[Federal Register Volume 88, Number 79 (Tuesday, April 25, 2023)]
[Proposed Rules]
[Pages 25080-25205]
[FR Doc No: 2023-07188]

Vol. 88

Tuesday,

No. 79

April 25, 2023

Part II

Environmental Protection Agency

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40 CFR Parts 60 and 63

New Source Performance Standards for the Synthetic Organic Chemical
Manufacturing Industry and National Emission Standards for Hazardous
Air Pollutants for the Synthetic Organic Chemical Manufacturing
Industry and Group I & II Polymers and Resins Industry; Proposed Rule

Federal Register / Vol. 88, No. 79 / Tuesday, April 25, 2023 /
Proposed Rules

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 60 and 63

[EPA-HQ-OAR-2022-0730; FRL-9327-01-OAR]
RIN 2060-AV71

New Source Performance Standards for the Synthetic Organic
Chemical Manufacturing Industry and National Emission Standards for
Hazardous Air Pollutants for the Synthetic Organic Chemical
Manufacturing Industry and Group I & II Polymers and Resins 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 New Source Performance Standards (NSPS) that apply to
the Synthetic Organic Chemical Manufacturing Industry (SOCMI) and to
the National Emission Standards for Hazardous Air Pollutants (NESHAP)
that apply to the SOCMI (more commonly referred to as the Hazardous
Organic NESHAP or HON) and Group I and II Polymers and Resins
Industries (P&R I and P&R II). The EPA is proposing decisions resulting
from the Agency's technology review of the HON, P&R I, and P&R II, and
its eight-year review of the NSPS that apply to the SOCMI. The EPA is
also proposing amendments to the NSPS for equipment leaks of volatile
organic compounds (VOC) in SOCMI 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 and chloroprene
emissions after considering the results of a risk assessment for the
HON and Neoprene Production processes subject to P&R I. Lastly, the EPA
is proposing to remove exemptions from standards for periods of
startup, shutdown, and malfunction (SSM), to add work practice
standards for such periods where appropriate, and to add provisions for
electronic reporting. We estimate that the proposed amendments to the
NESHAP would reduce hazardous air pollutants (HAP) emissions (excluding
EtO and chloroprene) from the SOCMI, P&R I, and P&R II sources by
approximately 1,123 tons per year (tpy), reduce EtO emissions from HON
processes by approximately 58 tpy, and reduce chloroprene emissions
from Neoprene Production processes in P&R I by approximately 14 tpy. We
also estimate that these proposed amendments to the NESHAP will reduce
excess emissions of HAP from flares in the SOCMI and P&R I source
categories by an additional 4,858 tpy. Lastly, we estimate that the
proposed amendments to the NSPS would reduce VOC emissions from the
SOCMI source category by approximately 1,609 tpy.

DATES:
    Comments. Comments must be received on or before June 26, 2023.
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 May 25, 2023.
    Public hearing: The EPA will hold a virtual public hearing on May
16, 2023. See SUPPLEMENTARY INFORMATION for information on the public
hearing.

ADDRESSES: You may send comments, identified by Docket ID No. EPA-HQ-
OAR-2022-0730, 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-2022-0730 in the subject line of the message.
     Fax:<PHONE_NUMBER>. Attention Docket ID No. EPA-HQ-OAR-
2022-0730.
     Mail: U.S. Environmental Protection Agency, EPA Docket
Center, Docket ID No. EPA-HQ-OAR-2022-0730, 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: Mr. Andrew Bouchard, Sector Policies
and Programs Division (E143-01), Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina 27711; telephone number:<PHONE_NUMBER>; and email
address: [email protected].

SUPPLEMENTARY INFORMATION:
    Participation in virtual public hearing. The public hearing will be
held via virtual platform on May 16, 2023. The hearing will convene at
11:00 a.m. Eastern Time (ET) and will conclude at 7:00 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
announce further details on the virtual public hearing website at
https://www.epa.gov/stationary-sources-air-pollution/synthetic-organic-chemical-manufacturing-industry-organic-national, https://www.epa.gov/stationary-sources-air-pollution/group-i-polymers-and-resins-national-emission-standards-hazardous, and https://www.epa.gov/stationary-sources-air-pollution/epoxy-resins-production-and-non-nylon-polyamides-national-emission. If the EPA receives a high volume of registrations
for the public hearing, we may continue the public hearing on May 17,
2023.
    The EPA will begin pre-registering speakers for the hearing no
later than 1 business day following the publication of this document in
the Federal Register. The EPA will accept registrations on an
individual basis. To register to speak at the virtual hearing, please
use the online registration form available at any of the following
websites: https://www.epa.gov/stationary-sources-air-pollution/synthetic-organic-chemical-manufacturing-industry-organic-national,
https://www.epa.gov/stationary-sources-air-pollution/group-i-polymers-and-resins-national-emission-standards-hazardous, or https://www.epa.gov/stationary-sources-air-pollution/epoxy-resins-production-and-non-nylon-polyamides-national-emission; or contact the public
hearing team at<PHONE_NUMBER> or by email at
[email protected]. The last day to pre-register to speak at the
hearing will be May 10, 2023. Prior to the hearing, the EPA will post a
general agenda that will list pre-registered speakers in approximate
order at: https://www.epa.gov/stationary-sources-air-pollution/synthetic-organic-chemical-manufacturing-industry-organic-national,
https://www.epa.gov/stationary-sources-air-pollution/group-i-polymers-and-resins-national-emission-standards-hazardous, and https://
www.epa.gov/stationary-sources-air-pollution/epoxy-resins-production-
and-

non-nylon-polyamides-national-emission.
    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/synthetic-organic-chemical-manufacturing-industry-organic-national, https://www.epa.gov/stationary-sources-air-pollution/group-i-polymers-and-resins-national-emission-standards-hazardous, and https://www.epa.gov/stationary-sources-air-pollution/epoxy-resins-production-and-non-nylon-polyamides-national-emission. While the EPA expects the
hearing to go forward as set forth above, please monitor these websites
or contact the public hearing team at<PHONE_NUMBER> 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.
    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 May 2,
2023. The EPA may not be able to arrange accommodations without
advanced notice.
    Docket. The EPA has established a docket for this rulemaking under
Docket ID No. EPA-HQ-OAR-2022-0730. 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 https://www.regulations.gov/
or in hard copy at the EPA Docket Center, Room 3334, WJC West Building,
1301 Constitution Avenue NW, Washington, DC. The Public Reading Room is
open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding
legal holidays. The telephone number for the Public Reading Room is
(202) 566-1744, and the telephone number for the EPA Docket Center is
(202) 566-1742.
    Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2022-0730. 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, 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: OAQPS Document Control Officer (C404-02),
OAQPS, U.S. Environmental Protection Agency, Research Triangle Park,
North Carolina 27711, Attention Docket ID No. EPA-HQ-OAR-2022-0730. 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:

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
AMEL alternative means of emission limitation
APCD air pollution control device
ATSDR Agency for Toxic Substances and Disease Registry
1-BP 1-bromopropane
BAAQMD Bay Area Air Quality Management District
BACT Best Available Control Technology
BLR basic liquid epoxy resins
BPT benefit per-ton
BSER best system of emissions reduction
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
EAV equivalent annual value
ECHO Enforcement and Compliance History Online
EFR external floating roof
EIS Emission Information System
EJ environmental justice
EMACT Ethylene Production MACT
EPA Environmental Protection Agency
EPPU elastomer product process unit
ERPG emergency response planning guidelines
ERT Electronic Reporting Tool
EtO Ethylene Oxide
FID flame ionization detector
GACT generally available control technologies
HAP hazardous air pollutant(s)
HCl hydrochloric acid
HEM Human Exposure Model
HF hydrofluoric acid
HON Hazardous Organic NESHAP
HQ hazard quotient
HQREL hazard quotient reference exposure level
HRVOC highly reactive volatile organic compound
ICR information collection request
IFR internal floating roof
IRIS Integrated Risk Information System
ISA Integrated Science Assessment
ISO International Standards Organization
km kilometer
kPa kilopascals
LAER Lowest Achievable Emission Rate
lb/hr pound per hour
LDAR leak detection and repair
LDSN leak detection sensor network
LEL lower explosive limit
MACT maximum achievable control technology
MPGF multi-point ground flare
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
NOAEL No Observed Adverse Effects Level
NOX nitrogen oxides
N2O nitrous oxide
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
OECA Office of Enforcement and Compliance Assurance's
OEL open-ended valves or lines
OGI optical gas imaging
OLD Organic Liquids Distribution
OMB Office of Management and Budget
OSHA Occupational Safety and Health Administration
P&R I Group I Polymers and Resins NESHAP
P&R II Group II Polymers and Resins NESHAP
PDF portable document format
PM2.5 particulate matter 2.5
POM polycyclic organic matter
ppm parts per million
ppmv parts per million by volume
ppmw parts per million by weight
PRA Paperwork Reduction Act
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
RIA Regulatory Impact Analysis
RTR Risk and Technology Reviews
SCAQMD South Coast Air Quality Management District
scmm standard cubic meter per minute
scf standard cubic foot
SOCMI Synthetic Organic Chemical Manufacturing Industry
SO2 sulfur dioxide
SSM startup, shutdown, and malfunction
TAC Texas Administrative Code
TCEQ Texas Commission on Environmental Quality
TOC total organic carbon
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
UPL upper prediction limit
URE unit risk estimate
U.S.C. United States Code
USGS U.S. Geological Survey
VOC volatile organic compound(s)
WSR wet strength resins

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

I. General Information
    A. Executive Summary
    B. Does this action apply to me?
    C. 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 are the source categories and how do the current
standards regulate emissions?
    C. What data collection activities were conducted to support
this action?
    D. What other relevant background information and data are
available?
    E. How do we consider risk in our decision-making?
    F. How do we estimate post-MACT risk posed by the source
category?
    G. How does the EPA perform the NESHAP technology review and
NSPS review?
III. Proposed Rule Summary and Rationale
    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 CAA
section 112(d)(6) technology review and CAA section 111(b)(1)(B)
NSPS reviews, and what are the rationale for those decisions?
    D. What actions related to CAA section 112(d)(2) and (3) are we
taking in addition to those identified in the CAA sections 112(f)(2)
and (d)(6) risk and technology reviews and CAA section 111(b)(1)(B)
NSPS reviews?
    E. What other actions are we proposing, and what is the
rationale for those actions?
    F. What compliance dates are we proposing, and what is the
rationale for the proposed compliance dates?
IV. 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?
V. Request for Comments
VI. Statutory and Executive Order Reviews

