[Federal Register Volume 87, Number 88 (Friday, May 6, 2022)]
[Rules and Regulations]
[Pages 27002-27024]
[FR Doc No: 2022-09658]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2020-0560; FRL-7546-02-OAR]
RIN 2060-AU59

National Emission Standards for Hazardous Air Pollutants: Mercury
Cell Chlor-Alkali Plants Residual Risk and Technology Review

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: This action finalizes the residual risk and technology review
(RTR) conducted for the Mercury Cell Chlor-Alkali Plants source
category regulated under national emission standards for hazardous air
pollutants (NESHAP). In addition, this action finalizes the beyond-the-
floor determination that EPA performed in response to a petition for
reconsideration of the 2003 NESHAP. These final amendments prohibit
mercury emissions from existing mercury cell chlor-alkali plants based
on the results of our technology review and our beyond-the-floor
maximum achievable control technology (MACT) determination. The
compliance date for this requirement is three years. Since mercury
emissions will be eliminated as a result of the final rule standards,
any adverse health or environmental effects from mercury emissions from
the source category will also be eliminated in that three-year time
frame. Furthermore, the EPA is finalizing work practice standards and
instrumental monitoring of mercury to minimize fugitive mercury
emissions from the cell rooms during the period of time before
emissions are eventually eliminated. In addition, the EPA is finalizing
work practice standards to minimize fugitive chlorine emissions from
mercury cell chlor-alkali plants, which were not previously regulated
under the NESHAP. The EPA is also finalizing revisions related to
emissions during periods of startup, shutdown, and malfunction (SSM)
and amendments to correct a few minor errors in compliance provisions
in the 2003 rule.

DATES: This final rule is effective on May 6, 2022.

ADDRESSES: The U.S. Environmental Protection Agency (EPA) has
established a docket for this action under Docket ID No. EPA-HQ-OAR-
2020-0560. 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 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 this final action,
contact Phil Mulrine, 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, contact James Hirtz, Health and
Environmental Impacts Division, 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. Throughout this document wherever ``we,''
``us,'' or ``our'' is used, it is intended to refer to the EPA. 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:

AEGL acute exposure guideline level two
CAA Clean Air Act
CFR Code of Federal Regulations
Cl2 Chlorine
CRA Congressional Review Act
EPA Environmental Protection Agency
ERT Electronic Reporting Tool
HAP hazardous air pollutants(s)
HCl hydrochloric acid
Hg mercury
HI hazard index
HQ hazard quotient
MACT maximum achievable control technology
MATS Mercury and Air Toxics Standards
NAIC North American Industry Classification System
NESHAP national emission standards for hazardous air pollutants
NTTAA National Technology Transfer and Advancement Act
NOCS Notification of Compliance Status report
NRDC Natural Resources Defense Council
OMB Office of Management and Budget
PB-HAP HAPs known to be persistent and bioaccumulative in the
environment
PDF portable document format
PM particulate matter
ppm parts per million
ppmv parts per million by volume
PRA Paperwork Reduction Act
REL reference exposure limit
RTR risk and technology review
SSM startup, shutdown, and malfunction
SV screening value
TOSHI target organ-specific hazard index
tpy tons per year
UMRA Unfunded Mandates Reform Act

    Background information. On January 8, 2021, the EPA proposed
revisions to the 2003 Mercury Cell Chlor-Alkali Plants NESHAP, 40 CFR
part 63, subpart IIIII, based on our RTR and MACT beyond-the-floor
analyses (86 FR 1362, January 8, 2021). In this action, we are
finalizing decisions and revisions for the rule. We summarize the
comments we timely received regarding the proposed rule and provide our
responses in this preamble. A ``track changes'' version of the
regulatory language that incorporates the changes in this action is
available in the docket.
    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 is the Mercury Cell Chlor-Alkali Plants source category
and how does the NESHAP regulate HAP emissions from the source
category?
    C. What changes did we propose for the Mercury Cell Chlor-Alkali
Plants source category in our January 8, 2021 proposal?
III. What is included in this final rule?
    A. What are the final rule amendments based on the risk review
for the Mercury Cell Chlor-Alkali Plants source category?
    B. What are the final rule amendments related to a non-mercury
option for the Mercury Cell Chlor-Alkali Plants Source Category
pursuant to CAA sections 112(d)(2), (3), and (6)?
    C. What are the final rule amendments based on the technology
review for the

Mercury Cell Chlor-Alkali Plants source category?
    D. What are the final rule amendments pursuant to sections
112(d)(2) and (3) and (h) for the Mercury Cell Chlor-Alkali Plants
source category?
    E. What are the final rule amendments addressing emissions
during periods of startup, shutdown, and malfunction?
    F. What are the effective and compliance dates of the standards?
IV. What is the rationale for our final decisions and amendments for
the Mercury Cell Chlor-Alkali Plants source category?
    A. Residual Risk Review for the Mercury Cell Chlor-Alkali Plants
Source Category
    B. Non-Mercury Option for the Mercury Cell Chlor-Alkali Plants
Source Category
    C. Technology Review for the Mercury Cell Chlor-Alkali Plants
Source Category
    D. Amendments Pursuant to Sections 112(d)(2) and (3) and (h) for
the Mercury Cell Chlor-Alkali Plants Source Category
    E. Amendments Addressing Emissions During Periods of Startup,
Shutdown, and Malfunction and Other Topics
    F. Public Notice and Comments
V. Summary of Cost, Environmental, and Economic Impacts and
Additional Analyses Conducted
    A. What are the affected facilities?
    B. What are the air quality and other environmental impacts?
    C. What are the cost impacts?
    D. What are the economic impacts?
    E. What are the benefits?
    F. What analysis of environmental justice did we conduct?
    G. What analysis of children's environmental health did we
conduct?
VI. 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. Categories and entities potentially regulated
by this action are shown in Table 1 of this preamble.

 Table 1--NESHAP and Industrial Source Categories Affected by This Final
                                 Action
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                                                               NAICS \1\
                 NESHAP and source category                      code
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Mercury Cell Chlor-Alkali Plants............................      325180
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\1\ North America Industry Classification System.

    Table 1 of this preamble 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 category 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 this 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 docket, 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/mercury-cell-chloralkali-plants-national-emissions-standards. Following
publication in the Federal Register, the EPA will post the Federal
Register version and key technical documents at this same website.
    Additional information is available on the RTR website at https://www.epa.gov/stationary-sources-air-pollution/risk-and-technology-review-national-emissions-standards-hazardous. This information
includes an overview of the RTR program and links to project websites
for the RTR source categories.

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 July 5, 2022. Under CAA section 307(b)(2), the
requirements established by this final rule 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 hazardous air pollutants (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 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). In conducting this review,
the EPA is not required to recalculate the MACT floors that were
established in earlier rulemakings. Natural Resources Defense Council
v. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008) (NRDC). Association of
Battery Recyclers, Inc. v. EPA, 716 F.3d 667 (D.C. Cir. 2013). The EPA
may consider cost in deciding whether to revise the standards pursuant
to CAA section 112(d)(6). The EPA is required to address regulatory
gaps, such as missing standards for listed air toxics known to be
emitted from the source category, and any new MACT standards must be
established under CAA sections 112(d)(2) and (3), or, in specific
circumstances, CAA sections 112(d)(4) or (h). Louisiana Environmental
Action Network v. EPA, 955 F.3d 1088 (D.C. Cir. 2020) (LEAN). 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 rule, see https://www.federalregister.gov/documents/2021/01/08/2021-00174/national-emission-standards-for-hazardous-air-pollutants-mercury-cell-chlor-alkali-plants-residual.
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    \1\ The Court has affirmed this approach of implementing CAA
section 112(f)(2)(A): NRDC, 529 F.3d at 1083 (``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 is the Mercury Cell Chlor-Alkali Plants source category and how
does the NESHAP regulate HAP emissions from the source category?

    The EPA promulgated the Mercury Cell Chlor-Alkali Plants NESHAP on
December 19, 2003 (68 FR 70904). The standards are codified at 40 CFR
part 63, subpart IIIII. The mercury cell chlor-alkali industry consists
of facilities that use mercury cells to manufacture product chlorine,
product caustic, and by-product hydrogen via an electrolytic process.
The source category covered by these MACT standards currently includes
one operating facility, Westlake located in West Virginia.
    Subpart IIIII covers both major and area sources. The single
remaining operational mercury cell-chlor-alkali plant in the category
is located at a major source site. In addition to subpart IIII,
processes at this major source site are subject to subparts ZZZZ
(Reciprocating Internal Combustion Engine NESHAP) and DDDDD
(Industrial/Commercial/Institutional Boilers and Process Heaters). The
mercury cell chlor-alkali NESHAP includes standards for mercury
emissions from two types of affected sources at plant sites where
chlorine and caustic are produced in mercury cells: Mercury cell chlor-
alkali production facility affected sources and mercury recovery
facility affected sources. The 2003 rule prohibited mercury emissions
from new and reconstructed mercury cell chlor-alkali production
affected sources. 40 CFR 63.8190(a)(1). For existing mercury cell
chlor-alkali production affected sources, the 2003 standards included
emission limitations for mercury emissions from process vents
(including emissions from end-box ventilation systems and hydrogen
systems) and work practices for fugitive mercury emissions from the
cell room. 40 CFR 63.8190(a)(2), 63.8192(a) through (f).
    For new, reconstructed, and existing mercury recovery facilities,
the 2003 NESHAP included emission limitations for mercury emissions
from oven type thermal recovery unit vents and non-oven type thermal
recovery unit vents. 40 CFR 63.8190(a)(3). Note that the single
remaining operational facility does not operate a mercury recovery
facility, so there are no operating mercury recovery facilities subject
to subpart IIIII.
    The 2003 rule did not promulgate standards for chlorine
(Cl2) or hydrochloric acid (HCl), citing the authority of
section 112(d)(4) of the CAA (68 FR 70906). In its 2003 action (68 FR
70904), the EPA promulgated the initial Mercury Cell Chlor-Alkali
Plants NESHAP pursuant to CAA section 112(d)(2) and (3) and added the
source category to the EPA's Source Category List under CAA sections
112(c)(1), as well as under (c)(3), (c)(6) and (k)(3)(B), in each case
because of the mercury emissions.
    Following promulgation of the 2003 Mercury Cell Chlor-Alkali Plants
NESHAP, the EPA received a petition to reconsider several aspects of
the rule from the Natural Resources Defense Council (NRDC). NRDC also
filed a petition for judicial review of the rule in the U.S. Court of
Appeals for the District of Columbia Circuit. In a letter dated April
8, 2004, the EPA granted NRDC's petition for reconsideration and on
July 20, 2004, the court placed the petition for judicial review in
abeyance pending the EPA's action on reconsideration.
    The EPA issued proposed revisions to the 2003 rule on June 11, 2008
(73 FR 33258) and on March 14, 2011 (76 FR 13852), to respond to the
reconsideration petition. This final action completes EPA's rulemaking
following those two proposals and the third action proposed on January
8, 2021 (86 FR 1362), and completes the EPA's action in response to the
2004 petition for reconsideration of the 2003 rule.

C. What changes did we propose for the Mercury Cell Chlor-Alkali Plants
source category in our January 8, 2021, proposal?

