Central Artery/Tunnel Project

Recognized as the largest, most complex, and technologically challenging highway project in the history of the United States, the Central Artery/Tunnel Project (CA/T) was a mega transportation project in Boston that rerouted the Central Artery—the principal highway through the heart of the city—and constructed the extension of Interstate 90 with the construction of the Ted Williams Tunnel to Logan International Airport.

This project was developed in response to traffic congestion and the failure of the 1950’s elevated six-lane highway to accommodate today’s transportation needs; the 1.5-mile long (2.4km) road section carried approximately 190,000 vehicles a day. The project included four major highway interchanges to connect the new roadways with the existing regional highway system, spanning 7.8 miles of highway, 161 lane miles in all, half of which were located below ground in newly dug tunnels. In total, the project used 3.8 million cubic yards of concrete – the equivalent of 2,350 acres, one foot thick – and excavated more than 16 million cubic yards of soil.

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Key Challenges

The unique challenge was to construct this project in the middle of Boston without crippling the city. Work of the CA/T project’s magnitude and duration had never been attempted in the heart of an urban area, but unlike any other major highway project, it was designed to maintain traffic capacity and access to residents and businesses – to keep the city open for business -throughout construction.

GEI managed the geotechnical program of this complex multi-year, multi-site, multi-client project, and brought many innovative solutions to the CA/T project including:

-Almost 5 miles of tunnels, for both auto and rail service, below crowded city streets, active commuter train tracks, and waterways, all in heavy use throughout the day and night

-Over 540 borings

-6 major pump tests

-A long-term test program of 14 permanent tie-down anchors in soil and rock for design of the central (downtown) section

-Geotechnical data and engineering reports with design and construction recommendations for 7 major construction contracts

-Detailed geotechnical analysis and design for retaining walls, abutments, bridge foundations, excavation support systems, dewatering, boat sections, cut-and-cover tunnels, and deep utility relocations

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