    A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and 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

I. General Information

A. Executive Summary

1. Purpose of the Regulatory Action
    The source categories that are the subject of this proposal are the
SOCMI and various polymers and resins source categories. The SOCMI
source category includes chemical manufacturing processes producing
commodity chemicals while the polymers and resins source categories
covered in this action include elastomers production processes and
resin production processes that use epichlorohydrin feedstocks (see
sections I.B and II.B of this preamble for detailed information about
these source categories). The EPA has previously promulgated maximum
achievable control technology (MACT) standards for certain processes in
the SOCMI source category in the HON rulemaking at 40 CFR part 63,
subparts F, G, and H. In 1994, the EPA finalized MACT standards in
subparts F, G, and H for SOCMI processes (59 FR 19454),\1\ and
conducted a residual risk and technology review for these NESHAP in
2006 (71 FR 76603). In 1995, the EPA finalized MACT standards in P&R II
(40 CFR part 63, subpart W) for epoxy resin and non-nylon polyamide
resin manufacturing processes (60 FR 12670) and completed a residual
risk and technology review for these standards in 2008 (73 FR 76220).
In 1996, the EPA finalized MACT standards in P&R I (40 CFR part 63,
subpart U) for elastomer manufacturing processes in the SOCMI source
category (61 FR 46906) and completed residual risk and technology
reviews for these standards in 2008 and 2011 (73 FR 76220 and 76 FR
22566).
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    \1\ Around the same time, the EPA set MACT standards for
equipment leaks from certain non-SOCMI processes at chemical plants
regulated under 40 CFR part 63, subpart I (59 FR 19587).
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    The EPA has also promulgated NSPS for certain processes in the
SOCMI source category. In 1983, the EPA finalized NSPS (40 CFR part 60,
subpart VV) for equipment leaks of VOC in SOCMI (48 FR 48328). In 1990,
the EPA finalized NSPS (40 CFR part 60, subparts III and NNN) for VOC
from air oxidation unit processes and distillation operations (55 FR
26912 and 55 FR 26931). In 1993, the EPA finalized NSPS (40 CFR part
60, subpart RRR) for VOC from reactor processes (58 FR 45948). In 2007,
the EPA promulgated NSPS (40 CFR part 60, subpart VVa) for VOC from
certain equipment leaks (72 FR 64883), which reflects the EPA's review
and revision of the standards in 40 CFR part 60, subpart VV.
    The statutory authority for this action is sections 111, 112,
301(a)(1), and 307(d)(7)(B) of the Clean Air Act (CAA). Section
111(b)(1)(B) of the CAA requires the EPA to promulgate standards of
performance for new sources in any category of stationary sources that
the Administrator has listed pursuant to 111(b)(1)(A). Section
111(a)(1) of the CAA provides that these performance standards are to
``reflect[ ] the degree of emission limitation achievable through the
application of the best system of emission reduction which (taking into
account the cost of achieving such reduction and any non-air quality
health and environmental impact and energy requirements) the
Administrator determines has been adequately demonstrated.'' We refer
to this level of control as the best system of emission reduction or
``BSER.'' Section 111(b)(1)(B) of the CAA requires the EPA to ``at
least every 8 years, review and, if appropriate, revise'' the NSPS.
    For NESHAP, CAA section 112(d)(2) requires the EPA to establish
MACT standards for listed categories of major sources of HAP. Section
112(d)(6) of the CAA 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 following
promulgation of those standards. This is referred to as a ``technology
review'' and is required for all standards established under CAA
section 112. Section 112(f) of the CAA requires the EPA to assess the
risk to public health remaining after the implementation of MACT
emission standards promulgated under CAA section 112(d)(2). If the
standards for a source category do not provide ``an ample margin of
safety to protect public health,'' the EPA must promulgate health-based
standards for that source category to further reduce risk from HAP
emissions.
    Section 301(a)(1) of the CAA authorizes the Administrator to
prescribe such regulations as are necessary to carry out his functions
under the CAA. Section 307(d)(7)(B) of the CAA requires the
reconsideration of a rule only if the person raising an objection to
the rule can demonstrate that it was impracticable to raise such
objection during the period for public comment or if the grounds for
the objection arose after the comment period (but within the time
specified for judicial review), and if the objection is of central
relevance to the outcome of the rule.
    The proposed new NSPS for SOCMI equipment leaks, air oxidation unit
processes, distillation operations, and reactor processes (i.e., NSPS
subparts VVb, IIIa, NNNa, and RRRa, respectively) are based on the
Agency's review of the current NSPS (subparts VVa, III, NNN, and RRR)
pursuant to CAA section 111(b)(1)(B), which requires that the EPA
review the NSPS every eight years and, if appropriate, revise. In
addition, the EPA is proposing amendments to the NSPS for equipment
leaks of VOC in SOCMI based on its reconsideration of certain aspects
of subparts VV and VVa that were raised in an administrative petition
and of which the Agency has granted reconsideration pursuant to section
307(d)(7)(B) of the CAA. These proposed amendments are primarily
included in the new NSPS subpart VVb; the EPA is not proposing to make
these changes in subparts VV and VVa because, in light of the time that
has passed since the promulgation of these two subparts, the EPA finds
it inappropriate to now change the obligations of sources subject to
these subparts after all these years. The proposed amendments to the
HON (NESHAP subparts F, G, H, and I), P&R I (NESHAP subpart U), and P&R
II (NESHAP subpart W) are based on the Agency's review of the current
NESHAP (subparts F, G, H, I, U, and W) pursuant to CAA section 112(d).
    Also, due to the development of the EPA's Integrated Risk
Information System (IRIS) inhalation unit risk estimate (URE) for
chloroprene in 2010, the EPA conducted a CAA section 112(f) risk review
for the SOCMI source category and Neoprene Production source category.
In the first step of the CAA section 112(f)(2) determination of risk
acceptability for this rulemaking, the use of the 2010 chloroprene risk
value resulted in the EPA identifying

unacceptable residual cancer risk caused by chloroprene emissions from
affected sources producing neoprene subject to P&R I.\2\ Consequently,
the proposed amendments to P&R I address the EPA review of additional
control technologies, beyond those analyzed in the technology review
conducted for P&R I, for one affected source producing neoprene and
contributing to unacceptable risk. Additionally, in 2016, the EPA
updated the IRIS inhalation URE for EtO. In the first step of the CAA
section 112(f)(2) determination of risk acceptability for this
rulemaking, the use of the updated 2016 EtO risk value resulted in the
EPA identifying unacceptable residual cancer risk driven by EtO
emissions from HON processes. Consequently, the proposed amendments to
the HON also address the EPA review of additional control technologies,
beyond those analyzed in the technology review conducted for the HON,
focusing on emissions sources emitting EtO that contribute to
unacceptable risk.
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    \2\ As discussed further in section III.B of this preamble,
chloroprene emissions from HON processes do not on their own present
unacceptable cancer risk.
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2. Summary of the Major Provisions of the Regulatory Action in Question
    The most significant amendments that we are proposing are described
briefly below. However, all of our proposed amendments, including
amendments to remove exemptions for periods of SSM, are discussed in
detail with rationale in section III of this preamble.
a. HON
    We are proposing amendments to the HON for heat exchange systems,
process vents, storage vessels, transfer racks, wastewater, and
equipment leaks.
i. NESHAP Subpart F
    As detailed in section II.B.1.a of this preamble, NESHAP subpart F
contains provisions to determine which chemical manufacturing processes
at a facility are subject to the HON, monitoring requirements for HAP
(i.e., HAP listed in Table 4 of NESHAP subpart F) that may leak into
cooling water from heat exchange systems, and requirements for
maintenance wastewater. For NESHAP subpart F, we are proposing:
     Compliance dates for all of the proposed HON requirements
(see proposed 40 CFR 63.100(k)(10) through (12); and section III.F of
this preamble).
     to move 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 (see proposed 40 CFR 63.101; and
section III.E.5.a of this preamble).
     a new definition for ``in ethylene oxide service'' (for
equipment leaks, heat exchange systems, process vents, storage vessels,
and wastewater) (see proposed 40 CFR 63.101; and section III.B.2.a of
this preamble).
     new operating and monitoring requirements for flares; and
a requirement that owners and operators can send no more than 20 tons
of EtO to all of their flares combined in any consecutive 12-month
period (see proposed 40 CFR 63.108; and section III.B.2.a.vi of this
preamble).
     sampling and analysis procedures for owners and operators
to demonstrate that process equipment does, or does not, meet the
proposed definition of being ``in ethylene oxide service'' (see
proposed 40 CFR 63.109; and section III.B.2.a.vii of this preamble).
    For heat exchange systems, we are proposing:
     To require owners or operators to use the Modified El Paso
Method and repair leaks of total strippable hydrocarbon concentration
(as methane) in the stripping gas of 6.2 parts per million by volume
(ppmv) or greater (see proposed 40 CFR 63.104(g) through (j); and
section III.C.1 of this preamble).
     to require owners or operators to conduct more frequent
leak monitoring (weekly instead of quarterly) for heat exchange systems
in EtO service and 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 in the HON), and delay of
repair would not be allowed (see proposed 40 CFR 63.104(g)(6) and
(h)(6); and section III.B.2.a.iii of this preamble).
     that the current leak monitoring requirements for heat
exchange systems at 40 CFR 63.104(b) may be used in limited instances
in lieu of using the Modified El Paso Method for heat exchange systems
cooling process fluids that will remain in the cooling water if a leak
occurs (see proposed 40 CFR 63.104(l); and section III.C.1 of this
preamble).
ii. NESHAP Subpart G
    As detailed in section II.B.1.b of this preamble, NESHAP subpart G
contains requirements for process vents, storage vessels, transfer
racks, wastewater streams, and closed vent systems.
    For process vents, we are proposing:
     To remove the 50 ppmv and 0.005 standard cubic meter per
minute (scmm) Group 1 process vent thresholds from the Group 1 process
vent definition, and instead require owners and operators of process
vents that emit greater than or equal to 1.0 pound per hour (lb/hr) of
total organic HAP to reduce emissions of organic HAP using a flare
meeting the proposed operating and monitoring requirements for flares
in NESHAP subpart F; or reduce emissions of total organic HAP or total
organic compounds (TOC) by 98 percent by weight or to an exit
concentration of 20 ppmv, whichever is less stringent (see proposed 40
CFR 63.101 and 40 CFR 63.113(a)(1) and (2); and section III.C.3.a of
this preamble).
     to remove the total resource effectiveness (TRE) concept
in its entirety (see proposed 40 CFR 63.113(a)(4); and section
III.C.3.a of this preamble).
     to add an emission standard of 0.054 nanograms per dry
standard cubic meter (ng/dscm) at 3 percent oxygen (toxic equivalency
basis) for dioxins and furans from chlorinated process vents (see
proposed 40 CFR 63.113(a)(5); and section III.D.5. of this preamble).
     that owners and operators reduce emissions of EtO from
process vents in EtO service by either: (1) Venting emissions through a
closed-vent system to a control device that reduces EtO by greater than
or equal to 99.9 percent by weight, to a concentration less than 1 ppmv
for each process vent, or to less than 5 lb/yr for all combined process
vents; or (2) venting emissions through a closed-vent system to a flare
meeting the proposed operating and monitoring requirements for flares
in NESHAP subpart F (see proposed 40 CFR 63.113(j), 40 CFR 63.108, and
40 CFR 63.124; and section III.B.2.a.i of this preamble).\3\
---------------------------------------------------------------------------

