# Pipeline Safety: Repair Criteria for Hazardous Liquid and Gas Transmission Pipelines

- **operation:** document
- **citation:** 91 FR 42272
- **title:** Pipeline Safety: Repair Criteria for Hazardous Liquid and Gas Transmission Pipelines
- **source type:** rulemaking
- **agency:** Pipeline and Hazardous Materials Safety Administration
- **status:** proposed
- **official:** true
- **published on:** 2026-07-08
- **effective on:** Not available
- **summary:** PHMSA proposes to modernize and to clarify the anomaly response criteria in the Federal pipeline safety regulations for gas transmission and hazardous liquid pipelines. Driven by twenty years of technological development, modern engineering concepts allow operators to identify, schedule, and remediate pipeline anomalies more effectively and in a less costly manner. PHMSA proposes incorporating these improved safety practices into its regulations by finalizing certain safety improvements advanced in recent rulemakings for gas transmission pipelines and extending those changes to hazardous liquid pipelines. In addition, PHMSA proposes certain non-substantive revisions to its gas and hazardous liquid repair regulations to improve compliance.
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Federal Register, Volume 91 Issue 129 (Wednesday, July 8, 2026) [Federal Register Volume 91, Number 129 (Wednesday, July 8, 2026)] [Proposed Rules] [Pages 42272-42306] From the Federal Register Online via the Government Publishing Office [ www.gpo.gov ] [FR Doc No: 2026-13805] [[Page 42271]] Vol. 91 Wednesday, No. 129 July 8, 2026 Part II Department of Transportation ----------------------------------------------------------------------- Pipeline and Hazardous Materials Safety Administration ----------------------------------------------------------------------- 49 CFR Parts 192 and 195 Pipeline Safety: Repair Criteria for Hazardous Liquid and Gas Transmission Pipelines; Proposed Rule Federal Register / Vol. 91, No. 129 / Wednesday, July 8, 2026 / Proposed Rules [[Page 42272]] ----------------------------------------------------------------------- DEPARTMENT OF TRANSPORTATION Pipeline and Hazardous Materials Safety Administration 49 CFR Parts 192 and 195 [Docket No. PHMSA-2025-0019] RIN 2137-AF44 Pipeline Safety: Repair Criteria for Hazardous Liquid and Gas Transmission Pipelines AGENCY: Pipeline and Hazardous Materials Safety Administration (PHMSA), Department of Transportation (DOT). ACTION: Notice of proposed rulemaking (NPRM). ----------------------------------------------------------------------- SUMMARY: PHMSA proposes to modernize and to clarify the anomaly response criteria in the Federal pipeline safety regulations for gas transmission and hazardous liquid pipelines. Driven by twenty years of technological development, modern engineering concepts allow operators to identify, schedule, and remediate pipeline anomalies more effectively and in a less costly manner. PHMSA proposes incorporating these improved safety practices into its regulations by finalizing certain safety improvements advanced in recent rulemakings for gas transmission pipelines and extending those changes to hazardous liquid pipelines. In addition, PHMSA proposes certain non-substantive revisions to its gas and hazardous liquid repair regulations to improve compliance. DATES: Submit comments by September 8, 2026. A public meeting of PHMSA's statutory advisory committees will be held on a date to be announced in the Federal Register. ADDRESSES: Submit comments by any of the following methods, identifying docket number PHMSA-2025-0019 at the top of the first page: On https://www.regulations.gov , follow instructions to ``submit a comment.'' By mail or hand delivery to Docket Management System, U.S. Department of Transportation, 1200 New Jersey Avenue SE, West Building Ground Floor, Room W12-140, Washington, DC 20590-0001. Hand delivery is available to this address between 9:00 a.m. and 5:00 p.m., Monday through Friday (except Federal holidays). Include two copies if submitting by mail and include a self-addressed and stamped postcard to receive confirmation of receipt. By fax to Docket Management System at (202) 493-2251. Comments may be viewed at https://www.regulations.gov/docket/PHMSA-2025-0019 . Comments are posted without changes or edits, including any personal information provided. DOT's privacy statement can be reviewed at https://www.dot.gov/privacy . As required by the Administrative Procedure Act (5 U.S.C. 553(b)(4)), a plain language summary of the proposed rule is also available in section I.B, and this proposal will be available online on the rulemaking docket. Confidential Business Information (CBI): You may designate a comment as CBI if your comment contains commercial or financial information that is customarily treated as private and that you actually treat as private by sending to Sayler Palabrica, at the contact information listed below, the following: (1) the original document with each page containing CBI marked as ``confidential;'' (2) a redacted copy with the CBI deleted; and (3) an explanation of why the information you are submitting