Redevelopment of the Oyster Point Landfill, South San Francisco, California-Paper

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The Oyster Point redevelopment in South San Francisco transforms a former municipal landfill into a life-science campus, hotel, and public open space. Phases 1 and 2 presented challenging and highly variable ground conditions: up to 40 feet of refuse, as much as 50 feet of compressible Bay Mud, deep and irregular bedrock, and corrosive soils. Added fill was expected to cause settlement of up to 5 feet in Phase 1 and 6 inches in Phase 2.<br /><br />Foundations were designed to bear in competent bedrock. Shallow foundations were used where bedrock was near the surface; elsewhere, deep foundations were designed for downdrag, settlement-related loss of lateral support, and corrosion. Utilities and exterior improvements incorporated flexible connections and settlement-accommodating details.<br /><br />Phase 1 used 14-inch driven steel HP-piles. They were selected because they can penetrate refuse, produce no drill spoils, and perform in areas with deep Bay Mud. Their disadvantages included the need for cathodic corrosion protection and difficulty adjusting pile lengths to variable bedrock. Of 1,500 production piles, only two were damaged; about 7% required additional splicing because bedrock conditions differed from estimates.<br /><br />Phase 2 used 16-inch augered cast-in-place (ACIP) piles. Shallower Bay Mud and less refuse made them practical. ACIP piles offered easier adjustment to bedrock variability and corrosion protection from the grout, but generated spoils requiring management. Only two of 700 piles encountered refuse obstructions and had to be relocated.<br /><br />Load testing established site-specific acceptance criteria and allowable capacities that were broadly similar for both pile types. The project demonstrates that both systems can work successfully at landfill sites, but selection should reflect Bay Mud depth, refuse extent, bedrock variability, corrosion requirements, and spoil-handling costs. Extensive testing and adaptable installation criteria were essential to managing the irregular bedrock.

Keywords

Oyster Point redevelopment

South San Francisco

life-science campus

municipal landfill

Bay Mud

bedrock variability

deep foundations

driven steel HP-piles

augered cast-in-place piles

corrosion protection