NTSB Safety Recommendation P-26-001

NTSB safety recommendation P-26-001.

TO THE UNITED STATES DEPARTMENT OF TRANSPORTATION OFFICE OF THE INSPECTOR GENERAL: Audit the Pipeline and Hazardous Materials Safety Administration’s ongoing joint assessment of Atmos Energy Corporation (with the eight state partners that regulate Atmos Energy Corporation’s facilities), including a review of Atmos Energy Corporation’s approach to the safety management of its pipeline and how it applies lessons learned across all its operating divisions.

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: DOT, Office of Inspector General

Addressee Status: Open - Initial Response Received

Addressee Organization Type: G-Federal Government

Communication Date: 2026-06-05

Communication Type: Recommendation Mention

Communication Contents: Atmos Energy Corporation Natural Gas–Fueled Home Explosion Pipeline Investigation Report PIR-26-03 published on June 5, 2026: Analysis The explosion and fire occurred after natural gas leaked from a fractured buried main, migrated through an uncapped underground sewer lateral, entered the accident home, and reached an explosive concentration near an unknown ignition source. The investigation did not identify issues with gas pressures in the area of the leak or the timeliness or efficacy of the local emergency response agencies. Postaccident bar-hole testing and excavations found only one source of natural gas: a leak in the gas main near a valve box on the eastern edge of the construction site. On-site examinations of the main found that it was fractured around most of its circumference with a thin strip of metal at the top (12 o’clock position) joining the southern section of pipe to the section still threaded into the valve body. This indicates tension—a stretching force—at the bottom of the pipe along its long axis. Tension along the bottom of the pipe is consistent with a bending stress created by an external downward force. Based on information provided to Atmos by the construction superintendent, a cement truck ran over a valve box at the leak’s location immediately before he heard and smelled natural gas being released. The investigation did not identify another plausible external force that could have damaged the main. The Materials Laboratory examination of the main found fracture characteristics typical of fast crack growth and no signs of significant corrosion or preexisting structural damage that could have contributed to the failure. The fracture was therefore consistent with a sudden application of force by the valve box to the main. Based on the fracture’s location, timing, and fast-cracking characteristics, the valve box transmitted part of the cement truck’s weight to the gas main, causing the main to fracture and leak. Examination of the gas main and valve box involved in this accident found coal tar coating the main and deposited on the bottom edge of the valve box. This indicates that the valve box was in contact with the main. The presence of coal tar alone does not indicate when the contact occurred, but the evidence is consistent with the valve box being installed in contact with the main and therefore able transmit the cement truck’s weight directly to the main near the fracture’s location. Federal regulations at 49 CFR 192.181(c)(3) require that valve boxes not be installed in a manner that transmits external loads to mains, and valve boxes are normally installed with a buffer of soil or other protection between the valve box and the assets immediately below. For example, Atmos’s newer valve boxes are installed with support and base pads to prevent load transmission. However, Atmos was not actively replacing cast iron valve boxes with this newer design. Further, the maintenance crew that removed and reinstalled the valve box about 2 months before the accident did not have a specific standard to follow for reinstalling cast iron valve boxes other than an expectation that the top of the valve box be level with the grade. The lack of a standard likely led to the common reinstallation of valve boxes in contact with mains, as described by an Atmos vice president of operations. If Atmos had adopted either a standard for safely installing cast iron valve boxes or a policy of replacing cast iron valve boxes with the newer design, the protective buffer of soil or support pad would have reduced the load transmitted to the pipe on the day of the accident. There is not enough evidence to determine whether a buffer or pad would have prevented the accident, but it would have made the infrastructure more resilient. Atmos has not reported making changes to its valve box installation practices. After the main fractured, gas propagated undetected through an uncapped underground sewer lateral into the sewer system and then into the accident home, where it reached an explosive concentration. The gas in the sewers remained undetected because Atmos personnel did not test the atmosphere in the sewers prior to the explosion. For about 35 minutes, most of the time between the initial leak and the explosion, there was only one Atmos employee on the scene: an experienced senior service technician. He was equipped with a CGI and checked nearby storm drains for the presence of gas, which was one step in Atmos’s subsurface leak investigation procedure. During his interview with the NTSB, he described planning to check the sewers, another required step, but said that he had already confirmed that there was no threat to life or property. His activities after checking the storm drains are also consistent with a belief that he had finished assessing the risk posed by the leak: he switched to the non-safety-critical work of recording billing information for the damage. The investigation did not find evidence of a natural gas alarm in the accident home, which did not have gas service but was still impacted by a leak from a gas main. It is likely that a natural gas alarm would have provided the home’s occupants with warning of accumulating natural gas and given them an opportunity to evacuate before the explosion. The NTSB has advocated wider installation and use of natural gas alarms for nearly 50 years, including following the investigation into a pair of 2024 home explosions in Jackson, Mississippi, that involved Atmos assets. As a result of that investigation, the NTSB reiterated a recommendation to the 50 states, the Commonwealth of Puerto Rico, and the District of Columbia: Require the installation of natural gas alarms that meet the specifications of National Fire Protection Association 715 in businesses, residences, and other buildings where people congregate that could be affected by a natural gas leak. (P-25-5) Footnote: See CAROL for the complete history and current status of this recommendation. The NTSB also recommended that Atmos “develop and implement a program that makes natural gas alarms available to members of the public who reside in its distribution areas” (P-26-10).11F Footnote: See CAROL for the complete history and current status of this recommendation.

