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Removing viaduct support columns

On June 11, crews removed two "outrigger" support columns from the southern section of the Alaskan Way Viaduct to narrow the width of the structure.

Narrowing the width provides crews the room they need to finish building the new SR 99 lanes alongside the existing viaduct. View photos of the progress.

Viaduct column removal locations


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The two concrete support columns are located between S. Atlantic and S. Holgate streets (where the double-deck structure descends to ground level). Temporary foundations and support systems to brace the viaduct will be installed before the bridge columns are removed.
 

Column removal steps

We will remove the viaduct support columns and install  temporary bridge support systems in two steps.

Step one




First, crews remove a section of the roadway and install temporary foundation supports called micro piles under the viaduct. 

Step two



Next, temporary bridge supports are installed and the "outrigger" column is removed.

Final configuration




The temporary support system remains in place until October 2011 when crews tear down the southern mile of the viaduct and shift traffic onto the new SR 99 lanes.