{"operation":"document","citation":"DCA03MP001","title":"Storage Tank Explosion and Fire","source_type":"incident","agency":"National Transportation Safety Board","status":"current","official":true,"published_on":"2026-01-30","effective_on":"2003-04-07","summary":"Accident. in Glenpool, OK, USA. on 2003-04-07. Other","machine_formats":{"json":"https://regulus.evalyn.ai/document/ntsb-case-dca03mp001.json","markdown":"https://regulus.evalyn.ai/document/ntsb-case-dca03mp001.md"},"app_url":"https://regulus.evalyn.ai/document/ntsb-case-dca03mp001","source_url":"https://www.ntsb.gov/investigations/Pages/DCA03MP001.aspx","body":"NTSB investigation DCA03MP001.\n\nEvent Type: Accident\n\nEvent Date: 2003-04-07\n\nEvent City: Glenpool\n\nEvent State Or Region: OK\n\nEvent Country: USA\n\nAccident Type: Other\n\nCompletion Status: Completed\n\nReport Number: PAR-04-02\n\nProbable cause: The National Transportation Safety Board determines that the probable cause of the April 7, 2003, storage tank explosion and fire in Glenpool, Oklahoma, was ignition of a flammable fuel-air mixture within the tank by a static electricity discharge due to the improper manner in which ConocoPhillips Company conducted tank operations. Contributing to the extent of the property damage and the magnitude of the impact on the local community was the failure of American Electric Power employees to recognize the risk the tank fire posed to the nearby power lines and take effective emergency action.\n\nTier1Name: Post-release\n\nTier2Name: Fire\n\nTier1Name: Other\n\nTier2Name: Explosion\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: (general)\n\nFinding Modifier Name: Other institution/organization\n\nFinding Report Text: Organizational - Development - (general) - Other institution/organization\n\nFinding Tier1Name: Personnel\n\nFinding Tier2Name: Action/decision\n\nFinding Tier3Name: Information processing/decision making\n\nFinding Modifier Name: Other company personnel\n\nFinding Report Text: Personnel - Action/decision - Information processing/decision making - Other company personnel\n\nFinding Tier1Name: Pipeline\n\nFinding Tier2Name: Miscellaneous equipment\n\nFinding Tier3Name: Liquid/gas product\n\nFinding Modifier Name: Incorrect use/operation\n\nFinding Report Text: Pipeline - Miscellaneous equipment - Liquid/gas product - Incorrect use/operation\n\nFinding Tier1Name: Environment/Infrastructure\n\nFinding Tier2Name: Operating environment/control system\n\nFinding Tier3Name: Product control system\n\nFinding Modifier Name: Effect on equipment\n\nFinding Report Text: Environment/Infrastructure - Operating environment/control system - Product control system - Effect on equipment\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 April 7, 2003, at about 8:55 p.m., central daylight time, an 80,000-barrel storage tank at ConocoPhillips Company’s Glenpool South tank farm in Glenpool, Oklahoma, exploded and burned as it was being filled with diesel. The tank, designated tank 11, had previously contained gasoline, which had been removed from the tank earlier in the day. The tank contained between 7,397 and 7,600 barrels of diesel at the time of the explosion.\n\nThe resulting fire burned for about 21 hours and damaged two other storage tanks in the area. The cost of the accident, including emergency response, environmental remediation, evacuation, lost product, property damage, and claims, was $2,357,483. There were no injuries or fatalities. Nearby residents were evacuated, and schools were closed for 2 days.\n\nWhat We Found\nWe determined that the probable cause of the April 7, 2003, storage tank explosion and fire in Glenpool, Oklahoma, was ignition of a flammable fuel-air mixture within the tank by a static electricity discharge due to the improper manner in which ConocoPhillips Company conducted tank operations.\nContributing to the extent of the property damage and the magnitude of the impact on the local community was the failure of American Electric Power employees to recognize the risk the tank fire posed to the nearby power lines and take effective emergency action.\n\nThe safety issues identified during the investigation of this accident are as follows:\n\nTank operations, including switch loading, at the ConocoPhillips tank farm.\nThe adequacy of emergency planning and emergency response by ConocoPhillips Company and American Electric Power.\nThe adequacy of Federal regulations and industry standards for emergency planning.\n\nWhat We Recommended\nAs a result of this investigation, we made the following new safety recommendations.