Why a chemical explosion in Orange County could be so catastrophic

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An “unprecedented” situation was taking hold in Orange County on Friday, as a chemical tank was at risk of exploding and releasing a highly toxic chemical that can cause severe respiratory distress and lead to hospitalization, officials said.An estimated 40,000 residents have been asked to evacuate, affecting portions of the cities of Garden Grove, Anaheim, Buena Park, Cypress, Stanton and Westminster.Disneyland is outside of the evacuation zone.

“This is highly volatile, it’s highly toxic, it’s highly flammable,” said Craig Covey, a division chief with the Orange County Fire Authority and the incident commander.Officials said they can’t recall a similar situation happening before.

So what’s the science of the leak and why do officials say it is so dangerous?There are three large tanks with a highly toxic chemical called methyl methacrylate, or MMA, used to make plastic, that are in crisis around the 12000 block of Western Avenue in Garden Grove.One tank that is the most compromised and in crisis has about 7,000 gallons of the chemical left in it, Covey said.There are two options with what will happen to the tank, Covey said, which started experiencing a rise in temperatures Thursday.

“One, it fails and cracks, and all the product leaks out onto the ground,” Covey said, and efforts are underway to try to prevent the liquid from “getting into the storm drains and the river channels and into our oceans.”That’s the best-case scenario, because once it leaks, it’s no longer at risk of exploding.From there, teams in hazardous material suits can go in and “neutralize and mitigate the vapors that will be coming off of that.” The worst-case scenario is an uncontrolled explosion.

“If you’ve ever seen videos of tank cars on a railroad track blowing up, and that fireball it puts out, and it blows half the tank car a half a mile down the train track, tha...