2009-10-16_PERMIT FILE - M2009082 ‎(13)‎

• Permit No: M2009082
• IBM Index Class Name: PERMIT FILE
• Doc Date: 10/16/2009
• Doc Name: Attachment G-4, Preliminary Drainage Report
• From: Lafarge West, Inc.
• To: DRMS
• Media Type: D
• Archive: No

Parsons Mine - Lafarge West, Inc
Preliminary Drainage" Report
Peak Runoff Calculations Using the Rational Method
Basin: H6 Condition: Existing Storm Return Period:
E
Area, A: 56.8 acres
Distance of Overland Flow, L, 1,764 ft
Distance of Channelized Flow, L,,: 1,055 ft
Average Basin Slope, S: 0.00496 'ftfft
Slope of Channelized Flow, Sw: 0.00025 ft/ft

Runoff Coefficient Equations
CA=KA + (1.31 i3 - 1.44i2 + 1.1351- 0.12) for CA a 0 else CA.= 0
Cco Kco + (0.8581 - 0.786i2 + 0174i + 0.04)
CB-(CA + Cco) / 2
Basin Imperviousness' (in percent), is 0.0%
Hydrologic Soils Group A Percent of Basin:' 24.8%
Hydrologic Soils Group B Percent of Basin: 64.71/o
Hydrologic Soils Groups C & D Percent of Basin: 10 5%
Conveyance;Coefficiene, C,: 15
iff Coefficient
For 100-yr Storm Return Period- KA = -0.25i + 0.32
K co = -0:39/ + 0.46
For 10-yr Storm,Retum'Pedod. KA =-0.14i + 0.17
Kcj) _-0.181+0.21
For 5-yr Storm Return Period: KA = -0.08i + 0.09
K --0<10'+01
Return Period C-mpos„ e CA Cs Cco KA KCD
5-Year 0.064 0.000 0.075 0.150 0.090 0.110
10-Year 0.136 0.050 0.150 0.250 0.170 0.210
100-Year 0.329 0.200 0.350 0.500 0.320 0.460
CD - ! 1
Time of Concentration Rainfall Intensity
Total time of concentration equation: Rainfall Intensity Equation:
Lesser oe: t ,=y + tt I=(28:5 ' P,,) / (10 + T.)0'86 where Pit, Is.the.1 hr-point rainfall depth
or t?=L 1180 +10 (if in urban area) `
Overland flow travel time equation: llc= 1'73 min
t-(0.395 •,(1.1 - Cs) . sgrt(L,)) / SO-" t= 99 min
Channelized flow travel flme equation- ti 74 min
t,=L? / (V ` 60) where V= (C„ - Stye) V= 0.237 ft/s
Pty
Return Period in in hr
5-Year 1.49 0.71
10-Year 1.76 0,84
100-Year 2.78 1.32
Peak Flow Rate:"
Rational Method Equation
Return
Period CCO„1e " i .
in / hr A
acres Q
CfS
5-Year 0.064 0.71 56.8 2.6
10-Year 0.136 0.84 56.8 6.4
100=Year 0.329 1.32 56.8 24.7
Notes:
1: Basin imperviousness determined from guidelines in UDFCD Drainage Criteria Manual Table RO-3
2: Conveyance coefficient determined from guidelines in UDFCD Drainage Criteria Manual Table RO-2
3: Minimum tc is 10 min. for non-urban areas ands min, for urban areas Date: 9/17/2009