More than 44,000 people remained under evacuation orders in several Southern California communities after a leaking chemical tank at an Orange County aerospace facility was judged likely to fail and could possibly explode. The incident is centered at the GKN Aerospace site in the 12000 block of Western Avenue in Garden Grove.
Orange County Fire Authority officials say one of three industrial storage tanks at the facility has a compromised cooling system. That tank is believed to hold roughly 6,000–7,000 gallons of methyl methacrylate, a highly volatile, highly flammable chemical used in plastics manufacturing. OCFA Chief Craig Covey said crews have been unable to fully secure the tank and warned its structural or thermal failure is probable unless a workable mitigation method is found.
Firefighters have focused on cooling and monitoring the tank to buy time. Unmanned hoses have been used to spray water on the vessel, keeping its temperature near 61 degrees at one point, and drones are being deployed to measure external temperatures. A county hazmat team has convened specialists statewide and nationally to explore ways to depressurize the tank or otherwise prevent a catastrophic release.
Officials described the two main scenarios they are preparing for: the tank could rupture and spill its contents onto the site, or it could enter a thermal runaway reaction and explode, potentially affecting nearby tanks that contain other fuels or chemicals. Authorities said the size and scope of any explosion are unknown and that there is no set timeline for when the danger will pass.
Air quality crews are actively monitoring the area. OCFA reported there is not an active airborne plume at this time and that instruments have not detected harmful particulates in the surrounding air, but residents in the evacuation zone were advised to stay indoors until further notice.
What is methyl methacrylate?
Methyl methacrylate is a flammable monomer often used in producing plastics and acrylics. It can self-heat during polymerization, a property that can trigger a runaway reaction if uncontrolled. Health experts warn it is a respiratory irritant; exposure can cause irritation to the lungs, skin and eyes, as well as nausea and dizziness. Because its vapor is heavier than air, it can pool at ground level in low-lying areas.
USC chemistry assistant professor Elias Picazo explained that when the chemical begins to polymerize, the reaction releases heat. That heat can accelerate further reaction, creating an uncontrollable cycle that can lead to rapid pressure build-up, fires or explosions.
How the event unfolded
Crews responded to a hazmat call at the Garden Grove facility shortly before 3:40 p.m. Thursday. Initially firefighters were able to maintain the tank temperature, but about four hours after arrival the temperature rose, activating a relief valve and the sprinkler cooling system. Early attempts to remove product from the tank showed progress, but by Friday morning authorities determined the most compromised tank could not be fully secured or mitigated.
No injuries have been reported. The cause of the leak is under investigation.
Evacuations and local impacts
On Friday, Orange County expanded evacuation orders to a roughly one-mile radius around the site, covering parts of Garden Grove, Cypress, Stanton, Anaheim, Buena Park and Westminster. The expanded evacuation borders included Valley View Street to the west, Ball Road to the north, Trask Avenue to the south and Dale Street to the east.
There is no set timetable for lifting evacuation orders. Evacuation and shelter locations include:
– Garden Grove (not overnight): Garden Grove Sports & Recreation Center, 13641 Deodara Dr.
– Cypress: Cypress Community Center, 5700 Orange Ave.
– Anaheim: Savannah High School, 301 N. Gilbert Street
– Fountain Valley: Mountain Square Regional Park—Freedom Hall, 16801 Euclid Street
– La Palma: John F. Kennedy High School, 8281 Walker Street
– Huntington Beach: Ocean View High School, 17071 Gothard Street
Local closures and cancellations
Garden Grove Unified School District closed 15 campuses and said closures will remain in effect until conditions are reassessed. The annual Garden Grove Strawberry Festival continued as scheduled, but the associated 5K race and parade were canceled. The County Registrar of Voters closed the Garden Grove Sports and Recreation Center vote center to operate the site as a care and shelter location instead.
Official guidance and contact information
Residents with questions can call the City of Garden Grove 24-hour call center at (714) 741-5444 or visit ggcity.org/emergency. Orange County’s public information hotline is (714) 628-7085.
Authorities said teams continue to pursue additional mitigation options and contingency plans, and emphasized they will not simply wait for a failure. They urged residents in affected areas to follow evacuation orders and safety guidance while specialists work to stabilize the situation.