The Tappan Zee (Governor Malcolm Wilson) Bridge is a cantilever truss bridge with a main span of 1,212 feet which was constructed across the Hudson River in 1955. The bridge is part of the New York State Thruway mainline, designated as Interstate 87 and Interstate 287.

In March 2008, the New York State Department of Transportation (NYSDOT) assembled a panel of experts on seismic, foundations and long span bridges to perform reviews and recommend refinements of the seismic analysis, proposed conceptual retrofit designs, and new foundation concepts for the replacement option for the Tappan Zee Bridge. Mark Ketchum of OPAC was invited to participate on the panel. The panel participated in a two-day workshop with the focus on reviewing the current seismic analyses, conceptual designs for retrofitting the existing floating caisson foundations, and new foundation concepts for the replacement option. The panel recommended modifications to the seismic analyses and developed alternate foundation design solutions.

In September 2008, New York state officials announced plans to replace the deteriorating Tappan Zee Bridge with a new bridge that will include commuter-train tracks and lanes for high-speed buses.