{"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.\n\nEvent Type: Accident\n\nEvent Date: 2010-09-09\n\nEvent City: San Bruno\n\nEvent State Or Region: CA\n\nEvent Country: USA\n\nPipeline Operator: Pacific Gas and Electric Company\n\nAccident Type: Rupture/fire\n\nCompletion Status: Completed\n\nReport Number: PAR1101\n\nProbable 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.\n\nTier1Name: System maintenance\n\nTier2Name: Inspection event\n\nTier1Name: System maintenance\n\nTier2Name: Miscellaneous/other\n\nTier1Name: Initiating product flow\n\nTier2Name: Inspection event\n\nTier1Name: System operating, changing flow/pressure\n\nTier2Name: Pressure/flow/temp event\n\nTier1Name: Post-release\n\nTier2Name: Explosion\n\nTier1Name: Post-release\n\nTier2Name: Fire (post-release)\n\nTier1Name: System shutdown\n\nTier2Name: Emergency shutoff\n\nTier1Name: System shutdown\n\nTier2Name: System warning/signal\n\nTier1Name: System shutdown\n\nTier2Name: Emergency response\n\nTier1Name: System shutdown\n\nTier2Name: Pipe structural malfunction/failure\n\nTier1Name: System shutdown\n\nTier2Name: Evacuation\n\nTier1Name: System shutdown\n\nTier2Name: Shutoff malfunction/failure\n\nTier1Name: System operating, changing flow/pressure\n\nTier2Name: System warning/signal\n\nTier1Name: System operating, changing flow/pressure\n\nTier2Name: Pressure/flow/temp event\n\nTier1Name: System operating, changing flow/pressure\n\nTier2Name: System/equipment malf/failure\n\nTier1Name: System not operating\n\nTier2Name: Fire/explosion (post-release)\n\nTier1Name: System operating, changing flow/pressure\n\nTier2Name: Product leak/release\n\nTier1Name: System maintenance\n\nTier2Name: Servicing event\n\nTier1Name: System not operating\n\nTier2Name: Inspection event\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Management\n\nFinding Tier3Name: Policy/procedure\n\nFinding Modifier Name: Pipeline operator\n\nFinding Report Text: Organizational - Management - Policy/procedure - Pipeline operator\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Management\n\nFinding Tier3Name: Policy/procedure\n\nFinding Modifier Name: Pipeline operator\n\nFinding Report Text: Organizational - Management - Policy/procedure - Pipeline operator\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Documentation/record keeping\n\nFinding Modifier Name: Pipeline operator\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Documentation/record keeping - Pipeline operator\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Enforcement\n\nFinding Modifier Name: Pipeline operator\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Enforcement - Pipeline operator\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Enforcement\n\nFinding Modifier Name: Pipeline operator\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Enforcement - Pipeline operator\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Development\n\nFinding Tier3Name: Selection/testing\n\nFinding Modifier Name: Pipeline operator\n\nFinding Report Text: Organizational - Development - Selection/testing - Pipeline operator\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Development\n\nFinding Tier3Name: Design\n\nFinding Modifier Name: Pipeline operator\n\nFinding Report Text: Organizational - Development - Design - Pipeline operator\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Oversight\n\nFinding Modifier Name: Pipeline operator\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Oversight - Pipeline operator\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Safety programs\n\nFinding Modifier Name: Pipeline operator\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Safety programs - Pipeline operator\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Management\n\nFinding Tier3Name: Culture\n\nFinding Modifier Name: Pipeline operator\n\nFinding Report Text: Organizational - Management - Culture - Pipeline operator\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Oversight\n\nFinding Modifier Name: Federal agency\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Oversight - Federal agency\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Development\n\nFinding Tier3Name: Selection/testing\n\nFinding Modifier Name: Emergency services\n\nFinding Report Text: Organizational - Development - Selection/testing - Emergency services\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Safety programs\n\nFinding Modifier Name: Emergency services\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Safety programs - Emergency services\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Enforcement\n\nFinding Modifier Name: Federal agency\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Enforcement - Federal agency\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Enforcement\n\nFinding Modifier Name: State/Local agency\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Enforcement - State/Local agency\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Safety programs\n\nFinding Modifier Name: State/Local agency\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Safety programs - State/Local agency\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Management\n\nFinding Tier3Name: