Folks should stop worrying about the Alaskan Way Viaduct collapsing. That's ridiculous. It's not going to collapse. It's going to tip over.
— Goldy (@GoldyHA) December 9, 2014
If you think some folks have been too alarmist over the news that the Alaskan Way Viaduct has “settled” a mere 1.2 inches in the vicinity of the Bertha rescue pit, then you’re probably not familiar with the Viaduct’s prior history of settling. Several segments of the aging freeway have long been settling unevenly—specifically, the structure is slowly toppling over onto the waterfront. The more the freeway leans, the more its high center of gravity accelerates the process—and the more vulnerable it becomes to even a modest quake.
Which is why SDOT and WSDOT need to focus now on engineering the Viaduct’s surface street replacement. Really.
The main selling point of a deep bore tunnel was that it would allow the Viaduct to remain open to traffic while its replacement was built, but the long delay, future uncertainty, and recent ground settling leaves that objective in doubt. The Viaduct could be deemed unsafe at any moment. So since we’re going to tear down the Viaduct and replace it with surface streets eventually, it would be prudent to finalize the design, engineering, and logistics as quickly as possible. That way, whatever becomes of Bertha, we would be prepared to tear down the Viaduct and replace it with surface streets with the least disruption we can manage.
Seriously. Whatever the odds, the sudden and permanent closure of the Viaduct is not a far-fetched scenario. And we would be crazy not to prepare for it.
Perhaps they’ll manage to get Bertha moving again, and perhaps the Viaduct will survive the tunnel’s construction. That would be great. But the prudent course of action would be to assume that it won’t, and move forward with its surface replacement with all due speed.