Failure Investigation Report Gulf South Pipeline Company, LLC. Feb 21, 2024

Page 1Official PDFPipeline and Hazardous Materials Safety Administration U.S. Department of Transportation Failure Investigation Report Office of Pipeline Safety – Accident Investigation Division Failure Investigation Report Gulf South Pipeline Company, LLC. Rupture – Natural Force Damage – Earth Movement Executive Summary On February 12, 2023, at 3:56 a.m.1, Gulf South Pipeline Company, LLC's (Gulf South) control center received a supervisory control and data acquisition (SCADA) alarm indicating a pressure drop on the Index 381 pipeline. Gulf South isolated the pipeline segment and technicians began walking the right of way (ROW) looking for a release point. The technicians discovered the pipeline had ruptured at a girth weld behind an earthen dam. The rupture of the pipeline released 20.96 million cubic feet (MMcf) of natural gas into the atmosphere. There was no ignition or explosion of the natural gas. Land movement along the nearby man-made dam was visibly evident along the ROW. The pipeline rupture occurred in a Class 1 area and was not in a High Consequence Area (HCA) or in a Historically Disadvantaged Community2. A nearby Historically Disadvantaged Community was affected however, by the temporary interruption of natural gas service while the Index 381 pipeline rupture was being isolated. The local gas distribution company, Atmos Energy Corporation – Mississippi (Atmos), estimated 217 residential customers had service interruptions lasting less than one day. The Pipeline and Hazardous Material Safety Administration’s (PHMSA’s) Accident Investigation Division (AID) deployed an investigator to the incident, with the investigator arriving on-site February 14, 2023. PHMSA determined the cause of the rupture to be a result natural force damage from land movement at the nearby man-made dam that put lateral strain on the girth weld to the point of failure. The land movement around the pipeline was not identified or mitigated prior to failure. 1. Operator, Location, Consequences Lead Investigator Curtis Huff Accident Investigation Director Chris Ruhl Date of Report February 21, 2024 Date of Failure February 12, 2023 Commodity Released Natural Gas City, County, and State Jackson, Hinds, Mississippi OpID and Operator Name 31728 – Gulf South Pipeline Company, LLC Unit # & Unit Name 1602 – MS-1 (Jackson – West) WMS Activity # 23-267701 1 All times are Central Standard Time unless otherwise noted. 2 The Department of Transportation’s interim definition for Disadvantaged Communities was developed by an internal and external collaborative research process. It includes data for 22 indicators collected at the census tract level and grouped into six (6) categories of transportation disadvantage. More information can be found at: https://www.transportation.gov/priorities/equity/justice40/transportation-disadvantaged-census-tracts-historically- disadvantaged. Incident: February 12, 2023 – Jackson, Hinds, MS 1 Gulf South Pipeline Company, LLC.#

Page 2U.S. DOT/PHMSA Huff Milepost / Location MP 117.7/Station 6180+60, 32.262952, -90.199256 Type of Failure Rupture – Natural Force Damage – Earth Movement Fatalities None Injuries None Description of Impacted Area Class 1 Location, not within a High Consequence Area Total Costs $4,781,185 2. System Description Gulf South, a subsidiary of Boardwalk Pipelines, operates a network of interstate natural gas pipelines that provides transportation and storage services. Gulf South transports natural gas directly from supply areas in Oklahoma, Texas, Louisiana, Mississippi, the Gulf of Mexico, and indirectly from the Appalachian Region. Natural gas is transported to markets throughout the South Central and Southeastern United States. Gulf South consists of a reticulated system of approximately 7,260 miles of pipeline with an average daily throughput of approximately 5,800 MMcf per day. The failure occurred in Gulf South’s Index 381 pipeline. Index 381 extends 20.5 miles from North of Raymond, Mississippi eastward to the Gulf South compressor station in Jackson, Mississippi. At the failure location the pipeline was bi-directional with flow east to west or west to east depending on supply needs. Index 381 was originally installed as an 18-inch pipeline in 1939. Due to the construction of an industrial plant and retention pond near Jackson, Mississippi, a section of Index 381 was rerouted around the retention pond in 1952 using 20-inch pipe. The failure occurred in a section of the 20-inch pipeline near the retention pond. The failed pipe section of Index 381 has the following properties: • 20-inch diameter • 0.250-inch wall thickness • API-5L, Grade X52 • Direct Current Electric resistance welded • Manufactured by Youngstown Steel • Installed in 1952 The pipeline was operating at 400 pounds per square inch gauge pressure (psig) at the time of the rupture. The maximum allowable operating pressure (MAOP) was 475-psig, established by 49 CFR section 192.619 (c) in 1971. The rupture occurred in a wooded, Class 1 area, next to a retention pond and was not in an HCA or Historically Disadvantaged Community. 3. Events Leading up to the Failure In 1952 a portion of the Index 381 pipeline was rerouted around a retention pond being built at an industrial facility. The original 18-inch pipeline was replaced with 20-inch pipe in the rerouted portion of the pipeline going around the back side of the retention pond dam (see Figure 1). The retention pond dam is adjacent to the Index 381 pipeline ROW. The retention pond dam, owned by US Silica, has had issues with soil stability and land movement. Historical satellite imagery shows evidence of previous remediation efforts going back to at least 2003. Other remediation efforts appear to have been undertaken between 2007 and 2010 and again between 2017 and 2018. In 2019 continued land movement is evident on satellite images. Between 2020 and the date of the failure on February 12, 2023, US Silica made at least three attempts to stabilize and remediate the land movement on the retention pond dam. The last remediation prior to the failure was in September 2022. The attempts to stabilize the pond dam are considered unsuccessful since the land moved again after the last attempt in September 2022. Foot patrols along the ROW, in the previous five years, were made with no mention of land movement along the ROW. Aerial patrols were performed in July and September 2022 reported earth moving equipment near the ROW. Gulf South followed up on the aerial reports and confirmed the equipment was not on the ROW but working in the pond dam area. Incident: February 12, 2023 – Jackson, Hinds, MS 2 Gulf South Pipeline Company, LLC#

Page 3U.S. DOT/PHMSA Huff The failed section of the Index 381 pipeline was most recently hydrostatically pressure tested in June 2019 to 760-psi. At the time of the failure the pipeline was under normal operations with an operating pressure of approximately 400-psi, which was below the MAOP of 475-psi. There were no failures associated with the hydrotest near the failure location. In 2017 Gulf South contracted ENTEGRA to perform an in-line inspection (ILI) of the index 381 pipeline. The ILI tool run consisted of an inertial mapping unit (IMU), a high-resolution magnaflux leakage (HR-MFL) tool, and a high-resolution caliper (HR-CAL) tool. In 2021 another ILI tool run performed by ROSEN using an axial magnaflux leakage (MFL-A) tool, a HR-CAL, and a IMU tool. 4. Emergency Response February 12, 2023: • 3:56 a.m. – Gulf South’s controller, while monitoring SCADA, discovered low pressure at the Jackson City Gate #5. • 3:57 a.m. – Low pressure at the Jackson 18” to Sterlington noted along with flow increases at the Jackson – Mag 6” and at the Cherry Grove regulator. • 3:58 a.m. – Multiple alarms for low pressure at other meters in the area. • 4:02 a.m. – Atmos gas control notified of Gulf South’s pipeline issue. • 4:45 a.m. – Interconnect valve closed on Index 302/381. • 4:55 a.m. – Interconnect valve closed on Index 381/381-1. • 5:00 a.m. – Index 381 valve V-208689 closed. • 5:30 a.m. – Index 381 valve V-276420 closed. • 5:30 a.m. – Index 381 release isolated. See Figure 1 for the location of the mainline valves used to isolate the release. • 7:20 a.m. – Gulf South Gas Control notified the Jackson, Mississippi Police Department of the release. • 7:23 a.m. – Notification of a natural gas release was made to the National Response Center (NRC), Report Number 1359833. • 7:25 a.m. – Gulf South notified the Rankin County, Mississippi Sheriff’s Office of the release. • 7:30 a.m. – Gulf South notified the Richland, Mississippi Police Department of the release. • 7:30 a.m. – Gulf South located the release site. • 7:58 a.m. – The NRC issued an updated report due to a system issue, Report Number 1359835. February 14, 2023: • 6:27 a.m. – Notification to the NRC was made, Report Number 1359969, providing a 48-hour update on the incident. Incident: February 12, 2023 – Jackson, Hinds, MS 3 Gulf South Pipeline Company, LLC#

Page 4U.S. DOT/PHMSA Huff Figure 1. Map Showing the Location and Distance Between Isolation Valves. 5. Summary of Return-to-Service The failed 20-inch section of the pipeline was removed from service on February 12, 2023. Near the transition of the 18-inch to 20-inch pipeline, at each end of the 20-inch, the pipeline was cut, and 18-inch end caps were welded in place. On February 13, 2023, the final end cap was welded in place and service was restored to the unaffected portions of the Index 381 pipeline. Gulf South has evaluated its transportation obligations in the Jackson area and determined that the failed and isolated 20-inch section of Index 381 will not be reconnected and placed back in service. 6. Investigation Details AID deployed an investigator who arrived on scene at 7:20 a.m. on February 14, 2023. A visual survey of the area noted that the incident occurred in a wooded area near an industrial retention pond dam. The investigator met with Gulf South personnel to review the incident and discuss data requests, plans for pipe specimen collection, repair and return to service. A crater was created around the rupture by the escaping natural gas. The crater was approximately 25-feet long by 15-feet wide (see Figure 2). Incident: February 12, 2023 – Jackson, Hinds, MS 4 Gulf South Pipeline Company, LLC#

Page 5U.S. DOT/PHMSA Huff Figure 2. Crater Created by the Rupture, Looking East. The rupture occurred at a girth weld and due to stresses on the pipeline, the pipe ends pulled away from each other. After the rupture there was a 14.5-inch horizontal separation (along the length of pipe), an 11-inch vertical separation and a one-inch separation laterally (side to side) (see Figure 2 and Figure 3). Incident: February 12, 2023 – Jackson, Hinds, MS 5 Gulf South Pipeline Company, LLC#

Page 6U.S. DOT/PHMSA Huff Figure 3. Separated Pipe Segments. Geohazards After the pipeline rupture on February 12, 2023, Gulf South contracted Geosyntec Consultants, Inc. (Geosyntec) to perform a geohazard assessment of the rupture site, the Index 381 ROW, and adjacent slopes. Geosyntec performed a visual assessment, photo documented and mapped the area around the rupture. A historical review of Google Earth imagery of the area was also performed. The area in the immediate vicinity of the rupture location did not show any indications of earth movement, such as ground cracks, bulges, or sunken ground. However, there was a large, active landslide on the pond dam about 160-feet to the west of the rupture location. A landslide measuring approximately 100 to 170-feet long by 400-feet wide was observed to crosscut the pond dam and the Index 381 pipeline ROW. The direction of the land movement is inferred to be towards the Index 381 pipeline. See Figure 4 for a map of the landslide, the Index 381 ROW, the Index 381 pipeline, and the rupture location. Figure 4. Land Movement Area Identified Near the Index 381 Failure (From Geosyntec Consultants, Inc.). Figure 5 is a photograph of the landslide taken the morning of February 14, 2023, showing large cracks and scarps along the slope of the pond dam. Tarps were placed over the landslide area by the pond dam property owner throughout the day on February 14, 2023, to prevent further saturation of the slope from rainfall. The depth of the landslide is estimated to be 3-6 feet on the western half of the landslide and 8-12 feet deep on the eastern half. Based on depth of cover measurements of 2.4 to 10.5- Incident: February 12, 2023 – Jackson, Hinds, MS 6 Gulf South Pipeline Company, LLC#

Page 7U.S. DOT/PHMSA Huff feet over the Index 381 pipeline, the pipeline would have been engaged by the landslide on the eastern half of the landslide. The impact of the land movement would have induced a tensional stress on the Index 381 pipeline. Figure 5. Land Movement Next to Index 381 (Arrows Point to Index 381 Pipeline Markers). The review of historical satellite imagery shows signs of earth movement and soil remediation efforts along the pond dam going back to at least 2003. All remediation efforts appear to have been taken place north of the Index 381 ROW on the pond dam and not on the Index 381 ROW itself. Gulf South’s land and aerial patrols have noted remediation efforts on the pond dam. Those notices of remediation activity were followed up with site visits to verify the remediation was not on the Index 381 ROW, however the geohazard threats of the landslide activity were not identified by Gulf South. Section 5010 of Gulf South’s Operations and Maintenance Manual specifies surveillance activities which includes, observing the surface conditions on and adjacent to the ROW, including earth movement. ADV Integrity, Inc.’s (ADV Integrity) root cause analysis found the training materials and task lists for documenting patrols, did not emphasize visual inspection for geohazards outside of the ROW or adequately describe earth movement indications. The guidance also does not adequately specify what response is required when hazards are identified. The lack of communication guidance contributed to a communication disconnect between the operations and integrity groups. Observations made during Geosyntec’s geohazard assessment indicate the landslide was active in the weeks prior to the Index 381 failure and the longitudinal stresses likely increased significantly during those prior weeks. Metallurgical Analysis The two pipe ends containing the failed girth weld were cut off the pipeline and were sent to ADV Integrity, in Magnolia, Texas, for metallurgical analysis. Two additional pipe segments, with intact girth welds, were also cut out and included for metallurgical analysis. Incident: February 12, 2023 – Jackson, Hinds, MS 7 Gulf South Pipeline Company, LLC#

Page 8U.S. DOT/PHMSA Huff ADV Integrity also conducted chemical and mechanical property testing on a sample of the pipe body to confirm that the pipe meets the specification of API-5LX, X-52 pipe. Chemical composition, hardness, tensile strength, and Charpy V-Notch (CVN) tests were performed. The chemical composition, tensile strength, and CVN tests confirmed that the pipe body is consistent with the API-5LX, X-52 pipe specification, API-5LX, 3rd Edition, (1951), in place at the time of manufacture. The failure origin occurred in a 26-inch-long area of incomplete weld penetration into the internal diameter (ID) which was identified along the bottom of the pipe. (see Figure 6). Figure 6. Photograph of Fracture Edges with Incomplete Weld Penetration. Upper Scale is in Inches. (From ADV Integrity). The incomplete weld penetration was 48% of the nominal thickness, about 0.12-inches deep, with most of the remaining fracture’s appearance being consistent with ductile overload. All welds examined during the metallurgical analysis would have failed the current API 1104 Standard3 for workmanship criteria. During the time of construction, 1952, nondestructive testing was not required by industry standards and was most likely not performed. Figure 7 is a close-up photograph of the fracture with the incomplete weld penetration identified above the white dashed line. Figure 7. Close-Up Photograph of Fracture Edge with Incomplete Weld Penetration. Major Scale is in Inches. (From ADV Integrity). 3 American Petroleum Institute Standard 1104, Welding of Pipelines and Related Facilities, 22nd Edition Incident: February 12, 2023 – Jackson, Hinds, MS 8 Gulf South Pipeline Company, LLC#

Page 9U.S. DOT/PHMSA Huff The pipe end samples were subjected to three-dimensional laser scans to measure the outer diameter and any ovality that was present in the vicinity of the fracture. Ovality was observed at the girth weld failure and within six to eight inches along the pipe adjacent to the failure. The ovality at the fracture origin is consistent with a pipe failure occurring from a tension or bending force. A graph of the outer diameters from the laser scan, showing the ovality near the fracture origin, are shown in Figure 8. Figure 8. Plot of Outer Diameter Measurements Near the Fracture Origin. (From ADV Integrity). ILI Analysis In December 2017 ENTEGRA performed an in-line inspection (ILI) of the Index 381 pipeline. The ILI tool run consisted of a HR- CAL, a HR-MFL, and an IMU tool. No Girth weld anomalies were reported from the 2017 tool run. The 2017 tool run was the first IMU data collected on the Index 381 pipeline, therefore, no data comparison was available for a bending strain analysis at the time. In December 2021 ROSEN performed another ILI tool run using a MFL-A, a HR-CAL, and an IMU tool. The MFL-A tool is oriented to detect circumferential defects. No girth weld anomalies were reported from the 2021 tool run. While IMU data was collected in the 2021 ILI run, no comparison of the IMU data from the 2017 and 2021 tool runs was requested by Gulf South as part of the 2021 ILI analysis. The bending strain analysis of the two IMU runs was not performed until after the pipeline rupture occurred in February 2023. A Bending Strain and Pipe Movement Assessment was performed by ROSEN after the incident using the 2017 ENTEGRA and 2021 ROSEN IMU data. The analysis identified the area around the pond dam as a potential location for bending strain and for pipe movement. Pipe movement in the horizontal direction was calculated to be 1.93-feet with a bending strain of 0.242%. A second independent bending strain and pipe movement analysis was performed by D2 Integrity. D2 Integrity’s analysis confirmed pipe movement and bending strain between the 2017 and 2021 IMU runs. D2 calculated 2.9-feet of horizontal pipe movement and 0.207% bending strain. Both ROSEN and D2 Integrity’s calculations are based only on movement between the 2017 and 2021 IMU runs. It is possible that there was pipe movement and bending strain on the Index 381 pipeline prior to the 2017 IMU run. Figure 9 shows the bending strain, and the pipe movement changes between 2017 and 2021 IMU runs. Incident: February 12, 2023 – Jackson, Hinds, MS 9 Gulf South Pipeline Company, LLC#

Page 10U.S. DOT/PHMSA Huff Figure 9. Horizontal Land Movement and Bending Strain (From AVD Integrity RCA Report). 7. Findings and Contributing Factors PHMSA’s investigation determined the failure was due to longitudinal stresses exerted on the pipe from nearby earth movement. The external forces caused a rupture, originating at a girth weld with a section of incomplete weld penetration in the ID portion of the weld. The fracture initiated at the incomplete weld penetration area and propagated outward until the remaining pipe ligament failed due to ductile overload. Contributing factors: • Remediation efforts by the retention pond owners to stabilize the pond dam next to the ROW have not been successful. Remediation has occurred several times going back to at least 2007. • Land patrol surveillance and leak detection surveys did not identify earth movement geohazards adjacent to the Index 381 pipeline. • Inadequate training guidance to Gulf South personnel for identifying earth movement geohazards. • Gaps in the communication of risks and hazards between operations and integrity groups. • Lack of industry standards and regulations for nondestructive testing of girth welds during original construction in 1952. Incident: February 12, 2023 – Jackson, Hinds, MS 10 Gulf South Pipeline Company, LLC#

Page 11U.S. DOT/PHMSA Huff Appendices A. Map of Rupture Location B. NRC Report Nos. 1359833, 1359835, 1359969 C. Incident Report-Gas Transmission, Gas Gathering, And Underground Natural Gas Storage Facilities - No. 20230026 D. Metallurgical Laboratory Analysis – Index 381 Failure Analysis Final Report, ADV Integrity, Inc., March 2023 E. Root Cause Failure Investigation Report – Index 381 RCA Final Report, ADV Integrity, Inc., March 2024 Incident: February 12, 2023 – Jackson, Hinds, MS 11 Gulf South Pipeline Company, LLC#

Page 12Appendix A. Map of Rupture Location#

Page 13U.S. DOT/PHMSA Huff Appendix A: Map of Rupture Location Incident: February 12, 2023 – Jackson, Hinds, MS 12 Gulf South Pipeline Company, LLC#

Page 14Appendix B. NRC Report Nos. 1359833, 1359835, 1359969#

Page 15NATIONAL RESPONSE CENTER 1-800-424-8802 *** For Public Use *** Information released to a third party shall comply with any applicable federal and/or state Freedom of Information and Privacy Laws Incident Report # 1359833 INCIDENT DESCRIPTION *Report taken by NRC on 12-FEB-23 at 08:24 ET. Incident Type: PIPELINE Incident Cause: UNKNOWN Affected Area: Incident occurred on 12-FEB-23 at 03:56 local incident time. Affected Medium: AIR / ATMOSPHERE _______________________________________________________________________ SUSPECTED RESPONSIBLE PARTY Organization: GULF SOUTH PIPELINE COMPANY OWENSBORO, KY 42301 Type of Organization: PRIVATE ENTERPRISE _______________________________________________________________________ INCIDENT LOCATION PEARL RIVER BOTTOMS County: RANKIN State: MS#

Page 16HINES & RANKIN COUNTY LINE - INDEX 38Q _______________________________________________________________________ RELEASED MATERIAL(S) CHRIS Code: ONG Official Material Name: NATURAL GAS Also Known As: Qty Released: 0 UNKNOWN AMOUNT _______________________________________________________________________ DESCRIPTION OF INCIDENT THE CALLER OBSERVED LOW PRESSURE, WHICH WAS THE RESULT OF THE RELEASE OF NATURAL GAS. _______________________________________________________________________ INCIDENT DETAILS Pipeline Type: TRANSMISSION DOT Regulated: YES Pipeline Above/Below Ground: ABOVE Exposed or Under Water: NO Pipeline Covered: UNKNOWN _______________________________________________________________________ IMPACT Fire Involved: NO Fire Extinguished: UNKNOWN INJURIES: NO Sent to Hospital: Empl/Crew: Passenger: FATALITIES: NO Empl/Crew: Passenger: Occupant: EVACUATIONS:NO Who Evacuated: Radius/Area: Damages: NO Hours Direction of#

Page 17Closure Type Description of Closure Closed Closure Air: NO Major Road: NO Artery:NO Waterway:NO Track: NO Passengers Transferred: NO Environmental Impact: UNKNOWN Media Interest: UNKNOWN ______________________________________________________________________ REMEDIAL ACTIONS FIELD PERSONNEL ON SITE Release Secured: UNKNOWN Release Rate: Estimated Release Duration: ______________________________________________________________________ WEATHER ______________________________________________________________________ ADDITIONAL AGENCIES NOTIFIED Federal: State/Local: JACKSON CITY PD, RANKIN CTY SHERIFFS State/Local On Scene: FIELD PERSONNEL, RICHALAND PD State Agency Number:#

Page 18_______________________________________________________________________ NOTIFICATIONS BY NRC CENTERS FOR DISEASE CONTROL (GRASP) 13-FEB-23 14:41 ASST COMDT FOR INTELLIGENCE (CG-2) (OFFICE OF INTELLIGENCE PLANS AND POLICY (CG-25)) 13-FEB-23 14:41 DEPT OF HEALTH AND HUMAN SERVICES (SECRETARY OPERATION CENTER (SOC)) 13-FEB-23 14:41 DHS CISA (CISA CENTRAL) 13-FEB-23 14:41 MS DEPT OF HOMELAND SECURITY (I&A FIELD OPS) 13-FEB-23 14:41 OFFICE OF ENV. POLICY & COMPLIANCE (OEPC REGION 4) 13-FEB-23 14:41 DOT CRISIS MANAGEMENT CENTER (MAIN OFFICE) 13-FEB-23 14:41 U.S. EPA IV (MAIN OFFICE) 13-FEB-23 14:44 MS ANALYSIS AND INFORMATION CENTER (FUSION CENTER) 13-FEB-23 14:41 NOAA RPTS FOR MS (MAIN OFFICE) 13-FEB-23 14:41 NTSB PIPELINE (MAIN OFFICE) 13-FEB-23 14:41 PIPELINE & HAZMAT SAFETY ADMIN (OFFICE OF PIPELINE SAFETY (AUTO)) 14-NOV-23 21:11 PIPELINE & HAZMAT SAFETY ADMIN (HAZARDOUS MATERIAL ACCIDENT INVESTIGATION) 13-FEB-23 14:41#

Page 19REPORTING PARTY (RP SUBMITTER) 13-FEB-23 14:41 SHELBY SHERIFF'S OFFICE (CRIMINAL INTELLIGENCE UNIT) 13-FEB-23 14:41 MS EMERGENCY MANAGEMENT AGENCY (MAIN OFFICE) 13-FEB-23 14:41 TENNESSEE VALLEY AUTHORITY (POLICE AND EMERGENCY MANAGEMENT) 13-FEB-23 14:41 TEXAS FUSION CENTER (COUNTER TERRORISM) 13-FEB-23 14:41 USCG DISTRICT 8 (MAIN OFFICE) 13-FEB-23 14:41 US COURTS JUDICIAL SECURITY DIV (FACILITIES AND SECURITY OFFICE (FSO)) 13-FEB-23 14:41 _______________________________________________________________________ ADDITIONAL INFORMATION _______________________________________________________________________ *** END INCIDENT REPORT #1359833 *** Report any problems by calling 1-800-424-8802 PLEASE VISIT OUR WEB SITE AT https://nrc.uscg.mil/#

Page 20NATIONAL RESPONSE CENTER 1-800-424-8802 *** For Public Use *** Information released to a third party shall comply with any applicable federal and/or state Freedom of Information and Privacy Laws Incident Report # 1359835 INCIDENT DESCRIPTION *Report taken by NRC on 12-FEB-23 at 08:58 ET. Incident Type: PIPELINE Incident Cause: UNKNOWN Affected Area: Incident occurred on 12-FEB-23 at 03:56 local incident time. Affected Medium: AIR / ATMOSPHERE _______________________________________________________________________ SUSPECTED RESPONSIBLE PARTY Organization: GULF SOUTH PIPELINE COMPANY OWENSBORO, KY 42301 Type of Organization: PRIVATE ENTERPRISE _______________________________________________________________________ INCIDENT LOCATION PEARL RIVER BOTTOMS County: RANKIN State: MS#

