50,000 Californians Still Evacuated Over Chemical Tank That Could Explode

If you live anywhere near Orange County, California — or just follow the news — you've probably heard about this one. A massive chemical emergency has been unfolding in Garden Grove since Thursday, May 22nd, and it's the kind of story that makes you realize how quickly everyday life can get upended.

Here's the deal: a storage tank holding between 6,000 and 7,000 gallons of methyl methacrylate — a chemical used to make plastic parts — overheated Thursday and began venting vapors into the air at an aerospace plastics facility in Garden Grove. The facility is owned by GKN Aerospace, which makes parts for commercial and military aircraft.

So what's methyl methacrylate (MMA)? Think of it as the stuff that goes into Plexiglass and other resins. It's a clear, colorless liquid that is highly volatile and releases energy exothermically when it reacts — meaning if that reaction occurs inside a container, it can cause a sudden pressure buildup, effectively turning the tank into an explosive. Not great when you live nearby.

The problem got worse fast. Officials said the valves on the tank are broken or "gummed up," which prevented crews from removing the chemical or relieving the pressure on the tank. Without a way to vent or neutralize the reaction, the temperature inside kept climbing. A chemistry professor at USC described it as a "thermal runaway" — a vicious cycle where the reaction produces heat, but heat also initiates the reaction. Crews have been fighting it with water since Friday.

In what's being called an "unprecedented" situation, tens of thousands of people in the area were told to leave their homes Friday, with officials issuing a dire warning that the chemical tank is in "crisis" and will either spill or explode. Evacuation orders were expanded to some parts of five other Orange County cities including Cypress, Stanton, Anaheim, Buena Park, and Westminster. That's a blast zone covering about 9 square miles surrounding the GKN Aerospace facility.

The industrial site is about 5 miles from Disneyland and about 4 miles from Knott's Berry Farm. Both parks, outside the evacuation zone, remain open and operational — though the optics of that aren't lost on residents who've been sleeping in shelters or their cars.

Here's the latest bit of cautious good news: experts trying to prevent the tank from exploding found a "potential crack" in the container that might be reducing the pressure. A crack could be a welcome development, as it could mean product or pressure inside the tank is being released, reducing the chance it explodes. Think of it like a soda can with a small hole — it won't explode the same way a fully sealed, pressurized one would.

By Monday morning, the threat of a chemical tank exploding has significantly decreased — but the danger has not been eliminated. A chemical blast could still occur, though the chance of a more catastrophic vapor explosion has been eliminated.

California Gov. Gavin Newsom declared a state of emergency in Orange County on Saturday as the state ramped up its response. Almost 800 state and local first responders have been deployed, including toxicologists, hazmat teams, and public health sheltering experts. And so far, no injuries have been reported, and air monitoring tests have found that air pollution around the evacuation zone is within normal limits.