​On December 2, 2024, about 6:26 a.m., a natural gas explosion destroyed a single-family residence (the incident home) at 535 Avondale Garden Road in Avondale, Louisiana.[1]1 One person died, and five people were injured. A neighboring residence was damaged, and its residents were displaced. At the time of the explosion, the weather was clear with winds of 11 mph; the temperature was 50°F with no precipitation.

Earlier on the morning of the explosion, a cement truck entering a construction site ran over a natural gas valve box about 340 feet from the incident home. (See figure.) The construction crew observed a gas leak and called Atmos Energy (Atmos) and 911 to respond. Emergency responders arrived at 5:15 a.m., and the first Atmos technician arrived at 5:35 a.m. The incident home exploded and caught fire while Atmos employees were assessing the leak near the valve box. Atmos employees discovered gas readings in the home’s sewer cleanout shortly after the explosion.[2]

​The natural gas system serving Avondale Garden Road comprises 2-inch coated steel main running along the west side of the road shoulder under an unpaved area. The gas main had been installed in two stages, one in 1952 and one in 1960. The gas system pressure was about 80 pounds per square inch (gauge) at the time of the explosion.[3] The gas-related infrastructure the cement mixer ran over was a cylindrical cast iron valve box positioned over the main. The valve box was there to provide access to a 2-inch threaded valve. The valve itself was about 2 feet below ground and had been installed in 1952. There was no gas service to the incident home.

​While on-scene, National Transportation Safety Board (NTSB) investigators identified an uncapped, abandoned sewer lateral near the leak location.[4] The sewer lateral had previously been connected to a different building near the construction site and was positioned to provide a potential path for natural gas to migrate into the sewer main and then into the incident home. The NTSB also conducted interviews, reviewed Atmos’ procedures, and recovered the gas valve, valve box, and sections of gas main for analysis.

The NTSB’s investigation is ongoing. Future investigative activity will focus on the cause of the leak and Atmos’ response to the leak report.

Parties to this NTSB investigation include:

• ​the Pipeline and Hazardous Materials Safety Administration, 
• the Louisiana Department of Energy and Natural Resources, and 
• Atmos Energy.
  

[1] All times in this report are local times.

[2] A sewer cleanout is a capped pipe that allows for blockage removal by providing access to a sewer line.

​[3] The maximum allowable operating pressure was 100 pounds per square inch (gauge).

[4] A sewer lateral is a pipe that c​arries wastewater from a home, business, or other building to a sewer system.