SR 99 Tunnel North Access Connection

As part of the Alaskan Way Viaduct replacement program, the project encompassed the construction of the SR 99 tunnel's north access entrance and exit roadways, starting from the portal structure at Harrison Street and extending northward beyond the Mercer Street bridge. Additionally, Atkinson constructed on- and off-ramps at Republican and Harrison streets, along with the extension of Sixth Avenue North from Harrison Street to Mercer Street.

Following the successful completion of the new roadways and bridges, Atkinson demolished the existing SR 99 Bridge over Broad Street and elevated the lowered roadway to match the surrounding grade. The comprehensive scope of work further involved the installation of traffic signals, illumination systems, and intelligent transportation systems (ITS). Additionally, there was a crucial task of relocating existing utilities, including water, stormwater, sewer, and high voltage electrical systems.

The SR 99 Tunnel North Access Connection project was adjacent to the ongoing Mercer Corridor West project. This proximity allowed for seamless coordination of construction sequencing and traffic control at the connection of these two projects. This coordination was important given the densely congested urban environment surrounding the Seattle Center, which includes iconic landmarks like the Space Needle and hosts numerous performance, sports, arts, and entertainment facilities. The area is also home to various businesses, including the Experience Music Project and the Bill and Melinda Gates Foundation.