2013-10-07_PERMIT FILE - C1981025A ‎(6)‎

• Permit No: C1981025A
• IBM Index Class Name: Permit File
• Doc Date: 10/7/2013
• Doc Name: Final Engineering Calculations
• Section_Exhibit Name: 4.0 Appendix 4-B
• Media Type: D
• Archive: Yes

•
Diversion Ditches
UPPER DIVERSION DITCH D-2B
FLOW IN A TRIANGULAR CHANNEL
DEPTH D 1.300 FEET
SLOPE S 0.020 EXPRESS AS DECIMAL
Mannings "N" N 0.030 EXPRESS AS DECIMAL
SIDE SLOPE X 1.500 SLOPE = X:1
AREA=(W*D)+(X*D^2)= 2.54 FEET^2
WETTED PERIMETER=(W)+2((XD^ 2+D^2))^.5 4.69 FEET
R=AREA/WETTED PERMITER 0.54
V=(1.49/N)*(R^.667)*(S^.5)=
Q = A X V =
Q REQUIRED
4.66 FEET/SEC
11.82 CFS
10.29
The diversion ditch will be a triangular channel 1.3
feet deep with 1.5h:1v side slopes. With a freeboard of 0.3'
the total depth of the upper diversion ditch is 1.6 feet.
The flow velocity is potentially erosive. However, the
ditch channel in this area is comprised of competent
gravels so erosion should not be a factor.
r 1
LJ
18" CMP C-2 & INLET DITCH
The capacity of the 18" CMP is 5.75 CFS so it is sized to
handle the design flow of 3.4 CFS.
Inlet Ditch D-11
' FLOW IN A TRIANGULAR CHANNEL
DEPTH D 0.900 FEET
SLOPE S 0.020 EXPRESS AS DECIMAL
Mannings "N" N 0.030 EXPRESS AS DECIMAL
SIDE SLOPE X 1.500 SLOPE = X:1
AREA=(W*D)+(X*D^2)= 1.22 FEET^2
WETTED PERIMETER=(W)+2((XD^ 2+D^2))^.5 3.24 FEET
R=AREA/WETTED PERMITER 0.37
V=(1.49/N)*(R^.667)*(S^.5)= 3.65 FEET/SEC
Q = A X V = 4.43 CFS
Q REQUIRED
3.43
Since the inlet ditch feeds water to an 18" CMP the ditch
will be at least 18" deep. The flow velocity is low enough
that erosion should not be a problem.
r1
U
4-B:8
October 1994