Boston’s Central Artery (“Big Dig”) Project: A Masterful Build

April 6, 2016

The Boston Central Artery/Tunnel project aka the “Big Dig” is one of the largest and most complex urban transportation project ever undertaken in the United States. As the result of more than 30 years of planning and 12 years of construction, the project was developed to alleviate the major traffic congestion that had plagued Boston for years. 

Before the Dig
Before the project started, the elevated six-lane highway, called the Central Artery, carried close to 200,000 vehicles a day through the center of downtown Boston. The roadway was considered one of the most congested highways in the United States with 10 hours of traffic each day. The accident rate on the deteriorating elevated highway was also four times the national average for urban Interstates. The same problem plagued the two tunnels under Boston Harbor between downtown Boston and East Boston/Logan Airport. 

During the Dig 
A work of this size and duration had never been attempted in the heart of an urban area. Bechtel and its joint-venture partner, Parsons Brinckerhoff had the challenge of completing the project without crippling the city, maintaining the city’s traffic capacity, and ensuring residences and businesses were accessible, all while building. Project planners worked with local agencies, community groups, businesses, and political leaders to create consensus on how the project would be built. 

Big Dig Facts

  • At the peak of construction 5,000 construction workers were on the job.
  • 16 million cubic yards of dirt were excavated, enough to fill a football stadium to the rim, 16 times. 
  • It took 541,000 truckloads to move the dirt on the project
  • The project placed 3.8 million cubic yards of concrete, enough to build a sidewalk three feet wide and four inches thick from Boston to San Francisco and back three times.
  • Reinforcing steel used in the project would make a one-inch steel bar long enough to wrap around the earth at the equator
  • The Ted Williams Tunnel interface is 90 feet below the surface of Boston Harbor, the deepest such connection in North America.
  • The project's underground utility relocation program moved 29 miles of gas, electric, telephone, sewer, water, and other utility lines maintained by 31 separate companies. 
  • 5,000 miles of fiber optic cable and 200,000 miles of copper telephone cable were installed. 
  • The 10-lane cable-stayed hybrid bridge is the widest ever built and the first with an asymmetrical design, using both steel (in the main span) and concrete (in the back spans). 

The project represented public works on a scale comparable to some of the great projects of the previous century including the Panama Canal and the Channel Tunnel.

After the Dig
The project was completed in 2006 and since completion the total vehicle-hours of travel on project highways dropped 62 percent between 1995 and 2003―saving travelers about $168 million annually in shorter travel times and lower transportation costs. 

The new artery/tunnel even had a major impact on the environment in Boston. The city’s carbon monoxide levels dropped 12 percent, because the flow of traffic allowed emissions to reduce significantly. 

The project also created more than 300 acres of new parks and open space, including 27 acres where the existing elevated highway stood, 105 acres at Spectacle Island, 40 acres along the Charles River, and 7 acres as part of an expanded Memorial Stadium Park in East Boston. The project also reconnected neighborhoods severed by the old elevated highway and improved the quality of life in the city beyond the confines of the highway.

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