853
Basin shape factor (hydraulic length 3,550 ft., equivalent area 115 ac.)
= 140/115 = 1.217
Corrected peak flow = 38.3 cfs x 0.853 x 1.217 = 39.8 cfs
Design: trapezoidal ditch, 3.0 ft. deep, bottom: width = 2.0 ft.,
side slope = 2:1, gradient = 0.005 ft/ft, n = 0.03
Flow conditions: depth = 1.90 ft., velocity = 3.62 fps, area
= 10.98 sq. ft.
Check calculation: Q = VA = 3.62 x 10.98 = 39.75 cfs
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