[Federal Register Volume 84, Number 23 (Monday, February 4, 2019)]
[Proposed Rules]
[Pages 1570-1597]
[FR Doc No: 2018-28322]

Vol. 84

Monday,

No. 23

February 4, 2019

Part III

Environmental Protection Agency

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40 CFR Part 63

National Emission Standards for Hazardous Air Pollutants: Hydrochloric
Acid Production Residual Risk and Technology Review; Proposed Rules

Federal Register / Vol. 84 , No. 23 / Monday, February 4, 2019 /
Proposed Rules

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2018-0417; FRL-9988-70-OAR]
RIN 2060-AT74

National Emission Standards for Hazardous Air Pollutants:
Hydrochloric Acid Production Residual Risk and Technology Review

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing
amendments to the National Emission Standards for Hazardous Air
Pollutants (NESHAP) for the Hydrochloric Acid (HCl) Production source
category. The proposed action presents the results of the residual risk
and technology reviews (RTRs) conducted as required under the Clean Air
Act (CAA). The proposed amendments address the startup, shutdown, and
malfunction (SSM) provisions of the rule, add electronic reporting, and
update the reporting and recordkeeping requirements.

DATES:  Comments. Comments must be received on or before March 21,
2019. Under the Paperwork Reduction Act (PRA), comments on the
information collection provisions are best assured of consideration if
the Office of Management and Budget (OMB) receives a copy of your
comments on or before March 6, 2019.
    Public Hearing. If anyone contacts us requesting a public hearing
on or before February 11, 2019, we will hold a hearing. Additional
information about the hearing, if requested, will be published in a
subsequent Federal Register document and posted at https://www.epa.gov/stationary-sources-air-pollution/hydrochloric-acid-production-national-emission-standards-hazardous. See SUPPLEMENTARY INFORMATION for
information on requesting and registering for a public hearing.

ADDRESSES: Comments. Submit your comments, identified by Docket ID No.
EPA-HQ-OAR-2018-0417, at https://www.regulations.gov. Follow the online
instructions for submitting comments. Once submitted, comments cannot
be edited or removed from Regulations.gov. See SUPPLEMENTARY
INFORMATION for detail about how the EPA treats submitted comments.
Regulations.gov is our preferred method of receiving comments. However,
the following other submission methods are also accepted:
     Email<EMAIL_ADDRESS>Include Docket ID No. EPA-
HQ-OAR-2018-0417 in the subject line of the message.
     Fax:<PHONE_NUMBER>. Attention Docket ID No. EPA-HQ-OAR-
2018-0417.
     Mail: To ship or send mail via the United States Postal
Service, use the following address: U.S. Environmental Protection
Agency, EPA Docket Center, Docket ID No. EPA-HQ-OAR-2018-0417, Mail
Code 28221T, 1200 Pennsylvania Avenue NW, Washington, DC 20460.
     Hand/Courier Delivery: Use the following Docket Center
address if you are using express mail, commercial delivery, hand
delivery, or courier: EPA Docket Center, EPA WJC West Building, Room
3334, 1301 Constitution Avenue NW, Washington, DC 20004. Delivery
verification signatures will be available only during regular business
hours.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed
action, contact Nathan Topham, Sector Policies and Programs Division
(Mail Code 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_ADDRESS>For specific information
regarding the risk modeling methodology, contact Terri Hollingsworth,
Health and Environmental Impacts Division (C539-02), Office of Air
Quality Planning and Standards, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina 27711; telephone number: (919)
541-2076; fax number:<PHONE_NUMBER>; and email address:
<EMAIL_ADDRESS>For information about the applicability of
the NESHAP to a particular entity, contact Marcia Mia, Office of
Enforcement and Compliance Assurance, U.S. Environmental Protection
Agency, EPA WJC South Building (Mail Code 2227A), 1200 Pennsylvania
Avenue NW, Washington, DC 20460; telephone number:<PHONE_NUMBER>; and
email address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:
    Public hearing. Please contact Adrian Gates at<PHONE_NUMBER> or by
email at<EMAIL_ADDRESS>to request a public hearing, to register
to speak at the public hearing, or to inquire as to whether a public
hearing will be held.
    Docket. The EPA has established a docket for this rulemaking under
Docket ID No. EPA-HQ-OAR-2018-0417. All documents in the docket are
listed in Regulations.gov. Although listed, some information is not
publicly available, e.g., confidential business information (CBI) or
other information whose disclosure is restricted by statute. Certain
other material, such as copyrighted material, is not placed on the
internet and will be publicly available only in hard copy. Publicly
available docket materials are available either electronically in
Regulations.gov or in hard copy at the EPA Docket Center, Room 3334,
EPA WJC West Building, 1301 Constitution Avenue NW, Washington, DC. The
Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through
Friday, excluding legal holidays. The telephone number for the Public
Reading Room is<PHONE_NUMBER>, and the telephone number for the EPA
Docket Center is<PHONE_NUMBER>.
    Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2018-0417. The EPA's policy is that all comments received will be
included in the public docket without change and may be made available
online at https://www.regulations.gov, including any personal
information provided, unless the comment includes information claimed
to be CBI or other information whose disclosure is restricted by
statute. Do not submit information that you consider to be CBI or
otherwise protected through https://www.regulations.gov or email. This
type of information should be submitted by mail as discussed below.
    The EPA may publish any comment received to its public docket.
Multimedia submissions (audio, video, etc.) must be accompanied by a
written comment. The written comment is considered the official comment
and should include discussion of all points you wish to make. The EPA
will generally not consider comments or comment contents located
outside of the primary submission (i.e., on the Web, cloud, or other
file sharing system). For additional submission methods, the full EPA
public comment policy, information about CBI or multimedia submissions,
and general guidance on making effective comments, please visit https://www2.epa.gov/dockets/commenting-epa-dockets.
    The https://www.regulations.gov website allows you to submit your
comment anonymously, which means the EPA will not know your identity or
contact information unless you provide it in the body of your comment.
If you send an email comment directly to the EPA without going through
https://www.regulations.gov, your email

address will be automatically captured and included as part of the
comment that is placed in the public docket and made available on the
internet. If you submit an electronic comment, the EPA recommends that
you include your name and other contact information in the body of your
comment and with any digital storage media you submit. If the EPA
cannot read your comment due to technical difficulties and cannot
contact you for clarification, the EPA may not be able to consider your
comment. Electronic files should not include special characters or any
form of encryption and be free of any defects or viruses. For
additional information about the EPA's public docket, visit the EPA
Docket Center homepage at https://www.epa.gov/dockets.
    Submitting CBI. Do not submit information containing CBI to the EPA
through https://www.regulations.gov or email. Clearly mark the part or
all of the information that you claim to be CBI. For CBI information on
any digital storage media that you mail to the EPA, mark the outside of
the digital storage media as CBI and then identify electronically
within the digital storage media the specific information that is
claimed as CBI. In addition to one complete version of the comments
that includes information claimed as CBI, you must submit a copy of the
comments that does not contain the information claimed as CBI directly
to the public docket through the procedures outlined in Instructions
above. If you submit any digital storage media that does not contain
CBI, mark the outside of the digital storage media clearly that it does
not contain CBI. Information not marked as CBI will be included in the
public docket and the EPA's electronic public docket without prior
notice. Information marked as CBI will not be disclosed except in
accordance with procedures set forth in 40 Code of Federal Regulations
(CFR) part 2. Send or deliver information identified as CBI only to the
following address: OAQPS Document Control Officer (C404-02), OAQPS,
U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina 27711, Attention Docket ID No. EPA-HQ-OAR-2018-0417.
    Preamble Acronyms and Abbreviations. We use multiple acronyms and
terms in this preamble. While this list may not be exhaustive, to ease
the reading of this preamble and for reference purposes, the EPA
defines the following terms and acronyms here:

AEGL acute exposure guideline level
AERMOD air dispersion model used by the HEM-3 model
CAA Clean Air Act
CalEPA California EPA
CBI Confidential Business Information
CFR Code of Federal Regulations
Cl2 chlorine
EPA Environmental Protection Agency
ERPG Emergency Response Planning Guideline
ERT Electronic Reporting Tool
HAP hazardous air pollutant(s)
HCl hydrochloric acid
HEM-3 Human Exposure Model, Version 1.1.0
HF hydrogen fluoride
HI hazard index
HQ hazard quotient
IRIS Integrated Risk Information System
km kilometer
MACT maximum achievable control technology
mg/m\3\ milligrams per cubic meter
MIR maximum individual risk
NAAQS National Ambient Air Quality Standards
NAICS North American Industry Classification System
NESHAP national emission standards for hazardous air pollutants
NTTAA National Technology Transfer and Advancement Act
OAQPS Office of Air Quality Planning and Standards
OECA Office of Enforcement and Compliance Assurance
OMB Office of Management and Budget
PB-HAP hazardous air pollutants known to be persistent and bio-
accumulative in the environment
POM polycyclic organic matter
REL reference exposure level
RFA Regulatory Flexibility Act
RfC reference concentration
RfD reference dose
RTR residual risk and technology review
SAB Science Advisory Board
SSM startup, shutdown, and malfunction
TOSHI target organ-specific hazard index
tpy tons per year
TRIM.FaTE Total Risk Integrated Methodology: Fate, Transport, and
Ecological Exposure model
UF uncertainty factor
UMRA Unfunded Mandates Reform Act
URE unit risk estimate

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

I. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document and other related
information?
II. Background
    A. What is the statutory authority for this action?
    B. What is this source category and how does the current NESHAP
regulate its HAP emissions?
    C. What data collection activities were conducted to support
this action?
    D. What other relevant background information and data are
available?
III. Analytical Procedures and Decision-Making
    A. How do we consider risk in our decision-making?
    B. How do we perform the technology review?
    C. How do we estimate post-MACT risk posed by the source
category?
IV. Analytical Results and Proposed Decisions
    A. What are the results of the risk assessment and analyses?
    B. What are our proposed decisions regarding risk acceptability,
ample margin of safety, and adverse environmental effect?
    C. What are the results and proposed decisions based on our
technology review?
    D. What other actions are we proposing?
    E. What compliance dates are we proposing?
V. Summary of Cost, Environmental, and Economic Impacts
    A. What are the affected sources?
    B. What are the air quality impacts?
    C. What are the cost impacts?
    D. What are the economic impacts?
    E. What are the benefits?
VI. Request for Comments
VII. Submitting Data Corrections
VIII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Executive Order 13771: Reducing Regulation and Controlling
Regulatory Costs
    C. Paperwork Reduction Act (PRA)
    D. Regulatory Flexibility Act (RFA)
    E. Unfunded Mandates Reform Act (UMRA)
    F. Executive Order 13132: Federalism
    G. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    H. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
    I. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
    J. National Technology Transfer and Advancement Act (NTTAA)
    K. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations

I. General Information

A. Does this action apply to me?

    Table 1 of this preamble lists the NESHAP and associated regulated
industrial source categories that are the subject of this proposal.
Table 1 is not intended to be exhaustive, but rather provides a guide
for readers regarding the entities that this proposed action is likely
to affect. The proposed standards, once promulgated, will be directly
applicable to the affected sources. Federal, state, local, and tribal
government entities will not be affected by this proposed action. As
defined in the Initial List of Categories of Sources Under Section
112(c)(1) of the Clean Air Act Amendments of 1990 (see 57 FR 31576,
July 16, 1992) and

Documentation for Developing the Initial Source Category List (see EPA-
450/3-91-030), the HCl Production source category includes any facility
engaged in the production of HCl. The category includes, but is not
limited to, production of hydrochloric acid via any of the following
methods: (1) Production of HCl as a by-product in the manufacture of
organic chemicals; (2) direct reaction of salts and sulfuric acid
(Mannheim process); (3) reaction of a salt, sulfur dioxide, oxygen, and
water (Hargreaves process); or (4) burning chlorine (Cl2) in
the presence of hydrogen gas. On September 18, 2001 (66 FR 48174), the
Fume Silica Production source category was combined with the HCl
Production source category. The Fume Silica Production source category
is any facility engaged in the production of fume silica. Fume silica
is a fine white powder used as a thickener, thixotropic, or reinforcing
agent in inks, resins, rubber, paints, and cosmetics. The category
includes the production of fume silica by the combustion of silicon
tetrachloride in hydrogen-oxygen furnaces.

