NTSB Safety Recommendation P-25-002

NTSB safety recommendation P-25-002.

TO THE PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION: Issue an advisory bulletin that reviews the details of the March 24, 2023, natural gas–fueled explosion and fire in West Reading, Pennsylvania, and advises all regulated natural gas distribution pipeline operators to address the risk associated with Aldyl A service tees with Delrin inserts, including replacing or remediating them.

Priority: CLASS II

Overall Status: Closed - Acceptable Action

Issued Date: 2025-04-08

Adopted Date: 2025-03-18

Overall Date Closed: 2026-04-22

Synopsis: 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.

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.

Ntsbnumber: PLD23LR002

Report Number: PIR-25-01

Addressee Name: PHMSA

Addressee Status: Closed - Acceptable Action

Addressee Date Closed: 2026-04-22

Addressee Acronym: PHMSA

Addressee Organization Type: G-Federal Government

Communication Date: 2025-04-08

Communication Type: Transmittal Letter

Communication Contents: This letter provides information about the National Transportation Safety Board’s (NTSB) March 18, 2025, report, UGI Corporation Natural Gas-Fueled Explosion and Fire, West Reading, Pennsylvania, March 24, 2023, NTSB/PIR-25/01. The details of this accident investigation and the resulting safety recommendations may be found in the attached report, which can also be accessed at http://www.ntsb.gov. As a result of this investigation, we identified the following safety issues: • Degradation of a retired Aldyl A service tee that was accelerated by elevated ground temperatures from a corroded and cracked steam pipe nearby. • UGI Corporation’s insufficient consideration of pipeline integrity threats, particularly Aldyl A service tees with Delrin inserts at elevated temperatures. • Presence of unmarked and unreported private assets crossing public rights-of-way, excluding them from the Pennsylvania One Call System and increasing the risk of damage to them. • Delayed evacuation of Palmer’s Building 2 despite detection of natural gas by employees and others. • Natural gas safety messaging from pipeline operator public awareness programs that may not reach certain members of the public. • Insufficient guidance on natural gas emergency procedures. • Absence of natural gas alarms in commercial buildings. • Insufficient accessibility of gas distribution line valves. Accordingly, the NTSB makes the following safety recommendations to PHMSA. Additional information regarding these recommendations can be found in the noted sections of the report. • Issue an advisory bulletin to all regulated natural gas distribution pipeline operators referencing distribution integrity management program regulations and encouraging operators to: • Complete a one-time inventory of all plastic assets that are located in environments that experience or are at risk of elevated temperatures; • Continue, during maintenance and new construction projects, to identify plastic assets that are in elevated temperature environments; and • Evaluate and mitigate risks to deter the degradation of these assets. (P 25 1) (See section 2.3.) • Issue an advisory bulletin that reviews the details of the March 24, 2023, natural gas–fueled explosion and fire in West Reading, Pennsylvania, and advises all regulated natural gas distribution pipeline operators to address the risk associated with Aldyl A service tees with Delrin inserts, including replacing or remediating them. (P-25-2) (See section 2.3.) • Identify effective means for natural gas distribution pipeline operators to communicate with people who live, work, or congregate within the coverage area of a natural gas distribution pipeline system and implement a plan to help operators drive continuous improvement in public awareness of natural gas safety. (P-25-3) (See section 2.5.) In addition, the NTSB reiterates the following recommendation to PHMSA: • 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) (See section 2.3.) The NTSB is vitally interested in these recommendations because they are designed to prevent accidents and save lives. We would appreciate