Authorities said Monday morning they had eliminated the threat of a bleve explosion at a pressurized tank filled with methyl methacrylate at GKN Aerospace in Garden Grove, ending a five-day emergency that forced about 50,000 people out of part of Orange County. The Orange County Fire Authority said the tank’s temperature had been stabilized and was falling to 93 degrees from 100 degrees.
The incident began Thursday, May 21, when the 34,000-gallon tank on Western Avenue started overheating. Fire crews had spent the weekend trying to keep it from reaching the point of rupture, using drones every 10 minutes to check temperatures and working around a faulty valve that prevented them from off-loading the chemical or adding a neutralizing stabilizer.
By Sunday night, officials were already sounding more hopeful. Orange County Fire Authority officials said the BLEVE threat was “off the table,” after crews carried out an all-night mission to confirm the pressure inside the tank had been released. That followed a late-Saturday recon mission in which firefighters said they may have found a crack in the tank. Interim Chief TJ McGovern said Sunday afternoon the crack could have been relieving some of the pressure, but he still pressed residents to stay away so crews could keep working.
The evacuation order covered areas north of Trask Avenue, south of Ball Road, east of Valley View Street and west of Dale Street, with small portions of West Anaheim, Cypress, Buena Park and Stanton also included. Garden Grove police said they used reverse 911 calls and went door to door urging people to leave. By Friday afternoon, police said about 15% of those contacted were refusing to evacuate, a sign of how difficult it was to clear a zone that stretched across neighborhoods and business corridors.
Methyl methacrylate, also called MMA, is used to make acrylic plastics such as plexiglass, but the chemical can become extremely dangerous when it overheats in a pressurized tank. Officials said they were working to bring the tank down to 50 degrees, though they never publicly identified the exact temperature that would trigger an explosion. The emergency underscored how little margin crews had at the site: one valve failure, one crack in the tank and one shift in temperature could have changed the outcome fast.
For now, the tank appears to have come through the most dangerous stretch. McGovern said Sunday night that the operation still needed to be finished before residents could move back in, but by Monday morning the immediate threat was gone and the temperature had begun to fall. The next step is the final confirmation that the pressure has been fully released and the site can be secured for good.