is CBI. See 49 CFR 190.343. Any comment not specifically designated as CBI will be placed in the public docket. FOR FURTHER INFORMATION CONTACT: Sayler Palabrica, Standards and Rulemaking Division, by phone at (202) 744-0825 or by email at [email protected] . SUPPLEMENTARY INFORMATION: I. Executive Summary A. Background B. Summary of Proposal C. Cost Benefit Summary II. Background A. Regulatory Origin B. Technological Development C. Modernization in PHMSA Regulations III. Advanced Notice of Proposed Rulemaking IV. Discussion of the Proposal A. Response Schedules B. Response Criteria i. Gas Transmission Response Criteria ii. Hazardous Liquid Response Criteria C. Anomaly Evaluation i. Anomaly Evaluation for Dents by the Dent ECA ii. Anomaly Evaluation for Metal Loss iii. Anomaly Evaluation for Cracks iv. Generally Applicable Components of Anomaly Evaluation D. Material Properties and Records i. Toughness and Material Property Values ii. Material Properties for Hazardous Liquid Pipelines iii. Recordkeeping for Hazardous Liquid Pipelines E. Response, Repair, and Remediation Requirements i. Discovery ii. Non-HCA Hazardous Liquid Response Requirements iii. Temporary Pressure Reduction iv. General Repair Requirements V. Section-by-Section Analysis VI. Legal Authority A. Pipeline Safety Laws B. Section 60102(b) Practicability Factors VII. Regulatory Analysis VIII. List of Subjects I. Executive Summary A. Background In the early 2000s, PHMSA created integrity management (IM) programs for gas transmission and hazardous liquid pipelines. Both IM programs included criteria for responding to anomalies.\1\ These requirements--which today apply approximately to 41 percent of hazardous liquid and less than 18 percent of gas mileage in high consequence areas (HCAs) and other higher risk locations--used generic depth measurements that did not account for the specific anomaly or the operating parameters of the pipeline.\2\ That approach has forced costly repair of pipelines in good serviceable condition, interrupting service for consumers and disrupting other proactive operational activities. --------------------------------------------------------------------------- \1\ Pipeline Safety: Pipeline Integrity Management in High Consequence Areas, 68 FR 69778 (Dec. 15, 2003); Pipeline Safety: Pipeline Integrity Management in High Consequence Areas (Repair Criteria), 67 FR 1650 (Jan. 14, 2002). \2\ Though a smaller portion of gas transmission pipelines are in an HCA than hazardous liquid pipelines, the gas response schedule also applies to Class 3, Class 4, and other moderate consequence areas with a high operating stress level. 49 CFR 192.710(a). The IM program for hazardous liquid pipelines applies to pipelines in, or that could affect, an HCA. Sec. 195.452(a). --------------------------------------------------------------------------- Technology has dramatically advanced in the quarter of a century since the adoption of the IM program. In-line inspection (ILI) tools can now detect more pipeline anomalies with a higher degree of certainty, even interacting threats and previously unreliably detected threats.\3\ Models can depict an entire pipeline with the impact of the anomaly and calculate the critical strain. All of this can be used to determine a pipeline's predicted failure pressure or fatigue life. --------------------------------------------------------------------------- \3\ Rosen USA (Rosen), Comment, Docket ID PHMSA-2017-0151-0025, at 1 (Sept. 28, 2018); see supra section II.B. --------------------------------------------------------------------------- In 2022, PHMSA amended its gas pipeline response criteria to incorporate some of these modern, engineering-based concepts.\4\ In this proceeding, PHMSA proposes to complete that work [[Page 42273]] and to extend the same concepts to hazardous liquid pipelines. --------------------------------------------------------------------------- \4\ Pipeline Safety: Safety of Gas Transmission Pipelines: Repair Criteria, Integrity Management Improvements, Cathodic Protection, Management of Change, and Other Related Amendments, 87 FR 52224 (Aug. 24, 2022) (2022 Safety of Gas Transmission Rule). --------------------------------------------------------------------------- B. Summary of Proposal ------------------------------------------------------------------------ Element Proposal ------------------------------------------------------------------------ Response schedule--gas....................... The anomaly response tiers in 49 CFR Sec. 192.714(d) are denoted as immediate, near-term, and other conditions. Near-term is one year under IM and two years otherwise. The duplicative schedule at Sec. 192.933 is removed to allow one central location for the gas response schedule. Response schedule--hazardous liquid.......... The same three anomaly response tiers apply for hazardous liquid IM pipelines. Near-term response is one-year. The hazardous liquid response schedule is placed in its own section at Sec. 195.453 as part of the IM program. Response criteria--gas....................... Editorial revisions are proposed to improve the clarity of the