Holding Back

Market Street Place, San Francisco, California

The Market Street Place development, a multi-use retail and office project, is located in downtown San Francisco. The site measures 275 x 170 feet in plan dimension and required a shored excavation depth of 40 feet. The subsurface materials at the site consisted of fill, fine dune sand, marsh deposits, and dense sands to a depth of 80 feet. Groundwater was approximately 30 feet below street level.

The project delivery was a design-build for the entire shoring system using deep soil mixing shoring walls, slant drilled underpinning piles with jet grout infills, and tie-backs for three sides of the project. The Market Street side required a large, two-level internal bracing scheme since tie-backs would have conflicted with the public transport tunnels running under Market Street. We prefabricated the up to 70 feet long raker pipes off-site, so that installation was as fast and efficient as possible. In addition to the shoring work, we also installed a crane trestle that was heavily utilized for deliveries, equipment staging, and material laydown. Last but not least, the site was dewatered by utilizing 10 dewatering wells inside the excavation and 5 recharge wells along Market Street as part of our design-build shoring and dewatering scope.