The risk of a “catastrophe” explosion in chemical tank in a Los Angeles-area city was averted Monday, but about 16,000 people remained under evacuation orders as some risks remained, officials said.
Liquid in the Garden Grove facility’s 7,000-gallon methyl methacrylate tank began overheating Thursday following a problem with a valve in its refrigeration system, setting the stage for several tense days as first responders and experts worked to prevent an explosion.
On Monday, officials said the biggest risk, that of a potential “boiling liquid expanding vapor explosion,” or BLEVE, had been averted.
“The most catastrophic, worst-case scenario has been mitigated and resolved,” Acting Orange County Fire Chief TJ McGovern said at a news conference Monday evening.
“It’s not over yet, and I want to emphasize again: it’s not over yet. We still have work to do,” he said.
McGovern said firefighters “still have to mitigate a fire and a very small explosion issue, as well as the potential for a spill.”
Evacuation orders in the northern Orange County city, about 35 miles southeast of Los Angeles and 4 miles from Disneyland in Anaheim, were reduced from about 60,000 to 16,000 on Monday.
The incident began Thursday at a GKN Aerospace facility, where Orange County firefighters reported “steam release.” Further investigation revealed that temperatures in a tank for methyl methacrylate, a toxic chemical used to make resins and plastics, were rising, officials said.
The tank overheated after a valve that was part of a recirculating refrigeration system, designed to keep the tank at 50 degrees, malfunctioned, Orange County Fire Division Chief Craig Covey said Monday.
“One of the valves in that system froze and circulation no longer occurred,” he said. “And because of this failure, the tank went into a warming process because it did not continue to be cooled.”
A BLEVE and spill on the property could have been one of the worst chemical events in state history, Covey said.
A temperature gauge read 100 degrees Fahrenheit, the maximum the gauge could reach, at any given time. On Monday, the temperature had dropped to 93 degrees, Covey said.
Millions of gallons of water were poured over the tank to lower the temperature inside, Covey said, and deluge sprinklers also mitigate the risk of fire.
On Monday, a crack in the tank released enough pressure without causing a leak, allowing more offensive action to be taken, he said. That night, a crew was able to remove insulation and other materials from the sides of the tank so the water could cool the contents more quickly, Covey said.
Covey said GKN has been responsive. “They were absolutely on our side there” and hired a contractor to help with the incident, he said.
A GKN spokesperson said in an online statement Monday that on Sunday his team removed insulation from the tank to help cool its contents. The company said “we continue to work around the clock” with federal and state agencies to prevent any leaks.
There were no injuries, Covey said.
With this progress, authorities reduced the size of the evacuation zone, allowing the majority of the 60,000 temporarily displaced people to return home.
Evacuation orders for the remaining 16,000 people will remain in effect until Monday evening and will be reevaluated Tuesday, Covey said.
Officials said during the news conference that there was no contamination resulting from the incident or response efforts.
Air monitoring with 20,000 instruments in the area detected “no exceedances” throughout the incident, Chris Myers, the Environmental Protection Agency’s federal on-scene coordinator, said Monday evening.
Garden Grove Police Chief Amir El-Farra asked for patience from those who were asked to leave their homes and from city residents. He urged the population to obey the evacuation orders in force.
“Please understand that we are doing this for your safety,” he said.