Sec. 192.714 response requirements. Criteria use a failure pressure ratio (FPR) rather than spelling out `predicted failure pressure times the maximum allowable operating pressure.' Substantively, for gas response: (1) a modern engineering-based criterion is added for the immediate response of cracks at an FPR of 1.1 and below; (2) the immediate crack depth criterion is revised to 70 percent or more; (3) immediate response to preferential seam corrosion is revised to an FPR of 1.1 and below; and (4) the dent interacting threat immediate criterion adds an exception for non- mechanical metal loss under 10 percent. Response criteria--hazardous liquid.......... Modern engineering-based metrics are added alongside the existing depth-based measurements for hazardous liquid response criteria. A consistent FPR of 1.1 and below is used for the immediate response of metal loss and cracks, with near-term response required at FPRs of 1.39 and below. On depth measurements, immediate response is added at 70 percent depth for cracks, with near-term response of cracks at 50 percent depth and higher. For dents, immediate response is required for interacting threats from mechanical damage (mechanical corrosion, cracking, gouging, and a stress riser) at any orientation, near-term response is required for all dents that were previously listed as 180- day conditions, while the seam corrosion provision is targeted to preferential metal loss. A dent ECA can be used to calculate an alternative timeline for all dent criteria. Finally, hazardous liquid pipelines not subject to IM should respond following API RP 1160. Anomaly evaluation........................... Update Sec. 192.712 and create a similar provision at Sec. 195.415: (a) Anomaly evaluation must be conducted by a subject matter expert and include uncertainties, like tool tolerance. (b) Metal loss analysis can use API 579 and Psqr, in addition to ASME B31G, R-STRENG, and other models demonstrated to provide comparable results. (c) A dent ECA is proposed with a reassessment safety factor of two for gas pipelines and five for hazardous liquid pipelines. (d) Crack analysis may use technically accepted fracture mechanic methods, including API 579 Level II or III, Modified Ln-Sec, and Raju-Newman equations. The in- situ crack exam provision is relocated to this paragraph. (e) Toughness can be derived by Charpy v- notch or other valid testing methods. The default toughness values are updated and the methods to obtain toughness and other material properties for the analysis are extended to part 195, including adding Sec. 195.407 to allow collection of material property records. Discovery.................................... A consistent anomaly discovery definition continues to apply from an operator having adequate information within an 180-day period. Expedited response to immediate conditions is required from preliminary ILI results, with discovery otherwise following the final ILI results. Temporary pressure reduction................. Two consistent options for temporary pressure reductions taken until gas and hazardous liquid pipelines are permanently repaired: a 20 percent reduction or reduction to a pressure below the predicted failure pressure times a design factor. General repair requirements.................. The disperse general repair requirements are editorially revised and centralized at Sec. Sec. 192.711 and 195.422 to encourage compliance. ------------------------------------------------------------------------ C. Cost-Benefit Summary PHMSA estimates that the proposed rule would generate substantial cost savings of approximately $390 million each year. Gas transmission pipeline operators are expected to experience between $214.6 and $241.7 million in cost savings each year, with hazardous liquid and carbon dioxide pipeline operators expected to experience cost savings of approximately $148.5 million in cost savings each year (both at a three percent discount rate). By accelerating responses to critical threats while eliminating unnecessary excavations, the proposal is also expected to enhance pipeline safety, to benefit worker safety, to minimize detrimental environmental impacts, to alleviate economic costs associated with congestion caused by work-zones from excavations, and to improve regulatory certainty and clarity for operators. The Preliminary Regulatory Impact Analysis (PRIA) provided in the rulemaking docket includes additional information regarding the costs, cost-savings, and benefits of the proposed rule. II. Background A. Regulatory Origin As originally adopted, the Federal Pipeline Safety Regulations generally required gas \5\ and hazardous liquid \6\ pipeline operators to repair safety impediments within a reasonable time.\7\ In the early 2000s, PHMSA established more detailed anomaly response schedules in adopting the IM program requirements for hazardous liquid and gas transmission pipelines.