    On January 8, 2021, the EPA published a proposed rule in the
Federal Register for the Mercury Cell Chlor-Alkali Plants NESHAP, 40
CFR part 63, subpart IIIII, that took into consideration the RTR
analyses and the MACT beyond-the-floor analysis. In the proposed rule,
we proposed: (1) The determination that risks due to emissions of HAP
are acceptable from the Mercury Cell Chlor-Alkali Plants source
category and that the 2003 NESHAP provides an ample margin of safety to
protect public health; (2) to amend the requirements for cell room
fugitive mercury emissions to require work practice standards for the
cell rooms plus instrumental monitoring of cell room fugitive mercury
emissions under the technology review; (3) work practice standards for
fugitive chlorine emissions from mercury cell chlor-alkali plants,
which were not previously regulated under the NESHAP; (4) revisions
related to emissions during periods of startup, shutdown and
malfunction (SSM), which had also been addressed in the 2011 proposed
rule; (5) provisions for electronic submission of performance test
results, compliance reports, and Notification of Compliance Status
(NOCS) reports; and (6) amendments to correct minor errors and improve
the compliance provisions of the rule, which had also been addressed in
the 2008 and 2011 proposals.
    With regard to our technology review and an overdue beyond-the-
floor determination, as explained in the January 2021 document (86 FR
1362, January 8, 2021), we evaluated two options: (1) Improved cell
room mercury monitoring and work practices to minimize emissions; and
(2) the elimination of Hg emissions by requiring the conversion to a
non-Hg technology.
    Based on this evaluation, we proposed option 1, as mentioned above,
however we also described option 2 (mercury elimination) in detail in
the January 2021 notice and solicited comments. Specifically, we
explained that based on consideration of the updated costs and cost
effectiveness and uncertainties, and given the passage of time, and the
fact that the cost-effectiveness data and analysis done in 2011 were
based on two facilities that are no longer operating, we questioned at
that time whether those 2011 analyses would still be transferable to
the one remaining operating facility. Consequently, we did not propose
to require the elimination of mercury in the January 2021 document.
However, we solicited comments, data, and other information regarding
this proposed decision, including data and information regarding the
capital and annual costs, cost effectiveness, non-air impacts, and
other relevant information that would be relevant for the remaining
facility regarding whether the NESHAP should include a zero-mercury
standard as a beyond-the-floor MACT standard. We also stated that we
intend to consider any such submitted data and information, in addition
to the data and information contained in the records for the 2008 and
2011 proposals and in the 2021 proposal, in reaching final conclusions
regarding a zero-mercury standard (see 86 FR 1362, January 8, 2021).

III. What is included in this final rule?

    This action finalizes the EPA's determinations pursuant to the RTR
and MACT provisions of CAA section 112 for the Mercury Cell Chlor-
Alkali Plants source category and amends the Mercury Cell Chlor-Alkali
Plants NESHAP based on those determinations.

A. What are the final rule amendments based on the risk review for the
Mercury Cell Chlor-Alkali Plants source category?

    No changes to the Mercury Cell Chlor-Alkali Plants NESHAP are being
promulgated to meet the requirements of CAA section 112(f). Under this
action, for purposes of section 112(f), we are finalizing the risk
assessments and our determination that the risks from the Mercury Cell
Chlor-Alkali Plants source category are acceptable, the 2003 standards
provide an ample margin of safety to protect public health, and more
stringent standards are not necessary to prevent an adverse
environmental effect.

B. What are the final rule amendments related to a non-mercury option
for the Mercury Cell Chlor-Alkali Plants Source Category pursuant to
sections 112(d)(2), (3), and (6)?

    To satisfy the requirements of CAA sections 112(d)(2), (d)(3), and
(6), including to respond to the petition for reconsideration of the
2003 rule by completing our MACT beyond-the-floor analysis, we are
revising the MACT standards to prohibit mercury emissions from existing
mercury cell chlor-alkali plants. Specifically, these amendments
prohibit mercury emissions from existing mercury chlor-alkali
production facility affected sources. This makes the mercury standard
for existing sources the same as the standard for new and reconstructed
sources that has been in the NESHAP since 2003. Since we conclude that
it is improbable that a mercury cell chlor-alkali plant can be operated
without mercury emissions, we expect this revision will effectively
require the lone remaining mercury cell chlor-alkali plant in operation
in the U.S. to cease production of chlorine with their single mercury
cell production unit. We anticipate the facility will continue to
produce chlorine through its other, higher-volume non-mercury chlorine
production units located at the Westlake facility and may convert the
mercury cell unit to a membrane cell or other non-mercury chlorine
production process. There are no mercury recovery facilities still in
operation in the U.S. This final rule provides a three-year period to
comply with the requirement to eliminate mercury emissions from the
single remaining existing affected source. To demonstrate compliance,
the owner or operator will need to submit a notification certifying
that all mercury emissions have been eliminated permanently no later
than 120 days after the compliance date.

C. What are the final rule amendments based on the technology review
for the Mercury Cell Chlor-Alkali Plants source category?

    We determined that there are developments in practices, processes,
and control technologies that warrant revisions to the MACT standards
for this source category. As noted above, we are revising the MACT
standards to include a prohibition of mercury emissions, which is based
on both a section 112(d)(6) technology review and our beyond-the-floor
review under section 112(d)(2) and (3) in response to NRDC's 2004
petition for reconsideration. Also based on the section 112(d)(6)
technology review and in response to NRDC's 2004 petition, we are
amending the requirements for cell room fugitive mercury emissions to
require work practice standards for the cell rooms along with
instrumental monitoring of cell room fugitive mercury emissions during
the period of time before emissions are eventually eliminated. In
addition, under the technology review, we identified a regulatory gap,
and as discussed below, we are establishing new standards under CAA
section 112(h).

D. What are the final rule amendments pursuant to sections 112(d)(2)
and (3) and (h) for the Mercury Cell Chlor-Alkali Plants source
category?

    In addition to the requirements for mercury described above, we are
also finalizing amendments pursuant to section 112(h) for chlorine
emissions, similar to the standards we proposed in January 2021 (86 FR
1362), that require implementation of work practices to minimize
chlorine emissions from the mercury cell chlor-alkali processes.
Further details regarding these work practice standards are described
in section IV.D of this document.

E. What are the final rule amendments addressing emissions during
periods of startup, shutdown, and malfunction?

    We are finalizing amendments related to provisions that apply
during periods of SSM that the EPA proposed on January 8, 2021. Further
details are provided in section IV.E of this document.

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

    The revisions to the MACT standards being promulgated in this
action are effective on May 6, 2022. The compliance date for existing
mercury cell chlor-alkali plants to eliminate mercury emissions is May
6, 2025.
    These final amendments will essentially require that the single
remaining operating mercury cell chlor-alkali facility either convert
its one mercury cell unit to a non-mercury technology (its other units
are already using non-mercury technology) or close that mercury cell
unit and thereafter rely solely on its other non-mercury units for
chlorine production. Either of these options will require significant
time for the company to reach a decision and to develop and implement a
plan of action. For example, it is expected that it could take between
six months and one year to develop an engineering design and plan for
conversion. The facility would then need to solicit bids for the
conversion, which could take up to six months. Construction could then
take up to two years. In addition, arrangements will need to be made to
dismantle the mercury cell facility, to store the elemental mercury
removed from the cells and to dispose of the mercury-contaminated
wastes. The most recent conversion in the U.S. was the facility in
Ashtabula, Ohio. This Ashtabula facility was, like the West Virginia,
facility, one of the smaller capacity mercury cell units in the U.S.
(less than 75,000 tons of chlorine per year). It was also of similar
age (Ashtabula constructed in 1963 and West Virginia in 1958) and was
located in a neighboring state. The company announced the plans to
convert their mercury cell process to membrane cells in 2014. They
broke ground in 2017 and the conversion was complete in 2020. In
conclusion, six years elapsed between the time the decision to convert
was made and the conversion was completed, which included three full
years for the dismantling/construction. Therefore, we conclude that the
full three-year compliance period allowed by section 112(i)(3) of the
CAA to meet new or revised emission standards is warranted. Moreover,
as discussed further below, this period will provide ample time for the
United States, via the elimination of mercury emissions from the plant,
to meet its obligations to eliminate mercury emissions from this source
category under the international treaty known as the Minamata
Convention.
    For existing sources, in 2021, we proposed two changes to the work
practice standards. One of these changes was the requirement to operate
a cell-room mercury monitoring program in addition to mercury work
practices. This change was proposed in both 2008 and 2011. The second
proposed change is a program to require work practices to reduce
fugitive chlorine emissions. While these proposed work practice
standards were based on the practices in place at the single facility
in the source category, they will require some modifications to the
procedures currently employed at the facility. Specifically, they will
need to develop and implement a recordkeeping system to record and
maintain the records required for the mercury cell and fugitive
chlorine work practices and to incorporate the required material in the
requisite reports. As proposed, we are providing 180 days for the
facility to modify their current procedures. Therefore, the mercury and
chlorine work practice standards being promulgated in this action
require compliance on November 2, 2022.
    We also proposed in January 2021, a change to the SSM requirements
to remove the exemption from the requirements to meet the standards
during SSM periods and to remove the requirement to develop and
implement an SSM plan. This change was also proposed in 2008 and 2011.
Our experience with similar industries shows that this sort of
regulated facility generally requires a time period of 6 months 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
plans to reflect the revised requirements. As proposed, we are
providing 180 days for the facility to comply with the revised SSM
requirements. As such, these revisions require compliance by November
2, 2022.

IV. What is the rationale for our final decisions and amendments for
the Mercury Cell Chlor-Alkali Plants source category?

    For each issue, this section provides a description of what we
addressed in the proposed rules for the source category and what we are
finalizing for the issue, the EPA's rationale for the final decisions
and amendments, and the comments and responses.

A. Residual Risk Review for the Mercury Cell Chlor-Alkali Plants Source
Category

1. What did we propose pursuant to CAA Section 112(f) for the Mercury
Cell Chlor-Alkali Plants source category?
    We proposed that health risks due to emissions of HAP from the
Mercury Cell Chlor-Alkali Plants source category are acceptable, that
the 2003 NESHAP provides an ample margin of safety to protect public
health, and that no additional standards are necessary to prevent an
adverse environmental effect.
    A two-step evaluation approach was used, similar to the approach
applied in the Benzene NESHAP, to determine whether or not risks are
acceptable and to determine whether the 2003 standards provide an ample
margin of safety to protect public health or needed to be revised to
meet this goal. We considered health risk and other health information;
information and additional factors relating to the appropriate level of
control were also considered--e.g., cost and economic impacts of
controls, technological feasibility, uncertainties, and any other
relevant factors.
    Table 2 below provides a summary of the results of the inhalation
risk assessment for the source category conducted for the January 2021
proposal. More detailed information on the risk assessment can be found
in the National Emission Standards for Hazardous Air Pollutants:
Mercury Cell

Chlor-Alkali Plants Residual Risk and Technology Review supporting
document, available in the docket for this action (Docket No.: EPA-HQ-
OAR-2020-0560-0014).

                                Table 2--Inhalation Risk Assessment Summary for the Mercury Cell Chlor-Alkali Plants \1\
                                                                    [Source category]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                       Maximum          Estimated
                                       Number of      individual      population at   Estimated annual
           Risk assessment             facilities  cancer risk (1-   increased risk   cancer incidence      Maximum chronic      Maximum screening acute
                                          \2\        in-1million)    of cancer  >=1-  (cases per year)    noncancer TOSHI \4\        noncancer HQ \5\
                                                         \3\          in-1 million
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                Baseline Actual Emissions
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source Category.....................            2            0.004                 0         0.0000003  0.05 (respiratory).....  2 (REL) 7E-4 (AEGL2).
Facility-Wide.......................            2              0.3                 0            0.0001  0.05 (respiratory).....
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              Baseline Allowable Emissions
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source Category.....................            2            0.004                 0         0.0000003  0.05 (respiratory).....
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Based on actual and allowable emissions.
\2\ When the risk assessment was completed in mid-2020, there were 2 operating facilities in the mercury cell chlor-alkali source category and both were
  subject to 40 CFR part 63, subpart IIIII. However, in late 2020 one of those facilities converted to a non-mercury process. Therefore, currently only
  one operating facility remains in the source category.
\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 source category is the respiratory 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 mercury (elemental). When an HQ exceeds 1, we also show the HQ using
  the next lowest available acute dose-response value.

