RegulusPipeline research91 FR 43015
Passage 1[Federal Register Volume 91, Number 132 (Monday, July 13, 2026)] [Notices] [Pages 43015-43018] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 2026-14071] ----------------------------------------------------------------------- Pipeline and Hazardous Materials Safety Administration Pipeline Safety: Guidance for Enhancing the Effectiveness of Distribution Integrity Management Programs AGENCY: Pipeline and Hazardous Materials Safety Administration (PHMSA), Department of Transportation (DOT or Department). ACTION: Notice; issuance of advisory bulletin. ----------------------------------------------------------------------- SUMMARY: PHMSA issues this advisory bulletin to remind owners and operators of gas distribution systems of the distribution integrity management program (DIMP) requirements under 49 CFR part 192, subpart P. The guidance is intended to improve implementation of DIMP risk evaluations by addressing factors such as high-risk infrastructure, interactive threats, and leak management effectiveness. In addition, the guidance urges pipeline operators to adopt the most appropriate risk models for use within their integrity management programs, with full consideration of probabilistic risk models. FOR FURTHER INFORMATION CONTACT: Nancy White by phone at 202-923-8268 or by email at [email protected]. SUPPLEMENTARY INFORMATION: To address National Transportation Safety Board (NTSB) Safety Recommendations P-21-2 and P-26-2, PHMSA is reminding owners and operators of gas distribution systems of existing DIMP risk evaluation requirements under 49 CFR part 192, subpart P. This guidance: Emphasizes ongoing efforts to advance pipeline safety risk management and risk evaluations, including foundational concepts developed by the PHMSA-organized Risk Modeling Work Group (RMWG) and its subsequent report, which provides an overview of models that may be universally applicable and used for improved DIMP implementation.\1\ ---------------------------------------------------------------------------#
Passage 2\1\ See https://www.phmsa.dot.gov/pipeline/risk-modeling-work-group/risk-modeling-work-group-overview (providing guidance for documenting RMWG activities); PHMSA, Pipeline Risk Modeling: Overview of Methods and Tools for Improved Implementation (Feb. 1, 2020) (2020 Risk Modeling Report) available at https://www.phmsa.dot.gov/pipeline/risk-modeling-work-group/pipeline-risk-modeling-overview-methods-and-tools-improved-implementation-report (discussing risk modeling principally in the context of gas transmission and hazardous liquid pipelines). --------------------------------------------------------------------------- Reinforces existing PHMSA safety initiatives, including the 2011 Call to Action to modernize aging and high-risk pipeline infrastructure; recent DIMP implementation guidance in ADB-2026-01; and the July 2025 Inspection and Enforcement Priorities memorandum, which prioritizes oversight of high-impact pipeline safety issues, including operator compliance with DIMP regulations.\2\ --------------------------------------------------------------------------- \2\ DOT, U.S. Department of Transportation Call to Action To Improve the Safety of the Nation's Energy Pipeline System (Nov. 1, 2011) (Call to Action), available at https://www.phmsa.dot.gov/safety-awareness/pipeline/call-to-action; PHMSA, ADB-2026-01, Pipeline Safety: Distribution Integrity Management Program Considerations for Plastic Piping and Components, 91 FR 2995 (Jan. 23, 2026); PHMSA, Pipeline Safety Inspection and Enforcement Priorities (July 17, 2025), available at https://www.phmsa.dot.gov/regulatory-compliance/phmsa-guidance/phmsa-pipeline-safety-inspection-and-enforcement-priorities. ---------------------------------------------------------------------------#
Passage 3Highlights recent updates to The Guide for Gas Transmission, Distribution, and Gathering Piping Systems (ANSI/GPTC Z380.1, 2022 edition) addressing interactive threats, system degradation over time, and leak investigation procedures. Urges pipeline operators to adopt the most appropriate risk models for use within their integrity management programs, with full consideration of probabilistic risk models. Guidance and advisory bulletins are intended to provide clarity regarding an operator's existing legal obligations but are not themselves rules meant to bind the public in any way; they do not assign duties, create legally enforceable rights, or impose new obligations that are not otherwise contained in regulations. Accordingly, this guidance