    Table 1--NESHAP and Industrial Source Categories Affected by This
                             Proposed Action
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          Source category                  NESHAP         NAICS code \1\
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HCl production and fume silica      HCl.................          325180
 production.
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\1\ North American Industry Classification System.

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

    In addition to being available in the docket, an electronic copy of
this action is available on the internet. Following signature by the
EPA Administrator, the EPA will post a copy of this proposed action at
https://www.epa.gov/hydrochloric-acid-production-national-emission-standards-hazardous. Following publication in the Federal Register, the
EPA will post the Federal Register version of the proposal and key
technical documents at this same website. Information on the overall
residual RTR program is available at https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html.
    A redline version of the regulatory language that incorporates the
proposed changes in this action is available in the docket for this
action (Docket ID No. EPA-HQ-OAR-2018-0417).

II. Background

A. What is the statutory authority for this action?

    The statutory authority for this action is provided by sections 112
and 301 of the CAA, as amended (42 U.S.C. 7401 et seq.). Section 112 of
the CAA establishes a two-stage regulatory process to develop standards
for emissions of hazardous air pollutants (HAP) from stationary
sources. Generally, the first stage involves establishing technology-
based standards and the second stage involves evaluating those
standards that are based on maximum achievable control technology
(MACT) to determine whether additional standards are needed to address
any remaining risk associated with HAP emissions. This second stage is
commonly referred to as the ``residual risk review.'' In addition to
the residual risk review, the CAA also requires the EPA to review
standards set under CAA section 112 every 8 years to determine if there
are ``developments in practices, processes, or control technologies''
that may be appropriate to incorporate into the standards. This review
is commonly referred to as the ``technology review.'' When the two
reviews are combined into a single rulemaking, it is commonly referred
to as the ``risk and technology review.'' The discussion that follows
identifies the most relevant statutory sections and briefly explains
the contours of the methodology used to implement these statutory
requirements. A more comprehensive discussion appears in the document
titled CAA Section 112 Risk and Technology Reviews: Statutory Authority
and Methodology in the docket for this rulemaking.
    In the first stage of the CAA section 112 standard setting process,
the EPA promulgates technology-based standards under CAA section 112(d)
for categories of sources identified as emitting one or more of the HAP
listed in CAA section 112(b). Sources of HAP emissions are either major
sources or area sources, and CAA section 112 establishes different
requirements for major source standards and area source standards.
``Major sources'' are those that emit or have the potential to emit 10
tons per year (tpy) or more of a single HAP or 25 tpy or more of any
combination of HAP. All other sources are ``area sources.'' For major
sources, CAA section 112(d)(2) provides that the technology-based
NESHAP must reflect the maximum degree of emission reductions of HAP
achievable (after considering cost, energy requirements, and non-air
quality health and environmental impacts). These standards are commonly
referred to as MACT standards. CAA section 112(d)(3) also establishes a
minimum control level for MACT standards, known as the MACT ``floor.''
The EPA must also consider control options that are more stringent than
the floor. Standards more stringent than the floor are commonly
referred to as beyond-the-floor standards. In certain instances, as
provided in CAA section 112(h), the EPA may set work practice standards
where it is not feasible to prescribe or enforce a numerical emission
standard. For area sources, CAA section 112(d)(5) gives the EPA
discretion to set standards based on generally available control
technologies or management practices (GACT standards) in lieu of MACT
standards.
    The second stage in standard-setting focuses on identifying and
addressing any remaining (i.e., ``residual'') risk according to CAA
section 112(f). For source categories subject to MACT standards,
section 112(f)(2) of the CAA requires the EPA to determine whether
promulgation of additional standards is needed to provide an ample
margin of safety to protect public health or to prevent an adverse
environmental effect. Section 112(d)(5) of the CAA provides that this
residual risk review is not required for categories of area sources
subject to GACT standards. Section 112(f)(2)(B) of the CAA further
expressly preserves the EPA's use of the two-step approach for
developing standards to address any residual risk and the Agency's
interpretation of ``ample margin of safety'' developed in the National
Emissions Standards for Hazardous Air Pollutants: Benzene Emissions
from Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, Benzene
Storage Vessels, Benzene Equipment Leaks, and Coke By-Product Recovery
Plants (Benzene NESHAP) (54 FR 38044, September 14, 1989). The EPA
notified Congress in the Risk Report that the Agency intended to use
the Benzene NESHAP approach in making CAA section 112(f) residual risk
determinations (EPA-453/R-99-001, p. ES-11). The EPA subsequently
adopted this approach in its residual risk determinations and the
United States

Court of Appeals for the District of Columbia Circuit (the Court)
upheld the EPA's interpretation that CAA section 112(f)(2) incorporates
the approach established in the Benzene NESHAP. See NRDC v. EPA, 529
F.3d 1077, 1083 (D.C. Cir. 2008).
    The approach incorporated into the CAA and used by the EPA to
evaluate residual risk and to develop standards under CAA section
112(f)(2) is a two-step approach. In the first step, the EPA determines
whether risks are acceptable. This determination ``considers all health
information, including risk estimation uncertainty, and includes a
presumptive limit on maximum individual lifetime [cancer] risk (MIR)
\1\ of approximately 1 in 10 thousand.'' 54 FR 38045, September 14,
1989. If risks are unacceptable, the EPA must determine the emissions
standards necessary to reduce risk to an acceptable level without
considering costs. In the second step of the approach, the EPA
considers whether the emissions standards provide an ample margin of
safety to protect public health ``in consideration of all health
information, including the number of persons at risk levels higher than
approximately 1 in 1 million, as well as other relevant factors,
including costs and economic impacts, technological feasibility, and
other factors relevant to each particular decision.'' Id. The EPA must
promulgate emission standards necessary to provide an ample margin of
safety to protect public health. After conducting the ample margin of
safety analysis, we consider whether a more stringent standard is
necessary to prevent, taking into consideration costs, energy, safety,
and other relevant factors, an adverse environmental effect.
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    \1\ Although defined as ``maximum individual risk,'' MIR refers
only to cancer risk. MIR, one metric for assessing cancer risk, is
the estimated risk if an individual were exposed to the maximum
level of a pollutant for a lifetime.
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    CAA section 112(d)(6) separately requires the EPA to review
standards promulgated under CAA section 112 and revise them ``as
necessary (taking into account developments in practices, processes,
and control technologies)'' no less often than every 8 years. In
conducting this review, which we call the ``technology review,'' the
EPA is not required to recalculate the MACT floor. Natural Resources
Defense Council (NRDC) v. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008).
Association of Battery Recyclers, Inc. v. EPA, 716 F.3d 667 (D.C. Cir.
2013). The EPA may consider cost in deciding whether to revise the
standards pursuant to CAA section 112(d)(6).

B. What is this source category and how does the current NESHAP
regulate its HAP emissions?

    As described in section I.A of this preamble, the HCl Production
source category includes facilities that are engaged in the production
of HCl. In the initial list of source categories, Fume Silica
Production was listed as a distinct source category. While developing
the NESHAP for HCl Production, the EPA determined that HAP emissions
from fume silica production were attributable to HCl production at
these facilities. Therefore, during the proposal and promulgation of
the NESHAP for HCl Production, the Fume Silica Production source
category was subsumed into the HCl Production source category and the
resulting HCl Production source category now includes HCl production at
fume silica production facilities as well as other facilities producing
HCl that were previously included in the source category.
    The HCl Production NESHAP covers sources located at major sources
of HAP emissions. HCl production facilities are typically co-located at
plant sites that include various other chemical manufacturing processes
such as pesticide or organic chemical manufacturing. The HCl production
facility is the basic unit defined in the NESHAP. Specifically, the
rule defines an HCl production facility as the collection of unit
operations and equipment associated with the production of liquid HCl
product of 30 weight percent or greater. The production of liquid HCl
product occurs through the absorption of gaseous HCl into either water
or an aqueous HCl solution. The HCl production facility includes HCl
storage tanks (as defined in 40 CFR 63.9075), HCl transfer operations
that load the HCl product into a tank truck, rail car, ship, or barge,
and equipment leaks. A plant site could have several separate and
distinct HCl production facilities. The affected source includes all
HCl production facilities at the same site.
    An HCl production facility begins at the point where a gaseous
stream containing HCl \2\ enters an absorber and ends at the point
where the liquid HCl product is loaded into a tank truck, rail car,
ship, or barge, at the point the HCl product enters another process on
the plant site, or at the point the HCl product leaves the plant site
via pipeline. The gaseous stream leaving the absorption column contains
HCl that was not absorbed into the liquid in the tower and any
Cl2 present in the inlet stream. If the outlet stream is
directly discharged to the atmosphere or if it is routed through other
control devices before being discharged to the atmosphere, it is
considered an HCl process vent from an HCl production facility. If the
outlet stream is routed (or recycled) to another process, it is not
regulated under the HCl Production NESHAP, but could be regulated under
a separate NESHAP related to the process to which it is routed. For
example, if an HCl process vent emission stream is routed to a
hazardous waste combustor regulated under 40 CFR part 63, subpart EEE,
as supplemental combustion air, that process vent stream is subject to
40 CFR part 63, subpart EEE rather than the HCl Production NESHAP.
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    \2\ For purposes of the HCl Production NESHAP, how the gaseous
HCl is produced does not affect applicability of the rule to the
source. The source category only addresses the production of liquid
HCl.
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C. What data collection activities were conducted to support this
action?

    The EPA used a variety of resources to obtain data about facilities
and their emissions for use in our risk assessment. We used the EPA's
Enforcement and Compliance History Online (ECHO) database to develop a
list of potentially subject facilities. Using this list, we searched
state environmental agency websites and correspondence with industry to
obtain copies of title V permits to confirm whether facilities have HCl
production subject to the NESHAP. Once the facility list was finalized,
the EPA used the 2014 National Emissions Inventory (NEI) to get
emissions data for each facility. We compared the NEI data to title V
permits to provide additional information regarding the applicability
of the HCl Production NESHAP. There were some instances in which
sources listed in title V permits did not include HAP emissions in the
NEI. As discussed in the memorandum titled HCl RTR Modeling File Data
Source Documentation, which is available in the docket for this action,
these gaps were filled using average data from other emission points
for which data were available. Further discussion of the methodology
used to develop the emissions dataset for the risk assessment can be
found in the memorandum titled HCl RTR Modeling File Data Source
Documentation, which is available in the docket for this action.
Industry representatives provided data corrections where facility
ownership or emission point parameters from the NEI were incorrect.

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

    We used information from the Reasonably Available Control
Technology (RACT), Best Available Control Technology (BACT), and Lowest
Achievable Emission Rate (LAER) Clearinghouse (RBLC) database, reviewed
title V permits for each HCl production facility, and reviewed
regulatory actions related to emissions controls at similar sources
that could be applicable to HCl production. We reviewed the RBLC to
identify potential additional control technologies. No additional
control technologies applicable to HCl production were found using the
RBLC. Additional information related to the original promulgation and
subsequent amendments of the NESHAP is available in Docket ID No. EPA-
HQ-OAR-2002-0057.

III. Analytical Procedures and Decision-Making

    In this section, we describe the analyses performed to support the
proposed decisions for the RTR and other issues addressed in this
proposal.

