Potential crack found in OC chemical tank as mass evacuation enters 4th day

Firefighters discovered a potential crack in an overheating chemical tank Sunday that may be relieving dangerous internal pressure, as tens of thousands of residents across five Orange County cities remained under mandatory evacuation orders stemming from a hazardous materials emergency at GKN Aerospace in Garden Grove.

The find offers the first sign of forward momentum in an incident that has upended daily life across Garden Grove, Anaheim, Buena Park, Cypress and Westminster since Thursday, when a tank of Methyl Methacrylate began dangerously overheating and triggered one of the largest peacetime evacuations in Orange County history.

OC Fire Authority interim Fire Chief TJ McGovern said overnight crews entered the facility and made the key observation, according to Voice of OC. "We developed a plan to go do an operation last night … during our operation our firefighters went in and they were able to visualize the tank. What they found was a potential crack in the tank which could potentially be relieving some of the pressure in there," McGovern said Sunday morning.

McGovern cautioned that officials were still evaluating the significance of the discovery. "We are vetting and validating that information. With this new information it could change our trajectory and strategy to this event. We're not there yet, but this is a step in the right direction and there's going to be a lot more coming shortly," he said.

The chemical at the center of the emergency is Methyl Methacrylate, a substance that poses compounding dangers. "Methyl methacrylate (MMA) is a clear, highly reactive organic compound that has a sharp, fruity smell. MMA is dangerous because it is toxic, flammable, and under certain conditions, can begin to react with itself in a process called polymerization," according to the California Department of Public Health. Officials also warned that standard N95 masks do not provide protection against MMA gas.

OC Health Officer Dr. Regina Chinsio-Kwong sought to reassure residents outside the cordoned area during a Saturday update. "If you are not in the evacuation zone, we do not expect any health impact," she said. The evacuation zone spans from Dale Street to Valley View Street and Ball Road to Trask Avenue.

By Sunday afternoon, four of the five designated evacuation centers had filled to capacity, Voice of OC reported. Nearby hotels were offering discounted rates of $189 per night for displaced residents. Gov. Gavin Newsom declared a state of emergency Saturday as the crisis stretched into its third day, with OC Fire Authority crews deploying continuous cooling measures on the tank since the incident began Thursday.

The Orange County Fire Authority said the crack discovery could alter the overall response strategy and that additional updates were expected as officials continued to vet and validate the new information.