For six days over a holiday weekend, a chemical tank in an Orange County aerospace plant threatened to explode, and more than 50,000 people had to leave while crews figured out how to stop it. The tank kept getting hotter. A valve in the tank’s cooling system had failed. Officials used drones to read the tank’s temperature from the outside. Ground crews set up an “unmanned ground monitor” — a portable water cannon — blasting water across the tank’s side.

At the height of the emergency at GKN Aerospace — which makes cockpit windows and shields for military aircraft in Garden Grove — officials feared the tank could explode. California deployed more than 700 people to the city, the governor’s office said.

The company’s tank cooled only after it cracked just enough to relieve pressure without unleashing a chemical explosion. By Tuesday night, the evacuations were lifted — but the questions remained.

The near-disaster exposed gaps among multiple regulatory systems that state and local agencies have not fully addressed.

Air quality regulators had flagged compliance problems years before the crisis. Prosecutors are investigating whether the company violated any laws. And community advocates and chemical-safety experts say residents still deserve a clearer accounting of what state and local regulators knew, what safeguards existed and why the tank came so close to catastrophe.

A history of violations

Even as GKN Aerospace worked to resolve environmental compliance notices, regulators and local planners began considering an expansion of the facility that would increase its capacity to manufacture components for military F-35 fighter jets.

The South Coast Air Quality Management District has inspected GKN three times in the last decade. For much of that time, the facility was classified as a “minor source” of emissions within the district’s permitting program, a designation that meant that regulators weren't required to inspect the facility frequently.

That limited oversight may have contributed to what records show was a yearslong compliance problem.

Those violations did not involve the problematic storage tank that holds methyl methacrylate, regulators said.

But in 2020, GKN self-reported certain issues that led South Coast air regulators to inspect the facility and review its records. The air district’s investigation found that the company was out of compliance with multiple rules stretching back to 2017. The facility, located within a mile of homes and schools, had failed to maintain required records about its emissions, was operating new equipment without permits and was using equipment that didn’t match the description in its existing permits, according to regulatory reports.

It took until April 2021 for the air district to issue a formal notice of violation, and until late 2024 for the agency to sign a settlement requiring GKN to pay more than $900,000. The company did not admit liability in the settlement, which resolved 14 alleged violations.

The district now treats GKN as a “major source” of emissions – a type of facility that the South Coast air district inspects yearly. A spokesman said that the company has applied for a more comprehensive permit, at the direction of regulators.

A community seeks answers

For Tracy La, the timeline told its own infuriating story.

“That delay and allowing GKN to operate with pretty much impunity has caused so many tens of thousands of residents of Garden Grove to pay for it,” said La, director of VietRISE, a nonprofit that supports Vietnamese and immigrant communities in Orange County. Displaced residents have had to pay for housing, replace medication, seek transportation and rack up other costs associated with evacuating their homes, she added.

“It's just frustrating that regular everyday people are constantly having to pay the price for our government officials unwilling to hold these powerful, rich corporations accountable,” La said.

Garden Grove is a cornerstone of Little Saigon, one of the largest Vietnamese American communities in the United States — a community that includes immigrants and refugees from the Vietnam War.

Some residents know methyl methacrylate not as an aerospace chemical but as a workplace hazard — one they spent years fighting to eliminate.

Lisa Fu directs the California Healthy Nail Salon Collaborative, which represents Vietnamese manicurists across the state. Her members waged a long campaign against the chemical, documenting its effects on workers' lungs, skin and eyes.

In 2015, the state banned the chemical from nail salons and cosmetology schools after workers flagged health concerns. Now the same chemical was leaking from a tank a few miles from Little Saigon. Fu says collaborative members and their neighbors reported nosebleeds, itchiness and the deaths of pet birds.

Air monitors deployed by the Environmental Protection Agency and the South Coast air district around the facility have shown pollution levels within normal ranges. But Fu said the gap between those readings and what residents experienced has deepened distrust of regulators and their enforcement record.

“You hear in the press conferences that there's no fumes, no vapors, no leak, no contamination,” Fu said. “They are saying it is safe. Safe for who? We believe the community when the stories don't stop coming.”

Community advocates are now asking Garden Grove city leaders to shut the facility down and adopt a moratorium on military manufacturing facilities and expansions in the city.

GKN has an application for a more comprehensive permit under consideration at the South Coast air district, and the public may soon have the opportunity to weigh in. A district spokesperson told CalMatters it had aimed to release the permit for public comment by year’s end, but the timeline may shift because of the emergency.

A potential chemical safety gap

California's toughest accidental-release prevention rules do not cover the chemical that nearly exploded in a Garden Grove tank and forced 50,000 people from their homes.

Methyl methacrylate is a volatile compound and one of the most widely used chemicals in plastics manufacturing. Officials feared the GKN tank would rupture as the liquid overheated, spilling thousands of gallons of chemicals or even exploding.

“It’s like a soda can that you left in your car in the middle of a hot summer,” said Andrew J. Whelton, a Purdue University environmental engineering professor. “The pressure built up within the can exceeds the capacity of that metal can.”

