[Federal Register Volume 86, Number 221 (Friday, November 19, 2021)]
[Rules and Regulations]
[Pages 66096-66129]
[FR Doc No: 2021-24204]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2020-0505, EPA-HQ-OAR-2020-0532; FRL-7523-03-OAR]
RIN 2060-AU66

National Emission Standards for Hazardous Air Pollutants: Carbon
Black Production and Cyanide Chemicals Manufacturing Residual Risk and
Technology Reviews, and Carbon Black Production Area Source Technology
Review

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: This action finalizes the residual risk and technology reviews
(RTR) conducted for the Carbon Black Production and Cyanide Chemicals
Manufacturing major source categories, and the technology review
conducted for Carbon Black Production area sources, regulated under
National Emission Standards for Hazardous Air Pollutants (NESHAP). In
addition, we are taking final action to add new emissions standards for
the Carbon Black Production and Cyanide Chemicals Manufacturing major
source categories to address hazardous air pollutant (HAP) emissions
not previously covered by these NESHAP. The EPA is also finalizing
amendments for both source categories that address the startup,
shutdown, and malfunction (SSM) provisions of the existing standards,
and require electronic reporting of certain notifications, performance
test results, and semiannual reports.

DATES: These final rules are effective on November 19, 2021. The
incorporation by reference (IBR) of certain publications listed in the
final rule is approved by the Director of the Federal Register as of
November 19, 2021.

ADDRESSES: The U.S. Environmental Protection Agency (EPA) has
established a docket for the Carbon Black Production source category
under Docket ID No. EPA-HQ-OAR-2020-0505, and a docket for the Cyanide
Chemicals Manufacturing source category under Docket ID EPA-HQ-OAR-
2020-0532. All documents in the docket are listed on the https://www.regulations.gov/ website. Although listed, some information is not
publicly available, e.g., Confidential Business Information 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 form. Publicly
available docket materials are available either electronically through
https://www.regulations.gov/, or in hard copy at the EPA Docket Center,
WJC West Building, Room Number 3334, 1301 Constitution Ave. NW,
Washington, DC. The Public Reading Room hours of operation are 8:30
a.m. to 4:30 p.m. Eastern Standard Time (EST), Monday through Friday.
The telephone number for the Public Reading Room is<PHONE_NUMBER>, and
the telephone number for the EPA Docket Center is<PHONE_NUMBER>. Hand
Deliveries and couriers may be received by scheduled appointment only.
For further information and updates on EPA Docket Center services and
the current status, please visit us online at https://www.epa.gov/dockets.

FOR FURTHER INFORMATION CONTACT: For questions about the Carbon Black
Production source category final action, contact Korbin Smith, Sector
Policies and Programs Division (D243-04), Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina 27711; telephone number:<PHONE_NUMBER>;
fax number:<PHONE_NUMBER>; and email address: [email protected].
For questions about the Cyanide Chemicals Manufacturing source category
final action, contact Nathan Topham, Sector Policies and Programs
Division (D243-02), Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina
27711; telephone number:<PHONE_NUMBER>; fax number:<PHONE_NUMBER>;
and email address: [email protected].
    For specific information regarding the risk modeling methodology
for both Carbon Black Production and Cyanide Chemicals Manufacturing,
contact James Hirtz, Health and Environmental Impacts Division (C539-
02), Office of Air Quality Planning and Standards, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina 27711;
telephone number:<PHONE_NUMBER>; fax number:<PHONE_NUMBER>; and email
address: [email protected].

SUPPLEMENTARY INFORMATION:
    Preamble acronyms and abbreviations. 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:

CAA Clean Air Act
CCD combustion control device
CCMPU cyanide chemicals manufacturing process unit
CDX Central Data Exchange
CEDRI Compliance and Emissions Data Reporting Interface
CFR Code of Federal Regulations
CO carbon monoxide
CRA Congressional Review Act
EAV equivalent annual value
EPA U.S. Environmental Protection Agency
GMACT Generic Maximum Achievable Control Technology
HAP hazardous air pollutant(s)
HCN hydrogen cyanide
HON Hazardous Organic NESHAP
HQ hazard quotient
ICBA International Carbon Black Association
ICR Information Collection Request
LEL lower explosive limit
MACT maximum achievable control technology
MUF main unit filter
NAICS North American Industry Classification System
NATA National Air Toxics Assessment
NESHAP national emission standards for hazardous air pollutants
NOCS Notification of Compliance Status
NSPS New Source Performance Standards
OAQPS Office of Air Quality Planning and Standards
OMB Office of Management and Budget
PEL permissible exposure limit
ppm parts per million
ppmv parts per million by volume
ppmw parts per million by weight
PRA Paperwork Reduction Act
PV present value
REL reference exposure level
RFA Regulatory Flexibility Act
RTR residual risk and technology review
SSM startup, shutdown, and malfunction
SSP startup and shutdown plan
STEL short term exposure limit
TOSHI target organ-specific hazard index
tpy tons per year

    Background information. On January 14, 2021, the EPA proposed
revisions to the Carbon Black Production NESHAP based on our RTR, and
proposed no revisions to the Carbon Black Production area source rule
based on our technology review. On January 15, 2021, the EPA proposed
revisions to the Cyanide Chemicals Manufacturing NESHAP based on our
RTR. In this action, we are finalizing decisions for, and revisions of,
the NESHAP for these source categories. We summarize some of the more
significant comments we timely received regarding the proposed rules
and provide our responses in this preamble. A summary of all other
public comments on these proposals and the EPA's responses to those
comments are available in the Summary of Comments and EPA's Responses
on the National Emission Standards for Hazardous Air

Pollutants Carbon Black Production Residual Risk and Technology Review
and Carbon Black Production Area Sources Technology Review Proposed
Rule (see Docket ID No. EPA-HQ-OAR-2020-0505) for the Carbon Black
Production source category, and Summary of Comments and EPA's Responses
on the National Emission Standards for Hazardous Air Pollutants:
Cyanide Chemicals Manufacturing Residual Risk and Technology Review
Proposed Rule (see Docket ID No. EPA-HQ-OAR-2020-0532) for the Cyanide
Chemicals Manufacturing source category. ``Track changes'' versions of
the regulatory language that incorporates the changes in this action
are available in the dockets.
    Organization of this document. The information in this preamble is
organized as follows:

I. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document and other related
information?
    C. Judicial Review and Administrative Reconsideration
II. Background
    A. What is the statutory authority for this action?
    B. What are the source categories and how do the current NESHAP
regulate HAP emissions from the source categories?
    C. What changes did we propose for the Carbon Black Production
source category in our January 14, 2021, RTR proposal?
    D. What changes did we propose for the Cyanide Chemicals
Manufacturing source category in our January 15, 2021, RTR proposal?
III. What is included in these final rules?
    A. What are the final rule amendments based on the risk reviews
for the Carbon Black Production and Cyanide Chemicals Manufacturing
source categories?
    B. What are the final rule amendments based on the technology
reviews for the Carbon Black Production and Cyanide Chemicals
Manufacturing source categories?
    C. What are the final rule amendments pursuant to CAA sections
112(d)(2) and (3) for the Carbon Black Production and Cyanide
Chemicals Manufacturing source categories?
    D. What are the final rule amendments addressing emissions
during periods of SSM for the Carbon Black Production and Cyanide
Chemicals Manufacturing source categories?
    E. What other changes have been made to the NESHAP?
    F. What are the effective and compliance dates of the standards?
IV. What is the rationale for our final decisions and amendments for
the Carbon Black Production source category?
    A. Residual Risk Review for the Carbon Black Production Source
Category
    B. Technology Review for the Carbon Black Production Source
Category
    C. What are the final rule amendments pursuant to 112(d)(2) and
(3) for the Carbon Black Production source category?
    D. Amendments Addressing Emissions During Periods of SSM for the
Carbon Black Production Source Category
    E. Other Technical Amendments to the Carbon Black Production
NESHAP
V. What is the rationale for our final decisions and amendments for
the Cyanide Chemicals Manufacturing source category?
    A. Residual Risk Review for the Cyanide Chemicals Manufacturing
Source Category
    B. Technology Review for the Cyanide Chemicals Manufacturing
Source Category
    C. Amendments Addressing Emissions During Periods of SSM for the
Cyanide Chemicals Manufacturing Source Category
    D. Other Technical Amendments to the Cyanide Chemicals
Manufacturing NESHAP
VI. Summary of Cost, Environmental, and Economic Impacts and
Additional Analyses Conducted
    A. Carbon Black Production
    B. Cyanide Chemicals Manufacturing
VII. Statutory and Executive Order Reviews
    A. Executive Orders 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)
    J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations K. Congressional Review Act (CRA)

I. General Information

A. Does this action apply to me?

    Regulated entities. The source categories that are the subject of
this final action are cyanide chemicals manufacturing and carbon black
production major sources regulated under 40 CFR part 63, subpart YY and
carbon black production area sources regulated under 40 CFR part 63,
subpart MMMMMM. The North American Industry Classification System
(NAICS) codes for the cyanide chemicals manufacturing industry are
325188 and 325199. The NAICS code for the carbon black production
industry is 325182.
    This list of categories and NAICS codes is not intended to be
exhaustive, but rather to provide a guide for readers regarding
entities likely to be affected by the final action for the source
categories listed. To determine whether your facility is affected, you
should examine the applicability criteria in the appropriate NESHAP. If
you have any questions regarding the applicability of any aspect of
these NESHAP, please contact the appropriate person listed in the
preceding FOR FURTHER INFORMATION CONTACT section of this preamble.

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

    In addition to being available in the dockets for these source
categories, an electronic copy of this final action will also be
available on the internet. Following signature by the EPA
Administrator, the EPA will post a copy of this final action at https://www.epa.gov/stationary-sources-air-pollution/acetal-resins-acrylic-modacrylic-fibers-carbon-black-hydrogen. Following publication in the
Federal Register, the EPA will post the Federal Register version of the
final rule and key technical documents at this same website.
    Additional information is available on the RTR website at https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html. This information includes an
overview of the RTR program, links to project websites for the RTR
source categories, and detailed emissions and other data we used as
inputs to the risk assessments.

C. Judicial Review and Administrative Reconsideration

    Under Clean Air Act (CAA) section 307(b)(1), judicial review of
this final action is available only by filing a petition for review in
the United States Court of Appeals for the District of Columbia Circuit
(the Court) by January 18, 2022. Under CAA section 307(b)(2), the
requirements established by these final rules may not be challenged
separately in any civil or criminal proceedings brought by the EPA to
enforce the requirements.
    Section 307(d)(7)(B) of the CAA further provides that only an
objection to a rule or procedure which was raised with reasonable
specificity during the period for public comment (including any public
hearing) may be raised during judicial review. This section also
provides a mechanism for the EPA to reconsider the rule if the person
raising an objection can demonstrate to the

Administrator that it was impracticable to raise such objection within
the period for public comment or if the grounds for such objection
arose after the period for public comment (but within the time
specified for judicial review) and if such objection is of central
relevance to the outcome of the rule. Any person seeking to make such a
demonstration should submit a Petition for Reconsideration to the
Office of the Administrator, U.S. EPA, Room 3000, WJC South Building,
1200 Pennsylvania Ave. NW, Washington, DC 20460, with a copy to both
the person(s) listed in the preceding FOR FURTHER INFORMATION CONTACT
section, and the Associate General Counsel for the Air and Radiation
Law Office, Office of General Counsel (Mail Code 2344A), U.S. EPA, 1200
Pennsylvania Ave. NW, Washington, DC 20460.