Page 21HINES & RANKIN COUNTY LINE - INDEX 38Q RELEASED MATERIAL(S) CHRIS Code: ONG Official Material Name: NATURAL GAS Also Known As: Qty Released: 0 UNKNOWN AMOUNT DESCRIPTION OF INCIDENT ****THIS IS AN UPDATE TO INCIDENT REPORT #1359833**** UPDATE IS AS FOLLOWS: - THE REPORT WAS ENTERED, AND THE SYSTEM DID NOT PROCESS NOTIFICATIONS. ORIGINAL REPORT THE CALLER OBSERVED LOW PRESSURE, WHICH WAS THE RESULT OF THE RELEASE OF NATURAL GAS. INCIDENT DETAILS Pipeline Type: TRANSMISSION DOT Regulated: YES Pipeline Above/Below Ground: ABOVE Exposed or Under Water: NO Pipeline Covered: UNKNOWN IMPACT Fire Involved: NO Fire Extinguished: UNKNOWN#

Page 22INJURIES: NO Sent to Hospital: Empl/Crew: Passenger: FATALITIES: NO Empl/Crew: Passenger: Occupant: EVACUATIONS:NO Who Evacuated: Radius/Area: Damages: NO Hours Direction of Closure Type Description of Closure Closed Closure Air: NO Major Road: NO Artery:NO Waterway:NO Track: NO Passengers Transferred: NO Environmental Impact: UNKNOWN Media Interest: UNKNOWN ______________________________________________________________________ REMEDIAL ACTIONS FIELD PERSONNEL ON SITE Release Secured: UNKNOWN Release Rate: Estimated Release Duration: ______________________________________________________________________ WEATHER#

Page 23______________________________________________________________________ ADDITIONAL AGENCIES NOTIFIED Federal: State/Local: JACKSON CITY PD, RANKIN CTY SHERIFFS State/Local On Scene: FIELD PERSONNEL, RICHLAND PD State Agency Number: _______________________________________________________________________ NOTIFICATIONS BY NRC CENTERS FOR DISEASE CONTROL (GRASP) 12-FEB-23 09:03 ASST COMDT FOR INTELLIGENCE (CG-2) (OFFICE OF INTELLIGENCE PLANS AND POLICY (CG-25)) 12-FEB-23 09:03 DEPT OF HEALTH AND HUMAN SERVICES (SECRETARY OPERATION CENTER (SOC)) 12-FEB-23 09:03 DHS CISA (CISA CENTRAL) 12-FEB-23 09:03 MS DEPT OF HOMELAND SECURITY (I&A FIELD OPS) 12-FEB-23 09:03 OFFICE OF ENV. POLICY & COMPLIANCE (OEPC REGION 4) 12-FEB-23 09:03 DOT CRISIS MANAGEMENT CENTER (MAIN OFFICE) 12-FEB-23 09:03 U.S. EPA IV (MAIN OFFICE) 12-FEB-23 09:05 MS ANALYSIS AND INFORMATION CENTER (FUSION CENTER) 12-FEB-23 09:03 NOAA RPTS FOR MS (MAIN OFFICE) 12-FEB-23 09:03#

Page 24NTSB PIPELINE (MAIN OFFICE) 12-FEB-23 09:03 PIPELINE & HAZMAT SAFETY ADMIN (OFFICE OF PIPELINE SAFETY (AUTO)) 14-NOV-23 21:11 PIPELINE & HAZMAT SAFETY ADMIN (HAZARDOUS MATERIAL ACCIDENT INVESTIGATION) 12-FEB-23 09:03 REPORTING PARTY (RP SUBMITTER) 12-FEB-23 09:03 SHELBY SHERIFF'S OFFICE (CRIMINAL INTELLIGENCE UNIT) 12-FEB-23 09:03 MS EMERGENCY MANAGEMENT AGENCY (MAIN OFFICE) 12-FEB-23 09:03 TENNESSEE VALLEY AUTHORITY (POLICE AND EMERGENCY MANAGEMENT) 12-FEB-23 09:03 TEXAS FUSION CENTER (COUNTER TERRORISM) 12-FEB-23 09:03 USCG DISTRICT 8 (MAIN OFFICE) 12-FEB-23 09:03 US COURTS JUDICIAL SECURITY DIV (FACILITIES AND SECURITY OFFICE (FSO)) 12-FEB-23 09:03 ADDITIONAL INFORMATION ****THIS IS AN UPDATE TO INCIDENT REPORT #1359833**** *** END INCIDENT REPORT #1359835 *** Report any problems by calling 1-800-424-8802 PLEASE VISIT OUR WEB SITE AT https://nrc.uscg.mil/#

Page 25NATIONAL RESPONSE CENTER 1-800-424-8802 *** For Public Use *** Information released to a third party shall comply with any applicable federal and/or state Freedom of Information and Privacy Laws Incident Report # 1359969 INCIDENT DESCRIPTION *Report taken by NRC on 14-FEB-23 at 07:27 ET. Incident Type: PIPELINE Incident Cause: EQUIPMENT FAILURE Affected Area: Incident occurred on 12-FEB-23 at 03:56 local incident time. Affected Medium: AIR / ATMOSPHERE _______________________________________________________________________ SUSPECTED RESPONSIBLE PARTY Organization: GULF SOUTH PIPELINE/BOARDWALK OWENSBORO, KY Type of Organization: PRIVATE ENTERPRISE _______________________________________________________________________ INCIDENT LOCATION SEE LAT/LONG County: HINDS State: MS Latitude: 32° 15' 47" N#

Page 26Longitude: 090° 11' 57" W PEARL RIVER BOTTOMS _______________________________________________________________________ RELEASED MATERIAL(S) CHRIS Code: ONG Official Material Name: NATURAL GAS Also Known As: Qty Released: 20 MIL CBF _______________________________________________________________________ DESCRIPTION OF INCIDENT ///THIS IS A 48 HOUR UPDATE TO NRC REPORT NUMBER 1359833. THE UPDATE IS TO THE LOCATION OF THE INCIDENT AND THE AMOUNT OF MATERIALS RELEASED, ALSO THE CAUSE OF THE RELEASE WAS DUE TO A LINE WELD RUPTURE./// ///ORIGINAL/// THE CALLER OBSERVED LOW PRESSURE, WHICH WAS THE RESULT OF THE RELEASE OF NATURAL GAS. _______________________________________________________________________ INCIDENT DETAILS Pipeline Type: TRANSMISSION DOT Regulated: YES Pipeline Above/Below Ground: ABOVE Exposed or Under Water: NO Pipeline Covered: UNKNOWN _______________________________________________________________________ IMPACT#

Page 27Fire Involved: NO Fire Extinguished: UNKNOWN INJURIES: NO Sent to Hospital: Empl/Crew: Passenger: FATALITIES: NO Empl/Crew: Passenger: Occupant: EVACUATIONS:NO Who Evacuated: Radius/Area: Damages: NO Hours Direction of Closure Type Description of Closure Closed Closure Air: NO Major Road: NO Artery:NO Waterway:NO Track: NO Passengers Transferred: NO Environmental Impact: UNKNOWN Media Interest: NONE ______________________________________________________________________ REMEDIAL ACTIONS FIELD PERSONNEL ON SITE Release Secured: YES Release Rate: Estimated Release Duration: ______________________________________________________________________#

Page 28WEATHER Weather: PARTLY CLOUDY, ºF ______________________________________________________________________ ADDITIONAL AGENCIES NOTIFIED Federal: State/Local: JACKSON CITY PD, RANKIN CITY SHERIFF State/Local On Scene: FIELD PERSONNEL, RICHLAND PD State Agency Number: _______________________________________________________________________ NOTIFICATIONS BY NRC CENTERS FOR DISEASE CONTROL (GRASP) 14-FEB-23 07:34 DEPT OF HEALTH AND HUMAN SERVICES (SECRETARY OPERATION CENTER (SOC)) 14-FEB-23 07:34 DHS CISA (CISA CENTRAL) 14-FEB-23 07:34 MS DEPT OF HOMELAND SECURITY (I&A FIELD OPS) 14-FEB-23 07:34 OFFICE OF ENV. POLICY & COMPLIANCE (OEPC REGION 4) 14-FEB-23 07:34 DOT CRISIS MANAGEMENT CENTER (MAIN OFFICE) 14-FEB-23 07:34 DOT OFFICE OF INSPECTOR GENERAL (ATLANTA, JRI-3) 14-FEB-23 07:34 U.S. EPA IV (MAIN OFFICE) 14-FEB-23 07:37 MS ANALYSIS AND INFORMATION CENTER (FUSION CENTER) 14-FEB-23 07:34 NOAA RPTS FOR MS (MAIN OFFICE)#

Page 2914-FEB-23 07:34 PIPELINE & HAZMAT SAFETY ADMIN (OFFICE OF PIPELINE SAFETY (AUTO)) 14-NOV-23 21:11 PIPELINE & HAZMAT SAFETY ADMIN (HAZARDOUS MATERIAL ACCIDENT INVESTIGATION) 14-FEB-23 07:34 REPORTING PARTY (RP SUBMITTER) 14-FEB-23 07:34 SHELBY SHERIFF'S OFFICE (CRIMINAL INTELLIGENCE UNIT) 14-FEB-23 07:34 MS EMERGENCY MANAGEMENT AGENCY (MAIN OFFICE) 14-FEB-23 07:34 TENNESSEE VALLEY AUTHORITY (POLICE AND EMERGENCY MANAGEMENT) 14-FEB-23 07:34 TEXAS FUSION CENTER (COUNTER TERRORISM) 14-FEB-23 07:34 USCG DISTRICT 8 (MAIN OFFICE) 14-FEB-23 07:34 _______________________________________________________________________ ADDITIONAL INFORMATION 48 HOUR UPDATE _______________________________________________________________________ *** END INCIDENT REPORT #1359969 *** Report any problems by calling 1-800-424-8802 PLEASE VISIT OUR WEB SITE AT https://nrc.uscg.mil/#

Page 30Appendix C. Incident Report-Gas Transmission, Gas Gathering, And Underground Natural Gas Storage Facilities - No. 20230026#

Page 31NOTICE: This report is required by 49 CFR Parts 191 and 195. Failure to report may result in a civil penalty as provided in 49 USC 60122. Form Approved: 9/26/2023 OMB No. 2137-0552 Expiration Date: 6/30/2026 Original Report Date: 03/14/2023 U.S Department of Transportation Pipeline and Hazardous Materials Safety Administration No. 20230026-39298 -------------------------------------------- (DOT Use Only) INCIDENT REPORT - GAS TRANSMISSION, GAS GATHERING, AND UNDERGROUND NATURAL GAS STORAGE FACILITIES A federal agency may not conduct or sponsor, and a person is not required to respond to, nor shall a person be subject to a penalty for failure to comply with a collection of information subject to the requirements of the Paperwork Reduction Act unless that collection of information displays a current valid OMB Control Number. The OMB Control Number for this information collection is 2137-0635. Public reporting for this collection of information is estimated to be approximately 12 hours per response, including the time for reviewing instructions, gathering the data needed, and completing and reviewing the collection of information. All responses to this collection of information are mandatory. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to: Information Collection Clearance Officer, PHMSA, Office of Pipeline Safety (PHP-30) 1200 New Jersey Avenue, SE, Washington, D.C. 20590 INSTRUCTIONS Use this form for Type A, B, and C gas gathering. Type R gas gathering is reported on Form PHMSA F 7100.2-2. Important: Please read the separate instructions for completing this form before you begin. They clarify the information requested and provide specific examples. If you do not have a copy of the instructions, you can obtain one from the PHMSA Pipeline Safety Community Web Page at http://www.phmsa.dot.gov/pipeline/library/forms. PART A - KEY REPORT INFORMATION Report Type: (select all that apply) Original: Supplemental: Yes Final: Yes Last Revision Date: 03/07/2024 A1. Operator’s OPS-issued Operator Identification Number (OPID): A2. Name of Operator A3. Address of Operator: A3a. Street Address 31728 GULF SOUTH PIPELINE COMPANY, LLC 9 GREENWAY PLAZA SUITE 2800 A3b. City A3c. State HOUSTON Texas A3d. Zip Code A4. Local time (24-hr clock) and date of incident: A4a. Time Zone for local time: (select only one) A4b. Daylight Saving in effect? A5. Location of Incident: 77046 02/12/2023 03:56 Central No Latitude / Longitude A6. Gas released: (select only one, based on predominant volume released) - Other Gas Released Name: 32.262952, -90.199256 Natural Gas A7. Estimated volume of commodity released unintentionally - thousand standard cubic feet (mcf) A8. Estimated volume of intentional and controlled release/blowdown - thousand standard cubic feet (mcf)) A9. Estimated volume of accompanying liquid release (Barrels): 0 A10. Were there fatalities? 20,960.00 0 No - If Yes, specify the number in each category: A10a. Operator employees A10b. Contractor employees working for the Operator A10c. Non-Operator emergency responders A10d. Workers working on the right-of-way, but NOT associated with this Operator A10e. General public A10f. Total fatalities (sum of above) 0 A11. Were there injuries requiring inpatient hospitalization? - If Yes, specify the number in each category: A11a. Operator employees A11b. Contractor employees working for the Operator A11c. Non-Operator emergency responders A11d. Workers working on the right-of-way, but NOT associated with this Operator A11e. General public A11f. Total injuries (sum of above) 0 No Form PHMSA F 7100.2 (Rev 9-2023) Page 1 of 16 Reproduction of this form is permitted#

Page 32A12. What was the Operator's initial indication of the Failure? (select only one) SCADA-based information (such as alarm(s), alert(s), event(s), and/or volume or pack calculations) If Other, Describe: A12a. If “Controller”, “Local Operating Personnel, including contractors”, “Air Patrol”, or “Ground Patrol by Operator or its contractor” is selected in Question 12, specify the following: (select only one) A13. Local time Operator identified failure A14. Part of system involved in Incident: (select only one) A15. Operational Status at time Operator identified failure: (select only one) A16. If A15 = Routine Start-Up or Normal Operation, was the pipeline/facility shut down due to the incident? 02/12/2023 03:56 Onshore Pipeline, Including Valve Sites Normal Operation, includes pauses during maintenance Yes - If No, Explain: - If Yes, complete Questions 16a and 16b: (use local time, 24-hr clock) A16a. Local time and date of shutdown 02/12/2023 05:30 A16b. Local time pipeline/facility restarted - Still shut down? (* Supplemental Report Required) - If A12. = Notification from Emergency Responder, skip A17. A17a. Did the operator communicate with Local, State, or Federal Emergency Responders about the incident? - If No, skip A17b and c. A17b. Which party initiated communication about the incident? A17c. Local time of initial Operator and Local/State/Federal Emergency Responder communication 02/12/2023 11:08 No A18. Local time operator resources arrived on site A19. Local time of confirmed discovery: A20a. Local time (24-hr clock) and date of initial operator report to the National Response Center A20b. Initial Operator National Response Center Report Number NRC Notification Required but Not Made A20c. Additional NRC Report numbers submitted by the operator A21. Did the gas ignite? - If A21. = Yes, then answer A21a through d: A21a. Local time of ignition: A21b. How was the fire extinguished? 02/12/2023 04:10 02/12/2023 05:30 02/12/2023 07:23 1359833 1359835, 1359969 No Specify: A21c. Estimated volume of gas consumed by fire (mcf): (must be less than or equal to A7.) A21d. Did the gas explode? - If A14. is “Onshore Pipeline, Including Valve Sites” OR “Offshore Pipeline, Including Riser and Riser Bend”, answer A22a through f A22a. Initial action taken to control flow upstream of failure location Valve Closure - If Valve Closure, answer A22.b and c: A22b. Local time of final upstream valve closure A22c. Type of upstream valve used to complete upstream isolation of release source: 02/12/2023 05:30 Manual A22d. Initial action taken to control flow downstream of failure location Valve Closure - If Valve Closure, answer A22e and f.: A22e. Local time of final downstream valve closure 02/12/2023 05:00 A22f. Type of downstream valve used to complete downstream isolation of release source Manual A23. Number of general public evacuated: 0 PART B - ADDITIONAL LOCATION INFORMATION B1. Was the origin of the Incident onshore? Auto-populated based on A14 Yes (Complete Questions B2-B11) No (Complete Questions B12-B14) B1a. Pipeline/Facility name: B1b. Segment name/ID: Yes Index 381 Jackson to Sterlington 18" If Onshore: B2. State: Form PHMSA F 7100.2 (Rev 9-2023) Mississippi Page 2 of 16 Reproduction of this form is permitted#

Page 33B3. Zip Code: B4. City B5. County or Parish B6. Operator designated location: (select only one) B7. Describe: 39204 Jackson Hinds Survey Station No. 6180+60 B8. Was Incident on Federal land, other than the Outer Continental Shelf (OCS)? B9. Location of Incident: B10. Area of Incident: (select only one) No Pipeline Right-of-way Underground Under soil Specify: If Other, Describe: B10a. Depth-of-Cover (in): B10b. Were other underground facilities found within 12 inches of the failure location? 64 No B11. Did Incident occur in a crossing? - If Yes, specify type below: - If Bridge crossing – Cased/Uncased: No - If Railroad crossing – Cased Uncased Bored/Drilled - If Road crossing – Cased Uncased Bored/Drilled - If Water crossing – Cased/Uncased: Name of body of water (If commonly known): Approx. water depth (ft) at the point of the Incident: Select: Is this water crossing 100 feet or more in length from high water mark to high water mark? If Offshore: B12. Approx. water depth (ft) at the point of the Incident: B13. Origin of Incident: - If “In State waters”: - State: - Area: - Block/Tract #: - Nearest County/Parish: - If “On the Outer Continental Shelf (OCS)”: (select only one) - Area: - Block/Tract #: B14. Area of Incident: PART C - ADDITIONAL FACILITY INFORMATION C1. Is the pipeline or facility: - Interstate - Intrastate C2. Material involved in Incident: (select only one) - If Material other than Carbon Steel or Plastic – Specify: C3. Item involved in Incident: - If Pipe – Specify: C3a. Nominal Pipe Size: - If Pipe Body: Was this a Puddle/Spot Weld? - If C2. is Carbon Steel Interstate Carbon Steel Weld/Fusion, including heat-affected zone 20 C3b. Wall thickness (in): C3c. SMYS (Specified Minimum Yield Strength) of pipe (psi): C3d. Pipe specification: .250 52,000 API 5LX Unknown C3e. Pipe Seam – Specify: - If Other, Describe: Other ERW - DC C3f. Pipe manufacturer: Form PHMSA F 7100.2 (Rev 9-2023) Youngstown Steel Page 3 of 16 Reproduction of this form is permitted#

Page 34Unknown C3g. Pipeline coating type at point of Incident – Specify: Coal Tar - If Other, Describe: C3h. Coating field applied? - If C2. is Plastic Unknown C3i. Specify type: - If Other, Describe C3j. Specify Standard Dimension Ratio (SDR): Wall Thickness Unknown C3k. If Polyethylene (PE) is selected as the type of plastic in C3j, specify PE Pipe Material Designation Code (i.e., 2406, 3408, etc.) Unknown - If Weld/Fusion, including heat-affected zone – Specify: - If Pipe Girth Weld is selected, complete items C3a through h above Are any of the C3b through h values different on either side of the girth weld? - If Yes, enter the different value(s) below: C3l. Wall thickness (in): C3m. SMYS (Specified Minimum Yield Strength) of pipe (psi): C3n. Pipe specification Pipe Girth Weld No Unknown C3o. Pipe Seam Describe: C3p. Pipe manufacturer Unknown C3q. Pipeline coating type at point of Accident Describe: C3r. Coating field applied? - If Plastic Pipe Fusion is selected, complete items C3a and C3i through k above - If Valve, excluding Regulator/Control Valves – Specify: - If Mainline – Specify: - If Other, Describe: C3s. Mainline valve manufacturer: Unknown C3t. Tubing material: (select only one) C3u. Type of tubing: (select only one) - If Other, Describe: C4. Year item involved in Incident was installed: 1952 Unknown C5. Year item involved in Incident was manufactured: 1952 Unknown C6. Type of release involved: (select only one) - If Mechanical Puncture – Specify Approx. size: Rupture in. (axial) by in. (circumferential) - If Leak - Select Type: - If Other, Describe: - If Rupture - Select Orientation: Circumferential - If Other, Describe: Approx. size: in. (widest opening): by in. (length circumferentially or axially): - If Other, Describe: 14.5 62.8 PART D - ADDITIONAL CONSEQUENCE INFORMATION D1. Class Location of Incident: Class 1 Location D2. Did this Incident occur in a High Consequence Area (HCA)? - If Yes: No D2a. Specify the Method used to identify the HCA: D3. What is the PIR (Potential Impact Radius) for the location of this Incident? Not Flammable Feet: 308 Form PHMSA F 7100.2 (Rev 9-2023) Page 4 of 16 Reproduction of this form is permitted#

Page 35D4. Were any structures outside the PIR impacted or otherwise damaged due to heat/fire resulting from the Incident? D5. Were any structures outside the PIR impacted or otherwise damaged NOT by heat/fire resulting from the Incident? D6. Were any of the fatalities or injuries (A11 only) reported for persons located outside the PIR? No No - If Yes, Describe the cause of the fatalities or injuries D7. Estimated Property Damage: D7a. Estimated cost of public and non-Operator private property damage paid/reimbursed by the Operator – effective 6-2011, “paid/reimbursed by the Operator” removed D7b. Estimated cost of Operator’s property damage & repairs D7c. Estimated cost of emergency response D7d. Estimated other costs $0 $4,702,999 $8,000 $5,000 Describe: Cost for Atmos Energy to relight customers' pilots $4,715,999 D7e. Property damage subtotal (sum of above) Cost of Gas Released Cost of Gas in $ per thousand standard cubic feet (mcf): D7f. Estimated cost of gas released unintentionally D7g. Estimated cost of gas released during intentional and controlled blowdown 3.1100 $65,186 $0 D7h. Total estimated cost of gas released (sum of D7f and D7g above) $65,186 D7i. Estimated Total Cost (sum of D7e and D7h) $4,781,185 Injured Persons not included in A11 The number of persons injured, admitted to a hospital, and remaining in the hospital for at least one are reported in A11. If a person is included in A11, do not include them in D8. D8. Estimated number of persons with injuries requiring treatment in a medical facility but not requiring overnight in-patient hospitalization: 0 If a person is included in D8, do not include them in D9. D9. Estimated number of persons with injuries requiring treatment by EMTs at the site of incident 0 overnight Buildings Affected D10. Number of residential buildings affected (evacuated or required repair or gas service interrupted): D11. Number of business buildings affected (evacuated or required repair or gas service interrupted): 0 D12. Wildlife impact: 12a. If Yes, specify all that apply: 215 No Fish/aquatic Birds Terrestrial D13. If D2. Is No, answer D13a. 13a. Did this incident occur in a Moderate Consequence Area (MCA)? If D13a. is Yes, answer D13b. No 13b. Select each of the items below that were present within the potential impact circle: 5 or more buildings intended for human occupancy Paved surface for a designated interstate, freeway, expressway, or other principal 4-lane arterial roadway PART E - ADDITIONAL OPERATING INFORMATION E1. Estimated pressure at the point and time of the Incident (psig): E1a. Estimated gas flow in pipe segment at the point and time of the incident (MSCF/D): E2. Maximum Allowable Operating Pressure (MAOP) at the point and time of the Incident (psig): E2a. MAOP established by 49 CFR section: 400.00 10,000.00 475.00 192.619(c) - If Other, specify: E2b. Date MAOP established: 03/12/1971 E2c. Was the MAOP in E2a and b established in conjunction with a reversal of flow direction? No E3. Describe the pressure on the system or facility relating to the Incident: E4. Was the system or facility relating to the Incident operating under an “established pressure restriction” with pressure limits below those normally allowed by the MAOP? Pressure did not exceed MAOP No Form PHMSA F 7100.2 (Rev 9-2023) Page 5 of 16 Reproduction of this form is permitted#