will not be relied upon by the Department as an independent basis for affirmative enforcement action or other administrative penalty. To: Owners and Operators of Gas Distribution Pipeline Systems Subject: Guidance for Enhancing the Effectiveness of Distribution Integrity Management Programs Advisory: On February 23, 2018, a natural gas distribution incident occurred on a system operated by Atmos Energy Corporation (Atmos) in Dallas, Texas. The incident resulted in one fatality, four injuries, and major structural damage to a home. Two separate gas-related incidents occurred two days earlier at nearby residences served by the same gas distribution system. Those incidents burned one occupant and caused significant structural damage to both residences. The NTSB determined the probable cause of the February 23 incident was: [T]he ignition of an accumulation of natural gas that leaked from the gas main that was damaged during a sewer replacement project 23 years earlier and was undetected by Atmos Energy Corporation's investigation of two related natural gas incidents on the 2 days prior to the explosion. Contributing to the explosion was Atmos Energy Corporation's insufficient wet weather leak investigation procedures. Contributing to the severity of the explosion was Atmos Energy Corporation's inaction to isolate the affected main and evacuate the houses. Contributing to the degradation of the pipeline system was Atmos Energy Corporation's inadequate integrity management program.\3\ ---------------------------------------------------------------------------#
Passage 4\3\ NTSB, PAR-21/01, Atmos Energy Corporation Natural Gas-Fueled Explosion, Dallas, Texas, Feb. 23, 2018, at 71 (Jan. 12, 2021) (PAR- 21/01), available at https://www.ntsb.gov/investigations/AccidentReports/Reports/PAR2101.pdf. --------------------------------------------------------------------------- NTSB found that rain inhibited the operator's ability to gather useful natural gas leak measurement data, inhibited venting, and increased the tendency of natural gas to migrate laterally where it could be stripped of odorant.\4\ In addition, NTSB noted that while these factors were discussed in the general, safety-related sections of ANSI/GPTC Z380.1, they were not integrated into sections of ANSI/GPTC Z380.1 focusing on best practices for operator DIMPs. Consequently, the increased risk associated with reduced mitigative capability was not considered by Atmos's DIMP evaluation of risks.\5\ --------------------------------------------------------------------------- \4\ NTSB, PAR-21/01 at 67. \5\ Id. --------------------------------------------------------------------------- NTSB determined that ``[l]eak surveys provide an indication of the leaks that may be present at the time they are performed but provide no information on leaks that may occur in the future.'' \6\ NTSB concluded that ``[w]hile Atmos Energy Corporation's periodic leak survey methodology and frequency complied with minimum state and federal requirements, it did not identify the degraded system that was found after the explosion.'' \7\ --------------------------------------------------------------------------- \6\ NTSB, PAR-21/01 at 68. \7\ NTSB, PAR-21/01 at 71. --------------------------------------------------------------------------- NTSB found that ``[i]n addressing the likelihood of failure, age is generally recognized as a strong indicator of performance. However, gas distribution operators are not explicitly required to assess the age of their pipeline in the likelihood of failure evaluation,'' even though ``[t]rending failure rates by system age can reveal degrading performance.'' \8\ --------------------------------------------------------------------------- \8\ NTSB, PAR-21/01 at 66. ---------------------------------------------------------------------------#
Passage 5NTSB issued several safety recommendations as a result of its investigation into this incident. Safety Recommendation P-21-2 in particular advised PHMSA to ``[e]valuate industry's implementation of the gas distribution pipeline integrity management requirements and develop updated guidance for improving their effectiveness. The evaluation should specifically consider factors that may increase the likelihood of failure such as age; increase the overall risk (including factors that simultaneously increase the likelihood and consequence of failure); and limit the effectiveness of leak management programs.'' \9\ In addition, NTSB issued safety recommendations P-21-13 \10\ and P- 21-14 \11\ to the Gas Piping Technology Committee (GPTC) to update ANSI/GPTC Z380.1.\12\ GPTC recently issued Addenda 2 and 4 of this standard to address these NTSB safety recommendations and, as a result, NTSB closed both recommendations as ``Closed--Acceptable Action.'' ---------------------------------------------------------------------------#
