Orange County tank crisis heats up toward explosion risk

Orange County – In Garden Grove, the temperature inside a failing tank of methyl methacrylate has climbed to 90 degrees—up from 77 the day before—raising fears of thermal runaway. Officials say spraying water to keep the tank cool is the main way to slow the chemical reaction

For the third straight day, firefighters in Orange County have been fighting a problem that won’t sit still: the temperature inside a critically failing tank filled with a highly toxic chemical is rising, not falling.

By Saturday morning. the pressurized tank at an aerospace firm in Garden Grove was at 90 degrees—up from 77 degrees a day earlier—Craig Covey. an Orange County Fire Authority division chief. said Saturday morning. Covey said temperatures are increasing about a degree per hour. The boiling point of the toxic chemical inside the tank—methyl methacrylate—is 101 degrees Celsius.

Officials say the narrow, immediate hope to avoid an explosion is simple in concept but difficult in practice: keep spraying water on the tank to hold temperatures down.

“There’s going to be a battle,” Covey said, as crews try to cool the tank and slow what is happening inside it.

The tank sits next to an elementary school and a residential neighborhood, adding urgency to decisions that have already expanded outward into the communities around it.

The basic danger isn’t just heat. The heat is tied to chemistry—and to the possibility of a runaway reaction.

Elias Picazo. an assistant professor of chemistry at USC. said it depends on the integrity of the tank. the composition of the tank. and the pressure capacity of the tank. But he said above 100 degrees. pressure can start to increase dramatically because the liquid phase shifts toward the gas phase. leaving less room and increasing pressure.

Picazo described what the temperature rise can mean in chemical terms: the liquid MMA molecules—monomers, essentially single-molecule building blocks—are reacting to form polymers, releasing heat. That released heat can then push more reaction to occur, he said, potentially even cascading.

Officials have described the threshold fear in similar language: Covey has said that if the temperature exceeds a threshold “we know the tank is going into thermal runaway, and we’re going to pull everybody out of the area, make sure it’s safe, and let the tank do what it’s going to do.”

Covey also tied today’s cooling effort to the same physics of pressure and reaction inside the tank. The tank has some capacity to hold in pressure, with empty space between the surface level of the MMA chemical and the ceiling of the tank.

“We’re hoping that that space can absorb a slower cure rate and not over-pressure and blow up,” Covey said.

Right now, crews cannot do the most direct fix that experts say would be ideal: neutralize the chemical.

The primary solution that would have been preferred would be to pump a neutralizing agent into the problem tank to quench the reaction and make it no longer explosive. But officials said the valve leading into the tank is clogged. That means there is no way to get the neutralizing agent inside. Officials also said there is no way to slowly drain the MMA toxic chemical from the tank.

As a result, the battle has shifted toward timing—buying time while trying to manage how quickly the reaction proceeds.

Covey said continuing to pour cool water on the tank could allow the liquid chemical inside to “cure” more slowly—becoming a solid at a slower speed—and reduce the buildup of pressure. He compared it to an ice cube freezing from the outside in. where the material heats up and cures from the outside in while building pressure throughout the process.

In other words, officials are trying to let the reaction move forward in the tank without letting it build enough pressure to turn dangerous heat into an explosion.

Picazo said one of the best-case scenarios is to let MMA monomers react, but in a controlled way. He said the goal would be to form solid within the tank in a way that keeps reactive monomers separated.

“If they don’t come into contact, therefore they cannot react,” Picazo said. He said solid state reduces the contact needed for reactivity, and once the unreacted starting material is left, crews could then think about other solutions to quench it.

The worst case remains on the table: firefighters said they were hopeful they can prevent an explosion, but the possibility of the tank still exploding or rupturing in a massive leak would not only endanger nearby residents but could send the chemical toward waterways and the ocean.

To prepare for that danger, officials marked a huge evacuation zone—anywhere from about 1 to 3 miles from the tank—affecting an estimated 40,000 residents across portions of the cities of Garden Grove, Anaheim, Buena Park, Cypress, Stanton and Westminster.

Officials have said they are optimistic and that letting the tank fail on its own is not acceptable.

“We’re optimistic,” Covey said. “We’re bringing people in from all over the country, talking to people all over the place, trying to come up with additional options. ‘Letting this thing just fail and blow up is unacceptable to us.’”

There’s also a hard lesson embedded in the timeline of the response.

On Friday, officials believed spraying water was cooling the problem tank, reducing how quickly temperatures rose. Picazo said that on Friday evening, drone thermometers indicated the tank was at 61 degrees, and the goal was to get the tank down to 50 degrees—what he called its “happy place.”

But the measurements turned out not to reflect what was happening inside the tank.

Drone thermometers were detecting temperatures only on the outside of the problem tank, not its inside. Officials discovered the error when a crew of workers returned overnight to the tank—home to an estimated 7,000 gallons of MMA.

Next to the failing tank is a second tank that officials said holds 15. 000 gallons of chemicals. though they said it is not at immediate risk of failure. Officials wanted to inject a neutralizing agent into that second tank in case the primary failing tank exploded. so that an even greater blast would not follow if the second tank ignited.

That led to an overnight operation of chemists and first responders sent in to try to get the neutralizing agent into the second tank, an effort Covey said put them “in harm’s way.”

When they arrived, they were able to manually read the internal temperature gauge of the failing tank. Covey said that gauge isn’t visible unless someone is there to read it; it’s covered by the cooling sprays of water and can’t be seen from a distance. Nor could a drone with a camera near it solve the issue. because the temperature readings were reflecting the tank’s exterior rather than the interior.

That’s when officials realized the tank’s internal temperature was 90 degrees.

Staff writers Hailey Branson-Potts, Hannah Fry and Eric Licas contributed to this report.

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