    As shown in the table above, for the Mercury Cell Chlor-Alkali
Plants source category, the maximum cancer risk to the individual most
exposed is less than 1-in-1 million based on actual emissions and
allowable emissions. The estimated incidence of cancer due to
inhalation exposures for the source category is 0.0000003 excess cancer
cases per year, or one excess case every 3 million years. No one is
exposed to cancer risk greater than or equal to 1-in-1 million based
upon actual and allowable emissions. We estimated that the maximum
chronic noncancer TOSHI from inhalation exposure is less than 1 (0.05
[respiratory]). For both actual and allowable emissions, respiratory
risks were driven by chlorine emissions from the mercury cell building.
    Based on our refined screening analysis of reasonable worst-case
acute exposure to actual emissions from the category, the facility
exceeded an HQ of 1 (the HQ was 2), when compared to the 1-hour REL for
mercury (elemental). As discussed in section III.C.3.c of the 2021
proposal preamble, we used an acute hourly multiplier of 10 for all
emission processes. For this HAP, there are no AEGL-1 or ERPG-1 values
for comparison, but AEGL-2 or ERPG-2 values are available. For
elemental mercury, when the maximum off-site concentration is compared
with the AEGL-2 and ERPG-2, the maximum acute noncancer HQ is well
below 1 (0.0007). With regard to multipathway exposures, HAP known to
be persistent and bioaccumulative in the environment (PB-HAP) emissions
(based on estimates of actual emissions) were reported from both
facilities in the source category with both exceeding the Tier 1 non-
cancer screening threshold emission rate for mercury. A Tier 2
screening analysis was conducted, and the facility did not have a
screening value (SV) greater than 1 for any scenario (the fisher and
farmer had the highest SV at 0.4). There are no carcinogenic PB-HAP
emitted from the source category, so there are no cancer SVs to report.
    Considering all the health risk information and factors noted, the
proposed determination was that the risks are acceptable and that no
additional standards are necessary to prevent an adverse environmental
effect. Under the ample margin of safety analysis, we evaluated the
cost and feasibility of available control technologies and other
measures that could be applied to further reduce the risks (or
potential risks) due to emissions of HAP from the source category.
After careful consideration of these options, since the risks due to
mercury emissions were already low, we did not propose any additional
standards for mercury under CAA section 112(f).
2. How did the risk review change for the Mercury Cell Chlor-Alkali
Plants source category?
    We made no changes to either the risk assessments or our
determinations regarding risk acceptability, ample margin of safety, or
adverse environmental effects for the Mercury Cell Chlor-Alkali Plants
source category since the proposal was published on January 8, 2021. We
are finalizing the risk review as proposed (86 FR 1362, January 8,
2021).
3. What key comments did we receive on the risk review, and what are
our responses?
    The only comment received regarding the risk assessment was that
one commenter agreed with our assessment that emissions were low and
that risks were low and at acceptable levels.
4. What is the rationale for our final approach and final decisions for
the risk review?
    As noted above, in 2021, we proposed that the 2003 Mercury Cell
Chlor-Alkali NESHAP provides an ample margin of safety to protect
public health without any revisions. Other than a general agreement
with the results, there were no specific comments submitted on the risk
review approach, results, or decision. Therefore, we are finalizing the
proposed determination that the risks are acceptable, that the 2003
rule provides an ample margin of safety to protect public health and
that no additional standards are necessary to prevent an adverse
environmental effect.

B. Non-Mercury Option for the Mercury Cell Chlor-Alkali Plants Source
Category

1. What did we propose related to the non-mercury option for the
Mercury Cell Chlor-Alkali Plants source category?
    We addressed this issue in all three of our proposed rules issued
following promulgation of the 2003 rule, in response to the 2004
petition for reconsideration of the 2003 rule's consideration of
section 112(d)(2) and (3) beyond-floor options and most recently as
part of the technology review under section 112(d)(6). In the 2021
proposal, we further considered our two prior proposals, but did not
re-propose the option to require non-mercury production technology for
existing sources, which has been the requirement for new and
reconstructed mercury cell chlor-alkali production sources since the
rule was originally promulgated in 2003. This option was considered
both as part of the technology review under the authority of section
112(d)(6) and as a ``beyond-the-floor'' option under sections 112(d)(2)
and (3). As explained in the several proposed rules, selecting this
option would eliminate all mercury emissions by forcing the remaining
facility to either convert to a non-mercury technology or close its
mercury cell chlor-alkali operations. While we did not in 2021, re-
propose this option under either 112(d)(2) and (3) or (d)(6), we
described this option in detail in the proposed rule's Federal Register
(FR) notice published on January 8, 2021 (86 FR 1362), including the
estimated capital costs, annualized costs and cost effectiveness if it
were to be adopted, and we specifically solicited comments, data, and
other information regarding this proposed decision. Furthermore, in the
January 2021 FR document, we discussed and referred to the previous
2011 proposed rule in which the EPA also analyzed expected capital
costs, annualized costs and cost effectiveness of the then proposed
non-mercury option but for which EPA had not taken final action at the
time of the 2021 proposal.
2. What changed related to the non-mercury option for the Mercury Cell
Chlor-Alkali Plants source category?
    After consideration of public comments received on the 2021
proposed rule and further assessment of the expected costs, we have
changed our 2021 proposed decisions under sections 112(d)(2) and (3)
and (6) regarding the non-mercury option and the final rule includes an
amendment that prohibits mercury emissions from existing mercury cell
chlor-alkali plants as was proposed in 2011 under section 112(d)(2) and
(3). Existing mercury cell chlor-alkali plants will have three years to
comply with this requirement.
3. What key comments did we receive on the non-mercury option, and what
are our responses?
    Comment: One commenter remarked that the EPA must revise MACT
standards when it finds there have been developments in processes,
products, or control technologies under CAA section 112(d)(6) to reduce
emissions to the maximum achievable degree. They further stated that it
is achievable for facilities to switch to membrane cell technology, as
demonstrated by the number of facilities that have already made this
switch since adoption of the 2003 rule, which would eliminate emissions
of mercury. The commenter also stated that because the EPA is also
responding to the 2004 petition for reconsideration in this rulemaking
regarding whether eliminating mercury emissions is achievable, the EPA
must either promulgate a zero-emissions standard or determine that such
as standard is not achievable. The commenter added that under the CAA,
the EPA cannot refuse to set such standards because it does not think
they are ``reasonable,'' but it must set them at the maximum degree of
reduction that is achievable.
    Response: We agree that it is technically achievable for facilities
to switch from mercury cell to membrane cell technology, as there are
many instances of successful switches spanning the last three decades.
We also agree that it is technologically achievable, as a section
112(d)(2) and (3) beyond-floor measure, to require elimination of
mercury emissions from the single remaining operating existing source.
However, we disagree with the commenter's assertion that the EPA must
promulgate a standard solely based on technical achievability in the
context of section 112(d)(6). Section 112(d)(6) requires the EPA to
review and revise emission standards as necessary, considering
developments in practices, processes, or control technologies, but does
not require revisions for all developments that are technically
achievable. Other factors are considered, including cost, economic
impacts, physical limitations of the site, etc.
    Nevertheless, based on consideration of public comments, and after
reassessing the costs and feasibility of converting to the non-mercury
technology, we have determined that the non-mercury option is
technically and economically feasible and is cost effective and
therefore reasonable to impose under both sections 112(d)(2) and (3)
and (d)(6). As explained elsewhere in this preamble, we estimate the
annualized costs to convert to a membrane process would be $2.7 million
per year (2019 dollars), with cost-effectiveness of $21,500 per pound
of reduced mercury emissions. This cost effectiveness is within the
range of cost effectiveness values the EPA has accepted historically
for mercury reduction. For example, in the 2012 Mercury and Air Toxics
(MATS) final rule, the EPA finalized a beyond-the-floor standard for
mercury with a cost effectiveness of $22,496 per pound (based on 2007
dollars), which would be approximately $27,500 per pound based on 2019
dollars. Furthermore, we conclude that conversion to a non-mercury
process is clearly feasible, as demonstrated by the six mercury cell
facilities in the U.S. that have converted to the non-mercury membrane
process since the year 2000. Additionally, non-mercury chlorine
production accounts for more than 98% of chlorine production in the
U.S.
    Comment: One commenter maintained that the EPA's vague
characterizations of costs and its ignorance of current costs for the
one remaining facility to switch to membrane technology did not
constitute an excuse for failing to determine whether the measure is
achievable. The commenter said that the Agency has had 17 years since
the 2004 petition for reconsideration to gather the data it needs, and
any uncertainty about costs due to the EPA's failure to gather the
necessary data is not a lawful or reasonable basis for not setting a
zero-emissions standard for mercury.
    Response: We disagree with the commenter's characterization of our
assessment of the costs of conversion. While the EPA did not commission
a comprehensive detailed study to assess the costs specifically for the
conversion of the West Virginia mercury cell chlor-alkali unit to
convert to membrane cells, the EPA did update the previous analysis to
incorporate new information to ensure that the estimated costs
reflected ``current'' costs expected to be incurred for a conversion.
The commenter did not mention or provide any specific comments on the
updated analysis.
    The foundation for the analysis was the series of evaluations
conducted by the EPA in 2008 through 2010, in support of the 2008 and
2011 proposed rules. The EPA first presented our evaluation of impacts
of requiring conversion of all operating mercury cell

