New law tightens rules on explosive chemicals after Garden Grove scare

California Gov. Gavin Newsom has signed SB 883, a bill by Sen. Tom Umberg (D-Santa Ana) that tightens building and safety rules for sites storing explosive chemicals, responding to a chemical scare in Garden Grove, Orange County, over Memorial Day weekend 2026.

In May 2026, a tank of methyl methacrylate at the GKN Aerospace plant in Garden Grove came close to exploding after it overheated. California deployed more than 700 people and about 50,000 residents were evacuated. The tank eventually cracked just enough to relieve pressure without unleashing an explosion. Investigations found that methyl methacrylate was not a regulated chemical under either the U.S. EPA's Risk Management Program or California's parallel CalARP system, exposing a regulatory gap.

SB 883 would prohibit a city or county from approving a building permit for a new reactive chemical storage facility with the potential for an explosion, including due to thermal runaway, unless the facility has a backup cooling system. It deems methyl methacrylate to pose a significant risk of accidental release, fire, explosion or catastrophic incident, adds it to the state's accidental release prevention program, and requires CalEPA to adopt a state threshold quantity through regulation. The bill also expands the program's definition of regulated substance, requires the Office of Environmental Health Hazard Assessment to consider reactive chemical storage facilities in CalEnviroScreen, requires the state Office of Emergency Services to maintain a statewide inventory of such facilities, and updates CEQA so that storage sites with an explosion risk are not exempt from environmental review.

The new building-permit requirements do not apply to existing facilities; sites such as GKN are not covered by that provision.

Translated by 119zj