`[Federal Register Volume 89, Number 248 (Friday, December 27, 2024)]
[Proposed Rules]
[Pages 105986-106061]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-29466]



[[Page 105985]]

Vol. 89

Friday,

No. 248

December 27, 2024

Part IV





Environmental Protection Agency





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40 CFR Part 63





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Review of National Emission Standards for Hazardous Air Pollutants for 
Polyether Polyols Production Industry; Proposed Rule

  Federal Register / Vol. 89 , No. 248 / Friday, December 27, 2024 / 
Proposed Rules  

[[Page 105986]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2023-0282; FRL-10854-01-OAR]
RIN 2060-AW01


Review of National Emission Standards for Hazardous Air 
Pollutants for Polyether Polyols Production Industry

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The U.S. Environmental Protection Agency (EPA) is proposing 
amendments to the National Emission Standards for Hazardous Air 
Pollutants (NESHAP) under the Clean Air Act (CAA) that apply to the 
Polyether Polyols (PEPO) Production industry (referred to as the PEPO 
NESHAP in this document). The EPA is proposing decisions resulting from 
the Agency's technology review of the PEPO NESHAP and decisions based 
on its reconsideration of certain issues raised in an administrative 
petition for reconsideration. Furthermore, the EPA is proposing to 
strengthen the emission standards for ethylene oxide (EtO) emissions 
after considering the results of a risk assessment for the PEPO NESHAP. 
The EPA is also proposing to require performance testing once every 5 
years, to add work practice standards for certain activities where 
alternatives are appropriate, and to add provisions for electronic 
reporting. We estimate that the proposed amendments to the PEPO NESHAP, 
excluding the EtO emission standards, would reduce hazardous air 
pollutant (HAP) emissions from PEPO sources by approximately 157 tons 
per year (tpy). Additionally, the proposed EtO emission standards are 
expected to reduce EtO emissions by approximately 14 tpy. We also 
estimate that these proposed amendments to the NESHAP will reduce 
excess emissions of HAP from flares in the PEPO Production source 
category by an additional 75 tpy.

DATES: 
    Comments. Comments must be received on or before February 25, 2025. 
Under the Paperwork Reduction Act (PRA), comments on the information 
collection provisions are best assured of consideration if the Office 
of Management and Budget (OMB) receives a copy of your comments on or 
before January 27, 2025.
    Public hearing. If anyone contacts us requesting a public hearing 
on or before January 3, 2025, we will hold a virtual public hearing. 
See SUPPLEMENTARY INFORMATION for information on requesting and 
registering for a public hearing.

ADDRESSES: You may send comments, identified by Docket ID No. EPA-HQ-
OAR-2023-0282, by any of the following methods:
     Federal eRulemaking Portal: https://www.regulations.gov 
(our preferred method). Follow the online instructions for submitting 
comments.
     Email: [email protected]. Include Docket ID No. EPA-
HQ-OAR-2023-0282 in the subject line of the message.
     Fax: 202-566-9744. Attention Docket ID No. EPA-HQ-OAR-
2023-0282.
     Mail: U.S. Environmental Protection Agency, EPA Docket 
Center, Docket ID No. EPA-HQ-OAR-2023-0282, Mail Code 28221T, 1200 
Pennsylvania Avenue NW, Washington, DC 20460.
     Hand/Courier Delivery: EPA Docket Center, WJC West 
Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004. 
The Docket Center's hours of operation are 8:30 a.m.-4:30 p.m., Monday-
Friday (except Federal Holidays).
    Instructions: All submissions received must include the Docket ID 
No. for this rulemaking. Comments received may be posted without change 
to https://www.regulations.gov/, including any personal information 
provided. For detailed instructions on sending comments and additional 
information on the rulemaking process, see the SUPPLEMENTARY 
INFORMATION section of this document.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed 
action, contact U.S. EPA, Attn: Ms. Johanna Klein, Mail Drop: E143-01, 
109 T.W. Alexander Drive, P.O. Box 12055, Research Triangle Park, North 
Carolina 27711; telephone number: (919) 541-2283; and email address: 
[email protected]. For specific information regarding the risk 
modeling methodology, contact U.S. EPA, Attn: Ms. Dianna Francisco, 
Mail Drop: C539-02, 109 T.W. Alexander Drive, P.O. Box 12055, Research 
Triangle Park, North Carolina 27711; telephone number: (919) 541-3182; 
and email address: [email protected].

SUPPLEMENTARY INFORMATION: 
    Participation in virtual public hearing. To request a virtual 
public hearing, contact the public hearing team at (888) 372-8699 or by 
email at [email protected]. If requested, the hearing will be 
held via virtual platform. The EPA will announce the date of the 
hearing and further details on the virtual public hearing at https://www.epa.gov/stationary-sources-air-pollution/polyether-polyols-production-national-emission-standards-hazardous. The hearing will 
convene at 11:00 a.m. Eastern Time (ET) and will conclude at 4:00 p.m. 
ET. The EPA may close a session 15 minutes after the last pre-
registered speaker has testified if there are not additional speakers.
    The EPA will begin pre-registering speakers for the hearing no 
later than 1 business day after a request has been received. To 
register to speak at the virtual hearing, please use the online 
registration form available at https://www.epa.gov/stationary-sources-air-pollution/polyether-polyols-production-national-emission-standards-hazardous or contact the public hearing team at (888) 372-8699 or by 
email at [email protected]. The last day to pre-register to 
speak at the hearing will be January 13, 2025. Prior to the hearing, 
the EPA will post a general agenda that will list pre-registered 
speakers at: https://www.epa.gov/stationary-sources-air-pollution/polyether-polyols-production-national-emission-standards-hazardous.
    The EPA will make every effort to follow the schedule as closely as 
possible on the day of the hearing; however, please plan for the 
hearings to run either ahead of schedule or behind schedule.
    Each commenter will have 4 minutes to provide oral testimony. The 
EPA encourages commenters to submit a copy of their oral testimony as 
written comments to the rulemaking docket.
    The EPA may ask clarifying questions during the oral presentations 
but will not respond to the presentations at that time. Written 
statements and supporting information submitted during the comment 
period will be considered with the same weight as oral testimony and 
supporting information presented at the public hearing.
    Please note that any updates made to any aspect of the hearing will 
be posted online at https://www.epa.gov/stationary-sources-air-pollution/polyether-polyols-production-national-emission-standards-hazardous. While the EPA expects the hearing to go forward as set forth 
above, please monitor these websites or contact the public hearing team 
at (888) 372-8699 or by email at [email protected] to determine 
if there are any updates. The EPA does not intend to publish a document 
in the Federal Register announcing updates.

[[Page 105987]]

    If you require the services of a translator or a special 
accommodation such as audio description, please pre-register for the 
hearing with the public hearing team and describe your needs by January 
7, 2025. The EPA may not be able to arrange accommodations without 
advance notice.
    Docket. The EPA has established a docket for this rulemaking under 
Docket ID No. EPA-HQ-OAR-2023-0282. All documents in the docket are 
listed in https://www.regulations.gov. Although listed, some 
information is not publicly available, e.g., Confidential Business 
Information (CBI) or other information whose disclosure is restricted 
by statute. Certain other material, such as copyrighted material, is 
not placed on the internet and will be publicly available only in hard 
copy. With the exception of such material, publicly available docket 
materials are available electronically in Regulations.gov.
    Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2023-0282. The EPA's policy is that all comments received will be 
included in the public docket without change and may be made available 
online at https://www.regulations.gov, including any personal 
information provided, unless the comment includes information claimed 
to be CBI or other information whose disclosure is restricted by 
statute. Do not submit electronically to https://www.regulations.gov 
any information that you consider to be CBI or other information whose 
disclosure is restricted by statue. This type of information should be 
submitted as discussed below.
    The EPA may publish any comment received to its public docket. 
Multimedia submissions (audio, video, etc.) must be accompanied by a 
written comment. The written comment is considered the official comment 
and should include discussion of all points you wish to make. The EPA 
will generally not consider comments or comment contents located 
outside of the primary submission (i.e., on the web, cloud, or other 
file sharing system). For additional submission methods, the full EPA 
public comment policy, information about CBI or multimedia submissions, 
and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
    The https://www.regulations.gov website allows you to submit your 
comment anonymously, which means the EPA will not know your identity or 
contact information unless you provide it in the body of your comment. 
If you send an email comment directly to the EPA without going through 
https://www.regulations.gov, your email address will be automatically 
captured and included as part of the comment that is placed in the 
public docket and made available on the internet. If you submit an 
electronic comment, the EPA recommends that you include your name and 
other contact information in the body of your comment and with any 
digital storage media you submit. If the EPA cannot read your comment 
due to technical difficulties and cannot contact you for clarification, 
the EPA may not be able to consider your comment. Electronic files 
should not include special characters or any form of encryption and be 
free of any defects or viruses. For additional information about the 
EPA's public docket, visit the EPA Docket Center homepage at https://www.epa.gov/dockets.
    Submitting CBI. Do not submit information containing CBI to the EPA 
through https://www.regulations.gov/. Clearly mark the part or all of 
the information that you claim to be CBI. For CBI information on any 
digital storage media that you mail to the EPA, note the docket ID, 
mark the outside of the digital storage media as CBI, and identify 
electronically within the digital storage media the specific 
information that is claimed as CBI. In addition to one complete version 
of the comments that includes information claimed as CBI, you must 
submit a copy of the comments that does not contain the information 
claimed as CBI directly to the public docket through the procedures 
outlined in Instructions above. If you submit any digital storage media 
that does not contain CBI, mark the outside of the digital storage 
media clearly that it does not contain CBI and note the docket ID. 
Information not marked as CBI will be included in the public docket and 
the EPA's electronic public docket without prior notice. Information 
marked as CBI will not be disclosed except in accordance with 
procedures set forth in 40 Code of Federal Regulations (CFR) part 2.
    Our preferred method to receive CBI is for it to be transmitted 
electronically using email attachments, File Transfer Protocol (FTP), 
or other online file sharing services (e.g., Dropbox, OneDrive, Google 
Drive). Electronic submissions must be transmitted directly to the 
Office of Air Quality Planning and Standards (OAQPS) CBI Office at the 
email address [email protected] and, as described above, should include 
clear CBI markings and note the docket ID. If assistance is needed with 
submitting large electronic files that exceed the file size limit for 
email attachments, and if you do not have your own file sharing 
service, please email [email protected] to request a file transfer link. 
If sending CBI information through the postal service, please send it 
to the following address: U.S. EPA, Attn: OAQPS Document Control 
Officer, Mail Drop: C404-02, 109 T.W. Alexander Drive, P.O. Box 12055, 
Research Triangle Park, North Carolina 27711, Attention Docket ID No. 
EPA-HQ-OAR-2023-0282. The mailed CBI material should be double wrapped 
and clearly marked. Any CBI markings should not show through the outer 
envelope.
    Preamble acronyms and abbreviations. Throughout this preamble the 
use of ``we,'' ``us,'' or ``our'' is intended to refer to the EPA. We 
use multiple acronyms and terms in this preamble. While this list may 
not be exhaustive, to ease the reading of this preamble and for 
reference purposes, the EPA defines the following terms and acronyms 
here:

ACC American Chemistry Council
ACS American Community Survey
ADAF age-dependent adjustment factor
AEGL acute exposure guideline levels
AERMOD American Meteorological Society/EPA Regulatory Model 
dispersion modeling system
AIHA American Industrial Hygiene Association
ANSI American National Standards Institute
APCD air pollution control device
ASME American Society of Mechanical Engineers
ATSDR Agency for Toxic Substances and Disease Registry
1-BP 1-bromopropane
BACT best available control technology
BTU British thermal units
CAA Clean Air Act
CBI Confidential Business Information
CDX Central Data Exchange
CEDRI Compliance and Emissions Data Reporting Interface
CFR Code of Federal Regulations
CMAS Chemical Manufacturing Area Sources
CMPU chemical manufacturing process unit
CO carbon monoxide
CO2 carbon dioxide
DNA deoxyribonucleic acid
EAV equivalent annualized value
ECHO Enforcement and Compliance History Online
ECO extended cookout
EFR external floating roof
EIA Economic Impact Analysis
EJ environmental justice
EMACT Ethylene Production MACT
EPA Environmental Protection Agency
ERPG emergency response planning guidelines
ERT Electronic Reporting Tool
EtO ethylene oxide
FID flame ionization detector
FTIR Fourier transform infrared spectrometry
GACT generally available control technologies

[[Page 105988]]

HAP hazardous air pollutant(s)
HCl hydrochloric acid
HEM Human Exposure Model
HF hydrofluoric acid
HON Hazardous Organic NESHAP
HQ hazard quotient
HRVOC highly reactive volatile organic compound
ICR information collection request
IFR internal floating roof
IRIS Integrated Risk Information System
ISA Integrated Science Assessment
km kilometer
kPa kilopascals
LAER lowest achievable emission rate
lb/hr pounds per hour
LDAR leak detection and repair
LEAN Louisiana Environmental Action Network
LEL lower explosive limit
MACT maximum achievable control technology
MIR maximum individual lifetime [cancer] risk
MON Miscellaneous Organic Chemical Manufacturing NESHAP
MTVP maximum true vapor pressure
NAAQS National Ambient Air Quality Standard
NAICS North American Industry Classification System
NEI National Emissions Inventory
NESHAP national emission standards for hazardous air pollutants
NHVcz net heating value in the combustion zone gas
NHVdil net heating value dilution parameter
NHVvg net heating value in the vent gas
NOX nitrogen oxides
NRDC Natural Resources Defense Council
NSPS new source performance standards
NTTAA National Technology Transfer and Advancement Act
OAQPS Office of Air Quality Planning and Standards
OAR Office of Air and Radiation
OLD Organic Liquids Distribution
OMB Office of Management and Budget
P&R I Group I Polymers and Resins NESHAP
PDF portable document format
PEPO polyether polyol
PMPU polyether polyol manufacturing process unit
POM polycyclic organic matter
ppmv parts per million by volume
ppmw parts per million by weight
PRA Paperwork Reduction Act
psia pounds per square inch absolute
psig pounds per square inch gauge
PRD pressure relief devices
PV present value
RACT reasonably available control technology
RDL representative detection limit
REL Reference Exposure Level
RFA Regulatory Flexibility Act
RfC reference concentration
RTR Risk and Technology Review
SAB Science Advisory Board
SCAQMD South Coast Air Quality Management District
scmm standard cubic meters per minute
scf standard cubic foot
SOCMI Synthetic Organic Chemical Manufacturing Industry
SO2 sulfur dioxide
SSM startup, shutdown, and malfunction
TCEQ Texas Commission on Environmental Quality
THF tetrahydrofuran
TOC total organic compound
TOSHI target organ-specific hazard index
tpy tons per year
TRE total resource effectiveness
TRIM Total Risk Integrated Methodology
UF uncertainty factor
UMRA Unfunded Mandates Reform Act
URE unit risk estimate
U.S. United States
U.S.C. United States Code
USGS U.S. Geological Survey
VCS voluntary consensus standards
VOC volatile organic compound(s)
[mu]g/m3 micrograms per cubic meter

    Organization of this document. The information in this preamble is 
organized as follows:

I. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document and other related 
information?
II. Background
    A. What is the statutory authority for this action?
    B. What is the source category and how do the current standards 
regulate its HAP emissions?
    C. What data collection activities were conducted to support 
this action?
    D. What other relevant background information and data are 
available?
    E. What outreach was conducted?
III. Analytical Procedures and Decision-Making
    A. How do we consider risk in our decision-making?
    B. How do we estimate post-MACT risk posed by the source 
category?
    C. How do we perform the technology review?
    D. How do we determine a MACT floor and consider beyond-the-
floor?
IV. Analytical Results and Proposed Decisions
    A. What are the results of the risk assessment and analyses?
    B. What are our proposed decisions regarding risk acceptability, 
ample margin of safety, and adverse environmental effect?
    C. What are the results and proposed decisions based on our 
technology review?
    D. What actions are we taking pursuant to CAA sections 112(d)(2) 
and (3) and 112(h)?
    E. What other actions are we proposing?
    F. What compliance dates are we proposing?
V. Summary of Cost, Environmental, and Economic Impacts
    A. What are the affected sources?
    B. What are the air quality impacts?
    C. What are the cost impacts?
    D. What are the economic impacts?
    E. What are the benefits?
    F. What analysis of environmental justice did we conduct?
    G. What analysis of children's environmental health did we 
conduct?
VI. Request for Comments
VII. Submitting Data Corrections
VIII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and 
Executive Order 14094: Modernizing Regulatory Review
    B. Paperwork Reduction Act (PRA)
    C. Regulatory Flexibility Act (RFA)
    D. Unfunded Mandates Reform Act (UMRA)
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act (NTTAA) and 
1 CFR Part 51
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations and Executive Order 14096: Revitalizing Our Nation's 
Commitment to Environmental Justice for All

I. General Information

A. Does this action apply to me?

    This action applies to the PEPO Production source category (and 
whose facilities, sources, and processes we often refer to as ``PEPO'' 
for purposes of the NESHAP). The PEPO NESHAP is codified at 40 CFR part 
63, subpart PPP. The North American Industry Classification System 
(NAICS) code for PEPO facilities is 325199, although this is not 
intended to be exhaustive but rather to provide a guide for readers 
regarding the entities that this proposed action is likely to affect. 
The proposed standards, once promulgated, will be directly applicable 
to the affected sources. Federal, State, local, and Tribal government 
entities would not be affected by this proposed action. As defined in 
the Initial List of Categories of Sources Under Section 112(c)(1) of 
the Clean Air Act Amendments of 1990 (see 57 FR 31576, July 16, 1992) 
and Documentation for Developing the Initial Source Category List, 
Final Report (see EPA-450/3-91-030, July 1992), the PEPO Production 
source category is any facility which ``manufactures these polymers by 
starting with cyclic ethers (e.g., oxides, epoxides) and initiating 
polymerization by adding ethylene oxide, butylene oxide, propylene 
oxide or other chemicals which would result in the potential emission 
of HAPs. The reaction is base-catalyzed, with potassium hydroxide being 
the most commonly used catalyst. The physical

[[Page 105989]]

properties of the polyols are influenced primarily by the functionality 
of the initiator molecules and by the type and quantity of alkylene 
oxide and hydroxyl groups present in the polyol.'' In the development 
of NESHAP for this source category, the EPA considered emission sources 
associated with equipment leaks (including leaks from heat exchange 
systems), process vents, storage vessels, and wastewater collection and 
treatment systems.

B. Where can I get a copy of this document and other related 
information?

    In addition to being available in the docket, an electronic copy of 
this action is available on the internet. In accordance with 5 U.S.C. 
553(b)(4), a brief summary of this rulemaking may be found at https://www.regulations.gov, Docket ID No. EPA-HQ-OAR-2023-0282. Following 
signature by the EPA Administrator, the EPA will post a copy of this 
proposed action at https://www.epa.gov/stationary-sources-air-pollution/polyether-polyols-production-national-emission-standards-hazardous. Following publication in the Federal Register, the EPA will 
post the Federal Register version of the proposal and key technical 
documents at this same website.
    A memorandum showing the edits that would be necessary to 
incorporate the changes to the PEPO NESHAP (40 CFR part 63, subpart 
PPP) proposed in this action is available in the docket (Docket ID No. 
EPA-HQ-OAR-2023-0282). Following signature by the EPA Administrator, 
the EPA also will post a copy of this document to https://www.epa.gov/stationary-sources-air-pollution/polyether-polyols-production-national-emission-standards-hazardous.

II. Background

A. What is the statutory authority for this action?

1. NESHAP
    The statutory authority for this action is provided by sections 112 
and 301 of the CAA, as amended (42 U.S.C. 7401 et seq.). Section 112 of 
the CAA establishes a two-stage regulatory process to develop standards 
for emissions of HAP from stationary sources. Generally, the first 
stage involves establishing technology-based standards and the second 
stage involves evaluating those standards that are based on maximum 
achievable control technology (MACT) to determine whether additional 
standards are needed to address any remaining risk associated with HAP 
emissions. This second stage is commonly referred to as the ``residual 
risk review.'' In addition to the residual risk review, the CAA also 
requires the EPA to review standards set under CAA section 112 every 8 
years and revise the standards as necessary taking into account any 
``developments in practices, processes, or control technologies.'' This 
review is commonly referred to as the ``technology review.'' When the 
two reviews are combined into a single rulemaking, it is commonly 
referred to as the ``risk and technology review.'' The discussion that 
follows identifies the most relevant statutory sections and briefly 
explains the contours of the methodology used to implement these 
statutory requirements. A more comprehensive discussion appears in the 
document titled CAA Section 112 Risk and Technology Reviews: Statutory 
Authority and Methodology, in the docket for this rulemaking.
    In the first stage of the CAA section 112 standard setting process, 
the EPA promulgates technology-based standards under CAA section 112(d) 
for categories of sources listed under section 112(c) and identified as 
emitting one or more of the HAP listed in CAA section 112(b). Sources 
of HAP emissions are either major sources or area sources, and CAA 
section 112 establishes different requirements for major source 
standards and area source standards. ``Major sources'' are those that 
emit or have the potential to emit 10 tpy or more of a single HAP or 25 
tpy or more of any combination of HAP. All other sources are ``area 
sources.'' For major sources, CAA section 112(d)(2) provides that the 
technology-based NESHAP must reflect the maximum degree of emission 
reductions of HAP achievable (after considering cost, energy 
requirements, and non-air quality health and environmental impacts). 
These standards are commonly referred to as MACT standards. CAA section 
112(d)(3) also establishes a minimum control level for MACT standards, 
known as the MACT ``floor,'' that the EPA must establish without 
consideration of costs. Under CAA section 112(d)(2), the EPA must also 
consider control options that are more stringent than the floor, taking 
into consideration costs, non-air quality health and environmental 
impacts, and energy requirements. Standards more stringent than the 
floor are commonly referred to as ``beyond-the-floor'' or ``BTF'' 
standards. In certain instances, as provided in CAA section 112(h), the 
EPA may set work practice standards in lieu of numerical emission 
standards. For area sources, CAA section 112(d)(5) gives the EPA 
discretion to set standards based on generally available control 
technologies or management practices (GACT standards) in lieu of MACT 
standards.
    The second stage in standard-setting focuses on identifying and 
addressing any remaining (i.e., ``residual'') risk pursuant to CAA 
section 112(f). For source categories subject to MACT standards, 
section 112(f)(2) of the CAA requires the EPA to determine whether 
promulgation of additional standards is needed to provide an ample 
margin of safety to protect public health or to prevent an adverse 
environmental effect. Section 112(d)(5) of the CAA provides that this 
residual risk review is not required for categories of area sources 
subject to GACT standards. Section 112(f)(2)(B) of the CAA further 
expressly preserves the EPA's use of the two-step approach for 
developing standards to address any residual risk and the Agency's 
interpretation of ``ample margin of safety'' developed in the National 
Emissions Standards for Hazardous Air Pollutants: Benzene Emissions 
from Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, Benzene 
Storage Vessels, Benzene Equipment Leaks, and Coke By-Product Recovery 
Plants (Benzene NESHAP) (54 FR 38044, September 14, 1989). The EPA 
notified Congress in the Residual Risk Report that the Agency intended 
to use the Benzene NESHAP approach in making CAA section 112(f) 
residual risk determinations (EPA-453/R-99-001, p. ES-11). The EPA 
subsequently adopted this approach in its residual risk determinations 
and the United States Court of Appeals for the District of Columbia 
Circuit affirmed that CAA section 112(f)(2) incorporates the approach 
established in the Benzene NESHAP. See Natural Resources Defense 
Council (NRDC) v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 2008).
    The approach incorporated into the CAA and used by the EPA to 
evaluate residual risk and to develop standards under CAA section 
112(f)(2) is a two-step approach. In the first step, the EPA determines 
whether risks are acceptable. This determination ``considers all health 
information, including risk estimation uncertainty, and includes a 
presumptive limit on maximum individual lifetime [cancer] risk (MIR) 
\1\ of approximately 1 in 10 thousand.'' (54 FR 38045). If risks are 
unacceptable, the EPA must determine the emissions standards necessary 
to reduce risk to an acceptable level without considering costs. In the 
second step of the approach, the EPA

[[Page 105990]]

considers whether the emissions standards provide an ample margin of 
safety to protect public health ``in consideration of all health 
information, including the number of persons at risk levels higher than 
approximately 1 in 1 million, as well as other relevant factors, 
including costs and economic impacts, technological feasibility, and 
other factors relevant to each particular decision.'' Id. The EPA must 
promulgate emission standards necessary to provide an ample margin of 
safety to protect public health or determine that the standards being 
reviewed provide an ample margin of safety without any revisions. After 
conducting the ample margin of safety analysis, we consider whether a 
more stringent standard is necessary to prevent, taking into 
consideration costs, energy, safety, and other relevant factors, an 
adverse environmental effect.
---------------------------------------------------------------------------

    \1\ Although defined as ``maximum individual risk,'' MIR refers 
only to cancer risk. MIR, one metric for assessing cancer risk, is 
the estimated risk if an individual were exposed to the maximum 
level of a pollutant for a lifetime.
---------------------------------------------------------------------------

    CAA section 112(d)(6) separately requires the EPA to review 
standards promulgated under CAA section 112 and revise them ``as 
necessary (taking into account developments in practices, processes, 
and control technologies)'' no less often than every 8 years. In 
conducting this review, which we call the ``technology review,'' the 
EPA is not required to recalculate the MACT floors that were 
established during earlier rulemakings. NRDC v. EPA, 529 F.3d at 1084 
(D.C. Cir. 2008); Association of Battery Recyclers, Inc. v. EPA, 716 
F.3d 667 (D.C. Cir. 2013). The EPA may consider cost in deciding 
whether to revise the standards pursuant to CAA section 112(d)(6). The 
EPA is required to address regulatory gaps, such as missing MACT 
standards for listed air toxics known to be emitted from the source 
category. Louisiana Environmental Action Network (LEAN) v. EPA, 955 
F.3d 1088 (D.C. Cir. 2020).
    The EPA conducted a residual risk and technology review (RTR) for 
the PEPO NESHAP in 2014, concluding that there was no need to revise 
the PEPO NESHAP under the provisions of either CAA sections 112(f) or 
(d)(6). However, the EPA did address emissions during periods of 
startup, shutdown, and malfunction (SSM), including from pressure 
relief devices (PRDs) in organic HAP service that release to the 
atmosphere, and also required electronic reporting of performance test 
results (see 79 FR 17340, March 27, 2014). As part of the 2014 residual 
risk review, the EPA conducted a risk assessment, and based on the 
results of the risk assessment, determined that the then current level 
of control called for by the existing MACT standards both reduced HAP 
emissions to levels that presented an acceptable level of risk and 
provided an ample margin of safety to protect public health.
    This action constitutes another CAA section 112(d)(6) technology 
review for the PEPO NESHAP. This action also constitutes an updated CAA 
section 112(f) risk review based on new information for the PEPO 
NESHAP. As noted above, CAA section 112(f)(2)(A) requires the EPA to 
promulgate standards that ``provide an ample margin of safety to 
protect public health'' and prevent ``an adverse environmental 
effect.'' While CAA section 112(f) does not require the EPA to 
periodically revisit a residual risk review, neither does it preclude 
the EPA from exercising its inherent authority to revisit a previous 
regulatory decision where new scientific, technical, or other relevant 
information indicates such action is warranted. Moreover, the Act does 
include a gap-filling provision that reinforces the authority for the 
EPA to do so. CAA section 301(a)(1) provides authority to the 
Administrator ``to prescribe such regulations as are necessary to carry 
out his functions'' under the CAA. Such authority extends to the EPA's 
discretion to revisit its section 112(f) residual risk review where the 
Agency deems warranted. See NRDC v. EPA, 22 F.3d 1125, 1148 (D.C. Cir. 
1994) (``[Section 301] is sufficiently broad to allow the promulgation 
of rules that are necessary and reasonable to effect the purposes of 
the Act.''). We note that although there is no statutory CAA obligation 
under CAA section 112(f) for the EPA to conduct a second residual risk 
review of the PEPO NESHAP, the EPA retains discretion to revisit its 
residual risk reviews where the Agency deems that it is warranted. See, 
e.g., Fed. Commc'ns Comm'n v. Fox Television Stations, Inc., 556 U.S. 
502, 515 (2009); Motor Vehicle Mfrs. Ass'n v. State Farm Mut. Auto. 
Ins. Co., 463 U.S. 29, 42 (1983); Ethylene Oxide Emissions Standards 
for Sterilization Facilities; Final Decision, 71 FR 17712, 17715 col. 1 
(April 7, 2006) (in the 2006 residual risk review of the EtO emissions 
standards for sterilization facilities, the EPA asserted its 
``authority to revisit (and revise, if necessary) any rulemaking if 
there is sufficient evidence that changes within the affected industry 
or significant improvements to science suggests the public is exposed 
to significant increases in risk as compared to the risk assessment 
prepared for the rulemaking (e.g., CAA section 301).''). Here, the 
specific changes to health information related to a certain pollutant 
emitted by the PEPO Production source category led us to determine that 
it is appropriate, in this case, to conduct this second residual risk 
review under CAA section 112(f). In particular, the EPA is concerned 
about the cancer risks posed from the PEPO Production source category 
based on the EPA's 2016 updated Integrated Risk Information System 
(IRIS) inhalation unit risk estimate (URE) for EtO, which shows EtO to 
be significantly more toxic than previously known.\2\ The EPA's 2014 
RTR could not have had the benefit of this updated URE at the time it 
was conducted, but if it had the RTR would have necessarily resulted in 
different conclusions about risk acceptability and the PEPO NESHAP's 
provision of an ample margin of safety to protect public health. To 
ensure our standards provide an ample margin of safety to protect 
public health following the new IRIS inhalation URE for EtO, we are 
exercising our discretion and conducting a risk assessment in this 
action for PEPO Production sources. In sum, even though we do not have 
a mandatory duty to conduct repeated residual risk reviews under CAA 
sections 112(f)(2) and 301(a)(1), we have the authority to revisit any 
rulemaking if there is sufficient evidence of changes within the 
affected industry or significant new scientific information suggesting 
the public is exposed to higher risks than previously understood. Our 
conducting a discretionary second residual risk review for the PEPO 
Production source category to account for the new IRIS inhalation URE 
for EtO is consistent with recent similar actions regarding other 
source categories. See 89 FR 24090, April 5, 2024, and 89 FR 42932, May 
16, 2024.
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    \2\ U.S. EPA. Evaluation of the Inhalation Carcinogenicity of 
Ethylene Oxide (CASRN 75-21-8) In Support of Summary Information on 
the Integrated Risk Information System (IRIS). December 2016. EPA/
635/R-16/350Fa. Available at: https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/1025tr.pdf. See also, 87 FR 
77985 (Dec. 21, 2022), Reconsideration of the 2020 National Emission 
Standards for Hazardous Air Pollutants: Miscellaneous Organic 
Chemical Manufacturing Residual Risk and Technology Review, Final 
action; reconsideration of the final rule.
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2. Petition for Reconsideration
    In addition to the proposed action under sections 112 and 301 of 
the CAA described above, this action includes proposed amendments to 
the PEPO NESHAP based on the EPA's reconsideration of certain aspects 
of the NESHAP that were raised in an administrative petition submitted 
pursuant to section 307(d)(7)(B) of the CAA. In May 2014, the EPA 
received one petition for reconsideration of the PEPO NESHAP (40 CFR 
part 63, subpart

[[Page 105991]]

PPP), Pesticide Active Ingredient Production NESHAP (40 CFR part 63, 
subpart MMM), and Group IV Polymers and Resins NESHAP (40 CFR part 63, 
subpart JJJ) pursuant to CAA section 307(d)(7)(B) from the Louisiana 
Environmental Action Network, Ohio Valley Environmental Coalition, and 
Sierra Club. A copy of the petition and subsequent EPA correspondence 
granting reconsideration is provided in the docket for this rulemaking 
(see Docket No. EPA-HQ-OAR-2023-0282).
    For the PEPO NESHAP, the petitioners requested that the EPA: (1) 
remove the affirmative defense provisions from the rules in light of 
the court opinion in Natural Resources Defence Council v. EPA (D.C. 
Cir. April 18, 2014); (2) provide adequate opportunity to comment on 
the requirements associated with emissions from PRDs (including 
associated compliance dates, the EPA's decision to not specifically 
require electronic indicators and alarms to monitor PRD releases to the 
atmosphere, and the standard's applicability to PRDs in organic HAP 
service versus PRDs in total HAP service); (3) redo the risk assessment 
using updated emission factors; (4) set additional monitoring 
requirements for flares to reduce flaring emissions; (5) set fenceline 
monitoring requirements; (6) reconsider its decision not to set 
standards that account for developments in leak detection and repair 
(LDAR); and (7) use existing regulatory authority to strengthen 
chemical facility safety and prevent accidents in accordance with the 
U.S. Chemical Safety and Hazard Investigation Board and Executive Order 
13650. On August 26, 2014, the EPA sent a letter to the petitioners 
informing them that the EPA was granting their request for 
reconsideration at least on issues (1) and (2) above. A copy of the 
August 26, 2014, letter is provided in the docket for this rulemaking 
(see Docket No. EPA-HQ-OAR-2023-0282). In the letter, the EPA also 
indicated that it would be initiating a notice and comment rulemaking 
on the issues for which we granted reconsideration; therefore, one 
purpose of this action is to formally respond to the issues raised in 
the petition with respect to the PEPO NESHAP.\3\
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    \3\ Although the issues identified in this paragraph (in 
addition to one other issue related to alternative compliance 
demonstration methods for periods of startup and shutdown) were also 
raised for 40 CFR part 63, subparts JJJ and MMM; this action does 
not respond to the reconsideration of these NESHAP, as the EPA is 
not reviewing these subparts in this action.
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    In a separate rulemaking (see 89 FR 52425, June 24, 2024), the EPA 
is addressing issue (1), the affirmative defense against civil 
penalties for violations occurring during malfunctions. That separate 
rulemaking removes affirmative defense provisions from both NSPS and 
NESHAP rules, including the PEPO NESHAP. Therefore, this proposed 
action does not address removal of the affirmative defense provisions.
    This action presents the EPA's proposed revisions to the PEPO 
NESHAP based on the EPA's reconsideration of issue (2) in the petition 
(see section IV.E.1 of this preamble for details about these proposed 
amendments). Coincidentally, we also believe this action addresses 
issues (3), (4), (5), and (6) in our normal course of review of the 
PEPO NESHAP in accordance with sections 112 and 301 of the CAA. See 
sections IV.A and IV.B of this preamble for our proposed decisions 
relvant to issue (3), section IV.D.1 of this preamble for our proposed 
decisions relevant to issue (4), section IV.C.6 of this preamble for 
our proposed decisions relevant to issue (5), and sections IV.B.2.b and 
IV.C.5 of this preamble for our proposed decisions relevant to issue 
(6). With regard to issue (7), the EPA's authority to address 
catastrophic releases under the NESHAP program was viewed as limited 
under the pre-1990 CAA. Congress added CAA section 112(r) to address 
this gap. In light of the extensive history and efforts of the agency 
on inherently safer technology specifically and catastrophic accidents 
generally under the section 112(r) program, and in light of the 
statutory structure of section 112, we view the request to enact such 
provisions in this rulemaking to be outside the scope of section 
112(f)(2) and section 112(d)(6). We note that the EPA's regulations on 
catastrophic releases appear in 40 CFR part 68. Prompted by Executive 
Order 13650, ``Improving Chemical Facility Safety and Security,'' the 
Risk Management Program regulations were amended on January 13, 2017, 
to include new provisions on safer technology and alternatives analysis 
and other prevention program elements; most recently, the regulations 
were amended on March 11, 2024, to further enhance the accident 
prevention and emergency preparedness requirements (89 FR 17622).

B. What is the source category and how do the current standards 
regulate its HAP emissions?

    The source category that is the subject of this proposal is the 
PEPO Production source category subject to the PEPO NESHAP. The EPA 
promulgated the PEPO NESHAP on June 1, 1999 (64 FR 29420), and codified 
the NESHAP at 40 CFR part 63, subpart PPP. As promulgated in 1999, and 
further amended on July 1, 2004 (69 FR 39862) and March 27, 2014 (59 FR 
17340), the PEPO NESHAP regulates HAP emissions from polyether polyol 
manufacturing process units (PMPUs) that produce PEPO as its primary 
product.4 5 A PMPU consists of purification systems, 
reactors and their associated product separators and recovery devices, 
distillation units and their associated distillate receivers and 
recovery devices, other associated unit operations, storage vessels, 
surge control vessels, bottoms receivers, product transfer racks, 
connected ducts and piping, combustion, recovery, or recapture devices 
or systems. A PMPU also includes pumps, compressors, agitators, PRDs, 
sampling connection systems, open-ended valves or lines, valves, 
connectors, and instrumentation systems.
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    \4\ PEPO are compounds formed through the polymerization of EtO 
or propylene oxide or other cyclic ethers with compounds having one 
or more reactive hydrogens (i.e., a hydrogen atom bonded to 
nitrogen, oxygen, phosphorus, sulfur, etc.) to form polyethers 
(i.e., compounds with two or more ether bonds). This definition of 
PEPO excludes cellulose ethers (such as methyl cellulose, 
carboxymethyl cellulose, hydroxyethyl cellulose, hydroxy ethyl 
cellulose, and hydroxypropyl methyl cellulose) and materials 
regulated under the HON, such as glycols and glycol ethers.
    \5\ A PMPU also includes flexible operation process units when 
an owner or operator cannot determine that a PEPO is not the primary 
product, and a PEPO is produced or anticipated to be produced during 
time spans described in 40 CFR 63.1420(e)(2).
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    PEPO are used to make a variety of other products including 
lubricants, adhesives, sealants, cosmetics, pharmaceuticals, soaps, and 
a feedstock for polyurethanes production. Urethane grade PEPO (i.e., 
those that are free of water) are used as raw material in the 
production of polyurethanes, including slabstock and molded flexible 
foams, rigid foams and other polyurethanes, including microcellular 
products, surface coatings, elastomers, fibers, adhesives, and 
sealants.
    PEPO can be produced by either polymerization of epoxides (i.e., a 
three-membered cyclic ether, such as EtO or propylene oxide) or 
tetrahydrofuran (THF). The former process is usually conducted as a 
batch process, while production of polyols using THF is generally a 
continuous process. EtO and propylene oxide are both HAP, but THF is 
not. For the MACT regulation, the EPA created two subcategories of PEPO 
based on the use of either epoxides or THF in polymerization.

[[Page 105992]]

    The HAP emission sources at PEPO facilities include process vents, 
storage vessels, equipment leaks, and wastewater. Additionally, some 
facilities have cooling towers or other heat exchangers which could 
become HAP emission sources if process fluids leak into the heat 
exchange water. In the production of PEPO, HAP are used primarily as 
reactants or extraction solvents. HAP emitted from PEPO facilities 
include EtO, propylene oxide, toluene, methanol, and glycol ethers. The 
MACT standards for PEPO production include emission limits for process 
vents; a combination of equipment standards and work practices for 
storage vessels, wastewater, and equipment leaks; and work practice 
standards for cooling towers.
    As of March 1, 2024, the EPA identified 25 PEPO facilities in 
operation that are subject to the PEPO NESHAP. The list of facilities 
located in the United States that are part of the PEPO Production 
source category with processes subject to the PEPO NESHAP is presented 
in the document titled List of Facilities Subject to the PEPO NESHAP, 
which is available in the docket for this action (Docket ID No. EPA-HQ-
OAR-2023-0282).

C. What data collection activities were conducted to support this 
action?

    The EPA used several data sources to determine the facilities that 
are subject to the PEPO NESHAP discussed in section II.B of this 
preamble. We identified facilities in the 2017 National Emissions 
Inventory (NEI) and the Toxics Release Inventory system having a 
primary facility NAICS code beginning with 325, Chemical Manufacturing. 
We also used information from the 2014 PEPO NESHAP RTR, other facility 
lists from the EPA's recent chemical sector rulemakings (e.g., HON), 
and the Office of Enforcement and Compliance Assurance's Enforcement 
and Compliance History Online (ECHO) tool (https://echo.epa.gov). To 
inform our reviews of the Agency's emission standards, we reviewed the 
EPA's Reasonably Available Control Technology (RACT)/Best Available 
Control Technology (BACT)/Lowest Achievable Emission Rate (LAER) 
Clearinghouse and regulatory development efforts for similar sources 
published after the PEPO NESHAP was developed. The EPA also reviewed 
air emissions permits issued by State regulatory agencies to determine 
facilities subject to the PEPO NESHAP. Additionally, we met with 
industry representatives from the American Chemistry Council (ACC) to 
collect data and discuss industry practices.
    In January 2022, the EPA issued requests, pursuant to CAA section 
114, to collect information from synthetic organic chemical 
manufacturing industry (SOCMI) facilities subject to the hazardous 
organic NESHAP (HON) at 40 CFR part 63, subparts F, G, and H (nine 
facilities being also subject to the PEPO NESHAP) owned and operated by 
eight entities (i.e., corporations). Many of the entities chosen for 
the CAA section 114 request own or operate facilities that produce, 
use, and emit EtO, which is a pollutant with considerable concern for 
cancer risk for the PEPO Production source category. This CAA section 
114 request focused on gathering comprehensive information about 
process equipment, control technologies, point and fugitive emissions, 
and other aspects of facility operations. Additionally, the EPA 
requested stack testing for certain emission sources (e.g., pollutants 
for vent streams associated with each EtO production line). Also, the 
EPA required, as part of the January 2022 CAA section 114 request, that 
facilities conduct fugitive emission testing (i.e., fenceline 
monitoring) for any of six specific HAP they emit: benzene; 1,3-
butadiene; chloroprene; EtO; ethylene dichloride; and vinyl chloride. 
Companies submitted responses (and follow-up responses) and testing 
results to the EPA during the summer and fall of 2022. The EPA used the 
collected information to fill data gaps, establish the baseline 
emissions and control levels for purposes of the regulatory reviews, 
identify the most effective control measures, and estimate the public 
health and environmental and cost impacts associated with the 
regulatory options considered and reflected in this proposed action. 
The information not claimed as CBI by respondents is available in the 
document titled Data Received from Information Collection Request for 
Chemical Manufacturers, in the docket for this action, Docket ID No. 
EPA-HQ-OAR-2023-0282.

D. What other relevant background information and data are available?

    As mentioned above, this action includes proposed amendments to the 
current flare requirements in the PEPO NESHAP. In proposing these 
amendments, we relied on certain technical reports and memoranda that 
the EPA developed for flares used as air pollution control devices 
(APCDs) in the Petroleum Refinery Sector RTR and new source performance 
standards (NSPS) rulemaking (80 FR 75178, December 1, 2015). The 
Petroleum Refinery Sector rulemaking docket is at Docket ID No. EPA-HQ-
OAR-2010-0682. For completeness of the rulemaking record for this 
action and for ease of reference in finding these items in the publicly 
available Petroleum Refinery Sector rulemaking docket, we are including 
the most relevant flare-related technical support documents in the 
docket for this proposed action (Docket ID No. EPA-HQ-OAR-2023-0282) 
and including a list of all documents used to inform the 2015 flare 
provisions in the Petroleum Refinery Sector RTR and NSPS rulemaking in 
the document titled Control Option Impacts for Flares in the PEPO 
Production Source Category that Control Emissions from Processes 
Subject to the PEPO NESHAP, which is available in the docket for this 
rulemaking.
    We are also relying on data gathered to support the rulemakings for 
the EMACT standards, HON, and MON, as well as memoranda documenting the 
technology reviews for those processes. Many of the emission sources 
for ethylene production facilities, HON facilities, and MON facilities 
are similar to PEPO facilities, so the EPA analyzed several control 
options for the PEPO NESHAP that the Agency also analyzed for the 
rulemakings for the EMACT standards, HON, and MON. The memoranda and 
background technical information can be found in the Ethylene 
Production RTR rulemaking docket (Docket ID No. EPA-HQ-OAR-2017-0357), 
the HON rulemaking docket (Docket ID No. EPA-HQ-OAR-2022-0730), and the 
MON RTR rulemaking docket (Docket ID No. EPA-HQ-OAR-2018-0746). 
Additional information related to the promulgation and subsequent 
amendments of the PEPO NESHAP is available in Docket ID Nos. A-96-38, 
EPA-HQ-OAR-2004-0467, and EPA-HQ-OAR-2011-0435.

E. What outreach was conducted?

    We conducted pre-proposal outreach by sharing an overview of the 
industry and planned rulemaking to the EPA's national environmental 
justice (EJ) engagement call on August 20, 2024, and the EPA's monthly 
call with the National Tribal Air Association on August 31, 2023, and 
August 29, 2024. We also met with members of the ACC on August 13, 
2024. The EPA also previously engaged in outreach activities with 
communities we expected to be impacted by chemical plants emitting EtO 
in 2021.\6\
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    \6\ https://www.epa.gov/hazardous-air-pollutants-ethylene-oxide/inspector-general-follow-ethylene-oxide-0.

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[[Page 105993]]

III. Analytical Procedures and Decision-Making

A. How do we consider risk in our decision-making?

    As discussed in section II.A of this preamble and in the Benzene 
NESHAP, in evaluating and developing standards under CAA section 
112(f)(2), we apply a two-step approach to determine whether or not 
risks are acceptable and to determine if the standards provide an ample 
margin of safety to protect public health. As explained in the Benzene 
NESHAP, ``the first step judgment on acceptability cannot be reduced to 
any single factor'' and, thus, ``[t]he Administrator believes that the 
acceptability of risk under section 112 is best judged on the basis of 
a broad set of health risk measures and information.'' (54 FR 38046). 
Similarly, with regard to the ample margin of safety determination, 
``the Agency again considers all of the health risk and other health 
information considered in the first step. Beyond that information, 
additional factors relating to the appropriate level of control will 
also be considered, including cost and economic impacts of controls, 
technological feasibility, uncertainties, and any other relevant 
factors.'' Id.
    The Benzene NESHAP approach provides flexibility regarding factors 
the EPA may consider in making determinations and how the EPA may weigh 
those factors for each source category. The EPA conducts a risk 
assessment that provides estimates of the MIR posed by emissions of HAP 
that are carcinogens from each source in the source category, the 
hazard index (HI) for chronic exposures to HAP with the potential to 
cause noncancer health effects, and the hazard quotient (HQ) for acute 
exposures to HAP with the potential to cause noncancer health 
effects.\7\ The assessment also provides estimates of the distribution 
of cancer risk within the exposed populations, cancer incidence, and an 
evaluation of the potential for an adverse environmental effect. The 
scope of the EPA's risk analysis is consistent with the explanation in 
the EPA's response to comments on our policy under the 1989 Benzene 
NESHAP:
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    \7\ The MIR is defined as the cancer risk associated with a 
lifetime of exposure at the highest concentration of HAP where 
people are likely to live. The HQ is the ratio of the potential HAP 
exposure concentration to the noncancer dose-response value; the HI 
is the sum of HQs for HAP that affect the same target organ or organ 
system.

    The policy chosen by the Administrator permits consideration of 
multiple measures of health risk. Not only can the MIR figure be 
considered, but also incidence, the presence of non-cancer health 
effects, and the uncertainties of the risk estimates. In this way, 
the effect on the most exposed individuals can be reviewed as well 
as the impact on the general public. These factors can then be 
weighed in each individual case. This approach complies with the 
Vinyl Chloride mandate that the Administrator ascertain an 
acceptable level of risk to the public by employing his expertise to 
assess available data. It also complies with the Congressional 
intent behind the CAA, which did not exclude the use of any 
particular measure of public health risk from the EPA's 
consideration with respect to CAA section 112 regulations, and 
thereby implicitly permits consideration of any and all measures of 
health risk which the Administrator, in his judgment, believes are 
---------------------------------------------------------------------------
appropriate to determining what will ``protect the public health''.

    (54 FR 38057). Thus, the level of the MIR is only one factor to be 
weighed in determining acceptability of risk. The Benzene NESHAP 
explained that ``an MIR of approximately one in 10 thousand should 
ordinarily be the upper end of the range of acceptability. As risks 
increase above this benchmark, they become presumptively less 
acceptable under CAA section 112, and would be weighed with the other 
health risk measures and information in making an overall judgment on 
acceptability. Or, the Agency may find, in a particular case, that a 
risk that includes an MIR less than the presumptively acceptable level 
is unacceptable in the light of other health risk factors.'' Id. at 
38045. In other words, risks that include an MIR above 100-in-1 million 
(1-in-10 thousand) may be determined to be acceptable, and risks with 
an MIR below that level may be determined to be unacceptable, depending 
on all of the available health information. Similarly, with regard to 
the ample margin of safety analysis, the EPA stated in the 1989 Benzene 
NESHAP that: ``EPA believes the relative weight of the many factors 
that can be considered in selecting an ample margin of safety can only 
be determined for each specific source category. This occurs mainly 
because technological and economic factors (along with the health-
related factors) vary from source category to source category.'' Id. at 
38061. We also consider the uncertainties associated with the various 
risk analyses, as discussed earlier in this preamble, in our 
determinations of acceptability and ample margin of safety.
    The EPA notes that it has not considered certain health information 
to date in making residual risk determinations. At this time, we do not 
attempt to quantify the HAP risk that may be associated with emissions 
from other facilities that do not include the source category under 
review, mobile source emissions, natural source emissions, persistent 
environmental pollution, or atmospheric transformation in the vicinity 
of the sources in the category.
    The EPA understands the potential importance of considering an 
individual's total exposure to HAP in addition to considering exposure 
to HAP emissions from the source category and facility. We recognize 
that such consideration may be particularly important when assessing 
noncancer risk, where pollutant-specific exposure health reference 
levels (e.g., reference concentrations (RfCs)) are based on the 
assumption that thresholds exist for adverse health effects. For 
example, the EPA recognizes that, although exposures attributable to 
emissions from a source category or facility alone may not indicate the 
potential for increased risk of adverse noncancer health effects in a 
population, the exposures resulting from emissions from the facility in 
combination with emissions from all of the other sources (e.g., other 
facilities) to which an individual is exposed may be sufficient to 
result in an increased risk of adverse noncancer health effects. In May 
2010, the Science Advisory Board (SAB) advised the EPA ``that RTR 
assessments will be most useful to decision makers and communities if 
results are presented in the broader context of aggregate and 
cumulative risks, including background concentrations and contributions 
from other sources in the area.'' \8\
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    \8\ Recommendations of the SAB Risk and Technology Review 
Methods Panel are provided in their report, which is available at: 
https://www.epa.gov/sites/default/files/2021-02/documents/epa-sab-10-007-unsigned.pdf.
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    In response to the SAB recommendations, the EPA incorporates 
cumulative risk analyses into its RTR risk assessments. The Agency: (1) 
conducts facility-wide assessments, which include source category 
emission points, as well as other emission points within the 
facilities; (2) combines exposures from multiple sources in the same 
category that could affect the same individuals; and (3) for some 
persistent and bioaccumulative pollutants, analyzes the ingestion route 
of exposure. In addition, the RTR risk assessments consider aggregate 
cancer risk from all carcinogens and aggregated noncancer HQs for all 
noncarcinogens affecting the same target organ or target organ system.
    Although we are interested in placing source category and facility-
wide HAP risk in the context of total HAP risk from all sources 
combined in the

[[Page 105994]]

vicinity of each source, we are concerned about the uncertainties of 
doing so. Estimates of total HAP risk from emission sources other than 
those that we have studied in depth during this RTR review would have 
significantly greater associated uncertainties than the source category 
or facility-wide estimates. While we evaluated the risk from HAP 
emitted by all stationary point sources near facilities within this 
source category in the community-based risk assessment, that assessment 
is intended to provide additional context to the public and was not 
used for decision-making in this proposed rule.

B. How do we estimate post-MACT risk posed by the source category?

    In this section, we provide a complete description of the types of 
analyses that we generally perform during the risk assessment process. 
In some cases, we do not perform a specific analysis because it is not 
relevant. For example, in the absence of emissions of HAP known to be 
persistent and bioaccumulative in the environment (PB-HAP), we would 
not perform a multipathway exposure assessment. Where we do not perform 
an analysis, we state that we do not and provide the reason. While we 
present all of our risk assessment methods, we only present risk 
assessment results for the analyses actually conducted (see section 
IV.A of this preamble).
    The EPA conducts a risk assessment that provides estimates of the 
MIR for cancer posed by the HAP emissions from each source in the 
source category, the HI for chronic exposures to HAP with the potential 
to cause noncancer health effects, and the HQ for acute exposures to 
HAP with the potential to cause noncancer health effects. The 
assessment also provides estimates of the distribution of cancer risk 
within the exposed populations, cancer incidence, and an evaluation of 
the potential for an adverse environmental effect. The nine sections 
that follow this paragraph describe how we estimated emissions and 
conducted the risk assessment. The docket for this rulemaking contains 
the following document which provides more information on the risk 
assessment inputs and models: Residual Risk Assessment for the 
Polyether Polyols (PEPO) Production Source Category in Support of the 
2024 Risk and Technology Review Proposed Rule. The methods used to 
assess risk (as described in the nine primary steps below) are 
consistent with those described by the EPA in the document reviewed by 
a panel of the EPA's SAB in 2009; \9\ and described in the SAB review 
report issued in 2010. They are also consistent with the key 
recommendations contained in that report.
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    \9\ U.S. EPA. Risk and Technology Review (RTR) Risk Assessment 
Methodologies: For Review by the EPA's Science Advisory Board with 
Case Studies--MACT I Petroleum Refining Sources and Portland Cement 
Manufacturing, June 2009. EPA-452/R-09-006. https://www3.epa.gov/airtoxics/rrisk/rtrpg.html.
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1. How did we estimate actual emissions and identify the emissions 
release characteristics?
    As previously discussed, we updated the risk assessment in this 
action for the PEPO Production source category because the source 
category has sources that emit EtO. The EPA developed the list of 25 
facilities for the PEPO Production source category as described in 
section II.B of this preamble. We developed the emissions modeling 
input files using the EPA's 2017 NEI. However, in a few instances where 
facility-specific data were not available or not reflective of current 
controls in the 2017 NEI, we obtained data from a more recent dataset 
(e.g., review of emissions inventory data from our CAA section 114 
request, more recent inventories submitted to States, or 2018 NEI). The 
EPA also used the NEI data to develop the other parameters needed to 
perform the risk modeling analysis including the emissions release 
characteristics, such as stack heights, stack diameters, volumetric 
flow rates, temperatures, and emission release point locations. For 
further details on the assumptions and methodologies used to estimate 
actual emissions, see appendix 1 of the document titled Residual Risk 
Assessment for the Polyether Polyols (PEPO) Production Source Category 
in Support of the 2024 Risk and Technology Review Proposed Rule, which 
is available in the docket for this rulemaking.
2. How did we estimate MACT-allowable emissions?
    The available emissions data in the RTR emissions dataset include 
estimates of the mass of HAP emitted during a specified annual time 
period. These ``actual'' emission levels are often lower than the 
emission levels allowed under the requirements of the current MACT 
standards. The emissions allowed under the MACT standards are referred 
to as the ``MACT-allowable'' emissions. We discussed the consideration 
of both MACT-allowable and actual emissions in the 2005 final RTR for 
Coke Oven Batteries (70 FR 19992, 19998-99, April 15, 2005) and in the 
2006 proposed and final RTR for the HON (71 FR 34421, 34428, June 14, 
2006, and 71 FR 76603, 76609, December 21, 2006, respectively). In 
those actions, we noted that assessing the risk at the MACT-allowable 
level is inherently reasonable since that risk reflects the maximum 
level facilities could emit and still comply with national emission 
standards. We also explained that it is reasonable to consider actual 
emissions, where such data are available, in both steps of the risk 
analysis, in accordance with the Benzene NESHAP approach. (54 FR 
38044.)
    For this analysis, we have determined that the actual emissions 
data are reasonable estimates of the MACT-allowable emissions levels 
for the PEPO Production source category, as we are not generally aware 
of any situations in which a facility is conducting additional work 
practices or operating a control device such that it achieves a far 
greater emission reduction than required by the NESHAP. However, in 
cases where we encountered a permit emissions limit that appeared to be 
higher than the reported emissions, we recorded that in the allowable 
emissions column of the modeling file to assess the risk of allowable 
emissions. For further details on the assumptions and methodologies 
used to estimate MACT-allowable emissions, see appendix 1 of the 
document titled Residual Risk Assessment for the Polyether Polyols 
(PEPO) Production Source Category in Support of the 2024 Risk and 
Technology Review Proposed Rule, which is available in the docket for 
this rulemaking.
3. How do we conduct dispersion modeling, determine inhalation 
exposures, and estimate individual and population inhalation risk?
    Both long-term and short-term inhalation exposure concentrations 
and health risk from the source category addressed in this proposal 
were estimated using the Human Exposure Model (HEM-4).\10\ The HEM-4 
performs three primary risk assessment activities: (1) conducting 
dispersion modeling to estimate the concentrations of HAP in ambient 
air, (2) estimating long-term and short-term inhalation exposures to 
individuals residing within 50 kilometers (km) of the modeled sources, 
and (3) estimating individual and population-level inhalation risk 
using the exposure estimates and quantitative dose-response 
information.
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    \10\ For more information about HEM-4, go to https://www.epa.gov/fera/risk-assessment-and-modeling-human-exposure-model-hem.

