Consolidated Edison Inc.’s poorly welded pipe joint was the primary cause of a natural gas explosion in New York City that killed eight people in March 2014, the National Transportation Safety Board said.
The weld was weakened by a sewer leak detected yet left unrepaired for eight years by the city’s Department of Environmental Protection, according to a report adopted by the board at a meeting in Washington Tuesday. The leak washed away soil that supported the pipe, the report found.
Both the bad weld and the neglected sewer breach were the probable cause of the explosion that destroyed two buildings in East Harlem, Eric Weiss, a spokesman to the board, said Tuesday in an e-mail.
Consolidated Edison Inc. has filed suit against the city over the blast, stating that neglected municipal infrastructure led to the rupture, the New York Daily News reported. The New York-based power and gas utility said in a statement that the sewer breach led its gas line to crack. The joint failed after the explosion during excavation of the site, the company said.
“A properly fused fusion joint would not have failed,” Amy Spitalnick, a city spokeswoman, said in a statement after the board voted to accept the findings. “The sewer was 43 feet north of Con Ed’s faulty gas service connection.”
The NTSB recommended that Con Edison improve quality control for gas lines and meet its own standards for placing cut-off valves, so that burning gas lines can be shut down sooner. The city overlooked the effect of the sewer breach on other buried utility lines, according to the report.
“Not all of the participants involved in this investigation reached the same conclusion concerning the sequence of infrastructure failures that led to the explosion,” Con Edison said in the e-mailed statement.
Con Edison fell 0.2 percent to $58.44 at the close in New York.
(An earlier version corrected primary cause in headline and first paragraph, spelling of mayor’s name in last paragraph.)