    \3\ We are also proposing to remove the option to allow use of a
design evaluation in lieu of performance testing to demonstrate
compliance for controlling various emission sources in ethylene
oxide service. In addition, owners or operators that choose to
control emissions with a non-flare control device would be required
to conduct an initial performance test on each control device in
ethylene oxide service to verify performance at the required level
of control, and would also be required to conduct periodic
performance testing on non-flare control devices in ethylene oxide
service every 5 years (see proposed 40 CFR 63.124).
---------------------------------------------------------------------------

     a work practice standard for maintenance vents requiring
that, prior to opening process equipment to the atmosphere, the
equipment must either: (1) Be drained and purged to a closed system so
that the hydrocarbon content is less than or equal to 10 percent of the
lower explosive limit (LEL); (2) be opened and vented to the atmosphere
only if the 10-percent LEL cannot be demonstrated and the pressure is
less than or equal to 5 pounds per square inch gauge (psig), provided
there is no active purging of the equipment to the atmosphere until the
LEL criterion is

met; (3) be opened when there is less than 50 lbs of VOC that may be
emitted to the atmosphere; or (4) for installing or removing an
equipment blind, depressurize the equipment to 2 psig or less and
maintain pressure of the equipment where purge gas enters the equipment
at or below 2 psig during the blind flange installation, provided none
of the other proposed work practice standards can be met (see proposed
40 CFR 63.113(k); and section III.D.4.a of this preamble).
     that owners and operators of process vents in EtO service
would not be allowed to use the proposed maintenance vent work practice
standards; instead, owners and operators would be prohibited from
releasing more than 1.0 ton of EtO from all maintenance vents combined
in any consecutive 12-month period (see proposed 40 CFR 63.113(k)(4);
and section III.B.2.a.v of this preamble).
    For storage vessels, we are proposing:
     That owners and operators reduce emissions of EtO from
storage vessels in EtO service by either: (1) Venting emissions through
a closed-vent system to a 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 storage vessel vent; or (2) venting emissions through a
closed-vent system to a flare meeting the proposed operating and
monitoring requirements for flares in NESHAP subpart F (see proposed 40
CFR 63.119(a)(5), 40 CFR 63.108, and 40 CFR 63.124; and section
III.B.2.a.i of this preamble).\4\
---------------------------------------------------------------------------

    \4\ See footnote 3.
---------------------------------------------------------------------------

     a work practice standard to allow storage vessels to be
vented to the atmosphere once a storage vessel degassing concentration
threshold is met (i.e., less than 10 percent of the LEL) and all
standing liquid has been removed from the vessel to the extent
practicable (see proposed 40 CFR 63.119(a)(6); and section III.D.4.b of
this preamble).
     to define pressure vessel and 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 (see proposed 40 CFR 63.101); and require initial and
annual performance testing using EPA Method 21 of 40 CFR part 60,
appendix A-7 to demonstrate no detectable emissions (i.e., would be
required to meet a leak definition of 500 parts per million (ppm) at
each point on the pressure vessel where total organic HAP could
potentially be emitted) (see proposed 40 CFR 63.119(a)(7); and section
III.D.6 of this preamble).
     to require all openings in an internal floating roof (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 the deck cover would be required to be equipped with a
gasket between the cover and the deck (see proposed 40 CFR
63.119(b)(5)(ix); and section III.C.2 of this preamble).
     controls for guidepoles for all storage vessels equipped
with an IFR (see proposed 40 CFR 63.119(b)(5)(x), (xi), and (xii); and
section III.C.2 of this preamble).
     a work practice standard that would apply during periods
of planned routine maintenance of a control device, fuel gas system, or
process equipment that is normally used for compliance with the storage
vessel emissions control requirements; owners and operators would not
be permitted 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 while working losses are controlled)
(see proposed 40 CFR 63.119(e)(7); and section III.D.4.c of this
preamble).
     to revise the Group 1 storage capacity criterion (for
storage vessels at existing sources) from between 75 cubic meters
(m\3\) and 151 m\3\ to between 38 m\3\ and 151 m\3\ (see proposed Table
5 to subpart G; and section III.C.2 of this preamble).
     to revise the Group 1 stored-liquid maximum true vapor
pressure (MTVP) of total organic HAP threshold (for storage vessels at
existing sources) from greater than or equal to 13.1 kilopascals (kPa)
to greater than or equal to 6.9 kPa (see proposed Table 5 to subpart G;
and section III.C.2 of this preamble).
    For transfer racks, we are proposing:
     To remove the exemption for transfer operations that load
``at an operating pressure greater than 204.9 kilopascals'' from the
definition of transfer operation (see proposed 40 CFR 63.101; and
section III.D.8 of this preamble).
    For wastewater streams, we are proposing:
     To revise the Group 1 wastewater stream threshold to
include wastewater streams in EtO service (i.e., wastewater streams
with total annual average concentration of EtO greater than or equal to
1 ppm by weight at any flow rate) (see proposed 40 CFR
63.132(c)(1)(iii) and (d)(1)(ii); and section III.B.2.a.iv of this
preamble).
     to prohibit owners and operators from injecting wastewater
into or disposing of water through any heat exchange system in a
chemical manufacturing process unit (CMPU) meeting the conditions of 40
CFR 63.100(b)(1) through (3) 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 63.101 (see
proposed 40 CFR 63.104(k); and section III.B.2.a.iv of this preamble).
    For closed vent systems, we are proposing:
     That owners and operators may not bypass an air pollution
control device (APCD) at any time (see proposed 40 CFR 63.114(d)(3), 40
CFR 63.127(d)(3), and 40 CFR 63.148(f)(4)), that a bypass is a
violation, and that owners and operators must estimate and report the
quantity of organic HAP released (see proposed 40 CFR 63.118(a)(5), 40
CFR 63.130(a)(2)(iv), 40 CFR 63.130(b)(3), 40 CFR 63.130(d)(7), and 40
CFR 63.148(i)(3)(iii) and (j)(4); and section III.D.3 of this
preamble).
iii. NESHAP Subparts H and I
    As detailed in sections II.B.1.c and II.B.1.d of this preamble,
NESHAP subparts H and I contain requirements for equipment leaks. Also,
due to space limitations in the HON, we are proposing fenceline
monitoring (i.e., monitoring along the perimeter of the facility's
property line) in NESHAP subpart H for all emission sources. For
equipment leaks and fenceline monitoring, we are proposing:
     That all connectors in EtO service would be required to be
monitored monthly at a leak definition of 100 ppm with no skip period,
and delay of repair would not be allowed (see proposed 40 CFR
63.174(a)(3), (b)(3)(vi), and (g)(3), and 40 CFR 63.171(f); and section
III.B.2.a.ii of this preamble).
     that all gas/vapor and light liquid valves in EtO service
would be required to be monitored monthly at a leak definition of 100
ppm with no skip period, and delay of repairs would not be allowed (see
proposed 40 CFR 63.168(b)(2)(iv) and (d)(5), and 40 CFR 63.171(f); and
section III.B.2.a.ii of this preamble).
     that all light liquid pumps in EtO service would be
required to be monitored monthly at a leak definition of 500 ppm, and
delay of repairs would not be allowed (see proposed 40 CFR
63.163(a)(1)(iii), (b)(2)(iv), (c)(4), and (e)(7), and 40 CFR
63.171(f); and section III.B.2.a.ii of this preamble).
     a work practice standard for pressure relief devices
(PRDs) that vent to the atmosphere that would require owners and
operators to implement at least three prevention measures, perform root
cause analysis and corrective action in the event that a PRD

