{"operation":"document","citation":"PLD19MR001","title":"Pacific Gas & Electric Third-Party Line Strike and Fire","source_type":"incident","agency":"National Transportation Safety Board","status":"current","official":true,"published_on":"2021-10-14","effective_on":"2019-02-06","summary":"Accident. in San Francisco, CA, USA. on 2019-02-06. Pacific Gas & Electric. Leak/explosion/fire","machine_formats":{"json":"https://regulus.evalyn.ai/document/ntsb-case-pld19mr001.json","markdown":"https://regulus.evalyn.ai/document/ntsb-case-pld19mr001.md"},"app_url":"https://regulus.evalyn.ai/document/ntsb-case-pld19mr001","source_url":"https://www.ntsb.gov/investigations/Pages/PLD19MR001.aspx","body":"NTSB investigation PLD19MR001.\n\nEvent Type: Accident\n\nEvent Date: 2019-02-06\n\nEvent City: San Francisco\n\nEvent State Or Region: CA\n\nEvent Country: USA\n\nPipeline Operator: Pacific Gas & Electric\n\nPipeline Type: Distribution\n\nAccident Type: Leak/explosion/fire\n\nCompletion Status: Completed\n\nReport Number: 67135\n\nReport Date: 2021-07-27\n\nProbable cause: The National Transportation Safety Board determines that the probable cause of the February 6, 2019 release of natural gas from a Pacific Gas & Electric distribution main and resulting fire was the failure of Kilford Engineering, Inc. to follow safe excavation practices within the tolerance zone which caused the impact of the bucket attachment of the mini excavator with the branch connection, that led to a longitudinal fracture in the 4-inch distribution main.\n\nTier1Name: Other\n\nTier2Name: Fire (post-release)\n\nTier1Name: System shutdown\n\nTier2Name: Emergency response\n\nTier1Name: Emergency response\n\nTier2Name: Evacuation\n\nTier1Name: System shutdown\n\nTier2Name: Product leak/release\n\nTier1Name: Other\n\nTier2Name: External/third-party damage\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Development\n\nFinding Tier3Name: Design\n\nFinding Modifier Name: Emergency services\n\nFinding Report Text: Organizational - Development - Design - Emergency services\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: Enforcement\n\nFinding Modifier Name: State/Local agency\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Enforcement - State/Local agency\n\nFinding Tier1Name: Personnel\n\nFinding Tier2Name: Action/decision\n\nFinding Tier3Name: Action\n\nFinding Modifier Name: Equipment/vehicle operator\n\nFinding Report Text: Personnel - Action/decision - Action - Equipment/vehicle operator\n\nFinding Tier1Name: Personnel\n\nFinding Tier2Name: Action/decision\n\nFinding Tier3Name: Information processing/decision making\n\nFinding Modifier Name: Equipment/vehicle operator\n\nFinding Report Text: Personnel - Action/decision - Information processing/decision making - Equipment/vehicle operator\n\nFinding Tier1Name: Personnel\n\nFinding Tier2Name: Action/decision\n\nFinding Tier3Name: Information processing/decision making\n\nFinding Modifier Name: Equipment/vehicle operator\n\nFinding Report Text: Personnel - Action/decision - Information processing/decision making - Equipment/vehicle operator\n\nFinding Tier1Name: Environment/Infrastructure\n\nFinding Tier2Name: Physical environment\n\nFinding Tier3Name: Vehicle/equipment operations\n\nFinding Modifier Name: Compliance w/ procedure\n\nFinding Report Text: Environment/Infrastructure - Physical environment - Vehicle/equipment operations - Compliance w/ procedure\n\nFinding Tier1Name: Environment/Infrastructure\n\nFinding Tier2Name: Operating environment/control system\n\nFinding Tier3Name: Communication system\n\nFinding Modifier Name: Availability of related info\n\nFinding Report Text: Environment/Infrastructure - Operating environment/control system - Communication system - Availability of related info\n\nFinding Tier1Name: Pipeline\n\nFinding Tier2Name: Pipline systems/equipment\n\nFinding Tier3Name: (general)\n\nFinding Modifier Name: Not specified\n\nFinding Report Text: Pipeline - Pipline systems/equipment - (general) - Not specified\n\nFinding Tier1Name: Personnel\n\nFinding Tier2Name: Experience/knowledge\n\nFinding Tier3Name: Knowledge\n\nFinding Modifier Name: Equipment/vehicle operator\n\nFinding Report Text: Personnel - Experience/knowledge - Knowledge - Equipment/vehicle operator\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 February 6, 2019, the excavator operator for a third-party contractor, Kilford Engineering Inc., impacted a Pacific Gas & Electric Company (PG&E) branch connection with the mini excavator trenching bucket attachment during mechanical excavation for fiberoptic conduit installation, which resulted in the release and ignition of natural gas. The accident occurred in the Richmond District, a neighborhood in San Francisco, California. A nearby restaurant with a rental unit above caught fire. There were no injuries. Estimated damages to nearby buildings and the pipeline system exceeded $10 million.