Document ID: EPA-HQ-OAR-2022-0730-0001
Agency: epa
Document Type: Proposed Rule
Title: New Source Performance Standards: Synthetic Organic Chemical Manufacturing Industry and National Emission Standards for Hazardous Air Pollutants for the Synthetic Organic Chemical Manufacturing Industry and Group I and II Polymers and Resins Industry
Posted Date: 2023-04-25T04:00Z

[Federal Register Volume 88, Number 79 (Tuesday, April 25, 2023)]
[Proposed Rules]
[Pages 25080-25205]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-07188]

[[Page 25079]]

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  

[[Page 25080]]

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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: (202) 566-9744. 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: (919) 541-4036; 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 (888) 372-8699 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-

[[Page 25081]]

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 (888) 372-8699 or by email at 
[email protected] to determine if there are any updates. The 
EPA does not intend to publish a document in the Federal Register 
announcing updates.
    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.

[[Page 25082]]

    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

[[Page 25083]]

    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

[[Page 25084]]

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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

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

[[Page 25085]]

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

[[Page 25086]]

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

[[Page 25087]]

(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

[[Page 25088]]

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.

[[Page 25089]]

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

[[Page 25090]]

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

[[Page 25091]]

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

[[Page 25092]]

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

[[Page 25093]]

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,

[[Page 25094]]

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.
---------------------------------------------------------------------------

    \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

[[Page 25095]]

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

[[Page 25096]]

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\
---------------------------------------------------------------------------

    \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 
not perform a multipathway exposure assessment. Where we do not perform 
an analysis, we state that we do not and provide the reason. While we 
present all of our risk assessment methods, we only present risk 
assessment results for the analyses actually conducted (see section 
III.B of this preamble).
    The EPA conducts a risk assessment that provides estimates of the 
MIR for cancer posed by the HAP emissions from each source in the 
source category, the HI for chronic exposures to HAP with the potential 
to cause noncancer health effects, and the HQ for acute exposures to 
HAP with the potential to cause noncancer health effects. The 
assessment also provides estimates of the distribution of cancer risk 
within the exposed populations, cancer incidence, and an evaluation of 
the potential for an adverse environmental effect. The eight sections 
that follow this paragraph describe how we estimated emissions and 
conducted the risk assessment. The docket for this rulemaking contains 
the following documents which provide more information on the risk 
assessment inputs and models: Residual Risk Assessment for the SOCMI 
Source Category in Support of the 2023 Risk and Technology Review 
Proposed Rule and Residual Risk Assessment for the Polymers & Resins I 
Neoprene Production Source Category in Support of the 2023 Risk and 
Technology Review Proposed Rule. The methods used to assess risk (as 
described in the eight primary steps below) are consistent with those 
described by the EPA in the document reviewed by a panel of the EPA's 
SAB in 2009; \25\ and described in the SAB review report issued in 
2010. They are also consistent with the key recommendations contained 
in that report.
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    \25\ U.S. EPA. Risk and Technology Review (RTR) Risk Assessment 
Methodologies: For Review by the EPA's Science Advisory Board with 
Case Studies--MACT I Petroleum Refining Sources and Portland Cement 
Manufacturing, June 2009. EPA-452/R-09-006. https://www3.epa.gov/airtoxics/rrisk/rtrpg.html.
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1. How did we estimate actual emissions and identify the emissions 
release characteristics?
    As previously discussed, we updated the risk assessment in this 
action for the SOCMI and Neoprene Production source categories because 
these source categories have sources that emit EtO and/or chloroprene. 
The SOCMI and Neoprene Production source category facility lists were 
developed as described in section II.C of this preamble and consist of 
207 HON facilities and one neoprene production facility.\26\ For the 
207 HON facilities, only 195 had reported HAP emissions in the 2017 
NEI, and we note that two facilities included in the 207 are new/under 
construction and were not operating in 2017. The emissions modeling 
input files were developed using the EPA's 2017 NEI. However, in a few 
instances where facility-specific

[[Page 25097]]

data were not available or not reflective of current controls in the 
2017 NEI, we attempted to obtain data from a more recent dataset (e.g., 
review of emissions inventory data from our CAA section 114 request, 
more recent inventories submitted to states, or 2018 NEI). Of note, for 
the one neoprene production facility (which is also part of the SOCMI 
source category), we used the 2019 emissions inventory that was 
provided to the EPA from our CAA section 114 request. The NEI data were 
also used to develop the other parameters needed to perform the risk 
modeling analysis, including the emissions release characteristics, 
such as stack heights, stack diameters, flow rates, temperatures, and 
emission release point locations. For further details on the 
assumptions and methodologies used to estimate actual emissions, see 
Appendix 1 of the document titled Residual Risk Assessment for the 
SOCMI Source Category in Support of the 2023 Risk and Technology Review 
Proposed Rule, which is available in the docket for this rulemaking.
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    \26\ The one neoprene production facility also has collocated 
HON emissions sources from the production of chloroprene.
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2. How did we estimate MACT-allowable emissions?
    The available emissions data in the RTR emissions dataset include 
estimates of the mass of HAP emitted during a specified annual time 
period. These ``actual'' emission levels are often lower than the 
emission levels allowed under the requirements of the current MACT 
standards. The emissions allowed under the MACT standards are referred 
to as the ``MACT-allowable'' emissions. We discussed the consideration 
of both MACT-allowable and actual emissions in the final Coke Oven 
Batteries RTR (70 FR 19992, 19998-19999, April 15, 2005) and in the 
proposed and final HON RTR (71 FR 34421, 34428, June 14, 2006, and 71 
FR 76603, 76609, December 21, 2006, respectively). In those actions, we 
noted that assessing the risk at the MACT-allowable level is inherently 
reasonable since that risk reflects the maximum level facilities could 
emit and still comply with national emission standards. We also 
explained that it is reasonable to consider actual emissions, where 
such data are available, in both steps of the risk analysis, in 
accordance with the 1989 Benzene NESHAP approach. (54 FR 38044.)
    For this analysis, we have determined that the actual emissions 
data are reasonable estimates of the MACT-allowable emissions levels 
for the SOCMI source category, as we are not generally aware of any 
situations in which a facility is conducting additional work practices 
or operating a control device such that it achieves a far greater 
emission reduction than required by the NESHAP. For the Neoprene 
Production source category, we do know that some emission sources 
(e.g., process vents) are being controlled beyond the current level of 
the NESHAP standards. However, because there is only one facility in 
the source category and because we are proposing to require these same 
control requirements in this action, we consider these to be part of 
the baseline actual emissions. We are also not aware of the neoprene 
production facility over-controlling fugitive emission sources, which 
tend to be the predominant risk drivers for this source category. We 
note that because of the difficulty and uncertainty around comparing 
fugitive emissions reported in emission inventories (i.e., assumptions 
and engineering calculations are generally used for fugitive emissions 
in emissions inventories since it is not practicable to measure them 
due to technological and economic limitations) to the MACT standards 
for both the SOCMI and Neoprene Production source categories and 
whether facilities are better controlling these emissions sources since 
they tend to drive risks, a separate assessment of risk for allowable 
emissions appears unnecessary given the finding that risks are 
unacceptable based on actual emissions (see section III.B of this 
preamble). For further details on the assumptions and methodologies 
used to estimate MACT-allowable emissions, see Appendix 1 of the 
document titled Residual Risk Assessment for the SOCMI Source Category 
in Support of the 2023 Risk and Technology Review Proposed Rule, which 
is available in the docket for this rulemaking.
3. How do we conduct dispersion modeling, determine inhalation 
exposures, and estimate individual and population inhalation risk?
    Both long-term and short-term inhalation exposure concentrations 
and health risk from the source category addressed in this proposal 
were estimated using the Human Exposure Model (HEM).\27\ The HEM 
performs three primary risk assessment activities: (1) Conducting 
dispersion modeling to estimate the concentrations of HAP in ambient 
air, (2) estimating long-term and short-term inhalation exposures to 
individuals residing within 50 kilometers (km) (~31 miles) of the 
modeled sources, and (3) estimating individual and population-level 
inhalation risk using the exposure estimates and quantitative dose-
response information.
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    \27\ For more information about HEM, go to https://www.epa.gov/fera/risk-assessment-and-modeling-human-exposure-model-hem.
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a. Dispersion Modeling
    The EPA's American Meteorological Society/EPA Regulatory Model 
dispersion modeling system (AERMOD), used by the HEM, is one of the 
EPA's preferred models for assessing air pollutant concentrations from 
industrial facilities.\28\ To perform the dispersion modeling and to 
develop the preliminary risk estimates, HEM draws on three data 
libraries. The first is a library of meteorological data, which is used 
for dispersion calculations. This library includes hourly surface and 
upper air observations for years ranging from 2016-2019 from over 800 
meteorological stations, selected to provide coverage of the United 
States and Puerto Rico. A second library of United States Census Bureau 
census block \29\ internal point locations and populations provides the 
basis of human exposure calculations (U.S. Census, 2010). In addition, 
for each census block, the census library includes the elevation and 
controlling hill height, which are also used in dispersion 
calculations. A third library of pollutant-specific dose-response 
values is used to estimate health risk. These are discussed below.
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    \28\ U.S. EPA. Revision to the Guideline on Air Quality Models: 
Adoption of a Preferred General Purpose (Flat and Complex Terrain) 
Dispersion Model and Other Revisions (70 FR 68218, November 9, 
2005).
    \29\ A census block is the smallest geographic area for which 
census statistics are tabulated.
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b. Risk From Chronic Exposure to HAP
    In developing the risk assessment for chronic exposures, we use the 
estimated annual average ambient air concentrations of each HAP emitted 
by each source in the source category. The HAP air concentrations at 
each nearby census block centroid located within 50 km (~31 miles) of 
the facility are a surrogate for the chronic inhalation exposure 
concentration for all the people who reside in that census block. A 
distance of 50 km is consistent with both the analysis supporting the 
1989 Benzene NESHAP (54 FR 38044) and the limitations of Gaussian 
dispersion models, including AERMOD.
    For each facility, we calculate the MIR as the cancer risk 
associated with a continuous lifetime (24 hours per day, 7 days per 
week, 52 weeks per year, 70 years) exposure to the maximum 
concentration at the centroid of each inhabited census block. We 
calculate individual cancer risk by multiplying the estimated lifetime 
exposure to the

[[Page 25098]]

ambient concentration of each HAP (in micrograms per cubic meter 
([mu]g/m\3\) by its URE. The URE is an upper-bound estimate of an 
individual's incremental risk of contracting cancer over a lifetime of 
exposure to a concentration of 1 microgram of the pollutant per cubic 
meter of air. For residual risk assessments, we generally use UREs from 
the EPA's IRIS. For carcinogenic pollutants without IRIS values, we 
look to other reputable sources of cancer dose-response values, often 
using California EPA (CalEPA) UREs, where available. In cases where 
new, scientifically credible dose-response values have been developed 
in a manner consistent with EPA guidelines and have undergone a peer 
review process similar to that used by the EPA, we may use such dose-
response values in place of, or in addition to, other values, if 
appropriate. The pollutant-specific dose-response values used to 
estimate health risk are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants.
    To estimate individual lifetime cancer risks associated with 
exposure to HAP emissions from each facility in the source category, we 
sum the risks for each of the carcinogenic HAP \30\ emitted by the 
modeled facility. We estimate cancer risk at every census block within 
50 km of every facility in the source category. The MIR is the highest 
individual lifetime cancer risk estimated for any of those census 
blocks. In addition to calculating the MIR, we estimate the 
distribution of individual cancer risks for the source category by 
summing the number of individuals within 50 km of the sources whose 
estimated risk falls within a specified risk range. We also estimate 
annual cancer incidence by multiplying the estimated lifetime cancer 
risk at each census block by the number of people residing in that 
block, summing results for all of the census blocks, and then dividing 
this result by a 70-year lifetime.
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    \30\ The EPA's 2005 Guidelines for Carcinogen Risk Assessment 
classifies carcinogens as: ``carcinogenic to humans,'' ``likely to 
be carcinogenic to humans,'' and ``suggestive evidence of 
carcinogenic potential.'' These classifications also coincide with 
the terms ``known carcinogen, probable carcinogen, and possible 
carcinogen,'' respectively, which are the terms advocated in the 
EPA's Guidelines for Carcinogen Risk Assessment, published in 1986 
(51 FR 33992, September 24, 1986). In August 2000, the document, 
Supplemental Guidance for Conducting Health Risk Assessment of 
Chemical Mixtures (EPA/630/R-00/002), was published as a supplement 
to the 1986 document. Copies of both documents can be obtained from 
https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=20533&CFID=70315376&CFTOKEN=71597944. Summing 
the risk of these individual compounds to obtain the cumulative 
cancer risk is an approach that was recommended by the EPA's SAB in 
their 2002 peer review of the EPA's National Air Toxics Assessment 
(NATA) titled NATA--Evaluating the National-scale Air Toxics 
Assessment 1996 Data--an SAB Advisory, available at https://
yosemite.epa.gov/sab/sabproduct.nsf/
214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf.
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    To assess the risk of noncancer health effects from chronic 
exposure to HAP, we calculate either an HQ or a target organ-specific 
hazard index (TOSHI). We calculate an HQ when a single noncancer HAP is 
emitted. Where more than one noncancer HAP is emitted, we sum the HQ 
for each of the HAP that affects a common target organ or target organ 
system to obtain a TOSHI. The HQ is the estimated exposure divided by 
the chronic noncancer dose-response value, which is a value selected 
from one of several sources. The preferred chronic noncancer dose-
response value is the EPA RfC, defined as ``an estimate (with 
uncertainty spanning perhaps an order of magnitude) of a continuous 
inhalation exposure to the human population (including sensitive 
subgroups) that is likely to be without an appreciable risk of 
deleterious effects during a lifetime'' (https://iaspub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&vocabName=IRIS%20Glossary). In cases where an RfC 
from the EPA's IRIS is not available or where the EPA determines that 
using a value other than the RfC is appropriate, the chronic noncancer 
dose-response value can be a value from the following prioritized 
sources, which define their dose-response values similarly to the EPA: 
(1) The Agency for Toxic Substances and Disease Registry (ATSDR) 
Minimal Risk Level (https://www.atsdr.cdc.gov/mrls/); (2) the CalEPA 
Chronic Reference Exposure Level (REL) (https://oehha.ca.gov/air/crnr/notice-adoption-air-toxics-hot-spots-program-guidance-manual-preparation-health-risk-0); or (3) as noted above, a scientifically 
credible dose-response value that has been developed in a manner 
consistent with the EPA guidelines and has undergone a peer review 
process similar to that used by the EPA. The pollutant-specific dose-
response values used to estimate health risks are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants.
c. Risk From Acute Exposure to HAP That May Cause Health Effects Other 
Than Cancer
    For each HAP for which appropriate acute inhalation dose-response 
values are available, the EPA also assesses the potential health risks 
due to acute exposure. For these assessments, the EPA makes 
conservative assumptions about emission rates, meteorology, and 
exposure location. As part of our efforts to continually improve our 
methodologies to evaluate the risks that HAP emitted from categories of 
industrial sources pose to human health and the environment,\31\ we 
revised our treatment of meteorological data to use reasonable worst-
case air dispersion conditions in our acute risk screening assessments 
instead of worst-case air dispersion conditions. This revised treatment 
of meteorological data and the supporting rationale are described in 
more detail in the documents titled Residual Risk Assessment for the 
SOCMI Source Category in Support of the 2023 Risk and Technology Review 
Proposed Rule and Residual Risk Assessment for the Polymers & Resins I 
Neoprene Production Source Category in Support of the 2023 Risk and 
Technology Review Proposed Rule, and in Appendix 5 of the report: 
Technical Support Document for Acute Risk Screening Assessment, which 
are available in the docket for this rulemaking. This revised approach 
has been used in this proposed rule and in all other RTR rulemakings 
proposed on or after June 3, 2019.
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    \31\ See, e.g., U.S. EPA. Screening Methodologies to Support 
Risk and Technology Reviews (RTR): A Case Study Analysis (Draft 
Report, May 2017. (https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html).
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    To assess the potential acute risk to the maximally exposed 
individual, we use the peak hourly emission rate for each emission 
point,\32\ reasonable worst-case air dispersion conditions (i.e., 99th 
percentile), and the point of highest off-site exposure. Specifically, 
we assume that peak emissions from the source category and reasonable 
worst-case air dispersion conditions co-occur

[[Page 25099]]

and that a person is present at the point of maximum exposure.
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    \32\ In the absence of hourly emission data, we develop 
estimates of maximum hourly emission rates by multiplying the 
average actual annual emissions rates by a factor (either a 
category-specific factor or a default factor of 10) to account for 
variability. This is documented in Residual Risk Assessment for the 
SOCMI Source Category in Support of the 2023 Risk and Technology 
Review Proposed Rule, Residual Risk Assessment for the Polymers & 
Resins I Neoprene Production Source Category in Support of the 2023 
Risk and Technology Review Proposed Rule, and in Appendix 5 of the 
report: Technical Support Document for Acute Risk Screening 
Assessment. All three of these documents are available in the docket 
for this rulemaking.
---------------------------------------------------------------------------

    To characterize the potential health risks associated with 
estimated acute inhalation exposures to a HAP, we generally use 
multiple acute dose-response values, including acute RELs, acute 
exposure guideline levels (AEGLs), and emergency response planning 
guidelines (ERPG) for 1-hour exposure durations, if available, to 
calculate acute HQs. The acute HQ is calculated by dividing the 
estimated acute exposure concentration by the acute dose-response 
value. For each HAP for which acute dose-response values are available, 
the EPA calculates acute HQs.
    An acute REL is defined as ``the concentration level at or below 
which no adverse health effects are anticipated for a specified 
exposure duration.'' \33\ Acute RELs are based on the most sensitive, 
relevant, adverse health effect reported in the peer-reviewed medical 
and toxicological literature. They are designed to protect the most 
sensitive individuals in the population through the inclusion of 
margins of safety. Because margins of safety are incorporated to 
address data gaps and uncertainties, exceeding the REL does not 
automatically indicate an adverse health impact. AEGLs represent 
threshold exposure limits for the general public and are applicable to 
emergency exposures ranging from 10 minutes to 8 hours.\34\ They are 
guideline levels for ``once-in-a-lifetime, short-term exposures to 
airborne concentrations of acutely toxic, high-priority chemicals.'' 
Id. at 21. The AEGL-1 is specifically defined as ``the airborne 
concentration (expressed as ppm (parts per million) or mg/m\3\ 
(milligrams per cubic meter)) of a substance above which it is 
predicted that the general population, including susceptible 
individuals, could experience notable discomfort, irritation, or 
certain asymptomatic nonsensory effects. However, the effects are not 
disabling and are transient and reversible upon cessation of 
exposure.'' The document also notes that ``Airborne concentrations 
below AEGL-1 represent exposure levels that can produce mild and 
progressively increasing but transient and nondisabling odor, taste, 
and sensory irritation or certain asymptomatic, nonsensory effects.'' 
Id. AEGL-2 are defined as ``the airborne concentration (expressed as 
parts per million or milligrams per cubic meter) of a substance above 
which it is predicted that the general population, including 
susceptible individuals, could experience irreversible or other 
serious, long-lasting adverse health effects or an impaired ability to 
escape.'' Id.
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    \33\ CalEPA issues acute RELs as part of its Air Toxics Hot 
Spots Program, and the 1-hour and 8-hour values are documented in 
Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The 
Determination of Acute Reference Exposure Levels for Airborne 
Toxicants, which is available at https://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-rel-summary.
    \34\ National Academy of Sciences, 2001. Standing Operating 
Procedures for Developing Acute Exposure Levels for Hazardous 
Chemicals, page 2. Available at https://www.epa.gov/sites/production/files/2015-09/documents/sop_final_standing_operating_procedures_2001.pdf. Note that the 
National Advisory Committee for Acute Exposure Guideline Levels for 
Hazardous Substances ended in October 2011, but the AEGL program 
continues to operate at the EPA and works with the National 
Academies to publish final AEGLs (https://www.epa.gov/aegl).
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    ERPGs are developed, by the American Industrial Hygiene Association 
(AIHA), for emergency planning and are intended to be health-based 
guideline concentrations for single exposures to chemicals. The ERPG-1 
is the maximum airborne concentration, established by AIHA, below which 
it is believed that nearly all individuals could be exposed for up to 1 
hour without experiencing other than mild transient adverse health 
effects or without perceiving a clearly defined, objectionable odor. 
Similarly, the ERPG-2 is the maximum airborne concentration, 
established by AIHA, below which it is believed that nearly all 
individuals could be exposed for up to one hour without experiencing or 
developing irreversible or other serious health effects or symptoms 
which could impair an individual's ability to take protective action.
    An acute REL for 1-hour exposure durations is typically lower than 
its corresponding AEGL-1 and ERPG-1. Even though their definitions are 
slightly different, AEGL-1s are often the same as the corresponding 
ERPG-1s, and AEGL-2s are often equal to ERPG-2s. The maximum HQs from 
our acute inhalation screening risk assessment typically result when we 
use the acute REL for a HAP. In cases where the maximum acute HQ 
exceeds 1, we also report the HQ based on the next highest acute dose-
response value (usually the AEGL-1 and/or the ERPG-1).
    For the SOCMI and Neoprene Production source categories, we did not 
use a default acute emissions multiplier of 10, but rather, we used 
process level-specific acute emissions multipliers, generally ranging 
from a factor of 2 to 10 as was done in past chemical and petrochemical 
residual risk reviews such as for the 2015 the Petroleum Refinery 
Sector rule, 2020 MON RTR, 2020 EMACT RTR, and 2020 OLD NESHAP RTR, 
where similar emission sources and standards exist. These refinements 
are discussed more fully in Appendix 1 of the document titled Residual 
Risk Assessment for the SOCMI Source Category in Support of the 2023 
Risk and Technology Review Proposed Rule, which is available in the 
docket for this rulemaking.
    In our acute inhalation screening risk assessment, acute impacts 
are deemed negligible for HAP for which acute HQs are less than or 
equal to 1, and no further analysis is performed for these HAP. In 
cases where an acute HQ from the screening step is greater than 1, we 
assess the site-specific data to ensure that the acute HQ is at an off-
site location. For these source categories, the data refinements 
employed consisted of reviewing satellite imagery of the locations of 
the maximum acute HQ values to determine if the maximum was off 
facility property. For any maximum value that was determined to be on 
facility property, the next highest value that was off facility 
property was used. These refinements are discussed more fully in the 
documents titled Residual Risk Assessment for the SOCMI Source Category 
in Support of the 2023 Risk and Technology Review Proposed Rule and 
Residual Risk Assessment for the Polymers & Resins I Neoprene 
Production Source Category in Support of the 2023 Risk and Technology 
Review Proposed Rule, which are available in the docket for this 
rulemaking.
4. How do we conduct the multipathway exposure and risk screening 
assessment?
    The EPA conducts a tiered screening assessment examining the 
potential for significant human health risks due to exposures via 
routes other than inhalation (i.e., ingestion). We first determine 
whether any sources in the source categories emit any HAP known to be 
persistent and bioaccumulative in the environment, as identified in the 
EPA's Air Toxics Risk Assessment Library (see Volume 1, Appendix D, at 
https://www.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library).
    For the Neoprene Production source category, we did not identify 
emissions of any PB-HAP in the reported emissions inventory. Because we 
did not identify reported PB-HAP emissions, we could not undertake the 
three-tier human health risk screening assessment of PB-HAP that we 
discuss below and which was conducted for the SOCMI source category. 
However, for dioxins we used the results of the SOCMI source category 
human health screening assessment at facilities with higher dioxin 
emission rates than the

[[Page 25100]]

ones proposed for the Neoprene Production source category to 
qualitatively assess the potential for human health risks.
    For the SOCMI source category, we identified PB-HAP emissions of 
arsenic compounds, cadmium compounds, dioxins, polycyclic organic 
matter (POM), and mercury, so we proceeded to the next step of the 
evaluation. Except for lead, the human health risk screening assessment 
for PB-HAP consists of three progressive tiers. In a Tier 1 screening 
assessment, we determine whether the magnitude of the facility-specific 
emissions of PB-HAP warrants further evaluation to characterize human 
health risk through ingestion exposure. To facilitate this step, we 
evaluate emissions against previously developed screening threshold 
emission rates for several PB-HAP that are based on a hypothetical 
upper-end screening exposure scenario developed for use in conjunction 
with the EPA's Total Risk Integrated Methodology.Fate, Transport, and 
Ecological Exposure (TRIM.FaTE) model. The PB-HAP with screening 
threshold emission rates are arsenic compounds, cadmium compounds, 
chlorinated dibenzodioxins and furans, mercury compounds, and POM. 
Based on the EPA estimates of toxicity and bioaccumulation potential, 
these pollutants represent a conservative list for inclusion in 
multipathway risk assessments for RTR rules. (See Volume 1, Appendix D 
at https://www.epa.gov/sites/production/files/2013-08/documents/volume_1_reflibrary.pdf.) In this assessment, we compare the facility-
specific emission rates of these PB-HAP to the screening threshold 
emission rates for each PB-HAP to assess the potential for significant 
human health risks via the ingestion pathway. We call this application 
of the TRIM.FaTE model the Tier 1 screening assessment. The ratio of a 
facility's actual emission rate to the Tier 1 screening threshold 
emission rate is a ``screening value.''
    We derive the Tier 1 screening threshold emission rates for these 
PB-HAP (other than lead compounds) to correspond to a maximum excess 
lifetime cancer risk of 1-in-1 million (i.e., for arsenic compounds, 
polychlorinated dibenzodioxins and furans, and POM) or, for HAP that 
cause noncancer health effects (i.e., cadmium compounds and mercury 
compounds), a maximum HQ of 1. If the emission rate of any one PB-HAP 
or combination of carcinogenic PB-HAP in the Tier 1 screening 
assessment exceeds the Tier 1 screening threshold emission rate for any 
facility (i.e., the screening value is greater than 1), we conduct a 
second screening assessment, which we call the Tier 2 screening 
assessment. The Tier 2 screening assessment separates the Tier 1 
combined fisher and farmer exposure scenario into fisher, farmer, and 
gardener scenarios that retain upper-bound ingestion rates.
    In the Tier 2 screening assessment, the location of each facility 
that exceeds a Tier 1 screening threshold emission rate is used to 
refine the assumptions associated with the Tier 1 fisher and farmer 
exposure scenarios at that facility. A key assumption in the Tier 1 
screening assessment is that a lake and/or farm is located near the 
facility. As part of the Tier 2 screening assessment, we use a U.S. 
Geological Survey (USGS) database to identify actual waterbodies within 
50 km (~31 miles) of each facility and assume the fisher only consumes 
fish from lakes within that 50 km zone. We also examine the differences 
between local meteorology near the facility and the meteorology used in 
the Tier 1 screening assessment. We then adjust the previously-
developed Tier 1 screening threshold emission rates for each PB-HAP for 
each facility based on an understanding of how exposure concentrations 
estimated for the screening scenario change with the use of local 
meteorology and the USGS lakes database.
    In the Tier 2 farmer scenario, we maintain an assumption that the 
farm is located within 0.5 km (~0.3 miles) of the facility and that the 
farmer consumes meat, eggs, dairy, vegetables, and fruit produced near 
the facility. We may further refine the Tier 2 screening analysis by 
assessing a gardener scenario to characterize a range of exposures, 
with the gardener scenario being more plausible in RTR evaluations. 
Under the gardener scenario, we assume the gardener consumes home-
produced eggs, vegetables, and fruit products at the same ingestion 
rate as the farmer. The Tier 2 screen continues to rely on the high-end 
food intake assumptions that were applied in Tier 1 for local fish 
(adult female angler at 99th percentile fish consumption \35\) and 
locally grown or raised foods (90th percentile consumption of locally 
grown or raised foods for the farmer and gardener scenarios \36\). If 
PB-HAP emission rates do not result in a Tier 2 screening value greater 
than 1, we consider those PB-HAP emissions to pose risks below a level 
of concern. If the PB-HAP emission rates for a facility exceed the Tier 
2 screening threshold emission rates, we may conduct a Tier 3 screening 
assessment.
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    \35\ Burger, J. 2002. Daily consumption of wild fish and game: 
Exposures of high end recreationists. International Journal of 
Environmental Health Research, 12:343-354.
    \36\ U.S. EPA. Exposure Factors Handbook 2011 Edition (Final). 
U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/
052F, 2011.
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    There are several analyses that can be included in a Tier 3 
screening assessment, depending upon the extent of refinement 
warranted, including validating that the lakes are fishable, locating 
residential/garden locations for urban and/or rural settings, 
considering plume-rise to estimate emissions lost above the mixing 
layer, and considering hourly effects of meteorology and plume-rise on 
chemical fate and transport (a time-series analysis). If necessary, the 
EPA may further refine the screening assessment through a site-specific 
assessment.
    In evaluating the potential multipathway risk from emissions of 
lead compounds, rather than developing a screening threshold emission 
rate, we compare maximum estimated chronic inhalation exposure 
concentrations to the level of the current National Ambient Air Quality 
Standard (NAAQS) for lead.\37\ Values below the level of the primary 
(health-based) lead NAAQS are considered to have a low potential for 
multipathway risk.
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    \37\ In doing so, the EPA notes that the legal standard for a 
primary NAAQS--that a standard is requisite to protect public health 
and provide an adequate margin of safety (CAA section 109(b))--
differs from the CAA section 112(f) standard (requiring, among other 
things, that the standard provide an ``ample margin of safety to 
protect public health''). However, the primary lead NAAQS is a 
reasonable measure of determining risk acceptability (i.e., the 
first step of the 1989 Benzene NESHAP analysis) since it is designed 
to protect the most susceptible group in the human population--
children, including children living near major lead emitting 
sources. 73 FR 67002/3; 73 FR 67000/3; 73 FR 67005/1. In addition, 
applying the level of the primary lead NAAQS at the risk 
acceptability step is conservative, since that primary lead NAAQS 
reflects an adequate margin of safety.
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    For further information on the multipathway assessment approach, 
see the documents titled Residual Risk Assessment for the SOCMI Source 
Category in Support of the 2023 Risk and Technology Review Proposed 
Rule and Residual Risk Assessment for the Polymers & Resins I Neoprene 
Production Source Category in Support of the 2023 Risk and Technology 
Review Proposed Rule, which are available in the docket for this 
rulemaking.
5. How do we assess risks considering emissions control options?
    In addition to assessing baseline inhalation risks and screening 
for potential multipathway risks, we also estimate risks considering 
the potential

[[Page 25101]]

emission reductions that would be achieved by the control options under 
consideration. In these cases, the expected emission reductions are 
applied to the specific HAP and emission points in the RTR emissions 
dataset to develop corresponding estimates of risk and incremental risk 
reductions.
6. How do we conduct the environmental risk screening assessment?
a. Adverse Environmental Effect, Environmental HAP, and Ecological 
Benchmarks
    The EPA conducts a screening assessment to examine the potential 
for an adverse environmental effect as required under section 
112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA defines ``adverse 
environmental effect'' as ``any significant and widespread adverse 
effect, which may reasonably be anticipated, to wildlife, aquatic life, 
or other natural resources, including adverse impacts on populations of 
endangered or threatened species or significant degradation of 
environmental quality over broad areas.''
    The EPA focuses on eight HAP, which are referred to as 
``environmental HAP,'' in its screening assessment: six PB-HAP and two 
acid gases. The PB-HAP included in the screening assessment are arsenic 
compounds, cadmium compounds, dioxins/furans, POM, mercury (both 
inorganic mercury and methyl mercury), and lead compounds. The acid 
gases included in the screening assessment are hydrochloric acid (HCl) 
and hydrofluoric acid (HF).
    HAP that persist and bioaccumulate are of particular environmental 
concern because they accumulate in the soil, sediment, and water. The 
acid gases, HCl and HF, are included due to their well-documented 
potential to cause direct damage to terrestrial plants. In the 
environmental risk screening assessment, we evaluate the following four 
exposure media: terrestrial soils, surface water bodies (includes 
water-column and benthic sediments), fish consumed by wildlife, and 
air. Within these four exposure media, we evaluate nine ecological 
assessment endpoints, which are defined by the ecological entity and 
its attributes. For PB-HAP (other than lead), both community-level and 
population-level endpoints are included. For acid gases, the ecological 
assessment evaluated is terrestrial plant communities.
    An ecological benchmark represents a concentration of HAP that has 
been linked to a particular environmental effect level. For each 
environmental HAP, we identified the available ecological benchmarks 
for each assessment endpoint. We identified, where possible, ecological 
benchmarks at the following effect levels: probable effect levels, 
lowest-observed-adverse-effect level, and no-observed-adverse-effect 
level. In cases where multiple effect levels were available for a 
particular PB-HAP and assessment endpoint, we use all of the available 
effect levels to help us to determine whether ecological risks exist 
and, if so, whether the risks could be considered significant and 
widespread.
    For further information on how the environmental risk screening 
assessment was conducted, including a discussion of the risk metrics 
used, how the environmental HAP were identified, and how the ecological 
benchmarks were selected, see Appendix 9 of the documents titled 
Residual Risk Assessment for the SOCMI Source Category in Support of 
the 2023 Risk and Technology Review Proposed Rule and Residual Risk 
Assessment for the Polymers & Resins I Neoprene Production Source 
Category in Support of the 2023 Risk and Technology Review Proposed 
Rule, which are available in the docket for this rulemaking.
b. Environmental Risk Screening Methodology
    For the environmental risk screening assessment, the EPA first 
determined whether any facilities in the SOCMI and Neoprene Production 
source categories emitted any of the environmental HAP. For the 
Neoprene Production source category, we did not identify reported 
emissions of any of the six environmental HAP included in the screen. 
Because we did not identify reported environmental HAP emissions from 
the neoprene source category, we could not proceed to the second step 
of the evaluation as discussed below for the HON. However, for dioxins 
we used the results of the SOCMI source category environmental risk 
screening assessment at facilities with higher dioxin emission rates 
than the ones proposed for the Neoprene Production source category to 
qualitative assess the potential for adverse environmental effects.
    For the SOCMI source category, we identified reported emissions of 
arsenic compounds, cadmium compounds, dioxins, POM, and mercury.\38\ 
Because one or more of the environmental HAP evaluated are emitted by 
at least one facility in the SOCMI source category, we proceeded to the 
second step of the evaluation.
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    \38\ We note that in many instances, we did not have sufficient 
information to parse out emissions from HON processes from facility-
wide emissions inventories, thus we took a conservative approach and 
modeled facility-wide emissions as if they were all from the SOCMI 
source category.
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c. PB-HAP Methodology
    The environmental screening assessment includes six PB-HAP, arsenic 
compounds, cadmium compounds, dioxins/furans, POM, mercury (both 
inorganic mercury and methyl mercury), and lead compounds. With the 
exception of lead, the environmental risk screening assessment for PB-
HAP consists of three tiers. The first tier of the environmental risk 
screening assessment uses the same health-protective conceptual model 
that is used for the Tier 1 human health screening assessment. 
TRIM.FaTE model simulations were used to back-calculate Tier 1 
screening threshold emission rates. The screening threshold emission 
rates represent the emission rate in tons of pollutant per year that 
results in media concentrations at the facility that equal the relevant 
ecological benchmark. To assess emissions from each facility in the 
category, the reported emission rate for each PB-HAP was compared to 
the Tier 1 screening threshold emission rate for that PB-HAP for each 
assessment endpoint and effect level. If emissions from a facility do 
not exceed the Tier 1 screening threshold emission rate, the facility 
``passes'' the screening assessment, and, therefore, is not evaluated 
further under the screening approach. If emissions from a facility 
exceed the Tier 1 screening threshold emission rate, we evaluate the 
facility further in Tier 2.
    In Tier 2 of the environmental screening assessment, the screening 
threshold emission rates are adjusted to account for local meteorology 
and the actual location of lakes in the vicinity of facilities that did 
not pass the Tier 1 screening assessment. For soils, we evaluate the 
average soil concentration for all soil parcels within a 7.5-km radius 
for each facility and PB-HAP. For the water, sediment, and fish tissue 
concentrations, the highest value for each facility for each pollutant 
is used. If emission concentrations from a facility do not exceed the 
Tier 2 screening threshold emission rate, the facility ``passes'' the 
screening assessment and typically is not evaluated further. If 
emissions from a facility exceed the Tier 2 screening threshold 
emission rate, we evaluate the facility further in Tier 3.
    As in the multipathway human health risk assessment, in Tier 3 of 
the environmental screening assessment, we examine the suitability of 
the lakes

[[Page 25102]]

around the facilities to support life and remove those that are not 
suitable (e.g., lakes that have been filled in or are industrial 
ponds), adjust emissions for plume-rise, and conduct hour-by-hour time-
series assessments. If these Tier 3 adjustments to the screening 
threshold emission rates still indicate the potential for an adverse 
environmental effect (i.e., facility emission rate exceeds the 
screening threshold emission rate), we may elect to conduct a more 
refined assessment using more site-specific information. If, after 
additional refinement, the facility emission rate still exceeds the 
screening threshold emission rate, the facility may have the potential 
to cause an adverse environmental effect.
    To evaluate the potential for an adverse environmental effect from 
lead, we compared the average modeled air concentrations (from HEM-3) 
of lead around each facility in the source category to the level of the 
secondary NAAQS for lead. The secondary lead NAAQS is a reasonable 
means of evaluating environmental risk because it is set to provide 
substantial protection against adverse welfare effects which can 
include ``effects on soils, water, crops, vegetation, man-made 
materials, animals, wildlife, weather, visibility and climate, damage 
to and deterioration of property, and hazards to transportation, as 
well as effects on economic values and on personal comfort and well-
being.''
d. Acid Gas Environmental Risk Methodology
    The environmental screening assessment for acid gases evaluates the 
potential phytotoxicity and reduced productivity of plants due to 
chronic exposure to HF and HCl. The environmental risk screening 
methodology for acid gases is a single-tier screening assessment that 
compares modeled ambient air concentrations (from AERMOD) to the 
ecological benchmarks for each acid gas. To identify a potential 
adverse environmental effect (as defined in section 112(a)(7) of the 
CAA) from emissions of HF and HCl, we evaluate the following metrics: 
the size of the modeled area around each facility that exceeds the 
ecological benchmark for each acid gas, in acres and square km; the 
percentage of the modeled area around each facility that exceeds the 
ecological benchmark for each acid gas; and the area-weighted average 
screening value around each facility (calculated by dividing the area-
weighted average concentration over the 50-km modeling domain by the 
ecological benchmark for each acid gas). For further information on the 
environmental screening assessment approach, see Appendix 9 of the 
documents titled Residual Risk Assessment for the SOCMI Source Category 
in Support of the 2023 Risk and Technology Review Proposed Rule and 
Residual Risk Assessment for the Polymers & Resins I Neoprene 
Production Source Category in Support of the 2023 Risk and Technology 
Review Proposed Rule, which are available in the docket for this 
rulemaking.
7. How do we conduct facility-wide assessments?
    To put the source category risks in context, we typically examine 
the risks from the entire ``facility,'' where the facility includes all 
HAP-emitting operations within a contiguous area and under common 
control. In other words, we examine the HAP emissions not only from the 
source category emission points of interest, but also emissions of HAP 
from all other emission sources at the facility for which we have data. 
For these source categories, we conducted the facility-wide assessment 
using a dataset compiled from the 2017 NEI and other emissions 
information discussed in section II.C of this preamble. Once a quality 
assured source category dataset was available, it was placed back with 
the remaining records from the emissions inventory for that facility 
(which in most instances was 2017 NEI data). The facility-wide file was 
then used to analyze risks due to the inhalation of HAP that are 
emitted ``facility-wide'' for the populations residing within 50 km 
(~31 miles) of each facility, consistent with the methods used for the 
source category analysis described above. For these facility-wide risk 
analyses, the modeled source category risks were compared to the 
facility-wide risks to determine the portion of the facility-wide risks 
that could be attributed to the source category addressed in this 
proposal. We also specifically examined the facility that was 
associated with the highest estimate of risk and determined the 
percentage of that risk attributable to the source category of 
interest. The documents titled Residual Risk Assessment for the SOCMI 
Source Category in Support of the 2023 Risk and Technology Review 
Proposed Rule and Residual Risk Assessment for the Polymers & Resins I 
Neoprene Production Source Category in Support of the 2023 Risk and 
Technology Review Proposed Rule, available through the docket for this 
rulemaking, provide the methodology and results of the facility-wide 
analyses, including all facility-wide risks and the percentage of 
source category contribution to facility-wide risks.
8. How do we conduct community-based risk assessments?
    In addition to the source category and facility-wide risk 
assessments, we also assessed the combined inhalation cancer risk from 
all local stationary sources of HAP for which we have emissions data. 
Specifically, we combined the modeled impacts from the facility-wide 
assessment (which includes category and non-category sources) with 
other nearby stationary point source model results. The facility-wide 
emissions used in this assessment are discussed in section II.C of this 
preamble. For the other nearby point sources, we used AERMOD model 
results with emissions based primarily on the 2018 NEI. After combining 
these model results, we assessed cancer risks due to the inhalation of 
all HAP emitted by point sources for the populations residing within 10 
km (~6.2 miles) of HON facilities. In the community-based risk 
assessment, the modeled source category and facility-wide cancer risks 
were compared to the cancer risks from other nearby point sources to 
determine the portion of the risks that could be attributed to the 
source category addressed in this proposal. The document titled 
Residual Risk Assessment for the SOCMI Source Category in Support of 
the 2023 Risk and Technology Review Proposed Rule, which is available 
in the docket for this rulemaking, provides the methodology and results 
of the community-based risks analyses.
9. How do we consider uncertainties in risk assessment?
    Uncertainty and the potential for bias are inherent in all risk 
assessments, including those performed for this proposal. Although 
uncertainty exists, we believe that our approach, which used 
conservative tools and assumptions, ensures that our decisions are 
health and environmentally protective. A brief discussion of the 
uncertainties in the RTR emissions datasets, dispersion modeling, 
inhalation exposure estimates, and dose-response relationships follows 
below. Also included are those uncertainties specific to our acute 
screening assessments, multipathway screening assessments, and our 
environmental risk screening assessments. A more thorough discussion of 
these uncertainties is included in the documents titled Residual Risk 
Assessment for the SOCMI Source Category in Support of the 2023 Risk 
and Technology Review

[[Page 25103]]

Proposed Rule and Residual Risk Assessment for the Polymers & Resins I 
Neoprene Production Source Category in Support of the 2023 Risk and 
Technology Review Proposed Rule, which are available in the docket for 
this rulemaking. If a multipathway site-specific assessment was 
performed for these source categories, a full discussion of the 
uncertainties associated with that assessment can be found in Appendix 
11 of that document, Site-Specific Human Health Multipathway Residual 
Risk Assessment Report.
a. Uncertainties in the RTR Emissions Datasets
    Although the development of the RTR emissions datasets involved 
quality assurance/quality control processes, the accuracy of emissions 
values will vary depending on the source of the data, the degree to 
which data are incomplete or missing, the degree to which assumptions 
made to complete the datasets are accurate, errors in emission 
estimates, and other factors. The emission estimates considered in this 
analysis generally are annual totals for certain years, and they do not 
reflect short-term fluctuations during the course of a year or 
variations from year to year. The estimates of peak hourly emission 
rates for the acute effects screening assessment were based on an 
emission adjustment factor applied to the average annual hourly 
emission rates, which are intended to account for emission fluctuations 
due to normal facility operations.
b. Uncertainties in Dispersion Modeling
    We recognize there is uncertainty in ambient concentration 
estimates associated with any model, including the EPA's recommended 
regulatory dispersion model, AERMOD. In using a model to estimate 
ambient pollutant concentrations, the user chooses certain options to 
apply. For RTR assessments, we select some model options that have the 
potential to overestimate ambient air concentrations (e.g., not 
including plume depletion or pollutant transformation). We select other 
model options that have the potential to underestimate ambient impacts 
(e.g., not including building downwash). Other options that we select 
have the potential to either under- or overestimate ambient levels 
(e.g., meteorology and receptor locations). On balance, considering the 
directional nature of the uncertainties commonly present in ambient 
concentrations estimated by dispersion models, the approach we apply in 
the RTR assessments should yield unbiased estimates of ambient HAP 
concentrations. We also note that the selection of meteorology dataset 
location could have an impact on the risk estimates. As we continue to 
update and expand our library of meteorological station data used in 
our risk assessments, we expect to reduce this variability.
c. Uncertainties in Inhalation Exposure Assessment
    Although every effort is made to identify all of the relevant 
facilities and emission points, as well as to develop accurate 
estimates of the annual emission rates for all relevant HAP, the 
uncertainties in our emission inventory likely dominate the 
uncertainties in the exposure assessment. Some uncertainties in our 
exposure assessment include human mobility, using the centroid of each 
census block, assuming lifetime exposure, and assuming only outdoor 
exposures. For most of these factors, there is neither an under nor 
overestimate when looking at the maximum individual risk or the 
incidence, but the shape of the distribution of risks may be affected. 
With respect to outdoor exposures, actual exposures may not be as high 
if people spend time indoors, especially for very reactive pollutants 
or larger particles. For all factors, we reduce uncertainty when 
possible. For example, with respect to census-block centroids, we 
analyze large blocks using aerial imagery and adjust locations of the 
block centroids to better represent the population in the blocks. We 
also add additional receptor locations where the population of a block 
is not well represented by a single location.
d. Uncertainties in Dose-Response Relationships
    There are uncertainties inherent in the development of the dose-
response values used in our risk assessments for cancer effects from 
chronic exposures and noncancer effects from both chronic and acute 
exposures. Some uncertainties are generally expressed quantitatively, 
and others are generally expressed in qualitative terms. We note, as a 
preface to this discussion, a point on dose-response uncertainty that 
is stated in the EPA's 2005 Guidelines for Carcinogen Risk Assessment; 
namely, that ``the primary goal of EPA actions is protection of human 
health; accordingly, as an Agency policy, risk assessment procedures, 
including default options that are used in the absence of scientific 
data to the contrary, should be health protective'''(the EPA's 2005 
Guidelines for Carcinogen Risk Assessment, page 1-7). This is the 
approach followed here as summarized in the next paragraphs.
    Cancer UREs used in our risk assessments are those that have been 
developed to generally provide an upper bound estimate of risk.\39\ 
That is, they represent a ``plausible upper limit to the true value of 
a quantity'' (although this is usually not a true statistical 
confidence limit). In some circumstances, the true risk could be as low 
as zero; however, in other circumstances the risk could be greater.\40\ 
Chronic noncancer RfC and reference dose values represent chronic 
exposure levels that are intended to be health-protective levels. To 
derive dose-response values that are intended to be ``without 
appreciable risk,'' the methodology relies upon an uncertainty factor 
(UF) approach,\41\ which considers uncertainty, variability, and gaps 
in the available data. The UFs are applied to derive dose-response 
values that are intended to protect against appreciable risk of 
deleterious effects.
---------------------------------------------------------------------------

    \39\ IRIS glossary (https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary).
    \40\ An exception to this is the URE for benzene, which is 
considered to cover a range of values, each end of which is 
considered to be equally plausible, and which is based on maximum 
likelihood estimates.
    \41\ See A Review of the Reference Dose and Reference 
Concentration Processes, U.S. EPA, December 2002, and Methods for 
Derivation of Inhalation Reference Concentrations and Application of 
Inhalation Dosimetry, U.S. EPA, 1994.
---------------------------------------------------------------------------

    Many of the UFs used to account for variability and uncertainty in 
the development of acute dose-response values are quite similar to 
those developed for chronic durations. Additional adjustments are often 
applied to account for uncertainty in extrapolation from observations 
at one exposure duration (e.g., 4 hours) to derive an acute dose-
response value at another exposure duration (e.g., 1 hour). Not all 
acute dose-response values are developed for the same purpose, and care 
must be taken when interpreting the results of an acute assessment of 
human health effects relative to the dose-response value or values 
being exceeded. Where relevant to the estimated exposures, the lack of 
acute dose-response values at different levels of severity should be 
factored into the risk characterization as potential uncertainties.
    Uncertainty also exists in the selection of ecological benchmarks 
for the environmental risk screening assessment. We established a 
hierarchy of preferred benchmark sources to allow selection of 
benchmarks for each environmental HAP at each ecological assessment 
endpoint. We searched for

[[Page 25104]]

benchmarks for three effect levels (i.e., no-effects level, threshold-
effect level, and probable effect level), but not all combinations of 
ecological assessment/environmental HAP had benchmarks for all three 
effect levels. Where multiple effect levels were available for a 
particular HAP and assessment endpoint, we used all of the available 
effect levels to help us determine whether risk exists and whether the 
risk could be considered significant and widespread.
    Although we make every effort to identify appropriate human health 
effect dose-response values for all pollutants emitted by the sources 
in this risk assessment, some HAP emitted by these source categories 
are lacking dose-response assessments. Accordingly, these pollutants 
cannot be included in the quantitative risk assessment, which could 
result in quantitative estimates understating HAP risk. To help to 
alleviate this potential underestimate, where we conclude similarity 
with a HAP for which a dose-response value is available, we use that 
value as a surrogate for the assessment of the HAP for which no value 
is available. To the extent use of surrogates indicates appreciable 
risk, we may identify a need to increase priority for an IRIS 
assessment for that substance. We additionally note that, generally 
speaking, HAP of greatest concern due to environmental exposures and 
hazard are those for which dose-response assessments have been 
performed, reducing the likelihood of understating risk. Further, HAP 
not included in the quantitative assessment are assessed qualitatively 
and considered in the risk characterization that informs the risk 
management decisions, including consideration of HAP reductions 
achieved by various control options.
    For a group of compounds that are unspeciated (e.g., groups of 
compounds that we do not know the exact composition of like glycol 
ethers), we conservatively use the most protective dose-response value 
of an individual compound in that group to estimate risk. Similarly, 
for an individual compound in a group (e.g., ethylene glycol diethyl 
ether) that does not have a specified dose-response value, we also 
apply the most protective dose-response value from the other compounds 
in the group to estimate risk.
e. Uncertainties in Acute Inhalation Screening Assessments
    In addition to the uncertainties highlighted above, there are 
several factors specific to the acute exposure assessment that the EPA 
conducts as part of the risk review under section 112 of the CAA. The 
accuracy of an acute inhalation exposure assessment depends on the 
simultaneous occurrence of independent factors that may vary greatly, 
such as hourly emissions rates, meteorology, and the presence of a 
person. In the acute screening assessment that we conduct under the RTR 
program, we assume that peak emissions from the source category and 
reasonable worst-case air dispersion conditions (i.e., 99th percentile) 
co-occur. We then include the additional assumption that a person is 
located at this point at the same time. Together, these assumptions 
represent a reasonable worst-case actual exposure scenario. In most 
cases, it is unlikely that a person would be located at the point of 
maximum exposure during the time when peak emissions and reasonable 
worst-case air dispersion conditions occur simultaneously.
f. Uncertainties in the Multipathway and Environmental Risk Screening 
Assessments
    For each source category, we generally rely on site-specific levels 
of PB-HAP or environmental HAP emissions to determine whether a refined 
assessment of the impacts from multipathway exposures is necessary or 
whether it is necessary to perform an environmental screening 
assessment. This determination is based on the results of a three-
tiered screening assessment that relies on the outputs from models--
TRIM.FaTE and AERMOD--that estimate environmental pollutant 
concentrations and human exposures for five PB-HAP (dioxins, POM, 
mercury, cadmium, and arsenic) and two acid gases (HF and HCl). For 
lead, we use AERMOD to determine ambient air concentrations, which are 
then compared to the secondary NAAQS standard for lead. Two important 
types of uncertainty associated with the use of these models in RTR 
risk assessments and inherent to any assessment that relies on 
environmental modeling are model uncertainty and input uncertainty.\42\
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    \42\ In the context of this discussion, the term ``uncertainty'' 
as it pertains to exposure and risk encompasses both variability in 
the range of expected inputs and screening results due to existing 
spatial, temporal, and other factors, as well as uncertainty in 
being able to accurately estimate the true result.
---------------------------------------------------------------------------

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

[[Page 25105]]

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

G. How does the EPA perform the NESHAP technology review and NSPS 
review?

1. NESHAP Technology Review
    Our technology review primarily focuses on the identification and 
evaluation of developments in practices, processes, and control 
technologies that have occurred since the previous HON, P&R I, and P&R 
II technology reviews were promulgated. Where we identify such 
developments, we analyze their technical feasibility, estimated costs, 
energy implications, and non-air environmental impacts. We also 
consider the emission reductions associated with applying each 
development. This analysis informs our decision of whether it is 
``necessary'' to revise the CAA section 112 emissions standards. In 
addition, we consider the appropriateness of applying controls to new 
sources versus retrofitting existing sources. For this exercise, we 
consider any of the following to be a ``development'':
     Any add-on control technology or other equipment that was 
not identified and considered during development of the original MACT 
standards;
     Any improvements in add-on control technology or other 
equipment (that were identified and considered during development of 
the original MACT standards) that could result in additional emissions 
reduction;
     Any work practice or operational procedure that was not 
identified or considered during development of the original MACT 
standards;
     Any process change or pollution prevention alternative 
that could be broadly applied to the industry and that was not 
identified or considered during development of the original MACT 
standards; and
     Any significant changes in the cost (including cost 
effectiveness) of applying controls (including controls the EPA 
considered during the development of the original MACT standards).
    In addition to reviewing the practices, processes, and control 
technologies that were considered at the time we originally developed 
the HON, P&R I, and P&R II, we review a variety of data sources in our 
investigation of potential practices, processes, or controls to 
consider. We also review the NESHAP and the available data to determine 
if there are any unregulated emissions of HAP within the source 
categories, and evaluate these data for use in developing new emission 
standards. When reviewing MACT standards, we also address regulatory 
gaps, such as missing standards for listed air toxics known to be 
emitted from the source category. See sections II.C and II.D of this 
preamble for information on the specific data sources that were 
reviewed as part of the technology review.
2. NSPS Review
    As noted in the section II.A.2 of this preamble, CAA section 111 
requires the EPA, at least every 8 years to review and, if appropriate 
revise the standards of performance applicable to new, modified, and 
reconstructed sources. If the EPA determines that it is appropriate to 
review the standards of performance, the revised standards must reflect 
the degree of emission limitation achievable through the application of 
the BSER considering the cost of achieving such reduction and any non-
air quality health and environmental impact and energy requirements. 
CAA section 111(a)(1).
    In reviewing an NSPS to determine whether it is ``appropriate'' to 
revise the standards of performance, the EPA evaluates the statutory 
factors, which may include consideration of the following information:
     Expected growth for the source category, including how 
many new facilities, reconstructions, and modifications may trigger 
NSPS in the future.
     Pollution control measures, including advances in control 
technologies, process operations, design or efficiency improvements, or 
other systems of emission reduction, that are ``adequately 
demonstrated'' in the regulated industry.
     Available information from the implementation and 
enforcement of current requirements indicating that emission 
limitations and percent reductions beyond those required by the current 
standards are achieved in practice.
     Costs (including capital and annual costs) associated with 
implementation of the available pollution control measures.
     The amount of emission reductions achievable through 
application of such pollution control measures.
     Any non-air quality health and environmental impact and 
energy requirements associated with those control measures.
    In evaluating whether the cost of a particular system of emission 
reduction is reasonable, the EPA considers various costs associated 
with the particular air pollution control measure or a level of 
control, including capital costs and operating costs, and the emission 
reductions that the control measure or particular level of control can 
achieve. The Agency considers these costs in the context of the 
industry's overall capital expenditures and revenues. The Agency also 
considers cost-effectiveness analysis as a useful metric and a means of 
evaluating whether a given control achieves emission reduction at a 
reasonable cost. A cost-effectiveness analysis allows comparisons of 
relative costs and outcomes (effects) of two or more options. In 
general, cost-effectiveness is a measure of the

[[Page 25106]]

outcomes produced by resources spent. In the context of air pollution 
control options, cost effectiveness typically refers to the annualized 
cost of implementing an air pollution control option divided by the 
amount of pollutant reductions realized annually.
    After the EPA evaluates the statutory factors, the EPA compares the 
various systems of emission reductions and determines which system is 
``best,'' and therefore represents the BSER. The EPA then establishes a 
standard of performance that reflects the degree of emission limitation 
achievable through the implementation of the BSER. In doing this 
analysis, the EPA can determine whether subcategorization is 
appropriate based on classes, types, and sizes of sources, and may 
identify a different BSER and establish different performance standards 
for each subcategory. The result of the analysis and BSER determination 
leads to standards of performance that apply to facilities that begin 
construction, reconstruction, or modification after the date of 
publication of the proposed standards in the Federal Register. Because 
the NSPS reflect the BSER under conditions of proper operation and 
maintenance, in doing its review, the EPA also evaluates and determines 
the proper testing, monitoring, recordkeeping and reporting 
requirements needed to ensure compliance with the emission standards.
    See section II.C of this preamble for information on the specific 
data sources that were reviewed as part of this action.

III. Proposed Rule Summary and Rationale

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

    As previously discussed, we conducted risk assessments for the 
SOCMI and Neoprene Production (within P&R I) source categories. We 
previously identified EtO as a cancer risk driver from facilities with 
HON-subject processes in the first risk assessment we conducted in 
2006. However, the EPA's IRIS inhalation URE for EtO was revised in 
2016,\43\ based on new data, showing EtO to be more carcinogenic than 
previously understood (i.e., resulting in a URE 60 times greater than 
the previous URE over a 70-year lifetime). Additionally, the EPA's IRIS 
inhalation URE for chloroprene was finalized in 2010 (there was no 
previous URE).\44\ Chloroprene is emitted from some HON-subject 
processes (e.g., chloroprene production, other chlorinated SOCMI 
chemical production processes), but is mostly emitted from neoprene 
production processes subject to P&R I. We briefly present results of 
the risk assessments below and in more detail in the documents titled 
Residual Risk Assessment for the SOCMI Source Category in Support of 
the 2023 Risk and Technology Review Proposed Rule and Residual Risk 
Assessment for the Polymers & Resins I Neoprene Production Source 
Category in Support of the 2023 Risk and Technology Review Proposed 
Rule, which are available in the docket for this rulemaking.
---------------------------------------------------------------------------

    \43\ 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.
    \44\ U.S. EPA. Toxicological Review of Chloroprene (CASRN 126-
99-8) In Support of Summary Information on the Integrated Risk 
Information System (IRIS). September 2010. EPA/635/R-09/010F. 
Available at: https://iris.epa.gov/static/pdfs/1021tr.pdf.
---------------------------------------------------------------------------

1. Chronic Inhalation Risk Assessment Results
a. SOCMI Source Category
    The results of the chronic baseline inhalation cancer risk 
assessment, which are estimated using modeling and is the case for all 
risk results presented here and in subsequent sections, indicate that, 
based on estimates of current actual and allowable emissions, the MIR 
posed by the source category is 2,000-in-1 million, driven by EtO 
emissions from PRDs (74 percent) and equipment leaks (20 percent). The 
total estimated cancer incidence based on actual and allowable emission 
levels is 2 excess cancer cases per year. EtO emissions contribute 89 
percent of the total cancer incidence. Within 50 km (~31 miles) of HON-
subject facilities, the population exposed to cancer risk greater than 
100-in-1 million for HON actual and allowable emissions is 
approximately 87,000 people, and the population exposed to cancer risk 
greater than or equal to 1-in-1 million is approximately 7.2 million 
people. Of the 195 facilities that were assessed for risk, 8 facilities 
have an estimated maximum cancer risk greater than 100-in-1 million. In 
addition, the maximum modeled chronic noncancer TOSHI for the source 
category based on actual and allowable emissions is estimated to be 2 
(for respiratory effects) at two different facilities (from maleic 
anhydride emissions at one facility and chlorine emissions at another 
facility). Approximately 83 people are estimated to be exposed to a 
TOSHI greater than 1. See Table 1 of this preamble for a summary of the 
HON inhalation risk assessment results.

                      Table 1--SOCMI Source Category Inhalation Risk Assessment Results Based on Actual and Allowable Emissions \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                 Maximum       Estimated population at increased
                                 Number of     individual               risk of cancer             Estimated  annual                     Refined maximum
        Risk assessment          facilities  cancer risk (- -------------------------------------- cancer  incidence   Maximum chronic   screening acute
                                    \2\       in-1 million)                                         (cases per year)   noncancer TOSHI    noncancer HQ
                                                   \3\       >100-in-1 million   >=1-in-1 million
--------------------------------------------------------------------------------------------------------------------------------------------------------
SOCMI Source Category.........          195           2,000  87,000 (50 km)...  7.2 million (50                    2  2 (maleic         HQREL = 3
                                                                                 km).                                  anhydride).       (chlorine).
                                                                                                                      2 (chlorine)....  HQREL = 3
                                                                                                                                         (acrolein).
Facility-wide \4\.............          195           2,000  95,000 (50 km)...  8.9 million (50                    2  4 (chlorine,
                                                                                 km).                                  acrylic acid,
                                                                                                                       and
                                                                                                                       acrylonitrile).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Actual emissions equal allowable emissions; therefore, actual risks equal allowable risks.
\2\ There are 207 HON facilities; however, only 195 of these facilities are included in the risk assessment based on available data, which corresponds
  to 222 Emission Information System (EIS) facility IDs.
\3\ Maximum individual excess lifetime cancer risk due to HAP emissions.
\4\ See ``Facility-Wide Risk Results'' in section III.A.5 of this preamble for more details on this risk assessment.

[[Page 25107]]

b. Neoprene Production Source Category
    The results of the chronic baseline inhalation cancer risk 
assessment indicate that, based on estimates of current actual and 
allowable emissions, the MIR posed by the Neoprene Production source 
category within P&R I is 500-in-1 million, driven by chloroprene 
emissions from maintenance vents (67 percent), storage vessels (11 
percent), wastewater (8 percent), and equipment leaks (4 percent).\45\ 
The total estimated cancer incidence based on actual and allowable 
emission levels is 0.05 excess cancer cases per year, or 1 cancer case 
every 20 years. Within 50 km (~31 miles) of the one facility in this 
source category, the population exposed to cancer risks greater than 
100-in-1 million for actual and allowable emissions is approximately 
2,100 people, and the population exposed to cancer risks greater than 
or equal to 1-in-1 million is approximately 690,000 people. In 
addition, the maximum modeled chronic noncancer TOSHI for the source 
category based on actual and allowable emissions is estimated to be 
0.05 (for respiratory effects) from chloroprene emissions. See Table 2 
of this preamble for a summary of the neoprene production inhalation 
risk assessment results.
---------------------------------------------------------------------------

    \45\ We note that chloroprene (and all other HAP) emissions from 
HON processes co-located at the neoprene production facility result 
in an MIR of 90-in-1 million.

               Table 2--Neoprene Production Source Category Inhalation Risk Assessment Results Based on Actual and Allowable Emissions \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                 Maximum       Estimated population at increased
                                 Number of     individual               risk of cancer             Estimated  annual                         Maximum
        Risk assessment          facilities  cancer risk (- -------------------------------------- cancer  incidence   Maximum chronic   screening acute
                                    \2\       in-1 million)                                         (cases per year)   noncancer TOSHI    noncancer HQ
                                                   \3\       >100-in-1 million   >=1-in-1 million
--------------------------------------------------------------------------------------------------------------------------------------------------------
Neoprene Production Source                1             500  2,100 (50 km)....  690,000 (50 km)..               0.05  0.05              HQREL = 0.3
 Category.                                                                                                             (chloroprene).    (chloroform).
Facility-wide \4\.............            1             600  2,300 (50 km)....  890,000 (50 km)..               0.06  0.3 (chlorine)..
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Actual emissions equal allowable emissions; therefore, actual risks equal allowable risks.
\2\ Number of facilities evaluated in the risk analysis.
\3\ Maximum individual excess lifetime cancer risk due to HAP emissions.
\4\ See ``Facility-Wide Risk Results'' in section III.A.5 of this preamble for more details on this risk assessment.

2. Screening Level Acute Risk Assessment Results
a. SOCMI Source Category
    As presented in Table 1 of this preamble, the estimated worst-case 
off-site acute exposures to emissions from the SOCMI source category 
result in a maximum modeled acute noncancer HQ of 3 based on the RELs 
for chlorine and acrolein. HON process emissions from two other 
facilities result in acute noncancer HQs of 2 based on the RELs for 
formaldehyde and chloroform. Detailed information about the assessment, 
including evaluation of the screening-level acute risk assessment 
results, is provided in the main body and Appendix 10 of the document 
titled Residual Risk Assessment for the SOCMI Source Category in 
Support of the 2023 Risk and Technology Review Proposed Rule, which is 
available in the docket for this rulemaking.
b. Neoprene Production Source Category
    As presented in Table 2 of this preamble, the estimated worst-case 
acute exposures to emissions from the Neoprene Production source 
category result in a maximum modeled acute noncancer HQ of 0.3 based on 
the REL for chloroform. Detailed information about the assessment is 
provided in the document titled Residual Risk Assessment for the 
Polymers & Resins I Neoprene Production Source Category in Support of 
the 2023 Risk and Technology Review Proposed Rule, which is available 
in the docket for this rulemaking.
3. Multipathway Risk Screening Results
a. SOCMI Source Category
    For the SOCMI source category, 71 facilities emitted at least 1 PB-
HAP, including arsenic, cadmium, dioxins, mercury, and POMs.\46\ 
Emissions of these PB-HAP from each facility were compared to the 
respective pollutant-specific Tier 1 screening emission thresholds. The 
Tier 1 screening analysis indicated 9 facilities exceeded the Tier 1 
emission threshold for arsenic, 3 facilities for cadmium, 9 facilities 
for dioxins, 9 facilities for mercury, and 20 facilities for POM.
---------------------------------------------------------------------------

    \46\ Note that while the multipathway risk screening results 
includes metals (e.g., arsenic, cadmium, mercury, arsenic) and POMs, 
the EPA in most instances used a conservative approach and modeled 
whole facility emissions inventories for the SOCMI source category. 
This means that emissions from other source categories were included 
for this analysis, and we have no information suggesting that metals 
or POMs are emitted from HON processes. See Appendix 1 of the 
document titled Residual Risk Assessment for the SOCMI Source 
Category in Support of the 2023 Risk and Technology Review Proposed 
Rule, which is available in the docket for this rulemaking for more 
details about development of the risk modeling file.
---------------------------------------------------------------------------

    For facilities that exceeded the Tier 1 multipathway screening 
threshold emission rate for one or more PB-HAP, we used additional 
facility site-specific information to perform a Tier 2 multipathway 
risk screening assessment. The Tier 2 assessment resulted in a maximum 
Tier 2 noncancer screening value of 60 from methyl mercury and 2 for 
cadmium based on the fisher scenario and a cancer screening value of 
100 from POM for the gardener scenario. The Tier 2 assessment indicated 
the maximum arsenic and dioxin cancer screening values were 30 and 2, 
respectively, for the gardener scenario, and therefore no further 
screening was performed.
    For mercury and cadmium, a Tier 3 screening assessment was 
conducted for the fisher scenario while a Tier 3 screening assessment 
was conducted for POM for the gardener scenario. In the Tier 3 
screening for the fisher scenario, lakes near the facilities were 
reviewed on aerial photographs to ensure they were accessible for 
fishing. Any lakes not accessible were removed from the assessment. 
After conducting the Tier 3 assessment, the screening values for 
mercury and cadmium remained at 60 and 2, respectively.
    The Tier 3 gardener scenario was refined by identifying the 
location of the residence most impacted by POM emissions from the 
facility as opposed to the worst-case near-field location used in the 
Tier 2 assessment. Based on these Tier 3 refinements to the gardener 
scenario, the maximum Tier 3 cancer screening value for POM was 20.
    An exceedance of a screening threshold emission rate in any of the 
tiers cannot be equated with a risk value or an HQ (or HI). Rather, it 
represents

[[Page 25108]]

a high-end estimate of what the risk or hazard may be. For example, a 
screening value of 2 for a non-carcinogen can be interpreted to mean 
that the Agency is confident that the HQ would be lower than 2. 
Similarly, a Tier 2 cancer screening value of 7 means that we are 
confident that the cancer risk is lower than 7-in-1 million. Our 
confidence comes from the conservative, or health-protective, 
assumptions encompassed in the screening tiers: the Agency chooses 
inputs from the upper end of the range of possible values for the 
influential parameters used in the screening tiers, and the Agency 
assumes that the exposed individual exhibits ingestion behavior that 
would lead to a high total exposure.
    The EPA determined that it is not necessary to go beyond the Tier 3 
lake analysis or conduct a site-specific assessment for cadmium, 
mercury, or POM. The EPA compared the Tier 2 screening results to site-
specific risk estimates for five previously assessed source categories. 
These are the five source categories, assessed over the past 4 years, 
which had characteristics that make them most useful for interpreting 
the HON screening results. For these source categories, the EPA 
assessed fisher and/or gardener risks for arsenic, cadmium, and/or 
mercury by conducting site-specific assessments. The EPA used AERMOD 
for modeling air dispersion and Tier 2 screens that used multi-facility 
aggregation of chemical loading to lakes where appropriate. These 
assessments indicated that cancer and noncancer site-specific risk 
values were at least 50 times lower than the respective Tier 2 
screening values for the assessed facilities, with the exception of 
noncancer risks for cadmium for the gardener scenario, where the 
reduction was at least 10 times (refer to EPA Docket ID: EPA-HQ-OAR-
2017-0015 and EPA-HQ-OAR-2019-0373 for a copy of these reports).\47\
---------------------------------------------------------------------------

    \47\ EPA Docket records (EPA-HQ-OAR-2017-0015): Appendix 11 of 
the Residual Risk Assessment for the Taconite Manufacturing Source 
Category in Support of the Risk and Technology Review 2019 Proposed 
Rule; Appendix 11 of the Residual Risk Assessment for the Integrated 
Iron and Steel Source Category in Support of the Risk and Technology 
Review 2019 Proposed Rule; Appendix 11 of the Residual Risk 
Assessment for the Portland Cement Manufacturing Source Category in 
Support of the 2018 Risk and Technology Review Final Rule; Appendix 
11 of the Residual Risk Assessment for the Coal and Oil-Fired EGU 
Source Category in Support of the 2018 Risk and Technology Review 
Proposed Rule; and EPA Docket: (EPA-HQ-OAR-2019-0373): Appendix 11 
of the Residual Risk Assessment for Iron and Steel Foundries Source 
Category in Support of the 2019 Risk and Technology Review Proposed 
Rule.
---------------------------------------------------------------------------

    Based on our review of these analyses, if the Agency was to perform 
a site-specific assessment for the SOCMI Source Category, the Agency 
would expect similar magnitudes of decreases from the Tier 2 SVs. As 
such, given the conservative nature of the screens and the level of 
additional refinements that would go into a site-specific multipathway 
assessment, were one to be conducted, we are confident that the HQ for 
ingestion exposure, specifically cadmium and mercury through fish 
ingestion, is at or below 1. For POM, the maximum cancer risk under the 
rural gardener scenario would likely decrease to below 1-in-1 million. 
Further details on the Tier 3 screening assessment can be found in 
Appendix 10-11 of Residual Risk Assessment for the SOCMI Source 
Category in Support of the 2023 Risk and Technology Review Proposed 
Rule.
    In evaluating the potential for multipathway risk from emissions of 
lead, we compared modeled annual lead concentrations to the primary 
NAAQS for lead (0.15 [micro]g/m\3\). The highest annual lead 
concentration of 0.004 [micro]g/m\3\ is well below the NAAQS for lead, 
indicating low potential for multipathway risk of concern due to lead 
emissions.
    Detailed information about the assessment is provided in the 
document titled Residual Risk Assessment for the SOCMI Source Category 
in Support of the 2023 Risk and Technology Review Proposed Rule, which 
is available in the docket for this rulemaking.
b. Neoprene Production Source Category
    As mentioned above, we did not identify reported PB-HAP emissions 
from the Neoprene Production source category, and we could not 
undertake the three-tier human health risk screening assessment that 
was conducted for the SOCMI source category. However, we note that we 
would expect dioxins likely to be formed by combustion controls used to 
control chlorinated chemicals such as chloroprene from this source 
category. As no facility exceeded a Tier 2 screening value for dioxins 
in the HON multipathway risk screening assessment, including 4 HON 
facilities with dioxin emission rates higher than the standard being 
proposed for dioxins for the Neoprene Production source category (and 1 
HON facility with a dioxins emission rate approximately 20 times higher 
than the proposed Neoprene Production emission limit), we would expect 
multipathway risk from dioxins from the Neoprene Production source 
category to screen lower than they are for the SOCMI source category 
after compliance with the proposed dioxin limit occurs.
4. Environmental Risk Screening Results
a. SOCMI Source Category
    As described in section III.A of this preamble, we conducted a 
screening assessment for adverse environmental effects for the SOCMI 
source category. The environmental screening assessment included the 
following HAP: arsenic, cadmium, dioxin, methyl mercury, divalent 
mercury, and POMs.\48\
---------------------------------------------------------------------------

    \48\ Note that while the environmental risk screening results 
includes metals (e.g., arsenic, cadmium, mercury, arsenic) and POMs, 
the EPA in most instances used a conservative approach and modeled 
whole facility emissions inventories for the SOCMI source category. 
This means that emissions from other source categories were included 
for this analysis, and we have no information suggesting that metals 
or POMs are emitted from HON processes. See Appendix 1 of the 
document titled Residual Risk Assessment for the SOCMI Source 
Category in Support of the 2023 Risk and Technology Review Proposed 
Rule, which is available in the docket for this rulemaking for more 
details about development of the risk modeling file.
---------------------------------------------------------------------------

    In the Tier 1 screening analysis for PB-HAP (other than lead, which 
was evaluated differently), arsenic emissions had no exceedances for 
any ecological benchmark. The maximum Tier 1 screening value was 200 
for methyl mercury emissions for the surface soil No Observed Adverse 
Effects Level (NOAEL) avian ground insectivores benchmark. The other 
pollutants (cadmium, dioxins, POMs, divalent mercury, methyl mercury) 
had Tier 1 screening values above various benchmarks. Therefore, a Tier 
2 screening assessment was performed for cadmium, dioxins, POMs, 
divalent mercury, and methyl mercury emissions.
    In the Tier 2 screen, cadmium, dioxins, and POM emissions did not 
exceed any ecological benchmark. The following Tier 2 screening values 
were exceeded for methyl mercury emissions: a screening value of 5 for 
the fish-eating birds NOAEL benchmark (specifically for the small duck 
called the merganser), a screening value of 2 for the maximum allowable 
toxicant level for the merganser, and a screening value of 3 for avian 
ground insectivores (woodcock). The following Tier 2 screening values 
were exceeded for divalent mercury emissions: a screening value of 4 
for a sediment threshold level and a screening value of 2 for an 
invertebrate threshold level. All of the Tier 2 exceedances for the 
merganser and sediment benchmarks are the result of emissions from 3 
facilities acting on the same lake. The invertebrate and

[[Page 25109]]

insectivore soil benchmarks are the result of emissions from 1 
facility.
    Since there were Tier 2 exceedances, we conducted a Tier 3 
environmental risk screen. In the Tier 3 environmental risk screen, we 
looked at aerial photos of the lake being impacted by mercury emissions 
from the three HON-subject facilities. The aerial photos show that the 
``lake'' is located in an industrialized area, has been channelized, 
and largely filled/drained. Therefore, it was determined that this 
``lake'' would not support a fish population. We also looked at aerial 
photos of the facility that was driving the invertebrate and 
insectivore Tier 2 soil exceedances due to mercury emissions. The 
aerial photos show that the facility is located in a heavily 
industrialized area with the nearest ``natural areas'' being located 
more than 1500 meters from the facility. We re-calculated the soil 
screening values with the industrial areas removed and calculated a 
maximum Tier 3 soil screen value for mercury of 1.
    We did not estimate any exceedances of the secondary lead NAAQS. 
The highest annual lead concentration of 0.004 [micro]g/m\3\ is well 
below the NAAQS for lead, indicating low potential for environmental 
risk of concern due to lead emissions.
    We also conducted an environmental risk screening assessment 
specifically for acid gases (i.e., HCl and HF) for the SOCMI source 
category. For HCl and HF, the average modeled concentration around each 
facility (i.e., the average concentration of all off-site data points 
in the modeling domain) did not exceed any ecological benchmark. In 
addition, each individual modeled concentration of HCl and HF (i.e., 
each off-site data point in the modeling domain) was below the 
ecological benchmarks for all facilities.
    Based on the results of the environmental risk screening analysis, 
we do not expect an adverse environmental effect as a result of HAP 
emissions from this source category. Detailed information about the 
assessment is provided in the document titled Residual Risk Assessment 
for the SOCMI Source Category in Support of the 2023 Risk and 
Technology Review Proposed Rule, which is available in the docket for 
this rulemaking.
b. Neoprene Production Source Category
    As mentioned above, because we did not identify reported PB-HAP 
emissions, we did not undertake the environmental risk screening 
assessment of PB-HAP for the Neoprene Production source category. 
However, we note that no facility exceeded a Tier 2 screening value for 
dioxins in the HON environmental risk screening assessment, including 4 
HON facilities with dioxin emission rates higher than those being 
proposed for the Neoprene Production source category and 1 HON facility 
with a dioxin emission rate approximately 20 times higher than the 
proposed emission limits for the Neoprene Production source category.
    Furthermore, we conducted an environmental risk screening 
assessment for acid gases (i.e., HCl and HF) for the Neoprene 
Production source category; however, there were no reported emissions 
of HF at this facility. For HCl, the average modeled concentration 
around the facility (i.e., the average concentration of all off-site 
data points in the modeling domain) did not exceed any ecological 
benchmark. In addition, each individual modeled concentration of HCl 
(i.e., each off-site data point in the modeling domain) was below the 
ecological benchmarks for the facility. Detailed information about the 
assessment is provided in the document titled Residual Risk Assessment 
for the Polymers & Resins I Neoprene Production Source Category in 
Support of the 2023 Risk and Technology Review Proposed Rule, which is 
available in the docket for this rulemaking.
5. Facility-Wide Risk Results
a. HON Facilities
    We conducted an assessment of facility-wide (or ``whole facility'') 
risk as described above to characterize the source category risk in the 
context of whole facility risk. We estimated whole facility risks using 
the NEI-based data described in section III.C of this preamble. The 
maximum lifetime individual cancer risk posed by the 195 modeled 
facilities (there are 207 HON facilities; however, only 195 of these 
facilities are included in the risk assessment based on available data, 
which corresponds to 222 EIS facility IDs) based on whole facility 
emissions is 2,000-in-1 million with EtO emissions from PRDs (74 
percent) and equipment leaks (20 percent) from SOCMI source category 
emissions driving the risk. The total estimated cancer incidence based 
on facility-wide emission levels is 2 excess cancer cases per year. EtO 
emissions contribute 81 percent and chloroprene emissions contribute 3 
percent of the total cancer incidence. Within 50 km (~31 miles) of HON-
subject facilities, the population exposed to cancer risk greater than 
100-in-1 million for HON facility-wide emissions is approximately 
95,000 people, and the population exposed to cancer risk greater than 
or equal to 1-in-1 million is approximately 8.9 million people. The 
maximum chronic noncancer TOSHI posed by whole facility emissions is 
estimated to be 4 (for respiratory effects) due mostly (98 percent) to 
emissions from 2 facilities. Emissions from one facility contribute to 
83 percent of the TOSHI, with approximately 60 percent of the total 
TOSHI from non-source category emissions of chlorine and another 15 
percent from source category emissions of chlorine. Emissions from the 
second facility contribute to 15 percent of the TOSHI, with 
approximately 11 percent of the total TOSHI from source category 
emissions of acrylic acid and 2 percent from source category emissions 
of acrylonitrile. Approximately 1,100 people are estimated to be 
exposed to a TOSHI greater than 1 due to whole facility emissions.
b. Neoprene Production Facility
    We also performed a facility-wide assessment for the facility in 
the Neoprene Production source category to characterize the source 
category risk in the context of whole facility risk. Note that this 
facility was also included the HON facility-wide risk assessment 
because it has HON sources as well as neoprene production sources (see 
section III.A.5.a of this preamble). The maximum lifetime individual 
cancer risk posed by the one neoprene production facility based on 
whole facility emissions is 600-in-1 million driven by chloroprene 
emissions from maintenance vents (66 percent total, 55 percent from 
neoprene production sources and 11 percent from HON sources), storage 
vessels (9 percent total, all from neoprene production sources), 
equipment leaks (7 percent total, 3 percent from neoprene production 
sources and 4 percent from HON sources), and wastewater (7 percent, all 
from neoprene production sources). The total estimated cancer incidence 
based on facility-wide emission levels is 0.06 excess cancer cases per 
year, or 1 case approximately every 17 years. Within 50 km (~31 miles) 
of the Neoprene Production facility, the population exposed to cancer 
risk greater than 100-in-1 million for facility-wide emissions is 
approximately 2,300 people, and the population exposed to cancer risk 
greater than or equal to 1-in-1 million is approximately 890,000 
people. The maximum chronic noncancer TOSHI posed by whole facility 
emissions is estimated to be 0.3 (for respiratory effects) due to 
chlorine emissions.
6. Community-Based Risk Assessment
    We also conducted a community-based risk assessment for HON-subject

[[Page 25110]]

facilities (which includes the one neoprene production facility). The 
goal of this assessment is to estimate cancer risk from HAP emitted 
from all local stationary point sources for which we have emissions 
data. We estimated the overall inhalation cancer risk due to emissions 
from all stationary point sources impacting census blocks within 10 km 
(~6.2 miles) of the 195 HON facilities. Specifically, we combined the 
modeled impacts from category and non-category HAP sources at HON 
facilities, as well as other stationary point source HAP emissions. 
Within 10 km of HON-subject facilities, we identified 2,700 non-source 
category facilities that could potentially also contribute to HAP 
inhalation exposures.
    We first looked at what the maximum risk is for communities around 
SOCMI facilities. The results indicate that the community-level maximum 
individual cancer risk is the same as in the source category MIR and 
maximum risk for the facility-wide assessment, 2,000-in-1 million. The 
assessment estimated that essentially all (greater than 99.9 percent) 
of the MIR is attributable to emissions from the SOCMI source category. 
We then looked at what the communities' risks are from all emissions 
sources for which we had data. Within 10 km, the population exposed to 
cancer risks greater than 100-in-1 million from all nearby emissions is 
approximately 104,000. For comparison, approximately 87,000 people have 
cancer risks greater than 100-in-1 million due to HON emissions and 
approximately 95,000 people have cancer risks greater than 100-in-1 
million due to HON facility-wide emissions (see Table 3 of this 
preamble). The overall cancer incidence for this exposed population 
(i.e., populations with risks greater than 100-in-1 million living 
within 10 km of HON facilities) is 0.5, with 91 percent of the cancer 
incidence from HON processes, 7 percent from non-HON processes at HON 
facilities (a total of 98 percent from HON facilities), and 2 percent 
from other nearby stationary point sources that are not HON facilities.
    The population exposed to cancer risks greater than or equal to 1-
in-1 million in the community-based assessment is approximately 5.8 
million people. For comparison, approximately 2.8 million people have 
cancer risks greater than or equal to 1-in-1 million due to HON process 
emissions and approximately 3.2 million people have cancer risks 
greater than 1-in-1 million due to HON facility-wide emissions (see 
Table 3 of this preamble). The overall cancer incidence for this 
exposed population (i.e., people with risks greater than or equal to 1-
in-1 million and living within 10 km of HON facilities) is 2, with 69 
percent of the incidence due to emissions from HON processes, 16 
percent from emissions of non-HON processes at HON facilities (that is, 
a total of 85 percent from emissions from HON facilities) and 15 
percent from emissions from other nearby stationary sources that are 
not HON facilities.
    After the controls proposed in this action are implemented for both 
the SOCMI and Neoprene Production source categories (see section 
III.B.2), the community-level maximum individual cancer risk will be 
reduced to the same as the facility-wide assessment, 1,000-in-1 
million, from non-HON processes emitting ethylene oxide at a single 
facility. The assessment estimated that 98 percent of the MIR is 
attributable to emissions from non-HON processes at a HON facility. The 
population (within 10 km of HON facilities) exposed to cancer risks 
greater than 100-in-1 million from all nearby emissions will be 
significantly reduced from 104,000 people to 4,200 people; a 96 percent 
reduction from the baseline. The populations exposed to cancer risks 
greater than 100-in-1 million from the SOCMI source category and 
facility-wide emissions are similarly reduced, from 87,000 people to 0 
for source category emissions and from 95,000 to 2,500 for facility-
wide emissions (see Table 3 of this preamble). Furthermore, the overall 
cancer incidence for this exposed population is expected to be reduced 
from 0.5 to 0.02. The percentage of the cancer incidence due to 
emissions of HON processes is reduced from 91 percent to 9 percent. The 
percentage of the cancer incidence due to emissions of non-HON 
processes at HON facilities and emissions from other nearby stationary 
sources proportionately shifts to 57 percent and 34 percent 
respectively. EtO emissions across these sources remain the largest 
source of incidence, accounting for 89 percent of the overall cancer 
incidence for this exposed population.
    The post-control population exposed to cancer risks greater than or 
equal to 1-in-1 million, 5.8 million people, would remain approximately 
the same as the baseline. In comparison, after the controls proposed in 
this action, the number of people with risks greater than or equal to 
1-in-1 million due to source category emissions would reduce from 2.8 
million to 2.5 million and due to facility-wide emissions from 3.2 
million to 3.1 million (see Table 3 of this preamble). The lack of 
change from the baseline is largely due to the impacts from non-HON 
processes at HON facilities and from other nearby stationary sources 
maintaining the risks greater than or equal to 1-in-1 million for the 
exposed population. However, the overall cancer incidence for this 
exposed population is expected to be reduced from 2 to 0.7. The 
percentage of the cancer incidence from HON processes is expected to 
decrease from 69 to 38 percent. The cancer incidence from non-HON 
processes at HON facilities and from other nearby stationary sources 
are expected to proportionately shift to 29 percent and 32 percent, 
respectively.
    Overall, the proposed emission reductions in this rule provide a 
substantial reduction in risks to the communities living around HON 
facilities. The number of people at cancer risks greater than 100-in-1 
million is reduced from 104,000 people to 4,200 people, a 96 percent 
reduction. EtO emissions are by far the largest source of remaining 
risk in the community-based risk assessment, accounting for 85 percent 
across all sources. Moving forward, the EPA expects to continue to 
address EtO emissions for other chemical sector source categories.

