It was also found that disbonding was not solely a gate valve problem; disbonding was also occurring in stop-check valves. A common theme though was disbonding occurring in F91 and C12A valves.

Overall, Martel said, PUC staffers' response to the leak and gate valve problem was exemplary. The report by the PUC, which operates the Hetch Hetchy system serving 2.4 million Bay Area residents ...