SEATTLE, WA – The new SR 99 tunnel under Seattle is basically done. Or as WSDOT puts it, the tunnel project has reached a phase called “substantial completion.”

That means the tunnel “could technically be operated as designed.” But, there are still two construction milestones before the tunnel can open to the public.

“What comes next is a variety of wrap-up work elements that, once completed, will result in the tunnel reaching the second milestone, known as ‘physical completion.’ Meanwhile, as STP works toward physical completion, WSDOT will continue to train maintenance and operations staff to ensure the tunnel and those responsible for its operation are ready to go in early 2019,” WSDOT wrote on the SR99 blog Tuesday.

“Final completion” of the tunnel happens when WSDOT and the contractor Seattle Tunnel Partners wrap up paperwork, but the tunnel will be open before that.

Reminder: starting Jan. 11, SR 99 through downtown Seattle will close for three weeks. That’s so crews can realign the roadway through the tunnel and off the viaduct.