Central Waterfront Transmission Line Relocation Project
Transmission lines that power Seattle have historically been attached to the vulnerable Alaskan Way Viaduct. Since 2008, Seattle City Light has been working to complete the full relocation of these transmission lines along Seattle's waterfront in advance of viaduct demolition. Crews relocated transmission lines near the sports stadiums and Pioneer Square before the southern mile of the viaduct was demolished in 2010.
In 2012, Seattle City Light completed the relocation of a section of these transmission lines along the central waterfront, moving them to a permanent location underground between Yesler Way and the Union Street substation. This section of transmission lines was Phase 1 of the central waterfront relocation. Today, Seattle City Light is ready to complete the design for permanent relocation of the final section of central waterfront transmission lines, also called Phase 2. This section of 115 kV transmission lines runs from King Street to Yesler Way. Seattle City Light is working to identify a route for the transmission lines in an underground duct bank in a path just west of the existing viaduct. The project also includes replacing gas insulated switch gear in the Union Street substation.
The first step toward a new waterfront
The Central Waterfront Transmission Line Relocation Project must be completed before Alaskan Way Viaduct removal, Elliott Bay Seawall construction and Waterfront Seattle public space and new Alaskan Way construction. Seattle City Light is collaborating with Seattle Tunnel Partners (STP), the Washington State Department of Transportation, and the Elliott Bay Seawall Project and Waterfront Seattle design teams on the proposed location and potential construction elements.
Planned fieldwork to complete the design
To complete design work, crews will be conducting fieldwork in 2013 to gather additional data. Fieldwork will include locating and verifying existing underground utilities, also called "potholing." Potholing requires the use of a truck-mounted machine called a vactor truck. Vactor trucks are similar to large vacuums, excavating concrete and dirt to help identify underground utilities. Other fieldwork activities could include soil boring to monitor groundwater levels, also known as a geoprobe.
Currently, most of the project area is occupied by STP construction work and most fieldwork activities will occur out of sight and within the fenced off work area maintained by STP. Detailed information about fieldwork and impacts will be made available via email and flyers as needed.
There are a number of waterfront construction project that are in construction or in the design phase that overlap with this project area. Links to each project is included below.
Elliott Bay Seawall Project:
Alaskan Way Viaduct and Seawall Replacement Program:
Project Fact Sheet