GARDEN GROVE, Calif. — Thousands of residents forced from their homes by a damaged chemical tank at an aerospace plant returned Monday after fire officials concluded that a catastrophic explosion was no longer imminent, though the site remained hazardous.
The Orange County Fire Authority partially lifted the mandatory evacuation order, allowing roughly 34,000 of the nearly 50,000 people who had been told to leave on Sunday to go back to their houses. The change came after an overnight evaluation showed that pressure inside the tank, which holds 6,000 to 7,000 gallons of methyl methacrylate, had dropped to safer levels.
A crack that engineers discovered on Sunday allowed the pressure to bleed off, eliminating the risk of a major rupture, officials said. Methyl methacrylate is a clear, colorless liquid used in making plastics and aerospace composites; it is highly flammable and can cause respiratory irritation.
“While there’s no longer a risk of a major explosion at the GKN Aerospace Transparency Systems plant in Garden Grove, there’s still a chance for a smaller blast or a fire,” division chief Craig Covey told reporters Monday.
About 16,000 residents in areas closest to the plant remained under evacuation orders as a precaution, Covey said. Fire crews continued to monitor the tank and work with company engineers to determine the cause of the crack and ensure the remaining chemical was stable.
The incident began Sunday when the tank’s contents overheated, building pressure and triggering the evacuation of approximately 50,000 residents. No injuries have been reported.