PLAINS PIPELINE MIDCON LLC — Corrective Action Order

52026009CAO_Corrective Action Order_04242026_(26-370329)_text.pdf, page 1Official PDFU.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration 1200 New Jersey Avenue, S.E. Washington, D.C. 20590 April 24, 2026 VIA ELECTRONIC MAIL TO: patrick.hodgins@plains.com Mr. Patrick Hodgins Vice President, HSE, Comms. & Govt. Regulatory Affairs Plains Pipeline, L.P. 333 Clay Street, Suite 1600 Houston, TX 77002 CPF No. 5-2026-009-CAO Dear Mr. Hodgins: Enclosed please find a Corrective Action Order (CAO or Order) issued by the Pipeline and Hazardous Materials Safety Administration (PHMSA), Office of Pipeline Safety (OPS), in the above-referenced case. The CAO requires Plains Pipeline MidCon, LLC, a subsidiary of Plains Pipeline, LP (Plains or Respondent), to take certain corrective actions with respect to the failures that occurred on April 21, 2026, and April 23, 2026, on its Buffalo Pipeline System located in Woodard and Harper County, Oklahoma. Service of the CAO by email is effective upon the date of transmission and acknowledgment of receipt as provided under 49 CFR § 190.5. The terms and conditions of this Order are effective upon completion of service. Sincerely, Linda Daugherty Acting Associate Administrator for Pipeline Safety Enclosure: CAO cc: Dustin Hubbard, Director, Western Region, Office of Pipeline Safety, PHMSA CONFIRMATION OF RECEIPT REQUESTED#

52026009CAO_Corrective Action Order_04242026_(26-370329)_text.pdf, page 2U.S. DEPARTMENT OF TRANSPORTATION PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION OFFICE OF PIPELINE SAFETY WASHINGTON, D.C. 20590 ____________________________________ In the Matter of ) Plains Pipeline MidCon, LLC, ) a subsidiary Plains Pipeline, LP, ) CPF No. 5-2026-009-CAO ) ) Respondent. ) ____________________________________) CORRECTIVE ACTION ORDER Background and Purpose The Pipeline and Hazardous Materials Safety Administration (PHMSA), Office of Pipeline Safety (OPS), is issuing this Corrective Action Order (CAO or Order) pursuant to the authority provided in 49 U.S.C. § 60112. The CAO requires Plains Pipeline MidCon, LLC, a subsidiary of Plains Pipeline, LP (Plains or Respondent), to take certain necessary corrective actions to protect the public, property, and the environment from the potential hazards associated with the continued operation of its Buffalo Pipeline System in Woodard and Harper County, Oklahoma, which recently experienced two failures and has a history of prior failures in 2024 and 2025. Specifically, on April 21, 2026, Plains’ control room received a pipeline monitoring (PLM) alert indicating a product loss on the Buffalo Pipeline System between mainline valves BV-9 and BV- 7. Plains responded by shutting down the line. Current estimates indicate that the failure led to the release of approximately 520 barrels (bbls) of crude oil. Two days later, on April 23, 2026, another failure occurred on the Buffalo Pipeline System approximately 50 miles from the earlier failure. This second failure occurred while Plains was running a cleaning pig through the pipeline as part of a planned repair. Initial estimates indicated that the second failure, which Plains discovered after receiving a call from a landowner, led to the release of 1 gallon of crude oil. Pursuant to 49 U.S.C. § 60117, PHMSA has initiated an investigation of both failures. The preliminary findings of PHMSA’s ongoing investigation are as follows: Preliminary Findings • Plains operates a pipeline known as the Buffalo Pipeline System that spans 60.9 miles between the Orion Pump Station and the Stockholm Pump Station.#

52026009CAO_Corrective Action Order_04242026_(26-370329)_text.pdf, page 3CPF No. 5-2026-009-CAO Page 2 • On April 21, 2026, Plains control room received a PLM alert indicating a pressure drop in the Buffalo Pipeline System segment located between Orion Pump Station and Stockholm Pump Station. The release was confirmed at 9:20 am CDT (First Failure). • At 10:02 am CDT, Plains called the National Response Center and reported a crude oil release of an unknown amount into a nearby water source.1 • Initial estimates indicated approximately 410 bbls of crude oil was released. That number was updated on April 23, 2026, to 520 bbls of crude oil. • The First Failure occurred 75 feet from a water source (a nearby 2-foot-wide creek). Crude oil reached the creek and migrated approximately 2,500 feet to a natural pond. • Mitigation efforts consisted of booms installed downstream of the last oil indication and upstream towards the release location to prevent further migration. Two skimmers were installed in the creek and crews used vacuum trucks and hand tools to remove oil and environmental contamination. Contaminated ground is being excavated between the failure point and the creek. • Prior to the accident, Plains personnel were in the area performing inline inspection (ILI) confirmation and remediation digs 1.5 miles upstream and downstream from the release location. • Previous ILI runs consisted of an MFL-A tool in 2024 and a UT tool in 2025. • Discussions with Plains personnel in the field indicated that the first failure location was not indicated on the previous ILI run. • On April 23, 2026, at 10:25 am CDT, Plains identified another leak occurring at an anomaly dig site approximately 50 miles away from the initial leak (Second Failure). Plains identified the Second Failure while starting a pig run with subsequent plans for a nitrogen purge. The site had been excavated, and the coating had already been removed. The leak was called in by a nearby landowner. • The First Failure occurred at MP 16.4. The line at that location was constructed in 1960 with a nominal diameter of 8.625 inches, wall thickness of 0.188 inches, X-52 Grade, Low Frequency Electric Resistance Welded pipe, manufactured on an unknown date, from an unknown manufacturer, with a coal tar coating. MOP on the pipe was established at 1250 psi in 2017 via a 2016 8 hour hydrotest. The pipe was operating under a pressure reduction to 600 psi at the time of failure. • The Second Failure was at Dig #61. The line at that location was constructed in 1960 with a nominal diameter of 8.625 inches, wall thickness of 0.188 inches, X-52 Grade, Low Frequency Electric Resistance Welded pipe, manufactured on an unknown date, 1 National Response Center (NRC) Report # 1460291.#

