[Federal Register Volume 84, Number 196 (Wednesday, October 9, 2019)]
[Proposed Rules]
[Pages 54278-54352]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-19875]



[[Page 54277]]

Vol. 84

Wednesday,

No. 196

October 9, 2019

Part II





Environmental Protection Agency





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40 CFR Part 63





National Emission Standards for Hazardous Air Pollutants: Generic 
Maximum Achievable Control Technology Standards Residual Risk and 
Technology Review for Ethylene Production; Proposed Rule

  Federal Register / Vol. 84 , No. 196 / Wednesday, October 9, 2019 / 
Proposed Rules  

[[Page 54278]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2017-0357; FRL-9999-59-OAR]
RIN 2060-AT02


National Emission Standards for Hazardous Air Pollutants: Generic 
Maximum Achievable Control Technology Standards Residual Risk and 
Technology Review for Ethylene Production

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The U.S. Environmental Protection Agency (EPA) is proposing 
amendments to the National Emission Standards for Hazardous Air 
Pollutants (NESHAP): Generic Maximum Achievable Control Technology 
Standards. The source category addressed in this action is Ethylene 
Production. The EPA is proposing decisions concerning the residual risk 
and technology review (RTR), including proposing amendments pursuant to 
technology review for storage vessels and heat exchange systems. The 
EPA is also proposing amendments to correct and clarify regulatory 
provisions related to emissions during periods of startup, shutdown, 
and malfunction (SSM), including removing general exemptions for 
periods of SSM, adding work practice standards for periods of SSM where 
appropriate, and clarifying regulatory provisions for certain vent 
control bypasses. Lastly the EPA is proposing to add monitoring and 
operational requirements for flares; and add provisions for electronic 
reporting of performance test results and reports and Notification of 
Compliance Status (NOCS) reports. We estimate that these proposed 
amendments will reduce hazardous air pollutants (HAP) emissions from 
this source category by 62 tons per year (tpy).

DATES: Comments. Comments must be received on or before November 25, 
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 November 8, 2019.
    Public hearing. If anyone contacts us requesting a public hearing 
on or before October 15, 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/acetal-resins-acrylic-modacrylic-fibers-carbon-black-hydrogen. See SUPPLEMENTARY INFORMATIONfor 
information on requesting and registering for a public hearing.

ADDRESSES: You may send comments, identified by Docket ID No. EPA-HQ-
OAR-2017-0357 by any of the following methods:
     Federal eRulemaking Portal: https://www.regulations.gov/ 
(our preferred method). Follow the online instructions for submitting 
comments.
     Email: [email protected]. Include Docket ID No. EPA-
HQ-OAR-2017-0357 in the subject line of the message.
     Fax: (202) 566-9744. Attention Docket ID No. EPA-HQ-OAR-
2017-0357.
     Mail: U.S. Environmental Protection Agency, EPA Docket 
Center, Docket ID No. EPA-HQ-OAR-2017-0357, Mail Code 28221T, 1200 
Pennsylvania Avenue NW, Washington, DC 20460.
     Hand/Courier Delivery: EPA Docket Center, WJC West 
Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004. 
The Docket Center's hours of operation are 8:30 a.m.-4:30 p.m., Monday-
Friday (except Federal holidays).
    Instructions: All submissions received must include the Docket ID 
No. for this rulemaking. Comments received may be posted without change 
to https://www.regulations.gov/, including any personal information 
provided. For detailed instructions on sending comments and additional 
information on the rulemaking process, see the SUPPLEMENTARY 
INFORMATION section of this document.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed 
action, contact Andrew Bouchard, Sector Policies and Programs Division 
(E-143-01), Office of Air Quality Planning and Standards, U.S. 
Environmental Protection Agency, Research Triangle Park, North Carolina 
27711; telephone number: (919) 541-4036; and email address: 
[email protected]. For specific information regarding the risk 
modeling methodology, contact Mark Morris, 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) 541-5416; and email 
address: [email protected]. For questions about monitoring and 
testing requirements, contact Gerri Garwood, Sector Policies and 
Programs Division (D-245-05), Office of Air Quality Planning and 
Standards, U.S. Environmental Protection Agency, Research Triangle 
Park, North Carolina 27711; telephone number: (919) 541-2406; and email 
address: [email protected]. For information about the applicability 
of the NESHAP to a particular entity, contact Marcia Mia, Office of 
Enforcement and Compliance Assurance (OECA), U.S. Environmental 
Protection Agency, WJC South Building (Mail Code 2227A), 1200 
Pennsylvania Avenue NW, Washington, DC 20460; telephone number: (202) 
564-7042; and email address: [email protected].

SUPPLEMENTARY INFORMATION: 
    Public hearing. Please contact Ms. Virginia Hunt at (919) 541-0832 
or by email at [email protected] 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-2017-0357. 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, 
WJC West Building, 1301 Constitution Avenue NW, Washington, DC. The 
Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through 
Friday, excluding legal holidays. The telephone number for the Public 
Reading Room is (202) 566-1744, and the telephone number for the EPA 
Docket Center is (202) 566-1742.
    Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2017-0357. 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

[[Page 54279]]

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://www.epa.gov/dockets/commenting-epa-dockets.
    The https://www.regulations.gov/ website allows you to submit your 
comment anonymously, which means the EPA will not know your identity or 
contact information unless you provide it in the body of your comment. 
If you send an email comment directly to the EPA without going through 
https://www.regulations.gov/, your email address will be automatically 
captured and included as part of the comment that is placed in the 
public docket and made available on the internet. If you submit an 
electronic comment, the EPA recommends that you include your name and 
other contact information in the body of your comment and with any 
digital storage media you submit. If the EPA cannot read your comment 
due to technical difficulties and cannot contact you for clarification, 
the EPA may not be able to consider your comment. Electronic files 
should not include special characters or any form of encryption and be 
free of any defects or viruses. For additional information about the 
EPA's public docket, visit the EPA Docket Center homepage at https://www.epa.gov/dockets.
    Submitting CBI. Do not submit information containing CBI to the EPA 
through https://www.regulations.gov/ 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-2017-0357.
    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:

ACC American Chemistry Council
AEGL acute exposure guideline level
AERMOD air dispersion model used by the HEM-3 model
AFPM American Fuel & Petrochemical Manufacturers
AMEL alternative means of emission limitation
APCD air pollution control device
ATSDR Agency for Toxic Substances and Disease Registry
BAAQMD Bay Area Air Quality Management District
BACT best available control technology
BDL elow detection levels
Btu British thermal units
BWON benzene waste operations NESHAP
CAA Clean Air Act
CalEPA California EPA
CBI Confidential Business Information
CDX Central Data Exchange
CEDRI Compliance and Emissions Data Reporting Interface
CEMS continuous emission monitoring system(s)
CFR Code of Federal Regulations
CMS continuous monitoring systems
CO carbon monoxide
CO2 carbon dioxide
CPMS continuous parametric monitoring system(s)
DLL detection level limited
EBU enhanced biological unit
ECHO enforcement and compliance history online
EFR external floating roof
EMACT ethylene production MACT
EPA Environmental Protection Agency
ERPG Emergency Response Planning Guideline
ERT Electronic Reporting Tool
FTIR Fourier transform infrared spectrometry
GACT generally available control technologies
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
HRVOC highly reactive volatile organic compounds
IBR incorporation by reference
ICR Information Collection Request
IFR internal floating roof
IRIS Integrated Risk Information System
km kilometer
kPa kilopascals
LAER lowest achievable emission rate
LDAR leak detection and repair
LEL lower explosive limit
lpm liters per minute
MACT maximum achievable control technology
m\3\ cubic meter
mg/m\3\ milligrams per cubic meter
Mg/yr megagrams per year
MIR maximum individual risk
MMBtu million British thermal units
MON miscellaneous organic chemical manufacturing NESHAP
MPGF multi-point ground flare(s)
MTVP maximum true vapor pressure
NAAQS National Ambient Air Quality Standards
NAICS North American Industry Classification System
NATA National Air Toxics Assessment
NEI national emission inventory
NESHAP national emission standards for hazardous air pollutants
NHVcz net heating value in the combustion zone gas
NHVdil net heating value dilution parameter
NHVvg net heating value in the vent gas
NOCS notification of compliance status
NPDES National Pollutant Discharge Elimination System
NRDC Natural Resources Defense Council
NSPS new source performance standards
NTTAA National Technology Transfer and Advancement Act
OAQPS Office of Air Quality Planning and Standards
OECA Office of Enforcement and Compliance Assurance
OMB Office of Management and Budget
OSHA Occupational Safety and Health Administration
PAH polycyclic aromatic hydrocarbons
PB-HAP hazardous air pollutants known to be persistent and bio-
accumulative in the environment
PDF portable document format
PM particulate matter
PM2.5 particulate matter less than 2.5 microns in 
diameter
POM polycyclic organic matter
ppm parts per million
ppmv parts per million by volume
ppmvd parts per million by volume, dry basis
ppmw parts per million by weight
PRA Paperwork Reduction Act
PRD pressure relief device(s)
psig pounds per square inch gauge
RACT reasonably available control technology
RATA relative accuracy test audit
REL reference exposure level

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RFA Regulatory Flexibility Act
RfC reference concentration
RfD reference dose
RTR residual risk and technology review
SAB Science Advisory Board
SCAQMD South Coast Air Quality Management District
SCC source classification code
SOCMI synthetic organic chemical manufacturing industry
SSM startup, shutdown, and malfunction
TAB total annual benzene
TAC Texas Administrative Code
TCEQ Texas Commission on Environmental Quality
TOSHI target organ-specific hazard index
tpy tons per year
TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport, and 
Ecological Exposure model
TSM total selected metals
UF uncertainty factor
[micro]g/m\3\ microgram per cubic meter
UMRA Unfunded Mandates Reform Act
URE unit risk estimate
VCS voluntary consensus standards
VOC volatile organic compound(s)

    Organization of this document. The information in this preamble is 
organized as follows below. In particular, section IV of this preamble 
describes the majority of the agency's rationale for the proposed 
actions in this preamble. Section IV.A specifies proposed monitoring 
and operational requirements for flares in the ethylene production 
source category to ensure that the level of control from the original 
MACT standards is achieved by these air pollution control devices 
(APCD). To ensure that CAA section 112 standards continuously apply 
(Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008), section IV.A also 
proposes work practice standards for periods of SSM for when flares are 
used as an APCD, proposes work practice standards for periods of SSM 
for certain vent streams (i.e. PRD releases and maintenance vents), 
proposes clarifications for vent control bypasses for certain vent 
streams (i.e., closed vent systems containing bypass lines, in situ 
sampling systems, and flares connected to fuel gas systems), and 
proposes work practice standards for decoking operations for ethylene 
cracking furnaces (which is currently defined as a shutdown activity in 
the Ethylene Production NESHAP).
    Section IV.B of this preamble summarizes the results of the risk 
assessment while section IV.C of this preamble summarizes our proposed 
decisions regarding the results of the risk assessment. Section IV.D of 
this preamble summarizes the results of our technology review, and 
proposes revisions for storage vessels and heat exchange systems. 
Section IV.E of this preamble summarizes other changes we are 
proposing, including general regulatory language changes related to the 
removal of SSM exemptions, electronic reporting, and other minor 
clarifications identified as part our review of the NESHAP and as part 
of the other proposed revisions in this action. Lastly, section IV.F of 
this preamble summarizes our rationale for the compliance dates we are 
proposing.

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 actions are we taking in addition to those identified in 
the risk and technology review?
    B. What are the results of the risk assessment and analyses?
    C. What are our proposed decisions regarding risk acceptability, 
ample margin of safety, and adverse environmental effect?
    D. What are the results and proposed decisions based on our 
technology review?
    E. What other actions are we proposing?
    F. 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?
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 Regulations 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) and 
1 CFR Part 51
    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 category that is 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 would not be affected by this proposed action. As 
defined in the National Emission Standards for Hazardous Air 
Pollutants; Revision of Initial List of Categories of Sources and 
Schedule for Standards Under Sections 112(c) and (e) of the Clean Air 
Act Amendments of 1990 (61 FR 28197, June 4, 1996), the Ethylene 
Production source category includes any chemical manufacturing process 
unit in which ethylene and/or propylene are produced by separation from 
petroleum refining process streams or by subjecting hydrocarbons to 
high temperatures in the presence of steam.\1\ The ethylene production 
unit includes the separation of ethylene and/or propylene from 
associated streams such as a C4 product,\2\ pyrolysis gasoline, and 
pyrolysis fuel oil. The ethylene production unit does not include the 
manufacture of Synthetic Organic Chemical Manufacturing Industry 
(SOCMI) chemicals such as the production of butadiene from the C4 
stream and aromatics from pyrolysis gasoline.
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    \1\ In the June 4, 1996, document that revised the Initial List 
of Source Categories, the EPA added seven categories of major 
sources that included a source category listed as ``Ethylene 
Processes,'' (61 FR 28197); however, subsequent regulatory actions 
taken by the EPA, including the initial NESHAP development (e.g., 65 
FR 76408, December 6, 2000) and current regulatory text at 40 CFR 
part 63, subpart YY refer to the source category as ``Ethylene 
Production.''
    \2\ The C4 product stream is a hydrocarbon product stream from 
an ethylene production unit consisting of compounds with four carbon 
atoms (e.g., butanes, butenes, butadienes).

[[Page 54281]]



    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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Ethylene Production...............  Generic Maximum               325110
                                     Achievable Control
                                     Technology
                                     Standards.
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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/stationary-sources-air-pollution/acetal-resins-acrylic-modacrylic-fibers-carbon-black-hydrogen. Following publication 
in the Federal Register, the EPA will post the Federal Register version 
of the proposal and key technical documents at this same website. 
Information on the overall 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-2017-0357).

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 Clean Air Act (CAA), as amended (42 U.S.C. 7401 et 
seq.). Section 112 of the CAA establishes a two-stage regulatory 
process to develop standards for emissions of HAP from stationary 
sources. Generally, the first stage involves establishing technology-
based standards and the second stage involves evaluating those 
standards that are based on 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 
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) 
\3\ 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

[[Page 54282]]

of all health information, including the number of persons at risk 
levels higher than approximately 1-in-1 million, as well as other 
relevant factors, including costs and economic impacts, technological 
feasibility, and other factors relevant to each particular decision.'' 
Id. The EPA must promulgate emission standards necessary to provide an 
ample margin of safety to protect public health or determine that the 
standards being reviewed provide an ample margin of safety without any 
revisions. After conducting the ample margin of safety analysis, the 
EPA considers whether a more stringent standard is necessary to 
prevent, taking into consideration costs, energy, safety, and other 
relevant factors, an adverse environmental effect.
---------------------------------------------------------------------------

    \3\ Although defined as ``maximum individual risk,'' MIR refers 
only to cancer risk. MIR, one metric for assessing cancer risk, is 
the estimated risk if an individual were exposed to the maximum 
level of a pollutant for a lifetime.
---------------------------------------------------------------------------

    CAA section 112(d)(6) 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?

    The Ethylene Production MACT standards (herein called the EMACT 
standards) for the Ethylene Production source category are contained in 
the Generic Maximum Achievable Control Technology (GMACT) NESHAP which 
also includes MACT standards for several other source categories. The 
EMACT standards were promulgated on July 12, 2002 (67 FR 46258) and 
codified at 40 CFR part 63, subparts XX and YY. As promulgated in 2002, 
and further amended on April 13, 2005 (70 FR 19266), the EMACT 
standards regulate HAP emissions from ethylene production units located 
at major sources. An ethylene production unit is a chemical 
manufacturing process unit in which ethylene and/or propylene are 
produced by separation from petroleum refining process streams or by 
subjecting hydrocarbons to high temperatures in the presence of steam. 
The EMACT defines the affected source as all storage vessels, ethylene 
process vents, transfer racks, equipment, waste streams, heat exchange 
systems, and ethylene cracking furnaces and associated decoking 
operations that are associated with each ethylene production unit 
located at a major source as defined in CAA section 112(a).
    As of January 1, 2017, there were 26 ethylene production facilities 
in operation and subject to the EMACT standards. This is based on our 
search of the National Emission Inventory (NEI) and the EPA's 
Enforcement and Compliance History Online (ECHO) database 
(www.echo.epa.gov), and facility responses to our CAA section 114 
request (see section II.C of this preamble for details about our CAA 
section 114 request). We are also aware of the expansion and 
construction of several facilities. Based upon this anticipated growth 
for the Ethylene Production source category, we estimate that a total 
of 31 ethylene production facilities will ultimately be subject to the 
EMACT standards. A complete list of facilities that are currently 
subject, or will be subject, to the EMACT standards is available in 
Appendix A of the memorandum titled Review of the RACT/BACT/LAER 
Clearinghouse Database for the Ethylene Production Source Category, 
which is available in Docket ID No. EPA-HQ-OAR-2017-0357.

C. What data collection activities were conducted to support this 
action?

    In July 2014, the EPA issued a request, pursuant to CAA section 
114, to collect information from ethylene production facilities owned 
and operated by nine entities (i.e., corporations). This effort focused 
on gathering comprehensive information about process equipment, control 
technologies, point and fugitive emissions, and other aspects of 
facility operations. Companies completed the survey and submitted 
responses (and follow-up responses) to the EPA between October 2014 and 
September 2015. Additionally, in April 2016, the EPA requested 
historical monitoring and compliance data for heat exchange systems and 
ethylene cracking furnaces, emissions source sampling for certain 
pollutants for heat exchange systems, and stack testing for certain 
pollutants for ethylene cracking furnaces under both normal operation 
as well as during decoking operations. The results of these requests 
were submitted to the EPA between the fall of 2016 and spring of 2017. 
The EPA has used the collected information to fill data gaps, establish 
the baseline emissions and control levels for purposes of the 
regulatory reviews, to identify the most effective control measures, 
and estimate the environmental and cost impacts associated with the 
regulatory options considered and reflected in this proposed action. 
The information not claimed as CBI by respondents is available in the 
memorandum titled Data Received From Information Collection Request for 
the Ethylene Production Source Category, in Docket ID No. EPA-HQ-OAR-
2017-0357.

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

    We are relying on certain technical reports and memoranda that the 
EPA developed for flares used as APCDs in the petroleum refinery sector 
and new source performance standards (NSPS) (80 FR 75178, December 1, 
2015). For completeness of the rulemaking record for this action and 
for ease of reference in finding these items in the publicly available 
Refinery rulemaking Docket, we are including in the docket for this 
rulemaking (Docket ID No. EPA-HQ-OAR-2017-0357) a list of specific 
technical support documents in Table 1 of the memorandum titled Control 
Option Impacts for Flares Located in the Ethylene Production Source 
Category. The Petroleum Refinery sector and NSPS rulemaking Docket is 
located at Docket ID No. EPA-HQ-OAR-2010-0682.
    In addition, the EPA is incorporating into the docket for this 
rulemaking, materials associated with a number of site-specific 
alternative means of emission limitation (AMEL) requests for facilities 
electing to use multi-point ground flares (MPGFs) as an APCD. These 
site-specific AMEL requests for MPGFs have been approved by the EPA 
because the MPGF can achieve at least equivalent reductions in 
emissions as the underlying flare operational standards in various 
NESHAP and/or NSPS. The EPA receives these AMEL requests because MPGF 
are designed to operate above the current maximum permitted velocity 
requirements for flares in the General Provisions at 40 CFR 63.11(b). 
Given that the EPA has provided notice and sought comments on certain 
specific AMEL requests, the underlying AMEL requests submitted by 
industry, MPGF test data, technical memorandums, Federal Register 
documents \4\ and other supporting and related material that formed the 
basis of the AMEL requests and approved alternative operating 
conditions have been placed in a publicly available docket at Docket ID 
No. EPA-HQ-OAR-2014-0738. We consider all items in

[[Page 54283]]

Docket ID No. EPA-HQ-OAR-2014-0738 part of our rulemaking record as 
well, given that this docket is specific to MPGF AMEL requests. We are, 
therefore, incorporating this docket by reference in this rule.
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    \4\ 80 FR 8023, February 13, 2015; 80 FR 52426, August 31, 2015; 
81 FR 23480, April 21, 2016; 82 FR 16392, April 4, 2017; 82 FR 
27822, June 19, 2017; and 83 FR 18034, April 25, 2018.
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    Lastly, the EPA is incorporating into the docket for this 
rulemaking, all materials associated with the development of the 
current GMACT and EMACT standards from Docket ID No. A-97-17, Docket ID 
No. A-98-22, and Docket ID No. OAR-2204-0411. Publicly available docket 
materials are available either electronically at https://www.regulations.gov/,or in hard copy at the EPA Docket Center, EPA WJC 
West Building, Room 3334, 1301 Constitution Ave. NW, Washington, DC. 
The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday 
through Friday, excluding legal holidays. The telephone number for the 
Public Reading Room is (202) 566-1744, and the telephone number for the 
EPA Docket Center is (202) 566-1742.

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.\5\ 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:
---------------------------------------------------------------------------

    \5\ 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 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 an 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 an increased risk of adverse noncancer health effects. In May 
2010, the Science Advisory Board (SAB) advised the EPA ``that RTR 
assessments will be most useful to decision makers and communities if 
results are presented in the broader context of aggregate and 
cumulative risks, including background concentrations and contributions 
from other sources in the area.'' \6\
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    \6\ Recommendations of the SAB Risk and Technology Review (RTR) 
Methods Panel are provided in their report, which is available at: 
https://yosemite.epa.gov/sab/sabproduct.nsf/
4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf.

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[[Page 54284]]

    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 
(or last updated) 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 Ethylene 
Production Source Category in Support of the 2019 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; 
\7\ and described in the SAB review report issued in 2010. They are 
also consistent with the key recommendations contained in that report.
---------------------------------------------------------------------------

    \7\ 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.
---------------------------------------------------------------------------

1. How did we estimate actual emissions and identify the emissions 
release characteristics?
    For each facility that we determined to be subject to the EMACT 
standards (see section II.B of this preamble), we gathered emissions 
data from Version 1 of the 2011 NEI. For each NEI record, we reviewed 
the source classification code (SCC), emission unit, and process 
descriptions, and then assigned the record to an emission source type 
(i.e., each record was labeled storage vessel, process vent, transfer 
rack, equipment leak, waste, heat exchange system, cracking furnace, 
decoking pot, PRD, other ethylene source type, or non-ethylene source 
type).
    In May 2014, the EPA provided member companies of the American 
Chemistry Council (ACC) and the American Fuel & Petrochemical 
Manufacturers (AFPM) an opportunity to voluntarily review their NEI 
records for completeness and accuracy, given that these records would 
form the underlying basis of our emissions modeling input files for the 
residual risk review. The NEI records were sent in separate 
Microsoft[supreg] Excel worksheet(s) via email to each company that 
operates at least one facility in the Ethylene Production source 
category. Each company was afforded an opportunity to review (and 
revise, if necessary) emission values, emission release point 
parameters, coordinates, and emission source type assignments. All 
revisions and changes from these voluntary reviews were received 
between June

[[Page 54285]]

2014 through October 2014, and then incorporated into the modeling 
file.
    Also, as part of the mandatory July 2014 CAA section 114 request 
(see section II.C of this preamble for details about our CAA section 
114 request), the EPA asked companies to provide emission release point 
parameters and coordinates, for all emission release points associated 
with ethylene production if this information had not been previously 
submitted as part of their voluntary review. In response to these 
requests, companies also submitted process flow diagrams illustrating 
the connectivity between each process and the emission release points. 
We used all this information to reevaluate each NEI record in the 
modeling file and to update emission release point parameter data. In 
other words, we used the CAA section 114 response data wherever 
possible in lieu of the 2011 NEI and/or voluntary review data.
    Finally, we reviewed each of the emission source types to 
incorporate recent data and to ensure the data were complete and 
representative. For instance, for the modeling file, we replaced the 
2011 NEI ethylene cracking furnace and decoking operation emissions 
data with the ethylene cracking furnace and decoking operation stack 
test data that we received from the CAA section 114 responses because 
we generally consider stack test data to be much more representative of 
emissions from these operations than emission estimates made in the 
absence of this data. For each of the other emission source types 
associated with an ethylene production unit (i.e., storage vessels, 
ethylene process vents, transfer racks, equipment leaks, waste streams, 
and heat exchange systems), we compared emissions between all 
facilities, and, based on this comparison, we observed some 
inconsistencies with the reported emissions between the different 
emission sources. For example, certain facilities did not report 
emissions for an emission source type while others did so. Therefore, 
we focused on the following two criteria to determine whether facility 
emissions were both complete and representative: (1) A facility should 
have emissions for all emission source types (provided that the 
emission source type exists at the facility), and (2) a facility should 
have emissions for all emission source types above source-specific 
emission thresholds. If either of those criteria were not met for an 
emission source type at a facility, then we applied a model emissions 
profile to update the modeling file. These model emissions profiles, in 
concert with the stack test data received from the CAA section 114 
responses, were also used to develop model plants for the new ethylene 
production facilities currently under construction and for recent major 
expansions at existing facilities for which annual emissions data were 
not available to the Agency. For further details on the assumptions and 
methodologies used to estimate actual emissions, identify the emissions 
release characteristics, develop model emissions profiles, and develop 
model plants, see Appendix 1 of the document titled Residual Risk 
Assessment for the Ethylene Production Source Category in Support of 
the 2019 Risk and Technology Review Proposed Rule, which is available 
in the docket for this rulemaking. We solicit comment on additional 
information for the Ethylene Production source category that the EPA 
could consider to estimate actual emissions.
2. How did we estimate MACT-allowable emissions?
    The available emissions data in the RTR emissions dataset include 
estimates of the mass of HAP emitted during a specified annual time 
period. These ``actual'' emission levels are often lower than the 
emission levels allowed under the requirements of the current MACT 
standards. The emissions allowed under the MACT standards are referred 
to as the ``MACT-allowable'' emissions. We discussed the consideration 
of both MACT-allowable and actual emissions in the final Coke Oven 
Batteries RTR (70 FR 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.)
    Apart from emissions from heat exchange systems and PRD releases, 
we have determined that the actual emissions data are reasonable 
estimates of the MACT-allowable emissions levels for the Ethylene 
Production source category. For heat exchange systems, the MACT-
allowable emissions were assessed using a HAP speciation profile at the 
annualized mass leak rate of 29.5 tpy allowed by the underlying MACT 
standard at 40 CFR part 63, subpart XX. For atmospheric PRD releases, 
the MACT-allowable emissions were assessed using a single atmospheric 
PRD release identified from a review of excess emissions reported over 
a 7.5-year period for approximately 30 percent of the facilities in the 
source category.
    The ability to estimate MACT-allowable emissions from the actual 
emissions dataset is largely dependent on the format of the standard 
for a given emissions source as well as the types of controls employed 
for the source. With respect to the various types of controls used 
within the Ethylene Production source category, the most prevalent is 
the use of a flare as a combustion control device. A flare can be used 
to control emissions for a single emissions source, or, as is generally 
the case, to control emissions from multiple emission sources/emission 
source types.
    Flares are designed to handle a large range of variable flowrates 
and compositions of combustible waste gases. Within the Ethylene 
Production source category, flares generally control emissions from 
multiple emission source types. Consideration of this, along with not 
having a specific limit on how much gas can be combusted in a flare 
(given that in many cases multiple emissions sources are being 
controlled by this control device), means that it is extremely 
difficult to determine an allowable emission rate for flares. For 
purposes of this RTR, we have determined that flares in the Ethylene 
Production source category are currently complying with certain design 
and operational requirements that are generally expected to achieve 98-
percent destruction efficiencies or control. HAP emissions inventories 
for flares in the Ethylene Production source category are developed 
using engineering knowledge and, in many instances, presume this 98-
percent level of control. The Agency is unaware of any data that 
suggest that flares used as controls in the Ethylene Production source 
category are consistently over-controlling HAP emissions beyond 98-
percent control. And, while the Agency is proposing new operating 
requirements for flares used as controls in this source category to 
ensure at least 98-percent control given that more recent studies have 
shown that some flares are operating less efficiently than 98-percent 
control (see section IV.A.1 of this preamble), for purposes of the 
MACT-allowable risk analysis, we are required to evaluate whether it is 
necessary to tighten the existing MACT standard and subsequent level of 
performance a flare is expected to