Resources\n\nFinding Modifier Name: State/Local agency\n\nFinding Report Text: Organizational - Management - Resources - State/Local agency\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Development\n\nFinding Tier3Name: Manufacture/production\n\nFinding Modifier Name: Other institution/organization\n\nFinding Report Text: Organizational - Development - Manufacture/production - Other institution/organization\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Safety programs\n\nFinding Modifier Name: State/Local agency\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Safety programs - State/Local agency\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Safety programs\n\nFinding Modifier Name: State/Local agency\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Safety programs - State/Local agency\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Safety programs\n\nFinding Modifier Name: Federal agency\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Safety programs - Federal agency\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Enforcement\n\nFinding Modifier Name: State/Local agency\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Enforcement - State/Local agency\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Enforcement\n\nFinding Modifier Name: Federal agency\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Enforcement - Federal agency\n\nFinding Tier1Name: Pipeline\n\nFinding Tier2Name: Pipeline structure\n\nFinding Tier3Name: Joint/weld/seam\n\nFinding Modifier Name: Related records\n\nFinding Report Text: Pipeline - Pipeline structure - Joint/weld/seam - Related records\n\nFinding Tier1Name: Pipeline\n\nFinding Tier2Name: Pipeline structure\n\nFinding Tier3Name: Pipe seam\n\nFinding Modifier Name: Incorrect service/maintenance\n\nFinding Report Text: Pipeline - Pipeline structure - Pipe seam - Incorrect service/maintenance\n\nFinding Tier1Name: Pipeline\n\nFinding Tier2Name: Pipeline structure\n\nFinding Tier3Name: Joint/weld/seam\n\nFinding Modifier Name: Related operating info\n\nFinding Report Text: Pipeline - Pipeline structure - Joint/weld/seam - Related operating info\n\nFinding Tier1Name: Personnel\n\nFinding Tier2Name: Action/decision\n\nFinding Tier3Name: Action\n\nFinding Modifier Name: SCADA operations personnel\n\nFinding Report Text: Personnel - Action/decision - Action - SCADA operations personnel\n\nFinding Tier1Name: Personnel\n\nFinding Tier2Name: Action/decision\n\nFinding Tier3Name: Information processing/decision making\n\nFinding Modifier Name: SCADA maintenance personnel\n\nFinding Report Text: Personnel - Action/decision - Information processing/decision making - SCADA maintenance personnel\n\nFinding Tier1Name: Environment/Infrastructure\n\nFinding Tier2Name: Operating environment/control system\n\nFinding Tier3Name: SCADA system\n\nFinding Modifier Name: Availability of related info\n\nFinding Report Text: Environment/Infrastructure - Operating environment/control system - SCADA system - Availability of related info\n\nFinding Tier1Name: Pipeline\n\nFinding Tier2Name: Pipeline operation/capability\n\nFinding Tier3Name: Pipeline temp/pressure/flow parameter(s)\n\nFinding Modifier Name: Design\n\nFinding Report Text: Pipeline - Pipeline operation/capability - Pipeline temp/pressure/flow parameter(s) - Design\n\nFinding Tier1Name: Pipeline\n\nFinding Tier2Name: Pipeline operation/capability\n\nFinding Tier3Name: Pipeline integrity/capacity\n\nFinding Modifier Name: Related operating info\n\nFinding Report Text: Pipeline - Pipeline operation/capability - Pipeline integrity/capacity - Related operating info\n\nFinding Tier1Name: Personnel\n\nFinding Tier2Name: Physical\n\nFinding Tier3Name: Sensory ability/limitation\n\nFinding Modifier Name: SCADA maintenance personnel\n\nFinding Report Text: Personnel - Physical - Sensory ability/limitation - SCADA maintenance personnel\n\nFinding Tier1Name: Personnel\n\nFinding Tier2Name: Physical\n\nFinding Tier3Name: Impairment/incapacitation\n\nFinding Modifier Name: Federal government personnel\n\nFinding Report Text: Personnel - Physical - Impairment/incapacitation - Federal government personnel\n\nFinding Tier1Name: Personnel\n\nFinding Tier2Name: Task performance\n\nFinding Tier3Name: Planning/preparation\n\nFinding Modifier Name: Not specified\n\nFinding Report Text: Personnel - Task performance - Planning/preparation - Not specified\n\nFinding Tier1Name: Pipeline\n\nFinding Tier2Name: Pipeline structure\n\nFinding Tier3Name: Pipe\n\nFinding Modifier Name: Design\n\nFinding Report Text: Pipeline - Pipeline structure - Pipe - Design\n\nOfficial NTSB investigation data. NTSB findings determine probable cause and make safety recommendations; they do not adjudicate civil liability or regulatory violations.\n\nWhat Happened\nOn 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.\n\nWhat We Found\nThe 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.\n\nContributing 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.\n\nContributing 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.\n\nWhat We Recommended\nWe 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.