{"operation":"document","citation":"DCA00MP005","title":"Hazardous Liquid Pipe Failure and Leak, Explorer Pipeline Company","source_type":"incident","agency":"National Transportation Safety Board","status":"current","official":true,"published_on":"2026-01-30","effective_on":"2000-03-09","summary":"Accident. in Greenville, TX, USA. on 2000-03-09. Explorer Pipeline Company. Rupture/release","machine_formats":{"json":"https://regulus.evalyn.ai/document/ntsb-case-dca00mp005.json","markdown":"https://regulus.evalyn.ai/document/ntsb-case-dca00mp005.md"},"app_url":"https://regulus.evalyn.ai/document/ntsb-case-dca00mp005","source_url":"https://www.ntsb.gov/investigations/Pages/DCA00MP005.aspx","body":"NTSB investigation DCA00MP005.\n\nEvent Type: Accident\n\nEvent Date: 2000-03-09\n\nEvent City: Greenville\n\nEvent State Or Region: TX\n\nEvent Country: USA\n\nPipeline Operator: Explorer Pipeline Company\n\nPipeline Type: Hazardous Liquid - Regulated\n\nAccident Type: Rupture/release\n\nCompletion Status: Completed\n\nReport Number: PAB-01-03\n\nProbable cause: The National Transportation Safety Board determines that the probable cause of the pipeline failure was corrosion-fatigue cracking that initiated at the edge of the longitudinal seam weld at a likely pre-existing weld defect. Contributing to the failure was the loss of pipe coating integrity.\n\nTier1Name: System operating\n\nTier2Name: Pipe structural malfunction/failure\n\nFinding Tier1Name: Pipeline\n\nFinding Tier2Name: Pipeline structure\n\nFinding Tier3Name: Joint/weld/seam\n\nFinding Modifier Name: Fatigue/wear/corrosion\n\nFinding Report Text: Pipeline - Pipeline structure - Joint/weld/seam - Fatigue/wear/corrosion\n\nFinding Tier1Name: Pipeline\n\nFinding Tier2Name: Pipline systems/equipment\n\nFinding Tier3Name: Coatings/anti-corrosion\n\nFinding Modifier Name: Failure\n\nFinding Report Text: Pipeline - Pipline systems/equipment - Coatings/anti-corrosion - Failure\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 March 9, 2000, about 10:20 p.m., central standard time, a 28-inch-diameter pipeline owned and operated by Explorer Pipeline Company (Explorer) ruptured and released 13,436 barrels (about 564,000 gallons) of gasoline. The pipeline was buried about 4 feet 6 inches under ranch land. The release site was near Greenville, Texas, about 45 miles northeast of Dallas.\nExplorer’s Greenville pumping station on the 28-inch pipeline was about 10.3 miles south and upstream of the rupture site. This station automatically shut down its two running pumping units when the rupture occurred. Before the failure, the pipeline had been in steady-state operation, and its flow rate was approximately 20,000 barrels per hour. About 2 minutes after the rupture and the automatic shutdown of the Greenville pumping station, the pipeline controller (located in Tulsa, Oklahoma) started a different pumping unit at the Greenville pumping station in an effort to keep the entire pipeline balanced and operating. Meanwhile, the operator of the Greenville pumping station attempted to determine the cause of the automatic shutdown of his pumping units. The pumping unit that the controller had started also shut down automatically after about 2 minutes. The controller shut down the entire line. After a few minutes, thinking that the cause of the initial shutdown had been a control valve problem, the controller restarted the line at a reduced rate. About 13 minutes later (around 10:49 p.m.), the controller shut the entire line down for evaluation.\n\nWhat We Found\nWe determined that the probable cause of the pipeline failure was corrosion-fatigue cracking that initiated at the edge of the longitudinal seam weld at a likely pre-existing weld defect. Contributing to the failure was the loss of pipe coating integrity.