location of the duct line, shall be placed approximately 300 mm 12 inches
below finished grade levels of such lines.
3.6
MANHOLES, HANDHOLES, AND PULLBOXES
3.6.1
General
Manholes shall be constructed approximately where shown. The exact
location of each manhole shall be determined after careful consideration
has been given to the location of other utilities, grading, and paving.
The location of each manhole shall be approved by the Contracting Officer
before construction of the manhole is started. Manholes shall be the type
noted on the drawings and shall be constructed in accordance with the
applicable details as indicated. Top, walls, and bottom shall consist of
reinforced concrete. Walls and bottom shall be of monolithic concrete
construction. The Contractor may at his option utilize monolithically
constructed precast-concrete manholes having the required strength and
inside dimensions as required by the drawings or specifications. In paved
areas, frames and covers for manhole and handhole entrances in vehicular
traffic areas shall be flush with the finished surface of the paving. In
unpaved areas, the top of manhole covers shall be approximately 15 mm 1/2
inch above the finished grade. Where existing grades that are higher than
finished grades are encountered, concrete assemblies designed for the
purpose shall be installed to elevate temporarily the manhole cover to
existing grade level. All duct lines entering manholes must be installed
on compact soil or otherwise supported when entering a manhole to prevent
shear stress on the duct at the point of entrance to the manhole. Duct
lines entering cast-in-place concrete manholes shall be cast in-place with
the manhole. Duct lines entering precast concrete manholes through a
precast knockout penetration shall be grouted tight with a portland cement
mortar. PVC duct lines entering precast manholes through a PVC endbell
shall be solvent welded to the endbell. A cast metal grille-type sump
frame and cover shall be installed over the manhole sump. A cable-pulling
iron shall be installed in the wall opposite each duct line entrance.
3.6.2
Electric Manholes
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NOTE: Provide the plastic coating or supports where
corrosive conditions in manholes are anticipated.
Determine from the Using Agency what types of
communication cables the Contractor should provide.
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Cables shall be securely supported from walls by hot-dip galvanized cable
racks with a plastic coating over the galvanizing and equipped with
adjustable hooks and insulators. The number of cable racks indicated shall
be installed in each manhole and not less than 2 spare hooks shall be
installed on each cable rack. Insulators shall be made of high-glazed
porcelain. Insulators will not be required on spare hooks.
3.6.3
Communications Manholes
The number of hot-dip galvanized cable racks with a plastic coating over
the galvanizing indicated shall be installed in each telephone manhole.
Each cable rack shall be provided with 2 cable hooks. Cables for the
telephone and communication systems will be installed by others.
SECTION 16375A
Page 57
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