Gov. Gavin Newsom Declares State of Emergency as 50,000 Garden Grove Residents Flee Overheating GKN Aerospace Tank of Methyl Methacrylate That Could 'Blow Up'

GARDEN GROVE, Calif. — California Gov. Gavin Newsom declared a state of emergency in Orange County as roughly 50,000 residents across Garden Grove, Cypress, Stanton, Anaheim, Buena Park and Westminster remained under mandatory evacuation orders Sunday night while firefighters raced to keep an overheating 34,000-gallon tank of methyl methacrylate from exploding at the GKN Aerospace Transparency Systems plant on the 12000 block of Western Avenue. The Orange County District Attorney's Office opened a criminal probe into the cause of the leak, and schools across the 10-square-mile evacuation zone announced extended closures into Tuesday.

The crisis began Thursday at 3:40 p.m. when hazardous-materials crews responded to reports of fumes at the GKN Aerospace facility, which manufactures acrylic canopies and transparencies for military and commercial aircraft. Internal tank temperatures, which sat at 77 degrees Fahrenheit Friday morning, rose to 90 degrees by Friday night and continued climbing at roughly one degree per hour through the weekend, threatening a runaway exothermic polymerization that chemists warn could rupture the steel vessel and ignite the surrounding industrial park. "This is as real as it gets. It's the worst-case scenario I've ever faced in my career," Orange County Fire Authority Division Chief Craig Covey told reporters Sunday afternoon.

Methyl methacrylate, known commercially as MMA, is a volatile and flammable monomer used to manufacture Plexiglas and acrylic resins. The chemical is a respiratory irritant and can cause skin and eye damage on contact, but its greater hazard at GKN is the heat of polymerization: the substance generates its own heat as it reacts, and an uncontrolled cascade can lead to fires and pressure explosions. "It can lead to, yes, fires, explosions, where pressure really builds up very quickly," a chemistry expert briefing fire commanders told the agency. Engineers estimated that a full rupture could produce a fireball capable of leveling structures within a quarter-mile.

By Sunday evening, fire crews discovered what they believe to be a stress crack in the tank wall that may be slowly venting pressure and reducing the explosion risk, OCFA Interim Chief TJ McGovern told reporters. "There's no precedent on this. No one knows," Covey said when pressed on a timeline. Crews continued to flood the tank's external jacket with water from elevated nozzles and erected a quarter-mile foam blanket downwind to suppress any potential vapor cloud, while National Guard chemical-response units staged on Interstate 5 in case a controlled burn became necessary.

The evacuation, one of the largest in Orange County history, has filled Red Cross shelters at the Anaheim Convention Center and the Westminster Mall and prompted hospitals to discharge stable patients to free beds. Newsom's emergency declaration unlocks state cash reserves and disaster-relief funds, and the DA's criminal probe will examine whether GKN Aerospace properly maintained the tank's cooling system, refrigeration units and pressure-relief valves. Company representatives said in a statement Sunday night that they were "fully cooperating" with investigators and "deeply sorry for the disruption" to the surrounding community.