LA's Methane Leak Was the Biggest in US History

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When Steven Conley first circled the cloud pouring out of a ruptured Los Angeles natural gas reservoir, he was shocked at the numbers his instruments were recording.

"Right away, I knew it was something strange. Either this was an equipment problem, or this was an off-the-scale, huge leak," said Conley, an atmospheric scientist at the University of California-Davis.

Conley has flown a small plane equipped with gas sensors around the Aliso Canyon reservoir more than a dozen times since the facility started pouring methane into the sky in October. The atmosphere normally contains methane at about 2 parts per million (ppm); a bad leak usually registers around 4 ppm. But the readings he was getting on that first flight, in early November, hit 50.

It wasn't the equipment. By the time the Aliso Canyon blowout was plugged in mid-February, it had belched more than 100,000 tons of the highly potent greenhouse gas into the air — a planet-warming punch comparable to driving 570,000 cars for a year, Conley and other scientists reported Thursday.

Related: Company Responsible for Huge Los Angeles Methane Leak Hit With Criminal Charges

That estimate comes as new figures from the US government suggest methane emissions from the oil and gas industry are far higher than previously thought. And since methane has 80 times the heat-trapping capacity of carbon dioxide over a 20-year time period and 25 times the punch over a century, that calls for a closer eye on the pipelines and storage tanks that supply millions of American homes, environmentalists said.

The Aliso Canyon blowout doubled the rate of methane emissions from the Los Angeles basin. It was the largest single-source methane release in US history, causing the eventual evacuation of about 11,000 people from nearby homes. Thursday's study, published in the peer-reviewed journal Science, involved researchers from the University of California system, state regulatory agencies, and the National Oceanic and Atmospheric Administration (NOAA). NOAA, the state of California, and Southern California Gas (SoCal Gas), the utility that owns the facility, funded the work.

In the Porter Ranch neighborhood, about two miles from the reservoir, air sampling found methane concentrations up to 10 times normal, said Donald Blake, a University of California-Irvine atmospheric chemist — levels rarely seen outside major methane sources like landfills and dairy farms. Though the gas itself isn't toxic, the chemicals used to give it a detectable odor can cause nausea, headaches, and nosebleeds.

"We do a lot of sampling, and we don't see 20 very often," said Blake, who has studied atmospheric methane since the 1970s. "We've sampled in lots of cities in China and the United States, and I don't think we've ever gotten more than about 5 parts per million. So this was very significant."

Related: LA's Massive Natural Gas Leak Has Officially Been Plugged

At the well itself, concentrations reached as high as 600 ppm, Conley said. The leak slowed dramatically as SoCal Gas tapped the reservoir to supply customers, with releases falling by about two-thirds before being capped altogether on February 11, Conley said.

SoCal Gas had little to say about the study.

"At this time, we do not have a calculation for how much gas is leaking," the company said in a written statement to VICE News. "Until we complete our own calculation of how much gas was lost, we are not in a position to comment on or otherwise confirm the accuracy of any other researcher." The utility said it's working on its own tally, but that "will take several weeks after the leak is stopped to complete."

Methane makes up about 10 percent of the greenhouse gases the US puts out every year, according to the US Environmental Protection Agency. About half of that comes from decaying waste in landfills and from belching, farting farm animals, the EPA estimates. But leaks from natural gas wells, pipelines, and other infrastructure make up the third-largest source, and the figure may be 27 percent higher than previously thought, the agency reported this week.

"There are sources of significant methane emissions that we simply have not had on our radar screen," EPA Administrator Gina McCarthy told reporters at an energy conference Wednesday. The EPA is getting ready to issue new rules to address those sources, which she said are "much larger than we ever anticipated or were able to calculate before."

New info shows methane emissions from existing sources in oil & gas sector are substantially higher than we previously understood. #CERAWeek

— Gina McCarthy (@GinaEPA) February 24, 2016

There's a financial incentive to plug those leaks, too: The nonprofit Environmental Defense Fund (EDF), which has raised alarms about those leaks before, estimates the value of that lost gas at $1.4 billion.

"The more that scientists learn about methane emissions in the oil and gas sector, the worse that picture gets — the bigger the problem appears to be," EDF spokesman Jon Coifman said. But it also gives regulators an opportunity to target a major source of greenhouse gases.

"Nobody has done anything serious about methane, which means there is a lot of low-hanging fruit out there," Coifman said. "We think there are relatively quick, relatively low-cost ways to put a big dent in emissions quickly."

Conley had been conducting aerial surveys of pipeline leaks for the California Energy Commission before being dispatched to monitor the Aliso Canyon leak. He said the disaster highlights the need to find and plug those leaks, big or small.

"In all likelihood, this failure didn't just happen overnight," he said. "It's very likely that had people been watching the emissions rate from this underground storage facility for years — let's say you went once a month — I would suspect that it wouldn't be unlikely that you'd have seen an upward trend over the last few months."

There are about 400 reservoirs similar to Aliso Canyon across the United States. Many of them — like Aliso Canyon — are old oil wells that have been turned into storage facilities. Utilities and regulators should be "looking for trouble before it happens," upgrading infrastructure and sniffing out leaks before they become disasters, Conley said.

"It's not a very big cost, but it could certainly be a very big savings if you could prevent another 5 billion cubic feet of methane from escaping into the atmosphere," Conley said. But whether there's a public will to pay for that work, "That's the question I don't know."

Related: Obama Tells Oil and Gas Companies to Get a Grip on Methane Emissions

Follow Matt Smith on Twitter: @mattsmithatl