Geotechnical Assessment of 2 North Point Street

San Francisco, California

Slate Geotechnical Consultants performed a geotechnical assessment following the provisions of the ASCE/SEI 41-17 design standards to support the proposed seismic retrofit of the existing building located at 2 North Point Street in San Francisco. The building is a three-story, reinforced concrete structure with a partial basement founded on driven, pre=cast concrete piles through fill debris and soft soil (Bay Mud) deposits to the underlying bedrock. The site is on the historic San Francisco Bay shoreline and marshland that was reclaimed by filling with dune sand, rock, and building rubble from the 1906 San Francisco earthquake. Upper granular fill soils were found to be potentially liquefiable during strong earthquake shaking, exposing the building to potential performance issues related to liquefaction-induced reconsolidation settlement and lateral spreading of the near-surface soils toward the sea wall of the current Bay shoreline.

The project scope included a comprehensive background data collection and review to characterize the subsurface soils and groundwater level for engineering assessment. Slate developed site-specific and building code-based ground motion response spectra and associated seismic design parameters including one-dimensional dynamic site response analysis. Slate performed a qualitative assessment of geologic hazards, including the potential for liquefaction. Slate provided an assessment of basement walls and existing pile capacities for axial, uplift, and lateral resistance, including the effects of pile groups.