The Department of Transportation's Pipeline and Hazardous Materials Safety Administration (PHMSA) has been an integral partner in investigations into this tragic pipeline incident. PHMSA staff were on scene in San Bruno the day after the pipeline rupture to assist the National Transportation Safety Board (NTSB) as it began its investigation to determine the cause of the rupture. PHMSA also participated in NTSB public meetings and provided factual information required for the NTSB report.
PHMSA holds all pipeline operators accountable for remaining in compliance with Federal pipeline safety regulations. In most States, PHMSA has forged a partnership with a State Agency to oversee gas pipelines operating solely within the State. PG&E pipelines are subject to regulation by the California Public Utility Commission (CA PUC), PHMSA’s gas pipeline safety partner in California.
PG&E System Overview
Pacific Gas & Electric Company (PG&E), headquartered in San Francisco, CA, operates nearly 5,700 miles of gas transmission pipelines and nearly 92,000 miles of gas distribution pipelines in central and northern California. These pipeline systems provide natural gas to over 4 million people.
PG&E Pipeline Failure and Consequences
On September 9, 2010 at 6:11 pm, a 30 inch diameter natural gas transmission pipeline in San Bruno, CA ruptured and released vast quantities of natural gas. The escaping gas ignited and initiated structure fires in the community surrounding the pipeline. Local emergency responders utilized air drops of fire retardant and water to limit the spread of the fire. At 7:40 pm, PG&E completed the isolation of the ruptured pipeline from sources of gas supply by closing valves upstream and downstream of the rupture site. Approximately 5 hours after the rupture, PG&E reported the pipeline rupture to the National Response Center (NRC). The consequences of the rupture and fire were devastating. Eight people lost their lives, 51 people required in-patient hospitalization, and 38 homes were destroyed. PG&E has estimated the property damage from the rupture to be over $220 million.
NTSB Investigation
On September 10, 2010, the National Transportation Board (NTSB) sent a team of staff to California to begin investigating the cause of the pipeline rupture. On October 13, 2010, the NTSB published a preliminary report stating that PG&E considered 400 psig to be the maximum allowable operating pressure (MAOP) and the pressure at the rupture site remained below this value. The NTSB report describes the portions of the pipeline ejected from the ground at the time of the rupture. In a December 14, 2010, press advisory, NTSB noted that the longitudinal seam of some pipe segments at the rupture site were welded on both the inside and outside of the pipe, but others were only welded from the outside. On January 3, 2011, the NTSB sent PG&E a recommendation letter describing contradictions between the pipeline at the rupture site and PG&E’s records for the pipeline. The NTSB recommended that PG&E conduct an aggressive and diligent search for records to verify the MAOP of certain gas transmission pipelines. If adequate records cannot be compiled, the NTSB recommended that PG&E conduct both spike tests and hydrostatic pressure tests to determine the MAOP. In early March 2011, the NTSB held a public meeting to gather additional factual information. On June 8, 2011, the NTSB issued an additional recommendation for immediate notification from PG&E control room operators to 911 emergency call centers when a pipeline rupture is suspected. On August 30, 2011, the NTSB published its complete investigation and made additional recommendations.
- NTSB Preliminary Report
- NTSB Press Advisory
- NTSB Recommendations to PG&E – January 3, 2011
- NTSB Public Meeting Website
- NTSB Recommendation to PG&E – June 8, 2011
- Access to Full NTSB Report
- NTSB Accident Dockets
Search by NTSB Accident ID DCA10MP008
NTSB Recommendations to PHMSA
The August 30, 2011 NTSB report includes 13 recommendations to PHMSA. The status of NTSB recommendations for pipeline safety is available on the PHMSA website.
PHMSA Actions Taken Related to the San Bruno Incident
As a result of the PG&E pipeline failure in San Bruno, CA, PHMSA took a number of actions to address the safety of natural gas pipelines.
CA Public Utility Commission Investigation
The CA PUC is conducted an investigation to determine if PG&E has complied with pipeline safety regulations. PHMSA has assisted, and will continue to assist, CA PUC staff as their investigation progresses.