STANDARD CONSTRUCTION SPECIFICATIONS PART 1 – ROADS
10.12.7 PVC Conduit and Concrete Encased Ducts
PVC conduit and concrete encased ducts shall be furnished and installed as indicated on the
Contract plans and as included in the Bills of Quantities. In general, PVC conduit and duct shall be
provided to permit routing for lighting system cables; LV, 11 KV, 22 KV, 33 KV and 132 KV electrical
distribution system cables below pavement or other areas as indicated on the Contract plans or
where directed by the ADWEA/ADDC and as specified herein and as directed by the Owner and/or
by the ADWEA/ADDC.
The conduits or ducts shall be PVC conduit and fittings complying with the requirements of Section
10.4.3.
The PVC conduits and ducts, except for 132 KV and 220 KV duct banks, shall be encased in Class C
20/20 concrete complying with the requirements of Section 4.3.9 of Chapter 4, Concrete Works, of
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these Standard Specifications. The dimensions of concrete encasement shall be as indicated on the
Contract plans.
The PVC ducts for 132 KV and 220 KV duct banks shall be encased in Class C 30/20 concrete with
standard reinforcing steel complying with requirements of Section 4.3.9 of Chapter 4, Concrete Works,
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of these Standard Specifications. The dimensions of concrete encasement shall be as indicated on
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the Contract plans.
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132 KV and 220 KV ducts shall be filled with bentonite around the cables. The Contractor shall furnish
and perform all the works required for providing bentonite in PVC ducts. Bentonite shall be filled in the
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ducts after the installation of cables. Bentonite materials and the method of filling shall be as approved
by the Engineer. Separate measurement and payment will be made for providing bentonite fill in 132
KV and 220 KV ducts.
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All trench and backfill at concrete encased PVC conduit and ducts shall comply with the requirements
of Section 10.3. Trench and backfill for concrete encased conduits and ducts shall be considered as
a subsidiary obligation to the work for the Items of concrete encased PVC conduits and ducts and
duct banks as described in the Bills of Quantities. No separate payment will be made by the Owner.
10.12.8 Protection of Existing Electric Cables
This work pertains to the protection of existing LV, 11 KV, 22 KV, 33 KV and 132 KV electric cables
exposed by manual excavation and which are to remain in operation as designated on the Contract
plans or where directed by the Engineer and/or the ADWEA/ADDC.
All excavation and backfill shall be in accordance with Section 10.3.
Precast concrete protection slabs, cast-in-situ concrete protection slabs, extensions of existing cast-
in-situ concrete protection slabs and extensions of the underlying existing concrete encased duct
banks shall be installed at road crossings, paved areas or other locations as detailed on the Contract
plans or where directed by the Engineer and/or the ADWEA/ADDC.
Existing occupied concrete encased PVC ducts shall be extended with concrete encased, matching
size, split polyvinylchloride (PVC) ducts and existing vacant, concrete encased PVC ducts shall be
extended with concrete encased, matching size, whole PVC ducts as specified herein and as
approved by the Engineer and/or the ADWEA/ADDC. Extensions of existing vacant ducts shall be
capped watertight upon installation.
New, split polyvinylchloride (PVC) ducts shall be installed around existing electric cables to form a
protective concrete encasement where such cables are to remain under a new paved area or are to
pass through the wall of a service chamber or other locations where designated by the Engineer and/or
the ADWEA/ADDC.
The installation of concrete encased, split PVC duct shall be made in the following manner:
1. Split PVC ducts shall be made by jointing two PVC pipe segments, a lower 270° segment and
an upper 120° segment of identical size and specifications. The pipe walls of the lower segment
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STANDARD CONSTRUCTION SPECIFICATIONS PART 1 – ROADS
shall be cut on a vertical making an obtuse angle at the inner surface so as to avoid sharp
edges. The cut surface shall be smooth without any projections. The lower segment shall be
placed surrounding the existing cable, with its 90° opening upwards. The upper 120° segment
shall be placed as a lid or cover to the opening of the lower segment, with an equal overlap on
either side. The overlapping portions of the pipes shall be jointed together by spot supplying
an approved PVC glue to avoid displacement while concentrating. After jointing the split PVC
ducts shall be wrapped twice with polyethylene film, 152 microns thick and the wrapping
securely fastened to prevent fresh concrete from entering the ducts. The ducts shall be
supported on suitable corrosion resistant spacers.
2. The existing occupied concrete encased PVC ducts shall be extended in the same manner as
above. The new split PVC duct shall be securely joined to existing ducts to be extended in
such a manner to insure against any displacement of the duct extensions during the placement
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of concrete to the satisfaction of the Engineer and/or the ADWEA/ADDC. The Contractor shall
submit shop drawings identifying all the details for the approval of the Engineer. Split PVC
ducts for 132 KV and 220 KV cables shall be filled with bentonite around the existing cables in
accordance with the applicable requirements as specified under Section 10.12.7. Separate
measurement and payment will be made for providing bentonite fill in split ducts for 132 KV
and 220 KV ducts.
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The cast-in-situ concrete protection slab and protection slab extensions shall be Class C 20/20
concrete and shall match the existing slabs as approved by the Engineer and/or the ADWEA/ADDC.
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The Contractor shall furnish and place precast, Class C 30/20, reinforced concrete protection slabs of
the sizes designated on the Contract plans where directed by the Engineer and/or the ADWEA/ADDC,
all in accordance with applicable Sections of Chapter 4, Concrete Works, of these Standard
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Specifications and as specified herein, and approved by the Engineer and/or the ADWEA/ADDC.
10.12.9 Supply of Cable Covering Tiles
Where any lighting, LV, 11 KV, 22 KV, 33 KV or 132 KV electrical cable are directly buried in trenches
in locations other than where such electrical cables are installed in concrete encased ducts, precast,
concrete cable covering tiles shall be installed over all new electrical cables and over all existing
electrical cables exposed by manual excavation to verify the location of such cables.
The Contractor shall supply precast, concrete cable covering tiles for electric cables according to the
requirements of the ADWEA/ADDC, the Engineer and the Owner and the following:
10.12.9.1 Materials, General
All materials for cable covering tiles shall comply with applicable Sections of Chapter 4, Concrete
works, of these Standard Specifications and as specified herein.
10.12.9.2 Concrete Mix
The ratio of the concrete mix for the cable covering tiles shall be as per class C15/20 of Table 4-16.
Cement and aggregate shall comply with the requirements of Section 4.3.7 of Chapter 4, Concrete
Works, of these Standard Specifications
10.12.9.3 Curing
The cable covering tiles shall be cured in clean, fresh water for at least seven (7) days after they are
cast.
10.12.9.4 Molding
The cable covering tiles shall be cast in appropriate accurately made molds and compacted by an
efficient hydraulic pressure method. The pressure employed for the hydraulic pressed cable covering
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