Evacuation zone shrinks after worst-case chemical tank explosion avoided

reduced evacuation – Officials say the most catastrophic scenario at an unstable chemical tank in Garden Grove has been avoided, and the Orange County evacuation zone has been reduced. Still, about 16,000 residents remain affected as crews work to prevent a small explosion, fire,

Monday evening brought a rare kind of relief—one that still came with a warning label.

At a press conference in Garden Grove, Orange County Fire Authority Interim Chief TJ McGovern said the worst-case scenario at the unstable chemical tank has been avoided. The danger, he explained, involved a potential BLEVE, or Boiling Liquid Expanding Vapor Explosion.

“The most catastrophic and worst-case scenario was mitigated and resolved,” McGovern said. “That was the case of a potential BLEVE… It’s not over yet, and I want to re-emphasize that. It’s not over yet. We still have work to do.”

With that update came a reduction in the evacuation zone for Orange County residents. But McGovern was clear about why the zone didn’t disappear.

The reduced evacuation area remains in place because crews are still working to lessen the chance of a small explosion, fire, or possible spill. McGovern said approximately 16,000 residents are still impacted.

Fire officials also shared more details about what has been happening inside and around the tank holding the toxic chemical methyl methacrylate. or MMA. OCFA Chief Craig Covey said firefighters approached the tank and checked the trends overnight because the temperature is most unstable during daylight hours.

Covey described a crucial moment when the tank cracked. In that instant, he said it released pressure without causing a leak or an explosion.

Now, he said, the internal temperature is finally dropping as the tank stabilizes. Previously, the tank reached over 100 degrees—hotter than their gauges could measure.

To help bring that temperature down, Covey said firefighters removed weather protection and insulation from the outside of the tank overnight, making it easier for water to cool the system more efficiently.

Throughout the incident, Covey stressed there have been no injuries to civilians or firefighters.

Officials said the tank initially held approximately 6,500 gallons of methyl methacrylate, or MMA. Now, they believe a lot of the chemical has cured.

“We don’t think there’s that much liquid potential left in it. We don’t know exactly how much… we know some of that is gelled up or hardened like it’s supposed to do,” Covey said.

Authorities tied the evacuation decisions to safety work that continues to unfold in real time. Covey said the reduced evacuation zone was established with residents’ safety as the top priority. and the county’s team of experts is focusing on a five-day risk assessment. while keeping the weather forecast in mind.

The adjusted zone also accounts for the risk of a potential plume or fire at the tank. For authorities to reduce the evacuation zone further—or eliminate it completely—Covey said they need to keep observing a trend of decreasing temperatures inside the tank, since that would lower the risk of fire.

He said there is no timeline for when the evacuation zone will be reduced again, and added that it will not happen on Monday.

In Garden Grove, leaders framed the moment as both progress and responsibility. Mayor Stephanie Klopfenstein said the city remains committed to understanding what happened, supporting those impacted, and working with the appropriate agencies so the incident is fully reviewed.

Klopfenstein also said Tuesday’s regularly scheduled city council meeting has been canceled. Instead. the city will hold a special meeting at the Community Meeting Center at 5:30 p.m. focused on the incident. the city’s response. and the latest information available. Residents were encouraged to attend and ask questions.

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