TM 5-820-3/AFM 88-5, Chap. 3
airfield or heliport pavements and therefore will not
3-5. Settlement of inlets and drains.
be used.
Failure of joints between sections of concrete pipe
in the vicinity of large concrete manholes indicates
3-8. Clogging.
the manhole has settled at a different rate than that
of the connecting pipe. Flexible joints should be
Partial or total restriction of open and grated inlets
required for all joints between sections of rigid pipe
caused by clogging with debris, sediments, and
in the vicinity of large manholes, say 3 to 5 joints
vegetation is a fairly common problem.
a. Major factors responsible for clogging of
along all pipe entering or leaving the manhole.
inlets are inadequate periodic inspection, inad-
equate maintenance, and improper location of the
3-6. Gutters.
inlet relative to the hydraulic gradient in the
In general, curb and gutters are not permitted to
drainage system.
interrupt surface runoff along a taxiway or runway.
The runoff must be allowed unimpeded travel
basins with characteristics and flows that contribute
transversely off the runway and thence directly by
and transport detritus, debris barriers should be
the shortest route across the turf to the field inlets.
provided upstream of them.
Inlets spaced throughout the paved apron
construction must be placed at proper intervals and
3-9. Ladders.
in well-drained depressed locations. Gutters are
discussed in chapter 4.
Adequate ladders should be provided to assure that
rapid entrance and egress may be made by
personnel during inspection of facilities. Ladder
3-7. Curb inlets.
rungs should be checked periodically, since they are
The hydraulic efficiency of curb inlets depends
often lost in the course of regular inspection and
upon depression of gutter invert and a relatively
maintenance work.
high curb; these conditions cannot be tolerated on
3-8
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