The Central Artery/Tunnel Project (CA/T Project), commonly known as the Big Dig, was a megaproject in Boston that rerouted the Central Artery of Interstate 93 (I-93), the chief highway through the heart of the city, into the 1.5-mile (2.4 km) tunnel named the Thomas P. O'Neill Jr. Tunnel. The project also included the construction of the Ted Williams Tunnel (extending I-90 to Logan International Airport), the Leonard P. Zakim Bunker Hill Memorial Bridge over the Charles River, and the Rose Kennedy Greenway in the space vacated by the previous I-93 elevated roadway. Initially, the plan was also to include a rail connection between Boston's two major train terminals. Planning began in 1982; the construction work was carried out between 1991 and 2006; and the project concluded on December 31, 2007, when the partnership between the program manager and the Massachusetts Turnpike Authority ended.
The Big Dig was the most expensive highway project in the United States, and was plague