NTSB Safety Recommendation P-26-009

NTSB safety recommendation P-26-009.

TO THE ATMOS ENERGY CORPORATION: Transition from a relative-risk model to a probabilistic distribution integrity management risk model.

Priority: CLASS II

Overall Status: Open - Initial Response Received

Issued Date: 2026-03-26

Adopted Date: 2026-03-12

Synopsis: This report discusses the January 2024 natural gas-fueled explosions and fires at two separate homes in Jackson, Mississippi, which occurred 3 days apart, collectively resulting in one injury, one fatality, and three destroyed homes. Safety issues identified in this report include compression coupling leaks, insufficient leak management program, inadequate distribution integrity management program, ineffective public awareness program, and absence of natural gas detection alarms in buildings.

Probable Cause: The National Transportation Safety Board determines that the probable cause of the two explosions at two separate homes in Jackson, Mississippi, was the service-line pipes partially pulling out of the compression couplings, likely because of soil movement (shrinking and swelling), creating natural gas leaks that Atmos Energy Corporation identified and left unrepaired for at least 8 weeks, which enabled gas to migrate to the nearby homes and ignite. Contributing to Atmos Energy Corporation’s failure to prevent the accidents were the operator’s: (1) insufficient leak management program, which did not determine appropriate monitoring timelines for leaks in adverse-soil conditions; (2) ineffective public awareness program, which did not adequately educate the public or emergency response officials on how to respond to a suspected natural gas leak; and (3) inadequate integrity management program, which did not appropriately assess and address risk in its Mississippi Division pipeline system.