chlor-alkali production plants to non-mercury technology in 2008. Based
on comments received after the June 11, 2008, proposed amendments (73
FR 33258), we updated this analysis and released it for public review
in June 2009. Comments were received on this revised analysis, and a
second revision was released for public review in September 2009. The
EPA received comments on this second revision of the analysis and
issued another revision in April 2010. Therefore, the 2010 analysis,
which was based on extensive research by the EPA, had undergone three
rounds of public review by the environmental community and the industry
before it was relied upon to support the 2011 proposed rule.
    The 2020 update to the 2010 conversion cost analysis involved
several steps to ensure that the cost estimates were current. These
included converting 2010 capital cost estimates, the savings associated
with compliance with the mercury cell room monitoring program, and the
electricity savings, to a 2019 base year. It also included
incorporation of the reported costs of the latest conversion of a
mercury cell facility in the U.S., which was the Ashta facility in Ohio
that completed its conversion in late 2020. In addition, the 2020
analysis considered the conversion cost estimate specifically provided
for the West Virginia facility by the previous owner in public comments
on the 2011 proposal and updated that estimate to base year 2019.
    Comment: One commenter (the owner of the single operating mercury
cell facility) noted that the facility has not revisited the cost
associated with converting to a non-mercury process since 2012, but
they believe it is significantly higher than the EPA's estimate of $69
million.
    Response: While the EPA recognizes that the facility may not have
recently performed an update of the cost to convert their mercury cell
unit to membrane technology, we believe there is sufficient information
available to obtain a reasonable estimate of this cost. In our 2020
analysis, we estimated the conversion costs using three approaches. One
was to base the capital cost of conversion solely on the highest cost
factor (dollars per ton of chlorine production capacity) from the
conversions considered in the 2010 analysis (after adjusting to a 2019
base year). The second approach used the cost factor calculated from
the reported cost for the most recent conversion at the Ashta facility
in Ohio. The cost factor for this Ashta conversion was over 20 percent
higher than the highest cost factor from the previous conversions after
updating them to a 2019 base year. The third approach was to
incorporate the Ashta factor into an average of all the cost factors
for conversions in the U.S. since 2003. These factors, which were in
units of dollars per ton of chlorine production capacity, were then
applied to the site-specific production capacity of the West Virginia
mercury cell unit. The resulting estimates of the capital cost of
conversion of the West Virginia facility using these three approaches
were approximately $76 million, $92 million, and $58 million,
respectively (in 2019 dollars). Given all the site-specific factors
that are inherent in the cost of conversion, we do not believe it is
appropriate to base an estimate on the factor from the conversion of a
single facility. So, we did not select either of the first two options
described above. We also did not want to potentially bias our estimate
low, so we did not select the third option (average factor for five
facilities that have converted since 2003). Therefore, we calculated
the average cost between the three options ($69.3 million) and selected
that average as our estimated cost of conversion for our consideration
for our 2021 proposal. Considering the inflation that has occurred
since 2019, the updated capital cost of conversion estimate is $80.7
million (in 2021 dollars). Our confidence in this estimate was
bolstered by a comparison of this result with the estimate that was
specifically provided earlier in 2011 for the West Virginia facility by
its previous owner. This estimate, when converted to 2019 to be
consistent with the year for our cost analysis, was $69.4 million (or
$80.8 million for 2021 base year). Since the commenter did not provide
any updated information in response to the 2020 analysis and 2021
proposed rule, we continue to maintain that our estimate is a
reasonable estimate of the capital costs of converting the West
Virginia mercury cell unit to membrane cell technology.
    Comment: One commenter stated that the EPA's proposal ignored the
U.S. obligations under the Minamata Convention on Mercury, which is a
global treaty that requires the phase-out of manufacturing processes
using mercury. The commenter remarked that under Article 5(2), the
phase-out date for chlor-alkali production using mercury is 2025,
unless an exemption is filed. The commenter noted that an exemption was
filed for these processes in the U.S., and the phase-out date is now
2030. According to the commenter, since companies are typically given
three years to comply with MACT standards, a final rule requiring the
phase-out of mercury would be required to be promulgated by the end of
2027 for the U.S. to meet its obligations under the Minamata
Convention. The commenter stated that since a final rule in 2021 that
does not require elimination of mercury would put the next 8-year
review completion time at the end of 2029 at the earliest, the U.S.
will then be out of compliance with the Minamata Convention. The
commenter stated that the EPA must issue a new proposal explaining how
the 2030 phase-out deadline will be met.
    Response: We agree with the commenter's summary of the U.S.
obligations under the Minamata Convention agreement. We also agree that
a NESHAP standard adopted under the authority of section 112 of the CAA
is a valid approach to meet this obligation. In fact, during treaty
negotiations, the U.S. specifically concluded that CAA section 112
gives the EPA the authority to require elimination of mercury
emissions. We also agree with the commenter's conclusions about the
timing of when a NESHAP would need to be promulgated. Assuming a 3-year
compliance timeframe would be needed for a final rule requirement that
prohibits mercury emissions, a section 112 NESHAP would need to either
be finalized as part of this review, or a separate ``out of cycle''
review would be needed prior to 2027 to meet the current phase-out date
of 2030 required under the Convention. (More information regarding the
Minamata Convention is available at: https://www.mercuryconvention.org/en/about).
    Comment: One commenter remarked that the environmental impacts the
EPA cites as a reason not to require a zero-emission standard for
mercury are actually environmental benefits. The commenter stated that
the 1,000 pounds of mercury that are discharged to the environment
every year would be eliminated. The commenter also stated that the EPA
ignored the fact that mercury-contaminated piping and equipment must be
removed at some point, and it is just a question of when. The commenter
added that the costs of storing and moving mercury to a secure location
is not a new expense, as the facility made a choice to continue
operations with mercury past the date the Mercury Export Ban of 2008
(Pub. L. 110-414) went into effect in 2013, and it determined at that
point to assume those costs.
    Response: We estimate that the non-mercury requirement would
eliminate just over 125 pounds of mercury released to the atmosphere
per year.

Furthermore, at proposal we stated the following: ``The EPA also
examined the non-air impacts associated with switching from mercury
cell to non-mercury cell processes. For 2019, the West Virginia
facility reported a total of 898.1 pounds of non-air mercury releases.
This consists of 9 pounds to streams/water bodies, 883.3 pounds to
Resource Conservation and Recovery Act, Subtitle C Landfills, and 5.8
pounds to other offsite sources. All these releases would be eliminated
with the conversion to non-mercury cell processes.'' (86 FR 1382-1383)
    We also acknowledge the point made by the commenter regarding the
costs associated with moving the mercury recovered from a conversion
and storing it. Even without a regulatory requirement to eliminate
mercury emissions from existing sources, the mercury cell unit would
eventually reach the end of its useful life and be shut down or
replaced. Since the standards for new and reconstructed sources in
subpart IIIII prohibit mercury emissions, the owner or operator could
not replace the unit with another mercury cell process. Even without
this standard, which has been in place since 2003, it is reasonable to
assume that a new mercury cell facility would not be built. Prior to
the promulgation of subpart IIIII, the use of the outdated mercury cell
technology had been declining for decades and no new mercury cell
facility had been constructed since the early 1970s. Hence, we agree
that the owner most likely recognized this future cost when the
decision was made not to convert prior to the effective date of the
mercury export ban. Therefore, we conclude that the costs of the
mercury storage should not be attributed to the non-mercury option
under this rulemaking.
    The cost of this mercury storage was estimated to be just over
$53,000 per year in our 2020 conversion cost analysis. Removing these
mercury storage costs lowers the overall estimated annual cost, which
includes the annualized capital cost, electricity savings and reduced
compliance costs from $2.77 million to just over $2.7 million. This
improves the cost effectiveness from just over $22,000 per pound of
mercury released to the air to around $21,500 per pound. In addition,
as noted above, it also results in the reduction of around 900 pounds
of mercury releases per year to other media.
    Comment: One commenter registered agreement with the EPA's proposal
to not require the elimination of mercury and stated that the NESHAP
should not include a zero-mercury standard at this time. The commenter
added that the single operating facility operates with low mercury
emissions and pointed out that risks due to mercury are already low and
at acceptable levels. However, another commenter expressed support for
a zero-emission policy and a switch to non-mercury polluting processes
at the West Virginia facility. This commenter stated that while the
current mercury emissions may be in compliance with the 2003 NESHAP's
standards, effort should be made to increase sustainable industrial
processes if possible. According to the commenter, considering the
cost-benefit analysis, it would be more beneficial for the chlor-alkali
plant to transition sooner rather than later because the plant will
eventually have to transition or adopt a zero-mercury emission policy
as our green infrastructure increases. The commenter added that when
considering pollution, especially mercury, the goal should be zero,
regardless of its economic impact. Additionally, the commenter
supported policies that are more proactive in tackling pollution
because accidents can happen and they're typically more of an economic
burden than taking proactive measures. Further, the commenter stated
that even if the data shows no benefits to human health or the
environment from further reducing the mercury emissions at the West
Virginia plant, it would ultimately be one step closer to the national
transition to cleaner, more sustainable industry.
    Response: As discussed above in section IV.A of this preamble, the
first commenter is correct that our conclusion of the section 112(f)
residual risk assessment was that health risks due to emissions of HAP
from the Mercury Cell Chlor-Alkali Plants source category are
acceptable, that the 2003 NESHAP provides an ample margin of safety to
protect public health, and that no additional standards are necessary
to prevent an adverse environmental effect. While the recommendations
of the second commenter generally lack any statutory authority to
implement measures for a ``green infrastructure'' to ``transition to
cleaner, more sustainable industry,'' their point about a transition to
zero mercury pollution is recognized.
    The residual risk assessment conducted under the authority of
section 112(f) is focused on the local impacts (within 50km) directly
resulting from HAP emissions from a NESHAP affected source. This type
of assessment does not necessarily capture all the potential risks or
impacts associated with mercury emissions. Mercury is a highly
neurotoxic contaminant that enters the food web as a methylated
compound, methylmercury. The contaminant is concentrated in higher
trophic levels, including fish eaten by humans. Mercury is emitted to
the air from various anthropogenic and natural sources. These emissions
transport through the atmosphere and eventually deposit to land or
water bodies. This deposition can occur locally, regionally, or
globally, depending on the form of mercury emitted and other factors
such as the weather. The form of mercury emitted from the single
remaining operating plant is estimated to be about 98 percent elemental
and two percent divalent mercury. Gaseous elemental mercury can be
transported very long distances, even globally, to regions far from the
emissions source (becoming part of the global ``pool'') before
deposition occurs. Inorganic ionic (divalent) mercury has a shorter
atmospheric lifetime and can deposit to land or water bodies closer to
the emissions source. Furthermore, elemental mercury in the atmosphere
can undergo transformation into ionic mercury, providing a significant
pathway for deposition of emitted elemental mercury (UNEP, Global
Mercury Assessments, available at: https://www.unep.org/resources/publication/global-mercury-assessment-2018).
    Therefore, even though the estimated risks due to the mercury
emissions are low based on our residual risk assessment, and the
results of the residual risk assessment do not necessitate additional
regulation to meet the requirements of CAA section 112(f), we agree
that there is merit in eliminating mercury emissions where it is
technically and economically feasible to do so, consistent with other
statutory authority and requirements. And, as the second commenter
points out, this is certainly possible in this situation, and the plant
would need to ultimately eliminate mercury emissions anyway in order
for the United States to meet its obligations under the Minamata
Convention.
4. What is the rationale for our final approach for the non-mercury
option?
    As noted above, we are finalizing an amendment that prohibits
mercury emissions from existing mercury cell chlor-alkali plants. Our
rationale for this decision is based on the following points. First,
our re-evaluation of the costs and associated emission reductions
reveal that the cost effectiveness is within the range considered
reasonable by the EPA for mercury and based on our economic analysis,
the estimated annualized costs are only about 0.04 percent of the

