# Enbridge Incorporated Hazardous Liquid Pipeline Rupture and Release - **operation:** document - **citation:** DCA10MP007 - **title:** Enbridge Incorporated Hazardous Liquid Pipeline Rupture and Release - **source type:** incident - **agency:** National Transportation Safety Board - **status:** current - **official:** true - **published on:** 2020-11-30 - **effective on:** 2010-07-25 - **summary:** Accident. in Marshall, MI, USA. on 2010-07-25. Enbridge Energy. Rupture/release - **machine formats:** - **json:** https://regulus.evalyn.ai/document/ntsb-case-dca10mp007.json - **markdown:** https://regulus.evalyn.ai/document/ntsb-case-dca10mp007.md - **app url:** https://regulus.evalyn.ai/document/ntsb-case-dca10mp007 - **source url:** https://www.ntsb.gov/investigations/Pages/DCA10MP007.aspx **body:** NTSB investigation DCA10MP007. Event Type: Accident Event Date: 2010-07-25 Event City: Marshall Event State Or Region: MI Event Country: USA Pipeline Operator: Enbridge Energy Accident Type: Rupture/release Completion Status: Completed Report Number: PAR1201 Probable cause: The National Transportation Safety Board (NTSB) determines that the probable cause of the pipeline rupture was corrosion fatigue cracks that grew and coalesced from crack and corrosion defects under disbonded polyethylene tape coating, producing a substantial crude oil release that went undetected by the control center for over 17 hours. The rupture and prolonged release were made possible by pervasive organizational failures at Enbridge Incorporated (Enbridge) that included the following: Deficient integrity management procedures, which allowed well-documented crack defects in corroded areas to propagate until the pipeline failed. Inadequate training of control center personnel, which allowed the rupture to remain undetected for 17 hours and through two startups of the pipeline. Insufficient public awareness and education, which allowed the release to continue for nearly 14 hours after the first notification of an odor to local emergency response agencies. Contributing to the accident was the Pipeline and Hazardous Materials Safety Administration’s (PHMSA) weak regulation for assessing and repairing crack indications, as well as PHMSA’s ineffective oversight of pipeline integrity management programs, control center procedures, and public awareness. Contributing to the severity of the environmental consequences were (1) Enbridge’s failure to identify and ensure the availability of well-trained emergency responders with sufficient response resources, (2) PHMSA’s lack of regulatory guidance for pipeline facility response planning, and (3) PHMSA’s limited oversight of pipeline emergency preparedness that led to the approval of a deficient facility response plan. Tier1Name: Initiating product flow Tier2Name: System warning/signal Tier1Name: System operating, changing flow/pressure Tier2Name: Emergency shutoff Tier1Name: System operating Tier2Name: Emergency shutoff Tier1Name: Initiating product flow Tier2Name: System warning/signal Tier1Name: System shutdown Tier2Name: System warning/signal Tier1Name: Post-release Tier2Name: Inspection event Tier1Name: Post-release Tier2Name: Emergency shutoff Tier1Name: Post-release Tier2Name: System disabled Tier1Name: Post-release Tier2Name: Emergency response Tier1Name: System operating, changing flow/pressure Tier2Name: System warning/signal Tier1Name: System maintenance Tier2Name: Product leak/release Finding Tier1Name: Organizational Finding Tier2Name: Management Finding Tier3Name: Policy/procedure Finding Modifier Name: Pipeline operator Finding Report Text: Organizational - Management - Policy/procedure - Pipeline operator Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Safety programs Finding Modifier Name: Pipeline operator Finding Report Text: Organizational - Support/oversight/monitoring - Safety programs - Pipeline operator Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Training Finding Modifier Name: Pipeline operator Finding Report Text: Organizational - Support/oversight/monitoring - Training - Pipeline operator Finding Tier1Name: Organizational Finding Tier2Name: Management Finding Tier3Name: Culture Finding Modifier Name: Pipeline operator Finding Report Text: Organizational - Management - Culture - Pipeline operator Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Oversight Finding Modifier Name: Pipeline operator Finding Report Text: Organizational - Support/oversight/monitoring - Oversight - Pipeline operator Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Safety programs Finding Modifier Name: Pipeline operator Finding Report Text: Organizational - Support/oversight/monitoring - Safety programs - Pipeline operator Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Oversight Finding Modifier Name: Federal agency Finding Report Text: Organizational - Support/oversight/monitoring - Oversight - Federal agency Finding Tier1Name: Organizational Finding Tier2Name: Management Finding Tier3Name: Resources Finding Modifier Name: Emergency services Finding Report Text: Organizational - Management - Resources - Emergency services Finding Tier1Name: Organizational Finding Tier2Name: Development Finding Tier3Name: Design Finding Modifier Name: Other institution/organization Finding Report Text: Organizational - Development - Design - Other institution/organization Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Safety programs Finding Modifier Name: Federal agency Finding Report Text: Organizational - Support/oversight/monitoring - Safety programs - Federal agency Finding Tier1Name: Organizational Finding Tier2Name: Development Finding Tier3Name: Selection/testing Finding Modifier Name: Inspection organization Finding