Mass & Main
Location: Cambridge, MA
Owner: Watermark Central Venture LLC
Completion Date: January, 2018
General Contractor: John Moriarty and Associates
Vital Statistics: Project Value: $3,500,000.00
Wall Type: 30" Reinforced Concrete Wall
Wall Area: 24,400 S.F.
Max. Excavated Depth: 66'
This site was in close proximity to the MBTA Red Line tunnel, built in the early 1900's, and several other abutting buildings. A stiff impervious excavation support system was necessary to control lateral movements during general excavation. An internally braced concrete diaphragm wall was constructed to provide temporary earth support and to serve as the permanent foundation wall. The slurry wall was designed as a load-bearing wall supporting vertical exterior wall and column loads through a combination of structural shear connection between the slurry wall and the footing/mat foundation, and on skin friction from the portion of the slurry wall extending below the bottom of the mat. A future storm water storage tank and 63" diameter pipe was planned to cross below the MBTA Red Line Tunnel in Massachusetts Avenue at a depth of 50 ft below street grade and parallel to the east side slurry wall. The slurry wall panels in this area were extended to 5 feet below the invert of the future pipe to mitigate potential impacts on the newly constructed building.