\nTo the Research and Special Programs Administration:\n\nRevise the emergency response planning requirements in the pipeline safety regulations to include coordination with electric and other utilities that may need to respond to a pipeline emergency. (P-04-07)\nIssue an advisory bulletin to liquid pipeline operators to validate the accuracy of their tank strapping tables. (P-04-08)\n\nTo ConocoPhillips Company:\nRevise your storage tank operating procedures to include instructions for minimizing the possibility of creating a flammable atmosphere and the occurrence of a static discharge inside a tank after a floating roof has been either intentionally or unintentionally landed, especially for tanks where switch loading is likely to occur. (P-04-09)\nEvaluate your storage tank operating procedures and make the revisions necessary to ensure that product flow rates in both the tank fill line and the discharge nozzles are restricted to provide a level of protection against excess static electricity that is at least commensurate with industry standards. (P-04-10)\nRevise your emergency response plan for the Glenpool South tank farm area and similar locations where ConocoPhillips Company facilities are near electric utilities to include preplanning with nearby electric facilities. (P-04-11)\n\nTo American Electric Power: Revise your emergency response plan to include areas, such as the ConocoPhillips Company Glenpool South tank farm, where pipeline transportation facilities are near American Electric Power facilities, and include a requirement that the American Electric Power emergency responders communicate and coordinate with the on-scene agency in charge. (P-04-12)\n\nTo the Institute of Electrical and Electronics Engineers:\nRevise the National Electrical Safety Code to establish requirements for\noperators to prepare and implement emergency response plans for electric\nfacilities where an emergency may affect pipeline facilities or that may be\naffected by emergencies at pipeline facilities. (P-04-13)\nTo the American Society of Mechanical Engineers:\nRevise the emergency response planning requirements in your gas and\nhazardous liquid pipeline codes to include coordination with electric and\nother utilities that may need to respond to a pipeline emergency. (P-04-14)\n\nPAR-04-02\n<<<PAGE 1>>>\n\nStorage Tank Explosion and Fire in\nGlenpool, Oklahoma\nApril 7, 2003\nPipeline Accident Report\nNTSB/PAR-04/02\nPB2004-916502\nNotation 7666\nNational\nTransportation\nSafety Board\nWashington, D.C.\n\n<<<PAGE 2>>>\n\nthis page intentionally left blank\n\n<<<PAGE 3>>>\n\nPipeline Accident Report\nStorage Tank Explosion and Fire in\nGlenpool, Oklahoma\nApril 7, 2003\nNTSB/PAR-04/02\nPB2004-916502 National Transportation Safety Board\nNotation 7666 490 L’Enfant Plaza, S.W.\nAdopted October 13, 2004 Washington, D.C. 20594\n\n<<<PAGE 4>>>\n\nNational Transportation Safety Board. 2004. Storage Tank Explosion and Fire in Glenpool,\nOklahoma, April 7, 2003. Pipeline Accident Report NTSB/PAR-04/02. Washington, DC.\nAbstract: About 8:55 p.m., central daylight time, on April 7, 2003, an 80,000-barrel storage tank at\nConocoPhillips Company’s Glenpool South tank farm in Glenpool, Oklahoma, exploded and burned as it\nwas being filled with diesel. Gasoline had been removed from the tank earlier in the day. The resulting fire\nburned for about 21 hours and damaged two other storage tanks in the area. The cost of the accident was\n$2,357,483. There were no injuries or fatalities. Nearby residents were evacuated, and schools were closed\nfor 2 days.\nThe safety issues identified in this accident are tank operations, including switch loading, at the\nConocoPhillips Company tank farm; the adequacy of emergency planning and emergency response by\nConocoPhillips and American Electric Power; and the adequacy of Federal regulations and industry\nstandards for emergency planning.\nAs a result of its investigation of this accident, the Safety Board makes safety recommendations to the\nResearch and Special Programs Administration, ConocoPhillips Company, American Electric Power, the\nAmerican Society of Mechanical Engineers, and the Institute of Electrical and Electronics Engineers.\nThe National Transportation Safety Board is an independent Federal agency dedicated to promoting aviation, railroad, highway, marine,\npipeline, and hazardous materials safety. Established in 1967, the agency is mandated by Congress through the Independent Safety Board\nAct of 1974 to investigate transportation accidents, determine the probable causes of the accidents, issue safety recommendations, study\ntransportation safety issues, and evaluate the safety effectiveness of government agencies involved in transportation. The Safety Board\nmakes public its actions and decisions through accident reports, safety studies, special investigation reports, safety recommendations, and\nstatistical reviews.