Source: National Transportation Safety Board
The National Transportation Safety Board issued seven safety recommendations, six of them classified as "Urgent," as a result of its investigation into the pipeline rupture and explosion that killed eight people and destroyed 37 homes in San Bruno, California, on September 9, 2010.
The recommendations were issued to address record-keeping problems that could create conditions in which a pipeline is operated at a higher pressure than the pipe was built to withstand, although it is not known at this time if that is what happened in the San Bruno accident. The urgent recommendations call on pipeline operators and regulators to ensure that the records, surveys, and documents for all pipeline systems accurately reflect the pipeline infrastructure as built throughout the United States so that maximum safe operating pressures are accurately calculated.
As detailed in an investigative update the NTSB issued on December 14, 2010, investigators found that although the records of the pipeline operator, Pacific Gas and Electric Company (PG&E), indicated that the pipeline in the area of the rupture was constructed of seamless pipe, it was instead, at least in part, constructed of longitudinal seam-welded pipe. In addition, some of the seams of this section of pipeline were welded from both the inside and the outside of the pipe, while others were welded only from the outside.
The NTSB is concerned that the seam-welded sections may not be as strong as the seamless pipe that was indicated in PG&E's records. Because it is critical to consider all of the characteristics of a pipeline in order to establish a safe maximum allowable operating pressure (MAOP), the NTSB believes that these inaccurate records may lead to potentially unsafe MAOPs.
To address this issue, the NTSB issued three safety recommendations, two of which were classified as urgent, to PG&E asking the utility operator to do the following: 1) Conduct an intensive records search to identify all the gas transmission lines that had not previously undergone a testing regimen designed to validate a safe operating pressure (urgent recommendation); 2) Determine the maximum operating pressure based on the weakest section of pipeline or component identified in the records search referenced above (urgent recommendation); and 3) If unable to validate a safe operating pressure through the methods described above, determine a safe operating pressure by a specified testing regimen.
The NTSB is also concerned that other pipeline operators may have discrepancies in their records that could potentially compromise the safe operation of pipelines throughout the United States. Because of this, the NTSB has made an urgent recommendation to the Pipeline and Hazardous Materials Safety Administration (PHMSA) to expeditiously inform the pipeline industry of the circumstances of the San Bruno accident and investigative findings so that pipeline operators can proactively implement any corrective measures for their respective pipeline systems.
"While it may seem like a small paperwork error, if companies are basing operating pressures on inadequate or erroneous information contained in their records, safety may be compromised," said NTSB Chairman Deborah A.P. Hersman. "We believe this safety-critical issue needs to be examined carefully to ensure that operators are accurately gauging their risk and that pipelines are being operated at pressures no higher than that for which they were built to withstand."
The NTSB also directed three of the urgent recommendations to the California Public Utilities Commission (CPUC), which regulates PG&E's pipeline operations as well as all intrastate pipeline operations within California. CPUC was asked to ensure that PG&E "aggressively and diligently" search documents and records to determine which pipeline segments had not previously gone through a testing regimen to determine a safe operating pressure and to provide oversight of any testing conducted by PG&E if the document and records search cannot be satisfactorily completed. CPUC was also asked to immediately inform California intrastate natural gas transmission operators of the circumstances of the San Bruno accident so these operators can likewise proactively implement any corrective measures for their pipeline systems.
Additionally, the five Members of the NTSB voted to hold a fact-finding hearing as part of the investigative process. "This accident has exposed issues that merit further attention and have implications for the pipeline infrastructure throughout the country," said Chairman Hersman. "The hearing will gather additional factual information for the investigation, and will also provide the pipeline industry, state and federal regulators, and our citizens with an opportunity to hear more about this accident and important safety issues as the investigation progresses."
The two-day en banc hearing, which will be chaired by NTSB Chairman Hersman and webcast at www.ntsb.gov, will be held on March 1-2, 2011, at the NTSB's Board Room and Conference Center, 429 L'Enfant Plaza, S.W., Washington, D.C. The hearing is open for public observation and free to attend; no registration is required. The agenda, including a list of technical witnesses called to testify, will be publicized several weeks prior to the proceedings.