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: H4 Condition: Existing Storm Return Period:

Basin Chracteristics
Area,A 96.9 acres Basin1mperviousness' (in percent), is 2,0%
Distance of Overland Flow, L„' 2,784 ft Hydrologic Soils GroupA Percent of Basin: 4.51
Distance of Channelized Flow, L,, 1,930 ft Hydrologic Soils Group B Percent of Basin: 24.6%
Average Basin Slope, S: 0.04965 ft/ft Hydrologic Soils Groups C 8 D Percent of Basin: 70.9%
Slope of Channelized Flow, 5,,: 0.06408 ft/ft Conveyance,Coefficientz, C,,: 15

Runoff Coefficient"
Runoff Coefficient Equations For 100-yr Storm Retum Period. KA = -0.251 + 0.32
C,,=K,q + (1.310 - 1.44i2 + 1.135i - 0,12) for CA2 0 else CA = 0 Kco = -0.391 + 0.46
CcD=Kco + (0.858i3 - 0.786i' + 0.774i + 0.04) For 14yr Storm Return Period: K,, = -0.141 + 0,17
CB=(CA + CAD) / 2
-0.181+0.21
Fors-yrStorm Return Period: K,; ' _ -0.08i + 0.09
K =-0 10i+011
Return Period C? P; to CA CB C', K. KID
5-Year 0.136 0.000 0.082 1163 0.088 0.108
10-Year 0.229 0.069 0.165 0.262 0167 0.206
100-Year 0.459 0.217 0.362, 0c507 0.315 0.452

Time of Concentration Rainfail Intensity
TTtal time of concentration equation: Rainfall Intensity Equation:'
Lesserot3: t<=t + 4 1=(28.5' P11,)1(10 + Tj0*7a6'where P,M is the 1hr point rainfall depth
or t,=L 1180 +10 (if in urban area)
Overland flow travel time equation: V 62 min
f+=(0:395' (1.1 - Cs) " s9rt(h)) / So." X= 54 min
Channeiized flow travel time equation: tt= 8 min
4=L? (V " 60) where V= (C' " SW05) V= 3.797 ft/s
Pier I
Return Period in in / hr
5-Year 1.49 1.47
10-Year 1.76 1.74
10o-Year 2.78 2.75
Peak Flow Rate
Rational Method Eggation:
Q=Cam"I•A
Return
Period C..q*.iW I
in1 hr J A
.-.acres., Q
_ eft
5-Year 0.136 1.47 96.9 19.4
10-Year 0.229 1.74 96.9 38.7
100-Year .0459 2.75 96.9 122.1
Notes:
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 t. is 10 min. for non-urban areas and 5 min. for urban areas Date: 9117/2009