{"operation":"document","citation":"DCA17MP007","title":"Natural Gas Explosion at Educational Facility","source_type":"incident","agency":"National Transportation Safety Board","status":"current","official":true,"published_on":"2021-05-18","effective_on":"2017-08-02","summary":"Accident. in Minneapolis, MN, USA. on 2017-08-02. CenterPoint Energy Minnesota Gas. Leak/explosion/fire","machine_formats":{"json":"https://regulus.evalyn.ai/document/ntsb-case-dca17mp007.json","markdown":"https://regulus.evalyn.ai/document/ntsb-case-dca17mp007.md"},"app_url":"https://regulus.evalyn.ai/document/ntsb-case-dca17mp007","source_url":"https://www.ntsb.gov/investigations/Pages/DCA17MP007.aspx","body":"NTSB investigation DCA17MP007.\n\nEvent Type: Accident\n\nEvent Date: 2017-08-02\n\nEvent City: Minneapolis\n\nEvent State Or Region: MN\n\nEvent Country: USA\n\nPipeline Operator: CenterPoint Energy Minnesota Gas\n\nAccident Type: Leak/explosion/fire\n\nCompletion Status: Completed\n\nReport Number: PAB1903\n\nReport Date: 2020-01-02\n\nProbable cause: The National Transportation Safety Board determines that the probable cause of the natural gas explosion at the Minnehaha Academy was the disassembling of piping upstream of a gas service meter in the building by a pipefitting crew, resulting in the release of natural gas, which subsequently ignited. Contributing to the accident was the lack of detailed documentation that clearly established the scope of work to be performed.\n\nTier1Name: Initiating product flow\n\nTier2Name: Pressure/flow control malf/failure\n\nTier1Name: Post-release\n\nTier2Name: Explosion\n\nTier1Name: Post-release\n\nTier2Name: Evacuation\n\nTier1Name: Post-release\n\nTier2Name: Fire\n\nTier1Name: Emergency response\n\nTier2Name: Emergency shutoff\n\nTier1Name: System operating, changing flow/pressure\n\nTier2Name: Product leak/release\n\nTier1Name: System maintenance\n\nTier2Name: Maintenance event\n\nTier1Name: System not operating\n\nTier2Name: Servicing event\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Documentation/record keeping\n\nFinding Modifier Name: Other institution/organization\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Documentation/record keeping - Other institution/organization\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\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\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 August 2, 2017, at 10:22 a.m., local time, a building on the north campus of the Minnehaha Academy, a private school in Minneapolis, Minnesota, was destroyed by a natural gas explosion. At the time of the explosion, two workers were installing piping to support the relocation of gas meters from the basement of the building to the outside. Two new meters mounted on an exterior wall were ready for the piping to be connected. While workers were removing the existing piping, a full-flow natural gas line at pressure was opened. The workers were unable to control the release of the gas; thus, they evacuated the building and warned others to evacuate. The explosion occurred during their evacuation. Two individuals were killed, and nine others were injured.\n\nWhat We Found\nWe determined that the probable cause of the natural gas explosion at the Minnehaha Academy was the disassembling of piping upstream of a gas service meter in the building by a pipefitting crew, resulting in the release of natural gas, which subsequently ignited. Contributing to the accident was the lack of detailed documentation that clearly established the scope of work to be performed.\n\nPAB-19-03\n<<<PAGE 1>>>\n\nNational Transportation Safety Board\nPipeline Accident Brief\nNatural Gas Explosion at Educational Facility\nMinneapolis, Minnesota\nAugust 2, 2017\nThe Accident\nOn August 2, 2017, at 10:22 a.m., local time, a building on the north campus of the\nMinnehaha Academy, a private school in Minneapolis, Minnesota, was destroyed by a natural gas\nexplosion. Figure 1 shows an aerial view of the north campus prior to the accident, with a yellow\narrow pointing toward the explosion site. Figure 2 is a photograph of the accident site taken after\nthe building explosion, with emergency responders and gas company personnel on scene. At the\ntime of the explosion, two workers were installing piping to support the relocation of gas meters\nfrom the basement of the building to the outside. Two new meters mounted on an exterior wall\nwere ready for the piping to be connected. While workers were removing the existing piping, a\nfull-flow natural gas line at pressure was opened. The workers were unable to control the release\nof the gas; thus, they evacuated the building and warned others to evacuate. The explosion occurred\nduring their evacuation. Two individuals were killed, and nine others were injured.1\n1 For more detailed information about this accident investigation and documents referenced in it, see the National\nTransportation Safety Board’s (NTSB) public docket at https://www.ntsb.gov/investigations/SitePages/dms.aspx and\nsearch for accident number DCA17MP007.