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: H9 Condition: Existing - Storm Return Period:

BaSin Chracteristics
Area, A: 25.0 acres Basin Imperviousness' (in percent), is 0.0%
Distance of Overland Flow, L,,: 1,136 ft Hydrologic Solis Group A Percent of Basin: 0.03
Distance of Channelized Flow, L 0 ft Hydrologic Soils Group B Percent of Basin: ` 5631".
Average Basin Slope, S: 0.01650 ft/ft Hydrologic Soils Groups C & D Percent of Basin: '. 43,7%
Slope of Channelized Flow, Sw. fvft Conveyance Coefficient2, C,,: 5

Runoff Coefficient
Runoff Coefficient Equations For 100-yrStonn Return Period.^ K„ = -0.25i + 032
CA=K, +(1.31 i3 -1.44i2 + 1.135i - 0.12) for CA 2: 0 else: CA =:0 KcD = -0.391 + 0.46
CCD=Kco +,(0.858i3 - 0.78612 + 0.7741 + 0.04) For 10-yr Storm Return Period: K,? _ -0.141 + 0.17
CB=(CA + Cco) / 2 K co = -0.187 + 0.21
For 5-yr Storm°Retum Period. KA = -0.081 + 0.09
K --010 +011
Return Period C-P-1, CA CB CcD K„ K.
5-Year 0.108 0.000 0.075 0.150 0.090 0.110
10-Year 0.194 0.050 0.150 0.250 0.170 0.210
100-Year 0.416 0.200 0.350 0:500 0.320 0.460
CD _ 1
Time of Concentration Rainfall Intensity-,
Total time of concentration equation: Rainfall Intensity Equation:
Lesser of3: Vti + 4 1=(28.5 - Ply,) / (10 +T?)o'86 where P,, is the 1hr.point rainfall depth
or t?=L / 180 +10 (if in urban area)
Overland flow travel time equation: t6--, 51 min
t;=(0,395 - (1.1 - CS) - sgrt(Lo)) / S0.33 4= 51 min
Channelized flow travel time equation t,= 0 min
4=Lc / (V • 60) where V= (C? • S„°'S) V= 0.000!' fVs

Peak Flow Rate
Rational Method Equation-
Q = CMTP=te • l . A
P1K I
Return Period in in / hr
5-Year 1.49 1.68
10-Year 1.76 1;98
100-Year _78 1,13
Retum C i
/ hr A
cres Q
CfS
E 0.108 1.68 25.0 4.5
0.194 1.98 25;0 9.6
0.416 3.13 25.0 32.5
Notes:
.1: Basin imperviousness determined from. guidelines in UDFCD Drainage Criteria Manual Table RO-3
2: Conveyance coefficient determined from guidelines in LlDFCD 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