The Stacked Drift Tunnel

by Rita Robison, Senior Editor; Civil Engineering, New York, NY,

Serial Information: Civil Engineering—ASCE, 1990, Vol. 60, Issue 7, Pg. 40-42

Document Type: Feature article


The Mount Baker Ridge Tunnel is the first of its kind and the last: a forward thrust of technology and a look back to the flow of federal highway funds, which paid 90% of its cost. The 1,500 ft tunnel and adjoining lidded structures, named the 1990 Outstanding Civil Engineering Achievement, provide a 3,400 ft long stretch of concealed traffic for the Seattle portion of I-90. The tunnel is the world's largest ever driven through soft soil. Its lighting and control systems are state of the art. The lids over the approaches support parks that unite neighborhoods long separated by an existing highway, which is being incorporated into I-90. The project is a major part of the $1.46 billion completion of I-90 between Seattle and Bellevue, Wash., 7 mi to the east. Its technical firsts include the stacked-drift method of constructing the 1,476 ft long, 63 ft interior diameter tunnel (CE, December 1985).

Subject Headings: Tunnels

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