52026009CAO_Corrective Action Order_04242026_(26-370329)_text.pdf, page 4CPF No. 5-2026-009-CAO Page 3 from an unknown manufacturer, with a coal tar and shrink sleeve coating. MOP on the pipe was established at 1250 psi in 2017 via a 2016 8 hour hydrotest. The pipe was operating under a pressure reduction to 600 psi at the time of failure. • PHMSA is aware of several previous failures on the Buffalo Pipeline System. In July of 2025, two failures occurred that resulted in the release of 100 and 179 bbls of crude oil, respectively. The cause of both failures was attributed to microbiologically induced corrosion and under deposit corrosion. • On October 26, 2024, 200 bbls of crude oil was released on the same segment with that failure also being attributed to microbiologically induced corrosion. • The 2024 and 2025 failures occurred on the Buffalo Pipeline System that spans 60.9 miles between the Orion Pump Station and the Stockholm Pump Station as part of the Buffalo Pipeline System. Determination of Necessity for Corrective Action Order and Right to Hearing Section 60112 of title 49, United States Code, authorizes PHMSA to determine that a pipeline facility is or would be hazardous to life, property, or the environment and if there is a likelihood of serious harm, to expeditiously order the operator of the facility to take necessary corrective action, including suspended or restricted use of the facility, physical inspection, testing, repair, replacement, or other appropriate action. An order issued expeditiously must provide an opportunity for a hearing as soon as practicable after the order is issued. In deciding whether to issue an order, PHMSA must consider the following, if relevant: (1) the characteristics of the pipe and other equipment used in the pipeline facility, including the age, manufacture, physical properties, and method of manufacturing, constructing, or assembling the equipment; (2) the nature of the material the pipeline facility transports, the corrosive and deteriorative qualities of the material, the sequence in which the material is transported, and the pressure required for transporting the material; (3) the aspects of the area in which the pipeline facility is located, including climatic and geologic conditions and soil characteristics; (4) the proximity of the area in which the facility is located to environmentally sensitive areas; (5) the population density and population and growth patterns of the area in which the pipeline facility is located; (6) any recommendation of the National Transportation Safety Board made under another law; and (7) any other factors PHMSA may consider as appropriate. After evaluating the foregoing preliminary findings of fact, and having considered the characteristics of the pipeline, the nature of the failures, the prior history of corrosion and failures on the pipeline; the hazardous nature of the material transported (crude oil); the existing and potential additional impacts to life, property, or the environment; the still-unknown cause of the Failures; and the possibility of additional failures on the pipeline system; it is hereby determined that continued operation of the Buffalo Pipeline System segment, as defined below, without corrective measures is or would be hazardous to life, property, or the environment, and that failure to issue this Order expeditiously would result in the likelihood of serious harm.#

52026009CAO_Corrective Action Order_04242026_(26-370329)_text.pdf, page 5CPF No. 5-2026-009-CAO Page 4 Accordingly, this Order mandating immediate corrective action is issued expeditiously without prior notice and opportunity for a hearing. The terms and conditions of this Order are effective upon completion of service. Within 10 days of receipt of this Order, Respondent may request a hearing to be held as soon as practicable, by notifying the Associate Administrator for Pipeline Safety in writing, with a copy to the Director, PHMSA, OPS Western Region. If a hearing is requested, it will be held in accordance with 49 CFR § 190.211. After receiving and analyzing additional data in the course of this investigation, PHMSA may identify other corrective measures that need to be taken. Respondent will be notified of any additional measures required and, if appropriate, PHMSA will consider a further amended order. To the extent consistent with safety, Respondent will be afforded notice and an opportunity for a hearing prior to the imposition of any additional corrective measures. Corrective Measures Definitions: Director – The Director, Western Region, PHMSA, OPS. Pipeline Segment – The 60.9 mile pipeline spanning from Orion Pump Station to Stockholm Pump Station as part of the Buffalo Pipeline System located in Woodard County, Oklahoma. 1. Shutdown of the Pipeline Segment. Respondent must shut down the Pipeline Segment immediately upon issuance of this Order. The Pipeline Segment must remain shut-in and may not be operated until authorized to be restarted by the Director in accordance with the terms of this Order. 2. Review of Prior Inline Inspection Results. Within 60 days of issuance of this Order, Respondent must conduct a review of any previous inline inspection (ILI) results of the Pipeline Segment. In its review, Respondent must re-evaluate all ILI results since 2015, including a review of the ILI vendors' raw data and analysis. Respondent must determine whether any features were present near the Failure sites. Respondent must also determine if any features with similar characteristics are present elsewhere on the Pipeline Segment. Respondent must submit documentation of this ILI review to the Director within 60 days of issuance of this Order as follows: a. List all ILI tool runs, tool types, and the calendar years of the tool runs. b. List, describe (type, size, wall loss, etc.), and identify the specific location of all ILI features present on the failed pipe and other pipe removed. c. List, describe (type, size, wall loss, etc.), and identify the specific location of all ILI features with similar characteristics present elsewhere on the Pipeline Segment. d. Explain the process used to review the ILI results and the results of the reevaluation. e. Conduct a review of all procedures and records related to Plains’ integrity assessment#

52026009CAO_Corrective Action Order_04242026_(26-370329)_text.pdf, page 6CPF No. 5-2026-009-CAO Page 5 program when conducting ILIs in accordance with 49 CFR § 195.591. 3. Mechanical and Metallurgical Testing. Within 45 days of issuance of this Order, Respondent must complete mechanical and metallurgical testing and failure analysis of the failed pipe, an analysis of representative soil samples from the Failures locations and product transported in pipe at the time of the failures, and any foreign materials. The testing must be conducted by an independent third-party acceptable to the Director. Respondent must complete the testing and analysis as follows: a. Document the chain-of-custody when handling and transporting the failed pipe sections and other evidence from the Failure sites. b. Within 10 days of issuance of this Order, develop and submit the testing protocol and the proposed testing laboratory to the Director for prior approval. c. Prior to beginning the mechanical and metallurgical testing, provide the Director with the scheduled date, time, and location of the testing to allow for an OPS representative to witness the testing. d. Ensure the testing laboratory distributes all reports whether draft or final in their entirety to the Director at the same time they are made available to Respondent. 4. Root Cause Failure Analysis. Within 90 days following issuance of this Order, complete a root cause failure analysis (RCFA) and submit a final report of this RCFA to the Director. The RCFA must be supplemented or facilitated by an independent third-party acceptable to the Director and must document the decision-making process and all factors contributing to the Failures, including potentially corrosive properties of the product or environment. The final report must include findings and any lessons learned and whether the findings and lessons learned are applicable to other locations within Respondent’s pipeline system. 5. Remedial Work Plan. a. Within 90 days following issuance of this Order, Respondent must submit a remedial work plan (RWP) to the Director for approval. b. The Director may approve the RWP incrementally without approving the entire RWP. c. Once approved by the Director, the RWP will be incorporated by reference into this Order. d. The RWP must specify the tests, inspections, assessments, evaluations, and remedial measures Respondent will use to verify the integrity of the Pipeline Segment. It must address all known or suspected factors and causes of the Failures. Respondent must consider the risks and consequences of another failure to develop a prioritized schedule for RWP-related work along the Pipeline Segment. e. The RWP must include a procedure or process to: i. Gather all data necessary to review the failure history (in service and pressure test failures) of the Pipeline Segment and to prepare a written report containing all the available information such as the locations, dates, and causes of leaks and failures. ii. Integrate the results of the metallurgical testing, root cause failure analysis, and other#

