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Los Angeles Just Saw the Worst Methane Leak in US History

At one point, the Porter Ranch leak doubled the LA basin's total methane emissions

Los Angeles has no shortage of honors to hang its hat on. It's the entertainment capital of the world, the second largest city in the nation, and even the only city in North America to host the Summer Olympics twice. And now Los Angeles can lay claim to the worst methane gas leak in the history of the United States, reports PBS.

More methane escaped Southern California Gas Company's leaky SS25 well at its Aliso Canyon storage facility over the last few months than any other methane leak in America. Sure, other gas storage fields around the country have also leaked in the past, some even had larger daily emissions of methane than Aliso Canyon, but what gives LA's leak the edge is how long it took to fix the problem.

At its worst point, the methane emissions rate for the entire LA basin had doubled.

SoCal Gas first detected the leak on October 23 (though no one found out for quite a while), and was not able to plug it for almost four months, only finally declaring the well dead on February 18. In the first few weeks of the disaster, 53 metric tons of methane was being released every hour. At its worst point, the methane emissions rate for the entire LA basin had doubled. Over the course of the entire ordeal, 97,100 metric tons of methane were released into the atmosphere from the faulty well, the emissions equivalent of burning a little over 900 million gallons of gasoline.

That's a pretty awful four months for the atmosphere, but there are long-term ramifications as well. According to the Environmental Defense Fund, methane gas "carries 84 times the warming power" of carbon dioxide in the first few decades after it's released, so it's an environmental disaster that LA County will be living with for years to come.

Then there's the benzene. Methane itself isn't deadly to humans, but it does contain trace amounts of benzene, a known carcinogen. When the South Coast Air Quality Management District studied the air in Porter Ranch on November 10, they found benzene levels at 3.7 parts per billion. That's seven times the normal amount of benzene in LA's atmosphere. At the leak itself, benzene levels were 10 times higher than normal.

Not everyone agrees on the effects of exposure to this level of benzene. The World Health Organization says no exposure to benzene is safe, while California's EPA says chronic exposure to benzene levels at 1 part per billion can be considered hazardous. South Coast Air Quality Management District, the group that did the air quality study, is less alarmed—they say the cancer risk in the area was raised by "less than two people in a million" as a result of the leaking well.

Whatever the risk, many residents of the nearby Porter Ranch neighborhood who were displaced by the disaster have returned or will be returning to their homes shortly. February 25 (Thursday) was supposed to be the last day SoCal Gas would pick up the tab for hotel stays, pet boarding, and mileage reimbursement for residents who relocated to escape the noxious gas fumes of the Aliso Canyon leak (and the headaches and nausea that accompanied them).

When the well was officially declared offline on February 18, residents were given just eight days to return to the houses they fled, though LA County Supervisor Michael Antonovich felt more time was needed to assess air safety in Porter Ranch. Antonovich was fighting for a 30-day timeline for Porter Ranch residents to return home.

Late in the day on Thursday, Antonovich got his wish. According to the LA Times, a Los Angeles County Superior Court judge ordered a 22-day extension for relocated residents that would have SoCal Gas continuing to pay their housing costs until March 18. One small hitch, though, is that those already checked out of their hotels are no longer eligible—about 2,000 displaced residents have already moved back home, since Thursday was the deadline, and the county's court filing says some that moved back are reporting that their nausea and headaches have already returned.

SoCal Gas is certainly not thrilled with the judge's ruling. They're saying the original eight-day window for relocating residents had already been fully negotiated with the city, and Thursday's "last-second ruling...upends this collaborative process." The objection is no surprise, as it adds a substantial unexpected cost to an already expensive environmental disaster. SoCal Gas had been shelling out around $2 million each day to keep 3,400 households in hotel rooms during the leak. The company is says the 22-day extension is "tantamount to an award of millions of dollars of damages" (and for only the small crime of creating the largest methane leak in history next door).

The county isn't budging. Deborah J. Fox, attorney for the county, acknowledges that it will be costly, but that's just the price SoCal Gas has to pay to "do the right thing" for Porter Ranch.