does release emissions directly to the atmosphere, and monitor PRDs
using a system that is capable of identifying and recording the time
and duration of each pressure release and of notifying operators that a
pressure release has occurred (see proposed 40 CFR 63.165(e); and
section III.D.2 of this preamble).
     that all surge control vessels and bottoms receivers would
be required to meet the requirements we are proposing for process vents
(see proposed 40 CFR 63.170(b); and section III.D.7 of this preamble).
     that owners and operators may not bypass an APCD at any
time (see proposed 40 CFR 63.114(d)(3), 40 CFR 63.127(d)(3), and 40 CFR
63.148(f)(4)), that a bypass is a violation, and that owners and
operators must estimate and report the quantity of organic HAP released
(see proposed 40 CFR 63.118(a)(5), 40 CFR 63.130(a)(2)(iv), 40 CFR
63.130(b)(3), 40 CFR 63.130(d)(7), and 40 CFR 63.148(i)(3)(iii) and
(j)(4); and section III.D.3 of this preamble).
     to add a fenceline monitoring standard that requires
owners and operators to monitor for any of 6 specific HAP they emit
(i.e., benzene, 1,3-butadiene, ethylene dichloride, vinyl chloride,
EtO, and chloroprene) and conduct root cause analysis and corrective
action upon exceeding the annual average concentration action level set
forth for each HAP (see proposed 40 CFR 63.184; and section III.C.7 of
this preamble).
b. P&R I
    As detailed in section II.B.2 of this preamble, P&R I (40 CFR part
63, subpart U) generally follows and refers to the requirements of the
HON, with additional requirements for batch process vents. We are
proposing amendments to P&R I for heat exchange systems, process vents,
storage vessels, wastewater, and equipment leaks. For NESHAP subpart U,
we are proposing:
     Compliance dates for all of the proposed P&R I
requirements (see proposed 40 CFR 63.481(n) and (o); and section III.F
of this preamble).
     new operating and monitoring requirements for flares (see
proposed 40 CFR 63.508; and section III.D.1 of this preamble).
     removing provisions to assert an affirmative defense to
civil penalties (see proposed 40 CFR 63.480(j)(4); and section III.E.2
of this preamble).
     to reference the same fenceline monitoring requirements
that we are proposing in Subpart H for HON sources.
     sampling and analysis procedures for owners and operators
of affected sources producing neoprene to demonstrate that process
equipment does, or does not, meet the proposed definition of being ``in
chloroprene service'' (see proposed 40 CFR 63.509; and section
III.B.2.b.iv of this preamble).
     A facility-wide chloroprene emissions cap of 3.8 tpy in
any consecutive 12-month period for all neoprene production emission
sources (see proposed 40 CFR 63.483(a)(10); and section III.B.2.b.v of
this preamble).
    For heat exchange systems, we are proposing:
     To add the same requirements (except for EtO standards)
listed in section I.A.2.a.i of this preamble that we are proposing for
heat exchange systems subject to the HON to also apply to heat exchange
systems subject to P&R I (see proposed 40 CFR 63.502(n)(7); and section
III.C.1 of this preamble).
    For continuous front-end process vents, we are proposing:
     That owners and operators reduce emissions of chloroprene
from continuous front-end process vents in chloroprene service at
affected sources producing neoprene by venting emissions through a
closed-vent system to a non-flare control device that reduces
chloroprene by greater than or equal to 99.9 percent by weight, to a
concentration less than 1 ppmv for each process vent, or to less than 5
lb/yr for all combined process vents (see proposed 40 CFR 63.485(y),
and 40 CFR 63.510; and sections III.B.2.b.i of this preamble).\5\
---------------------------------------------------------------------------

    \5\ We are also proposing to remove the option to allow use of a
design evaluation in lieu of performance testing to demonstrate
compliance for controlling various emission sources in chloroprene
service. In addition, owners or operators would be required to
conduct an initial performance test on each non-flare control device
in chloroprene service to verify performance at the required level
of control, and would also be required to conduct periodic
performance testing on non-flare control devices in chloroprene
service every 5 years (see proposed 40 CFR 63.510).
---------------------------------------------------------------------------

     to add the same requirements (except for EtO standards)
listed in section I.A.2.a.ii of this preamble that we are proposing for
process vents subject to the HON to also apply to continuous front-end
process vents subject to P&R I (see proposed 40 CFR 63.482, 40 CFR
63.485(l)(6), (o)(6), (p)(5), and (x), 40 CFR 63.113(a)(1) and (2), 40
CFR 63.113(a)(4), 40 CFR 63.113(k), 40 CFR 63.114(a)(5)(v); and section
III.C.3 of this preamble).
     that continuous front-end process vents in chloroprene
service would not be allowed to use the proposed maintenance vent work
practice standards; instead, owners and operators would be prohibited
from releasing more than 1.0 ton of chloroprene from all maintenance
vents combined in any consecutive 12-month period (see proposed 40 CFR
63.485(z); and section III.B.2.b.iii of this preamble).
     to add an emission standard of 0.054 ng/dscm at 3 percent
oxygen (toxic equivalency basis) for dioxins and furans from
chlorinated continuous front-end process vents (see proposed 40 CFR
63.485(x); and section III.D.5. of this preamble).
    For batch front-end process vents, we are proposing:
     To remove the annual organic HAP emissions mass flow rate,
cutoff flow rate, and annual average batch vent flow rate Group 1
process vent thresholds from the Group 1 batch front-end process vent
definition (these thresholds are currently determined on an individual
batch process vent basis). Instead, owners and operators of batch
front-end process vents that release total annual organic HAP emissions
greater than or equal to 4,536 kilograms per year (kg/yr) (10,000
pounds per year (lb/yr)) from all batch front-end process vents
combined would be required to 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 total organic carbon (TOC) by 90 percent by weight (or to an exit
concentration of 20 ppmv if considered an ``aggregate batch vent
stream'' as defined by the rule) (see proposed 40 CFR 63.482, 40 CFR
63.487I(1)(iv), 40 CFR 63.488(d)(2), (e)(4), (f)(2), and (g)(3); and
section III.C.3 of this preamble).
     to add the same chloroprene standards that we are
proposing for continuous front-end process for batch front-end process
vents at affected sources producing neoprene (see proposed 40 CFR
63.487(j); and section III.B.2.b.i of this preamble).
     to add the same work practice standards that we are
proposing for maintenance vents as described for HON to P&R I (see
proposed 40 CFR 63.487(i); and section III.D.4.a of this preamble).
     that batch front-end process vents in chloroprene service
would not be allowed to use the proposed maintenance vent work practice
standards; instead, owners and operators would be prohibited from
releasing more than 1.0 tons of chloroprene from all maintenance vents
combined in any consecutive 12-month period (see proposed 40 CFR
63.487(i)(4); and section III.B.2.b.v of this preamble).
     to add an emission standard of 0.054 ng/dscm at 3 percent
oxygen

(toxic equivalency basis) for dioxins and furans from chlorinated batch
front-end process vents (see proposed 40 CFR 63.487(a)(3) and (b)(3);
and section III.D.5. of this preamble).
    For storage vessels, we are proposing:
     That owners and operators reduce emissions of chloroprene
from storage vessels in chloroprene service at affected sources
producing neoprene by venting emissions through a closed-vent system to
a non-flare control device that reduces chloroprene by greater than or
equal to 99.9 percent by weight or to a concentration less than 1 ppmv
for each storage vessel vent (see proposed 40 CFR 63.484(u) and 40 CFR
63.510; and section III.B.2.b.i of this preamble).\6\
---------------------------------------------------------------------------

    \6\ See footnote 5.
---------------------------------------------------------------------------

     to add the same requirements (except for EtO standards)
listed in section I.A.2.a.ii of this preamble that we are proposing for
storage vessels subject to the HON except the proposed requirements
would apply to storage vessels subject to P&R I (see proposed 40 CFR
63.484(t); and section III.C.2 of this preamble).
    For wastewater streams, we are proposing:
     To revise the Group 1 wastewater stream threshold to
include wastewater streams in chloroprene service at affected sources
producing neoprene (i.e., wastewater streams with total annual average
concentration of chloroprene greater than or equal to 10 parts per
million by weight (ppmw) at any flow rate) (see proposed 40 CFR
63.501(a)(10)(iv); and section III.B.2.b.ii of this preamble).
     to prohibit owners and operators from injecting wastewater
into or disposing of water through any heat exchange system in an
elastomer product process unit (EPPU) if the water contains any amount
of chloroprene, has been in contact with any process stream containing
chloroprene, or the water is considered wastewater as defined in 40 CFR
63.482 (see proposed 40 CFR 63.502(n)(8); and section III.B.2.b.ii of
this preamble).
    For equipment leaks and fenceline monitoring, we are proposing:
     To add the same requirements (except for EtO standards)
listed in section I.A.2.a.iii of this preamble that we are proposing
for equipment leaks subject to the HON except the proposed requirements
would apply to equipment leaks subject to P&R I (see proposed 40 CFR
63.502(a)(1) through (a)(6); and sections III.D.2 and III.D.3 of this
preamble).
     to cross-reference P&R I facilities to the same fenceline
monitoring standard in the HON (see proposed 40 CFR 63.184) that
requires owners and operators to monitor for any of 6 specific HAP they
emit (i.e., benzene, 1,3-butadiene, ethylene dichloride, vinyl
chloride, EtO, and chloroprene) and conduct root cause analysis and
corrective action upon exceeding the annual average concentration
action level set forth for each HAP (see section III.C.7 of this
preamble).
c. P&R II
    The most significant amendments that we are proposing for P&R II
(40 CFR part 63, subpart W) are to add requirements for heat exchange
systems (see proposed 40 CFR 63.523(d) and 40 CFR 63.524(c); and
section III.D.9 of this preamble) and require owners and operators of
wet strength resins (WSR) sources to comply with both the equipment
leak standards in the HON and the HAP emissions limitation for process
vents, storage tanks, and wastewater systems (see proposed 40 CFR
63.524(a)(3) and (b)(3); and section III.D.10 of this preamble). We are
also proposing to add the same dioxin and furan emission standard of
0.054 ng/dscm at 3 percent oxygen (toxic equivalency basis) for
chlorinated process vents as in the HON and P&R I (see proposed 40 CFR
63.523(e) (for process vents associated with each existing, new, or
reconstructed affected basic liquid epoxy resins (BLR) source), 40 CFR
63.524(a)(3) (for process vents associated with each existing affected
WSR source), and 40 CFR 63.524(b)(3) (for process vents associated with
each new or reconstructed affected WSR source)).
d. NSPS Subparts III, NNN, and RRR
    We are proposing to amend the applicability of NSPS subparts III,
NNN, and RRR so that they would only apply to sources constructed,
reconstructed, or modified on or before April 25, 2023. Affected
facilities that are constructed, reconstructed, or modified after April
25, 2023 would be subject to the new proposed NSPS subparts IIIa, NNNa,
and RRRa (see section A.2.e of this preamble).
e. NSPS Subparts IIIa, NNNa, and RRRa
    Rather than comply with a TRE concept which is currently used in
NSPS subparts III, NNN, and RRR, we are proposing in new NSPS subparts
IIIa, NNNa, and RRRa to require owners and operators to reduce
emissions of total organic carbon (TOC) (minus methane and ethane) from
all vent streams of an affected facility (i.e., SOCMI air oxidation
unit processes, distillation operations, and reactor processes for
which construction, reconstruction, or modification occurs after April
25, 2023) by 98 percent by weight or to a concentration of 20 ppmv on a
dry basis corrected to 3 percent oxygen, whichever is less stringent,
or combust the emissions in a flare meeting the same operating and
monitoring requirements for flares that we are proposing for flares
subject to the HON. We are also proposing to eliminate the relief valve
discharge exemption from the definition of ``vent stream'' such that
any relief valve discharge to the atmosphere of a vent stream is a
violation of the emissions standard. In addition, we are proposing the
same work practice standards for maintenance vents that we are
proposing for HON process vents, and the same monitoring requirements
that we are proposing for HON process vents for adsorbers that cannot
be regenerated and regenerative adsorbers that are regenerated offsite
(see section III.C.3.b of this preamble).
f. NSPS Subpart VVa
    We are proposing to amend the applicability of the existing NSPS
subpart VVa so that it would apply to only sources constructed,
reconstructed, or modified after November 6, 2006, and on or before
April 25, 2023. Affected facilities that are constructed,
reconstructed, or modified after April 25, 2023 would be subject to the
new proposed NSPS subpart VVb.
g. NSPS Subpart VVb
    We are proposing in a new NSPS subpart VVb the same requirements in
NSPS subpart VVa plus requiring that all gas/vapor and light liquid
valves be monitored quarterly at a leak definition of 100 ppm and all
connectors be monitored once every 12 months at a leak definition of
500 ppm (see section III.C.6.b of this preamble). For each of these two
additional requirements, we are also proposing skip periods for good
performance.
3. Costs and Benefits
    Pursuant to E.O. 12866, the EPA prepared an analysis of the
potential costs and benefits associated with this action. This analysis
titled Regulatory Impact Analysis, (referred to as the RIA in this
document) is available in the docket, and is also briefly summarized in
section VI of this preamble.

