The Pier 70 Special Use District consists of an approximately 35-acre area on a site with a rich past with multiple buildings within it designated as historical structures. The project incorporates this historical background with a new a vibrant neighborhood for the City of San Francisco.
The Project consists of a mixed-use land redevelopment program that includes residential, commercial office, retail, arts, light-industrial, and open-space uses. The Project will be developed in three phases.
ENGEO performed geotechnical engineering services for the site redevelopment, including seismic engineering for the proposed residential and commercial buildings. We provided geotechnical services for the seismic retrofit and the lifting of three existing, pre-WWII era structures. Foundation challenges included bay fill, soft and compressible bay muds, liquefiable material, and dipping bedrock.
To tackle the subsurface conditions within the historical fill that included materials like concrete foundations, railway lines, pile foundations, and organic debris, ENGEO developed multiple strategies that involved discriminating between unsuitable and suitable materials during excavation and reusing the geotechnically suitable material as engineered fill.
Considering a projected sea-level rise of 5 ½ feet by 2100, elevation adjustments, such as raising grades up to 10 feet, were implemented. Notably, Building 12 was raised, with ENGEO actively involved in evaluating deflection differentials at the columns during lifting. Building 15 was also moved to higher ground, requiring foundation evaluations.
As part of geotechnical assessments for Phase 1, ENGEO conducted stability analyses for existing Slipway structures during seismic events. The stability of these structures was crucial for the project’s feasibility, and the analysis considered factors such as resistance from existing timber piles and sheet piles. The results indicated that the amount of deformation in the existing Slipways was within the expected performance limits for the site.
The main geotechnical challenges at Pier 70 are the non-engineered fills, existing subsurface structures, liquefaction and lateral spread potential, seismic shoreline instability, sea-level rise, rock excavatability, consolidation settlement of the Young Bay Mud, and naturally occurring asbestos (NOA). Other challenges at the site included demonstrating to public entities with jurisdiction over the project, that the site is being designed to perform well geotechnically and seismically. As an example, our expert team earned approval by the Bay Conservation and Development Commission (BCDC) staff, without the need for a major review from its engineering criteria review board. ENGEO was able to answer the staff’s questions and comments clearly and was able to show the BCDC staff that the proposed geotechnical design of the site meets the objectives of BCDC.
