In California, where the environment is already endangered by severe drought, a natural gas leak has quietly released enough methane to create as much impact on the atmosphere as up to 2.9 million metric tons of carbon dioxide emissions. The California Air Resources Board issued a statement this week containing that estimate, which comes one month after the initial leak was reported. The size and extent of the leak is enormous, and the 20-year warming impact is said to exceed that of all the state’s oil refineries combined, or of burning 300 million gallons of gasoline.

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The leak was first discovered at Southern California Gas Company’s Aliso Canyon storage facility on October 23. Initially, the utility company tried plugging the leaky pipe casing, which was a few hundred feet below the well’s surface. The attempt failed, so the repair will require a hefty construction job involving drilling a separate ‘relief well’ to reach the source of the leak. It will end up taking months to complete.

Related: Abandoned oil and gas wells are leaking methane across the USA

In addition to the long-term impact on global warming, the leak is having an immediate impact on local residents. Methane has been detected in the Porter Ranch neighborhood in the affluent San Fernando Valley, which had previously been known for having some of the cleanest air in the city. For the past several weeks, residents there have reported a variety of ailments, including headaches, nosebleeds, and nausea. Until the leak is fully repaired, the air quality in the area will continue to suffer, so it may be several months before it returns to normal. The Los Angeles Daily News reports that at least 30 families have been relocated, and protesters are calling for county leaders to investigate the leak.

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The statement issued by the California Air Resources Board reports that, from October 23 to November 20, the Aliso Canyon gas leak pumped 50,000 kilograms of methane into the air every hour. The gas emanating from the leak adds up to one-quarter of the total methane emissions in all of California. The agency also found that 0.8 million metric tons of carbon dioxide has leaked from the site, which is the equivalent of driving 160,000 cars for a year or consuming 90 million gallons of gasoline.

+ California Air Resources Board

Images via Wikipedia and Gene Blevins/Los Angeles Daily News