B. Does this action apply to me?

    The source categories that are the subject of this proposal include
the SOCMI source category (and whose facilities, sources and processes
we often refer to as ``HON facilities,'' ``HON sources,'' and ``HON
processes'' for purposes of the NESHAP) and several

Polymers and Resins Production source categories covered in P&R I and
P&R II (see section II.B of this preamble for detailed information
about the source categories).\7\ The North American Industry
Classification System (NAICS) code for SOCMI facilities begins with
325, for P&R I is 325212, and for P&R II is 325211. The list of NAICS
codes is not intended to be exhaustive, but rather provides 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 and/or affected facilities. Federal,
state, local, and tribal government entities would not be affected by
this proposed action.
---------------------------------------------------------------------------

    \7\ P&R I includes nine listed elastomer production source
categories (i.e., Butyl Rubber Production, Epichlorohydrin
Elastomers Production, Ethylene-Propylene Elastomers Production,
HypalonTM Production, Neoprene Production, Nitrile
Butadiene Rubber Production, Polybutadiene Rubber Production,
Polysulfide Rubber Production, and Styrene-Butadiene Rubber and
Latex Production). P&R II includes two listed source categories that
use epichlorohydrin feedstock (Epoxy Resins Production and Non-Nylon
Polyamides Production).
---------------------------------------------------------------------------

    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 SOCMI source category is any facility engaged in ``manufacturing
processes that produce one or more of the chemicals [listed] that
either: (1) Use an organic HAP as a reactant or (2) produce an organic
HAP as a product, co-product, by-product, or isolated intermediate.''
\8\ 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, transfer racks,
storage vessels, and wastewater collection and treatment systems. The
elastomer production source categories in P&R I and resins produced
with epichlorohydrin feedstock in P&R II have many similar emission
sources with SOCMI sources and are discussed further in section II.B of
this preamble.
---------------------------------------------------------------------------

    \8\ The original list of chemicals is located in Appendix A
(beginning on page A-71) of EPA-450/3-91-030 dated July 1992.
Alternatively, the most recent list of chemicals is documented in
the HON applicability rule text at 40 CFR 63.100(b)(1) and (2). The
original list of organic HAPs for the SOCMI source category is
located in Table 3.1 of Section 3.0 of EPA-450/3-91-030.
---------------------------------------------------------------------------

    The EPA Priority List (40 CFR 60.16, 44 FR 49222, August 21, 1979)
included ``Synthetic Organic Chemical Manufacturing'' \9\ as a source
category for which standards of performance were to be promulgated
under CAA section 111. In the development of NSPS for this source
category, the EPA considered emission sources associated with unit
processes, storage and handling equipment, fugitive emission sources,
and secondary sources.
---------------------------------------------------------------------------

    \9\ For readability, we also refer to this as the SOCMI source
category for purposes of the NSPS.
---------------------------------------------------------------------------

C. 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. 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/synthetic-organic-chemical-manufacturing-industry-organic-national, https://www.epa.gov/stationary-sources-air-pollution/group-i-polymers-and-resins-national-emission-standards-hazardous, and https://www.epa.gov/stationary-sources-air-pollution/epoxy-resins-production-and-non-nylon-polyamides-national-emission. Following publication in the Federal Register, the
EPA will post the Federal Register version of the proposal and key
technical documents at these same websites.
    A memorandum showing the edits that would be necessary to
incorporate the changes to: 40 CFR part 60, subparts VV, VVa, III, NNN,
RRR; 40 CFR part 63, subparts F, G, H and I (HON), U (P&R I), and W
(P&R II); and 40 CFR part 60, new subparts VVb, IIIa, NNNa, and RRRa
proposed in this action are available in the docket (Docket ID No. EPA-
HQ-OAR-2022-0730). Following signature by the EPA Administrator, the
EPA also will post a copy of these documents to https://www.epa.gov/stationary-sources-air-pollution/synthetic-organic-chemical-manufacturing-industry-organic-national, https://www.epa.gov/stationary-sources-air-pollution/group-i-polymers-and-resins-national-emission-standards-hazardous, and https://www.epa.gov/stationary-sources-air-pollution/epoxy-resins-production-and-non-nylon-polyamides-national-emission.

II. Background

A. What is the statutory authority for this action?

1. NESHAP
    The statutory authority for this action related to NESHAP 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 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, and 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 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.''
In certain instances, as provided in CAA section 112(h), the EPA may
set work practice standards in lieu of numerical emission standards.

The EPA must also consider control options that are more stringent than
the floor. Standards more stringent than the floor are commonly
referred to as beyond-the-floor 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 1989 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 upheld the EPA's interpretation that CAA section 112(f)(2)
incorporates the approach established in the 1989 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)
\10\ 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 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.
---------------------------------------------------------------------------

    \10\ 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) 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 in
earlier rulemakings. NRDC v. EPA, 529 F.3d at 1084; 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 major source categories, and any new MACT standards must
be established under CAA sections 112(d)(2) and (3), or, in specific
circumstances, CAA sections 112(d)(4) or (h). Louisiana Environmental
Action Network (LEAN) v. EPA, 955 F.3d 1088 (D.C. Cir. 2020).
    The EPA conducted a residual risk and technology review for the HON
in 2006, concluding that there was no need to revise the HON under the
provisions of either CAA section 112(f) or 112(d)(6). As part of the
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 (see 71 FR
76603, December 21, 2006 for additional details). In 2008, the EPA
conducted a residual risk and technology review for four of the P&R I
source categories (including the Polysulfide Rubber Production,
Ethylene-Propylene Elastomers Production, Butyl Rubber Production, and
Neoprene Production source categories) and all P&R II source categories
(Epoxy Resins Production and Non-Nylon Polyamides Production source
categories). In 2011, the EPA completed the residual risk and
technology review for the remaining five P&R I source categories
(Epichlorohydrin Elastomers Production, Hypalon\TM\ Production,
Polybutadiene Rubber Production, Styrene-Butadiene Rubber and Latex
Production, and Nitrile Butadiene Rubber Production); and the EPA
concluded in these actions that there was no need to revise standards
for any of the nine P&R I source categories and two P&R II source
categories under the provisions of either CAA section 112(f) or
112(d)(6) (see 73 FR 76220, December 16, 2008 and 77 FR 22566, April
21, 2011 for additional details).
    This action constitutes another CAA section 112(d)(6) technology
review for the HON, P&R I, and P&R II. This action also constitutes an
updated CAA section 112(f) risk review based on new information for the
HON and for affected sources producing neoprene subject to P&R I. 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 HON or standards for affected sources producing neoprene subject to
P&R I, the EPA retains discretion to revisit its residual risk reviews
where the Agency deems that 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 residual risk review for EtO, EPA asserting 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 certain
pollutants emitted by these unique categories led us to determine that
it is appropriate, in this case, to conduct these second residual risk
reviews under section 112(f). In particular, the EPA is concerned about
the cancer risks posed from the SOCMI (i.e., HON) source category due
to the EPA's 2016 updated IRIS inhalation URE for EtO, which shows EtO
to be significantly more toxic than previously known.\11\ The EPA's
2006 risk and technology review (RTR) could not have had the benefit of
this updated URE at the time it was conducted, but if it had would have
necessarily resulted in different conclusions about risk acceptability
and the HON's provision of an ample margin of safety to protect public
health. Similarly, for chloroprene, when the EPA conducted the first
residual risk assessment for the SOCMI and Neoprene Production source
categories, there was no inhalation URE for chloroprene and, therefore,
no cancer risk was attributed to chloroprene emissions in either of
those risk reviews. The EPA's 2006 and 2008 RTRs could not have had the
benefit of this new URE at the time they were conducted, but if they
had would have necessarily resulted in different conclusions about risk
acceptability and P&R I's provision of an ample margin of safety to
protect public health. The development of the EPA's IRIS inhalation URE
for chloroprene was concluded in 2010, which allows us to assess cancer
risks posed by chloroprene for the first time. Thus, we are conducting
this analysis in this action. In order to ensure our standards provide
an ample margin of safety to protect public health following the new
IRIS inhalation UREs for EtO and chloroprene, we are exercising our
discretion and conducting risk assessments in this action for HON
sources and for affected sources producing neoprene subject to P&R I.
Finally, we note that on September 15, 2021, the EPA partially granted
a citizen administrative petition requesting that the EPA conduct a
second residual risk review under CAA section 112(f)(2) for the HON,
stating our intent to conduct a human health risk assessment
concurrently with the section 112(d)(6) review.\12\ Likewise, on March
4, 2022, the EPA partially granted another citizen administrative
petition requesting that the EPA also conduct a second residual risk
review under CAA section 112(f) for P&R I, stating that we intend to
conduct a human health risk assessment concurrently with the section
112(d)(6) review.\13\ This proposed rulemaking is partly undertaken to
take action in response to those citizen administrative petitions. In
sum, even though we do not have a mandatory duty to conduct repeated
residual risk reviews under CAA section 112(f)(2), we have the
authority to revisit any rulemaking if there is sufficient evidence
that changes within the affected industry or significant new scientific
information suggesting the public is exposed to significant increases
in risk as compared to the previous risk assessments prepared for
earlier rulemakings.
---------------------------------------------------------------------------

