GARDEN GROVE — Approximately 50,000 residents near the GKN Aerospace plant in Garden Grove, California, were evacuated ahead of Memorial Day weekend due to overheating of up to 7,000 gallons of methyl methacrylate in an industrial storage tank. The chemical, used to make plastics and known for its low boiling point, created dangerous pressure levels as gas built up inside the tank.

Orange County health officials stated on Tuesday that there were no chemical leaks from the tank and that it no longer posed a risk to the public. The U.S. Environmental Protection Agency reported that air monitors around the facility did not detect methyl methacrylate or volatile organic compounds and showed “no exceedances” of hazardous chemicals. The EPA deployed photoionization detectors (PIDs) as the primary sensor for chemical detection and used Hawk IR monitoring on the tank to check for escaping chemicals.

The South Coast Air Quality Management District sent a mobile air monitoring unit to the perimeter of the evacuation zone six times between May 21 and May 22, gathering real-time data. The agency reported that air quality measurements showed typical background levels both upwind and downwind of the GKN Aerospace facility. However, local and federal agencies did not provide detailed air test results to the public following the evacuation.

Hernando Morales and his family were among those forced to leave their Garden Grove home due to the potential explosion risk from the tank located just over a mile away. “Thank God we are able to now be back home. From what I’ve heard there could be toxic chemicals in the air and that’s what worries us. For their health,” Morales said.

Andrew Whelton, professor at the Lyles School of Civil and Construction Engineering at Purdue University, questioned the conclusion that no chemical was released. “To me, it doesn't make sense that there was absolutely no chemical release from the tank. If you have a pressurized soda can and you pop a hole in it, something will come out. I know the chemicals may have been captured (during the) water-spraying activity, so they didn't leave the site, but these statements that absolutely no chemical was released from the tank are unsupported by the science and physics that I understand,” Whelton said. He also criticized the reliance on PID-only testing, stating, “There's a waterfall of evidence showing PID-only testing for emergencies and disasters isn't health protective. PIDs can be used to help inform decisions, but should not be used to determine safe versus unsafe environments.”

Steve Carlin, GKN senior vice president overseeing the Garden Grove site, apologized for the disruption. “On behalf of the team at GKN Aerospace, I want to say how sorry we are for the uncertainty and disruption this situation has caused. Officials have reported that there was no chemical leak, no contamination, and (there) have been no reported injuries,” Carlin said.