52026009CAO_Corrective Action Order_04242026_(26-370329)_text.pdf, page 7CPF No. 5-2026-009-CAO Page 6 corrective actions required by this Order with all relevant pre-existing operational and assessment data for the Pipeline Segment. Pre-existing operational data includes, but is not limited to, design, construction, operations, maintenance, testing, repairs, prior metallurgical analyses, and any third-party consultation information. Pre-existing assessment data includes, but is not limited to, ILI tool runs, hydrostatic pressure testing, direct assessments, inhibitor injection, corrosion coupon data or other internal corrosion prevention activities, close interval surveys, and DCVG/ACVG surveys. iii. Determine if conditions similar to those contributing to the Failures are likely to exist elsewhere on the Pipeline Segment. iv. Conduct additional field tests, inspections, assessments, and evaluations to determine whether, and to what extent, the conditions associated with the Failures and other failures from the failure history (see (e)(ii) above) or any other integrity threats are present elsewhere on the Pipeline Segment. At a minimum, this process must consider all failure causes and specify the use of one or more of the following: 1) ILI tools that are technically appropriate for assessing the pipeline system based on the cause of the Failures and that can reliably detect and identify anomalies; 2) Hydrostatic pressure testing; 3) Close-interval surveys; 4) Cathodic protection surveys, to include interference surveys in coordination with other utilities/pipelines in the area; 5) Coating surveys; 6) Stress corrosion cracking surveys; 7) Selective seam corrosion surveys; and 8) Other tests, inspections, assessments, and evaluations appropriate for the failure causes. v. Describe the inspection and repair criteria Respondent will use to prioritize, excavate, evaluate, and repair anomalies, imperfections, and other identified integrity threats. Include a description of how any defects will be graded and a schedule for repairs or replacement. vi. Based on the known history and condition of the Pipeline Segment, describe the methods Respondent will use to repair, replace, or take other corrective measures to remediate the conditions associated with the Failures and to address other known integrity threats along the Pipeline Segment. The repair, replacement, or other corrective measures must meet the criteria specified in (e)(vi) above. vii. Implement continuing long-term periodic testing and integrity verification measures to ensure the ongoing safe operation of the Pipeline Segment#

52026009CAO_Corrective Action Order_04242026_(26-370329)_text.pdf, page 8CPF No. 5-2026-009-CAO Page 7 considering the results of the analyses, inspections, evaluations, and corrective measures undertaken pursuant to the Order. f. Include a proposed schedule for completion of the RWP. g. Respondent must revise the RWP as necessary to incorporate new information obtained during the failure investigation and remedial activities, to incorporate the results of actions undertaken pursuant to this Order, and to incorporate modifications required by the Director. h. Submit any plan revisions to the Director for prior approval. The Director may approve plan revisions incrementally. All revisions to the RWP after it has been approved and incorporated by reference into this Order will be fully described and documented in the CAO Documentation Report. i. Implement the RWP as it is approved by the Director, including any revisions to the plan. 6. Restart Plan. Prior to resuming operation of the Pipeline Segment, develop and submit a written Restart Plan to the Director for prior approval. a. The Director may approve the Restart Plan incrementally without approving the entire plan, but the Pipeline Segment cannot resume operation until the Restart Plan is approved in its entirety. b. Once approved by the Director, the Restart Plan will be incorporated by reference into this Order. c. The Restart Plan must provide for adequate patrolling of the Pipeline Segment during the restart process and must include incremental pressure increases during start up, with each increment to be held for at least two hours. d. The Restart Plan must include sufficient surveillance of the pipeline during each pressure increment to ensure that no leaks are present when operation of the line resumes. e. The Restart Plan must specify a daylight restart and include advance communications with local emergency response officials. f. The Restart Plan must provide for a review of the Pipeline Segment for conditions similar to those of the Failures including a review of construction, operating and maintenance (O&M) and integrity management records such as ILI results, hydrostatic tests, root cause failure analysis of prior failures, aerial and ground patrols, corrosion, cathodic protection, excavations, and pipe replacements. Respondent must address any findings that require remedial measures to be implemented prior to restart. g. The Restart Plan must also include documentation of the completion of all mandated actions, and a management of change plan to ensure that all procedural modifications are incorporated into Respondent’s O&M procedures manual. h. The Restart Plan must provide for hydrostatic pressure testing of the Pipeline Segment.#