    \11\ 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.
    \12\ See letter dated September 15, 2021, from Joseph Goffman to
Kathleen Riley, Emma Cheuse, and Adam Kron which is available in the
docket for this rulemaking.
    \13\ See letter dated March 4, 2022, from Joseph Goffman to Emma
Cheuse, Deena Tumeh, Michelle Mabson, Maryum Jordan, and Dorian
Spence which is available in the docket for this rulemaking.
---------------------------------------------------------------------------

2. NSPS
    The EPA's authority for this proposed rule related to NSPS is CAA
section 111, which governs the establishment of standards of
performance for stationary sources. Section 111(b)(1)(A) of the CAA
requires the EPA Administrator to list categories of stationary sources
that in the Administrator's judgment cause or contribute significantly
to air pollution that may reasonably be anticipated to endanger public
health or welfare. The EPA must then issue performance standards for
new (and modified or reconstructed) sources in each source category
pursuant to CAA section 111(b)(1)(B). These standards are referred to
as new source performance standards, or NSPS. The EPA has the authority
to define the scope of the source categories, determine the pollutants
for which standards should be developed, set the emission level of the
standards, and distinguish among classes, types, and sizes within
categories in establishing the standards.
    CAA section 111(b)(1)(B) requires the EPA to ``at least every 8
years review and, if appropriate, revise'' NSPS. However, the
Administrator need not review any such standard if the ``Administrator
determines that such review is not appropriate in light of readily
available information on the efficacy'' of the standard. When
conducting a review of an existing performance standard, the EPA has
the discretion and authority to add emission limits for pollutants or
emission sources not currently regulated for that source category.
    In setting or revising a performance standard, CAA section
111(a)(1) provides that performance standards are to reflect ``the
degree of emission limitation achievable through the application of the
BSER which (taking into account the cost of achieving such reduction
and any non-air quality health and environmental impact and energy
requirements) the Administrator determines has been adequately
demonstrated.'' The term ``standard of performance'' in CAA section
111(a)(1) makes clear that the EPA is to determine both the BSER for
the regulated sources in the source category and the degree of emission
limitation achievable through application of the BSER. The EPA must
then, under CAA section 111(b)(1)(B), promulgate standards of
performance for new sources that reflect that level of stringency. CAA
section 111(h)(1) authorizes the Administrator to promulgate ``a
design, equipment, work practice, or operational standard, or
combination thereof'' if in his or her judgment, ``it is not feasible
to prescribe or enforce a standard of performance.'' CAA section
111(h)(2) provides the circumstances under which prescribing or
enforcing a standard of performance is ``not feasible,'' such as, when
the pollutant cannot be emitted through a conveyance designed to emit
or capture the pollutant, or when there is no practicable measurement
methodology for the particular class of sources. CAA section 111(b)(5)
precludes the EPA from prescribing a particular technological system
that must be used to comply with a standard of performance. Rather,
sources can select any measure or combination of measures that will
achieve the standard.
    Pursuant to the definition of new source in CAA section 111(a)(2),
standards of performance apply to facilities that begin construction,
reconstruction, or modification after the date of publication of the
proposed standards in the Federal Register. Under CAA section
111(a)(4), ``modification'' means any physical change in, or change in
the method of operation of, a stationary source which increases the
amount of any air pollutant emitted by such source or which results in
the emission of any air pollutant not previously emitted. Changes to an
existing facility that do

not result in an increase in emissions are not considered
modifications. Under the provisions in 40 CFR 60.15, reconstruction
means the replacement of components of an existing facility such that:
(1) The fixed capital cost of the new components exceeds 50 percent of
the fixed capital cost that would be required to construct a comparable
entirely new facility; and (2) it is technologically and economically
feasible to meet the applicable standards. Pursuant to CAA section
111(b)(1)(B), the standards of performance or revisions thereof shall
become effective upon promulgation.
    In the development of NSPS for the SOCMI source category, the EPA
considered emission sources associated with unit processes, storage and
handling equipment, fugitive emission sources, and secondary sources.
In 1983, the EPA promulgated NSPS for VOC from equipment leaks in SOCMI
(40 CFR part 60, subpart VV). In 1990, the EPA promulgated NSPS (40 CFR
part 60, subparts III and NNN) for VOC from air oxidation unit
processes and distillation operations in the SOCMI (55 FR 26912 and 55
FR 26931). In 1993, the EPA promulgated NSPS (40 CFR part 60, subpart
RRR) for VOC from reactor processes in the SOCMI (58 FR 45948). In
2007, based on its review of NSPS subpart VV, the EPA promulgated
certain amendments to NSPS subpart VV and new NSPS (40 CFR part 60,
subpart VVa) for VOC from certain equipment leaks in the SOCMI (72 FR
64883). This proposed action presents the required CAA 111(b)(1)(B)
review of the NSPS for the air oxidation unit processes (subpart III),
distillation operations (subpart NNN), reactor processes (subpart RRR),
and equipment leaks (subpart VVa).
3. Petition for Reconsideration
    In addition to the proposed action under section 111(b)(1)(B)
described above, this action includes proposed amendments to the NSPS
for VOC from equipment leaks in SOCMI based on its reconsideration of
certain aspects of NSPS subparts VV and VVa that were raised in an
administrative petition and of which the Agency has granted
reconsideration pursuant to section 307(d)(7)(B) of the CAA. In January
2008, the EPA received one petition for reconsideration of the NSPS for
VOC from equipment leaks in SOCMI (40 CFR part 60, subparts VV and VVa)
and the NSPS for equipment leaks in petroleum refineries (40 CFR part
60, subparts GGG and GGGa) pursuant to CAA section 307(d)(7)(B) from
the following petitioners: American Chemistry Council, American
Petroleum Institute, and National Petrochemical and Refiners
Association (now the American Fuel and Petrochemical Manufacturers). 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-2022-0730). The petitioners primarily requested
the EPA reconsider four provisions in those rules: (1) The
clarification of the definition of process unit in subparts VV, VVa,
GGG, and GGGa; (2) the assignment of shared storage vessels to specific
process units in subparts VV, VVa, GGG, and GGGa; (3) the monitoring of
connectors in subpart VVa; and (4) the definition of capital
expenditure in subpart VVa.\14\ The rationale for this request is
provided in the petition. The petitioners also requested that the EPA
stay the effectiveness of these provisions of the rule pending
resolution of their petition for reconsideration. On March 4, 2008, the
EPA sent a letter to the petitioners informing them that the EPA was
granting their request for reconsideration on issues (2) through (4)
above. The letter also indicated that the EPA was not taking action on
the first issue related to the definition of process unit. Finally, the
letter indicated that the EPA was granting a 90-day stay of the
provisions of the rules under reconsideration (see CAA section
307(d)(7)(B)), as well as the clarification of the definition of
process unit, because of its reliance upon the new provision on the
allocation of shared storage vessels. On June 2, 2008, the EPA
published three actions in the Federal Register relative to extending
the 90-day stay. Specifically, the EPA published a direct final rule
(73 FR 31372) and a parallel proposal (73 FR 31416) in the Federal
Register to extend the stay until we take final action on the issues of
which EPA granted reconsideration. Under the direct final rule, the
stay would take effect 30 days after the close of the comment period on
the proposed stay if no adverse comments were received. The third
notice published that same day was an interim final rule extending the
90-day stay at the time for an additional 60 days so that the stay
would not expire before the direct final rule could take effect (73 FR
31376). The EPA did not receive adverse comments on the proposed stay
and, as a result, the stay became effective August 1, 2008.
---------------------------------------------------------------------------

    \14\ Note that this action does not respond to the
reconsideration of NSPS subparts GGG and GGGa, as the EPA is not
reviewing those subparts in this action.
---------------------------------------------------------------------------

    In the June 2, 2008, actions, the EPA indicated that it would be
publishing a Federal Register notice in response to the petition;
therefore, the purpose of today's notice is to formally respond to the
issues raised in the petition with respect to NSPS subparts VV and VVa.
This proposed action presents the EPA's proposed revisions to the NSPS
for VOC from equipment leaks in SOCMI based on the EPA's
reconsideration of issues (2) through (4) in the petition. We are also
proposing amendments that address the stay on issue (1) in the
petition. See section III.E.4 of this preamble for details about these
proposed amendments.

B. What are the source categories and how do the current standards
regulate emissions?

    The source categories that are the subject of this proposal are the
SOCMI source category subject to the HON and 11 Polymers and Resins
Production source categories subject to P&R I and P&R II. The NESHAP
and NSPS included in this action that regulate emission sources from
the SOCMI and Polymers and Resins Production source categories are
described below.
1. HON
    The sources affected by the current HON include heat exchange
systems and maintenance wastewater located at SOCMI facilities that are
regulated under NESHAP subpart F; process vents, storage vessels,
transfer racks, and wastewater streams located at SOCMI facilities that
are regulated under NESHAP subpart G; equipment leaks associated with
SOCMI processes regulated under NESHAP subpart H; and equipment leaks
from certain non-SOCMI processes at chemical plants regulated under
NESHAP subpart I. As previously mentioned, these four NESHAP are more
commonly referred together as the HON.
    In general, the HON applies to CMPUs that: (1) Produce one of the
listed SOCMI chemicals,\15\ and (2) either use as a reactant or produce
a listed organic HAP in the process. A CMPU means the equipment
assembled and connected by pipes or ducts to process raw materials and
to manufacture an intended product. A CMPU consists of more than one
unit operation. A CMPU includes air oxidation reactors and their
associated product separators and recovery devices; reactors and their
associated product separators and recovery devices; distillation units
and their associated distillate receivers and recovery devices;
associated unit

operations; associated recovery devices; and any feed, intermediate and
product storage vessels, product transfer racks, and connected ducts
and piping. A CMPU includes pumps, compressors, agitators, PRDs,
sampling connection systems, open-ended valves or lines (OEL), valves,
connectors, instrumentation systems, and control devices or systems. A
CMPU is identified by its primary product.
---------------------------------------------------------------------------

