Massachusetts Turnpike Authority

Traffic, Tolls, Maps, Service & Tourist Centers, Park & Ride, Emergency Services, Truck Regulations, and Tourist Destinations

News from the Turnpike Authority and our Meeting Calendar

Big Dig Project Background, Updates, Photos and Artist Gallery

Turnpike History and Turnpike Regulations

Contracts and Business Opportunities with the Turnpike

E-mail Form, Our Address and Phone Numbers

• Project Updates
• Parks and Urban Restoration
• Multimedia and Publications
• Project Background
  • Tunnels and Bridges
  • Facts & Figures
  • Archaeology
  • Environmental
  • Engineering Marvels
  • Mitigation
  • Equipment
  • History

Mitigation

Working in the Heart of the City

The Central Artery/Tunnel (CA/T) Project in Boston is the largest, most complex highway project in American history, and was built through the heart of one of the nation's oldest cities. The project included a tunnel under Boston Harbor, a 14-lane crossing of the Charles River, and an eight-to-ten-lane underground expressway to replace a deteriorated six-lane elevated highway built in the 1950s, the only major highway route through the city. 

The continuing economic vitality of the city depended on the project allowing businesses to operate normally, traffic and pedestrians to move comfortably through the downtown, and residents to endure as little disruption to their lives as possible during a construction period that ran from 1991 to 2005. The project had to remain friendly to the environment during construction. The project's effort to keep Boston "open for business" during this unprecedented construction period was called "mitigation."

Without the mitigation program, the city would have faced devastating disruption from noise, dust, and traffic gridlock, and economic damage not easily or quickly undone. Downtown residents, businesses, and workers; drivers (more than 190,000 a day) on the old highway that the mitigation program kept open while the replacement was built directly underneath it; thousands more downtown drivers and pedestrians; the tourism industry in Massachusetts - all were helped by the mitigation program.

As Big As The Project

The scope of the Mitigation Program reflected the spectacular size of the CA/T project itself. Mitigation cost about one-third of the project's budget. Activities ranged from one-on-one contacts with residents and business people up to temporary viaducts costing dozens of millions of dollars. Keeping the elevated highway open as tunneling proceeded directly underneath cost $600 million in itself, which reflects the engineering complexity of mitigation.

Broadly defined, mitigation's key innovation was finding ways to break the massive project down into manageable human terms, controlling the impact of construction while maintaining a viable project budget. Mitigation was the practical mechanism by which the CA/T project turned the history of urban highway construction on its head: Where highway projects once bulldozed neighborhoods and bisected cities in the name of mobility, the CA/T project  reunited neighborhoods and preserved the fabric of a city, even as it made dramatic improvements in its transportation system.

Mitigation measures fell into three broad categories: Traffic, community outreach, and environment. Each program was guided by such criteria as the need to include all affected community and business groups in project planning, the need to keep the city open for business and traffic moving throughout construction, and to respond proactively to community requirements as the work proceeds. Among the innovative techniques for implementing this mitigation framework:

• A computerized tracking system and reporting structure ensured that all mitigation commitments were monitored and met.
• A distinctive signage/construction barrier system called the "kit of parts" that helped route drivers and pedestrians through construction areas, proteced bystanders while allowing them to look into construction zones, added an attractive and informative but functional signature to the project's downtown presence, and helped keep Boston open for business by adding quality directional information to a downtown not known for good signs.
• A staff of community liaisons responsible for fielding neighborhood/community/abutter concerns and resolving them, speaking for the project at public meetings, distributing information to concerned groups and individuals.
• A 24-hour monitoring center, called the Interim Operations Center (IOC), that provided around-the-clock telephone access for the public to forward complaints and incident reports to the project, and maintained video surveillance of traffic and construction.
• A nighttime "noise patrol," composed of project and City of Boston staff, that monitored construction noise and enforced regulations (up to and including the shutdown of construction in extreme cases) to make sure that residents near construction sites could sleep at night.

Impact of Mitigation

Traffic in notoriously congested downtown Boston - which many feared would be tied in knots during construction - was no worse and in some cases actually improved during construction Early opening of the Ted Williams Tunnel under Boston Harbor drew traffic off the existing tunnels and off the elevated Central Artery, reducing backups in the old tunnels by more than fifty percent. Conversion of parallel two-way streets along the elevated highway to one-ways to accommodate construction improved traffic flow, as did diversion of traffic from a congested through street via a relocated highway ramp to an under-used street.

Day-to-day management of traffic issues was accomplished with close inter-agency cooperation with the City of Boston, as evidenced by normal traffic without unusual congestion in every case following the implementation of planned new traffic patterns due to construction.

Dirt - millions of cubic yards of it - were disposed in an environmentally sound but economical way. Learn more about how that was done at digging and dumping dirt. See how the mitigation program turned this problem into a creative solution by . . .

• Making an agreement with the City of Boston to use project dirt to cap an old landfill on an island in Boston Harbor, stopping the leaching of toxic materials into the harbor and converting the island into a public park.
• Sending clay excavated from downtown Boston to cap area landfills, preventing more costly disposal at distant sites and saving municipal governments millions of dollars.

Noise complaints dropped by fifty percent after the implementation of the nighttime noise patrol, which monitored and enforced regulations on construction noise. As a result of regular meetings with community and resident groups, a detailed noise policy was adopted in response to their concerns about the impact of construction severely, restricting noise while preserving the project's ambitious schedule. More details are available describing the CA/T Project's construction noise control program (PDF 48K).

Harbor life, including fish and lobsters, could have been harmed or seriously disrupted by dredging and blasting on the harbor floor during construction of the Ted Williams Tunnel. A program called "fish startling" drove fish away from blast zones with sound waves, and close scheduling of dredging work prevented disruption to lobster migrations. Also, to compensate for construction impacts on wetland areas, the project reclaimed an intertidal wetland area at Rumney Marsh and created an artificial reef system in Boston Harbor for shellfish and other sea life.

Inclusion of all affected groups and constituencies in project planning has produced consensus decisions acceptable to all parties on such important issues as restoration of surface streets and development of parcels in the 27 acres of open space to be created by the old highway demolition.

Creation of more than 300 acres of new parks (three quarters of the 27 acres of downtown open space will remain open after development) and open space in and around downtown Boston was the result of mitigation-related negotiation with the city and community groups affected by construction. The guiding principle was to leave the city with more than it had before construction began, even beyond the significant transportation improvements.

Lessons Learned

A key benefit of the CA/T Project is the lessons that any city contemplating a project like this will inevitably  have to look at. Every element of the mitigation program - public participation, community outreach, environmental sensitivity, keeping the city open for business - is fully replicable elsewhere. Key challenges include integrating each of these aspects of mitigation with project design and construction, from the beginning, and adopting a sincere spirit of mitigation throughout. The key to success is skilled consensus and coalition building, and steady focus on project benefits.