Thousands of residents in Garden Grove, California, woke up Friday morning under evacuation orders they thought had been lifted the night before.
The Orange County Fire Authority reissued mandatory evacuations at 6:30 AM Friday for a large section of the Orange County city after an inoperable valve on the 34,000-gallon tank at the center of the crisis prevented hazmat crews from completing the mitigation operation they had spent hours working on Thursday night.
The tank in question is at the GKN Aerospace facility at 12122 Western Avenue in Garden Grove, an aerospace manufacturing plant that uses methyl methacrylate, a volatile and flammable industrial chemical, to produce acrylic plastic components for the aerospace industry.
On Thursday afternoon at approximately 3:30 PM, the tank overheated. The safety system designed to handle exactly this situation activated as intended, releasing vapors through a relief valve at the top of the tank and triggering a sprinkler system to begin cooling it.
What was not intended was what happened approximately four hours later, when the chemical’s temperature rose again instead of falling, and the situation that crews thought they were managing became more complicated.
By Thursday night, the Orange County Fire Authority had worked for hours and lifted the evacuation orders at approximately 8:40 PM.
The crews had made progress. The tank appeared more stable. Residents and businesses in the affected area were allowed to return.
By 6:30 Friday morning, those same residents were being told to leave again.
“Yesterday’s cooling operation was successful, and the facility and industrial crews initially made progress toward product removal,” the OCFA said in a statement.
“However, an inoperable valve on the tank has created additional operational challenges, preventing complete mitigation at this time.” Deputies from the Orange County Sheriff’s Department were going door to door Friday morning to assist residents with the mandatory evacuation. The duration of the current evacuation order is unknown.
What Happened Inside The Tank
The GKN Aerospace facility at 12122 Western Avenue manufactures acrylic plastic components for the aerospace industry, components that require methyl methacrylate, known as MMA, in their production process.
The 34,000-gallon storage tank on the facility’s property holds the MMA used in that manufacturing.
OCFA Captain Sean Doran described the initial situation when crews first arrived on Thursday afternoon. “We arrived to a 34,000-gallon tank containing an industrial chemical that had been overheated inside the vessel. The system activated as it was designed to, released vapors through the top and the sprinkler system was activated to start the cooling process.”
The overheating of MMA is not a simple cooling problem. Methyl methacrylate is a flammable plastic epoxy that generates its own heat, a property called exothermic polymerization, in which the chemical reaction that produces the plastic material releases heat as a byproduct.
When an MMA tank begins to overheat, that heat can accelerate the polymerization reaction, which releases more heat, which accelerates the reaction further.
The safety systems, the relief valve and the sprinkler system, are designed to interrupt this feedback loop by releasing pressure and cooling the exterior of the tank. On Thursday, those systems activated correctly.
The problem is that approximately four hours after firefighters arrived, the chemical’s temperature rose again despite the cooling efforts.
The relief valve activated a second time. The sprinkler system continued running.
By Friday morning, the crews discovered that an inoperable valve on the tank was preventing them from removing the chemical from the vessel, the step that would definitively end the crisis by eliminating the source of the hazard.
That inoperable valve is what has turned a Thursday emergency into a Friday evacuation that has no announced end time.
The Evacuation Zone
The mandatory evacuation zone as of Friday morning covers a significant residential and commercial area in Garden Grove.
The boundaries are north of Garden Grove Boulevard, east of Springdale Avenue, west of Dale Street and south of Orangewood Avenue.
Anyone inside that zone is required to leave. Orange County Sheriff’s Department deputies are going door to door to assist residents who need help evacuating and to ensure compliance with the order.
The duration of the evacuation is unknown, it will remain in effect until OCFA determines that the mitigation is sufficiently complete to allow residents to return safely.
A temporary shelter has been established at Stanton City Hall and Community Center at 7800 Katella Avenue in the neighboring city of Stanton. Residents who cannot stay with family or friends outside the evacuation zone are directed to that facility.
The School Closures That Expanded The Impact
The evacuation order has rippled beyond the residential community. Several Garden Grove Unified School District campuses closed Friday at the direction of law enforcement and emergency response officials because of their proximity to the GKN Aerospace facility near Chapman and Western avenues.
The district notified families Friday morning that those campuses would remain closed until further notice.
School closures during an active hazmat situation affecting a residential neighborhood introduce a specific set of complications for working families.
Parents who would normally have their children in school during mitigation operations instead need to manage childcare while the evacuation order is in effect. Those who live inside the evacuation zone have been required to leave.
Those who live outside it but whose children’s school is closed are dealing with unexpected disruption to their Friday while monitoring news coverage for when the situation will be resolved.
What Is Methyl Methacrylate?
Methyl methacrylate is not a household name, but it is a common industrial chemical with a specific combination of properties that make a large-scale release genuinely hazardous.
It is highly flammable. Its vapors are heavier than air, which means they settle and travel at ground level rather than dispersing rapidly upward, making them more likely to reach areas away from the immediate tank location and more likely to accumulate in low-lying areas, basements and enclosed spaces.
Vapor concentrations sufficient for ignition can build up at significant distances from the source.
It is also an irritant. At lower concentrations, MMA vapors cause irritation to the eyes, skin and respiratory tract, headaches and nausea in people who are exposed. At higher concentrations, the effects are more severe.
The evacuation orders are designed to keep the population outside the zone of meaningful exposure while the chemical levels in the air around the facility remain elevated.
The self-heating property, the exothermic polymerization that makes the tank challenging to manage, is the factor that distinguishes MMA from most other industrial chemical spills.
Many hazmat situations involve containing a leak and waiting for the hazard to dissipate or be neutralized.
MMA can continue generating heat internally even after the visible release has been addressed, which is why the temperature rise four hours after Thursday’s initial response was so concerning and why the inoperable valve preventing product removal has elevated this from a resolved situation back to an active emergency.
GKN Aerospace And The Facility
GKN Aerospace is a global aerospace manufacturer and one of the world’s largest suppliers of airframe and engine structures to companies including Boeing and Airbus.
The Garden Grove facility is one of its California manufacturing sites and uses MMA in the production of the acrylic composite materials that are standard components in commercial and defense aircraft.
The company issued a statement acknowledging the situation. “We are currently responding to a situation at our Garden Grove site. Emergency response protocols were activated immediately, and the area has been secured. Fire Brigade and specialized hazardous material teams are on site and assessing the situation. There are no reports of injuries at this time and our priority remains the safety of our employees, responders, and the surrounding community. We will provide verified updates as soon as more information becomes available.”
The cause of the initial overheating that triggered the Thursday incident remains under investigation.
No injuries have been reported among employees, first responders or community members, a result that reflects both the performance of the facility’s safety systems in containing the release to vapor rather than liquid and the rapid evacuation response from OCFA and Orange County sheriff’s deputies.
The situation as of Friday morning is active and unresolved. The tank contains MMA that cannot be fully removed due to the inoperable valve.
Hazmat crews are continuing mitigation operations. The evacuation order will remain in effect until authorities determine it is safe to lift.