Passage 6\9\ NTSB, PAR-21/01 at 72. \10\ Safety Recommendation P-21-13 to GPTC: ``Develop additional guidance that identifies steps gas distribution operators can take to safely respond to leaks, fires, explosions, and emergency calls, considering the limitations due to wet weather conditions, that includes: (1) criteria for when to shut down or isolate gas distribution systems, pressure test main and service lines, and begin evacuations; (2) leak investigation methods that are reliable in wet weather; (3) require an alternate safe response, such as an evacuation when reliable leak investigations are not possible due to wet weather; and (4) leak investigations that assess all viable gas migration paths, including granular backfill and crawlspaces.'' See https://data.ntsb.gov/carol-main-public/sr-details/P-21-013. \11\ Safety Recommendation P-21-14 to GPTC: ``Develop guidance that identifies steps that gas distribution operators can take to ensure that their gas distribution integrity management program, at a minimum, appropriately considers: (1) threats that degrade a system over time, and (2) the increased risk that can result from factors that simultaneously increase the likelihood and consequence of failure.'' See https://data.ntsb.gov/carol-main-public/sr-details/P-21-014. \12\ PHMSA, Gas Distribution Integrity Management Frequently Asked Questions, at 4 (Oct. 26, 2015) (DIMP FAQs), https://www.phmsa.dot.gov/pipeline/gas-distribution-integrity-management/gas-distribution-integrity-management-faqs (``[While] [o]perators may use other approaches to meet the high-level requirements of the [DIMP] regulation . . . PHMSA, State pipeline safety regulators and industry all participated in the development of the [ANSI/GPTC Z380.1] guidelines and have confidence that operators who use them in their programs will comply with the requirements of the rule.''). ---------------------------------------------------------------------------#
Passage 7Further underscoring the need for effective risk management through DIMP, on January 24, 2024, a home explosion and fire occurred in Jackson, Mississippi. The incident resulted in one fatality and one injury and destroyed the home. Three days later, on January 27, 2024, about 0.7 miles southeast of the first explosion, another home explosion and fire occurred and destroyed two homes. NTSB's investigation revealed, in relevant part, that the operator's inadequate leak management program and its relative-risk model failed to classify incident locations as high-risk. These failures highlighted systemic inadequacies within the operator's distribution integrity management program. NTSB determined the probable cause of the January 2024 incidents was the operator's: inadequate leak management program, which allowed for known natural gas leaks, from service-line pipes that had partially pulled out of compression couplings due to soil movement, to be left unrepaired for at least 8 weeks, resulting in gas leaking from the compression couplings and then migrating to the nearby homes and igniting. Contributing to the explosions was Atmos Energy Corporation's inadequate integrity management program, which did not appropriately assess and address risk in its pipeline system. Also contributing was an 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.\13\ --------------------------------------------------------------------------- Consequently, NTSB reiterated Safety Recommendation P-21-2 to PHMSA and issued a new recommendation, P-26-2, urging PHMSA to advise operators to adopt more robust probabilistic risk models where appropriate.\14\ --------------------------------------------------------------------------- \14\ NTSB, PIR-26/01, Atmos Energy Corporation Natural Gas- Fueled Home Explosions and Fires, Jackson, Mississippi, January 24, 2024, and January 27, 2024, at 86 (Mar. 12, 2026) (PIR-26/01), available at: https://www.ntsb.gov/investigations/AccidentReports/Reports/PIR2601.pdf. ---------------------------------------------------------------------------#