\nRecent publications are available in their entirety on the Web at <http://www.ntsb.gov>. Other information about available publications also\nmay be obtained from the Web site or by contacting:\nNational Transportation Safety Board\nPublic Inquiries Section, RE-51\n490 L’Enfant Plaza, S.W.\nWashington, D.C. 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 Information Service. To\npurchase this publication, order report number PB2004-916502 from:\nNational Technical Information Service\n5285 Port Royal Road\nSpringfield, Virginia 22161\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 or use of Board reports\nrelated to an incident or accident in a civil action for damages resulting from a matter mentioned in the report.\n\n<<<PAGE 5>>>\n\niii Pipeline Accident Report\nContents\nExecutive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v\nFactual Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1\nAccident Synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1\nAccident Narrative . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1\nEmergency Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6\nMeteorological Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8\nConocoPhillips Glenpool Facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8\nTank 11 and Appurtenances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9\nTank Farm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13\nControl Centers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14\nExplorer Glenpool Facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15\nAmerican Electric Power Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15\nPostaccident Field Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15\nTank 11 Wreckage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15\nConocoPhillips Crude Oil Pipeline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16\nAEP Power Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17\nConocoPhillips Electrical Facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17\nTests and Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18\nSafety Board Materials Laboratory Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18\nDiesel Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18\nDesign Criteria for Tank Fill Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19\nSwitch Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19\nSwitch Loading and Tank 11 Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20\nSafety Board Vapor Concentration Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21\nConocoPhillips Crude Oil Pipeline Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23\nOperating Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23\nExplorer Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23\nIndustry Recommended Tank Filling Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23\nConocoPhillips Tank Filling Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24\nPostaccident Actions at ConocoPhillips Glenpool South Tank Farm . . . . . . . . . . . . . . . . . 25\nFederal Safety Regulations – Emergency Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26\nIndustry Emergency Response Plan Guidance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26\nConocoPhillips Emergency Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27\nFederal Safety Regulations – Ignition Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27\nTank Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28\nOffice of Pipeline Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28\nConocoPhillips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28\nNational Electrical Safety Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29\nAnalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30\nExclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30\nStatic Electricity and Prevention of Accidental Ignition at Storage Tanks . . . . . . . . . . . . . 30\nStatic Charge Generation, Accumulation, and Dissipation . . . . . . . . . . . . . . . . . . . . . . 30\nFloating Roof Position and Spark Gap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32\n\n<<<PAGE 6>>>\n\nContents iv Pipeline Accident Report\nAccident Switch Loading and Flammable Vapors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33\nEmergency Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35\nAmerican Electric Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35\nConocoPhillips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35\nEmergency Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36\nFederal Oversight of Pipeline Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38\nConclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39\nFindings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39\nProbable Cause . