{"operation":"document","citation":"DCA17FP005","title":"Natural Gas Explosion at Family Residence","source_type":"incident","agency":"National Transportation Safety Board","status":"current","official":true,"published_on":"2021-05-18","effective_on":"2017-04-17","summary":"Accident. in Firestone, CO, USA. on 2017-04-17. Leak/explosion/fire","machine_formats":{"json":"https://regulus.evalyn.ai/document/ntsb-case-dca17fp005.json","markdown":"https://regulus.evalyn.ai/document/ntsb-case-dca17fp005.md"},"app_url":"https://regulus.evalyn.ai/document/ntsb-case-dca17fp005","source_url":"https://www.ntsb.gov/investigations/Pages/DCA17FP005.aspx","body":"NTSB investigation DCA17FP005.\n\nEvent Type: Accident\n\nEvent Date: 2017-04-17\n\nEvent City: Firestone\n\nEvent State Or Region: CO\n\nEvent Country: USA\n\nAccident Type: Leak/explosion/fire\n\nCompletion Status: Completed\n\nReport Number: PAB1902\n\nReport Date: 2019-10-18\n\nProbable cause: The National Transportation Safety Board determines that the probable cause of the explosion and fire at the Firestone, Colorado, residence was the ignition of fugitive natural gas that had migrated from the Coors V6-14Ji well through a pipeline that was not abandoned by Patina Oil and Gas Corporation and that was most likely severed in 2015 during the construction of the house. Contributing to the accident was the approval by local authorities to allow occupied structures to be built on land adjacent to or previously part of oil and gas production fields without complete documentation from the operator, Anadarko Petroleum Corporation, on the location and status of its gathering system pipelines.\n\nTier1Name: System operating\n\nTier2Name: Security/intentional event\n\nTier1Name: System operating\n\nTier2Name: Evacuation\n\nTier1Name: Post-release\n\nTier2Name: Fire/explosion (post-release)\n\nTier1Name: System operating, changing flow/pressure\n\nTier2Name: External/third-party damage\n\nTier1Name: System shutdown\n\nTier2Name: System disabled\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Management\n\nFinding Tier3Name: Policy/procedure\n\nFinding Modifier Name: Product source organization\n\nFinding Report Text: Organizational - Management - Policy/procedure - Product source organization\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Documentation/record keeping\n\nFinding Modifier Name: Product source organization\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Documentation/record keeping - Product source organization\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Management\n\nFinding Tier3Name: Resources\n\nFinding Modifier Name: State/Local agency\n\nFinding Report Text: Organizational - Management - Resources - State/Local agency\n\nFinding Tier1Name: Personnel\n\nFinding Tier2Name: Action/decision\n\nFinding Tier3Name: Action\n\nFinding Modifier Name: State/Local government personnel\n\nFinding Report Text: Personnel - Action/decision - Action - State/Local government personnel\n\nFinding Tier1Name: Environment/Infrastructure\n\nFinding Tier2Name: Operating environment/control system\n\nFinding Tier3Name: Product control system\n\nFinding Modifier Name: Awareness of condition\n\nFinding Report Text: Environment/Infrastructure - Operating environment/control system - Product control system - Awareness of condition\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 17, 2017, about 4:45 p.m. local time, a single-family home in Firestone, Colorado, was destroyed by an explosion. A resident and a plumber who was working at the house died in the explosion, and two other residents were injured. At the time of the explosion, the fatally injured resident and plumber were replacing a water heater in the basement.\nThe explosion also damaged the adjacent house, which later was demolished. The Frederick-Firestone Fire Protection District responded to the accident, with mutual aid from three other fire departments and the Firestone Police Department.\n\nWhat We Found\nWe determined that the probable cause of the explosion and fire at the Firestone, Colorado, residence was the ignition of fugitive natural gas that had migrated from the Coors V6-14Ji well through a pipeline that was not abandoned by Patina Oil and Gas Corporation and that was most likely severed in 2015 during the construction of the house. Contributing to the accident was the approval by local authorities to allow occupied structures to be built on land adjacent to or previously part of oil and gas production fields without complete documentation from the operator, Anadarko Petroleum Corporation, on the location and status of its gathering system pipelines.