For more than 100 days in 2015 and 2016, gas leaked out of the Aliso Canyon Natural Gas Storage Facility near Los Angeles — the largest known leak of methane in United States history. More than 8,300 households were evacuated, and people exposed to the gas reported nosebleeds, dizziness and respiratory problems.
This week, California regulators said they now knew why the environmental catastrophe happened.
In a 258-page report, investigators said that groundwater had corroded the metal lining of a more-than-50-year-old underground well, leading to its rupture at 892 feet below ground. The report also said that SoCalGas, the company that owns and operates the natural gas well, did not meaningfully investigate or analyze more than 60 previous leaks at the complex. The company did not properly monitor its wells at the site, the report said, adding that “the approach to well integrity at Aliso Canyon had been reactive rather than proactive.”
In a statement on Friday, SoCalGas said the report “marks an important milestone in helping the region and California move forward from the Aliso Canyon natural gas leak.” The company said that it had addressed “most, if not all” of the causes of the leak identified in the investigation, which was conducted by a private company, Blade Energy Partners, at the request of California regulators.
“In Blade’s opinion, there were measures, though not required by the gas storage regulations at the time, that could have been taken to aid in the early identification of corrosion and that, in their opinion, would have prevented or mitigated the leak,” SoCalGas said in its statement. “We look forward to reviewing the report in detail and to receiving the supplementary reports, so we can better understand the technical basis for some of Blade’s conclusions.”
To Matt Pakucko, who evacuated his nearby home in the Porter Ranch neighborhood during the leak and is suing SoCalGas, the report’s findings were validation of his long-held suspicion of the site and its possible environmental and health risks. Mr. Pakucko is president of Save Porter Ranch, an activist group he founded. It has been scrutinizing the Aliso Canyon site since before the 2015 leak.
“We’re shocked,” he said. “We were expecting a whitewash. For this to come out like this, it’s like ‘Hallelujah!’”
The Aliso Canyon rupture has led to state reforms dictating how natural gas wells are regulated statewide. State officials are currently conducting a separate investigation into SoCalGas’s compliance with regulations that could eventually lead to penalties for the company.
The natural gas storage field is more than 20 miles northwest of Los Angeles. The well that leaked was initially drilled in April 1954 as part of an oil field that had been depleted. Since 1973, the wells have been used to store natural gas.
The leak itself began on Oct. 23, 2015, and it emitted about 100,000 metric tons of methane, state regulators said.
The leak was eventually plugged and the storage site was temporarily shut down until state regulators determined in 2017 that it was safe to reopen, though at a “greatly reduced capacity,” regulators said.
In September 2016, SoCalGas reached a $4 million settlement with state prosecutors, in which the company pleaded no contest to a misdemeanor charge of failing to immediately report the gas leak.
Victims of the leak, however, have appealed the settlement, said Patricia Oliver, a lawyer representing them. Depending on what the appellate court decides, she said, the case could be reprosecuted.
There are also more than 36,000 other people suing the company in civil court, Ms. Oliver said. She said that the report released this week supported those cases by describing negligence that lasted over several years.
“It definitely opens up a lot of questions,” she said.