Underground Transmission: Steps to a Successful Project
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Underground Transmission: Steps to a Successful Project



At the 2012 RMEL Transmission Planning and Operations Conference, Burns & McDonnell department manager Chris Norquist presented "Underground Transmission: Steps to a Successful Project." ...

At the 2012 RMEL Transmission Planning and Operations Conference, Burns & McDonnell department manager Chris Norquist presented "Underground Transmission: Steps to a Successful Project."

Underground transmission projects present a lot of unique difficulties and risks that can be mitigated through successful planning and design. This presentation will discuss some of the key elements to successfully navigating the potential pitfalls of underground transmission projects.



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Underground Transmission: Steps to a Successful Project Underground Transmission: Steps to a Successful Project Presentation Transcript

  • Steps to a Successful Underground ProjectNavigating the Pitfalls by Understanding and Managing Risks March 6, 2012 Chris Norquist, P.E. Burns & McDonnell
  • Agenda• Overview• Planning Throughout Project Life Cycle – Project Siting – Routing – Design – Procurement – Construction• Conclusions
  • Overview View slide
  • Overview• A lot of negative stigmas associated with underground transmission: – Cost – Performance issues in past – Fear of the unknown• It is critical that a successful underground project: – Identify instead of ignore potential risks – Proactively manage them throughout the process View slide
  • Project Siting
  • Project Siting• The two-faced nature of underground transmission: – Go Underground!!!
  • Project Siting• The two-faced nature of underground transmission: – But I don’t want to pay for it! – And not in front of my house!
  • Project Siting• No Magic Bullet• Ways to Make It As Palatable As Possible – Do Your Homework • Know your audience • Anticipate the issues – Early and Concise Communication • Beat the misinformation to the punch • Meet with stakeholders – Public Involvement
  • Underground Routing
  • Project Routing• Primary Objectives: – First chance to Identify, Review, and Minimize Risks. – Which route provides the best chance for success• Potential Pitfalls: – Physical Constraints – Socio-economic Issues – Permitting
  • Underground Routing• Steps to Successful Routing: – Investigate and Identify all Routing Constraints – Investigate and Identify all Routing Opportunities – Establish Routing Criteria and Priorities – Quantify Routing Options Based on Criteria and Priority Weighting – Select Primary and Alternative Routes
  • Underground Design
  • Underground Design• Primary Design Objectives: – Detailed investigation of unknowns identified in routing stage – Provide clear and complete construction packages based on results of investigations
  • Underground Design• Field Investigations: – Subsurface Utility Engineering (SUE) – Geotechnical Investigation – Trenchless Crossing Design/Feasibility – Phase 1/Phase 2 Environmental Reviews
  • Underground Design• Subsurface Utility Engineering (SUE) – Critical in urban areas to minimize surprises during construction – FHWA SUE Quality Level Designations: • Quality Level D – Utility Record Research • Quality Level C – Surveying Visible Utility Features
  • Underground Design• Subsurface Utility Engineering (cont.) • Quality Level B – Locating Subsurface Utilities utilizing ‘geophysical methods’ – For example, electromagnetic induction or ground penetrating radar • Quality Level A – Potholing with vacuum excavation or other – Physically identifying the depth, type, size, condition, material of facility
  • Underground Design• Geotechnical Engineering – Thermal Resistivity Testing • Major impact to cable design • Can’t pinpoint with traditional geotechnical data • Qualifications of geotechnical testing firm – IEEE 442 – Guide for Soil Thermal Resistivity Measurements – Rock Probing • Important to identify early to avoid costly change orders and schedule delays for getting necessary equipment on site. – Other
  • Underground Design• Trenchless Crossings – Select Proper Drilling Technology: • Horizontal Directional Drill (HDD) • Jack & Bore • Microtunneling
  • Underground Design• Trenchless Crossings – Site Review • Soil Conducive? • Adequate Real Estate for Required Set Back and Equipment? – Identify Permitting/Environmental Issues – Contingency Plan if Construction Issues Arise
  • Underground Design• Environmental Reviews – Phase 1 • Historical review of known contamination in area – Phase 2 • Field testing to verify presence and level of contamination – Develop Soils Management Plan • Prepare for expected and unexpected disposal • Identify removal procedures and disposal sites
  • Procurement
  • Procurement• Civil Material Specifications – Qualified Suppliers • Understand sensitivities of high voltage system • For example: – Mix designs for concrete or thermal backfill » Thermal tests up front, no air entrainment – Precast vendors » Understand the amount of tension required for pulling eyes » Grounding provisions » Knockouts for conduits w/o rebar loops
  • Procurement• Electrical Material Specifications – Qualified Suppliers • Warranties – Duration – 5 years? – Contracting to avoid finger pointing • Support During Supply/Construction/Warranty – Local Representatives? – Mobilize quickly if issues arise. • Factory QA/QC Program • Accessories – Qualified with cable system
  • Construction
  • Construction Sequencing Step A. Splice Vault Installation Step D. Cable Pulling* Step C. Construction Restoration Construction Period (months) A B C D EConstruction Start start Step B. Duct Bank Installation Step E. Cable Splicing*
  • Construction• Civil – Qualified Contractor • Understands specification requirements • Manage! – Up front unit rates, as possible, for unknowns • Increased Depth • Rock • Dewatering • Contaminated Soils
  • Construction• Civil – Testing • Manage QC Program • Material Testing • Conduit Installation/Jointing • Duct Cleaning & Proofing
  • Construction• Electrical – Qualified Contractor • Workmanship in accessory installation is paramount – Testing & Commissioning • Jacket Integrity Test (JIT): 10-kV DC applied to cable sheath for 60 seconds. • AC HiPot Test: – 24 hours at system voltage – 1 hour at 1.3 to 1.7 times Uo
  • Conclusions
  • Conclusions• How to successfully navigate the unknowns: – Develop Plan Early • Project Execution Plan – Identify Risks & Unknowns Early • Routing • Field Investigations • Contracting – Manage throughout