\nThe San Francisco Fire Department was dispatched and arrived on scene and focused on containing the fire and minimizing its spread while PG&E crews worked to isolate and shut down the gas pipeline line. The fire department and police department evacuated about 100 persons, and PG&E shut off natural gas service to 328 customers. At 3:36 p.m., the damaged pipelines and branch connection were isolated, and the fire department extinguished the gas fire 2 minutes later.\n\nWhat We Found\nWe determined that the probable cause of the release of natural gas from the Pacific Gas & Electric Company distribution pipeline and the subsequent fire was the failure of the Kilford Engineering Inc. operator and spotter to follow safe excavation practices within the tolerance zone, which resulted in the mini excavator trenching bucket attachment impacting the branch connection.\n\nWhat We Recommended\nAs a result of the investigation, we made one recommendation each to the San Francisco Police Department, Fire\nDepartment, and Department of Emergency Management and two recommendations to PG&E.\n\nPAR-21-02\n<<<PAGE 1>>>\n\nPacific Gas & Electric Third-Party Line Strike and Fire\nSan Francisco, California\nFebruary 6, 2019\nAccident Report\nNTSB/PAR-21/02\nPB2021-100925\nNational\nTransportation\nSafety Board\n\n<<<PAGE 2>>>\n\nNTSB/PAR-21/02\nPB2021-100925\nNotation 67135\nAdopted July 27, 2021\nPipeline Accident Report\nPacific Gas & Electric Third-Party Line Strike and Fire\nSan Francisco, California\nFebruary 6, 2019\nNational\nTransportation\nSafety Board\n490 L’Enfant Plaza, S.W.\nWashington, D.C. 20594\n\n<<<PAGE 3>>>\n\nNational Transportation Safety Board. 2021. Pacific Gas & Electric Third-Party Line Strike and Fire,\nSan Francisco, California, February 6, 2019. NTSB/PAR-21/02. Washington, DC: NTSB.\nAbstract: On February 6, 2019, at 1:07 p.m. local time, the excavator operator for a third-party contractor,\nKilford Engineering Inc., impacted a Pacific Gas & Electric Company (PG&E) branch connection with a\nmini excavator trenching bucket attachment during mechanical excavation for fiberoptic conduit\ninstallation, which resulted in the release and ignition of natural gas. The accident occurred in the Richmond\nDistrict of San Francisco, California. A nearby restaurant with a rental unit above caught fire. There were\nno injuries. Estimated damages to nearby buildings and the pipeline system exceeded $10 million. The\nNational Transportation Safety Board (NTSB) determined that the probable cause of the accident was the\nfailure of the Kilford operator and spotter to follow safe excavation practices within the tolerance zone,\nwhich resulted in the mini excavator trenching bucket attachment impacting the pipeline’s branch\nconnection. The investigators focused on the safety issues of third-party excavation damage to buried\nnatural gas pipelines, enforcement challenges of California’s damage prevention law, PG&E’s data\nintegration gaps during the development of the valve isolation plan, and insufficient joint emergency\nresponse planning between PG&E and San Francisco emergency response agencies. As a result of the\ninvestigation, the NTSB makes one recommendation each to the San Francisco Police Department, Fire\nDepartment, and Department of Emergency Management and two recommendations to PG&E.\nThe National Transportation Safety Board (NTSB) is an independent federal agency dedicated to promoting aviation,\nrailroad, highway, marine, and pipeline safety. Established in 1967, the agency is mandated by Congress through the\nIndependent Safety Board Act of 1974, to investigate transportation accidents, determine the probable causes of the\naccidents, issue safety recommendations, study transportation safety issues, and evaluate the safety effectiveness of\ngovernment agencies involved in transportation. The NTSB makes public its actions and decisions through accident\nreports, safety studies, special investigation reports, safety recommendations, and statistical reviews.\nThe NTSB does not assign fault or blame for an accident or incident; rather, as specified by NTSB regulation,\n“accident/incident investigations are fact-finding proceedings with no formal issues and no adverse parties … and are\nnot conducted for the purpose of determining the rights or liabilities of any person” (Title 49 Code of Federal\nRegulations section 831.4). Assignment of fault or legal liability is not relevant to the NTSB’s statutory mission to\nimprove transportation safety by investigating accidents and incidents and issuing safety recommendations. In\naddition, statutory language prohibits the admission into evidence or use of any part of an NTSB report related to an\naccident in a civil action for damages resulting from a matter mentioned in the report (Title 49 United States Code\nsection 1154(b)).\nFor more detailed background information on this report, visit the Accident Dockets link and search for NTSB accident\nID PLD19MR001. Recent publications are available in their entirety on the NTSB website. 