Taking stock at the tunnel’s halfway point

Bertha has reached the halfway point in her journey beneath downtown, but tunneling crews aren't the only ones making progress on the Alaskan Way Viaduct Replacement Program. Here's a round-up of all the work that's happening along the SR 99 corridor. 

Interior structures

There's more to building a tunnel than simply digging through the earth. A separate crew is hard at work building the double-deck highway inside the concrete tube built by Bertha.

The northernmost section of the tunnel's interior structures is now more than 3,000 feet from the tunnel entrance. The upper road deck stretches more than 1,500 feet from the entrance.

Completed sections of the SR 99 tunnel’s top, southbound roadway deck

Operations buildings

Operations buildings at the tunnel's north and south portals will control lighting, ventilation and safety systems inside the tunnel. Both of these buildings, with their distinctive yellow stacks, are now more than 90 percent complete. 

At the north portal operations building, crews have completed installation of the four massive fans that are part of the tunnel’s extensive ventilation system. Fans in the south building will be installed soon. With the buildings structurally complete, crews are hard at work painting and putting the finishing touches on the building's interiors.

South portal operations building 

North portal work

The North Access Project, a separate contract being completed by Atkinson Construction, is pushing toward completion. Crews have finished many of the ramp and highway connections at the tunnel’s north portal, and have begun striping the roadway.

Installation of overhead highway signs will begin Oct. 10 and will occur at night. These electronic message and directional signs will serve drivers on both the existing highway and the future tunnel.

The SR 99 tunnel north portal as seen from the Space Needle

South portal work

At the tunnel's future south portal, contractor Interwest Construction is building the future northbound off-ramp that will connect drivers to downtown and the stadiums. Construction of the ramp began this summer and is expected to be complete early next year.