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

• SPILLWAY SIZING
The spillway for sediment pond 1 is a trapazoidal
channel 10.0 feet wide and 0.5 feet deep
with a freeboard of 12" for a total depth of 1.500
feet. Rip rap, 6" minus is installed in the channel
to prevent erosion.
The spillway has a capacity of 16.76 cfs which is well
over the required capacity of 8.62 cfs.
RIPRAP SIZING
D50 = Size of Riprap
D50 = ((V X S^.17)/7.58))^2
D50 = Diameter in feet
V = Velocity
5 = Slope
D50 = 0.045 feet 0.537 inches
COLLECTION DITCH B
Collection ditch B is the collection ditch located on the north
edge of the coal pad. This ditch collects the drainage from
drainage areas 1 - 7. The required peak flow for this ditch
is taken from the pond sizing calculation sheet located on the
• on the following pages. Page 7.
COLLECTION DITCH "B"
MANNING'S EQUATION
FLOW IN A TRAPIZODIAL CHANNEL
DEPTH D 0.700 FEET
WIDTH W 1.600 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)= 1.86 FEET^2
WETTED PERIMETER=(W)+2((XD^2+D^2))^.5 4.12 FEET
R=AREA/WETTED PERMITER 0.45
V=(1.49/N)*(R^.667)*(S^.5)= 3.09 FT/SEC
Q = A X V = 5.74 CFS
Q REQUIRED 5.63 CFS
Collection Ditch "B" will be a trapezoidal channel 0.7
feet deep with 1.5h:1v side sloes. With a freeboard of 0.3'
the total depth of collection ditch "B" is 1.0 feet.
The flow velocity is slow enough that erosion should not be a
problem. Eighteen inch (18") diameter culverts are required
to handle the flow under the roads along this ditch

-5a- 6/03/93