Federal safety investigators found a leak on a natural gas pipeline next to a New York City building destroyed in a fatal explosion last week.
The 8-inch main pipeline, parts of which are 120-years old, failed a pressure test, the National Transportation Safety Board said in a statement today. Segments of service pipelines found in the basements of the buildings have been removed and will be shipped to the NTSB lab for further investigation.
“The leak is a potential cause of the accident and something investigators will be looking at,” said Brigham McCown, an industry consultant and former acting administrator of the Pipeline and Hazardous Materials Safety Administration. “It suggests a path for natural gas to potentially escape and pool,” he said in a telephone interview today.
The explosion near 116th Street, reported about 9:30 a.m. March 12, collapsed two buildings at 1644 and 1646 Park Ave. and killed at least eight people, according to an Associated Press report. The blast was heard miles away and turned into a five- alarm fire. Windows were blown out as far as 10 blocks away, and cars parked on the street were wrecked. Debris flung onto adjacent elevated train tracks disrupted commuter rail services in and out of Grand Central Terminal.
The NTSB sent a team of investigators to the scene. The cast iron line was installed in 1887, the agency said.
Consolidated Edison Inc., the utility serving that part of the city, has said it received a report of a suspected gas leak before the explosion in East Harlem and had dispatched a crew in response.
Con Edison workers detected gas in the ground in the area after the explosion, NTSB member Robert L. Sumwalt said in a March 14 press conference at the site. Gas analyzers detected methane in five of 50 holes dug, with gas concentration in one hole at about 20 percent, he said. The samples were taken before Con Edison had cut off gas service to the area, he said.
Soil in New York City normally contains no natural gas, Sumwalt said.
“We’d expect to find zero gas,” Sumwalt said. “This was a pretty good concentration. It further leads to the hypothesis that this may have been a natural gas leak.”
Con Edison spokesman Bob McGee had no comment on the NTSB statement or on the investigation into the explosion. He referred all questions to the NTSB. The agency has not yet identified a cause of the explosion.
The investigation will include collection and review of Con Edison documents, and interviews with Con Edison employees, first responders to the explosion and witnesses, Sumwalt said in the March 14 press conference.
Investigators and other regulators are zeroing in on pipe age and condition as a possible cause, McCown said. It’s possible that the explosion could have weakened the gas pipe or created the leak, he said.
“We’ve known for some time we have aging infrastructure,” he said. “Cast iron pipe is really old and utilities have embarked on replacing it.”
It’s too early to tell if Con Edison was responsible for the leak in the main pipeline, said Samya Lutz, outreach coordinator for the Pipeline Safety Trust, a watchdog group. Main lines can be damaged by a variety of causes, she said. The NTSB statement also doesn’t clarify whether the leak is in a cast iron or plastic segment of the line, she said. Regulators have been pressing utilities to replace cast iron, which has been implicated in leaks, with plastic, she said.
(With assistance from Michelle Kaske and Henry Goldman in New York.)
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