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SEM Tunneling for Chinatown Station and Crossover Caverns

San Francisco Municipal Transportation Agency (SFMTA)

Phase 2 of the Third Street Light Rail Project is currently underway, which includes the construction of the Chinatown Station, cavern, crossover and cross-cut caverns using the Sequential Excavation Method (SEM).

Expert Review Services:

Gall Zeidler Consultants provides expert design review services on the SEM tunneling for the Chinatown Station and associated  SEM caverns, which includes review and recommendation of the following aspects of the work: construction staging, multiple drift excavation sequencing, structural design calculations, use of ground improvement measures for dewaterwing and grouting, settlement mitigation measures involving compensation grouting, structural design calculations, instrumentation and monitoring, waterproofing, contact packaging, and SEM specifications.


San Francisco, California


2009 – Present


Mined Underground Center Platform Stations with Ancillary Caverns


Cross Cut Cavern 2,700 square feet (250 square meters)
Station Caverns 2,300 square feet (213 square meters)
Cross Over Cavern 1,750 square feet (163 square meters)


Cross Cut Cavern 67 feet (20 meters)
Station Caverns 290 feet (90 meters)
Cross Over Cavern 310 square feet (95 meters)


Highly Deformed Fractured Rock, (Melange, Franciscan Rock Formation), Colluvium Consisting of Very Stiff, Brown and Gray Silty Clays, Old Bay Deposits, Sedimentary Marine Deposits, Fluvial Deposits and Fill


Approximately $1.5 Billion


PB Americas / Wong JV


San Francisco Municipal Transportation Agency (SFMTA)