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August 01, 2012
Derailments and underground pipelines

The intersection of railroad tracks and buried hazardous liquid and gas pipelines creates the potential for pipeline damage caused by railway accidents. Pipeline owners/operators should therefore ensure that they are immediately informed of railroad accidents near their pipelines and inspect their facilities to ensure that structural integrity has not been compromised.

That’s the main message of Advisory Bulletin ADB-2012-08 issued by the Pipeline and Hazardous Materials Safety Administration (PHMSA). The bulletin was primarily motivated by a June 19, 2009, derailment of 19 cars in a 114-car freight train in Cherry Valley, Illinois. All of the derailed cars were tank cars carrying denatured fuel ethanol, a flammable liquid. The resulting fire injured eight people, one fatally, waiting in cars at the crossing. About 600 residences within a one-half mile radius were evacuated.

Depth no assurance

At the site of the derailment, a 12-inch-diameter natural gas pipeline operated by Nicor Gas was buried 11 feet underground. The depth exceeded federal standards for protective ground cover by a factor of three. It was also five times as deep as the industry-recommended protection requirement for depth of cover that was in effect at the time the pipeline was constructed. In addition, the pipeline was enclosed in a 16-inch-diameter casing.

Despite this high degree of protection, Nicor crews discovered that the derailment resulted in considerable damage to the pipeline. Following an investigation, the National Transportation Safety Board (NTSB) concluded that the wheel and axle assembly of a derailed car impinged on the pipeline. The impact caused severe flattening of the pipe casing with sharp angular bends at two locations. This degree of deformation of the casing likely caused similar damage to the 12-inch carrier pipe, said the NTSB.

In addition to the specific damage at the site, injuries to people, and evacuation of 600 residences, the major concern was that the impact would likely have caused a rupture had the pipeline been buried under the minimum level of ground cover indicated by federal requirements.

The PHMSA researchers found only five reportable incidents since 1984 in which a train derailment caused damage to pipelines crossing under tracks. However, despite the infrequency of such incidents, the NTSB expressed the belief that pipeline owners/operators should be informed about the potential risks of damage to pipelines whenever a train derails. “Given the prevalence both of underground pipelines and aboveground railroad tracks, the two must, of necessity, cross at numerous locations,” said the NTSB.

Essential information exchange

Accordingly, PHMSA’s bulletin makes the following recommendations:

  • Pipeline owners/operators should inspect their facilities following a railroad accident or other significant event occurring in right-of-ways to ensure pipeline integrity.
  • During response operations, pipeline owners/operators must inform rail operators and emergency response officials of the presence, depth, and location of pipelines so that the movement of heavy equipment on the right-of-way does not damage or rupture the pipeline or otherwise pose a hazard to people working in and around the accident location.
  • As part of their public awareness programs, pipeline owners/operators are encouraged to inform rail operators and emergency response officials of the benefits of using the 811 Call Before You Dig program to identify and notify underground utilities that an incident has occurred in the vicinity of their buried pipelines.

PHMSA’s bulletin was published in the July 31, 2012, FR. The NTSB safety recommendation to the PHMSA is at http://phmsa.dot.gov/staticfiles/PHMSA/DownloadableFiles/NTSB/R-12-5%20thru-8_PHMSA%20Original%20Letter.pdf.

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