Client: Port of San Francisco
The main objective of our scope was to construct a concrete headwall as part of the outfall structure for the new 36” storm drain line that discharges into the bay at Pier 94. The new line was a combination of HDPE and RCP pipe and drains the newly overhauled backlands area, approx. 15 acres.
The base of the headwall was 15’ below the level of the high tide in the Bay. This meant the design and construction of a sheet pile cofferdam to keep the water out of our work area. Dewatering pumps were run 24/7 to keep groundwater 3’ below the bottom of the excavation. Headwall work was tidal dependent which meant restrictive working periods for our crews.
Another major challenge of the project involved slip lining an existing CMP pipe that runs 250’ beneath a busy street (Amador St.) and a concrete plant (Central Concrete). The job was made more difficult as the existing CMP was in bad condition and was collapsed in certain areas due to heavy loading from trucks and plant equipment passing above. We worked with closely with central concrete to ensure no disruption to the plant while this work was being carried out.
Work included constructing 3 large cast in place manholes to achieve bends and transitions between the different pipe types.