Passage 8PHMSA has long concluded that ``[t]he overriding principle in employing any type of risk model/assessment is that it supports risk management decisions to reduce risks.'' \15\ In 2020, PHMSA issued its Risk Modeling Report, providing an overview of the major types of pipeline risk models: qualitative models, relative assessment/index models, quantitative system models, and probabilistic models, and their effectiveness in supporting risk assessments. The report noted that each risk model provides distinct capabilities depending on an operator's specific system complexity, data availability, and resources. For example, qualitative and relative assessment/index models can be effective and well-suited for smaller, less complex distribution networks. PHMSA noted that less complex pipeline systems can be characterized by limited geographic extent and lower mileage; simple system configuration; uniform risk factors throughout the system; and single, small operating organizations.\16\ PHMSA further noted that ``[w]hile different risk model types have different capabilities for evaluating risk reduction actions, quantitative system models or probabilistic models are more versatile and provide greater capabilities to provide risk insights and support decision making.'' \17\ The report also noted that probabilistic models are ``distinguished from other quantitative system models by the use of probability distributions, rather than single point value estimates, to represent model inputs,'' and ``are considered a best practice for supporting all decision types.'' \18\ --------------------------------------------------------------------------- \15\ PHMSA, Pipeline Risk Modeling: Overview of Methods and Tools for Improved Implementation, at 6 (Feb. 1, 2020) (2020 Risk Modeling Report), available at: https://www.phmsa.dot.gov/pipeline/risk-modeling-work-group/pipeline-risk-modeling-overview-methods-and-tools-improved-implementation-report. \16\ 2020 Risk Modeling Report, at 26. \17\ 2020 Risk Modeling Report, at 6. \18\ 2020 Risk Modeling Report, at 82, 26. ---------------------------------------------------------------------------#
Passage 9Pursuant to Sec. 192.1007(f), operators must re-evaluate their DIMP as frequently as determined to be appropriate, not to exceed five years. PHMSA emphasizes that risk assessment is a dynamic process, and that owners and operators should update the risks and threats supporting their DIMP assessments as frequently as each calendar year when there is a change in knowledge or factors that alter the risk of failure.\19\ Evolving system conditions and knowledge may be identified through many means, including records research, maintenance and repair records, existing safety programs such as leak management programs, excavations, lessons learned from industry incidents, or emerging threat data.\20\ --------------------------------------------------------------------------- \19\ See 49 CFR 192.1007(f) and DIMP FAQs C.4.f.1. \20\ For distribution-focused guidance, see PHMSA's historical DIMP development and implementation meetings at https://www.phmsa.dot.gov/pipeline/gas-distribution-integrity-management/gas-distribution-integrity-management-program-meetings. See also PHMSA, DIMP Implementation Insights for Operators (July 2013), available at https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2025-08/SGA_07232013_PHMSA_DIMP_McLaren.pdf. --------------------------------------------------------------------------- Regardless of the risk model used, PHMSA reminds operators that identified threats may be interactive because factors impacting the likelihood and consequence of failure from one threat may be intensified by factors impacting the likelihood and consequence of failure from another threat. Interactive threats may result in an otherwise premature failure at a location on the pipeline.\21\ Typical pipeline threats include corrosion, natural forces (including soil movement), excavation damage, other outside force damage (e.g. vehicle impacts), material or weld defects, equipment failure, incorrect operations, and any other issues that could threaten integrity. An example of interactive threats would be natural forces, including weather and earth movement/soil issues in interaction with corrosion. ---------------------------------------------------------------------------#
