The project provides a new, high-density, mixed-use community with a variety of housing types, a retail core, open space and recreation opportunities, on-site infrastructure, and public and community facilities and services.
In 2014, 2015, and 2016 ENGEO conducted the design-level geotechnical study for the first Major Phase of development, an approximately 171-acre parcel with a new ferry terminal, approximately 3,700 residential units, and 100 acres of parks and open space.
At Yerba Buena Island, the geotechnical considerations and design features include: slope and foundation design issues associated with existing cut slopes and hillside fills; stability of existing retaining walls; slope stability issues associated with the steep perimeter slopes; slope stability issues associated with the slopes under and adjacent to the Treasure Island Road Viaduct.
The main geotechnical challenges at the site included:
(1) seismic stabilization of the perimeter shoreline and causeway that connect Treasure Island to Yerba Buena Island,
(2) mitigation of long-term static settlements under the development footprint due to the presence of Bay Mud, and
(3) mitigation of liquefaction-induced settlement within the development footprint.
ENGEO designed and managed a large scale ground improvement test section, high-end cyclic testing on the soils and finite element dynamic analyses to demonstrate that a proprietary ground improvement technique would stabilize and mitigate liquefaction-induced lateral spread, thereby making high-rise development feasible, and saving over $5MM in the process.