II. Background

A. What is the statutory authority for this action?

    Section 112 of the CAA establishes a two-stage regulatory process
to address emissions of HAP from stationary sources. In the first
stage, we must identify categories of sources emitting one or more of
the HAP listed in CAA section 112(b) and then promulgate technology-
based NESHAP for those sources. ``Major sources'' are those that emit,
or have the potential to emit, any single HAP at a rate of 10 tons per
year (tpy) or more, or 25 tpy or more of any combination of HAP. For
major sources, these standards are commonly referred to as maximum
achievable control technology (MACT) standards and must reflect the
maximum degree of emission reductions of HAP achievable (after
considering cost, energy requirements, and non-air quality health and
environmental impacts). In developing MACT standards, CAA section
112(d)(2) directs the EPA to consider the application of measures,
processes, methods, systems, or techniques, including, but not limited
to, those that reduce the volume of or eliminate HAP emissions through
process changes, substitution of materials, or other modifications;
enclose systems or processes to eliminate emissions; collect, capture,
or treat HAP when released from a process, stack, storage, or fugitive
emissions point; are design, equipment, work practice, or operational
standards; or any combination of the above.
    For these MACT standards, the statute specifies certain minimum
stringency requirements, which are referred to as MACT floor
requirements, and which may not be based on cost considerations. See
CAA section 112(d)(3). For new sources, the MACT floor cannot be less
stringent than the emission control achieved in practice by the best-
controlled similar source. The MACT standards for existing sources can
be less stringent than floors for new sources, but they cannot be less
stringent than the average emission limitation achieved by the best-
performing 12 percent of existing sources in the category or
subcategory (or the best-performing five sources for categories or
subcategories with fewer than 30 sources). In developing MACT
standards, we must also consider control options that are more
stringent than the floor under CAA section 112(d)(2). We may establish
standards more stringent than the floor, based on the consideration of
the cost of achieving the emissions reductions, any non-air quality
health and environmental impacts, and energy requirements.
    In the second stage of the regulatory process, the CAA requires the
EPA to undertake two different analyses, which we refer to as the
technology review and the residual risk review. Under the technology
review, we must review the technology-based standards and revise them
``as necessary (taking into account developments in practices,
processes, and control technologies)'' no less frequently than every 8
years, pursuant to CAA section 112(d)(6). The EPA is required to
address regulatory gaps, such as missing standards for listed air
toxics known to be emitted from the source category. Louisiana
Environmental Action Network (LEAN) v. EPA, 955 F.3d 1088 (D.C. Cir.
2020). Under the residual risk review, we must evaluate the risk to
public health remaining after application of the technology-based
standards and revise the standards, if 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. The residual risk review is required
within 8 years after promulgation of the technology-based standards,
pursuant to CAA section 112(f). In conducting the residual risk review,
if the EPA determines that the current standards provide an ample
margin of safety to protect public health, it is not necessary to
revise the MACT standards pursuant to CAA section 112(f).\1\ For more
information on the statutory authority for this action, see 86 FR 3054,
for the Carbon Black Production NESHAP and 86 FR 3906, for the Cyanide
Chemicals Manufacturing NESHAP.
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    \1\ The Court has affirmed this approach of implementing CAA
section 112(f)(2)(A): NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. Cir.
2008) (``If EPA determines that the existing technology-based
standards provide an `ample margin of safety,' then the Agency is
free to readopt those standards during the residual risk
rulemaking.'').
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B. What are the source categories and how do the current NESHAP
regulate HAP emissions from the source categories?

    The MACT standards for both the Carbon Black Production and Cyanide
Chemicals Manufacturing source categories are contained in the Generic
Maximum Achievable Control Technology (GMACT) NESHAP, which also
includes MACT standards for several other source categories. Section
II.B.1 of this preamble discusses the current Carbon Black Production
major and area source rules and section II.B.2 discusses the Cyanide
Chemicals Manufacturing source category standards.
1. Carbon Black Production
    The EPA promulgated the Carbon Black Production NESHAP for major
sources on July 12, 2002 (67 FR 46258). The major source standards are
codified at 40 CFR part 63, subpart YY. Additionally, the Carbon Black
Production area source NESHAP was promulgated on July 16, 2007 (72 FR
38864). The area source standards are codified at 40 CFR part 63,
subpart MMMMMM. Subpart MMMMMM was subsequently amended by a direct
final rule on March 26, 2008 (73 FR 15923). As promulgated, the Carbon
Black Production major source and area source NESHAP apply to carbon
black production facilities that are, respectively, major sources and
area sources of HAP. The affected source covered by the major and area
source subparts is each new, reconstructed, or existing facility that
produces carbon black by either the furnace, thermal, acetylene
decomposition, or lampblack processes. The source category covered by
this MACT standard currently includes 15 major source facilities; no
area source facilities were identified.
    Emissions limits in the 2002 major source NESHAP for the Carbon
Black Production source category were set for process vents associated
with the main unit filter (MUF). Process vents at the MUF that have a
HAP concentration of equal to or greater than 260 parts per million by
volume (ppmv) are required to reduce emissions of HAP by the use of a
flare meeting the requirements of 40 CFR part 63, subpart SS, or reduce
emissions of total HAP by 98 weight-

percent or to a concentration of 20 ppmv, whichever is less stringent.
The Carbon Black Production area source NESHAP requires area source
facilities to meet the requirements of the Carbon Black Production
major source NESHAP found at 40 CFR 63.1103(f) of subpart YY.
2. Cyanide Chemicals Manufacturing
    The EPA promulgated the Cyanide Chemicals Manufacturing NESHAP on
July 12, 2002 (67 FR 46258). The standards are codified at 40 CFR part
63, subpart YY. The cyanide chemicals manufacturing industry consists
of facilities producing hydrogen cyanide or sodium cyanide. The source
category covered by this MACT standard currently includes 13
facilities. As promulgated in 2002, the cyanide chemicals manufacturing
standards regulate HAP emissions from cyanide chemicals manufacturing
units located at major sources. The HAP emitted from the source
category include cyanide compounds (hydrogen cyanide and sodium
cyanide), acetonitrile, and acrylonitrile.
    The NESHAP defines the affected source as each cyanide chemicals
manufacturing process unit (CCMPU). The rule states that the CCMPU is
the equipment assembled and connected by hard-piping or duct work to
process raw materials to manufacture, store, and transport a cyanide
chemicals product. Section II.B of the proposed cyanide chemicals
manufacturing RTR provides more information about the source category
(86 FR 3906, 3910).
    The 2002 NESHAP established emissions standards for process vents,
storage vessels, transfer racks, equipment leaks, and some wastewater
sources. Cyanide process vents are subject to either a 98 weight-
percent reduction of total HAP \2\ performance standard or a 20 ppmv
total HAP outlet exit concentration limit. For storage vessels in the
Cyanide Chemicals Manufacturing source category, sources may either
choose to comply with a 98 weight-percent reduction of hydrogen cyanide
performance standard, a 20 ppmv hydrogen cyanide exit outlet
concentration limit, or equipment standards (e.g., use of a flare).
Transfer racks are subject to either equipment standards or the same
performance standard or concentration limit \3\ as cyanide process
vents. Equipment leaks are subject to work practice standards required
by either 40 CFR part 63, subpart TT or subpart UU.
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    \2\ ``Dry end'' process vents at sodium cyanide units must meet
a 98 percent reduction performance standard for emissions of sodium
cyanide since this is the form of cyanide compounds emitted from
these emission points. The HAP emitted from other process vents that
make up the ``total HAP'' emitted from these sources are hydrogen
cyanide, acetonitrile, and acrylonitrile.
    \3\ Transfer racks emissions limits are expressed in terms of
hydrogen cyanide as this is the only HAP emitted from these sources.
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    During development of the initial MACT standards, we identified
process wastewater at existing sources as a potential source of
emissions of hydrogen cyanide, acetonitrile, and acrylonitrile. See 65
FR 76408, 76411, and 76413, December 6, 2000, for a discussion of the
HAP emitted from cyanide chemicals manufacturing. The 2002 NESHAP
established requirements that HAP emissions from applicable process
wastewater streams be controlled while the wastewater is being conveyed
to treatment and specified requirements for the controls to reduce the
hydrogen cyanide and acetonitrile concentration in the process
wastewater. For a new CCMPU that generates process wastewater, the
NESHAP requires a combined 93 weight-percent removal and control of HAP
from process wastewater generated from hydrogen cyanide purification,
ammonia purification, or flare blowdown. At the time the initial MACT
standards were developed, we identified measures undertaken at cyanide
chemicals manufacturing facilities to comply with other NESHAP as the
``MACT floor'' for process wastewater at existing sources, but we did
not include these measures in subpart YY for existing CCMPUs. For a
cyanide chemicals manufacturing process unit that generates maintenance
wastewater, the NESHAP requires that an owner or operator comply with
Hazardous Organic NESHAP (HON) maintenance wastewater requirements.

C. What changes did we propose for the Carbon Black Production source
category in our January 14, 2021, RTR proposal?

    On January 14, 2021, the EPA published a proposed rule in the
Federal Register for the Carbon Black Production NESHAP, 40 CFR part
63, subpart YY, that took into consideration the RTR analyses. In the
proposed rule, we proposed to find that the risk from the source
category is acceptable, the current standards provide an ample margin
of safety to protect public health, and more stringent standards are
not necessary to prevent an adverse environmental effect. Based on the
technology review, we proposed that it is not necessary to revise the
existing standards because we did not identify developments in
practices, processes, or control technologies that would result in
cost-effective emission reductions for the Carbon Black Production
source category.
    The EPA did, however, propose to broaden the scope of the original
NESHAP, which applied to process vents associated with the MUF only, to
include previously unregulated process vents associated with the carbon
black production unit. The EPA proposed to require all process vents
that have a HAP concentration of the emission stream equal to or
greater than 260 ppmv, including those located after the MUF, to reduce
emissions of HAP by using a flare meeting the requirements of 40 CFR
part 63, subpart SS, or to reduce emissions of total HAP by 98 weight-
percent or to a concentration of 20 ppmv, whichever is less stringent.
The EPA also proposed to require facilities to conduct performance
testing on the additional process vents located after the MUF.
    The proposal preamble also stated that the EPA did not identify any
currently operating area sources in the carbon black production source
category. The EPA is not proposing to change the existing area source
standards. However, the area source standard requires all facilities to
meet all the requirements in 40 CFR 63.1103(f) of subpart YY (major
source standard). The provisions in 40 CFR 63.1103(f) include carbon
black production applicability, definitions, and requirements.
Therefore, all changes discussed below, which impact the requirements
laid out in 40 CFR 63.1103(f), also impact the requirements of the area
source rule for carbon black production.
    The EPA proposed the following amendments to the Carbon Black
Production major source NESHAP:
     Expansion of the process vent emission standards to cover
all applicable (based on an applicability threshold) carbon black
production process vents;
     A requirement for boilers/process heaters that receive
tail gas for use as fuel gas to comply with annual tune-up requirements
specified in 40 CFR 63.1103(f)(3)(iii);
     Addition of a work practice standard for periods of
startup, as specified in 40 CFR 63.1103(f)(5);
     Revision of the MACT standard compliance provisions for
the Carbon Black Production source category to require owners and
operators of carbon black production process vent affected sources to
conduct periodic performance tests every 5 years;

     Elimination of the startup, shutdown, malfunction (SSM)
exemption, which currently appears at 40 CFR 63.1108, and any
references to SSM requirements in subpart YY that apply to Carbon Black
Production source category affected sources;
     Requirements for submission of electronic copies of
required performance test reports, Notification of Compliance Status
(NOCS), and periodic reports through the EPA's Central Data Exchange
(CDX) using the Compliance and Emissions Data Reporting Interface
(CEDRI); and
     Minor editorial and technical changes in the subpart.

D. What changes did we propose for the Cyanide Chemicals Manufacturing
source category in our January 15, 2021, RTR proposal?

