Q13 reports:

The Alaskan Way Viaduct has settled up to 4/10 of an inch as a result of contractor work on the Highway 99 replacement tunnel, according to WSDOT.

The Seattle City Council took up the issue at a meeting Monday afternoon. Council members say if the viaduct continues to settle, it may need to be shut down, and it’s time to start thinking about a contingency plan.

Sounds like the viaduct has 6/10 of an inch more to go before people like Council Member Mike O'Brien start calling for it to be closed to traffic.