​On December 2, 2024, about 6:26 a.m., a natural gas explosion and fire destroyed a single-family residence at 535 Avondale Garden Road in Avondale, Louisiana. The Atmos Energy Corporation provided natural gas service in the area, but the destroyed residence did not have gas service. One person was fatally injured, and five other people sustained injuries. A neighboring residence was damaged, and its residents were displaced. 

​We determined that the probable cause of the Avondale, Louisiana, home explosion was the release and underground migration of natural gas from a gas main that failed when a cement truck drove over a valve box that the Atmos Energy Corporation installed in contact with the gas main; the valve box transmitted the truck’s weight to the main and fractured it. Contributing to the severity of the accident was the Atmos Energy Corporation’s failure to identify the underground migration of gas during its leak investigation and to recognize the need to evacuate structures outside the immediate area of the leak.​​

​Federal regulations require that valve boxes be installed such that they do not transmit external loads to buried natural gas assets, as occurred in the Avondale accident. Natural gas operators can improve safety by making sure that employees have the tools, knowledge, and clear procedures they need to comply with federal regulations when installing or maintaining valve boxes, and by taking every opportunity to update legacy valve boxes with modern designs and materials. ​​

The unidentified danger of underground gas migration in the Avondale accident illustrates the importance of completing a thorough leak investigation before shifting to non-safety-critical tasks. Operators can protect the quality of leak investigations through means such as oversight, regular training, and work aids to ensure employees know and follow leak response procedures.

This accident also underscores the value of natural gas alarms even in buildings that do not have natural gas service but are located near natural gas assets. Natural gas alarms provide both early warning of dangerous gas concentrations and a last line of defense when a leak investigation fails to identify a hazard. Further information about natural gas alarms is available on the NTSB website.