Report Text: Organizational - Development - Selection/testing - Inspection organization Finding Tier1Name: Organizational Finding Tier2Name: Management Finding Tier3Name: Policy/procedure Finding Modifier Name: Product source organization Finding Report Text: Organizational - Management - Policy/procedure - Product source organization Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Safety programs Finding Modifier Name: Emergency services Finding Report Text: Organizational - Support/oversight/monitoring - Safety programs - Emergency services Finding Tier1Name: Organizational Finding Tier2Name: Management Finding Tier3Name: Policy/procedure Finding Modifier Name: Federal agency Finding Report Text: Organizational - Management - Policy/procedure - Federal agency Finding Tier1Name: Personnel Finding Tier2Name: Experience/knowledge Finding Tier3Name: Training Finding Tier4Name: (general) Finding Modifier Name: Other company personnel Finding Report Text: Personnel - Experience/knowledge - Training - Other company personnel Finding Tier1Name: Personnel Finding Tier2Name: Experience/knowledge Finding Tier3Name: Training Finding Tier4Name: (general) Finding Modifier Name: SCADA operations personnel Finding Report Text: Personnel - Experience/knowledge - Training - SCADA operations personnel Finding Tier1Name: Personnel Finding Tier2Name: Task performance Finding Tier3Name: Planning/preparation Finding Modifier Name: Emergency services personnel Finding Report Text: Personnel - Task performance - Planning/preparation - Emergency services personnel Finding Tier1Name: Pipeline Finding Tier2Name: Pipeline operation/capability Finding Tier3Name: Pipeline integrity/capacity Finding Modifier Name: Related operating info Finding Report Text: Pipeline - Pipeline operation/capability - Pipeline integrity/capacity - Related operating info Finding Tier1Name: Personnel Finding Tier2Name: Experience/knowledge Finding Tier3Name: Training Finding Tier4Name: (general) Finding Modifier Name: Emergency services personnel Finding Report Text: Personnel - Experience/knowledge - Training - Emergency services personnel Finding Tier1Name: Pipeline Finding Tier2Name: Pipline systems/equipment Finding Tier3Name: Leak sensors Finding Modifier Name: Design Finding Report Text: Pipeline - Pipline systems/equipment - Leak sensors - Design Finding Tier1Name: Personnel Finding Tier2Name: Action/decision Finding Tier3Name: Information processing/decision making Finding Modifier Name: SCADA operations personnel Finding Report Text: Personnel - Action/decision - Information processing/decision making - SCADA operations personnel Finding Tier1Name: Pipeline Finding Tier2Name: Pipeline handling/service Finding Tier3Name: Maintenance/inspection Finding Modifier Name: Fatigue/wear/corrosion Finding Report Text: Pipeline - Pipeline handling/service - Maintenance/inspection - Fatigue/wear/corrosion Official NTSB investigation data. NTSB findings determine probable cause and make safety recommendations; they do not adjudicate civil liability or regulatory violations. What Happened On July 25, 2010, a segment of a 30-inch-diameter pipeline (Line 6B), owned and operated by Enbridge Incorporated (Enbridge) ruptured in a wetland in Marshall, Michigan. The rupture occurred during the last stages of a planned shutdown and was not discovered or addressed for over 17 hours. During the time lapse, Enbridge twice pumped additional oil (81 percent of the total release) into Line 6B during two startups; the total release was estimated to be 843,444 gallons of crude oil. The oil saturated the surrounding wetlands and flowed into the Talmadge Creek and the Kalamazoo River. Local residents self-evacuated from their houses, and the environment was negatively affected. Cleanup efforts continue as of the adoption date of this report, with continuing costs exceeding $767 million. About 320 people reported symptoms consistent with crude oil exposure. No fatalities were reported. What We Found The probable cause of the pipeline rupture was corrosion fatigue cracks that grew and coalesced from crack and corrosion defects under disbonded polyethylene tape coating, producing a substantial crude oil release that went undetected by the control center for over 17 hours. The rupture and prolonged release were made possible by pervasive organizational failures at Enbridge Incorporated (Enbridge) that included the following: Deficient integrity management procedures, which allowed well-documented crack defects in corroded areas to propagate until the pipeline failed. Inadequate training of control center personnel, which allowed the rupture to remain undetected for 17 hours and through two startups of the pipeline. Insufficient public awareness and education, which allowed the release to continue for nearly 14 hours after the first notification of an odor to local emergency response agencies. Contributing to the accident was the Pipeline and Hazardous Materials Safety Administration’s (PHMSA) weak regulation for assessing and repairing crack indications, as well as PHMSA’s ineffective oversight of pipeline integrity management programs, control center procedures, and public awareness. Contributing to the severity of the environmental consequences were (1) Enbridge’s failure to identify and ensure the availability of well-trained emergency responders with sufficient response resources, (2) PHMSA’s lack of regulatory guidance for pipeline facility response planning, and (3) PHMSA’s limited oversight of pipeline emergency preparedness that led to the approval of a deficient facility response plan. What We Recommended As a result of its investigation of this accident, we made recommendations to the U.S. Secretary of Transportation, the Pipeline and Hazardous Materials Safety Administration (PHMSA), Enbridge, the American Petroleum Institute, the Pipeline Research Council International, the International Association of Fire Chiefs, and the National Emergency Number Association. The NTSB also reiterates a previous recommendation to PHMSA. PAR-12-01 <<>> Enbridge Incorporated Hazardous Liquid Pipeline Rupture and Release Marshall, Michigan July 25, 2010 Accident Report NTSB/PAR-12/01 PB2012-916501 National Transportation Safety Board <<>> NTSB/PAR-12/01 PB2012-916501 Notation 8423 Adopted July 10, 2012 Pipeline Accident Report Enbridge Incorporated Hazardous Liquid Pipeline Rupture and Release Marshall, Michigan July 25, 2010 National Transportation Safety Board 490 L’Enfant Plaza, S.W. Washington, D.C. 20594 <<>> National Transportation Safety Board. 