[[Page 54286]]

achieve. Thus, weighing all of these factors for flares, we believe 
that the actual emission levels are a reasonable estimation of the 
MACT-allowable emissions levels where the performance standards allow 
the use of a flare as an APCD (e.g., storage vessels, ethylene process 
vents, equipment leaks, transfer racks, and waste operations).
    For equipment leaks, which are currently subject to work practice 
standards, there would be no difference between actual and MACT-
allowable emissions for facilities in the Ethylene Production source 
category, provided the facilities are complying with the EMACT 
standards as well as not conducting additional work practices proven to 
reduce emissions beyond those required by the rule. We are aware of 
only one rule in the State of Texas, which is the Texas Commission of 
Environmental Quality (TCEQ) Highly Reactive Volatile Organic Compounds 
(HRVOC) Rule (i.e., 30 TAC Chapter 115, Subchapter H, Division 3), that 
may contain more stringent leak definitions and/or monitoring 
frequencies for certain pieces of equipment for the eight facilities 
located in Texas that might be subject to this rule. However, we note 
based on our review of the Texas rule that specific facilities, which 
are located in the Houston-Galveston-Brazoria area, still conduct a 
leak detection and repair (LDAR) program using EPA Method 21; that the 
vast majority of equipment (i.e., more than 95 percent of all equipment 
surveyed in the CAA section 114 request), including almost all pieces 
of equipment in gas and vapor service that would tend to highly 
contribute to the overall equipment leak air emissions, are complying 
with the same leak definition as in the EMACT standards; and that the 
TCEQ HRVOC Rule generally requires quarterly monitoring while the EMACT 
standards have varying degrees of monitoring frequencies depending on 
the percentage of leaking equipment that could lead to more stringent, 
the same, or less stringent frequencies that would require an EPA 
Method 21 measurement and repair of a leaking component (if measured). 
Therefore, weighing all of these factors for equipment leaks, we 
determined that the actual emission levels for equipment leaks are a 
reasonable estimation of the MACT-allowable emissions levels.
    For waste operations, the EMACT standards include various work 
practice standards for the collection system of waste streams as well 
as a performance standard for the treatment of these waste streams. 
Assuming that the equipment in the collection system is maintained 
properly and is in good working condition (as required), and that no 
facilities are employing additional work practices proven to reduce 
emissions beyond those required in the rule (we are unaware of any that 
are doing additional work practices), there would be no difference in 
the actual emissions level and the level allowed by the work practice 
standards for the collection of waste streams. In general, for this 
performance standard, it is possible that sources could over-control 
emission sources resulting in the actual emissions being lower than the 
MACT-allowable emissions. However, for waste operations, we are not 
aware of any such over-control. Therefore, we believe that the actual 
waste operations emission levels are a reasonable estimation of the 
MACT-allowable emissions levels.
    For heat exchange systems, the EMACT standards include a LDAR work 
practice where facilities are required to monitor for potential leaks 
of HAP from process fluids into the cooling water of a heat exchange 
system. Emissions of HAP from heat exchange systems result when leakage 
of HAP from process fluids into the cooling water occurs and then that 
cooling water is exposed to air (e.g., in a cooling tower for a closed-
loop system or from trenches/ponds in a once-through system). If a leak 
is detected, it is only required to be repaired in a heat exchange 
system if the exit mean concentration is at least 10 percent greater 
than the entrance mean of the listed HAP (total or speciated) in Table 
1 to subpart XX of 40 CFR part 63 (using a one-sided statistical 
procedure at the 0.05 level of significance) and if it is at least 3.06 
kilograms per hour (kg/hr). Therefore, for example, a leak of 3.05 kg/
hr or less of any HAP (total or speciated) that is listed in Table 1 to 
subpart XX of 40 CFR part 63 need not be repaired. If we assume that 
all the HAP at a 3.05 kg/hr leak rate would be emitted to the 
atmosphere after the process fluids leak into cooling water and then 
that cooling water is exposed to atmosphere, we would be left with an 
annual MACT-allowable emissions level for heat exchange systems of 29.5 
tpy (i.e., 3.05 kg/hr x 0.00110231 tons/kg x 8,760 hours per year (hr/
yr)) of HAP (total or speciated) listed in Table 1 to subpart XX of 40 
CFR part 63. In order to determine a reasonable HAP speciation profile 
to assess the MACT-allowable risk at the 29.5 tpy mass emission rate, 
we reviewed historical heat exchange system compliance data gathered 
under our CAA section 114 request. Given that 40 CFR part 63, subpart 
XX requires a monitoring sensitivity that would enable detection of a 
leak of 3.06 kg/hr or greater of the HAP listed in Table 1 to subpart 
XX of 40 CFR part 63, we focused our analysis on determining a 
reasonable HAP speciation profile based on historical leaks at or above 
3.06 kg/hr. This was done for the purposes of removing records in the 
dataset that have a higher level of uncertainty surrounding them (given 
the monitoring sensitivity requirement in the rule), as well as to 
remove the uncertainty in biased data where any reported historical 
smaller leaks may have been predominately driven by data that were 
reported at the detection level but were not actually measured. Thus, 
upon reviewing the historical heat exchange system compliance data, we 
found records of 10 speciated HAP leaks above 3.06 kg/hr that we 
averaged for purposes of forming the basis of our HAP speciation 
profile for the MACT-allowable emission level for heat exchange 
systems. The HAP speciation profile analysis is available in Appendix 1 
of the document titled Residual Risk Assessment for the Ethylene 
Production Source Category in Support of the 2019 Risk and Technology 
Review Proposed Rule, which is available in the docket for this 
rulemaking.
    For ethylene cracking furnaces and associated decoking operations, 
based on new information obtained through our CAA section 114 request, 
we have determined that HAP are being emitted from these source types 
and their actual emissions, which were measured from various ethylene 
cracking furnaces and associated decoking operations during the stack 
testing conducted pursuant to the CAA section 114 request, are allowed 
by the rule. As such, we determined that the actual emissions are equal 
to MACT-allowable emissions for these operations.
    Finally, in order to estimate the risk impacts of emissions from a 
PRD release, we reviewed TCEQ's Air Emission Event Report Database 
(http://www2.tceq.texas.gov/oce/eer/) over a 7.5-year period (i.e., 
January 1, 2010, to July 7, 2017) for roughly 30 percent of all 
operating ethylene production facilities (i.e., seven of 26 ethylene 
production facilities) in the source category that were chosen at 
random and that have been in operation since January 1, 2010. 
Accordingly, we believe these randomly selected facilities are a good 
representation of all ethylene production facilities in the source 
category. After reviewing TCEQ's database for reportable air emissions 
events for these seven facilities over a 7.5-year period, we determined 
that there were four reported emissions events that occurred from 
atmospheric

[[Page 54287]]

PRDs (e.g., events where a PRD did not release emissions to an APCD 
like a flare) on equipment in the Ethylene Production source category. 
A closer inspection of these records, however, reveals that only one of 
these events was actually an atmospheric PRD release on a properly 
operating PRD. Therefore, for MACT-allowable emissions for PRD 
releases, and in keeping with our conservative approach, we assumed 
that each facility would have this reported release of HAP (i.e., 46.8 
pounds (lbs) of 1,3-butadiene) occur once in a 7.5-year period (given 
that this is the duration of the data we reviewed) and modeled an 
annualized PRD release of HAP of 0.003 tpy of 1,3-butadiene from the 
centroid of each ethylene production facility.
    For further details on the assumptions and methodologies used to 
estimate MACT-allowable emissions, see Appendix 1 of the document 
titled Residual Risk Assessment for the Ethylene Production Source 
Category in Support of the 2019 Risk and Technology Review Proposed 
Rule, which is available in the docket for this rulemaking.
3. How do we conduct dispersion modeling, determine inhalation 
exposures, and estimate individual and population inhalation risks?
    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).\8\ 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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    \8\ For more information about HEM-3, go to https://www.epa.gov/fera/risk-assessment-and-modeling-human-exposure-model-hem.
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a. Dispersion Modeling
    The air dispersion model AERMOD, used by the HEM-3 model, is one of 
the EPA's preferred models for assessing HAP concentrations from 
industrial facilities.\9\ 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 (2017) 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 \10\ 
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.
---------------------------------------------------------------------------

    \9\ 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).
    \10\ 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 the 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 \11\ emitted by the 
modeled facility. We estimate cancer risk at every census block within 
50 km of every facility in the source category. The MIR is the highest 
individual lifetime cancer risk estimated for any of those census 
blocks. In addition to calculating the MIR, we estimate the 
distribution of individual cancer risks for the source category by 
summing the number of individuals within 50 km of the sources whose 
estimated risk falls within a specified risk range. We also estimate 
annual cancer incidence by multiplying the estimated lifetime cancer 
risk at each census block by the number of people residing in that 
block, summing results for all of the census blocks, and then dividing 
this result by a 70-year lifetime.
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    \11\ 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 EPA's 
Guidelines for Carcinogen Risk Assessment, published in 1986 (51 FR 
33992, September 24, 1986). In August 2000, the document, 
Supplemental Guidance for Conducting Health Risk Assessment of 
Chemical Mixtures (EPA/630/R-00/002), was published as a supplement 
to the 1986 document. Copies of both documents can be obtained from 
https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=20533&CFID=70315376&CFTOKEN=71597944. Summing 
the risk of these individual compounds to obtain the cumulative 
cancer risk is an approach that was recommended by the EPA's SAB in 
their 2002 peer review of the EPA's National Air Toxics Assessment 
(NATA) titled NATA--Evaluating the National-scale Air Toxics 
Assessment 1996 Data--an SAB Advisory, available at https://
yosemite.epa.gov/sab/sabproduct.nsf/
214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf.
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    To assess the risk of noncancer health effects from chronic 
exposure to HAP, we calculate either an HQ or a target organ-specific 
hazard index (TOSHI). We calculate an HQ when a single noncancer HAP is 
emitted. Where more than one noncancer HAP is emitted, we sum the HQ 
for each of the HAP that affects a common target organ or target

[[Page 54288]]

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 (https://www.atsdr.cdc.gov/mrls/index.asp); (2) the 
CalEPA Chronic Reference Exposure Level (REL) (https://oehha.ca.gov/air/crnr/notice-adoption-air-toxics-hot-spots-program-guidance-manual-preparation-health-risk-0); or (3) as noted above, a scientifically 
credible dose-response value that has been developed in a manner 
consistent with the EPA guidelines and has undergone a peer review 
process similar to that used by the EPA. The pollutant-specific dose-
response values used to estimate health risks are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants.
c. Risk From Acute Exposure to HAP That May Cause Health Effects Other 
Than Cancer
    For each HAP for which appropriate acute inhalation dose-response 
values are available, the EPA also assesses the potential health risks 
due to acute exposure. For these assessments, the EPA makes 
conservative assumptions about emission rates, meteorology, and 
exposure location. In this proposed rulemaking, as part of our efforts 
to continually improve our methodologies to evaluate the risks that HAP 
emitted from categories of industrial sources pose to human health and 
the environment,\12\ we are revising our treatment of meteorological 
data to use reasonable worst-case air dispersion conditions in our 
acute risk screening assessments instead of worst-case air dispersion 
conditions. This revised treatment of meteorological data and the 
supporting rationale are described in more detail in Residual Risk 
Assessment for Ethylene Production Source Category in Support of the 
2019 Risk and Technology Review Proposed Rule and in Appendix 5 of the 
report: Technical Support Document for Acute Risk Screening Assessment. 
We will be applying this revision in RTR rulemakings proposed on or 
after June 3, 2019.
---------------------------------------------------------------------------

    \12\ See, e.g., U.S. EPA. Screening Methodologies to Support 
Risk and Technology Reviews (RTR): A Case Study Analysis (Draft 
Report, May 2017. https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html).
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    To assess the potential acute risk to the maximally exposed 
individual, we use the peak hourly emission rate for each emission 
point, reasonable worst-case air dispersion conditions, and the point 
of highest off-site exposure. Specifically, we assume that peak 
emissions from the source category and reasonable worst-case air 
dispersion conditions (i.e., 99th percentile) co-occur and that a 
person is present at the point of maximum exposure.
    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.'' \13\ 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.\14\ 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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    \13\ CalEPA issues acute RELs as part of its Air Toxics Hot 
Spots Program, and the 1-hour and 8-hour values are documented in 
Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The 
Determination of Acute Reference Exposure Levels for Airborne 
Toxicants, which is available at https://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-rel-summary.
    \14\ National Academy of Sciences, 2001. Standing Operating 
Procedures for Developing Acute Exposure Levels for Hazardous 
Chemicals, page 2. Available at https://www.epa.gov/sites/production/files/2015-09/documents/sop_final_standing_operating_procedures_2001.pdf. Note that the 
National Advisory Committee for Acute Exposure Guideline Levels for 
Hazardous Substances ended in October 2011, but the AEGL program 
continues to operate at the EPA and works with the National 
Academies to publish final AEGLs (https://www.epa.gov/aegl).
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    ERPGs are ``developed for emergency planning and are intended as 
health-based guideline concentrations for single exposures to 
chemicals.'' \15\ 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

[[Page 54289]]

1 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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    \15\ ERPGS Procedures and Responsibilities. March 2014. American 
Industrial Hygiene Association. Available at: https://www.aiha.org/get-involved/AIHAGuidelineFoundation/mergencyResponsePlanningGuidelines/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 the acute inhalation risk assessment of the Ethylene Production 
source category, we did not use the default acute emissions multiplier 
of 10, but rather factors of 2, 4, 5, and 10, depending on the emission 
process group. In general, hourly emissions estimates were based on 
peak-to-mean ratios for 37 emission process groups ranging from a 
factor of 2 to 10, with emissions from transfer racks and other 
emission process groups where sufficient information did not exist to 
adequately assess peak hourly emissions (e.g., flares controlling 
various unknown emissions sources) having the highest hourly peak 
emissions at a factor of 10 times the annual average. A further 
discussion of why these factors were chosen can be found in Appendix 1 
of the document titled Residual Risk Assessment for the Ethylene 
Production Source Category in Support of the 2019 Risk and Technology 
Review Proposed Rule, which is available in the docket for this 
rulemaking.
    In our acute inhalation screening risk assessment, acute impacts 
are deemed negligible for HAP for which acute HQs are less than or 
equal to 1 (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 employed consisted of determining 
the highest HQ value that might occur outside facility boundaries. 
These refinements are discussed more fully in the document titled 
Residual Risk Assessment for the Ethylene Production Source Category in 
Support of the 2019 Risk and Technology Review Proposed Rule, which is 
available in the docket for this rulemaking.
4. How do we conduct the multipathway exposure and risk screening 
assessment?
    The EPA conducted 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 determined 
whether any sources in the source category emit any HAP known to be 
persistent and bioaccumulative in the environment (PB-HAP), as 
identified in the EPA's Air Toxics Risk Assessment Library (See Volume 
1, Appendix D, at http://www.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library).
    For the Ethylene Production source category, we identified PB-HAP 
emissions of arsenic compounds, cadmium compounds, lead compounds, 
mercury compounds, and polycyclic organic matter (POM) (of which 
polycyclic aromatic hydrocarbons (PAH) is a subset), so we proceeded to 
the next step of the evaluation. With the exception of lead, the human 
health risk screening assessment for PB-HAP consists of three tiers. We 
call this first evaluation the Tier 1 screening assessment. In a Tier 1 
screening assessment, we determine whether the facility-specific 
emission rates of PB-HAP are large enough to warrant further evaluation 
of the human health risk through ingestion exposure under reasonable 
worst-case conditions. To facilitate this step, we used previously 
developed screening threshold emission rates for several PB-HAP that 
are based on a hypothetical upper-end screening exposure scenario 
developed for use in conjunction with the EPA's Total Risk Integrated 
Methodology.Fate, Transport, and Ecological Exposure (TRIM.FaTE) model. 
The PB-HAP with screening threshold emission rates are arsenic 
compounds, cadmium compounds, chlorinated dibenzodioxins and furans, 
mercury compounds, and POM. Based on the EPA estimates of toxicity and 
bioaccumulation potential, the pollutants above represent a 
conservative list for inclusion in multipathway risk assessments for 
RTR rules. (See Volume 1, Appendix D at https://www.epa.gov/sites/production/files/201308/documents/volume_1_reflibrary.pdf.) In this 
assessment, we compare the facility-specific emission rates of these 
PB-HAP to the screening threshold emission rates for each PB-HAP to 
assess the potential for significant human health risks via the 
ingestion pathway. We call this application of the TRIM.FaTE model the 
Tier 1 screening assessment. The ratio of a facility's actual emission 
rate to the Tier 1 screening threshold emission rate is a ``screening 
value.''
    We derive the Tier 1 screening threshold emission rates for these 
PB-HAP (other than lead compounds) to correspond to a maximum excess 
lifetime cancer risk of 1-in-1 million (i.e., for arsenic compounds, 
polychlorinated dibenzodioxins and furans, and POM) or, for HAP that 
cause noncancer health effects (i.e., cadmium compounds and mercury 
compounds), a maximum HQ of 1. If the emission rate of any one PB-HAP 
or combination of carcinogenic PB-HAP in the Tier 1 screening 
assessment exceeds the Tier 1 screening threshold emission rate for any 
facility (i.e., the screening value is greater than 1), we conduct a 
second screening assessment, which we call the Tier 2 screening 
assessment (ingestion rates are decoupled into separate upper-bound 
ingestion rates for the fisher, farmer, and gardener scenarios).
    In the Tier 2 screening assessment, the location of each facility 
that exceeds a Tier 1 screening threshold emission rate is used to 
refine the assumptions associated with the Tier 1 fisher/farmer 
scenario. A key assumption in the Tier 1 screening assessment is that a 
lake and/or farm is located near the facility. As part of the Tier 2 
screening assessment, we use a U.S. Geological Survey (USGS) database 
to identify actual waterbodies within 50 km of each facility and assume 
the fisher only consumes fish from lakes within that 50 km zone. For 
the Tier 2 farmer scenario, we assume the farmer consumes meat, eggs, 
vegetables, and fruit grown near the facility. If further Tier 2 
screening is necessary for the farmer scenario, we may apply the 
gardener scenario. For the gardener scenario, we assume the gardener 
only grows and consumes eggs, vegetables, and fruit products at the 
same ingestion rate as the farmer. If PB-HAP emission rates do not 
exceed a Tier 2 screening value of 1, we consider those PB-HAP 
emissions to pose risks below a level of concern.
    We also examine the differences between local meteorology near the 
facility and the meteorology used in the Tier 1 screening assessment. 
We then adjust the previously developed Tier 1 screening threshold 
emission rates for each PB-HAP for each facility based on an 
understanding of how exposure concentrations estimated for the 
screening scenario change with the use of local meteorology and USGS 
waterbody data. If the PB-HAP emission rates for a facility exceed the 
Tier 2 screening threshold emission rates and sufficient data are 
available, we may conduct a Tier 3 screening assessment. If PB-HAP 
emission rates do not exceed

[[Page 54290]]

a Tier 2 screening value of 1, we consider those PB-HAP emissions to 
pose risks below a level of concern. If, based on additional analysis 
and review, it is determined that no subsistence farming operations are 
in the area, then the farmer scenario is not used in Tier 3 and only 
gardener screening values are reported. If information obtained 
suggests that subsistence farming operations do not exist, the EPA 
considers the gardener scenario to be the most possible in all RTR 
evaluations.
    There are several analyses that can be included in a Tier 3 
screening assessment, depending upon the extent of refinement 
warranted, including validating that the lakes are fishable, locating 
residential/garden locations for urban and/or rural settings, 
considering plume-rise to estimate emissions lost above the mixing 
layer, and considering hourly effects of meteorology and plume rise on 
chemical fate and transport (a time-series analysis). If necessary, the 
EPA may further refine the screening assessment through a site-specific 
assessment if the Tier 3 screening assessment indicates that risks 
above levels of concern cannot be ruled out.
    In evaluating the potential multipathway risk from emissions of 
lead compounds, rather than developing a screening threshold emission 
rate, we compare maximum estimated chronic inhalation exposure 
concentrations to the level of the current National Ambient Air Quality 
Standard (NAAQS) for lead.\16\ Values below the level of the primary 
(health-based) lead NAAQS are considered to have a low potential for 
multipathway risk.
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    \16\ In doing so, the EPA notes that the legal standard for a 
primary NAAQS--that a standard is requisite to protect public health 
and provide an adequate margin of safety (CAA section 109(b))--
differs from the CAA section 112(f) standard (requiring, among other 
things, that the standard provide an ``ample margin of safety to 
protect public health''). However, the primary lead NAAQS is a 
reasonable measure of determining risk acceptability (i.e., the 
first step of the Benzene NESHAP analysis) since it is designed to 
protect the most susceptible group in the human population--
children, including children living near major lead emitting 
sources. 73 FR 67002/3; 73 FR 67000/3; 73 FR 67005/1. In addition, 
applying the level of the primary lead NAAQS at the risk 
acceptability step is conservative, since that primary lead NAAQS 
reflects an adequate margin of safety.
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    For further information on the multipathway assessment approach, 
see the document titled Residual Risk Assessment for the Ethylene 
Production Source Category in Support of the 2019 Risk and Technology 
Review Proposed Rule, which is available in the docket for this 
rulemaking.
5. How did we conduct the environmental risk screening assessment?
a. Adverse Environmental Effect, Environmental HAP, and Ecological 
Benchmarks
    The EPA conducts a screening assessment to examine the potential 
for an adverse environmental effect as required under section 
112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA defines ``adverse 
environmental effect'' as ``any significant and widespread adverse 
effect, which may reasonably be anticipated, to wildlife, aquatic life, 
or other natural resources, including adverse impacts on populations of 
endangered or threatened species or significant degradation of 
environmental quality over broad areas.''
    The EPA focuses on eight HAP, which are referred to as 
``environmental HAP,'' in its screening assessment: Six PB-HAP and two 
acid gases. The PB-HAP included in the screening assessment are arsenic 
compounds, cadmium compounds, dioxins/furans, POM, mercury (both 
inorganic mercury and methyl mercury), and lead compounds. The acid 
gases included in the screening assessment are hydrochloric acid (HCl) 
and 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 document titled 
Residual Risk Assessment for the Ethylene Production Source Category in 
Support of the 2019 Risk and Technology Review Proposed Rule, which is 
available in the docket for this rulemaking.
b. Environmental Risk Screening Methodology
    For the environmental risk screening assessment, the EPA first 
determined whether any facilities in the Ethylene Production source 
category emitted any of the environmental HAP. For the Ethylene 
Production source category, we identified emissions of arsenic 
compounds, cadmium compounds, HCl, hydrofluoric acid, lead, mercury, 
and POM. Because one or more of the environmental HAP evaluated are 
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 tons of pollutant per year that 
results in media concentrations at the facility that equal the relevant 
ecological benchmark. To assess emissions from each facility in the 
category, the reported emission rate for each PB-HAP was compared to 
the Tier 1 screening threshold emission rate for that PB-HAP for each 
assessment endpoint and effect level. If emissions from a facility do 
not exceed the Tier 1 screening threshold emission rate, the facility 
``passes'' the screening assessment, and, therefore, is

[[Page 54291]]

not evaluated further under the screening approach. If emissions from a 
facility exceed the Tier 1 screening threshold emission rate, we 
evaluate the facility further in Tier 2.
    In Tier 2 of the environmental screening assessment, the screening 
threshold emission rates are adjusted to account for local meteorology 
and the actual location of lakes in the vicinity of facilities that did 
not pass the Tier 1 screening assessment. For soils, we evaluate the 
average soil concentration for all soil parcels within a 7.5-km radius 
for each facility and PB-HAP. For the water, sediment, and fish tissue 
concentrations, the highest value for each facility for each pollutant 
is used. If emission concentrations from a facility do not exceed the 
Tier 2 screening threshold emission rate, the facility ``passes'' the 
screening assessment and typically is not evaluated further. If 
emissions from a facility exceed the Tier 2 screening threshold 
emission rate, we evaluate the facility further in Tier 3.
    As in the multipathway human health risk assessment, in Tier 3 of 
the environmental screening assessment, we examine the suitability of 
the lakes around the facilities to support life and remove those that 
are not suitable (e.g., lakes that have been filled in or are 
industrial ponds), adjust emissions for plume-rise, and conduct hour-
by-hour time-series assessments. If these Tier 3 adjustments to the 
screening threshold emission rates still indicate the potential for an 
adverse environmental effect (i.e., facility emission rate exceeds the 
screening threshold emission rate), we may elect to conduct a more 
refined assessment using more site-specific information. If, after 
additional refinement, the facility emission rate still exceeds the 
screening threshold emission rate, the facility may have the potential 
to cause an adverse environmental effect.
    To evaluate the potential for an adverse environmental effect from 
lead, we compared the average modeled air concentrations (from HEM-3) 
of lead around each facility in the source category to the level of the 
secondary NAAQS for lead. The secondary lead NAAQS is a reasonable 
means of evaluating environmental risk because it is set to provide 
substantial protection against adverse welfare effects which can 
include ``effects on soils, water, crops, vegetation, man-made 
materials, animals, wildlife, weather, visibility and climate, damage 
to and deterioration of property, and hazards to transportation, as 
well as effects on economic values and on personal comfort and well-
being.''
d. Acid Gas Environmental Risk Methodology
    The environmental screening assessment for acid gases evaluates the 
potential phytotoxicity and reduced productivity of plants due to 
chronic exposure to HF and HCl. The environmental risk screening 
methodology for acid gases is a single-tier screening assessment that 
compares modeled ambient air concentrations (from AERMOD) to the 
ecological benchmarks for each acid gas. To identify a potential 
adverse environmental effect (as defined in section 112(a)(7) of the 
CAA) from emissions of HF and HCl, we evaluate the following metrics: 
the size of the modeled area around each facility that exceeds the 
ecological benchmark for each acid gas, in acres and 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 
document titled Residual Risk Assessment for the Ethylene Production 
Source Category in Support of the 2019 Risk and Technology Review 
Proposed Rule, which is available in the docket for this action.
6. How did 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 2011 NEI. The source category records 
of that NEI dataset were removed, evaluated, and updated as described 
in section II.C of this preamble. Once a quality assured source 
category dataset was available, it was placed back with the remaining 
records from the NEI for that facility. Also, because a preliminary 
screening of facility-wide risks based on the 2011 NEI indicated the 
potential for ethylene oxide to be a whole facility risk driver, we 
updated the facility-wide modeling file for ethylene oxide emissions 
using the 2014 NEI data set given that this was the best available data 
for this pollutant. 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 document titled: Residual Risk Assessment for 
the Ethylene Production Source Category in Support of the 2019 Risk and 
Technology Review Proposed Rule, which is available in the docket for 
this rulemaking, 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 document titled Residual Risk 
Assessment for the Ethylene Production Source Category in Support of 
the 2019 Risk and Technology Review Proposed Rule, which is available 
in the docket for this rulemaking. 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.

[[Page 54292]]

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 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.\17\ 
That is, they represent a ``plausible upper limit to the true value of 
a quantity'' (although this is usually not a true statistical 
confidence limit). In some circumstances, the true risk could be as low 
as zero; however, in other circumstances the risk could be greater.\18\ 
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,\19\ 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.
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    \17\ IRIS glossary (https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary).
    \18\ 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.
    \19\ See A Review of the Reference Dose and Reference 
Concentration Processes, U.S. EPA, December 2002, and Methods for 
Derivation of Inhalation Reference Concentrations and Application of 
Inhalation Dosimetry, U.S. EPA, 1994.
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    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

[[Page 54293]]

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 a 
person. In the acute screening assessment that we conduct under the RTR 
program, we assume that peak emissions from the source category and 
reasonable worst-case air dispersion conditions (i.e., 99th percentile) 
co-occur. We then include the additional assumption that a person is 
located at this point at the same time. Together, these assumptions 
represent a reasonable worst-case exposure scenario. In most cases, it 
is unlikely that a person would be located at the point of maximum 
exposure during the time when peak emissions and reasonable worst-case 
air dispersion conditions occur simultaneously.
f. Uncertainties in the Multipathway and Environmental Risk Screening 
Assessments
    For each source category, we generally rely on site-specific levels 
of PB-HAP or environmental HAP emissions to determine whether a refined 
assessment of the impacts from multipathway exposures is necessary or 
whether it is necessary to perform an environmental screening 
assessment. This determination is based on the results of a three-
tiered screening assessment that relies on the outputs from models--
TRIM.FaTE and AERMOD--that estimate environmental pollutant 
concentrations and human exposures for five PB-HAP (dioxins, POM, 
mercury, cadmium, and arsenic) and two acid gases (HF and 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.\20\
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    \20\ 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.
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    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

[[Page 54294]]

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, EPA may 
evaluate other relevant HAP in the future, as modeling science and 
resources allow.

