# Pacific Gas and Electric Company Natural Gas Transmission Pipeline Rupture and Fire - **operation:** document - **citation:** DCA10MP008 - **title:** Pacific Gas and Electric Company Natural Gas Transmission Pipeline Rupture and Fire - **source type:** incident - **agency:** National Transportation Safety Board - **status:** current - **official:** true - **published on:** 2020-11-24 - **effective on:** 2010-09-09 - **summary:** Accident. in San Bruno, CA, USA. on 2010-09-09. Pacific Gas and Electric Company. Rupture/fire - **machine formats:** - **json:** https://regulus.evalyn.ai/document/ntsb-case-dca10mp008.json - **markdown:** https://regulus.evalyn.ai/document/ntsb-case-dca10mp008.md - **app url:** https://regulus.evalyn.ai/document/ntsb-case-dca10mp008 - **source url:** https://www.ntsb.gov/investigations/Pages/DCA10MP008.aspx **body:** NTSB investigation DCA10MP008. Event Type: Accident Event Date: 2010-09-09 Event City: San Bruno Event State Or Region: CA Event Country: USA Pipeline Operator: Pacific Gas and Electric Company Accident Type: Rupture/fire Completion Status: Completed Report Number: PAR1101 Probable cause: The National Transportation Safety Board determines that the probable cause of the accident was the Pacific Gas and Electric Company's (PG&E) (1) inadequate quality assurance and quality control in 1956 during its Line 132 relocation project, which allowed the installation of a substandard and poorly welded pipe section with a visible seam weld flaw that, over time grew to a critical size, causing the pipeline to rupture during a pressure increase stemming from poorly planned electrical work at the Milpitas Terminal; and (2) inadequate pipeline integrity management program, which failed to detect and repair or remove the defective pipe section. Tier1Name: System maintenance Tier2Name: Inspection event Tier1Name: System maintenance Tier2Name: Miscellaneous/other Tier1Name: Initiating product flow Tier2Name: Inspection event Tier1Name: System operating, changing flow/pressure Tier2Name: Pressure/flow/temp event Tier1Name: Post-release Tier2Name: Explosion Tier1Name: Post-release Tier2Name: Fire (post-release) Tier1Name: System shutdown Tier2Name: Emergency shutoff Tier1Name: System shutdown Tier2Name: System warning/signal Tier1Name: System shutdown Tier2Name: Emergency response Tier1Name: System shutdown Tier2Name: Pipe structural malfunction/failure Tier1Name: System shutdown Tier2Name: Evacuation Tier1Name: System shutdown Tier2Name: Shutoff malfunction/failure Tier1Name: System operating, changing flow/pressure Tier2Name: System warning/signal Tier1Name: System operating, changing flow/pressure Tier2Name: Pressure/flow/temp event Tier1Name: System operating, changing flow/pressure Tier2Name: System/equipment malf/failure Tier1Name: System not operating Tier2Name: Fire/explosion (post-release) Tier1Name: System operating, changing flow/pressure Tier2Name: Product leak/release Tier1Name: System maintenance Tier2Name: Servicing event Tier1Name: System not operating Tier2Name: Inspection event Finding Tier1Name: Organizational Finding Tier2Name: Management Finding Tier3Name: Policy/procedure Finding Modifier Name: Pipeline operator Finding Report Text: Organizational - 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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: Federal agency Finding Report Text: Organizational - Support/oversight/monitoring - Oversight - Federal agency Finding Tier1Name: Organizational Finding Tier2Name: Development Finding Tier3Name: Selection/testing Finding Modifier Name: Emergency services Finding Report Text: Organizational - Development - Selection/testing - Emergency services 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: Support/oversight/monitoring Finding Tier3Name: Enforcement Finding Modifier Name: Federal agency Finding Report Text: Organizational - Support/oversight/monitoring - Enforcement - Federal agency Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Enforcement Finding Modifier Name: State/Local agency Finding Report Text: Organizational - Support/oversight/monitoring - Enforcement - State/Local agency Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Safety programs Finding Modifier Name: State/Local agency Finding Report Text: Organizational - Support/oversight/monitoring - Safety programs - State/Local agency Finding Tier1Name: Organizational Finding Tier2Name: Management Finding Tier3Name: Resources Finding Modifier Name: State/Local agency Finding Report Text: Organizational - Management - Resources - State/Local agency Finding Tier1Name: Organizational Finding Tier2Name: Development Finding Tier3Name: Manufacture/production Finding Modifier Name: Other institution/organization Finding Report Text: Organizational - Development - Manufacture/production - Other institution/organization Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Safety programs Finding Modifier Name: State/Local agency Finding Report Text: Organizational - Support/oversight/monitoring - Safety programs - State/Local agency Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Safety programs Finding Modifier Name: State/Local agency Finding Report Text: Organizational - Support/oversight/monitoring - Safety programs - State/Local agency 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: Support/oversight/monitoring Finding Tier3Name: Enforcement Finding Modifier Name: State/Local agency Finding Report Text: Organizational - Support/oversight/monitoring - Enforcement - State/Local agency Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Enforcement Finding Modifier Name: Federal agency Finding Report Text: Organizational - Support/oversight/monitoring - Enforcement - Federal agency Finding Tier1Name: Pipeline Finding Tier2Name: Pipeline structure Finding Tier3Name: Joint/weld/seam Finding Modifier Name: Related records Finding Report Text: Pipeline - Pipeline structure - Joint/weld/seam - Related records Finding