\n\nPAB-19-02\n<<<PAGE 1>>>\n\nNational Transportation Safety Board\nPipeline Accident Brief\nNatural Gas Explosion at Family Residence\nFirestone, Colorado\nApril 17, 2017\nAccident Narrative\nOn April 17, 2017, about 4:45 p.m. local time, a single-family home in Firestone, Colorado,\nwas destroyed by an explosion. (See figure 1.) A resident and a plumber who was working at the\nhouse died in the explosion, and two other residents were injured. At the time of the explosion, the\nfatally injured resident and plumber were replacing a water heater in the basement.\nFigure 1. Photograph of the residence before and after the accident. Photograph on the left was\nprovided by Weld County, photograph on the right was provided by the Pipeline and Hazardous\nMaterials Safety Administration.\nThe explosion also damaged the adjacent house, which later was demolished. The\nFrederick-Firestone Fire Protection District responded to the accident, with mutual aid from three\nother fire departments and the Firestone Police Department.\nOn-scene Investigation\nRepresentatives from the Colorado Oil and Gas Conservation Commission (COGCC), the\nFrederick-Firestone Fire Protection District, Black Hills Energy (Black Hills), Anadarko\n59871 NTSB/PAB-19/02\n\n<<<PAGE 2>>>\n\nNatural Gas Explosion at Family Residence\nPetroleum Corporation (Anadarko), and the Pipeline and Hazardous Materials Safety\nAdministration (PHMSA) responded to the accident site to conduct an investigation.1 A National\nTransportation Safety Board (NTSB) investigator later went to the accident site to review the initial\ninvestigative findings and support subsequent on-scene work.\nSince the residence at 6312 Twilight Avenue had domestic natural gas utility service,\ntechnicians from Black Hills located and marked the service line in the front of the house, which\nconnected to the distribution main along Twilight Avenue. Black Hills excavated and exposed the\ninterconnect between the service line and the distribution main on the north side of the residence.\nThey found the excess flow valve was closed and no gas was detected in the excavation trench.2\nAfter excavating and exposing the interconnect between the service line and the side of the\nresidence, Black Hills pressure tested the service line for 10 minutes at 30 pounds per square inch,\ngauge (psig). The service line held pressure, indicating there were no leaks present. Because the\nservice line held pressure, the excess flow valve likely activated after the house piping was severed\nin the explosion.\nThree severed pipelines were found beneath a concrete pad about 6 feet from the foundation\nof the house. The three lines were originally connected to natural gas wells as part of a production\nfield. The lines included one 1-inch diameter polyethylene (PE) line and two 2-inch diameter steel\nlines. The PE line had a tee connection south of the residence, with one branch of the line connected\nto the Coors V6-14Ji well southeast of the residence, and the other branch running to the Coors\nV6-13 well to the south and farther west of the residence. (See figure 2.) One of the steel lines had\nbeen previously connected to the Coors V6-14Ji well and was later disconnected and abandoned.\nThe other severed steel line was a discontinuous abandoned line which went in the direction of the\nnearby Coors V6-13 well.\n1 Black Hills is the local gas distribution company.\n2 Excess flow valves are safety devices installed on natural gas distribution pipelines to reduce the risk of accidents.\nWhen flow rates through them exceed design limits, the valve automatically closes. Most types of excess flow valves\nrequire a technician to reset the valve after a high-flow incident or for it to be replaced altogether.\n2\n\n<<<PAGE 3>>>\n\nNatural Gas Explosion at Family Residence\nFigure 2. Aerial view of Anadarko production field from late 2015 with illustration of the pipelines\nand the Coors V6-14Ji well location.\nNo records are available that show when the three lines under the concrete pad were cut.