A woman walks past a Porter Ranch sign at the entrance to Southern California Gas Co.’s Aliso Canyon storage field. REUTERS/Lucy Nicholson
A woman walks past a Porter Ranch sign at the entrance to Southern California Gas Co.’s Aliso Canyon storage field. REUTERS/Lucy Nicholson

The gas leak from the Aliso Canyon storage facility in Porter Ranch spewed more than 100,000 tons of methane into the air, making it the largest methane leak in U.S. history, according to a study released Thursday.

The study by UC Davis, the National Oceanic and Atmospheric Administration and others — and published in the journal Science — found that the daily amount of methane leaked between Oct. 23 and Feb. 11 was enough to fill a balloon the size of the Rose Bowl.

Stephen Conley, a pilot and UC Davis researcher, said when he began taking readings of the methane in November, the readings were so high he thought his equipment was faulty.

“It became obvious that there wasn’t anything wrong with the instruments. This was just a huge event,” Conley said.

According to the study, at the peak of the leak, the amount of methane pouring into the air from the damaged pipe was double the rate of methane emissions from the entire Los Angeles basin, and it was the largest “human- caused point source of methane in the United States,” doubling the methane released by an Alabama coal mine.

The methane released is roughly the equivalent to the annual greenhouse gas emissions from more than 500,000 passenger cars, the study found, dramatically impacting the state’s ability to meet its emission targets for the year.

Study co-author Donald Blake of UC Irvine said air samples at the Aliso Canyon site also found compounds such as benzene, butane and pentanes.

“The methane concentrations were extraordinarily high, the highest we’ve seen in ambient samples,” Blake said.

—City News Service

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