Ntsbnumber: PLD24FR003

Report Number: PIR-26-01

Addressee Name: ATMOS Energy Corporation

Addressee Status: Open - Initial Response Received

Addressee Organization Type: P-Private Industry

Communication Date: 2026-03-26

Communication Type: Transmittal Letter

Communication Contents: The National Transportation Safety Board (NTSB) is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant accidents in other modes of transportation—railroad, highway, marine, and pipeline. We determine the probable cause of the accidents and issue safety recommendations aimed at preventing future accidents. In addition, we carry out special studies concerning transportation safety and coordinate the resources of the federal government and other organizations to assist victims and their family members affected by major transportation disasters. We are providing the following information to urge Atmos Energy Corporation to act on the safety recommendation in this letter because we believe your organization can help reduce the risk of future accidents. For more information about the NTSB and our recommendation process, please see the attached one-page summary. This letter also includes information about our March 12, 2026, report, Atmos Energy Corporation Natural Gas-Fueled Home Explosions and Fires, Jackson, Mississippi, January 24, 2024, and January 27, 2024, NTSB/PIR-26-01. The details of this accident investigation and the resulting safety recommendations may be found in the attached report, which can also be accessed at http://www.ntsb.gov. As a result of this investigation, we identified the following safety issues: • Compression coupling leaks that the natural gas distribution operator had identified and left unrepaired. • Insufficient leak management program, which did not determine appropriate monitoring timelines for leaks in adverse-soil conditions. • Ineffective public awareness program, which did not adequately educate the public or emergency response officials on how to respond to a suspected natural gas leak. • Inadequate distribution integrity management program, which did not appropriately assess and address risk in its pipeline system. • Absence of natural gas detection alarms in buildings, which left occupants vulnerable to the dangers of unrecognized gas leaks. Accordingly, the NTSB makes the following safety recommendations to Atmos Energy Corporation (additional information regarding this recommendation can be found in the noted section of the report): • Develop and implement a program to locate and replace all mechanical couplings and mechanical joints located in expansive soils that are not resistant to pipe pullout with couplings and joints developed specifically for those conditions. The program should establish and make public the project milestones and timeline. (P-26-3) (See section 2.2.) • Update your companywide leak management program procedures to require weekly monitoring of nonhazardous (grade 2 or grade 3) belowground leaks identified in locations with adverse-soil conditions (such as water-saturated soil, flooding, drought, frozen ground, or settlement). (P-26-4) (See section 2.3.) • After completing the action described in P-26-4, implement a training program to maintain employee and contractor proficiency on the updated procedures. (P-26-5) (See section 2.3.) • Develop and implement a program to provide more frequent training to emergency response officials in all the distribution areas that you serve, including training on how to respond to natural gas-leak calls, and monitor the program for effectiveness. (P-26-6) (See section 2.4.) • Require your technicians who identify but do not repair a belowground natural gas leak to immediately notify people near the unrepaired leak that (1) the hazard potential of a leak can change over time, and (2) they should evacuate and then call 9 1 1 and Atmos Energy Corporation every time they smell natural gas odorant. (P-26-7) (See section 2.4.) • Develop and implement a program to proactively identify and collect missing service-line information for all your operating divisions. The program should (1) identify one or more methods for gaining additional system data and (2) establish and make public the milestones and timeline for acquiring the unknown system data. (P-26-8) (See section 2.5.) • Transition from a relative-risk model to a probabilistic distribution integrity management risk model. (P-26-9) (See section 2.5.) • Develop and implement a program that makes natural gas alarms available to members of the public who reside in your distribution areas. (P-26-10) (See section 2.6.) The NTSB is vitally interested in these recommendations because they are designed to prevent accidents and save lives. We would appreciate a response within 90 days of the date of this letter, detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendations by number (Safety Recommendation P-26-3 through -10). We encourage you to submit your response to ExecutiveSecretariat@ntsb.gov. If your reply, including attachments, exceeds 20 megabytes, please e mail us at the same address for instructions on how to send larger documents. Please do not submit both an electronic copy and a hard copy of the same response. All communications regarding safety recommendations are stored by the NTSB and viewable by the public. Please do not send privileged or confidential communications in response to this recommendation. Responses marked as confidential or privileged (or similar designations) will be considered nonresponsive. In the likely event that your organization uses auto generated and/or preformatted confidentiality statements on letterhead or outgoing e-mails, please include a statement in your letter indicating that the information can be publicly released. If you have concerns about this protocol, please contact us at ExecutiveSecretariat@ntsb.gov. From Pipeline Investigation Report PIR-26-01 “Atmos Energy Corporation Natural Gas Fueled Home Explosions and Fires Jackson, Mississippi January 24, 2024, and January 27, 2024” published on March 26, 2026: Inadequate Distribution Integrity Management Program System Data As discussed in 1.7.1.2, over 15 years ago, the Pipeline and Hazardous Materials Safety Administration introduced distribution integrity management requirements to enhance safety by identifying and reducing pipeline integrity risks. The first required element for natural gas distribution pipeline integrity management programs is system data (or system knowledge), and Atmos lacked system data for its Mississippi Division. After the Jackson accidents, Atmos told the NTSB that it did not have service-line installation records for over 63% of the service lines in its Mississippi Division. Therefore, at the time of the accidents, Atmos did not have system data for over 193,024 of the 306,387 service lines in its Mississippi Division, including the accident service lines. Atmos’s lack of system data for its Mississippi Division affected its leak management program and its risk model. The lacking system data affected Atmos’s leak management program because, despite Atmos’s knowledge of the threat of compression coupling failure in expansive-soil environments, like Jackson, Mississippi, (see section 2.2 for more information on this), its lack of system data for its Mississippi Division service lines prevented it from identifying the locations of most of the compression couplings in that system, including the accident couplings. The lacking system data affected Atmos’s risk model because system data was a primary input in the model. Although Atmos’s risk model assigned higher risk-factor weights to service lines that were missing system data (see section 1.9.3.2 for more on this), the model was incapable of determining which of the data lacking service lines posed the greatest threat to the system because of all the missing data. (See section 2.5.2 for more information on how Atmos’s lack of system data impacted its risk model.) As of this repo

Addressee Organization Type: P-Private Industry

Communication Date: 2026-06-24

Communication Type: Official Correspondence

Communication Contents: -From John McDill, Senior Vice President Utility Operations: Atmos Energy is actively advancing its risk modeling capabilities to enhance system safety and decision-making. Atmos Energy is actively engaged with industry developments on risk modeling, including PHMSA’s 2024 Risk Modeling Workship and encouragement to consider more advanced modeling techniques, including probabilistic approaches. While we currently use a robust, risk-informed relative-risk Pipeline Replacement Prioritization model as well as a Distribution Risk Assessment Model (DRAM), we have evaluated probabilistic modeling offerings and opportunities and are in the process of expanding our risk modeling through the implementation of probabilistic methodologies for specific applications within our risk evaluation processes. Under this approach, probabilistic models will be used to supplement and refine decision-making for enhanced safety outcomes and used in conjunction with our relative risk models, which are designed to prioritize risk reduction activities based on available data, engineering judgment, and operational experience. Our risk modeling is further enhanced by the operational system data that is collected through multiple efforts including that of our leak management efforts as outlined in our responses to Recommendations P-26-3 and P-26-4. This approach is consistent with regulatory requirements and industry practices for enhanced safety outcomes. Atmos Energy will continue to evaluate probabilistic modeling resources and capabilities and explore additional analytical capabilities through specific probabilistic applications. Based on the outcomes, we will use those to guide our next steps for our risk modeling efforts as we chart a path to the adoption of probabilistic modeling over time. Accordingly, we ask that the NTSB close this Recommendation as acceptable.