approximate densities of surrounding firm soil before installing ducts.
Joints in adjacent tiers of duct shall be vertically staggered at least 150
mm 6 inches. The first 150 mm 6 inch layer of backfill cover shall be sand
compacted as previously specified. The rest of the excavation shall be
backfilled and compacted in 75 to 150 mm 3 to 6 inch layers. Duct banks
may be held in alignment with earth. However, high-tiered banks shall use
a wooden frame or equivalent form to hold ducts in alignment prior to
backfilling.
3.5.5
Installation of Couplings
Joints in each type of duct shall be made up in accordance with the
manufacturer's recommendations for the particular type of duct and coupling
selected and as approved.
3.5.5.1
Bituminized-Fiber Ducts
**************************************************************************
NOTE: Bituminized fiber duct should be specified
only for connection to existing bituminized fiber
duct systems. Delete the paragraph if not required.
Specify thin-wall or schedule 40 plastic duct for
concrete encasement and thick-wall or schedule 40 or
schedule 80 plastic duct for direct-burial and riser
applications (riser bends should be metallic conduit
where cables are to be pulled into ductline).
**************************************************************************
Bituminized-fiber ducts shall be used to interface with existing
bituminized-fiber duct as shown. To ensure a watertight joint, tapered
ends or joints of the same material as the ducts shall be swabbed with
bituminous or joint-sealing compound before couplings are applied. Plastic
or nonmetallic couplings shall be tightly driven onto unswabbed ducts. Due
to the brittleness of plastic couplings at low temperatures, such couplings
shall not be installed when temperatures are below minus 18 degrees C 0
degrees F. Couplings shall be warmed in hot water or by another approved
method when installed at temperatures below 0 degrees C 32 degrees F.
3.5.5.2
Plastic Duct
Duct joints shall be made by brushing a plastic solvent cement on insides
of plastic coupling fittings and on outsides of duct ends. Each duct and
fitting shall then be slipped together with a quick 1/4-turn twist to set
the joint tightly.
3.5.6
Duct Line Markers
**************************************************************************
NOTE: Coordinate with UF-02300 for underground
marking requirements.
**************************************************************************
Duct line markers shall be provided [as indicated] [at the ends of long
duct line stubouts or for other ducts whose locations are indeterminate
because of duct curvature or terminations at completely below-grade
structures]. In addition to markers, 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 with a continuous metallic backing
and a corrosion-resistant 0.0254 mm 1 mil metallic foil core to permit easy
SECTION 16375A
Page 56
Previous Page
