337105_Underground_Ducts_and_Raceways.pdf

UNITED STATES DEPARTMENT OF STATE UNCLASSIFIED JANUARY 2019

OVERSEAS BUILDINGS OPERATIONS

OBO STANDARD SPECIFICATIONS

UNDERGROUND DUCTS AND RACEWAYS UNCLASSIFIED SECTION 337105 - 1

SECTION 337105 - UNDERGROUND DUCTS AND RACEWAYS

PART 1 - GENERAL

1.1 SUMMARY

A. This Section includes the following:

1. Ducts in direct-buried duct banks.

2. Ducts in concrete-encased duct banks.

3. Handholes and handhole accessories.

4. Manholes and manhole accessories.

5. Locking devices for handholes, manholes and other devices provided to allow access to power and signal wiring for security devices (i.e., vehicle barriers, cameras, TSS equipment).

B. Related Sections include the following:

1. Section 033000 “Cast-in-Place Concrete,” including but not limited to provisions for field conditions, materials, and installation.

2. Section 260518 “Low-Voltage Electrical Power Conductors and Cables.”

3. Section 260525 "Grounding and Bonding for Electrical Systems" for grounding electrodes, counterpoise conductors, clamps and connectors for grounding metallic manhole and handhole accessories, and testing of grounds.

4. Division 26 Section on “Raceways and Boxes.”

5. Section 270526 “Grounding and Bonding for Communications Systems.”

6. Division 27 Sections on communications.

7. Section 28 Sections on technical security systems and fire alarm systems.

1.2 SUBMITTALS

A. Product Data: For the following:

1. Manhole and handhole hardware.

2. Conduit and ducts, including elbows, bell ends, bends, fittings, and solvent cement.

3. Duct-bank materials, including spacers and miscellaneous components.

4. Warning tape.

5. Locking devices.

B. Shop Drawings: For cast-in-place and precast manholes and handles, submit shop drawings showing construction/fabrication and installation details for the items below. Precast elements shall have shop drawings signed and sealed by qualified professional engineer.

1. For cast-in-place manholes and handholes:

a. Duct sizes and locations of duct entries.

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b. Reinforcement details for cast-in-place structures.

c. Manhole cover design.

d. Step details.

e. Grounding details.

f. Dimensioned locations of cable rack inserts, pulling-in irons.

g. Locking devices.

C. Coordination Drawings: Show duct profiles and coordination with other utilities and underground structures. Include plans and sections drawn to scale, and show all bends and location of expansion fittings.

D. Splice Documentation: Document location and installation of splices for work in this Section.

Documentation shall be by trained splice technician that performed work.

E. Product Certificates: For concrete and steel used in underground precast manholes, according to

ASTM C 858.

F. Product Test Reports: Indicate compliance of precast manholes with ASTM C 857 and

ASTM C 858, based on factory inspection.

G. Thermal Imaging Report: Documentation of imaging; see the Article on FIELD QUALITY

CONTROL.

1.3 QUALITY ASSURANCE

A. Electrical Components, Devices, and Accessories (Including Ducts for Communications and

Telephone Service) Listed and labeled as defined in NFPA 70, Article 100, by a testing agency acceptable to authorities having jurisdiction, and marked for intended use.

B. Comply with ANSI C2.

C. Comply with the OBO Electrical Code and OBO Zoning Code.

1.4 DELIVERY, STORAGE, AND HANDLING

A. Deliver ducts to Project site with ends capped. Store nonmetallic ducts with supports to prevent bending, warping, and deforming.

B. Store precast concrete units at Project site as recommended by manufacturer to prevent physical damage. Arrange so identification markings are visible.

C. Lift and support precast concrete units only at designated lifting or supporting points.

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1.5 COORDINATION

A. Coordinate layout and installation of ducts, manholes, and handholes with final arrangement of other utilities and site grading, as determined in the field.

B. Coordinate elevations of ducts and duct-bank entrances into manholes and handholes with final profiles of conduits as determined by coordination with other utilities and underground obstructions. Revise locations and elevations from those indicated as required to suit field conditions and to ensure duct runs drain to manholes and handholes, and as approved by Project

Director/COR.

PART 2 - PRODUCTS

2.1 CONDUIT

A. Conduit and fittings are specified in Division 26 Section on "Raceways and Boxes.”

2.2 DUCTS

A. Rigid Nonmetallic Conduit: NEMA TC 2, Type EPC-40-PVC, UL 651, with matching fittings by the same manufacturer as the conduit, complying with NEMA TC 3 and UL 514B.

