TM 5-820-3/AFM 88-5, Chap. 3
airfield or heliport pavements and therefore will not
3-5. Settlement of inlets and drains.
in the vicinity of large concrete manholes indicates
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
inlet relative to the hydraulic gradient in the
In general, curb and gutters are not permitted to
interrupt surface runoff along a taxiway or runway.
To prevent clogging of inlets serving drainage
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
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
high curb; these conditions cannot be tolerated on