Third Coast Infrastructure LLC Crude Oil Release

What HappenedOn November 15, 2023, about 7:00 p.m. local time, an 18-inch underwater crude oil pipeline released about 1.1 million gallons of crude oil into an unusually sensitive area in Main Pass 69 in the Gulf of America, southeast of Venice, Louisiana, in Louisiana state waters. The pipeline is part of the Main Pass Oil Gathering (MPOG) pipeline system, owned by Houston, Texas–based midstream company Third Coast Infrastructure LLC and operated by affiliate Panther Operating Company.2 The weather at the time of the accident was 73°F with light rain and east-northeast winds of 41 mph with 48-mph gusts. No injuries were reported, and the crude oil did not ignite.#

What We FoundWe determined the probable cause of the 18-inch diameter Main Pass Oil Gathering pipeline crude oil release was the loss of seal in a collet grip pipeline fitting from pipeline movement caused by geohazards that had not been addressed previously by Third Coast’s insufficient integrity management program. Contributing to the volume of crude oil released was an inappropriate control room response that did not shut down the pipeline system because of the controller’s uncertainty about the accuracy of data from a supervisory control and data acquisition system that indicated but did not alert the operator of a leak for more than 11 hours.#

Lessons LearnedPipeline operators must manage and address all threats to pipeline integrity, including those from weather events and geohazards. After the accident, Third Coast developed a program to monitor the MPOG pipeline system and collet grip fittings for possible pipe movement and to test and confirm the function of the fitting seals. PHMSA is overseeing modifications to Third Coast’s risk management program to include evaluations when mudflows or other geohazards occur. In this accident, uncertainty about the accuracy of the supervisory control and data acquisition (SCADA) system data led to a delayed shutdown of the pipeline. The NTSB has investigated other accidents in which controllers, faced with control system information indicating an anomaly, have failed to shut down pipelines. In Marshall, Michigan, in 2010, controllers’ flawed interpretations of system data and alarms contributed to the delayed shutdown of a pipeline, which released 843,000 gallons of crude oil into wetlands. More recently, in 2021, pipeline controllers in San Pedro Bay, near Huntington Beach, California, did not shut down a leaking underwater crude oil pipeline for 14 hours after incorrectly determining that leak alarms were false. Leak detection tools help reduce uncertainty for controllers interpreting abnormal control system data. After the accident, Third Coast reported that it is implementing a leak detection software system specifically for MPOG and has added a leak detection alarm to its SCADA system, with a tolerance level based on historical flow patterns. The company also added information on leak detection to its control center operational procedures and related training.#

PIR-25-02, page 1Official PDFPipeline Investigation Report PIR-25-02 Issued: June 13, 2025 Pipeline Investigation Report: PIR-25-02 Third Coast Infrastructure LLC Crude Oil Release Location Main Pass 69, Louisiana state waters, Gulf of America Date November 15, 2023 System type Hazardous liquid Accident type Leak Pipeline operator Panther Operating Company, Third Coast Infrastructure LLC Pipeline system Main Pass Oil Gathering System Hazardous materials Crude oil Fatalities/injuries None Damages $30 million Summary On November 15, 2023, about 7:00 p.m. local time, an 18-inch underwater crude oil pipeline released about 1.1 million gallons of crude oil into an unusually sensitive area in Main Pass 69 in the Gulf of America, southeast of Venice, Louisiana, in Louisiana state waters. 1 (See figure 1.) The pipeline is part of the Main Pass Oil Gathering (MPOG) pipeline system, owned by Houston, Texas–based midstream company Third Coast Infrastructure LLC and operated by affiliate Panther Operating Company. 2 The weather at the time of the accident was 73°F with light rain and east-northeast winds of 41 mph with 48-mph gusts. No injuries were reported, and the crude oil did not ignite. On November 16, the US Coast Guard and Third Coast began the initial response to the accident. The following day, the Coast Guard convened a unified command, comprised of federal and state agencies including the Pipeline and Hazardous Materials Safety Administration, the Bureau of Safety and Environmental Enforcement, the 1 (a) All times in this report are local. (b) Visit ntsb.gov to find additional information in the public docket for this NTSB accident investigation (case number PLD24FR001), including detailed factual reports about the circumstances of the accident. (c) Title 49 Code of Federal Regulations (CFR) Part 195.6 defines an unusually sensitive area as a drinking water or ecological resource area that is unusually sensitive to environmental damage from a hazardous liquid pipeline release. 2 The MPOG crude oil pipeline system starts in Main Pass 225 and delivers crude oil to the MP69 station, a facility in Main Pass 69 owned by Crescent Midstream. Crude oil is introduced into the system at six pipeline connection points in the Gulf. 1#

