An explosion that rocked Sissonville this week could have been caused by deterioration within a natural gas pipeline.
According to Robert Sumwalt from the National Transportation Safety Board, a six-foot area along the bottom of the pipe had thin walls, in some places less than a tenth of an inch in thickness, or about 70 percent thinner than designed. This loss of wall thickness could have contributed to the Dec. 11 explosion near Sissonville.
Sumwalt said this section of pipeline SM-80 was connected to the Lanham Compression Station owned by NiSource/Columbia Gas. Pressure within the pipe dropped at approximately 12:41 p.m. Dec. 11, but Sumwalt said NTSB investigators don't know if the pressure drop contributed to the blast or was a result of the pipe rupture.
This was the second day NTSB investigators were on the ground in Sissonville. Sumwalt said investigators are working to gather as much information about the blast as they can. He said determining how the pipeline could have deteriorated so much is one focus of the investigation.
"Today was a productive day for our investigative team," Sumwalt said at a Dec. 13 press briefing.
Investigators spent the afternoon interviewing Columbia Gas' central command center personnel. Sumwalt told reporters Dec. 12 that the blast triggered no alarms at the central command center. He said at the Dec. 13 briefing that changes in pressure have to be significant to trigger alarms. But, he said, NTSB investigators would evaluate NiSource's response to the blast.
"We will be evaluating their response to see if it was adequate and efficient," Sumwalt said.
He also said he wasn't sure how NISource found out about the blast. That question would be answered in the evaluation.
Sumwalt said investigators will conduct more interviews tomorrow, as well as send the ruptured pipe to labs in Washington, D.C., for further testing. Investigators also will extract a portion of SM-80 that was undamaged and continue to gather documents and records.
"We want to make sure this pipeline is not affected in an adverse way in other areas," he said.
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