Buried Duct Network for Upgrading Utility Cables –

Recent Field Trials

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Outside Plant Consulting Services, Inc.

Dr. Lawrence M. SlavinOutside Plant Consulting Services, Inc.973-983-0813lslavin@ieee.orgwww.outsideplantconsulting.com

2009 AASHTO Right of Way & UtilitiesSubcommittee ConferenceOklahoma CityApril 20, 2009

Sponsor

Funding:US Department of Transportation

Technical Oversight:FHWA Turner-Fairbank Highway Research Center

Objectives & Goals

Short-Term:Develop improved method of buried

construction for utility cables (telecommunications, CATV, power)

Long-Term:• Avoid damage to roads and

transportation systems• Minimize proliferation of utility

poles

Background

Cable Construction Methods

Overhead Utility Poles

Below ground• Underground conduit• Direct-Buried

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cables placed directly in trench PS

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Direct-Buried Philosophy

• Cables directly placed in trench

• Robust cable designs•electrically insulated (power, ...)•waterproof•mechanical protection (armor, …)

• Sized for “ultimate” future needs

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Direct-Buried Philosophy

• Typically, no convenient means of cable addition, replacement or

upgrade*

* Sometimes a duct is provided in trench by a utility, but is not a uniform practice across all utilities and regions, or necessarily done in the most cost-effective manner

Direct-Buried Philosophy• Does it usually work (successful) ?

• Often (in use for several decades)

• Does it always work ?

• No•new technology•exhausted capacity•cable degradation or damage•new service providers

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Direct-Buried Philosophy

• Cable additions require aggressive construction (open-cut trenching, directional drilling, …)

THUS

• Possible damage to roads, property, utilities, ...

• Safety hazards PS

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Buried Duct Network (BDN)

Benefits

* e.g., US DOT - Office of Pipeline Safety

For buried facilities (requiring future upgrades, maintenance, …), avoids

• Road damage (road cuts, ...)• Corresponding traffic delays• Damage to buried lines (gas*, electric,…)• Damage to Intelligent Transportation

System (cables, …)

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Benefits

* A Policy for Accommodating Utilities Within Highway Right-of-Way, A Policy on the Accommodation of Utilities Within Freeway Right-of- Way, Guidance on Sharing Freeway and Highway Rights-of-Way for

Telecommunications, Highway/Utility Guide.

Consistent with AASHTO & FHWA Recommendations*

• Belowground lines• Access and Upgradability• Joint Usage of Infrastructure & Facilities

BDN Concept/Design

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Hybrid system; combines

• Advantages of underground conduit (upgradability)

with

• Advantages of direct-buried construction (low cost)

BDN Concept/Design

Specify standard, optimized, cost-effective Buried Duct Network:

• Initially installed distribution cables are selected, sized and directly-buried in joint-use trench, following present recommended (cost-effective) practices

• Two large diameter (e.g., 4-in.) main distribution ducts, initially vacant, accessed at common handholes, also placed as an overlay in the same joint-use trench

BDN Strategy*• Add minimum duct network for

insurance for atypical (but not uncommon) cases when need upgrade

• Consistent with shared/joint-usage philosophy

• Space-efficient

• Cost-effective* Does not apply to applications that warrant full-scale underground

conduit systems (e.g., banks of conduits, manholes, …)

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BDN Detail

power

CATV

tele

three individual service ducts

common (joint) service trench

common (joint) main trench along ROW

two vacant large (e.g., 4-in.) ducts through handhole

initial distribution cables(direct-buried, w/o duct)

handhole

initial primary power distribution cables(direct-buried, w/o duct)

Note: for thoroughfare application, possibly omit service lines

utility terminals/equipment/hardware(power, telephony, CATV)

patent pending

(Nominal 2 ft. wide x 3 ft. long x 36+ inches deep)

mouseholes(e.g., 4-in. duct)

flared sides(avoid uplift -- frost, duct, …)

bottomless

lid

6 knockouts(both sides)

