Firefighters said Sunday that the immediate risk of an explosion from a cracked chemical tank at GKN Aerospace in Garden Grove, Orange County, has been eliminated after an overnight pressure-test operation. The all-night response followed a leak discovered Thursday; more than 50,000 people remain under evacuation orders while crews continue monitoring the scene. Officials reported internal tank temperature fell from about 100°F to 93°F and described the removed threat as a potential BLEVE — a Boiling Liquid Expanding Vapor Explosion. Evacuations and air monitoring remain in place as investigators and hazardous‑materials teams work toward stabilization.
Key takeaways
- OCFA Interim Chief TJ McGovern said the BLEVE risk has been removed after an overnight operation and pressure testing on Sunday.
- The tank is estimated to contain about 7,000 gallons of methyl methacrylate; the tank’s 34,000‑gallon capacity was noted in on‑site descriptions.
- More than 50,000 people across Garden Grove and nearby cities remain under evacuation orders with no set re-entry date.
- Internal temperature readings dropped from roughly 100°F to 93°F after crews cooled the tank; firefighters previously reported readings pegged at the gauge maximum of 100°F.
- OCFA said one known crack exists; early on-scene confusion about additional cracks was attributed to weather stripping peeling from continuous cooling streams.
- Federal, state and local resources have been mobilized: Gov. Gavin Newsom requested a federal emergency declaration, and about 785 state and first‑responder personnel were deployed.
- Air monitoring by EPA and regional agencies reported no detected gas releases from stationary monitors; specialized monitoring and drone temperature checks continue.
Background
The incident began Thursday afternoon when crews responded to a hazardous‑materials call at the GKN Aerospace facility on Western Avenue in Garden Grove just before 3:40 p.m. Firefighters found a tank containing methyl methacrylate — a flammable, self‑heating industrial monomer — that later showed elevated internal temperatures and evidence of a pressure release. Methyl methacrylate is heavier than air, has a low boiling point and can polymerize exothermically, which creates the risk of thermal runaway if uncontrolled. Because of those properties, a potential BLEVE became the center of concern for incident commanders and public‑safety officials.
Local authorities expanded evacuation orders on Friday to roughly a one‑mile radius encompassing parts of Garden Grove, Cypress, Stanton, Anaheim, Buena Park and Westminster. Evacuation centers were established across the area to support displaced residents and first responders; relief organizations, charities and private companies offered assistance. County and state officials quickly mobilized resources, while elected officials sought federal support to unlock additional assets and funding.
Main event
Friday and Saturday saw teams attempt to cool and assess the compromised tank while balancing the significant safety risks. Crews reported a pressure release and identified at least one crack on the tank Saturday night; continuous water streams were applied overnight to reduce temperature and pressure. OCFA Incident Commander and Division Chief Craig Covey confirmed the crack and said the measured internal temperature decreased — a development officials described as positive.
On Sunday, OCFA Interim Chief TJ McGovern announced in an incident update that the BLEVE threat had been eliminated following pressure testing and the cooling operation. Public information officers emphasized that while the highest immediate explosion risk has been removed, the tank still poses hazards: additional cracking, the potential for liquid leakage and plume formation remain possible while the substance is present.
Authorities reported there was no active major leak detected at the time of the update. EPA and South Coast Air Quality Management District monitors, including 24 EPA stationary monitors deployed since Friday, have so far not recorded hazardous concentrations. Nevertheless, evacuation orders will remain in effect until officials can confirm long‑term containment and safety for re‑entry.
Analysis & implications
Removing the immediate BLEVE risk reduces the chance of a catastrophic detonation that could have caused broad structural damage within the mapped blast rings and exposed thousands to intense thermal and overpressure effects. However, the presence of methyl methacrylate means secondary hazards remain: liquid release could vaporize and form a denser‑than‑air plume that would pool in low areas and present inhalation and irritation risks.
The state’s swift request for a federal emergency declaration — a preemptive mechanism that activates FEMA coordination and federal funding — signals the potential scale of recovery and the logistical needs for sheltering, air monitoring and long‑term public‑health follow‑up. If granted, federal support could bring specialized hazmat assets, additional air‑sampling capacity and public‑health resources to manage screening and long‑term sampling of homes and businesses in the evacuation zone.
Legally and operationally, the event raises questions about industrial maintenance, tank design and oversight. The Orange County District Attorney opened an investigation and has invited whistleblowers and employees to provide information about operations and maintenance. Pending that inquiry, the incident may spur regulatory reviews or operational changes for storage and handling of self‑heating monomers in populated areas.
Comparison & data
| Item | Reported value |
|---|---|
| Estimated chemical in tank | ~7,000 gallons methyl methacrylate |
| Tank capacity (site reference) | 34,000 gallons |
| Internal temperature (peak gauge) | ~100°F (later 93°F) |
| People evacuated | More than 50,000 |
| State/first‑responder personnel deployed | ~785 |
The table above summarizes key figures reported by incident commanders and state officials. Temperature reductions and pressure testing are the principal operational metrics crews use to judge whether the immediate explosive risk has passed; sustained cooling and absence of active leakage are required before evacuation orders can be safely rescinded.
Reactions & quotes
Officials, experts and community leaders framed the update as cautiously positive while keeping the focus on continued monitoring and public safety.
“We are happy to report that the threat of a BLEVE is now off the table. That threat has been eliminated.”
OCFA Interim Chief TJ McGovern
McGovern’s statement followed the overnight testing that lowered pressure and temperature. He and other OCFA leaders stressed the distinction between eliminating the explosion risk and concluding the broader incident response.
“The experts are talking to each other and determining when the safest time to approach the tank and make these assessments. It’s very calculated, there’s a lot of risk involved.”
OCFA Fire Captain Brian Yau
Captain Yau emphasized methodical, expert‑led tactics for assessing remaining structural damage and potential leak paths. Fire command repeatedly declined to rush in because missteps could prompt renewed hazard escalation.
“In an uncontrolled environment with a leak, you can potentially have a lot in the atmosphere…you get what we call ‘runaway,’ where it’s uncontrolled. It can lead to fires, explosions.”
Elias Picazo, USC Assistant Professor of Chemistry
Picazo explained the polymerization and exothermic risks inherent to methyl methacrylate, reinforcing why temperature control and ventilation are critical to preventing thermal runaway and rapid pressure rise.
Unconfirmed
- Whether additional, smaller structural cracks existed under protective stripping at the bottom of the tank remains under further engineering assessment.
- It is not yet confirmed if vapor buildup directly caused the initial crack or if maintenance issues contributed to the tank failure; the DA’s probe is ongoing.
- Timing for lifting evacuation orders and a full timeline for re‑entry have not been finalized and remain dependent on air sampling and structural inspections.
Bottom line
The recent pressure testing and cooling operation materially reduced the immediate explosion threat at the Garden Grove site, a step that lowers the probability of a catastrophic BLEVE. Yet the presence of several thousand gallons of methyl methacrylate and a confirmed tank crack mean the incident is not fully resolved: leakage, plume formation and secondary hazards still require active mitigation and monitoring.
Residents should continue following official evacuation orders and check designated county and state hotlines for updates. In parallel, the district attorney’s investigation and any subsequent regulatory reviews will be important to determine root causes and whether changes in industrial storage practices are needed to prevent similar crises near populated neighborhoods.