52026009CAO_Corrective Action Order_04242026_(26-370329)_text.pdf, page 9CPF No. 5-2026-009-CAO Page 8 7. Return to Service. After the Director approves the Restart Plan, Respondent may return the Pipeline Segment to service in accordance with the approved Restart Plan, but the operating pressure must not exceed the pressure restrictions in accordance with this Order. 8. Operating Pressure Restriction. In accordance with the terms of this Order, Respondent must reduce and maintain no less than a twenty percent (20%) pressure reduction in the actual operating pressure along the entire length of the Pipeline Segment such that the operating pressure along the Pipeline Segment will not exceed eighty percent (80%) of the actual operating pressure in effect immediately prior to the Failures. a. This pressure restriction is to remain in effect until written approval to increase the pressure or return the pipeline to its pre-failure operating pressure is obtained from the Director in accordance with the terms of this order. b. Within 10 days of receipt of this Order, Plains must provide the Director the actual operating pressures of each pump/compressor station on the Affected Segment at the time of failure and the reduced pressure restriction set-points at these same locations. c. This pressure restriction requires any relevant remote or local alarm limits, software programming set-points or control points, and mechanical over-pressure devices to be adjusted accordingly. d. When determining the pressure restriction set-points, Respondent must take into account any ILI features or anomalies present in the Pipeline Segment to provide for continued safe operation while further corrective actions are completed. e. Respondent must review the pressure restriction monthly by analyzing the operating pressure data, taking into account any ILI features or anomalies present in the Pipeline Segment. Respondent must immediately reduce the operating pressure further to maintain the safe operations of the Pipeline Segment, if warranted by the monthly review. Further, Respondent must submit the results of the monthly review to the Director including, at a minimum, the current discharge set-points (including any additional pressure reductions), and any pressure exceedance at discharge set- points. Submittals must be made quarterly, in accordance with the terms of this Order. 9. Removal of Pressure Restriction. a. The Director may allow the removal or modification of the pressure restriction upon a written request from Respondent demonstrating that restoring the pipeline to its pre- failure operating pressure is justified based on a reliable engineering analysis showing that the pressure increase is safe considering all known defects, anomalies, and operating parameters of the pipeline. b. The Director may allow the temporary removal or modification of the pressure restrictions upon a written request from Respondent demonstrating that temporary mitigative and preventive measures are implemented prior to and during the temporary removal or modification of the pressure restriction. The Director's determination will be based on the failures, causes, and evidence that preventative and mitigative actions taken by the operator provide for the safe operation of the Pipeline Segment during the temporary removal or modification of the pressure restriction. Appeals to#

52026009CAO_Corrective Action Order_04242026_(26-370329)_text.pdf, page 10CPF No. 5-2026-009-CAO Page 9 determinations of the Director in this regard will be decided by the Associate Administrator for Pipeline Safety. 10. CAO Documentation Report. Respondent must create and revise, as necessary, a CAO Documentation Report (CDR). When Respondent has concluded all the items in this Order it will submit the final CDR in its entirety to the Director. This will allow the Director to complete a thorough review of all actions taken by Respondent with regards to this Order prior to approving the closure of this Order. The intent is for the CDR to summarize all activities and documentation associated with this Order in one document. a. The Director may approve the CDR incrementally without approving the entire CDR. b. Once approved by the Director, the CDR will be incorporated by reference into this Order. c. The CDR must include, but is not necessarily limited to, the following: i. Table of Contents; ii. Summary of the Failures and the response activities; iii. Summary of pipe data, material properties and all prior assessments of the Pipeline Segment; iv. Summary of all tests, inspections, assessments, evaluations, and analysis required by the Order; v. Summary of the Mechanical and Metallurgical Testing as required by the Order; vi. Summary of the RCFA with all root causes as required by the Order; vii. Documentation of all actions taken by Respondent to implement the RWP, the results of those actions, and the inspection and repair criteria used; viii. Documentation of any revisions to the RWP including those necessary to incorporate the results of actions undertaken pursuant to this Order and whenever necessary to incorporate new information obtained during the failure investigation and remedial activities; ix. Lessons learned while completing this Order; x. A path forward describing specific actions Respondent will take on its entire pipeline system as a result of the lessons learned from work on this Order; and xi. Appendices (if required). Other Requirements: 11. Approvals. With respect to each submission under this Order that requires the approval of the Director, the Director may: (a) approve, in whole or part, the submission; (b) approve the submission on specified conditions; (c) modify the submission to cure any deficiencies; (d) disapprove in whole or in part, the submission, directing that Respondent modify the submission, or (e) any combination of the above. In the event of approval, approval upon conditions, or modification by the Director, Respondent shall proceed to take all action required by the submission as approved or modified by the Director. If the#

52026009CAO_Corrective Action Order_04242026_(26-370329)_text.pdf, page 11CPF No. 5-2026-009-CAO Page 10 Director disapproves all or any portion of the submission, Respondent must correct all deficiencies within the time specified by the Director and resubmit it for approval. 12. Extensions of Time. The Director may grant an extension of time for compliance with any of the terms of this Order upon a written request timely submitted demonstrating good cause for an extension. 13. Reporting. Plains must submit quarterly reports to the Director that: (1) include all available data and results of the testing and evaluations required by this Order; and (2) describe the progress of the repairs or other remedial actions being undertaken. The first quarterly report is due on May 29, 2026. The Director may change the interval for the submission of these reports. 14. Documentation of the Costs. It is requested that Respondent maintain documentation of the costs associated with implementation of this CAO. Include in each quarterly report submitted the to-date total costs associated with: (1) preparation and revision of procedures, studies, and analyses; (2) physical changes to pipeline infrastructure, including repairs, replacements, and other modifications; and (3) environmental remediation, if applicable. Be advised that all material submitted in response to this enforcement action is subject to being made publicly available. If you believe that any portion of your responsive material qualifies for confidential treatment under 5 U.S.C. § 552(b), along with the complete original document you must provide a second copy of the document with the portions you believe qualify for confidential treatment redacted and an explanation of why you believe the redacted information qualifies for confidential treatment under 5 U.S.C. § 552(b). In your correspondence on this matter, please refer to “CPF No. 5-2026-009-CAO” and for each document you submit, please provide a copy in electronic format whenever possible. The actions required by this Order are in addition to and do not waive any requirements that apply to Respondent’s pipeline system under 49 CFR Parts 190 through 199, under any other order issued to Respondent under authority of 49 U.S.C. Chapter 601, or under any other provision of federal or state law. Respondent may appeal any decision of the Director to the Associate Administrator for Pipeline Safety. Decisions of the Associate Administrator shall be final. Failure to comply with this Order may result in the assessment of civil penalties and in referral to the Attorney General for appropriate relief in United States District Court pursuant to 49 U.S.C. § 60120. The terms and conditions of this Order are effective upon service in accordance with 49 CFR § 190.5. _________________________________ ________________________ Linda Daugherty Date Issued Acting Associate Administrator for Pipeline Safety#

