I-5 Meltdown ... what's Plan B?

I think it's a question worth asking right now, in light of what happened in Oakland. If an overpass were struck by a tanker and the explosion collapsed a 4 lane overpass over I-5, and the freeway was closed for 2 weeks as they worked to fix it ... what's Plan B for Tacoma commuters?

I'm guessing the Sounder would get a lot more riders. And 99 would be awful to drive on. And some might go through Bremerton and the ferries. Others might sleep on a cot in Seattle for awhile.

I-5 is a pretty vital link for this region and anything we can do to find alternate routes between Tacoma and Seattle--before we're faced with an emergency--would be a very good thing, I feel.

Note: here's a slideshow of the damage from insidebayarea.com.