Tier1Name: Pipeline Finding Tier2Name: Pipeline structure Finding Tier3Name: Pipe seam Finding Modifier Name: Incorrect service/maintenance Finding Report Text: Pipeline - Pipeline structure - Pipe seam - Incorrect service/maintenance Finding Tier1Name: Pipeline Finding Tier2Name: Pipeline structure Finding Tier3Name: Joint/weld/seam Finding Modifier Name: Related operating info Finding Report Text: Pipeline - Pipeline structure - Joint/weld/seam - Related operating info Finding Tier1Name: Personnel Finding Tier2Name: Action/decision Finding Tier3Name: Action Finding Modifier Name: SCADA operations personnel Finding Report Text: Personnel - Action/decision - Action - SCADA operations personnel Finding Tier1Name: Personnel Finding Tier2Name: Action/decision Finding Tier3Name: Information processing/decision making Finding Modifier Name: SCADA maintenance personnel Finding Report Text: Personnel - Action/decision - Information processing/decision making - SCADA maintenance personnel Finding Tier1Name: Environment/Infrastructure Finding Tier2Name: Operating environment/control system Finding Tier3Name: SCADA system Finding Modifier Name: Availability of related info Finding Report Text: Environment/Infrastructure - Operating environment/control system - SCADA system - Availability of related info Finding Tier1Name: Pipeline Finding Tier2Name: Pipeline operation/capability Finding Tier3Name: Pipeline temp/pressure/flow parameter(s) Finding Modifier Name: Design Finding Report Text: Pipeline - Pipeline operation/capability - Pipeline temp/pressure/flow parameter(s) - Design 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: Physical Finding Tier3Name: Sensory ability/limitation Finding Modifier Name: SCADA maintenance personnel Finding Report Text: Personnel - Physical - Sensory ability/limitation - SCADA maintenance personnel Finding Tier1Name: Personnel Finding Tier2Name: Physical Finding Tier3Name: Impairment/incapacitation Finding Modifier Name: Federal government personnel Finding Report Text: Personnel - Physical - Impairment/incapacitation - Federal government personnel Finding Tier1Name: Personnel Finding Tier2Name: Task performance Finding Tier3Name: Planning/preparation Finding Modifier Name: Not specified Finding Report Text: Personnel - Task performance - Planning/preparation - Not specified Finding Tier1Name: Pipeline Finding Tier2Name: Pipeline structure Finding Tier3Name: Pipe Finding Modifier Name: Design Finding Report Text: Pipeline - Pipeline structure - Pipe - Design 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 September 9, 2010, about 6:11 p.m. Pacific daylight time, a 30-inch-diameter segment of an intrastate natural gas transmission pipeline known as Line 132, owned and operated by the Pacific Gas and Electric Company (PG&E), ruptured in a residential area in San Bruno, California. The rupture occurred at mile point 39.28 of Line 132, at the intersection of Earl Avenue and Glenview Drive. The rupture produced a crater about 72 feet long by 26 feet wide. The section of pipe that ruptured, which was about 28 feet long and weighed about 3,000 pounds, was found 100 feet south of the crater. PG&E estimated that 47.6 million standard cubic feet of natural gas was released. The released natural gas ignited, resulting in a fire that destroyed 38 homes and damaged 70. Eight people were killed, many were injured, and many more were evacuated from the area. What We Found The probable cause of the accident was the Pacific Gas and Electric Company’s (PG&E) (1) inadequate quality assurance and quality control in 1956 during its Line 132 relocation project, which allowed the installation of a substandard and poorly welded pipe section with a visible seam weld flaw that, over time grew to a critical size, causing the pipeline to rupture during a pressure increase stemming from poorly planned electrical work at the Milpitas Terminal; and (2) inadequate pipeline integrity management program, which failed to detect and repair or remove the defective pipe section. Contributing to the accident were the California Public Utilities Commission’s (CPUC) and the U.S. Department of Transportation’s exemptions of existing pipelines from the regulatory requirement for pressure testing, which likely would have detected the installation defects. Also contributing to the accident was the CPUC’s failure to detect the inadequacies of PG&E’s pipeline integrity management program. Contributing to the severity of the accident were the lack of either automatic shutoff valves or remote control valves on the line and PG&E’s flawed emergency response procedures and delay in isolating the rupture to stop the flow of gas. What We Recommended We made recommendations to the U.S. Secretary of Transportation, the Pipeline and Hazardous Materials Safety Administration, the Governor of the State of California, the California Public Utilities Commission, the Pacific Gas and Electric Company, the American Gas Association and the Interstate Natural Gas Association of America. Previously issued recommendations to the Pipeline and Hazardous Materials Safety Administration, the California Public Utilities Commission, the Pacific Gas and Electric Company. PAR-11-01 <<>> Pacific Gas and Electric Company Natural Gas Transmission Pipeline Rupture and Fire San Bruno, California September 9, 2010 Accident Report NTSB/PAR-11/01 PB2011-916501 National Transportation Safety Board <<>> NTSB/PAR-11/01 PB2011-916501 Notation 8275C Adopted August 30, 2011 Pipeline Accident Report Pacific Gas and Electric Company Natural Gas Transmission Pipeline Rupture and Fire San Bruno, California September 9, 2010 National Transportation Safety Board 490 L’Enfant Plaza, S.W. Washington, DC 20594 <<>> National Transportation Safety Board. 