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[[Page 105995]]

a. Dispersion Modeling
    The air dispersion model AERMOD (American Meteorological Society/
EPA Regulatory Model dispersion modeling system), used by the HEM-4, is 
one of the EPA's preferred models for assessing air pollutant 
concentrations from industrial facilities.\11\ To perform the 
dispersion modeling and to develop the preliminary risk estimates, HEM-
4 draws on three data libraries. The first is a library of 
meteorological data, which is used for dispersion calculations. This 
library includes 1 year (2019) of hourly surface and upper air 
observations from over 800 meteorological stations, selected to provide 
coverage of the United States and Puerto Rico. A second library of 
United States Census Bureau census block \12\ internal point locations 
and populations provides the basis of human exposure calculations (U.S. 
Census, 2020). In addition, for each census block, the census library 
includes the elevation and controlling hill height, which are also used 
in dispersion calculations. A third library of pollutant-specific dose-
response values is used to estimate health risk. These are discussed 
below.
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    \11\ U.S. EPA. Revision to the Guideline on Air Quality Models: 
Adoption of a Preferred General Purpose (Flat and Complex Terrain) 
Dispersion Model and Other Revisions (70 FR 68218, November 9, 
2005).
    \12\ A census block is the smallest geographic area for which 
census statistics are tabulated.
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b. Risk From Chronic Exposure to HAP
    In developing the risk assessment for chronic exposures, we use the 
estimated annual average ambient air concentrations of each HAP emitted 
by each source in the source category. The HAP air concentrations at 
each nearby census block centroid located within 50 km of the facility 
are a surrogate for the chronic inhalation exposure concentration for 
all the people who reside in that census block. A distance of 50 km is 
consistent with both the analysis supporting the 1989 Benzene NESHAP 
(54 FR 38044) and the limitations of Gaussian dispersion models, 
including AERMOD.
    For each facility, we calculate the MIR as the cancer risk 
associated with a continuous lifetime (24 hours per day, 7 days per 
week, 52 weeks per year, 70 years) exposure to the maximum annual 
average concentration at the centroid of each inhabited census block. 
We calculate individual cancer risk by multiplying the estimated 
lifetime exposure to the ambient concentration of each HAP (in 
micrograms per cubic meter ([mu]g/m\3\)) by its URE. The URE is an 
upper-bound estimate of an individual's incremental risk of contracting 
cancer over a lifetime of exposure to a concentration of 1 [mu]g/m\3\ 
of air. For residual risk assessments, we generally use UREs from the 
EPA's IRIS. For carcinogenic pollutants without IRIS values, we look to 
other reputable sources of cancer dose-response values, often using 
California EPA (CalEPA) UREs, where available. In cases where new, 
scientifically credible dose-response values have been developed in a 
manner consistent with EPA guidelines and have undergone a peer review 
process similar to that used by the EPA, we may use such dose-response 
values in place of, or in addition to, other values, if appropriate. 
The pollutant-specific dose-response values used to estimate health 
risk are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants.
    To estimate individual lifetime cancer risks associated with 
exposure to HAP emissions from each facility in the source category, we 
sum the risks for each of the carcinogenic HAP \13\ emitted by the 
modeled facility. We estimate cancer risk at every census block within 
50 km of every facility in the source category. The MIR is the highest 
individual lifetime cancer risk estimated for any of those census 
blocks. In addition to calculating the MIR, we estimate the 
distribution of individual cancer risks for the source category by 
summing the number of individuals within 50 km of the sources whose 
estimated risk falls within a specified risk range. We also estimate 
annual cancer incidence by multiplying the estimated lifetime cancer 
risk at each census block by the number of people residing in that 
block, summing results for all of the census blocks, and then dividing 
this result by a 70-year lifetime.
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    \13\ The EPA's 2005 Guidelines for Carcinogen Risk Assessment 
classifies carcinogens as: ``carcinogenic to humans,'' ``likely to 
be carcinogenic to humans,'' and ``suggestive evidence of 
carcinogenic potential.'' These classifications also coincide with 
the terms ``known carcinogen,'' ``probable carcinogen,'' and 
``possible carcinogen,'' respectively, which are the terms advocated 
in the EPA's Guidelines for Carcinogen Risk Assessment, published in 
1986 (51 FR 33992, September 24, 1986). In August 2000, the 
document, Supplemental Guidance for Conducting Health Risk 
Assessment of Chemical Mixtures (EPA/630/R-00/002), was published as 
a supplement to the 1986 document. Copies of both documents can be 
obtained from https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=20533&CFID=70315376&CFTOKEN=71597944. Summing 
the risk of these individual compounds to obtain the cumulative 
cancer risk is an approach that was recommended by the EPA's SAB in 
their 2002 peer review of the EPA's National Air Toxics Assessment 
(NATA) titled NATA--Evaluating the National-scale Air Toxics 
Assessment 1996 Data--an SAB Advisory, available at https://
yosemite.epa.gov/sab/sabproduct.nsf/
214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf.
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    To assess the risk of noncancer health effects from chronic 
exposure to HAP, we calculate either an HQ or a target organ-specific 
hazard index (TOSHI). We calculate an HQ when a single noncancer HAP is 
emitted. Where more than one noncancer HAP is emitted, we sum the HQ 
for each of the HAP that affects a common target organ or target organ 
system to obtain a TOSHI. The HQ is the estimated exposure divided by 
the chronic noncancer dose-response value, which is a value selected 
from one of several sources. The preferred chronic noncancer dose-
response value is the EPA RfC, defined as ``an estimate (with 
uncertainty spanning perhaps an order of magnitude) of a continuous 
inhalation exposure to the human population (including sensitive 
subgroups) that is likely to be without an appreciable risk of 
deleterious effects during a lifetime'' (https://iaspub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&vocabName=IRIS%20Glossary). In cases where an RfC 
from the EPA's IRIS is not available or where the EPA determines that 
using a value other than the RfC is appropriate, the chronic noncancer 
dose-response value can be a value from the following prioritized 
sources, which define their dose-response values similarly to the EPA: 
(1) the Agency for Toxic Substances and Disease Registry (ATSDR) 
Minimal Risk Level (https://www.atsdr.cdc.gov/mrls/index.asp); (2) the 
CalEPA Chronic Reference Exposure Level (REL) (https://oehha.ca.gov/air/crnr/notice-adoption-air-toxics-hot-spots-program-guidance-manual-preparation-health-risk-0); or (3) as noted above, a scientifically 
credible dose-response value that has been developed in a manner 
consistent with the EPA guidelines and has undergone a peer review 
process similar to that used by the EPA. The pollutant-specific dose-
response values used to estimate health risks are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants.
c. Risk From Acute Exposure to HAP That May Cause Health Effects Other 
Than Cancer
    For each HAP for which appropriate acute inhalation dose-response 
values are available, the EPA also assesses the potential health risks 
due to acute exposure. For these assessments, the EPA makes health 
protective

[[Page 105996]]

assumptions about emission rates, meteorology, and exposure location. 
As part of our efforts to continually improve our methodologies to 
evaluate the risks that HAP emitted from categories of industrial 
sources pose to human health and the environment,\14\ we revised our 
treatment of meteorological data to use reasonable worst-case air 
dispersion conditions in our acute risk screening assessments instead 
of worst-case air dispersion conditions. This revised treatment of 
meteorological data and the supporting rationale are described in more 
detail in the document titled Residual Risk Assessment for the 
Polyether Polyols (PEPO) Production Source Category in Support of the 
2024 Risk and Technology Review Proposed Rule and in appendix 5 of the 
report Technical Support Document for Acute Risk Screening Assessment, 
which are available in the docket for this rulemaking. This revised 
approach has been used in this proposed rule and in all other RTR 
rulemakings proposed on or after June 3, 2019.
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    \14\ See, e.g., U.S. EPA. Screening Methodologies to Support 
Risk and Technology Reviews (RTR): A Case Study Analysis (Draft 
Report, May 2017. (https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html).
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    To assess the potential acute risk to the maximally exposed 
individual, we use the peak hourly emission rate for each emission 
point,\15\ reasonable worst-case air dispersion conditions (i.e., 99th 
percentile), and the point of highest off-site exposure. Specifically, 
we assume that peak emissions from the source category and reasonable 
worst-case air dispersion conditions co-occur and that a person is 
present at the point of maximum exposure.
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    \15\ In the absence of hourly emission data, we develop 
estimates of maximum hourly emission rates by multiplying the 
average actual annual emissions rates by a factor (either a 
category-specific factor or a default factor of 10) to account for 
variability. This is documented in Residual Risk Assessment for the 
Polyether Polyols (PEPO) Production Source Category in Support of 
the 2024 Risk and Technology Review Proposed Rule, and in appendix 5 
of the report: Technical Support Document for Acute Risk Screening 
Assessment. Both of these documents are available in the docket for 
this rulemaking.
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    To characterize the potential health risks associated with 
estimated acute inhalation exposures to a HAP, we generally use 
multiple acute dose-response values, including acute RELs, acute 
exposure guideline levels (AEGLs), and emergency response planning 
guidelines (ERPG) for 1-hour exposure durations, if available, to 
calculate acute HQs. The acute HQ is calculated by dividing the 
estimated acute exposure concentration by the acute dose-response 
value. For each HAP for which acute dose-response values are available, 
the EPA calculates acute HQs.
    An acute REL is defined as ``the concentration level at or below 
which no adverse health effects are anticipated for a specified 
exposure duration.'' \16\ Acute RELs are based on the most sensitive, 
relevant, adverse health effect reported in the peer-reviewed medical 
and toxicological literature. They are designed to protect the most 
sensitive individuals in the population through the inclusion of 
margins of safety. Because margins of safety are incorporated to 
address data gaps and uncertainties, exceeding the REL does not 
automatically indicate an adverse health impact. AEGLs represent 
threshold exposure limits for the general public and are applicable to 
emergency exposures ranging from 10 minutes to 8 hours.\17\ They are 
guideline levels for ``once-in-a-lifetime, short-term exposures to 
airborne concentrations of acutely toxic, high-priority chemicals.'' 
Id. at 21. The AEGL-1 is specifically defined as ``the airborne 
concentration (expressed as ppm (parts per million) or mg/m3 
(milligrams per cubic meter)) of a substance above which it is 
predicted that the general population, including susceptible 
individuals, could experience notable discomfort, irritation, or 
certain asymptomatic nonsensory effects. However, the effects are not 
disabling and are transient and reversible upon cessation of 
exposure.'' The document also notes that ``Airborne concentrations 
below AEGL-1 represent exposure levels that can produce mild and 
progressively increasing but transient and nondisabling odor, taste, 
and sensory irritation or certain asymptomatic, nonsensory effects.'' 
Id. AEGL-2 are defined as ``the airborne concentration (expressed as 
parts per million or milligrams per cubic meter) of a substance above 
which it is predicted that the general population, including 
susceptible individuals, could experience irreversible or other 
serious, long-lasting adverse health effects or an impaired ability to 
escape.'' Id.
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    \16\ CalEPA issues acute RELs as part of its Air Toxics Hot 
Spots Program, and the 1-hour and 8-hour values are documented in 
Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The 
Determination of Acute Reference Exposure Levels for Airborne 
Toxicants, which is available at https://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-rel-summary.
    \17\ National Academy of Sciences, 2001. Standing Operating 
Procedures for Developing Acute Exposure Levels for Hazardous 
Chemicals, page 2. Available at https://www.epa.gov/sites/production/files/2015-09/documents/sop_final_standing_operating_procedures_2001.pdf. Note that the 
National Advisory Committee for Acute Exposure Guideline Levels for 
Hazardous Substances ended in October 2011, but the AEGL program 
continues to operate at the EPA and works with the National 
Academies to publish final AEGLs (https://www.epa.gov/aegl).
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    ERPGs are developed, by the American Industrial Hygiene Association 
(AIHA), for emergency planning and are intended to be health-based 
guideline concentrations for single exposures to chemicals. The ERPG-1 
is the maximum airborne concentration, established by AIHA, below which 
it is believed that nearly all individuals could be exposed for up to 1 
hour without experiencing other than mild transient adverse health 
effects or without perceiving a clearly defined, objectionable odor. 
Similarly, the ERPG-2 is the maximum airborne concentration, 
established by AIHA, below which it is believed that nearly all 
individuals could be exposed for up to 1 hour without experiencing or 
developing irreversible or other serious health effects or symptoms 
which could impair an individual's ability to take protective action.
    An acute REL for 1-hour exposure durations is typically lower than 
its corresponding AEGL-1 and ERPG-1. Even though their definitions are 
slightly different, AEGL-1s are often the same as the corresponding 
ERPG-1s, and AEGL-2s are often equal to ERPG-2s. The maximum HQs from 
our acute inhalation screening risk assessment typically result when we 
use the acute REL for a HAP. In cases where the maximum acute HQ 
exceeds 1, we also report the HQ based on the next highest acute dose-
response value (usually the AEGL-1 and/or the ERPG-1).
    For the PEPO Production source category, we did not use a default 
acute emissions multiplier of 10, but rather we used process level-
specific acute emissions multipliers, generally ranging from a factor 
of 2 to 10 as was done in past chemical and petrochemical residual risk 
reviews such as for the 2015 Petroleum Refinery Sector rule, 2024 HON 
rulemaking, 2020 MON RTR, and 2020 EMACT standards RTR, where similar 
emission sources and standards exist. These refinements are discussed 
more fully in appendix 1 of the document titled Residual Risk 
Assessment for the Polyether Polyols (PEPO) Production Source Category 
in Support of the 2024 Risk and Technology Review Proposed Rule, which 
is available in the docket for this rulemaking.
    In our acute inhalation screening risk assessment, acute impacts 
are deemed negligible for HAP for which acute HQs are less than or 
equal to 1, and no further analysis is performed for these HAP. In 
cases where an acute HQ from the screening step is greater than 1, we 
assess the site-specific data to ensure

[[Page 105997]]

that the acute HQ is at an off-site location. For the PEPO Production 
source category, the data refinements employed consisted of reviewing 
satellite imagery of the locations of the maximum acute HQ values to 
determine if the maximum was off facility property. For any maximum 
value that was determined to be on facility property, the next highest 
value that was off facility property was used. These refinements are 
discussed more fully in the document titled Residual Risk Assessment 
for the Polyether Polyols (PEPO) Production Source Category in Support 
of the 2024 Risk and Technology Review Proposed Rule, which is 
available in the docket for this rulemaking.
4. How do we conduct the multipathway exposure and risk screening 
assessment?
    The EPA conducts a tiered screening assessment examining the 
potential for significant human health risks due to exposures via 
routes other than inhalation (e.g., ingestion). We first determine 
whether any sources in the source category emit any HAP known to be 
persistent and bioaccumulative in the environment, as identified in the 
EPA's Air Toxics Risk Assessment Library (see Volume 1, appendix D, at 
https://www.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library).
    For the PEPO Production source category, we identified PB-HAP 
emissions of arsenic compounds, cadmium compounds, polycyclic organic 
matter (POM), and mercury, so we proceeded to the next step of the 
evaluation. Except for lead, the human health risk screening assessment 
for PB-HAP consists of three progressive tiers. In a Tier 1 screening 
assessment, we determine whether the magnitude of the facility-specific 
emissions of PB-HAP warrants further evaluation to characterize human 
health risk through ingestion exposure. To facilitate this step, we 
evaluate emissions against previously developed screening threshold 
emission rates for several PB-HAP that are based on a hypothetical 
upper-end screening exposure scenario developed for use in conjunction 
with the EPA's Total Risk Integrated Methodology--Fate, Transport, and 
Ecological Exposure (TRIM.FaTE) model. The PB-HAP with screening 
threshold emission rates are arsenic compounds, cadmium compounds, 
chlorinated dibenzodioxins and furans, mercury compounds, and POM. 
Based on the EPA estimates of toxicity and bioaccumulation potential, 
these pollutants represent a health protective list for inclusion in 
multipathway risk assessments for RTR rules. (See Volume 1, Appendix D 
at https://www.epa.gov/sites/production/files/2013-08/documents/volume_1_reflibrary.pdf.) In this assessment, we compare the facility-
specific emission rates of these PB-HAP to the screening threshold 
emission rates for each PB-HAP to assess the potential for significant 
human health risks via the ingestion pathway. We call this application 
of the TRIM.FaTE model the Tier 1 screening assessment. The ratio of a 
facility's actual emission rate to the Tier 1 screening threshold 
emission rate is a ``screening value.''
    We derive the Tier 1 screening threshold emission rates for these 
PB-HAP (other than lead compounds) to correspond to a maximum excess 
lifetime cancer risk of 1-in-1 million (i.e., for arsenic compounds, 
polychlorinated dibenzodioxins and furans, and POM) or, for HAP that 
cause noncancer health effects (i.e., cadmium compounds and mercury 
compounds), a maximum HQ of 1. If the emission rate of any one PB-HAP 
or combination of carcinogenic PB-HAP in the Tier 1 screening 
assessment exceeds the Tier 1 screening threshold emission rate for any 
facility (i.e., the screening value is greater than 1), we conduct a 
second screening assessment, which we call the Tier 2 screening 
assessment. The Tier 2 screening assessment separates the Tier 1 
combined fisher and farmer exposure scenario into fisher, farmer, and 
gardener scenarios that retain upper-bound ingestion rates.
    In the Tier 2 screening assessment, the location of each facility 
that exceeds a Tier 1 screening threshold emission rate is used to 
refine the assumptions associated with the Tier 1 fisher and farmer 
exposure scenarios at that facility. A key assumption in the Tier 1 
screening assessment is that a lake and/or farm is located near the 
facility. As part of the Tier 2 screening assessment, we use a U.S. 
Geological Survey (USGS) database to identify actual waterbodies within 
50 km of each facility and assume the fisher only consumes fish from 
lakes within that 50-km zone. We also examine the differences between 
local meteorology near the facility and the meteorology used in the 
Tier 1 screening assessment. We then adjust the previously-developed 
Tier 1 screening threshold emission rates for each PB-HAP for each 
facility based on an understanding of how exposure concentrations 
estimated for the screening scenario change with the use of local 
meteorology and the USGS lakes database.
    In the Tier 2 farmer scenario, we maintain an assumption that the 
farm is located within 0.5 km of the facility and that the farmer 
consumes meat, eggs, dairy, vegetables, and fruit produced near the 
facility. We may further refine the Tier 2 screening analysis by 
assessing a gardener scenario to characterize a range of exposures, 
with the gardener scenario being more plausible in RTR evaluations. 
Under the gardener scenario, we assume the gardener consumes home-
produced eggs, vegetables, and fruit products at the same ingestion 
rate as the farmer. The Tier 2 screen continues to rely on the high-end 
food intake assumptions that were applied in Tier 1 for local fish 
(adult female angler at 99th percentile fish consumption \18\) and 
locally grown or raised foods (90th percentile consumption of locally 
grown or raised foods for the farmer and gardener scenarios \19\). If 
PB-HAP emission rates do not result in a Tier 2 screening value greater 
than 1, we consider those PB-HAP emissions to pose risks below a level 
of concern. If the PB-HAP emission rates for a facility exceed the Tier 
2 screening threshold emission rates, we may conduct a Tier 3 screening 
assessment.
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    \18\ Burger, J. 2002. Daily consumption of wild fish and game: 
Exposures of high end recreationists. International Journal of 
Environmental Health Research, 12:343-354.
    \19\ U.S. EPA. Exposure Factors Handbook 2011 Edition (Final). 
U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/
052F, 2011.
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    There are several analyses that can be included in a Tier 3 
screening assessment, depending upon the extent of refinement 
warranted, including validating that the lakes are fishable, locating 
residential/garden locations for urban and/or rural settings, 
considering plume-rise to estimate emissions lost above the mixing 
layer, and considering hourly effects of meteorology and plume-rise on 
chemical fate and transport (a time-series analysis). If necessary, the 
EPA may further refine the screening assessment through a site-specific 
assessment.
    In evaluating the potential multipathway risk from emissions of 
lead compounds, rather than developing a screening threshold emission 
rate, we compare maximum estimated chronic inhalation exposure 
concentrations to the level of the current National Ambient Air Quality 
Standard (NAAQS) for lead.\20\ Values below the level of the

[[Page 105998]]

primary (health-based) lead NAAQS are considered to have a low 
potential for multipathway risk.
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    \20\ In doing so, the EPA notes that the legal standard for a 
primary NAAQS--that a standard is requisite to protect public health 
and provide an adequate margin of safety (CAA section 109(b))--
differs from the CAA section 112(f) standard (requiring, among other 
things, that the standard provide an ``ample margin of safety to 
protect public health''). However, the primary lead NAAQS is a 
reasonable measure of determining risk acceptability (i.e., the 
first step of the 1989 Benzene NESHAP analysis) since it is designed 
to protect the most susceptible group in the human population--
children, including children living near major lead emitting 
sources. 73 FR 67002/3; 73 FR 67000/3; 73 FR 67005/1. In addition, 
applying the level of the primary lead NAAQS at the risk 
acceptability step is conservative, since that primary lead NAAQS 
reflects an adequate margin of safety.
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    For further information on the multipathway assessment approach, 
see the document titled Residual Risk Assessment for the Polyether 
Polyols (PEPO) Production Source Category in Support of the 2024 Risk 
and Technology Review Proposed Rule, which is available in the docket 
for this rulemaking.
5. How do we assess risks considering emissions control options?
    In addition to assessing baseline inhalation risks and screening 
for potential multipathway risks, we also estimate risks considering 
the potential emission reductions that would be achieved by the control 
options under consideration. In these cases, the expected emission 
reductions are applied to the specific HAP and emission points in the 
RTR emissions dataset to develop corresponding estimates of risk and 
incremental risk reductions.
6. How do we conduct the environmental risk screening assessment?
a. Adverse Environmental Effect, Environmental HAP, and Ecological 
Benchmarks
    The EPA conducts a screening assessment to examine the potential 
for an adverse environmental effect as required under section 
112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA defines ``adverse 
environmental effect'' as ``any significant and widespread adverse 
effect, which may reasonably be anticipated, to wildlife, aquatic life, 
or other natural resources, including adverse impacts on populations of 
endangered or threatened species or significant degradation of 
environmental quality over broad areas.''
    The EPA focuses on eight HAP, which are referred to as 
``environmental HAP,'' in its screening assessment: six PB-HAP and two 
acid gases. The PB-HAP included in the screening assessment are arsenic 
compounds, cadmium compounds, dioxins/furans, POM, mercury (both 
inorganic mercury and methyl mercury), and lead compounds. The acid 
gases included in the screening assessment are hydrochloric acid (HCl) 
and hydrofluoric acid (HF).
    HAP that persist and bioaccumulate are of particular environmental 
concern because they accumulate in the soil, sediment, and water. The 
acid gases, HCl and HF, are included due to their well-documented 
potential to cause direct damage to terrestrial plants. In the 
environmental risk screening assessment, we evaluate the following four 
exposure media: terrestrial soils, surface water bodies (includes 
water-column and benthic sediments), fish consumed by wildlife, and 
air. Within these four exposure media, we evaluate nine ecological 
assessment endpoints, which are defined by the ecological entity and 
its attributes. For PB-HAP (other than lead), both community-level and 
population-level endpoints are included. For acid gases, the ecological 
assessment evaluated is terrestrial plant communities.
    An ecological benchmark represents a concentration of HAP that has 
been linked to a particular environmental effect level. For each 
environmental HAP, we identified the available ecological benchmarks 
for each assessment endpoint. We identified, where possible, ecological 
benchmarks at the following effect levels: probable effect levels, 
lowest-observed-adverse-effect level, and no-observed-adverse-effect 
level. In cases where multiple effect levels were available for a 
particular PB-HAP and assessment endpoint, we use all of the available 
effect levels to help us to determine whether ecological risks exist 
and, if so, whether the risks could be considered significant and 
widespread.
    For further information on how the environmental risk screening 
assessment was conducted, including a discussion of the risk metrics 
used, how the environmental HAP were identified, and how the ecological 
benchmarks were selected, see appendix 9 of the document titled 
Residual Risk Assessment for the Polyether Polyols (PEPO) Production 
Source Category in Support of the 2024 Risk and Technology Review 
Proposed Rule, which is available in the docket for this rulemaking.
b. Environmental Risk Screening Methodology
    For the environmental risk screening assessment, the EPA first 
determined whether any facilities in the PEPO Production source 
category emitted any of the environmental HAP. For the PEPO Production 
source category, we identified emissions of arsenic compounds, cadmium 
compounds, POM, and mercury.\21\ Because one or more of the 
environmental HAP evaluated are emitted by at least one facility in the 
PEPO Production source category, we proceeded to the second step of the 
evaluation.
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    \21\ We note that in many instances, we did not have sufficient 
information to parse out emissions from PEPO processes from 
facility-wide emissions inventories; thus, to avoid underestimating 
emissions from PEPO sources, we modeled most or all of certain 
facilities' emissions records as if they all are from the PEPO 
Production source category.
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c. PB-HAP Methodology
    The environmental screening assessment includes six PB-HAP, arsenic 
compounds, cadmium compounds, dioxins/furans, POM, mercury (both 
inorganic mercury and methyl mercury), and lead compounds. With the 
exception of lead, the environmental risk screening assessment for PB-
HAP consists of three tiers. The first tier of the environmental risk 
screening assessment uses the same health-protective conceptual model 
that is used for the Tier 1 human health screening assessment. 
TRIM.FaTE model simulations were used to back-calculate Tier 1 
screening threshold emission rates. The screening threshold emission 
rates represent the emission rate in tons of pollutant per year that 
results in media concentrations at the facility that equal the relevant 
ecological benchmark. To assess emissions from each facility in the 
category, the reported emission rate for each PB-HAP was compared to 
the Tier 1 screening threshold emission rate for that PB-HAP for each 
assessment endpoint and effect level. If emissions from a facility do 
not exceed the Tier 1 screening threshold emission rate, the facility 
``passes'' the screening assessment, and, therefore, is not evaluated 
further under the screening approach. If emissions from a facility 
exceed the Tier 1 screening threshold emission rate, we evaluate the 
facility further in Tier 2.
    In Tier 2 of the environmental screening assessment, the screening 
threshold emission rates are adjusted to account for local meteorology 
and the actual location of lakes in the vicinity of facilities that did 
not pass the Tier 1 screening assessment. For soils, we evaluate the 
average soil concentration for all soil parcels within a 7.5-km radius 
for each facility and PB-HAP. For the water, sediment, and fish tissue 
concentrations, the highest value for each facility for each pollutant. 
If emissions from a facility do not exceed the Tier 2 screening 
threshold emission rate, the facility ``passes'' the screening

[[Page 105999]]

assessment and typically is not evaluated further. If emissions from a 
facility exceed the Tier 2 screening threshold emission rate, we 
evaluate the facility further in Tier 3.
    As in the multipathway human health risk assessment, in Tier 3 of 
the environmental screening assessment, we examine the suitability of 
the lakes around the facilities to support life and remove those that 
are not suitable (e.g., lakes that have been filled in or are 
industrial ponds), adjust emissions for plume rise, and conduct hour-
by-hour time-series assessments. If these Tier 3 adjustments to the 
screening threshold emission rates still indicate the potential for an 
adverse environmental effect (i.e., facility emission rate exceeds the 
screening threshold emission rate), we may elect to conduct a more 
refined assessment using more site-specific information. If, after 
additional refinement, the facility emission rate still exceeds the 
screening threshold emission rate, the facility may have the potential 
to cause an adverse environmental effect.
    To evaluate the potential for an adverse environmental effect from 
lead, we compared the average modeled air concentrations (from HEM-4) 
of lead around each facility in the source category to the level of the 
secondary NAAQS for lead. The secondary lead NAAQS is a reasonable 
means of evaluating environmental risk because it is set to provide 
substantial protection against adverse welfare effects which can 
include ``effects on soils, water, crops, vegetation, man-made 
materials, animals, wildlife, weather, visibility and climate, damage 
to and deterioration of property, and hazards to transportation, as 
well as effects on economic values and on personal comfort and well-
being.''
d. Acid Gas Environmental Risk Methodology
    The environmental screening assessment for acid gases evaluates the 
potential phytotoxicity and reduced productivity of plants due to 
chronic exposure to HF and HCl. The environmental risk screening 
methodology for acid gases is a single-tier screening assessment that 
compares modeled ambient air concentrations (from AERMOD) to the 
ecological benchmarks for each acid gas. To identify a potential 
adverse environmental effect (as defined in section 112(a)(7) of the 
CAA) from emissions of HF and HCl, we evaluate the following metrics: 
the size of the modeled area around each facility that exceeds the 
ecological benchmark for each acid gas, in acres and square km; the 
percentage of the modeled area around each facility that exceeds the 
ecological benchmark for each acid gas; and the area-weighted average 
screening value around each facility (calculated by dividing the area-
weighted average concentration over the 50-km modeling domain by the 
ecological benchmark for each acid gas). For further information on the 
environmental screening assessment approach, see appendix 9 of the 
document titled Residual Risk Assessment for the Polyether Polyols 
(PEPO) Production Source Category in Support of the 2024 Risk and 
Technology Review Proposed Rule, which is available in the docket for 
this rulemaking.
7. How do we conduct facility-wide assessments?
    To put the source category risks in context, we typically examine 
the risks from the entire ``facility,'' where the facility includes all 
HAP-emitting operations within a contiguous area and under common 
control. In other words, we examine the HAP emissions not only from the 
source category emission points of interest, but also emissions of HAP 
from all other emission sources at the facility for which we have data. 
For the PEPO Production source category, we conducted the facility-wide 
assessment using a dataset compiled from the 2017 NEI and other 
emissions information discussed in section II.C of this preamble. Once 
a quality assured source category dataset was available, it was placed 
back with the remaining records from the NEI for that facility (which 
in most instances was 2017 NEI data). The facility-wide file was then 
used to analyze risks due to the inhalation of HAP that are emitted 
``facility-wide'' for the populations residing within 50 km of each 
facility, consistent with the methods used for the source category 
analysis described above. For these facility-wide risk analyses, the 
modeled source category risks were compared to the facility-wide risks 
to determine the portion of the facility-wide risks that could be 
attributed to the source category addressed in this proposal. We also 
specifically examined the facility that was associated with the highest 
estimate of risk and determined the percentage of that risk 
attributable to the source category of interest. The document titled 
Residual Risk Assessment for the Polyether Polyols (PEPO) Production 
Source Category in Support of the 2024 Risk and Technology Review 
Proposed Rule, available through the docket for this rulemaking, 
provides the methodology and results of the facility-wide analyses, 
including all facility-wide risks and the percentage of source category 
contribution to facility-wide risks.
8. How do we conduct community-based risk assessments?
    In addition to the source category and facility-wide risk 
assessments, we also assessed the combined inhalation cancer risk from 
all local stationary sources of HAP for which we have emissions data. 
Specifically, we combined the modeled impacts from the facility-wide 
assessment (which includes category and non-category sources) with 
other nearby stationary point source model results. Section II.C of 
this preamble discusses the facility-wide emissions used in this 
assessment. For the other nearby point sources, we used AERMOD model 
results with emissions based primarily on the 2020 NEI. After combining 
these model results, we assessed cancer risks due to the inhalation of 
all HAP emitted by point sources for the populations residing within 10 
km (~6.2 miles) of PEPO facilities. In the community-based risk 
assessment, we compared the modeled source category and facility-wide 
cancer risks to the cancer risks from other nearby point sources to 
determine the portion of the risks that could be attributed to the 
source category addressed in this proposal. The document titled 
Residual Risk Assessment for the Polyether Polyols (PEPO) Production 
Source Category in Support of the 2024 Risk and Technology Review 
Proposed Rule, which is available in the docket for this rulemaking, 
provides the methodology and results of the community-based risks 
analyses.
9. How do we consider uncertainties in risk assessment?
    Uncertainty and the potential for bias are inherent in all risk 
assessments, including those performed for this proposal. Although 
uncertainty exists, we believe that our approach, which used health 
protective tools and assumptions, ensures that our decisions are health 
and environmentally protective. A brief discussion of the uncertainties 
in the RTR emissions dataset, dispersion modeling, inhalation exposure 
estimates, and dose-response relationships follows below. Also included 
are those uncertainties specific to our acute screening assessments, 
multipathway screening assessments, and our environmental risk 
screening assessments. A more thorough discussion of these 
uncertainties is included in the document titled Residual Risk 
Assessment for the Polyether Polyols (PEPO) Production

[[Page 106000]]

Source Category in Support of the 2024 Risk and Technology Review 
Proposed Rule, which is available in the docket for this rulemaking. If 
a multipathway site-specific assessment was performed for this source 
category, a full discussion of the uncertainties associated with that 
assessment can be found in appendix 11 of that document, Site-Specific 
Human Health Multipathway Residual Risk Assessment Report.
a. Uncertainties in the RTR Emissions Dataset
    Although the development of the RTR emissions dataset involved 
quality assurance/quality control processes, the accuracy of emissions 
values will vary depending on the source of the data, the degree to 
which data are incomplete or missing, the degree to which assumptions 
made to complete the datasets are accurate, errors in emission 
estimates, and other factors. The emission estimates considered in this 
analysis generally are annual totals for certain years, and they do not 
reflect short-term fluctuations during the course of a year or 
variations from year to year. The estimates of peak hourly emission 
rates for the acute effects screening assessment were based on an 
emission adjustment factor applied to the average annual hourly 
emission rates, which are intended to account for emission fluctuations 
due to normal facility operations.
b. Uncertainties in Dispersion Modeling
    We recognize there is uncertainty in ambient concentration 
estimates associated with any model, including the EPA's recommended 
regulatory dispersion model, AERMOD. In using a model to estimate 
ambient pollutant concentrations, the user chooses certain options to 
apply. For RTR assessments, we select some model options that have the 
potential to overestimate ambient air concentrations (e.g., not 
including plume depletion or pollutant transformation). We select other 
model options that have the potential to underestimate ambient impacts 
(e.g., not including building downwash). Other options that we select 
have the potential to either under- or overestimate ambient levels 
(e.g., meteorology and receptor locations). On balance, considering the 
directional nature of the uncertainties commonly present in ambient 
concentrations estimated by dispersion models, the approach we apply in 
the RTR assessments should yield unbiased estimates of ambient HAP 
concentrations. We also note that the selection of meteorology dataset 
location could have an impact on the risk estimates. As we continue to 
update and expand our library of meteorological station data used in 
our risk assessments, we expect to reduce this variability.
c. Uncertainties in Inhalation Exposure Assessment
    Although every effort is made to identify all of the relevant 
facilities and emission points, as well as to develop accurate 
estimates of the annual emission rates for all relevant HAP, the 
uncertainties in our emissions inventory likely dominate the 
uncertainties in the exposure assessment. Some uncertainties in our 
exposure assessment include human mobility, using the centroid of each 
census block, assuming lifetime exposure, and assuming only outdoor 
exposures. For most of these factors, there is neither an under nor 
overestimate when looking at the maximum individual risk or the 
incidence, but the shape of the distribution of risks may be affected. 
With respect to outdoor exposures, actual exposures may not be as high 
if people spend time indoors, especially for very reactive pollutants 
or larger particles. For all factors, we reduce uncertainty when 
possible. For example, with respect to census-block centroids, we 
analyze large blocks using aerial imagery and adjust locations of the 
block centroids to better represent the population in the blocks. We 
also add additional receptor locations where the population of a block 
is not well represented by a single location.
d. Uncertainties in Dose-Response Relationships
    There are uncertainties inherent in the development of the dose-
response values used in our risk assessments for cancer effects from 
chronic exposures and noncancer effects from both chronic and acute 
exposures. Some uncertainties are generally expressed quantitatively, 
and others are generally expressed in qualitative terms. We note, as a 
preface to this discussion, a point on dose-response uncertainty that 
is stated in the EPA's 2005 Guidelines for Carcinogen Risk Assessment; 
namely, that ``the primary goal of EPA actions is protection of human 
health; accordingly, as an Agency policy, risk assessment procedures, 
including default options that are used in the absence of scientific 
data to the contrary, should be health protective'' (the EPA's 2005 
Guidelines for Carcinogen Risk Assessment, page 1-7). This is the 
approach followed here as summarized in the next paragraphs.
    Cancer UREs used in our risk assessments are those that have been 
developed to generally provide an upper bound estimate of risk.\22\ 
That is, they represent a ``plausible upper limit to the true value of 
a quantity'' (although this is usually not a true statistical 
confidence limit). In some circumstances, the true risk could be as low 
as zero; however, in other circumstances the risk could be greater.\23\ 
Chronic noncancer RfC and reference dose values represent chronic 
exposure levels that are intended to be health-protective levels. To 
derive dose-response values that are intended to be ``without 
appreciable risk,'' the methodology relies upon an uncertainty factor 
(UF) approach,\24\ which considers uncertainty, variability, and gaps 
in the available data. The UFs are applied to derive dose-response 
values that are intended to protect against appreciable risk of 
deleterious effects.
---------------------------------------------------------------------------

    \22\ IRIS glossary (https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary).
    \23\ An exception to this is the URE for benzene, which is 
considered to cover a range of values, each end of which is 
considered to be equally plausible, and which is based on maximum 
likelihood estimates.
    \24\ See A Review of the Reference Dose and Reference 
Concentration Processes, U.S. EPA, December 2002, and Methods for 
Derivation of Inhalation Reference Concentrations and Application of 
Inhalation Dosimetry, U.S. EPA, 1994.
---------------------------------------------------------------------------

    Many of the UFs used to account for variability and uncertainty in 
the development of acute dose-response values are quite similar to 
those developed for chronic durations. Additional adjustments are often 
applied to account for uncertainty in extrapolation from observations 
at one exposure duration (e.g., 4 hours) to derive an acute dose-
response value at another exposure duration (e.g., 1 hour). Not all 
acute dose-response values are developed for the same purpose, and care 
must be taken when interpreting the results of an acute assessment of 
human health effects relative to the dose-response value or values 
being exceeded. Where relevant to the estimated exposures, the lack of 
acute dose-response values at different levels of severity should be 
factored into the risk characterization as potential uncertainties.
    Uncertainty also exists in the selection of ecological benchmarks 
for the environmental risk screening assessment. We established a 
hierarchy of preferred benchmark sources to allow selection of 
benchmarks for each environmental HAP at each ecological assessment 
endpoint. We searched for benchmarks for three effect levels (i.e., no-
effects level, threshold-effect level,

[[Page 106001]]

and probable-effect level), but not all combinations of ecological 
assessment/environmental HAP had benchmarks for all three effect 
levels. Where multiple effect levels were available for a particular 
HAP and assessment endpoint, we used all of the available effect levels 
to help us determine whether risk exists and whether the risk could be 
considered significant and widespread.
    Although we make every effort to identify appropriate human health 
effect dose-response values for all pollutants emitted by the sources 
in this risk assessment, some HAP emitted by the source category are 
lacking dose-response assessments. Accordingly, these pollutants cannot 
be included in the quantitative risk assessment, which could result in 
quantitative estimates understating HAP risk. To help to alleviate this 
potential underestimate, where we conclude similarity with a HAP for 
which a dose-response value is available, we use that value as a 
surrogate for the assessment of the HAP for which no value is 
available. To the extent use of surrogates indicates appreciable risk, 
we may identify a need to increase priority for an IRIS assessment for 
that substance. We additionally note that, generally speaking, HAP of 
greatest concern due to environmental exposures and hazard are those 
for which dose-response assessments have been performed, reducing the 
likelihood of understating risk. Further, HAP not included in the 
quantitative assessment are assessed qualitatively and considered in 
the risk characterization that informs the risk management decisions, 
including consideration of HAP reductions achieved by various control 
options.
    For a group of compounds that are unspeciated (e.g., groups of 
compounds that we do not know the exact composition of like glycol 
ethers), we conservatively use the most protective dose-response value 
of an individual compound in that group to estimate risk. Similarly, 
for an individual compound in a group (e.g., ethylene glycol diethyl 
ether) that does not have a specified dose-response value, we also 
apply the most protective dose-response value from the other compounds 
in the group to estimate risk.
e. Uncertainties in Acute Inhalation Screening Assessments
    In addition to the uncertainties highlighted above, there are 
several factors specific to the acute exposure assessment that the EPA 
conducts as part of the risk review under section 112 of the CAA. The 
accuracy of an acute inhalation exposure assessment depends on the 
simultaneous occurrence of independent factors that may vary greatly, 
such as hourly emissions rates, meteorology, and the presence of a 
person. In the acute screening assessment that we conduct under the RTR 
program, we assume that peak emissions from the source category and 
reasonable worst-case air dispersion conditions (i.e., 99th percentile) 
co-occur. We then include the additional assumption that a person is 
located at this point at the same time. Together, these assumptions 
represent a reasonable worst-case actual exposure scenario. In most 
cases, it is unlikely that a person would be located at the point of 
maximum exposure during the time when peak emissions and reasonable 
worst-case air dispersion conditions occur simultaneously.
f. Uncertainties in the Multipathway and Environmental Risk Screening 
Assessments
    For each source category, we generally rely on site-specific levels 
of PB-HAP or environmental HAP emissions to determine whether a refined 
assessment of the impacts from multipathway exposures is necessary or 
whether it is necessary to perform an environmental screening 
assessment. This determination is based on the results of a three-
tiered screening assessment that relies on the outputs from models--
TRIM.FaTE and AERMOD--that estimate environmental pollutant 
concentrations and human exposures for five PB-HAP (dioxins, POM, 
mercury, cadmium, and arsenic) and two acid gases (HF and HCl). For 
lead, we use AERMOD to determine ambient air concentrations, which are 
then compared to the secondary NAAQS standard for lead. Two important 
types of uncertainty associated with the use of these models in RTR 
risk assessments and inherent to any assessment that relies on 
environmental modeling are model uncertainty and input uncertainty.\25\
---------------------------------------------------------------------------

    \25\ In the context of this discussion, the term ``uncertainty'' 
as it pertains to exposure and risk encompasses both variability in 
the range of expected inputs and screening results due to existing 
spatial, temporal, and other factors, as well as uncertainty in 
being able to accurately estimate the true result.
---------------------------------------------------------------------------

    Model uncertainty concerns whether the model adequately represents 
the actual processes (e.g., movement and accumulation) that might occur 
in the environment. For example, does the model adequately describe the 
movement of a pollutant through the soil? This type of uncertainty is 
difficult to quantify. However, based on feedback received from 
previous EPA SAB reviews and other reviews, we are confident that the 
models used in the screening assessments are appropriate and state-of-
the-art for the multipathway and environmental screening risk 
assessments conducted in support of RTRs.
    Input uncertainty is concerned with how accurately the models have 
been configured and parameterized for the assessment at hand. For Tier 
1 of the multipathway and environmental screening assessments, we 
configured the models to avoid underestimating exposure and risk. This 
was accomplished by selecting upper-end values from nationally 
representative datasets for the more influential parameters in the 
environmental model, including selection and spatial configuration of 
the area of interest, lake location and size, meteorology, surface 
water, soil characteristics, and structure of the aquatic food web. We 
also assume an ingestion exposure scenario and values for human 
exposure factors that represent reasonable maximum exposures.
    In Tier 2 of the multipathway and environmental screening 
assessments, we refine the model inputs to account for meteorological 
patterns in the vicinity of the facility versus using upper-end 
national values, and we identify the actual location of lakes near the 
facility rather than the default lake location that we apply in Tier 1. 
By refining the screening approach in Tier 2 to account for local 
geographical and meteorological data, we decrease the likelihood that 
concentrations in environmental media are overestimated, thereby 
increasing the usefulness of the screening assessment. In Tier 3 of the 
screening assessments, we refine the model inputs again to account for 
hour-by-hour plume-rise and the height of the mixing layer. We can also 
use those hour-by-hour meteorological data in a TRIM.FaTE run using the 
screening configuration corresponding to the lake location. These 
refinements produce a more accurate estimate of chemical concentrations 
in the media of interest, thereby reducing the uncertainty with those 
estimates. The assumptions and the associated uncertainties regarding 
the selected ingestion exposure scenario are the same for all three 
tiers.
    For the environmental screening assessment for acid gases, we 
employ a single-tiered approach. We use the modeled air concentrations 
and compare those with ecological benchmarks.
    For all tiers of the multipathway and environmental screening 
assessments, our approach to addressing model input uncertainty is 
generally cautious. We

[[Page 106002]]

choose model inputs from the upper end of the range of possible values 
for the influential parameters used in the models, and we assume that 
the exposed individual exhibits ingestion behavior that would lead to a 
high total exposure. This approach reduces the likelihood of not 
identifying high risks for adverse impacts.
    Despite the uncertainties, when individual pollutants or facilities 
do not exceed screening threshold emission rates (i.e., screen out), we 
are confident that the potential for adverse multipathway impacts on 
human health is very low. On the other hand, when individual pollutants 
or facilities do exceed screening threshold emission rates, it does not 
mean that impacts are significant, only that we cannot rule out that 
possibility and that a refined assessment for the site might be 
necessary to obtain a more accurate risk characterization for the 
source category.
    The EPA evaluates the following HAP in the multipathway and/or 
environmental risk screening assessments, where applicable: arsenic, 
cadmium, dioxins/furans, lead, mercury (both inorganic and methyl 
mercury), POM, HCl, and HF. These HAP represent pollutants that can 
cause adverse impacts either through direct exposure to HAP in the air 
or through exposure to HAP that are deposited from the air onto soils 
and surface waters and then through the environment into the food web. 
These HAP represent those HAP for which we can conduct a meaningful 
multipathway or environmental screening risk assessment. For other HAP 
not included in our screening assessments, the model has not been 
parameterized such that it can be used for that purpose. In some cases, 
depending on the HAP, we may not have appropriate multipathway models 
that allow us to predict the concentration of that pollutant. The EPA 
acknowledges that other HAP beyond these that we are evaluating may 
have the potential to cause adverse effects and, therefore, the EPA may 
evaluate other relevant HAP in the future, as modeling science and 
resources allow.

C. How do we perform the technology review?

    Our technology review primarily focuses on the identification and 
evaluation of developments in practices, processes, and control 
technologies that have occurred since the previous PEPO NESHAP 
technology review was promulgated. Where we identify such developments, 
we analyze their technical feasibility, estimated costs, energy 
implications, and non-air environmental impacts. We also consider the 
emission reductions associated with applying each development. This 
analysis informs our decision of whether it is ``necessary'' to revise 
the CAA section 112 emissions standards. In addition, we consider the 
appropriateness of applying controls to new sources versus retrofitting 
existing sources. For this exercise, we consider any of the following 
to be a ``development'':
     Any add-on control technology or other equipment that was 
not identified and considered during development of the original MACT 
standards;
     Any improvements in add-on control technology or other 
equipment (that were identified and considered during development of 
the original MACT standards) that could result in additional emissions 
reduction;
     Any work practice or operational procedure that was not 
identified or considered during development of the original MACT 
standards;
     Any process change or pollution prevention alternative 
that could be broadly applied to the industry and that was not 
identified or considered during development of the original MACT 
standards; and
     Any significant changes in the cost (including cost 
effectiveness) of applying controls (including controls the EPA 
considered during the development of the original MACT standards).
    In addition to reviewing the practices, processes, and control 
technologies that were considered at the time we originally developed 
(or last updated) the PEPO NESHAP, we review a variety of data sources 
in our investigation of potential practices, processes, or controls to 
consider. We also review the NESHAP and the available data to determine 
if there are any unregulated emissions of HAP within the source 
category, and evaluate these data for use in developing new emission 
standards. See sections II.C and II.D of this preamble for information 
on the specific data sources that were reviewed as part of the 
technology review.

D. How do we determine a MACT floor and consider beyond-the-floor?

    MACT standards must reflect the maximum degree of emissions 
reduction achievable through the application of measures, processes, 
methods, systems or techniques, including, but not limited to, measures 
that (1) reduce the volume of or eliminate pollutants through process 
changes, substitution of materials or other modifications; (2) enclose 
systems or processes to eliminate emissions; (3) capture or treat 
pollutants when released from a process, stack, storage or fugitive 
emissions point; (4) are design, equipment, work practice or 
operational standards (including requirements for operator training or 
certification); or (5) are a combination of the above. CAA section 
112(d)(2)(A)-(E). The MACT standards may take the form of design, 
equipment, work practice or operational standards where the EPA first 
determines either that (1) a pollutant cannot be emitted through a 
conveyance designed and constructed to emit or capture the pollutant, 
or that any requirement for, or use of, such a conveyance would be 
inconsistent with law; or (2) the application of measurement 
methodology to a particular class of sources is not practicable due to 
technological and economic limitations. CAA section 112(h)(1)-(2).
    The MACT ``floor'' is the minimum control level allowed for MACT 
standards promulgated under CAA section 112(d)(3) and may not be based 
on cost considerations. For new sources located at facilities that are 
major sources of HAP, section 112 of the CAA requires the EPA to 
establish standards that are no less stringent than the emissions 
control that is achieved in practice by the best controlled similar 
source. The statute does not define ``achieved in practice'' nor does 
it dictate the manner in which the agency determines which source is 
the best controlled similar source, instead leaving it to the agency's 
discretion to make those determinations. For existing sources located 
at facilities that are major sources of HAP, standards must be no less 
stringent than the average emissions limitation achieved by the best 
performing sources for which the EPA has emissions information. Again, 
the CAA leaves to the EPA's discretion the manner in which to calculate 
``the average emission limitation achieved'' by the best performing 
sources. Under section 112, the CAA recognizes that source categories 
and subcategories have differing numbers of sources and provides 
category size-specific instructions on determining standard stringency 
for existing sources. Specifically, standards for categories or 
subcategories with fewer than 30 sources must be based on the average 
emission limitation achieved by the best performing 5 sources, and 
standards for categories or subcategories with 30 or more sources must 
be based on the average emission limitation achieved by the best 
performing 12 percent of sources for which the EPA has emissions 
information. In developing MACT standards, the EPA must also

[[Page 106003]]

consider control options that are more stringent than the floor (i.e., 
``beyond-the-floor'' options) under CAA section 112(d)(2). We may 
establish beyond-the-floor standards more stringent than the floor 
based on considerations of the cost of achieving the emission 
reductions, any non-air quality health and environmental impacts, and 
energy requirements.

IV. Analytical Results and Proposed Decisions

A. What are the results of the risk assessment and analyses?

    As previously discussed, we conducted a risk assessment for the 
PEPO Production source category. We previously identified EtO as a 
cancer risk driver from facilities with PEPO NESHAP-subject processes 
in the first risk assessment we conducted in 2014. However, the EPA's 
IRIS inhalation URE for EtO was revised in 2016,\26\ based on new data, 
showing EtO to be more carcinogenic than previously understood (i.e., 
resulting in a URE 60 times greater than the previous URE over a 70-
year lifetime). We briefly present the results of the risk assessment 
below and in more detail in the document titled Residual Risk 
Assessment for the Polyether Polyols (PEPO) Production Source Category 
in Support of the 2024 Risk and Technology Review Proposed Rule, which 
is available in the docket for this rulemaking.
---------------------------------------------------------------------------

    \26\ U.S. EPA. Evaluation of the Inhalation Carcinogenicity of 
Ethylene Oxide (CASRN 75-21-8) In Support of Summary Information on 
the Integrated Risk Information System (IRIS). December 2016. EPA/
635/R-16/350Fa. Available at: https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/1025tr.pdf.
---------------------------------------------------------------------------

1. Chronic Inhalation Risk Assessment Results
    Out of the 25 facilities identified as subject to the PEPO NESHAP, 
two facilities do not have source category emissions included in our 
risk assessment. One facility has a PEPO source under construction 
while the other facility did not report records in its emissions 
inventory with names that that could be linked to its PEPO process and 
thus we did not have sufficient information to parse out the source 
category records.\27\ The results of the chronic baseline inhalation 
cancer risk assessment, which are estimated using modeling and is the 
case for all risk results presented here and in subsequent sections, 
indicate that, based on estimates of current actual emissions, the MIR 
posed by the source category is 1,000-in-1 million, driven by EtO 
emissions from wastewater (77 percent) and equipment leaks (21 
percent). The total estimated cancer incidence based on actual emission 
levels is 0.3 excess cancer cases per year (or 1 cancer case every 3.3 
years). EtO emissions contribute 99.6 percent of the total cancer 
incidence. Within 50 km of PEPO NESHAP-subject facilities, the 
population exposed to cancer risk greater than 100-in-1 million for 
PEPO NESHAP actual emissions is approximately 3,300 people, and the 
population exposed to cancer risk greater than or equal to 1-in-1 
million is approximately 3.8 million people. Of the 23 facilities that 
the EPA assessed for source category risk, 6 facilities have an 
estimated maximum cancer risk greater than 100-in-1 million. In 
addition, the maximum modeled chronic noncancer TOSHI for the source 
category based on actual emissions is estimated to be 0.1 (for 
respiratory effects). No populations are estimated to be exposed to a 
TOSHI greater than 1.
---------------------------------------------------------------------------

    \27\ When considering all emissions reported by the facility for 
which we could not identify PEPO emissions records, we estimated a 
facility-wide maximum cancer risk of 70-in-1 million, so including 
this facility in the PEPO source category risk assessment would not 
have changed our decisions on standards to address unacceptable 
risk.
---------------------------------------------------------------------------

    Of the 23 facilities that the EPA assessed for the source category 
risk, 5 facilities have allowable emissions that differ from the actual 
emissions (see section III.B.2 of this preamble). For the other 18 
facilities, actual emissions equal allowable emissions, and therefore, 
actual risks equal allowable risks for these 18 facilities. Our risk 
assessment based on allowable emissions includes all 23 facilities. 
This assessment estimates the MIR posed by the source category is 
unchanged at 1,000-in-1 million, driven by EtO emissions from 
wastewater (77 percent) and equipment leaks (21 percent). The total 
estimated cancer incidence is 0.4 excess cancer cases per year (or 1 
cancer case every 2.5 years). EtO emissions contribute 99.6 percent of 
the total cancer incidence. Within 50 km of PEPO NESHAP-subject 
facilities, the population exposed to cancer risk greater than 100-in-1 
million for PEPO NESHAP allowable emissions is approximately 6,700 
people, and the population exposed to cancer risk greater than or equal 
to 1-in-1 million is approximately 4.7 million people. Of the 23 
facilities that the EPA assessed for source category risk, 8 facilities 
have an estimated maximum cancer risk greater than 100-in-1 million. In 
addition, the EPA estimated the maximum modeled chronic noncancer TOSHI 
for the source category based on allowable emissions to be less than 1.
    See table 1 of this preamble for a summary of the PEPO NESHAP 
inhalation risk assessment results.

                 Table 1--PEPO Production Source Category Inhalation Risk Assessment Results Based on Actual and Allowable Emissions \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                            Maximum     Estimated population at   Estimated                                    Refined
                                                           individual  increased risk of cancer     annual                                     maximum
                                              Number of   cancer risk --------------------------    cancer      Maximum chronic noncancer     screening
              Risk assessment                 facilities     (-in-1                               incidence               TOSHI                 acute
                                                 \2\        million)     >=1-in-1    >100-in-1    (cases per                                  noncancer
                                                              \3\        million      million       year)                                         HQ
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                         Baseline (Pre-control) Actual Emissions
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source Category............................           23        1,000          3.8        3,300          0.3  0.1 (respiratory)............            1
Facility-wide \4\..........................           25        2,000          7.3        4,000          0.6  3 (respiratory)..............
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                       Baseline (Pre-control) Allowable Emissions
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source Category \1\........................           23        1,000          4.7        6,700          0.4  0.1 (respiratory)............
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ There are allowable emissions for 5 facilities. For the other 18 facilities, actual emissions equal allowable emissions.
\2\ There are 25 PEPO production facilities; however, only 23 of these facilities are included in the source category risk assessment based on available
  data.
\3\ Maximum individual excess lifetime cancer risk due to HAP emissions.
\4\ See ``Facility-Wide Risk Results'' in section IV.A.5 of this preamble for more details on this risk assessment.


