# UGI Corporation Natural Gas–Fueled Explosion and Fire - **operation:** document - **citation:** PLD23LR002 - **title:** UGI Corporation Natural Gas–Fueled Explosion and Fire - **source type:** incident - **agency:** National Transportation Safety Board - **status:** current - **official:** true - **published on:** 2025-04-18 - **effective on:** 2023-03-24 - **summary:** Accident. in West Reading, PA, USA. on 2023-03-24. UGI Utilities. Leak/explosion/fire - **machine formats:** - **json:** https://regulus.evalyn.ai/document/ntsb-case-pld23lr002.json - **markdown:** https://regulus.evalyn.ai/document/ntsb-case-pld23lr002.md - **app url:** https://regulus.evalyn.ai/document/ntsb-case-pld23lr002 - **source url:** https://www.ntsb.gov/investigations/Pages/PLD23LR002.aspx **body:** NTSB investigation PLD23LR002. Event Type: Accident Event Date: 2023-03-24 Event City: West Reading Event State Or Region: PA Event Country: USA Pipeline Operator: UGI Utilities Pipeline Type: Distribution Accident Type: Leak/explosion/fire Completion Status: Completed Report Number: PIR2501 Report Date: 2025-03-18 Probable cause: The National Transportation Safety Board determines that the probable cause of the explosion was degradation of a retired 1982 Aldyl A polyethylene service tee with a Delrin polyacetal insert that allowed natural gas to leak and migrate underground into the R.M. Palmer Company candy factory buildings, where it was ignited by an unknown source. Contributing to the degradation of the service tee and insert were significantly elevated ground temperatures from steam escaping R.M. Palmer Company’s corroded underground steam pipe, located near the service tee, that had been unmarked and cracked. Contributing to the steam pipe crack was soil movement and R.M. Palmer Company’s lack of awareness of the pipe’s corroded state. Contributing to the natural gas leak was UGI Corporation’s lack of awareness of the nearby steam pipe, which led to an incomplete integrity management program evaluation that did not consider or manage the risk posed by the steam pipe. Contributing to the accident’s severity was R.M. Palmer Company’s insufficient emergency response procedures and training of its employees, who did not understand the hazard and did not evacuate the buildings before the explosion. Tier1Name: System operating, changing flow/pressure Tier2Name: System disabled Tier1Name: Initiating product flow Tier2Name: Pressure/flow/temp event Tier1Name: Post-release Tier2Name: Emergency shutoff Tier1Name: Emergency response Tier2Name: Fire/explosion (post-release) Tier1Name: System not operating Tier2Name: Servicing event Tier1Name: System operating Tier2Name: Servicing event Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Safety programs Finding Modifier Name: Pipeline operator Finding Report Text: Organizational - Support/oversight/monitoring - Safety programs - Pipeline operator Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Training Finding Modifier Name: Pipeline operator Finding Report Text: Organizational - Support/oversight/monitoring - Training - Pipeline operator Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Safety programs Finding Modifier Name: State/Local agency Finding Report Text: Organizational - Support/oversight/monitoring - Safety programs - State/Local agency Finding Tier1Name: Organizational Finding Tier2Name: Management Finding Tier3Name: Communication (organizational) Finding Modifier Name: Other institution/organization Finding Report Text: Organizational - Management - Communication (organizational) - Other institution/organization Finding Tier1Name: Organizational Finding Tier2Name: Management Finding Tier3Name: Policy/procedure Finding Modifier Name: Other institution/organization Finding Report Text: Organizational - Management - Policy/procedure - Other institution/organization Finding Tier1Name: Organizational Finding Tier2Name: Support/oversight/monitoring Finding Tier3Name: Safety programs Finding Modifier Name: Federal agency Finding Report Text: Organizational - Support/oversight/monitoring - Safety programs - Federal agency Finding Tier1Name: Environment/Infrastructure Finding Tier2Name: Operating environment/control system Finding Tier3Name: Sensor/detector coverage/availability Finding Modifier Name: Contributed to outcome Finding Report Text: Environment/Infrastructure - Operating environment/control system - Sensor/detector coverage/availability - Contributed to outcome Finding Tier1Name: Pipeline Finding Tier2Name: Pipline systems/equipment Finding Tier3Name: Fittings Finding Modifier Name: Damaged/degraded Finding Report Text: Pipeline - Pipline systems/equipment - Fittings - Damaged/degraded Finding Tier1Name: Environment/Infrastructure Finding Tier2Name: Conditions/weather/phenomena Finding Tier3Name: Temperature Finding Modifier Name: Effect on equipment Finding Report Text: Environment/Infrastructure - Conditions/weather/phenomena - Temperature - Effect on equipment Finding Tier1Name: Pipeline Finding Tier2Name: Miscellaneous