\n\nPAR-11-01\n<<<PAGE 1>>>\n\nPacific Gas and Electric Company\nNatural Gas Transmission Pipeline Rupture and Fire\nSan Bruno, California\nSeptember 9, 2010\nAccident Report\nNTSB/PAR-11/01\nPB2011-916501\nNational\nTransportation\nSafety Board\n\n<<<PAGE 2>>>\n\nNTSB/PAR-11/01\nPB2011-916501\nNotation 8275C\nAdopted August 30, 2011\nPipeline Accident Report\nPacific Gas and Electric Company\nNatural Gas Transmission Pipeline Rupture and Fire\nSan Bruno, California\nSeptember 9, 2010\nNational\nTransportation\nSafety Board\n490 L’Enfant Plaza, S.W.\nWashington, DC 20594\n\n<<<PAGE 3>>>\n\nNational Transportation Safety Board. 2011. Pacific Gas and Electric Company Natural Gas\nTransmission Pipeline Rupture and Fire, San Bruno, California, September 9, 2010. Pipeline\nAccident Report NTSB/PAR-11/01. Washington, DC.\nAbstract: On September 9, 2010, about 6:11 p.m. Pacific daylight time, a 30-inch-diameter segment of\nan intrastate natural gas transmission pipeline known as Line 132, owned and operated by the Pacific Gas\nand Electric Company, ruptured in a residential area in San Bruno, California. The rupture occurred at\nmile point 39.28 of Line 132, at the intersection of Earl Avenue and Glenview Drive. The rupture\nproduced a crater about 72 feet long by 26 feet wide. The section of pipe that ruptured, which was about\n28 feet long and weighed about 3,000 pounds, was found 100 feet south of the crater. The Pacific Gas and\nElectric Company estimated that 47.6 million standard cubic feet of natural gas was released. The\nreleased natural gas ignited, resulting in a fire that destroyed 38 homes and damaged 70. Eight people\nwere killed, many were injured, and many more were evacuated from the area.\nAs a result of its investigation of this accident, the National Transportation Safety Board makes\nrecommendations to the U.S. Secretary of Transportation, the Pipeline and Hazardous Materials Safety\nAdministration, the governor of the state of California, the California Public Utilities Commission, the\nPacific Gas and Electric Company, the American Gas Association, and the Interstate Natural Gas\nAssociation of America.\nThe National Transportation Safety Board is an independent Federal agency dedicated to promoting aviation,\nrailroad, highway, marine, pipeline, and hazardous materials safety. Established in 1967, the agency is mandated by\nCongress through the Independent Safety Board Act of 1974 to investigate transportation accidents, determine the\nprobable causes of the accidents, issue safety recommendations, study transportation safety issues, and evaluate the\nsafety effectiveness of government agencies involved in transportation. The Safety Board makes public its actions\nand decisions through accident reports, safety studies, special investigation reports, safety recommendations, and\nstatistical reviews.\nRecent publications are available in their entirety on the Internet at <http://www.ntsb.gov>. Other information about\navailable publications also may be obtained from the website or by contacting:\nNational Transportation Safety Board\nRecords Management Division, CIO-40\n490 L’Enfant Plaza, SW\nWashington, DC 20594\n(800) 877-6799 or (202) 314-6551\nSafety Board publications may be purchased, by individual copy or by subscription, from the National Technical\nInformation Service. To purchase this publication, order report number PB2011-916501 from:\nNational Technical Information Service\n5301 Shawnee Road\nAlexandria, Virginia 22312\n(800) 553-6847 or (703) 605-6000\nThe Independent Safety Board Act, as codified at 49 U.S.C. Section 1154(b), precludes the admission into evidence\nor use of Board reports related to an incident or accident in a civil action for damages resulting from a matter\nmentioned in the report.\n\n<<<PAGE 4>>>\n\nNTSB Pipeline Accident Report\nContents\nFigures ........................................................................................................................................... vi\nTables ........................................................................................................................................... vii\nAcronyms and Abbreviations ................................................................................................... viii\nExecutive Summary .......................................................................................................................x\nInvestigation Synopsis .....................................................................................................................x\nProbable Cause.............................................................................................................................. xii\nRecommendations ......................................................................................................................... xii\n1. Factual Information ...................................................................................................................1\n1.1 Accident Narrative .....................................................................................................................1\n1.1.1 Preaccident Events ...........................................................................................................3\n1.1.2 Events Leading Up to Rupture ........................................................................................5\n1.1.3 The Rupture ...................................................................................................................12\n1.2 Emergency Response ...............................................................................................................12\n1.3 Injuries .....................................................................................................................................18\n1.4 Damage ....................................................................................................................................18\n1.5 Meteorological Information .....................................................................................................21\n1.6 Personnel Information ..............................................................................................................21\n1.6.1 Milpitas Technician and Other Workers at the Milpitas Terminal ................................21\n1.6.2 SCADA Operators .........................................................................................................22\n1.7 Pipeline Information ................................................................................................................23\n1.7.1 Line 132 .........................................................................................................................23\n1.7.2 1956 Relocation Project (Segment 180) ........................................................................25\n1.7.3 Multiyear Replacement Project and Seismic Risk .........................................................29\n1.7.4 Underground Environment at Accident Location ..........................................................30\n1.7.4.1 2008 Sewer Replacement .................................................................................30\n1.7.4.2 Guidelines for Pipe Bursting ............................................................................33\n1.7.4.3 Pipe Bursting Study .........................................................................................33\n1.7.5 Pipeline MAOP ..............................................................................................................33\n1.7.5.1 “Grandfather Clause” .......................................................................................34\n1.7.5.2 MAOP for Line 132 .........................................................................................35\n1.7.5.3 Periodic Pressure Increases to MAOP .............................................................36\n1.7.6 History of Seam Defects in PG&E Gas Transmission Pipelines ...................................38\n1.7.7 Protection Against Accidental Overpressure .................................................................39\n1.8 Examination of Accident Pipe .................................................................................................39\n1.8.1 Welds .............................................................................................................................41\n1.8.2 Crack Initiation ..............................................................................................................43\n1.8.3 Material Properties .........................................................................................................46\n1.8.4 Historical Information About Steel Grades ...................................................................47\n1.8.5 Burst Pressure Study and Finite Element Modeling ......................................................48\niii\n\n<<<PAGE 5>>>\n\nNTSB Pipeline Accident Report\n1.9 Pipeline Operations and Management .....................................................................................51\n1.9.1 SCADA System Operations ..........................................................................................51\n1.9.1.1 Milpitas Terminal.............................................................................................52\n1.9.1.2 Work Clearance Procedures .............................................................................54\n1.9.1.3 Emergency Response Procedures ....................................................................55\n1.9.2 Use of Automatic Shutoff Valves and Remote Control Valves ....................................56\n1.9.3 Public Awareness ...........................................................................................................57\n1.9.4 PG&E Risk Management/Integrity Management Program ...........................................59\n1.9.4.1 Geographic Information System ......................................................................59\n1.9.4.2 Risk Management Procedures..........................................................................61\n1.9.4.3 Threats Identified for Line 132 ........................................................................65\n1.10 Oversight ................................................................................................................................67\n1.10.1 State Oversight by CPUC ............................................................................................67\n1.10.2 