annual revenue of the facility's ultimate parent company in 2020 and
therefore the amendment is reasonable as a beyond-floor standard under
section 112(d)(2) and (3). Second, this action will also eliminate the
non-air releases that occur from the remaining mercury cell plant.
Third, using the authority under section 112(d) of the CAA at this time
is the most effective mechanism to ensure the U.S complies with the
Minamata Convention agreement by the 2030 deadline. Finally, as
mentioned above, we conclude that conversion to a non-mercury process
is clearly feasible and has been shown to be a development in
practices, processes and control technologies under section 112(d)(6),
as demonstrated by six facilities in the U.S. that have converted to
the non-mercury membrane process since the year 2000. Some of these
points are discussed in more detail below.
    In response to a comment discussed above, we adjusted the annual
costs to remove the mercury storage cost. This resulted in the cost
effectiveness of the non-mercury option decreasing slightly to $21,500
per pound of mercury emission reduction. While this cost effectiveness
is near the upper end of the range of cost effectiveness values the EPA
has accepted historically for achievable mercury control, the EPA has
previously determined that cost effectiveness values higher than this
are acceptable and achievable. For example, in the 2012 MATS final
rule, the EPA finalized a beyond-the-floor standard for mercury of
$22,496 per pound (based on 2007 dollars), which would be about $27,500
per pound based on 2019 dollars. Therefore, we conclude that the cost
effectiveness of $21,500 per pound of mercury emissions reduction is
reasonable especially given the other factors described above, and we
have decided to finalize the amendment to prohibit mercury emissions
from existing sources as an achievable beyond-floor measure under
section 112(d)(2) and (3).
    As noted above, we evaluated the economic impacts of this amendment
and determined that the impacts are not substantial, with the
annualized costs being less than 0.04 percent of sales for the subject
facility's ultimate parent company (Westlake). We determined that the
environmental benefit of the non-mercury option warranted these
economic impacts.
    The primary reasons provided at proposal for discussing but not re-
proposing the non-mercury option were related to costs, cost
effectiveness, and uncertainties. For example, in the January 2021
proposal FR document, the EPA stated that ``first, mercury emissions
are based on calculations and assumptions regarding the facility's
emissions (no test data are available for this facility), and second,
because there are uncertainties with the cost estimates from the 2011
proposal as being transferable to the remaining facility. In the 2011
proposal, the estimated cost effectiveness was $20,000 per pound for
the industry (see 76 FR 13852, March 14, 2011), but this was
substantially based on the studies conducted for the two no longer
operating sources.'' (86 FR 1378-1379)
    While no additional emissions data based on testing was submitted
in response to the 2021 proposal, we point out that subpart IIIII
requires that measurements of the stack emissions be taken. The
estimates reported by the West Virginia facility that were used in our
analyses for fugitive emissions (121.4 pounds per year) are lower than
the average level of 362 pounds per year per plant found during the
extensive study conducted by the EPA prior to the 2008 proposal (see
description in the June 11, 2008, proposal at 73 FR 33263-33266).
Therefore, if the confidence is lacking regarding these estimates, it
is realistic to consider that emissions, and thus emission reductions,
would likely only be higher. This would result in improved cost
effectiveness values (i.e., the requirements would be more cost
effective), providing further justification for our decision to
finalize the non-mercury option.
    In the 2021 proposal we stated, ``Based on consideration of the
updated costs and cost effectiveness and uncertainties, and given the
passage of time, and the fact that the cost- effectiveness data and
analysis done in 2011 were based on two facilities that are no longer
operating, we question whether those 2011 analyses would still be
transferable to the one remaining operating facility.'' (86 FR 1378)
Upon additional consideration, we have determined that this point is
not relevant to the decision regarding the cost effectiveness of a non-
mercury standard for the West Virginia facility. In 2011, we calculated
an average cost effectiveness for the conversion of the four mercury
cell facilities operating at that time. The range was between $13,000
to $31,000 per pound for the four individual facilities. However, the
estimated cost effectiveness values for the two facilities that closed
prior to 2020 is not determinative of the estimate of the conversion
cost for the West Virginia facility. Also, the cost effectiveness for
these two facilities does not compel what the EPA considers a
reasonable cost effectiveness level for mercury. Therefore, we now
reject the two major points used as rationale in the 2021 proposal for
not accepting and proposing the non-mercury option. We are confident
that the mercury emissions estimates for the West Virginia facility are
reliable and, if anything, are underestimated. We also have determined
that the cost estimate is reasonable and applicable and could be even
more cost effective than presented here due to potential
underestimation of the emissions. Consequently, the non-mercury option
is a reasonable beyond-floor measure under section 112(d)(2) and (3),
and the fact that six mercury cell facilities have converted to non-
mercury membrane technology since 2000 and only a single mercury cell
source remains at a facility that already has two non-mercury chlorine
production units shows that is necessary to revise our existing source
standard to take into account developments in practices, processes and
control technologies.
    Regarding the Minamata Convention on Mercury, this is a global
treaty to protect human health and the environment from the adverse
effects of mercury. It was agreed at the fifth session of the
Intergovernmental Negotiating Committee on mercury in Geneva,
Switzerland on January 19, 2013, and adopted later that year on October
10. The Minamata Convention entered into force on August 16, 2017.
    Major highlights of the Minamata Convention include a ban on new
mercury mines, the phase-out of existing ones, the phase out and phase
down of mercury use in a number of products and processes, control
measures on emissions to air and on releases to land and water, and the
regulation of the informal sector of artisanal and small-scale gold
mining. The Convention also addresses interim storage of mercury and
its disposal once it becomes waste, sites contaminated by mercury, and
health issues.
    Under the Minamata Convention, the U.S. has specifically addressed
mercury cell chlor-alkali production. For example, in the registration
for an extension of the mercury phase out deadline from 2025 to 2030,
the U.S. stated the following:
    ``Pursuant to Article 6, paragraph 1 of the Minamata Convention on
Mercury, the United States hereby registers for an exemption from the
phase-out date listed in Annex B for the use of mercury in chlor-alkali
production.'' \2\ The United States also provides the

following statement explaining the need for the exemption:
---------------------------------------------------------------------------

    \2\ https://www.mercuryconvention.org/en/parties/exemptions.
---------------------------------------------------------------------------

    ``The United States supports the phase-out of mercury use in chlor-
alkali production facilities. It has implemented domestic strategies to
encourage a timely transition to mercury-free alternative technologies
with a view to phasing out all mercury use in domestic chlor-alkali
production facilities. New or reconstructed chlor-alkali production
facilities in the United States are already effectively prohibited from
using mercury under section 112 of the Clean Air Act. See 40 CFR
63.8190. Most mercury cell chlor-alkali facilities in the United States
have already closed or converted. While there were 14 such facilities
in 1998, only two remained as of late 2013. The United States will,
pursuant to Article 6, paragraph 7, withdraw this exemption if that
becomes possible prior to its expiration date.'' \3\
---------------------------------------------------------------------------

    \3\ Ibid.
---------------------------------------------------------------------------

    Therefore, the U.S. is committed to phasing out all mercury
emissions in domestic chlor-alkali facilities by 2030. The EPA is not
aware of any plans by the owner of the lone remaining mercury cell
chlor-alkali facility in West Virginia to close or convert their
mercury cell facility before 2030. Therefore, we have determined that
it is necessary to require this action to ensure the facility converts
or closes the mercury cell chlor-alkali production process in order to
eliminate mercury emissions and section 112 of the CAA provides an
appropriate regulatory mechanism to enact such a requirement to
eliminate emissions. The two main options regarding timing are: (1)
Promulgate a non-mercury standard at this time under section 112(d)(2)
and (3) and/or section 112(d)(6); or (2) promulgate a non-mercury
standard by fall 2027 (i.e., before the next 8-year cycle for a
technology review required by section 112(d)(6)).
    As pointed out by commenters, the next 8-year review will not be
required until 2030. If a non-mercury standard was promulgated in 2030
and included the 3-year compliance date allowed by CAA section 112, the
phase-out would not occur in time to comply with the 2030 deadline. We
do not think it is prudent to plan a separate ``out of cycle'' review
to promulgate a non-mercury standard in 2027, especially since the
review shows that the non-mercury standard is technologically feasible,
cost effective and will not impose significant economic impacts at this
time, and there is no reason to think a decision would be any different
in 2027. Therefore, we concluded that the best option to ensure
compliance with the Minamata Convention is to promulgate a non-mercury
standard at this time.
    We recognize that we did not specifically propose this option in
the January 2021 proposal. However, we did include it as an option that
was considered and described it in detail, we provided our analysis of
this option and specifically requested comment on the option.
Specifically, we stated the following:
    ``However, we are soliciting comments, data, and other information
regarding these proposed decisions, including data and information
regarding the costs, cost effectiveness, non-air, and economic impacts
and other relevant information regarding whether the NESHAP should
include a non-mercury standard as either a beyond-the-floor MACT
standard or a revised standard under the technology review, and whether
the proposed work practices for chlorine emissions and proposed
amendments to the mercury work practices would be necessary if a non-
mercury standard were to be adopted.''
    EPA also stated that ``We intend to consider any such submitted
data and information, in addition to the data and information contained
in the records for the 2008 and 2011 proposals and in this proposal, in
reaching final conclusions under CAA sections 112(d)(2) and (6)
regarding a non-mercury standard.'' (86 FR 1383)
    Furthermore, the EPA proposed the non-mercury option in 2011 and
referred to this 2011 proposal in the January 2021 FR document.
Therefore, we provided sufficient notice of the potential that we would
finalize a non-mercury option, and we are finalizing the non-mercury
requirement based on a logical outgrowth of comments on our proposal
and the record that public commenters had an opportunity to review and
address.

C. Technology Review for the Mercury Cell Chlor-Alkali Plants Source
Category

1. What did we propose pursuant to CAA section 112(d)(6) for the
Mercury Cell Chlor-Alkali Plants source category?
    Pursuant to CAA section 112(d)(6), we proposed amendments to the
rule that would have required the combination of both a cell room
monitoring program to continuously monitor mercury vapor in the cell
room and a suite of equipment standards and work practices to reduce
fugitive mercury emissions. This is different from the NESHAP
promulgated in 2003, which required either the equipment standards and
work practices or the cell room monitoring program. As described above,
we also evaluated the non-mercury option under our section 112(d)(6)
technology review.
2. How did the technology review change for the Mercury Cell Chlor-
Alkali Plants source category?
    As discussed above in section IV.B, we changed our decision related
to the non-mercury option and are promulgating a prohibition of mercury
emissions from the source category. The result of this final amendment
prohibiting mercury emissions will be that there will no longer be any
operating mercury cell chlor-alkali plants in the U.S. after May 6,
2025.
3. What key comments did we receive on the technology review, and what
are our responses?
    The only comment received on our proposed technology review, other
than those related to the non-mercury option discussed above in section
IV.B.3, was one from the facility that clarified that the existing
continuous monitor analyzers for mercury at the facility are capable of
detecting mercury concentration of 0.1 [micro]g/m\3\, which would meet
the EPA's proposed detection requirements.
4. What is the rationale for our final approach for the technology
review?
    The rationale for our final decision regarding the non-mercury
option is discussed above in section IV.B.4. Regarding the cell room
monitoring program and equipment and work practice standards to reduce
fugitive mercury emissions, the facility complies with the fugitive
mercury standards by operating a continuous cell room monitoring
program in accordance with paragraph 63.8192(g) as an alternative to
the equipment standards and work practices in paragraphs 63.8192(a)
through (d). However, while not required to do so under the NESHAP
promulgated in 2003, the facility also implements those equipment
standards and work practices. Therefore, the EPA determined that the
combination of implementing a cell room monitoring program and
performing work practices constitutes a development in emissions
control practices and is finalizing the proposed requirement that both
a cell room monitoring program and equipment and work practices be
implemented during the period of up to 3 years before the facility
converts the mercury cell process to a non-mercury process or closes
the mercury cell process.