\8\ The IM rules required operators to assess the integrity of higher-risk pipelines in HCAs at certain intervals, i.e., at least once every five years for hazardous liquid and at least once every seven years for gas transmission pipelines. The IM rules also included response criteria in Sec. Sec. 192.933 and 195.452(h) that applied to anomalies detected during these assessments. This led to specific response requirements for anomalies discovered in HCAs [[Page 42274]] compared with longstanding generic requirements to make repairs as needed. --------------------------------------------------------------------------- \5\ ``Gas'' pipeline is used throughout this document to refer to pipelines regulated under part 192, which can be natural gas and any ``flammable gas, or gas which is toxic or corrosive.'' 49 CFR 192.3 (definition of ``gas''). \6\ ``Hazardous liquid'' pipeline is used throughout this document to refer to pipelines regulated under part 195, which includes hazardous liquid and carbon dioxide pipelines. Sec. 195.2 (definition of ``pipeline''). In addition to carbon dioxide, ``hazardous liquid'' includes ``petroleum, petroleum products, anhydrous ammonia, and ethanol or other non-petroleum fuel, including biofuel, which is flammable, toxic, or would be harmful to the environment if released in significant quantities.'' Sec. 195.2 (definition of ``hazardous liquid''). \7\ Establishment of Minimum Standards, 35 FR 13248, 13274 (Aug. 19, 1970) (codifying Sec. Sec. 192.711 and 192.713); Transportation of Liquids by Pipeline--Requirements for the Design, Construction, Operation, and Maintenance, 34 FR 15473, 38369 (Oct. 4, 1969); Transportation of Liquids by Pipeline, 46 FR 38357, 38369 (July 27, 1981) (recodifying Sec. 195.401 and the part 195 regulations to reflect the enactment of the Hazardous Liquid Pipeline Safety Act of 1979 (Pub. L. 96-129)). \8\ Pipeline Safety: Pipeline Integrity Management in High Consequence Areas, 68 FR 69778 (Dec. 15, 2003); Pipeline Safety: Pipeline Integrity Management in High Consequence Areas (Repair Criteria), 67 FR 1650 (Jan. 14, 2002). See also Pipeline Safety: Pipeline Integrity Management in High Consequence Areas (Hazardous Liquid Operators With 500 or More Miles of Pipeline), 65 FR 75378 (Dec. 1, 2000) (promulgating rest of hazardous liquid IM). --------------------------------------------------------------------------- The original response criteria in the IM rules reflected the limited assessment technology and evaluation methods available at the time. Relying on traditional measurements, the criteria defined anomalies by location (e.g., top- vs. bottom-side dents) or depth (e.g., a crack at 50 percent depth). The response times for these criteria largely were not based on the anomaly's remaining safe life.\9\ Though ILI tools could reliably measure the maximum depth of certain anomaly types, tool technologies and analytical methods were not sufficiently mature to produce high-resolution anomaly profiles reliably, to detect and classify interacting threats (such as selective seam weld corrosion and dents with interacting features), or to predict the remaining life of cracks and dents. --------------------------------------------------------------------------- \9\ Consistent with the technology of the time, remaining strength calculation criteria were limited to metal loss. --------------------------------------------------------------------------- By looking solely at measured anomaly size, the first IM response criteria overlooked the interaction between an anomaly and the specific characteristics of the pipeline (e.g., size, material, and operating conditions), both of which must be considered to understand the likely impact on integrity and serviceability. As a result, the response margins in the original IM rules required remediation of anomalies in advance of what would otherwise be necessary to maintain pipeline integrity in many cases. B. Technological Development Pipeline technology has improved dramatically since the adoption of the anomaly response criteria in the original IM rules. Modern ILI tools can detect a wider range of defects with greater accuracy, particularly when compared to the technology available in the early 2000s. Today, commercially available ILI tools can detect pipe body crack sizing with 90 percent certainty to one millimeter via an Electromagnetic Acoustic Transducer (EMAT) tool,\10\ and axial Magnetic Flux Leakage (MFL-A) tools can size corrosion depth with 80 percent certainty to 0.1 times the wall thickness.\11\ Much of this technological improvement can be attributed to an increase in the number of sensors on modern ILI tools, which has improved both accuracy and probability of detection.\12\ For example, sensors on crack ILI tools have increased from 480 in 2000 to over 1000 on today's tools, while MFL ILI corrosion tools have increased from 240 sensors in 2000 to about 1250 today. This corresponds to an improvement from +/- 10 percent wall thickness depth accuracy and 80 percent probability of detection in tools used in 2000 to +/- 0.03 inch and 90 percent probability of detection in tools used today.\13\ Further, with dents, ILI tools now can detect a dent as small as 0.2 percent of wall thickness on large diameter pipelines.