Addressee Organization Type: G-Federal Government

Communication Date: 2026-03-26

Communication Type: Transmittal Letter

Communication Contents: This letter provides information about the National Transportation Safety Board’s (NTSB) 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 recommendation to the Department of Transportation Office of the Inspector General (additional information regarding this recommendation can be found in the noted section of the report): • Audit the Pipeline and Hazardous Materials Safety Administration’s ongoing joint assessment of Atmos Energy Corporation (with the eight state partners that regulate Atmos Energy Corporation’s facilities), including a review of Atmos Energy Corporation’s approach to the safety management of its pipeline and how it applies lessons learned across all its operating divisions. (P-26-1) (See section 2.3.) The NTSB is vitally interested in this recommendation because it is 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 this recommendation. When replying, please refer to the safety recommendation by number (Safety Recommendation P-26-1). 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. 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: 2.3 Insufficient Leak Management Program Leak Repair and Leak Reevaluation The leaks Atmos identified and classified on Bristol Boulevard (a grade 2 leak) and Shalimar Drive (a grade 3 leak) became hazardous before Atmos’s leak management program procedures required them to be reevaluated or repaired. Atmos’s Mississippi procedures required a grade 2 leak to be reevaluated at least once every 6 months and repaired within one calendar year (but no later than 15 months). The accident on Bristol Boulevard occurred about 2 months after Atmos identified the grade 2 leak there, which was about 4 months before Atmos procedures required its technicians to reevaluate the leak and about 13 months before Atmos procedures required its technicians to repair it. Atmos’s Mississippi procedures required a grade 3 leak to be reevaluated during the next scheduled survey or within 15 months, whichever came first, and repaired or cleared within 36 months. The accident on Shalimar Drive occurred about 2 months after Atmos identified the grade 3 leak there, which was about 13 months before Atmos procedures required its technicians to reevaluate the leak and about 34 months before Atmos procedures required its technicians to repair or clear it. After the two accidents, Atmos updated its companywide leak management program to reduce the reevaluation and repair timelines for all nonhazardous natural gas leaks to every 30 days and within 6 months, respectively. Leak Monitoring Between November 2023 and January 2024, when weather conditions in Jackson adversely affected the soil, changing the natural gas migration patterns of at least 2 of the 289 open (unrepaired) leaks in the city (leaks open on the day of the Bristol Boulevard accident), Atmos’s Mississippi leak management program procedures did not prompt employees to monitor the open leaks. However, unlike Atmos’s Mississippi procedures, Atmos’s procedures for classifying grade 2 leaks in the state of Kansas included adverse-soil considerations. These procedures stated that under adverse-soil conditions, which included soil affected by flooding, drought, frozen ground, and settlement, a grade 2 leak must be monitored weekly to ensure that the leak would not represent a probable hazard and that it reasonably could be expected to remain nonhazardous. In the nearly 2.5 months between the time Atmos first identified the grade 2 leak at Bristol Boulevard and the time the leak became hazardous, Jackson experienced drought conditions, which Atmos’s Kansas procedures would have considered adverse. During that time, Jackson also experienced a period of heavy rains that resulted in water saturated soil, something Atmos’s companywide procedures required employees to consider when determining grade 2 leak repair priority but did not require them to consider when determining grade 2 leak monitoring frequency because it did not have companywide leak monitoring procedures for grade 2 leaks or grade 3 leaks. Footnote: Additionally, because Atmos lacked system data for most of the service lines in its Mississippi Division (and several other of its divisions), it could not effectively prioritize the grade 2 leaks that required repair. (See section 2.5.1 for more information on Atmos’s lack of service-line data.) Atmos’s Kansas leak management program procedures applied only to grade 2 leaks, not grade 3 leaks. However, after the two accidents, Atmos found that nearly 15% of the grade 3 leaks open on the day of the Bristol Boulevard accident met the criteria for grade 1 or grade 2 leaks upon reevaluation. This indicates that Atmos’s classifications of leaks can change over time, in some cases, because of environmental factors, including soil conditions. As such, the operator’s more stringent leak monitoring procedures should apply to all nonhazardous leaks in adverse-soil conditions, no matter the grade. Therefore, the NTSB concludes that Atmos’s lack of companywide leak management procedures requiring employees to frequently monitor open, belowground natural gas leaks located in adverse-soil conditions permitted the accident leaks to become hazardous before Atmos repaired them. After the two accidents, Atmos reduced the reevaluation and repair timelines for all nonhazardous leaks companywide. Atmos has not updated its leak management program procedures companywide to include frequent monitoring of natural gas leaks in adverse-soil conditions, as included in its Kansas procedures. Therefore, the NTSB recommends that Atmos update its 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). The NTSB also recommends that Atmos, after completing the action described in P-26-4, implement a training program to maintain employee and contractor proficiency on the updated procedures. Footnote: See section 4 for a full listing of the recommendations in this report. Atmos operates in eight states, and this investigation determined that the state specific pipeline requirements in Kansas coul

