Wedged between South Lake Union and Denny Triangle like a crash-landed spaceship, Seattle’s new Denny Substation cost $100 million more than initially estimated, will send power through a special network to companies like Amazon and is equipped with its very own dog park.

The $210 million complex with shining walls and jutting angles is the first new substation Seattle City Light has constructed in more than 30 years — made largely to pump energy into the area’s booming tech sector, even as electricity consumption has declined across the city as a whole.

The utility describes it as a wonder of engineering and design, while critics have questioned its price tag.

“We’ve never built a substation like this before. Nobody has,” City Light spokesman Scott Thomsen said. “This is an investment not only in our electrical system but also in our community’s values.”

Nearly complete after three years of construction, the project is the last piece in a puzzle that then-Mayor Greg Nickels and late billionaire Paul Allen began putting together in South Lake Union long ago.

Determined to develop the dingy warehouse district where Allen’s Vulcan Real Estate had amassed land into a high-tech hub, they said a power upgrade would be needed alongside other changes.


Since planning for the substation started, South Lake Union has acquired a streetcar, Mercer Street has been rechanneled, a Highway 99 tunnel has been bored, Denny Triangle has sprouted towers and the area has absorbed 45,000 Amazon workers.

“There was a whole list of public and private investments proposed to achieve the build-out vision,” said Tim Ceis, who served as deputy mayor under Nickels and whose political firm lobbies for Vulcan. “To attract the companies we were looking for … an uninterrupted electrical supply was a big deal.”

The new substation’s inductor will help City Light moderate high voltages traveling across the grid, improving the entire system.

And the complex will support commercial and residential development in South Lake Union and the Denny Triangle directly by feeding dense loads through the underground Denny Network, which the utility has laid out simultaneously.

The network will provide customers, such as Amazon, Facebook and Google, with superior connections and will back up the existing Downtown Network, reducing stress at other substations.

“An overhead radial system is like a tree. When something goes wrong on a branch, you lose power,” said City Light’s Michael Clark, program manager for the substation project. “A network is like a copper-welded spider web.”


The new substation won’t immediately provide electricity to ordinary customers through overhead wires, although that equipment could be installed. It also won’t direct high voltages along new routes, because a new transmission line to the site has been postponed.

The rates that all City Light customers pay are covering the utility’s debts for the substation, while premium users will pay for the $77 million network. Including $65 million in related projects, the outlay has eclipsed $350 million.

City Light’s citizen-review panel recently cited Denny in ringing an “alarm bell” over capital projects driving rate hikes.

The utility’s strategic plan calls for the typical residential customer to pay nearly $85 per month by 2024, up from $65 last year, with substation debt service responsible for an approximately $2 per month increase this year, Thomsen said.

“This is why the rates go up,” said Eugene Wasserman, who heads the North Seattle Industrial Association and previously co-chaired the review panel. “Maybe it should have been a normal substation.”

Bells and whistles required as public benefits — like the artificial-turf dog park and a quarter-mile elevated walkway around the complex — added tens of millions of dollars, as did environmental cleanup and changes in scope.



Private-sector projects in the area complicated City Light’s work and caused delays. “Right when we started construction here, the whole neighborhood exploded,” Clark said.

Growing demand

The city began budgeting for the Denny in 2003, as Allen and Nickels unveiled a proposal to create a biotech center in South Lake Union.

The project was reconsidered in 2005, when City Light said the area’s growing demand could be met at the Broad Street Substation, near Seattle Center. Interest rebounded in 2007, after the City Council upzoned the Denny Triangle.

“They got approval to proceed, just looking at the development we were already seeing, and then six months later, Amazon made their big purchase,” Clark said.

The city subsequently bought a site, spending $44 million for a Greyhound bus garage, a parking lot and a third parcel. Serious design and environmental work didn’t get underway until 2012, when City Light estimated the substation could cost $111 million.

That number shot up to $174 million in 2015, after neighbors and the Seattle Design Commission weighed in, directing City Light to draw up “not just a substation, but an architectural marvel,” Thomsen said.


With the area developing even quicker than expected, the utility also decided to equip Denny with more feeders and transformers. Rather than screen the site with a basic concrete wall, City Light agreed to erect a sculpted metal-and-glass structure.

The larger design meant taking over a block of Pontius Street. To repay the public and win council approval, the utility tacked on the walkway, plus community rooms and pedestrian improvements.

City Light also included an off-leash area partly because “Amazon was moving in and encouraging people to bring their dogs to work,” Clark said.

The walkway should help seniors stay fit, he said, noting hundreds live across the street in The Mirabella building. An open space will accommodate food trucks.

Councilmember Mike O’Brien was a proponent. “There was significant pressure from community residents,” O’Brien said. “We needed an architectural design … a building that wasn’t going to be an eyesore.”

The substation’s budget climbed yet again in 2015, to $210 million, with the increase attributed to equipment prices, the public benefits and soil-cleanup requirements.


Construction began in 2016 and has just about wrapped up, with the complex’s public spaces scheduled to open in the coming months.

“I had a mountain of rubble outside my window,” said Sean Phelan, who lives in The Brewster building next to the substation. “We need this for the high-tech, bio-tech and all that. But it’s been a brutal process.”

Councilmember Lisa Herbold recently secured legislation requiring Seattle departments to report when capital projects are at risk for cost overruns.

Inside and out

The substation’s steel-trimmed shell is supposed to “pick up the color of the sky” and embody Seattle’s “very rugged” character, said Jose Sama, the lead architect.

Wall panels that flutter and light up in the wind have been incorporated as part of the project’s 1 percent-for-art contribution, and City Light will soon add a sculpture called “Transforest.” The 10-story piece will resemble a transmission tower mashed up with a tree.

“This could have been a bunch of transformers in a yard surrounded by a fence,” said Sama, a partner with the firm NBBJ. “Instead, we said to City Light, ‘Why don’t we celebrate this substation?’ “


Inside the walls, the complex also is somewhat unusual. Unlike many substations, which use air to insulate their conductors, Denny has gas-insulated switch gears that take up less room.

Because the switch gears are housed inside buildings and other components are underground, the site has none of the wires, pipes and screw-shaped insulators that characterize older substations.

Transmission lines linking Denny to Broad Street and the East Pine Substation went live last year, energizing the complex. Previously, those substations were linked directly.

Construction of a line between Denny and the Massachusetts Substation, which would open up new transmission routes, won’t begin until at least 2020.

City Light has been able to help tech companies flourish without network service until now, but not without risk.

“When Amazon moved, we had to scramble to feed that out of Broad Street, which was near capacity,” Clark said. “Now we’re in a better position.”


The new substation will distribute network power starting this summer, as buildings tap in.

When Vulcan was initially lobbying for the substation, Wasserman asked whether City Light could make the company pay for part of the project and was told there was “no precedent,” he recalled.

Like the utility’s dams, substations are considered assets to the entire electrical system, so everyone chips in.

“That’s the way rates are designed in Seattle,” though the council recently launched a process to reassess the utility’s rate structure, Clark said.