Page 36No - If Yes - (Complete 4a and 4b below) E4a. Did the pressure exceed this established pressure restriction? E4b. Was this pressure restriction mandated by PHMSA or the State? E5. Was the gas at the point of failure required to be odorized in accordance with §192.625? - If Yes, Was the gas at the point of failure odorized in accordance with §192.625? - If A14 is “Onshore Pipeline, Including Valve Sites” or “Offshore Pipeline, Including Riser and Riser Bend”, complete E6 through E8 E6. Length of segment between upstream and downstream shut-off valves closest to failure location (ft): E7. Is the pipeline configured to accommodate internal inspection tools? 7,100 Yes - If No, Which physical features limit tool accommodation? (select all that apply) - Changes in line pipe diameter - Presence of unsuitable mainline valves - Tight or mitered pipe bends - Other passage restrictions (i.e. unbarred tee’s, projecting instrumentation, etc.) - Extra thick pipe wall (applicable only for magnetic flux leakage internal inspection tools) - Other - If Other, Describe: E8. For this pipeline, are there operational factors which significantly complicate the execution of an internal inspection tool run? - If Yes, Which operational factors complicate execution? (select all that apply) - Excessive debris or scale, wax or other wall build-up - Low operating pressure(s) - Low flow or absence of flow No - Incompatible commodity - Other - If Other, Describe: E9. Function of pipeline system: (select only one) E10. Was a Supervisory Control and Data Acquisition (SCADA)-based system in place on the pipeline or facility involved in the Incident? - If Yes: Transmission System Yes E10a. Was it operating at the time of the Incident? E10b. Was it fully functional at the time of the Incident? E10c. Did SCADA-based information (such as alarm(s), alert(s), event(s), and/or volume or pack calculations) assist with the initial indication of the Incident? E10d. Did SCADA-based information (such as alarm(s), alert(s), event(s), and/or volume calculations) assist with the confirmed discovery of the Incident? E11. Was an investigation initiated into whether or not the controller(s) or control room issues were the cause of or a contributing factor to the Incident? - If No, the operator did not find that an investigation of the controller(s) actions or control room issues was necessary due to: (provide an explanation for why the operator did not investigate) - If Yes, Describe investigation result(s): (select all that apply) - Investigation reviewed work schedule rotations, continuous hours of service (while working for the operator) and other factors associated with fatigue - Investigation did NOT review work schedule rotations, continuous hours of service (while working for the operator) and other factors associated with fatigue Yes Yes Yes Yes Yes, specify investigation result(s): (select all that apply) - Provide an explanation for why not: - Investigation identified no control room issues - Investigation identified no controller issues - Investigation identified incorrect controller action or controller error - Investigation identified that fatigue may have affected the controller(s) involved or impacted the involved controller(s) response - Investigation identified incorrect procedures - Investigation identified incorrect control room equipment operation - Investigation identified maintenance activities that affected control room operations, procedures, and/or controller response - Investigation identified areas other than those above – Yes Describe: PART F - DRUG & ALCOHOL TESTING INFORMATION Form PHMSA F 7100.2 (Rev 9-2023) Page 6 of 16 Reproduction of this form is permitted#

Page 37F1. As a result of this Incident, were any Operator employees tested under the post- accident drug and alcohol testing requirements of DOT’s Drug & Alcohol Testing regulations? - If Yes: No F1a. How many were tested: F1b. How many failed: F2. As a result of this Incident, were any Operator contractor employees tested under the post-accident drug and alcohol testing requirements of DOT’s Drug & Alcohol Testing regulations? - If Yes: No F2a. How many were tested: F2b. How many failed: PART G - APPARENT CAUSE Select only one box from PART G in the shaded column on the left representing the APPARENT Cause of the Incident, and answer the questions on the right. Enter secondary, contributing, or root causes of the Incident in Part K – Contributing Factors. Apparent Cause: G2 - Natural Force Damage G1 - Corrosion Failure - only one sub-cause can be picked from shaded left-hand column Corrosion Failure – Sub-cause: - If External Corrosion: 1. Results of visual examination: - If Other, Describe: 2. Type of corrosion: (select all that apply) - Galvanic - Atmospheric - Stray Current - Microbiological - Selective Seam - Other - If Other, Describe: 2a. If 2 is Stray Current, specify 2b. Describe the stray current source: 3. The type(s) of corrosion selected in Question 2 is based on the following: (select all that apply) - Field examination - Determined by metallurgical analysis - Other - If Other – Describe: 4. Was the failed item buried or submerged? - If Yes: 4a. Was failed item considered to be under cathodic protection at the time of the incident? - If Yes, Year protection started: 4b. Was shielding, tenting, or disbonding of coating evident at the point of the incident? 4c. Has one or more Cathodic Protection Survey been conducted at the point of the incident? (select all that apply) If “Yes, CP Annual Survey” – Most recent year conducted: If “Yes, Close Interval Survey” – Most recent year conducted: If “Yes, Other CP Survey” – Most recent year conducted: Describe other CP survey - If No: 4d. Was the failed item externally coated or painted? 5. Was there observable damage to the coating or paint in the vicinity of the corrosion? - If Internal Corrosion: 6. Results of visual examination: - If Other, Describe: 7. Cause of corrosion: (select all that apply) - Corrosive Commodity - Water drop-out/Acid - Microbiological - Erosion Form PHMSA F 7100.2 (Rev 9-2023) Page 7 of 16 Reproduction of this form is permitted#

Page 38- Other - If Other, Describe: 8. The cause(s) of corrosion selected in Question 7 is based on the following: (select all that apply) - Field examination - Determined by metallurgical analysis - Other - If Other, Describe: 9. Location of corrosion: (select all that apply) - Low point in pipe - Elbow - Drop-out - Dead Leg - Other - If Other, Describe: 10. Was the gas/fluid treated with corrosion inhibitors or biocides? 11. Was the interior coated or lined with protective coating? 12. Were cleaning/dewatering pigs (or other operations) routinely utilized? 13. Were corrosion coupons routinely utilized? G2 - Natural Force Damage - only one sub-cause can be picked from shaded left-handed column Natural Force Damage – Sub-Cause: Earth Movement, NOT due to Heavy Rains/Floods - If Earth Movement, NOT due to Heavy Rains/Floods: 1. Specify: - If Other, Describe: Other A root cause analysis performed by a third-party consultant determined the pipe ruptured at a girth weld due to tension imposed by a landslide which was the result of a man- made pond that had become unstable. This landslide is located on the same berm slope where historical landslides and landslide remediation has occurred by the property owner (the current owner is US Silica). The landslide is located approximately 160-feet from the failure location. - If Heavy Rains/Floods: 2. Specify: - If Other, Describe: - If Lightning: 3. Specify: - If Temperature: 4. Specify: - If Other, Describe: - If Other Natural Force Damage: 5. Describe: Complete the following if any Natural Force Damage sub-cause is selected. 6. Were the natural forces causing the Incident generated in conjunction with an extreme weather event? No 6a. If Yes, specify: (select all that apply) - Hurricane - Tropical Storm - Tornado - Other - If Other, Describe: G3 - Excavation Damage - only one sub-cause can be picked from shaded left-hand column Excavation Damage – Sub-Cause: Complete the following if any Excavation Damage sub-cause is selected. 1. Did the operator get prior notification of the excavation activity? 1a. If Yes, Notification received from: (select all that apply) - One-Call System - Excavator Form PHMSA F 7100.2 (Rev 9-2023) Page 8 of 16 Reproduction of this form is permitted#

Page 39- Contractor - Landowner 1b. Per the primary Incident Investigator results, did State law exempt the excavator from notifying the one-call center? - If Yes, answer 1c through 1e 1c. select one of the following: Describe: 1d. Exempting authority 1e. Exempting criteria 2. Do you want PHMSA to upload the following information to CGA-DIRT (www.cga- dirt.com)? 3. Right-of-Way where event occurred: (select all that apply) - Public - If Public, Specify: - Private - If Private, Specify: - Pipeline Property/Easement - Power/Transmission Line - Railroad - Dedicated Public Utility Easement - Federal Land - Unknown/Other 4. 5. Was the facility part of a Joint Trench: Did this event involve a Cross Bore: 6. Measured Depth from Grade: Measured depth From Grade in inches 7. Type of excavator: 8. Type of excavation equipment: 9. Type of work performed: 10. Was the One-Call Center notified? - Yes - No - If No, skip to question 11 10a. If Yes, specify ticket number: 10b. If this is a State where more than a single One-Call Center exists, list the name of the One-Call Center notified: 10c. Was work area white lined: 11. Type of Locator: 12. Were facility locate marks visible in the area of excavation? 13. Did the damage cause an interruption in service? 13a. If Yes, specify duration of the interruption: (hours) 14. Description of the CGA-DIRT Root Cause (select the predominant CGA-DIRT Root Cause): - Root Cause Category: - Root Cause Type: (Comment required) G4 - Other Outside Force Damage - only one sub-cause can be selected from the shaded left-hand column Other Outside Force Damage – Sub-Cause: - If Damage by Car, Truck, or Other Motorized Vehicle/Equipment NOT Engaged in Excavation: 2. Vehicle/Equipment operated by: - If this sub-section is picked, please complete questions 5-11 below - If Damage by Boats, Barges, Drilling Rigs, or Other Maritime Equipment or Vessels Set Adrift or Which Have Otherwise Lost Their Mooring: 2. Select one or more of the following IF an extreme weather event was a factor: - Hurricane - Tropical Storm - Tornado - Heavy Rains/Flood - Other - If Other, Describe: - If Intentional Damage: Form PHMSA F 7100.2 (Rev 9-2023) Page 9 of 16 Reproduction of this form is permitted#

Page 403. Specify: - If Other, Describe: - If Other Outside Force Damage: 4. Describe: Complete the following if Damage by Car, Truck, or Other Motorized Vehicle/Equipment NOT Engaged in Excavation sub-cause is selected. 5. Was the driver of the vehicle or equipment issued one or more citations related to the incident? - If 5 is Yes, what was the nature of the citations: (select all that apply) 5a. Excessive Speed 5b. Reckless Driving 5c. Driving Under the Influence 5d. Other Describe: 6. Was the driver under control of the vehicle at the time of the collision 7. Estimated speed of the vehicle at the time of impact (miles per hour)? Unknown 8. Type of vehicle? 9. Where did the vehicle travel from to hit the pipeline facility? 10. Shortest distance from answer in 9. to the damaged pipeline facility (in feet): 11. At the time of the Incident, were protections installed to protect the damaged pipeline facility from vehicular damage? - If 11. is Yes, specify type of protection: (select all that apply) 11a. Bollards/Guard Posts 11b. Barricades - include Jersey barriers and fences in instructions 11c. Guard Rails 11d. Other Describe: G5 - Pipe, Weld, or Joint Failure Use this section to report material failures ONLY IF the “Item Involved in Incident” (from PART C, Question 3) is “Pipe” or “Weld.” Only one sub-cause can be selected from the shaded left- hand column Pipe, Weld or Join Failure – Sub-Cause: 1. The sub-cause shown above is based on the following: (select all that apply) - Field Examination - Determined by Metallurgical Analysis - Other Analysis - If “Other Analysis”, Describe: - Sub-cause is Tentative or Suspected; Still Under Investigation (Supplemental Repot required) - Design-, Construction-, IInstallation- ,or Fabrication-related 2. List contributing factors: (select all that apply) - Fatigue or Vibration related: Specify: - If Other, Describe: - Mechanical Stress - Other - If Other, Describe: - Original Manufacturing-related (NOT girth weld or other welds formed in the field) 2. List contributing factors: (select all that apply) - Fatigue or Vibration related: Specify: - If Other, Describe: - Mechanical Stress - Other - If Other, Describe: - If Environmental Cracking-related: 3. Specify: Form PHMSA F 7100.2 (Rev 9-2023) Page 10 of 16 Reproduction of this form is permitted#

Page 41- If Other, Describe: Complete the following if any Material Failure of Pipe or Weld sub-cause is selected. 4. Additional Factors: (select all that apply) - Dent - Gouge - Pipe Bend - Arc Burn - Crack - Lack of Fusion - Lamination - Buckle - Wrinkle - Misalignment - Burnt Steel - Other - If Other, Describe: 5. Post-construction pressure test value (psig) Unknown G6 - Equipment Failure - only one sub-cause can be selected from the shaded left-hand column Equipment Failure – Sub-Cause: - If Malfunction of Control/Relief Equipment: 1. Specify: - Control Valve - Instrumentation - SCADA - Communications - Block Valve - Check Valve - Relief Valve - Power Failure - Stopple/Control Fitting - Pressure Regulator - ESD System Failure - Other - If Other, Describe: - If Compressor or Compressor-related Equipment: 2. Specify: - If Other, Describe: - If Threaded Connection/Coupling Failure: 3. Specify: - If Other, Describe: - If Non-threaded Connection Failure: 4. Specify: - If Other, Describe: - If Other Equipment Failure: 5. Describe: Complete the following if any Equipment Failure sub-cause is selected. Form PHMSA F 7100.2 (Rev 9-2023) Page 11 of 16 Reproduction of this form is permitted#

Page 426. Additional factors that contributed to the equipment failure: (select all that apply) - Excessive vibration - Overpressurization - No support or loss of support - Manufacturing defect - Loss of electricity - Improper installation - Improper maintenance - Mismatched items (different manufacturer for tubing and tubing fittings) - Dissimilar metals - Breakdown of soft goods due to compatibility issues with transported gas/fluid - Valve vault or valve can contributed to the release - Alarm/status failure - Misalignment - Thermal stress - Erosion/abnormal wear - Other - If Other, Describe: G7 - Incorrect Operation - only one sub-cause can be selected from the shaded left-hand column Incorrect Operation - Sub-Cause: - If Underground Gas Storage, Pressure Vessel, or Cavern Allowed or Caused to Overpressure: 1. Specify: - If Other, Describe: - If Other Incorrect Operation: 2. Describe: Complete the following if any Incorrect Operation sub-cause is selected. 3. Was this Incident related to: (select all that apply) - Inadequate procedure - No procedure established - Failure to follow procedure - Other: - If Other, Describe: 4. What category type was the activity that caused the Incident: 5. Was the task(s) that led to the Incident identified as a covered task in your Operator Qualification Program? 5a. If Yes, were the individuals performing the task(s) qualified for the task(s)? G8 - Other Incident Cause - only one sub-cause can be selected from the shaded left-hand column Other Incident Cause – Sub-Cause: - If Miscellaneous: 1. Describe: - If Unknown: 2. Specify: Unknown PART H - NARRATIVE DESCRIPTION OF THE INCIDENT Form PHMSA F 7100.2 (Rev 9-2023) Page 12 of 16 Reproduction of this form is permitted#

Page 43On 2/12/2023 at approximately 03:56, Gulf South Pipeline Company's Gas Control received a SCADA alarm indicating a pressure drop at the Jackson City Gate #5 on its Index 381. Gas Control dispatched local Operations personnel to investigate. Two interconnect valves were closed and the section was isolated at approximately 05:40. Operations personnel then began to walk the line to inspect for leaks and identified the rupture site at approximately 07:30. The PHMSA accident investigation team visited the rupture site and Gulf South is working with PHMSA to develop and implement a Restart Plan that is acceptable to PHMSA. The cost shown for this incident includes the requirements of the Restart Plan. In response to questions D10 and D11, Gulf South's customer, the local distribution company (LDC), estimated 217 customers who were impacted. The LDC nor Gulf South has an exact count nor knowledge of the portion that were residential customers vs. businesses. 8/30/2023: Update to document cause of failure and repair cost. 9/18/2023: Update cause from "G4 - Other" to "G2 - Natural Force Damage" per PHMSA's instruction. Note that a root cause analysis performed by a third-party consultant determined the pipe ruptured at a girth weld due to tension imposed by a landslide which was the result of a man-made pond that had become unstable. This landslide is located on the same berm slope where historical landslides and landslide remediation has occurred by the property owner (the current owner is US Silica). The landslide is located approximately 160-feet from the failure location. 9/18/2023 Update to show additional NRC follow-up call number per PHMSA. 3/7/2024 Updated to correct responses to questions E2a and E2b. PART I - PREPARER AND AUTHORIZED SIGNATURE Preparer's Name Preparer's Title Preparer’s Telephone Number Preparer's E-mail Address Preparer’s Facsimile Number Local Contact Name Shannon Mattingly Compliance Program Leader 2706886357 Shannon.Mattingly@bwpipelines.com Optional Local Contact Email Optional Local Contact Phone Authorized Signer’s Name Authorized Signer’s Title Authorized Signer’s Telephone Number Authorized Signer’s Email Tina Baker Manager Compliance Services 2706886497 Tina.Baker@bwpipelines.com PART J - INTEGRITY INSPECTIONS Complete the following if the “Item Involved in Accident” (from PART C, Question 3) is Pipe or Weld and the “Cause” (from Part G) is: Corrosion (any subCause in Part G1); or Previous Damage due to Excavation Activity (subCause in Part G3); or Previous Mechanical Damage NOT Related to Excavation (subCause in Part G4); or Material Failure of Pipe or Weld (any subCause in Part G5) J1. Have internal inspection tools collected data at the point of the Incident? J1a. If Yes, for each tool and technology used provide the information below for the most recent and previous tool runs: Axial Magnetic Flux Leakage Most recent run Year: Most recent run Propulsion Method (select only one): Most recent run Attuned to Detect (select only one): Describe: - If Metal Loss, specify (select only one): Describe: Previous run Year: Previous run Propulsion Method (select only one): Previous run Attuned to Detect (select only one): Describe: - If Metal Loss, specify (select only one): Describe: Circumferential/Transverse Wave Magnetic Flux Leakage Most recent run Year: Most recent run Propulsion Method (select only one): Most recent run Resolution (select only one): Describe: Previous run Year: Previous run Propulsion Method (select only one): Form PHMSA F 7100.2 (Rev 9-2023) Page 13 of 16 Reproduction of this form is permitted#

Page 44Previous run Resolution (select only one): Describe: Ultrasonic Most recent run Year: Most recent run Propulsion Method (select only one): Most recent run Attuned to Describe: - If Attuned to Wall Measurement, most recent run Metal Loss Resolution (select only one): Describe: Previous run Year: Previous run Propulsion Method (select only one): Previous run Attuned to Describe: - If Attuned to Wall Measurement, previous run Metal Loss Resolution (select only one): Describe: Geometry/Deformation Most recent run Year: Most recent run Propulsion Method (select only one): Most recent run Resolution (select only one): Describe: Most recent run Measurement Cups (select only one): Previous run Year: Previous run Propulsion Method (select only one): Previous run Resolution Describe: Previous run Measurement Cups (select only one): Electromagnetic Acoustic Transducer (EMAT) (EMAT) Most recent run Year: Most recent run Propulsion Method (select only one): Previous run Year: Previous run Propulsion Method (select only one): Cathodic Protection Current Measurement (CPCM) Most recent run Year: Most recent run Propulsion Method (select only one): Previous run Year: Previous run Propulsion Method (select only one): Other Specify tool: Most recent run Year: Most recent run Propulsion Method (select only one): Previous run Year: Previous run Propulsion Method (select only one): Answer J1b only when the cause is: Previous Damage due to Excavation Activity (subCause in Part G3); or Previous Mechanical Damage NOT Related to Excavation (subCause in Part G4) J1b. Do you have reason to believe that the internal inspection was completed BEFORE the damage was sustained? J2. Has one or more hydrotest or other pressure test been conducted since original construction at the point of the Incident? (initial post construction pressure test is NOT reported here) Most recent year tested: Test pressure (psig): J3. Has Direct Assessment been conducted on the pipeline segment? - If Yes, and an investigative dig was conducted at the point of the Accident Most recent year conducted - If Yes, but the point of the Accident was not identified as a dig site Most recent year conducted - If Yes, J3a. For each type, indicate the year of the most recent assessment: Form PHMSA F 7100.2 (Rev 9-2023) Page 14 of 16 Reproduction of this form is permitted#

Page 45External Corrosion Direct Assessment (ECDA) Internal Corrosion Direct Assessment (ICDA) Stress Corrosion Cracking Direct Assessment (SCCDA) Confirmatory Direct Assessment Other, specify type J4. Has one or more non-destructive examination been conducted prior to the Incident at the point of the Incident since January 1, 2002? J4a. If Yes, for each examination conducted, select type of non-destructive examination and indicate most recent year the examination was conducted: Radiography Guided Wave Ultrasonic Handheld Ultrasonic Tool Wet Magnetic Particle Test Dry Magnetic Particle Test Other Specify Type: PART K - CONTRIBUTING FACTORS The Apparent Cause of the accident is contained in Part G. Do not report the Apparent Cause again in this Part K. If Contributing Factors were identified, select all that apply below and explain each in the Narrative: External Corrosion External Corrosion, Galvanic External Corrosion, Atmospheric External Corrosion, Stray Current Induced External Corrosion, Microbiologically Induced External Corrosion, Selective Seam Internal Corrosion Internal Corrosion, Corrosive Commodity Internal Corrosion, Water drop-out/Acid Internal Corrosion, Microbiological Internal Corrosion, Erosion Natural Forces Earth Movement, NOT due to Heavy Rains/Floods Heavy Rains/Floods Lightning Temperature High Winds Tree/Vegetation Root Excavation Damage Excavation Damage by Operator (First Party) Excavation Damage by Operator’s Contractor (Second Party) Excavation Damage by Third Party Previous Damage due to Excavation Activity Other Outside Force Nearby Industrial, Man-made, or Other Fire/Explosion Damage by Car, Truck, or Other Motorized Vehicle/Equipment NOT Engaged in Excavation Damage by Boats, Barges, Drilling Rigs, or Other Adrift Maritime Equipment Routine or Normal Fishing or Other Maritime Activity NOT Engaged in Excavation Electrical Arcing from Other Equipment or Facility Previous Mechanical Damage NOT Related to Excavation Intentional Damage Other underground facilities buried within 12 inches of the failure location Pipe/Weld Failure Design-related Construction-related Yes Installation-related Fabrication-related Original Manufacturing-related Environmental Cracking-related, Stress Corrosion Cracking Environmental Cracking-related, Sulfide Stress Cracking Form PHMSA F 7100.2 (Rev 9-2023) Page 15 of 16 Reproduction of this form is permitted#

Page 46Environmental Cracking-related, Hydrogen Stress Cracking Environmental Cracking-related, Hard Spot Equipment Failure Malfunction of Control/Relief Equipment Compressor or Compressor-related Equipment Threaded Connection/Coupling Failure Non-threaded Connection Failure Defective or Loose Tubing or Fitting Failure of Equipment Body (except Compressor), Vessel Plate, or other Material Incorrect Operation Damage by Operator or Operator’s Contractor NOT Excavation and NOT Vehicle/Equipment Damage Valve Left or Placed in Wrong Position, but NOT Resulting in Overpressure Pipeline or Equipment Overpressured Equipment Not Installed Properly Wrong Equipment Specified or Installed Inadequate Procedure No procedure established Failure to follow procedures Form PHMSA F 7100.2 (Rev 9-2023) Page 16 of 16 Reproduction of this form is permitted#

Page 47Appendix D. Metallurgical Laboratory Analysis – Index 381 Failure Analysis Final Report, ADV Integrity, Inc., March 2023#

Page 48Index 381 Failure Analysis Final Report Prepared for Boardwalk Pipelines, LP 100785-RP01-RevB-032823 March 2023#

Page 49Index 381 Failure Analysis Final Report Prepared for Boardwalk Pipelines, LP Houston, TX March 2023 Prepared by: Checked by: Reviewed by: David Futch, PE Rhett Dotson, PE Cary Windler, PE david.futch@advintegrity.com rdotson@D2Integrity.com Cary.windler@advintegrity.com 100785-RP01-RevB-032823 Rev Date Description Prepared Checked Reviewed B 03.28.2023 Issued for Client Review DBF RLD CBW Texas Registered Engineering Firm F-19081 www.advintegrity.com#

Page 50Tuesday, March 28, 2023 100785-RP01-RevB-032823 Rodney Clayton, Materials Integrity Supervisor Boardwalk Pipelines, LP 9 Greenway Plaza, Suite 2800, Houston, TX 77046 Rodney, Enclosed is our report documenting the failure analysis on an in-service failure that occurred on February 12, 2023 on Gulf South Pipeline Company’s Index 381 pipeline. The pipe in question was reported as nominal 20-inch OD x 0.250-inch WT, direct current electric resistance welded (DC-ERW), API 5LX, Grade X52 pipeline manufactured by Youngstown Sheet and Tube and installed in 1952. ADV concluded that the subject failure occurred due to an applied tensile/bending load, which resulted in plastic deformation along the minor axis of the observed ovality, and eventually propagated in the weld metal around the remaining circumference. The subject failure origin coincided with a 26-inch-long x 0.120-inch deep (48% of nominal wall thickness) incomplete penetration feature identified along the bottom of the pipe. The majority of the remaining fracture appeared consistent with ductile overload. Strain capacity calculations were performed; however, these results are based on the matrix of feature sizes examined. Features found during the metallurgical examination and those potentially found in the field may exceed this and therefore may limit the applicability of the resultant strain capacity calculations. All welds examined would have failed API 1104 workmanship criteria; however, NDE was not required by industry codes at the time construction. Mechanical properties of the pipe examined were consistent with API 5LX, Grade X52 material. Thank you for the opportunity to complete this work and please do not hesitate to contact us with any questions. Regards, David Futch, PE | Director, Materials Engineering ADV Integrity, Inc. 4027 Pinehurst Meadow | Magnolia, TX 77355 Office: (832) 409-4529 | E-mail: david.futch@advintegrity.com Texas Registered Engineering Firm F-19081 Reviewed by: Cary Windler, PE | Staff Consultant#

