TM 5-820-3/AFM 88-5, Chap. 3
surfaced fields. Underground conduits are subject
2-4. Restricted use of bituminous-coated pipe.
to two principal types of loads: dead loads caused
The installation of corrugated-metal pipe with any
by embankment or trench backfill plus
percentage of bituminous coating should be re-
superimposed stationary surface loads, uniform or
stricted where fuel spillage, wash rack waste, and/
concentrated; and live or moving loads, including
or solvents can be expected to enter the pipe.
impact.
2-5. Minimum and maximum cover.
vide the greatest possible capacity to serve the
a. Heliport and airport layout will typically in-
planned pavement configuration. Additions to or
clude underground conduits which pass under run-
replacements of drainage lines following initial
ways, taxiways, aprons, helipads, and other hard-
construction are both costly and disrupting to air-
stands. In the design and construction of the
craft traffic.
drainage system it will be necessary to consider
both minimum and maximum earth cover allowable
sion control facilities at military installations were
in the underground conduits to be placed under
made during the period 1966 to 1972. The facilities
both flexible and rigid pavements as well as beneath
observed varied from 1 to more than 30 years of
unsurfaced airfields and medium-duty landing-mat-
2-2
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