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\nCopies of NTSB publications may be downloaded at no cost from the National Technical Information Service, at the\nNational Technical Reports Library search page, using product number PB2021-100925. For additional assistance,\ncontact—\nNational Technical Information Service\n5301 Shawnee Rd. Alexandria, VA 22312\n(800) 553-6847 or (703) 605-6000\nNTIS website\n\n<<<PAGE 4>>>\n\nNTSB Pipeline Accident Report\nContents\nContents ......................................................................................................................................i\nFigures ..................................................................................................................................... iii\nTables........................................................................................................................................ iv\nAbbreviations and Acronyms ................................................................................................... v\nExecutive Summary ................................................................................................................. vi\nAccident Summary ..................................................................................................................... vi\nProbable Cause .......................................................................................................................... vi\nSafety Issues .............................................................................................................................. vi\nFindings ....................................................................................................................................vii\nRecommendations ................................................................................................................... viii\n1 Factual Information ............................................................................................................ 1\n1.1 Accident Description ........................................................................................................... 1\n1.1.1 Excavation Planning .................................................................................................. 2\n1.1.2 Excavation Operation................................................................................................. 4\n1.2 Response to Gas Release and Fire ........................................................................................ 8\n1.2.1 San Francisco Police and Fire Department Response ................................................. 8\n1.2.2 Pacific Gas & Electric Response ................................................................................ 9\n1.3 PG&E Natural Gas Systems and Main Specifications ........................................................ 13\n1.3.1 PG&E Overview ...................................................................................................... 13\n1.3.2 Pipeline System ....................................................................................................... 14\n1.3.3 Emergency Response Procedures ............................................................................. 15\n1.4 Postaccident Pipeline Examination ..................................................................................... 15\n1.5 Kilford Engineering ........................................................................................................... 19\n1.5.1 Licensing ................................................................................................................. 19\n1.5.2 Safety Procedures .................................................................................................... 20\n1.5.3 Postaccident interviews with Kilford’s Mini Excavator Operator ............................. 21\n1.5.4 Past Incident ............................................................................................................ 21\n1.6 California Damage Prevention Regulations ........................................................................ 22\n1.6.1 Excavation Regulations............................................................................................ 22\n1.6.2 California Public Utilities Commission .................................................................... 22\n1.6.3 Contractors State License Board .............................................................................. 23\n1.6.4 California Underground Facilities Safe Excavation Board ........................................ 24\n1.6.5 Damage Prevention Program Evaluation .................................................................. 25\n2 Analysis .............................................................................................................................. 26\n2.1 Introduction ....................................................................................................................... 26\n2.2 Exclusions ......................................................................................................................... 26\n2.3 Third-Party Excavation Damage ........................................................................................ 