The leak stemmed from a 34,000-gallon tank containing methyl methacrylate—an industrial chemical used in plastics and manufacturing—after the tank's temperature spiked, triggering a relief valve and an overhead sprinkler system designed to cool the tank.
By Friday morning, what had initially appeared to be a manageable situation had escalated into a crisis.
"I actually went home from the bed thinking we got this thing going in the right direction," OCFA Division Chief Craig Covey, the incident commander, said at a news conference Friday. "Got woken up at four in the morning—going the wrong direction now."
Covey said the primary tank of concern still holds an estimated 7,000 gallons of methyl methacrylate. A damaged valve has made it impossible for crews to offload the chemical through normal channels. The tank had already visibly bulged from heat on Thursday—a sign, Covey said, that it was approaching what firefighters call a BLEVE, or boiling liquid expanding vapor explosion.
"If you've ever seen videos of tank cars on a railroad track blowing up and that fireball puts out and it blows half the tank car half a mile down the train track, that's the incident potential we are dealing with," Covey said.
Officials said they are now left with essentially two outcomes: the tank cracks and leaks its contents onto the ground, or it explodes.
Covey described a controlled leak as the better of the two scenarios. Containment barriers, including sand berms, have been constructed around the tank to prevent the chemical from reaching storm drains, river channels, and the ocean. If the chemical leaks rather than explodes, hazmat crews in protective suits could move in to neutralize the vapors.
The other two tanks at the facility have been more successfully addressed. Crews were able to introduce a neutralizing agent into one, stabilizing it. The second, while not fully neutralized, is not in crisis.
As a precaution, evacuation orders were reissued Friday morning and expanded. The orders were initially lifted Thursday evening after cooling efforts showed progress.
The current evacuation zone covers an area bounded by Wall Street to the north, Press Avenue to the south, Dale Street to the east, and Valley View Boulevard to the west, affecting residents in Garden Grove, Cypress, Stanton, Anaheim, Buena Park, and Westminster, according to Garden Grove Police Chief Amir El-Farra.
"This evacuation needs to be paid attention to," Covey said. "People need to get out of their houses and get into a safe space, because when this thing goes, depending on wind direction, we cannot control the weather."
OCFA Interim Fire Chief TJ McGovern said OCFA units arrived on scene in under six minutes Thursday and immediately prioritized civilian safety. "Hazardous material incidents can evolve quickly and unpredictably, and so did our response," McGovern said.
Garden Grove Mayor Stephanie Klopfenstein urged residents still in the evacuation zone to leave immediately. "Please follow all evacuation orders, road closures, and instructions from emergency personnel," Klopfenstein said. "Now is not the time to wait. Please leave now."
Officials said they are actively consulting hazmat specialists from across the state and country in search of a solution to safely depressurize the tank. Crews are monitoring the tank's temperature around the clock using drones. A temperature threshold has been established—if reached, all personnel will be pulled from the area entirely.
"I cannot emphasize—this is not precautionary," Covey said. "This thing is going to fail."
Evacuation centers are open at the Garden Grove Sports and Recreation Center, 13641 Deodara Drive, Garden Grove, and at 5700 Orange Avenue in Cypress, according to El-Farra and OCFA. Residents are urged to monitor official social media channels for updates.