Notice2026-01321
Pipeline Safety: Distribution Integrity Management Program Considerations for Plastic Piping and Components
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
January 23, 2026
Issuing agencies
Transportation DepartmentPipeline and Hazardous Materials Safety Administration
Abstract
PHMSA is issuing this advisory bulletin to remind owners and operators of natural gas distribution systems of requirements under the distribution integrity management program (DIMP) regulations regarding certain plastic piping and components.
Full Text
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<title>Federal Register, Volume 91 Issue 15 (Friday, January 23, 2026)</title>
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[Federal Register Volume 91, Number 15 (Friday, January 23, 2026)]
[Notices]
[Pages 2995-2998]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-01321]
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DEPARTMENT OF TRANSPORTATION
Pipeline and Hazardous Materials Safety Administration
[Docket No. PHMSA-2026-0166]
Pipeline Safety: Distribution Integrity Management Program
Considerations for Plastic Piping and Components
AGENCY: Pipeline and Hazardous Materials Safety Administration (PHMSA),
Department of Transportation (DOT).
ACTION: Notice; issuance of advisory bulletin.
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SUMMARY: PHMSA is issuing this advisory bulletin to remind owners and
operators of natural gas distribution systems of requirements under the
distribution integrity management program (DIMP) regulations regarding
certain plastic piping and components.
FOR FURTHER INFORMATION CONTACT: Nancy White by phone at 202-923-8268
or by email at <a href="/cdn-cgi/l/email-protection#125c737c716b3c457a7b66772352767d663c757d64"><span class="__cf_email__" data-cfemail="bdf3dcd3dec493ead5d4c9d88cfdd9d2c993dad2cb">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION: On March 24, 2023, a natural gas
distribution incident occurred in West Reading, Pennsylvania, resulting
in seven fatalities, 10 injuries, the destruction of one building, and
damage to two nearby buildings. The National Transportation Safety
Board (NTSB) investigated the incident and subsequently issued Pipeline
Investigation Report NTSB/PIR-25/01 (``Investigation Report'').\1\
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\1\ NTSB, PIR-25/01, UGI Corporation Natural Gas-Fueled
Explosion and Fire, West Reading, Pennsylvania, Mar. 24, 2023 (Mar.
18, 2025) (NTSB/PIR-25/01), available at <a href="https://www.ntsb.gov/investigations/AccidentReports/Reports/PIR2501.pdf">https://www.ntsb.gov/investigations/AccidentReports/Reports/PIR2501.pdf</a>.
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In the Investigation Report, NTSB issued Safety Recommendation P-
25-1 to PHMSA, advising the Agency to issue an advisory bulletin (ADB)
to all regulated gas distribution pipeline operators ``referencing
distribution integrity management program regulations and encouraging
operators to: [c]omplete a one-time inventory of all plastic assets
that are located in environments that experience or are at risk of
elevated temperatures; [c]ontinue, during maintenance and new
construction projects, to identify plastic assets that are in elevated
temperature environments; and [e]valuate and mitigate risks to deter
the degradation of these assets.'' \2\ NTSB also issued Safety
Recommendation P-25-2 to PHMSA, advising the issuance of an ADB ``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.'' \3\
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\2\ NTSB/PIR-25/01 at 85.
\3\ Id.
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This ADB alerts owners and operators of natural gas distribution
pipeline systems to the West Reading incident; outlines NTSB's
findings, recommendations to PHMSA, and probable cause; and provides
guidance to operators on implementing DIMP requirements under 49 Code
of Federal Regulations (CFR) part 192, subpart P. These regulations
require gas distribution pipeline operators to develop and implement a
DIMP and to demonstrate an understanding of their gas distribution
system, including identifying ``the characteristics of the pipeline's
design and operations and the environmental factors that are necessary
to assess the applicable threats and risks to its gas distribution
pipeline.'' PHMSA reminds operators to consider accelerated degradation
risks associated with elevated temperature environments and encourages
operators to complete an inventory of plastic pipe and components that
may be susceptible to such environments. The advisory bulletin also
summarizes relevant past PHMSA advisories, guidance, Frequently Asked
Questions, and research related to brittle-like cracking of plastic
pipe, temperature-related degradation, and management of plastic piping
materials.