27\n2.3.1 Kilford Engineering Inc. .......................................................................................... 27i\n\n<<<PAGE 5>>>\n\nNTSB Pipeline Accident Report\n2.3.2 Enforcement Challenges of California Damage Prevention Law .............................. 29\n2.4 Data Integration and Emergency Response ........................................................................ 30\n2.5 Coordination of Emergency Response ................................................................................ 30\n3 Conclusions ........................................................................................................................ 32\n3.1 Findings ............................................................................................................................. 32\n3.2 Probable Cause .................................................................................................................. 32\n4 Recommendations ............................................................................................................. 34\nAppendix A: Investigation ...................................................................................................... 35\nAppendix B: Consolidated Recommendation Information ................................................... 36\nReferences................................................................................................................................ 38\nii\n\n<<<PAGE 6>>>\n\nNTSB Pipeline Accident Report\nFigures\nFigure 1. Northwest-facing view of fire during emergency response. ..........................................2\nFigure 2 Kilford’s project area. ...................................................................................................3\nFigure 3. One-call street markings at northwest corner of Parker Ave. and Geary Blvd. ..............4\nFigure 4. Excavation work plan on the day of the accident. ........................................................5\nFigure 5. Mini excavator in storage postaccident. .......................................................................6\nFigure 6. Trench depth comparisons. ..........................................................................................7\nFigure 7. Postfire south-facing view of trench and excavator on Parker Ave. ..............................8\nFigure 8. Map of location of gas pipelines affected the accident. .............................................. 11\nFigure 9. Final valve isolation plan with valves closed and location of damage......................... 12\nFigure 10. Postaccident 2-inch pipeline, 4-inch pipeline, branch connection, and cutter insert .16\nFigure 11. Close-up view of bend area in 2-inch pipeline. ........................................................ 17\nFigure 12. Side view of cutter insert showing diagonal gouge. .................................................. 18\nFigure 13. View of fracture area in the 4-inch pipeline. ............................................................ 19\niii\n\n<<<PAGE 7>>>\n\nNTSB Pipeline Accident Report\nTables\nTable 1. Valve isolation plan (VIP) development timeline for February 6, 2019. ...................... 12\nTable 2. Valve closure times. .................................................................................................... 13\nTable 3. Timeline of emergency response events. ..................................................................... 13\nTable 4. Specifications for pipelines involved in accident. ........................................................ 14\nTable 5. Laboratory-measured pipeline dimensions. ................................................................. 16\niv\n\n<<<PAGE 8>>>\n\nNTSB Pipeline Accident Report\nAbbreviations and Acronyms\n911 dispatch Department of Emergency Management Public Safety Dispatch Center\nCFR Code of Federal Regulations\nCGA Common Ground Alliance\nCPUC California Public Utilities Commission\nCSLB Contractors State License Board\nDig Safe Board California Underground Facilities Safe Excavation Board\nGDCC Gas Distribution Control Center\nGIS geographic information system\nGM&C Gas Maintenance and Construction\nGOV State of California Government Code\nGPOM Gas Pipeline Operations and Maintenance\nGSP gas system planning\nIC incident commander\nNOPV Notice of Probable Violation\nNTSB National Transportation Safety Board\nOSHA Occupational Safety and Health Administration\nPG&E Pacific Gas & Electric Company\nPHMSA Pipeline and Hazardous Materials Safety Administration\nSFDEM San Francisco Department of Emergency Management\nSFFD San Francisco Fire Department\nSFPD San Francisco Police Department\nUSC United States Code\nVIP valve isolation plan\nv\n\n<<<PAGE 9>>>\n\nNTSB Pipeline Accident Report\nExecutive Summary\nAccident Summary\nOn February 6, 2019, at 1:07 p.m. local time, the excavator operator for a third-party\ncontractor, Kilford Engineering Inc., impacted a Pacific Gas & Electric Company (PG&E) branch\nconnection with the mini excavator trenching bucket attachment during mechanical excavation for\nfiberoptic conduit installation, which resulted in the release and ignition of natural gas. The\naccident occurred in the Richmond District, a neighborhood in San Francisco, California. A nearby\nrestaurant with a rental unit above caught fire. There were no injuries. Estimated damages to\nnearby buildings and the pipeline system exceeded $10 million.