IV. Analytical Results and Proposed Decisions

A. What actions are we taking in addition to those identified in the 
risk and technology review?

    In addition to the proposed actions on the risk review and 
technology review discussed further in this section, we are proposing 
the following: (1) Adding monitoring and operational requirements for 
flares used as APCDs; (2) consistent with Sierra Club v. EPA, 551 F.3d 
1019 (D.C. Cir. 2008), ensuring that CAA section 112 standards apply 
continuously by proposing to add provisions and clarifications for 
periods of SSM and bypasses, including for PRD releases, bypass lines 
on closed vent systems, in situ sampling systems, maintenance 
activities, and certain gaseous streams routed to a fuel gas system; 
and (3) consistent with Sierra Club v. EPA, 551 F.3d 1019 (D.C. Cir. 
2008), proposing to remove the shutdown exemption for decoking 
operations (i.e., the decoking of ethylene cracking furnace radiant 
tubes) and add work practice standards for this emission source. The 
results and proposed decisions based on the analyses performed pursuant 
to CAA section 112(d)(2) and (3) are presented below.
1. Flares
    The EPA is proposing under CAA section 112(d)(2) and (3) to amend 
the operating and monitoring requirements for flares used as APCDs in 
the Ethylene Production source category. We have determined that the 
current requirements for flares are not adequate to ensure the level of 
destruction efficiency needed to conform with the EMACT standards. As 
previously explained, with respect to the various types of controls 
used within the Ethylene Production source category, a flare is the 
most prevalent APCD. A flare can be used to control emissions from 
either a single emissions source (e.g., ethylene process vent), or 
multiple emission sources (e.g., storage vessels, process vents, and 
transfer racks). In the development of the EMACT standards, the EPA 
stated that ``It is generally accepted that combustion devices achieve 
a 98 weight-percent reduction in HAP emissions. . .'' (65 FR 76428, 
December 6, 2000). The requirements applicable to flares, which are 
used to control emissions from various emission sources in this source 
category, are set forth in the General Provisions to 40 CFR part 63 and 
cross-referenced in 40 CFR part 63, subpart SS for storage vessels, 
ethylene process vents, transfer racks, and equipment leaks; and set 
forth in the General Provisions to 40 CFR part 60 and cross-referenced 
in 40 CFR part 61, subpart FF for waste operations. In general, flares 
used as APCDs are expected to achieve 98-percent HAP destruction 
efficiencies when designed and operated according to the requirements 
in the General Provisions. Studies on flare performance,\21\ however, 
indicate that these General Provisions requirements are inadequate to 
ensure proper performance of flares at refineries and other 
petrochemical facilities (including ethylene production units), 
particularly when either assist steam or assist air is used. In 
addition, over the last decade, flare minimization efforts at these 
facilities have led to an increasing number of flares operating at well 
below their design capacity, and while these efforts have resulted in 
reduced flaring of gases by a number of facilities implementing cost 
saving projects to recover gases that would otherwise be flared and 
extract usable fuel value from them (e.g., by using these gases to 
offset costs of natural gas that would have been used in a boiler or 
process heater at the ethylene production facility), situations of over 
assisting with either steam or air have become exacerbated, leading to 
the degradation of flare combustion efficiency. Therefore, these 
proposed amendments will ensure that ethylene production facilities 
that use flares as APCDs meet the MACT standards at all times when 
controlling HAP emissions.
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    \21\ For a list of studies, refer to the technical report titled 
Parameters for Properly Designed and Operated Flares, in Docket ID 
No. EPA-HQ-OAR-2010-0682-0191, which has been incorporated into the 
docket for this rulemaking. (See section II.D of this preamble, 
which addresses the incorporation of certain EPA rulemaking dockets 
such as this one into the docket for this rulemaking.)
---------------------------------------------------------------------------

    The General Provisions of 40 CFR 60.18(b) and 40 CFR 63.11(b) each 
specify that flares be: (1) Steam-assisted, air-assisted, or non-
assisted; (2) operated at all times when emissions may be vented to 
them; (3) designed for and operated with no visible emissions (except 
for periods not to exceed a total of 5 minutes during any 2 consecutive 
hours); and (4) operated with the presence of a pilot flame at all 
times. These General Provisions also specify both the minimum heat 
content of gas combusted in the flare and maximum exit velocity at the 
flare tip. The General Provisions specify monitoring for the presence 
of the pilot flame and the operation of a flare with no visible 
emissions. For other operating limits, 40 CFR part 63, subpart SS 
includes an initial flare compliance assessment to demonstrate 
compliance but specifies no monitoring requirements to ensure 
continuous compliance.
    In 2012, the EPA compiled information and test data collected on 
flares and summarized its preliminary findings on operating parameters 
that affect flare combustion efficiency in a technical report titled 
Parameters for Properly Designed and Operated Flares, in Docket ID No. 
EPA-HQ-OAR-2010-0682-0191, which has been incorporated into the docket 
for this rulemaking.\22\ The EPA submitted this report, along with a 
charge statement and a set of charge questions to an external peer 
review panel.\23\ The panel,

[[Page 54295]]

consisting of individuals representing a variety of backgrounds and 
perspectives (i.e., industry, academia, and environmental experts, and 
industrial flare consultants), concurred with the EPA's assessment that 
the following three primary factors affect flare performance: (1) The 
flow of the vent gas to the flare; (2) the amount of assist media 
(e.g., steam or air) added to the flare; and (3) the combustibility of 
the vent gas/assist media mixture in the combustion zone (i.e., the net 
heating value, lower flammability, and/or combustibles concentration) 
at the flare tip. In response to peer review comments, the EPA 
performed a validation and usability analysis on all available test 
data as well as a failure analysis on potential parameters discussed in 
the technical report as indicators of flare performance. The peer 
review comments are in the memorandum titled Peer Review of Parameters 
for Properly Designed and Operated Flares, available in Docket ID No. 
EPA-HQ-OAR-2010-0682-0193, which has been incorporated into the docket 
for this rulemaking. These analyses resulted in a change to the 
population of test data the EPA used, and helped form the basis for the 
flare operating limits promulgated in the 2015 Petroleum Refinery 
Sector final rule at 40 CFR part 63, subpart CC (80 FR 75178, December 
1, 2015).\24\ We are also relying on the same analyses and proposing 
the same operating limits for flares used as APCDs in the Ethylene 
Production source category. The Agency believes, given the results from 
the various data analyses conducted for the Petroleum Refinery Sector 
final rule, that the operating limits promulgated for flares used in 
the petroleum refinery sector are also appropriate, reasonable, and 
will ensure flares used as APCDs in the Ethylene Production source 
category meet 98-percent destruction efficiency at all times. 
Therefore, we are proposing at 40 CFR 63.1103(e)(4) to directly apply 
the petroleum refinery flare rule requirements in 40 CFR part 63, 
subpart CC to flares in the Ethylene Production source category with 
clarifications, including, but not limited to, specifying that several 
definitions in 40 CFR part 63, subpart CC, that apply to petroleum 
refinery flares also apply to flares in the Ethylene Production source 
category, adding a definition and requirements for pressure-assisted 
multi-point flares, and specifying additional requirements when a gas 
chromatograph or mass spectrometer is used for compositional analysis.
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    \22\ See section II.D of this preamble, which addresses the 
incorporation of certain EPA rulemaking dockets such as this one 
into the docket for this rulemaking.
    \23\ These documents can also be found at https://www.epa.gov/stationary-sources-air-pollution/review-peer-review-parameters-properly-designed-and-operated-flares.
    \24\ See technical memorandum titled Flare Performance Data: 
Summary of Peer Review Comments and Additional Data Analysis for 
Steam-Assisted Flares, in Docket ID No. EPA-HQ-OAR-2010-0682-0200 
for a more detailed discussion of the data quality and analysis; the 
technical memorandum titled Petroleum Refinery Sector Rule: 
Operating Limits for Flares, in Docket ID No. EPA-HQ-OAR-2010-0682-
0206 for a more detailed discussion of the failure analysis and the 
technical memorandum titled Flare Control Option Impacts for Final 
Refinery Sector Rule, in Docket ID No. EPA-HQ-OAR-2010-0682-0748 for 
additional analyses on flare performance standards based on public 
comments received on the proposed Refinery Sector Rule.
---------------------------------------------------------------------------

    The remainder of this section of the preamble includes a discussion 
of requirements that we are proposing for flares used as APCDs in the 
Ethylene Production source category, along with impacts and costs 
associated with these proposed revisions. Specifically, this action 
proposes to retain the General Provisions requirements of 40 CFR 
63.11(b) and 40 CFR 60.18(b) that flares used as APCDs in the Ethylene 
Production source category operate pilot flame systems continuously and 
that flares operate with no visible emissions (except for periods not 
to exceed a total of 5 minutes during any 2 consecutive hours) when the 
flare vent gas flow rate is below the smokeless capacity of the flare. 
In addition, this action proposes to consolidate measures related to 
flare tip velocity and proposes new operational and monitoring 
requirements related to the combustion zone gas. Further, in keeping 
with the elimination of the SSM exemption as discussed in section 
IV.E.1.a of this preamble, this action proposes a work practice 
standard related to the visible emissions and velocity limits during 
periods when the flare is operated above its smokeless capacity (e.g., 
periods of emergency flaring). Currently, the EMACT standards cross-
reference the General Provisions at 40 CFR 60.18(b) and 40 CFR 63.11(b) 
for the operational requirements for flares used as APCD (through 
reference of 40 CFR part 63, subpart SS, and 40 CFR part 61, subpart 
FF). This proposal eliminates cross-references to the General 
Provisions and instead specifies all operational and monitoring 
requirements that are intended to apply to flares used as APCDs in the 
EMACT standards.
a. Pilot Flames
    The EMACT standards reference the flare requirements in 40 CFR 
60.18(b) and 40 CFR 63.11(b) (through reference of 40 CFR part 63, 
subpart SS, and 40 CFR part 61, subpart FF), which specify that a flare 
used as an APCD should operate with a pilot flame present at all times. 
Pilot flames are proven to improve flare flame stability and even short 
durations of an extinguished pilot could cause a significant reduction 
in flare destruction efficiency. In this action, we are proposing to 
remove the cross-reference to the General Provisions and instead 
include the existing provision that flares operate with a pilot flame 
at all times and be continuously monitored for a pilot flame using a 
thermocouple or any other equivalent device directly in the EMACT 
standards. We are also proposing to add a continuous compliance measure 
that would consider each 15-minute block when there is at least 1 
minute where no pilot flame is present when regulated material is 
routed to the flare as a deviation of the standard. See section 
IV.A.1.e of this preamble for our rationale for proposing to use a 15-
minute block averaging period for determining continuous compliance. We 
solicit comment on the proposed revisions for flare pilot flames.
b. Visible Emissions
    The EMACT standards reference 40 CFR 60.18(b) and 40 CFR 63.11(b) 
(through reference of 40 CFR part 63, subpart SS and 40 CFR part 61, 
subpart FF), which specify that a flare used as an APCD should operate 
with visible emissions for no more than 5 minutes in a 2-hour period. 
Owners or operators of these flares are required to conduct an initial 
performance demonstration for visible emissions using EPA Method 22 of 
40 CFR part 60, appendix A-7. We are proposing to remove the cross-
reference to the General Provisions and include the limitation on 
visible emissions directly in the EMACT standards. We are also 
proposing to clarify that the initial 2-hour visible emissions 
demonstration should be conducted the first time regulated materials 
are routed to the flare.
    With regard to continuous compliance with the visible emissions 
limitation, we are proposing daily visible emissions monitoring for 
whenever regulated material is routed to the flare and also visible 
emissions monitoring for whenever visible emissions are observed from 
the flare. On days the flare receives regulated material, we are 
proposing to require owners or operators of flares to monitor visible 
emissions at a minimum of once per day while the flare is receiving 
regulated material using an observation period of 5 minutes and EPA 
Method 22 of 40 CFR part 60, appendix A-7. Additionally, whenever 
regulated material is routed to the flare and there are visual 
emissions from the flare, we are proposing that another 5-minute 
visible emissions observation period be performed using EPA Method 22 
of 40 CFR part 60, appendix A-7, even if the minimum required daily 
visible

[[Page 54296]]

emission monitoring has already been performed. For example, if an 
employee observes visual emissions, the owner or operator of the flare 
would perform a 5-minute EPA Method 22 observation in order to check 
for compliance upon initial observation or notification of such event. 
In addition, in lieu of daily visible emissions observations performed 
using EPA Method 22 of 40 CFR part 60, appendix A-7, we are proposing 
that owners and operators be allowed to use video surveillance cameras. 
We believe that video surveillance cameras would be at least as 
effective as the proposed daily 5-minute visible emissions observations 
using EPA Method 22.
    We are also proposing to extend the observation period for a flare 
to 2 hours whenever visible emissions are observed for greater than 1 
continuous minute during any of the 5-minute observation periods. We 
acknowledge that operating a flare near the incipient smoke point (the 
point at which black smoke begins to form within the flame) results in 
good combustion at the flare tip; however, smoking flares can 
contribute significantly to emissions of particulate matter 2.5 
micrometers in diameter and smaller (PM2.5) emissions. Thus, 
while increasing the allowable period for visible emissions may be 
useful from an operational perspective, we do not believe the allowable 
period for visible emissions should be increased to more than 5 minutes 
in any 2-hour period. We solicit comment on the proposed allowable 
period for visible emissions from flares.
    As discussed later in this section, we are proposing additional 
operational and monitoring requirements for flares used as APCDs in the 
Ethylene Production source category that we expect will result in 
owners or operators of ethylene production units installing equipment 
that can be used to fine-tune and control the amount of assist steam or 
air introduced at the flare tip such that combustion efficiency of the 
flare will be maximized. These monitoring and control systems will 
assist flare owners or operators to operate near the incipient smoke 
point without exceeding the visible emissions limit. While combustion 
efficiency may be highest at the incipient smoke point, it is not 
significantly higher than the combustion efficiency achieved by the 
proposed operating limits discussed in section IV.A.1.d of this 
preamble. As seen in the performance curves for flares, there is very 
limited improvement in flare performance beyond the performance 
achieved at the proposed operating limits (see technical memorandum 
titled Petroleum Refinery Sector Rule: Operating Limits for Flares, in 
Docket ID No. EPA-HQ-OAR-2010-0682-0206, which has been incorporated 
into the docket for this rulemaking). We solicit comments and data on 
appropriate periods of visible emissions that would encourage operation 
at the incipient smoke point.
    In addition, we are proposing that the owner or operator establish 
the smokeless capacity of each flare based on design specification of 
the flare, and that the visible emissions limitation only apply when 
the flare vent gas flow rate is below its smokeless capacity. We are 
proposing a work practice standard for the limited times (i.e., during 
emergency releases) when the flow to the flare exceeds the smokeless 
capacity of the flare, based on comments the EPA received on the 
proposed Petroleum Refinery Sector Rule. In the Petroleum Refinery 
Sector final rule, the EPA explained that numerous comments on the 
proposal suggested that flares are not designed to meet the visible 
emissions requirements when operated beyond their smokeless capacity 
(80 FR 75178, December 1, 2015). According to commenters, flares are 
typically designed to operate in a smokeless manner at 20- to 30-
percent of full hydraulic load. Thus, they claimed, flares have two 
different design capacities: A ``smokeless capacity'' to handle normal 
operations and typical process variations and a ``hydraulic load 
capacity'' to handle very large volumes of gases discharged to the 
flare as a result of an emergency shutdown. According to commenters, 
this is inherent in all flare designs and has not previously been an 
issue because flare operating limits did not apply during malfunction 
events.
    For this proposed work practice standard, owners or operators would 
need to develop a flare management plan that identifies procedures for 
limiting discharges to the flare as a result of process upsets or 
malfunctions that cause the flare to exceed its smokeless capacity. In 
addition, for any flare that exceeds both the smokeless design capacity 
and visible emissions limit, we are proposing that owners or operators 
would need to conduct a specific root cause analysis and take 
corrective action to prevent the recurrence of a similarly caused event 
(similar to the prevention measures we are proposing in this rule to 
minimize the likelihood of a PRD release, see section IV.A.2.a of this 
preamble). We are proposing that if the root cause analysis indicates 
that the exceedance of the visible emissions limit is caused by 
operator error or poor maintenance, then the exceedance would be 
considered a deviation from the work practice standard. We are also 
proposing that a second event within a rolling 3-year period from the 
same root cause on the same equipment would be considered a deviation 
from the standard. Further, we are proposing that events caused by 
force majeure would be excluded from a determination of whether there 
has been a second event. Finally, and again excluding force majeure 
events, we are proposing that a third visible emissions limit 
exceedance occurring from the same flare in a rolling 3-year period 
would be a deviation of the work practice standard, regardless of the 
cause. We are proposing to define a force majeure event as a release of 
HAP, either directly to the atmosphere from a PRD or discharge via a 
flare, that is demonstrated to the satisfaction of the Administrator to 
result from an event beyond the owner or operator's control, such as 
natural disasters; acts of war or terrorism; loss of a utility external 
to the ethylene production unit (e.g., external power curtailment), 
excluding power curtailment due to an interruptible service agreement; 
and fire or explosion originating at a near or adjoining facility 
outside of the owner or operator's control that impacts the ethylene 
production unit's ability to operate.
    With regard to the proposed rolling 3-year period for assessing a 
deviation of the work practice standard, the EPA evaluated the impacts 
of different frequencies and time periods to the number of events that 
would be the ``backstop'' (i.e., a deviation of the standard) to ensure 
that corrective actions are meaningfully applied (see the memorandum, 
Control Option Impacts for Flares Located in the Ethylene Production 
Source Category, in Docket ID No. EPA-HQ-OAR-2017-0357). The EPA 
assumed, based on a survey of a subset of ethylene production flares 
and their visible emission events and velocity exceedances over a 
number of years, that the best performers would have no more than one 
event every 7 years, or a probability of 14.3 percent of having an 
event in any given year (see Appendix B of the memorandum, Control 
Option Impacts for Flares Located in the Ethylene Production Source 
Category, in Docket ID No. EPA-HQ-OAR-2017-0357 for more information). 
The EPA found that, over a long period of time such as 20 years, about 
half of these best performers would have two events in a 3-year period, 
which would still result in about half of the ``best performing'' 
flares having a deviation of the work practice

[[Page 54297]]

standard if it was limited to two events in 3 years. Conversely, the 
EPA found that, over a long period of time such as 20 years, only 6 
percent of the best performing flares would have three events in 3 
years. Based on this analysis, three events in 3 years would appear to 
be ``achievable'' for the average of the best performing flares.
c. Flare Tip Velocity
    The EMACT standards reference the flare provisions in 40 CFR 
60.18(b) and 40 CFR 63.11(b) (through reference of 40 CFR part 63, 
subpart SS and 40 CFR part 61, subpart FF), which specify maximum flare 
tip velocities based on flare type (non-assisted, steam-assisted, or 
air-assisted) and the net heating value of the flare vent gas. (Based 
on responses to the CAA section 114 request previously discussed in 
section II.C of this preamble, approximately 95 percent of all flares 
used as APCDs in the Ethylene Production source category are either 
steam- or air-assisted.) These maximum flare tip velocities are 
required to ensure that the flame does not ``lift off'' the flare 
(i.e., a condition where a flame separates from the tip of the flare 
and there is space between the flare tip and the bottom of the flame), 
which could cause flame instability and/or potentially result in a 
portion of the flare gas being released without proper combustion. We 
are proposing to remove the cross-reference to the General Provisions 
and consolidate the provisions for maximum flare tip velocity into the 
EMACT standards as a single equation, irrespective of flare type (i.e., 
steam-assisted, air-assisted, or non-assisted).
    Based on analysis conducted for the Petroleum Refinery Sector final 
rule, the EPA identified air-assisted test runs with high flare tip 
velocities that had high combustion efficiencies (see technical 
memorandum, Petroleum Refinery Sector Rule: Evaluation of Flare Tip 
Velocity Requirements, in Docket ID No. EPA-HQ-OAR-2010-0682-0212). 
These test runs exceeded the maximum flare tip velocity limits for air-
assisted flares using the linear equation in 40 CFR 63.11(b)(8). When 
these test runs were compared with the test runs for non-assisted and 
steam-assisted flares, air-assisted flares appeared to have the same 
operating envelope as the non-assisted and steam-assisted flares. 
Therefore, for air-assisted flares used as APCDs in the Ethylene 
Production source category, we are proposing to require the use of the 
same equation that non-assisted and steam-assisted flares currently use 
to establish the flare tip velocity operating limit. We are also 
proposing that the owner or operator determine the flare tip velocity 
on a 15-minute block average basis. See section IV.A.1.e of this 
preamble for our rationale for proposing to use a 15-minute block 
averaging period for determining continuous compliance.
    In addition, we are proposing the same work practice standard for 
flare tip velocity during emergency releases (when the flow to the 
flare exceeds the smokeless capacity of the flare) as we are proposing 
for visible emissions. Specifically, instead of owners and operators 
meeting the flare tip velocity operating limit at all times, we are 
proposing that the owner or operator establish the smokeless capacity 
of each flare based on design specification of the flare, and that the 
flare tip velocity operating limit would only apply when the flare vent 
gas flow rate is below its smokeless capacity. We are proposing a work 
practice standard for the limited times (i.e., during emergency 
releases) when the flow to the flare exceeds the smokeless capacity of 
the flare, based on comments the EPA received on the proposed Petroleum 
Refinery Sector Rule. In the Petroleum Refinery Sector final rule, the 
EPA explained that numerous comments on the proposal suggested that 
flares are not designed to meet the flare tip velocity requirements 
when being operated beyond their smokeless capacity (80 FR 75178, 
December 1, 2015). According to commenters, flares are commonly 
operated during emergency releases at exit velocities greater than 400 
feet per second (which is 270 miles per hour) and that this is inherent 
in all flare designs and has not previously been an issue because flare 
operating limits did not apply during malfunction events.
    For the proposed work practice standard, owners or operators would 
develop a flare management plan identifying procedures that they intend 
to follow in order to limit discharges to the flare as a result of 
process upsets or malfunctions that cause the flare to exceed its flare 
tip velocity operating limit. In addition, we are proposing that owners 
or operators would conduct a specific root cause analysis and take 
corrective action to prevent the recurrence of a similarly caused 
event, similar to the prevention measures we are proposing in this rule 
to minimize the likelihood of a PRD release (see section IV.A.2.a of 
this preamble), for any flare event above smokeless design capacity 
that also exceeds the flare tip velocity operating limit. We are 
proposing that if the root cause analysis indicates that the exceedance 
is caused by operator error or poor maintenance, then the exceedance 
would be considered a deviation from the work practice standard. We are 
also proposing that a second event within a rolling 3-year period from 
the same root cause on the same equipment would be considered a 
deviation from the standard. Further, we are proposing that events 
caused by force majeure (see section IV.A.1.b of this preamble for a 
proposed definition of force majeure) would be excluded from a 
determination of whether there has been a second event. Finally, and 
again excluding force majeure events, we are proposing that a third 
opacity exceedance occurring from the same flare in a rolling 3-year 
period would be a deviation of the work practice standard, regardless 
of the cause. As previously explained in section IV.A.1.b of this 
preamble, we believe three events in 3 years appear to be 
``achievable'' for the average of the best performing flares. We 
solicit comment on the proposed work practice standard for flare tip 
velocity during emergency releases (when the flow to the flare exceeds 
the smokeless capacity of the flare).
    Finally, we are also proposing not to include the provision for the 
special flare tip velocity equation in the General Provisions at 40 CFR 
63.18(c)(3)(i)(A) and 40 CFR 63.11(b)(6)(i)(A) for non-assisted flares 
with hydrogen content greater than 8 percent. This equation, which was 
developed based on limited data from a chemical manufacturer, has very 
limited applicability for flares used as APCDs in the Ethylene 
Production source category because it only provides an alternative for 
non-assisted flares with large quantities of hydrogen. Based on the 
response from the CAA section 114 request, approximately 95 percent of 
all flares (operated by the 21 facilities that responded to the CAA 
section 114 request) are either steam- or air-assisted. Furthermore, we 
are proposing other compliance alternatives that we believe provide a 
better way for flares used as APCDs in the Ethylene Production source 
category with high hydrogen content to comply with the rule while 
ensuring proper destruction performance of the flare (see section 
IV.A.1.d of this preamble for the proposed compliance alternatives). 
Therefore, for non-assisted flares with hydrogen content greater than 8 
percent that are used as APCDs in the Ethylene Production source 
category, we are not proposing including this special flare tip 
velocity equation as a compliance alternative. We request comment on 
the need to include this equation.

