Landmark Cable-Stayed Bridge over the Charles River, Boston, Massachusetts

Boston, in the forefront of the American Revolution two centuries ago, is now in the forefront of another revolution in the field of cable-stayed bridge technology. New technologies and innovations have become hallmarks of the Leonard P. Zakim Bunker Hill Bridge—a structure unique in the world. This crossing of the Charles River brought the community, engineers, and architects together to create a “signature bridge” and a “gateway” to the city. Located at a preeminent point where Paul Revere crossed in 1775, the bridge took on special meaning from a historical perspective. Numerous alternatives were studied for the crossing and the interchange configurations on both sides of the river. Based on significant community input and evaluation of costs for different alternatives, the option known as the “non-river tunnel” alternative was chosen, which required a 10-lane crossing of the river. The 10 lanes include 4 lanes each for I-93 northbound and southbound and a 2-lane ramp on the east side. Some impediments the bridge had to contend with included the Orange Line subway adjacent to and below the bridge; the close proximity of the Charles River lock and dam and the need to maintain navigation; a major water main in the area of the south tower footing; a cantilevered 2-lane ramp on only one side of the structure; the existing Storrow Drive ramps at the south end, dictating the arrangement of the stay cables in the back spans; and a new tunnel at the south end of the structure.