Pollution regulators are combing through a report by Marathon Petroleum Corp. revealing details behind a powerful inferno at the company’s Carson refinery earlier this year, while mulling whether to levy penalties, City News Service has learned.

The blast and fire at the refinery at 2350 E. 223rd St. happened around 10:50 p.m. on Feb. 25 and took six hours for firefighters to put out, authorities said.

According to the report, the incident resulted from the ignition of volatile material that escaped from a unit that collects vapor while propane is being extracted, the South Coast Air Quality Management District said.

Marathon did not respond to a request for comment.

The incident involved the release of so-called “light-ends” (industry jargon for substances that come from crude oil with a lighter molecular structure, like methane, ethane, propane and butane) from a deficient condensing system at the top of a tower.

“The hydrocarbons were released from a crack at the Depropanizer Overhead Condenser,” said Nahal Mogharabi, an AQMD spokesperson. “South Coast AQMD is still in the process of reviewing that report and evaluating all of the facts and circumstances surrounding the incident in order to make a final determination as to whether any rule violations occurred and/or any reporting requirements were not met.”

No one was injured in the fire. But while a preliminary AQMD investigation in the aftermath confirmed benzene, toluene, styrene and tetrachloroethylene levels were no higher than normal, some local residents have questioned just how such an inferno could have been set off.

The February fire prompted concerns from residents who said they did not receive proper notification.

“If we can do an Amber Alert in geographic areas, if we can do flood warning alerts … why can’t these warning systems be implemented in these types of situations?” Carson Mayor Albert Robles said at the time.

In its Spring 2020 newsletter, Marathon Petroleum Los Angeles Vice President Brad Levi addressed the incident head-on, noting it did occur in a depropanizer. “On behalf of Marathon, I would like to thank our first responders, our local police forces, LA County Fire and HazMat, CalWater, and all those who helped us bring a swift end to the event,” he said. “We deeply regret the incident and I apologize for the inconvenience and concern.”

This community update — the most recent one available — announced there would be a more thorough investigation. It was unclear why that full report was not readily available for public review.

With a 363,000 barrel per day capacity, Marathon’s Carson complex, notable to locals for the giant American flag at the facility, is the largest West Coast refinery. It processes crude oil from across Los Angeles, the San Joaquin Valley, and places further afield (like Alaska’s North Slope, South America and West Africa), pumping out kerosene, diesel, heating oil, lubricants, and gasoline.

But rearranging hydrogen and carbon atoms can be a labyrinthine — and sometimes dangerous — process. In order to produce its series of oil-based consumer products, Marathon deploys time-tested techniques, like injecting chemicals and separating components. After all, crude oil isn’t a single chemical compound, but made up of thousands of different ones — each with its own boiling temperature.

Large cylinders — known as distillation columns, fractionation towers, or light ends units — change the phase of the crude under different temperature and pressure combinations, depending on what product operators are trying to siphon off. Of course, the depropanizer is what’s used to manufacture propane.

But this process comes with risks, said Norman Lieberman, a chemical engineer with decades of industry experience, who frequently works with Marathon Petroleum.

He says he doesn’t have direct knowledge of the Feb. 25 incident. But he did write a book on troubleshooting gas plants problems.

Unfortunately, the kind of cracks reported in the Carson refinery are “extremely common,” he said, adding that doesn’t let the company — or its employees — off the hook.

“All refinery accidents are fully and totally preventable,” he said. “It’s all due to negligence, and that is universally true.”

In 1976 he was in charge of a depropanizer that detonated after a vapor line connected to the condenser became corroded.

“I was so involved with problems at home with the wife and the children, that I forgot that I needed to concentrate on my job,” he said. “Thus, we had this stupendous failure, which is probably rather similar to your failure.”

In his view, it’s important to take responsibility in the wake of this kind of workplace mishap, drawing parallels with the recent HBO Chernobyl mini-series.

“It doesn’t matter whether it’s a nuclear power plant or a refinery, all accidents like this are fully preventable,” he said. “It’s just a combination of engineering error and operator negligence and disinterest.”

A depropanizer that develops cracks in the condensing system can be deadly.

Shell`s Norco refinery detonated in 1988 after corrosion developed in this type of system.

“It blew the distillation column off of its foundation and it landed on a control room, and it killed all the operators in the control room,” he said, adding he served as the lead technical expert for area residents in the court battle that followed. ”The lawsuit sought $2 billion, but the case was ultimately settled for $700 million.”

Lieberman would like to see better education for plant operators and engineers — right across the industry. But he also believes the main way to avoid incidents like these is to prevent substances like hydrochloric acid used in refining from getting wet (which they aren’t supposed to anyways), since that’s what causes the corrosion.

“You need to keep in mind that refinery accidents are always, always, always, always preventable,” he said. “You could prevent this sort of failure.”

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