40,000 evacuated in Orange County as toxic chemical tank risks explosion

Forty thousand people woke up Friday morning in Orange County, California, and were told to leave their homes. They had hours, maybe less, to gather what they could and drive away from a nine-square-mile zone around an industrial facility in Garden Grove. The reason was a tank filled with methyl methacrylate—a chemical used to make plastics—that had begun to overheat and now threatened to either rupture or explode, potentially releasing seven thousand gallons of toxic vapor into the air.

Authorities had been fighting the problem for two days. On Thursday, they detected a vapor release from one of three tanks at the facility and initially ordered evacuations, then lifted them that evening when conditions seemed to improve. But as crews tried to drain the chemical from the overheating tank, they discovered a damaged valve that made removal impossible. The evacuation orders went back into effect, this time with no clear end date.

The chemical in question, known as MMA, is heavier than air and can cause severe respiratory damage if inhaled—significant irritation of the lungs and nasal passages, dizziness, nausea. The problem is that there aren't many documented cases of human exposure to large quantities of it, which means nobody really knows what would happen if the tank failed. "We're entering into unique times and we have limited information," said Dr. Regina Chinsio-Kwong, the county's health officer. The facility sits about five miles from Disneyland and four miles from Knott's Berry Farm, in one of the most densely populated parts of Southern California.

Craig Covey, the incident commander and division chief of the Orange County Fire Authority, was blunt about the situation. "This is going to happen unless some brilliant person behind me here figures out how we can mitigate this," he said at a Friday afternoon press conference. "This thing is going to fail." He described the chemical as "highly volatile, highly toxic, and highly flammable." The only two outcomes authorities could envision were the tank cracking and leaking its contents across the surrounding parking lot, or the tank exploding outright.

By Friday morning, police were making reverse 911 calls telling residents to evacuate and posting on social media. Thirteen schools and two educational facilities in the Garden Grove Unified School District were cleared. But about fifteen percent of the people in the evacuation zone—roughly six thousand residents—refused to leave. One woman, Diane Chavira, told a local news affiliate that she had been asleep in her house until that morning, when she was suddenly told to go. She had to gather her four dogs and leave.

The temperature of the tank had stabilized by Friday afternoon, which gave officials some breathing room. "That gives us time to continue working on how to fix this," Covey said. Teams from the facility's manufacturer and from across the region were working to prevent failure, but the manufacturer's own response team had already tried everything they could think of without success. The only variables anyone could control were time and luck—and the wind. "People need to get out of their homes and get to a safe place because when this happens, depending on wind direction, we can't control the weather," Covey said. The air outside the evacuation zone should be safe, authorities said, but that assumption rested on the wind staying in one direction and the chemical behaving as predicted. In a situation with limited information and high stakes, that was not a guarantee anyone could make with confidence.