52026009CAO_Corrective Action Order (AMENDED)_05222026_(26-370329)_text.pdf, page 1Official PDFU.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration 1200 New Jersey Avenue, S.E. Washington, D.C. 20590 May 22, 2026 VIA ELECTRONIC MAIL TO: patrick.hodgins@plains.com Mr. Patrick Hodgins Vice President, HSE, Comms. & Govt. Regulatory Affairs Plains Pipeline, L.P. 333 Clay Street, Suite 1600 Houston, TX 77002 CPF No. 5-2026-009-CAO Dear Mr. Hodgins: Enclosed please find an Amended Corrective Action Order (ACAO or Order) issued by the Pipeline and Hazardous Materials Safety Administration (PHMSA), Office of Pipeline Safety (OPS), in the above-referenced case. The ACAO amends certain preliminary findings and corrective measures in the Corrective Action Order that was issued on April 24, 2026 for failures on the Buffalo Pipeline System located in Woodard and Harper County, Oklahoma. Specifically, the ACAO corrects the date and other information about the First Failure in the second and third bullets of the Preliminary Findings and removes the word compressor from paragraph 8, subparagraph b of the Corrective Measures. Service of the ACAO by email is effective upon the date of transmission and acknowledgment of receipt as provided under 49 CFR § 190.5. The terms and conditions of this Order are effective upon completion of service. Sincerely, Linda Daugherty Acting Associate Administrator for Pipeline Safety Enclosure: ACAO cc: Dustin Hubbard, Director, Western Region, Office of Pipeline Safety, PHMSA CONFIRMATION OF RECEIPT REQUESTED#

52026009CAO_Corrective Action Order (AMENDED)_05222026_(26-370329)_text.pdf, page 2U.S. DEPARTMENT OF TRANSPORTATION PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION OFFICE OF PIPELINE SAFETY WASHINGTON, D.C. 20590 ____________________________________ In the Matter of ) Plains Pipeline MidCon, LLC, ) a subsidiary Plains Pipeline, LP, ) CPF No. 5-2026-009-CAO ) ) Respondent. ) ____________________________________) AMENDED CORRECTIVE ACTION ORDER Background and Purpose The Pipeline and Hazardous Materials Safety Administration (PHMSA), Office of Pipeline Safety (OPS), is issuing this Amended Corrective Action Order (“ACAO” or “Order”)1 pursuant to the authority provided in 49 U.S.C. § 60112. The ACAO requires Plains Pipeline MidCon, LLC, a subsidiary of Plains Pipeline, LP (Plains or Respondent), to take certain necessary corrective actions to protect the public, property, and the environment from the potential hazards associated with the continued operation of its Buffalo Pipeline System in Woodard and Harper County, Oklahoma, which recently experienced two failures and has a history of prior failures in 2024 and 2025. Specifically, on April 20, 2026, Plains’ control room received a pipeline monitoring (PLM) alert indicating a product loss on the Buffalo Pipeline System between mainline valves BV-9 and BV- 7. Plains responded by shutting down the line. Current estimates indicate that the failure led to the release of approximately 520 barrels (bbls) of crude oil. Two days later, on April 23, 2026, another failure occurred on the Buffalo Pipeline System approximately 50 miles from the earlier failure. This second failure occurred while Plains was running a cleaning pig through the pipeline as part of a planned repair. Initial estimates indicated that the second failure, which Plains discovered after receiving a call from a landowner, led to the release of 1 gallon of crude oil. 1 To the extent this ACAO is modified from the original CAO issued to Respondent under CPF No. 5-2026-009- CAO on April 24, 2026, this ACAO supersedes and replaces the original CAO. To the extent this ACAO is unmodified from the original CAO, this ACAO retains the full force and effect of the original CAO. All deadlines noted in the order which refer to the date “this Order is issued” or “receipt of this Order” refer to the issuance of the original CAO on April 24, 2026.#

52026009CAO_Corrective Action Order (AMENDED)_05222026_(26-370329)_text.pdf, page 3CPF No. 5-2026-009-CAO Page 2 Pursuant to 49 U.S.C. § 60117, PHMSA has initiated an investigation of both failures. The preliminary findings of PHMSA’s ongoing investigation are as follows: Preliminary Findings • Plains operates a pipeline known as the Buffalo Pipeline System that spans 60.9 miles between the Orion Pump Station and the Stockholm Pump Station. • On April 20, 2026, Plains control room received a PLM alert indicating a product loss in the Buffalo Pipeline System segment located between Orion Pump Station and Stockholm Pump Station. The release was confirmed on April 21, 2026 at 9:20 am CDT (First Failure). • On April 21, 2026 at 10:02 am CDT, Plains called the National Response Center and reported a crude oil release of an unknown amount into a nearby water source.2 • Initial estimates indicated approximately 410 bbls of crude oil was released. That number was updated on April 23, 2026, to 520 bbls of crude oil. • The First Failure occurred 75 feet from a water source (a nearby 2-foot-wide creek). Crude oil reached the creek and migrated approximately 2,500 feet to a natural pond. • Mitigation efforts consisted of booms installed downstream of the last oil indication and upstream towards the release location to prevent further migration. Two skimmers were installed in the creek and crews used vacuum trucks and hand tools to remove oil and environmental contamination. Contaminated ground is being excavated between the failure point and the creek. • Prior to the accident, Plains personnel were in the area performing inline inspection (ILI) confirmation and remediation digs 1.5 miles upstream and downstream from the release location. • Previous ILI runs consisted of an MFL-A tool in 2024 and a UT tool in 2025. • Discussions with Plains personnel in the field indicated that the first failure location was not indicated on the previous ILI run. • On April 23, 2026, at 10:25 am CDT, Plains identified another leak occurring at an anomaly dig site approximately 50 miles away from the initial leak (Second Failure). Plains identified the Second Failure while starting a pig run with subsequent plans for a nitrogen purge. The site had been excavated, and the coating had already been removed. The leak was called in by a nearby landowner. 2 National Response Center (NRC) Report # 1460291.#

