On an evening 10 years ago, Porter Ranch resident Matt Pakucko stepped out of his music studio and was walloped by the smell of gas — like sticking your head in an oven, he recalled.

Pakucko called the fire department. It turned out crews had already been up to the Aliso Canyon gas storage facility in the Santa Susana Mountains behind the neighborhood, responding to a report of a leak. Many of his neighbors were beginning to feel ill, reporting issues such as heart palpitations, vomiting, burning eyes and bloody noses.

“I swear I thought I was standing behind a 747 with its engines blowing — it was not just gas, it was oil smell, it was chemical smell that permeated,” recalled Pakucko, who went on to co-found the advocacy group Save Porter Ranch. “I couldn’t stay out there for 30 seconds. It tasted like f— gasoline.”

Soon it was clear that this wasn’t just a leak — it was a blowout. Over the course of 112 days, the Aliso Canyon facility would spew an estimated 120,000 tons of methane and toxic chemicals into the atmosphere. It was the worst natural-gas well blowout in U.S. history, and an environmental disaster whose effects will be unpacked for generations.

The event was widely seen as a wake-up call to the dangers of methane and underground natural gas storage. Methane, a planet-warming greenhouse gas, is about 80 times more potent than carbon dioxide and is responsible for about a quarter of all the human-caused climate change we are experiencing. A study published by UCLA researchers last month found that women in their final trimester of pregnancy who were living within 6.2 miles downwind of the blowout in 2015 had a nearly 50% higher-than-expected chance of having a low birth-weight baby.

The blowout ushered in a wave of new regulations to strengthen the governance of natural gas storage facilities in California and the United States, as well as new tools and technology to monitor methane emissions.

But 10 years later, some Porter Ranch residents say the wounds still feel fresh, and too many promises have been broken. After the disaster, then-Gov. Jerry Brown called for the permanent closure of Aliso Canyon by 2027 — a goal his successor, Gavin Newsom, called a top priority and vowed to meet even sooner.

Instead, Aliso Canyon remains open, with regulators voting in December to continue using the facility for years — probably into the 2030s — citing the need for natural gas to help maintain affordable energy rates and grid reliability in California.

The facility is a key asset for Southern California Gas. In an emailed statement, the company said the state would struggle to meet electricity demand without Aliso Canyon’s storage. The site fuels 17 power plants and helps keep the lights on during the hours that can’t yet be met by solar, wind and other renewable resources, the company said. Natural gas still represents about 40% of the state’s electricity supply.

“There’s a lot of work to do to get off natural gas and oil in California,” said Adam Peltz, senior attorney with the nonprofit Environmental Defense Fund. “That work is underway, but it’s not complete. If you’ve built an economy on fossil fuels, it takes awhile to get off of it.”

Aliso Canyon was originally drilled as an oil field in the late 1930s before SoCalGas converted it to natural gas storage in the early 1970s. Utilities often use played out crude oil fields as places to pump gas downward under pressure and hold it until it is needed.

Aliso Canyon is one of the largest natural gas storage facilities in the U.S.

In the lead-up to the blowout, SoCalGas was filling the site in preparation for the winter heating season. Crews were using tremendous force to pump gas down a well that was more than 60 years old. But a metal casing on well SS-25 had corroded, and gas began blowing out at very high volumes.

Methane is not visible to the naked eye, but aerial images captured with infrared cameras and released by the Environmental Defense Fund showed a geyser-like eruption of the flammable, climate changing gas — making it clear to the whole world the magnitude of the disaster.

Matt Pakucko, right, founder of Save Porter Ranch, and other protesters against SoCalGas hold a rally at the intersection of Tampa Avenue and Rinaldi Street on Sept. 28, 2021, in Porter Ranch.

(Irfan Khan / Los Angeles Times)

It took nearly four months for crews to stop the leak. By that time, damage was done. More than 8,000 households were temporarily displaced, businesses were shut down, and two schools were relocated for several months.

Researchers are still working to unpack the health outcomes of the event. SoCalGas, meanwhile, has paid about $2 billion in settlements and agreed to operate the facility at a lower maximum pressure.

Officials with the gas company said they have shored up the facility, including replacing the inner steel tubing on all operating wells and conducting continuous ambient methane monitoring. All wells at the site are subject to real-time pressure readings and visual inspections four times a day, among other protocols, SoCalGas said.

“Over the past 10 years, SoCalGas has conducted comprehensive safety reviews and implemented multiple safety layers that protect one of California’s most important assets for energy reliability and affordability,” the company said.

While the maximum allowable operating pressure at the site remains reduced — about 3,183 pounds per square inch compared with 3,600 pounds per square inch in 2015 — state officials recently voted to let SoCalGas increase storage at the facility to 68.6 billion cubic feet of natural gas from 41 billion cubic feet, outraging many in the community.

But experts say there are silver linings to the disaster. California overhauled its underground natural gas storage regulations to make them the strongest in the nation and among the strongest in the world, according to Peltz, of the Environmental Defense Fund. The changes include more thoughtful rules for well construction, better monitoring and risk management, and improved planning and emergency response.