Federal Oversight by PHMSA .....................................................................................69\n1.11 Postaccident Actions ..............................................................................................................71\n1.11.1 Actions Taken by PG&E .............................................................................................71\n1.11.2 Actions Taken by CPUC .............................................................................................72\n1.11.3 Actions Taken by PHMSA ..........................................................................................74\n1.11.4 Actions Taken by Congress .........................................................................................74\n1.12 Previous NTSB Safety Recommendations ............................................................................75\n1.12.1 January 3, 2011, Safety Recommendations to PG&E, CPUC, and\nPHMSA Regarding Record-keeping and Hydrostatic Pressure Testing ................................75\n1.12.2 June 8, 2011, Safety Recommendations to PHMSA and PG&E\nConcerning Emergency Response ..........................................................................................77\n1.12.3 Other Relevant Recommendations ..............................................................................78\n1.12.3.1 Grandfathering of Higher Permissible Stress Levels for Pre-\n1970 Pipelines ..............................................................................................................78\n1.12.3.2 Constructing and Modifying Pipelines to Accommodate Use\nof In-Line Inspection Equipment .................................................................................79\n1.12.3.3 Rapid Shutdown and ASVs and RCVs ..........................................................80\n1.13 Other Information ..................................................................................................................81\n1.13.1 Pipeline Assessment Methods for Integrity Management ...........................................81\n1.13.1.1 Pressure Testing .............................................................................................82\n1.13.1.2 In-line Inspection ...........................................................................................83\n1.13.1.3 Direct Assessment ..........................................................................................85\n1.13.2 Automatic Shutoff Valve Technology .........................................................................86\n1.13.3 2008 Natural Gas Explosion in Rancho Cordova, California ......................................87\n2. Analysis .....................................................................................................................................88\n2.1 Introduction ..............................................................................................................................88\n2.2 Preaccident Events ...................................................................................................................90\n2.2.1 Work Clearance Procedures for Electrical Work at Milpitas Terminal ........................90\n2.2.2 Internal Line Pressure Prior to Failure ...........................................................................91\n2.3 Cause of Pipeline Rupture .......................................................................................................92\n2.3.1 Fracture Origin and Failure ...........................................................................................93\n2.3.2 Deficiencies in Fabrication of Accident Pipe Segment .................................................94\niv\n\n<<<PAGE 6>>>\n\nNTSB Pipeline Accident Report\n2.3.3 Deficiencies in Quality Control Associated with 1956 Relocation\nProject .....................................................................................................................................95\n2.3.4 2008 Sewer Pipe Bursting Operation ............................................................................96\n2.4 Adequacy of PG&E Emergency Response ..............................................................................97\n2.4.1 Internal Communication and Coordination ...................................................................98\n2.4.2 Notifying Emergency Responders ...............................................................................100\n2.4.3 Line Break Recognition ...............................................................................................101\n2.4.4 Rapid Shutdown, ASVs, and RCVs ............................................................................102\n2.4.5 Deficiencies in Postaccident Drug and Alcohol Testing .............................................104\n2.5 MAOP ....................................................................................................................................106\n2.5.1 MAOP of Line 132 ......................................................................................................106\n2.5.2 Grandfathering of Pre-1970 Pipelines .........................................................................106\n2.6 Integrity Management