    On January 15, 2021, the EPA published a proposed rule in the
Federal Register for the Cyanide Chemicals Manufacturing NESHAP (86 FR
3906) that took into consideration the RTR analyses. In the proposed
rule, we proposed to find that the risk from the source category is
acceptable, the current standards provide an ample margin of safety to
protect public health, and more stringent standards are not necessary
to prevent an adverse environmental effect. Based on the technology
review, we proposed that it is not necessary to revise the existing
standards because we did not identify developments in practices,
processes, or control technologies that would result in cost-effective
emission reductions for the Cyanide Chemicals Manufacturing source
category.
    However, the EPA proposed standards pursuant to CAA section
112(d)(2) for process wastewater from existing CCMPUs, which was
previously unregulated.\4\ We proposed that process wastewater sources
at existing sources comply with HON wastewater requirements.
Specifically, for an existing cyanide chemicals manufacturing process
unit that generates process wastewater from hydrogen cyanide
purification, ammonia purification, or flare blowdown, we proposed that
owners or operators comply with the requirements of 40 CFR 63.138(a)(1)
of the HON if the total annual average concentration of Table 9 of 40
CFR part 63, subpart G compounds and cyanide compounds \5\ is greater
than or equal to 10,000 parts per million by weight (ppmw) at any flow
rate, or the total annual average concentration of Table 9 compounds
and cyanide compounds is greater than or equal to 1,000 ppmw, and the
annual average flow rate is greater than or equal to 10 liters per
minute (according to the procedures in 40 CFR 63.144(a)). We also
proposed revising the new source standard to add the HON requirements
for waste management units upstream of an open or closed biological
treatment process to ensure demonstrable compliance measures are in
place for these sources.
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    \4\ The EPA not only has authority under CAA sections 112(d)(2)
and (3) to set MACT standards for previously unregulated HAP
emissions at any time but is required to address any previously
unregulated HAP emissions as part of its periodic review of MACT
standards under CAA section 112(d)(6). LEAN v. EPA, 955 F3d at 1091-
1099.
    \5\ In the final rule, we have clarified that this requirement
applies to ``free cyanide'' rather than ``cyanide compounds'' in
response to public comments.
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    The EPA also proposed the following amendments:
     Revisions to the MACT rule at 40 CFR 63.1108 through 40
CFR 63.1112 to eliminate references to SSM requirements in subpart YY
to reduce confusion that may result from referenced subparts associated
with the GMACT that may contain SSM exemptions for other source
categories;
     Requirements for submission of electronic copies of
required performance test reports, NOCS, and periodic reports through
the EPA's CDX using CEDRI; and
     Minor editorial and technical changes in the subpart.

III. What is included in these final rules?

    This action finalizes the EPA's determinations pursuant to the RTR
provisions of CAA section 112 for the Carbon Black Production and
Cyanide Chemicals Manufacturing source categories.
    For the Carbon Black Production source category, this action
finalizes changes to the major source NESHAP, including elimination of
the SSM exemption and any reference to SSM requirements for carbon
black production facilities, inclusion of a work practice standard for
startup and shutdown periods, inclusion of boiler and process heater
annual tune-up requirements, expansion of process vent standard
applicability, addition of periodic process vent performance testing
requirements, inclusion of electronic reporting requirements, and
editorial and technical changes. This final action also reflects
several changes to the RTR proposal in consideration of comments
received during the public comment period. Section IV presents our
rationale for our final decisions and changes to the proposed
amendments based on comments received on the proposal.
    For the Cyanide Chemicals Manufacturing source category, this
action finalizes changes to the NESHAP, including: Eliminating any
reference to SSM exemptions for cyanide chemicals manufacturing
facilities, adding electronic reporting requirements, adding HON
requirements for process wastewater from existing cyanide chemical
manufacturing process units, adding HON requirements for waste
management units upstream of an open or closed biological treatment
process to the new source standard, and making editorial/technical
changes. This action also reflects several changes to the RTR proposal
in consideration of comments received during the public comment period
as described in section V of this preamble.

A. What are the final rule amendments based on the risk reviews for the
Carbon Black Production and Cyanide Chemicals Manufacturing source
categories?

    This section introduces the final determinations for the Carbon
Black Production and Cyanide Chemicals Manufacturing NESHAP pursuant to
CAA section 112(f). Section III.A.1 presents the final decisions based
on the risk review for the Carbon Black Production source category.
Section III.A.2 presents the final decisions based on the risk review
for the Cyanide Chemicals Manufacturing source category.
1. Carbon Black Production
    The EPA is not amending the major source Carbon Black Production
NESHAP based on the risk reviews conducted pursuant to CAA section
112(f). In this action, we are finalizing our proposed determination
that the risk from HAP emissions from the Carbon Black Production
source category is acceptable, and that the standards provide an ample
margin of safety to protect public health and prevent an adverse
environmental effect.
2. Cyanide Chemicals Manufacturing
    The EPA is not amending the Cyanide Chemicals Manufacturing NESHAP
based on the risk review conducted pursuant to CAA section 112(f). In
this action, we are finalizing our proposed determination that the risk
from HAP emissions from the Cyanide Chemicals Manufacturing source
category is acceptable, and that the standards provide an ample margin
of safety to protect public health and prevent an adverse environmental
effect.

B. What are the final rule amendments based on the technology reviews
for the Carbon Black Production and Cyanide Chemicals Manufacturing
source categories?

    This section summarizes the results of the technology reviews for
the Carbon Black Production and Cyanide Chemicals Manufacturing NESHAP.
Section III.B.1 presents the final decisions based on the technology
review for the Carbon Black Production source category. Section III.B.2
presents the final decisions based on the technology review for the
Cyanide Chemicals Manufacturing source category.
1. Carbon Black Production
    We determined that there are no developments in practices,
processes, and control technologies that warrant revisions to the MACT
standards for this source category. Therefore, we are not finalizing
revisions to the MACT standards for this source category under CAA
section 112(d)(6). However, as part of the technology review, we
identified regulatory gaps (previously unregulated processes or
pollutants), and are establishing new standards to fill those gaps as
described in section III.C of this preamble.
    As discussed in the Carbon Black Production source category
proposal preamble, we also performed a technology review of the Carbon
Black Production area source NESHAP. As part of that review, the EPA
did not identify any currently operating area source facilities. We are
finalizing our conclusion that it is not necessary to make changes to
the existing area source standards as a result of this review.
2. Cyanide Chemicals Manufacturing
    We determined that there are no developments in practices,
processes, and control technologies that warrant revisions to the MACT
standards for this source category. Therefore, we are not finalizing
revisions to the MACT standards for this source category under CAA
section 112(d)(6). However, as part of the technology review, we
identified regulatory gaps (previously unregulated processes or
pollutants), and are establishing new standards to fill those gaps as
described in section III.C of this preamble.

C. What are the final rule amendments pursuant to CAA sections
112(d)(2) and (3) for the Carbon Black Production and Cyanide Chemicals
Manufacturing source categories?

    This section describes the final rule amendments to the Carbon
Black Production and Cyanide Chemicals Manufacturing NESHAP pursuant to
CAA sections 112(d)(2) and (3). Section III.C.1 presents the final rule
amendments for the Carbon Black Production source category. Section
III.C.2 presents the final rule amendments for the Cyanide Chemicals
Manufacturing source category.
1. Carbon Black Production
    Pursuant to CAA sections 112(d)(2) and (3), the EPA is finalizing
its proposal to broaden the scope of the current emission limits for
new and existing sources in the major source NESHAP, which applies to
process vents associated with the MUF, to include all process vents
associated with the carbon black production unit. This amendment
requires all process vents, including those located after the MUF that
meet the applicability threshold, to reduce emissions of total HAP by
98 weight-percent or to a concentration of 20 ppmv, whichever is less
stringent, by venting emissions through a closed vent system to any
combination of control devices meeting the requirements of 40 CFR
63.982(a)(2). Additionally, these final amendments require facilities
to conduct an applicability determination test on the additional
process vents located after the MUF.
2. Cyanide Chemicals Manufacturing
    Pursuant to CAA sections 112(d)(2) and (3), the EPA is finalizing
its proposal to add standards for process wastewater at existing CCMPUs
with minor applicability-related clarifications (see section V.D.3.d
(Request for Clarification)). The final standards require that
individual wastewater streams from CCMPU HCN purification, ammonia
purification, or flare blowdown, comply with the requirements of 40 CFR
63.138(a)(1) of the HON if the total annual average concentration of
Table 9 of 40 CFR part 63, subpart G compounds and free cyanide from
each process wastewater stream is greater than or equal to 10,000 ppmw
at any flow rate, or the total annual average concentration of Table 9
compounds and free cyanide from each process wastewater stream is
greater than or equal to 1,000 ppmw and the annual average flow rate is
greater than or equal to 10 liters per minute (according to the
procedures in 40 CFR 63.144(a)). The EPA is also finalizing its
proposal to add the HON requirements for waste management units
upstream of an open or closed biological treatment process for process
wastewater at new sources.

D. What are the final rule amendments addressing emissions during
periods of SSM for the Carbon Black Production and Cyanide Chemicals
Manufacturing source categories?

    This section describes the final rule amendments to the Carbon
Black Production and Cyanide Chemicals Manufacturing NESHAP that
address emissions during periods of SSM. Section III.D.1 presents the
final rule amendments for the Carbon Black Production source category.
Section III.D.2 presents the final rule amendments for the Cyanide
Chemicals Manufacturing source category.
1. Carbon Black Production
    The EPA is finalizing the proposed SSM provision amendments for the
Carbon Black Production major source NESHAP in subpart YY in order to
ensure consistency with the decision in Sierra Club v. EPA, 551 F. 3d
1019 (D.C. Cir. 2008). As noted in the proposal for the Carbon Black
Production source category, under this decision, the Court vacated two
provisions that exempted sources from the requirement to comply with
otherwise applicable CAA section 112(d) emission standards during
periods of SSM. We proposed and are finalizing revisions to the MACT
rule at 40 CFR 63.1108 through 40 CFR 63.1112 that remove the SSM
exemption under the Carbon Black Production NESHAP and any references
to SSM-related requirements.
    The EPA is also finalizing startup and shutdown work practice
standards to address safety and combustibility concerns in the absence
of the SSM exemption. The work practice standard, as amended under the
final rule, is discussed in greater detail in section IV.C of this
preamble.
2. Cyanide Chemicals Manufacturing
    The EPA is finalizing the proposed SSM provision amendments for the
Cyanide Chemicals Manufacturing NESHAP in order to ensure consistency
with the decision in Sierra Club v. EPA, 551 F. 3d 1019 (D.C. Cir.
2008). The Cyanide Chemicals Manufacturing NESHAP promulgated in 2002
is consistent with the Court decision mentioned above. However, we
proposed and are finalizing revisions to the NESHAP at 40 CFR 63.1108
through 40 CFR 63.1112 to ensure that no confusion results from
referenced subparts in subpart YY that may contain SSM exemptions for
other source categories. See section V.C of this preamble for more
information regarding SSM provisions under subpart YY.

E. What other changes have been made to the NESHAP?

    This section describes other amendments to the final Carbon Black
Production and Cyanide Chemicals Manufacturing NESHAP. Section III.E.1
presents the other final rule amendments for the Carbon Black
Production source category. Section III.E.2 presents the other final
rule amendments for the Cyanide Chemicals Manufacturing source
category.
1. Carbon Black Production
    Other final amendments to the Carbon Black Production NESHAP
include boiler and process heater annual tune-up requirements,
electronic reporting requirements, and periodic performance testing
requirements for process vents to demonstrate initial and continued
compliance with the standards, as discussed below.
a. Boiler and Process Heater Annual Tune-Up Provisions
    The EPA is finalizing annual tune-up requirements for boilers and
process heaters that utilize tail gas for use as fuel. These provisions
are specified in 40 CFR 63.1103(f)(3)(iii) of the final rule. To better
reflect boilers and process heaters used in the carbon black production
source category, the final annual boiler and process heater tune-up
requirements were revised from the proposal, based on comments received
(see section IV.D of this preamble for detail related to comments
received, as well as the EPA's revisions and rationale).
b. Electronic Reporting Requirements
    The EPA is finalizing its proposal that owners and operators of
carbon black production facilities submit electronic copies of required
performance test reports, NOCS, and periodic reports through the EPA's
CDX using CEDRI. A description of the electronic data submission
process is provided in the memorandum, ``Electronic Reporting
Requirements for New Source Performance Standards (NSPS) and National
Emission Standards for Hazardous Air Pollutants (NESHAP) Rules'',
available in the docket for the Carbon Black Production NESHAP (see
Docket ID No. EPA-HQ-OAR-2020-0505-0018).
c. Periodic Performance Testing
    The EPA is finalizing rule amendments, as proposed, that require
owners and operators of carbon black production process vents subject
to the rule, in addition to the already required initial performance
test, to conduct performance tests every 5 years to demonstrate
continued compliance with the NESHAP.
2. Cyanide Chemicals Manufacturing
    The EPA is finalizing its proposal that owners and operators of
cyanide chemicals manufacturing facilities submit electronic copies of
required performance test reports, NOCS, and periodic reports through
the EPA's CDX using CEDRI. A description of the electronic data
submission process is provided in the memorandum, Electronic Reporting
Requirements for New Source Performance Standards (NSPS) and National
Emission Standards for Hazardous Air Pollutants (NESHAP) Rules,
available in the docket for the Cyanide Chemicals Manufacturing NESHAP
action (see Docket ID No. EPA-HQ-OAR-2020-0532-0003). Specific comments
received on the proposed periodic report electronic data template and
the EPA's response to those comments are provided in a memorandum to
the docket, Summary of Comments and EPA's Responses on the National
Emission Standards for Hazardous Air Pollutants: Cyanide Chemicals
Manufacturing Residual Risk and Technology Review Proposed Rule,
available in the Cyanide Chemicals Manufacturing NESHAP docket (see EPA
HQ-OAR-2020-0532).