Page 51Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 CONTENTS 1.0 Introduction and Background ........................................................................................................... 6 2.0 Visual Examination ............................................................................................................................ 9 3.0 Non-Desctructive Examination ....................................................................................................... 15 4.0 Fractographic Examination ............................................................................................................. 17 5.0 Metallographic Examination ........................................................................................................... 41 5.1 6:00 o’clock Match Fracture ....................................................................................................... 41 5.2 8:00 o’clock Match Fracture ....................................................................................................... 46 5.3 2:00 o’clock Match Fracture ....................................................................................................... 49 5.4 11:00 o’clock Match Fracture ..................................................................................................... 50 5.5 ERW Seam Welds ........................................................................................................................ 53 6.0 Hardness Testing ............................................................................................................................. 55 7.0 Mechanical Testing and Chemical Analysis..................................................................................... 57 8.0 Strain Capacity Testing of Intact Girth Weld ................................................................................... 62 8.1 Dimensional Analysis .................................................................................................................. 62 8.2 Non-Destructive Examination ..................................................................................................... 62 8.3 Tensile Tests ................................................................................................................................ 67 8.4 Crack Tip Opening Displacements (CTODs)................................................................................. 69 8.5 Girth Weld Macros and Hardness Testing .................................................................................. 70 8.6 Charpy V-notch Testing of Girth Weld ........................................................................................ 73 8.7 Chemical Analysis of Girth Weld ................................................................................................. 75 8.8 Calculated Tensile Strain Capacity (TSC) ..................................................................................... 76 9.0 Discussion ....................................................................................................................................... 78 10.0 Conclusions ..................................................................................................................................... 79 APPENDIX A: Chain of Custody .......................................................................................................... 80 APPENDIX B: Ovality Cross Sections ................................................................................................... 83 APPENDIX C: Match Fracture Hardness Report ............................................................................... 102 APPENDIX D: ERW Hardness Reports .............................................................................................. 125 APPENDIX E: Chemical Analysis Report ........................................................................................... 133 APPENDIX F: NDE Report ................................................................................................................. 135 APPENDIX G: CTOD Report .............................................................................................................. 173 APPENDIX H: Intact Hardness Testing Report .................................................................................. 183 LIST OF FIGURES Page i#

Page 52Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 1-1: Screenshot of failure location captured from Google Earth. ..................................................... 7 Figure 1-2: Close-up shreenshot of failure location captured from Google Earth. ...................................... 7 Figure 1-3: Photograph of failure (provided by Boardwalk). ........................................................................ 8 Figure 2-1: Photograph of samples as-received by ADV. ............................................................................ 11 Figure 2-2: Photograph of samples as-received by ADV. ............................................................................ 11 Figure 2-3: Photograph of external coating present................................................................................... 12 Figure 2-4: Photograph of samples after removal of the coating............................................................... 12 Figure 2-5: Photograph of West pipe sample. Ruler is 12-inches long. ...................................................... 12 Figure 2-6: Photograph of East pipe sample. Ruler is 12-inches long. ........................................................ 13 Figure 2-7: Photograph of internal pipe surfaces. No signs of internal corrosion were identified. ........... 13 Figure 2-8: Plot comparing outer diameter measurements at the fracture to API 5L limits for out of roundness. .................................................................................................................................................. 13 Figure 2-9: Plot comparing outer diameter measurements at the end of the as-received sample to API 5L limits for out of roundness. ........................................................................................................................ 14 Figure 3-1: 3D rendering of the West Joint showing locations of ovality calculations. .............................. 15 Figure 3-2: 3D rendering of the East Joint showing locations of ovality calculations. ............................... 16 Figure 3-3: Plot comparing outer diameter measurements at the fracture (0-inch reading) and along the sample received (West and East). ............................................................................................................... 16 Figure 4-1: Photograph of fractures after cleaning. Ruler is 12 inches long. ............................................. 18 Figure 4-2: Photograph showing the 1:00 o’clock orientation of both fractures. Upper numbered scale divisions are inches. .................................................................................................................................... 19 Figure 4-3: Photograph showing a portion of the East fracture. Numbered scale divisions are inches. ... 20 Figure 4-4: Photograph showing the 6:00 o’clock orientation of both fractures. Upper numbered scale divisions are inches. .................................................................................................................................... 21 Figure 4-5: Photograph showing the internal surface at the 12:00 o’clock orientation of both fractures. Numbered scale divisions are inches. ......................................................................................................... 22 Figure 4-6: Photograph showing the internal surface at the 2:00 o’clock orientation of both fractures. Numbered scale divisions are inches. ......................................................................................................... 23 Figure 4-7: Photograph showing the internal surface at the 6:00 o’clock orientation of both fractures. Numbered scale divisions are inches. ......................................................................................................... 24 Figure 4-8: Photograph of the 6:00 o’clock orientation. Major numbered scale divisions are inches. ...... 25 Figure 4-9: Photograph of the 6:00 o’clock orientation. Two main fracture regions were identified denoted with the white dotted line. Major numbered scale divisions are inches. .................................... 25 Figure 4-10: Photograph of the 6:00 o’clock orientation after cleaning. Original magnification is 0.6x. ... 25 Figure 4-11: Photograph showing transition between fracture faces. Original magnification is 1.28x. .... 26 Figure 4-12: Secondary electron image from the 6:00 o’clock orientation. ............................................... 26 Figure 4-13: Secondary electron image from the 6:00 o’clock orientation. ............................................... 27 Figure 4-14: Secondary electron image from the internal surface of the 6:00 o’clock orientation. .......... 28 Figure 4-15: Secondary electron image from the midwall of the 6:00 o’clock orientation........................ 29 Figure 4-16: Secondary electron image from the external surface of the 6:00 o’clock orientation. ......... 30 Figure 4-17: Secondary electron image from a portion of the external surface of the 8:00 o’clock orientation. ................................................................................................................................................. 31 Figure 4-18: Secondary electron image from the 6:00 o’clock orientation. ............................................... 32 Figure 4-19: Secondary electron image from the midwall of the 6:00 o’clock orientation........................ 33 Page ii#

Page 53Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 4-20: Secondary electron image from the midwall of the 6:00 o’clock orientation........................ 34 Figure 4-21: Photograph of the 8:00 o’clock orientation. Two main fracture regions were identified denoted with the white dotted line. Major numbered scale divisions are inches. .................................... 34 Figure 4-22: Photograph of the 8:00 o’clock orientation after cleaning. Original magnification is 0.6x. ... 35 Figure 4-23: Photograph showing transition between fracture faces. Original magnification is 1.28x. .... 35 Figure 4-24: Secondary electron image from the 8:00 o’clock orientation. ............................................... 36 Figure 4-25: Secondary electron image from the 8:00 o’clock orientation. ............................................... 37 Figure 4-26: Secondary electron image from the internal surface of the 8:00 o’clock orientation. .......... 38 Figure 4-27: Secondary electron image from the midwall of the 8:00 o’clock orientation........................ 39 Figure 4-28: Secondary electron image from the external surface of the 8:00 o’clock orientation. ......... 40 Figure 5-1: Photomicrograph of metallurgical cross section prepared at the 6:00 o’clock orientation. Etchant is 2% Nital; original magnification is 0.6x. ..................................................................................... 42 Figure 5-2: Photomicrograph along the pipe’s internal surface. Etchant is 2% Nital; original magnification is 50x. .......................................................................................................................................................... 43 Figure 5-3: Photomicrograph showing transition between base pipe material and weld metal, outlined with a red dotted line. Etchant is 2% Nital; original magnification is 50x. ................................................. 44 Figure 5-4: Photomicrograph of final fracture along the external pipe surface. Etchant is 2% Nital; original magnification is 50x. ...................................................................................................................... 44 Figure 5-5: Photomicrograph of the base material from the West joint. Etchant is 2% Nital; original magnification is 200x. ................................................................................................................................. 45 Figure 5-6: Photomicrograph of the base material from the East joint. Etchant is 2% Nital; original magnification is 200x. ................................................................................................................................. 45 Figure 5-7: Photomicrograph of metallurgical cross section prepared at the 8:00 o’clock orientation. Etchant is 2% Nital; original magnification is 0.6x. ..................................................................................... 46 Figure 5-8: Photomicrograph along the pipe’s internal surface. Etchant is 2% Nital; original magnification is 50x. .......................................................................................................................................................... 47 Figure 5-9: Photomicrograph showing transition between base pipe material and weld metal, outlined with a red dotted line. Etchant is 2% Nital; original magnification is 50x. ................................................. 48 Figure 5-10: Photomicrograph of final fracture along the external pipe surface. Etchant is 2% Nital; original magnification is 50x. ...................................................................................................................... 48 Figure 5-11: Photomicrograph of metallurgical cross section prepared at the 2:00 o’clock orientation. Etchant is 2% Nital; original magnification is 0.6x. ..................................................................................... 49 Figure 5-12: Photomicrograph of the weld indication identified in the 2:00 o’clock metallurgical cross section, identified as slag/porosity. Etchant is 2% Nital; original magnification is 50x. ............................. 50 Figure 5-13: Photomicrograph of metallurgical cross section prepared at the 11:00 o’clock orientation. Etchant is 2% Nital; original magnification is 0.6x. ..................................................................................... 51 Figure 5-14: Photomicrograph along the pipe’s internal surface. Etchant is 2% Nital; original magnification is 50x. ................................................................................................................................... 52 Figure 5-15: Photomicrograph showing transition between base pipe material and weld metal, outlined with a red dotted line. Etchant is 2% Nital; original magnification is 100x. ............................................... 53 Figure 5-16: Photomicrograph of the ERW seam from the West joint. ERW bondline is identified with a red arrow. Etchant is 2% Nital; original magnification is 0.6x. ................................................................... 54 Figure 5-17: Photomicrograph of the ERW seam from the East joint. ERW bondline is identified with a red arrow. Etchant is 2% Nital; original magnification is 0.6x. ................................................................... 54 Page iii#

Page 54Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 6-1: Hardness map output for the 6:00 o’clock match fracture metallographic cross section. ...... 56 Figure 7-1: West Joint pipe body CVN transition curve. ............................................................................. 60 Figure 7-2: West Joint ERW bondline CVN transition curve. ...................................................................... 60 Figure 7-3: East Joint pipe body CVN transition curve. ............................................................................... 61 Figure 7-4: East Joint ERW bondline CVN transition curve. ........................................................................ 61 Figure 8-1: RT images from intact weld West of Failure. ............................................................................ 65 Figure 8-2: RT images from intact weld East of Failure. ............................................................................. 66 Figure 8-3: DIC output from 12:00 o’clock cross weld tensile test. ............................................................ 68 Figure 8-4: DIC output from 12:00 o’clock cross weld tensile test. ............................................................ 69 Figure 8-5: Photomicrograph of the 12:00 o’clock orientation. Etchant is 2% Nital; original magnification is 0.6x. ......................................................................................................................................................... 70 Figure 8-6: Photomicrograph of volumetric feature identified. Etchant is 2% Nital; original magnification is 50x. .......................................................................................................................................................... 71 Figure 8-7: Photomicrograph of volumetric features identified. Etchant is 2% Nital; original magnification is 50x. .......................................................................................................................................................... 71 Figure 8-8: Photomicrograph of external undercut identified. Etchant is 2% Nital; original magnification is 50x. .......................................................................................................................................................... 72 Figure 8-9: Photomicrograph of the 3:00 o’clock orientation. Etchant is 2% Nital; original magnification is 0.6x. ............................................................................................................................................................. 72 Figure 8-10: HV0.5 hardness map from the 12:00 o’clock orientation. ..................................................... 73 Figure 8-11: HV0.5 hardness map from the 3:00 o’clock orientation. ....................................................... 73 Figure 8-12: Girth weld centerline CVN transition curve. ........................................................................... 74 Figure 8-13: Girth weld HAZ CVN transition curve. .................................................................................... 75 Page iv#

Page 55Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 LIST OF TABLES Table 2-1: Pipe Dimensional Analysis ......................................................................................................... 10 Table 2-2: Wall Thickness Readings along Fracture .................................................................................... 10 Table 2-3: Outside Diameter Readings along Fracture and at End of As-Received Sample ....................... 10 Table 6-1: Girth Weld Hardness Testing Results ......................................................................................... 55 Table 6-2: DC-ERW Hardness Testing Results ............................................................................................. 55 Table 7-1: Chemical Analysis Results .......................................................................................................... 57 Table 7-2: Tensile Strength Results ............................................................................................................. 58 Table 7-3: Charpy V-notch Results, West Joint ........................................................................................... 58 Table 7-4: Charpy V-notch Results, East Joint ............................................................................................. 59 Table 8-1: Pipe Dimensional Analysis ......................................................................................................... 62 Table 8-2: Summary of Features Identified via UT ..................................................................................... 64 Table 8-3: Tensile Strength Results ............................................................................................................. 67 Table 8-4: CTOD Results .............................................................................................................................. 69 Table 8-5: Charpy V-notch Results .............................................................................................................. 74 Table 8-6: Chemical Analysis Results .......................................................................................................... 76 Table 8-7: Tensile Strain Capacity Inputs and Results at MAOP (475 psig) ................................................ 77 Table 8-8: Tensile Strain Capacity Inputs and Results at Failure Pressure (400 psig) ................................. 77 Table 9-1: Summary of Acceptance Criteria ............................................................................................... 78 Page v#

Page 56Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 1.0 INTRODUCTION AND BACKGROUND Boardwalk Pipelines, LP (Boardwalk) contracted ADV Integrity, Inc. (ADV) to perform a failure analysis on an in-service failure that occurred on February 12, 2023 at approximately 3:56 AM Central Time. This failure occurred during normal operations at an estimated pressure of 400 psig on Gulf South Pipeline Company’s Index 381 pipeline. The failure occurred at the approximate Station Number of 6180+60 (GPS coordinates: 32.262952, -90.199256). Google Earth images showing the approximate failure location are provided in Figure 1-1 and Figure 1-2. Boardwalk reported that this pipeline transported natural gas at a maximum allowable operating pressure (MAOP) of 475 psig as a nominal 20-inch OD x 0.250-inch WT, direct current electric resistance welded (DC-ERW), API 5LX, Grade X52 pipeline manufactured by Youngstown Sheet and Tube and installed in 1952. The pipeline was coated with coal tar enamel. The last hydrostatic test was performed in 2019 at a pressure of 760 psig with no historic failures nearby the failure location. Boardwalk personnel indicated that the failure occurred at an original construction girth weld resulting in a full separation of the pipeline, shown in Figure 1-3. Measurements in the field indicated that the failure resulted in a 14.5-inch horizontal separation (along the length of the pipeline) and an 11-inch vertical displacement (perpendicular to the pipeline). Boardwalk also removed two intact girth welds remote of the failure. These welds were reported as “West of the Failure” (GPS coordinates: 32.262948, -90.199316, Station 6180+47) and “East of the Failure” (GPS coordinates: 32.263028, -90.198988, Station 6181+51). Boardwalk requested that ADV determine the likely metallurgical cause of the observed failure, document the mechanical properties of the adjacent pipe joints, and document the mechanical properties of a representative intact girth weld removed in the vicinity of the failure in an attempt to determine the strain capacity of a representative girth weld. Page 6#

Page 57Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 1-1: Screenshot of failure location captured from Google Earth. Figure 1-2: Close-up shreenshot of failure location captured from Google Earth. Page 7#

Page 58Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Vertical Displacement: 11 inches Horizontal Displacement: 14.5 inches Figure 1-3: Photograph of failure (provided by Boardwalk). Page 8#

Page 59Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 2.0 VISUAL EXAMINATION ADV received the subject pipes containing the fracture on February 15, 2023, shown in Figure 2-1. The completed Chain of Custody for the received pipe are attached in Appendix A. The pipe samples contained the original coal tar enamel coating, shown in Figure 2-2. The coating on the sides of the pipe (3:00 o’clock or 9:00 o’clock orientation) appeared wrinkled, shown in Figure 2-3. The fracture surface present was protected using a split, circular foam material. The coal tar coating was removed from the external pipe surface by a licensed contractor ensuring the fracture surfaces were protected during removal. Both pipe samples received by ADV, measured 79 inches long, shown collectively in Figure 2-4 and individually in Figure 2-5 and Figure 2-6. The two samples contained markings indicating one was the “West” portion of the fracture and the other was the “East” portion of the fracture. Boardwalk reported the line was bi-directional so the flow direction varies changing the resultant o’clock orientation around the pipe’s circumference. ADV designated the flow direction for this analysis to be “West” to “East”. Therefore, all o’clock orientations discussed in this report are based on this direction. The ERW seam welds were identified on both samples: at approximately the 7:15 o’clock orientation on the “West” joint and approximately the 1:15 o’clock orientation on the “East” joint. The external and internal pipe surfaces appeared free of obvious external and internal corrosion. A photograph of the internal surface of both samples is shown in Figure 2-7. ADV received two additional girth welds on February 21, 2021, which were reported as intact girth welds removed further West and East of the failed girth weld. The examination of these girth welds is discussed in Section 8.0. ADV recorded the dimensions of the failed pipes just inside the fracture and at the field cut end (79-inches from the fracture). The diameter was measured with a Pi tape and the wall thickness was measured at twelve evenly spaced locations (coinciding with the pipe o’clock orientation) around the circumference with a rounded tip micrometer. These results are summarized in Table 2-1 and Table 2-2. Both pipe samples remote of the fracture were consistent with nominal 20-inch OD x 0.250-inch WT pipe. The East side of the fracture contained necking reducing the wall thickness approximately 8% from the readings at the end of the East joint. ADV also measured the pipeline diameter at varying o’clock orientations 180 degrees apart with a tube micrometer at the fracture and at the end of the as-received sample, which can further be interpreted as out of roundness (or ovality), shown in Table 2-3 and graphically in Figure 2-8 and Figure 2-9. The API 5L limit for outer diameter (+/- 1%) is also presented in Figure 2-8 and Figure 2-9 for comparison. The minor axis of the observed ovality was identified between at approximately the 1:00-7:00 o’clock reading and the major axis of the observed ovality was identified at approximately the 4:00-10:00 o’clock reading. It should be noted that these measurements were post-failure; therefore, these measurements cannot be used to comment on the acceptability of the pipe before failure. This trend in the measured outer diameter (and resultant ovality) was not identified at the end of the as-received sample. Therefore, the Page 9#

Page 60Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 pipe wall thickness and roundness changed during the process of failure. Additional outer diameter measurements are examined in Section 3.0. Table 2-1: Pipe Dimensional Analysis Location Outside Diameter (in) Wall Thickness (in) High Low Average West Pipe Fracture End 19.99 0.256 0.250 0.253 Cut End 20.07 0.268 0.264 0.266 East Pipe Fracture End 19.95 0.237 0.221 0.230 Cut End 20.05 0.254 0.247 0.250 Table 2-2: Wall Thickness Readings along Fracture Wall Thickness (in) o’clock Orientation Inside Fracture End of As-Rec Material West Joint East Joint West Joint East Joint 12:00 0.256 0.221 0.267 0.250 1:00 0.255 0.222 0.265 0.247 2:00 0.250 0.230 0.266 0.253 3:00 0.252 0.233 0.265 0.253 4:00 0.252 0.223 0.266 0.249 5:00 0.253 0.225 0.265 0.248 6:00 0.252 0.233 0.264 0.249 7:00 0.250 0.231 0.266 0.254 8:00 0.256 0.237 0.268 0.250 9:00 0.253 0.235 0.266 0.249 10:00 0.255 0.235 0.267 0.249 11:00 0.256 0.230 0.268 0.247 Table 2-3: Outside Diameter Readings along Fracture and at End of As-Received Sample At Fracture End of As-Rec Material o’clock Outside Diameter (in) Outside Diameter (in) Orientation Upstream Joint Downstream Joint Upstream Joint Downstream Joint 12:00-6:00 19.808 19.722 20.087 20.022 1:00-7:00 19.528 19.406 19.962 19.985 2:00-8:00 19.863 19.754 19.920 19.979 3:00-9:00 19.985 20.005 20.031 20.027 4:00-10:00 20.152 20.215 20.104 20.063 5:00-11:00 20.156 20.170 20.150 20.050 Page 10#

Page 61Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 2-1: Photograph of samples as-received by ADV. Figure 2-2: Photograph of samples as-received by ADV. Page 11#

Page 62Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 2-3: Photograph of external coating present. Fracture West East Figure 2-4: Photograph of samples after removal of the coating. West Fracture/Girth Weld Figure 2-5: Photograph of West pipe sample. Ruler is 12-inches long. Page 12#

Page 63Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 East Fracture/Girth Weld Figure 2-6: Photograph of East pipe sample. Ruler is 12-inches long. West East Figure 2-7: Photograph of internal pipe surfaces. No signs of internal corrosion were identified. Figure 2-8: Plot comparing outer diameter measurements at the fracture to API 5L limits for out of roundness. Page 13#

Page 64Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 2-9: Plot comparing outer diameter measurements at the end of the as-received sample to API 5L limits for out of roundness. Page 14#

Page 65Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 3.0 NON-DESCTRUCTIVE EXAMINATION ADV performed a 3D laser scan of all pipe samples received. The laser scan was performed using a Creaform HandyScan 307 with reflective positioning targets applied to the outside pipe surface. The scan had a resolution of 0.0039 inch with an accuracy of +/- 0.0016 inch. The main goal of the inspection was to document the outer diameter (and resultant ovality) more accurately in the vicinity of the fracture. ADV post-processed the scan using Pipecheck to better quantify the ovality present. Virtual cross sections were performed every two inches in a two-foot region on both sides of the fracture (shown in Figures 3- 1 and 3-2, and graphically in Figure 3-3) and every foot along the remainder of the sample. Outer diameter measurements at the fracture (referred to a “0”) and four (4) inches from the fracture were outside the API 5L limits on both joints (West and East). Both the upstream and downstream joint measurements revealed a smaller amount of variation at locations eight (8) inches past the fracture. Therefore, the observed ovality was concentrated to a short (6-8 inches) section of pipe adjacent to the girth weld, with the East joint ovalizing more than the West joint. Additional data showing the virtual cross sections are attached in Appendix B. Fracture/Girth Weld Figure 3-1: 3D rendering of the West Joint showing locations of ovality calculations. Page 15#

Page 66Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Fracture/Girth Weld Figure 3-2: 3D rendering of the East Joint showing locations of ovality calculations. Figure 3-3: Plot comparing outer diameter measurements at the fracture (0-inch reading) and along the sample received (West and East). Page 16#

Page 67Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 4.0 FRACTOGRAPHIC EXAMINATION ADV removed both ends of the fracture by torch cutting approximately 4 inches on either side of the fracture. ADV then ultrasonically cleaned the fracture surface in an Alconox® and water solution. The resulting fracture surfaces are shown in Figure 4-1. ADV first visually examined the fracture surfaces. An image of both fracture surfaces at the 1:00 o’clock orientation is shown in Figure 4-2. An area of brittle fracture was identified, shown in Figure 4-3. Both fracture surfaces at the 6:00 o’clock orientation are shown in Figure 4-4. This location was examined further, discussed below. ADV then examined the internal pipe surface of both fracture surfaces. Both fracture surfaces at the 12:00 o’clock orientation are shown in Figure 4-5. The fracture deviated from the girth weld into the East joint at this location. Areas of intact girth weld metal revealed areas of incomplete penetration. Both fracture surfaces at the 2:00 o’clock orientation are shown in Figure 4-6. The fracture deviated from the girth weld into the East joint allowing for later metallurgical examination of what the girth weld looked like absent of internal or external features. Both fracture surfaces at the 6:00 o’clock orientation are shown in Figure 4-7. No obvious root penetration was identified along a 26-inch-long region spanning from approximately the 4:00 o’clock orientation to the 8:45 o'clock orientation. ADV further examined the 26-inch-long region, shown in Figure 4-8. ADV selected two areas for more detailed examination based on their appearance varying from the surrounding weld metal: the 6:00 o’clock orientation and the 8:00 o’clock orientation. A portion of the fracture surface at the 6:00 o’clock orientation is shown in Figure 4-9 before cleaning and Figure 4-10 after cleaning in an Evaporust solution. An internal surface breaking feature was identified propagating approximately half of the wall thickness. That feature appeared relatively featureless and transitioned into an area of obvious fracture, shown in Figure 4-11. Based on the visual appearance, the internal surface breaking feature appeared consistent with incomplete penetration present since the time of construction. ADV contracted Texas A&M University (TAMU) in College Station, Texas to perform SEM of the material removed from the 6:00 o’clock orientation (shown in Figure 4-10) as directed by ADV. The SEM used in this analysis was a Tescan Vega 3 XMU with an accelerating voltage of 30 kV. The working distance was varied in this examination between approximately 25 mm and 70 mm. An overall image of the fracture surface is shown in Figure 4-12. The first area of interest examined is shown in Figure 4-13. ADV examined the fracture surface where the internal surface appeared featureless showing signs of metal smearing consistent with an unwelded cut metal bevel, shown in Figure 4-14. That transitioned into ductile fracture, shown as microvoid coalescence in Figure 4-15. That then transitioned at the external surface, shown in Figure 4-16, to an isolated area of brittle fracture, shown as cleavage in Figure 4-17. It seems likely that this isolated area of brittle fracture occurred during the process of a quickly propagating fracture. ADV examined a second location show in Figure 4-18. The midwall portion of the fracture surface is shown in Figure 4-19. This region appeared consistent with ductile fracture, shown as microvoid coalescence in Figure 4-20. Page 17#

