the requirement for a type of 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, brightly
colored plastic tape not less than 75 mm 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 m 1000 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.
3.2.2.5
Surface Markers
Markers shall be located near the ends of cable runs, at each cable joint
or splice, at approximately every 150 m 500 feet along cable runs, and at
changes in direction of cable runs. Markers shall be constructed as
SECTION 16526A
Page 31
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