2011. Pacific Gas and Electric Company Natural Gas Transmission Pipeline Rupture and Fire, San Bruno, California, September 9, 2010. Pipeline Accident Report NTSB/PAR-11/01. Washington, DC. Abstract: On September 9, 2010, about 6:11 p.m. Pacific daylight time, a 30-inch-diameter segment of an intrastate natural gas transmission pipeline known as Line 132, owned and operated by the Pacific Gas and Electric Company, ruptured in a residential area in San Bruno, California. The rupture occurred at mile point 39.28 of Line 132, at the intersection of Earl Avenue and Glenview Drive. The rupture produced a crater about 72 feet long by 26 feet wide. The section of pipe that ruptured, which was about 28 feet long and weighed about 3,000 pounds, was found 100 feet south of the crater. The Pacific Gas and Electric Company estimated that 47.6 million standard cubic feet of natural gas was released. The released natural gas ignited, resulting in a fire that destroyed 38 homes and damaged 70. Eight people were killed, many were injured, and many more were evacuated from the area. As a result of its investigation of this accident, the National Transportation Safety Board makes recommendations to the U.S. Secretary of Transportation, the Pipeline and Hazardous Materials Safety Administration, the governor of the state of California, the California Public Utilities Commission, the Pacific Gas and Electric Company, the American Gas Association, and the Interstate Natural Gas Association of America. The National Transportation Safety Board 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 Safety Board 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, DC 20594 (800) 877-6799 or (202) 314-6551 Safety Board publications may be purchased, by individual copy or by subscription, from the National Technical Information Service. To purchase this publication, order report number PB2011-916501 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 Board 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 ........................................................................................................................................... vi Tables ........................................................................................................................................... vii Acronyms and Abbreviations ................................................................................................... viii Executive Summary .......................................................................................................................x Investigation Synopsis .....................................................................................................................x Probable Cause.............................................................................................................................. xii Recommendations ......................................................................................................................... xii 1. Factual Information ...................................................................................................................1 1.1 Accident Narrative .....................................................................................................................1 1.1.1 Preaccident Events ...........................................................................................................3 1.1.2 Events Leading Up to Rupture ........................................................................................5 1.1.3 The Rupture ...................................................................................................................12 1.2 Emergency Response ...............................................................................................................12 1.3 Injuries .....................................................................................................................................18 1.4 Damage ....................................................................................................................................18 1.5 Meteorological Information .....................................................................................................21 1.6 Personnel Information ..............................................................................................................21 1.6.1 Milpitas Technician and Other Workers at the Milpitas Terminal ................................21 1.6.2 SCADA Operators .........................................................................................................22 1.7 Pipeline Information ................................................................................................................23 1.7.1 Line 132 .........................................................................................................................23 1.7.2 1956 Relocation Project (Segment 180) ........................................................................25 1.7.3 Multiyear Replacement Project and Seismic Risk .........................................................29 1.7.4 Underground Environment at Accident Location ..........................................................30 1.7.4.1 2008 Sewer Replacement .................................................................................30 1.7.4.2 Guidelines for Pipe Bursting ............................................................................33 1.7.4.3 Pipe Bursting Study .........................................................................................33 1.7.5 Pipeline MAOP ..............................................................................................................33 1.7.5.1 “Grandfather Clause” .......................................................................................34 1.7.5.2 MAOP for Line 132 .........................................................................................35 1.7.5.3 Periodic Pressure Increases to MAOP .............................................................36 1.7.6 History of Seam Defects in PG&E Gas Transmission Pipelines ...................................38 