F. What are the effective and compliance dates of the standards?

    This section describes the effective dates and compliance dates for
the final amendments to the Carbon Black Production and Cyanide
Chemicals Manufacturing NESHAP. Section III.F.1 presents the effective
dates and compliance dates for the Carbon Black Production NESHAP
amendments. Section III.F.2 presents the effective dates and compliance
dates for the Cyanide Chemicals Manufacturing NESHAP amendments.
1. Carbon Black Production
a. Effective Date of the Final Rule
    The revisions to the Carbon Black Production MACT standards being
promulgated in this action are effective on November 19, 2021.
b. Compliance Dates
    For new sources (affected sources that commenced construction or
reconstruction after January 14, 2021), the EPA is finalizing, as
proposed, that affected sources must comply with all of the final rule
requirements immediately upon the effective date of the rule, November
19, 2021, or upon startup, whichever is later.
    The EPA is finalizing, as proposed, that existing Carbon Black
Production affected sources that commenced construction or
reconstruction on or before January 14, 2021 (existing sources), must
comply with the following requirements of the rule no later than
November 20, 2022: (1) Process vent emission standards applicability
testing for carbon black production process vents; (2) the requirement
to conduct performance tests no more than 60 months after the preceding
test when demonstrating compliance with process vent emission control
requirements; and (3) boiler and process heater annual tune-up
requirements.
    The EPA is finalizing a requirement that previously unregulated
process vents from Carbon Black Production sources that commenced
construction or reconstruction on or before January 14, 2021, will have
until November 19, 2024 to comply with final rule requirements for
process vents. This represents a change from the proposal. The EPA
determined that changing the proposed compliance period is necessary,
in the event that the applicability test indicates that previously
unregulated process vents are required to route emissions to an
existing control device or to a newly constructed control device. Based
on comments received, the EPA believes providing a 3-year compliance
period for newly subject process vents, instead of 1 year, is necessary
and appropriate in order to ensure sufficient time for facilities to
conduct the necessary process design planning, purchases, construction,
and changes to come into compliance and then perform the initial
performance test.
    For requirements related to SSM-related amendments and electronic
reporting, the EPA is finalizing, as proposed, that all existing
sources must be in compliance with the: (1) SSM-related amendments
(changes proposed as a result of removing the SSM exemption from the
requirements); (2) the alternative work practice standard specified in
40 CFR 63.1103(f)(5) related to the requirement that a closed vent
system route the collected vapors to a control device when
demonstrating compliance; and (3) the addition of requirements to
submit reports electronically by May 18, 2022. Based on our assessment
for existing sources, 180 days is the most expeditious compliance
period practicable for complying with SSM-related and electronic
reporting requirements.
    The EPA considers 180 days to be sufficient for owners and
operators of affected sources to comply with the

alternative work practice standard for startup and shutdown.\6\ Many of
the work practice standard requirements included in the final rule are
already implemented by industry.
---------------------------------------------------------------------------

    \6\ Section 63.983(a)(1) of 40 CFR part 63, subpart SS requires
that each closed vent system be designed and operated to collect the
regulated material vapors from the emission point, and to route the
collected vapors to a control device, apply at all times.
---------------------------------------------------------------------------

    Our experience with similar industries that are required to convert
reporting mechanisms, to install necessary hardware and software,
become familiar with the process of submitting performance test results
electronically through the EPA's CEDRI, test these new electronic
submission capabilities, and reliably employ electronic reporting,
shows that a time period of a minimum of 90 days, and, more typically,
180 days is generally necessary to successfully accomplish these
revisions.
    Our experience with similar industries further shows that owners
and operators generally require a time period of 180 days 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;
and to update their operation, maintenance, and monitoring plan to
reflect the revised requirements.
2. Cyanide Chemicals Manufacturing
a. Effective Date of the Final Rule
    The revisions to the Cyanide Chemicals Manufacturing standards
being promulgated in this action are effective on November 19, 2021.
b. Compliance Dates
    New sources (affected sources that commenced construction or
reconstruction after January 15, 2021) must comply with all of the
standards immediately upon the effective date of the standard, November
19, 2021, or upon startup, whichever is later.
    The compliance date for existing Cyanide Chemicals Manufacturing
affected sources (affected sources that commenced construction or
reconstruction on or before January 15, 2021) to comply with the final
process wastewater standards is November 20, 2022. The EPA determined
that affected sources are already complying with similar or
substantially equivalent process wastewater requirements. The EPA is
allowing one year to comply with the final process wastewater
requirements in order to provide owners and operators the time to
evaluate process wastewater rule requirements and applicability to
their operations, perform compliance calculations, and adjust plans and
reports, as necessary.
    For requirements related to SSM-related amendments (removing
references to SSM-related exemptions in other subparts) and electronic
reporting, the compliance date is May 18, 2022. Based on our assessment
for existing sources, 180 days is the most expeditious compliance
period practicable for complying with SSM-related and electronic
reporting requirements.
    For SSM-related amendments, our experience with similar industries
indicates that regulated facilities generally require a time period of
180 days 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; and to update their operations to reflect
the revised requirements.
    For electronic reporting changes, our experience with similar
industries that are required to convert reporting mechanisms, to
install necessary hardware and software, become familiar with the
process of submitting performance test results electronically through
the EPA's CEDRI, test these new electronic submission capabilities, and
reliably employ electronic reporting indicates that a time period of a
minimum of 90 days, and, more typically, 180 days is generally
necessary to successfully accomplish these revisions.

IV. What is the rationale for our final decisions and amendments for
the Carbon Black Production source category?

    For each issue, this section provides a description of what we
proposed and what we are finalizing for the issue, the EPA's rationale
for the final decisions and amendments, and a summary of key comments
and responses. For all comments not discussed in this preamble, comment
summaries and the EPA's responses can be found in the comment summary
and response document available in the docket for this source category.

A. Residual Risk Review for the Carbon Black Production Source Category

1. What did we propose pursuant to CAA section 112(f) for the Carbon
Black Production source category?
    On January 14, 2020 (86 FR 3056), the EPA proposed that risk posed
by major sources in the Carbon Black Production source category is
acceptable, that the current NESHAP provides an ample margin of safety
to protect public health, and that additional standards are not
necessary to prevent an adverse environmental effect. The estimated
cancer risks were below the presumptive limit of acceptability and the
noncancer risk results indicate there is minimal likelihood of adverse
noncancer health effects due to HAP emissions from this source
category. The proposed decision on ample margin of safety was based on
weighing factors relevant to this particular source category, including
the risk posed by point sources and the costs and cost-effectiveness of
additional controls to reduce risk further, as well as uncertainties in
the baseline emissions estimates used in estimating risk, the costs and
effectiveness of the work practices we considered to reduce these
emissions, and the amount of risk reduction that could be achieved with
the work practices. The EPA sets standards under CAA section 112(f)(2)
using ``a two-step standard-setting approach, with an analytical first
step to determine an `acceptable risk' that considers all health
information, including risk estimation uncertainty, and includes a
presumptive limit on maximum individual risk (MIR) of approximately 1-
in-10 thousand.'' (54 FR 38045, September 14, 1989). In the proposal,
the EPA estimated risks based on actual and allowable emissions from
carbon black production sources, and we considered these in determining
acceptability. A more thorough discussion of the risk assessment is
included in the Residual Risk Assessment for the Carbon Black
Production Source Category in Support of the Risk and Technology Review
2021 Final Rule document, available in the docket for this final rule
(Docket-EPA-HQ-OAR-2020-0505).
    In the proposed rule, as presented in Table 1 below, based on
modeling actual emissions from the Carbon Black Production source
category for all 15 facilities, we estimated inhalation cancer risk to
the individual most exposed was less than 1-in-1 million. The estimated
incidence of cancer due to inhalation exposures resulting from
emissions from the source category was 0.00004 excess cancer cases per
year, or one excess case every 25,000 years with no-one exposed to an
excess cancer risk greater than or equal to 1-in-1 million due to
inhalation exposure to HAP emissions from this source category. The
Agency estimated that the maximum chronic noncancer target

organ-specific hazard index (TOSHI) from inhalation exposure from this
source category was 0.06. In the screening assessment of worst-case
acute inhalation impacts, we estimated a maximum hazard quotient (HQ)
of 0.09 (due to hydrogen cyanide) based on the reference exposure level
(REL). As shown in Table 1, the chronic cancer and non-cancer risks are
the same for allowable and facility-wide emissions as they are for
actuals.

                               Table 1--Inhalation Risk Assessment Summary for Carbon Black Production \1\ Source Category
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                           Maximum        Estimated       Estimated       Estimated
                                         individual     population at   population at   annual cancer                                  Maximum screening
   Risk assessment        Number of    cancer risk (1- increased risk  increased risk     incidence       Maximum chronic noncancer     acute noncancer
                       facilities \2\  in-1  million)  of cancer >=1-  of cancer >=10-   (cases per               TOSHI \4\                  HQ \5\
                                             \3\        in-1 million    in-1  million       year)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                Baseline Actual Emissions
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source Category......              15            0.06               0               0         0.00004  <1 (neurological).............  0.09 (REL)
Facility-wide........              15            0.06               0               0         0.00004  <1 (neurological).............
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              Baseline Allowable Emissions
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source Category......              15            0.06               0               0         0.00004  <1 (neurological).............
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Based on actual and allowable emissions.
\2\ Number of facilities evaluated in the risk assessment. Includes 15 operating facilities subject to 40 CFR part 63, subpart YY.
\3\ Maximum individual excess lifetime cancer risk due to HAP emissions from the source category.
\4\ Maximum TOSHI. The target organ with the highest TOSHI for the Carbon Black Production source category is the neurological system.
\5\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of HQ values. The acute
  HQ shown was based upon the lowest acute 1-hour dose-response value, the REL for hydrogen cyanide. When an HQ exceeds 1, we also show the HQ using the
  next lowest available acute dose-response value.