    Table 3--Inhalation Cancer Risk Assessment Results for Communities Living Within 10 km of HON Facilities
----------------------------------------------------------------------------------------------------------------
                                              Maximum         Estimated population at increased risk of cancer
                                            individual    ------------------------------------------------------
            Risk assessment              cancer risk (-in-
                                            1 million)          >100-in-1 million           >=1-in-1 million
----------------------------------------------------------------------------------------------------------------
                                             Baseline (Pre-Control)
----------------------------------------------------------------------------------------------------------------
SOCMI Source Category..................             2,000  87,000 (10 km)............  2.8 million (10 km).
Facility-wide..........................             2,000  95,000 (10 km)............  3.2 million (10 km).
Community..............................             2,000  104,000 (10 km)...........  5.8 million (10 km).
----------------------------------------------------------------------------------------------------------------

[[Page 25111]]

 
                            After Implementation of Proposed Controls (Post-Control)
----------------------------------------------------------------------------------------------------------------
SOCMI Source Category..................               100  0 (10 km).................  2.5 million (10 km).
Facility-wide \1\......................             1,000  2,500 (10 km).............  3.1 million (10 km).
Community..............................             1,000  4,200 (10 km).............  5.8 million (10 km).
----------------------------------------------------------------------------------------------------------------
\1\ Facility-wide post-control risks include proposed controls for the SOCMI and Neoprene Production source
  categories.

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

1. Risk Acceptability Under the Current MACT Standards
    As noted in section II.D of this preamble, we weigh a wide range of 
health risk measures and factors in our risk acceptability 
determination, including the cancer MIR, the number of persons in 
various cancer and noncancer risk ranges, cancer incidence, the maximum 
noncancer TOSHI, the maximum acute noncancer HQ, the extent of 
noncancer risks, the distribution of cancer and noncancer risks in the 
exposed population, and risk estimation uncertainties (54 FR 38044, 
September 14, 1989).
    Under the current MACT standards for the SOCMI source category, the 
risk results indicate that the MIR is 2,000-in-1 million, driven by 
emissions of EtO, and well above 100-in-1 million, which is the 
presumptive limit of acceptability. The estimated incidence of cancer 
due to inhalation exposures is 2 excess cancer case per year. The 
population estimated to be exposed to cancer risks greater than 100-in-
1 million is approximately 87,000, and the population estimated to be 
exposed to cancer risks greater than or equal to 1-in-1 million is 
approximately 7.2 million. The estimated maximum chronic noncancer 
TOSHI from inhalation exposure for this source category is 2 for 
neurological effects. The acute risk screening assessment of reasonable 
worst-case inhalation impacts indicates a maximum acute HQ of 3.
    Under the current MACT standards for the Neoprene Production source 
category, the risk results indicate that the MIR is 500-in-1 million, 
driven by emissions of chloroprene, and is above 100-in-1 million, the 
presumptive limit of acceptability. The estimated incidence of cancer 
due to inhalation exposures is 0.05 excess cancer case per year. The 
population estimated to be exposed to cancer risks greater than 100-in-
1 million is approximately 2,100, and the population estimated to be 
exposed to cancer risks greater than or equal to 1-in-1 million is 
approximately 690,000 million. The estimated maximum chronic noncancer 
TOSHI from inhalation exposure for this source category is 0.05 for 
neurological effects, indicating low likelihood of adverse noncancer 
effects from long-term inhalation exposures. The acute risk screening 
assessment of reasonable worst-case inhalation impacts indicates a 
maximum acute HQ of 0.3. Therefore, we conclude that adverse effects 
from acute exposure to emissions from this category are not 
anticipated.
    Considering all of the health risk information and factors 
discussed above, particularly the high MIR for both the SOCMI and 
Neoprene Production source categories, the EPA proposes that the risks 
for both source categories are unacceptable. As noted in section II.A 
of this preamble, when risks are unacceptable, under the 1989 Benzene 
NESHAP approach and CAA section 112(f)(2)(A), the EPA must first 
determine the emissions standards necessary to reduce risk to an 
acceptable level, and then determine whether further HAP emissions 
reductions are necessary to provide an ample margin of safety to 
protect public health or to prevent, taking into consideration costs, 
energy, safety, and other relevant factors, an adverse environmental 
effect. Therefore, pursuant to CAA section 112(f)(2), we are proposing 
certain standards for emission sources of EtO in the HON and certain 
standards for emission sources of chloroprene from the Neoprene 
Production source category that are more protective than the current 
HON and P&R I MACT standards.
2. Proposed Controls To Address Unacceptable Risks
    As previously discussed, we conducted risk assessments of the SOCMI 
and Neoprene Production source categories because the 2016 revisions to 
the EPA's IRIS inhalation URE for EtO and the 2010 development of the 
EPA's IRIS inhalation URE for chloroprene showed that both these 
pollutants are more toxic than previously known.
    For the SOCMI source category, we identified EtO as the cancer risk 
driver from HON sources. We are aware of 15 HON facilities reporting 
more than 0.1 tpy of EtO emissions in their emissions inventories from 
HON processes and two other facilities that are new or under 
construction with HON processes that we expect will exceed this 
threshold (but for which we do not yet have emissions inventory 
information). Of these 17 facilities, 12 facilities produce and emit 
EtO, which is a process subject to the HON MACT standards. In addition, 
all 17 of these facilities have additional HON processes that use and 
emit EtO in the production of glycols, glycol ethers, or ethanolamines. 
From our residual risk assessment, eight facilities with emissions of 
EtO from various HON processes have cancer risks above 100-in-1 
million, and many different emission sources drive risk at these 
facilities. Thus, in order to reduce emissions of EtO from HON 
processes, the EPA is proposing more stringent control requirements for 
process vents, storage vessels, equipment leaks, heat exchange systems, 
wastewater, maintenance vents, flares, and PRDs that emit or have the 
potential to emit EtO. As discussed later in this preamble, we are 
proposing that these requirements that will reduce risk to an 
acceptable level also provide an ample margin of safety to protect 
public health, and that no additional requirements are needed to 
prevent an adverse environmental effect.
    For the Neoprene Production source category, we identified 
chloroprene as the HAP cancer risk driver from the only facility in the 
Neoprene Production source category. Thus, in order to reduce risk 
posed by emissions from

[[Page 25112]]

neoprene production processes to an acceptable level, the EPA is 
proposing more stringent control requirements for process vents, 
storage vessels, wastewater, maintenance vents, and PRDs that emit or 
have the potential to emit chloroprene. Also, as discussed later in 
this preamble, we are proposing that these requirements that will 
reduce risk to an acceptable level also provide an ample margin of 
safety to protect public health, and that no additional requirements 
are needed to prevent an adverse environmental effect.
    We discuss the control options we evaluated for reducing EtO 
emissions from HON processes in section III.B.2.a of this preamble and 
discuss the control options we evaluated for reducing chloroprene 
emissions from P&R I processes producing neoprene in section III.B.2.b 
of this preamble.
a. EtO Controls for HON Processes
i. Process Vents and Storage Vessels
    Emissions of EtO can occur from several types of gas streams 
associated with HON processes, such as distillation columns, evaporator 
vents, and vacuum operations, as well as during vapor displacements and 
heating losses. HON storage vessels are used to store liquid and 
gaseous feedstocks for use in a process, as well as to store liquid and 
gaseous products from a process. EtO is typically stored under pressure 
as a liquified gas, but may also be found in small amounts in 
atmospheric storage vessels storing liquid products that are formed 
with ethylene oxide as a reactant in their production. Typical 
emissions from atmospheric storage tanks occur from working and 
breathing losses while pressure vessels are considered closed systems 
and, if properly maintained and operated, should have virtually no 
emissions. In some instances, pressurized vessels also could use a 
blanket of inert gas, most often nitrogen, to maintain a non-
decomposable vapor space, and continuous purge of vapor space from non-
loading operations could also lead to emissions from storage vessels.
    The current HON standards divide process vents into Group 1 process 
vents, which require control, and Group 2 process vents, which 
generally do not require controls provided they do not exceed Group 1 
thresholds. All HON Group 1 and Group 2 process vents are continuous. 
The Group 1 and Group 2 designations for process vents are based on 
volumetric flow rate, total organic HAP concentration, and the TRE 
index value.\49\ The current HON standard requires uncontrolled Group 1 
process vents to reduce total organic HAP emissions by 98 percent by 
weight by venting emissions through a closed vent system to any 
combination of control devices or to vent emissions through a closed 
vent system to a flare. We provide more details about process vents in 
our technology review discussion (see section III.C.3 of this 
preamble).
---------------------------------------------------------------------------

    \49\ 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.
---------------------------------------------------------------------------

    Similarly, the current HON standards divide storage vessels into 
Group 1 storage vessels, which require control, and Group 2 storage 
vessels, which generally do not require controls provided they do not 
exceed Group 1 thresholds. The Group 1 and Group 2 designation for 
storage vessels is based on the volume of the storage vessel and MTVP 
of the material stored. Group 1 storage vessels are those with 
capacities between 75 m\3\ and 151 m\3\ and a MTVP greater than or 
equal to 13.1 kPa, and those with capacities greater than or equal to 
151 m\3\ and a MTVP greater than or equal to 5.2 kPa. The current HON 
standards require Group 1 storage vessels to reduce total HAP emissions 
by 95 percent (or 90 percent if the storage vessel was installed on or 
before December 31, 1992) by venting emissions through a closed vent 
system to any combination of control devices or to vent emissions 
through a closed vent system to a flare. Owners and operators of Group 
1 storage vessels storing a liquid with a MTVP of total organic HAP 
less than 76.6 kPa are also allowed to reduce organic HAP by utilizing 
an IFR, an EFR, an EFR converted to an IFR, routing the emissions to a 
process or a fuel gas system, or vapor balancing. For Group 1 storage 
vessels storing a liquid with a MTVP of total organic HAP greater than 
or equal to 76.6 kPa, owners and operators can reduce organic HAP 
emissions by 95 percent by venting emissions through a closed vent 
system to any combination of control devices, control emissions by 
routing them to a process or a fuel gas system, or by using vapor 
balancing. Pressure vessels (operating in excess of 204.9 kPa without 
emissions to the atmosphere) may also store materials with EtO. For 
storage vessels, the HON allows use of a design evaluation instead of a 
performance test to determine the percent reduction of control devices 
for any quantity of total uncontrolled organic HAP emissions being sent 
to the control device. We provide more details about storage vessels in 
our technology review discussion (see section III.C.2 of this preamble)
    Results of our risk assessment indicate that two HON facilities 
present cancer risks greater than 100-in-1 million just from EtO 
emissions from process vent sources. At one of the two facilities, EtO 
risk from process vent emission sources emitted through PRDs is 
approximately 75 percent of the facility's total SOCMI source category 
risk of 2000-in-1 million. At the other facility, EtO risk from process 
vent emission sources is approximately 20 percent of the facility's 
total SOCMI source category risk of 500-in-1 million. Additionally, EtO 
from storage vessels accounts for approximately 70-in-1 million of the 
source category MIR of 2,000-in-1 million risk. To understand how to 
best address risk within the SOCMI source category, we reviewed 
information from our CAA section 114 request for this rulemaking (see 
section II.C of this preamble) and identified six facilities that 
measured EtO emissions from 14 emission points associated with process 
vents and storage vessels. The information gathered for these emission 
points indicates that HON sources with EtO emissions from process vents 
and storage vessels typically use combustion devices (e.g., thermal 
oxidizers) to control EtO emissions. Of these 14 emission points, seven 
are controlled by either a thermal incinerator, regenerative thermal 
oxidizer, vapor combustion unit, or catalytic oxidation unit; three are 
controlled by a scrubber; and the remaining four are uncontrolled. 
Based on results from the risk assessment, we determined that the 
current MACT standards for HON process vents and storage vessels do not 
result in sufficient reductions of EtO emissions to reduce risk to an 
acceptable level, and, therefore, we evaluated available control 
technologies with a higher level of control, as discussed below.
    In the MON final RTR (see 85 FR 49084, August 12, 2020), the EPA 
evaluated options to control EtO emissions from process vents and 
storage tanks ``in ethylene oxide service'' \50\ regardless of whether 
the emission source is classified as Group 1 or Group 2. To reduce EtO 
emissions from MON process vents and storage

[[Page 25113]]

tanks in EtO service, the EPA finalized a requirement to either: (1) 
Vent 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 process vent and storage tank 
vent (or, for multiple process vents, to less than 5 lb/yr for all 
combined process vents); or (2) vent emissions through a closed-vent 
system to a flare meeting the flare operating requirements discussed in 
section III.D.1 of this preamble.
---------------------------------------------------------------------------

    \50\ In the MON, a process vent in ethylene oxide service means 
each batch and continuous process vent in a process that, when 
uncontrolled, contains a concentration of greater than or equal to 1 
ppmv undiluted ethylene oxide, and when combined, the sum of all 
these process vents would emit uncontrolled, ethylene oxide 
emissions greater than or equal to 5 lb/yr (2.27 kg/yr); a storage 
vessel in ethylene oxide service means a storage tank of any 
capacity and vapor pressure storing a liquid that is at least 0.1 
percent by weight of ethylene oxide.
---------------------------------------------------------------------------

    We are proposing the same ``in ethylene oxide service'' definitions 
as used in MON. For process vents, we are proposing to define ``in 
ethylene oxide service'' in the HON at 40 CFR 63.101 to mean each 
process vent in a process that, when uncontrolled, contains a 
concentration of greater than or equal to 1 ppmv undiluted EtO, and 
when combined, the sum of all these process vents would emit 
uncontrolled EtO emissions greater than or equal to 5 pounds per year 
(2.27 kilograms per year). For storage vessels of any capacity and 
vapor pressure, we are proposing to define ``in ethylene oxide 
service'' in the HON at 40 CFR 63.101 to mean that the concentration of 
EtO of the stored liquid is at least 0.1 percent by weight. 
Additionally, we are proposing that unless specified by the 
Administrator, owners and operators may calculate the concentration of 
EtO of the fluid stored in a storage vessel if information specific to 
the fluid stored is available such as concentration data from safety 
data sheets. We are also proposing that the exemption for ``vessels 
storing organic liquids that contain organic hazardous air pollutants 
only as impurities'' listed in the definition of ``storage vessel'' at 
40 CFR 63.101 does not apply for storage vessels in EtO service.
    We are proposing the same MON EtO-specific requirements \51\ in the 
HON for HON process vents and storage vessels ``in ethylene oxide 
service,'' except that we are proposing to add a requirement that if a 
combustion device is used to comply with the concentration standard, 
then the concentration must be corrected to 3 percent oxygen to 
determine compliance.\52\ Accordingly, to help reduce risk from the 
SOCMI source category to an acceptable level, we are proposing that HON 
process vents in EtO service either reduce emissions of EtO by: (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 process vent, or to less than 5 
pounds per year for all combined process vents; or (2) venting 
emissions through a closed vent system to a flare meeting the proposed 
flare operating requirements discussed in section III.D.1 of this 
preamble (see proposed 40 CFR 63.113(j)). To help reduce risks from the 
SOCMI source category to an acceptable level, we are proposing that HON 
storage vessels in EtO service either reduce emissions of EtO by: (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 tank vent; or (2) 
venting emissions through a closed-vent system to a flare meeting the 
proposed flare operating requirements discussed in section III.D.1 of 
this preamble (see proposed 40 CFR 63.119(a)(5)). Additionally, we 
propose removing the option to allow use of a design evaluation in lieu 
of performance testing to demonstrate compliance for storage vessels in 
EtO service to ensure that the required level of control is achieved 
(see proposed 40 CFR 63.124(a)(1)(i) and (b)(3)). We are also proposing 
that after promulgation of the rule, owners or operators that choose to 
control emissions with a non-flare control device conduct an initial 
performance test according to proposed 40 CFR 63.124 on each existing 
control device in EtO service and on each newly installed control 
device in EtO service to verify performance at the required level of 
control. Additionally, we are proposing at 40 CFR 63.124(b) that owners 
or operators conduct periodic performance testing on non-flare control 
devices in EtO service every 5 years. Additional information on these 
evaluated control options to reduce EtO risk from HON process vents and 
storage vessels is found in the document titled Analysis of Control 
Options for Process Vents and Storage Vessels to Reduce Residual Risk 
of Ethylene Oxide in the SOCMI Source Category for Processes Subject to 
HON, which is available in the docket for this action.
---------------------------------------------------------------------------

    \51\ See 40 CFR 63.2493.
    \52\ We are proposing the concentration correction requirement 
because, unlike MON sources with ethylene oxide which were using 
scrubber controls, HON sources are generally using combustion 
controls for ethylene oxide and a concentration correction for 
combustion controls assures dilution with air is not an additional 
strategy that facilities could use to bypass control requirements.
---------------------------------------------------------------------------

ii. Equipment Leaks
    Emissions of EtO from equipment leaks occur in the form of gases or 
liquids that escape to the atmosphere through connection points (e.g., 
threaded fittings) or through the moving parts of valves, pumps, 
compressors, PRDs, and certain types of process equipment. The 
applicable equipment is those components, including pumps, compressors, 
agitators, PRDs, sampling collection systems, OEL, valves, and 
connectors that contain or contact material that is 5 percent by weight 
or more of organic HAP, operate 300 hours per year or more, and are not 
in vacuum service. The equipment leak HON requirements vary by 
equipment (component) type but require LDAR using monitoring with EPA 
Method 21 of appendix A-7 to 40 CFR part 60 at certain frequencies 
(e.g., monthly, quarterly, every 2 quarters, annually) and have varying 
leak definitions (e.g., 500 ppm, 1,000 ppm, 10,000 ppm) depending on 
the type of service (e.g., gas and vapor service or in light liquid 
service). The LDAR requirements for components in heavy liquid service 
include sensory monitoring and the use of EPA Method 21 monitoring if a 
leak is identified. We provide more details about equipment leaks in 
our technology review discussion (see section III.C.6 of this 
preamble).
    Results from our risk assessment indicate that, for the source 
category MIR of 2,000-in-1 million, approximately 20 percent is from 
emissions of EtO related to HON equipment leaks. We also note that the 
risk from EtO from HON equipment leaks at seven facilities (including 
the facility driving the MIR) is >=100-in-1 million. To help reduce the 
risk from the SOCMI source category to an acceptable level, for EtO 
emissions from HON equipment leaks, we performed a review of available 
measures for reducing EtO emissions from components that are most 
likely to be in EtO service, which include connectors (in gas and vapor 
service or light liquid service), pumps (in light liquid service), and 
valves (in gas or light liquid service). Almost all equipment leak 
emissions of EtO come from these three pieces of equipment. We 
identified options to further strengthen LDAR practices for these three 
pieces of equipment, including by lowering the leak definitions and/or 
requiring more frequent monitoring with EPA Method 21 of 40 CFR part 
60, appendix A-7, to find more equipment leaks faster and fix them.
    For gas/vapor and light liquid connectors in EtO service, we 
identified three options: (1) Require connector monitoring at a leak 
definition of 500 ppm with annual monitoring and no reduction in 
monitoring frequency (i.e., no skip periods), (2) require connector 
monitoring at a leak definition of 100 ppm with annual monitoring and 
no reduction in monitoring frequency, and

[[Page 25114]]

(3) require connector monitoring at a leak definition of 100 ppm with 
monthly monitoring and no reduction in monitoring frequency.
    For light liquid pumps in EtO service, we identified three options: 
(1) Lower the leak definition from 1,000 ppm to 500 ppm with monthly 
monitoring, (2) lower the leak definition from 1,000 ppm to 100 ppm 
with monthly monitoring, or (3) require the use of leakless pumps 
(i.e., canned pumps, magnetic drive pumps, diaphragm pumps, pumps with 
tandem mechanical seals, pumps with double mechanical seals) with 
annual monitoring with a leak definition of any reading above 
background concentration levels.
    For gas/vapor and light liquid valves in EtO service, we identified 
two options: (1) Require a leak definition of 500 ppm with monthly 
monitoring and no reduction in monitoring frequency, or (2) lower the 
leak definition from 500 ppm to 100 ppm with monthly monitoring and no 
reduction in monitoring frequency.
    Due to the high residual risk for some of the facilities from 
equipment leaks of EtO and the potential need for greater emission 
reduction to meet an acceptable level of risk for the SOCMI source 
category, we also evaluated a more stringent option that combines 
several of the component options. We evaluated the combined option of 
requiring monthly monitoring for valves (in gas/vapor and light liquid 
service), connectors (in gas/vapor and light liquid service), and pumps 
(light liquid service) in EtO service at a leak definition of 100 ppm 
for valves and connectors and 500 ppm for pumps using EPA Method 21 of 
40 CFR part 60, appendix A-7. This combined option also does not allow 
equipment in EtO service to be monitored less frequently with skip 
periods nor allow facilities to take advantage of the delay of repair 
provisions. Increasing the monitoring frequency to monthly was analyzed 
for connectors because they are the most numerous equipment components 
at chemical facilities, and they contribute the most to the baseline 
emissions from leaking equipment at the EtO emitting facilities.
    For the component specific control options, we calculated the EtO 
baseline emissions and emissions after implementation of controls for 
each facility using average VOC emission rates for each component, and 
the component counts and the EtO weight percent of the process from the 
responses to the EPA's CAA section 114 request. For the combined option 
of monthly monitoring of gas and light liquid valves and connectors at 
100 ppm and light liquid pumps at 500 ppm, we do not have emission 
factors to estimate reductions for increased monitoring frequencies for 
connectors. Where no simplified emission factor method exists to 
determine potential reductions of applying the option, we estimated 
emissions reductions based on the approach used in other rules,\53\ 
where detailed leak data was available or where a leak distribution 
could be assumed. The equipment leaks model uses a Monte Carlo analysis 
to estimate emissions from EtO facility equipment leaks. A detailed 
discussion of the model is found in the memorandum Analysis of Control 
Options for Equipment Leaks to Reduce Residual Risk of Ethylene Oxide 
in the SOCMI Source Category for Processes Subject to HON, which is 
available in the docket for this action.
---------------------------------------------------------------------------

    \53\ Gas Plant Equipment Leak Monte Carlo Model Code and 
Instructions. October 21, 2021. EPA Docket No. EPA-HQ-OAR-2021-0317. 
Control Options for Equipment Leaks at Gasoline Distribution 
Facilities. October 20, 2021. EPA Docket No. EPA-HQ-OAR-2020-0371.
---------------------------------------------------------------------------

    We are proposing the same ``in ethylene oxide service'' definition 
for equipment as used in MON.\54\ For equipment leaks, we are proposing 
to define ``in ethylene oxide service'' in the HON at 40 CFR 63.101 to 
mean any equipment that contains or contacts a fluid (liquid or gas) 
that is at least 0.1 percent by weight of EtO. For HON equipment in EtO 
service, in order to achieve greater emissions reductions to help meet 
an acceptable level of risk for the SOCMI source category, we are 
proposing the following combined requirements: monitoring of connectors 
in gas/vapor and light liquid service at a leak definition of 100 ppm 
on a monthly basis with no reduction in monitoring frequency or delay 
of repair (see proposed 40 CFR 63.174(a)(3) and 40 CFR 
63.174(b)(3)(vi)); light liquid pump monitoring at a leak definition of 
500 ppm monthly (see proposed 40 CFR 63.163(b)(2)(iv)); and gas/vapor 
and light liquid valve monitoring at a leak definition of 100 ppm 
monthly with no reduction in monitoring frequency or delay of repair 
(see proposed 40 CFR 63.168(b)(2)(iv) and 40 CFR 63.168(d)(5)). 
Additional information on all evaluated control options to reduce EtO 
risk from HON equipment leaks is found in the document titled Analysis 
of Control Options for Equipment Leaks to Reduce Residual Risk of 
Ethylene Oxide in the SOCMI Source Category for Processes Subject to 
HON, which is available in the docket for this action.
---------------------------------------------------------------------------

    \54\ See 40 CFR 63.2550.
---------------------------------------------------------------------------

iii. Heat Exchange Systems
    Emissions of EtO from heat exchange systems occur when a heat 
exchanger's internal tubing material corrodes or cracks, allowing some 
process fluids to mix or become entrained with the cooling water. 
Pollutants (e.g., EtO) in the process fluids may subsequently be 
released from the cooling water into the atmosphere when the water is 
exposed to air (e.g., in a cooling tower for closed-loop systems or 
trenches/ponds in a once-through system). Heat exchange systems subject 
to the HON are required to monitor for leaks of process fluids into 
cooling water and take actions to repair leaks within 45 days if they 
are detected (and facilities may delay the repair of leaks if they meet 
certain criteria). The current HON MACT standard for heat exchange 
systems allows the use of any method listed in 40 CFR part 136 to be 
used to sample cooling water for leaks for the HAP listed in Table 4 to 
subpart F (recirculating systems) and Table 9 to subpart G (once-
through systems) (and other representative substances such as TOC or 
VOC that can indicate the presence of a leak can also be used). In 
addition, the HON allows facilities to monitor for leaks using a 
surrogate indicator of leaks (e.g., ion specific electrode monitoring, 
pH, conductivity), provided that certain criteria in 40 CFR 63.104(c) 
are met. We provide more details about heat exchange systems in our 
technology review discussion (see section III.C.1 of this preamble).
    Results from our risk assessment indicate that EtO leaks from heat 
exchange systems result in risks of 400-in-1 million at one facility 
and 90-in-1 million at another. The HON heat exchange system technology 
review (see section III.C.1 of this preamble) identified use of the 
Modified El Paso Method as a development in practice for heat exchange 
systems at HON-subject facilities. Specifically, we identified the 
following control option for heat exchange systems: quarterly 
monitoring with the Modified El Paso Method, using a leak action level 
defined as a total strippable hydrocarbon concentration (as methane) in 
the stripping gas of 6.2 ppmv (and not allowing delay of repair of 
leaks for more than 30 days where a total strippable hydrocarbon 
concentration (as methane) in the stripping gas of 62 ppmv or higher is 
found). This option would also require follow-up monitoring at the same 
monitoring location where the leak was identified to ensure that any 
leaks found were fixed. For heat exchange systems, we are proposing to 
define ``in ethylene oxide

[[Page 25115]]

service'' in the HON at 40 CFR 63.101 to mean each heat exchange system 
in a process that cools process fluids (liquid or gas) that are 0.1 
percent or greater by weight of EtO. To address the risk from EtO 
emissions due to HON heat exchange system leaks, we evaluated the 
following option for HON heat exchange systems ``in ethylene oxide 
service'': (A) require use of the Modified El Paso Method (see section 
III.C.1 of this preamble), (B) increase the Modified El Paso Method 
monitoring frequency from quarterly to weekly, (C) reduce the allowed 
amount of repair time from 45 days after finding a leak to 15 days from 
the sampling date, and (D) prohibit delay of repair. We anticipate this 
option would reduce EtO emissions from leaking heat exchange systems by 
93 percent because leaks would be identified and repaired quicker, and 
this is needed to help reduce risk from the SOCMI source category. For 
this reason, we are proposing to require weekly monitoring for leaks 
for heat exchange systems in EtO service using the Modified El Paso 
Method (see proposed 40 CFR 63.104(g)(6)), and if a leak is found, we 
are proposing owners and operators must repair the leak to reduce the 
concentration or mass emissions rate to below the applicable leak 
action level as soon as practicable, but no later than 15 days after 
the sample was collected with no delay of repair allowed (see proposed 
40 CFR 63.104(h)(6)). Additional information on this evaluated control 
option to reduce EtO risk from HON heat exchange systems is found in 
the document titled Analysis of Control Options for Heat Exchange 
Systems to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source 
Category for Processes Subject to HON, which is available in the docket 
for this action.
iv. Wastewater
    EtO is emitted into the air from wastewater collection, storage, 
and treatment systems that are uncovered or open to the atmosphere 
through volatilization of the compound at the liquid surface. Emissions 
occur by diffusive or convective means, or both. Diffusion occurs when 
organic pollutant concentrations at the water surface are much higher 
than ambient concentrations. The organic pollutants volatilize, or 
diffuse into the air, to reach equilibrium between the aqueous and 
vapor phases. Convection occurs when air flows over the water surface, 
sweeping organic vapors from the water surface into the air. The rate 
of volatilization is related directly to the speed of the air flow over 
the water surface.
    The current HON standards divide wastewater streams into Group 1 
wastewater streams, which require controls, and Group 2 wastewater 
streams, which generally do not require controls provided they do not 
exceed Group 1 thresholds. The Group 1 and Group 2 designations for 
wastewater streams are based on volumetric flow rate and total annual 
average organic HAP concentration. The HON specifies performance 
standards for treating Group 1 wastewater streams using open or closed 
biological treatment systems or using a design steam stripper with vent 
control. For APCDs (e.g., thermal oxidizers) used to control emissions 
from collection system components, steam strippers, or closed 
biological treatment, the HON provides owners or operators several 
compliance options, including 95 percent destruction efficiency, a 20 
ppmv outlet concentration, or design specifications for temperature and 
residence time. We provide more details about wastewater streams in our 
technology review discussion (see section III.C.5 of this preamble).
    Results from our risk assessment indicate that EtO emissions from 
wastewater result in risks of 200-in-1 million at one facility and 70-
in-1 million at another. For wastewater, we are proposing to define 
``in ethylene oxide service'' in the HON at 40 CFR 63.101 to mean each 
wastewater stream that contains total annual average concentration of 
EtO greater than or equal to 1 part per million by weight at any flow 
rate. To help reduce the risk from EtO emissions to an acceptable 
level, we are proposing that owners and operators of HON sources manage 
and treat any wastewater streams that are ``in ethylene oxide service'' 
(see proposed 40 CFR 63.132(c)(1)(iii) and (d)(1)(ii)) as they would a 
Group 1 wastewater stream. Additional information on this evaluated 
control option to reduce EtO risk from HON wastewater streams is found 
in the document titled Analysis of Control Options for Wastewater 
Streams to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source 
Category for Processes Subject to HON, which is available in the docket 
for this action.
    Finally, we are aware of at least two HON-subject facilities that 
reported EtO emissions from heat exchange systems due to disposing EtO 
entrained water (e.g., condensate water, quench and glycol bleeds) into 
their cooling water. While these are not ``leaks'' from heat exchange 
systems, this water is being combined with water in heat exchange 
systems that should actually be considered a potential source of 
wastewater, as it contains EtO. One of these facilities reported 
approximately 2.5 tpy EtO were released to the atmosphere in 2017 from 
this activity; the other facility reported about 0.5 tpy EtO emissions 
(for 2017) from a similar activity. In order to help reduce risk from 
the SOCMI source category to an acceptable level, and in an effort to 
eliminate these types of EtO emissions from wastewater being injected 
into heat exchange systems, we are also proposing to prohibit owners 
and operators from injecting water into or disposing of water through 
any heat exchange system in a 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)).
v. Maintenance Vents
    We are proposing the new term ``maintenance vent'' for process 
vents that are only used as a result of startup, shutdown, maintenance, 
or inspection of equipment where equipment is emptied, depressurized, 
degassed, or placed into service. We provide more details about 
maintenance vents in section III.D.4 of this preamble. We identified 
three HON-subject facilities that reported EtO emissions from 
maintenance vents in their 2017 NEI from HON processes that use and 
emit EtO. We determined that, in order to help reduce EtO risk from the 
SOCMI source category to an acceptable level, facilities would need to 
limit their amount of EtO being emitted through maintenance vents 
(i.e., equipment openings). For this reason, we are proposing a 
requirement that owners and operators cannot release 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)). We based this proposed limit 
on the largest amount of EtO emissions reported in the 2017 NEI for all 
maintenance vents combined at any single HON-subject facility (i.e., 
one facility reported about 1 ton of EtO from maintenance activities 
which corresponded to 80-in-1 million risk). Facilities could use a 
portable thermal oxidizer to control excess EtO emissions from their 
maintenance vents in order to meet the proposed 1.0 tpy EtO maintenance 
vent limit; \55\ however,

[[Page 25116]]

based on the 2017 NEI, we anticipate that all HON-subject facilities 
with processes that use and emit EtO can already meet this proposed 
emissions limit without additional control.
---------------------------------------------------------------------------

    \55\ We surmised that a portable thermal oxidizer is a 
reasonable control option for maintenance vents because it would 
require a significant effort to identify and characterize each 
potential release point to install permanent APCDs.
---------------------------------------------------------------------------

vi. Flares
    We determined that to achieve an acceptable level of risk, 
facilities need to limit the amount of ethylene oxide they are emitting 
from flaring from all HON emission sources at their facility, even 
after applying the control options for the other HON emission sources 
that we evaluated to reduce risk to an acceptable level. This 
determination is supported by the fact that there is one facility with 
a risk of 500-in-1 million from flaring EtO and another facility with 
risk of 90-in-1 million as a result of this same operation. Therefore, 
we are proposing 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 from all HON emission sources at a facility 
(see proposed 40 CFR 63.108(p)).
    We identified nine HON-subject facilities that reported the use of 
flares in their 2017 NEI to control EtO emissions from HON processes 
that use and emit EtO. Two of these facilities each reported about two 
times more EtO emissions from their flares than the reported EtO 
emissions from all the other seven HON-subject facilities combined. 
Based on this reported emissions data, the highest risk source for 
flaring emitted a combined total of 2.87 tpy of EtO from its flares. In 
order to reduce the HON risk to an acceptable level, the EtO emissions 
from all flares would need to be less than or equal to 0.40 tpy (in 
addition to complying with other standards designed to reduce risk to 
an acceptable level). Assuming 98 percent flare control efficiency and 
back-calculating an EtO waste gas flare load, the maximum inlet load to 
all flares combined would need to be 20 tpy. Using the reported EtO 
emissions of 2.87 tpy from the highest emitting facility, we estimate 
that the facility's current combined total EtO load to flares is about 
143.5 tpy, and that the facility would need to reduce the combined 
total EtO load to their flares by about 124 tpy to meet the EtO load 
limit of 20 tpy. For these reasons, we are proposing 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(p)) to get to an acceptable level of risk from all HON 
emission sources at a facility. A more thorough discussion of this 
analysis is included in the document titled Analysis of Control Options 
for Flares to Reduce Residual Risk of Ethylene Oxide in the SOCMI 
Source Category for Processes Subject to HON, which is available in the 
docket for this action.
vii. PRDs
    The HON currently regulates PRDs through equipment leak provisions 
that are applied only after the pressure release event relief occurs 
(i.e., conduct monitoring with EPA Method 21 of Appendix A-7 to 40 CFR 
part 60 after each pressure release using a leak definition of 500 ppm) 
to ensure they are properly reseated and not leaking after a PRD 
release occurs; however, these provisions do not apply to an emissions 
release from a PRD (see section III.D.2 of this preamble for more 
detail). As previously discussed in section III.B.2.a.i of this 
preamble, we are aware of some instances where PRD releases of EtO 
emissions occurred for gas streams that would otherwise be treated as 
process vents. These PRD releases contribute to a large portion of the 
2000-in-1 million MIR (i.e., 75 percent) that we are proposing is 
unacceptable. While the EPA is proposing to set work practice standards 
for PRD releases (see section III.D.2 of the preamble), in order to 
help reduce risk from the SOCMI source category to an acceptable level 
we are also proposing at 40 CFR 63.165(e)(3)(v)(D) that any release 
event from a PRD in EtO service is a violation of the standard to 
ensure that these process vent emissions are controlled and do not 
bypass controls.
viii. Summary
    For process vents, storage vessels, equipment leaks, heat exchange 
systems, wastewater, maintenance vents, flares, and PRDs, we considered 
the control options described above for reducing EtO risk from the 
SOCMI source category that are associated with processes subject to the 
HON. To reduce risk from the source category to an acceptable level, we 
propose to require control of EtO emissions from: (1) Process vents, 
(2) storage vessels, (3) equipment leaks, (4) heat exchange systems, 
and (5) wastewater ``in ethylene oxide service'' (defined in this 
proposal). We are also proposing requirements to reduce EtO emissions 
from maintenance vents, flares, and PRDs. For process vents and storage 
vessels in EtO service, we are proposing owners and operators reduce 
emissions of EtO by either: (1) Venting emissions through a closed-vent 
system to a 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 and storage vessel, 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. For equipment leaks in EtO 
service, we are proposing the following combined requirements: 
monitoring of connectors in gas/vapor and light liquid service at a 
leak definition of 100 ppm on a monthly basis with no reduction in 
monitoring frequency and no delay of repair; light liquid pump 
monitoring at a leak definition of 500 ppm monthly; and gas/vapor and 
light liquid valve monitoring at a leak definition of 100 ppm monthly 
with no reduction in monitoring frequency and no delay of repair. For 
heat exchange systems in EtO service, we are proposing to require 
owners or operators to conduct more frequent leak monitoring (weekly 
instead of quarterly) and repair leaks within 15 days from the sampling 
date (in lieu of the current 45-day repair requirement after receiving 
results of monitoring indicating a leak), and delay of repair would not 
be allowed. For wastewater in EtO service, we are proposing to revise 
the Group 1 wastewater stream threshold for sources to include 
wastewater streams in EtO service. For maintenance vents, we are 
proposing a requirement that owners and operators cannot release more 
than 1.0 ton of EtO from all maintenance vents combined in any 
consecutive 12-month period. For flares, we are proposing a requirement 
that owners and operators can send no more than 20 tons of EtO to all 
of their flares combined from all HON emission sources at a facility in 
any consecutive 12-month period. For PRDs in EtO service, we are 
proposing that any atmospheric PRD release is a violation of the 
standard.
    In all cases, we are proposing that if information exists that 
suggests EtO could be present in these processes, then the emission 
source is considered to be in EtO service unless sampling and analysis 
is performed to demonstrate that the emission source does not meet the 
definition of being in EtO service. We are proposing sampling and 
analysis procedures at 40 CFR 63.109. Examples of information that 
could suggest EtO is present in a process stream include calculations 
based on safety data sheets, material balances, process stoichiometry, 
or previous test results provided the results are still relevant to the 
current operating conditions.
    Based on the proposed applicability thresholds, we expect that up 
to 17 facilities will be affected by one or more

[[Page 25117]]

of the proposed EtO-specific standards; and we anticipate that all of 
these facilities will be subject to the process vent, storage vessel, 
equipment leak, wastewater, and PRD provisions. We do not expect any 
facility to be impacted by the proposed 1.0 tpy maintenance vent EtO 
emission limit, and only two facilities will be affected by the 
proposed 20 tpy EtO flare load limit, although all facilities will be 
required to comply with these standards.
b. Chloroprene Controls for P&R I Neoprene Production Processes
i. Process Vents and Storage Vessels
    Results from our risk assessment indicate that for the Neoprene 
Production source category, 65 percent of the risk presented by 
neoprene production processes (i.e., 300-in-1 million) and 12 of the 
17.5 tpy of chloroprene in the reported emissions inventory are from 
emissions associated with reaction processes and supporting equipment, 
and storage vessels at the one neoprene production facility. 
Specifically, 58 percent of the risk is associated with emissions from 
the polymer building wall fans housing much of the operations for 
creating neoprene, of which most of the emissions are from the opening 
of the polymer reactors and straining of coagulate generated after the 
batch polymerization occurs to make neoprene; 5 percent of the risk is 
from emissions from unstripped emulsion storage vessels as they are 
being opened and/or degassed; and 2 percent of the risk is from 
emissions from the wash belt dryers. An additional 18 percent of the 
risk is from wastewater sources, which are discussed in III.B.2.b.ii of 
this preamble.
    For process vents, we are proposing to define ``in chloroprene 
service'' in P&R I at 40 CFR 63.482 to mean each continuous front-end 
process vent and each batch front-end process vent in a process at 
affected sources producing neoprene that, when uncontrolled, contains a 
concentration of greater than or equal to 1 ppmv undiluted chloroprene, 
and when combined, the sum of all these process vents would emit 
uncontrolled, chloroprene emissions greater than or equal to 5 lb/yr 
(2.27 kg/yr). For storage vessels, we are proposing to define ``in 
chloroprene service'' in P&R I at 40 CFR 63.482 to mean storage vessels 
of any capacity and vapor pressure in a process at affected sources 
producing neoprene storing a liquid that is at least 0.1 percent by 
weight of chloroprene, which would require control of the unstripped 
resin storage vessels and emissions from opening or degassing of these 
sources. Additionally, we are proposing that unless specified by the 
Administrator, owners and operators may calculate the concentration of 
chloroprene of the fluid stored in a storage vessel if information 
specific to the fluid stored is available such as concentration data 
from safety data sheets. We are proposing to require emissions from 
process vents and storage vessels in chloroprene service be routed to a 
closed vent system to a non-flare control device that reduces 
chloroprene by greater or equal to 99.9 percent by weight, or to a 
concentration less than 1 ppmv for each process vent or storage vessel 
vent, or less than 5 pounds per year for all combined process vents. 
(see proposed 40 CFR 63.484(u)(1), 40 CFR 63.485(y)(1), and 40 CFR 
63.487(j)(1)). Our proposed approach would require control of process 
vent emissions from batch polymer reactors that the one neoprene 
facility has already voluntarily controlled (but that are not currently 
required to be controlled in P&R I) and that are considered in the 
baseline emissions of our risk assessment. These proposed standards 
would also capture emissions from the emulsion storage vessels, 
strainers, and wash belt dryers. We determined that the only viable way 
to meet these proposed standards is to enclose all of the polymer batch 
reactors, emulsion storage vessels, strainers, and wash belt dryers and 
route the vapors to a thermal oxidizer (and thereby reduce chloroprene 
emissions from these sources, which are fugitive in nature). We costed 
out permanent total enclosures, a thermal oxidizer, and ductwork and 
associated support equipment using the procedures in EPA's Control Cost 
Manual. Enclosing and routing vapors to a thermal oxidizer is expected 
to achieve at least 99.9 percent reduction in chloroprene emissions 
from the storage vessels and wash belt dryers. Due the openness of the 
polymer building and other emission sources that could contribute to 
emissions coming from the polymer building overall, we estimate that 90 
percent of the chloroprene emissions will be collected in the 
enclosures and be reduced by at least 99.9 percent in the thermal 
oxidizer. The result of the control option is to reduce chloroprene 
emissions and risk from the polymer building, unstripped resin emulsion 
storage vessels, and the wash belt dryers from 12 tpy to 0.7 tpy. 
Because of concerns that some of these emission sources may not 
necessarily be considered process vents or emissions regulated for 
storage vessels (e.g., since we are assuming permanent total enclosures 
will be needed to collect these emissions since they could be 
fugitive), we are also proposing a facility-wide chloroprene emissions 
cap for all neoprene production emission sources as a backstop, the 
result of which is based on our post-control emissions and risk for all 
neoprene emission sources emitting chloroprene that are reported in the 
emissions inventory and which is discussed in section III.B.2.b.v of 
this preamble.
    Additional information on this evaluated control option to reduce 
chloroprene risk from fugitives from polymer batch reactors, emulsion 
storage vessels, strainers, and wash belt dryers with affected P&R I 
sources producing neoprene is found in the document titled Analysis of 
Control Options for Process Vents and Storage Vessels to Reduce 
Residual Risk of Chloroprene Emissions at P&R I Affected Sources 
Producing Neoprene, which is available in the docket for this action.
ii. Wastewater
    Chloroprene is emitted into the air from wastewater collection, 
storage, and treatment systems that are uncovered or open to the 
atmosphere through volatilization of the compound at the liquid 
surface. Emissions occur by diffusive or convective means, or both. 
Diffusion occurs when organic concentrations at the water surface are 
much higher than ambient concentrations. The organics volatilize, or 
diffuse into the air, to reach equilibrium between aqueous and vapor 
phases. Convection occurs when air flows over the water surface, 
sweeping organic vapors from the water surface into the air. The rate 
of volatilization is related directly to the speed of the air flow over 
the water surface.
    Similar to the HON, as discussed in section III.B.2.a.iv of this 
preamble, the current P&R I standards divide wastewater streams into 
Group 1 wastewater streams, which require controls, and Group 2 
wastewater streams, which generally do not require controls provided 
they remain below Group 1 thresholds. The Group 1 and Group 2 
designations for wastewater streams are based on volumetric flow rate 
and total annual average organic HAP concentration. P&R I specifies 
performance standards for treating Group 1 wastewater streams using 
open or closed biological treatment systems or using a design steam 
stripper with vent control. For APCDs (e.g., thermal oxidizers) used to 
control emissions from collection system components, steam strippers, 
or closed biological treatment, P&R I provides owners or

[[Page 25118]]

operators several compliance options, including 95 percent destruction 
efficiency, a 20 ppmv outlet concentration, or design specifications 
for temperature and residence time. We provide more details about 
wastewater streams in our technology review.
    Results from our risk assessment indicate that, for the Neoprene 
Production source category, 18 percent of the risk (i.e., 80-in-1 
million) and 2.6 of the 17.5 tpy of chloroprene in the reported 
emissions inventory are from emissions associated with wastewater. For 
wastewater, we are proposing to define ``in chloroprene service'' in 
P&R I at 40 CFR 63.482 to mean each wastewater stream that contains 
total annual average concentration of chloroprene greater than or equal 
to 10.0 ppmw at any flow rate. To address the risk from chloroprene 
emissions related to wastewater associated with affected P&R I sources 
producing neoprene, we are proposing that owners and operators manage 
and treat any existing wastewater streams that are ``in chloroprene 
service'' (see proposed 40 CFR 63.501(a)(10)(iv)) as they would a Group 
1 wastewater stream. Additional information on this evaluated control 
option to reduce chloroprene risk from wastewater streams associated 
with affected P&R I sources producing neoprene is found in the document 
titled Analysis of Control Options for Wastewater Streams to Reduce 
Residual Risk of Chloroprene From Neoprene Production Processes Subject 
to P&R I, which is available in the docket for this action.
    Finally, for consistency with our proposal for the HON to eliminate 
EtO emissions from wastewater being injected into heat exchange systems 
(see section III.B.2.a.iv of this preamble), we are also proposing to 
prohibit owners and operators from injecting water into or disposing of 
water through any heat exchange system in an 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)). The result 
of all these wastewater controls will reduce chloroprene emissions from 
wastewater from 2.6 tpy to 0.18 tpy in the reported emissions 
inventory.
iii. Maintenance Vents
    We are proposing at 40 CFR 63.485(x) and 40 CFR 63.487(i) the new 
term ``maintenance vent'' for process vents that are only used as a 
result of startup, shutdown, maintenance, or inspection of equipment 
where equipment is emptied, depressurized, degassed, or placed into 
service. We provide more details about maintenance vents in section 
III.D.4 of this preamble as well. We evaluated the option of limiting 
the amount of chloroprene that a neoprene production facility can emit 
annually through maintenance vents (i.e., equipment openings). Using 
their reported emissions, we determined that in order to reduce the 
neoprene source category risk to an acceptable level, the one neoprene 
production facility would need to (in addition to complying with other 
standards designed to reduce chloroprene risk) maintain its combined 
total chloroprene maintenance vent emission releases at less than or 
equal to 1.0 tpy. For this reason, we are proposing a requirement that 
owners and operators cannot release more than 1.0 tons of chloroprene 
from all maintenance vents combined in any consecutive 12-month period 
(see proposed 40 CFR 63.485(z) and 40 CFR 63.487(i)(4)). We note that, 
based on reported emissions, the neoprene production facility is 
already meeting this proposed 1.0 tpy chloroprene maintenance vent 
limit from its neoprene processes.\56\
---------------------------------------------------------------------------

    \56\ From reported Neoprene Unit Condition XVII permitted 
emissions.
---------------------------------------------------------------------------

iv. PRDs
    P&R I currently regulates PRDs through equipment leak provisions 
that are applied only after the pressure release event relief occurs 
(i.e., conduct monitoring with EPA Method 21 of Appendix A-7 to 40 CFR 
part 60 after each pressure release using a leak definition of 500 ppm) 
to ensure they are properly reseated and not leaking after a PRD 
release occurs; however, these provisions do not apply to an emissions 
release from a PRD (see section III.D.2 of this preamble for more 
detail). While we are not aware of PRD releases occurring from the 
Neoprene Production source category, we are concerned that allowing 
them could compound already unacceptable risk. Thus, while the EPA is 
proposing to set work practice standards for PRD releases (see section 
III.D.2 of the preamble), given the high potential risk posed by 
chloroprene from PRD releases, we are also proposing at 40 CFR 
63.165(e)(3)(v)(D) (by way of proposed 40 CFR 63.502(a)(2)) that any 
release event from PRDs in chloroprene service in the Neoprene 
Production source category facilities is a violation of the standard. 
This is the same provision that we finalized in the MON for PRDs in EtO 
service (see 40 CFR 63.2493(d)(4)(iv)), and that we are proposing for 
HON PRDs in EtO service, to ensure that these emissions are controlled 
and do not bypass controls.
v. Summary
    For process vents, storage vessels, wastewater, maintenance vents, 
and PRDs, we considered the control options described above for 
reducing chloroprene risk from the Neoprene Production source category. 
To reduce risk from the source category to an acceptable level, we 
propose to require control of chloroprene for: (1) Process vents, (2) 
storage vessels, and (3) wastewater ``in chloroprene service'' (defined 
in this proposal). We are also proposing requirements to reduce 
chloroprene emissions from maintenance vents and PRDs. For process 
vents and storage vessels in chloroprene service, we are proposing 
owners and operators reduce emissions of chloroprene by venting 
emissions through a closed-vent system to a 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 and storage 
vessel, or to less than 5 lb/yr for all combined process vents. For 
wastewater in chloroprene service, we are proposing to revise the Group 
1 wastewater stream threshold for sources to include wastewater streams 
in chloroprene service. For maintenance vents, we are proposing a 
requirement that owners and operators cannot release more than 1.0 ton 
of chloroprene from all maintenance vents combined in any consecutive 
12-month period. For PRDs in chloroprene service, we are proposing that 
any atmospheric PRD release is a violation of the standard. Lastly, in 
order to ensure reductions in emissions and risk given that many 
sources within the neoprene process are fugitive in nature, we are also 
proposing a facility-wide chloroprene emissions cap for all neoprene 
production emission sources as a backstop. After application of the 
proposed controls to address unacceptable risk for process vents, 
storage vessels, wastewater, maintenance vents, and PRDs, and including 
remaining sources of emissions in the emissions inventory (e.g., 
equipment leaks), we are proposing at 40 CFR 63.483(a)(10) a facility-
wide chloroprene emissions cap of 3.8 tpy in any consecutive 12-month 
period for all neoprene production emission sources.
    In all cases, we are proposing that if information exists that 
suggests chloroprene could be present in these processes, then the 
emission source is considered to be in chloroprene service unless 
sampling and analysis is performed to demonstrate that the

[[Page 25119]]

emission source does not meet the definition of being in chloroprene 
service. We are proposing sampling and analysis procedures at 40 CFR 
63.509. Examples of information that could suggest chloroprene is 
present in a process stream include calculations based on safety data 
sheets, material balances, process stoichiometry, or previous test 
results provided that the results are still relevant to the current 
operating conditions.
    Based on the proposed applicability thresholds, we expect that only 
one facility (i.e., the neoprene production facility) will be affected 
by the proposed chloroprene-specific standards, and we anticipate that 
this facility will be subject to the process vent, storage vessel, 
wastewater, maintenance vent, and PRD provisions.
3. Determination of Risk Acceptability After Proposed Emission 
Reductions
    As noted in sections II.A.1 and II.E of this preamble and in the 
1989 Benzene NESHAP, the EPA sets standards under CAA section 112(f)(2) 
using a two-step approach, with an analytical first step to determine 
whether risks are acceptable. This determination ``considers all health 
information, including risk estimation uncertainty, and includes a 
presumptive limit on maximum individual lifetime [cancer] risk (MIR) of 
approximately 1 in 10 thousand'' (54 FR 38044, 38045/col. 1, September 
14, 1989). In the 1989 Benzene NESHAP, the EPA explained that ``[i]n 
establishing a presumption for MIR, rather than a rigid line for 
acceptability, the Agency intends to weigh it with a series of other 
health measures and factors'' (id., at 38045/ col. 3). ``As risks 
increase above this benchmark, they become presumptively less 
acceptable under section 112, and would be weighed with the other 
health risk measures and information in making an overall judgement on 
acceptability'' (id.).
a. SOCMI
    Presented in the Table 4 of this preamble are the levels of 
emissions control proposed to address unacceptable risks for the SOCMI 
source category. This includes reducing emissions of EtO for HON 
processes and requiring more stringent controls for process vents, 
storage vessels, equipment leaks, heat exchange systems, wastewater, 
maintenance vents, flares, and PRDs without considering costs.

Table 4--Nationwide EtO Risk Impact Control Options for the SOCMI Source
                                Category
------------------------------------------------------------------------
                                                             Percent
        Emission source             Description of      reduction of EtO
                                    proposed option         emissions
------------------------------------------------------------------------
Process Vent Controls \1\.....  Control emissions       99.9 percent.
                                 through a closed-vent
                                 system to a non-flare
                                 control device that
                                 reduces EtO by
                                 greater than or equal
                                 to 99.9 percent by
                                 weight, to a
                                 concentration less
                                 than 1 ppmv for each
                                 process vent, or to
                                 less than 5 lb/yr for
                                 all combined process
                                 vents.
Storage Vessel Controls \1\...  Control emissions       99.9 percent.
                                 through a closed-vent
                                 system to a non-flare
                                 control device that
                                 reduces EtO by
                                 greater than or equal
                                 to 99.9 percent by
                                 weight or to a
                                 concentration less
                                 than 1 ppmv.
Equipment Leak Controls.......  Monthly M21 monitoring  70-74 percent.
                                 of valves and
                                 connectors with a 100
                                 ppm leak definition
                                 and monthly
                                 monitoring of pumps
                                 at 500 ppm leak
                                 definition without
                                 skip periods or delay
                                 of repair for these
                                 pieces of equipment
                                 that are in EtO
                                 service.
Heat Exchange Systems Controls  Weekly monitoring for   93 percent.
                                 leaks using the
                                 Modified El Paso
                                 Method and repair of
                                 leaks required no
                                 later than 15 days
                                 after date of weekly
                                 sampling occurs.
Wastewater Controls...........  Control all wastewater  98 percent.
                                 with a total annual
                                 average concentration
                                 of EtO greater than
                                 or equal to 1 ppmw at
                                 any flow rate as if
                                 it were Group 1
                                 wastewater.
Maintenance Vent Emission Cap.  1.0 tpy limit.........  Proposing to
                                                         limit to
                                                         existing level
                                                         in emissions
                                                         inventory.
Flare Load Limit..............  20 tpy limit on amount  Site specific
                                 of EtO that could be    and would
                                 sent to a flare.        likely require
                                                         two facilities
                                                         to use a 99.9
                                                         percent control
                                                         rather than a
                                                         flare achieving
                                                         98 percent.
PRD releases..................  Work practice           Assumed 99.9
                                 standards make          percent
                                 atmospheric releases    control, as it
                                 from PRDs in EtO        would be
                                 service a violation     controlled as a
                                 from the standard.      process vent.
------------------------------------------------------------------------
\1\ Flares may also be used up to the flare load limit, though we do not
  expect this to occur given facilities would need to meet these more
  stringent control requirements after reaching the 20 tpy load limit.

    For the SOCMI source category, after implementation of the proposed 
controls to address unacceptable risks, the MIR is reduced to 100-in-1 
million (down from 2,000-in-1 million) with no facilities or 
populations exposed to risk levels greater than 100-in-1 million. The 
total population exposed to risk levels greater than or equal to 1-in-1 
million living within 50 km (~31 miles) of a facility would be reduced 
from 7.2 million people to 5.7 million people. The total estimated 
cancer incidence of 2 drops to 0.4 excess cancer cases per year. The 
maximum modeled chronic noncancer TOSHI for the source category remains 
unchanged. It is estimated to be 2 (for respiratory effects) at two 
different facilities (from maleic anhydride emissions at one facility 
and chlorine emissions at another facility) with approximately 83 
people estimated to be exposed to a TOSHI greater than 1. The estimated 
worst-case off-site acute exposures to emissions from the SOCMI source 
category also remain
unchanged, with a maximum modeled acute HQ of 3 based on the RELs for 
chlorine and acrolein. Table 5 of this preamble summarizes the 
reduction in cancer risks based on the proposed controls.

[[Page 25120]]

          Table 5--Cancer Risks After Implementation of Proposed Control for the SOCMI Source Category
----------------------------------------------------------------------------------------------------------------
                                        MIR (x-in-1      Population (>=1-   Population (>100-
          Control scenario                million)        in-1 million)       in-1 million)     Cancer incidence
----------------------------------------------------------------------------------------------------------------
Pre-Control Baseline...............              2,000          7,200,000              87,000                  2
Post-Control.......................                100          5,700,000                   0                0.4
----------------------------------------------------------------------------------------------------------------

    As noted earlier in this section, the EPA considers an MIR of 
``approximately 1-in-10 thousand'' (i.e., 100-in-1 million) to be the 
presumptive limit of acceptability (54 FR 38045, September 14, 1989) 
and the proposed controls lower the MIR to 100-in-1 million. This is a 
significant reduction from the pre-control MIR of 2,000-in-1 million. 
For noncancer effects, the EPA has not established under section 112 of 
the CAA a numerical range for risk acceptability as it has with 
carcinogens, nor has it determined that there is a bright line above 
which acceptability is denied. However, the Agency has established 
that, as exposure increases above a reference level (as indicated by a 
HQ or TOSHI greater than 1), confidence that the public will not 
experience adverse health effects decreases and the likelihood that an 
effect will occur increases.
    In considering the potential implications of HIs above 1 (and equal 
to 2) for chlorine and maleic anhydride emissions, we note the basis 
and development of the underlying noncancer health benchmarks. Both 
chlorine and maleic anhydride are portal of entry irritants that, with 
sufficient exposure, act as potent irritants of the eyes and 
respiratory tract. Chronic exposure in human workers has been 
associated with airflow obstruction and asthma-like attacks, indicating 
a potential for people with asthma to have greater sensitivity to 
effects of these pollutants. The health benchmarks for chlorine and 
maleic anhydride represent exposure levels at (and below) which there 
is not likely to be appreciable risk of deleterious effects over a 
lifetime exposure, including for sensitive groups; however, the EPA has 
not estimated an exposure level at and above which an appreciable risk 
of deleterious effects would be expected.
    In the case of chlorine, the sensitive effect on which the 
benchmark is based is an increased risk of nasal lesions. The chronic 
exposure level at which this effect, which was observed in an 
experimental animal study, is estimated is 0.004 mg/m\3\.\57\ \58\ In 
the case of maleic anhydride, the sensitive effect is the occurrence of 
mild hyperplasia in the nasal epithelium.59 60 The chronic 
exposure level at which this effect, which was observed in several 
experimental animal studies, is estimated is 0.021 mg/m\3\. To derive 
the chronic health benchmarks, both of these human equivalent exposure 
values were divided by 30 to account for the potential for people to be 
more sensitive than animals and for some population groups, such as 
people with asthma, to be more sensitive than the general population.
---------------------------------------------------------------------------

    \57\ Agency for Toxic Substances and Disease Registry (ATSDR). 
2010. Toxicological profile for Chlorine. Atlanta, GA: U.S. 
Department of Health and Human Services, Public Health Service.
    \58\ Klonne DR, Ulrich CE, Riley MG, et al. 1987. One-year 
inhalation toxicity study of chlorine in Rhesus monkeys (Macaca 
mulatta). Fundam Appl Toxicol 9:557-572.
    \59\ Office of Environmental Health Hazard Assessment (OEHHA). 
2008. Technical Supporting Document for Noncancer RELs, Appendix D3.
    \60\ Short RD, Minor JL, Winston JM, Seifter J, and Lee C. 1978. 
Inhalation of ethylene dibromide during gestation by rats and mice. 
Toxicol. Appl. Pharmacol. 46:173-182.
---------------------------------------------------------------------------

    For both chlorine and maleic hydride, we note the small size of the 
HI (2) in relation to the total uncertainty factor of 30 used in 
derivation of both health benchmarks. In so doing, we also note a 
somewhat reduced confidence in a conclusion that exposure at these 
levels is without appreciable risk due to uncertainty, particularly for 
sensitive populations. Finally, we note that the population exposed to 
a TOSHI greater than 1 is relatively small (83 people).
    Therefore, considering all health information, including risk 
estimation uncertainty, the EPA proposes that the resulting risks after 
implementation of the proposed controls for the SOCMI source category 
detailed in Section III.B.2.a. would be acceptable. We solicit comment 
on all the proposed control requirements to reduce risk to an 
acceptable level for the SOCMI source category.
b. Neoprene Production
    Presented in Table 6 of this preamble are the levels of emissions 
control proposed to address unacceptable risks for the Neoprene 
Production source category. This includes emission reductions of 
chloroprene from process vents, storage vessels, wastewater, 
maintenance vents, and PRDs without considering costs, as well as a 
facility-wide emissions cap for chloroprene from all Neoprene 
Production emission sources.

   Table 6--Nationwide Chloroprene Risk Impact Control Options for the
                   Neoprene Production Source Category
------------------------------------------------------------------------
                                                             Percent
                                    Description of        reduction of
        Emission source             proposed option        chloroprene
                                                            emissions
------------------------------------------------------------------------
Process Vent Controls.........  Control emissions       99.9 percent.
                                 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. This includes
                                 also capturing and
                                 controlling emissions
                                 from opening of the
                                 polymer reactors and
                                 strainers.
Storage Vessel Controls.......  Control emissions       99.9 percent.
                                 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. This
                                 includes also
                                 capturing and
                                 controlling emissions
                                 from opening and/or
                                 degassing of the
                                 unstripped resin
                                 emulsion tanks.

[[Page 25121]]

 
Wastewater Controls...........  Control all wastewater  93 percent.
                                 with a total annual
                                 average concentration
                                 of chloroprene
                                 greater than or equal
                                 to 10 ppmw at any
                                 flow rate as if it
                                 were Group 1
                                 wastewater.
Maintenance Vent Emission Cap.  1.0 tpy limit.........  Proposing to
                                                         limit to
                                                         existing level
                                                         in emissions
                                                         inventory.
PRD releases..................  Work practice           None were
                                 standards make          reported in
                                 atmospheric releases    emissions
                                 from PRDs in            inventory,
                                 chloroprene service a   proposing
                                 violation from the      standard to
                                 standard.               ensure this
                                                         remains the
                                                         case.
Facility-wide emissions cap     3.8 tpy limit, which    79 percent.
 for chloroprene from all        is a backstop to
 Neoprene Production emission    ensure reductions in
 sources.                        emissions and risk
                                 given that many
                                 sources within the
                                 neoprene process are
                                 fugitive.
------------------------------------------------------------------------

    For the Neoprene Production source category, after implementation 
of the proposed controls to address unacceptable risks, the MIR is 
reduced to 100-in-1 million (down from 500-in-1 million) with zero 
people exposed to risk levels greater than 100-in-1 million. The total 
population exposed to risk levels greater than or equal to 1-in-1 
million living within 50 km (~31 miles) of the facility would be 
reduced from 690,000 people to 48,000 people. The total estimated 
cancer incidence of 0.05 drops to 0.008 excess cancer cases per year. 
Table 7 of this preamble summarizes the reduction in cancer risks based 
on the proposed controls.

  Table 7--Nationwide Risk Impacts After Implementation of Proposed Controls for the Neoprene Production Source
                                                    Category
----------------------------------------------------------------------------------------------------------------
                                         MIR (x-in-1      Population (>=1-  Population (>100-
          Control scenario                 million)        in-1 million)      in-1 million)     Cancer incidence
----------------------------------------------------------------------------------------------------------------
Pre-Control Baseline................                500            690,000              2,100               0.05
Post-Control........................                100             48,000                  0              0.008
----------------------------------------------------------------------------------------------------------------

    Again, as noted earlier in this section, the EPA considers an MIR 
of ``approximately 1-in-10 thousand'' (i.e., 100-in-1 million) to be 
the presumptive limit of acceptability (54 FR 38045, September 14, 
1989) and the proposed controls lower the MIR to 100-in-1 million, a 
significant reduction in the pre-control MIR of 500-in-1 million. 
Therefore, after implementation of the proposed controls for the 
Neoprene Production source category detailed in Section III.B.2.a. and 
considering all health information, including risk estimation 
uncertainty, the EPA proposes that the resulting risks would be 
acceptable for the Neoprene Production source category. We solicit 
comment on all the proposed control requirements to reduce risk to an 
acceptable level for the source category.
4. Ample Margin of Safety Analysis
    The second step in the residual risk decision framework is a 
determination of whether the emission standards proposed to achieve an 
acceptable risk level provide an ample margin of safety to protect 
public health, or whether more stringent emission standards would be 
required for this purpose. In making this determination, we considered 
the health risk and other health information considered in our 
acceptability determination, along with additional factors not 
considered in the risk acceptability step, including costs and economic 
impacts of controls, technological feasibility, uncertainties, and 
other relevant factors, consistent with the approach of the 1989 
Benzene NESHAP. Table 8 of this preamble presents the summary of costs 
and EtO emission reductions we estimated for the proposed control 
requirements to get the risks to an acceptable level for the SOCMI 
source category. For details on the assumptions and methodologies used 
in the costs and impacts analyses, see the technical documents titled, 
Analysis of Control Options for Process Vents and Storage Vessels to 
Reduce Residual Risk of Ethylene Oxide in the SOCMI Source Category for 
Processes Subject to HON; Analysis of Control Options for Equipment 
Leaks to Reduce Residual Risk of Ethylene Oxide in the SOCMI Source 
Category for Processes Subject to HON; Analysis of Control Options for 
Heat Exchange Systems to Reduce Residual Risk of Ethylene Oxide in the 
SOCMI Source Category for Processes Subject to HON; Analysis of Control 
Options for Wastewater Streams to Reduce Residual Risk of Ethylene 
Oxide in the SOCMI Source Category for Processes Subject to HON; and 
Analysis of Control Options for Flares to Reduce Residual Risk of 
Ethylene Oxide in the SOCMI Source Category for Processes Subject to 
HON, which are available in the docket for this rulemaking. We note 
that for two fugitive EtO emission sources (i.e., equipment leaks and 
wastewater), emission reductions (and subsequent cost-effectiveness 
values for EtO) differ from reductions expected to occur from reported 
emissions inventories due to use of model plants, engineering 
assumptions made to estimate baseline emissions, and uncertainties in 
how fugitive emissions may have been calculated for reported 
inventories compared to our model plants analyses (and are documented 
in the aforementioned technology review memorandum).

[[Page 25122]]

  Table 8--Nationwide EtO Emission Reductions and Cost Impacts for Control Options Considered for HON Processes
----------------------------------------------------------------------------------------------------------------
                                                   Total capital       Total       EtO emission        Cost
                 Control option                     investment      annualized      reductions     effectiveness
                                                       (MM$)      costs (MM$/yr)       (tpy)        ($/ton EtO)
----------------------------------------------------------------------------------------------------------------
A--Process Vent & Storage Vessel Controls.......            10.2            5.28            32.0         165,000
B--Equipment Leak Controls......................            0.18            3.53            42.3          83,500
C--Heat Exchange System Controls................           0.043            0.19            6.06          31,400
D--Wastewater Controls..........................            65.8            41.1             396         103,800
E--Maintenance Vent Emission Cap \1\............           0.017          0.0027               0             N/A
F--Flare Load Limit.............................            0.28            0.46            5.04          91,300
                                                 ---------------------------------------------------------------
    Total (A + B + C + D + E + F)...............            76.5            50.6             481         105,000
----------------------------------------------------------------------------------------------------------------
\1\ We anticipate that all facilities with HON processes that use and emit EtO can already meet the proposed
  maintenance vent emissions limit without additional control, thus only minimal costs are included.

    Table 9 of this preamble presents the summary of costs and 
chloroprene emission reductions we estimated for the proposed control 
options to get the risks to an acceptable level for the Neoprene 
Production source category. For details on the assumptions and 
methodologies used in the costs and impacts analyses, see the technical 
documents titled Analysis of Control Options for Process Vents and 
Storage Vessels to Reduce Residual Risk of Chloroprene Emissions at P&R 
I Affected Sources Producing Neoprene; and Analysis of Control Options 
for Wastewater Streams to Reduce Residual Risk of Chloroprene From 
Neoprene Production Processes Subject to P&R I, which are available in 
the docket for this rulemaking. We note that chloroprene emission 
reductions from wastewater (and subsequent cost-effectiveness values 
for chloroprene from wastewater) differ from reductions expected to 
occur from reported emissions inventories due to use of model plants, 
engineering assumptions made to estimate baseline emissions, and 
uncertainties in how fugitive emissions may have been calculated for 
reported inventories compared to our model plants analysis (and are 
documented in the aforementioned memorandum).

  Table 9--Nationwide Chloroprene Emission Reductions and Cost Impacts for Control Options Considered for P&R I
                                          Processes Producing Neoprene
----------------------------------------------------------------------------------------------------------------
                                                                                    Chloroprene        Cost
                                                   Total capital       Total         emission      effectiveness
                 Control option                     investment      annualized      reductions        ($/ton
                                                       (MM$)      costs (MM$/yr)       (tpy)       chloroprene)
----------------------------------------------------------------------------------------------------------------
A--Process Vent, Storage Vessel, & Maintenance              10.1            2.80            11.3         247,800
 Vent Controls..................................
B--Wastewater Controls..........................            5.84            7.56            17.7         427,000
                                                 ---------------------------------------------------------------
    Total (A + B)...............................            15.9            10.4            29.0         359,000
----------------------------------------------------------------------------------------------------------------

    For the ample margin of safety analyses, we evaluated the cost and 
feasibility of available control technologies that could be applied to 
HON processes and neoprene production processes to reduce risks 
further, considering all of the health risks and other health 
information considered in the risk acceptability determination 
described above and the additional information that can be considered 
only in the ample margin of safety analysis (i.e., costs and economic 
impacts of controls, technological feasibility, uncertainties, and 
other relevant factors). We note that the EPA previously made a 
determination that the standards for the SOCMI source category and 
Neoprene Production source category provide an ample margin of safety 
to protect public health, and that the most significant changes since 
that determination were the revised 2016 IRIS inhalation URE for EtO 
and new 2010 IRIS inhalation URE for chloroprene. As such, we focused 
our ample margin of safety analysis on cancer risk for these two 
pollutants since EtO, even after application of controls needed to get 
risks to an acceptable level, drives cancer risk and cancer incidence 
(i.e., 60 percent of remaining cancer incidence is from EtO) for the 
SOCMI source category and almost all the remaining cancer risk and 
cancer incidence (i.e., 99.995 percent of remaining cancer incidence) 
is from chloroprene for the Neoprene Production source category.
    For the SOCMI source category, no other control options for EtO 
were identified beyond those proposed to reduce risks to an acceptable 
level. Furthermore, the proposed EtO controls for process vents, 
storage vessels, equipment leaks, heat exchange systems, wastewater, 
and PRDs to reduce risks to an acceptable level are far more stringent 
than other options we identified to control HAP generally (i.e., see 
sections III.C and III.D of this preamble).
    For chloroprene emissions from HON-subject sources, we identified 
control options for equipment leaks and maintenance activities in our 
review of these standards (see sections III.C.6 and III.D.4 of this 
preamble). These controls would likely reduce the cancer incidence and 
number of people exposed to risks greater than or equal to 1. However, 
the overall source category risk reductions would be relatively small. 
Only approximately 3 percent of the SOCMI source category cancer 
incidence after the proposed controls in section III.B.2 to reduce 
risks to an acceptable level is due to chloroprene emissions. Also, of 
the 5.7 million people with cancer risks greater than or equal to 1-in-
1 million after the proposed controls to reduce risks to an

[[Page 25123]]

acceptable level, approximately 48,000 people (or 0.8 percent of the 
total) have risks greater than or equal to 1-in-1 million due to 
chloroprene emissions from the SOCMI source category. However, as 
described in sections III.C.6 and III.D.4, the options we evaluated for 
equipment leaks and maintenance activities beyond the standards 
currently in the HON (or that are being proposed for maintenance 
activities) are not cost-effective.
    For the Neoprene Production source category, we did not identify 
control options for chloroprene emissions from process vents, storage 
vessels, wastewater, maintenance vents, and PRDs that reduced emissions 
beyond those proposed in section III.B.2 to reduce risks to an 
acceptable level. We also considered other potential sources of 
chloroprene, in particular heat exchange systems and equipment leaks. 
For heat exchange systems, no chloroprene emissions were reported in 
the emissions inventory from this source and as such, no risk 
reductions would be realized by requiring more stringent controls. For 
equipment leaks, additional control options were identified that could 
reduce risks further from this source and are discussed as part our 
technology review (see section III.C.6 of this preamble). The options 
would reduce chloroprene equipment leak emissions by 10-20 percent. 
Approximately 14 percent of the Neoprene Production source category 
cancer incidence after the proposed controls in section III.B.2 to 
reduce risks to an acceptable level is due to chloroprene emissions 
from equipment leaks. Also, of the 48,000 people with cancer risks 
greater than or equal to 1-in-1 million after the proposed controls to 
reduce risks to an acceptable level, approximately 16,000 people (or 34 
percent of the total) have risks greater than or equal to 1-in-1 
million due to chloroprene emissions from equipment leaks. Therefore, a 
10-20 percent reduction in equipment leak emissions would reduce the 
cancer incidence by approximately 1 to 4 percent and the number of 
people with cancer risks greater than or equal to 1-in-1 million by 
approximately 2,000 to 3,000 people (3 to 7 percent of the total). 
However, as described in sections III.C and III.D, the options we 
evaluated for equipment leaks are not cost-effective.
    In summary, based on our ample margin of safety analysis, we 
propose that controls to reduce EtO emissions at HON processes and 
chloroprene emissions at neoprene production processes to get risks to 
an acceptable level would also provide an ample margin of safety to 
protect public health. We also note the proposed changes to the flare 
requirements, proposed standards for dioxins/furans, and proposed 
standards to remove SSM exemptions (or provide alternative standards in 
limited instances) that are in this proposed action and that we are 
proposing under CAA sections 112(d)(2) and (3) will achieve additional 
reductions in emissions and further strengthen our conclusions that the 
standards continue to provide an ample margin of safety to protect 
public health for the SOCMI and Neoprene Production source categories.
5. Adverse Environmental Effects
    Based on our screening assessment of environmental risk presented 
in section III.A.4 of this preamble, we did not identify any areas of 
concern with respect to environmental risk. Therefore, we have 
determined that HAP emissions from the source categories do not result 
in an adverse environmental effect, and we are proposing that it is not 
necessary to set a more stringent standard to prevent, taking into 
consideration costs, energy, safety, and other relevant factors, an 
adverse environmental effect.

C. What are the results and proposed decisions based on our CAA section 
112(d)(6) technology review and CAA section 111(b)(1)(B) NSPS reviews, 
and what are the rationale for those decisions?