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40\nRecommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41\nAppendix A: Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43\n\n<<<PAGE 7>>>\n\nv Pipeline Accident Report\nExecutive Summary\nOn April 7, 2003, at about 8:55 p.m., central daylight time, an 80,000-barrel\nstorage tank at ConocoPhillips Company’s Glenpool South tank farm in Glenpool,\nOklahoma, exploded and burned as it was being filled with diesel. The tank, designated\ntank 11, had previously contained gasoline, which had been removed from the tank earlier\nin the day. The tank contained between 7,397 and 7,600 barrels of diesel at the time of the\nexplosion. The resulting fire burned for about 21 hours and damaged two other storage\ntanks in the area. The cost of the accident, including emergency response, environmental\nremediation, evacuation, lost product, property damage, and claims, was $2,357,483.\nThere were no injuries or fatalities. Nearby residents were evacuated, and schools were\nclosed for 2 days.\nThe National Transportation Safety Board determines that the probable cause of\nthe April 7, 2003, storage tank explosion and fire in Glenpool, Oklahoma, was ignition of\na flammable fuel-air mixture within the tank by a static electricity discharge due to the\nimproper manner in which ConocoPhillips Company conducted tank operations.\nContributing to the extent of the property damage and the magnitude of the impact on the\nlocal community was the failure of American Electric Power employees to recognize the\nrisk the tank fire posed to the nearby power lines and take effective emergency action.\nThe safety issues identified during the investigation of this accident are as follows:\n• Tank operations, including switch loading, at the ConocoPhillips tank farm.\n• The adequacy of emergency planning and emergency response by\nConocoPhillips Company and American Electric Power.\n• The adequacy of Federal regulations and industry standards for emergency\nplanning.\nAs a result of its investigation of this accident, the National Transportation Safety\nBoard makes safety recommendations to the Research and Special Programs\nAdministration, ConocoPhillips Company, American Electric Power, the American\nSociety of Mechanical Engineers, and the Institute of Electrical and Electronics\nEngineers.\n\n<<<PAGE 8>>>\n\nthis page intentionally left blank\n\n<<<PAGE 9>>>\n\n1 Pipeline Accident Report\nFactual Information\nAccident Synopsis\nOn April 7, 2003, at about 8:55 p.m., central daylight time,1 an 80,000-barrel\nstorage tank at ConocoPhillips Company’s (ConocoPhillips) Glenpool South tank farm in\nGlenpool, Oklahoma, exploded and burned as it was being filled with diesel. The tank,\ndesignated tank 11, had previously contained gasoline, which had been removed from the\ntank earlier in the day. The tank contained between 7,397 and 7,600 barrels of diesel at the\ntime of the explosion. The resulting fire burned for about 21 hours and damaged two other\nstorage tanks in the area. The cost of the accident, including emergency response,\nenvironmental remediation, evacuation, lost product, property damage, and claims, was\n$2,357,483. There were no injuries or fatalities. Nearby residents were evacuated, and\nschools were closed for 2 days.\nAccident Narrative\nTank 11 contained about 8,710 barrels2 of gasoline on the afternoon of the\naccident. The ConocoPhillips operator who was on duty at the time of the accident stated\nthat when she reported for work at Glenpool Terminal at about 3:30 p.m.3 on April 7,\n2003, a transfer of gasoline from tank 11 at Glenpool South tank farm, a nearby\nConocoPhillips facility, to tankage at Glenpool Terminal, was in progress. Explorer\nPipeline Company (Explorer) was scheduled to deliver a batch of diesel into tank 11 about\n8:30 p.m., and before that time, the operator would need to complete the transfer of\ngasoline to Glenpool Terminal and remove the gasoline that remained in the manifold\npiping and the piping to tank 11. The gasoline from the piping would be transferred to tank\n12 at Glenpool South tank farm.4\n1 Unless otherwise specified, the times used in this report are central daylight time.\n2 A barrel is a liquid measure that, for petroleum, is equal to 42 U.S. gallons.\n3 Times in this section are from interviews with ConocoPhillips, Explorer Pipeline Company, and\nAmerican Electric Power personnel, ConocoPhillips and Explorer Pipeline computer data, the Glenpool fire\ncaptain’s summary report, the Glenpool police daily radio log, ConocoPhillips incident tracking notification\ndata, and the Explorer Pipeline Company batch end report.