NTSB Safety Recommendation P-22-004

NTSB safety recommendation P-22-004.

TO ENBRIDGE, INC.: Evaluate the effectiveness of your corrosion control equipment and infrastructure following any major change in operations, such as a gas flow reversal.

Priority: CLASS II

Overall Status: Closed - Acceptable Action

Issued Date: 2022-09-14

Adopted Date: 2022-08-15

Overall Date Closed: 2023-06-30

Synopsis: On August 1, 2019, at 1:23 a.m. local time, an Enbridge Inc. (Enbridge) 30-inch natural gas transmission pipeline ruptured in Danville, Kentucky, releasing about 101.5 million cubic feet of natural gas that ignited. The accident resulted in 1 fatality, 6 injuries, and the evacuation of over 75 individuals in the Indian Camp Subdivision. Five residences were destroyed by resulting structure fires, and an additional fourteen were damaged. A nearby railroad track was also damaged, and over 30 acres of land were burned.

Probable Cause: The National Transportation Safety Board determines that the probable cause of the August 1, 2019, rupture of an Enbridge Inc. natural gas transmission pipeline and resulting fire was hydrogen-induced cracking at the surface of Line 15 in an area of damaged coal tar enamel coating resulting from a 2014 gas flow reversal project that increased corrosion rates and hydrogen generation. Contributing to this accident was Enbridge’s integrity management program, which did not accurately assess the integrity of the pipeline or estimate the risk from interacting threats.

Ntsbnumber: PLD19FR002

Report Number: PIR-22-02

Addressee Name: Enbridge, Inc.

Addressee Status: Closed - Acceptable Action

Addressee Date Closed: 2023-06-30

Addressee Organization Type: P-Private Industry

Communication Date: 2022-09-14

Communication Type: Transmittal Letter

Communication Contents: This letter provides information about the National Transportation Safety Board’s (NTSB) August 15, 2022, report Enbridge Inc. Natural Gas Transmission Pipeline Rupture and Fire, Danville, Kentucky, August 1, 2019, NTSB/PIR-22/02. 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: • Nonconservative assumptions used to calculate potential impact radius. • Incomplete evaluation of the risks caused by a change of gas flow direction. • Limitations in data analysis related to the 2011 in-line inspection. • Operators’ potential for incomplete assessment of threats and threat interactions. • Missed opportunities in training and requalification practices at Enbridge. Accordingly, the NTSB makes the following safety recommendations to the Pipeline and Hazardous Materials Safety Administration. Additional information regarding these recommendations can be found in the noted sections of the report. • Revise the calculation methodology used in your regulations to determine the potential impact radius of a pipeline rupture based on the accident data and human response data discussed in this report. (P-22-1) (See section 2.3) • Advise natural gas transmission pipeline operators on (a) the circumstances of this accident; (b) the need to evaluate the risks associated with flow reversal projects; and (c) the impacts of such projects on hydrogen-induced cracking. (P-22-2) (See section 2.4) • Advise natural gas transmission pipeline operators of the possible data limitations associated with hard spot magnetic flux leakage in-line inspection tools and analyses used in hard spot management programs and reinforce the need to follow industry best practices when conducting in-line inspection data analysis. (P-22-3) (See section 2.5) The NTSB is vitally interested in these recommendations because they are designed to prevent accidents and save lives. We would appreciate a response within 90 days of the date of this letter, detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendations by number (Safety Recommendations P-22-1, -2 and -3). 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 the pipeline investigation report (PIR-22-02), "Enbridge Inc. Natural Gas Transmission Pipeline Rupture and Fire, Danville, Kentucky, August 1, 2019." Published on September 14, 2022. 2.4 Management of Gas Flow Reversal As stated previously, because the pipe was under cathodic protection following the gas flow reversal, areas with coating defects had increased hydrogen evolution, which reduced the pipeline integrity. However, after the gas flow reversal in 2014, neither Spectra nor Enbridge evaluated the data available on temperatures, cathodic protection, and external corrosion anomalies in L15 VS4 to determine the impacts of the project on pipeline integrity. These data are difficult to predict in advance, and cathodic protection may not respond to operational changes in a predictable way. Extensive research on the effects of major operational changes has not been performed, leaving operators only able to plan for general effects (for example, adding gas coolers to address increased temperatures) and requiring them to perform further study after operational changes to detect more subtle effects (such as unstable or ineffective cathodic protection leading to hydrogen evolution). Because Enbridge and its predecessor did not review critical data, they did not identify the suitability of its corrosion control equipment and infrastructure for reversed flow, recognize indicators of coating damage, or identify the cathodic protection system as a likely source of hydrogen evolution. The NTSB concludes that Enbridge and Spectra did not effectively identify, investigate, or manage the impact of the gas flow reversal project on the level of hydrogen evolution in the pipeline surface, which ultimately contributed to the failure of the pipeline. Therefore, the NTSB recommends that Enbridge evaluate the effectiveness of its corrosion control equipment and infrastructure following any major change in operations, such as a gas flow reversal. The NTSB further concludes that comprehensive management of the changes resulting from the gas flow reversal project on Line 15 would have identified and addressed risks such as coating damage, ineffective cathodic protection, and suitability of corrosion control equipment and infrastructure that led to hydrogen-induced cracking in the pipeline surface. Therefore, the NTSB recommends that PHMSA advise natural gas transmission pipeline operators on a) the circumstances of this accident; b) the need to evaluate the risks associated with flow reversal projects; and c) the impacts of such projects on hydrogen-induced cracking.