[[Page 106004]]

2. Screening Level Acute Risk Assessment Results
    As presented in table 1 of this preamble, the estimated worst-case 
off-site acute inhalation exposures to emissions from the PEPO 
Production source category result in a maximum modeled acute noncancer 
HQ equal to 1 based on the REL for methoxytriglycol (a glycol ether). 
Acute impacts are deemed negligible for HAP for which acute HQs are 
less than or equal to 1, and no further analysis is performed for these 
HAP. The main body and appendix 10 of the document titled Residual Risk 
Assessment for the Polyether Polyols (PEPO) Production Source Category 
in Support of the 2024 Risk and Technology Review Proposed Rule, which 
is available in the docket for this rulemaking, provides detailed 
information about the assessment, including evaluation of the 
screening-level acute risk assessment results.
3. Multipathway Risk Screening Results
    For the PEPO Production source category, three facilities emitted 
at least 1 PB-HAP, including arsenic, cadmium, mercury, and POM.\28\ 
Emissions of these PB-HAP from each facility were compared to the 
respective pollutant-specific Tier 1 screening emission thresholds. The 
Tier 1 screening analysis for PB-HAP (other than lead, which was 
evaluated differently), indicated no facilities exceeded the Tier 1 
emission threshold for arsenic, cadmium, mercury, or POM.
---------------------------------------------------------------------------

    \28\ Note that while the multipathway risk screening results 
includes metals (e.g., arsenic, cadmium, mercury) and POM, the EPA 
used a health-protective approach and included emissions inventory 
records that were not clearly labeled (not easily categorized) in 
modeling of emissions from the PEPO Production source category. This 
means that emissions from other source categories were likely 
included for this analysis in certain instances. We have no 
information suggesting that metals or POM are emitted from PEPO 
processes. See appendix 1 of the document titled Residual Risk 
Assessment for the Polyether Polyols (PEPO) Production Source 
Category in Support of the 2024 Risk and Technology Review Proposed 
Rule, which is available in the docket for this rulemaking, for more 
details about development of the risk modeling file.
---------------------------------------------------------------------------

    In evaluating the potential for multipathway risk from emissions of 
lead, the modeled maximum annual ambient lead concentration (0.000002 
[mu]g/m\3\) was compared to the NAAQS for lead (0.15 [mu]g/m\3\, 3-
month rolling average). We did not estimate any exceedance of the NAAQS 
for lead. The modeled maximum annual lead concentration is well below 
the NAAQS for lead, indicating low potential for multipathway risk of 
concern due to lead emissions.
    Detailed information about the assessment is provided in the 
document titled Residual Risk Assessment for the Polyether Polyols 
(PEPO) Production Source Category in Support of the 2024 Risk and 
Technology Review Proposed Rule, which is available in the docket for 
this rulemaking.
4. Environmental Risk Screening Results
    As described in section IV.A of this preamble, we conducted a 
screening assessment for adverse environmental effects for the PEPO 
Production source category. The environmental screening assessment 
included the following HAP: arsenic, cadmium, methyl mercury, divalent 
mercury, and POM.\29\
---------------------------------------------------------------------------

    \29\ Note that while the environmental risk screening results 
includes metals (e.g., arsenic, cadmium, lead, mercury), POM, and 
acid gases (e.g., HCl), the EPA used a health-protective approach 
and included emissions inventory records that were not clearly 
labeled (not easily categorized) in modeling of emissions from the 
PEPO Production source category to avoid underestimating emissions 
from PEPO sources. This means that emissions from other source 
categories were likely included for this analysis in certain 
instances. We have no information suggesting that metals, POM, or 
HCl are emitted from PEPO processes. See appendix 1 of the document 
titled Residual Risk Assessment for the Polyether Polyols (PEPO) 
Production Source Category in Support of the 2024 Risk and 
Technology Review Proposed Rule, which is available in the docket 
for this rulemaking, for more details about development of the risk 
modeling file.
---------------------------------------------------------------------------

    In the Tier 1 screening analysis for PB-HAP (other than lead, which 
was evaluated differently), none of the PB-HAP had exceedances for any 
ecological benchmark.
    In evaluating the potential adverse environmental risks associated 
with emissions of lead, the modeled maximum annual ambient lead 
concentration (0.000002 [mu]g/m\3\) was compared to the NAAQS for lead 
(0.15 [mu]g/m\3\, 3-month rolling average). We did not estimate any 
exceedance of the NAAQS for lead. The modeled maximum annual lead 
concentration is well below the NAAQS for lead, indicating low 
potential for environmental risk of concern due to lead emissions.
    We also conducted an environmental risk screening assessment 
specifically for acid gases (i.e., HCl and HF) for the PEPO Production 
source category. There are no facilities with HF emissions. There are 
three facilities with HCl emissions. For HCl, the average modeled 
concentration around each facility (i.e., the average concentration of 
all off-site data points in the modeling domain) did not exceed any 
ecological benchmark. In addition, each individual modeled 
concentration of HCl (i.e., each off-site data point in the modeling 
domain) was below the ecological benchmarks for all facilities.
    Based on the results of the environmental risk screening analysis, 
we do not expect an adverse environmental effect as a result of HAP 
emissions from this source category. Detailed information about the 
assessments is provided in the document titled Residual Risk Assessment 
for the Polyether Polyols (PEPO) Production Source Category in Support 
of the 2024 Risk and Technology Review Proposed Rule, which is 
available in the docket for this rulemaking.
5. Facility-Wide Risk Results
    We assessed facility-wide risk, as described in section III.B.7 of 
this preamble, to characterize the source category risk in the context 
of ``whole facility'' risk using the NEI-based data described in 
section II.C of this preamble. Facility-wide risk was modeled using 
post-control emissions from the processes subject to the HON to reflect 
the emissions reductions expected from the HON rulemaking that was 
signed in early 2024 (89 FR 42932). The maximum lifetime individual 
cancer risk posed by the 25 modeled facilities based on facility-wide 
emissions is 2,000-in-1 million with EtO emissions from wastewater (72 
percent) and equipment leaks (20 percent) from PEPO production source 
category emissions driving the risk. The total estimated cancer 
incidence based on facility-wide emission levels is 0.6 excess cancer 
cases per year. EtO emissions contribute 94 percent of the total cancer 
incidence. Within 50 km of PEPO NESHAP-subject facilities, the 
population exposed to cancer risk greater than 100-in-1 million for 
PEPO facility-wide emissions is approximately 4,000 people, and the 
population exposed to cancer risk greater than or equal to 1-in-1 
million is approximately 7.3 million people. The maximum chronic 
noncancer TOSHI due to facility-wide emissions is estimated to be 3 
(for respiratory effects) due to emissions of chlorine from 1 facility. 
A different facility has a chronic noncancer TOSHI of 2 (for 
respiratory effects) due to facility-wide emissions of maleic 
anhydride. Approximately 60 people are estimated to be exposed to a 
TOSHI greater than 1 due to facility-wide emissions. Of the 
approximately 60 people, 44 people are exposed to a TOSHI of 3 due to 
emissions of chlorine and 16 people are exposed to a TOSHI of 2 due to 
emissions of maleic anhydride.
    After the controls proposed in this action are implemented for the 
PEPO Production source category (see section IV.B.2 of this preamble), 
the post-

[[Page 106005]]

control facility-wide cancer risk remains greater than 100-in-1 million 
at two facilities.
6. Community-Based Risk Assessment
    We also conducted a community-based risk assessment for PEPO 
NESHAP-subject facilities. The goal of this assessment was to estimate 
cancer risk from HAP emitted from all local stationary point sources 
for which we have emissions data. We estimated the overall inhalation 
cancer risk due to emissions from all stationary point sources 
impacting census blocks within 10 km of the 25 PEPO production 
facilities. Specifically, we combined the modeled impacts from category 
and non-category HAP sources at PEPO production facilities, as well as 
other stationary point source HAP emissions. Within 10 km of PEPO 
NESHAP-subject facilities, we identified 823 non-source category 
facilities that could potentially also contribute to HAP inhalation 
exposures. Similar to the facility-wide risk assessment, the community-
based risk assessment uses post-control emissions from the processes 
subject to the HON to reflect the emissions reductions expected from 
the HON rulemaking that was signed in early 2024 (89 FR 42932).
    We first looked at what the maximum cancer risk is for communities 
around PEPO production facilities. The results indicate that the 
community-level maximum individual cancer risk is the same as both the 
source category MIR and the maximum individual cancer risk for the 
facility-wide assessment, 2,000-in-1 million. The community-based risk 
assessment estimated that greater than 99 percent of the community-
level maximum individual cancer risk is attributable to emissions from 
PEPO production facilities (including both source category and non-
category emissions). We then looked at the risks to the communities 
from all emissions sources for which we had data. Within 10 km, the 
population exposed to cancer risks greater than 100-in-1 million from 
all nearby emissions is approximately 5,300. For comparison, 
approximately 3,300 people have cancer risks greater than 100-in-1 
million due to PEPO production emissions and approximately 4,000 people 
have cancer risks greater than 100-in-1 million due to PEPO facility-
wide emissions (see table 2 of this preamble). The overall cancer 
incidence for this exposed population (i.e., populations with risks 
greater than 100-in-1 million living within 10 km of PEPO production 
facilities) is 0.02, with 84 percent of the cancer incidence from PEPO 
production processes, 9 percent from non-PEPO processes at PEPO 
production facilities (a total of 93 percent from PEPO production 
facilities), and 7 percent from other nearby stationary point sources 
that are not PEPO production facilities.
    The population exposed to cancer risks greater than or equal to 1-
in-1 million in the community-based assessment is approximately 1.2 
million people. For comparison, approximately 830,000 people have 
cancer risks greater than or equal to 1-in-1 million due to PEPO 
production process emissions and approximately 1.1 million people have 
cancer risks greater than 1-in-1 million due to PEPO facility-wide 
emissions (see table 2 of this preamble). The overall cancer incidence 
for this exposed population (i.e., people with risks greater than or 
equal to 1-in-1 million and living within 10 km of PEPO production 
facilities) is 0.4, with 34 percent of the incidence due to emissions 
from PEPO production processes, 30 percent from emissions of non-PEPO 
processes at PEPO production facilities (that is, a total of 64 percent 
from emissions from PEPO production facilities) and 36 percent from 
emissions from other nearby stationary sources that are not PEPO 
production facilities.
    After the controls proposed in this action are implemented for the 
PEPO Production source category (see section IV.B.2 of this preamble), 
the community-level maximum individual cancer risk will be reduced to 
the same as the facility-wide assessment, 300-in-1 million. The 
assessment estimated that 51 percent of the MIR is attributable to 
emissions from non-PEPO processes at a PEPO production facility, 43 
percent from PEPO processes and 6 percent from other nearby stationary 
point sources that are not PEPO production facilities. The population 
(within 10 km of PEPO facilities) exposed to cancer risks greater than 
100-in-1 million from all nearby emissions will be significantly 
reduced from 5,300 people to 500 people; a 91 percent reduction from 
the baseline. The populations exposed to cancer risks greater than 100-
in-1 million from the PEPO Production source category and facility-wide 
emissions are similarly reduced, from 3,300 people to 0 for source 
category emissions and from 4,000 to 200 for facility-wide emissions 
(see table 2 of this preamble). Furthermore, the overall cancer 
incidence for this exposed population is expected to be reduced from 
0.02 to 0.001. The percentage of cancer incidence due to emissions from 
PEPO processes is reduced from 84 percent to 28 percent. The percentage 
of the cancer incidence due to emissions from non-PEPO processes at 
PEPO production facilities and emissions from other nearby stationary 
sources proportionately shifts to 46 percent and 26 percent 
respectively. EtO emissions across these sources remain the largest 
source of incidence, accounting for 93 percent of the overall cancer 
incidence for this exposed population.
    The post-control population exposed to cancer risks greater than or 
equal to 1-in-1 million will be reduced from 1.2 million to 1.1 
million. In comparison, after the controls proposed in this action, the 
number of people with risks greater than or equal to 1-in-1 million due 
to source category emissions would reduce from 830,000 to 560,000 and 
due to facility-wide emissions from 1.1 million to 1 million (see table 
2 of this preamble). The overall cancer incidence for this exposed 
population is expected to be reduced from 0.4 to 0.3. The percentage of 
cancer incidence from PEPO processes is expected to decrease from 34 to 
11 percent. The cancer incidence from non-PEPO processes at PEPO 
production facilities and from other nearby stationary sources are 
expected to proportionately shift to 40 percent and 49 percent, 
respectively.
    More results from the community-based assessment are provided in 
the document titled Analysis of Demographic Factors For Populations 
Living Near Polyether Polyols (PEPO) Production Facilities--Community-
Based Assessment, which is available in the docket for this rulemaking.

[[Page 106006]]



    Table 2--Inhalation Cancer Risk Assessment Results for Communities Living Within 10 km of PEPO Production
                                                   Facilities
----------------------------------------------------------------------------------------------------------------
                                                                                      Estimated population at
                                                                      Maximum        increased risk of cancer
                         Risk assessment                            individual   -------------------------------
                                                                  cancer risk  (-    >100-in-1       >=1-in-1
                                                                   in-1 million)      million         million
----------------------------------------------------------------------------------------------------------------
                                             Baseline (Pre-control)
----------------------------------------------------------------------------------------------------------------
PEPO Production Source Category.................................           1,000           3,300         830,000
Facility-wide...................................................           2,000           4,000     1.1 million
Community-based.................................................           2,000           5,300     1.2 million
----------------------------------------------------------------------------------------------------------------
                            After Implementation of Proposed Controls (Post-control)
----------------------------------------------------------------------------------------------------------------
PEPO Production Source Category.................................             100               0         560,000
Facility-wide...................................................             300             200       1 million
Community-based.................................................             300             500     1.1 million
----------------------------------------------------------------------------------------------------------------

7. What demographic groups might benefit from this regulation?
    To examine the potential for EJ concerns, the EPA conducted three 
different demographic analyses: a proximity analysis, baseline cancer 
risk-based analysis (i.e., before implementation of any controls 
required by this proposed action), and post-control cancer risk-based 
analysis (i.e., after implementation of the controls required by this 
proposed action). The proximity demographic analysis is an assessment 
of individual demographic groups in the total population living within 
10 km (~6.2 miles) and 50 km (~31 miles) of the facilities. The 
baseline risk-based demographic analysis is an assessment of risks to 
individual demographic groups in the population living within 10 km and 
50 km of the facilities prior to the implementation of any controls 
required by this proposed action (``baseline''). The post-control risk-
based demographic analysis is an assessment of risks to individual 
demographic groups in the population living within 10 km and 50 km of 
the facilities after implementation of the controls required by this 
proposed action (``post-control''). Each of these demographic analyses 
were performed for the following three different HAP emissions 
scenarios: PEPO category HAP emissions (10 km and 50 km), whole-
facility HAP emissions (10 km and 50 km), and community HAP emissions 
(10 km only). Demographic groups included in the analyses are: White, 
Black, American Indian and Alaskan Native, other races and multiracial, 
Hispanic or Latino, children 17 years of age and under, adults 18 to 64 
years of age, adults 65 years of age and over, adults over 25 without a 
high school diploma, people living below the poverty level, people 
living below two times the poverty level, and linguistically isolated 
people. For a detailed discussion of the types of EJ analyses performed 
for this proposal and their results see section V.F of this preamble, 
``What analysis of environmental justice did we conduct?''

B. What are our proposed decisions regarding risk acceptability, ample 
margin of safety, and adverse environmental effect?

1. Risk Acceptability Under the Current MACT Standards
    As noted in section III.A of this preamble, we weigh a wide range 
of health risk measures and factors in our risk acceptability 
determination, including the cancer MIR, the number of persons in 
various cancer and noncancer risk ranges, cancer incidence, the maximum 
noncancer TOSHI, the maximum acute noncancer HQ, the extent of 
noncancer risks, the distribution of cancer and noncancer risks in the 
exposed population, and risk estimation uncertainties (54 FR 38044, 
September 14, 1989).
    Under the current MACT standards for the PEPO Production source 
category, the risk results indicate that the MIR is 1,000-in-1 million, 
driven by emissions of EtO, and well above 100-in-1 million, which is 
the presumptive limit of acceptability. The estimated incidence of 
cancer due to inhalation exposures is 0.3 excess cancer case per year. 
The population estimated to be exposed to cancer risks greater than 
100-in-1 million is approximately 3,300, and the population estimated 
to be exposed to cancer risks greater than or equal to 1-in-1 million 
is approximately 3.8 million. The estimated maximum chronic noncancer 
TOSHI from inhalation exposure for this source category is 0.1 (for 
respiratory effects). The acute risk screening assessment of reasonable 
worst-case inhalation impacts indicates a maximum acute noncancer HQ of 
1.
    Considering all of the health risk information and factors 
discussed above, particularly the high MIR for the PEPO Production 
source category, the EPA proposes that the risks for the source 
category are unacceptable. As noted in section II.A of this preamble, 
when risks are unacceptable, under the 1989 Benzene NESHAP approach and 
CAA section 112(f)(2)(A), the EPA must first determine the emissions 
standards necessary to reduce risk to an acceptable level, and then 
determine whether further HAP emissions reductions are necessary to 
provide an ample margin of safety to protect public health or to 
prevent, taking into consideration costs, energy, safety, and other 
relevant factors, an adverse environmental effect. Therefore, pursuant 
to CAA section 112(f)(2), we are proposing certain standards for 
emission sources of EtO in the PEPO Production source category that are 
more protective than the current PEPO NESHAP MACT standards.
2. Proposed Controls To Address Unacceptable Risks
    As previously discussed, we conducted a risk assessment of the PEPO 
Production source category because the 2016 revision to the EPA's IRIS 
inhalation URE for EtO showed that EtO is more toxic than previously 
known.
    For the PEPO Production source category, we identified EtO as the 
cancer risk driver from PEPO sources. We are aware of 20 PEPO 
facilities reporting EtO emissions in their emissions inventories from 
PEPO production processes. From our residual risk assessment, six 
facilities with emissions of EtO from process vents, storage vessels, 
equipment leaks, and wastewater have estimated cancer risks

[[Page 106007]]

greater than 100-in-1 million in nearby communities. Additionally, an 
allowable leak of EtO from a heat exchange system contributes to cancer 
risks greater than 100-in-1 million. Thus, to reduce emissions of EtO 
from PEPO processes, the EPA is proposing more stringent control 
requirements for process vents, storage vessels, equipment leaks, heat 
exchange systems, and wastewater that emit or have the potential to 
emit EtO. As discussed later in this preamble, we are proposing that 
these requirements will reduce risk to an acceptable level and provide 
an ample margin of safety to protect public health, and no additional 
requirements are needed to prevent an adverse environmental effect.
    We discuss the control options we evaluated for reducing EtO 
emissions from PEPO processes in sections IV.B.2.a through IV.B.2.e of 
this preamble.
a. Process Vents and Storage Vessels
    Process vents that emit EtO are primarily associated with reactors 
(from batch unit operations and continuous unit operations) that 
produce PEPO products using epoxides as a reactant. Other unit 
operations within the PMPU may also have process vents that emit EtO, 
such as process vents on condensers and distillation units.
    The PEPO NESHAP (40 CFR 63.1425) specifies control requirements for 
process vents, based on the PEPO polymerization process (i.e., 
polymerization using epoxides versus using THF). For PEPO processes 
that use epoxides as the reactant, the PEPO NESHAP specifies emissions 
limits for: (1) epoxide emissions, (2) nonepoxide organic HAP emissions 
from processes that use nonepoxide HAP to make or modify the product, 
and (3) nonepoxide organic HAP emissions from catalyst extraction. For 
the epoxide standards, the PEPO NESHAP (40 CFR 63.1425(b)) requires 
owners or operators to either: (1) reduce emissions at existing sources 
by 98 percent and new sources by 99.9 percent; (2) control emissions 
using a flare (existing sources only); (3) achieve an outlet 
concentration of 20 parts per million by volume (ppmv) or less; or (4) 
limit emissions to 1.69 x 10-2 kilogram of epoxide per 
megagram of product at existing sources and 4.43 x 10-3 
kilogram of epoxide per megagram of product at new sources. We provide 
more details about process vents in our technology review discussion 
(see section IV.C.3 of this preamble) including specifics about the 
process vent standards for nonepoxide organic HAP emissions from 
processes that use nonepoxide HAP to make or modify the product, and 
for nonepoxide organic HAP emissions from catalyst extraction.
    PEPO facilities use storage vessels to hold liquid and gaseous 
feedstocks for use in a process, as well as to store liquid and gaseous 
products from a process. Facilities typically store EtO under pressure 
as a liquified gas, but EtO may also be found in small amounts in 
atmospheric storage vessels storing liquid products that use EtO as a 
reactant in their production. Typical emissions from atmospheric 
storage tanks occur from working and breathing losses, while pressure 
vessels are considered closed systems and, if properly maintained and 
operated, should have virtually no emissions. In some instances, there 
may be low levels of fugitive emissions from pressure vessels, and 
pressure vessels storing liquefied gases may be vented periodically to 
purge inerts.
    The PEPO NESHAP (40 CFR 63.1432) cites the control provisions 
specified in the HON (40 CFR 63.119 through 63.123) which require 
owners or operators determine Group 1 or Group 2 designations of 
affected storage vessels, based on the volume of the storage vessel and 
maximum true vapor pressure (MTVP) of the material stored. Group 1 
storage vessels are those with capacities between 75 m\3\ (inclusive) 
and 151 m\3\ and a MTVP greater than or equal to 13.1 kilopascals 
(kPa), and those with capacities greater than or equal to 151 m\3\ and 
a MTVP greater than or equal to 5.2 kPa. The HON storage vessel 
standards that PEPO affected sources are currently subject to \30\ 
require Group 1 storage vessels to reduce total HAP emissions by 95 
percent (or 90 percent if the storage vessel was installed on or before 
December 31, 1992) by venting emissions through a closed vent system to 
any combination of control devices or to vent emissions through a 
closed vent system to a flare. Owners and operators of Group 1 storage 
vessels storing a liquid with a MTVP of total organic HAP less than 
76.6 kPa are also allowed to reduce organic HAP by utilizing an 
internal floating roof (IFR), an external floating roof (EFR), an EFR 
converted to an IFR, vapor balancing, or by routing the emissions to a 
process or a fuel gas system. For Group 1 storage vessels storing a 
liquid with a MTVP of total organic HAP greater than or equal to 76.6 
kPa, owners and operators can reduce organic HAP emissions by 95 
percent by venting emissions through a closed vent system to any 
combination of control devices, controlling emissions by routing them 
to a process or a fuel gas system, or by using vapor balancing. 
Pressure vessels (operating in excess of 204.9 kPa without emissions to 
the atmosphere) may also store materials with EtO. For storage vessels, 
the PEPO NESHAP, by reference to the HON, allows use of a design 
evaluation instead of a performance test to determine the percent 
reduction of control devices for any quantity of total uncontrolled 
organic HAP emissions being sent to the control device. We provide more 
details about storage vessels in our technology review discussion (see 
section IV.C.2 of this preamble).
---------------------------------------------------------------------------

    \30\ The HON requirements that were added in 2024 (89 FR 42932, 
May 16, 2024) apply to only the SOCMI source category; therefore, 
those 2024 HON amendments are currently not applicable to the PEPO 
Production source category. In other words, when we discuss the 
current PEPO NESHAP requirements that refer to HON, we mean pre-2024 
HON requirements.
---------------------------------------------------------------------------

    Based on results from the risk assessment, we determined that the 
current MACT standards for PEPO process vents and storage vessels do 
not result in sufficient control of EtO emissions to prevent 
unacceptable risk. For example, emissions of EtO from PEPO process 
vents and storage vessels contribute to 72 percent of one facility's 
maximum individual cancer risk of 500-in-1 million. Therefore, we 
evaluated available control technologies with a higher level of 
control, as discussed below.
    To lower the risk for PEPO facilities with EtO emissions, we 
analyzed a control option for process vents and storage vessels that 
are in EtO service which requires all process vents and storage vessels 
in EtO service to be controlled. This control option is based on 
requirements that were recently finalized in the MON and HON because of 
unacceptable risk (see 85 FR 49084, August 12, 2020, and 89 FR 42932, 
May 16, 2024, respectively). The definitions of process vents and 
storage vessels ``in ethylene oxide service'' from the MON and HON are 
presented here:
     For process vents, ``in ethylene oxide service'' means, 
when uncontrolled, each process vent contains a concentration of 
greater than or equal to 1 ppmv undiluted EtO, and when combined, the 
sum of all process vents within the process would emit uncontrolled EtO 
emissions greater than or equal to 5 lb/yr.
     For storage vessels of any capacity and vapor pressure, 
``in ethylene oxide service'' means that the concentration of EtO 
within the tank liquid is greater than or equal to 0.1 percent by 
weight.
    The MON and HON standards for process vents and storage vessels in 
EtO service, require owners and operators to route emissions through a 
closed vent

[[Page 106008]]

system to a: (1) control device that reduces EtO by at least 99.9 
percent by weight or to a concentration less than 1 ppmv for each 
process vent and storage vessel vent (or, for multiple process vents 
within a process, to less than 5 lb/yr for all combined process vents), 
or (2) flare meeting certain flare operating and monitoring 
requirements.
    To ensure emissions from PEPO affected sources are controlled to an 
acceptable level of risk under the PEPO NESHAP, we are proposing to 
incorporate the same EtO emissions standards for process vents and 
storage vessels from the MON and HON into the PEPO NESHAP. 
Specifically, we are proposing at 40 CFR 63.1423(b) to refer to subpart 
F of the HON which defines the term ``in ethylene oxide service'' for 
process vents to mean each process vent in a process that, when 
uncontrolled, contains a concentration of greater than or equal to 1 
ppmv undiluted EtO, and when combined, the sum of all these process 
vents within the process would emit uncontrolled EtO emissions greater 
than or equal to 5 pounds per year (lb/yr) (2.27 kilograms per year, 
kg/yr). We are also proposing to update the definition of ``process 
vent'' at 40 CFR 63.1423(b) to align with this proposed change. We are 
also proposing in the PEPO NESHAP at 40 CFR 63.1423(b) to refer to 
subpart F of the HON which defines the term ``in ethylene oxide 
service'' for storage vessels to mean that the concentration of EtO of 
the stored liquid is at least 0.1 percent by weight. We are also 
proposing that the exemption for ``vessels and equipment storing and/or 
handling material that contains no organic HAP, or organic HAP as 
impurities only'' listed in the definition of ``storage vessel'' at 40 
CFR 63.1423(b) does not apply for storage vessels in EtO service. We 
are proposing procedures for determining whether process vents and/or 
storage vessels are in EtO service within the proposed definition of 
the term ``in ethylene oxide service'' (by reference to 40 CFR 63.109 
for PEPO process vents and storage vessels in EtO service). We are 
proposing at 40 CFR 63.1425(g) that PEPO process vents in EtO service 
either reduce emissions of EtO by: (1) venting emissions through a 
closed vent system to a non-flare control device that reduces EtO by at 
least 99.9 percent by weight, or to a concentration less than 1 ppmv 
for each process vent, or to less than 5 lb/yr for all combined process 
vents within the process; or (2) routing emissions through a closed 
vent system to a flare meeting the proposed flare operating 
requirements discussed in section IV.D.1 of this preamble (see proposed 
40 CFR 63.1436). We are proposing at 40 CFR 63.1432(a) by reference to 
the HON (40 CFR 63.119(a)(5)) that PEPO storage vessels in EtO service 
either reduce emissions of EtO by: (1) venting emissions through a 
closed vent system to a non-flare control device that reduces EtO by at 
least 99.9 percent by weight or to a concentration less than 1 ppmv for 
each storage tank vent; or (2) venting emissions through a closed vent 
system to a flare meeting the proposed flare operating requirements 
discussed in section IV.D.1 of this preamble (see proposed 40 CFR 
63.1436). We are proposing procedures to determine compliance with 
these proposed EtO standards at 40 CFR 63.1426(g) (by reference to 40 
CFR 63.124 for PEPO process vents in EtO service) and 40 CFR 63.1432(v) 
(by reference to 40 CFR 63.124 for PEPO storage vessels in EtO 
service). In section IV.D.1 of this preamble, we recognized flares 
cannot achieve 99.9 percent EtO reduction. We also noted that as part 
of the CAA section 114 request, five facilities measured EtO emissions 
from their EtO emission points and only one of these five facilities 
currently use a flare to control EtO emissions from process vents or 
storage vessels. Even so, our modeling file does include several other 
PEPO facilities that do use flares to control process vents and storage 
vessels that emit EtO. Therefore, we accounted for these flares 
operating at 98 percent EtO reduction in our risk assessment and 
determined that it is not necessary for flares to achieve 99.9 percent 
EtO reduction to reduce risk to an acceptable level and provide an 
ample margin of safety to protect public health (provided that owners 
and operators still comply with the entire suite of EtO control 
requirements that we are proposing in this action).
    Additionally, we propose removing the option to allow use of a 
design evaluation in lieu of performance testing to demonstrate 
compliance for storage vessels in EtO service to ensure that the 
required level of control is achieved (see proposed 40 CFR 63.1432(v) 
by reference to the HON (40 CFR 63.124(a)(2)(i) and (b)(3))). We are 
also proposing that after promulgation of the rule, owners or operators 
that choose to control emissions with a non-flare control device 
conduct an initial performance test according to proposed 40 CFR 
63.1426(g) and 63.1432(v) by reference to the HON (40 CFR 63.124) on 
each existing control device in EtO service and on each newly installed 
control device in EtO service to verify performance at the required 
level of control. We are also proposing at 40 CFR 63.1426(g) and 
63.1432(v) by reference to the HON (40 CFR 63.124(b)) that owners or 
operators conduct periodic performance testing on non-flare control 
devices in EtO service every 5 years.
    Finally, we are proposing at 40 CFR 63.1427(a) that owners and 
operators may not use the extended cookout (ECO) pollution prevention 
technique to show compliance with the proposed standard for PEPO 
process vents in EtO service. The PEPO NESHAP at 40 CFR 63.1427(a) 
allows the use of ECO as a means of reducing epoxide emissions by the 
required percentage (98 or 99.9 percent) or complying with the 
production-based limit (<=1.69 x 10-2 or 4.43 x 
10-3 kilograms of epoxide emissions per megagram of product 
made). This pollution prevention technique reduces emissions by 
extending the time of reaction, thus leaving less unreacted epoxides to 
be emitted downstream. To demonstrate a percent efficiency, it is 
necessary to designate the basis, or the ``uncontrolled'' emissions, 
for assessing the percent reduction. The point where uncontrolled 
emissions are to be assessed, called the ``onset'' of the ECO, is 
defined in the PEPO NESHAP at 40 CFR 63.1427(c) as the point when the 
epoxide concentration in the reactor liquid is equal to 25 percent of 
the concentration of epoxide in the liquid at the end of the epoxide 
feed. Procedures to calculate epoxide emissions at the end of ECO are 
provided in 40 CFR 63.1427(d). The EPA determined the default onset of 
ECO based on CBI from the Society of the Plastics Industry, which 
indicated the economic breakpoint for when a cookout is no longer 
economically advantageous (see 62 FR 46804, September 4, 1997). 
However, new economic conditions suggest the ECO compliance option may 
no longer be viable. For instance, one facility reported, in response 
to the EPA's CAA section 114 request, that their customers require less 
than 1 ppm residual EtO, i.e., it is economically advantageous to 
continue the reaction until 1 ppm is reached. It is impractical to 
achieve a 99.9 percent reduction from an onset of 1 ppm. Additionally, 
using the current definition of onset, ECO could lead to high EtO 
emissions relative to the starting amount of epoxide used. Therefore, 
we believe it is not appropriate to continue allowing the ECO pollution 
prevention technique to demonstrate compliance with the proposed EtO 
emissions standards (i.e., reduce EtO by at least 99.9 percent by 
weight) that are intended to control

[[Page 106009]]

emissions from process vents and storage vessels to an acceptable risk 
level. We are also proposing that it is not appropriate to continue to 
allow the existing production-based limits (i.e., <=1.69 x 
10-2 or 4.43 x 10-3 kilograms of epoxide 
emissions per megagram of product made) in place of the new EtO 
emissions standards. The 1.69 x 10-3 production-based limit 
is an alternative to the 98 percent emission reduction standard for 
existing affected sources which is not as stringent as the proposed 
99.9 percent emission reduction standard for EtO. While the 4.43 x 
10-3 production-based limit is an alternative to the 99.9 
percent emission reduction standard for new affected sources, it is 
related to the aggregate reduction of total epoxide emissions and not 
specifically to EtO emissions. Additionally, it is not clear how these 
production-based limits (also referred to ``as emission factors'') were 
derived \31\ and we do not have enough information to set a new 
production-based limit that would be equivalent to the proposed EtO 
emissions standards.
---------------------------------------------------------------------------

    \31\ Although the original proposal for the PEPO NESHAP (62 FR 
46804, September 4, 1997) mentions that the method for determining 
these emission factors is detailed in the Supplementary Information 
Document, we could not locate this derivation in the document titled 
Hazardous Air Pollutant Emissions from the Production of Polyether 
Polyols--Supplementary Information Document for Proposed Standards.
---------------------------------------------------------------------------

    See the document titled Analysis of Control Options for Process 
Vents and Storage Vessels to Reduce Residual Risk of Ethylene Oxide in 
the PEPO Production Source Category, which is available in the docket 
for this action, for more information on the control option the EPA 
evaluated to reduce EtO risk from PEPO process vents and storage 
vessels.
b. Equipment Leaks
    Emissions of EtO from equipment leaks occur in the form of gases or 
liquids that escape to the atmosphere through connection points (e.g., 
threaded fittings) or through the moving parts of valves, pumps, 
compressors, PRDs, and certain types of process equipment. The PEPO 
NESHAP defines equipment leaks as ``emissions of organic HAP from a 
connector, pump, compressor, agitator, pressure relief device, sampling 
connection system, open-ended valve or line, valve, surge control 
vessel, bottoms receiver, or instrumentation system in organic HAP 
service.'' The equipment leak requirements apply to equipment that 
contain or contact material that are 5 percent by weight or more of 
organic HAP, operate 300 hours per year or more, and are not in vacuum 
service.
    The PEPO NESHAP requirements for equipment leaks directly reference 
the provisions in 40 CFR part 63, subpart H (which is part of the HON). 
The HON equipment leak requirements vary by equipment component type, 
but require LDAR using monitoring with EPA Method 21 of appendix A-7 to 
40 CFR part 60 at certain frequencies (e.g., monthly, quarterly, every 
2 quarters, annually) and varying leak definitions (e.g., 500 ppmv; 
1,000 ppmv; 10,000 ppmv) depending on the type of service (e.g., gas 
and vapor service or in light liquid service). The LDAR requirements 
for components in heavy liquid service include sensory monitoring and 
the use of EPA Method 21 monitoring if a leak is identified. We provide 
more details about equipment leaks in our technology review discussion 
(see section IV.C.5 of this preamble).
    Results from our risk assessment indicate that, for the source 
category MIR of 1,000-in-1 million, more than 20 percent is from 
emissions of EtO related to PEPO equipment leaks. We also note that the 
risk from EtO from PEPO equipment leaks at three facilities (including 
the facility driving the MIR) is >=100-in-1 million. To help reduce the 
risk associated with EtO emissions from equipment leaks in the PEPO 
Production source category, we performed a review of available measures 
for reducing EtO emissions from components that are most likely to be 
in EtO service, which include connectors (in gas and vapor service or 
light liquid service), pumps (in light liquid service), and valves (in 
gas or light liquid service). We identified options for further 
strengthening LDAR practices to find and repair equipment leaks from 
these three pieces of equipment more quickly, including lowering the 
leak definitions and/or requiring more frequent monitoring with EPA 
Method 21 of appendix A-7 to 40 CFR part 60, which align with the 
recently finalized EtO standards for equipment leaks in the HON (89 FR 
42932, May 16, 2024).
    For gas/vapor and light liquid connectors in EtO service, we 
identified two options: (1) require connector monitoring at a leak 
definition of 500 ppmv with annual monitoring and no reduction in 
monitoring frequency (i.e., no skip periods), and (2) require connector 
monitoring at a leak definition of 100 ppmv with annual monitoring and 
no reduction in monitoring frequency.
    For light liquid pumps in EtO service, we identified three options: 
(1) lower the leak definition from 1,000 ppmv to 500 ppmv with monthly 
monitoring, (2) lower the leak definition from 1,000 ppmv to 100 ppmv 
with monthly monitoring, or (3) require the use of leakless pumps 
(i.e., canned pumps, magnetic drive pumps, diaphragm pumps, pumps with 
tandem mechanical seals, pumps with double mechanical seals) with 
annual monitoring and a leak defined as any reading above background 
concentration levels.
    For gas/vapor and light liquid valves in EtO service, we identified 
two options: (1) require a leak definition of 500 ppmv with monthly 
monitoring and no reduction in monitoring frequency, and (2) lower the 
leak definition from 500 ppmv to 100 ppmv with monthly monitoring and 
no reduction in monitoring frequency.
    Due to the high residual risk for some of the facilities from 
equipment leaks of EtO and the potential need for greater emission 
reduction to meet an acceptable level of risk for the PEPO Production 
source category, we also evaluated a more stringent combined option 
which requires monthly monitoring for valves (in gas/vapor and light 
liquid service), connectors (in gas/vapor and light liquid service), 
and pumps (light liquid service) in EtO service at a leak definition of 
100 ppmv for valves and connectors and 500 ppmv for light liquid pumps 
using EPA Method 21 of appendix A-7 to 40 CFR part 60. This combined 
option also does not allow equipment in EtO service to be monitored 
less frequently with skip periods, nor does the option allow facilities 
to take advantage of the delay of repair provisions. We analyzed 
increasing the monitoring frequency to monthly for connectors because 
they are the most numerous equipment components at chemical facilities, 
and they are the most significant contribution to the baseline 
emissions from leaking equipment at the EtO-emitting facilities.
    For the component-specific control options, we calculated the EtO 
baseline emissions and emissions after implementation of controls for 
each facility using average volatile organic compound (VOC) emission 
rates for each component, and the component counts and the EtO weight 
percent of the process from the responses to the EPA's CAA section 114 
request. For the combined option of monthly monitoring of gas and light 
liquid valves and connectors at 100 ppmv and light liquid pumps at 500 
ppmv, we do not have emission factors to estimate reductions for 
increased monitoring frequencies for connectors. Where a simplified 
emission factor method for determining the potential reductions of 
applying the

[[Page 106010]]

option did not exist, we estimated emissions reductions based on the 
approach used in other rules,\32\ where detailed leak data or an 
assumed leak distribution were available. The equipment leaks model 
uses a Monte Carlo analysis to estimate emissions from EtO facility 
equipment leaks. The memorandum Analysis of Control Options for 
Equipment Leaks to Reduce Residual Risk of Ethylene Oxide in the PEPO 
Production Source Category, which is available in the docket for this 
action, provides a detailed discussion of the model.
---------------------------------------------------------------------------

    \32\ Gas Plant Equipment Leak Monte Carlo Model Code and 
Instructions. October 21, 2021. EPA Docket No. EPA-HQ-OAR-2021-0317. 
Control Options for Equipment Leaks at Gasoline Distribution 
Facilities. October 20, 2021. EPA Docket No. EPA-HQ-OAR-2020-0371.
---------------------------------------------------------------------------

    In this action, we are also proposing the same definition for the 
term ``in ethylene oxide service'' for equipment as used in the final 
amendments to the HON (89 FR 42932, May 16, 2024).\33\ For equipment 
leaks, we are proposing to define ``in ethylene oxide service'' in the 
PEPO NESHAP at 40 CFR 63.1423(b) (by reference to 40 CFR 63.101) to 
mean any equipment that contains or contacts a fluid (liquid or gas) 
that is at least 0.1 percent by weight of EtO. We are proposing 
procedures for determining whether equipment is in EtO service within 
the proposed definition of the term ``in ethylene oxide service'' (by 
reference to 40 CFR 63.109 for PEPO equipment in EtO service). We are 
proposing that any piece of equipment that is in ethylene oxide service 
is also in organic HAP service. For PEPO equipment in EtO service, to 
achieve greater emissions reductions to help meet an acceptable level 
of risk for the PEPO Production source category, we are proposing the 
following combined requirements: monitoring of connectors in gas/vapor 
and light liquid service at a leak definition of 100 ppmv on a monthly 
basis with no reduction in monitoring frequency or delay of repair; 
monthly monitoring of light liquid pumps at a leak definition of 500 
ppmv; and monthly monitoring of gas/vapor and light liquid valves at a 
leak definition of 100 ppmv with no reduction in monitoring frequency 
or delay of repair (see proposed 40 CFR 63.1434(a) by reference to the 
HON). The document titled Analysis of Control Options for Equipment 
Leaks to Reduce Residual Risk of Ethylene Oxide in the PEPO Production 
Source Category, which is available in the docket for this action, 
provides additional information on all evaluated control options to 
reduce EtO risk from PEPO equipment leaks.
---------------------------------------------------------------------------

    \33\ See 40 CFR 63.101.
---------------------------------------------------------------------------

c. Heat Exchange Systems
    Emissions of EtO from heat exchange systems occur due to corrosion 
or cracks in internal tubing materials, which allows some process 
fluids to mix or become entrained with the cooling water. Pollutants 
(e.g., EtO) in the process fluids may subsequently be released from the 
cooling water into the atmosphere when the water is exposed to air 
(e.g., in a cooling tower for closed-loop systems or trenches/ponds in 
a once-through system). The HON heat exchange system standards that 
PEPO affected sources are currently subject to require owners or 
operators to monitor heat exchange systems for leaks of process fluids 
into cooling water and take actions to repair leaks within 45 days if 
they are detected (facilities may delay the repair of leaks if they 
meet certain criteria). To comply with the provisions, owners or 
operators can use any method listed in 40 CFR part 136 to sample 
cooling water for leaks for the HAP listed in table 4 to subpart F 
(recirculating systems) and table 9 to subpart G (once-through systems) 
(and other representative substances such as total organic compounds 
(TOC) or VOC that can indicate the presence of a leak can also be 
used). In addition, owners or operators can monitor for leaks using a 
surrogate indicator (e.g., ion specific electrode monitoring, pH, 
conductivity), provided that they meet certain criteria in 40 CFR 
63.104(c). We provide more details about heat exchange systems in our 
technology review discussion (see section IV.C.1 of this preamble).
    For heat exchange systems, we found that, while we did not identify 
a report of EtO emissions from a PEPO heat exchange system leak, a 
model using representative leaks (and the current standards for 
monitoring and repair) indicated that a potential leak currently 
allowed by the PEPO NESHAP containing EtO from a facility's cooling 
tower could significantly contribute to unacceptable risk. Thus, we are 
proposing to use the same definition of the term ``in ethylene oxide 
service'' as used in the final amendments to the HON (89 FR 42932, May 
16, 2024). We are proposing in the PEPO NESHAP at 40 CFR 63.1423 to 
refer to subpart F of the HON which defines the term ``in ethylene 
oxide service'' for heat exchange systems to mean any heat exchange 
system in a process that cools process fluids (liquid or gas) that are 
0.1 percent or greater by weight of EtO. We are proposing procedures 
for determining whether heat exchange systems are in EtO service within 
the proposed definition of the term ``in ethylene oxide service'' (by 
reference to 40 CFR 63.109 for PEPO heat exchange systems in EtO 
service). We are proposing that any heat exchange system that is in 
ethylene oxide service is also in organic HAP service. To address risk 
from EtO allowable emissions due to PEPO heat exchange system leaks, we 
evaluated the following option for PEPO heat exchange systems ``in 
ethylene oxide service'' which: (1) requires use of the Modified El 
Paso Method (see section IV.C.1 of this preamble), (2) requires 
quarterly monitoring using the Modified El Paso Method, (3) reduces the 
allowed amount of repair time from 45 days after finding a leak to 15 
days from the sampling date, and (4) prohibits delay of repair. We also 
evaluated this same option except with varying monitoring frequencies 
(i.e., monthly and weekly) instead of quarterly. Using equation 7-2 
from appendix P of the Texas Commission on Environmental Quality's 
(TCEQ) Sampling Procedures Manual,\34\ model leak distributions and 
concentrations, and other model input parameters, we anticipate the 
quarterly option would reduce EtO emissions from leaking PEPO heat 
exchange systems by 54 percent because owners or operators would 
identify and repair leaks more quickly, which is needed to help reduce 
potential unacceptable risk from the PEPO Production source category. 
See section IV.B.4 of this preamble for an analysis of the monthly and 
weekly options to provide an ample margin of safety. We are proposing 
weekly monitoring at 40 CFR 63.1435(a) by reference to the HON (40 CFR 
63.104(g)(6)) based on that ample margin of safety analysis. The 
document titled Analysis of Control Options for Heat Exchange Systems 
to Reduce Residual Risk of Ethylene Oxide in the PEPO Production Source 
Category, which is available in the docket for this action, provides 
additional information on this evaluated control option to reduce EtO 
risk from PEPO heat exchange systems.
---------------------------------------------------------------------------

    \34\ See appendix B in the document titled: The Air Stripping 
Method (Modified El Paso Method) for Determination of Volatile 
Organic Compound (VOC) Emissions from Water Sources, which is 
included in the docket for this rulemaking.
---------------------------------------------------------------------------

d. Wastewater
    EtO is emitted from wastewater collection, storage, and treatment 
systems that are uncovered or open to the atmosphere through 
volatilization of the compound at the liquid surface. Emissions occur 
by diffusive or convective means, or both. Diffusion occurs when 
organic pollutant

[[Page 106011]]

concentrations at the water surface are much higher than ambient 
concentrations. The organic pollutants volatilize, or diffuse into the 
air, to reach equilibrium between the aqueous and vapor phases. 
Convection occurs when air flows over the water surface, sweeping 
organic vapors from the water surface into the air. The rate of 
volatilization is related directly to the speed of the air flow over 
the water surface.
    The HON wastewater standards that PEPO affected sources are 
currently subject to (40 CFR 63.1433 cites the control provisions 
specified in the HON at 40 CFR 63.132 through 63.147) divide wastewater 
streams into Group 1 wastewater streams, which require controls, and 
Group 2 wastewater streams, which generally do not require controls 
provided they do not exceed Group 1 thresholds. The Group 1 and Group 2 
designations for wastewater streams are based on volumetric flow rate 
and total annual average organic HAP concentration. The HON specifies 
performance standards for treating Group 1 wastewater streams using 
open or closed biological treatment systems or using a design steam 
stripper with vent control. For APCDs (e.g., thermal oxidizers) used to 
control emissions from collection system components, steam strippers, 
or closed biological treatment, the HON provides owners or operators 
several compliance options including achieving a 95-percent destruction 
efficiency, achieving a 20-ppmv outlet concentration, or implementing 
design specifications for temperature and residence time. We provide 
more details about wastewater streams in our technology review 
discussion (see section IV.C.4 of this preamble).
    The results from our risk assessment show that EtO emissions from 
wastewater contribute 77 percent of the source category MIR (the MIR is 
1,000-in-1-million), thus wastewater is one of the EtO emission sources 
contributing to the EPA's finding of unacceptable risk for the PEPO 
Production source category. To lower the risk for the PEPO facilities 
with EtO emissions, we are proposing at 40 CFR 63.1423(b) to use the 
same definition of the term ``in ethylene oxide service'' for 
wastewater as used in the recently amended HON (89 FR 42932, May 16, 
2024) which means any wastewater stream that contains total annual 
average concentration of EtO greater than or equal to 1 part per 
million by weight (ppmw) at any flow rate. We are proposing procedures 
for determining whether a wastewater stream is in EtO service within 
the proposed definition of the term ``in ethylene oxide service'' (by 
reference to 40 CFR 63.109 for PEPO wastewater streams in EtO service). 
We are also proposing, by reference to the amended HON, that a 
wastewater stream in EtO service would be considered a Group 1 
wastewater stream (see 40 CFR 63.1433(a)(23) and (27) and 
63.132(c)(1)(iii) and (d)(1)(ii)). In addition, we are proposing to 
update the definition of ``wastewater'' at 40 CFR 63.1423(b) to align 
with these proposed changes. As part of the management and treatment 
requirements for Group 1 wastewater streams, owners and operators would 
be required at 40 CFR 63.138(b)(3) and (c)(3) to reduce, by removal or 
destruction, the concentration of EtO to a level less than 1 ppmw. We 
anticipate that owners and operators will use stream stripping to 
comply with this proposed requirement. While we acknowledge EtO can be 
biodegraded, the compound is not on table 37 to subpart G of the HON, 
suggesting that it is not a readily biodegradable compound when using a 
biological treatment method, and EtO would need to be stripped out of 
the wastewater to meet the standard at 40 CFR 63.138(b)(3) and (c)(3). 
Therefore, we evaluated Control Option 1 using a steam stripper 
achieving a 98 percent reduction of EtO emissions (based on the 
fraction removed (Fr) value of EtO \35\ in table 9 to subpart G of the 
HON).
---------------------------------------------------------------------------

    \35\ The Fr is the fraction of a HAP that is stripped from 
wastewater and is an indicator of the extent to which a HAP is 
effectively removed during the steam stripping process, which for 
EtO is 98 percent.
---------------------------------------------------------------------------

    Additionally, we are aware that some chemical manufacturing 
facilities dispose of certain wastewater streams that contain EtO by 
adding those wastewaters to the cooling water of their heat exchange 
systems, rather than considering those EtO-containing streams to be 
potential sources of wastewater. To help reduce risk from the PEPO 
Production source category by eliminating these types of EtO emissions 
from wastewater being injected into heat exchange systems, we are also 
proposing to prohibit owners and operators from injecting water into or 
disposing of water through any heat exchange system in a PMPU meeting 
the conditions of 40 CFR 63.1420 if the water contains any amount of 
EtO, has been in contact with any process stream containing EtO, or the 
water is considered wastewater as defined in 40 CFR 63.1423 (see 40 CFR 
63.1435(i). The document titled Analysis of Control Options for 
Wastewater Streams to Reduce Residual Risk of Ethylene Oxide in the 
PEPO Production Source Category, which is available in the docket for 
this action, provides additional information on this evaluated control 
option to reduce EtO risk from PEPO wastewater streams.
e. Summary
    For process vents, storage vessels, equipment leaks, heat exchange 
systems, and wastewater, we considered the control options described 
above for reducing EtO risk from the PEPO Production source category 
that are associated with processes subject to the PEPO NESHAP. To 
reduce risk from the source category to an acceptable level, we propose 
to require control of EtO emissions from: (1) process vents, (2) 
storage vessels, (3) equipment leaks, (4) heat exchange systems, and 
(5) wastewater in EtO service, as defined in this proposal. For process 
vents and storage vessels in EtO service, we are proposing owners and 
operators reduce emissions of EtO by either: (1) venting emissions 
through a closed vent system to a non-flare control device that reduces 
EtO by greater than or equal to 99.9 percent by weight or to a 
concentration less than 1 ppmv for each process vent and storage 
vessel, or (2) venting emissions through a closed vent system to a 
flare meeting the proposed operating and monitoring requirements for 
flares (see section IV.D.1 of this preamble). For process vents, we are 
also proposing an annual limit of 5 lb/yr or less for all combined 
process vents as an alternative to the percent control and 
concentration options. For equipment leaks in EtO service, we are 
proposing the following combined requirements: monitoring of connectors 
in gas/vapor and light liquid service at a leak definition of 100 ppmv 
on a monthly basis with no reduction in monitoring frequency and no 
delay of repair; monthly monitoring of light liquid pumps at a leak 
definition of 500 ppmv; and monthly monitoring of gas/vapor and light 
liquid valves at a leak definition of 100 ppmv with no reduction in 
monitoring frequency and no delay of repair. For heat exchange systems 
in EtO service, we are proposing to require owners or operators to 
conduct more frequent leak monitoring (weekly instead of quarterly) and 
to repair leaks within 15 days from the sampling date (in lieu of the 
current 45-day repair requirement after receiving results of monitoring 
indicating a leak), and to not allow owners or operators to delay 
repairs. For wastewater in EtO service, we are proposing to revise the 
Group 1 wastewater stream threshold for sources to include wastewater 
streams in EtO service, and to prohibit owners and

[[Page 106012]]

operators from injecting wastewater in EtO service into or disposing of 
water through any heat exchange system in a PMPU.
    In all cases, we are proposing that, if information exists that 
suggests EtO could be present in these processes, then the emission 
source is considered to be in EtO service unless the owner or operator 
conducts the procedures specified in 40 CFR 63.109 to demonstrate that 
the emission source does not meet the definition of being in EtO 
service (see proposed definition of the term ``in ethylene oxide 
service'' at 40 CFR 63.1423(b) (by reference to 40 CFR 63.101) and 
proposed 40 CFR 63.1425(g) for process vents, 40 CFR 63.1432(v) for 
storage vessels, 40 CFR 63.1433(a)(27) for wastewater, 40 CFR 
63.1434(a)(6) for equipment leaks, and 40 CFR 63.1435(j) for heat 
exchange systems). Examples of information that could suggest EtO is 
present in a process stream include calculations based on safety data 
sheets, material balances, process stoichiometry, or previous test 
results provided the results are still relevant to the current 
operating conditions.
    Based on the proposed applicability thresholds, we expect that up 
to 21 PEPO facilities will be affected by one or more of the proposed 
EtO-specific standards; and we anticipate that all of these facilities 
will be subject to the process vent, storage vessel, equipment leak, 
heat exchange system, and wastewater EtO-specific provisions.
3. Determination of Risk Acceptability After Proposed Emission 
Reductions
    As noted in sections II.A.1 and III.A of this preamble and in the 
1989 Benzene NESHAP, the EPA sets standards under CAA section 112(f)(2) 
using a two-step approach, with an analytical first step to determine 
whether risks are acceptable. This determination ``considers all health 
information, including risk estimation uncertainty, and includes a 
presumptive limit on maximum individual lifetime [cancer] risk (MIR) of 
approximately 1 in 10 thousand'' (54 FR 38044, 38045/col. 1, September 
14, 1989). In the 1989 Benzene NESHAP, the EPA explained that ``[i]n 
establishing a presumption for MIR, rather than a rigid line for 
acceptability, the Agency intends to weigh it with a series of other 
health measures and factors'' (Id., at 38045/col. 3). ``As risks 
increase above this benchmark, they become presumptively less 
acceptable under section 112, and would be weighed with the other 
health risk measures and information in making an overall judgement on 
acceptability'' (Id.).
    Table 3 of this preamble presents the levels of emissions control 
proposed to address unacceptable risks for the PEPO Production source 
category, which includes reducing emissions of EtO for PEPO processes 
and requiring more stringent controls for process vents, storage 
vessels, equipment leaks, heat exchange systems, and wastewater without 
considering costs.
---------------------------------------------------------------------------

    \1\ Owners or operators can also use a flare that meets the 
proposed requirements at 40 CFR 63.1436 discussed in section IV.D.1 
of this preamble).
    \2\ Quarterly monitoring of heat exchange systems addresses the 
source category's unacceptable risk, but the EPA is proposing to 
require weekly monitoring to provide an ample margin of safety.

                    Table 3--EtO Risk Control Options for the PEPO Production Source Category
----------------------------------------------------------------------------------------------------------------
                                                                                                      Percent
      Emission source  (in EtO service)              Description of proposed control option        reduction of
                                                                                                  EtO  emissions
----------------------------------------------------------------------------------------------------------------
Process Vent.................................  Route emissions through a closed vent system to a            99.9
                                                non-flare control device \1\ that reduces EtO by
                                                greater than or equal to 99.9 percent by weight,
                                                to a concentration less than or equal to 1 ppmv
                                                for each process vent, or to less than 5 lb/yr
                                                for all combined process vents
Storage Vessel...............................  Route emissions through a closed vent system to a            99.9
                                                non-flare control device \1\ that reduces EtO by
                                                greater than or equal to 99.9 percent by weight
                                                or to a concentration less than or equal to 1
                                                ppmv
Equipment Leaks..............................  For equipment components that are in EtO service,              70
                                                monthly monitoring using EPA Method 21 of
                                                connectors in gas/vapor and light liquid service
                                                at a leak definition of 100 ppmv with no
                                                reduction in monitoring frequency and no repair
                                                delays; monthly monitoring of light liquid pumps
                                                at a leak definition of 500 ppmv; and monthly
                                                monitoring of gas/vapor and light liquid valves
                                                at a leak definition of 100 ppmv with no
                                                reduction in monitoring frequency and no delay
                                                of repair
Heat Exchange Systems........................  Quarterly \2\ monitoring for leaks using the                   54
                                                Modified El Paso Method and repair of leaks
                                                required no later than 15 days after the date
                                                sampling occurs.
Wastewater...................................  Control all wastewater with a total annual                     98
                                                average concentration of EtO greater than or
                                                equal to 1 ppmw at any flow rate as if it were a
                                                Group 1 wastewater
----------------------------------------------------------------------------------------------------------------

    For the PEPO Production source category, after implementation of 
the proposed controls to address unacceptable risks, the MIR is reduced 
to 100-in-1 million (down from 1,000-in-1 million) with no facilities 
or populations exposed to risk levels greater than 100-in-1 million. 
The population exposed to risk levels greater than or equal to 1-in-1 
million living within 50 km of affected facilities would be reduced 
from 3.8 million people to 1.7 million people. The total estimated 
cancer incidence for the source category of 0.3 (pre-control) is 
reduced to 0.08 (post-control) excess cancer cases per year. The 
maximum modeled chronic noncancer TOSHI for the source category remains 
unchanged. It is estimated to be 0.1 (for respiratory effects) with no 
populations estimated to be exposed to a TOSHI greater than 1. The 
estimated worst-case off-site acute exposures to emissions from the 
PEPO Production source category also remain unchanged, with a maximum 
modeled acute noncancer HQ of 1 based on the REL for methoxytriglycol 
(a glycol ether). Acute impacts are deemed negligible for HAP for which 
acute HQs are less than or equal to 1. Table 4 of this preamble 
summarizes the reduction in cancer risks associated with the source 
category based on the proposed controls. More detail is available in 
the document titled Residual Risk Assessment for the Polyether Polyols 
(PEPO) Production Source Category in Support of the 2024 Risk and

[[Page 106013]]

Technology Review Proposed Rule, which is available in the docket for 
this rulemaking.

     Table 4--Cancer Risks After Implementation of Proposed Control for the PEPO Production Source Category
----------------------------------------------------------------------------------------------------------------
                                                                    Population      Population
                Control scenario                    MIR (x-in-1      (>=1-in-1      (>100-in-1        Cancer
                                                     million)        million)        million)        incidence
----------------------------------------------------------------------------------------------------------------
Pre-Control Baseline............................           1,000       3,800,000           3,300             0.3
Post-Control....................................             100       1,700,000               0            0.08
----------------------------------------------------------------------------------------------------------------

    As noted earlier in this section, the EPA considers an MIR of 
``approximately 1-in-10 thousand'' (i.e., 100-in-1 million) to be the 
presumptive limit of acceptability (54 FR 38045, September 14, 1989) 
and the proposed controls lower the MIR of the PEPO Production source 
category to 100-in-1 million. This is a significant reduction from the 
pre-control MIR of 1,000-in-1 million. For noncancer effects, the EPA 
has not established under section 112 of the CAA a numerical range for 
risk acceptability as it has with carcinogens, nor has it determined 
that there is a bright line above which acceptability is denied. 
However, the Agency has established that, as exposure increases above a 
reference level (as indicated by a HQ or TOSHI greater than 1), 
confidence that the public will not experience adverse health effects 
decreases and the likelihood that an effect will occur increases.
    Therefore, considering all health information, including risk 
estimation uncertainty, the EPA proposes that the resulting risks after 
implementation of the proposed controls for the PEPO Production source 
category detailed in section IV.B.2 would be acceptable. We solicit 
comments on all the proposed control requirements to reduce risk to an 
acceptable level for the PEPO Production source category.
4. Ample Margin of Safety Analysis
    The second step in the residual risk decision framework is a 
determination of whether the emission standards proposed to achieve an 
acceptable risk level provide an ample margin of safety to protect 
public health, or whether more stringent emission standards would be 
required for this purpose. In making this determination, we considered 
the health risk and other health information considered in our 
acceptability determination, along with additional factors not 
considered in the risk acceptability step, including costs and economic 
impacts of controls, technological feasibility, uncertainties, and 
other relevant factors, consistent with the approach of the 1989 
Benzene NESHAP. Table 5 of this preamble summarizes the costs and EtO 
emission reductions we estimated for the proposed control requirements 
to reduce the risks to an acceptable level for the PEPO Production 
source category. For details on the assumptions and methodologies used 
in the costs and impacts analyses, see the technical documents titled, 
Analysis of Control Options for Process Vents and Storage Vessels to 
Reduce Residual Risk of Ethylene Oxide in the PEPO Production Source 
Category; Analysis of Control Options for Equipment Leaks to Reduce 
Residual Risk of Ethylene Oxide in the PEPO Production Source Category; 
Analysis of Control Options for Heat Exchange Systems to Reduce 
Residual Risk of Ethylene Oxide in the PEPO Production Source Category; 
and Analysis of Control Options for Wastewater Streams to Reduce 
Residual Risk of Ethylene Oxide in the PEPO Production Source Category, 
which are available in the docket for this rulemaking. We note that for 
three fugitive EtO emission sources (i.e., equipment leaks, heat 
exchange systems, and wastewater), the emission reductions (and 
subsequent cost effectiveness values for EtO) differ from reductions 
expected to occur from reported emissions inventories due to use of 
model plants, engineering assumptions made to estimate baseline 
emissions, and uncertainties in how fugitive emissions may have been 
calculated for reported inventories compared to our model plants 
analyses (see the aforementioned technical documents).