\n60032 NTSB/PAB-19/03\nThis report was reissued on December 6, 2019, with corrections to the Probable Cause on page 10.\nThis report was reissued on January 2, 2020, with corrections to the section on the Minnesota Public Utility Commission on page\n9.\n\n<<<PAGE 2>>>\n\nMinneapolis Natural Gas Explosion\nFigure 1. Photograph of north campus area at Minnehaha Academy prior to explosion. (Source:\nminnehahaacademy.net.)\nFigure 1. Photo of accident site taken after building explosion. (Source: Minneapolis Fire\nDepartment.)\nThe Accident Site\nMinnehaha Academy was in recess for summer vacation, but 36 Academy staff were\npresent to perform administrative tasks. Six students and the basketball coach were in the\ngymnasium. The basement of the central building structure contained a utilities/storage room, a\nboiler room, and a “utility bunker.” The utility bunker was an extension of the basement spaces\nconstructed beneath a ground-level concrete slab that extended out from the west basement wall\nof the building. The utility bunker, which was outside the foundation footprint of the building,2\n\n<<<PAGE 3>>>\n\nMinneapolis Natural Gas Explosion\ncontained the gas service meter equipment and was accessed by a basement door from the boiler\nroom.\nCenterPoint Energy Minnesota Gas\nNatural gas was supplied to the school by CenterPoint Energy Minnesota Gas (CPEMG).\nCPEMG performed maintenance on its own natural gas service meters and distribution pipelines\nand also hired contractors to perform specialized pipefitting services. The maintenance activity on\nthe day of the accident was being performed by such a contractor.\nGas was supplied to the school through two meters, an arrangement that allowed the gas\ncompany flexibility in its ability to supply gas to customers. When the demand for natural gas is\nhigh (for example, when outdoor temperatures are cold) and CPEMG may need delivery capacity\nelsewhere in its system, CPEMG offers commercial customers the option, if they have the ability,\nto use either natural gas or, alternately, some other form of fuel such as fuel oil. CPEMG may offer\nthe customer advantageous pricing if the customer is willing to shift to the alternate fuel at that\ntime. CPEMG supports this alternate fuel supply arrangement by the installation of (1) a “firm”\ncustomer gas meter that supplies a continuous source of gas for appliances that require an\nuninterruptable gas supply, such as for hot water or cooking, and (2) an “interruptible” customer\ngas meter that can interrupt (temporarily suspend) the flow of gas that would supply appliances\nsuch as large boilers, where the appliance can be readily switched over to the alternate fuel source.\nMinnesota Office of Pipeline Safety\nJurisdictional pipes fall under the Minnesota Office of Pipeline Safety (MNOPS) for safety\noversight to ensure enforcement for construction, operations, and maintenance pursuant to Title 49\nCode of Federal Regulations (CFR) Part 192 Transportation of Natural and Other Gas by Pipeline\n– Minimum Federal Safety Standards. Non-DOT jurisdictional pipes (also called customer pipes)\ndo not fall under federal requirements; instead, these pipes belong to the gas customers and are\nconstructed under permit from the local jurisdiction. Generally, customer piping within a facility\nup to the outlet of the service meter are nonjurisdicational; whereas, from the service meter\noutward to the distribution system, they are jurisdicational.\nMaster Mechanical, Incorporated\nMaster Mechanical, Inc. (MMI) was the contractor hired by CPEMG to perform the\npipefitting work at the accident site. MMI is a professional mechanical contracting company, based\nin Eagan, Minnesota, that has about 125 employees; the technical field personnel were hired\nthrough local unions, which provided apprenticeship training programs.\nThe MMI work involved a project to relocate the gas service meters from the inside of the\nbuilding to the outside of that building. The construction print ticket for the specific phase of the\nproject involving the MMI personnel on the day of the accident included connecting CPEMG’s\nrelocated meters using 2-inch black threaded gas piping, welding 4-inch gas piping, welding\nunderground pipes, conducting core-drilling as necessary, performing the work during normal\nbusiness hours, and securing the Minneapolis city permit for the work. About a month prior,\nCPEMG had installed two new sets of gas service meter equipment on the outside of the building.