33 70 02 - Underground Electric Duct Banks.docx

SECTION 33 70 02

Underground Electric Duct Banks

PART 1 GENERAL

1.01 REFERENCES

The publications referenced within this specification are referred to by the basic designation only.

A. UFGS 33 70 02.00 10 Electrical Distribution System, Underground B. NFPA 70- National Electric Code C. IEEE C2- National Electrical Safety Code D. ACI 318- Building Code Requirements for Reinforced Concrete

1.02 SUBMITTALS

A. Government approval is required for submittals with a "G" designation; submittals not having a "G" designation are for information only. Submit the following in accordance with the “Statement of Work - SUBMITTAL REQUIREMENTS”:

a. SD-01 Preconstruction Submittals

1. Construction Plan

2. Material Safety Data Sheets (MSDS)

b. SD-03 Product Data

1. PVC Pipe and fittings

2. Conduit Spacers

3. Concrete Mix Data

PART 2 PRODUCTS

2.01 MATERIALS

A. Conduit

a. 5” Schedule 80 PVC Pipe, Type E

b. Schedule 80 PVC couplings and fittings

B. Reinforced Concrete

a. 4000 PSI, maximum aggregate size of ½”

b. ½” Reinforcing Steel, Epoxy Coated, Grade 60

c. 3/8” Reinforcing Ties, Epoxy Coated, Grade 60

PART 3 EXECUTION

3.01 GENERAL

A. Provide underground duct bank with the number and size of ducts as shown on the attached drawing.

B. All work shall be done in compliance with the applicable standards listed above.

C. Contractor is required to obtain a Utility Clearance Permit prior to any excavation or digging.

D. The contractor is responsible for providing road closure and detour signs. The contractor must provide barricades and devices to secure the work site and keep pedestrians and vehicle traffic safe.

E. All work shall be in accordance with NEC 310.60.

3.02 EXCAVATION

A. Contractor shall saw cut along the path of the new duct bank. Duct bank routing shown on drawing is approximate, route duct bank as required to complete the path.

B. The trench shall be excavated to allow for space for safe work in and around the trench. This is to include space for shoring, and any required formwork.

C. The trench shall be excavated to allow for drainage of the ducts. The slope shall be a minimum of 4 inches per 100 feet.

D. The minimum manufactured bend radius shall be 36 inches for ducts 3 inches or greater in diameter. Otherwise, long sweep bends having a minimum radius of 25 feet shall be used for a change of direction of more than 5 degrees, either horizontally or vertically. Both curved and straight sections may be used to form long sweep bends, but the maximum curve used shall be 30 degrees.

E. All dirt and excavated materials not used for backfill shall be removed by the contractor.

F. Spoil banks shall be placed away from the edge of the trench so that no loose dirt falls into the trench.

G. The contractor shall operate pumps as necessary to keep the trench free of water.

H. The entire run from manhole to manhole shall be excavated, graded, and prepped for conduit prior to installing any ducts.

I. Final elevation of the top of the duct bank shall be a minimum of 24” below grade.

3.03 CONDUIT

A. Ducts shall be installed in minimum of 10 foot lengths. All connections shall be watertight. Spacers shall be used to set the ducts and hold in place.

B. Ducts shall be stored to avoid warping and deterioration with ends sufficiently plugged to prevent entry of any water or solid substances. Ducts shall be thoroughly cleaned before being laid. Plastic ducts shall be stored on a flat surface and protected from the direct rays of the sun.

C. Separators or spacing blocks shall be made of steel, concrete, plastic, or a combination of these materials placed not farther apart than 4 feet on centers. Ducts shall be securely anchored to prevent movement during the placement of concrete.

D. Ducts shall be provided with end bells whenever duct lines terminate in manholes or hand holes.

E. All conduit shall have pull wires installed at the completion of the project.

3.04 CONCRETE and REINFORCING

A. If the sides of the trench allow, forms will not be required for the concrete work. If this is not possible then forms shall be installed that withstand the forces of the concrete and match the desired path of the duct bank.

B. Continuous steel reinforcing shall be furnished and installed along the entire concrete pour. Reinforcing steel includes top and bottom longitudinal steel as well as transverse ties.

C. Conduit and steel shall be cleaned of all dirt and debris prior to placing concrete.

D. Concrete shall be placed and finished according to ACI 318.

E. Concrete shall be placed continuously in a manner that minimizes the need for any construction joints.

F. All areas of the duct bank to include under spacers, rebar, and conduit require a minimum of 3” of coverage.

G. Forms and shoring shall be removed in a manner that does not damage the new concrete.

3.05 CONNECTION AT MANHOLES

A. Conduit shall terminate in bell end and be flush with the inside wall of the manhole.

B. Duct bank shall be doweled to the manhole using rebar and epoxy.

C. All penetrations shall be made to provide a watertight, flush, finish of the connection of the duct bank to the manhole.

3.06 BACKFILL, PAVING, CLEANUP

A. The trench will not be backfilled until the concrete has adequately cured.

B. The top of the trench shall be backfilled with crushed stone and compacted in 6” lifts. The stone will provide a sub base for the asphalt or concrete top course.

C. Warning tape shall be laid above the duct bank indicating buried power lines.

D. The contractor shall place a minimum of 6” of Hot Mix Asphalt along the duct bank path in roadways. Paving shall be done in two lifts, with 4” of asphalt placed and 2” of top coat. Paving shall be done in accordance with Specification 32 12 00.

E. Additional areas shall be brought to surrounding grade and backfilled with gravel/topsoil and seed as necessary.

F. Once completed the contractor shall test and clean each conduit by pulling a mandrel or wire brush through the run. The mandrel shall be a ¼” less than the diameter of the conduit.

G. Once each conduit has been tested to the satisfactory of the COR, each unused conduit shall be sealed at the ends to prevent moisture and debris from entering the conduit.

H. The contractor shall remove all remaining debris, equipment, tools, etc from the work site. The area shall be swept of excess dirt and dust.

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GYPSUM BOARD

09 28 00 Underground Duct Banks- 33 70 02 - Page 3