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

    As discussed in section II.A of this preamble and in the Benzene
NESHAP, in evaluating and developing standards under CAA section
112(f)(2), we apply a two-step approach to determine whether or not
risks are acceptable and to determine if the standards provide an ample
margin of safety to protect public health. As explained in the Benzene
NESHAP, ``the first step judgment on acceptability cannot be reduced to
any single factor'' and, thus, ``[t]he Administrator believes that the
acceptability of risk under section 112 is best judged on the basis of
a broad set of health risk measures and information.'' 54 FR 38046,
September 14, 1989. Similarly, with regard to the ample margin of
safety determination, ``the Agency again considers all of the health
risk and other health information considered in the first step. Beyond
that information, additional factors relating to the appropriate level
of control will also be considered, including cost and economic impacts
of controls, technological feasibility, uncertainties, and any other
relevant factors.'' Id.
    The Benzene NESHAP approach provides flexibility regarding factors
the EPA may consider in making determinations and how the EPA may weigh
those factors for each source category. The EPA conducts a risk
assessment that provides estimates of the MIR posed by the HAP
emissions from each source in the source category, the hazard index
(HI) for chronic exposures to HAP with the potential to cause noncancer
health effects, and the hazard quotient (HQ) for acute exposures to HAP
with the potential to cause noncancer health effects.\3\ The assessment
also provides estimates of the distribution of cancer risk within the
exposed populations, cancer incidence, and an evaluation of the
potential for an adverse environmental effect. The scope of the EPA's
risk analysis is consistent with the EPA's response to comments on our
policy under the Benzene NESHAP where the EPA explained that:
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    \3\ The MIR is defined as the cancer risk associated with a
lifetime of exposure at the highest concentration of HAP where
people are likely to live. The HQ is the ratio of the potential
exposure to the HAP to the level at or below which no adverse
chronic noncancer effects are expected; the HI is the sum of HQs for
HAP that affect the same target organ or organ system.

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

    See 54 FR 38057, September 14, 1989. Thus, the level of the MIR is
only one factor to be weighed in determining acceptability of risk. The
Benzene NESHAP explained that ``an MIR of approximately one in 10
thousand should ordinarily be the upper end of the range of
acceptability. As risks increase above this benchmark, they become
presumptively less acceptable under CAA section 112, and would be
weighed with the other health risk measures and information in making
an overall judgment on acceptability. Or, the Agency may find, in a
particular case, that a risk that includes MIR less than the
presumptively acceptable level is unacceptable in the light of other
health risk factors.'' Id. at 38045. Similarly, with regard to the
ample margin of safety analysis, the EPA stated in the Benzene NESHAP
that: ``EPA believes the relative weight of the many factors that can
be considered in selecting an ample margin of safety can only be
determined for each specific source category. This occurs mainly
because technological and economic factors (along with the health-
related factors) vary from source category to source category.'' Id. at
38061. We also consider the uncertainties associated with the various
risk analyses, as discussed earlier in this preamble, in our
determinations of acceptability and ample margin of safety.
    The EPA notes that it has not considered certain health information
to date in making residual risk determinations. At this time, we do not
attempt to quantify the HAP risk that may be associated with emissions
from other facilities that do not include the source category under
review, mobile source emissions, natural source emissions, persistent
environmental pollution, or atmospheric transformation in the vicinity
of the sources in the category.
    The EPA understands the potential importance of considering an
individual's total exposure to HAP in addition to considering exposure
to HAP emissions from the source category and facility. We recognize
that such consideration may be particularly important when assessing
noncancer risk, where pollutant-specific exposure health reference
levels (e.g., reference concentrations (RfCs)) are based on the
assumption that thresholds exist for adverse health effects. For
example, the EPA recognizes that, although exposures attributable to
emissions from a source category or facility alone may not indicate the
potential for increased risk of adverse noncancer health effects in a
population, the exposures resulting from emissions from the facility in
combination with emissions from all of the other sources (e.g., other
facilities) to which an individual is exposed may be sufficient to
result in increased risk of adverse noncancer health effects. In May
2010, the Science Advisory Board (SAB) advised the EPA ``that RTR
assessments will be most useful to decision makers and communities if
results are presented in the broader context of aggregate and
cumulative risks, including background concentrations and contributions
from other sources in the area.'' \4\
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    \4\ Recommendations of the SAB RTR Panel are provided in their
report, which is available at: http://yosemite.epa.gov/sab/
sabproduct.nsf/4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-
007-unsigned.pdf.
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    In response to the SAB recommendations, the EPA incorporates

cumulative risk analyses into its RTR risk assessments, including those
reflected in this proposal. The Agency (1) conducts facility-wide
assessments, which include source category emission points, as well as
other emission points within the facilities; (2) combines exposures
from multiple sources in the same category that could affect the same
individuals; and (3) for some persistent and bioaccumulative
pollutants, analyzes the ingestion route of exposure. In addition, the
RTR risk assessments consider aggregate cancer risk from all
carcinogens and aggregated noncancer HQs for all noncarcinogens
affecting the same target organ or target organ system.
    Although we are interested in placing source category and facility-
wide HAP risk in the context of total HAP risk from all sources
combined in the vicinity of each source, we are concerned about the
uncertainties of doing so. Estimates of total HAP risk from emission
sources other than those that we have studied in depth during this RTR
review would have significantly greater associated uncertainties than
the source category or facility-wide estimates. Such aggregate or
cumulative assessments would compound those uncertainties, making the
assessments too unreliable.

B. How do we perform the technology review?

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

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

    In this section, we provide a complete description of the types of
analyses that we generally perform during the risk assessment process.
In some cases, we do not perform a specific analysis because it is not
relevant. For example, in the absence of emissions of HAP known to be
persistent and bioaccumulative in the environment (PB-HAP), we would
not perform a multipathway exposure assessment. Where we do not perform
an analysis, we state that we do not and provide the reason. While we
present all of our risk assessment methods, we only present risk
assessment results for the analyses actually conducted (see section
IV.B of this preamble).
    The EPA conducts a risk assessment that provides estimates of the
MIR for cancer posed by the HAP emissions from each source in the
source category, the HI for chronic exposures to HAP with the potential
to cause noncancer health effects, and the HQ for acute exposures to
HAP with the potential to cause noncancer health effects. The
assessment also provides estimates of the distribution of cancer risk
within the exposed populations, cancer incidence, and an evaluation of
the potential for an adverse environmental effect. The seven sections
that follow this paragraph describe how we estimated emissions and
conducted the risk assessment. The docket for this rulemaking contains
the following document which provides more information on the risk
assessment inputs and models: Residual Risk Assessment for the
Hydrochloric Acid Production Source Category in Support of the 2018
Risk and Technology Review Proposed Rule. The methods used to assess
risk (as described in the seven primary steps below) are consistent
with those described by the EPA in the document reviewed by a panel of
the EPA's SAB in 2009,\5\ and described in the SAB review report issued
in 2010. They are also consistent with the key recommendations
contained in that report.
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    \5\ U.S. EPA. Risk and Technology Review (RTR) Risk Assessment
Methodologies: For Review by the EPA's Science Advisory Board with
Case Studies--MACT I Petroleum Refining Sources and Portland Cement
Manufacturing, June 2009. EPA-452/R-09-006. https://www3.epa.gov/airtoxics/rrisk/rtrpg.html.
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1. How did we estimate actual emissions and identify the emissions
release characteristics?
    As discussed in the memorandum titled, HCl RTR Modeling File Data
Source Documentation, emissions data for sources subject to the HCl
Production NESHAP were gathered primarily from the 2014 NEI. We
compared the NEI data for each facility to title V permits to determine
which emission points listed in the NEI are subject to the HCl
Production NESHAP and made corrections when data were missing from the
NEI or appeared to be incorrect. For example, if the flow rate for an
emission point was missing, we calculated this release characteristic
using the stack velocity and cross-sectional area of the stack. Each
correction we made is discussed in the memorandum and supporting
documents, available in the docket for this action. Industry provided a
few corrections of facility ownership and emission point parameters,
which are also available in the docket for this action.
2. How did we estimate MACT-allowable emissions?
    The available emissions data in the RTR emissions dataset include
estimates of the mass of HAP emitted during a specified annual
timeperiod. These ``actual'' emission levels are often lower than the
emission levels allowed under the requirements of the current MACT
standards. The emissions allowed under the MACT standards are referred
to as the ``MACT-allowable'' emissions. We discussed the consideration
of both MACT-allowable and actual emissions in the final Coke Oven
Batteries RTR (70 FR 19998-19999, April 15, 2005) and in the proposed
and final Hazardous Organic NESHAP RTR (71 FR 34428, June 14, 2006, and
71 FR 76609,

December 21, 2006, respectively). In those actions, we noted that
assessing the risk at the MACT-allowable level is inherently reasonable
since that risk reflects the maximum level facilities could emit and
still comply with national emission standards. We also explained that
it is reasonable to consider actual emissions, where such data are
available, in both steps of the risk analysis, in accordance with the
Benzene NESHAP approach (54 FR 38044, September 14, 1989).
    We were unable to use the NEI data to calculate allowable emissions
based on the concentration-based standard. We attempted to calculate
allowable emission rates using the flow rates in the NEI and the
concentration based standards for HCl and Cl2. For a number
of sources, the calculated allowable emission values were substantially
lower than actual emissions. This discrepancy could be due to incorrect
flow rates in the NEI, conservatively high estimates of actual
emissions, or actual emission estimates including HCl and
Cl2 emissions from sources not subject to the HCl NESHAP. We
determined these estimates of allowable emission rates would not be
appropriate. Instead, we estimated allowable emission rates by applying
a factor of ten to actual emissions for process vents, material storage
and loading, and storage tanks. Based on our engineering judgement,
this factor of ten provides a very conservative estimate of allowable
emission rates. Indeed, correspondence with industry suggests the
allowable emission rates estimated using this method may be higher than
facility-wide permitted emission rates for some facilities. Facilities
typically operate below the level of the standard to provide a buffer
between actual emission levels and the level of the standard. While we
were not able to calculate the exact magnitude of this buffer for this
source category, we believe that using a multiplier of 10 ensures we
are not underestimating allowable emission rates. For more detail about
the MACT-allowable emission levels, see the memorandum, HCl RTR
Modeling File Data Source Documentation, which is available in the
docket for this action. The standard for equipment leaks requires
facilities to operate a leak detection and repair (LDAR) program.
Consistent with other source categories with LDAR standards, we
estimated that allowable emissions for equipment leaks are equal to
actual emissions, since both actual and allowable emissions reflect the
use of an LDAR program. Our estimates of actual and allowable emissions
are further discussed in the memorandum titled HCl RTR Modeling File
Data Source Documentation.
3. How do we conduct dispersion modeling, determine inhalation
exposures, and estimate individual and population inhalation risk?
    Both long-term and short-term inhalation exposure concentrations
and health risk from the source category addressed in this proposal
were estimated using the Human Exposure Model (HEM-3).\6\ The HEM-3
performs three primary risk assessment activities: (1) Conducting
dispersion modeling to estimate the concentrations of HAP in ambient
air, (2) estimating long-term and short-term inhalation exposures to
individuals residing within 50 kilometers (km) of the modeled sources,
and (3) estimating individual and population-level inhalation risk
using the exposure estimates and quantitative dose-response
information.
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    \6\ For more information about HEM-3, go to https://www.epa.gov/fera/risk-assessment-and-modeling-human-exposure-model-hem.
---------------------------------------------------------------------------

