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December 30, 2016
Crews from The Walsh Group have been erecting structural steel “cranes” that will support the outer wall of the Denny Substation near Denny Way and Stewart Street.
Walsh is installing other structural steel elements and early next year will pour the concrete foundation for the electrical substation that will serve north downtown, provide back-up power to other substations and support the regional transmission grid.
When the $209.5 million substation is energized in mid-2018, it will be the largest in Seattle City Light's system.
The project includes an underground network distribution system serving the South Lake Union and Denny Triangle areas that is expected to cost another $17 million. Shimmick Construction Co. is doing the civil work for the network and City Light crews are in charge of electrical work.
The walls of the substation will be similar to a picture frame, with space within the frame for maintenance operations and a community center. The City Council directed City Light to add the 3,650-square-foot community/cultural center at a cost of $5.4 million. Another 2,875 square feet will be available within the frame for a to-be-determined use.
The working parts of the substation will be surrounded by the picture frame walls.
An existing transmission line will power the Denny Substation until a new $66.2 million transmission line connecting to an existing substation in the Sodo neighborhood goes into service. Transmission line design will take place in 2017 and 2018, with construction to start in 2019 and finish in late 2020.
Here is the project team: NBBJ, architect; Power Engineers, electrical design; and KPFF Consulting Engineers, structural and civil engineer. Valley Electric, W.A. Chester and Transcon are key subcontractors. ABB and Mitsubishi are major electrical equipment suppliers and installers.
The new substation will deliver reliable power to the growing areas of South Lake Union, Cascade, Denny Triangle, Uptown, Belltown and First Hill. It has been 30 years since City Light has built a substation.