PIR-25-02, page 2Pipeline Investigation Report PIR-25-02 Louisiana Oil Spill Coordinator’s Office, and the Louisiana Department of Wildlife and Fisheries, which coordinated oil spill response activities until April 2024. 3 Figure 1. Oil slick in Main Pass 69, observed November 18, 2023. (Source: Bureau of Safety and Environmental Enforcement.) At the time of the accident, the MPOG system provided midstream services to crude oil producers in the Main Pass area and included 4 miles of 20-inch- and 61.8 miles of 18-inch-diameter hazardous liquid pipeline, with a maximum operating pressure of 1,950 pounds per square inch, gauge (psig). The control room for the MPOG system 3 The unified command observed about 19 brown pelicans with oil residue on their feathers on November 19, 2023. All were capable of flight. 2#

PIR-25-02, page 3Pipeline Investigation Report PIR-25-02 was located in Houston and staffed by pipeline controllers working 24 hours a day, 365 days a year, with one controller per 12-hour shift dedicated to MPOG and to nearby pipeline systems. 4 The controller on duty at the time of the accident began his shift at 6:00 p.m. on November 15. He reported to the National Transportation Safety Board (NTSB) that he first noticed the supervisory control and data acquisition (SCADA) system indicate pressure changes in the MPOG system around 6:45 p.m. but added that these are common on an active pipeline. 5 The controller recalled that he began investigating this event because the volume of oil entering the pipeline was larger than the volume exiting the pipeline at its delivery point. The controller conducted various troubleshooting activities throughout the evening of November 15 in response to the observed volume imbalance and changes in pressure and flow rate data. 6 SCADA system records reviewed by the NTSB indicated changes in flow rate and pressure for the MP69 station on the evening of November 15 with no change in the operating conditions of any of the MPOG pipeline system assets. Flow rate fluctuations were recorded starting about 6:12 p.m., with a significant decrease in flow rate beginning just before 7:00 p.m. About 10:15 p.m. on November 15, the controller reported the abnormal data to his supervisor, who recommended not shutting down the pipeline. About 12:29 a.m., the flow rate at the MP69 station went to zero.7 SCADA system records also indicated a decrease in the volume of oil leaving the system through the night, with about 1,100 barrels unaccounted for about 8:30 p.m. and 11,000 barrels at 1:30 a.m. on November 16. He spoke with colleagues again after the data showed a zero flow rate at the MP69 station about 12:29 a.m. The controller told the NTSB that the valves at the MP69 station were programmed to close when the flow rate went to zero, but for unknown reasons, they did not close in this instance. The controller concluded, based on the 4 A control room is a central location for monitoring and controlling pipeline operations. 5 SCADA is a computer-based system used in a pipeline control room that collects and displays information about pipeline facilities. 6 The controller told the NTSB that about 9:00 p.m. he called personnel at two other control rooms, including at the MP69 station, to verify whether they observed similar flow data decreases. In both cases, the flow rates matched those shown by the SCADA system at his location. About 1:30 a.m., he requested a platform operator at the MP69 station walk through to assess the equipment, but the team there reported they found no equipment problems. 7 Third Coast procedures did not require controllers to take an action when MP69 had zero flow. 3#

PIR-25-02, page 4Pipeline Investigation Report PIR-25-02 conversations with his colleagues and on the performance of the valves, that the data were the result of equipment issues and did not shut down the pipeline. The controller ended his shift about 6:00 a.m. on November 16. Shortly after the shift change, day shift personnel reviewed pipeline pressure and flow trend data and noted the zero flow reading at the MP69 station. 8 They began shutdown procedures about 6:30 a.m., and the pipeline system was isolated by 9:00 a.m.9 Third Coast reported a leak to the US Environmental Protection Agency National Response Center about 9:51 a.m. After the accident, Third Coast contracted divers and underwater remote-operated vehicles to survey the pipeline for the failure location. On December 21, the divers found oil residue in the area of a collet grip fitting, approximately 40 feet below the surface of the water; this location was later confirmed as the leak location. 10 (See figure 2.) 8 Shift leads joined controllers during daytime shifts Monday through Friday. 9 By the time the pipeline was shut down, the volume imbalance recorded by the SCADA system was nearly 27,000 barrels. 10 A collet grip fitting joins two segments of pipe by surrounding and gripping the outer pipe circumference. 4#