a. Dispersion Modeling
    The air dispersion model AERMOD, used by the HEM-3 model, is one of
the EPA's preferred models for assessing air pollutant concentrations
from industrial facilities.\7\ To perform the dispersion modeling and
to develop the preliminary risk estimates, HEM-3 draws on three data
libraries. The first is a library of meteorological data, which is used
for dispersion calculations. This library includes 1 year (2016) of
hourly surface and upper air observations from 824 meteorological
stations, selected to provide coverage of the United States and Puerto
Rico. A second library of United States Census Bureau census block \8\
internal point locations and populations provides the basis of human
exposure calculations (U.S. Census, 2010). In addition, for each census
block, the census library includes the elevation and controlling hill
height, which are also used in dispersion calculations. A third library
of pollutant-specific dose-response values is used to estimate health
risk. These are discussed below.
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    \7\ U.S. EPA. Revision to the Guideline on Air Quality Models:
Adoption of a Preferred General Purpose (Flat and Complex Terrain)
Dispersion Model and Other Revisions (70 FR 68218, November 9,
2005).
    \8\ A census block is the smallest geographic area for which
census statistics are tabulated.
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b. Risk From Chronic Exposure to HAP
    In developing the risk assessment for chronic exposures, we use the
estimated annual average ambient air concentrations of each HAP emitted
by each source in the source category. The HAP air concentrations at
each nearby census block centroid located within 50 km of the facility
are a surrogate for the chronic inhalation exposure concentration for
all the people who reside in that census block. A distance of 50 km is
consistent with both the analysis supporting the 1989 Benzene NESHAP
(54 FR 38044, September 14, 1989) and the limitations of Gaussian
dispersion models, including AERMOD.
    For each facility, we calculate the MIR as the cancer risk
associated with a continuous lifetime (24 hours per day, 7 days per
week, 52 weeks per year, 70 years) exposure to the maximum
concentration at the centroid of each inhabited census block. We
calculate individual cancer risk by multiplying the estimated lifetime
exposure to the ambient concentration of each HAP (in micrograms per
cubic meter ([mu]g/m\3\)) by its unit risk estimate (URE). The URE is
an upper-bound estimate of an individual's incremental risk of
contracting cancer over a lifetime of exposure to a concentration of 1
microgram of the pollutant per cubic meter of air. For residual risk
assessments, we generally use UREs from the EPA's Integrated Risk
Information System (IRIS). For carcinogenic pollutants without IRIS
values, we look to other reputable sources of cancer dose-response
values, often using California EPA (CalEPA) UREs, where available. In
cases where new, scientifically credible dose-response values have been
developed in a manner consistent with EPA guidelines and have undergone
a peer review process similar to that used by the EPA, we may use such
dose-response values in place of, or in addition to, other values, if
appropriate. The pollutant-specific dose-response values used to
estimate health risk are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants.
    To estimate individual lifetime cancer risks associated with
exposure to HAP emissions from each facility in the source category, we
sum the risks for each of the carcinogenic HAP \9\ emitted

by the modeled facility. We estimate cancer risk at every census block
within 50 km of every facility in the source category. The MIR is the
highest individual lifetime cancer risk estimated for any of those
census blocks. In addition to calculating the MIR, we estimate the
distribution of individual cancer risks for the source category by
summing the number of individuals within 50 km of the sources whose
estimated risk falls within a specified risk range. We also estimate
annual cancer incidence by multiplying the estimated lifetime cancer
risk at each census block by the number of people residing in that
block, summing results for all of the census blocks, then dividing this
result by a 70-year lifetime.
---------------------------------------------------------------------------

    \9\ The EPA's 2005 Guidelines for Carcinogen Risk Assessment
classifies carcinogens as: ``carcinogenic to humans,'' ``likely to
be carcinogenic to humans,'' and ``suggestive evidence of
carcinogenic potential.'' These classifications also coincide with
the terms ``known carcinogen, probable carcinogen, and possible
carcinogen,'' respectively, which are the terms advocated in the
EPA's Guidelines for Carcinogen Risk Assessment, published in 1986
(51 FR 33992, September 24, 1986). In August 2000, the document,
Supplemental Guidance for Conducting Health Risk Assessment of
Chemical Mixtures (EPA/630/R-00/002), was published as a supplement
to the 1986 document. Copies of both documents can be obtained from
https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=20533&CFID=70315376&CFTOKEN=71597944. Summing
the risk of these individual compounds to obtain the cumulative
cancer risk is an approach that was recommended by the EPA's SAB in
their 2002 peer review of the EPA's National Air Toxics Assessment
(NATA) titled NATA--Evaluating the National-scale Air Toxics
Assessment 1996 Data--an SAB Advisory, available at http://
yosemite.epa.gov/sab/sabproduct.nsf/
214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf.
---------------------------------------------------------------------------

    To assess the risk of noncancer health effects from chronic
exposure to HAP, we calculate either an HQ or a target organ-specific
hazard index (TOSHI). We calculate an HQ when a single noncancer HAP is
emitted. Where more than one noncancer HAP is emitted, we sum the HQ
for each of the HAP that affects a common target organ or target organ
system to obtain a TOSHI. The HQ is the estimated exposure divided by
the chronic noncancer dose-response value, which is a value selected
from one of several sources. The preferred chronic noncancer dose-
response value is the EPA RfC defined as ``an estimate (with
uncertainty spanning perhaps an order of magnitude) of a continuous
inhalation exposure to the human population (including sensitive
subgroups) that is likely to be without an appreciable risk of
deleterious effects during a lifetime'' (https://iaspub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&vocabName=IRIS%20Glossary). In cases where an RfC
from the EPA's IRIS is not available or where the EPA determines that
using a value other than the RfC is appropriate, the chronic noncancer
dose-response value can be a value from the following prioritized
sources, which define their dose-response values similarly to the EPA:
(1) The Agency for Toxic Substances and Disease Registry (ATSDR)
Minimum Risk Level (http://www.atsdr.cdc.gov/mrls/index.asp); (2) the
CalEPA Chronic Reference Exposure Level (REL) (http://oehha.ca.gov/air/crnr/notice-adoption-air-toxics-hot-spots-program-guidance-manual-preparation-health-risk-0); or (3), as noted above, a scientifically
credible dose-response value that has been developed in a manner
consistent with EPA guidelines and has undergone a peer review process
similar to that used by the EPA. The pollutant-specific dose-response
values used to estimate health risks are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants.
c. Risk From Acute Exposure to HAP That May Cause Health Effects Other
Than Cancer
    For each HAP for which appropriate acute inhalation dose-response
values are available, the EPA also assesses the potential health risks
due to acute exposure. For these assessments, the EPA makes
conservative assumptions about emission rates, meteorology, and
exposure location. We use the peak hourly emission rate,\10\ worst-case
dispersion conditions, and, in accordance with our mandate under
section 112 of the CAA, the point of highest off-site exposure to
assess the potential risk to the maximally exposed individual.
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    \10\ In the absence of hourly emission data, we develop
estimates of maximum hourly emission rates by multiplying the
average actual annual emissions rates by a factor (either a
category-specific factor or a default factor of 10) to account for
variability. This is documented in Residual Risk Assessment
Hydrochloric Acid Production Source Category in Support of the 2018
Risk and Technology Review Proposed Rule and in Appendix 5 of the
report: Analysis of Data on Short-term Emission Rates Relative to
Long-term Emission Rates. Both are available in the docket for this
rulemaking.
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    To characterize the potential health risks associated with
estimated acute inhalation exposures to a HAP, we generally use
multiple acute dose-response values, including acute RELs, acute
exposure guideline levels (AEGLs), and emergency response planning
guidelines (ERPG) for 1-hour exposure durations, if available, to
calculate acute HQs. The acute HQ is calculated by dividing the
estimated acute exposure by the acute dose-response value. For each HAP
for which acute dose-response values are available, the EPA calculates
acute HQs.
    An acute REL is defined as ``the concentration level at or below
which no adverse health effects are anticipated for a specified
exposure duration.'' \11\ Acute RELs are based on the most sensitive,
relevant, adverse health effect reported in the peer-reviewed medical
and toxicological literature. They are designed to protect the most
sensitive individuals in the population through the inclusion of
margins of safety. Because margins of safety are incorporated to
address data gaps and uncertainties, exceeding the REL does not
automatically indicate an adverse health impact. AEGLs represent
threshold exposure limits for the general public and are applicable to
emergency exposures ranging from 10 minutes to 8 hours.\12\ They are
guideline levels for ``once-in-a-lifetime, short-term exposures to
airborne concentrations of acutely toxic, high-priority chemicals.''
Id. at 21. The AEGL-1 is specifically defined as ``the airborne
concentration (expressed as ppm (parts per million) or mg/m\3\
(milligrams per cubic meter)) of a substance above which it is
predicted that the general population, including susceptible
individuals, could experience notable discomfort, irritation, or
certain asymptomatic nonsensory effects. However, the effects are not
disabling and are transient and reversible upon cessation of
exposure.'' The document also notes that ``Airborne concentrations
below AEGL-1 represent exposure levels that can produce mild and
progressively increasing but transient and nondisabling odor, taste,
and sensory irritation or certain asymptomatic, nonsensory effects.''
Id. AEGL-2 are defined as ``the airborne concentration (expressed as
parts per million or milligrams per cubic meter) of a substance above
which it is predicted that the general population, including
susceptible individuals, could experience irreversible or other
serious, long-lasting adverse health effects or an impaired ability to
escape.'' Id.
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    \11\ CalEPA issues acute RELs as part of its Air Toxics Hot
Spots Program, and the 1-hour and 8-hour values are documented in
Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The
Determination of Acute Reference Exposure Levels for Airborne
Toxicants, which is available at http://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-rel-summary.
    \12\ National Academy of Sciences, 2001. Standing Operating
Procedures for Developing Acute Exposure Levels for Hazardous
Chemicals, page 2. Available at https://www.epa.gov/sites/production/files/2015-09/documents/sop_final_standing_operating_procedures_2001.pdf. Note that the
National Advisory Committee for Acute Exposure Guideline Levels for
Hazardous Substances ended in October 2011, but the AEGL program
continues to operate at the EPA and works with the National
Academies to publish final AEGLs (https://www.epa.gov/aegl).
---------------------------------------------------------------------------

    ERPGs are ``developed for emergency planning and are intended as
health-based guideline concentrations for