D. Amendments Pursuant to Sections 112(d)(2) and (3) and (h) for the
Mercury Cell Chlor-Alkali Plants Source Category

1. What did we propose pursuant to CAA section 112(d)(2) and (3) and
(h) for the Mercury Cell Chlor-Alkali Plants source category?
    Pursuant to CAA sections 112(d)(2) and (3) and (h), in 2021 we
proposed amendments to the rule that would have required a leak
detection and repair program to identify chlorine equipment leaks in
the cell room and throughout the other parts of the mercury cell chlor-
alkali production facility affected source that handle and process the
chlorine gas produced. The proposed rule would have also required that
chlorine monitors be installed and operated continuously throughout the
affected source and that each time one of these sensors measured a
chlorine concentration of 2 ppmv or greater, a complete inspection for
leaks of all equipment containing 5 percent chlorine by volume would
have been required within 1 hour of detection.
    In addition, we evaluated the beyond-the-floor non-mercury option
under our consideration of section 112(d)(2) and (3); however, we did
not propose the non-mercury standard in the January 8, 2021 proposal.
2. How did the decision related to CAA section 112(d)(2) and (3) change
for the Mercury Cell Chlor-Alkali Plants source category?
    As discussed above in section IV.B, we changed our decision related
to the non-mercury option and are promulgating a prohibition of mercury
emissions from the source category. The result of this final amendment
prohibiting mercury emissions will be that there will no longer be any
operating mercury cell chlor-alkali plants in the U.S. after May 6,
2025.
3. What key comments did we receive on our proposed decision related to
CAA sections 112(d)(2) and (3) and (h), and what are our responses?
    As discussed above in section IV.B.3, comments were received
regarding the proposed determination not to require the non-mercury
option as a beyond-the-floor requirement. Comments were also received
related to the proposed fugitive chlorine requirements. In addition,
comments were received claiming that standards should have been
proposed for emissions of HCl. These comments, along with responses
from the EPA, are provided below in this section.
    Comment: The single operating facility provided several comments
regarding the proposed requirements to reduce chlorine emissions. While
they corrected the EPA's assumption that the cell room was under
negative pressure, they noted that most of the equipment containing
chlorine gas is under negative pressure, which would be excluded from
the proposed leak detection requirements. They noted that the facility
already complies with most of the proposed fugitive chlorine
requirements, and they explained how they would comply with the
additional requirements. They agreed that the proposed olfactory
observations are appropriate versus visual or auditory inspections, due
to the low odor threshold of chlorine. They did, however, register
concern about the chlorine leak repair requirements, noting that final
repairs to leaks from some causes may take more than one day to
complete, as required in the proposal. They also provided responses to
the EPA's requests for comments regarding the proposed requirements for
continuous chlorine sensors and the proposed 2 parts per million by
volume (ppmv) action level and averaging time. In response to the EPA's
request for comment regarding whether the EPA should specify sensor
placement locations, they expressed concern about placing chlorine
sensors in the cell room, as they stated that the high magnetic field
in the cell room has historically caused unreliable transmitter
responses. They indicated that, if the EPA finalized a requirement to
place chlorine sensors in the cell room, additional time would be
needed to comply with the standard, as the facility would need to
evaluate whether the use of a chlorine sensor(s) in the cell room is
technically feasible and, if feasible, to procure and install the
sensors.
    Response: The EPA appreciates the effort provided by the commenter
to carefully review the proposed fugitive chlorine requirements, to
provide thoughtful comments, and to put forth preliminary ideas on how
they would comply. We also appreciate the concerns raised about the
repair timing requirement and the placement of chlorine sensors in the
cell room. Based on these comments, we have revised the final
requirements to add time to make repairs, which would allow time to
obtain equipment that is not kept onsite, by increasing the time for
final repairs to be made from 24 to 72 hours. Further, based on these
comments and the technical feasibility of placing sensors in certain
locations, we have not added requirements stipulating sensor locations
in the final rule. Finally, we agree that an action level for equipment
inspections based on a single sensor reading may not be indicative of a
problem that warrants special investigation. Accordingly, we have
revised the action level that triggers an inspection of all chlorine-
containing equipment to be detection by a sensor of a one-hour average
chlorine concentration of 2 ppmv or greater.
    Comment: One commenter stated that the EPA must set emissions
standards for HCl. The commenter contended that even if the HCl
emissions are from direct synthesis HCl production units, these units
are part of the mercury cell chlor-alkali plant and must be regulated.
The commenter stated that these units would be affected sources because
they are ``cell rooms and ancillary operations used in the manufacture
of product chlorine, product caustic, and by-product hydrogen at a
plant site'' and ``processes and associated operations needed for
mercury recovery from wastes at a plant site.''
    Response: We disagree with the commenter's rationale of why the
direct synthesis HCl production units would be part of an affected
source under subpart IIIII. They are not part of the cell room or the
ancillary operations used in the manufacture of product chlorine,
product caustic, or by-production hydrogen. In fact, the HCl production
units are downstream operations from the chlor-alkali process, as they
use the product chlorine and by-product hydrogen to create HCl.
Additionally, these units are not associated with the processes needed
for the recovery of mercury.
    While not cited by the commenter, the EPA has previously considered
direct synthesis HCl units co-located with chlor-alkali plants to be
part of the chlor-alkali plant. In the July 3, 2002, proposal for the
chlorine production source category, the EPA stated ``Since chlor-
alkali processes produce both chlorine and hydrogen, it is common for a
direct synthesis HCl production unit to be incorporated into a chlor-
alkali facility. Therefore, we consider these direct synthesis HCl
production units to be a part of the chlor-alkali facilities.'' (67 FR
44713). The HCl (and chlorine) emissions from the co-located direct
synthesis HCl plants were included in the risk assessment that led to
the EPA's decision in 2003 not to develop any NESHAP for non-mercury
cell chlor-alkali plants and to delete the non-mercury subcategory.
Further, because these units were considered part of the deleted non-
mercury cell chlorine production subcategory, they were specifically
exempted from the HCl

NESHAP, 40 CFR subpart NNNNN, at 63.8985(d).
    At the West Virginia facility, there are three chlor-alkali units:
The mercury cell unit and two diaphragm cell units. According to the
air permit for the facility, the diaphragm cell units produce
approximately four times as much chlorine as the mercury cell unit.
Therefore, if the HCl production units were assigned to one of the
chlorine production subcategories based on the contribution of the
chlorine and hydrogen contributed, they would be considered part of the
non-mercury cell subcategory of chlor-alkali plants. In addition, when
the EPA finalized the decision to delete the non-mercury subcategory on
December 19, 2003, we stated ``we have clarified that chlorine and HCl
emissions from the absorber vents of direct synthesis HCl production
units at chlor-alkali facilities, as well as the associated storage
tanks and transfer operations specified above, are included in the non-
mercury cell chlorine production subcategory . . .'' (68 FR 70948)
    As shown through this cited history, the EPA has clearly
established that HCl direct synthesis units are not part of the mercury
cell chlor-alkali source category, and we are not pursuing their
regulation under subpart IIIII.
    Comment: One commenter stated that the EPA proposed to limit the
applicability of the rule with changes to -63.8182, -63.8184(a) and
definitions in -62.8266. The commenter asserted that the EPA did not
provide any explanation or justification for these proposed changes,
which is a violation of the CAA and makes it impossible to determine
what the EPA is intending to accomplish. The commenter's interpretation
was that the EPA was changing the existing regulation to avoid
regulating HCl emissions from the plant. The commenter stated that if
that is the case, the EPA is acting unlawfully by attempting to bypass
its statutory obligations to regulate all HAP and HAP emission points
within a source category.
    Response: The commenter is correct that these changes were not
explained in the January 2021 proposal. They were changes that were
proposed in both the 2008 proposal and the 2011 supplemental proposal,
with the purpose of ensuring that a mercury thermal recovery unit
affected source at a site where the mercury cell production facility
was either converted or closed would continue to be subject to the
emission limitations while processing the wastes from the closed
mercury cell plant. Since the single remaining mercury cell chlor-
alkali plant does not have a thermal mercury recovery unit, these
changes are not necessary and should not have been included. They are
in no way related to HCl emissions from the plant. In fact, as noted
above, these amendments were holdovers from the 2008 proposal and the
2011 supplemental proposal when only mercury emissions were under
consideration.
4. What is the rationale for our final approach for the CAA sections
112(d)(2) and (3) and (h)?
    The rationale for our final decision regarding the non-mercury
option is discussed above in section IV.B.4. For the fugitive chlorine
work practices, the facility voluntarily implements work practices that
are consistent with the proposed requirements and represents the MACT
floor. As these chlorine emissions are fugitive in nature resulting
from potential equipment leaks, they cannot be emitted through a
conveyance designed and constructed to emit or capture such pollutant
or measured. Therefore, we are finalizing the proposed amendments
requiring work practices to minimize chlorine emissions. Further, as
discussed above, we are not developing standards under section
112(d)(2) and (3) for the HCl emissions from the direct synthesis HCl
production units at the West Virginia site.

E. Amendments addressing emissions during periods of startup, shutdown,
and malfunction and other topics?

1. What did we propose related to emissions during periods of startup,
shutdown, and malfunction and other topics?
    We proposed revisions related to emissions during periods of
startup, shutdown, and malfunction (SSM); provisions for electronic
submission of performance test results, performance evaluation reports,
and Notification of Compliance Status (NOCS) reports; and corrections
of various errors in compliance provisions in the NESHAP.
2. How did the decision related to emissions during periods of startup,
shutdown, and malfunction and other topics change?
    No changes have been made regarding our decisions concerning
periods of SSM and the corrections of various compliance provisions in
the current rule. For submission of performance test results,
performance evaluation reports, and Notification of Compliance Status
(NOCS) reports, we have determined it is necessary for the facility to
switch to electronic reporting, considering the timing of the final
non-mercury emission standard and related upcoming closure or
conversion of the one remaining mercury cell chlor-alkali unit.
3. What key comments did we receive on proposed decision related to
emissions during periods of startup, shutdown, and malfunction and
other topics?
    Comment: One commenter relayed several concerns regarding the
proposed startup, shutdown, and malfunction provisions. According to
the commenter, higher mercury emissions may occur during startup due to
the hydrogen vent system and its control device, which will cause
compliance concerns until alternative work practices can be developed
to reduce emissions from this system. The commenter stated, at the time
they submitted public comments, that the control device cannot be
operated until the exhaust stream composition can be regulated, and the
facility would need additional time to evaluate operational methods to
improve operation of the control device. The commenter added that
additional time would also be needed to determine the modifications
necessary to reduce emissions during startup, to develop and implement
a recordkeeping system, and perform operator training. The commenter
requested a time frame of 12 months rather than 6 months for compliance
with all the proposed SSM requirements.
    Response: To understand the commenter's concerns better and to
determine whether a different standard was needed for startup periods,
the EPA had a teleconference meeting with the commenter to discuss the
issue. During this discussion, the commenter indicated that the
facility had found a way to comply with the emissions standards at all
times, including startup. The notes of the meeting are in the docket
for this rulemaking (EPA-HQ-OAR-2020-0560). Therefore, with the issue
resolved, the EPA is finalizing the proposed requirements that the
emissions limits apply at all times and no separate requirements are
necessary for periods of startup, and further, no additional time is
necessary or provided for compliance.
    Comment: One commenter supported electronic reporting in general
but stated a preference to submit any such information in PDF format.
    Response: Given that the facility could operate for up to 3 more
years before it converts to a non-mercury process or shut down, we have
decided

to require the facility to switch to electronic reporting.
    Comment: One commenter noted that the EPA proposed to add a
performance testing requirement at 40 CFR 63.8232(a). The commenter
believes that the annual calibration testing at the facility satisfies
the requirements of a performance test, and additional performance
testing is not needed.
    Response: The commenter misinterpreted the proposed changes to 40
CFR 63.8323(a), which did not add a new performance testing
requirement. Rather, these proposed changes clarified the conditions
under which the performance test must be conducted. These changes
establish that performance tests must be conducted during normal
operations and remove a reference to 40 CFR 63.7(e)(1), which conflicts
with the requirement to comply with the standards at all times,
including during periods of SSM. As these requirements are simply
clarifying performance test conditions and ensuring the standards are
met at all times, we are finalizing the revised provisions as proposed.
4. What is the rationale for our final approach for requirements
related to emissions during periods of startup, shutdown, and
malfunction and other topics?
    The rationale for our final decision regarding the non-mercury
option is discussed above in section IV.B.4. As discussed in the
responses in the previous section, we are finalizing the proposed
electronic reporting amendments for the reasons described above.
Furthermore, we have not changed our final approach to the requirements
for periods of SSM, and we are finalizing these requirements as
proposed based on the considerations described above.