    In addition to the proposed EtO- and chloroprene-specific 
requirements discussed in section III.B.2 of this preamble, under CAA 
section 112(d)(6) we also evaluated developments in practices, 
processes, and control technologies for heat exchange systems, storage 
vessels, process vents, transfer racks, wastewater, and equipment leaks 
for processes subject to the HON, P&R I, and P&R II (see sections 
III.C.1 through III.C.6 of this preamble, respectively). Under CAA 
section 111(b)(1)(B), for the review of NSPS subpart VVa, we evaluated 
BSER for equipment leaks (see section III.C.6.b of this preamble); and 
for the review of NSPS subparts III, NNN, and RRR we evaluated BSER for 
process vents associated with air oxidation units, distillation 
operations, and reactor processes, respectively (see section III.C.3.b 
of this preamble). We analyzed costs and emissions reductions for each 
emission source (e.g., process vents) by each rule. For NSPS, we 
determined cost-effectiveness, cost per ton of emissions reduced, on a 
VOC basis. For NESHAP, we determined cost-effectiveness on a HAP basis 
from the VOC emissions. We also evaluated fenceline monitoring as a 
development in practices considered under CAA section 112(d)(6) for the 
purposes of managing fugitive emissions from sources subject to the HON 
and P&R I (see section III.C.7 of this preamble).
1. Standards for Heat Exchange Systems
    Heat exchangers are devices or collections of devices used to 
transfer heat from process fluids to another process fluid (typically 
water) without intentional direct contact of the process fluid with the 
cooling fluid (i.e., non-contact heat exchanger). There are two types 
of heat exchange systems: Closed-loop recirculation systems and once-
through systems. Closed-loop recirculation systems use a cooling tower 
to cool the heated water leaving the heat exchanger and then return the 
newly cooled water to the heat exchanger for reuse. Once-through 
systems typically use surface freshwater (e.g., from rivers) as the 
influent cooling fluid to the heat exchangers, and the heated water 
leaving the heat exchangers is then discharged from the facility. At 
times, the internal tubing material of a heat exchanger can corrode or 
crack, allowing some process fluids to mix or become entrained with the 
cooling water. Pollutants in the process fluids may subsequently be 
released from the cooling water into the atmosphere when the water is 
exposed to air (e.g., in a cooling tower for closed-loop systems or 
trenches/ponds in a once-through system). The term ``heat exchange 
system'' is defined in HON and P&R I at 40 CFR 63.101 and 40 CFR 63.482 
(which references 40 CFR 63.101) as any cooling tower system or once-
through cooling water system (e.g., river or pond water). A heat 
exchange system can include more than one heat exchanger and can 
include an entire recirculating or once-through cooling system. 
However, the HON and P&R I do not describe a heat exchanger, closed-
loop recirculation system, or once-through cooling system as part of 
its definition of ``heat exchange system''. Therefore, we are proposing 
to revise the definition of ``heat exchange system'' at 40 CFR 63.101 
and 40 CFR 63.482 (which references 40 CFR 63.101) to mean a device or 
collection of devices used to transfer heat from process fluids to 
water without intentional direct contact of the process fluid with the 
water (i.e., non-contact heat exchanger) and to transport and/or cool 
the water in a closed-loop recirculation system (cooling tower system) 
or a once-through system (e.g., river or pond water). This is 
consistent with the definition of ``heat exchange system'' used in the 
MON. We are also

[[Page 25124]]

proposing (as is done in the MON) to make clear in this definition 
that: (1) For closed-loop recirculation systems, the heat exchange 
system consists of a cooling tower, all CMPU heat exchangers that are 
in organic HAP service (for HON) or all EPPU heat exchangers that are 
in organic HAP service (for P&R I), serviced by that cooling tower, and 
all water lines to and from these process unit heat exchangers.; (2) 
for once-through systems, the heat exchange system consists of all heat 
exchangers that are in organic HAP service, servicing an individual 
CMPU (for HON) or EPPU (for P&R I) and all water lines to and from 
these heat exchangers; (3) sample coolers or pump seal coolers are not 
considered heat exchangers for the purpose of this proposed definition 
and are not part of the heat exchange system; and (4) intentional 
direct contact with process fluids results in the formation of a 
wastewater. This proposed definition would also apply to heat exchange 
systems in ethylene oxide service as described in section III.B.2.iii 
of this preamble.
    The HON and P&R I include an LDAR program for owners or operators 
of certain heat exchange systems which meets the requirements of 40 CFR 
63.104 (National Emission Standards for Organic Hazardous Air 
Pollutants from the Synthetic Organic Chemical Manufacturing Industry). 
The LDAR program specifies that heat exchange systems be monitored for 
leaks of process fluids into cooling water and that owners or operators 
take actions to repair detected leaks within 45 days. Owners or 
operators may delay the repair of leaks if they meet the applicable 
criteria in 40 CFR 63.104. The current HON and P&R I MACT standards for 
heat exchange systems allow the use of any method listed in 40 CFR part 
136 to be used to sample cooling water for leaks for the HAP listed in 
Table 4 to subpart F (for HON) or Table 5 to 40 CFR 63, subpart U (for 
P&R I) (recirculating systems) and Table 9 to subpart G (for HON) or 
Table 5 to 40 CFR 63, subpart U (for P&R I) (once-through systems) (and 
other representative substances such as TOC or VOC that can indicate 
the presence of a leak can also be used). A leak in the heat exchange 
system is detected if the exit mean concentration of HAP (or other 
representative substance) in the cooling water is at least 1 ppmw or 10 
percent greater than (using a one-sided statistical procedure at the 
0.05 level of significance) the entrance mean concentration of HAP (or 
other representative substance) in the cooling water. Furthermore, the 
HON and P&R I allow owners or operators to monitor for leaks using a 
surrogate indicator of leaks (e.g., ion-specific electrode monitoring, 
pH, conductivity), provided that certain criteria in 40 CFR 63.104(c) 
are met. The HON and P&R I initially require 6 months of monthly 
monitoring for existing heat exchange systems. Thereafter, the 
frequency can be reduced to quarterly. The leak monitoring frequencies 
are the same whether water sampling and analysis or surrogate 
monitoring is used to identify leaks.
    Our technology review identified one development in LDAR practices 
and processes for heat exchange systems, the use of the Modified El 
Paso Method \61\ to monitor for leaks. The Modified El Paso Method, 
which is included in the MON, EMACT standards, and the Petroleum 
Refinery Sector rule, was identified in our review of the RACT/BACT/
LAER clearinghouse database. It is also required by the Texas 
Commission on Environmental Quality (TCEQ) for facilities complying 
with their highly reactive volatile organic compound (HRVOC) rule 
(i.e., 30 Texas Administrative Code (TAC) Chapter 115, Subchapter H, 
Division 3). The Modified El Paso Method measures a larger number of 
compounds than the current methods required in the HON and P&R I and is 
more effective in identifying leaks. For heat exchange system LDAR 
programs, the compliance monitoring option, leak definition, and 
frequency of monitoring for leaks are all important considerations 
affecting emission reductions by identifying when there is a leak and 
when to take corrective actions to repair the leak. Therefore, we 
evaluated the Modified El Paso Method for use at HON and P&R I 
facilities, including an assessment of appropriate leak definitions and 
monitoring frequencies.
---------------------------------------------------------------------------

    \61\ The Modified El Paso Method uses a dynamic or flow-through 
system for air stripping a sample of the water and analyzing the 
resultant off-gases for VOC using a common flame ionization detector 
(FID) analyzer. The method is described in detail in Appendix P of 
the TCEQ's Sampling Procedures Manual: The Air Stripping Method 
(Modified El Paso Method) for Determination of Volatile Organic 
Compound (VOC) Emissions from Water Sources. Appendix P is included 
in the docket for this rulemaking.
---------------------------------------------------------------------------

    In order to identify an appropriate Modified El Paso Method leak 
definition for HON-subject facilities, we identified four rules, TCEQ's 
HRVOC rule, the MON, the EMACT standards, and the Petroleum Refinery 
Sector rule, all of which incorporate this monitoring method and have 
leak definitions corresponding to the use of this methodology. We also 
reviewed data submitted in response to a CAA section 114 request for 
the Ethylene Production RTR where facilities performed sampling using 
the Modified El Paso Method.
    The TCEQ's HRVOC rule, the MON, the EMACT standards, and the 
Petroleum Refinery Sector rule have leak definitions of total 
strippable hydrocarbon concentration (as methane) in the stripping gas 
ranging from 3.1 ppmv to 6.2 ppmv. In addition, sources subject to the 
MON, the EMACT standards, or the Petroleum Refinery Sector rule may not 
delay the repair of leaks for more than 30 days where, during 
subsequent monitoring, a total strippable hydrocarbon concentration (as 
methane) in the stripping gas of 62 ppmv or higher is found. In 
reviewing the Ethylene Production RTR CAA section 114 data, a clear 
delineation in the hydrocarbon mass emissions data was noticed at 6.1 
ppmv of total strippable hydrocarbon (as methane) in the stripping gas. 
In addition, given that both the leak concentration and water 
recirculation rate of the heat exchange system are key variables 
affecting the hydrocarbon mass emissions from heat exchange systems, 
the overall Ethylene Production RTR CAA section 114 data for all heat 
exchange systems sampled generally showed lower hydrocarbon mass 
emissions for leaks at or below 6.1 ppmv of total strippable 
hydrocarbon (as methane) in the stripping gas compared to leaks found 
above 6.1 ppmv of total strippable hydrocarbon (as methane) in the 
stripping gas. Taking into account the range of actionable leak 
definitions in use by other rules that require use of the Modified El 
Paso Method currently (i.e., 3.1 ppmv-6.2 ppmv of total strippable 
hydrocarbon (as methane) in the stripping gas), and the magnitude of 
emissions for leaks as a result of total strippable hydrocarbon (as 
methane) in the stripping gas above 6.1 ppmv compared to leaks 
identified in the CAA section 114 sampling data as a result of other 
actionable leak definitions, we chose to evaluate a leak definition at 
the upper end of identified actionable leak definitions in our 
analysis. Thus, the Modified El Paso Method leak definition we 
evaluated was 6.2 ppmv of total strippable hydrocarbon concentration 
(as methane) in the stripping gas for both new and existing heat 
exchange systems, along with not allowing delay of repair of leaks for 
more than 30 days where, during subsequent monitoring, a total 
strippable hydrocarbon concentration (as methane) in the stripping gas 
of 62 ppmv or higher is found.
    We determined an appropriate leak monitoring frequency by reviewing 
the

[[Page 25125]]

current monitoring frequencies that HON and P&R I facilities are 
subject to, along with frequencies for the TCEQ's HRVOC rule, the MON, 
the EMACT standards, and the Petroleum Refinery Sector rule, and 
information gathered in the Ethylene Production RTR CAA section 114 
survey. As a first step, we reviewed whether it was still reasonable to 
specify more frequent monitoring for a 6-month period after repair of 
leaks. Our review of the Ethylene Production RTR CAA section 114 data 
showed that no leaks were identified during the 6-month period post 
repair for any of the facilities that reported leak emissions in their 
heat exchange system compliance data. Thus, we find that re-monitoring 
once after repair of a leak, at the monitoring location where the leak 
was identified, is sufficient from a continuous compliance perspective 
to demonstrate a successful repair. The monitoring frequencies 
currently required by the HON and P&R I when no leaks are found were, 
thus, considered the base frequencies (i.e., quarterly monitoring for 
existing and new heat exchange systems). Once we determined the base 
frequencies, we next considered more stringent monitoring frequencies. 
Both the Petroleum Refinery Sector rule, which includes monthly 
monitoring for existing sources, under certain circumstances, and the 
TCEQ HRVOC rule, which includes continuous monitoring provisions for 
existing and new sources, have more stringent monitoring frequencies. 
However, the incremental HAP cost effectiveness to change from 
quarterly to monthly monitoring and monthly to continuous monitoring 
was found to be $40,000/ton and $500,000/ton, respectively. We conclude 
that these costs are not reasonable for HON and P&R I facilities. Thus, 
we chose to evaluate quarterly monitoring for existing and new heat 
exchange systems (i.e., the base monitoring frequency currently in the 
rule).
    Based on this technology review, we identified the following 
control option for heat exchanger systems as a development in practice 
that can be implemented at a reasonable cost: Quarterly monitoring for 
existing and new heat exchange systems (after an initial 6 months of 
monthly monitoring) with the Modified El Paso Method and a leak 
definition of 6.2 ppmv of total strippable hydrocarbon concentration 
(as methane) in the stripping gas.
    We then estimated the impacts of this control option assuming that 
all 207 HON facilities and 19 P&R I facilities (10 of which are 
collocated with HON facilities) would be affected by requiring the use 
of the Modified El Paso Method. As part of our analysis, we assumed 
owners or operators conducting quarterly monitoring for three or more 
of these heat exchange systems would elect to purchase a stripping 
column and FID analyzer and perform in-house Modified El Paso 
monitoring (because the total annualized costs for in-house Modified El 
Paso monitoring are less than the costs for contracted services). In 
addition, we assumed repairs could be performed by plugging a specific 
heat exchanger tube, and if a heat exchanger is leaking to the extent 
that it needs to be replaced, then it is effectively at the end of its 
useful life. Therefore, we determined that the cost of replacing a heat 
exchanger is an operational cost that would be incurred by the facility 
as a result of routine maintenance and equipment replacement, and it is 
not attributable to the control option.
    Table 10 of this preamble presents the nationwide impacts for 
requiring owners or operators at HON facilities (including 10 P&R I 
facilities collocated with HON facilities) to use the Modified El Paso 
Method and repair leaks of total strippable hydrocarbon concentration 
(as methane) in the stripping gas of 6.2 ppmv or greater. Table 11 of 
this preamble presents the nationwide impacts for requiring owners or 
operators at P&R I facilities (not collocated with HON facilities) to 
use the Modified El Paso Method and repair leaks of total strippable 
hydrocarbon concentration (as methane) in the stripping gas of 6.2 ppmv 
or greater. See the document titled Clean Air Act Section 112(d)(6) 
Technology Review for Heat Exchange Systems Located in the SOCMI Source 
Category that are Associated with Processes Subject to HON and for Heat 
Exchange Systems that are Associated with Processes Subject to Group I 
Polymers and Resins NESHAP; and Control Option Impacts for Heat 
Exchange Systems that are Associated with Processes Subject to Group II 
Polymers and Resins NESHAP, which is available in the docket for this 
rulemaking, for details on the assumptions and methodologies used in 
this analysis.
    Based on the costs and emission reductions for the identified 
control option, we are proposing to revise the HON and P&R I for heat 
exchange systems pursuant to CAA section 112(d)(6). We are proposing at 
40 CFR 63.104(g)(4) \62\ to specify quarterly monitoring for existing 
and new heat exchange systems (after an initial 6 months of monthly 
monitoring) using the Modified El Paso Method and a leak definition of 
6.2 ppmv of total strippable hydrocarbon concentration (as methane) in 
the stripping gas. Owners and operators would be required to repair the 
leak to reduce the concentration or mass emissions rate to below the 
leak action level as soon as practicable, but no later than 45 days 
after identifying the leak. We are also proposing at 40 CFR 
63.104(j)(3) a delay of repair action level of total strippable 
hydrocarbon concentration (as methane) in the stripping gas of 62 ppmv, 
that if exceeded during leak monitoring, would require immediate repair 
(i.e., the leak found cannot be put on delay of repair and would be 
required to be repaired within 30 days of the monitoring event). This 
would apply to both monitoring heat exchange systems and individual 
heat exchangers by replacing the use of any 40 CFR part 136 water 
sampling method with the Modified El Paso Method and removing the 
option that allows for use of a surrogate indicator of leaks. We are 
also proposing at 40 CFR 63.104(h) and (i) that repair include re-
monitoring at the monitoring location where a leak is identified to 
ensure that any leaks found are fixed. We are proposing that none of 
these proposed requirements would apply to heat exchange systems that 
have a maximum cooling water flow rate of 10 gallons per minute or less 
because owners and operators of smaller heat exchange systems would be 
disproportionally affected and forced to repair leaks with a much lower 
potential HAP emissions rate than owners and operators of heat exchange 
systems with larger recirculation rate systems. Finally, we are 
proposing at 40 CFR 63.104(l) that the leak monitoring requirements for 
heat exchange systems at 40 CFR 63.104(b) may be used in limited 
instances, instead of using the Modified El Paso Method to monitor for 
leaks. We still maintain that the Modified El Paso Method is the 
preferred method to monitor for leaks in heat exchange systems and are 
proposing that the requirements of 40 CFR 63.104(b) may only be used if 
99 percent by weight or more of all the organic compounds that could 
potentially leak into the cooling water have a Henry's Law Constant 
less than 5.0E-6 atmospheres per mole per cubic meter (atm-m\3\/mol) at 
25[deg] Celsius. We selected this threshold based on a review of 
Henry's Law Constants for the HAP listed in Table 4 to subpart F of 40

[[Page 25126]]

CFR part 63, as well as the water-soluble organic compounds listed in a 
recent alternative monitoring request from a MON facility.\63\ Henry's 
Law Constants are available from the EPA at https://comptox.epa.gov/dashboard/. Examples of HAP that have a Henry's Law Constant of less 
than 5.0E-6 atm-m\3\/mol at 25[deg] Celsius are aniline, 2-
chloroacetophenone, diethylene glycol diethyl ether, diethylene glycol 
dimethyl ether, dimethyl sulfate, 2,4-dinitrotoluene, 1,4-dioxane, 
ethylene glycol monoethyl ether acetate, ethylene glycol monomethyl 
ether acetate, methanol, and toluidine. Many of these HAP also have 
very high boiling points, with most above 300 Fahrenheit, which means 
they will generally stay in the cooling water and not be emitted to the 
atmosphere. We solicit comment on all of the proposed requirements 
related to heat exchange systems.
---------------------------------------------------------------------------

    \62\ We note that each of the HON citations mentioned in this 
paragraph of this preamble are also applicable to P&R I facilities 
pursuant to 40 CFR 63.502(n). In order for these proposed HON 
citations to properly apply to P&R I facilities, we are proposing 
substitution rule text at 40 CFR 63.502(n)(7).
    \63\ In May 2021, EPA Region 4 received a request from Eastman 
Chemical Company to perform alternative monitoring instead of the 
Modified El Paso Method to monitor for leaks in Eastman's Tennessee 
Operations heat exchange systems, which primarily have cooling water 
containing soluble HAP with a high boiling point. Eastman 
specifically identified two HAP, 1,4-dioxane and methanol, which do 
not readily strip out of water using the Modified El Paso Method. 
Eastman's application for alternative monitoring included 
experimental data showing that the Modified El Paso Method would 
likely not identify a leak of these HAP in heat exchange system 
cooling water. Eastman conducted Modified El Paso Method monitoring 
under controlled scenarios to determine how much methanol and 1,4-
dioxane would be detected. The scenarios included solutions of water 
and either methanol or 1,4-dioxane at concentrations of 1 part per 
million by weight (ppmw), 20 ppmw, and 100 ppmw (as measured using 
water sampling methods allowed previously in the MON). The Modified 
El Paso Method did not detect any methanol or 1,4-dioxane from the 1 
ppmw and 20 ppmw solutions (i.e., methanol and 1,4-dioxane did not 
strip out of the water in detectable amounts). The Modified El Paso 
Method detected very little HAP from the 100 ppmw solutions, with a 
maximum of only 0.17 percent of the 1,4-dioxane stripping out and 
being detected.

     Table 10--Nationwide Emissions Reductions and Cost Impact for Requiring the Modified El Paso Method for Heat Exchange Systems at HON Facilities
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                             Total
                                                         Total         VOC emission     HAP emission       HAP cost        annualized        HAP cost
          Control option            Total capital      annualized         table          reductions     effectiveness      costs with     effectiveness
                                    investment ($)     costs w/o        reductions         (tpy)         w/o recovery       recovery      with recovery
                                                     credits ($/yr)       (tpy)                        credits ($/ton)   credits ($/yr)  credits ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1................................         770,000          228,000              934               93            2,440        (612,700)          (6,560)
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Table 11--Nationwide Emissions Reductions and Cost Impact for Requiring the Modified El Paso Method for Heat Exchange Systems at P&R I Facilities
                                                          [Not collocated with HON facilities]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                             Total
                                                         Total         VOC emission     HAP emission       HAP cost        annualized        HAP cost
          Control option            Total capital      annualized       reductions       reductions    effectiveness w/    costs with     effectiveness
                                    investment ($)     costs w/o          (tpy)            (tpy)          o recovery        recovery      with recovery
                                                     credits ($/yr)                                    credits ($/ton)   credits ($/yr)  credits ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1................................          48,300            9,900               33                3            3,050         (19,320)          (5,940)
--------------------------------------------------------------------------------------------------------------------------------------------------------

2. Standards for Storage Vessels
    Storage vessels are used to store liquid and gaseous feedstocks for 
use in a process, as well as to store liquid and gaseous products from 
a process. Most HON, P&R I, and P&R II storage vessels are designed for 
operation at atmospheric or near atmospheric pressures; pressure 
vessels are used to store compressed gases and liquefied gases. 
Atmospheric storage vessels are typically cylindrical with a vertical 
orientation, and they are constructed with either a fixed roof or a 
floating roof. Some, generally small, atmospheric storage vessels are 
oriented horizontally. Pressure vessels are either spherical or 
horizontal cylinders.
    The HON requires owners and operators control emissions from 
storage vessels with capacities between 75 m\3\ and 151 m\3\ and a MTVP 
greater than or equal to 13.1 kPa, and storage vessels with capacities 
greater than or equal to 151 m\3\ and a MTVP greater than or equal to 
5.2 kPa. Storage vessels meeting this criteria are considered Group 1 
storage vessels. Owners and operators of HON Group 1 storage vessels 
storing a liquid with a MTVP of total organic HAP less than 76.6 kPa 
are required to reduce emissions of organic HAP by 95 percent (or 90 
percent if the storage vessel was installed on or before December 31, 
1992) utilizing a closed vent system and control device, or reduce 
organic HAP emissions either by utilizing an IFR, an EFR, or by routing 
the emissions to a process or a fuel gas system, or vapor balancing. 
Owners and operators of HON Group 1 storage vessels storing a liquid 
with a MTVP of total organic HAP greater than or equal to 76.6 kPa are 
required to reduce emissions of organic HAP by 95 percent (or 90 
percent if the storage vessel was installed on or before December 31, 
1992) utilizing a closed vent system and control device, or reduce 
organic HAP emissions by routing the emissions to a process or a fuel 
gas system, or vapor balancing. In general, HON storage vessels that do 
not meet the MTVP and capacity thresholds described above are 
considered Group 2 storage vessels and are not required to apply any 
additional emission controls provided they remain under 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. Generally, the 
P&R I standards for storage vessels refer to the provisions in the HON. 
As such, owners and operators of Group 1 storage vessels subject to P&R 
I are required to control these vessels as prescribed in the HON.
    The P&R II standards for storage tanks (P&R II uses the term 
``storage tank'' in lieu of ``storage vessel'' like the HON and P&R I) 
do not specify any sort of stratification into groups. P&R II defines 
``storage tank'' to mean tank or other vessel that is used to store 
liquids that contain one or more HAP compounds.

[[Page 25127]]

As previously mentioned, 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) standard 
for existing sources in both BLR (130 pounds) and WSR (10 pounds). For 
new sources, BLR requires 98 percent reduction or an overall limit of 
5,000 pounds of HAP per year. New WSR sources are limited to 7 pounds 
of HAP per million pounds WSR produced.
    As part of our technology review for HON and P&R I storage vessels, 
we identified the following emission reduction options: (1) Revising 
the capacity and MTVP thresholds of the HON and P&R I to reflect the 
MON existing source threshold which requires existing storage vessels 
between 38 m\3\ and 151 m\3\ with a vapor pressure greater than or 
equal to 6.9 kPa to reduce emissions of organic HAP by 95 percent 
utilizing a closed vent system and control device, or reduce organic 
HAP emissions either by utilizing an IFR, an EFR, or by routing the 
emissions to a process or a fuel gas system, or vapor balancing; (2) in 
addition to requirements specified in option 1, requiring upgraded deck 
fittings \64\ and controls for guidepoles for all storage vessels 
equipped with an IFR as already required in 40 CR 63, subpart WW; and 
(3) in addition to requirements specified in options 1 and 2, requiring 
the conversion of EFRs to IFRs through use of geodesic domes. We did 
not identify any control options for storage tanks subject to P&R II.
---------------------------------------------------------------------------

    \64\ Require all openings in an IFR (except those for automatic 
bleeder vents (vacuum breaker vents), rim space vents, leg sleeves, 
and deck drains) be equipped with a deck cover; and the deck cover 
would be required to be equipped with a gasket between the cover and 
the deck.
---------------------------------------------------------------------------

    We identified option 1 as a technologically feasible development in 
practices, processes, and control technologies for storage vessels used 
at HON and P&R I facilities because it reflects requirements for 
similar storage vessels that are located at chemical manufacturing 
facilities subject to the MON. Option 2 is an improvement in practices 
because these upgraded deck fittings and guidepole controls have been 
required by other regulatory agencies and other EPA regulatory action 
(e.g., Petroleum Refinery Sector rulemaking) since promulgation of the 
HON and P&R I and are being used by some of the sources covered by the 
SOCMI source category. Finally, we consider option 3 to be a 
development in control technology because we found that some storage 
vessels with EFRs have installed geodesic domes since promulgation of 
the HON and P&R I.
    We used information about storage vessel capacity, design, and 
stored materials that industry provided to the EPA in response to our 
CAA section 114 request (see section II.C of this preamble) to evaluate 
the impacts of all three of the options presented. We identified eight 
HON storage vessels and two P&R I storage vessels from our CAA section 
114 request that would be impacted by option 1; extrapolating this data 
to all 207 HON facilities and 19 P&R I facilities (10 of which are 
collocated with HON facilities), we estimated costs and emissions 
reductions for 63 HON storage vessels and 4 P&R I storage vessels that 
would be impacted by option 1. This same distribution would apply to 
option 2. For option 3, we identified five HON EFR storage vessels and 
zero P&R I EFR storage vessels from our CAA section 114 request that 
would be impacted; extrapolating this data to all 207 HON facilities 
and 19 P&R I facilities (10 of which are collocated with HON 
facilities) we estimated costs and emissions reductions for 159 HON EFR 
storage vessels and 5 P&R I EFR storage vessels \65\ that would be 
impacted by option 3.
---------------------------------------------------------------------------

    \65\ Although no EFR tanks were reported for P&R I as part of 
our CAA section 114 request, we assumed five P&R I EFR storage 
vessels based on the number of HON average EFR storage vessels per 
HON CMPU that were reported.
---------------------------------------------------------------------------

    Table 12 of this preamble presents the nationwide impacts for the 
three options considered for HON facilities (including 10 P&R I 
facilities collocated with HON facilities). Table 13 of this preamble 
presents the nationwide impacts for the three options considered for 
P&R I facilities (not collocated with HON facilities). See the document 
titled Clean Air Act Section 112(d)(6) Technology Review for Storage 
Vessels Located in the SOCMI Source Category that are Associated with 
Processes Subject to HON, Storage Vessels Associated with Processes 
Subject to Group I Polymers and Resins NESHAP, and Storage Vessels 
Associated with Processes Subject to Group II Polymers and Resins 
NESHAP, which is available in the docket for this rulemaking, for 
details on the assumptions and methodologies used in this analysis, 
including the calculations we used to account for additional HON and 
P&R I facilities that did not receive a CAA section 114 request.
    We determined that option 2 (which includes option 1) is cost 
effective and we are proposing, pursuant to CAA section 112(d)(6), to 
revise the Group 1 storage capacity criterion (for HON and P&R I 
storage vessels at existing sources) from between 75 m\3\ and 151 m\3\ 
to between 38 m\3\ and 151 m\3\ (see proposed Table 5 to subpart G), 
and require upgraded deck fittings and controls for guidepoles for all 
storage vessels equipped with an IFR as already required in 40 CR 63, 
subpart WW (see proposed 40 CFR 63.119(b)(5)(ix), (x), (xi), and 
(xii)). Considering the emissions reductions and high incremental cost 
effectiveness, we determined that storage vessel option 3 is not cost 
effective and are not proposing to revise the HON and P&R I to reflect 
the requirements of this option pursuant to CAA section 112(d)(6). We 
solicit comment on the proposed revisions for storage vessels.

             Table 12--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for Storage Vessels at HON Facilities
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                        HAP incremental
                                                                            Total       VOC emission    HAP emission      HAP cost            cost
                    Control option                      Total capital    annualized      reductions      reductions     effectiveness    effectiveness
                                                       investment ($)   costs ($/yr)        (tpy)           (tpy)          ($/ton)      (from Option 1)
                                                                                                                                            ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1....................................................       1,727,000         327,400            58.0            40.6           8,070  .................
2....................................................       2,191,500         415,500            68.2            47.7           8,710             12,400
3....................................................      28,916,200       4,065,700            84.3            59.0          68,880                N/A
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 25128]]

            Table 13--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for Storage Vessels at P&R I Facilities
                                                          [Not collocated with HON facilities]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                        HAP  incremental
                                                                            Total       VOC emission    HAP emission      HAP cost            cost
                    Control option                      Total capital    annualized      reductions      reductions     effectiveness    effectiveness
                                                       investment ($)   costs ($/yr)        (tpy)           (tpy)          ($/ton)      (from Option 1)
                                                                                                                                            ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1....................................................         109,000          20,700             3.7             2.6           7,960  .................
2....................................................         131,000          24,800             4.1             2.9           8,550             13,700
3....................................................         912,200         128,300             2.7             1.9          67,500                N/A
--------------------------------------------------------------------------------------------------------------------------------------------------------

3. Standards for Process Vents
    A process vent is a gas stream that is discharged during the 
operation of a particular unit operation (e.g., separation processes, 
purification processes, mixing processes, reaction processes). The gas 
stream(s) may be routed to other unit operations for additional 
processing (e.g., a gas stream from a reactor that is routed to a 
distillation column for separation of products), sent to one or more 
recovery devices, sent to a process vent header collection system 
(e.g., blowdown system) and APCD (e.g., flare, thermal oxidizer, carbon 
adsorber), and/or vented to the atmosphere. Process vents may be 
generated from continuous and/or batch operations,\66\ as well as from 
other intermittent types of operations (e.g., maintenance operations). 
If process vents are required to be controlled prior to discharge to 
the atmosphere to meet an applicable emissions standard, then they are 
typically collected and routed to an APCD through a closed vent system.
---------------------------------------------------------------------------

    \66\ P&R I and P&R II regulate process vents from both 
continuous and batch operations. The HON and NSPS subparts III, NNN, 
and RRR only regulate process vents if some, or all, of the gas 
stream originates as a continuous flow.
---------------------------------------------------------------------------

    NSPS subparts III, NNN, and RRR regulate gas streams from air 
oxidation reactors, distillation columns, and other reactor processes, 
respectively. Importantly, the NSPS subparts III, NNN, and RRR formed 
the basis for the HON process vent MACT standards in that to be 
considered a HON process vent, some or all of the gas stream must 
originate as a continuous flow from an air oxidation reactor, 
distillation unit, or other reactor process during operation of a CMPU. 
P&R I regulates batch front-end process vents, continuous front-end 
process vents, and aggregate batch vent streams from condensers, 
distillation units, reactors, or other unit operations within an EPPU. 
Generally, process vents subject to NSPS subparts III, NNN, or RRR, or 
the HON and/or P&R I are grouped based on the flow rate, HAP 
concentration, and a TRE index value.\67\ P&R II defines a process vent 
as a point of emission from a unit operation, such as condenser vents, 
vacuum pumps, steam ejectors and atmospheric vents from reactors and 
other process vessels; and no further stratification into groups for 
applicability is specified.
---------------------------------------------------------------------------

    \67\ TRE is discussed in more detail below in section III.C.3.a 
of this preamble (for NESHAP) and section III.C.3.b of this preamble 
(for NSPS).
---------------------------------------------------------------------------

    The results of our CAA section 112(d)(6) technology review for 
process vents associated with HON, P&R I, and P&R II processes are 
discussed in section III.C.3.a of this preamble. The results of our CAA 
111(b)(1)(B) review for process vents subject to NSPS subparts III, 
NNN, or RRR are discussed in section III.C.3.b of this preamble.
a. HON, P&R I, and P&R II
    As previously mentioned, the HON standards divide process vents 
into Group 1 process vents, which require controls, and Group 2 process 
vents, which generally do not require controls provided they remain 
below Group 1 thresholds. A Group 1 HON process vent is a process vent 
for which the vent stream flow rate is greater than or equal to 0.005 
scmm, the total organic HAP concentration is greater than or equal to 
50 ppmv, and the TRE index value is less than or equal to 1.0 
(according to the determination procedures at 40 CFR 63.115). The TRE 
index value is a measure of the supplemental total resource requirement 
per unit VOC (or HAP) reduction. It takes into account all the 
resources which are expected to be used in VOC (or HAP) control by 
thermal oxidation and provides a dimensionless measure of resource 
burden based on cost effectiveness. Resources include supplemental 
natural gas, labor, and electricity. Additionally, if the off-gas 
contains halogenated compounds, resources will also include caustic and 
scrubbing and quench makeup water. For the HON and P&R I, the TRE index 
value is derived from the cost effectiveness associated with HAP 
control by a flare or thermal oxidation, and is a function of vent 
stream flowrate, vent stream net heating value, hourly emissions, and a 
set of coefficients. The TRE index value was first introduced in an EPA 
document titled: Guideline Series for Control of Volatile Organic 
Compound (VOC) Emissions from Air Oxidation Processes in Synthetic 
Organic Chemical Manufacturing Industry (SOCMI) (see EPA-450/3-84-015, 
December 1984). The EPA incorporated the TRE concept into the original 
HON (see 59 FR 19468, April 22, 1994) and the original P&R I rulemaking 
(see 61 FR 46906, September 5, 1996). The TRE index value is used in 40 
CFR 63 subpart G and 40 CFR 63 subpart U as an alternative mode of 
compliance for process vent regulations. The TRE index value can also 
trigger monitoring, recordkeeping, and reporting requirements. In 
general, as previously mentioned for the HON and P&R I, continuous 
process vents with a TRE index value equal to or less than 1.0 are 
required to be controlled. For additional details regarding the TRE 
index value (including the equation and coefficients used to calculate 
the TRE index value for the HON and P&R I), see the document titled 
Clean Air Act Section 112(d)(6) Technology Review for Continuous 
Process Vents Located in the SOCMI Source Category that are Associated 
with Processes Subject to HON, Continuous Front-end and Batch Front-end 
Process Vents Associated with Processes Subject to Group I Polymers and 
Resins NESHAP, and Process Vents Associated with Processes Subject to 
Group II Polymers and Resins NESHAP, which is available in the docket 
for this rulemaking.
    The HON standards require uncontrolled Group 1 process vents to 
reduce total organic HAP \68\ emissions by 98 percent by weight by 
venting emissions through a closed vent system to any combination of 
control devices or by venting emissions through a closed

[[Page 25129]]

vent system to a flare.\69\ The P&R I standards for continuous front-
end process vents use the same Group 1 flow rate, HAP concentration, 
and TRE index value threshold criterion as the HON; refer to the same 
provisions in the HON for group determination (i.e., owners and 
operators of continuous front-end process vents subject to P&R I 
determine whether control is required based on the flow rate, HAP 
concentration, and TRE index value using the same HON determination 
procedures at 40 CFR 63.115); and require the same level as control as 
the HON (i.e., reduce total organic HAP \70\ emissions by 98 percent by 
weight by venting emissions through a closed vent system to any 
combination of control devices or by venting emissions through a closed 
vent system to a flare).\71\
---------------------------------------------------------------------------

    \68\ For HON, organic HAP refers to chemicals listed in Table 2 
to NESHAP subpart F.
    \69\ See also, footnote 16, for halogenated vent streams that 
are Group 1.
    \70\ For P&R I, organic HAP refers to chemicals listed in Table 
5 to NESHAP subpart U.
    \71\ See also, footnote 16, for halogenated vent streams that 
are Group 1.
---------------------------------------------------------------------------

    The P&R I standards do not refer to the HON for batch front-end 
process vents. The P&R I group determination for batch front-end vents 
is based on annual HAP emissions and annual average batch vent flow 
rate. Group 1 batch front-end process vent means a batch front-end 
process vent releasing annual organic HAP emissions greater than or 
equal to 11,800 kg/yr (26,014 lb/yr) and with a cutoff flow rate 
greater than or equal to the annual average batch vent flow rate.\72\ 
The cutoff flow rate is calculated in accordance with 40 CFR 63.488(f). 
Annual organic HAP emissions and annual average batch vent flow rate 
are determined at the exit of the batch unit operation, as described in 
40 CFR 63.488(a)(2). Annual organic HAP emissions are determined as 
specified in 40 CFR 63.488(b), and annual average batch vent flow rate 
is determined as specified in 40 CFR 63.488(e).
---------------------------------------------------------------------------

    \72\ P&R I also contains standards for halogenated batch process 
vents.
---------------------------------------------------------------------------

    The P&R II standards for process vents do not specify any sort of 
stratification into groups. However, the rule does have different 
performance testing requirements depending on whether the process vent 
is part of a continuous process \73\ or if flow of gaseous emissions is 
intermittent. As previously mentioned, 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) standard for existing sources in both BLR (130 pounds) 
and WSR (10 pounds). For new sources, BLR requires 98 percent reduction 
or an overall limit of 5,000 pounds of HAP per year. New WSR sources 
are limited to 7 pounds of HAP per million pounds WSR produced.
---------------------------------------------------------------------------

    \73\ P&R II defines ``continuous process'' to mean a process 
where the inputs and outputs flow continuously throughout the 
duration of the process. Continuous processes are typically steady-
state.
---------------------------------------------------------------------------

    As part of our technology review for HON and P&R I continuous 
process vents, we identified the following emission reduction options: 
(1) Remove the TRE concept in its entirety, remove the 50 ppmv and 
0.005 scmm Group 1 process vent thresholds, and redefine a HON Group 1 
process vent and P&R I Group 1 continuous front-end process vent 
(require control) as any process vent that emits greater than or equal 
to 1.0 lb/hr of total organic HAP; (2) the same requirements specified 
in option 1, but redefine a HON Group 1 process vent and P&R I Group 1 
continuous front-end process vent (require control) as any process vent 
that emits greater than or equal to 0.10 lb/hr of total organic HAP; 
and (3) keep the TRE concept and keep the 50 ppmv and 0.005 scmm Group 
1 process vent thresholds, but change the TRE index value threshold 
from 1.0 to 5.0. We did not identify any control options for P&R II 
process vents.
    We identified options 1 and 2 as developments in practices, 
processes, and control technologies for multiple reasons. First, we 
identified at least one chemical manufacturing NESHAP (i.e., ethylene 
production) that does not use the TRE index value as criteria for 
determining whether a process vent should be controlled. Second, based 
on the responses to our CAA section 114 request, we observed that some 
facilities are voluntarily controlling continuous process vents that 
are not required by the HON and P&R I to be controlled per the results 
of the TRE index value calculation. Of the 13 HON facilities that 
received the CAA section 114 request, at least three facilities 
confirmed they were voluntarily controlling some of their Group 2 
process vents. We expect other HON and P&R I facilities will do this 
too because some facilities stated in their response to the CAA section 
114 request that, pursuant to 40 CFR 63.113(h), many of their process 
vents are voluntarily designated as Group 1 process vents ``so that TRE 
calculations are not required.'' In other words, some facilities are 
likely electing to control certain process vents that have TRE index 
values greater than 1.0. Third, based on the responses to our CAA 
section 114 request, we observed that facilities are routing multiple 
continuous process vents to a single APCD. This is significant because 
the current use of the TRE index value is only based on controlling a 
single process vent with a single APCD, an unrealistic scenario when 
compared to how chemical manufacturing facilities actually control 
their process vents. It is much more likely that a facility routes 
numerous process vents to the same APCD. Finally, also based on 
responses to our CAA section 114 request, one facility provided over 
300 pages of modeled runs that were used to help the facility determine 
certain characteristics of their continuous HON and P&R I process vents 
for inputs to TRE index value calculations. The facility had originally 
included these modeled runs with their Notification of Compliance 
Status report; we reviewed this information and concluded that 
determining a TRE index value for certain process vent streams is often 
theoretical, can be extremely complicated, and is uncertain. In 
addition, because the TRE index value is largely a theoretical 
characterization tool, it can be very difficult to enforce. In order to 
calculate a TRE index value, owners and operators must determine 
numerous input values; and without the correct amount of process 
knowledge, verifying inputs can be problematic.
    We identified option 3 as a development in practices, processes, 
and control technologies because we determined that another chemical 
manufacturing NESHAP (i.e., the MON) contains a TRE index value 
threshold criteria (i.e., less than or equal to 1.9) that is more 
stringent than the HON and P&R I TRE index value threshold criteria 
(i.e., less than or equal to 1.0). Additionally, we identified one 
particular state rule that uses a more stringent TRE index value 
threshold than the HON and P&R I TRE index value threshold 
criteria.\74\ This state rule requires owners and operators of air 
oxidation processes to control any process vent stream or combination 
of process vent streams with a TRE index value less than or equal to 
6.0.\75\
---------------------------------------------------------------------------

    \74\ See Illinois Title 35: Subtitle B: Chapter I: Subchapter C: 
Parts 218 and 219 (i.e., Organic Material Emission Standards And 
Limitations For The Chicago Area Subpart V: Batch Operations And Air 
Oxidation Processes; and Organic Material Emission Standards And 
Limitations For The Metro East Area Subpart V: Batch Operations And 
Air Oxidation Processes).
    \75\ Although the TRE equation for Illinois Title 35: Subtitle 
B: Chapter I: Subchapter C: Parts 218 and 219 has a different set of 
TRE coefficients than that of the HON and P&R I, we examined 
multiple scenarios and determined that a process vent not required 
to be controlled by the HON or P&R I could still be required to be 
controlled by this Illinois rule. For example, a halogenated process 
vent with a net heating value of 100 MJ/scm, a flowrate of 0.82 scm/
min, a TOC mass flow rate of 9 kg/hr, and a HAP mass flow rate of 1 
kg/hr would yield a TRE of 3.87 using the HON and/or the P&R I TRE 
equation (and 3.87 is above the HON and P&R I index value thresholds 
of 1.0 so no control would be required); however, this same stream 
would yield a TRE of 5.28 using the Illinois rule TRE equation (and 
5.28 is below the Illinois rule TRE index value threshold of 6.0, so 
control is required).

---------------------------------------------------------------------------

[[Page 25130]]

    To evaluate impacts of all three of the options presented, we used 
information from about 50 Group 2 continuous process vents that was 
provided by 9 of the 13 HON facilities (including 1 P&R I facility 
collocated with a HON facility) that received the CAA section 114 
request. Using vent stream flowrates, vent stream net heating values, 
and VOC and HAP emission rates (which we obtained from TRE index value 
calculations that facilities provided in their response to the CAA 
section 114 request) and the methodology from the sixth edition of the 
EPA Air Pollution Control Cost Manual,\76\ we first calculated a cost 
effectiveness for installing ductwork and a blower on each vent, 
assuming each of these vents could be routed to an existing control 
device achieving 98 percent by weight emission reduction. Given that 
many of the Group 2 continuous process vents have a very low flow rate 
and/or emission rate, we found that even installing simple ductwork and 
a blower would not be cost effective for the majority of these vents. 
However, we did identify 23 of these Group 2 continuous process vents 
(a subset of the 50 Group 2 process vents from responses to our CAA 
section 114 request) for which we found this scenario to be cost 
effective (i.e., $1,100 per ton of VOC/HAP or less). Using this subset 
of Group 2 continuous process vents, we extrapolated a set of 
distributions and parameters that we could apply to all 207 HON 
facilities and 19 P&R I facilities in order to evaluate impacts of all 
three of the options presented for continuous HON and P&R I process 
vents, noting that six of the 23 Group 2 continuous process vents are 
already voluntarily controlled even though the HON and P&R I do not 
require them to be. For Group 2 continuous process vents already 
voluntarily being controlled, we assumed owners and operators use 
existing APCDs. For Group 2 process vents not already being voluntarily 
controlled, we assumed owners and operators would need to install an 
APCD; therefore, we estimated costs to install a thermal oxidizer using 
the EPA's control cost template.\77\ We estimated that 16 HON 
facilities operating 48 HON Group 2 process vents (32 of which are 
already voluntarily controlled and 16 that are not currently 
controlled) and 3 P&R I facilities operating 9 P&R I Group 2 continuous 
front-end process vents (in which all nine are not currently 
controlled) would be impacted by option 1 (i.e., control process vents 
with a total organic HAP emission rate greater than 1.0 lb/hr). For 
option 2 (i.e., control process vents with a total organic HAP emission 
rate greater than 0.10 lb/hr), we estimated that 48 HON facilities 
operating 287 HON Group 2 process vents (96 of which are already 
voluntarily controlled and 191 that are not currently controlled) and 3 
P&R I facilities operating 30 P&R II Group 2 continuous front-end 
process vents (in which all 30 are not currently controlled) would be 
impacted. For option 3 (i.e., control process vents with a TRE index 
value less than or equal to 5.0), we estimated that 16 HON facilities 
operating 64 HON Group 2 process vents (32 of which are already 
voluntarily controlled and 32 that are not currently controlled) and 3 
P&R I facilities operating nine P&R II Group 2 continuous front-end 
process vents (in which all 9 are not currently controlled) would be 
impacted.
---------------------------------------------------------------------------

    \76\ EPA, 2002. EPA Control Cost Manual, Sixth Edition. January 
2002. Publication Number EPA/452/B-02-001.
    \77\ Refer to the file ``Incinerators and Oxidizers Calculation 
Spreadsheet (note: updated on 1/16/2018) (xlsm)'' which follows the 
methodology from the sixth edition of the EPA Air Pollution Control 
Cost Manual and can be found at the following website: https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution.
---------------------------------------------------------------------------

    Table 14 of this preamble presents the nationwide impacts for the 
three options considered for continuous process vents at HON 
facilities. Table 15 of this preamble presents the nationwide impacts 
for the three options considered for continuous process vents at P&R I 
facilities. We determined that option 1 is cost effective and we are 
proposing, pursuant to CAA section 112(d)(6), to remove the TRE concept 
in its entirety from the HON and P&R I. We are also proposing, pursuant 
to CAA section 112(d)(6), to remove the 50 ppmv and 0.005 scmm Group 1 
process vent thresholds from the HON Group 1 process vent definition 
and P&R I Group 1 continuous front-end process vent definition, and 
instead require owners and operators of HON or P&R I process vents that 
emit greater than or equal to 1.0 lb/hr of total organic HAP to reduce 
emissions of organic HAP using a flare meeting the proposed operating 
and monitoring requirements for flares (see section III.D.1 of this 
preamble); or 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. We are not proposing to revise the HON and P&R I to 
reflect the requirements of process vent options 2 and 3 pursuant to 
CAA section 112(d)(6). We determined that process vent option 2 is not 
cost effective, and while we believe option 3 is cost effective, it 
would require keeping the TRE concept in the rule which for reasons 
explained above is not desired. We solicit comment on the proposed 
revisions for process vents for the HON and P&R I.

 Table 14--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for Continuous Process
                                             Vents at HON Facilities
----------------------------------------------------------------------------------------------------------------
                                                       Total       VOC emission    HAP emission      HAP cost
         Control option            Total capital    annualized      reductions      reductions     effectiveness
                                  investment ($)   costs ($/yr)        (tpy)           (tpy)          ($/ton)
----------------------------------------------------------------------------------------------------------------
1...............................       1,218,000       3,150,000             436             436           7,200
2...............................       5,732,000      10,329,000             809             533          19,400
3...............................       1,493,000       3,208,000             441             441           7,300
----------------------------------------------------------------------------------------------------------------

[[Page 25131]]

 Table 15--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for Continuous Process
                                            Vents at P&R I Facilities
----------------------------------------------------------------------------------------------------------------
                                                       Total       VOC emission    HAP emission      HAP cost
         Control option            Total capital    annualized      reductions      reductions     effectiveness
                                  investment ($)   costs ($/yr)        (tpy)           (tpy)          ($/ton)
----------------------------------------------------------------------------------------------------------------
1...............................         198,000         586,000            51.0            51.0          11,500
2...............................         557,000       1,242,000            80.1            72.4          17,200
3...............................         215,000         590,000            54.8            54.8          10,800
----------------------------------------------------------------------------------------------------------------

    As part of our technology review for P&R I batch front-end process 
vents, we identified the following emission reduction option: revise 
the P&R I control threshold for batch front-end process vents from 
26,014 lb/yr on an individual vent basis to 10,000 lb/yr on an 
aggregate vent basis. We identified this option as a development in 
practices, processes, and control technologies based on our comparison 
of the batch process vent requirements in the NESHAP for Chemical 
Manufacturing Area Sources (CMAS) compared to those in P&R I. We note 
that CMAS regulates batch process vents from nine area source 
categories in the chemical manufacturing sector. Owners and operators 
of a CMAS CMPU with collective uncontrolled organic HAP emissions 
greater than or equal to 10,000 lb/yr from all batch process vents 
associated with an affected CMPU must meet emission limits for organic 
HAP emissions. GACT for batch process vents is defined in the CMAS 
NESHAP as 85 percent control for existing batch process units (and 90 
percent for new units) that have uncontrolled organic HAP emissions 
equal to or greater than 10,000 lb/yr. As mentioned in the CMAS NESHAP 
rulemaking,\78\ this applicability threshold of 10,000 lb/yr per batch 
process was also used in the MON and provides indicia of the size of a 
CMPU because the MON applies to major sources of HAP. The EPA used 
information from the baseline facility MON database and determined that 
costs to meet an 85 percent control requirement for existing CMAS CMPUs 
with uncontrolled organic HAP emissions equal to or greater than 10,000 
lb/yr were reasonable ($8,700/ton). We also note that, based on a 
response to our CAA section 114 request, a facility (the only facility 
that received the CAA section 114 request and is subject to P&R I) 
reported to the EPA that it is controlling its five batch front-end 
process vents even though P&R I does not require these vents to be 
controlled.\79\
---------------------------------------------------------------------------

    \78\ See 74 FR 56008, October 29, 2009.
    \79\ As previously mentioned, the P&R I control threshold for 
batch front-end process vents is on an individual vent basis; and 
each of the batch front-end process vents at this facility releases 
annual organic HAP emissions less than 11,800 kg/yr (26,014 lb/yr) 
which is below the control threshold of P&R I.
---------------------------------------------------------------------------

    To evaluate impacts of the option presented for P&R I batch front-
end process vents, we used information from the batch process vent 
impacts analysis for the CMAS final rule.\80\ We selected the 90 
percent control option model plant shown in Table 3 of this impacts 
analysis for sources subject to P&R I (instead of the 85 percent 
control option model plant shown in Table 2 of the impacts analysis) to 
prevent backsliding of the current P&R I requirements which reflect 
MACT instead of the GACT standards of CMAS. We assumed that all 
facilities subject to P&R I have batch process vents that would require 
control under the option evaluated (i.e., under the option to change 
the Group 1 batch front-end process vent threshold to 10,000 lb/yr on 
an aggregate vent basis), but as previously mentioned, one facility is 
already voluntarily controlling their batch front-end process vents. As 
a result, we estimated impacts to the remaining 18 facilities subject 
to P&R I.
---------------------------------------------------------------------------

    \80\ RTI, 2009. Revised Impacts Analysis for Batch Process Vents 
Chemical Manufacturing Area Source NESHAP. October 14, 2009. EPA 
Docket No. EPA-HQ-OAR-2008-0334-0075.
---------------------------------------------------------------------------

    Table 16 of this preamble presents the nationwide impacts for the 
option considered for batch front-end process vents at P&R I 
facilities. We determined that this option is cost effective and we are 
proposing, pursuant to CAA section 112(d)(6), 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 in P&R I at 40 CFR 
63.482 (these thresholds are currently determined on an individual 
batch process vent basis). Instead, owners and operators of batch 
front-end process vents that release a total of annual organic HAP 
emissions greater than or equal to 4,536 kg/yr (10,000 lb/yr) from all 
batch 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 (see 
section III.D.1 of this preamble); or reduce emissions of organic HAP 
or 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). We solicit comment on the proposed revisions for batch process 
vents for P&R I.

     Table 16--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for Batch Front-End Process Vents at P&R I Facilities
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                           Total         VOC emission     HAP emission       HAP cost
                           Control option                             Total capital      annualized       reductions       reductions     effectiveness
                                                                      investment ($)    costs ($/yr)        (tpy)            (tpy)           ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1..................................................................         811,000          650,700              105              105            6,200
--------------------------------------------------------------------------------------------------------------------------------------------------------

    We did not identify any developments in practices, processes, or 
control technologies for P&R II process vents that would achieve a 
greater HAP emission reduction beyond the emission reduction already 
required by P&R II. Therefore, we are not proposing any changes to P&R 
II for this emission

[[Page 25132]]

process group based on our technology review.
    For further details on all of our assumptions and methodologies we 
used in these analyses, see the document titled Clean Air Act Section 
112(d)(6) Technology Review for Continuous Process Vents Located in the 
SOCMI Source Category that are Associated with Processes Subject to 
HON, Continuous Front-end and Batch Front-end Process Vents Associated 
with Processes Subject to Group I Polymers and Resins NESHAP, and 
Process Vents Associated with Processes Subject to Group II Polymers 
and Resins NESHAP, which is available in the docket for this 
rulemaking.
b. NSPS Subparts III, NNN, and RRR
    As previously mentioned, this action presents the EPA's review of 
the requirements of 40 CFR part 60, subparts III, NNN, and RRR pursuant 
to CAA section 111(b)(1)(B). As described in section II.G.2 of this 
preamble, the statutory review of these NSPS focused on whether there 
are any emission reduction techniques that are used in practice that 
achieve greater emission reductions than those currently required by 
these NSPS and whether any of these developments in practices have 
become the BSER. Based on this review, we have determined that the BSER 
for reducing VOC emissions from these SOCMI processes remain 
combustion, and the current standards of 98 percent reduction of TOC 
(minus methane and ethane) or reduction of TOC (minus methane and 
ethane) to an outlet concentration of 20 ppmv on a dry basis corrected 
to 3 percent oxygen, or use of a flare as an APCD continue to reflect 
the BSER. However, we are proposing to remove the alternative of 
maintaining a TRE index value greater than 1 without the use of control 
device. In addition, we are proposing additional requirements to 
provide greater assurance of compliance with the standards. We are also 
proposing standards that would apply during startup, shutdown, 
maintenance, or inspection of any of the air oxidation units, 
distillation operations, and reactor processes affected facilities 
under the applicable NSPS where the affected facility is emptied, 
depressurized, degassed, or placed into service. The rationales for 
each of these proposed actions are presented in more detail below. 
Pursuant to CAA section 111(a), the proposed NSPS included in this 
action would apply to facilities that begin construction, 
reconstruction, or modification after April 25, 2023 (see section 
III.F.2 of this preamble).
    NSPS subparts III, NNN, and RRR regulate vent streams \81\ from: 
SOCMI air oxidation units for which construction, reconstruction, or 
modification commenced after October 21, 1983 that use air (or a 
combination of air and oxygen) as an oxidizing agent to produce one or 
more of the chemicals listed in 40 CFR 60.617; SOCMI distillation 
operations for which construction, reconstruction, or modification 
commenced after December 30, 1983 which produce any of the chemicals 
listed in 40 CFR 60.667 as a product; and SOCMI reactor processes for 
which construction, reconstruction, or modification commenced after 
June 29, 1990 which operate as part of a process unit which produces 
any of the chemicals listed in 40 CFR 60.707 as a product. The SOCMI 
NSPS subparts III, NNN, and RRR regulate VOC emissions in the form of 
TOC. In promulgating these rules, the EPA determined that, for sources 
with a TRE index value equal to or less than 1.0, the BSER is the use 
of thermal incineration or flare achieving 98 percent by weight control 
efficiency or a concentration of 20 ppmv on a dry basis corrected to 3 
percent oxygen. At the time of promulgation, the EPA stated that any 
control technology can be used to meet BSER as long as it can be 
demonstrated that the selected control technology is at least as 
effective as BSER at reducing VOC emissions. For affected facilities 
with a TRE index value greater than 1.0, BSER is no control and sources 
are required to maintain a TRE index value greater than 1.0. As 
previously mentioned, the TRE index value is a measure of the 
supplemental total resource requirement per unit VOC (or HAP for 
NESHAP) reduction (see section III.C.3.a of this preamble). It takes 
into account all the resources which are expected to be used in VOC (or 
HAP) control by thermal oxidation and provides a dimensionless measure 
of resource burden based on cost effectiveness. Resources include 
supplemental natural gas, labor, and electricity. Additionally, if the 
off-gas contains halogenated compounds, resources will also include 
caustic and scrubbing and quench makeup water. For the SOCMI NSPS 
subparts III, NNN, and RRR, the TRE index value is derived from the 
cost effectiveness associated with VOC control thermal oxidation, and 
is a function of vent stream flowrate, vent stream net heating value, 
hourly emissions, and a set of coefficients. The TRE index value was 
first introduced in an EPA document titled: Guideline Series for 
Control of Volatile Organic Compound (VOC) Emissions from Air Oxidation 
Processes in Synthetic Organic Chemical Manufacturing Industry (SOCMI) 
(see EPA-450/3-84-015, December 1984). In general, similar to the HON 
and P&R I, process vents with a TRE index value equal to or less than 
1.0 are required to be controlled under SOCMI NSPS III, NNN and RRR. 
For additional details regarding the TRE index value (including the 
equation and coefficients used to calculate the TRE index value for the 
SOCMI NSPS subparts III, NNN, and RRR), see the document titled CAA 
111(b)(1)(B) review for the SOCMI air oxidation unit processes, 
distillation operations, and reactor processes NSPS subparts III, NNN, 
and RRR, which is available in the docket for this rulemaking.
---------------------------------------------------------------------------

    \81\ Vent stream means: any gas stream, containing nitrogen 
which was introduced as air to the air oxidation reactor, released 
to the atmosphere directly from any air oxidation reactor recovery 
train or indirectly, after diversion through other process equipment 
(for NSPS subpart III); any gas stream discharged directly from a 
distillation facility to the atmosphere or indirectly to the 
atmosphere after diversion through other process equipment (for NSPS 
subpart NNN); and any gas stream discharged directly from a reactor 
process to the atmosphere or indirectly to the atmosphere after 
diversion through other process equipment (for NSPS subpart RRR). In 
all cases, the vent stream excludes relief valve discharges and 
equipment leaks.
---------------------------------------------------------------------------

    We reviewed the RACT/BACT/LAER clearinghouse database, other 
subsequent EPA, state, and local regulatory development efforts related 
to process vents, and responses to our CAA section 114 request for 
advances in process operations, design or efficiency improvements, or 
other systems of emission reduction.
    While we find no change in the BSER for reducing VOC emissions from 
air oxidation units, distillation operations, and reactor processes, we 
are proposing certain revisions to the current standards. First, we are 
proposing to remove the option of maintaining a TRE index value greater 
than 1 as an alternative to controlling emissions. We are proposing 
this change based on the following observations we made with respect to 
the NSPS TRE index. We observed that some facilities subject to NSPS 
subpart III, NNN, and/or RRR are voluntarily controlling process vents 
even though such control is not required under the applicable NSPS 
because their calculated NSPS TRE index value is greater than 1. At 
least three HON facilities that are also subject to at least one of the 
three process vent NSPS confirmed in response to our CAA section 114 
request, that they were voluntarily controlling some of their Group 2 
process vents even though control is not required under either the HON 
or the applicable NSPS. We expect

[[Page 25133]]

other facilities that are subject to the HON and at least one of the 
NSPS subparts III, NNN, and RRR will do this too because some 
facilities stated in their response to the CAA section 114 request 
that, pursuant to 40 CFR 63.113(h), many of their process vents are 
voluntarily designated as HON Group 1 process vents ``so that TRE 
calculations are not required.'' In other words, some facilities are 
likely electing to control certain process vents that have TRE index 
values greater than 1.0. In addition, based on the responses to our CAA 
section 114 request, we observed that facilities are routing multiple 
process vents to a single APCD. This is significant because the current 
use of the TRE index value is only based on controlling a single 
process vent with a single APCD, an unrealistic scenario when compared 
to how chemical manufacturing facilities actually control their process 
vents. It is much more likely that a facility routes numerous process 
vents to the same APCD. For the reason stated above, we no longer 
believe that TRE index value accurately represents the BSER, and 
because a single APCD can control emissions from multiple process 
vents, control could be cost-effective even at a TRE index value of 
greater than 1. Finally, also based on responses to our CAA section 114 
request, one HON and P&R I facility (that is also subject to all three 
process vent NSPS) provided over 300 pages of modeled runs that were 
used to help the facility determine certain characteristics of their 
process vents for inputs to HON and P&R I TRE index value calculations. 
We reviewed this information and concluded that determining a TRE index 
value for certain process vent streams is often theoretical, can be 
extremely complicated, and is uncertain. In addition, because the TRE 
index value is largely a theoretical characterization tool, it can be 
very difficult to enforce. In order to calculate a TRE index value, 
owners and operators must determine numerous input values; and without 
the correct amount of process knowledge, verifying inputs can be 
problematic. We evaluated the cost of requiring that a facility control 
all process vents irrespective of its TRE index value and the average 
cost per facility is provided in Table 17 of this preamble. In 
addition, given the complexity of chemical manufacturing facilities and 
their use of APCDs (e.g., integrated with numerous emission sources 
subject to various chemical manufacturing related NSPS and NESHAP), we 
found the cost to be cost effective based on the cost-effectiveness we 
evaluated for four different NSPS triggering scenarios described 
further below (see Table 18 of this preamble). For the reasons stated 
above, we believe that proposing to remove the option to maintain a 
greater than 1 TRE index value as an alternative to emission reduction 
under NSPS subparts IIIa, NNNa, and RRRa make practical and enforceable 
sense. In other words, for NSPS subparts IIIa, NNNa, and RRRa, we are 
proposing owners and operators 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, reactor processes for which construction, reconstruction, 
or modification 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 more stringent operating and monitoring requirements for flares 
(we discuss these flare requirements further below in this section) 
(see proposed 40 CFR 612a(a), 40 CFR 60.662a(a), and 40 CFR 
60.702a(a)).
    We are also proposing to tighten up the requirements for flares. 
All three NSPS subparts allow the use of a flare in accordance with the 
flare general provisions at 40 CFR 60.18 as an alternative to meeting 
the numeric standards. The EPA had previously believed flares could 
achieve 98 percent emission reduction if it were operated in accordance 
with 40 CFR 60.18. See, e.g., 55 FR 26913. Because the NSPS reflect the 
BSER under conditions of proper operation and maintenance, in doing its 
review, we also evaluate and determine the proper testing, monitoring, 
recordkeeping and reporting requirements needed to ensure compliance 
with the emission standards. In doing so, in our review of several 
chemical and petrochemical sector related NESHAP, such as MON, the 
EMACT standards, and Petroleum Refineries NESHAP, we identified new 
operating and monitoring requirements for flares that are different 
than those specified in 40 CFR 60.18.\82\ The EPA included these flare 
requirements in recent RTR rulemakings in order to ensure flares used 
as APCDs achieve 98 percent HAP destruction efficiencies and these 
flare requirements are also being proposed for HON and P&R I (this is 
discussed in detail in section III.D.1 of this preamble). We evaluated 
the costs of these improved flared requirements and the average cost 
per facility is provided in Table 17 of this preamble. In addition, 
given the complexity of chemical manufacturing facilities and their use 
of APCDs (e.g., integrated with numerous emission sources subject to 
various chemical manufacturing related NSPS and NESHAP), we found the 
cost to be cost effective based on the cost-effectiveness we evaluated 
for four different NSPS triggering scenarios described further below 
(see Table 18 of this preamble). In light of the above, we are 
proposing to include in the new NSPS subparts the same operating and 
monitoring requirements for flares that we are proposing for flares 
subject to the HON and P&R I (see proposed 40 CFR 619a, 40 CFR 60.669a, 
and 40 CFR 60.709a).
---------------------------------------------------------------------------

    \82\ In general the differences include: new requirements to 
operate pilot flame systems continuously and that flares operate 
with no visible emissions (except for periods not to exceed a total 
of 5 minutes during any 2 consecutive hours) when the flare vent gas 
flow rate is below the smokeless capacity of the flare; new 
requirements related to flare tip velocity and the combustion zone 
gas; and new work practice standards related to the visible 
emissions and velocity limits during periods when the flare is 
operated above its smokeless capacity (e.g., periods of emergency 
flaring). For the specific flare requirements, refer to: 40 CFR 
63.1103(e)(4) (EMACT standards), 40 CFR 63.2450(e)(5) (MON), and 40 
CFR 63.670 and 40 CFR 63.671 (Petroleum Refinery Sector rule).
---------------------------------------------------------------------------

    Third, we are proposing to amend the definition of vent streams 
such that the emission standards would also apply to PRD emissions. 
Currently, the NSPS subparts III, NNN, and RRR exclude ``relief valve 
discharges'' from the definition of vent stream (see 40 CFR 60.611, 40 
CFR 60.661, and 40 CFR 60.701) and therefore, emissions from PRDs \83\ 
are currently excluded from emissions standards in these NSPS. However, 
the preambles to the proposed and final subparts were silent on the 
reason for this exclusion in the definition of a ``vent stream.'' 
Further, in reviewing the RACT/BACT/LAER clearinghouse database, we 
identified at least one SOCMI facility that has requirements for 
reactor process vents such that no PRD may emit directly to the 
atmosphere under any circumstance, and the capture system must be 
inspected regularly to verify integrity. In light of the above, we are 
proposing to the ``vent stream'' definition to remove the exclusion of 
``relief valve discharge.''
---------------------------------------------------------------------------

    \83\ The acronym ``PRD'' means pressure relief device and is 
common vernacular to describe a variety of devices regulated as 
relief valve discharges.
---------------------------------------------------------------------------

    Fourth, we are proposing to expressly prohibit emissions from 
affected facilities bypassing an APCD at any time. In our review of 
several chemical and petrochemical sector related NESHAP, none of the 
rules allow regulated emissions from a process vent to bypass an APCD 
at any time, and if a bypass is used, it is considered a

[[Page 25134]]

violation and the owner or operator is required to estimate and report 
the quantity of regulated emissions released.\84\ The EPA included 
these requirements for bypasses in recent RTR rulemakings because 
bypassing an APCD could result in a release of regulated emissions from 
a process vent into the atmosphere.\85\ Currently, the NSPS subparts 
III and NNN do not contain any requirements for bypass lines, and NSPS 
subpart RRR only requires owners and operators to document when a vent 
stream being routed to an APCD is diverted through a bypass line 
resulting in emissions to the atmosphere; therefore, it is unclear 
whether the current standards prohibit bypassing an APCD, which could 
result in a release of otherwise regulated emissions from a process 
vent into the atmosphere. We are therefore proposing in NSPS subparts 
IIIa, NNNa, and RRRa that an owner or operator may not bypass the APCD 
at any time, that a bypass is a violation (see proposed 40 CFR 
60.612a(b)(2), 40 CFR 60.662a(b)(2), and 40 CFR 60.702a(b)(2)), and 
that owners and operators must estimate and report the quantity of TOC 
released should any such violation occur (see proposed 40 CFR 
60.615a(d)(1) and (2), 40 CFR 60.665a(d)(1) and (2), and 40 CFR 
60.705a(d)(1) and (2)).
---------------------------------------------------------------------------

    \84\ See 40 CFR 63.1103(e)(6), 40 CFR 63.1109(g), and 40 CFR 
63.1110(e)(6) (EMACT standards); 40 CFR 63.2450(e)(6), 40 CFR 
63.2520(e)(12), and 40 CFR 63.2525(n) (MON); and 40 CFR 63.644(c), 
40 CFR 63.660(i)(2), and 40 CFR 63.655(g)(6)(iii) and (i)(4) 
(Petroleum Refinery Sector rule).
    \85\ See 85 FR 40386, July 6, 2020 (EMACT standards), 85 FR 
49084, August 12, 2020 (MON), and 80 FR 75178, December 1, 2015 
(Petroleum Refinery Sector rule).
---------------------------------------------------------------------------

    Also, we are proposing in the new NSPS subparts additional control 
device requirements for adsorbers when such APCD is used to meet the 
emission standards in the applicable NSPS. In our review of the MON, we 
identified requirements for adsorbers that cannot be regenerated and 
regenerative adsorbers that are regenerated offsite (see 40 CFR 
63.2450(e)(7)). The MON requires owners and operators of this type of 
APCD to use dual adsorbent beds in series and conduct daily monitoring 
because the use of a single bed does not ensure continuous compliance 
unless the bed is replaced well before breakthrough.\86\ The EPA 
included these requirements in their recent RTR rulemaking for MON in 
order to ensure owners and operators monitor for performance 
deterioration for these specific types of APCDs and these requirements 
are also being proposed for HON and P&R I (see section III.E.5.b of 
this section for additional information about this). Currently, the 
NSPS subparts III, NNN, and RRR do not contain any requirements for 
adsorbers that cannot be regenerated and regenerative adsorbers that 
are regenerated offsite. We evaluated the cost of these requirements 
for adsorbers and the average cost per facility is provided in Table 17 
of this preamble. In addition, given the complexity of chemical 
manufacturing facilities and their use of APCDs (e.g., integrated with 
numerous emission sources subject to various chemical manufacturing 
related NSPS and NESHAP), we found the cost to be cost effective based 
on the cost-effectiveness we evaluated for four different NSPS 
triggering scenarios described further below (see Table 18 of this 
preamble); therefore, in order to ensure that continuous compliance is 
achieved for NSPS subpart IIIa, NNNa, and RRRa facilities at all times 
when controlling VOC emissions (i.e., for those facilities that choose 
to use adsorbers that cannot be regenerated and regenerative adsorbers 
that are regenerated offsite as BSER to meet the 98-percent control or 
a 20 ppmv TOC outlet concentration emission standard), we are proposing 
to include at 40 CFR 60.613a(a)(6), 40 CFR 60.663a(a)(6), and 40 CFR 
60.703a(a)(6) the same monitoring requirements for adsorbers that 
cannot be regenerated and regenerative adsorbers that are regenerated 
offsite that we are proposing for the HON and P&R I.
---------------------------------------------------------------------------

    \86\ According to the MON, ``breakthrough'' means the time when 
the level of HAP or TOC, measured at the outlet of the first bed, 
has been detected is at the highest concentration allowed to be 
discharged from the adsorber system and indicates that the adsorber 
bed should be replaced.
---------------------------------------------------------------------------

    Lastly, consistent with Sierra Club v. EPA, 551 F.3d 1019 (D.C. 
Cir. 2008),\87\ we are proposing standards for periods of startup and 
shutdown, which are currently not subject to the emission standards in 
NSPS subparts III, NNN and RRR. For this effort, we identified, as part 
of our review of the RACT/BACT/LAER clearinghouse database, some SOCMI 
facilities in Texas that have specific requirements related to 
maintenance, startup, and shutdown for equipment and vessel openings 
related to process vents (i.e., opening air oxidation unit processes, 
distillation operations, and reactor processes) and we found that these 
requirements are included in several SOCMI related NESHAP (i.e., EMACT 
standards, the MON, and/or the petroleum refineries NESHAP) (we discuss 
these requirements further below in this section of the preamble). 
Given that many SOCMI processes that are subject to the SOCMI NSPS are 
also located at chemical plants subject to these related NESHAP and 
these facilities use the same APCDs to comply with all of these rules 
(to reduce both VOC and HAP emissions), we also examined the process 
vent provisions from each of these rules. Review of the NESHAP 
standards mentioned above revealed several related requirements that 
did not exist at the time the EPA promogulated NSPS subparts III, NNN, 
and RRR.
---------------------------------------------------------------------------

    \87\ In Sierra Club, the court vacated the SSM exemption 
contained in 40 CFR 63.6(f)(1) and 40 CFR 63.6(h)(1). The court 
explained that under section 302(k) of the CAA, emissions standards 
or limitations must be continuous in nature and that an SSM 
exemption violates this requirement. The EPA believes the reasoning 
in Sierra Club applies equally to section 111 standards.
---------------------------------------------------------------------------

    As previously mentioned in our review of the RACT/BACT/LAER 
clearinghouse database and as found in our review of in several 
chemical and petrochemical sector related NESHAP,\88\ the EPA has 
included a work practice standard for maintenance vents requiring 
owners and operators to meet certain conditions before they open 
equipment to the atmosphere, including opening equipment to the 
atmosphere that are related to NSPS process vents (e.g., air oxidation 
units, distillation operations, and reactor processes). This work 
practice standard requires 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 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 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 pounds 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.\89\ We evaluated the cost 
associated with this work practice standard and the average cost per 
facility is provided in Table 17 of this preamble. In addition, given 
the complexity of chemical manufacturing facilities and their use of 
APCDs (e.g., integrated with numerous emission

[[Page 25135]]

sources subject to various chemical manufacturing related NSPS and 
NESHAP), we found the cost to be cost effective based on the cost-
effectiveness we evaluated for four different NSPS triggering scenarios 
described further below (see Table 18 of this preamble). We determined 
that these work practice standards for maintenance vents (i.e., 
equipment openings related to process vents) is a technique used in 
practice that achieves emission reductions during startup, shutdown, 
maintenance, or inspection of any of the air oxidation units, 
distillation operations, and reactor processes affected facilities 
under the applicable NSPS where the affected facility is emptied, 
depressurized, degassed, or placed into service. 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.'' Equipment openings related to process vents 
are not ``emitted through a conveyance designed and constructed to emit 
or capture such pollutant'' (see CAA section 111(h)(2)) and it is not 
possible to characterize each of these potential release points. For 
these reasons (which are the same reasons we discuss in section 
III.D.4.a of this preamble for including a work practice standard for 
maintenance activities in the HON and P&R I), we are proposing these 
work practice standards for maintenance vents in NSPS subparts IIIa, 
NNNa, and RRRa as the standards reflecting the BSER during periods of 
startup and shutdown (see proposed 40 CFR 612a(c), 40 CFR 60.662a(c), 
and 40 CFR 60.702a(c)).
---------------------------------------------------------------------------

    \88\ See 40 CFR 63.1103(e)(5) (EMACT standards), 40 CFR 
63.2450(v) (MON), and 40 CFR 63.642(c) (Petroleum Refinery Sector 
rule).
    \89\ The EPA added these equipment opening requirements in the 
recent RTR to be consistent with Sierra Club.
---------------------------------------------------------------------------

    As mentioned above, we analyzed cost and emission reductions as 
part of our evaluation of each of the options considered above. We used 
the average cost and emission reductions that we determined for process 
vents subject to the HON to evaluate the costs, emission reductions, 
and cost-effectiveness of each of the options considered above for NSPS 
subparts IIIa, NNNa, and RRRa. Table 17 of this preamble summarizes 
these average HON cost and emission reductions.

    Table 17--Average Cost and Emission Reductions for Process Vents Subject to the HON Used for the Suite of
             Proposed Process Vent Requirements Evaluated for the NSPS Subparts IIIa, NNNa, and RRRa
----------------------------------------------------------------------------------------------------------------
                                                                                  Total annual     VOC emission
                  Description                    Total capital   Total annual    cost w/recovery    reductions
                                                investment ($)    cost ($/yr)    credits ($/yr)        (tpy)
----------------------------------------------------------------------------------------------------------------
Flare monitoring requirements \1\.............       3,752,200         789,200           789,200              93
Maintenance vent requirements \2\.............  ..............             460               460  ..............
Revising the standard from a TRE calculation            39,300          98,400            98,400             9.1
 to control of all vent streams \3\...........
Adsorber monitoring (carbon cannisters) \4\...          26,500           2,500             2,500            0.21
----------------------------------------------------------------------------------------------------------------
\1\ For additional details, see 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.
\2\ For additional details, see the document titled Review of Regulatory Alternatives for Certain Vent Streams
  in the SOCMI Source Category that are Associated with Processes Subject to HON and Processes Subject to Group
  I and Group II Polymers and Resins NESHAPs, which is available in the docket for this rulemaking.
\3\ For additional details, see the document titled Clean Air Act Section 112(d)(6) Technology Review for
  Continuous Process Vents Located in the SOCMI Source Category that are Associated with Processes Subject to
  HON, Continuous Front-end and Batch Front-end Process Vents Associated with Processes Subject to Group I
  Polymers and Resins NESHAP, and Process Vents Associated with Processes Subject to Group II Polymers and
  Resins NESHAP, which is available in the docket for this rulemaking.
\4\ For additional details, see the document titled Analysis of Monitoring Costs and Dual Bed Costs for Non-
  Regenerative Carbon Adsorbers Used in the SOCMI Source Category that are Associated with Processes Subject to
  HON and for Non-Regenerative Carbon Adsorbers that are Associated with Processes Subject to Group I Polymers
  and Resins NESHAP, which is available in the docket for this rulemaking.

    We also evaluated the costs of requiring the suite of proposed 
requirements described above to SOCMI nationwide. We conducted an 
analysis to estimate how many non-HON NSPS affected facilities are 
expected/projected to be subject to the suite of proposed process vent 
requirements presented above. Given that we are proposing these same 
suite of process vent requirements for HON facilities, we only 
considered non-HON NSPS affected facilities here under CAA section 111 
so as to not double count cost and emission reductions from affected 
facilities that are subject to both these SOCMI NSPS and the HON. An 
affected facility can become subject to SOCMI NSPS subpart IIIa, NNNa, 
or RRRa under one of the following scenarios: (1) The affected facility 
is at a new greenfield facility; (2) the affected facility is a new 
affected facility at an existing plant site; (3) an existing affected 
facility is modified; or (4) an existing affected facility triggers the 
reconstruction requirements. For scenario 1 (i.e., affected facility is 
at a new greenfield facility), we assumed only one non-HON greenfield 
facility will trigger NSPS subpart IIIa, NNNa, or RRRa over the next 5 
years (we do not expect any non-HON greenfield facilities, but to be 
comprehensive in our analysis, we assumed one). For comprehensiveness, 
we also assumed this greenfield facility would not be subject to the 
EMACT standards, MON, and Petroleum Refinery Sector rule; and the 
facility will use one flare and one non-flare APCD to control all their 
process vents from SOCMI NSPS unit operations. We used facility 
responses to our CAA section 114 request to help us determine the 
number of facilities that could potentially trigger scenarios 2, 3, and 
4.
    For scenario 2 (i.e., new affected facilities constructed at 
existing plant sites), we estimate six new affected facilities will be 
built and be subject to new requirements in a new NSPS subpart IIIa, 
NNNa, or RRRa over the next 5 years. Facilities responding to our CAA 
section 114 request had 500 unit operations subject to either NSPS 
subpart III, NNN, or RRR; and only one of these unit operations was new 
construction in the last 5 years and not subject to the HON. We 
determined that there are currently 284 SOCMI facilities subject to 
either NSPS subpart III, NNN, or RRR; and 196 of these are non-HON-
subject facilities.\90\ Based on responses

[[Page 25136]]

to our CAA section 114 request, HON facilities have on average 45 unit 
operations per facility. Assuming non-HON facilities are smaller, we 
estimate that non-HON facilities subject to either NSPS subpart III, 
NNN, or RRR have 15 unit operations per facility. Assuming the same 
distribution of new construction for non-HON facilities, we estimate 
that six new affected facilities (one new unit operation per non-HON 
facility subject to either NSPS subpart III, NNN, or RRR), would have 
been constructed in the last 5 years (1/500*15*196). This analysis 
assumes that the same number of unit operations that were constructed 
in the last 5 years would be constructed in the next 5 years. We then 
assumed two of the six new affected facilities (or about 33 percent) 
are collocated at a petroleum refinery, MON, and/or EMACT facility. 
Therefore, two of the six unit operations would already be complying 
with requirements in the NSPS (because of the NESHAP); and we also 
assumed that of the remaining four new unit operations, two will not 
use a flare to comply with the NSPS.
---------------------------------------------------------------------------

    \90\ As of March 2022, according to the OECA's ECHO tool, there 
were 284 facilities located in the United States that are 
potentially subject to at least one of the process vent NSPS 
subparts III, NNN, and/or RRR. The list of facilities 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, which is available in the docket for this 
rulemaking.
---------------------------------------------------------------------------

    For Scenarios 3 and 4 (i.e., existing facility is modified or 
reconstructed), we estimate 12 existing affected facilities will 
trigger new requirements in a new NSPS subpart IIIa, NNNa, or RRRa over 
the next 5 years due to modification or reconstruction. As mentioned 
previously, facilities responding to our CAA section 114 request had 
500 unit operations subject to either III, NNN, or RRR; however, only 
two of these unit operations were modified or reconstructed in the last 
5 years and not subject to the HON. Using similar procedure as 
described above for scenario 2, we estimate that 12 modified or 
reconstructed affected facilities (one modified or reconstructed unit 
operation per non-HON facility subject to the NSPS), would have been 
modified or reconstructed in the last 5 years (2/500*15*196). This 
analysis assumes that the same number of unit operations that were 
modified or reconstructed in the last 5 years would be modified or 
reconstructed in the next 5 years. We then assumed four of the 12 (or 
about 33 percent) modified or reconstructed affected facilities are 
collocated at a refinery, MON, and/or EMACT facility. Therefore, four 
of the 12 unit operations are already complying with requirements in 
the NSPS (because of the NESHAP); and we also, assumed that of the 
remaining eight modified or reconstructed unit operations, four will 
not use a flare to comply with the NSPS.
    Table 18 of this preamble below presents the nationwide impacts for 
the suite of proposed process vent requirements presented above that we 
considered for vent streams subject to new NSPS subparts IIIa, NNNa, 
and RRRa. The cost-effectiveness for the suite of process vent 
requirements evaluated under this NSPS review is $4,570 per ton VOC 
(cost-effectiveness w/recovery credits), which we consider to be cost 
effective. See the document titled CAA 111(b)(1)(B) review for the 
SOCMI air oxidation unit processes, distillation operations, and 
reactor processes NSPS subparts III, NNN, and RRR, which is available 
in the docket for this rulemaking, for details on the assumptions and 
methodologies used in this analysis.
    For the reasons stated above, pursuant to CAA section 111(b)(1)(B), 
we are proposing new SOCMI NSPS to: (1) Remove the TRE index value 
concept in its entirety and require all process vents from an affected 
facility be controlled; (2) 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; (3) prohibit an owner or operator from 
bypassing the APCD at any time, and to report any such violation 
(including the quantity of TOC released to the atmosphere); (4) require 
that flares used to reduce emissions comply with the same flare 
operating and monitoring requirements as those we have promulgated for 
flares used in SOCMI-related NESHAP; (5) require work practice 
standards for maintenance vents during startup, shutdown, maintenance, 
or inspection of any of the air oxidation units, distillation 
operations, and reactor processes affected facilities under the 
applicable NSPS where the affected facility is emptied, depressurized, 
degassed, or placed into service; and (6) add control device 
operational and monitoring requirements for adsorbers that cannot be 
regenerated and regenerative adsorbers that are regenerated offsite 
(see section III.E.5.b of this preamble). We are proposing that 
affected facilities that are constructed, reconstructed, or modified 
after April 25, 2023 would be subject to these proposed requirements in 
NSPS subparts IIIa, NNNa, and/or RRRa.

    Table 18--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for Non-HON Vent
                            Streams Triggering NSPS Subparts IIIa, NNNa, and/or RRRa
----------------------------------------------------------------------------------------------------------------
                                                                                                       Cost-
                                                                   Total annual    VOC emission    effectiveness
            Scenario               Total capital   Total annual      cost  w/       reductions      w/recovery
                                  investment ($)    cost ($/yr)      recovery          (tpy)      credits ($/ton
                                                                  credits ($/yr)                       VOC)
----------------------------------------------------------------------------------------------------------------
Scenario 1 (i.e., one affected         1,665,300         461,000         461,000              93           4,960
 facility at a new greenfield
 facility)......................
Scenario 2 (i.e., new affected         7,609,500       1,780,000       1,780,000             392           4,540
 facility at six existing
 facilities)....................
Scenarios 3 and 4 (i.e., 12           15,192,500       3,558,000       3,558,000             783           4,540
 existing affected facilities
 modified or triggers the
 reconstruction requirements)...
                                 -------------------------------------------------------------------------------
    Total.......................      24,467,300       5,799,800       5,799,800           1,269           4,570
----------------------------------------------------------------------------------------------------------------

4. Standards for Transfer Racks
    We did not identify any developments in practices, processes, or 
control technologies for HON transfer racks that would achieve a 
greater HAP emission reduction beyond the emission reduction already 
required by the HON. Therefore, under CAA section 112(d)(6) we are not 
proposing any changes to the

[[Page 25137]]

HON for this emission process group based on our technology review.\91\ 
We note, however, that under CAA section 112(d)(2) and (3) we are 
proposing changes to the applicability threshold for HON transfer racks 
to fill a regulatory gap in the current HON (see section III.D.8 of 
this preamble).
---------------------------------------------------------------------------

    \91\ P&R I and P&R II sources do not have transfer racks as 
emission sources.
---------------------------------------------------------------------------

5. Standards for Wastewater
    As previously mentioned, HAP are emitted into the air from 
wastewater collection, storage, and treatment systems that are 
uncovered or open to the atmosphere through volatilization of organic 
compounds at the liquid surface. Emissions occur by diffusive or 
convective means, or both. Diffusion occurs when organic concentrations 
at the water surface are much higher than ambient concentrations. The 
organics volatilize, or diffuse into the air, to reach equilibrium 
between aqueous and vapor phases. Convection occurs when air flows over 
the water surface, sweeping organic vapors from the water surface into 
the air. The rate of volatilization is related directly to the speed of 
the air flow over the water surface.
    The HON defines wastewater to mean water that: (1) Contains either: 
(i) an annual average concentration of Table 9 (to NESHAP subpart G) 
compounds of at least 5 ppmw and has an annual average flow rate of 
0.02 liter per minute (lpm) or greater or (ii) an annual average 
concentration of Table 9 (to NESHAP subpart G) compounds of at least 
10,000 ppmw at any flow rate, and that (2) is discarded from a CMPU 
that meets all of the criteria specified in 40 CFR 63.100 (b)(1) 
through (3). Wastewater is process wastewater or maintenance 
wastewater. For process and maintenance wastewaters and certain liquid 
streams in open systems within a CMPU, the HON defines Group 1 
wastewater streams at existing sources as having: either a total annual 
average concentration of Table 9 (to NESHAP subpart G) compounds 
greater than or equal to 10,000 ppmw at any flow rate; or a total 
annual average concentration of compounds in Table 9 to NESHAP subpart 
G greater than or equal to 1,000 ppmw, and the annual average flow rate 
is greater than or equal to 10 liter per minute. NESHAP subpart G 
provides owners and operators several control options for wastewater 
tanks, surface impoundments, containers, individual drain systems, and 
oil-water separators. NESHAP subpart G also specifies performance 
standards for treating wastewater streams using open or closed 
biological treatment systems or using a design steam stripper with vent 
control. For APCDs (e.g., thermal oxidizers) used to control emissions 
from collection system components, steam strippers, or closed 
biological treatment, NESHAP subpart G provides owners or operators 
several compliance options, including 95-percent destruction 
efficiency, a 20 ppmv outlet concentration, or design specifications 
for temperature and residence time.
    P&R I defines wastewater similarly to how the term is defined in 
the HON, except instead of referring to Table 9 (to NESHAP subpart G) 
compounds, P&R I refers to Table 5 (to NESHAP subpart U) compounds. The 
standards for wastewater in NESHAP subpart U refer to the provisions in 
NESHAP subpart G. Generally, the P&R I Group 1 wastewater threshold is 
the same as in the HON, except P&R I refers to compounds that meet the 
definition of organic HAP in 40 CFR 63.482 in addition to those listed 
in table 9 of NESHAP subpart G, and P&R I exempts wastewater that 
pertain solely and exclusively to organic HAP listed on table 8 of 
NESHAP subpart G).
    P&R II defines wastewater as aqueous liquid waste streams exiting 
equipment at an affected source. No further stratification into groups 
for applicability is specified. As previously mentioned, process vents, 
storage tanks, and wastewater systems \92\ combined are regulated 
according to a production-based emission rate (e.g., pounds HAP per 
million pounds BLR or WSR produced) standard for existing sources in 
both BLR (130 pounds) and WSR (10 pounds). For new sources, BLR sources 
require 98 percent reduction or an overall limit of 5,000 pounds of HAP 
per year. New WSR sources are limited to 7 pounds of HAP per million 
pounds WSR produced.
---------------------------------------------------------------------------

    \92\ P&R II defines a wastewater system as a system made up of a 
drain system and one or more waste management units; and a 
wastewater management unit means any component, piece of equipment, 
structure, or transport mechanism used in storing, treating, or 
disposing of wastewater streams, or conveying wastewater between 
storage, treatment, or disposal operations.
---------------------------------------------------------------------------

    As part of our CAA section 112(d)(6) technology review for HON and 
P&R I wastewater streams, we evaluated tightening the HON and P&R I 
wastewater Group 1 applicability thresholds. Specifically, we evaluated 
the option (option 1) to require owners and operators to manage and 
treat existing wastewater streams with total annual average 
concentration of Table 9 (to NESHAP subpart G) compounds (for HON) and 
Table 5 (to NESHAP subpart U) compounds (for P&R I) greater than or 
equal to 1,000 ppmw at any flow rate; or greater than or equal to 10 
ppmw at a flow rate of 10 lpm or greater. We did not identify any 
control options for P&R II wastewater streams.
    Table 19 of this preamble presents the nationwide costs and impacts 
for the wastewater stream control option considered for HON facilities. 
Table 20 of this preamble presents the nationwide costs and impacts for 
the wastewater stream control option considered for P&R I facilities. 
For details on the assumptions and methodologies used in this analysis, 
see the document titled Clean Air Act Section 112(d)(6) Technology 
Review for Wastewater Streams Located in the SOCMI Source Category that 
are Associated with Processes Subject to HON and for Wastewater Streams 
that are Associated with Processes Subject to Group I and II Polymers 
and Resins NESHAP, which is available in the docket for this 
rulemaking.
    We determined that the option to revise wastewater stream Group 1 
threshold applicability (i.e., to require control of existing 
wastewater streams with total annual average concentration of Table 9 
to subpart G compounds (for HON) or Table 5 to 40 CFR 63, subpart U 
compounds (for P&R I) greater than or equal to 1,000 ppmw at any flow 
rate; or greater than or equal to 10 ppmw at a flow rate of 10 lpm or 
greater) is not cost effective based on the costs and emission 
reductions presented. Therefore, we are not proposing to revise the HON 
and P&R I to reflect the requirements of this option pursuant to CAA 
section 112(d)(6). Also, we did not identify any developments in 
practices, processes, or control technologies for P&R II wastewater 
that would achieve a greater HAP emission reduction beyond the emission 
reduction already required by P&R II. Therefore, we are not proposing 
any changes to P&R II for this emission process group based on our 
technology review.