Page 68Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 A portion of the fracture surface at the 8:00 o’clock orientation is shown in Figure 4-21 before cleaning and Figure 4-22 after cleaning in an Evaporust solution. An internal surface breaking feature was identified propagating approximately half of the wall thickness. That feature appeared relatively featureless and transitioned into an area of obvious fracture, shown in Figure 4-23. Based on the visual appearance, the internal surface breaking feature appeared consistent with incomplete penetration. This region was also examined via the SEM. An overall image of the fracture surface is shown in Figure 4-24. The area of interest examined is shown in Figure 4-25. ADV examined the fracture surface where internal surface appeared featureless showing signs of metal smearing consistent with an unwelded cut metal bevel, shown in Figure 4-26. That transitioned into ductile fracture at the midwall and external surface, shown as microvoid coalescence in Figure 4-27 and Figure 4-28, respectively. After careful examination of the fracture surface, ADV determined the origin area coincided with the 26- inch-long incomplete penetration based upon: (1) the length and depth of the feature was visually the largest along the fracture, (2) being located along the minor axis of the observed ovality, and (3) the lack of other features along the fracture surface which may indicate another origin area. Based upon the SEM examination, it seems likely that the fracture propagated via ductile overload. No signs of fatigue or growth were identified. West Joint East Joint Figure 4-1: Photograph of fractures after cleaning. Ruler is 12 inches long. Page 18#

Page 69Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 See Figure 4-3 Figure 4-2: Photograph showing the 1:00 o’clock orientation of both fractures. Upper numbered scale divisions are inches. Page 19#

Page 70Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 External Surface Internal Surface Figure 4-3: Photograph showing a portion of the East fracture. Numbered scale divisions are inches. Page 20#

Page 71Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 4-4: Photograph showing the 6:00 o’clock orientation of both fractures. Upper numbered scale divisions are inches. Page 21#

Page 72Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Internal Surface West Joint East Joint 12:00 o’clock orientation Metallurgical Cross Section 11:00 o’clock orientation Figure 4-5: Photograph showing the internal surface at the 12:00 o’clock orientation of both fractures. Numbered scale divisions are inches. Page 22#

Page 73Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Internal Surface West Joint East Joint 2:00 o’clock orientation Metallurgical Cross Section Figure 4-6: Photograph showing the internal surface at the 2:00 o’clock orientation of both fractures. Numbered scale divisions are inches. Page 23#

Page 74Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Internal Surface 6:00 o’clock orientation Metallurgical Cross Section West Joint East Joint 5:00 o’clock orientation Figure 4-7: Photograph showing the internal surface at the 6:00 o’clock orientation of both fractures. Numbered scale divisions are inches. Page 24#

Page 75Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Internal Surface See Figure 4-9 External Surface Figure 4-8: Photograph of the 6:00 o’clock orientation. Major numbered scale divisions are inches. Internal Surface External Surface Figure 4-9: Photograph of the 6:00 o’clock orientation. Two main fracture regions were identified denoted with the white dotted line. Major numbered scale divisions are inches. External Surface See Figure 4-11 Internal Surface Figure 4-10: Photograph of the 6:00 o’clock orientation after cleaning. Original magnification is 0.6x. Page 25#

Page 76Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Internal Surface Breaking Feature Figure 4-11: Photograph showing transition between fracture faces. Original magnification is 1.28x. External Surface See Figure 4-13 Internal Surface See Figure 4-18 Figure 4-12: Secondary electron image from the 6:00 o’clock orientation. Page 26#

Page 77Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 External Surface See Figure 4-16 See Figure 4-15 See Figure 4-14 Internal Surface Figure 4-13: Secondary electron image from the 6:00 o’clock orientation. Page 27#

Page 78Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 4-14: Secondary electron image from the internal surface of the 6:00 o’clock orientation. Page 28#

Page 79Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 4-15: Secondary electron image from the midwall of the 6:00 o’clock orientation. Page 29#

Page 80Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 See Figure 4-17 Figure 4-16: Secondary electron image from the external surface of the 6:00 o’clock orientation. Page 30#

Page 81Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 4-17: Secondary electron image from a portion of the external surface of the 8:00 o’clock orientation. Page 31#

Page 82Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 External Surface See Figure 4-19 Internal Surface Figure 4-18: Secondary electron image from the 6:00 o’clock orientation. Page 32#

Page 83Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 See Figure 4-20 Figure 4-19: Secondary electron image from the midwall of the 6:00 o’clock orientation. Page 33#

Page 84Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 4-20: Secondary electron image from the midwall of the 6:00 o’clock orientation. Internal Surface External Surface Figure 4-21: Photograph of the 8:00 o’clock orientation. Two main fracture regions were identified denoted with the white dotted line. Major numbered scale divisions are inches. Page 34#

Page 85Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 External Surface See Figure 4-23 Internal Surface Figure 4-22: Photograph of the 8:00 o’clock orientation after cleaning. Original magnification is 0.6x. Internal Surface Breaking Feature Internal Surface Figure 4-23: Photograph showing transition between fracture faces. Original magnification is 1.28x. Page 35#

Page 86Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 External Surface See Figure 4-25 Internal Surface Figure 4-24: Secondary electron image from the 8:00 o’clock orientation. Page 36#

Page 87Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 External Surface See Figure 4-28 See Figure 4-27 See Figure 4-26 Internal Surface Figure 4-25: Secondary electron image from the 8:00 o’clock orientation. Page 37#

Page 88Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 4-26: Secondary electron image from the internal surface of the 8:00 o’clock orientation. Page 38#

Page 89Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 4-27: Secondary electron image from the midwall of the 8:00 o’clock orientation. Page 39#

Page 90Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 4-28: Secondary electron image from the external surface of the 8:00 o’clock orientation. Page 40#

Page 91Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 5.0 METALLOGRAPHIC EXAMINATION ADV prepared six metallurgical cross sections outlined and discussed in the subsections below: • Cross Section 1: Match fracture prepared at the 6:00 o’clock orientation • Cross Section 2: Match fracture prepared at the 8:00 o’clock orientation • Cross Section 3: Match fracture prepared at the 2:00 o’clock orientation • Cross Section 4: Match fracture prepared at the 11:00 o’clock orientation • Cross Section 5: Intact ERW seam weld from the West joint • Cross Section 6: Intact ERW seam weld from the East joint Metallurgical Cross Sections 1 and 2 were prepared to further investigate the suspected origin area. Metallurgical Cross Sections 3 and 4 were prepared to further investigate other areas of interest within the girth weld. Metallurgical Cross Sections 5 and 6 were prepared to investigate the metallurgical condition of the DC-ERW seam. Cross sections were mounted and polished per ASTM E3 and etched with 2% Nital per ASTM E407. 5.1 6:00 o’clock Match Fracture ADV prepared a match fracture metallurgical cross section within a portion of the origin area identified at the 6:00 o’clock orientation, shown in Figure 5-1. The fracture progresses along the internal surface through the weld metal towards the external surface, partially shown in Figure 5-2. A distinct transition was identified approximately 0.116-inches (46% nominal wall thickness) from the internal pipe surface. This transition is shown in more detail in Figure 5-3. A rounded welding flaw was identified at the transition. Material below this feature appeared consistent with base material and material above this feature appeared consistent with weld metal. Based on this appearance, ADV confirmed the presence of inadequate penetration along the internal pipe surface. The external surface appeared consistent with a 45-degree shear plane, shown in Figure 5-4. Little to no mismatch (hi-lo) between the two pipes was identified. The base material microstructure remote of the fracture on the West joint end, shown in Figure 5-5, and the East joint, shown in Figure 5-6, are consistent with a ferrite/pearlite mixture typical of carbon steel pipe material. Page 41#

Page 92Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 External Surface See Figure 5-4 Weld Root See Figure 5-2 Internal Surface Figure 5-1: Photomicrograph of metallurgical cross section prepared at the 6:00 o’clock orientation. Etchant is 2% Nital; original magnification is 0.6x. Page 42#

Page 93Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Weld Metal See Figure 5-3 Incomplete Penetration 0.116 inch (46% NWT) Internal Surface Figure 5-2: Photomicrograph along the pipe’s internal surface. Etchant is 2% Nital; original magnification is 50x. Page 43#

Page 94Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 5-3: Photomicrograph showing transition between base pipe material and weld metal, outlined with a red dotted line. Etchant is 2% Nital; original magnification is 50x. External Surface Figure 5-4: Photomicrograph of final fracture along the external pipe surface. Etchant is 2% Nital; original magnification is 50x. Page 44#

Page 95Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 5-5: Photomicrograph of the base material from the West joint. Etchant is 2% Nital; original magnification is 200x. Figure 5-6: Photomicrograph of the base material from the East joint. Etchant is 2% Nital; original magnification is 200x. Page 45#

Page 96Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 5.2 8:00 o’clock Match Fracture ADV prepared a match fracture metallurgical cross section within a portion of the origin area identified at the 8:00 o’clock orientation, shown in Figure 5-7. The fracture progresses along the internal surface through the weld metal towards the external surface, partially shown in Figure 5-8. A distinct transition was identified approximately 0.120-inches (48% nominal wall thickness) from the internal pipe surface. This transition is shown in more detail in Figure 5-9. Material below this transition appeared consistent with base material and material above this feature appeared consistent with weld metal. Based on this appearance, ADV confirmed the presence of inadequate penetration along the internal pipe surface. The external surface appeared consistent with a 45-degree shear plane, shown in Figure 5-10. Mismatch (hi- lo) was measured at approximately 0.05-inch, which is within the recommended maximum in API 1104 of 1/8-inch. External Surface See Figure 5-10 Weld Root 0.05 inch See Figure 5-8 Internal Surface Figure 5-7: Photomicrograph of metallurgical cross section prepared at the 8:00 o’clock orientation. Etchant is 2% Nital; original magnification is 0.6x. Page 46#

Page 97Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Weld Metal See Figure 5-9 Incomplete Penetration 0.120 inch (48% NWT) Internal Surface Figure 5-8: Photomicrograph along the pipe’s internal surface. Etchant is 2% Nital; original magnification is 50x. Page 47#

Page 98Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 5-9: Photomicrograph showing transition between base pipe material and weld metal, outlined with a red dotted line. Etchant is 2% Nital; original magnification is 50x. External Surface Figure 5-10: Photomicrograph of final fracture along the external pipe surface. Etchant is 2% Nital; original magnification is 50x. Page 48#

Page 99Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 5.3 2:00 o’clock Match Fracture ADV prepared a metallurgical cross section at the 2:00 o’clock orientation, shown in Figure 5-11, to further investigate a visually complete portion of the weld. At this location, the fracture progressed along the base pipe adjacent to the girth weld. An indication was identified below in the fill pass, shown in Figure 5- 12. This indication appears consistent with slag/porosity. Mismatch (hi-lo) was measured at approximately 0.08-inch, which is within the recommended maximum in API 1104 of 1/8-inch, and the prior root gap was approximated at 0.220-inch. External Surface Fracture See Figure 5-12 Weld Root 0.08 inch Internal Surface Figure 5-11: Photomicrograph of metallurgical cross section prepared at the 2:00 o’clock orientation. Etchant is 2% Nital; original magnification is 0.6x. Page 49#

Page 100Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 5-12: Photomicrograph of the weld indication identified in the 2:00 o’clock metallurgical cross section, identified as slag/porosity. Etchant is 2% Nital; original magnification is 50x. 5.4 11:00 o’clock Match Fracture ADV prepared a metallurgical cross section at the 11:00 o’clock orientation, shown in Figure 5-13, to further investigate visible indications present along the fracture surface. At this location, the fracture progressed along the base pipe adjacent to the girth weld. The fracture progresses along the internal surface through the weld metal towards the external surface, partially shown in Figure 5-14. A distinct transition was identified approximately 0.075-inches (30% nominal wall thickness) from the internal pipe surface. This transition is shown in more detail in Figure 5-15. Material below this transition appeared consistent with base material and material above this feature appeared consistent with weld metal. Based on this appearance, ADV confirmed the presence of inadequate penetration along the internal pipe surface. Mismatch (hi-lo) was measured at approximately 0.07-inch, which is within the recommended maximum in API 1104 of 1/8-inch. Page 50#

Page 101Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 External Surface Fracture See Figure 5-14 0.07 inch Internal Surface Figure 5-13: Photomicrograph of metallurgical cross section prepared at the 11:00 o’clock orientation. Etchant is 2% Nital; original magnification is 0.6x. Page 51#

Page 102Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Weld Metal Incomplete Penetration 0.075 inch (30% NWT) Internal Surface Figure 5-14: Photomicrograph along the pipe’s internal surface. Etchant is 2% Nital; original magnification is 50x. Page 52#

Page 103Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 5-15: Photomicrograph showing transition between base pipe material and weld metal, outlined with a red dotted line. Etchant is 2% Nital; original magnification is 100x. 5.5 ERW Seam Welds ADV prepared a metallurgical cross section of the ERW seam from both joints. The cross sections for the West and East joint are shown in Figure 5-16 and Figure 5-17, respectively. The ERW seams appeared consistent with a DC-ERW seam weld. Page 53#

Page 104Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 External Surface Internal Surface Figure 5-16: Photomicrograph of the ERW seam from the West joint. ERW bondline is identified with a red arrow. Etchant is 2% Nital; original magnification is 0.6x. External Surface Internal Surface Figure 5-17: Photomicrograph of the ERW seam from the East joint. ERW bondline is identified with a red arrow. Etchant is 2% Nital; original magnification is 0.6x. Page 54#

Page 105Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 6.0 HARDNESS TESTING ADV performed a Vickers hardness map on the 6:00 o’clock match fracture metallurgical girth weld cross section, shown in Figure 5-1. This hardness map was performed per ASTM E384 with a 500-gram force and a 0.5 mm spacing. The resulting map is shown in Figure 6-1. The color variation represents the hardness across the weld, with blue shades having a lower hardness (softer) than red shades. The lower hardness (appearing blue) along the internal surface and higher hardness (appearing yellow/red) along the midwall/external surface further confirms the presence of inadequate penetration as the internal surface did not experience significant heat from welding to soften or harden. The minimum, maximum, and average hardness in the three regions are summarized in Table 6-1. The full hardness testing report is attached in Appendix C. Vickers hardness testing (HV10) was performed on the DC-ERW metallurgical cross section from the West and East joint, shown in Figure 5-16 and Figure 5-17, respectively. The hardness traverse was performed similar to API 5L (45th Edition), Figure J.1 with three through-wall traverses (external surface, midwall, and internal surface) with readings in the base material, HAZ, bondline, HAZ, and base material. These results are shown in Table 6-2. These results are consistent with a DC-ERW seam weld. The full reports are attached in Appendix D. Table 6-1: Girth Weld Hardness Testing Results Hardness (HV) Maximum Minimum Average 257 139 174 Note: All readings are HV0.5. Table 6-2: DC-ERW Hardness Testing Results Joint Location Base HAZ Bondline HAZ Base OD 189, 198, 195 213, 215 207 203, 212 187, 192, 185 West MID 195, 202, 195 198, 198 199 199, 195 184, 191, 187 ID 189, 196, 208 198, 196 196 195, 187 189, 199, 199 OD 189, 193, 193 202, 205 198 198, 200 196, 188, 175 East MID 183, 179, 187 203, 194 204 191, 189 185, 184, 178 ID 191, 190, 186 194, 197 208 197, 187 177, 193, 189 Note: All readings are HV10. Page 55#

Page 106Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 External Surface Internal Surface Figure 6-1: Hardness map output for the 6:00 o’clock match fracture metallographic cross section. Page 56#

Page 107Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 7.0 MECHANICAL TESTING AND CHEMICAL ANALYSIS ADV performed a series of mechanical testing to better understand both joints provided (West and East). The chemical analysis was contracted Bryan Laboratory, Inc. The results were compared to the 3rd Edition of API 5LX (1951), which is the closest edition to the time of manufacturing. API 5LX, Grade X52 was not included in the 3rd Edition, therefore, the properties would have been by agreement. The comparisons in the tables below contain values from API 5LX (1954), 5th Edition, which was the first edition to contain Grade X52. Chemical analysis of a small specimen of the girth weld was also performed and compared to the nominal chemistry of the current edition of AWS A5.1 E6010 and AWS A5.5 E7010-P1 consumable. Chemical analysis (per ASTM A751) and tensile test (per ASTM A370) results, summarized in Table 7-1 and Table 7-2, respectively, are consistent with the requirement of API 5LX (1951/1954), Grade X52 material. The weld metal chemistry is also consistent with the nominal chemistry of a E6010 or E7010-P1 consumable. Pipe body and ERW bondline, half-sized Charpy V-notch tests (per ASTM A370) were performed on the West and East joints to generate transition curves; results are summarized in Table 7-3 and Table 7-4. Charpy V-notch transition curves were generated using a hyperbolic tangent curve-fit (API 579, Annex 9F) and summarized in Figure 7-1 through Figure 7-4. It should be noted that toughness testing was not a requirement for API 5LX (1951) pipe. The chemical analysis report is attached in Appendix E. Table 7-1: Chemical Analysis Results Composition (%) Element West Joint East Joint API 5LX, Grade X52 3rd Edition (1951)1 Girth AWS AWS Weld E6010 E7010-P1 Carbon 0.16 0.23 0.28 (max) 0.10 0.20 (max) 0.20 (max) Manganese 0.84 0.96 1.25 (max) 0.40 1.20 (max) 1.20 (max) Phosphorus 0.003 0.013 0.04 (max) 0.007 --- 0.03 (max) Sulfur 0.011 0.034 0.05 (max) 0.022 --- 0.03 (max) Silicon <0.01 <0.01 --- 0.09 1.00 (max) 0.60 (max) Chromium 0.03 0.04 --- 0.03 0.20 (max) 0.30 (max) Nickel 0.03 0.03 --- 0.05 0.30 (max) 1.00 (max) Molybdenum <0.01 <0.01 --- 0.17 0.30 (max) 0.50 (max) Copper 0.04 0.05 --- 0.11 --- --- Aluminum <0.01 0.02 --- <0.01 --- --- Vanadium <0.01 <0.01 --- <0.01 0.08 (max) 0.10 (max) Titanium 0.01 0.01 --- <0.01 --- --- Niobium <0.01 <0.01 --- <0.01 --- --- Boron <0.001 <0.001 --- <0.001 --- --- 1 By agreement. Electric-furnace, open-hearth, cold expanded. Page 57#

Page 108Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Table 7-2: Tensile Strength Results Location Sample Yield Strength (psi) Tensile Strength Elongation (psi) (%) West Joint 56,500 72,900 29.5 Pipe Body - Transverse East Joint 62,500 78,100 30.6 West Joint Pipe Body - Longitudinal East Joint 55,200 77,200 29.5 West Joint --- 78,300 --- Cross ERW Weld East Joint --- 80,000 --- API 5LX, Grade X52, 3rd Edition (1951) 52,000 (min) 66,000 (min) 17.5 (min) 1-1/2" wide flattened reduced sections, Transverse, 180° from the seam weld (Body), across the Weld, and Longitudinal, 90° from the seam weld Table 7-3: Charpy V-notch Results, West Joint Absorbed Approx. Full-Size Equivalent Percent Location Specimen Temperature Energy Absorbed Energy Shear (%) (ft-lb) (ft-lb) 1 10 20 100 2 10 74 3 10 20 95 20 95 1 10 20 95 50 2 10 3 10 20 90 20 95 1 3 6 40 2 4 0 3 5 8 50 10 50 Pipe Body 1 2.5 5 10 -30 2 2.5 3 3 5 20 6 30 1 2 4 10 -50 2 2 3 2 4 10 4 10 1 1.5 3 0 2 1.5 -70 3 1.5 3 0 3 0 1 8 16 85 200 2 8 16 80 3 7 14 80 1 6 12 60 2 6 160 3 6 12 65 12 75 ERW Bondline 1 5 10 50 120 2 5 3 5 10 60 10 40 1 3.5 7 30 2 2.5 74 3 4 5 20 8 30 1 50 4 8 0 Page 58#

Page 109Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 2 4 8 10 3 3 6 15 1 2 4 0 0 2 2 3 2 4 0 4 0 Table 7-4: Charpy V-notch Results, East Joint Absorbed Approx. Full-Size Equivalent Percent Location Specimen Temperature Energy Absorbed Energy Shear (%) (ft-lb) (ft-lb) 1 21 42 95 160 2 21 3 22 42 100 44 100 1 20 40 80 2 23 120 3 20 46 90 40 95 1 15 30 70 2 11 74 3 13.5 22 50 27 60 Pipe Body 1 8 16 40 2 11 50 3 10 22 50 20 50 1 2.5 5 10 0 2 5 3 3 10 10 6 10 1 3 6 0 -30 2 2.5 3 3 5 0 6 0 1 12 24 90 200 2 12.5 3 9 25 90 18 70 1 12.5 25 80 40 2 20 160 3 13 26 70 100 1 8.5 17 60 2 7.5 120 3 10 15 40 ERW Bondline 20 60 1 11 22 60 74 2 5 3 2.5 10 20 5 20 1 4.5 9 20 2 7 50 3 8 14 30 16 20 1 6 12 10 0 2 7 3 5.5 14 0 11 0 Page 59#

Page 110Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 7-1: West Joint pipe body CVN transition curve. Figure 7-2: West Joint ERW bondline CVN transition curve. Page 60#

Page 111Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 7-3: East Joint pipe body CVN transition curve. Figure 7-4: East Joint ERW bondline CVN transition curve. Page 61#

Page 112Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 8.0 STRAIN CAPACITY TESTING OF INTACT GIRTH WELD ADV also received two representative intact girth welds, one removed West of the Failure and one East of the Failure. Boardwalk reported these welds as original construction, therefore, welded to the same WPS with the same consumables. Boardwalk requested testing of the girth weld to better characterize the mechanical properties and strain capacity of the girth welds. Testing included dimensional analysis (See Section 8.1), non-destructive examination (see Section 8.2), tensile testing of the pipe and weld (see Section 8.3), CTODs per API 1104, Appendix A (see Section 8.4), metallographic examination and hardness mapping (see Section 8.5), Charpy V-notch testing of the weld metal and HAZ (see Section 8.6), chemical analysis of the weld metal (see Section 8.7), and tensile strain capacity calculations (see Section 8.8). 8.1 Dimensional Analysis ADV recorded the dimensions at the upstream and downstream end of the pipe material received. The diameter was measured with a Pi tape and the wall thickness was measured at eight evenly spaced locations around the circumference with a rounded tip micrometer. These results are summarized in Table 8-1 and are consistent with nominal 20-inch OD x 0.250-inch WT pipe. Girth weld mismatch was measured across the girth weld using a dial gage. The maximum mismatch (hi- lo) measured from the external surface from the West and East weld was 0.164 inch and 0.174-inch, respectively, which is outside the recommended maximum in API 1104 of 1/8-inch. Table 8-1: Pipe Dimensional Analysis Location Outside Diameter (in) Wall Thickness (in) High Low Average West of Fracture End 1 20.07 0.268 0.261 0.264 End 2 20.09 0.252 0.248 0.250 East of Fracture End 1 20.06 0.254 0.250 0.252 End 2 20.08 0.251 0.247 0.250 8.2 Non-Destructive Examination ADV contracted Integrity Assessment Group (IAG) to perform UT of the girth weld to API 1104. Areas of planar indications (such as incomplete penetration and crack-like features) and volumetric indications (such as slag and porosity) were identified. A table of the features identified in both girth welds are summarized in Table 8-2. ADV contracted Acuren Inspection, Inc. to perform RT of the girth weld to API 1104. Areas of incomplete fusion, incomplete penetration, and porosity were identified, outside the limits of the current edition of Page 62#

Page 113Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 API 1104. Images of the RT film are shown in Figure 8-1 and Figure 8-2. The feature locations were also utilized to ensure features were not present within the material selected for mechanical testing. The NDE reports (reader sheets and UT reports) are attached in Appendix F. The intact girth weld East of the Failure was selected for further mechanical testing due to fewer indications present within the weld metal. Page 63#