[[Page 54298]]

d. Net Heating Value of the Combustion Zone Gas
    The current provisions for flares in 40 CFR 60.18(b) and 40 CFR 
63.11(b) specify that the flare vent gas meet a minimum net heating 
value of 200 British thermal units per standard cubic foot (Btu/scf) 
for non-assisted flares and 300 Btu/scf for air- and steam-assisted 
flares. The EMACT standards reference these provisions (through 
reference of 40 CFR part 63, subpart SS and 40 CFR part 61, subpart 
FF), but neither the General Provisions nor the EMACT standards include 
specific requirements for monitoring the net heating value of the flare 
vent gas. Moreover, recent flare testing results indicate that the 
minimum net heating value alone does not address instances when the 
flare may be over-assisted because it only considers the gas being 
combusted in the flare and nothing else (e.g., no assist media). 
However, many industrial flares use steam or air as an assist medium to 
protect the design of the flare tip, promote turbulence for the mixing, 
induce air into the flame, and operate with no visible emissions. Using 
excessive steam or air results in dilution and cooling of flared gases 
and can lead to operating a flare outside its stable flame envelope, 
reducing the destruction efficiency of the flare. In extreme cases, 
over-steaming or excess aeration can snuff out a flame and allow 
regulated material to be released into the atmosphere without complete 
combustion. As previously noted, because approximately 95 percent of 
all flares used as APCDs in the Ethylene Production source category are 
either steam- or air-assisted (based on the 21 facilities that 
responded to the CAA section 114 request), it is critical that we 
ensure the assist media is accounted for in some form or fashion. 
Recent flare test data have shown that the best way to account for 
situations of over-assisting is to consider the properties of the 
mixture of all gases at the flare tip in the combustion zone when 
evaluating the ability to combust efficiently. As discussed in the 
introduction to this section, the external peer review panel concurred 
with our assessment that the combustion zone properties at the flare 
tip are critical parameters to know in determining whether a flare will 
achieve good combustion. The General Provisions, however, solely rely 
on the net heating value of the flare vent gas.
    In this action, in lieu of requiring compliance with the operating 
limits for net heating value of the flare vent gas in the General 
Provisions, we are proposing a single minimum operating limit for the 
net heating value in the combustion zone gas (NHVcz) of 270 Btu/scf 
during any 15-minute period for steam-assisted, air-assisted, and non-
assisted flares used as APCDs in the Ethylene Production source 
category. The Agency believes, given the results from the various data 
analyses conducted for the Petroleum Refinery Sector Rule, that this 
NHVcz operating limit promulgated for flares used in the Petroleum 
Refinery Sector source category is also appropriate, reasonable, and 
will ensure flares used as APCDs in the Ethylene Production source 
category meet 98-percent destruction efficiency at all times when 
operated in concert with the other proposed suite of requirements that 
flares need to comply with (e.g., continuously lit pilot flame 
requirements, visible emissions requirements, and flare tip velocity 
requirements) (see the memoranda titled Petroleum Refinery Sector Rule: 
Operating Limits for Flares and Flare Control Option Impacts for Final 
Refinery Sector Rule in Docket ID Nos. EPA-HQ-OAR-2010-0682-0206 and 
EPA-HQ-OAR-2010-0682-0748, respectively). In addition, we are proposing 
that owners or operators may use a corrected heat content of 1,212 Btu/
scf for hydrogen, instead of 274 Btu/scf, to demonstrate compliance 
with the NHVcz operating limit; however, owners or operators who wish 
to use the corrected hydrogen heat content must have a system capable 
of monitoring for the hydrogen content in the flare vent gas. The 1,212 
Btu/scf value is based on a comparison between the lower flammability 
limit and net heating value of hydrogen compared to light organic 
compounds and has been used in several consent decrees to which the EPA 
is a party. Based on analyses conducted for the Petroleum Refinery 
Sector Rule (see the memorandum titled Flare Control Option Impacts for 
Final Refinery Sector Rule, in Docket ID No. EPA-HQ-OAR-2010-0682-
0748), the EPA determined that using a 1,212 Btu/scf value for hydrogen 
greatly improves the correlation between combustion efficiency and the 
combustion zone net heating value over the entire array of data. Using 
the net heating value of 1,212 Btu/scf for hydrogen also greatly 
reduced the number of ``type 2 failures,'' which are instances when the 
combustion efficiency is high, but the gas does not meet the NHVcz 
limit.
    Furthermore, in addition to the NHVcz operating limit, we are 
proposing a net heating value dilution parameter (NHVdil) for certain 
flares that operate with perimeter assist air. For air-assisted flares, 
use of too much perimeter assist air can lead to poor flare 
performance. Further, based on our analysis of the air-assisted flare 
dataset, (see technical memorandum, Petroleum Refinery Sector Rule: 
Operating Limits for Flares, in Docket ID No. EPA-HQ-OAR-2010-0682-
0206), we determined a NHVdil of 22 British thermal units per square 
foot is necessary to ensure that there is enough combustible material 
available to adequately combust the gas and pass through the 
flammability region and also ensure that degradation of flare 
performance from excess aeration does not occur. We found that 
including the flow rate of perimeter assist air in the calculation of 
the NHVcz does not identify all instances of excess aeration and could 
(in some instances) even allow facilities to send very dilute vent 
gases to the flare that would not combust (i.e., vent gases below their 
lower flammability limit could be sent to flare). Instead, the data 
suggest that the diameter of the flare tip, in concert with the amount 
of perimeter assist air (and other parameters used to determine NHVcz), 
provides inputs necessary to calculate whether this type of flare is 
over-assisted. This dilution parameter is consistent with the 
combustion theory that the more time the gas spends in the flammability 
region above the flare tip, the more likely it will combust. Also, 
because both the volume of the combustion zone (represented by the 
diameter here) and how quickly this gas is diluted to a point below the 
flammability region (represented by perimeter assist air flow rate) 
characterize this time, it is logical that we propose such a parameter.
    We also found that some assist steam lines are purposely designed 
to entrain air into the lower or upper steam at the flare tip; and for 
flare tips with an effective tip diameter of 9 inches or more, there 
are no flare tip steam induction designs that can entrain enough assist 
air to cause a flare operator to have a deviation of the NHVdil 
operating limit without first deviating from the NHVcz operating limit. 
Therefore, we are proposing to allow owners or operators of flares 
whose only assist air is from perimeter assist air entrained in lower 
and upper steam at the flare tip and with a flare tip diameter of 9 
inches or greater to comply only with the NHVcz operating limit. Steam-
assisted flares with perimeter assist air and an effective tip diameter 
of less than 9 inches would remain subject to the requirement to 
account for the amount of assist air intentionally entrained within the 
calculation of NHVdil. However, we recognize that this assist air 
cannot be directly measured, but the quantity of

[[Page 54299]]

air entrained is dependent on the assist steam rate and the design of 
the steam tube's air entrainment system. Therefore, we are proposing 
provisions to specify that owners or operators of these smaller 
diameter steam-assisted flares use the steam flow rate and the maximum 
design air-to-steam ratio of the steam tube's air entrainment system 
for determining the flow rate of this assist air. Using the maximum 
design ratio will tend to over-estimate the assist air flow rate, which 
is conservative with respect to ensuring compliance with the NHVdil 
operating limit.
    Finally, we are proposing to require owners or operators to record 
and calculate 15-minute block average values for these parameters. Our 
rationale for selecting a 15-minute block averaging period is provided 
in section IV.A.1.e of this preamble.
e. Data Averaging Periods for Flare Gas Operating Limits
    We are proposing to use a 15-minute block averaging period for each 
proposed flare operating parameter to ensure that the flare is operated 
within the appropriate operating conditions. We consider a short 
averaging time to be the most appropriate for assessing proper flare 
performance because flare vent gas flow rates and composition can 
change significantly over short periods of time. Furthermore, because 
destruction efficiency can fall precipitously when a flare is 
controlling vent gases below (or outside) the proposed operating 
limits, short time periods where the operating limits are not met could 
seriously impact the overall performance of the flare.
    Moreover, a 15-minute averaging period is consistent with the test 
data and the analysis used to establish the operating limits in this 
proposed rule. Ninety-three percent of the flare test runs used as 
bases for establishing the proposed operating limits ranged in duration 
from 5 to 30 minutes, and 77 percent of the runs ranged in duration 
from 5 to 20 minutes. As previously explained, the failure analysis 
considered minute-by-minute test run data, but gas chromatography 
compositional analyses generally require 10 to 15 minutes to conduct. 
Therefore, many of the compositional data still reflect set values over 
10- to 15-minute time intervals and shorter averaging times are not 
practical. To be consistent with the available test data and to ensure 
there are no short periods of significantly poor destruction 
efficiencies, we are proposing 15-minute block averaging times.
    In addition, the EPA conducted a Monte Carlo analysis (based on 
comments the EPA received on the proposed Petroleum Refinery Sector 
Rule) to help assess the impacts of extending the averaging time on the 
test average flare dataset of 15-minute runs to 1-hour or 3-hour 
averaging time alternatives (see the memorandum, Flare Control Option 
Impacts for Final Refinery Sector Rule, in Docket ID No. EPA-HQ-OAR-
2010-0682-0748). While the EPA considered it reasonable to provide a 
longer averaging time for logistical reasons, the Monte Carlo analysis 
demonstrated that short periods of poor flare performance can affect 
the ability of a flare to achieve the desired control efficiency. 
Consequently, the EPA promulgated a 15-minute averaging period 
requirement to ensure that the 98-percent control efficiency for flares 
is achieved at all times (80 FR 75178, December 1, 2015).
    Given the short averaging times for the operating limits, we are 
proposing special calculation methodologies to enable owners or 
operators to use ``feed forward'' calculations to ensure compliance 
with the operating limits on a 15-minute block average. Specifically, 
we propose using the results of the compositional analysis determined 
just prior to a 15-minute block period for the next 15-minute block 
average. Owners or operators of flares will then know the vent gas 
properties for the upcoming 15-minute block period and can adjust 
assist gas flow rates relative to vent gas flow rates to comply with 
the proposed operating limits. In other words, ``feed forward'' means 
that owners or operators would use the net heating value in the vent 
gas (NHVvg) going into the flare in one 15-minute period to adjust the 
assist media (i.e., steam or air) and/or the supplemental gas in the 
next 15-minute period, as necessary, to calculate an NHVcz limit of 270 
Btu/scf or greater using the proposed equation. We recognize that when 
a subsequent measurement value is determined, the instantaneous NHVcz 
based on that compositional analysis and the flow rates that exist at 
the time may not be above 270 Btu/scf. We are proposing that this is 
not a deviation of the operating limit. Rather, we propose that the 
owner or operator is only required to make operational adjustments 
based on that information to achieve, at a minimum, the net heating 
value limit for the subsequent 15-minute block average. We are, 
however, proposing that failure to make adjustments to assist media or 
supplemental natural gas using the NHVvg from the previous period in 
the equation provided for calculating an NHVcz limit of 270 Btu/scf, 
would be a deviation of the operating limit. Alternatively, because the 
owner or operator could directly measure the NHVvg on a more frequent 
basis, such as with a calorimeter (and optional hydrogen analyzer), the 
process control system is able to adjust more quickly, and the owner or 
operator can make adjustments to assist media or supplemental natural 
gas more quickly. In this manner, the owner or operator is not limited 
by relying on NHVvg data that may not represent the current conditions. 
We are, therefore, also proposing that the owner or operator may opt to 
use the NHVvg in such instances from the same period to comply with the 
operating limit. For examples of ``feed forward'' calculations, please 
see Attachment 3 of the memorandum titled Flare Control Option Impacts 
for Final Refinery Sector Rule, in Docket ID No. EPA-HQ-OAR-2010-0682-
0748.
    In addition, we are also proposing that owners or operators of 
flares that elect to use grab sampling and engineering calculations to 
determine compliance must still assess compliance on a 15-minute block 
average. The composition of each grab sample is to be used for the 
duration of the episode or until the next grab sample is taken. We are 
soliciting comment on whether this approach is appropriate, and whether 
grab samples are needed on a more frequent basis to ensure compliance 
with the operating limits.
    Finally, we are proposing to clarify at 40 CFR 63.1103(e)(4)(xiii) 
that when determining compliance with the flare tip velocity and 
combustion zone operating limits specified in 40 CFR 63.670(d) and (e), 
the initial 15-minute block period starts with the 15-minute block that 
includes a full 15 minutes of the flaring event. In other words, we are 
proposing to clarify that the owner or operator demonstrate compliance 
with the velocity and NHVcz requirements starting with the block that 
contains the fifteenth minute of a flaring event; and the owner or 
operator is not required to demonstrate compliance for the previous 15-
minute block in which the event started and contained only a fraction 
of flow.
f. Flares in Dedicated Service
    We are proposing an alternative monitoring approach for flares in 
dedicated service that have consistent composition and flow. We believe 
that these types of flares, which have limited flare vent gas streams, 
do not need to have the same type of ongoing monitoring requirements as 
those with more variable waste streams. Thus, we are proposing an 
option that owners or operators can use to demonstrate

[[Page 54300]]

compliance with the operating requirements for flares that are in 
dedicated service to a specific emission source, such as a transfer 
rack operation consistently loading the same material. We are proposing 
that owners or operators will need to submit an application for the use 
of this alternative compliance option. We are proposing that the 
application must include a description of the system, characterization 
of the vent gases that could be routed to the flare based on a minimum 
of seven grab samples (14 daily grab samples for continuously operated 
flares), and specification of the net heating value that will be used 
for all flaring events (based on the minimum net heating value of the 
grab samples). We are also proposing to allow engineering estimates to 
characterize the amount of gas flared and the amount of assist gas 
introduced into the system. For example, we believe that the use of fan 
curves to estimate air assist rates would be acceptable. We propose 
that flare owners or operators would use the net heating value 
determined from the initial sampling phase and measured or estimated 
flare vent gas and assist gas flow rates, if applicable, to demonstrate 
compliance with the standards.
g. Pressure-Assisted Multi-Point Flares
    Pressure-assisted flares are conceptually similar, yet technically 
different in both design and operation compared to more traditional 
elevated flare tip designs (e.g., steam-assisted, air-assisted, and 
non-assisted flare tips). Pressure-assisted flares operate by taking 
advantage of the pressure upstream of the flare tip to create a 
condition whereby air is drawn into contact and mixed with high exit 
velocity flared gas, resulting in smokeless flare operation and 
emissions reductions at least as equivalent to those of traditional 
flares types, if properly designed and operated. Pressure-assisted 
flares can be used in a single flare burner type layout or in staged 
arrays with many identical flare burners. These staged arrays can 
either be elevated or at ground level. In the Ethylene Production 
source category, we are only aware of ground level staged array systems 
that are commonly referred to as multi-point ground flares (MPGF) given 
that they have multiple (e.g., hundreds) of flare burners at ground 
level. The flare burners in a MPGF are designed with a staging system 
that opens and closes staging valves according to gas pressure in the 
flare header with the result that stages, and accompanying flare 
burners for those stages, are either activated to control emissions as 
the flare vent gas flow and pressure increase in the flare header or 
deactivated as the flare vent gas flow and pressure decrease in the 
flare header. The flare burners in a MPGF are typically lit with a 
pilot flame system where the first burners on a stage are lit by the 
pilot flame and the flame propagates (i.e., cross-lights) down the 
stage to the remaining burners on the stage. The MPGF system is 
typically surrounded by a panel type fence to allow air in for 
combustion as well as to protect nearby workers from the radiant heat 
of the flare system.
    In the Ethylene Production source category, MPGF are currently used 
as secondary flares to control large emissions events that result 
during periods of SSM. With the elimination of the SSM exemption (see 
section IV.E.1 of this preamble for additional discussion), proposing 
requirements for this unique flare type is an important consideration 
given that some facilities currently use them as APCD. Based on our 
review of recently approved AMEL requests for MPGF and the underlying 
data analyses that supported those decisions (see section II.D of this 
preamble), MPGF can achieve at least equivalent reductions in volatile 
organic compounds (VOC) and organic HAP as traditional elevated flares, 
however, different operating requirements are needed for these flare 
types to ensure a high level of control is achieved given that the 
individual flare burners are designed to operate at high velocities 
(i.e., up to sonic velocity).
    In reviewing the initial MPGF AMEL requests by Dow Chemical and 
ExxonMobil (80 FR 8023-8030, February 13, 2015), the Agency noted two 
general conclusions from the test data supporting the AMEL requests 
that were consistent with 1985 studies \25\ conducted by the EPA on 
pressure-assisted flares. The first general conclusion was that ``flare 
head design can influence the flame stability curve.'' The second 
general conclusion was that ``stable flare flames and high (>98-99%) 
combustion and destruction efficiencies are attained when flares are 
operated within operating envelopes specific to each flare burner and 
gas mixture tested. Operation beyond the edge of the operating envelope 
can result in rapid flame de-stabilization and a decrease in combustion 
and destruction efficiencies.'' In reviewing all the available data in 
the MPGF AMEL docket (i.e., Docket ID No. EPA-HQ-OAR-2014-0738), we 
found these two general observations were still valid conclusions and 
focused our analyses of the test data on tests where olefinic waste gas 
mixtures were being combusted. This was done because, as discussed 
earlier, waste gas characteristics (along with flare burner design) can 
influence the flame stability curve. Thus, since these tests are 
representative of waste gas mixtures expected to be controlled at 
ethylene production facilities, we focused our review on these specific 
data. The data clearly show that for some test runs flare flameouts 
occurred, meaning the flares were not operated within the proper 
envelope to produce a stable flame. The data from the AMEL requests 
also show flare flameouts occur from various burners when the NHVcz of 
the olefin waste gas mixture are less than 800 Btu/scf. Thus, we 
selected a minimum NHVcz of 800 Btu/scf to ensure the MPGF is operated 
within the proper envelope to produce a stable flame and achieve high 
destruction efficiencies at least equivalent to those as the underlying 
Ethylene Production MACT standards. Also, given that rapid flame de-
stabilization can occur when pressure-assisted multi-point flares are 
operated outside their proper operating envelope, ensuring there is 
always enough heat content in the vent gases sent to these types of 
flares so that flare flameouts will not occur is critically important. 
Thus, to that end, we are proposing to not allow use of the ``feed 
forward'' calculation approach (discussed in section IV.A.1.e of this 
preamble) to demonstrate compliance with the NHVcz limit of 800 Btu/
scf. We are only proposing allowance of complying with a straight 15-
minute block average for these flare types.
---------------------------------------------------------------------------

    \25\ Pohl, J. and N. Soelberg. 1985. Evaluation of the 
efficiency of industrial flares: Flare head design and gas 
composition. EPA-600/2-85-106. Prepared for U.S. EPA Office of Air 
Quality Planning and Standards.
---------------------------------------------------------------------------

    Another unique characteristic of MPGF is that they may use a cross-
lighting pilot flame system as a means of ignition to initially combust 
the waste gases sent to the flare burners on a particular staged array. 
Thus, we also reviewed the equipment specific set-ups in the test data 
that allowed for successful cross-lighting of MPGF. Based on our review 
of the data, it appears that one option would be for facilities to 
conduct performance demonstrations to demonstrate successful cross-
lighting on a minimum of three burners (i.e., as outlined in the 
Framework for Streamlining Approval of Future Pressure-Assisted MPGF 
AMEL Requests, 81 FR 23480, April 21, 2016). However, given the data 
before us in the MPGF AMEL docket, and rather than requiring facilities 
to conduct a performance demonstration, it appears

[[Page 54301]]

that an equipment standard that sets an upper end on the distance 
between burners of 6 feet is adequate to ensure a successful cross-
lighting on a stage of burners in a MPGF.
    Furthermore, in reviewing the site-specific AMEL standards that 
facilities are complying with for MPGF,\26\ we believe that if these 
same site-specific standards are applied to all MPGF at ethylene 
production facilities, owners or operators would demonstrate at least 
equivalent emissions reductions as the underlying Ethylene Production 
MACT standards as well as demonstrate at least equivalent reductions 
with the operational and monitoring requirements we are proposing for 
more traditional, elevated flare tips. Therefore, we are proposing that 
owners or operators of MPGF: (1) Maintain an NHVcz >= 800 Btu/scf; (2) 
continuously monitor the NHVcz and flare vent gas flow rate; (3) 
continuously monitor for the presence of a pilot flame, and if cross-
lighting is used on a particular stage of burners, then continuously 
monitor to ensure that the stage has a minimum of two pilots per stage 
that will ignite all flare vent gases sent to that stage; (4) operate 
the MPGF with no visible emissions (except for 5 minutes during any 2 
consecutive hours); (5) maintain a distance of no greater than 6 feet 
between any two burners in series on a stage of burners that use cross-
lighting; and (6) monitor to ensure staging valves for each stage of 
the MPGF operate properly so that the flare will control vent gases 
within the proper flow and pressure ranges based on the flare 
manufacturer's recommendations.
---------------------------------------------------------------------------

    \26\ 80 FR 52426, August 31, 2015; 81 FR 23480, April 21, 2016; 
and 82 FR 27822, June 19, 2017.
---------------------------------------------------------------------------

    Finally, although we are unaware of any ethylene production 
facilities that use multi-point elevated flares, we recognize that an 
owner or operator may elect to use this type of flare design in the 
future. Given the design similarities of a multi-point elevated flare 
when compared to a MPGF (i.e., each flare type uses pressure-assisted 
burners with staged arrays), we determined that our analyses of the 
test data (including our review of approved AMEL requests) related to 
MPGF that control olefin waste gases, could also apply to multi-point 
elevated flares that combust olefin waste gases. Therefore, we are 
proposing that owners and operators of multi-point elevated flares must 
meet the same requirements that we are proposing for MPGF. In other 
words, the proposed requirements discussed in this section of the 
preamble would apply to all pressure-assisted multi-point flares (i.e., 
MPGF and multi-point elevated flares). We are soliciting comment on 
whether this approach is appropriate, and whether test data are 
available for multi-point elevated flares that control olefin waste 
gases. We are also soliciting comment on whether the proposed 
requirements for pressure-assisted multi-point flares should ultimately 
supersede the currently approved MPGF AMEL requests at ethylene 
production facilities.
h. Impacts of the Flare Operating and Monitoring Requirements
    The EPA expects that the newly proposed requirements for flares 
used as APCDs in the Ethylene Production source category discussed in 
this section will affect all flares at ethylene production units. Based 
on facility responses to our CAA section 114 request, we estimate that 
there are 96 flares of traditional elevated flare tip designs (e.g., 
steam-assisted, air-assisted, and non-assisted flare tips) operating at 
ethylene production units that receive flare vent gas flow on a regular 
basis (i.e., other than during periods of SSM). Also, based on 
information received from AMEL requests (see section II.D of this 
preamble), we estimate there are six pressure-assisted MPGF in the 
source category. Costs were estimated for each flare for a given 
facility, considering current monitoring systems already installed on 
each individual flare. Given that the same type of equipment is used 
for flares in the Ethylene Production source category and for the 
petroleum refinery sector, costs for any additional monitoring systems 
needed were estimated based on installed costs received from petroleum 
refineries and, if installed costs were unavailable, costs were 
estimated based on vendor-purchased equipment. The baseline emission 
estimate and the emission reductions achieved by the proposed rule were 
estimated based on current vent gas and steam flow data submitted by 
industry representatives. The results of the impact estimates are 
summarized in Table 2 of this preamble. We note that the requirements 
for flares we are proposing in this action will ensure compliance with 
the EMACT standards when flares are used as an APCD. Because we are not 
changing the underlying EMACT standards, we did not include any of the 
estimated excess emissions from flares in the summary of total 
estimated emissions reductions for this action (i.e., 62 tpy of HAP). 
However, we estimate that the proposed operational and monitoring 
requirements have the potential to reduce excess emissions from flares 
by approximately 1,430 tpy of HAP and 13,020 tpy of VOC. The VOC 
compounds are non-methane, non-ethane total hydrocarbons. According to 
the modeling file we used to assess residual risk (see section III.C.1 
of this preamble), there are approximately 30 individual HAP compounds 
included in the emission inventory for flares, but many of these are 
emitted in trace quantities. A little more than half of the HAP 
emissions from flares are attributable to 1,3-butadiene and benzene, 
followed by hexane, toluene, and xylenes. For more detail on the impact 
estimates, see the technical memorandum titled Control Option Impacts 
for Flares Located in the Ethylene Production Source Category in Docket 
ID No. EPA-HQ-OAR-2017-0357.

Table 2--Nationwide Cost Impacts of Proposed Amendments To Ensure Proper
                            Flare Performance
------------------------------------------------------------------------
                                                               Total
                                           Total capital    annualized
           Control description              investment    costs (million
                                            (million $)        $/yr)
------------------------------------------------------------------------
Flare Operational and Monitoring                    44.8             9.8
 Requirements...........................
Work Practice Standards for Flares                  0.75            0.18
 Operating Above Their Smokeless
 Capacity...............................
                                         -------------------------------
    Total...............................            45.6            9.98
------------------------------------------------------------------------


[[Page 54302]]

2. Vent Control Bypasses
a. Pressure Relief Devices
    The current definition of ``ethylene process vent'' at 40 CFR 
63.1103(e)(2) states that ``relief valve discharges'' are not ethylene 
process vents. Instead, the EMACT standard recognizes relief valve 
discharges to be the result of malfunctions. The acronym ``PRD'' means 
pressure relief device and is common vernacular to describe the variety 
of devices regulated as pressure relief valves (see the end of this 
section for our proposed revisions to the definitions of pressure 
relief device and relief valve, to provide clarity). PRDs are designed 
to remain closed during normal operation. Typically, the Agency 
considers PRD releases as the result of an overpressure in the system 
caused by operator error, a malfunction such as a power failure or 
equipment failure, or other unexpected cause that results in immediate 
venting of gas from process equipment in order to avoid safety hazards 
or equipment damage. For the Ethylene Production source category, 
emissions vented directly to the atmosphere by a PRD in organic HAP 
service contain HAP that are otherwise regulated under the EMACT 
standards.
    The EMACT standards regulate PRDs when they are seated through 
equipment leak provisions (i.e., conduct EPA Method 21 monitoring after 
each pressure release using a leak definition of 500 ppm); however, 
these provisions do not apply to an emissions release from a PRD. In 
addition, the EMACT standards follow the EPA's previous practice of 
exempting SSM events from otherwise applicable emission standards. 
Consequently, with PRD releases defined as unplanned, nonroutine, and 
the result of malfunctions, the EMACT standards did not restrict PRD 
releases to the atmosphere but instead treated them similar to all 
malfunctions that are subject to the SSM exemption provision. In Sierra 
Club v. EPA, 551 F.3d 1019 (D.C. Cir. 2008), the Court determined SSM 
exemptions in section 112 standards violate the CAA. Section IV.E.1 of 
this preamble contains additional discussions on the removal of the SSM 
exemption provision for this source category. As a result, we evaluated 
the EMACT standard for PRDs to ensure a standard continuously applies, 
consistent with the Sierra Club v. EPA decision.
    CAA section 112(d)(1) specifies that the EPA may ``distinguish 
among classes, types, and sizes of sources'' when establishing 
standards. (In establishing standards under CAA section 112(d), the EPA 
may ``distinguish among classes, types, and sizes of sources within a 
category or sub-category.'' CAA section 112(d)(1). See Sierra Club v. 
EPA, 479 F.3d 875, 885 (D.C. Cir. 2007). We are proposing two 
subcategories of PRDs for the EMACT standard to distinguish between 
classes of PRDs: (1) PRDs designed to vent through a closed vent system 
to a control device or to a process, fuel gas system, or drain system 
(referred to as PRDs that vent to a control system); and (2) PRDs 
designed to vent to the atmosphere. We are proposing to subcategorize 
PRDs by class because of design differences between the numerous PRDs 
at ethylene production facilities that are vented to a control system 
and PRDs that vent to the atmosphere. Ethylene production facilities 
are currently required to evaluate PRDs as part of their risk 
management and process safety management programs. When implementing 
these programs, facilities identify PRDs that they intend to control as 
compared to those they elect not to control (and that are vented to the 
atmosphere). Facilities do not control certain PRDs because of 
technical or site-specific safety considerations, such as PRDs that 
release chemicals that could result in freezing or plugging the vent to 
the control system.
    We evaluated each subcategory of PRDs separately to ensure that a 
standard would apply continuously. Essentially, PRDs that vent to a 
control system are already complying with the process vent standards 
(see section IV.D.2 of this preamble for a summary of the EMACT 
standards for ethylene process vents) and are, thus, already 
appropriately regulated. Therefore, minimal revisions to the EMACT 
standard for PRDs that vent to a control system are warranted as a 
result of removing the SSM exemption. We are proposing at 40 CFR 
63.1107(h)(4) that PRDs that vent through a closed vent system to a 
control device or to a process, fuel gas system, or drain system must 
meet minimum requirements for the applicable control system. However, 
PRDs that vent to atmosphere cannot meet the current ethylene process 
vent standards. Therefore, we examined whether it would be feasible to 
regulate PRDs that vent to atmosphere under CAA section 112(d)(2) and 
(3). As detailed here, we determined it was feasible to regulate PRDs 
that vent to atmosphere under CAA section 112(h) and are proposing work 
practice standards at 40 CFR 63.1107(h)(3) that are intended to reduce 
the number of PRD releases and will incentivize owners or operators to 
eliminate the causes of PRD releases to the atmosphere.
    No ethylene production facility is subject to numeric emission 
limits for PRDs that vent to the atmosphere. In addition, we do not 
believe it is appropriate to subject PRDs that vent to the atmosphere 
to numeric emission limits due to technological and economical 
limitations that make it impracticable to measure emissions from such 
PRDs. CAA section 112(h)(1) states that the EPA may prescribe a work 
practice standard or other requirement, consistent with the provisions 
of CAA sections 112(d) or (f), in those cases where, in the judgment of 
the Administrator, it is not feasible to enforce an emission standard. 
CAA section 112(h)(2)(B) further defines the term ``not feasible'' in 
this context as meaning that ``the application of measurement 
technology to a particular class of sources is not practicable due to 
technological and economic limitations.'' We consider it appropriate to 
establish a work practice standard for PRDs that vent to atmosphere as 
provided in CAA section 112(h), because the application of a 
measurement methodology for PRDs that vent to atmosphere is not 
practicable due to technological and economic limitations. First, it is 
not practicable to use a measurement methodology for PRD releases that 
vent to atmosphere. PRDs are designed to remain closed during normal 
operations and release emissions only during nonroutine and unplanned 
events, and the venting time can be very short and may vary widely in 
composition and flow rate. These unique event characteristics make it 
infeasible to collect a grab sample of the gases when a PRD release 
occurs, and a single grab sample would also likely not account for 
potential variation in vent gas composition. Additionally, it would be 
economically prohibitive to construct an appropriate conveyance and 
install and operate continuous monitoring systems for each individual 
PRD that vents to atmosphere in order to attempt to quantitatively 
measure a release event that may occur only a few times in a 3-year 
period. See U.S. v. Sugar Corp., 830 F.3d 579, 664-67 (D.C. Cir. 2016). 
Further, we have not identified any available, technically feasible 
continuous emission monitoring system (CEMS) that can accurately 
determine a mass release quantity of VOC or HAP given the flow, 
composition, and composition variability of potential PRD releases that 
vent to the atmosphere from ethylene production units. Rather, we have 
identified only monitoring