equipment Finding Tier3Name: Misc equipment/hardware Finding Modifier Name: Damaged/degraded Finding Report Text: Pipeline - Miscellaneous equipment - Misc equipment/hardware - Damaged/degraded Finding Tier1Name: Environment/Infrastructure Finding Tier2Name: Physical environment Finding Tier3Name: Soil Finding Modifier Name: Effect on equipment Finding Report Text: Environment/Infrastructure - Physical environment - Soil - Effect on equipment Finding Tier1Name: Pipeline Finding Tier2Name: Pipline systems/equipment Finding Tier3Name: Fittings Finding Modifier Name: Damaged/degraded Finding Report Text: Pipeline - Pipline systems/equipment - Fittings - Damaged/degraded Finding Tier1Name: Environment/Infrastructure Finding Tier2Name: Operating environment/control system Finding Tier3Name: Markings/signage Finding Modifier Name: Awareness of condition Finding Report Text: Environment/Infrastructure - Operating environment/control system - Markings/signage - Awareness of condition Official NTSB investigation data. NTSB findings determine probable cause and make safety recommendations; they do not adjudicate civil liability or regulatory violations. What Happened On March 24, 2023, around 4:55 p.m., natural gas, which was transported through a UGI Corporation–owned pipeline, leaked into and accumulated in the basement of an R.M. Palmer Company candy factory building in West Reading, Pennsylvania. The gas ignited, causing an explosion and fire that killed 7 Palmer employees, injured 10 people, and destroyed the building. Another Palmer building, as well as an adjacent apartment building, were also severely damaged. Three families were displaced from the apartment building. Safety issues included degradation of a retired service tee, insufficient consideration of threats to pipeline integrity, the risk associated with unmarked private pipeline assets crossing public rights-of-way (for example, a public street), delayed evacuation of Building 2 despite detection of natural gas, natural gas safety messaging that may not reach certain members of the public, insufficient guidance on gas leak emergency procedures, absence of natural gas detection alarms in commercial buildings, and insufficient accessibility of gas distribution line valves. What We Found We determined that the probable cause of the explosion was degradation of a retired 1982 Aldyl A polyethylene service tee with a Delrin polyacetal insert that allowed natural gas to leak and migrate underground into the R.M. Palmer Company candy factory buildings, where it was ignited by an unknown source. Contributing to the degradation of the service tee and insert were significantly elevated ground temperatures from steam escaping R.M. Palmer Company’s corroded underground steam pipe, located near the service tee, that had been unmarked and cracked. Contributing to the steam pipe crack was soil movement and R.M. Palmer Company’s lack of awareness of the pipe’s corroded state. Contributing to the natural gas leak was UGI Corporation’s lack of awareness of the nearby steam pipe, which led to an incomplete integrity management program evaluation that did not consider or manage the risk posed by the steam pipe. Contributing to the accident’s severity was R.M. Palmer Company’s insufficient emergency response procedures and training of its employees, who did not understand the hazard and did not evacuate the buildings before the explosion. What We Recommended As a result of this investigation, we issued 18 new recommendations. Read the complete list of recommendations. We issued recommendations to: the Pipeline and Hazardous Materials Safety Administration, the Occupational Safety and Health Administration, 50 states along with the Commonwealth of Puerto Rico and the District of Columbia, the Commonwealth of Pennsylvania, the Pennsylvania Public Utility Commission, the American Gas Association, the American Petroleum Institute, the Gas Piping Technology Committee, the Common Ground Alliance, the International Code Council, the National Fire Protection Association, UGI Corporation, and R.M. Palmer Company. We also reiterated the following safety recommendation: To the Pipeline and Hazardous Materials Safety Administration: Evaluate industry’s implementation of the gas distribution pipeline integrity management requirements and develop updated guidance for improving their effectiveness. The evaluation should specifically consider factors that may increase the likelihood of failure such as age, increase the overall risk (including factors that simultaneously increase the likelihood and consequence of failure), and limit the effectiveness of leak management programs. (P-21-2) PIR-25-01 <<>> March 18, 2025 Pipeline Investigation Report PIR-25-01 UGI Corporation Natural Gas-Fueled Explosion and Fire West Reading, Pennsylvania March 24, 2023 Abstract: This report discusses the March 24, 2023, natural gas–fueled explosion and fire at Building 2 of the R.M. Palmer Company, a candy manufacturer located in West Reading, Pennsylvania. The