A chemical tank in Garden Grove, California was becoming dangerously hot. The temperature inside the 34,000-gallon tank had climbed from 77 degrees Fahrenheit to nearly 90 degrees, and then it rose by about one degree every hour. Inside was methyl methacrylate, a colorless, flammable chemical used to make clear acrylic plastics for aircraft windows.
The problem was thermal runaway. As the chemical warmed, it began to react with itself, releasing more heat, which caused the reaction to speed up and release even more heat. This process could end with the tank rupturing or exploding. Firefighters could not simply drain the tank because a damaged valve had become stuck.
Craig Covey, a division chief with the Orange County Fire Authority, explained that there were only two bad options: the tank could fail and spill 6,000 to 7,000 gallons of dangerous chemicals into the parking lot, or it could explode and damage other tanks containing fuel and chemicals.
The crisis began on Thursday, May 21. By Saturday, May 24, around 50,000 people across Orange County were under evacuation orders. The evacuation included the cities of Garden Grove, Cypress, Stanton, Anaheim, Buena Park and Westminster. Governor Gavin Newsom declared a state of emergency for Orange County.
The tank belonged to GKN Aerospace, a UK-based aircraft components manufacturer. So far, no injuries had been reported and no hazardous chemicals had drifted into nearby neighborhoods. Crews continued cooling the tank while hoping to find a solution.