Cooling system at chemical tanks likely failed, forcing mass O.C. evacuations, fire officials say

A Garden Grove aerospace firm incident led to the evacuation of an estimated 50,000 people after officials determined one tank faced a risk of BLEVE, a massive explosion. Orange County Fire Authority interim chief TJ McGovern said the likely cause was failure of a cooling system meant to regulate chemical tank temperatures. Without cooling, heat likely built up in a pressurized tank holding 7,000 gallons of methyl methacrylate, a highly flammable plastic monomer. Later evaluations found a crack that reduced pressure, eliminating the possibility of a catastrophic blast. With the tank no longer pressurized, responders moved closer to peel back external wall and insulation and used hose lines to cool the chemical, lowering temperature to about 92°F. Authorities reduced the evacuation zone but warned the danger was not over.

"“We don't know why, but it stopped cooling,” McGovern said. “So that's what started this event, to where the product heated up...and that's how this whole response started. We're just now being able to get to the tanks, so there's definitely more to come of what caused it.”"

"Officials evacuated an estimated 50,000 people on Friday after determining one of the three tanks at the aerospace company was in danger of a massive explosion called a boiling liquid expanding vapor explosion, or BLEVE, which would have caused widespread damage. Further evaluations over the Memorial Day weekend found the tank had a crack that had reduced pressure, eliminating the possibility of a catastrophic blast. “Yesterday we really turned a corner,” McGovern said."

"The confirmation that the tank was no longer pressurized allowed them to get members of the team-comprised of experts from OCFA, Los Angeles and Long Beach fire departments, Los Angeles County and San Bernardino County fire departments, and the California Office of Emergency Services-closer to the tank to peel back the external wall and insulation, McGovern said. This enabled them to focus their unstaffed hose lines on the internal tank to cool the chemical more effectively, dropping the temperature to around 92 degrees Fahrenheit."

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