An Immersed Tube Tunnel (ITT) will be placed in a dredged corridor across the Fort Point Channel in Boston, MA. Construction is complicated by the existence of active Red Line Subway Tunnels (RLT) located beneath the channel and about 1.8 meters below the base of the ITT. Geotechnical and structural investigations, and numerical studies were performed to evaluate the impacts on the RLT. Pilot programs were conducted to select instruments for monitoring settlements, joint openings, and water flow in the RLT. An open channel type liquid level system 1310-meters long with 125 gages was installed to monitor settlements. More than 700 strain gages and jointmeters were attached to the concrete liner surface using a novel epoxy bonding technique. In situ stresses in concrete were investigated by using a patent pending flat jack method. An Automated Data Acquisition System (ADAS) has monitored more than 900 gages for more than three years.
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