Investigation Follows Bison Blowout

July 2011, Vol. 238 No. 7

After TransCanada’s Bison pipeline experienced an as-yet-unexplained rupture in Wyoming July 20, an investigation is under way but has not yet uncovered the cause of the accident. The rupture occurred in remote country and did not result in any injuries or property damage aside from the pipeline itself.

July 27, TransCanada said the rupture was unrelated to operating pressure and caused by a mechanical event. The operating pressure question was raised due to the fact that Bison is licensed to operate at a higher-than-standard 80% MAOP and is therefore subject to stricter safety regulations. David Dodson of TransCanada estimated that a 50-foot chunk of pipe was affected, at the very beginning of the line. TransCanada’s control room in Houston noticed the drop in pressure from the rupture and called the Anadarko-owned compressor station; the flow of gas was shut off within about 15 minutes from the event.

The line was repaired by July 28, but the line will not be put back in service until a PHMSA investigation is completed. According to Dodson PHMSA will require at least two in-line inspections of the pipe before recertification. The nature of the event that caused the rupture is still unclear.

From the Casper Star-Tribune, 7/28: “’Something hit it,’ said James Millar of Calgary-based TransCanada Corp . . . ‘Usually we don’t get something this early that you get an indication what occurred,’ he said. ‘On this one they were able to see from visual inspections that gave them a pretty good indication of what would have caused the break.’”

Casper Star-Tribune, 7/25 features a description of the incident from an area resident: “If you’ve ever heard a jet fighter going off, like an F-16 or something like that, it sounded like many of them going off at the same time,” he said. “It roared, it just screamed.” Upstream Online estimates that area natural gas transportation will not be immediately affected, though there is no plan yet to repair the pipeline. P&GJ‘s own article on the first months of Bison’s operation, from the May 2011 issue, outlines the additional safety precautions taken with the project, which the company said contributed to its late start.


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