explosion destroyed the manufacturer’s Building 2 and caused significant structural damage to its adjacent Building 1 and other surrounding structures. In total, 7 people were killed, 10 people were injured, and 3 families were displaced from a neighboring apartment building. Safety issues identified in this report include degradation of a retired service tee, insufficient consideration of threats to pipeline integrity, the risk associated with unmarked private pipeline assets crossing public rights-of-way (for example, a public street), delayed evacuation of Building 2 despite detection of natural gas, natural gas safety messaging that may not reach certain members of the public, insufficient guidance on gas leak emergency procedures, absence of natural gas detection alarms in commercial buildings, and insufficient accessibility of gas distribution line valves. As part of this investigation, the National Transportation Safety Board issued recommendations to the Pipeline and Hazardous Materials Safety Administration, the Occupational Safety and Health Administration, 50 states along with the Commonwealth of Puerto Rico and the District of Columbia, the Commonwealth of Pennsylvania, the Pennsylvania Public Utility Commission, the American Gas Association, the American Petroleum Institute, the Gas Piping Technology Committee, the Common Ground Alliance, the International Code Council, the National Fire Protection Association, UGI Corporation, and R.M. Palmer Company. <<>> Pipeline Investigation Report Report Number PIR-25-01 Contents Figures ..................................................................................................................iv Tables .................................................................................................................. v Acronyms and Abbreviations ................................................................................vi Executive Summary ..............................................................................................vii What Happened.............................................................................................................. vii What We Found .............................................................................................................. vii What We Recommended ............................................................................................... ix 1 Factual Information .................................................................................. 1 1.1 The Accident ........................................................................................................... 1 1.1.1 Area Layout ...................................................................................................... 2 1.1.2 Service Line and Tee Replacement at Palmer Building 2 ........................... 5 1.1.3 Natural Gas Leak and Explosion .................................................................... 8 1.2 Injuries and Damages from the Explosion and Gas Fire ................................. 12 1.3 Emergency Response........................................................................................... 12 1.3.1 R.M. Palmer Emergency Response ............................................................. 13 1.3.2 Local Emergency Response ......................................................................... 13 1.3.3 UGI Emergency Response ............................................................................ 14 1.4 R.M. Palmer Facilities and Heating System........................................................ 16 1.5 UGI Corporation ................................................................................................... 17 1.5.1 Cherry Street Gas Main and Service Information ...................................... 17 1.5.2 UGI Leak Surveys Since 2011 ....................................................................... 19 1.5.3 Valve Inspections ........................................................................................... 19 1.6 Postaccident Examinations and Testing ............................................................ 21 1.6.1 On-Scene Examinations ................................................................................ 22 1.6.2 Laboratory Examinations and Research ..................................................... 30 1.7 Regulations, Advisories, and Standards ............................................................ 38 1.7.1 Pipeline and Hazardous Materials Safety Administration ........................ 38 1.7.2 Pennsylvania Public Utility Commission ..................................................... 39 1.7.3 Occupational Safety and Health Administration ....................................... 40 i <<>> Pipeline Investigation Report Report Number PIR-25-01 1.7.4 Codes .............................................................................................................. 40 1.8 Plans, Procedures, and Programs ....................................................................... 