2.3 HANDHOLES

A. Cast-in-Place or Precast: Fabricate according to requirements for cast-in-place handholes in the

Article on UNDERGROUND ENCLOSURE APPLICATION.

2.4 MANHOLES

A. Cast-in-place or precast enclosures.

B. Precast Units:

1. ASTM 478, with interlocking mating sections, complete with accessories, hardware, and features as indicated. Include concrete knockout panels for conduit entrance and sleeve for ground rod.

2. Design and fabricate structure according to ASTM C 858.

3. Design structure according to details on Drawings.

4. Source Quality Control: Inspect structures according to ASTM C 1037.

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2.5 ACCESSORIES

A. Duct Spacers: Rigid PVC interlocking spacers, selected to provide minimum duct spacings and cover depths indicated while supporting ducts during concreting and backfilling; produced by the same manufacturer as the ducts.

B. Manhole Frames and Covers: Comply with AASHTO loading specified for manhole.

1. Provide cast covers with cast-in legend as applicable:

a. "ELECTRIC-LV" for duct systems with power wires and cables for systems operating at 600 V and less.

b. "ELECTRIC-HV" for duct systems with medium-voltage cables.

c. "SIGNAL" for communications, data, and telephone duct systems.

2. Cast iron with cast-in legend "ELECTRIC" as indicated. Milled cover-to-frame bearing surfaces.

3. Manhole Frames and Covers: ASTM A 48; Class 30B gray iron, 762 mm size, machine-finished with flat bearing surfaces.

4. Special Covers: Recess on cover designed to accept finish material in paved areas.

C. Handhole Frames and Covers: Provide cast covers with cast-in legend:

a. "ELECTRIC."

D. Cover Lock Bolts: At office compounds, provide manhole and handhole lock bolts for covers;

bolts shall have patterned heads.

E. Sump Frame and Grate: ASTM A 48, Class 30B gray cast iron.

F. Pulling Eyes in Walls: Eyebolt with reinforcing-bar fastening insert 50 mm diameter eye and 25-by-100-mm bolt.

1. Working Load Embedded in 150 mm, 25 MPa Concrete: 60 kN minimum tension.

G. Pulling and Lifting Irons in Floor: 22 mm diameter, hot-dip-galvanized, bent steel rod; stress relieved after forming; and fastened to reinforced rod. Exposed triangular opening.

1. Ultimate Yield Strength: 180 kN shear and 270 kN tension.

H. Bolting Inserts for Cable Stanchions: Flared, threaded inserts of noncorrosive, chemical-resistant, nonconductive thermoplastic material; 13 mm ID by 70 mm deep, flared to 30 mm minimum at base.

1. Tested Ultimate Pullout Strength: 53 kN minimum.

I. Expansion Anchors for Installation after Concrete Is Cast: Zinc-plated, carbon-steel-wedge type with stainless-steel expander clip with 12 mm bolt, 24 kN rated pullout strength, and minimum

30 kN rated shear strength.

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J. Cable Stanchions: Heavy duty PVC; punched with 14 holes on 40 mm centers for cable-arm attachment.

K. Cable Arms: 5 mm thick, hot-rolled, hot-dip-galvanized, steel sheet pressed to channel shape;

300 mm wide by 350 mm long and arranged for secure mounting in horizontal position at any location on cable stanchions.

L. Cable-Support Insulators: High-glaze, wet-process porcelain arranged for mounting on cable arms.

M. Grounding Materials: Comply with Section 260525 "Grounding and Bonding for Electrical

Systems."

N. Ladder: UL-listed, fiberglass specifically designed for electrical manhole use. Minimum length equal to distance from deepest manhole floor to grade plus 900 mm.

O. Duct-Sealing Compound: Nonhardening, safe for contact with human skin, not deleterious to cable insulation, and workable at temperatures as low as 2 deg C. Capable of withstanding temperature of 150 deg C without slump and of adhering to clean surfaces of plastic ducts, metallic conduits, conduit coatings, concrete, masonry, lead, cable sheaths, cable jackets, insulation materials, and common metals.

P. Warning Tape: Underground-line warning tape specified in Division 26 Section on

"Identification for Electrical Systems."