Addressee Organization Type: G-Federal Government

Communication Date: 2026-06-17

Communication Type: Official Correspondence

Communication Contents: -From Mitch Behmn Deputy Inspector General performing the duties of Inspector General: Thank you for your letter dated March 26, 2026, regarding the National Transportation Safety Board’s (NTSB) report Atmos Energy Corporation Natural Gas-Fueled Home Explosions and Fires, Jackson, Mississippi, January 24, 2024, and January 27, 2024 (NTSB/PIR-26-01). In this report, NTSB recommended that the U.S. Department of Transportation (DOT) Office of Inspector General (OIG) audit the Pipeline and Hazardous Materials Safety Administration’s (PHMSA) ongoing joint assessment of Atmos Energy Corporation, including a review of Atmos Energy Corporation’s approach to the safety management of its pipeline. Under the authority of the Inspector General Act of 1978, as amended (IG Act), OIG conducts independent and objective investigations and audits of DOT’s operations and activities. Footnote: 5 U.S. Code § 401 et seq. Our work supports DOT’s transportation safety goals; protects taxpayer dollars; and promotes the economy, efficiency, and effectiveness of DOT programs. In accordance with the IG Act, and to maintain our independence and objectivity, OIG does not engage in making policy decisions for the Department or assist in operating DOT programs. As required by the IG Act, OIG conducts audits in accordance with the Government Accountability Office’s generally accepted Government auditing standards (GAGAS). Footnote: Government Accountability Office, Generally Accepted Government Auditing Standards (February 1, 2024). Those standards require that we obtain sufficient, appropriate evidence to provide a reasonable basis for our findings and conclusions. We appreciate NTSB’s interest in our work and our shared mission to protect transportation safety. However, due to limitations related to OIG’s statutory authority and audit requirements, we have the following concerns about NTSB’s recommendation: • Limited authority. In accordance with the IG Act, our audit work centers on the Department’s transportation programs and operations. We do not have the authority to audit non-DOT programs, operations, or entities, including non-DOT public or private transportation organizations or companies. As such, we cannot directly review Atmos Energy Corporation’s safety management approach. To the extent our work addresses private companies, it is in the context of the Department’s oversight of the transportation and utility industry. • Ongoing efforts. As noted in NTSB’s recommendation, PHMSA’s joint assessment remains ongoing, and its current status is unclear. To meet our GAGAS requirements and to ensure efficient use of our resources, we generally do not audit ongoing efforts. Auditing incomplete efforts would create a risk that our findings would be based on incomplete evidence or that our findings would be overtaken by an auditee’s ongoing progress, rendering potential recommendations obsolete. • Insufficient criteria. Per GAGAS requirements, we plan and select audit topics that allow us to measure the Department’s actions against objective, measurable, and reliable criteria, such as laws, regulations, established standards, or formal policy. Because PHMSA’s ongoing Atmos assessment is not being conducted in fulfilment of statute or other requirement, we would not have suitable criteria against which to assess it. While we are currently unable to meet the intent of NTSB’s recommendation regarding PHMSA’s Atmos Energy Corporation assessment, we remain committed to identifying opportunities to improve PHMSA’s safety oversight. We are currently conducting an audit of PHMSA’s oversight of Natural Gas Distribution Infrastructure Safety and Modernization (NGDISM) grants. In addition, we plan to conduct additional work related to PHMSA’s oversight when this audit is complete. We would be glad to discuss our work and authority further at your convenience. If you have any questions, please contact me or Nelda Z. Smith, Principal Assistant Inspector General for Auditing and Evaluation.