\nAt 1:09 p.m., the San Francisco Fire Department was dispatched and arrived on scene at\n1:12 p.m. The fire department focused on containing the fire and minimizing its spread while\nPG&E crews worked to isolate and shut down the gas pipeline line. The fire department and police\ndepartment evacuated about 100 persons, and PG&E shut off natural gas service to 328 customers.\nAt 3:36 p.m., the damaged pipelines and branch connection were isolated, and the fire department\nextinguished the gas fire 2 minutes later.1\nProbable Cause\nThe National Transportation Safety Board determines that the probable cause of the\nFebruary 6, 2019, release of natural gas from the Pacific Gas & Electric Company distribution\npipeline and the subsequent fire was the failure of the Kilford Engineering Inc. operator and spotter\nto follow safe excavation practices within the tolerance zone, which resulted in the mini excavator\ntrenching bucket attachment impacting the pipeline’s branch connection.\nSafety Issues\nThis report focuses on the following safety issues:\n• Third-party excavation damage to buried natural gas pipelines. Third-party excavation\ndamage is the number one cause of pipeline accidents. In this case, Kilford failed to follow\nsafe excavation practices within the tolerance zone of the existing underground utilities by\nmechanically excavating near the gas pipeline.\n• Enforcement challenges of California’s damage prevention law. At the time of the\naccident, California did not have an operational damage prevention enforcement program\nin place; the program became operational in July 2020. Enforcement has been shown to be\n1 For more information, see the factual information and analysis sections of this report. Additional information\ncan be found in the public docket for this National Transportation Safety Board (NTSB) accident investigation\n(accident number PLD19MR001) by accessing the Accident Dockets link at www.ntsb.gov. For information about\nour safety recommendations, see the Safety Recommendation Database at the same website.\nvi\n\n<<<PAGE 10>>>\n\nNTSB Pipeline Accident Report\nthe strongest method of preventing damage to buried utilities. Kilford had previously\ndamaged an underground utility during excavation; however, because California’s damage\nprevention enforcement program was not yet in place, no actions were taken against the\ncompany. On January 26, 2021, the Pipeline and Hazardous Materials Safety\nAdministration changed its evaluation of the state of California’s damage prevention\nenforcement program from inadequate to adequate.\n• PG&E’s data integration gaps during the development of the VIP. A critical part of\nany emergency response to a natural gas distribution incident is the development of a valve\nisolation plan, which is used by field personnel to isolate a damaged portion of pipeline\nand stop the release of gas. Any delays in the creation of such a plan can result more gas\nrelease and greater impact to customers. In this accident, it took PG&E about an hour to\nidentify the specific locations of the valves that needed to be isolated.\n• Insufficient joint emergency response planning between PG&E and San Francisco,\nCalifornia, emergency response agencies. During the emergency response, an important\npiece of equipment needed to isolate a gas supply pipeline was delayed en route to the\naccident scene. While it ultimately did not affect the overall response, such delays in the\nevent of a gas release could have negative impacts. By coordinating with emergency\nresponse agencies, such delays could be reduced or eliminated.\nFindings\n• The following factors did not contribute to the cause of the accident: two one-call ticket\nrequests, locate and mark activities, and California regulations regarding the tolerance\nzone. Further, Pacific Gas & Electric Company’s pipeline was intact and operating as\ndesigned prior to the accident.\n• Natural gas facilities were accurately marked, and Kilford Engineering Inc. employees\nworking at the site were aware of the markings indicating the locations of the 4-inch gas\npipeline, 2-inch gas pipeline, and branch connection before the start of excavation.\n• Kilford Engineering Inc. did not follow safe excavation practices when it mechanically\nexcavated within the tolerance zone, resulting in the Kilford Engineering Inc. operator\nimpacting the 2-inch branch connection with the mini excavator trenching bucket,\ncausing the release of natural gas.\n• Because California did not have an excavation damage enforcement program at the time\nof the water line strike, the state missed an opportunity to identify and deter poor safety\nactivities presented by a new contractor.