\n3\n\n<<<PAGE 4>>>\n\nMinneapolis Natural Gas Explosion\nThe MMI on-site work crew consisted of a field foreman and a construction helper; the\nfield foreman was the father of the construction helper. The field foreman was trained to the job\nclassification level of a journeyman/pipefitter, and he was hired by MMI in March 2009 and had\nworked there about 8 years. He had held the journeyman/pipefitter job classification for about 5\nyears. Although the journeyman/pipefitter was licensed and trained to meet state and local\nrequirements, he was not qualified to work on DOT-jurisdictional piping. He had not completed\nthe CPEMG Operator qualifications program, as required by 49 CFR Part 192, Subpart N, to work\non the covered tasks associated with jurisdictional piping.\nThe construction helper, who was working on the gas piping immediately preceding the\nexplosion, was a part-time employee. He was not trained to any pipefitter job classification level.\nHe was initially hired by MMI in June 2015, departing and returning to the company in\nJanuary 2017. At the time of the accident, the construction helper had been in that job position for\nless than 6 months, with total accumulated work experience with MMI of a little more than\n8 months. The construction helper also had not completed the CPEMG operator qualifications\nprogram.\nCPEMG contracted with MMI to perform piping modifications to support the relocation of\nthe gas meters from inside the building to the outside of the building. Normally, CPEMG would\nsend a contract work request to MMI, which would then respond by sending CPEMG an\nacceptance letter to execute the project at a cost, which would then become the contract agreement.\nHowever, for the Minnehaha Academy Upper School meter relocation project, the CPEMG stated\ncontract with MMI was the MMI proposal (work bid) for the project. The written terms of the\ncontract were as follows:\nMMI would:\n• Connect CPEMG’s relocated meters to the building\n• Use 2-inch black threaded gas piping\n• Weld 4-inch gas piping\n• Weld underground pipes\n• Conduct core drilling as necessary\n• Perform the work during normal business hours\n• Secure the Minneapolis City permit for the work\nMMI would not:\n• Paint\n• Start-up or re-light customer equipment\n• Pressure test customer piping\n• Work overtime\n• Demolish piping,\n• Work on existing meter\n• Dig underground\nThere was no additional or specific written documentation on the terms of the proposal.\n4\n\n<<<PAGE 5>>>\n\nMinneapolis Natural Gas Explosion\nOn the day of the accident, the two-person MMI pipefitting contractor crew was making\nmodifications to piping upstream of the firm and interruptible meters, meaning the two-person\ncrew was working on jurisdictional piping. Figure 3 is a photo taken before the accident showing\nthe vault area of the center section of the building basement and describing the individual damaged\npiping elements involved in the accident. The photo depicts the location of the nonjurisdictional\nsection of gas pipe and the jurisdictional piping that was being dismantled by the contractor work\ncrew during the accident.\nFigure 3. Photo taken before the accident of vault area of the center section of the building\nbasement. (Source: CPEMG.)\nNatural Gas Service System\nNatural gas service to the school could be shut off using the manually operated customer\nservice valve (also known as a curb valve or fire valve), which was located in an underground\nvalve box (also known as a curb box). Beyond the curb valve, the natural gas supply line penetrated\nthe utility bunker wall and branched to supply gas to the firm and interruptible meters. The branch\nto the interruptible meter passed through a manually operated plug valve (involved in the accident),\nmanufactured by The Walworth Company. The end of the plug is square, for attachment of a handle\nhaving a compatibly sized opening to accommodate the square stub on the plug. The handle can\nbe attached in any of four different orientations. The square hole of the handle was also equipped\nwith a setscrew to lock the handle in place. The plug in the valve turns 90 degrees; in one\norientation, a passage through the plug aligns with the attached piping and gas can flow; when\n5\n\n<<<PAGE 6>>>\n\nMinneapolis Natural Gas Explosion\nturned 90 degrees, to achieve the closed position, the passage is perpendicular to the attached\npiping and gas cannot flow.