42 1.8.1 R.M. Palmer .................................................................................................... 42 1.8.2 UGI Corporation ............................................................................................ 44 1.9 Postaccident Actions ............................................................................................ 49 1.9.1 Occupational Safety and Health Administration Investigation ................ 49 1.9.2 Pennsylvania Public Utility Commission ..................................................... 50 1.9.3 R.M. Palmer .................................................................................................... 51 1.9.4 UGI Corporation ............................................................................................ 51 1.10 Pennsylvania Public Utility Commission Party Removal ................................... 54 2 Analysis................................................................................................... 55 2.1 Introduction ........................................................................................................... 55 2.2 The Accident ......................................................................................................... 56 2.2.1 Source of Natural Gas that Fueled the Explosion...................................... 56 2.2.2 Delayed Evacuation ....................................................................................... 62 2.3 Insufficient Consideration of Known Threats from Plastic Piping ................... 64 2.4 Unmarked Private Assets in Public Rights-of-Way ............................................ 69 2.5 Public Awareness and Preparedness ................................................................. 71 2.5.1 Natural Gas Alarms ........................................................................................ 73 2.5.2 Companies’ Emergency Response Procedures ........................................ 77 2.6 Valve Accessibility ................................................................................................. 78 2.7 Withholding Safety-Related Information from the NTSB ................................. 80 3 Conclusions ............................................................................................ 82 3.1 Findings ................................................................................................................. 82 3.2 Probable Cause ..................................................................................................... 84 4 Recommendations .................................................................................. 85 4.1 New Recommendations ....................................................................................... 85 4.2 Previously Issued Recommendation Reiterated in This Report ...................... 87 Appendixes ......................................................................................................... 89 Appendix A: Investigation ............................................................................................ 89 Appendix B: Consolidated Recommendation Information ..................................... 90 ii <<>> Pipeline Investigation Report Report Number PIR-25-01 References........................................................................................................... 96 iii <<>> Pipeline Investigation Report Report Number PIR-25-01 Figures Figure 1. Overhead image of the accident. ........................................................................ 2 Figure 2. South 2nd Avenue before the accident. ............................................................. 3 Figure 3. Arrangement of Palmer-owned pipes. ................................................................ 4 Figure 4. Natural gas distribution system and Palmer-owned pipes. .............................. 6 Figure 5. Cherry Street gas main and Building 2 service tees, viewed from above. ..... 8 Figure 6. Underground gas main valves involved in response to the March 24 incident. ................................................................................................................................. 15 Figure 7. Aldyl A service tee and its components. ........................................................... 18 Figure 8. South 2nd Avenue and Penn Avenue intersection in 2018 and during an excavation in 2024; water valve A had a gas cover. ......................................................... 21 Figure 9. Bar hole test readings conducted in March 2023 and April 2023. ................ 24 Figure 10. Smoke from conduit visible near gas service line to Building 2. ................. 27 Figure 11. Excavation of pipes at the accident location. ................................................. 27 Figure 12. A view of one of the chocolate pipe conduits from the Building 2 basement. .............................................................................................................................. 