Page 114Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Table 8-2: Summary of Features Identified via UT Depth to # Type Position Start (in) End (in) Length (in) Depth to Bottom Height (in) Top (in) (in) West of Failure 1 Incomplete Penetration Internal 0.544 1.548 1.00 0.112 0.250 0.138 2 Lack of Fusion Internal 2.844 4.978 2.13 0.183 0.250 0.067 3 Incomplete Penetration Internal 5.103 7.404 2.30 0.189 0.250 0.061 4 Lack of Fusion Internal 7.478 11.995 4.52 0.162 0.250 0.088 5 Inclusions Mid-Wall 13.506 15.555 2.05 0.149 0.174 0.025 6 Incomplete Penetration Internal 16.601 21.035 4.43 0.173 0.250 0.077 7 Inclusions Mid-Wall 21.077 21.286 0.21 0.034 0.075 0.041 8 Incomplete Penetration Internal 21.453 21.83 0.38 0.189 0.250 0.061 9 Inclusions Mid-Wall 23.085 23.503 0.42 0.067 0.106 0.039 10 Crack Internal 25.046 36.005 10.96 0.078 0.250 0.172 11 Incomplete Penetration Internal 37.506 41.928 4.42 0.178 0.250 0.072 12 Incomplete Penetration Internal 48.798 62.95 14.15 0.201 0.250 0.049 East of Failure 1 Incomplete Penetration Internal 5.689 7.236 1.55 0.141 0.250 0.109 2 Incomplete Penetration Internal 8.659 8.868 0.21 0.205 0.250 0.045 3 Crack Internal 10.248 11.021 0.77 0.198 0.250 0.052 4 Inclusions Mid-Wall 13.297 13.84 0.54 0.107 0.159 0.052 5 Crack Internal 13.71 14.384 0.67 0.176 0.250 0.074 6 Crack Internal 16.936 19.069 2.13 0.144 0.250 0.106 7 Crack Internal 20.993 22.164 1.17 0.146 0.250 0.104 8 Inclusions Mid-Wall 23.545 24.005 0.46 0.152 0.184 0.032 9 Crack External 24.125 30.525 6.40 0.000 0.092 0.092 10 Incomplete Penetration Internal 36.209 37.339 1.13 0.198 0.250 0.052 11 Inclusions Mid-Wall 37.088 37.38 0.29 0.123 0.163 0.040 12 Porosity Mid-Wall 38.008 38.677 0.67 0.037 0.125 0.088 13 Lack of Fusion Internal 40.225 41.856 1.63 0.000 0.000 0.000 14 Incomplete Penetration Internal 44.951 45.704 0.75 0.217 0.250 0.033 15 Incomplete Penetration Internal 46.917 47.924 1.01 0.189 0.250 0.061 16 Inclusions Mid-Wall 50.217 50.384 0.17 0.165 0.205 0.040 17 Incomplete Penetration Internal 53.396 54.023 0.63 0.210 0.250 0.040 18 Incomplete Penetration Internal 58.541 62.807 4.27 0.186 0.250 0.064 19 Inclusions Internal 60.491 61.160 0.67 0.079 0.142 0.063 Page 64#

Page 115Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 8-1: RT images from intact weld West of Failure. Page 65#

Page 116Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 8-2: RT images from intact weld East of Failure. Page 66#

Page 117Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 8.3 Tensile Tests ADV performed tensile testing of the base pipe from both sides of the girth weld and two cross weld tensile tests around the circumference of the girth weld. The tensile straps were removed from the top of the pipe (12:00 o’clock orientation) and either the 3:00 o’clock orientation or 9:00 o’clock orientation guided by the RT images in an attempt to avoid flaws present. The cross-girth weld tensile tests were monitored via digital image correlation (DIC). DIC utilizes a defined speckle pattern applied to the viewing surface (in this case the through thickness weld profile) created through black and white spray paint to monitor displacement over a given time. Relationship between the starting pattern and how that pattern deforms relative to adjacent patterns is then later interpreted as strain. Two all weld metal tensiles were also performed from weld metal removed from approximately the 2:00 o’clock and the 5:00 o’clock orientation. The results were compared to the closest API 5L edition from the time of manufacturing: API 5LX, 3rd Edition (1951). API 5LX, Grade X52 was not included in the 3rd Edition, therefore, the properties would have been by agreement. The comparisons in the table below are based on API 5LX (1954), 5th Edition, which was the first edition to contain Grade X52. Tensile test (per ASTM A370) results, summarized in Table 8-3, are consistent with the requirements of API 5L, Grade X52 material. The all weld metal tensiles appear to be consistent with an E6010 consumable. Videos of the DIC tests were provided in a separate file and images are shown in Figure 8-3 and Figure 8-4. Both samples failed in the base material remote of the weld/HAZ. These results are considered further in the tensile strain capacity calculations. Table 8-3: Tensile Strength Results Sample Yield Strength (psi) Tensile Strength Elongation (psi) (%) Pipe Body, Longitudinal, Side 1 60,600 82,300 29.1 Pipe Body, Longitudinal, Side 2 57,600 75,300 28.7 API 5LX, Grade X52 3rd Edition (1951) 52,000 (min) 66,000 (min) 17.5 (min) Cross Girth Weld 1 --- 74,800 1 --- Cross Girth Weld 2 --- 75,300 1 --- All Weld Metal 1 (2:00) 49,200 70,300 23.8 All Weld Metal 2 (5:00) 57,400 78,800 30.9 Transverse, 1-1/2" wide reduced sections, 180° from the weld (Body), and across ERW weld 1 Failed in base material Page 67#

Page 118Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 8-3: DIC output from 12:00 o’clock cross weld tensile test. Page 68#

Page 119Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 8-4: DIC output from 12:00 o’clock cross weld tensile test. 8.4 Crack Tip Opening Displacements (CTODs) ADV contracted Anderson and Associates to perform Bx2B SE(B) CTODs notched in the weld HAZ and the weld centerline. These tests were performed at ambient temperature at three circumferential locations: 12:00 o’clock, 3:00 o'clock, and 6:00 o'clock orientation. The results are summarized in Table 8-4. The full report is attached in Appendix G. Table 8-4: CTOD Results Location CTOD (in) Average CTOD (in) 12:00 0.0088 HAZ 3:00 0.0047 0.0061 6:00 0.0049 12:00 0.0065 Weld Centerline 3:00 0.0063 0.0068 6:00 0.0075 Page 69#

Page 120Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 8.5 Girth Weld Macros and Hardness Testing ADV prepared two metallurgical cross sections of the intact girth weld, one at the 12:00 o’clock and one at the 3:00 o’clock orientation. These cross sections are shown in Figure 8-5 and Figure 8-9, respectively. Little to no mismatch (hi-lo) was identified in both cross sections. Areas of volumetric features were identified in both cross sections appearing consistent with slag (wagon tracks), with representative images from the 12:00 o’clock cross section shown in Figure 8-6 and Figure 8-7. An area of external undercut was also identified on the weld toe of the 12:00 o’clock cross section, shown in Figure 8-8. Full hardness maps were performed on the cross sections at a 500-gram load (HV0.5). Images of the hardness traverse are shown in Figure 8-10 and Figure 8-11, respectively. No evidence of widespread heat affected zone softening was identified. ADV further calculated a weld strength factor (weld strength / pipe strength) for each macro: approximately 1.0 for both welds. The full hardness reports are attached in Appendix H. External Surface See Figure 8-8 See Figure 8-6 See Figure 8-7 Internal Surface Figure 8-5: Photomicrograph of the 12:00 o’clock orientation. Etchant is 2% Nital; original magnification is 0.6x. Page 70#

Page 121Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 8-6: Photomicrograph of volumetric feature identified. Etchant is 2% Nital; original magnification is 50x. Figure 8-7: Photomicrograph of volumetric features identified. Etchant is 2% Nital; original magnification is 50x. Page 71#

Page 122Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 External Surface Figure 8-8: Photomicrograph of external undercut identified. Etchant is 2% Nital; original magnification is 50x. External Surface Internal Surface Figure 8-9: Photomicrograph of the 3:00 o’clock orientation. Etchant is 2% Nital; original magnification is 0.6x. Page 72#

Page 123Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 8-10: HV0.5 hardness map from the 12:00 o’clock orientation. Figure 8-11: HV0.5 hardness map from the 3:00 o’clock orientation. 8.6 Charpy V-notch Testing of Girth Weld Girth weld centerline and girth weld heat affected zone (HAZ), full wall thickness (0.180-inch) Charpy V- notch tests (per ASTM A370) were performed to generate a transition curve; results are summarized in Table 8-5. Charpy V-notch transition curves were generated using a hyperbolic tangent curve-fit (API 579, Annex 9F) and summarized in Figure 8-12 and Figure 8-13. Page 73#

Page 124Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Table 8-5: Charpy V-notch Results Absorbed Approx. Full-Size Equivalent Percent Location Specimen Temperature Energy Absorbed Energy Shear (%) (ft-lb) (ft-lb) 1 66 19.5 42.7 100 2 0 22 48.2 100 Weld Centerline 3 -30 22 48.2 100 1 -60 22 48.2 100 2 -90 14 30.6 50 3 -110 9.5 20.8 40 1 120 29 63.5 100 2 66 22 48.2 60 3 0 23 50.3 60 Weld HAZ 1 -30 11.5 25.2 40 2 -60 3 6.6 20 3 -90 2 4.4 0 Figure 8-12: Girth weld centerline CVN transition curve. Page 74#

Page 125Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Figure 8-13: Girth weld HAZ CVN transition curve. 8.7 Chemical Analysis of Girth Weld ADV contracted Bryan Laboratory, Inc. to perform chemical analysis of the girth weld. Chemical analysis (per ASTM A751) results, summarized in Table 8-6, are consistent with the requirements of an E6010 or E7010 consumable. Page 75#

Page 126Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Table 8-6: Chemical Analysis Results Composition (%) Element Girth Weld AWS E6010 AWS E7010-P1 Carbon 0.09 0.20 (max) 0.20 (max) Manganese 0.31 1.20 (max) 1.20 (max) Phosphorus 0.005 --- 0.03 (max) Sulfur 0.02 --- 0.03 (max) Silicon 0.10 1.00 (max) 0.60 (max) Chromium 0.03 0.20 (max) 0.30 (max) Nickel 0.06 0.30 (max) 1.00 (max) Molybdenum 0.18 0.30 (max) 0.50 (max) Copper 0.12 --- --- Aluminum <0.01 --- --- Vanadium <0.01 0.08 (max) 0.10 (max) Titanium 0.01 --- --- Niobium <0.01 --- --- Boron <0.001 --- --- 8.8 Calculated Tensile Strain Capacity (TSC) ADV followed PRCI SIA-1-7 to estimate the TSC of the weld at MAOP (475 psig) and the failure pressure (400 psig), which contains a 0.67 safety factor. The assumptions utilized in the calculations are shown in Table 8-7 and Table 8-8, respectively. These assumptions were based upon the test results described in the subsections above. Load cases 1 and 2 are based on a flaw length of 51 mm with a depth of 4.3 mm, which is the maximum allowable aspect ratio (51/4.3≈12) allowable within PRCI SIA-1-7. Load cases 3-6 are based on an average flaw length from a review of the RT images with depths ranging from 2.5-4.3 mm. Load case 7 and 8 is based on a length of 15 mm and a depth of 2.5 mm based on smaller features identified via NDE. It should be noted that that the TSC will vary based on the individual flaw dimension and misalignment identified on any specific weld. PRCI SIA-1-7 does not allow for features greater than 12 times longer than they are deep (referred to as an aspect ratio), therefore, some of the longer features observed via RT and metallography are outside these calculations. This includes the 26-inch-long incomplete penetration feature identified on the failed weld, which was not captured in these calculations. Confirmation of the tensile strain capacity via alternative methods may be warranted due to the density of features present. Additionally, all cross weld tensile tests failed in the base pipe remote of the HAZ or weld metal when a flaw was not present. Page 76#

Page 127Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Table 8-7: Tensile Strain Capacity Inputs and Results at MAOP (475 psig) Input Case 1 2 3 4 5 6 7 8 Pipe OD (in) 20 Pipe WT (in) 0.250 Pipe Grade Grade X52 (52,000 yield) Pressure Factor 0.365 (MAOP, 475 psi) Misalignment (mm) 0.8 1.6 0.8 0.8 1.6 1.6 0.8 1.6 Weld Strength Factor 1.0 Flaw Length (mm) 51 30 15 Flaw Depth (mm) 4.3 2.5 4.3 2.5 4.3 2.5 CTOD (mm) 0.15 (Avg), 0.12 (Low) Apparent Toughness, CTODa (mm) 0.45 Result (TSC %) 0.56 0.51 1.2 0.92 0.83 0.82 >2.0 1.4 These results are representative of the feature length/depth above. These do not represent the flaws found during the metallurgical examination. Table 8-8: Tensile Strain Capacity Inputs and Results at Failure Pressure (400 psig) Input Case 1 2 3 4 5 6 7 8 Pipe OD (in) 20 Pipe WT (in) 0.250 Pipe Grade Grade X52 (52,000 yield) Pressure Factor 0.308 (Failure Pressure, 400 psi) Misalignment (mm) 0.8 1.6 0.8 0.8 1.6 1.6 0.8 1.6 Weld Strength Factor 1.0 Flaw Length (mm) 51 30 15 Flaw Depth (mm) 4.3 2.5 4.3 2.5 4.3 2.5 CTOD (mm) 0.15 (Avg), 0.12 (Low) Apparent Toughness, CTODa (mm) 0.45 Result (TSC %) 0.59 0.53 1.2 0.96 0.87 0.85 >2.0 1.4 These results are representative of the feature length/depth above. These do not represent the flaws found during the metallurgical examination. Page 77#

Page 128Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 9.0 DISCUSSION The observed failure occurred at an original construction girth weld. The observed ovality at the fractures is consistent with how a pipe would fail in tension and/or bending. The circular shape would begin to contract along the minor axis once sufficient axial load is applied. Once initial fracture has occurred, additional tensile load would act to further fracture the pipe circumference. In this case, the failure origin was identified to have occurred along the 26-inch-long x 0.120-inch deep (48% of nominal wall thickness) incomplete penetration feature, which coincided with the minor axis of the ovality measured. The presence of this incomplete penetration feature was confirmed via visual examination, SEM examination, metallography, and hardness mapping. A metallurgical cross section prepared at the 12:00 o’clock orientation contained a prior root gap of approximately 0.25-inch. Therefore, it seems likely that the fit- up of this girth weld was poor leaving the land/bevel in contact along the bottom of the pipe resulting in the inability to penetrate the full wall thickness. Based on the year of construction, ADV reviewed ASA B31.1 (1951) as this was prior to development of ASME B31.8 for gas pipelines. ASA B31.1 (1951), Section 631 states that weld inspection would have been by agreement with no specified amount of required inspection. A summary of the indications and their acceptance criteria is shown in Table 9-1. All three welds (failed and two intact welds) would not have meet current or prior API 1104 acceptance criteria. Table 9-1: Summary of Acceptance Criteria Feature Acceptance Criteria Lack of Penetration Individual: 1 inch long Aggregate Length: 1 inch long in a 12 inch portion of weld Lack of Fusion Individual: 1 inch long Aggregate Length: 1 inch long in a 12 inch portion of weld Burn Through Individual: 3/4 inch long Aggregate Length: 1.5 inch long in a 12 inch portion of weld Elongated Slag Inclusions Individual: 2 inch long Aggregate Length: 2 inch long in a 12 inch portion of weld Isolated Slag Inclusions Individual: 1/8 inch long Aggregate Length: 1 inch long in a 12 inch portion of weld Cracks None Page 78#

Page 129Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 10.0 CONCLUSIONS ADV concluded the following as the result of this examination: 1. The subject failure occurred due to an applied tensile/bending load, which resulted in plastic deformation along the minor axis of the observed ovality, and eventually propagated in the weld metal around the remaining circumference. 2. The subject failure origin coincided with a 26-inch-long x 0.120-inch deep (48% of nominal wall thickness) incomplete penetration feature identified along the bottom of the pipe. The majority of the remaining fracture appeared consistent with ductile overload. 3. Strain capacity calculations were performed; however, these results are based on the matrix of feature sizes examined. Features found during the metallurgical examination and those potentially found in the field may exceed this and therefore may limit the applicability of the resultant strain capacity calculations. 4. All welds examined would have failed API 1104 workmanship criteria; however, NDE was not required by industry codes at the time construction. 5. Mechanical properties of the pipe examined were consistent with API 5LX, Grade X52 material. Page 79#

Page 130Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 APPENDIX A: CHAIN OF CUSTODY Page 80#

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Page 133Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 APPENDIX B: OVALITY CROSS SECTIONS Page 83#

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Page 151Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Page 101#

Page 152Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 APPENDIX C: MATCH FRACTURE HARDNESS REPORT Page 102#

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Page 174Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 Page 124#

Page 175Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 APPENDIX D: ERW HARDNESS REPORTS Page 125#

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Page 183Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 APPENDIX E: CHEMICAL ANALYSIS REPORT Page 133#

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Page 185Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 APPENDIX F: NDE REPORT Page 135#

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Page 223Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 APPENDIX G: CTOD REPORT Page 173#

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Page 233Index 381 Failure Analysis 100785-RP01-RevB-032823 Boardwalk Pipelines, LP March 2023 APPENDIX H: INTACT HARDNESS TESTING REPORT Page 183#

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Page 266Appendix E. Root Cause Failure Investigation Report – Index 381 RCA Final Report, ADV Integrity, Inc., March 2024#

Page 267Index 381 RCA Final Report Prepared for Boardwalk Pipelines, LP 100785-RP02-Rev1-032124 March 2024#

Page 268Index 381 RCA Final Report Prepared for Boardwalk Pipelines, LP Houston, TX March 2024 Prepared by: Reviewed by: Cary Windler, PE David Futch, PE cary.windler@advintegrity.com david.futch@advintegrity.com 100785-RP02-Rev1-032124 Rev Date Description Prepared Checked Reviewed 0 06.05.2023 Issued for Review CBW --- DBF 1 03.21.2024 Issued for Use CBW --- DBF Texas Registered Engineering Firm F-19081 www.advintegrity.com#

Page 269Thursday, March 21, 2024 100785-RP02-Rev1-032124 Rodney Clayton, Materials Integrity Supervisor Boardwalk Pipelines, LP 9 Greenway Plaza, Suite 2800 | Houston, TX 77046 Rodney, Enclosed is our root cause analysis (RCA) relating to the recent failure that occurred on the 20-inch natural gas pipeline Index 381 near Jackson, Mississippi. During the RCA process, conversations were held with multiple Boardwalk Pipelines, LP, and Gulf South Pipelines Company, LLC, personnel as well as representatives from the geohazard analysis contractor, Geosyntec Consultants, and historical data was reviewed. In conjunction with this RCA report, ADV Integrity (ADV) also completed a separate metallurgical failure analysis of the failed segment of Index 381 (report number: 100785-RP01-RevB- 032823). This report provides the observations and recommendations based on the RCA, which includes information gathered from the Index 381 metallurgical failure report, geohazard analysis reports by Geosyntec Consultants, Bending Strain Review reports by D2 Integrity, ILI reports by Entegra and Rosen, as well as other data provided by Boardwalk. As a result of the RCA effort three causal factors, seven root causes and six recommended corrective actions were identified. Thank you for the opportunity to complete this work and please do not hesitate to contact us with any questions. Regards, David Futch, PE | Director – Materials Engineering ADV Integrity, Inc. 4027 Pinehurst Meadow | Magnolia, TX 77355 Office: (832) 409-4529 | E-mail: david.futch@advintegrity.com Texas Registered Engineering Firm F-19081 Prepared by: Cary Windler, PE | Staff Consultant#

Page 270Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 CONTENTS 1.0 Executive Summary ........................................................................................................................... 4 2.0 Introduction and Background ........................................................................................................... 7 3.0 Definitions and Abbreviations .......................................................................................................... 8 4.0 Root Cause Analysis and findings.................................................................................................... 11 4.1 RCA Approach ............................................................................................................................. 11 4.2 Timeline Overview ...................................................................................................................... 11 4.3 Overview of Potential Causal Factors ......................................................................................... 14 4.3.1 US Silica slope stability remediation efforts at retention pond berm ................................ 14 4.3.2 Results of bending strain and pipeline movement analysis................................................ 24 4.3.3 Land Patrol training for Gulf South personnel .................................................................... 25 4.3.4 Land Patrol guidance documents regarding earth movement ........................................... 26 4.3.5 Communications between Operations and Asset Integrity ................................................ 28 4.3.6 Communications between US Silica and Gulf South ........................................................... 28 4.4 Additional Factors of Interest ..................................................................................................... 28 4.4.1 Routine IMU analysis for bending strain and pipeline movement ..................................... 28 4.4.2 Hydrostatic pressure test in 2019 ....................................................................................... 29 4.4.3 The root cause of the destabilized slope or earth movement at US Silica retention pond berm 29 4.5 Causal Factors and Root Causes.................................................................................................. 30 4.6 Recommendations and Corrective Actions ................................................................................. 31 5.0 Conclusions ..................................................................................................................................... 33 APPENDIX A: Detailed Index 381 Timeline ......................................................................................... 34 Page 2#

Page 271Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 LIST OF FIGURES Figure 1: US Silica slope remediation work in 2020. ................................................................................... 12 Figure 2: Index 381 timeline of significant activity. .................................................................................... 13 Figure 3: US Silica retention pond berm conditions in 2002. ..................................................................... 15 Figure 4: US Silica retention pond berm conditions in 2004. ..................................................................... 15 Figure 5: US Silica retention pond berm conditions in 2005. ..................................................................... 16 Figure 6: US Silica retention pond berm conditions in 2010. ..................................................................... 16 Figure 7: US Silica retention pond berm conditions in 2017 & 2018. ......................................................... 17 Figure 8: US Silica retention pond berm conditions in early 2019. ............................................................ 17 Figure 9: US Silica remediation efforts in early 2020. ................................................................................. 18 Figure 10: Evidence of erosion in late 2020. ............................................................................................... 19 Figure 11: Evidence of erosion in late 2020 (zoomed in). .......................................................................... 19 Figure 12: Late 2021 remediation efforts. .................................................................................................. 20 Figure 13: September 2022 remediation efforts. ....................................................................................... 21 Figure 14: General overview of conditions observed on 2/16/2023. ......................................................... 22 Figure 15: Looking upslope (north) at transition from landslide lateral boundary to the head scarp. The top of the pond berm is at the top of the photo. ....................................................................................... 23 Figure 16: Looking east across the head scarp and graben. Graben measured between 15 feet on east side to 36 feet wide on west side. (Yellow dashed line is approximate pipeline location. ....................... 23 Figure 17: Looking east, recently formed landslide toes, collectively total about 6 feet high. This toe is located about 30 feet south of the ROW. ................................................................................................... 24 Figure 18: Horizontal bending strain changes between 2017 and 2021. ................................................... 25 Figure 19: Horizontal pipeline movement between 2017 and 2021. ......................................................... 25 Page 3#

Page 272Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 1.0 EXECUTIVE SUMMARY On February 12, 2023, Gulf South Pipelines Company, LLC (Gulf South), a subsidiary of Boardwalk Pipelines, LP, (Boardwalk) natural gas pipeline Index 381 failed at a girth weld (GW) at station number 6180+60, near Jackson, MS. This segment of Index 381 was constructed in 1952 using nominal 20-inch OD x 0.250-inch WT, direct current electric resistance welded (DC-ERW), Grade X52 pipe manufactured by Youngstown Sheet & Tube. Metallurgical analysis determined the failure coincided with a 26-inch long segment of incomplete penetration in the ID portion of the failed GW. Due to longitudinal stresses resulting from nearby earth movement, a fracture initiated at the incomplete penetration feature and propagated towards the OD until the remaining ligament failed due to ductile overload. Note: The retention pond was originally built by BASF in the late 1950s or early 1960s. Through sales and acquisitions, the plant and retention berm have been owned and operated by US Silica since 2018. For simplicity, the retention berm will be referred to as the “US Silica retention pond” in this report and represent all previous Jackson Plant owners and operators (BASF, EP Minerals, and US Silica). The earth movement occurred at the US Silica retention pond berm, an area roughly 160 feet to 560 feet west of the failure location. There is evidence of earth movement and soil stability remediation efforts by US Silica dating back as far as 2003. Satellite imagery of the US Silica retention pond berm and Index 381 ROW is not available prior to 2003. Other than One-Call ticket submissions, US Silica does not coordinate any soil stability remediation efforts with Gulf South Operations personnel. All remediation activities by US Silica appear to have taken place north of the ROW on the berm and not on the ROW itself. Land patrols and aerial patrols have noted the US Silica slope stabilization/remediation work over the years. Since none of the earth movement indications or slope remediation activities were on the Index 381 ROW, they were not included in the OMS system or the Form 5000-30 Land Patrol Report. Aerial patrols did report slope remediation efforts using the Form 5000-34 Aerial Patrol Report and Operations responded to these reports in a timely manner. Current patrol requirements outlined in Common Covered Task OQ-701 Patrolling Pipeline & Leak Survey without Instrument, OM-NG 5010 Surveillance Program and Leak Surveys, and Boardwalk’s Class 1 and 2 Land Patrols Task List (Natural Gas), do not emphasize visual inspection for possible geohazards outside the ROW. Based on this Root Cause Analysis (RCA), three Causal Factors, seven Root Causes and six Corrective Actions were identified. The Causal Factors, Root Causes and Corrective Actions are listed below. Not all recommended corrective actions may need to be implemented since implementation of one corrective action may make another one ineffective and/or unnecessary. Causal Factors: 1. CF1 – The girth weld at the failure location was constructed in 1952 with a 26-inch long incomplete penetration feature. Page 4#

