© 2009 Dominion August 5, 2009 Underground Transmission Lines at Dominion Virginia Power Update for...

© 2009 Dominion

August 5, 2009

Underground Transmission Lines at Dominion Virginia Power

Update for the Joint Committee on Technology and Science

Presented by: Kevin CurtisDominion Virginia PowerDirector – Electric Transmission Planning

August 5, 2009

© 2003 Dominion2

© 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

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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

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Garrisonville (Stafford County): 230kV

• SCC Final Order for UG in April 2008

• Just north of Fredericksburg

• Target Date – 2010

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Garrisonville Sub.Garrisonville Sub.

Aquia Harbor Sub.Aquia Harbor Sub.

230kV double circuit line230kV double circuit line

Fredericksburg

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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

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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

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Garrisonville Project:Trenching configuration

Line #1 Line #2

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Garrisonville Project:Drilled hole configuration

Line #1 Line #2

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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

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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

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Garrisonville Project – OH vs. UG Comparisons

Reliability:Line

Outage Duration

Life Cycle(yrs)

Construction Time

(months)Personnel required

Conductor & CablePrices

($/line foot)

Total Costs

per line mile($)

TotalCosts

($)

OH

Hours 70 6-8 20 $8.10 $1.3M $14M

UG

Days to Weeks

35 18-24 150 $850 $11M $120M

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Right of Way Clearing

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Installing conduits for cable in open trenches

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Concrete encasement of conduits

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Horizontal Directional Drilling (HDD)

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Horizontal Directional Drilling (HDD)

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

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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

230kV and 69kV lines230kV and 69kV lines

69kV lines69kV lines

Rosslyn Sub.Rosslyn Sub.

Ballston Sub.Ballston Sub.Clarendon Sub.Clarendon Sub.

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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.Hamilton Sub.

PleasantView Sub.

PleasantView Sub.

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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.Beaumeade Sub.

NIVO Sub.NIVO Sub.

Ashburn

Sterling

© 2009 Dominion August 5, 2009 Underground Transmission Lines at Dominion Virginia Power Update for...

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