52026009CAO_Corrective Action Order (AMENDED)_05222026_(26-370329)_text.pdf, page 4CPF No. 5-2026-009-CAO Page 3 • The First Failure occurred at MP 16.4. The line at that location was constructed in 1960 with a nominal diameter of 8.625 inches, wall thickness of 0.188 inches, X-52 Grade, Low Frequency Electric Resistance Welded pipe, manufactured on an unknown date, from an unknown manufacturer, with a coal tar coating. MOP on the pipe was established at 1250 psi in 2017 via a 2016 8 hour hydrotest. The pipe was operating under a pressure reduction to 600 psi at the time of failure. • The Second Failure was at Dig #61. The line at that location was constructed in 1960 with a nominal diameter of 8.625 inches, wall thickness of 0.188 inches, X-52 Grade, Low Frequency Electric Resistance Welded pipe, manufactured on an unknown date, from an unknown manufacturer, with a coal tar and shrink sleeve coating. MOP on the pipe was established at 1250 psi in 2017 via a 2016 8 hour hydrotest. The pipe was operating under a pressure reduction to 600 psi at the time of failure. • PHMSA is aware of several previous failures on the Buffalo Pipeline System. In July of 2025, two failures occurred that resulted in the release of 100 and 179 bbls of crude oil, respectively. The cause of both failures was attributed to microbiologically induced corrosion and under deposit corrosion. • On October 26, 2024, 200 bbls of crude oil was released on the same segment with that failure also being attributed to microbiologically induced corrosion. • The 2024 and 2025 failures occurred on the Buffalo Pipeline System that spans 60.9 miles between the Orion Pump Station and the Stockholm Pump Station as part of the Buffalo Pipeline System. Determination of Necessity for Corrective Action Order and Right to Hearing Section 60112 of title 49, United States Code, authorizes PHMSA to determine that a pipeline facility is or would be hazardous to life, property, or the environment and if there is a likelihood of serious harm, to expeditiously order the operator of the facility to take necessary corrective action, including suspended or restricted use of the facility, physical inspection, testing, repair, replacement, or other appropriate action. An order issued expeditiously must provide an opportunity for a hearing as soon as practicable after the order is issued. In deciding whether to issue an order, PHMSA must consider the following, if relevant: (1) the characteristics of the pipe and other equipment used in the pipeline facility, including the age, manufacture, physical properties, and method of manufacturing, constructing, or assembling the equipment; (2) the nature of the material the pipeline facility transports, the corrosive and deteriorative qualities of the material, the sequence in which the material is transported, and the pressure required for transporting the material; (3) the aspects of the area in which the pipeline facility is located, including climatic and geologic conditions and soil characteristics; (4) the proximity of the area in which the facility is located to environmentally sensitive areas; (5) the population density and population and growth patterns of the area in which the pipeline facility is#

52026009CAO_Corrective Action Order (AMENDED)_05222026_(26-370329)_text.pdf, page 5CPF No. 5-2026-009-CAO Page 4 located; (6) any recommendation of the National Transportation Safety Board made under another law; and (7) any other factors PHMSA may consider as appropriate. After evaluating the foregoing preliminary findings of fact, and having considered the characteristics of the pipeline, the nature of the failures, the prior history of corrosion and failures on the pipeline; the hazardous nature of the material transported (crude oil); the existing and potential additional impacts to life, property, or the environment; the still-unknown cause of the Failures; and the possibility of additional failures on the pipeline system; it is hereby determined that continued operation of the Buffalo Pipeline System segment, as defined below, without corrective measures is or would be hazardous to life, property, or the environment, and that failure to issue this Order expeditiously would result in the likelihood of serious harm. Accordingly, this Order mandating immediate corrective action is issued expeditiously without prior notice and opportunity for a hearing. The terms and conditions of this Order are effective upon completion of service. Within 10 days of receipt of this Order, Respondent may request a hearing to be held as soon as practicable, by notifying the Associate Administrator for Pipeline Safety in writing, with a copy to the Director, PHMSA, OPS Western Region. If a hearing is requested, it will be held in accordance with 49 CFR § 190.211. After receiving and analyzing additional data in the course of this investigation, PHMSA may identify other corrective measures that need to be taken. Respondent will be notified of any additional measures required and, if appropriate, PHMSA will consider a further amended order. To the extent consistent with safety, Respondent will be afforded notice and an opportunity for a hearing prior to the imposition of any additional corrective measures. Corrective Measures Definitions: Director – The Director, Western Region, PHMSA, OPS. Pipeline Segment – The 60.9 mile pipeline spanning from Orion Pump Station to Stockholm Pump Station as part of the Buffalo Pipeline System located in Woodard County, Oklahoma. 1. Shutdown of the Pipeline Segment. Respondent must shut down the Pipeline Segment immediately upon issuance of this Order. The Pipeline Segment must remain shut-in and may not be operated until authorized to be restarted by the Director in accordance with the terms of this Order. 2. Review of Prior Inline Inspection Results. Within 60 days of issuance of this Order, Respondent must conduct a review of any previous inline inspection (ILI) results of the Pipeline Segment. In its review, Respondent must re-evaluate all ILI results since 2015, including a review of the ILI vendors' raw data and analysis. Respondent must determine whether any features were present near the Failure sites. Respondent must also determine if any features with similar characteristics are present elsewhere on the Pipeline Segment.#

52026009CAO_Corrective Action Order (AMENDED)_05222026_(26-370329)_text.pdf, page 6CPF No. 5-2026-009-CAO Page 5 Respondent must submit documentation of this ILI review to the Director within 60 days of issuance of this Order as follows: a. List all ILI tool runs, tool types, and the calendar years of the tool runs. b. List, describe (type, size, wall loss, etc.), and identify the specific location of all ILI features present on the failed pipe and other pipe removed. c. List, describe (type, size, wall loss, etc.), and identify the specific location of all ILI features with similar characteristics present elsewhere on the Pipeline Segment. d. Explain the process used to review the ILI results and the results of the reevaluation. e. Conduct a review of all procedures and records related to Plains’ integrity assessment program when conducting ILIs in accordance with 49 CFR § 195.591. 3. Mechanical and Metallurgical Testing. Within 45 days of issuance of this Order, Respondent must complete mechanical and metallurgical testing and failure analysis of the failed pipe, an analysis of representative soil samples from the Failures locations and product transported in pipe at the time of the failures, and any foreign materials. The testing must be conducted by an independent third-party acceptable to the Director. Respondent must complete the testing and analysis as follows: a. Document the chain-of-custody when handling and transporting the failed pipe sections and other evidence from the Failure sites. b. Within 10 days of issuance of this Order, develop and submit the testing protocol and the proposed testing laboratory to the Director for prior approval. c. Prior to beginning the mechanical and metallurgical testing, provide the Director with the scheduled date, time, and location of the testing to allow for an OPS representative to witness the testing. d. Ensure the testing laboratory distributes all reports whether draft or final in their entirety to the Director at the same time they are made available to Respondent. 4. Root Cause Failure Analysis. Within 90 days following issuance of this Order, complete a root cause failure analysis (RCFA) and submit a final report of this RCFA to the Director. The RCFA must be supplemented or facilitated by an independent third-party acceptable to the Director and must document the decision-making process and all factors contributing to the Failures, including potentially corrosive properties of the product or environment. The final report must include findings and any lessons learned and whether the findings and lessons learned are applicable to other locations within Respondent’s pipeline system. 5. Remedial Work Plan. a. Within 90 days following issuance of this Order, Respondent must submit a remedial work plan (RWP) to the Director for approval. b. The Director may approve the RWP incrementally without approving the entire RWP. c. Once approved by the Director, the RWP will be incorporated by reference into this Order.#

