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The vice chairman of the National Transportation Safety Board this evening described his initial reaction to the devastation wrought by Thursday’s explosion and fire in San Bruno.

“My immediate assessment was the amazing destruction: the charred trees, the area that was completely flattened,” vice chairman Christopher Hart said. “It was an amazing scene of destruction.”

The NTSB arrived on the scene Thursday, but information was limited today because the agency’s investigative team had only recently arrived when Hart addressed the public at 5 p.m.

During a preliminary walk-through of the neighborhood, Hart saw about 170 houses that had either been destroyed or damaged in the sweeping fire, he said.

“Obviously we’re here because of the enormous impact of this disaster on many lives,” Hart said.

The eight-member NTSB investigative team will work to “not just understand what happened, but why it happened,” Hart said, and will then submit recommendations to help prevent such disasters in the future.

Hart said the team would investigate the insulation, operation, and history of the natural gas pipeline that exploded, as well as the peak levels of pressure it was meant to withstand, the highest levels it did stand, and what safety measures were in place to prevent the pipe from becoming over-pressurized.

The investigators will also look into the people who were operating the pipeline at the time of the explosion, Hart said, particularly their experience, training, history, blood-alcohol levels at the time of the eruption, and what they were doing in the hours before the disaster.

The team will also examine “survivability factors” surrounding the pipe’s operation, namely the emergency preparedness plans PG&E had in place for such a disaster and what response was actually executed when it took place, Hart said.

In addition to the investigative team, the NTSB will provide family assistance specialists to offer mental health care and emotional support to victims and their families, Hart said.

Hart stressed that the investigative team is not in San Bruno to ascribe blame or liability for the accident, and he would not speculate about a cause before one could be concretely determined.

He estimated it would be 14 to 18 months before a final report and recommendations to prevent future explosions would be complete.

If, however, major safety concerns are found before the investigation is complete, the board will immediately offer recommended practice changes to PG&E, Hart said.

He encouraged any witnesses who have not yet given a statement to police to do so because any information could help the investigation.

Residents who smelled gas in the air prior to the explosion – as many have claimed to – can definitely provide pertinent information, he said.

Hart said the investigation would include looking into whether or not PG&E had ever been cited for the operation of the pipe that exploded.

A portion of the pipeline that exploded was found a great distance from the hole it flew out of, which “tells me the magnitude of the explosion that took place,” Hart said.

When asked if that magnitude was unusual, Hart replied, “In explosions, nothing is unusual.”

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