 Table 5--Nationwide EtO Emission Reductions and Cost Impacts for Control Options Considered for PEPO Processes
----------------------------------------------------------------------------------------------------------------
                                               Total capital       Total       EtO emission
               Control option                   investment      annualized      reductions    Cost-effectiveness
                                                   (MM$)      costs (MM$/yr)       (tpy)          ($/ton EtO)
----------------------------------------------------------------------------------------------------------------
A--Process Vent & Storage Vessel Controls...            2.55            2.91            10.8             269,400
B--Equipment Leak Controls..................            0.06            1.23            20.3              60,600
C--Heat Exchange System Controls............            0.21            0.36            12.1              29,800
D--Wastewater Controls......................            14.4            5.75             312              18,400
                                             -------------------------------------------------------------------
    Total (A + B + C + D)...................            17.2            10.2             355              28,700
----------------------------------------------------------------------------------------------------------------

    For the ample margin of safety analyses, we evaluated the cost and 
feasibility of available control technologies that could be applied to 
PEPO processes to reduce risks further, considering all of the health 
risks and other health information evaluated in the risk acceptability 
determination described above and the additional information that we 
can consider only in the ample margin of safety analysis (i.e., costs 
and economic impacts of controls, technological feasibility, 
uncertainties, and other relevant factors). We note that the EPA 
previously determined that the standards for the PEPO Production source 
category provide an ample

[[Page 106014]]

margin of safety to protect public health (79 FR 17340, March 27, 
2014), and that the most significant change since that determination 
was the revised 2016 IRIS inhalation URE for EtO. As such, we focused 
our ample margin of safety analysis on cancer risk for EtO since, even 
after application of controls needed to get risks to an acceptable 
level, EtO drives cancer risk and cancer incidence (i.e., 98 percent of 
remaining cancer incidence of 0.08 is from EtO) for the PEPO Production 
source category.
    For process vents, storage vessels, equipment leaks, and wastewater 
in the PEPO Production source category, we did not identify any other 
control options for EtO emissions beyond those proposed in this action 
to reduce risks to an acceptable level. Furthermore, the proposed EtO 
controls for process vents, storage vessels, equipment leaks, and 
wastewater to reduce risks to an acceptable level are far more 
stringent than other options we identified to control HAP generally 
(i.e., see sections IV.D and IV.C of this preamble). Therefore, we 
conclude that these controls to reduce EtO emissions from PEPO 
processes to reduce risks to an acceptable level would also provide an 
ample margin of safety to protect public health.
    For EtO emissions from leaks in heat exchangers, we found that 
weekly monitoring is a cost-effective option to provide an ample margin 
of safety. Considering the incremental cost effectiveness from 
quarterly to monthly ($197,200 per ton of EtO emissions reductions) and 
from monthly to weekly ($1,734,200 per ton of EtO emissions reductions) 
are within the range of accepted values of cost effectiveness for EtO 
reductions,\36\ we find it appropriate to propose the weekly option 
(which is required by the HON) to provide an ample margin of safety. 
For this reason, we are proposing weekly monitoring for leaks for heat 
exchange systems in EtO service using the Modified El Paso Method (see 
40 CFR 63.1435(a) by reference to the HON (40 CFR 63.104(g)(6)). If the 
owner or operator finds a leak, we are proposing to require repair of 
the leak to reduce the concentration or mass emissions rate below the 
applicable leak action level as soon as practicable, but no later than 
15 days after collecting the sample with no delay of repair allowed 
(see 40 CFR 63.1435(a) by reference to the HON (40 CFR 63.104(h)(6)). 
The document titled Analysis of Control Options for Heat Exchange 
Systems to Reduce Residual Risk of Ethylene Oxide in the PEPO 
Production Source Category, which is available in the docket for this 
action, provides additional information on this evaluated control 
option to reduce EtO risk from PEPO heat exchange systems. We solicit 
comments on the proposed control requirements to provide an ample 
margin of safety for the PEPO Production source category.
---------------------------------------------------------------------------

    \36\ See 89 FR 24110, April 5, 2024.
---------------------------------------------------------------------------

5. Adverse Environmental Effects
    Based on our screening assessment of environmental risk presented 
in section IV.A.4 of this preamble, we did not identify any areas of 
concern with respect to environmental risk. Therefore, we have 
determined that HAP emissions from the PEPO Production source category 
do not result in an adverse environmental effect, and we are proposing 
that it is not necessary to set a more stringent standard to prevent, 
taking into consideration costs, energy, safety, and other relevant 
factors, an adverse environmental effect.

C. What are the results and proposed decisions based on our technology 
review?

    In addition to the proposed EtO-specific requirements discussed in 
section IV.B.2 of this preamble, under CAA section 112(d)(6) we also 
evaluated developments in practices, processes, and control 
technologies for reducing HAP emissions from heat exchange systems, 
storage vessels, process vents, wastewater, and equipment leaks for 
processes subject to the PEPO NESHAP (see sections IV.C.1 through 
IV.C.5 of this preamble, respectively). We analyzed costs and emissions 
reductions for each emission source (e.g., process vents) and 
determined cost effectiveness (annualized cost/Mg or ton of emissions 
reduction) on a HAP basis. We also evaluated fenceline monitoring as a 
development in practices considered under CAA section 112(d)(6) for the 
purposes of managing fugitive emissions from sources subject to the 
PEPO NESHAP (see section IV.C.6 of this preamble).
1. Standards for Heat Exchange Systems
    Heat exchangers are devices or collections of devices used to 
transfer heat from process fluids to another process fluid (typically 
water) without intentional direct contact of the process fluid with the 
cooling fluid (i.e., non-contact heat exchanger). There are two types 
of heat exchange systems: closed-loop recirculation systems and once-
through systems. Closed-loop recirculation systems use a cooling tower 
to cool the heated water leaving the heat exchanger and then return the 
newly cooled water to the heat exchanger for reuse. Once-through 
systems typically use surface freshwater (e.g., from a nearby river) as 
the influent cooling fluid to the heat exchangers, and the heated water 
leaving the system is then discharged from the facility. At times, the 
internal tubing material of a heat exchanger can corrode or crack, 
allowing some process fluids to mix or become entrained with the 
cooling water. Pollutants in the process fluids may subsequently be 
released from the cooling water into the atmosphere when the water is 
exposed to air (e.g., in a cooling tower for closed-loop systems or 
trenches/ponds in a once-through system).
    The PEPO NESHAP at 40 CFR 63.1423 currently refers to the HON (40 
CFR 63.101) to define a heat exchange system as ``a device or 
collection of devices used to transfer heat from process fluids to 
water without intentional direct contact of the process fluid with the 
water (i.e., non-contact heat exchanger) and to transport and/or cool 
the water in a closed-loop recirculation system (cooling tower system) 
or a once-through system (e.g., river or pond water).'' We are 
proposing to delete the reference to the HON definition and instead 
define a heat exchange system in the PEPO NESHAP so it refers to a PMPU 
(see section IV.E.4 of this preamble). The definition also clarifies 
that: (1) for closed-loop recirculation systems, the heat exchange 
system consists of a cooling tower, all PMPU heat exchangers that are 
in organic HAP service serviced by that cooling tower, and all water 
lines to and from these process unit heat exchangers; (2) for once-
through systems, the heat exchange system consists of all heat 
exchangers that are in organic HAP service, servicing an individual 
PMPU and all water lines to and from these heat exchangers; (3) sample 
coolers or pump seal coolers are not considered heat exchangers for the 
purpose of this proposed definition and are not part of the heat 
exchange system; and (4) intentional direct contact with process fluids 
results in the formation of a wastewater. This definition also applies 
to heat exchange systems in EtO service as described in section 
IV.B.2.c of this preamble.
    The PEPO NESHAP requirements for heat exchange systems at 40 CFR 
63.1435, by reference to the HON (40 CFR 63.104), includes an LDAR 
program for owners or operators of certain heat exchange systems that 
do not meet one or more of the conditions in 40 CFR 63.104(a). The LDAR 
program specifies that owners or operators must monitor heat exchange 
systems for leaks of process fluids into cooling water and take actions 
to repair detected leaks

[[Page 106015]]

within 45 days. Owners or operators may delay the repair of leaks if 
they meet the applicable criteria in 40 CFR 63.104. The PEPO NESHAP 
allows owners or operators to use any method listed in 40 CFR part 136 
to sample cooling water for leaks for the HAP listed in table 4 to 40 
CFR part 63, subpart F (for HON) that is also listed in table 4 to 40 
CFR part 63, subpart PPP (recirculating systems) and table 9 to 40 CFR 
part 63, subpart G (for HON) that is also listed in table 4 to 40 CFR 
part 63, subpart PPP (once-through systems) (and other representative 
substances such as TOC or VOC that can indicate the presence of a leak 
can also be used). A leak in the heat exchange system is detected if 
the exit mean concentration of HAP (or other representative substance) 
in the cooling water is at least 1 ppmw or 10 percent greater than 
(using a one-sided statistical procedure at the 0.05 level of 
significance) the entrance mean concentration of HAP (or other 
representative substance) in the cooling water. Furthermore, the PEPO 
NESHAP allows owners or operators to monitor for leaks using a 
surrogate indicator (e.g., ion-specific electrode monitoring, pH, 
conductivity), provided that certain criteria in 40 CFR 63.104(c) are 
met. The PEPO NESHAP initially requires 6 months of monthly monitoring 
for existing heat exchange systems. Thereafter, the frequency can be 
reduced to quarterly. The leak monitoring frequencies are the same 
whether the owner or operator uses water sampling and analysis or 
surrogate monitoring to identify leaks.
    As part of our technology review, we reviewed the criteria in 40 
CFR 63.104 that exempt certain heat exchange systems from the LDAR 
requirements in the PEPO NESHAP to see if the exemptions were still 
reasonable to maintain. We identified two criteria in 40 CFR 63.104 
dealing with once-through heat exchange systems meeting certain 
National Pollution Discharge Elimination System (NPDES) permit 
conditions (i.e., 40 CFR 63.104(a)(3) and (4)) that warranted further 
assessment. Once-through heat exchange systems typically have systems 
open to the air (e.g., open sewer lines, trenches, and ponds) that are 
utilized to transport used cooling water to a discharge point (e.g., an 
outfall) of a facility. This cooling water can also be mixed with other 
sources of water (e.g., cooling water used in once-through heat 
exchange systems in non-PEPO processes, stormwater, treated wastewater, 
etc.) in sewers, trenches, and ponds prior to discharge from the plant. 
If this point of discharge from the plant is into a ``water of the 
United States,'' the facility is required to have a NPDES permit and to 
meet certain pollutant discharge limits. In reviewing the requirements 
of 40 CFR 63.104(a)(3), we find that there is a clear disconnect 
between having a NPDES permit that meets certain allowable discharge 
limits (i.e., 1 part per million by volume (ppmv) or less above 
influent concentration, or 10 percent or less above influent 
concentration, whichever is greater) at the discharge point of a 
facility (e.g., outfall) versus being able to adequately identify a 
leak from a once-through heat exchange system, given that these systems 
are open to the atmosphere prior to this discharge point and, 
therefore, any volatile HAP leaking from a once-through heat exchange 
system would likely be emitted to the atmosphere prior to the NPDES 
outfall. Similarly, while the requirements of 40 CFR 63.104(a)(4) allow 
facilities with once-through heat exchange systems that have certain 
requirements (i.e., the requirements of 40 CFR 63.104(a)(3) and (4)) 
incorporated into their NPDES permit to not comply with the 
requirements of 40 CFR 63.104(b) and 63.104(c), we find this exemption 
to be problematic. Specifically, the NPDES requirements at 40 CFR 
63.104(a)(4) lack the specificity of where a sample must be taken to 
adequately find and quantify a leak from a once-through heat exchange 
system (e.g., just prior to the outfall from the plant versus from the 
exit of the once-through heat exchange system prior to being open to 
atmosphere), what concentration and/or mass emissions rate constitutes 
a leak that must be fixed, how quickly a leak must be fixed, what 
pollutants must be adequately accounted for, and what test method(s)/
surrogates facilities are allowed. As such, we find 40 CFR 63.104(a)(4) 
to be inadequate in terms of being able to detect and repair leaks that 
are at least as equivalent to those that would be identified if once-
through heat exchange systems were complying with 40 CFR 63.104(b) or 
(c) instead. Therefore, for purposes of demonstrating continuous 
compliance with the underlying MACT standard, we are proposing at 40 
CFR 63.1435(a), by reference to 40 CFR 63.104(a)(4)(v), to remove the 
exemptions for once-through heat exchange systems meeting certain NPDES 
permit conditions at 40 CFR 63.104(a)(3) and (4) and instead to require 
that facilities comply with the requirements of 40 CFR 63.104(b) and 
63.104(c).
    Our technology review identified one development in LDAR practices 
and processes for heat exchange systems (i.e., broader than our review 
of heat exchange systems in EtO service discussed in section IV.B.2.c 
of this preamble): the use of the Modified El Paso Method \37\ to 
monitor for leaks. The Modified El Paso Method is included in the HON, 
MON, EMACT standards, the Petroleum Refinery Sector rule, and in the 
RACT/BACT/LAER clearinghouse database. TCEQ also requires the method 
for facilities complying with TCEQ's highly reactive volatile organic 
compound (HRVOC) rule (i.e., 30 Texas Administrative Code Chapter 115, 
Subchapter H, Division 3). The Modified El Paso Method measures a 
larger number of compounds than the current methods required in the 
PEPO NESHAP and is more effective in identifying leaks. For LDAR 
programs applied to heat exchange systems, the compliance monitoring 
option, leak definition, and frequency of monitoring for leaks are all 
important considerations affecting emission reductions because they 
identify when there is a leak and when to take corrective actions to 
repair the leak. Therefore, we evaluated the Modified El Paso Method 
for use at PEPO facilities, including an assessment of appropriate leak 
definitions and monitoring frequencies.
---------------------------------------------------------------------------

    \37\ The Modified El Paso Method uses a dynamic or flow-through 
system for air stripping a sample of the water and analyzing the 
resultant off-gases for VOC using a flame ionization detector (FID) 
analyzer. The method is described in detail in appendix P of the 
TCEQ's Sampling Procedures Manual: The Air Stripping Method 
(Modified El Paso Method) for Determination of Volatile Organic 
Compound (VOC) Emissions from Water Sources. Appendix P is included 
in the docket for this rulemaking.
---------------------------------------------------------------------------

    To identify an appropriate Modified El Paso Method leak definition 
for facilities subject to the PEPO NESHAP, we identified five rules 
(i.e., TCEQ HRVOC rule, the HON, the MON, the EMACT standards, and the 
Petroleum Refinery Sector rule) that incorporate this monitoring method 
and have leak definitions corresponding to the use of this methodology. 
We also reviewed data submitted in response to a CAA section 114 
request for PEPO production facilities. The TCEQ HRVOC rule, the HON, 
the MON, EMACT standards, and the Petroleum Refinery Sector rule have 
leak definitions of total strippable hydrocarbon concentration (as 
methane) in the stripping gas ranging from 3.1 ppmv to 6.2 ppmv. In 
addition, sources subject to the HON, the MON, EMACT standards, or the 
Petroleum Refinery Sector rule must repair a leak no later than 45 days 
after first identifying the leak and cannot delay the repair of leaks 
for more than 30 days where, during subsequent monitoring, owners or

[[Page 106016]]

operators find a total strippable hydrocarbon concentration (as 
methane) in the stripping gas of 62 ppmv or higher. Taking into account 
the range of actionable leak definitions in use by other rules that 
require use of the Modified El Paso Method currently (i.e., 3.1 ppmv to 
6.2 ppmv of total strippable hydrocarbon (as methane) in the stripping 
gas), we chose to evaluate a leak definition at the upper end of 
identified actionable leak definitions in our analysis. Thus, we 
evaluated the Modified El Paso Method leak definition of 6.2 ppmv of 
total strippable hydrocarbon concentration (as methane) in the 
stripping gas for both new and existing heat exchange systems, along 
with not allowing delay of repair of leaks for more than 30 days where, 
during subsequent monitoring, a total strippable hydrocarbon 
concentration (as methane) in the stripping gas of 62 ppmv or higher is 
found.
    We also considered more stringent monitoring frequencies. Both the 
Petroleum Refinery Sector rule, which includes monthly monitoring for 
existing sources under certain circumstances, and the TCEQ HRVOC rule, 
which includes continuous monitoring provisions for existing and new 
sources, have more stringent monitoring frequencies. However, the 
petroleum refinery rule analysis found the incremental HAP cost 
effectiveness to change from quarterly to monthly monitoring and 
monthly to continuous monitoring (at the same leak definition) of 
refinery heat exchange systems to be $40,000/ton and $500,000/ton, 
respectively. We conclude that these costs are not reasonable for PEPO 
facilities. Thus, we chose to evaluate quarterly monitoring for 
existing and new heat exchange systems (i.e., the base monitoring 
frequency currently in the rule). We also evaluated monthly monitoring 
to confirm the anticipated higher incremental HAP cost effectiveness.
    Based on this technology review, we identified the following 
control options for heat exchange systems as a development in practice 
that can be implemented at a reasonable cost: (1) quarterly monitoring 
for existing and new heat exchange systems (after an initial 6 months 
of monthly monitoring) with the Modified El Paso Method and a leak 
definition of 6.2 ppmv of total strippable hydrocarbon concentration 
(as methane) in the stripping gas, and (2) same as Control Option 1, 
except monthly monitoring with the Modified El Paso Method instead of 
quarterly monitoring.
    We then estimated the impacts of these control options assuming 24 
PEPO facilities \38\ would be affected by requiring the use of the 
Modified El Paso Method. As part of our analysis, we assumed owners or 
operators conducting monitoring for three or more heat exchange systems 
would elect to purchase a stripping column and FID analyzer and perform 
in-house Modified El Paso monitoring because the total annualized costs 
for in-house Modified El Paso monitoring are less than the costs for 
contracted services. In addition, we assumed that owners or operators 
could repair leaks by plugging a specific heat exchanger tube, and if a 
heat exchanger is leaking to the extent that it needs to be replaced, 
then it is effectively at the end of its useful life. Therefore, we 
determined that the cost of replacing a heat exchanger is an 
operational cost that would be incurred by the facility as a result of 
routine maintenance and equipment replacement, and it is not 
attributable to the control option.
---------------------------------------------------------------------------

    \38\ We note that while there are 25 PEPO facilities, one PEPO 
facility is currently co-located with a HON facility. This facility 
is a small business that only receives and treats wastewater. 
Therefore, we do not expect this facility to have heat exchange 
systems on site.
---------------------------------------------------------------------------

    Table 6 of this preamble presents the nationwide impacts for 
requiring owners or operators at PEPO facilities to use the Modified El 
Paso Method quarterly or monthly (Control Options 1 and 2), and repair 
leaks of total strippable hydrocarbon concentration (as methane) in the 
stripping gas of 6.2 ppmv or greater. See the document titled Clean Air 
Act Section 112(d)(6) Technology Review for Heat Exchange Systems 
Located in the PEPO Production Source Category that are Associated with 
Processes Subject to the PEPO NESHAP, which is available in the docket 
for this rulemaking, for details on the assumptions and methodologies 
used in this analysis.

          Table 6--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for Heat Exchange Systems at PEPO Facilities
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                              Average
                                                            Total        Total        Total      Total HAP    Average HAP    Average HAP    incremental
                                                           capital     annualized   annualized    emission       cost-          cost-        HAP cost-
                     Control option                       investment   costs w/o     costs w/    reductions  effectiveness  effectiveness  effectiveness
                                                             ($)      credits ($/  credits ($/     (tpy)     w/credits ($/   w/o credits   w/credits ($/
                                                                          yr)          yr)                        ton)         ($/ton)          ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1......................................................       54,700       30,700       10,400         17.4           600          1,800   .............
2......................................................      492,400       82,200       61,200         18.0         3,400          4,500         80,400
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Based on the costs and emission reductions for the identified 
control options, we are proposing Control Option 1 to revise the PEPO 
NESHAP for heat exchange systems pursuant to CAA section 112(d)(6). We 
are not proposing Control Option 2 because it is not cost-effective 
given the high incremental total HAP cost effectiveness (i.e., $80,400/
ton HAP) from Control Option 1. We are proposing Control Option 1 at 40 
CFR 63.1435, by reference to the HON (40 CFR 63.104(g)(4)),\39\ to 
specify quarterly monitoring for existing and new heat exchange systems 
(after an initial 6 months of monthly monitoring) using the Modified El 
Paso Method and a leak definition of 6.2 ppmv of total strippable 
hydrocarbon concentration (as methane) in the stripping gas. We are 
proposing to require owners and operators to repair the leak to reduce 
the concentration or mass emissions rate to below the leak action level 
as soon as practicable, but no later than 45 days after identifying the 
leak. We are also proposing, by reference to 40 CFR 63.104(j)(3), a 
delay of repair action level of total strippable hydrocarbon 
concentration (as methane) in the stripping gas of 62 ppmv, that if 
exceeded during leak monitoring, would require immediate repair (i.e., 
the leak found cannot be put on delay of repair and would be required 
to be repaired within 30 days of the monitoring event). This would 
apply to both monitoring heat exchange systems and individual

[[Page 106017]]

heat exchangers by replacing the use of any 40 CFR part 136 water 
sampling method with the Modified El Paso Method and removing the 
option that allows for use of a surrogate indicator of leaks. We are 
also proposing, by reference to 40 CFR 63.104(h) and (i), that repair 
include re-monitoring at the monitoring location where a leak is 
identified to ensure that any leaks found are fixed. We are proposing 
that none of these requirements would apply to heat exchange systems 
that have a maximum cooling water flow rate of 10 gallons per minute or 
less because owners and operators of smaller heat exchange systems 
would be disproportionately affected and forced to repair leaks with a 
much lower potential HAP emissions rate than owners and operators of 
heat exchange systems with larger recirculation rate systems. Finally, 
we are proposing by reference to 40 CFR 63.104(l) that the leak 
monitoring requirements for heat exchange systems at 40 CFR 63.104(b) 
may be used in limited instances, instead of using the Modified El Paso 
Method, to monitor for leaks. We continue to maintain that the Modified 
El Paso Method is the preferred method to monitor for leaks in heat 
exchange systems and we are proposing that the requirements of 40 CFR 
63.104(b) may only be used if 99 percent by weight or more of all the 
organic compounds that could potentially leak into the cooling water 
have a Henry's Law Constant less than 5.0E-6 atmospheres per mole per 
cubic meter (atm-m\3\/mol) at 25[deg] Celsius. As noted in the proposal 
for the HON amendments (88 FR 25080), we selected this threshold based 
on a review of Henry's Law Constants for the HAP listed in table 4 to 
40 CFR part 63, subpart F, as well as the water-soluble organic 
compounds listed in a recent alternative monitoring request from a MON 
facility.\40\ Henry's Law Constants are available from the EPA at 
https://comptox.epa.gov/dashboard/. Examples of HAP that have a Henry's 
Law Constant less than 5.0E-6 atm-m\3\/mol at 25[deg] Celsius are: 
aniline; 2-chloroacetophenone; diethylene glycol diethyl ether; 
diethylene glycol dimethyl ether; dimethyl sulfate; 2,4-dinitrotoluene; 
1,4-dioxane; ethylene glycol monoethyl ether acetate; ethylene glycol 
monomethyl ether acetate; methanol; and toluidine. Many of these HAP 
also have very high boiling points, with most above 300 [deg]F, which 
means they will generally stay in the cooling water and not be emitted 
to the atmosphere. We solicit comments on the proposed requirements 
related to heat exchange systems.
---------------------------------------------------------------------------

    \39\ We note that each of the HON citations mentioned in this 
paragraph of this preamble are also applicable to PEPO facilities 
pursuant to 40 CFR 63.1435. For these HON citations to properly 
apply to PEPO facilities, we are proposing substitution rule text at 
40 CFR 63.1435(f) and (g).
    \40\ In May 2021, EPA Region 4 received a request from Eastman 
Chemical Company to perform an alternative method instead of the 
Modified El Paso Method to monitor for leaks in Eastman's Tennessee 
Operations heat exchange systems, which primarily have cooling water 
containing soluble HAP with a high boiling point. Eastman 
specifically identified two HAP (1,4-dioxane and methanol), which do 
not readily strip out of water using the Modified El Paso Method. 
Eastman's application for alternative monitoring included 
experimental data showing that the Modified El Paso Method would 
likely not identify a leak of these HAP in heat exchange system 
cooling water. Eastman conducted Modified El Paso Method monitoring 
under controlled scenarios to determine how much methanol and 1,4-
dioxane would be detected. The scenarios included solutions of water 
and either methanol or 1,4-dioxane at concentrations of 1 ppmw, 20 
ppmw, and 100 ppmw (as measured using water sampling methods allowed 
previously in the MON). The Modified El Paso Method did not detect 
any methanol or 1,4-dioxane from the 1 ppmw and 20 ppmw solutions 
(i.e., methanol and 1,4-dioxane did not strip out of the water in 
detectable amounts). The Modified El Paso Method detected very 
little HAP from the 100-ppmw solutions, with a maximum of only 0.17 
percent of the 1,4-dioxane stripping out and being detected.
---------------------------------------------------------------------------

2. Standards for Storage Vessels
    Storage vessels are used to store liquid and gaseous feedstocks for 
use in a process, as well as to store liquid and gaseous products from 
a process. Most PEPO storage vessels are designed for operation at 
atmospheric or near atmospheric pressures; pressure vessels are used to 
store compressed gases and liquefied gases. Atmospheric storage vessels 
are typically cylindrical with a vertical orientation, and they are 
constructed with either a fixed roof or a floating roof. Some, 
generally small, atmospheric storage vessels are oriented horizontally. 
Pressure vessels are either spherical or horizontal cylinders.
    The HON storage vessel standards that PEPO affected sources are 
currently subject to, by reference to NESHAP subpart G at 40 CFR 63.119 
through 63.123, require that owners and operators control emissions 
from storage vessels with capacities between 75 m\3\ (inclusive) and 
151 m\3\ and a MTVP greater than or equal to 13.1 kPa, and storage 
vessels with capacities greater than or equal to 151 m\3\ and a MTVP 
greater than or equal to 5.2 kPa. Storage vessels meeting these 
capacity and size criteria capacity are considered Group 1 storage 
vessels. Generally, the standards in the PEPO NESHAP for storage 
vessels refer to the provisions in the HON. As such, owners and 
operators of PEPO Group 1 storage vessels storing a liquid with a MTVP 
of total organic HAP less than 76.6 kPa must reduce emissions of 
organic HAP by 95 percent (or 90 percent if the storage vessel was 
installed on or before September 4, 1997) using a closed vent system 
and control device, or reduce organic HAP emissions either by utilizing 
an IFR or EFR, routing the emissions to a process or a fuel gas system, 
or through vapor balancing. Owners and operators of PEPO Group 1 
storage vessels containing a liquid with a MTVP of total organic HAP 
greater than or equal to 76.6 kPa must reduce emissions of organic HAP 
by 95 percent (or 90 percent if the storage vessel was installed on or 
before September 4, 1997) utilizing a closed vent system and control 
device, or reduce organic HAP emissions by routing the emissions to a 
process or a fuel gas system, or using vapor balancing. In general, 
PEPO storage vessels that do not meet the MTVP and capacity thresholds 
described above are considered Group 2 storage vessels and owners or 
operators are not required to apply any additional emission controls 
provided they remain under Group 1 thresholds; however, Group 2 storage 
vessels are subject to certain monitoring, reporting, and recordkeeping 
requirements to ensure that they were correctly determined to be Group 
2 storage vessels and that they remain in Group 2.
    As part of our technology review for PEPO storage vessels (i.e., 
broader than our review of storage vessels in EtO service discussed in 
section IV.B.2.a of this preamble), we identified the following 
emission reduction options: (1) revising the capacity and MTVP 
thresholds of the PEPO NESHAP to reflect the HON existing source 
threshold which requires existing storage vessels between 38 m\3\ 
(inclusive) and 151 m\3\ with an MTVP greater than or equal to 6.9 kPa 
to reduce emissions of organic HAP by 95 percent utilizing a closed 
vent system and control device, or reduce organic HAP emissions either 
by utilizing an IFR, an EFR, by routing the emissions to a process or a 
fuel gas system, or using vapor balancing; (2) same as Control Option 1 
plus requiring upgraded deck fittings \41\ and controls for guidepoles 
for all storage vessels equipped with an IFR as already required in 40 
CR 63, subpart WW (NESHAP for Storage Vessels--Control Level (2); and 
(3) in addition to requirements specified in Control Options 1 and 2, 
requiring the conversion of EFRs to IFRs through use of geodesic domes 
and upgrades to deck fittings and guidepoles.
---------------------------------------------------------------------------

    \41\ Require all openings in an IFR (except those for automatic 
bleeder vents (vacuum breaker vents), rim space vents, leg sleeves, 
and deck drains) be equipped with a deck cover; and require the deck 
cover to be equipped with a gasket between the cover and the deck.
---------------------------------------------------------------------------

    We identified Control Option 1 as a technologically feasible 
development in practices, processes, and control

[[Page 106018]]

technologies for storage vessels used at PEPO facilities because it 
reflects requirements for similar storage vessels that are located at 
chemical manufacturing facilities subject to the HON. Control Option 2 
is an improvement in practices because these upgraded deck fittings and 
guidepole controls have been required by other regulatory agencies and 
other EPA regulatory action (e.g., Petroleum Refinery Sector 
rulemaking) since promulgation of the PEPO NESHAP. Finally, we consider 
Control Option 3 to be a development in control technology because we 
found that some storage vessels with EFRs have installed geodesic domes 
since promulgation of the PEPO NESHAP.
    We used information about storage vessel capacity, design, and 
stored materials that industry provided to the EPA in response to our 
CAA section 114 request (see section II.C of this preamble) to evaluate 
the impacts of all three of the options presented. We did not identify 
any PEPO storage vessels from our CAA section 114 request that would be 
impacted by Control Option 1. Given that materials used in PEPO 
production have very low vapor pressures, the majority of PEPO Group 2 
storage vessels do not meet the vapor pressure portion of the revised 
Control Option 1 applicability. Furthermore, our CAA section 114 
request data shows zero Group 2 storage vessels fitted with an IFR or 
EFR, meaning no additional storage vessels would be affected by Control 
Option 2 or 3. To verify these findings, we conducted an air permit 
review alongside analysis of our CAA section 114 request data to 
identify any additional Group 2 storage vessels at PEPO facilities 
outside of the CAA section 114 respondents. We reviewed title V permits 
for the remaining 16 facilities subject to the PEPO NESHAP and 
determined that no additional Group 2 storage vessels would be affected 
by any of the aforementioned options. Based on these analyses, we 
estimate that applying any of the aforementioned options to the PEPO 
NESHAP would not result in cost impacts or emission reductions for PEPO 
facilities. See the document titled Clean Air Act Section 112(d)(6) 
Technology Review for Storage Vessels Located in the PEPO Production 
Source Category that are Associated with Processes Subject to the PEPO 
NESHAP, which is available in the docket for this rulemaking, for 
details on the assumptions and methodologies used in this analysis.
    We are proposing storage vessel Control Option 2 (which includes 
Control Option 1), pursuant to CAA section 112(d)(6), to revise the 
Group 1 storage capacity criterion for PEPO storage vessels at new and 
existing sources from between 75 m\3\ (inclusive) and 151 m\3\ to 
between 38 m\3\ (inclusive) and 151 m\3\ (see proposed table 3 to 40 
CFR part 63, subpart PPP), and to require upgraded deck fittings and 
controls for guidepoles for all storage vessels equipped with an IFR as 
already required in 40 CFR part 63, subpart WW (see proposed 40 CFR 
63.1432 which refers to the HON including 40 CFR 63.119(b)(5)(ix), (x), 
(xi), and (xii)). We note that the EPA recently finalized these same 
options for the HON, finding them to be cost effective for HON storage 
vessels (see 89 FR 42932, May 16, 2024). Given that the PEPO NESHAP 
directly references the HON storage vessel provisions (40 CFR part 63, 
subpart G), we believe it is reasonable for PEPO facilities to comply 
with these same final HON provisions. Although we did not find any PEPO 
storage vessels that would be affected by these proposed provisions, we 
believe it would be unnecessarily cumbersome to exclude these vessels 
by caveat in the storage vessel provisions of the PEPO NESHAP. Also, 
given that the EPA determined that Control Option 3 was not cost 
effective and did not propose this option for HON storage vessels, we 
are not proposing to revise the PEPO NESHAP to reflect the requirements 
of Control Option 3 pursuant to CAA section 112(d)(6). Materials used 
in PEPO production have very low vapor pressures so we anticipate that 
the cost effectiveness of Control Option 3 would be worse for PEPO 
storage vessels. We also anticipate that EFR storage vessels would not 
be considered for any new PEPO affected sources given we did not 
identify any existing EFR storage vessels subject to the PEPO NESHAP. 
We solicit comments on the proposed revisions for storage vessels.
3. Standards for Process Vents
    A process vent is a gas stream that is discharged during the 
operation of a particular unit operation (e.g., separation processes, 
purification processes, mixing processes, reaction processes). The gas 
stream(s) may be routed to other unit operations for additional 
processing (e.g., a gas stream from a reactor that is routed to a 
distillation column for separation of products), sent to one or more 
recovery devices, sent to a process vent header collection system 
(e.g., blowdown system) and APCD (e.g., flare, thermal oxidizer, carbon 
adsorber), and/or vented to the atmosphere. Process vents may be 
generated from continuous and/or batch operations, as well as from 
other intermittent types of operations (e.g., maintenance operations). 
If process vents are required to be controlled prior to discharge to 
the atmosphere to meet an applicable emissions standard, then they are 
typically collected and routed to an APCD through a closed vent system.
    The PEPO NESHAP specifies process vent control provisions for 
affected sources depending on the type of PEPO production process used: 
(1) polymerization of epoxides, or (2) polymerization of THF. 
Typically, PEPO processes that use epoxide reactants are batch 
processes, although some epoxide reactions are continuous, while 
production processes that use THF are continuous. For the PEPO 
production processes that use epoxides as a reactant, the NESHAP groups 
the process vent control provisions based on the function of the 
organic HAP in the production process and the resulting HAP emissions. 
Table 7 of this preamble shows the process vent emission standards of 
the PEPO NESHAP for each of these groups for existing and new affected 
sources.

Table 7--Process Vent Emission Standards in the PEPO NESHAP for Affected Sources That Produce PEPO Using Epoxide
                                                    Reactants
----------------------------------------------------------------------------------------------------------------
                                           Process vent standards for existing       Process vent standards for
          Process vent group                        affected sources                    new affected sources
----------------------------------------------------------------------------------------------------------------
Epoxides emissions...................   98-percent aggregate reduction of   99.9 percent
                                        total epoxide emissions; \1\                aggregate reduction of total
                                        flare total epoxide emissions;      epoxide emissions; \1\
                                        maintain an outlet concentration    maintain an outlet
                                        of <=20 ppmv of total epoxides or TOC; or   concentration <=20 ppmv of
                                        maintain <=1.69 x 10-2 kilograms    total epoxides or TOC; or
                                        of epoxide emissions per megagram of        maintain <=4.43 x 10-
                                        product made                                3 kilograms of epoxide
                                                                                    emissions per megagram of
                                                                                    product made.

[[Page 106019]]

 
Nonepoxide organic HAP emissions from  Group 1 combination of process vents from   Same as existing affected
 making or modifying the product.       batch unit operations:                      sources.
                                        90-percent aggregate emission
                                        reduction; or
                                        flare emissions from all vents
                                       Group 1 process vents from continuous unit
                                        operations:
                                        98-percent aggregate emission
                                        reduction; or
                                        flare emissions
Nonepoxide organic HAP emissions from   90-percent aggregate emission      Same as existing affected
 catalyst extraction.                   reduction; or                               sources.
                                        flare emissions from all vents
----------------------------------------------------------------------------------------------------------------
\1\ The PEPO NESHAP allows the use of ECO as a means of reducing emissions by the required percentage (98 or
  99.9 percent) or complying with the production-based limits (1.69 x 10-2 or 4.43 x 10-3). This pollution
  prevention technique reduces emissions by extending the time of reaction, thus leaving less unreacted epoxides
  to be emitted downstream. To demonstrate a percent efficiency, it is necessary to designate the basis, or the
  ``uncontrolled'' emissions, for assessing the percent reduction. The point where uncontrolled emissions are to
  be assessed, called the ``onset'' of the ECO, is defined in the PEPO NESHAP as the point when the epoxide
  concentration in the reactor liquid is equal to 25 percent of the concentration of epoxide in the liquid at
  the end of the epoxide feed.

    For the control requirements for nonepoxide organic HAP from making 
or modifying the product specified in table 7 of this preamble, owners 
or operators must determine whether the process vent is a Group 1 or 
Group 2 process vent. The PEPO NESHAP defines a ``Group 1 combination 
of batch process vents'' as a collection of process vents in a PMPU 
from batch unit operations that are associated with the use of a 
nonepoxide organic HAP to make or modify the product that has: (1) 
annual nonepoxide organic HAP emissions of 11,800 kg/yr (approximately 
26,014 lb/yr) or greater, and (2) a cutoff flow rate that is greater 
than or equal to the annual average flow rate. The PEPO NESHAP defines 
a ``Group 1 continuous process vent'' as a process vent from a 
continuous unit operation that is associated with the use of a 
nonepoxide organic HAP to make or modify the product and that has: (1) 
a flow rate greater than or equal to 0.005 standard cubic meters per 
minute (scmm), (2) a total organic HAP concentration greater than or 
equal to 50 ppmv, and (3) a total resource effectiveness (TRE) index 
value less than or equal to 1.0. As discussed further below, the TRE 
index value is a measure of the supplemental total resource requirement 
per unit VOC (or HAP) reduction. The PEPO NESHAP defines a Group 2 
process vent as a process vent that is associated with the use of a 
nonepoxide organic HAP to make or modify the product that is not 
classified as either a Group 1 combination of batch process vents or a 
Group 1 continuous process vent. In general, Group 2 process vents are 
not required to apply any additional emission controls; however, they 
are subject to certain monitoring, reporting, and recordkeeping 
requirements to ensure that they were correctly determined to be Group 
2 and that they remain Group 2.
    The HON process vent standards that certain PEPO affected sources 
(i.e., those that produce PEPO using THF) are currently subject to 
require a Group 1/Group 2 determination:
     A Group 1 process vent associated with a PMPU using THF is 
a process vent for which the vent stream flow rate is greater than or 
equal to 0.005 scmm, the total organic HAP concentration is greater 
than or equal to 50 ppmv, and the TRE index value is less than or equal 
to 1.0. Owners or operators of Group 1 process vents at PEPO processes 
that use THF are required to either: reduce emissions of organic HAP 
using a flare meeting 40 CFR 63.11(b); reduce emissions of total 
organic HAP or TOC by 98 weight percent or to an exit concentration of 
20 ppmv, whichever is less stringent; or achieve and maintain a TRE 
index value greater than 1.0.
     A Group 2 process vent associated with a PMPU using THF is 
process vent for which the vent stream flow rate is less than 0.005 
scmm, the total organic HAP concentration is less than 50 ppmv, or the 
TRE index value is greater than 1.0.
    As previously mentioned in this section of the preamble, the PEPO 
NESHAP contains a TRE index value threshold of 1.0 as part of the 
criteria used to determine whether owners or operators must control 
continuous process vents associated with nonepoxide organic HAP from 
making or modifying product and process vents associated with affected 
sources that produce PEPO using THF. In both of these process vent 
scenarios, the PEPO NESHAP requires owners or operators to calculate 
the TRE index using the procedures in the HON. The TRE index value 
accounts for all the resources which are expected to be used in VOC (or 
HAP) control by thermal oxidation and provides a dimensionless measure 
of resource burden based on cost effectiveness. Resources include 
supplemental natural gas, labor, and electricity. Additionally, if the 
off-gas contains halogenated compounds, resources will also include 
caustic and scrubbing and quench makeup water. For the PEPO NESHAP, 
owners or operators derive the TRE index value from the cost 
effectiveness associated with HAP control by a flare or thermal 
oxidation, and is a function of vent stream flowrate, vent stream net 
heating value, hourly emissions, and a set of coefficients. The EPA 
first introduced the TRE index value in an Agency document titled: 
Guideline Series for Control of Volatile Organic Compound (VOC) 
Emissions from Air Oxidation Processes in Synthetic Organic Chemical 
Manufacturing Industry (SOCMI) (see EPA-450/3-84-015, December 1984). 
The EPA incorporated the TRE concept into the original HON (see 59 FR 
19468, April 22, 1994) and the original PEPO NESHAP rulemaking (see 64 
FR 29420, June 1, 1999). The PEPO NESHAP uses the TRE index value as an 
alternative mode of compliance for process vent regulations. The TRE 
index value can also trigger monitoring, recordkeeping, and reporting 
requirements. For additional details regarding the TRE index value 
(including the equation and coefficients used to calculate the TRE 
index value for the PEPO NESHAP), see the document titled Clean Air Act 
Section 112(d)(6) Technology Review for Batch and Continuous Process 
Vents in the PEPO Production Source Category that are Associated with 
Processes Subject to the PEPO NESHAP, which is available in the docket 
for this rulemaking.
    Our technology review for PEPO process vents (i.e., broader than 
our review of process vents in EtO service discussed in section 
IV.B.2.a of this preamble) did not identify any control options 
associated with: (1) epoxide (i.e., EtO, propylene oxide, and

[[Page 106020]]

epichlorohydrin) emissions resulting from the use of these chemicals as 
reactants, or (2) emissions of nonepoxide organic HAP resulting from 
their use in catalyst extraction. However, we identified the following 
emission reduction options as part of our technology review for 
continuous process vents associated with nonepoxide organic HAP from 
making or modifying product and process vents associated with affected 
sources that produce PEPO using THF: (1) remove the TRE concept in its 
entirety, remove the 50-ppmv and 0.005-scmm Group 1 process vent 
thresholds, and redefine a Group 1 process vent as any process vent 
that emits greater than or equal to 1.0 pound per hour (lb/hr) of total 
organic HAP; (2) the same requirements specified in Control Option 1, 
but redefine a Group 1 process vent as any process vent that emits 
greater than or equal to 0.10 lb/hr of total organic HAP; and (3) 
retain the TRE concept and the 50-ppmv and 0.005-scmm Group 1 process 
vent thresholds, but increase the TRE index value threshold from 1.0 to 
5.0.
    We identified Control Options 1 and 2 as developments in practices, 
processes, and control technologies for multiple reasons. First, we 
identified at least two chemical manufacturing NESHAP (i.e., EMACT 
standards and the HON) that do not use the TRE index value as criteria 
for determining whether a process vent should be controlled.\42\ 
Second, based on the responses to our CAA section 114 request (see 
section II.C of this preamble), we observed that some facilities are 
voluntarily controlling continuous process vents that are not required 
to be controlled per the results of the TRE index value calculation. Of 
the 13 HON facilities that received the CAA section 114 request, at 
least three facilities confirmed they were voluntarily controlling some 
of their Group 2 process vents. We expect PEPO facilities will also 
voluntarily control some of their Group 2 process vents, because 
facilities responded in the CAA section 114 request that, pursuant to 
40 CFR 63.113(h), many of their process vents are voluntarily 
designated as Group 1 process vents ``so that TRE calculations are not 
required.'' In other words, some facilities are likely electing to 
control certain process vents that have TRE index values greater than 
1.0.\43\ Third, based on the responses to our CAA section 114 request, 
we observed that facilities are routing multiple continuous process 
vents to a single APCD. This practice is significant because the 
current use of the TRE index value is only based on controlling a 
single process vent with a single APCD, which is an unrealistic 
scenario when compared to how chemical manufacturing facilities 
actually control their process vents. We believe that it is much more 
likely that a facility routes numerous process vents to the same APCD. 
Finally, we concluded that the TRE index is difficult to enforce 
because it is largely a theoretical characterization tool that 
incorporates numerous input values provided by owners or operators, and 
verifying the inputs without site-specific process knowledge can be 
problematic. We based our conclusion on a response to the CAA section 
114 request received from one facility that provided over 300 pages of 
modeled runs that the facility used to help determine certain 
characteristics of their continuous process vents for use as inputs to 
TRE index value calculations (the facility had originally included 
these modeled runs with their Notification of Compliance Status report 
for the HON). Our review of this information identified numerous 
instances where the facility noted difficulties or uncertainties 
associated with modeling the process vent characteristics.
---------------------------------------------------------------------------

    \42\ The EPA recently removed the TRE index value from the HON 
(see 89 FR 42932, May 16, 2024). The EMACT standards never used the 
TRE index value.
    \43\ None of the nine PEPO facilities that received our CAA 
section 114 request reported having any Group 2 continuous process 
vents associated with processes subject to the PEPO NESHAP; and only 
one of these facilities designated eight of their process vents as 
Group 1 continuous process vents subject to the PEPO NESHAP. We note 
that facilities can voluntarily designate a Group 2 process vent as 
a Group 1 process vent and control it according to Group 1 
requirements. In these instances, the owner or operator is not 
required to keep calculations supporting a TRE index value. 
Therefore, it is possible that some of these Group 1 process vents 
are Group 2 process vents designated as Group 1 process vents.
---------------------------------------------------------------------------

    We identified Control Option 3 as a development in practices, 
processes, and control technologies because we determined that another 
chemical manufacturing NESHAP (i.e., the MON) contains a TRE index 
value threshold criteria (i.e., less than or equal to 1.9) that is more 
stringent than the PEPO NESHAP TRE index value threshold criteria 
(i.e., less than or equal to 1.0). Additionally, we identified one 
State regulatory agency rule that uses a more stringent TRE index value 
threshold than the value specified in the PEPO NESHAP.\44\
---------------------------------------------------------------------------

    \44\ See Illinois Title 35: Subtitle B: Chapter I: Subchapter C: 
Parts 218 and 219 (i.e., Organic Material Emission Standards And 
Limitations For The Chicago Area Subpart V: Batch Operations And Air 
Oxidation Processes; and Organic Material Emission Standards And 
Limitations For The Metro East Area Subpart V: Batch Operations And 
Air Oxidation Processes). However, it is unlikely to be applicable 
to process vents in the PEPO Production source category because it 
applies specifically to air oxidation processes, which are not 
typically used in PEPO production.
---------------------------------------------------------------------------

    To evaluate impacts of the three control options presented above, 
we used information for approximately 50 continuous process vents 
designated as Group 2 that was provided by nine of the 13 HON 
facilities that received the CAA section 114 request. We determined it 
was reasonable to use the CAA section 114 response data for HON Group 2 
process vents to extrapolate impacts for certain continuous Group 2 
process vents subject to the PEPO NESHAP given that PMPU sources 
subject to the PEPO NESHAP are similar to CMPU (chemical manufacturing 
process unit) sources that are subject to the HON. Additionally, there 
are 15 PEPO facilities co-located with HON facilities; therefore, we 
believe it is reasonable to assume that developments in practices, 
processes, and control technologies would be implemented across the 
entire facility, given the similarities between HON and PEPO process 
units. We also reviewed several air emissions permits issued by State 
regulatory agencies to validate our assumptions and estimates of the 
number of Group 2 process vents located at PEPO facilities. Although we 
were unable to determine the exact number of Group 2 process vents 
(both continuous and batch) that are located at each PEPO facility, we 
believe that, based on our air permit review, our Group 2 process vent 
estimates are reasonable. It is evident from our air permit review that 
some PEPO facilities have between one and six Group 2 process vents.
    We estimated that process vent Control Option 1 would impact four 
PEPO facilities; one facility would need to install a thermal oxidizer 
and three facilities would either use existing controls or are already 
voluntarily controlling their Group 2 process vents. We estimated that 
process vent Control Option 2 would impact eight PEPO facilities; five 
facilities would need to install a thermal oxidizer and three 
facilities would either use existing controls or are already 
voluntarily controlling their Group 2 process vents. For process vent 
Control Option 3, we estimated that four PEPO facilities would be 
impacted by this option with one PEPO facility needing to install a 
thermal oxidizer and three facilities using either existing controls or 
are already voluntarily controlling their Group 2 process vents (i.e., 
the same impacts as estimated for process vent

[[Page 106021]]

Control Option 1). We then used information about the composition of 
process vent streams, net heating value, and volumetric and mass flow 
rate that industry provided to the EPA in response to the CAA section 
114 request for HON Group 2 process vents to estimate the total capital 
investment and total annual cost of: (1) installing thermal oxidizers 
for reducing HAP emissions from certain PEPO Group 2 process vents, or 
(2) installing ductwork and a blower to route certain PEPO Group 2 
process vents to an existing control device. For facilities that would 
need to install a thermal oxidizer, we used a total capital investment 
of $1,000,000 provided by commenters in the HON rulemaking (see 89 FR 
42932, May 16, 2024). For total annual cost, we used the value the 
Agency determined for the HON rulemaking ($377,000 after adjusting for 
a higher interest rate and year 2022 dollars) for installing a new 
recuperative thermal oxidizer with 70-percent energy recovery following 
the procedures contained in the EPA Control Cost Manual.\45\ For 
facilities that would not need to install a thermal oxidizer and would 
instead route Group 2 process vent emissions to an existing control 
device at the facility, we also estimated the average total capital 
investment and total annual cost values and emission reductions to 
install ductwork and a blower using the EPA Control Cost Manual.
---------------------------------------------------------------------------

    \45\ EPA, 2002. EPA Control Cost Manual, Sixth Edition. January 
2002. Publication Number EPA/452/B-02-001.
---------------------------------------------------------------------------

    Table 8 of this preamble presents the nationwide impacts for the 
three options considered for continuous process vents associated with 
nonepoxide organic HAP (from making or modifying product) and process 
vents associated with affected sources that produce PEPO using THF. We 
determined that Control Option 1 is cost effective; therefore, we are 
proposing, pursuant to CAA section 112(d)(6), to remove the TRE concept 
in its entirety from the PEPO NESHAP (see proposed 40 CFR 63.1425(c)(4) 
and (f)(7), 63.1428(h) and (i), 63.1429(b)(2), and 63.1430(e)(2), 
(f)(2) through (f)(5), and (j)). We are also proposing, pursuant to CAA 
section 112(d)(6), to remove the 50-ppmv and 0.005-scmm thresholds from 
the Group 1 definition for continuous process vents at 40 CFR 
63.1423(b) associated with nonepoxide organic HAP and the Group 1 
process vent applicability associated with a PMPU using THF, and 
instead require owners and operators of these process vents that emit 
greater than or equal to 1.0 lb/hr of total organic HAP to meet the 
current control standards in the PEPO NESHAP. We are also proposing to 
revise 40 CFR 63.1430(g)(3) to align to the proposed 1.0 lb/hr 
threshold. In this action, we are not proposing to revise the PEPO 
NESHAP to reflect the requirements of process vent Control Options 2 
and 3 pursuant to CAA section 112(d)(6). We determined that process 
vent Control Option 2 is not cost effective, and while we believe 
Control Option 3 is cost effective, it would require retaining the TRE 
concept in the rule which, for the reasons explained above, we believe 
is not desirable. We solicit comments on the proposed revisions to the 
process vent requirements for the PEPO NESHAP.

   Table 8--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for Certain Process
                                          Vents \1\ at PEPO Facilities
----------------------------------------------------------------------------------------------------------------
                                                       Total       VOC emission    HAP emission      HAP cost-
         Control option            Total capital    annualized      reductions      reductions     effectiveness
                                  investment ($)   costs ($/yr)        (tpy)           (tpy)          ($/ton)
----------------------------------------------------------------------------------------------------------------
1...............................       1,023,000         380,000              45              45          $8,500
2...............................       3,040,000       1,135,000              34              21          53,700
3...............................       1,023,000         380,000              37              37          10,200
----------------------------------------------------------------------------------------------------------------
\1\ For continuous process vents associated with nonepoxide organic HAP (from making or modifying product) and
  process vents associated with affected sources that produce PEPO using THF.

    As part of our technology review for the combination of batch 
process vents that are associated with the use of a nonepoxide organic 
HAP to make or modify the product, we identified the following emission 
reduction option: revise the PEPO NESHAP control threshold from 26,014 
lb/yr to 10,000 lb/yr and remove the associated flow rate applicability 
threshold. We identified this option as a development in practices, 
processes, and control technologies based on our comparison of the 
batch process vent requirements in the NESHAP for Chemical 
Manufacturing Area Sources (CMAS) to those specified in the PEPO 
NESHAP. Also, as part of a recent technology review, the EPA updated 
the Group I Polymers and Resins (P&R I) NESHAP (see 89 FR 42932, May 
16, 2024) to reflect the applicability threshold used in the CMAS 
NESHAP. We note that the CMAS NESHAP regulates batch process vents from 
nine area source categories in the chemical manufacturing sector. 
Owners and operators of a CMAS CMPU with collective uncontrolled 
organic HAP emissions greater than or equal to 10,000 lb/yr from all 
batch process vents associated with an affected CMPU must meet emission 
limits for organic HAP emissions. The CMAS NESHAP defines GACT for 
batch process vents as 85-percent control for existing batch process 
units (and 90-percent control for new units) that have uncontrolled 
organic HAP emissions equal to or greater than 10,000 lb/yr. As 
discussed in the CMAS NESHAP rulemaking,\46\ the EPA also used the 
applicability threshold of 10,000 lb/yr per batch process in the MON 
and this threshold indicates the size of a CMPU because the MON applies 
to major sources of HAP. The EPA used information from the baseline 
facility MON database and determined that costs to meet an 85-percent 
control requirement for existing CMAS CMPUs with uncontrolled organic 
HAP emissions equal to or greater than 10,000 lb/yr were reasonable 
($8,700/ton). We note that the applicability threshold for uncontrolled 
organic HAP emissions of 10,000 lb/yr used in the CMAS NESHAP is more 
stringent than the applicability threshold of 26,014 lb/yr specified in 
the PEPO NESHAP for nonepoxide organic HAP emitted from Group 1 
combination of batch process vents that are associated with the use of 
a nonepoxide organic HAP to make or modify the product.
---------------------------------------------------------------------------

    \46\ See 74 FR 56008, October 29, 2009.
---------------------------------------------------------------------------

    To evaluate impacts of the option presented for the combination of 
batch

[[Page 106022]]

process vents that are associated with the use of a nonepoxide organic 
HAP to make or modify the product, we used information from the batch 
process vent impacts analysis for the CMAS final rule.\47\ We selected 
the model plant for the 90-percent control option shown in table 3 of 
the CMAS NESHAP impacts analysis memorandum for sources subject to the 
PEPO NESHAP (instead of the 85-percent control option model plant shown 
in table 2 of the impacts analysis memorandum) to prevent backsliding 
of the current PEPO NESHAP requirements, which reflect MACT instead of 
the GACT standards of the CMAS NESHAP. We assumed that all facilities 
subject to the PEPO NESHAP, except for the nine that received our CAA 
section 114 request,\48\ have batch process vents that would require 
control under the option evaluated (i.e., under the option to change 
the Group 1 combination of batch process vents threshold to 10,000 lb/
yr). Additionally, we determined that one facility is a small business 
that is co-located with a HON facility, and already accounted for under 
the recent HON rulemaking (see 89 FR 42932, May 16, 2024). As a result, 
we estimated impacts to the remaining 15 PEPO facilities.
---------------------------------------------------------------------------

    \47\ RTI, 2009. Revised Impacts Analysis for Batch Process Vents 
Chemical Manufacturing Area Source NESHAP. October 14, 2009. EPA 
Docket No. EPA-HQ-OAR-2008-0334-0075.
    \48\ None of the nine PEPO facilities reported having any Group 
2 combinations of batch process vents associated with processes 
subject to the PEPO NESHAP; however, five of the nine facilities 
reported having several Group 1 combinations of batch process vents 
subject to the PEPO NESHAP. We note that facilities can voluntarily 
designate a Group 2 process vent a Group 1 process vent and control 
it according to Group 1 requirements. In these instances, the owner 
or operator is not required to keep calculations supporting a TRE 
index value. Therefore, it is possible that some of these Group 1 
process vents are Group 2 process vents designated as Group 1 
process vents.
---------------------------------------------------------------------------

    Table 9 of this preamble presents the nationwide impacts for the 
option considered for the combination of batch process vents that are 
associated with the use of a nonepoxide organic HAP to make or modify 
the product at PEPO facilities. We determined that this option is cost 
effective, and we are proposing, pursuant to CAA section 112(d)(6), to 
remove the Group 1 process vent thresholds of annual organic HAP 
emissions mass flow rate, cutoff flow rate, and the annual average 
batch vent flow rate from the definition of ``Group 1 combination of 
batch process vents'' specified in the PEPO NESHAP at 40 CFR 
63.1423(b). We are also proposing to remove rule text associated with 
these process vent thresholds at 40 CFR 63.1428(c), (d), and (e). 
Instead, using the procedures specified in 40 CFR 63.1428(b), owners 
and operators of Group 1 combination of batch process vents that 
release a total of annual nonepoxide organic HAP emissions greater than 
or equal to 4,536 kg/yr (10,000 lb/yr) would be required at 40 CFR 
63.1425(c) to reduce emissions of nonepoxide organic HAP from these 
process vents using a flare meeting the proposed operating and 
monitoring requirements for flares (see section IV.D.1 of this 
preamble); or reduce emissions of nonepoxide organic HAP by 90 percent 
by weight. We are also proposing to revise 40 CFR 63.1430(e)(1)(vii) to 
align to the proposed 4,536 kg/yr threshold. We solicit comments on the 
proposed revisions to the PEPO NESHAP for the combination of batch 
process vents that are associated with the use of a nonepoxide organic 
HAP to make or modify the product.

