PHMSA just issued ADB-2026-06, an advisory bulletin reminding gas distribution operators of their existing obligations under 49 CFR Part 192, subpart P, and pushing them to sharpen how they evaluate risk. The bulletin does not create any new rules, but it does put a fine point on where PHMSA thinks distribution integrity management programs (DIMPs) are falling short: interactive threats, system degradation, and the risk models operators use to tie it all together.
Why Now
The bulletin responds to two NTSB safety recommendations, P-21-2 and P-26-2, both born out of fatal gas distribution incidents. PHMSA is using this guidance to point operators back toward the 2011 Call to Action, Advisory Bulleting ADB-2026-01, and the July 2025 Inspection and Enforcement Priorities memo - all of which already flagged evaluation of risk and DIMP compliance as a top oversight priority.
The Incidents Behind the Guidance
PHMSA walks through two accident investigations to make its point. Neither incident is unique to one operator. The underlying failure patterns are the kind any distribution system could be exposed to.
- Dallas, Texas — February 2018. A gas explosion caused one fatality, four injuries, and major structural damage to a home, two days after two related incidents burned a resident and damaged nearby homes on the same system. NTSB's report (PAR-21/01) found the probable cause of the incident was an accumulation of gas that leaked from a gas main damaged 23 years earlier during a sewer project. The leak was undetected during the local distribution company’s investigation of two related natural gas incidents in the 2 days prior to the explosion. The NTSB report also claimed that insufficient wet weather leak investigation procedures contributed to the incident, failure to isolate the main and evacuate houses contributed to the severity of the incident, and an inadequate DIMP contributed to the degradation of the pipeline system.
- Jackson, Mississippi — January 2024. Two separate home explosions, three days and about 0.7 miles apart, killed one person, injured another, and destroyed three homes. NTSB's report (PIR-26/01) pointed to an inadequate leak management program that left known leaks from service lines pulled apart by soil movement unrepaired for at least eight weeks. The report also stated that the operator’s distribution integrity management program didn't properly assess and address risk and a public awareness program fell short on educating the public and emergency response officials on how to respond to a suspected gas leak.
The Recurring Theme: Interactive Threats
Both incidents share a common thread PHMSA wants operators to address in their DIMP: threats rarely act alone. A pipe weakened by corrosion behaves differently once soil movement or wet weather is added to the mix, and a risk evaluation that scores each threat independently can miss that compounding effect entirely. PHMSA's advisory is explicit that operators need to evaluate how threats like corrosion, natural forces, excavation damage, and material defects can interact to increase both the likelihood and consequence of failure, not just tally them separately.
Risk Models: PHMSA Wants Operators Thinking Harder About the Risk Model They Use
The bulletin doesn't mandate a specific risk model. However, it does nudge operators toward more sophisticated ones where appropriate. Qualitative and index-based models may still be a reasonable fit for smaller, simpler systems, but PHMSA notes that quantitative and probabilistic models offer more versatility and better decision support for systems with more complexity. Use of probabilistic models is described as a best practice for supporting the full range of DIMP decisions.
Updated Guide Material Worth Bookmarking
PHMSA points operators to two recent addenda of ANSI/GPTC Z380.1 (2022 edition). Here's the short version of what each section covers:
- GMA G-192-8, Sections 3.3 and 4.1 - how to account for time-dependent threats that may degrade pipeline assets over time.
- GMA G-192-8, Section 4.4 - how to identify and rank threats that interact and compound one another's severity, likelihood, or consequence of a failure.
- GM 192.615, Section 1.3 - emergency response guidance, including how to handle non-typical soil conditions that affect gas migration.
- GM 192.723, Section 1.4 - when and how to run special one-time leak surveys when weather or migration patterns could hide a leak.
- GM 192.803, Section 1.2 - updated definitions and examples of abnormal operating conditions.
- GMA G-192-11/G-192-11A, Sections 5 and 5.5 (new) - leak investigation and classification guidance, with new detail specifically for non-typical soil conditions.
What PHMSA Is Asking Operators to Do
- Review NTSB's PAR-21/01 and PIR-26/01 reports for the underlying lessons on interactive threats and leak management.
- Adopt the most appropriate risk model that actually fits your system's complexity, giving real consideration to probabilistic models.
- Build interactive threats into your DIMP risk ranking, not just a list of standalone threats.
- Review the updated ANSI/GPTC Z380.1 guide material – including Addendum 2 and 4.
- Determine and implement measures to reduce the risks associated with the failure of gas distribution pipeline assets as required by 192.1007(d). These measures must include having an effective leak management program.
- Re-evaluate your DIMP as often as new knowledge warrants, and no less than every five years, per 192.1007(f).
- Keep records demonstrating DIMP compliance for at least ten years, per 192.1011.
Bottom Line
ADB-2026-06 isn't a new rule, but it's a clear signal about where PHMSA's attention is going next: interactive threats, leak management effectiveness, and the rigor behind your risk model choice. Operators who treat this as a checklist item are missing the point. The two incidents behind this guidance both involved programs that technically met minimum requirements and still missed a degrading system. Now is a reasonable time to test your own DIMP against these questions before someone else does it for you.