(Machinery photographed at Highway 99 tunnel launch-pit site by Don Brubeck)

By Tracy Record

West Seattle Blog editor

The Highway 99 tunneling machine is here, and being re-assembled. But once it goes into the ground, it won’t be “out of sight, out of mind” by any means.

Drivers and bus riders, in particular, might wind up noticing in a big way:

WSB has learned that the Alaskan Way Viaduct might close for an unspecified amount of time later this year when the machine arrives 80 feet below what remains of the elevated roadway, despite the work that’s been done to reinforce it so it could stay “safely open” during the tunnel construction.

We first heard about this last night from Don Brubeck, president of West Seattle Bike Connections, who mentioned it during an unrelated presentation at the Morgan Community Association meeting (separate coverage of that is in the works).

Brubeck explained that SDOT director Peter Hahn brought up the potential Viaduct closure during this week’s Freight Advisory Board meeting; it’s noted in Brubeck’s meeting notes on the new WSBC website. He quoted Hahn as saying that local transportation authorities are gearing up now to get the word out about alternative transportation.

Since The Viaduct is part of a state highway – and the tunnel, a state project – we followed up this morning with WSDOT spokesperson Travis Phelps.

He confirmed that WSDOT is talking about a possible closure when the tunneling machine goes under what he described as the southernmost part of what’s left of the elevated Viaduct, but said no final decision has been made yet.

What’s the timetable for that decision? Sometime this spring, according to Phelps – maybe by the time the project-related “working groups” have their meeting in early May. Right now, they’re still hashing out details such as, “how long would we close it if we close it?” and the idea is “just sort of out there.”

He also mentioned that even once the machine goes into the ground, it starts with “three safe havens” that are more or less test digs before it really gets to the dirt.

You’ll recall the Viaduct itself already has been the subject of extensive reinforcement work, mostly done during overnight and weekend closures over the past year-plus. In a March 2012 news release, deputy program administrator Matt Preedy was quoted as saying that the reinforcement work “allows us to keep the viaduct safely open to traffic while we build the tunnel …” but apparently that assessment is evolving.

We’ll keep following up to see what WSDOT decides.