SR 99 Tunnel North Access Connection
As part of the Alaskan Way Viaduct replacement program, the Atkinson team constructed the SR 99 tunnel’s north access entrance and exit roadways from the portal structure at Harrison Street to north of the Mercer Street bridge. The team also built on- and off-ramps at Republican and Harrison streets and extended Sixth Avenue North from Harrison Street to Mercer Street.
Once the new roadways and bridges were complete, Atkinson demolished the existing SR 99 Bridge over Broad Street and raised the lowered roadway up to the surrounding grade. The scope of work also included installing traffic signals, illumination, and intelligent transportation systems (ITS) as well as relocating existing utilities including water, storm, sewer, and high voltage electrical systems.
The SR 99 Tunnel North Access Connection project is adjacent to Atkinson’s Mercer Corridor West project—giving Atkinson control of the interface between the two projects for construction sequencing and traffic control. This was critical in this highly congested urban area surrounding the Seattle center—which includes the Space Needle and multiple performance, sports, arts, and entertainment facilities as well as other businesses such as the Experience Music Project and Bill and Melinda Gates Foundation.