    We also conducted a multipathway screening assessment for the
source category, and the results of the screening assessment are
presented in the risk report titled Residual Risk Assessment for the
Carbon Black Production Source Category in Support of the 2021 Risk and
Technology Review Final Rule, and section IV of the proposal preamble
(86 FR 3054), January 14, 2021) available in the docket for this
action.
    A screening value is not an estimate of the cancer risk or a
noncancer HQ (or HI). Rather, a screening value represents a high-end
estimate of what the risk or HQ may be. For the Carbon Black Production
source category, the highest cancer screening value was from arsenic
emissions, with a Tier 2 cancer screening value of 9, and the highest
non-cancer screening value was from mercury emissions, with a Tier 3
non-cancer screening value of 2. We are confident that if a refined
multipathway risk assessment was conducted, the HQ for mercury would be
lower than 2. Further details on the Tier 3 screening assessment can be
found in Appendix 11 of the Residual Risk Assessment for the Carbon
Black Production Source Category in Support of the Risk and Technology
Review 2021 Final Rule. Arsenic emissions resulted in a Tier 2 cancer
screening value of 9, which means that we are confident that the
multipathway cancer risk is lower than 9-in-1 million. The EPA has
determined that it is not necessary to go beyond the Tier 3 assessment
for mercury (to a site-specific assessment) or beyond the Tier 2 cancer
screening assessment. As explained above, the mercury screening value
of 2 is a high-end estimate of what the risk or hazard may be and can
be interpreted to mean that we are confident that the HQ would be lower
than 2. Similarly, we are confident that the excess cancer risk is less
than 9-in-1 million, and evaluation under Tier 3 or a site-specific
assessment would further reduce the estimated risk. Further, risk
results from five site-specific mercury assessments the EPA has
conducted for five RTR source categories resulted in noncancer HQs that
range from 50 times to 800 times lower than the respective Tier 2
mercury screening value for those facilities (refer to the identified
Docket ID No. EPA-HQ-OAR-2017-0015 for a copy of these reports).\7\
Based on our review of these analyses, we expect if we were to perform
a site-specific assessment for the Carbon Black Production source
category, the mercury HQ would be at least a one order of magnitude
less than the modeled Tier 3 non-cancer screening value of 2 for
mercury. Thus, the EPA is confident that the mercury HQ would be less
than 1, if further refined to incorporate enhanced site-specific
analyses such as improved model boundary identification with improved
soil/water run-off calculations and AERMOD deposition outputs used in
the TRIM.FaTE model.
---------------------------------------------------------------------------

    \7\ 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, and
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 record: EPA-HQ-OAR-2019-0373,
Appendix 11 of the Residual Risk Assessment for the Iron and Steel
Foundries Source Category in Support of the Risk and Technology
Review 2019 Proposed Rule.
---------------------------------------------------------------------------

    In evaluating the potential for multipathway effects from emissions
of lead for the Carbon Black Production source category, the EPA
compared modeled annual lead concentrations to the secondary National
Ambient Air Quality Standards (NAAQS) level for lead (0.15 micrograms
per cubic meter ([micro]g/m\3\), arithmetic mean concentration over a
3-month period). The highest annual average lead concentration,
0.000099 [micro]g/m\3\, is far below the NAAQS level for lead,
indicating a low potential for multipathway impacts from lead.
    In determining whether risk is acceptable for this source category,
the EPA considered all available health information and risk estimation

uncertainty that includes the uncertainty in the data (See proposal at
86 FR 3054, section III.C.7, How do we consider uncertainties in risk
assessment?). The maximum cancer risk for all facilities was below 1-
in-1 million; in addition, there were no facilities with an estimated
maximum chronic noncancer HI or maximum HQ greater than or equal to 1.
The EPA weighed all health risk factors in our risk acceptability
determination, and we proposed that the risk from this source category
is acceptable. We then considered whether the NESHAP provides an ample
margin of safety to protect public health, and whether more stringent
standards were necessary to prevent an adverse environmental effect, by
taking into consideration costs, energy, safety, and other relevant
factors. Based upon these considerations, we proposed and are
finalizing the determination that the 2002 Carbon Black Production
NESHAP requirements provide an ample margin of safety to protect public
health. Based on the results of our environmental risk screening
assessment, we also proposed and are finalizing the determination that
more stringent standards are not necessary to prevent an adverse
environmental effect.
2. How did the risk review change for the Carbon Black Production
source category?
    We did not receive any information that changed our determination
concerning risk and we are finalizing our proposed conclusion on the
risk review.
3. What key comments did we receive on the risk review, and what are
our responses?
    We received several comments regarding the proposed risk review and
our proposed determination that no revisions to the standard were
warranted under CAA section 112(f)(2). One commenter supported the
proposed determination, while another, stated that EPA underestimated
risks. After review of these comments, we disagreed with the
commenter's assertion that risks were underestimated and determined no
changes to the standard were necessary. The comments and our specific
responses can be found in the document, Summary of Comments and EPA's
Responses on the National Emission Standards for Hazardous Air
Pollutants Carbon Black Production Residual Risk and Technology Review
and Carbon Black Production Area Sources Technology Review Proposed
Rule, which is available in docket: EPA-HQ-OAR-2020-0505.
4. What is the rationale for our final approach and final decisions for
the risk review?
    We evaluated all the comments on the EPA's risk review and
determined that no changes are needed. For the reasons explained in the
proposed rule, we determined that the risk from the Carbon Black
Production source category is acceptable, the current standards provide
an ample margin of safety to protect public health, and more stringent
standards are not necessary to prevent an adverse environmental effect.
Therefore, pursuant to CAA section 112(f)(2), we are finalizing our
residual risk determination as proposed.

B. Technology Review for the Carbon Black Production Source Category

1. What did we propose pursuant to CAA section 112(d)(6) for the Carbon
Black Production source category?
    We proposed a determination that it is not necessary to revise the
existing standards because we did not identify developments in
practices, processes, or control technologies that would result in
cost-effective emission reductions for the Carbon Black Production
source category. However, we did identify a potential gap in the
regulation, and proposed to broaden the scope of the standards under
the CAA sections 112(d)(2) and (3). The final approach related to that
issue is discussed in section IV.C of this preamble. Additional
information on our technology review can be found in the memorandum,
Technology Review for Carbon Black Production Source Category, which is
available in docket: EPA-HQ-OAR-2020-0505.
    We also performed a technology review of the Carbon Black
Production area source NESHAP. As part of that review, the EPA did not
identify any currently operating sources in the Carbon Black Production
area source category, and therefore, we proposed no changes. In this
action, we are finalizing our proposed determination. For more
information on the review of potential area source facilities see the
memorandum, Identification of Area Sources for the Carbon Black
Production NESHAP, which is available in docket: EPA-HQ-OAR-2020-0505.
2. How did the technology review change for the Carbon Black Production
source category?
    The technology review did not change from proposal. Therefore, we
are finalizing our determination that no revisions to the NESHAP are
necessary pursuant to CAA section 112(d)(6) for both the major and area
source categories.
3. What key comments did we receive on the technology review, and what
are our responses?
    We received two comments regarding the major source proposed
technology review and our proposed determination that no revisions were
warranted under CAA section 112(d)(6). Comments suggested changes to
our technology review to include additional technologies mentioned in
consent decrees, including incinerators, wet or dry gas scrubbers, and
selective catalytic reduction technologies. After review of these
comments, we determined that no changes to the standards were
necessary. Specifically, we determined that these technologies were not
cost-effective for controlling HAP from carbon black facilities. The
comments and our specific responses can be found in the document,
Summary of Comments and EPA's Responses on the National Emission
Standards for Hazardous Air Pollutants Carbon Black Production Residual
Risk and Technology Review and Carbon Black Production Area Sources
Technology Review Proposed Rule, which is available in docket: EPA-HQ-
OAR-2020-0505. We did not receive any comments on the area source
category proposed technology review.
4. What is the rationale for our final approach and final decisions for
the technology review?
    Our technology review sought to identify add-on control technology
that was not identified during the original NESHAP development and
improvements to existing add-on controls. We also sought to identify
new work practices, operational procedures, process changes, pollution
prevention alternatives, or techniques that have the potential to
reduce emissions. Based on our review, we did not identify any
technologies, that would result in cost-effective emission reductions
for the Carbon Black Production source category. Since proposal, no
information has been presented to cause us to change the proposed
determination. Consequently, we are finalizing our CAA section
112(d)(6) determination as proposed.

C. What are the final rule amendments pursuant to 112(d)(2) and (3) for
the Carbon Black Production source category?

1. What did we propose pursuant to CAA sections 112(d)(2) and (3) for
the Carbon Black Production source category?
    Under CAA sections 112(d)(2) and (3) we proposed to broaden the
scope of the existing emission limit in the major source NESHAP, which
applies to process vents associated with the MUF, to include all
process vents associated with the carbon black production unit. The
expansion to cover all process vents under the Carbon Black Production
MACT standard is in accordance with LEAN v. EPA, 955 F. 3d. 1088 (D.C.
Cir. 2020), in which the Court held that the EPA has an obligation to
set standards for unregulated pollutants which the EPA is required to
regulate as part of technology reviews under CAA section 112(d)(6).
    We proposed to require all process vents that have a HAP
concentration of the emission stream equal to or greater than 260 ppmv,
including those located after the MUF, to reduce emissions of total HAP
by 98 weight-percent or to a concentration of 20 ppmv, whichever is
less stringent. We also proposed to require applicability testing of
process vents located after the MUF and compliance with process vent
standards (where applicability threshold was exceeded) within 1 year
after the effective date of the final rule.
2. What changed since proposal?
    We are finalizing a longer timeframe for previously unregulated
process vents to come into compliance with the requirements, since this
may require the addition of add-on controls. The extension changes the
proposed compliance date of 1 year from the effective date of the final
rule to 3 years from the effective date of the final rule.
3. What are the key comments and responses?
    The EPA received comments generally supporting the proposal to
broaden the emission limit to apply to all process vents that have a
HAP concentration of the emission stream equal to or greater than 260
ppmv, associated with the carbon black production unit. One commenter
requested an extension to the compliance date.
a. Compliance Date Extension
    Comment: The commenter stated that they do not believe carbon black
facilities will be able to implement the carbon black process vent
requirements for any previously unregulated process vents within 1 year
of the effective date. In support of their comment, the commenter
stated that the EPA has addressed similar situations in final rules by
allowing up to 3 years from the effective date of the final rule for
facilities to complete any necessary capital projects as allowed for by
CAA section 112(i). For a detailed summary of the comment, see the
document Summary of Comments and EPA's Responses on the National
Emission Standards for Hazardous Air Pollutants Carbon Black Production
Residual Risk and Technology Review and Carbon Black Production Area
Sources Technology Review Proposed Rule, available in the docket for
this source category.
    Response: The EPA agrees with the commentor that, in the event that
the applicability test indicates that any newly identified process
vents are subject and require re-routing to an existing control device
or the construction of a new control device, the 1-year time period
that the EPA proposed to allow for carbon black facilities to bring the
process vents into compliance may be insufficient. As noted by the
commenter, while the 1-year time frame is sufficient for conducting the
applicability test, it may not provide enough time to complete the
process of safely designing and constructing the ductwork necessary to
either re-route the vent to an existing control device or design and
construct ductwork for re-routing the vent and a new control device. To
address this concern, the EPA is extending this time period in the
final rule and allowing up to 3 years from the effective date of the
final rule for facilities to complete any necessary capital projects as
allowed for by CAA section 112(i). The language at 40 CFR 63.1102(e)
has been amended in the final rule to reflect this change.

D. Amendments Addressing Emissions During Periods of SSM for the Carbon
Black Production Source Category

1. What amendments did we propose to address emissions during periods
of SSM?
    The EPA proposed to remove the exemption for periods of startup and
shutdown. Additionally, we proposed a work practice standard during
periods of startup that would have allowed carbon black manufacturing
facilities to vent tail gas upon startup for a period not to exceed 13
minutes, and to begin running control devices thereafter. The proposed
work practice standard sought to address safety concerns surrounding
startup processes at carbon black manufacturing facilities. The EPA
proposed the work practice standard to mitigate the risk of explosion
at carbon black manufacturing facilities upon startup due to the
characteristics of the tail gas. The proposed work practice standard
addressed combustibility concerns by allowing tail gas to be vented
through the MUF vent for a short, time-limited period in order to
prevent excess oxygen from mixing with tail gas. The EPA time-limited
the proposed work practice standard to ensure sources would begin
routing tail gas to control devices as soon as practicable, while
accounting for variability across facilities that impact startup
procedures.
2. How did the proposed amendments to address emissions during periods
of SSM requirements change in the final rule?
    The EPA initially proposed that the work practice standard would
apply for 13 minutes upon startup. Due to comments received on the
proposal, the EPA is finalizing a work practice standard that applies
to both startup and shutdown of the reactor. The work practice standard
allows the closed vent system to the control device to be bypassed,
during both startup and shutdown of a reactor, when the excess oxygen
concentration in the closed vent system is greater than or equal to 3
percent. Additionally, the maximum bypass period for the work practice
standard is extended from 13 minutes to 15 minutes. To determine when
the oxygen concentration of the closed vent system falls below 3
percent, each facility must use the calculated purge duration method or
oxygen sensors. The language at 40 CFR 63.1003(f)(5) has been amended
in the final rule to reflect these changes.
3. What key comments did we receive on the SSM revisions and what are
our responses?
    The EPA received comments on several aspects of the proposed work
practice standard. Comments received include requests for (1) site-
specific procedures, (2) expansion of the standard to shutdown periods
(in addition to startup periods), (3) an increase in the time period
allowed under the work practice standard, and (4) specific regulatory
language changes. We are only revising requirements where credible
technical and/or safety issues were identified, while maintaining the
goal of minimizing emissions during periods of startup and shutdown to
the maximum extent practicable. These comments and the