[[Page 54303]]

systems capable of alerting an owner or operator of when a PRD release 
occurs. Consequently, we propose to conclude that it is appropriate to 
establish a work practice standard for PRDs that vent to atmosphere as 
provided in CAA section 112(h).
    We also reviewed information about ethylene production facilities 
to determine how the best performers are minimizing emissions from PRDs 
that vent to atmosphere. We first reviewed the requirements in EPA's 
Chemical Accident Prevention Provisions (40 CFR part 68) and 
Occupational Safety and Health Administration's (OSHA) Process Safety 
Management rule (29 CFR 1910.119). These rules focus on planning for 
and minimizing or preventing scenarios which would result in releases 
of chemicals. For example, as stated in appendix C to the OSHA rule: 
``Process safety management is the proactive identification, evaluation 
and mitigation or prevention of chemical releases that could occur as a 
result of failures in process, procedures or equipment.'' The rules are 
applicable to any equipment in the process, and relief valves are 
identified in each rule as an applicable source to evaluate. The EPA 
and OSHA rules have similar requirements, except that applicability 
determination is unique to each rule. Owners or operators are subject 
to the EPA's Chemical Accident Prevention Provisions at 40 CFR part 68 
if a process has more than a threshold quantity of a regulated 
substance. Regulated substances and their thresholds are listed at 40 
CFR 68.130. Owners or operators are subject to OSHA's Process Safety 
Management rule at 29 CFR 1910.119 if a process involves either a 
chemical that is above specified threshold quantities (listed in 
appendix A to 29 CFR 1910.119) or a Category 1 flammable gas or liquid. 
Ethylene production facilities are subject to the Chemical Accident 
Prevention Provisions rule, as identified in their title V permit (40 
CFR 68.215 requires permits to list part 68 as an applicable 
requirement, if subject). As a result, we further reviewed this rule 
for consideration in developing the work practice standard.
    The EPA's Chemical Accident Prevention Provisions require a 
prevention program. Ethylene production facilities would fall under 
either prevention program 1 or 3 (due to the NAICS code). We evaluated 
program 3, which is more stringent, because it is our understanding 
that ethylene production facilities would not meet the program 1 
criteria, based on a review of the rule's applicability requirements 
and preamble rationale. Furthermore, since program 3 is the most 
stringent program, we believe the best performers in the source 
category are following this program. The program 3 prevention program 
includes: Documentation of process safety information, conducting a 
hazard analysis, documentation of operating procedures, employee 
training, on-going maintenance, and incident investigations. The 
process safety information documented must include information 
pertaining to the hazards of the regulated substances in the process, 
the technology of the process, and the process equipment (including 
relief valves). When conducting the hazard analysis, facilities must 
identify, evaluate, and control the hazards in the process; controls 
may consider the application of detection methodologies (e.g., process 
monitoring and control instrumentation) to provide early warning of 
releases. The operating procedures must address multiple operating 
scenarios (e.g., normal operations, startup, emergency shutdown) and 
provide instructions for safely conducting process activities. The acts 
of conducting the hazard analysis and documenting operating procedures 
are similar to prevention measures, discussed below, though we note a 
specific number of measures or controls is not specified for the 
program 3 prevention program. Incident investigations must document the 
factors that contributed to an incident and any resolutions and 
corrective actions (incident investigations are consistent with root 
cause analysis and corrective action, discussed below). Facilities are 
also required to document this information in a Risk Management Plan 
that must be updated at least every 5 years.
    Next, we considered that some companies operating ethylene 
production facilities also own and operate petroleum refineries and may 
have established company-wide best practices as a result of specific 
state and Federal requirements. For example, petroleum refineries 
located in certain counties in California are subject to and complying 
with specific requirements for PRDs such as the Bay Area Air Quality 
Management District (BAAQMD) Rule 8-28-304 and South Coast Air Quality 
Management District (SCAQMD) Rule 1173. The BAAQMD rule requires 
implementation of three prevention measures and both rules require root 
cause analysis and corrective action for certain PRDs. These rules also 
formed the basis of the work practice standards promulgated for PRD 
releases at petroleum refineries in the Petroleum Refinery Sector RTR 
performed by the EPA (80 FR 75178, December 1, 2015).
    Considering our review of the EPA's Chemical Accident Prevention 
Provisions and company-wide best practices that ethylene facilities may 
have implemented, we expect that the best performing ethylene 
production facilities have implemented a program for PRDs that vent to 
atmosphere that consists of using at least three prevention measures 
and performing root cause analysis and corrective action in the event 
that a PRD does release emissions directly to the atmosphere. We used 
this information as the basis of the work practice standards that we 
are proposing at 40 CFR 63.1107(h)(3). Examples of prevention measures 
include: Flow indicators, level indicators, temperature indicators, 
pressure indicators, routine inspection and maintenance programs or 
operator training, inherently safer designs or safety instrumentation 
systems, deluge systems, and staged relief systems where the initial 
PRD discharges to a control system.
    We are also proposing a limit on the number of PRD releases that 
would result in a deviation to the work practice standard for PRDs that 
vent to atmosphere. We believe setting criteria to determine a 
deviation is necessary for the work practice to be effective. We 
considered limits on the number of PRD releases in both 3- and 5-year 
periods. Based on a Monte Carlo analysis of random rare events (as 
conducted for the Petroleum Refinery Sector MACT),\27\ we note that it 
is quite likely to have two or three events in a 5-year period when a 
long time horizon (e.g., 20 years) is considered. Therefore, we are 
proposing to limit the number of PRD releases from a single PRD to 
either two or three (depending on the root cause) in a 3-year period as 
the basis of a deviation of the work practice standard. We considered 
it reasonable to use a 3-year period rather than a 5-year period given 
that company-wide best practices forming the basis of the work practice 
standards promulgated for PRD releases at petroleum refineries are also 
our underlying basis for the proposed work practice standards at 
ethylene production facilities. We are proposing that it is a deviation 
of the work practice standard if a single PRD that vents to atmosphere 
has two releases within a 3-year period due to the same root cause. We 
believe that this provision will help ensure that root cause/corrective 
action are conducted effectively. Otherwise, we are proposing that it 
is a deviation of the work practice standard if a single

[[Page 54304]]

PRD that vents to atmosphere has three releases within a 3-year period 
for any reason. In addition, we are proposing that any PRD release for 
which the root cause was determined to be operator error or poor 
maintenance is a deviation of the work practice standard. We are 
proposing that ``force majeure'' events would not be included when 
counting the number of releases. As previously discussed in section 
IV.A.1.b of this preamble, we are proposing to define ``Force majeure'' 
as including events resulting from natural disasters, acts of war or 
terrorism, or external power curtailment beyond the facility's control. 
These types of events are beyond the control of the owner or operator. 
We are providing that these events should not be included in the event 
count, but that they would be subject to the root cause analysis in 
order to confirm whether the release was caused by a force majeure 
event.
---------------------------------------------------------------------------

    \27\ See 80 FR 75217, December 1, 2015.
---------------------------------------------------------------------------

    In addition, consistent with our treatment of ethylene process 
vents (in general, an open PRD is essentially the same as an ethylene 
process vent that is vented directly to the atmosphere), we believe 
that it is appropriate to exclude certain types of PRDs that have very 
low potential to emit based on their type of service, size, and/or 
pressure from the proposed work practice standard for PRD releases that 
vent to atmosphere. Both the Chemical Accident Prevention Provisions 
and the California Petroleum Refinery PRD rules also exempt or impose 
simpler requirements for certain PRDs. We are proposing at 40 CFR 
63.1107(h)(5) that the following types of PRDs would not be subject to 
the work practice standard for PRDs that vent to the atmosphere: (1) 
PRDs with a design release pressure of less than 2.5 pounds per square 
inch gauge (psig); (2) PRDs in heavy liquid service; (3) PRDs that are 
designed solely to release due to liquid thermal expansion; and (4) 
pilot-operated and balanced bellows PRDs if the primary release valve 
associated with the PRD is vented through a control system. Each of the 
types of PRDs that we are proposing are not subject to the work 
practice standard are discussed in greater detail here. With regard to 
PRDs with a design release pressure of less than 2.5 psig, it is 
technically infeasible to pipe sources with a release pressure of less 
than 2.5 psig to a flare (or other similar control system) because the 
back pressure in the flare header system generally exceeds 2.5 psig. 
Therefore, we are proposing that PRDs with a design release pressure of 
less than 2.5 psig are not subject to the work practice standard. With 
regard to PRDs in heavy liquid service, any release from a PRD in heavy 
liquid service would have a visual indication of a leak and any repairs 
to the valve would have to be further inspected and, if necessary, 
repaired under the existing equipment leak provisions. Therefore, we 
are proposing that PRDs in heavy liquid service are not subject to the 
work practice standard. In addition, we are proposing that PRDs 
designed solely to release due to liquid thermal expansion are not 
subject to the work practice standard. We expect that releases from 
these thermal relief valves would be small. Finally, we are also 
proposing that pilot-operated PRDs (where emissions can be released to 
the atmosphere through a pilot discharge vent) and balanced bellow PRDs 
(where emissions can be released to the atmosphere through a bonnet 
vent) are not subject to the work practice standard, if the primary 
release valve associated with the pilot-operated or balanced bellows 
PRD is vented through a control system. Pilot-operated and balanced 
bellows PRDs are primarily used for pressure relief when the back 
pressure of the discharge vent may be high or variable. Conventional 
pressure relief devices act on a differential pressure between the 
process gas and the discharge vent. If the discharge vent pressure 
increases, the vessel pressure at which the PRD will open increases, 
potentially leading to vessel over-pressurization that could cause 
vessel failure. Balanced bellows PRDs use a bellow to shield the 
pressure relief stem and top portion of the valve seat from the 
discharge vent pressure. A balanced bellows PRD will not discharge gas 
to the atmosphere during a release event, except for leaks through the 
bonnet vent due to bellows failure or fatigue. Pilot-operated PRDs use 
a small pilot safety valve that discharges to the atmosphere to effect 
actuation of the primary valve or piston, which then discharges to a 
control system. Balanced bellows or pilot operated PRDs are considered 
a reasonable and necessary means to safely control the primary PRD 
release.
    For all PRDs in organic HAP service, owners or operators would 
still be required to comply with the LDAR provisions, as they are 
currently applicable. Therefore, all PRDs that vent to the atmosphere 
would still perform LDAR to ensure the PRD properly reseats if a 
release does occur, and PRDs that vent to control systems would still 
be exempt from LDAR requirements given that if a release were to occur 
from these specific class of PRDs, it would vent to a closed vent 
system and control device.
    Finally, to ensure compliance with the proposed work practice 
standard for PRDs that vent to the atmosphere, we are also proposing to 
require that sources monitor these PRDs using a system that is capable 
of identifying and recording the time and duration of each pressure 
release and of notifying operators that a pressure release has 
occurred. Pressure release events from PRDs that vent to atmosphere 
have the potential to emit large quantities of HAP. Where a pressure 
release occurs, it is important to identify and mitigate it as quickly 
as possible. For purposes of estimating the costs of this requirement, 
we assumed that operators would install electronic monitors on PRDs 
that vent to atmosphere to identify and record the time and duration of 
each pressure release. However, we are proposing to allow owners and 
operators to use a range of methods to satisfy these requirements, 
including the use of a parameter monitoring system (that may already be 
in place) on the process operating pressure that is sufficient to 
indicate that a pressure release has occurred as well as record the 
time and duration of that pressure release. Based on our cost 
assumptions, the nationwide capital cost of installing these electronic 
monitors is $966,000 and the annualized capital cost is $130,000 per 
year.
    We also considered requiring all PRDs to be vented to a control 
device as a beyond-the-floor requirement. While this would provide 
additional emission reductions beyond those we are establishing as the 
MACT floor, these reductions come at significant costs. Capital costs 
for requiring control of all PRDs that vent to atmosphere is estimated 
to be approximately $13.1 million compared to $1.43 million for the 
requirements described above. The total annualized cost for requiring 
control of all PRDs that vent to atmosphere is estimated to be 
approximately $2.58 million/year compared to $270,000 per year for the 
requirements described above. We estimate that the incremental cost-
effectiveness of requiring control of all PRDs that vent to atmosphere 
compared to the requirements described above exceeds $40 million per 
ton of HAP reduced. Consequently, we conclude that this is not a cost-
effective option.
    The EPA is also proposing a requirement that any future installed 
pilot-operated PRDs be the non-flowing type. As previously noted, under 
CAA section 112(d)(1), the EPA may ``distinguish among classes, types, 
and sizes of sources'' when establishing standards. There are two 
designs of pilot-operated PRDs: Flowing and non-flowing. When a flowing 
pilot-operated PRD is actuated, the pilot discharge vent

[[Page 54305]]

continuously releases emissions; however, when a non-flowing pilot-
operated PRD is actuated, the pilot discharge vent does not vent 
continuously. Although we expect pilot discharge vent emissions to be 
minimal for both designs, limiting the future use of flowing pilot-
operated PRDs is warranted to prevent continuous release of emissions. 
Therefore, we are proposing at 40 CFR 63.1107(h)(8) to require future 
installation and operation of non-flowing pilot-operated PRDs at all 
affected sources.
    Although ``pressure relief device'' is defined in 40 CFR part 63, 
subpart YY (and applies to the other source categories regulated under 
the NESHAP, including Acetal Resins Production, Acrylic and Modacrylic 
Fiber Production, Carbon Black Production, Cyanide Chemicals 
Manufacturing, Hydrogen Fluoride Production, Polycarbonate Production, 
and Spandex Production source categories), ``relief valve'' is not 
defined. Therefore, we are proposing a definition of ``pressure relief 
device'' and ``relief valve'' that would only apply to the EMACT 
standards. We are proposing to define ``pressure relief device'' as a 
valve, rupture disk, or similar device used only to release an 
unplanned, nonroutine discharge of gas from process equipment in order 
to avoid safety hazards or equipment damage. A pressure relief device 
discharge can result from an operator error, a malfunction such as a 
power failure or equipment failure, or other unexpected cause. Such 
devices include conventional, spring-actuated relief valves, balanced 
bellows relief valves, pilot-operated relief valves, rupture disks, and 
breaking, buckling, or shearing pin devices. We are proposing to define 
``relief valve'' as a type of pressure relief device that is designed 
to re-close after the pressure relief.
    For details on the assumptions and methodologies used in this 
analysis, see the technical memorandum titled Review of Regulatory 
Alternatives for Certain Vent Streams in the Ethylene Production Source 
Category, which is in Docket ID No. EPA-HQ-OAR-2017-0357.
b. Closed Vent System Containing Bypass Lines
    The EMACT standards require ethylene process vents to vent through 
a closed vent system and APCD that meet the requirements of 40 CFR part 
63, subpart SS. For a closed vent system containing bypass lines that 
can divert the stream away from the APCD to the atmosphere, the EMACT 
standards require the owner or operator to either: (1) Install, 
maintain, and operate a continuous parametric monitoring system (CPMS) 
for flow on the bypass line that is capable of detecting whether a vent 
stream flow is present at least once every hour, or (2) secure the 
bypass line valve in the non-diverting position with a car-seal or a 
lock-and-key type configuration (These bypass line requirements are in 
40 CFR part 63, subpart SS.) Under option 2, the owner or operator is 
also required to inspect the seal or closure mechanism at least once 
per month to verify the valve is maintained in the non-diverting 
position (see 40 CFR 63.998(d)(1)(ii)(B) for more details). To ensure 
standards apply to ethylene process vents at all times, we are 
proposing at 40 CFR 63.1103(e)(6) that an owner or operator may not 
bypass the APCD at any time, and if a bypass is used, then we are 
proposing that owners or operators estimate and report the quantity of 
organic HAP released. We are proposing this revision because bypassing 
APCD could result in a release of regulated organic HAP to the 
atmosphere to be consistent with Sierra Club v. EPA, 551 F.3d 1019 
(D.C. Cir. 2008), where the Court determined that standards under CAA 
section 112(d) must provide for compliance at all times. We are also 
proposing that the use of a cap, blind flange, plug, or second valve on 
an open-ended valve or line is sufficient to prevent a bypass.
c. In Situ Sampling Systems (Online Analyzers)
    The current definition of ``ethylene process vent'' at 40 CFR 
63.1103(e)(2) states that ``in situ sampling systems (online 
analyzers)'' are not ethylene process vents. For several reasons, we 
are proposing to remove ``in situ sampling systems (online analyzers)'' 
from the list of vents not considered ethylene process vents. First, 
the language used in this exclusion is inconsistent. We generally 
consider ``in situ sampling systems'' to be non-extractive samplers or 
in-line samplers. There are certain in situ sampling systems where the 
measurement is determined directly through a probe placed in the 
process stream line. Such sampling systems do not have an atmospheric 
vent, so excluding these from the definition of ``ethylene process 
vent'' is not meaningful. The parenthetical term ``online analyzers'' 
generally refers to sampling systems that feed directly to an analyzer 
located at the process unit and has been interpreted to exclude the 
``online'' analyzer's vent from the definition of ethylene process 
vent. As these two terms do not consistently refer to the same type of 
analyzer, the provision is ambiguous.
    Second, we find that there is no technical reason to include 
analyzer vents in a list of vents not considered ethylene process 
vents. For extractive sampling systems and systems with purges, the 
equipment leak provisions in the EMACT standards require that the 
material be returned to the process or controlled. Thus, the only 
potential emissions from any sampling system compliant with the EMACT 
equipment leak provisions would be from the analyzer's ``exhaust gas'' 
vent. The parenthetical term ``online analyzers'' indicates that the 
focus of the exemption is primarily on the analyzer (or analyzer vent) 
rather than the sampling system. This phrase has been interpreted to 
exclude the ``online'' analyzer's vent from the definition of ethylene 
process vents. Analyzer venting is expected to be routine (continuous 
or daily intermittent venting).
    We are proposing to delete this exclusion from the definition of 
``ethylene process vent'' and to require these vents to meet the 
standards applicable to ethylene process vents at all times. We solicit 
comment on the existence of any online analyzers and why such vents are 
not amenable to control.
d. Maintenance Activities
    The current definition of ``ethylene process vent'' at 40 CFR 
63.1103(e)(2) states that ``episodic or nonroutine releases such as 
those associated with startup, shutdown, and malfunction'' are not 
ethylene process vents. We are proposing to remove ``episodic or 
nonroutine releases'' from the list of vents not considered ethylene 
process vents in order to ensure that the EMACT standard includes 
emission limits that apply at all times consistent with Sierra Club v. 
EPA. Because the definition of ``ethylene process vent'' only includes 
gas streams that are continuously discharged, clarification in this 
definition is also needed to ensure ``episodic or nonroutine releases'' 
are also covered. Thus, we are proposing that gas streams that are 
``periodically discharged'' be included in the definition of ethylene 
process vent, and we are proposing a definition for ``periodically 
discharged'' at 40 CFR 63.1103(e)(2). Since vent streams that are 
``periodically discharged'' were previously excluded from control 
requirements, we determined that the best performers would be 
controlling vent streams that had concentrations greater than 20 parts 
per million by volume HAP (i.e., the control level

[[Page 54306]]

currently for ethylene process vents) and total volatile organic 
compound emissions of 50 lbs per day or more (i.e., the control level 
of mass emissions for vent streams during periods of startup, shutdown, 
and maintenance from state permits for the best performing sources 
discussed further in this section).
    We recognize that this proposed change for vent streams that are 
``periodically discharged'' will affect certain maintenance activities 
such as those that require equipment openings, and we consider 
maintenance activities a separate class of startup and shutdown 
emissions because there must be a point in time when the equipment can 
be opened and any emissions are vented to the atmosphere. We also 
acknowledge that it would require a significant effort to identify and 
characterize each of these potential release points (e.g., for 
permitting purposes).
    We reviewed state permit conditions and determined the best 
performers permits specify that they meet certain conditions before 
they open equipment to the atmosphere. The conditions include 
thresholds regarding the lower explosive limit (LEL) and the mass of 
gas that may be emitted. Therefore, we are proposing a work practice 
standard at 40 CFR 63.1103(e)(5) that prior to opening process 
equipment to the atmosphere during maintenance events, the equipment 
first be drained and purged to a closed system so that the hydrocarbon 
content is less than or equal to 10 percent of the LEL. For those 
situations where 10-percent LEL cannot be demonstrated, we are 
proposing that the equipment may be opened and vented to the atmosphere 
if the pressure is less than or equal to 5 psig, provided there is no 
active purging of the equipment to the atmosphere until the LEL 
criterion is met. We are proposing this 5 psig threshold to acknowledge 
a certain minimum pressure must exist for the flare header system (or 
other similar control system) to operate properly. We are also 
proposing that equipment may be opened when there is less than 50 lbs 
of VOC that may be emitted to the atmosphere.
    We also acknowledge that installing a blind to prepare equipment 
for maintenance may be necessary and by doing so, the owner or operator 
may not be able to meet the proposed maintenance vent conditions 
mentioned above (e.g., a valve used to isolate the equipment will not 
seat fully so organic material may continually leak into the isolated 
equipment). To limit the emissions during the blind installation, we 
are proposing to require depressurizing the equipment to 2 psig or less 
prior to equipment opening and maintaining pressure of the equipment 
where purge gas enters the equipment at or below 2 psig during the 
blind flange installation. The low allowable pressure limit will reduce 
the amount of process gas that will be released during the initial 
equipment opening and the ongoing 2 psig pressure requirement will 
limit the rate of purge gas use. Together, these proposed provisions 
will limit the emissions during blind flange installation and will 
result in comparable emissions allowed under the proposed maintenance 
vent conditions mentioned above. We expect these situations to be rare 
and that the owner or operator would remedy the situation as soon as 
practical (e.g., replace the isolation valve or valve seat during the 
next turnaround in the example provided above). Therefore, we are only 
proposing that this alternative maintenance vent limit be used under 
those situations where the proposed primary limits (i.e., hydrocarbon 
content is less than or equal to 10 percent of the LEL, pressure is 
less than or equal to 5 psig, or VOC is less than 50 lbs) are not 
achievable and blinding of the equipment is necessary.
    To demonstrate compliance with this work practice standard, we are 
proposing provisions that include documenting procedures for equipment 
openings and verifying that events meet the specific conditions above 
using site procedures for de-inventorying of equipment for safety 
purposes (i.e., hot work or vessel entry procedures). We are also 
proposing that owners or operators document each circumstance where the 
alternative maintenance vent limit is used, providing an explanation 
why other criteria could not be met prior to equipment blinding and an 
estimate of the emissions that occurred during the equipment blinding 
process. We calculated the capital costs for this work practice to be 
$26,000, with annualized capital costs of $16,000.
    See the technical memorandum titled Review of Regulatory 
Alternatives for Certain Vent Streams in the Ethylene Production Source 
Category, in Docket ID No. EPA-HQ-OAR-2017-0357, for additional details 
and discussion.
e. Flares and Fuel Gas Systems
    The current definition of ``ethylene process vent'' at 40 CFR 
63.1103(e)(2) states that ``gaseous streams routed to a fuel gas 
system'' are not ethylene process vents because the combustion device 
(typically a boiler or process heater) burning these gaseous streams as 
fuel effectively achieve the most stringent level of control (i.e., 98-
percent organic HAP reduction or an outlet organic HAP concentration of 
20 parts per million by volume (ppmv) for all vent streams). In 
addition, other EMACT standards (e.g., standards for transfer racks) 
also allow emissions to be routed to a fuel gas system for compliance 
purposes. However, there can be instances when gaseous streams from the 
fuel gas system that would otherwise be combusted in a boiler or 
process heater are instead routed to a flare (e.g., overpressure in the 
fuel gas system, used as flare sweep gas, used as flare purge gas). In 
cases where an emission source is required to be controlled in the 
EMACT standards but is routed to a fuel gas system, we are proposing 
that any flare receiving gases from that fuel gas system comply with 
the flare operating and monitoring requirements discussed in section 
IV.A.1 of this preamble. We recognize that this proposed provision may 
require owners or operators that use fuel gas for any purpose (e.g., 
flare sweep gas, flare purge gas, flare supplemental gas) in other 
flare APCDs that predominately control emissions from other source 
categories to comply with the proposed flare revisions discussed in 
section IV.A.1 of this preamble. Thus, in order to minimize this 
impact, we are proposing that any flare that utilizes fuel gas whereby 
the majority (i.e., 50 percent or more) of the fuel gas in the fuel gas 
system is derived from an ethylene production unit comply with the 
flare operating and monitoring requirements discussed in section IV.A.1 
of this preamble.
3. Ethylene Cracking Furnace Decoking Operations
    During normal operation, an ethylene cracking furnace is designed 
to subject certain hydrocarbon feedstocks (i.e., ethane, propane, 
butane, naptha, or gas oils) to high temperatures in the presence of 
steam to ``crack'' the feedstock (i.e., break the feedstock molecules 
apart). The feedstock travels through the furnace through piping (or 
tubing) and is designed such that the feedstock (and subsequent 
products formed from the ``cracking'' of the feedstock) should never 
come into direct contact with the fuel being burned in the furnace. The 
feedstock first passes through piping in the top portion of the furnace 
(called the ``convection'' section) for preheating; steam is then added 
after the feedstock has traveled through a portion of the piping. This 
steam is called diluted steam because it acts as a diluting agent that 
lowers the partial pressure of the feedstock and keeps the feedstock 
molecules from recombining once broken apart. The feedstock/steam 
mixture then passes through piping in

[[Page 54307]]

the bottom portion of the furnace (called the ``radiant'' section or 
``firebox'') where the ``cracking'' of the hydrocarbon feedstock occurs 
inside the piping (or ``radiant tube''). The cracked gas products 
formed from the ``cracking'' of the hydrocarbon feedstock in each 
furnace are passed through one or more heat exchangers and aggregated 
into a cracked gas header via a system of transfer line valves prior to 
downstream operations.
    As hydrocarbon feedstock and steam passes through the radiant tubes 
of an ethylene cracking furnace, over time, a layer of carbon (i.e., 
coke) builds up on the interior of the tubing forming a physical 
restrictive barrier. Because of this buildup, the tubing gradually gets 
hotter during the cracking process (i.e., the temperature of the tubing 
typically increases by 3 to 4 degrees Fahrenheit per day even with a 
constant firebox temperature, because the coke acts as an insulator on 
the tubing). Eventually, the ethylene cracking furnace must be taken 
out of production, so that coke buildup can be removed from the tubing. 
This removal of coke buildup is done through combustion and is known as 
a decoking operation. The EPA considers the coke combustion activity 
that occurs within the process (i.e., inside the radiant tubes) the 
emission source from decoking operations, whereas the emissions 
generated from the fuel combustion activity in the ethylene cracking 
furnace radiant section (or firebox) a different emission source part 
of normal operations (65 FR 76408, December 6, 2000).
    Prior to decoking, the fuel firing rate of the ethylene cracking 
furnace is reduced, and the hydrocarbon feedstock that would otherwise 
be thermally cracked is stopped, leaving steam as the only stream being 
sent through the piping (or ``radiant tubes''). During this time the 
radiant tube(s) continues to be purged of any remaining feedstock using 
steam, and this purge stream is sent downstream through the cracked gas 
header and into the ethylene production process. After all hydrocarbon 
feedstock is purged from the radiant tube(s), the steam is stopped, and 
the radiant tube(s) is isolated from the process using transfer line 
and decoking valves. Once isolated, oxygen (i.e., air) and steam is 
gradually added inside the radiant tube(s) until the coke ignites, and 
the exhaust is diverted through a decoke header to either a large 
cyclone separation device called a ``decoking pot'' or back into the 
ethylene cracking furnace firebox. In the current EMACT standards, 
decoking an ethylene cracking furnace is specifically listed in the 
definition of ``shutdown,'' and procedures to minimize emissions from 
decoking are required to be addressed in a facility's SSM plan.\28\ 
However, with the elimination of the SSM exemption (see section IV.E.1 
of this preamble for additional discussion), we are proposing work 
practice standards to control HAP emissions from decoking operations. 
The work practices would apply to the decoking of any ethylene cracking 
furnace at a new or existing affected source subject to this subpart.
---------------------------------------------------------------------------

    \28\ In other words, the EPA considered only the coke removal 
activity that takes place inside the radiant tube(s) as the 
``decoking'' operation regulated as a shutdown activity. Ethylene 
cracking furnaces also experience complete shutdowns (where the 
furnace firebox is taken completely off-line for maintenance or a 
scheduled turnaround), and cold startups (where the furnace firebox 
is initially started up following off-line maintenance or a 
scheduled turnaround).
---------------------------------------------------------------------------

