PERMFILE138126

• Permit No: C1991078A
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: Exhibit 09 Protection of the Hydrologic Balance
• Media Type: D
• Archive: Yes

• ACCESS & HAUL ROAD CULVERTS AND BORROW DITCHES
According the the Handbook of Steel Drainage & Highway
Construction Products the maximum flow that 12", 18" &
24" CMP's can handle with no head is as follows:
12" CMP - 2 CFS; 18" CMP - 5.5 CFS; 24" CMP - 12 CFS
The borrow ditches for the roads will be sized to handle
peak flow for the culvert that the borrow ditch flows to.
Assume that the minimum ditch gradient will be 2X.
BORROW DITCHES - 12" CMP FLOW IN A TRIANGULAR CHANNEL
ENTER DEPTH D 0.750 FEET
ENTER SLOPE S 0.020 EXPRESS AS DECIMAL
ENTER "N" N 0.040 EXPRESS AS DECIMAL
ENTER SIDE SLOPE X 1.500 SLOPE = X:1
AREA=(W#D)+(X#D"2)= 0.84 FEET"2
WETTED PERIMETER=(W)+2((XD"2+D"2))".5 2.70 FEET
R=AREA/WETTED PERMITER 0.31
V=(1.49/N)*(R".667)#(S".5)= 2.42 FEET/SEC
Q = A X V = 2.04 CFS
With Freeboard of 0.3' the depth of the ditch will be 1.050 feet.
BORROW DITCHES - 18" CMP FLOW IN A TRIANGULAR CHANNEL
•
fiNTER DEPTH D 1.100 FEET
ENTER SLOPE S 0.020 EXPRESS AS DECIMAL
ENTER "N" N 0.040 BXPRESS AS DECIMAL
ENTER SIDE SLOPE X 1.500 SLOPE = X:1
AREA=(W#D)+(R#D"2)= 1.82 FEET"2
WETTED PERIMETER=(W)+2((XD"2+D"2))".5 3.97 FEET
R=AREA/WETTED PERMITER 0.46
V=(1.49/N)#(R".667)*(S".5)= 3.13 FEET/SEC
Q = A X V = 5.68 CFS
With Freeboard of 0.3' the depth of the ditch will be 1.400 feet.
BORROW DITCHES - 24" CMP FLOW IN A TRIANGULAR CHANNEL
ENTER DEPTH D 1.500 FEET
ENTER SLOPE S 0.020 EXPRESS AS DECIMAL
ENTER "N" N 0.040 EXPRESS AS DECIMAL
ENTER SIDE SLOPE X 1.500 SLOPE = X:1
AREA=(W#D1+(X#D"2)= 3.38 FEET"2
WETTED PERIMETER=(W)+21(XD"2+D"2))".5 5.41 FEET
R=AREA/WETTED PERMITER 0.62
• V=(1.49/N-*(R".667-#(S".5)= 3.85 F EET/SEC
Q = A X V = 12.98 CFS
With Freeboard of 0.3' the depth of the ditch will be 1.800 feet.
9-26 July 1991