#NEC CONCRETE ENCASED DUCT BANK INSTALL#
#NEC CONCRETE ENCASED DUCT BANK FREE#

The concrete shall be pigmented with a minimum of 6 kg of red oxide additive per cubic yard.

Concrete mixture shall have pea gravel aggregate not exceeding 19mm (¾ inch) in size.

The concrete shall meet strength requirements of.

The concrete envelope for conduit stub-ups shall extend 150 mm (6 inches) above grade.

This minimum shall be increased to 610 mm (24 in) under roadways.

The top of the concrete envelope of the duct bank shall be a minimum of 610 mm (24-inches) below grade.

Underground duct banks running under roadways and other areas of high loading shall be concrete encased rigid galvanized steel conduit.

Installation shall be as defined in the installation details and per the requirements of this specification.

Underground duct banks shall be routed to manholes and pull boxes located along the duct bank as shown on the drawings.

Trenching Excavation for Concrete Encased Conduit – Duct Bank

The minimum depth of direct buried conduit shall meet the requirements of Table 1.

#NEC CONCRETE ENCASED DUCT BANK INSTALL#

Install red concrete tiles or pour 25 mm (1 in.) thick layer of red concrete to extend 100 mm (4in.) in width past outermost conduits. Backfill with material as required per Backfill Requiement paragraph, for 100mm (4in.) over top of conduit.Under no circumstances should bricks or other supports except the bedding be used to bring the conduit to elevation. Bed the conduit in the selected backfill one-fourth to one-third of the conduit diameter.

#NEC CONCRETE ENCASED DUCT BANK FREE#

Fill bottom 100 mm (4 in) of the trench with selected backfill free from stones and tamp lightly.Holes and depressions shall be filled and tamped to thoroughly.All trenches shall not be less than 100 mm (4 in) below the desired elevation of the bottom of the conduit.The installation of conduit without concrete encasement is similar to that for concrete-encased conduit.Authorized installations shall be in accordance with the following requirements. Non-concrete encased, direct buried conduit installations must be approved by company.All trenches shall be checked for depth, width and pitch prior to installing any raceway or forms.Ĭonduit Installations Trenching Excavation for Direct Buried Conduit or Non-Concrete Encased The Contractor shall repair any damage to existing services which may occur during trenching operations.The trench must be pumped where there is an excessive amount of water. The duct structure should be kept dry until the concrete envelope has been poured. If the ground in the trench bottom is muddy or wet, the trench bottom should be built up with rock or gravel. Trenches should be planned so that the spoil does not interfere with the storage and handling of duct.All sharp bends should be avoided in the excavation. The levelness of the duct structure is determined by the levelness of the trench bottom. The depth of the excavation necessary for conduits and directly buried cables depends upon the cover, the depth of the duct bank or cable, the bedding and other buried objects such as pipe.It is possible that obstructions of one kind or another may be countered which will necessitate changing the grade or the route of the trench. The trench should be excavated from one manhole location to the next before grading the trench or laying conduit is attempted.No excavation shall take place until the permit is issued.

The Contractor shall submit a request for an excavation permit and include a trench layout drawing showing coordinates and elevations as well as any crossings with existing pipe/cables.

The Contractor shall be responsible for coordinating the trenching work with other discipline underground work, to resolve conflicts in level and/or space allocation.

Trench sides shall be appropriately sloped and/or shored to prevent cave-ins.

The depth of underground electrical duct banks and cable installations shall be in accordance with article Click Here and all drawings.

Trenching Excavation Requirements in Plants

Nec concrete encased duct bank