    We are proposing work practices for decoking operations instead of 
emission limits due to technological and economic limitations. CAA 
section 112(h)(1) states that the Administrator may prescribe a work 
practice standard or other requirements, consistent with the provisions 
of CAA sections 112(d) or (f), in those cases where, in the judgment of 
the Administrator, it is not feasible to enforce an emission standard. 
CAA section 112(h)(2)(B) further defines the term ``not feasible'' in 
this context to apply when ``the application of measurement technology 
to a particular class of sources is not practicable due to 
technological and economic limitations.''
    The emissions stream generated from decoking operations (i.e., the 
combination of coke combustion constituents, air, and steam from the 
radiant tube(s)) is very dilute with a high moisture content (e.g., 
generally >95 percent water). As part of our CAA section 114 request, 
we required companies to perform testing for HAP from this emissions 
source at certain ethylene cracking furnaces (see section II.C of this 
preamble for details about our CAA section 114 request). A minimum of 
three decoking cycles were required to be tested; and emissions data 
were obtained for three test runs spaced over the entire duration of 
each decoking cycle. The test data collected from industry confirm that 
HAP emissions, such as non-PAH organic HAP, occur during decoking 
operations. However, the majority (i.e., 88 percent) of non-PAH organic 
HAP were found to be below detection levels (BDL). We regard situations 
where, as here, the majority of measurements are below detection 
limits, as measurements that are not ``technologically practicable'' 
within the meaning of CAA section 112(h). We have also previously 
reasoned that ``application of measurement methodologies'' under CAA 
section 112(h) must also mean that a measurement has some reasonable 
relation to what the source is emitting (i.e., that the measurement 
yields a meaningful value). We have further explained that unreliable 
measurements raise issues of practicability, feasibility, and 
enforceability. Additionally, we have posited that the application of 
measurement methodology would also not be ``practicable due to. . . 
economic limitation'' within the meaning of CAA section 112(h) because 
it would result in cost expended to produce analytically suspect 
measurements. Refer to area source Boiler Rule (75 FR 31906, June 4, 
2010) and the NESHAP for the Wool Fiberglass Manufacturing source 
category (80 FR 45280 and 45312, July 29, 2015).
    While the CAA section 114 test data show that PAHs and metal HAP 
are emitted during decoking operations, the majority of the test runs 
do not meet the underlying requirements of the test methods to be 
within +/-10 percent of isokinetic. Isokinetic sampling is required for 
any method where compounds may exist in a particle or aerosol phase in 
order to collect a representative sample with respect to a flow 
weighted average concentration and particle or aerosol size 
distribution. Without an appropriate isokinetic sample, the data may be 
biased and unreliable for compliance demonstrations. The EPA was aware 
that it would be extremely difficult for facilities to meet the +/-10-
percent isokinetic requirement of the sampling methods during the 
majority of a decoking cycle; however, data were still gathered so that 
the Agency could better understand the types of HAP that may be 
potentially emitted from decoking operations. In order to pull a sample 
in an isokinetic manner, the tester must have knowledge of the large 
components of the gas stream such as moisture, oxygen, and carbon 
dioxide (CO2). When a gas stream is nearly pure moisture 
(greater than 90-percent moisture), even slight deviations in the 
assumed moisture can cause large changes in the flow through the 
sampling nozzle, which is controlled through dry gas measurements. For 
example, an assumed gas stream moisture content of 97 percent with a 
true gas stream moisture content of 98 percent would cause the 
isokinetic rate to be off by around 30 percent. The same margin of 
error in moisture assumption at 10- to 20-percent gas stream moisture 
content (normal combustion levels) would only cause

[[Page 54308]]

the isokinetic rate to be off by a couple of percent. This thin margin 
of error for moisture assumption makes it extremely difficult to 
achieve required isokinetic rates at these high moisture conditions. 
Because it is technically and economically impracticable to achieve 
representative and precise samples for PAHs and metal HAP for all 
decoking operations, work practice standards are appropriate. Refer to 
U.S. Sugar Corp. v. EPA, 830 F.3d 579, 666-667 (2016).
    As coke builds up in radiant tubes, ethylene yield from cracking 
furnaces decreases and decoking becomes inevitable. Decoking events are 
undesirable primarily because owners and operators must take the 
ethylene cracking furnace completely out of ethylene production 
service; and radiant tube life is shortened from thermal stresses 
during decoking. Therefore, there is already incentive to minimize coke 
formation and decoking events. Based on discussions with industry, as 
well as a review of facility-specific SSM plans that were submitted to 
the EPA in response to the CAA section 114 request, we determined that 
owners and operators already conduct work practices to minimize 
emissions due to coke combustion. In the next few paragraphs below, we 
discuss the work practices we identified, and explain how each are 
feasible and effective in reducing coke combustion emissions.
    Ethylene cracking furnace flame impingement occurs when flames from 
the firebox burners make direct contact with the radiant tube(s), 
creating hot spots on the interior wall of the radiant tube(s) which 
can lead to coke buildup and eventual tube failure. Generally, during 
normal operations, owners and operators visually inspect their firebox 
burners daily for flame impingement. An inspection may include, but is 
not limited to, visual inspection of the radiant tube(s) for localized 
bright spots (this may be confirmed with a temperature gun), use of 
luminescent powders injected into the burner to illuminate the flame 
pattern, or continued localized coke build-up causing short runtimes 
between decoking cycles. During the inspection, if the owner or 
operator finds flame impingement is occurring, then the burner creating 
the flame impingement on the radiant tube(s) is taken out of service or 
the alignment of the burner is adjusted such that it no longer impinges 
on the radiant tube(s). Other actions taken to correct the flame 
impingement include: Replacing the burner, adjusting burner 
configuration, making burner air corrections, repairing a malfunction 
of the fuel liquid removal equipment, or adding insulation around the 
radiant tube(s). By preventing flame impingement during normal 
operations, thermal stress on the radiant tube(s) is reduced (thus, 
prolonging radiant tube life) and coke formation inside the radiant 
tube(s) is minimized, which ultimately leads to less frequent decoking 
and lower coke combustion emissions.
    During decoking operations, some owners and operators also 
continuously monitor (or use grab samples to monitor) the 
CO2 concentration at the radiant tube outlet for indication 
that the coke combustion in the ethylene cracking furnace radiant 
tube(s) is complete or near completion. A decrease in CO2 
concentration level indicates that there is less coke buildup inside 
the radiant tube(s) and the majority of the coke has been removed. By 
identifying when combustion of the coke inside the radiant tube(s) is 
slowing or stopping; owners and operators can more accurately predict 
when to stop decoking operations, thus, reducing thermal stress on the 
radiant tube(s) (prolonging radiant tube life) and preventing 
unnecessary coke combustion emissions.
    In addition to monitoring the CO2 concentration, some 
owners and operators continuously monitor the radiant tube(s) outlet 
temperature (or coil outlet temperature) during decoking operations to 
ensure the coke combustion occurring inside the radiant tube(s) is not 
so aggressive (i.e., too hot) that it damages either the radiant 
tube(s) or ethylene cracking furnace isolation valve(s). If the radiant 
tube(s) or ethylene cracking furnace isolation valve(s) is damaged, 
then coke combustion emissions could leak downstream, upsetting the 
ethylene production process, instead of being routed through the 
decoking pot and/or cracking furnace firebox.
    Furthermore, after decoking operations are complete, but before 
returning the ethylene cracking furnace back to normal operations, 
owners and operators may perform the following two additional 
maintenance steps: Owners and operators purge the radiant tube(s) with 
steam and verify that all air is removed. This purge step ensures coke 
formation is minimized once a feedstock is placed back into the radiant 
tube(s) during normal operations. Also, some owners and operators apply 
a coating material to the interior of the radiant tube(s) to protect 
against coke formation inside the radiant tube(s) during normal 
operation. As mentioned earlier, minimizing coke formation inside the 
radiant tube(s) ultimately leads to less frequent decoking and less 
coke combustion emissions.
    Based on our review of the SSM plans as well as discussions with 
stakeholders, we determined that the best performers conduct daily 
inspections for flame impingement, while also conducting at least two 
of the other work practices identified above for reducing coke 
combustion emissions. Based on this information, we are proposing at 40 
CFR 63.1103(e)(7) that owners and operators conduct daily inspections 
for flame impingement and implement at least two of the other work 
practices we identified above to minimize coke combustion emissions 
from the decoking of the radiant tube(s) in each ethylene cracking 
furnace. If the owner or operator chooses to conduct daily firebox 
flame impingement inspections during normal operations, we are 
proposing that records be kept that document the day and time each 
inspection took place, the results of each inspection, and any repairs 
made to correct the flame impingement. If the owner or operator chooses 
to monitor the CO2 concentration during decoking, we are 
proposing that records be kept for all measured CO2 
concentration values and the target used to indicate combustion is 
complete. If the owner or operator chooses to monitor the temperature 
at the radiant tube(s) outlet during decoking, we are proposing that 
records be kept for all measured temperature values and the target used 
to indicate a reduction in temperature of the inside of the radiant 
tube(s) is necessary. If the owner or operator chooses to purge the 
radiant tube(s) with steam after decoking, but before returning the 
ethylene cracking furnace back to normal operations, we are proposing 
that records be kept to document the verification that all air is 
removed (e.g., some owners and operators monitor the lower explosive 
limit). If the owner or operator chooses to apply a coating material to 
the interior of the radiant tube(s) after decoking, but before 
returning the ethylene cracking furnace back to normal operations, we 
are proposing that records be kept to document when the coating was 
applied. In addition, we are proposing that owners and operators 
include in the periodic report (already required under this rule), 
instances where the control measures that the owner or operator 
selected were not followed. We also did not identify any additional 
options beyond those identified above (i.e., beyond-the-floor options) 
for minimizing coke formation and minimizing coke combustion emissions.
    Finally, we also identified a work practice that the best 
performers use to

[[Page 54309]]

prevent non-coke combustion HAP emissions from escaping to the 
atmosphere caused by leaks in the transfer line and decoking valves. To 
minimize the introduction of additional sources of HAP into the 
ethylene production process or into the atmosphere, some owners and 
operators conduct inspections of ethylene cracking furnace isolation 
valves both prior to decoking the radiant tube(s) (to prevent leaks 
into the ethylene production process which could lead to unnecessary 
flare activity) and also prior to returning the ethylene cracking 
furnace to normal operations (to prevent product from escaping to the 
atmosphere through the decoking pot or furnace firebox). We note that 
during a 2013 investigation (see Appendix D of the memorandum titled 
Assessment of Work Practice Standards for Ethylene Cracking Furnace 
Decoking Operations Located in the Ethylene Production Source Category, 
which is available in Docket ID No. EPA-HQ-OAR-2017-0357), TCEQ staff 
documented that a facility released more than 800 tons of VOC 
(including more than 20 tons of 1,3-butadiene) to the atmosphere 
through a decoking pot because two motor operated valves remained 
partially open following a decoking cycle. This release allowed loss of 
process gases during normal operations. We believe that routine 
inspections of the ethylene cracking furnace isolation valve could have 
prevented this incident. Based on this information, we are proposing at 
40 CFR 63.1103(e)(8) that owners and operators inspect the applicable 
ethylene cracking furnace isolation valve(s) prior to decoking the 
radiant tube(s) to confirm that the radiant tube(s) being decoked is 
completely isolated from the ethylene production process. Additionally, 
prior to returning the ethylene cracking furnace to normal operation, 
we are proposing owners and operators inspect the applicable ethylene 
cracking furnace isolation valve(s) to confirm that the radiant tube(s) 
that was decoked is completely isolated from the decoking pot or 
furnace firebox. We are also proposing that records documenting the day 
and time each inspection took place be kept, along with the results of 
each inspection, and any repairs made to correct any isolation issues 
that were identified. In addition, we are proposing that owners and 
operators include in the periodic report (already required under this 
rule), instances where an isolation valve inspection was not conducted. 
We did not identify any additional options beyond those identified 
above (i.e., beyond-the-floor options) that would limit non-coke 
combustion HAP emissions from escaping to the atmosphere when the 
ethylene cracking furnaces are taken offline for decoking operations 
and put back online after decoking operations.
    We estimate the nationwide annual cost for implementing these 
proposed work practices is $151,300 per year. Further discussion on the 
proposed work practices is provided in the memorandum titled Assessment 
of Work Practice Standards for Ethylene Cracking Furnace Decoking 
Operations Located in the Ethylene Production Source Category, which is 
available in Docket ID No. EPA-HQ-OAR-2017-0357. We solicit comment on 
the proposal to implement the work practices we identified above to 
minimize coke combustion emissions from the decoking of the radiant 
tube(s) in each ethylene cracking furnace, and whether facilities 
already have these work practices in place or will need to implement 
one or more for minimizing emissions from decoking operations from 
ethylene cracking furnaces. We are also seeking comment on the proposal 
to inspect isolation valves both prior to decoking and prior to 
returning the ethylene cracking furnace to normal operations, and on 
other approaches for minimizing emissions from decoking operations.

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

    As described above, for the Ethylene Production source category, we 
conducted an inhalation risk assessment for all HAP emitted, and 
multipathway and environmental risk screening assessments on the PB-HAP 
emitted. We present results of the risk assessment briefly below and in 
more detail in the document titled Residual Risk Assessment for the 
Ethylene Production Source Category in Support of the 2019 Risk and 
Technology Review Proposed Rule, which is available in the docket for 
this rulemaking.
1. Inhalation Risk Assessment Results
    Table 3 of this preamble provides a summary of the results of the 
inhalation risk assessment for the source category.

                                                                 Table 3--Ethylene Production Inhalation Risk Assessment Results
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                    Maximum individual cancer risk  Population at increased risk of cancer  Annual cancer Incidence (cases     Maximum chronic noncancer     Maximum  screening
                                          (in 1 million) \2\                   >= 1-in-1 million                       per year)                       TOSHI \3\             acute noncancer HQ
                                   ----------------------------------------------------------------------------------------------------------------------------------------          \4\
                                            Based on . . .                      Based on . . .                      Based on . . .                  Based on . . .         ---------------------
     Number of facilities \1\      ----------------------------------------------------------------------------------------------------------------------------------------
                                       Allowable        Actual                                                 Allowable        Actual          Actual         Allowable      Based on  actual
                                       emissions       emissions         Allowable       Actual  emissions     emissions       emissions       emissions       emissions      emissions  level
                                         level           level       emissions  level          level             level           level           level           level
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
31................................             100             100  2.8 million.......  4.6 million.......             0.1             0.2               1               1  HQREL = <1
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Number of facilities evaluated in the risk analysis.
\2\ Maximum individual excess lifetime cancer risk due to HAP emissions from the source category.
\3\ Maximum TOSHI. The target organ systems with the highest TOSHI for the source category are neurological and reproductive. The respiratory TOSHI was calculated using the CalEPA chronic REL
  for acrolein. The EPA is in the process of updating the IRIS RfC for acrolein.
\4\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of HQ values. HQ values shown use the lowest available acute
  threshold value, which in most cases is the REL. When an HQ exceeds 1, we also show the HQ using the next lowest available acute dose-response value.

    The results of the inhalation risk modeling using actual emissions 
data, as shown in Table 3 of this preamble, indicate the estimated 
cancer MIR is 100-in-1 million, with naphthalene and benzene as the 
major contributors to the risk. The total estimated cancer incidence 
from this source category is 0.1 excess cancer cases per year, or one 
excess case in every 10 years. Approximately 2.8 million people were 
estimated to have cancer risks above 1-in-1 million from HAP emitted 
from the facilities in this source category. The estimated maximum 
chronic noncancer TOSHI for the source category is 1 (neurological and 
respiratory) driven by emissions of manganese and epichlorohydrin. No 
one is exposed to TOSHI levels above 1.
    Risk results from the inhalation risk assessment using the MACT-
allowable emissions indicate that the estimated cancer MIR is 100-in-1 
million with naphthalene and benzene emissions driving the risks, and 
that the estimated maximum chronic noncancer TOSHI is

[[Page 54310]]

1 with manganese and epichlorohydrin as the major contributors to the 
TOSHI. The total estimated cancer incidence from this source category 
considering allowable emissions is 0.2 excess cancer cases per year or 
1 excess case in every 5 years. Based on allowable emission rates, 4.6 
million people were estimated to have cancer risks above 1-in-1 
million.
2. Acute Risk Results
    As shown in Table 3 of this preamble, the worst-case acute HQ 
(based on the REL) is less than 1. This value is the highest HQ that is 
outside facility boundaries. No facilities are estimated to have an HQ 
greater or equal to than 1 based on any benchmark (REL, AEGL, or EPRG). 
Acute risk estimates for each facility and pollutant are provided in 
the risk document titled Residual Risk Assessment for the Ethylene 
Production Source Category in Support of the 2019 Risk and Technology 
Review Proposed Rule, which is available in the docket for this 
rulemaking.
3. Multipathway Risk Screening Results
    Potential multipathway health risks under a fisher and farmer/
gardener scenario were identified using a three-tier screening 
assessment of the PB-HAP emitted by facilities in this source category. 
All 31 of the ethylene production facilities have reported emissions of 
carcinogenic PB-HAP (arsenic and POM). All 31 facilities exceeded a 
Tier 1 cancer screening value for arsenic, and all but five exceeded a 
Tier 1 cancer screening value for POM. All 31 facilities have reported 
emissions of non-carcinogenic PB-HAP (cadmium and mercury). Nineteen 
facilities exceeded a Tier 1 cancer screening value for mercury, and 
four exceeded a Tier 1 noncancer screening value for cadmium. For 
facilities that exceeded the Tier 1 multipathway screening values for 
one or more PB-HAP, we used additional facility site-specific 
information to perform an assessment through Tiers 2 and 3, as 
necessary, to determine the maximum chronic cancer and noncancer 
impacts for the source category. For cancer, the highest exceedance of 
a Tier 2 screening value was by a factor of 30, and further analyses 
were not performed. For noncancer, there are two facilities that exceed 
a Tier 3 screening value by a factor of 2 for mercury. In other RTRs 
where we have exceeded either Tier 2 or Tier 3 screening values of 1 
and performed refined facility-specific assessments, the refined 
estimates have always been at least 80 percent lower than those 
estimated by the Tier 2 or Tier 3 screening values. For example, in the 
petroleum refinery RTR, a refined facility-specific assessment was 
performed for noncancer risk from mercury. The results of this analysis 
showed that estimated noncancer risk for mercury from the refined 
assessment was 7 times lower than that predicted by the screening 
approach (79 FR 36936, June 30, 2014). Given that only an estimated 15-
percent reduction in media concentrations for mercury are needed in a 
refined facility-specific risk assessment to lower the values to 1 (to 
one significant figure) compared to the Tier 3 screen, and given the 
fact that results from facility-specific assessments performed for 
other source categories always have significant trends down in risk, we 
conclude that a refined facility-specific assessment for the Ethylene 
Production source category would show a reduction of noncancer risk by 
at least 15-percent to result in a value of 1 or lower. For this reason 
and considering the conservative nature of the multipathway exposure 
screening scenario, further analyses were not performed.
4. Environmental Risk Screening Results
    A screening-level evaluation of the potential adverse environmental 
risk associated with emissions of arsenic, cadmium, hydrochloric acid, 
hydrofluoric acid, lead, mercury, and POMs indicated that no ecological 
benchmarks are exceeded.
5. Facility-Wide Risk Results
    The results of the inhalation risk modeling using facility-wide 
emissions data indicate that the estimated cancer MIR is 2,000-in-1 
million, with the major contributor to the risk being ethylene oxide 
emissions from sources outside the source category (non-ethylene 
production processes). The total estimated cancer incidence is 1 excess 
cancer case per year. Approximately 6.5 million people are estimated to 
have cancer risks above 1-in-1 million. The estimated maximum chronic 
noncancer TOSHI value is 4 (for the respiratory HI), driven by 
emissions of chlorine from non-category (non-ethylene production) 
processes. Approximately 200 people are estimated to be exposed to 
noncancer HI levels above 1.
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 risks 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 risks from the Ethylene Production 
source category across different demographic groups within the 
populations living near facilities.\29\
---------------------------------------------------------------------------

    \29\ 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.
---------------------------------------------------------------------------

    The results of the demographic analysis are summarized in Table 4 
of this preamble. These results, for various demographic groups, are 
based on the estimated risk from actual emissions levels for the 
population living within 50 km of the facilities.

                         Table 4--Ethylene Production Demographic Risk Analysis Results
----------------------------------------------------------------------------------------------------------------
                                                                            Population with
                                                                           cancer risk at or    Population with
                                                                             above 1-in-1     chronic HI above 1
                                                          Nationwide        million due to      due to ethylene
                                                                               ethylene           production
                                                                              production
----------------------------------------------------------------------------------------------------------------
Total Population....................................         317,746,049           2,780,122                   0
----------------------------------------------------------------------------------------------------------------
                                          White and Minority by Percent
----------------------------------------------------------------------------------------------------------------
White...............................................                  62                  38                   0
All Other Races.....................................                  38                  62                   0
----------------------------------------------------------------------------------------------------------------

[[Page 54311]]

 
                                           Minority Detail by Percent
----------------------------------------------------------------------------------------------------------------
African American....................................                  12                  21                   0
Native American.....................................                 0.8                 0.2                   0
Hispanic or Latino (includes white and nonwhite)....                  18                  37                   0
Other and Multiracial...............................                   7                   4                   0
----------------------------------------------------------------------------------------------------------------
                                                Income by Percent
----------------------------------------------------------------------------------------------------------------
Below Poverty Level.................................                  14                  18                   0
Above Poverty Level.................................                  86                  82                   0
----------------------------------------------------------------------------------------------------------------
                                              Education by Percent
----------------------------------------------------------------------------------------------------------------
Over 25 and without High School Diploma.............                  14                  23                   0
Over 25 and with a High School Diploma..............                  86                  77                   0
----------------------------------------------------------------------------------------------------------------

    The results of the Ethylene Production source category demographic 
analysis indicate that emissions from the source category expose 
approximately 2.8 million people to a cancer risk at or above 1-in-1 
million and no people to a chronic noncancer TOSHI greater than 1. The 
percentages of the at-risk population in the African American and the 
Hispanic or Latino demographic groups are higher than their respective 
nationwide percentages.
    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 Ethylene Production 
Source Category Operations, available in the docket for this action.

C. 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 maximum individual 
lifetime [cancer] risk (MIR) of approximately 1-in-10 thousand.'' 54 FR 
38045, September 14, 1989. In this proposal, the EPA estimated risks 
based on actual and allowable emissions from ethylene production 
sources, and we considered these in determining acceptability.
    The estimated inhalation cancer risk to the individual most exposed 
to actual emissions from the source category is 100-in-1 million. The 
estimated incidence of cancer due to inhalation exposures is 0.1 excess 
cancer cases per year, or one excess case every 10 years. Approximately 
2.8 million people face an increased cancer risk greater than 1-in-1 
million due to inhalation exposure to HAP emissions from this source 
category. The Agency estimates that the maximum chronic noncancer TOSHI 
from inhalation exposure for this source category is 1. Based on 
allowable emissions, the estimated inhalation cancer risk to the 
individual most exposed to actual emissions from the source category is 
also 100-in-1 million, but the estimated incidence of cancer due to 
inhalation exposures is 0.2 excess cancer cases per year, or one excess 
case every 5 years. Approximately 4.6 million people face an increased 
cancer risk greater than 1-in-1 million due to inhalation exposure to 
allowable HAP emissions from this source category. The maximum chronic 
noncancer TOSHI from inhalation exposure is 1 based on allowable 
emissions. The screening assessment of worst-case acute inhalation 
impacts indicates no facility is estimated to have an HQ greater than 1 
based on the REL, AEGL-1 or ERPG-1.
    Potential multipathway human health risks were estimated using a 
three-tier screening assessment of the PB-HAP emitted by facilities in 
this source category, where the highest exceedance of a Tier 2 
screening value is by a factor of 30. For noncancer, the highest 
exceedance of a Tier 3 screening value is by a factor of 2 for mercury. 
In evaluating the potential for multipathway effects from emissions of 
lead from the source category, we compared modeled maximum annual lead 
concentrations to the primary NAAQS for lead (0.15 [mu]g/m\3\). Results 
of this analysis estimate that the NAAQS for lead would not be exceeded 
at any off-site locations.
    For a summary of risk assessment report results for the source 
category and facility-wide emission impacts, refer to Table 3 of this 
preamble.
    In determining whether risks are acceptable for this source 
category, the EPA considered all available health information and risk 
estimation uncertainty as described above. The risk results indicate 
that the inhalation cancer risks to the individual most exposed are no 
greater than approximately 100-in-1 million, which is at the 
presumptive limit of acceptability (see, for example, 54 FR 38045, 
September 14, 1989). There is only one facility at this risk level and 
only one person estimated to be exposed at this risk level based on 
actual emissions, and only one facility and 60 people estimated to be 
exposed at this risk level based on allowable emissions. The remaining 
facilities have much lower estimated cancer risks, 30-in-1 million or 
lower based on actual emissions and 80-in-1 million or lower based on 
allowable emissions. There are no facilities with an estimated maximum 
chronic noncancer HI greater than 1. There are no facilities with an 
acute HQ >1 based on the REL, AEGL-1 or ERPG-1.
    Multipathway human health risks are also within limits of 
acceptability. For cancer, the highest exceedance of a Tier 2 screening 
value was by a factor of 30, which is well below the presumptive

[[Page 54312]]

limit of acceptability. For noncancer, there are two facilities that 
exceed a Tier 3 screening value by a factor of 2 for mercury. In other 
RTRs where we have exceeded either Tier 2 or Tier 3 screening values of 
1 and performed refined facility-specific assessments, the refined 
estimates have always been at least 80 percent lower than those 
estimated by the Tier 2 or Tier 3 screening values. Given that only an 
estimated 15-percent reduction in media concentrations for mercury are 
needed in a refined facility-specific risk assessment to lower the 
values to 1 (to one significant figure) compared to the Tier 3 screen, 
and given the fact that results from facility-specific assessments 
performed for other source categories always have significant trends 
down in risk, we conclude that a refined facility-specific assessment 
for the Ethylene Production source category would show a reduction of 
noncancer risk by at least 15-percent to result in a value of 1 or 
lower. For this reason and considering the conservative nature of the 
multipathway exposure screening scenario, we conclude these levels are 
acceptable. The multipathway screening analysis indicates that 
emissions of lead do not result in concentrations that exceed the NAAQS 
value.
    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 are acceptable 
because the cancer risks do not exceed the presumptive limit of 
acceptability and the noncancer results indicate there is minimal 
likelihood of adverse noncancer health effects due to HAP emissions 
from this source category.
2. Ample Margin of Safety Analysis
    We next considered whether the existing MACT standards provide an 
ample margin of safety to protect public health. In addition to 
considering all of the health risks and other health information 
considered in the risk acceptability determination, in the ample margin 
of safety analysis we evaluated the cost and feasibility of available 
control technologies and other measures (including the controls, 
measures, and costs reviewed under the technology review) that could be 
applied to the source category to further reduce the risks due to 
emissions of HAP. For purposes of the ample margin of safety analysis, 
we evaluated the changes in risk that would occur through adoption of a 
specific technology by looking at the changes to the risk due to both 
actual and allowable emissions.
    As noted in our discussion of the technology review in section IV.D 
of this preamble, we identified several developments in practices, 
processes, or control technologies for reducing HAP emissions from 
emission sources in the Ethylene Production source category. As part of 
the risk review, we evaluated these developments to determine if any of 
them could reduce risks and whether it is necessary to require any of 
these developments to provide an ample margin of safety to protect 
public health.
    We evaluated the health information and control options for all of 
the emission sources located at ethylene production facilities, 
including: storage vessels, heat exchange systems, ethylene process 
vents, transfer racks, equipment leaks, waste operations, ethylene 
cracking furnaces, flares, decoking operations of ethylene cracking 
furnaces, and PRDs. For each of these sources, we considered chronic 
cancer and noncancer risk metrics as well as acute risk. Regarding 
chronic noncancer risk, we note that no facility in the source category 
has a baseline TOSHI exceeding 1. Therefore, we did not quantitatively 
evaluate reductions in the chronic noncancer TOSHI for any emission 
source in the ample margin of safety analysis. Regarding our assessment 
of potential acute effects, we note that baseline emissions are 
unlikely to result in acute health effects because no facility is 
estimated to have an HQ >1 based on the REL, AEGL-1 or ERPG-1. 
Accordingly, the following paragraphs focus on cancer risk in the 
determination of whether the standards provide an ample margin of 
safety to protect public health.
    For storage vessels, as discussed in section IV.D of this preamble, 
we identified three options that represent developments in practices, 
processes or control technologies as part of our technology review 
under CAA section 112(d)(6). We determined that only one of the 
options, which we call option 1, is cost effective. We evaluated those 
same control options to determine whether any of them are needed to 
provide an ample margin of safety as part of our CAA section 112(f)(2) 
risk analysis. Option 1 would affect only about 4 percent of the 
storage vessel population in the Ethylene Production source category 
(i.e., 12 storage vessels at six ethylene production facilities would 
require additional controls resulting in approximately 34.6 tpy 
reduction in HAP). Given that only one storage vessel at the facility 
that is the cancer risk driver would be impacted and that all storage 
vessels at that facility only contribute to an estimated cancer risk of 
5-in-1 million (for both actual emissions and allowable emissions), we 
estimate that option 1 would not change the cancer risk to the 
individual most exposed (rounded to one significant figure). 
Furthermore, given that all storage vessels account for only about 6 
percent of the overall cancer incidence in the source category based on 
actual emissions (and 3 percent based on allowable emissions) and that 
option 1 will only impact a very small percentage of all storage 
vessels in the source category, we estimate option 1 would not change 
the cancer incidence and would have no discernible impact on the number 
of people with an estimated cancer risk greater than 1-in-1 million. 
For the same reasons mentioned above, we expect any reduction in cancer 
incidence and MIR that would result from options 2 or 3, and reduction 
in the number of people with a cancer risk greater than 1-in-1 million 
from implementation of options 2 or 3, would be minimal. Therefore, we 
are proposing that additional controls for storage vessels are not 
necessary to provide an ample margin of safety.
    For heat exchange systems, as discussed in section IV.D of this 
preamble, we identified one control option that represents a 
development in practices, processes or control technologies as part of 
our technology review under CAA section 112(d)(6). We determined the 
control option is cost effective and would reduce HAP emissions by 25 
tpy. We evaluated whether the control option would be needed to provide 
an ample margin of safety as part of our CAA section 112(f)(2) risk 
analysis. Given that heat exchange systems have a small contribution to 
cancer risk to the individual most exposed (i.e., <1-in-1 million based 
on actual emissions and 6-in-1 million based on allowable emissions), 
we estimate that the control option would not change the cancer risk to 
the individual most exposed (rounded to one significant figure). In 
assessing the impacts of the control option on cancer incidence, given 
that heat exchange systems contribute only 3 percent to the overall 
cancer incidence based on actual emissions, and given that actual HAP 
emissions would be reduced by about 30 percent, we estimate that this 
reduction would not have a discernible impact on the cancer incidence 
or the number of people with an estimated cancer risk greater than 1-
in-1 million. With respect to estimating the impacts of the control 
option on cancer incidence based on allowable emissions, heat exchange 
systems drive about half of the overall cancer

