The Dewey Square Tunnel Air Intake Structure is located within Parcel 22 on the southerly side of Congress Street and adjacent to the existing I-93 Southbound/DST Purchase Street Off-Ramp RR boat section. The 4-story building is a steel and concrete framed building with exterior granite wall cladding and metal rain-screen panels on the roof. The exterior walls of the structure will provide tunnel ventilation both fresh air supply and exhaust capacities for the rehabilitated Dewey Square (South Station) tunnel below. Even though the steel will not be exposed to view, it is in an extremely aggressive and corrosive environment. The superior barrier and cathodic protection of galvanized steel will protect this structure from corrosion due to a moist environment, car splash-back, and constant exposure to pollution and exhaust fumes from vehicles.

Because the structure is hard-to-access, a coating system that would retain the original pleasing aesthetics with little to no maintenance was chosen. The specifier for the building had extensive experience with hot-dip galvanizing on other contracts and felt confident galvanizing was the best choice to fulfill these goals. Two hundred tons of structural steel for the vent building was galvanized, and maintaining the curve of the barrel arch detail required special attention and handling. By galvanizing the structural elements of this project, galvanized steel will continue to keep this project functioning maintenance-free for decades.