2012. Enbridge Incorporated Hazardous Liquid Pipeline Rupture and Release, Marshall, Michigan, July 25, 2010. Pipeline Accident Report NTSB/PAR-12/01. Washington, D.C. Abstract: On Sunday, July 25, 2010, at 5:58 p.m., eastern daylight time, a segment of a 30-inch-diameter pipeline (Line 6B), owned and operated by Enbridge Incorporated (Enbridge) ruptured in a wetland in Marshall, Michigan. The rupture occurred during the last stages of a planned shutdown and was not discovered or addressed for over 17 hours. During the time lapse, Enbridge twice pumped additional oil (81 percent of the total release) into Line 6B during two startups; the total release was estimated to be 843,444 gallons of crude oil. The oil saturated the surrounding wetlands and flowed into the Talmadge Creek and the Kalamazoo River. Local residents self-evacuated from their houses, and the environment was negatively affected. Cleanup efforts continue as of the adoption date of this report, with continuing costs exceeding $767 million. About 320 people reported symptoms consistent with crude oil exposure. No fatalities were reported. As a result of its investigation of this accident, the National Transportation Safety Board (NTSB) makes recommendations to the U.S. Secretary of Transportation, the Pipeline and Hazardous Materials Safety Administration (PHMSA), Enbridge, the American Petroleum Institute, the Pipeline Research Council International, the International Association of Fire Chiefs, and the National Emergency Number Association. The NTSB also reiterates a previous recommendation to PHMSA. The National Transportation Safety Board (NTSB) is an independent Federal agency dedicated to promoting aviation, railroad, highway, marine, pipeline, and hazardous materials safety. Established in 1967, the agency is mandated by Congress through the Independent Safety Board Act of 1974 to investigate transportation accidents, determine the probable causes of the accidents, issue safety recommendations, study transportation safety issues, and evaluate the safety effectiveness of government agencies involved in transportation. The NTSB makes public its actions and decisions through accident reports, safety studies, special investigation reports, safety recommendations, and statistical reviews. Recent publications are available in their entirety on the Internet at . Other information about available publications also may be obtained from the website or by contacting: National Transportation Safety Board Records Management Division, CIO-40 490 L’Enfant Plaza, SW Washington, D.C. 20594 (800) 877-6799 or (202) 314-6551 NTSB publications may be purchased, by individual copy or by subscription, from the National Technical Information Service. To purchase this publication, order report number PB2012-916501 from: National Technical Information Service 5301 Shawnee Road Alexandria, Virginia 22312 (800) 553-6847 or (703) 605-6000 The Independent Safety Board Act, as codified at 49 U.S.C. Section 1154(b), precludes the admission into evidence or use of NTSB reports related to an incident or accident in a civil action for damages resulting from a matter mentioned in the report. <<>> NTSB Pipeline Accident Report Contents Figures .......................................................................................................................................... vii Tables ............................................................................................................................................ ix Acronyms and Abbreviations .......................................................................................................x Executive Summary .................................................................................................................... xii 1 Factual Information .................................................................................................................1 1.1 Introduction ..............................................................................................................................1 1.2 Accident Narrative ...................................................................................................................8 1.2.1 Preaccident Events .........................................................................................................8 1.2.2 The Rupture—Shift A ....................................................................................................8 1.2.3 First Line 6B Startup—Shift B ....................................................................................10 1.2.4 Second Line 6B Startup—Shift B ................................................................................13 1.2.5 Discovery—Shift C ......................................................................................................14 1.2.6 Enbridge Initial Response ............................................................................................15 1.3 Injuries and Evacuations ........................................................................................................18 1.3.1 Injuries .........................................................................................................................18 1.3.2 Evacuations ..................................................................................................................18 1.4 Damages .................................................................................................................................18 1.4.1 Pipeline ........................................................................................................................18 1.4.2 Environment .................................................................................................................19 1.5 Environmental Conditions ......................................................................................................19 1.5.1 Meteorological .............................................................................................................19 1.5.2 Kalamazoo River Conditions .......................................................................................19 1.6 Pipeline Information ...............................................................................................................19 1.6.1 Pipeline History ...........................................................................................................19 1.6.2 Pipeline Operating Pressure .........................................................................................20 1.6.3 Site Description ............................................................................................................20 1.6.4 Other Enbridge Pipeline Incidents ...............................................................................20 1.6.4.1 Cohasset, Minnesota....................................................................................21 1.6.4.2 Glenavon, Saskatchewan .............................................................................22 1.7 Examination of the Accident Pipe ..........................................................................................23 1.7.1 Coating .........................................................................................................................24 1.7.2 Corrosion......................................................................................................................24 1.7.3 Microbial Corrosion .....................................................................................................24 1.7.4 The Fracture .................................................................................................................25 1.7.5 Crack and Corrosion Depth Profile..............................................................................28 1.7.6 Mechanical Testing and Chemical Analysis ................................................................29 1.8 PHMSA Integrity Management Regulation ...........................................................................29 1.8.1 Pipeline Integrity Management in High Consequence Areas ......................................29 1.8.2 Elements of Integrity Management and Integration of Threats ...................................30 iii <<>> NTSB Pipeline Accident Report 1.8.3 Discovery of Condition ................................................................................................30 1.8.4 Immediate and 180-Day Conditions ............................................................................31 1.9 Enbridge Integrity Management Program ..............................................................................31 1.9.1 Corrosion Management ................................................................................................32 1.9.2 Crack Management ......................................................................................................32 1.9.3 In-line Inspection Intervals ..........................................................................................33 1.9.4 Stress Corrosion Cracking ...........................................................................................34 1.9.5 Coating and Cathodic Protection .................................................................................34 1.9.6 In-line Inspection Tools ...............................................................................................35 1.9.6.1 USCD Tool ..................................................................................................35 1.9.7 Enbridge Postaccident Threat Assessment Review .....................................................36 1.9.8 Prior In-Line Inspections of Line 6B ...........................................................................37 1.9.8.1 2004 Ultrasonic Wall Measurement In-Line Inspection .............................37 1.9.8.2 2005 In-Line Inspection—PII USCD Crack Tool Results ..........................39 1.9.8.3 2007 In-Line Inspection—PII High-Resolution MFL Tool Results ...........41 1.9.8.4 2009 In-Line Inspection—PII USWM Tool Results ...................................41 1.10 Pipeline Public Awareness Programs .....................................................................................42 1.10.1 Regulatory Requirements.............................................................................................42 1.10.2 API Recommended Practice 1162 ...............................................................................42 1.10.3 Enbridge’s PAP ............................................................................................................42 