Alaskan Way Viaduct and Battery Street Tunnel, Seattle, King County, WA

Significance: The Alaskan Way Viaduct is significant for its double-deck configuration, the first such bridge built in the state of Washington. The structure encompasses two different designs and crosses over highly complex subsurface conditions, supported throughout its length on pile foundations.
The Battery Street Tunnel was the City of Seattle Engineering Department's first venture into tunnel design. It was designed and built to minimize traffic disruption and reduce risk to neighboring buildings. Its health and safety features were innovative at the time, including a ventilation system actuated by carbon monoxide monitors and a heat-actuated automatic sprinkler system.
The viaduct and the tunnel played an important role in the development of Seattle and the region by providing a direct connection through downtown Seattle and to the industrial areas to the south.
Unprocessed Field note material exists for this structure: N1131
Survey number: HAER WA-184
Building/structure dates: 1949-1966 Initial Construction