Sempra Natural Gas Leak Was Largest in U.S. History, Study Says

  • More than 100,000 tons of methane released from broken well
  • NOAA and UC Davis issue first study since leak sealed

Sempra Energy’s natural gas leak from a broken well in California was the largest in U.S. history, federal and university researchers said.

The leak, detected Oct. 23, released more than 100,000 tons of the powerful greenhouse gas methane before being initially plugged by Sempra’s Southern California Gas Co. on Feb. 11, according to a study by the National Oceanic and Atmospheric Administration, the University of California at Davis and other partners and published Thursday in the journal Science.

The incident near Los Angeles will “substantially” affect California’s ability to meet state greenhouse gas emission targets for the year, the researchers said in a statement. The study found that the Aliso Canyon leak spewed enough methane into the air every day to fill a balloon the size of the Rose Bowl stadium and that the total impact on the climate will be the equivalent to the annual greenhouse gas emissions from over a half a million cars.

Sempra didn’t immediately respond to a request for comment. California regulators said last week that Sempra’s utility had permanently sealed the leaking well.

Federal lawmakers, state agencies and local officials opened investigations into the leak, threatened fines and questioned whether Sempra’s gas storage complex should remain open. The company is facing more than 60 lawsuits, including one filed by the California Attorney General.

“Our results show how failures of natural gas infrastructure can significantly impact greenhouse gas control efforts,” NOAA’s Tom Ryerson, co-lead scientist on the study, said in the statement.

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