National Transportation Safety Board Concludes Investigation at Explosion Epicenter
The NTSB has shipped the gas pipe that exploded in San Bruno to Washington, D.C. for further tests and will issue an initial report in a month.
The National Transportation Safety Board has finished its investigation at the explosion epicenter and is turning over the area to the city of San Bruno and PG&E, the Vice Chairman of NTSB, Christopher Hart, said at a briefing at the Bayhill Shopping Center Monday afternoon.
The pipe that exploded is now being shipped by truck to Washington, D.C. where scientists will test it in a metallurgy lab to determine what caused the pipe to fail. They will examine the pipe for metal fatigue, corrosion, and physical damage. Hart asked people to send any pipe fragments that they find to the board.
Small sections of the gas pipe were welded together to form a curve. Hart said that this is a very common way of snaking pipes into the ground.
Utility pipes, for water and sewage, by the gas pipe do not show signs of visible damage, Hart reported. NTSB will visit local control sites in Milpitas and Visitacion Valley and will examine records of seismic activity for the region. Drug and alcohol tests for PG&E employees who worked in the area have come back negative.
NTSB has been unable so far to confirm reports that residents complained to PG&E about the smell of natural gas before the explosion, Hart said. The board will continue to look into claims that residents filed and e-mailed to them though. Investigators are asking bystanders to send photos and videos of the explosion.
Hart said that PG&E is being very cooperative and has already sent some requested documents.
The board expects to issue an initial report on the cause of the explosion in a month.
A nearby segment of the gas pipe was due to be replaced because the risk of failure was "unacceptably high" and the line ran through a heavily urbanized area.
On Sunday, the California Public Utilities Commission ordered PG&E to inspect its natural gas system through California. The company will have to:
•conduct leak surveys on all natural gas lines in California;
•preserve all records and accident reports from the San Bruno incident, including work at the Milpitas Terminal during the month of September;
•ensure all PG&E employees and contractors are available for interviews with investigators;
•review and report the classifications of all natural gas transmission designs and determine if the classification has changed;
•report to CPUC immediately for procedures on responding to gas leak reports in the affected area, it will also provide data on all leak reports and PG&E's response time system-wide;
• report to CPUC on how much money PG&E assigned to pipeline safety and pipeline replacements, and how much money the company actually spent from 2005 to present.
The last incident involving PG&E that was investigated federally was a gas leak and explosion that killed one and injured five others in Rancho Cordova in 2008. A faulty pipe repair was the cause, and investigators cited PG&E's delayed response.
Officials say a final report could take between 14 to 18 months, but that any safety concerns will be addressed as soon as possible.
"If it is ultimately determined that we were responsible for the cause of the accident, we will take accountability," PG&E said in a statement.