A large pressurized tank filled with a toxic chemical in Orange County is at risk of exploding or leaking, and officials say their options are very limited.
As of Friday night, fire crews were making progress in reducing the temperature of the chemical tank, which has dropped to about 61 degrees, with the goal being 50 degrees, said Craig Covey, division chief of the Orange County Fire Authority.
That could allow crews to implement some solutions that don't involve an explosion or destructive leak. But there is still a long way to go before the area is safe for people to return.
Why is the chemical in this tank so dangerous right now?
Inside the tank are approximately 7,000 gallons of a chemical used to make plastics called methyl methacrylate, or MMA, stored in liquid form.
“It's durable, lightweight and transparent, so it could even be used as a glass substitute,” Elías Picazo, an assistant professor of chemistry at USC, said of the final plastic product. The polymer can also be used in household items.
The polymer itself is not toxic, but its liquid predecessor, MMA, a monomer, essentially a group of individual molecules, is. If it reaches the air, it can harm people in high concentrations and through chronic or prolonged exposure.
“The other danger is the explosion itself. And it seems like the reaction has already started, and that's where the concern about the explosion arises,” Picazo said.
In chemistry, there is a concept known as “thermal runaway reactions. And those are really difficult to control,” Picazo said.
If the tank temperature exceeds a certain threshold, Covey said, “we know the tank is going to go into thermal runaway and we'll get everyone out of the area, make sure it's safe and let the tank do what it needs to do.”
How did the crisis start?
The crisis began in Garden Grove on Thursday, when a tank containing MMA began to experience a rise in temperature. At one point, the tank began to bulge and “got to a point where it does what we call BLEVE, which is a 'boiling liquid expanding vapor explosion,'” Covey said Friday afternoon.
It is unclear what problem caused the temperature rise in the chemical tank.
But it's something that shouldn't have happened, experts say.
What happens when you combine heat with this chemical in a large pressurized tank?
Some chemical reactions can be started with heat. With MMA, heat can cause a reaction, but then it causes more heat.
“You can start to see the problem. There is a reaction that starts with heat, but it also releases heat as it progresses, which then leads to the leak, where it is uncontrollable,” Picazo said. “And this is a very large-scale reaction that produces a lot of heat very quickly.”
And all this happens in a tank with high pressure.
“If too much heat or pressure is generated, the explosion occurs. And the material is also highly flammable, in addition to being toxic, so toxin vapors, flames like literal fireballs and the explosion itself can be produced,” Picazo said.
The worst case scenario is an uncontrolled explosion. “If you've ever seen videos of tank cars on a railroad track exploding, and that fireball that puts out, and blows half the tank car half a mile down the railroad track, that's the potential incident that we're dealing with if this thing suffers a catastrophic failure,” Covey said.
Another scenario that could involve significant environmental damage to waterways and the ocean is a massive leak, although such a leak would make the chemicals no longer at risk of exploding.
From there, teams in hazmat suits can go in and “neutralize and mitigate the vapors that are going to come out of that,” Covey said.
Can anything be done beyond waiting for an explosion or a massive leak that threatens streams, rivers and the ocean?
The main strategy at this time is to do everything you can to keep the tank cool.
On Thursday, crews were able to cool the tank with sprinklers, leading officials to believe the problem was being resolved. But conditions worsened Friday when they discovered they couldn't discharge a neutralizing agent into the faulty tank because the valves had broken and were stuck.
This would have been a good solution if they could have gotten the neutralizing agent into the tank. MMA is an electrophile: it likes to take electrons and “if you add another molecule that is a nucleophile that likes to give electrons, you can turn it off, you can kill the reaction, you can stop the reactivity of whatever is left,” Picazo said.
On Friday, firefighters reissued evacuation orders and expanded the zone to include parts of the cities of Garden Grove, Anaheim, Buena Park, Cypress, Stanton and Westminster. They warned that they were told that at that moment the only two options before them were a massive leak or an explosion.
But now they are buying time by using cold sprays to try to keep the tank temperature down.
That's a viable solution, Picazo said, “just wait it out by keeping the tanks cold. Then, by controlling the runaway, you can slow the reaction and do everything you can to maintain pressure.”
Covey said in an update Friday night that efforts to cool the tank by spraying it with water have been successful so far.
“Those efforts are having success and are giving us an opportunity to reconsider engaging closely to implement some of the concepts … to mitigate this,” he said.
The key questions for officials, Picazo said, will be determining how much MMA is left in the tank “and how to put out what's left.”
On Thursday, a tank released steam after it experienced a temperature rise. By Friday afternoon, firefighters had cooled the tank enough that a valve at the top of the tank would no longer purge any chemicals.
If the temperature is equilibrating and the tank is no longer venting substances into the air, one possibility is that the reaction can occur. “I wonder what would happen if they stopped trying to cool the tank, if it started heating itself up again,” Picazo said. “Basically, I'm wondering if the reaction is over or if stopping the cooling mechanism would restart it.”
What could have caused the tank valve to become clogged, making it impossible to place a neutralizer in the tank that would resolve this crisis?
One possibility is that the MMA chemical has already reacted in the valve and gone from a liquid state to a solid state.
“Maybe the material has already polymerized in that outlet,” Picazo said. “And then nothing can get in or out, because the monomer, which is a liquid, once it polymerizes, it becomes this plastic, glass-like material, and it's solid, so nothing will get in or out.”
Has anything like this happened before?
Authorities called this particular situation unprecedented on Friday. But in a region filled with chemical facilities, refineries and other heavy industries, accidents happen.
A recent incident occurred in October at the Chevron oil refinery in El Segundo, sparked after a large fire broke out in a corner of the refinery where crude oil is converted into jet fuel, and resulted in a violent explosion that shook homes up to a mile away. No details have been published about the cause and extent of the environmental consequences.
In 2015, an Exxon Mobile refinery in Torrance suffered an explosion; no one was seriously injured. The U.S. Chemical Safety Board said Exxon Mobile relied on outdated procedures and used equipment that was older than its safe operating life, adding that the explosion had the potential to be catastrophic due to the presence of a highly toxic chemical, hydrofluoric acid, at the site, which can immediately penetrate skin and destroy tissue.
One of the deadliest industrial accidents in U.S. history involved the ignition of highly flammable fertilizer aboard a freighter, the SS Grandcamp, in Texas in 1947, according to the Bullock Texas State History Museum. The ignition was caused by a fire on board the ship, which ignited 2,300 tons of ammonium nitrate, killing about 581 people and injuring thousands. The first explosion triggered a second explosion at a nearby Monsanto Chemical Co. plant and caused a fire on another ship, the SS Highflyer, which then exploded 16 hours later.
That disaster “triggered new regulations for the chemical manufacturing industry,” the museum said, including requiring cool temperatures and special containers for shipping ammonium nitrate and prohibiting storage near other reactive materials.
Times staff writer Tony Briscoe contributed to this report.