F. Public Notice and Comments

    In addition to the comments on the proposal, one commenter objected
to the EPA's decision not to publish the proposed rule amendments in
the Federal Register.
    Comment: The commenter observed that the EPA proposed significant
changes to the regulatory language, but these changes were not in the
EPA's proposed rule. The commenter remarked that the CAA and the
Administrative Procedures Act (APA) both make plain that proposed rules
must be published in the Federal Register (42 U.S.C. 7607(d)(3); 5
U.S.C. 553(b)). Further, the commenter stated that the CAA requires the
EPA to include a summary of the major legal interpretations and policy
considerations underlying its proposed rules, and the EPA did not
provide this explanation nor any explanation for its proposed changes
to the regulatory text. The commenter states that if the EPA wishes to
make changes to the Code of Federal Regulations, it must withdraw this
proposal, publish the proposed changes in the Federal Register and
provide a new opportunity for public comment.
    Response: The proposal met all APA and CAA notice and comment
requirements. Nothing in the APA or the CAA, including the language the
commenter cites, requires the EPA to publish proposed rule text in the
Federal Register. The commenter suggests that because the EPA did not
publish the proposed rule text, the EPA failed to meet the CAA
307(d)(3) requirement to publish a ``notice of proposed rulemaking.''
However, the requirement to publish a ``notice of proposed rulemaking''
is not a requirement to publish ``proposed rule text.'' Section
307(d)(3) specifies the required elements of a ``notice of proposed
rulemaking'' and ``proposed rule text'' is not a required element. The
elements the commenter cites that are required to be included in the
notice of proposed rulemaking (a ``statement of basis and purpose,''
``a summary of . . . the major legal interpretations and policy
considerations underlying the proposed rule, etc. . .'') were included,
and commenter does not suggest otherwise.
    The APA does not require publication of proposed rule text in the
Federal Register either. Section 553(b)(3) of the APA provides that a
notice of proposed rulemaking shall include ``either the terms or
substance of the proposed rule or a description of the subjects and
issues involved.'' (emphases added). Thus, the APA clearly provides
flexibility to describe the ``subjects and issues involved'' as an
alternative to inclusion of the ``terms or substance'' of the proposed
rule. See also Rybachek v. U.S. E.P.A., 904 F.2d 1276, 1287 (9th Cir.
1990). (The EPA's failure to propose in advance the actual wording of a
regulation does not make the regulation invalid where the EPA's
discussion of the regulatory provisions ``clearly describe `the
subjects and issues involved.' '').
    The commenter claims that the EPA did not publish ``any explanation
for its proposed changes''. However, the commenter does not identify
any specific regulatory text that was not explained or specify any
deficiency in any explanation of regulatory text in the Federal
Register document. Such a generalized objection is not sufficiently
specific. See, e.g., Appalachian Power Co. v. E.P.A., 251 F.3d 1026,
1036 (D.C. Cir. 2001) (`` `An objection must be made with sufficient
specificity reasonably to alert the agency.' '' (quoting Tex Tin Corp.
v. EPA, 935 F.2d 1321, 1323 (D.C. Cir. 1991)).
    The commenter makes a vague assertion that the EPA's approach was
prejudicial to the ability of the public to be able to find and comment
on the proposed regulatory changes but does not claim any actual
difficulty in finding or commenting on the proposed rule language. The
EPA approach was not prejudicial to the commenter or any member of the
public. The notice of proposed rulemaking clearly explained that the
proposed amendatory language and a redline strikeout version of the
subpart IIIII showing proposed changes were available in the docket and
on EPA's website: https://www.epa.gov/stationary-sources-air-pollution/mercury-cell-chloralkali-plants-national-emissions-standards.
    The proposed changes to the CFR that would be necessary to
incorporate the changes proposed in this action are set out in an
attachment to the memorandum titled Proposed Regulation Edits for 40
CFR part 63, subpart IIIII, available in the docket for this action
(EPA-HQ-OAR-2020-0560). The document includes the specific proposed
amendatory language for revising the CFR and, for the convenience of
interested parties, a redline version of the regulation.
    Although the EPA's recent practice has generally been to publish
proposed amendatory regulatory text, the EPA's practice has varied.
See, e.g., Hazardous Air Pollutants: Proposed Regulations Governing
Constructed, Reconstructed or Modified Major Sources, 59 FR 15504
(April 1, 1994) (``The proposed regulatory text is not included in the
Federal Register document, but is available in Docket No. A-91-64 or by
request from the EPA contact persons designated earlier in this note.
The proposed regulatory language is also available on the technology
Transfer Network (TTN), of EPA's electronic bulletin boards.'');
Federal Standards for Marine Tank Vessel Loading and Unloading
Operations and National Emission Standards for Hazardous Air Pollutants
for Marine Tank Vessel Loading and Unloading Operations, 59 FR 25004
(May 13, 1994) (``The proposed regulatory text and other materials
related to this rulemaking are available for review in the docket.'').
And even when we do include the proposed text in the Federal Register,
we often include a redline version of proposed regulations in the
docket for

rulemakings to assist the public in understanding the proposed
regulatory changes. In our experience, stakeholders find the redline
version far more useful than the proposed amendatory language in the
format required by the Office of the Federal Register. Although
appropriate for the task of revising the Code of Federal Regulations,
this language can be difficult to assess without the accompanying full
regulatory text. Given this and given that we rarely receive comments
on the proposed amendatory language or on proposed regulatory language
at all, we determined that for rulemakings such as these, it would be
more efficient to take the approach here of making both easily
accessible but not including the proposed amendatory text in the
document.

V. Summary of Cost, Environmental, and Economic Impacts and Additional
Analyses Conducted

A. What are the affected facilities?

    There is one facility affected by this action, which is the one
remaining mercury cell chlor-alkali facility operating in the U.S. This
facility is located in West Virginia.

B. What are the air quality and other environmental impacts?

    The air quality impacts of this final action will be the
elimination of approximately 125 pounds of mercury emissions annually.
In addition to this air quality impact, this action will result in the
elimination of around 900 pounds of mercury that are released annually
to other media.
    In addition, it is estimated that the conversion of the remaining
mercury cell facility to membrane cells will result in an energy
savings of around 25 percent which results in an estimated cost savings
of around $1.5 million per year.

C. What are the cost impacts?

    The capital cost of complying with the promulgation of the non-
mercury requirement is estimated to be $69.4 million if the facility
chooses to convert its mercury unit to a non-mercury process rather
than rely on its two existing non-mercury units. The total estimated
annual costs, including the annualized capital costs minus the savings
realized from the lower electricity needs and the savings related to
the elimination of the burden of the environmental regulations
associated with mercury, are $2.7 million per year in 2019 dollars.
Table 3 presents the estimated annual cost components for conversion
from mercury cell to membrane cell technology.

  Table 3--Total Annual Cost of Conversion of the West Virginia Mercury
                         Cells to Membrane Cells
                                 [2019$]
------------------------------------------------------------------------
                                                          Annual cost ($/
                  Annual cost component                         yr)
------------------------------------------------------------------------
Capital Recovery........................................      $4,764,982
Mercury Storage.........................................          53,364
Compliance Savings......................................        -546,572
Electricity Savings.....................................      -1,504,893
                                                         ---------------
    Total Annual........................................       2,766,880
------------------------------------------------------------------------

D. What are the economic impacts?

    The net present value of the estimated cost impacts of the final
amendments to the Mercury Cell Chlor-Alkali NESHAP is $43.0 million,
discounted at a 7 percent rate to 2020 over a 20-year analytic time
frame from 2021 to 2040 in 2019 dollars. Using a 3 percent discount
rate, the net present value of the estimated cost impacts is $39.4
million. The equivalent annualized value, which is a measure of the
annualized costs of the final rule consistent with the net present
value, is $4.0 million and $2.6 million for 7 and 3 percent discount
rates respectively.
    As stated previously in section B.3., the estimated total annual
costs are $2.7 million for the Westlake facility. Based on our
analysis, the estimated annualized costs are only about 0.04 percent of
the annual revenue of the facility's ultimate parent company in 2020.
Since the estimated cost impacts are minimal, no significant economic
impacts to the ultimate parent company nor its consumers are
anticipated due to the final amendments. For additional details on the
economic impact analysis please see the memorandum entitled Economic
Impact Analysis for the Final Mercury Cell Chlor-Alkali National
Emission Standard for Hazardous Air Pollutants (NESHAP) Beyond-Floor
Determination and Risk and Technology Review (RTR) available in the
docket (EPA-HQ-OAR-2020-0560).

E. What are the benefits?

    The EPA anticipates a complete elimination of mercury emissions at
the one remaining mercury cell chlor-alkali plant as a result of the
final amendments to the Mercury Cell Chlor-Alkali Plants NESHAP. This
is estimated to be a reduction of 125 pounds of mercury emitted to the
atmosphere annually and approximately 900 pounds of mercury released
annually to other media. EPA has not monetized the health benefits of
reduced mercury emissions due to this rulemaking due to the lack of
site specific data and insufficient economic research to support the
valuation of the health impacts often associated with exposure to
individual HAP. For the 2022 proposed rule for the Mercury Air Toxics
Standard (MATS) EPA did develop bounding estimates for the risk and
associated dollar valuation associated with mercury emitted from U.S.
Electric Utility Steam Generating Units. These estimates focused on
exposure of the general population to methylmercury through commercial
fish consumption and included IQ loss for children exposed in-vitro and
adult myocardial infarction (MI)-related mortality. These bounding
estimates are subject to uncertainty which is discussed in the rule
language.\4\ While the risk assessment conducted for the RTR indicates
that risks from the source category are already low, future risks from
this source category will be reduced to zero. Furthermore, as described
above, this action will eliminate the releases of mercury to the global
pool from this source.
---------------------------------------------------------------------------

    \4\ National Emission Standards for Hazardous Air Pollutants:
Coal- and Oil-Fired Electric Utility Steam Generating Units--
Revocation of the 2020 Reconsideration, and Affirmation of the
Appropriate and Necessary Supplemental Finding; Notice of Proposed
Rulemaking (87 FR 7624, February 9, 2022).
---------------------------------------------------------------------------

F. What analysis of environmental justice did we conduct?

    Consistent with EPA's commitment to integrating environmental
justice (EJ) in the agency's actions, and following the directives set
forth in multiple Executive Orders, the Agency has carefully considered
the impacts of this action on communities with EJ concerns. For this
action, we performed a demographic analysis, which is an assessment of
risks to individual demographic groups of the populations living within
5 kilometers (km) and within 50 km of the single Mercury Cell Chlor-
Alkali facility associated with this rule. While there are three
demographic groups (i.e., over age 25 without a high school diploma,
those below the poverty level, and those aged 65 and up) around this
facility that are higher than the national average, we find that no one
is exposed to a cancer risk at or above 1-in-1 million or to a chronic
noncancer TOSHI greater than 1. As such, the EPA determined that this
action provides an ample margin of safety to protect public health for
all populations, including communities already overburdened by
pollution. Following is a more detailed description of how the agency
considers

