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: H2 Condition: Existing Storm Return Period:
Basin Chracteristics
Area, A: 159 acres Basin Imperviousness' (in percent), is 2.0%
Distance of Overland Flow, L,, 3,028 ft Hydrologic Soils-Group A Percent of Basin: 0.050
"Distance of Channelized Flow, IY: 3,090 ft Hydrologic Soils Group B Percent of Basin: 74.2%
Average Basin Slope, S: 0.01174 ftlft Hydrologic Soils Groups C & D Percent of Basin: 25.8%
Slope of Channelized Flow, S,,,: 0.00258 ftlft Conveyance Coefficient 2. C,,: 15
Runoff Coefficient
Runoff Coefficient Equations For 100-yr Storm,Retum Period: KA = -0.25i + 0.32
CA=KA + (1.31 i3 - 1.4412 +' 1.1351- 0.12) for CA! 0 else C4- 0 K cD = -0.39i +`0.46
CcD=Kco + (0.85813 - 0.78612 + 0.7741+ 0.04) For 10-yr Storm Retum Period: K,, = -0.14i + 0:17
CS=(CA + CCD)12 K cD = -0:181 + 0.21
For 5-yr Storm Return Period: KA = -0.08i + 0.09
KcD =-0.101 +0.11
Return Period C..Pa ?te CA CB CCD KA KCD
5-Year 0.103 0.000 0.082 ' 0.163 0.088 0.108
10-Year 0.190 0.069 0.165 0.262 0.167 0.206
100-Year 0.400 0.217 0.362 0.507 0.315 0.452
Time of Concentration Rainfall Intensity
Total time of concentration equation: Rainfall Intensity Equation:
Lesseroe: tc=ti + Tt 1=(28.5 ` Pa.) / 10,+ T f 7G where P1hr is the 1 hr point rainfall depth
or t,=L ! 180 +10 (if in urban area)
Overland flow travel time eguatiom t?= 162 min
t;=(0.395' (1.1 - Cs) * sgrt(L,))/ SO-33 94 min
Channelized flow travel time equation: 68 min
t,=L, ! (V 60) where V= (C; ` Swos) V= 0.762 ft/s
P1hr 1
Return Period in in / hr -
5-Year 1.49 0.74
10-Year 1.76 0.88
100-Year 2.78 1.39
Peak Flow Rate
Rational Method Equation:
Return
Period Cam, I
in / hr A
acres Q ..
CFS
5-Year 0.103 0.74 159 12.1'
10-Year 0.190 0.88 159 26.5
100-Year 0.400 1.39 159 87.9:
Notes:
1: 'Basinimperviousness'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 t. is 10 min. for non-urban areas and 5 min. for urban areas Date: 9/17/2009