\n\nPAB-01-03\n<<<PAGE 1>>>\n\nNational Transportation Safety Board\nWashington, D.C. 20594\nPipeline Accident Brief\nPipeline Accident Number: DCA-00-MP-005\nType of System: Hazardous liquid\nAccident Type: Pipe failure and leak\nLocation: Greenville, Texas\nDate and Time: March 9, 2000, at 10:20 p.m., central standard time\nOwner/Operator: Explorer Pipeline Company\nFatalities/Injuries: None\nDamage/Clean Up Cost: $18 million\nMaterial Released: Gasoline\nQuantity Released: Approximately 564,000 gallons\nPipeline Pressure: 705 pounds per square inch, gauge, (psig)\nat site of failure\nComponent Affected: 28-inch-diameter, American Petroleum Institute\nSpecification 5LX, Grade X-52, 0.281-inch-wall-\nthickness, DSAW (double seam submerged-arc\nwelded) steel pipe\nThe Accident\nOn March 9, 2000, about 10:20 p.m., central standard time,1 a 28-inch-diameter\npipeline owned and operated by Explorer Pipeline Company (Explorer) ruptured and\nreleased 13,436 barrels (about 564,000 gallons) of gasoline. The pipeline was buried\nabout 4 feet 6 inches under ranch land. The release site was near Greenville, Texas, about\n45 miles northeast of Dallas.\nExplorer’s Greenville pumping station on the 28-inch pipeline was about\n10.3 miles south and upstream of the rupture site. This station automatically shut down its\ntwo running pumping units when the rupture occurred. Before the failure, the pipeline had\nbeen in steady-state operation, and its flow rate was approximately 20,000 barrels per\nhour. About 2 minutes after the rupture and the automatic shutdown of the Greenville\npumping station, the pipeline controller (located in Tulsa, Oklahoma) started a different\npumping unit at the Greenville pumping station in an effort to keep the entire pipeline\nbalanced and operating. Meanwhile, the operator of the Greenville pumping station\nattempted to determine the cause of the automatic shutdown of his pumping units. The\npumping unit that the controller had started also shut down automatically after about\n2 minutes. The controller shut down the entire line. After a few minutes, thinking that the\n1 All times reported are central standard time.\nNTSB/PAB-01/03\n\n<<<PAGE 2>>>\n\n2\ncause of the initial shutdown had been a control valve problem, the controller restarted\nthe line at a reduced rate. About 13 minutes later (around 10:49 p.m.), the controller shut\nthe entire line down for evaluation.\nLeak Reporting and Response\nIndividuals near the rupture began calling 911 soon after the pipeline failure. Other\nresidents who detected the odor of gasoline called Explorer personnel because they were\naware that the Explorer pipeline passed through the area.\nThe released gasoline flowed a few hundred feet across the surrounding terrain and\ninto a dry creek bed, which was a tributary to East Caddo Creek. From the tributary, the\ngasoline flowed downstream into East Caddo Creek. The banks of the tributary and creek\ncontained the escaping gasoline as it flowed away from the ruptured pipe.\nExplorer closed remotely operated valves at pump stations about 10:59 p.m. to\nisolate the ruptured section of pipeline. By 11:05 p.m., Explorer personnel were on the\nscene and meeting with emergency responders. About midnight, a local contractor arrived\non the scene to construct dams across East Caddo Creek to stop the flow of gasoline.\nAbout 1:30 a.m., Explorer personnel manually closed a mainline valve to further isolate\nthe rupture area.\nBy morning, three dams had been constructed across the East Caddo Creek. The\nleading edge of the escaping gasoline was eventually contained about 2 1/2 miles from\nthe rupture site. Then, about 8:30 a.m. the morning after the rupture, heavy rains began to\nfall. The rain lasted throughout much of the day. An estimated 1.5 to 2 inches of rain fell\nin the area, and East Caddo Creek rose about 12 feet. The rising waters destroyed the\nthree dams that had been constructed in the night and allowed the gasoline to move\nfurther downstream.\nWork continued during the day, and the leading edge of the gasoline appeared to\nhave been stopped about 15 miles from the rupture site, about 7 miles upstream of Lake\nTawakoni. The lake is a major water supply for Dallas and numerous smaller\ncommunities. After the accident, the chemical MTBE (methyl tertiary butyl ether), a\ncomponent of the gasoline, was found in Lake Tawakoni.\nPreaccident Information\nThe line pipe was 28 inches in diameter, with a wall thickness of 0.281 inch. The\ndouble seam submerged-arc welded pipe had been manufactured in 1970 by the Steel\nCompany of Canada to conform to American Petroleum Institute Specification 5LX,\nNTSB/PAB-01/03\n\n<<<PAGE 3>>>\n\n3\nGrade X-52. The pipeline had been constructed in 1970. The soil in the area of the\nrupture consisted of “gumbo” clay and limestone marl. Koppers Bitumastic pipe coating\nwas applied during construction to this section of the line.