The investigation of last week's enormous, deadly gas main explosion in San Bruno is now focusing on PG&E's inability to quickly shut off the flow of gas after the explosion occurred. It took nearly two hours for the utility to access and manually shut the valves that controlled the flow of gas, causing the fire to burn longer and to injure and kill more people. Had there been remote-access valves or an automatic-shutoff system triggered by a loss of pressure in the pipe, the gas would have shut off within minutes, not hours.
Christopher Hart, vice chairman of the National Transportation Safety Board, is now pointing the Chronicle back to a well known 1981 disaster that occurred at a construction site at Sacramento and Battery Streets in S.F. in which a 16-inch gas main ruptured and caused the evacuation of 30,000 people as the line spewed gas laced with toxic PCBs. As they report, "It took nine hours to crimp off the flow of gas as workers struggled with manual valves -- including one that had been paved over and made inaccessible, and another that didn't work." PG&E was subsequently put on notice regarding shut-off valves, and in the subsequent decades (!) have continued to maintain that remote-access valves are better, as they did again in a 1999 report.
The valves that needed to be accessed to stop the San Bruno leak were 1 mile and 1.5 miles away, and workers apparently had trouble accessing the secure locations both because of rush hour traffic and due to the keys needed to unlock the valve enclosures.