Waldron Island and President Channel seen from Orcas Island, Washington. Photo by Somelab
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Denny Substation Project
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Denny Substation Design - Not your typical substation

Seattle City Light is committed to designing a substation that will fit with the neighborhood, advance community goals, and meet the City's goals for sustainability. Located near Denny Way and Stewart Street, the Denny Substation is being designed to support and serve the future expansion and anticipated growth of the area.

Though the majority of the site will be utilized for substation operations, City Light and the project team are exploring opportunities to advance neighborhood goals and priorities. The team took guidance from existing planning documents such as the South Lake Union Neighborhood Plan and Urban Design Framework and the Denny Triangle Neighborhood Plan. The design team used these documents and others as starting points for the design of the substation.

What has evolved from this early guidance, as well as ongoing input from the public, is a design that features a sloped building enclosure that is comprised of metal cladding and translucent glass panels that will emit a soft glow at night. By sloping the enclosure walls inward towards the substation, the size of the facility is decreased at the pedestrian level, creating a friendlier urban environment along the edges. Additionally as part of the terracing, an "elevated interpretative pedestrian walkway" wraps the Denny Way edge and continues north along the alley. This elevated zone will be fully accessible with gentle slopes to allow opportunities to view into the substation at key moments and have a unique elevated viewpoint of Denny Way and the cityscape beyond.

To see the latest conceptual drawings of the preferred alternative click here.

The project team will continue reaching out to and working with the neighborhoods and other stakeholders to ensure the community is involved in the final design of the substation. We want to hear from you. If there is something you would like the project team to consider as the design of the Denny Substation progresses, please let us know by emailing: SCL_dennysub@seattle.gov.

For those who want to know what's inside the substation, here's a list of the equipment:
  1. (4-bays) 115kV Gas Insulated Switchgear (GIS)
  2. (3) 115-13.8kV power transformers
  3. (1) 115kV line reactor with integrated GIS
  4. (1) 13.8kV switchgear building
  5. (2) 13.8kV capacitor banks
  6. (3) 13.8kV grounding banks
  7. (1 lot) 115kV XLPE cable between equipment supplier equipment
  8. (1 lot) 15kV EPR cable between equipment supplier equipment

A new transmission line from the Massachusetts substation in SODO will be added to provide power to the Denny Substation. To learn more about the transmission line click here. A new underground network power distribution system that connects and provides electricity to customers will also be built. To learn more about the distribution network, click here.
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