Chemical spill, explosion risks trigger evacuations in California

methyl methacrylate – A chemical leak in Garden Grove has led to expanded evacuations in Orange County after officials said a 34,000-gallon tank remains in “biggest crisis” conditions. Authorities prepared for two outcomes—an estimated 6,000 to 7,000-gallon spill or a thermal runaw

When the alarm first went out in Garden Grove on May 21. officials said firefighters were responding to a vapor release from a 34. 000-gallon tank holding methyl methacrylate—an industrial chemical used in plastics and manufacturing. By the next day, the tone had hardened. Emergency leaders described the tank as one they feared could fail and either spill a dangerous amount of chemical or trigger a blast that could spread risk to nearby tanks.

Orange County Fire Authority officials said that as of May 22. an estimated 40. 000 residents in the evacuation area—within Orange County—were under evacuation orders. OCFA described the situation as a “tank actively in crisis” after efforts to mitigate a tank failure did not succeed. prompting a widening evacuation effort.

“The best case scenario” is a spill, one official said during a May 22 press conference. Authorities were also preparing for the possibility the tank could “blows up,” with officials laying out what that would mean for the surrounding area.

Garden Grove Police Chief Amir El-Farra said officials expanded evacuation areas just before noon on May 22. Garden Grove Mayor Stephanie Klopfenstein urged residents still in evacuation zones to leave immediately, saying just after 2 p.m. on May 22 that “this is a serious situation and now it is not the time to wait. Please leave now.” Garden Grove activated its emergency operations center and opened two evacuation centers in Garden Grove and Cypress.

A harmful chemical, and a tank officials couldn’t secure

OCFA said firefighters were called to an aerospace manufacturing company in Garden Grove for a “vapor release” from the 34. 000-gallon tank on May 21. Officials said they were “stabilizing the incident. ” and an evacuation order was issued for Garden Grove. a city within Orange County. according to an update posted May 21 by the city.

Residents were allowed to return home later that night after an initial cooling operation succeeded, according to Covey. But officials said the tank that was now in the “biggest crisis” could not be secured or mitigated with the information they were receiving from the manufacturer.

In explaining the danger on May 22. Covey said officials believed there were “literally two options left remaining.” In one. the tank fails and spills a total of about 6-7. 000 gallons of “very bad chemicals” into the parking lot and nearby area. In the other. Covey said the tank could enter thermal runaway and “blows up. ” affecting nearby tanks containing fuel or chemicals.

Covey said there was no active gas leak or plume in the area. but evacuations were being set up “in preparation for these two options — it fails. or it blows up.” OCFA also posted on X that it understood the incident was “a unique hazmat incident. ” adding that “subject matter experts are working around the clock to mitigate the emergency safely and effectively.”.

Officials described the chemical in the tank as methyl methacrylate, which health officials said is “very toxic,” used to manufacture resins and plastics, according to an Environmental Protection Agency fact sheet. Officials also said mitigation efforts were hindered by a damaged valve.

Preparing barriers, calling for help

During the May 22 press conference, officials said mitigation efforts involving the tank were hindered due to a damaged valve. Covey said officials were “calling people all over the state and the country” to find a way to safely enter and depressurize a pressurized tank. He said officials had created “containment barriers in anticipation” of roughly 7,000 gallons of liquid going out on the ground.

“We’ve made sand barriers,” Covey said, describing steps officials were taking to keep the chemical from reaching storm drains, river channels, and nearby oceans.

Covey said the “best case scenario” is that once the chemical comes out, it is no longer an explosive hazard and hazmat teams in chemical protective suits can go in, neutralize, and mitigate the vapors.

What health officials said residents might face

OCFA said the tank contained methyl methacrylate, and a county health officer warned that the chemical is “very toxic.” The health officer said there are very limited case reports of exposure.

For limited short-term exposure—described as inhaling vapor—the county health officer said it can cause significant irritation in the lungs and nasal passages. and it can also cause nausea and dizziness. At very high levels, the health officer said it can cause severe respiratory distress and hospitalization. She urged residents to heed evacuation orders.

She also said long-term consequences could include effects on other organs. The health officer added that the evacuation zone was expanded to account for the potential of a plume.

What remains unknown is when the tank could fail, leaving residents in Orange County to wait through the uncertainty of two competing risks: a spill or a possible explosion.

The timeline that began with a stabilizing effort in Garden Grove on May 21 ended on May 22 with a wider evacuation and a more urgent message to leave—before the tank’s condition decides what comes next.

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