     Table 9--Nationwide Emissions Reductions and Cost Impacts of the Control Option Considered for the Combination of Batch Process Vents (That Are
                          Associated With the Use of a Nonepoxide Organic HAP To Make or Modify the Product) at PEPO Facilities
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                          Organic HAP      Organic HAP
                                                                      Total capital        Total         VOC emission       emission          cost-
                           Control option                             investment ($)     annualized       reductions       reductions     effectiveness
                                                                                        costs ($/yr)        (tpy)            (tpy)           ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1..................................................................         778,950          625,050             87.8             87.8            7,120
--------------------------------------------------------------------------------------------------------------------------------------------------------

    For further details on our assumptions and methodologies used in 
these analyses, see the document titled Clean Air Act Section 112(d)(6) 
Technology Review for Batch and Continuous Process Vents in the PEPO 
Production Source Category that are Associated with Processes Subject 
to the PEPO NESHAP, which is available in the docket for this 
rulemaking.
4. Standards for Wastewater
    As previously mentioned in this preamble, HAP are emitted from 
wastewater collection, storage, and treatment systems that are 
uncovered or open to the atmosphere through volatilization of organic 
compounds at the liquid surface. Emissions occur by diffusive or 
convective means, or both. Diffusion occurs when organic concentrations 
at the water surface are much higher than ambient concentrations. The 
organics volatilize, or diffuse into the air, to reach equilibrium 
between aqueous and vapor phases. Convection occurs when air flows over 
the water surface, which reduces the concentration at the boundary 
layer between the liquid and air, thereby sweeping organic vapors from 
the water surface into the air. The rate of volatilization is related 
directly to the speed of the air flow over the water surface.
    The PEPO NESHAP defines wastewater to mean water that contains 
either: (1) an annual average concentration of compounds specified in 
table 4 to 40 CFR part 63, subpart PPP, of at least 5 ppmw and has an 
annual average flow rate of 0.02 liters per minute (lpm) or greater, or 
(2) an annual average concentration of compounds specified in table 4 
to 40 CFR part 63, subpart PPP, of at least 10,000 ppmw at any flow 
rate. The PEPO NESHAP definition of wastewater also includes water 
discarded from a PMPU that is part of an affected source (see 40 CFR 
63.1420(a) for the definition of an affected source). Wastewater can be 
process wastewater or maintenance wastewater. For process and 
maintenance wastewaters, and certain liquid streams in open systems 
within a PMPU, the PEPO NESHAP defines Group 1 wastewater streams at 
existing and new sources as having a total annual average concentration 
of compounds specified in table 4 to 40 CFR part 63, subpart PPP, that 
are also in table 9 to 40 CFR part 63, subpart G, greater than or equal 
to 10,000 ppmw at any flow rate, or greater than or equal to 1,000 ppmw 
with an annual average flow rate greater than or equal to 10 liters per 
minute. The HON wastewater standards that PEPO sources are currently 
subject to directly reference (with differences specified in 40 CFR 
63.1433(a)) NESHAP subpart G at 40

[[Page 106023]]

CFR 63.132 through 63.147, which provide owners and operators several 
control options for wastewater tanks, surface impoundments, containers, 
individual drain systems, and oil-water separators. NESHAP subpart G 
also specifies performance standards for treating wastewater streams 
using open or closed biological treatment systems or using a design 
steam stripper with vent control. For APCDs (e.g., thermal oxidizers) 
used to control emissions from collection system components, steam 
strippers, or closed biological treatment systems, NESHAP subpart G 
provides owners or operators several compliance options, including 95-
percent destruction efficiency, a 20-ppmv outlet concentration, or 
temperature and residence time design specifications for enclosed 
combustion devices.
    The HON maintenance wastewater standards that PEPO sources are 
currently subject to directly reference (with exceptions specified in 
40 CFR 63.1433(b)) NESHAP subpart F at 40 CFR 63.105, which requires 
owners or operators to prepare a description of the maintenance 
procedures for managing wastewaters generated from the emptying and 
purging of equipment during shutdowns, maintenance, and repair. For 
certain liquid streams in open systems within a PMPU, NESHAP subpart G 
requires drain, manhole, lift station, and trench components to be 
equipped with a tightly fitting solid cover, a cover with vent control, 
or water seals; pipes to have no visible gaps or other emissions 
interfaces; oil/water separators to be equipped with a fixed roof with 
vent control or a floating roof; and tanks to have a fixed roof (with 
vent control if the tank contents are sparged, are heated, or are 
treated using an exothermic reaction).
    As part of our CAA section 112(d)(6) technology review for PEPO 
wastewater streams (i.e., broader than our review of wastewater streams 
in EtO service discussed in section IV.B.2.d of this preamble), we 
evaluated tightening the PEPO wastewater Group 1 applicability 
thresholds. Specifically, we evaluated the option to require owners and 
operators to manage and treat existing wastewater streams with total 
annual average concentration of compounds specified in table 4 to 40 
CFR part 63, subpart PPP (that are also in table 9 to NESHAP subpart G) 
greater than or equal to 1,000 ppmw at any flow rate, or greater than 
or equal to 10 ppmw at a flow rate of 10 lpm or greater.
    Table 10 of this preamble presents the nationwide costs and impacts 
for the wastewater stream control option considered for PEPO 
facilities. For details on the assumptions and methodologies used in 
this analysis, see the document titled Clean Air Act Section 112(d)(6) 
Technology Review for Wastewater Streams Located in the PEPO Production 
Source Category that are Associated with Processes Subject to the PEPO 
NESHAP, which is available in the docket for this rulemaking.

          Table 10--Nationwide Emissions Reductions and Cost Impacts of the Control Option Considered for Wastewater Streams at PEPO Facilities
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                          Organic HAP      Organic HAP
                                                                      Total capital        Total         VOC emission       emission           cost
                           Control option                             investment ($)     annualized       reductions       reductions     effectiveness
                                                                                        costs ($/yr)        (tpy)            (tpy)           ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1..................................................................      57,128,000       22,600,000              693              693           32,600
--------------------------------------------------------------------------------------------------------------------------------------------------------

    We determined that the option to revise wastewater stream Group 1 
threshold applicability in the PEPO NESHAP (i.e., to require control of 
existing wastewater streams with total annual average concentration of 
table 4 to subpart PPP compounds (that are also in table 9 to NESHAP 
subpart G) greater than or equal to 1,000 ppmw at any flow rate, or 
greater than or equal to 10 ppmw at a flow rate of 10 lpm or greater) 
is not cost effective based on the costs and emission reductions 
presented. Therefore, we are not proposing to revise the PEPO NESHAP to 
reflect the requirements of this option pursuant to CAA section 
112(d)(6).
5. Standards for Equipment Leaks
    As previously mentioned in this preamble, emissions of VOC and HAP 
from equipment leaks occur in the form of gases or liquids that escape 
to the atmosphere through many types of connection points (e.g., 
threaded fittings) or through the moving parts of certain types of 
process equipment during normal operation. Equipment regulated by the 
PEPO NESHAP includes agitators, compressors, connectors, 
instrumentation systems, OEL, PRDs, pumps, sampling collection systems, 
and valves that contain or contact material having 5 percent by weight 
or more of organic HAP, operate 300 hours per year or more, and are not 
in vacuum service.
    The equipment leak standards that PEPO sources are currently 
subject to directly reference the provisions in the HON at 40 CFR part 
63, subpart H, which require LDAR using monitoring with EPA Method 21 
of appendix A-7 to 40 CFR part 60 at certain frequencies (e.g., 
monthly, quarterly, every 2 quarters, annually) and varying leak 
definitions (e.g., 500 ppmv; 1,000 ppmv; 10,000 ppmv) depending on the 
type of component and service (e.g., in gas and vapor service or in 
light liquid service). The LDAR requirements for components in heavy 
liquid service include sensory monitoring (e.g., visual, audible, 
olfactory).
    The practices, processes, and control technologies we considered 
during MACT development for equipment leaks at PEPO facilities included 
LDAR and equipment standards. To identify developments for the 
technology review, we evaluated responses to our CAA section 114 
request, the RACT/BACT/LAER database, and other Federal regulations 
(i.e., the Petroleum Refinery Sector rule, HON, MON, and NSPS subpart 
VVb) and State regulations (i.e., the Texas fugitive emissions rules 
\49\ applicable to petrochemical processes). Also, the EPA conducted a 
general analysis in a 2011 equipment leaks study \50\ to identify the 
latest developments in practices, processes, and control technologies 
for equipment leaks at chemical manufacturing facilities and petroleum 
refineries, and to estimate the impacts of applying those practices, 
processes, and control technologies to model facilities. We used this 
2011 equipment leaks analysis as a reference for conducting the 
technology review for equipment leaks at PEPO facilities.
---------------------------------------------------------------------------

    \49\ 30 TAC 115, subchapters D and H, Division 3.
    \50\ Hancy. 2011. Memorandum from Hancy, C., RTI International, 
to Howard, J., EPA/OAQPS. Analysis of Emissions Reduction Techniques 
for Equipment Leaks. December 21, 2011. EPA Docket ID No. EPA-HQ-
OAR-2010-0869.
---------------------------------------------------------------------------

    Our technology review for equipment leaks of HAP (i.e., broader 
than the EtO

[[Page 106024]]

emissions discussed in section IV.B.2.b of this preamble) did not find 
any new control technologies for equipment leak emissions to evaluate. 
However, we did identify developments in LDAR practices and processes 
(i.e., lower leak definitions) for valves in gas and vapor service or 
in light liquid service, and pumps in light liquid service. We 
evaluated three control options to reduce HAP emissions from equipment 
leaks: (Control Option 1) lowering the leak definition for valves in 
light liquid service from 500 ppmv to 100 ppmv, (Control Option 2) same 
as Control Option 1, plus lowering the leak definition for valves in 
gas and vapor service from 500 ppmv to 100 ppmv, and (Control Option 3) 
same as Control Option 2, plus lowering the leak definition for pumps 
in light liquid service from 1,000 ppmv to 500 ppmv. For all other 
component and service types, we did not identify developments in LDAR 
practices and processes in the chemical sector.\51\
---------------------------------------------------------------------------

    \51\ We note that while other technologies such as optical gas 
imaging and sensor networks may be considered developments in 
monitoring for equipment leaks, the EPA did not evaluate those 
options further as we have insufficient information on how use of 
such monitoring technology compares to current EPA Method 21 
practices for chemical sector sources.
---------------------------------------------------------------------------

    The EPA estimated emission reductions for the developments that we 
identified using component counts and emission factors. We derived the 
component counts using data provided to the EPA in response to our CAA 
section 114 request (see section II.C of this preamble) and we 
developed model component counts for 25 PEPO facilities. We then 
multiplied the number of nationwide PEPO processes \52\ by the model 
component counts to estimate the nationwide component counts. 
Subsequently, we calculated baseline emissions and emissions after 
implementation of the proposed controls for each component using these 
nationwide component counts and emission factors and leak frequencies 
for the chemical manufacturing industry obtained from the 2011 
equipment leaks study.
---------------------------------------------------------------------------

    \52\ We used data provided to the EPA in response to our CAA 
section 114 request to estimate an average of two PMPUs per facility 
for the 16 PEPO facilities that did not receive the CAA section 114 
request. Including the estimate for the 16 PEPO facilities that did 
not receive the CAA section 114 request with the 18 PMPUs that were 
reported in the CAA section 114 request, we estimate 50 PMPUs 
nationwide.
---------------------------------------------------------------------------

    The EPA then calculated the costs for the baseline and control 
options, which reflect the cost to implement an LDAR program for each 
component. Note that the difference between the costs for the baseline 
and control options is the incremental cost to comply with the control 
requirements. Furthermore, because the control options result in 
chemicals in process lines not leaking (i.e., not being lost), we 
present costs both with and without this consideration. To estimate 
savings in chemicals not being emitted (i.e., lost) due to the 
equipment leak control options, we applied a recovery credit of $900 
per ton of VOC to the emission reductions in the analyses.
    We calculated the VOC and HAP cost effectiveness by dividing the 
incremental annual costs by the emissions reductions. Table 11 of this 
preamble presents the nationwide costs and impacts for the suite of 
equipment leak control options considered for PEPO facilities. For 
details on the assumptions and methodologies used in this analysis, see 
the document titled Clean Air Act Section 112(d)(6) Technology Review 
for Equipment Leaks Located in the PEPO Production Source Category that 
are Associated with Processes Subject to the PEPO NESHAP, which is 
available in the docket for this rulemaking.

                       Table 11--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for PEPO Equipment
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                              Average
                                                         Total        Total        Total      Total HAP     Average HAP     Average HAP     incremental
                                                        capital     annualized   annualized    emission        cost            cost          HAP cost
                   Control option                      investment   costs w/o     costs w/    reductions   effectiveness   effectiveness   effectiveness
                                                          ($)      credits ($/  credits ($/     (tpy)      w/credits ($/  w/o credits ($/  w/credits ($/
                                                                       yr)          yr)                        ton)            ton)            ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1...................................................       42,300       11,700        9,200         2.20           4,200           5,300
2...................................................       72,700       18,800       15,300         2.99           5,100           6,300           7,700
3...................................................       99,000       28,100       24,200         3.29           7,400           8,500          30,500
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Based on the costs and emission reductions for each of the options, 
we determined that Control Option 2 (which includes Control Option 1) 
is cost effective. Therefore, we are proposing, pursuant to CAA section 
112(d)(6), to revise the PEPO NESHAP at 40 CFR 63.1434(a)(7) to use a 
leak definition of 100 ppmv for valves that are in either gas/vapor 
service or light liquid service. In this action, we are not proposing 
to revise the PEPO NESHAP to reflect the requirements of Control Option 
3 pursuant to CAA section 112(d)(6), because we determined that Control 
Option 3 is not cost effective due to its high incremental HAP cost 
effectiveness (i.e., $30,500/ton of HAP) from Control Option 2. We 
solicit comments on the proposed revisions to the equipment leak 
requirements for the PEPO NESHAP.
6. Standards for Fenceline Monitoring
    Fenceline monitoring refers to the placement of monitors along the 
perimeter of a facility to measure pollutant concentrations. Coupled 
with requirements for root cause analysis and corrective action upon 
triggering an actionable level, this work practice standard is a 
development in practices considered under CAA section 112(d)(6) for the 
purposes of managing fugitive emissions. The measurement of pollutant 
concentrations and comparison to concentrations estimated from mass 
emissions via dispersion modeling is used to verify emission estimates 
from a facility's emissions inventory. If concentrations at the 
fenceline are greater than expected, potential causes may include 
underreported or unknown emissions, leaking equipment, or other issues, 
usually related to ground-level fugitive emissions. Fenceline 
monitoring also provides information on the location of these potential 
emissions sources because it provides complete spatial coverage of a 
facility. Further, when used with a mitigation strategy, such as root 
cause analysis and corrective action upon exceedance of an action 
level, fenceline monitoring can be effective in reducing emissions and 
reducing the uncertainty associated with emissions estimation and 
characterization. Finally, public reporting of fenceline monitoring 
data provides public transparency and greater visibility, leading to 
more focus and effort in reducing emissions.

[[Page 106025]]

    The EPA has successfully applied fenceline monitoring to the 
petroleum refineries source category as a technique to manage and 
reduce benzene emissions from fugitive emissions sources such as 
storage vessels, wastewater treatment systems, and leaking equipment. 
In 2015, the EPA promulgated the RTR for the petroleum refineries 
source category and required that refineries install and operate 
fenceline monitors following EPA Methods 325A/B to monitor benzene 
emissions. Additionally, the 2015 rule required that refineries conduct 
a root cause analysis to identify sources of high fenceline monitoring 
readings (i.e., above an annual action level) and then develop a 
corrective action plan to address the sources and reduce emissions to a 
level that will bring fenceline monitoring concentrations below the 
action level.\53\ To date, the EPA has received fenceline monitoring 
data for more than 5 years.\54\ These data show that petroleum refinery 
fenceline concentrations have dropped by an average of 30 percent since 
the inception of the monitoring program requirements and illustrate 
that fenceline monitoring is an effective tool in reducing emissions 
and preserving emission reductions on an ongoing basis for these 
sources.
---------------------------------------------------------------------------

    \53\ 40 CFR 63.658(f) through (h).
    \54\ Quarterly fenceline monitoring reports are available 
through the EPA's WebFIRE database at https://cfpub.epa.gov/webfire/. The EPA has also developed a dashboard to improve public 
access to this data. The dashboard is available at https://awsedap.epa.gov/public/extensions/Fenceline_Monitoring/Fenceline_Monitoring.html?sheet=MonitoringDashboard.
---------------------------------------------------------------------------

    Additionally, in 2024, the EPA promulgated amendments to the HON 
(40 CFR part 63, subpart G) and the P&R I NESHAP (40 CFR part 63, 
subpart U) that included work practice standards requiring owners and 
operators to conduct fenceline monitoring for any of six specific HAP 
(i.e., benzene; 1,3-butadiene; ethylene dichloride; vinyl chloride; 
EtO; and chloroprene) if their affected source uses, produces, stores, 
or emits any of them, and conduct root cause analysis and corrective 
action upon exceeding annual average concentration action levels 
established for each HAP. The final HON and P&R I NESHAP amendments 
require owners and operators to conduct passive diffusive tube 
fenceline monitoring for benzene, 1,3-butadiene, chloroprene, and 
ethylene dichloride in accordance with EPA Methods 325A/B of 40 CFR 
part 63, appendix A, and to use canister sampling in accordance with 
EPA Method 327 of 40 CFR part 63, appendix A, for EtO and vinyl 
chloride.\55\
---------------------------------------------------------------------------

    \55\ In the same action (see 89 FR 42932, May 16, 2024), the EPA 
also finalized EPA Method 327 of 40 CFR part 63, appendix A, as a 
canister sampling and analysis method that provides procedures for 
measuring trace levels of targeted VOC (including organic HAP) in 
ambient air.
---------------------------------------------------------------------------

    Given the similarities between PMPUs subject to the PEPO NESHAP and 
CMPU sources that are subject to the HON, we evaluated the application 
of fenceline monitoring at PEPO facilities as a development in 
practices, processes, and control technologies pursuant to CAA section 
112(d)(6). Like some CMPUs, PMPUs can be a significant source of EtO 
emissions from ground-level or near ground level fugitive sources such 
as storage vessels, wastewater treatment systems, and leaking 
equipment. On the other hand, we determined that PMPUs are not 
significant sources of emissions of benzene, 1,3-butadiene, 
chloroprene, ethylene dichloride, and vinyl chloride. In the risk 
modeling file, which uses data from the 2017 NEI,\56\ we did not 
attribute any records of vinyl chloride or chloroprene emissions to 
PEPO processes, and only small amounts of 1,3-butadiene, benzene, and 
ethylene dichloride emissions are attributed to PEPO processes (none of 
these emissions is clearly from a PMPU). Any significant emissions of 
these HAP from PEPO facilities are attributed to non-source category 
emission sources from facilities that are subject to the HON fenceline 
monitoring requirements. Considering the available information, we 
conclude that, for the PEPO NESHAP, a fenceline monitoring requirement 
for EtO is appropriate, but a fenceline monitoring requirement for 
benzene, 1,3-butadiene, chloroprene, ethylene dichloride, and vinyl 
chloride would not lead to an appreciable reduction in emissions.
---------------------------------------------------------------------------

    \56\ See appendix 1 of the document titled Residual Risk 
Assessment for the Polyether Polyols (PEPO) Production Source 
Category in Support of the 2024 Risk and Technology Review Proposed 
Rule, which is available in the docket for this rulemaking, for more 
details about development of the risk modeling file.
---------------------------------------------------------------------------

    Based on this information, the EPA is proposing in this action to 
implement a fenceline monitoring program under CAA section 112(d)(6) to 
limit fugitive emissions of EtO. We are proposing at 40 CFR 63.1434(i), 
by reference to 40 CFR 63.184, to require fenceline monitoring at 
facilities in the PEPO Production source category that use, produce, 
store, or emit EtO. A brief summary of the proposed fenceline sampling 
requirements and our rationale for selecting the corrective action 
concentration levels are provided as follows. We solicit comments on 
the proposed standards for fenceline monitoring.
a. Developments in Monitoring Technology and Practices
    In developing the fenceline monitoring requirements for the 
Petroleum Refinery NESHAP, the HON, and the P&R I NESHAP, the EPA 
identified two different methods for monitoring fugitive emissions: (1) 
passive diffusive tube monitoring networks, and (2) canister monitoring 
networks. Given the similarities between PMPUs subject to the PEPO 
NESHAP and CMPU sources that are subject to the HON, and the extent of 
co-location between PEPO and HON facilities (15 of the 25 PEPO 
facilities are co-located with HON facilities), we considered these 
monitoring methods as developments in practices under CAA section 
112(d)(6) for purposes of managing fugitive EtO emission sources at 
PEPO production facilities.
    In the promulgated amendments to the HON, the EPA finalized a new 
EPA method (EPA Method 327 of 40 CFR part 63, appendix A) to monitor 
the concentration of EtO at facility fenceline locations. EPA Method 
327 provides procedures for canister sampling and analysis for 
measuring trace levels of targeted VOC (including organic HAP) in air. 
The method draws upon the guidance in Method TO-15A \57\ for canister 
sampling and further develops this guidance into a robust method 
specific to fenceline monitoring, defining required data quality 
objectives, and incorporating existing best practices into the method. 
EPA Method 327 collects ambient air samples using specially prepared 
and pre-cleaned evacuated stainless-steel canisters. For analysis, the 
method specifies procedures for concentrating the target VOC (i.e., 
EtO) in a known volume of air drawn from the canister, desorbing the 
target VOC from the preconcentrator, and determining the concentration 
of the target VOC using a gas chromatograph-mass spectrometer (GC-MS). 
The EPA continues to investigate cost-effective monitoring methods and 
technologies that could offer improved sensitivity, improved time 
resolution, or increased time integration.
---------------------------------------------------------------------------

    \57\ https://www.epa.gov/sites/default/files/2019-12/documents/to-15a_vocs.pdf.
---------------------------------------------------------------------------

    In this action, the EPA is proposing at 40 CFR 63.1434(i), by 
reference to 40 CFR 63.184(b)(2), to require fenceline monitoring of 
EtO concentrations for one 24-hour period every 5 days using canister 
sampling in accordance with

[[Page 106026]]

EPA Method 327 of 40 CFR part 63, appendix A. This monitoring frequency 
is necessary to ensure that all onsite processes are monitored 
regularly while maintaining the cost effectiveness of implementing a 
canister monitoring network. A sampling frequency of every 5 days also 
ensures that the annual average concentration derived from the 
fenceline data are indicative of the actual average emissions from the 
site by reducing the possibility that sampling occurs only during 
emission spikes. Additionally, to accommodate continued advancements 
and improvements in monitoring technology, we are also proposing to 
amend the entry for 40 CFR 63.7(f) of table 1 to the PEPO NESHAP 
(applicability of the NESHAP general provisions) to clarify that an 
owner or operator can request to use another type of monitoring network 
to demonstrate compliance with the fenceline standards, provided they 
achieve adequate coverage and detection capabilities.
b. Siting, Design, and Sampling Requirements for Fenceline Monitors
    The EPA is proposing at 40 CFR 63.1434(i), by reference to 40 CFR 
63.184(b)(3), that owners or operators deploy monitors to measure 
fenceline concentrations of EtO at facilities subject to the PEPO 
NESHAP. A primary requirement for a fenceline monitoring system is that 
it provides adequate spatial coverage for determination of 
representative pollutant concentrations at the boundary of the 
facility. In an ideal scenario, owners or operators would place 
fenceline monitors so that any fugitive plume originating within the 
facility would have a high probability of intersecting one or more 
monitors, regardless of wind direction. Therefore, we are proposing 
that each facility would place eight canisters evenly spaced on the 
monitoring perimeter. The monitoring perimeter may be the facility 
fenceline or may be inside the facility fenceline, provided all sources 
of EtO are contained within the perimeter. The EPA is also proposing to 
require that facilities move the canister sampling locations with 
alternating sampling periods to ensure complete spatial coverage of the 
facility. For facilities with perimeters less than or equal to 5,000 
meters, all eight sampling points would be monitored during each 
sampling period. For facilities with perimeters greater than 5,000 
meters but less than or equal to 10,000 meters, 16 sampling points 
would be required; for facilities with perimeters greater than 10,000 
meters, 24 sampling points would be required. For facilities with EtO 
emission sources that are not contained within one contiguous area, the 
EPA is proposing monitoring of these secondary areas as well, with the 
size of the secondary area dictating the number of canisters. While we 
recognize that EPA Method 325A contains an option for siting passive 
tubes by determining the geographic center of the facility and spacing 
the tubes based on measured angles from the center point, the EPA is 
not providing a similar approach to simplify the siting of the 
canisters.
    The EPA is proposing at 40 CFR 63.1434(i), by reference to 40 CFR 
63.184(d), that for each 24-hour sampling period, the facility would 
determine a ``delta c,'' calculated as the lowest sample value for EtO 
subtracted from the highest sample value for EtO. This approach 
subtracts the estimated contribution from background emissions that do 
not originate from the facility. The owner or operator would average 
the delta c for the most recent year of samples (73 sampling periods) 
to calculate an annual average delta c on a rolling basis (i.e., 
calculate a new annual average delta c every 5 days using data from the 
most recent 73 sampling periods). The owner or operator would compare 
this rolling annual average delta c against the concentration action 
level for EtO.
c. Action Levels and Rationale
    As mentioned earlier in this preamble, the EPA is proposing to 
require facilities subject to the PEPO NESHAP to take corrective action 
to reduce fugitive emissions if monitored fenceline concentrations 
exceed the concentration action level on a rolling annual average 
basis.\58\
---------------------------------------------------------------------------

    \58\ Calculated every 5 days for EtO.
---------------------------------------------------------------------------

    Due to current limitations in method detection limits for EtO, we 
selected the proposed fenceline action level to be equal to three times 
the representative detection limit (RDL) for EtO, as this is the 
minimum concentration that can be measured with reasonable certainty. 
The RDL is based on the results of the best performing testing 
companies and laboratories using the most sensitive analytical 
procedures. The EPA used a multiplication factor of three to reduce the 
imprecision of the method until the imprecision in the sampling and 
analysis is similar to the precision of other EPA methods. For the 2024 
final amendments to the HON and P&R I NESHAP, the EPA determined an EtO 
RDL of 0.07 [micro]g/m\3\, which resulted in an EtO action level of 0.2 
[micro]g/m\3\. Therefore, in this action the EPA is similarly proposing 
at 40 CFR 63.1434(i), by reference to 40 CFR 63.184(d)(3)(iv), an 
action level of 0.2 [micro]g/m\3\ for EtO. If the reported inventories 
are accurate, and considering the anticipated emissions reductions from 
controls we are proposing, our modeling of fenceline EtO concentrations 
indicates that all facilities should be able to meet the fenceline 
concentration action level. For further details of the analysis, see 
the document titled Clean Air Act Section 112(d)(6) Technology Review 
for Fenceline Monitoring Located at Facilities with PEPO Production 
Processes Subject to the PEPO NESHAP, which is available in the docket 
for this rulemaking.
d. Non-Source Category Emissions
    This proposed approach also considers the possibility that offsite 
sources could contribute to modeled concentrations at a facility's 
fenceline. Additionally, non-PEPO sources could be located within 
facility property boundaries that also contribute to monitor readings. 
In this proposal, we are allowing the subtraction of offsite 
interfering sources (as they are not within the control of the owner or 
operator) through site-specific monitoring plans, but we are not 
providing this option for onsite, non-source category emissions. We 
based the action level on facility-wide emissions; therefore, we 
considered these non-source category sources in its development. 
Applying the fenceline standard to the whole facility will also limit 
emissions of EtO from all sources and provide more certainty in 
decisions being made as to whether the entire facility emissions align 
with what is expected from the EPA's analysis. It will also provide 
assurance to fenceline communities that emission reductions are 
achieved and maintained. This is important in the chemical sector, 
where there could be numerous source categories that can be co-located 
within a larger facility and have common tank farms, wastewater 
systems, heat exchangers, APCDs, fuel gas systems, etc., that may be 
assigned or apportioned to various source categories.
e. Corrective Action Requirements
    The proposed fenceline monitoring provisions would require the 
initiation of root cause analysis upon the facility's annual average 
concentration exceeding the action level, as determined on a rolling 
average every sampling period. The root cause analysis is an assessment 
conducted through a process of investigation to determine the primary 
underlying cause and other contributing

[[Page 106027]]

causes of an exceedance of the action level. The proposed provisions at 
40 CFR 63.1434(i), by reference to 40 CFR 63.184(e)(1), would require 
an owner or operator to initiate a root cause analysis within 5 days of 
determining that an updated annual average concentration for EtO 
exceeds the action level. Owners or operators must conduct a root cause 
analysis following each sampling period in which the annual average EtO 
concentration remain above the action level, to determine whether the 
monitoring results and associated data indicate additional sources of 
emissions contributing to concentrations remaining above the action 
level. If the owner or operator cannot determine the root cause of the 
exceedance within 30 days of determining that there was an exceedance 
of an action level, the proposed revisions require use of real-time 
sampling techniques (e.g., mobile gas chromatographs) to determine the 
root cause of the exceedance.
    If the underlying causes of the action level exceedance are deemed 
to be from sources under the control of the owner or operator, we are 
proposing that the owner or operator take corrective action to address 
the underlying cause of the exceedance and to reduce concentrations 
below the action level as expeditiously as possible. We are proposing 
that owners or operators complete the root cause analysis and initial 
corrective action within 45 days after determining that there was an 
exceedance of the action level. If the owner or operator requires 
longer than 45 days to implement the corrective actions identified by 
the root cause analysis, the owner or operator would be required to 
submit a corrective action plan no later than 60 days after completion 
of the root cause analysis.
    After completion of the initial corrective action, if the delta c 
for each of the next three sampling periods for samples collected by 
EPA Method 327 \59\ is below the action level, then the corrective 
action is assumed to have fixed the problem, and the owner and/or 
operator would have no obligation for additional corrective action. 
However, if the delta c for any of the three subsequent sampling 
periods after initial corrective action is over the action level, then 
the owner or operator would have to submit a corrective action plan and 
schedule for implementing design, operation, and maintenance changes to 
eliminate as quickly as possible and prevent recurrence of the primary 
cause and other contributing causes to the exceedance of the action 
level, to reduce annual average concentrations below the action level. 
The proposed provisions would require the owner or operator to include 
the implementation of real-time sampling techniques to locate the 
primary and other contributing causes of the exceedance in the 
corrective action plan. While the action level is based on annual 
average concentrations, once the action level is exceeded, each 
sampling period that exceeds the action level contributes to the delta 
c remaining above the action level. Following these high biweekly 
periods, owners or operators must investigate to determine the root 
cause and, if appropriate, to correct the root cause expeditiously to 
reduce the annual average delta c below the action level.
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    \59\ The EPA is proposing that three sample periods must remain 
below the action level for samples taken by EPA Method 327 because 
this ensures that a sample will have been taken at every monitoring 
location at the site following the completion of the corrective 
action.
---------------------------------------------------------------------------

f. Costs Associated With Fenceline Monitoring Requirements
    Our cost estimate for implementing the same EtO fenceline 
monitoring work practice standard that is in the HON for the PEPO 
NESHAP follows the cost analysis already discussed in the document 
titled Clean Air Act Section 112(d)(6) Technology Review for Fenceline 
Monitoring located in the SOCMI Source Category that are Associated 
with Processes Subject to HON and for Fenceline Monitoring that are 
Associated with Processes Subject to Group I Polymers and Resins NESHAP 
(Docket Item No. EPA-HQ-OAR-2022-0730-0091). We estimated fenceline 
monitoring costs for eight canisters around the fenceline every 5 days. 
Table 12 of this preamble provides the estimated nationwide costs for 
fenceline monitoring as applied to facilities subject to the PEPO 
NESHAP. Note that 12 of the impacted facilities covered under the 
analysis have co-located sources subject to both the HON and the PEPO 
NESHAP and require EtO fenceline monitoring under both rules. For the 
purposes of this analysis, costs for these co-located facilities are 
included under the SOCMI source category for impacts to prevent costs 
being double counted. For further information, see the document titled 
Clean Air Act Section 112(d)(6) Technology Review for Fenceline 
Monitoring Located at Facilities with PEPO Production Processes Subject 
to the PEPO NESHAP, which is available in the docket for this 
rulemaking.

 Table 12--Nationwide Cost Impacts of Fenceline Monitoring for the PEPO
                                 NESHAP
------------------------------------------------------------------------
     No. of                                                   Total
   facilities          Monitoring        Total capital      annualized
    impacted           description       investment ($)    costs ($/yr)
------------------------------------------------------------------------
10..............  Canisters only......          88,720        4,453,600
------------------------------------------------------------------------

g. Additional Requirements of the Fenceline Monitoring Program
    The EPA is proposing, by reference to the HON at 40 CFR 63.182(e), 
that owners or operators report fenceline data on a quarterly basis. 
Each report would contain the results for each sample where the field 
portion of sampling is completed by the end of the quarter, as well as 
for associated field and method blanks (i.e., each report would contain 
data for at 18 canister sampling periods). Owners or operators would 
report these data electronically to the EPA within 45 days after the 
end of each quarterly period. See section IV.E.2 of this preamble for 
further discussion on electronic reporting and section IV.F of this 
preamble for further discussion on the compliance dates we are 
proposing.

D. What actions are we taking pursuant to CAA sections 112(d)(2) and 
(3) and 112(h)?

    In addition to the proposed actions discussed in section IV.B of 
this preamble to reduce risk from EtO emission sources (from PEPO 
processes) and our proposed actions discussed in section IV.C of this 
preamble based on our on technology review, we are proposing other 
requirements for the PEPO NESHAP, based on analyses

[[Page 106028]]

performed pursuant to CAA sections 112(d)(2) and (3) and 
112(h).60 61 We are proposing to: (1) add new monitoring and 
operational requirements for flares used to reduce emissions from PEPO 
production processes, (2) clarify regulatory provisions for vent 
control bypasses for closed vent systems containing bypass lines, (3) 
add work practice standards for startup and shutdown periods for 
maintenance vents and planned routine maintenance of storage vessels, 
(4) add new monitoring requirements for PEPO pressure vessels, (5) add 
new emission standards for PEPO surge control vessels and bottoms 
receivers, (6) add new emission standards for PEPO transfer operations, 
(7) add butylene oxide to the list of HAP presented in table 4 to 
subpart PPP, and (8) remove the 40 CFR 63.1420(d)(3) exemption for 
certain processes currently excluded from the affected source. See the 
following subsections for specific details regarding these proposed 
actions.
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    \60\ The EPA has authority under CAA section 112(d)(2) and (3) 
to set MACT standards for previously unregulated emission points. 
The EPA also retains the discretion to revise a MACT standard under 
the authority of CAA section 112(d)(2) and (3) (see Portland Cement 
Ass'n v. EPA, 665 F.3d 177, 189 (D.C. Cir. 2011)), such as when it 
identifies an error in the original standard. See also Medical Waste 
Inst. v. EPA, 645 F.3d 420, 426 (D.C. Cir. 2011) (upholding the EPA 
action establishing MACT floors, based on post-compliance data, when 
originally-established floors were improperly established).
    \61\ The PEPO NESHAP requires that emission limits apply at all 
times (see 40 CFR 63.1420(h)).
---------------------------------------------------------------------------

1. Flares
    The EPA is proposing under CAA section 112(d)(2) and (3) to amend 
the operating and monitoring requirements for flares, which are 
commonly used as APCDs in the PEPO Production source category, because 
we have determined that the current requirements for flares are not 
adequate to ensure the level of destruction efficiency needed to comply 
with the process vent, storage vessel, wastewater stream, and equipment 
leak MACT standards in the PEPO NESHAP. The requirements applicable to 
flares, which are used to control emissions from various emission 
sources, are set forth in the general provisions of 40 CFR part 63 and 
are cross-referenced in the PEPO NESHAP.
    The general provisions of 40 CFR 63.11(b) specify that flares be: 
(1) steam-assisted, air-assisted, or non-assisted; (2) operated at all 
times when emissions may be vented to them; (3) designed for and 
operated with no visible emissions (except for periods not to exceed a 
total of 5 minutes during any 2 consecutive hours); and (4) operated 
with the presence of a pilot flame at all times. These general 
provisions also specify both the minimum heat content of gas combusted 
in the flare and the maximum exit velocity at the flare tip. The 
general provisions specify monitoring for the presence of the pilot 
flame and the operation of a flare with no visible emissions.
    In general, flares used as APCDs are expected to achieve 98-percent 
HAP destruction efficiencies when designed and operated according to 
the requirements in the general provisions. Studies on flare 
performance,\62\ however, indicate that these general provision 
requirements are inadequate to ensure proper performance of flares at 
refineries and other petrochemical facilities, particularly when the 
flares are either steam- or air-assisted. In addition, over the last 
decade, flare minimization efforts at these facilities have led to an 
increasing number of flares operating at well below their design 
capacity, and while these efforts have resulted in reduced flaring of 
gases, situations of over-assisting with either steam or air have 
become exacerbated, leading to the degradation of flare combustion 
efficiency. Many PEPO facilities operate directly downstream from 
refineries and other petrochemical plants (e.g., ethylene and EtO 
production plants) and, consequently, they likely flare waste gas 
constituents that are similar to those of a refinery or petrochemical 
plant. Given that the flare dataset that formed the underlying basis of 
the new standards for refinery flares also included flares at 
petrochemical plants, we are proposing at 40 CFR 63.1426(a) and 
(e)(2)(i), 63.1429(a)(8), 63.1430(b)(1), and 63.1437(c), each by 
reference to proposed 40 CFR 63.1436, to apply the finalized suite of 
operational and monitoring requirements for refinery flares \63\ to 
those flares in the PEPO Production source category that control 
emissions from PEPO processes. Therefore, these proposed amendments at 
40 CFR 63.1436 will ensure that continuous compliance with the CAA 
section 112(d)(2) and (3) standards is achieved for PEPO facilities 
that use flares as APCDs to meet the MACT standards at all times when 
controlling HAP emissions. We are also proposing to revise the entry 
for 40 CFR 63.11 of table 1 to the PEPO NESHAP to show that the 
provisions at 40 CFR 63.11(b) do not apply to flares because we are 
proposing to replace these provisions with new standards for flares 
used to comply with the MACT standards in the PEPO NESHAP.
---------------------------------------------------------------------------

    \62\ For a list of studies, refer to the technical report titled 
Parameters for Properly Designed and Operated Flares, in Docket Item 
No. EPA-HQ-OAR-2010-0682-0191.
    \63\ See 40 CFR 63.670 and 63.671 (originally finalized in 80 FR 
75178 on December 1, 2015; and amended at 81 FR 45232 on July 13, 
2016, 83 FR 60696 on November 26, 2018, 85 FR 6064 on February 4, 
2020, and 89 FR 23860 on April 4, 2024).
---------------------------------------------------------------------------

    In 2012, the EPA compiled information and test data collected on 
flares and summarized its preliminary findings on operating parameters 
that affect flare combustion efficiency in a technical report titled 
Parameters for Properly Designed and Operated Flares, available in 
Docket Item No. EPA-HQ-OAR-2010-0682-0191.\64\ The EPA submitted this 
report, along with a charge statement and a set of charge questions, to 
an external peer review panel.\65\ The panel, consisting of individuals 
representing a variety of backgrounds and perspectives (i.e., industry, 
academia, environmental experts, and industrial flare consultants), 
concurred with the EPA's assessment that the following three primary 
factors affect flare performance: (1) the flow of the vent gas to the 
flare; (2) the amount of assist media (e.g., steam or air) added to the 
flare; and (3) the combustibility of the vent gas/assist media mixture 
in the combustion zone (i.e., the net heating value, lower 
flammability, and/or combustibles concentration) at the flare tip. In 
response to peer review comments, the EPA performed a validation and 
usability analysis on all available test data as well as a failure 
analysis on potential parameters discussed in the technical report as 
indicators of flare performance. The document titled Peer Review of 
Parameters for Properly Designed and Operated Flares, which is 
available in Docket Item No. EPA-HQ-OAR-2010-0682-0193, contains the 
peer review comments, and we have incorporated that document into the 
docket for this rulemaking. These analyses resulted in a change to the 
population of test data that the EPA evaluated, and they helped form 
the basis for the flare operating limits promulgated in the 2015 
Petroleum Refinery Sector final rule at 40 CFR part 63, subpart CC (80 
FR 75178).\66\ In this

[[Page 106029]]

action, we are also relying on the flare analyses discussed earlier in 
this preamble and proposing to apply the operating limits contained in 
the final rule for petroleum refineries to the flares used as APCDs in 
the PEPO Production source category (hereafter referred to as ``PEPO 
flares''). The Agency believes, given the results from the various data 
analyses conducted for the Petroleum Refinery Sector rule, that the 
operating limits promulgated for flares used in the petroleum refinery 
sector are also appropriate and reasonable for PEPO flares to ensure 
that these flares meet the HAP destruction and removal efficiency at 
all times, consistent with the MACT standards established in the PEPO 
NESHAP in 1999 (64 FR 29420). Therefore, we are proposing at 40 CFR 
63.1436 to replace all flare requirements throughout the PEPO NESHAP 
\67\ with the Petroleum Refinery Sector rule flare definitions and 
requirements in 40 CFR part 63, subpart CC, with certain clarifications 
and exemptions discussed in this section of the preamble, including, 
but not limited to, specifying that several definitions in 40 CFR part 
63, subpart CC, that apply to petroleum refinery flares also apply to 
flares in the PEPO Production source category, adding a definition and 
requirements for pressure-assisted multi-point flares, and specifying 
additional requirements for when an owner or operator uses a gas 
chromatograph or mass spectrometer for compositional analysis.
---------------------------------------------------------------------------

    \64\ See section II.D. of this preamble, which addresses the 
incorporation by reference of certain docket files such as this one 
into the docket for this rulemaking.
    \65\ These documents can be found at https://www.epa.gov/stationary-sources-air-pollution/review-peer-review-parameters-properly-designed-and-operated-flares.
    \66\ See the document titled Flare Performance Data: Summary of 
Peer Review Comments and Additional Data Analysis for Steam-Assisted 
Flares in Docket Item No. EPA-HQ-OAR-2010-0682-0200 for a more 
detailed discussion of the data quality and analysis; the document 
titled Petroleum Refinery Sector Rule: Operating Limits for Flares 
in Docket Item No. EPA-HQ-OAR-2010-0682-0206 for a more detailed 
discussion of the failure analysis, and the document titled Flare 
Control Option Impacts for Final Refinery Sector Rule in Docket Item 
No. EPA-HQ-OAR-2010-0682-0748 for additional analyses on flare 
performance standards based on public comments received on the 
proposed Petroleum Refinery Sector rule.
    \67\ Refer to proposed 40 CFR 63.1436(a)(1) through (25) for a 
list of provisions that would no longer apply.
---------------------------------------------------------------------------

    The remainder of this section of the preamble includes a discussion 
of requirements that we are proposing for PEPO flares, along with 
impacts and costs associated with these proposed revisions. 
Specifically, this action proposes to require that PEPO flares operate 
pilot flame systems continuously and that flares operate with no 
visible emissions (except for periods not to exceed a total of 5 
minutes during any 2 consecutive hours) when the flare vent gas flow 
rate is below the smokeless capacity of the flare. In addition, this 
action proposes to consolidate measures related to flare tip velocity 
and proposes new operational and monitoring requirements related to the 
combustion zone gas. Further, this action proposes a work practice 
standard related to the visible emissions during periods when the flare 
is operated above its smokeless capacity (e.g., periods of emergency 
flaring). Currently, the MACT standards in the PEPO NESHAP cross-
reference the general provisions at 40 CFR 63.11(b) for the operational 
requirements for flares used as APCD. This proposal eliminates cross-
references to the general provisions and instead specifies all new 
operational and monitoring requirements that are intended to apply to 
flares used as APCDs in the PEPO NESHAP.
a. Pilot Flames
    The PEPO NESHAP references the flare requirements in 40 CFR 
63.11(b), which specify that a flare used as an APCD should operate 
with a pilot flame present at all times. The provisions at 40 CFR 
63.1429(a)(2) also require a device (including but not limited to a 
thermocouple, ultraviolet beam sensor, or infrared sensor) capable of 
continuously detecting the presence of a pilot flame. Pilot flames are 
proven to improve flare flame stability, and even short durations of an 
extinguished flame could cause a significant reduction in flare 
destruction efficiency. In this proposal, we are proposing to remove 
the cross-reference to the general provisions for PEPO flares and the 
requirement at 40 CFR 63.1429(a)(2), and instead cross-reference 40 CFR 
part 63, subpart CC, to include in the PEPO NESHAP the existing 
provisions requiring that flares operate with a pilot flame at all 
times and that owners or operators continuously monitor for a pilot 
flame using a thermocouple or any other equivalent device. We are also 
proposing to add a continuous compliance provision that would consider 
each 15-minute block where there is at least 1 minute without a pilot 
flame present when regulated material is routed to the flare as a 
violation of the standard. Refer to 40 CFR 63.1436 and 63.670(b) and 
(g) for these proposed requirements. See section IV.D.1.e of this 
preamble for our rationale for proposing to use a 15-minute block 
averaging period for determining continuous compliance. We solicit 
comments on the proposed revisions for flare pilot flames.
b. Visible Emissions
    The PEPO NESHAP references 40 CFR 63.11(b), which specifies that a 
flare used as an APCD should operate with visible emissions for no more 
than 5 minutes in a 2-hour period. Owners or operators of these flares 
are required to conduct an initial performance demonstration for 
visible emissions using EPA Method 22 of appendix A-7 to 40 CFR part 
60. We are proposing to remove the cross-reference to the general 
provisions for PEPO flares and instead cross-reference 40 CFR part 63, 
subpart CC, to include this same limitation on visible emissions. We 
are also proposing to clarify that owners or operators should conduct 
an initial 2-hour visible emissions demonstration the first time that 
regulated materials are routed to the flare.
    With regard to continuous compliance with the visible emissions 
limitation, we are proposing daily visible emissions monitoring for 
PEPO flares whenever regulated material is routed to the flare and also 
visible emissions monitoring whenever owners or operators observe 
visible emissions from the flare. On days that the flare receives 
regulated material, we are proposing that owners or operators of PEPO 
flares monitor visible emissions at a minimum of once per day while the 
flare is receiving regulated material using an observation period of 5 
minutes and EPA Method 22. Additionally, whenever regulated material is 
routed to a flare and there are visual emissions from the flare, we are 
proposing that owners or operators perform another 5-minute visible 
emissions observation using EPA Method 22, even if they have already 
performed the minimum required daily visible emission monitoring. For 
example, if an employee observes visible emissions, the owner or 
operator of the flare would perform a 5-minute EPA Method 22 
observation to check for compliance upon initial observation or 
notification of such event. In addition, in lieu of daily visible 
emissions observations performed using EPA Method 22, we are proposing 
that owners and operators be allowed to use video surveillance cameras. 
We believe that video surveillance cameras would be at least as 
effective for the PEPO flares as the proposed daily 5-minute visible 
emissions observations using EPA Method 22.
    We are also proposing to extend the observation period for a PEPO 
flare to 2 hours whenever visible emissions are observed for greater 
than 1 continuous minute during any of the 5-minute observation 
periods. Refer to 40 CFR 63.1436 and 63.670(c) and (h) for these 
proposed requirements. We acknowledge that operating a flare near the 
incipient smoke point (the point at which black smoke begins to form 
within the flame) results in good combustion at the flare tip; however, 
smoking flares can contribute significantly to emissions of particulate 
matter that is 2.5 micrometers in diameter or smaller. Thus, while

[[Page 106030]]

increasing the allowable period for visible emissions may be useful 
from an operational perspective, we do not believe the allowable period 
for visible emissions should be increased to more than 5 minutes in any 
2-hour period. We solicit comments on the proposed allowable period for 
visible emissions from flares.
    As discussed later in this section, we are proposing additional 
operational and monitoring requirements for PEPO flares that we expect 
will result in owners or operators of PMPUs installing equipment that 
can be used to fine-tune and control the amount of assist steam or air 
introduced at the flare tip, thereby maximizing the flare combustion 
efficiency. These monitoring and control systems will assist flare 
owners or operators in operating near the incipient smoke point without 
exceeding the visible emissions limit. While combustion efficiency may 
be highest at the incipient smoke point, it is not significantly higher 
than the combustion efficiency achieved by the proposed operating 
limits discussed in section IV.D.1.d of this preamble. As seen in the 
performance curves for flares, there is very limited improvement in 
flare performance beyond the performance achieved at the proposed 
operating limits (see document titled Petroleum Refinery Sector Rule: 
Operating Limits for Flares, available in Docket Item No. EPA-HQ-OAR-
2010-0682-0206, which we have incorporated into the docket for this 
rulemaking). We solicit comments and data on appropriate periods of 
visible emissions that would encourage flare operation at the incipient 
smoke point.
    In addition, we are proposing that the owner or operator establish 
the smokeless capacity of each PEPO flare based on design specification 
of the flare and that the visible emissions limitation only apply when 
the flare vent gas flow rate is below its smokeless capacity. We are 
proposing a work practice standard that applies during emergency 
releases when the flow to a flare exceeds the smokeless capacity of the 
flare, based on comments the EPA received on the proposed Petroleum 
Refinery Sector rule. Refer to 40 CFR 63.1436 and 63.670(o) for these 
proposed provisions. In the Petroleum Refinery Sector final rule, the 
EPA explained that numerous comments on the proposal suggested that 
flares are not designed to meet the visible emissions requirements when 
operated beyond their smokeless capacity (80 FR 75178). According to 
commenters, flares are typically designed to operate in a smokeless 
manner at 20- to 30-percent of full hydraulic load. Thus, they claimed, 
flares have two different design capacities: (1) a ``smokeless 
capacity'' to handle normal operations and typical process variations, 
and (2) a ``hydraulic load capacity'' to handle very large volumes of 
gases discharged to the flare as a result of an emergency shutdown. 
According to commenters, these capacity considerations are inherent in 
all flare designs, and the issue of flares not meeting visible 
emissions requirements when beyond their smokeless capacity has not 
previously been an issue because flare operating limits did not apply 
during malfunction events.
    For this proposed work practice standard, the NESHAP would require 
owners or operators to develop a flare management plan for PEPO flares 
that identifies procedures for limiting discharges to the flare as a 
result of process upsets or malfunctions that cause the flare to exceed 
its smokeless capacity. In addition, for any flare that exceeds both 
the smokeless design capacity and visible emissions limit, we are 
proposing that owners or operators conduct a specific root cause 
analysis and take corrective action to prevent the recurrence of a 
similarly caused event. We are proposing that if the root cause 
analysis indicates that the exceedance of the visible emissions limit 
is caused by operator error or poor maintenance, then the exceedance 
would be considered a violation of the work practice standard. We are 
also proposing that a second event that occurs within a rolling 3-year 
period from the same root cause on the same equipment would be 
considered a violation of the standard. Finally, we are proposing that 
a third visible emissions limit exceedance occurring from the same 
flare in a rolling 3-year period would be a violation of the work 
practice standard, regardless of the cause.
    In several of the EPA's previous impact analyses (for petroleum 
refinery flares and ethylene production flares),\68\ the EPA 
established the number of events in a given time period that would be 
the ``backstop'' (i.e., a violation of the standard). In each of these 
analyses, the EPA evaluated four different timing alternatives (two 
events in 5 years; two events in 3 years; two events in 5 years; and 
three events in 3 years) based on the number of existing flares 
evaluated over a 20-year period, and ultimately concluded that three 
events in 3 years would be ``achievable'' for the average of the best 
performing flares. We see no reason why this would be any different for 
PEPO flares. Even if a best-performing flare ``typically'' only has one 
event every 7 years, the fact that these events are random by nature 
(unpredictable, not under the direct control of the owner or operator) 
makes it difficult to use a 5-year time span. Based on this analysis, 
three events in 3 years would appear to be ``achievable'' for the 
average of the best performing flares.
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    \68\ See EPA-HQ-OAR-2010-0682-0793, EPA-HQ-OAR-2010-0682-0794, 
and EPA-HQ-OAR-2017-0357-0017.
---------------------------------------------------------------------------

c. Flare Tip Velocity
    This proposed action consolidates provisions related to flare tip 
velocity for PEPO flares. The PEPO NESHAP references the flare 
provisions in 40 CFR 63.11(b), which specify maximum flare tip 
velocities based on flare type (non-assisted, steam-assisted, or air-
assisted) and the net heating value of the flare vent gas. Based on 
data provided to the EPA in response to our CAA section 114 request 
(see section II.C of this preamble), four of the nine flares that PEPO 
facilities reported using as APCDs are either steam- or air-assisted 
(see the document titled Control Option Impacts for Flares in the PEPO 
Production Source Category that Control Emissions from Processes 
Subject to the PEPO NESHAP, which is available in the docket for this 
rulemaking). Maximum flare tip velocities are required to ensure that 
the flame does not ``lift off'' the flare (i.e., a condition where a 
flame separates from the tip of the flare and there is space between 
the flare tip and the bottom of the flame), which could cause flame 
instability and/or potentially result in a portion of the flare gas 
being released without proper combustion. We are proposing to remove 
the cross-reference to the general provisions for PEPO flares and 
instead to cross-reference 40 CFR part 63, subpart CC, to consolidate 
the provisions for maximum flare tip velocity into the PEPO NESHAP as a 
single equation, irrespective of flare type (i.e., steam-assisted, air-
assisted, or non-assisted). Refer to 40 CFR 63.1436 and 63.670(d), (i), 
and (k) for these proposed provisions.
    Based on analysis conducted for the Petroleum Refinery Sector rule, 
the EPA identified test runs of air-assisted flares with high tip 
velocities that had high combustion efficiencies (see the document 
titled Petroleum Refinery Sector Rule: Evaluation of Flare Tip Velocity 
Requirements in Docket Item No. EPA-HQ-OAR-2010-0682-0212). These test 
runs exceeded the maximum flare tip velocity limits for air-assisted 
flares using the linear equation in 40 CFR 63.11(b)(8). When the EPA 
compared these test runs to the test runs for non-assisted and steam-
assisted

[[Page 106031]]

flares, we determined that air-assisted flares appeared to have the 
same operating envelope as the non-assisted and steam-assisted flares. 
Therefore, for air-assisted PEPO flares, we are proposing the use of 
the same equation that non-assisted and steam-assisted flares currently 
use to establish the flare tip velocity operating limit. We are also 
proposing that the owner or operator determine the flare tip velocity 
on a 15-minute block average basis. See section IV.D.1.e of this 
preamble for our rationale for proposing to use a 15-minute block 
averaging period for determining continuous compliance.
    Finally, we are proposing to exclude the provision for the special 
flare tip velocity equation in the general provisions at 40 CFR 
63.11(b)(6)(i)(A) for non-assisted PEPO flares used to control gases 
with hydrogen content greater than 8 percent. This equation, which was 
developed based on limited data from a chemical manufacturer, has very 
limited applicability for flares used as APCDs in the PEPO Production 
source category because it only provides an alternative for non-
assisted flares that are used to control gases with large quantities of 
hydrogen. Available data indicates that there are 18 flares in the PEPO 
Production source category; approximately 45 percent of these flares 
are either steam-assisted or air-assisted and 55 percent are non-
assisted flares. Instead, we are proposing compliance alternatives that 
we believe provide a better way for PEPO flares combusting gases with 
high hydrogen content to comply with the rule while ensuring proper 
destruction performance of the flare (see section IV.D.1.d of this 
preamble for the proposed compliance alternatives). Therefore, for non-
assisted PEPO flares used as APCDs for gases with hydrogen content 
greater than 8 percent, we are proposing to exclude this special flare 
tip velocity equation as a compliance alternative. We request comment 
on the need to include this equation in the PEPO NESHAP.
d. Net Heating Value of the Combustion Zone Gas
    The current provisions for flares in 40 CFR 63.11(b) specify that 
the flare vent gas meet a minimum net heating value of 200 British 
thermal units per standard cubic foot (Btu/scf) for non-assisted flares 
and 300 Btu/scf for air- and steam-assisted flares. The PEPO NESHAP 
references these provisions, but neither the general provisions nor the 
PEPO NESHAP includes specific requirements for monitoring the net 
heating value of the flare vent gas. Moreover, recent flare testing 
results indicate that meeting a minimum net heating value limit alone 
does not address instances when the flare may be over-assisted because 
it only considers the net heating value of the gas being combusted in 
the flare and does not consider other parameters (e.g., absence of 
assist media). However, many industrial flares use steam or air as an 
assist medium to protect the flare tip, promote turbulence for the 
mixing, induce air into the flame, and operate with no visible 
emissions. Using excessive steam or air results in dilution and cooling 
of flared gases and can lead to operating a flare outside its stable 
flame envelope, reducing the destruction efficiency of the flare. In 
extreme cases, over-steaming or excess aeration can snuff out a flame 
and allow regulated material to be released into the atmosphere without 
complete combustion. As previously noted in section IV.D.1.c of this 
preamble, because available data indicate that about half of all PEPO 
flares are either steam- or air-assisted, it is critical that we ensure 
that the determination of flare combustion efficiency account for 
assist media in some form. Recent flare test data have shown that the 
best way to account for situations of over-assisting is to consider the 
gas mixture properties at the flare tip in the combustion zone when 
evaluating the ability to combust efficiently. As discussed in the 
introduction to this preamble section, the external peer review panel 
concurred with our assessment that the combustion zone properties at 
the flare tip are critical parameters to know in determining whether a 
flare will achieve good combustion. The general provisions, however, 
solely rely on the net heating value of the flare vent gas, and we have 
determined that that information is not sufficient for determining 
flare combustion efficiency of PEPO flares.
    In this proposal, in lieu of requiring compliance with the 
operating limits for net heating value of the flare vent gas specified 
in the general provisions, we are proposing to cross-reference 40 CFR 
part 63, subpart CC, to include in the PEPO NESHAP a single minimum 
operating limit for the net heating value in the combustion zone gas 
(NHVcz) of 270 Btu/scf during any 15-minute period for steam-assisted, 
air-assisted, and non-assisted PEPO flares. Refer to 40 CFR 63.1436 and 
63.670(l) and (m) for these proposed provisions. The Agency believes, 
given the results from the various data analyses conducted for the 
Petroleum Refinery Sector rule, that this NHVcz operating limit 
promulgated for flares in the Petroleum Refinery Sector source category 
is also appropriate and reasonable and will ensure PEPO flares meet the 
HAP destruction efficiencies in the standard at all times when operated 
in concert with the other proposed flare provisions such as the pilot 
flame, visible emissions, and flare tip velocity requirements. See the 
documents titled Petroleum Refinery Sector Rule: Operating Limits for 
Flares and Flare Control Option Impacts for Final Refinery Sector Rule 
in Docket Item Nos. EPA-HQ-OAR-2010-0682-0206 and EPA-HQ-OAR-2010-0682-
0748, respectively). In addition, we are proposing that owners or 
operators may use a corrected heat content of 1,212 Btu/scf for 
hydrogen, instead of 274 Btu/scf, to demonstrate compliance with the 
NHVcz operating limit for PEPO flares; however, owners or operators who 
intend to use the corrected hydrogen heat content must have a system 
capable of monitoring for the hydrogen content in the flare vent gas. 
The EPA determined the 1,212 Btu/scf value based on a comparison 
between the lower flammability limit and net heating value of hydrogen 
compared to light organic compounds and we have used this value in 
several consent decrees issued by the EPA. Based on analyses conducted 
for the Petroleum Refinery Sector rule (see the document titled Flare 
Control Option Impacts for Final Refinery Sector in Docket Item No. 
EPA-HQ-OAR-2010-0682-0748), the EPA determined that using a 1,212 Btu/
scf value for hydrogen greatly improves the correlation between 
combustion efficiency and the combustion zone net heating value over 
the entire array of data.
    Furthermore, in addition to the NHVcz operating limit, we are 
proposing a net heating value dilution parameter (NHVdil) for certain 
PEPO flares that operate with perimeter assist air. Refer to 40 CFR 
63.1436 and 63.670(f) and (n) for these proposed provisions. For air-
assisted flares, use of too much perimeter assist air can lead to poor 
flare performance. Furthermore, based on our analysis of the air-
assisted flare datasets (see the document titled Petroleum Refinery 
Sector Rule: Operating Limits for Flares in Docket Item No. EPA-HQ-OAR-
2010-0682-0206), we determined that a NHVdil of 22 Btu/scf is necessary 
to ensure that there is enough combustible material available to 
adequately burn the gas and pass through the flammability region and 
also ensure that degradation of flare performance from excess aeration 
does not occur. We found that including the flow rate of perimeter 
assist air in the calculation of the NHVcz does not

