Release of Methyl Methacrylate; Garden Grove, California

12242 Western Ave, Garden Grove, CA 92841, USA | 2026-May-22

Initial Notification: On May 22, 2026, the U.S. Coast Guard (USCG) District Response Advisory Team (DRAT) for the Southwest District contacted the NOAA Scientific Support Coordinator (SSC) regarding a damaged container of methyl methacrylate (MMA) monomer at the GKN Aerospace plant in Garden Grove, California, approximately 15 miles east-southeast of USCG Base Los Angeles-Long Beach. The damaged tank was reported to contain approximately 6,500 gallons of MMA. Local responders were concerned that, in addition to the potential for toxic exposure, the tank could explode. An evacuation order for nearby areas was issued. On May 24, the EPA contacted the NOAA SSC to request air hazard modeling in the event that the contents of the tank leaked into the secondary containment, and also requested information about what would happen if the mixture of cooling water and MMA were to breach the secondary containment and enter the sewer system. The NOAA OR&R chemistry team provided hazard analysis for the behavior of MMA with water, the consequences of a breach of secondary containment, and ALOHA modeling results for the evaporation of 7,000 gallons of MMA from the secondary containment berm. The situation resolved when the overheating tank naturally cracked just enough to release internal pressure safely, allowing the reactive chemical to cool and solidify. This averted an explosion or toxic spill, enabling officials to lift all evacuation orders for roughly 50,000 residents by May 27.