Guidance and advisory bulletins are intended to provide clarity
regarding an operator's existing legal obligations but are not
themselves rules meant to bind the public in any way; they do not
assign duties, create legally enforceable rights, or impose new
obligations that are not otherwise contained in regulations.
Accordingly, this guidance will not be relied upon by the Department as
an independent basis for affirmative enforcement action or other
administrative penalty.
I. Advisory Bulletin (ADB-2026-01)
To: Owners and Operators of Natural Gas Distribution Pipeline
Systems.
Subject: Distribution Integrity Management Program Considerations
for Plastic Piping and Components.
Advisory: On March 24, 2023, a natural gas distribution incident
occurred in West Reading, Pennsylvania, resulting in seven fatalities,
10 injuries, the destruction of one building, and damage to two nearby
buildings. The National Transportation Safety Board's (NTSB)
investigation into this incident revealed the gas distribution
operator's retired 1982 Aldyl A service tee with Delrin insert leaked
natural gas, which migrated underground into the basement of a candy
factory building, accumulated, and then ignited by an unknown source,
causing an explosion.\4\ NTSB determined the probable cause of the
incident was:
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\4\ NTSB/PIR-25/01 at vii-viii.
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[D]egradation 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
[[Page 2996]]
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.\5\
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\5\ NTSB/PIR-25/01 at 84.
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NTSB found that ``without sufficient threat information available
for analysis in its [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.'' \6\ NTSB's report noted that elevated ground temperature
may cause increased slow crack growth in susceptible plastic piping
materials, and the crack growth rate can increase exponentially with
small increases in temperature. Elevated temperature can also increase
the rate of thermal decomposition in the Delrin insert material.\7\
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\6\ NTSB/PIR-25/01 at vii.
\7\ NTSB/PIR-25/01 at 58, 67.
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NTSB 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.'' \8\ In addition, NTSB found that ``UGI lacked procedures
and training for its field crews to report sources of elevated
temperatures near their assets thus the threat posed by the steam pipe
was not identified, and mitigative measures were not implemented.'' \9\
NTSB concluded that ``the 1982 retired service tee leaked because of
degradation caused by exposure to elevated temperatures [from steam
escaping through a crack in a nearby corroded steam pipe]; more
specifically, slow crack growth of the Aldyl A tower shell and thermal
decomposition of the Delrin insert.'' \10\
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\8\ NTSB/PIR-25/01 at vii.
\9\ NTSB/PIR-25/01 at vii-viii.
\10\ NTSB/PIR-25/01 at 59.
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Following its investigation, NTSB issued several safety
recommendations, including Safety Recommendation P-25-1, advising PHMSA
to issue an advisory bulletin (ADB) to all regulated gas distribution
pipeline operators ``referencing distribution integrity management
program regulations and encouraging operators to: [c]omplete a one-time
inventory of all plastic assets that are located in environments that
experience or are at risk of elevated temperatures; [c]ontinue, during
maintenance and new construction projects, to identify plastic assets
that are in elevated temperature environments; and [e]valuate and
mitigate risks to deter the degradation of these assets.'' \11\ NTSB
also issued Safety Recommendation P-25-2 advising PHMSA to issue an ADB
reviewing the details of the incident and advise ``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.'' \12\
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\11\ NTSB/PIR-25/01 at 85.
\12\ Id.
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PHMSA and its predecessor Agency, the Research and Special Programs
Administration (RSPA), previously issued several ADBs addressing
premature brittle-like cracking \13\ in older plastic pipe materials
relevant to the West Reading incident:
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\13\ Brittle-like cracking refers to crack initiation in a
plastic pipe wall which does not immediately result in a full break
but is followed by stable crack growth at stress levels much lower
than the pipe material's yield stress.
