3.2.2.2
Cable Installation
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NOTE: Where a buried cable warning is necessary,
the requirement for a tape or approved warning
indication will be provided. Where soil is known to
be rocky, provide selected backfill for cable
protection.
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Cables shall be unreeled along the sides of or in trenches and carefully
placed on sand or earth bottoms. Pulling cables into direct-burial
trenches from a fixed reel position will not be permitted, except as
required to pull cables through conduits under paving or railroad tracks.
Where cables cross or are installed in layers at different depths, a
separation of at least 75 mm 3 inches vertically and 50 mm 2 inches
horizontally shall be provided, unless each cable circuit is protected by a
nonmetallic conduit sleeve at the crossing. Where single-conductor cable
is installed for three-phase circuits, all three phases and the neutral
shall be installed in the same sleeve. Bend radius of any cable shall be
not less than 10 times the diameter of the cable. In no case shall cables
be left under longitudinal tension. The first 100 mm 4 inch layer of
backfill shall be of sand or stone-free earth. [A 0.127 mm (5 mil), 5 mil,
brightly colored plastic tape not less than (75 mm (3 inches) 3 inches in
width and suitably inscribed at not more than 3 m 10 feet on centers, or
other approved dig-in warning indication, shall be placed approximately 300
mm 12 inches below finished grade levels of trenches.] [Selected backfill
of sand or stone-free earth shall be provided to a minimum depth of 75 mm 3
inches above cables.]
3.2.2.3
Other Requirements
Where direct-burial cables cross under roads or other paving exceeding 1.5 m
5 feet in width, such cables shall be installed in concrete-encased ducts.
Where direct-burial cables cross under railroad tracks, such cables shall
be installed in reinforced concrete-encased ducts. Ducts shall extend at
least 300 mm 1 foot beyond each edge of any paving and at least 1.5 m 5 feet
beyond each side of any railroad tracks. Cables may be pulled into conduit
from a fixed reel where suitable rollers are provided in the trench.
Direct-burial cables shall be centered in duct entrances. A suitable
waterproof nonhardening mastic compound shall be used to facilitate such
centering. If paving or railroad tracks are in place where cables are to
be installed, coated rigid steel conduits driven under the paving or
railroad tracks may be used in lieu of concrete-encased ducts. Damage to
conduit coatings shall be prevented by providing ferrous pipe jackets or by
suitable predrilling. Where cuts are made in any paving, the paving and
sub-base shall be restored to their original condition.
3.2.2.4
Medium-Voltage Cable Joints or Low-Voltage Cable Splices
Cable joints or splices in direct-burial cables are not permitted in runs
of 300 m 1000 feet or less, nor at intervals of less than 300 m1000 feet in
longer runs, except as required for taps. Locations of cable joints or
splices in shorter intervals, where required to avoid obstructions or
damage to cables, shall be approved. Cable joints or splices shall be
installed in cable boxes, except that medium-voltage separable connectors
or low-voltage sealed insulated connectors do not require cable boxes.
SECTION 16525A
Page 25
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