2.6 CONSTRUCTION MATERIALS

A. Waterproofing: Comply with Division 07 Sections.

B. Mortar: Comply with ASTM C 270, Type M, except for quantities less than 60 L where packaged mix complying with ASTM C 387, Type M, may be used.

C. Concrete: Use 25 MPa minimum, 28-day compressive strength and 10-mm maximum aggregate size. Concrete and reinforcement are specified in Section 033000 "Cast-in-Place Concrete."

PART 3 - EXECUTION

3.1 PREPARATION

A. Coordinate layout and installation of duct bank, manholes, and handholes with final arrangement of other utilities, site grading, and surface features in accordance with Drawings and as determined in the field. Notify Project Director/COR if there is a conflict between areas of excavation and existing structures identified to remain, vegetation identified to remain (e.g,, trees), or archaeological sites.

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B. Coordinate elevations of duct-bank entrances into manholes, and handholes with final locations and profiles of duct banks, as determined by coordination with other utilities, underground obstructions, and surface features. Revise locations and elevations as required to suit field conditions and to ensure that duct bank will drain to manholes and handholes, and as approved by Project Director/COR.

C. Clear and grub vegetation to be removed, protect vegetation to remain, and remove and stockpile topsoil for reapplication according to Drawings or other Specification Sections.

3.2 EARTHWORK

A. Excavation and Backfill: Comply with Division 31 Sections for earthwork and backfill but do not use heavy-duty, hydraulic-operated, compaction equipment.

B. Restore surface features at areas disturbed by excavation and reestablish original grades, unless otherwise indicated. Replace removed sod immediately after backfilling is completed.

C. Restore all areas disturbed by trenching, storing of dirt, cable laying, and other work. Restore vegetation and include necessary topsoiling, fertilizing, liming, seeding, sodding, sprigging, and mulching. Comply with Division 32 Sections for landscaping.

D. Restore disturbed pavement. Refer to Division 01 Sections for cutting and patching for additional information for this Section.

3.3 CORROSION PROTECTION

A. Corrosion protection shall conform to OBO Electrical Code Chapter 1 and OBO Building Code

Appendix R.

B. Do not combine materials that can form an electrolytic couple that will accelerate corrosion in the presence of moisture unless moisture is permanently excluded from junction of such materials.

C. Use conductors with protective coatings where conditions would cause deterioration or corrosion of conductors.

3.4 UNDERGROUND DUCT APPLICATION

A. Underground Ducts for Electrical Cables Higher Than 600 V: Type EPC-80-PVC, concrete-encased duct bank.

B. Underground Ducts for Electrical Feeders 600 V and Less: Type EPC-40-PVC, concrete-encased duct bank.

C. Underground Ducts for Communications Utility Service: Type EPC-40-PVC, concrete encased duct bank, except use Type EPC-80-PVC when crossing roads.

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D. Underground Ducts for Communication Circuits: Type EPC-40-PVC, concrete encased duct bank.

3.5 UNDERGROUND ENCLOSURE APPLICATION

A. Loading Design: Reference standard identified below identifies the Basis-of-Design utilizing precast concrete enclosures unless noted otherwise. Cast-in-place enclosures shall be designed for equivalent loading.

1. Handholes and Boxes for 600 V and Less:

a. Units in Roadways and Other Deliberate Traffic Paths: H-20 structural load rating according to AASHTO HB 17.

b. Units in Driveway, Parking Lot, and Off-Roadway Locations, Subject to Occasional, Nondeliberate Loading by Heavy Vehicles: H-20 structural load rating according to

AASHTO HB17.

c. Units in Sidewalk and Similar Applications with a Safety Factor for Nondeliberate

Loading by Vehicles: H-10 structural load rating according to AASHTO HB17.

d. Units Subject to Light-Duty Pedestrian Traffic Only: Cast-in-place with structural loading to 20 MPa (3000 psi).

e. Cover design load shall not exceed the design load of the handhole or box.

2. Manholes:

a. Units Located in Roadways and Other Deliberate Traffic Paths by Heavy or Medium

Vehicles: H-20 structural load rating according to AASHTO HB 17.

b. Units Not Located in Deliberate Traffic Paths by Heavy or Medium Vehicles: H-10 load rating according to AASHTO HB17.

B. Cast-in-Place Manhole and Handhole Construction:

1. Reinforced concrete, monolithically poured walls and bottom, with steel frame and access door assembly as the top of handhole. Locate duct entrances and windows near corners to facilitate racking of cabling and conductors. Place built-in items shall be installed before pouring concrete.

