Buried Duct Network for Upgrading Utility Cables –
Recent Field Trials
PSC
Outside Plant Consulting Services, Inc.
Dr. Lawrence M. SlavinOutside Plant Consulting Services, [email protected]
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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