Determine the difference in elevation between the edge of the runway and the culvert outlet and fill slope.
F2 = EL3 - EL4
F2 = 607.00 - 599.62 = 7.38 ft
Determine the horizontal distance between the edge of the runway and the intersection of the culvert and
S2 = F2 x Y
S2 = 7.38 x 10 = 73.8 ft
Determine the actual slope of the culvert.
Determine the incremental elevation difference between the elevation of the upstream invert and the
invert of culvert at critical fill section.
0.005 ft/ft = 0.5 percent
F3 = S x S1
F3 = 62 x 0.005 = 0.31 ft
Determine the depth of critical fill section.
6.2 + .31 = 6.51'
Ft = F1 + F3
Ft = 6.2 + 0.31 = 6.51 ft. (Length of horizontal projection of the culvert.) The upstream invert elevation to
downstream invert elevation is-
LIP = S1 + TW = S2 + 2 ft
LIP = 62 + 100 + 73.8 + 2 = 237.8 ft; (Round up to 238 ft)
NOTE: These computations depict
section and figure 5-11 summarizes
From these calculations, it has been determined that-
(1) The actual length of the culvert is 235.8 feet. (2) A 2-foot projection is added because there is to
be no downstream headwall. (3) The pipe must be rounded up to an even length of 238 feet. (4) This
gives a culvert length of 238 feet for a single pipe.