EPA's response to these comments are provided below.
a. Site-Specific Startup and Shutdown Procedures
    Comment: The commenter stated that factors affecting the time
needed for startup and shutdown procedures are specific to each
facility because the time needed to purge the closed vent system and/or
open and close valves depends on the configuration of the facility,
common tail gas header, and the production line; the volume of the
production line; the size of the valves; the production rate; and the
facility-specific operating procedures and provides an example. To
allow for this source-specific variability, the commenter suggested
that instead of relying solely on oxygen concentration, the regulation
should allow bypass of the control device during startup and shutdown
of a reactor in accordance with the maximum duration calculated using
the calculated purge duration method located in the startup and
shutdown plan (SSP) and that the startup and shutdown occur ``as
expeditiously as possible.'' The commenter stated that the use of
oxygen sensors in the MUF is not current industry practices, and that
of the current 15 major source facilities, only two of them have oxygen
sensors. The commenter also stated that the calculated purge duration
method in the SSP would include a calculation of the amount of time it
takes to purge the production line, as well as a safety factor that
accounts for the physical and technological constraints of the
facility; the maximum duration could not be more than 15 minutes. The
commenter stated that the SSP would provide the amount of time needed
when completing startup and shutdown ``as expeditiously as possible.''
For a more detailed summary of the comment, see the document Summary of
Comments and EPA's Responses on the National Emission Standards for
Hazardous Air Pollutants Carbon Black Production Residual Risk and
Technology Review and Carbon Black Production Area Sources Technology
Review Proposed Rule, which is available in docket: EPA-HQ-OAR-2020-
0505.
    Response: The EPA agrees that the bypass time allowed for a reactor
to startup or shutdown should be source specific. The EPA acknowledges
that most facilities currently do not operate oxygen sensors and
relying solely on oxygen sensors to detect oxygen content in the
ductwork upon startup and shutdown could lead to undetected pockets of
high-oxygen concentration gases escaping the sensors, creating an
explosion risk within the ductwork at a facility.
    Additionally, the EPA agrees that during startup the MUF vent must
be open and the common tail gas header closed when initially burning
feedstock oil to purge the line of excess oxygen. If the common tail
gas header is opened while the oxygen level was above 3 percent, there
is a risk of explosion due to the combustible nature of the tail gas.
Once the oxygen level falls below 3 percent (determined by using the
calculated purge duration method discussed below), the MUF vent must
gradually close while the common tail gas header is gradually opened.
This gradual change helps to ensure that constant pressure is
maintained within the closed vent system and common tail gas header.
The EPA acknowledges that maintaining constant pressure is important. A
sudden surge or interruption in tail gas flow could extinguish the
flame on the control device located downstream of the common tail gas
header. If the flame is extinguished, there is a risk that combustible
gases will build up in the common tail gas header; if combustible gases
build up in the common tail gas header, then these gases could cause an
explosion when the flame is relit.
    The EPA found that all facilities currently use the calculated
purge duration method to predict when the oxygen level in the ductwork
drops below 3 percent. The calculated purge duration method estimates
the total time a facility needs to safely startup or shutdown a carbon
black production line by taking into account several factors, including
the volume of tail gas in the closed vent system, the flowrate within
the closed vent system, a safety factor, and the time needed to balance
pressure by opening and closing the necessary valves. Using the
calculated purge duration method is industry practice for facilities to
determine when oxygen levels are below 3 percent.
    Since all facilities currently utilize the calculated purge
duration method, the EPA finds this practice to be representative of
the best performing facilities within the industry. The EPA is
declining to require SSPs in the final rule; instead, the EPA is
finalizing a change from proposal at 40 CFR 63.1103(f) to require
facilities to utilize the calculated purge duration method to determine
a site-specific maximum bypass duration upon startup and shutdown. The
EPA determined that including site-specific requirements at 40 CFR
63.1103(f) would accomplish the same goal as SSPs without adding
additional reporting burden.
b. Work Practice Standard Should Apply During Startup and Shutdown
    Comment: The commenter requested that the proposed work practice
standard be revised to apply during shutdown as well as during startup.
In support of their comment, the commenter provided a comprehensive
discussion of the carbon black production startup and shutdown
processes and the reasoning for their request for modifications to the
proposed work practice standard requirements. Reasons for expanding the
work practice to shutdown as well as startup include the similarities
in the need to maintain constant pressure and to reduce the oxygen
content in the closed vent system to under 3 percent due to the risk of
explosion for both startup and shutdown. For a summary of their
detailed comments regarding startup and shutdown, see the document
Summary of Comments and EPA's Responses on the National Emission
Standards for Hazardous Air Pollutants Carbon Black Production Residual
Risk and Technology Review and Carbon Black Production Area Sources
Technology Review Proposed Rule, available in the docket for this
rulemaking.
    Response: Based on the information provided by the commenter, EPA
agrees that shutdown operations present safety concerns similar to
those associated with startup. Accordingly, the EPA is finalizing a
revision to the proposed work practice standard so that it applies to
both startup and shutdown operations.
    The EPA agrees that the shutdown process presents combustibility
concerns similar to startup. When facilities stop burning feedstock
oil, higher oxygen content is created in the closed vent system. This
creates an explosion risk if the oxygen level rises above 3 percent.
Therefore, prior to removing feedstock oil from the reactor, the common
tail gas header vent must be closed completely, diverting closed vent
system emissions from the common tail gas header to the MUF, before the
oxygen content begins to increase.
    Similar to startup, constant pressure must be maintained within the
closed vent system during shutdown operations to reduce the risk of
explosion. To achieve constant pressure within the closed vent system,
the MUF vent must be slowly opened while the tail gas header vent is
slowly closed. Once the tail gas header has been completely closed and
the MUF vent is completely open, the burning of feedstock oil in the
reactor ceases. The

EPA acknowledges that maintaining constant pressure is important. A
sudden surge or interruption in tail gas flow could extinguish the
flame on the CCD or other combustion device located downstream of the
common tail gas header. If the flame is extinguished, there is a risk
that combustible gases will build up in the common tail gas header; if
combustible gases build up in the common tail gas header, then these
gases create an explosion risk when the flame is relit.
c. Work Practice Standard Time Allotment
    Comment: The commenter requested that the maximum time allowed to
bypass the control device during startup and shutdown of a reactor be
increased from 13 minutes to 15 minutes. The commenter explained that
their request for this increase in time is based on the minimum time
necessary to completely purge the ductwork and MUF of certain
facilities. The commenter provided that this was previously agreed to
by the EPA in the consent decrees below.
    In 2007, the EPA began a National Enforcement Initiative to
investigate the carbon black manufacturing sector. As a result of this
initiative, each of the International Carbon Black Association (ICBA)
member companies in the United States entered into a settlement with
the EPA and the Department of Justice regarding CAA claims
(hereinafter, the ``Consent Decrees''). The implementation of the terms
of these Consent Decrees has and will result in substantial changes to
the facilities as flares are removed and different control technologies
are installed at a significant cost. Many facilities have already
implemented the agreed upon technologies and others are in the
procurement stages.
    The commenter stated that, in the preamble, the EPA explains that
``the 13-minute allotment to bypass the control device, corresponds
with the minimum time necessary to completely purge the ductwork and
primary bag filter of the facility representing the lowest production
rate.'' However, the commenter suggested that when setting the 13-
minute limit, it appears that the EPA did not fully consider the
agreed-upon time limit in all of the consent decrees or all of the
factors which affect how long it takes a facility to purge excess
oxygen and introduce tail gas to the common tail gas header while
balancing pressure. The commenter stated that the consent decree for
Sid Richardson Carbon, Ltd. allowed a 15-minute bypass.8 9
---------------------------------------------------------------------------

    \8\ United States v. Sid Richardson Carbon, Ltd., 3:17-cv-01792-
SDD-RLB (M.D. La.), Consent Decree, filed Dec. 22, 2017, at Sec.
III.8.oo.
    \9\ United States v. Sid Richardson Carbon, Ltd., 3:17-cv-01792-
SDD-RLB (M.D. La.), Consent Decree, filed Dec. 22, 2017, at Sec.
III.8.oo.
---------------------------------------------------------------------------

    Response: The EPA acknowledges that the consent decree cited by the
commenter allows a 15-minute control device bypass upon startup for the
facility subject to the consent decree allotment to bypass the control
device. In their comment, the commenter provided information to the EPA
concerning the source-specific nature of startup and shutdown
operations at carbon black manufacturing facilities, including
technical support demonstrating that one source subject to this
rulemaking may need up to 15 minutes to purge the excess oxygen content
in the MUF vent during startup and shutdown operations in order to
mitigate combustibility concerns. To address this comment, in the final
rule, the EPA is extending the proposed 13-minute bypass period to a
maximum 15-minute bypass period. However, this time period is further
constrained by the calculated purge duration method. The EPA is also
finalizing a requirement that facilities subject to this rule use the
calculated purge duration method to determine the length of the startup
and/or shutdown bypass period required for a specific facility before
that specific facility may begin to safely operate control devices, and
the facility must begin operating control devices as soon as the
facility may safely do so. In no case do the finalized requirements
allow the startup or shutdown bypass period to exceed 15 minutes for
any facility. The EPA is also amending the work practice standard to
apply to periods of shutdown as well as startup.
    As previously mentioned, carbon black production facilities
currently use the calculated purge duration method to predict when the
oxygen level in the closed vent system drops below 3 percent. The
calculated purge duration method considers the volume of tail gas in
the closed vent system, with an appropriate safety factor, and the time
needed to balance pressure and close or open the necessary valves.
Using the calculated purge duration method is common industry practice
for facilities to determine when oxygen levels are below 3 percent.
    Since all facilities currently utilize the calculated purge
duration method, the EPA finds this practice to be representative of
the best performing facilities within the industry. As previously
discussed, the EPA is declining to require SSPs. Instead, the EPA is
modifying the proposed standard at 40 CFR 63.1103(f)(5) to require
facilities to utilize the calculated purge duration method or oxygen
sensors to determine a site-specific maximum bypass duration upon
startup and shutdown. In no case shall the maximum bypass duration
period exceed 15 minutes for any facility. The calculated purge
duration method is the same approach underlying the control device
bypass timeframes included in the enforcement-related consent decrees
for the carbon black industry.
4. What is the rationale for our changes to the proposed amendments to
address emissions during periods of SSM in the final rule?
    Based on the consideration of comments received concerning
technical and safety concerns with the proposed work practice standard,
the EPA revised the work practice standard provisions in the final
rule. As discussed in our responses to comments in section IV.C.3 of
this preamble, we are only revising requirements where credible
technical and/or safety issues were identified, while maintaining the
goal of minimizing emissions during periods of startup and shutdown to
the maximum extent practicable.