\nBoth the curb valve (outside the accident building) and the 3-inch Walworth plug valve\n(located in the utility bunker) were part of the “distribution system,” and as such, both comprised\nthe “regulated” section of the gas service pipeline. The Walworth Lubricated Plug Valve (product\nline) service manual for the type of plug valve involved in the accident recommends that the in-\nservice valve be periodically lubricated, although there is no specific time when such maintenance\nshould be performed.\nCPEMG maintenance records reviewed during the investigation indicated the following:\n• Maintenance on the customer curb valve was performed at least three times in the\n5 years prior to the accident (in December 2012 and twice in November 2013);\nhowever, no notations were cited in the documentation that indicated the operating\nconditions of the curb valve or specific maintenance activities that were performed\non that curb valve.\n• CPEMG provided documentation of the following activities which CPEMG\nindicated would have required the Walworth plug valve to be exercised: an\ninterruptible meter oil change that took place on December 2, 2011, a pressure test\nassociated with the service line replacement in 2002, and a pressure test associated\nwith the installation of a Kerotest valve in 1971. CPEMG further indicated that\nmeter oil changes would have been completed about every 5 years since the plug\nwas installed in 1959.\nActivities Immediately Preceding the Explosion\nOn the day of the accident, the MMI field foreman and construction helper were at the job\nsite to perform the piping relocation work. CPEMG did not have any employees at the job site at\nthe time of the explosion; the closest CPEMG employee was a block away in a company vehicle\nawaiting arrival of a construction vehicle that was enroute to the job site.\nNational Transportation Safety Board (NTSB) interview statements by the two MMI\nemployees indicated that, prior to the explosion, they had encountered a plug valve that was\nconnected to and located immediately prior to the interruptible meter in which the wrench was\n“stuck” in the closed position (that is, the wrench could not be turned). The construction helper\nstated that he knew the valve was closed because the wrench was positioned perpendicular to the\nvalve piping (the inlet/outlet connection ports of the valve).\nThe field foreman also stated that he had determined that the plug valve was closed and\nthat it was safe for the construction helper to begin dissembling piping downstream of the valve.\nBased on NTSB interviews, upon instruction from the field foreman, the construction helper,\nworking alone in the utility bunker, was then assigned to disconnect the piping from the\ninterruptible gas service meter\nA school maintenance worker located on a floor above the basement heard a “horrendous\nflow of air,” and he immediately went to investigate the strong odor of natural gas and the loud\nnoise coming from the basement. As he exited the basement, he made an announcement over his\n6\n\n<<<PAGE 7>>>\n\nMinneapolis Natural Gas Explosion\nhandheld radio that there was gas in the building and to evacuate immediately. As he made his\nradio announcement, he ran up the stairs and searched for occupants. Less than 1 minute later, the\nbuilding exploded.\nEmergency Response\nAt 10:23:06 a.m., the Minneapolis Emergency Communications Center received a call\nreporting the incident, which was initially described as a building collapse. After several\nsubsequent 9-1-1 calls, this was amended to an explosion with fire response, in which it was also\nindicated “2 people were buried under a wall.\n” The Minneapolis Fire Department (MFD) was\ndispatched at 10:24:39 a.m., and the first unit arrived at 10:30:57 a.m. The MFD response\neventually totaled 31 emergency services vehicles and at least 79 MFD personnel. The\nMinneapolis Police Department was also dispatched to the scene. The arriving MFD personnel\nobserved debris in the parking lot in front of the school building and reported a “strong odor of\ngas” in that area. They also observed a structural collapse of a section of the school building, with\nan ensuing fire within the collapsed structure debris, along with numerous blown out windows in\nthe remaining noncollapsed sections of that building.2\nAn apparent free flow of burning natural gas was occurring beneath the debris pile of the\ncollapsed structure, which resulted in an inability to suppress the fire. The curb valve was beneath\ndebris remnants of a collapsed brick wall, which was cleared by on-scene personnel; CPEMG\nclosed this valve at 11:18 a.m. The fire was subsequently suppressed by firefighters.