[[Page 106032]]

identify all instances of excess aeration and could (in some instances) 
even allow facilities to send very dilute vent gases to the flare that 
would not combust (i.e., vent gases below their lower flammability 
limit could be sent to flare). Instead, the data suggest that the 
diameter of the flare tip, in concert with the amount of perimeter 
assist air (and other parameters used to determine NHVcz), provide the 
inputs necessary to calculate whether this type of flare is over-
assisted. This dilution parameter is consistent with the combustion 
theory that the more time the gas spends in the flammability region 
above the flare tip, the more likely it will combust. Also, because 
both the volume of the combustion zone (represented by the diameter) 
and how quickly this gas is diluted to a point below the flammability 
region (represented by perimeter assist air flow rate) characterize 
this time duration, it is logical that we propose such a parameter.
    We also found that some assist steam lines are purposely designed 
to entrain air into the lower or upper steam at the flare tip; and for 
flare tips with an effective tip diameter of 9 inches or more, there 
are no flare tip steam induction designs that can entrain enough assist 
air to cause a flare operator to have a deviation from the NHVdil 
operating limit without first deviating from the NHVcz operating limit. 
Therefore, we are proposing to allow owners or operators of PEPO flares 
that only use perimeter assist air entrained in lower and upper steam 
at the flare tip and that have a flare tip diameter of 9 inches or 
greater to comply only with the NHVcz operating limit. Steam-assisted 
flares with perimeter assist air and an effective tip diameter of less 
than 9 inches would remain subject to the requirement to account for 
the amount of assist air intentionally entrained within the calculation 
of NHVdil. However, we recognize that owners or operators cannot 
directly measure this assist air, but the quantity of air entrained is 
dependent on the assist steam rate and the design of the steam tube's 
air entrainment system. Therefore, we are proposing provisions to 
specify that owners or operators of these smaller diameter steam-
assisted PEPO flares use the steam flow rate and the maximum design 
air-to-steam ratio of the steam tube's air entrainment system for 
determining the flow rate of this assist air. Using the maximum design 
ratio will tend to over-estimate the assist air flow rate, which is 
conservative with respect to ensuring compliance with the NHVdil 
operating limit.
    Finally, we are proposing that owners or operators record and 
calculate 15-minute block average values for these parameters. Section 
IV.D.1.e of this preamble provides our rationale for selecting a 15-
minute block averaging period. We solicit comments on the proposed 
revisions related to NHVcz.
e. Data Averaging Periods for Flare Gas Operating Limits
    Except for the visible emissions operating limits described in 
section IV.D.1.b of this preamble, we are proposing to use a 15-minute 
block averaging period for each proposed flare operating parameter 
(i.e., presence of a pilot flame, flare tip velocity, and NHVcz) to 
ensure that PEPO flares operate within the appropriate operating 
conditions. We consider a 15-minute averaging time to be the most 
appropriate for assessing proper flare performance because flare vent 
gas flow rates and composition can change significantly over short 
periods of time. Furthermore, because destruction efficiency can fall 
precipitously when a flare is controlling vent gases below (or outside) 
the proposed operating limits, short time periods where the operating 
limits are not met could seriously decrease the overall performance of 
the flare. Refer to the Petroleum Refinery Sector rule preambles (79 FR 
36880 and 80 FR 75178) for further details supporting why we believe a 
15-minute averaging period is appropriate.
    Given the short averaging times for the operating limits, we are 
proposing calculation methodologies to enable owners or operators to 
use ``feed forward'' calculations to ensure compliance with the 
operating limits on a 15-minute block average for PEPO flares. 
Specifically, we propose using the results of the compositional 
analysis determined just prior to a 15-minute block period for the next 
15-minute block average. Owners or operators of PEPO flares will then 
know the vent gas properties for the upcoming 15-minute block period 
and can adjust assist gas flow rates relative to vent gas flow rates to 
comply with the proposed operating limits. In other words, ``feed 
forward'' means that owners or operators would use the net heating 
value in the vent gas (NHVvg) going into the flare in one 15-minute 
period to adjust the assist media (i.e., steam or air) and/or the 
supplemental gas in the next 15-minute period, as necessary, to 
calculate an NHVcz limit of 270 Btu/scf or greater using the proposed 
equation. We recognize that when a subsequent measurement value is 
determined, the instantaneous NHVcz based on that compositional 
analysis and the flow rates that exist at the time may not be above 270 
Btu/scf. We are proposing that this is not a violation of the operating 
limit. Rather, we are proposing that the owner or operator is only 
required to make operational adjustments based on that information to 
achieve, at a minimum, the net heating value limit for the subsequent 
15-minute block average. We are, however, proposing that failure to 
adjust the assist media or supplemental natural gas using the NHVvg 
from the previous period in the equation provided for calculating an 
NHVcz limit of 270 Btu/scf would be a violation of the operating limit. 
Alternatively, because the owner or operator could directly measure the 
NHVvg on a more frequent basis, such as with a calorimeter (and 
optional hydrogen analyzer), the process control system is able to 
adjust more quickly, and the owner or operator can adjust the assist 
media or supplemental natural gas more quickly. In this manner, the 
owner or operator is not limited by relying on NHVvg data that may not 
represent the current conditions. We are, therefore, also proposing 
that the owner or operator may opt to use the NHVvg in such instances 
from the same period to comply with the operating limit. For examples 
of ``feed forward'' calculations, see attachment 3 of the document 
titled Flare Control Option Impacts for Final Refinery Sector Rule in 
Docket Item No. EPA-HQ-OAR-2010-0682-0748.
    We are also proposing to clarify that when determining compliance 
with the flare tip velocity and combustion zone operating limits 
specified in 40 CFR 63.670(d) and (e), the initial 15-minute block 
period starts with the 15-minute block that includes a full 15 minutes 
of the flaring event. In other words, we are proposing to clarify that 
the owner or operator demonstrate compliance with the velocity and 
NHVcz requirements starting with the block that contains the fifteenth 
minute of a flaring event; and the owner or operator is not required to 
demonstrate compliance for the previous 15-minute block in which the 
event started and contained only a fraction of flow. We solicit 
comments on these proposed revisions.
f. Flares in Dedicated Service
    In lieu of the requirement that owners or operators continuously 
monitor the composition of the vent gas and the NHVvg, we are proposing 
an alternative monitoring approach for PEPO flares in dedicated service 
where the flare vent gas has consistent composition and flow. We 
believe that these flares do not

[[Page 106033]]

need to have the same type of ongoing monitoring requirements as those 
with more variable waste streams. Thus, we are proposing an option that 
owners or operators can use to demonstrate compliance with the 
operating requirements for PEPO flares that are in dedicated service to 
a specific emission source, such as a transfer rack operation 
consistently loading the same material. We are proposing that owners or 
operators submit an application to the Administrator to allow the use 
of this alternative compliance option. We are proposing that the 
application include a description of the system, characterization of 
the vent gases that could be routed to the flare based on a minimum of 
7 grab samples (14 daily grab samples for continuously operated 
flares), and specification of the net heating value that will be used 
for all flaring events (based on the minimum net heating value of the 
grab samples). In other words, for PEPO flares that are in dedicated 
service, we are proposing that owners or operators could use the 
minimum NHVvg determined from the grab samples in the equation at 40 
CFR 63.670(m)(1) for all flaring events to determine NHVcz. We are also 
proposing to allow engineering estimates to characterize the amount of 
gas flared and the amount of assist gas introduced into the system. For 
example, we believe that the use of fan curves to estimate air assist 
rates would be acceptable. We propose that flare owners or operators 
would use the net heating value determined from the initial sampling 
phase and measured or estimated flare vent gas and assist gas flow 
rates, if applicable, to demonstrate compliance with the standards. 
Refer to 40 CFR 63.1436 and 63.670(j)(6) for these proposed provisions. 
Finally, for owners and operators that must comply with the continuous 
monitoring requirements, we are proposing additional clarifications and 
requirements at 40 CFR 63.1436 when using a gas chromatograph or mass 
spectrometer for compositional analysis. We solicit comments on the 
proposed revisions related to flares in dedicated service.
g. Impacts of the Proposed Flare Operating and Monitoring Requirements
    The EPA expects that the requirements for flares used as APCDs in 
the PEPO Production source category discussed in this section will 
affect all flares at PEPO processes. As previously mentioned, based on 
facility responses to our CAA section 114 request (see section II.C of 
this preamble), we estimate that there are 18 flares of traditional 
elevated flare tip designs (e.g., steam-assisted, air-assisted, and 
non-assisted flare tips). The EPA estimated the costs for each flare 
for a given facility, considering current monitoring systems already 
installed on each individual flare. Given that the same type of 
equipment is used for flares in the PEPO Production source category and 
for the petroleum refinery sector, we estimated the costs for any 
additional monitoring systems needed based on installed costs received 
from petroleum refineries and, if installed costs were unavailable, we 
based the cost estimates on vendor-purchased equipment. The EPA 
estimated the baseline emissions and the emission reductions achieved 
by the proposed rule based on current vent gas and steam flow data 
submitted by industry representatives. We note that the requirements 
for PEPO flares that we are proposing will ensure compliance with the 
MACT standards in the PEPO NESHAP when flares are used as an APCD. 
Because we are not changing the underlying MACT standards in the PEPO 
NESHAP, we did not include any of the estimated excess emissions from 
flares in the summary of total estimated emissions reductions for this 
action. However, we estimate that the proposed operational and 
monitoring requirements have the potential to reduce excess emissions 
from PEPO flares by approximately 75 tpy of HAP and 281 tpy of VOC 
(i.e., non-methane, non-ethane total hydrocarbons). According to the 
emissions inventory file we used to assess residual risk (see section 
IV.C.1 of this preamble), there are 10 individual HAP compounds 
included in the emissions inventory for PEPO flares, including 
propylene oxide, EtO, toluene, glycol ethers, and hexane. For more 
detail on the impact estimates, see the document titled Control Option 
Impacts for Flares in the PEPO Production Source Category that Control 
Emissions from Processes Subject to the PEPO NESHAP, which is available 
in the docket for this rulemaking.
2. Closed Vent System Containing Bypass Lines
    For a closed vent system containing bypass lines that can divert 
the stream away from the APCD to the atmosphere, the PEPO NESHAP 
requires the owner or operator to either: (1) install, maintain, and 
operate a continuous parametric monitoring system for flow on the 
bypass line that is capable of detecting whether a vent stream flow is 
present at least once every 15 minutes, or (2) secure the bypass line 
valve in the non-diverting position with a car-seal or a lock-and-key 
type configuration. Under option 2, the PEPO NESHAP also requires 
owners or operators to inspect the seal or closure mechanism at least 
once per month to verify the valve is maintained in the non-diverting 
position (see 40 CFR 63.1429(c)(2) for more details). To expressly 
prohibit bypassing an APCD at affected sources, as implied by option 2, 
we are proposing that an owner or operator may not bypass the APCD at 
any time and that a bypass is a violation (see proposed 40 CFR 
63.1429(c)(3)), and owners and operators must estimate, maintain 
records, and report the quantity of organic HAP released (see proposed 
40 CFR 63.1430(d)(6) and (h)(7)). These proposed requirements are also 
being proposed at 40 CFR 63.1425(f), by reference to 40 CFR 
63.114(d)(2) and (3) and 63.118(a)(5) and (f)(7), for process vents in 
a PMPU that use THF to produce one or more PEPO products. We are 
proposing these revisions to ensure continuous compliance with the MACT 
standards, consistent with Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 
2008) (where the Court determined that standards under CAA section 
112(d) must provide for compliance at all times), because bypassing an 
APCD could result in a release of regulated organic HAP to the 
atmosphere that would be required to be controlled under the existing 
MACT standards in the PEPO NESHAP. We are also proposing that the use 
of a cap, blind flange, plug, or second valve on open-ended valves or 
lines (following the requirements specified in 40 CFR 60.482-6(a)(2), 
(b), and (c) or following requirements codified in another regulation 
that are the same as 40 CFR 60.482-6(a)(2), (b), and (c)) is sufficient 
to prevent a bypass. We solicit comments on these proposed revisions.
3. Maintenance Activities
    In the 2014 final rule (79 FR 17340, March 27, 2014), we removed 
the exemption from emissions standards for periods of SSM in accordance 
with a decision of the United States Court of Appeals for the District 
of Columbia Circuit, Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 
2008), cert. denied, 130 S. Ct. 1735 (U.S. 2010). This decision stated 
that the EPA must have standards in place at all times, even during 
periods of SSM. As a result, the process vent and storage vessel 
provisions (as well as other provisions) in the PEPO NESHAP apply at 
all times. Although the EPA eliminated the SSM exemption from the PEPO 
NESHAP in 2014, we recognize that owners or operators periodically 
discharge vent streams during certain maintenance activities, such as 
those that require equipment openings, and we consider maintenance

[[Page 106034]]

activities a separate class of startup and shutdown emissions because 
there must be a point in time when the equipment can be opened, and any 
remaining emissions vented to the atmosphere. We also acknowledge that 
it would require a significant effort to identify and characterize each 
of these potential release points (e.g., for permitting purposes). 
Therefore, we are proposing to establish MACT standards for maintenance 
activities (i.e., equipment openings, storage vessel degassing, and 
periods of planned routine maintenance of the emission control system 
for the vent on a fixed roof tank at a new or existing affected 
source). CAA section 112(h)(1) states that the Administrator may 
prescribe a work practice standard or other requirements, consistent 
with the provisions of CAA section 112(d) or (f), in those cases where, 
in the judgment of the Administrator, it is not feasible to enforce an 
emission standard. We are proposing work practices instead of numeric 
emission limits for maintenance activities because it is ``not feasible 
to prescribe or enforce an emission standard'' for these emissions. 
Emissions from maintenance activities are not ``emitted through a 
conveyance designed and constructed to emit or capture such pollutant'' 
(see CAA section 112(h)(2)(A)) and it is not possible to characterize 
each of these potential release points.
a. Equipment Openings (Excluding Storage Vessel Degassing)
    To determine what MACT standards should be established for 
equipment openings, we reviewed State permit conditions and determined 
that the air emissions permits for the best performers specify that 
owners or operators meet certain conditions before they open equipment 
to the atmosphere. The conditions include thresholds regarding the 
lower explosive limit (LEL) and the amount of gas that may be emitted. 
Based on our review of these permits, we have determined that a work 
practice standard that allows opening process equipment to the 
atmosphere during maintenance events only after meeting certain 
conditions (as specified in this section IV.D.3.a of the preamble) 
represents the MACT floor level of control for equipment openings at 
new and existing affected sources. Therefore, we are proposing a work 
practice standard at 40 CFR 63.1425(h)(1)(i) to specify that, prior to 
opening process equipment to the atmosphere during maintenance events, 
owners or operators must first drain the equipment before purging to a 
closed vent system so that the concentration of the vapor in the 
equipment served by the maintenance vent is less than or equal to 10 
percent of the LEL. For those situations where owners or operators 
cannot demonstrate 10-percent LEL, we are proposing at 40 CFR 
63.1425(h)(1)(ii) that owners or operators may open and vent the 
equipment to the atmosphere if the pressure is less than or equal to 5 
pounds per square inch gauge (psig), provided that owners or operators 
do not actively purge the equipment to the atmosphere until meeting the 
LEL criterion. We are proposing this 5-psig threshold to acknowledge 
that a certain minimum pressure must exist for the flare header system 
(or other similar control system) to operate properly. We are also 
proposing at 40 CFR 63.1425(h)(1)(iii) that owners or operators can 
open equipment when the amount of VOC contained in the equipment is 
less than 50 pounds. These proposed work practice standards are also 
being proposed at 40 CFR 63.1425(f), by reference to 40 CFR 63.113(k), 
for maintenance vents in a PMPU that use THF to produce one or more 
PEPO products.
    We acknowledge that installing a blind flange to prepare equipment 
for maintenance may be necessary and that by doing so, the owner or 
operator may not be able to meet the proposed maintenance vent 
conditions mentioned earlier in this section (e.g., a valve used to 
isolate the equipment will not seat fully, so organic material may 
continually leak into the isolated equipment). To limit the emissions 
during the blind flange installation, we are proposing at 40 CFR 
63.1425(h)(1)(iv) depressurizing the equipment to 2 psig or less prior 
to equipment opening and maintaining pressure of the equipment where 
purge gas enters the equipment at or below 2 psig during the blind 
flange installation. The low allowable pressure limit will reduce the 
amount of process gas released during the initial equipment opening, 
and the ongoing 2 psig pressure requirement will limit the purge gas 
rate. Together, these proposed provisions will limit the emissions 
during blind flange installation and will result in comparable 
emissions allowed under the proposed maintenance vent conditions 
mentioned earlier in this section. We expect these situations to be 
rare and expect that the owner or operator would remedy the situation 
as soon as practical (e.g., replace the isolation valve or valve seat 
during the next turnaround in the example provided earlier in this 
paragraph). Therefore, we are only proposing that owners or operators 
use this alternative maintenance vent limit under those situations 
where the proposed primary limits (i.e., the concentration of the vapor 
in the equipment served by the maintenance vent is less than or equal 
to 10 percent of the LEL, pressure is less than or equal to 5 psig, or 
VOC is less than 50 pounds) are not achievable and blinding of the 
equipment is necessary. We did not identify any additional options 
beyond those identified here (i.e., beyond-the-floor options) for 
controlling emissions from equipment openings.
    To demonstrate compliance with the proposed equipment opening work 
practice standards, we are proposing at 40 CFR 63.1430(a) that owners 
and operators must keep standard site procedures used to deinventory 
equipment for safety purposes (e.g., hot work or vessel entry 
procedures), as well the following additional records (as applicable):
     The concentration of the vapor at the time of the vessel 
opening exceeds 10 percent of its LEL, identification of the 
maintenance vent, the process units or equipment associated with the 
maintenance vent, the date of maintenance vent opening, and the 
concentration of the vapor at the time of the vessel opening;
     Either the vessel pressure at the time of the vessel 
opening exceeds 5 psig or the concentration of the vapor at the time of 
the active purging was initiated exceeds 10 percent of its LEL, 
identification of the maintenance vent, the process units or equipment 
associated with the maintenance vent, the date of maintenance vent 
opening, the pressure of the vessel or equipment at the time of 
discharge to the atmosphere and, if applicable, the concentration of 
the vapors in the equipment when active purging was initiated;
     Records of the estimating procedures used to determine the 
total quantity of VOC in the equipment and the type and size limits of 
equipment that contain less than 50 pounds of VOC at the time of 
maintenance vent opening;
     For each maintenance vent opening that contains greater 
than 50 pounds of VOC for which the deinventory procedures are not 
followed or for which the equipment opened exceeds the type and size 
limits established in the records, records that identify the 
maintenance vent, the process units or equipment associated with the 
maintenance vent, the date of maintenance vent opening, and records 
used to estimate the total quantity of VOC in the equipment at the time 
the

[[Page 106035]]

maintenance vent was opened to the atmosphere; and
     Identification of the maintenance vent, the process units 
or equipment associated with the maintenance vent, records documenting 
actions taken to comply with other applicable alternatives and why 
utilization of this alternative was required, the date of maintenance 
vent opening, the equipment pressure and concentration of the vapors in 
the equipment at the time of discharge, an indication of whether active 
purging was performed and the pressure of the equipment during the 
installation or removal of the blind if active purging was used, the 
duration the maintenance vent was open during the blind installation or 
removal process, and records used to estimate the total quantity of VOC 
in the equipment at the time the maintenance vent was opened to the 
atmosphere for each applicable maintenance vent opening.
    For any maintenance vent release exceeding the proposed applicable 
limits (e.g., the maintenance vent release is greater than 10 percent 
of the LEL), we are proposing that the owner or operator include in the 
next periodic report: (1) identification of the maintenance vent and 
the equipment served by the maintenance vent; (2) the date and time the 
maintenance vent was opened to the atmosphere; (3) the LEL in percent, 
vessel pressure in psig, or mass in pounds of VOC in the equipment, as 
applicable, at the start of atmospheric venting, and if the 5 psig 
vessel pressure option was used and active purging was initiated while 
the concentration of the vapor was 10 percent or greater of its LEL, 
also include the concentration of the vapors at the time active purging 
was initiated; and (4) an estimate of the mass in pounds of organic HAP 
released during the entire atmospheric venting event.
    We solicit comments on the proposed revisions related to 
maintenance activities. For additional details and discussion, see the 
document titled Review of Regulatory Alternatives for Certain Vent 
Streams in the PEPO Production Source Category that are Associated with 
Processes Subject to the PEPO NESHAP, which is available in the docket 
for this rulemaking.
b. Storage Vessel Degassing
    The PEPO NESHAP does not currently contain a standard specific to 
storage vessel degassing when storage vessels are using control devices 
to comply with the requirements in 40 CFR 63.119(a)(2) (via reference 
by 40 CFR 63.1432). We acknowledge that storage vessel degassing is 
similar to maintenance vents (e.g., equipment openings) and that there 
must be a point in time when the owner or operator can open the storage 
vessel and vent any remaining gas into the atmosphere. Therefore, to 
determine what MACT standards should be established for storage vessel 
degassing operations, we reviewed available data to determine how the 
best performers are controlling storage vessel degassing emissions.
    We identified three regulations that address emissions from storage 
vessel degassing: two in Texas and one in California. The Texas 
Administrative Code \69\ specifies degassing provisions and TCEQ 
implements those provisions through operating permit conditions.\70\ In 
California, the South Coast Air Quality Management District (SCAQMD) 
specifies degassing requirements in their Rule 1149.\71\
---------------------------------------------------------------------------

    \69\ See 30 Texas Administrative Code Chapter 115, Subchapter F, 
Division 3, available at https://texreg.sos.state.tx.us/public/readtac%24ext.ViewTAC?tac_view=5&ti=30&pt=1&ch=115&sch=F&div=3&rl=Y.
    \70\ See https://www.tceq.texas.gov/assets/public/permitting/air/Guidance/NewSourceReview/mss/chem-mssdraftconditions.pdf.
    \71\ See http://www.aqmd.gov/docs/default-source/rule-book/reg-xi/rule-1149.pdf.
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    The Texas Administrative Code requirements are the least stringent 
and require control of degassing emissions until the vapor space 
concentration is less than 35,000 ppmv as methane or 50 percent of the 
LEL. The TCEQ permit conditions require control of degassing emissions 
until the vapor space concentration is less than 10 percent of the LEL 
or until the VOC concentration is less than 10,000 ppmv, and SCAQMD 
Rule 1149 requires control of degassing emissions until the vapor space 
concentration is less than 5,000 ppmv as methane. The EPA considers the 
TCEQ permit conditions to be equivalent to SCAQMD Rule 1149 control 
requirements because 5,000 ppmv as methane equals 10 percent of the LEL 
for methane.
    Currently, 8 of the 25 existing PEPO facilities are located in 
Texas and subject to the TCEQ permit conditions; however, no PEPO 
facilities are located in California and subject to the SCAQMD rule. 
Therefore, the TCEQ permit conditions relying on storage vessel 
degassing until 10 percent of the LEL is achieved reflect what the best 
performers have implemented for storage vessel degassing.
    We reviewed TCEQ operating permit condition 6 (applicable to 
floating roof storage vessels) and permit condition 7 (applicable to 
fixed roof storage vessels) for key information that we could implement 
to form the basis of a standard for storage vessel degassing. The TCEQ 
operating permit conditions require control of degassing emissions for 
floating roof and fixed roof storage vessels until the vapor space 
concentration is less than 10 percent of the LEL and the owner or 
operator has removed all the standing liquid from the vessel to the 
extent practicable. The permit conditions also specify that facilities 
have the option of degassing a storage vessel until reaching a VOC 
concentration of 10,000 ppmv.
    We do not consider the 10,000 ppmv concentration cutoff option in 
the TCEQ permit conditions to be equivalent to or as stringent as the 
compliance option to meet 10 percent of the LEL. Therefore, we are not 
proposing the 10,000 ppmv concentration as a compliance option. We also 
do not expect that the best performers would use this concentration for 
compliance because the TCEQ permit conditions allow facilities to 
calibrate their LEL monitor using methane.
    Based on review of this information, we are proposing that the TCEQ 
requirements to reduce the vapor space concentration to less than 10 
percent of the LEL and to remove all the standing liquid from the 
vessel to the extent practicable reflect the MACT floor for both new 
and existing PEPO sources. We did not identify any additional options 
beyond this (i.e., beyond-the-floor options) for controlling emissions 
from storage vessel degassing. Therefore, we are proposing these 
requirements at 40 CFR 63.1432(a) by reference to 40 CFR 63.119(a)(6). 
However, because we recognize that in some cases (e.g., use of an inert 
blanket) the storage vessel atmosphere would not have an LEL, the EPA 
is also proposing an organic HAP concentration cutoff of 5,000 ppmv 
(measured as methane) as an equivalent alternative to reducing the 
vapor space concentration to less than 10 percent of the LEL. These are 
considered equivalent because 5,000 ppmv as methane equals 10 percent 
of the LEL for methane.
    Additionally, in petitions for reconsideration that the EPA 
recently received on the MON, EMACT standards, Petroleum Refinery 
Sector rule, and OLD NESHAP, petitioners asserted that it is necessary 
to make connections to a temporary control device to control the 
degassing emissions from floating roof storage vessels, which may 
require opening the storage vessel to make these connections. 
Therefore, we are proposing that owners or operators may open a 
floating roof storage vessel prior to degassing to set up equipment 
(i.e., make connections to a temporary

[[Page 106036]]

control device), but owners or operators must use this approach in a 
limited manner and must not actively purge the storage vessel while 
making connections.
    We estimated the emissions reductions that would result from this 
proposed change to the PEPO NESHAP by evaluating the population of 
storage vessels that are subject to control under 40 CFR 63.119(a)(2) 
(by reference in 40 CFR 63.1432) and not located in Texas. Storage 
vessels regulated by the PEPO NESHAP in Texas are already subject to 
the degassing requirements; therefore, those PEPO facilities would not 
achieve additional emissions reductions. Additionally, the PEPO 
facility that is owned by a small business also has processes subject 
to the HON, and the impacts of such degassing requirements on the 
facility were already accounted for under the recent HON rulemaking 
(see 89 FR 42932). Based on a review of facility responses to our CAA 
section 114 request (see section II.C of this preamble), owners or 
operators degas most storage vessels an average of once every 11 years. 
Using this average, and the population of PEPO storage vessels that are 
not in Texas (15 vessels) based on the assumption of one Group 1 
storage vessel per non-Texas facility, we estimated that one storage 
vessel degassing event would be newly subject to control each year. 
Controlling PEPO storage vessel degassing would reduce HAP emissions by 
0.87 tpy. See the document titled Degassing Cost and Emissions Impacts 
for Storage Vessels Located in the PEPO Production Source Category that 
are Associated with Processes Subject to the PEPO NESHAP, which is 
available in the docket for this rulemaking, for details on the 
assumptions and methodologies used in this analysis.
c. Planned Routine Maintenance for Storage Vessel Control Devices
    Although the PEPO NESHAP currently allows owners and operators to 
disconnect the fixed roof storage vessel vent from the closed vent 
system and control device, fuel gas system, or process equipment for up 
to 240 hours per year during planned, routine maintenance (see 40 CFR 
63.119(e)(3) through (5) (by reference in 40 CFR 63.1432)), we are 
proposing at 40 CFR 64.1432(a) by reference to 40 CFR 63.119(e)(7) that 
owners and operators would not be allowed to fill the storage vessel 
during these periods (such that the vessel would emit HAP to the 
atmosphere for a limited amount of time due to breathing losses only). 
Our proposal is based on our review of other chemical sector NESHAP 
(HON, P&R I NESHAP, and Group II Polymers and Resins (P&R II) NESHAP 
(89 FR 42932, May 16, 2024)) where we have determined that a work 
practice standard that allows owners and operators up to 240 hours per 
year during planned routine maintenance of the emission control system, 
provided that there are no working losses from the vessel, represents 
the MACT floor level of control for fixed roof storage vessel vents at 
new and existing affected sources. We expect PEPO sources are using 
these same types of practices to limit emissions, so we are proposing 
that this work practice represents the MACT floor level of control for 
fixed roof storage vessel vents at new and existing sources. However, 
if these processes are currently uncontrolled, the cost effectiveness 
of this work practice ($2,250 per ton of HAP reduced), minimal energy 
requirements, and limited non-air quality health and environmental 
impacts would likely result in the EPA establishing beyond-the-floor 
requirements based on the same practice. These proposed requirements 
ensure that a CAA section 112 standard is in place at all times, given 
that all working loss emissions from fixed roof storage vessels would 
be controlled during these periods of planned routine maintenance of 
the emission control system, thus satisfying Sierra Club v. EPA, 551 
F.3d 1019 (D.C. Cir. 2008).
    We estimated the emissions reductions that would result from this 
proposed change to the PEPO NESHAP. We assumed that owners and 
operators would install a secondary control device system (to control 
emissions from vessels during periods of planned routine maintenance of 
the primary control device) and that owners and operators would choose 
activated carbon canisters as the method of control. Based on the 
facility responses to our CAA section 114 request (see section II.C of 
this preamble), we identified one facility that operates one Group 1 
fixed roof storage vessel subject to controls according to table 3 to 
the PEPO NESHAP. We were also able to determine from an air permit 
review that another PEPO facility (i.e., one that did not receive our 
CAA section 114 request) does not have any Group 1 storage vessels 
subject to controls according to table 3 to the PEPO NESHAP. 
Furthermore, we determined that one facility is a small business that 
is co-located with a HON facility, and already accounted for under the 
recent HON rulemaking (see 89 FR 42932). Using all of this information, 
we then extrapolated and estimated that the total number of Group 1 
fixed roof storage vessels subject to the PEPO NESHAP nationwide is 15, 
assuming one vessel per facility. We then estimated that the highest 
amount of HAP emissions that would be expected to occur from a PEPO 
fixed roof storage vessel during the 240 hours of planned routine 
maintenance would be 262 pounds, if the emissions are not controlled. 
This emissions estimate includes 19.3 pounds of breathing losses and 
243 pounds of working losses. We based these emissions on the average 
vessel capacity and average vapor pressure material stored in a vessel 
reported (for all HON and PEPO fixed roof storage vessels) in response 
to our CAA section 114 request, and we estimated using the emission 
estimation procedures from chapter 7 of the EPA's Compilation of Air 
Pollutant Emission Factors.\72\ We assumed that activated carbon 
canisters would achieve a 95 percent reduction in HAP emissions, which 
would reduce emissions per vessel by 230 pounds of HAP per year of 
working loss emissions.
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    \72\ Compilation of Air Pollutant Emission Factors. Volume 1: 
Stationary Point and Area Sources. AP-42, Fifth Edition. Chapter 7: 
Liquid Storage Tanks. OAQPS, Research Triangle Park, NC.
---------------------------------------------------------------------------

    As a beyond-the-floor control option, we considered requiring 
owners and operators to also control breathing losses from storage 
vessels during periods of planned routine maintenance of the emission 
control system. However, we concluded that this option would not be 
cost effective because we estimated it would cost $28,360 per ton of 
HAP reduced.
    See the document titled Cost and Emissions Impacts for 240-Hour 
Planned Routine Maintenance Work Practice Standard on Storage Vessels 
Located in the PEPO Production Source Category that are Associated with 
Processes Subject to the PEPO NESHAP, which is available in the docket 
for this rulemaking, for details on the assumptions and methodologies 
used in this analysis.
4. Pressure Vessels
    We are proposing to establish separate MACT standards for pressure 
vessels that are associated with processes subject to the PEPO NESHAP. 
The rule does not currently regulate HAP emissions from pressure 
vessels. The EPA is proposing to define ``pressure vessel'' at 40 CFR 
63.1423(a) (by reference to 40 CFR 63.101) to mean ``a storage vessel 
that is used to store liquids or gases and is designed not to vent to 
the atmosphere as a result of compression of the vapor headspace in the 
pressure vessel during filling of the

[[Page 106037]]

pressure vessel to its design capacity.'' To eliminate any ambiguity in 
applicability or control requirements, the EPA is also proposing at 40 
CFR 63.1423(b) to remove the exemption for ``pressure vessels designed 
to operate in excess of 204.9 kilopascals and without emissions to the 
atmosphere'' from the definition of storage vessel. This longstanding 
exemption is ambiguous with respect to what ``without emissions to the 
atmosphere'' means. For example, most pressure vessels have relief 
devices that allow for venting when pressure exceeds setpoints. In many 
cases, these vents are routed to control devices; however, control 
devices are not completely effective (e.g., they may achieve only 98-
percent control), and therefore pressure vessels are sources of 
emissions to the atmosphere, even if they are controlled. There are 
also instances where other components in pressure systems may allow for 
fugitive releases because of leaks from fittings or cooling systems. 
All of these events arguably are ``emissions to the atmosphere,'' and 
it is likely that even if the PEPO NESHAP maintained this exemption, 
owners and operators of pressure vessels would still have uncertainty 
regarding whether or not they were subject to substantive requirements. 
Therefore, the proposed revisions remove the ambiguity associated with 
the exemption and set new MACT standards intended to limit emissions to 
the atmosphere from pressure vessels at new and existing affected 
sources. We are also clarifying in the definition of PMPU at 40 CFR 
63.1423(b) that the collection of equipment that is part of a PMPU 
includes pressure vessels.
    We are proposing LDAR requirements at 40 CFR 63.1432(a) by 
reference to 40 CFR 63.119(a)(7) that are based on similar no-
detectable emission requirements required for closed vent systems in 
most chemical sector NESHAP. These proposed requirements, which apply 
to each point on the pressure vessel through which total organic HAP 
could potentially be emitted,\73\ are consistent with CAA section 
112(d) controls and reflect the MACT floor at new and existing affected 
sources. We did not identify any additional options beyond this (i.e., 
beyond-the-floor options) for controlling emissions from pressure 
vessels. As such, these proposed requirements impose a standard that 
requires no detectable emissions at all times (i.e., the proposed 
standard would require owners and operators to meet a leak definition 
of 500 ppmv at each point on the pressure vessel where total organic 
HAP could potentially be emitted); require initial and annual leak 
monitoring using EPA Method 21 of 40 CFR part 60, appendix A-7; and 
require routing organic HAP through a closed vent system to a control 
device (i.e., no releases to the atmosphere through any points on the 
pressure vessel). These proposed LDAR requirements exclude connectors 
in EtO service, gas/vapor or light liquid valves in EtO service, and 
light liquid pumps in EtO service because those would be subject to 
more stringent LDAR requirements under the proposed EtO equipment leak 
standards.
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    \73\ Except for connectors in EtO service, gas/vapor or light 
liquid valves in EtO service, light liquid pumps in EtO service, and 
except for equipment that meet the unsafe-to-monitor or difficult-
to-monitor criteria specified in 40 CFR 63.168(h) and (i) (for 
valves in gas/vapor service and in light liquid service) and in 40 
CFR 63.174(f) and (h) (for connectors in gas/vapor service and in 
light liquid service).
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    We estimated the emissions reductions that would result from this 
proposed change to the PEPO NESHAP. Based on facility responses to our 
CAA section 114 request (see section II.C of this preamble) and an air 
permit review of PEPO facilities, we estimated that there are 15 
pressure vessels located at PEPO facilities. Using information from a 
2012 analysis that identified developments for storage vessels at 
chemical manufacturing facilities and petroleum refineries,\74\ we 
estimate a total HAP emission reduction of 1.5 tpy for all affected 
pressure vessels associated with processes subject to the PEPO NESHAP. 
See the document titled Cost and Emissions Impacts for Pressure Vessels 
Located in the PEPO Production Source Category that are Associated with 
Processes Subject to the PEPO NESHAP, which is available in the docket 
for this rulemaking, for details on the assumptions and methodologies 
used in this analysis. We solicit comments on the proposed revisions 
for pressure vessels.
---------------------------------------------------------------------------

    \74\ Randall, 2012. Memorandum from Randall, D., RTI 
International, to Parsons, N., EPA/OAQPS. Survey of Control 
Technology for Storage Vessels and Analysis of Impacts for Storage 
Vessel Control Options. January 20, 2012. EPA Docket No. EPA-HQ-OAR-
2010-0871.
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5. Surge Control Vessels and Bottoms Receivers
    The PEPO NESHAP, via reference to 40 CFR part 63, subpart H, 
defines a surge control vessel to mean feed drums, recycle drums, and 
intermediate vessels. PMPUs use surge control vessels when in-process 
storage, mixing, or management of flow rates or volumes is needed to 
assist in manufacturing of a product. The PEPO NESHAP defines a bottoms 
receiver, via reference to 40 CFR part 63, subpart H, as a tank that 
collects distillation bottoms before the stream is sent to storage or 
for further downstream processing.
    The PEPO NESHAP does not consider surge control vessels and bottoms 
receivers to be storage vessels because they are covered by the 
equipment leak provisions. Although these emissions sources are 
regulated under the equipment leak provisions (i.e., 40 CFR 63.1434 by 
reference to NESHAP subpart H), the equipment leak requirements refer 
to the storage vessel requirements in NESHAP subpart G. Owners and 
operators of surge control vessels and bottoms receivers are required 
to comply with the HON storage vessel requirements in 40 CFR part 63, 
subpart G (i.e., use a floating roof or route emissions to a closed 
vent system and control to achieve 95-percent control), provided the 
surge control vessel or bottoms receiver meets certain capacity and 
vapor pressure requirements. For PEPO surge control vessels and bottoms 
receivers at existing sources, storage vessel control requirements 
apply if the capacity is between 75 m\3\ (inclusive) and 151 m\3\ and 
the MTVP is greater than or equal to 13.1 kPa, or the capacity is 
greater than or equal to 151 m\3\ and the MTVP is greater than or equal 
to 5.2 kPa. For PEPO surge control vessels and bottoms receivers at new 
sources, storage vessel control requirements apply if the capacity is 
between 38 m\3\ (inclusive) and 151 m\3\ and the MTVP is greater than 
or equal to 13.1 kPa, or the capacity is greater than or equal to 151 
m\3\ and the MTVP is greater than or equal to 0.7 kPa. The PEPO NESHAP 
excludes all other surge control vessels and bottoms receivers from 
emissions control requirements.
    We are proposing at 40 CFR 63.1423(b) to remove surge control 
vessels and bottoms receivers from the list of equipment included in 
the definition of equipment leak, and we are proposing at 40 CFR 
63.1434(a)(8) to require that owners and operators of all surge control 
vessels and bottoms receivers shall reduce emissions of organic HAP 
consistent with the process vent control requirements at 40 CFR 63.1425 
through 63.1431, as applicable. The proposed requirements for surge 
control vessels and bottoms receivers also represent the level of 
control found to be cost-effective for process vents under the 
technology review in section IV.C.3 of this preamble and, therefore, 
the level of control we are proposing for process vents. Emissions from 
surge control vessels and bottoms receivers are characteristic of 
process vents, not emissions from storage vessels. These

[[Page 106038]]

vessels operate at process temperatures, rather than ambient storage 
temperatures; typically do not undergo level changes that larger 
storage vessels undergo; and are most often operated under pressure 
with and without intake or discharge of non-condensable gases. The size 
of these vessels is also typically not correlated with emissions, as 
are storage vessels. We solicit comments on the proposed revisions for 
surge control vessels and bottoms receivers.
6. Transfer Racks
    We are proposing to establish MACT standards for transfer racks 
that are associated with processes subject to the PEPO NESHAP. The EPA 
considers transfer racks to be part of the collection of equipment that 
comprise a PMPU, as defined in the PEPO NESHAP; however, the rule does 
not currently regulate HAP emissions from transfer racks.
    Because the equipment used in transfer racks at PEPO production 
facilities is similar to the equipment used at HON facilities, we are 
proposing to define a ``transfer rack'' based on a similar definition 
used in the HON (40 CFR 63.101). We are proposing to define ``transfer 
rack'' at 40 CFR 63.1423(b) to mean the collection of loading arms and 
loading hoses, at a single loading rack, that are assigned to a PMPU 
according to the procedures specified in 40 CFR 63.1420(f)(1) through 
(5) (where the term ``transfer rack'' is substituted for ``storage 
vessel'') and are used to fill tank trucks and/or railcars with organic 
liquids that contain one or more organic HAP. A transfer rack also 
includes the associated pumps, meters, shutoff valves, relief valves, 
and other piping and valves. We are also proposing at 40 CFR 63.1423(a) 
(by reference to 40 CFR 63.101) to define a ``loading rack'' to mean 
``a single system used to fill tank trucks and railcars at a single 
geographic site. Loading equipment and operations that are physically 
separate (i.e., do not share common piping, valves, and other 
equipment) are considered to be separate loading racks.'' The HON 
definition of transfer rack explicitly excludes racks, arms, or hoses 
that only transfer liquids containing organic HAP as impurities or that 
use vapor balancing during all loading operations. We note that the 
PEPO NESHAP already provides these exclusions at 40 CFR 63.1420(c)(10) 
and (11).
    Loading losses are the primary source of evaporative emissions from 
rail tank car or tank truck operations. Loading losses occur as the 
liquid entering the tank during loading displaces the organic vapors 
from the tank headspace into the atmosphere. These organic vapors are a 
combination of vapors: (1) formed in the empty tank by evaporation of 
residual product from previous loads, (2) transferred to the tank by 
vapor balance systems during product unloading, and (3) generated in 
the tank during loading of new product.
    Based on data provided to the EPA in response to our CAA section 
114 request (see section II.C of this preamble), we identified 17 
transfer racks located at 6 of the 25 PEPO facilities.\75\ We also 
identified another transfer rack at a seventh facility based on our 
review of the facility operating permit. One of the 25 PEPO facilities 
is a small business and is only subject to the PEPO NESHAP because it 
receives and treats wastewater from another PEPO facility; therefore, 
we do not expect this small business facility to have a transfer rack 
on site that would be associated with a PMPU. For the remaining 17 
facilities, we used CAA section 114 request data to estimate averages 
of 2 PMPUs per facility and 1 transfer rack per PMPU. Based on these 
assumptions, we estimated that there are 34 transfer racks associated 
with the 17 facilities (17 facilities x 2 PMPUs/facility x 1 transfer 
rack/PMPU = 34 transfer racks). Therefore, we estimated a nationwide 
total of 52 transfer racks in the PEPO Production source category that 
are associated with processes subject to the PEPO NESHAP.
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    \75\ As of March 1, 2024, there were 25 facilities that are 
major sources of HAP emissions in operation that are subject to the 
PEPO NESHAP. The list of facilities located in the United States 
that are part of the PEPO Production source category with processes 
subject to the PEPO NESHAP is presented in the document titled List 
of Facilities Subject to the PEPO NESHAP, which is available in the 
docket for this action.
---------------------------------------------------------------------------

    We reviewed available data to determine how the best performers are 
controlling emissions from PEPO transfer racks. Given that 14 of the 25 
PEPO facilities are located in either Louisiana or Texas, we evaluated 
the transfer rack provisions contained in the administrative code for 
these two States. The Texas provisions \76\ for transfer racks 
provisions apply to materials containing VOC having a true vapor 
pressure greater than or equal to 0.5 pounds per square inch absolute 
(psia) (3.45 kPa) under actual storage conditions, and the Louisiana 
provisions \77\ apply to materials containing VOC with a true vapor 
pressure of 1.5 psia (10.3 kPa) or greater at loading conditions. In 
each of these rules, owners and operators are required to use a vapor 
balance system or reduce emissions by 90 percent during loading 
operations (at a transfer rack). We also reviewed the transfer rack 
requirements in the HON because one PEPO facility said (in response to 
our CAA section 114 request) that they voluntarily comply with the HON 
for their PEPO transfer racks. The HON regulates transfer operations at 
40 CFR 63.126 through 63.130. The HON requires owners and operators of 
each HON transfer rack that annually loads greater than or equal to 
0.65 million liters of liquid products that contain organic HAP with a 
rack weighted average vapor pressure greater than or equal to 10.3 kPa 
to equip each transfer rack with a vapor collection system and control 
device to reduce total organic HAP emissions by 98 percent by weight or 
to an exit concentration of 20 ppmv. The HON also allows multiple other 
options to control emissions from applicable transfer racks, including 
use of a flare or collecting emissions for use in the process, a fuel 
gas system, or a vapor balance system.
---------------------------------------------------------------------------

    \76\ See 30 Texas Administrative Code Chapter 115, Subchapter C, 
Division 1, available at https://www.tceq.texas.gov/permitting/air/rules/state/115/r5211hp.html.
    \77\ See Louisiana Administrative Code 33:III.2107, Chapter 21, 
available at https://www.deq.louisiana.gov/resources/category/regulations-lac-title-33.
---------------------------------------------------------------------------

    For the purpose of addressing regulatory gaps, we are proposing in 
this action that the requirements to use a vapor balance system or 
reduce emissions by 90 percent during loading operations (at a transfer 
rack) are consistent with CAA section 112(d) controls and reflect the 
MACT floor for transfer racks at existing PEPO sources. We also propose 
that the transfer rack requirements in the HON (i.e., reduce emissions 
by 98 percent by weight or to an exit concentration of 20 ppmv during 
loading operations at a transfer rack) are consistent with CAA section 
112(d) controls and reflect the MACT floor for transfer racks at new 
PEPO sources and beyond-the-floor control for transfer racks at 
existing PEPO sources.
    We consider the vapor pressure applicability threshold in the Texas 
transfer rack provisions to be more stringent than the vapor pressure 
applicability thresholds contained in the HON and the Louisiana 
provisions. Therefore, we are proposing the vapor pressure 
applicability threshold specified in the Texas transfer rack provisions 
in addition to the HON transfer rack requirements. In summary, we are 
proposing at 40 CFR 63.1434(j), by reference to 40 CFR 63.126 through 
63.130, that owners and operators of PEPO transfer racks that load 
materials with an MTVP greater than or equal to 0.5 psia (3.45 kPa) 
under actual storage conditions (i.e., Group 1 transfer racks as 
defined in 40 CFR 63.1423(b)) must comply with the HON requirements at 
40 CFR 63.126 through 63.130, if the

[[Page 106039]]

material contains organic HAP as defined by 40 CFR 63.1423(b). To 
accommodate these proposed requirements, we are also proposing to 
remove the exemption of the terms ``transfer'' and ``transferred'' in 
the definition of ``maximum true vapor pressure'' at 40 CFR 63.1423(b). 
We anticipate that these proposed requirements achieve any additional 
emission reductions because we believe that transfer racks operating at 
PEPO sources load materials with very low true vapor pressures (i.e., 
less than 0.3 psia based on data provided to the EPA in response to our 
CAA section 114 request) or are using vapor balancing as a control 
option. As a beyond-the-floor control option, we explored controlling 
the organic HAP emissions from PEPO transfer racks with add-on controls 
(i.e., thermal oxidizers) and we determined that, although feasible, 
such add-on controls were unreasonably expensive, given that organic 
HAP emissions from PEPO transfer racks are expected to be small due to 
their low true vapor pressures (e.g., all but one of the PEPO transfer 
racks in the modeling file are reported as each emitting less than 
about 380 pounds of organic HAP per year). Therefore, we concluded that 
the control of organic HAP using a thermal oxidizer would not be 
reasonable. For example, the EPA estimated a cost of approximately 
$1,700,000 per ton of HAP emissions reduced for use of a thermal 
oxidizer. We solicit comments on the proposed standards for transfer 
racks.
7. Butylene Oxide
    In this action, we are proposing to add butylene oxide (also known 
as 1,2-epoxybutane) to the definition of ``epoxide'' in 40 CFR 
63.1423(b) and to the list of HAP presented in table 4 to the PEPO 
NESHAP. In a 1997 document supporting the establishment of the PEPO 
Production source category titled Polyether Polyols Production Industry 
Characterization, which is available in the docket for this action 
(Docket ID No. EPA-HQ-OAR-2023-0282), the EPA established two 
subcategories for the purpose of analyzing MACT floors and regulatory 
alternatives: (1) PEPO made from polymerization of epoxides (i.e., EtO, 
propylene oxide, butylene oxide), and (2) PEPO made from the 
polymerization of THF. While the EPA recognized in this supporting 
documentation that butylene oxide is an epoxide used as a reactant to 
make PEPO, the EPA incorrectly stated that butylene oxide was not a 
HAP; therefore, the EPA did not include this compound in the epoxide 
definition or table 4 to subpart PPP.
    Because most PEPO process units make a variety of products, 
including copolymers made from more than one type of epoxide, we have 
determined that any process unit using butylene oxide is likely to also 
use other epoxides (i.e., EtO or propylene oxide); as such, gas streams 
from the process are already required to be monitored and controlled 
according to the PEPO NESHAP. For example, one facility reports EtO, 
propylene oxide, and 1,2-epoxybutane from the same PEPO reactor in the 
2017 NEI. Therefore, we conclude that this proposed action will not 
result in the control of processes that are not already subject to the 
epoxide emissions standards specified in the PEPO NESHAP and that 
impacts will be minimal. We solicit comments on the proposed inclusion 
of butylene oxide.
8. 40 CFR 63.1420(d)(3) Exemption
    The PEPO NESHAP (40 CFR 63.1420(d)(3)) exempts from the definition 
of affected source reactions or processing that occur after completion 
of epoxide polymerization and all catalyst removal steps, if any. In 
this action, the EPA is proposing at 40 CFR 63.1420(d)(4) to remove the 
exemption in 40 CFR 63.1420(d)(3) and to require capture and control of 
emissions from these currently unregulated steps in the PEPO production 
process (which may include, but are not limited to, solvent removal, 
purification, drying, and solids handling operations).
    The reactions or processing that occur after completion of epoxide 
polymerization and catalyst removal steps are included in the PEPO 
Production source category. The EPA is proposing to expand the 
definition of the affected source because HAP emissions are possible 
from these steps \78\ and are thus a regulatory gap that the EPA is 
required to address. Additionally, because the EPA concludes that the 
current MACT standards for process vents are appropriate for sources 
associated with reactions or processing that occur after completion of 
epoxide polymerization and catalyst removal steps,\79\ the EPA is 
proposing that it is not necessary to evaluate alternative MACT limits 
for these currently unregulated steps beyond subjecting them to the 
previously established MACT limits for process vents. We solicit 
comments on the proposed removal of the exemption in 40 CFR 
63.1420(d)(3).
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    \78\ For example, a facility reports EtO emissions from a dryer 
and a solids handling system that are not considered part of the 
affected source subject to the PEPO NESHAP because they occur after 
epoxide polymerization and catalyst removal steps.
    \79\ For example, the facility reporting EtO emissions from a 
dryer and a solids handling system has used a flare to control 
emissions from the dryer and a baghouse to control emissions from 
the vent collection system associated with the solids handling 
system.
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E. What other actions are we proposing?