1.11 Enbridge Operations ...............................................................................................................44 1.11.1 Edmonton Control Center ............................................................................................44 1.11.2 Control Center Personnel Experience ..........................................................................45 1.11.3 Toxicology ...................................................................................................................47 1.11.4 Training and Qualifications .........................................................................................47 1.11.4.1 Control Center Operations ..........................................................................47 1.11.4.2 MBS Analyst ...............................................................................................48 1.11.5 MBS Leak Detection....................................................................................................49 1.11.5.1 Federal Regulations .....................................................................................49 1.11.5.2 API 1130 Computational Pipeline Monitoring for Liquids ........................49 1.11.5.3 Enbridge’s MBS ..........................................................................................50 1.11.5.4 Column Separation ......................................................................................51 1.11.6 Procedures ....................................................................................................................52 1.11.6.1 10-Minute Restriction .................................................................................52 1.11.6.2 Suspected Column Separation .....................................................................52 1.11.6.3 MBS Alarm .................................................................................................53 1.11.6.4 SCADA Leak Triggers ................................................................................53 1.11.6.5 Suspected Leak—Volume Difference .........................................................54 1.11.6.6 Leak and Obstruction Trigger—On Startup from SCADA Data ................54 1.11.7 Fatigue Management ....................................................................................................54 1.11.8 Enbridge Health and Safety Management System.......................................................55 1.12 Environmental Response ........................................................................................................55 1.12.1 Volume Released .........................................................................................................55 1.12.2 Hazardous Materials Information ................................................................................56 1.12.3 Overview of the Oil Spill Response.............................................................................56 1.12.3.1 Notifications ................................................................................................58 iv <<>> NTSB Pipeline Accident Report 1.12.4 Enbridge Facility Response Plan .................................................................................58 1.12.5 EPA Oversight of Spill Response Efforts ....................................................................61 1.12.6 Environmental Monitoring...........................................................................................62 1.12.6.1 Air Quality...................................................................................................62 1.12.6.2 Potable Water ..............................................................................................62 1.12.6.3 Surface Water and Sediment .......................................................................62 1.12.7 Natural Resources and Wildlife ...................................................................................63 1.13 Previous NTSB Investigations and Studies ............................................................................63 1.13.1 NTSB SCADA 2005 Study .........................................................................................63 1.13.2 NTSB 2010 Pipeline Investigation of Pacific Gas and Electric Company ..................64 1.13.3 Carmichael, Mississippi ...............................................................................................65 1.14 Postaccident Actions ..............................................................................................................65 1.14.1 PHMSA Corrective Action Order ................................................................................65 1.14.2 PHMSA’s Notice of Probable Violation......................................................................66 1.14.3 Enbridge Actions .........................................................................................................66 1.14.3.1 Line 6B Replacement Projects ....................................................................66 1.14.3.2 Enbridge Operator Training ........................................................................67 1.14.3.3 Integrity Management .................................................................................67 1.14.3.4 Enbridge Control Center .............................................................................67 1.15 Federal Oversight ...................................................................................................................68 1.15.1 Canadian and U.S. Regulation .....................................................................................68 1.15.2 Enbridge 2010 Long-Term Pressure Reduction Notification ......................................69 1.15.3 PHMSA Inspections.....................................................................................................69 1.15.4 Pipeline Safety, Regulatory Certainty, and Job Creation Act of 2011 ........................71 1.15.5 National Energy Board ................................................................................................71 1.15.6 PHMSA Inspection of Enbridge’s PAP .......................................................................72 1.15.7 PHMSA Facility Response Plan Review and Approval ..............................................73 1.15.8 PHMSA Facility Response Plan Advisory Bulletin ....................................................75 1.15.9 Response Preparedness ................................................................................................75 1.15.10 PHMSA Control Center Management ...................................................................76 1.16 Other Information ...................................................................................................................78 1.16.1 Oil Spill Response Methods.........................................................................................78 1.16.2 API Standard 1160—Managing System Integrity for Hazardous Liquid Pipelines ....80 2 Analysis ...................................................................................................................................81 2.1 Introduction ............................................................................................................................81 2.2 Pipeline Failure .......................................................................................................................82 2.2.1 The Rupture .................................................................................................................82 2.2.2 Fracture Mechanism.....................................................................................................82 2.3 Federal Regulations Governing Hazardous Liquid Pipelines ................................................84 2.4 Deficiencies in the Integrity Management Program ...............................................................87 2.4.1 Engineering Assessment of Cracks and Margin of Safety ...........................................88 2.4.2 In-line Inspection Tool Tolerances ..............................................................................88 2.4.3 Improper Wall Thickness .............................................................................................89 2.4.4 Corrosion and Cracking Interactions ...........................................................................89 2.4.5 Crack Growth Rate Not Considered ............................................................................90 2.4.6 Need for Continuous Reassessment .............................................................................90 v <<>> NTSB Pipeline Accident Report 2.4.7 Effect of Integrity Management Deficiencies ..............................................................91 2.5 Mischaracterization of the Crack Feature ..............................................................................93 2.6 Control Center ........................................................................................................................93 2.6.1 Team Performance .......................................................................................................94 2.6.2 Training ........................................................................................................................97 2.6.3 Procedures ....................................................................................................................98 2.6.4 Tolerance for Procedural Deviance ...........................................................................101 2.6.5 Alcohol and Drug Testing ..........................................................................................101 2.6.6 Work/Sleep/Wake History .........................................................................................102 2.7 Pipeline Public Awareness ...................................................................................................103 2.8 Environmental Response ......................................................................................................105 2.8.1 Effectiveness of the Emergency Response to this Accident ......................................105 2.8.2 Facility Response Planning ........................................................................................108 2.8.2.1 Regulatory Requirements for Facility Response Planning .......................109 2.8.2.2 Adequacy of Enbridge Facility Response Plan .........................................111 2.8.2.3 PHMSA Oversight of Facility Response Plans .........................................112 2.9 Summary of Enbridge Organizational Deficiencies .............................................................114 3 Conclusions ...........................................................................................................................118 3.1 Findings ................................................................................................................................118 3.2 Probable Cause .....................................................................................................................121 4 Recommendations ................................................................................................................122 4.1 New Recommendations ........................................................................................................122 4.2 Reiterated