"Those [concrete] Y-columns and four chevrons [super-size buttresses] held up the roof [from 1962 until now]," says Ken Johnsen, construction executive for Oak View Group and NHL Seattle. "Underneath each one is a huge concrete block that we have to demolish and excavate."
The first of those concrete blocks has been drilled, chipped and generally pulverized so that one of those Y-columns now appears suspended in mid-air. More concrete blocks are under demolition. Each week this fall, it will seem increasingly that the entire roof is suspended in airspace.
But it won't be easy. There's a massive amount of concrete below each Y-column and the chevron under-blocks are, let's call it, eight to 10 times bigger than Y-column blocks.
Johnsen says the early blocks are revealing more rebar or a steel reinforcement cage-like material than anticipated. More-than-specified concrete has been poured for a number of blocks when compared with the 1962 plans.
"That first block is a learning process," says Johnsen. "You might realize a different piece of machinery would work better. You want to get into a rhythm and be more efficient [at demolishing the blocks]. It will take some work, we don't quite know how much work each one is going to be."