The roof covering the under-construction Seattle Center Arena will remain. And it won’t move, even as contractors remake the entire arena beneath it. 

OVG-Seattle has started the task of remaking the city-owned structure—and the only major arena within a park in North America—into the home for the expansion NHL Seattle franchise and the start of the 2021 NHL season. 

The trickiest part of the upgrade, though, comes in keeping the landmark-status roof. While the arena was originally constructed in 1962, a major rebuild that opened in 1995 dug out the arena bowl an additional 35 ft and built a new roof using four trusses from the original truss-supported cable roof and more than 260 new trusses that replaced the cables. The current update keeps that most recent roof build in place, even as everything underneath gets rebuilt. And dug out. 

To make it work, crews from Mortenson will erect steel falsework to hold the 22,000-ton roof, then remove the existing bowl and arena below before rebuilding the arena and permanent supports. In the process, Mortenson will need to dig another 15 ft down—and dig horizontally—to extend the entire project 53 ft below grade, creating a subterranean venue nearly double the size of what currently exists. The 600,000 cu yd of excavation will help extend the arena to roughly 855,000 sq ft while compacting the seating bowl to 17,300 seats for hockey. 

The effort won’t come cheap. Early estimates of a $600-million project have increased to between $900 million and $930 million. “The market index in Seattle is well above other markets, but we didn’t value engineer,” says Tod Leiweke, CEO of Seattle Hockey Partners and part of the OVG ownership group led by David Bonderman and Jerry Bruckheimer. “We didn’t cut things out. It is more money than we thought, but we realize how epic this project is. It took courage from day one. Everybody said it couldn’t be done, but if the arena was dead, what did that mean for Seattle Center?”

With the construction documents complete, demolition is revving up. To date, crews have removed seats, furnishings and signage and have begun removing concrete. Once the rebuild really starts, construction crews will be thrown right into the mix, says Greg Huber, Mortenson project executive. “Reestablishing the roof is the most complex part of the project,” he says. With no margin for error with an existing roof in place, construction will happen from the bottom up, but with the top already completed. “Once we have the foundation and structure in, then it becomes more standard.”

Much of the growth of the arena will come underground for the back-of-house operations, including eight underground loading docks. Inside the bowl, expect the Populous design to feature a ring of 40 suites cantilevered over the lower bowl. 

As part of the landmark status, Mortenson is also removing, cataloging and storing all the glass windows from the current arena. The team plans to reuse them to recreate much of the exterior of the arena when it reopens. 

Ken Johnson, construction executive for OVG-Seattle, says the contract with Mortenson includes financial incentives to finish the project in early summer 2021. 

Follow Tim Newcomb on Twitter at @tdnewcomb