Going, going, soon gone

If you talk to NHL Seattle leaders about the New Arena at Seattle Center, they are always happy to reiterate one point: This project is not a renovation.
"People say, 'I understand you're renovating the Key," explains Ken Johnsen, construction executive for the New Arena. "We aren't."
Eight months after breaking ground, Johnsen and NHL Seattle CEO Tod Leiweke now have all of the evidence they need to dissuade Seattleites and hockey fans everywhere from any misconception.

The proof: Approximately 10 to 12 days from now, there will be nothing left to renovate. Workers and heavy machinery are about to knock down, crunch up and haul away the last truckload of concrete and steel that held up the original building's stands encircling the playing surface.
"That bowl is gone," says Johnsen, pausing for effect. "Gone. We will build a brand-new bowl. All of the supports, the seats, the concession areas, it's a brand-new arena."
The only remaining items will be the historic-landmark roof, which of course won't be altered, and the original glass at ground level that is currently numbered, cataloged and stored at a warehouse in Kent. The 1962 World's Fair glass will be back in place before the arena opens in the summer of 2021.
Johnsen says he estimates the "major excavation" to dig out 600,000 cubic yards of dirt will start around June 15th.

One highly intriguing facet of the New Arena build will occur during the dig. The excavation crew will go down as far as 70 feet below ground level so there is ample support for 24 temporary steel columns that will hold up the roof during excavation and beyond. Johnsen is happy to provide more detail.
"Let's talk about how we do this for the roof because it's a fantastic piece of engineering," says Johnsen. "You will see people around the country, probably around the world, come [to Seattle] to ask, 'How are they doing this?'"
Here's how: there are 20 "Y" columns and four larger buttresses (aka chevrons) currently holding up the 44-million-pound roof. As the excavation unfolds, those Y columns and buttresses will have nothing but air beneath them. There's that 'nothing' word again.
"We're going down another 15 feet just from the base floor and much more than that on the sides, closer to 70 feet," says Johnsen. "Again, we're putting up temporary steel to hold the roof in place while those buttresses and Ys aren't doing their job because we're excavating underneath them.
"Then we will extend the buttresses and the Ys so that they're doing their job holding up the roof again and we'll take out the temporary steel. It's an exciting piece of engineering. Really smart people put it together. It will be fun to watch."

The excavation will last into the fall. All sorts of laser monitors and other high-tech survey devices will make sure the hole is perfectly dug and shaped. Then the new building will commence.
"I like to explain the project this way," says Johnsen. "It helps me out. For 2019, we're going down. We're demoing things. We're taking out the soil. We are putting in the underground mechanical/electrical/plumbing, which is a big part of this project. That carries us through 2019."
OK, tear down, dig down and build underground in 2019. Got it.
"In 2020, we start going back up again," continues Johnsen. "We start building the building, being able to take away some of the temporary steel that's holding up the roof, start building the walls. We build a brand-new arena underneath this historic roof we have saved while all the construction's going on.
"Then in 2021, until we open in the summer, we're finishing the inside."
OK, Ken Johnsen, one last question: In one word, how do you feel when you show up at this site every work morning?
Johnsen grins: "Pumped."