According to the final estimates from the California Air Resources Board, the leak emitted 109,000 metric tons of methane from late October 2015 to mid-February 2016, which is about the equivalent of the carbon dioxide emissions released from burning over 1 billion gallons of gasoline.
SoCalGas, which operates the Aliso Canyon natural gas storage facility, will be required to mitigate the climate impacts of the leak by funding projects that reduce methane emissions by an equivalent amount.
“This was the largest methane leak in the history of the state and CARB is determined to ensure that the environmental damage caused by this potent greenhouse gas is fully addressed and mitigated by the Southern California Gas Company,” said CARB chair Mary D. Nichols in a statement.
Also last week, the federal Interagency Task Force on Natural Gas Storage Safety, established in the wake of the leak, issued a new report intended to reduce the risk of future such incidents. The report analyzes 400-plus underground natural gas storage wells in the US and provides 44 recommendations to industry, federal, state and local regulators.
Following the Aliso Canyon leak, the facility was temporarily closed and the California legislature passed a law requiring strict new safety procedures for the state’s 14 underground gas storage facilities.
The leaking well was permanently sealed in February. In an Oct. 19 statement, SoCalGas said 27 storage wells at the facility have passed all of the tests required by the California Division of Oil, Gas, and Geothermal Resources. Additionally, the inner tubing of every approved well has been replaced with more than 40 miles of new steel piping. The remaining wells have been either temporarily sealed or permanently plugged and taken out of service.
“The company continues to make significant progress towards completing the Comprehensive Safety Review required by California’s Division of Oil, Gas, and Geothermal Resources,” SoCalGas said.
But according to an Environmental Defense Fund blog, not enough has been done to prevent future blowouts at Aliso Canyon or similar facilities in more than 30 states. California’s proposed laws in response to the leak will likely be the most comprehensive in the US, but other states — and the federal government — should review their regulatory efforts, the blog says.