Some 50,000 residents of Garden Grove, California remained under an evacuation order Sunday as emergency crews worked to contain a dangerous situation at a nearby aerospace manufacturing plant.
The tank, located in the southeastern corner of the GKN Aerospace facility, holds approximately 7,000 gallons of methyl methacrylate, a highly toxic and flammable chemical used in the manufacturing of resins and plastics. The incident began Thursday, according to NPR, though it remains unclear exactly what triggered the malfunction. What is known is that temperatures inside the tank climbed above safe levels, setting off a chain of events that has kept emergency responders on site for days.
Late Saturday, firefighters moved closer to the tank to assess conditions. TJ McGovern, interim county fire chief for the Orange County Fire Authority, said in a post on social media that what they found was a potential crack in the tank. A crack, while alarming, may actually represent a better outcome than the alternative.
Craig Covey, the incident commander at Orange County Fire, explained the reasoning earlier in the week. The danger with methyl methacrylate is that when it reacts inside a sealed container, it releases energy and causes pressure to build rapidly, effectively turning the tank into a bomb. A similar incident at a resin manufacturing plant in the United Kingdom in October 2009 destroyed the factory and shattered windows as far as 600 feet from the blast site. No one was killed in that explosion, but the structural damage was extensive.
The tank at GKN Aerospace had already begun to bulge outward before the crack appeared. Emergency crews have been spraying it continuously with water to keep temperatures down. The tank sits alongside two others. One was safely drained and neutralized. The other appeared stable as of Sunday.
If the damaged tank cracks and releases its contents slowly, Covey said that would reduce the explosive risk, though it would introduce a different set of hazards. "In a weird world that's the best case scenario believe it or not," he said. "Because once it comes out it is no longer an explosive hazard."
Slow release of the chemical still poses serious risks to people and the environment. Methyl methacrylate can irritate skin and eyes, cause respiratory problems, and produce neurological symptoms including headache and lethargy. Prolonged exposure can lead to lung and organ damage. The environmental impact of a large release remains less well understood.
GKN Aerospace said Sunday it was working around the clock to limit the risk of a leak. Evacuation orders for the surrounding area remained in place as crews continued monitoring the tank.
