Underground Transmission Lines at Dominion Virginia Power Update

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

Approved Underground (UG) Transmission Projects Currently Under Construction l Garrisonville (Stafford Co. ) – dual 230, 000 volt lines l Clarendon/Ballston (Arlington) – 230, 000/69, 000 volt lines Future UG Construction (2010) – HB 1319 projects l Pleasant View/Hamilton (Leesburg, Loudoun Co. ) – 230, 000 volts l NIVO Substation (Ashburn area, Loudoun Co. ) – 230, 000 volts 2009 Dominion © 2003 2

Related UG Legislation in Virginia HB 1319 – Delegate May l Allows for four UG transmission pilot projects in Virginia l Two approved to date HB 1729 – Delegate Cole l l 2009 Dominion © 2003 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 3

Garrisonville (Stafford County): 230 k. V • SCC Final Order for UG in April 2008 • Just north of Fredericksburg • Target Date – 2010 230 k. V double circuit line Aquia Harbor Sub. Garrisonville Sub. Fredericksburg © 2003 Dominion 4 4

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 l Overhead estimate - $14 M ($1. 3 M/mile) l Underground projection - $120 M ($11 M/line mile) - 8. 5 times cost of overhead 2009 Dominion © 2003 5

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 2009 Dominion © 2003 § 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 6

Garrisonville Project: Trenching configuration Line #1 2009 Dominion © 2003 Line #2 7

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

Garrisonville Project – cont’d Construction Challenges l Terrain and road crossings – requires drilling ($$) l Soil conditions - - l l 2009 Dominion © 2003 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 9

Garrisonville Project – cont’d Cost Drivers l l 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. 5 M/mile for each line l Rolling terrain requires drilling which adds significant cost l Soil conditions (drilling rate and frac-out) l 2009 Dominion © 2003 Right of way acquisition: previously purchased easements were for overhead line - did not have UG easements 10

Garrisonville Project – OH vs. UG Comparisons Reliability: Line Outage Duration O H U G Total Costs per line mile ($) Total Costs ($) Life Cycle (yrs) Construction Time (months) Personnel required Conductor & Cable Prices ($/line foot) Hours 70 6 -8 20 $8. 10 $1. 3 M $14 M Days to Weeks 35 18 -24 150 $850 $11 M $120 M 2009 Dominion © 2003 11

Right of Way Clearing 2009 Dominion © 2003 12

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

Concrete encasement of conduits 2009 Dominion © 2003 14

Horizontal Directional Drilling (HDD) 2009 Dominion © 2003 15

Horizontal Directional Drilling (HDD) 2009 Dominion © 2003 16

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

Conduits being prepared for drilled holes 2009 Dominion © 2003 18

Conduits being prepared for drilled holes 2009 Dominion © 2003 19

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

Arlington Area – Clarendon/Ballston/Rosslyn: 230/69 k. V UG Rosslyn Sub. 69 k. V lines Clarendon Sub. • • • 2. 5 miles $60 M Located in streets XLPE cable Extensive community information effort • Target Date – October 2009 Ballston Sub. 230 k. V and 69 k. V lines © 2003 Dominion 21 21

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

Pleasant View – Hamilton: 230 k. V Partial UG Hamilton Sub. • • 2 miles of UG along the W&OD Trail 12 miles total 2 miles of UG $107 M total HB 1319 pilot project New substation XLPE cable Target Date – Oct 2010 • • • Pleasant View Sub. © 2003 Dominion 23 23

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