    In addition to the proposed actions related to CAA sections 
112(d)(2), (3), and (6), 112(h), and 112(f) discussed in sections IV.B 
through IV.D of this preamble, we are proposing to address selected 
issues raised in the petition for reconsideration (see section II.A.2 
of this preamble). In addition, we are proposing changes to the PEPO 
NESHAP recordkeeping and reporting requirements to require the use of 
electronic reporting of certain reports, and we are proposing other 
technical amendments and definition revisions to improve the clarity 
and enforceability of certain provisions in the PEPO NESHAP. Our 
rationale and proposed changes related to all these issues are 
discussed as follows.
1. Reconsideration Issues
    The EPA discusses certain issues raised in the petition for 
reconsideration (see section II.A.2 of this preamble) related to 
affirmative defense and PRDs as described in this section IV.E.1 of the 
preamble.
a. Affirmative Defense
    As part of the 2014 PEPO NESHAP RTR rulemaking (see 59 FR 17340, 
March 27, 2014), the EPA included the ability to assert an affirmative 
defense to civil penalties for violations caused by malfunctions (see 
40 CFR 63.1420(i)) to create a system that incorporated some 
flexibility, recognizing that there is a tension inherent in many types 
of air regulations to ensure adequate compliance while simultaneously 
recognizing that, despite the most diligent of efforts, owners or 
operators may violate emission standards under circumstances entirely 
beyond the control of the source. Although the EPA recognized that its 
case-by-case enforcement discretion provides sufficient flexibility in 
these circumstances, we included the affirmative defense provision to 
provide a more formalized approach and more regulatory clarity. See 
Weyerhaeuser Co. v. Costle, 590 F.2d 1011, 1057-58 (D.C. Cir. 1978) 
(holding that an informal case-by-case enforcement discretion approach 
is adequate); but see Marathon Oil Co. v. EPA, 564 F.2d 1253, 1272-73 
(9th Cir. 1977) (requiring a more formalized approach to consideration 
of ``upsets beyond the control of the permit holder.''). Under the 
EPA's regulatory affirmative defense provisions, if a source could 
demonstrate in a judicial

[[Page 106040]]

or administrative proceeding that it had met the requirements of the 
affirmative defense in the regulation, civil penalties would not be 
assessed. However, the petitioners argued that the EPA should remove 
the affirmative defense provisions in the PEPO NESHAP because the court 
vacated the affirmative defense in one of the EPA's other CAA section 
112 regulations. NRDC v. EPA, 749 F.3d 1055 (D.C. Cir. 2014) (vacating 
affirmative defense provisions in the CAA section 112 rule establishing 
emission standards for Portland cement kilns). The court found that the 
EPA lacked authority to establish an affirmative defense for private 
civil suits and held that under the CAA, the authority to determine 
civil penalty amounts in such cases lies exclusively with the courts, 
not the EPA. Specifically, the court found: ``As the language of the 
statute makes clear, the courts determine, on a case-by-case basis, 
whether civil penalties are `appropriate.' '' See NRDC, 749 F.3d at 
1063 (``[U]nder this statute, deciding whether penalties are 
`appropriate' in a given private civil suit is a job for the courts, 
not EPA.'').\80\
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    \80\ The court's reasoning in NRDC focuses on civil judicial 
actions. The court noted that ``EPA's ability to determine whether 
penalties should be assessed for CAA violations extends only to 
administrative penalties, not to civil penalties imposed by a 
court.'' Id.
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    In light of NRDC (and as requested by the petitioners), the EPA 
published a separate proposal (89 FR 52425, June 24, 2024) to remove 
regulatory affirmative defense provisions from three NSPS and 15 NESHAP 
(including the PEPO NESHAP). The public comment period for that 
proposal closed on August 8, 2024, and in this proposal, the EPA is not 
reopening the comment period or otherwise seeking additional public 
comments on this issue. The EPA will take separate final action on this 
issue, including responding to public comments submitted on the June 
24, 2024, proposal. That final action will constitute the EPA's 
response to the petition for reconsideration on the affirmative defense 
provision promulgated in the 2014 final rule (79 FR 17340, March 27, 
2014). Consequently, it is not necessary for the EPA to further address 
this issue in this proposed rulemaking.
b. PRDs
    The petitioners stated that, although the PEPO NESHAP RTR proposal 
(77 FR 1268, January 9, 2012) required facilities to install electronic 
indicators and alarms to ensure compliance with the proposed 
prohibition of pressure releases to the atmosphere from PRDs in organic 
HAP service, the EPA made these types of equipment optional in the 
final rule (79 FR 17340, March 27, 2014), allowing sources to use ``a 
device or system that is capable of identifying and recording the time 
and duration of each pressure release (e.g., rupture disk indicators, 
magnetic sensors, motion detectors on the pressure relief valve stem, 
flow monitors, and pressure monitors) in lieu of prescribing that PRDs 
be equipped with release indicators and alarms.'' The petitioners 
contended that it was not feasible to comment on the EPA's change to 
allow other indicators of atmospheric releases from PRDs. Additionally, 
the petitioners argued that the EPA did not provide the public an 
opportunity to comment when it narrowed the applicability of the PRD 
release prohibition in the final rule to PRDs ``in organic HAP 
service,'' and that, at a minimum, the EPA must narrow the 
applicability to only PRDs ``in HAP service'' to affect all HAP. 
Finally, the petitioners asserted that the EPA did not adequately 
justify giving PEPO facilities 3 years to comply with the PRD 
requirements in the PEPO NESHAP.
    The PEPO NESHAP codifies the PRD requirements at 40 CFR 63.1434(c). 
We are not proposing to make any changes to the PRD requirements at 40 
CFR 63.1434(c) as we believe the 2014 final rule (79 FR 17340, March 
27, 2014) reached appropriate conclusions regarding each of these 
issues; however, we request comment on these requirements. We note that 
neither the proposed nor final rule was specific to a particular type 
of release indicator, and both the proposed and final rules anticipated 
use of a device capable of immediately notifying the facility of a 
release. Additionally, both the proposal and the final rule specified 
requirements for PRDs ``in organic HAP service,'' and we disagree with 
the petitioners that we should expand the scope of the PRD requirements 
because the PEPO production process includes reacting organic chemicals 
together to make an organic chemical product. Also, we believe other 
changes we made to the PRD requirements between proposal and final were 
for clarification and were a reasonable outgrowth of public comments. 
Finally, we stated in the preamble to the final rule (see 79 FR 17345) 
that time to comply with the PRD requirements is needed for facilities 
to ``research equipment and vendors, purchase, install, test and 
properly operate any necessary equipment.'' Even so, the petitioners' 
argument that the EPA did not adequately justify giving PEPO facilities 
3 years to comply with the PRD requirements is no longer relevant, 
given that all new and existing sources have been complying with the 
PRD requirements for over 7 years (i.e., since March 27, 2017).
2. Electronic Reporting
    As part of the 2014 PEPO NESHAP RTR rulemaking (see 59 FR 17340, 
March 27, 2014), the EPA began requiring owners or operators of PEPO 
facilities to submit electronic copies of certain required performance 
test reports. The proposed rule amendments in this action would require 
owners and operators of PEPO processes to submit electronic copies of 
required performance test reports using new procedures. In lieu of 
requiring owners and operators to submit the results of performance 
tests ``by direct computer-to-computer electronic transfer via EPA-
provided software'' (see 40 CFR 63.1439(e)(9)(i)), we are proposing at 
40 CFR 63.1426(b)(6) and 63.1439(e)(9)(iii) that owners and operators 
must submit the results of the performance test following the 
procedures specified in 40 CFR 63.9(k), which requires use of the EPA's 
Central Data Exchange (CDX) using the Compliance and Emissions Data 
Reporting Interface (CEDRI). The proposed rule amendments would also 
require owners or operators to submit flare management plans and 
periodic reports (including fenceline monitoring reports) through the 
EPA's CDX using CEDRI (see proposed 40 CFR 63.1436(b), 63.1439(e)(6), 
and 63.1434(i)). A description of the electronic data submission 
process is provided in the document titled Electronic Reporting 
Requirements for New Source Performance Standards (NSPS) and National 
Emission Standards for Hazardous Air Pollutants (NESHAP) Rules, 
available in the docket for this action.
    The proposed rule would require that performance test results 
collected using test methods that are supported by the EPA's Electronic 
Reporting Tool (ERT) as listed on the ERT website \81\ at the time of 
the test be submitted in the format generated through the use of the 
ERT or an electronic file consistent with the XML schema on the ERT 
website, and other performance test results be submitted in portable 
document format (PDF) using the attachment module of the ERT. Flare 
management plans would be uploaded as a PDF file.
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    \81\ https://www.epa.gov/electronic-reporting-air-emissions/electronic-reporting-tool-ert.
---------------------------------------------------------------------------

    For periodic reports (including fenceline monitoring reports), the 
proposed rule would require that

[[Page 106041]]

owners and operators use an appropriate spreadsheet template to submit 
information to CEDRI. A draft version of the proposed templates for 
these reports is included in the docket for this action.\82\ The EPA 
specifically requests comment on the content, layout, and overall 
design of the templates. We are proposing that owners and operators 
begin using the templates for periodic reports other than fenceline 
reports 3 years after the final rule is published in the Federal 
Register, or after the reporting template for the subpart has been 
available on the CEDRI website for 1 year, whichever date is later. 
Owners and operators would begin using the templates for fenceline 
monitoring reports starting when the first fenceline monitoring report 
is due.
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    \82\ See Part_63_Subpart_PPP_63.1439(e)(6)_Periodic_Report.xlsx, 
which is available in the docket for this action.
---------------------------------------------------------------------------

    Additionally, the EPA has identified two broad circumstances in 
which electronic reporting extensions may be provided. These 
circumstances are: (1) outages of the EPA's CDX or CEDRI which preclude 
an owner or operator from accessing the system and submitting required 
reports, and (2) force majeure events, which are defined as events that 
will be or have been caused by circumstances beyond the control of the 
affected facility, its contractors, or any entity controlled by the 
affected facility that prevent an owner or operator from complying with 
the requirement to submit a report electronically. Examples of force 
majeure events are acts of nature, acts of war or terrorism, or 
equipment failure or safety hazards beyond the control of the facility. 
The EPA is providing these potential extensions for submitting 
electronic copies of required performance test reports, flare 
management plans, and periodic reports (including fenceline monitoring 
reports) to protect owners and operators from noncompliance in cases 
where they cannot successfully submit a report by the reporting 
deadline for reasons outside of their control. In both circumstances, 
the decision to accept the claim of needing additional time to report 
is within the discretion of the Administrator, and reporting should 
occur as soon as possible. These potential extensions were recently 
added to 40 CFR part 63, subpart A, General Provisions at 40 CFR 
63.9(k) and we are proposing to amend the entry for 40 CFR 63.9(k) of 
table 1 to the PEPO NESHAP (Applicability of General Provisions to 
Subpart PPP Affected Sources) to remove the constraint that 40 CFR 
63.9(k) applies ``only as specified in Sec. 63.9(j)'' such that 40 CFR 
63.9(k) would apply for any notifications or reports required by the 
PEPO NESHAP to be submitted electronically.
    The electronic submittal of the reports addressed in this proposed 
rulemaking will increase the usefulness of the data contained in those 
reports, is in keeping with current trends in data availability and 
transparency, will further assist in the protection of public health 
and the environment, will improve compliance by facilitating the 
ability of regulated facilities to demonstrate compliance with 
requirements and by facilitating the ability of delegated State, local, 
Tribal, and territorial air agencies and the EPA to assess and 
determine compliance, and will ultimately reduce burden on regulated 
facilities, delegated air agencies, and the EPA.\83\ Electronic 
reporting also eliminates paper-based, manual processes, thereby saving 
time and resources, simplifying data entry, eliminating redundancies, 
minimizing data reporting errors, and providing data quickly and 
accurately to the affected facilities, air agencies, the EPA, and the 
public. Moreover, electronic reporting is consistent with the EPA's 
plan \84\ to implement Executive Order 13563 and is in keeping with the 
EPA's Agency-wide policy \85\ developed in response to the White 
House's Digital Government Strategy.\86\ For more information on the 
benefits of electronic reporting, see the document titled Electronic 
Reporting Requirements for New Source Performance Standards (NSPS) and 
National Emission Standards for Hazardous Air Pollutants (NESHAP) 
Rules, referenced earlier in this section.
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    \83\ We are proposing at 40 CFR 63.1421(c)(5) that the approval 
to an alternative to any electronic reporting to the EPA proposed 
for the PEPO NESHAP cannot be delegated to State, local, or Tribal 
agencies.
    \84\ EPA's Final Plan for Periodic Retrospective Reviews, August 
2011. Available at: https://www.regulations.gov/document?D=EPA-HQ-OA-2011-0156-0154.
    \85\ E-Reporting Policy Statement for EPA Regulations, September 
2013. Available at: https://www.epa.gov/sites/production/files/2016-03/documents/epa-ereporting-policy-statement-2013-09-30.pdf.
    \86\ Digital Government: Building a 21st Century Platform to 
Better Serve the American People, May 2012. Available at: https://obamawhitehouse.archives.gov/sites/default/files/omb/egov/digital-government/digital-government.html.
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3. Performance Testing
    The EPA is proposing at 40 CFR 63.1437(a) performance testing once 
every 5 years to demonstrate compliance with emission limits for 
certain process vents (if you route emissions to a control device other 
than a flare). We determined that periodic emission testing should be 
required to help ensure continuous compliance. Repeat performance tests 
are already required by permitting authorities for some facilities. 
Further, requiring periodic repeat performance tests will help to 
ensure that control systems are properly maintained over time, thereby 
reducing the potential for acute emissions episodes. Currently, 
facilities conduct a one-time performance test or design evaluation and 
then monitor operating parameters. A design evaluation (in lieu of 
performance testing) is currently allowed for control techniques that 
receive less than 10 tpy of uncontrolled organic HAP emissions from one 
or more PMPU. However, we are proposing to remove the design evaluation 
option at 40 CFR 63.1426(b)(6) and (7) and (f), and require ongoing 
performance tests for owners and operators using a combustion, 
recovery, or recapture device to comply with an epoxide or organic HAP 
percent reduction efficiency requirement in 40 CFR 63.1425(b)(1)(i), 
(b)(2)(ii), (c)(1)(ii), (c)(3)(ii), or (d)(2); an epoxide concentration 
limitation in 40 CFR 63.1425(b)(1)(ii) or (b)(2)(iii); or an annual 
epoxide emission limitation in 40 CFR 63.1425(b)(1)(iii) or (b)(2)(iv). 
We are proposing that the ongoing performance tests be conducted at a 
minimum frequency of once every 5 years to supplement the parameter 
monitoring and to ensure that emission controls continue to operate as 
demonstrated during the initial performance test. Currently 40 CFR 
63.1437(a) also requires the owner or operator to record the necessary 
process information to document operating conditions during the test. 
We are proposing to clarify that this includes an explanation to 
support that the operating conditions during each test represent the 
entire range of normal operation, including conditions for maximum 
emissions, even if such emissions are not expected during maximum 
production.
    In addition, we are proposing to eliminate the option in 40 CFR 
63.1427(a)(2)(ii) that exempts owners or operators using ECO as a 
control technique from directly measuring the concentration of 
unreacted epoxide when determining the batch cycle percent epoxide 
emission reduction. Currently, the rule requires comparing the epoxide 
concentration obtained through direct measurement for one product from 
each product class with the concentration determined using

[[Page 106042]]

process knowledge, reaction kinetics, and engineering knowledge. Owners 
and operators are exempt at 40 CFR 63.1427(a)(2)(ii) from this direct 
measurement comparison if uncontrolled epoxide emissions before the end 
of the ECO are less than 10 tpy. However, we are proposing to remove 
this exemption and to require that owners and operators conduct the 
comparison of epoxide concentration using direct measurement for one 
product from each product class even if uncontrolled epoxide emissions 
before the end of the ECO are less than 10 tpy.
    We solicit comments on the proposed revisions to the performance 
testing and ECO direct measurement requirements.
4. Certain Definitions That Refer to the HON
    We note that in an effort to remove redundancy and improve 
consistency, the EPA recently finalized moving all of the definitions 
from NESHAP subparts G and H (i.e., 40 CFR 63.111 and 40 CFR 63.161, 
respectively) into the definition section of NESHAP subpart F (i.e., 40 
CFR 63.101) (see 89 FR 42932, May 16, 2024). Given that the PEPO NESHAP 
directly references these provisions for certain definitions (see 40 
CFR 63.1423), we are proposing to revise the phrasing used in 40 CFR 
63.1423(a) to refer to NESHAP subpart F in instances where a definition 
in the PEPO NESHAP points to either NESHAP subpart G or H.
    We are also proposing editorial changes that clarify references in 
the PEPO NESHAP definitions at 40 CFR 63.1423(b) to properly reference 
the correct HON citation for ``continuous recorder,'' ``maximum true 
vapor pressure,'' ``residual,'' and ``waste management unit.''
    We are proposing to delete ``heat exchange system'' from the list 
of terms in 40 CFR 63.1423(a) that refer to subpart F for their 
definition. We are proposing to define ``heat exchange system'' at 40 
CFR 63.1423(b) so the definition refers to PMPUs instead of CMPUs. We 
are proposing ``heat exchange system'' to mean a device or collection 
of devices used to transfer heat from process fluids to water without 
intentional direct contact of the process fluid with the water (i.e., 
non-contact heat exchanger) and to transport and/or cool the water in a 
closed-loop recirculation system (cooling tower system) or a once-
through system (e.g., river or pond water). For closed-loop 
recirculation systems, the heat exchange system consists of a cooling 
tower, all PMPU heat exchangers that are in organic HAP service and 
serviced by that cooling tower, and all water lines to and from these 
process unit heat exchangers. For once-through systems, the heat 
exchange system consists of all heat exchangers that are in organic HAP 
service servicing an individual PMPU and all water lines to and from 
these heat exchangers. Sample coolers or pump seal coolers are not 
considered heat exchangers for the purpose of this definition and are 
not part of the heat exchange system. Intentional direct contact with 
process fluids results in the formation of a wastewater. We are also 
proposing to revise the definition of ``in organic HAP service'' to 
include a heat exchange system, to be consistent with the use of ``in 
organic HAP service'' in the definition of ``heat exchange system.''
5. Monitoring for Adsorbers That Cannot Be Regenerated and Regenerative 
Adsorbers That Are Regenerated Offsite
    We are proposing to add monitoring requirements at 40 CFR 
63.1429(a)(9) for adsorbers that cannot be regenerated and regenerative 
adsorbers that are regenerated offsite because the PEPO NESHAP does not 
currently include specific monitoring requirements for this type of 
APCD and it is possible that owners and operators may use this type of 
APCD to control emissions from PEPO sources. We are proposing that 
owners and operators of this type of APCD use dual adsorbent beds in 
series. We are proposing to prescribe a dual-bed system because the use 
of a single bed does not ensure continuous compliance unless the bed is 
replaced significantly before breakthrough.\87\ The proposed monitoring 
requirements for non-regenerative adsorbers fulfill the EPA's 
obligation to establish monitoring requirements to ensure continuous 
compliance with the emission limits (e.g., 98-percent control or a 20-
ppmv TOC outlet concentration) when owners or operators are using these 
types of control devices to comply with the standards. A dual-bed 
system will allow one bed to be saturated before it is replaced and, 
therefore, makes efficient use of the adsorber bed without exceeding 
the emission limits.
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    \87\ We are proposing to define the term ``breakthrough'' at 40 
CFR 63.1423(a) (by reference to 40 CFR 63.101) to mean the time when 
the level of HAP or TOC detected is at the highest concentration 
allowed to be discharged from an adsorber system.
---------------------------------------------------------------------------

    Similar to regenerative adsorbers, to monitor performance 
deterioration, we are proposing measurements of HAP or TOC using a 
portable analyzer or chromatographic analysis for non-regenerative 
absorbers. We are proposing that owners or operators obtain these 
measurements at the outlet of the first adsorber bed in series using a 
sampling port, and that they obtain measurements monthly (if the bed 
has at least 2 months of the bed design life remaining), weekly (if the 
bed has between 2 months and 2 weeks of bed design life remaining), or 
daily (when the bed has less than 2 weeks of bed design life 
remaining). Also, we propose to require that owners and operators 
establish an average adsorber bed life from a design evaluation as well 
as conduct monitoring no later than 3 days after a bed is put into 
service as the first bed in series to confirm that it is functioning 
properly.
    We did not identify any carbon adsorbers in the risk modeling file. 
To validate this finding, we conducted an air permit review alongside 
analysis of our CAA section 114 request data and confirmed that PEPO 
facilities do not currently use carbon adsorbers to control HAP 
emissions from PEPO sources. Therefore, we do not anticipate any cost 
associated with adding these proposed monitoring and operation 
requirements to the PEPO NESHAP for non-regenerative adsorbers and 
adsorbers with beds that are regenerated off-site. Additionally, the 
EPA acknowledges that these proposed requirements could be considered 
under CAA section 112(d)(6) because of the specification to have two 
adsorber beds in series, instead of as a proposed change to the 
monitoring requirements. However, our rationale for why a second bed is 
needed would not be any different if we described these proposed 
changes under CAA section 112(d)(6) instead of as a monitoring change. 
As previously mentioned, we are proposing these changes because the 
current PEPO NESHAP does not contain monitoring requirements for non-
regenerative adsorbers, and it is possible that owners and operators 
may use this type of APCD to control emissions from PEPO sources.
6. Listing of 1-Bromopropane (1-BP) as a HAP
    On January 5, 2022, the EPA published in the Federal Register (87 
FR 393) a final rule amending the list of HAP under the CAA to add 1-
bromopropane in response to public petitions previously granted by the 
EPA. For the PEPO Production source category, we conclude that the 
inclusion of 1-BP as an organic HAP will not have any effect on the 
MACT standards. First, 1-BP is not an epoxide, nor is it THF. 
Furthermore, we have no information showing that 1-BP is used, 
produced, or emitted to make or modify the PEPO product. Accordingly, 
we are proposing

[[Page 106043]]

that no further action is required related to 1-BP. We solicit comments 
on this approach, and should new information submitted to the EPA show 
that 1-BP is emitted from this source category, the EPA will consider 
this information in the context of developing any MACT standards that 
may be needed to address emissions of 1-BP. We also note that in 
several instances in the PEPO NESHAP, facilities can comply with a TOC 
concentration standard (e.g., 20 ppmv), which could adequately regulate 
emissions of 1-BP if it is emitted from this source category.
7. Other Editorial Changes
    The EPA is proposing additional changes that address technical and 
editorial corrections for the PEPO NESHAP and overlap with the P&R I 
NESHAP as detailed here:
     The EPA is proposing to replace ``elastomer'' with 
``polyether polyol'' in 40 CFR 63.1420(e)(3) to correct a typographical 
error, given that the PEPO NESHAP applies to PMPUs and does not use the 
term ``elastomer'' anywhere else in the rule.
     The EPA is proposing to delete ``parts per million by 
volume'' in 40 CFR 63.1425(f)(7)(iv) because ``ppmv'' is defined 
previously in the rule.
     The EPA is proposing at 40 CFR 63.1426(b)(4) and (5) to 
allow owners and operators of emission sources controlled by a boiler 
or process heater burning hazardous waste to comply with the provisions 
of 40 CFR part 63, subpart EEE, rather than complying with the 
performance test provisions in the PEPO NESHAP.
     The EPA is proposing to clarify at 40 CFR 63.1426(c)(2) 
that performance tests and compliance determinations must be conducted 
according to the schedule and procedures in 40 CFR 63.1437.
     The EPA is proposing to remove the exemption at 40 CFR 
63.1426(d)(1) that allows owners and operators to be exempt from 
determining uncontrolled organic HAP emissions for process vents in a 
PMPU if all process vents subject to the emission reduction 
requirements of 40 CFR 63.1425(b), (c)(1), or (d)(2) are controlled at 
all times using a combustion, recovery, or recapture device, or ECO. 
Based on our review of historical documents, it is not clear why this 
exemption is needed. Instead, we are proposing that owners and 
operators must determine uncontrolled emissions for each process vent 
at a PMPU that is complying with the process vent control requirements 
in 40 CFR 63.1425(b)(1)(i), (b)(1)(iii), (b)(2)(ii), (b)(2)(iv), 
(c)(1)(ii), or (d)(2) using a combustion, recovery, recapture device, 
or ECO.
     The EPA is proposing to correct a reference error in 40 
CFR 63.1430(c), (d)(1), (d)(1)(i), and (k) such that the paragraphs 
point to not only table 5 to 40 CFR part 63, subpart PPP, but also 
table 6 to 40 CFR part 63, subpart PPP.
     The EPA is proposing to add at 40 CFR 63.1439(d)(11) 
requirements to maintain records of excursions. The EPA is proposing to 
require that sources keep records of this information to ensure that 
there is adequate information to allow the EPA to determine the 
severity of any failure to meet a standard, and to provide data that 
may document how the source met the general duty to minimize emissions 
when the source has failed to meet an applicable standard.
     The EPA is proposing to clarify at 40 CFR 63.1439(e)(6)(i) 
that all Periodic Reports must contain the company name and address 
(including county), as well as the beginning and ending dates of the 
reporting period.
     The EPA is proposing to clarify at 40 CFR 
63.1439(e)(6)(iii)(B) that for each excursion reported in a Periodic 
Report, the owner or operator must include the start date and time, 
duration, cause, a list of the affected sources or equipment, an 
estimate of the quantity of each regulated pollutant emitted over any 
emission limit, a description of the method used to estimate the 
emissions, actions taken to minimize emissions, and any corrective 
action taken.
     The EPA is proposing to clarify at 40 CFR 
63.1439(e)(6)(iii)(C) that for periods when monitoring data were not 
collected, the Periodic Report must include start date, start time, and 
duration of each period when monitoring data were not collected.
     The EPA is proposing to clarify at 40 CFR 
63.1439(e)(6)(ix)(C)(2) that for PRDs in organic HAP service, Periodic 
Reports must include ``start date, start time, and duration in minutes 
of the pressure release'' instead of ``date, time, and duration of the 
pressure release.''
     The EPA is proposing to insert the missing word 
``releases'' at 40 CFR 63.1439(e)(6)(ix)(C)(5) to clarify that we mean 
``pressure releases,'' not ``pressure.''
     The EPA is proposing to remove the entry for 40 CFR 
63.6(e) of table 1 to the PEPO NESHAP because it is unnecessary given 
that there are already entries in the table for all subparagraphs 
associated with 40 CFR 63.6(e). We are also proposing to change ``yes'' 
to ``no'' for the entry for 40 CFR 63.6(e)(2) because this provision 
has no requirement and is ``[Reserved].''
     The EPA is proposing to add an entry for 40 CFR 63.7(a)(4) 
into table 1 to the PEPO NESHAP because it is missing and is 
applicable.
     The EPA is proposing to revise the entries for 40 CFR 
63.10(b)(2) and (d)(5) of table 1 to the PEPO NESHAP to specify where 
the recordkeeping and reporting requirements are in the PEPO NESHAP.
     The EPA is proposing to edit the title of table 2 to the 
PEPO NESHAP to include ``and Group 1 Polymers and Resins'' because the 
content in the table contains provisions related the P&R I NESHAP.
     The EPA is proposing to correct several explanations in 
table 2 to the PEPO NESHAP to refer to the correct paragraph(s) for 
certain requirements being proposed in this action.
     In reviewing cross-references between the PEPO NESHAP and 
P&R I NESHAP, the EPA noticed that, even though the rule text exists, 
the EPA inadvertently removed the ``(iii)'' for paragraph 40 CFR 
63.506(e)(6)(iii) in its recent final rulemaking (see 89 FR 42932, May 
16, 2024) and is proposing to correct this typographical error by 
adding the ``(iii)'' back into the P&R I NESHAP. This proposed edit 
does not change any rule text within 40 CFR 63.506(e)(6)(iii).

F. What compliance dates are we proposing?

    The proposed amendments in this rulemaking for adoption under CAA 
sections 112(d)(2) and (3) and 112(h) (see section IV.D of this 
preamble) and CAA section 112(d)(6) (see section IV.C of this preamble) 
are subject to the compliance deadlines outlined in the CAA under 
section 112(i). The proposed amendments in this rulemaking for adoption 
under CAA section 112(f) (see section IV.B of this preamble) are 
subject to the compliance deadlines outlined in the CAA under section 
112(f)(4).
    For all the requirements we are proposing under CAA sections 
112(d)(2), (3), and (6), and 112(h) (except for the fenceline 
monitoring requirements), we are proposing at 40 CFR 63.1422(h) that 
existing affected sources and affected sources that were new sources 
under the current PEPO NESHAP (i.e., they commenced construction or 
reconstruction after September 4, 1997, and on or before December 27, 
2024 must comply with all of the amendments no later than 3 years after 
the effective date of the final rule or upon startup, whichever is 
later. For existing sources, CAA section 112(i) provides that the 
compliance date shall be as expeditious as practicable, but no later 
than 3 years after the effective date of the standard. (``Section 
112(i)(3)'s

[[Page 106044]]

three-year maximum compliance period applies generally to any emission 
standard . . . promulgated under [section 112].'' Association of 
Battery Recyclers v. EPA, 716 F.3d 667, 672 (D.C. Cir. 2013)). In 
determining what compliance period is as expeditious as practicable, we 
consider the amount of time needed to plan and construct projects and 
to change operating procedures. As provided in CAA section 112(i) and 5 
U.S.C. 801(3), all new affected sources that commenced construction or 
reconstruction after December 27, 2024 would be required to comply with 
these requirements upon the effective date of the final rule or upon 
startup, whichever is later. The EPA anticipates that the effective 
date of the final rule will be the publication date of the final rule.
    For fenceline monitoring, we are proposing at 40 CFR 63.1422(n) 
that owners and operators of all existing affected sources and all 
affected sources that were new under the current rule (i.e., sources 
that commenced construction or reconstruction after September 4, 1997, 
and on or before December 27, 2024) must begin fenceline monitoring 2 
years after the effective date of the final rule and, starting 3 years 
after the effective date of the final rule, must perform root cause 
analysis and apply corrective action requirements upon exceedance of 
the annual average concentration action level.
    For all of the requirements we are proposing under CAA section 
112(f), we are proposing at 40 CFR 63.1422(m) a compliance date of 2 
years after the effective date of the final rule or upon startup, 
whichever is later, for all existing affected sources and for all 
affected sources that were new sources under the current PEPO NESHAP 
(i.e., they commenced construction or reconstruction after September 4, 
1997, and on or before December 27, 2024), to comply with the proposed 
EtO requirements. For all new affected sources that commence 
construction or reconstruction after December 27, 2024, we are 
proposing that owners or operators comply with the EtO requirements 
upon the effective date of the final rule or upon startup, whichever is 
later.
1. Rationale for Proposed Compliance Dates of Proposed CAA Sections 
112(d)(2) and (3) and 112(h) Amendments
    We are proposing new operating and monitoring requirements under 
CAA sections 112(d)(2) and (3) for PEPO flares. We anticipate that 
these provisions would require the installation of new flare monitoring 
equipment, and we project that most PMPUs would install new control 
systems to monitor and adjust assist gas (air or steam) addition rates. 
Similar to the addition of new control equipment, these new monitoring 
requirements for flares would require engineering evaluations, 
solicitation and review of vendor quotes, contracting and installation 
of the equipment, and operator training. Installation of new monitoring 
and control equipment on flares will require the flare to be taken out 
of service. Depending on the configuration of the flares and flare 
header system, taking the flare out of service may also require a 
significant portion of the PMPU to be shut down. Therefore, for all 
existing affected sources, and all new affected sources under the 
current PEPO NESHAP that commenced construction or reconstruction after 
September 4, 1997, and on or before December 27, 2024, we are proposing 
that it is necessary to provide 3 years after the effective date of the 
final rule (or upon startup, whichever is later) for owners or 
operators to comply with the new operating and monitoring requirements 
for flares. For all new affected sources that commence construction or 
reconstruction after December 27, 2024, we are proposing that owners or 
operators comply with the new operating and monitoring requirements for 
flares upon the effective date of the final rule or upon startup, 
whichever is later.
    Under CAA sections 112(d)(2) and (3), we are proposing new vent 
control requirements for bypasses. These requirements would typically 
require the addition of piping and potentially new control 
requirements. As owners or operators would most likely route these 
bypass emissions to a flare, we are proposing for all existing affected 
sources, and new affected sources under the current PEPO NESHAP that 
commenced construction or reconstruction after September 4, 1997, and 
on or before December 27, 2024, to provide 3 years after the effective 
date of the final rule (or upon startup, whichever is later) to allow 
for owners or operators to coordinate these bypass modifications with 
the installation of the new monitoring equipment for the flares. For 
all new affected sources that commence construction or reconstruction 
after December 27, 2024, we are proposing that owners or operators 
comply with the new vent control requirements for bypasses upon the 
effective date of the final rule or upon startup, whichever is later.
    We are also proposing to establish work practice standards in the 
PEPO NESHAP for maintenance activities. We anticipate that sources will 
need time to: review and update their standard operating procedures for 
maintenance activities; identify the most appropriate preventive 
measures or control approaches; design, install, and test the control 
systems; and install necessary process instrumentation and safety 
systems if so required. Therefore, for all existing affected sources, 
and all new affected sources under the current PEPO NESHAP that 
commenced construction or reconstruction after September 4, 1997, and 
on or before December 27, 2024, we are proposing a compliance date of 3 
years after the effective date of the final rule (or upon startup, 
whichever is later) for owners or operators to comply with the work 
practice standards for maintenance activities. For all new affected 
sources that commence construction or reconstruction after December 27, 
2024, we are proposing that owners or operators comply with the work 
practice standards for maintenance activities upon the effective date 
of the final rule or upon startup, whichever is later.
    Other amendments we are proposing under CAA sections 112(d)(2) and 
(3) include LDAR requirements for pressure vessels, process vent 
control requirements for certain surge control vessels and bottoms 
receivers, control requirements for certain transfer racks, the 
addition of butylene oxide to the definition of ``epoxide'' in 40 CFR 
63.1423(b) and to the list of HAP presented in table 4 to the PEPO 
NESHAP, and the removal of the exemption in 40 CFR 63.1420(d)(3) for 
reactions or processing that occur after completion of epoxide 
polymerization and all catalyst removal steps. We anticipate that any 
of these proposed provisions may require additional time to plan, 
purchase, and install equipment for emissions control; however, even if 
additional time is not needed, the EPA recognizes the confusion that 
multiple different compliance dates for individual requirements would 
create and the additional burden such an assortment of dates would 
impose. Therefore, for all existing affected sources, and all new 
affected sources under the current rules that commenced construction or 
reconstruction after September 4, 1997, and on or before December 27, 
2024, we are proposing a compliance date of 3 years after the effective 
date of the final rule (or upon startup, whichever is later) for owners 
or operators to comply with these other proposed amendments. For all 
new

[[Page 106045]]

affected sources that commence construction or reconstruction after 
December 27, 2024, we are proposing that owners or operators comply 
with these other proposed amendments upon the effective date of the 
final rule or upon startup, whichever is later.
2. Rationale for Proposed Compliance Dates of Proposed CAA Section 
112(d)(6) Amendments
    As a result of our technology review for PEPO heat exchange 
systems, we are proposing to replace the existing leak definition and 
monitoring method with a new leak definition and monitoring method. We 
project that some owners and operators would require engineering 
evaluations, solicitation and review of vendor quotes, contracting and 
installation of monitoring equipment, and operator training. In 
addition, facilities will need time to read and understand the amended 
rule requirements and to update standard operating procedures. 
Therefore, we are proposing that all existing affected sources, and all 
new affected sources under the current rule that commenced construction 
or reconstruction after September 4, 1997, and on or before December 
27, 2024, must comply with the new monitoring requirements for heat 
exchange systems no later than 3 years after the effective date of the 
final rule (or upon startup, whichever is later). For all new affected 
sources that commence construction or reconstruction after December 27, 
2024, we are proposing that owners or operators comply with the new 
monitoring requirements for heat exchange systems upon the effective 
date of the final rule or upon startup, whichever is later.
    Under our technology review for PEPO storage vessels under CAA 
section 112(d)(6), we are revising the PEPO NESHAP to reflect more 
stringent storage vessel capacity and MTVP thresholds. Although we did 
not find any PEPO storage vessels that would be affected by these 
proposed provisions, we believe it would be unnecessarily cumbersome to 
impose different compliance dates for these new storage vessel 
requirements. The EPA recognizes the confusion that multiple different 
compliance dates for individual requirements would create and the 
additional burden that such an assortment of dates would impose. 
Therefore, we are proposing that all existing affected sources, and all 
new affected sources under the current rules that commenced 
construction or reconstruction after September 4, 1997, and on or 
before December 27, 2024, must comply with the new storage vessel 
requirements no later than 3 years after the effective date of the 
final rule (or upon startup, whichever is later). For all new affected 
sources that commence construction or reconstruction after December 27, 
2024, we are proposing that owners or operators comply with the new 
storage vessel requirements upon the effective date of the final rule 
or upon startup, whichever is later.
    We are also proposing, pursuant to CAA section 112(d)(6), to remove 
the 50-ppmv and 0.005-scmm Group 1 process vent thresholds from the 
definition of ``Group 1 continuous process vent'' for continuous 
process vents associated with nonepoxide organic HAP and the Group 1 
process vent applicability associated with a PMPU using THF, and to 
instead require owners and operators of these process vents that emit 
greater than or equal to 1.0 lb/hr of total organic HAP to meet the 
current control standards in the PEPO NESHAP. Additionally, as a result 
of our technology review for PEPO Group 1 combination of batch process 
vents, we are proposing that owners and operators of batch process 
vents that release a total of annual organic HAP emissions greater than 
or equal to 4,536 kg/yr (10,000 lb/yr) from all batch process vents 
combined reduce emissions of organic HAP from these process vents using 
a flare meeting the proposed operating and monitoring requirements for 
flares; or reduce emissions of organic HAP or TOC by 90-percent by 
weight. We project that some owners and operators will need to install 
new control equipment and/or new hard-piping or ductwork for certain 
process vents because of the proposed applicability revisions. The 
addition of new control equipment would require engineering design, 
solicitation, and review of vendor quotes, and contracting and 
installation of the equipment, which would need to be timed with 
process unit outage and operator training. Therefore, we are proposing 
that all existing affected sources, and all new affected sources under 
the current rules that commenced construction or reconstruction after 
September 4, 1997, and on or before December 27, 2024, must comply with 
the new process vent requirements no later than 3 years after the 
effective date of the final rule (or upon startup, whichever is later). 
For all new affected sources that commence construction or 
reconstruction after December 27, 2024 we are proposing that owners or 
operators comply with the new process vent requirements upon the 
effective date of the final rule or upon startup, whichever is later.
    Compliance dates for the fenceline monitoring provisions proposed 
under CAA section 112(d)(6) consider the amount of time that it will 
take owners and operators to develop their siting plans and secure the 
capabilities to conduct the monitoring and analyze the results. For 
fenceline monitoring, the compliance timeline also must consider the 
timeline for controls addressing EtO emissions to be installed and 
operational before monitoring can begin to develop the annual average 
concentration baseline. After a year, if the annual average 
concentration exceeds the action level, root cause analysis and 
application of corrective measures can take place. Therefore, we are 
proposing that owners and operators of all existing sources and all new 
affected sources under the current rule that commenced construction or 
reconstruction after September 4, 1997, and on or before December 27, 
2024 must begin fenceline monitoring 2 years after the effective date 
of the final rule. The 2-year period provides owners and operators with 
time to: read and assess the new fenceline monitoring requirements; 
prepare sampling and analysis plans; develop and submit site-specific 
monitoring plans; identify representative, accessible, and secure 
monitoring locations for offsite monitors and obtain permission from 
the property owner to both place and routinely access the monitors; 
make any necessary physical improvements to fenceline areas to 
accommodate site monitors, including construction of access roads, 
physical fencing, and potential drainage improvements; and obtain 
approval of any necessary capital expenditures. We are also proposing 
that owners and operators of such sources perform root cause analysis 
and apply corrective action requirements upon exceedance of an annual 
average concentration action level starting 3 years after the effective 
date of the final rule.
    For all new affected sources that commence construction or 
reconstruction after December 27, 2024, we are proposing that owners or 
operators begin fenceline monitoring upon the effective date of the 
final rule or upon startup, whichever is later. We are also proposing 
to require quarterly reporting of fenceline results beginning 1 year 
after monitoring begins for such sources.
3. Rationale for Proposed Compliance Dates of Proposed CAA Section 
112(f) Amendments
    As previously mentioned in this preamble, we are proposing, under 
CAA

[[Page 106046]]

section 112(f), new provisions considering results of the risk 
assessments to address emissions of EtO from equipment leaks, heat 
exchange systems, process vents, storage vessels, and wastewater at 
PEPO processes. CAA section 112(f)(4) prescribes the compliance date 
for emission standards issued under CAA section 112(f). Ass'n of 
Battery Recyclers v. EPA, 716 F.3d 667, 672 (D.C. Cir. 2013) 
(``[S]ection 112(f)(4)'s two-year maximum applies more specifically to 
standards `under this subsection,' i.e., section 112(f).''). For 
existing sources, the earliest compliance date for CAA section 112(f) 
standards is 90 days after the effective date. However, the compliance 
period can be extended up to 2 years after the effective date if the 
EPA finds that more time is needed for the installation of controls and 
that steps will be taken during the period of the waiver to assure that 
the health of persons will be protected from imminent endangerment. 42 
U.S.C. 7412(f)(4)(B). The EPA anticipates that the proposed provisions 
will require additional time to plan, purchase, and install equipment 
for EtO control. For example, for PEPO process vents in EtO service, if 
the affected source cannot demonstrate 99.9-percent control of EtO 
emissions, or reduce EtO emissions to less than 1 ppmv (from each 
process vent) or 5 lb/yr (for all combined process vents), then the 
owner or operator would need to install a new control system, such as a 
scrubber with piping, ductwork, feed tanks, etc. Similarly, this same 
scenario (i.e., installation of a new control system) may be necessary 
for storage vessels in order to reduce EtO emissions by greater than or 
equal to 99.9 percent by weight or to a concentration of less than 1 
ppmv. Likewise, a new steam stripper may be needed to control 
wastewater with a total annual average concentration of EtO greater 
than or equal to 1 ppmw. Additional permits may be required for this 
new emission control equipment (e.g., New Source Review and/or title V 
permit modifications). In other words, the EPA anticipates that 
facilities will need sufficient time to properly engineer the project, 
obtain capital authorization and funding, procure the equipment, obtain 
permits, and construct and start up the equipment. Therefore, in the 
absence of any determination by the EPA that a PEPO affected source is 
presenting imminent endangerment, we are proposing a compliance date of 
2 years after the effective date of the final rule or upon startup, 
whichever is later, for all existing affected sources, and all new 
affected sources under the current rule that commenced construction or 
reconstruction after September 4, 1997, and on or before December 27, 
2024 to comply with the proposed EtO requirements. For all new affected 
sources that commence construction or reconstruction after December 27, 
2024, we are proposing that owners or operators comply with the EtO 
requirements upon the effective date of the final rule or upon startup, 
whichever is later.
4. Rationale for Proposed Compliance Dates of Other Proposed Amendments
    We are proposing electronic reporting requirements (see section 
IV.E.2 of this preamble) and we anticipate that facilities would need 
some time to successfully accomplish these reporting revisions, 
including time to read and understand the amended rule requirements, to 
make any necessary adjustments (including adjusting standard operating 
procedures), and to convert reporting mechanisms and install necessary 
hardware and software. We are also proposing to add control device 
operational and monitoring requirements for adsorbers that cannot be 
regenerated and regenerative adsorbers that are regenerated offsite 
(including a requirement to use dual adsorbent beds in series) (see 
section IV.E.5. of this preamble). We anticipate that facilities would 
need some time to purchase and install a second adsorber bed. As 
previously mentioned, the EPA recognizes the confusion that multiple 
different compliance dates for individual requirements would create and 
the additional burden that such an assortment of dates would impose. 
From our assessment of the timeframe needed for compliance with both 
the new proposed electronic reporting requirements for flare management 
plans, compliance reports, and performance evaluation reports, and the 
new proposed adsorber requirements, the EPA considers a period of 3 
years after the effective date of the final rule to be the most 
expeditious compliance period practicable. Thus, we are proposing that 
all existing affected sources, and all new affected sources under the 
current rule that commenced construction or reconstruction after 
September 4, 1997, and on or before December 27, 2024 be in compliance 
with these revised requirements upon initial startup or within 3 years 
of the effective date of the final rule, whichever is later. For all 
new affected sources that commence construction or reconstruction after 
December 27, 2024, we are proposing that owners or operators comply 
with these revised requirements upon the effective date of the final 
rule or upon startup, whichever is later. However, we are proposing to 
provide 60 days after the effective date of the final rule (or upon 
startup, whichever is later) for owners or operators of all affected 
sources to comply with the requirement to submit performance test 
reports electronically according to the proposed procedures specified 
in 40 CFR 63.1439(e)(9)(iii).

V. Summary of Cost, Environmental, and Economic Impacts

A. What are the affected sources?

    There are 25 facilities subject to the PEPO NESHAP. The list of 
facilities is available in the document titled List of Facilities 
Subject to the PEPO NESHAP, which is available in the docket for this 
rulemaking.

B. What are the air quality impacts?

    This proposed action would reduce HAP and VOC emissions from PEPO 
emission sources. We estimate that the proposed amendments to the 
NESHAP, excluding the proposed EtO emission standards, would reduce 
overall VOC and HAP emissions from the PEPO Production source category 
by approximately 164 and 157 tpy, respectively. Additionally, the 
proposed EtO emission standards are expected to reduce EtO emissions by 
approximately 14 tpy. We note that these emissions reductions do not 
consider the potential excess emissions reductions from flares that 
could result from the proposed monitoring requirements; we estimate 
flare excess emissions reductions of 75 tpy HAP and 281 tpy VOC.
    Considering secondary impacts (e.g., emission increases associated 
with supplemental fuel or additional electricity), the EPA estimates 
that the proposed action would result in additional emissions of 155 
tpy of carbon monoxide (CO), 242,000 tpy of carbon dioxide 
(CO2), 188 tpy of nitrogen oxides (NOX) 
(including 4 tpy of nitrous oxide), 14 tpy of particulate matter, 1.0 
tpy of sulfur dioxide (SO2), and a reduction of 996 tpy of 
methane emissions. More information about the estimated emission 
reductions and secondary impacts of this proposed action for the PEPO 
NESHAP can be found in the Economic Impact Analysis (EIA) accompanying 
this proposal and in documents referenced in sections IV.B through IV.D 
of this preamble.

C. What are the cost impacts?

    The EPA estimates that this proposed action would cumulatively cost 
(in 2022 dollars) approximately $31.0 million in total capital costs 
and $18.7 million per year in total annualized costs (including

[[Page 106047]]

product recovery), based on our analysis of the proposed action 
described in sections IV.B through IV.D of this preamble. The present 
value (PV) of the estimated costs of this proposed rule, discounted at 
a 2 percent rate over the 2026 to 2040 period, is estimated at $236 
million with an estimated equivalent annualized value (EAV) of $18.4 
million without product recovery. With product recovery, the PV is 
estimated at $235 million with an estimated EAV of $18.3 million. The 
overall difference caused by product recovery is relatively minor, at 
less than a 0.43 percent decrease in both the PV and EAV.
    Although the EPA does not factor in cost when setting a MACT floor 
level of control, we estimated the cost of the standards proposed 
pursuant to CAA sections 112(d)(2) and (3) and 112(h) to include in the 
cumulative costs of the proposed action.
    Table 13 of this preamble summarizes the results of the impact 
estimates for flares in the PEPO Production source category that 
control emissions from PEPO processes.

   Table 13--Nationwide Cost Impacts for Flares in the PEPO Production
       Source Category That Control Emissions From PEPO Processes
------------------------------------------------------------------------
                                                               Total
                                           Total capital    annualized
           Control description              investment    costs (million
                                            (million $)        $/yr)
------------------------------------------------------------------------
Flare Operational and Monitoring                    11.5            2.82
 Requirements...........................
Work Practice Standards for Flares                  0.20            0.05
 Operating Above Their Smokeless
 Capacity...............................
                                         -------------------------------
    Total...............................            11.7            2.88
------------------------------------------------------------------------

    For the proposed equipment opening work practice standard, 
discussed in section IV.D.3.a, we expect that all PEPO facilities 
already have standard procedures in place when performing equipment 
openings (at the very least for safety reasons), with the exception of 
one facility, which is a small business that is co-located with a HON 
facility and is already accounted for under the recent HON rulemaking 
(see 89 FR 42932). As such, the only costs incurred are for 
recordkeeping after each non-conforming event. We estimated the annual 
costs to be $11,000 per year.
    We estimated the annual cost of the proposed storage vessel 
degassing work practice standard, discussed in section IV.D.3.b, to be 
$7,100.
    For the proposed requirement to control working emissions from 
storage vessels during routine maintenance, discussed in section 
IV.D.3.c, we determined that the total capital cost of a 55-gallon 
activated carbon drum with two connections, including piping and 
ductwork, is approximately $1,500, based on vendor quotes. Following 
the guidelines of the EPA Control Cost Manual,\88\ we estimated that 
the annual cost per PMPU is $259. Thus, we estimated the nationwide 
capital cost for removal of the 240-hour exemption provisions (except 
for vessel breathing losses) for the PEPO NESHAP would be $22,500 and 
the annualized costs would be $3,900.
---------------------------------------------------------------------------

    \88\ EPA Air Pollution Control Cost Manual--Section 3: VOC 
Controls; Section 3.1: VOC Recapture Controls, Carbon Adsorbers 
Calculation Spreadsheet. Retrieved from https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution. October 2018.
---------------------------------------------------------------------------

    We estimate that the nationwide capital cost for the proposed 
pressure vessel LDAR requirements discussed in section IV.D.4 would be 
about $3,800 and the annualized capital costs would be $3,500.
    We anticipate that the following proposed changes would impose 
minimal costs: prohibiting bypasses of the APCD (discussed in section 
IV.D.2); setting MACT standards for transfer racks (discussed in 
section IV.D.6); inclusion of butylene oxide in the definition of 
epoxide and the list of HAP in table 4 to the PEPO NESHAP (discussed in 
section IV.D.7).

D. What are the economic impacts?

    The EPA conducted an EIA for this proposal, in a document titled 
Economic Impact Analysis, which is available in the docket for this 
action. The EIA contains two parts. The EPA calculated the economic 
impacts of the proposal on small entities as the percentage of total 
annualized costs incurred by affected ultimate parent owners to their 
revenues. This ratio provides a measure of the direct economic impact 
to ultimate parent owners of PEPO facilities while presuming no impact 
on consumers. We estimate that the only small business impacted by the 
proposal will incur total annualized costs of 0.68 percent of its 
revenue both with and without product recovery. The Regulatory 
Flexibility Act (RFA) section later in this preamble and the EIA for 
this proposed rulemaking provide more explanation of these economic 
impacts.

E. What are the benefits?

    The emissions controls required by these rules are expected to 
reduce emissions of a number of HAP. The proposed amendments to the 
PEPO NESHAP, excluding the EtO emission standards and the new flare 
requirements, would reduce HAP emissions from PEPO sources by 
approximately 157 tpy. The proposed EtO emission standards are 
projected to reduce EtO emissions from PEPO processes by approximately 
14 tpy. We also estimate that the proposed amendments to the NESHAP 
will reduce excess emissions of HAP from flares in the PEPO Production 
source category by an additional 75 tpy.
    Quantifying and monetizing the economic value of reducing the risk 
of cancer and non-cancer effects is made difficult by the lack of a 
central estimate of cancer and non-cancer risk and the lack of 
estimates of the value of an avoided case of cancer (fatal and non-
fatal) and morbidity effects. Due to methodology and data limitations, 
we did not attempt to monetize the health benefits of reductions in HAP 
emissions in this analysis. With regard to emissions changes, the EPA 
is unable to assess the total costs, benefits, and distributional 
consequences of these actions at the community/neighborhood level.
    EtO is used in the production of PEPO. Health effects from acute 
(short-term) exposure to EtO in humans consist mainly of central 
nervous system depression and irritation of the eyes and mucous 
membranes. Chronic (long-term) exposure to EtO in humans can cause 
irritation of the eyes, skin, nose, throat, and lungs, and damage to 
the brain and nervous system. There is also some evidence linking EtO

[[Page 106048]]

exposure to reproductive effects.\89\ The International Agency for 
Research on Cancer has classified EtO as a known human carcinogen.\90\ 
The EPA's IRIS characterized EtO as ``carcinogenic to humans'' by the 
inhalation route of exposure based on the total weight of evidence 
(U.S. EPA, 2016), in accordance with the EPA's Guidelines for 
Carcinogen Risk Assessment.\91\ The EPA concluded that there was 
strong, but less than conclusive on its own, epidemiological evidence 
of lymphohematopoietic cancers and breast cancer in EtO-exposed workers 
(U.S. EPA, 2016). People living near PEPO production facilities that 
emit EtO may have an increased risk of developing lymphoid cancers and, 
for females, breast cancer.\92\ We conclude that reducing EtO emissions 
from PEPO production facilities will significantly reduce the cancer 
risk for exposed populations (see sections IV.A.1 and IV.B.3 of this 
preamble).
---------------------------------------------------------------------------

    \89\ ATSDR. Toxicological Profile for Ethylene Oxide. U.S. 
Department of Health and Human Services. 2022. Available at https://www.atsdr.cdc.gov/toxprofiles/tp137.pdf.
    \90\ International Agency for Research on Cancer. Chemical 
Agents and Related Occupations. Volume 100F, A Review of Human 
Carcinogens. 2012. Available at https://publications.iarc.fr/Book-And-Report-Series/Iarc-Monographs-On-The-Identification-Of-Carcinogenic-Hazards-To-Humans/Chemical-Agents-And-Related-Occupations-2012.
    \91\ U.S. EPA. Guidelines for Carcinogen Risk Assessment. 2005. 
Available at https://www.epa.gov/risk/guidelines-carcinogen-risk-assessment.
    \92\ U.S. EPA. Evaluation of the Inhalation Carcinogenicity of 
Ethylene Oxide. Integrated Risk Information System (IRIS) on 
Ethylene Oxide. National Center for Environmental Assessment, 
Washington DC. 2016.
---------------------------------------------------------------------------

    The emission controls installed to comply with these proposed rules 
are also expected to reduce VOC emissions which, in conjunction with 
NOX and in the presence of sunlight, form ground-level ozone 
(O3). To assess O3-related human health impacts, 
the EPA consults the Integrated Science Assessment for Ozone (Ozone 
ISA) \93\ as summarized in the Technical Support Document for the Final 
Revised Cross State Air Pollution Rule Update.\94\ In brief, the Ozone 
ISA found short-term (less than 1 month) exposures to ozone to be 
causally related to respiratory effects, a ``likely to be causal'' 
relationship with metabolic effects, and a ``suggestive of, but not 
sufficient to infer, a causal relationship'' for central nervous system 
effects, cardiovascular effects, and total mortality. The Ozone ISA 
reported that long-term exposures (1 month or longer) to ozone are 
``likely to be causal'' for respiratory effects including respiratory 
mortality, and a ``suggestive of, but not sufficient to infer, a causal 
relationship'' for cardiovascular effects, reproductive effects, 
central nervous system effects, metabolic effects, and total mortality.
---------------------------------------------------------------------------

    \93\ U.S. EPA (2020). Integrated Science Assessment for Ozone 
and Related Photochemical Oxidants. U.S. EPA. Washington, DC. Office 
of Research and Development. EPA/600/R-20/012. Available at: https://www.epa.gov/isa/integrated-science-assessment-isa-ozone-and-related-photochemical-oxidants.
    \94\ U.S. EPA. 2021. Technical Support Document (TSD) for the 
Final Revised Cross-State Air Pollution Rule Update for the 2008 
Ozone Season NAAQS Estimating PM2.5- and Ozone-
Attributable Health Benefits. https://www.epa.gov/sites/default/files/2021-03/documents/estimating_pm2.5-_and_ozone-attributable_health_benefits_tsd.pdf.
---------------------------------------------------------------------------

F. What analysis of environmental justice did we conduct?

    For purposes of analyzing regulatory impacts, the EPA relies upon 
its June 2016 Technical Guidance for Assessing Environmental Justice in 
Regulatory Analysis, which provides recommendations that encourage 
analysts to conduct the highest quality analysis feasible, recognizing 
that data limitations, time, resource constraints, and analytical 
challenges will vary by media and circumstance. The Technical Guidance 
states that a regulatory action may involve potential EJ concerns if it 
could: (1) create new disproportionate impacts on communities with EJ 
concerns; (2) exacerbate existing disproportionate impacts on 
communities with EJ concerns; or (3) present opportunities to address 
existing disproportionate impacts on communities with EJ concerns 
through this action under development.
    The EPA's EJ technical guidance states that ``[t]he analysis of 
potential EJ concerns for regulatory actions should address three 
questions: (A) Are there potential EJ concerns associated with 
environmental stressors affected by the regulatory action for 
population groups of concern in the baseline? (B) Are there potential 
EJ concerns associated with environmental stressors affected by the 
regulatory action for population groups of concern for the regulatory 
option(s) under consideration? (C) For the regulatory option(s) under 
consideration, are potential EJ concerns created or mitigated compared 
to the baseline?'' \95\
---------------------------------------------------------------------------

    \95\ Technical Guidance for Assessing Environmental Justice in 
Regulatory Analysis, U.S. EPA, June 2016. Quote is from Section 3--
Key Analytic Considerations, page 11.
---------------------------------------------------------------------------

    The EJ analysis is presented for the purpose of providing the 
public with as full as possible an understanding of the potential 
impacts of this proposed action. The EPA notes that analysis of such 
impacts is distinct from the determinations proposed in this action 
under CAA section 112, which are based solely on the statutory factors 
the EPA is required to consider under that section.
1. PEPO Production Source Category Demographics
    For the PEPO Production source category, the EPA examined the 
potential for the 23 PEPO facilities (for which the EPA had HAP 
emissions inventories for emissions from the PEPO category) \96\ to 
pose concerns to communities living in proximity to facilities, both in 
the baseline and under the control option proposed in this proposed 
action. Specifically, to examine the potential for EJ concerns, the EPA 
conducted three different demographic analyses of the populations 
living within 10 km and 50 km of the PEPO facilities: a proximity 
analysis; a baseline cancer risk-based analysis (i.e., before 
implementation of any controls required by this proposed action); and a 
post-control cancer risk-based analysis (i.e., after implementation of 
the controls proposed to be required by this proposed action). In this 
preamble, we focus on the results from the demographic analyses using a 
10 km radius because this area captures the majority of the population 
with higher cancer risks due to HAP emissions from PEPO facilities. 
Specifically, 100 percent of the population with baseline cancer risks 
greater than or equal to 50-in-1 million from PEPO Production source 
category emissions lives within 10 km of the PEPO facilities. The 
methodology and detailed results of the demographic analyses, including 
the demographic analyses for populations living within 50 km of 
facilities, are presented in the document titled Analysis of 
Demographic Factors for Populations Living Near Polyether Polyols 
(PEPO) Production Facilities--Source Category Analysis of Proposed 
Amendments, which is available in the docket for this rulemaking.
---------------------------------------------------------------------------

    \96\ Note that there are 25 facilities identified as subject to 
the PEPO NESHAP. However, one of these facilities has a PEPO source 
still under construction and another facility did not have 
sufficient information to parse out the source category records. 
Therefore, only 23 facilities were included for the PEPO Production 
source category analyses.
---------------------------------------------------------------------------

    For all three demographic analyses, the affected populations (i.e., 
those living within 10 km of the facilities) are compared to the 
national population. The total population, population percentages, and 
population count for each demographic group for the entire U.S. 
population are shown in the column titled ``Nationwide Average for

[[Page 106049]]

Reference'' in tables 14 through 16 of this preamble. These national 
data are provided as a frame of reference to compare the results of the 
proximity analysis, the baseline cancer risk-based analysis, and the 
post-control cancer risk-based analysis.
    Detailed results of the PEPO Production source category demographic 
analyses are located in subsections a (proximity analysis), b (baseline 
risk-based analysis), and c (post-control risk-based analysis) of this 
section V.F.1 of the preamble. The following paragraphs briefly 
summarize the results of these demographic analyses.
    The results of the proximity analysis indicate that a total of 1.4 
million people live within 10 km of the 23 PEPO facilities analyzed. 
The percent of the population living within 10 km of the PEPO 
facilities is above the corresponding national average for the 
following demographic groups: Black, Hispanic or Latino, people living 
below the poverty level, people living below two times the poverty 
level, people over the age of 25 without a high school diploma, and 
people that are age 0 to 17. The results of the proximity analysis 
indicate that the proportion of other demographic groups living within 
10 km of PEPO facilities is similar to or below the national average. 
The baseline cancer risk-based demographic analysis, which focuses on 
populations that have higher cancer risks, suggests that disparities 
exist for the same demographic groups as seen in the proximity 
analysis.
    The post-control risk-based demographic analysis shows that the 
controls proposed to be required by this proposed action would notably 
reduce the number of people who are exposed to cancer risks resulting 
from PEPO Production source category emissions at all risk levels. At 
greater than or equal to a cancer risk of 1-in-1 million, the number of 
individuals exposed would decrease from 834,000 to 592,000. The 
demographic composition of those individuals exposed to cancer risk 
greater than or equal to 1-in-1 million post-control is similar to the 
demographic composition of the individuals exposed to a cancer risk of 
1-in-1 million at baseline. At greater than or equal to a cancer risk 
of 50-in-1 million, the number of individuals exposed would decrease 
from 28,000 to 1,600. The demographic composition of those individuals 
exposed to cancer risk greater than or equal to 50-in-1 million post-
control is above the corresponding national average for the following 
demographic groups: Black, Hispanic or Latino, age 0-17, people living 
below the poverty level, people living below two times the poverty 
level, and those over 25 without a high school education. After control 
is implemented, the number of people who are exposed to cancer risks 
greater than 100-in-1 million resulting from PEPO Production source 
category emissions would decrease from 3,300 to zero. Therefore, there 
are no disparities among demographic groups at this risk level. The 
actions of this proposed rulemaking would improve human health of 
current and future populations that live near these facilities. For 
more details see the remainder of this section V.F of the preamble.
a. Proximity Analysis
    The column titled ``Proximity Analysis for Population Living Within 
10 km of PEPO Facilities'' in tables 14 through 16 of this preamble 
shows the share and count of people for each of the demographic 
categories for the total population living within 10 km (~6.2 miles) of 
PEPO facilities. These are the results of the proximity analysis and 
are repeated in tables 14 through 16 of this preamble for easy 
comparison to the risk-based analyses discussed later in this preamble.
    Approximately 1.4 million people live within 10 km of the 23 PEPO 
facilities assessed. The results of the proximity demographic analysis 
indicate that the percentages of the population that is Black (13 
percent, 192,000 people), Hispanic or Latino (22 percent, 320,000 
people) are higher than the national average (12 percent and 19 
percent, respectively). The percentages of people living below the 
poverty level (14 percent, 196,000 people) and below 2 times the 
poverty level (31 percent, 446,000 people) are also higher than the 
national average (14 percent and 31 percent, respectively). In 
addition, the percentage of people over the age of 25 without a high 
school diploma (14 percent, 197,000 people) is higher than the national 
average (12 percent). The proximity analysis indicates that the 
proportion of other demographic groups living within 10 km of PEPO 
facilities is similar to or below the national average.
b. Baseline Risk-Based Demographics
    The baseline risk-based demographic analysis results are shown in 
the ``baseline'' column of tables 14 through 16 of this preamble. This 
analysis focused on the populations living within 10 km (~6.2 miles) of 
the PEPO facilities with estimated cancer risks greater than or equal 
to 1-in-1 million resulting from PEPO Production source category 
emissions (table 14 of this preamble), greater than or equal to 50-in-1 
million (table 15 of this preamble), and greater than 100-in-1 million 
(table 16 of this preamble). The risk analysis indicated that emissions 
from the source category, prior to the controls proposed to be required 
in this action, expose 834,000 people living near 18 facilities to a 
cancer risk greater than or equal to 1-in-1 million, 28,000 people 
living near 10 facilities to a cancer risk greater than or equal to 50-
in-1 million, and 3,300 people living near 6 facilities to a cancer 
risk greater than 100-in-1 million.
    In the baseline, there are 834,000 people living around 18 PEPO 
facilities with a cancer risk greater than or equal to 1-in-1 million 
resulting from PEPO Production source category emissions. The 18 PEPO 
facilities are located across 7 States, but more than two-thirds (14 
facilities) of the facilities are located in Texas, West Virginia, and 
Louisiana. Ninety-seven percent of the people with risks greater than 
or equal to 1-in-1 million live around these 14 PEPO facilities in 
Texas, West Virginia, and Louisiana. The overall percent of the 
baseline population with estimated cancer risks greater than or equal 
to 1-in-1 million who are Black (15 percent, 129,000 people) is above 
the average percentage of the national population that is Black (12 
percent). Around five PEPO facilities located in Louisiana, the percent 
of the population with cancer risks greater than or equal to 1-in-1 
million resulting from PEPO baseline source category emissions that is 
Black is more than two times the national average (greater than 24 
percent). These five PEPO facilities account for about half of the 
Black population living within 10 km of PEPO facilities with risks 
greater than or equal to 1-in-1 million resulting from PEPO Production 
source category baseline emissions.
    The overall percent of the population with cancer risks greater 
than or equal to 1-in-1 million resulting from PEPO Production source 
category baseline emissions that is Hispanic or Latino (26 percent, 
218,000 people) is higher than that in the baseline proximity analysis 
(22 percent, 320,000 people) and well above the national average (19 
percent). Around three PEPO facilities located in Texas, the percent of 
the population that is Hispanic or Latino with cancer risks greater 
than or equal to 1-in-1 million resulting from PEPO baseline source 
category emissions is more than two times the national average. These 
three PEPO facilities account for over half of the Hispanic or Latino 
population living within 10 km of PEPO facilities with risks greater 
than or equal to 1-in-1 million resulting from PEPO Production source 
category baseline emissions. The

[[Page 106050]]

percent of the population that is linguistically isolated with baseline 
cancer risks greater than or equal to 1-in-1 million is more than twice 
the national average for one of these three Texas facilities. The 
percent of the population that is American Indian or Alaskan Native or 
Other and Multiracial with risks greater than or equal to 1-in-1 
million resulting from PEPO Production source category baseline 
emissions is below the national average for all facilities.
    The percent of the population living below the poverty level and 
below two times the poverty level with cancer risks greater than or 
equal to 1-in-1 million resulting from PEPO baseline source category 
emissions (15 percent and 34 percent, respectively) is above the 
national average (13 percent and 30 percent, respectively). Around 
three facilities located in West Virginia, the percent of the 
population living below the poverty level and below two times the 
poverty level within 10 km of PEPO facilities with risks greater than 
or equal to 1-in-1 million resulting from PEPO Production source 
category baseline emissions is about 10 percent higher than the 
national average. The percent of the population over 25 years old 
without a high school diploma with cancer risks greater than or equal 
to 1-in-1 million resulting from PEPO Production source category 
baseline emissions (15 percent, 128,000 people) is greater than the 
national average (12 percent).
    In the baseline, there are about 28,000 people living around 10 
PEPO facilities with a cancer risk greater than or equal to 50-in-1 
million resulting from PEPO Production source category baseline 
emissions. These 10 PEPO facilities are located across 4 States 
(Louisiana, Texas, West Virginia, and Kentucky). Sixty percent of the 
people with risks greater than or equal to 50-in-1 million resulting 
from PEPO Production source category baseline emissions live within 10 
km of one facility, which is located in Louisiana. The overall percent 
of the population that is Black with baseline cancer risk greater than 
or equal to 50-in-1 million resulting from PEPO Production source 
category emissions (10 percent, 2,800 people) is below the national 
average (12 percent). However, around four PEPO facilities located in 
Louisiana and West Virginia, the percent of the population with cancer 
risks greater than or equal to 50-in-1 million resulting from PEPO 
baseline source category emissions that is Black is more than two times 
the national average (greater than 24 percent).
    The overall percent of the population that is Hispanic or Latino 
with baseline cancer risk greater than or equal to 50-in-1 million 
resulting from PEPO Production source category emissions (10 percent, 
2,700 people) is below the national average (19 percent). However, 
around two PEPO facilities located in Texas, the percent of the 
population with cancer risks greater than or equal to 50-in-1 million 
resulting from PEPO baseline source category emissions that is Hispanic 
or Latino is more than two times the national average (i.e., greater 
than 38 percent). The population near these two facilities in Texas 
accounts for about 77 percent of the number of Latino/Hispanic people 
with risks greater than or equal to 50-in-1 million resulting from the 
PEPO Production source category emissions. The percent of the 
population that is American Indian or Alaskan Native with risks greater 
than or equal to 50-in-1 million resulting from PEPO Production source 
category baseline emissions is below the national average for all 
facilities. The percent of the population that is Other or Multiracial 
with risks greater than or equal to 50-in-1 million resulting from PEPO 
Production source category baseline emissions is below the national 
average for all but one facility located in West Virginia.
    The percentage of the population with cancer risks resulting from 
PEPO Production source category baseline emissions greater than or 
equal to 50-in-1 million that are below the poverty level (14 percent), 
below two times the poverty level (35 percent), and over 25 years old 
without a high school diploma (16 percent) are above the respective 
national averages. Around four facilities located in West Virginia, the 
percentages of the population living below the poverty level and below 
two times the poverty level within 10 km of PEPO facilities with risks 
greater than or equal to 50-in-1 million resulting from PEPO Production 
source category baseline emissions are about 10 percent higher than the 
national average.
    In the baseline, there are 3,300 people living around 6 PEPO 
facilities with a cancer risk resulting from PEPO Production source 
category baseline emissions greater than 100-in-1 million. These six 
PEPO facilities are located in Texas, West Virginia and Louisiana. The 
percent of the population that is Black with cancer risk greater than 
100-in-1 million resulting from PEPO Production source category 
baseline emissions (14 percent, 500 people) is above the national 
average (12 percent). Around two facilities in West Virginia, the 
percentage of the Black population with cancer risks greater than 100-
in-1 million resulting from PEPO Production source category emissions 
is over two times the national average.
    The percentage of the population that is Hispanic/Latino with risks 
greater than 100-in-1 million resulting from PEPO Production source 
category emissions (21 percent, 700 people) is above the national 
average (19 percent). The share of the Hispanic and Latino population 
with cancer risks greater than 100-in-1 million resulting from PEPO 
Production source category emissions is driven by one facility in Texas 
where the percent of the population that is Hispanic/Latino is over 
three times the national average. The percent of the population that is 
American Indian or Alaskan Native with risks greater than 100-in-1 
million resulting from PEPO Production source category baseline 
emissions is well below the national average for all facilities.
    The percentages of the population with cancer risks greater than 
100-in-1 million resulting from PEPO Production source category 
baseline emissions that are below the poverty level (26 percent, 900 
people), below 2 times the poverty level (46 percent, 1,500 people), 
and over 25 without a high school diploma (30 percent, 1,000 people) 
are above the respective national averages.
    Around four facilities located in West Virginia and Louisiana, the 
percent of the population with cancer risks greater than 100-in-1 
million resulting from PEPO Production source category baseline 
emissions that are below the poverty level is two to four times the 
national average. In addition, for two of these facilities located in 
West Virginia, the population with cancer risks greater than 100-in-1 
million resulting from PEPO Production source category baseline 
emissions that are below two times the poverty level is two times the 
national average.
    In summary, the baseline risk-based demographic analysis, which 
focuses on populations that are expected to have higher cancer risks 
resulting from PEPO Production source category emissions, suggests that 
Blacks and Hispanic or Latino individuals are disproportionately 
overrepresented at cancer risk levels of greater than or equal to 1-in-
1 million and greater than 100-in-1 million. In addition, the baseline 
risk-based demographic analysis suggests that populations living below 
the poverty level and living below two times the poverty level are 
disproportionately overrepresented at all cancer risk levels. This 
disproportionate overrepresentation is the greatest in the population 
with cancer risks greater than 100-in-1 million.