    \15\ See Table 1 to NESHAP subpart F.
---------------------------------------------------------------------------

a. NESHAP Subpart F
    NESHAP subpart F contains provisions to determine which chemical
manufacturing processes at a SOCMI facility are subject to the HON.
Table 1 of NESHAP subpart F contains a list of SOCMI chemicals, and
Table 2 of NESHAP subpart F contains a list of organic HAP regulated by
the HON. In general, if a process both: (1) Produces one of the listed
SOCMI chemicals and (2) either uses as a reactant or produces a listed
organic HAP in the process, then that SOCMI process is subject to the
HON. Details on how to determine which emission sources (i.e., heat
exchange systems, process vents, storage vessels, transfer racks,
wastewater, and equipment leaks) are part of a chemical manufacturing
process are also contained in NESHAP subpart F. NESHAP subpart F also
contains monitoring requirements for HAP (i.e., HAP listed in Table 4
of NESHAP subpart F) that may leak into cooling water from heat
exchange systems. Additionally, NESHAP subpart F requires sources to
prepare a description of procedures for managing maintenance wastewater
as part of a SSM plan.
b. NESHAP Subpart G
    NESHAP subpart G contains the standards for process vents, transfer
racks, storage vessels, and wastewater at SOCMI facilities; it also
includes emissions averaging provisions. NESHAP subpart G provides an
equation representing a site-specific allowable overall emission limit
for the combination of all emission sources subject to the HON at a
SOCMI facility. Existing sources must demonstrate compliance using one
of two approaches: the point-by-point compliance approach or the
emissions averaging approach. New sources are not allowed to use
emissions averaging, but rather must demonstrate compliance using the
point-by-point approach. Under the point-by-point approach, the owner
or operator would apply control to each Group 1 emission source. A
Group 1 emission source is a point which meets the control
applicability criteria, and the owner or operator must reduce emissions
to specified levels; whereas a Group 2 emission source is one that does
not meet the criteria and no additional emission reduction is required.
Under the emissions averaging approach, an owner or operator may elect
to control different groups of emission sources to different levels
than specified the point-by-point approach, as long as the overall
emissions do not exceed the overall allowable emission level. For
example, an owner or operator can choose not to control a Group 1
emission source (or to control the emission source with a less
effective control technique) if the owner or operator over-controls
another emission source. For the point-by-point approach, NESHAP
subpart G contains the following standards:
     Group 1 process vents must reduce emissions of organic HAP
using a flare meeting 40 CFR 63.11(b); reduce emissions of total
organic HAP or TOC by 98 percent by weight or to an exit concentration
of 20 ppmv, whichever is less stringent; or achieve and maintain a TRE
index value \16\ greater than 1.0.\17\
---------------------------------------------------------------------------

    \16\ See section III.C.3.a of this preamble for a description of
the TRE index value and how the concept is currently used in the
HON.
    \17\ Halogenated vent streams (as defined in NESHAP subpart G)
from Group 1 process vents may not be vented to a flare and must
reduce the overall emissions of hydrogen halides and halogens by 99
percent (or 95 percent for control devices installed prior to
December 31, 1992) or reduce the outlet mass emission rate of total
hydrogen halides and halogens to less than 0.45 kg/hr.
---------------------------------------------------------------------------

     Group 1 transfer racks must reduce emissions of total
organic HAP by 98 percent by weight or to an exit concentration of 20
ppmv, whichever is less stringent; or reduce emissions of organic HAP
using a flare meeting 40 CFR 63.11(b), using a vapor balancing system,
or by routing emissions to a fuel gas system or to a process.
     Group 1 storage vessels must reduce emissions of organic
HAP using a fixed roof tank equipped with an IFR; using an external
floating roof (EFR); using an EFR tank converted to a fixed roof tank
equipped with an IFR; by routing emissions to a fuel gas system or to a
process; or reduce emissions of organic HAP by 95 percent by weight
using a closed vent system (i.e., vapor collection system) and control
device, or combination of control devices (or reduce emissions of
organic HAP by 90 percent by weight using a closed vent system and
control device if the control device was installed before December 31,
1992).
     Group 1 process wastewater streams and equipment managing
such streams at both new and existing sources must meet control
requirements for: (1) Waste management units including wastewater
tanks, surface impoundments, containers, individual drain systems, and
oil-water separators; (2) treatment processes including the design
steam stripper, biological treatment units, or other treatment devices;
and (3) closed vent systems and control devices such as flares,
catalytic incinerators, etc. Existing sources are not required to meet
control requirements if Group 1 process wastewater streams are included
in a 1 megagram per year source-wide exemption allowed by NESHAP
subpart G.
     In general, Group 2 emission sources are not required to
apply any additional emission controls (provided they remain below
Group 1 thresholds); 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.
c. NESHAP Subpart H
    NESHAP subpart H contains the standard for equipment leaks at SOCMI
facilities, including leak detection and repair (LDAR) provisions and
other control requirements. Equipment regulated includes pumps,
compressors, agitators, PRDs, sampling connection systems, OEL, valves,
connectors, surge control vessels, bottoms receivers, and
instrumentation systems in organic HAP service. A piece of equipment is
in organic HAP service if it contains or contacts a fluid that is at
least 5 percent by weight organic HAP. Depending on the type of
equipment, the standards require either periodic monitoring for and
repair of leaks, the use of specified equipment to minimize leaks, or
specified work practices. Monitoring for leaks must be conducted using
EPA Method 21 in appendix A-7 to 40 CFR part 60 or other approved
equivalent monitoring techniques.
d. NESHAP Subpart I
    NESHAP subpart I provides the applicability criteria for certain
non-SOCMI processes subject to the negotiated regulation for equipment
leaks. Regulated equipment is the same as that for NESHAP subpart H.
2. P&R I
    P&R I generally follows and refers to the requirements of the HON,
with additional requirements for batch process vents. Generally, P&R I
applies to EPPUs and associated equipment. Similar to a CMPU in the
HON, an EPPU means a collection of equipment assembled and connected by
hard-piping or duct work used to process raw materials and manufacture
elastomer

product. The EPPU includes unit operations, recovery operations,
process vents, storage vessels, and equipment that are covered by
equipment leak standards and produce one of the elastomer types listed
as an elastomer product, including: butyl rubber, epichlorohydrin
elastomer, ethylene propylene rubber, halobutyl rubber,
HypalonTM, neoprene, nitrile butadiene latex, nitrile
butadiene rubber, polybutadiene rubber/styrene butadiene rubber by
solution, polysulfide rubber, styrene butadiene latex, and styrene
butadiene rubber by emulsion. An EPPU consists of more than one unit
operation. An EPPU includes, as ``equipment,'' pumps, compressors,
agitators, PRDs, sampling connection systems, OEL, valves, connectors,
surge control vessels, bottoms receivers, instrumentation systems, and
control devices or systems.
    The emissions sources affected by P&R I include heat exchange
systems and maintenance wastewater at P&R I facilities regulated under
NESHAP subpart F; storage vessels, transfer racks, and wastewater
streams at P&R I facilities regulated under NESHAP subpart G; and
equipment leaks at P&R I facilities regulated under NESHAP subpart H.
Process vents are also regulated emission sources but, unlike the HON,
these emissions sources are subdivided into front and back-end process
vents in P&R I. The front-end are unit operations prior to and
including the stripping operations. These are further subdivided into
continuous front-end process vents regulated under NESHAP subpart G and
batch front-end process vents that are regulated according to the
requirements within P&R I. Back-end unit operations include filtering,
coagulation, blending, concentration, drying, separating, and other
finishing operations, as well as latex and crumb storage. The
requirements for back-end process vents are not subcategorized into
batch or continuous and are also found within P&R I.
3. P&R II
    P&R II regulates HAP emissions from two source categories, Epoxy
Resins Production (also referred to as basic liquid epoxy resins or
BLR) and Non-Nylon Polyamides Production (also referred to as wet
strength resins or WSR). P&R II takes a different regulatory and format
approach from P&R I but still refers to HON provisions for a portion of
the standards. BLR are resins made by reacting epichlorohydrin and
bisphenol A to form diglycidyl ether of bisphenol-A. WSR are polyamide/
epichlorohydrin condensates which are used to increase the tensile
strength of paper products.
    The emission sources affected by P&R II are all HAP emission points
within a facility related to the production of BLR or WSR. These
emission points include process vents, storage tanks, wastewater
systems, and equipment leaks. Equipment includes connectors, pumps,
compressors, agitators, PRDs, sampling connection systems, OEL, and
instrumentation system in organic HAP service. Equipment leaks are
regulated under the HON (i.e., NESHAP subpart H).
    Process vents, storage tanks, and wastewater systems combined are
regulated according to a production-based emission rate (e.g., pounds
HAP per million pounds BLR or WSR produced). For existing sources, the
rate shall not exceed 130 pounds per 1 million pounds of BLR produced
and 10 pounds per 1 million pounds of WSR produced. For new sources,
BLR requires all uncontrolled emissions to achieve 98 percent reduction
or limits the total emissions to 5,000 pounds of HAP per year. New WSR
sources are limited to 7 pounds of HAP per 1 million pounds of WSR
produced.
4. NSPS Subpart VVa
    NSPS subpart VVa contains VOC standards for leaks from equipment
within a process unit for which construction, reconstruction, or
modification commenced after November 7, 2006. Under NSPS subpart VVa,
equipment means each pump, compressor, PRD, sampling connection system,
OEL, valve, and flange or other connector in VOC service and any
devices or systems required by the NSPS. Process units consist of
components assembled to produce, as intermediate or final products, one
or more of the chemicals listed in 40 CFR 60.489. A process unit can
operate independently if supplied with sufficient feed or raw materials
and sufficient storage facilities for the product. The standards in
NSPS subpart VVa include LDAR provisions and other control
requirements. A piece of equipment is in VOC service if it contains or
contacts a fluid that is at least 10 percent by weight VOC. Depending
on the type of equipment, the standards require either periodic
monitoring for and repair of leaks, the use of specified equipment to
minimize leaks, or specified work practices. Monitoring for leaks must
be conducted using EPA Method 21 in appendix A-7 to 40 CFR part 60 or
other approved equivalent monitoring techniques.
5. NSPS Subpart III
    NSPS subpart III regulates VOC emissions from SOCMI air oxidation
reactors for which construction, reconstruction, or modification
commenced after October 21, 1983. For the purpose of NSPS subpart III,
air oxidation reactors are devices or process vessels in which one or
more organic reactants are combined with air, or a combination of air
and oxygen, to produce one or more organic compounds. The affected
facility is designated as a single air oxidation reactor with its own
individual recovery system (if any) or the combination of two or more
air oxidation reactors and the common recovery system they share that
produces one or more of the chemicals listed in 40 CFR 60.617 as a
product, co-product, by-product, or intermediate. Owners and operators
of an affected facility must reduce emissions of TOC (minus methane and
ethane) by 98 percent by weight or to a concentration of 20 ppmv on a
dry basis corrected to 3 percent oxygen, whichever is less stringent;
combust the emissions in a flare meeting 40 CFR 60.18(b); or maintain a
TRE index value \18\ greater than 1.0 without use of VOC emission
control devices.
---------------------------------------------------------------------------