29 Figure 13. Longitudinal fracture in retired service tee. ................................................... 31 Figure 14. Interior of retired service tee tower with top portion of Delrin insert missing. .................................................................................................................................. 32 Figure 15. Longitudinal fracture from top to base of tower and detailed image of slow crack growth region. ............................................................................................................ 33 Figure 16. Image of fracture surface on Delrin insert for retired service tee. ............... 34 Figure 17. Through-wall cracks in steam pipe. ................................................................. 36 Figure 18. UGI crew during service line replacement project, 2021. ............................ 37 iv <<>> Pipeline Investigation Report Report Number PIR-25-01 Tables Table 1. Surveillance camera data from in and around Buildings 1 and 2 before the explosion. .............................................................................................................................. 11 Table 2. Reported valve inspections. ................................................................................. 20 Table 3. Estimated UGI Aldyl A and total assets. .............................................................. 47 Table 4. Palmer OSHA-issued violations. .......................................................................... 50 v <<>> Pipeline Investigation Report Report Number PIR-25-01 Acronyms and Abbreviations API American Petroleum Institute CEO Palmer Chief Executive Officer CFR Code of Federal Regulations CGA Common Ground Alliance DDRM data-driven risk model GOM Gas Operations Manual DIMP distribution integrity management program GIS geographic information system GPTC Gas Piping Technology Committee GPTC Guide Guide for Gas Transmission, Distribution, and Gathering Piping Systems ICC International Code Council IFC International Fuel Code IFGC International Fuel Gas Code IM integrity management Inside SLIP inside service line inspection program NFPA National Fire Protection Association NFPA 54 National Fuel Gas Code NPRM notice of proposed rulemaking OSHA Occupational Safety and Health Administration PA One Call Pennsylvania One Call System PA PUC Pennsylvania Public Utility Commission PHMSA Pipeline and Hazardous Materials Safety Administration psig pounds per square inch, gauge PSMS pipeline safety management system RP Recommended Practice SME subject-matter expert VP Palmer vice president of operations and technical services vi <<>> Pipeline Investigation Report Report Number PIR-25-01 Executive Summary What Happened On March 24, 2023, around 4:55 p.m., natural gas, which was transported through a UGI Corporation–owned pipeline, leaked into and accumulated in the basement of an R.M. Palmer Company candy factory building in West Reading, Pennsylvania. The gas ignited, causing an explosion and fire that killed 7 Palmer employees, injured 10 people, and destroyed the building. Another Palmer building, as well as an adjacent apartment building, were also severely damaged. Three families were displaced from the apartment building. What We Found In 2021, a UGI Corporation crew retired the Aldyl A polyethylene service tee, joining UGI’s gas main to the service line for Palmer Building 2. The crew capped off the retired tee, which had been installed in 1982, and installed a new tee. The retired Aldyl A tee remained connected to the natural gas distribution system. We found that natural gas had migrated from the retired Aldyl A service tee through the ground then into the Palmer Building 2 basement, chocolate pipe conduits, and Building 1, and fueled the explosion in the Building 2 basement. We found that the 1982 retired service tee leaked because of degradation (slow crack growth of the Aldyl A tower shell and thermal decomposition of the Delrin insert) caused by exposure to elevated temperatures. Steam escaping through a crack in a corroded steam pipe nearby had significantly elevated the ground temperatures near the tee. We found that the omission from PA's One Call law of certain assets whose lines transport steam or other high temperature substances across public rights-of-way can pose a risk during nearby excavation. We further found that widespread adoption of best practices on 811 center membership can increase awareness of certain underground pipelines that cross public rights-of-way and prevent an accident like this one. We found that, without sufficient threat information available for analysis in its distribution integrity management program (DIMP), UGI could not effectively evaluate and address the risk to pipeline integrity of plastic piping in elevated temperature environments and that by not addressing the threat posed by the steam pipe, UGI’s DIMP was not effective in preventing the accident. We further found that operators may not be aware of where they may have plastic natural gas assets that