The last of 72 temporary steel columns once holding up the Climate Pledge Arena’s landmark roof has been removed, finishing a vital and many-thought-impossible step in the project’s construction
By Bob Condor
Climate Pledge Arena stands for many memorable experiences coming our way: Top music and entertainment events, Kraken games, Storm games, community happenings, family fun, making new friends, renewing ties with pals, global warming awareness, planet healing through tangible actions, so much more.
And Climate Pledge Arena will stand on the original 20 Y-columns and four pronged-buttresses to hold up the original 1962 World’s Fair roof hanging over a brand-new, best-in-world arena. The national and local landmark status of the roof, designed by architect Paul Thiry to look like a Native traditional cedar-woven rain hat, halted many previous parties to conclude saving the roof and constructing a world-class venue could not be done.
Then Tim Leiweke and Oak View Group, along with an ownership group led by David Bonderman and Jerry Bruckheimer, entered to offer a resounding “yes” to the city, no question a subterranean arena—with floor level 53 feet below ground—was feasible. More than that, the OVG plan to build the privately-funded arena was the perfect fit for the Seattle Center campus. It would maintain the roof and keep the iconic glass “curtain wall” every fan, Seattleite and visitor will see walking to or by Climate Pledge Arena, plus keep everyone’s previous view of the Space Needle, cityscape and more.
One major challenge: How to hold up that roof, all 44 million pounds of it, while the construction crew excavated 600,000 cubic yards of dirt underneath to build the brand-new arena below. The answer: Install 72 temporary steel columns, each drilling down 70 to 90 feet for secure footing, to substitute for those aforementioned Y-columns and buttresses. The process took a good part of 2019—adding nearly a year to the project timeline—and used an amount of steel equal to the typical required for a modern-day NFL football stadium.
The plan worked and produced a “floating” roof appearance that was magical to see, especially at night when it was hard to even see the orange temporary steel (coated to alert all vehicles to avoid even tapping those vital temporary supports). By early 2020, workers were busy creating new supports of concrete and steel rebar for the Y-columns and buttresses, starting 70-plus feet below ground and reaching up to the columns and buttresses that were hanging in mid-air for months.
As that feat was accomplished, general construction partner Mortenson and its various subcontractors began strategically removing the temporary steel columns since the newly fortified Y’s and buttresses were now holding their share of the roof load.
“In a lot of ways, it is like climbing a mountain,” says Ken Johnsen, construction executive for OVG and the Seattle Kraken. “It’s tough going and just as tough going down. It was a really complicated set of exercise among the engineers, contractors and the trades people to say what is the sequence we use to build the temp [steel], what is the sequence we use to take it off?”
The work was intricate at times, especially in later 2020, because those orange columns were laced in between permanent concrete floors that will in part form the seating and concourses of the arena bowl. Some of the steel columns were cut into pieces and removed in sections, floor by floor.
The last of the steel was removed earlier this month as workers and machinery pulled up the last cut section.
“It culminates the last 18 months of work to temporarily support the roof structure and then re-support it,” says Will Traylor, senior project manager, Mortenson.
The moment was an ordinary part of another workday on this extraordinary project, but make no mistake. It completed a critical chapter of Climate Pledge Arena’s promise of hopeful, sustainable and memorable days ahead for the Seattle and Pacific Northwest communities.