E. Other Technical Amendments to the Carbon Black Production NESHAP

1. Boiler and Process Heater Annual Tune-Up Requirements
a. What amendments did we propose for boiler and process heater annual
tune-up requirements?
    As a result of the EPA's assessment of the MACT standards that
currently apply to the Carbon Black Production source category under
subpart YY, the EPA received a comment that there may be instances
where carbon black production process vents at affected sources route
emissions to a boiler or process heater for use as fuel gas and may not
be subject to any requirements. Under the existing standards, although
emission streams may be subject to the Carbon Black Production MACT,
these streams are exempt from any requirements under the rule when
emissions are routed to a boiler or process heater for use as fuel gas.
Under the Boiler MACT, process heaters and boilers covered under
another standard (as with the Carbon Black Production MACT) are not
subject to the Boiler MACT.
    The EPA proposed to revise subpart YY to include boiler and process
heater annual tune-up requirements for those boilers and process
heaters that receive

tail gas for use as fuel gas. These provisions were proposed in 40 CFR
63.1103(f)(3)(iii) of the final rule. The annual tune-up provisions
paralleled those specified under the Boiler MACT.
b. How did the proposed boiler and process heater tune-up requirements
change in the final rule?
    The final rule revises the definition for ``process vent'' to
remove the fuel gas exemption for the Carbon Black Production source
category. This revised change ensures that the annual tune-up
requirements apply to process heaters and boilers, as intended.
    The final rule also revises the text at 40 CFR
63.1103(f)(3)(iii)(A) (first sentence) to require inspection to be of
the ``combustion device'' instead of the ``burner,'' and at 40 CFR
63.1103(f)(iii)(B), (C), (D) and (E) to provide industry-specific
clarification on tune-up requirements.
c. What key comments did we receive on the proposed annual boiler and
process heater tune-up requirements and what are our responses?
    The EPA received comments on the proposed boiler and process heater
tune-up requirements related to the applicability language and
specified tune-up procedures. These comments and the EPA's responses
and subsequent changes to the proposed boiler and process heater tune-
up provisions are provided below.
i. Applicability
    Comment: The commenter suggested that the proposed language for the
annual tune-up requirement be changed so that it applies to the process
heaters and boilers that the EPA intended. The commenter noted that the
EPA explained that it added the annual tune-up requirement to close a
perceived loophole. The commenter stated that they are unsure whether
the proposed modifications in the proposal achieved the EPA's goal. The
commenter noted that while the preamble to the proposed rule identifies
the target of the annual tune-up requirements to be boilers and process
heaters receiving emissions to use as fuel gas, the language in the
proposed rule may not apply to the intended boilers or process heaters.
    The commenter explained that, in the current regulations, emission
streams that are routed to a boiler or process heater for fuel gas are
not regulated as a process vent, because ``[g]as streams transferred
for fuel value (i.e., net positive heating value), use reuse, or sale
for fuel value, use, or reuse,'' are excluded from the definition of
process vent. 40 CFR 63.1101. Therefore, the commenter noted that when
emissions are routed to a boiler or process heater for use as fuel gas
at a carbon black production facility, those points of discharge are
not process vents. The proposed rule does not alter the definition of
process vent, and the commenter was uncertain what effect the changes
to Table 8 of the proposed regulatory text would have on the current
standards. The commenter stated that changes in Table 8 of the proposed
regulatory text apply only to ``process vents'' and under the
definition of process vents, this would necessarily mean that it could
not include gas streams routed to boilers or process heaters for fuel
value. For a more detailed summary of the comment, see Summary of
Comments and EPA's Responses on the National Emission Standards for
Hazardous Air Pollutants Carbon Black Production Residual Risk and
Technology Review and Carbon Black Production Area Sources Technology
Review Proposed Rule, which is available in docket: EPA-HQ-OAR-2020-
0505.
    Response: The EPA acknowledges that the proposed regulatory text
was unclear and could lead to subject facilities not complying with the
added boiler and process heater requirements. To resolve this issue,
the EPA is revising the definition for process vent to remove the fuel
gas exemption for the Carbon Black Production source category.
Specifically, the EPA is finalizing an amended definition of ``process
vent'' to remove the exemption for gas streams transferred for fuel
value, use, reuse, or sale for fuel value, use, or reuse for the carbon
black production source category.
ii. Annual Tune-Up Requirements
    Comment: Commenters also requested tailored modifications to the
tune-up requirements to better reflect the specifications of combustion
devices typically used in the carbon black production process. The
commenter noted that carbon black combustion devices differ
significantly from natural gas combustion devices such that not all of
the proposed tune-up requirements apply In support of their comment,
the commenter states that additional optimization outside of inspection
and cleaning may not be possible for all facilities. For a more
detailed summary of the comment, see Summary of Comments and EPA's
Responses on the National Emission Standards for Hazardous Air
Pollutants Carbon Black Production Residual Risk and Technology Review
and Carbon Black Production Area Sources Technology Review Proposed
Rule, which is available in docket: EPA-HQ-OAR-2020-0505.
    Response: The EPA agrees with the commenter that, as a result of
the nature of the burner configuration and design of tail gas fired
boilers and process heaters in the Carbon Black Production source
category, the tune-up requirements of the proposed rule may not be able
to be performed as written. As the commenter noted, due to the lack of
an inspection port for the ``typical'' burner configuration used in the
carbon black production process, it may not be possible to perform a
direct inspection of the burner in operation, as described in 40 CFR
63.1103(f)(3)(iii)(A). Thus, the EPA is finalizing the suggested
revision to the regulatory text at 40 CFR 63.1103(f)(3)(iii)(A) to read
``[i]nspect the combustion device for damage, wear, and buildup of
material that could impact effectiveness'' rather than ``inspect the
burner.'' The EPA disagrees in part with the other changes suggested by
the commenter. As noted by the commenter, a ``typical'' burner
configuration may not be amenable to inspection of the flame pattern
and adjustment of the burner, but it is possible in some
configurations. The regulatory text at 40 CFR 63.1103(f)(iii)(B) has
been amended to require the inspection and adjustment only when
possible based upon the physical configuration of the burner.
Similarly, the requirements of 40 CFR 63.1103(f)(iii)(C) state to
``[i]nspect the system controlling the air-to-fuel ratio, as
applicable, and ensure that it is correctly calibrated and functioning
properly.'' The EPA agrees that not all configurations of systems
controlling air-to-fuel ratio have calibrated components, but some
systems may have components that are calibrated and would need that
calibration verified. However, if a burner system does not have
anything to be calibrated, then ensuring proper calibration is not
necessary; the inspection of the fuel to air ratio controlling
mechanism in that case could be as simple as verifying that there are
no obstructions to the air intake in a natural draft system and
verifying proper fan operation for a fixed air flow fan. For these
reasons, the EPA also agrees that 40 CFR 63.1103(f)(iii)(C) should not
be finalized as proposed and is amending the final language to reflect
that ensuring proper calibration is only necessary for calibrated
components of the air-to-fuel system.
    The EPA disagrees with the commenter that 40 CFR 63.1103(f)(iii)(D)
and (E) should not be finalized and disagrees that measurement of
carbon monoxide (CO)

is a poor indicator of optimized performance. As CO is a primary
component of tail gas, any tail gas not combusted by the boiler or
process heater will result in CO emissions. Additionally, CO is
produced from the incomplete combustion of hydrocarbons in the tail
gas. During proper operation of the combustion device, the output of CO
from either uncombusted tail gas or from incomplete combustion is
minimized. The EPA agrees that optimization beyond the inspection and
cleaning required in 40 CFR 63.1103(f)(iii)(A) may not be possible for
the configuration of some carbon black facility combustion devices. In
such a scenario, the proposed language of 40 CFR 63.1103(f)(iii)(D) was
clear that ``[t]his optimization should be consistent with the
manufacturer's specifications, if available.'' In instances where there
are no manufacturer's recommendations for optimization, the cleaning of
the combustion device constitutes the optimization procedure, and CO
measurement should be taken before and after cleaning the combustion
device. The regulatory text at 40 CFR 63.1103(f)(iii)(D) has been
amended from that proposed to more clearly reflect that, in the cases
where no manufacturer's specification for optimization are available,
the inspection and cleaning procedures of 40 CFR 63.1103(f)(iii)(A)
fulfill the requirements of optimization and that when available,
manufacturer's specification should be used for the optimization
procedure. The regulatory text at 40 CFR 63.1103(f)(iii)(E) has been
amended from that proposed to reflect that if adjustments are not or
cannot be made, the measurements of CO are performed after the
inspection and cleaning procedures of 40 CFR 63.1103(f)(iii)(A) are
performed.
d. What is the rationale for our final changes to the proposed boiler
and process heater annual tune-up provisions?
    Based on the consideration of comments received on the combustion
devices typically used in the carbon black production process, we
clarified and revised the applicability and requirements of the annual
boiler and process heater tune-up requirements to better reflect the
combustion devices typically used. See our comment response directly
above in subsection ii, for our rationale for revisions based on our
evaluation of comments.

V. What is the rationale for our final decisions and amendments for the
Cyanide Chemicals Manufacturing source category?

    For each issue, this section provides a description of what we
proposed and what we are finalizing for the issue, the EPA's rationale
for the final decisions and amendments, and a summary of key comments
and responses (when applicable). For all comments not discussed in this
preamble, comment summaries and the EPA's responses can be found in the
comment summary and response document available in the docket for this
source category.

A. Residual Risk Review for the Cyanide Chemicals Manufacturing Source
Category

1. What did we propose pursuant to CAA section 112(f) for the Cyanide
Chemicals Manufacturing source category?
    On January 15, 2021 (86 FR 3906), the EPA proposed that risk posed
by emissions from the source category is acceptable, that the current
NESHAP provides an ample margin of safety to protect public health, and
that additional standards are not necessary to prevent an adverse
environmental effect. The EPA sets standards under CAA section
112(f)(2) using ``a two-step standard-setting approach, with an
analytical first step to determine an `acceptable risk' that considers
all health information, including risk estimation uncertainty, and
includes a presumptive limit on MIR of approximately 1-in-10
thousand.'' (54 FR 38045, September 14, 1989). The maximum estimated
cancer risk was below the presumptive limit of acceptability and the
noncancer risk results indicate there is minimal likelihood of adverse
noncancer health effects due to HAP emissions from this source
category. The proposed decision on ample margin of safety was based on
weighing factors relevant to this particular source category, including
the risk posed by emissions from the category and the costs and cost-
effectiveness of additional controls to reduce risk further, as well as
uncertainties in the baseline emissions estimates used in estimating
risk, the costs and effectiveness of the work practices we considered
to reduce these emissions, and the amount of risk reduction that could
be achieved with the work practices. A more thorough discussion of the
risk assessment is included in the Residual Risk Assessment for the
Cyanide Chemicals Manufacturing Source Category in Support of the Risk
and Technology Review 2021 Final Rule document, available in the docket
for cyanide chemicals manufacturing (Docket-EPA-HQ-OAR-2020-0532). In
the proposed rule, as presented in Table 2 below, based on modeling
actual emissions from the source category for all 13 facilities, we
estimated inhalation cancer risk to the individual most exposed was
equal to 5-in-1 million. The estimated incidence of cancer due to
inhalation exposures resulting from emissions from the source category
was 0.004 excess cancer cases per year, or one excess case every 250
years with 61,653 people exposed to an excess cancer risk greater than
or equal to 1-in-1 million due to inhalation exposure to HAP emissions
from the source category. Emissions of acrylonitrile from process vents
account for 95 percent of the cancer incidence. The Agency estimated
that the maximum chronic noncancer TOSHI from inhalation exposure for
this source category was equal to 1. In the screening assessment of
worst-case acute inhalation impacts, we estimated a maximum HQ of 1
(due to hydrogen cyanide) based on the REL. In the proposal, the EPA
estimated risks based on actual and allowable emissions from cyanide
chemicals manufacturing sources, and we considered these in determining
acceptability. As shown in Table 2, the chronic cancer and non-cancer
risks are the same for allowable emissions as they are for actual
emissions.

                                               Table 2--Inhalation Risk Assessment Summary for Cyanide Chemicals Manufacturing \1\ Source Category
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                               Estimated
                                                               Maximum       population at      Estimated
                                             Number of       individual     increased risk    population at   Estimated annual     Maximum  chronic noncancer        Maximum  screening acute
             Risk assessment              facilities \2\  cancer risk  (1-     of cancer     increased risk   cancer incidence             TOSHI \4\                     noncancer HQ \5\
                                                            in-1 million)      >=1-in-1     of cancer  >=10-  (cases per year)
                                                                 \3\            million       in-1 million
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Baseline Actual Emissions
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Source Category.........................              13                 5          61,653                 0             0.004  1 (neurological)...............  1 (REL).
Facility-wide...........................              13               200         266,532            58,000              0.04  1 (neurological).                ...............................
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

                                                                                Baseline Allowable Emissions
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Source Category.........................              13                 5          61,653                 0             0.004  1 (neurological).                ...............................
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Based on actual and allowable emissions.
\2\ Number of facilities evaluated in the risk assessment. Includes 13 operating cyanide chemicals manufacturing facilities subject to 40 CFR part 63, subpart YY.
\3\ Maximum individual excess lifetime cancer risk due to HAP emissions.
\4\ Maximum TOSHI. The target organ with the highest TOSHI for the Cyanide Chemical Manufacturing source category is the neurological system.
\5\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of HQ values. The acute HQ shown was based upon the lowest acute
  1-hour dose-response value, the REL for hydrogen cyanide. When an HQ exceeds 1, we also show the HQ using the next lowest available acute dose-response value.