[[Page 25138]]

            Table 19--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for Wastewater Streams at HON Facilities
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                           Total         VOC emission     HAP emission       HAP cost
                           Control option                             Total capital      annualized       reductions       reductions     effectiveness
                                                                      investment ($)    costs ($/yr)        (tpy)            (tpy)           ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1..................................................................     504,766,000      210,739,500            2,755            2,755           76,500
--------------------------------------------------------------------------------------------------------------------------------------------------------

           Table 20--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for Wastewater Streams at P&R I Facilities
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                           Total         VOC emission     HAP emission       HAP cost
                           Control option                             Total capital      annualized       reductions       reductions     effectiveness
                                                                      investment ($)    costs ($/yr)        (tpy)            (tpy)           ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1..................................................................      46,847,800       22,548,200              220              220          102,500
--------------------------------------------------------------------------------------------------------------------------------------------------------

6. Standards for Equipment Leaks
    As previously mentioned, emissions of VOC and HAP from equipment 
leaks occur in the form of gases or liquids that escape to the 
atmosphere through many types of connection points (e.g., threaded 
fittings) or through the moving parts of certain types of process 
equipment during normal operation. Equipment regulated by the HON, P&R 
I, and P&R II includes agitators, compressors, connectors, 
instrumentation systems, OEL, PRDs, pumps, sampling collection systems, 
and valves \93\ that contain or contact material that is 5 percent by 
weight or more of organic HAP, operate 300 hours per year or more, and 
are not in vacuum service. The results of our CAA section 112(d)(6) 
technology review for equipment leaks associated with HON, P&R I, and 
P&R II processes are discussed in section III.C.6.a of this preamble. 
Equipment regulated by NSPS subpart VVa includes connectors, 
compressors, PRDs, pumps, sampling collection systems, OEL, and valves 
that contain or contact material that are 10 percent by weight or more 
of VOC, operate 300 hours per year or more, and are not in vacuum 
service. The results of our CAA 111(b)(1)(B) review for equipment leaks 
subject to NSPS subpart VVa are discussed in section III.C.6.b of this 
preamble.
---------------------------------------------------------------------------

    \93\ We believe P&R II contains a typographical error in that 
valves are currently excluded from the definition of equipment leaks 
at 40 CFR 63.522; see section III.D.10 of this preamble for our 
rationale for this conclusion and our proposal to address this 
issue.
---------------------------------------------------------------------------

a. HON, P&R I, and P&R II
    The HON, P&R I, and P&R II standards for BLR, require owners or 
operators to meet the control requirements of NESHAP subpart H which 
contains the MACT standard for equipment leaks, including LDAR 
provisions and other control requirements. Subpart H was also 
identified in P&R II as the appropriate level of control for facilities 
producing WSR, but additional compliance options were allowed in the 
P&R II rule for WSR sources. We are proposing to no longer allow the 
additional compliance options for WSR sources, and to require that all 
sources comply with the HON equipment leaks regulations (see section 
III.D.10 of this preamble for further details about this proposed 
amendment). 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 generally must be conducted using EPA Method 21 in 
appendix A-7 to 40 CFR part 60 or other approved equivalent monitoring 
techniques. The equipment leak HON, P&R I, and P&R II requirements vary 
by equipment (component) type but require LDAR using monitoring with 
EPA Method 21 of appendix A-7 to 40 CFR part 60 at certain frequencies 
(e.g., monthly, quarterly, every 2 quarters, annually) and have varying 
leak definitions (e.g., 500 ppm, 1,000 ppm, 10,000 ppm) depending on 
the type of service (e.g., gas and vapor service or in light liquid 
service). The LDAR requirements for components in heavy liquid service 
include sensory monitoring (e.g., visual, audible, olfactory).
    The practices, processes, and control technologies considered 
during MACT development for equipment leaks at HON, P&R I, and P&R II 
facilities included LDAR. To identify developments for the technology 
review, we reviewed responses to our CAA section 114 request, the BACT/
LAER database, and evaluated other federal regulations (i.e., the 
Petroleum Refinery Sector rule, MON, and NSPS subpart VVa) and state 
regulations (i.e., the Texas fugitive emissions rules \94\ applicable 
to petrochemical processes). Also, the EPA conducted a general analysis 
in a 2011 equipment leaks study \95\ to identify the latest 
developments in practices, processes, and control technologies for 
equipment leaks at chemical manufacturing facilities and petroleum 
refineries and estimated the impacts of applying those practices, 
processes, and control technologies to model facilities. We used this 
2011 equipment leaks analysis as a reference for conducting the 
technology review for equipment leaks at HON, P&R I, and P&R II 
facilities.
---------------------------------------------------------------------------

    \94\ 30 TAC 115, subchapters D and H, Division 3.
    \95\ Hancy. 2011. Memorandum from Hancy, C., RTI International 
to Howard, J., EPA/OAQPS. Analysis of Emissions Reduction Techniques 
for Equipment Leaks. December 21, 2011. EPA Docket ID No. EPA-HQ-
OAR-2010-0869.
---------------------------------------------------------------------------

    Our technology review for equipment leaks of HAP (e.g., broader 
than the EtO discussed in section II.B.2.a.ii of this preamble) 
identified several developments in LDAR practices and processes: (1) 
Lowering the leak definition for valves in light liquid service from 
500 ppm to 100 ppm with monthly monitoring and skip periods; (2) in 
addition to requirements specified in option 1, lowering the leak 
definition for valves in gas and vapor service from 500 ppm to 100 ppm 
with monthly monitoring and skip periods; and (3) in addition to 
requirements specified in option 2, lowering the leak definition for 
pumps in light liquid service from 1,000 ppm to 500 ppm with monthly 
monitoring. For all other component types, we did not identify 
developments in LDAR practices and processes in the chemical 
sector.\96\
---------------------------------------------------------------------------

    \96\ We note that while other technologies such as optical gas 
imaging and sensor networks may be considered developments in 
monitoring for equipment leaks, the EPA did not evaluate these 
options further as we have insufficient information on how use of 
such monitoring technology compares to current EPA Method 21 
practices for chemical sector sources and we are soliciting comment 
on these technologies. See section V of this preamble for more 
details.

---------------------------------------------------------------------------

[[Page 25139]]

    Emissions reductions were estimated for the new developments that 
we identified using component counts and emission factors. The 
component counts were derived using data provided to the EPA in 
response to our CAA section 114 request (see section II.C of this 
preamble). We developed model component counts for 207 HON facilities, 
19 P&R I facilities (and 10 of the P&R I facilities are collocated with 
HON processes), and 5 P&R II facilities (and 3 of the P&R II facilities 
are collocated with HON processes). We then multiplied the number of 
nationwide HON, P&R I, and P&R II processes \97\ by the model component 
counts to estimate the nationwide component counts. Subsequently, 
baseline emissions and emissions after implementation of the controls 
for each component were calculated using these nationwide component 
counts and emission factors and leak frequencies for the chemical 
manufacturing industry from the 2011 equipment leaks study.
---------------------------------------------------------------------------

    \97\ We used information from the 2006 RTR HON proposal preamble 
(see pg. 34434: https://www.govinfo.gov/content/pkg/FR-2006-06-14/pdf/06-5219.pdf) to estimate the number of HON CMPUs nationwide. In 
2006, the EPA estimated 729 CMPUs nationwide from 238 HON facilities 
based off information from the American Chemistry Council. We scaled 
this data to 207 HON facilities [(207 x 729)/238 = 634]. For P&R I 
facilities we assumed 1 EPPU per facility resulting in 19 EPPU's. 
For P&R II facilities we assumed each facility had 1 process unit 
associated with either WSR or BLR processes resulting in 5 process 
units total.
---------------------------------------------------------------------------

    Costs were then calculated for the baseline and control options, 
which reflect the cost to implement an LDAR program for each component. 
Note that the difference between the costs for the baseline and control 
options is the incremental cost to comply with the controls. 
Furthermore, because the control options result in chemicals in process 
lines not leaking and therefore, not being lost, we present costs both 
with and without this consideration. To estimate savings in chemicals 
not being emitted (i.e., lost) due to the equipment leak control 
options, we applied a recovery credit of $900 per ton of VOC to the 
emission reductions in the analyses.
    We calculated the VOC and HAP cost effectiveness by dividing the 
incremental annual costs by the emissions reductions. Table 21 of this 
preamble presents the nationwide costs and impacts for the suite of 
equipment leak control options considered for HON facilities (including 
10 P&R I facilities and 3 P&R II facilities collocated with HON 
facilities). Table 22 of this preamble presents the nationwide costs 
and impacts for the suite of equipment leak control options considered 
for P&R I facilities (not collocated with HON facilities). Table 23 of 
this preamble presents the nationwide costs and impacts for the suite 
of equipment leak control options considered for P&R II facilities (not 
collocated with HON facilities). For details on the assumptions and 
methodologies used in this analysis, see the document titled Clean Air 
Act Section 112(d)(6) Technology Review for Equipment Leaks Located in 
the SOCMI Source Category that are Associated with Processes Subject to 
HON and for Equipment Leaks that are Associated with Processes Subject 
to Group I and II Polymers and Resins NESHAP, which is available in the 
docket for this rulemaking.
    Based on the costs and emission reductions for each of the options, 
we determined that none of them are cost effective. Therefore, we are 
not proposing to revise the HON, P&R I, and P&R II to reflect the 
requirements of these options pursuant to CAA section 112(d)(6).

              Table 21--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for HON Equipment Not in EtO Service
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                              Average
                                                               Total           Total                       Average  HAP    Average  HAP     incremental
                                           Total capital    annualized      annualized     HAP emission        cost            cost          HAP cost
             Control option               investment ($)     costs w/o      costs with      reductions     effectiveness   effectiveness   effectiveness
                                                          credits ($/yr)  credits ($/yr)       (tpy)       with credits   w/o credits ($/  with credits
                                                                                                              ($/ton)          ton)           ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.......................................       2,079,000         538,400         393,000              16          25,000          34,000  ..............
2.......................................       3,637,000         872,000         672,000              22          31,000          40,000          47,000
3.......................................        4,926,00       1,325,000       1,105,000              24          46,000          55,000         217,000
--------------------------------------------------------------------------------------------------------------------------------------------------------

                      Table 22--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for P&R I Equipment
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                              Average
                                                               Total           Total                         HAP cost        HAP cost       incremental
                                           Total capital    annualized      annualized     HAP emission    effectiveness   effectiveness     HAP cost
             Control option               investment ($)     costs w/o      costs with      reductions     with credits   w/o credits ($/  effectiveness
                                                          credits ($/yr)  credits ($/yr)       (tpy)          ($/ton)          ton)        with credits
                                                                                                                                              ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.......................................          62,300          16,100          11,700            0.48          24,000          34,000  ..............
2.......................................         109,000          26,200          20,200            0.67          30,000          39,000          45,000
3.......................................         148,000          40,500          33,900            0.73          46,000          55,000         228,000
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 25140]]

                      Table 23--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for P&R II Equipment
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                              Average
                                                               Total           Total                         HAP cost        HAP cost       incremental
                                           Total capital    annualized      annualized     HAP emission    effectiveness   effectiveness     HAP cost
             Control option               investment ($)     costs w/o      costs with      reductions     with credits   w/o credits ($/  effectiveness
                                                          credits ($/yr)  credits ($/yr)       (tpy)          ($/ton)          ton)        with credits
                                                                                                                                              ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.......................................          16,400           4,300           3,200            0.13          25,000          33,000  ..............
2.......................................          28,700           7,000           5,400            0.18          30,000          39,000          44,000
3.......................................          39,400          10,700           8,900            0.19          47,000          56,000         350,000
--------------------------------------------------------------------------------------------------------------------------------------------------------

b. NSPS Subpart VVa
    This action presents the EPA's review of the requirements of 40 CFR 
part 60, subpart VVa pursuant to CAA section 111(b)(1)(B). As described 
in section II.G.2 of this preamble, the statutory review of these NSPS 
focused on whether there are any emission reduction techniques that are 
used in practice that achieve greater emission reductions than those 
currently required by these NSPS and whether any of these developments 
in practices have become the BSER. Based on this review, we have 
determined that the BSER for reducing VOC emissions from equipment 
leaks from SOCMI processes remain work practice standards based on 
LDAR. However, we have determined that there are techniques used in 
practice related to LDAR of certain equipment that achieve greater 
emission reductions than those currently required by NSPS subpart VVa. 
We are proposing that BSER for gas and light liquid valves is the same 
monitoring in an LDAR program as NSPS subpart VVa, but now at a leak 
definition of 100 ppm, and BSER for connectors is monitoring in the 
LDAR program at a leak definition of 500 ppm and monitored annually, 
with reduced frequency for good performance. The rationale for this 
proposed action is presented in more detail below. Pursuant to CAA 
section 111(a), the proposed NSPS included in this action would apply 
to facilities that begin construction, reconstruction, or modification 
after April 25, 2023 (see section III.F.2 of this preamble).
    NSPS subpart VVa regulates equipment leaks from SOCMI affected 
facilities whose construction, reconstruction, or modification 
commenced after November 7, 2006. NSPS subpart VVa addresses fugitive 
emissions of VOC from SOCMI affected facilities. Fugitive emissions are 
emissions caused by leaks in processing equipment. NSPS subpart VVa 
defines the affected facility as the ``group of all equipment within a 
process unit,'' with equipment meaning ``each pump, compressor, 
pressure relief device, sampling connection system, open-ended valve or 
line, valve, and flange or other connector in VOC service and any 
devices or systems required by this subpart.'' In other words, the 
affected facility is the collection of all the valves, pumps, etc., 
within a process unit. For the purpose of NSPS subpart VVa, the process 
units are those components assembled to produce any of the chemicals 
listed in 40 CFR 60.489a of subpart VVa. In promulgating NSPS subpart 
VVa, the EPA determined that BSER is work practice standards for 
equipment leaks based on LDAR and other control requirements. The 
standards apply to connectors, compressors, PRDs, pumps, sampling 
collection systems, OEL, and valves in VOC service. A piece of 
equipment is in VOC service if it contains or contacts a fluid that is 
at least 10 percent by weight or more of 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. These standards are generally the 
same as those for HON equipment leaks, except the standards apply to 
VOC instead of HAP, and the connector monitoring requirements in VVa 
were stayed.\98\
---------------------------------------------------------------------------

    \98\ See 73 FR 31372, June 2, 2008.
---------------------------------------------------------------------------

    For our review of NSPS subpart VVa, we reviewed the RACT/BACT/LAER 
clearinghouse database, and other EPA, state, and local regulatory 
development efforts related to equipment leaks to determine advances in 
process operations, design or efficiency improvements, or other systems 
of emission reduction. The 2011 equipment leaks study (see section 
III.C.6.a of the preamble) considered a 100 ppm leak definition, and we 
identified at least one regulation, in the Bay Area Air Quality 
Management District (BAAQMD), that requires gas and light liquid valves 
to meet a 100 ppm leak definition. Additionally, in recent consent 
decrees, the EPA has required low-emitting gas and light liquid valves 
be used.\99\ Low-emitting valves use low emission packing in the valve 
stem to reduce emissions below 100 ppm, but even these low-emitting 
valves can eventually leak over time, as valve packing can deteriorate 
as valves get used more and more. Discussions with valve manufacturers 
have also shown that low-emitting valves are comparable in cost to 
normal valves and are considered by at least one manufacturer to be the 
valve standard commonly used by their customers. Because low-emitting 
valves do not continually keep leaks below 100 ppm, the EPA did not 
consider these valves as best system of emission reduction. Instead, 
the EPA evaluated BSER based on LDAR at different leak definitions.
---------------------------------------------------------------------------

    \99\ https://www.epa.gov/sites/default/files/2013-09/documents/dowchemical-cd.pdf.
---------------------------------------------------------------------------

    We also evaluated the HON equipment leak requirements as many NSPS 
process units are already complying with such requirements. The HON 
equipment leak standards require monitoring connectors at a leak 
definition of 500 ppm annually, with reduced monitoring frequency with 
good performance. These are the same requirements as the stayed VVa 
connector monitoring requirements.
    Based on the information gathered from our review of NSPS subpart 
VVa, we evaluated the following two control options. Option 1 was 
lowering the leak definition for gas and light liquid valves from 500 
ppm to 100 ppm. Option 2 was Option 1 plus adding connector monitoring 
requirements from the stayed 2006 subpart VVa final rule, which is also 
consistent with the current HON requirements.
    For both options considered, we calculated the average costs and 
cost effectiveness on an affected facility basis. Table 24 of this 
preamble summarizes these average costs, cost-effectiveness, and 
emissions reductions on an affected facility basis. For

[[Page 25141]]

additional details, see the document titled CAA 111(b)(1)(B) review for 
the SOCMI Equipment Leaks NSPS Subpart VVa which is available in the 
docket for this rulemaking.

                            Table 24--Average Cost and Environmental Impacts for Equipment Leak Options per Affected Facility
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                           Total annual                    Cost-effectiveness w/recovery
                                                           Total capital   Total annual       cost w/      VOC emission         credits ($/ton VOC)
                     Control option                       investment ($)    cost ($/yr)      recovery       reductions   -------------------------------
                                                                                          credits ($/yr)       (tpy)          Average       Incremental
--------------------------------------------------------------------------------------------------------------------------------------------------------
Option 1: Gas and LL valve monitoring monthly at a leak           10,100           2,360           1,780            0.64           2,780             N/A
 definition of 100 ppm, with skip periods \1\...........
Option 2: Option 1 plus connector monitoring annually at         208,300          38,800          30,500               9           3,390           3,400
 a leak definition of 500 ppm, with skip periods........
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Skip periods refers to reduced monitoring frequency, i.e., skipping monitoring during some periods due to good performance.

    We are proposing to determine Option 2 to be cost-effective for 
new, modified, and reconstructed sources. Many SOCMI facilities are 
already complying with these requirements. Based on the results of our 
analysis, we are proposing BSER for NSPS subpart VVb to be NSPS subpart 
VVa plus revising the equipment leak standards in a new subpart VVb to 
lower the leak definition for gas and light liquid valves from 500 ppm 
to 100 ppm and include requirements for connectors consistent with the 
HON requirements.
    We conducted an analysis to estimate how many affected facilities 
are expected/projected to be subject to the proposed equipment leak 
requirements presented above. An affected facility can become subject 
to NSPS subpart VVb under one of the following scenarios: (1) The 
affected facility is at a new greenfield facility; (2) the affected 
facility is a new affected facility at an existing plant site; (3) an 
existing affected facility is modified; or (4) an existing affected 
facility triggers the reconstruction requirements. For scenario 1 
(i.e., affected facility is at a new greenfield facility), we assumed 
only one greenfield facility, with two process units, will trigger NSPS 
subpart VVb over the next 5 years. We used facility responses to our 
CAA section 114 request to help us determine the number of facilities 
that could potentially trigger scenarios 2, 3, and 4.
    For scenario 2 (i.e., new affected facilities constructed at 
existing plant sites), we assessed information from facilities 
responding to the EPA's CAA section 114 request. The responses to the 
CAA section 114 request showed 34 affected facilities subject to NSPS 
subparts VV or VVa. One of the affected facilities was a new 
construction in the last 5 years. The OECA's ECHO tool (https://echo.epa.gov) indicates there are currently 592 SOCMI facilities 
subject to subpart VV or VVa. We assumed an average of two affected 
facilities per plant site. Assuming the same distribution of new 
construction, 34 new affected facilities would have been constructed in 
the last 5 years for all SOCMI facilities. The analysis assumes that 
the same number of affected facilities that were constructed in the 
last 5 years would be constructed in the next 5 years.
    For scenario 3 (i.e., existing facility is modified) and scenario 4 
(i.e., existing facility triggers reconstruction requirements), 
facilities responding to the EPA's CAA section 114 request did not 
report any modified or reconstructed facilities in the last 5 years or 
in the last 10 years. Eight of the 34 affected facilities discussed in 
scenario 2 indicated either modification or reconstruction since their 
construction, ranging back to the 1940's. We assumed the eight affected 
facilities were modifications because the reconstruction requirements 
are less likely to be triggered. For scenario 3 we assumed that at 
least one affected facility would be modified in the next 5 years, 
likely by addition of new unit operations that would increase the 
number of components. We also assumed that no affected facilities will 
trigger the reconstruction requirements in scenario 4.
    Table 25 of this preamble presents the nationwide impacts for the 
Option 2. See the document titled CAA 111(b)(1)(B) review for the SOCMI 
Equipment Leaks NSPS Subpart VVa, which is available in the docket for 
this rulemaking, for details on the assumptions and methodologies used 
in this analysis. We are proposing that affected facilities that are 
constructed, reconstructed, or modified after April 25, 2023 would be 
subject to these proposed requirements in NSPS subpart VVb. We solicit 
comment on all of the proposed requirements related to standards for 
equipment leaks in new NSPS subpart VVb.

Table 25--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for Affected Facilities
                                           Triggering NSPS Subpart VVb
----------------------------------------------------------------------------------------------------------------
                                                                                                       Cost-
                                                                   Total annual    VOC emission    effectiveness
            Scenario               Total capital   Total annual       cost w/       reductions      w/recovery
                                  investment ($)    cost ($/yr)      recovery          (tpy)      credits ($/ton
                                                                  credits ($/yr)                       VOC)
----------------------------------------------------------------------------------------------------------------
Scenario 1 (i.e., two affected           416,600          77,500          60,900              18           3,380
 facilities at a new greenfield
 facility)......................
Scenario 2 (i.e., 34 new               7,081,700       1,317,900       1,035,800             313           3,310
 affected facilities)...........
Scenarios 3 and (i.e., one               208,300          38,800          30,500               9           3,390
 modified existing affected
 facility)......................
                                 -------------------------------------------------------------------------------

[[Page 25142]]

 
    Total.......................       7,706,600       1,434,200       1,127,200             340           3,320
----------------------------------------------------------------------------------------------------------------

7. Standards for Fenceline Monitoring
    Fenceline monitoring refers to the placement of monitors along the 
perimeter of a facility to measure pollutant concentrations. Coupled 
with requirements for root cause analysis and corrective action upon 
triggering an actionable level, this work practice standard is a 
development in practices considered under CAA section 112(d)(6) for the 
purposes of managing fugitive emissions. The measurement of these 
pollutant concentrations and comparison to concentrations estimated 
from mass emissions via dispersion modeling is used to ground-truth 
emission estimates from a facility's emissions inventory. If 
concentrations at the fenceline are greater than expected, the likely 
cause is that there are underreported or unknown emission sources 
affecting the monitors. In addition to the direct indication that 
emissions may be higher than inventories would suggest, fenceline 
monitoring provides information on the location of potential emissions 
sources because it provides complete spatial coverage of a facility. 
Further, when used with a mitigation strategy, such as root cause 
analysis and corrective action upon exceedance of an action level, 
fenceline monitoring can be effective in reducing emissions and 
reducing the uncertainty associated with emissions estimation and 
characterization. Finally, public reporting of fenceline monitoring 
data provides public transparency and greater visibility, leading to 
more focus and effort in reducing emissions. Fenceline monitoring has 
not yet been required or considered in prior rulemaking actions or 
regulations governing SOCMI, P&R I or P&R II HAP emissions, but has 
been required for Petroleum Refineries in 40 CFR part 63, subpart CC 
(see 40 CFR 63.658). As such we evaluated the application of fenceline 
monitoring as a development in practices, processes, and control 
technologies pursuant to CAA section 112(d)(6). As further explained 
below, our evaluation only focuses on HON and P&R I facilities that 
use, produce, store, or emit benzene, 1,3-butadiene, chloroprene, 
ethylene dichloride, EtO, or vinyl chloride.
    Fenceline monitoring has been successfully applied to the petroleum 
refineries source category as a technique to manage and reduce benzene 
emissions from fugitive emissions sources such as storage vessels, 
wastewater treatment systems, and leaking equipment. In 2015, the EPA 
promulgated the RTR for the petroleum refineries source category and 
required that refineries install and operate fenceline monitors 
following EPA Reference Method 325 A/B to monitor benzene emissions. 
The 2015 rule (80 FR 75178) required that refineries install and begin 
operating passive diffusive tube monitors by 2018 and report benzene 
emissions monitoring data to the EPA beginning in 2019.\100\ 
Additionally, the 2015 rule required that refineries conduct a root 
cause analysis to identify sources of high fenceline monitoring 
readings (i.e., above an annual action level) and then develop a 
corrective action plan to address the sources and reduce emissions to a 
level that will bring fenceline monitoring concentrations below the 
action level.\101\ To date, the EPA has received fenceline monitoring 
data for more than four years.\102\ These data show that petroleum 
refinery fenceline concentrations have dropped by an average of 30 
percent since the inception of the monitoring program requirements. 
These results illustrate that fenceline monitoring is an effective tool 
in reducing emissions and preserving emission reductions on an ongoing 
basis for these sources.
---------------------------------------------------------------------------

    \100\ See 40 CFR 63.658(a) and 40 CFR 63.655(h)(8).
    \101\ 40 CFR 63.658(f)-(h).
    \102\ Quarterly fenceline monitoring reports are available 
through the EPA's WebFIRE database at https://cfpub.epa.gov/webfire/. The EPA has also developed a dashboard to improve public 
access to this data. The dashboard is available at https://awsedap.epa.gov/public/extensions/Fenceline_Monitoring/Fenceline_Monitoring.html?sheet=MonitoringDashboard.
---------------------------------------------------------------------------

    The majority of emissions from sources covered by the HON and P&R I 
are fugitive in nature and are often difficult to characterize and 
quantify. In order to assess the effect of emissions for purposes of 
risk characterization, we rely on the assumption that reported 
emissions are accurate. Thus, if the reported inventories are accurate, 
all facilities should be able to meet the fenceline concentration 
action levels considering the controls we are proposing. Further, 
fenceline monitoring provides the facility and the EPA with an 
understanding of where the concentrations of toxic HAP exceed expected 
concentrations and provide a path for owners and operators to further 
identify the root causes of such exceedances and to mitigate emissions 
from these sources. For facilities regulated by the HON or P&R I, the 
EPA identified six specific HAP that we determined were the most 
appropriate, useful, and suitable for inclusion on the fenceline 
monitoring program. These compounds were identified as cancer risk 
drivers in the prior RTRs for the HON and P&R I conducted in 2006 (HON) 
and 2008 and 2011 (P&R I) or identified as cancer risk drivers in the 
residual risk reviews proposed in this action, and each is emitted 
(largely as fugitive emissions) from processes at HON and P&R I 
sources.\103\ As part of our CAA section 114 request, we also collected 
fenceline monitoring data for these compounds at various facilities and 
often found them to be present in concentrations that were higher than 
our modeling of reported emissions inventories would predict.\104\ 
Although the model to monitor averages are not quantitatively 
comparable because they are based on different time periods (i.e., an 
annual average versus 7 sampling periods), the monitored concentrations 
typically exceeded concentrations established by the modeling; in some 
cases, by multiple orders of magnitude. This is an indicator that 
reported emissions may be underestimated. Therefore, in this action, 
the EPA is proposing at 40 CFR 63.184 to implement a fenceline 
monitoring

[[Page 25143]]

program under CAA section 112(d)(6) to limit fugitive emissions. We are 
proposing to require fenceline monitoring at facilities in the SOCMI 
and P&R I source categories that use, produce, store, or emit benzene, 
1,3-butadiene, chloroprene, EtO, ethylene dichloride, or vinyl 
chloride. A brief summary of the proposed fenceline sampling 
requirements and our rationale for selecting the corrective action 
concentration levels are provided below. We solicit comment on the 
proposed standards for fenceline monitoring.
---------------------------------------------------------------------------

    \103\ P&R II sources do not emit any of these six pollutants.
    \104\ See model to monitor comparison in the document entitled 
Clean Air Act Section 112(d)(6) Technology Review for Fenceline 
Monitoring located in the SOCMI Source Category that are Associated 
with Processes Subject to HON and for Fenceline Monitoring that are 
Associated with Processes Subject to Group I Polymers and Resins 
NESHAP, which is available in the docket for this rulemaking.
---------------------------------------------------------------------------

    Developments in monitoring technology and practices. The EPA 
reviewed the available literature and identified two different methods 
for monitoring fugitive emissions of benzene, 1,3-butadiene, 
chloroprene, ethylene dichloride, EtO, and vinyl chloride around a 
chemical facility. These methods include: (1) Passive diffusive tube 
monitoring networks for the measurement of benzene, 1,3-butadiene, 
chloroprene, and ethylene dichloride; and (2) Canister monitoring 
networks for the measurement of EtO and vinyl chloride. We considered 
these monitoring methods as developments in practices under CAA section 
112(d)(6) for purposes of managing fugitive emission sources at 
chemical manufacturing facilities.
    Fenceline passive diffusive tube monitoring networks employ a 
series of diffusive tube samplers at set intervals along the fenceline 
to measure a time-integrated \105\ ambient air concentration at each 
sampling location. A diffusive tube sampler consists of a small tube 
filled with an adsorbent, selected based on the pollutant(s) of 
interest, and capped with a specially designed cover with small holes 
that allow ambient air to diffuse into the tube at a small, fixed rate. 
Diffusive tube samplers have been demonstrated to be a cost-effective, 
accurate technique for measuring concentrations of pollutants (e.g., 
benzene) resulting from fugitive emissions in a number of studies 
106 107 as well as in the petroleum refining sector.\108\ In 
addition, diffusive samplers are used in the European Union to monitor 
and maintain air quality, as described in European Union directives 
2008/50/EC and Measurement Standard EN 14662-4:2005 for benzene. The 
International Organization for Standardization developed a standard 
method for diffusive sampling (ISO/FDIS 16017-2). In recent years, the 
EPA has expanded the use of diffusive sorbent tubes through our CAA 
Section 114 authority to evaluate fenceline concentrations of HAP in 
addition to benzene, such as chloroprene and 1,3-butadiene. To support 
these efforts, the EPA used existing uptake rates included in EPA 
Methods 325A/B at 40 CFR part 63, Appendix A, and when necessary, 
developed new uptake rates.\109\ Therefore, the EPA is proposing to 
require fenceline monitoring of benzene, chloroprene, 1,3-butadiene, 
and ethylene dichloride measured with 14-day sampling periods using 
diffusive tube samplers in accordance with EPA Methods 325A/B at 40 CFR 
part 63, Appendix A. The EPA notes that based on recent studies, we 
will be incorporating new sorbents and revised uptake rates for certain 
pollutants in an upcoming revision to EPA Method 325B.\110\
---------------------------------------------------------------------------

    \105\ Time-integrated sampling refers to the collection of a 
sample at a controlled rate. The sample provides an average 
concentration over the sample period. For the diffusive tube 
samplers, the controlled rate of sampling is dictated by the uptake 
rate. The uptake rate is the amount of a compound that can be 
absorbed by a particular sorbent over time during the sampling 
period.
    \106\ McKay, J., M. Molyneux, G. Pizzella, V. Radojcic. 
Environmental Levels of Benzene at the Boundaries of Three European 
Refineries, prepared by the CONCAWE Air Quality Management Group's 
Special Task Force on Benzene Monitoring at Refinery Fenceline (AQ/
STF-45), Brussels, June 1999.
    \107\ Thoma, E.D., M.C. Miller, K.C. Chung, N.L. Parsons, B.C. 
Shine. 2011. Facility Fenceline Monitoring using Passive Samplers, 
J. Air & Waste Manage Assoc. 61: 834-842.
    \108\ See EPA-HQ-OAR-2010-0682; fenceline concentration data 
collected for the petroleum refining sector rulemaking can be 
accessed via the Benzene Fenceline Monitoring Dashboard at https://awsedap.epa.gov/public/extensions/Fenceline_Monitoring/Fenceline_Monitoring.html?sheet=MonitoringDashboard.
    \109\ Docket Reference to ``Method 325B Addendum A, Evaluation 
of Chloroprene Uptake Rate Report.''
    \110\ Markes International Ltd. Uptake Rate Tests: Tests for a 
range of compounds onto four sorbent types over periods of 1 and 2 
weeks. September 27, 2022.
---------------------------------------------------------------------------

    In this action, the EPA is proposing a new EPA reference method to 
monitor the concentration of EtO and vinyl chloride from facility 
fenceline locations, EPA Method 327 to 40 CFR part 63, Appendix A. EPA 
Method 327 is a canister sampling and analysis method that provides 
procedures for measuring trace levels of targeted VOC (including 
organic HAP) in ambient air. It draws upon the guidance in Method TO-
15A \111\ for canister sampling and further develops this guidance into 
a robust method specific for fenceline monitoring, defining required 
data quality objectives, and incorporating existing best practices into 
the method. In EPA Method 327, ambient air samples are collected using 
specially prepared and pre-cleaned evacuated stainless-steel canisters. 
For analysis, a known volume of air is directed from the canister to a 
pre-concentrator, and the targeted VOC from the sample are measured 
using a gas chromatograph-mass spectrometer (GC-MS). The EPA is 
proposing to require fenceline monitoring of EtO and vinyl chloride 
with 24-hour sampling periods once every 5 days using canister sampling 
in accordance with EPA Method 327 at 40 CFR part 63, appendix A. This 
monitoring frequency is necessary to ensure that all onsite processes 
are monitored regularly and approaches the time-integrated sampling of 
EPA Methods 325A/B, while still maintaining the cost effectiveness of 
implementing a canister monitoring network. A sampling frequency of 
every five days will also help to reduce the possibility of only 
monitoring emission spikes such that the annual average concentration 
is indicative of the actual average emissions from the site.
---------------------------------------------------------------------------

    \111\ https://www.epa.gov/sites/default/files/2019-12/documents/to-15a_vocs.pdf.
---------------------------------------------------------------------------

    The EPA considered requiring EPA Method 327 for monitoring ethylene 
dichloride, because ethylene dichloride is almost always going to be 
monitored alongside vinyl chloride. Because vinyl chloride is monitored 
with EPA Method 327, monitoring ethylene dichloride with EPA Method 327 
would simplify the monitoring and increase the cost effectiveness of 
implementing the fenceline monitoring program. However, in this action 
EPA has chosen to require EPA Methods 325A/B for monitoring ethylene 
dichloride because based on the available data, at least one vinyl 
chloride monomer facility reported emissions of chloroprene, which 
would require that facility to monitor for chloroprene with EPA Methods 
325A/B. Because monitoring with EPA Methods 325A/B is more continuous 
than with EPA Method 327 and the results with EPA Methods 325A/B 
generally have less variability, monitoring with EPA Methods 325A/B is 
the preferred approach. We are however soliciting comment on whether we 
should allow the use of EPA Method 327 for monitoring fenceline 
concentration of ethylene dichloride for sites that have to monitor 
fenceline concentrations of vinyl chloride but do not have to monitor 
fenceline concentrations of chloroprene, benzene, or 1,3-butadiene.
    While EPA Method 327 is based on Method TO-15A, there are notable 
differences between the two methods. EPA Method 327 addresses some of 
the challenges encountered while performing sampling and analysis of 
EtO with Method TO-15A by incorporating best practices into the method. 
EPA Method 327 also is written

[[Page 25144]]

to mandate actions within the method as opposed to providing guidance 
on how the method should be performed. The major differences between 
Method TO-15A and Method 327 include the following, but are not limited 
to:
     Updated sample cleanliness requirements and removal of the 
option for glass bottles and non-rigid containers.
     invalidation of samples that do not meet initial and final 
canister pressure requirements.
     requirement to examine chromatograms for potential 
interferences, with a strong recommendation for the use of full scan 
ion spectra MS mode during analysis.
     requirements for certification and recertification of 
standards to ensure the quality and stability of the standards.
     requirements for one field blank and one field duplicate 
for each sampling period.
     requirement for the field blank diluent gas to be 
humidified zero air.
     maximum allowed sample holding time of 7 days.
     requirement to drift correct measured values based on 
continuous calibration verification criteria according to the 
procedures in EPA Method 325B.
    To achieve the lowest possible detection limits with canister 
sampling, the EPA has determined that it is necessary to mandate these 
best practices within EPA Method 327. Although facilities were asked to 
follow these best practices in the CAA section 114 request, the data 
submitted in response to the request indicated there are sampling and 
analysis issues that still need to be addressed, especially in regard 
to measuring EtO.
    While the EPA acknowledges that there are some drawbacks of time-
integrated sampling, including the lack of immediate feedback on the 
acquired data and the loss of short-term temporal information, our 
experience with the fenceline monitoring program in the petroleum 
refining sector has proven that these systems are capable of achieving 
meaningful emissions reductions by allowing earlier detection of 
significant fugitive emissions than conventional source-specific 
monitoring, such as through a periodic leak detection program with EPA 
Method 21 of 40 CFR part 60, appendix A-7. Additionally, time-
integrated monitoring systems are generally lower-cost and require less 
labor than time-resolved \112\ monitoring systems; they generally have 
lower detection capabilities as well. Time-resolved monitoring stations 
have been used for a variety of pollutants in a variety of settings and 
the methods are well-established. However, compared to the passive 
diffusive tube monitoring stations or canister sampling, time-resolved 
monitoring stations are more expensive, more labor-intensive, and 
generally require highly-trained staff to operate. The EPA acknowledges 
the state of technology is advancing and that the capabilities of these 
systems will continue to improve and that the costs will likely 
decrease. Therefore, we are providing a pathway for an owner or 
operator to request use of other types of monitoring networks to 
demonstrate compliance with the fenceline standards through a request 
for an alternative test method under the provisions of 40 CFR 63.7(f).
---------------------------------------------------------------------------

    \112\ Time resolved monitoring involves sampling within short 
timeframes (generally on the magnitude of minutes to hours) in order 
to see the variation in concentration of a compound in near real 
time.
---------------------------------------------------------------------------

    Siting, design, and sampling requirements for fenceline monitors. 
The EPA is proposing that fenceline monitors be deployed to measure 
fenceline concentrations of benzene, 1,3-butadiene, chloroprene, 
ethylene dichloride, EtO, and vinyl chloride at chemical manufacturing 
facilities subject to the HON or P&R I. A primary requirement for a 
fenceline monitoring system is that it provides adequate spatial 
coverage for determination of representative pollutant concentrations 
at the boundary of the facility. In an ideal scenario, fenceline 
monitors would be placed so that any fugitive plume originating within 
the facility would have a high probability of intersecting one or more 
monitors, regardless of wind direction. Therefore, we are proposing 
that for passive diffuse tube monitoring of benzene, 1,3-butadiene, 
chloroprene, and ethylene dichloride, facilities determine the 
appropriate number and location of fenceline sampling monitors using 
the siting method requirements described in EPA Method 325A of 40 CFR 
part 63, Appendix A. Sample collection and analysis of the passive 
tubes would be performed according to EPA Methods 325A and 325B of 40 
CFR part 63, appendix A.
    For canister monitoring of EtO and vinyl chloride, the EPA is 
proposing that each facility would place 8 canisters evenly spaced on 
the monitoring perimeter. The monitoring perimeter may be the facility 
fenceline or may be inside the facility fenceline as long as all 
sources of the monitored compound(s) are contained within the 
perimeter. Because we recognize that the spatial coverage provided by 
this arrangement is less than that provided under EPA Method 325A, the 
EPA is also proposing that facilities would be required to move the 
canister sampling locations with alternating sampling periods in order 
to ensure complete spatial coverage of the facility. For facilities 
with emission sources of monitored pollutants that are not contained 
within one contiguous area, the EPA is proposing that these secondary 
areas would be monitored as well, with the number of canisters on the 
secondary area dictated by the size of the area. The proposed 
requirements for siting the canisters are described in NESHAP subpart H 
(see proposed 40 CFR 63.184). While we recognize that EPA Method 325A 
contains an option for siting passive tubes by determining the 
geographic center of the facility and spacing the tubes based on 
measured angles from the center point, the EPA has chosen not to 
provide a similar approach for the canisters in order to simplify the 
siting of the canisters. We request comment on the proposed approach 
for siting the canisters and whether we should provide an alternative 
siting approach based on measured angles from the center point.
    For each sampling period (2-week period for passive tubes or 24-
hour period for canisters), the facility would determine a delta c, 
calculated as the lowest sample value for the compound of interest 
subtracted from the highest sample value for the compound of interest. 
This approach is intended to subtract out the estimated contribution 
from background emissions that do not originate from the facility. The 
delta c for the most recent year of samples (26 sampling periods for 
passive tubes and 73 sampling periods for canisters) would be averaged 
to calculate an annual average delta c. The annual average delta c 
would be determined on a rolling basis, meaning that it is updated with 
every new sample (i.e., for passive tubes, every 2 weeks a new annual 
average delta c is determined from the most recent 26 sampling periods 
and for canisters, every 5 days a new annual average delta c is 
determined from the most recent 73 sampling periods). This rolling 
annual average delta c would be calculated for each compound of 
interest and compared against a concentration action level for each 
pollutant.
    Action levels and rationale. As mentioned above, the EPA is 
proposing to require facilities subject to the HON and P&R I to take 
corrective action to reduce fugitive emissions if monitored fenceline 
concentrations exceed a specific concentration action level on a

[[Page 25145]]

rolling annual average basis.\113\ For benzene, 1,3-butadiene, ethylene 
dichloride, and vinyl chloride, we selected the proposed fenceline 
action levels by modeling fenceline HAP concentrations using the 
emissions inventories used in the residual risk assessment of the 
facility-wide review of the SOCMI source category and Neoprene 
Production source category (e.g., 2017 NEI), assuming that those 
reported emissions represented full compliance with all proposed HON or 
P&R I requirements, adjusted for additional control requirements we are 
proposing in this action.\114\ We estimated the long-term fenceline 
post-control HAP concentrations at each facility using the post-control 
facility-wide emissions inventory and the EPA's HEM. Concentrations 
were estimated by the model at a set of polar grid receptors centered 
on each facility, as well as surrounding census block centroid 
receptors extending from the facility outward to 50 km (~31 miles). For 
purposes of this modeling analysis, we assumed that the nearest off-
site polar grid receptor was the best representation of each facility's 
fenceline concentration in the post-control case, unless there was a 
census block centroid nearer to the fenceline than the nearest off-site 
polar grid receptor or an actual receptor was identified from review of 
the site map. In those instances, we estimated the fenceline 
concentration as the concentration at the census block centroid. Only 
receptors (either the polar or census block) that were estimated to be 
outside the facility fenceline were considered in determining the 
maximum HAP concentration level for each facility. After modeling each 
facility, we then selected the maximum annual average benzene, 1,3-
butadiene, ethylene dichloride, and vinyl chloride fenceline 
concentration modeled at any facility as the action level for that HAP. 
Thus, if the reported inventories are accurate, all facilities should 
be able to meet the fenceline concentration action levels. We note that 
this analysis does not correlate to any particular metric related to 
risk. The maximum annual average HAP concentrations modeled at the 
fenceline for any facility, rounded to one significant figure, were 9 
micrograms per cubic meter ([mu]g/m\3\, benzene),\115\ 3 [mu]g/m\3\ 
(1,3-butadiene), 4 [mu]g/m\3\ (ethylene dichloride), and 3 [mu]g/m\3\ 
(vinyl chloride). Therefore, the EPA is proposing these fenceline 
concentrations as action levels for these four HAP.
---------------------------------------------------------------------------

    \113\ Calculated every two weeks for benzene, 1,3-butadiene, 
ethylene dichloride, and chloroprene. Calculated every five days for 
ethylene oxide and vinyl chloride.
    \114\ We note that 10 of the 19 facilities with P&R I processes 
also have HON processes.
    \115\ Since we are considering facility-wide emissions, an 
action level of 9 [mu]g/m\3\ was chosen for benzene since the 
refinery who set the action level in 2015 for that source category 
is also a HON facility.
---------------------------------------------------------------------------

    Due to current limitations in method detection limits for EtO and 
chloroprene, and the concerns for cancer risk driven by these two 
pollutants, we selected the proposed fenceline action levels to be 
equal to three times the representative detection limit (RDL) for these 
two pollutants, as this is the minimum concentration that can be 
measured with reasonable certainty. The RDL is based on the results of 
the best performing testing companies and laboratories using the most 
sensitive analytical procedures. A multiplication factor of three is 
used to reduce the imprecision of the method until the imprecision in 
the sampling and analysis is similar to the precision of other EPA 
methods. The RDL for chloroprene was determined to be 0.09 [mu]g/m\3\, 
and the RDL for EtO was determined to be 0.07 [mu]g/m\3\. Therefore, 
the EPA is proposing action levels of 0.3 [mu]g/m\3\ for chloroprene 
and 0.2 [mu]g/m\3\ for EtO. We acknowledge that these proposed 
concentrations are lower than the fenceline modeled concentrations for 
EtO and chloroprene from facilities in the SOCMI and Neoprene 
Production source categories after implementation of our proposed 
standards; however, considering whole facility risks, and in light of 
the configuration of the emission sources subject to these rules that 
contribute to whole facility risk that remain for the impacted 
communities after the imposition of controls, we set the action levels 
of chloroprene and EtO at facility boundaries as low as possible 
(considering method detection limitations) to ensure emission 
reductions anticipated from implementation of controls used to meet the 
proposed standards and to achieve additional HAP emission reductions. 
Though we have not proposed to prescribe additional specific controls 
to the existing inventories because remaining emissions are fugitive in 
nature and less certain in terms of frequency of events and 
characterization of emissions, there are still measures that are likely 
available that could be employed to address emission sources in a more 
directed manner. For example, identifying and reducing emissions from 
sources such as maintenance events that could not be accounted for in 
the post control modeling exercise would be effective in achieving 
additional emission reductions. In addition to proposing this fenceline 
monitoring work practice standard under CAA section 112(d)(6) 
reflecting developments in practices, processes, and control 
technologies, we also request comment on whether it would be 
appropriate, in the final rulemaking, to promulgate these proposed 
fenceline monitoring work practice standards, including the proposed 
fenceline action levels for EtO and chloroprene, under the second step 
of the CAA section 112(f)(2) residual risk decision framework to 
provide an ample margin of safety to protect public health. Making such 
a determination might be warranted, for example, in light of the fact 
that we considered the facility-wide risk as an additional factor not 
considered in the source category-specific risk acceptability decisions 
for the SOCMI and Neoprene Production source categories that are both 
the subject of this single combined rulemaking action.
    For further details of the analysis, see the document titled Clean 
Air Act Section 112(d)(6) Technology Review for Fenceline Monitoring 
located in the SOCMI Source Category that are Associated with Processes 
Subject to HON and for Fenceline Monitoring that are Associated with 
Processes Subject to Group I Polymers and Resins NESHAP, which is 
available in the docket for this rulemaking.
    Non-source category emissions. This proposed approach also 
considers the possibility that offsite sources could contribute to 
modeled concentrations at a facility's fenceline. Additionally, non-HON 
and non-P&R I sources could be located within facility property 
boundaries that also contribute to monitor readings. In this proposal, 
we are allowing the subtraction of offsite interfering sources (as they 
are not within the control of the owner or operator) through site 
specific monitoring plans, but we are not providing this option for 
onsite, non-source category emissions. The action levels above were 
based on facility-wide emissions, and therefore these non-source 
category sources have been considered in their development. Applying 
the fenceline standard to the whole facility will also limit emissions 
of toxic HAP from all sources and provide more certainty in decisions 
being made on whether the entire facility emissions align with what is 
expected from the EPA's analysis. It will also provide assurances to 
fenceline communities that emission reductions are achieved and 
maintained. This is important in the chemical sector, where there could 
be numerous source

[[Page 25146]]

categories that can be collocated within a larger facility, and have 
common tank farms, wastewater systems, heat exchangers, APCDs, fuel gas 
systems, etc., that may be assigned or apportioned to various source 
categories.
    Corrective action requirements. The proposed fenceline monitoring 
provisions would require the initiation of root cause analysis upon 
exceeding the annual average concentration as determined on a rolling 
average every sampling period. The root cause analysis is an assessment 
conducted through a process of investigation to determine the primary 
underlying cause and other contributing causes of an exceedance of the 
action level. The root cause analysis would be required to be initiated 
within 5 days of determining that an updated annual average 
concentration of a target pollutant exceeds the applicable action 
level. A root cause analysis must be conducted following each 14-day 
sampling period in which the annual average concentration(s) remain 
above the action level to determine whether the monitoring results and 
associated data indicate additional sources of emissions contributing 
to concentrations remaining above the action level. If the owner or 
operator cannot determine the root cause of the exceedance within 30 
days of determining there was an exceedance of an action level, the 
owner or operator would be required to use real-time sampling 
techniques (e.g., mobile gas chromatographs) to determine the root 
cause of the exceedance.
    If the underlying causes of the action level exceedance are deemed 
to be from sources under the control of the owner or operator, the 
owner or operator would be required to take corrective action to 
address the underlying cause of the exceedance and to bring 
concentrations back below the action level as expeditiously as 
possible. Completion of the root cause analysis and initial corrective 
action would be required within 45 days of determining that there was 
an exceedance of an action level. If the owner or operator requires 
longer than 45 days to implement the corrective actions identified by 
the root cause analysis, the owner or operator would be required to 
submit a corrective action plan no later than 60 days after completion 
of the root cause analysis.
    After completion of the initial corrective action, if the delta c 
for the next sampling period for samples collected by EPA Methods 325A/
B or the next three sampling periods for samples collected by EPA 
Method 327 \116\ are below the action level, then the corrective action 
is assumed to have fixed the problem, and the owner and/or operator 
would have no further obligation for additional corrective action. 
However, if the delta c for the subsequent sampling periods after 
initial corrective action is over the action level, then the owner or 
operator would have to submit a corrective action plan and schedule for 
implementing design, operation, and maintenance changes to eliminate as 
quickly as possible and prevent recurrence of the primary cause and 
other contributing causes to the exceedance of the action level in 
order to reduce annual average concentrations below the action level. 
The owner or operator would be required to include the implementation 
of real-time sampling techniques to locate the primary and other 
contributing causes of the exceedance in the corrective action plan. 
While the action level(s) are based on annual average concentrations, 
once an action level is exceeded, each sampling period that exceeds the 
action level contributes to the delta c remaining above the action 
level. An investigation must be conducted following these high biweekly 
periods to determine the root cause and, if appropriate, to correct the 
root cause expeditiously in order to bring the annual average delta c 
below the action level.
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    \116\ The EPA is proposing that three sample periods must remain 
below the action level for samples taken by EPA Method 327 because 
three is equal to the number of samples that would be taken during 
one sample period for EPA Methods 325A/B. Requiring three sample 
periods also ensures that a sample will have been taken at every 
monitoring location at the site following the completion of the 
corrective action.
---------------------------------------------------------------------------

    Costs associated with fenceline monitoring requirements. We 
estimated costs to monitor for benzene, 1,3-butadiene, chloroprene, and 
ethylene dichloride at the fenceline using final rule costs for passive 
diffusive tube monitoring using the medium model plant costs for the 
2015 Petroleum Refinery Sector final rule (80 FR 75178, December 1, 
2015) and scaled costs to 2021 dollars. For EtO and vinyl chloride, we 
estimated fenceline monitoring costs for 8 summa cannisters around the 
fenceline every 5 days. We also note that there a number of HON 
facilities that are either collocated with refineries who are already 
conducting passive diffusion tube fenceline monitoring for benzene as 
well as some HON facilities under consent decree conducting fenceline 
monitoring for benzene with passive diffusion tubes, so costs to add 
laboratory analysis for a second analyte under this action are minimal 
(i.e., $1,300 more per year) for these facilities, and why monitoring 
scenario 2 in the table below for the HON is less costly than 
monitoring scenario 1 even though more facilities fall into the 
monitoring scenario 2 category. In total for this proposed rulemaking 
package, we estimate nationwide impacts for fenceline monitoring to be 
$9,881,000 for total capital investment and $33,310,000 per year for 
total annualized cost, and estimate that 126 of the 207 HON facilities 
and 12 of the 19 P&R I facilities would be required to conduct 
fenceline monitoring as they emit at least one of the six HAP of 
interest. Tables 26 and 27 provide the breakdown of estimated 
nationwide costs for fenceline monitoring as applied to all HON and P&R 
I sources. Note that ten facilities have collocated sources subject to 
multiple NESHAP (i.e., the HON and P&R I) and would be required to 
conduct fenceline monitoring under both rules, therefore where this 
occurred, we assigned costs and included the facility under the SOCMI 
source category for impacts to avoid double counting. For further 
information, see the document titled Clean Air Act Section 112(d)(6) 
Technology Review for Fenceline Monitoring located in the SOCMI Source 
Category that are Associated with Processes Subject to HON and for 
Fenceline Monitoring that are Associated with Processes Subject to 
Group I Polymers and Resins NESHAP, which is available in the docket 
for this rulemaking.

[[Page 25147]]

                        Table 26--Nationwide Cost Impacts of Fenceline Monitoring for HON
----------------------------------------------------------------------------------------------------------------
                                                                                                       Total
                                         Number           Monitoring option        Total capital    annualized
        Monitoring scenario            facilities            description          investment ($)  costs (million
                                        impacted                                                       $/yr)
----------------------------------------------------------------------------------------------------------------
1..................................              35  Passives only (1 analyte)..       4,016,000       2,141,000
2..................................              46  Passives only (2 analytes).       2,295,000       1,282,000
3..................................               9  Cannisters only............         115,500       5,366,000
4..................................              16  Cannisters and passives (1        1,606,000      10,397,000
                                                      analyte).
5..................................              20  Cannisters and passives (2        1,721,000      12,869,000
                                                      analytes).
----------------------------------------------------------------------------------------------------------------

                       Table 27--Nationwide Cost Impacts of Fenceline Monitoring for P&R I
----------------------------------------------------------------------------------------------------------------
                                         Number                                                        Total
        Monitoring scenario            facilities         Monitoring option        Total capital    annualized
                                        impacted             description          investment ($)   costs ($/yr)
----------------------------------------------------------------------------------------------------------------
1..................................               1  Cannisters and passives (2          114,700         659,000
                                                      analytes).
2..................................               1  Cannisters only............          12,800         596,000
----------------------------------------------------------------------------------------------------------------

    Additional requirements of the fenceline monitoring program. The 
EPA is proposing at 40 CFR 63.182(e) that fenceline data be reported on 
a quarterly basis. Each report would contain the results for each 
sample where the field portion of sampling is completed by the end of 
the quarter, as well as for associated field and method blanks (i.e., 
each report would contain data for at least 6, 2-week sampling periods 
and 18 canister sampling periods). These data would be reported 
electronically to the EPA within 45 days of the end of each quarterly 
period. See section III.E.3 of this preamble for further discussion on 
electronic reporting and section III.F.1 of this preamble for further 
discussion on the compliance dates we are proposing.

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?

    In addition to the proposed actions discussed in this section III.B 
of this preamble to reduce risk from EtO emission sources (from HON 
processes) and chloroprene emission sources (from P&R I affected 
sources producing neoprene), and our proposed actions discussed in this 
section III.C of this preamble on NESHAP technology reviews, we are 
also proposing other requirements for the HON, P&R I, and P&R II based 
on analyses performed pursuant to CAA section 112(d)(2) and (3),\117\ 
and that are consistent with Sierra Club v. EPA, 551 F.3d 1019 (D.C. 
Cir. 2008), ensuring that CAA section 112 standards apply continuously. 
We are proposing to: (1) Add new monitoring and operational 
requirements for HON and P&R I flares, (2) add work practice standards 
for periods of SSM for certain HON and P&R I vent streams (i.e., PRD 
releases, maintenance vents, and planned routine maintenance of storage 
vessels), (3) clarify regulatory provisions for vent control bypasses 
for certain HON and P&R I vent streams (i.e., closed vent systems 
containing bypass lines), (4) add dioxins and furans emission limits to 
the HON, P&R I, and P&R II, (5) add new monitoring requirements for HON 
and P&R I pressure vessels, (6) add new emission standards for HON & 
P&R I surge control vessels and bottoms receivers, (7) revise the 
applicability threshold for HON transfer racks, (8) add requirements to 
P&R II for heat exchange systems, and (9) add requirements to P&R II 
for WSR sources and equipment leaks. See the subsections below for 
specific details regarding these proposed actions, and for which rules 
(i.e., HON, P&R I, and/or P&R II) we are proposing these actions.
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    \117\ The EPA has authority under CAA section 112(d)(2) and (3) 
to set MACT standards for previously unregulated emission points. 
The EPA also retains the discretion to revise a MACT standard under 
the authority of CAA section 112(d)(2) and (3) (see Portland Cement 
Ass'n v. EPA, 665 F.3d 177, 189 (D.C. Cir. 2011)), such as when it 
identifies an error in the original standard. See also Medical Waste 
Inst. v. EPA, 645 F.3d 420, 426 (D.C. Cir. 2011) (upholding the EPA 
action establishing MACT floors, based on post-compliance data, when 
originally-established floors were improperly established).
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1. Flares
    The EPA is proposing under CAA section 112(d)(2) and (3) to amend 
the operating and monitoring requirements for flares used as APCDs in 
the SOCMI and P&R I source categories because we have determined that 
the current requirements for flares are not adequate to ensure the 
level of destruction efficiency needed to conform with the MACT 
standards in the HON and P&R I.\118\ As previously mentioned in section 
III.C.3.b of this preamble, we are also proposing these same operating 
and monitoring requirements for flares for NSPS subparts IIIa, NNNa, 
and RRRa under CAA section 111(b)(1)(B). Flares are commonly used 
within the SOCMI and P&R I source categories. The requirements 
applicable to flares, which are used to control emissions from various 
emission sources (e.g., process vents, storage vessels, transfer racks, 
equipment leaks, wastewater streams), are set forth in the General 
Provisions to 40 CFR part 63 and are cross-referenced in the HON and 
P&R I. In general, flares used as APCDs are expected to achieve 98 
percent HAP destruction efficiencies when designed and operated 
according to the requirements in the General Provisions. Studies on 
flare performance,\119\ however, indicate that these General Provision 
requirements are inadequate to ensure proper performance of flares at 
refineries and other petrochemical facilities (including SOCMI 
facilities), particularly when either assist steam or assist air is 
used. In addition, over the last decade, flare minimization efforts at 
these facilities have led to an increasing number of flares operating 
at well below their

[[Page 25148]]

design capacity, and while these efforts have resulted in reduced 
flaring of gases, situations of over assisting with either steam or air 
have become exacerbated, leading to the degradation of flare combustion 
efficiency. Many HON and P&R I facilities operate directly downstream 
from refineries and other petrochemical plants (e.g., ethylene 
production plants) and, consequently, likely burn similar types of 
waste gas constituents to a refinery or petrochemical plant (e.g., 
olefins and hydrogen). Given that flares at petrochemical plants, SOCMI 
facilities, and a polymers and resins plant were also included in the 
flare dataset that formed the underlying basis of the new standards for 
refinery flares, we are proposing to apply the finalized suite of 
operational and monitoring requirements for refinery flares \120\ to 
those flares in the SOCMI source category that control emissions from 
HON and P&R I processes. Therefore, these proposed amendments at 40 CFR 
63.108 (for HON) and 40 CFR 63.508 (for P&R I) will ensure that 
continuous compliance with the CAA section 112(d)(2) and (3) standards 
is achieved for HON and P&R I facilities that use flares as APCDs to 
meet the MACT standards at all times when controlling HAP emissions.
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    \118\ P&R II sources do not use flares as APCDs as they are 
making resins from chlorinated chemicals (i.e., epichlorohydrin 
feedstocks), and chlorinated chemicals are not controlled with 
flares.
    \119\ For a list of studies, refer to the technical report 
titled Parameters for Properly Designed and Operated Flares, in 
Docket ID Item No. EPA-HQ-OAR-2010-0682-0191.
    \120\ See 40 CFR 63.670 and 40 CFR 63.671 (originally finalized 
in 80 FR 75178 on December 1, 2015; and amended in 81 FR 45232 on 
July 13, 2016, in 83 FR 60696 on November 26, 2018, and in 85 FR 
6064 on February 4, 2020).
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    The General Provisions of 40 CFR 63.11(b) specify that flares be: 
(1) Steam-assisted, air-assisted, or non-assisted; (2) operated at all 
times when emissions may be vented to them; (3) designed for and 
operated with no visible emissions (except for periods not to exceed a 
total of 5 minutes during any 2 consecutive hours); and (4) operated 
with the presence of a pilot flame at all times. These General 
Provisions also specify both the minimum heat content of gas combusted 
in the flare and maximum exit velocity at the flare tip. The General 
Provisions specify monitoring for the presence of the pilot flame and 
the operation of a flare with no visible emissions. We are proposing to 
revise the General Provisions table to NESHAP subpart F (Table 3) and 
the General Provisions table to NESHAP subpart U (Table 1), entries for 
40 CFR 63.8(a)(4) and 40 CFR 63.11 such that these provisions do not 
apply to flares because we are proposing to replace these provisions 
with new standards we are proposing for flares used to comply with the 
MACT standards in the HON and P&R I.
    In 2012, the EPA compiled information and test data collected on 
flares and summarized its preliminary findings on operating parameters 
that affect flare combustion efficiency in a technical report titled 
Parameters for Properly Designed and Operated Flares, in Docket ID Item 
No. EPA-HQ-OAR-2010-0682-0191.\121\ The EPA submitted this report, 
along with a charge statement and a set of charge questions, to an 
external peer review panel.\122\ The panel, consisting of individuals 
representing a variety of backgrounds and perspectives (i.e., industry, 
academia, environmental experts, and industrial flare consultants), 
concurred with the EPA's assessment that the following three primary 
factors affect flare performance: (1) The flow of the vent gas to the 
flare; (2) the amount of assist media (e.g., steam or air) added to the 
flare; and (3) the combustibility of the vent gas/assist media mixture 
in the combustion zone (i.e., the net heating value, lower 
flammability, and/or combustibles concentration) at the flare tip. In 
response to peer review comments, the EPA performed a validation and 
usability analysis on all available test data as well as a failure 
analysis on potential parameters discussed in the technical report as 
indicators of flare performance. The peer review comments are in the 
document titled Peer Review of Parameters for Properly Designed and 
Operated Flares, available in Docket ID Item No. EPA-HQ-OAR-2010-0682-
0193, which has been incorporated into the docket for this rulemaking. 
These analyses resulted in a change to the population of test data that 
the EPA used and helped form the basis for the flare operating limits 
promulgated in the 2015 Petroleum Refinery Sector MACT final rule at 40 
CFR part 63, subpart CC (80 FR 75178).\123\ We are also relying on the 
same analyses and proposing the same operating limits for flares used 
as APCDs in the SOCMI source category that control emissions from HON 
processes (hereafter referred to as ``HON flares''). The Agency 
believes, given the results from the various data analyses conducted 
for the Petroleum Refinery Sector rule, that the operating limits 
promulgated for flares used in the petroleum refinery sector are also 
appropriate and reasonable for HON flares, and will ensure that these 
flares meet the HAP destruction and removal efficiency at all times. 
Therefore, we are proposing at 40 CFR 63.108 (for HON processes) and 40 
CFR 63.508 (for P&R I processes) to replace all flare requirements 
throughout the HON \124\ and P&R I \125\ with the Petroleum Refinery 
Sector rule flare definitions and requirements in 40 CFR part 63, 
subpart CC, with certain clarifications and exemptions discussed in 
this section of the preamble, including, but not limited to, specifying 
that several definitions in 40 CFR part 63, subpart CC, that apply to 
petroleum refinery flares also apply to flares in the SOCMI source 
category, adding a definition and requirements for pressure-assisted 
multi-point flares, and specifying additional requirements when a gas 
chromatograph or mass spectrometer is used for compositional analysis.
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    \121\ See section II.D of this preamble, which addresses the 
incorporation by reference of certain docket files such as this one 
into the docket for this rulemaking.
    \122\ These documents can also be found at https://www.epa.gov/stationary-sources-air-pollution/review-peer-review-parameters-properly-designed-and-operated-flares.
    \123\ See the document titled Flare Performance Data: Summary of 
Peer Review Comments and Additional Data Analysis for Steam-Assisted 
Flares, in Docket ID Item No. EPA-HQ-OAR-2010-0682-0200 for a more 
detailed discussion of the data quality and analysis; the document 
titled Petroleum Refinery Sector Rule: Operating Limits for Flares, 
in Docket ID Item No. EPA-HQ-OAR-2010-0682-0206 for a more detailed 
discussion of the failure analysis and the document titled Flare 
Control Option Impacts for Final Refinery Sector Rule, in Docket ID 
Item No. EPA-HQ-OAR-2010-0682-0748 for additional analyses on flare 
performance standards based on public comments received on the 
proposed Petroleum Refinery Sector rule.
    \124\ Refer to proposed 40 CFR 63.108(a)(1) through (a)(22) for 
a list of HON provisions that would no longer apply.
    \125\ Refer to proposed 40 CFR 63.508(a)(1) through (a)(32) for 
a list of P&R I provisions that would no longer apply.
---------------------------------------------------------------------------

    The remainder of this section of the preamble includes a discussion 
of requirements that we are proposing for HON and P&R I flares, along 
with impacts and costs associated with these proposed revisions. 
Specifically, this action proposes that HON and P&R I flares operate 
pilot flame systems continuously and that flares operate with no 
visible emissions (except for periods not to exceed a total of 5 
minutes during any 2 consecutive hours) when the flare vent gas flow 
rate is below the smokeless capacity of the flare. In addition, this 
action proposes to consolidate measures related to flare tip velocity 
and proposes new operational and monitoring requirements related to the 
combustion zone gas. Further, in keeping with the elimination of the 
SSM exemption as discussed in section III.E.1 of this preamble, this 
action proposes a work practice standard related to the visible 
emissions during periods when the flare is operated above its smokeless 
capacity (e.g., periods of emergency flaring). Currently, the MACT 
standards in the HON and P&R I cross-reference the General Provisions 
at 40 CFR

[[Page 25149]]

63.11(b) for the operational requirements for flares used as APCD. This 
proposal eliminates cross-references to the General Provisions and 
instead specifies all new operational and monitoring requirements that 
are intended to apply to flares used as APCDs in the HON and P&R I 
standards. We are also proposing to include provisions at 40 CFR 
63.110(j) that address compliance with the proposed operating and 
monitoring requirements for flares in lieu of flare-related 
requirements of any other 40 CFR part 60, 61, or 63 rule.
a. Pilot Flames
    The HON and P&R I reference the flare requirements in 40 CFR 
63.11(b), which specify that a flare used as an APCD should operate 
with a pilot flame present at all times. Pilot flames are proven to 
improve flare flame stability, and even short durations of an 
extinguished pilot could cause a significant reduction in flare 
destruction efficiency. In this proposal, we are proposing to remove 
the cross-reference to the General Provisions for HON and P&R I flares 
and instead cross-reference 40 CFR part 63, subpart CC, to include in 
the HON the existing provision that flares operate with a pilot flame 
at all times and be continuously monitored for a pilot flame using a 
thermocouple or any other equivalent device. We are also proposing to 
add a continuous compliance measure that would consider each 15-minute 
block when there is at least 1 minute where no pilot flame is present 
when regulated material is routed to the flare as a deviation from the 
standard. Refer to 40 CFR 63.108 (for HON), 40 CFR 63.508 (for P&R I), 
and 40 CFR 63.670(b) and (g) for these proposed requirements. See 
section III.D.1.e of this preamble for our rationale for proposing to 
use a 15-minute block averaging period for determining continuous 
compliance. We solicit comment on the proposed revisions for flare 
pilot flames.
b. Visible Emissions
    The HON and P&R I reference 40 CFR 63.11(b), which specifies that a 
flare used as an APCD should operate with visible emissions for no more 
than 5 minutes in a 2-hour period. Owners or operators of these flares 
are required to conduct an initial performance demonstration for 
visible emissions using Method 22 of Appendix A-7 to 40 CFR part 60 
(``Method 22''). We are proposing to remove the cross-reference to the 
General Provisions for HON and P&R I flares and instead cross-reference 
40 CFR part 63, subpart CC, to include this same limitation on visible 
emissions. We are also proposing to clarify that the initial 2-hour 
visible emissions demonstration should be conducted the first time 
regulated materials are routed to the flare.
    With regard to continuous compliance with the visible emissions 
limitation, we are proposing daily visible emissions monitoring for HON 
and P&R I flares whenever regulated material is routed to the flare and 
also visible emissions monitoring whenever visible emissions are 
observed from the flare. On days that the flare receives regulated 
material, we are proposing that owners or operators of HON and P&R I 
flares monitor visible emissions at a minimum of once per day while the 
flare is receiving regulated material using an observation period of 5 
minutes and Method 22. Additionally, whenever regulated material is 
routed to a flare and there are visual emissions from the flare, we are 
proposing that another 5-minute visible emissions observation period be 
performed using Method 22, even if the minimum required daily visible 
emission monitoring has already been performed. For example, if an 
employee observes visible emissions, the owner or operator of the flare 
would perform a 5-minute Method 22 observation to check for compliance 
upon initial observation or notification of such event. In addition, in 
lieu of daily visible emissions observations performed using Method 22, 
we are proposing that owners and operators be allowed to use video 
surveillance cameras. We believe that video surveillance cameras would 
be at least as effective as the proposed daily 5-minute visible 
emissions observations using Method 22.
    We are also proposing to extend the observation period for a HON or 
P&R I flare to 2 hours whenever visible emissions are observed for 
greater than 1 continuous minute during any of the 5-minute observation 
periods. Refer to 40 CFR 63.108 (for HON), 40 CFR 63.508 (for P&R I), 
and 40 CFR 63.670(c) and (h) for these proposed requirements. We 
acknowledge that operating a flare near the incipient smoke point (the 
point at which black smoke begins to form within the flame) results in 
good combustion at the flare tip; however, smoking flares can 
contribute significantly to emissions of particulate matter that is 2.5 
micrometers in diameter or smaller (PM2.5). Thus, while 
increasing the allowable period for visible emissions may be useful 
from an operational perspective, we do not believe the allowable period 
for visible emissions should be increased to more than 5 minutes in any 
2-hour period. We solicit comment on the proposed allowable period for 
visible emissions from flares.
    As discussed later in this section, we are proposing additional 
operational and monitoring requirements for HON and P&R I flares that 
we expect will result in owners or operators of CMPUs installing 
equipment that can be used to fine-tune and control the amount of 
assist steam or air introduced at the flare tip such that combustion 
efficiency of the flare will be maximized. These monitoring and control 
systems will assist these flare owners or operators to operate near the 
incipient smoke point without exceeding the visible emissions limit. 
While combustion efficiency may be highest at the incipient smoke 
point, it is not significantly higher than the combustion efficiency 
achieved by the proposed operating limits discussed in section 
III.D.1.d of this preamble. As seen in the performance curves for 
flares, there is very limited improvement in flare performance beyond 
the performance achieved at the proposed operating limits (see document 
titled Petroleum Refinery Sector Rule: Operating Limits for Flares, in 
Docket ID Item No. EPA-HQ-OAR-2010-0682-0206, which has been 
incorporated into the docket for this rulemaking). We solicit comments 
and data on appropriate periods of visible emissions that would 
encourage operation at the incipient smoke point.
    In addition, we are proposing that the owner or operator establish 
the smokeless capacity of each HON and P&R I flare based on design 
specification of the flare, and that the visible emissions limitation 
only apply when the flare vent gas flow rate is below its smokeless 
capacity. We are proposing a work practice standard for the limited 
times (i.e., during emergency releases) when the flow to a flare 
exceeds the smokeless capacity of the flare, based on comments the EPA 
received on the proposed Petroleum Refinery Sector rule. Refer to 40 
CFR 63.108 (for HON), 40 CFR 63.508 (for P&R I), and 40 CFR 63.670(o) 
for these proposed provisions. In the Petroleum Refinery Sector final 
rule, the EPA explained that numerous comments on the proposal 
suggested that flares are not designed to meet the visible emissions 
requirements when operated beyond their smokeless capacity (80 FR 
75178). According to commenters, flares are typically designed to 
operate in a smokeless manner at 20 to 30 percent of full hydraulic 
load. Thus, they claimed, flares have two different design capacities: 
A ``smokeless capacity'' to handle normal operations and typical 
process variations and a ``hydraulic load capacity'' to handle very 
large volumes

[[Page 25150]]

of gases discharged to the flare as a result of an emergency shutdown. 
According to commenters, this is inherent in all flare designs and has 
not previously been an issue because flare operating limits did not 
apply during malfunction events.
    For this proposed work practice standard, owners or operators would 
need to develop a flare management plan for HON and P&R I flares that 
identifies procedures for limiting discharges to the flare as a result 
of process upsets or malfunctions that cause the flare to exceed its 
smokeless capacity. In addition, for any flare that exceeds both the 
smokeless design capacity and visible emissions limit, we are proposing 
that owners or operators would need to conduct a specific root cause 
analysis and take corrective action to prevent the recurrence of a 
similarly caused event (similar to the prevention measures we are 
proposing in this rule to minimize the likelihood of a PRD release, see 
section III.D.2.a of this preamble). We are proposing that if the root 
cause analysis indicates that the exceedance of the visible emissions 
limit is caused by operator error or poor maintenance, then the 
exceedance would be considered a deviation from the work practice 
standard. We are also proposing that a second event within a rolling 3-
year period from the same root cause on the same equipment would be 
considered a deviation from the standard. Finally, we are proposing 
that a third visible emissions limit exceedance occurring from the same 
flare in a rolling 3-year period would be a deviation from the work 
practice standard, regardless of the cause.
    In several of the EPA's previous impact analyses (for petroleum 
refinery flares and ethylene production flares),\126\ the EPA 
established the number of events in a given time period that would be 
the ``backstop'' (i.e., a violation of the standard). In each of these 
analyses, the EPA evaluated four different timing alternatives (2 in 5 
years; 2 in 3 years; 3 in 5 years; and 3 in 3 years) based on the 
number of existing flares evaluated over a 20-year period, and 
ultimately the EPA concluded that 3 events in 3 years would be 
``achievable'' for the average of the best performing flares. We see no 
reason why this would be any different for HON and P&R I flares. Even 
if a best-performing flare ``typically'' only has one event every seven 
years, the fact that these events are random by nature (unpredictable, 
not under the direct control of the owner or operator) makes it 
difficult to use a 5-year time span. Based on this analysis, three 
events in 3 years would appear to be ``achievable'' for the average of 
the best performing flares.
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    \126\ See EPA-HQ-OAR-2010-0682-0793, EPA-HQ-OAR-2010-0682-0794, 
and EPA-HQ-OAR-2017-0357-0017.
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c. Flare Tip Velocity
    This action consolidates provisions related to flare tip velocity 
for HON and P&R I flares. The HON and P&R I reference the flare 
provisions in 40 CFR 63.11(b), which specify maximum flare tip 
velocities based on flare type (non-assisted, steam-assisted, or air-
assisted) and the net heating value of the flare vent gas. Based on 
data provided to EPA in response to our CAA section 114 request (see 
section II.C of this preamble), 10 of the 18 flares that HON and P&R I 
facilities reported using as APCDs are either steam- or air-assisted 
(see 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). Maximum flare tip velocities are 
required to ensure that the flame does not ``lift off'' the flare 
(i.e., a condition where a flame separates from the tip of the flare 
and there is space between the flare tip and the bottom of the flame), 
which could cause flame instability and/or potentially result in a 
portion of the flare gas being released without proper combustion. We 
are proposing to remove the cross-reference to the General Provisions 
for HON and P&R I flares and instead cross-reference 40 CFR part 63, 
subpart CC, to consolidate the provisions for maximum flare tip 
velocity into the HON and P&R I as a single equation, irrespective of 
flare type (i.e., steam-assisted, air-assisted, or non-assisted). Refer 
to 40 CFR 63.108 (for HON), 40 CFR 63.508 (for P&R I), and 40 CFR 
63.670(d), (i), and (k) for these proposed provisions.
    Based on analysis conducted for the Petroleum Refinery Sector rule, 
the EPA identified air-assisted test runs with high flare tip 
velocities that had high combustion efficiencies (see the document 
titled Petroleum Refinery Sector Rule: Evaluation of Flare Tip Velocity 
Requirements, in Docket ID Item No. EPA-HQ-OAR-2010-0682-0212). These 
test runs exceeded the maximum flare tip velocity limits for air-
assisted flares using the linear equation in 40 CFR 63.11(b)(8). When 
these test runs were compared with the test runs for non-assisted and 
steam-assisted flares, air-assisted flares appeared to have the same 
operating envelope as the non-assisted and steam-assisted flares. 
Therefore, for air-assisted HON and P&R I flares, we are proposing the 
use of the same equation that non-assisted and steam-assisted flares 
currently use to establish the flare tip velocity operating limit. We 
are also proposing that the owner or operator determine the flare tip 
velocity on a 15-minute block average basis. See section III.D.1.e of 
this preamble for our rationale for proposing to use a 15-minute block 
averaging period for determining continuous compliance.
    Finally, we are also proposing not to include the provision for the 
special flare tip velocity equation in the General Provisions at 40 CFR 
63.11(b)(6)(i)(A) for non-assisted HON and P&R I flares with hydrogen 
content greater than 8 percent. This equation, which was developed 
based on limited data from a chemical manufacturer, has very limited 
applicability for flares used as APCDs in the SOCMI source category 
because it only provides an alternative for non-assisted flares with 
large quantities of hydrogen. Available data indicates that 
approximately 50 percent of the flares used at HON and P&R I facilities 
are either steam-assisted or air-assisted, which seems to indicate that 
approximately 50 percent are non-assisted flares. Instead, we are 
proposing compliance alternatives that we believe provide a better way 
for HON and P&R I flares with high hydrogen content to comply with the 
rule while ensuring proper destruction performance of the flare (see 
section III.D.1.d of this preamble for the proposed compliance 
alternatives). Therefore, for non-assisted HON and P&R I flares with 
hydrogen content greater than 8 percent that are used as ACPDs, we are 
not proposing to include this special flare tip velocity equation as a 
compliance alternative. We request comment on the need to include this 
equation.
d. Net Heating Value of the Combustion Zone Gas
    The current provisions for flares in 40 CFR 63.11(b) specify that 
the flare vent gas meet a minimum net heating value of 200 British 
thermal units per standard cubic foot (Btu/scf) for non-assisted flares 
and 300 Btu/scf for air- and steam-assisted flares. The HON and P&R I 
reference these provisions, but neither the General Provisions nor the 
HON or P&R I include specific requirements for monitoring the net 
heating value of the flare vent gas. Moreover, recent flare testing 
results indicate that meeting a minimum net heating value limit alone 
does not address instances when the flare may be

[[Page 25151]]

over-assisted because it only considers the net heating value of the 
gas being combusted in the flare and nothing else (e.g., no assist 
media). However, many industrial flares use steam or air as an assist 
medium to protect the design of the flare tip, promote turbulence for 
the mixing, induce air into the flame, and operate with no visible 
emissions. Using excessive steam or air results in dilution and cooling 
of flared gases and can lead to operating a flare outside its stable 
flame envelope, reducing the destruction efficiency of the flare. In 
extreme cases, over-steaming or excess aeration can snuff out a flame 
and allow regulated material to be released into the atmosphere without 
complete combustion. As previously noted, because available data 
indicate that a preponderance of all HON and P&R I flares are either 
steam- or air-assisted, it is critical that we ensure the assist media 
is accounted for in some form. Recent flare test data have shown that 
the best way to account for situations of over-assisting is to consider 
the gas mixture properties at the flare tip in the combustion zone when 
evaluating the ability to combust efficiently. As discussed in the 
introduction to this section, the external peer review panel concurred 
with our assessment that the combustion zone properties at the flare 
tip are critical parameters to know in determining whether a flare will 
achieve good combustion. The General Provisions, however, solely rely 
on the net heating value of the flare vent gas, and we have determined 
that is not sufficient for the flares at issue.
    In this proposal, in lieu of requiring compliance with the 
operating limits for net heating value of the flare vent gas in the 
General Provisions, we are proposing to cross-reference 40 CFR part 63, 
subpart CC, to include in the HON and P&R I a single minimum operating 
limit for the net heating value in the combustion zone gas (NHVcz) of 
270 Btu/scf during any 15-minute period for steam-assisted, air-
assisted, and non-assisted HON and P&R I flares. Refer to 40 CFR 63.108 
(for HON), 40 CFR 63.508 (for P&R I), and 40 CFR 63.670I and (m) for 
these proposed provisions. The Agency believes, given the results from 
the various data analyses conducted for the Petroleum Refinery Sector 
rule, that this NHVcz operating limit promulgated for flares in the 
Petroleum Refinery Sector source category is also appropriate and 
reasonable and will ensure HON and P&R I flares meet the HAP 
destruction efficiencies in the standard at all times when operated in 
concert with the other proposed flare provisions (e.g., pilot flame, 
visible emissions, and flare tip velocity requirements) (see the 
memoranda titled: Petroleum Refinery Sector Rule: Operating Limits for 
Flares and Flare Control Option Impacts for Final Refinery Sector Rule, 
in Docket ID Item No. EPA-HQ-OAR-2010-0682-0206 and EPA-HQ-OAR-2010-
0682-0748, respectively). In addition, we are proposing that owners or 
operators may use a corrected heat content of 1,212 Btu/scf for 
hydrogen, instead of 274 Btu/scf, to demonstrate compliance with the 
NHVcz operating limit for HON and P&R I flares; however, owners or 
operators who wish to use the corrected hydrogen heat content must have 
a system capable of monitoring for the hydrogen content in the flare 
vent gas. The 1,212 Btu/scf value is based on a comparison between the 
lower flammability limit and net heating value of hydrogen compared to 
light organic compounds and has been used in several consent decrees 
issued by the EPA. Based on analyses conducted for the Petroleum 
Refinery Sector rule (see the document titled Flare Control Option 
Impacts for Final Refinery Sector in Docket ID Item No. EPA-HQ-OAR-
2010-0682-0748), the EPA determined that using a 1,212 Btu/scf value 
for hydrogen greatly improves the correlation between combustion 
efficiency and the combustion zone net heating value over the entire 
array of data.
    Furthermore, in addition to the NHVcz operating limit, we are 
proposing a net heating value dilution parameter (NHVdil) for certain 
HON and P&R I flares that operate with perimeter assist air. Refer to 
40 CFR 63.108 (for HON), 40 CFR 63.508 (for P&R I), and 40 CFR 
63.670(f) and (n) for these proposed provisions. For air-assisted 
flares, use of too much perimeter assist air can lead to poor flare 
performance. Furthermore, based on our analysis of the air-assisted 
flare datasets (see the document titled Petroleum Refinery Sector Rule: 
Operating Limits for Flares, in Docket ID Item No. EPA-HQ-OAR-2010-
0682-0206), we determined a NHVdil of 22 British thermal units per 
square foot is necessary to ensure that there is enough combustible 
material available to adequately combust the gas and pass through the 
flammability region and also ensure that degradation of flare 
performance from excess aeration does not occur. We found that 
including the flow rate of perimeter assist air in the calculation of 
the NHVcz does not identify all instances of excess aeration and could 
(in some instances) even allow facilities to send very dilute vent 
gases to the flare that would not combust (i.e., vent gases below their 
lower flammability limit could be sent to flare). Instead, the data 
suggest that the diameter of the flare tip, in concert with the amount 
of perimeter assist air (and other parameters used to determine NHVcz), 
provide the inputs necessary to calculate whether this type of flare is 
over-assisted. This dilution parameter is consistent with the 
combustion theory that the more time the gas spends in the flammability 
region above the flare tip, the more likely it will combust. Also, 
because both the volume of the combustion zone (represented by the 
diameter) and how quickly this gas is diluted to a point below the 
flammability region (represented by perimeter assist air flow rate) 
characterize this time, it is logical that we propose such a parameter.
    We also found that some assist steam lines are purposely designed 
to entrain air into the lower or upper steam at the flare tip; and for 
flare tips with an effective tip diameter of 9 inches or more, there 
are no flare tip steam induction designs that can entrain enough assist 
air to cause a flare operator to have a deviation from the NHVdil 
operating limit without first deviating from the NHVcz operating limit. 
Therefore, we are proposing to allow owners or operators of HON and P&R 
I flares whose only assist air is from perimeter assist air entrained 
in lower and upper steam at the flare tip and with a flare tip diameter 
of 9 inches or greater to comply only with the NHVcz operating limit. 
Steam-assisted flares with perimeter assist air and an effective tip 
diameter of less than 9 inches would remain subject to the requirement 
to account for the amount of assist air intentionally entrained within 
the calculation of NHVdil. However, we recognize that this assist air 
cannot be directly measured, but the quantity of air entrained is 
dependent on the assist steam rate and the design of the steam tube's 
air entrainment system. Therefore, we are proposing provisions to 
specify that owners or operators of these smaller diameter steam-
assisted HON flares use the steam flow rate and the maximum design air-
to-steam ratio of the steam tube's air entrainment system for 
determining the flow rate of this assist air. Using the maximum design 
ratio will tend to over-estimate the assist air flow rate, which is 
conservative with respect to ensuring compliance with the NHVdil 
operating limit.
    Finally, we are proposing that owners or operators record and 
calculate 15-minute block average values for these parameters. Our 
rationale for selecting a

