Air entrain concrete exposed to weather using and air-entraining admixture
conforming to ASTM C 260. Air content shall be between 4 and 6 percent.]
3.1.3
Direct Burial System
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NOTE: Direct earth burial cables generally require
direct burial splices. Observe marker slab
requirements previously covered in this
specification.
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Bury cables directly in earth, except under [railroad tracks,] [paved
areas,] and [roadways], and install cables in conduit encased in concrete.
Install cables buried directly in earth in the following manner:
a.
Slope ducts to drain.
b.
Excavate trenches in which the cables are placed by hand or with
mechanical trenching equipment, and provide a minimum cable cover
of 610 mm 24 inches below finished grade for power conductors
operated at 600 volts and less, and 765 mm 30 inches to the top of
the cables for over 600 volts. Trenches shall be not less than
[150] [200] mm [6] [8] inches wide, and shall be in straight lines
between cable markers. [Cable plows shall not be used.] Bends in
trenches shall have a radius of not less than 915 mm 36 inches.
Where two or more cables are laid parallel in the same trench,
space cables laterally at not less than 75 mm 3 inches apart,
except that communication cable shall be separated from power
cable by a minimum distance of 305 mm 12 inches.
c.
When rock is encountered, remove to a depth of at least 75 mm 3
inches below the cable and fill the space with sand or clean earth
free from particles larger than 6 mm 1/4 inch.
d.
Do not unreel and pull cables into the trench from one end.
However, the cable [may] [shall] be unreeled on grade and lifted
into position [[on a 75 mm 3 inch sand bedding] with 75 mm 3 inches
more sand placed on top of cable and a redwood plank placed on
top of the sand the entire length of the cable run. Plank shall be
50 by 200 mm 2 by 8 inch [redwood], [_____] brush treated three
coats with a pentachlorophenol light oil solution]. [Cable
bedding and cover shall consist of material which would pass a 6 mm
1/4 inch screen with no sharp material.]
e.
Provide color, type and depth of warning tape as specified in
Section 02300 EARTHWORK.
3.1.3.1
Cutting Cable
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NOTE: Delete this paragraph for LANTNAVFACENGCOM
projects.
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Use heat shrink adhesive coated caps on cable ends or tape cable ends
immediately after cutting to prevent moisture from entering the cable.
Varnish the tape when cable is not expected to be connected for at least 72
hours.
SECTION 16302N
Page 23
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