Puget Sound Energy Columbia Grid Presentation June 19, 2007 John Phillips

2 PSE Strategy Meet service obligations Follow best practices for reliable, cost efficient system Work collaboratively with stakeholders Consider all alternatives (single utility)

3 Areas of Concern Transmission capacity for Whatcom and Skagit Counties King County capacity Cross Cascade capacity Transmission capacity for Pierce and Thurston Counties

4 BPA’s 500 kV Monroe – Echo LakeWinter/Spring Power Flow

5 BPA’s 500 kV Monroe – Echo LakeSummer/Fall Power Flow Raver - Paul

6 Whatcom/Skagit Counties South of Sedro Cut Plane operational limits  Can be limiting S-N and N-S with single 230kV line outages New service needs  New resources being proposed in US and Canada  Changing generation and industrial loads BPA and Snohomish in parallel

7 Identified Alternatives Sedro-Horse Ranch #2 230kV line  Rebuild 30 miles of existing 115kV  Utilizes existing ROW  Adds third 230kV line across South of Sedro Cutplane

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9 King County Monroe-Echo Lake Cutplane  BPA internal cutplane  Operational limitations  Highest PSE load density North of Covington  Operational limitations  Growing load service needs BPA, SCL, and Snohomish in parallel

10 Monroe-Echo Lake Alternative Sammamish-Lakeside-Talbot 230kV line  Rebuild 16 miles of existing 115kV  Utilize existing ROW  Adds fourth 230kV line across Monroe-Echo Lake  Provide load service to North King County

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12 North of Covington Covington-Berrydale 230kV project scheduled for 2008 Relieves operational limits north of Covington Provides loop feed to PSE loads at Berrydale and Talbot

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14 Cross-Cascades New PSE owned wind generation in Eastern Washington More eastern renewables expected as part of state initiative Growing Puget Sound Load Usage change in Westside resources to firm renewables BPA in parallel and preliminary studies are underway

15 Identified PSE Alternative Conversion of I.P. 115kV line to 230kV  Adds new 230kV line across Cascades  Directly connects to wind resources  Improves load service to Kittitas County  Mostly on existing R.O.W.

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17 Pierce and Thurston Counties New load growth pushing 230/115kV transformation capacity Raver-Paul cutplane impacts BPA and Tacoma Power in parallel

18 Pierce County Alternative Add 230/115kV transformer at Alderton Substation 230kV source from White River or BPA  Interconnection studies initiated with BPA Provides load service to south King & Pierce Counties Relieves Raver-Paul 115kV constraints north of Alderton

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20 Thurston County Alternative Add 230/115kV transformer at Saint Clair or Spurgeon Creek (pending site adequacy review) 230kV source from BPA  Interconnection studies being initiated with BPA Provides load service to south Thurston County Relieves BPA Olympia and Tono loading

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22 Additional 115kV Projects Reconductor Bellingham-Sedro Woolley 115kV lines  Ties between Whatcom and Skagit Counties  4/0 CU to 1272 Bittern Novelty 230/115kV transformer  Load service to north King County Woodland-St Clair 115kV project  Adds 3 rd 115kV line between Pierce and Thurston Counties. (contingent on Timing of 230 kV projects)