Building a stadium in seismic Seattle

This stadium is ready to shake, rattle and roll

By Les Carpenter
Seattle Times staff reporter

The stadium stands on the most unstable of surfaces — dirt and tree stumps and old railroad ties dumped long ago in the receding waters of Elliott Bay. And while the goo appears as solid as bedrock to the naked eye, let the ground shake in an earthquake and suddenly it is a milky mess of liquefied mud.

This made for some tricky maneuvering for the Ellerbe Becket designers who had to put together a stadium that could roll freely if the ground started to shake. And none of it came cheaply. Kelly Kerns, project manager for the stadium, estimates that these special functions added 5 percent to the overall construction costs.

Like many West Coast buildings, including Safeco Field, Seahawks Stadium is actually eight structures held together by a series of joints, long metal planks that run through the stands and across concourses at various points of the stadium. The planks cover a small gap, which allows the stadium to have flexibility.

Thus, when the ground shakes, the separate sections will have room to move on their own, jiggling in place. The designers believe this elasticity will keep chunks of concrete from breaking away or, worse, collapsing.

Ellerbe Becket got a good test of the design last year during the Nisqually quake. Within hours, the stadium builders discovered that their structure suffered insignificant damage while several buildings right outside were nearly destroyed.