When the tank started overheating, it triggered a chemical reaction that responders could not stop — in part because the reaction had “gummed up” the valves they needed to inject a neutralizing agent, Orange County Fire Authority Division Chief Craig Covey said at a May 22 press conference.

Methyl methacrylate is not a regulated chemical under either the U.S. Environmental Protection Agency’s Risk Management Program or California's parallel system, known as CalARP. That may mean the tank was regulated under an alternate or lower-tier hazardous-materials program — leaving regulators with fewer tools to oversee its storage.

“If you’re living there — you’re a neighbor — can you go see what chemicals they have stored on site?” said Jane Williams, executive director of California Communities Against Toxics. “No, you can’t.”

The federal program’s chemical list has not added reactive chemicals to its list of covered chemicals, despite recommendations from the U.S. Chemical Safety Board, which investigates chemical accidents. The Trump administration aims to eliminate funding for the chemical safety board after October and proposes to roll back the 2024 Risk Management Program amendments that had begun to expand chemical safety requirements.

The same gap exists in California.

The California Environmental Protection Agency confirmed to CalMatters that methyl methacrylate is not a regulated substance under the state's Accidental Release Program.

Orange County health officials confirmed to CalMatters that GKN had a hazardous materials business plan on file — a lower-tier document listing chemicals stored on site — but no risk management plan. The agency said CalARP does not apply to the facility because methyl methacrylate is not a listed chemical under the program.

CalMatters also asked the California Division of Occupational Safety and Health whether worker-safety rules for high-hazard industrial processes applied at the facility — which would have made it eligible for the accidental release program under a separate pathway. The facility had been the subject of multiple workplace safety and health inspections before the tank emergency. Cal/OSHA did not answer that question by deadline.

Chemicals that fall outside federal and state accident prevention programs may also be left out of community emergency planning and drills, Williams said. That means nearby residents may not know what risks they face or how officials would respond.

GKN did not respond to written questions on deadline. In recent days, the company’s statements have emphasized gratitude for the community and first responders. “We recognize there is more work ahead,” said GKN Senior Vice President Steve Carlin, who oversees the Garden Grove site’s programs.

Angela Johnson Meszaros, an attorney for the environmental group Earthjustice, said neighbors to companies like GKN have every reason to think someone’s enforcing rules.

When something like this happens, people “get angry because they were like, ‘Wait, nobody was paying attention to this and now I'm sleeping on the sidewalk?’”

The system, she said, was built around the wrong goal entirely. “We have a system that's built on the notion of getting facilities to return to compliance, but we need to have a system that's about making sure facilities are operating in a way that is safe — and some facilities may not have a culture that allows us to put our lives into their hands.”

A district attorney may prosecute 

Whether any single institution will provide a comprehensive accounting of what went wrong is unclear.

The Orange County District Attorney’s Office has opened a criminal inquiry, spokesperson Kimberly Edds confirmed to CalMatters. Prosecutors sent letters to GKN ordering the company not to destroy or manipulate evidence.

At an anonymous tipline, the office is seeking information about the chemical release, the facility’s operations and the maintenance of the tanks and systems involved.

California law makes it a crime to knowingly or recklessly handle or store hazardous waste in a way that creates an unreasonable risk of fire, explosion, serious injury or death. Edds declined to say what areas of the law the investigation would cover.

In a similar case in 2024, Alameda County prosecutors indicted a scrap metal company after a fire exposed years of hazardous materials violations. They later said they could not prove their case beyond a reasonable doubt and dropped it.

On the regulatory side, no single agency has the task of producing a comprehensive account of the event. Rather than one joint review, each agency involved in the emergency will produce its own separate findings, released according to its own policies and timelines, said Brian Yau, a spokesperson for the Orange County Fire Authority.

Hazardous materials officials, air regulators, environmental officials and the company were developing a site cleanup plan, Yau said. On Friday, the fire authority handed over cleanup and remediation oversight to the county health care agency, said Greg Barta, a spokesperson for the fire authority.

Asked whether he was concerned about industrial facilities operating near dense residential neighborhoods, Gov. Gavin Newsom praised local and state first responders and said the state is reviewing the facility's safety records. Then he offered a candid assessment of the limits of state action.

“As it relates to industrial facilities in and around urban centers,” Newsom said at a press conference Thursday, “that’s a more challenging issue of geography.”

State Sen. Tom Umberg, a Democrat from Santa Ana, said there will be new proposed laws in response to the narrowly-averted disaster.

Williams, of California Communities Against Toxics, said the incident should force a broader look at California’s rules for hazardous industrial sites – not just at GKN, but at every facility storing chemicals that fall outside the state's toughest oversight programs.

“Everyone wants to return to normalcy as quickly as possible, because their nervous systems are all on fire, and the way in which you calm your nervous system is to be in your house and sit on the couch and hold your cat,” she said. “But in a situation like this — where you had a massive near miss — you really need to make sure that the safety systems that failed are not the only safety systems there at risk.”

This article was originally published on CalMatters and was republished under the Creative Commons Attribution-NonCommercial-NoDerivatives license.