\nAn in-line inspection tool (“smart pig”) was run through this section of line in\n1997. Anomalies meeting Explorer criteria were excavated, evaluated, and repaired. No\nanomalies meeting Explorer’s 1997 criteria were reported in the area of the March 2000\nfailure during the in-line inspection, so the pipe was not visually examined at this location\nbefore the failure.\nPostaccident Examination of the Failed Pipe Segment\nPostaccident laboratory examination of the failed pipe segment showed that the\nrupture area had a typical “fish-mouth type” crack; when one looked north along the\npipeline, the crack was at about the 1 o’clock position on the pipe. The crack was about\n50 1/2 inches long, and its maximum width was about 6 3/4 inches. The ends of the crack\nwere located off the edge of the longitudinal seam weld, and about the middle one-third\nof the crack was directly adjacent to the pipe’s longitudinal seam weld.\nThe surface of the main fracture was examined. In the middle region, where the\ncrack was located directly adjacent to the longitudinal seam weld, a portion of the fracture\nsurface appeared relatively smooth, and crack arrest marks typical of fatigue were\nobserved. Crack arrest lines appeared to nearly intersect the inner edge of the main\nfracture surface, but the fracture plane was at an angle of about 45 degrees, consistent\nwith high-stress, low-cycle fatigue. In another region of the fracture surface adjacent to\nthe outer edge, fracture features were obliterated by corrosion.\nThe pipe coating in the rupture area appeared wrinkled and torn. The coating bore\nmeandering cracks, ranging up to 2 1/2 inches wide, which exposed the pipeline surface.\nCorrosion pits were observed on the outer surface of the pipe in areas where the coating\nwas cracked. The corrosion pitting was generally isolated, except in the area adjacent to\nthe failure, where zones of continuous corrosion pitting were observed. Pitting was found\non the longitudinal weld, and crack-like features were observed at the longitudinal weld\nboundary in some of the pitted areas. The crack-like features were typical of a weld\ndefect, such as incomplete fusion. No crack-like features were observed in any pits not on\nthe longitudinal weld. (Upon examination after the accident, Explorer noted that, during\ninitial construction of the pipeline section surrounding the failure site, the pipe and\ncoating may have been backfilled before the coating had cooled sufficiently. This could\nhave caused extensive wrinkling in the coating, as well as pulling and tearing the coating\nmaterials.)\nNTSB/PAB-01/03\n\n<<<PAGE 4>>>\n\n4\nPostaccident Activities\nBefore Explorer restarted the pipeline, it established a testing plan, which it gave\nto the U.S. Department of Transportation’s Research and Special Programs\nAdministration (RSPA) for review and approval. The plan established repair procedures,\nrequired a pressure reduction to 20 percent below the calculated failure pressure of the\npipe at the rupture location, set a refilling and startup procedure, and mandated a pipeline\nincident review that addressed controller training and SCADA2 design improvements,\nincluding simulation training. Additional in-line testing was conducted, and several\nrepairs to the pipeline were made. On December 15, 2000, RSPA gave Explorer\npermission to return pipeline operation to the operating pressures that had been in effect\nbefore the accident.\nProbable Cause\nThe National Transportation Safety Board determines that the probable cause of\nthe pipeline failure was corrosion-fatigue cracking that initiated at the edge of the\nlongitudinal seam weld at a likely pre-existing weld defect. Contributing to the failure\nwas the loss of pipe coating integrity.\nJuly 6, 2001\n2 Pipeline controllers use SCADA (supervisory control and data acquisition) systems to remotely\nmonitor and control movement through pipelines. Using a SCADA system, controllers can monitor flow\nrates and pressures along the lines, control valves, and pumps to adjust the flow at pump stations and other\nlocations throughout the pipeline system.\nNTSB/PAB-01/03","truncated":false,"body_characters":12156}