3.6 CONDUIT AND DUCT INSTALLATION

A. Slope: Pitch ducts a minimum slope of 1:300 down toward manholes and handholes and away from buildings and equipment. Slope ducts from a high point in runs between two manholes to drain in both directions.

B. Curves and Bends: Use manufactured elbows for stub-ups at equipment and at building entrances.

Use manufactured long sweep bends with a minimum radius as indicated on Drawings, with no less than 7.50 m radius, both horizontally and vertically, at other locations.

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C. Use solvent-cement joints in ducts and fittings and make watertight according to manufacturer's written instructions. Stagger couplings so those of adjacent ducts do not lie in the same plane.

D. Duct Entrances to Manholes and Handholes: Space end bells approximately 250 mm o.c. for

125-mm ducts and vary proportionately for other duct sizes. Change from regular spacing to end-bell spacing 3 m from the end bell without reducing duct line slope and without forming a trap in the line. Grout end bells into manhole walls from both sides to provide watertight entrances.

E. Building Entrances: Make a transition from underground duct to conduit at least 3 m outside the building wall. Use fittings manufactured for this purpose. Follow the appropriate installation instructions below:

1. Concrete-Encased Ducts: Install reinforcement in duct banks passing through disturbed earth near buildings and other excavations. Coordinate duct bank with structural design to support duct bank at wall without reducing structural or watertight integrity of building wall.

2. Waterproofed Wall and Floor Penetrations: Install a watertight entrance-sealing device with sealing gland assembly on the inside. Anchor device into masonry construction with one or more integral flanges. Secure membrane waterproofing to the device to make permanently watertight.

F. Concrete-Encased, Nonmetallic Ducts: Support ducts on duct spacers, spaced as recommended by manufacturer and coordinated with duct size, duct spacing, and outdoor temperature. Install as follows:

1. Separator Installation: Space separators close enough to prevent sagging and deforming of ducts and secure separators to earth and to ducts to prevent floating during concreting.

Stagger spacers approximately 150 mm between tiers. Tie entire assembly together using fabric straps; do not use tie wires or reinforcing steel that may form conductive or magnetic loops around ducts or duct groups.

2. Concreting: Spade concrete carefully during pours to prevent voids under and between conduits and at exterior surface of envelope. Do not allow a heavy mass of concrete to fall directly onto ducts. Use a plank to direct concrete down sides of bank assembly to trench bottom. Allow concrete to flow to center of bank and rise up in middle, uniformly filling all open spaces. Do not use power-driven agitating equipment unless specifically designed for duct-bank application. Pour each run of envelope between manholes or other terminations in one continuous operation. If more than one pour is necessary, terminate each pour in a vertical plane and install 20 mm (#6) reinforcing rod dowels extending

450 mm into concrete on both sides of joint near corners of envelope.

3. Reinforcement: Reinforce duct banks where they cross disturbed earth and where indicated.

4. Forms: Use walls of trench to form side walls of duct bank where soil is self-supporting and concrete envelope can be poured without soil inclusions; otherwise, use forms.

5. Depth: Install top of duct bank at least 600 mm below finished grade in nontraffic areas and at least 750 mm below finished grade in vehicular traffic areas, unless otherwise indicated, or where frost depth exceeds those dimensions.

G. Warning Tape: Bury warning tape approximately 300 mm above all concrete-encased duct banks.

Align tape parallel to and within 75 mm of the centerline of duct bank.

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H. Stub-ups: Use rigid steel conduit for stub-ups to equipment. For equipment mounted on outdoor concrete bases, extend steel conduit a minimum of 1.5 m from edge of base. Install insulated grounding bushings on terminations. Couple steel conduits to ducts with adapters designed for this purpose and encase coupling with 75 mm of concrete.

I. Sealing: Seal all penetrations into manholes, hand holes, and building penetrations. Provide temporary closure at terminations of ducts that have cables pulled. Seal spare ducts at terminations. Seal around empty conduit. Use sealing compound and plugs to withstand at least

1.00 MPa (150 psi) hydrostatic pressure.

J. Identify spare ducts with stamped stainless steel tags where ducts terminate at other structures such as handholes, manholes, pullboxes, and buildings.

