PERMFILE72878

• Permit No: C1983059A
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: EXHIBIT 9 DRAINAGE & SEDIMENT CONTROL PLAN CALCULATIONS
• Media Type: D
• Archive: Yes

SED.WK1
• SEDIMENT POND CAPACITY
The sediment pond is constructed in the southeast portion of
the facilities area. Calculations on the following pages
indicate that the pond is to have a capactiy of 0.48 A-F
and the emergency spillway is to have a capactiy of 8.62 CFS.
The purpose of this calculation is to determine the sediment
volume to be expected in the pond, to check the size of the
emergency spillway and to size collection ditchs B & C.
REQUIRED WATER VOLUME - Acre Feet
SEDIMENT VOLUME
0.480
The only area on the site that will contribute significant
sediment to the pond is the coal pad, Area 7. Deposition
from the other areas will occur before run-off from them
reaches the sediment pond.
USING THE UNIVERSAL SOIL LOSS EQUATION
A= R K L S C P
R = rainfall factor 30.00
K = soil erodibility factor - Conservative 0.70
LS = combined length slope factor 2$ - 900' 0.39
C = cropping management factor 1.00
P = erosion control practice factor 1.00
n
U

A = sediment,tons/acre/year 8.19
THREE YEAR SEDIMENT VOLUME ACRE FEET
5.2 Acres @ 115 #/Cubic Feet 0.05
TOTAL REQUIRED SEDIMENT POND CAPACITY -- AF 0.53
EMERGENCY SPILLWAY
MANNING'S EQUATION
FLOW IN A TRAPIZODIAL CHANNEL
DEPTH D 0.500 FEET
WIDTH W 10.000 FEET (Bottom Width)
SLOPE S 0.020 EXPRESS AS DECIMAL
"N" N 0.040 EXPRESS AS DECIMAL
SIDE SLOPE X 1.500 SLOPE = X:1
AREA=(W*D)+(X*D^2)= 5.36 FEET^2
WETTED PERIMETER=(W)+2((XD^2+D^2))^.5 11.80 FEET
R=AREA/WETTED PERMITER 0.46
V=(1.49/N)*(R^.667)*(S^.5)= 3.12 FT/SEC
Q = A X V = 16.76 CFS
Q REQUIRED 8.62 CFS
-5- 6/03/93