SR 99

Alaska Way Viaduct Replacement Tunnel

Project Details

ROLE
Drilled-Shaft Subcontractor

CONTRACT AMOUNT
$4.6 Million

OWNER
Washington State Department of Transportation

LOCATION
Seattle, WA

ARCHITECT
HNTB

SIZE
1.8 Miles

COMPLETION
2019

Project Description

The SR 99 Alaskan Way Viaduct was replaced with an approximately two-mile-long double-deck tunnel underneath downtown Seattle. Replacing the viaduct with a tunnel allows the highway to remain open for much of construction, thus minimizing closures and impacts to traffic. Once the tunnel opens, the viaduct will be taken down to clear the way for new public space along Seattle’s downtown waterfront.

Photo Credits: WSDOT