PIR-25-02, page 5Pipeline Investigation Report PIR-25-02 Figure 2. Main Pass Oil Gathering pipeline and approximate leak location. The NTSB recovered the fitting and piping for evaluation. The evaluation determined the fitting, as recovered, was capable of functioning as designed. (See figure 3.) The NTSB Materials Laboratory then evaluated the pipe that had been installed in the fitting, and the evaluation revealed that at the time of recovery, it had been pulled about 34 inches out of the fitting and was no longer in contact with the sealing surfaces in the fitting. 5#

PIR-25-02, page 6Pipeline Investigation Report PIR-25-02 Figure 3. Collet grip fitting recovered from the seafloor. (Photo: MPOG) The NTSB reviewed records of MPOG system integrity assessments for the decade preceding the accident. In 2012, a high-resolution magnetic flux leakage inline inspection (ILI) tool run found no pipeline anomalies that required action, and a high-resolution geometry and dent assessment ILI run in 2019 reported some corrosion metal loss anomalies but no deformation anomalies. An acoustic resonance technology ILI tool was run in October 2023, several weeks before the failure. After the accident, at the request of the NTSB, the ILI vendor completed an enhanced evaluation of the data from this inspection. At the time of the October 2023 inspection, the pipe was found to have moved within the fitting about 7.6 inches upstream from its original installation location but was still in contact with the fitting’s seals. 6#

PIR-25-02, page 7Pipeline Investigation Report PIR-25-02 Analysis The crude oil leak in this accident resulted from weather-related geohazards, which likely imposed forces that moved the pipe within its fitting over time.11 The leak continued from about 6:30 p.m. on November 15 until about 07:30 a.m. on November 16, releasing about 1.1 million gallons of crude oil into an unusually sensitive area into Louisiana state waters in the Gulf of America. When the pipeline controller on duty on the night of the accident observed SCADA system data that indicated a possible leak, he consulted with colleagues and tried to evaluate the problem from the control room. Trending SCADA system data offered justification for the pipeline controller to shut down the pipeline system. However, although no equipment issues were observed, the controller told the NTSB that his consultations with colleagues and the failure of the valves at MP69 to perform as programmed led him to doubt the accuracy of the SCADA data and deterred him from shutting down the pipeline. It was shut down the next morning by personnel on the following shift. Had the controller shut down the pipeline when he first identified a flow mismatch, or when he first reported the issue to his management, far less crude oil would have been released. After the accident, divers identified a likely failure location. Evaluations of the pipe and fitting at the location indicated that the pipe had moved within the fitting, leading to a loss of the seal between the fitting and the pipe. The failure was consistent with land movement caused by resident geohazards and weather events. Over time, the land movement imposed forces on the underwater pipeline that stressed the underwater pipeline, increasing pipeline integrity threats and affecting safe operation. In the years leading up to the accident, Third Coast missed several opportunities to evaluate how geohazards may threaten the integrity of their pipeline. Information widely available within the industry suggested that land movement related to hurricane activity was a threat to pipelines in the Gulf of America, including the MPOG 18-inch pipeline. Alignment maps from 2005, created after the pipeline was damaged by Hurricane Ivan the year before, showed significant areas of exposed pipeline and mudflows over or near it, along with a mudflow in the same area as the November 2023 failure. Although the pipeline owner at the time repaired this damage, the National Oceanic and Atmospheric Administration’s National Hurricane Center recorded 12 additional hurricanes and 6 tropical storms in Main Pass 69 since Hurricane Ivan. 11 Marine geohazards include submarine landslides or mudflows induced by natural processes that can harm, endanger, or affect seafloor facilities. A mudflow is the movement of underwater sediment caused by gravity or other forces. 7#

