https://arstechnica.com/information-technology/2018/06/in-california-natural-gas-availability-still-an-issue-3-years-after-major-leak/

In 2015, one of 115 natural gas storage wells at the Aliso Canyon storage facility in Southern California started leaking methane, an extremely potent greenhouse gas. The leak took months to seal, becoming the second largest methane leak in US history but likely the most environmentally damaging methane leak in US history due to the fact that none of the methane combusted before being released to the atmosphere.