40,000 evacuated in California chemical leak as officials warn tank may explode

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More than 40,000 people were evacuated in multiple Southern California cities on Friday after officials warned a leaking toxic chemical tank at an Orange County aerospace facility would inevitably fail and potentially explode.

The industrial tank at the Garden Grove facility is estimated to contain 7,000 gallons of methyl methacrylate, a "highly volatile" and "highly flammable" toxic substance used in the production of plastics, said Orange County Fire Authority Chief Craig Covey.

"This is gonna happen unless some brilliant guy behind me here figures out how we can mitigate this incident," Covey said at a news conference Friday afternoon. "This thing is gonna fail. We don't know when."

Orange County officials expanded evacuation orders on Friday to several cities, including Garden Grove, Cypress, Stanton, Anaheim, Buena Park, and Westminster.

OCFA officials said there are three tanks in total, with one of the three compromised in its cooling system.

"There are literally two options left remaining, one, the tank fails and spills a total of about 6-7,000 gallons of very bad chemicals into the parking lot and that area, or two, the tank goes into a thermal runaway and blows up, affecting the tanks that are around it that have fuel or chemicals in them as well," the OCFA said.

How widespread or dangerous an explosion could be, and the timeline, "That we don't know," Covey said. "We want to prepare for the worst, but expect for things to get better."

He noted that a team has been assembled to "think outside the box," with a county hazmat team calling on experts throughout the state and nation, searching for solutions to depressurize the affected tank and mitigate exposure.

"Right now, there is no active gas leak coming off that thing. We have cooled it down enough that the purge valve that is on top of it is no longer purging any kind of product from the liquids there," Covey said Friday afternoon, noting there is nothing currently harmful in the air.

Air quality remains a concern, but Covey said that there is not an active plume, and no air particulates are "compromising anybody." People are advised to stay indoors.

Health experts said that methyl methacrylate is a respiratory irritant and potential exposure could lead to skin and eye irritation, nausea, dizziness, and lung irritation. The chemical is heavier than air, so it would settle and sink.

Air monitoring is ongoing, and drones are monitoring the temperature of the tank.

Crews arrived at the facility in the 12000 block of Western Avenue in Garden Grove after receiving a hazardous materials call just before 3:40 p.m. on Thursday, according to OCFA. The incident occurred at GKN Aerospace, an aerospace plastics facility.

The chemical initially stayed at the same temperature. However, about four hours after firefighters arrived, it rose, causing a relief valve and sprinkler system to activate.

The OCFA says crews initially made progress toward removing the product but determined Friday morning that the "tank that is in the biggest crisis is in fact unable to be secured and mitigated."

Officials said there is no active gas leak or plume in the area, but residents in the area should adhere to all evacuation orders.

The leaking tank contained a chemical called methyl methacrylate, a flammable plastic epoxy that generates its own heat, according to OCFA. Firefighters said the sprinkler safety system is designed to cool off the tank if it starts leaking.

The cause of the leak remains under investigation. No injuries have been reported.