PIR-25-02, page 8Pipeline Investigation Report PIR-25-02 Further, a 2022 hydrographic survey showed more than a dozen exposed sections of the MPOG 18-inch pipeline, as well as 24 locations where the pipeline may have been unsupported by the sea floor.12 Exposures and suspensions such as these can indicate detrimental forces acting on a pipeline. An effective pipeline integrity program would have incorporated information on potential weather-related geohazards to identify pipeline areas for further assessment. Although Third Coast corrected the unsupported and exposed sections of the MPOG 18-inch pipeline in 2023, it did not evaluate the potential for the pipeline to move and for the fitting to fail before the accident. Probable Cause The National Transportation Safety Board determines the probable cause of the 18-inch diameter Main Pass Oil Gathering pipeline crude oil release was the loss of seal in a collet grip pipeline fitting from pipeline movement caused by geohazards that had not been addressed previously by Third Coast’s insufficient integrity management program. Contributing to the volume of crude oil released was an inappropriate control room response that did not shut down the pipeline system because of the controller’s uncertainty about the accuracy of data from a supervisory control and data acquisition system that indicated but did not alert the operator of a leak for more than 11 hours. Lessons Learned Pipeline operators must manage and address all threats to pipeline integrity, including those from weather events and geohazards. After the accident, Third Coast developed a program to monitor the MPOG pipeline system and collet grip fittings for possible pipe movement and to test and confirm the function of the fitting seals. PHMSA is overseeing modifications to Third Coast’s risk management program to include evaluations when mudflows or other geohazards occur. In this accident, uncertainty about the accuracy of SCADA data led to a delayed shutdown of the pipeline. The NTSB has investigated other accidents in which controllers, faced with control system information indicating an anomaly, have failed to shut down pipelines. In Marshall, Michigan, in 2010, controllers’ flawed interpretations of system data and alarms contributed to the delayed shutdown of a pipeline, which 12 Title 49 CFR 192.327 specifies the burial requirements for an offshore pipeline in shallow water (200 feet deep or less). In water between 12 and 200 feet deep, the pipe must be installed so the top of the pipe is below the natural bottom, or seafloor. 8#

PIR-25-02, page 9Pipeline Investigation Report PIR-25-02 released 843,000 gallons of crude oil into wetlands. 13 More recently, in 2021, pipeline controllers in San Pedro Bay, near Huntington Beach, California, did not shut down a leaking underwater crude oil pipeline for 14 hours after incorrectly determining that leak alarms were false. 14 Leak detection tools help reduce uncertainty for controllers interpreting abnormal control system data. After the accident, Third Coast reported that it is implementing a leak detection software system specifically for MPOG and has added a leak detection alarm to its SCADA system, with a tolerance level based on historical flow patterns. The company also added information on leak detection to its control center operational procedures and related training. 13 NTSB. 2012. Enbridge Incorporated Hazardous Liquid Pipeline Rupture and Release, Marshall, Michigan, July 25, 2010. PAR-12/01. Washington, DC: NTSB. 14 NTSB. 2024. Anchor Strike of Underwater Pipeline and Eventual Crude Oil Release, San Pedro Bay, Near Huntington Beach, California, October 1, 2021. MIR-24/01. Washington, DC: NTSB. 9#

PIR-25-02, page 10Pipeline Investigation Report PIR-25-02 The NTSB is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant events in the other modes of transportation—railroad, transit, highway, marine, pipeline, and commercial space. We determine the probable causes of the accidents and events we investigate and issue safety recommendations aimed at preventing future occurrences. In addition, we conduct transportation safety research studies and offer information and other assistance to family members and survivors for each accident or event we investigate. We also serve as the appellate authority for enforcement actions involving aviation and mariner certificates issued by the Federal Aviation Administration (FAA) and US Coast Guard, and we adjudicate appeals of civil penalty actions taken by the FAA. The NTSB does not assign fault or blame for an accident or incident; rather, as specified by NTSB regulation, “accident/incident investigations are fact-finding proceedings with no formal issues and no adverse parties … and are not conducted for the purpose of determining the rights or liabilities of any person” (Title 49 Code of Federal Regulations section 831.4). Assignment of fault or legal liability is not relevant to the NTSB’s statutory mission to improve transportation safety by investigating accidents and incidents and issuing safety recommendations. In addition, statutory language prohibits the admission into evidence or use of any part of an NTSB report related to an accident in a civil action for damages resulting from a matter mentioned in the report (Title 49 United States Code section 1154(b)). For more detailed background information on this report, visit the NTSB Case Analysis and Reporting Online (CAROL) website and search for NTSB accident ID PLD24FR001. Recent publications are available in their entirety on the NTSB website. Other information about available publications also may be obtained from the website or by contacting— National Transportation Safety Board Records Management Division, CIO-40 490 L’Enfant Plaza, SW Washington, DC 20594 (800) 877-6799 or (202) 314-6551 10#