No headwall will be constructed downstream. The following are known conditions:
Aircraft SR-71C. (Refer to table 5-1, page 5-9, and table 5-2, page 5-10.)
Culvert weight type = 9.
Q to be handled by culvert = 32 cfs.
Soil type is bare SC; therefore, the maximum allowable outlet velocity = 3.4 fps.
Pipe sizes available: 24-, 30-, 36-, and 42-inch CMP, 10 gauge.
Referring to figure 5-11, page 5-18, note that the following information is required before design can be
Horizontal length of one culvert, L.
Slope of culvert pipe needed to determine the flow characteristics of various pipe diameters (see table 5-3,
page 5-16) and Fc, which is a portion of the critical fill depth, Ft.
Critical fill depth, Ft, in order to determine if the cover over the pipe meets the requirements of table 5-2.
STEP 1. Determine the runoff rate. Given for this example Q = 32 cfs.
STEP 2. Determine airfield culvert use.
STEP 3. Calculate the critical dimensions. Computations should be made in the following sequence (see figure
Determine the difference in elevation between the edge of the runway and the culvert upstream invert.
F1= EL1 - EL2
F1 = 607.00 - 600.80 = 6.20 ft
Determine the horizontal distance between the culvert invert and the shoulder edge.
S1= F1 x X
S1 = 6.20 x 10 = 62 ft