EJ in the context of regulatory development.
    Executive Order 12898 directs the EPA to identify the populations
of concern who are most likely to experience unequal burdens from
environmental harms; specifically, populations of people of color, low-
income populations, and indigenous peoples (59 FR 7629, February 16,
1994). Additionally, Executive Order 13985 is intended to advance
racial equity and support underserved communities through federal
government actions (86 FR 7009, January 20, 2021). Executive Order
14008 further declares a policy ``to secure environmental justice and
spur economic opportunity for disadvantaged communities that have been
historically marginalized overburdened by pollution and under-
investment in housing, transportation, water and wastewater
infrastructure, and health care'' (86 FR 7619, February 1, 2021). The
EPA defines EJ as ``the fair treatment and meaningful involvement of
all people regardless of race, color, national origin, or income with
respect to the development, implementation, and enforcement of
environmental laws, regulations, and policies \5\''. The EPA further
defines the term fair treatment to mean that ``no group of people
should bear a disproportionate burden of environmental harms and risks,
including those resulting from the negative environmental consequences
of industrial, governmental, and commercial operations or programs and
policies''. In recognizing that people of color and low-income
populations often bear an unequal burden of environmental harms and
risks, the EPA continues to consider ways of protecting them from
adverse public health and environmental effects of air pollution.
---------------------------------------------------------------------------

    \5\ See https://www.epa.gov/environmentaljustice.
---------------------------------------------------------------------------

    To examine the potential for any environmental justice issues that
might be associated with the source category, we performed a
demographic analysis, which is an assessment of risks to individual
demographic groups of the populations living within 5 kilometers (km)
and within 50 km of the facilities. In the analysis, we evaluated the
distribution of HAP-related cancer and noncancer risks from the Mercury
Cell Chlor-Alkali Plants source category across different demographic
groups within the populations living near facilities.
    As mentioned above, the results of the demographic analysis for the
source category indicate that three demographic groups included in the
analysis are higher than the national average in percentage terms
within 5 km of the facility.\6\ These groups include those over 25
without a high school diploma (17 percent versus 14 percent
nationally), those below the poverty level (25 percent versus 14
percent nationally) and those aged 65 and up (18 percent versus 14
percent nationally). When examining the risk levels of those exposed to
emissions from Mercury Cell Chlor-Alkali plants, we determined that no
one is exposed to a cancer risk at or above 1-in-1 million or to a
chronic noncancer TOSHI greater than 1. The methodology and the results
of the demographic analysis are presented in a technical report, Risk
and Technology Review--Analysis of Demographic Factors for Populations
Living Near Mercury Cell Chlor-Alkali Plants Source Category
Operations, which is available in the docket.
---------------------------------------------------------------------------

    \6\ When the demographic analysis was completed in mid-2020,
there were 2 facilities in the mercury cell chlor-alkali source
category and both were subject to 40 CFR part 63, subpart IIIII.
However, in late 2020 one of those facilities converted to a non-
mercury process. Therefore, currently only one facility remains in
the source category.
---------------------------------------------------------------------------

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

    The EPA does not believe the environmental health or safety risks
addressed by this action present a disproportionate risk to children.
The health risk assessments for this action are contained in the
document titled Residual Risk Assessment for the Mercury Cell Chlor-
Alkali Plants Source Category in Support of the 2021 Risk and
Technology Review Final Rule, available in the docket (Docket ID No.
EPA-HQ-OAR-2020-0560).

VI. Statutory and Executive Order Reviews

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

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

    This action is a significant regulatory action that was submitted
to the Office of Management and Budget (OMB) for review because it
raises novel legal or policy issues. Any changes made in response to
OMB recommendations have been documented in the docket.

B. Paperwork Reduction Act (PRA)

    The information collection activities in rule have been submitted
for approval to OMB under the PRA. The Information Collection Request
(ICR) document that the EPA prepared has been assigned EPA ICR number
2046.11. You can find a copy of the ICR in the docket for this rule,
and it is briefly summarized here. The information collection
requirements are not enforceable until OMB approves them.
    The information requirements in this rulemaking are based on the
notification, recordkeeping, and reporting requirements in the NESHAP
General Provisions (40 CFR part 63, subpart A), which are mandatory for
all operators subject to national emission standards. These
notifications, reports, and records are essential in determining
compliance, and are specifically authorized by CAA section 114 (42
U.S.C. 7414). All information submitted to the EPA pursuant to the
recordkeeping and reporting requirements for which a claim of
confidentiality is made is safeguarded according to Agency policies set
forth in 40 CFR part 2, subpart B.
    The EPA is finalizing amendments to eliminate the SSM plan and
reporting requirements; add requirements for electronic reporting of
notifications and reports and performance test results; and add a
reporting requirement for meeting the mercury emissions prohibitions.
This information will be collected to assure compliance with the
Mercury Cell Chlor-Alkali Plants NESHAP.
    Respondents/affected entities: The respondents to the recordkeeping
and reporting requirements are owners or operators of flexible
polyurethane foam fabrication operations subject to 40 CFR part 63,
subpart IIIII.
    Respondent's obligation to respond: Mandatory (40 CFR part 63,
subpart IIIII).
    Estimated number of respondents: 1 facility.
    Frequency of response: Initially, occasionally, and semi-annually.
    Total estimated burden: 3,567 total hours (per year). Burden is
defined at 5 CFR 1320.3(b).
    Total estimated cost: $457,200 (per year), includes $29,200
annualized capital or operation & maintenance costs.
    An agency may not conduct or sponsor, and a person is not required
to respond to, a collection of information unless it displays a
currently valid OMB control number. The OMB control numbers for the
EPA's regulations in 40 CFR are listed in 40 CFR part 9. When OMB
approves this ICR, the Agency will announce that approval in the
Federal Register and publish a technical amendment to 40 CFR part 9 to
display the OMB control number for the

approved information collection activities contained in this final
rule.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic
impact on a substantial number of small entities under the RFA. This
action will not impose any requirements on small entities. The ultimate
parent company for the single affected facility in the source category
is not a small entity given the Small Business Administration small
business size definition for this industry (1,000 employees or greater
for NAICS 325180).

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain an unfunded mandate of $100 million or
more as described in UMRA, 2 U.S.C. 1531-1538, and does not
significantly or uniquely affect small governments. While this action
creates an enforceable duty on the private sector, the cost does not
exceed $100 million or more in any one year.

E. Executive Order 13132: Federalism

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

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

    This action does not have tribal implications as specified in
Executive Order 13175. The mercury cell chlor-alkali plant affected by
this final action is not owned or operated by tribal governments or
located within tribal lands. Thus, Executive Order 13175 does not apply
to this action.

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

    This action is not subject to Executive Order 13045 because it is
not economically significant as defined in Executive Order 12866, and
because the EPA does not believe the environmental health or safety
risks addressed by this action present a disproportionate risk to
children. This action's health and risk assessments are contained in
section IV.A of this preamble and the document, Residual Risk
Assessment for the Mercury Cell Chlor-Alkali Plants Source Category in
Support of the 2021 Risk and Technology Review Final Rule, which is
available in the docket for this rulemaking.

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

    This action is not a ``significant energy action'' because it is
not likely to have a significant adverse effect on the supply,
distribution, or use of energy. New standards are proposed for 40 CFR
part 63, subpart IIIII to limit mercury and Cl emissions from mercury
cell chlor-alkali plants. The proposed limits will have lower
electricity costs for the one affected facility so it will not have a
significant adverse effect on the supply, distribution, or use of
energy.

I. National Technology Transfer and Advancement Act (NTTAA)

    This rulemaking does not involve technical standards.

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

    The EPA believes that this action does not have disproportionately
high and adverse human health or environmental effects on minority
populations, low-income populations, and/or indigenous peoples, as
specified in Executive Order 12898 (59 FR 7629, February 16, 1994).
    The documentation for this decision is contained in the technical
report titled, Risk and Technology Review--Analysis of Demographic
Factors for Populations Living Near Mercury Cell Chlor-Alkali Plants
Source Category Operations, available in the docket for this action.

K. Congressional Review Act (CRA)

    This action is subject to the CRA, and the EPA will submit a rule
report to each House of the Congress and to the Comptroller General of
the United States. This action is not a ``major rule'' as defined by 5
U.S.C. 804(2).

List of Subjects in 40 CFR Part 63

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

Michael S. Regan,
Administrator.
    For the reasons set out in the preamble, 40 CFR part 63 is amended
as follows:

PART 63--NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS
FOR SOURCE CATEGORIES

0
1. The authority citation for part 63 continues to read as follows:

    Authority:  42 U.S.C. 7401 et seq.

0
2. The heading for subpart IIIII is revised to read as follows:

Subpart IIIII--National Emission Standards for Hazardous Air
Pollutants for Mercury Cell Chlor-Alkali Plants

0
3. Section 63.8180 is revised to read as follows:

Sec.  63.8180   What is the purpose of this subpart?

    This subpart establishes national emission standards for hazardous
air pollutants (NESHAP) for affected sources at mercury cell chlor-
alkali plants. This subpart also establishes requirements to
demonstrate initial and continuous compliance with all applicable
emission limitations and work practice standards in this subpart.

0
4. Section 63.8182 is amended by revising paragraph (c) introductory
text to read as follows:

Sec.  63.8182   Am I subject to this subpart?

* * * * *
    (c) Beginning on December 19, 2006, the provisions of subpart E of
40 CFR part 61 that apply to mercury cell chlor-alkali plants, which
are listed in paragraphs (c)(1) through (3) of this section, are no
longer applicable.
* * * * *

0
5. Section 63.8184 is amended by revising paragraphs (a)(1) and (2) to
read as follows:

Sec.  63.8184   What parts of my plant does this subpart cover?

    (a) * * *
    (1) The mercury cell chlor-alkali production facility designates an
affected source consisting of all cell rooms and ancillary operations
used in the manufacture of product chlorine, product caustic, and by-
product hydrogen at a plant site. This subpart covers mercury emissions
from by-product hydrogen streams and end box ventilation system vents,
mercury fugitive emissions associated with cell rooms, hydrogen
systems, caustic systems, and storage areas for mercury-containing
wastes; and chlorine fugitive emissions associated with the mercury
cell chlor-alkali production facility.
    (2) The mercury recovery facility designates an affected source
consisting of all processes and associated operations needed for
mercury recovery

from wastes at a plant site. This subpart covers mercury emissions from
mercury thermal recovery unit vents and fugitive emission sources of
mercury associated with storage areas for mercury-containing wastes.
* * * * *

0
6. Section 63.8186 is amended by revising paragraph (a) to read as
follows:

Sec.  63.8186   When do I have to comply with this subpart?

    (a) If you have an existing affected source, you must comply
according to the dates specified in paragraphs (a)(1) through (5) of
this section, as applicable.
    (1) You must comply with each emission limitation, each work
practice standard specified in paragraphs Sec.  63.8192(a) through (f)
or each work practice standard in paragraphs Sec.  63.8192(e) through
(g), and with each recordkeeping and reporting requirement in this
subpart that applies to you by December 19, 2006, except as specified
in paragraphs (a)(2) through (5) of this section.
    (2) You must comply with each work practice standard in Sec.
63.8192(a) through (c) and (e) through (h) and the electronic reporting
requirements in Sec.  63.8232(g), Sec.  63.8252(g), and Sec.
63.8254(e) by November 7, 2022.
    (3) Until November 7, 2022, you must comply with the requirements
in Sec.  63.8226(a) and the requirements specified in the startup,
shutdown, and malfunction plan required at Sec.  63.8226(b).
    (4) On and after November 7, 2022, you must comply with the
applicable requirements in paragraph Sec.  63.8226(c).
    (5) On and after May 6, 2025, you must comply with the emission