\nResidential building approvals indicate the only known construction at the residence occurred\nwhen it was built in 2015. However, the materials associated with these approvals did not contain\ninformation about the production field.\nAfter being isolated from the pipeline which went to Coors V6-13, the PE line was field\ntested between its severed end and the Coors V6-14Ji wellhead and had continuity. The same\nsegment of PE line between the wellhead and its end at the house was pressure tested with nitrogen\nat 5 psig and also held pressure, indicating that it was sound. During the excavation, natural gas\nwas found at the rear of the residence.\n3 Specifically, the soil under the concrete slab had a reading\nof 10 percent of the lower explosive limit for natural gas, indicating that excessive amounts of\nnatural gas were present in the soil immediately outside the rear of the residence. Natural gas likely\nleaked from the well and traveled through the PE line toward the residence, where it exited the\nsevered end and migrated through the soil into the basement, where it fueled the explosion. The\n3 Natural gas is a naturally occurring hydrocarbon gas mixture consisting primarily of methane which often\nincludes higher alkanes and a small percentage of other components. It is a common well-production by-product and\nis also used as a fuel gas for residential and commercial use, such as on a gas stovetop. The National Fire Protection\nAssociation refers to natural gas not used for residential or commercial purposes as “fugitive gas”. In this report,\nunless otherwise noted, the terms “natural gas” and “fugitive gas” are synonymous.\n3\n\n<<<PAGE 4>>>\n\nNatural Gas Explosion at Family Residence\nsegment of the PE line beyond the tee connection and running toward the Coors C6-13 well and\nthe multiwell separator did not pass a pressure test. Because this segment was not sound, it was\nnot believed to be a pathway for the gas to travel from the Coors V6-13 well or the separator\ntoward the residence.\nA 2-inch steel flowline ran from the V6-14Ji well to a separator and tank storage facility\nto the west, running south of the residence and parallel to Twilight Avenue. This line was\npressurized to 500 psig for 1 hour and held pressure, indicating that the flowline had no leaks.\nInformation gathered during the investigation found that the most likely source of the\nnatural gas that fueled the explosion was the Coors V6-14Ji well, and the pathway for the natural\ngas to reach the residence was the 1-inch PE line.\nHistory of the Well\nOn August 31, 1993, Gerrity Oil and Gas received approval from the COGCC to drill the\nsubject well, Coors V6-14Ji. Drilling began November 30 and the casing was set and cemented 5\ndays later. It was a vertical well that produced natural gas, as well as natural gas liquids (low\nmolecular-weight hydrocarbons), brine, and crude oil. The well was located about 170 feet south\nof what would eventually become the residence.\n4 Coors V6-14Ji was one of hundreds of wells that\nwere drilled in an area of the Denver Basin known as the Wattenberg Gas Field. Patina Oil and\nGas Corporation (Patina) acquired the subject well in 1997.\nIn 1999, in preparation for a planned housing development, Patina planned to shut down\nand remove a production facility to the north of the subject well, abandon the existing underground\nlines from the subject well to that production facility, and install new flowlines to a newly\nconstructed multiwell separator and tank storage facility about a quarter-mile west of the subject\nwell.5 However, the original production facility to the north remained in use until 2018 and not all\nflowlines were properly abandoned, including several of the lines involved in this accident.\nAlthough a Patina 1999 record stated the abandonment was completed, COGCC records showed\nthis to be incorrect. The well was acquired one more time before the ownership was transferred to\nAnadarko in October 2013.\nOn December 14, 2015, Anadarko temporarily “shut in” multiple wells, including Coors\nV6-14Ji, for emissions upgrades; however, the well was not plugged and no pipelines were\nabandoned.6 Anadarko owned and operated this well at the time of the accident and had resumed\nproduction from this well less than 3 months prior to the accident.