Environment & Science

FAQ: SoCalGas has resumed injections at Aliso Canyon — What's different?

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Nearly two years after a massive leak forced its closure, the Aliso Canyon natural gas storage field near Porter Ranch has resumed operations. But the facility won't be able to operate as it did before the leak.

What is Aliso Canyon?

The Aliso Canyon gas field covers 3,600 acres in the Santa Susana foothills in the northern San Fernando Valley. It's dotted by more than 100 wells that used to be used to extract petroleum but were later repurposed to inject and withdraw natural gas. At the time of the leak, most of the wells were more than 50 years old.

The Southern California Gas Company, which owns and operates the facility, injects gas into a giant underground cavity that used to be a crude oil desposit. Gas stored there before the leak was held in reserve to even out shortages and gluts in gas supplies moving through the region's network of delivery pipes.

What happened?

In Oct. 2015, one of the gas wells at the facility ruptured, pouring about 109,000 metric tons of methane into the atmosphere over the next four months in the nation's largest-ever natural gas leak.

The leak caused nearly ten thousand families to leave their homes until the well was capped in February 2016.

After leak, the state ordered the gas level to be drawn down, and it placed a moratorium on refilling the field until extensive safety upgrades and inspections were completed.

An independent research firm is still analyzing the cause of the gas well break.

Why is Aliso Canyon re-opening now?

In July, two state agencies - the state Department of Conservation's Division of Oil, Gas and Geothermal Resources and the California Public Utilities Commission – gave SoCalGas the green light to reopen the facility. They confirmed the company had completed the required safety upgrades.

In an e-mail to residents of the Northern San Fernando Valley, SoCalGas said it must begin injections, "to comply with the CPUC directive to maintain sufficient natural gas inventories at Aliso Canyon to support the reliability of the region’s natural gas and electricity systems.

"The CPUC has reported 'delaying the resumption of injections after DOGGR completed its safety determination may itself pose a continued public safety and reliability risk to the Los Angeles Basin,'" the gas company said.

Now that injections have resumed, the company must do additional monitoring and reporting, including surveying for leaks and methane levels.

How have operations changed since the blowout?

The facility can now only be used, "as a last resort for reliability purposes," the Public Utilities Commission said.

The agency has capped the amount of gas that can be stored there. It says SoCalGas must keep the volume and pressure of gas at less than one-third of what it was in October 2015 when the gas well ruptured. 

At full capacity, the storage field can hold 86 billion cubic feet of gas. But under the new rules, the field can hold no more than 23.6 billion cubic feet. That's the amount state energy officials calculate is enough gas to avoid a shortage when demand peaks on the state's hottest or coldest days.

SoCal Gas can use Aliso Canyon only after all of its other storage facilities are at full usage and the company has taken steps to reduce or shift demand.

CPUC has told SoCal Gas it has to maintain maximum storage levels at its other facilities to meet demand in the Los Angeles Basin.

What else has changed at the facility?

One of the key changes was to limit how the gas moves in and out of the underground storage area

Previously, gas moved through the center tubing as well as the donut-shaped space between that tubing and the well casing. That is a method that, while not unusual in the gas industry, is not considered to be a best practice because that donut-shaped space is meant to be a secondary layer of protection against a leak or break in a gas well.

There are other new safety protocols: Sixty percent of the wells have now been taken out of operation, according to the PUC. The remaining active wells are now equipped with real-time pressure monitors.

Who's opposed to the re-opening of Aliso Canyon?

Los Angeles County officials tried unsuccessfully to block the re-opening of the facility, arguing that SoCal Gas had not sufficiently studied the risk of a catastrophic earthquake at the storage field.

The county argued DOGGR hadn't completed the required safety review because it hadn't done seismic testing to address and mitigate the risk of a huge earthquake rupturing multiple wells. They county also said a risk management plan, including a facility-wide emergency response plan, had to be in place before the facility could be deemed safe for operation.

The Aliso Canyon facility lies directly on the Santa Susana fault, and there are other faults nearby. The county says seismic experts agree there is a high probability – between 60 and 80 percent – of an earthquake 6.3 magnitude or greater within the next 50 years.

Activists who have been fighting to keep the facility closed expressed are disappointed.

"This is a significant setback, because it increases the potential for releases and for leakage," said Issam Najm, board president for the Porter Ranch Neighborhood Council. "However, by no means does it give them permission to go back to normal operations."

Is Aliso Canyon open for good now?

Gov. Jerry Brown has called for the eventual closure of the facility. State Energy Commission Chairman Robert B. Weisenmiller is prepared to work with the PUC and other agencies on a plan to phase out the use of Aliso Canyon within ten years, he wrote in a letter to PUC Commission chairman Michael Picker.