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[ssquf] ADB-99-02 \14\ advised operators of the potential
susceptibility of certain plastic pipe installed between 1960 and the
early 1980s to premature failure due to brittle-like cracking.
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\14\ RSPA, ADB-99-02, Potential Failures Due to Brittle-Like
Cracking of Older Plastic Pipe in Natural Gas Distribution Systems,
64 FR 12212 (Mar. 11, 1999).
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[ssquf] ADB-02-07 \15\ provided recommendations for identifying and
managing brittle-like cracking for certain vintage polyethylene pipe
and noted the susceptibility of older plastic pipe to premature failure
by brittle-like cracking. Susceptible materials included ``low-ductile
inner wall `Aldyl A' polyethylene piping manufactured by Dupont Company
before 1973'' and polyethylene gas pipe designated PE 3306. It also
identified other environmental, installation, and service conditions
that could contribute to premature failure of polyethylene pipe such as
inadequate support and backfill during installation; rock impingement;
nearby excavation; service temperatures; and higher ground
temperatures.
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\15\ RSPA, ADB-02-07, Notification of the Susceptibility to
Premature Brittle-like Cracking of Older Plastic Pipe, 67 FR 70806
(Nov. 26, 2002).
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[ssquf] ADB-07-01 \16\ updated the list of pipe material
susceptible to brittle-like cracking to include Delrin insert tap tees
and Plexco service tee Celcon (polyacetal) caps.
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\16\ PHMSA, ADB-07-01, Updated Notification of the
Susceptibility to Premature Brittle-Like Cracking of Older Plastic
Pipe, 72 FR 51301 (Sep. 6, 2007).
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In addition, PHMSA issued ADB-2012-03, Notice to Operators of
Driscopipe[supreg] 8000 High Density Polyethylene Pipe of the Potential
for Material Degradation, 77 FR 13387 (Mar. 6, 2012). This ADB alerted
operators using Driscopipe 8000 high-density polyethylene (HDPE) pipe
of the potential for material degradation. At the time of the ADB's
publication, the root cause of the material degradation had not been
determined. The manufacturer has since investigated and determined the
root cause of degradation to be thermal oxidation for both Driscopipe
7000 and 8000 HDPE piping. The manufacturer also concluded that the
potential for thermal oxidation increases with increased temperature of
the pipe and with increased time at the elevated temperature
conditions.\17\ Together, these advisories alerted operators to the
risk of premature, brittle-like cracking and outline contributing
environmental and installation factors.
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\17\ See <a href="https://www.cpchem.com/sites/default/files/2020-05/DriscopipeDegradation.pdf">https://www.cpchem.com/sites/default/files/2020-05/DriscopipeDegradation.pdf</a> and <a href="https://apgasif.org/wp-content/uploads/2015/07/Driscopipe-degradation-111213.pdf">https://apgasif.org/wp-content/uploads/2015/07/Driscopipe-degradation-111213.pdf</a>.
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More recently, PHMSA published ADB-2020-02, Overpressure Protection
on Low-pressure Natural Gas Distribution Systems,\18\ which reminded
operators of their obligation to comply with gas DIMP regulations,
including requirements for an operator to demonstrate knowledge of
their system and to identify the characteristics of its pipeline
design, operation, and environment when assessing applicable threats
and risks.\19\ The ADB also provided guidance in identifying threats,
ranking risk, and determining and implementing measures designed to
reduce the risk of failure. Specifically, PHMSA advised that ``[a]
potential accident of relatively low likelihood but one that would
produce significant consequences may be a higher risk than an accident
with somewhat greater likelihood, but one that is not expected to
produce major consequences.'' \20\
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\18\ PHMSA, ADB-2020-02, Overpressure Protection on Low-pressure
Natural Gas Distribution Systems, 85 FR 61097 (Sep. 29, 2020).
\19\ Id. at 61099, 61100.
\20\ Id. at 61101.
