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: P1-6,(H8) Condition: Developing Storm Return Period:

Basin Chracteristics
Area, A: 3.5 acres Basin Imperviousness' (in percent), is 0.0%
Distance of Overland Flow, L.,: 265 it Hydrologic Soils Group A Percent of Basin: 2.9%
Distance of Channelized Flow, 4: 0 it
Hydrologic Soils Group B Percent of Basin:
4.5ib
Average Basin Slope, S: 0.00730 IWit, Hydrologic Soils Groups C & D Percent of Basin:
Slope of Channelized Flow, Sw,: ft/ft Conveyance Coefficient?, C,: 5

Runoff Coiefficient
Runoff Coefficient Equations
CA=KA-+ (1.310- 1.44i' + 1.135i - 0.12) for CA 2 0 else CA = 0
Cco=K,, + (0.8581 0.78612 + 0.774i + 0.04)
Cg=(CA + CcD) / 2
nitration
Time of Co
Total time of concentration equation: `
Lesser oe: vt, + 4
or t,=L / 180 +10 (if in urban area)
Overland flow travel time equation:
?=(0.395',(1.1 - Cs) . sgrt(L,)) / SO-3'
Channelized flow travel time equation:
L=4 / (V 60) where V= (C, S0.5)
Rational Method Equation,,
Q - CmmposNe I A
Peak F
For 100-yr Storm Return Period: KA = -0.25i + 0:32
K co = -0.391 + 0.46
For 10-yr Storm Return Period: KA = -0.14i + 0.17
K ci) = -0.18i + 0.21
For 5-yr Storm Return Period: KA-0.08i + 0.09
K - 0 10'
Rainfall inte
co - r + 0:11
P1hf) / (10 + 700786 where P1hr is the 1 hr point rainfall depth
P1M 1
Return Period in in / hr
5 Year 1.49 2.21
10-Year 1.76 2.61
100-Year 2.78 4.12
Rate'
Return
Period C?om ce „1
in t hr A
acres Q
US
5-Year 0:082 2.21 3.5 0.6
10-Year 0.1&0 2.61 3:5 1.5
100-Year 0.365 4.12 3.5 5.3
Notes;
1Basin imperviousness determined from guidelines in LIDFCD 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
Retum d Cmmpoi e CA C, KA KB D
n
r 0.082 0.000 0.075 0.150 0.090 0.110
r 0.160 0.050 0.150 0.250 0.170 0.210
r 0.365 0.200 0.350 0.500 0.320 0.460