52026009CAO_Corrective Action Order (AMENDED)_05222026_(26-370329)_text.pdf, page 7CPF No. 5-2026-009-CAO Page 6 d. The RWP must specify the tests, inspections, assessments, evaluations, and remedial measures Respondent will use to verify the integrity of the Pipeline Segment. It must address all known or suspected factors and causes of the Failures. Respondent must consider the risks and consequences of another failure to develop a prioritized schedule for RWP-related work along the Pipeline Segment. e. The RWP must include a procedure or process to: i. Gather all data necessary to review the failure history (in service and pressure test failures) of the Pipeline Segment and to prepare a written report containing all the available information such as the locations, dates, and causes of leaks and failures. ii. Integrate the results of the metallurgical testing, root cause failure analysis, and other corrective actions required by this Order with all relevant pre-existing operational and assessment data for the Pipeline Segment. Pre-existing operational data includes, but is not limited to, design, construction, operations, maintenance, testing, repairs, prior metallurgical analyses, and any third-party consultation information. Pre-existing assessment data includes, but is not limited to, ILI tool runs, hydrostatic pressure testing, direct assessments, inhibitor injection, corrosion coupon data or other internal corrosion prevention activities, close interval surveys, and DCVG/ACVG surveys. iii. Determine if conditions similar to those contributing to the Failures are likely to exist elsewhere on the Pipeline Segment. iv. Conduct additional field tests, inspections, assessments, and evaluations to determine whether, and to what extent, the conditions associated with the Failures and other failures from the failure history (see (e)(ii) above) or any other integrity threats are present elsewhere on the Pipeline Segment. At a minimum, this process must consider all failure causes and specify the use of one or more of the following: ILI tools that are technically appropriate for assessing the pipeline system based on the cause of the Failures and that can reliably detect and identify anomalies; 1) Hydrostatic pressure testing; 2) Close-interval surveys; 3) Cathodic protection surveys, to include interference surveys in coordination with other utilities/pipelines in the area; 4) Coating surveys; 5) Stress corrosion cracking surveys; 6) Selective seam corrosion surveys; and 7) Other tests, inspections, assessments, and evaluations appropriate for the failure causes. v. Describe the inspection and repair criteria Respondent will use to prioritize, excavate, evaluate, and repair anomalies, imperfections, and other identified integrity threats. Include a description of how any defects will be graded and a schedule for repairs or replacement.#

52026009CAO_Corrective Action Order (AMENDED)_05222026_(26-370329)_text.pdf, page 8CPF No. 5-2026-009-CAO Page 7 vi. Based on the known history and condition of the Pipeline Segment, describe the methods Respondent will use to repair, replace, or take other corrective measures to remediate the conditions associated with the Failures and to address other known integrity threats along the Pipeline Segment. The repair, replacement, or other corrective measures must meet the criteria specified in (e)(vi) above. vii. Implement continuing long-term periodic testing and integrity verification measures to ensure the ongoing safe operation of the Pipeline Segment considering the results of the analyses, inspections, evaluations, and corrective measures undertaken pursuant to the Order. f. Include a proposed schedule for completion of the RWP. g. Respondent must revise the RWP as necessary to incorporate new information obtained during the failure investigation and remedial activities, to incorporate the results of actions undertaken pursuant to this Order, and to incorporate modifications required by the Director. h. Submit any plan revisions to the Director for prior approval. The Director may approve plan revisions incrementally. All revisions to the RWP after it has been approved and incorporated by reference into this Order will be fully described and documented in the CAO Documentation Report. i. Implement the RWP as it is approved by the Director, including any revisions to the plan. 6. Restart Plan. Prior to resuming operation of the Pipeline Segment, develop and submit a written Restart Plan to the Director for prior approval. a. The Director may approve the Restart Plan incrementally without approving the entire plan, but the Pipeline Segment cannot resume operation until the Restart Plan is approved in its entirety. b. Once approved by the Director, the Restart Plan will be incorporated by reference into this Order. c. The Restart Plan must provide for adequate patrolling of the Pipeline Segment during the restart process and must include incremental pressure increases during start up, with each increment to be held for at least two hours. d. The Restart Plan must include sufficient surveillance of the pipeline during each pressure increment to ensure that no leaks are present when operation of the line resumes. e. The Restart Plan must specify a daylight restart and include advance communications with local emergency response officials. f. The Restart Plan must provide for a review of the Pipeline Segment for conditions similar to those of the Failures including a review of construction, operating and maintenance (O&M) and integrity management records such as ILI results, hydrostatic tests, root cause failure analysis of prior failures, aerial and ground patrols, corrosion, cathodic protection, excavations, and pipe replacements. Respondent must address any findings that require remedial measures to be implemented prior to restart.#

