Garden Grove California Chemical Tank Crack Averts Blast, 16,000 Still Under Evacuation Orders

In Garden Grove, California, about 16,000 people remained under evacuation orders as an overheated chemical tank at GKN Aerospace Transparency Systems still posed a risk to homes closest to the site, with officials giving no word yet on when residents could return.

The crisis forced 50,000 people to evacuate in and around the Orange County city of Garden Grove last week, but a crack that formed by chance on the tank relieved pressure and helped avert a catastrophic explosion over the Memorial Day weekend.

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Officials said the tank contained 6,000 to 7,000 gallons of methyl methacrylate, a highly flammable chemical used to make plastics, and they continued to keep orders in place for about a third of evacuees due to the risk of a smaller explosion or potential spill.

Crews worked to cool the tank after a valve on the cooling system failed, and fire officials said they sprayed water on the tank until the interior temperature stabilized to 92 F (33.3 C), down from 100 F (37.7 C) over the weekend.

Orange County Fire Capt. Brian Yau said crews worked overnight to ensure two nearby tanks were neutralized and would not be affected by the compromised tank, while the company said its technical specialists and firefighters removed insulation to help cool it.

Residents described ongoing uncertainty and health concerns during the evacuation, including Isabel Mendez, who told reporters she broke out in a rash on her face and developed tingling lips and a sore throat while evacuating last week.

The AP reported that exposure to methyl methacrylate can cause serious respiratory problems, neurological problems and irritation to the skin, eyes and throat, citing the federal Environmental Protection Agency.

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Orange County Health Director Regina Chinsio-Kwong said at a Monday news conference, "There was no contamination," and she added, "You should feel comfortable going home even if you’re across the street from that new zone line."

The Guardian said the South Coast Air Quality Management District will monitor the air for several months and the EPA will be checking sewer and storm drains for spills, while Andrew Whelton, a Purdue University engineering professor, said the tank was on track for a catastrophic explosion and that the crack allowed pressure to vent.

NBC Los Angeles reported that no chemical product was leaking from the tank and nothing harmful was detected through atmospheric monitoring, while Fire Capt. Wayhowe Huang said the tank’s risk had shifted to smaller explosion concerns as crews continued mitigation.

Even after officials said the catastrophic explosion threat was mitigated, the risk was not treated as fully over, with Orange County Fire Authority incident commander Craig Covey saying more work was needed before the evacuation could be lifted entirely.

“We're learning new details on the next steps in the effort to gain control of an unstable chemical tank in Garden Grove”

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USA Today reported that teams were checking the temperature of the tank every 30 minutes, hoping to confirm a downward trend, while Covey said there was still a potential for fire in the smaller risk zone.

KTLA said Orange County Fire Authority officials reported that the threat of a BLEVE was off the table, and it quoted OCFA Chief TJ McGovern explaining that evacuation zones were set based on the BLEVE radius and would be reevaluated as mitigation continued.

In the meantime, residents were urged not to enter evacuation zones, and USA Today quoted Sen. Adam Schiff of California saying, "Nothing is worth risking and endangering your lives by trying to go back to your home while an evacuation order is still in effect."

ABC7 Los Angeles said crews were slowly reducing the amount of water applied to the tank to see if it could stabilize on its own, and it reported that officials believed the chemical methyl methacrylate (MMA) is solidifying but would not know how much until they could get inside the tank.