Mount Baker Ridge Tunnel, Interstate 90, passing under Mount Baker Ridge, Seattle, King County, WA

Significance: In the context of Western tunneling, it is remarkable for both the material it was driven through (clay), and the form it took (twin bore). It ranks as the world's largest diameter soft earth tunnel. The highly stylized treatment of the east portal demonstrates the way in which Modernistic Architecture was applied to engineering structures. It was a part of the Lake Washington Floating Bridge/Lacey V. Murrow Memorial Bridge (HAER No. WA-2) project.
Unprocessed Field note material exists for this structure: N462
Survey number: HAER WA-109