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August 5, 2009

Underground Transmission Lines at Dominion Virginia Power Update for the Joint Committee on Technology and Science Presented by: Kevin Curtis Dominion Virginia Power Director – Electric Transmission Planning August 5, 2009. August 5, 2009.

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August 5, 2009

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  1. Underground Transmission Lines at Dominion Virginia Power Update for the Joint Committee on Technology and SciencePresented by: Kevin Curtis Dominion Virginia Power Director – Electric Transmission Planning August 5, 2009 August 5, 2009

  2. Approved Underground (UG) Transmission Projects Currently Under Construction • Garrisonville (Stafford Co.) – dual 230,000 volt lines • Clarendon/Ballston (Arlington) – 230,000/69,000 volt lines Future UG Construction (2010) – HB1319 projects • Pleasant View/Hamilton (Leesburg, Loudoun Co.) – 230,000 volts • NIVO Substation (Ashburn area, Loudoun Co.) – 230,000 volts

  3. Related UG Legislation in Virginia • HB1319 – Delegate May • Allows for four UG transmission pilot projects in Virginia • Two approved to date • HB1729 – Delegate Cole • Structure for customers in local jurisdictions to pay for UG transmission • Authorizes the governing body of any locality to enter into an agreement with an electric utility that provides that the locality will impose an assessment on customers in a special rate district to cover the utility's additional costs of constructing, operating, and maintaining the proposed line as an underground rather than an overhead line

  4. Garrisonville (Stafford County): 230kV • SCC Final Order for UG in April 2008 • Just north of Fredericksburg • Target Date – 2010 230kV double circuit line Aquia Harbor Sub. Garrisonville Sub. Fredericksburg

  5. Garrisonville Project – Understanding UG Construction • Project Overview • 5.5 mile double circuit (11 line miles) • Serves new substation in Garrisonville area • Utilizing XLPE (cross-link polyethylene) cable – 6 cables/line (12 total) • Work began in December of 2008 – 25% complete • Cost Breakdown • Overhead estimate - $14M ($1.3M/mile) • Underground projection - $120M ($11M/line mile) • - 8.5 times cost of overhead

  6. Garrisonville Project – cont’d • Construction Overview • Rolling terrain and rocky soil conditions • Interstate and highway crossings • Trenching and horizontal directional drilling (HDD) • - 70% trenching • Continuous excavation along right of way • Two 5-foot trenches separated by 20 feet • Conduits encased in concrete • - 30% drilling • Right of way clearing required for installation of conduits • Four 42-inch holes: each requires 3 passes – 12”, 28”, 42” • Conduits encased in grout-type mixture

  7. Garrisonville Project: Trenching configuration Line #1 Line #2

  8. Garrisonville Project: Drilled hole configuration Line #1 Line #2

  9. Garrisonville Project – cont’d Construction Challenges • Terrain and road crossings – requires drilling ($$) • Soil conditions • - Drill rates • Slow progress - 6 inches per hour in some locations • Took three months to drill first of 4 holes under Interstate 95 • - “Frac-out” – drilling mud eruptions in “proximity” of drill site • 100,000’s of gallons at 100+ locations • Drilling stops until all material recovered and site cleaned up • - Sink holes • Noise/vibration of drilling equipment has become problematic for some residents and businesses • Weather – extensive rain affects drilling and trenching

  10. Garrisonville Project – cont’d • Cost Drivers • Construction complexity of UG requires more time and personnel • - 18-24 months • - 150 personnel • Cable prices • - $850/line foot (for each set of 6 cables), $4.5M/mile for each line • Rolling terrain requires drilling which adds significant cost • Soil conditions (drilling rate and frac-out) • Right of way acquisition: previously purchased easements were for overhead line - did not have UG easements

  11. Garrisonville Project – OH vs. UG Comparisons

  12. Right of Way Clearing

  13. Installing conduits for cable in open trenches

  14. Concrete encasement of conduits

  15. Horizontal Directional Drilling (HDD)

  16. Horizontal Directional Drilling (HDD)

  17. 42” Drill Bit (Reamer)

  18. Conduits being prepared for drilled holes

  19. Conduits being prepared for drilled holes

  20. Cable splice connections in vault(located every 1800 feet due to cable length limitations)

  21. Arlington Area – Clarendon/Ballston/Rosslyn: 230/69kV UG • 2.5 miles • $60M • Located in streets • XLPE cable • Extensive community information effort • Target Date – October 2009 Rosslyn Sub. 69kV lines Clarendon Sub. Ballston Sub. 230kV and 69kV lines

  22. Arlington Area – Clarendon/Ballston/Rosslyn: 230/69kV UG • Picture

  23. Pleasant View – Hamilton: 230kV Partial UG • 12 miles total • 2 miles of UG • $107M total • HB1319 pilot project • New substation • XLPE cable • Target Date – • Oct 2010 2 miles of UG along the W&OD Trail Hamilton Sub. Pleasant View Sub.

  24. NIVO Substation – 230 kV Underground (DuPont Fabros Data Center Expansion) • 3/4 mile • $11M • HB 1319 UG pilot • XLPE cable • Double circuit & new substation • 200 MWload • Target Date: April 2010 Ashburn Beaumeade Sub. NIVO Sub. Sterling 24

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