An interstate natural gas pipeline that exploded in Salem Township in April had lost about 30 percent of its steel wall to corrosion four years earlier, Spectra Energy officials said Tuesday.
But officials said what was then considered a minor anomaly — a small area flagged for reinspection five years later — corroded at an unprecedented rate that caused the explosion and spurred the company to re-evaluate longstanding industry standards.
Spectra officials said they have shortened the length of time between inspections of similar transmission lines from every five years to every three to four years. They will lower the threshold for flagging anomalies for action and will add an additional measurement to the industry standard, officials said.
Federal officials have yet to issue a determination on the cause of the blast that sent a fireball hundreds of feet into the air, scorched about 40 acres of farmland and severely burned a Salem man whose home was destroyed.
However, Spectra officials said they believe a combination of issues affecting weld joints on 40-foot sections of pipe caused the rupture of the line.
A preliminary investigation by the U.S. Pipeline and Hazardous Materials Safety Administration this year suggested corrosion at weld joints contributed to the explosion.
Andy Drake, vice president of operations for Spectra, detailed the company’s analysis during a news conference Tuesday afternoon, hours before company officials and federal regulators were scheduled to address Salem residents at a town hall meeting.
Drake said company records revealed corrosion at the Salem Township site during a 2012 in-line inspection of the 30-inch pipe, but nothing that suggested immediate action was warranted.
“It was very small. It was smaller than any threshold we’d be required to investigate,” he said.
“Based on research and engineering practice, we would expect to see corrosion of 2 to 3 percent a year in the worst case. What we saw was upwards of 10-15 percent a year, or about five times what conservative engineering estimates would be based on,” Drake said. “It is truly an outlier — not just for Spectra, for the industry,” he said.
Not all of the approximately 80 Salem residents gathered at Tuesday night’s town hall meeting in Crabtree were reassured by Spectra’s explanation.
Dana Shondelmyer, who said she could hear the blast from her nearby Fennelltown Road home, conceded the company’s explanation sounded plausible.
“But in my experience, most if not all of the time, we are not told the truth or the whole truth,” she said.
Drake said a combination of “unique factors coming together” appear to have contributed to the explosion.
Federal investigators have said one factor was failure of the tape coating used to seal the weld joints when the line was installed in 1981. The tape, which has been replaced by new technology, tended to shield the lines from electrical charges as an additional protection.
Officials said Spectra used the tape coating from 1975-85, but it was used in some sectors as recently as the 1990s.
Then there were factors that Drake said were unique to the Salem site.
“The gas is a little warmer there, given that it is closer to the compression station. And there were some local environmental factors that have led to an intensive wet–dry cycling on this particular site,” he said.
Tom Wooden, Spectra’s vice president of field operations, said the company has undertaken an extensive review of its 265-mile Delmont-Lambertville, N.J., line. He said Spectra has excavated 400 of 625 sites but has found nothing comparable to the conditions at the Salem Township site.
Wooden said the company intends to continue excavating sites flagged for additional inspection and will share findings from the Westmoreland investigation with the natural gas industry.
Responding to a question from Salem resident Angela Davis, Wooden said Spectra employees working under the supervision of representatives of the Pipeline and Hazardous Materials Safety Administration made repairs at about one-third of those 400 sites.
“I personally want to apologize to everyone who’s here. The impact that it has had on you and your families is completely unacceptable, and we want to prevent it from happening again here of anywhere else,” Drake told the crowd.
In its most recent public update last month, the Texas-based energy company reported it had spent $16 million on repairs and testing since the April 29 explosion in Salem.
In a communication to shareholders, company officials estimated they would spend another $75 million to $100 million on testing sections of the line between Delmont and New Jersey.
Last week, Enbridge Inc., a Canadian oil and gas transmission company, announced it was purchasing Spectra in a $28 billion stock deal that would create the largest energy infrastructure company in North America.