Big Dig

The Big Dig was a megaproject in Boston that rerouted the then elevated Central Artery of Interstate 93 that cut across Boston into the O'Neill Tunnel and built the Ted Williams Tunnel to extend Interstate 90 to Logan International Airport. Those two projects were the origin of the official name, the Central Artery/Tunnel Project (CA/T Project). The project constructed the Zakim Bunker Hill Bridge over the Charles River, created the Rose Kennedy Greenway in the space vacated by the previous I-93 elevated roadway, and funded more than a dozen projects to improve the region's public transportation system. Planning for the project began in 1982. Construction work was carried out between 1991 and 2006. The project concluded in December 2007. The project's general contractor was Bechtel, with Parsons Brinckerhoff as the engineers, who worked as a consortium, both overseen by the Massachusetts Highway Department.

The Big Dig was the most expensive highway project in the United States, and was plagued by cost overruns, delays, leaks, design flaws, accusations of poor execution and use of substandard materials, criminal charges and arrests, and the death of one motorist. The project was originally scheduled to be completed in 1998 at an estimated cost of $2.8 billion, US$7.4 billion adjusted for inflation as of 2020. The project was completed in December 2007 at a cost of over $8.08 billion in 1982 dollars, $21.5 billion adjusted for inflation, a cost overrun of about 190%. As a result of a death, leaks, and other design flaws, the Parsons Brinckerhoff and Bechtel consortium agreed to pay $407 million in restitution, and several smaller companies agreed to pay a combined sum of approximately $51 million.