are vulnerable to degradation in elevated temperature environments, so appropriate mitigations may not be in place. In this accident, we found that UGI lacked procedures and training for its field crews to report sources of elevated temperatures vii <<>> Pipeline Investigation Report Report Number PIR-25-01 near their assets thus the threat posed by the steam pipe was not identified, and mitigative measures were not implemented. In addition, industry guidance highlighting the threat to pipeline integrity of exposure to elevated temperatures could improve awareness so that operators can effectively identify and manage the threat. Although several employees reported smelling the gas in the buildings before the explosion, few evacuated. We found that had Palmer implemented natural gas emergency procedures and training before the accident, employees and managers could have responded by immediately evacuating and moving to a safe location. We further found that when businesses that use natural gas do not have natural gas emergency procedures and training, employees may be unaware or unsure of what to do if they smell natural gas. Further, we determined that natural gas alarms can alert people of a gas leak so they can evacuate the area; however, natural gas customers may not be aware of the necessity of such alarms. We also found that, because of their consensus-based nature and wide reach, model building or gas codes can be effective instruments to address natural gas–related risks to employees of businesses that use natural gas. Because adoption of these fuel gas codes and other rules related to natural gas alarms depends on state and local policies, widespread requirement of natural gas alarms will rely on action at the state and local level. We found that natural gas pipeline operator public awareness programs may not reach certain members of the public who do not directly receive bill stuffers, making them potentially unaware of natural gas safety guidance. Further, because customers vary significantly in the number of occupants or residents, criteria for designating emergency valves that only count customers may not accurately reflect who could be affected by a natural gas outage or emergency or the severity of the effect. We also found that UGI did not effectively inspect and maintain its valves through its valve maintenance program, which led to a delay in shutting off gas to the affected area. Lastly, we found that the Pennsylvania Public Utility Commission refused to provide investigative information pursuant to the NTSB’s federal authority. We determined that the probable cause of the explosion was degradation of a retired 1982 Aldyl A polyethylene service tee with a Delrin polyacetal insert that allowed natural gas to leak and migrate underground into the R.M. Palmer Company candy factory buildings, where it was ignited by an unknown source. Contributing to the degradation of the service tee and insert were significantly elevated ground temperatures from steam escaping R.M. Palmer Company’s corroded underground steam pipe, located near the service tee, that had been unmarked and cracked. Contributing to the steam pipe crack was soil movement and R.M. Palmer Company’s viii <<>> Pipeline Investigation Report Report Number PIR-25-01 lack of awareness of the pipe’s corroded state. Contributing to the natural gas leak was UGI Corporation’s lack of awareness of the nearby steam pipe, which led to an incomplete integrity management program evaluation that did not consider or manage the risk posed by the steam pipe. Contributing to the accident’s severity was R.M. Palmer Company’s insufficient emergency response procedures and training of its employees, who did not understand the hazard and did not evacuate the buildings before the explosion. What We Recommended We recommended that the Pipeline and Hazardous Materials Safety Administration (PHMSA) issue an advisory bulletin reviewing the details of this accident to natural gas distribution pipeline operators and advising them to address the risk associated with Aldyl A service tees with Delrin inserts by replacing or remediating them. We also recommended that PHMSA issue an advisory bulletin to operators referencing DIMP regulations and encouraging a one-time inventory of all plastic assets that are located in environments that experience or are at risk of elevated temperatures, identifying plastic assets in elevated temperature environments, and evaluating and mitigating risks to deter the degradation of these assets. In addition, we recommended that UGI inventory all its plastic natural gas assets that may be in elevated temperature environments and address the risk associated with these assets. We reiterated a 2021 recommendation to PHMSA to evaluate industry implementation of gas distribution pipeline integrity management requirements and develop updated guidance for improving the effectiveness of the requirements. We further recommended that PHMSA find effective ways for operators to communicate with people