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PHMSA has also provided ongoing guidance through its Distribution
Integrity Management Frequently Asked Questions (FAQs) stating that
brittle-like cracking of Aldyl A piping should be considered a threat
in a DIMP under the category of ``material,'' even if operators have
not experienced any issues or leaks from Aldyl A piping. The FAQ notes
that ``premature brittle-like cracking of certain Aldyl `A' pipe, along
with other vintages and manufacturer[s'] products,
[[Page 2997]]
is a well-documented problem in the [gas distribution] industry.'' \21\
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\21\ PHMSA, Gas Distribution Integrity Management Frequently
Asked Questions, at 15 (Oct. 26, 2015), <a href="https://www.phmsa.dot.gov/pipeline/gas-distribution-integrity-management/gas-distribution-integrity-management-faqs">https://www.phmsa.dot.gov/pipeline/gas-distribution-integrity-management/gas-distribution-integrity-management-faqs</a>.
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Through its DIMP Enforcement Guidance,\22\ PHMSA further clarified
that ``[p]otential threats are threats where the operator has not
necessarily experienced a leak (i.e., release of gas) but they have
conditions conducive to the threat,'' including ``[p]ipe materials
susceptible to brittle failure modes.'' \23\ The guidance advises that
operators use information sources such as operation and maintenance
procedures, purchase orders, material lists from old field orders or
standards, information from industry sources (e.g., plastic pipe data
committee), and PHMSA advisories.\24\
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\22\ PHMSA, Gas Distribution Pipeline Integrity Management
Enforcement Guidance, <a href="https://www.phmsa.dot.gov/pipeline/enforcement/dimp-enforcement-guidance">https://www.phmsa.dot.gov/pipeline/enforcement/dimp-enforcement-guidance</a> (December 7, 2015) (``DIMP
Enforcement Guidance'').
\23\ Id. at 19.
\24\ Id. at 58.
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Further, PHMSA sponsored a research and development project
completed in April 2024 titled ``Validating Models for Predicting Gas
Migration and Mitigating its Occurrences/Consequences.'' \25\ The
project's final report, hereby known as Gas Migration Report, discussed
how environmental surface conditions affect underground gas migration
and noted that ``[c]hanges in surface conditions impact how far and how
fast the gas travels below the ground. Moisture, snow, and asphalt can
block gas from escaping the surface and result in gas moving both
downwards and outwards away from the leak location.'' \26\
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\25\ Understanding of the Degree to Which Parameters Affect the
Subsurface Natural Gas Migration with Significant Flow Rates, (Apr.
29, 2024) (``Gas Migration Report''), available at: <a href="https://primis.phmsa.dot.gov/matrix/PrjHome.rdm?prj=917">https://primis.phmsa.dot.gov/matrix/PrjHome.rdm?prj=917</a>.
\26\ Id. at 72.
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Collectively, these actions demonstrate PHMSA's longstanding
commitment to address safety concerns associated with older plastic
pipe materials and to provide guidance on DIMP requirements. PHMSA
continues to remind owners and operators of natural gas distribution
systems of the DIMP requirement to demonstrate an understanding of
their system using knowledge ``developed from reasonably available
information.'' \27\ This includes having access to and gaining
additional information that allows for understanding of pipe
construction, location, age, material composition, and environmental
conditions of the underground and surrounding environment.
Specifically, operators must identify ``the characteristics of the
pipeline's design and operations and the environmental factors that are
necessary to assess the applicable threats and risks to its gas
distribution pipeline.'' \28\ PHMSA further reminds operators of the
DIMP requirements to consider threats that may accelerate crack growth
or degradation and to determine and implement measures designed to
reduce the risks of pipeline failure.
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\27\ Section 192.1007(a).
\28\ Section 192.1007(a)(1).
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In addition, PHMSA reminds operators that under Sec. 192.325(c)
plastic mains must be installed with sufficient clearance or insulation
from any sources of heat to prevent the heat from undermining the
integrity of pipelines and ancillary components, and from impairing the
serviceability of the pipe.
PHMSA advises gas distribution pipeline operators to take the
following actions to address risks associated with certain plastic
natural gas pipeline assets exposed to elevated temperatures:
1. Review NTSB's Pipeline Investigation Report PIR-25-01 on the
details of the March 24, 2023 incident in West Reading and the risks
associated with Aldyl A piping and Aldyl A tees with Delrin polyacetal
inserts.
