Battery Street Underpinning - The Importance of Structural Stability
Located in the historic Jackson Square District of downtown San Francisco, the 717 Battery Street project involved the revitalization of an old waterfront structure. With its origins dating back to the 1800s and subsequent retrofitting after the devastating 1906 earthquake, the building required seismic strengthening to ensure its structural integrity.
To address the seismic concerns of this three-story unreinforced masonry timber pile supported building, Malcolm implemented a micropile foundation. Additionally, hand-mined piers were installed to reinforce the masonry walls and timber columns, allowing for the creation of a deeper basement beneath the existing one. The expansion of a new basement underneath a plaza was facilitated by the installation of drilled soldier piles supported with tieback anchors and internal braces.
However, several unique challenges emerged during the project. The presence of steeply sloping bedrock, a high groundwater table, soft clay atop rock, limited workspaces, and stringent project requirements required careful navigation. To stabilize the individual timber columns in the basement, our dedicated crews constructed small cofferdams in extremely tight conditions. These cofferdams were phased in, enabling effective dewatering as the original columns were lifted to replace the old concrete pile caps.
By undertaking these extensive measures, the renovation of 717 Battery Street successfully addressed the structural challenges, ensuring the preservation and future usability of this historical San Francisco landmark.