3.1.5.8
Connections to Existing Concrete Pads
For duct bank connections to concrete pads, break an opening in the pad out
to the dimensions required and preserve steel in pad. Cut the steel and
[extend into] [bend out to tie into the reinforcing of] the duct bank
envelope. Chip out the opening in the pad to form a key for the duct bank
envelope.
3.1.5.9
Connections to Existing Ducts
Where connections to existing duct banks are indicated, excavate the banks
to the maximum depth necessary. Cut off the banks and remove loose
concrete from the conduits before new concrete-encased ducts are installed.
Provide a reinforced concrete collar, poured monolithically with the new
duct bank, to take the shear at the joint of the duct banks. [Remove
existing cables which constitute interference with the work.] [Abandon in
place those no longer used ducts and cables which do not interfere with the
work.]
3.1.5.10
Partially Completed Duct Banks
During construction wherever a construction joint is necessary in a duct
bank, prevent debris such as mud, and, and dirt from entering ducts by
providing suitable conduit plugs. Fit concrete envelope of a partially
completed duct bank with reinforcing steel extending a minimum of 610 mm 2
feet back into the envelope and a minimum of 610 mm 2 feet beyond the end
of the envelope. Provide one No. 4 bar in each corner, 75 mm 3 inches
from the edge of the envelope. Secure corner bars with two No. 3 ties,
spaced approximately 305 mm one footapart. Restrain reinforcing assembly
from moving during concrete pouring.
[3.1.5.11
Removal of Ducts
Where duct lines are removed from existing underground structures, close
the openings to waterproof the structure. Chip out the wall opening to
provide a key for the new section of wall.
][3.1.5.12
Optional Precast Sectional Underground Duct Bank
**************************************************************************
NOTE: Delete this paragraph for LANTNAVFACENGCOM
projects.
**************************************************************************
The Contractor may choose to substitute concrete, precast, sectional,
underground duct bank, with PVC conduits, for the cast-in-place underground
conduit with concrete encasement. Key and tie together precast sections in
a manner to provide the strength and integrity of a cast-in-place
structure. Keep conduits in alignment from section to section to provide a
smooth surface for pulling cables. Lock precast sections together so that
the maximum gap after settlement does not exceed 6 mm 1/4 inch. Fill gaps
between concrete sections with flexible plastic grouting material to
prevent entry of water and foreign material. Install rebar in precast
sections in accordance with the requirements of cast-in-place duct banks.
Key the precast duct bank into manholes, with a cast-in-place section, of
915 mm 3 feet minimum, joining the last section to each manhole. The
alignment vertically and horizontally of any two adjacent sections shall
not vary more than 6 mm 1/4 inch when measured from end of conduit to end
of conduit. Concrete strength shall be the same as for cast-in-place
SECTION 16302N
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