Thousands still evacuated near Southern California chemical tank despite eased explosion fears
SANTA ANA, Calif. (AP) — A crack relieved pressure in an overheated chemical tank in Southern California and averted a catastrophic explosion, but it's still not safe enough for 16,000 people who live closest to the aerospace plant to go home, authorities said Tuesday.
The crisis forced 50,000 people to evacuate in the Orange County city of Garden Grove last week. Most returned home after the crack formed over the Memorial Day weekend but the risk of a small explosion or potential spill kept a third of the evacuation orders in place.
Exposure to methyl methacrylate — a highly flammable chemical used to make plastics — can cause serious respiratory problems, neurological problems and irritation to the skin, eyes and throat, according to the federal Environmental Protection Agency. The tank contains 6,000 to 7,000 gallons (22,700 to 26,500 liters) of the chemical.
Crews worked overnight at the GKN Aerospace Transparency Systems plant to ensure two nearby tanks were neutralized and would not be affected by the compromised tank, Orange County Fire Capt. Brian Yau said, adding that material from one of these two tanks was transferred to another that has a neutralizing agent.
It's unclear what caused the tank to overheat. Crews were able to stop spraying cooling water on the tank once the interior temperature stabilized to 92 degrees F (33.3 degrees C), down from 100 degrees (37.7 degrees C) over the weekend, the fire department said Tuesday. The sprinkler system at the facility continues to douse the tank, and the company said its technical specialists and firefighters removed insulation from the tank to help cool it.
Health officials sought to reassure people that it was safe to go home.
“There was no contamination. There were no fumes,” Orange County Health Director Regina Chinsio-Kwong said at a Monday news conference. “There was not a leak. So it should be, you should feel comfortable going home even if you’re across the street from that new zone line.”
Isabel Mendez, 34, on Tuesday still wasn’t allowed back to her Garden Grove mobile home as it’s too close to the plant. She was evacuated Thursday, then let back in overnight, and woke up to chaos outside Friday with authorities telling residents they had to get out immediately.
Mendez said she broke out in a rash on her face and had tingling lips and a sore throat while she was getting ready to leave. Her symptoms disappeared a few hours later. She spent the first few days at a hotel, which was expensive. She said she is now staying with her mother north of Los Angeles.
She hopes to return home soon but said she doesn't believe officials who have sought to assure people allowed back that it's safe.
“Of course it is still dangerous," she said.
Garden Grove Unified School District said last week it was shutting a dozen schools through what was supposed to be the last day of the school year on Wednesday but later said only three would remain closed Tuesday. It was unclear if they would reopen before the school year ends this week.
Garden Grove is next to Anaheim, home to Disneyland’s two theme parks, which were not under evacuation orders. Park officials said they were monitoring the incident and supporting employees impacted by the evacuations.
The South Coast Air Quality Management District will monitor the air for several months and the EPA will be checking sewer and storm drains for spills, Orange County Supervisor Janet Nguyen said.
As the tank heated up, the chemical converted from liquid to gas, ramping up the pressure and explosion risk, said Andrew Whelton, a Purdue University engineering professor who has studied environmental contamination. Some of the methyl methacrylate may already have hardened into a stable plastic similar to plexiglass, reducing the danger, he said.
The tank could eventually cool enough for crews to safely stabilize and drain the remaining material without triggering a spark or ignition, Whelton said.
However, he said there is still a risk of an explosion while the chemical remains hot and reactive. Temperatures need to fall closer to 60 to 70 degrees Fahrenheit (15.6 to 21.1 degrees C) before conditions are considered significantly safer, he said.
GKN Aerospace Transparency Systems makes cockpit windows, canopies and windshields for military and commercial aircraft. It employs about 16,000 people across 32 manufacturing sites in 12 countries, according to the company website.
“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 company said.
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.
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An earlier version of this story was corrected to attribute a quote to TJ McGovern, interim fire chief of the Orange County Fire Authority, not to division chief Craig Covey.
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Willingham reported from Boston. Contributing were Associated Press journalists Jamie Stengle in Dallas; Ethan Swope in Garden Grove, California; and Christopher Weber in Los Angeles.
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