\14\ Together, these advances have increased the probability of detection, probability of identification, and accuracy of sizing of pipeline anomalies. --------------------------------------------------------------------------- \10\ Lacking precision when introduced in the mid-2000s, EMAT tools can now reliably detect smaller cracks with greater accuracy due to innovation in tool sizing and sensor count. Kinder Morgan, Technical Justification for Use of EMAT as an Alternative Technology for Integrity Assessment of SCC in HCAs, Docket ID PHMSA-2011-0023- 0773 at 7-9 (Aug. 2019) (describing operator's development of EMAT ILI assessment and continued advancement of the technology over the 2010s). Previously, cracking was indicated by ILI run and not sized. Jeff Aron et al., Development of an EMAT In-Line Inspection System For Detection, Discrimination, and Grading of Stress Corrosion Cracking in Pipelines (Feb. 2005), https://www.netl.doe.gov/sites/default/files/2018-03/FG013105.PDF (``Cracks of 30 [percent] or greater of the wall thickness in depth were imaged. Their depths and lengths could be estimated from the data.''). \11\ See, e.g., Rosen, RoCorr MFL-A Service: In-line Ultra-High- Resolution Metal Loss Detection and Sizing (2024), https://contenthub.rosen-group.com/api/public/content/729e05931aca4953ac0a47dbdf2c6566?v=f9378e13 ; Rosen, RoCD EMAT-C Service: In-line High-Resolution Detection and Sizing of Axial Cracks (2024), https://contenthub.rosen-group.com/api/public/content/7e9f40578f924917a4403fa7fc5ba41e?v=0071d845 . \12\ Colonial Pipeline Co. (Colonial), Comment, Docket ID PHMSA- 2025-0019-0013, at 7 (July 21, 2025). \13\ Colonial, Comment, Docket ID PHMSA-2025-0019-0013, at 7. \14\ See Rosen, In-line Inspection Services for Deformation, Geometry and Mapping, available at: https://www.rosen-group.com/en/expertise/product-and-service-finder/in-line-inspection-services-for-deformation-geometry-and-mapping#ro-geo-xt-service (noting how sensors improve accuracy and data quality, with more accurate tools ``[m]inimiz[ing] conservatism of integrity assessments based on exceptionally detailed anomaly profiles''). --------------------------------------------------------------------------- The experience gained by deploying ILI to more pipelines has led to further advancements in the detection and modelling of increasingly complex defect types.\15\ New ILI tools are being designed and developed to assess anomalies with increasing accuracy and to address threats that could not previously be detected on a reliable basis. For example, to address hard to detect defects on double submerged arc welded pipe, Colonial Pipeline and NDT Global collaborated to create a multi-diameter and multi-threat tool that can be adjusted in the field for the size and threat to the pipeline.\16\ Preferential metal loss, once thought not capable of reliable detection by ILI,\17\ can now be assessed using a tool train that combines MFL-C corrosion and EMAT crack tools. Inertial Mapping Units have been updated to sub-meter accuracy with speed control, offering accurate measurement of bending strain caused by geohazards or construction activity through comparison to past tool runs.\18\ --------------------------------------------------------------------------- \15\ Rosen, Comment, Docket ID PHMSA-2017-0151-0025, at 1 (Sept. 28, 2018); The Williams Companies, Inc., Comment, Docket ID PHMSA- 2024-0005-0421, at 3, 5 (Aug. 27, 2024) (noting how study and application ``drives the vendors to constantly improve and refine their tools,'' and today ``[o]perators . . . who regularly deploy [ILI] technology across its enterprise of pipeline systems[ ] can assess risk with a level of detail and certainty that was not available 10 years ago'' with ``the data provided by the current generation of [ILI] tools giv[ing] [an operator] certainty and clarity around the risk assessment decisions . . . regarding potential threats''). \16\ Nathan Leslie et al., Compact 36'' Ultrasonic ILI Tool for Enhanced Pipeline Integrity Management, NDT Global, available at: https://www.ndt-global.com/resources/white-paper/compact-36-ultrasonic-ili-tool-for-enhanced-pipeline-integrity-management/ . \17\ See, e.g., Michael Baker Jr., Inc, Kiefner & Assoc., TTO No. 5, Low Frequency ERW and Lap Welded Longitudinal Seam Evaluation, at 6, 47, 60 (Apr. 2004), available at: https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/docs/technical-resources/pipeline/gas-transmission-integrity-management/65266/tto05lowfrequencyerwfinalreportrev3april2004.pdf (finding ILI tools in 2004 unreliable to identify longitudinal seam anomalies). \18\ Rosen, RoGeo XYZ Service: In-line High-Resolution Pipeline Route Mapping, Curvature Measurement and Strain Assessment, available at: https://contenthub.rosen-group.com/api/public/content/cc5d8df35a384c0a95e69d30122e31f8?v=9790a90c . --------------------------------------------------------------------------- As ILI tools and modeling have advanced, critical strain levels and predicted failure pressure have become the preeminent, technically based option for evaluating anomalies to ensure pipeline safety. Until the 1970s, operators relied on burst tests, manufacture specifications, and Barlow's formula to predict potential failures. From the 1980s through the 2000s, operators began to use metal loss analysis to assess corrosion, starting with B31G and then Effective Area Method computer software like Remaining Strength (RSTRENG), which allows for more accurate representation to calculate predicted failure pressure.