Today in History: State of Emergency Declared During Largest Methane Leak in U.S. History

by M.C. Millman

On January 6, 2016, the  Governor of California, Jerry Brown, declared a  state of emergency over a methane gas leak on the outskirts of Los Angeles.

The 112-day leak came from a well blowout at an underground natural gas storage facility in Aliso Canyon. The leak was discovered on October 23, 2016, when workers found a seven-inch casing in one of those wells had ruptured. Due to the break, the well was pouring methane into the atmosphere at a peak rate of 60,000 kilograms per hour. But it wasn't until a few months later, on January 6, after the invisible leak led residents to flee the area after reporting symptoms such as headaches and nausea, that the governor declared a state of emergency. 

The final estimate is that one hundred thousand tons of methane, a greenhouse gas more harmful than carbon dioxide, spewed into the air, equivalent to annual emissions from half a million cars. The amount of methane leaked over the 112 days was equal to one-quarter of all methane pollution from every other source in Los Angeles for the year. The sheer amount of gas leaked led to the event being declared the largest methane leak in U.S. history.

To measure the output and the contents of the leak, scientists flew an airplane equipped with sensors through the plume of natural gas thirteen times. From the first flight through the plume, the sensors showed twenty times larger measurements than any other methane leak. This led to a declaration that the leak had added 25 percent to California's daily methane output.

The leak was finally plugged on February 18, 2016, allowing residents to return to their homes and state lawmakers to figure out where to go from there.