City Light Relocating Transmission Lines Beneath Alaskan Way Viaduct

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.

City Light Reliability Work Will Affect Traffic on I-5

Seattle City Light is enhancing the reliability of its electrical system by transferring transmission lines onto new poles on the east and west sides of Interstate 5 at NE 60th Street. Intermittent rolling slowdowns in both directions on I-5 between Northgate Way and State Route 520 are necessary for motorist and worker safety.

The two-day project is planned for early Tuesday morning, June 21, and early Wednesday morning, June 22, from 12:01 a.m. to 4 a.m. and is being coordinated with the Washington State Patrol. Traffic will be escorted through the construction zone. The map below shows the area affected by the rolling slowdowns. Multiple rolling slowdowns will be necessary with each lasting from 20 to 25 minutes. All on-ramp traffic from Northgate Way through SR 520 will be held and will merge with the next rolling slowdown. The I-5 express lanes will be closed.

Drivers are advised to carefully abide by traffic restrictions and consider using alternate routes during construction. Normal traffic flow will follow once the transfer of wire is complete.

Seattle City Light is the 10th largest public electric utility in the United States. It has some of the lowest cost customer rates of any urban utility, providing reliable, renewable and environmentally responsible power to about 750,000 Seattle area residents. City Light has been greenhouse gas neutral since 2005, the first electric utility in the nation to achieve that distinction