[[Page 54313]]

incidence, and we estimate that allowable emissions would be reduced by 
the control option evaluated, bringing the allowable cancer incidence 
down to a level approximately equal to that of the actual cancer 
incidence (within one significant figure). Thus, in considering all the 
health risks associated with emissions from heat exchange systems and 
the minimal risk impact of the control option based on actual 
emissions, we are proposing that additional controls for this emission 
source is not necessary to provide an ample margin of safety.
    For ethylene process vents, we did not identify any additional 
control options. Therefore, we are proposing that additional controls 
for this emission source are not necessary to provide an ample margin 
of safety.
    For transfer racks, we identified and evaluated one control option 
discussed in the technology review section of this preamble (section 
IV.D). We estimated that there would be no emission reductions 
associated with this change, and hence, no reduction in risk. Thus, we 
propose that this control option for transfer racks is not necessary to 
provide an ample margin of safety.
    For equipment leaks and waste operations, we identified various 
control options discussed in the technology review section of this 
preamble (section IV.D). While we estimate that these control options 
would reduce emissions and that most options would reduce overall 
cancer risk, the control options evaluated for equipment leaks and 
waste operations are not cost effective. Thus, considering all of the 
health risks and other health information considered in the risk 
acceptability determination, and considering that no cost-effective 
options were identified for equipment leaks and waste operations, we 
propose that additional controls for these emissions sources are not 
necessary to provide an ample margin of safety.
    For ethylene cracking furnaces, as previously explained, we 
requested under our CAA section 114 authority that ethylene production 
facilities stack test this emissions source. The results of these stack 
tests were then used to assess risk for the source category. We believe 
that there is already an inherent level of HAP emissions control 
realized for emissions generated from ethylene cracking furnaces given 
the operational characteristics needed for the steam cracking reaction 
to occur to produce ethylene and/or propylene. In particular, HAP 
emissions, which are generated because of fuel combustion activities in 
the ethylene cracking furnace firebox, are controlled as a result of 
the high temperatures (i.e., in excess of 2,000 degrees Fahrenheit) 
needed in the furnace firebox in order to provide process heat to the 
steam cracking reaction. Thus, ethylene cracking furnaces effectively 
function like a combustion APCD as a general result of the operating 
parameters needed for the reaction kinetics driving the commercial 
production of ethylene and/or propylene. Also, the fuels predominately 
used in the ethylene cracking furnaces (e.g., natural gas, refinery 
fuel gas, and/or tail gas from the production process (tail gas from an 
ethylene production process primarily contains hydrogen, methane, 
acetylene, and/or other olefins) contain little to no HAP. In addition, 
emissions from this source are generally released at an elevated height 
with high flow and high temperature, leading to better dispersion such 
that impacts on nearby communities are minimized. In assessing the 
baseline risk impacts from ethylene cracking furnaces, we note that 
while ethylene cracking furnaces are the largest source of emissions in 
the source category, these sources have a very small contribution to 
cancer risk to the individual most exposed (i.e., <1-in-1 million) and 
contribute to about 20 percent of the overall cancer incidence based on 
actual emissions and to about 10 percent based on allowable emissions. 
Thus, in considering all of the health risks associated with emissions 
from ethylene cracking furnaces and the minimal risk impact of this 
emissions source, we are proposing that additional controls for this 
emission source are not necessary to provide an ample margin of safety.
    For flares, which are control devices that control emissions from 
multiple emission source types within the Ethylene Production source 
category, under CAA sections 112(d)(2) and (3), we are proposing 
operating and monitoring requirements to ensure flares achieve the 98-
percent HAP destruction efficiency identified as the MACT floor in the 
initial MACT rulemaking in 2002. Flares are critical safety devices 
that effectively reduce emissions during startup, shutdown, and process 
upsets or malfunctions, and in many cases, flares are the only means by 
which emissions from PRDs can be controlled. Thus, we find that 
properly functioning flares act to reduce HAP emissions, and thereby 
risk, from this source category. The changes to the flare requirements 
that we are proposing under CAA sections 112(d)(2) and (3) will result 
in sources meeting the level required by the original standards. We did 
not identify any control options that would further reduce the HAP 
emissions from flares. Therefore, we are proposing that additional 
controls for flares are not necessary to provide an ample margin of 
safety.
    In summary, we propose that the existing EMACT standards provide an 
ample margin of safety to protect public health. We are also 
specifically requesting comment on whether there are additional control 
measures for emission sources subject to the EMACT standards that are 
necessary to provide an ample margin of safety to protect public 
health.
    Further, we note that the decoking of ethylene cracking furnace 
radiant tubes and PRD releases are emission sources with respect to 
risk from ethylene production facilities. As described in section IV.A 
of this preamble, we are proposing requirements for the decoking of the 
ethylene cracking furnace radiant tube(s) and PRD releases. As part of 
our risk assessment for this source category, we also considered the 
risk reductions that would result from implementation of those 
standards. Because we anticipate some small level of unquantifiable 
emission reductions from decoking operations and PRD releases, these 
reductions would likely have no discernable impact on the cancer risk 
to the individual most exposed or cancer incidence. While our decisions 
on risk acceptability and ample margin of safety are supported even in 
the absence of these reductions, if we finalize the proposed 
requirements for decoking operations and PRD releases, these proposed 
requirements would further strengthen our conclusions that the 
standards provide an ample margin of safety to protect public health.
    Lastly, regarding the facility-wide risks due to ethylene oxide 
(described above), which are due to emission sources that are not part 
of the Ethylene 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 (NATA is the 
Agency's nationwide air toxics screening tool, designed to help the EPA 
and state, local, and tribal air agencies identify areas, pollutants, 
or types of sources for further examination). 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).

[[Page 54314]]

These elevated risks are largely driven by an EPA risk value that was 
updated in late 2016. 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 and, as appropriate, 
revising 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) 
conducting site-specific risk assessments and, as necessary, 
implementing emission control strategies for targeted high-risk 
facilities. 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 Effects
    Based on the results of our environmental risk screening 
assessment, we are proposing that HAP emissions from the Ethylene 
Production source category do not present an adverse environmental 
effect. Thus, we are proposing that it is not necessary to set a more 
stringent standard to prevent, taking into consideration costs, safety, 
and other relevant factors, an adverse environmental effect.

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

    The ethylene production source category is composed of the 
following emission sources: Storage vessels, ethylene process vents, 
transfer racks, equipment leaks, waste streams, heat exchange systems, 
and ethylene cracking furnaces and associated decoking operations. To 
inform our technology reviews for these emissions sources, we reviewed 
the EPA's Reasonably Available Control Technology/Best Available 
Control Technology/Lowest Achievable Emission Rate (RACT/BACT/LAER) 
clearinghouse, subsequent regulatory development efforts, and facility 
responses to our CAA section 114 request. We then used information 
provided by facilities that responded to our CAA section 114 request to 
evaluate the impacts of requiring additional controls identified in the 
technology review for the Ethylene Production source category. For 
details about the information we requested under our CAA section 114 
request from ethylene production facilities, see section II.C of this 
preamble. After reviewing information from the aforementioned sources, 
we have identified certain cost-effective developments in practices, 
processes, or control technologies to reduce emissions from some of the 
sources of HAP emissions regulated by the EMACT standards. Therefore, 
we are proposing revisions to the EMACT standards for storage vessels 
and heat exchange systems pursuant to CAA section 112(d)(6).
1. Storage Vessels
    Storage vessels are used for storing liquid and gaseous feedstocks 
used in the ethylene production process, as well as to store liquid and 
gaseous products from the ethylene production process. Types of storage 
vessels used in the ethylene production process include atmospheric and 
high pressure storage vessels. Most storage vessels, which are used for 
storing process liquids and feedstocks, are designed for operation at 
atmospheric or near atmospheric pressures. High pressure vessels are 
used to store compressed gases and liquefied gases. Atmospheric storage 
vessels are typically cylindrical with a vertical orientation, and are 
constructed with either a fixed roof or a floating roof. Some, 
generally small, atmospheric storage vessels are oriented horizontally. 
High pressure vessels are either spherical or horizontal cylinders.
    Under Table 7 to 40 CFR 63.1103(e)(3), the owner or operator of a 
storage vessel must reduce the organic HAP emissions by 98 weight-
percent for storage vessels with a maximum true vapor pressure (MTVP) 
of total organic HAP of 76.6 kilopascals (kPa) or greater using a 
closed vent system routed to a flare, non-flare APCD, or fuel gas 
system or process meeting applicable requirements of 40 CFR part 63, 
subpart SS. Owners or operators of storage vessels with an MTVP of 
total organic HAP of 3.4 kPa or greater but less than 76.6 kPa and a 
capacity of 95 cubic meters (m\3\) or greater can elect to comply with 
this same control requirement or install either an internal floating 
roof (IFR) with proper seals or an external floating roof (EFR) with 
proper seals, and install enhanced fitting controls meeting applicable 
requirements of 40 CFR part 63, subpart WW. Owners or operators of 
smaller storage vessels (i.e., those with an MTVP of total organic HAP 
of 3.4 kPa or greater but less than 76.6 kPa and a capacity of 4 m\3\ 
or greater but less than 95 m\3\) must, at a minimum, fill the storage 
vessel through a submerged pipe.\30\
---------------------------------------------------------------------------

    \30\ These smaller storage vessels can also elect to comply with 
the more stringent control requirements of reducing organic HAP 
emissions by 98 weight-percent by routing emissions to closed vent 
system and APCD (or fuel gas system) meeting 40 CFR part 63, subpart 
SS or control emissions by using an EFR or IFR storage vessel that 
meets the requirements of 40 CFR part 63, subpart WW.
---------------------------------------------------------------------------

    As part of our technology review for storage vessels, we identified 
the following emission reduction options: (1) Revising the capacity and 
MTVP thresholds of the EMACT standards to require storage vessels as 
small as 59 m\3\ storing organic liquid with an MTVP of total organic 
HAP of 0.69 kPa or greater but less than 76.6 kPa to reduce organic HAP 
emissions by 98 weight-percent by routing emissions to closed vent 
system and APCD (or fuel gas system) meeting 40 CFR part 63, subpart 
SS, or controlling emissions through use of an EFR or IFR storage 
vessel according to the requirements of 40 CFR part 63, subpart WW. For 
storage vessels as small as 4 m\3\ but less than 59 m\3\ with an MTVP 
of total organic HAP of 0.69 kPa or greater but less than 76.6 kPa, 
they must either meet these same control requirements or fill the 
vessel through use of a submerged pipe; (2) in addition to requirements 
specified in option 1, requiring LDAR for fittings on fixed roof 
storage vessels (e.g., access hatches) using EPA Method 21, and the use 
of liquid level overfill warning monitors and roof landing warning 
monitors on storage vessels with an IFR or EFR; and (3) in addition to 
requirements specified in option 1, the conversion of EFRs to IFRs 
through use of geodesic domes.
    We identified option 1 as a development in practices, processes, 
and control technologies because it reflects requirements for similar 
storage vessels that are located at chemical manufacturing facilities 
subject to the new source Miscellaneous Organic Chemical Manufacturing 
NESHAP (MON). We believe that option 1 is technologically feasible for 
storage vessels used at ethylene production facilities. Option 2 is an 
improvement in practices because these monitoring methods have been 
required by other regulatory agencies since promulgation of the EMACT 
and are being used by some of the sources covered by the Ethylene 
Production source category. Finally, we consider option 3 to be a 
development in control technology because we found that some storage 
vessels with EFR have installed geodesic domes since promulgation of 
the 2002 EMACT standards. A VOC recovery credit for product not lost to 
the atmosphere from storage vessels was also considered for all three 
of the options presented.\31\
---------------------------------------------------------------------------

    \31\ A VOC recovery credit for storage vessels of $380 per ton 
(approximately $1.20/gallon) was used and is based on an August 2016 
market price for naphtha. For more details, see the technical 
memorandum titled Clean Air Act Section 112(d)(6) Technology Review 
for Storage Vessels Located in the Ethylene Production Source 
Category, which is available in Docket ID No. EPA-HQ-OAR-2017-0357.

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

[[Page 54315]]

    Under option 1, we considered the impacts of tightening the 
capacity and MTVP thresholds of the EMACT standards to reflect the 
capacity and MTVP threshold of the new source MON standards. This would 
require tightening both the threshold for MTVP of total organic HAP 
(i.e., decreasing it from 3.4 kPa or greater to 0.69 kPa or greater) 
and the threshold for storage vessel capacity (i.e., decreasing it from 
95 m\3\ to 38 m\3\) specified in Table 7 at 40 CFR 63.1103(e)(3)(a)(1) 
and 40 CFR 63.1103(e)(3)(b)(1), respectively. However, upon further 
evaluation of our CAA section 114 Ethylene Production source category 
information specific to storage vessels, the smallest storage vessel 
that would be required to add additional controls is an infrequently 
used fixed roof storage vessel with a capacity of 58 m\3\. Based on the 
response from the CAA section 114 request, this storage vessel reported 
using a form of submerged fill to minimize emissions but did not 
operate in 2013. We determined that it would not be cost effective for 
this particular storage vessel to add additional controls due to its 
infrequent use. Thus, in lieu of evaluating impacts for option 1 at the 
new source MON capacity threshold of 38 m\3\, a threshold of 59 m\3\ 
was chosen so that this storage vessel could continue to use submerged 
fill as a method of control. After reviewing the CAA section 114 
request data, we identified only seven storage vessels that would be 
impacted by option 1. All of these storage vessels have capacities 
greater than or equal to 59 m\3\ and store material with an MTVP of 
total organic HAP of 0.69 kPa or greater but less than 76.6 kPa. 
Therefore, these storage vessels would need to either install an IFR or 
EFR with proper seals and install enhanced fitting controls as required 
in 40 CFR part 63, subpart WW. In the alternative, they would need to 
reduce emissions of total organic HAP by 98 weight-percent by venting 
emissions through a closed vent system to any combination of APCDs that 
meet the requirements of 40 CFR 63.982(a)(1).
    For option 2, we evaluated the impacts of requiring leak detection 
monitoring of fittings (e.g., access hatches) on fixed roof storage 
vessels using EPA Method 21 (annually) and to repair a leak if it is 
detected. A leak would be defined as an instrument reading greater than 
500 ppmv using EPA Method 21. We also evaluated the impacts of enhanced 
monitoring of the liquid level in the storage vessel (i.e., requiring 
liquid level overfill warning monitors and roof landing warning 
monitors on EFRs and IFRs). Levels below a low set point would provide 
warning of a potential floating roof landing, and levels above a high 
set point would provide warning of potential overfill. Based on the CAA 
section 114 request data, we identified 78 storage vessels that would 
be subject to option 2, of which 14 have fixed roofs (although, in this 
analysis, seven of these are considered to have been converted to IFR 
due to option 1, and six of the other seven fixed roof storage vessels 
route emissions to a process or to a closed vent system and APCD) and 
the remaining 64 have either an IFR or EFR. In addition, two of the 
storage vessels with an IFR and one of the storage vessels with an EFR 
route emissions to a closed vent system and APCD. In order to determine 
costs for option 2, we added costs for enhanced monitoring requirements 
to costs determined for option 1.
    Under option 3, we considered the impacts of converting storage 
vessels with EFRs to IFRs through the use of geodesic domes. We assumed 
for this option that only those storage vessels with EFRs with a 
capacity greater than or equal to 59 m\3\ and that contain liquid with 
an MTVP of total organic HAP of 0.69 kPa or greater but less than 76.6 
kPa would be required to retrofit their storage vessel with a geodesic 
dome. After reviewing the CAA section 114 request data, we identified 
32 storage vessels with EFRs that would be subject to option 3. 
Therefore, we estimated costs and emissions reductions for 32 EFRs. The 
costs were added to the costs determined for option 1 to determine the 
cost of option 3.
    Table 5 of this preamble presents the nationwide impacts for the 
three options considered. See the technical memorandum titled Clean Air 
Act Section 112(d)(6) Technology Review for Storage Vessels Located in 
the Ethylene Production Source Category, which is available in Docket 
ID No. EPA-HQ-OAR-2017-0357 for details on the assumptions and 
methodologies used in this analysis, including the calculations we used 
to account for additional ethylene production facilities that did not 
receive a CAA section 114 request, additional facilities that would be 
subject to the proposed control options and storage vessels from new 
ethylene production facilities that are either under construction or 
that started operation in 2017, and major expansions of currently 
operating facilities. The calculation of the incremental cost 
effectiveness allows us to assess the impacts of the incremental change 
between option 1 and the other options.
    We determined that option 1 is cost effective and we are proposing 
to revise the EMACT standards to reflect the more stringent storage 
vessel capacity and MTVP thresholds of option 1 pursuant to CAA section 
112(d)(6). Considering the emissions reductions and high incremental 
cost effectiveness, we determined that storage vessel options 2 and 3 
are not cost effective and are not proposing to revise the EMACT 
standards to reflect the requirements of these options pursuant to CAA 
section 112(d)(6).

                             Table 5--Nationwide Emissions Reduction and Cost Impacts of Control Options Considered for Storage Vessels at Ethylene Production Units
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                                                                        HAP
                                                                                       Total                                         HAP cost          Total         HAP cost       incremental
                                                                   Total capital    annualized     VOC emission    HAP emission    effectiveness    annualized     effectiveness       cost
                         Control option                           investment ($)   costs w/o VOC    reductions      reductions    w/o credits ($/ costs with VOC   with credits    effectiveness
                                                                                   credit ($/yr)       (tpy)           (tpy)           ton)        credit ($/yr)      ($/ton)      with credits
                                                                                                                                                                                      ($/ton)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1...............................................................         820,000         152,000             309            34.6           4,400          34,000           1,000  ..............
2...............................................................       1,453,000         373,800             328            40.7           9,190         248,700           6,120          35,400
3...............................................................      19,909,000       2,723,000             383            58.3          46,700       2,547,000          44,100         107,100
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------


[[Page 54316]]

2. Ethylene Process Vents
    Ethylene production units generate gaseous streams containing HAP. 
These streams may be routed to other unit operations for additional 
processing (e.g., a gas stream from a reactor that is routed to a 
distillation unit for separation), may be sent to one or more recovery 
devices, a process vent header collection system (e.g., blowdown 
system) and APCD, and/or may be vented to the atmosphere. Ethylene 
process vents are gas streams with a flow rate greater than 0.005 
standard m\3\ per minute containing greater than 20 ppmv HAP that are 
continuously discharged during operation of an ethylene production 
unit.
    Under Table 7 to 40 CFR 63.1103(e)(3), the owner or operator must 
reduce organic HAP emissions from ethylene process vents by 98 weight-
percent or reduce organic HAP or total organic compounds to a 
concentration of 20 ppmv, whichever is less stringent, by venting 
emissions through a closed vent system to any combination of APCDs 
(e.g., a flare, thermal oxidizer, boiler, process heater, absorber, 
condenser, or carbon adsorber) that meet applicable requirements of 40 
CFR part 63, subpart SS.
    In the technology review for process vents, we did not identify any 
practices, processes, or control technologies beyond those already 
required by the EMACT standards for process vents. Therefore, we are 
proposing that it is not necessary to revise EMACT standards for 
ethylene process vents pursuant to CAA section 112(d)(6). For further 
details on the assumptions and methodologies used in this analysis, see 
the technical memorandum titled Clean Air Act Section 112(d)(6) 
Technology Review for Ethylene Process Vents Located in the Ethylene 
Production Source Category, which is available in Docket ID No. EPA-HQ-
OAR-2017-0357.
3. Transfer Racks
    Transfer racks at ethylene production units are equipment that are 
used to transfer materials (primarily liquid products) from the 
facility into either tank trucks or railcars. Emissions from transfer 
racks may be released when material loaded into tank trucks or railcars 
displaces vapors inside these transport vehicles.
    The EMACT standards at Table 7 to 40 CFR 63.1103(e)(3) allow 
multiple options to control emissions from applicable transfer racks. 
These options include the use of APCDs or collecting emissions for use 
in the production process, a fuel gas system, or a vapor balance 
system. To be subject to these requirements, the owner or operator must 
load materials that have a true vapor pressure of total organic HAP of 
3.4 kPa or greater and must load 76 m\3\ of HAP-containing material or 
greater per day (averaged over any consecutive 30-day period).
    In our technology review for transfer racks, we identified one 
emission reduction option which would require changing the transfer 
rack applicability threshold (for volumetric throughput of liquid 
loaded) from 76 m\3\ per day to 1.8 m\3\ per day to reflect the more 
stringent applicability threshold of other chemical sector standards 
that regulate emissions from transfer rack operations (i.e., 40 CFR 
part 63, subparts F and G and 40 CFR part 63, subpart FFFF).
    Upon review of the CAA section 114 request data, we identified only 
one transfer rack that would be subject to this revision. This transfer 
rack loads red oil material (containing benzene, ethyl benzene, 
toluene, and xylene) with a true vapor pressure of total organic HAP of 
3.4 kPa or greater at a maximum 30-day average throughput of about 48 
m\3\ per day into tank trucks. We also found that emissions from this 
transfer rack are routed to a flare, and we, therefore, expect that the 
owner or operator of this transfer rack is already complying with the 
requirement to reduce emissions of organic HAP by 98 weight-percent as 
specified in Table 7 to 40 CFR 63.1103(e)(3). As such, we determined 
that none of the 21 facilities that responded to the CAA section 114 
request would be impacted by changing the transfer rack applicability 
threshold (for volumetric throughput of liquid loaded) from 76 m\3\ per 
day to 1.8 m\3\ per day. We also estimated that there would be no 
emission reductions associated with this change. While this change 
would not have direct implementation costs, it would still impose a 
certain burden on facilities because they would need to read the rule, 
determine applicability, and meet additional recordkeeping and 
reporting requirements. Because there are no emissions reductions, and 
there would be a certain burden to industry, we do not consider this to 
be a cost-effective option. Therefore, we are proposing that it is not 
necessary to revise the EMACT standards for transfer racks pursuant to 
CAA section 112(d)(6). For further details on the assumptions and 
methodologies used in this analysis, see the technical memorandum 
titled Clean Air Act Section 112(d)(6) Technology Review for Transfer 
Racks Located in the Ethylene Production Source Category, which is 
available in Docket ID No. EPA-HQ-OAR-2017-0357.
4. Equipment Leaks
    Emissions from equipment leaks occur in the form of gases or 
liquids that escape to the atmosphere through many types of connection 
points (e.g., threaded fittings) or through the moving parts of valves, 
pumps, compressors, PRDs, and certain types of process equipment.
    The requirements of 40 CFR part 63, subpart UU (National Emission 
Standards for Equipment Leaks--Control Level 2 Standards), represent 
the MACT floor for equipment leaks at both new and existing ethylene 
production units. 40 CFR part 63, subpart UU, specifies LDAR 
requirements for applicable equipment. The applicable equipment 
includes: pumps, compressors, agitators, PRDs, sampling collection 
systems, open-ended valves or lines, valves, connectors, and 
instrumentation systems that contain or contact material that is 5 
percent by weight or more of organic HAP, operate 300 hr/yr or more, 
and are not in vacuum service. The LDAR requirements vary by equipment 
(component) type but include EPA Method 21 monitoring at certain 
frequencies (e.g., monthly, quarterly, every two quarters, annually) 
and leak definitions (e.g., 500 ppm, 1,000 ppm, 10,000 ppm) if the 
component is in either gas and vapor service or in light liquid 
service. The LDAR requirements for components in heavy liquid service 
include sensory monitoring, and the use of EPA Method 21 monitoring if 
a leak is identified.
    Our technology review for equipment leaks identified two 
developments in LDAR practices and processes: (1) Lowering the leak 
definition for valves in gas and vapor service or in light liquid 
service from 500 ppm to 100 ppm and (2) lowering the leak definition 
for pumps in light liquid service from 1,000 ppm to 500 ppm. The leak 
definition for option 1 was identified in the petroleum refinery sector 
technology review and, based on a recent air permit application, a new 
ethylene production facility will comply with this leak definition. The 
leak definition for option 2 was reported by seven ethylene production 
facilities in the CAA section 114 responses, and this leak definition 
is also applicable to certain facilities in Texas. We, therefore, 
considered both options as developments in technology given that they 
are either required by other regulatory agencies or are in use by some 
sources covered by the Ethylene Production source category.
    Table 6 of this preamble presents the nationwide impacts for the 
two options considered. A VOC recovery credit for

[[Page 54317]]

product not lost to the atmosphere from equipment leaks was also 
considered for both options presented.\32\ See the technical memorandum 
titled Clean Air Act Section 112(d)(6) Technology Review for Equipment 
Leaks in the Ethylene Production Source Category, which is available in 
Docket ID No. EPA-HQ-OAR-2017-0357 for details on the assumptions and 
methodologies used in this analysis, including the calculations we used 
to account for additional ethylene production facilities that did not 
receive a CAA section 114 request, new ethylene production facilities 
that are either under construction or that started operation in 2017, 
and major expansions of currently operating facilities.
---------------------------------------------------------------------------

    \32\ A VOC recovery credit of $776 per ton was used and is based 
on a November 2016 market price for ethylene.
---------------------------------------------------------------------------

    Based on the costs and emission reductions for each of the options, 
we consider none of these identified options as cost effective for 
reducing emissions from equipment leaks at ethylene production units. 
We are proposing that it is not necessary to revise the EMACT standards 
for equipment leaks pursuant to CAA section 112(d)(6).