1.7.7 Protection Against Accidental Overpressure .................................................................39 1.8 Examination of Accident Pipe .................................................................................................39 1.8.1 Welds .............................................................................................................................41 1.8.2 Crack Initiation ..............................................................................................................43 1.8.3 Material Properties .........................................................................................................46 1.8.4 Historical Information About Steel Grades ...................................................................47 1.8.5 Burst Pressure Study and Finite Element Modeling ......................................................48 iii <<>> NTSB Pipeline Accident Report 1.9 Pipeline Operations and Management .....................................................................................51 1.9.1 SCADA System Operations ..........................................................................................51 1.9.1.1 Milpitas Terminal.............................................................................................52 1.9.1.2 Work Clearance Procedures .............................................................................54 1.9.1.3 Emergency Response Procedures ....................................................................55 1.9.2 Use of Automatic Shutoff Valves and Remote Control Valves ....................................56 1.9.3 Public Awareness ...........................................................................................................57 1.9.4 PG&E Risk Management/Integrity Management Program ...........................................59 1.9.4.1 Geographic Information System ......................................................................59 1.9.4.2 Risk Management Procedures..........................................................................61 1.9.4.3 Threats Identified for Line 132 ........................................................................65 1.10 Oversight ................................................................................................................................67 1.10.1 State Oversight by CPUC ............................................................................................67 1.10.2 Federal Oversight by PHMSA .....................................................................................69 1.11 Postaccident Actions ..............................................................................................................71 1.11.1 Actions Taken by PG&E .............................................................................................71 1.11.2 Actions Taken by CPUC .............................................................................................72 1.11.3 Actions Taken by PHMSA ..........................................................................................74 1.11.4 Actions Taken by Congress .........................................................................................74 1.12 Previous NTSB Safety Recommendations ............................................................................75 1.12.1 January 3, 2011, Safety Recommendations to PG&E, CPUC, and PHMSA Regarding Record-keeping and Hydrostatic Pressure Testing ................................75 1.12.2 June 8, 2011, Safety Recommendations to PHMSA and PG&E Concerning Emergency Response ..........................................................................................77 1.12.3 Other Relevant Recommendations ..............................................................................78 1.12.3.1 Grandfathering of Higher Permissible Stress Levels for Pre- 1970 Pipelines ..............................................................................................................78 1.12.3.2 Constructing and Modifying Pipelines to Accommodate Use of In-Line Inspection Equipment .................................................................................79 1.12.3.3 Rapid Shutdown and ASVs and RCVs ..........................................................80 1.13 Other Information ..................................................................................................................81 1.13.1 Pipeline Assessment Methods for Integrity Management ...........................................81 1.13.1.1 Pressure Testing .............................................................................................82 1.13.1.2 In-line Inspection ...........................................................................................83 1.13.1.3 Direct Assessment ..........................................................................................85 1.13.2 Automatic Shutoff Valve Technology .........................................................................86 1.13.3 2008 Natural Gas Explosion in Rancho Cordova, California ......................................87 2. Analysis .....................................................................................................................................88 2.1 Introduction ..............................................................................................................................88 2.2 Preaccident Events ...................................................................................................................90 2.2.1 Work Clearance Procedures for Electrical Work at Milpitas Terminal ........................90 2.2.2 Internal Line Pressure Prior to Failure ...........................................................................91 2.3 Cause of Pipeline Rupture .......................................................................................................92 2.3.1 Fracture Origin and Failure ...........................................................................................93 2.3.2 Deficiencies in Fabrication of Accident Pipe Segment .................................................94 iv <<>> NTSB Pipeline Accident Report 2.3.3 Deficiencies in Quality Control Associated with 1956 Relocation Project .....................................................................................................................................95 2.3.4 2008 Sewer Pipe Bursting Operation ............................................................................96 2.4 Adequacy of PG&E Emergency Response ..............................................................................97 2.4.1 Internal Communication and Coordination ...................................................................98 2.4.2 Notifying Emergency Responders ...............................................................................100 2.4.3 Line Break Recognition ...............................................................................................101 2.4.4 Rapid Shutdown, ASVs, and RCVs ............................................................................102 2.4.5 Deficiencies in Postaccident Drug and Alcohol Testing .............................................104 2.5 MAOP ....................................................................................................................................106 2.5.1 MAOP of Line 132 ......................................................................................................106 2.5.2 Grandfathering of Pre-1970 Pipelines .........................................................................106 2.6 Integrity Management Program .............................................................................................107 2.6.1 PG&E GIS and Pipeline Record-keeping ....................................................................108 2.6.2 Threat Identification and Risk Assessment .................................................................110 2.6.2.1 Weighting of Threats .....................................................................................110 2.6.2.2 Identification and Assessment of Design/Material and Construction Threats on Line 132..............................................................................110 2.6.2.3 Regulatory Assumption of Stable Manufacturing- and Construction-Related Defects .....................................................................................112 2.6.3 Self-Assessment of Program Effectiveness .................................................................113 2.6.4 Summary of PG&E Integrity Management Practices ..................................................114 2.7 Adequacy of PG&E’s Public Awareness Program Evaluation..............................................115 2.8 Summary of PG&E Practices.................................................................................................116 2.9 Inspection Technology ...........................................................................................................118 2.10 Oversight ..............................................................................................................................119 2.10.1 Performance-Based Safety Programs ........................................................................119 2.10.2 Authority and Enforcement .......................................................................................122 3. Conclusions .............................................................................................................................124 3.1 Findings..................................................................................................................................124 3.2 Probable Cause.......................................................................................................................127 4. Recommendations ..................................................................................................................128 4.1 New Recommendations .........................................................................................................128 4.2 Previously Issued Recommendations ....................................................................................132 4.3 Previously Issued Recommendations Classified in This Report ...........................................134 5. Appendix .................................................................................................................................140 v <<>> NTSB Pipeline Accident Report Figures Figure 1. Picture of crater and ruptured pipeline. .......................................................................... 2 Figure 2. Picture of ejected pipe section. ....................................................................................... 2 Figure 3. Aerial view of fire........................................................................................................... 3 Figure 4. Overview of Line 132. .................................................................................................... 4 Figure 5. Picture of local control panel. ......................................................................................... 6 Figure 6a. Normal electrical configuration at the Milpitas Terminal. ........................................... 7 Figure 6b. Temporary electrical configuration at the Milpitas Terminal preceding the accident. .................................................................................................................................... 8 Figure 7. Schematic showing regulating valve control. ................................................................. 8 Figure 8a. Valve configuration at the Milpitas Terminal prior to 5:22 p.m. ............................... 10 Figure 8b. Valve configuration at the Milpitas Terminal about 5:25 p.m. .................................. 