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 - LafargeWest, Inc
Preliminary Drainage Report
Peak Runoff Calculations Using the Rational Method`
Basin R81 "(H1) Condition: Reclaimed Storm Return Period:
Area, A. 134 acres Basin Imperviousness( in percent), is 2.0%
Distance of Overland Flow, Lo: 5,532 ft Hydrologic Soils Group A Percent of Basin: 10.11%
Distance of Channelized Flow, L.: 0 ft Hydrologic Soils Group B Percent of Basin: , 82.9%
Average Basin Slope, S 0.00720 fUft Hydrologic Soils Groups C & D Percent of Basin: 7.1
Slope of Channelized Flow, S. ft/ft Conveyance Coefficiene, C,: 5
Runoff; Coefficient
Runoff Coefficient Equations For 100-yr Storm Return Period: K„ = -0.25i + 0.32
CA=Kr, + (1.310- 1-44i2 + 1:1351- 0.12) for CA z 0 else 01= 0 KcD = -0.39i + 0.46
CcD=KcD + (0.85810 - 0.78612 +0.7741 + 0.04) For 10-yr Storm Return Period. K,, = -0.14i + 0.17
CB=(CA + CcD) / 2 KcD = -0.18i + 0.21
For s-yr Storm Return Period: K,,-= -0.08i + 0.09
Return Period C?mp,1e CA CB CcD K,, KcD
5 -Year 0.079 0.000 0.082 0.163 0.088 0.108
10-Year 0.163 0.069 0.165 0.262 0.167 0.206
100-Year 0.358 0.217 0.362 0.507 0.315 0.452
K co = -0.101 + 0.11
- - Time of Concentration Rainfall Intensity
Total time of concentration equation Rainfall Intensity Equation:
Lesserof0: tc=t + 4 1=(28.5 - P,,,) / (10 + T?)0786 where Pit, is the 1 hr point rainfall depth
or VL / 180 +10 (if in urban area)
Overland flow travel time equation- tc= 153 min
t °(0.395' (1.1 - C5) `sgrt(L.)) / So.33' 153. min .
Ghannelized flow travel time equation t,= 0 -min
4=1_ ° (V ` 60) where V= (C,, . S.0.5) V= 0.000 ft/s
P,?,
Return Period in in / hr
5-Year 1.49 0.77
10-Year 1.76 0.92
100-Year 2.78 1.45
Peak Flow Rate
Rational Method Equation:
Q=Ccjq .,I.A.
C I
in/hr A
acres Q
Cfs
E 0.079 0.T7 134 8.2
0.163 0.92. 134 20.0
i.
0.358
1.45
134
69:5
Notes:
1: B
asin 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 t. is 10 min. for non-urban areas and 5 min, for urban areas
Date: 9/18/2009