NEW YORK, N.Y. – A gas leak that was reported just before a deadly explosion in East Harlem last year may have come from a relatively new section of plastic pipe, not the cast-iron segment that was installed in 1887, according to a report released Wednesday.
At the time of the explosion, when the National Transportation Safety Board said it had detected gas leaks, attention was focused on Con Edison’s old main as indicative of the aging infrastructure in New York and other cities.
But a new NTSB report said that during testing with a tracer gas, high gas concentrations were found coming from a plastic segment that was installed in 2011.
Con Edison said it was “prohibited from commenting” until the NTSB investigation is complete.
The March 12, 2014, blast demolished two buildings, killed eight people and injured about 50.
The report was among 161 documents, totalling about 3,000 pages, that were made public Wednesday in connection with the NTSB investigation. It did not include any conclusions about the root cause of the explosion.
The report also found that the 69-foot plastic pipe segment had not been tested to federal specifications because New York regulations exempt it.
It said federal guidelines call for pressure testing new plastic pipe at 150 per cent of maximum operating pressure. But state regulations exempt pipe lengths under 100 feet, and the new pipe was tested for leaks with a visual inspection and a soap-bubble test, the report said.
Another document shows Con Edison was admittedly deficient in making sure gas-line installers were properly certified. A Con Ed letter to the Public Service Commission acknowledges “lapses in our installer qualification process” but expresses confidence that the lapses “did not compromise the integrity of the gas system.”
Other findings in the documents include:
—Several gas-leak surveys in the area of the explosion, including two in the month before, did not detect any leaks.
—Several repairs were made in recent years to depressions in the road near the buildings at Park Avenue and East 116th Street. One was reported as a “cave-in” measuring 20-by-30 feet. One of the issues being examined by the NTSB is whether leaks from sewer or water mains could have caused earth to settle, compromising the gas main.
—The water main, which dates back to 1897, had several leaks including a crack that was three-quarters of an inch wide and nearly circled the main.
Other documents included transcripts of interviews with several Con Edison executives and supervisors, photos from videos inside pipes, and a copy of a scratch-and-sniff card Con Ed uses to help customers recognize the smell of natural gas.