[[Page 106051]]

c. Post-Control Risk-Based Demographics
    This analysis focused on the populations living within 10 km (~6.2 
miles) of the facilities with estimated cancer risks greater than or 
equal to 1-in-1 million (table 14 of this preamble), greater than or 
equal to 50-in-1 million (table 15 of this preamble), and greater than 
100-in-1 million (table 16 of this preamble) resulting from PEPO 
Production source category emissions after implementation of the 
proposed controls (``post-control''). The results of the post-control 
risk-based demographics analysis are in the column titled ``Post-
Control'' of tables 14 through 16 of this preamble. In this analysis, 
we evaluated how the projected EtO emission reductions of the proposed 
standards for PEPO processes described in this action affect the 
distribution of risks. This evaluation makes it possible to 
characterize the post-control risks and to evaluate whether the 
proposed action would create or mitigate potential EJ concerns as 
compared to the baseline.
    The risk analysis indicated that the number of people within 10 km 
of a facility exposed to risks greater than or equal to 1-in-1 million 
resulting from PEPO Production source category emissions (table 14 of 
this preamble) would be reduced from approximately 834,000 people in 
the baseline to 592,000 people after implementation of the PEPO 
controls in this proposal. The populations with a cancer risk greater 
than or equal to 1-in-1 million resulting from PEPO Production source 
category emissions are located around 18 facilities in the baseline and 
16 facilities for post-control.
    The post-control population living within 10 km of a facility with 
estimated cancer risks greater than or equal to 1-in-1 million 
resulting from PEPO Production source category emissions (table 14 of 
this preamble) has similar demographic percentages to the baseline 
population with risks greater than or equal to 1-in-1 million. However, 
the number of individuals with risks greater than or equal to 1-in-1 
million resulting from PEPO Production source category emissions would 
be reduced in each demographic.
    The percentage of the population with risks greater than or equal 
to 1-in-1 million resulting from PEPO Production source category 
emissions that is Black is 3 percent higher in the post-control 
population (18 percent) than in the baseline population (15 percent). 
However, the number of Black individuals with risks at or above 1-in-1 
million would be reduced by almost 25,000 people from 129,000 in the 
baseline to 105,000 in the post-control scenario.
    Similarly, the percentage of the population with risks greater than 
or equal to 1-in-1 million resulting from PEPO Production source 
category post-control emissions that is Hispanic/Latino would still be 
above the national average (25 percent versus 19 percent), but the 
number of Hispanic/Latino individuals with risks at or above 1-in-1 
million would be reduced by about 70,000 people from 218,000 in the 
baseline to 148,000 in the post-control scenario.
    The percent of the population that is American Indian or Alaskan 
Native with risks greater than or equal to 1-in-1 million resulting 
from PEPO Production source category emissions (0.2 percent) is below 
the national average (0.6 percent) in the post-control analysis and 
populations around all facilities are below the national average. The 
number of American Indians or Alaskan Natives with risks greater than 
or equal to 1-in-1 million resulting from PEPO Production source 
category emissions would be reduced from 2,100 in the baseline to 1,200 
in the post-control scenario.
    The percentages of the population with risks greater than or equal 
to 1-in-1 million resulting from PEPO Production source category 
emissions below the poverty level (15 percent) and below two times the 
poverty level (34 percent) are the same in the post-control scenario as 
in the baseline. However, the number of individuals with risks greater 
than or equal to 1-in-1 million resulting from PEPO Production source 
category emissions that are below the poverty level would be reduced by 
about 35,000 (from 125,000 to 91,000) and those below 2 times the 
poverty level is reduced by about 78,000 (from 281,000 to 203,000). The 
percent of individuals over 25 years old without a high school diploma 
is 1 percent higher in the post-control scenario (16 percent) than in 
the baseline (15 percent), but the number of individuals with risks 
greater than or equal to 1-in-1 million resulting from PEPO Production 
source category emissions would be reduced by almost 35,000, from 
128,000 to 93,000. The percentage of the population that is in 
linguistic isolation with risks greater than or equal to 1-in-1 million 
resulting from PEPO Production source category emissions is the same in 
the post-control scenario (5 percent), but the number of individuals 
would be reduced by almost 11,000 compared to the baseline, from 38,000 
to 27,000.
    The risk analysis indicated that the number of people living within 
10 km of a facility and exposed to risks greater than or equal to 50-
in-1 million resulting from PEPO Production source category emissions 
(table 15 of this preamble) would be reduced significantly, from 28,000 
people in the baseline to 1,600 people after implementation of the 
controls in this proposal. This represents more than a 90 percent 
reduction in the number of individuals with risk greater than or equal 
to 50-in-1 million when compared to the baseline. The populations 
living within 10 km of a facility and with a cancer risk greater than 
or equal to 50-in-1 million resulting from PEPO Production source 
category emissions are located around four facilities in the post-
control scenario, six fewer facilities than in the baseline. These four 
facilities are located in Louisiana, Texas, and West Virginia (two 
facilities). The communities within 10 km of two of those facilities 
(in Louisiana and Texas) comprise over 80 percent of the population 
with risks greater than or equal to 50-in-1 million resulting from PEPO 
Production source category post-control emissions.
    The number of individuals with risks greater than or equal to 50-
in-1 million would be reduced significantly for each demographic 
category in the post-control scenario. The percentage of the population 
with risks greater than or equal to 50-in-1 million resulting from PEPO 
Production source category emissions that is Black would increase from 
10 percent in the baseline to 17 percent in the post-control scenario, 
which is above the national average (12 percent). However, the number 
of Black individuals with risks at or above 50-in-1 million would be 
reduced from 2,800 in the baseline to 300 post-control. Similarly, the 
percentage of the population with risks greater than or equal to 50-in-
1 million resulting from PEPO Production source category emissions that 
is Hispanic/Latino would increase from 10 percent in the baseline to 25 
percent post-control, but the number of Hispanic/Latino individuals 
with risks at or above 50-in-1 million would be reduced from 2,700 in 
the baseline to 400 post-control. The number of American Indians or 
Alaskan Natives with risks greater than or equal to 50-in-1 million 
resulting from PEPO Production source category emissions would be 
reduced from about 100 in the baseline to zero post-control.
    The percentages of the population with risks greater than or equal 
to 50-in-1 million resulting from PEPO Production source category post-
control emissions whose income is below the poverty level (22 percent) 
and below two times the poverty level (42 percent)

[[Page 106052]]

would be higher than from the baseline (14 percent and 35 percent, 
respectively). However, the number of individuals with risks greater 
than or equal to 50-in-1 million resulting from PEPO Production source 
category emissions that are below the poverty level would be reduced 
from by about 3,700 people (from 4,100 to 400) and those below two 
times the poverty level would be reduced by about 9,200 people (from 
9,900 to 700). The number of individuals with risks greater than or 
equal to 50-in-1 million resulting from PEPO Production source category 
emissions that are over 25 years old without a high school diploma or 
are linguistically isolated would also be greatly reduced post-control.
    The risk analysis indicated that the number of people living within 
10 km of a facility with risks greater than 100-in-1 million resulting 
from PEPO Production source category emissions (table 16 of this 
preamble) would be reduced from 3,300 individuals in the baseline to 
zero individuals after application of the PEPO controls in this 
proposal. Therefore, for the post-control risk-based demographic 
results, there would be no ``greater than 100-in-1 million'' 
demographic results to discuss.
    In summary, as shown in the post-control risk-based demographic 
analysis, the controls proposed to be required by this proposal would 
significantly reduce the number of people expected to have cancer risks 
greater than or equal to 1-in-1 million, greater than or equal to 50-
in-1 million, and greater than 100-in-1 million resulting from PEPO 
Production source category emissions. Although the number of 
individuals with risks greater than or equal to 1-in-1 million would be 
reduced in the post-control scenario (reduced from 834,000 people to 
592,000 people), populations of Black individuals, Hispanic/Latino 
individuals, those living below the poverty level and two times the 
poverty level, and those over 25 without a high school diploma would 
remain disproportionately represented. Similarly, the number of 
individuals with risks greater than or equal to 50-in-1 million would 
be reduced significantly in the post-control scenario (reduced from 
28,000 to 1,600), but the population of Black individuals, Hispanic/
Latino individuals, those living below the poverty level and two times 
the poverty level, and those over 25 without a high school diploma 
would remain disproportionately represented. Post-control, there would 
be no individuals with risks greater than 100-in-1 million resulting 
from PEPO Production source category emissions (reduced from 3,300 
people to 0 people).

 Table 14--Source Category: Comparison of Baseline and Post-Control Demographics of Populations With Cancer Risk
Greater Than or Equal to 1-in-1 Million Resulting From PEPO NESHAP Source Category Emissions Living Within 10 km
                        of Facilities to the National Average and Proximity Demographics
----------------------------------------------------------------------------------------------------------------
                                                                                          Cancer risk >=1-in-1
                                                                   Proximity analysis    million within 10 km of
                                                      Nationwide  for total population       PEPO facilities
                 Demographic group                   average for   living within 10 km -------------------------
                                                      reference    of PEPO facilities                   Post-
                                                                                          Baseline     control
----------------------------------------------------------------------------------------------------------------
Total Population...................................         330M                  1.4M         834K         592K
Number of Facilities...............................  ...........                    23           18           16
----------------------------------------------------------------------------------------------------------------
                                Race and Ethnicity by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
White..............................................          60%                   59%          54%          53%
                                                          [196M]                [847K]       [450K]       [313K]
Black..............................................          12%                   13%          15%          18%
                                                           [40M]                [192K]       [129K]       [105K]
American Indian and Alaskan Native.................         0.6%                  0.2%         0.3%         0.2%
                                                          [2.1M]                [3.3K]       [2.1K]       [1.2K]
Hispanic or Latino (white and nonwhite)............          19%                   22%          26%          25%
                                                           [63M]                [320K]       [218K]       [148K]
Other and Multiracial..............................           9%                    5%           4%           4%
                                                           [29M]                 [68K]        [34K]        [26K]
----------------------------------------------------------------------------------------------------------------
                                        Age by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Age 0 to 17 years..................................          22%                   24%          24%          25%
                                                           [74M]                [345K]       [204K]       [147K]
Age 18 to 64 years.................................          62%                   61%          61%          61%
                                                          [203M]                [876K]       [511K]       [363K]
Age >=65 years.....................................          16%                   15%          14%          14%
                                                           [53M]                [210K]       [118K]        [83K]
----------------------------------------------------------------------------------------------------------------
                                      Income by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Below Poverty Level................................          13%                   14%          15%          15%
                                                           [42M]                [196K]       [125K]        [91K]
Below 2x Poverty Level.............................          30%                   31%          34%          34%
                                                          [100M]                [446K]       [281K]       [203K]
----------------------------------------------------------------------------------------------------------------
                                     Education by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High School Diploma..........          12%                   14%          15%          16%
                                                           [38M]                [197K]       [128K]        [93K]
----------------------------------------------------------------------------------------------------------------

[[Page 106053]]

 
                              Linguistically Isolated by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated............................           5%                    4%           5%           5%
                                                           [17M]                 [59K]        [38K]        [27K]
----------------------------------------------------------------------------------------------------------------
Notes:
 Nationwide population and demographic percentages are based on Census' 2016-2020 American Community
  Survey (ACS) 5-year block group averages. Total population count is based on 2020 Decennial Census block
  population.
 To avoid double counting, the ``Hispanic or Latino'' category is treated as a distinct demographic
  category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race.
 The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR
  was located at a user assigned receptor at an individual residence and not at a census block centroid, we were
  unable to estimate population and demographics for that facility.
 The sum of individual populations with a demographic category may not add up to total due to rounding.
  K = Thousands, M = Millions.


 Table 15--Source Category: Comparison of Baseline and Post-Control Demographics of Populations With Cancer Risk
 Greater Than or Equal to 50-in-1 Million Resulting From PEPO NESHAP Source Category Emissions Living Within 10
                       km of Facilities to the National Average and Proximity Demographics
----------------------------------------------------------------------------------------------------------------
                                                                                          Cancer risk >=50-in-1
                                                                   Proximity analysis    million within 10 km of
                                                      Nationwide  for total population       PEPO facilities
                 Demographic group                   average for   living within 10 km -------------------------
                                                      reference    of PEPO facilities                   Post-
                                                                                          Baseline     control
----------------------------------------------------------------------------------------------------------------
Total Population...................................         330M                  1.4M          28K         1.6K
Number of Facilities...............................  ...........                    23           10            4
----------------------------------------------------------------------------------------------------------------
                                Race and Ethnicity by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
White..............................................          60%                   59%          77%          56%
                                                          [196M]                [847K]        [22K]        [900]
Black..............................................          12%                   13%          10%          17%
                                                           [40M]                [192K]       [2.8K]        [300]
American Indian and Alaskan Native.................         0.6%                  0.2%         0.3%         0.0%
                                                          [2.1M]                [3.3K]       [<100]          [0]
Hispanic or Latino (white and nonwhite)............          19%                   22%          10%          25%
                                                           [63M]                [320K]       [2.7K]        [400]
Other and Multiracial..............................           9%                    5%           3%           3%
                                                           [29M]                 [68K]        [900]       [<100]
----------------------------------------------------------------------------------------------------------------
                                        Age by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Age 0 to 17 years..................................          22%                   24%          23%          29%
                                                           [74M]                [345K]       [6.4K]        [500]
Age 18 to 64 years.................................          62%                   61%          57%          57%
                                                          [203M]                [876K]      [16.3K]        [900]
Age >=65 years.....................................          16%                   15%          20%          15%
                                                           [53M]                [210K]       [5.7K]        [200]
----------------------------------------------------------------------------------------------------------------
                                      Income by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Below Poverty Level................................          13%                   14%          14%          22%
                                                           [42M]                [196K]       [4.1K]        [300]
Below 2x Poverty Level.............................          30%                   31%          35%          42%
                                                          [100M]                [446K]       [9.9K]        [700]
----------------------------------------------------------------------------------------------------------------
                                     Education by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High School Diploma..........          12%                   14%          16%          32%
                                                           [38M]                [197K]       [4.4K]        [500]
----------------------------------------------------------------------------------------------------------------

[[Page 106054]]

 
                              Linguistically Isolated by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated............................           5%                    4%           2%           1%
                                                           [17M]                 [59K]        [500]       [<100]
----------------------------------------------------------------------------------------------------------------
Notes:
 Nationwide population and demographic percentages are based on Census' 2016-2020 ACS 5-year block group
  averages. Total population count is based on 2020 Decennial Census block population.
 To avoid double counting, the ``Hispanic or Latino'' category is treated as a distinct demographic
  category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race.
 The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR
  was located at a user assigned receptor at an individual residence and not at a census block centroid, we were
  unable to estimate population and demographics for that facility.
 The sum of individual populations with a demographic category may not add up to total due to rounding.
  K = Thousands, M = Millions.
 When the population being characterized is very small, the demographic distributions provided by the
  Census can be subject to a high level of uncertainty. To avoid implying a level of precision that is not
  supported by the data, when the population of an individual demographic is less than 100, we have indicated it
  on the demographic tables as <100.


 Table 16--Source Category: Comparison of Baseline and Post-Control Demographics of Populations With Cancer Risk
    Greater Than 100-in-1 Million Resulting From PEPO NESHAP Source Category Emissions Living Within 10 km of
                          Facilities to the National Average and Proximity Demographics
----------------------------------------------------------------------------------------------------------------
                                                                                          Cancer risk >100-in-1
                                                                   Proximity analysis    million within 10 km of
                                                      Nationwide  for total population       PEPO facilities
                 Demographic group                   average for   living within 10 km -------------------------
                                                      reference    of PEPO facilities                   Post-
                                                                                          Baseline     control
----------------------------------------------------------------------------------------------------------------
Total Population...................................         330M                  1.4M         3.3K            0
Number of Facilities...............................  ...........                    23            6            0
----------------------------------------------------------------------------------------------------------------
                                Race and Ethnicity by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
White..............................................          60%                   59%          61%         100%
                                                          [196M]                [847K]         [2K]          [0]
Black..............................................          12%                   13%          14%           0%
                                                           [40M]                [192K]        [500]          [0]
American Indian and Alaskan Native.................         0.6%                  0.2%         0.0%         0.0%
                                                          [2.1M]                [3.3K]          [0]          [0]
Hispanic or Latino (white and nonwhite)............          19%                   22%          21%           0%
                                                           [63M]                [320K]        [700]          [0]
Other and Multiracial..............................           9%                    5%           5%           0%
                                                           [29M]                 [68K]        [100]          [0]
----------------------------------------------------------------------------------------------------------------
                                        Age By Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Age 0 to 17 years..................................          22%                   24%          25%           0%
                                                           [74M]                [345K]        [800]          [0]
Age 18 to 64 years.................................          62%                   61%          58%           0%
                                                          [203M]                [876K]       [1.9K]          [0]
Age >=65 years.....................................          16%                   15%          17%           0%
                                                           [53M]                [210K]        [600]          [0]
----------------------------------------------------------------------------------------------------------------
                                      Income by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Below Poverty Level................................          13%                   14%          26%           0%
                                                           [42M]                [196K]        [900]          [0]
Below 2x Poverty Level.............................          30%                   31%          46%           0%
                                                          [100M]                [446K]       [1.5k]          [0]
----------------------------------------------------------------------------------------------------------------
                                     Education by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High School Diploma..........          12%                   14%          30%           0%
                                                           [38M]                [197K]         [1k]          [0]
----------------------------------------------------------------------------------------------------------------

[[Page 106055]]

 
                              Linguistically Isolated by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated............................           5%                    4%           1%           0%
                                                           [17M]                 [59K]       [<100]          [0]
----------------------------------------------------------------------------------------------------------------
Notes:
 Nationwide population and demographic percentages are based on Census' 2016-2020 ACS 5-year block group
  averages. Total population count is based on 2020 Decennial Census block population.
 To avoid double counting, the ``Hispanic or Latino'' category is treated as a distinct demographic
  category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race.
 The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR
  was located at a user assigned receptor at an individual residence and not at a census block centroid, we were
  unable to estimate population and demographics for that facility.
 The sum of individual populations with a demographic category may not add up to total due to rounding.
  K = Thousands, M = Millions.

2. PEPO Production Whole-Facility Demographics
    As described in section III.B.7 of this preamble, we assessed the 
facility-wide (or ``whole-facility'') risks for 25 PEPO facilities in 
order to compare the PEPO Production source category risk to the whole-
facility risks, accounting for HAP emissions from the entire major 
source and not just those resulting from PEPO Production source 
category emissions at the major source as discussed in the previous 
section (V.F.1). The whole-facility risk analysis includes all sources 
of HAP emissions at each facility as reported in the NEI (described in 
section III.B of this preamble). Since PEPO facilities tend to include 
HAP emissions sources from many source categories, the EPA conducted a 
whole-facility demographic analysis focused on post-control risks. This 
whole-facility demographic analysis characterizes the remaining risks 
that communities would face after implementation of the controls 
proposed to be required in this proposal (i.e., post-control).
    The whole-facility demographic analysis is an assessment of 
individual demographic groups in the total population living within 10 
km (~6.2 miles) and 50 km (~31 miles) of the facilities. In this 
preamble, we focus on the results from the demographic analyses using a 
10 km radius because this area captures the majority of the population 
with higher cancer risks due to HAP emissions from PEPO facilities. 
Specifically, 100 percent of the population with baseline cancer risks 
greater than or equal to 50-in-1 million from PEPO Production source 
category emissions lives within 10 km of the PEPO facilities. The 
results of the whole-facility demographic analysis for populations 
living within 50 km are included in the document titled Analysis of 
Demographic Factors for Populations Living Near Polyether Polyols 
(PEPO) Production Facilities--Whole Facility Analysis of Proposed 
Amendments, which is available in the docket for this rulemaking.
    The whole-facility demographic analysis post-control results are 
shown in table 17 of this preamble. This analysis focused on the 
populations living within 10 km of the PEPO facilities with estimated 
whole-facility post-control cancer risks greater than or equal to 1-in-
1 million, greater than or equal to 50-in-1 million, and greater than 
100-in-1 million. The risk analysis indicated that all emissions from 
the PEPO facilities, after the reductions proposed to be imposed by the 
proposed rule, would expose a total of about 1 million people living 
around 22 facilities to a cancer risk greater than or equal to 1-in-1 
million, 13,000 people living around 12 facilities to a cancer risk 
greater than or equal to 50-in-1 million, and about 200 people living 
around 1 facility to a cancer risk greater than 100-in-1 million.
    When the PEPO whole-facility populations are compared to the PEPO 
Production source category populations in the post-control scenarios, 
we see 400,000 additional people with risks greater than or equal to 1-
in-1 million, 11,000 additional people with risks greater than or equal 
to 50-in-1 million, and 200 additional people with risks greater than 
100-in-1 million.
    The demographic distribution of the whole-facility population with 
post-control cancer risks greater than or equal to 1-in-1 million is 
similar to the distribution of the source category population with 
post-control cancer risks greater than or equal to 1-in-1 million. 
Therefore, the whole-facility population with post-control cancer risks 
greater than or equal to 1-in-1 million has disproportionately high 
representation from Blacks, Hispanics and Latinos, people living below 
the poverty level, people living below two times the poverty level, and 
those over 25 without a high school education.
    The population with post-control cancer risks greater than or equal 
to 50-in-1 million in the whole-facility analysis has a much different 
demographic distribution than the source category population with post-
control cancer risks greater than or equal to 50-in-1 million. The 
percent of the population that is Black with risks greater than or 
equal to 50-in-1 million is lower for the whole-facility post-control 
analysis (9 percent) versus the category post-control analysis (17 
percent) and is therefore below the national average (12 percent). The 
lower representation of the Black population is reflected in slightly 
higher (1 to 2 percent) greater representation of the other races/
ethnicities. As such, the Hispanic and Latino population is still 
disproportionately represented at 27 percent, which is well above the 
national average of 19 percent. The percentage of the population with 
risks greater than or equal to 50-in-1 million that is below the 
poverty level (8 percent) and below two times the poverty level (21 
percent) is about half that for the whole-facility post-control 
population than for the category post-control population. This means 
that the whole-facility population is below the national average for 
both poverty demographics.
    Based on results from the whole-facility emissions analysis, there 
would be about 200 people with post-control risks greater than 100-in-1 
million. Earlier in this preamble, we showed that

[[Page 106056]]

the PEPO Production source category emissions analysis indicated that 
there would be no people with post-control risks greater than 100-in-1 
million. The increased cancer risk for most of these 200 people is 
driven by EtO emissions from non-PEPO processes (HON, MON, and R&D 
Testing) co-located at PEPO facilities.
    The percent of the population in the whole-facility analysis with 
post-control risks greater than 100-in-1 million that is Black (26 
percent, <100 people) is more than double the national average (12 
percent). In addition, the percentages of the population in the whole-
facility analysis with a post-control risk greater than 100-in-1 
million that are below the poverty level (21 percent, <100 people), 
below 2 times the poverty level (44 percent, <100 people), and over 25 
years old without a high school diploma (25 percent, <100 people) are 
all above the national average (13 percent, 30 percent and 12 percent, 
respectively).

 Table 17--Whole Facility: Whole-Facility Post-Control Demographics for PEPO Production Facilities by Risk Level
                                for Populations Living Within 10 km of Facilities
----------------------------------------------------------------------------------------------------------------
                                                                     Post-control cancer risk for populations
                                                                          within 10 km of PEPO facilities
                Demographic group                   Nationwide   -----------------------------------------------
                                                                     >=1-in-1        >=50-in-1       >100-in-1
                                                                      million         million         million
----------------------------------------------------------------------------------------------------------------
Total Population................................     329,824,950              1M             13K             200
Number of Facilities............................  ..............              22              12               1
----------------------------------------------------------------------------------------------------------------
                                Race and Ethnicity by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
White...........................................             60%             52%             59%             61%
                                                          [196M]          [520K]          [7.6K]          [<100]
Black...........................................             12%             15%              9%             26%
                                                           [40M]          [149K]          [1.2K]          [<100]
American Indian and Alaskan Native..............            0.6%            0.2%            0.6%            0.0%
                                                          [2.1M]            [2K]          [<100]             [0]
Hispanic or Latino (white and nonwhite).........             19%             28%             27%             10%
                                                           [63M]          [282K]          [3.5K]          [<100]
Other and Multiracial...........................              9%              5%              4%              3%
                                                           [29M]           [49K]           [500]          [<100]
----------------------------------------------------------------------------------------------------------------
                                        Age By Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Age 0 to 17 years...............................             22%             25%             21%             13%
                                                           [74M]          [249K]          [2.7K]          [<100]
Age 18 to 64 years..............................             62%             62%             62%             58%
                                                          [203M]          [616K]          [7.9K]          [<100]
Age >=65 years..................................             16%             14%             17%             29%
                                                           [53M]          [135K]          [2.2K]          [<100]
----------------------------------------------------------------------------------------------------------------
                                      Income by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Below Poverty Level.............................             13%             14%              8%             21%
                                                           [42M]          [144K]          [1.1K]          [<100]
Below 2x Poverty Level..........................             30%             32%             21%             44%
                                                          [100M]          [320K]          [2.7K]          [<100]
----------------------------------------------------------------------------------------------------------------
                                     Education by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High School Diploma.......             12%             15%             16%             25%
                                                           [38M]          [150K]            [2K]          [<100]
----------------------------------------------------------------------------------------------------------------
                              Linguistically Isolated by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated.........................              5%              5%              2%              2%
                                                           [17M]           [53K]           [300]          [<100]
----------------------------------------------------------------------------------------------------------------
Notes:
 Nationwide population and demographic percentages are based on Census' 2016-2020 ACS 5-year block group
  averages. Total population count is based on 2020 Decennial Census block population.
 To avoid double counting, the ``Hispanic or Latino'' category is treated as a distinct demographic
  category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race.
 The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR
  was located at a user assigned receptor at an individual residence and not at a census block centroid, we were
  unable to estimate population and demographics for that facility.
 The sum of individual populations with a demographic category may not add up to total due to rounding.
 As indicated in the table there is only one facility with an MIR above 100-in-1 million in the whole-
  facility post-control analysis (75 people). However, emissions of two other facilities (located next to each
  other) impact one census block and yield additional population above 100-in-1 million (78 people). Thus, 75 +
  78 = 153 people with risks greater than 100-in-1 million. In addition, not shown in the table, is a facility
  where the MIR was located at a cluster of residences with a user assigned receptor and was not located at a
  census block centroid. Population data are only provided by the Census Bureau at census blocks, therefore, the
  number of people living at the households was estimated manually and demographic data were not available. We
  estimate that there are an additional 60 people exposed to risks greater than 100-in-1 million living around
  this facility, bringing the total to about 200 people for whole-facility risks.

[[Page 106057]]

 
 When the population being characterized is very small, the demographic distributions provided by the
  Census can be subject to a high level of uncertainty. To avoid implying a level of precision that is not
  supported by the data, when the population of an individual demographic is less than 100, we have indicated it
  on the demographic tables as <100.

3. PEPO Production Community Demographics
    As described in section III.B.8 of this preamble, we assessed the 
community-based risks for 25 PEPO facilities in order to compare the 
PEPO Production source category risk to the community risks. The 
community risks include HAP emissions from all major stationary sources 
within 10 km of the PEPO facilities as reported in the NEI (described 
in section III.B of this preamble). The discussion of the community 
risk analysis is focused on post-control risks. This community 
demographic analysis characterizes the remaining risks that communities 
would face after implementation of the controls proposed to be required 
in this proposal.
    The community demographic analysis is an assessment of individual 
demographic groups in the total population living within 10 km (~6.2 
miles) of the PEPO facilities. The community risk assessment and 
demographics were only conducted at the 10 km radius because, based on 
PEPO category emissions, this distance includes 100 percent of the 
population with cancer risks greater than or equal to 50-in-1 million. 
The full results of the community demographic analysis are in the 
document titled Analysis of Demographic Factors for Populations Living 
Near Polyether Polyols (PEPO) Production Facilities--Community-Based 
Assessment, which is available in the docket for this rulemaking.
    The community demographic analysis post-control results are shown 
in table 18 of this preamble. This analysis focused on the populations 
living within 10 km of the PEPO facilities with estimated community 
post-control cancer risks greater than or equal to 1-in-1 million, 
greater than or equal to 50-in-1 million, and greater than 100-in-1 
million. The risk analysis indicated that all emissions from all 
facilities within 10 km of the PEPO facilities, after the reductions 
proposed to be imposed by the proposed rule, would expose a total of 
about 1.1 million people living around 25 facilities to a cancer risk 
greater than or equal to 1-in-1 million, 66,000 people living around 20 
facilities to a cancer risk greater than or equal to 50-in-1 million, 
and about 500 people living around 8 facilities to a cancer risk 
greater than 100-in-1 million.
    When the PEPO community populations are compared to the PEPO 
Production source category populations in the post-control scenarios, 
we see 500,000 additional people with risks greater than or equal to 1-
in-1 million, 64,000 additional people with risks greater than or equal 
to 50-in-1 million, and 500 additional people with risks greater than 
100-in-1 million.
    The demographic distribution of the community population with 
cancer risks greater than or equal to 1-in-1 million is very similar to 
the category population and the whole-facility population with cancer 
risks greater than or equal to 1-in-1 million in the post-control 
scenario. Therefore, the community population with post-control cancer 
risks greater than or equal to 1-in-1 million has disproportionately 
high representation from Blacks, Hispanics and Latinos, people living 
below the poverty level, people living below two times the poverty 
level, and those over 25 without a high school education.
    The population with cancer risks greater than or equal to 50-in-1 
million in the community analysis has a much different demographic 
distribution than the source category population with cancer risks 
greater than or equal to 50-in-1 million in the post-control scenario. 
The percent of the population that is Black with risks greater than or 
equal to 50-in-1 million is lower for the community post-control 
analysis (7 percent) versus the category post-control analysis (17 
percent). The lower representation of the Black population is reflected 
in greater representation of the other races/ethnicities. In 
particular, the percent of the population that is Hispanic or Latino is 
considerably disproportionately represented at 33 percent, which is 
significantly above the national average of 19 percent. The percentage 
of the population with risks greater than or equal to 50-in-1 million 
that is below the poverty level, below two times the poverty level, or 
over 25 years old without a high school diploma is about half that for 
the community post-control population than for the category post-
control population.
    Based on results from the community emissions analysis, there are 
about 500 people with post-control risks greater than 100-in-1 million. 
The PEPO Production source category emissions analysis indicated that 
there are no people with post-control risks greater than 100-in-1 
million. The increased cancer risk for most of these 500 people is 
driven largely by EtO emissions from non-PEPO processes (HON, MON, and 
R&D Testing) at PEPO facilities and other facilities within 10 km of 
PEPO facilities.
    The percent of the population in the community analysis with post-
control risks greater than 100-in-1 million that is Black (16 percent, 
<100 people) is above the national average (12 percent). The percent of 
the population in the community analysis with a post-control risk 
greater than 100-in-1 million that is below the poverty level (12 
percent, <100 people) and below 2 times the poverty level (26 percent, 
100 people) is below the national average (13 percent and 30 percent, 
respectively). The percent of the population in the community analysis 
with a post-control risk greater than 100-in-1 million that is over 25 
years old without a high school diploma (16 percent, <100 people) is 
above the national average (12 percent).

   Table 18--Community: Community Post-Control Demographics for PEPO Facilities by Risk Level for Populations
                                        Living Within 10 km of Facilities
----------------------------------------------------------------------------------------------------------------
                                                                     Post-control cancer risk for populations
                                                                          within 10 km of PEPO facilities
                Demographic group                   Nationwide   -----------------------------------------------
                                                                     >=1-in-1        >=50-in-1       >100-in-1
                                                                      million         million         million
----------------------------------------------------------------------------------------------------------------
Total Population................................     329,824,950            1.1M             66K             500
Number of Facilities............................  ..............              25              20               8
----------------------------------------------------------------------------------------------------------------

[[Page 106058]]

 
                                Race and Ethnicity by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
White...........................................             60%             53%             53%             64%
                                                          [196M]          [611K]           [35K]           [300]
Black...........................................             12%             15%              7%             16%
                                                           [40M]          [169K]          [4.8K]          [<100]
American Indian and Alaskan Native..............            0.6%            0.2%            0.3%            0.0%
                                                          [2.1M]          [2.6K]           [200]             [0]
Hispanic or Latino (white and nonwhite).........             19%             27%             33%             19%
                                                           [63M]          [306K]           [22K]          [<100]
Other and Multiracial...........................              9%              5%              6%              2%
                                                           [29M]           [55K]          [4.2K]          [<100]
----------------------------------------------------------------------------------------------------------------
                                        Age By Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Age 0 to 17 years...............................             22%             25%             25%             22%
                                                           [74M]          [283K]           [16K]           [100]
Age 18 to 64 years..............................             62%             62%             61%             57%
                                                          [203M]          [705K]           [41K]           [300]
Age >=65 years..................................             16%             14%             14%             21%
                                                           [53M]          [156K]          [9.4K]           [100]
----------------------------------------------------------------------------------------------------------------
                                      Income by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Below Poverty Level.............................             13%             15%             10%             12%
                                                           [42M]          [175K]          [6.3K]          [<100]
Below 2x Poverty Level..........................             30%             34%             23%             26%
                                                          [100M]          [384K]           [15K]           [100]
----------------------------------------------------------------------------------------------------------------
                                     Education by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High School Diploma.......             12%             16%             14%             16%
                                                           [38M]          [183K]            [9K]           [100]
----------------------------------------------------------------------------------------------------------------
                              Linguistically Isolated by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated.........................              5%              5%              4%              1%
                                                           [17M]           [57K]          [2.7K]          [<100]
----------------------------------------------------------------------------------------------------------------
Notes:
 Nationwide population and demographic percentages are based on Census' 2016-2020 ACS 5-year block group
  averages. Total population count is based on 2020 Decennial Census block population.
 To avoid double counting, the ``Hispanic or Latino'' category is treated as a distinct demographic
  category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race.
 The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR
  was located at a user assigned receptor at an individual residence and not at a census block centroid, we were
  unable to estimate population and demographics for that facility.
 The sum of individual populations with a demographic category may not add up to total due to rounding.
 Not shown in the table is a facility where the MIR was located at a cluster of residences with a user
  assigned receptor and was not located at a census block centroid. Population data are only provided by the
  Census Bureau at census blocks, therefore, the number of people living at the households was estimated
  manually and demographic data were not available. We estimate that there are an additional 60 people exposed
  to risks greater than 100-in-1 million living around this facility, bringing the total to about 600 people for
  Community risks.
 When the population being characterized is very small, the demographic distributions provided by the
  Census can be subject to a high level of uncertainty. To avoid implying a level of precision that is not
  supported by the data, when the population of an individual demographic is less than 100, we have indicated it
  on the demographic tables as <100.

G. What analysis of children's environmental health did we conduct?

    This action proposes to address risk from EtO. In addition, the 
EPA's Policy on Children's Health \97\ also applies to this action. 
Accordingly, we have evaluated the environmental health or safety 
effects of EtO emissions and exposures on children.
---------------------------------------------------------------------------

    \97\ Children's Health Policy. Available at: https://www.epa.gov/children/childrens-health-policy-and-plan.
---------------------------------------------------------------------------

    Because EtO is mutagenic (i.e., it can damage deoxyribonucleic 
acid, DNA), children are expected to be more susceptible to its harmful 
effects. To take this into account, as part of the risk assessment in 
support of this rulemaking, the EPA followed its guidelines \98\ and 
applied age-dependent adjustment factors (ADAF) for childhood exposures 
(from birth up to 16 years of age). With the ADAF applied to account 
for greater susceptibility of children, the adjusted EtO inhalation

[[Page 106059]]

URE is 5 x 10-3 per [micro]g/m\3\. We note that, because EtO 
is mutagenic, emission reductions proposed in this action would be 
particularly beneficial to children. The results of the risk assessment 
are contained in sections IV.A and IV.B of this preamble and further 
documented in the risk report, Residual Risk Assessment for the 
Polyether Polyols (PEPO) Production Source Category in Support of the 
2024 Risk and Technology Review Proposed Rule, which is available in 
the docket for this rulemaking.
---------------------------------------------------------------------------

    \98\ U.S. EPA. 2005. Supplemental Guidance for Assessing 
Susceptibility from Early-Life Exposure to Carcinogens. U.S. EPA, 
Washington, DC, EPA/630/R-03/003F. https://www.epa.gov/sites/default/files/2013-09/documents/childrens_supplement_final.pdf.
---------------------------------------------------------------------------

VI. Request for Comments

    We solicit comments on this proposed action. In addition to general 
comments on this proposed action, we are also interested in additional 
data that may improve the risk assessments and other analyses. We are 
specifically interested in receiving any information regarding 
developments in practices, processes, and control technologies that 
reduce emissions. We are also interested in receiving information on 
costs, emissions, and product recovery, and we request comment on how 
to address the non-monetized costs and benefits of the proposed rule. 
We request comment on data and approaches to monetize the health 
benefits of reducing exposure to EtO and other HAP emitted from PEPO 
sources.

VII. Submitting Data Corrections

    The site-specific emissions profiles used in the source category 
risk and demographic analyses and instructions are available for 
download on the project website at https://www.epa.gov/stationary-sources-air-pollution/polyether-polyols-production-national-emission-standards-hazardous. The data files include detailed information for 
each HAP emissions release point for the facilities in the source 
category.
    If you believe that the data are not representative or are 
inaccurate, please identify the data in question, provide your reason 
for concern, and provide any ``improved'' data that you have, if 
available. When you submit data, we request that you provide 
documentation of the basis for the revised values to support your 
suggested changes. To submit comments on the data downloaded from the 
project website, complete the following steps:
    1. Within this downloaded file, enter suggested revisions to the 
data fields appropriate for that information.
    2. Gather documentation for any suggested emissions revisions 
(e.g., performance test reports, material balance calculations).
    3. Send the entire downloaded file with suggested revisions and all 
accompanying documentation to Docket ID No. EPA-HQ-OAR-2023-0282 
(through the method described in the ADDRESSES section of this 
preamble).
    5. If you are providing comments on a single facility or multiple 
facilities, you need only submit one file for all facilities. The file 
should contain all suggested changes for all sources at that facility 
(or facilities).

VIII. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive orders 
can be found at https://www.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review and Executive 
Order 14094: Modernizing Regulatory Review

    This action is not a significant regulatory action as defined in 
Executive Order 12866, as amended by Executive Order 14094, and was 
therefore not subject to a requirement for Executive Order 12866 
review.

B. Paperwork Reduction Act (PRA)

    The information collection activities in this proposed rule have 
been submitted for approval to the OMB under the PRA. The information 
collection request (ICR) document that the EPA prepared has been 
assigned EPA ICR number 1811.13. You can find a copy of the ICR in the 
docket for this rulemaking, and it is briefly summarized here.
    In this action, the EPA is proposing to add new monitoring and 
operational requirements for flares, add work practice standards for 
startup and shutdown periods for maintenance vents and planned routine 
maintenance of storage vessels, clarify regulatory provisions for vent 
control bypasses, add new monitoring requirements for PEPO pressure 
vessels, add new emission standards for PEPO surge control vessels and 
bottoms receivers, and add new emission standards for PEPO transfer 
operations. The EPA is also proposing to require control of EtO 
emissions from process vents, storage vessels, equipment leaks, heat 
exchange systems, and wastewater in EtO service. In addition, the EPA 
is proposing amendments to the PEPO NESHAP that add requirements for 
electronic reporting of periodic reports and performance test results, 
add requirements for fenceline monitoring, and make other minor 
clarifications and corrections. This information will be collected to 
ensure compliance with the PEPO NESHAP.
    Respondents/affected entities: Owners or operators of PEPO 
production facilities.
    Respondent's obligation to respond: Mandatory (40 CFR part 63, 
subpart PPP).
    Estimated number of respondents: 27 (assumes 2 new respondents over 
the next 3 years).
    Frequency of response: Initially, semiannually, and annually.
    Total estimated burden: 12,000 hours (per year). Burden is defined 
at 5 CFR 1320.3(b).
    Total estimated cost: Average annual cost is $12,800,000 (per year) 
which includes $11,600,000 annualized capital or operation & 
maintenance costs.
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for the 
EPA's regulations in 40 CFR are listed in 40 CFR part 9.
    Submit your comments on the Agency's need for this information, the 
accuracy of the provided burden estimates, and any suggested methods 
for minimizing respondent burden to the EPA using the docket identified 
at the beginning of this rulemaking. The EPA will respond to any ICR-
related comments in the final rule. You may also send your ICR-related 
comments to OMB's Office of Information and Regulatory Affairs using 
the interface at https://www.reginfo.gov/public/do/PRAMain. Find this 
particular information collection by selecting ``Currently under 
Review--Open for Public Comments'' or by using the search function. OMB 
must receive comments no later than January 27, 2025.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. We 
identified that one of the 25 facilities in the PEPO Production source 
category affected by this proposed action is a small business. This 
facility is subject to the PEPO NESHAP because it receives and treats 
wastewater from a PEPO production facility. The EIA conducted for this 
proposal (see Economic Impact Analysis, which is available in the 
docket for this action) showed that this small business will not incur 
total annualized costs greater than one percent of its revenue.

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain an unfunded mandate of $100 million or

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more (adjusted for inflation) as described in UMRA, 2 U.S.C. 1531-1538, 
and does not significantly or uniquely affect small governments. The 
costs involved in this action are estimated not to exceed $176 million 
in 2022$ ($100 million in 1995$ adjusted for inflation using the gross 
domestic product implicit price deflator) or more in any one year.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have 
substantial direct effects on the States, on the relationship between 
the National Government and the Sstates, or on the distribution of 
power and responsibilities among the various levels of government.

F. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    This action does not have Tribal implications as specified in 
Executive Order 13175. None of the facilities that have been identified 
as being affected by this action are owned or operated by Tribal 
governments or are located within Tribal lands. Thus, Executive Order 
13175 does not apply to this action.

G. Executive Order 13045: Protection of Children From Environmental 
Health Risks and Safety Risks

    Executive Order 13045 directs Federal agencies to include an 
evaluation of the health and safety effects of the planned regulation 
on children in Federal health and safety standards and explain why the 
regulation is preferable to potentially effective and reasonably 
feasible alternatives. While the environmental health or safety risks 
addressed by this action present a disproportionate risk to children 
because EtO is mutagenic (i.e., EtO can damage DNA), this action is not 
subject to Executive Order 13045 because it is not a significant 
regulatory action under section 3(f)(1) of Executive Order 12866. 
However, the EPA's Policy on Children's Health applies to this action. 
Information on how the Policy was applied is available in section V.G 
of this preamble.

H. Executive Order 13211: Actions Concerning Regulations that 
Significantly Affect Energy Supply, Distribution, or Use

    This action is not subject to Executive Order 13211, because it is 
not a significant regulatory action under Executive Order 12866.

I. National Technology Transfer and Advancement Act (NTTAA) and 1 CFR 
Part 51

    This proposed action involves technical standards. Therefore, the 
EPA conducted searches for the PEPO NESHAP through the Enhanced 
National Standards Systems Network Database managed by the American 
National Standards Institute (ANSI). We also conducted a review of 
voluntary consensus standards (VCS) organizations and accessed and 
searched their databases. We conducted searches for EPA Methods 1, 1A, 
2, 2A, 2C, 2D, 2F, 2G, 3B, 4, 18, 21, 22, and 25A of 40 CFR part 60, 
appendix A, and EPA Methods 301 and 320 of 40 CFR part 63, appendix A. 
During the EPA's VCS search, if the title or abstract (if provided) of 
the VCS described technical sampling and analytical procedures that are 
similar to the EPA's reference method, the EPA ordered a copy of the 
standard and reviewed it as a potential equivalent method. We reviewed 
all potential standards to determine the practicality of the VCS for 
this rulemaking. This review requires significant method validation 
data that meet the requirements of EPA Method 301 for accepting 
alternative methods or scientific, engineering, and policy equivalence 
to procedures in the EPA reference methods. The EPA may reconsider 
determinations of impracticality when additional information is 
available for particular VCS.
    We did not identify any applicable VCS for EPA Methods 1A, 2A, 2D, 
2F, 2G, 21, and 22. However, the EPA is proposing amendments to 40 CFR 
63.14 to incorporate by reference the following three VCS: ANSI/ASME 
PTC 19.10-1981--Part 10, ``Flue and Exhaust Gas Analyses'' as an 
acceptable alternative to EPA Method 3B (manual portion only); ASTM 
D6420-18, ``Standard Test Method for Determination of Gaseous Organic 
Compounds by Direct Interface Gas Chromatography-Mass Spectrometry'' as 
an acceptable alternative to EPA Method 18; and ASTM D6348-12e1, 
``Determination of Gaseous Compounds by Extractive Direct Interface 
Fourier Transform (FTIR) Spectroscopy'' as an acceptable alternative to 
EPA Method 320.
    ANSI/ASME PTC 19.10-1981--Part 10, ``Flue and Exhaust Gas 
Analyses'' quantitatively determines the gaseous constituents of 
exhausts including oxygen, CO2, CO, nitrogen, 
SO2, sulfur trioxide, nitric oxide, nitrogen dioxide, 
hydrogen sulfide, and hydrocarbons. This method incorporates both 
manual and instrumental methodologies for the determination of oxygen 
content. The manual method segment of the oxygen determination is 
performed through the absorption of oxygen. This method is available at 
the ANSI, 1899 L Street NW, 11th Floor, Washington, DC 20036 and the 
American Society of Mechanical Engineers (ASME), Three Park Avenue, New 
York, NY 10016-5990; telephone number: 1-800-843-5990; and email 
address: [email protected]. See https://wwww.ansi.org and https://www.asme.org. The standard is available to everyone at a cost 
determined by ANSI/ASME ($88). ANSI/ASME also offer memberships or 
subscriptions for reduced costs. The cost of obtaining these methods is 
not a significant financial burden, making the methods reasonably 
available.
    ASTM D6420-18, ``Standard Test Method for Determination of Gaseous 
Organic Compounds by Direct Interface Gas Chromatography-Mass 
Spectrometry'' uses a direct interface gas chromatograph/mass 
spectrometer to measure 36 VOC and provide an on-site analysis of 
extracted, unconditioned, and unsaturated (at the instrument) gas 
samples from stationary sources. In this action, the EPA is proposing 
ASTM D6420-18 as an alternative to EPA Method 18 with the following 
caveats:
     The target compounds are known and are listed in ASTM 
D6420-18 as measurable.
     ASTM D6420-18 is not used for methane and ethane because 
the atomic mass is less than 35.
     ASTM D6420-18 is never specified as a total VOC method.
    ASTM D6348-12e1, ``Standard Test Method for Determination of 
Gaseous Compounds by Extractive Direct Interface Fourier Transform 
(FTIR) Spectroscopy'' is an extractive FTIR spectroscopy-based field 
test method and is used to quantify gas phase concentrations of 
multiple target compounds in emissions streams from stationary sources. 
When using ASTM D6348-12e1, the EPA proposes the following conditions: 
(1) The test plan preparation and implementation in the Annexes to ASTM 
D6348-03 sections Al through A8 are mandatory; and (2) in Annex A5 
(Analyte Spiking Technique) to ASTM D6348-103, the owner or operator 
must determine the percent (%) R for each target analyte (Equation 
A5.5). For the test data to be acceptable for a compound, %R must be 
70% >= R <= 130%. If the %R value does not meet this criterion for a 
target compound, the test data is not acceptable for that compound and 
the owner or operator must repeat the test for that analyte (i.e.,

[[Page 106061]]

the sampling and/or analytical procedure should be adjusted before a 
retest). We are proposing that owners or operators must report the %R 
value for each compound in the test report, and all field measurements 
must be corrected with the calculated %R value for that compound by 
using the following equation:
    Reported Results = Measured Concentration in Stack/%R x 100.
    ASTM D6420-18 and ASTM D6348-12e1 are available at ASTM 
International, 1850 M Street NW, Suite 1030, Washington, DC 20036. See 
https://www.astm.org/. These standards are available to everyone at a 
cost determined by the ASTM ($63 and $83, respectively). The ASTM also 
offers memberships or subscriptions that allow unlimited access to 
their methods. The cost of obtaining these methods is not a significant 
financial burden, making the methods reasonably available to 
stakeholders.
    The search identified 11 VCS that were potentially applicable for 
this rulemaking in lieu of EPA reference methods. After reviewing the 
available standards, the EPA determined that the 11 candidate VCS (ASTM 
D3154-00 (2006), ASTM D3464-96 (2007), ASTM 3796-90 (2004), ISO 
10780:1994, ASME B133.9-1994 (2001), ANSI/ASME PTC 19-10-198-Part 10, 
NIOSH Method 2010 ``Amines, Aliphatic,'' ASTM D6060-96 (2009), ISO 
14965:2000(E), EN 12619 (1999), ASTM D4855-97 (2002)) identified for 
measuring emissions of pollutants or their surrogates subject to 
emission standards in the rule would not be practical due to lack of 
equivalency, documentation, and validation data, and due to other 
important technical and policy considerations. The EPA documented the 
search and review results in the memorandum, Voluntary Consensus 
Standard Results for National Emission Standards for Hazardous Air 
Pollutants: Polyether Polyols Production Industry Residual Risk and 
Technology Review, which is available in the docket for this action. 
The EPA welcomes comments on this aspect of the proposed rulemaking 
and, specifically, invites the public to identify potentially 
applicable VCS and to explain why such standards should be used in this 
regulation.
    Under 40 CFR 63.7(f) and 63.8(f), subpart A--General Provisions, a 
source may apply to the EPA for permission to use alternative test 
methods or alternative monitoring requirements in place of any required 
testing methods, performance specifications, or procedures in the final 
rule or any amendments.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations and 
Executive Order 14096: Revitalizing Our Nation's Commitment to 
Environmental Justice for All

    The EPA believes that the human health or environmental conditions 
that exist prior to this action result in or have the potential to 
result in disproportionate and adverse human health or environmental 
effects on communities with EJ concerns. For the PEPO NESHAP, a total 
of approximately 1.5 million people live within 10 km of the 25 PEPO 
facilities that were assessed for risk. Based on the whole-facility 
proximity analysis summarized in section V.F of this preamble, the 
percentages of the population that are Black (13 percent versus 12 
percent) and Hispanic or Latino (22 percent versus 19 percent) are 
higher than the national averages. In addition, the percentages of the 
population that are below the poverty level (14 percent versus 12 
percent), below two times the poverty level (32 percent versus 30 
percent), and over 25 years of age without a high school diploma (14 
percent versus 12 percent) are higher than the national averages. The 
proportions of other demographic groups living within 10 km of PEPO 
facilities are lower than the national average. The EPA also conducted 
a risk assessment of possible cancer risks and other adverse health 
effects and found that prior to this proposed regulation, cancer risks 
for the PEPO Production source category were above acceptable levels 
for a number of areas in which these demographic groups live. See 
section V.F of this preamble for an analysis that characterizes 
populations living in proximity to facilities and risks prior to the 
proposed regulation.
    The EPA believes that this proposed action is likely to reduce 
existing disproportionate and adverse effects on communities with EJ 
concerns. This action would establish standards for EtO emission 
sources at PEPO processes (i.e., process vents, storage vessels, heat 
exchange systems, equipment leaks, and wastewater). This action 
proposes to require fenceline monitoring for EtO, which drives cancer 
risks for PEPO production sources, and proposes to address flare 
combustion efficiency. The EPA is also proposing that fenceline 
monitoring data be reported electronically to the EPA so that it can be 
made public and provide fenceline communities with greater access to 
information about potential emissions impacts.
    As a result of these proposed changes, we expect zero people to be 
exposed to risk levels above 100-in-1 million due to emissions from the 
source category. See sections IV.A and IV.B of this preamble for more 
information about the control requirements of the regulation and the 
resulting reduction in cancer risks. Also, see section V.F of this 
preamble for an analysis that characterizes populations living in 
proximity to facilities after implementation of the proposed regulation 
(post-control).
    The information supporting this Executive order review is contained 
in section V.F of this preamble, as well as in the technical reports, 
Analysis of Demographic Factors for Populations Living Near Polyether 
Polyols (PEPO) Production Facilities--Source Category Analysis of 
Proposed Amendments, Analysis of Demographic Factors for Populations 
Living Near Polyether Polyols (PEPO) Production Facilities--Whole 
Facility Analysis of Proposed Amendments, and Analysis of Demographic 
Factors for Populations Living Near Polyether Polyols (PEPO) Production 
Facilities--Community-Based Assessment, which are available in the 
docket for this action.

List of Subjects in 40 CFR Part 63

    Environmental protection, Administrative practice and procedures, 
Air pollution control, Hazardous substances, Incorporation by 
reference, Intergovernmental relations, Reporting and recordkeeping 
requirements.

Michael S. Regan,
Administrator.
[FR Doc. 2024-29466 Filed 12-26-24; 8:45 am]
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