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  4. Seattle City Light’s Denny Substation

Seattle’s reputation for being a tech center dates back to the 1980s when Microsoft arrived. Today, technology and innovation companies like Amazon and others continue to come, many choosing the vibrant South Lake Union and Denny Triangle neighborhoods as their homes.

In addition to new office buildings, the rapidly developing north downtown area has also added apartment towers and the Pacific Northwest’s largest hotel. And they all have one thing in common—the need for reliable electrical power.

For the local utility, Seattle City Light (SCL), those requirements translated to a new substation, their first in 30 years. We served as the program manager for the project’s 75-member consultant team and oversaw the electrical design.

 

Resident-driven design

The new distribution substation needed to be near the densely populated load centers. At the top of the list was a property on Denny Way—a former bus maintenance facility with an underground 115 kV line running through the site.

Most substations use the open air as an insulator, which can require a relatively large facility footprint. In contrast, a gas-insulated substation encases the equipment, using a dielectric gas for insulation and arc quenching. Gas-insulated substations offer better reliability and enhanced safety. They also require a lot less space.
For the Denny Way property, designing a smaller footprint GIS substation meant there was 44,000 square feet of open space available for additional development. As part of their commitment to providing public benefit, SCL turned to the local residents to learn what amenities they might desire.

Their list included a dog park, and a quarter-mile walking loop that provided views of the city. They asked for space for food trucks to serve their favorite fare during lunch or neighborhood events. Other desirable features included art installations, viewing windows of the substation equipment, a learning center, a public meeting area and a small theater.
Bringing the substation’s concept to reality required reconciling demands for a functional substation with those for a community-friendly facility.

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Location

  • Seattle, Washington, USA

Client

  • Seattle City Light

Architect

  • NBBJ

Project status

  • Completed 2019

Awards

  • ENR 2020 Northwest’s Best Project Award, Energy-Industrial

75-member consultant team

The Denny Substation project required architects, landscape designers, environmental specialists, traffic engineers and dozens more. The consultant team interfaced with SCL and city departments, from parks and neighborhoods to planning, finance and transportation.

Our team also had extensive meetings with the Seattle Design Commission—professionals who advise the city on capital improvement projects. The final design redefined the standards for an urban substation.

Seattle architecture firm NBBJ angled the facility’s screening walls inward to lower its visual profile. The walls were finished with a combination of metal cladding and glass panels. By day, the Denny Substation invites the local community to enjoy its park, elevated walkway and other amenities. At night, its translucent glass panels emit a soft glow.

Behind its shimmering walls, the substation transforms high-voltage energy from SCL’s renewable resources into lower voltages used by the growing number of South Lake Union and Denny Triangle residences and businesses.

Utilities are increasingly building new substations such as Denny in busy central districts to provide power to the additional loads associated with city development.

Quiet, safe and sustainable

When SCL first proposed Denny Substation, residents in nearby buildings raised questions about noise and potential effects of an electromagnetic field (EMF). The utility committed early to being a good neighbor and sought to address these concerns.

We created 3-D models to represent the noise emitters and structural components that would affect sound travel. The consultant team used acceptable sound levels to specify equipment that would fall within these sound emitter limits. To reduce the potential for noise, designers placed low-noise transformers in the center of the station with firewalls on two sides.

“Denny’s design features rendered EMF to very low levels,” Denny Substation Project Manager Jay Keeling says. Analysis confirmed that the EMF in the area would be no greater after construction of Denny than before.

Among many sustainable features built into Denny are solar panels that feed the station and a heat recovery system that provides building heating needs. Nearly one-third of the site is planted with trees, shrubs and groundcover. Containment vaults can capture potential transformer oil spills and serve to collect stormwater runoff from the substation interior area.

Infrastructure projects from substations to generating plants can be built in the middle of a big city and not be eyesores. It starts with being sincere about making the project a benefit to both the utility and the public.

    Single Circuit Breaker Bays of Gas Insulated Switchgear

Ready for future growth

The Denny Substation was designed to last the next 50 to 100 years.

“When Denny needs to expand, residents and businesses won’t have to contend with the disruption of significant construction again,” Keeling says. “The substation was built to accept additional equipment for its ultimate sizing.”

For example, we designed and installed inactive duct banks ready for use when new transmission lines and distribution feeders are needed. Additionally, shoring piles for future vaults were installed to prevent excessive vibration from pile driving to an energized station.

Denny Substation was part of a project to convert the area’s overhead radial distribution system to an underground network distribution system to provide more reliable electrical service.

The distribution project, which our team also worked on, involved design and construction of 30 new network feeders that exit the substation in seven duct banks through heavily trafficked roadways in north downtown.

 

Meet the Visioneer

A Power and Energy Program Manager and electrical engineer, Jay Keeling brings his specialized skills in both nontraditional compact station design and multidiscipline program management to successfully complete electrical infrastructure projects that power communities.

Other challenges that we have overcome

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