Southern California authorities extended evacuations into the Memorial Day weekend for about 40,000 residents after a pressurized chemical tank at a company site in Garden Grove overheated and began venting vapors, officials said, with no injuries reported. The evacuation order, initially issued for parts of Garden Grove, was expanded to some areas of several nearby Orange County cities, leaving families and residents waiting for updates and uncertain timelines for when they could return home.
Orange County Fire Authority said the incident began Thursday when the tank overheated and started to vent vapors at a company site about 40 miles (60 kilometers) south of downtown Los Angeles. Officials said firefighters were monitoring for changing conditions while they tried to prevent a leak or an explosion that could spread the chemical over a broader area.
Craig Covey, an Orange County Fire Authority division chief, said the tank’s valves were “broken or gummed up,” which prevented crews from removing the chemical or relieving the pressure on the tank. Covey said firefighters’ first hope was to cool the chemical inside the tank so it would not leak or explode, but he also acknowledged that there was no guarantee the tank would not breach and release material.
Planning during the holiday period also involved preparations for how to limit the consequences if a release occurred. Covey said drones were monitoring temperatures at 10-minute intervals and that officials were planning to keep any possible leak from reaching waterways or the ocean, and said containment barriers had been set up to prevent the chemical from getting into storm drains, creeks or the nearby ocean in the event of a spill.
As crews assessed their strategy, Covey later said the temperature readings complicated early assumptions about whether the tank was cooling. He said a reading conducted by drones showed the temperature on the outside of the tank, not the inside, and he reported that the temperature was 90 degrees, up from 77 Fahrenheit (25 Celsius) the previous morning.
The chemical in the damaged tank was methyl methacrylate, which officials said is used to make plastic parts at GKN Aerospace. The tank held between 6,000 and 7,000 gallons (22,700 and 26,500 liters) of the chemical, and health officials said it is easy to smell, meaning residents might notice vapors over a large area without necessarily being harmed.
Orange County health officials said exposure could cause serious respiratory problems and could even render someone unconscious, and that the chemical can also cause neurological problems and irritate the skin, eyes and throat. Purdue University engineering professor Andrew Whelton said many effects would be acute and fast-acting, but that longer contact could increase the potential for significant damage.
Whelton also described firefighting concerns if the tank’s temperature and pressure continued to rise, noting that pressure relief valves on the tank were no longer working and that methyl methacrylate can change from a liquid to a gas as conditions worsen. He said it would be best if the tank sprang a leak so the chemical could be mostly contained, but he cautioned against attempts to create a hole because of fears a spark could ignite the volatile and flammable gas.
Officials said that if there were an explosion, they expected “severe structural damage and significant harm” in the blast zone closest to the tank, and Whelton said any event that released methyl methacrylate into the air would require detailed air monitoring specifically for that chemical rather than generic tests used in some other incidents. Whelton said general tests often completed with handheld detectors might not detect the chemical, and that officials could need indoor testing before residents returned home; he compared the planning to what he studied during a 2023 train derailment in East Palestine, Ohio, involving the release of vinyl chloride.
Residents in the affected area said the evacuation stress continued through the weekend. Marco Solano, 32, spent Friday night at his parents’ home while monitoring news to see if he could return, and he said he did not believe dangerous chemicals should be in a neighborhood setting where evacuation becomes necessary. Solano said he felt very tired and weak and believed the stress of the chemical leak was worsening his anemia and ulcerative colitis, and he also said he was worried about neighbors who remained in their apartments after he went to retrieve belongings.
Authorities said state support was activated as the evacuation extended. Gov. Gavin Newsom declared a state of emergency in Orange County, making state resources available to local agencies and allowing the use of state-owned properties and fairgrounds for shelters if needed, while several shelters remained open Saturday, including at high schools.