The San Francisco Bay Area Rapid Transit District commissioned the Berkeley Hills Tunnels Lining Surface Treatment Project to address fractures in the tunnels’ reinforced concrete lining and to prevent loose concrete from falling onto trains crossing the Hayward Fault, which runs along the foothills of the East Bay.

The Hayward Fault, part of the San Andreas Fault system that stretches from the Gulf of California to Cape Mendocino, poses a particular concern because it runs under major cities such as San Jose, Fremont, Hayward, Oakland, Berkeley and El Cerrito that are home to more than 2 million people.

The survey work involved tying into existing tunnel control surveying and using 3D laser scans and an orthophoto survey to document existing conditions.

During structural crack repairs, the project team found that the fault crack was bigger than initially estimated. The team designed a custom on-rail vehicle for transport to and from the tunnel work area and an integrated scissor-lift work platform that allowed work crews and engineers safer access.

The team conducted all surveying, inspection and construction during non-revenue hours to avoid disrupting normal train operation.  A modular design system allowed the contractor to complete and fully secure the elements being installed each night before train operations resumed in the morning. The team completed the work four months ahead of schedule and under budget.

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