Passage 10\21\ For discussions specifically on interactive threats in distribution systems, see PHMSA Risk Modeling Work Group, Interactive Threats (Aug. 2016), available at https://www.phmsa.dot.gov/pipeline/risk-modeling-work-group/interactive-threats-discussion. --------------------------------------------------------------------------- PHMSA reminds operators that pursuant to Sec. 192.1007, an operator must develop an understanding of its pipeline system based on reasonably available information. This would include identifying additional information needed to fill gaps caused by missing, inaccurate, or incomplete records and developing a plan to collect the information. Operators can collect this information through their normal activities, including those that go beyond the activities specified in Part 192. For example, missing facility location, material, and condition data can be captured when a pipe is located or exposed. Maintenance personnel could be surveyed about unusual circumstances they have encountered or asked to review system descriptions to identify useful information that might not already be included.\22\ --------------------------------------------------------------------------- \22\ DIMP FAQs, at 12-13. ---------------------------------------------------------------------------#
Passage 11In addition, PHMSA reminds operators that maintaining the effectiveness of a DIMP requires both record preservation and continual program updates. Under Sec. 192.1011, operators must maintain records demonstrating compliance with DIMP requirements for at least 10 years. PHMSA takes this opportunity to remind operators of the following agency actions: [ssquf] 2011 DOT ``Call to Action,'' which emphasizes pipeline age and material are significant risk indicators, requiring operators to rigorously evaluate risks associated with older, degraded facilities; [ssquf] July 2025 Inspection and Enforcement Priorities memorandum, which identifies gas distribution integrity management programs as a top priority for Federal and State inspections; [ssquf] Advisory Bulletin ADB-2026-01, which reinforces the existing requirements of 49 CFR 192.1007(b) and (c) to identify threats and evaluate and rank risks, specifically highlighting how interactive threats can compound the likelihood and consequence of a failure. PHMSA advises gas distribution pipeline operators to take the following actions to improve DIMP effectiveness: [ssquf] Review NTSB's Pipeline Accident Report PAR-21/01 (Dallas, Texas, February 23, 2018) for information on risks of interactive threats, which may increase the likelihood and consequence of failure and factors that may limit the effectiveness of an operator's leak management program. [ssquf] Review NTSB's Pipeline Investigation Report PIR 26/01 (Jackson, Mississippi, January 24, 2024) for information on the importance of understanding pipeline systems, risk modeling, and further discussion of leak management. [ssquf] In conducting evaluations of DIMP as required by Sec. 192.1007(f), PHMSA urges pipeline operators to adopt the most appropriate risk models for use within their distribution integrity management programs, including consideration of probabilistic risk models. PHMSA acknowledges that each risk model has its benefits. [ssquf] Develop and implement a DIMP plan to evaluate and rank risks. Pursuant to Sec. Sec. 192.1005 and 192.1007(c), operators must consider the likelihood and consequence of failure for all applicable threats. An effective risk evaluation should account for how interactive threats can simultaneously increase both the likelihood and consequences of an accident. Operators are also encouraged to account for time-dependent factors#
Passage 12, such as the performance characteristics of legacy materials or pipeline age. In addition, operators should evaluate the potential for interactive threats, where multiple factors like weather conditions, soil type, and mechanical damage may interact to increase risk. An effective evaluation should be sufficiently detailed to identify where these interactive threats may exist and may require review and integration of historical construction, design, maintenance, operating, and leak records, and review of PHMSA's legacy DIMP guidance. [ssquf] Review updates to ANSI/GPTC Z380.1, 2022 Edition, Addendum 2, Guide Material Appendix (GMA) G-192-8 (DIMP). This addendum provides updated guidance on fulfilling Sec. 192.1007 requirements. Specifically, operators should review GMA G-192-8: Section 3.3 (Knowledge, Additional Information) and Section 4.1 (Identify Threats, Primary Threats), which provide information on accounting for time-dependent threats that may degrade pipeline assets over time. Section 4.4 (Identify Threats, Handling Interactive Threats), which provides information on identifying and ranking threats that interact and may increase overall risk, compounding the severity, likelihood, or consequence of a failure. [ssquf] Review updates to ANSI/GPTC Z380.1, 2022 Edition, Addendum 4. This addendum provides guidance on enhancing the effectiveness of a leak management program (Sec. 192.1007(d)), addressing challenges such as environmental conditions that may affect emergency response and leak detection. Key sections are as follows: GM 192.615: Section 1.3 (Emergency Plans), which provides guidance on prompt and effective response to each type of emergency, including response guidance for emergencies involving non-typical soil conditions which may adversely affect gas migration or leak investigation effectiveness.