Folks may have been reading about the bad accident on I-5 near Santa Clarita this morning (LA Times, Daily News, KNBC), and wondering exactly where it was. This page makes it clear. It is the truck route tunnel from I-5 SB, where the truck route goes under the main lanes of the entire freeway to the eastern side, then running parallel to the freeway, eventually crossing back in with another tunnel just N of Balboa Blvd. It is clear that it is the northern tunnel by the alternate routing the CHP is suggesting, which diverts traffic onto Route 14. You can also see from the map why this is such a problem: if the structural integrity of the tunnel was compromised, then the I-5 mainline would be compromised, prompting significant reconstruction and delays. In some ways, this is potentially worse damage than occured when the Route 14 overpasses collapsed during the earthquake, given what must be shutdown. I expect, if there is structural damage, for there to be completion bonuses analgous to those given when the I-80 connected required emergency reconstruction.