SEATTLE – The culmination of 10 years of technical analysis and public, agency, and tribal review came to fruition July 7 when the Federal Highway Administration (FHWA), Washington State Department of Transportation (WSDOT), and city of Seattle released the State Route 99 Alaskan Way Viaduct replacement project’s final environmental impact statement (EIS).

"The final EIS represents countless hours of debate, town halls, public outreach, and technical review," said Washington Governor Chris Gregoire. "Completing this review process wasn’t a sprint, it was a marathon. Now the finish line is in sight, and we’ll begin construction of the bored tunnel this fall."

The final EIS examines the potential environmental effects of viaduct replacement alternatives, including a bored tunnel, and builds on the analysis included in the 2004 draft EIS, the 2006 supplemental draft EIS, and the 2010 supplemental draft EIS. The document compares the effects of all three build alternatives – bored tunnel, cut-and-cover tunnel, and an elevated structure – and explains why a bored tunnel is the preferred alternative.

According to the EIS, benefits of a bored tunnel include the following:

  • improved safety – creates a new SR 99 with wider lanes and less-abrupt curves, and is built to withstand a 9.0 earthquake;
  • fewer disruptions – keeps SR 99 open throughout construction;
  • opportunities for public open space along the downtown Seattle waterfront;
  • improved mobility between neighborhoods north and south of downtown for bicyclists, pedestrians, freight, and other vehicles; and
  • improved waterfront environment by reducing noise, treating stormwater runoff, and enhancing views and mobility from neighborhoods, including downtown, Pioneer Square, and Belltown.

Also discussed in the document are details about the three alternatives with and without tolls. Because the analysis shows that tolling would cause some drivers to shift to downtown streets, Alaskan Way, and I-5, WSDOT and the city agreed to establish a committee to assess and make recommendations to mitigate traffic impacts caused by tolling. The Tolling Advisory Committee will commence its work this fall. The final EIS also contains responses to more than 3,000 comments received during the comment periods of the three previous draft documents.

"We’re eager to turn this project into reality," said Washington Transportation Secretary Paula Hammond. "We’ve already started rebuilding SR 99 through SODO and have hired a contractor for the tunnel. The sooner we get going, the sooner drivers have safer and more reliable routes into, out of, and through downtown Seattle."

In January, WSDOT signed a design-build contract with Seattle Tunnel Partners to advance the bored tunnel’s preliminary design. The agency plans to direct the design-build team to begin final design and construction of the bored tunnel in mid to late August, after FHWA officially approves the project through a record of decision.

For more information on the Alaskan Way Viaduct and Seawall Replacement Program, visit The final EIS is available online at