who live, work, or congregate near natural gas distribution pipelines and help operators improve public awareness of natural gas safety. We then recommended that, based on these findings, the American Petroleum Institute update its public awareness standard to provide specific guidance to natural gas distribution pipeline operators on effective safety communications. We recommended that the Occupational Safety and Health Administration require employers whose facilities use natural gas to implement natural gas emergency procedures and that Palmer revise its natural gas emergency procedure to direct all employees to immediately evacuate to a safe location when they smell natural gas. We also recommended that Pennsylvania modify its law on underground utility protection to require all owners and operators of pipelines transporting steam or other high-temperature materials located in public rights-of-way to register their ix <<>> Pipeline Investigation Report Report Number PIR-25-01 assets with Pennsylvania One Call and that the Common Ground Alliance identify opportunities for improving adoption of its best practices on 811 center membership. To make sure operators consider consequences and emergency response times in determining the locations of critical valves, we recommended the Pennsylvania Public Utility Commission assess operators’ methodology for this determination. We recommended that the American Gas Association share the details of this accident with its members, encouraging them to evaluate the effectiveness of their public awareness programs and to promote the installation of natural gas alarms. We also recommended that the Gas Piping Technology Committee develop guidance to ensure natural gas pipeline operators’ DIMPs appropriately assess and address threats to plastic pipelines from nearby temperature-elevating assets. We recommended that 50 states, Puerto Rico, and the District of Columbia require the installation of natural gas alarms and that the International Code Council and the National Fire Protection Association revise codes to provide for natural gas emergency procedures and revise the fuel gas codes to provide for the required installation of natural gas alarms. Finally, we recommended that the Commonwealth of Pennsylvania review and amend its statutes to facilitate sharing investigative information with the NTSB. x <<>> Pipeline Investigation Report Report Number PIR-25-01 1 Factual Information 1.1 The Accident On March 24, 2023, about 4:55 p.m. local time, a natural gas–fueled explosion and fire occurred at Building 2 of the R.M. Palmer Company candy factory in West Reading, a borough in Berks County, Pennsylvania. The explosion destroyed Building 2 and caused significant structural damage to the adjacent Building 1 and other surrounding structures, including an apartment building. (See figure 1.) In total, 7 people were killed, 10 people were injured, and 3 families were displaced from their apartments. The accident caused an estimated $42 million in property damage. 1 Weather conditions at the time of the accident were clear with no precipitation, the temperature was 52°F, and winds were about 5 mph from the southwest by south. 1 Visit ntsb.gov to find additional information in the public docket for this NTSB accident investigation (case number PLD23LR002). Use the CAROL Query to search safety recommendations and investigations. 1 <<>> Pipeline Investigation Report Report Number PIR-25-01 Figure 1. Overhead image of the accident. (Source: Western Berks Fire Department.) 1.1.1 Area Layout Building 2, a two-story brick structure, was located at 17 South 2nd Avenue in West Reading. The four-story brick Building 1 was located at 77 South 2nd Avenue, south of Building 2. Cherry Street, a public right-of-way (alley), separated the two buildings. The affected apartment building, which comprised three households, was located 5 feet north of Building 2. (See figure 2.) 2 <<>> Pipeline Investigation Report Report Number PIR-25-01 Figure 2. South 2nd Avenue before the accident. (Source: Google Photos.) UGI Corporation owned and operated natural gas pipeline assets located within the public right-of-way near the accident site.2 Natural gas was distributed to Palmer Buildings 1 and 2 from a UGI natural gas main that ran lengthwise underneath Cherry Street (Cherry Street main). 3 Near the intersection with South 2nd Avenue, the Cherry Street main transitioned from a short section of steel and then reduced to a 1.25-inch-diameter Aldyl A main, which was installed in 1982 (see section 1.5.1). 4 Aldyl A is the trademarked name of a polyethylene plastic gas pipeline product that was manufactured by the DuPont chemical company using a proprietary polymer resin. At the time of the accident, the Cherry Street main was operating about 53 pounds per square inch, gauge (psig). The maximum allowable operating pressure of the Cherry Street main was 60 psig. The main was about 3 feet below the road surface. Palmer produces chocolate novelty candies for sale in the United States and internationally and has been in business in Pennsylvania since 1948. It has about 550 full-time employees and about 300 seasonal workers. Palmer’s facilities at the time of the accident comprised six buildings, two in West Reading and four in Wyomissing, 2 (a) See section 1.5 for UGI company information. (b) This report uses the term asset to refer to the specific elements of a pipeline distribution system. 