\n4 The diesel delivery normally would have been to tank 8, but because of scheduling considerations,\nthe naphtha in tank 8 had not been shipped, making it necessary to empty tank 11 in preparation for the\nscheduled diesel delivery. In 2002 and 2003, tank 11 was used to store naphtha, toluene, gasoline, and diesel.\nNaphtha is a petroleum distillate used as a paint solvent, cleaning fluid, and blendstock in gasoline\nproduction. Toluene is a petroleum distillate used as an octane booster in fuel and as a solvent in paints and\npaint thinners, rubber, printing, adhesives, cosmetics, fingernail polish, lacquers, leather tanning,\ndisinfectants, and perfumes.\n\n<<<PAGE 10>>>\n\nFactual Information 2 Pipeline Accident Report\nThe piping system at the Glenpool South tank farm allowed products to be\ndelivered to and received from Explorer’s facility, which was northwest of and adjacent to\nthe ConocoPhillips tank farm. (See figure 1.) The piping system also allowed products to\nbe delivered to and received from the ConocoPhillips Glenpool Terminal (also identified\nby ConocoPhillips as Glenpool Station), which was about 2.7 miles northeast of the\nGlenpool South tank farm, through a 12-inch-diameter ConocoPhillips pipeline.\n~ 2000 feet\nExplorer Pipeline Glenpool Tank Farm\nExplorer measurement\nfacilities & delivery valves\nN\nExplorer 24” line\nto ConocoPhillips\n12” crude\noil pipeline\n30” line\nto tank 11\n9\n8\n7\n12\n11\nExplorer 28”\nmainline\nConocoPhillips Glenpool\nSouth Tank Farm\nPower lines\nFigure 1. Schematic of Explorer Pipeline Glenpool tank farm and ConocoPhillips Glen-\npool South tank farm showing tank 11, pipelines, and power lines located along dike east\nof Glenpool South tank farm.\nAbout 4:00 p.m. at Glenpool Terminal, the ConocoPhillips operator obtained a\nvalve lineup sheet and prepared it jointly with the outgoing shift operator for the\nupcoming operations. Before leaving the office for the tank farm, the operator verified\nhow much gasoline was in the piping system so that, once the removal operation was\ncomplete, she could confirm that all the gasoline had been removed. She went to the\nGlenpool South tank farm about 4:30 p.m. and began transferring gasoline from the\nmanifold piping to tank 12. When the transfer of gasoline from tank 11 to Glenpool\nterminal was completed, about 5:33 p.m., she transferred the gasoline in the tank’s piping\nto tank 12.\n\n<<<PAGE 11>>>\n\nFactual Information 3 Pipeline Accident Report\nWhen all transfers were complete, about 6:10 p.m., the operator lined up the valves\nso tank 11 could receive diesel from Explorer. ConocoPhillips representatives told\ninvestigators that even though no gasoline remained in the tank 11 lines or manifold\npiping at the conclusion of the transfer operation, about 55 barrels of gasoline remained in\nthe tank 11 sump5 between the sump floor and the bottom of the 30-inch-diameter\nfill/drain pipe (which was about 21 inches above the sump floor).\nAbout 6:15 p.m. on April 7, 2003, the ConocoPhillips operator went to the office\nat the Explorer Glenpool tank farm and spoke with the Explorer operator. The\nConocoPhillips operator confirmed with the Explorer operator that the delivery was a\n24,500-barrel batch of diesel going into tank 11, which was empty (except for the residual\ngasoline in the sump). The diesel delivery was from Explorer’s 28-inch-diameter\nmainline. After the diesel was measured and sampled at the Explorer Glenpool facility, the\ndelivery would continue through Explorer’s 24-inch-diameter line to the ConocoPhillips\n30-inch-diameter line and then into tank 11. The ConocoPhillips operator also confirmed\nthat the maximum allowable fill amount was 75,079 barrels. The ConocoPhillips operator\nthen opened two valves in Explorer’s yard to line up the delivery; the delivery to\nConocoPhillips commenced when Explorer control room personnel opened the delivery\nvalve. Except for the opening of the delivery valve, lining up the valves, including the two\nvalves in Explorer’s yard, was the responsibility of the ConocoPhillips operator. About\n6:30 p.m., after the valve lineup was completed, the ConocoPhillips operator returned to\nGlenpool Terminal.\nAbout 8:33 p.m., Explorer switched the delivery of diesel to the line serving\nConocoPhillips at an initial flow rate of 24,000 to 27,500 barrels per hour. The\nConocoPhillips operator stated that at about 8:55 p.m., there was a high (product) level\nalarm in tank 11 and that this was odd because the delivery had just begun and tank 11 had\nbeen empty.