An independent panel of experts in steel structures, fracture mechanics and metallurgy is reviewing every step taken by the Transbay Joint Powers Authority team investigating the cause of two cracked girders at the Salesforce Transit Center in San Francisco. TJPA, which opened the 4.5-block-long depot on Aug. 12, shuttered it on September 25, after a ceiling installer noticed a deep fissure in one of the twin girders spanning 80 ft across Fremont Street.

Specimens, called coupons, of the cracked areas in the girders’ bottom flanges are under scrutiny at LPI Inc. in New York City. TJPA expects to have the results of the LPI investigation by the end of November. Concurrent with testing and analysis, the TJPA team is considering various potential repair strategies, "to expedite the construction schedule once a cause is determined," said TJPA, in a statement released November 27.