Boston's Home Run

Robison, Rita; ,

Boston's Home Run

by Rita Robison, Contributing editor; Civil Engineering, 345 E. 47th St., New York, NY 10017,

Serial Information: Civil Engineering—ASCE, 1996, Vol. 66, Issue 7, Pg. 36-39

Document Type: Feature article

Abstract:

The $1.3 billion Ted Williams Tunnel, the first part of Boston's Central Artery/Third Harbor Tunnel Project to be completed, has been designated the Outstanding Civil Engineering Achievement of 1996. It is an immersed marine tube that lies in a trench as deep as 100 ft below the surface of Boston Harbor, doubling the city's traffic capacity to Logan Airport. As usual with OCEA winners, the project description is studded with superlatives. Tunnel construction included the largest circular cofferdam and the deepest interface in North America, first use in the northeastern U.S. of a patented Japanese soil mix method, and the trench on harbor bottom, 3,850 ft long, 100 ft wide and 50 ft deep, was dredged by the world's largest clamshell dredge, called the Superscoop. The 12 immersed tube sections, each 320 ft long, were assembled in Baltimore as side-by-side tubes enclosed in a rectangular frame. They were barged to Boston Harbor and placed individually into the trench. Their connections, including that of the concrete roadway, are flexible. At each end are cut-and-cover tunnel approaches and vent buildings, one of which was built in the cofferdam. At the airport end, the 3,000 ft cut-and-cover approach became, at $246 million, the state's largest single public works contract up to that time. The work included relocating one of the airport's taxiways, moving an existing blast wall and constructing 6,000 ft of retaining walls by a patented soil mix method imported from Japan.

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