\19\ Analytical methods have continued to [[Page 42275]] advance over time, becoming more precise and expanding to other types of anomalies, such as cracking and dents, allowing operators to engage in increasingly complex analysis and assessment of a pipeline's fitness for service. --------------------------------------------------------------------------- \19\ Am. Soc. of Mech. Eng'rs (ASME), Supplement to ASME B31 Code for Pressure Piping, ASME B31G-1991, Manual for Determining the Remaining Strength of Corroded Pipelines (1991) (first edition as its own standard); Kiefner & Assocs. Inc., Validity of Standard Defect Assessment Methods for the Alliance Pipeline Operating at 80% of SMYS, at 3-4 (Sept. 6, 2018), available at: https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/docs/technical-resources/pipeline/gas-transmission-integrity-management/65316/validityofcorrosionassessmentsr1.pdf (noting ASME B31G was first introduced as a supplement to B31.8 in 1984). --------------------------------------------------------------------------- Today, with enhanced accuracy and data quality, computational algorithms can provide fracture mechanics, critical strain analysis, and remaining strength calculations to better predict when a defect might fail. API 579 contains three different levels of engineering calculations and analysis for each anomaly type, scalable based on the amount of data available.\20\ Models are capable of overlaying multiple data inputs from different threats to provide a clearer understanding of the pipeline and potential anomalies.\21\ Innovations in data processing and machine learning enable real-time algorithmic analysis of tool results, better interpreting complex signals and deformation shapes, and expediting decision-making.\22\ --------------------------------------------------------------------------- \20\ American Petroleum Institute (API) & ASME, API 579-1/ASME FFS-1, Fitness-for-Service (4th ed., Dec. 2021) (``API 579''); see INGAA Integrity Management Continuous Improvement Group, Definition and Application of Fitness for Service to Gas Pipelines (May 31, 2012), available at: https://ingaa.org/wp-content/uploads/2013/04/20024.pdf . \21\ E.g., Creaform, Pipeline Integrity Assessment Software for NFT Pipeline Inspection, available at: https://www.creaform3d.com/en/products/software/creaform-integrity-suite/pipeline (discussing use of 3D analysis to show full coverage of pipeline surfaces and damages, feeding assessment calculation models). \22\ See NDT Global, Evolving from a Leading ILI Company to a Preferred Provider of Integrity Management Solutions, available at: https://www.ndt-global.com/resources/news/evolving-from-a-leading-ili-company-to-a-preferred-provider-of-integrity/ (``We are leveraging machine learning and artificial intelligence techniques and use our big data platforms to improve the accuracy and reliability of the results from our inspection tools continuously. This is the key to delivering the greatest value in integrity assessments to enable proactive pipeline integrity management.''); Rosen, Comment, Docket ID PHMSA-2011-0151-0025, at 1; T.D. Williamson, Comment, Docket ID PHMSA-2017-0151-0024, at 2. --------------------------------------------------------------------------- Use of 3D modelling of ILI data, including through the use of models like Plausible Profiles (Psqr), has allowed for ``a data driven and more accurate probabilistic representation of corrosion features in pipelines that was not operationally feasible before the data revolution.'' \23\ Fracture mechanics analysis provides an avenue to consider all variables in the predicted failure of a crack or crack- like anomaly by quantifying the relationship between material properties, stresses, and crack propagation. This demonstrates that the propensity for crack failures is not based on depth alone, and depth- based crack response metrics must be overly conservative as a result.\24\ Dent analysis has also undergone significant recent study and advancement. Contrary to historical practice and understanding, the latest research has shown that ``dent depth alone is not a great predictor of the effect a dent can have on the fatigue life of a pipeline.'' \25\ API developed and released RP 1183 in 2020 to provide guidance using engineering critical assessment (ECA) to evaluate a dent's fitness for service.\26\ Finite element analysis, which would not be possible without the more precise data derived from advanced ILI tools, provides the ability to simulate full-scale testing with numerical modeling.