    The EPA also estimated inhalation risk based on facility-wide
emissions. The estimated maximum individual excess lifetime cancer risk
based on facility-wide emissions was 200-in-1 million, with 0.04 excess
cancer cases per year, or one case every 25 years. This cancer risk is
driven by emissions sources that are not in the Cyanide Chemicals
Manufacturing source category; specifically, emissions of ethylene
oxide and polycyclic organic matter from non-category sources account
for 95 percent of the cancer incidence. Approximately 150 people are
exposed to an excess cancer risk greater than or equal to 100-in-1
million, with 266,532 people exposed to an excess cancer risk above 1-
in-1 million. The estimated maximum chronic noncancer TOSHI values for
the facility-wide assessment was the same as estimated based on actual
and allowable emissions from the source category. The TOSHI value was
equal to 1 for neurological effects driven by hydrogen cyanide
emissions from process vents, wastewater, and equipment leaks.
    Regarding the facility-wide risks due to ethylene oxide emissions,
which are emitted by sources that are not part of the Cyanide Chemicals
Manufacturing source category, we intend to continue to evaluate those
facility-wide estimated emissions and risks further and may address
these in separate actions, as appropriate. In particular, the EPA is
addressing ethylene oxide in response to the results of the latest
National Air Toxics Assessment (NATA) released in August 2018, which
identified the chemical as a potential concern in several areas across
the country.\10\ The latest NATA estimates that ethylene oxide
significantly contributes to potential elevated cancer risks in some
census tracts across the U.S. (less than 1 percent of the total number
of tracts). These elevated risks are largely driven by an EPA risk
value that was updated in late 2016. The EPA is taking steps to address
ethylene oxide emissions by: (1) Reviewing and, as appropriate,
revising CAA regulations for facilities that emit ethylene oxide--
starting with air toxics emissions standards for miscellaneous organic
chemical manufacturing facilities (85 FR 49084, August 12, 2020) and
commercial sterilizers; and (2) working with industry and state, local,
and tribal air agencies to achieve near-term emission reductions. The
EPA posts updates on its work to address ethylene oxide at: https://www.epa.gov/ethylene-oxide.
---------------------------------------------------------------------------

    \10\ NATA is the Agency's nationwide air toxics screening tool,
designed to help the EPA and state, local, and tribal air agencies
identify areas, pollutants, or types of sources for further
examination.
---------------------------------------------------------------------------

    We also conducted a multipathway screening assessment for the
source category, and the results of the screening assessment are
presented in the risk report titled Residual Risk Assessment for the
Cyanide Chemicals Manufacturing Source Category in Support of the 2021
Risk and Technology Review Final Rule, and section IV of the proposal
preamble (86 FR 3906, January 15, 2021) available in the docket for
this action. A screening value is not an estimate of the cancer risk or
a noncancer HQ (or HI). Rather, a screening value represents a high-end
estimate of what the risk or HQ may be. For this source category the
highest cancer screening value was a Tier 2 cancer screening value less
than 1 for arsenic emissions, which means that we are confident that
the multipathway cancer risk is lower than 1-in-1 million. The highest
Tier 2 non-cancer screening value for the category was less than 1 for
mercury emissions, which can be interpreted to mean that we are
confident that the chronic HQ for mercury is less than 1.
    In evaluating the potential for multipathway effects from emissions
of lead, the EPA compared modeled annual lead concentrations to the
secondary NAAQS level for lead (0.15 micrograms per cubic meter (ug/
m\3\), arithmetic mean concentration over a 3-month period). The
highest annual average lead concentration, 0.000004 ug/m\3\, is far
below the NAAQS level for lead, indicating a low potential for
multipathway impacts from lead.
    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. For further additional detail on
the environmental risk screening assessment, refer to the Residual Risk
Assessment for the Cyanide Chemicals Manufacturing Source Category in
Support of the Risk and Technology Review 2021 Final Rule.
    In determining whether risk is acceptable for this source category,
the EPA considered all available health information and risk estimation
uncertainty, including the uncertainty in the emissions data. Further
discussion of the uncertainties in our risk assessment can be found in
section III.C.7 of the preamble to the proposed rule at 86 FR 3918.
Under the ample margin of safety analysis, we evaluated the cost and
feasibility of available control technologies and other measures
(including the controls, measures, and costs reviewed under the
technology review) that could be applied to this source category to
further reduce the risks (or potential risks) due to emissions of HAP
from the source category. At proposal, we determined that the risk from
Cyanide Chemicals Manufacturing emissions is acceptable and that the
standards provide an ample margin of safety to protect public health
and prevent an adverse environmental effect. In this action, we are
finalizing our proposed determination. See section IV.C of the proposal
preamble (86 FR 3906, 3923-3924) for a discussion of the results of our
risk assessment and analyses and our proposed decisions

regarding risk acceptability, ample margin of safety, and adverse
environmental effects. The EPA is not amending the Cyanide Chemicals
Manufacturing NESHAP based on the risk review conducted pursuant to CAA
section 112(f). The maximum cancer risk for all facilities was 5-in-1
million, which is 20 times below 100-in-1 million, the presumptive
upper limit of acceptable risk. In addition, there were no facilities
with an estimated maximum chronic noncancer HI or maximum HQ greater
than 1. Based upon these considerations and the lack of additional
cost-effective control technologies to reduce risk further, we proposed
and are finalizing a determination that the 2002 Cyanide Chemicals
Manufacturing NESHAP requirements provide an ample margin of safety to
protect public health. Based on the results of our environmental risk
screening assessment, we also proposed and are finalizing a
determination that more stringent standards are not necessary to
prevent an adverse environmental effect.
2. How did the risk review change for the Cyanide Chemicals
Manufacturing source category?
    We did not receive any information that changed our determination
concerning risk and we are finalizing our proposed conclusion on the
risk review.
3. What key comments did we receive on the risk review, and what are
our responses?
    We received several comments regarding the proposed risk review and
our proposed determination that no revisions to the standard were
warranted under CAA section 112(f)(2). Comments both supported and
suggested changes to our risk review. Commenters opposed our proposed
decisions regarding risk acceptability and certain aspects of our risk
assessment methodology. After review of these comments, we determined
that no changes to the standard were necessary because the current
standards provide an ample margin of safety to protect public health.
The comments and our specific responses can be found in the document,
Summary of Comments and EPA's Responses on the National Emission
Standards for Hazardous Air Pollutants: Cyanide Chemicals Manufacturing
Residual Risk and Technology Review Proposed Rule, which is available
in docket: EPA-HQ-OAR-2020-0532.
4. What is the rationale for our final approach and final decisions for
the risk review?
    We evaluated all the comments on the EPA's risk review and
determined that no changes are needed. For the reasons explained in the
proposed rule, we determined that the risk from the Cyanide Chemicals
Manufacturing source category is acceptable, the current standards
provide an ample margin of safety to protect public health, and more
stringent standards are not necessary to prevent an adverse
environmental effect. Therefore, pursuant to CAA section 112(f)(2), we
are finalizing our residual risk determination as proposed.

B. Technology Review for the Cyanide Chemicals Manufacturing Source
Category

1. What did we propose pursuant to CAA section 112(d)(6) for the
Cyanide Chemicals Manufacturing source category?
    At proposal, we proposed to determine that it is not necessary to
revise the existing standards pursuant to CAA section 112(d)(6) because
we did not identify developments in practices, processes, or control
technologies that would result in cost-effective emission reductions
for the Cyanide Chemicals Manufacturing source category. Additional
information on our technology review can be found in the memorandum,
Technical Support Document for the Cyanide Chemicals Manufacturing
NESHAP Residual Risk and Technology Review Proposal, which is available
in the docket for this action (see Docket ID No. EPA-HQ-OAR-2020-0532-
0025) and section IV.D of the proposal preamble (86 FR 3924). The EPA
is not amending the Cyanide Chemicals Manufacturing NESHAP based on our
technology review. However, we did identify a potential gap in the
regulation, and proposed standards for process wastewater at existing
sources and upstream suppression of process wastewater at new sources
under CAA sections 112(d)(2) and (3). The final approach related to
that issue is discussed in section V.C of this preamble.
2. How did the technology review change for the Cyanide Chemicals
Manufacturing source category?
    The technology review did not change from proposal. Therefore, we
are finalizing our determination that no revisions to the NESHAP are
necessary pursuant to CAA section 112(d)(6).
3. What key comments did we receive on the technology review, and what
are our responses?
    We received two comments regarding the proposed technology review
and our proposed determination that no revisions were warranted under
CAA section 112(d)(6). One commenter suggested changes to our
technology review to include additional technologies related to flares
and equipment leaks. After review of these comments, we determined that
no changes to the standards were necessary because these technologies
would not result in cost-effective emission reductions for the cyanide
chemicals manufacturing source category. The comments and our specific
responses can be found in the document, Summary of Comments and EPA's
Responses on the National Emission Standards for Hazardous Air
Pollutants: Cyanide Chemicals Manufacturing Residual Risk and
Technology Review Proposed Rule, which is available in docket: EPA-HQ-
OAR-2020-0532.
4. What is the rationale for our final approach and final decisions for
the technology review?
    Our technology review sought to identify add-on control technology
that was not identified during the original NESHAP development and
improvements to existing add-on controls. We also sought to identify
new work practices, operational procedures, process changes, pollution
prevention alternatives, or techniques that have the potential to
reduce emissions. Based on our review, we did not identify any such
developments that would result in cost-effective emission reductions
for the Cyanide Chemicals Manufacturing source category. Since
proposal, no information has been presented to cause us to change the
proposed determination. Consequently, we are finalizing our CAA section
112(d)(6) determination as proposed.

C. Amendments Addressing Emissions During Periods of SSM for the
Cyanide Chemicals Manufacturing Source Category

1. What amendments did we propose to address emissions during periods
of SSM?
    Consistent with the 2008 decision in Sierra Club v. EPA, the EPA
evaluated the Cyanide Chemicals Manufacturing NESHAP requirements to
identify the need to eliminate any SSM exemptions in the rule to ensure
that standards that apply during normal operations apply at all times.
As noted at proposal (86 FR 3906, 3924), the Cyanide Chemicals

Manufacturing source category NESHAP did not include an exemption for
SSM events, and already included standards that apply at all times,
including periods of SSM. Therefore, we determined that the NESHAP was
already consistent with Sierra Club v. EPA, in which the Court vacated
two provisions that exempted sources from the requirement to comply
with otherwise applicable CAA section 112(d) emission standards during
periods of SSM. However, we proposed revisions to subpart YY at 40 CFR
63.1108 through 40 CFR 63.1112 to remove any references associated with
the GMACT that contained SSM exemptions for other source categories and
from referenced subparts to reduce confusion. The EPA did not propose
any other amendments addressing emissions during SSM periods because of
our determination that the NESHAP already included standards that apply
at all times, including periods of SSM.
2. How did the proposed SSM-related amendments change in the final
rule?
    We are finalizing our proposal to remove SSM exemption language
included in 40 CFR 63.1108 through 40 CFR 63.1112 and GMACT referenced
subparts.
3. What key comments did we receive on SSM-related emissions and what
are our responses?
    While one commenter provided support for the EPA's removal of
references to provisions that contained SSM exemptions for other source
categories and from referenced subparts to reduce confusion, the
commenter expressed concern that the EPA had not removed references to
SSM exemptions in HON-referenced provisions and that the EPA must
assure full removal of SSM exemptions in the final rule to assure
compliance with the CAA.
    Other commenters expressed concern that the EPA had not established
work practice standards to cover situations that they contend had been
covered under their SSM plan included under the SSM exemption
requirements that were proposed to be removed. The commenter requested
that the EPA include provisions for specified circumstances that were
previously covered under their SSM plan similar to what was included
for the ethylene production source category in subpart YY.
    These comments and the EPA's responses to these comments are
provided below.
a. Elimination of the SSM Exemption
    Comment: One commenter noted that SSM events play a considerable
role in the issue of pollution and environmental contamination as these
processes increase an industrial plant's pollution and noted concern
that the EPA would continue to maintain SSM exemptions in this rule.
Another commenter supported the removal of the SSM exemptions, stating
that removal of these provisions is required to assure compliance with
the CAA because this is a `necessary' revision under CAA section
112(d)(6).
    Response: As discussed in section V.C.1 of this preamble, we are
finalizing revisions (as proposed) to subpart YY at 40 CFR 63.1108
through 40 CFR 63.1112 to remove any references associated with the
GMACT that contained SSM exemptions for other source categories and
referenced subparts.