Recommendation ................................................................................................124 5 Appendixes............................................................................................................................126 5.1 Appendix A: Investigation ...................................................................................................126 5.2 Appendix B: Enbridge’s MBS and Control Center Operations Procedures ........................127 5.3 Appendix C: Supervisory Control and Data Acquisition Plots ............................................146 vi <<>> NTSB Pipeline Accident Report Figures Figure 1. Enbridge’s Liquids System and the 1,900-mile Lakehead System (the U.S. portion). Inset shows Line 6B, the 293-mile extension from Griffith to Sarnia installed in 1969. ........................................................................................................................................... 2 rupture. The fracture face measured about 6 feet 8.25 inches long and was 5.32 inches wide Figure 2 . The ruptured segment of Line 6B in the trench following the July 25, 2010, at the widest opening. The fracture ran just below the seam weld that was oriented just below the 3 o’clock position. A red circle shows a location where the coating was wrinkled and had separated from the pipe surface. ........................................................................................ 3 Figure 3. Aerial view of the accident location showing the rupture site to the left and the Talmadge Creek flowing west toward the Kalamazoo River. ........................................................ 4 Figure 4. Cleanup efforts in an oil-soaked wetland near the rupture site. Saturated soil complicated the cleanup and excavation efforts. An excavator with a vacuum attachment is shown situated on wooden matting near the rupture site. ............................................................... 5 Figure 5. Key events timeline of the Line 6B rupture in Marshall, Michigan, showing the events from the time of rupture on July 25, 2010, to the time of discovery on July 26, 2010. ...... 6 Figure 6. Key Enbridge staff involved in the 17-hour accident sequence. MBS refers to Material Balance System. ............................................................................................................... 7 Figure 7. Simplified schematic of Line 6B, showing pump stations and delivery locations. ........ 9 Figure 8. Emergency response and 911 calls from nearby residents. First and last calls are noted. ............................................................................................................................................. 11 Figure 9. Area between rupture site and the Kalamazoo River where first responders concentrated efforts to contain the released oil. ............................................................................ 15 Figure 10. Underflow dam on Talmadge Creek on July 30, 2010. .............................................. 17 Figure 11. Line 6B ruptured segment showing upstream and downstream sections used for Materials Laboratory examination. Detail B shows tented coating over the longitudinal seam weld...................................................................................................................................... 23 Figure 12. The outside surface of the pipe looking at the fracture area cut for lab examination. .................................................................................................................................. 25 Figure 13. Curving arrest lines of preexisting cracks along the upper fracture face shown after cleaning to remove oxides. White arrows indicate multiple origin areas of preexisting cracks. ........................................................................................................................................... 26 vii <<>> NTSB Pipeline Accident Report Figure 14. Close view of fracture surface area in the area of deepest crack penetration. The solid blue line indicates the extent of the preexisting crack penetration. ..................................... 27 Figure 15. Transverse section through the top of the fracture showing multiple parallel cracks emanating from corrosion pits on the outside surface. ...................................................... 28 Figure 16. Lab measurements of crack and corrosion depths along the fracture face measured from images similar to figure 14 near area of deepest penetration (about 344 inches from upstream girth weld). ......................................................................................... 29 Figure 17. 2004 corrosion inspection of Line 6B and 16 regions of corrosion identified by the tool on the ruptured pipe segment. The detail view shows the areas of corrosion overlapped with the rupture location. ........................................................................................... 38 Figure 18. 2005 in-line inspection regions where crack-like characterizations were reported by PII on the ruptured segment of Line 6B. ................................................................... 40 Figure 19. Map showing rupture location and affected waterways from Talmadge Creek to Morrow Lake. ............................................................................................................................... 57 Figure 2 0. Enbridge PLM emergency response trailer containing the company’s Tier 1 oil containment equipment, October 17, 2010. .................................................................................. 60 Figure 2 1. (Left) Enbridge employees install sorbent boom in f - **truncated:** true - **body characters:** 407832