Seattle fifth-graders try to solve Bertha’s big mystery

The Seattle TimesJanuary 2, 2014 

Construction on the Highway 99 tunnel in Seattle is shown in this 2013 photo from the state Department of Transportation.


When Bertha, the world’s largest tunneling machine, got stuck a few weeks ago, a fifth-grade teacher at Seattle’s Thornton Creek Elementary seized the chance for his students to play history detective.

“They had just learned about the Great Seattle Fire when Bertha got stuck under the Seattle Waterfront,” said Todd Bohannon, and suddenly they had a mystery that made their study of state history immediately relevant:

What was blocking Bertha’s path?

Progress on the four-lane tunnel from Sodo to South Lake Union has stalled since Dec. 6. Bohannon assigned the class to write essays on what could be so large that the 54.3-foot-diameter drill couldn’t chew its way through it — a question that’s still confounding project engineers.

“The possibilities are endless, but we had to narrow it down,” Bohannon said.

Of course the first thing the fifth-graders imagined was a buried flying saucer — a theory the teacher quickly nixed.

“The requirement was really for them to come up with a theory that was realistic and then for them to find an article that supported that theory,” he said.


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