a response within 90 days of the date of this letter, detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendations by number (Safety Recommendations P-25-1 through -3 and reiterated Safety Recommendation P-21-2). We encourage you to submit your response to ExecutiveSecretariat@ntsb.gov. If your reply, including attachments, exceeds 20 megabytes, please e mail us at the same address for instructions on how to send larger documents. Please do not submit both an electronic copy and a hard copy of the same response. The attached letter from the NTSB Chairman provides information about the report UGI Corporation Natural Gas-Fueled Explosion and Fire, West Reading, Pennsylvania, March 24, 2023, PIR-25-1. The details of this accident investigation and the resulting safety recommendations may be found in the attached report, which can also be accessed at http://www.ntsb.gov. The NTSB is vitally interested in these recommendations because they are designed to prevent accidents and save lives. We would appreciate a response within 90 days of the date of this letter detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendations by number (for example, P-25-1 through P-25-3). We encourage you to submit your response to ExecutiveSecretariat@ntsb.gov. If your reply exceeds 20 megabytes, including attachments, please e mail us at the same address for instructions on how to send larger documents. Please do not submit both an electronic copy and a hard copy of the same response. From the report UGI Corporation Natural Gas-Fueled Explosion and Fire, West Reading, Pennsylvania, March 24, 2023, PIR-25-1: 2.3 Insufficient Consideration of Known Threats from Plastic Piping The vulnerability to slow crack growth, also called brittle-like cracking, of early vintage Aldyl A and other early vintage polyethylene piping materials under certain environmental (such as high ground temperatures), installation, and service conditions has been extensively documented. In 1998, the NTSB issued a special investigation report, Brittle-Like Cracking in Plastic Pipe for Gas Service, which concluded that the procedure used in the United States to rate the strength of plastic pipe may have overrated the strength and resistance to brittle-like cracking of much of the plastic pipe manufactured and used for gas service from the 1960s through the early 1980s. The report found that much of this early vintage plastic piping may therefore be susceptible to premature brittle-like cracking failures when subjected to stress intensification (NTSB 1998). In response, PHMSA and its predecessor, the Research and Special Programs Administration, issued four advisory bulletins addressing brittle-like cracking in plastic pipe materials. The 2002 bulletin Notification of the Susceptibility to Premature Brittle-Like Cracking of Older Plastic Pipe warned that “brittle-like cracking (also known as slow crack growth) can substantially reduce the service life of polyethylene piping systems” (Research and Special Programs Administration 2002). The bulletin specifically cited certain Aldyl A piping material manufactured by DuPont Company before 1973—the same material as the retired Building 2 service tee—as potentially susceptible to brittle-like cracking. A 2007 update to the advisory bulletin added Delrin-insert tapping tees to the list of polyethylene pipe materials susceptible to brittle-like cracking. District heating systems that use underground steam pipes like the one used by Palmer can be found throughout the United States, particularly in large cities like New York; San Francisco, California; Philadelphia, Pennsylvania; and Denver, Colorado. Of the 68 district heating systems still operating, just over half were built before 1950—with one quarter built before 1900 (Pierce 2022). The extent of district heating systems nationwide means that other natural gas pipeline operators may have assets near steam pipes. Research has established that elevated temperatures can affect the pressure rating of polyethylene plastic piping, with one study citing the adverse effects of district heating systems on polyethylene gas pipelines (Akhmerova and others 2021). Early vintag