3 A gas main is a natural gas distribution pipeline that serves as a common source of supply for more than one service line. Service lines transport gas to a customer. 4 In 1982, the Aldyl A gas main was installed by inserting it into a bare steel main from 1911. As was common practice at the time, once the Aldyl A main was inserted, the steel main was then abandoned. An abandoned pipeline is one permanently removed from service, no longer containing natural gas, as defined in Title 49 Code of Federal Regulations (CFR) 192.3. 3 <<>> Pipeline Investigation Report Report Number PIR-25-01 Pennsylvania. In West Reading, Building 1 was used for candy production and as corporate headquarters, and Building 2 was used for candy production. Palmer- owned pipes (private pipes) ran underneath Cherry Street between Buildings 1 and 2: a steam pipe that delivered steam from the boiler to heat areas of Building 2, a condensate pipe that channeled condensation back to the boiler, and two conduits that together contained six supply pipes that delivered liquid chocolate from storage tanks in the basement of Building 2 to production areas in Building 1. 5 One conduit contained four chocolate supply pipes, and the other conduit contained two chocolate pipes. (See figure 3.) Electric heat tape affixed to the outside of the chocolate pipes kept the chocolate from solidifying in the pipes. The top of the steam pipe was about 1.5 feet below the road surface.6 Figure 3. Arrangement of Palmer-owned pipes. 5 These pipes were partially destroyed in the explosion and are no longer in use. 6 Palmer began production in Building 2 in the mid-1960s. The National Transportation Safety Board (NTSB) interviewed a former Palmer employee who indicated the steam pipe had been installed before he began working there in the mid-1970s. 4 <<>> Pipeline Investigation Report Report Number PIR-25-01 The Palmer-owned pipes laid above and perpendicular to the gas main, with steam flowing from Building 1 to Building 2. Palmer kept maintenance records of the steam heating system boiler unit. These records indicated that the unit was checked daily by Palmer mechanics and inspected annually by a contractor, but Palmer did not have any maintenance records for the steam pipe to Building 2. 1.1.2 Service Line and Tee Replacement at Palmer Building 2 Two years before this accident, on February 16, 2021, a UGI crew conducted a routine inspection of the Building 2 gas meter, which at the time was in the basement.7 The crew detected gas inside the basement of Building 2 and at the service curb valve outside the building. UGI recorded this as a “grade C” leak, which required immediate attention or repair, and began a project to replace the service line and service tee from the Cherry Street gas main to Building 2 and to move the meter outdoors as required by UGI procedures. The service tee joined the service line to the main. The alignment of the private pipes and natural gas distribution system assets after the replacement project is shown in figure 4. 7 This type of inspection, required by UGI’s Gas Operations Manual (GOM) and federal regulation to be conducted every 3 years on a medium-pressure system, is described further in section 1.5.2. 5 <<>> Pipeline Investigation Report Report Number PIR-25-01 Figure 4. Natural gas distribution system and Palmer-owned pipes. Before beginning excavation to replace the service line and move the gas meter, UGI submitted an emergency underground utility line locate request to the Pennsylvania One Call System (PA One Call) to mark existing utilities so UGI could repair a gas leak at Building 2. 8 Pennsylvania’s Underground Utility Line Protection Law, Pennsylvania Act 287, as amended, requires owners or operators of underground lines that serve one or more customers or consumers in Pennsylvania to be a member of PA One Call, a privately funded nonprofit corporation that facilitates utility line location in all Pennsylvania counties.9 PA One Call’s interpretation of this law did not require Palmer to be a member, so its underground pipes were not included in the PA One Call database. 8 Pennsylvania has recognized and adopted the uniform pavement marking colors outlined in the Common Ground Alliance’s Best Practices Guide for underground piping or other utility assets. 9 See Pennsylvania Statutes, Title 73 P.S. Section 176 et. Seq. 6 <<>> Pipeline Investigation Report Report Number PIR-25-01 After the accident, the NTSB interviewed UGI crewmembers about the 2021 replacement of the Building 2 servic - **truncated:** true - **body characters:** 238207