Geotechnical projects - Transportation - I-84 Sandy River Bridge Geotechnical Investigation
Old Tanana River Bridge, Tok, Alaska

The Alaska Department of Transportation and Public Facilities needed to construct a new Tanana River Bridge at Mile 1303.3 of the Alaska Highway. The existing through-truss steel bridge was 60 years old and had suffered damage during the magnitude 7.9 earthquake that occurred in 2002. In that event, the foundation liquefied enough that the bridge shifted several inches on its bearing plates, and needed to be repositioned.

Due to the a very short design schedule, Landslide Technology, a division of Cornforth Consultants, Inc. joined the DOT team to provide site seismic analysis' liquefaction assessment, stability analysis of both abutments and embankments, rock cut slope and foundation recommendations, and a constructability review.

The replacement structure will be 900 feet long and consist of six concrete girder spans supported on five large-diameter, drilled shaft concrete piers in the river with smaller-diameter shafts at the east abutment and a pile foundation at the west abutment. In spite of the short timeframe, the design and construction documents were completed in time to preserve the project funding, which otherwise would have been in jeopardy.