\nThe Explorer operator at the Glenpool tank farm stated that he observed a fireball\nbut that he was near operating pumps and did not hear an explosion. He described the\naccident as a flash, followed by smoke and fire, after which the fire totally engulfed tank\n11. He said he went to his truck and drove to the Explorer control room, where he called\nthe Explorer central control dispatcher. He said he then drove in his truck toward the fire\nto verify its location. It was determined that about 8:55 p.m., after tank 11 had been filling\nwith diesel for about 22 minutes, the tank exploded. The fixed roof separated from the\ntank shell and was blown northward and folded over on itself, coming to rest on top of the\ncollapsed north wall of the tank. (See figures 2 and 3.)\n5 The 15-foot-diameter by 6-foot-deep sump was in the northwest area of the tank floor, which sloped\ntoward the sump. The design of tank 11 is discussed in more detail later in this report.\n\n<<<PAGE 12>>>\n\nFactual Information 4 Pipeline Accident Report\nFigure 2. View of wreckage of tank 11 facing south. Note power lines and earthen dike at\nleft and overpressure piping at right.\nFigure 3. Wreckage of tank 11.\n\n<<<PAGE 13>>>\n\nFactual Information 5 Pipeline Accident Report\nThe Explorer operator then returned to the Explorer control room, and about\n8:59 p.m. closed a valve to stop the diesel delivery to ConocoPhillips and switched the\ndelivery to other tankage in the Explorer yard. At this time, the ConocoPhillips facility\nwas isolated from Explorer's piping system. The Explorer operator called and informed\nthe Explorer central control dispatcher that the delivery had been switched. He also called\nthe operator at the ConocoPhillips Glenpool Terminal.\nAbout this same time, the ConocoPhillips operator was calling the Explorer\noperator. The Explorer operator told the ConocoPhillips operator about the ball of fire,\nwhich they concluded was a tank on fire at the ConocoPhillips Glenpool South tank farm.\nThe ConocoPhillips operator asked that the delivery be stopped. The two operators agreed\nthat the Explorer operator would call 911 while the ConocoPhillips operator notified her\nsupervisor.\nAfter the Explorer operator called 911, he called his supervisor and asked that the\nsupervisor contact Explorer central control and have controllers shut down the 28-inch\npipeline that was supplying the diesel to the Explorer facility. Explorer shut down its 28-\ninch-diameter pipeline at Glenpool tank farm at about 9:35 p.m. and had all tank and\nheader valves closed by about 9:45 p.m. Explorer’s incident command was initially set up\nat 9:33 p.m. in the Glenpool tank farm control room and was moved to a conference room\nat 10:40 p.m.\nA resident who was inside her house, about 1,000 feet east of tank 11, reported\nhearing a sound like thunder that rattled her house. She said she exited her house less than\n30 seconds later, at which time there was a second explosion, this one with a higher\npitched sound than the first. She observed that the north side of the tank had collapsed and\nwas on fire and that the wind was blowing the flames south.\nPower poles owned by American Electric Power (AEP)6 were east of the tank farm\nover a wall on the dike that surrounded the tank farm. The electric power facilities\nincluded three conductor wires and two shield wires7 supported by a single crossbar on\ndual wooden poles. Just before 6:00 a.m. on April 8, one or more wires on these poles fell\nto the ground. (See figure 4.) A fire then started in the unburned diesel that was being\ncontained in the dike north of tank 11.\nAbout 6:10 a.m. on April 8, 2003, crude oil at 550 pounds per square inch, gauge\n(psig) was released from aboveground piping between tanks 7 and 8 inside the dike after\nthe piping was engulfed in fire started by the power lines. The piping system provided\noverpressure protection for ConocoPhillips’ 12-inch-diameter crude oil pipeline. An\nisolation flange assembly in the piping failed because of the fire, allowing the pressurized\ncrude oil to spray the surrounding area through the loosened flange assembly. By\n6:17 a.m., ConocoPhillips had shut down the pipeline pumps and closed the remotely\noperated valves in the pipeline.\n6 AEP, which is based in Columbus, Ohio, operates an electricity transmission and distribution grid and\nis the Nation’s largest electricity generator.\n7 A shield wire is a grounded conductor installed to shield a phase conductor from a direct lightning strike.\n\n<<<PAGE 14>>>\n\nFactual Information 6 Pipeline Accident Report\nFigure 4. View of downed AEP power lines on east dike wall.