K. Pulling Cord: Install 450 N (100 lbf) test nylon cord in ducts, including spares.

L. Cable splices are not permitted in ductbanks or conduits; they are only permitted in manholes.

3.7 MANHOLE AND HANDHOLE INSTALLATION

A. Elevation: Install manholes with rooftop at least 375 mm below finished grade. Install handholes with depth as indicated. Where indicated, cast handhole cover frame directly into roof of handhole and set roof surface 25 mm above grade.

B. Incorporate clear vertical access area to allow insertion and removal of portable pump to drain manholes and vaults prior to start of work. Cables and supports shall not be located within, or intrude upon, pump access area.

C. Drainage: Install drains in bottom of units where indicated. Coordinate with drainage provisions indicated.

D. Access: Install cast-iron frame and cover at top of access. Set frames in paved areas and trafficways flush with finished grade, and set other frames 25 mm above finished grade. Install accessways in one of the following manner:

1. Install brick chimney to support frame and cover and to connect cover with roof opening.

Provide moisture-tight masonry joints and waterproof grouting for cast-iron frame to chimney.

2. Install precast collars and rings to support frame and cover and to connect cover with roof opening. Provide moisture-tight masonry joints and waterproof grouting for cast-iron frame to chimney.

E. Racking: Rack cabling and conductors in manholes and utility trenches against walls of each.

Cables and conductors are not permitted to be placed in center portion of manholes; they shall be positioned to ensure safe personnel access at manhole.

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F. Waterproofing: Apply waterproofing to exterior surfaces of units after concrete has cured at least three days. Apply according to Division 07 Sections for waterproofing sheet membrane, if applicable. After ducts have been connected and grouted, and before backfilling, waterproof joints and connections and touch up abrasions and scars. Waterproof exterior of manhole and handhole chimneys after brick mortar has cured at least three days.

G. Hardware: Install removable hardware, including pulling eyes, cable stanchions, cable arms, and insulators, as required for installation and support of cables and conductors and as indicated.

H. Field-Installed Bolting Anchors: Do not drill deeper than 98 mm for anchor bolts installed in the field. Use a minimum of two anchors for each cable stanchion.

I. Cable Splices: Limit splices for work in this Section. Splices shall be UL listed for applications.

Splice installation shall be performed and documented by trained splice technician; see the Article on SUBMITTALS. Splices shall have identification tags; these shall be visible in manhole where splice occurs.

J. Grounding: Install ground rod through floor in each structure with top protruding 100 mm above floor. Seal floor opening against water penetration with waterproof nonshrink grout. Ground exposed metal components and hardware with bare-copper ground conductors. Train conductors neatly around corners. Use cable clamps secured with expansion anchors to attach ground conductors.

K. Cast-in-Place Manhole Installation: Comply with applicable requirements in Section 033000

"Cast-in-Place Concrete."

1. Finish interior surfaces with a smooth-troweled finish.

2. Windows for Future Duct Connections: Where indicated on Drawings or otherwise required, form and pour concrete knockout panels 38 to 50 mm thick, arranged as indicated.

L. Precast Concrete Manhole Installation: Unless otherwise indicated, comply with ASTM C 891.

1. Install units level and plumb and with orientation and depth coordinated with connecting ducts to minimize bends and deflections required for proper entrances.

2. Unless otherwise indicated, support units on a level bed of crushed stone or gravel, graded from 25-mm sieve to 4.75-mm sieve and compacted to same density as adjacent undisturbed earth.

3.8 FIELD QUALITY CONTROL

A. Testing: Demonstrate capability and compliance with requirements on completion of installation of underground ducts and utility structures.

B. Grounding: Test manhole grounding to ensure electrical continuity of grounding and bonding connections. Measure and report ground resistance as specified in Section 260525 "Grounding and Bonding for Electrical Systems."

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C. Duct Integrity: Pull aluminum or wood test mandrel through duct to prove joint integrity and test for out-of-round duct. Provide mandrel equal to 80 percent fill of the duct. If obstructions are indicated, remove obstructions and retest.

D. Thermal Imaging: Upon completion of installation and full energization of system, exam all racking with thermal imaging to ensure minimal heating from Electromagnetic Interference.

E. Correct installations if possible and retest to demonstrate compliance. Remove and replace defective products and retest.

3.9 CLEANING

A. Pull leather-washer-type duct cleaner, with graduated washer sizes, through full length of ducts.

Follow with rubber duct swab for final cleaning and to assist in spreading lubricant throughout ducts.

B. Clean internal surfaces of manholes, including sump. Remove foreign material.

END OF SECTION 337105