Here are the official documents released by the NTSB Tuesday during its San Bruno pipeline explosion hearing in Washington, D.C.
PG&E's "litany of failures'' led to last year's pipeline explosion near San Bruno that killed eight people and incinerated a suburban neighborhood, federal accident investigators said Tuesday.
The Pacific Gas & Electric Co. also exploited weak safety oversight by state and federal regulators who placed ``a blind trust'' in the utility, Deborah Hersman, chairman of the National
Transportation Safety Board, said.
``It was not a question of if this pipeline would burst. It was a question of when,'' Hersman said.
Investigators are presenting the results of a yearlong investigation into the accident to the board, which is expected to vote on the probable cause of the accident and make safety recommendations.
Among PG&E's failures, some dating back decades, were faulty record-keeping, using ``woefully inadequate pipe'' during the 1956 installation of the ruptured line, insufficient inspections and a weak emergency response plan, Hersman and NTSB investigators said.
The company also missed two prior opportunities to address shortcomings in its pipeline system, after similar systemic problems emerged following accidents on the company's pipelines in 1981 in San Francisco and 2008 in Rancho Cordova, Calif.
``PG&E missed earlier opportunities to make corrections that could have prevented the San Bruno tragedy,'' said NTSB lead investigator Ravindra Chhatre.
The explosion of a gas transmission line buried beneath San Bruno, Calif., last September sent a giant plume of fire into the air that continued to burn for 95 minutes before PG&E employees
were able to shut off the flow of gas. In addition to the eight deaths, dozens of people were injured and 55 homes destroyed or damaged. It was the worst pipeline accident in a decade.
The board has made public 14,000 pages of information related to the accident. The investigation has raised questions about whether PG&E's corporate culture put profits ahead of safety, contributing to the accident.
Investigators identified a substandard seam weld that went only halfway through the pipe wall at the rupture point. The 30-inch circumference pipe had other substandard welds as well. Evidence indicates the pipe was composed of several short welded pieces that didn't meet any known specifications, investigators said.
PG&E has said it didn't know of the welds because its records incorrectly listed the pipe as seamless. The utility also has been unable to produce other key records regarding the pipeline.
The pipeline also lacked automatic or remotely controlled shut-off valves. If valves on the line had closed immediately after the initial explosion, the gas-fed fire probably would have gone out in under 10 minutes, according to safety experts.
Coroner's reports indicate at least five of the eight killed were trying to flee when they died. It is unclear based on information released so far whether the deaths of any of the five could have been avoided if different valves were in place, but experts said it was possible and that others who were injured and homes that were leveled might have been spared.
Four years before the accident, PG&E officials rejected installing more automatic shut-off valves. A 2006 company memo said installing the valves would have "little or no effect on
increasing human safety or protecting properties.''
A month after the San Bruno explosion, PG&E wrote California regulators that replacing or retrofitting the current 300 manual values in the company's network with automatic or remote valves
would cost $100,000 to $1.5 million per valve, depending on the difficulty of the installation.
Last week, federal regulators proposed forcing utilities to step up testing of older transmission lines and install more automatic shut-off valves.