\nThe ConocoPhillips Glenpool area supervisor initially estimated that about 7,400\nbarrels of diesel were in tank 11 at the time of the explosion. This figure was different\nfrom the 8,420 barrels read by Explorer’s meter because some product was in the piping\nsystem downstream of the meter on its way to tank 11 when the explosion occurred.\nSafety Board investigators calculated the amount of diesel that was in tank 11 at\nthe time of the explosion. These calculations were based on the amount of gasoline that\nwas in the tank 11 sump when delivery of diesel began, the quantity of diesel metered by\nExplorer during the delivery, the diesel that was metered after the explosion but that did\nnot enter tank 11, and the quantity of diesel that remained in the previously empty delivery\nmanifold and tank 11 piping at the time of the explosion. Based on these calculations, tank\n11 contained between 7,397 and 7,600 barrels of liquid (diesel and a small amount of\ngasoline) at the time of the explosion.\nEmergency Response\nThe Glenpool Fire Department received a 911 report of tank explosion and fire at\n9:00 p.m. and was on scene by 9:06 p.m., at which time tank 11 had collapsed and was\nengulfed by flames 75 feet high.\n\n<<<PAGE 15>>>\n\nFactual Information 7 Pipeline Accident Report\nThe emergency response eventually involved 13 fire departments and firefighting\npersonnel from ConocoPhillips, Sun Refinery, and Williams Fire and Hazard Control.\nConocoPhillips had preplanned with Sun Refinery for mutual assistance in firefighting.\nInitially, the fire departments applied foam from the west side of the dike between tanks 7\nand 12 and placed it around the burning tank so that the wind would disperse the foam to\ncontain the ground fire. However, the manner in which the tank collapsed hindered the\napplication of foam to the tank. Firefighters also applied water to tank 12, which contained\ngasoline, to cool it. Explorer and ConocoPhillips checked the dike drain valves to ensure\nthat they were closed. After the power lines fell and diesel in the north area of the dike\ncaught fire, a fire started inside tank 8 (which contained naphtha) in the area of the internal\nfloating roof seal. This fire eventually extinguished itself, and the heat from the internal\nfire damaged tank 8. Also, the burning diesel in the north area of the dike caused a flange\nassembly in the crude oil pipeline overpressure protection system to fail and release crude\noil in the area.\nThe ConocoPhillips Glenpool area supervisor stated that because of a concern\nabout the quantity of foam available, he called ConocoPhillips in Ponca City for additional\nsupplies. Another ConocoPhillips employee called the Sinclair Refinery and the Tulsa\nairport and asked for information about available foam supplies. A staging area was set up\nto receive foam deliveries.\nIn addition to a family living approximately 1,000 feet east of the tank farm, about\n300 families living near the tank farm were evacuated. This was a voluntary evacuation\nthat was lifted on the afternoon of April 9. ConocoPhillips provided housing for the\nevacuees. Nearby schools were closed for 2 days.\nSeveral AEP employees called the AEP transmission system operator between\n9:00 p.m. and 9:30 p.m. to notify him of the accident, but he had already seen the fire on\nthe television news. He stated that he knew the AEP power lines were near the fire.\nAbout midnight, ConocoPhillips personnel called the AEP dispatcher and\nrequested that an AEP representative inspect the power lines near and to the east of the\ntank, because the flames were impinging on them. At 12:30 a.m. on April 8, an AEP\nservicer was dispatched to the site, and by 1:14 a.m., he had inspected the power lines and\nreported to the transmission system operator. No sag in the lines was observed, and the\nservicer, who did not communicate with any incident command staff, returned home. He\ndid suggest to the AEP transmission system operator that an AEP representative inspect\nthe wooden power pole near the fire, but there is no record of action being taken.\nAbout 3:43 a.m., the incident command noted that the wind had shifted to the east,\nbut the tank 11 fire appeared contained, the cooling operation on tanks 7 and 12 was\nsuccessful, and the incident appeared to be stable. Within an hour, however, the fire in\ntank 11 was worse, possibly because the firefighting foam inside the tank was degrading.\nAbout 5:00 a.m., after having been contacted again by on-scene personnel at\n4:45 a.m., the AEP dispatcher again called the servicer at home. The transmission system\noperator documented in his log that the fire had restarted and was worse than before and\n\n<<<PAGE 16>>>\n\nFactual Information 8 Pipeline Accident Report\nthat AEP should recheck the lines. The servicer returned to the scene at about 5:30 a.m.