single exposures to chemicals.'' \13\ Id. at 1. The ERPG-1 is defined
as ``the maximum airborne concentration below which it is believed that
nearly all individuals could be exposed for up to 1 hour without
experiencing other than mild transient adverse health effects or
without perceiving a clearly defined, objectionable odor.'' Id. at 2.
Similarly, the ERPG-2 is defined as ``the maximum airborne
concentration below which it is believed that nearly all individuals
could be exposed for up to one hour without experiencing or developing
irreversible or other serious health effects or symptoms which could
impair an individual's ability to take protective action.'' Id. at 1.
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    \13\ ERPGS Procedures and Responsibilities, March 2014. American
Industrial Hygiene Association. Available at: https://www.aiha.org/get-involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Documents/ERPG%20Committee%20Standard%20Operating%20Procedures%20%20-%20March%202014%20Revision%20%28Updated%2010-2-2014%29.pdf.
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    An acute REL for 1-hour exposure durations is typically lower than
its corresponding AEGL-1 and ERPG-1. Even though their definitions are
slightly different, AEGL-1s are often the same as the corresponding
ERPG-1s, and AEGL-2s are often equal to ERPG-2s. The maximum HQs from
our acute inhalation screening risk assessment typically result when we
use the acute REL for a HAP. In cases where the maximum acute HQ
exceeds 1, we also report the HQ based on the next highest acute dose-
response value (usually the AEGL-1 and/or the ERPG-1).
    For this source category, we used the default factor of 10 for the
acute inhalation screening and refined screening assessment. In our
acute inhalation screening risk assessment, acute impacts are deemed
negligible for HAP for which acute HQs are less than or equal to 1
(even under the conservative assumptions of the screening assessment),
and no further analysis is performed for these HAP. In cases where an
acute HQ from the screening step is greater than 1, we consider
additional site-specific data to develop a more refined estimate of the
potential for acute exposures of concern. For this source category, the
data refinements consisted of determining the highest HQ value that
occurs outside facility boundaries. These refinements are discussed
more fully in the Residual Risk Assessment for the Hydrochloric Acid
Production Source Category in Support of the Risk and Technology Review
2018 Proposed Rule, which is available in the docket for this source
category.
4. How do we conduct the multipathway exposure and risk screening
assessment?
    The EPA conducts a tiered screening assessment examining the
potential for significant human health risks due to exposures via
routes other than inhalation (i.e., ingestion). We first determine
whether any sources in the source category emit any PB-HAP, as
identified in the EPA's Air Toxics Risk Assessment Library (See Volume
1, Appendix D, at http://www2.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library).
    For the HCl Production source category, we did not identify
emissions of any PB-HAP. Because we did not identify PB-HAP emissions,
no further evaluation of multipathway risk was conducted for this
source category.
5. How do we conduct the environmental risk screening assessment?
a. Adverse Environmental Effect, Environmental HAP, and Ecological
Benchmarks
    The EPA conducts a screening assessment to examine the potential
for an adverse environmental effect as required under section
112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA defines ``adverse
environmental effect'' as ``any significant and widespread adverse
effect, which may reasonably be anticipated, to wildlife, aquatic life,
or other natural resources, including adverse impacts on populations of
endangered or threatened species or significant degradation of
environmental quality over broad areas.''
    The EPA focuses on eight HAP, which are referred to as
``environmental HAP,'' in its screening assessment: Six PB-HAP and two
acid gases. The PB-HAP included in the screening assessment are arsenic
compounds, cadmium compounds, dioxins/furans, polycyclic organic matter
(POM), mercury (both inorganic mercury and methyl mercury), and lead
compounds. The acid gases included in the screening assessment are HCl
and hydrogen fluoride (HF).
    HAP that persist and bioaccumulate are of particular environmental
concern because they accumulate in the soil, sediment, and water. The
acid gases, HCl and HF, are included due to their well-documented
potential to cause direct damage to terrestrial plants. In the
environmental risk screening assessment, we evaluate the following four
exposure media: Terrestrial soils, surface water bodies (includes
water-column and benthic sediments), fish consumed by wildlife, and
air. Within these four exposure media, we evaluate nine ecological
assessment endpoints, which are defined by the ecological entity and
its attributes. For PB-HAP (other than lead), both community-level and
population-level endpoints are included. For acid gases, the ecological
assessment evaluated is terrestrial plant communities.
    An ecological benchmark represents a concentration of HAP that has
been linked to a particular environmental effect level. For each
environmental HAP, we identified the available ecological benchmarks
for each assessment endpoint. We identified, where possible, ecological
benchmarks at the following effect levels: Probable effect levels,
lowest-observed-adverse-effect level, and no-observed-adverse-effect
level. In cases where multiple effect levels were available for a
particular PB-HAP and assessment endpoint, we use all of the available
effect levels to help us to determine whether ecological risks exist
and, if so, whether the risks could be considered significant and
widespread.
    For further information on how the environmental risk screening
assessment was conducted, including a discussion of the risk metrics
used, how the environmental HAP were identified, and how the ecological
benchmarks were selected, see Appendix 9 of the Residual Risk
Assessment for the Hydrochloric Acid Production Source Category in
Support of the Risk and Technology Review 2018 Proposed Rule, which is
available in the docket for this action.
b. Environmental Risk Screening Methodology
    For the environmental risk screening assessment, the EPA first
determined whether any facilities in the HCl Production source category
emitted any of the environmental HAP. For the HCl Production source
category, we identified emissions of HCl. Because one or more of the
environmental HAP evaluated (HCl) is emitted by at least one facility
in the source category, we proceeded to the second step of the
evaluation.
c. PB-HAP Methodology
    The environmental screening assessment includes six PB-HAP, arsenic
compounds, cadmium compounds, dioxins/furans, POM, mercury (both
inorganic mercury and methyl mercury), and lead compounds. With the
exception of lead, the environmental risk screening assessment for PB-
HAP consists of three tiers. The first tier of the environmental

risk screening assessment uses the same health-protective conceptual
model that is used for the Tier 1 human health screening assessment.
TRIM.FaTE model simulations were used to back-calculate Tier 1
screening threshold emission rates. The screening threshold emission
rates represent the emission rate in tpy that results in media
concentrations at the facility that equal the relevant ecological
benchmark. To assess emissions from each facility in the category, the
reported emission rate for each PB-HAP was compared to the Tier 1
screening threshold emission rate for that PB-HAP for each assessment
endpoint and effect level. If emissions from a facility do not exceed
the Tier 1 screening threshold emission rate, the facility ``passes''
the screening assessment, and, therefore, is not evaluated further
under the screening approach. If emissions from a facility exceed the
Tier 1 screening threshold emission rate, we evaluate the facility
further in Tier 2.
    In Tier 2 of the environmental screening assessment, the screening
threshold emission rates are adjusted to account for local meteorology
and the actual location of lakes in the vicinity of facilities that did
not pass the Tier 1 screening assessment. For soils, we evaluate the
average soil concentration for all soil parcels within a 7.5-km radius
for each facility and PB-HAP. For the water, sediment, and fish tissue
concentrations, the highest value for each facility for each pollutant
is used. If emission concentrations from a facility do not exceed the
Tier 2 screening threshold emission rate, the facility ``passes'' the
screening assessment and typically is not evaluated further. If
emissions from a facility exceed the Tier 2 screening threshold
emission rate, we evaluate the facility further in Tier 3.
    Like in the multipathway human health risk assessment, in Tier 3 of
the environmental screening assessment, we examine the suitability of
the lakes around the facilities to support life and remove those that
are not suitable (e.g., lakes that have been filled in or are
industrial ponds), adjust emissions for plume-rise, and conduct hour-
by-hour time-series assessments. If these Tier 3 adjustments to the
screening threshold emission rates still indicate the potential for an
adverse environmental effect (i.e., facility emission rate exceeds the
screening threshold emission rate), we may elect to conduct a more
refined assessment using more site-specific information. If, after
additional refinement, the facility emission rate still exceeds the
screening threshold emission rate, the facility may have the potential
to cause an adverse environmental effect.
    To evaluate the potential for an adverse environmental effect from
lead, we compared the average modeled air concentrations (from HEM-3)
of lead around each facility in the source category to the level of the
secondary National Ambient Air Quality Standards (NAAQS) for lead. The
secondary lead NAAQS is a reasonable means of evaluating environmental
risk because it is set to provide substantial protection against
adverse welfare effects which can include ``effects on soils, water,
crops, vegetation, man-made materials, animals, wildlife, weather,
visibility and climate, damage to and deterioration of property, and
hazards to transportation, as well as effects on economic values and on
personal comfort and well-being.''
d. Acid Gas Environmental Risk Methodology
    The environmental screening assessment for acid gases evaluates the
potential phytotoxicity and reduced productivity of plants due to
chronic exposure to HF and HCl. The environmental risk screening
methodology for acid gases is a single-tier screening assessment that
compares modeled ambient air concentrations (from AERMOD) to the
ecological benchmarks for each acid gas. To identify a potential
adverse environmental effect (as defined in section 112(a)(7) of the
CAA) from emissions of HF and HCl, we evaluate the following metrics:
The size of the modeled area around each facility that exceeds the
ecological benchmark for each acid gas, in acres and km\2\; the
percentage of the modeled area around each facility that exceeds the
ecological benchmark for each acid gas; and the area-weighted average
screening value around each facility (calculated by dividing the area-
weighted average concentration over the 50-km modeling domain by the
ecological benchmark for each acid gas). For further information on the
environmental screening assessment approach, see Appendix 9 of the
Residual Risk Assessment for the Hydrochloric Acid Production Source
Category in Support of the Risk and Technology Review 2018 Proposed
Rule, which is available in the docket for this action.
6. How do we conduct facility-wide assessments?
    To put the source category risks in context, we typically examine
the risks from the entire ``facility,'' where the facility includes all
HAP-emitting operations within a contiguous area and under common
control. In other words, we examine the HAP emissions not only from the
source category emission points of interest, but also emissions of HAP
from all other emission sources at the facility for which we have data.
For this source category, we conducted the facility-wide assessment
using a dataset compiled from the 2014 NEI. The source category records
of that NEI dataset were removed, evaluated, and updated as described
in section II.C of this preamble: What data collection activities were
conducted to support this action? Once a quality assured source
category dataset was available, it was placed back with the remaining
records from the NEI for that facility. The facility-wide file was then
used to analyze risks due to the inhalation of HAP that are emitted
``facility-wide'' for the populations residing within 50 km of each
facility, consistent with the methods used for the source category
analysis described above. For these facility-wide risk analyses, the
modeled source category risks were compared to the facility-wide risks
to determine the portion of the facility-wide risks that could be
attributed to the source category addressed in this proposal. We also
specifically examined the facility that was associated with the highest
estimate of risk and determined the percentage of that risk
attributable to the source category of interest. The Residual Risk
Assessment for the Hydrochloric Acid Production Source Category in
Support of the Risk and Technology Review 2018 Proposed Rule, available
through the docket for this action, provides the methodology and
results of the facility-wide analyses, including all facility-wide
risks and the percentage of source category contribution to facility-
wide risks.
    For this source category, we conducted the facility-wide assessment
using a dataset that the EPA compiled from the 2014 NEI. We used the
NEI data for the facility and did not adjust any category or ``non-
category'' data. Therefore, there could be differences in the dataset
from that used for the source category assessments described in this
preamble. We analyzed risks due to the inhalation of HAP that are
emitted ``facility-wide'' for the populations residing within 50 km of
each facility, consistent with the methods used for the source category
analysis described above. For these facility-wide risk analyses, we
made a reasonable attempt to identify the source category risks, and
these risks were compared to the facility-wide risks to determine the
portion of facility-wide risks that could be attributed to the source
category

addressed in this proposal. We also specifically examined the facility
that was associated with the highest estimate of risk and determined
the percentage of that risk attributable to the source category of
interest. The Residual Risk Assessment for the Hydrochloric Acid
Production Source Category in Support of the Risk and Technology Review
2018 Proposed Rule, available through the docket for this action,
provides the methodology and results of the facility-wide analyses,
including all facility-wide risks and the percentage of source category
contribution to facility-wide risks.
7. How do we consider uncertainties in risk assessment?
    Uncertainty and the potential for bias are inherent in all risk
assessments, including those performed for this proposal. Although
uncertainty exists, we believe that our approach, which used
conservative tools and assumptions, ensures that our decisions are
health and environmentally protective. A brief discussion of the
uncertainties in the RTR emissions dataset, dispersion modeling,
inhalation exposure estimates, and dose-response relationships follows
below. Also included are those uncertainties specific to our acute
screening assessments, multipathway screening assessments, and our
environmental risk screening assessments. A more thorough discussion of
these uncertainties is included in the Residual Risk Assessment for the
Hydrochloric Acid Production Source Category in Support of the Risk and
Technology Review 2018 Proposed Rule, which is available in the docket
for this action. If a multipathway site-specific assessment was
performed for this source category, a full discussion of the
uncertainties associated with that assessment can be found in Appendix
11 of that document, Site-Specific Human Health Multipathway Residual
Risk Assessment Report.
a. Uncertainties in the RTR Emissions Dataset
    Although the development of the RTR emissions dataset involved
quality assurance/quality control processes, the accuracy of emissions
values will vary depending on the source of the data, the degree to
which data are incomplete or missing, the degree to which assumptions
made to complete the datasets are accurate, errors in emission
estimates, and other factors. The emission estimates considered in this
analysis generally are annual totals for certain years, and they do not
reflect short-term fluctuations during the course of a year or
variations from year to year. The estimates of peak hourly emission
rates for the acute effects screening assessment were based on an
emission adjustment factor applied to the average annual hourly
emission rates, which are intended to account for emission fluctuations
due to normal facility operations.
b. Uncertainties in Dispersion Modeling
    We recognize there is uncertainty in ambient concentration
estimates associated with any model, including the EPA's recommended
regulatory dispersion model, AERMOD. In using a model to estimate
ambient pollutant concentrations, the user chooses certain options to
apply. For RTR assessments, we select some model options that have the
potential to overestimate ambient air concentrations (e.g., not
including plume depletion or pollutant transformation). We select other
model options that have the potential to underestimate ambient impacts
(e.g., not including building downwash). Other options that we select
have the potential to either under or overestimate ambient levels
(e.g., meteorology and receptor locations). On balance, considering the
directional nature of the uncertainties commonly present in ambient
concentrations estimated by dispersion models, the approach we apply in
the RTR assessments should yield unbiased estimates of ambient HAP
concentrations. We also note that the selection of meteorology dataset
location could have an impact on the risk estimates. As we continue to
update and expand our library of meteorological station data used in
our risk assessments, we expect to reduce this variability.
c. Uncertainties in Inhalation Exposure Assessment
    Although every effort is made to identify all of the relevant
facilities and emission points, as well as to develop accurate
estimates of the annual emission rates for all relevant HAP, the
uncertainties in our emission inventory likely dominate the
uncertainties in the exposure assessment. Some uncertainties in our
exposure assessment include human mobility, using the centroid of each
census block, assuming lifetime exposure, and assuming only outdoor
exposures. For most of these factors, there is neither an under nor
overestimate when looking at the maximum individual risk or the
incidence, but the shape of the distribution of risks may be affected.
With respect to outdoor exposures, actual exposures may not be as high
if people spend time indoors, especially for very reactive pollutants
or larger particles. For all factors, we reduce uncertainty when
possible. For example, with respect to census-block centroids, we
analyze large blocks using aerial imagery and adjust locations of the
block centroids to better represent the population in the blocks. We
also add additional receptor locations where the population of a block
is not well represented by a single location.
d. Uncertainties in Dose-Response Relationships
    There are uncertainties inherent in the development of the dose-
response values used in our risk assessments for cancer effects from
chronic exposures and noncancer effects from both chronic and acute
exposures. Some uncertainties are generally expressed quantitatively,
and others are generally expressed in qualitative terms. We note, as a
preface to this discussion, a point on dose-response uncertainty that
is stated in the EPA's 2005 Guidelines for Carcinogen Risk Assessment;
namely, that ``the primary goal of EPA actions is protection of human
health; accordingly, as an Agency policy, risk assessment procedures,
including default options that are used in the absence of scientific
data to the contrary, should be health protective'' (EPA's 2005
Guidelines for Carcinogen Risk Assessment, page 1-7). This is the
approach followed here as summarized in the next paragraphs.
    Cancer UREs used in our risk assessments are those that have been
developed to generally provide an upper bound estimate of risk. That
is, they represent a ``plausible upper limit to the true value of a
quantity'' (although this is usually not a true statistical confidence
limit).\14\ In some circumstances, the true risk could be as low as
zero; however, in other circumstances the risk could be greater.\15\
Chronic noncancer RfC and reference dose (RfD) values represent chronic
exposure levels that are intended to be health-protective levels. To
derive dose-response values that are intended to be ``without
appreciable risk,'' the methodology relies upon an uncertainty factor
(UF) approach (U.S. EPA, 1993 and 1994) which considers uncertainty,
variability, and gaps in the available data. The UFs are applied to