\27\ --------------------------------------------------------------------------- \23\ TC Energy, TC Energy wins Global Pipeline Award (Nov. 17, 2021), available at: https://www.tcenergy.com/stories/2021/2021-11-17-tc-energy-wins-global-pipeline-award/ . \24\ See Vlad Semiga, BMT Fleet Technology, Fatigue Considerations for Natural Gas Transmission Pipelines, at 10 (June 30, 2016), available at: https://ingaa.org/wp-content/uploads/2016/07/29846.pdf (noting how the geometry factor is built into the equation, providing growth rate constraints that include material properties). \25\ Semiga, Fatigue Considerations for Natural Gas Transmission Pipelines, at 65. \26\ API, Recommended Practice (RP) 1183, Assessment and Management of Pipeline Dents (1st Ed. Nov. 2020). \27\ ``Due to the complexity and variability of dent shapes, dimensions, and the potential for coincident features, full-scale testing and numerical modeling (FEA) have been the two essential tools that have been deployed by the industry to assess the fundamental behavior of dents.'' Aaron Dinovitzer et al., PR214- 203804-R01, Systematize 20 Years of Mechanical Damage Research, sec. 3.4.2.6 (May 31, 2022), available at: https://primis.phmsa.dot.gov/rd/FileGet/17097/Systematize_20_Years_of_Mechanical_Damage_Research_V2.pdf . --------------------------------------------------------------------------- C. Modernization in PHMSA Regulations PHMSA has modernized its regulations in recent years to account for many of these technological advancements. In 2019, for example, PHMSA revised its assessment requirements for gas transmission pipelines to apply to certain non-HCA locations and made similar revisions to its assessment requirements for hazardous liquid pipelines.\28\ In 2022, PHMSA revised its anomaly response and evaluation requirements for gas transmission pipelines, adding detailed scheduling requirements at Sec. Sec. 192.714 and 192.933 that incorporate predicted failure pressure- and strain-based criteria ``to assure that anomalies are repaired before they become an immediate condition and are at or near failure.'' \29\ PHMSA also added analysis calculation criteria to Sec. 192.712.\30\ As explained below, PHMSA proposes to apply these concepts to the response and evaluation criteria for hazardous liquid pipelines. --------------------------------------------------------------------------- \28\ Pipeline Safety: Safety of Gas Transmission Pipelines: MAOP Reconfirmation, Expansion of Assessment Requirements, and Other Related Amendments, 84 FR 52180 (Oct. 1, 2019) (2019 Safety of Gas Transmission Rule); Pipeline Safety: Safety of Hazardous Liquid Pipelines, 84 FR 52260 (Oct. 1, 2019). \29\ 2022 Safety of Gas Transmission Rule, 87 FR at 52245. These modern criteria were added alongside the traditional depth-based measurements for operators who so prefer. \30\ Section 192.712(c) was remanded without vacatur by the court in INGAA v. PHMSA, 114 F.4d 744 (D.C. Cir. 2024) for PHMSA to reconsider the dent ECA process. Order on Pet. for Panel Reh'g, INGAA v. PHMSA, 114 F.4th 744 (D.C. Cir. Dec. 10, 2024) (No. 23- 1173). Section 192.712(b) and (d) for corrosion and cracks were created in the 2019 Safety of Gas Transmission Rule. --------------------------------------------------------------------------- III. Advanced Notice of Proposed Rulemaking In a May 2025 advanced notice of proposed rulemaking (ANPRM), PHMSA solicited public feedback on improving anomaly response requirements for gas and hazardous liquid pipelines.\31\ Public response overwhelmingly favored modernizing these requirements to incorporate a performance-based, engineering-focused approach--one that prioritizes anomalies based on calculated predicted failure pressure, strain, and remaining life rather than one dimensional thresholds. Comments submitted by the Liquid Associations--API, the Liquid Energy Pipeline Association (LEPA), GPA Midstream Association, and the American Fuel & Petrochemical Manufacturers--note that the existing hazardous liquid anomaly response requirements are obsolete and fail to leverage over twenty years of advancement in ILI technology and data analytics.\32\ Comments by the Gas Associations--the Interstate Natural Gas Association of America (INGAA), American Gas Association (AGA), and GPA Midstream Association--supported using modern anomaly evaluation, as did individual gas and hazardous liquid pipeline operators.\33\ Representatives of smaller operators requested that in any modernization effort PHMSA retain the existing depth-based options, stating that engineering-based analyses can be costly and resource- intensive up-front, before reaping substantial cost-savings.\34\ The Pipeline Safety Trust (PST) supported improving the clarity of response requirements but cautioned [[Page 42276]] against reducing the safety level for gas transmission IM regulations or making deregulatory changes without considering safety benefits, environmental impact, and public participation.\35\ The National Association of Pipeline Safety Representatives (NAPSR) similarly cautioned not to reduce the standard of care in IM regulations, which NAPSR credited with the declining rate of incidents and accidents.