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Tunnel Boring Machine on Display at Milepost 31

SR 99TBM model now on display at Milepost 31 (Photo courtesy of WSDOT)

Will you be down in Pioneer Square for First Thursday? Then, come on down to Milepost 31 to see the model of the world’s largest diameter tunnel boring machine! This 10-foot-long, motorized model offers you an up-close look at the machine’s inner workings of the five-story high machine that will dig the SR 99 tunnel. Pretty cool…

It takes a team – the core of the SR 99 tunnel boring machine is assembled (Photo courtesy of WSDOT)

The tunnel boring machine is scheduled to arrive next year.

So, you may be asking yourself “what and where is Milepost 31?” Well, it is an award-winning information center located in the heart of Pioneer Square at 211 First Ave. S., Seattle, which highlights the people and the projects that shaped the neighborhood and provides a special look at the SR 99 Tunnel Project.

Admission to the center is always free – opened Tuesdays through Saturdays, 11 a.m. to 5 p.m. (open until 8 p.m. on the First Thursday of each month; closed on state holidays).

You will also have an opportunity to join project leaders on September 6th at 6 p.m. for a walking tour  of the SR 99 Tunnel Project work zone.

For more information about Milepost 31, visit