\nSummary of Damage/Injuries\nThe estimated total property damages resulting from the explosion and fire were about\n$30 million.\n3 Two individuals were killed, and nine were injured as a result of the explosion and\nfire. The injured were transported to local medical facilities by the jurisdictional ambulance\nservices for medical evaluation and/or treatment. About 42 staff members and students, were\nevacuated from the school immediately prior to the explosion.\nThe Investigation\nExamination of Plug Valve\nThe on-scene examination by the NTSB of the plug valve, which the two MMI on-site\nemployees had identified as having been “stuck” in the closed position, showed that the valve\nwrench was positioned perpendicular to the piping. Disassembly of the valve components showed\nthat the internal “flow control” component of the valve (the valve plug) was in the open position.\nThe investigators were unable to determine how the valve wrench became positioned in that\nperpendicular orientation because preaccident photographs, provided by CPEMG and taken about\n2 Minneapolis Fire Department Incident Detail Report(s): Incident Number(s) 17-0028219 and 17-0028220 and\ninterview (transcript) testimony of several witnesses to the emergency response at the scene, available in the NTSB\npublic docket at https://www.ntsb.gov/investigations/SitePages/dms.aspx by searching for accident number\nDCA17MP007.\n3 PHMSA Incident Report (Form F7100.1): Gas Distribution System, Number 20170111-16716, dated December\n5, 2017.\n7\n\n<<<PAGE 8>>>\n\nMinneapolis Natural Gas Explosion\n1.5 years prior to the accident, showed the wrench positioned parallel to the piping, thus indicating\nthe valve was open.\nIt is customary to align the handle so that it is parallel with the piping when the valve is\nopen and positioning the handle perpendicular to the piping when the valve is closed. However,\nconfirmation of this is the responsibility of the crew working on the piping. This confirmation\nwould entail removal of the handle and noting the position of plug assembly and viewing the\nindicator or witness mark on the body of the valve.\nBriefly summarized, the NTSB Materials Laboratory report indicated (1) the valve wrench\nwas found oriented perpendicular to the valve body, (2) the valve plug was oriented in the open\nposition, (3) “witness marks” were found on two surfaces of the valve stem that were consistent\nwith contact by a valve wrench set screw, (4) the valve stem collar had embossed arrows indicating\nthe state of the valve (open or closed), in which the arrows were oriented parallel to the direction\nof flow, which was consistent with the valve being open, and (5) measurements of 344 and then\n152 foot-pounds of torque were required to rotate the valve wrench (handle) of an exemplar plug\nvalve, which compared to a measurement of 721 foot-pounds of torque that was applied to the\nwrench (handle) of the accident plug valve that had been exposed to the fire and had a 4-foot\nextension attached to the wrench (for additional leverage), in which no rotation was achieved.\nPostaccident Actions\nFollowing the accident, CPEMG took action to improve the safety of its work activities,\nwhich was documented to the investigation as follows.4\nFollowing the incident, Minnesota Gas [CPEMG] suspended company-initiated\ncommercial meter moves from inside to outside. Over a period of several months,\na cross-functional team including representatives from operations, engineering,\npurchasing, and compliance reviewed the existing process and ultimately\nrecommended the following actions to improve project oversight, project\ndocumentation, and internal and external project communications. Minnesota Gas\nimplemented these recommendations and has used the revised process several times\nnow to successfully complete company-initiated commercial meter moves from\ninside to outside. The implemented initiative actions are briefly summarized as\nfollows:\n• Formally document the process for company-initiated commercial meter moves\nfrom inside to outside, beginning with identification of project need through\ncompletion in the field and assigning responsible parties for each step in the\nprocess, with oversight provided by a project manager who is accountable for\nthe project in which––\no The revised process includes written and verbal communications to\naffected customers throughout the project; multiple checkpoints with\ncustomers and mechanical contractors to coordinate work; defining the\n4 E-mail correspondence from CPEMG to NTSB, dated July 26, 2019 (mostly quoted verbatim).