photo credit: Jason Hashim / Pittsburgh Post-Gazette
Investigators have named “rapid corrosion” as one of the factors contributing to the natural gas pipeline explosion that occurred in a Pittsburgh suburb in April, according to the Pittsburgh Tribune-Review.
Officials from Spectra Energy, the Houston-based company pipeline operator, shared their findings with residents, township board supervisors, and state and federal officials at a public meeting in Salem Township, Westmoreland County, Tuesday (Sept. 13). The fast-acting corrosion not only played a role in the blast but has also led the company to update its inspection routines, it said.
The April 29 explosion produced a 30-foot-wide, 50-feet-long, 12-foot-deep crater and a burn zone of a quarter-mile radius. It also destroyed one home; damaged at least three others; singed acres of farmland; and sent nearby resident James Baker, 26, to a Pittsburgh hospital burn unit with extensive injuries.
Aggressive, Fast-Moving Corrosion
During the public meeting, Andy Drake, Spectra’s vice president of operations and environmental health and safety, told attendees that the company had never seen corrosion so aggressive or fast-moving in a pipeline before.
According to officials, a 2012 inspection of the area of pipeline where the failure ultimately occurred showed that the steel wall had lost about a third of its metal to corrosion. This was reportedly considered a “minor anomaly,” the Tribune-Review noted, and the spot was flagged for reinspection in 2019 according to standard procedure.
“It was very small. It was smaller than any threshold we'd be required to investigate,” Drake said.
At the time, prior experience led officials to believe that in a worst-case-scenario the pipe walls would lose only another 2 percent or 3 percent a year, the Pittsburgh Post-Gazette reported.
“What we saw was about 10 to 15 percent a year, or about five times what conservative assessments would be based on,” Drake said.
Explaining that they have not seen anything like this before, Drake added, “It is truly an outlier—not just for Spectra, for the industry.”
“Here we stand before you apologizing that we were not far enough ahead of this,” Drake told the community. “This is the challenges we’ve put to ourselves: Imagine a person standing next to this pipe—your son, your mother—are we comfortable that this pipe is absolutely safe everywhere?”
In July, similar corrosion patterns were found on another nearby pipeline operated by Spectra.
The company continues to investigate the length of the pipeline, according to Tom Wooden, Spectra's vice president of field operations.
Having excavated 400 of 625 identified anomaly sites, he said Spectra has not found conditions similar to Salem Township elsewhere but confirmed that, working with the Pipeline and Hazardous Materials Safety Administration (PHMSA) officials, Spectra crews have made repairs at about one-third of those 400 sites.
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Spectra noted that it will share investigation results from its Salem Township site with the natural gas industry in order to prevent similar events from happening elsewhere, he said.
While federal investigators haven’t yet released a cause of the blast, tape coatings remain a primary focus, and many pipelines laid from the 1970s through as recently as the 1990s used similar coatings, Drake said.
As reported earlier, the affected pipeline was coated with Fusion Bond Epoxy with tape-coat coating at girth weld joints. Spectra officials confirmed the company used the tape coating from 1975 to 1985; the Salem Township pipeline was installed in 1981.
The material was an accepted method of coating pipeline weld joints at the time but has since been replaced by newer technology.
In its preliminary investigation, PHMSA had identified areas of corrosion that suggested the tape coating around welds in the interstate pipeline was a factor in the event.
“The pattern of corrosion indicates a possible flaw in the coating material applied to girth weld joints following construction welding procedures in the field at that time,” a PHMSA Corrective Action Order stated.