Tens of thousands of Southern California residents have been evacuated after officials warned a leaking chemical tank holding a «highly flammable» substance at an aerospace facility would inevitably fail and potentially explode.
The tank at GKN Aerospace is estimated to contain 7,000 gallons of methyl methacrylate, a «highly volatile» substance used in the production of plastics, according to Orange County Fire Authority incident commander Craig Covey. It is not clear when the tank will fail, Covey said.
Firefighters may have found a crack in the tank during an overnight operation at the facility, «which could potentially be relieving some of the pressure in there,» said Orange County Fire Authority interim chief T.J. McGovern on Sunday. He called the discovery «a step in the right direction.»
Later Sunday, McGovern said firefighters would be conducting another mission beginning Sunday night.
«It’ll be an all-night mission in order to confirm that the pressure in the tank has been released and that the BLEVE [Boiling Liquid Expanding Vapor Explosion] threat is eliminated,» he said. «The BLEVE threat is the worst-case catastrophic event that we’ve been talking about. We are not there yet.»
The Federal Emergency Management Agency is also responding to the leak. In an update early Sunday, the agency said a malfunctioning valve on the tank «remains unmitigated as the chemical reaction continues without a way to neutralize it.» Two other tanks at the facility have also been affected, but both were deemed «structurally sound» as of the update.
Roughly 50,000 residents of surrounding areas are under mandatory evacuation orders, according to FEMA.
McGovern urged people on Sunday night: «Please help us. Stay out of the evacuation zone. Let us run our operation.»
California Gov. Gavin Newsom declared a state of emergency for Orange County Saturday, saying he was «mobilizing every state resource available to support local responders and make sure the community has what they need to stay safe.»
Allen J. Schaben/Los Angeles Times via Getty Images 
Methyl methacrylate is a flammable substance that generates heat on its own. That means if it leaks into the atmosphere, any spark or flash could lead to an uncontrolled fire or explosion, said Elias Picazo, an associate professor of chemistry at the University of Southern California. At the moment, fire officials are working to keep the tank cooled.
Authorities previously believed the temperatures inside the Garden Grove industrial tank were cooling. However, after crews embarked on a risky operation inside the danger zone, they learned that temperatures were increasing at about 1 degree per hour. It was at 90 degrees on Friday night after starting the day at 77, Covey said in a video posted to X on Saturday. As of Saturday night, firefighters said that the internal temperature of the tank was over 100 degrees, more than double the «happy place» for the substance.
Earlier, Covey told CBS Los Angeles that this is «the most significantly dangerous event» he’s been a part of in his decades in fire service.
«This is bad as I’ve ever seen,» he added.
So far, no injuries or deaths have been reported. GKN Aerospace is in Garden Grove, a town about 38 miles south of Los Angeles.
Health risks of methyl methacrylate
Methyl methacrylate is a respiratory irritant, health experts told CBS Los Angeles. Exposure to the chemical can cause lung, skin and eye irritation, nausea and dizziness.
Covey said there are «two options» right now. In one scenario, the tank could fail and spill thousands of gallons of «very bad chemicals into the parking lot and that area,» he said.
Because the chemical is heavier than air, its vapor would settle and sink. Covey said crews have used sandbags to build containment barriers so that any spilled chemicals do not leak into storm drains or nearby waterways.
Jeff Gritchen, MediaNews Group/Orange County Register via Getty Images 
In the second scenario, the tank could blow up, Covey said. This would send methyl methacrylate particles into the air. Covey said it’s unclear how widespread or dangerous such an explosion could be. An uncontrolled explosion would also affect surrounding tanks, which hold chemicals and fuel.
Covey said he and other officials are working to determine other options to safely end the incident.
«Letting this thing just fail and blow up is unacceptable to us,» Covey said. «Our goal is to find something and not allow that to happen.»
The cause of the leak remains under investigation.
