State Route 99 – Two years in the transformation of Seattle’s first freeway

Friday, September 21, 2012

By guest blogger Greg Phipps

In summer 2010 contractor crews working for WSDOT started work to replace the aging Alaskan Way Viaduct south of Downtown Seattle. Two years later the seismically vulnerable viaduct is gone and drivers are traveling on a brand new, seismically-strong State Route 99 from SODO to Pioneer Square. This section of SR 99 won’t be truly complete until it connects to the SR 99 tunnel at the end of 2015. Still, it’s pretty cool to see how replacing the southern mile of the viaduct has changed the landscape south of downtown.

The southern mile
Our first photo shows the southern mile of the viaduct in May 2010, before crews started building the new SR 99. Besides the viaduct, keep an eye on a couple things that will change. The first thing is Alaskan Way South, the street on the west side of the viaduct. The second thing is the railroad tracks between the viaduct and Alaskan Way South.















The southern mile in September 2011
One year ago crews were close to finishing the western half of the new SR 99, the piece that would eventually become the southbound lanes of the highway. What happened to Alaskan Way South? Part of it is in the footprint of the new SR 99 bridge, while the rest has become a construction zone. And the railroad tracks? They’ve moved west, out of the way of the new highway.
















Southern mile demolition – October 2011
Just one month later and the viaduct is a shell of its former self, literally. Demolition machines are hammering and crunching the double-deck viaduct into piles of concrete and rebar rubble.  In a little more than a week most of the southern mile has disappeared. Meanwhile, crews are getting ready to open the western half of the new highway and the construction bypass that takes traffic from the new highway up to the remaining section of the viaduct north of South King Street.
















The new Highway 99 - September 2012
It’s 11 months after the southern mile demolition and we’ve got twins!  Bridges, that is.  Southbound traffic rides on the west bridge and northbound traffic uses the east bridge, until they meet again and travel on a construction bypass around SR 99 tunnel construction.  On the photo trace a line from the end of the east bridge through the tunnel construction zone toward the blue cranes on the bottom right. That’s your route into the tunnel starting at the end of 2015.

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Seattle Tunnel Partners digging the circular pit that will be used to access and repair Bertha
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