Two Seattle construction snafus ... and what we learned from them May 09, 2019 at 1:03 pm

We still don’t have an official explanation for why a crane collapsed in Seattle’s South Lake Union neighborhood, killing four people. But we know we'll learn from it. Because that's what has happened, following other construction accidents in local history.

Leonard Garfield, executive director of the Museum of History and Industry, gave me two examples of times we learned from local construction accidents. “One of the biggest accidents that happened during a construction project was the sinking of the I-90 bridge back in 1990," Garfield said. " It was the original bridge that had been open since 1940 that was being refurbished to server a greater number of cars. The construction project was almost complete." As part of that project, the pontoons that held up the bridge were left open like giant bathtubs. Then a storm came, and waves filled those bathtubs with water. And the bridge sank to the bottom of the lake. Luckily, no one was hurt. "Anyone who was in Seattle remembers it well, because we were dealing with this incredible Thanksgiving storm and suddenly the bridge that linked Bellevue and Seattle and the whole region was no longer," said Garfield. King 5 captured the sight in the video below.

What did we learn from that? A Blue Ribbon Panel had some advice, which I paraphrase this way: A floating bridge is more like a boat than a road. So, treat it like a boat! That means, next time, pay more attention to experts in marine construction techniques. A nother big reform came when we discovered an accident waiting to happen and prevented it with an extreme response. The project was the McGuire apartment building in Seattle’s Belltown neighborhood.

“The McGuire apartments were built in 2001," said Garfield. "And they were kind of a symbol of the boom of Belltown in the late 1990s and the early part of this century. Twenty-five stories, hundreds of tenants. It was really a symbol of the new Seattle." Some news reports put the building at 26 stories, others at 25. Either way, it was a fine expression of Seattle’s first dot-com boom. "A few years after it opened, they discovered some engineering flaws, some construction flaws, that were really beyond repair,” Garfield said. The McGuire apartments used a technique called "post tension slab" construction. This common technique lets you pour much thinner concrete slabs for each floor. To make that thin slab stronger, you use a ratchet tool to tighten the rebar inside. It’s kind of like taking a rubber band ... made of steel ... and stretching it tightly.

That’s fine if the rubber band doesn’t break. But in this case, the rebar, which was metal, was not properly waterproofed and it rusted. Which meant it could have snapped, catastrophically. In this weakened state, it was like a cross between a rusty bear trap and a giant whip made of metal. You can hear the sound of a piece of rebar snapping – in the industry safety video below.

People can’t live around a threat like that. "In 2010, they began to deconstruct the building," Garfield said. "In 2011, there was no more McGuire apartment building. Twenty-five story building, taken down to the ground because of construction flaws."

In the video below, KOMO captured the reaction from angry neighbors who had to listen to the building being demolished.

The building’s failure had implications all over the country. Now, you have to waterproof the exposed ends of the rebar in slabs like that. It’s written into the building code. S ometimes, workers die.