The wall thickness of a section of pipe on the 20-inch diameter Columbia Gas Transmission system that ruptured Tuesday in West Virginia was significantly deteriorated, said National Transportation Safety Board (NTSB) investigators Thursday. There also was a pressure drop on the line, but the magnitude of the decrease is unknown as was whether drop was the result of the rupture or its cause.
“In parts of [the] area, pipe wall thickness was measured to be less than a 10th of an inch thick,” said NTSB board member Robert Sumwalt after the second day of inspecting the rupture site near the pipeline’s Lanham Compressor Station in the rural community of Sissonville, WV, which is about 15 miles north of Charleston.
He said the pipe wall was only 0.078 inch thick in certain areas, which amounts to about a 70% loss in wall thickness. The agency estimated that the wall was thinner along the bottom of the pipeline for about six feet.
Sumwalt declined to say what caused the pipe wall deterioration and whether it contributed to the cause of the explosion. “There are many things that can cause pipe wall thickness to deteriorate, and that is exactly what we will be looking at…and then what finally led to the actual rupture and explosion of the pipeline.” The NTSB did not say when the Columbia Gas pipeline was last inspected or how old it is.
Sumwalt further said they have not determined whether the the drop in pressure was to such a low level that it should have sounded alarms at the Columbia Gas control center in Charleston. The pressure drop occurred at the upstream Lanham Compressor Station, according to Sumwalt. No alarms were sounded at the control center, he said.
“As we speak…investigators are interviewing control center personnel to find out what indications the pipeline controller may have had associated with the pressure drop,” he said.
Columbia CEO Jimmy Staton Friday issued an open letter from Columbia Gas to the affected families of Kanawha County, WV, saying that “something went terribly wrong with our natural gas pipeline near Sissonville [Tuesday], and we are working tirelessly — in full cooperation with state and federal authorities — to find out why.”
While the company is “thankful” that there were no serious injuries, it recognizes that members of the community are going through significant hardship, particularly those whose homes were lost or damaged, he said. “Along with community partners and support groups, we are working to help those in need, providing temporary houses and other essentials.”
On Friday, the NTSB said it would continue to interview control center personnel; ready the damaged section of the pipeline for shipment to Washington, DC; and begin the process of extracting parts of the pipeline that were not ejected from the explosion crater.
NTSB investigators arrived at the scene in Sissonville just hours after the blast on Dec. 11 and have been onsite since then. The 10-member investigation team is being lead by Ravi Chhatre, an expert on pipeline operations, fire and explosions and emergency-response efforts (see Shale Daily, Dec. 14; Dec. 12). Chhatre was the NTSB’s investigator in charge of the four-member team that investigated the fatal San Bruno, CA, pipeline explosion in September 2010.
“We have not spoken in detail to Columbia Gas at this point, but certainly that is something that we will be doing, and we will have their representatives here working with us for the next several days,” Sumwalt said last Wednesday.
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