feet of conduit assembly.
3.1.5
Underground Duct with Concrete Encasement
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NOTE: Edit this paragraph to comply with project
requirements concerning type of structure or duct,
strength of concrete, concrete mix, metal
accessories, and excavating and grading. Indicate
special reinforcing where required, particularly
with duct banks of non-rectangular cross-section.
Designer shall contact local telephone company,
where applicable, concerning size of signal manholes
and number and type of signal duct required.
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NOTE: See standard plates 1 through 4 attached
hereto, covering manholes and handholes. For
projects other than LANTNAVFACENGCOM: Plates needed
may be modified and used on drawings or attached to
contract specification. For LANTNAVFACENGCOM
projects: DO NOT attached plates to contract
specifications. Plates should be put on drawings
without modifications. Provide notes below the
plates to indicate changes or clarifications to the
plates.
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Construct underground duct lines of individual conduits encased in
concrete. Except where rigid galvanized steel conduit is indicated or
specified, the conduit shall be PVC Type EB-35. Do not mix different kinds
of conduit in any one duct bank. Ducts shall not be smaller than [100]
[125] mm [4] [5] inches in diameter unless otherwise indicated. Concrete
encasement surrounding the bank shall be rectangular in cross-section and
shall provide at least 75 mm 3 inches of concrete cover for ducts.
Separate conduits by a minimum concrete thickness of [50] [65] mm [2] [2
1/2] inches, except separate light and power conduits from control, signal,
and telephone conduits by a minimum concrete thickness of 75 mm 3 inches.
[Provide color, type and depth of warning tape as specified in Section 02300
EARTHWORK.]
3.1.5.1
Depth of Encasement
Top of the concrete encasement shall not be less than 450 mm 18 inches
below grade [except that under roads and pavement concrete be a minimum of
610 mm 24 inches below grade] [and under railroad tracks a minimum of 1270
mm 50 inches below top of rails].
3.1.5.2
Slope of Encasement
Duct banks shall have a continuous slope downward toward underground
structures and away from buildings with a minimum pitch of 75 mm in 30
meters 3 inches in 100 feet. Except at conduit risers, accomplish changes
in direction of runs exceeding a total of 0.175 rad 10 degrees, either
vertical or horizontal, by long sweep bends having a minimum radius of
curvature of7.62 meters 25 feet; sweep bends may be made up of one or more
curved or straight sections or combinations thereof. Manufactured bends
shall have a minimum radius of 455 mm 18 inches for use with conduits of
SECTION 16302N
Page 26
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