Swirlygrrl raises an excellent point: With the cost of fixing, um, replacing, the Storrow tunnel suddenly up past the $100-million mark (raise your hand if you really think it'll "only" wind up costing $130 million), why not just shut the road altogether and figure out how to divert traffic to other roads? That money will buy an awful lot of improvements to those roads (such as the turnpike for people coming in from Allston/Brighton and Newton) and give us even more parkland along the Charles.
Even better, why not take a look at what San Francisco did after an elevated highway collapsed during the 1989 earthquake - replace the whole thing with a trolley line. No doubt there would be some interesting engineering challenges connecting it to the Green Line in the Leverett Circle area, but, again, we're talking $130 million, maybe more, just for the Storrow tunnel, and so far state officials haven't asked where that money is coming from. Maybe even think really big and have Riverside II continue along Soldiers Field Road to Harvard's new mega-campus (and give the northern parts of Brighton and Allston real rapid transit in the process).