Emergency officials have lifted an evacuation order for some of the tens of thousands of people who live near a damaged tank containing a hazardous chemical in Southern California. The decision came after temperatures inside the tank fell enough to eliminate the risk of a catastrophic explosion.
Current Situation at GKN Aerospace Plant
While there is no longer a risk of a major explosion at the GKN Aerospace Transparency Systems plant in Garden Grove, there remains a possibility of a smaller blast or a fire, Orange County Fire Authority division chief Craig Covey said during a news conference on Monday. An overnight evaluation of the tank containing 6,000 to 7,000 gallons (22,700 to 26,500 liters) of highly flammable methyl methacrylate showed a reduction in pressure inside the tank thanks to a crack discovered Sunday. About two-thirds — roughly 34,000 — of the evacuated residents can now return home, Covey confirmed.
“It’s not over yet. We still have work to do,” Covey said. “We still have to mitigate a fire and very small explosion concern, and also a spill potential.”
Evacuation Timeline and Safety Measures
Officials began ordering residents of Garden Grove, near Los Angeles, to evacuate their homes on Thursday after the tank overheated. By the weekend, about 50,000 residents had been told to leave. Authorities said they needed to cool the tank to prevent a toxic leak or explosion. The tank’s interior had cooled to 93 degrees F (33.9 degrees C) on Monday, down from 100 degrees (37.7 degrees C) a day earlier.
Orange County Health Director Regina Chinsio-Kwong reassured returning residents that they can feel safe. Exposure to methyl methacrylate can cause serious respiratory problems, neurological issues, and irritation to the skin, eyes, and throat, according to the federal Environmental Protection Agency. “There was no contamination. There were no fumes. There were not vapors that came from this incident,” she said at the news conference. “There was not a leak. So you should feel comfortable going home even if you’re across the street from that new zone line.”
Environmental Risks Remain
The tank may eventually cool enough for crews to safely stabilize and drain the remaining material without triggering a spark or ignition, said Andrew Whelton, a Purdue University engineering professor who has studied environmental contamination. Whelton cautioned that there is still some risk of an explosion while the chemical inside the tank remains hot and reactive. He said temperatures need to fall closer to ambient levels — roughly 60 to 70 degrees Fahrenheit (15.6 to 21.1 degrees C) — before conditions are considered significantly safer.
As the interior temperature of the tank increased, methyl methacrylate — used to make plastics — converted from liquid to gas, ramping up pressure and the risk of explosion, Whelton explained. Some of the methyl methacrylate may already have hardened into a stable plastic similar to plexiglass, reducing the risk inside the tank.
Orange County Supervisor Janet Nguyen said the South Coast Air Quality Management District will monitor the air for several months, and the EPA will check the sewer and storm drains. County health officials have stated that the chemical is easy to smell and people may notice it over a large area without being harmed.
Relief Among Residents
Authorities have not defined what a catastrophic explosion might mean, but said Monday that the worst-case scenario is off the table. Kim Yen, a retiree who had to evacuate her Garden Grove home, said she has been closely following the news and is relieved to learn that the worst has passed. “I am happy and many of us are happy but, still, we are still on our evacuation,” she said. Yen, who lives two blocks from the plant, said she is ready to return home but first wants to be sure it is safe. She also expressed concern for the emergency crews: “They are really our heroes.”
The parking lot was full Monday at a large park in Fountain Valley, just southwest of Garden Grove, as people sought refuge in an ad hoc shelter or pitched tents outside. Others gathered in the park to enjoy Memorial Day.
GKN Aerospace Response and Background
GKN Aerospace Transparency Systems, which owns the plant, is a British company that makes cockpit windows, canopies, and windshields for military and commercial aircraft. GKN Aerospace technical specialists and the Orange County Fire Authority removed external insulation material from the tank to help cool its contents, according to a GKN Aerospace statement released Monday. “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 statement said.
GKN Aerospace employs about 16,000 people across 32 manufacturing sites in 12 countries and supplies technologies and components used by major commercial and military aircraft manufacturers worldwide. It remains unknown when the operation will reopen. GKN Aerospace agreed in 2025 to pay state regulators more than $900,000 to settle violations involving recordkeeping, permitting issues, and nitrogen oxide emissions, according to a report on the South Coast Air Quality Management District website.
Impact on Aircraft Manufacturing
Disruptions at facilities producing specialized aircraft components can be difficult for the global aerospace industry to absorb because supply chains are highly concentrated and already strained, said Richard Aboulafia, managing director of the aerospace consulting firm AeroDynamic Advisory. Aboulafia noted that aerospace manufacturing differs from many other industries because aircraft production rates are relatively low, leaving only a small number of suppliers for many specialized parts and systems. “There’s just not a lot of margin in the system,” he said.