Not to Scale

patent pending

Direct-Buried Initial Cables plus Vacant Main Ducts thru Handhole

initial distribution cables(direct buried, w/o duct)

two vacant main ducts (HDPE, PVC, …) (future distribution cables)handhole

express duct (alternative)

cut/sealed duct

same (joint) trench

e.g., communications (telephone, CATV)

e.g., power (primary and/or secondary)

patent pending

• Main distribution ducts are initially vacant

BDN Concept/Design

• Future Use of main distribution ducts efficiently allocated, as necessary (telephone, CATV, power)

• Individual, smaller diameter, service wire ducts are routed from terminals to residence or small business, to provide protection for initial service wires, and facilitate future upgrade or replacement

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BDN Concept/Design

• Handhole NOT intended for routine maintenance (no terminals, splices, ... ) -- avoids exposure of communications workers to high voltages

• Accessed only if and when the need arises for future addition of cable(s)

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Alternatives

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Phase I (Feasibility) 6 Months

Phase II (R&D)

24 Months

Phase II Effort

Develop design, construction, maintenance, and management guidelines and practices

• ASCE Pipeline Division•“ASCE Manual of Practice for Belowground Pipeline Networks for Utility Cables”

•Anticipated availability Summer 2009

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Phase II Effort

Ensure availability of prototype hardware for future applications, field trials, ...

• Handholes (load ratings, ...)• Ducts, conduits• Security system (locks, …)• …..

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Handholes (TIER 15)

Polymer Concrete (Quazite®)

Handholes (“20K”)

HDPE(Pencell Plastics)

Phase II Effort

Arrange appropriate full-scale field trials• Permanent installation• e.g., 1 kft• Road, highway, residential, …

• Identify & address various issues• Leverage for future introduction into utility and transportation industry practices

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Phase II Effort

Completed or planned field trials•Arlington, Texas – November 2008

•Monroe, NC – March 2009

•Danvers, MA – June 2009•........

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Monroe, NCRoad Widening SR1223 (NCDOT)

• Moving Verizon and Time Warner Cable• Outer edge of ROW• Tier 15 handholes (NC DOT)• Open-cut trenching• Conventional PVC (adhesive joints)• 1 kft (<800 ft.)• Conduits (and innerduct) for future (and initial) cables

Monroe, NC

Thanks, Gus !

Not to Scale

Handhole Locations for Verizon BDN /Time Warner Installation (Monroe, NC)

390 ft. 330 ft.

2 Time Warner Cable innerducts(outside handholes)

two 4-in. conduits(e.g., Schedule 40 PVC)

All conduits plugged at all exposed ends

30” x 48” x 36-in deep handholes(Quazite PG3048)

36” width trench

increase trench width in vicinity of handholes

initial Verizon cables through one conduit

Verizon equipment/pedestal

Time Warner Cable mini-vault

Not to Scale

surface

36”

Trench Cross-Section for Verizon BDN /Time Warner Cable Installation (Monroe, NC)

two 4” (Verizon) conduits

two 2” (Time Warner Cable) innerducts,including tracer wire

fiber cable + 600 pr copper cable (+ vacant path ?)

fiber cable + pull rope

pull rope

36”+

Martin Luther King, Jr. Blvd (SR 1223)

Trenching & Conduit/Handholes

video

Installed BDN Conduit & Handholes

video

Time Warner Cable Direct-Buried Innerduct

Installed Innerduct

Backfilling & Compacting

video

Backfilling & Compacting

Finishing

video

Finishing

Phase II Effort

Implementation issues• Ownership• Joint-usage agreements (compensation, …)

• Road and construction permits• ...

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HOWYOUCANHELP

How You Can Help (Permits, ...)

•Encourage (require ?) use of upgradable networks (BDN, other, ...)

•Stricter specifications

•Uniformity (across states, ...)

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How You Can Help (Permits, ...)

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Suggestions• Existing related efforts ?

• Individual states ?• Nationally ?

• How to proceed ?• .......

Thank You !

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