Program .............................................................................................107\n2.6.1 PG&E GIS and Pipeline Record-keeping ....................................................................108\n2.6.2 Threat Identification and Risk Assessment .................................................................110\n2.6.2.1 Weighting of Threats .....................................................................................110\n2.6.2.2 Identification and Assessment of Design/Material and\nConstruction Threats on Line 132..............................................................................110\n2.6.2.3 Regulatory Assumption of Stable Manufacturing- and\nConstruction-Related Defects .....................................................................................112\n2.6.3 Self-Assessment of Program Effectiveness .................................................................113\n2.6.4 Summary of PG&E Integrity Management Practices ..................................................114\n2.7 Adequacy of PG&E’s Public Awareness Program Evaluation..............................................115\n2.8 Summary of PG&E Practices.................................................................................................116\n2.9 Inspection Technology ...........................................................................................................118\n2.10 Oversight ..............................................................................................................................119\n2.10.1 Performance-Based Safety Programs ........................................................................119\n2.10.2 Authority and Enforcement .......................................................................................122\n3. Conclusions .............................................................................................................................124\n3.1 Findings..................................................................................................................................124\n3.2 Probable Cause.......................................................................................................................127\n4. Recommendations ..................................................................................................................128\n4.1 New Recommendations .........................................................................................................128\n4.2 Previously Issued Recommendations ....................................................................................132\n4.3 Previously Issued Recommendations Classified in This Report ...........................................134\n5. Appendix .................................................................................................................................140\nv\n\n<<<PAGE 7>>>\n\nNTSB Pipeline Accident Report\nFigures\nFigure 1. Picture of crater and ruptured pipeline. .......................................................................... 2\nFigure 2. Picture of ejected pipe section. ....................................................................................... 2\nFigure 3. Aerial view of fire........................................................................................................... 3\nFigure 4. Overview of Line 132. .................................................................................................... 4\nFigure 5. Picture of local control panel. ......................................................................................... 6\nFigure 6a. Normal electrical configuration at the Milpitas Terminal. ........................................... 7\nFigure 6b. Temporary electrical configuration at the Milpitas Terminal preceding\nthe accident. .................................................................................................................................... 8\nFigure 7. Schematic showing regulating valve control. ................................................................. 8\nFigure 8a. Valve configuration at the Milpitas Terminal prior to 5:22 p.m. ............................... 10\nFigure 8b. Valve configuration at the Milpitas Terminal about 5:25 p.m. .................................. 11\nFigure 9. Firefighters approaching accident scene. ...................................................................... 13\nFigure 10. Location of valve closures. ......................................................................................... 17\nFigure 11. Picture showing area of damage from blast and fire. ................................................. 19\nFigure 12. Picture of destroyed houses. ....................................................................................... 20\nFigure 13. Picture of a burned car in front of several destroyed houses. ..................................... 20\nFigure 14. Map showing PG&E peninsula gas transmission lines. ............................................. 24\nFigure 15. Line 132 installation, relocations, and replacements. ................................................. 26\nFigure 16. Sketch of underground utilities environment. ............................................................ 