[[Page 25152]]

15-minute block averaging period is provided in section III.D.1.e of 
this preamble. We solicit comment on the proposed revisions related to 
NHVcz.
e. Data Averaging Periods for Flare Gas Operating Limits
    Except for the visible emissions operating limits as described in 
section III.D.1.b of this preamble, we are proposing to use a 15-minute 
block averaging period for each proposed flare operating parameter 
(i.e., presence of a pilot flame, flare tip velocity, and NHVcz) to 
ensure that HON and P&R I flares are operated within the appropriate 
operating conditions. We consider a short averaging time to be the most 
appropriate for assessing proper flare performance because flare vent 
gas flow rates and composition can change significantly over short 
periods of time. Furthermore, because destruction efficiency can fall 
precipitously when a flare is controlling vent gases below (or outside) 
the proposed operating limits, short time periods where the operating 
limits are not met could seriously impact the overall performance of 
the flare. Refer to the Petroleum Refinery Sector rule preambles (79 FR 
36880 and 80 FR 75178) for further details supporting why we believe a 
15-minute averaging period is appropriate.
    Given the short averaging times for the operating limits, we are 
proposing special calculation methodologies to enable owners or 
operators to use ``feed forward'' calculations to ensure compliance 
with the operating limits on a 15-minute block average for HON and P&R 
I flares. Specifically, we propose using the results of the 
compositional analysis determined just prior to a 15-minute block 
period for the next 15-minute block average. Owners or operators of HON 
and P&R I flares will then know the vent gas properties for the 
upcoming 15-minute block period and can adjust assist gas flow rates 
relative to vent gas flow rates to comply with the proposed operating 
limits. In other words, ``feed forward'' means that owners or operators 
would use the net heating value in the vent gas (NHVvg) going into the 
flare in one 15-minute period to adjust the assist media (i.e., steam 
or air) and/or the supplemental gas in the next 15-minute period, as 
necessary, to calculate an NHVcz limit of 270 Btu/scf or greater using 
the proposed equation. We recognize that when a subsequent measurement 
value is determined, the instantaneous NHVcz based on that 
compositional analysis and the flow rates that exist at the time may 
not be above 270 Btu/scf. We are proposing that this is not a deviation 
from the operating limit. Rather, we propose that the owner or operator 
is only required to make operational adjustments based on that 
information to achieve, at a minimum, the net heating value limit for 
the subsequent 15-minute block average. We are, however, proposing that 
failure to make adjustments to assist media or supplemental natural gas 
using the NHVvg from the previous period in the equation provided for 
calculating an NHVcz limit of 270 Btu/scf, would be a deviation from 
the operating limit. Alternatively, because the owner or operator could 
directly measure the NHVvg on a more frequent basis, such as with a 
calorimeter (and optional hydrogen analyzer), the process control 
system is able to adjust more quickly, and the owner or operator can 
make adjustments to assist media or supplemental natural gas more 
quickly. In this manner, the owner or operator is not limited by 
relying on NHVvg data that may not represent the current conditions. We 
are, therefore, also proposing that the owner or operator may opt to 
use the NHVvg in such instances from the same period to comply with the 
operating limit. For examples of ``feed forward'' calculations, please 
see Attachment 3 of the document titled Flare Control Option Impacts 
for Final Refinery Sector Rule, in Docket ID Item No. EPA-HQ-OAR-2010-
0682-0748.
    We are also proposing to clarify that when determining compliance 
with the flare tip velocity and combustion zone operating limits 
specified in 40 CFR 63.670(d) and (e), the initial 15-minute block 
period starts with the 15-minute block that includes a full 15 minutes 
of the flaring event. In other words, we are proposing to clarify that 
the owner or operator demonstrate compliance with the velocity and 
NHVcz requirements starting with the block that contains the fifteenth 
minute of a flaring event; and the owner or operator is not required to 
demonstrate compliance for the previous 15-minute block in which the 
event started and contained only a fraction of flow. We solicit comment 
on these proposed revisions.
f. Flares in Dedicated Service
    In lieu of requiring the composition of the vent gas and the NHVvg 
to be continuously monitored, we are proposing an alternative 
monitoring approach for HON and P&R I flares that are in dedicated 
service that have consistent composition and flow. We believe that 
these types of flares, which have limited flare vent gas streams, do 
not need to have the same type of ongoing monitoring requirements as 
those with more variable waste streams. Thus, we are proposing an 
option that owners or operators can use to demonstrate compliance with 
the operating requirements for HON and P&R I flares that are in 
dedicated service to a specific emission source, such as a transfer 
rack operation consistently loading the same material. We are proposing 
that owners or operators will need to submit an application for the use 
of this alternative compliance option. We are proposing that the 
application include a description of the system, characterization of 
the vent gases that could be routed to the flare based on a minimum of 
seven grab samples (14 daily grab samples for continuously operated 
flares), and specification of the net heating value that will be used 
for all flaring events (based on the minimum net heating value of the 
grab samples). In other words, for HON and P&R I flares that are in 
dedicated service, we are proposing that the minimum NHVvg determined 
from the grab samples could be used in the equation at 40 CFR 
63.670(m)(1) for all flaring events to determine NHVcz. We are also 
proposing to allow engineering estimates to characterize the amount of 
gas flared and the amount of assist gas introduced into the system. For 
example, we believe that the use of fan curves to estimate air assist 
rates would be acceptable. We propose that flare owners or operators 
would use the net heating value determined from the initial sampling 
phase and measured or estimated flare vent gas and assist gas flow 
rates, if applicable, to demonstrate compliance with the standards. 
Refer to 40 CFR 63.108 and 40 CFR 63.670(j)(6) for these proposed 
provisions. Finally, for owners and operators that must comply with the 
continuous monitoring requirements, we are proposing additional 
clarifications and requirements at 40 CFR 63.108 when using a gas 
chromatograph or mass spectrometer for compositional analysis. We 
solicit comment on the proposed revisions related to flares in 
dedicated service.
g. Pressure-Assisted Multi-Point Flares
    The EPA is also proposing to add requirements into the HON (but not 
P&R I) for pressure-assisted multi-point flares given that these types 
of APCD are used to control waste gases from processes subject to the 
HON during SSM. Pressure-assisted flares are conceptually similar, yet 
technically different in both design and operation compared to more 
traditional elevated flare tip designs (e.g., steam-assisted, air-
assisted, and non-assisted flare tips). Pressure-assisted flares 
operate by taking advantage of the pressure upstream of

[[Page 25153]]

the flare tip to create a condition whereby air is drawn into contact 
and mixed with high exit velocity flared gas, resulting in smokeless 
flare operation and emissions reductions at least equivalent to those 
of traditional flare types, if properly designed and operated. 
Pressure-assisted flares can be used in a single flare burner type 
layout or in staged arrays with many identical flare burners. These 
staged arrays can be elevated or at ground level; however, we are only 
aware of ground level staged array systems, that are commonly referred 
to as multi-point ground flares (MPGFs), at six facilities used as 
APCDs in the SOCMI source category that control emissions from HON 
processes.\127\ MPGFs have multiple (e.g., hundreds) flare burners at 
ground level. The flare burners in a MPGF are designed with a staging 
system that opens and closes staging valves according to gas pressure 
in the flare header such that the stages, and accompanying flare 
burners for those stages, are activated to control emissions as the 
flare vent gas flow and pressure increase in the flare header, or are 
deactivated as the flare vent gas flow and pressure decrease in the 
flare header. The flare burners in a MPGF are typically lit with a 
pilot flame system where the first burners on a stage are lit by the 
pilot flame and the flame propagates (i.e., cross-lights) down the 
stage to the remaining burners on the stage (similar to how burners on 
a gas grill would light). The MPGF system is surrounded by a panel type 
fence to allow air in for combustion as well as to protect nearby 
workers from the radiant heat of the flare system.
---------------------------------------------------------------------------

    \127\ One HON flare was reported as a pressure-assisted ground 
flare in response to our CAA section 114 request. Based on this 
information, in addition to information from alternative means of 
emission limitation requests (see Docket ID No. EPA-HQ-OAR-2014-
0738), we estimate there are 6 pressure-assisted MPGF located in the 
SOCMI source category that control emissions from processes subject 
to the HON.
---------------------------------------------------------------------------

    MPGF are often used as secondary flares to control large emissions 
events that result during periods of SSM. With the elimination of the 
SSM exemption (see section III.E.1 of this preamble for additional 
discussion), proposing requirements for this unique flare type for HON 
flares is an important consideration given that some facilities 
currently use them as APCD. Based on our review of recently approved 
alternative means of emission limitation (AMEL) requests for MPGF and 
the underlying data analyses that supported those decisions (see 
section II.D of this preamble), MPGF can achieve reductions in VOC and 
organic HAP at least equivalent to those from traditional elevated 
flares; however, different operating requirements are needed for these 
flare types to ensure a high level of control is achieved given that 
the individual flare burners are designed to operate at high velocities 
(i.e., up to sonic velocity). Important considerations for proper 
design and operation of MPGF center around the following: (1) Flare 
flame stability, (2) pilot flame presence and its interplay with proper 
cross-lighting, (3) operation of the MPGF with no visible emissions, 
and (4) monitoring of certain parameters of the MPGF and the vent gases 
it controls for purposes of compliance assurance.
    In reviewing the initial MPGF AMEL requests by Dow Chemical and 
ExxonMobil (80 FR 8023-8030, February 13, 2015), the Agency noted two 
general conclusions from the test data supporting the AMEL requests 
that were consistent with 1985 studies \128\ conducted by the EPA on 
pressure-assisted flares. The first general conclusion was that flare 
head design can influence the flame stability curve. The second general 
conclusion was that stable flare flames and high (greater than 98-99 
percent) combustion and destruction efficiencies are attained when 
flares are operated within operating envelopes specific to each flare 
burner and gas mixture tested. Operation beyond the edge of the 
operating envelope can result in rapid flame de-stabilization and a 
decrease in combustion and destruction efficiencies. In reviewing all 
the available data in the MPGF AMEL docket (i.e., Docket ID No. EPA-HQ-
OAR-2014-0738), we found these two general observations were still 
valid conclusions. The data clearly show that for some test runs flare 
flameouts occurred, meaning the flares were not operated within the 
proper envelope to produce a stable flame. In reviewing these data, we 
observed that all flare flameouts occurred for the various burners/
waste gas mixtures tested below an NHVcz of 800 Btu/scf. Thus, we 
selected a minimum NHVcz of 800 Btu/scf to ensure the MPGF at 
facilities in the SOCMI source category that control emissions from HON 
processes are operated within the proper envelope to produce a stable 
flame and achieve high destruction efficiencies at least equivalent to 
those as the underlying HON MACT standards. Above this level, no flare 
flameouts are observed, and high combustion/destruction efficiencies at 
least equivalent to those as the underlying HON MACT standards are 
achieved. Thus, to that end, we are proposing to not allow use of the 
``feed forward'' calculation approach (discussed in section III.D.1.e 
of this preamble) to demonstrate compliance with the NHVcz limit of 800 
Btu/scf.
---------------------------------------------------------------------------

    \128\ Pohl, J. and N. Soelberg. 1985. Evaluation of the 
efficiency of industrial flares: Flare head design and gas 
composition. EPA-600/2-85-106. Prepared for U.S. EPA Office of Air 
Quality Planning and Standards.
---------------------------------------------------------------------------

    Another unique characteristic of MPGF is that they may use a cross-
lighting pilot flame system as a means of ignition to initially combust 
the waste gases sent to the flare burners on a particular staged array. 
Thus, we also reviewed the equipment-specific set-ups in the test data 
that allowed for successful cross-lighting of MPGF. Based on review of 
the data, it appears that one option would be for facilities to conduct 
performance demonstrations to demonstrate successful cross-lighting on 
a minimum of three burners (i.e., as outlined in the Framework for 
Streamlining Approval of Future Pressure-Assisted MPGF AMEL Requests, 
81 FR 23480, April 21, 2016). However, given the data before us in the 
MPGF AMEL docket, and rather than requiring facilities to conduct a 
performance demonstration, it appears that an equipment standard that 
sets an upper limit on the distance between burners of 6 feet will 
ensure a successful cross-lighting on a stage of burners in a MPGF.
    Furthermore, in reviewing the site-specific AMEL standards that 
facilities are complying with for MPGF,\129\ we believe these same 
site-specific standards, if applied to all MPGF in the specified 
subset, would demonstrate at least equivalent emissions reductions to 
the underlying HON MACT standards as well as demonstrate at least 
equivalent reductions to the new operational and monitoring 
requirements we are proposing for more traditional, elevated flare 
tips. Therefore, we are proposing at 40 CFR 63.108(i) that owners or 
operators of MPGF at facilities in the SOCMI source category that 
control emissions from HON processes: (1) Maintain an NHVcz greater 
than or equal to 800 Btu/scf over a short averaging period (i.e., 15-
minutes); (2) continuously monitor the NHVcz and flare vent gas flow 
rate; (3) continuously monitor for the presence of a pilot flame, and 
if cross-lighting is occurring on a particular stage of burners, 
ensuring that each stage of burners that cross-lights must have at 
least two pilots with at least one continuously lit and capable of 
igniting all regulated material
---------------------------------------------------------------------------

    \129\ 80 FR 52426, August 31, 2015; 81 FR 23480, April 21, 2016; 
and 82 FR 27822, June 19, 2017.

---------------------------------------------------------------------------

[[Page 25154]]

that is routed to that stage of burners; (4) operate the MPGF with no 
visible emissions (except for 5 minutes during any 2 consecutive 
hours); (5) maintain a distance of no greater than 6 feet between any 
two burners on a stage of burners that use cross-lighting; \130\ and 
(6) monitor to ensure the staging valves for each stage of the MPGF 
operate properly so that the flare will control vent gases within the 
range of the tested conditions based on the flare manufacturer's 
recommendations.
---------------------------------------------------------------------------

    \130\ We are proposing that this burner-to-burner distance is 
the distance when measured from the center of one burner to the next 
burner.
---------------------------------------------------------------------------

    Finally, although we are unaware of any HON facilities that use 
multi-point elevated flares in the specified flare subset, we recognize 
that an owner or operator may elect to use this type of flare design in 
the future. Given the design similarities of a multi-point elevated 
flare when compared to a MPGF (i.e., each flare type uses pressure-
assisted burners with staged arrays), we determined that our analyses 
of the test data (including our review of approved AMEL requests) 
related to MPGF that control waste gases could also apply to multi-
point elevated flares in the specified subset that combust waste gases. 
Therefore, we are proposing that owners and operators of multi-point 
elevated flares meet the same requirements that we are proposing for 
MPGF. In other words, the proposed requirements discussed in this 
section of the preamble would apply to all pressure-assisted multi-
point flares (i.e., MPGF and multi-point elevated flares) at facilities 
in the SOCMI source category that control emissions from HON processes. 
We are soliciting comment on whether this approach is appropriate, and 
whether test data are available for multi-point elevated flares that 
control waste gases from HON facilities. Also, given that some owners 
and operators of CMPUs are currently operating under an approved AMEL, 
and these owners and operators are likely to have already installed 
more sophisticated equipment (e.g., a gas chromatograph) than what is 
required to comply with these proposed requirements for pressure-
assisted multi-point flares, we are proposing that pressure-assisted 
multi-point flares subject to an approved AMEL may continue to comply 
with the approved AMEL in lieu of these proposed requirements for 
pressure-assisted multi-point flares. We also are soliciting comment on 
whether we should extend allowance of this option to P&R I facilities, 
as many sources are collocated with HON and may use this same type of 
control device as a backup. As we are currently unaware of any P&R I 
facilities using pressure-assisted multi-point flares, we solicit 
comment whether test data are available for these flare types that 
control waste gases from P&R I processes.
h. Impacts of the Proposed Flare Operating and Monitoring Requirements
    The EPA expects that the newly proposed requirements for flares 
used as APCDs in the SOCMI source category discussed in this section 
will affect all flares at HON and P&R I processes. Based on facility 
responses to our CAA section 114 request, we estimate that there are 
345 flares of traditional elevated flare tip designs (e.g., steam-
assisted, air-assisted, and non-assisted flare tips) operating at HON 
CMPUs that receive flare vent gas flow on a regular basis (i.e., other 
than during periods of SSM). We estimate that there are 31 flares of 
traditional elevated flare tip designs operating at P&R I EPPUs that 
receive flare vent gas flow on a regular basis. Also, based on facility 
responses to our CAA section 114 request and information received from 
AMEL requests (see section II.D of this preamble), we estimate there 
are six pressure-assisted MPGF used to control waste gases from 
processes subject to the HON during SSM. Costs were estimated for each 
flare for a given facility, considering current monitoring systems 
already installed on each individual flare. Given that the same type of 
equipment is used for flares in the SOCMI source category and for the 
petroleum refinery sector, costs for any additional monitoring systems 
needed were estimated based on installed costs received from petroleum 
refineries and, if installed costs were unavailable, costs were 
estimated based on vendor-purchased equipment. The baseline emission 
estimate and the emission reductions achieved by the proposed rule were 
estimated based on current vent gas and steam flow data submitted by 
industry representatives. The results of the impact estimates are 
summarized in Table 28 of this preamble for Flares in the SOCMI Source 
Category that control emissions from HON processes including P&R I & II 
flares collocated with HON processes. The results of the impact 
estimates are summarized in Table 29 of this preamble for Flares in the 
SOCMI source category that control emissions from P&R I processes. We 
note that the requirements for HON and P&R I flares that we are 
proposing will ensure compliance with the MACT standards in the HON and 
P&R I when flares are used as an APCD. Because we are not changing the 
underlying MACT standards in the HON and P&R I, we did not include any 
of the estimated excess emissions from flares in the summary of total 
estimated emissions reductions for this action. However, we estimate 
that the proposed operational and monitoring requirements have the 
potential to reduce excess emissions from HON flares (including from 
P&R I flares collocated with HON processes) by approximately 4,717 tpy 
of HAP and 19,325 tpy of VOC; and from P&R I flares (not collocated 
with HON processes) by approximately 141 tpy of HAP and 564 tpy of VOC. 
The VOC compounds are non-methane, non-ethane total hydrocarbons. 
According to the emissions inventory file we used to assess residual 
risk (see section II.F.1 of this preamble), there are approximately 80 
individual HAP compounds included in the emission inventory for flares, 
but many of these are emitted in trace quantities. Almost half of the 
HAP emissions from flares are attributable to hexane, benzene, and 
methanol, followed by 1,3-butadiene and vinyl acetate. For more detail 
on the impact estimates, see 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. As 
previously mentioned in section III.C.3.b of this preamble, we are also 
proposing these same flare operating and monitoring requirements for 
NSPS subpart IIIa, NNNa, and RRRa under CAA section 111(b)(1)(B).

[[Page 25155]]

    Table 28--Nationwide Cost Impacts for Flares in the SOCMI Source
   Category That Control Emissions From HON Processes Including P&R I
                  Flares Collocated With HON Processes
------------------------------------------------------------------------
                                                               Total
                                           Total capital    annualized
           Control description              investment    costs (million
                                            (million $)        $/yr)
------------------------------------------------------------------------
Flare Operational and Monitoring                   323.1            67.8
 Requirements...........................
Work Practice Standards for Flares                  3.34            0.79
 Operating Above Their Smokeless
 Capacity...............................
                                         -------------------------------
    Total...............................           326.4            68.7
------------------------------------------------------------------------

    Table 29--Nationwide Cost Impacts for Flares in the SOCMI Source
          Category That Control Emissions From P&R I Processes
------------------------------------------------------------------------
                                                               Total
                                           Total capital    annualized
           Control description              investment         costs
                                            (million $)   (million $/yr)
------------------------------------------------------------------------
Flare Operational and Monitoring                    6.93            1.46
 Requirements...........................
Work Practice Standards for Flares                  0.08            0.02
 Operating Above Their Smokeless
 Capacity...............................
                                         -------------------------------
    Total...............................            7.01            1.48
------------------------------------------------------------------------

2. PRDs
    The HON defines several terms applicable to process vents at 40 CFR 
63.101 and 40 CFR 63.107; similarly, P&R I defines several terms 
applicable to process vents at 40 CFR 63.482. The current HON 
definition of ``process vent'' excludes a ``relief valve discharge,'' 
(see 40 CFR 63.107(h)(1)) and the term ``process vent'' in P&R I at 40 
CFR 63.482 excludes ``pressure releases.'' Instead, these MACT 
standards in the HON and P&R I recognize HON relief valve discharges 
and P&R I pressure releases to be the result of malfunctions. The 
acronym ``PRD'' means pressure relief device and is common vernacular 
to describe the variety of devices regulated as pressure relief valves 
(to provide clarity, see the end of this section for our proposed 
revision to the definition of ``pressure relief device'' for the HON 
and P&R I, our proposed definition of ``relief valve'' for the HON and 
P&R I, and our proposal to add a definition in P&R II for ``pressure 
relief device''). PRDs are designed to remain closed during normal 
operation. Typically, the Agency considers PRD releases as the result 
of an overpressure in the system caused by operator error, a 
malfunction such as a power failure or equipment failure, or other 
unexpected cause that results in immediate venting of gas from process 
equipment to avoid safety hazards or equipment damage. The discussion 
that follows within this section of the preamble primarily focuses on 
the HON and P&R I because any release of HAP to the atmosphere from a 
P&R II PRD should already be accounted for when determining compliance 
with the production-based emission rate MACT standard (e.g., pounds HAP 
per million pounds BLR or WSR produced).
    The HON and P&R I currently regulate PRDs when they are seated 
through equipment leak provisions that are applied only after the 
pressure release event occurs (i.e., conduct monitoring with EPA Method 
21 of appendix A-7 to 40 CFR part 60 after each pressure release using 
a leak definition of 500 ppm); however, these provisions do not apply 
to an emissions release from a PRD. In addition, the HON and P&R I 
follow the EPA's pre-2008 practice of exempting SSM events from 
otherwise applicable emission standards. Consequently, with PRD 
releases treated as unplanned, nonroutine, and the result of 
malfunctions, the HON and P&R I did not restrict PRD releases to the 
atmosphere but instead treated them in the same manner as malfunctions 
subject to the SSM exemption provision. In Sierra Club v. EPA, 551 F.3d 
1019 (D.C. Cir. 2008), the Court determined that the SSM exemption 
violates the CAA. We have previously explained the relationship between 
this ruling and PRDs in other rulemakings revising section 112 
standards (see, e.g., 85 FR 6067, February 4, 2020, and 85 FR 40386, 
July 6, 2020). Section III.E.1 of this preamble contains additional 
discussions on the removal of the SSM exemption provision for the SOCMI 
and P&R I source categories. As a result, we evaluated the MACT 
standards in the HON and P&R I for PRD HAP releases to the atmosphere 
to ensure a standard continuously applies during these malfunction 
events, consistent with the Sierra Club decision.
    CAA section 112(d)(1) specifies that the EPA may ``distinguish 
among classes, types, and sizes of sources'' when establishing 
standards. (In establishing standards under CAA section 112(d), the EPA 
may ``distinguish among classes, types, and sizes of sources within a 
category or sub-category.'' CAA section 112(d)(1). See Sierra Club v. 
EPA, 479 F.3d 875, 885 (D.C. Cir. 2007)). We are proposing two 
subcategories of PRDs for the MACT standard in the HON and P&R I to 
distinguish between classes of PRDs: (1) PRDs designed to vent through 
a closed-vent system to a control device or to a process, fuel gas 
system, or drain system (referred to as PRDs that vent to a control 
system); and (2) PRDs designed to vent to the atmosphere, if a release 
were to occur. We are proposing to subcategorize PRDs by class because 
of design differences between the numerous PRDs at HON and P&R I 
facilities that vent to a control system and that vent to the 
atmosphere. Currently, HON and P&R I facilities are required to 
evaluate PRDs as part of their risk management and process safety 
management programs. When implementing these programs, facilities 
identify PRDs that they intend to control as compared to those they 
elect not to control (and that have the potential to vent to the 
atmosphere if a release were to occur). Facilities do not control 
certain PRDs because of technical or site-specific safety 
considerations, such as PRDs that release chemicals that could be 
incompatible with vent streams in downstream controls.

[[Page 25156]]

    We evaluated each subcategory of PRDs separately to ensure that a 
standard continuously applies. Essentially, PRDs that vent to a control 
system are already complying with the process vent standards and are, 
thus, presumably, already appropriately controlled. However, PRDs that 
vent to atmosphere do not meet the current continuous process vent 
standards. Therefore, we examined how to regulate PRDs that vent to 
atmosphere under CAA section 112(d)(2) and (3). CAA section 112(h)(1) 
states that the Administrator may prescribe a work practice standard or 
other requirements, consistent with the provisions of CAA sections 
112(d) or (f), in those cases where, in the judgment of the 
Administrator, it is not feasible to enforce an emission standard. CAA 
section 112(h)(2)(B) further defines the term ``not feasible'' in this 
context to apply when ``the application of measurement technology to a 
particular class of sources is not practicable due to technological and 
economic limitations.'' As detailed here, we identified as the MACT 
level of control work practice standards to regulate PRDs that vent to 
atmosphere under CAA section 112(h), and are proposing such work 
practice standards at proposed 40 CFR 63.165(e) (for HON) and proposed 
40 CFR 63.502(a)(1) and (a)(2) (which references 40 CFR 63.165, for P&R 
I) that are intended to reduce the number of PRD releases and will 
incentivize owners or operators to eliminate the causes of PRD releases 
to the atmosphere.
    No HON or P&R I facility is subject to numeric emission limits for 
PRDs that vent to the atmosphere.\131\ Further, we do not believe it is 
appropriate to subject PRDs that vent to the atmosphere to numeric 
emission limits due to technological and economical limitations that 
make it impracticable to measure emissions from such PRDs. CAA section 
112(h)(1) states that the EPA may prescribe a work practice standard or 
other requirement, consistent with the provisions of CAA sections 
112(d) or (f), in those cases where, in the judgment of the 
Administrator, it is not feasible to enforce an emission standard. CAA 
section 112(h)(2)(B) further defines the term ``not feasible'' in this 
context as meaning that ``the application of measurement technology to 
a particular class of sources is not practicable due to technological 
and economic limitations.'' We consider it appropriate to establish a 
work practice standard for PRDs that vent to atmosphere as provided in 
CAA section 112(h), because the application of a measurement 
methodology for PRDs that vent to atmosphere is not practicable due to 
technological and economic limitations. First, it is not practicable to 
use a measurement methodology for PRD releases that vent to atmosphere. 
PRDs are designed to remain closed during normal operations and release 
emissions only during nonroutine and unplanned events, and the venting 
time can be very short and may vary widely in composition and flow 
rate. These unique event characteristics make it infeasible to collect 
a grab sample of the gases when a PRD release occurs, and a single grab 
sample would also likely not account for potential variation in vent 
gas composition. Additionally, it would not be cost-effective to 
construct an appropriate conveyance and install and operate continuous 
monitoring systems for each individual PRD that vents to atmosphere in 
order to attempt to quantitatively measure a release event that may 
occur only a few times in a 3-year period. (See U.S. Sugar Corp. v. 
EPA, 830 F.3d 579, 664-67 (2016).) Further, we have not identified any 
available, technically feasible CEMS that can accurately determine a 
mass release quantity of VOC or HAP given the flow, composition, and 
composition variability of potential PRD releases that vent to the 
atmosphere from CMPUs or EPPUs. Rather, we have identified only 
monitoring systems capable of alerting an owner or operator when a PRD 
release occurs. Consequently, we have concluded that it is appropriate 
to establish a work practice standard for PRDs that vent to the 
atmosphere as provided in CAA section 112(h).
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    \131\ As previously mentioned, P&R II is different from the HON 
and P&R I because P&R II defines a process vent as a ``a point of 
emission from a unit operation. Typical process vents include 
condenser vents, vacuum pumps, steam ejectors, and atmospheric vents 
from reactors and other process vessels.'' As such, P&R II does not 
exclude PRD releases from its production-based emission rate MACT 
standard.
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    We also reviewed information about HON and P&R I facilities to 
determine how the best performers are minimizing emissions from PRDs 
that vent to the atmosphere. We first reviewed the requirements in the 
EPA's Chemical Accident Prevention Provisions (40 CFR part 68) and 
Occupational Safety and Health Administration's (OSHA) Process Safety 
Management rule (29 CFR 1910.119). These rules focus on planning for 
and minimizing or preventing scenarios which would result in releases 
of chemicals. For example, as stated in Appendix C to the OSHA rule, 
``Process safety management is the proactive identification, evaluation 
and mitigation or prevention of chemical releases that could occur as a 
result of failures in process, procedures or equipment.'' The rules are 
applicable to any equipment in the process, and relief valves are 
identified in each rule as an applicable source to evaluate. The EPA 
and OSHA rules have similar requirements, except that the applicability 
determinations are unique to each rule. Owners or operators are subject 
to the EPA's Chemical Accident Prevention Provisions at 40 CFR part 68 
if a process has more than a threshold quantity of a regulated 
substance. Regulated substances and their thresholds are listed at 40 
CFR 68.130. Owners or operators are subject to OSHA's Process Safety 
Management rule at 29 CFR 1910.119 if a process involves either a 
chemical that is at or above specified threshold quantities (listed in 
appendix A to 29 CFR 1910.119) or a Category 1 flammable gas (as 
defined in 29 CFR 1910.1200(c)) or flammable liquid with a flashpoint 
below 100 degrees Fahrenheit. HON and P&R I facilities may be subject 
to the Chemical Accident Prevention Provisions rule, as identified in 
their title V permit (40 CFR 68.215 requires permits to list part 68 as 
an applicable requirement, if subject). As a result, we further 
reviewed this rule for consideration in developing the work practice 
standard.
    The EPA's Chemical Accident Prevention Provisions require a 
prevention program. Facilities subject to the HON or P&R I would fall 
under prevention program 3. Prevention program 3 includes the 
following: Documentation of process safety information, conducting a 
hazard analysis, documentation of operating procedures, employee 
training, on-going maintenance, and incident investigations. The 
process safety information documented must include information 
pertaining to the hazards of the regulated substances in the process, 
the technology of the process, and the process equipment (including 
relief valves). When conducting the hazard analysis, facilities must 
identify, evaluate, and control the hazards in the process; controls 
may consider the application of detection methodologies (e.g., process 
monitoring and control instrumentation) to provide early warning of 
releases. The operating procedures must address multiple operating 
scenarios (e.g., normal operations, startup, emergency shutdown) and 
provide instructions for safely conducting process activities. 
Conducting the hazard analysis and

[[Page 25157]]

documenting operating procedures are similar to prevention measures, 
discussed below, though we note a specific number of measures or 
controls is not specified for the program 3 prevention program. 
Incident investigations must document the factors that contributed to 
an incident and any resolutions and corrective actions (incident 
investigations are consistent with root cause analysis and corrective 
action, discussed below). Facilities are also required to document this 
information in a Risk Management Plan that must be updated at least 
every 5 years.
    Next, we considered that some companies operating HON and P&R I 
facilities also own and operate petroleum refineries and may have 
established company-wide best practices as a result of specific state 
and federal requirements. For example, petroleum refineries and 
chemical plants located in certain counties in California are subject 
to and complying with specific requirements for PRDs such as the Bay 
Area Air Quality Management District (BAAQMD) Rule 8-28-304 and South 
Coast Air Quality Management District (SCAQMD) Rule 1173. The BAAQMD 
rule requires implementation of three prevention measures, and both 
rules require root cause analysis and corrective action for certain 
PRDs. These rules also formed the basis of the work practice standards 
promulgated at 40 CFR 63.648(j) for PRD releases at petroleum 
refineries in the Petroleum Refinery Sector RTR performed by the EPA 
(80 FR 75178, December 1, 2015).
    Considering our review of the EPA's Chemical Accident Prevention 
Provisions and company-wide best practices that HON and P&R I 
facilities may have implemented, we expect that the best performing HON 
and P&R I facilities have implemented a program for PRDs that vent to 
the atmosphere that consists of using at least three prevention 
measures and performing root cause analysis and corrective action in 
the event that a PRD does release emissions directly to the atmosphere. 
In fact, we confirmed this to be true for HON facilities based on 
facility responses to our CAA section 114 request. We used this 
information as the basis of the work practice standards that we are 
proposing at 40 CFR 63.165(e) (for HON) and 40 CFR 63.502(a)(1) and (2) 
(which references 40 CFR 63.165, for P&R I). Examples of prevention 
measures include the following: Flow indicators, level indicators, 
temperature indicators, pressure indicators, routine inspection and 
maintenance programs, operator training, inherently safer designs, 
safety instrumentation systems, deluge systems, and staged relief 
systems where the initial PRD discharges to a control system.
    We are also proposing a limit on the number of PRD releases that 
can take place within a 3-yr period. Any PRD releases in excess of the 
limit would result in a deviation from the work practice standard for 
PRDs that vent to the atmosphere. We believe setting criteria to 
determine a deviation is necessary for the work practice to be 
effective. We considered limits on the number of PRD releases in both 
3- and 5-year periods. Based on a Monte Carlo analysis of random rare 
events (as conducted for the Petroleum Refinery Sector rule \132\), we 
note that it is quite likely to have two or three events in a 5-year 
period when a long time horizon (e.g., 20 years) is considered. 
Therefore, we are proposing to limit the number of PRD releases from a 
single PRD to either one, two, or three (depending on the root cause) 
in a 3-year period as the basis of a deviation from the work practice 
standard. We are proposing that it is a deviation from the work 
practice standard if a single PRD that vents to atmosphere has two 
releases within a 3-year period due to the same root cause. We believe 
that this provision will help ensure that root cause/corrective actions 
are conducted effectively. Otherwise, we are proposing that it is a 
deviation from the work practice standard if a single PRD that vents to 
the atmosphere has three releases within a 3-year period for any 
reason. In addition, we are proposing that any PRD release for which 
the root cause was determined to be operator error or poor maintenance 
is a deviation from the work practice standard. Refer to proposed 40 
CFR 63.165(e)(3)(v) (for HON) and proposed 40 CFR 63.502(a)(1) and (2) 
(which references 40 CFR 63.165, for P&R I) for these proposed 
provisions. Based on our cost assumptions, the nationwide capital cost 
for complying with the PRD work practice requirements for the HON is 
$13.7 million and the annualized capital costs is $7.1 million; and for 
P&R I is $0.41 million and the annualized capital costs is $0.12 
million.
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    \132\ See 80 FR 75217, December 1, 2015.
---------------------------------------------------------------------------

    In addition, we believe that it is appropriate to exclude certain 
types of PRDs that have very low/no potential to emit based on their 
type of service, size, and/or pressure from the proposed work practice 
standard for PRD releases that vent to atmosphere, provided they are 
subject to other continuously applicable emission standards. Both the 
Chemical Accident Prevention Provisions and the California petroleum 
refinery PRD rules also exempt or impose simpler requirements for 
certain PRDs. We are proposing at 40 CFR 63.165(e)(5) (for HON) and 40 
CFR 63.502(a)(1) and (2) (which references 40 CFR 63.165, for P&R I) 
that the following types of PRDs would not be subject to the work 
practice standard for PRDs that vent to the atmosphere, but instead 
would be covered by other continuously applicable emission 
standards:\133\ (1) PRDs in heavy liquid service; (2) PRDs that are 
designed solely to release due to liquid thermal expansion; (3) PRDs on 
mobile equipment, and (4) pilot-operated and balanced bellows PRDs if 
the primary release valve associated with the PRD is vented through a 
closed vent system to a control device or back into the process, to the 
fuel gas system, or to a drain system. Each of the types of PRDs that 
we are proposing would not be subject to the work practice standard are 
discussed in greater detail here. With regard to PRDs in heavy liquid 
service, any HAP release to the atmosphere from a PRD in heavy liquid 
service would have a visual indication of a leak and any repairs to the 
valve would have to be further inspected and, if necessary, repaired 
under the existing equipment leak provisions. Therefore, we are 
proposing that PRDs in heavy liquid service need not be additionally 
subject to the work practice standard. In addition, we are proposing 
that PRDs designed solely to release due to liquid thermal expansion 
would not be subject to the work practice standard. We expect that 
releases from these thermal relief valves would be insignificant. 
Finally, we are also proposing that pilot-operated PRDs (where 
emissions can be released to the atmosphere through a pilot discharge 
vent) and balanced bellow PRDs (where emissions can be released to the 
atmosphere through a bonnet vent) would not be subject to the work 
practice standard, if the primary release valve associated with the 
pilot-operated or balanced bellows PRD is vented through a closed vent 
system to a control device or back into the process, to the fuel gas 
system, or to a drain system. Pilot-operated and balanced bellows PRDs 
are primarily used for pressure relief when the back pressure of the 
discharge vent may be high or variable. Conventional PRDs act on a 
differential pressure between the process gas and the discharge vent. 
If the discharge vent pressure increases, the vessel pressure at which 
the PRD will open increases, potentially leading

[[Page 25158]]

to vessel over-pressurization that could cause vessel failure. Balanced 
bellows PRDs use a bellow to shield the pressure relief stem and top 
portion of the valve seat from the discharge vent pressure. A balanced 
bellows PRD will not discharge gas to the atmosphere during a release 
event, except for leaks through the bonnet vent due to bellows failure 
or fatigue. Pilot-operated PRDs use a small pilot safety valve that 
discharges to the atmosphere to effect actuation of the primary valve 
or piston, which then discharges to a control system. Balanced bellows 
or pilot operated PRDs are considered a reasonable and necessary means 
to safely control the primary PRD release.
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    \133\ Pursuant to 40 CFR 63.165(a), each pressure relief device 
in organic HAP gas or vapor service must continue to be operated 
with an instrument reading of less than 500 ppm above background.
---------------------------------------------------------------------------

    For all PRDs in organic HAP service, owners or operators would 
still be required to comply with the LDAR provisions, as they are 
currently applicable. Therefore, all PRDs that vent to the atmosphere 
would still perform LDAR to ensure the PRD properly reseats if a 
release does occur, and PRDs that vent to control systems would still 
be exempt from LDAR requirements given that if a release were to occur 
from this specific class of PRDs, it would vent to a closed vent system 
and control device.
    Finally, to ensure compliance with the proposed work practice 
standard for PRDs that vent to the atmosphere, we are also proposing at 
40 CFR 63.165(e)(3) (for HON) and 40 CFR 63.502(a)(1) and (2) (which 
references 40 CFR 63.165, for P&R I) that sources monitor these 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. Pressure release events from PRDs that 
vent to the atmosphere have the potential to emit large quantities of 
HAP. When a pressure release occurs, it is important to identify and 
mitigate it as quickly as possible. For purposes of estimating the 
costs of this requirement, we assumed that operators would install 
electronic monitors on PRDs that vent to atmosphere to identify and 
record the time and duration of each pressure release. However, we are 
proposing to allow owners and operators to use a range of methods to 
satisfy these requirements, including the use of a parameter monitoring 
system (that may already be in place) on the process operating pressure 
that is sufficient to indicate that a pressure release has occurred as 
well as record the time and duration of that pressure release. Based on 
our cost assumptions, the nationwide capital cost of installing these 
electronic monitors for the HON is $3.1 million and the annualized 
capital costs are $0.41 million; and for P&R I is $0.09 million and the 
annualized capital costs are $0.01 million.
    We also considered requiring all PRDs to be vented to a control 
device as a beyond-the-floor requirement. While this would provide 
additional emission reductions beyond those we are establishing as the 
MACT floor, these reductions come at significant costs. For example, 
the EPA estimated that the capital cost for controlling MON PRDs ranged 
from $2,540 million to $5,070 million, and the annualized cost ranged 
from $330 million to $660 million; and the incremental cost 
effectiveness for requiring control of all MON PRDs that vent to the 
atmosphere compared to the requirements described above exceeded $80 
million per ton of HAP reduced (see 84 FR 69182, December 17, 2019). 
Consequently, we conclude that this is not a cost-effective option.
    The EPA is also proposing a requirement that any future installed 
pilot-operated PRDs be the non-flowing type. As previously noted, under 
CAA section 112(d)(1), the EPA may ``distinguish among classes, types, 
and sizes of sources'' when establishing standards. There are two 
designs of pilot-operated PRDs: flowing and non-flowing. When a flowing 
pilot-operated PRD is actuated, the pilot discharge vent continuously 
releases emissions; however, when a non-flowing pilot-operated PRD is 
actuated, the pilot discharge vent does not vent continuously. Although 
we expect pilot discharge vent emissions to be minimal for both 
designs, limiting the future use of flowing pilot-operated PRDs is 
warranted to prevent continuous release of emissions. Therefore, we are 
proposing at 40 CFR 63.165(e)(8) (for HON) and 40 CFR 63.502(a)(1) and 
(2) (which references 40 CFR 63.165, for P&R I) to require future 
installation and operation of non-flowing pilot-operated PRDs at all 
affected sources.
    We are also proposing at 40 CFR 63.101 (for HON) and 40 CFR 63.482 
(for P&R I) to clarify the definitions of ``pressure release,'' 
``pressure relief device,'' and ``relief valve.'' We are proposing to 
define ``pressure release'' as the emission of materials resulting from 
the system pressure being greater than the set pressure of the pressure 
relief device. This release can be one release or a series of releases 
over a short time period. We are proposing to define ``pressure relief 
device'' as a valve, rupture disk, or similar device used only to 
release an unplanned, nonroutine discharge of gas from process 
equipment in order to avoid safety hazards or equipment damage. A 
pressure relief device discharge can result from an operator error, a 
malfunction such as a power failure or equipment failure, or other 
unexpected cause. Such devices include conventional, spring-actuated 
relief valves, balanced bellows relief valves, pilot-operated relief 
valves, rupture disks, and breaking, buckling, or shearing pin devices. 
We are proposing to define ``relief valve'' as a type of pressure 
relief device that is designed to re-close after the pressure relief. 
For clarity, we are also proposing for P&R II the same definition of 
``pressure relief device'' that we are proposing for the HON and P&R I 
because P&R II currently does not define this term. Although we are not 
proposing for P&R II the same work practice standard for PRDs that vent 
to the atmosphere that we are proposing for the HON and P&R I (because 
as explained earlier in this section of the preamble any release of HAP 
to the atmosphere from a P&R II pressure relief device should already 
be accounted for when determining compliance with the production-based 
emission rate MACT standard), we are proposing at 40 CFR 63.527(f) and 
40 CFR 63.528(a)(6), that owners and operators keep records and report 
the start and end time and date of each pressure release to the 
atmosphere, an estimate of the mass quantity in pounds of each organic 
HAP released, as well as any data, assumptions, and calculations used 
to estimate of the mass quantity of each organic HAP released during 
the event. These proposed records and reports for P&R II will assist 
stakeholders in determining compliance with the production-based 
emission rate MACT standard.
    We solicit comment on all of the proposed revisions for PRDs. See 
the document titled Review of Regulatory Alternatives for Certain Vent 
Streams in the SOCMI Source Category that are Associated with Processes 
Subject to HON and Processes Subject to Group I and Group II Polymers 
and Resins NESHAPs, in the docket for this rulemaking for details on 
the assumptions and methodologies used in this analysis.
3. Closed Vent System Containing Bypass Lines
    For a closed-vent system containing bypass lines that can divert 
the stream away from the APCD to the atmosphere, the HON and P&R I 
require the owner or operator to either: (1) Install, maintain, and 
operate a continuous parametric monitoring system for flow on the 
bypass line that is capable of detecting whether a vent stream flow is 
present at least once every 15 minutes or (2) secure the bypass line 
valve in the

[[Page 25159]]

non-diverting position with a car-seal or a lock-and-key type 
configuration. Under option (2), the owner or operator is also required 
to inspect the seal or closure mechanism at least once per month to 
verify the valve is maintained in the non-diverting position (e.g., see 
40 CFR 63.114(d)(2) for more details). To ensure standards apply to HON 
and P&R I emission sources at all times, we are proposing at 40 CFR 
63.114(d)(3), 40 CFR 63.127(d)(3), 40 CFR 63.148(f)(4), and 40 CFR 
63.172(j)(4) (for HON), and 40 CFR 63.485(x), 40 CFR 63.489(d)(3), and 
40 CFR 63.502(a)(2) (for P&R I) that an owner or operator may not 
bypass the APCD at any time, that a bypass is a violation (see proposed 
40 CFR 63.118(a)(5) and (f)(7), 40 CFR 63.130(a)(2)(iv), (b)(3), and 
(d)(7), 40 CFR 63.148(i)(3)(iii) and (j)(4), Tables 3, 7, and 20 to 40 
CFR 63, subpart G, 40 CFR 63.181(g)(3)(iii), and 40 CFR 63.182(d)(xix) 
(for HON), and 40 CFR 63.485(x), 40 CFR 63.489(d)(3), and 40 CFR 
63.502(a)(2) (for P&R I)), and owners and operators must estimate and 
report the quantity of organic HAP released. We are proposing this 
revision because bypassing an APCD could result in a release of 
regulated organic HAP to the atmosphere and to be consistent with 
Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008), where the Court 
determined that standards under CAA section 112(d) must provide for 
compliance at all times. These requirements are consistent with CAA 
section 112(d) controls and reflect the MACT floor. We did not identify 
any additional options beyond this (i.e., beyond-the-floor options) for 
minimizing emissions from closed-vent systems that are used to comply 
with the emission standards. We are also proposing that the use of a 
cap, blind flange, plug, or second valve on an OEL (following the 
requirements specified in 40 CFR 60.482-6(a)(2), (b), and (c) or 
following requirements codified in another regulation that are the same 
as 40 CFR 60.482-6(a)(2), (b), and (c)) is sufficient to prevent a 
bypass. We solicit comment on these proposed revisions.
4. Maintenance Activities
    The EPA is proposing that emission limits apply at all times 
consistent with Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008). We 
recognize that this proposed change for vent streams that are 
periodically discharged will affect certain maintenance activities such 
as those that require equipment openings, and we consider maintenance 
activities a separate class of startup and shutdown emissions because 
there must be a point in time when the equipment can be opened, and any 
remaining emissions are vented to the atmosphere. We also acknowledge 
that it would require a significant effort to identify and characterize 
each of these potential release points (e.g., for permitting purposes). 
CAA section 112(h)(1) states that the Administrator may prescribe a 
work practice standard or other requirements, consistent with the 
provisions of CAA sections 112(d) or (f), in those cases where, in the 
judgment of the Administrator, it is not feasible to enforce an 
emission standard. We are proposing work practices instead of numeric 
emission limits for maintenance activities because it is ``not feasible 
to prescribe or enforce an emission standard'' for these emissions. 
Maintenance activities are not ``emitted through a conveyance designed 
and constructed to emit or capture such pollutant'' (see CAA section 
112(h)(2)(A)) and it is not possible to characterize each of these 
potential release points. The discussion that follows within this 
section of the preamble primarily focuses on the HON and P&R I because 
any release to the atmosphere from P&R II maintenance activities should 
already be accounted for when determining compliance with the 
production-based emission rate MACT standard (e.g., pounds HAP per 
million pounds BLR or WSR produced).
a. Equipment Openings (Excluding Storage Vessel Degassing)
    We reviewed state permit conditions and determined the best 
performers' permits specify that they meet certain conditions before 
they open equipment to the atmosphere. The conditions include 
thresholds regarding the LEL and the mass of gas that may be emitted. 
These requirements are consistent with CAA section 112(d) controls and 
reflect the level of performance analogous to a MACT floor. Therefore, 
we are proposing a work practice standard at 40 CFR 63.113(k)(1)(i) 
(for HON), and at 40 CFR 63.485(x) and 40 CFR 63.487(i)(1)(i) (for P&R 
I), that prior to opening process equipment to the atmosphere during 
maintenance events, the equipment first be drained and purged to a 
closed system so that the hydrocarbon content is less than or equal to 
10 percent of the LEL. For those situations where 10-percent LEL cannot 
be demonstrated, we are proposing at 40 CFR 63.113(k)(1)(ii) (for HON), 
and at 40 CFR 63.485(x) and 40 CFR 63.487(i)(1)(ii) (for P&R I), that 
the equipment may be opened and vented to the atmosphere if the 
pressure is less than or equal to 5 psig, provided there is no active 
purging of the equipment to the atmosphere until the LEL criterion is 
met. We are proposing this 5 psig threshold to acknowledge that a 
certain minimum pressure must exist for the flare header system (or 
other similar control system) to operate properly. We are also 
proposing at 40 CFR 63.113(k)(1)(iii) (for HON), and at 40 CFR 
63.485(x) and 40 CFR 63.487(i)(1)(iii) (for P&R I), that equipment may 
be opened when there is less than 50 pounds of VOC that may be emitted 
to the atmosphere.
    We also acknowledge that installing a blind flange to prepare 
equipment for maintenance may be necessary and by doing so, the owner 
or operator may not be able to meet the proposed maintenance vent 
conditions mentioned above (e.g., a valve used to isolate the equipment 
will not seat fully, so organic material may continually leak into the 
isolated equipment). To limit the emissions during the blind flange 
installation, we are proposing at 40 CFR 63.113(k)(1)(iv) (for HON), 
and at 40 CFR 63.485(x) and 40 CFR 63.487(i)(1)(iv) (for P&R I), 
depressurizing the equipment to 2 psig or less prior to equipment 
opening and maintaining pressure of the equipment where purge gas 
enters the equipment at or below 2 psig during the blind flange 
installation. The low allowable pressure limit will reduce the amount 
of process gas that will be released during the initial equipment 
opening, and the ongoing 2 psig pressure requirement will limit the 
purge gas rate. Together, these proposed provisions will limit the 
emissions during blind flange installation and will result in 
comparable emissions allowed under the proposed maintenance vent 
conditions mentioned above. We expect these situations to be rare and 
that the owner or operator would remedy the situation as soon as 
practical (e.g., replace the isolation valve or valve seat during the 
next turnaround in the example provided above). Therefore, we are only 
proposing that this alternative maintenance vent limit be used under 
those situations where the proposed primary limits (i.e., hydrocarbon 
content is less than or equal to 10 percent of the LEL, pressure is 
less than or equal to 5 psig, or VOC is less than 50 pounds) are not 
achievable and blinding of the equipment is necessary. We did not 
identify any additional options beyond those identified above (i.e., 
beyond-the-floor options) for controlling emissions from equipment 
openings.
    We expect that all HON and P&R I facilities already have standard 
procedures in place when performing equipment openings (at the very 
least for safety reasons). As such, the only costs incurred are for 
recordkeeping

[[Page 25160]]

after each non-conforming event. We are proposing that owners or 
operators document each circumstance under which the alternative 
maintenance vent limit is used, providing an explanation as to why 
other criteria could not be met prior to equipment blinding and an 
estimate of the emissions that occurred during the equipment blinding 
process. For the HON, we calculated the annual costs to be $94,250 per 
year. For P&R I, we calculated the annual costs to be $8,650 per year. 
We solicit comment on the proposed revisions related to maintenance 
activities. For additional details and discussion, see the document 
titled Review of Regulatory Alternatives for Certain Vent Streams in 
the SOCMI Source Category that are Associated with Processes Subject to 
HON and Processes Subject to Group I and Group II Polymers and Resins 
NESHAPs, which is available in the docket for this rulemaking. As 
previously mentioned in section III.C.3.b of this preamble, we are also 
proposing these same maintenance vent standards for NSPS subpart IIIa, 
NNNa, and RRRa under CAA section 111(b)(1)(B).
b. Storage Vessel Degassing
    With the proposed removal of SSM requirements, a standard specific 
to storage vessel degassing does not exist when storage vessels are 
using control devices to comply with the requirements in 40 CFR 
63.119(a)(2) (for HON) and 40 CFR 63.484(a) (for P&R I, which 
references 40 CFR 63.119). We acknowledge that storage vessel degassing 
is similar to maintenance vents (e.g., equipment openings) and that 
there must be a point in time when the storage vessel can be opened and 
any emissions vented to the atmosphere. We reviewed available data to 
determine how the best performers are controlling storage vessel 
degassing emissions.
    We are aware of three regulations regarding storage vessel 
degassing, two in the state of Texas and the third for the SCAQMD in 
California. Texas has degassing provisions in the TAC \134\ and through 
permit conditions,\135\ while Rule 1149 contains the SCAQMD degassing 
provisions.\136\ The TAC requirements are the least stringent and 
require control of degassing emissions until the vapor space 
concentration is less than 35,000 ppmv as methane or 50 percent of the 
LEL. The Texas permit conditions require control of degassing emissions 
until the vapor space concentration is less than 10 percent of the LEL 
or until the VOC concentration is less than 10,000 ppmv, and SCAQMD 
Rule 1149 requires control of degassing emissions until the vapor space 
concentration is less than 5,000 ppmv as methane. The Texas permit 
conditions requiring compliance with 10 percent of the LEL and SCAQMD 
Rule 1149 control requirements are considered equivalent because 5,000 
ppmv as methane equals 10 percent of the LEL for methane.
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    \134\ See 30 TAC Chapter 115, Subchapter F, Division 3, 
available at https://texreg.sos.state.tx.us/public/readtac%24ext.ViewTAC?tac_view=5&ti=30&pt=1&ch=115&sch=F÷=3&rl=Y.
    \135\ See https://www.tceq.texas.gov/assets/public/permitting/air/Guidance/NewSourceReview/mss/chem-mssdraftconditions.pdf.
    \136\ See http://www.aqmd.gov/docs/default-source/rule-book/reg-xi/rule-1149.pdf.
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    HON and P&R I facilities located in Texas are subject to the permit 
conditions, but no HON or P&R I facility is subject to the SCAQMD rule. 
Of the 207 currently operating HON facilities, 78 are in Texas (four of 
which are collocated with P&R I processes). Of the 19 currently 
operating P&R I facilities, 6 are in Texas (including the four 
collocated with HON processes). Therefore, the Texas permit conditions 
relying on storage vessel degassing until 10 percent of the LEL is 
achieved reflect what the best performers have implemented for storage 
vessel degassing, and we considered this information as the MACT floor 
for both new and existing HON and P&R I sources.
    We reviewed Texas permit condition 6 (applicable to floating roof 
storage vessels) and permit condition 7 (applicable to fixed roof 
storage vessels) for key information that could be implemented to form 
the basis of a standard for storage vessel degassing. The Texas permit 
conditions require control of degassing emissions for floating roof and 
fixed roof storage vessels until the vapor space concentration is less 
than 10 percent of the LEL. The permit conditions also specify that 
facilities can also degas a storage vessel until they meet a VOC 
concentration of 10,000 ppmv, but we do not consider 10,000 ppmv to be 
equivalent to or as stringent as the compliance option to meet 10 
percent of the LEL and are not including this as a compliance option. 
We also do not expect the best performers would be using this 
concentration for compliance because the Texas permit conditions allow 
facilities to calibrate their LEL monitor using methane. Storage 
vessels may be vented to the atmosphere once the 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. We are proposing that these requirements are 
considered MACT floors for both new and existing HON and P&R I sources; 
therefore, we are proposing these requirements at 40 CFR 63.119(a)(6) 
(for HON) and 40 CFR 63.484(a) and (t) (which references 40 CFR 63.119, 
for P&R I). Additionally, in petitions for reconsideration that the EPA 
recently received on the MON, EMACT standards, the Petroleum Refinery 
Sector rule, and OLD NESHAP, petitioners asserted that it is necessary 
to make connections to a temporary control device to control the 
floating roof storage vessel degassing emissions, which may require 
opening the storage vessel to make these connections. While we do not 
believe the current language precludes a facility from taking this 
step, we are revising the standard to include related language for 
clarity. Therefore, we are proposing that a floating roof storage 
vessel may be opened prior to degassing to set up equipment (i.e., make 
connections to a temporary control device), but this must be done in a 
limited manner and must not actively purge the storage vessel while 
connections are made.
    We calculated the impacts due to controlling storage vessel 
degassing emissions by evaluating the population of storage vessels 
that are subject to control under 40 CFR 63.119(a)(2) (for HON) and 40 
CFR 63.484(a) (for P&R I, which references 40 CFR 63.119), and not 
located in Texas. Storage vessels regulated by the HON or P&R I in 
Texas would already be subject to the degassing requirements, and there 
would not be additional costs or emissions reductions for these 
facilities. We estimated there are an average of four Group 1 HON 
storage vessels per CMPU and two Group 1 P&R I storage vessels per 
EPPU. We applied these counts to the number of HON and P&R I processes 
that are not located in Texas, resulting in 1,580 HON storage vessels 
and 26 P&R I storage vessels newly applicable to vessel degassing 
requirements. Based on a review of facility responses to our CAA 
section 114 request, most storage vessels are degassed an average of 
once every 13 years. Using this average and the population of storage 
vessels that are not in Texas, we estimated 122 HON storage vessel 
degassing events and two P&R I storage vessel degassing events would be 
newly subject to control each year. Controlling HON storage vessel 
degassing would reduce HAP emissions by 106 tpy, with a total annual 
cost of approximately $751,500. Controlling P&R I storage vessel 
degassing would reduce HAP emissions by 1.70 tpy, with

[[Page 25161]]

a total annual cost of approximately $12,300. See the document titled 
Degassing Cost and Emissions Impacts for Storage Vessels Located in the 
SOCMI Source Category that are Associated with Processes Subject to HON 
and for Storage Vessels Subject to Either the Group I Polymers and 
Resins NESHAP or Group II Polymers and Resins NESHAP, which is 
available in the docket for this rulemaking, for details on the 
assumptions and methodologies used in this analysis. We also considered 
options beyond-the-floor, but we did not identify and are not aware of 
storage vessel degassing control provisions more stringent than those 
discussed above and being proposed in this rule; therefore, no beyond-
the-floor option was evaluated.
c. Planned Routine Maintenance for Storage Vessels
    Although the HON and P&R I currently allow owners and operators to 
disconnect the fixed roof vessel vent from the closed vent system and 
control device, fuel gas system, or process equipment for up to 240 
hours per year during planned, routine maintenance (see 40 CFR 
63.119(e)(3) through (5) (for HON) and 40 CFR 63.484(a) (for P&R I)), 
we are proposing at 40 CFR 63.119(e)(7) that 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). The removal of the 240-hr 
exemption provisions except for vessel breathing losses is based upon 
our position that removal is needed to satisfy Sierra Club v. EPA, 551 
F.3d 1019 (D.C. Cir. 2008). These requirements are consistent with CAA 
section 112(d) controls and reflect the MACT floor, as all working loss 
emissions from storage vessels would be controlled during these 
periods, ensuring a CAA section 112 standard is in place at this time. 
We note that in 2018, the EPA finalized these same work practice 
standards for the Amino/Phenolic Resins NESHAP (83 FR 51842, October 
15, 2018). To evaluate the impacts of this proposed change to the HON 
and P&R I, we assumed owners and operators would install a secondary 
control device system (to control emissions from vessels during periods 
of planned routine maintenance of the primary control device) and that 
activated carbon canisters would be chosen as the method of control. 
Based on vendor quotes, we determined that the total capital cost of a 
55-gallon activated carbon drum with two connections, including piping 
and duct work, is approximately $1,040. Following the guidelines of the 
EPA's Seventh Edition OAQPS Control Cost Manual,\137\ we estimate that 
the annual cost per CMPU or EPPU is $180. We also used information 
about fixed roof storage vessels (including stored materials) that 
industry provided to EPA in response to our CAA section 114 request 
(see section II.C of this preamble). We estimate that there could be up 
to 4 fixed roof storage vessels per CMPU requiring emissions control 
under the HON. We multiplied this estimate (4) by the total HON 
processes nationwide (634) and approximated that there are 2,536 fixed 
roof storage vessels requiring emissions control under the HON 
nationwide. For P&R I, we assumed that each P&R I facility has two 
fixed roof storage vessels per EPPU that are subject to control.\138\ 
We also assumed that each facility has one P&R process. Using these 
assumptions, we approximated that there are 38 fixed roof storage 
vessels requiring emissions control under P&R I nationwide. We then 
estimated that the highest amount of HAP emissions that would be 
expected to occur from a HON or P&R I fixed roof storage vessel during 
the 240 hours of planned routine maintenance would be 19.3 pounds, if 
the emissions are not controlled. These emissions were based on the 
largest vessel capacity and highest vapor pressure material stored in a 
vessel that was reported in response to our CAA section 114 request, 
and estimated using the emission estimation procedures from Chapter 7 
of EPA's Compilation Of Air Pollutant Emission Factors,\139\ assuming 
that only breathing losses would occur during this period. We assumed 
that activated carbon canisters would achieve a 95 percent reduction in 
HAP emissions, which would reduce emissions per vessel by 18.3 lbs HAP. 
Based on our cost and emissions assumptions, the nationwide capital 
cost for removal of the 240-hr exemption provisions (except for vessel 
breathing losses) for the HON is $2.64 million and the annualized 
capital costs is $0.46 million; and for P&R I is $0.04 million and the 
annualized capital costs is about $0.01 million. See the document 
titled Cost and Emissions Impacts for 240 Hour Planned Routine 
Maintenance Work Practice Standard on Storage Vessels Located in the 
SOCMI Source Category that are Associated with Processes Subject to HON 
and for Storage Vessels Subject to the Group I Polymers and Resins 
NESHAP, which is available in the docket for this rulemaking, for 
details on the assumptions and methodologies used in this analysis.
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    \137\ Air Pollution Control Cost Manual--Section 3: VOC 
Controls; Section 3.1: VOC Recapture Controls, Carbon Adsorbers 
Calculation Spreadsheet. Retrieved from https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution. October 2018.
    \138\ This assumption is based on the median between four and 
zero because our HON average is four, and the one facility that 
received the CAA section 114 request and is subject to both the HON 
and P&R I, reported zero Group 1 storage vessels subject to P&R I.
    \139\ Compilation of Air Pollutant Emission Factors. Volume 1: 
Stationary Point and Area Sources. AP-42, Fifth Edition. Chapter 7: 
Liquid Storage Tanks. Office of Air Quality Planning and Standards, 
Research Triangle Park, NC.
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    As a beyond-the-floor control option, we considered requiring 
owners and operators to also control breathing losses from storage 
vessels during periods of planned routine maintenance of the emission 
control system. However, this option is expected to be not cost 
effective. For example, the EPA estimated a cost of $62,400 per ton of 
HAP emissions reduced in their analysis conducted for this same option 
in the Amino/Phenolic Resins NESHAP (82 FR 40103, August 24, 2017).
5. Dioxins and Furans Emission Limits
    The HON, P&R I, and P&R II do not currently regulate emissions of 
polychlorinated dibenzo-p-dioxins (dioxins) and polychlorinated 
dibenzofurans (furans). Dioxins and furans can be formed when 
chlorinated compounds are present and combusted in, for example, a 
thermal oxidizer. HON facilities that release dioxins and furans 
include those that manufacture chlorinated SOCMI chemicals (e.g., 
chloroform, chloroprene, ethylene dichloride, methyl chloride, 
trichloroethylene, vinyl chloride). While the HON has 207 facilities 
and 634 CMPUs, we estimated that at least 18 HON facilities and 34 
CMPUs manufacture these chlorinated compounds and would have emissions 
of dioxins and furans. As neoprene production facilities and 
epichlorohydrin elastomer facilities in P&R I use, produce, or emit 
chlorinated chemicals and all P&R II facilities use epichlorohydrin as 
a feedstock, they can also produce and emit dioxins and furans through 
combustion controls. Since dioxins and furans are currently an 
unregulated pollutant in these NESHAP, we are proposing dioxins and 
furans MACT standards under CAA section 112(d)(2) and (3) for the HON, 
P&R I, and P&R II.
    The MACT standard setting process starts with determining the level 
of HAP emissions limitation that is currently achieved by the best-
controlled similar source (for new source standards) or by the average 
of the best-performing

[[Page 25162]]

sources (for existing source standards). Specifically for categories 
with 30 or more sources, the MACT floor for existing sources must be at 
least as stringent as the average emissions limitation achieved by the 
best performing 12 percent of existing sources for which the EPA has 
emissions information. For source categories with fewer than 30 
sources, the MACT floor for existing sources is the average emission 
limitation achieved by the best performing five sources. See CAA 
sections 112(d)(2)-(3)(A) and (B). We applied the upper prediction 
limit (UPL) and information on the RDL to calculate the MACT floor. 
Once the UPL is calculated for new sources and existing sources, the 
UPL must be compared to the three times the RDL value as a final step 
to assess variability. If the three times the RDL value is greater than 
the UPL, then three times the RDL is selected as the MACT floor 
emission level.
    Dioxins and furans stack test data are available for nine HON 
facilities, and we assessed this data to conduct our MACT analyses and 
develop the emission limits for the HON sources. Multiple stack tests 
included values below the detection level for certain dioxins and 
furans congeners. Therefore, we evaluated the RDL and calculated a 
three times the RDL value of 0.054 ng/dscm at 3 percent oxygen (toxic 
equivalency basis). Since the HON has well over 30 sources (i.e., 634 
CMPUs), we calculated the existing source UPL using data from the top 
two facilities (i.e., nine times 12 percent rounds up to two) and 
calculated the new source UPL using data from the best performer. The 
existing source UPL was calculated as 0.032 ng/dscm at 3 percent oxygen 
(toxic equivalency basis) and the new source UPL equaled 0.031 ng/dscm 
at 3 percent oxygen (toxic equivalency basis). For both existing 
sources and new sources, the three times the RDL value for dioxins and 
furans was greater than the calculated UPL. As such, we are proposing 
at 40 CFR 63.113(a)(5) that the dioxins and furans emissions limit for 
HON facilities is the three times the RDL value of 0.054 ng/dscm at 3 
percent oxygen (toxic equivalency basis). To ensure compliance with 
this limit, we are proposing performance testing requirements that 
include the use of Method 23 of 40 CFR part 60, appendix A-7 at 40 CFR 
63.116(h). We are also proposing a definition for the term ``dioxins 
and furans'' at 40 CFR 63.101 to mean total tetra--through 
octachlorinated dibenzo-p-dioxins and dibenzofurans. Finally, we are 
proposing owners and operators comply with the same monitoring, 
recordkeeping, and reporting requirements that are already required for 
compliance with the current process vent standards. We did not identify 
additional controls or perform a beyond-the-floor analysis for reducing 
dioxins and furans emissions further because the proposed emission 
limit is based on the detection limit of the method and represents the 
lowest concentration of dioxins and furans that can be measured; 
therefore no further reductions can be achieved that are measurable. We 
solicit comment on the proposed standards for dioxins and furans for 
the HON, P&R I, and P&R II. For details on the emission limit 
calculations, see the document titled Dioxins and Furans MACT Floor in 
the SOCMI Source Category for Processes Subject to HON and Processes 
Subject to Group I and Group II Polymers and Resins NESHAPs, which is 
available in the docket for this rulemaking.
    Dioxins and furans stack test data are not available for P&R I and 
P&R II facilities, and in our review of reported emissions inventories, 
none of these facilities reported emissions of these pollutants from 
these source categories. However, given that neoprene production 
facilities and epichlorohydrin facilities in P&R I and all facilities 
in P&R II have chlorinated chemicals that could be controlled with 
combustion controls, the mechanism of formation of dioxins and furans 
is the same as for HON sources controlling chlorinated SOCMI chemicals. 
Given that no facilities are reporting emissions of these pollutants in 
their inventories, we believe that the best performing sources that 
would constitute the MACT floor would have emissions below three times 
the RDL, which would be the lowest MACT emission standard the EPA would 
set due to measurement limitations. Thus, we are proposing dioxins and 
furans emissions limits for P&R I and P&R II facilities using, 
producing, or emitting chlorinated chemicals that are the same as we 
are proposing for the HON (i.e., 0.054 ng/dscm at 3 percent oxygen, 
toxic equivalency basis). We are proposing the dioxins and furans 
emission limit for P&R I at 40 CFR 63.485(x) (which points to 40 CFR 
63.113(a)(5) for continuous front-end process vents) and 40 CFR 
63.487(a)(3) and (b)(3) (for batch front-end process vents); and the 
P&R II emission limit at 40 CFR 63.523(e) (for process vents associated 
with each existing, new, or reconstructed affected 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). To ensure compliance 
with the proposed limit, we are proposing performance testing 
requirements that include the use of Method 23 of 40 CFR part 60, 
appendix A-7 at 40 CFR 63.485(x) (which points to 40 CFR 63.116(h) for 
P&R I continuous front-end process vents) and 40 CFR 63.490(g) (for P&R 
I batch front-end process vents) and 63.525(m) (for P&R II sources). We 
are also proposing a definition for the term ``dioxins and furans'' at 
40 CFR 63.482 (for P&R I sources) and 40 CFR 63.522 (for P&R II 
sources) to mean total tetra--through octachlorinated dibenzo-p-dioxins 
and dibenzofurans. Finally, we are proposing owners and operators 
comply with the same monitoring, recordkeeping, and reporting 
requirements that are already required for compliance with the current 
process vent standards. We solicit comment on the types of emission 
controls used and stack test data for emissions of dioxins and furans 
from the P&R I and P&R II source categories.
    To evaluate the cost impacts of the proposed emissions limits, we 
assumed select facilities would install a condenser prior to the 
existing control device (e.g., thermal oxidizer) to remove chlorinated 
compounds from the stream and prevent the formation of dioxins and 
furans in the thermal oxidizer. Of the nine HON facilities with stack 
test data, two facilities do not meet the proposed emission limit and 
would need to install a condenser to reduce dioxins and furans 
emissions.\140\ For the twelve HON facilities that do not have stack 
test data available, we assumed that five facilities would not meet the 
emission limits and would need to install a condenser to reduce their 
emissions. We assumed the one P&R I facility with dioxins and furans 
emissions in the risk modeling file and all five P&R II facilities 
would need to install a condenser to meet the dioxins and furans 
emissions limit. Based on our cost assumptions, the nationwide costs to 
comply with the dioxins and furans emissions limits are $3.9 million in 
capital costs and $2.3 million in annual costs for the HON; $0.56 
million in capital costs and $0.33 million in annual costs for P&R I; 
and $2.8 million

[[Page 25163]]

in capital costs and $1.6 million in annual costs for P&R II.
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    \140\ Note that four facilities do not meet the dioxins and 
furans emission limit in our dataset, however two of the four 
facilities are subject to 40 CFR part 63, subpart HHHHHHH, and are 
complying with a 0.051 ng/dscm at 3 percent oxygen, toxic 
equivalency basis, limit for PVC-combined process vents and are 
using the same control device for emissions from HON processes.
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    We solicit comment on all aspects of the proposed emissions limits 
for dioxins and furans. See the document titled Dioxins and Furans MACT 
Floor in the SOCMI Source Category for Processes Subject to HON and 
Processes Subject to Group I and Group II Polymers and Resins NESHAPs, 
which is available in the docket for this rulemaking, for details on 
the assumptions and methodologies used in the analyses.
6. Pressure Vessels
    We are proposing new requirements for pressure vessels that are 
associated with processes subject to the HON or P&R I. The EPA is 
proposing to define pressure vessel at 40 CFR 63.101 (for HON) and 40 
CFR 63.482 (for P&R I) to mean ``a storage vessel that is used to store 
liquids or gases and is designed not to vent to the atmosphere as a 
result of compression of the vapor headspace in the pressure vessel 
during filling of the pressure vessel to its design capacity.'' To 
eliminate any ambiguity in applicability or control requirements, the 
EPA is also proposing 40 CFR 63.101 (for HON) and 40 CFR 63.482 (for 
P&R I) to remove the exemption for ``pressure vessels designed to 
operate in excess of 204.9 kilopascals and without emissions to the 
atmosphere'' from the definition of storage vessel.\141\ This long-
standing exemption is ambiguous with respect to what ``without 
emissions to the atmosphere'' means. For example, most pressure vessels 
have relief devices that allow for venting when pressure exceeds 
setpoints. In many cases, these vents are routed to control devices; 
however, control devices are not completely effective (e.g., achieve 98 
percent control), and therefore there are emissions to the atmosphere 
from these pressure vessels, even if they are controlled. There are 
also instances where other components in pressure systems may allow for 
fugitive releases because of leaks from fittings or cooling systems. 
All of these events arguably are ``emissions to the atmosphere'' and 
therefore it is likely that even if this exemption were maintained, 
owners and operators of pressure vessels would still have uncertainty 
regarding whether or not they were subject to substantive requirements. 
Therefore, the proposed revisions remove the ambiguity associated with 
the exemption and set standards intended to limit emissions to the 
atmosphere from pressure vessels. Given that we have seen large 
emission events from PRDs on pressure vessels (e.g., a 155 tpy 1,3-
butadiene atmospheric PRD release was documented from a HON pressure 
vessel in 2015),\142\ we are also proposing at 40 CFR 63.119(a)(7)(v) 
and 40 CFR 63.484(t) that any atmospheric PRD release from a pressure 
vessel is a deviation of the PRD work practice standards (see section 
III.D.2 of this preamble for more information on the proposed PRD work 
practice standards).
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    \141\ We note that P&R II does not have a pressure vessel 
exemption in its definition of storage tank (see 40 CR 63.522).
    \142\ See the Appendix to the document titled Cost and Emissions 
Impacts for Pressure Vessels Located in the SOCMI Source Category 
that are Associated with Processes Subject to HON and for Pressure 
Vessels Subject to the Group I Polymers and Resins NESHAP, which is 
available in the docket for this rulemaking.
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    We are proposing LDAR requirements at 40 CFR 63.119(a)(7) (for HON) 
and 40 CFR 63.484(t) (for P&R I) that are based on similar no-
detectable emission requirements required for closed vent systems in 
most chemical sector NESHAP. These requirements are consistent with CAA 
section 112(d) controls and reflect the MACT floor. As such, these 
proposed requirements impose a standard that requires no detectable 
emissions at all times (i.e., would be required to meet a leak 
definition of 500 ppm at each point on the pressure vessel where total 
organic HAP could potentially be emitted); require initial and annual 
leak monitoring using EPA Method 21 of 40 CFR part 60, Appendix A-7; 
and require routing organic HAP through a closed vent system to a 
control device (i.e., no releases to the atmosphere through a pressure 
vessel's PRD). The proposed standards recognize that pressure vessels 
can be designed with appropriate capture and containment systems for 
leak interfaces and pressure vessel PRDs such that the owner or 
operator can avoid ``willful'' deviations. We also did not identify any 
additional options beyond those identified above (i.e., beyond-the-
floor options) for minimizing emissions to the atmosphere from pressure 
vessels.
    Based on facility responses to our CAA section 114 request, we 
estimate that there could be up to one pressure vessel per every two 
CMPUs for a total of 317 pressure vessels requiring emissions control 
under the HON nationwide (1 pressure vessel per 2 CMPUs x 634 CMPUs = 
317 pressure vessels). We also estimate that there are nine P&R I 
facilities that each have one pressure vessel (for a total of nine 
pressure vessels requiring emissions control under P&R I nationwide) 
given that: (1) We are aware of three P&R I facilities within the 
polybutadiene rubber source category that each have a pressure vessel, 
(2) there are five P&R I facilities that make styrene butadiene rubber 
and are therefore likely to each have one 1,3-butadiene pressure 
vessel, and (3) we are aware of one other pressure vessel (storing EtO) 
located at a P&R I facility producing epichlorohydrin elastomer. Using 
information from a 2012 analysis that identified developments for 
storage vessels at chemical manufacturing facilities and petroleum 
refineries,\143\ we estimate a total HAP emission reduction of 244 tpy 
for all affected pressure vessels associated with processes subject to 
the HON and 6.9 tpy HAP for pressure vessels subject to P&R I; the 
nationwide capital cost for the proposed pressure vessel LDAR 
requirements for the HON is about $78,000 and the annualized capital 
costs is $73,000, and for P&R I the nationwide capital cost is $2,200 
and the annualized capital costs is about $2,000. See the document 
titled Cost and Emissions Impacts for Pressure Vessels Located in the 
SOCMI Source Category that are Associated with Processes Subject to HON 
and for Pressure Vessels Subject to the Group I Polymers and Resins 
NESHAP, which is available in the docket for this rulemaking, for 
details on the assumptions and methodologies used in this analysis. We 
solicit comment on the proposed revisions for pressure vessels.
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    \143\ Randall, 2012. Memorandum from Randall, D., RTI 
International to Parsons, N., EPA/OAQPS. Survey of Control 
Technology for Storage Vessels and Analysis of Impacts for Storage 
Vessel Control Options. January 20, 2012. EPA Docket No. EPA-HQ-OAR-
2010-0871.
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7. Surge Control Vessels and Bottoms Receivers
    The HON and P&R I define a surge control vessel to mean feed drums, 
recycle drums, and intermediate vessels. Surge control vessels are used 
within a CMPU or an EPPU when in-process storage, mixing, or management 
of flow rates or volumes is needed to assist in production of a 
product. The HON and P&R I define a bottoms receiver as a tank that 
collects distillation bottoms before the stream is sent for storage or 
for further downstream processing. Surge control vessels and bottoms 
receivers are not considered storage vessels under the HON and P&R I 
because they are covered by the equipment leak provisions. Although 
these emissions sources are regulated under the equipment leak 
provisions (i.e., NESHAP subpart H), the equipment leak requirements 
point back to the storage vessel requirements in NESHAP subpart G. 
Owners and operators of surge

[[Page 25164]]

control vessels and bottoms receivers are required to comply with the 
HON storage vessel requirements in NESHAP subpart G (i.e., use a 
floating roof or route emissions to closed vent system and control to 
get 95 percent control) provided the surge control vessel or bottoms 
receiver meets certain capacity and vapor pressure requirements. For 
HON and P&R I surge control vessels and bottoms receivers at existing 
sources, storage vessel control requirements apply if the capacity is 
between 75 m\3\ and 151 m\3\ and the MTVP is greater than or equal to 
13.1 kPa, or the capacity is greater than or equal to 151 m\3\ and the 
MTVP is greater than or equal to 5.2 kPa. For HON and P&R I surge 
control vessels and bottoms receivers at new sources, storage vessel 
control requirements apply if the capacity is between 38 m\3\ and 151 
m\3\ and the MTVP is greater than or equal to 13.1 kPa, or the capacity 
is greater than or equal to 151 m\3\ and the MTVP is greater than or 
equal to 0.7 kPa. The HON and P&R I exclude all other surge control 
vessels and bottoms receivers from emissions control requirements.
    We are proposing at 40 CFR 63.170(b) (for HON) and 40 CFR 63.485(d) 
(for P&R I) that owners and operators of all surge control vessels and 
bottoms receivers that emit greater than or equal to 1.0 lb/hr of total 
organic HAP would be required to reduce emissions of organic HAP using 
a flare meeting the proposed operating and monitoring requirements for 
flares (see section III.D.1 of this preamble); or 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. These 
requirements are consistent with CAA section 112(d) controls and 
reflect the MACT floor.\144\ Emissions from surge control vessels and 
bottoms receivers are characteristic of process vents, not emissions 
from storage vessels. These vessels operate at process temperatures, 
not ambient storage temperatures; typically do not undergo level 
changes that larger storage vessels undergo; and are most often 
operated under pressure with and without non-condensable gases flowing 
into and out of them. The size of these vessels is also typically not 
correlated with emissions, as are storage vessels. We did not identify 
any additional options beyond those identified above (i.e., beyond-the-
floor options) for controlling emissions from surge control vessels and 
bottoms receivers. We solicit comment on the proposed revisions for 
surge control vessels and bottoms receivers.
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    \144\ They also represent the level of control found to be cost-
effective for process vents and that we are proposing for HON 
process vents under technology review in section III.C.3 of this 
preamble.
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8. Transfer Operations (for HON)
    Generally, transfer operations refer to the equipment (e.g., 
transfer racks) that are used to transfer materials (primarily liquid 
products) from the facility, typically from storage vessels, into 
transport vehicles, portable cargo units, and marine vessels that are 
used to carry the material to another site or location. The combination 
of the transfer rack, storage vessel, connecting piping, and equipment 
used/on the connecting piping are typically part of the process unit or 
affected source in existing regulations. The HON regulates transfer 
operations at 40 CFR 63.126 through 40 CFR 63.130. Transfer operations 
are defined in the HON at 40 CFR 63.101 to mean the loading, into a 
tank truck or railcar, of organic liquids that contain one or more of 
the organic HAP listed in table 2 to NESHAP subpart F from a transfer 
rack; and transfer operations do not include loading at an operating 
pressure greater than 204.9 kPa. Transfer racks are also defined in the 
HON at 40 CFR 63.101. Under the HON, transfer racks mean the collection 
of loading arms and loading hoses, at a single loading rack, that are 
assigned to a CMPU subject to NESHAP subpart F according to the 
procedures specified in 40 CFR 63.100(h) and are used to fill tank 
trucks and/or railcars with organic liquids that contain one or more of 
the organic HAP listed in table 2 to NESHAP subpart F. A transfer rack 
includes the associated pumps, meters, shutoff valves, relief valves, 
and other piping and valves, but does not include: (1) Racks, arms, or 
hoses that only transfer liquids containing organic HAP as impurities; 
(2) racks, arms, or hoses that vapor balance during all loading 
operations; or (3) racks transferring organic liquids that contain 
organic HAP only as impurities.
    In general, when the equipment and operations are physically 
separate (i.e., do not share common piping, valves, and other 
equipment), the transfer racks are considered separate transfer racks. 
Transfer rack emissions depend on several factors, including the 
physical and chemical characteristics of the liquid being loaded, the 
quantity of material loaded, and the loading conditions. Primarily, 
these characteristics boil down to the volatility (or vapor pressure) 
and molecular weight of the liquid being transferred, the temperature 
and pressure conditions of the transfer operation, the loading method 
employed (e.g., submerged loading versus splash loading), and the 
volume of material transferred. In addition, during the loading of 
liquid into transport vehicles, VOC and HAP vapors present in the 
transport vehicle are displaced by the liquid being loaded. The vapors 
in the transport vehicle include either vapors generated as the liquid 
is being loaded, and/or vapors remaining from residual commodity or 
liquid from the previous load (if present). For uncontrolled 
operations, transfer rack emissions typically occur at the loading 
hatch or opening of the transport vehicle. Emissions can also occur 
from leaks in the transport vehicle. The rate at which these VOC and 
HAP are emitted varies depending on which type of transport vehicle is 
being loaded (tank truck or railcar), whether the transport vehicle was 
empty before filling or refilled while still containing a heel and 
vapors, the physical and chemical characteristics of the liquid being 
loaded, and the type of loading method used.
    Owners and operators of each HON transfer rack that annually loads 
greater than or equal to 0.65 million liters of liquid products that 
contain organic HAP with a rack weighted average vapor pressure greater 
than or equal to 10.3 kPa are required to equip each transfer rack with 
a vapor collection system and control device to reduce total organic 
HAP emissions by 98 percent by weight or to an exit concentration of 20 
ppmv, whichever is less stringent. The HON also allows multiple other 
options to control emissions from applicable transfer racks, including: 
use of a flare, or collecting emissions for use in the process, a fuel 
gas system, or a vapor balance system. However, as previously 
mentioned, the HON excludes transfer racks with an operating pressure 
greater than 204.9 kPa from these requirements. While we recognize that 
these high operating pressure transfer racks are likely being 
controlled by owners and operators, the HON does not currently require 
them to be controlled on the presupposition that transfer racks with an 
operating pressure greater than 204.9 kPa do not leak emissions to the 
atmosphere. We consider the lack of control requirements for transfer 
racks with an operating pressure greater than 204.9 kPa to be a gap in 
the current HON. As such, we are proposing to remove the 204.9 kPa 
operating pressure exemption from the definition of transfer operations 
at 40 CFR 63.101 on the premise that, just like pressure vessels (as 
discussed in section III.D.6 of this preamble), these high operating 
pressure transfer racks can have

