The damaged storage tank at the GKN Aerospace facility in Garden Grove, Orange County, forced the largest evacuation in the region since a 2013 wildfire, as thousands of residents spent the weekend away from their homes. Officials said Monday that an inspection earlier that morning found a crack in the tank, which allowed pressure to dissipate — a development that erased the immediate threat of a large explosion and allowed the partial return of evacuees.
The tank contained methyl methacrylate, a volatile acrylic compound used in aerospace manufacturing. It overheated late last week, a source of the incident that remained under investigation, and began venting vapors. Throughout the event, air monitoring stations around the plant recorded no hazardous concentrations, and no hospital visits tied to the release were reported.
“We are breathing a sigh of relief that the tank didn’t fail in a catastrophic way, but this is still a very active incident,” said Orange County Supervisor Craig Covey. “The risk hasn’t disappeared — it’s been downgraded.”
The county health officer, Dr. Regina Chinsio-Kwong, said teams were working around the clock to stabilize the tank and prevent any release of the remaining chemical. State Senator Tom Umberg, whose district includes Garden Grove, said he had been briefed by emergency managers and that a full investigation into what triggered the overheating would follow once the site is secure.
A small crew remained on site Monday evening to monitor the tank’s temperature and pressure, officials said. The evacuation order remained in effect for a roughly one-third arc closest to the facility, affecting about 16,000 residents. Authorities expected those orders could be lifted as soon as Tuesday if the tank remained stable.
GKN Aerospace said in a statement that it was cooperating with regulators and local emergency officials and that the safety of employees and the surrounding community was its highest priority.
The incident recalled a string of hazardous-material scares in Southern California and came as the region marked the Memorial Day holiday under partly disrupted routines. Earlier stories in Main Street Independent’s continuing coverage chronicled the initial evacuation order, the overnight discovery of the crack, and the gradual lifting of restrictions.