\nPipeline Abandonment Prior to Incident\nWhen Patina planned to abandon the flowlines from the Coors V6-14Ji well in 1999,\nCOGCC regulations required only that the line be “disconnected from all sources and supplies of\n4 The local police department indicated the well was 150 feet south of what would become the property.\n5 A separator is a pressure vessel used to separate production fluids into crude oil, natural gas, and water/sediment.\nA multiwell separator performs the same function for the gathered products from multiple wells.\n6 Plugging a well is a process of inserting plugs into a well to prevent flow between different geological formation\nzones. Plugs can be cement or mechanical, and the plugging may involve inserting multiple plugs at different depths.\n4\n\n<<<PAGE 5>>>\n\nNatural Gas Explosion at Family Residence\nnatural gas and petroleum, purged of liquid hydrocarbons, depleted to atmospheric pressure, and\nsealed at the ends.” None of the three lines found at the residence were properly abandoned in\naccordance with these requirements.\nPostaccident Actions\nAnadarko conducted a magnetic survey in the vicinity of the accident site to locate any\nabandoned pipelines that would not be included in its existing surveys of wells and active pipelines.\nThe survey noted the length and location of flow and return lines, as well as the locations of several\nwells adjacent to the residential neighborhood. (See figure 2.) Although most pipeline damage and\naccidents occur with transmission and distribution pipelines, the safety risks associated with strikes\nto gathering pipelines that carry flammable liquids and gases are similarly hazardous to workers\nand the public. It is important that pipeline owners and operators maintain and distribute accurate\ninformation on the location of pipelines since inadvertent strikes during construction and\nexcavation work is a leading cause of pipeline damage and accidents.\n7\nFlowlines and other associated production well pipelines, including the lines involved in\nthis accident, fall under the jurisdiction of state, rather than federal authorities. Following the\naccident, the Colorado state government and the COGCC made several regulatory changes related\nto flow and return lines.\nOn May 2, 2017, the COGCC issued a statewide notice to operators (NTO) mandating new\nrequirements for oil and gas operators with facilities containing flowlines, which were defined to\ninclude “well site flowline, return line, sales line, dump line, process piping, fuel gas supply line,\nand non-well site flowline.\n”8 The NTO required all oil and gas operators to “re-inspect any existing\nflowlines and pipelines located within 1,000 feet of a building unit” and provide data on those lines\nto the COGCC. Also, oil and gas operators were required to “inspect all existing flowlines and\npipelines, regardless of distance to a building unit, to verify that any existing flowline or pipeline\nnot in use, regardless of when it was installed or taken out of service, is abandoned.\n”9 The deadline\nfor compliance with this part of the NTO was May 30, 2017.\nThe NTO also required oil and gas operators to “ensure and document that all flowlines\nwithin 1,000 feet of a building unit have integrity” and noted that exemptions for pressure testing\ndid not apply to low-pressure flowlines. Additionally, the NTO required oil and gas operators to\n“complete abandonment of any flowline or pipeline not actively operated”. This NTO requirement\nwas included because flowlines abandoned prior to July 30, 2001, were not required to be cut\nbelow grade. The deadline for compliance with this part of the NTO was June 30, 2017.\n7 Pipeline and Hazardous Materials Safety Administration, Pipeline Incident 20 Year Trends, (Washington, DC:\nUS Department of Transportation, Pipeline and Hazardous Materials Safety Administration, 2019).\nhttps://www.phmsa.dot.gov/data-and-statistics/pipeline/pipeline-incident-20-year-trends. Accessed October 4, 2019.\n8 Colorado Oil and Gas Conservation Commission, Notice to Operators Statewide, “Flowlines or Pipelines – 1100\nSeries Rules”, (Denver, Colorado: Colorado Department of Natural Resources, Colorado Oil and Gas Conservation\nCommission, 2017).\n9 The line is to be cut off below grade at the lesser of 3 feet below the ground surface or at the depth of the flowline\nand sealed as described in the NTO.