2. Review advisory bulletins ADB-99-02, ADB-02-07, ADB-07-01, ADB-
2012-03, and ADB-2020-02; DIMP Frequently Asked Questions; DIMP
Enforcement Guidance; and the Gas Migration Report.
3. Develop and implement an integrity management plan, based on
reasonably available information, to identify the characteristics of
the pipeline's design and operations, as well as environmental factors
such as sources of elevated temperatures (e.g., underground steam lines
or electric lines), that are necessary to assess applicable threats and
risks to its gas distribution pipelines (Sec. Sec. 192.1005 and
192.1007(a)(1)).
4. Consider these environmental factors (e.g., sources of elevated
temperatures) to identify existing and potential threats. Consideration
may include completing an inventory of all plastic pipe and components
potentially susceptible to premature failure due to slow crack growth
or brittle-like cracking, and those that may be susceptible to
accelerated degradation in environments that experience or may
experience elevated temperatures (``plastic assets'') (Sec.
192.1007(b)). Operators must consider, as categories of threat,
materials, welds, and any other issues that could threaten the
integrity of its pipeline (Sec. 192.1007(b)). Susceptible materials of
plastic assets may include:
<bullet> Plastic pipe installed between 1960 and early 1980s.
<bullet> Low-ductile inner wall Aldyl A piping manufactured by
DuPont Company before 1973.
<bullet> Polyethylene gas pipe designated PE 3306.
<bullet> Aldyl A tees with Delrin polyacetal insert.
<bullet> Plexco service tee Celcon (Polyacetal) caps.
<bullet> Driscopipe 7000 and 8000 High Density Polyethylene Pipe.
5. Where elevated temperatures may pose a threat to plastic assets,
identify additional information needed to assess the threat and develop
a plan to gather information over time through activities conducted on
the pipeline, such as design, operations, maintenance, and construction
(Sec. 192.1007(a)(3)).
6. Evaluate and rank the risks associated with identified plastic
assets that are exposed to, or may be exposed to, elevated temperatures
(Sec. 192.1007(c)). Operators should consider the effects of various
surface conditions on the potential extent and migration rate of
natural gas from an underground leak when evaluating and ranking risks.
PHMSA reiterates guidance provided in advisory bulletin ADB-2020-02: a
potential incident of relatively low likelihood, but one that would
produce significant consequences, may entail a higher risk than an
incident with somewhat greater likelihood, but that is not expected to
produce major consequences.
7. Determine and implement measures to reduce the risks associated
with the failure of plastic distribution pipeline assets (Sec.
192.1007(d)). These measures must include an effective leak management
program. Such measures may also include replacement or remediation
efforts designed to reduce the risk to plastic assets; opportunistic
material type verification during routine operation and maintenance;
additional leak surveys; or integration of leak survey results to
support prioritizing segments for replacement.
8. Maintain records, for a period of at least 10 years,
demonstrating compliance with requirements of part 192, subpart P
(Sec. 192.1011). Such records may include location and material type
of operators' pipe and components; documents supporting threat
identification and risk analysis; and records documenting measures
implemented by the operator to reduce the risk to its pipeline.
9. When constructing new or replacement plastic mains, provide
sufficient clearance or insulation from
[[Page 2998]]
any sources of heat to prevent the heat from impairing the
serviceability of the pipe, in accordance with requirements in Sec.
192.325(c).
PHMSA notes that this advisory bulletin does not have the force and
effect of law and is not meant to bind owners, operators, or the public
in any way. This guidance will not be relied upon by the Department as
an independent basis for affirmative enforcement action or other
administrative penalty.
Issued in Washington, DC, on January 21, 2026, under authority
delegated in Sec. 1.97.
Linda Daugherty,
Acting Associate Administrator for Pipeline Safety.
[FR Doc. 2026-01321 Filed 1-22-26; 8:45 am]
BILLING CODE 4910-60-P
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