BOSTON: TWO BY LAND, ONE BY SEA

A series of articles describes how contractors are sinking giant steel tunnel sections to create an underwater highway between Boston and Logan airport. The tunnel is the first link in the $6.4 billion Central Artery/Tunnel project that will depress the elevated Interstate 93 extending through downtown Boston. Highlights of this project are described in these brief articles. The details of the construction of the immersed twin steel tubes, and how they are tightly pulled together by hydraulic pressure are described. It is also described how the tunnel design hinges on the high water table at the city end. It is described how, before tunnel work could start, an airport taxiway had to be relocated and the airport's blast wall was moved back from the highway alignment. An airport terminal will be demolished and rebuilt atop the cut-and-cover tunnel.