derive dose-response values that are intended to protect against
appreciable risk of deleterious effects.
---------------------------------------------------------------------------

    \14\ IRIS glossary (https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary).
    \15\ An exception to this is the URE for benzene, which is
considered to cover a range of values, each end of which is
considered to be equally plausible, and which is based on maximum
likelihood estimates.
---------------------------------------------------------------------------

    Many of the UFs used to account for variability and uncertainty in
the development of acute dose-response values are quite similar to
those developed for chronic durations. Additional adjustments are often
applied to account for uncertainty in extrapolation from observations
at one exposure duration (e.g., 4 hours) to derive an acute dose-
response value at another exposure duration (e.g., 1 hour). Not all
acute dose-response values are developed for the same purpose, and care
must be taken when interpreting the results of an acute assessment of
human health effects relative to the dose-response value or values
being exceeded. Where relevant to the estimated exposures, the lack of
acute dose-response values at different levels of severity should be
factored into the risk characterization as potential uncertainties.
    Uncertainty also exists in the selection of ecological benchmarks
for the environmental risk screening assessment. We established a
hierarchy of preferred benchmark sources to allow selection of
benchmarks for each environmental HAP at each ecological assessment
endpoint. We searched for benchmarks for three effect levels (i.e., no-
effects level, threshold effect level, and probable effect level), but
not all combinations of ecological assessment/environmental HAP had
benchmarks for all three effect levels. Where multiple effect levels
were available for a particular HAP and assessment endpoint, we used
all of the available effect levels to help us determine whether risk
exists and whether the risk could be considered significant and
widespread.
    Although we make every effort to identify appropriate human health
effect dose-response values for all pollutants emitted by the sources
in this risk assessment, some HAP emitted by this source category are
lacking dose-response assessments. Accordingly, these pollutants cannot
be included in the quantitative risk assessment, which could result in
quantitative estimates understating HAP risk. To help to alleviate this
potential underestimate, where we conclude similarity with a HAP for
which a dose-response value is available, we use that value as a
surrogate for the assessment of the HAP for which no value is
available. To the extent use of surrogates indicates appreciable risk,
we may identify a need to increase priority for an IRIS assessment for
that substance. We additionally note that, generally speaking, HAP of
greatest concern due to environmental exposures and hazard are those
for which dose-response assessments have been performed, reducing the
likelihood of understating risk. Further, HAP not included in the
quantitative assessment are assessed qualitatively and considered in
the risk characterization that informs the risk management decisions,
including consideration of HAP reductions achieved by various control
options.
    For a group of compounds that are unspeciated (e.g., glycol
ethers), we conservatively use the most protective dose-response value
of an individual compound in that group to estimate risk. Similarly,
for an individual compound in a group (e.g., ethylene glycol diethyl
ether) that does not have a specified dose-response value, we also
apply the most protective dose-response value from the other compounds
in the group to estimate risk.
e. Uncertainties in Acute Inhalation Screening Assessments
    In addition to the uncertainties highlighted above, there are
several factors specific to the acute exposure assessment that the EPA
conducts as part of the risk review under section 112 of the CAA. The
accuracy of an acute inhalation exposure assessment depends on the
simultaneous occurrence of independent factors that may vary greatly,
such as hourly emissions rates, meteorology, and the presence of humans
at the location of the maximum concentration. In the acute screening
assessment that we conduct under the RTR program, we assume that peak
emissions from the source category and worst-case meteorological
conditions co-occur, and, thus, resulting in maximum ambient
concentrations. These two events are unlikely to occur at the same
time, making these assumptions conservative. We then include the
additional assumption that a person is located at this point during
this same time period. For this source category, these assumptions
would tend to be worst-case actual exposures as it is unlikely that a
person would be located at the point of maximum exposure during the
time when peak emissions and worst-case meteorological conditions occur
simultaneously.
f. Uncertainties in the Multipathway and Environmental Risk Screening
Assessments
    For each source category, we generally rely on site-specific levels
of PB-HAP or environmental HAP emissions to determine whether a refined
assessment of the impacts from multipathway exposures is necessary or
whether it is necessary to perform an environmental screening
assessment. This determination is based on the results of a three-
tiered screening assessment that relies on the outputs from models--
TRIM.FaTE and AERMOD--that estimate environmental pollutant
concentrations and human exposures for five PB-HAP (dioxins, POM,
mercury, cadmium, and arsenic) and two acid gases (HCl and hydrogen
chloride). For lead, we use AERMOD to determine ambient air
concentrations, which are then compared to the secondary NAAQS standard
for lead. Two important types of uncertainty associated with the use of
these models in RTR risk assessments and inherent to any assessment
that relies on environmental modeling are model uncertainty and input
uncertainty.\16\
---------------------------------------------------------------------------

    \16\ In the context of this discussion, the term ``uncertainty''
as it pertains to exposure and risk encompasses both variability in
the range of expected inputs and screening results due to existing
spatial, temporal, and other factors, as well as uncertainty in
being able to accurately estimate the true result.
---------------------------------------------------------------------------

    Model uncertainty concerns whether the model adequately represents
the actual processes (e.g., movement and accumulation) that might occur
in the environment. For example, does the model adequately describe the
movement of a pollutant through the soil? This type of uncertainty is
difficult to quantify. However, based on feedback received from
previous EPA SAB reviews and other reviews, we are confident that the
models used in the screening assessments are appropriate and state-of-
the-art for the multipathway and environmental screening risk
assessments conducted in support of RTR.
    Input uncertainty is concerned with how accurately the models have
been configured and parameterized for the assessment at hand. For Tier
1 of the multipathway and environmental screening assessments, we
configured the models to avoid underestimating exposure and risk. This
was accomplished by selecting upper-end values from nationally
representative datasets for the more influential parameters in the
environmental model, including selection and spatial configuration of
the area of interest, lake location and size, meteorology, surface
water, soil characteristics, and structure of the aquatic food web. We
also assume an ingestion exposure scenario and values for human
exposure factors that represent reasonable maximum exposures.
    In Tier 2 of the multipathway and environmental screening
assessments,

we refine the model inputs to account for meteorological patterns in
the vicinity of the facility versus using upper-end national values,
and we identify the actual location of lakes near the facility rather
than the default lake location that we apply in Tier 1. By refining the
screening approach in Tier 2 to account for local geographical and
meteorological data, we decrease the likelihood that concentrations in
environmental media are overestimated, thereby increasing the
usefulness of the screening assessment. In Tier 3 of the screening
assessments, we refine the model inputs again to account for hour-by-
hour plume rise and the height of the mixing layer. We can also use
those hour-by-hour meteorological data in a TRIM.FaTE run using the
screening configuration corresponding to the lake location. These
refinements produce a more accurate estimate of chemical concentrations
in the media of interest, thereby reducing the uncertainty with those
estimates. The assumptions and the associated uncertainties regarding
the selected ingestion exposure scenario are the same for all three
tiers.
    For the environmental screening assessment for acid gases, we
employ a single-tiered approach. We use the modeled air concentrations
and compare those with ecological benchmarks.
    For all tiers of the multipathway and environmental screening
assessments, our approach to addressing model input uncertainty is
generally cautious. We choose model inputs from the upper end of the
range of possible values for the influential parameters used in the
models, and we assume that the exposed individual exhibits ingestion
behavior that would lead to a high total exposure. This approach
reduces the likelihood of not identifying high risks for adverse
impacts.
    Despite the uncertainties, when individual pollutants or facilities
do not exceed screening threshold emission rates (i.e., screen out), we
are confident that the potential for adverse multipathway impacts on
human health is very low. On the other hand, when individual pollutants
or facilities do exceed screening threshold emission rates, it does not
mean that impacts are significant, only that we cannot rule out that
possibility and that a refined assessment for the site might be
necessary to obtain a more accurate risk characterization for the
source category.
    The EPA evaluates the following HAP in the multipathway and/or
environmental risk screening assessments, where applicable: Arsenic,
cadmium, dioxins/furans, lead, mercury (both inorganic and methyl
mercury), POM, HCl, and HF. These HAP represent pollutants that can
cause adverse impacts either through direct exposure to HAP in the air
or through exposure to HAP that are deposited from the air onto soils
and surface waters and then through the environment into the food web.
These HAP represent those HAP for which we can conduct a meaningful
multipathway or environmental screening risk assessment. For other HAP
not included in our screening assessments, the model has not been
parameterized such that it can be used for that purpose. In some cases,
depending on the HAP, we may not have appropriate multipathway models
that allow us to predict the concentration of that pollutant. The EPA
acknowledges that other HAP beyond these that we are evaluating may
have the potential to cause adverse effects and, therefore, the EPA may
evaluate other relevant HAP in the future, as modeling science and
resources allow.

IV. Analytical Results and Proposed Decisions

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

    As described above, for the HCl Production source category, we
conducted an inhalation risk assessment and an environmental risk
screening assessment on the only two HAP emitted, HCl and
Cl2. No PB-HAP are emitted from this source category;
therefore, a multipathway risk assessment was not warranted. We present
results of the risk assessment briefly below and in more detail in the
residual risk document titled Residual Risk Assessment for the
Hydrochloric Acid Production Source Category in Support of the Risk and
Technology Review 2018 Proposed Rule, which is available in the docket
for this action.
1. Inhalation Risk Assessment Results
    Table 2 of this preamble provides an overall summary of the results
of the inhalation risk assessment.

