Diaphragm Walls (D-walls) at SFPUC Biosolids

As a result of the proximity of the active railroad lines, the 200,000 square feet  support of excavation (SOE) wall for building 610 had to also act as a cutoff wall reaching a depth of 160-feet to key in the low permeable old bay clay layer. Malcolm chose a 36-inch-wide structural diaphragm wall, which was laterally supported by tiebacks and corner bracing. Reinforcement was terminated at about 75-feet, tie back sleeves and bracing embed plates were installed within the diaphragm wall reinforcement. For the excavation of each diaphragm wall panel, we utilized several Bauer BC40/BC48 cutters mounted on Bauer MC96 cranes, mechanical grabs, and hydraulic grabs. One Liebherr LR1300 and one Bauer MC96 service crane were utilized to support the rebar cage installation and tremie concrete operation. The diaphragm wall (D-wall) achieved the required water cutoff and kept the maximum deflection and settlement within the tight project requirements.