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Puget Sound Transportation Projects

Alaskan Way/SR 99 Viaduct - Seattle, WA

Alaskan Way Viaduct along the Seattle Waterfront

Current Proposed Plan:

Other projects underway:

The Alaskan Way/SR 99 Viaduct was built in the early 1950's1. It serves as an important bypass for downtown Seattle and takes some of the load off of Interstate 5. As it also cross-connects with the West Seattle Freeway it is an important connector to West Seattle.

The viaduct became a cause for concern after the collapse of the Cypress viaduct in the 1989 San Francisco earthquake. These concerns increased after the 2001 Nisqually Earthquake damaged the viaduct further.

As of 2011 the current plan is to replace the viaduct with a stacked bored tunnel. While the plan has been approved by the state and work is underway, concerns about cost overruns have led the City of Seattle to be mixed on their support for the bored tunnel.

Interesting facts: Back to Top

  • The viaduct was planned to connect to I-90, stub ramps around the stadiums exist for this purpose.
  • The viaduct was built around a brick building downtown; the building extends a couple inches into the actual viaduct.

Thoughts: Back to Top

I have taken the viaduct into the city, and especially to the Seattle Center many times. It is one of the more interesting ways to come into the city, especially at night, as you are on the upper deck and have an amazing view of downtown and Elliot Bay. I didn't think much about the potential problems with the design until after the 1989 quake, and it really sunk home after taking the tour in March 2004.

However the best routing for a replacement is via a tunnel. The viaduct as it stands today blocks off downtown from the waterfront. Removing the viaduct without a replacement is unreasonable given the amount of traffic it handles. The current tunnel plan will serve as a bypass of downtown, while improvements to Alaskan Way will allow access into downtown for former users of the viaduct.

Future: Back to Top

  • Replacement with bored tunnel, barring any more legal challenges.

Links: Back to Top

Images: Ben Brooks (all)

1 http://en.wikipedia.org/wiki/Alaskan_Way_Viaduct