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DEEP EXCAVATION CASE STUDY:
Rowes Wharf, Boston, MA

The Rowes Wharf building is located on the easterly flank of Fort Hill, one of the three original drumlins in Boston. The project consists of a main 15-story building along with three wharf buildings extending out over the water, and a 700-car five level underground parking. A 2.5' thick, 65' deep, with 10' embedment perimeter slurry wall. Rowes Wharf saw the introduction of Up/Down construction in the northeastern U.S. (Becker & Haley, 1990). The included figures show the plan, a typical cross section of the excavation, and measured wall deflections of the project.

In addition to providing excavation support the slurry walls were designed to reduce leakage and avoid excavation dewatering. A major issue that had to be addressed was that the uplift pressure was greater than the building weight. This problem was addressed by providing seepage cutoff with the diaphragm wall extending below the excavation level into the glacial till. This allowed for the lowest level floor to be designed as a fully relieved slab-on grade. Slurry wall panels were typically constructed in alternate 20' sections

According to Haley (1986), wall movements were small. This project faced serious problems with seepage through panel construction joints and through the slurry wall itself. The slurry wall panel bottoms wall were not cleaned adequately before concreting, and as a result waste material had accumulated at the panel bottom. Concrete tremieing pushed part of this waste material to the top of the slurry wall but a lot of that material got entrapped between panel joints, and at the bottom corners of the slurry wall panels. These zones of soft material leaked excessively when they where exposed by the excavation activities. Major sealing efforts including grouting behind the wall and filling with hydraulic cement were undertaken.