\n• Although sufficient data are not yet available to determine if the California Underground\nFacilities Safe Excavation Board’s enforcement actions have been effective in deterring\nfuture damage, enforcement is a step in the right direction for preventing third party\ndamage to buried utilities.\nvii\n\n<<<PAGE 11>>>\n\nNTSB Pipeline Accident Report\n• Had Pacific Gas & Electric Company incorporated geographic information system\nlocation data into the software program used to develop its valve isolation plan prior to\nthis accident, it would have reduced the time to isolate the natural gas release.\n• Pacific Gas & Electric Company did not follow its own procedures regarding requests\nfor police escorts, which may have delayed the arrival of Pacific Gas & Electric Company\npersonnel on scene during the emergency response.\n• While the lack of a memorandum of understanding with the San Francisco Department\nof Emergency Management, San Francisco Police Department, or San Francisco Fire\nDepartment addressing emergency response plans did not affect the timeliness of the\nPacific Gas & Electric Company shutting off the flow of gas in this accident, it could\npotentially affect other responses where the squeeze-off point is accessible and/or the\nvalve locations are readily known.\nRecommendations\nTo the San Francisco Police Department, San Francisco Fire Department, and San\nFrancisco Department of Emergency Management:\nWork with Pacific Gas & Electric Company to establish an agreement to provide a\ncoordinated response and reduce response times for Pacific Gas & Electric Company’s\ncrews to arrive at the scene of a pipeline accident. (P-21-15)\nTo Pacific Gas & Electric Company:\nIn collaboration with the San Francisco Police Department, San Francisco Fire Department,\nand the San Francisco Department of Emergency Management, establish an agreement to\nprovide a coordinated response and reduce response times for your crews to arrive at the\nscene of a pipeline accident. (P-21-16)\nComplete the integration of detailed location data into your hydraulic modeling software\nso that this information is readily available for all system assets when developing a valve\nisolation plan. (P-21-17)\nviii\n\n<<<PAGE 12>>>\n\nNTSB Pipeline Accident Report\n1 Factual Information\n1.1 Accident Description\nOn February 6, 2019, Kilford Engineering Inc. (Kilford), a third-party contractor, was\nexcavating a trench to install fiberoptic conduit at the intersection of Geary Boulevard and Parker\nAvenue in San Francisco, California.1 During mechanical excavation, at 1:07 p.m., the operator of\na mini excavator impacted a Pacific Gas & Electric Company (PG&E) branch connection between\na 4-inch natural gas distribution pipeline and a 2-inch natural gas pipeline with the mini excavator’s\ntrenching bucket.2 Shortly after the branch connection was damaged, the releasing gas ignited,\nresulting in structure fires in several surrounding buildings. (See figure 1.) The damaged segment\nwas isolated at 3:36 p.m., and the structure fires were contained at 4:24 p.m. No injuries occurred\nas a result of this accident.\n3\n1 A third-party contractor is a contractor who performs excavation work independently of natural gas companies.\nFor more information on third-party contractors and third-party damage, see the analysis section of this report.\n2 All times in this report are in local time.\n3 For more information, see the factual information and analysis sections of this report. Additional information\ncan be found in the public docket for this National Transportation Safety Board (NTSB) accident investigation\n(accident number PLD19MR001) by accessing the Accident Dockets link at www.ntsb.gov. For information about\nour safety recommendations, see the Safety Recommendation Database at the same website.\n1\n\n<<<PAGE 13>>>\n\nNTSB Pipeline Accident Report\nFigure 1. Northwest-facing view of fire during emergency response. (Photo courtesy of PG&E.)\n1.1.1 Excavation Planning\nThrough multiple subcontracts, Kilford was hired to conduct excavation work and install\nconduit for fiberoptic cabling for Verizon along Geary Boulevard in San Francisco. (See\nsection 1.5 for more information about Kilford.) The project extended from 3310 Geary Boulevard\nto the intersection of Geary Boulevard and Masonic Avenue, and the trench excavation was in the\nnorthernmost lane of Geary Boulevard. (See figure 2.) The project was segmented into\n13 subprojects, each about one-half block long. The first segment was from 3310 Geary Boulevard\nto the intersection of Geary Boulevard and Parker Avenue.\n2\n\n<<<PAGE 14>>>\n\nNTSB Pipeline Accident Report\nFigure 2 Kilford’s project area.\nThe scope of work called for 1,888 feet of trench excavation and the installation of 3,798\nfeet of 2-inch high-density polyethylene conduit inside 4-inch polyvinyl chloride piping at a depth\nof 36 inches. As part of the work, Kilford was responsible for maintaining a minimum of 24 inches\nof separation from existing utilities and for determining the location and depth of the existing\nutilities.