\n8\n\n<<<PAGE 9>>>\n\nMinneapolis Natural Gas Explosion\ndemarcation point between utility facilities and customer piping; and\ndiscussing when, where, and how gas will be turned off;\no Based on feedback from the customer and through engineering review,\na plan is tailored to meet the customer’s unique needs and to carry out\nthe work at each location; and\no On the tie-in day, a group safety meeting will be held at the worksite\ninvolving all parties (Minnesota Gas, customer, and mechanical\ncontractor) to go over the plan, review each party’s responsibilities, and\nclarify any questions.\n Train and provide instruction to Minnesota Gas management, engineering, and\nfield personnel on the revised process; the company’s expectations; and their\nrespective roles and responsibilities, with update and refresher training as\nneeded.\n Send a letter annually to licensed mechanical contractors regarding the\ndemarcation point between Minnesota Gas facilities and customer piping and\nreiterate they are not authorized to work on or operate Minnesota Gas facilities.\n For residential customers, information about the demarcation point between\nutility facilities and customer piping has also been published on the company’s\nexternal website at https://www.centerpointenergy.com/en-\nus/residential/safety/meter-safety?sa=mn.\nMinnesota Public Utility Commission Action\nIn response to the Minnehaha Academy accident and several similar prior natural gas\nrelease and explosion accidents, the Minnesota Public Utility Commission (MN-PUC) issued a\nmemorandum, dated March 20, 2019, titled “Gas Utility Installation of Excess Flow Valves and\nManual Service Line Shutoff Valves,” which described the new requirements of the MN-PUC,\nregarding the installation of excess flow valves and manual service line shutoff valves for\nMinnesota natural gas distribution systems. In addition, MN-PUC also provided a document, dated\nMarch 18, 2019, to the Minnesota Department of Commerce, Division of Energy Resources, that\nprovides a description, a history, and the response from utilities related to the requirement for\nexcess flow valves.\nMinnesota Department Public Safety/Office of Pipeline Safety Action\nIn response to the Minnehaha Academy accident and in reference to case number\n145744454-1, the Minnesota Department of Public Safety issued (1) a Notice of Probable Violation\nto CERC, relative to actions under 49 CFR 192.13(c) General, 49 CFR 192.703(a) General, and\n49 CFR 191.9 Distribution System: Incident Report and issued (2) a Warning Letter to CERC,\nrelative to actions under 49 CFR 192.605(b) Procedural Manual for Operations, Maintenance, and\nEmergencies and 49 CFR 192.727(d) Abandonment or Deactivation of Facilities.\n9 CORRECTED COPY\n\n<<<PAGE 10>>>\n\nMinneapolis Natural Gas Explosion\nMinnesota OSHA Action\nFollowing the accident, Minnesota OSHA conducted an inspection of the accident site on\nAugust 3, 2017, in which CenterPoint Energy, Inc., issued official correspondence stating, “… the\ninspection resulted in no proposed citations.”5\nProbable Cause\nThe National Transportation Safety Board determines that the probable cause of the natural\ngas explosion at the Minnehaha Academy was the disassembling of piping upstream of a gas\nservice meter in the building by a pipefitting crew, resulting in the release of natural gas, which\nsubsequently ignited. Contributing to the accident was the lack of detailed documentation that\nclearly established the scope of work to be performed.\nFor more details about this accident, visit www.ntsb.gov/investigations/dms.html, and\nsearch for NTSB accident identification number DCA17MP007.\nDate: January 2, 2020\nThe NTSB has authority to investigate and establish the facts, circumstances, and cause or probable\ncause of a pipeline accident in which there is a fatality or substantial property damage. (Title 49\nUnited States Code (USC) 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 and\nno adverse parties . . . and are not conducted for the purpose of determining the rights or liabilities\nof any person.” Title 49 Code of Federal Regulations, Section 831.4. Assignment of fault or legal\nliability is not relevant to the NTSB’s statutory mission to improve transportation safety by\ninvestigating 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 USC,\nSection 1154[b].)\n5 Reference correspondence Minnesota Department of Labor & Industry/Occupational Safety and Health Division\nto CenterPoint Energy, Inc., dated Jan. 12, 2018, RE “OSHA Inspection 318101185 OSHI ID: O1457 05317,\nInspection Site 3100 W River Pkwy, Minneapolis, Minnesota, 55406”; for further information, see\nhttps://www.dli.mn.gov/about-department/our-areas-service/minnesota-osha-compliance.\n10 CORRECTED COPY","truncated":false,"body_characters":28213}