Page 273Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 2. CF2 – An area of earth movement located at the US Silica retention pond berm affected the Index 381 ROW. 3. CF3 – Gulf South personnel were not aware of the earth movement issues affecting the Index 381 ROW at the US Silica retention pond berm area. Root Causes: • RC1 – The conditions present during the creation of the girth weld, including the welder and the fit-up, resulted in weld flaws. • RC2 – It is unlikely an NDE inspection was made of this weld in 1952 since it was not required by industry standards or regulations. • RC3 – The US Silica retention pond berm is unstable and US Silica efforts to stabilize the slope have been inadequate. • RC4 – US Silica personnel did not communicate with Gulf South personnel about the ongoing earth movement problems at the retention pond berm area. • RC5 – CCT701 Training Guide and Boardwalk’s Class 1 and 2 Land Patrol Task List (Natural Gas) guidance do not adequately describe earth movement indications, include an observation task specific to earth movement, or emphasize observations off of, but near, the ROW. • RC6 – OM-NG 5010 Surveillance Program and Leak Surveys guidance does not adequately specify what response is required when certain hazards are identified. • RC7 – OM-NG 5010 Surveillance Program and Leak Surveys guidance does not adequately address earth movement issues or hazards near, but off of, the ROW. Recommended Corrective Actions: 1. CA1 – The requirements for welder qualification and NDE of girth welds are now well established in both industry standards and federal and state regulations.  No further action required. 2. CA2 – Improve communications between US Silica personnel and Gulf South Gulf South personnel.  Gulf South Operations and/or Asset Integrity personnel need to collaborate in the slope stabilization remediation effort and pipeline safety activities at the US Silica retention pond berm area.  This corrective action will not be necessary if Index 381 remains out of service at the US Silica retention pond berm location. Page 5#

Page 274Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 3. CA3 – Asset Integrity should consider shorter reassessment intervals for ILI technology assessments for the segment of Index 381 which includes the US Silica retention pond berm area.  Significant pipe movement and bending strain changes occurred between the 2017 and 2021 IMU tool runs.  The interval between IMU runs and analysis will be dependent on the earth movement activity occurring at the US Silica retention pond berm area.  IMU based bending strain and pipeline movement analyses should be completed during each ILI assessment.  This corrective action will not be necessary if Index 381 remains out of service at the US Silica retention pond berm location. 4. CA4 – Update OM-NG 5010 Surveillance Program and Leak Surveys guidance document.  OM-NG 5010 needs to include more information about the evidence of and impacts of earth movement – both on the ROW and adjacent to the ROW.  OM-NG 5010 updates should include guidance on what response is required if any earth movement issues are noted on or near the ROW. 5. CA5 – Provide training to Boardwalk Operations personnel on identification of geohazards.  Training should include specific information about signs of and indications of earth movement. Photos or diagrams of scarps, grabens and toes would be beneficial.  Training should include guidance that patrol observations need to extend beyond the ROW boundaries for issues like earth movement. 6. CA6 – Update Boardwalk’s Class 1 and 2 Land Patrol Task List (Natural Gas).  Task List needs to specify earth movement as one of the required observation tasks.  Include guidance for observations of earth movement indications both on the ROW and adjacent to the ROW.  Review Boardwalk’s Class 3 and 4 Land Patrol Task List (Natural Gas) to determine if similar updates are needed. Page 6#

Page 275Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 2.0 INTRODUCTION AND BACKGROUND Boardwalk contracted ADV Integrity, Inc. (ADV) to perform a root cause analysis (RCA) on a recent pipeline failure which occurred on a natural gas transmission pipeline known as Index 381. Index 381 is a 20-inch OD pipeline constructed in 1952. The failure occurred near Jackson, Mississippi (station number 6180+60; GPS coordinates 32.262984, -90.199278) on February 12, 2023. ADV performed a metallurgical failure analysis on the Index 381 failure and this report further examines potential root causes for this failure. Note: The retention pond was originally built by BASF in the late 1950s or early 1960s. Through sales and acquisitions, the plant and retention berm have been owned and operated by US Silica since 2018. For simplicity, the retention berm will be referred to as the “US Silica retention pond” in this report and represent all previous Jackson Plant owners and operators (BASF, EP Minerals, and US Silica). Index 381 was originally installed in 1939 as an 18-inch OD pipeline. Due to planned construction by BASF (now US Silica) at their Jackson, MS, plant, a short segment of Index 381 was rerouted in 1952 using nominal 20-inch OD x 0.250-inch WT, direct current electric resistance welded (DC-ERW), API 5L Grade X52, pipe material manufactured by Youngstown Sheet and Tube. The failure occurred approximately 160 feet from the western edge of the US Silica retention pond berm, located at the US Silica Jackson Plant. Based on onsite investigations immediately after the failure, evidence of earth movement was observed at the US Silica retention pond area. To determine the underlying cause of the failure at this location, an RCA was performed by ADV to determine the root cause(s) leading to the failure and corrective actions necessary to reduce the likelihood of repeat failures in the future. Gulf South personnel and representatives from the geohazard assessment contractor were interviewed and historical data was reviewed during the RCA process. ADV also subcontracted D2 Integrity to perform a review of 2017 and 2021 IMU data to evaluate bending strains and pipe movement at the failure location. The results of the RCA are included in this report. This RCA primarily focused on investigating the physical causes of the failure – rather than any human factors or procedural issues – however, a high-level review of select guidance documents and training was performed. Page 7#

Page 276Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 3.0 DEFINITIONS AND ABBREVIATIONS BASF: The owner and operator of the Jackson Plant during the 1950’s when then retention pond berm was constructed. The plant and retention pond berm are now owned and operated by US Silica. Berm: an embankment; for this report, an earthen dam retaining the contents of a pond. Brow Ditch: a ditch constructed to intercept and convey minor surface drainage runoff. Causal Factor: actions which directly lead to or cause an incident; or fail to minimize the consequences once an incident has begun. (TapRooT® definition: a mistake, error, or failure that directly leads to (or causes) an incident, or fails to mitigate the consequences of the original error.) Corrective Action: an action which will minimize the likelihood of the reoccurrence of a root cause or minimize the effects if the root cause does reoccur. Critical Covered Task (CCT): an activity identified by the operator that: 1. Is performed on a pipeline facility; 2. Is an operations or maintenance task; 3. Is performed as a requirement of 49 CFR 192; and 4. Affects the operation or integrity of the pipeline. Defect: a physically examined anomaly with dimensions or characteristics that exceed acceptable limits. Electric-resistance welded (ERW) pipe: pipe having one longitudinal seam produced by low or high frequency electric resistance welding. Also see high-frequency electric-resistance welded. Environment: surroundings or conditions (physical, chemical, mechanical) in which a material exists. Evaluation: a review following the characterization of an actionable anomaly to determine whether the anomaly meets specified acceptance criteria. Failure: general term used to imply that a part in service has become completely inoperable; is still operable but is incapable of satisfactorily performing its intended function; or has deteriorated seriously to the point that it has become unreliable or unsafe for continued use. Head scarp: the upper most or starting scarp of a landslide area. Hydrostatic test or hydrostatic pressure test: a pressure test using water as the test medium. Incident: unintentional release of gas and/or produced liquids due to the failure of a pipeline. Page 8#

Page 277Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 Incomplete Penetration: incomplete filling of the weld root during the welding process; also known as inadequate penetration. Inertial tool: an ILI tool equipped with an inertial measurement unit (IMU) or other mapping technology. Inertial measurement unit (IMU): see inertial tool. In-line inspection (ILI): steel pipeline inspection technique that uses devices known in the industry as intelligent or smart pigs. These devices run inside the pipe and provide indications of metal loss, deformation, and other defects. In-line Inspection (ILI) tools: any instrumented device or vehicle that records data and uses nondestructive test methods or other techniques to inspect the pipeline from inside. Also see in-line inspection. Integrity assessment: process that includes inspection of pipeline facilities, evaluating the indications resulting from the inspections, examining the pipe using a variety of techniques, evaluating the results of the examinations, characterizing the evaluation by defect type and severity, and determining the resulting integrity of the pipeline through analysis. Landslide: the naturally occurring or human-caused downward (or downslope) movement of a mass of soil or rock due to gravity. Landslide Toe: the toe of a landslide marks the end of the moving material; the runout or maximum distance travelled of the landslide. Leak: unintentional escape of gas or produced liquid from the pipeline. May: used to denote permission, and is neither a requirement or a recommendation. Maximum Allowable Operating Pressure (MAOP): maximum pressure at which a natural gas pipeline system may be operated. On-the-Job Training (OJT): training or instruction for employees that takes place at work; typically involves a combination of observation and hands-on experience completing a task under supervision of a qualified instructor or mentor. Pressure test: a pipeline assessment method where the pipe is filled with a fluid, sealed, and subjected to a sufficiently high pressure. It is used to validate the integrity and detect construction defects, manufacturing defects, and defective materials. Qualification: demonstration and documented knowledge, skills, and abilities, along with documented training and/or experience required for personnel to properly perform the duties of a specific job or task. Page 9#

Page 278Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 Root Cause: actions or lack of actions that directly lead to a Causal Factor. (TapRooT® definition: the absence of a best practice or the failure to apply knowledge that would have prevented the problem, or significantly reduced its likelihood or consequences.) Root Cause Analysis (RCA): family of processes implemented to determine the primary cause of an event. These processes all seek to examine a cause-and-effect relationship through the organization and analysis of data. Such processes are often used in failure analyses, TapRooT® is one example of these processes. Rupture: complete failure of any portion of the pipeline that allows the product to escape into the environment. Scarp: a region of steep (nearly vertical) exposed soil and rock at the head of a landslide where the failure surface ruptures the ground surface; a feature that identify active or recently active landslides. Toe: see Landslide Toe. US Silica: The current owners and operators of the Jackson Plant, including the retention pond and berm. For this report, the term “US Silica” will collectively represent all known historical owners of the Jackson Plant (BASF, EP Minerals and US Silica) for the period from 1939 to May 2023. Water Bar: see Brow Ditch. Page 10#

Page 279Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 4.0 ROOT CAUSE ANALYSIS AND FINDINGS 4.1 RCA Approach This RCA was completed primarily by ADV personnel. Gulf South personnel were collaborated with throughout the process. The primary RCA participants were: • Rodney Clayton – Boardwalk Pipelines, LP, Materials Integrity Supervisor • David Futch – ADV Integrity, Director of Materials Engineering • Cary Windler – ADV Integrity, Staff Consultant The RCA process was based on the System Improvements TapRooT® methodology. During the RCA data gathering process, conversations were held with multiple Gulf South employees and representatives from the geohazard assessment contractor, and historical Gulf South information was reviewed. The data used was entirely from Gulf South historical archives (including third-party reports prepared at the request of Boardwalk) and assumed to be accurate based on the information known at the time the data was captured. A site visit was not performed as the failure location attributes were well documented in the Geohazard Assessment Memorandum produced by Geosyntec Consultants (Geosyntec). Based on the information gathered during the RCA, the ADV Failure Analysis Report (ADV report number 100785-RP01- RevB-032823), two geohazard analysis memorandums by Geosyntec, the Bending Strain Review reports by D2 Integrity, the 2017 Entegra ILI report and data, the 2021 Rosen ILI report and data and Gulf South historical information, there is significant earth movement activity at the US Silica retention pond berm area which is affecting Index 381. This RCA focuses on Index 381 at the failure location and the retention pond berm area, but not the entirety of Index 381. It is possible some recommended Corrective Actions may be appropriate for other segments of Index 381 and/or other pipelines within the Gulf South pipeline system. 4.2 Timeline Overview Index 381 was originally constructed in 1939 but the failure location was part of a 1952 reroute. The reroute was due to planned construction by BASF (now US Silica), which included the construction of a retention pond with a berm (earthen dam) to contain the pond water. At least as far back as 2003, US Silica has been conducting sporadic slope stabilization efforts along the south side of the berm. Based on aerial imagery, the most recent slope stabilization/remediation efforts were in 2020, 2021 and 2022. Index 381 ROW follows along the southern base of the berm for approximately 1,000 feet. The slope remediation activities by US Silica were not on the ROW, but adjacent to the ROW on the actual berm (northern edge of ROW). See Figure 1 for an example of remediation activity in 2020. Gulf South’s knowledge of US Silica’s slope remediation activities was limited to One-Call submissions by the contractors performing the work for US Silica. Page 11#

Page 280Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 Figure 1: US Silica slope remediation work in 2020. In 2017, Gulf South contracted with Entegra to perform an ILI assessment of this 24-mile segment of Index 381. The Entegra ILI tool included HR-MFL, HR Deformation and HR IMU technologies, all combined into one tool run. No girth weld (GW) defects were reported by the HR-MFL tool. In 2019, Gulf South performed a hydrostatic pressure test to 760 psig, which is 1.6 times the MAOP (475 psig). No pressure test failures were noted in the vicinity of the failure location. In 2021, Gulf South contracted with Rosen to perform a second ILI assessment of the 24-mile segment of Index 381 containing the failure location. The Rosen ILI tool included HR-MFL, HR Deformation and HR IMU technologies, but divided into two separate tool runs. The deformation and IMU tool were run together and then the HR-MFL tool was run on a second run. No GW anomalies were reported by Rosen and bending strain and pipe movement analyses were not requested by Gulf South until after the failure. On February 12, 2023, approximately 160’ east of the edge of the berm, a girth weld (GW) failed. The failure resulted in a 14.5-inch longitudinal gap at the GW as the pipe segments pulled away from each other due to forces acting in the longitudinal direction. An abbreviated timeline of events for Index 381 is summarized in Figure 2 (See Appendix A for a more detailed timeline of activities). Page 12#

Page 281Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 Figure 2: Index 381 timeline of significant activity. Page 13#

Page 282Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 4.3 Overview of Potential Causal Factors Metallurgical analysis of the GW failure was performed by ADV. The analysis identified a 26-inch long area of incomplete penetration in the failed GW, this feature was created at the time of construction in 1952. Geosyntec performed a geohazard assessment of the failure location. Geosyntec identified an area of earth movement at the US Silica retention pond berm, which is near the failure location. After the incident, Rosen performed a Bending Strain Level 1 Assessment and Pipeline Movement Assessment based on the 2017 and 2021 IMU data from the ILI runs. Gulf South also asked D2 Integrity to perform an independent Bending Strain Review using the IMU data from Rosen’s 2021 ILI run. This RCA will pull information from all of these sources, as well as personnel interviews and guidance reviews to determine the underlying root cause(s) for this incident and propose corrective actions to reduce the likelihood of reoccurrence. The RCA focused on the following areas: • US Silica slope stability remediation efforts at retention pond berm • Results of bending strain and pipeline movement analyses • Land Patrol training for Gulf South personnel • Land Patrol guidance documents regarding earth movement • Communications between US Silica and Gulf South Each of these areas were further examined as a function of this RCA. 4.3.1 US Silica slope stability remediation efforts at retention pond berm 4.3.1.1 Remediation efforts prior to 2020 It is unknown when US Silica first identified and attempted to remediate the earth movement on the retention pond berm. Google Earth satellite imagery as far back as 2005 shows evidence of previous remediation efforts. Based on satellite imagery, it appears US Silica performed a remediation effort prior to 2005 and again between 2007 and 2010 (See Figure 3 through Figure 6). Another remediation effort appears to have been attempted between 2017 and 2018 (see Figure 7). Page 14#

Page 283Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 Figure 3: US Silica retention pond berm conditions in 2002. Figure 4: US Silica retention pond berm conditions in 2004. Page 15#

Page 284Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 Figure 5: US Silica retention pond berm conditions in 2005. Figure 6: US Silica retention pond berm conditions in 2010. Page 16#

Page 285Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 Figure 7: US Silica retention pond berm conditions in 2017 & 2018. In 2019, additional evidence of continued earth movement and slope stability issues are evident. In January 2019 imagery, an area of earth movement is visible on the lower 1/3 of the berm and includes what appears to be a scarp and graben (see Figure 8). Also noticeable in Figure 8 is the appearance of earth movement on pond side of the berm, just uphill (north) of the scarp/graben feature. Figure 8: US Silica retention pond berm conditions in early 2019. 4.3.1.2 Remediation efforts between 2020 and 2022 During the three years preceding the failure, US Silica made at least three unsuccessful attempts to stabilize and remediate the earth movement issues at the retention pond berm area. These are Page 17#

Page 286Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 considered “unsuccessful” since the earth moved again between the last attempted remediation in September 2022 and the failure in February 2023. In early 2020, US Silica conducted a soil stabilization project on the retention pond berm. Figure 9 shows significant construction activity. Also notice the area of movement on the pond side of the berm is still evident, and possibly increased slightly. Figure 9: US Silica remediation efforts in early 2020. By November 2020, less than a year later, significant erosion can be seen at the 2020 remediation site. Figure 10 shows the general berm area and Figure 11 shows a close up of the erosion. Notice in Figure 10 that the pond side earth movement appears more distinct and perhaps larger. Page 18#

Page 287Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 Figure 10: Evidence of erosion in late 2020. Figure 11: Evidence of erosion in late 2020 (zoomed in). By November 2021, US Silica had remediated the erosion area and added a brow ditch (also called a water bar) to divert rain water from flowing directly down the berm towards the ROW. The brow ditch, seen in Page 19#

Page 288Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 Figure 12, does not traverse the entire berm length. It appears that water would be diverted onto the eastern and western portions of the berm. The eastern 1/3 of the berm is the area identified by Geosyntec as the landslide area in 2023. Notice in Figure 12 that the pond side earth movement has continued to slide into the pond and is more pronounced in late 2021. Figure 12: Late 2021 remediation efforts. In the timeframe between November 2021 and September 2022, US Silica undertook additional slope stabilization and water control measures. Figure 13 shows the area after the remediation efforts. US Silica added two rip-rap lined water run-off paths on the east and west sides of the brow ditch. This was likely done to minimize the erosion. Also in Figure 13 there is evidence of slope stabilization work on the pond side of the berm where the previous earth movement was observed. Earth movement issues on both sides of the berm, acting simultaneously and in near proximity, could indicate an increased geohazard threat in the US Silica retention pond berm area. Page 20#

Page 289Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 Figure 13: September 2022 remediation efforts. 4.3.1.3 Conditions at the time of and immediately after the failure On February 16, 2023, four days after the Index 381 failure, Geosyntec personnel performed a site visit to the failure location and nearby US Silica retention pond berm area. Geosyntec observed evidence of recent earth movement in the vicinity of berm but not at the immediate area around the failure location. By the time Geosyntec observed the ROW conditions heavy equipment had traversed the ROW enroute to the failure location. However, Gulf South personnel stated that no evidence of earth movement was observed on the ROW adjacent to the US Silica retention pond berm immediately after the failure. Geosyntec only observed indications of earth movement off of the ROW – scarps and a graben on the berm above the ROW and landslide toes in the woods below (or south of) the ROW. Figure 14, Figure 15, Figure 16 and Figure 17 are extracted from the Geosyntec Memorandum and provide a good summary of the conditions four days after the failure. Based on observations by Gulf South Operations personnel, US Silica installed blue tarps across portions of the earth movement area on the berm in the November-December 2022 timeframe. It is believed this was to prevent the recent heavy rainfall from soaking into the berm soil. Geosyntec also observed four slope inclinometers installed on the berm by US Silica. The slope inclinometer standpipes were damaged by the recent earth movement and did not appear to be functioning as intended. However, in the days after the failure, Terracon personnel (likely a geohazard consultant hired by US Silica) was on-site and taking readings from the inclinometers. The full details of the Geosyntec observations and conclusions can be found in the March 8, 2023, Geosyntec Memorandum for Geohazard Assessment. Page 21#

Page 290Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 Figure 14: General overview of conditions observed on 2/16/2023. Page 22#

Page 291Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 Figure 15: Looking upslope (north) at transition from landslide lateral boundary to the head scarp. The top of the pond berm is at the top of the photo. Figure 16: Looking east across the head scarp and graben. Graben measured between 15 feet on east side to 36 feet wide on west side. (Yellow dashed line is approximate pipeline location. Page 23#

Page 292Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 Figure 17: Looking east, recently formed landslide toes, collectively total about 6 feet high. This toe is located about 30 feet south of the ROW. 4.3.2 Results of bending strain and pipeline movement analysis Rosen performed a Bending Strain Level 1 and Pipeline Movement Assessment shortly after the incident. This analysis was based on a comparison of the 2017 Entegra IMU data and the 2021 Rosen IMU data. Rosen identified the US Silica retention pond area as a potential location for increased bending strain and for pipe movement. The bending strain was identified in the horizontal direction and calculated to be 0.242%. The pipe movement was calculated to be 1.93 feet (±1.31 feet). These were the only significant horizontal strains and pipe movement areas noted in the Rosen analysis of the area surrounding the US Silica retention pond berm. These calculations are based on the changes detected by the IMU tools between December 2017 (Entegra) and December 2021 (Rosen). There could have been latent pipe movement which preceded the 2017 Entegra IMU run. D2 Integrity performed an independent bending strain and pipe movement analysis utilizing the 2017 and 2021 IMU data provided by Gulf South. D2 Integrity’s analysis confirms horizontal bending strain and pipeline movement changed at the US Silica retention pond berm area between the 2017 and 2021 IMU runs. The horizontal bending strain increased by 0.132%, with a calculated value of 0.207% in 2021 (reporting threshold is 0.125%). The comparison between the 2017 and 2021 IMU runs also showed 2.9 feet of horizontal pipeline movement. Based on the D2 Integrity analysis, the data was available in 2017, and confirmed in 2021, to identify the retention pond berm area as an area recommended for additional on-site assessments. Figure 18 and Figure 19 show the horizontal bending strain and pipe movement changes in the US Silica retention pond berm area, based on the 2017 and 2021 IMU data. Page 24#

Page 293Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 Figure 18: Horizontal bending strain changes between 2017 and 2021. Figure 19: Horizontal pipeline movement between 2017 and 2021. 4.3.3 Land Patrol training for Gulf South personnel Gulf South personnel performing land patrols on a pipeline ROW must be qualified and current for Common Cover Task 701P (CCT701) Patrolling Pipeline and Leakage Survey without Instrument. Gulf South utilizes Veriforce to manage the CCT701 training, qualification and documentation. The Field Technician who performed the Land Patrols from 2018 to 2022 was current and qualified for CCT701. The Veriforce CCT701 Training Guide indicates the training and qualification for CCT701 is completed via on- the-job training (OJT). The CCT701 Training Guide seems to focus the training on the actual ROW and not the areas immediately adjacent to the ROW. Several examples from the Knowledge Tasks outlined in CCT701 are listed below. 4.3.3.1 Knowledge: Identify methods of pipeline patrol When discussing which methods of pipeline patrols are available (aerial patrol or ground patrol) the Training Guide states that “potential problems can arise within a right-of-way”. This wording implies the problems to be identified by pipeline patrols are limited to “within” the ROW. Page 25#

Page 294Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 4.3.3.2 Knowledge: Identify the items that may be observed while patrolling This Knowledge section of the Training Guide covers a variety of items which should be observed during the patrol. In the introduction to this section, the Training Guide emphasizes the importance to monitor and detect any changes “on the ROW” which could jeopardize the integrity of the pipeline. The wording of the Training Guide implies that only changes “on the ROW” can be an issue, and no mention is made of the areas adjacent to the ROW. “General conditions of the Right-of-Way” is one of the items that must be observed during the patrol. Notice that the wording draws the focus to the actual ROW and not the general area on and around the ROW. In this section about general conditions, the Training Guide does instruct the trainee to look for “soil slips, subsidence and soil erosion” over the buried pipeline. It does not define or provide pictures of soil slips, subsidence or erosion. It also focuses the trainees attention on the area “over the pipeline” which is perhaps even more restrictive than “on the ROW”, as used in other areas of the Training Guide. The General Conditions section also states that soil slips, subsidence and erosion can lead to exposed pipe and implies that pipe exposure is what jeopardizes the integrity of the pipeline. It does not mention that soil slips or earth movement can jeopardize the integrity of the pipeline with or without creating an exposure. An additional item covered in the General Conditions section is Exposed Pipe. The Training Guide lists “landslides” as one of the potential causes of pipe exposure. There is no mention of stresses on the pipeline due to landslides or earth movement. Again, the hazard from landslides is implied to be only related to exposed pipe. 4.3.3.3 On-the-job training The qualification process for CCT701 relies heavily on OJT. Earth movement issues are not normally a widespread issue, so most OJT pipeline patrol training sessions are unlikely to experience earth movement issues. This means the trainee may become qualified without seeing or experiencing any evidence of earth movement along or near the ROW. It does not appear that pictures of different hazardous phenomena are provided in the CCT701 training. The CCT701 qualification process appears to rely on the Training Guide information and whatever the trainee experiences or observes on the ROW during OJT. 4.3.4 Land Patrol guidance documents regarding earth movement The Boardwalk land patrol guidance documents consist of OM-NG 5010 – Surveillance Program and Leak Surveys (OM-NG 5010), as well as Boardwalk’s Class 1 and 2 Land Patrols Task List (Natural Gas) (Land Patrols Task List). These documents provide the guidance for Land Patrols and are required to be followed during the performance of Land Patrols. These two documents will be discussed separately. 4.3.4.1 OM-NG 5010 – Surveillance Program and Leak Surveys Surveillance Activities: The Surveillance Activities section includes “adjacent to the ROW” as part of the surveillance definition. The surveillance definition continues to include “earth movement” as one of the issues which could affect pipeline safety. Based on this section, land patrols should be observant for earth Page 26#