Addressee Organization Type: P-Private Industry

Communication Date: 2023-03-31

Communication Type: Official Correspondence

Communication Contents: -From Garrett Wilkie, Director Operational Excellence Enbridge GTM- Engineering and Asset Management, Enbridge, Inc.: Enbridge Inc. (Enbridge or the Company) appreciates the National Transportation Safety Board’s (NTSB or the Board) March 30, 2023 letter classifying Enbridge’s actions performed in response to the above-referenced recommendations issued by the NTSB. Footnote: On September 14, 2022 the NTSB issued recommendations P-22-4, P-22-5, and P-22-6 to Enbridge, concerning the NTSB’s August 15, 2022 Pipeline Investigation Report on the rupture of natural gas pipeline, Line 15 on Enbridge’s TETLP pipeline system that occurred in Danville, Kentucky on August 1, 2019. The recommendations are associated with the NTSB’s investigation of the rupture of natural gas pipeline, Line 15 on Enbridge’s Texas Eastern Transmission, L.P. (TETLP) pipeline system that occurred in Danville, Kentucky on August 1, 2019. The NTSB determined that Enbridge’s actions performed in response to recommendations P-22-5 and P-22-6 satisfy the Board’s recommendations and classified them as “Closed-Acceptable Action.” With respect to recommendation P-22-4, the NTSB determined that the actions outlined by Enbridge may satisfy the recommendation, once completed, and classified it as “Open Acceptable Response.” Enbridge submits this update to its December 13, 2022 letter to confirm completion of outstanding actions associated with P-22-4. At the time of its December 13, 2022 letter, Enbridge was finalizing (1) a third party review of historical operating data on TETLP Line 15 and (2) implementing changes associated with Enbridge’s internal management of change process (MOC), a part of Enbridge’s integrated management system (IMS) consistent with the American Petroleum Institute’s Recommended Practice (RP) 1173, Pipeline Safety Management Systems. Below is a summary of the reviews that have now been completed and procedural revisions that have been implemented. 1. Third Party Review of Historical Operating Data: Enbridge engaged third party experts to conduct a review of historical operating data on TETLP Line 15 since before the flow reversal projects began in 2014 to the present for any impacts on corrosion control effectiveness. The historical review integrated data from 2010 to 2022 on Line 15 to review cathodic protection (CP) levels and pipeline coating effectiveness through evaluation of annual survey data, CP ground bed and rectifier current output history, supplemental CP ground bed installations, compressor discharge temperatures in both flow direction, and corrosion in-line inspection data. Other than what the NTSB identified in its Pipeline Investigation Report (PIR-22/02), there has not been any indication that the flow reversal project adversely impacted corrosion control equipment effectiveness. Enbridge concluded that revisions to the Gas Transmission and Midstream (GTM) integrity management plan (IMP) are not warranted as a result of this historical data review. Footnote: Enbridge GTM includes pipeline transmission systems located in the U.S. and Canada where operated by Enbridge or its subsidiaries. See https://www.enbridge.com/about-us/natural-gas-transmission-and-midstream 2. MOC Process: Enbridge completed a review and revision of its program level processes in alignment with the IMS MOC process requirements and incorporated consideration of the NTSB’s recommendation. Specifically, Enbridge identified certain areas of improvement within the MOC process and implemented associated revisions to account for adequate MOC reviews for potential impacts to integrity performance and integration into ongoing integrity assessment planning of major projects, including gas flow reversals. Consistent with its goal of continuous improvement, Enbridge also regularly incorporates appropriate updates to these processes based on lessons learned and when implementing new rulemakings. With this update, Enbridge’s entire Gas Transmission and Midstream business unit, including TETLP, has fully implemented all of the NTSB recommendations. The initiatives that Enbridge has undertaken in response to the Danville, Kentucky incident and the relevant NTSB recommendations have enhanced Enbridge’s programs and efforts. Enbridge believes they will lead to significant advancement of the industry’s management of the hard spot threat. Enbridge is determined to continually improve its safety culture, performance, and to lead industry in safety best practices. Please do not hesitate to contact me if you have any questions or concerns regarding this update.

