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: H8 Condition: Existing Storm Return Period:
Basin Chracteristics
Area, A: 84.8 acres Basin Imperviousness' (in percent), is 0.0°6 .
Distance of Overland Flow, L,: 3,944 ft Hydrologic Soils Group A Percent of Basin: 2.995
Distance of Channelized Flow, L,,: 0 ft Hydrologic Soils Group B Percent of Basin 84.5°%
Average Basin Slope, Si 0.01028 fGft Hydrologic Soils Groups C & D Percent of Basin: 126%
Slope of Channelized Flow, S„: ft/ft, Conveyance Coefficient, C,,:
Runoff Coefficient
unoff Coefficient Equations For 100-yr Storm Retum Period: KA = -0.25i + 0.32
C,=K, + (1.31 i3 - 1.4412 + 1.1351 - 0.12) for CA Z"0 else CA = 0 _ Kr-D = -0.39i + 0.46
Cco=KCD + (0.858i3 - 0.78612 + 0.7741 + 0.04) For 10-yr Storm Retum Period. K
A = -0.141 + 0.17
Ce=(CA + Cco)2 Ko° = OA&+ 0.21
For 5-yr Storm Retum Period: KA = -0.081 + 0.09
K - -0 0"
Return Period C_-Po'jko CA Ce Cco KA K.
5-Year 0.082 0.000 0.075 0.150 0.090 0.110
10-Year 0.160 0.050 ' . 0:150 0.250 0.170 0.210
100-Year 0.365 0.200 0.350 0.500 0.320 0.460
co- 1+0.11
Time of Concentration Rainfall Intensity
Total time of concentration equation' Rainfall Intensity Equation:
Lesser of: t,=t, + < 1=(28.5 • P,,) / (10 + T,)0"6 where P1hr is the 1hr point rainfall depth
or t=L / 180 +10 (if in urban area)
Overland flow travel time equation: tc 114 min
1{={0.395 • (1.1 - C5) . sgrt(L.)) / SO-33 114 min
Channeiized flow travel time equation: 1r= 0 min
y" 4=1_? / (V ' 60) where V= (C„ " S?os) V= 0:000 tVs
Pm I:
Return Period in in / hr
5-Year 1.49 0.96
10-Year 1.76 1.13
100-Year 2.78 1.79
Peak Flow Rate
Rational Method `Eouafion:
Q=C M I'A
Return
Period ; Q,e _ I
in / hr A
acres Q
Cfs_
5-Year 0.082 - 0.96 84.8 6.7
10-Year 0.160 1.13 84.8 16.4
100-Year 0.365 1.79 84.8 55:4
Notes:
1Basin imperviousness determined from guidelines in UDFCD Drainage Criteria Manual Table RO-3
2i' Conveyance coefficient determined from guidelines in UDFCD Drainage Criteria Manual Table RO-2
3: Minimum t. is 10 min. for non-urban areas and 5 min. for urban areas Date: 9117/2009