                                     Table 2--Inhalation Risk Assessment Summary for HCl Production Source Category
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                               Cancer MIR (in 1 million)                      Population      Population
                                           --------------------------------     Cancer        with cancer     with cancer
                                               Based on        Based on        incidence    risk of 1-in-1  risk of 10-in-    Max chronic noncancer HI
                                                actual         allowable      (cases per      million or     1 million or     actuals (and allowables)
                                               emissions       emissions         year)           more            more
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source Category...........................               0               0               0               0               0  0.2 (actuals)
                                                                                2 (allowables)
Whole Facility............................             600  ..............            0.09         980,000         130,000  6
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The inhalation risk modeling performed to estimate risks based on
actual emissions relied primarily on emissions data from the NEI. For
allowable emissions, the NEI data was used to calculate conservative
estimates of emissions. The results of the inhalation cancer risk
assessment, as shown in Table 2 of this preamble, indicate there is no
quantifiable cancer risk posed by the source category since the two HAP
emitted from the HCl Production source category are not known or
suspected carcinogens. Neither the EPA nor the International Agency for
Research on Cancer (IARC) has evaluated the weight of evidence with
respect to human carcinogenicity for Cl2. However, IARC has
determined that hydrogen chloride is not classifiable as a human
carcinogen. Likewise, the total estimated cancer incidence is 0 (zero)
excess cancer cases per year and no people are estimated to have cancer
risk associated with this source category. The maximum modeled chronic
noncancer HI (TOSHI) value for the source category based on actual
emissions is estimated to be 0.2, driven by emissions of Cl2
from process vents. The target organ affected is the respiratory
system. Exposure to HI levels will be less than 1 for populations in
the vicinity of an HCl production facility as a result of emissions
from this source category. The maximum chronic noncancer TOSHI would
increase when based on allowable emissions, with a TOSHI as high as 2
(respiratory) driven by Cl2 emissions from process vents at
two facilities. Based on allowable emissions, 300 people are estimated
to

have a noncancer HI above 1 at these two facilities.
2. Acute Risk Results
    The screening and refined analyses for acute impacts was based on
actual emissions, and to estimate the peak emission rates from the
average rates, a default multiplier of 10 was used for emission points
in the source category. The choice of a default multiplier of 10 is
discussed in section III.C.3.c of this preamble. The results of the
acute refined analysis indicate that the maximum off-facility-site
acute HQ is 0.7, based on the REL value for HCl, and occurs at one
facility. Refer to the document titled HCl RTR Modeling File Data
Source Documentation (available in the docket for this action) for a
detailed description of how the acute factors were developed for this
source category. For more detailed acute risk results, refer to the
residual risk document titled Residual Risk Assessment for the
Hydrochloric Acid Production Source Category in Support of the Risk and
Technology Review 2018 Proposed Rule, which is available in the docket
for this action.
3. Multipathway Risk Screening Results
    No PB-HAP (cadmium, dioxins, POM, mercury, arsenic, and lead) are
emitted from this source category. Therefore, a multi-pathway
assessment is not warranted.
4. Environmental Risk Screening Results
    The only environmental HAP emitted by facilities in this source
category is HCl. Results of the analysis for HCl indicate that, based
on actual emissions, the maximum annual off-site concentration is below
all ecological benchmarks for all facilities. Therefore, we do not
expect an adverse environmental effect as a result of HAP emissions
from this source category. For more detail on the environmental risk
screening assessment, refer to the residual risk document titled
Residual Risk Assessment for the Hydrochloric Acid Production Source
Category in Support of the Risk and Technology Review 2018 Proposed
Rule, which is available in the docket for this action.
5. Facility-Wide Risk Results
    We performed an assessment of the facility-wide risks to provide
context for the source category risks, using NEI data as described
above. The maximum facility-wide cancer MIR is 600-in-1 million, mainly
driven by ethylene oxide emissions from a variety of industrial
processes, none of which are part of this source category. The total
estimated cancer incidence from the facility-wide assessment is 0.09
excess cancer cases per year, or one excess case in every 11 years. We
estimate that approximately 980,000 people have cancer risks greater
than 1-in-1 million from exposure to HAP emitted from sources not
subject to the HCl Production NESHAP. We estimate that the maximum
facility-wide TOSHI is 6, mainly driven by emissions of
trichloroethylene from chemical manufacturing processes that are not
part of this source category. The target organs affected are kidney,
immunological, developmental, neurological, reproductive, and liver. We
estimate that approximately 760 people are exposed to noncancer HI
levels above 1, based on facility-wide emissions (not subject to the
HCl Production NESHAP) from the 19 facilities within this source
category.
6. What demographic groups might benefit from this regulation?
    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 risk to individual
demographic groups of the populations living within 5 km and within 50
km of the facilities. In the analysis, we evaluated the distribution of
HAP-related cancer and noncancer risk from the HCl Production source
category across different demographic groups within the populations
living near facilities.\17\
---------------------------------------------------------------------------

    \17\ Demographic groups included in the analysis are: White,
African American, Native American, other races and multiracial,
Hispanic or Latino, children 17 years of age and under, adults 18 to
64 years of age, adults 65 years of age and over, adults without a
high school diploma, people living below the poverty level, people
living two times the poverty level, and linguistically isolated
people.
---------------------------------------------------------------------------

    Results of the demographic analysis indicate that, for 3 of the 11
demographic groups, minorities, African American, and below the poverty
level, the percentage of the population living within 5 km of
facilities in the source category is greater than the corresponding
national percentage for the same demographic groups. When examining the
risk levels of those exposed to emissions from HCl production
facilities, we find that no one within 50 km (risk modeling domain) is
exposed to a cancer risk because the two HAP emitted are not known
carcinogens. Furthermore, no person is exposed to a noncancer TOSHI
greater than 1 due to HAP emissions from the HCl Production source
category.
    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 Hydrochloric Acid
Production, available in the docket for this action.

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

1. Risk Acceptability
    As noted in section II.A of this preamble, the EPA sets standards
under CAA section 112(f)(2) using ``a two-step standard-setting
approach, with an analytical first step to determine an `acceptable
risk' that considers all health information, including risk estimation
uncertainty, and includes a presumptive limit on MIR of `approximately
1-in-10 thousand.' '' See 54 FR 38045, September 14, 1989. We weigh all
health risk factors in our risk acceptability determination, including
the cancer MIR, cancer incidence, the maximum noncancer TOSHI, the
maximum acute noncancer HQ, the extent of noncancer risk, the
distribution of cancer and noncancer risk in the exposed population,
and the risk estimation uncertainties.
    For this risk assessment, the EPA estimated risk based on actual
and allowable emissions from HCl production sources. There are no
quantifiable cancer risk or cancer incidence associated with this
source category. Likewise, a TOSHI less than 1 indicates that the
combined HAP affecting a particular target organ are not likely to
cause adverse chronic noncancer health effects. Also, the acute refined
assessment indicates little potential concern of acute noncancer health
impacts. We identified no PB-HAP emitted from the source category, and,
thus, no known potential for multi-pathway effects.
    Considering all of the health risk information and factors
discussed above, including the uncertainties discussed in section III
of this preamble, the EPA proposes that the risks from the HCl
Production source category are acceptable.
2. Ample Margin of Safety Analysis
    As directed by CAA section 112(f)(2), we conducted an analysis to
determine if the current emissions standards provide an ample margin of
safety to protect public health. Under the ample margin of safety
analysis, the EPA considers all health factors evaluated in the risk
assessment and evaluates the cost and feasibility of available control
technologies and other measures

(including the controls, measures, and costs reviewed under the
technology review) that could be applied to this source category to
further reduce the risks (or potential risks) due to emissions of HAP
identified in our risk assessment. In this analysis, we considered the
results of the technology review, risk assessment, and other aspects of
our MACT rule review to determine whether there are any cost-effective
controls or other measures that would reduce emissions further to
provide an ample margin of safety with respect to the risks associated
with these emissions.
    As provided in more detail in section IV.D below, we did not
identify any developments in processes, practices, or controls for HCl
production facilities during our analysis for this proposal.
Hydrochloric acid production facilities use scrubbers to control
emissions of HCl and Cl2. These devices are capable of
achieving high levels of emission reductions and we did not identify
additional technologies capable of further reducing emissions from HCl
production facilities or any improvements to the existing technologies
that would result in further reduction of emissions. Given that we did
not identify any developments in practices, process, or control
technologies and the low risks remaining after implementation of the
NESHAP, we are proposing that the existing standards for the HCl
Production source category provide an ample margin of safety.
    Regarding the facility-wide risks due to ethylene oxide and
trichloroethylene (described above), which are due to emission sources
that are not part of the HCl Production source category, we intend to
evaluate those facility-wide estimated emissions and risks further and
may address these in a separate future action, as appropriate. In
particular, the EPA is addressing ethylene oxide based on the results
of the latest NATA released in August 2018, which identified the
chemical as a potential concern in several areas across the country.
The latest NATA estimates that ethylene oxide significantly contributes
to potential elevated cancer risks in some census tracts across the
U.S. (less than 1 percent of the total number of tracts). As noted on
the EPA's NATA website, NATA is a screening tool for state, local, and
tribal air agencies and the EPA suggests that NATA results be used
cautiously.\18\ These elevated risks are largely driven by an EPA risk
value that was updated in late 2016. Although this updated risk value
is also responsible for the elevated facility-wide risks calculated
here, as noted earlier, these risks are due to emission sources that
are not part of the HCl Production source category. Nevertheless, the
EPA is interested in receiving public comments on the use of the update
risk value for regulatory purposes.
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    \18\ In particular, the EPA has identified limitations to
consider when looking at the results (e.g., data gaps, default
assumptions, and regional differences in emissions data
completeness). A number of other aspects of the results are also
worth noting, such as the results apply best to larger areas, not
specific places; apply only to the analysis year (when the source
data were collected); and assume a person breathes the air toxics
emitted in the analysis every day for 70 years. See https://www.epa.gov/national-air-toxics-assessment/nata-limitations for a
more complete discussion.
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    The EPA will work with industry and state, local, and tribal air
agencies as the EPA takes a two-pronged approach to address ethylene
oxide emissions: (1) Reviewing CAA regulations for facilities that emit
ethylene oxide--starting with air toxics emissions standards for
miscellaneous organic chemical manufacturing facilities and commercial
sterilizers; and (2) getting additional information on ethylene oxide
emissions. This information will help the EPA as it evaluates
opportunities to reduce ethylene oxide emissions as part of its
regulations review, and will help the agency determine whether more
immediate emission reduction steps are necessary in any particular
locations. The EPA will post updates on its work to address ethylene
oxide on its website at: https://www.epa.gov/ethylene-oxide.
3. Adverse Environmental Effect
    The emissions data for this source category indicate the presence
of one environmental HAP, HCl, emitted by sources within this source
category. Based on the results of our environmental risk screening
assessment, we conclude that there is not an adverse environmental
effect as a result of HAP emissions from the HCl Production source
category. Thus, we are proposing that it is not necessary to set a more
stringent standard to prevent an adverse environmental effect.

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

    We did not identify any developments in processes, practices, or
controls for HCl production facilities during our analysis for this
proposal. We are not proposing any changes to the NESHAP based on our
technology review. Scrubbers are used across the industry to control
emissions of HCl and Cl2, with similar performance among
facilities. We reviewed the EPA's RACT/BACT/LAER Clearinghouse to
identify possible developments and none were found. Additionally, we
reviewed title V permits for all facilities and found no substantive
differences in the control strategies employed for HCl production
facilities. Finally, a search of peer reviewed literature did not yield
any information regarding technology developments for HCl production.