52026009CAO_Corrective Action Order (AMENDED)_05222026_(26-370329)_text.pdf, page 9CPF No. 5-2026-009-CAO Page 8 g. The Restart Plan must also include documentation of the completion of all mandated actions, and a management of change plan to ensure that all procedural modifications are incorporated into Respondent’s O&M procedures manual. h. The Restart Plan must provide for hydrostatic pressure testing of the Pipeline Segment. 7. Return to Service. After the Director approves the Restart Plan, Respondent may return the Pipeline Segment to service in accordance with the approved Restart Plan, but the operating pressure must not exceed the pressure restrictions in accordance with this Order. 8. Operating Pressure Restriction. In accordance with the terms of this Order, Respondent must reduce and maintain no less than a twenty percent (20%) pressure reduction in the actual operating pressure along the entire length of the Pipeline Segment such that the operating pressure along the Pipeline Segment will not exceed eighty percent (80%) of the actual operating pressure in effect immediately prior to the Failures. a. This pressure restriction is to remain in effect until written approval to increase the pressure or return the pipeline to its pre-failure operating pressure is obtained from the Director in accordance with the terms of this order. b. Within 10 days of receipt of this Order, Plains must provide the Director the actual operating pressures of each pump station on the Affected Segment at the time of failure and the reduced pressure restriction set-points at these same locations. c. This pressure restriction requires any relevant remote or local alarm limits, software programming set-points or control points, and mechanical over-pressure devices to be adjusted accordingly. d. When determining the pressure restriction set-points, Respondent must take into account any ILI features or anomalies present in the Pipeline Segment to provide for continued safe operation while further corrective actions are completed. e. Respondent must review the pressure restriction monthly by analyzing the operating pressure data, taking into account any ILI features or anomalies present in the Pipeline Segment. Respondent must immediately reduce the operating pressure further to maintain the safe operations of the Pipeline Segment, if warranted by the monthly review. Further, Respondent must submit the results of the monthly review to the Director including, at a minimum, the current discharge set-points (including any additional pressure reductions), and any pressure exceedance at discharge set-points. Submittals must be made quarterly, in accordance with the terms of this Order. 9. Removal of Pressure Restriction. a. The Director may allow the removal or modification of the pressure restriction upon a written request from Respondent demonstrating that restoring the pipeline to its pre- failure operating pressure is justified based on a reliable engineering analysis showing that the pressure increase is safe considering all known defects, anomalies, and operating parameters of the pipeline. b. The Director may allow the temporary removal or modification of the pressure restrictions upon a written request from Respondent demonstrating that temporary mitigative and preventive measures are implemented prior to and during the temporary#

52026009CAO_Corrective Action Order (AMENDED)_05222026_(26-370329)_text.pdf, page 10CPF No. 5-2026-009-CAO Page 9 removal or modification of the pressure restriction. The Director's determination will be based on the failures, causes, and evidence that preventative and mitigative actions taken by the operator provide for the safe operation of the Pipeline Segment during the temporary removal or modification of the pressure restriction. Appeals to determinations of the Director in this regard will be decided by the Associate Administrator for Pipeline Safety. 10. CAO Documentation Report. Respondent must create and revise, as necessary, a CAO Documentation Report (CDR). When Respondent has concluded all the items in this Order it will submit the final CDR in its entirety to the Director. This will allow the Director to complete a thorough review of all actions taken by Respondent with regards to this Order prior to approving the closure of this Order. The intent is for the CDR to summarize all activities and documentation associated with this Order in one document. a. b. The Director may approve the CDR incrementally without approving the entire CDR. Once approved by the Director, the CDR will be incorporated by reference into this Order. c. The CDR must include, but is not necessarily limited to, the following: i. Table of Contents; ii. iii. Summary of the Failures and the response activities; Summary of pipe data, material properties and all prior assessments of the Pipeline Segment; Summary of all tests, inspections, assessments, evaluations, and analysis required by the Order; Summary of the Mechanical and Metallurgical Testing as required by the Order; Summary of the RCFA with all root causes as required by the Order; Documentation of all actions taken by Respondent to implement the RWP, the results of those actions, and the inspection and repair criteria used; Documentation of any revisions to the RWP including those necessary to incorporate the results of actions undertaken pursuant to this Order and whenever necessary to incorporate new information obtained during the failure investigation and remedial activities; Lessons learned while completing this Order; A path forward describing specific actions Respondent will take on its entire pipeline system as a result of the lessons learned from work on this Order; and xi. Appendices (if required). Other Requirements: 11. Approvals. With respect to each submission under this Order that requires the approval of the Director, the Director may: (a) approve, in whole or part, the submission; (b) approve the submission on specified conditions; (c) modify the submission to cure any deficiencies; iv. v. vi. vii. viii. ix. x.#

52026009CAO_Corrective Action Order (AMENDED)_05222026_(26-370329)_text.pdf, page 11CPF No. 5-2026-009-CAO Page 10 (d) disapprove in whole or in part, the submission, directing that Respondent modify the submission, or (e) any combination of the above. In the event of approval, approval upon conditions, or modification by the Director, Respondent shall proceed to take all action required by the submission as approved or modified by the Director. If the Director disapproves all or any portion of the submission, Respondent must correct all deficiencies within the time specified by the Director and resubmit it for approval. 12. Extensions of Time. The Director may grant an extension of time for compliance with any of the terms of this Order upon a written request timely submitted demonstrating good cause for an extension. 13. Reporting. Plains must submit quarterly reports to the Director that: (1) include all available data and results of the testing and evaluations required by this Order; and (2) describe the progress of the repairs or other remedial actions being undertaken. The first quarterly report is due on May 29, 2026. The Director may change the interval for the submission of these reports. 14. Documentation of the Costs. It is requested that Respondent maintain documentation of the costs associated with implementation of this CAO. Include in each quarterly report submitted the to-date total costs associated with: (1) preparation and revision of procedures, studies, and analyses; (2) physical changes to pipeline infrastructure, including repairs, replacements, and other modifications; and (3) environmental remediation, if applicable. Be advised that all material submitted in response to this enforcement action is subject to being made publicly available. If you believe that any portion of your responsive material qualifies for confidential treatment under 5 U.S.C. § 552(b), along with the complete original document you must provide a second copy of the document with the portions you believe qualify for confidential treatment redacted and an explanation of why you believe the redacted information qualifies for confidential treatment under 5 U.S.C. § 552(b). In your correspondence on this matter, please refer to “CPF No. 5-2026-009-CAO” and for each document you submit, please provide a copy in electronic format whenever possible. The actions required by this Order are in addition to and do not waive any requirements that apply to Respondent’s pipeline system under 49 CFR Parts 190 through 199, under any other order issued to Respondent under authority of 49 U.S.C. Chapter 601, or under any other provision of federal or state law. Respondent may appeal any decision of the Director to the Associate Administrator for Pipeline Safety. Decisions of the Associate Administrator shall be final. Failure to comply with this Order may result in the assessment of civil penalties and in referral to the Attorney General for appropriate relief in United States District Court pursuant to 49 U.S.C. § 60120. The terms and conditions of this Order are effective upon service in accordance with 49 CFR § 190.5. __________________________________________________________ Linda Daugherty Date Issued Acting Associate Administrator for Pipeline Safety#