[[Page 25165]]

emissions to the atmosphere. Considering this, owners and operators 
would be required to equip each transfer rack with an operating 
pressure greater than 204.9 kPa with a vapor collection system and 
control device to reduce total organic HAP emissions by 98 percent by 
weight or to an exit concentration of 20 parts per million by volume, 
whichever is less stringent. These requirements are consistent with CAA 
section 112(d) controls and reflect the MACT floor, and we did not 
identify any additional options beyond this (i.e., beyond-the-floor 
options) for controlling emissions from these transfer racks.
    We anticipate that the proposed removal of the 204.9 kPa operating 
pressure exemption from the definition of transfer operations would not 
impose a cost increase because we believe that owners and operators are 
already controlling emissions from transfer racks with an operating 
pressure greater than 204.9 kPa. For example, as discussed in an EPA 
published document regarding sources of EtO,\145\ EtO is normally 
shipped in 38,000 and 76,000 liter (10,000 and 20,000 gallon) railroad 
tank cars, which are normally loaded directly from plant storage 
vessels. The transfer generally occurs at about 350 kPa. At most 
facilities, displaced vapors from the filling of tank cars and storage 
vessels are either recycled to the process or scrubbed prior to 
incineration or flaring. When the vapors are scrubbed, the liquid 
effluent from the scrubber is routed to the desorber for EtO recovery. 
Emissions of EtO from storage and loading are assumed to be nearly zero 
if either control approach is used. We solicit comment on the proposed 
removal of the 204.9 kPa operating pressure exemption from the 
definition of transfer operations and whether our assumption that these 
types of transfer racks are already being controlled is reasonable.
---------------------------------------------------------------------------

    \145\ EPA. Locating And Estimating Air Emissions From Sources Of 
Ethylene Oxide. September 1986. EPA-450/4-84-007L.
---------------------------------------------------------------------------

9. Heat Exchange Systems (for P&R II)
    P&R II currently does not regulate HAP emissions from heat exchange 
systems. However, as previously discussed in sections III.B.2.a.iii and 
III.C.1 of this preamble, the internal tubing material of a heat 
exchanger can corrode or crack, allowing some process fluids to mix or 
become entrained with the cooling water. Pollutants in the process 
fluids may subsequently be released from the cooling water into the 
atmosphere when the water is exposed to air (e.g., in a cooling tower 
for closed-loop systems or trenches/ponds in a once-through system). 
For this reason, we are proposing under CAA section 112(d)(2) and (3) 
to include in P&R II the same LDAR program for heat exchange systems as 
in the HON and P&R I, and we are proposing the same changes to this 
LDAR program for P&R II that we are proposing in this action for the 
HON and P&R I (see section III.C.1 of this preamble). Specifically, we 
are proposing at 40 CFR 63.522 to revise the definition of ``affected 
source'' to include heat exchange systems; and we are proposing the 
same definition of ``heat exchange systems'' for P&R II that is already 
used in the HON and P&R I to mean ``any cooling tower system or once-
through cooling water system (e.g., river or pond water). A heat 
exchange system can include more than one heat exchanger and can 
include an entire recirculating or once-through cooling system.''
    We reviewed publicly available air permits for the five facilities 
subject to either the BLR or WSR standards in P&R II and found that 
some of these facilities do have heat exchange systems. In reviewing 
air permits, three of the five facilities subject to P&R II are 
collocated with HON sources. Furthermore, we also anticipate that the 
heat exchange systems used at these sources are small (<10,000 gallons 
per minute) and would likely be sent to large, integrated cooling 
towers subject to other NESHAP, like the HON, that are already 
conducting water sampling at the cooling tower for leaks. Additionally, 
we expect that most water used by heat exchange systems in P&R II 
processes are likely from water jacketed reactors that either have 
large pressure differentials (i.e., >35 kPa) between the cooling water 
side and process side or have intervening cooling fluids between the 
process and cooling water such that leaks of HAP would not occur in 
heat exchange systems that would lead to air emissions. Given this, we 
assumed that adding requirements for heat exchange systems would 
already be accounted for in the HON or that heat exchange systems would 
not be required to conduct such monitoring at P&R II sources because 
they meet criteria that exempt heat exchange systems with no potential 
for air emissions from the LDAR requirements. Thus, conducting an LDAR 
program consistent with what is in the HON constitutes what the best 
performers are doing and is the MACT floor level of control for P&R II 
facilities. We note that even if a P&R II facility were to incur a cost 
to implement a LDAR program for a heat exchange system, we would expect 
this cost to be small (i.e., $4,300 in total capital investment and 
$4,500/yr in total annualized cost) per the costs for a single heat 
exchange system conducting El Paso monitoring and that this work 
practice standard would be cost-effective for P&R II sources as a 
beyond-the-floor control option. Thus, we are proposing that P&R II 
sources comply with the same standard as we are proposing for HON and 
P&R I heat exchange systems as part of our technology review (see 
section III.C.1 of this preamble). For further information, see the 
document titled Clean Air Act Section 112(d)(6) Technology Review for 
Heat Exchange Systems Located in the SOCMI Source Category that are 
Associated with Processes Subject to HON and for Heat Exchange Systems 
that are Associated with Processes Subject to Group I Polymers and 
Resins NESHAP; and Control Option Impacts for Heat Exchange Systems 
that are Associated with Processes Subject to Group II Polymers and 
Resins NESHAP, which is available in the docket for this rulemaking.
    We are proposing at 40 CFR 63.523(d) (for BLR manufacturers) and 40 
CFR 63.524(c) (for WSR manufacturers) that owners and operators of each 
affected source comply with the requirements of 40 CFR 63.104 for heat 
exchange systems, except we are proposing to require quarterly 
monitoring for existing and new heat exchange systems (after an initial 
6 months of monthly monitoring) using the Modified El Paso Method and a 
leak definition of 6.2 ppmv of total strippable hydrocarbon 
concentration (as methane) in the stripping gas. We are also proposing 
at 40 CFR 63.104(j)(3) a delay of repair action level of total 
strippable hydrocarbon concentration (as methane) in the stripping gas 
of 62 ppmv, that if exceeded during leak monitoring, would require 
immediate repair (i.e., the leak found cannot be put on delay of repair 
and would be required to be repaired within 30 days of the monitoring 
event). This would apply to both monitoring heat exchange systems and 
individual heat exchangers by replacing the use of any 40 CFR part 136 
water sampling method with the Modified El Paso Method and removing the 
option that allows for use of a surrogate indicator of leaks. We are 
also proposing at 40 CFR 63.104(h) and (i) re-monitoring at the 
monitoring location where a leak is identified to ensure that any leaks 
found are fixed. Finally, we are proposing that none of these proposed 
requirements would apply to heat exchange systems that have a maximum 
cooling water flow rate of 10 gallons per minute or less. We solicit

[[Page 25166]]

comment on the proposed standards for heat exchange systems for P&R II.
10. WSR Sources and Equipment Leaks (for P&R II)
    P&R II currently contains an alternative standard for WSR sources 
that establishes a regulatory gap in the rule at 40 CFR 63.524(a) and 
(b). The alternative standard allows owners and operators of WSR 
sources to choose between complying with a production-based emission 
limit for process vents, storage tanks, and wastewater systems, or the 
requirements of NESHAP subpart H to control emissions from equipment 
leaks. In other words, owners and operators of WSR sources are 
currently not required to control emissions from all of their P&R II 
emission sources.\146\ In the original proposed rulemaking, the EPA 
stated that: ``Because no existing facility in the WSR source category 
controls equipment leak emissions, the MACT floor for the equipment 
leaks portion of the source represents an uncontrolled situation.'' 
\147\ Instead, the EPA promulgated the alternative standard for WSR 
sources and said ``an alternative standard was specified that allows 
facilities to implement the requirements of subpart H to control 
emissions from equipment leaks. The alternative standard is much more 
cost effective, and will result in a greater overall HAP emission 
reduction. However, the alternative standard is not being required 
because the cost was considered to be too high to justify requiring 
more control than that achieved at the MACT floor. Section 112(d) of 
the Clean Air Act requires standards to be set at a level no less 
stringent than the MACT floor but requires consideration of the cost of 
achieving further reductions before requiring reductions beyond the 
MACT floor.'' \148\ We are proposing to address this regulatory gap by 
requiring owners and operators of existing, new, or reconstructed 
affected 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)). We are also proposing to remove several introductory phrases 
in P&R II that currently indicate the alternative standard is optional; 
and instead, we are proposing to replace these phrases with text that 
indicate the alternative standard is no longer optional, but required 
(see proposed 40 CFR 63.525(e) through (i), 40 CFR 63.526(b) and (d), 
and 40 CFR 63.527(b) through (d)). As previously mentioned, the EPA 
determined that no WSR source was originally complying with the 
requirements of NESHAP subpart H; instead, these WSR sources were 
originally complying with the production-based emission limit for 
process vents, storage tanks, and wastewater systems. However, a review 
of the publicly available permits for the two WSR sources indicates 
that they are currently complying with the equipment leak requirements 
of the HON; thus, we believe the requirements are consistent with CAA 
section 112(d) controls, reflect the MACT floor, and there are no 
additional costs from this change. We also did not identify any 
additional options beyond those identified above (i.e., beyond-the-
floor options) for reducing emissions from WSR sources. We solicit 
comment on our proposal to require owners and operators of existing, 
new, or reconstructed affected 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, and whether 
our assumption that the affected WSR sources are already complying with 
both standards is reasonable.
---------------------------------------------------------------------------

    \146\ This alternative standard is not an option for BLR 
sources; therefore, there is no regulatory gap in P&R II for BLR 
sources. Instead, owners and operators of BLR sources are subject to 
both a production-based emission limit for process vents, storage 
tanks, and wastewater systems, and the requirements of NESHAP 
subpart H to control emissions from equipment leaks (see 40 CFR 
63.523).
    \147\ See 59 FR 25387, May 16, 1994.
    \148\ See 60 FR 12670, March 8, 1995.
---------------------------------------------------------------------------

    In addition, the definition of equipment leaks in P&R II at 40 CFR 
63.522 excludes ``valves'' in the list of components; therefore, P&R II 
currently does not regulate HAP emissions from leaking valves. We 
believe this is a typographical error in P&R II and the EPA has always 
intended to include valves as part of the equipment leaks LDAR program 
requirements in P&R II. We note that in the original P&R II proposal 
(see 59 FR 25387, May 16, 1994), the EPA referred to equipment leak 
emission points using a phrase implying valve inclusivity (i.e., ``such 
as pumps and valves''). Additionally, the BLR and WSR model plants used 
to assess impacts of implementing the LDAR requirements in P&R II 
included valve component counts; \149\ and no adverse comment was 
received on this topic between proposal and final rulemaking for P&R 
II. As previously mentioned, emissions of HAP from equipment leaks 
occur in the form of gases or liquids that escape to the atmosphere 
through many types of connection points (including valves). For this 
reason, we are proposing under CAA section 112(d)(2) and (3) to include 
valves in the definition of ``equipment leaks'' at 40 CFR 63.522 such 
that owners and operators of an existing, new, or reconstructed 
affected BLR or WSR source would be required to comply with the same 
LDAR program that already exists in the HON and P&R I for valves that 
contain or contact material that is 5 percent by weight or more of 
organic HAP, operate 300 hours per year or more, and are not in vacuum 
service. Specifically, our proposal would require owners or operators 
to meet the control requirements for valves in NESHAP subpart H (see 
section III.C.6.a of this preamble for a more detailed description of 
the MACT standard for equipment leaks). A review of the publicly 
available permits for P&R II sources indicates that P&R II facilities 
are already complying with the equipment leak requirements of the HON 
(which include LDAR requirements for valves), so we believe there are 
no additional cost or emissions reduction from this proposed 
typographical correction. We solicit comment on the proposed revisions 
for equipment leaks from WSR sources in P&R II.
---------------------------------------------------------------------------

    \149\ See Appendix G of the document titled Hazardous Air 
Pollutants From Epoxy Resins And Non-nylon Polyamide Resins 
Production (Docket ID A-92-37, Item II-A-008).
---------------------------------------------------------------------------

E. What other actions are we proposing, and what is the rationale for 
those actions?

    In addition to the proposed actions on the CAA 111(b)(1)(B) and 
112(d)(6) reviews discussed in section III.A of this preamble, we are 
proposing to remove exemptions in the HON, P&R I, and P&R II from the 
requirement to comply during periods of SSM; similarly, we are 
proposing standards in NSPS subparts VVb, IIIa, NNNa, and RRRa that 
apply at all times. We are also proposing to remove the affirmative 
defense provisions from P&R I that were adopted in 2011. In addition, 
we are proposing changes to the HON, P&R I, and P&R II recordkeeping 
and reporting requirements to require the use of electronic reporting 
of performance test reports and periodic reports; and we are proposing 
similar standards in NSPS subparts VVb, IIIa, NNNa, and RRRa. We are 
also proposing in the HON, P&R I, and P&R II to correct section 
reference errors and make other minor editorial revisions. Finally, in 
response to a petition for reconsideration, we are proposing to amend 
NSPS subpart VVa; and although not part of the petition for 
reconsideration, we are also proposing to clarify (in NSPS subpart VVa) 
the

[[Page 25167]]

calibration drift assessment and correct the incorporations by 
reference. Our rationale and proposed changes related to all of these 
issues are discussed below.
1. SSM
    In its 2008 decision in Sierra Club v. EPA, 551 F.3d 1019 (D.C. 
Cir. 2008), the United States Court of Appeals for the District of 
Columbia Circuit (the court) vacated portions of two provisions in the 
EPA's CAA section 112 regulations governing the emissions of HAP during 
periods of SSM. Specifically, the court vacated the SSM exemption 
contained in 40 CFR 63.6(f)(1) and 40 CFR 63.6(h)(1), holding that 
under section 302(k) of the CAA, emissions standards or limitations 
must be continuous in nature and that the SSM exemption violates the 
CAA's requirement that some section 112 standards apply continuously. 
With the issuance of the mandate in Sierra Club v. EPA, the exemption 
language in 63.6(f)(1) and (h)(1) are null and void and any cross 
reference to those provisions have no effect.
    In March 2021, the EPA issued a rule \150\ to reflect the court 
vacatur that revised the Part 63 General Provisions to remove the SSM 
exemptions at 40 CFR 63.6(f)(1) and (h)(1). In this action, we are 
proposing to eliminate references in the HON, P&R I, and P&R II to 
these SSM exemptions in the General Provisions that are null and void 
and are no longer printed in the CFR, remove any additional SSM 
exemptions or references to SSM exemptions in the HON, P&R I, and P&R 
II, and remove any cross-references in the HON, P&R I, and P&R II to 
provisions in 40 CFR part 63 (General Provisions) that are unnecessary, 
inappropriate or redundant in the absence of the SSM exemption.\151\ 
See section III.E.1.a of this preamble for our proposed amendments to 
the HON, P&R I, and P&R II related to the SSM exemptions. The EPA has 
attempted to ensure that the general provisions we are proposing to 
override are inappropriate, unnecessary, or redundant in the absence of 
the SSM exemption. We specifically seek comment on whether we have 
successfully done so.
---------------------------------------------------------------------------

    \150\ U.S. EPA, Court Vacatur of Exemption From Emission 
Standards During Periods of Startup, Shutdown, and Malfunction. (86 
FR 13819, March 11, 2021).
    \151\ We note that on April 21, 2011 (see 77 FR 22566), the EPA 
finalized amendments to eliminate the SSM exemption in P&R I; 
however, for consistency with the SSM related amendments that we are 
proposing for the HON and P&R II, we are also proposing (as detailed 
in this section of this preamble) additional amendments to P&R I 
related to the SSM exemption that were not addressed in the April 
21, 2011, P&R I rule.
---------------------------------------------------------------------------

    Additionally, the EPA has determined the reasoning in the court's 
decision in Sierra Club applies equally to CAA section 111 because the 
definition of emission or standard in CAA section 302(k), and the 
embedded requirement for continuous standards, also applies to the 
NSPS.\152\ Therefore, we are proposing standards in NSPS subparts VVb, 
IIIa, NNNa, and RRRa that apply at all times, and more specifically 
during periods of SSM, to match the proposed revised SSM provisions in 
the HON, P&R I, and P&R II. The NSPS general provisions in 40 CFR 
60.8(c) currently exempt non-opacity emission standards during periods 
of SSM. We are proposing in NSPS subparts VVb, IIIa, NNNa, and RRRa 
specific requirements \153\ that override the general provisions for 
SSM. See section E.1.b of this preamble for our proposed standards 
related to the SSM exemptions for NSPS subparts VVb, IIIa, NNNa, and 
RRRa.
---------------------------------------------------------------------------

    \152\ See, e.g., 88 FR 11556 (Feb. 23, 2023) (removing SSM 
exemptions from NSPS for lead acid battery manufacturing plants); 87 
FR 73708 (Dec. 1, 2022) (proposing to remove SSM exemptions from 
NSPS for secondary lead smelters); 77 FR 49490 (Aug. 16, 2012) 
(removing SSM exemptions from NSPS for oil and natural gas sector).
    \153\ See proposed 40 CFR 60.482-1b, 40 CFR 60.612a, 40 CFR 
60.662a, and 40 CFR 60.702a, respectively.
---------------------------------------------------------------------------

a. Proposed Elimination of the SSM Exemption in the HON, P&R I, and P&R 
II
    We are proposing the elimination of the vacated exemption provision 
and several revisions to Table 3 to subpart F of part 63 (the General 
Provisions Applicability Table to subparts F, G, and H of 40 CFR part 
63, hereafter referred to as the ``General Provisions table to HON''), 
Table 1 to subpart U of part 63 (the General Provisions Applicability 
Table to subpart U of 40 CFR part 63, hereafter referred to as the 
``General Provisions table to P&R I''), and Table 1 to subpart W of 
part 63 (the General Provisions Applicability Table to subpart W of 40 
CFR part 63, hereafter referred to as the ``General Provisions table to 
P&R II'') as is explained in more detail below. For example, we are 
proposing to eliminate the incorporation of the General Provisions' 
requirement that the source develop an SSM plan. We also are proposing 
to eliminate and revise certain recordkeeping and reporting 
requirements related to the SSM exemption. The EPA has attempted to 
ensure that the provisions we are proposing to eliminate are 
inappropriate, unnecessary, or redundant in the absence of the SSM 
exemption.
    For the HON and P&R II, we are proposing (as already required in 
P&R I at 40 CFR 63.480(j)) that emissions from startup and shutdown 
activities be included when determining if all the standards are being 
met. As currently proposed in 40 CFR 63.102(e) and 40 CFR.525(j), 
compliance with the emission limitations (including operating limits) 
in the HON and P&R II is required ``at all times.'' We solicit comment 
on whether owners and operators of affected sources subject to the HON 
or P&R II will be able to comply with the standards during these times. 
We also note that we are proposing standards for maintenance activities 
that occur during periods of startup and shutdown (see section III.D.4 
of this preamble). Emission reductions for storage vessel, process 
vent, transfer rack, and wastewater operations (as well as other 
emission sources) are typically achieved by routing vapors to an APCD 
such as a flare, thermal oxidizer, or carbon adsorber. It is common 
practice in this source category to start an APCD prior to startup of 
the emissions source it is controlling, so the APCD would be operating 
before emissions are routed to it. We expect APCDs would be operating 
during startup and shutdown events in a manner consistent with normal 
operating periods, and that these APCDs will be operated to maintain 
and meet the monitoring parameter operating limits set during the 
performance test.
    Periods of startup, normal operations, and shutdown are all 
predictable and routine aspects of a source's operations. Malfunctions, 
in contrast, are neither predictable nor routine. Instead, they are, by 
definition, sudden, infrequent, and not reasonably preventable failures 
of emissions control, process, or monitoring equipment. (40 CFR 60.2 
and 40 CFR 63.2) (definition of ``malfunction''). The EPA interprets 
CAA section 112 as not requiring emissions that occur during periods of 
malfunction to be factored into development of CAA section 112 
standards and this reading has been upheld as reasonable by the D.C. 
Circuit in U.S. Sugar Corp. v. EPA, 830 F.3d 579, 606-610 (2016). 
Therefore, the standards that apply during normal operation apply 
during periods of malfunction.
    Although no statutory language compels the EPA to set standards for 
malfunctions, the EPA has the discretion to do so where feasible. For 
example, in the Petroleum Refinery Sector RTR, the EMACT standards, and

[[Page 25168]]

the MON, the EPA established a work practice standard for unique types 
of malfunction that result in releases from PRDs or emergency flaring 
events because the EPA had information to determine that such work 
practices reflected the level of control that applies to the best 
performers (see 80 FR 75178, December 1, 2015, 85 FR 40386, July 6, 
2020, and 85 FR 49084, August 12, 2020, respectively). The EPA will 
consider whether circumstances warrant setting standards for a 
particular type of malfunction in the SOCMI, P&R I, and P&R II source 
categories, and, if so, whether the EPA has sufficient information to 
identify the relevant best performing sources and establish a standard 
for such malfunctions. We also encourage commenters to provide any such 
information. These are discussed further in section III.D.1 and III.D.2 
of this preamble.
    We are also proposing the following revisions to the General 
Provisions table to HON, the General Provisions table to P&R I, and the 
General Provisions table to P&R II as detailed below.
i. General Duty
    We are proposing to revise the General Provisions table to the HON 
entry for 40 CFR 63.6(e) by adding a footnote to the ``yes'' entry in 
column 2 to clarify that the row for the ``63.6(e)'' entry would no 
longer be applicable beginning 3 years after publication of the final 
rule in the Federal Register because the General Provisions table to 
HON already contains other entries that breakdown the specific 
paragraphs of 63.6(e) that are applicable to the HON. Some of the 
language in section 63.6(e) is no longer necessary or appropriate in 
light of the elimination of the SSM exemption. Section 63.6(e)(1)(i) 
describes the general duty to minimize emissions and section 63.6(e)(3) 
describes requirements for an SSM plan. We are proposing instead to add 
general duty regulatory text at 40 CFR 63.102(f) (for HON) and 40 CFR 
63.525(k) (for P&R II) that reflects the general duty to minimize 
emissions while eliminating the reference to periods covered by an SSM 
exemption. The current language in 40 CFR 63.6(e)(1)(i) characterizes 
what the general duty entails during periods of SSM. With the 
elimination of the SSM exemption, there is no need to differentiate 
between normal operations, startup and shutdown, and malfunction events 
in describing the general duty. We are also proposing to revise the 
General Provisions table to P&R II entry for 40 CFR 63.6(e)(1)(i) by 
adding a separate row for 40 CFR 63.6(e)(1)(i) and changing the ``yes'' 
in columns 2, 3, and 4 to a ``no'' in which 40 CFR 63.6(e)(1)(i) would 
no longer be applicable beginning 3 years after publication of the 
final rule in the Federal Register. Section 63.6(e)(1)(i) imposes 
requirements that are not necessary with the elimination of the SSM 
exemption or are redundant with the general duty requirement being 
added at 40 CFR 63.102(f) and 40 CFR 63.525(k). Therefore, the language 
the EPA is proposing for 40 CFR 63.102(f) and 40 CFR 63.525(k) does not 
include the language from 40 CFR 63.6(e)(1). We note that the EPA 
already added a similar general duty provision to P&R I at 40 CFR 
63.483(a) (see 77 FR 22566, April 21, 2011); however, we are proposing 
to correct a referencing error in the General Provisions table to P&R I 
entry for 40 CFR 63.6(e)(1)(i) by changing ``Sec.  63.483(a)(1)'' to 
``Sec.  63.483(a)''. We are also proposing revisions at 40 CFR 
63.483(a) to be consistent with the general duty requirement we are 
proposing to add to 40 CFR 63.102(f) and 40 CFR 63.525(k).We are also 
proposing to revise the General Provisions table to HON entry for 40 
CFR 63.6(e)(1)(ii) by changing the ``yes'' in column 2 to a ``no'' in 
which 40 CFR 63.6(e)(1)(ii) would no longer be applicable beginning 3 
years after publication of the final rule in the Federal Register. We 
are proposing similar revisions for the General Provisions table to P&R 
II by adding a separate row for 40 CFR 63.6(e)(1)(ii) and changing the 
``yes'' in columns 2, 3, and 4 to a ``no'' in which 40 CFR 
63.6(e)(1)(ii) would no longer be applicable beginning 3 years after 
publication of the final rule in the Federal Register. We note that the 
EPA already made a similar revision to the General Provisions table to 
P&R I (see 77 FR 22566, April 21, 2011).
ii. SSM Plan
    As noted in the previous paragraph, the proposed revisions to the 
General Provisions table to the HON and the General Provisions table to 
P&R II for 40 CFR 63.6(e) will also remove provisions that require an 
SSM plan. We are proposing to revise the General Provisions table to 
HON entries for 40 CFR 63.6(e)(3)(i), 63.6(e)(3)(i)(B), (C), 
63.6(e)(3)(ii) and (vi) through (ix) by changing the ``yes'' in column 
2 to a ``no'' in which these provisions would no longer be applicable 
beginning 3 years after publication of the final rule in the Federal 
Register. We are proposing similar revisions for the General Provisions 
table to P&R II by adding a separate row for 40 CFR 63.6(e)(3) and 
changing the ``yes'' in columns 2, 3, and 4 to a ``no'' in which 40 CFR 
63.6(e)(3) would no longer be applicable beginning 3 years after 
publication of the final rule in the Federal Register. We note that the 
EPA already made a similar revision to the General Provisions table to 
P&R I (see 77 FR 22566, April 21, 2011). Generally, the paragraphs 
under 40 CFR 63.6(e)(3) require development of an SSM plan and specify 
SSM recordkeeping and reporting requirements related to the SSM plan. 
As noted, the EPA is proposing to remove the SSM exemptions. Therefore, 
affected units are subject to an emission standard during such events. 
The applicability of a standard during such events will ensure that 
sources have ample incentive to plan for and achieve compliance and 
thus the SSM plan requirements are no longer necessary.
iii. Compliance With Standards
    We are proposing to clarify the comment in the General Provisions 
table to HON entry for 40 CFR 63.6(f)(1) to include a reference to the 
new proposed general duty requirements at 40 CFR 63.102(e). We are also 
proposing to add a separate row for 40 CFR 63.7(a)(4) to the General 
Provisions tables to the HON, P&R I, and P&R II to make 40 CFR 
63.7(a)(4) applicable to each of these NESHAP for when an owner or 
operator intends to assert a claim of force majeure.
iv. Performance Testing
    We are proposing to revise the General Provisions table to HON 
entry for 40 CFR 63.7(e)(1) by changing the ``yes'' in column 2 to a 
``no'' in which 40 CFR 63.7(e)(1) would no longer be applicable 
beginning 3 years after publication of the final rule in the Federal 
Register. Section 63.7(e)(1) describes performance testing 
requirements. We are proposing a similar revision to the General 
Provisions table to P&R II entry for 40 CFR 63.7(e)(1) by changing the 
``yes'' in columns 2, 3, and 4 to a ``no'' in which 40 CFR 63.7(e)(1) 
would no longer be applicable beginning 3 years after publication of 
the final rule in the Federal Register. We note that the EPA already 
made a similar revision to the General Provisions table to P&R I (see 
77 FR 22566, April 21, 2011). The EPA is instead proposing to add a 
performance testing requirement at 40 CFR 63.103(b)(3)(ii) (for HON), 
40 CFR 63.504(a)(1)(iii) (for P&R I), and 40 CFR 63.525(l) (for P&R 
II). The performance testing requirements we are proposing differ from 
the General Provisions performance testing provisions in several 
respects. The regulatory text does not include the language in 40 CFR 
63.7(e)(1) that restated the SSM

[[Page 25169]]

exemption and language that precluded startup and shutdown periods from 
being considered ``representative'' for purposes of performance 
testing. The proposed performance testing provisions will exclude 
periods of startup or shutdown as representative conditions for 
conducting performance testing. As in 40 CFR 63.7(e)(1), performance 
tests conducted under this subpart should not be conducted during 
malfunctions because conditions during malfunctions are often not 
representative of normal operating conditions. The EPA is proposing to 
add language that requires the owner or operator to record the process 
information that is necessary to document operating conditions during 
the test and include in such record an explanation to support that such 
conditions represent normal operation. Section 63.7(e)(1) requires that 
the owner or operator make such records ``as may be necessary to 
determine the condition of the performance test'' available to the 
Administrator upon request but does not specifically require the 
information to be recorded. The regulatory text the EPA is proposing to 
add to this provision builds on that requirement and makes explicit the 
requirement to record the information.
v. Monitoring
    We are proposing to revise the General Provisions tables to the HON 
and P&R I entries for 40 CFR 63.8(c)(1)(i) and (iii) by changing the 
``yes'' in column 2 to a ``no'' in which 40 CFR 63.8(c)(1)(i) and (iii) 
would no longer be applicable beginning 3 years after publication of 
the final rule in the Federal Register. We are proposing similar 
revisions for the General Provisions table to P&R II entries for 40 CFR 
63.8(c)(1)(i) and (iii) by changing the ``yes'' in columns 2, 3, and 4 
to a ``no'' in which 40 CFR 63.8(c)(1)(i) and (iii) would no longer be 
applicable beginning 3 years after publication of the final rule in the 
Federal Register. The cross-references to the general duty and SSM plan 
requirements in those subparagraphs are not necessary in light of other 
requirements of 40 CFR 63.8 that require good air pollution control 
practices (40 CFR 63.8(c)(1)).
vi. Reporting
    We are proposing to revise the General Provisions table to the HON 
entry for 40 CFR 63.10(d)(5) by changing the ``yes'' in column 2 to a 
``no'' in which 40 CFR 63.10(d)(5) would no longer be applicable 
beginning 3 years after publication of the final rule in the Federal 
Register. We are proposing similar revisions for the General Provisions 
table to P&R II entry for 40 CFR 63.10(d)(5) by changing the ``yes'' in 
columns 2, 3, and 4 to a ``no'' in which 40 CFR 63.10(d)(5) would no 
longer be applicable beginning 3 years after publication of the final 
rule in the Federal Register. We note that the EPA already made a 
similar revision to the General Provisions table to P&R I (see 77 FR 
22566, April 21, 2011). Section 63.10(d)(5) describes the reporting 
requirements for SSM. To replace the General Provisions reporting 
requirement, the EPA is proposing to add reporting requirements to 40 
CFR 63.152(c)(2)(ii)(F) (for HON), 40 CFR 63.506(e)(6)(iii)(C) (for P&R 
I), and 40 CFR 63.528(a)(4) (for P&R II). The replacement language 
differs from the General Provisions requirement in that it eliminates 
periodic SSM reports as a stand-alone report. We are proposing language 
that requires sources that fail to meet an applicable standard at any 
time to report the information concerning such events in the periodic 
report already required under the HON, P&R I, and P&R II. We are 
proposing that the report must contain the cause of such events 
(including unknown cause, if applicable), a list of the affected source 
or equipment, an estimate of the quantity of each regulated pollutant 
emitted over any emission limit, and a description of the method used 
to estimate the emissions. Examples of such methods would include 
product-loss calculations, mass balance calculations, measurements when 
available, or engineering judgment based on known process parameters. 
The EPA is proposing this requirement to ensure that there is adequate 
information to determine compliance, to allow the EPA to determine the 
severity of the failure to meet an applicable standard, and to provide 
data that may document how the source met the general duty to minimize 
emissions during a failure to meet an applicable standard.
    We will no longer require owners or operators to determine whether 
actions taken to correct a malfunction are consistent with an SSM plan, 
because plans would no longer be required. The proposed amendments at 
63.10(d)(5), therefore, eliminate the cross-reference to 40 CFR 
63.10(d)(5)(i) that contains the description of the previously required 
SSM report format and submittal schedule from this section. These 
specifications are no longer necessary because the events will be 
reported in otherwise required reports with similar format and 
submittal requirements.
    The proposed amendments at 63.10(d)(5) will also eliminate the 
cross-reference to 40 CFR 63.10(d)(5)(ii). Section 63.10(d)(5)(ii) 
describes an immediate report for startups, shutdown, and malfunctions 
when a source failed to meet an applicable standard but did not follow 
the SSM plan. We will no longer require owners or operators to report 
when actions taken during a startup, shutdown, or malfunction were not 
consistent with an SSM plan, because plans would no longer be required.
b. Proposal of NSPS Subparts VVb, IIIa, NNNa, and RRRa Without SSM 
Exemptions
    We are proposing standards in the NSPS subparts VVb, IIIa, NNNa, 
and RRRa that apply at all times. For NSPS VVb, we are proposing that 
the work practice standards will apply at all times, including during 
SSM. For NSPS subparts IIIa, NNNa, and RRRa, these standards include 
the performance standards when the affected facilities are operational 
and work practice standards that will apply during periods of startup 
and shutdown (including when maintenance and inspection activities are 
being conducted). The NSPS general provisions in 40 CFR 60.8(c) contain 
an exemption from non-opacity standards. Therefore, we are also 
proposing in NSPS subparts VVb, IIIa, NNNa, and RRRa specific 
requirements at 40 CFR 60.482-1b, 40 CFR 60.612a, 40 CFR 60.662a, and 
40 CFR 60.702a, respectively that override the general provisions for 
SSM. Accordingly, our proposed NSPS subparts VVb, IIIa, NNNa, and RRRa 
would include standards that apply at all times, including during 
periods of startup and shutdown.
    Periods of startup, normal operations, and shutdown are all 
predictable and routine aspects of a source's operations. Malfunctions, 
in contrast, are neither predictable nor routine. Instead they are, by 
definition, sudden, infrequent, and not reasonably preventable failures 
of emissions control, process, or monitoring equipment. (40 CFR 60.2). 
The EPA interprets CAA section 111 as not requiring emissions that 
occur during periods of malfunction to be factored into development of 
CAA section 111 standards. Nothing in CAA section 111 or in case law 
requires that the EPA consider malfunctions when determining what 
standards of performance reflect the degree of emission limitation 
``achievable through the application of the best system of emission 
reduction'' that the EPA determines is adequately demonstrated. While 
the EPA accounts for variability in setting emissions standards, the 
EPA is not required to treat a malfunction in

[[Page 25170]]

the same manner as the type of variation in performance that occurs 
during routine operations of a source. A malfunction is a failure of 
the source to perform in a ``normal or usual manner'' (40 CFR 60.2), 
and no statutory language compels the EPA to consider such events in 
setting section 111 standards of performance. The EPA's approach to 
malfunctions when interpreting analogous language under CAA section 112 
has been upheld as reasonable by the D.C. Circuit in U.S. Sugar Corp. 
v. EPA, 830 F.3d 579, 606-610 (D.C. Cir. 2016) (affirming as reasonable 
the EPA's approach to setting ``achievable'' standards under section 
112 as measured by the ``best controlled similar source'' without 
considering malfunctions, instead accounting for them in its 
enforcement discretion).
    Also, as previously discussed, although no statutory language 
compels the EPA to set standards for malfunctions, the EPA has the 
discretion to do so where feasible. The EPA is proposing to establish 
work practice standards for unique types of malfunction that result in 
releases from emergency flaring events because the EPA had information 
to determine that such work practices reflected the level of control 
that applies to the BSER. The EPA will consider whether circumstances 
warrant setting standards for a particular type of malfunction in the 
SOCMI NSPS rules, and, if so, whether the EPA has sufficient 
information to identify the relevant best performing sources and 
establish a standard for such malfunctions. We also encourage 
commenters to provide any such information. These are discussed further 
in sections III.D.1, III.C.3.b, and III.C.6.b of this preamble.
2. Affirmative Defense (Related to P&R I)
    As part of one of the P&R I RTR rulemakings (see 77 FR 22566, April 
21, 2011), the EPA included the ability to assert an affirmative 
defense to civil penalties for violations caused by malfunctions (see 
40 CFR 63.480(j)(4)) in an effort to create a system that incorporated 
some flexibility, recognizing that there is a tension, inherent in many 
types of air regulation, to ensure adequate compliance while 
simultaneously recognizing that despite the most diligent of efforts, 
emission standards may be violated under circumstances entirely beyond 
the control of the source.\154\ Although the EPA recognized that its 
case-by-case enforcement discretion provides sufficient flexibility in 
these circumstances, it included the affirmative defense provision to 
provide a more formalized approach and more regulatory clarity. See 
Weyerhaeuser Co. v. Costle, 590 F.2d 1011, 1057-58 (D.C. Cir. 1978) 
(holding that an informal case-by-case enforcement discretion approach 
is adequate); but see Marathon Oil Co. v. EPA, 564 F.2d 1253, 1272-73 
(9th Cir. 1977) (requiring a more formalized approach to consideration 
of ``upsets beyond the control of the permit holder.''). Under the 
EPA's regulatory affirmative defense provisions, if a source could 
demonstrate in a judicial or administrative proceeding that it had met 
the requirements of the affirmative defense in the regulation, civil 
penalties would not be assessed. However, the court vacated the 
affirmative defense in one of the EPA's CAA section 112 regulations. 
NRDC v. EPA, 749 F.3d 1055 (D.C. Cir., 2014) (vacating affirmative 
defense provisions in the CAA section 112 rule establishing emission 
standards for Portland cement kilns). The court found that the EPA 
lacked authority to establish an affirmative defense for private civil 
suits and held that under the CAA, the authority to determine civil 
penalty amounts in such cases lies exclusively with the courts, not the 
EPA. Specifically, the court found: ``As the language of the statute 
makes clear, the courts determine, on a case-by-case basis, whether 
civil penalties are `appropriate.''' See NRDC, 749 F.3d at 1063 
(``[U]nder this statute, deciding whether penalties are `appropriate' 
in a given private civil suit is a job for the courts, not 
EPA.'').\155\ In light of NRDC, the EPA is proposing to remove all of 
the regulatory affirmative defense provisions from P&R I at 40 CFR 
480(j)(4) in its entirety and all other rule text that references these 
provisions (i.e., the reference to ``Sec.  63.480(j)(4)'' in 40 CFR 
63.506(b)(1)(i)(A) and (b)(1)(i)(B)). As explained above, if a source 
is unable to comply with emissions standards as a result of a 
malfunction, the EPA may use its case-by-case enforcement discretion to 
provide flexibility, as appropriate. Further, as the court recognized, 
in an EPA or citizen enforcement action, the court has the discretion 
to consider any defense raised and determine whether penalties are 
appropriate. Cf. NRDC, 749 F.3d at 1064 (arguments that violation was 
caused by unavoidable technology failure can be made to the courts in 
future civil cases when the issue arises). The same is true for the 
presiding officer in EPA administrative enforcement actions.\156\
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    \154\ We note that the HON and P&R II do not include affirmative 
defense rule text.
    \155\ The court's reasoning in NRDC focuses on civil judicial 
actions. The court noted that ``EPA's ability to determine whether 
penalties should be assessed for CAA violations extends only to 
administrative penalties, not to civil penalties imposed by a 
court.'' Id.
    \156\ Although the NRDC case does not address the EPA's 
authority to establish an affirmative defense to penalties that are 
available in administrative enforcement actions, we are not 
including such an affirmative defense in the proposed rule. As 
explained above, such an affirmative defense is not necessary. 
Moreover, assessment of penalties for violations caused by 
malfunctions in administrative proceedings and judicial proceedings 
should be consistent. Cf. CAA section 113(e) (requiring both the 
Administrator and the court to take specified criteria into account 
when assessing penalties).
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3. Electronic Reporting
    The EPA is proposing that owners and operators of SOCMI processes 
located at chemical plants submit electronic copies of required 
performance test reports, flare management plans, and periodic reports 
(including fenceline monitoring reports) through the EPA's Central Data 
Exchange (CDX) using the Compliance and Emissions Data Reporting 
Interface (CEDRI) (see proposed 40 CFR 63.108(e), 40 CFR 63.152(c) and 
(h), and 40 CFR 63.182(d) and (e) (for HON), 40 CFR 63.506(e)(6), and 
(i)(3) (for P&R I), and 40 CFR 63.528(a) and (d) (for P&R II), 40 CFR 
60.486(l), and 60.487(a) and (g) through (i) (for NSPS subpart VV), 40 
CFR 60.486a(l), and 60.487a(a) and (g) through (i) (for NSPS subpart 
VVa), 40 CFR 60.486b(l), and 60.487b(a) and (g) through (i) (for NSPS 
subpart VVb), 40 CFR 60.615(b), (j), (k), and (m) through (o) (for NSPS 
subpart III), 40 CFR 60.615a(b), (h) through (l), and (n), and 40 CFR 
619a(e) (for NSPS subpart IIIa), 40 CFR 60.665(b), (l), (m), and (q) 
through (s) (for NSPS subpart NNN), 40 CFR 60.665a(b), (h), (k) through 
(n), and (p), and 40 CFR 669a(e) (for NSPS subpart NNNa), 40 CFR 
60.705(b), (l), (m), and (u) through (w) (for NSPS subpart RRR), and 40 
CFR 60.705a(b), (k) through (o), and (v), and 40 CFR 709a(e) (for NSPS 
subpart RRRa)). We note that for NSPS VV, VVa, III, NNN, and RRR, we 
are only proposing to change the format of the reporting requirements 
to require electronic reporting (i.e., we are not proposing any new 
data elements). A description of the electronic data submission process 
is provided in the document titled Electronic Reporting Requirements 
for New Source Performance Standards (NSPS) and National Emission 
Standards for Hazardous Air Pollutants (NESHAP) Rules, available in the 
docket for this action.
    The proposed rules require that performance test results collected 
using test methods that are supported by the

[[Page 25171]]

EPA's Electronic Reporting Tool (ERT) as listed on the ERT website 
\157\ at the time of the test be submitted in the format generated 
through the use of the ERT or an electronic file consistent with the 
xml schema on the ERT website, and other performance test results be 
submitted in portable document format (PDF) using the attachment module 
of the ERT. Flare management plans would be uploaded as a PDF file.
---------------------------------------------------------------------------

    \157\ https://www.epa.gov/electronic-reporting-air-emissions/electronic-reporting-tool-ert.
---------------------------------------------------------------------------

    For periodic reports (including fenceline monitoring reports), the 
proposed rules require that owners and operators use an appropriate 
spreadsheet template to submit information to CEDRI. A draft version of 
the proposed templates for these reports is included in the docket for 
this action.\158\ The EPA specifically requests comment on the content, 
layout, and overall design of the templates. For NSPS subpart VV, VVa, 
III, NNN, and RRR, we are proposing owners and operators begin using 
the templates one year after the final rule is published in the Federal 
Register or once the reporting template for the subpart has been 
available on the CEDRI website for 1 year, whichever date is later. For 
NSPS subparts VVb, IIIa, NNNa, and RRRa, we are proposing owners and 
operators begin using the templates 60 days after the final rule is 
published in the Federal Register or once the reporting template for 
the subpart has been available on the CEDRI website for 1 year, 
whichever date is later. For HON, P&R I, and P&R II, we are proposing 
owners and operators begin using the templates for periodic reports 
other than fenceline reports three years after the final rule is 
published in the Federal Register, or once the reporting template for 
the subpart has been available on the CEDRI website for 1 year, 
whichever date is later. Owners and operators would begin using the 
templates for fenceline monitoring reports starting when the first 
fenceline monitoring report is due.
---------------------------------------------------------------------------

    \158\ See Part_60_Subpart_VV_60.487(a)_Semiannual_Report.xlsx, 
Part_60_Subpart_III_60.615_Semiannual_Report.xlsx, 
Part_60_Subpart_NNN_60.665_Report.xlsx, 
Part_60_Subpart_RRR_60.705_Report.xlsx, 
Part_63_Subpart_G_63.152(c)_Periodic_Report.xlsx, 
Part_63_Subpart_H_63.182(d)_Periodic_Report.xlsx, 
Part_63_Subpart_H_63.182(e)_Fenceline_Quarterly_Report.xlsx, 
Part_63_Subpart_U_63.506(e)(6)_Periodic_Report.xlsx, and 
Part_63_Subpart_W_63.528(a)_Periodic_Report.xlsx, available in the 
docket for this action.
---------------------------------------------------------------------------

    Additionally, the EPA has identified two broad circumstances in 
which electronic reporting extensions may be provided. These 
circumstances are: (1) Outages of the EPA's CDX or CEDRI which preclude 
an owner or operator from accessing the system and submitting required 
reports and (2) force majeure events, which are defined as events that 
will be or have been caused by circumstances beyond the control of the 
affected facility, its contractors, or any entity controlled by the 
affected facility that prevent an owner or operator from complying with 
the requirement to submit a report electronically. Examples of force 
majeure events are acts of nature, acts of war or terrorism, or 
equipment failure or safety hazards beyond the control of the facility. 
The EPA is providing these potential extensions in NSPS subparts VVb, 
IIIa, NNNa, and RRRa (see proposed 40 CFR 60.487b (h) and (i), 40 CFR 
60.615a (j) and (k), 40 CFR 60.665a(l) and (m), and 40 CFR 60.705(m) 
and (n), respectively) to protect owners and operators from 
noncompliance in cases where they cannot successfully submit a report 
by the reporting deadline for reasons outside of their control. In both 
circumstances, the decision to accept the claim of needing additional 
time to report is within the discretion of the Administrator, and 
reporting should occur as soon as possible. These potential extensions 
are not necessary to add to the HON, P&R I, and P&R II because they 
were recently added to 40 CFR part 63, subpart A, General Provisions at 
40 CFR 63.9(k).
    The electronic submittal of the reports addressed in these proposed 
rulemakings will increase the usefulness of the data contained in those 
reports, is in keeping with current trends in data availability and 
transparency, will further assist in the protection of public health 
and the environment, will improve compliance by facilitating the 
ability of regulated facilities to demonstrate compliance with 
requirements and by facilitating the ability of delegated state, local, 
tribal, and territorial air agencies and the EPA to assess and 
determine compliance, and will ultimately reduce burden on regulated 
facilities, delegated air agencies, and the EPA. Electronic reporting 
also eliminates paper-based, manual processes, thereby saving time and 
resources, simplifying data entry, eliminating redundancies, minimizing 
data reporting errors, and providing data quickly and accurately to the 
affected facilities, air agencies, the EPA, and the public. Moreover, 
electronic reporting is consistent with the EPA's plan \159\ to 
implement Executive Order 13563 and is in keeping with the EPA's 
Agency-wide policy \160\ developed in response to the White House's 
Digital Government Strategy.\161\ For more information on the benefits 
of electronic reporting, see the document titled Electronic Reporting 
Requirements for New Source Performance Standards (NSPS) and National 
Emission Standards for Hazardous Air Pollutants (NESHAP) Rules, 
referenced earlier in this section.
---------------------------------------------------------------------------

    \159\ EPA's Final Plan for Periodic Retrospective Reviews, 
August 2011. Available at: https://www.regulations.gov/document?D=EPA-HQ-OA-2011-0156-0154.
    \160\ E-Reporting Policy Statement for EPA Regulations, 
September 2013. Available at: https://www.epa.gov/sites/production/files/2016-03/documents/epa-ereporting-policy-statement-2013-09-30.pdf.
    \161\ Digital Government: Building a 21st Century Platform to 
Better Serve the American People, May 2012. Available at: https://obamawhitehouse.archives.gov/sites/default/files/omb/egov/digital-government/digital-government.html.
---------------------------------------------------------------------------

4. NSPS Subpart VVa Reconsideration Issues
    In January 2008, the EPA received one petition for reconsideration 
of the NSPS subpart VVa rulemaking 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). 
See section II.A.3 of this preamble for additional details about this 
petition for reconsideration. On June 2, 2008, the EPA indicated (73 FR 
31372) that it would be publishing a Federal Register notice in 
response to the petition for reconsideration on: (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 at 40 CFR 60.481a and 40 CFR 60.482-
1a(g); (3) the monitoring of connectors in subpart VVa at 40 CFR 
60.482-11a; and (4) the definition of capital expenditure in subpart 
VVa at 40 CFR 60.481a. These provisions were stayed pending resolution 
of the reconsideration.\162\ 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 and instead is only proposing 
to address issues 1 through 4 for subparts VV and VVa.
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    \162\ The EPA only granted reconsideration of issues 2 through 4 
in their March 4, 2008 letter to petitioners, however, we are 
proposing reconsideration on issue 1 (the clarification of the 
definition of process unit) as well because of its reliance on issue 
2 (the assignment of shared storage vessels to specific process 
units).
---------------------------------------------------------------------------

    On November 16, 2007, the EPA promulgated amendments to the NSPS 
subpart VV as well as new equipment leak requirements in NSPS subpart 
VVa.

[[Page 25172]]

As part of the rulemaking, the EPA finalized a definition for ``process 
unit'' that included a phrase that a process unit ``includes all 
equipment as defined in this subpart'' which was intended to clarify 
what equipment was covered by the rule. However, petitioners stated 
that the ``EPA must reconsider its `clarification' of the definition of 
process unit'' because ``the new process unit definition is 
inconsistent with the originally promulgated definition.'' The 
petitioners alleged that the new definition ``substantially expands'' 
the definition of process unit, thereby expanding applicability of the 
NSPS ``to equipment not previously subject to those requirements.'' 
They also state that because the EPA characterized this change as a 
``clarification,'' we failed to solicit and consider public comments on 
the impacts of this requirement for both existing and new SOCMI 
facilities. After further review, the November 16, 2007, definition is 
imprecise with respect to the usage of the terms ``equipment'' versus 
``components.'' Equipment is a separately defined term and should not 
be included within the definition of process unit to establish 
applicability. The reader instead should be able to refer to 40 CFR 
60.480(a) (for NSPS subpart VV) and 40 CFR 60.480a(a) (for NSPS subpart 
VVa) for applicability and designation of the affected facility and 
refer to 40 CFR 60.481 (for NSPS subpart VV) and 40 CFR 60.481a (for 
NSPS subpart VVa) for definitions of terms used within the 
applicability section. Therefore, we are proposing to revert back to 
the same definition for ``process unit'' that is currently being used 
in NSPS subpart VV and NSPS subpart VVa according to the stay 
requirements. For NSPS subpart VV, we are proposing that ``process 
unit'' means components assembled to produce, as intermediate or final 
products, one or more of the chemicals listed in 40 CFR 60.489 of this 
part. A process unit can operate independently if supplied with 
sufficient feed or raw materials and sufficient storage facilities for 
the product. For NSPS subpart VVa, we are proposing that ``process 
unit'' means components assembled to produce, as intermediate or final 
products, one or more of the chemicals listed in 40 CFR 60.489a of this 
part. A process unit can operate independently if supplied with 
sufficient feed or raw materials and sufficient storage facilities for 
the product. These proposed definitions for ``process unit'' for NSPS 
subparts VV and VVa avoid accidentally retroactively expanding coverage 
of NSPS subparts VV and VVa to previously uncovered facilities.
    Also, as part of the November 16, 2007 rulemaking, the EPA 
finalized procedures at 40 CFR 60.482-1(g) (for NSPS subpart VV) and 40 
CFR 60.482-1a(g) (for NSPS subpart VVa) intended to clarify how to 
assign storage vessels that are shared among multiple process units to 
a specific process unit. The EPA also revised the process unit 
definition at 40 CFR 60.481 (for NSPS subpart VV) and 40 CFR 60.481a 
(for NSPS subpart VVa) because of its reliance upon the new provision 
on the allocation of shared storage vessels. Petitioners stated that 
the EPA did not propose its method for addressing shared storage 
vessels in the proposed rules published November 7, 2006, giving no 
opportunity for public comment. The petitioners alleged that the 
allocation of shared storage vessels is a new requirement ``that cannot 
lawfully be imposed, with or without notice and comment, on existing 
sources.'' After further review, we are proposing that a method for 
assigning shared storage vessels to specific process units is not 
needed. Therefore, we are proposing to remove the requirements in 40 
CFR 60.482-1(g) (for NSPS subpart VV) and 40 CFR 60.482-1a(g) (for NSPS 
subpart VVa). For sources subject to NSPS subparts VV and VVa, any 
storage vessel that is located within the battery limits \163\ of a 
process unit is already associated with that process unit; therefore, 
allocation is not necessary. We are soliciting comment on this proposed 
decision, specifically regarding situations when allocation would be 
necessary.
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    \163\ Statements made in the 1981 proposal preamble (46 FR 1136, 
January 5, 1981) provide our clear intent of the components included 
in the definition of process unit. First, the EPA specifically 
stated that ``[a] process unit includes intermediate storage or 
surge tanks and all fluid transport equipment connecting the 
reaction, separation and purification devices.'' 46 FR 1139. This 
statement clarified that the definition includes components 
indirectly but still integrally involved in ``producing'' the 
chemical (i.e., not a reaction, separation or purification unit 
operation). Second, EPA stated: ``All equipment within the battery 
limits is included'' but that ``offsite fluid transport and storage 
facilities are excluded.'' Id. These terms, ``within the battery 
limits'' and ``offsite,'' are industry terms of art used throughout 
the SOCMI and petroleum refining industry. ``Within the battery 
limits'' refers to the boundary around the components assembled to 
perform a specific process function or to produce a product, whereas 
``offsite'' refers to locations outside the fence line of a 
facility. By using these terms, the EPA was emphasizing that all 
components are part of the ``process unit'' if contained within the 
battery limit boundary, but are not part of the process unit if 
located ``offsite.'' Id.
---------------------------------------------------------------------------

    In the November 16, 2007, rulemaking, the EPA finalized new 
connector monitoring requirements for SOCMI units. Petitioners stated 
that the ``EPA must reconsider its new connector monitoring 
requirements for SOCMI units, as the regulated community was denied 
notice of and an opportunity to comment on this requirement.'' The 
Petitioners stated that the ``EPA expanded the definition of connector 
in the final rule without notice and an opportunity to comment.'' The 
EPA agrees that it did not include these new requirements and this new 
definition in its proposal published on November 7, 2006. Therefore, we 
are proposing to remove the connector monitoring provisions from NSPS 
subpart VVa at 40 CFR 60.482-11a in their entirety. Instead, we are 
reproposing connector monitoring provisions in NSPS subpart VVb (see 
section III.C.6.b of this preamble).
    Lastly, in the November 16, 2007 rulemaking, the EPA finalized a 
definition of ``capital expenditure'' in NSPS subpart VVa. Petitioners 
stated that the ``EPA must reconsider its new definition of `capital 
expenditure' in subpart VVa, which was never proposed and which 
retroactively triggers `modification' status for facility changes 
commenced since November 7, 2006.'' The petitioners' concern was 
specifically limited to the retroactive application, and not 
application after November 16, 2007, and they did not seek 
reconsideration with respect to the change in the definition of capital 
expenditure generally. Therefore, we are proposing to revise the 
``capital expenditure'' definition in NSPS subpart VVa at 40 CFR 
60.481a to reflect the definition used in NSPS subpart VV at 40 CFR 
60.481 for owners or operators that start a new, reconstructed, or 
modified affected source prior to November 16, 2007 (as is currently 
required in NSPS subpart VVa due to the stayed provisions). 
Specifically, we are proposing that the value of ``X'' in the capital 
expenditure definition in 40 CFR 60.481a be 1982 minus the year of 
construction for owners or operators that start a new, reconstructed, 
or modified affected source prior to November 16, 2007, because using 
any more recent year than 1982 as ``X'' in the equation would require 
owners and operators to determine former (historical) capital 
expenditures in order to meet modification and reconstruction 
requirements. This would not be practical given that a significant 
amount of time has passed since the capital expenditure provisions were 
stayed. However, we are proposing to update the definition of ``capital 
expenditure'' in NSPS subpart VVb for evaluating changes that occur at 
existing SOCMI facilities after April 25, 2023. We are proposing that 
the value of ``X'' in the

[[Page 25173]]

capital expenditure definition in 40 CFR 60.481b be 2023 minus the year 
of construction, where the date of original construction was after 
January 6, 1982, but before January 1, 2023. Where the date of original 
construction was on or after January 1, 2023, but on or before April 
25, 2023, we are proposing the value of X be 1.
5. Technical and Editorial Changes
    We are proposing several technical amendments and definition 
revisions to improve the clarity and enforceability of certain 
provisions in the HON, P&R I, and P&R II, and NSPS subpart VVa. These 
additional proposed revisions and our rationale for the proposed 
revisions are described in this section.
a. HON Definition Sections
    In an effort to remove redundancy and improve consistency, we are 
proposing 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 (i.e., 40 CFR 63.101). We are 
proposing new text in 40 CFR 63.111 to point to 40 CFR 63.101, as 
follows: ``All terms used in this subpart shall have the meaning given 
them in the Act and in subpart F of this part.'' We are proposing new 
text in 40 CFR 63.161 to point to 40 CFR 63.101, as follows: ``All 
terms used in this subpart shall have the meaning given them in the Act 
and in subpart F of this part, except as provided in any subpart that 
references this subpart.'' We are also proposing to revise certain 
terms that have minor differences between their definition in these 
subparts. See Table 30 for additional details. These proposed changes 
will resolve inconsistencies that lead to interpretation issues between 
each of these subparts. We are not proposing to combine the definitions 
from NESHAP subpart I into the definitions section of NESHAP subpart F 
because those definitions are specifically for negotiated non-SOCMI 
processes.

          Table 30--Proposed Definition Changes To Resolve Minor Differences Between NESHAP F, G, and H
----------------------------------------------------------------------------------------------------------------
                                                                                             Proposed revised
Current definition in NESHAP  subpart   Current definition in    Current definition in     definition in NESHAP
                  F                       NESHAP  subpart G        NESHAP  subpart H            subpart F
----------------------------------------------------------------------------------------------------------------
None.................................  Closed-vent system       Closed-vent system       Closed-vent system
                                        means a system that is   means a system that is   means a system that is
                                        not open to the          not open to the          not open to the
                                        atmosphere and is        atmosphere and that is   atmosphere and is
                                        composed of piping,      composed of hard-        composed of piping,
                                        ductwork, connections,   piping, ductwork,        ductwork, connections,
                                        and, if necessary,       connections and, if      and, if necessary,
                                        flow inducing devices    necessary, flow-         flow inducing devices
                                        that transport gas or    inducing devices that    that transport gas or
                                        vapor from an emission   transport gas or vapor   vapor from an emission
                                        point to a control       from a piece or pieces   point to a control
                                        device.                  of equipment to a        device.
                                                                 control device or back
                                                                 into a process.
Control device means any combustion    Control device means     Control device means     Control device means
 device, recovery device, or            any combustion device,   any equipment used for   any combustion device,
 recapture device. Such equipment       recovery device, or      recovering,              recovery device, or
 includes, but is not limited to,       recapture device. Such   recapturing, or          recapture device. Such
 absorbers, carbon adsorbers,           equipment includes,      oxidizing organic        equipment includes,
 condensers, incinerators, flares,      but is not limited to,   hazardous air            but is not limited to,
 boilers, and process heaters. For      absorbers, carbon        pollutant vapors. Such   absorbers, carbon
 process vents (as defined in this      adsorbers, condensers,   equipment includes,      adsorbers, condensers,
 section), recapture devices are        incinerators, flares,    but is not limited to,   incinerators, flares,
 considered control devices but         boilers, and process     absorbers, carbon        boilers, and process
 recovery devices are not considered    heaters. For process     adsorbers, condensers,   heaters. For process
 control devices. For a steam           vents, recapture         flares, boilers, and     vents, recapture
 stripper, a primary condenser is not   devices are considered   process heaters.         devices are considered
 considered a control device.           control devices but                               control devices but
                                        recovery devices are                              recovery devices are
                                        not considered control                            not considered control
                                        devices, and for a                                devices, and for a
                                        steam stripper, a                                 steam stripper, a
                                        primary condenser is                              primary condenser is
                                        not considered a                                  not considered a
                                        control device.                                   control device.
None.................................  First attempt at repair  First attempt at repair  First attempt at repair
                                        means to take action     means to take action     means to take action
                                        for the purpose of       for the purpose of       for the purpose of
                                        stopping or reducing     stopping or reducing     stopping or reducing
                                        leakage of organic       leakage of organic       leakage of organic
                                        material to the          material to the          material to the
                                        atmosphere.              atmosphere, followed     atmosphere, followed
                                                                 by monitoring as         by monitoring as
                                                                 specified in Sec.        specified in Sec.
                                                                 63.180 (b) and (c), as   63.180 (b) and (c), as
                                                                 appropriate, to verify   appropriate, to verify
                                                                 whether the leak is      whether the leak is
                                                                 repaired, unless the     repaired, unless the
                                                                 owner or operator        owner or operator
                                                                 determines by other      determines by other
                                                                 means that the leak is   means that the leak is
                                                                 not repaired.            not repaired.
Initial start-up means the first time  None...................  Initial start-up means   Initial start-up means
 a new or reconstructed source begins                            the first time a new     the first time a new
 production, or, for equipment added                             or reconstructed         or reconstructed
 or changed as described in Sec.                                 source begins            source begins
 63.100 (l) or (m) of this subpart,                              production. Initial      production, or, for
 the first time the equipment is put                             start-up does not        equipment added or
 into operation. Initial start-up                                include operation        changed as described
 does not include operation solely                               solely for testing       in Sec.   63.100 (l)
 for testing equipment. For purposes                             equipment. Initial       or (m) of this
 of subpart G of this part, initial                              start-up does not        subpart, the first
 start-up does not include subsequent                            include subsequent       time the equipment is
 start-ups (as defined in this                                   start-ups (as defined    put into operation.
 section) of chemical manufacturing                              in this section) of      Initial start-up does
 process units following malfunctions                            process units            not include operation
 or shutdowns or following changes in                            following malfunctions   solely for testing
 product for flexible operation units                            or process unit          equipment. For
 or following recharging of equipment                            shutdowns.               purposes of subpart G
 in batch operation. For purposes of                                                      of this part, initial
 subpart H of this part, initial                                                          start-up does not
 start-up does not include subsequent                                                     include subsequent
 start-ups (as defined in Sec.                                                            start-ups (as defined
 63.161 of subpart H of this part) of                                                     in this section) of
 process units (as defined in Sec.                                                        chemical manufacturing
 63.161 of subpart H of this part)                                                        process units
 following malfunctions or process                                                        following malfunctions
 unit shutdowns.                                                                          or shutdowns or
                                                                                          following changes in
                                                                                          product for flexible
                                                                                          operation units or
                                                                                          following recharging
                                                                                          of equipment in batch
                                                                                          operation. For
                                                                                          purposes of subpart H
                                                                                          of this part, initial
                                                                                          start-up does not
                                                                                          include subsequent
                                                                                          start-ups (as defined
                                                                                          in Sec.   63.161 of
                                                                                          subpart H of this
                                                                                          part) of process units
                                                                                          (as defined in Sec.
                                                                                          63.161 of subpart H of
                                                                                          this part) following
                                                                                          malfunctions or
                                                                                          process unit
                                                                                          shutdowns.

[[Page 25174]]

 
None.................................  Process unit has the     Process unit means a     Process unit means a
                                        same meaning as          chemical manufacturing   chemical manufacturing
                                        chemical manufacturing   process unit as          process unit as
                                        process unit as          defined in subpart F     defined in subpart F
                                        defined in this          of this part, a          of this part, a
                                        section.                 process subject to the   process subject to the
                                                                 provisions of subpart    provisions of subpart
                                                                 I of this part, or a     I of this part, or a
                                                                 process subject to       process subject to
                                                                 another subpart in 40    another subpart in 40
                                                                 CFR part 63 that         CFR part 63 that
                                                                 references this          references this
                                                                 subpart.                 subpart.
Surge control vessel means feed        Surge control vessel     Surge control vessel     Surge control vessel
 drums, recycle drums, and              means feed drums,        means feed drums,        means feed drums,
 intermediate vessels. Surge control    recycle drums, and       recycle drums, and       recycle drums, and
 vessels are used within a chemical     intermediate vessels.    intermediate vessels.    intermediate vessels.
 manufacturing process unit when in-    Surge control vessels    Surge control vessels    Surge control vessels
 process storage, mixing, or            are used within a        are used within a        are used within a
 management of flow rates or volumes    chemical manufacturing   process unit (as         chemical manufacturing
 is needed to assist in production of   process unit when in-    defined in the           process unit when in-
 a product.                             process storage,         specific subpart that    process storage,
                                        mixing, or management    references this          mixing, or management
                                        of flow rates or         subpart) when in-        of flow rates or
                                        volumes is needed to     process storage,         volumes is needed to
                                        assist in production     mixing, or management    assist in production
                                        of a product.            of flow rates or         of a product.
                                                                 volumes is needed to
                                                                 assist in production
                                                                 of a product.
----------------------------------------------------------------------------------------------------------------

    Finally, we are also proposing editorial changes that clarify 
reference citations in the definitions (to properly point to the 
correct HON subpart) for ``annual average concentration,'' ``annual 
average flow rate,'' ``closed biological treatment process,'' 
``compliance date,'' ``connector,'' ``continuous record,'' ``equipment 
leak,'' ``group 1 process vent,'' ``group 1 storage vessel,'' ``group 1 
wastewater stream,'' ``group 2 process vent,'' ``halogenated vent 
stream,'' ``in organic hazardous air pollutant service,'' ``in volatile 
organic compound service,'' ``instrumentation system,'' ``point of 
determination,'' ``process vent,'' ``process wastewater stream,'' 
``recovery device,'' ``reference control technology for storage 
vessels,'' ``reference control technology for wastewater,'' 
``repaired,'' ``table 8 compound,'' ``table 9 compound,'' ``total 
resource effectiveness index value,'' ``treatment process,'' 
``wastewater,'' and ``wastewater stream''.
b. Monitoring for Adsorbers That Cannot Be Regenerated and Regenerative 
Adsorbers That Are Regenerated Offsite
    We are proposing to add monitoring requirements at 40 CFR 
63.114(a)(5)(v), 40 CFR 63.120(d)(1)(iii), 40 CFR 63.127(b)(4), and 40 
CFR 63.139(d)(5) (for HON), and 40 CFR 63.484(t), 40 CFR 63.485(x), and 
40 CFR 63.489(b)(10) (for P&R I) for adsorbers that cannot be 
regenerated and regenerative adsorbers that are regenerated offsite 
because the HON and P&R I do not currently include specific monitoring 
requirements for this type of APCD.\164\ We are proposing owners and 
operators of this type of APCD use dual adsorbent beds in series. We 
have prescribed a dual bed system because the use of a single bed does 
not ensure continuous compliance unless the bed is replaced 
significantly before breakthrough.\165\ The proposed monitoring 
requirements for non-regenerative adsorbers fulfill the EPA's 
obligation to establish monitoring requirements to ensure continuous 
compliance with the emission limits (e.g., 98-percent control or a 20 
ppm TOC outlet concentration) when owners or operators are using these 
types of control devices to comply with the standards. A dual bed 
system will allow one bed to be saturated before it is replaced and, 
therefore, makes efficient use of the adsorber bed without exceeding 
the emission limits.
---------------------------------------------------------------------------

    \164\ We did not find any P&R II facilities that have processes 
controlled by adsorbers.
    \165\ We are proposing to define the term ``breakthrough'' at 40 
CFR 63.101 (for HON) and 40 CFR 63.482 (for P&R I) to mean the time 
when the level of HAP or TOC detected is at the highest 
concentration allowed to be discharged from an adsorber system.
---------------------------------------------------------------------------

    Similar to regenerative adsorbers, in order to monitor performance 
deterioration, we are proposing measurements of HAP or TOC using a 
portable analyzer or chromatographic analysis for non-regenerative 
absorbers. We are proposing that these measurements be taken on the 
outlet of the first adsorber bed in series using a sample port; and 
they be taken monthly (if the bed has at least two months of the bed 
design life remaining), weekly (if the bed has between two months and 
two weeks of bed design life remaining), or daily (once the bed has 
less than two weeks of bed design life remaining). Also, owners and 
operators would be required to establish an average adsorber bed life 
from a design evaluation as well as conduct monitoring no later than 3 
days after a bed is put into service as the first bed to confirm that 
it is functioning properly.
    We used the EPA's cost algorithms to estimate the cost of a second 
carbon adsorber bed for two adsorber scenarios. In the first scenario, 
the EPA estimated the cost of a replaceable-canister type adsorber 
holding 180 lbs of carbon. The total capital investment of the second 
bed (including installation and auxiliary equipment) is about $6,000, 
and the total annual cost is about $800. In the second scenario, we 
estimated the cost of an adsorber that holds 3,000 lbs of carbon and in 
which the carbon is removed and replaced by fresh carbon when needed. 
The total capital investment of the second bed (including installation 
and auxiliary equipment) is about $26,600, and the total annual cost is 
about $2,250. We assumed no additional labor would be required for 
operation and maintenance of the second adsorber bed compared to 
operating and maintaining a single bed adsorber. A more thorough 
discussion of this analysis is included in the document titled Analysis 
of Monitoring Costs and Dual Bed Costs for Non-Regenerative Carbon 
Adsorbers Used in the SOCMI Source Category that are Associated with 
Processes Subject to HON and for Non-Regenerative Carbon Adsorbers that 
are Associated with Processes Subject to Group I Polymers and Resins 
NESHAP, which is available in the docket for this rulemaking.
    We anticipate that the use of two beds in series and the use of 
monitoring will maximize the life of each bed and reduce adsorber media 
replacement costs. In both scenarios described above, we assumed that 
the first bed would be replaced when it reached breakthrough (i.e., its 
equilibrium capacity, which is when the adsorption zone of the bed 
reaches the bed outlet and the volatile

[[Page 25175]]

concentration in the exhaust begins to rise) based on monitoring at the 
outlet of the first bed. At that time, the owner or operator would 
divert the flow from the first to the second bed, the canisters or 
carbon would be replaced in the first bed, and it would then be 
returned to service as the second bed in the series. We did not include 
the cost of replacing the canisters or the carbon in the annual costs 
because the amount of carbon used would not increase as a result of 
using a second bed in series. We anticipate that having two beds in 
series and performing monitoring at the outlet of the first bed will 
reduce the amount of adsorber media (e.g., activated carbon) used by 
facilities because they will not have to replace the adsorber media 
until it reaches equilibrium capacity. With only a single bed and no 
monitoring, facilities would need to replace the adsorber media more 
frequently based on the estimated working capacity of the bed (which is 
a fraction of the equilibrium capacity) so as to maintain compliance 
and to avoid exceeding outlet concentration limits.
    As previously mentioned in section III.C.3.b of this preamble, we 
are also proposing these same monitoring requirements for NSPS subpart 
IIIa, NNNa, and RRRa under CAA section 111(b)(1)(B). The EPA 
acknowledges that these proposed requirements could be considered under 
CAA section 112(d)(6) because of the specification to have two adsorber 
beds in series, instead of as a proposed change to the monitoring 
requirements. However, our rationale for why a second bed is needed 
would not be any different if we described these proposed changes under 
CAA section 112(d)(6) instead of as a monitoring change. These changes 
are being proposed because the current HON and P&R I contain no 
monitoring requirements for non-regenerative adsorbers.
c. Calibration Drift Assessment (Related to NSPS Subpart VVa)
    We are proposing several corrections to the calibration drift 
assessment requirements in NSPS subpart VVa at 40 CFR 60.485a(b)(2). 
These amendments are being proposed to: (1) Correct a regulatory 
citation to read ``Sec.  60.486a(e)(8)'' instead of ``Sec.  
60.486a(e)(7)''; (2) remove the extraneous sentence ``Calculate the 
average algebraic difference between the three meter readings and the 
most recent readings and the most recent calibration value.''; (3) 
provide clarity in the mathematical step of the assessment by replacing 
the sentence ``Divide this algebraic difference by the initial 
calibration value and multiply by 100 to express the calibration drift 
as a percentage.'' with ``Divide the arithmetic difference of the 
initial and post-test calibration response by the corresponding 
calibration gas value for each scale and multiply by 100 to express the 
calibration drift as a percentage.''; and (4) provide clarity by making 
other minor textural changes to the provisions related to the 
procedures for when a calibration drift assessment shows negative or 
positive drift of more than 10 percent. We note that we are proposing 
these same calibration drift assessment requirements in NSPS subpart 
VVb at 40 CFR 60.485b(b)(2).
d. Control of Sweep, Purge, and Inert Blankets From IFRs
    The EPA is proposing that owners and operators that use a sweep, 
purge, or inert blanket between the IFR and fixed roof of a storage 
vessel would be required to route emissions through a closed vent 
system and control device (see proposed 40 CFR 63.119(b)(7)).
e. Overlap Provisions
    The EPA is proposing to remove the provisions that allow compliance 
with certain portions of 40 CFR part 264, subpart AA or CC in lieu of 
portions of NESHAP subpart G (see proposed 40 CFR 63.110(h)) because 
revisions being proposed in the HON are and not reflective of the same 
standards and associated monitoring, recordkeeping, and reporting 
requirements for certain control devices such as flares. In addition, 
requiring all facilities to have the same set of monitoring, 
recordkeeping, and reporting requirements allows for better 
enforceability of the rule by the EPA.
    Also, the EPA is proposing to remove the provisions that allow 
compliance with certain portions of 40 CFR part 65 in lieu of portions 
of NESHAP subparts G and H (see proposed 40 CFR 63.110(i) and 40 CFR 
60.160(g)) because our proposed requirements for HON processes (i.e., 
requirements we are proposing for heat exchange systems, storage 
vessels, process vents, transfer racks, wastewater, and equipment 
leaks) are more stringent than those required by 40 CFR part 65.
f. Other Editorial Corrections
    The EPA is proposing additional changes that address technical and 
editorial corrections for the HON as follows:
     The EPA is proposing to remove the word ``Organic'' before 
Hazardous Air Pollutants from the 40 CFR part 63 titles of subparts F 
through I to reflect the acronym NESHAP more accurately and for 
consistency in naming convention across all 40 CFR part 63 subparts; 
and
     The EPA is proposing to add the phrase ``and Fenceline 
Monitoring for All Emission Sources'' to the title of NESHAP subpart H 
to reflect the contents of the NESHAP more accurately. The EPA is 
proposing to include fenceline monitoring standards in NESHAP subpart H 
(see section III.C.7 of this preamble).
6. Listing of 1-bromopropane as a HAP
    On January 5, 2022, the EPA published in the Federal Register (87 
FR 393) a final rule amending the list of HAP under the CAA to add 1-
bromopropane (1-BP) in response to public petitions previously granted 
by the EPA. For the source categories covered by the HON, P&R I, and 
P&R II, we do not believe that the inclusion of 1-BP as an organic HAP 
would have any effect on the MACT standards. First, 1-BP is not a SOCMI 
chemical. Furthermore, we have no information showing that 1-BP is 
used, produced, or emitted to make any SOCMI chemicals regulated by the 
HON, and we are unaware of any information showing that it is used, 
produced, or emitted in the production of any of the polymers and 
resins processes covered by the P&R I or P&R II. Accordingly, we 
believe there is no further action required by the EPA needed to 
address emissions of 1-BP from these source categories. We solicit 
comment on this approach, and should new information submitted to the 
EPA show that 1-BP is emitted from these source categories, the EPA 
will consider this information in the context of developing any MACT 
standards that may be needed to address emissions of 1-BP. We also note 
that in many instances in the HON and P&R I, many MACT emission 
standards allow facilities to comply with a total organic compound 
concentration standard (e.g., 20 ppmv), which could adequately regulate 
emissions of 1-BP should we receive additional information that it is 
emitted from these source categories.

