Holgate to King Street Viaduct Replacement - Complete February 2014

Project Overview

The South Holgate to South King Street Viaduct Replacement Project, completed in early 2014, was an early phase of the Alaskan Way Viaduct Replacement Program in Seattle, Washington.

Needs & benefits

One of the first big projects of the Alaskan Way Viaduct Replacement Program was building a new roadway to replace the viaduct’s southern mile, which ran along the waterfront south of Seattle’s stadiums. The foundations of this section of viaduct rested in soil at high risk of liquefying in an earthquake, and were not deep enough reach into solid ground.

This section of State Route 99 was replaced with two side-by-side bridges. These bridges provide much better seismic stability, with foundations reaching up to 260 feet deep. Wider shoulders provide more space for traffic incident and emergency responses. Bridge construction was completed in September 2012, one year ahead of schedule.

This project also built a new overpass above the BNSF railroad tracks near Alaskan Way South and South Atlantic Street. This overpass improves traffic flow to and from one of the Port of Seattle’s busiest terminals, and eliminates severe backups caused by the at-grade railroad crossing. This overpass opened in January 2014.


  • Fall 2011: Southern mile of the Alaskan Way Viaduct demolished.
  • September 2012: Twin SR 99 bridges completed.
  • January 2014: South Atlantic Street overpass opens to drivers.


The SR 99 South Holgate Street to South King Street project was part of the Alaskan Way Viaduct Replacement Program. This project’s portion of the budget was $347.7 million. Funding came from state, federal and local sources.



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Map showing highlighted section of highway 99 and Atlantic Street overpass in Seattle