The 1940s-era construction process that ExxonMobil said caused an oil pipe to rupture in Arkansas earlier this year is a common and well-documented problem the pipeline industry has battled for decades—and one the industry believes can be detected and controlled with appropriate vigilance.
"With proper inspection and maintenance, these catastrophic events can be prevented," said Mohammad Najafi, a pipeline construction expert and engineering professor at the University of Texas at Arlington. "As pipelines exceed their design lives, they need more maintenance and a proper asset management strategy to prevent or minimize these ruptures."
That leaves the public and regulators with two critical questions: Did Exxon manage and test its broken Pegasus pipeline according to established guidelines? And, if it did, is the Arkansas accident a warning that other pipelines might be at risk?
If so, the repercussions would be nationwide, since many of the nation's liquid fuel and natural gas pipelines are of similar vintage and were built using the same inferior construction techniques. The gas line that ruptured in San Bruno, Calif. in September 2010, killing eight people and destroying 38 homes, included segments made with the same process as the Pegasus pipe. Investigators found that the pipeline's owner, Pacific Gas & Electric, had neglected to properly inspect and repair the line and that regulators issued testing exemptions and placed "blind trust" in the company's assurances.
Recent maintenance and testing records for the Pegasus, as well as the metal analysis report that blamed the accident primarily on a 65-year-old manufacturing defect, would offer important insight into why the pipeline failed. Those documents, however, are being withheld from the public as well as from a Congressional committee, two Arkansas Congressmen and a water utility worried that the pipeline could foul drinking water for nearly half a million people.
Exxon has given pertinent data to the Pipeline and Hazardous Materials Safety Administration (PHMSA), the federal agency that regulates the nation's pipelines, and to Arkansas Attorney General Dustin McDaniel (in response to a subpoena). But Exxon says the two most recent inspections it conducted on the Pegasus are proprietary and confidential, so they shouldn’t be shared with the public.
InsideClimate News has filed a formal request with PHMSA for the metallurgy report, along with a Federal Freedom of Information Act request for additional documents connected to the spill investigation.
PHMSA hasn't responded to the Freedom of Information Act request, which was filed in early June, and has refused to release the metallurgy report, citing the agency's ongoing investigation of the accident. Exxon spokesman Aaron Stryk said the company is concerned only about keeping the inspection reports private. As far as the metallurgy report is concerned, "it is up to PHMSA when to make that publicly available," he said.
Jonathan Phillips, senior policy adviser for the House Natural Resources Committee, rejects the notion that the records should be kept from public view.
"If there is information about the chance of this becoming a pattern, then it is information that should be made known," he said. "Without that information, how do you know?"
Exxon tested the Pegasus just a few weeks before the spill by sending a sophisticated inspection device called a pig through the line to look for flaws from the inside. Pipeline owners and regulators rely on pigs to detect corrosion, and specialized pigs are increasingly used to find potentially dangerous seam weld and other pipeline cracks.
If the pigs used by Exxon in 2010 and 2013 both failed to detect the crack that turned into a 22-foot breach, it will cast doubt on their reliability for seam weld inspection.
Carl Weimer, executive director of the Pipeline Safety Trust, a nonprofit watchdog organization based in Bellingham, Wash., said Exxon’s February test should have flagged the defect that ripped open the pipe.
"If it wasn't detected, then that says maybe there is no way of finding these flaws," Weimer said.
The section that failed was constructed using low frequency electric resistance welded (ERW) pipe to create long seams down the length of the pipe. The technique was discontinued by 1970.
Not all the pipelines of that vintage and built that way have defects, but they are all suspect and require constant monitoring to avoid disaster, experts say. Several industry reports offer step-by-step guidelines for monitoring and maintaining pipelines with these specific flaws.
Richard Kuprewicz, president of the pipeline consulting firm Accufacts Inc., said the known pipe manufacturing defects is like being predisposed to a grave illness.
"It may be a dormant gene or it may be an active gene," Kuprewicz said. Depending on how you treat and test the pipeline, "It may go to cancer, or you could live your entire life and it's not a problem."
Worrisome Regulatory Gap