Addressee Acronym: PHMSA

Addressee Organization Type: G-Federal Government

Communication Date: 2026-04-22

Communication Type: Official Correspondence

Communication Contents: In our November 24, 2025, letter, the Board classified Safety Recommendations P-25-1 and -2 Open—Acceptable Response after PHMSA committed to publishing the recommended ADB. We understand that PHMSA published Pipeline Safety: Distribution Integrity Management Program Considerations for Plastic Piping and Components (ADB-2026-01) in the Federal Register on January 23, 2026. The ADB provides details of the March 24, 2023, natural gas-fueled explosion and fire in West Reading, Pennsylvania, and encourages operators to address risks associated with Aldyl A service tees with Delrin inserts, including replacing or remediating them. Additionally, the ADB encourages operators to complete a one-time inventory of plastic pipe components located in environments that experience, or are at risk of experiencing, elevated temperatures; continue identifying plastic assets exposed to elevated temperatures; and evaluate and mitigate risks to deter the degradation of these assets. The ADB meets the intent of these recommendations. Accordingly, the Board has classified Safety Recommendations P-25-1 and -2 CLOSED-- ACCEPTABLE ACTION.

Addressee Acronym: PHMSA

Addressee Organization Type: G-Federal Government

Communication Date: 2025-11-24

Communication Type: Official Correspondence

Communication Contents: We understand PHMSA plans to publish an ADB that advises operators to address the risks associated with Aldyl A service tees with Derlin inserts. Pending our receipt and review of the published ADB, the Board has classified Safety Recommendation P-25-2 OPEN—ACCEPTABLE RESPONSE.

Addressee Acronym: PHMSA

Addressee Organization Type: G-Federal Government

Communication Date: 2025-07-01

Communication Type: Official Correspondence

Communication Contents: -From Ben Kochman, Acting Administrator: Concur. PHMSA plans to issue an advisory bulletin (ADB) that reviews the details of the March 24, 2023 incident and advises “all regulated natural gas distribution pipeline operators to address the risk associated with Aldyl A service tees with Delrin inserts, including replacing or remediating them.”

Addressee Acronym: PHMSA

Addressee Organization Type: G-Federal Government

Communication Date: 2026-02-20

Communication Type: Official Correspondence

Communication Contents: -From Paul J. Roberti, Administrator: I am writing to request the closure of Safety Recommendations P-25-1 and P-25-2, which the National Transportation Safety Board (NTSB) issued to the Pipeline and Hazardous Materials Safety Administration (PHMSA) in Pipeline Investigation Report 25-01, UGI Corporation Natural Gas-Fueled Explosion and Fire, West Reading, Pennsylvania (March 24, 2023) (PIR-25-01). NTSB recommended PHMSA issue an advisory bulletin (ADB) to natural gas distribution operators detailing the West Reading incident and encouraging operators to complete a one-time inventory of all plastic assets in environments that experience, or are at risk of, elevated temperatures; continue to identify such assets during maintenance and construction projects; and identify, assess, and mitigate associated risks. NTSB also recommended PHMSA advise operators to address risks associated with Aldyl A service tees with Delrin inserts. PHMSA recently issued an ADB as recommended and requests that Safety Recommendations P-25-1 and P-25-2 be classified as “Closed—Acceptable Action.” PHMSA Action to Address Safety Recommendations P-25-1 and P-25-2 PHMSA published Advisory Bulletin, Pipeline Safety: Distribution Integrity Management Program Considerations for Plastic Piping and Components (ADB-2026-01) in the Federal Register on January 23, 2026. Footnote: PHMSA, ADB-2026-01, Distribution Integrity Management Program Considerations for Plastic Piping and Components, 91 FR 2995 (Jan. 23, 2026). The ADB details the March 24, 2023, West Reading incident and provides guidance to natural gas distribution pipeline system owners and operators on implementing distribution integrity management program (DIMP) requirements. The ADB specifically encourages operators to complete a one-time inventory of plastic pipe components located in environments that experience, or are at risk of experiencing, elevated temperatures; continue identifying plastic assets exposed to elevated temperatures; and evaluate and mitigate risks posed by accelerated degradation, brittle-like cracking, or slow crack growth in certain plastic materials. The ADB also promotes the identification, evaluation, and mitigation of risks associated with certain plastic piping components, including Aldyl A service tees with Delrin inserts. It reminds operators of their responsibility to use reasonably available information to understand their systems; identify design, operational, and environmental factors that may pose threats; rank associated risks; and implement measures to reduce them. These measures may include replacement or remediation of vulnerable plastic assets. In addition, the ADB summarizes relevant past PHMSA advisories, guidance, frequently asked questions, and research related to brittle-like cracking, temperature-related degradation, and management of plastic piping materials. The ADB also reiterates the requirement in 49 Code of Federal Regulations § 192.325(c) for sufficient clearance or insulation between plastic mains and heat sources. Request For Closure of Recommendations The ADB described above responds to Safety Recommendations P-25-1 and P-25-2, and PHMSA requests that NTSB classify them as “Closed—Acceptable Action.” If you have any questions or require additional information, please do not hesitate to contact me, or have your staff contact Emily Wong, Director of Governmental, International, and Public Affairs.