D. What other actions are we proposing?

    In addition to the proposed determinations regarding the RTRs
described above, we are proposing some revisions to the NESHAP to
address other issues. We are proposing revisions to the SSM provisions
of the MACT rule in order to ensure that they are consistent with the
Court decision in Sierra Club v. EPA, 551 F. 3d 1019 (D.C. Cir. 2008),
which vacated two provisions that exempted sources from the requirement
to comply with otherwise applicable CAA section 112(d) emission
standards during periods of SSM. We also are proposing various changes
to recordkeeping and reporting requirements and adding electronic
reporting. Our analyses and proposed changes related to these issues
are discussed below.
1. SSM Requirements
    In its 2008 decision in Sierra Club v. EPA, 551 F.3d 1019 (D.C.
Cir. 2008), the Court vacated portions of two provisions in the EPA's
CAA section 112 regulations governing the emissions of HAP during
periods of SSM. Specifically, the Court vacated the SSM exemption
contained in 40 CFR 63.6(f)(1) and 40 CFR 63.6(h)(1), holding that
under section 302(k) of the CAA, emissions standards or limitations
must be continuous in nature and that the SSM exemption violates the
CAA's requirement that some CAA section 112 standards apply
continuously.
    We are proposing the elimination of the SSM exemption in this rule
which appears at 40 CFR 63.9005(a). Consistent with Sierra Club v. EPA,
we are proposing standards in this rule that apply at all times. We are
also proposing several revisions to Table 7 (the General Provisions
Applicability Table) as explained in more detail below. For example, we
are proposing to eliminate the incorporation of the General Provisions'
requirement that the source develop an SSM plan. We also are proposing
to eliminate and revise certain recordkeeping and reporting
requirements related to the SSM exemption as further described below.
    The EPA has attempted to ensure that the provisions we are
proposing to eliminate are inappropriate,

unnecessary, or redundant in the absence of the SSM exemption. We are
specifically seeking comment on whether we have successfully done so.
    In proposing the standards in this rule, the EPA has taken into
account startup and shutdown periods. For the reasons explained below,
the EPA is not proposing alternate standards for those periods, but is
instead proposing that the source meet the otherwise applicable
standards during these periods. We have no data indicating that
emissions are different during startup or shutdown. For add-on control
systems, the HCl Production NESHAP requires the measurement of scrubber
flow rate and pH parameter limits apply at all times, including during
periods of startup and shutdown. The HCl Production NESHAP requires
add-on control device operating parameters to be recorded at least once
every 15 minutes. The HCl Production NESHAP specifies in 40 CFR
63.9040(c) that if an operating parameter is out of the allowed range,
this is a deviation from the operating limit and must be reported as
specified in 40 CFR 63.9050(d).
    The EPA is also proposing that the otherwise applicable limits
would apply during periods of malfunction. Periods of startup, normal
operations, and shutdown are all predictable and routine aspects of a
source's operations. Malfunctions, in contrast, are neither predictable
nor routine. Instead they are, by definition, sudden, infrequent and
not reasonably preventable failures of emissions control, process or
monitoring equipment (40 CFR 63.2 [Definition of malfunction]). The EPA
interprets CAA section 112 as not requiring emissions that occur during
periods of malfunction to be factored into development of CAA section
112 standards and this reading has been upheld as reasonable by the
Court in U.S. Sugar Corp. v. EPA, 830 F.3d 579, 606-610 (2016). Under
CAA section 112, emissions standards for new sources must be no less
stringent than the level ``achieved'' by the best controlled similar
source and emissions standards for existing sources generally must be
no less stringent than the average emission limitation ``achieved'' by
the best performing 12 percent of sources in the category. There is
nothing in CAA section 112 that directs the Agency to consider
malfunctions in determining the level ``achieved'' by the best
performing sources when setting emission standards. As the Court has
recognized, the phrase ``average emissions limitation achieved by the
best performing 12 percent of'' sources ``says nothing about how the
performance of the best units is to be calculated.'' Nat'l Ass'n of
Clean Water Agencies v. EPA, 734 F.3d 1115, 1141 (D.C. Cir. 2013).
While the EPA accounts for variability in setting emissions standards,
nothing in CAA section 112 requires the Agency to consider malfunctions
as part of that analysis. The EPA is not required to treat a
malfunction in the same manner as the type of variation in performance
that occurs during routine operations of a source. A malfunction is a
failure of the source to perform in a ``normal or usual manner'' and no
statutory language compels the EPA to consider such events in setting
CAA section 112 standards.
    As the Court recognized in U.S. Sugar Corp, accounting for
malfunctions in setting standards would be difficult, if not
impossible, given the myriad different types of malfunctions that can
occur across all sources in the category and given the difficulties
associated with predicting or accounting for the frequency, degree, and
duration of various malfunctions that might occur. Id. at 608; ``the
EPA would have to conceive of a standard that could apply equally to
the wide range of possible boiler malfunctions, ranging from an
explosion to minor mechanical defects. Any possible standard is likely
to be hopelessly generic to govern such a wide array of
circumstances.'' As such, the performance of units that are
malfunctioning is not ``reasonably'' foreseeable. See, e.g. Sierra Club
v. EPA, 167 F.3d 658, 662 (D.C. Cir. 1999 [``The EPA typically has wide
latitude in determining the extent of data-gathering necessary to solve
a problem. We generally defer to an agency's decision to proceed on the
basis of imperfect scientific information, rather than to invest the
resources to conduct the perfect study].'') See also, Weyerhaeuser v.
Costle, 590 F.2d 1011, 1058 (D.C. Cir. 1978) (``In the nature of
things, no general limit, individual permit, or even any upset
provision can anticipate all upset situations. After a certain point,
the transgression of regulatory limits caused by `uncontrollable acts
of third parties,' such as strikes, sabotage, operator intoxication or
insanity, and a variety of other eventualities, must be a matter for
the administrative exercise of case-by-case enforcement discretion, not
for specification in advance by regulation.''). In addition, emissions
during a malfunction event can be significantly higher than emissions
at any other time of source operation. For example, if an air pollution
control device with 99-percent removal goes off-line as a result of a
malfunction (as might happen if, for example, the bags in a baghouse
catch fire) and the emission unit is a steady state type unit that
would take days to shut down, the source would go from 99-percent
control to zero control until the control device was repaired. The
source's emissions during the malfunction would be 100 times higher
than during normal operations. As such, the emissions over a 4-day
malfunction period would exceed the annual emissions of the source
during normal operations. As this example illustrates, accounting for
malfunctions could lead to standards that are not reflective of (and
significantly less stringent than) levels that are achieved by a well-
performing non-malfunctioning source. It is reasonable to interpret CAA
section 112 to avoid such a result. The EPA's approach to malfunctions
is consistent with CAA section 112 and is a reasonable interpretation
of the statute.
    Although no statutory language compels the EPA to set standards for
malfunctions, the EPA has the discretion to do so where feasible. For
example, in the Petroleum Refinery Sector Risk and Technology Review,
the EPA established a work practice standard for unique types of
malfunction that result in releases from pressure relief devices or
emergency flaring events because the EPA had information to determine
that such work practices reflected the level of control that applies to
the best performers. 80 FR 75178, 75211-14 (December 1, 2015). The EPA
will consider whether circumstances warrant setting standards for a
particular type of malfunction and, if so, whether the EPA has
sufficient information to identify the relevant best performing sources
and establish a standard for such malfunctions. We also encourage
commenters to provide any such information.
    In the event that a source fails to comply with the applicable CAA
section 112(d) standards as a result of a malfunction event, the EPA
would determine an appropriate response based on, among other things,
the good faith efforts of the source to minimize emissions during
malfunction periods, including preventative and corrective actions, as
well as root cause analyses to ascertain and rectify excess emissions.
The EPA would also consider whether the source's failure to comply with
the CAA section 112(d) standard was, in fact, sudden, infrequent, not
reasonably preventable and was not instead caused in part by poor
maintenance or careless operation. 40 CFR 63.2 (definition of
malfunction).
    If the EPA determines in a particular case that an enforcement
action against a source for violation of an emission

standard is warranted, the source can raise any and all defenses in
that enforcement action and the federal district court will determine
what, if any, relief is appropriate. The same is true for citizen
enforcement actions. Similarly, the presiding officer in an
administrative proceeding can consider any defense raised and determine
whether administrative penalties are appropriate.
    The EPA is not aware of circumstances that would allow for
establishing different emissions standard for some or all malfunctions
that may occur at HCl production facilities and, therefore, is not
proposing an alternative standard that would apply during periods of
malfunction.
    In summary, the EPA's interpretation of the CAA and, in particular,
CAA section 112, is reasonable and encourages practices that will avoid
malfunctions. Administrative and judicial procedures for addressing
exceedances of the standards fully recognize that violations may occur
despite good faith efforts to comply and can accommodate those
situations. U.S. Sugar Corp. v. EPA, 830 F.3d 579, 606-610 (2016).
2. 40 CFR 63.9005 General Duty
    We are proposing to revise the General Provisions table (Table 7)
entry for 40 CFR 63.6(e)(1)(i) by changing the ``yes'' in column 3 to a
``no.'' Section 63.6(e)(1)(i) describes the general duty to minimize
emissions during periods of SSM. With the elimination of the SSM
exemption, there is no need to differentiate between normal operations,
startup and shutdown, and malfunction events in describing the general
duty. We are proposing instead to add general duty regulatory text at
40 CFR 63.9005(b) that reflects the general duty to minimize emissions
during all periods of operation. Therefore, the language the EPA is
proposing for 40 CFR 63.9005(b) does not include that language from 40
CFR 63.6(e)(1).
    We are also proposing to revise the General Provisions table (Table
7) entry for 40 CFR 63.6(e)(1)(ii) by changing the ``yes'' in column 3
to a ``no.'' This provision requires malfunctions to be corrected as
quickly as practicable and minimize emissions consistent with safety
and good air pollution control practices. Section 63.6(e)(1)(ii)
imposes requirements that are not necessary with the elimination of the
SSM exemption or are redundant with the general duty requirement being
added at 40 CFR 63.9005(b).
3. SSM Plan
    We are proposing to revise the General Provisions table (Table 7)
entry for 40 CFR 63.6(e)(3) by changing the ``yes'' in column 3 to a
``no.'' Generally, these paragraphs require development of an SSM plan
and specify SSM recordkeeping and reporting requirements related to the
SSM plan. As noted, the EPA is proposing to remove the SSM exemptions.
Therefore, affected units will be subject to an emission standard
during such events. The applicability of a standard during such events
will ensure that sources have ample incentive to plan for and achieve
compliance as they do during periods of normal operation and, thus,
planning requirements specific for SSM are no longer necessary.
4. Compliance With Standards
    We are proposing to revise the General Provisions table (Table 7)
entry for 40 CFR 63.6(f)(1) by changing the ``yes'' in column 3 to a
``no.'' The current language of 40 CFR 63.6(f)(1) exempts sources from
non-opacity standards during periods of SSM. As discussed above, the
Court in Sierra Club vacated the exemptions contained in 40 CFR
63.6(f)(1) and held that the CAA requires a standard to apply
continuously. Consistent with Sierra Club, the EPA is proposing to
revise standards in this rule to apply at all times.
5. 40 CFR 63.9020 Performance Testing
    We are proposing to revise the General Provisions table (Table 7)
entry for 40 CFR 63.7(e)(1) by changing the ``yes'' in column 3 to a
``no.'' Section 63.7(e)(1) describes performance testing requirements.
The EPA is instead proposing to add a performance testing requirement
at 40 CFR 63.9020(a)(3). The performance testing requirements we are
proposing to add differ from the General Provisions performance testing
provisions in several respects. Specifically, the new proposed
performance testing requirements do not include the language in 40 CFR
63.7(e)(1) restating the SSM exemption. However, we are including
similar language that precludes startup and shutdown periods from being
considered ``representative'' for purposes of performance testing. As
provided in 40 CFR 63.7(e)(1), we are including language in 40 CFR
63.9020(a)(3) providing that performance tests conducted under this
subpart should not be conducted during malfunctions. This is because
conditions during malfunctions are often not representative of normal
operating conditions. The EPA is proposing to add language that
requires the owner or operator to record the process information that
is necessary to document operating conditions during the test and