LOS ANGELES – A natural gas well in California that spewed more than 100,000 tons of the harmful greenhouse gas methane into the atmosphere was the largest methane leak in U.S. history, researchers said Thursday.
The study in the journal Science is the first to be published regarding the impact of the Aliso Canyon natural gas well blowout, which lasted 112 days before it was finally plugged on Feb. 11.
“The methane releases were extraordinarily high, the highest we’ve seen,” said Donald Blake, an atmospheric chemist at the University of California, Irvine, and co-author of the study.
Lead scientist Stephen Conley of the University of California, Davis, said that when he first began measuring the outpouring of methane in early November, the readings were so high that thought his equipment was malfunctioning.
“It became obvious that there wasn’t anything wrong with the instruments,” Conley said.
“This was just a huge event.”
At its worst, “the blowout doubled the rate of methane emissions from the entire Los Angeles Basin and temporarily created the largest known human-caused point source of methane in the U.S.,” said the study.
The next largest source of methane in the United States is an Alabama coal mine, researchers said.
Surface air samples collected near homes in the adjacent Porter Ranch residential area showed “above-normal levels of several potentially dangerous compounds present in natural gas, including benzene, toluene and xylenes,” said the study.
Long-term exposure to some of these volatile organic compounds has been linked to health damages, but it remains unclear what effect the blowout has had on the health of nearby residents — more than 11,000 of whom were evacuated.
The study found that impact of the leak would be equal to the greenhouse gas emissions from over half a million cars.
It will also “substantially affect California’s ability to meet greenhouse gas emission targets for the year.”
The research team included scientists who used airborne chemical sampling to measure the 2010 Deepwater Horizon spill off the coast of Louisiana.