\n5\n\n<<<PAGE 6>>>\n\nNatural Gas Explosion at Family Residence\nOn September 8, 2017, the COGCC initiated rulemaking to strengthen flowline regulations\nand to enhance 8-1-1 programs for natural gas operations, which was finalized on March 8, 2018.10\nThe new regulations applied to all pipelines used for “transferring oil, gas, or condensate between\na wellhead and processing equipment to the load point or point of delivery…” such as the return\nand flowlines involved in this accident.\nThe new regulations for natural gas operations established requirements for better pipeline\nintegrity management practices because operators are required to “integrity test all new or repaired\nflowline and crude oil transfer line segments prior to putting them into service and periodically\nthereafter until the lines are abandoned.\n”11 The regulations also established requirements for better\npipeline abandonment practices by specifying that all flowlines and crude oil transfer lines are\nconsidered active until the line has been abandoned properly; operators are required to conduct\nperiodic integrity tests on all active lines.\nOn April 16, 2019, the governor of Colorado signed Senate Bill 19-181 into law, requiring\nthe COGCC to undertake additional rulemakings to improve flowline and leak detection\nrequirements, as well as to improve site analysis requirements. This law also amended Colorado’s\nOil and Gas Conservation Act.12\nProbable Cause\nThe National Transportation Safety Board determines that the probable cause of the\nexplosion and fire at the Firestone, Colorado, residence was the ignition of fugitive natural gas that\nhad migrated from the Coors V6-14Ji well through a pipeline that was not abandoned by Patina\nOil and Gas Corporation and that was most likely severed in 2015 during the construction of the\nhouse. Contributing to the accident was the approval by local authorities to allow occupied\nstructures to be built on land adjacent to or previously part of oil and gas production fields without\ncomplete documentation from the operator, Anadarko Petroleum Corporation, on the location and\nstatus of its gathering system pipelines.\n10 Colorado Oil and Gas Conservation Commission, Flowline Rulemaking, (Denver, Colorado: Colorado\nDepartment of Natural Resources, Colorado Oil and Gas Conservation Commission, 2018).\nhttp://cogcc.state.co.us/reg.html#/rules/flowlinerulemaking. Accessed October 7, 2019.\n11 Colorado Oil and Gas Conservation Commission, Statement of Basis, Specific Statutory Authority, and\nPurpose; “New Rules and Amendments to Current Rules of the Colorado Oil and Gas Conservation Commission,”\n2 CCR 404-1; Cause No. 1R Docket No. 171200767, (Denver, Colorado: Colorado Department of Natural Resources,\nColorado Oil and Gas Conservation Commission, 2018). https://assets.bouldercounty.org/wp-\ncontent/uploads/2017/04/crestone-exhibit-1-pages-from-cogcc-final-spb-121708.pdf. Accessed October 7, 2019.\n12 Colorado Oil and Gas Conservation Commission, Senate Bill 19-181, (Denver, Colorado: Colorado Department\nof Natural Resources, Colorado Oil and Gas Conservation Commission, 2019).\nhttps://cogcc.state.co.us/sb19181.html#/overview. Accessed October 7, 2019.\n6\n\n<<<PAGE 7>>>\n\nNatural Gas Explosion at Family Residence\nFor more details about this accident, visit www.ntsb.gov/investigations/dms.html and\nsearch for NTSB accident ID DCA17FP005.\nReport Date: October 18, 2019\nThe NTSB has authority to investigate and establish the facts, circumstances, and cause or\nprobable cause of a pipeline accident in which there is a fatality or substantial property damage,\nor significant injury to the environment. (49 U.S. Code, Section 1131 - General authority)\nThe NTSB does not assign fault or blame for an accident or incident: rather, as specified by NTSB\nregulation, “accident/incident investigations are fact-finding proceedings with no formal issues\nand no adverse parties…and are not conducted for the purpose of determining the rights or\nliabilities of any person.” Title 49 Code of Federal Regulations, Section 831.4. Assignment of fault\nor legal liability is not relevant to the NTSB’s statutory mission to improve transportation safety\nby investigating accidents and incidents and issuing safety recommendations. In addition, statutory\nlanguage 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. 49 U.S.\nCode, Section 1154(b).\n7","truncated":false,"body_characters":21293}