Work continues on the new Tappan Zee Bridge near Tarrytown, N.Y., Tuesday, Dec. 20, 2016. The $4 billion bridge replacement is of the biggest infrastructure efforts currently underway in the U.S. TARRYTOWN, N.Y. - The concrete needed for New York's new, $4 billion Tappan Zee Bridge, under construction over the Hudson River, would be enough to make a 1,500-mile sidewalk reaching all the way to Florida's Key West.