    \18\ See section III.C.3.b of this preamble for a description of
the TRE index value and how the concept is currently used in NSPS
Subpart III.
---------------------------------------------------------------------------

6. NSPS Subpart NNN
    NSPS subpart NNN regulates VOC emissions from SOCMI distillation
operations for which construction, reconstruction, or modification
commenced after December 30, 1983. For the purpose of NSPS subpart NNN,
distillation operations are operations separating one or more feed
stream(s) into two or more exit stream(s), each exit stream having
component concentrations different from those in the feed stream(s);
and the separation is achieved by the redistribution of the components
between the liquid and vapor-phase as they approach equilibrium within
a distillation unit. The affected facility is designated as a single
distillation column with its own individual recovery system (if any) or
the combination of two or more distillation columns and the common
recovery system they share that is part of a process unit that produces
any of the chemicals listed in 40 CFR 60.667 as a product, co-product,
by-product, or intermediate. Owners and operators of an affected
facility must reduce emissions of TOC (minus methane and ethane) by 98
percent by weight or to a concentration of 20 ppmv on a dry basis
corrected to 3 percent oxygen,

whichever is less stringent; combust the emissions in a flare meeting
40 CFR 60.18(b); or maintain a TRE index value \19\ greater than 1.0
without use of VOC emission control devices.
---------------------------------------------------------------------------

    \19\ See section III.C.3.b of this preamble for a description of
the TRE index value and how the concept is currently used in NSPS
Subpart NNN.
---------------------------------------------------------------------------

7. NSPS Subpart RRR
    NSPS subpart RRR regulates VOC emissions from SOCMI reactor
processes for which construction, reconstruction, or modification
commenced after June 29, 1990. For the purpose of NSPS subpart RRR,
reactor processes are unit operations in which one or more chemicals,
or reactants other than air, are combined or decomposed in such a way
that their molecular structures are altered and one or more new organic
compounds are formed. The affected facility is designated as a single
reactor process with its own individual recovery system (if any) or the
combination of two or more reactor processes and the common recovery
system they share that is part of a process unit that produces any of
the chemicals listed in 40 CFR 60.707 as a product, co-product, by-
product, or intermediate. Owners and operators of an affected facility
must reduce emissions of TOC (minus methane and ethane) by 98 percent
by weight or to a concentration of 20 ppmv on a dry basis corrected to
3 percent oxygen, whichever is less stringent; combust the emissions in
a flare meeting 40 CFR 60.18(b); or maintain a TRE index value \20\
greater than 1.0 without use of VOC emission control devices.
---------------------------------------------------------------------------

    \20\ See section III.C.3.b of this preamble for a description of
the TRE index value and how the concept is currently used in NSPS
Subpart RRR.
---------------------------------------------------------------------------

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 NESHAP and NSPS 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 2006 HON RTR, the 2008 and 2011 P&R
RTRs, other internal chemical sector facility lists from the EPA's
recent petrochemical sector RTR rulemakings (e.g., Miscellaneous
Organic Chemical Manufacturing NESHAP (MON), Organic Liquids
Distribution (Non-Gasoline) NESHAP (OLD), Ethylene Production MACT
standards (EMACT), and Petroleum Refinery MACT 1 standards (the
Petroleum Refinery Sector rule)), and the Office of Enforcement and
Compliance Assurance's (OECA) Enforcement and Compliance History Online
(ECHO) tool (https://echo.epa.gov). To inform our reviews of our
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 rules that
are subject to this proposal were developed. The EPA also reviewed air
permits to determine facilities subject to the HON, and P&R I and P&R
II. We also met with industry representatives from the American
Chemistry Council, American Fuel & Petrochemical Manufacturers, and
Vinyl Institute to collect data and discuss industry practices.
    In June 2021 and January 2022, the EPA issued requests, pursuant to
CAA section 114, to collect information from HON facilities (one being
also subject to P&R I and several being also subject to NSPS subparts
III, NNN, and/or RRR) owned and operated by nine entities (i.e.,
corporations). Many of the entities chosen have facilities that
produce, use, and emit EtO or chloroprene, which are pollutants with
considerable concern for cancer risk for the SOCMI and Neoprene
Production source categories. This effort focused on gathering
comprehensive information about process equipment, control
technologies, point and fugitive emissions, and other aspects of
facility operations. Companies submitted responses (and follow-up
responses) to the EPA between March 2022 and December 2022 (for the
January 2022 request). Additionally, as part of the January 2022 CAA
section 114 requests, 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 benzene, 1,3-
butadiene, chloroprene, EtO, ethylene dichloride, or vinyl chloride.
The results of the January 2022 requests were submitted to the EPA
during the summer and fall of 2022. For the one facility that received
a CAA section 114 request in June 2021, the EPA has received responses
(and follow-up responses) from them in the fall and winter of 2021, and
also began receiving fenceline monitoring data for chloroprene and 1,3-
butadiene in January 2022 (and is continuing to receive this data).\21\
The EPA has 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-2022-0730. A list of facilities
located in the United States that are part of the SOCMI source category
with processes subject to the HON, P&R I, P&R II, and/or the SOCMI NSPS
(40 CFR part 60, subparts VVa, III, NNN, and RRR), is available in the
document titled Lists of Facilities Subject to the HON, Group I and
Group II Polymers and Resins NESHAPs, and NSPS subparts VV, VVa, III,
NNN, and RRR, in the docket for this action, Docket ID No. EPA-HQ-OAR-
2022-0730.
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    \21\ As fenceline monitoring data continues to be gathered for
this facility, it is being posted on the following web page: https://www.epa.gov/la/denka-air-monitoring-data-summaries.
---------------------------------------------------------------------------

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

    As mentioned above, today's action includes proposed amendments to
the current flare requirements in the SOCMI NSPS for air oxidation
reactors, distillation columns, and reactor processes, and NESHAP for
the HON and P&R I. In proposing these amendments, we relied on certain
technical reports and memoranda that the EPA developed for flares used
as APCDs in the Petroleum Refinery Sector residual risk and technology
review and NSPS rulemaking (80 FR 75178, December 1, 2015). The
Petroleum Refinery sector docket is at Docket ID No. EPA-HQ-OAR-2010-
0682. For completeness of the rulemaking record for today's 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-2022-0730) and including
a list of all documents used to inform the 2015 flare provisions in the
Petroleum Refinery Sector residual risk and technology review and NSPS
rulemaking in the document titled Control Option Impacts for Flares
Located in the SOCMI Source Category

that Control Emissions from Processes Subject to HON and for Flares
that Control Emissions from Processes Subject to Group I and Group II
Polymers and Resins NESHAPs, which is available in the docket for this
rulemaking.
    We are also relying on data gathered to support the RTRs for the
EMACT standards, MON, and OLD NESHAP, as well as memoranda documenting
the technology reviews for those processes. Many of the emission
sources for ethylene production facilities, MON facilities, and OLD
facilities are similar to HON, P&R I, and P&R II facilities, and
several of the control options analyzed for the HON, and P&R I and P&R
II, were also analyzed for the RTRs for the EMACT standards, MON, and
OLD NESHAP. 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 MON RTR rulemaking docket, Docket ID No. EPA-
HQ-OAR-2018-0746; and the OLD RTR rulemaking docket, Docket ID No. EPA-
HQ-OAR-2018-0074.
    Additional information related to the promulgation and subsequent
amendments of the NSPS subparts VVa, III, NNN, and RRR, the HON, and
P&R I and P&R II is available in Docket ID Nos. A-80-25, A-81-22, A-83-
29, A-90-19, EPA-HQ-OAR-2002-0026, EPA-HQ-OAR-2002-0281, EPA-HQ-OAR-
2002-0284, EPA-HQ-OAR-2002-0475, EPA-HQ-OAR-2006-0699, EPA-HQ-OAR-2007-
0211, and EPA-HQ-OAR-2010-0600.
    Lastly, the EPA acknowledges that there is also some unique ambient
community monitoring data available for chloroprene concentrations near
the Neoprene Production facility that was developed since 2016
separately from this rulemaking process.\22\ This unique ambient
community monitoring data includes data gathered by the EPA and the
Louisiana Department of Environmental Quality and consists of short-
term, 24-hour cannister sampling data gathered over various days
throughout a four-year period both before and after the Neoprene
Production facility installed controls to reduce emissions of
chloroprene. The data generally indicate that concentrations in the
community have decreased over time, but the current levels corroborate
the need for further reductions.
---------------------------------------------------------------------------

    \22\ https://www.epa.gov/la/denka-air-monitoring-data-summaries.
---------------------------------------------------------------------------

    Consistent with our usual practice in developing proposed rules
under CAA section 112(f)(2), the EPA has conducted its risk assessment
based on modeling of current allowable and/or actual emissions and
projected future emissions. The EPA has not relied on the unique
ambient community monitoring data for the Neoprene Production facility:
(1) In assessing the remaining risk from chloroprene emissions from the
SOCMI or Neoprene Production source categories after compliance with
existing emission standards or (2) in projecting future risks that
would remain after compliance with the proposed standards here.
Consequently, the unique ambient community monitoring data is not part
of our rulemaking record.
    The EPA relies on modeling, which is not dependent on the
availability (or lack thereof) of monitoring data, to perform our risk
assessments when developing residual risk analyses under CAA section
112(f)(2). Modeling provides the EPA with the ability and flexibility
to estimate risks for all populations living near the sources across an
impacted industrial source category, and to estimate various risk
metrics, such as the MIR, cancer incidence, and number of people above
specific risk thresholds. Modeling also allows the EPA to assess the
risks that will remain after the implementation of proposed controls.
With these caveats in mind, the EPA seeks comment on the relevance (if
any) of the unique ambient community monitoring data to the EPA's
rulemaking.

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

    As discussed in section II.A.1 of this preamble and in the 1989
Benzene NESHAP, in evaluating and developing standards under CAA
section 112(f)(2), our longstanding and consistent policy is that 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 1989 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 1989 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.\23\ 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
EPA's response to comments on our policy under the 1989 Benzene NESHAP:
---------------------------------------------------------------------------

    \23\ 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 1989 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
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.'' \24\
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    \24\ 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.
---------------------------------------------------------------------------

    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 vicinity of each source, we note there are
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.

F. 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