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© 2009 Dominion August 5, 2009 Underground Transmission Lines at Dominion Virginia Power Update for the Joint Committee on Technology and Science Presented.

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Presentation on theme: "© 2009 Dominion August 5, 2009 Underground Transmission Lines at Dominion Virginia Power Update for the Joint Committee on Technology and Science Presented."— Presentation transcript:

1 © 2009 Dominion 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

2 © 2003 Dominion 2 © 2009 Dominion 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 © 2003 Dominion 3 © 2009 Dominion 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 © 2003 Dominion 4 Garrisonville (Stafford County): 230kV SCC Final Order for UG in April 2008 Just north of Fredericksburg Target Date – Garrisonville Sub. Aquia Harbor Sub. 230kV double circuit line Fredericksburg

5 © 2003 Dominion 5 © 2009 Dominion 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 © 2003 Dominion 6 © 2009 Dominion Garrisonville Project – contd 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 © 2003 Dominion 7 © 2009 Dominion Garrisonville Project: Trenching configuration Line #1Line #2

8 © 2003 Dominion 8 © 2009 Dominion Garrisonville Project: Drilled hole configuration Line #1Line #2

9 © 2003 Dominion 9 © 2009 Dominion Garrisonville Project – contd 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 100,000s 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 © 2003 Dominion 10 © 2009 Dominion Garrisonville Project – contd Cost Drivers Construction complexity of UG requires more time and personnel 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 © 2003 Dominion 11 © 2009 Dominion Garrisonville Project – OH vs. UG Comparisons

12 © 2003 Dominion 12 © 2009 Dominion Right of Way Clearing

13 © 2003 Dominion 13 © 2009 Dominion Installing conduits for cable in open trenches

14 © 2003 Dominion 14 © 2009 Dominion Concrete encasement of conduits

15 © 2003 Dominion 15 © 2009 Dominion Horizontal Directional Drilling (HDD)

16 © 2003 Dominion 16 © 2009 Dominion Horizontal Directional Drilling (HDD)

17 © 2003 Dominion 17 © 2009 Dominion 42 Drill Bit (Reamer)

18 © 2003 Dominion 18 © 2009 Dominion Conduits being prepared for drilled holes

19 © 2003 Dominion 19 © 2009 Dominion Conduits being prepared for drilled holes

20 © 2003 Dominion 20 © 2009 Dominion Cable splice connections in vault (located every 1800 feet due to cable length limitations)

21 © 2003 Dominion 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 kV and 69kV lines 69kV lines Rosslyn Sub. Ballston Sub. Clarendon Sub.

22 © 2003 Dominion 22 © 2009 Dominion Picture Arlington Area – Clarendon/Ballston/Rosslyn: 230/69kV UG

23 © 2003 Dominion 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 miles of UG along the W&OD Trail Hamilton Sub. Pleasant View Sub. Pleasant View Sub.

24 © 2003 Dominion 24 3/4 mile $11M HB 1319 UG pilot XLPE cable Double circuit & new substation 200 MW load Target Date: April 2010 NIVO Substation – 230 kV Underground (DuPont Fabros Data Center Expansion) Beaumeade Sub. NIVO Sub. Ashburn Sterling


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