Page 295Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 movement adjacent to the ROW. This section is more of an overview and this information is not repeated clearly in the following, more detailed, sections of OM-NG 5010. Factors That May Require Frequency Change or Special Patrols: Landslides are mentioned in this section but are included in “other extreme geological events”. This implies that landslides are a major, or extreme, event and not a general area of earth movement. The landslide occurring at US Silica retention pond berm was a more general or localized landslide and an observer may not have considered it “extreme”. Performing Patrols: A list of issues which require Operations Personnel to continuously be observant for is provided. While this list is a “may include, but not limited to” type of list – it should be noted that the list does not include landslides or other geohazard related earth movement issues. The list does include “Areas of continual earth movement activities (i.e., gravel/sand pits, quarries, landfills, etc.)”. An area of “continual earth movement” does not appear to include naturally occurring geohazard type earth movement issues such as landslides. Documentation: For land patrols, documentation in OMS is required – but the use of Form 5000-30: Land Patrol Report for field data collection is optional. Performing Aerial Patrols: This section requires aerial patrol personnel to observe and immediately report land movement. Any issues noted during an aerial patrol shall be documented on the Form 5000-34: Aerial Patrol Form and followed-up by Operations personnel. Several instances of excavation activity by US Silica at the retention pond area were reported by aerial patrol personnel on the Form 5000-34. Each report was followed up by Operations personnel in a timely manner, and in most cases, Operations was already aware of the activity before the report. Other Issues Identified: If other issues (such as erosion) are noted by Operations, the issues can be annotated in the comments section of OMS. There are no requirements, other than documentation, if earth movement is observed on or near the ROW. In the case of the US Silica retention pond earth movement, Operations was aware of the US Silica slope stability remediation efforts but not aware of the slope stability issue. In the case of the US Silica retention pond issue, there does not appear to be any physical evidence or indications of earth movement on the ROW itself. All the earth movement indications or evidence was adjacent to the ROW, but not on it. 4.3.4.2 Class 1 and 2 Land Patrols Task List (Natural Gas) There is no mention of earth movement, landslides, or geohazards in the Land Patrols Task List. There is a mention of “erosion” in the 11th bullet point. The Land Patrol Task List needs to include a task to observe for landslides, fractures in the earth, or any other signs of earth movement. The Land Patrol Task List also needs to clarify that earth movement observations need to include both the ROW and the area adjacent to the ROW, as well as what response is required when signs of earth movement are identified. . The Page 27#

Page 296Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 Class 1 and 2 Land Patrol Task List does not include guidance to include any significant observations in the comments section of OMS. 4.3.5 Communications between Operations and Asset Integrity There is no requirement in OM-NG-5010 or the Land Patrol Task for Operations personnel to make notification to other departments if an earth movement issue is noted on or near the ROW. From historical records, Operations was aware of the slope stabilization rehabilitation efforts performed by US Silica over the years. It is difficult to know for certain, but it is unlikely, that Operations knew the exact magnitude of the slope stability issue that US Silica was attempting to correct. Based on information gained from Gulf South personnel, it does not appear that Asset Integrity personnel were aware of the slope stability issue that was affecting the ROW at the US Silica retention pond berm location. Better communications between Operations and Asset Integrity on the issue of earth movement would have increased Asset Integrity’s awareness of the situation. Asset Integrity had additional earth movement threat data available for analysis but did not perform the earth movement analysis due to lack of threat awareness. 4.3.6 Communications between US Silica and Gulf South Based on the historical imagery from Google Earth and summary in Section 4.3.1, it is apparent that US Silica has attempted to stabilize the slope on the retention pond berm since at least 2005. Other than One-Call ticket submissions, US Silica has not communicated any information regarding the slope stabilization efforts to current Gulf South Operations personnel. Due to the reorganizations of US Silica plant personnel after the EP Minerals and US Silica acquisitions in 2017 and 2018 communications were even more difficult, based on the perspective of Gulf South Operations personnel. Established relationships between Gulf South and US Silica personnel were severed due to significant US Silica plant personnel changes. Activities at the US Silica retention pond berm location need to be coordinated by both parties. The US Silica activities on the berm can impact the ROW at the base of the berm. It is also very likely that any pipe excavation activity by Gulf South along the ROW at the base of the berm would have a significant impact on the slope stability of the berm. 4.4 Additional Factors of Interest During the course of the RCA investigation, other areas of interest were considered, but determined not directly related to this incident or be beyond the control of Gulf South. Some of these factors are noteworthy and will be discussed briefly. 4.4.1 Routine IMU analysis for bending strain and pipeline movement The Asset Integrity group did not originally include IMU bending strain and pipe movement analyses in the original Purchase Order for Rosen’s 2021 ILI run. The IMU tool was run through the pipeline and Page 28#

Page 297Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 collected the required data but the analysis was not performed. The bending strain and pipeline movement analysis performed by D2 Integrity confirms that IMU data from both the 2017 and 2021 ILI runs was adequate to point to the US Silica retention pond berm as an area warranting further investigation. The decision by Asset Integrity to not perform the bending strain and pipeline movement analyses is a contributing factor for this incident. Without the knowledge about the active earth movement issue at the retention pond berm area, Asset Integrity lacked sufficient data to fully understand the threats present at this location. When patrols identify a possible geohazard, Asset Integrity should evaluate the geohazard threat and its potential impact on the integrity of the pipeline. If the geohazard threat is confirmed to exist, Asset Integrity should perform bending strain and/or pipe movement analyses whenever IMU data is available. The additional costs of the analyses should be weighed against the possibility of identifying a previously unknown earth movement threat acting upon the pipeline. In areas where the terrain elevations change frequently and visibility off of the ROW is limited, the benefits of the analysis may outweigh the cost. If the segment of Index 381 in the vicinity of the US Silica retention pond berm is returned to service, the recommendation is for Asset Integrity to monitor the US Silica retention pond area for signs of earth movement and adjust the reassessment interval, if necessary. If US Silica cannot permanently remediate the earth movement issues at the retention pond berm area, Asset Integrity should ensure that IMU technology is included in each ILI tool run and bending strain and pipe movement analysis is performed during the ILI run analysis. Currently, Gulf South is considering permanently abandoning the segment of Index 381 adjacent to the US Silica retention pond berm which would eliminate the geohazard risk and need for reassessment. 4.4.2 Hydrostatic pressure test in 2019 The hydrostatic pressure test performed in 2019 did not play a significant role in this incident since the GW failed due to longitudinal stresses. A pressure test provides a larger safety margin in the hoop or circumferential orientation of the pipeline versus the axial or longitudinal orientation. Based on the Poisson Effect for steel pipelines with fixed ends, the longitudinal stresses due to internal pressures are 30% of the hoop stresses. In the case of the Gulf South pressure test of Index 381, the maximum pressure test pressure was 760 psig and the MAOP was 475 psig. The pressure test increased the hoop stress by 22% of SMYS (or 11,440 psi) during the pressure test. In the longitudinal orientation, the stress increased by about 6.6% SMYS (or 3,422 psi). Unless the GW was within 3,422 psi of critical failure stress in the longitudinal direction, it would not have failed during the pressure test. Based on observations by Geosyntec, the earth movement was active in the weeks prior to the failure and the longitudinal stresses on the pipeline likely increased significantly during that span of time. 4.4.3 The root cause of the destabilized slope or earth movement at US Silica retention pond berm The actual root cause of the soil stability on the US Silica property at the retention pond berm was not analyzed. Full analysis would require access to all the geohazard data US Silica has accumulated over the Page 29#

Page 298Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 years. Based on the extensive history of slope stability remediation efforts by US Silica over the past 16+ years (see Section 4.3.1), stabilizing this particular slope may be beyond US Silica’s (or their geohazard contractor’s) capabilities. Unless US Silica successfully remediates the soil stability in the retention pond berm area, Index 381 will likely continue to experience additional longitudinal stresses due to earth movement if Index 381 is returned to service in this area. 4.5 Causal Factors and Root Causes The RCA evaluated the data and reports available, as well as conducted interviews with Gulf South and Geosyntec personnel. The RCA followed the TapRooT® methodology. The RCA focused primarily on the physical causes of the incident, however a high-level review of Land Patrol training and written guidance was included. There are three causal factors identified for this incident. There are a combined seven root causes for these three causal factors. Causal Factor #1: The girth weld at the failure location was constructed in 1952 with a 26-inch long incomplete penetration feature. • Root Cause #1: The conditions present during the creation of the girth weld, including the welder and the fit-up, resulted in weld flaws. o Metallurgical analysis revealed three consecutive girth welds were created with defects which would have failed API 1104 inspection criteria, if constructed today. • Root Cause #2 – It is unlikely an NDE inspection was made of this weld in 1952 since it was not required by industry standards or regulations. Causal Factor #2: An area of earth movement located at the US Silica retention pond berm affected the Index 381 ROW. • Root Cause #3 – The US Silica retention pond berm is unstable and US Silica efforts to stabilize the slope have been inadequate. o Evidence shows US Silica has been attempting to stabilize the slope on the retention pond berm for at least 16 years. Causal Factor #3: Gulf South personnel were not aware of the earth movement issues affecting the Index 381 ROW at the US Silica retention pond berm area. • Root Cause #4 – US Silica personnel did not communicate with Gulf South personnel about the ongoing earth movement problems at the retention pond berm area. o Other than One-Call tickets submissions, US Silica did not share information about the severity of the soil stability issues at the retention pond berm area. Page 30#

Page 299Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 • Root Cause #5 – CCT701 Training Guide and Boardwalk’s Class 1 and 2 Land Patrol Task List (Natural Gas) guidance do not adequately describe earth movement indications, include an observation task specific to earth movement, or emphasize observations off of, but near, the ROW. • Root Cause #6 – OM-NG 5010 Surveillance Program and Leak Surveys guidance does not adequately specify what response is required when certain hazards are identified. • Root Cause #7 – OM-NG 5010 Surveillance Program and Leak Surveys guidance does not adequately address earth movement issues or hazards near, but off of, the ROW. 4.6 Recommendations and Corrective Actions A total of six corrective actions were identified to address the root causes. Not all recommended corrective actions may need to be implemented since implementation of one corrective action may make another one ineffective and/or unnecessary. • Corrective Action #1: The requirements for welder qualification and NDE of girth welds are now well established in both industry standards and federal and state regulations. (RC1 and RC2) o No further action required. • Corrective Action #2 – Improve communications between US Silica personnel and Gulf South personnel. (RC3 and RC4) o Gulf South Operations and/or Asset Integrity personnel need to collaborate with US Silica in the slope stabilization remediation effort and pipeline safety activities at the US Silica retention pond berm area. o This corrective action will not be necessary if Index 381 remains out of service at the US Silica retention pond berm location. • Corrective Action #3 – Asset Integrity should consider shorter reassessment intervals for ILI technology assessments for the segment of Index 381 which includes the US Silica retention pond berm area. (RC3) o Significant pipe movement and bending strain changes occurred between the 2017 and 2021 IMU tool runs. o The interval between IMU runs and analysis will be dependent on the earth movement activity occurring at the US Silica retention pond berm area. o IMU based bending strain and pipeline movement analyses should be completed during each ILI assessment of Index 381 in the US Silica retention pond berm area. Page 31#

Page 300Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 o This corrective action will not be necessary if Index 381 remains out of service at the US Silica retention pond berm location. • Corrective Action #4 – Update OM-NG 5010 Surveillance Program and Leak Surveys guidance document. (RC6 and RC7) o OM-NG 5010 needs to include more information about the evidence of and impacts of earth movement – both on the ROW and adjacent to the ROW. o OM-NG 5010 updates should include guidance on notifications if any earth movement issues are noted on or near the ROW. • Corrective Action #5 – Provide training to Boardwalk Operations personnel on identification of geohazards. (RC5) o Training should include specific information about signs of and indications of earth movement. Photos or diagrams of scarps, grabens and toes would be beneficial. o Training should include guidance that patrol observations need to extend beyond the ROW boundaries for issues like earth movement. • Corrective Action #6 – Update Boardwalk’s Class 1 and 2 Land Patrol Task List (Natural Gas). (RC5) o Task List needs to specify earth movement as one of the required observation tasks. o Include guidance for observations of earth movement indications both on the ROW and adjacent to the ROW. o Review Boardwalk’s Class 3 and 4 Land Patrol Task List (Natural Gas) to determine if similar updates are needed. Page 32#

Page 301Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 5.0 CONCLUSIONS The failure of Index 381 on February 12, 2023, was the result of increased longitudinal stresses acting upon a GW containing a 26-inch long incomplete penetration feature. The incomplete penetration feature was the product of the welding process at the time of construction in 1952. The longitudinal stresses were created by earth movement acting across the ROW near the US Silica retention pond berm, approximately 160’ from the failure site. US Silica has attempted to remediate the earth movement feature several times in the past 16+ years, the most recent attempt was in September 2022. While Operations was aware of the US Silica earth movement rehabilitation efforts (via One-Call tickets), they were not aware of the exact nature of the earth movement severity. The 2023 scarp, graben and landslide toe were off of the ROW and on US Silica property. The ROW itself was void of any earth movement indications. In spite of the lack of earth movement indications, the ROW was moving towards the south and inducing bending strain and longitudinal stress on Index 381. On the morning of February 12, 2023, the longitudinal stresses exceeded the load bearing capacity of the GW, a fracture formed and grew until ductile overload occurred on the remaining ligament of the GW resulting in a pipeline failure. Records show that between 2018 and 2022 the Land Patrols of the earth movement area were accomplished by qualified Gulf South personnel, as required. Deficiencies were noted in the Land Patrol guidance document (OM-NG 5010) and Boardwalk’s Land Patrols Task List related to earth movement observation guidance. The Veriforce CCT701 Training Guide did not provide photographic examples of earth movement and relied solely on OJT to qualify individuals for Land Patrols. It is unlikely that many trainees happen to observe indications of earth movement during an OJT land patrol for qualification. The root cause analysis (RCA) investigation was not able to determine the exact mechanism creating the earth movement environment on the US Silica retention pond berm area. US Silica appears to have contracted with one or more geohazard consultants to develop a remediation plan. US Silica has not shared any geohazard information with Gulf South personnel. Until US Silica permanently stabilizes the slope (i.e. remediates the earth movement) at the retention pond berm area, the Index 381 pipeline will have a higher likelihood of increased longitudinal stress and bending strains due to earth movement if the pipeline returns to service in the US Silica retention pond berm location. A combination of the recommended corrective actions should be implemented by Gulf South to ensure Index 381 can maintain operational integrity. Not all recommended corrective actions may need to be implemented since implementation of one corrective action may make another one ineffective and/or unnecessary. Note: Currently, Gulf South has opted to keep the section of Index 381 in the immediate area traversing the US Silica retention pond berm isolated and out of service. Unless US Silica can provide evidence of permanent earth movement stabilization at the retention pond berm area, Gulf South should consider rerouting Index 381 away from the berm or keeping this short segment of Index 381 out of service indefinitely. Page 33#

Page 302Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 APPENDIX A: DETAILED INDEX 381 TIMELINE Page 34#

Page 303Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 • Index 381 originally constructed in 1939. • Due to planned BASF (now US Silica) construction, Gulf South reroutes a section of Index 381 in 1952. o Replacement segment between 6168+08 and 6188+06; ≈ 0.38 miles. o Original pipeline is 18” OD; reroute is 20” OD. o A 26” long section of incomplete penetration was created in failed GW during 1952 construction. • BASF (now US Silica) builds retention pond which includes a berm (dam) on the north side of the ROW. o Exact date of pond construction unknown, likely in 1959 or early 1960s. • As far back as 2003, satellite imagery shows cycles of ground disturbance and slope remediation at the retention pond berm location. o Most recent major slope remediation efforts in 2020 to 2022. o Erosion damage remediated in 2021. o Two areas of rip-rap added to improve drainage on south side of berm in 2022. o Rip-rap also added to pond side of berm to remediate a “leak in the pond” in 2022. • Aerial Patrols of ROW were completed regularly as an additional preventive and mitigative measure (P&MM) to the Class 1 and 2 land patrols. o Most recent aerial patrol completed on September 7, 2022.  Pilot B reported an “idle skidsteer” near US Silica pond.  Operator A confirmed skidsteer was at US Silica pond area and not on ROW.  The Form 5000-34 Aerial Patrol Report was used for documentation. The form was filled out by pilot on 9/7/2022 and Operations responded on 9/9/2022. o A prior aerial patrol (July 28,2022) also reported activity near the US Silica pond area.  Pilot reported “equipment active at dirt work” on Index 381, 0.5 mi. east of I-55.  Operations confirmed activity was US Silica “fixing levee” and reported having been onsite during the work.  The Form 5000-34 Aerial Patrol Report was used for documentation. The form was filled out by pilot on 7/28/2022 and Operations responded on 7/29/2022. • Land patrols (foot patrols along ROW) are completed twice each year and were reviewed for the years 2018 to 2022. o Reviewed data for 2018 to 2022, no patrols were missed. o Operator performing patrols was qualified for CCT701. o No mention of earth movement issues along the ROW in OMS or on the Form 5000-30, Land Patrol Report. o Note: Gulf South personnel arriving at scene after failure commented that there were no signs of earth movement within the 30’ wide ROW. • EP Minerals purchases the BASF Jackson Plant in July 2017. • Entegra ILI tool run on December 14, 2017. o Entegra 18/20” HR MFL-Cal-IMU combo ILI tool. Page 35#

Page 304Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 o No GW anomalies reported. o No previous ILI runs so no run comparisons available. o No bending strain analysis was completed. • US Silica buys the Jackson Plant from EP Minerals in 2018. o Significant change in management personnel as a result of the US Silica purchase.  Based on conversations with Gulf South Operations personnel, the new plant operators are easy to communicate with, but getting results (action) is slow. o All previous documents and local nomenclature continue to refer this area as the BASF retention pond and berm – even after the US Silica purchase  This report will refer to this area as the “US Silica” retention pond and berm. • At some point, likely 2017 or earlier – based on IMU data, Index 381 pipeline and soil in ROW begins to shift to South in the area of the retention pond berm. o A noticeable pipe deflection to the South is noted in the centerline taken during the Geosyntec site visit on February 16, 2023. o The movement precedes the December 7, 2021, Rosen ILI run since the IMU sensors picked up the pipe deflection during the ILI run. o As soil around pipe moves in southerly direction, longitudinal loads are imposed on the pipeline as the pipeline resists the movement being restrained at both ends. • A pressure test for assessment was completed in 2019. o Test pressure was 760 psig – 1.6 times MAOP. o There were no PT failures reported near this incident location. • US Silica performs significant earth movement stabilization efforts in 2020. o This may have been when the brow ditch (water bar) was installed along the pond berm to divert water from main area of the berm. o One call was utilized by US Silica, but no other coordination was made for the work. • US Silica remediates some areas of erosion along the berm in 2021. o The erosion occurred in area of 2020 earth movement remediation. o One call was utilized by US Silica, but no other coordination was made for the work. • US Silica performs additional slope remediation in September 2022. o Remediations made for recent earth movement issues. o Rip-Rap added in two areas down southern face of pond berm to channel water.  Rip-rap drainage guides water onto ROW, which is downhill.  Rip-rap also added to area on pond (north) side of berm, along pond shoreline. o One call was utilized by US Silica, but no other coordination was made for the work. • Rosen ILI tool run on December 7, 2021. o Rosen 18/20” RoGeo XT HR-deformation and IMU tool run first. o Rosen RoCorr MFL-A HR-MFL tool run second. o The RoCorr MFL-A ILI tool is oriented to detect circumferential defects. o Final report dated March 7, 2022.  No GW anomalies reported. o No bending strain analysis was included in the original project scope. Page 36#

Page 305Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024  Bending Strain Level 1 and Pipeline Movement Assessment was added in response to GW failure. • At some point, likely around November to December 2022, US Silica took additional action to prevent earth movement along pond berm. o A blue tarp was laid out over some areas of the berm, likely to prevent expected rain from soaking into the soil on the berm. o 4 slope inclinometers were also installed (US Silica has not shared any resulting data with Gulf South) o Geosyntec also noted several water wells along the berm, assume the purpose of the wells is for taking samples of the water within the berm soil. No information from US Silica related to the purpose of the wells or the resulting data. o The months of November – February are historically heavier (generally) rain months for the Jackson, MS, area. The average monthly rainfall for these months is 5.02” per month. o The tarps were oriented such that they would shed water onto the ROW.  Geosyntec did not feel like this was a significant issue. 1) The soil movement was likely already active before the tarps were installed; and 2) The soil movement was deep enough to avoid most effects of surface water runoff. • Heavy rains experienced in Jackson, MS, area during early 2023. o Jackson, MS, weather station recorded 9.67” of rain between 1/12/2023 and 2/12/2023.  Almost 4” more than average for the timespan and time of year. o Pearl River was near minor flood stage at time of incident. • In January and February 2023, the landslide on the US Silica pond berm (later assigned unique ID of LS-MS-001 by Geosyntec) continued moving down slope (south) across, and under, the Index 381 ROW. o Longitudinal stresses along Index 381 increased in this area as the pipeline resisted the earth movement. o Geosyntec noted the landslide features were observed to have fresh and unweathered surfaces.  Geosyntec estimates that landslide features were fairly recent, “weeks old and not months old”.  Distinct head scarp, graben, and toe features of the landslide were present and all seemed to be recently created or impacted.  The head scarp and graben were located on the pond berm, above or north of the ROW (but not on it).  The landslide toe was located in the woods below (south) the ROW (but not on it). • At approximately 3:56 AM, February 12, 2023, the longitudinal stresses from the earth movement exceeded the strength of the GW and the GW failed. o Index 381 separated at the GW due to fracture initiation at a 26” long incomplete penetration feature, which progressed to ductile overload. o Due to the stresses on the pipeline, the pipe shifted once separated. Page 37#

Page 306Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024  Lateral separation = 14.5”  Vertical separation = 11”  Horizontal separation = 1” o No ignition and no injuries. o Approximately 20.96 MMCF gas released. o 4 Atmos taps and approximately 217 Atmos customers affected. • Operations crews (Operator A & Operator B) located and isolated the leak by 5:40 AM on February 12, 2023. o MLV 208689 closed at 5:00 AM. o MLV 276420 closed at 5:40 AM. • The failure location on Index 381 remains out of service and isolated. o MLVs 208689 and 276420 remain closed, possibly permanently. o Index 381 on either side of failure has returned to service. • After the failure, Rosen was asked to review the 2021 Rosen IMU data and the 2017 Entegra IMU data and produce a Bending Strain Level 1 and Pipeline Movement Assessment. o Rosen identified the following:  19 bending strain anomalies.  1 pipeline movement feature or “observed change” of pipeline location.  2 pipeline movement areas of interest o The US Silica retention pond area was identified as one of the 19 bending strain anomalies (referred to as PLMM #14980).  Horizontal strain level indicated was -0.237%.  Vertical strain level indicated was -0.050%.  Total strain level indicated was 0.242%. o The US Silica retention pond area was identified as the single pipeline movement feature (referred to as BSTR #14980).  Maximum projected pipeline movement was 1.93’ ±1.31’.  Maximum bending strain difference calculated was 0.158%. • Geosyntec Consultants visits failure location on February 16, 2023, to conduct a visual examination of the ROW and surrounding slopes near the US Silica retention pond berm. o Geosyntec produced a Geohazard Assessment of the failure location and nearby retention pond berm. o Geosyntec did not find any signs of earth movement at the failure location. o Obvious earth movement indications were visible at the US Silica retention pond berm area on both sides of the ROW.  Approximately 160-560’ from the failure location.  No obvious earth movement indications on the ROW. But there had been vehicle & equipment traffic on the ROW for pipe excavation and removal, which may have obscured some visual evidence on the ROW. o Memorandum of Geohazard Assessment produced on March 8, 2023. Page 38#

Page 307Index 381 RCA 100785-RP02-Rev1-032124 Boardwalk Pipelines, LP March 2024 • D2 Integrity was contracted by Gulf South to perform an independent bending strain review based on the Rosen 2021 IMU data. D2 Integrity collaborated with Geosyntec to complete the analysis. o The review was accomplished on a segment of Index 381 which includes both the failure location and US Silica retention pond berm area. o D2 Integrity identified a Priority 3 feature at the US Silica retention pond berm area (BSTR #14980 from Rosen analysis).  The strains at the GW in this area remain a concern and additional testing, analysis or remediation was recommended.  This segment of Index 381 is currently out of service and may not return to service. o The Bending Strain Review report was completed on March 23, 2023. Page 39#