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The following are the planned transmission project at SCL for the next ten year. All the projects has no major impact to the bulk transmission system. Most of our work are all internal transmission lines and generator reconnection.

• 115kV North Seattle Transmission Lines upgrade• 230kV Transmission lines to proposed new substation• Boundary Transformer replacement with connection to existing

115kV transmission line• BPA’s Proposed Summer Falls and Main Canal Hydropower

interconnection 115kV Transmission Line

Seattle City Light’s 10 – Year Transmission Expansion Plan

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Project: 115kV North Seattle Transmission Lines upgrade

Description:Increase North Seattle 115kV Transmission line capacity and to improve transmission reliability. Perform retension, reconductor, and/or raise existing 115kV transmission lines in the northend of Seattle to 100 degree C conductor temperature if possible. Eight lines need to improve ratings. Four lines have been improved to 65 degree C so far. The other four (BO-SH#1, BO-SH#2, BO-NO, & BO-UN) are being evaluated for improvement.Sponsor: SCLConstruction consists of:

• Fixes to BO-SH#1, 11.27 miles, 954 kcmil ACSR Rail• Fixes to BO-SH#2, 10.93 miles, 954 kcmil ACSR Rail• Fixes to BO-NO, 14.61 miles, 795 kcmil AAC Arbutus• Fixes to BO-UN, 16.69 miles, 795 kcmil AAC Arbutus

Schedule completion: 2007 - 2008Status: PlanningProject Manager: SCL

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Project: 230kV Transmission lines to proposed new substation

Description: Proposed to build a new substation in the north of downtown area to serve load growth. A 200MVA, 230kV substation with connection to 3 transmission lines. Construct 230kv transmission lines. Location to be determinedSponsor: SCLConstruction:

• Install 2 miles of underground 230kV transmission line from East Pine Substation to New Substation and 230kV/115kV autotransformer• Install 6.5 miles (4.5 miles of overhead and 2 miles of underground 230kV

construction) energized 115kV transmission lines from Canal Substation to New Substation• Connect existing 115kV transmission from Broad St. Substation to New

Substation Schedule: 2010-2012Status: Planning stage, commitment base on load growth and type of distribution system.Project Manager: SCL

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Project: Boundary Transformer replacement with connection to existing 115kV transmission line

Description:Bonneville Power Administration (BPA), Seattle City Light (SCL) and Pend Oreille PUD (POPUD) have negotiated the Boundary Transformer Agreement, which provides for installation and operation of a transformer and breaker in the Boundary Substation to allow for the cost-effective delivery of Article 49 Power and tailwater encroachment compensation from the Boundary Project to the POPUD via SCL’s Boundary Tap Line and BPA’s Box Canyon Tap Line.Installation of a 230/115KV autotransformer in the Boundary Switchyard to interconnect to SCL's 115KV Boundary transmission tap line will also enhanced electric grid reliability.Sponsor: SCL, BPA, Pend Oreille PUDSchedule completion: 2009Construction consists of:

• Remove old transformer• Install a new 160MVA, 230kV/115kV autotransformer• Install a new 115kV breaker• Connect to existing 115kV transmission line

Status: Transformer purchase with construction scheduledProject Manager: BPA

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Project: BPA’s Proposed Summer Falls and Main Canal Hydropower interconnection 115kV Transmission Line

Description:BPA proposes to construct a new Main Canal-Pinto Ridge single circuit 115-kV wood pole transmission line from the Main Canal hydropower project for eight miles and connect to the new Pinto Ridge Substation. BPA also proposes to construct a new Summer Falls – Pinto Ridge single circuit 115-kV wood pole transmission line from the Summer Falls hydropower project for two miles and connect into Pinto Ridge Substation. The proposed transmission lines and 100 foot wide easements would be purchased and owned by Seattle City Light and Tacoma PowerSponsor: SCL, TPConstruction consists of:

• Constructed 115kV transmission line from Main Canal to new 230kV substation called Pinto Ridge• Constructed 115 kV transmission line from Summer Fall to new 230kV substation.

Schedule Completion: 2008Status: PlanningProject Manager: BPA

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