\nIn preparation for excavation, Kilford placed a “one-call” ticket on January 21, 2019, to\nrequest the location and marking of buried utilities within the project area.\n4 Information from the\nJanuary 21, 2019, one-call ticket indicated that a PG&E representative called the Kilford employee\nlisted as the contact to clarify the excavation location because Kilford did not provide a complete\nlocation on the tickets. Kilford submitted a second ticket on January 22, 2019 in an effort to address\nthe issue. PG&E located and marked its natural gas utilities within the requested area on\nJanuary 28 and 29, 2019. The depths of the utilities were not marked (nor were they required to be\nmarked. (See section 1.6.1 for more information.) Figure 3 shows the one-call markings at the\nintersection of Geary Boulevard and Parker Avenue before excavation.\n4 One-call is the phone number (811) to call to request a location of all buried utilities in the area where excavation\nis to occur. Title 49 Code of Federal Regulations (CFR) 192.614 requires pipeline operators to participate in a one-\ncall center and provide locate-and-mark services to excavators that notify the operator of any planned excavation work\nin the region of their utilities. Excavators call 811 and place a ticket, known as a one-call ticket, which is used to track\nthe locate-and-mark activities of the various owners of the buried utilities. In the state of California, this one-call ticket\ncan be accessed online by the excavator and the utilities.\n3\n\n<<<PAGE 15>>>\n\nNTSB Pipeline Accident Report\nFigure 3. One-call street markings at northwest corner of Parker Ave. and Geary Blvd. (Photo\nCourtesy of PG&E.)\nNote: The buried gas utilities are marked in yellow. A green circle has been placed on the figure to indicate\nthe location of the branch connection that was ultimately struck.\n1.1.2 Excavation Operation\nOn February 4 and 5, 2019, the asphalt on the roadway was cut in the area where the\nexcavation work was to be performed; Kilford began the asphalt removal and excavation work on\nFebruary 6, 2019, and five Kilford employees were on site to perform the work.\nKilford employees arrived at the site about 7:30 a.m. and held a safety briefing where they\ndiscussed topics such as personal protective equipment, finding buried utilities, and damage to\ntools. Excavation work began about 9:00 a.m., once traffic control was in place.\n5 The work plan\nfor that day was for three lines of conduit to be placed along Geary Boulevard 50 feet west of the\nintersection with Parker Avenue at a new handhole and run to the intersection where one of the\nthree lines of conduit would then run north along Parker Avenue to a telecommunications\n(telecom) pole. (See figure 4.)\n5 Traffic control was performed by two employees of City Rise Safety and Services Traffic Control.\n4\n\n<<<PAGE 16>>>\n\nNTSB Pipeline Accident Report\nFigure 4. Excavation work plan on the day of the accident.\nAccording to the job foreman, he began work by breaking up and removing the asphalt\nroad top with a skid steer while the other employees used hand shovels.6 After the asphalt road top\nwas removed, the job foreman (mini excavator operator) used a mini excavator to excavate the\ntrenches.7 (See figure 5.) While using the mini excavator, he relied on a spotter to help locate\nutilities.\n8 The spotter determines the depth of underground utilities and performs other safety tasks,\nsuch as keeping the operator aware of personnel in the area or other hazards because of the limited\nview from inside the mini excavator (CGA 2018).\n6 (a) A skid steer is a small engine-powered machine with a front loader and four wheels or two tracks that is\ncommonly used for heavy excavation work such as breaking up and removing concrete. (b) State of California\nGovernment Code (GOV) 4216.4(a)(2)(B) states a person performing excavation work may use power-operated\nequipment for the removal of pavement if there are no known utilities within such pavement.\n7 A mini excavator is a small engine-powered machine used for finer excavation work such as trenching. For the\nmajority of its mechanical excavation activities, Kilford used a 2018 CAT 305E2 CR mini excavator. The attached\ntrenching bucket had three teeth that were connected via a 3-inch-wide welded bar.\n8 Common Ground Alliance’s (CGA) Best Practices Guide recommends the contractor have an observer to assist\nthe operator of the excavator when operating around underground utilities; this person is often referred to as a spotter\n(CGA 2018).\n5\n\n<<<PAGE 17>>>\n\nNTSB Pipeline Accident Report\n3-inch wide\nwelded bar\nTrenching bucket\nFigure 5. Mini excavator in storage postaccident.