Addressee Organization Type: P-Private Industry

Communication Date: 2022-12-13

Communication Type: Official Correspondence

Communication Contents: -From Al Monaco, President and Chief Executive Officer, Enbridge Inc.: Enbridge agrees with NTSB Recommendation P-22-4. Enbridge utilizes an Integrated Management System (IMS) to manage its business. Foundational to the IMS are the following Enbridge GTM programs: Safety Management; Environmental Management; Integrity Management; Emergency Management; Damage Prevention; and Security. Enbridge leverages the IMS to evaluate major changes in operations, such as a gas flow reversal, to ensure operational readiness, safety, and compliance. The IMS mandates a management of change (MOC) process to assess the impact of the project scope and identify scope modifications required to meet integrity standards or address past lessons learned. Integrity subject matter experts review factors that may impact the ongoing integrity of the impacted pipeline system that are directly tied to integrity performance, including, but not limited to, operating pressures and stresses, temperature, flow velocity, corrosion control equipment, coating type, threat susceptibility, pipe specifications, equipment type, and accessibility for integrity monitoring (i.e., suitable launching and receiving facilities for ILI). A key aspect of the IMS is the continuous improvement Plan, Do, Check, Act cycle, consistent with the American Petroleum Institute’s Recommended Practice (RP) 1173, Pipeline Safety Management Systems. We strive to apply this cycle to all elements, programs, and processes, including the MOC process, to improve and apply lessons learned. When this NTSB recommendation was issued, Enbridge was already in the process of evaluating the effectiveness of its corrosion control equipment and infrastructure following any major change in operations, such as a gas flow reversal, by performing the following to enhance the MOC process: 1. Third Party Review of Historical Operating Data: Enbridge engaged third party experts to conduct a review of historical operating data on TETLP Line 15 since the flow reversal projects began in 2014 to the present for any impacts on corrosion control effectiveness. This review is based on the integration of corrosion ILI data, cathodic protection, and compressor discharge pressures and temperatures. Other than what the NTSB identified in its Pipeline Investigation Report (PIR-22/02), there has not yet been any indication that the flow reversal project adversely impacted corrosion control equipment effectiveness based on the review performed to date. Enbridge will finalize this review and update its GTM IMP, as needed, by March 31, 2023. 2. MOC Process: Enbridge is in the process of reviewing and revising its program level processes in alignment with the IMS MOC process requirements and will now incorporate consideration of the NTSB’s recommendation. Where Enbridge identifies applicable areas of improvement within the MOC process, it will implement changes to account for adequate MOC reviews of major projects, including gas flow reversals. Enbridge will finalize this review and any necessary revisions by March 31, 2023. Consistent with its goal of continuous improvement, Enbridge also regularly incorporates appropriate updates to these processes based on lessons learned and when implementing new rulemakings.

Addressee Organization Type: P-Private Industry

Communication Date: 2023-03-30

Communication Type: Official Correspondence

Communication Contents: We are aware that you use an integrity management system (IMS) that mandates a management-of-change (MOC) process consistent with the “Plan, Do, Check, Act” cycle in the American Petroleum Institute’s Recommended Practice (RP) 1173, Pipeline Safety Management Systems. In addition to reviewing your MOC process requirements, you contracted with third-party experts to review historical operating data on the Texas Eastern Transmission LP Line 15, from when the flow reversal projects began in 2014 to the present, for any impacts on corrosion control effectiveness. These actions, once completed, may satisfy this recommendation. Accordingly, Safety Recommendation P-22-4 is classified OPEN-- ACCEPTABLE RESPONSE.

Addressee Organization Type: P-Private Industry

Communication Date: 2023-06-30

Communication Type: Official Correspondence

Communication Contents: We note that you reviewed the historical operating data on the Texas Eastern Transmission LP Line 15 since the flow reversal projects began in 2014 to the present to evaluate impacts on corrosion control effectiveness. The historical review evaluated cathodic protection (CP) levels and pipeline coating effectiveness by analyzing annual survey data, CP ground bed and rectifier current output history, supplemental CP ground bed installations, compressor discharge temperatures in both flow directions, and corrosion in-line inspection data. Your historical review did not find any indication that the 2014 flow reversal project adversely impacted corrosion control equipment effectiveness. We are aware that you use an integrated management system (IMS) to manage your business. In addition to your pipeline integrity management plan, your IMS mandates a management-of-change (MOC) process consistent with the “Plan, Do, Check, Act” cycle in the American Petroleum Institute’s Recommended Practice 1173, Pipeline Safety Management Systems. To address our recommendation, we note that you reviewed and revised your program-level processes to ensure MOC reviews are conducted for potential impacts to integrity performance and integration into ongoing integrity assessment of major projects, including gas flow reversals. These actions satisfy Safety Recommendation P-22-4, which is classified CLOSED-- ACCEPTABLE ACTION.