Congress reacted to the disaster by requiring its regulatory agency, the Pipeline and Hazardous Materials Safety Administration, to issue safety standards for natural gas storage nationwide. In 2016, it adopted best practices recommended by the American Petroleum Institute, which were strengthened at the beginning of this month.

Many states with natural gas storage previously had no regulations at all, Peltz said.

“On a national basis, the systems will be safer as a result of that change,” he said.

There have been technological advancements too. The infrared aerial recording of the leak captured in 2015 was a relatively new technique at the time, but has now become commonplace. The California Air Resources Board conducted its first large-scale statewide aerial methane survey in 2016, identifying many of the largest methane sources in the state.

There have also been considerable advancements in the ability to observe methane super-emitters through satellites and remote sensors, according to Seth Shonkoff, executive director at the science research institute PSE Healthy Energy and an associate researcher at the UC Berkeley School of Public Health.

“The rub is that we know more than we ever have, and we’re perhaps controlling more than we would have if we didn’t have the technology to see them, but we’re still seeing more and more of these large-scale emission events all across the United States and all across the world,” he said.

Methane concentrations in the atmosphere are still rising. It is streaming, often constantly, from facilities associated with the oil and gas industry, landfills and dairy farms, among other sources.

The Aliso Canyon Southern California Gas storage facility on May 28, 2020.

(Robert Gauthier / Los Angeles Times)

Methane isn’t the only concern either. Researchers now have a better understanding of what’s in the gas that blew from Aliso Canyon and that continues to be stored in natural gas facilities around the country. Although it is primarily composed of methane, roughly 99% of samples analyzed by Shonkoff and his team have contained hazardous air pollutants such as benzene, hexane and toluene, largely as a result of commingling with depleted oil and other subsurface materials.

Moving forward, he said, it will be critically important for gas companies to disclose to regulators and risk managers what their gas is composed of, so that if it leaks, responders can quickly determine the appropriate response.

“If we had had that with Aliso Canyon, we could have, within a matter of hours, understood whether people should get out of the way or stay inside, and we wouldn’t have had as many people suffering from health symptoms,” Shonkoff said.

In 2024, the Biden administration passed the first comprehensive rules to limit methane pollution by fining oil and gas developers for excessive emissions. But this year, the Trump administration revoked the rule, which it described as a tax.

At the same time, many natural gas storage facilities across the country are old and require retrofitting to meet current regulations, but such upgrades can be slow and expensive — often leaving ratepayers on the hook.

Residents near Aliso Canyon have also long feared an earthquake or wildfire in the area. The gas field sits along the Santa Susana fault and is in a high fire hazard severity zone. SoCalGas says it has numerous safety plans and procedures in place.

Perhaps the greatest tension remains between those who wish to see Aliso Canyon shuttered and the officials who say the facility is critically important to California’s energy supply, which is increasingly trying to serve power-hungry artificial intelligence data centers.

Dozens of Porter Ranch protesters chant “shut it all down,” as they demonstrate at the Aliso Canyon gas storage facility in Porter Ranch on May 15, 2016.

(Francine Orr / Los Angeles Times)

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California has committed to reaching 100% carbon neutrality by 2045. But SoCalGas says it still needs Aliso Canyon.

“SoCalGas is aligned with the state of California in pursuing the technologies and infrastructure that supports California’s climate plan, including clean renewable hydrogen and renewable natural gas, that could, over time with other renewable energy projects, deliver the reliability and affordability Aliso Canyon supports today,” the utility said in a statement. However, any decision to reduce or eliminate operations at Aliso Canyon must be based on genuine reduced demand that is permanent, the company said.

Pakucko, of Save Porter Ranch, noted that the facility was offline for two years after the blowout without an interruption in service.

“Two years!” he said. “And guess what? We managed without the facility.”

For others in the area, it feels like the latest in string of broken promises.

Among SoCalGas’s settlement agreements was a $120-million consent decree with the state of California requiring the utility to fund methane mitigation projects, air monitoring and other initiatives to address alleged harms caused by the blowout. About $25 million of that went toward a long-term health study on the effects of natural gas exposure, which is being conducted by researchers at UCLA. The results are eagerly awaited.

About $26 million went to a program for dairy digesters in the Central Valley, which capture methane from cow manure before it enters the atmosphere. Many had hoped those funds would be spent closer to home, including former L.A. Mayor Eric Garcetti, who at one point envisioned the mitigation money being used to transform Porter Ranch into a net-zero community.

“That would have been so great,” said Patty Gleuck, a Porter Ranch resident who served on the community advisory group for the health study. Instead, “that money went to this dairy digester program that does not benefit this area.”

Like Pakucko, Gleuck recalled suffering health effects during the blowout, including a tightness in her chest and a metallic taste in her mouth that dissipated when she left the area and resumed when she returned.

She still suffers from a chronic cough and uses an inhaler, she said, adding that “a lot of inhalers were prescribed in the area.”

“A lot of people moved away, taking a loss on their homes because they were so sick, or their family members were sick,” she said. “I just don’t think that there has been justice.”