\nExcavation began in front of 3310 Geary Boulevard using a combination of hand digging\nwith shovels and mechanical excavation using the trenching bucket attachment on the mini\nexcavator. Excavation continued along Geary Boulevard to Parker Avenue; then the mini\nexcavator operator and spotter started digging at the telecom pole on Parker Avenue working south\ntoward the intersection. The operator then moved the mini excavator to Geary Boulevard and\nbegan digging to join the two trenches together. The spotter was in the Parker Ave. trench at that\ntime. The other three employees began to install conduit along Geary Boulevard in the first trench.\nThe operator stated that they had previously located the 4-inch gas pipeline and the 2-inch\ngas pipeline at 48 inches depth. The operator stated that they only exposed a portion of each\npipeline and did not expose the branch connection where the two pipelines met. He stated that he\nwas digging at least 2 to 3 feet from the 2-inch gas pipeline that had been exposed along Parker\nand was likely higher than the 2-inch gas pipeline; he reported that he was about 4 feet from where\nthe spotter exposed the 4-inch gas pipeline along Geary Avenue. The spotter reported that he could\nnot see either of the gas pipelines (he never saw the yellow plastic of the pipelines) in the trench,\nalthough he could see an electrical conduit and a metal line. He also stated that the mini excavator\nbucket was about 2 feet south of where the gas pipeline was.\nThe operator also reported that he decided to dig to 30 inches, even though the scope of\nwork called for 36-inch trench depth. The spotter reported that the trench was only 24 to 30 inches\ndeep where the mini excavator was working at the intersection. (See figure 6.)\n6\n\n<<<PAGE 18>>>\n\nNTSB Pipeline Accident Report\nFigure 6. Trench depth comparisons.\nAs the operator continued to remove dirt with the mini excavator, the gas started to escape;\nhe did not notice an impact or scraping before the gas release. Once the release began, the spotter\nimmediately climbed out of the trench and ran north, away from the release site. The operator got\nout of the excavator as the spotter exited the trench. As the operator was returning to the excavator\nto retrieve his phone, the gas ignited.\n7\n\n<<<PAGE 19>>>\n\nNTSB Pipeline Accident Report\nFigure 7. Postfire south-facing view of trench and excavator on Parker Ave. (Photo courtesy of\nPG&E)\nNote: Figure 7 shows the mini excavator as found after the fire was extinguished.\nOnce the gas ignited, the flames, which extended above the height of a 2-story building,\nimpinged on a nearby, fully occupied restaurant at 3300 Geary Boulevard. This caused a structure\nfire at the restaurant. Employees and customers self-evacuated immediately. Later, the fire spread\nto neighboring buildings, causing smaller structure fires at 3308, 3310, and 3250 Geary Boulevard.\n1.2 Response to Gas Release and Fire\n1.2.1 San Francisco Police and Fire Department Response\nAt 1:08 p.m., the San Francisco Department of Emergency Management (SFDEM) Public\nSafety Dispatch Center (911 dispatch) received multiple calls from the public reporting a fire and\npossible explosion at the intersection of Geary Boulevard and Parker Avenue.\nSan Francisco Police Department (SFPD) officers were first on scene at 1:09 p.m. and\nbegan performing evacuations and controlling traffic. San Francisco Fire Department (SFFD)\nBattalion 7, Engine 10, and Truck 10 were dispatched to the scene at 1:09 p.m., were en route\nwithin 1 minute, and were on scene by 1:12 p.m. The Battalion 7 chief designated the event a\n8\n\n<<<PAGE 20>>>\n\nNTSB Pipeline Accident Report\nworking fire with a gas explosion and assigned it as a first-alarm fire.9 An SFFD assistant chief\nwas dispatched at 1:17 p.m. and assumed command as the SFFD incident commander (IC) while\nen route. An additional battalion, three more engines, and one truck were also dispatched at that\ntime.\nAs the SFFD IC approached the site, he could see flames from three blocks away, so he\nupgraded the response to a second-alarm fire at 1:20 p.m. as he was en route. An additional two\nbattalions, four engines, and one truck were dispatched in response to the second-alarm\ndesignation. When the SFFD IC arrived at 1:22 p.m., he recognized that the SFFD was not going\nto be able to put out the gas fire. SFFD procedures for Class 2 flammable gases stated that\ngas-based fires were not to be put out unless the gas has first been shut off. Instead, the fire had to\nbe contained and surrounded until the fuel source was removed. The SFFD IC deployed four\nbattalions around the fire to keep it contained until the gas release was isolated. The SFFD IC\ndeclared a third alarm at 1:36 p.m., and two additional battalions, four engines, and two trucks\nwere dispatched at that time. After the fire was extinguished, an additional engine was dispatched\nto monitor for possible rekindling.\nIn addition to the restaurant, all buildings within a half-block radius of the restaurant fire\nas well as an extra half block to the north were cleared as fully evacuated at 1:56 p.m. SFPD\ncontrolled public access to the active fire area by blocking the main and side streets for a 4-block\nradius centered on 3300 Geary B","truncated":true,"body_characters":111147}