\nand observed that the conductor closest to the fire now had a slight sag. This indicated that\nheat from the fire was affecting the power line. Incident command was notified that the\nservicer was on site, but the servicer did not check in or otherwise communicate with\nincident command. About 20 minutes later, one or more wires fell onto the diked area east\nof the tanks and the diesel that was contained inside that area of the dike ignited.\nThe AEP transmission system operator stated that any decision to deenergize the\nlines was to be made by him based on information provided by the on-site inspectors and\nan AEP field representative. He stated that if these lines had been deenergized, power\nwould have been cut to the AEP substation at an Explorer pump station (not at the\nGlenpool tank farm) and to the pump station. No other outages would have been expected,\nbecause the system would have automatically rerouted power.\nThe AEP transmission system operator stated that his emergency response training\nhad not included training for nonelectrical issues. He said his training had involved neither\nvisits to the ConocoPhillips Glenpool South tank farm nor face-to-face meetings with\nConocoPhillips personnel. The AEP field representative stated that his training had been\nprimarily on the job and that he had gained experience in actual emergencies.\nMeteorological Information\nNo lightning was reported or noted in the area at the time of the explosion. The\ntemperature was about 52° F, and the relative humidity was 54 percent. The wind was\nfrom the north at 7 mph gusting to 16 mph.\nConocoPhillips Glenpool Facilities\nThe ConocoPhillips8 Glenpool South tank farm, constructed between 1978 and\n1981, was originally a Conoco facility and consisted of four storage tanks, which were\ndesignated 7, 8, 11, and 12, and one smaller tank, designated 9, that was used for mixed\nproducts. The tanks were inside a dike consisting of earthen walls and a crushed rock\nsurface. Outside the dike were a control building, valve manifolds, product pumps, a\nvacuum pump and tank, and an underground sump connected to the vacuum tank.\nExcept for tank 9, the tanks had a “drain dry” design. The floor of tank 11 was\nsloped to a sump inside the tank, and the 30-inch-diameter common fill/drain piping\nterminated in the sump. When the tank was drained dry, the only liquid that remained in\nthe tank was approximately 55 barrels in the sump below the bottom of the fill/drain\npiping.\n8 ConocoPhillips was founded in 2002 when Conoco, Inc., and Phillips Petroleum Company merged.\n\n<<<PAGE 17>>>\n\nFactual Information 9 Pipeline Accident Report\nTank 11 and Appurtenances\nConocoPhillips representatives told investigators that no as-built design or\nconstruction drawings for tank 11 could be found. According to ConocoPhillips, tanks 11\nand 12 were both constructed in 1981 and were similar in design and construction.\nThe following information was obtained from the tank nameplates, the inspection\nreport from the tank 11 external inspection performed in July 2000, the construction\nspecification for tanks 11 and 12, a ConocoPhillips as-built drawing of the tank 11 and\ntank 12 sump, and photographic evidence and known data from tank 12.9 Tank 11 was a\n48-foot-high by 109-foot-diameter welded steel storage tank with a cone-type fixed roof\nand an internal floating roof (see figure 5). The purpose of a floating roof is to minimize\nemissions and evaporative losses. It floated on pontoons on top of the product and was\nequipped with legs that supported the roof when product was drained from the tank and\nthe volume of liquid in the tank decreased to the level at which the roof no longer floated.\nThe ability to “land” the roof, meaning that the roof was sitting on and fully supported by\nthe legs, also prevented it from being damaged by contacting the tank floor. The legs\ntypically are set so the roof is about 3 feet above the tank floor but they can be set at\napproximately 6 feet to facilitate personnel entering the tank and working under the roof.\nPressure/vacuum vent\nin floating roof\nVent in tank roof and shell\nInternal floating roof\n(with straps holding pontoons)\nSeal around\nfloating roof\n10\" diameter\npontoon\nDrain tube\nSupport leg for roof\n(with sleeves at pontoon)\nproduct\nFlow\nSump cover\nSump\nTank dimensions: 109' diameter x 48‘ high\n(drawing not to scale)\n30” diameter\nfill/drain pipe\nFigure 5. Diagram of storage tank showing float","truncated":true,"body_characters":131177}