\36\ --------------------------------------------------------------------------- \31\ Pipeline Safety: Repair Criteria for Hazardous Liquid and Gas Transmission Pipelines, 90 FR 21715 (adv. notice May 21, 2025). \32\ Liquid Associations, Comment, Docket ID PHMSA-2025-0019- 0021, at 2-4 (July 21, 2025). \33\ Gas Associations, Comment, Docket ID PHMSA-2025-0019-0017, at 4-5 (July 21, 2025). \34\ Air Liquide Large Indus. US, L.P., Comment, Docket ID PHMSA-2025-0019-0012, at 3 (July 21, 2025); Compressed Gas Ass'n, Comment, Docket ID PHMSA-2025-0019-0009, at 5 (July 18, 2025). \35\ PST, Comment, Docket ID PHMSA-2025-0019-0016, at 2 (July 21, 2025). \36\ NAPSR, Comment, Docket ID PHMSA-2025-0019-0025, at 4 (Aug. 1, 2025). --------------------------------------------------------------------------- The Liquid Associations and operators like Colonial Pipeline Co. (Colonial) and Marathon Pipe Line (Marathon) commented that incorporating improved evaluation methods for hazardous liquid pipelines would enable the consolidation of near-term response timelines.\37\ Hazardous liquid operators also requested that PHMSA allow an ECA to respond to dents based on a detailed calculation of strain and fatigue life.\38\ Commenters suggested certain changes to the criteria and evaluation methods adopted in a recent rulemaking for gas transmission lines to provide greater flexibility and to reflect modern technologies and practices, though PST cited the need to maintain the safety margins established in these new regulations.\39\ --------------------------------------------------------------------------- \37\ Colonial, Comment, Docket ID PHMSA-2025-0019-0013, at 2, 7; Liquid Associations, Comment, Docket ID PHMSA-2025-0019-0021, at 49- 50; Marathon, Comment, Docket ID PHMSA-2025-0019-0018, at 4-5 (July 21, 2025). \38\ See, e.g., Liquid Associations, Comment, Docket ID PHMSA- 2025-0019-0021, at 5; Colonial, Comment, Docket ID PHMSA-2025-0019- 0013, at 3; Enterprise Prods. Operating LLC (Enterprise), Comment, Docket ID PHMSA-2025-0019-0015 at 4 (July 21, 2025). \39\ Gas Associations, Comment, Docket ID PHMSA-2025-0019-0022, at 7; PST, Comment, Docket ID PHMSA-2025-0019-0016, at 2. --------------------------------------------------------------------------- As engineering-based criteria depend on an evaluation of the anomaly, commenters suggested revisions to anomaly evaluation methods for gas transmission and that these revisions be adopted for hazardous liquid pipelines. Suggestions included explicitly approving additional metal loss and crack evaluation methods; \40\ revising default toughness values based on recent research; \41\ and allowing a process in part 195 to determine material properties by extending the procedures in Sec. 192.607.\42\ --------------------------------------------------------------------------- \40\ Gas Associations, Comment, Docket ID PHMSA-2025-0019-0022, at 20; Liquid Associations, Comment, Docket ID PHMSA-2025-0019-0021, at 19. \41\ Gas Associations, Comment, Docket ID PHMSA-2025-0019-0022, at 10; TC Energy, Comment, Docket ID PHMSA-2025-0019-0019, at 5 (July 21, 2025). \42\ Energy Transfer LP, Comment, Docket ID PHMSA-2025-0019- 0020, at 18 (July 21, 2025). --------------------------------------------------------------------------- IV. Discussion of the Proposal To address concerns with the use of inconsistent or imprecise terminology in the existing regulations, PHMSA proposes to use the terms ``anomaly'' and ``response criteria'' throughout the regulations.\43\ The use of these terms is consistent with ASME B31.8S and other industry sources. An anomaly is an unexamined deviation from the norm in pipeline material, coatings, or welds, which includes defects and imperfections identified upon further examination.\44\ Sections 192.714 and 195.453 list ``response criteria'' that require response in a set time for an anomaly that meets those levels, though PHMSA has previously used the term ``repair criteria'' interchangeably.\45\ Response refers to the action an operator takes on an identified anomaly, including remediation, to ensure safety such as a repair or temporary pressure reduction.\46\ Response is completed by permanent repair, which means replacing the pipe cylinder containing the defect, removing the anomaly, or taking other actions permanently to restore pipeline serviceability. --------------------------------------------------------------------------- \43\ See Gas Associations, Comment, Docket ID PHMSA-2025-0019- 0017, at 4-5 (noting that current requirements usage of interchangeable terminology is confusing); PST, Comment, Docket ID PHMSA 2025-0019-0016, at 1. As each are consistent terms, PHMSA does not propose defining these terms in Sec. Sec. 192.3 and 195.2. \44\ See ASME, Code for Pressure Piping Supplement to ASME B31.8, B31.8S-2018, Managing System Integrity of Gas Pipelines, sec. 13 (2018). \45\ See PST, Comment, Docket ID PHMSA 2025-0019-0016, at 1. \46\ See ASME, B31.8S-18, sec. 7. --------------------------------------------------------------------------- A. Response Schedules Existing requirement: Anomaly response schedules set timelines to respond to criteria based on severity. The gas response criteria are broken out by immediate, scheduled (one-year in HC
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