11 Figure 9. Firefighters approaching accident scene. ...................................................................... 13 Figure 10. Location of valve closures. ......................................................................................... 17 Figure 11. Picture showing area of damage from blast and fire. ................................................. 19 Figure 12. Picture of destroyed houses. ....................................................................................... 20 Figure 13. Picture of a burned car in front of several destroyed houses. ..................................... 20 Figure 14. Map showing PG&E peninsula gas transmission lines. ............................................. 24 Figure 15. Line 132 installation, relocations, and replacements. ................................................. 26 Figure 16. Sketch of underground utilities environment. ............................................................ 30 Figure 17. Diagram of excavations relative to Segment 180. ...................................................... 32 Figure 18. Schematic of accident pipe. ........................................................................................ 40 Figure 19a. Picture showing cross section of longitudinal seam in pup 1. .................................. 42 Figure 19b. Picture showing cross section of longitudinal seam in typical DSAW pipe. ............................................................................................................................................... 42 Figure 20. Picture of pipe section with white arrows showing direction of crack propagation. .................................................................................................................................. 44 Figure 21. Pictures highlighting rupture initiation site in pup 1 longitudinal seam. .................... 45 Figure 22a. Stress contours at an internal pressure of 375 psig for the finite element model of the weld geometry similar to pup 1. Contour values are the same as in figure 22b. ................................................................................................................... 50 Figure 22b. Stress contours at an internal pressure of 375 psig for the finite element model of a DSAW seam. Contour values are the same as in figure 22a. ........................ 50 Figure 23. Flowchart of PG&E’s emergency response procedures. ............................................ 55 vi <<>> NTSB Pipeline Accident Report Tables Table 1. Injuries............................................................................................................................ 18 Table 2. PG&E gas transmission pipeline seam leaks or test failures, 1948–2011. .................... 39 Table 3. Average and standard deviation of mechanical test data for all lengths of pipe. ............................................................................................................................................... 46 Table 4. Minimum yield strength, tensile strength, and elongation requirements according to PG&E and API pipe specifications. ......................................................................... 47 Table 5. Incoming and outgoing lines at Milpitas Terminal. ....................................................... 53 Table 6. Survey postcard responses to public awareness brochures. ........................................... 59 Table 7. PG&E’s reportable events by cause for 2004–2010. ..................................................... 65 Table 8. Line 132 risk values. ...................................................................................................... 66 vii <<>> NTSB Pipeline Accident Report Acronyms and Abbreviations AGA American Gas Association ANPRM advance notice of proposed rulemaking API American Petroleum Institute ASME American Society of Mechanical Engineers ASOS Automated Surface Observing System ASTM American Society for Testing and Materials ASV automatic shutoff valve CFR Code of Federal Regulations COF consequence of failure Consolidated Western Consolidated Western Steel Corporation CPUC California Public Utilities Commission DOT U.S. Department of Transportation DSAW double submerged arc welded ECDA external corrosion direct assessment ERW electric resistance welded GIS geographic information system GRI Gas Research Institute GSR gas service representative GTI Gas Technology Institute HCA high consequence area HV Vickers hardness number INGAA Interstate Natural Gas Association of America KSFO San Francisco International Airport viii <<>> NTSB Pipeline Accident Report ksi 1,000 pounds per square inch LOF likelihood of failure MAOP maximum allowable operating pressure MOP maximum operating pressure MP mile point NPRM notice of proposed rulemaking NTSB National Transportation Safety Board PAPERS Public Awareness Program Effectiveness Research Survey PG&E Pacific Gas and Electric Company PHMSA Pipeline and Hazardous Materials Safety Administration PLC programmable logic controller psi pounds per square inch psig pounds per square inch, gauge RCV remote control valve RMP risk management procedure RSPA Research and Special Programs Administration SBFD San Bruno Fire Department SCADA supervisory control and data acquisition SMLS seamless SMYS specified minimum yield strength the Corps U.S. Army Corps of Engineers UPS uninterruptible power supply ix <<>> NTSB Pipeline Accident Report Executive Summary On September 9, 2010, about 6:11 p.m. Pacific daylight time, a 30-inch-diameter segment of an intrastate natural gas transmission pipeline known as Line 132, owned and operated by the Pacific Gas and Electric Company (PG&E), ruptured in a residential area in San Bruno, California. The rupture occurred at mile point 39.28 of Line 132, at the intersection of Earl Avenue and Glenview Drive. The rupture produced a crater about 72 feet long by 26 feet wide. The section of pipe that ruptured, whic - **truncated:** true - **body characters:** 418846