1. Buried Duct Network for Upgrading Utility Cables – Recent Field Trials
Outside Plant Consulting Services, Inc. P S C
Buried Duct Network for Upgrading Utility Cables – Recent Field Trials
Dr. Lawrence M. Slavin
Outside Plant Consulting Services, Inc.
2009 AASHTO Right of Way & Utilities
Subcommittee Conference
Oklahoma City
April 20, 2009

2. Sponsor Funding: US Department of Transportation Technical Oversight:
FHWA Turner-Fairbank Highway Research Center

3. Objectives & Goals Short-Term: Long-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

4. Background

5. Cable Construction Methods
Overhead Utility Poles
Below ground
Underground conduit
Direct-Buried P S C

6. cables placed directly in trench

7. Direct-Buried Philosophy
Cables directly placed in trench
Robust cable designs
electrically insulated (power, ...)
waterproof
mechanical protection (armor, …)
Sized for “ultimate” future needs P S C

8. 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

9. 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 P S C 2

10. Direct-Buried Philosophy
THUS
Cable additions require aggressive construction (open-cut trenching, directional drilling, …)
Possible damage to roads, property, utilities, ...
Safety hazards P S C 2

11. Buried Duct Network (BDN)

12. Benefits
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, …) P S C
* e.g., US DOT - Office of Pipeline Safety

13. Benefits Consistent with AASHTO & FHWA Recommendations*
Belowground lines
Access and Upgradability
Joint Usage of Infrastructure & Facilities
* 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.

14. BDN Concept/Design Hybrid system; combines
Advantages of underground conduit (upgradability)
with
Advantages of direct-buried construction (low cost) P S C 2

15. 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

16. 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 P S C
* Does not apply to applications that warrant full-scale underground conduit systems (e.g., banks of conduits, manholes, …) 2

17. BDN Detail patent pending 2
Note: for thoroughfare application, possibly omit service lines
common (joint)
service trench
utility terminals/equipment/hardware
(power, telephony, CATV)
three individual service ducts
power
handhole
tele
CATV
two vacant large (e.g., 4-in.) ducts through handhole
common (joint)
main trench along ROW
initial distribution cables
(direct-buried, w/o duct)
initial primary power distribution cables
(direct-buried, w/o duct)
patent pending
BDN Detail 2

18. (Nominal 2 ft. wide x 3 ft. long x 36+ inches deep)
Not to Scale
6 knockouts
(both sides)
flared sides
(avoid uplift -- frost, duct, …)
lid
mouseholes
(e.g., 4-in. duct)
bottomless
patent pending
(Nominal 2 ft. wide x 3 ft. long x 36+ inches deep)

19. Direct-Buried Initial Cables plus Vacant Main Ducts thru Handhole
initial distribution cables
(direct buried, w/o duct)
e.g., communications (telephone, CATV)
handhole
two vacant main ducts (HDPE, PVC, …) (future distribution cables)
e.g., power (primary and/or secondary)
express duct (alternative)
cut/sealed duct
same (joint) trench
patent pending
Direct-Buried Initial Cables plus Vacant Main Ducts thru Handhole 2

20. BDN Concept/Design Main distribution ducts are initially vacant
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 P S C 2

21. 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) P S C 2

22. Alternatives

23. P S C 2

24. P S C 2

25. P S C 2

26. Phase I (Feasibility) 6 Months2

27. Phase II (R&D) 24 Months 2

28. 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 P S C 2

29. Phase II Effort
Ensure availability of prototype hardware for future applications, field trials, ...
Handholes (load ratings, ...)
Ducts, conduits
Security system (locks, …)
….. P S C 2

30. Polymer Concrete (Quazite®)
Handholes (TIER 15)
Polymer Concrete (Quazite®) 2

31. Handholes (“20K”)
HDPE
(Pencell Plastics) 2

32. 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 P S C 2

33. Phase II Effort Completed or planned field trials
Arlington, Texas – November 2008
Monroe, NC – March 2009
Danvers, MA – June 2009 P S C 2

34. Monroe, NC Road 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 2

35. Monroe, NC
Thanks, Gus !

36. All conduits plugged at all exposed ends
Handhole Locations for Verizon BDN /Time Warner Installation (Monroe, NC)
30” x 48” x 36-in deep handholes
(Quazite PG3048)
36” width trench
Verizon equipment/pedestal
 390 ft.
 330 ft.
two 4-in. conduits
(e.g., Schedule 40 PVC)
2 Time Warner Cable innerducts
(outside handholes)
Time Warner Cable mini-vault
increase trench width in vicinity of handholes
initial Verizon cables through one conduit
All conduits plugged at all exposed ends
Not to Scale

37. two 4” (Verizon) conduits pull rope
Trench Cross-Section for Verizon BDN /Time Warner Cable Installation (Monroe, NC)
surface
two 4” (Verizon) conduits
pull rope
 36”
fiber cable + pull rope
fiber cable pr copper cable (+ vacant path ?)
36”+
two 2” (Time Warner Cable) innerducts,
including tracer wire
Not to Scale

38. Martin Luther King, Jr. Blvd (SR 1223)

39. Trenching & Conduit/Handholes
video

40. Installed BDN Conduit & Handholes

41. Time Warner Cable Direct-Buried Innerduct
video

42. Installed Innerduct

43. Backfilling & Compacting
video

44. Backfilling & Compacting

45. Finishing
video

46. Finishing

47. Phase II Effort Implementation issues Ownership
Joint-usage agreements (compensation, …)
Road and construction permits
... P S C 2

48. HOW
YOU
CAN
HELP

49. How You Can Help (Permits, ...)
Encourage (require ?) use of upgradable networks (BDN, other, ...)
Stricter specifications
Uniformity (across states, ...) P S C 2

50. How You Can Help (Permits, ...)
Suggestions
Existing related efforts ?
Individual states ?
Nationally ?
How to proceed ? P S C 2

51. Thank You ! P S C 2