F. What compliance dates are we proposing, and what is the rationale 
for the proposed compliance dates?

1. HON, P&R I, and P&R II
    The proposed amendments to the HON, P&R I, and P&R II in this 
rulemaking for adoption under CAA section 112(d)(2) and (3) (see 
section III.D of this preamble) and CAA section 112(d)(6) (see section 
III.C of this preamble) are subject to the compliance deadlines 
outlined in the CAA under section 112(i). The proposed amendments to 
the HON and P&R I in

[[Page 25176]]

this rulemaking for adoption under CAA section 112(f) (see section 
III.C of this preamble) are subject to the compliance deadlines 
outlined in the CAA under section 112(f)(4).
    For all of the requirements we are proposing under CAA sections 
112(d)(2), (3), and (d)(6), we are proposing that all existing affected 
sources and all affected sources that were new sources under the 
current HON and P&R I (i.e., they commenced construction or 
reconstruction after December 31, 1992 (for HON) or after June 12, 1995 
(for P&R I), and on or before April 25, 2023), must comply with all of 
the amendments no later than 3 years after the effective date of the 
final rule, or upon startup, whichever is later. For existing sources, 
CAA section 112(i) provides that the compliance date shall be as 
expeditious as practicable, but no later than 3 years after the 
effective date of the standard. (``Section 112(i)(3)'s three-year 
maximum compliance period applies generally to any emission standard . 
. . promulgated under [section 112].'' Association of Battery Recyclers 
v. EPA, 716 F.3d 667, 672 (D.C. Cir. 2013)). In determining what 
compliance period is as expeditious as practicable, we consider the 
amount of time needed to plan and construct projects and change 
operating procedures. As provided in CAA section 112(i) and 5 U.S.C. 
801(3), all new affected sources that commenced construction or 
reconstruction after April 25, 2023 would be required to comply with 
these requirements within 60 days after the publication of the final 
amendments to the HON, P&R I, and P&R II standards or upon startup, 
whichever is later.
    For all of the requirements we are proposing under CAA sections 
112(f), we are proposing a compliance date of 2 years after the 
effective date of the final rule, or upon startup, whichever is later 
for all existing affected sources and for all affected sources that 
were new sources under the current HON and P&R I (i.e., they commenced 
construction or reconstruction after December 31, 1992 (for HON) or 
after June 12, 1995 (for P&R I), and on or before April 25, 2023, to 
comply with the proposed EtO requirements (for HON) and the proposed 
chloroprene requirements (for P&R I affected sources producing 
neoprene). For all new affected sources that commence construction or 
reconstruction after April 25, 2023, we are proposing owners or 
operators comply with the EtO requirements (for HON) and the 
chloroprene requirements (for P&R I affected sources producing 
neoprene) within 60 days after the publication date of the final rule 
(or upon startup, whichever is later).
a. Rationale for Proposed Compliance Dates of Proposed CAA Section 
112(d)(2) and (3) Amendments
    We are proposing new operating and monitoring requirements for the 
HON and P&R I under CAA section 112(d)(2) and (3). We anticipate that 
these requirements would require the installation of new flare 
monitoring equipment, and we project most CMPUs and EPPUs would install 
new control systems to monitor and adjust assist gas (air or steam) 
addition rates. Similar to the addition of new control equipment, these 
new monitoring requirements for flares would require engineering 
evaluations, solicitation and review of vendor quotes, contracting and 
installation of the equipment, and operator training. Installation of 
new monitoring and control equipment on flares will require the flare 
to be taken out of service. Depending on the configuration of the 
flares and flare header system, taking the flare out of service may 
also require a significant portion of the CMPU or EPPU to be shutdown. 
Therefore, for all existing affected sources, and all new affected 
sources under the current HON and P&R I that commenced construction or 
reconstruction after December 31, 1992 (for HON) or after June 12, 1995 
(for P&R I), and on or before April 25, 2023, we are proposing that it 
is necessary to provide 3 years after the publication date of the final 
rule (or upon startup, whichever is later) for owners or operators to 
comply with the new operating and monitoring requirements for flares. 
For all new affected sources that commence construction or 
reconstruction after April 25, 2023, we are proposing owners or 
operators comply with the new operating and monitoring requirements for 
flares within 60 days after the publication date of the final rule (or 
upon startup, whichever is later).
    Under CAA section 112(d)(2) and (3), we are proposing new vent 
control requirements for bypasses for the HON and P&R I. These 
requirements would typically require the addition of piping and 
potentially new control requirements. As these vent controls would most 
likely be routed to the flare, we are proposing, for all existing 
affected sources, and all new affected sources under the current HON 
and P&R I that commenced construction or reconstruction after December 
31, 1992 (for HON) or after June 12, 1995 (for P&R I), and on or before 
April 25, 2023, to provide 3 years after the publication date of the 
final rule (or upon startup, whichever is later) for owners or 
operators to allow coordination of these bypass modifications with the 
installation of the new monitoring equipment for the flares. For all 
new affected sources that commence construction or reconstruction after 
April 25, 2023, we are proposing owners or operators comply with the 
new vent control requirements for bypasses within 60 days after the 
publication date of the final rule (or upon startup, whichever is 
later).
    For atmospheric PRD in HAP service, we are establishing a work 
practice standard in the HON and P&R I that requires a process hazard 
analysis and implementation of a minimum of three redundant measures to 
prevent atmospheric releases. Alternately, owners or operators may 
elect to install closed-vent systems to route these PRDs to a flare, 
drain (for liquid thermal relief valves), or other control system. We 
anticipate that sources will need to identify the most appropriate 
preventive measures or control approach; design, install, and test the 
system; install necessary process instrumentation and safety systems; 
and may need to time installations with equipment shutdown or 
maintenance outages. Therefore, for all existing affected sources, and 
all new affected sources under the current HON and P&R I that commenced 
construction or reconstruction after December 31, 1992 (for HON) or 
after June 12, 1995 (for P&R I), and on or before April 25, 2023, we 
are proposing a compliance date of 3 years from the publication date of 
the final rule (or upon startup, whichever is later) for owners or 
operators to comply with the work practice standards for atmospheric 
PRD releases. For all new affected sources that commence construction 
or reconstruction after April 25, 2023, we are proposing owners or 
operators comply with the work practice standards for atmospheric PRD 
releases within 60 days after the publication date of the final rule 
(or upon startup, whichever is later).
    We are also establishing work practice standards in the HON and P&R 
I for maintenance activities. We anticipate sources will need time to 
review and update their standard operating procedures for maintenance 
activities; identify the most appropriate preventive measures or 
control approaches; design, install, and test the control systems; and 
install necessary process instrumentation and safety systems if so 
required. Therefore, for all existing affected sources, and all new 
affected sources under the current HON and P&R I that commenced 
construction or reconstruction after December 31, 1992

[[Page 25177]]

(for HON) or after June 12, 1995 (for P&R I), and on or before April 
25, 2023, we are proposing a compliance date of 3 years from the 
publication date of the final rule (or upon startup, whichever is 
later) for owners or operators to comply with the work practice 
standards for maintenance activities. For all new affected sources that 
commence construction or reconstruction after April 25, 2023, we are 
proposing owners or operators comply with the work practice standards 
for maintenance activities within 60 days after the publication date of 
the final rule (or upon startup, whichever is later).
    Under CAA section 112(d)(2) and (3), we are also proposing new 
dioxins and furans emission limits for the HON, P&R I, and P&R II. The 
proposed provisions may require additional time to plan, purchase, and 
install equipment for dioxins and furans control. Therefore, for all 
existing affected sources, and all new affected sources under the 
current HON, P&R I, and P&R II that commenced construction or 
reconstruction after December 31, 1992 (for HON), or after May 16, 1994 
(for P&R II), or after June 12, 1995 (for P&R I), and on or before 
April 25, 2023, we are proposing a compliance date of 3 years from the 
publication date of the final rule (or upon startup, whichever is 
later) for owners or operators to comply with the dioxins and furans 
emission limits. For all new affected sources that commence 
construction or reconstruction after April 25, 2023, we are proposing 
owners or operators comply with the dioxins and furans emission limits 
within 60 days after the publication date of the final rule (or upon 
startup, whichever is later).
    Other amendments we are proposing under CAA section 112(d)(2) and 
(3) include LDAR requirements for HON and P&R I pressure vessels, 
process vent control requirements for certain HON and P&R I surge 
control vessels and bottoms receivers, control requirements for certain 
HON transfer racks with an operating pressure greater than 204.9 kPa, 
and a LDAR program for P&R II heat exchange systems for BLR and WSR 
sources and equipment leaks for WSR sources in P&R II. Any of these 
proposed provisions may require additional time to plan, purchase, and 
install equipment for emissions control; and even if not, the EPA 
recognizes the confusion that multiple different compliance dates for 
individual requirements would create and the additional burden such an 
assortment of dates would impose. Therefore, for all existing affected 
sources, and all new affected sources under the current rules that 
commenced construction or reconstruction after December 31, 1992 (for 
HON), or after May 16, 1994 (for P&R II), or after June 12, 1995 (for 
P&R I), and on or before April 25, 2023, we are proposing a compliance 
date of 3 years from the publication date of the final rule (or upon 
startup, whichever is later) for owners or operators to comply with 
these other proposed amendments. For all new affected sources that 
commence construction or reconstruction after April 25, 2023, we are 
proposing owners or operators comply with these other proposed 
amendments within 60 days after the publication date of the final rule 
(or upon startup, whichever is later).
b. Rationale for Proposed Compliance Dates of Proposed CAA Section 
112(d)(6) Amendments
    As a result of our technology review for HON and P&R I heat 
exchange systems, we are proposing to replace the existing HON and P&R 
I leak definition and monitoring method with a new leak definition and 
monitoring method. We project some owners and operators would require 
engineering evaluations, solicitation and review of vendor quotes, 
contracting and installation of monitoring equipment, and operator 
training. In addition, facilities will need time to read and understand 
the amended rule requirements and update standard operating procedures. 
Therefore, we are proposing that all existing affected sources, and all 
new affected sources under the current rules that commenced 
construction or reconstruction after December 31, 1992 (for HON) or 
after June 12, 1995 (for P&R I), and on or before April 25, 2023, must 
comply with the new monitoring requirements for heat exchange systems 
no later than 3 years from the publication date of the final rule (or 
upon startup, whichever is later). For all new affected sources that 
commence construction or reconstruction after April 25, 2023, we are 
proposing owners or operators comply with the new monitoring 
requirements for heat exchange systems within 60 days after the 
publication date of the final rule (or upon startup, whichever is 
later).
    Under our technology review for HON and P&R I storage vessels under 
CAA section 112(d)(6), we are revising HON and P&R I to reflect more 
stringent storage vessel capacity and MTVP thresholds. We project that 
some owners and operators will need to install new control equipment on 
certain storage vessels because of the proposed applicability 
revisions. The addition of new control equipment would require 
engineering design, solicitation, and review of vendor quotes, and 
contracting and installation of the equipment, which would need to be 
timed with process unit outage and operator training. Therefore, we are 
proposing that all existing affected sources, and all new affected 
sources under the current rules that commenced construction or 
reconstruction after December 31, 1992 (for HON) or after June 12, 1995 
(for P&R I), and on or before April 25, 2023, must comply with the new 
storage vessel requirements no later than 3 years from the publication 
date of the final rule (or upon startup, whichever is later). For all 
new affected sources that commence construction or reconstruction after 
April 25, 2023, we are proposing owners or operators comply with the 
new storage vessel requirements within 60 days after the publication 
date of the final rule (or upon startup, whichever is later).
    We are also proposing, pursuant to CAA section 112(d)(6), to remove 
the 50 ppmv and 0.005 scmm Group 1 process vent thresholds from the HON 
Group 1 process vent definition and P&R I Group 1 continuous front-end 
process vent definition, and instead require owners and operators of 
HON or P&R I process vents that emit greater than or equal to 1.0 lb/hr 
of total organic HAP to reduce emissions of organic HAP using a flare 
meeting the proposed operating and monitoring requirements for flares; 
or 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. 
Additionally, as a result of our technology review for P&R I batch 
front-end process vents, we are proposing owners and operators of batch 
front-end process vents that release a total of annual organic HAP 
emissions greater than or equal to 4,536 kg/yr (10,000 lb/yr) from all 
batch 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 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). We project that some owners and 
operators will need to install new control equipment and/or new hard-
piping or duct work for certain process vents because of the proposed 
applicability revisions. The addition of new control equipment would 
require engineering design, solicitation, and review of vendor quotes, 
and contracting and installation of the equipment, which would need to 
be timed with process unit outage and

[[Page 25178]]

operator training. Therefore, we are proposing that all existing 
affected sources, and all new affected sources under the current rules 
that commenced construction or reconstruction after December 31, 1992 
(for HON) or after June 12, 1995 (for P&R I), and on or before April 
25, 2023, must comply with the new process vent requirements no later 
than 3 years from the publication date of the final rule (or upon 
startup, whichever is later). For all new affected sources that 
commence construction or reconstruction after April 25, 2023, we are 
proposing owners or operators comply with the new process vent 
requirements within 60 days after the publication date of the final 
rule (or upon startup, whichever is later).
    Compliance dates for the fenceline monitoring provisions proposed 
under CAA section 112 (d)(6) consider the amount of time that it will 
take owners and operators to develop their siting plans and secure the 
capabilities to conduct the monitoring and analyze the results. For 
fenceline monitoring, the compliance timeline also must consider the 
timeline for controls to be installed and operational before root cause 
analysis and application of corrective measures can take place. 
However, the actual monitoring can and must begin at least a year 
before to develop the annual average concentration baseline. Therefore, 
we are proposing that owners and operators of all existing sources and 
all new affected sources under the current rules that commenced 
construction or reconstruction after December 31, 1992 (for HON) or 
after June 12, 1995 (for P&R I), and on or before April 25, 2023 must 
begin fenceline monitoring one year after the publication date of the 
final rule and must perform root cause analysis and apply corrective 
action requirements upon exceedance of an annual average concentration 
action level starting 3 years after the publication date of the final 
rule (i.e., such that by after two years after the publication date of 
this rule, facilities will have installed controls to reduce EtO and 
chloroprene (as discussed in section III.F.1.c of this preamble) and be 
able to compare 1 year of data to the annual average concentration 
action level by year 3). For all new affected sources that commence 
construction or reconstruction after April 25, 2023, we are proposing 
owners or operators begin fenceline monitoring within 60 days after the 
publication date of the final rule (or upon startup, whichever is 
later). We are also proposing to require quarterly reporting of 
fenceline results beginning 1 year after monitoring begins.
c. Rationale for Proposed Compliance Dates of Proposed CAA Section 
112(f) Amendments
    As previously mentioned in this preamble, we are proposing under 
CAA section 112(f), new provisions considering results of the risk 
assessments to address emissions of EtO from equipment leaks, flares, 
heat exchange systems, maintenance vents, process vents, storage 
vessels, and wastewater at HON processes; and emissions of chloroprene 
from continuous front-end process vents, batch front-end process vents, 
maintenance vents, storage vessels, and wastewater associated with 
neoprene production processes subject to P&R I. The proposed provisions 
will require additional time to plan, purchase, and install equipment 
for EtO or chloroprene control. For example, for HON process vents in 
EtO service, if the affected source cannot demonstrate 99.9 percent 
control of EtO emissions, or reduce EtO emissions to less than 1 ppmv 
(from each process vent) or 5 pounds per year (for all combined process 
vents), then a new control system will need to be installed. Therefore, 
we are proposing a compliance date of 2 years after the publication 
date of the final rule, or upon startup, whichever is later for all 
existing affected sources, and all new affected sources under the 
current rules that commenced construction or reconstruction after 
December 31, 1992 (for HON) or after June 12, 1995 (for P&R I), and on 
or before April 25, 2023 to comply with the proposed EtO and 
chloroprene requirements. For all new affected sources that commence 
construction or reconstruction after April 25, 2023, we are proposing 
owners or operators comply with the EtO and chloroprene requirements 
within 60 days after the publication date of the final rule (or upon 
startup, whichever is later).
d. Rationale for Proposed Compliance Dates of Other Proposed Amendments
    We are proposing to change the HON, P&R I, and P&R II requirements 
for SSM by removing the exemption from the requirements to meet the 
standard during SSM periods, proposing alternative standards where 
needed, and by removing the requirement to develop and implement an SSM 
plan. In addition, we are proposing to remove all of the regulatory 
affirmative defense provisions from P&R I. We are also proposing 
electronic reporting requirements for the HON, P&R I, and P&R II. For 
details on these proposed amendments, see section III.E of this 
preamble. Except for the removal of the affirmative defense provisions 
in P&R I, we are positing that facilities would need some time to 
successfully accomplish these revisions, including time to read and 
understand the amended rule requirements, to evaluate their operations 
to ensure that they can meet the standards during periods of startup 
and shutdown, as defined in the rule, and make any necessary 
adjustments, including making adjustments to standard operating 
procedures, and to convert reporting mechanisms to install necessary 
hardware and software. As previously mentioned, the EPA recognizes the 
confusion that multiple different compliance dates for individual 
requirements would create and the additional burden such an assortment 
of dates would impose. From our assessment of the timeframe needed for 
compliance with the entirety of the proposed revisions to SSM 
requirements as well as the new proposed electronic reporting 
requirements for flare management plans, compliance reports, and 
performance evaluation reports, the EPA considers a period of 3 years 
after the publication date of the final rule to be the most expeditious 
compliance period practicable and, thus, is proposing that all affected 
sources be in compliance with these revised requirements upon initial 
startup or within 3 years of the publication date of the final rule, 
whichever is later. However, we are proposing to provide 60 days after 
the publication date of the final rule (or upon startup, whichever is 
later) for owners or operators of all affected sources to comply with 
the requirement to report electronically. We are also proposing to 
provide 60 days after the publication date of the final rule (or upon 
startup, whichever is later) for owners or operators of P&R I affected 
sources to comply with the removal of the affirmative defense 
provisions.
2. NSPS Subparts VVb, IIIa, NNNa, RRRa
    We are proposing that all sources of equipment leaks in the SOCMI 
(regulated under 40 CFR part 60, subpart VVb) and all SOCMI air 
oxidation unit processes, distillation operations, and reactor 
processes (regulated under 40 CFR part 60, subparts IIIa, NNNa, and 
RRRa, respectively), that commenced construction, reconstruction, or 
modification on or after April 25, 2023, would need to meet the 
requirements of the new NSPS upon startup of the new, reconstructed or 
modified facility or 60

[[Page 25179]]

days after publication of the final rule, whichever is later. This 
proposed compliance schedule is consistent with the requirements in 
section 111 of the CAA and the Congressional Review Act.

IV. Summary of Cost, Environmental, and Economic Impacts

A. What are the affected sources?

    There are approximately 207 facilities subject to the HON, 19 P&R I 
facilities (and 10 of these P&R I facilities are collocated with HON 
processes), and 5 P&R II facilities (and 3 of these P&R II facilities 
are collocated with HON processes). We also estimate that two 
additional HON facilities will be newly constructed over the next three 
years. The OECA's ECHO tool (https://echo.epa.gov) indicates there are 
currently 592 SOCMI facilities subject to subpart VV or VVa; and 284 
SOCMI facilities subject to at least one of the process vent NSPS 
subparts III, NNN, and/or RRR. The list of facilities 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, which is available in the docket for this rulemaking. We 
estimated that there would be one new greenfield facility, six new 
affected facilities constructed at existing plant sites, and 12 
modified/reconstructed facilities subject to NSPS subpart IIIa, NNNa, 
and/or RRRa in the next 5 years. We estimated there would be one new 
greenfield facility, 34 new affected facilities constructed at existing 
plant sites, and one modified facility subject to NSPS subpart VVb in 
the next 5 years (and no affected facilities would trigger NSPS subpart 
VVa reconstruction requirements).

B. What are the air quality impacts?

    This proposed action would reduce HAP and VOC emissions from HON, 
P&R I, and P&R II emission sources as well as the NSPS SOCMI air 
oxidation unit processes, distillation operations, reactor processes, 
and equipment leaks sources. Considering reported emissions inventories 
for EtO and chloroprene, we estimate that the proposed amendments to 
the NESHAP would reduce overall HAP emissions from the SOCMI source 
category by approximately 1,009 tpy, reduce overall HAP emissions from 
the P&R I source categories by approximately 185 tpy, and reduce 
overall HAP emissions from the P&R II source categories by 
approximately 1 tpy. We note that these emissions reductions do not 
consider the potential excess emissions reductions from flares that 
could result from the proposed monitoring requirements; we estimate 
flare excess emissions reductions of 4,858 tpy HAP and 19,889 tpy VOC. 
Based on our analysis of the proposed actions described in sections 
III.C.3.b and III.C.6.b of this preamble for the NSPS, we estimate that 
the proposed amendments to the NSPS would reduce VOC emissions from the 
SOCMI source category by approximately 1,609 tpy. Emission reductions 
and secondary impacts (e.g., emission increases associated with 
supplemental fuel or additional electricity) by rule are listed below.
1. HON
    For the HON, the EPA estimates HAP and VOC emission reductions of 
approximately 1,009 and 1,817 tpy, respectively. The EPA estimates 
these reductions include an approximate 58 tpy reduction in EtO 
emissions (from reported emissions inventories). The EPA also estimates 
that the proposed action would result in additional emissions of 714 
tpy of carbon monoxide (CO), 609,761 tpy of carbon dioxide 
(CO2), 277 tpy of nitrogen oxides (NOX) 
(including 5.3 tpy of nitrous oxide (N2O)), 12.7 tpy of 
particulate matter, 1.0 tpy of sulfur dioxide (SO2), and a 
reduction of 20,177 tpy of methane emissions. More information about 
the estimated emission reductions and secondary impacts of this 
proposed action for the HON can be found in the RIA accompanying this 
proposal and in the documents referenced in sections III.B through 
III.D of this preamble.
2. P&R I
    For P&R I, the EPA estimates HAP and VOC emission reductions of 
approximately 185 and 199 tpy, respectively. The EPA estimates these 
reductions include an approximate 14 tpy reduction in chloroprene 
emissions (from reported emissions inventories). The EPA also estimates 
that the proposed action would result in additional emissions of 110 
tpy of CO, 115,975 tpy of CO2, 75 tpy of NOX 
(including 1.5 tpy of N2O), 4.8 tpy of particulate matter, 
0.4 tpy of SO2, and a reduction of 2,018 tpy of methane 
emissions. More information about the estimated emission reductions and 
secondary impacts of this proposed action for P&R I can be found in the 
RIA accompanying this proposal and in the documents referenced in 
sections III.B through III.D of this preamble.
3. P&R II
    For P&R II, the EPA estimates 1 tpy of HAP and VOC emission 
reductions. The EPA also estimates that the proposed action would not 
have any secondary pollutant impacts. More information about the 
estimated emission reductions and secondary impacts of this proposed 
action for P&R II can be found in the RIA accompanying this proposal 
and in the documents referenced in sections III.B through III.D of this 
preamble.
4. NSPS Subpart VVb
    For the proposed NSPS subpart VVb, the EPA estimates VOC emission 
reductions of approximately 340 tpy. The EPA estimates that the 
proposed action would not have any secondary pollutant impacts. More 
information about the estimated emission reductions and secondary 
impacts of this proposed action for NSPS subpart VVb can be found in 
the RIA accompanying this proposal and in the document titled CAA 
111(b)(1)(B) review for the SOCMI Equipment Leaks NSPS Subpart VVa, 
which is available in the docket for this rulemaking.
5. NSPS Subparts IIIa, NNNa, and RRRa
    For the proposed NSPS subparts IIIa, NNNa, and RRRa, the EPA 
estimates VOC emission reductions of approximately 1,269 tpy. The EPA 
estimates that the proposed action result in additional emissions of 
21.5 tpy of CO, 15,370 tpy of CO2, and 4.0 tpy of 
NOX (including 0.1 tpy of N2O), and a reduction 
of 757 tpy of methane emissions. More information about the estimated 
emission reductions and secondary impacts of this proposed action for 
NSPS subparts IIIa, NNNa, and RRRa can be found in the RIA accompanying 
this proposal and in the document titled CAA 111(b)(1)(B) review for 
the SOCMI air oxidation unit processes, distillation operations, and 
reactor processes NSPS subparts III, NNN, and RRR, which is available 
in the docket for this rulemaking.

C. What are the cost impacts?

    This proposed action would cumulatively cost (in 2021 dollars) 
approximately $501 million in total capital costs and $190 million per 
year in total annualized costs (including product recovery), based on 
our analysis of the proposed action described in sections III.B through 
III.D of this preamble. Costs by rule are listed below.
1. HON
    For the HON, the EPA estimates this proposed action would cost 
approximately $441 million in total capital costs and $166 million per 
year in total annualized costs (including product recovery). More 
information about the estimated cost of this

[[Page 25180]]

proposed action for the HON can be found in the documents referenced in 
sections III.B through III.D of this preamble.
2. P&R I
    For P&R I, the EPA estimates this proposed action would cost 
approximately $25 million in total capital costs and $15 million per 
year in total annualized costs (including product recovery). More 
information about the estimated cost of this proposed action for P&R I 
can be found in the documents referenced in sections III.B through 
III.D of this preamble.
3. P&R II
    For P&R II, the EPA estimates this proposed action would cost 
approximately $2.9 million in total capital costs and $1.7 million per 
year in total annualized costs (including product recovery). More 
information about the estimated cost of this proposed action for P&R II 
can be found in the documents referenced in sections III.B through 
III.D of this preamble.
4. NSPS Subpart VVb
    For the proposed NSPS subpart VVb, the EPA estimates this proposed 
action would cost approximately $7.7 million in total capital costs and 
$1.1 million per year in total annualized costs (including product 
recovery). More information about the estimated cost of this proposed 
action for NSPS subpart VVb can be found in the document titled CAA 
111(b)(1)(B) review for the SOCMI Equipment Leaks NSPS Subpart VVa, 
which is available in the docket for this rulemaking.
5. NSPS Subparts IIIa, NNNa, and RRRa
    For the proposed NSPS subparts IIIa, NNNa, and RRRa, the EPA 
estimates this proposed action would cost approximately $24 million in 
total capital costs and $5.8 million per year in total annualized costs 
(including product recovery). More information about the estimated cost 
of this proposed action for NSPS subparts IIIa, NNNa, and RRRa can be 
found in the document titled CAA 111(b)(1)(B) review for the SOCMI air 
oxidation unit processes, distillation operations, and reactor 
processes NSPS subparts III, NNN, and RRR, which is available in the 
docket for this rulemaking.

D. What are the economic impacts?

    The EPA conducted economic impact analyses for this proposal, in a 
document titled Regulatory Impact Analysis, which is available in the 
docket for this action. The economic impact analyses contain two parts. 
The economic impacts of the proposal on small entities are calculated 
as the percentage of total annualized costs incurred by affected 
ultimate parent owners to their revenues. This ratio provides a measure 
of the direct economic impact to ultimate parent owners of HON, P&R I, 
and P&R II facilities and NSPS VVb, IIIa, NNNa, and RRRa facilities 
while presuming no impact on consumers. We estimate the average small 
entity impacted by the proposal will incur total annualized costs of 
0.46 percent of their revenue, with none exceeding 1.5 percent, not 
considering product recovery from compliance. With product recovery, 
the EPA estimates that the average small entity impacted by the 
proposal will incur total annualized costs of 0.43 percent of their 
revenue, with none exceeding 1.3 percent. We estimate that 20 percent 
(2 in total) of impacted small entities will incur total annualized 
costs greater than 1 percent of their revenue, and none will incur 
total annualized costs greater than 3 percent of their revenue. These 
estimates are unchanged when including product recovery. This is based 
on a conservative estimate of costs imposed on ultimate parent 
companies, where total annualized costs are imposed on a facility are 
at the upper bound of what is possible under the rule and do not 
include product recovery as a credit.
    In addition, we provide an economic impact analysis using costs of 
the HON and Polymers and Resins I and II NESHAP that estimates changes 
in affected chemical product price and output related to the impact of 
the compliance costs on producers and consumers of such chemical 
products for each of these proposed rules. There are seven chemical 
products included in the economic impact analysis--butadiene, styrene, 
acetone, acrylonitrile, ethylene dichloride, ethylene glycol, and 
ethylene oxide. For the HON, chemical product prices are estimated to 
increase from less than 0.01 percent to 0.61 percent, and output by 
product is estimated to decrease by less than 0.01 percent to 0.54 
percent. For the two Polymers and Resins NESHAP, chemical product 
prices are estimated to increase by less than 0.01 percent to 0.05 
percent, and output by product is estimated to decrease by less than 
0.01 percent to 0.09 percent. More explanation of these economic 
impacts can be found in the Regulatory Flexibility Act (RFA) section 
later in this preamble and in the RIA for this proposed rulemaking.

E. What are the benefits?

    The emissions controls required by these rules are expected to 
reduce emissions of a number of HAP. The health effects associated with 
the main HAP of concern from SOCMI (found within the HON), P&R I, and 
P&R II source categories are discussed fully in Chapter 4 of the RIA: 
ethylene oxide (Section 4.1.1), chloroprene (Section 4.1.2), benzene 
(Section 4.1.3), 1,3-butadiene (Section 4.1.4), vinyl chloride (Section 
4.1.5), ethylene dichloride (Section 4.1.6), chlorine (Section 4.1.7), 
maleic anhydride (Section 4.1.8) and acrolein (Section 4.1.9). This 
proposal is projected to reduce ethylene oxide emissions from HON 
processes by approximately 58 tons per year (tpy) and reduce 
chloroprene emissions from Neoprene Production processes in P&R I by 
approximately 14 tpy. We also estimate that the proposed amendments to 
the NESHAP would reduce other HAP emissions (excluding ethylene oxide 
and chloroprene) from the SOCMI, P&R I, and P&R II source categories by 
approximately 1,123 tpy. We also estimate that the 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. The 
Agency was unable to estimate HAP emission reductions for the proposed 
amendments to the NSPS in this rulemaking.
    Quantifying and monetizing the economic value of reducing the risk 
of cancer and non-cancer effects is made difficult by the lack of a 
central estimate of estimate of cancer and non-cancer risk and 
estimates of the value of an avoided case of cancer (fatal and non-
fatal) and morbidity effects. Due to methodology and data limitations, 
we did not attempt to monetize the health benefits of reductions in HAP 
in this analysis. Instead, we are providing a qualitative discussion in 
the RIA of the health effects associated with HAP emitted from sources 
subject to control under the proposed action.
    The emission controls installed to comply with these proposed rules 
are also expected to reduce VOC emissions which, in conjunction with 
NOX and in the presence of sunlight, form ground-level ozone 
(O3). This section reports the estimated ozone-related 
benefits of reducing VOC emissions in terms of the number and value of 
avoided ozone-attributable deaths and illnesses.
    As a first step in quantifying O3-related human health 
impacts, the EPA consults the Integrated Science

[[Page 25181]]

Assessment for Ozone (Ozone ISA) \166\ as summarized in the Technical 
Support Document for the Final Revised Cross State Air Pollution Rule 
Update.\167\ This document synthesizes the toxicological, clinical, and 
epidemiological evidence to determine whether each pollutant is 
causally related to an array of adverse human health outcomes 
associated with either acute (i.e., hours or days-long) or chronic 
(i.e., years-long) exposure. For each outcome, the Ozone ISA reports 
this relationship to be causal, likely to be causal, suggestive of a 
causal relationship, inadequate to infer a causal relationship, or not 
likely to be a causal relationship.
---------------------------------------------------------------------------

    \166\ U.S. EPA (2020). Integrated Science Assessment for Ozone 
and Related Photochemical Oxidants. U.S. Environmental Protection 
Agency. Washington, DC. Office of Research and Development. EPA/600/
R-20/012. Available at: https://www.epa.gov/isa/integrated-science-assessment-isa-ozone-and-related-photochemical-oxidants.
    \167\ U.S. EPA. 2021. Technical Support Document (TSD) for the 
Final Revised Cross-State Air Pollution Rule Update for the 2008 
Ozone Season NAAQS Estimating PM2.5- and Ozone-
Attributable Health Benefits. https://www.epa.gov/sites/default/files/2021-03/documents/estimating_pm2.5-_and_ozone-attributable_health_benefits_tsd.pdf.
---------------------------------------------------------------------------

    In brief, the Ozone ISA found short-term (less than one month) 
exposures to ozone to be causally related to respiratory effects, a 
``likely to be causal'' relationship with metabolic effects and a 
``suggestive of, but not sufficient to infer, a causal relationship'' 
for central nervous system effects, cardiovascular effects, and total 
mortality. The Ozone ISA reported that long-term exposures (one month 
or longer) to ozone are ``likely to be causal'' for respiratory effects 
including respiratory mortality, and a ``suggestive of, but not 
sufficient to infer, a causal relationship'' for cardiovascular 
effects, reproductive effects, central nervous system effects, 
metabolic effects, and total mortality.
    For all estimates, we summarized the monetized ozone-related health 
benefits using discount rates of 3 percent and 7 percent for the 15-
year analysis period of these rules discounted back to 2023 rounded to 
2 significant figures. For the full set of underlying calculations see 
the benefits workbook in the RIA, which is available in the docket for 
this rulemaking. In addition, we include the monetized disbenefits 
(i.e., negative effects) from additional CO2 and 
NOX emissions, which occur with the HON, P&R I and NSPS 
IIIa, NNNa, and RRRa, but not P&R II or NSPS VVb since there are no 
additional CO2 emissions as a result of these two proposed 
rules.
1. HON
    The present value (PV) of the net monetized benefits (monetized 
health benefits plus monetized climate benefits minus climate 
disbenefits) for the proposed amendments for the HON are $103.4 million 
at the 3 percent discount rate to $78.4 million at the 7 percent 
discount rate and $715.4 million at the 3 percent discount rate to 
$495.4 million at the 7 percent discount rate. The equivalent annual 
value (EAV) of the benefits for the proposed amendments for the HON are 
$8.6 million at the 3 percent discount rate to $7.9 million at the 7 
percent discount rate and $60.1 million at the 3 percent discount rate 
to $53.1 million at the 7 percent discount rate.
2. P&R I
    The PV of the net monetized benefits (monetized health benefits 
plus monetized climate benefits minus monetized climate disbenefits) 
for the proposed amendments for P&R I are minus $37.8 million at the 3 
percent discount rate to minus $38.6 million at the 7 percent discount 
rate and minus $17.5 million at the 3 percent discount rate to minus 
$24.5 million at the 7 percent discount rate. The EAV of the benefits 
for the proposed amendments for P&R I are minus $0.8 million at the 3 
percent discount rate to minus $1.6 million at the 7 percent discount 
rate and minus $1.5 million at the 3 percent discount rate to minus 
$1.7 million at the 7 percent discount rate.
3. P&R II
    The PV of the net monetized benefits (monetized health benefits 
plus monetized climate benefits minus monetized climate disbenefits) 
for the proposed amendments for P&R II are zero since there are minimal 
VOC emission reductions (no more than 1 tpy), and there are no changes 
in climate-related emissions (CO2, methane, N2O).
4. NSPS Subpart VVb
    Because the estimated emissions reductions due to this proposed 
rule are relatively small and because we cannot be confident of the 
location of new facilities that would be subject to the proposed NSPS 
subpart VVb, the EPA elected to use the benefit per-ton (BPT) approach. 
BPT estimates provide the total monetized human health benefits (the 
sum of premature mortality and premature morbidity) of reducing one ton 
of the VOC precursor for ozone from a specified source. Specifically, 
in this analysis, we multiplied the estimates from the SOCMI sector by 
the corresponding emission reductions. Also, there are no climate 
benefits or disbenefits associated with this proposed NSPS. Thus, all 
monetized benefits are human health benefits from VOC reductions.
    The PV of the net monetized benefits (monetized health benefits 
only) for the proposed NSPS subpart VVb are $1.2 million at the 3 
percent discount rate to $0.9 million at the 7 percent discount rate 
and $11 million at the 3 percent discount rate to $7.5 million at the 7 
percent discount rate. The EAV of the benefits for the proposed NSPS 
subpart VVb are $0.10 million at the 3 percent discount rate to $0.09 
million at the 7 percent discount rate and $0.93 million at the 3 
percent discount rate to $0.82 million at the 7 percent discount rate.
5. NSPS Subpart IIIa, NNNa, and RRRa
    Because the estimated emissions reductions due to this rule are 
relatively small and because we cannot be confident of the location of 
new facilities that would be subject to the proposed NSPS subparts 
IIIa, NNNa, and RRRa, the EPA elected to use the BPT approach. BPT 
estimates provide the total monetized human health benefits (the sum of 
premature mortality and premature morbidity) of reducing one ton of the 
VOC precursor for ozone from a specified source. Specifically, in this 
analysis, we multiplied the estimates from the SOCMI sector by the 
corresponding emission reductions. We then add these monetized human 
health benefits to the monetized climate benefits and disbenefits to 
provide a total estimate of monetized benefits for these proposed NSPS.
    The PV of the net monetized benefits (monetized health benefits 
plus monetized climate benefits minus monetized climate disbenefits) 
for the proposed NSPS subparts IIIa, NNNa, and RRRa are $11.4 million 
at the 3 percent discount rate to $10.0 million at the 7 percent 
discount rate and $47.8 million at the 3 percent discount rate to $34.8 
million at the 7 percent discount rate. The EAV of the benefits for the 
proposed NSPS subparts IIIa, NNNa, and RRRa are $1.0 million at the 3 
percent discount rate to $0.9 million at the 7 percent discount rate 
and $4.1 million at the 3 percent discount rate to $3.6 million at the 
7 percent discount rate.

F. What analysis of environmental justice did we conduct?

    Executive Order 12898 directs EPA to identify the populations of 
concern who are most likely to experience unequal burdens from 
environmental harms, which are specifically minority populations 
(people of color), low-

[[Page 25182]]

income populations, and Indigenous peoples (59 FR 7629, February 16, 
1994). Additionally, Executive Order 13985 is intended to advance 
racial equity and support underserved communities through Federal 
government actions (86 FR 7009, January 20, 2021). For this action, 
pursuant to these Executive Orders, the EPA conducted an assessment of 
the impacts that would result from the proposed rule amendments, if 
promulgated, on communities with environmental justice (EJ) concerns. 
However, this assessment did not inform the technical and scientific 
determinations made to support the proposed rule amendments in this 
action. The EPA defines EJ as ``the fair treatment and meaningful 
involvement of all people regardless of race, color, national origin, 
or income, with respect to the development, implementation, and 
enforcement of environmental laws, regulations, and policies.'' \168\ 
The EPA further defines fair treatment to mean that ``no group of 
people should bear a disproportionate burden of environmental harms and 
risks, including those resulting from the negative environmental 
consequences of industrial, governmental, and commercial operations or 
programs and policies.'' In recognizing that people of color and low-
income populations often bear an unequal burden of environmental harms 
and risks, the EPA continues to consider ways of protecting them from 
adverse public health and environmental effects of air pollution. For 
purposes of analyzing regulatory impacts, the EPA relies upon its June 
2016 ``Technical Guidance for Assessing Environmental Justice in 
Regulatory Analysis,'' \169\ which provides recommendations that 
encourage analysts to conduct the highest quality analysis feasible, 
recognizing that data limitations, time, resource constraints, and 
analytical challenges will vary by media and circumstance. The 
Technical Guidance states that a regulatory action may involve 
potential EJ concerns if it could: (1) Create new disproportionate 
impacts on minority populations, low-income populations, and/or 
Indigenous peoples; (2) exacerbate existing disproportionate impacts on 
minority populations, low-income populations, and/or Indigenous 
peoples; or (3) present opportunities to address existing 
disproportionate impacts on minority populations, low-income 
populations, and/or Indigenous peoples through this action under 
development.
---------------------------------------------------------------------------

    \168\ https://www.epa.gov/environmentaljustice.
    \169\ See https://www.epa.gov/environmentaljustice/technical-guidance-assessing-environmental-justice-regulatory-analysis.
---------------------------------------------------------------------------

1. SOCMI Source Category Demographics
    For the SOCMI source category, the EPA examined the potential for 
the 195 HON facilities (for which the EPA had HAP emissions 
inventories) to pose concerns to communities living in proximity to 
facilities, both in the baseline and under the control option 
considered in this proposal. Specifically, the EPA analyzed how 
demographics and risk are distributed both pre- and post-control, 
enabling us to address the core questions that are posed in the EPA's 
2016 Technical Guidance for Assessing Environmental Justice in 
Regulatory Analysis. In conducting this analysis, we considered key 
variables highlighted in the guidance including ``minority populations 
(people of color and Hispanic or Latino), low-income populations, and/
or indigenous peoples.'' The methodology and detailed results of the 
demographic analysis are presented in the document titled Analysis of 
Demographic Factors for Populations Living Near Hazardous Organic 
NESHAP (HON) Facilities, which is available in the docket for this 
action.
    To examine the potential for EJ concerns, the EPA conducted a 
baseline proximity analysis, baseline risk-based analysis (i.e., before 
implementation of any controls proposed by this action), and post-
control risk-based analysis (i.e., after implementation of the controls 
proposed by this action). The baseline proximity demographic analysis 
is an assessment of individual demographic groups in the total 
population living within 10 km (~6.2 miles) and 50 km (~31 miles) of 
the facilities. The baseline risk-based demographic analysis is an 
assessment of risks to individual demographic groups in the population 
living within 10 km and 50 km of the facilities prior to the 
implementation of any controls proposed by this action (``baseline''). 
The post-control risk-based demographic analysis is an assessment of 
risks to individual demographic groups in the population living within 
10 km and 50 km of the facilities after implementation of the controls 
proposed by this action (``post-control''). In this preamble, we focus 
on the 10 km radius for the demographic analysis because it encompasses 
all the facility MIR locations, captures 97 percent of the population 
with baseline cancer risks greater than or equal to 50-in-1 million 
from SOCMI source category emissions, and captures 100 percent of the 
population with such baseline risks greater than 100-in-1 million. The 
results of the proximity analysis for populations living within 50 km 
are included in the document titled Analysis of Demographic Factors for 
Populations Living Near Hazardous Organic NESHAP (HON) Facilities, 
which is available in the docket for this action.
    Under the risk-based demographic analysis, the total population, 
population percentages, and population count for each demographic group 
for the entire U.S. population is shown in the column titled 
``Nationwide Average for Reference'' in Tables 31 through 33 of this 
preamble of this document. These national data are provided as a frame 
of reference to compare the results of the baseline proximity analysis, 
the baseline risk-based analyses, and the post-control risk-based 
analyses.
    The results of the proximity demographic analysis indicate that a 
total of 9.3 million people live within 10 km of the 195 HON 
facilities. The percent of the population that is African American is 
more than double the national average and the percent of the population 
that is Hispanic or Latino (22 percent) is also higher than the 
national average (19 percent). The percent of people living below the 
poverty level and the percent of people over the age of 25 without a 
high school diploma are higher than the national averages. The results 
of the baseline proximity analysis indicate that the proportion of 
other demographic groups living within 10 km of HON facilities is 
similar to or below the national average. The baseline risk-based 
demographic analysis, which focuses on populations that have higher 
cancer risks, suggests that Hispanic/Latinos and African Americans are 
overrepresented at all cancer risk levels greater than 1-in-1 million. 
In addition, linguistic isolation increases as the Hispanic/Latino 
population increases. At all risk levels, in most cases, populations 
living around facilities where the percentage of the population below 
the poverty level is 1.5 to 2 times the national average also are above 
the national average for African American, Native American, Hispanic/
Latino, or Other/Multiracial. The post-control risk-based demographic 
analysis shows that the controls under consideration in this proposal 
would reduce the number of people who are exposed to cancer risks 
resulting from SOCMI source category emissions greater than or equal to 
1-in-1 million, greater than or equal to 50-in-1 million, and greater 
than 100-in-1 million significantly, which will

[[Page 25183]]

improve human health of current and future populations that live near 
these facilities. After the control has been implemented, there will be 
no people who are exposed to cancer risks greater than 100-in-1 million 
resulting from SOCMI source category emissions. For more details see 
the remainder of this section.
a. Baseline Proximity Analysis
    The column titled ``Baseline Proximity Analysis for Pop. Living 
within 10 km of HON Facilities'' in Tables 31 through 33 of this 
preamble shows the share and count of people for each of the 
demographic categories for the total population living within 10 km 
(~6.2 miles) of HON facilities. These are the results of the baseline 
proximity analysis. These baseline proximity results are repeated in 
Tables 31 through 33 of this preamble for easy comparison to the risk-
based analyses discussed later.
    Approximately 9.3 million people live within 10 km of the 195 HON 
facilities assessed. The results of the proximity demographic analysis 
indicate that the percent of the population that is African American 
(25 percent, 2.35M people) is more than double the national average (12 
percent). The percent of the population that is Hispanic or Latino (22 
percent, 2M people) is higher than the national average (19 percent). 
The percent of people living below the poverty level (19 percent, 1.75M 
people) and percent of people over the age of 25 without a high school 
diploma (16 percent, 1.5M people) are higher than the national averages 
(13 percent and 12 percent, respectively). The baseline proximity 
analysis indicates that the proportion of other demographic groups 
living within 10 km of HON facilities is similar to or below the 
national average.
b. Baseline Risk-Based Demographics
    The baseline risk-based demographic analysis results are shown in 
the ``baseline'' column of Tables 31 through 33 of this preamble. This 
analysis focused on the populations living within 10 km (~6.2 miles) of 
the HON facilities with estimated cancer risks greater than or equal to 
1-in-1 million resulting from SOCMI source category emissions (Table 31 
of this preamble), greater than or equal to 50-in-1 million (Table 32 
of this preamble), and greater than 100-in-1 million (Table 33 of this 
preamble). The risk analysis indicated that emissions from the source 
category, prior to the controls we are proposing, expose 2.8 million 
people living near 111 facilities to a cancer risk greater than or 
equal to 1-in-1 million, 342,000 people living near 21 facilities to a 
cancer risk greater than or equal to 50-in-1 million, and 87,000 people 
living near 8 facilities to a cancer risk greater than 100-in-1 
million.
    In the baseline, there are 2.8 million people living around 111 HON 
facilities with a cancer risk greater than or equal to 1-in-1 million 
resulting from SOCMI source category emissions. The 111 HON facilities 
are located across 17 states, but two-thirds of them are located in 
Texas and Louisiana (50 in Texas and 33 in Louisiana). Ninety percent 
of the people with risks greater than or equal to 1-in-1 million are 
living around 29 of the 111 HON facilities. All but three of these 29 
facilities are located in Texas and Louisiana. The percent of the 
baseline population with estimated cancer risks greater than or equal 
to 1-in-1 million who are African American (25 percent, 692,000 people) 
is well above the average percentage of the national population that is 
African American (12 percent). The African American population living 
within 10 km of two facilities in Louisiana account for about a quarter 
of the total African American population with risks greater than or 
equal to 1-in-1 million resulting from SOCMI source category emissions.
    The percent of the population with cancer risks greater than or 
equal to 1-in-1 million resulting from SOCMI source category emissions 
prior to the proposed controls that is Hispanic or Latino (34 percent, 
958,000 people) is significantly higher than that in the baseline 
proximity analysis (22 percent, 2 million people) and well above the 
national average (19 percent). The population around an Illinois 
facility is over 75 percent Hispanic or Latino, and accounts for a 
quarter of the Hispanic/Latino population with risks greater than or 
equal to 1-in-1 million resulting from SOCMI source category emissions. 
Another group of 5 facilities in the Houston/Channelview Texas area 
have local populations that are between 60 and 90 percent Hispanic/
Latino, and those communities account for 31 percent of the Hispanic/
Latino population with risks greater than or equal to 1-in-1 million 
resulting from SOCMI source category emissions. The percent of the 
population that is linguistically isolated in the baseline with cancer 
risks greater than or equal to 1-in-1 million (8 percent, 228,000 
people) is higher than the percentage in the baseline proximity 
analysis (5 percent, 510,000 people). The areas with the highest 
Hispanic/Latino population are some of those with the highest percent 
linguistic isolation.
    Overall, the percent of the baseline population that is Native 
American with risks greater than or equal to 1-in-1 million resulting 
from SOCMI source category emissions (0.2 percent) is well below the 
national average (0.7 percent). The population with baseline risks 
resulting from SOCMI source category emissions greater than or equal to 
1-in-1 million have a percent Native American population that is more 
than 2 times the national average. These facilities are located in 
Texas (3), Louisiana, Montana, Illinois, and Kansas.
    The percent of the population below the poverty level with cancer 
risks greater than or equal to 1-in-1 million resulting from SOCMI 
source category emissions (18 percent, 513K people) is above the 
national average (13 percent). The percent of the population living 
below the poverty level within 10 km of 19 facilities is twice the 
national average. The percent of the population over 25 years old 
without a high school diploma with cancer risks greater than or equal 
to 1-in-1 million resulting from SOCMI source category emissions (20 
percent, 561,000 people) is greater than the national average (13 
percent) as well as greater than the overall percent of the population 
living near HON facilities who are over 25 years old without a high 
school diploma (16 percent, 1.5 million people).
    In the baseline, there are 342,000 people living around 21 HON 
facilities with a cancer risk greater than or equal to 50-in-1 million 
resulting from SOCMI source category emissions. The 21 HON facilities 
are located across 6 states, but two-thirds of them are located in 
Texas and Louisiana. Ninety-six percent of the people with risks 
greater than or equal to 50-in-1 million resulting from SOCMI source 
category emissions live around 5 HON facilities, which are located in 
Texas or Louisiana. The percent of the population that is African 
American with baseline cancer risk greater than or equal to 50-in-1 
million resulting from SOCMI source category emissions (19 percent, 
65,000 people) is above the national average (12 percent) but is 
significantly lower than the percent of the population that is African 
American with risks greater than or equal to 1-in-1 million resulting 
from SOCMI source category emissions (25 percent, 692,000 people). The 
percentage of African Americans is greater than the national average 
near over half of the facilities (12 facilities) where cancer risk is 
greater than 50-in-1 million resulting from HON source category 
emissions. The populations near two facilities in Texas account for 
about 70 percent of the number of African Americans with risks greater 
than or equal to 50-in-1

[[Page 25184]]

million resulting from SOCMI source category emissions.
    The percentage of the population that is Hispanic/Latino with risks 
greater than or equal to 50-in-1 million resulting from SOCMI source 
category emissions (24 percent, 83,000 people) is similar to the 
percentage of the population that is Hispanic/Latino in the total 
population living within 10 km of the facilities (22 percent). The 
percent of population that is Hispanic/Latino with cancer risks greater 
than or equal to 50-in-1 million resulting from SOCMI source category 
emissions is above the national average at over half of the facilities 
(13 facilities). The population near three facilities in Texas account 
for about 80 percent of the number of Latino/Hispanic people with risks 
greater than or equal to 50-in-1 million resulting from SOCMI source 
category emissions.
    Overall, the percent of the population that is Native American with 
risks greater than or equal to 50-in-1 million resulting from SOCMI 
source category emissions (0.2 percent) is below the national average 
(0.7 percent). Populations near four facilities with baseline risks 
greater than or equal to 50-in-1 million resulting from SOCMI source 
category emissions that have a percent Native American population that 
is more than 2 times the national average. These facilities are located 
in Texas (3) and Louisiana.
    The percentage of the population with cancer risks resulting from 
SOCMI source category emissions greater than or equal to 50-in-1 
million that are below the poverty level (14 percent), over 25 years 
old without a high school diploma (15 percent), or are linguistically 
isolated (5 percent) are similar or slightly above the respective 
national averages. Of the population with risks greater than or equal 
to 50-in-1 million resulting from SOCMI source category emissions, the 
percentage of the population below the poverty level is twice the 
national average near five facilities. For all 5 of these facilities, 
the percentage of the population is also 2 times the national average 
percentage for at least one race/ethnic demographic category.
    In the baseline, there are 88,000 people living around 8 HON 
facilities with a cancer risk resulting from SOCMI source category 
emissions greater than 100-in-1 million. These 8 HON facilities are 
located in Texas and Louisiana. The percent of the population that is 
African American with baseline cancer risk greater than 100-in-1 
million resulting from SOCMI source category emissions (15 percent) is 
just above the national average (12 percent). The percentage of the 
African American population with cancer risks greater than 100-in-1 
million resulting from SOCMI source category emissions is between 2 to 
4 times greater than the national average at three facilities in Texas 
and one in Louisiana.
    The percentage of the population that is Hispanic/Latino with risks 
greater than 100-in-1 million resulting from SOCMI source category 
emissions (25 percent, 22,000 people) is above the national average (19 
percent) and is similar to the share of the population with cancer 
risks resulting from SOCMI source category emissions greater than or 
equal to 50-in-1 million (24 percent, 83,000 people). The share of the 
Hispanic and Latino population with cancer risks greater than 100-in-1 
million resulting from SOCMI source category emissions is between 2 to 
3 times greater than the national average at five facilities in Texas 
and one in Louisiana.
    Overall, the percent of the baseline population that is Native 
American with risks greater than or equal to 100-in-1 million resulting 
from SOCMI source category emissions (0.2 percent) is well below the 
National Average (0.7 percent).
    The percentage of the population with cancer risks greater than 
100-in-1 million resulting from SOCMI source category emissions that 
are below the poverty level (14 percent), over 25 without a high school 
diploma (14 percent), or linguistically isolated (5 percent) are 
similar or slightly above the respective national averages. The percent 
of the population below the poverty level is 1.5 times the national 
average at five facilities. The population living around three of these 
facilities is also 1.5 times the national average for at least one 
race/ethnic demographic.
    In summary, the baseline risk-based demographic analysis, which 
focuses on populations that are expected to have higher cancer risks 
resulting from SOCMI source category emissions, suggests that Hispanics 
or Latinos are disproportionally overrepresented at all cancer risk 
levels. Specifically, the percent of the population that is Hispanic/
Latino is almost twice the national average at a cancer risk equal to 
or greater than 1-in-1 million and almost 1.5 times the national 
average at the 50 in a million and 100 in a million risk levels. 
Similarly, the African American population is disproportionately 
overrepresented at all cancer risk levels in the baseline risk 
analysis. The percentage of African American individuals with risks 
greater than or equal to 1-in-1 million resulting from SOCMI source 
category emissions is twice the national average and 1.25 times the 
national average for the percentage with risks greater than 100-in-1 
million. In most cases, when the percentage of the population below the 
poverty level is greater than 1.5 times the national average the 
percentage of the populations that is African American, Native 
American, Hispanic/Latino, or Other/Multiracial residents is above the 
national average.
c. Post-Control Risk-Based Demographics
    This analysis focused on the populations living within 10 km (~6.2 
miles) of the facilities with estimated cancer risks greater than or 
equal to 1-in-1 million (Table 31 of this preamble), greater than or 
equal to 50-in-1 million (Table 32 of this preamble), and greater than 
100-in-1 million (Table 33 of this preamble) resulting from SOCMI 
source category emissions after implementation of the control options 
for HON sources investigated under the residual risk analysis as 
described in section III.B.2.a of this preamble (``post-control''). The 
results of the post-control risk-based demographics are in the columns 
titled ``Post-Control'' of Tables 31 through 33 of this preamble. In 
this analysis, we evaluated how all of the proposed controls and 
emission reductions for HON processes described in this action affect 
the distribution of risks. This enables us to characterize the post-
control risks and to evaluate whether the proposed action creates or 
mitigates potential EJ concerns as compared to the baseline.
    The risk analysis indicated that the number of people within 10 km 
of a facility exposed to risks greater than or equal to 1-in-1 million 
resulting from SOCMI source category emissions (Table 31 of this 
preamble) is reduced from 2.8 million people in the baseline to 
approximately 2.5 million people after implementation of the proposed 
HON controls. The populations with a cancer risk greater than or equal 
to 1-in-1 million resulting from SOCMI source category emissions are 
located around 111 facilities for both the baseline and post-control.
    The post-control population living within 10 km of a facility with 
estimated cancer risks greater than or equal to 1-in-1 million 
resulting from SOCMI source category emissions (Table 31 of this 
preamble) has similar demographic percentages to the baseline 
population with risks greater than or equal to 1-in-1 million. However, 
the number of individuals with risks greater than or equal to 1-in-1 
million resulting from SOCMI source category emissions is reduced in 
each demographic.

[[Page 25185]]

Specifically, percentage of the population with risks greater than or 
equal to 1-in-1 million resulting from SOCMI source category emissions 
that is African American remains high at 23 percent in the post-control 
scenario, but the number of African Americans with risks at or above 1-
in-1 million is reduced by over 100,000 people from 692,000 in the 
baseline to 583,000 in the post-control scenario.
    Similarly, the percentage of the population with risks greater than 
or equal to 1-in-1 million resulting from SOCMI source category 
emissions that is Hispanic/Latino is almost twice the national average 
in the post-control scenario (37 percent versus 19 percent), but the 
number of Hispanic/Latino individuals with risks at or above 1-in-1 
million is reduced by about 40,000 people from 958,000 in the baseline 
to 917,000 in the post-control scenario.
    The percent of the population that is Native American with risks 
greater than or equal to 1-in-1 million resulting from SOCMI source 
category emissions (0.2 percent) is below the national average (0.7 
percent) in the post-control analysis. Nevertheless, there are seven 
facilities post-control with risks greater than or equal to 1-in-1 
million with a percent Native American population that is more than 2 
times the national average. However, the number of Native Americans 
with risks greater than or equal to 1-in-1 million resulting from SOCMI 
source category emissions is reduced from 6,000 in the baseline to 
5,000 in the post-control scenario.
    The percent of the population below the poverty level is the same 
in the post-control scenario as in the baseline (18 percent), but the 
number of individuals with risks greater than or equal to 1-in-1 
million resulting from SOCMI source category emissions that are below 
the poverty level is reduced by 56,000, from 513,000 to 457,000. The 
percent of individuals over 25 years old without a high school diploma 
is the same in the post-control scenario as in the baseline (20 
percent), but the number of individuals with risks greater than or 
equal to 1-in-1 million resulting from SOCMI source category emissions 
is reduced by almost 50,000, from 561,000 to 513,000. The percentage of 
the population that is in linguistic isolation with risks greater than 
or equal to 1-in-1 million resulting from SOCMI source category 
emissions is higher in the post-control scenario (9 percent), but the 
number of individuals is reduced by 14,000 compared to the baseline, 
from 228,000 to 214,000.
    The risk analysis indicated that the number of people living within 
10 km of a facility and exposed to risks greater than or equal to 50-
in-1 million resulting from SOCMI source category emissions (Table 32 
of this preamble) is reduced significantly from 342,000 people in the 
baseline to 29,000 after implementation of the proposed controls. This 
represents more than a 90 percent reduction in the number of 
individuals with risk greater than or equal to 50-in-1 million when 
compared to the baseline. The populations living within 10 km of a 
facility and with a cancer risk greater than or equal to 50-in-1 
million resulting from SOCMI source category emissions are located 
around 13 facilities in the post-control scenario, 8 fewer facilities 
than in the baseline. These 13 facilities are located in Alabama, 
Arkansas, Illinois, Kentucky, Louisiana (5 facilities), and Texas (4 
facilities). The communities within 10 km of five of those facilities 
(in Texas (3 facilities), Alabama, and Illinois) comprise 95 percent of 
the population with risks greater than or equal to 50-in-1 million 
resulting from SOCMI source category emissions.
    The number of individuals with risks greater than or equal to 50-
in-1 million is reduced significantly for each demographic category in 
the post-control scenario. Specifically, the percentage of the 
population with risks greater than or equal to 50-in-1 million 
resulting from SOCMI source category emissions that is African American 
decreased in the post-control scenario and is equal to the national 
average (12 percent). The number of African Americans with risks at or 
above 50-in-1 million is reduced from 65,000 in the baseline to 4,000 
post-control. The percentage of the population with risks greater than 
or equal to 50-in-1 million resulting from SOCMI source category 
emissions that is Hispanic/Latino increased from 24 percent in the 
baseline to 29 percent post-control, but the number of Hispanic/Latino 
individuals with risks at or above 50-in-1 million is reduced from 
83,000 in the baseline to 9,000 post-control.
    Overall, the percent of the population that is Native American with 
risks greater than or equal to 50-in-1 million resulting from SOCMI 
source category emissions (0.3 percent) is well below the national 
average (0.7 percent) in the post-control scenario. In addition, the 
number of Native Americans with risks greater than or equal to 50-in-1 
million resulting from SOCMI source category emissions is reduced from 
700 in the baseline to less than 100 post-control.
    The percent of the population with risks greater than or equal to 
50-in-1 million resulting from SOCMI source category emissions whose 
income is below the poverty level (11 percent) is reduced from the 
baseline (14 percent) post-control. In addition, the number of 
individuals with risks greater than or equal to 50-in-1 million 
resulting from SOCMI source category emissions who are below the 
poverty level is reduced from 49,000 to 3,000. The number of 
individuals with risks greater than or equal to 50-in-1 million 
resulting from SOCMI source category emissions that are over 25 years 
old without a high school diploma or are linguistically isolated are 
greatly reduced post-control.
    The risk analysis indicated that the number of people living within 
10 km of a facility with risks greater than 100-in-1 million resulting 
from SOCMI source category emissions (Table 33 of this preamble) is 
reduced from over 87,000 individuals in the baseline to zero 
individuals after application of the proposed SOCMI controls. 
Therefore, for the post-control risk-based demographic results, there 
are no greater than 100-in-1 million demographic results to discuss.
    In summary, as shown in the post-control risk-based demographic 
analysis, the controls under consideration in this proposal would 
significantly reduce the number of people expected to have cancer risks 
greater than or equal to 1-in-1 million, greater than or equal to 50-
in-1 million, and greater than 100-in-1 million resulting from SOCMI 
source category emissions. Although the number of individuals with 
risks greater than or equal to 1-in-1 million is reduced in the post-
control scenario (reduced from 2.8 million people to 2.5 million 
people), populations of African Americans, Hispanics/Latinos, those 
living below the poverty level, and those over 25 without a high school 
diploma remain disproportionately represented. Similarly, the number of 
individuals with risks greater than or equal to 50-in-1 million is 
reduced significantly in the post-control scenario (reduced from 
342,000 to 29,000), but the population of African Americans remains 
disproportionately represented. Post-control there are no individuals 
with risks greater than 100-in-1 million resulting from SOCMI source 
category emissions (reduced from 87,000 people to 0 people).

[[Page 25186]]

 Table 31--Source Category: Comparison of Baseline and Post-Control Demographics of Populations With Cancer Risk
  Greater Than or Equal to 1-in-1 Million Resulting From SOCMI Source Category Emissions Living Within 10 km of
                          Facilities to the National Average and Proximity Demographics
----------------------------------------------------------------------------------------------------------------
                                                      Baseline proximity  Cancer risk >=1-in-1 million within 10
                                                       analysis for pop.           km of  HON facilities
        Demographic group         Nationwide average   living  within 10 ---------------------------------------
                                     for reference        km of  HON
                                                          facilities           Baseline          Post-control
----------------------------------------------------------------------------------------------------------------
Total Population................  328M..............  9,271,798.........  2,798,319.........  2,512,518.
Number of Facilities............  ..................  195...............  111...............  111.
----------------------------------------------------------------------------------------------------------------
                                Race and Ethnicity by Percent [number of people]
----------------------------------------------------------------------------------------------------------------
White...........................  60 [197M].........  47 [4.4M].........  37 [1.04M]........  37 [919K].
African American................  12 [40M]..........  25 [2.35M]........  25 [692K].........  23 [583K].
Native American.................  0.7 [2M]..........  0.2 [20K].........  0.2 [6K]..........  0.2 [5K].
Hispanic or Latino (includes      19 [62M]..........  22 [2M]...........  34 [958K].........  37 [917K].
 white and nonwhite).
Other and Multiracial...........  8 [27M]...........  5 [493K]..........  4 [101K]..........  4 [89K].
----------------------------------------------------------------------------------------------------------------
                                      Income by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Below Poverty Level.............  13 [44M]..........  19 [1.75M]........  18 [513K].........  18 [457K].
Above Poverty Level.............  87 [284M].........  81 [7.5M].........  82 [2.3M].........  82 [2.1M].
----------------------------------------------------------------------------------------------------------------
                                     Education by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High        12 [40M]..........  16 [1.5M].........  20 [561K].........  20 [513K].
 School Diploma.
Over 25 and with a High School    88 [288M].........  84 [7.8M].........  80 [2.2M].........  80 [2M].
 Diploma.
----------------------------------------------------------------------------------------------------------------
                              Linguistically Isolated by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated.........  5 [18M]...........  5 [510K]..........  8 [228K]..........  9 [214K].
----------------------------------------------------------------------------------------------------------------
Notes:
 There are 207 HON facilities; however, only 195 of these facilities are included in the proximity
  analysis based on available data, which corresponds to 222 EIS facility IDs.
 Nationwide population and demographic percentages are based on Census' 2015-2019 American Community
  Survey (ACS) 5-year block group averages. Total population count within 10 km is based on 2010 Decennial
  Census block population.
 To avoid double counting, the ``Hispanic or Latino'' category is treated as a distinct demographic
  category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race.
 The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR
  was located at a user assigned receptor at an individual residence and not at a census block centroid, we were
  unable to estimate population and demographics for that facility.
 The sum of individual populations with a demographic category may not add up to total due to rounding.

 Table 32--Source Category: Comparison of Baseline and Post-Control Demographics of Populations With Cancer Risk
 Greater Than or Equal to 50-in-1 Million Resulting From SOCMI Source Category Emissions Living Within 10 km of
                          Facilities to the National Average and Proximity Demographics
----------------------------------------------------------------------------------------------------------------
                                                      Baseline proximity  Cancer risk >=1-in-1 million within 10
                                                       analysis for pop.           km of  HON facilities
        Demographic group         Nationwide average   living  within 10 ---------------------------------------
                                     for reference        km of  HON
                                                          facilities           Baseline          Post-control
----------------------------------------------------------------------------------------------------------------
Total Population................  328M..............  9,271,798.........  341,638...........  29,355.
Number of Facilities............  ..................  195...............  21................  13.
----------------------------------------------------------------------------------------------------------------
                                Race and Ethnicity by Percent [number of people]
----------------------------------------------------------------------------------------------------------------
White...........................  60 [197M].........  47 [4.4M].........  52 [177K].........  54 [16K].
African American................  12 [40M]..........  25 [2.35M]........  19 [65K]..........  12 [4K].
Native American.................  0.7 [2M]..........  0.2 [20K].........  0.2 [660].........  0.3 [81].
Hispanic or Latino (includes      19 [62M]..........  22 [2M]...........  24 [83K]..........  29 [9K] .
 white and nonwhite).
Other and Multiracial...........  8 [27M]...........  5 [493K]..........  5 [17K]...........  4 [1.2K].
----------------------------------------------------------------------------------------------------------------
                                      Income by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Below Poverty Level.............  13 [44M]..........  19 [1.75M]........  14 [49K]..........  11 [3.3K].
Above Poverty Level.............  87 [284M].........  81 [7.5M].........  86 [293K].........  89 [26K].
----------------------------------------------------------------------------------------------------------------
                                     Education by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High        12 [40M]..........  16 [1.5M].........  15 [50K]..........  12 [4K].
 School Diploma.
Over 25 and with a High School    88 [288M].........  84 [7.8M].........  85 [291K].........  88 [26K].
 Diploma.
----------------------------------------------------------------------------------------------------------------
                              Linguistically Isolated by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated.........  5 [18M]...........  5 [510K]..........  5 [15K]...........  3 [766].
----------------------------------------------------------------------------------------------------------------
Notes:
 There are 207 HON facilities; however, only 195 of these facilities are included in the proximity
  analysis based on available data, which corresponds to 222 EIS facility IDs.
 Nationwide population and demographic percentages are based on Census' 2015-2019 ACS 5-year block group
  averages. Total population count within 10 km is based on 2010 Decennial Census block population.
 To avoid double counting, the ``Hispanic or Latino'' category is treated as a distinct demographic
  category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race.
 The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR
  was located at a user assigned receptor at an individual residence and not at a census block centroid, we were
  unable to estimate population and demographics for that facility.

[[Page 25187]]

 
 The sum of individual populations with a demographic category may not add up to total due to rounding.

 Table 33--Source Category: Comparison of Baseline and Post-Control Demographics of Populations With Cancer Risk
 Greater Than 100-in-1 Million Resulting From SOCMI Source Category Emissions Living Within 10 km of Facilities
                               to the National Average and Proximity Demographics
----------------------------------------------------------------------------------------------------------------
                                                      Baseline proximity  Cancer risk >=1-in-1 million within 10
                                                       analysis for pop.           km of  HON facilities
        Demographic group         Nationwide average   living  within 10 ---------------------------------------
                                     for reference        km of  HON
                                                          facilities           Baseline          Post-control
----------------------------------------------------------------------------------------------------------------
Total Population................  328M..............  9,271,798.........  87,464............  0
Number of Facilities............  ..................  195...............  8.................  0
----------------------------------------------------------------------------------------------------------------
                                Race and Ethnicity by Percent [number of people]
----------------------------------------------------------------------------------------------------------------
White...........................  60 [197M].........  47 [4.4M].........  54 [47K]..........
African American................  12 [40M]..........  25 [2.35M]........  15 [13K]..........
Native American.................  0.7 [2M]..........  0.2 [20K].........  0.2 [202].........
Hispanic or Latino (includes      19 [62M]..........  22 [2M]...........  25 [22K]..........
 white and nonwhite).
Other and Multiracial...........  8 [27M]...........  5 [493K]..........  6 [5.5K]..........
----------------------------------------------------------------------------------------------------------------
                                      Income by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Below Poverty Level.............  13 [44M]..........  19 [1.75M]........  14 [12K]..........
Above Poverty Level.............  87 [284M].........  81 [7.5M].........  86 [75K]..........
----------------------------------------------------------------------------------------------------------------
                                     Education by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High        12 [40M]..........  16 [1.5M].........  14 [12K]..........
 School Diploma.
Over 25 and with a High School    88 [288M].........  84 [7.8M].........  86 [75K]..........
 Diploma.
----------------------------------------------------------------------------------------------------------------
                              Linguistically Isolated by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated.........  5 [18M]...........  5 [510K]..........  5 [4K]............
----------------------------------------------------------------------------------------------------------------
Notes:
 There are 207 HON facilities; however, only 195 of these facilities are included in the proximity
  analysis based on available data, which corresponds to 222 EIS facility IDs.
 Nationwide population and demographic percentages are based on Census' 2015-2019 ACS 5-year block group
  averages. Total population count within 10 km is based on 2010 Decennial Census block population.
 To avoid double counting, the ``Hispanic or Latino'' category is treated as a distinct demographic
  category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race.
 The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR
  was located at a user assigned receptor at an individual residence and not at a census block centroid, we were
  unable to estimate population and demographics for that facility.
 The sum of individual populations with a demographic category may not add up to total due to rounding.

2. HON Whole-Facility Demographics
    As described in section III.A.5 of this preamble, we assessed the 
facility-wide (or ``whole-facility'') risks for 195 HON facilities in 
order to compare the SOCMI source category risk to the whole facility 
risks, accounting for HAP emissions from the entire major source and 
not just those resulting from SOCMI source category emissions at the 
major source as discussed in the previous section. The whole facility 
risk assessment includes all sources of HAP emissions at each facility 
as reported in the NEI (described in section III.C of this preamble). 
Since HON facilities tend to include HAP emissions sources from many 
source categories, the EPA conducted a whole-facility demographic 
analysis focused on post-control risks. This whole-facility demographic 
analysis characterizes the remaining risks communities face after 
implementation of the controls proposed in this for both the SOCMI 
source category and the Neoprene Production source category.
    The whole-facility demographic analysis is an assessment of 
individual demographic groups in the total population living within 10 
km (~6.2 miles) and 50 km (~31 miles) of the facilities. In this 
preamble, we focus on the 10 km radius for the demographic analysis 
because, based on SOCMI category emissions, this distance includes all 
the facility MIR locations, includes 97 percent of the population with 
cancer risks greater than or equal to 50-in-1 million, and includes 100 
percent of the population with risks greater than 100-in-1 million. The 
results of the whole-facility demographic analysis for populations 
living within 50 km are included in the document titled Analysis of 
Demographic Factors for Populations Living Near Hazardous Organic 
NESHAP (HON) Facilities, which is available in the docket for this 
action.
    The whole-facility demographic analysis post-control results are 
shown in Table 34 of this preamble. This analysis focused on the 
populations living within 10 km of the HON facilities with estimated 
whole-facility post-control cancer risks greater than or equal to 1-in-
1 million, greater than or equal to 50-in-1 million, and greater than 
100-in-1 million. The risk analysis indicated that all emissions from 
the HON facilities, after the proposed reductions, expose a total of 
about 3 million people living around 140 facilities to a cancer risk 
greater than or equal to 1-in-1 million, 78,000 people living around 24 
facilities to a cancer risk greater than or equal to 50-in-1 million, 
and 2,500 people living around 4 facilities to a cancer risk greater 
than 100-in-1 million.
    When the HON whole-facility populations are compared to the SOCMI 
source category populations in the post-control scenarios, we see 
500,000 additional people with risks greater than or equal to 1-in-1 
million, 29,000 additional people with risks greater than or equal to 
50-in-1 million, and 2,500 additional people with risks greater than 
100-in-1 million. With the exception of a smaller percentage of 
affected Hispanic/Latino individuals (37 percent for category versus 33 
percent whole-facility), the demographic distribution of the whole-
facility population with risks greater than or equal to 1-in-million is 
similar to the category population with risks greater than or equal to 
1-in-1 million in the post-

[[Page 25188]]

control scenario. The population with risks greater than or equal to 
50-in-1 million in the whole-facility analysis has a lower percent of 
Hispanic/Latino individuals than the category population with risks 
greater than or equal to 50-in-1 million (25 percent versus 29 
percent). The percentage of the population with risks greater than or 
equal to 50-in-1 million that is below the poverty level or over 25 
years old without a high school diploma is higher for the whole-
facility post-control population than for the category post-control 
population. The SOCMI category emissions analysis indicated that there 
are no people with post-control risks greater than 100-in-1 million. 
Based on results from the whole-facility emissions analysis, there are 
2,500 people with post-control risks greater than 100-in-million. The 
increased cancer risk for most of these 2,500 people is driven by EtO 
emissions from non-HON processes and whole-facility emissions from the 
neoprene production facility (a combination of the remaining SOCMI 
category risk and neoprene production category risk at this facility). 
The percent of the population in the whole facility analysis with post-
control risks greater than 100-in-1 million that is African American 
(29 percent, 700 individuals) is well above the national average (12 
percent). In addition, the percent of the population in the whole 
facility analysis with a post control risk greater than 100-in-1 
million that is below the poverty level (21 percent,500 individuals), 
and the percent of the population that is over 25 years old without a 
high school diploma (25 percent, 600 individuals) are above the 
national average (13 percent and 12 percent, respectively).

     Table 34--Whole Facility: Whole-Facility Post-Control Demographics for HON Facilities by Risk Level for
                                  Populations Living Within 10 km of Facilities
----------------------------------------------------------------------------------------------------------------
                                                         Post-control cancer risk for populations within 10 km
        Demographic group             Nationwide     -----------------------------------------------------------
                                                       >=1-in-1 million    >=50-in-1 million   >100-in-1 million
----------------------------------------------------------------------------------------------------------------
Total Population................  328M..............  3,119,955.........  78,144............  2,498.
Number of Facilities............  ..................  140...............  24................  4.
----------------------------------------------------------------------------------------------------------------
                                Race and Ethnicity by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
White...........................  60 [197M].........  39 [1.2M].........  57 [45K]..........  53 [1.3K].
African American................  12 [40M]..........  24 [760K].........  14 [11K]..........  29 [727].
Native American.................  0.7 [2M]..........  0.2 [6.5K]........  0.2 [174].........  0.0 [1].
Hispanic or Latino (includes      19 [62M]..........  33 [1M]...........  25 [20K]..........  17 [434].
 white and nonwhite).
Other and Multiracial...........  8 [27M]...........  4 [113K]..........  4 [3K]............  1 [22] .
----------------------------------------------------------------------------------------------------------------
                                      Income by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Below Poverty Level.............  13 [44M]..........  18 [576K].........  14 [11K]..........  21 [531].
Above Poverty Level.............  87 [284M].........  82 [2.5M].........  86 [67K]..........  79 [2K] .
----------------------------------------------------------------------------------------------------------------
                                     Education by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High        12 [40M]..........  20 [614K].........  16 [12.5K]........  25 [619].
 School Diploma.
Over 25 and with a High School    88 [288M].........  80 [2.5M].........  84 [66K]..........  75 [2K].
 Diploma.
----------------------------------------------------------------------------------------------------------------
                              Linguistically Isolated by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated.........  5 [18M]...........  8 [236K]..........  3 [3K]............  2 [43].
----------------------------------------------------------------------------------------------------------------
Notes:
 Nationwide population and demographic percentages are based on Census' 2015-2019 ACS 5-year block group
  averages. Total population count within 10 km is based on 2010 Decennial Census block population.
 To avoid double counting, the ``Hispanic or Latino'' category is treated as a distinct demographic
  category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race.
 The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR
  was located at a user assigned receptor at an individual residence and not at a census block centroid, we were
  unable to estimate population and demographics for that facility.
 The sum of individual populations with a demographic category may not add up to total due to rounding.

3. Neoprene Production Source Category Demographics
    For the Neoprene Production source category, the EPA examined the 
potential for the one neoprene production facility to pose EJ concerns 
to communities both in the baseline and under the control option 
considered in this proposal. Specifically, the EPA analyzed how 
demographics and risk are distributed both pre- and post-control, 
enabling us to address the core questions that are posed in the EPA's 
2016 Technical Guidance for Assessing Environmental Justice in 
Regulatory Analysis. In conducting this analysis, we considered key 
variables highlighted in the guidance including minority populations 
(people of color and Hispanic or Latino), low-income populations, and/
or indigenous peoples. The methodology and detailed results of the 
demographic analysis are presented in a technical report, Analysis of 
Demographic Factors for Populations Living Near Neoprene Production 
Facilities, available in the docket for this action.
    To examine the potential for EJ concerns in the pre-control 
baseline, the EPA conducted a baseline proximity analysis, baseline 
risk-based analysis, and post-control risk-based analysis. These 
analyses (total baseline, baseline risk, and post-control risks) 
assessed the demographic groups in the populations living within 5 km 
(~3.1 miles) and 50 km (~31 miles) of the facility. For the Neoprene 
Production source category, we focus on the 5 km radius for the 
demographic analysis because it encompasses the facility MIR location 
and captures 100 percent of the population with cancer risks resulting 
from Neoprene Production source category emissions greater than or 
equal to 50-in-1 million and greater than 100-in-1 million. The results 
of the proximity analysis for populations living within 50 km are 
included in the technical report included in the docket for this 
proposed rule. Nationwide average demographics data are provided as a 
frame of reference.
    The results of the proximity demographic analysis indicate that a 
total of about 29,000 people live within 5 km of the Neoprene facility. 
The percent of the population that is African

[[Page 25189]]

American is more than four times the national average. The percent of 
people living below the poverty level is almost double the national 
average.
    The baseline risk-based demographic analysis indicates that African 
Americans are disproportionally overrepresented at all cancer risk 
levels resulting from Neoprene Production source category emissions 
(Percent African Americans ranges from 5 to 7 times the national 
average percent). The percent of the population that is below the 
poverty level is twice the national average within 5 km of the Neoprene 
facility.
    The post-control risk-based demographic analysis indicates that the 
controls under consideration for Neoprene Production source category in 
this proposal do not reduce the number of people with cancer risks 
resulting from Neoprene Production source category emissions greater 
than or equal to 1-in-1 million at the 5 km distance. However, the 
controls do significantly reduce the number of people with risks 
resulting from Neoprene Production source category emissions greater 
than or equal to 1-in-1 million within 50 km. The demographics of this 
population in the post-control risk-based analysis are similar to the 
baseline population. The populations with risks resulting from Neoprene 
Production source category emissions greater than or equal to 50-in-1 
million and greater than 100-in-1 million are reduced at all distances 
by more than 90 percent by the controls for the Neoprene Production 
source category under consideration. In the post-control scenario, 
there are no people with risks resulting from Neoprene Production 
source category emissions greater than 100-in-1 million.
a. Baseline Proximity Analysis
    The column titled ``Total Population Living within 5 km of Neoprene 
Facility'' in Tables 35 through 37 of this preamble shows the 
demographics for the total population living within 5 km (~3.1 miles) 
of the neoprene facility. A total of about 29,000 people live within 5 
km of the one neoprene facility. The results of the proximity 
demographic analysis indicate that the percent of the population that 
is African American (56 percent, 16,000 people) is more than four times 
the national average (12 percent). The percent of people living below 
the poverty level (23 percent, 6,500 people) and those over the age of 
25 without a high school diploma (16 percent, 4,500 people) are higher 
than the national averages (13 percent and 12 percent, respectively). 
The baseline proximity analysis indicates that the proportion of other 
demographic groups living within 5 km of the neoprene facility is 
similar to or below the national average.
b. Baseline Risk-Based Demographics
    The baseline risk-based demographic analysis results are shown in 
the ``baseline'' column of Tables 35 through 37 of this preamble. This 
analysis focused on the populations living within 5 km (~3.1 miles) of 
the neoprene facility with estimated cancer risks resulting from 
Neoprene Production source category emissions greater than or equal to 
1-in-1 million (Table 35 of this preamble), greater than or equal to 
50-in-1 million (Table 36 of this preamble), and greater than 100-in-1 
million Table 37 of this preamble) in the absence of the reductions we 
are proposing.
    In the baseline, emissions from the Neoprene Production source 
category expose all individuals within 5 km of the facility (29,000 
people) to a cancer risk greater than or equal to 1-in-1 million. Since 
the entire population within 5 km are exposed to risks greater than or 
equal to 1-in-1 million, the demographics of the baseline at-risk 
population are the same as the total baseline population. Specifically, 
a high percentage of the population is African American (56 percent 
versus 12 percent nationally), below the poverty line (23 percent 
versus 13 percent nationally), and over the age of 25 without a high 
school diploma (16 percent versus 12 percent nationally). The 
percentages of other demographic groups within the population with 
risks resulting from Neoprene Production source category emissions 
greater than or equal to 1-in-1 million living within 5 km of the 
neoprene facility are similar to or below the national average. Within 
50 km (~31 miles) of the facility, about 70 percent of the population 
(687,000 people of the 1 million total within 50 km) is exposed to a 
cancer risk resulting from Neoprene Production source category 
emissions greater than or equal to 1-in-1 million. Additional details 
on the 50 km results can be found in the demographics report located in 
the docket.
    The risk-based demographics analysis indicates that emissions from 
the source category, prior to the reductions we are proposing, expose 
about 13,000 individuals within 5 km of the facility to a cancer risk 
greater than or equal to 50-in-1 million (about half of the total 
population within 5 km). As seen at the lower risk level of greater 
than or equal to 1-in-1 million, the population with risks greater than 
or equal to 50-in-1 million has a very high percentage of African 
Americans; that percent is almost 6 times the national average (68 
percent versus 12 percent nationally). The percent of the population 
that is below the poverty line is more than double the national average 
(27 percent versus 13 percent nationally), and the percent of the 
population that is over the age of 25 without a high school diploma is 
1.5 times the national average (18 percent versus 12 percent 
nationally). The percentages of other demographic groups within the 
population with risks resulting from Neoprene Production source 
category emissions greater than or equal to 50-in-1 million living 
within 5 km of the Neoprene facility are similar to or below the 
national average.
    In the baseline, there are 2,000 people living within 5 km of the 
Neoprene facility with a cancer risk resulting from Neoprene Production 
source category emissions greater than 100-in-1 million. The percent of 
the population that is African American with baseline cancer risk 
greater than 100-in-1 million (85 percent, 1,753 people) is over 7 
times the national average (12 percent). The percentage of the 
population with cancer risks greater than 100-in-1 million that is 
below the poverty level (31 percent, 600 people) is about 2.5 times the 
national average (13 percent). The percent of the population that is 
over 25 without a high school diploma (14 percent, 300 people) is just 
above the national average (12 percent).
    In summary, the baseline risk-based demographic analysis, which 
focuses on those specific locations that are expected to have higher 
cancer risks in the baseline, indicates that African Americans are 
disproportionally overrepresented at all cancer risk levels. 
Specifically, at all risk levels, the percent of the population that is 
African American is 5 to 7 times the national average and the percent 
of the population that is below the poverty level is twice the national 
average within 5 km of the neoprene production facility.
c. Post-Control Risk-Based Demographics
    This analysis focused on the populations living within 5 km (~3.1 
miles) of the facility with estimated cancer risks resulting from 
Neoprene Production source category emissions greater than or equal to 
1-in-1 million (Table 35 of this preamble), greater than or equal to 
50-in-1 million (Table 36 of this preamble), and greater than 100-in-1 
million (Table 37 of this preamble) after implementation of the 
Neoprene Production source category control options as described in 
section III.B.2.b of this preamble. The results of the post-control 
risk-based demographics

[[Page 25190]]

analysis are in the columns titled ``Post-Control'' of Tables 35 
through 37 of this preamble. In this analysis, we evaluated how all of 
the proposed controls and emission reductions for the Neoprene 
Production source category described in this action affect the 
distribution of risks. This enables us to characterize the post-control 
risks and to evaluate whether the proposed action creates or mitigates 
potential EJ concerns as compared to the baseline.
    The risk analysis indicated that the number of people exposed to 
risks resulting from Neoprene Production source category emissions 
greater than or equal to 1-in-1 million within 5 km of the facility 
(Table 35 of this preamble) is unchanged from the baseline (29,000 
people). Therefore, the population living within 5 km of the facility 
with estimated cancer risks greater than or equal to 1-in-1 million in 
the post-control scenario (Table 35 of this preamble) has the same 
demographic percentages as the total population in the proximity 
analysis and the population with risks greater than or equal to 1-in-1 
million in the baseline risk analysis. Specifically, the percentage of 
the population with risks resulting from Neoprene Production source 
category emissions in the post-control analysis that is greater than or 
equal to 1-in-1 million and is African American (56 percent) is almost 
5 times the national average (12 percent), and the percent below the 
poverty level (23 percent) is almost 2 times the national average (13 
percent). However, after control, the number of people exposed to risk 
greater than or equal to 1-in-1 million within 50 km (~31 miles) of the 
facility is significantly reduced from 687,000 to 48,000.
    The risk analysis indicated that the number of people living within 
5 km of the facility and exposed to risks resulting from Neoprene 
Production source category emissions greater than or equal to 50-in-1 
million (Table 36 of this preamble) is reduced significantly from about 
13,000 people in the baseline to 700 people after implementation of the 
proposed controls. This represents more than a 90 percent reduction in 
the size of the populations at risk when compared to the baseline 
population. The post-control population living within 5 km of the 
facility with estimated cancer risks greater than or equal to 50-in-1 
million for post-control (Table 36 of this preamble) is almost entirely 
African American (99 percent). The number of African Americans with 
risks greater than or equal to 50-in-1 million is reduced from about 
9,000 in the baseline to 700 people post-control. Similarly, the post-
control population with risks greater than or equal to 50-in-1 million 
has a high percent of people below poverty (33 percent). The number of 
people with risks greater than or equal 50-in-1 million that are below 
the poverty level is reduced from 3,400 in the baseline to 200 people 
post-control.
    The risk analysis indicated that the number of people living within 
5 km of the facility and exposed to risks resulting from Neoprene 
Production source category emissions greater than 100-in-1 million 
(Table 37 of this preamble) is reduced from over 2,000 people in the 
baseline to zero people after application of the proposed controls. 
Therefore, for the post-control risk-based demographics, no people with 
risks resulting from Neoprene Production source category emissions 
above 100-in-1 million.
    In summary, as shown in the post-control risk-based demographic 
analysis, the controls under consideration in this proposal do not 
reduce the number of people expected to have cancer risks resulting 
from Neoprene Production source category emissions greater than or 
equal to 1-in-1 million at the 5 km distance. The controls do 
significantly reduce the number of people with risks resulting from 
Neoprene Production source category emissions greater than or equal to 
1-in-1 million within 50 km. In the post-control population with risks 
greater than or equal to 1-in-1 million, African Americans and those 
living below the poverty level remain disproportionately represented. 
For the populations with risks greater than or equal to 50-in-1 million 
and greater than 100-in-1 million, the controls under consideration 
reduce the at-risk populations by more than 90 percent at all 
distances. In the post-control population with risks greater than or 
equal to 50-in-1 million, African Americans and those living below the 
poverty level remain disproportionately represented. Post-control, 
there are no people with risks resulting from Neoprene Production 
source category emissions greater than 100-in-1 million.
    We also evaluated the whole-facility post-control risks at the 
neoprene production facility. The whole-facility post-control risks 
include all known sources of HAP emissions at the neoprene production 
facility, not just those from neoprene production processes. This 
whole-facility demographic analysis provides a more complete picture of 
the remaining risks at the facility after implementation of the 
controls proposed in this action and the populations exposed to 
emissions resulting from them. The post-control whole-facility 
emissions at the neoprene production facility are a combination of the 
remaining SOCMI category risk and Neoprene Production category risk at 
this facility. Based on whole-facility emissions, there are a total of 
about 47,000 people living within 10 km (~6.2 miles) with risks greater 
than or equal to 1-in-1 million after controls, which is unchanged from 
the baseline. There are 86,000 people within 50 km of the neoprene 
facility with post-control whole-facility risks greater than or equal 
to 1-in-1 million, which is a 90 percent reduction of the 893,000 
people in the baseline. The population within 10 km with post-control 
whole-facility risks of greater than or equal to 1-in-1 million is 55 
percent African American, and 19 percent are below the poverty level. 
Based on whole-facility emissions there are a total of about 2,000 
people remaining after controls living within 10 km and 50 km of the 
neoprene facility with risks greater than or equal to 50-in-1 million 
(a reduction of 83 percent from the baseline of 16,000 people). This 
population is 83 percent African American and 32 percent below the 
poverty level. Based on whole-facility emissions, about 300 people with 
risks greater than 100-in-1 million remain after controls are 
implemented living within 10 km and 50 km of the neoprene production 
facility (a reduction of 86 percent from the baseline of 2,300 people). 
This population is 99 percent African American, and 33 percent are 
below the poverty level. We note that as further discussed in section 
III.C.7 of this preamble, the EPA is proposing a fenceline action level 
of 0.3 [micro]g/m\3\ for chloroprene for the whole facility. As such, 
we believe once fenceline monitoring is fully implemented, that whole 
facility post-control risks will be reduced to 100-in-1 million and 
that 0 people (rather than 300 people as shown in this analysis) will 
remain with risks greater than 100-in-1 million.