\23\ --------------------------------------------------------------------------- \23\ In March 2025, NTSB issued Safety Alert, SA-098, Natural Gas Alarms Save Lives, noting that natural gas odorant may be stripped out if natural gas migrates through soil. See https://www.ntsb.gov/Advocacy/safety-alerts/Pages/SA-098.aspx. ---------------------------------------------------------------------------#
Passage 13GM 192.723: Section 1.4 (Distribution Systems: Leakage Surveys), which provides guidance on conducting special one-time surveys, when gas migration or weather-related conditions may hinder leak detection. GM 192.803: Section 1.2 (Definitions), which provides examples of abnormal operating conditions. GMA G-192-11/G-192-11A: Section 5 (Gas Leakage Control Guidelines for Natural/Petroleum Gas Systems), which provides information on leak investigation and classification. Section 5.5 is a new section which provides specific guidance for the effective emergency response and leak investigation in non-typical soil conditions. [ssquf] Determine and implement measures to reduce the risks associated with the failure of gas distribution pipeline assets as required by Sec. 192.1007(d). These measures must include having an effective leak management program. PHMSA notes that data from DIMP risk models may help with determining whether the current leak management method is effective. In addition, gas distribution operators are encouraged to incorporate the updated ANSI/GPTC Z380.1 standard with considerations for non-typical soil conditions and special one-time leak surveys into their DIMP or incorporate other approaches to meet the requirements of 49 CFR part 192, subpart P (See DIMP FAQs, Section B.3). [ssquf] Conduct evaluations of DIMP. Section 192.1007(f) requires operators to re-evaluate their DIMP at an interval that considers the complexity of the system and the types of threats present, but not less than every five years. Operators should ensure their re-evaluation cycle is frequent enough to incorporate ``new knowledge'' gained from incidents, leak history, or changes in environmental conditions (including conditions discussed in this advisory). PHMSA notes through its DIMP Enforcement Guidance that ``[t]he period for the evaluation of program effectiveness must be as frequent as needed to assure distribution system integrity . . .'' \24\ and that many industry best practices and consensus standards, such as ANSI/GPTC Z380.1, use a five-year maximum interval for comprehensive program reviews to ensure the program remains effective as system knowledge evolves. ---------------------------------------------------------------------------#
Passage 14\24\ PHMSA, Gas Distribution Pipeline Integrity Management Enforcement Guidance, at 36 (Dec. 7, 2015), available at https://www.phmsa.dot.gov/pipeline/enforcement/dimp-enforcement-guidance (``DIMP Enforcement Guidance''). --------------------------------------------------------------------------- [ssquf] Maintain records, for a period of at least 10 years, demonstrating compliance with requirements of 49 CFR part 192, subpart P as required by Sec. 192.1011. Such records may include documents supporting threat identification and risk analysis. Examples include records of identified interactive threats in the operator's system and records documenting measures implemented by the operator to reduce the risk to its pipeline system. PHMSA notes that this advisory bulletin does not have the force and effect of law and is not meant to bind owners, operators, or the public in any way. This guidance will not be relied upon by the Department as an independent basis for affirmative enforcement action or other administrative penalty. Issued in Washington, DC, on July 9, 2026, under authority delegated in 49 CFR 1.97. Thomas Correll, Associate Administrator for Pipeline Safety. [FR Doc. 2026-14071 Filed 7-10-26; 8:45 am] BILLING CODE 4910-60-P#
This material provides agency context. It does not replace binding regulatory text, and its legal effect depends on the underlying authority and facts.