Yerba Buena Island (YBI) Southgate Road Realignment Improvements

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San Francisco County Transportation Authority

Project Name
Yerba Buena Island (YBI) Southgate Road Realignment Improvements

Construction management
Constructability review
Contract management
Construction inspection


MNS is providing complete construction management for this $30M three-phase project involving realignment improvements to increase the length of the on-ramp and off-ramp on a new alignment to allow the Yerba Buena Island (YBI) WB Ramps project to function as designed.

The realignment of the Southgate Road will allow the roadway to function as an extension of the on- and off-ramps for the YBI WB Ramp Project and will separate the traffic heading to the westbound and eastbound Interstate 80. This traffic separation will eliminate a queue spillback on Interstate 80.

To ensure all truck turning movements are accommodated, the extended ramps will provide direct access from Hillcrest Road to the westbound on-ramp. The project includes two cast-in-place post-tensioned box girder bridges, multiple retaining walls including a multiple level tieback wall, and concrete barriers. The project also includes cast-in-drilled-hole (CIDH) piles with steel casing, significant earthwork, complicated utility relocations, drainage and temporary drainage structures, temporary bike path, and ongoing traffic control.

Various wall types are used for this project, including cantilever soldier pile and lagging walls, soldier pile and lagging walls with sub-horizontal ground anchors (SHGA) walls, semi-gravity (Caltrans standard Types 1, 5, and 7) walls, and a MSE wall. Over 375 ground anchors are being used in the SGHA walls.

The project is very challenging due to the limited, tight working area while keeping traffic running through construction. MNS provides construction management activities during all phases of construction.

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