[[Page 25191]]

 Table 35--Source Category: Comparison of Baseline and Post-Control Demographics of Populations With Cancer Risk
 Greater Than or Equal to 1-in-1 Million Living Within 5 km of the Neoprene Production Facility to the National
                                     Average and the Proximity Demographics
----------------------------------------------------------------------------------------------------------------
                                                                              Total       Cancer risk >=1-in-1
                                                                            population   million within 5 km of
                                                                              living        neoprene facility
                      Demographic group                        Nationwide   within  5  -------------------------
                                                                              km of
                                                                             neoprene     Baseline      Post-
                                                                             facility                  control
----------------------------------------------------------------------------------------------------------------
Total population............................................         328M       28,571       28,571      28,571.
Number of Facilities........................................  ...........            1            1           1.
----------------------------------------------------------------------------------------------------------------
                                Race and Ethnicity by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
White.......................................................    60 [197M]     35 [10K]     35 [10K]    35 [10K].
African American............................................     12 [40M]     56 [16K]     56 [16K]    56 [16K].
Native American.............................................     0.7 [2M]          0.0          0.0         0.0.
Hispanic or Latino (includes white and nonwhite)............     19 [62M]     5 [1.5K]     5 [1.5K]    5 [1.5K].
Other and Multiracial.......................................      8 [27M]      3 [900]      3 [900]     3 [900].
----------------------------------------------------------------------------------------------------------------
                                      Income by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Below Poverty Level.........................................     13 [44M]    23 [6.5K]    23 [6.5K]   23 [6.5K].
Above Poverty Level.........................................    87 [284M]     77 [22K]     77 [22K]    77 [22K].
----------------------------------------------------------------------------------------------------------------
                                     Education by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High School Diploma...................     12 [40M]    16 [4.6K]    16 [4.6K]   16 [4.6K].
Over 25 and with a High School Diploma......................    88 [288M]     84 [24K]     84 [24K]    84 [24K].
----------------------------------------------------------------------------------------------------------------
                              Linguistically Isolated by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated.....................................      5 [18M]      1 [300]      1 [300]     1 [300].
----------------------------------------------------------------------------------------------------------------
Notes:
 Nationwide population and demographic percentages are based on Census' 2015-2019 ACS 5-year block group
  averages. Total population count within 5 km is based on 2010 Decennial Census block population.
 To avoid double counting, the ``Hispanic or Latino'' category is treated as a distinct demographic
  category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race.
 The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR
  was located at a user assigned receptor at an individual residence and not at a census block centroid, we were
  unable to estimate population and demographics for that facility.
 The sum of individual populations with a demographic category may not add up to total due to rounding.

 Table 36--Source Category: Comparison of Baseline and Post-Control Demographics of Populations With Cancer Risk
Greater Than or Equal to 50-in-1 Million Living Within 5 km of the Neoprene Facility to the National Average and
                                           the Proximity Demographics
----------------------------------------------------------------------------------------------------------------
                                                                              Total       Cancer risk >=50-in-1
                                                                            population   million within 5 km of
                                                                              living     the  neoprene facility
                      Demographic group                        Nationwide   within  5  -------------------------
                                                                            km of the
                                                                             neoprene     Baseline      Post-
                                                                             facility                  control
----------------------------------------------------------------------------------------------------------------
Total Population............................................         328M       28,571       12,801         727.
Number of Facilities........................................  ...........            1            1           1.
----------------------------------------------------------------------------------------------------------------
                                Race and Ethnicity by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
White.......................................................    60 [197M]     35 [10K]    26 [3.3K]    1 [<100].
African American............................................     12 [40M]     56 [16K]    68 [8.6K]    99 [700].
Native American.............................................     0.7 [2M]          0.0          0.0        0.0 .
Hispanic or Latino (includes white and nonwhite)............     19 [62M]     5 [1.5K]      4 [500]          0 .
Other and Multiracial.......................................      8 [27M]      3 [900]      2 [200]          0 .
----------------------------------------------------------------------------------------------------------------
                                      Income by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Below Poverty Level.........................................     13 [44M]    23 [6.5K]    27 [3.4K]    33 [200].
Above Poverty Level.........................................    87 [284M]     77 [22K]    73 [9.3K]    67 [500].
----------------------------------------------------------------------------------------------------------------
                                     Education by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High School Diploma...................     12 [40M]    16 [4.6K]    18 [2.3K]   12 [<100].
Over 25 and with a High School Diploma......................    88 [288M]     84 [24K]   82 [10.5K]    88 [600].
----------------------------------------------------------------------------------------------------------------

[[Page 25192]]

 
                              Linguistically Isolated by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated.....................................      5 [18M]      1 [300]     1 [<100]          0 .
----------------------------------------------------------------------------------------------------------------
Notes:
 Nationwide population and demographic percentages are based on Census' 2015-2019 ACS 5-year block group
  averages. Total population count within 5 km is based on 2010 Decennial Census block population.
 To avoid double counting, the ``Hispanic or Latino'' category is treated as a distinct demographic
  category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race.
 The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR
  was located at a user assigned receptor at an individual residence and not at a census block centroid, we were
  unable to estimate population and demographics for that facility.
 The sum of individual populations with a demographic category may not add up to total due to rounding.

 Table 37--Source Category: Comparison of Baseline and Post-Control Demographics of Populations With Cancer Risk
    Greater Than 100-in-1 Million Living Within 5 km of the Neoprene Facility to the National Average and the
                                             Proximity Demographics
----------------------------------------------------------------------------------------------------------------
                                                                              Total       Cancer risk >100-in-1
                                                                            population   million within 5 km of
                                                                              living     the  neoprene facility
                      Demographic group                        Nationwide   within  5  -------------------------
                                                                            km of the
                                                                             neoprene     Baseline      Post-
                                                                             facility                  control
----------------------------------------------------------------------------------------------------------------
Total population............................................         328M       28,571        2,052            0
Number of Facilities........................................  ...........            1            1            0
----------------------------------------------------------------------------------------------------------------
                                Race and Ethnicity by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
White.......................................................    60 [197M]     35 [10K]     11 [200]            0
African American............................................     12 [40M]     56 [16K]    85 [1.8K]            0
Native American.............................................     0.7 [2M]          0.0          0.0          0.0
Hispanic or Latino (includes white and nonwhite)............     19 [62M]     5 [1.5K]     3 [<100]            0
Other and Multiracial.......................................      8 [27M]      3 [900]            0            0
----------------------------------------------------------------------------------------------------------------
                                      Income by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Below Poverty Level.........................................     13 [44M]    23 [6.5K]     31 [600]            0
Above Poverty Level.........................................    87 [284M]     77 [22K]    69 [1.4K]            0
----------------------------------------------------------------------------------------------------------------
                                     Education by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High School Diploma...................     12 [40M]    16 [4.6K]     14 [300]            0
Over 25 and with a High School Diploma......................    88 [288M]     84 [24K]    86 [1.8K]            0
----------------------------------------------------------------------------------------------------------------
                              Linguistically Isolated by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated.....................................      5 [18M]      1 [300]            0           0
----------------------------------------------------------------------------------------------------------------
Notes:
 Nationwide population and demographic percentages are based on Census' 2015-2019 ACS 5-year block group
  averages. Total population count within 5 km is based on 2010 Decennial Census block population.
 To avoid double counting, the ``Hispanic or Latino'' category is treated as a distinct demographic
  category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race.
 The number of facilities represents facilities with a cancer MIR above level indicated. When the MIR
  was located at a user assigned receptor at an individual residence and not at a census block centroid, we were
  unable to estimate population and demographics for that facility.
 The sum of individual populations with a demographic category may not add up to total due to rounding.

4. P&R I and P&R II Source Categories Demographics
    As stated above, for P&R I and P&R II, other than the Neoprene 
Production source category within P&R I, we have not conducted a risk 
assessment for this proposal. Therefore, to examine the potential for 
any EJ concerns that might be associated with P&R I (excluding 
neoprene) or P&R II facilities, we performed a proximity demographic 
analysis, which is an assessment of individual demographic groups of 
the populations living within 5 km (~3.1 miles) and 50 km (~31 miles) 
of the facilities. The EPA then compared the data from this analysis to 
the national average for each of the demographic groups. In this 
preamble, we focus on the proximity results for the populations living 
within 10 km (~6.2 miles) of the

[[Page 25193]]

facilities. The results of the proximity analysis for populations 
living within 50 km are included in the document titled Analysis of 
Demographic Factors for Populations Living Near Hazardous Organic 
NESHAP (HON) Facilities, which is available in the docket for this 
action.
    The results show that for populations within 5 km of the 18 P&R I 
facilities (5 in Louisiana, 6 in Texas, 2 in Kentucky, one each in 
Georgia, Minnesota, Mississippi, Ohio, Michigan), the following 
demographic groups were above the national average: African American 
(37 percent versus 12 percent nationally), Hispanic/Latino (24 percent 
versus 19 percent nationally), people living below the poverty level 
(24 percent versus 13 percent nationally), people over the age of 25 
without a high school diploma (21 percent versus 12 percent 
nationally), and linguistically isolated households (7 percent versus 5 
percent nationally).
    The results show that for populations within 5 km of the 5 P&R II 
facilities (2 in Texas, one each in Alabama, Arkansas, Oregon), the 
following demographic groups were above the national average: Native 
American (0.9 percent versus 0.7 percent nationally), Hispanic/Latino 
(27 percent versus 19 percent nationally), and people over the age of 
25 without a high school diploma (13 percent versus 12 percent 
nationally).
    A summary of the proximity demographic assessment performed is 
included as Table 38 of this preamble. The methodology and the results 
of the demographic analysis are presented in the document titled 
Analysis of Demographic Factors for Populations Living Near Polymers 
and Resins I and Polymer and Resins II Facilities, which is available 
in the docket for this action.

         Table 38--Proximity Demographic Assessment Results for Polymers and Resins I and II Facilities
----------------------------------------------------------------------------------------------------------------
                                                                   P&R I: population        P&R II: population
          Demographic group             Nationwide average for     within  5 km of 18       within  5 km of 5
                                              reference                facilities               facilities
----------------------------------------------------------------------------------------------------------------
Total Population.....................  328M...................  627,823................  124,050
----------------------------------------------------------------------------------------------------------------
                                Race and Ethnicity by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
White................................  60 [197M]..............  35 [218K]..............  62 [76K].
African American.....................  12 [40M]...............  37 [234K]..............  5 [7K].
Native American......................  0.7 [2M]...............  0.2 [1K]...............  0.9 [1K].
Hispanic or Latino (includes white     19 [62M]...............  24 [150K]..............  27 [34K].
 and nonwhite).
Other and Multiracial................  8 [27M]................  4 [24K]................  5 [6K].
----------------------------------------------------------------------------------------------------------------
                                      Income by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Below Poverty Level..................  13 [44M]...............  24 [150K]..............  13 [16K].
Above Poverty Level..................  87 [284M]..............  76 [478K]..............  87 [108K].
----------------------------------------------------------------------------------------------------------------
                        Education by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High School      12 [40M]...............  21 [130K]..............  13 [16K].
 Diploma.
Over 25 and with a High School         88 [288M]..............  79 [498K]..............  87 [108K].
 Diploma.
----------------------------------------------------------------------------------------------------------------
                              Linguistically Isolated by Percent [Number of People]
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated..............  5 [18M]................  7 [43K]................  2 [3K].
----------------------------------------------------------------------------------------------------------------
Notes:
 Nationwide population and demographic percentages are based on Census' 2015-2019 ACS 5-year block group
  averages. Total population count within 10 km is based on 2010 Decennial Census block population.
 To avoid double counting, the ``Hispanic or Latino'' category is treated as a distinct demographic
  category. A person who identifies as Hispanic or Latino is counted as Hispanic or Latino, regardless of race.
 The sum of individual populations with a demographic category may not add up to total due to rounding.

5. Proximity Demographics Analysis for NSPS Subpart VVb
    Consistent with the EPA's commitment to integrating EJ in the 
Agency's actions, and following the directives set forth in multiple 
Executive Orders as well as CAA section 111(b)(1)(B), the Agency has 
carefully considered the impacts of the proposed NSPS subpart VVb on 
communities with EJ concerns. The proposed NSPS subpart VVb covers VOC 
emissions from certain equipment leaks in the SOCMI from sources that 
are constructed, reconstructed, or modified after April 25, 2023.
    Executive Order 12898 directs the EPA to identify the populations 
of concern who are most likely to experience unequal burdens from 
environmental harms; specifically, minority populations, low-income 
populations, and indigenous peoples (59 FR 7629, February 16, 1994). 
Additionally, Executive Order 13985 is intended to advance racial 
equity and support underserved communities through Federal government 
actions (86 FR 7009, January 20, 2021). The EPA defines EJ as ``the 
fair treatment and meaningful involvement of all people regardless of 
race, color, national origin, or income with respect to the 
development, implementation, and enforcement of environmental laws, 
regulations, and policies.'' \170\ The EPA further defines the term 
fair treatment to mean that ``no group of people should bear a 
disproportionate burden of environmental harms and risks, including 
those resulting from the negative environmental consequences of 
industrial, governmental, and commercial operations or programs and 
policies.'' In recognizing that minority and low-income populations 
often bear an unequal burden of environmental harms and risks, the EPA 
continues to consider ways of protecting them from adverse public 
health and environmental effects of air pollution.
---------------------------------------------------------------------------

    \170\ See footnote 168.
---------------------------------------------------------------------------

    The locations of the new, modified, and reconstructed sources that 
will become subject to NSPS subpart VVb are not known. Therefore, to 
examine

[[Page 25194]]

the potential for any EJ issues that might be associated with the 
proposed NSPS subpart VVb, we performed a proximity demographic 
analysis for 575 existing facilities that are currently subject to NSPS 
subparts VV or VVa. These represent facilities that might modify or 
reconstruct in the future and become subject to the NSPS subpart VVb 
requirements. This proximity demographic analysis characterized the 
individual demographic groups of the populations living within 5 km and 
within 50 km (~31 miles) of the existing facilities. The EPA then 
compared the data from this analysis to the national average for each 
of the demographic groups.
    The proximity demographic analysis shows that, within 5 km of the 
facilities, the percent of the population that is African American is 
double the national average (24 percent versus 12 percent). The percent 
of people within 5 km living below the poverty level is significantly 
higher than the national average (20 percent versus 13 percent). The 
percent of people living within 5 km that are over 25 without a high 
school diploma is also higher than the national average (17 percent 
versus 12 percent). The proximity demographics analysis shows that 
within 50 km of the facilities, the percent of the population that is 
African American is above the national average (15 percent versus 12 
percent). At 50 km, the remaining percentages for the demographics are 
similar to or below the national average.

 Table 39--Proximity Demographic Assessment Results for Existing Facilities Subject to NSPS Subparts VV and VVa
----------------------------------------------------------------------------------------------------------------
                                                                Population within 50 km   Population within 5 km
          Demographic group                   Nationwide           of 575 facilities        of 575 facilities
----------------------------------------------------------------------------------------------------------------
Total Population.....................  328,016,242............  140,946,443............  8,084,246
----------------------------------------------------------------------------------------------------------------
                                          Race and Ethnicity by Percent
----------------------------------------------------------------------------------------------------------------
White................................  60.....................  62.....................  50
African American.....................  12.....................  15.....................  24
Native American......................  0.7....................  0.4....................  0.4
Hispanic or Latino (includes white     19.....................  15.....................  20
 and nonwhite).
Other and Multiracial................  8......................  8......................  5
----------------------------------------------------------------------------------------------------------------
                                                Income by Percent
----------------------------------------------------------------------------------------------------------------
Below Poverty Level..................  13.....................  14.....................  20
Above Poverty Level..................  87.....................  86.....................  80
----------------------------------------------------------------------------------------------------------------
                                              Education by Percent
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High School      12.....................  12.....................  17
 Diploma.
Over 25 and with a High School         88.....................  88.....................  83
 Diploma.
----------------------------------------------------------------------------------------------------------------
                                       Linguistically Isolated by Percent
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated..............  5......................  5......................  6
----------------------------------------------------------------------------------------------------------------
Notes:
 The nationwide population count and all demographic percentages are based on the Census' 2015-2019
  American Community Survey five-year block group averages and include Puerto Rico. Demographic percentages
  based on different averages may differ. The total population counts are based on the 2010 Decennial Census
  block populations.
 To avoid double counting, the ``Hispanic or Latino'' category is treated as a distinct demographic
  category for these analyses. A person is identified as one of five racial/ethnic categories above: White,
  African American, Native American, Other and Multiracial, or Hispanic/Latino. A person who identifies as
  Hispanic or Latino is counted as Hispanic/Latino for this analysis, regardless of what race this person may
  have also identified as in the Census.

    The proposed NSPS subpart VVb covers VOC emissions from certain 
equipment leaks in the SOCMI from sources that are constructed, 
reconstructed, or modified after April 25, 2023. NSPS subpart VVb will 
result in reduced VOC emissions by requiring 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. For each of these requirements, we are proposing skip periods 
for good performance.
    The methodology and the results (including facility-specific 
results) of the demographic analysis are presented in the document 
titled Analysis of Demographic Factors for Populations Living Near 
Existing Facilities Subject to NSPS Subparts VV or VVa, which is 
available in the docket for this action.
6. Proximity Demographics Analysis for NSPS Subparts IIIa, NNNa, and 
RRRa
    Consistent with the EPA's commitment to integrating EJ in the 
Agency's actions, and following the directives set forth in multiple 
Executive Orders as well as CAA section 111(b)(1)(B), the Agency has 
carefully considered the impacts of the proposed NSPS subparts IIIa, 
NNNa, and RRRa on communities with EJ concerns. The proposed NSPS 
subparts IIIa, NNNa, and RRRa cover VOC emissions from certain process 
vents in the SOCMI from sources that are constructed, reconstructed, or 
modified after April 25, 2023.
    Executive Order 12898 directs the EPA to identify the populations 
of concern who are most likely to experience unequal burdens from 
environmental harms; specifically, minority populations, low-income 
populations, and indigenous peoples (59 FR 7629, February 16, 1994). 
Additionally, Executive Order 13985 is intended to advance racial 
equity and support underserved communities through Federal government 
actions (86 FR 7009, January 20, 2021). The EPA defines EJ as ``the 
fair treatment and meaningful involvement of all people regardless of 
race, color, national origin, or income with respect to the 
development, implementation, and

[[Page 25195]]

enforcement of environmental laws, regulations, and policies.'' \171\ 
The EPA further defines the term fair treatment to mean that ``no group 
of people should bear a disproportionate burden of environmental harms 
and risks, including those resulting from the negative environmental 
consequences of industrial, governmental, and commercial operations or 
programs and policies.'' In recognizing that minority and low-income 
populations often bear an unequal burden of environmental harms and 
risks, the EPA continues to consider ways of protecting them from 
adverse public health and environmental effects of air pollution.
---------------------------------------------------------------------------

    \171\ See footnote 168.
---------------------------------------------------------------------------

    The locations of the new, modified, and reconstructed sources that 
will become subject to NSPS subparts IIIa, NNNa, and RRRa are not 
known. Therefore, to examine the potential for any EJ issues that might 
be associated with the proposed subparts, we performed a proximity 
demographic analysis for 266 existing facilities that are currently 
subject to NSPS subpart III, NNN, or RRR. These represent facilities 
that might modify or reconstruct in the future and become subject to 
the proposed NSPS requirements. This proximity demographic analysis 
characterized the individual demographic groups of the populations 
living within 5 km (~3.1 miles) and within 50 km (~31 miles) of the 
existing facilities. The EPA then compared the data from this analysis 
to the national average for each of the demographic groups.
    The proximity demographic analysis shows that, within 5 km of the 
facilities, the percent of the population that is African American is 
almost double the national average (23 percent versus 12 percent). In 
addition, the percent of the population within 5 km of the facilities 
that is Hispanic or Latino is also above the national average (23 
percent versus 19 percent). The percent of people within 5 km living 
below the poverty level is significantly higher than the national 
average (20 percent versus 13 percent). The percent of people living 
within 5 km that are over 25 without a high school diploma is also 
higher than the national average (17 percent versus 12 percent). The 
proximity demographics analysis shows that within 50 km of the 
facilities, the percent of the population that is African American is 
above the national average (18 percent versus 12 percent). At 50 km, 
the remaining percentages for the demographics are similar to or below 
the national average.

Table 40--Proximity Demographic Assessment Results for Existing Facilities Subject to NSPS Subparts III, NNN, or
                                                       RRR
----------------------------------------------------------------------------------------------------------------
                                                                                    Population
                                                                                   within 50 km     Population
                        Demographic group                           Nationwide        of 266      within 5 km of
                                                                                    facilities    266 facilities
----------------------------------------------------------------------------------------------------------------
Total Population................................................     328,016,242      96,017,770       4,624,154
----------------------------------------------------------------------------------------------------------------
                                          Race and Ethnicity by Percent
----------------------------------------------------------------------------------------------------------------
White...........................................................              60              59              48
African American................................................              12              18              23
Native American.................................................             0.7             0.4             0.4
Hispanic or Latino (includes white and nonwhite)................              19              15              23
Other and Multiracial...........................................               8               7               5
----------------------------------------------------------------------------------------------------------------
                                                Income by Percent
----------------------------------------------------------------------------------------------------------------
Below Poverty Level.............................................              13              14              20
Above Poverty Level.............................................              87              86              80
----------------------------------------------------------------------------------------------------------------
                                              Education by Percent
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High School Diploma.......................              12              12              17
Over 25 and with a High School Diploma..........................              88              88              83
----------------------------------------------------------------------------------------------------------------
                                       Linguistically Isolated by Percent
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated.........................................               5               5               6
----------------------------------------------------------------------------------------------------------------
Notes:
 The nationwide population count and all demographic percentages are based on the Census' 2015-2019
  American Community Survey five-year block group averages and include Puerto Rico. Demographic percentages
  based on different averages may differ. The total population counts are based on the 2010 Decennial Census
  block populations.
 To avoid double counting, the ``Hispanic or Latino'' category is treated as a distinct demographic
  category for these analyses. A person is identified as one of five racial/ethnic categories above: White,
  African American, Native American, Other and Multiracial, or Hispanic/Latino. A person who identifies as
  Hispanic or Latino is counted as Hispanic/Latino for this analysis, regardless of what race this person may
  have also identified as in the Census.

    The proposed NSPS subparts IIIa, NNNa, and RRRa cover VOC emissions 
from certain process vents in the SOCMI from sources that are 
constructed, reconstructed, or modified after April 25, 2023. The 
proposed NSPS subparts IIIa, NNNa, and RRRa will result in reduced VOC 
emissions by requiring all vent streams from an affected facility to be 
controlled, eliminating 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, and prohibiting an owner or operator from bypassing the APCD 
at any time, and if a bypass is used, it is considered a violation. In 
addition, we are proposing the same operating and monitoring 
requirements for flares that we are proposing for flares subject to the 
HON, the same work practice standards for maintenance vents that we are

[[Page 25196]]

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).
    The methodology and the results (including facility-specific 
results) of the demographic analysis are presented in the document 
titled Analysis of Demographic Factors for Populations Living Near 
Existing Facilities Subject to NSPS Subparts III, NNN, or RRR, which is 
available in the docket for this action.

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

    This action proposes to address risk from, among other HAP, EtO and 
chloroprene. In addition, the EPA's Policy on Children's Health \172\ 
also applies to this action. Accordingly, we have evaluated the 
environmental health or safety effects of EtO and chloroprene emissions 
and exposures on children.
---------------------------------------------------------------------------

    \172\ Children's Health Policy Available at: https://www.epa.gov/children/childrens-health-policy-and-plan.
---------------------------------------------------------------------------

    Because EtO and chloroprene are mutagenic (i.e., they can damage 
DNA), children are expected to be more susceptible to their harmful 
effects. To take this into account, as part of the risk assessment in 
support of this rulemaking, the EPA followed its guidelines \173\ and 
applied age-dependent adjustment factors (ADAFs) for childhood 
exposures (from birth up to 16 years of age). With the ADAF applied to 
account for greater susceptibility of children, the adjusted EtO 
inhalation URE is 5 x 10-\3\ per [micro]g/m\3\ and the 
adjusted chloroprene inhalation URE is 4.8 x 10-\4\ per 
[micro]g/m\3\. It should be noted that, because EtO and chloroprene are 
mutagenic, emission reductions proposed in this preamble will be 
particularly beneficial to children. The results of the risk assessment 
are contained in sections III.A and B of this preamble and further 
documented in the risk reports, Residual Risk Assessment for the SOCMI 
Source Category in Support of the 2023 Risk and Technology Review 
Proposed Rule and Residual Risk Assessment for the Polymers & Resins I 
Neoprene Production Source Category in Support of the 2023 Risk and 
Technology Review Proposed Rule, which are available in the docket for 
this rulemaking.
---------------------------------------------------------------------------

    \173\ U.S. EPA. 2005. Supplemental Guidance for Assessing 
Susceptibility from Early-Life Exposure to Carcinogens. U.S. 
Environmental Protection Agency, Washington, DC, EPA/630/R-03/003F. 
https://www.epa.gov/sites/default/files/2013-09/documents/childrens_supplement_final.pdf.
---------------------------------------------------------------------------

V. Request for Comments

    We solicit comments on this proposed action. In addition to general 
comments on this proposed action, we are also interested in additional 
data that may improve the analyses. We are specifically interested in 
receiving any information regarding developments in practices, 
processes, and control technologies that reduce emissions. We are also 
interested in receiving information on costs, emissions, and product 
recovery and we request comment on how to address the non-monetized 
costs and benefits of the proposed rule. We request comment on data and 
approaches to monetize the health benefits of reducing exposure to 
ethylene oxide, chloroprene, benzene, 1,3-butadiene, ethylene 
dichloride, vinyl chloride, chlorine, maleic anhydride, and acrolein. 
For our production estimates, we request comment on the assumptions of 
the simulation model and their consistency with market conditions and 
dynamics. We welcome specific comment on impacts on downstream 
industries and markets, including prices for medical supplies, foods, 
microchips, semiconductors, gasoline, or other products. In addition, 
we request estimates of any potential loss of production while bringing 
facilities into compliance and forgone returns due to displaced 
investment. Finally, the EPA attempted to ensure that the SSM 
provisions we are proposing to eliminate are inappropriate, 
unnecessary, or redundant in the absence of the SSM exemption and are 
specifically seeking comment on whether we have successfully done so.
    With respect to EtO emissions from equipment leaks, given the 
uncertainty of emissions from these fugitive sources and that they 
drive risk for a number of HON facilities (i.e., seven HON facilities 
present >=100-in-1 million cancer risk from emissions of EtO from 
equipment leaks at HON processes), the EPA is also soliciting comment 
on whether additional control options should be considered for 
equipment leaks beyond those discussed in section III.B.2.a.ii of this 
preamble, which proposes that valves, connectors, and pumps in EtO 
service be monitored monthly using EPA Method 21 of 40 CFR part 60, 
appendix A-7, with leak definitions of 100 ppm, 100 ppm, and 500 ppm, 
respectively. In particular, the EPA is aware of a number of additional 
technologies used by other regulated industries that could be 
implemented to monitor and/or reduce leaks of EtO, including requiring 
use of ``leakless'' (i.e., low-emitting) equipment for valves and pumps 
in EtO service, use of optical gas imaging (OGI) (i.e., use of a 
thermal infrared camera) to find large leaks faster, and use of leak 
detection sensor networks (LDSNs) that could potentially identify leaks 
of EtO at HON facilities.\174\ OGI refers to the creation of images of 
gas emissions through thermal infrared cameras. While the application, 
specification, and target gases of an OGI instrument may differ, the 
general function of an OGI camera is to detect the infrared energy of 
the target gas and filter out the light outside of the infrared 
frequency range to create an image of the target gas plume. In the 
context of leak detection, a hand-held OGI camera can create a video 
image of a plume of gas emanating from a leak. A LDSN comprises a 
network of leak detection sensor nodes installed to provide coverage of 
all LDAR applicable components in a process unit and an accompanying 
analytics platform for identifying potential leak source locations. A 
short-term excursion of an individual sensor's output above a set 
baseline level would indicate a possible leak. Facilities can 
investigate the possible leak within the potential leak source 
location. The network, analytics platform, and detection response 
framework are generally designed to enable timely detection of 
significant emissions so that facilities can more rapidly mitigate 
leaks.
---------------------------------------------------------------------------

    \174\ See, e.g., 40 CFR 60.18(g), 40 CFR 61.65(b)(8), 40 CFR 
63.11(c), and 40 CFR 63.11956; U.S. Envtl. Prot. Agency, Standards 
of Performance for New, Reconstructed, and Modified Sources and 
Emissions Guidelines for Existing Sources: Oil and Natural Gas 
Sector Climate Review, 87 FR 74,702 (Dec. 6, 2022); Notice of Final 
for Approval of Alternative Means of Emission Limitation (88 FR 
8844, February 10, 2023).
---------------------------------------------------------------------------

    As EPA does not have sufficient information to evaluate potential 
additional HAP reductions that may be realized by these technologies in 
the chemical sector, we solicit comment on the emissions reductions 
that have been or could be achieved by use of ``leakless'' valves and 
pumps, use of OGI, and use of LDSNs, the costs and cost-effectiveness 
of applying these technologies, including any cost-effectiveness 
comparisons of applying the technologies for different components and 
at different frequencies, and any relevant available data and studies.
    We also request comment on whether and how the application of these 
technologies would reduce risk, and whether and how EPA should consider 
application of these technologies to reinforce or enhance the proposed

[[Page 25197]]

equipment leak control requirements. EPA also requests comments on ways 
to streamline approval of alternative LDAR programs, use of remote 
sensing techniques, use of sensor networks, or other alternatives for 
detection of equipment leaks.

VI. Statutory and Executive Order Reviews

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

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

    Under section 3(f)(1) of Executive Order 12866, this action is a 
significant regulatory action that was submitted to the Office of 
Management and Budget (OMB) for review. Any changes made in response to 
recommendations received as part of Executive Order 12866 review have 
been documented in the docket. The EPA prepared an analysis of the 
potential costs and benefits associated with this action. This 
analysis, the Regulatory Impact Analysis, is available in the docket 
for this action.
    To satisfy requirements of E.O. 12866, the EPA projected the 
emissions reductions, costs, and benefits that may result from these 
proposed rulemakings. These results are presented in detail in the 
regulatory impact analysis (RIA) accompanying this proposal developed 
in response to E.O. 12866. We present these results for each of the 10 
subparts included in this proposed action, and also cumulatively. This 
action is economically significant according to E.O. 12866 due to the 
proposed amendments to the HON. The RIA focuses on the elements of the 
proposed rulemaking that are likely to result in quantifiable cost or 
emissions changes compared to a baseline without the proposal that 
incorporates changes to regulatory requirements. We estimated the cost, 
emissions, and benefits for the 2024 to 2038 period. We show the PV and 
EAV of costs, benefits, and net benefits of this action in 2021 
dollars.
    The initial analysis year in the RIA is 2024 because we assume the 
large majority of impacts associated with the proposed rulemakings will 
begin in that year. The NSPS will take effect immediately upon the 
effective date of the final rule (i.e., 60 days after publication of 
the final rule in the Federal Register) and impact sources constructed 
after publication of the proposed rule, but these impacts are much 
lower than those of the other three NESHAP rulemakings in this action. 
The other three rules, all under the provisions of CAA section 112, 
will also take effect 60 days after publication of the final rule in 
the Federal Register, but not require compliance with new requirements 
in some cases until three years after the effective date). Therefore, 
their impacts (at least the great majority of them) will begin in 2024. 
The final analysis year for benefits and costs is 2038, which allows us 
to provide 15 years of projected impacts after all of these rules are 
assumed to require compliance.
    The cost analysis presented in the RIA reflects a nationwide 
engineering analysis of compliance cost and emissions reductions, of 
which there are two main components. The first component is a set of 
representative or model plants for each regulated facility, segment, 
and control option. The characteristics of the model plant include 
typical equipment, operating characteristics, and representative 
factors including baseline emissions and the costs, emissions 
reductions, and product recovery resulting from each control option. 
The second component is a set of projections of data for affected 
facilities, distinguished by vintage, year, and other necessary 
attributes (e.g., precise content of material in storage vessels). 
Impacts are calculated by setting parameters on how and when affected 
facilities are assumed to respond to a particular regulatory regime, 
multiplying data by model plant cost and emissions estimates, 
differencing from the baseline scenario, and then summing to the 
desired level of aggregation. In addition to emissions reductions, some 
control options result in product recovery, which can then be sold 
where possible. Where applicable, we present projected compliance costs 
with and without the projected revenues from product recovery.
    The EPA expects health benefits due to the emissions reductions 
projected under these proposed rulemakings. We expect that HAP emission 
reductions will improve health and welfare associated with exposure by 
those affected by these emissions. In addition, the EPA expects that 
VOC emission reductions that will occur concurrent with the reductions 
of HAP emissions will improve air quality and are likely to improve 
health and welfare associated with exposure to ozone, PM2.5, 
SO2, and HAP. The EPA also expects disbenefits from 
secondary increases of CO2, NOX, CO, and benefits 
from reductions in methane emissions associated with the control 
options included in the cost analysis. We estimate the social benefits 
of GHG reductions expected to occur as a result of the proposed 
standards using estimates of the social cost of greenhouse gases (SC-
GHG),\175\ specifically using the social cost of carbon (SC-
CO2), social cost of methane (SC-CH4), and social 
cost of nitrous oxide (SC-N2O). The SC-GHG is the monetary 
value of the net harm to society associated with a marginal increase in 
GHG emissions in a given year, or the benefit of avoiding that 
increase. In principle, SC-GHG includes the value of all climate change 
impacts (both negative and positive), including (but not limited to) 
changes in net agricultural productivity, human health effects, 
property damage from increased flood risk and natural disasters, 
disruption of energy systems, risk of conflict, environmental 
migration, and the value of ecosystem services. The SC-GHG, therefore, 
reflects the societal value of reducing emissions of the gas in 
question by one metric ton and is the theoretically appropriate value 
to use in conducting benefit-cost analyses of policies that affect GHG 
emissions. In practice, data and modeling limitations naturally 
restrain the ability of SC-GHG estimates to include all the important 
physical, ecological, and economic impacts of climate change, such that 
the estimates are a partial accounting of climate change impacts and 
will therefore tend to be underestimates of the marginal benefits of 
abatement. The EPA and other Federal agencies began regularly 
incorporating SC-GHG estimates in their benefit-cost analyses conducted 
under Executive Order (E.O.) 12866 \176\ since 2008, following a Ninth 
Circuit Court of Appeals remand of a rule for failing to monetize the 
benefits of reducing GHG emissions in that rulemaking process. We 
conduct such

[[Page 25198]]

an analysis to monetize the benefits of reducing GHG emissions (or 
disbenefits, if these emissions increase) for this proposal as the EPA 
has done for recent rulemakings (e.g., the recently promulgated Good 
Neighbor rule).
---------------------------------------------------------------------------

    \175\ Estimates of the social cost of greenhouse gases are gas-
specific (e.g., social cost of carbon (SC-CO2), social 
cost of methane (SC-CH4), social cost of nitrous oxide 
(SC-N2O)), but collectively they are referenced as the 
social cost of greenhouse gases (SC-GHG).
    \176\ Presidents since the 1970s have issued executive orders 
requiring agencies to conduct analysis of the economic consequences 
of regulations as part of the rulemaking development process. E.O. 
12866, released in 1993 and still in effect today, requires that for 
all significant regulatory actions, an agency provide an assessment 
of the potential costs and benefits of the regulatory action, and 
that this assessment include a quantification of benefits and costs 
to the extent feasible. Many statutes also require agencies to 
conduct at least some of the same analyses required under E.O. 
12866, such as the Energy Policy and Conservation Act, which 
mandates the setting of fuel economy regulations. For purposes of 
this action, monetized climate benefits are presented for purposes 
of providing a complete benefit-cost analysis under E.O. 12866 and 
other relevant executive orders. The estimates of change in GHG 
emissions and the monetized benefits associated with those changes 
play no part in the record basis for this action.
---------------------------------------------------------------------------

    Discussion of the monetized and non-monetized benefits and climate 
disbenefits can be found in Chapter 4 of the RIA which is available in 
the docket for this rulemaking.
    Tables 41 through 45 of this preamble present the emission changes, 
and PV and EAV of the projected monetized benefits, compliance costs, 
and net benefits over the 2024 to 2038 period under the proposed 
rulemaking for each subpart. Table 46 of this preamble presents the 
same results for the cumulative impact of these rulemakings. All 
discounting of impacts presented, except for compliance costs, uses 
discount rates of 3 and 7 percent.

     Table 41--Monetized Benefits, Costs, and Net Benefits of the Proposed HON Amendments, 2024 Through 2038
                               [Dollar estimates in millions of 2021 dollars] \a\
----------------------------------------------------------------------------------------------------------------
                                          3 Percent discount rate                 7 Percent discount rate
                                 -------------------------------------------------------------------------------
                                          PV                  EAV                 PV                  EAV
----------------------------------------------------------------------------------------------------------------
Benefits \b\....................  $78 and $690......  $6.5 and $58......  $53 and $470......  $5.8 and $51.
Climate Disbenefits (3 percent)   $(25.4)...........  $(2.1)............  $(25.4)...........  $(2.1).
 \c\.
Net Compliance Costs \d\........  $1,385............  $116..............  $922..............  $101.
Compliance Costs................  $1,393............  $117..............  $927..............  $102.
Value of Product Recovery.......  $8................  $1................  $5................  $0.8.
Net Benefits....................  $(1,280) and        $(107) and $(56)..  $(844) and $(427).  $(93) and $(48).
                                   $(670).
----------------------------------------------------------------------------------------------------------------
Nonmonetized Benefits: HAP emissions reductions of 5,726 tpy including 58 tpy reduction in ethylene oxide
 emissions. Health effects of reduced exposure to ethylene oxide and also chloroprene, benzene, 1,3-butadiene,
 vinyl chloride, ethylene dichloride, chlorine, maleic anhydride, and acrolein.
----------------------------------------------------------------------------------------------------------------
\a\ Values rounded to two significant figures. Totals may not appear to add correctly due to rounding. Short
  tons are standard English tons (2,000 pounds).
\b\ Monetized benefits include ozone related health benefits associated with reductions in VOC emissions. The
  health benefits are associated with several point estimates and are presented at real discount rates of 3 and
  7 percent. The two benefits estimates are separated by the word ``and'' to signify that they are two separate
  estimates. The estimates do not represent lower- and upper-bound estimates. Benefits from annual HAP
  reductions and VOC reductions outside of the ozone season remain unmonetized and are thus not reflected in the
  table. Climate benefits and disbenefits are estimated at a real discount rate of 3 percent. The unmonetized
  effects also include disbenefits resulting from the secondary impact of an increase in CO emissions. Please
  see Chapter 4 of the RIA for more discussion of the health and climate benefits and disbenefits.
\c\ Climate benefits and disbenefits are based on changes (decreases and increases) in CO2, methane and N2O
  emissions and are calculated using four different estimates of the social cost of carbon (SC-GHG) (model
  average at 2.5 percent, 3 percent, and 5 percent discount rates; 95th percentile at 3 percent discount rate).
  For the presentational purposes of this table, we show the benefits and disbenefits associated with the
  average SC-GHG at a 3 percent discount rate, but the Agency does not have a single central SC-GHG point
  estimate. We emphasize the importance and value of considering the disbenefits calculated using all four SC-
  GHG estimates. As discussed in Chapter 4 of the RIA, a consideration of climate disbenefits calculated using
  discount rates below 3 percent, including 2 percent and lower, is also warranted when discounting
  intergenerational impacts. The use of parentheses surrounding a number denotes a negative value for that
  number. For climate disbenefits, a negative disbenefit is a benefit (and thus a positive value).
\d\ Net compliance costs are the rulemaking costs minus the value of recovered product. A negative net
  compliance costs occurs when the value of the recovered product exceeds the compliance costs.

 Table 42--Monetized Benefits, Compliance Costs, and Net Benefits of the Proposed P&R I Amendments, 2024 Through
                                                      2038
                               [Dollar estimates in millions of 2021 dollars] \a\
----------------------------------------------------------------------------------------------------------------
                                          3 Percent discount rate                 7 Percent discount rate
                                 -------------------------------------------------------------------------------
                                          PV                  EAV                 PV                  EAV
----------------------------------------------------------------------------------------------------------------
Benefits \b\....................  $2.6 and $23......  $0.22 and $1.9....  $1.8 and $16......  $0.19 and $1.7.
Climate Disbenefits (3 percent)   $40.5.............  $3.4..............  $40.5.............  $3.4.
 \c\.
Net Compliance Costs \d\........  $121..............  $10...............  $78...............  $8.6.
Compliance Costs................  $122..............  $10.2.............  $79...............  $8.7.
Value of Product Recovery.......  $1................  $0.2..............  $1................  $0.1.
Net Benefits....................  $(159) and $(139).  $(13) and $(12)...  $(116) and $(103).  $(12) and $(10).
----------------------------------------------------------------------------------------------------------------
Nonmonetized Benefits: HAP emissions reductions 326 tpy including 14 tpy reduction in chloroprene emissions.
 Health effects of reduced exposure to chloroprene and benzene, 1,3-butadiene, vinyl chloride, ethylene
 dichloride, chlorine, maleic anhydride, and acrolein.
----------------------------------------------------------------------------------------------------------------
\a\ Values rounded to two significant figures. Totals may not appear to add correctly due to rounding. Short
  tons are standard English tons (2,000 pounds).
\b\ Monetized benefits include ozone related health benefits associated with reductions in VOC emissions. The
  health benefits are associated with several point estimates and are presented at real discount rates of 3 and
  7 percent. The two benefits estimates are separated by the word ``and'' to signify that they are two separate
  estimates. The estimates do not represent lower- and upper-bound estimates and should not be summed. Benefits
  from annual HAP reductions and VOC reductions outside of the ozone season remain unmonetized and are thus not
  reflected in the table.

[[Page 25199]]

 
\c\ Climate benefits and disbenefits are based on changes (decreases and increases) in CO2, methane and N2O
  emissions and are calculated using four different estimates of the social cost of carbon (SC-GHG) (model
  average at 2.5 percent, 3 percent, and 5 percent discount rates; 95th percentile at 3 percent discount rate).
  For the presentational purposes of this table, we show the benefits and disbenefits associated with the
  average SC-GHG at a 3 percent discount rate, but the Agency does not have a single central SC-GHG point
  estimate. We emphasize the importance and value of considering the disbenefits calculated using all four SC-
  GHG estimates. As discussed in Chapter 4 of the RIA, a consideration of climate disbenefits calculated using
  discount rates below 3 percent, including 2 percent and lower, is also warranted when discounting
  intergenerational impacts. The use of parentheses surrounding a number denotes a negative value for that
  number.
\d\ Net compliance costs are the rulemaking costs minus the value of recovered product. A negative net
  compliance costs occurs when the value of the recovered product exceeds the compliance costs.

   Table 43--Monetized Benefits, Compliance Costs, Emission Reductions and Net Benefits of the Proposed P&R II
                                          Amendments, 2024 Through 2038
                               [Dollar estimates in millions of 2021 dollars] \a\
----------------------------------------------------------------------------------------------------------------
                                          3 Percent discount rate                 7 Percent discount rate
                                 -------------------------------------------------------------------------------
                                          PV                  EAV                 PV                  EAV
----------------------------------------------------------------------------------------------------------------
Benefits \b\....................  <$0.1.............  <$0.1.............  <$0.1.............  <$0.1.
Net Compliance Costs \c\........  $4................  $0.4..............  $3................  $0.4
Compliance Costs................  $4................  $0.4..............  $3................  $0.4
Value of Product Recovery.......  $0................  $0................  $0................  $0
Net Benefits....................  $(4)..............  $(0.4)............  $(3)..............  $(0.4).
----------------------------------------------------------------------------------------------------------------
Nonmonetized Benefits: HAP emissions reductions 1 tpy. Health effects of reduced exposure to epichlorohydrin.
----------------------------------------------------------------------------------------------------------------
\a\ Values rounded to two significant figures. Totals may not appear to add correctly due to rounding. Short
  tons are standard English tons (2,000 pounds).
\b\ Monetized benefits include ozone related health benefits associated with reductions in VOC emissions. The
  health benefits are associated with several point estimates and are presented at real discount rates of 3 and
  7 percent. The two benefits estimates are separated by the word ``and'' to signify that they are two separate
  estimates. The estimates do not represent lower- and upper-bound estimates. Benefits from VOC reductions
  outside of the ozone season remain unmonetized and are thus not reflected in the table.
\c\ Net compliance costs are the rulemaking costs minus the value of recovered product. A negative net
  compliance costs occurs when the value of the recovered product exceeds the compliance costs.

      Table 44--Monetized Benefits, Costs, and Net Benefits of Proposed NSPS Subpart VVb, 2024 Through 2038
                               [Dollar estimates in millions of 2021 dollars] \a\
----------------------------------------------------------------------------------------------------------------
                                          3 Percent discount rate                 7 Percent discount rate
                                 -------------------------------------------------------------------------------
                                          PV                  EAV                 PV                  EAV
----------------------------------------------------------------------------------------------------------------
Benefits \b\....................  $1.2 and $11......  $0.10 and $0.93...  $0.85 and $7.5....  $0.09 and $0.82.
Net Compliance Costs \c\........  $11...............  $0.9..............  $8................  $0.9.
Compliance Costs................  $13.3.............  $1.1..............  $9.7..............  $1.1.
Value of Product Recovery.......  $2.3..............  $0.2..............  $1.7..............  $0.2.
Net Benefits....................  $(9.8) and $0.....  $(0.8) and $0.03..  $(7.15) and $(0.5)  $(0.81) and
                                                                                               $(0.08).
----------------------------------------------------------------------------------------------------------------
\a\ Values rounded to two significant figures. Totals may not appear to add correctly due to rounding. Short
  tons are standard English tons (2,000 pounds).
\b\ Monetized benefits include ozone related health benefits associated with reductions in VOC emissions. The
  health benefits are associated with several point estimates and are presented at real discount rates of 3 and
  7 percent. The two benefits estimates are separated by the word ``and'' to signify that they are two separate
  estimates. The estimates do not represent lower- and upper-bound estimates. Benefits from HAP reductions and
  VOC reductions outside of the ozone season remain unmonetized and are thus not reflected in the table. There
  are no climate benefits and disbenefits for this proposed rule.
\c\ Net compliance costs are the rulemaking costs minus the value of recovered product. A negative net
  compliance costs occurs when the value of the recovered product exceeds the compliance costs.

   Table 45--Monetized Benefits, Costs, and Net Benefits of Proposed NSPS Subparts IIIa, NNNa, and RRRa, 2024
                                                  Through 2038
                               [Dollar estimates in millions of 2021 dollars] \a\
----------------------------------------------------------------------------------------------------------------
                                          3 Percent discount rate                 7 Percent discount rate
                                 -------------------------------------------------------------------------------
                                          PV                  EAV                 PV                  EAV
----------------------------------------------------------------------------------------------------------------
Benefits \b\....................  $4.6 and $41......  $0.39 and $3.5....  $3.2 and $28......  $0.35 and $3.0.
Climate Disbenefits (3 percent)   $(6.8)............  $(0.57)...........  $(6.8)............  $(0.57).
 \c\.
Net Compliance Costs \d\........  $56...............  $4.7..............  $40...............  $4.4.
Compliance Costs................  $56...............  $4.7..............  $40...............  $4.4.
Value of Product Recovery.......  $0................  $0................  $0................  $0.
Net Benefits....................  $(45) and $(8)....  $(3.7) and $(0.6).  $(30) and $(5)....  $(3.5) and $(0.8).
----------------------------------------------------------------------------------------------------------------
\a\ Values rounded to two significant figures. Totals may not appear to add correctly due to rounding. Short
  tons are standard English tons (2,000 pounds).

[[Page 25200]]

 
\b\ Monetized benefits include ozone related health benefits associated with reductions in VOC emissions. The
  health benefits are associated with several point estimates and are presented at real discount rates of 3 and
  7 percent. The two benefits estimates are separated by the word ``and'' to signify that they are two separate
  estimates. The estimates do not represent lower- and upper-bound estimates. Benefits from HAP reductions and
  VOC reductions outside of the ozone season remain unmonetized and are thus not reflected in the table. Climate
  disbenefits are estimated at a real discount rate of 3 percent. The unmonetized effects also include
  disbenefits resulting from the secondary impact of an increase in CO emissions. Please see Chapter 4 of the
  RIA for more discussion of the climate disbenefits.
\c\ Climate disbenefits (inclusive of benefits) are based on changes (increases) in CO2 and N2O emissions and
  decreases in methane emissions and are calculated using four different estimates of the social cost of carbon
  (SC-GHG) (model average at 2.5 percent, 3 percent, and 5 percent discount rates; 95th percentile at 3 percent
  discount rate). For the presentational purposes of this table, we show the disbenefits associated with the
  average SC-GHG at a real 3 percent discount rate, but the Agency does not have a single central SC-GHG point
  estimate. We emphasize the importance and value of considering the disbenefits calculated using all four SC-
  GHG estimates. Please see Table 4-11 of the RIA for the full range of SC-GHG estimates. As discussed in
  Chapter 4 of the RIA, a consideration of climate benefits and disbenefits calculated using discount rates
  below 3 percent, including 2 percent and lower, is also warranted when discounting intergenerational impacts.
\d\ Net compliance costs are the rulemaking costs minus the value of recovered product. A negative net
  compliance costs occurs when the value of the recovered product exceeds the compliance costs. A number in
  parentheses denotes a negative value.

      Table 46--Cumulative Monetized Benefits, Costs, Emission Reductions and Net Benefits of the Proposed
                                         Rulemakings, 2024 Through 2038
                               [Dollar estimates in millions of 2021 dollars] \a\
----------------------------------------------------------------------------------------------------------------
                                          3 Percent discount rate                 7 Percent discount rate
                                 -------------------------------------------------------------------------------
                                          PV                  EAV                 PV                  EAV
----------------------------------------------------------------------------------------------------------------
Benefits \b\....................  $81 and $730......  $6.8 and $61......  $56 and $490......  $6.1 and $54.
Climate Disbenefits (3 percent)   $8.2..............  $0.7..............  $8.2..............  $0.7.
 \c\.
Net Compliance Costs \d\........  $1,579............  $132..............  $1,052............  $121.
Compliance Costs................  $1,590............  $133.4............  $1,059.7..........  $122.1.
Value of Product Recovery.......  $11...............  $1.4..............  $7.7..............  $1.1.
Net Benefits....................  $(1,506) and        $(126) and $(71)..  $(1,100) and        $(110) and $(63).
                                   $(857).                                 $(570).
----------------------------------------------------------------------------------------------------------------
Nonmonetized Benefits: HAP emissions reductions of 6,053 tons of HAP. Health effects of reduced exposure to
 ethylene oxide, chloroprene, benzene, 1,3-butadiene, vinyl chloride, ethylene dichloride, chlorine, maleic
 anhydride, acrolein, and epichlorohydrin.
----------------------------------------------------------------------------------------------------------------
\a\ Values rounded to two significant figures. Totals may not appear to add correctly due to rounding. Short
  tons are standard English tons (2,000 pounds).
\b\ Monetized benefits include ozone related health benefits associated with reductions in VOC emissions. The
  health benefits are associated with several point estimates and are presented at real discount rates of 3 and
  7 percent. The two benefits estimates are separated by the word ``and'' to signify that they are two separate
  estimates. The estimates do not represent lower- and upper-bound estimates. Benefits from HAP reductions and
  VOC reductions outside of the ozone season remain unmonetized and are thus not reflected in the table. Climate
  disbenefits (inclusive of benefits) are estimated at a real discount rate of 3 percent. The unmonetized
  effects also include disbenefits resulting from the secondary impact of an increase in CO emissions. Please
  see Chapter 4 of the RIA for more discussion of the climate disbenefits.
\c\ Climate disbenefits are based on changes (increases) in CO2 and N2O emissions and decreases in methane
  emissions and are calculated using four different estimates of the social cost of carbon (SC-GHG) (model
  average at 2.5 percent, 3 percent, and 5 percent discount rates; 95th percentile at 3 percent discount rate).
  For the presentational purposes of this table, we show the disbenefits associated with the average SC-GHG at a
  3 percent discount rate, but the Agency does not have a single central SC-GHG point estimate. We emphasize the
  importance and value of considering the disbenefits calculated using all four SC-GHG estimates. Please see
  Table 4-11 of the RIA for the full range of SC-GHG estimates. As discussed in Chapter 4 of the RIA, a
  consideration of climate disbenefits calculated using discount rates below 3 percent, including 2 percent and
  lower, is also warranted when discounting intergenerational impacts.
\d\ Net compliance costs are the rulemaking costs minus the value of recovered product. A negative net
  compliance costs occurs when the value of the recovered product exceeds the compliance costs.

B. Paperwork Reduction Act (PRA)

1. HON
    The information collection activities in this proposed rule have 
been submitted for approval to the OMB under the PRA. The ICR document 
that the EPA prepared has been assigned EPA ICR number 2753.01. You can 
find a copy of the ICR in the docket for this rule, and it is briefly 
summarized here.
    The EPA is proposing amendments to the HON that revise provisions 
pertaining to emissions from flares, PRDs, process vents, storage 
vessels, pressure vessels, storage vessel degassing, heat exchange 
systems, maintenance vents, wastewater, and equipment leaks. The EPA is 
also proposing to add requirements pertaining to EtO emissions from 
flares, process vents, storage vessels, heat exchange systems, 
equipment leaks, and wastewater; and dioxins and furans emissions from 
process vents. In addition, the EPA is proposing amendments to the HON 
that revise provisions pertaining to emissions during periods of SSM, 
add requirements for electronic reporting of periodic reports and 
performance test results, fenceline monitoring, carbon adsorbers, and 
bypass monitoring, and make other minor clarifications and corrections. 
This information will be collected to assure compliance with the HON.
     Respondents/affected entities: Owners or operators of HON 
facilities. Respondent's obligation to respond: Mandatory (40 CFR part 
63, subparts F, G, H, and I).
     Estimated number of respondents: 209 (assumes two new 
respondents over the next 3 years). Frequency of response: Initially, 
quarterly, semiannually, and annually.
     Total estimated burden: average annual recordkeeping and 
reporting burden is 83,600 hours (per year) to comply with the proposed 
amendments in the HON. Burden is defined at 5 CFR 1320.3(b).
     Total estimated cost: average annual cost is $70,900,000 
(per year) which includes $62,700,000 annualized capital and operations 
and maintenance costs, to comply with the proposed amendments in the 
HON.
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for the 
EPA's regulations in 40 CFR are listed in 40 CFR part 9.
    Submit your comments on the Agency's need for this information, the

[[Page 25201]]

accuracy of the provided burden estimates, and any suggested methods 
for minimizing respondent burden to the EPA using the docket identified 
at the beginning of this rule. You may also send your ICR-related 
comments to OMB's Office of Information and Regulatory Affairs via 
email to [email protected], Attention: Desk Officer for the 
EPA. Since OMB is required to make a decision concerning the ICR 
between 30 and 60 days after receipt, OMB must receive comments no 
later than May 25, 2023. The EPA will respond to any ICR-related 
comments in the final rule.
2. P&R I
    The information collection activities in this proposed rule have 
been submitted for approval to the OMB under the PRA. The ICR document 
that the EPA prepared has been assigned EPA ICR number 2410.06. You can 
find a copy of the ICR in the docket for this rule, and it is briefly 
summarized here.
    The EPA is proposing amendments to P&R I that revise provisions 
pertaining to emissions from flares, PRDs, continuous process vents, 
batch process vents, storage vessels, pressure vessels, storage vessel 
degassing, heat exchange systems, maintenance vents, wastewater, and 
equipment leaks. The EPA is also proposing to add requirements 
pertaining to: chloroprene emissions from process vents, storage 
vessels, and wastewater; and dioxins and furans emissions from 
continuous process vents and batch process vents. In addition, the EPA 
is proposing amendments to P&R I that revise provisions pertaining to 
emissions during periods of SSM, add requirements for electronic 
reporting of periodic reports and performance test results, fenceline 
monitoring, carbon adsorbers, and bypass monitoring, and make other 
minor clarifications and corrections. This information will be 
collected to assure compliance with P&R I.
     Respondents/affected entities: Owners or operators of P&R 
I facilities. Respondent's obligation to respond: Mandatory (40 CFR 
part 63, subpart U).
     Estimated number of respondents: 19 (assumes no new 
respondents over the next 3 years). Frequency of response: Initially, 
quarterly, semiannually, and annually.
     Total estimated burden: average annual recordkeeping and 
reporting burden is 8,126 hours (per year) to comply with the proposed 
amendments in P&R I. Burden is defined at 5 CFR 1320.3(b).
     Total estimated cost: average annual cost is $3,480,000 
(per year) which includes $2,680,000 annualized capital and operations 
and maintenance costs, to comply with the proposed amendments in P&R I.
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for the 
EPA's regulations in 40 CFR are listed in 40 CFR part 9.
    Submit your comments on the Agency's need for this information, the 
accuracy of the provided burden estimates, and any suggested methods 
for minimizing respondent burden to the EPA using the docket identified 
at the beginning of this rule. You may also send your ICR-related 
comments to OMB's Office of Information and Regulatory Affairs via 
email to [email protected], Attention: Desk Officer for the 
EPA. Since OMB is required to make a decision concerning the ICR 
between 30 and 60 days after receipt, OMB must receive comments no 
later than May 25, 2023. The EPA will respond to any ICR-related 
comments in the final rule.
3. P&R II
    The information collection activities in this proposed rule have 
been submitted for approval to the OMB under the PRA. The ICR document 
that the EPA prepared has been assigned EPA ICR number 1681.11. You can 
find a copy of the ICR in the docket for this rule, and it is briefly 
summarized here.
    The EPA is proposing amendments to P&R II to add requirements 
pertaining to: heat exchange systems, PRDs, dioxins and furans 
emissions from process vents, and maintenance vents. In addition, the 
EPA is proposing amendments to P&R II that revise provisions pertaining 
to emissions during periods of SSM, add requirements for electronic 
reporting of periodic reports and performance test results, and make 
other minor clarifications and corrections. This information will be 
collected to assure compliance with P&R II.
     Respondents/affected entities: Owners or operators of P&R 
II facilities. Respondent's obligation to respond: Mandatory (40 CFR 
part 63, subpart W).
     Estimated number of respondents: 5 (assumes no new 
respondents over the next 3 years). Frequency of response: Initially, 
semiannually, and annually.
     Total estimated burden: average annual recordkeeping and 
reporting burden is 202 hours (per year) to comply with the proposed 
amendments in P&R II. Burden is defined at 5 CFR 1320.3(b).
     Total estimated cost: average annual cost is $1,780,000 
(per year) which includes $1,760,000 annualized capital and operations 
and maintenance costs, to comply with the proposed amendments in P&R 
II.
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for the 
EPA's regulations in 40 CFR are listed in 40 CFR part 9.
    Submit your comments on the Agency's need for this information, the 
accuracy of the provided burden estimates, and any suggested methods 
for minimizing respondent burden to the EPA using the docket identified 
at the beginning of this rule. You may also send your ICR-related 
comments to OMB's Office of Information and Regulatory Affairs via 
email to [email protected], Attention: Desk Officer for the 
EPA. Since OMB is required to make a decision concerning the ICR 
between 30 and 60 days after receipt, OMB must receive comments no 
later than May 25, 2023. The EPA will respond to any ICR-related 
comments in the final rule.
4. NSPS Subparts VV, VVa, III, NNN, and RRR
    This action does not impose any new information collection burden 
under the PRA for NSPS subparts VV, VVa, III, NNN, and RRR. OMB has 
previously approved the information collection activities contained in 
the existing regulations and has assigned OMB Control number 2060-0443 
for 40 CFR part 60 subparts VV, VVa, III, NNN, and RRR (this one OMB 
Control number is for the Consolidated Federal Air Rule in 40 CFR part 
65 which presents the burden for complying with 40 CFR part 65, but 
also presents the burden for facilities complying with each individual 
subpart). This action is believed to result in no changes to the 
information collection requirements of these NSPS, so that the 
information collection estimate of project cost and hour burden from 
these NSPS have not been revised.
5. NSPS Subpart VVb
    The information collection activities in this proposed rule have 
been submitted for approval to the OMB under the PRA. The ICR document 
that the EPA prepared has been assigned EPA ICR number 2755.01. You can 
find a copy of the ICR in the docket for this rule, and it is briefly 
summarized here.
    The EPA is proposing in a new NSPS subpart VVb the same 
requirements in NSPS subpart VVa plus requiring that

[[Page 25202]]

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. In addition, the EPA is 
proposing to remove SSM provisions (the standards apply at all times), 
add requirements for electronic reporting of periodic reports, and make 
other minor clarifications and corrections. This information will be 
collected to assure compliance with the NSPS subpart VVb.
     Respondents/affected entities: Owners or operators of 
certain equipment leaks in the SOCMI. Respondent's obligation to 
respond: Mandatory (40 CFR part 60, subpart VVb).
     Estimated number of respondents: 36 (assumes 36 new 
respondents over the next 3 years). Frequency of response: Initially, 
occasionally, and annually.
     Total estimated burden: average annual recordkeeping and 
reporting burden is 5,414 hours (per year) to comply with all of the 
requirements in the NSPS. Burden is defined at 5 CFR 1320.3(b).
     Total estimated cost: average annual cost is $4,540,000 
(per year) which includes $4,000,000 annualized capital and operations 
and maintenance costs, to comply with all of the requirements in the 
NSPS.
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for the 
EPA's regulations in 40 CFR are listed in 40 CFR part 9.
    Submit your comments on the Agency's need for this information, the 
accuracy of the provided burden estimates, and any suggested methods 
for minimizing respondent burden to the EPA using the docket identified 
at the beginning of this rule. You may also send your ICR-related 
comments to OMB's Office of Information and Regulatory Affairs via 
email to [email protected], Attention: Desk Officer for the 
EPA. Since OMB is required to make a decision concerning the ICR 
between 30 and 60 days after receipt, OMB must receive comments no 
later than May 25, 2023. The EPA will respond to any ICR-related 
comments in the final rule.
6. NSPS Subpart IIIa
    The information collection activities in this proposed rule have 
been submitted for approval to the OMB under the PRA. The ICR document 
that the EPA prepared has been assigned EPA ICR number 2756.01. You can 
find a copy of the ICR in the docket for this rule, and it is briefly 
summarized here.
    The EPA is proposing requirements for new, modified, or 
reconstructed sources as follows: require owners and operators reduce 
emissions of TOC (minus methane and ethane) from all vent streams of an 
affected facility (and not allow the alternative of maintaining a TRE 
index value greater than 1 without the use of a control device); 
exclude SSM provisions (and instead, the standards apply at all times); 
revise monitoring requirements for flares; add maintenance vent 
requirements; revise requirements for adsorber monitoring; exclude the 
relief valve discharge exemption such that any relief valve discharge 
to the atmosphere of a vent stream is a violation of the emissions 
standard; and prohibit an owner or operator from bypassing the control 
device at any time, and to report any such violation. This information 
will be collected to assure compliance with the NSPS subpart IIIa.
     Respondents/affected entities: Owners or operators of air 
oxidation unit processes in the SOCMI. Respondent's obligation to 
respond: Mandatory (40 CFR part 60, subpart IIIa).
     Estimated number of respondents: 6 (assumes 6 new 
respondents over the next 3 years). Frequency of response: Initially, 
semiannually, and annually.
     Total estimated burden: average annual recordkeeping and 
reporting burden is 275 hours (per year) to comply with all of the 
requirements in the NSPS. Burden is defined at 5 CFR 1320.3(b).
     Total estimated cost: average annual cost is $3,820,000 
(per year) which includes $3,800,000 annualized capital and operations 
and maintenance costs, to comply with all of the requirements in the 
NSPS.
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for the 
EPA's regulations in 40 CFR are listed in 40 CFR part 9.
    Submit your comments on the Agency's need for this information, the 
accuracy of the provided burden estimates, and any suggested methods 
for minimizing respondent burden to the EPA using the docket identified 
at the beginning of this rule. You may also send your ICR-related 
comments to OMB's Office of Information and Regulatory Affairs via 
email to [email protected], Attention: Desk Officer for the 
EPA. Since OMB is required to make a decision concerning the ICR 
between 30 and 60 days after receipt, OMB must receive comments no 
later than May 25, 2023. The EPA will respond to any ICR-related 
comments in the final rule.
7. NSPS Subpart NNNa
    The information collection activities in this proposed rule have 
been submitted for approval to the OMB under the PRA. The ICR document 
that the EPA prepared has been assigned EPA ICR number 2757.01. You can 
find a copy of the ICR in the docket for this rule, and it is briefly 
summarized here.
    The EPA is proposing requirements for new, modified, or 
reconstructed sources as follows: require owners and operators reduce 
emissions of TOC (minus methane and ethane) from all vent streams of an 
affected facility (and not allow the alternative of maintaining a TRE 
index value greater than 1 without the use of a control device); 
exclude SSM provisions (and instead, the standards apply at all times); 
revise monitoring requirements for flares; add maintenance vent 
requirements; revise requirements for adsorber monitoring; exclude the 
relief valve discharge exemption such that any relief valve discharge 
to the atmosphere of a vent stream is a violation of the emissions 
standard; and prohibit an owner or operator from bypassing the control 
device at any time, and to report any such violation. This information 
will be collected to assure compliance with the NSPS subpart NNNa.
     Respondents/affected entities: Owners or operators of 
distillation operations in the SOCMI. Respondent's obligation to 
respond: Mandatory (40 CFR part 60, subpart NNNa).
     Estimated number of respondents: 7 (assumes 7 new 
respondents over the next 3 years). Frequency of response: Initially, 
semiannually, and annually.
     Total estimated burden: average annual recordkeeping and 
reporting burden is 288 hours (per year) to comply with all of the 
requirements in the NSPS. Burden is defined at 5 CFR 1320.3(b).
     Total estimated cost: average annual cost is $4,460,000 
(per year) which includes $4,430,000 annualized capital and operations 
and maintenance costs, to comply with all of the requirements in the 
NSPS.
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for the 
EPA's regulations in 40 CFR are listed in 40 CFR part 9.
    Submit your comments on the Agency's need for this information, the 
accuracy of the provided burden

[[Page 25203]]

estimates, and any suggested methods for minimizing respondent burden 
to the EPA using the docket identified at the beginning of this rule. 
You may also send your ICR-related comments to OMB's Office of 
Information and Regulatory Affairs via email to 
[email protected], Attention: Desk Officer for the EPA. Since 
OMB is required to make a decision concerning the ICR between 30 and 60 
days after receipt, OMB must receive comments no later than May 25, 
2023. The EPA will respond to any ICR-related comments in the final 
rule.
8. NSPS Subpart RRRa
    The information collection activities in this proposed rule have 
been submitted for approval to the OMB under the PRA. The ICR document 
that the EPA prepared has been assigned EPA ICR number 2759.01. You can 
find a copy of the ICR in the docket for this rule, and it is briefly 
summarized here.
    The EPA is proposing requirements for new, modified, or 
reconstructed sources as follows: require owners and operators reduce 
emissions of TOC (minus methane and ethane) from all vent streams of an 
affected facility (and not allow the alternative of maintaining a TRE 
index value greater than 1 without the use of a control device); 
exclude SSM provisions (and instead, the standards apply at all times); 
revise monitoring requirements for flares; add maintenance vent 
requirements; revise requirements for adsorber monitoring; exclude the 
relief valve discharge exemption such that any relief valve discharge 
to the atmosphere of a vent stream is a violation of the emissions 
standard; and prohibit an owner or operator from bypassing the control 
device at any time, and to report any such violation. This information 
will be collected to assure compliance with the NSPS subpart RRRa.
     Respondents/affected entities: Owners or operators of 
reactor processes in the SOCMI. Respondent's obligation to respond: 
Mandatory (40 CFR part 60, subpart RRRa).
     Estimated number of respondents: 6 (assumes 6 new 
respondents over the next 3 years). Frequency of response: Initially, 
semiannually, and annually.
     Total estimated burden: average annual recordkeeping and 
reporting burden is 275 hours (per year) to comply with all of the 
requirements in the NSPS. Burden is defined at 5 CFR 1320.3(b).
     Total estimated cost: average annual cost is $3,820,000 
(per year) which includes $3,800,000 annualized capital and operations 
and maintenance costs, to comply with all of the requirements in the 
NSPS.
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for the 
EPA's regulations in 40 CFR are listed in 40 CFR part 9.
    Submit your comments on the Agency's need for this information, the 
accuracy of the provided burden estimates, and any suggested methods 
for minimizing respondent burden to the EPA using the docket identified 
at the beginning of this rule. You may also send your ICR-related 
comments to OMB's Office of Information and Regulatory Affairs via 
email to [email protected], Attention: Desk Officer for the 
EPA. Since OMB is required to make a decision concerning the ICR 
between 30 and 60 days after receipt, OMB must receive comments no 
later than May 25, 2023. The EPA will respond to any ICR-related 
comments in the final rule.

C. Regulatory Flexibility Act (RFA)

    I certify that each of the proposed rules in this action will not 
have a significant economic impact on a substantial number of small 
entities under the RFA. The small entities subject to the requirements 
of this action are small businesses. For the proposed amendments to the 
HON, the Agency has determined that all small entities affected by this 
action, estimated to be 10, may experience an average impact of costs 
being less than 0.5 percent of revenues, not including product 
recovery, or about 0.43 percent, including product recovery from 
compliance. Two of these ten entities experienced costs above one 
percent of revenues, neither had costs exceeding three percent of 
revenues and represent a small total number of impacted entities. For 
the proposed amendments to P&R I, one small entity is impacted and its 
impact is costs less than 0.5 percent of revenues. For the proposed 
amendments to P&R II, no small entities are impacted. Details of the 
analysis for each proposed rule are presented in the Regulatory Impact 
Analysis for this action, which is found in the docket.

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate as described in 
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect 
small governments. The action imposes no enforceable duty on any state, 
local or tribal governments or the private sector.

E. Executive Order 13132: Federalism

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

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

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

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

    This action is subject to Executive Order 13045 because it is an 
economically significant regulatory action under section 3(f)(1) of 
Executive Order 12866, and the EPA believes that the environmental 
health or safety risk addressed by this action may have a 
disproportionate effect on children. Accordingly, we have evaluated the 
environmental health or safety effects of EtO and chloroprene emissions 
on children. The results of this evaluation are contained in sections 
II.E and F, III.A and B, and IV.G of this preamble and further 
documented in the risk reports, Residual Risk Assessment for the SOCMI 
Source Category in Support of the 2023 Risk and Technology Review 
Proposed Rule and Residual Risk Assessment for the Polymers & Resins I 
Neoprene Production Source Category in Support of the 2023 Risk and 
Technology Review Proposed Rule, which are available in the docket.

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

    This action is not a ``significant energy action'' because it is 
not likely to have a significant adverse effect on the supply, 
distribution, or use of energy. The EPA expects this proposed action 
would not reduce crude oil supply, fuel production, coal production, 
natural gas production, or electricity production. We estimate that 
this proposed action would have minimal impact on the amount of imports 
or exports of crude oils, condensates, or other organic liquids used in 
the energy supply industries. Given the minimal impacts on energy 
supply, distribution, and use

[[Page 25204]]

as a whole nationally, no significant adverse energy effects are 
expected to occur. For more information on these estimates of energy 
effects, please refer to the Regulatory Impact Analysis for this 
proposed rulemaking.

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

    This action involves technical standards. Therefore, the EPA 
conducted searches for the HON, P&R I, and P&R II through the Enhanced 
National Standards Systems Network (NSSN) Database managed by the 
American National Standards Institute (ANSI). We also conducted a 
review of voluntary consensus standards (VCS) organizations and 
accessed and searched their databases. We conducted searches for EPA 
Methods 1, 1A, 2, 2A, 2C, 2D, 2F, 2G, 3B, 4, 18, 21, 22, 25A, 25D, 26, 
26A, 27 of 40 CFR part 60, Appendix A, 301, 305, 316 and 320 of 40 CFR 
part 63, Appendix A, 624, 625, 1624, and 1625 of 40 CFR part 136 
Appendix A, 624.1 of 40 CFR part 163, Appendix A. During the EPA's VCS 
search, if the title or abstract (if provided) of the VCS described 
technical sampling and analytical procedures that are similar to the 
EPA's reference method, the EPA ordered a copy of the standard and 
reviewed it as a potential equivalent method. We reviewed all potential 
standards to determine the practicality of the VCS for this rule. This 
review requires significant method validation data that meet the 
requirements of EPA Method 301 for accepting alternative methods or 
scientific, engineering, and policy equivalence to procedures in the 
EPA reference methods. The EPA may reconsider determinations of 
impracticality when additional information is available for particular 
VCS.
    No applicable voluntary consensus standards were identified for EPA 
Methods 1A, 2A, 2D, 2F, 2G, 21, 22, 25D, 27, 305, 316, 624, 624.1, 625, 
1624 and 1625. Three voluntary consensus standards were identified as 
an acceptable alternative to EPA Methods 3B, 18, and 320 for the 
purposes of this proposed rule, as follows.
    The EPA proposes to use the VCS ANSI/ASME PTC 19-10-1981--Part 10, 
``Flue and Exhaust Gas Analyses'' as an acceptable alternative to EPA 
Method 3B (referenced in NSPS subpart RRR and NESHAP subpart G) for the 
manual procedures only and not the instrumental procedures. The ANSI/
ASME PTC 19-10-1981--Part 10 method incorporates both manual and 
instrumental methodologies for the determination of oxygen content. The 
manual method segment of the oxygen determination is performed through 
the absorption of oxygen. This method is available at the American 
National Standards Institute (ANSI), 1899 L Street NW, 11th Floor, 
Washington, DC 20036 and the American Society of Mechanical Engineers 
(ASME), Three Park Avenue, New York, NY 10016-5990. See https://wwww.ansi.org and https://www.asme.org. The standard is available to 
everyone at a cost determined by ANSI/ASME ($96). ANSI/ASME also offer 
memberships or subscriptions for reduced costs. The cost of obtaining 
these methods is not a significant financial burden, making the methods 
reasonably available.
    Also, the EPA proposes to use the VCS ASTM D6420-18, ``Standard 
Test Method for Determination of Gaseous Organic Compounds by Direct 
Interface Gas Chromatography-Mass Spectrometry'' as an acceptable 
alternative to EPA Method 18 (referenced in NSPS subparts VV, VVa, VVb, 
III, IIIa, NNN, NNNa, RRR, and RRRa, and NESHAP subparts F, G, H, I, U, 
and W) with the following caveats. This ASTM procedure has been 
approved by the EPA as an alternative to EPA Method 18 only when the 
target compounds are all known and the target compounds are all listed 
in ASTM D6420 as measurable. We are proposing that ASTM D6420-18 should 
not be used for methane and ethane because the atomic mass is less than 
35; and ASTM D6420 should never be specified as a total VOC method. The 
ASTM D6420-18 test method employs a direct interface gas chromatograph/
mass spectrometer to measure 36 VOC. The test method provides on-site 
analysis of extracted, unconditioned, and unsaturated (at the 
instrument) gas samples from stationary sources.
    In addition, the EPA proposes to use the VCS ASTM D6348-12e1, 
``Determination of Gaseous Compounds by Extractive Direct Interface 
Fourier Transform (FTIR) Spectroscopy'' as an acceptable alternative to 
EPA Method 320 (referenced in NESHAP subparts F, G, and U) with caveats 
requiring inclusion of selected annexes to the standard as mandatory. 
ASTM D6348-03(2010) was determined to be equivalent to EPA Method 320 
with caveats. ASTM D6348-12e1 is a revised version of ASTM D6348-
03(2010) and includes a new section on accepting the results from the 
direct measurement of a certified spike gas cylinder, but lacks the 
caveats placed on the ASTM D6348-03(2010) version. The VCS ASTM D6348-
12e1 method is an extractive FTIR Spectroscopy-based field test method 
and is used to quantify gas phase concentrations of multiple target 
compounds in emission streams from stationary sources. When using ASTM 
D6348-12e, we are proposing the following conditions must be met: (1) 
The test plan preparation and implementation in the Annexes to ASTM D 
6348-03, Sections A1 through A8 are mandatory; and (2) in ASTM D6348-03 
Annex A5 (Analyte Spiking Technique), the percent (%) R must be 
determined for each target analyte (Equation A5.5). We are proposing 
that in order for the test data to be acceptable for a compound, %R 
must be 70% >= R <= 130%. If the %R value does not meet this criterion 
for a target compound, the test data is not acceptable for that 
compound and the test must be repeated for that analyte (i.e., the 
sampling and/or analytical procedure should be adjusted before a 
retest). We are proposing that the %R value for each compound must be 
reported in the test report, and all field measurements must be 
corrected with the calculated %R value for that compound by using the 
following equation:

Reported Results = ((Measured Concentration in Stack))/(%R) x 100.

    The two ASTM methods (ASTM D6420-18 and ASTM D6348-12e1) are 
available at ASTM International, 1850 M Street NW, Suite 1030, 
Washington, DC 20036. See https://www.astm.org/. These standards are 
available to everyone at a cost determined by the ASTM ($57 and $76, 
respectively). The ASTM also offers memberships or subscriptions that 
allow unlimited access to their methods. The cost of obtaining these 
methods is not a significant financial burden, making the methods 
reasonably available to stakeholders.
    The search identified 13 VCS that were potentially applicable for 
this rule in lieu of EPA reference methods. After reviewing the 
available standards, EPA determined that 13 candidate VCS (ASTM D3154-
00 (2006), ASTM D3464-96 (2007), ASTM 3796-90 (2004), ISO 10780:1994, 
ASME B133.9- 1994 (2001), ANSI/ASME PTC 19-10-198-Part 10, National 
Institute of Occupational Safety and Health (NIOSH) Method 2010 
``Amines, Aliphatic'', ASTM D6060-96 (2009), ISO 14965:2000(E), EN 
12619 (1999), EN 1911-1,2,3 (1998), ASTM D6735-01 (2009), ASTM D4855-97 
(2002)) identified for measuring emissions of pollutants or their 
surrogates subject to emission standards in the rule would not be 
practical due to lack of equivalency, documentation, validation

[[Page 25205]]

data and other important technical and policy considerations.
    Additional information for the VCS search and determinations can be 
found in the document titled: Voluntary Consensus Standard Results for 
National Emission Standards for Hazardous Air Pollutants From the 
Synthetic Organic Chemical Manufacturing Industry, which is available 
in the docket for this action. The EPA welcomes comments on this aspect 
of the proposed rulemaking and, specifically, invites the public to 
identify potentially applicable VCS and to explain why such standards 
should be used in this regulation.
    We are also proposing amendments to 40 CFR part 60, subpart A and 
40 CFR part 63, subpart A to address incorporations by reference. We 
are proposing that 40 CFR 60.485(g)(5) and 40 CFR 60.485a(g)(5) be 
added to 40 CFR 60.17--``Incorporations by Reference'' paragraph 
(a)(184) since they were mistakenly not added to 40 CFR 60.17 during 
the last amendment to this rule.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations

    Executive Order 12898 (59 FR 7629, February 16, 1994) directs 
federal agencies, to the greatest extent practicable and permitted by 
law, to make environmental justice part of their mission by identifying 
and addressing, as appropriate, disproportionately high and adverse 
human health or environmental effects of their programs, policies, and 
activities on minority populations (people of color and/or Indigenous 
peoples) and low-income populations.
    The EPA believes that the human health or environmental conditions 
that exist prior to this action result in or have the potential to 
result in disproportionate and adverse human health or environmental 
effects on people of color, low-income people, and/or Indigenous 
peoples. For the HON, a total of 9.3 million people live within 10 km 
(~6.2 miles) of the 195 HON facilities that were assessed for risk. The 
percentages of the population that are African American (25 percent 
versus 12 percent) and Hispanic or Latino (22 percent versus 19 
percent) are higher than the national averages. The proportion of other 
demographic groups living within 10 km of HON facilities is similar or 
lower than the national average. For the Neoprene Production source 
category, a total of 29,000 people live within 5 km of the one neoprene 
production facility in the country. The percent of the population that 
is African American (56 percent versus 12 percent) is substantially 
higher than the national average. The proportion of other demographic 
groups living within 10 km of HON facilities is similar or lower than 
the national average. The EPA also conducted a risk assessment of 
possible cancer risks and other adverse health effects, and found that 
prior to this proposed regulation, cancer risks were above acceptable 
levels for a number of areas in which these demographic groups live for 
the SOCMI and Neoprene Production source categories. See section IV.F 
for an analysis that characterizes populations living in proximity of 
facilities and risks prior to the proposed regulation.
    The EPA believes that this action is likely to reduce existing 
disproportionate and adverse effects on people of color, low-income 
populations and/or Indigenous peoples. This action proposes to 
establish standards for EtO emission sources at HON processes and 
chloroprene emission sources at neoprene production processes. This 
action also proposes amendments to correct and clarify regulatory 
provisions related to emissions during periods of SSM, including 
removing general exemptions for periods of SSM and adding work practice 
standards for periods of SSM where appropriate, address flare 
combustion efficiency, and require fenceline monitoring for pollutants 
that drive cancer risks for HON and neoprene production sources. As a 
result of these proposed changes, we expect zero people to be exposed 
to risk levels above 100-in-1 million due to emissions from each of 
these source categories. See sections III.A and B of this preamble for 
more information about the control requirements of the regulation and 
the resulting reduction in cancer risks.
    The EPA additionally identified and addressed EJ concerns by 
engaging in outreach activities to communities we expect to be impacted 
by chemical plants emitting EtO \177\ and by requiring the neoprene 
production facility to take a number of actions to reduce and monitor 
for fenceline concentrations of chloroprene.\178\ The EPA is also 
proposing that HON and P&R I facilities conduct fenceline monitoring 
for a number of HAP (i.e., EtO, chloroprene, benzene, 1,3-butadiene, 
ethylene dichloride and vinyl chloride) and report these data 
electronically to the EPA so that it can be made public and provide 
fenceline communities with greater access to information about 
potential emissions impacts.
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    \177\ https://www.epa.gov/hazardous-air-pollutants-ethylene-oxide/inspector-general-follow-ethylene-oxide-0.
    \178\ https://www.epa.gov/la/laplace-st-john-baptist-parish-louisiana.
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    The information supporting this Executive Order review is contained 
in section IV.F of this preamble, as well as in the technical reports, 
Analysis of Demographic Factors for Populations Living Near Hazardous 
Organic NESHAP (HON) Facilities, Analysis of Demographic Factors for 
Populations Living Near Neoprene Production Facilities, and Analysis of 
Demographic Factors for Populations Living Near Polymers and Resins I 
and Polymer and Resins II Facilities, which are available in the 
docket.

List of Subjects

40 CFR Part 60

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

40 CFR Part 63

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

Michael S. Regan,
Administrator.
[FR Doc. 2023-07188 Filed 4-24-23; 8:45 am]
BILLING CODE 6560-50-P