• Hurst Metallurgical report

So, that forensic metallurgical report ExxonMobil ordered after its Pegasus Pipeline split. You want it. We got it.


You can read the full report, by Hurst Metallurgical Research Laboratory Inc., at this link. Unless you work for that firm, Exxon, or the U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA), or you happen to be a bellicose elected official in Arkansas, this is probably the first chance you’ve had to eyeball these 200-plus pages of verbal Ambien. It contains Hurst’s take on why the old pipeline burst and dumped hundreds of thousands of gallons of oil into the streets and yards and waterways of Mayflower.

A few noteworthy passages:


The subject section of the 20″ Patoka to Corsicana #1-20″ North Pipeline, the segment from Conway to Corsicana, consisted of approximately 50′ long sections of 20″ O.D. x 0.312″ thick wall DC Electric Resistance Welded (ERW) pipe that was manufactured in 1947 and 1948 by Youngstown Sheet and Tube Company in Youngstown, Ohio. — pg. 2

Prior to failure, the pipeline was reported to typically operate between 47°F and 78° at pressures ranging between 240 psig and 820 psig. — pg. 3

The basic pipe bio. The split measured 22 feet long on one 50-foot section of pipe.

No trees, roads, or buildings were located directly above the pipeline where the fracture occurred. As shown in Photograph No. 1, two (2) homes were built in close proximity to the pipeline, with driveways crossing over the pipeline at two (2) points downstream of the fractured segment. During construction of the homes, the pipeline may have experienced vehicle loadings caused by construction equipment and/or vehicles crossing the pipeline at multiple locations, including over the fractured segment. There was no indication of construction, digging, localized flooding, or other ground movements in the area of the fractured segment occurring during or immediately prior to the pipeline rupture. —pg. 3

If you look at an aerial map of Mayflower, you’ll see the pipe’s path cuts mostly through rural stretches like a scar. For the break to occur beneath a neighborhood seems unlikely, if the site were randomly picked along the 850-mile pipeline. The report at least gives a nod to possible causation there.


The hook cracks initiated and followed the brittle upturned grain flow lines or bands that were created during the manufacturing of the pipe due to effects of the stresses induced by hydrostatic testing, thermal stresses, residual stresses, and/or pressure cycles. The hook cracks may not have all occurred simultaneously … and potential microcracks in the upset/heat-affected zones may have then merged due to stresses during service. — pg. 31


  • Hurst Metallurgical report

This passage appears to give some lie to any reading that says the break owed only to “manufacturing defects” (also pg. 31). After Exxon reviewed the report, it stated publicly that “the independent laboratory concluded that the root cause of the failure can be attributed to original manufacturing defects — namely hook cracks near the seam.” While that may be so, the report also doesn’t ignore the actual use of the pipe as a contributing factor. That may seem patently obvious, but as we’ve seen for the past four months, there are no apparent breaks in the old pipe when no one is pushing 95,000 gallons of oil through it daily.

This report hasn’t been made publicly available until now. Exxon spokesman Aaron Stryk emailed an InsideClimate News reporter July 11 to explain that “It is up to PHMSA when they decide to make the report publically available.” We’ve emailed Stryk to see whether he has any response to this post and will update it if he responds.

Without having seen the report, Richard Kuprewicz, president of the pipeline consulting firm Accufacts Inc., commented to InsideClimate News that “not disclosing the forensic metallurgical report is nuts” and “that’s stuff that’s eventually going to be made public.” (Kuprewicz is now consulting for Central Arkansas Water.)


This still leaves a couple of documents pertaining to the oil spill investigation lurking in the weeds. The most interesting one is the inline inspection report that Exxon made of the Pegasus in the month before it broke. Stryk has previously gone on record saying those data are still being analyzed.

Arkansas Attorney General Dustin McDaniel, whose office filed suit against Exxon in June, said Wednesday that he’s pushing for all the germane reports to be released. “The sooner they are made public, the sooner scrutiny from independent experts and journalists can begin,” he said. “But I’m not being critical in saying who’s holding up the process. I’m just calling for those who can expedite release to expedite release.”

Asked whether Exxon could be slow-pedaling that process, he said that hasn’t been Exxon’s M.O. to date.

“He who controls the information has the upper hand in such a technical situation as this,” McDaniel said. “I have, however, not seen [Exxon] withholding information from me or from PHMSA that I know of. I think they’ve had some pretty cold-hearted policy positions and they’ve had some pretty unpleasant public relations stumbles. But I cannot at this point say that they have not been cooperative with our requests for them to produce information.”

Elizabeth Douglass of InsideClimate News contributed to this report, which is part of a joint investigative project by Arkansas Times and InsideClimate News. Funding for the report comes from people like you who donated to an ioby.org crowdfunding campaign and for the Fund for Investigative Journalism.