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Study: California blowout led to largest U.S. methane release ever

February 25, 2016 Researchers quantified emissions from the Aliso Canyon well leak, which was equal to one-quarter of Los Angeles’ annual methane pollution.
The Aliso Canyon well is located in the Santa Susanna Mountains of southern California. The actual well site is indicated by the circle.

When pilot Stephen Conley of Scientific Aviation first flew above the leaking Aliso Canyon natural gas well in southern California, he thought the instruments in his specially equipped plane had gone haywire. They hadn’t.

“This was just a huge event,” Conley said.

Conley and NOAA’s Tom Ryerson quickly built a team of researchers to investigate the blowout of the SoCalGas well. The results, published Feb. 25 in the journal Science, showed that the accident released over 100,000 tons of the powerful greenhouse gas methane before the well was plugged on February 11. 

At its peak, the Aliso Canyon well leaked enough methane every day to fill a balloon the size of the Rose Bowl, doubling the rate of methane emissions from all other sources in the Los Angeles basin combined. The study confirmed that this was largest methane leak in U.S. history and was temporarily the largest point-source of methane anywhere in the United States.

The team’s work has implications for states or countries trying to meet pollution targets in the future.

“Our results show how failures of natural gas infrastructure can significantly impact greenhouse gas control efforts,” said Ryerson.

Read NOAA's news release