City Light Relocating Transmission Lines Beneath Alaskan Way Viaduct

Transmission lines that power downtown Seattle have been attached to the Alaskan Way Viaduct since it was constructed in 1953. Seattle City Light has been working to complete the full relocation of these transmission lines to a permanent location underground.

Have you ever stood beneath the Alaskan Way Viaduct and looked up? You may have noticed cables running along the underbelly of the viaduct. These 115 kV transmission lines look unassuming, but they are major conduits of electricity, powering downtown Seattle and the entire western seaboard!

Transmission lines which power downtown Seattle and the western seaboard will be relocated underground from beneath the Alaskan Way Viaduct.

Transmission lines which power downtown Seattle have been attached to the Alaskan Way Viaduct since it was constructed in 1953. Seattle City Light has been working to complete the full relocation of these transmission lines to a permanent location underground along Seattle’s waterfront since 2008. The Central Waterfront Transmission Line Relocation Project (TLR) must be completed before the Alaskan Way Viaduct demolition, scheduled for 2019, and the subsequent Waterfront Seattle Program which will reconnect downtown to the waterfront. The new waterfront will include new parks, paths and viewpoints.

In 2012, Seattle City Light completed TLR Phase 1 and relocated a section of transmission lines between Yesler Way and the Union Street substation. Due to changes in the project schedule related to the SR 99 Tunnel Project delay, construction of the final section of the TLR project was paused. TLR Phase 2, from South King Street to Yesler Way, is up and running.

Construction for TLR Phase 2 began in April 2017 at Yesler Way and will move south towards South King Street.

Construction for Phase 2 began in April 2017 and is expected to last six months, with two additional months of cable pulling and splicing to connect with the lines already installed underground during Phase 1. Construction will start at Yesler Way and end at South King Street. The project is expected to be finished in fall 2017. The completion of this work sets the stage for future waterfront improvements.