California Chemical Tank Threat Eases as Residents Go Home

Emergency officials have lifted evacuation orders for approximately 34,000 residents near a damaged chemical tank in Garden Grove, California, after a five-day crisis that threatened a catastrophic explosion. The Orange County Fire Authority (OCFA) confirmed Monday that the risk of a boiling liquid expanding vapor explosion (BLEVE) had been eliminated, though roughly 16,000 residents remain under evacuation orders as crews continue to monitor the tank.

The Incident

The crisis began on May 21 when a storage tank containing 6,000 to 7,000 gallons of methyl methacrylate (MMA) — a highly flammable chemical used in plastics manufacturing — overheated at the GKN Aerospace Transparency Systems facility in Garden Grove. The tank, which had a total capacity of 34,000 gallons, began off-gassing vapor, triggering one of the largest hazardous material evacuations in Southern California history.

Over the following days, the evacuation zone expanded to cover 9 square miles across six Orange County cities — Garden Grove, Anaheim, Buena Park, Cypress, Stanton, and Westminster — affecting up to 50,000 residents.

A Race Against Time

Firefighters faced an escalating emergency as the tank’s internal temperature rose steadily. By Sunday, the temperature had reached at least 100°F (37.7°C) — the maximum reading on the gauge — and a crack was discovered in the tank during overnight operations.

“That is what we were handed: a leaking tank or a tank that blows up,” OCFA Division Chief Craig Covey said during a May 22 press conference, as reported by Voice of OC. He warned that the potential for a catastrophic failure was unprecedented in his career.

Purdue University engineering professor Andrew Whelton, who has studied environmental contamination, provided a simple analogy for the crack discovered in the tank. “Think of a soda can. If you leave it in a hot car it can explode. But if you put a hole in the can, the product is released and the can itself doesn’t explode,” Whelton told The Guardian.

Breakthrough and Relief

The turning point came overnight on May 25 when a second all-night operation confirmed that the crack had relieved excess pressure, causing the internal temperature to drop to 93°F (33.9°C). OCFA Interim Fire Chief TJ McGovern announced: “The threat of a BLEVE has been eliminated.”

However, McGovern cautioned that the danger had not fully passed. “It’s not over yet. We still have work to do,” he said. “We still have to mitigate a fire and very small explosion concern, and also a spill potential.”

Orange County Health Director Regina Chinsio-Kwong reassured returning residents that they could feel safe. “There was no contamination. There were no fumes. There were not vapors that came from this incident. There was not a leak,” she said. “So it should be, you should feel comfortable going home even if you’re across the street from that new zone line.”

Government Response

California Governor Gavin Newsom declared a state of emergency for Orange County on May 23, and President Donald Trump signed a federal emergency declaration on May 25, unlocking federal assistance through FEMA. The response involved 785 state and local first responders, drones monitoring temperatures at 10-minute intervals, and 24 stationary air monitors deployed across the affected area.

Regulatory History and Legal Fallout

GKN Aerospace, a British company that has operated the Garden Grove facility since 1993, has a documented history of regulatory violations at the site. In January 2025, the company agreed to pay more than $900,000 to settle violations involving recordkeeping, permitting issues, and nitrogen oxide emissions with the South Coast Air Quality Management District, as reported by the New York Post. The company also faced OSHA violations in 2018, 2019, and 2022.

A class-action lawsuit was filed against GKN Aerospace on May 23 by affected residents, seeking damages for evacuation costs, property devaluation, and health risks.

What Remains

As of May 26, crews continue cooling and monitoring the tank. The remaining 16,000 evacuees cannot return until the risk of a smaller explosion or chemical spill is fully resolved. Air quality monitoring remains ongoing, and the Orange County District Attorney’s office has launched an investigation into the incident.

GKN Aerospace apologized for the disruption, stating: “We apologize for the ongoing disruption this incident is causing and our priority remains its safe resolution, so that residents can return to their homes as quickly as possible.”

The incident has raised broader questions about the storage of hazardous chemicals in densely populated urban areas and the adequacy of regulatory oversight at facilities with documented safety violations.