The probable cause of the fatal explosion on one of the mainlines of El Paso Natural Gas in August 2000 was “severe internal corrosion” of the line, the three-member National Transportation Safety Board (NTSB) concluded Tuesday, citing the pipeline’s inadequate corrosion-control program and lax oversight by the federal Office of Pipeline Safety (OPS).

The explosion and fire near Carlsbad, NM, which killed 12 members of an extended family (see Daily GPI, Aug. 22, 2000), occurred because corrosion of El Paso’s Line 1103 on its South Mainline system had eaten away up to 72% of the pipeline wall and “the remaining metal could no longer contain the pressure within the pipe,” the NTSB’s final conclusion read.

El Paso “failed to prevent, detect or control” the corrosion due to an inadequate corrosion-control program in effect at the time. Had the pipeline been able to accommodate cleaning pigs, and used those pigs regularly, corrosion “would likely have been less severe,” according to the board. Likewise, had El Paso regularly sampled the quality of the gas entering the pipe or the contents of the pipe, it would have likely detected the presence of materials that contribute to corrosion, the NTSB said.

NTSB Commissioner John Goglia noted that El Paso “obviously” didn’t believe it needed to inspect its line regularly since it had been around such a long time. But “the more you’ve been around, the more you need to check, not less.”

A contributing factor to the blast was the fact that the OPS did not make accurate pre-accident assessments of El Paso’s internal corrosion program, the NTSB also concluded. While OPS had inspected the pipeline 18 times between June 1990 and August 1998, no deficiencies were identified by its inspectors. After the Carlsbad explosion, however, the OPS found there had been numerous violations on El Paso related to corrosion, but its inspectors had failed to act on any of them, according to the NTSB.

The NTSB report did not make any recommendations for El Paso, given that the pipeline already has made “significant improvement” in its corrosion-monitoring program since the New Mexico rupture, and has replaced the ruptured pipe segment with new pipe, which now enables it to use cleaning and inspection tools to detect and address corrosion problems.

“We have been deeply afffected by the Carlsbad tragedy, and we have sought to learn from it. We have implemented an aggressive, comprehensive approach to pipeline integrity that addresses the full range of known risks, including internal corrosion,” said El Paso Corp., parent of the pipeline, in a statement Tuesday.

The NTSB, however, recommended that the Research and Special Programs Administration (RSPA), which oversees the OPS, require that new or replaced pipelines be designed and constructed with features to mitigate internal corrosion. At a minimum, pipelines should be configured to reduce the potential for liquids to accumulate, be equipped with effective liquid-removal features, and be able to accommodate corrosion monitoring devices at locations with the greatest potential for internal corrosion, it said.

It also called on the RSPA to develop requirements to ensure pipeline operators’ internal corrosion-control programs address the role of water and other contaminants in the corrosion process. Lastly, the NTSB recommended that the RSPA evaluate its OPS pipeline operator inspection program to find out why its inspectors failed to identify the problems with El Paso’s internal corrosion-control program prior to the fatal explosion.

In addition, the NTSB urged the National Association of Corrosion Engineers (NACE) to establish an accelerated schedule for completing a new industry-wide standard for the control of internal corrosion in steel pipeline — one that would replace or update the existing NACE standard RP-011-75.

Acting NTSB Chairman John Hammerschmidt, speaking at a special meeting called to consider staff’s findings with respect to the El Paso blast, said the accident and its aftermath should “serve as a wake-up call for other pipeline operators.” The explosion reveals an industry-wide need for “better testing and assessment” of gas pipelines, he noted. The full NTSB report on the accident, which is subject to further review and editing, is expected to be out in a couple of weeks, agency spokesman Keith Holloway said.

Killed in the explosion, which occurred early on Aug. 19, 2000, were seven adults and five children of an extended family who were camping and fishing along the banks of the Pecos River near the New Mexico-Texas border. The victims were camped approximately 675 feet from the point where the El Paso pipe ruptured. They were consumed in a fireball that shot 500 feet in the air, and ripped open a 113-foot long, 51-foot wide trench.

The NTSB’s investigation of the El Paso blast took about two and a half years to complete. “Because of the prominence of this accident, they [NTSB staff] wanted to dig into it in the detail that it deserved,” said Hammerschmidt, who extended the agency’s condolences to those whose family members were killed that day in New Mexico.

The blast that put one segment of El Paso’s mainline out of service for an extended period has been cited by some as a contributing factor to a shortfall in gas supplies going into storage in California, and helping to boost gas prices during the western energy crisis.

The NTSB does not assess penalties, but its conclusions are likely to be used in private lawsuits involving the blast.

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