Title:
I-90 First Hill Lid: Challenging Schedule and Constructibility
Author(s):
Donald Schaap
Publication:
Concrete International
Volume:
11
Issue:
2
Appears on pages(s):
37-41
Keywords:
concrete construction; girders; mix proportioning; tunnels; precast concrete; prestressed concrete; reinforced concrete; retaining walls; vehicular tunnels; Construction
DOI:
Date:
2/1/1989
Abstract:
Describes construction in progress on the First Hill Lid structure, a three-quarter mile long (1.2 km) five-lane double tunnel on Mercer Island, Washington, that is part of the $1.4 billion Washington State Department of Transportation I-90 corridor project. Completed, it will include state-of-the-art monitoring and communication systems, a 75,000 ftý (6970 mý) ventilation building, and over 105,000 yd3 (88,000 m3) of concrete. Custom "Y-wall" gang forms were devised for use in a 5-day construction cycle for the tunnel walls, and a one-of-a-kind traveling hydraulic gantry was fashioned to set many of the prestressed concrete girders.