30\nFigure 17. Diagram of excavations relative to Segment 180. ...................................................... 32\nFigure 18. Schematic of accident pipe. ........................................................................................ 40\nFigure 19a. Picture showing cross section of longitudinal seam in pup 1. .................................. 42\nFigure 19b. Picture showing cross section of longitudinal seam in typical DSAW\npipe. ............................................................................................................................................... 42\nFigure 20. Picture of pipe section with white arrows showing direction of crack\npropagation. .................................................................................................................................. 44\nFigure 21. Pictures highlighting rupture initiation site in pup 1 longitudinal seam. .................... 45\nFigure 22a. Stress contours at an internal pressure of 375 psig for the finite\nelement model of the weld geometry similar to pup 1. Contour values are the\nsame as in figure 22b. ................................................................................................................... 50\nFigure 22b. Stress contours at an internal pressure of 375 psig for the finite\nelement model of a DSAW seam. Contour values are the same as in figure 22a. ........................ 50\nFigure 23. Flowchart of PG&E’s emergency response procedures. ............................................ 55\nvi\n\n<<<PAGE 8>>>\n\nNTSB Pipeline Accident Report\nTables\nTable 1. Injuries............................................................................................................................ 18\nTable 2. PG&E gas transmission pipeline seam leaks or test failures, 1948–2011. .................... 39\nTable 3. Average and standard deviation of mechanical test data for all lengths of\npipe. ............................................................................................................................................... 46\nTable 4. Minimum yield strength, tensile strength, and elongation requirements\naccording to PG&E and API pipe specifications. ......................................................................... 47\nTable 5. Incoming and outgoing lines at Milpitas Terminal. ....................................................... 53\nTable 6. Survey postcard responses to public awareness brochures. ........................................... 59\nTable 7. PG&E’s reportable events by cause for 2004–2010. ..................................................... 65\nTable 8. Line 132 risk values. ...................................................................................................... 66\nvii\n\n<<<PAGE 9>>>\n\nNTSB Pipeline Accident Report\nAcronyms and Abbreviations\nAGA American Gas Association\nANPRM advance notice of proposed rulemaking\nAPI American Petroleum Institute\nASME American Society of Mechanical Engineers\nASOS Automated Surface Observing System\nASTM American Society for Testing and Materials\nASV automatic shutoff valve\nCFR Code of Federal Regulations\nCOF consequence of failure\nConsolidated Western Consolidated Western Steel Corporation\nCPUC California Public Utilities Commission\nDOT U.S. Department of Transportation\nDSAW double submerged arc welded\nECDA external corrosion direct assessment\nERW electric resistance welded\nGIS geographic information system\nGRI Gas Research Institute\nGSR gas service representative\nGTI Gas Technology Institute\nHCA high consequence area\nHV Vickers hardness number\nINGAA Interstate Natural Gas Association of America\nKSFO San Francisco International Airport\nviii\n\n<<<PAGE 10>>>\n\nNTSB Pipeline Accident Report\nksi 1,000 pounds per square inch\nLOF likelihood of failure\nMAOP maximum allowable operating pressure\nMOP maximum operating pressure\nMP mile point\nNPRM notice of proposed rulemaking\nNTSB National Transportation Safety Board\nPAPERS Public Awareness Program Effectiveness Research Survey\nPG&E Pacific Gas and Electric Company\nPHMSA Pipeline and Hazardous Materials Safety Administration\nPLC programmable logic controller\npsi pounds per square inch\npsig pounds per square inch, gauge\nRCV remote control valve\nRMP risk management procedure\nRSPA Research and Special Programs Administration\nSBFD San Bruno Fire Department\nSCADA supervisory control and data acquisition\nSMLS seamless\nSMYS specified minimum yield strength\nthe Corps U.S. Army Corps of Engineers\nUPS uninterruptible power supply\nix\n\n<<<PAGE 11>>>\n\nNTSB Pipeline Accident Report\nExecutive Summary\nOn September 9, 2010, about 6:11 p.m. Pacific daylight time, a 30-inch-diameter\nsegment of an intrastate natural gas transmission pipeline known as Line 132, owned and\noperated by the Pacific Gas and Electric Company (PG&E), ruptured in a residential area in\nSan Bruno, California. The rupture occurred at mile point 39.28 of Line 132, at the intersection\nof Earl Avenue and Glenview Drive. The rupture produced a crater about 72 feet long by 26 feet\nwide. The section of pipe that ruptured, whic","truncated":true,"body_characters":418846}