                             Table 6--Nationwide Emissions Reduction and Cost Impacts of Control Options Considered for Equipment Leaks at Ethylene Production Units
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       Total           Total                                         VOC cost        VOC cost        HAP cost        HAP cost
                                                   Total capital    annualized      annualized     VOC emission    HAP emission    effectiveness   effectiveness   effectiveness   effectiveness
                 Control option                   investment ($)     costs w/o      costs with      reductions      reductions    w/o credits ($/  with credits   w/o credits ($/  with credits
                                                                  credits ($/yr)  credits ($/yr)       (tpy)           (tpy)           ton)           ($/ton)          ton)           ($/ton)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1...............................................       1,628,500         713,600         575,500             178            19.6           4,000           3,200          36,500          29,400
2...............................................         143,300          67,800          65,000             3.5            0.38          19,500          18,700         177,200         170,200
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

5. Waste Streams
    Examples of waste streams at ethylene production units include 
process wastewater, product tank drawdown, sludge and slop oil removed 
from waste management units, and landfill leachate. Owners and 
operators of waste streams use wastewater collection systems (including 
drains, manholes, trenches, lift stations, sumps, and/or junction 
boxes) to combine waste streams prior to treatment. Wastewater 
treatment systems are divided into three categories: Primary treatment 
operations, which include oil-water separators and equalization basins; 
secondary treatment systems, such as biological treatment units or 
steam strippers; and tertiary treatment systems, which further treat or 
filter wastewater prior to discharge to a receiving body of water or 
reuse in a process. Emissions from these systems occur by 
volatilization of organic compounds at any water/air interface.
    The EMACT standards apply to waste streams that contain benzene and 
continuous butadiene waste streams and are dependent on a facility's 
total annual benzene (TAB) quantity. For a TAB quantity of 10 megagrams 
per year (Mg/yr) or greater, owners or operators of all waste streams 
that have flow rates of at least 0.02 liters per minute (lpm), 
wastewater quantities of at least 10 Mg/yr, and benzene concentrations 
of at least 10 parts per million by weight (ppmw), must either manage 
and treat these waste streams according to any of the options in the 
Benzene Waste Operations NESHAP (BWON), or transfer the waste off-site. 
For a TAB quantity of less than 10 Mg/yr, owners or operators of waste 
streams that contain benzene and are either spent caustic waste streams 
or dilution steam blowdown waste streams that have flow rates of at 
least 0.02 lpm and wastewater quantities of at least 10 Mg/yr, must 
manage and treat the waste streams according to the BWON, but are not 
allowed to use any of the 1, 2, or 6 Mg/yr compliance options.\33\ For 
any facility TAB quantity, owners and operators of all waste streams 
that have flow rates of at least 0.02 lpm and 1-3-butadiene 
concentrations of at least 10 ppmw, must also manage and treat these 
waste streams according to the BWON (but the treatment and control 
efficiencies required for benzene in BWON for these waste streams are 
instead required for 1-3 butadiene, and owners and operators are also 
not allowed to use any of the 1, 2, or 6 Mg/yr compliance options).
---------------------------------------------------------------------------

    \33\ The BWON requires removal of benzene from the waste stream 
to 10 ppmw or by 99 weight-percent. For each closed vent system and 
APCD used to comply with the BWON, a benzene reduction of 98 weight-
percent must be achieved. However, the BWON also includes three 
compliance options that allow a facility to choose which streams to 
manage and treat if certain conditions are met: either the TAB 
quantity for the untreated waste streams cannot exceed 2 Mg/yr, the 
facility TAB quantity for treated and untreated process wastewater 
streams is less than 1 Mg/yr, or the facility TAB quantity for all 
waste streams with at least 10-percent water content is less than 6 
Mg/yr. These options are referred to as the 1, 2, and 6 Mg/yr 
compliance options. The waste or wastewater streams that can be 
exempted from management and treatment vary with the different 
compliance options. Details of these compliance options are 
specified in 40 CFR 61.342(c) through (e) of the BWON.
---------------------------------------------------------------------------

    The emission reduction options we identified in the waste stream 
technology review are: (1) Specific performance parameters for an 
enhanced biological unit (EBU) beyond those required in the BWON; and 
(2) treatment of wastewater streams with a VOC content of 750 ppmv or 
higher by steam stripping prior to any other treatment process for 
facilities with high organic loading rates (i.e., facilities with total 
annualized benzene quantity of 10 Mg/yr or more). Option 1 is intended 
to improve the performance of wastewater treatment systems that use an 
EBU, and thereby achieve additional emission reductions. The BWON, as 
it applies to sources covered under EMACT, has limited operational 
requirements for an EBU. Available data suggest that these systems are 
generally effective for degrading benzene and other organic HAP; 
however, without specific performance or operational requirements, the 
effectiveness of the EBU to reduce emissions can be highly variable. 
Under option 1, more stringent operating requirements are considered 
for the EBU at ethylene production units. Option 2 considers segregated 
treatment of wastewater streams with a volatile organic content of 
greater than 750 ppmw, or high-strength wastewater streams, directly in 
a steam stripper (i.e., not allowing these streams to be mixed and 
treated in the EBU).
    Table 7 of this preamble presents the nationwide impacts for the 
two options considered. See the technical memorandum titled Clean Air 
Act Section 112(d)(6) Technology Review for Waste Streams Located in 
the Ethylene Production Source Category, in Docket ID No. EPA-HQ-OAR-
2017-0357 for details on the assumptions and methodologies used in this 
analysis, including the calculations we used to account for additional 
ethylene production facilities that did not receive a CAA section 114 
request, additional

[[Page 54318]]

impacted facilities from new ethylene production facilities under 
construction or that started operation in 2017, and major expansions of 
currently operating facilities. The costs and emissions impacts 
presented in Table 7 of this preamble are not incremental between 
options, but rather incremental from the baseline of compliance with 
the BWON.
    Based on the costs and emission reductions for each of the options, 
we consider none of the options identified to be cost effective for 
reducing emissions from waste streams at ethylene production units. We 
are proposing that it is not necessary to revise the EMACT standards 
for waste streams pursuant to CAA section 112(d)(6).

         Table 7--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for Waste Streams at Ethylene Production Units
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                               Total       VOC emission    HAP emission      VOC cost        HAP cost
                     Control option                        Total capital    annualized      reductions      reductions     effectiveness   effectiveness
                                                          investment ($)   costs ($/yr)        (tpy)           (tpy)          ($/ton)         ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.......................................................     224,050,000      24,727,000           1,986             529          12,450          46,700
2.......................................................      34,987,000      11,579,000           2,253             600           5,140          19,300
--------------------------------------------------------------------------------------------------------------------------------------------------------

6. Heat Exchange Systems
    Heat exchangers are devices or collections of devices used to 
transfer heat from process fluids to another process fluid (typically 
water) without intentional direct contact of the process fluid with the 
cooling fluid (i.e., non-contact heat exchanger). The term ``heat 
exchange system'' is used in this preamble to refer collectively to 
water-cooled heat exchangers and the associated cooling water handling 
system. There are two types of heat exchange systems: Closed-loop 
recirculation systems and once-through systems. Closed-loop 
recirculation systems use a cooling tower to cool the heated water 
leaving the heat exchanger and then return the newly cooled water to 
the heat exchanger for reuse. Once-through systems typically use river 
water as the influent cooling fluid to the heat exchangers, and the 
heated water leaving the heat exchangers is then discharged from the 
facility. At times, the internal tubing material of a heat exchanger 
can corrode or crack, allowing some process fluids to mix or become 
entrained with the cooling water. Pollutants in the process fluids may 
subsequently be released from the cooling water into the atmosphere 
when the water is exposed to air (e.g., in a cooling tower for closed-
loop systems or trenches/ponds in a once-through system).
    The EMACT standards include an LDAR program for owners or operators 
of certain heat exchange systems. The LDAR program specifies that heat 
exchange systems be monitored for leaks of process fluids into cooling 
water and that owners or operators take actions to repair detected 
leaks within 45 days. Owners or operators may delay the repair of leaks 
if they meet the applicable criteria in 40 CFR 63.1088. The current 
EMACT standards for heat exchange systems allow the use of any method 
listed in 40 CFR part 136 for sampling cooling water for leaks for the 
HAP listed in Table 1 to 40 CFR part 63, subpart XX. Other 
representative substances such as total organic carbon or VOC that can 
indicate the presence of a leak can also be used. According to the 
EMACT standards, a leak in the heat exchange system is detected if the 
exit mean concentration of HAP (or other representative substance) in 
the cooling water is at least 10 percent greater than (using a one-
sided statistical procedure at the 0.05 level of significance) the 
entrance mean concentration of HAP (or other representative substance) 
in the cooling water, and the leak is at least 3.06 kg/hr. Individual 
heat exchangers are considered leaking, according to the EMACT 
standards, if the cooling water in the heat exchanger has an exit mean 
concentration (of HAP or of another representative substance) that is 
at least 1 ppmw or 10 percent greater than the entrance mean 
concentration, whichever is greater. Furthermore, the EMACT standards 
allow owners or operators to monitor for leaks using a surrogate 
indicator of leaks (e.g., ion specific electrode monitoring, pH, 
conductivity), provided that certain criteria in 40 CFR 63.1086(c) are 
met. The EMACT standards for monitoring heat exchange systems according 
to 40 CFR 63.1086(a) or for monitoring individual heat exchangers 
according to 40 CFR 63.1086(b) initially require 6 months of monthly 
monitoring for heat exchange systems at existing sources. If no leaks 
are detected, the frequency decreases to quarterly monitoring for heat 
exchange systems at existing sources, until a leak is detected. Once a 
leak is detected, the frequency changes to monthly monitoring until the 
leak is repaired and for the following 6 months, at which point the 
heat exchange system's monitoring frequency can be reduced back to 
quarterly. The EMACT standards initially require 6 months of weekly 
monitoring for heat exchange systems at new sources. If no leaks are 
detected, the frequency decreases to monthly monitoring for heat 
exchange systems at new sources, until a leak is detected. Once a leak 
is detected, the frequency changes to weekly monitoring until the leak 
is repaired and for the following 6 months, at which point the heat 
exchange system's monitoring frequency can revert to monthly 
monitoring. Where surrogate monitoring is used for heat exchange 
systems according to 40 CFR 63.1086(c), heat exchange systems at 
existing sources must follow the same monitoring frequency as 
previously discussed in this section; however, heat exchange systems at 
new sources must always perform weekly monitoring.
    Our technology review identified one development in LDAR practices 
and processes for heat exchange systems. Specifically, the use of the 
Modified El Paso Method \34\ to monitor for leaks. The Modified El Paso 
Method, which is included in the Petroleum Refinery Sector MACT rule 
(i.e., 40 CFR part 63, subpart CC), was identified in our review of the 
RACT/BACT/LAER clearinghouse database. It is also required by the TCEQ 
for facilities (including eight ethylene production facilities) 
complying with their HRVOC rule (i.e., 30 TAC Chapter 115, Subchapter 
H, Division 3). For heat exchange system LDAR programs, the compliance 
monitoring option, leak

[[Page 54319]]

definition, and frequency of monitoring for leaks are all important 
considerations for being able to identify when there is a leak and when 
to take corrective actions to repair the leak. We, therefore, evaluated 
the Modified El Paso Method for use at ethylene production facilities, 
including an assessment of appropriate leak definitions and monitoring 
frequencies.
---------------------------------------------------------------------------

    \34\ The Modified El Paso Method uses a dynamic or flow-through 
system for air stripping a sample of the water and analyzing the 
resultant off-gases for VOC using a common flame ionization detector 
(FID) analyzer. The method is described in detail in Appendix P of 
the TCEQ's Sampling Procedures Manual: The Air Stripping Method 
(Modified El Paso Method) for Determination of Volatile Organic 
Compound (VOC) Emissions from Water Sources. Appendix P is included 
in Docket ID No. EPA-HQ-OAR-2017-0357.
---------------------------------------------------------------------------

    In order to identify an appropriate Modified El Paso Method leak 
definition for ethylene production facilities, we identified two rules, 
TCEQ's HRVOC rule and the Petroleum Refinery Sector MACT rule, that 
incorporate this monitoring method and have leak definitions 
corresponding to use of this methodology. We also reviewed data 
submitted from our CAA section 114 request, where ethylene production 
facilities performed sampling using the Modified El Paso Method. The 
Petroleum Refinery MACT rule and TCEQ's HRVOC rule have leak 
definitions of total strippable hydrocarbon concentration (as methane) 
in the stripping gas ranging from 3.1 ppmv to 6.2 ppmv. In addition, 
sources subject to the Petroleum Refinery Sector MACT rule may not 
delay the repair of leaks for more than 30 days where, during 
subsequent monitoring, a total strippable hydrocarbon concentration (as 
methane) in the stripping gas of 62 ppmv or higher is found. In 
reviewing the CAA section 114 data, a clear delineation in the 
hydrocarbon mass emissions data was noticed at 6.1 ppmv of total 
strippable hydrocarbon (as methane) in the stripping gas. In addition, 
given that both the leak concentration and water recirculation rate of 
the heat exchange system are key variables affecting the hydrocarbon 
mass emissions from heat exchange systems, the overall CAA section 114 
data for all heat exchange systems sampled generally showed lower 
hydrocarbon mass emissions for leaks at or below 6.1 ppmv of total 
strippable hydrocarbon (as methane) in the stripping gas compared to 
leaks found above 6.1 ppmv of total strippable hydrocarbon (as methane) 
in the stripping gas. Taking into account the range of actionable leak 
definitions in use by other rules that require use of the Modified El 
Paso Method currently (i.e., 3.1 ppmv-6.2 ppmv of total strippable 
hydrocarbon (as methane) in the stripping gas), and the magnitude of 
emissions for leaks of total strippable hydrocarbon (as methane) in the 
stripping gas above 6.1 ppmv compared to other leaks identified in the 
CAA section 114 sampling data, we chose to evaluate a leak definition 
at the upper end of identified actionable leak definitions in our 
analysis. Thus, the Modified El Paso Method leak definition we 
evaluated was 6.2 ppmv of total strippable hydrocarbon concentration 
(as methane) in the stripping gas for both new and existing ethylene 
heat exchange systems, along with not allowing delay of repair of leaks 
for more than 30 days where, during subsequent monitoring, a total 
strippable hydrocarbon concentration (as methane) in the stripping gas 
of 62 ppmv or higher is found.
    We determined an appropriate leak monitoring frequency by reviewing 
the current monitoring frequencies that ethylene production facilities 
are subject to, along with frequencies for the Petroleum Refinery 
Sector MACT rule and the TCEQ HRVOC rule. As a first step, we reviewed 
whether it was still reasonable to specify more frequent monitoring for 
a 6-month period after repair of leaks. Our review of the CAA section 
114 data showed that no leaks were identified during the 6-month period 
for any of the ethylene production facilities that reported heat 
exchange system compliance data that had leaks. Thus, we find that re-
monitoring once after repair of a leak, at the monitoring location 
where the leak was identified, is sufficient from a continuous 
compliance perspective to demonstrate a successful repair. The 
monitoring frequencies currently in 40 CFR part 63, subpart XX, for 
where no leaks are found were, thus, considered the base frequencies: 
i.e., quarterly monitoring for existing heat exchange systems and 
monthly monitoring for new heat exchange systems. Once we determined 
the base frequencies, we next considered more stringent monitoring 
frequencies. Both the Petroleum Refinery Sector MACT rule, which 
includes monthly (or quarterly) monitoring for existing sources, and 
the TCEQ HRVOC rule, which includes continuous monitoring provisions 
for existing and new sources, have more stringent monitoring 
frequencies. However, analysis done for the Petroleum Refinery Sector 
MACT rule showed that the incremental HAP cost-effectiveness to change 
from quarterly to monthly monitoring and monthly to continuous 
monitoring was found to be $40,000/ton and $500,000/ton, respectively. 
Given that the assumed leak distributions used in the analysis to 
estimate emissions from heat exchange systems at ethylene production 
facilities are considerably smaller than those used in the Petroleum 
Refinery Sector MACT analysis (by over an order of magnitude), higher 
incremental HAP cost effectiveness are expected for these options at 
ethylene production facilities compared to petroleum refineries, making 
them not cost-effective options. Thus, we chose to evaluate quarterly 
monitoring for heat exchange systems at existing sources and monthly 
monitoring for heat exchange systems at new sources (i.e., the base 
monitoring frequency currently in the rule after the initial 6-months 
of more frequent monitoring is performed).
    Based on this technology review, we identified the following 
control option as a development in practice for heat exchange systems: 
Quarterly monitoring for heat exchange systems at existing sources 
(after an initial 6 months of monthly monitoring) and monthly 
monitoring for heat exchange systems at new sources (after an initial 6 
months of weekly monitoring) with the Modified El Paso Method, and 
using a leak definition of 6.2 ppmv of total strippable hydrocarbon 
concentration (as methane) in the stripping gas.
    We then reviewed the CAA section 114 request data to determine the 
impacts of this control option. We identified 67 heat exchange systems 
at 31 ethylene production facilities that would be impacted by 
requiring the use of the Modified El Paso Method. As part of our 
analysis, we assumed owners or operators conducting monthly monitoring 
or quarterly monitoring for three or more of these heat exchange 
systems would elect to purchase a stripping column and FID analyzer and 
perform in-house Modified El Paso Method monitoring (because the total 
annualized costs for in-house Modified El Paso Method monitoring is 
less than the costs for contracted services for monthly monitoring and 
because of logistics with facilities having three or more heat exchange 
systems performing quarterly monitoring). In addition, because owners 
and operators of 20 of these heat exchange systems (at eight 
facilities) are required by TCEQ's HRVOC rule to conduct continuous 
Modified El Paso Method monitoring, we assumed these owners or 
operators would only incur an annualized repair cost (and no capital 
costs). Further, we assumed repairs could be performed by plugging a 
specific heat exchanger tube and, if a heat exchanger that is leaking 
to the extent that it needs to be replaced, then it is effectively at 
the end of its useful life. Therefore, we determined that the cost of 
replacing a heat exchanger is an operational cost that would be 
incurred by the facility as a result of routine maintenance and 
equipment replacement and it is not attributable to the control option.

[[Page 54320]]

    Table 8 of this preamble presents the nationwide impacts for 
requiring owners or operators to use the Modified El Paso Method and 
repair leaks of total strippable hydrocarbon concentration (as methane) 
in the stripping gas of 6.2 ppmv or greater. A VOC recovery credit for 
product not lost to the atmosphere from leaks in heat exchange systems 
was also considered for the option presented.\35\ See the technical 
memorandum titled Clean Air Act Section 112(d)(6) Technology Review for 
Heat Exchange Systems in the Ethylene Production Source Category, which 
is available in Docket ID No. EPA-HQ-OAR-2017-0357 for details on the 
assumptions and methodologies used in this analysis, including the 
calculations we used to account for additional ethylene production 
facilities that did not receive a CAA section 114 request, new ethylene 
production facilities that are either under construction or that 
started operation in 2017, and major expansions of currently operating 
facilities.
---------------------------------------------------------------------------

    \35\ A VOC recovery credit of $776 per ton was used and is based 
on a November 2016 market price for ethylene.
---------------------------------------------------------------------------

    Based on the costs and emission reductions for the identified 
control option, we are proposing to revise the EMACT standards for heat 
exchange systems pursuant to CAA section 112(d)(6). We are proposing at 
40 CFR 63.1086(e)(4) to retain quarterly monitoring for heat exchange 
systems at existing sources (after an initial 6-months of monthly 
monitoring) and monthly monitoring for heat exchange systems at new 
sources (after an initial 6-months of weekly monitoring) using the 
Modified El Paso Method, and a leak definition of 6.2 ppmv of total 
strippable hydrocarbon concentration (as methane) in the stripping gas. 
We are also proposing at 40 CFR 63.1088(d) a delay of repair action 
level of total strippable hydrocarbon concentration (as methane) in the 
stripping gas of 62 ppmv, that if exceeded during leak monitoring, 
would require immediate repair (i.e., the leak found cannot be put on 
delay of repair and would be required to be repaired within 30 days of 
the monitoring event). This would apply to both monitoring heat 
exchange systems and individual heat exchangers by replacing the use of 
any 40 CFR part 136 water sampling method with the Modified El Paso 
Method and removing the option that allows for use of a surrogate 
indicator of leaks. We are also proposing re-monitoring at the 
monitoring location where a leak is identified to ensure that any leaks 
found are fixed.

   Table 8--Nationwide Emissions Reductions and Cost Impact for Requiring the Modified El Paso Method for Heat Exchange Systems at Ethylene Production
                                                                          Units
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                               Total
                                          Total  capital       Total       VOC emission    HAP emission      HAP cost       annualized       HAP cost
             Control option                  investment     annualized      reductions      reductions     effectiveness    costs with     effectiveness
                                                ($)       costs w/o  VOC       (tpy)           (tpy)        w/o credits   VOC Credit  ($/  with credits
                                                          credit  ($/yr)                                      ($/ton)           yr)           ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.......................................         136,000          26,400             227              25           1,060       (149,600)         (5,980)
--------------------------------------------------------------------------------------------------------------------------------------------------------

E. What other actions are we proposing?

    In addition to the proposed actions described above, we are 
proposing additional revisions to the NESHAP. 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 portions of 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 revisions to require electronic 
reporting of performance test results and reports, performance 
evaluation reports, and NOCS reports, to remove certain exemptions for 
once-through heat exchange systems, to include overlap provisions for 
equipment at ethylene production facilities subject to both the EMACT 
standards and synthetic organic chemicals manufacturing equipment leak 
standards at 40 CFR part 60, subpart VVa, and to clarify text or 
correct typographical errors, grammatical errors, and cross-reference 
errors. Our analyses and proposed changes related to these issues are 
discussed below.
1. SSM
    In its 2008 decision in Sierra Club v. EPA, 551 F.3d 1019 (D.C. 
Cir. 2008), the 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.
a. Proposed Elimination of the SSM Exemption
    We are proposing the elimination of the SSM exemption in this rule 
which appears at 40 CFR 63.1108(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 40 CFR part 63, subpart YY as is 
explained in more detail below. For example, we are proposing to 
eliminate the 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.
    We are proposing that startups and shutdowns are normal operation 
for the Ethylene Production source category. We, therefore, believe 
that emissions from startup and shutdown activities should be included 
when determining if all the standards are being attained. As currently 
proposed in 40 CFR 63.1108(a)(4)(i), compliance with the emission 
limitations (including operating limits) in this subpart is required 
``at all times,'' except during periods of nonoperation of the affected 
source (or specific portion thereof) resulting in cessation of the 
emissions to which this subpart applies. Based on the information for 
APCD operation

[[Page 54321]]

received in the CAA section 114 survey issued to the Ethylene 
Production source category, we conclude that ethylene production 
facilities will generally be able to comply with the standards during 
periods of startup and shutdown for the reasons discussed below. Where 
appropriate, we have also proposed in this preamble alternative 
standards for certain emission points during periods of SSM to ensure a 
standard applies ``at all times.'' Emission reductions for process 
vents and transfer rack operations are typically achieved by routing 
vapors to an APCD such as a flare, thermal oxidizer, or carbon 
adsorber. It is common practice in this source category to start an 
APCD prior to startup of the emissions source it is controlling, so the 
APCD would be operating before emissions are routed to it. We expect 
APCDs would be operating during startup and shutdown events in a manner 
consistent with normal operating periods, and that these APCDs will be 
operated to maintain and meet the monitoring parameter operating limits 
set during the performance test. We do not expect startup and shutdown 
events to affect emissions from storage vessels, equipment leaks, waste 
sources (e.g., surface impoundments, oil-water separators, organic-
water separators), or heat exchange systems. Working and breathing 
losses from storage vessels are the same regardless of whether the 
process is operating under normal operating conditions or if it is in a 
startup or shutdown event. Leak detection programs associated with 
equipment leaks and heat exchange systems are in place to detect leaks, 
and, therefore, it is inconsequential whether the process is operating 
under normal operating conditions or is in startup or shutdown. Waste 
emissions are also not expected to be significantly affected by startup 
or shutdown events.
    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 (D.C. Cir. 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 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.
    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 APCD 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 APCD 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 RTR, the EPA established a 
work practice standard for unique types of malfunction that result in 
releases from PRDs or emergency flaring events because we had 
information to determine that such work practices reflected the level 
of control that applies to the best performing sources. 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. As discussed in sections IV.A.1 and IV.A.2.a of 
this preamble, we are proposing work practice standards that will apply 
to PRD releases and flares, respectively, due to their similarities to 
PRD releases and flares used in the Petroleum Refinery Sector source 
category. As also previously explained, many parent companies that own 
and operate facilities subject to the EMACT standards also own and 
operate

[[Page 54322]]

petroleum refineries that are subject to the Petroleum Refinery Sector 
Rule.
    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.
    Finally, in keeping with the elimination of the SSM exemption, we 
are proposing in the EMACT standards at 40 CFR 63.1103(e)(11) to remove 
the following SSM exemption provisions from the subparts referenced by 
the EMACT standards.
     The second sentence of 40 CFR 63.181(d)(5)(i) of subpart 
H.
     40 CFR 63.983(a)(5) of subpart SS.
     The phrase ``except during periods of start-up, shutdown 
and malfunction as specified in the referencing subpart'' in 40 CFR 
63.984(a) of subpart SS.
     The phrase ``except during periods of start-up, shutdown 
and malfunction as specified in the referencing subpart'' in 40 CFR 
63.985(a) of subpart SS.
     The phrase ``other than start-ups, shutdowns, or 
malfunctions'' in 40 CFR 63.994(c)(1)(ii)(D) of subpart SS.
     40 CFR 63.996(c)(2)(ii) of subpart SS.
     40 CFR 63.997(e)(1)(i) of subpart SS.
     The term ``breakdowns'' from 40 CFR 63.998(b)(2)(i) of 
subpart SS.
     40 CFR 63.998(b)(2)(iii) of subpart SS.
     The phrase ``other than periods of startups, shutdowns, 
and malfunctions'' from 40 CFR 63.998(b)(5)(i)(A) of subpart SS.
     The phrase ``other than periods of startups, shutdowns, 
and malfunctions'' from 40 CFR 63.998(b)(5)(i)(C) of subpart SS.
     The phrase ``except as provided in paragraphs (b)(6)(i)(A) 
and (B) of this section'' from 40 CFR 63.998(b)(6)(i) of subpart SS.
     The second sentence of 40 CFR 63.998(b)(6)(ii) of subpart 
SS.
     40 CFR 63.998(c)(1)(ii)(D), (E), (F), and (G) of subpart 
SS.
     40 CFR 63.998(d)(1)(ii) of subpart SS.
     40 CFR 63.998(d)(3)(i) and (ii) of subpart SS.
     The phrase ``(except periods of startup, shutdown, or 
malfunction)'' from 40 CFR 63.1026(e)(1)(ii)(A) of subpart UU.
     The phrase ``(except periods of startup, shutdown, or 
malfunction)'' from 40 CFR 63.1028(e)(1)(i)(A) of subpart UU.
     The phrase ``(except periods of startup, shutdown, or 
malfunction)'' from 40 CFR 63.1031(b)(1) of subpart UU.
b. General Duty
    We are proposing to remove the requirements at 40 CFR 63.1108(a)(5) 
and 40 CFR 63.1111(a)(2) and are proposing instead to add general duty 
regulatory text at 40 CFR 63.1108(a)(4)(ii) that reflects the general 
duty to minimize emissions ``at all times,'' while eliminating the 
reference to periods covered by an SSM exemption. The current language 
in 40 CFR 63.1108(a)(5) and 40 CFR 63.1111(a)(2) characterizes what the 
general duty entails during periods of SSM. With the elimination of the 
SSM exemption, there is no need to differentiate between normal 
operations, startup and shutdown, and malfunction events in describing 
the general duty. Therefore, the language the EPA is proposing for 40 
CFR 63.1108(a)(4)(ii) does not include that language from 40 CFR 
63.1108(a)(5) and 40 CFR 63.1111(a)(2).
c. SSM Plan
    We are proposing to remove certain language at 40 CFR 63.1103(e)(3) 
and 40 CFR 63.1111(a) requiring owners or operators to develop 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 and, thus, the SSM plan requirements are no 
longer necessary.
d. Compliance With Standards
    We are proposing to remove the current language of 40 CFR 
63.1108(a)(1) and (2) which exempts sources from non-opacity standards 
during periods of SSM. As discussed above, the Court in Sierra Club 
vacated the exemptions contained in this provision and held that the 
CAA requires that some CAA section 112 standard apply continuously. 
Consistent with Sierra Club, the EPA is proposing to revise standards 
in this rule to apply at all times.
e. Performance Testing
    We are proposing to add a performance testing requirement at 40 CFR 
63.1108(b)(4)(ii)(B) intended to replace the performance testing 
requirements of 40 CFR 63.997(e)(1) (as referenced in 40 CFR 
63.1108(b)(4)(ii)(A)). The proposal does not include the language that 
precludes startup and shutdown periods from being considered 
``representative'' for purposes of performance testing, and instead 
allows performance testing during periods of startup or shutdown if 
specified by the Administrator. As in 40 CFR 63.997(e)(1), performance 
tests conducted under this subpart should not be conducted during 
malfunctions because conditions during malfunctions are often not 
representative of normal operating conditions. The EPA is also 
proposing to add language at 40 CFR 63.1108(b)(4)(ii)(B) that requires 
the owner or operator maintain records of process information that is 
necessary to document operating conditions during the test and include 
in such record an explanation to support that such conditions represent 
normal operation. Finally, the EPA is proposing to add language 
clarifying that the owner or operator make such records available to 
the Administrator upon request.
f. Recordkeeping
    We are not proposing to change the language at 40 CFR 63.1109(a) 
requiring owners or operators of each affected source to keep copies of 
reports. However, we are proposing to completely remove 40 CFR 
63.1111(b), which eliminates periodic SSM reports, consequently 
eliminating the requirement to keep a copy of this report. These 
requirements are no longer appropriate for startup and shutdown because 
SSM plans will no longer be required and the EPA is proposing that 
recordkeeping and reporting applicable to normal operations will apply 
to startup and shutdown. In the absence of special provisions 
applicable to startup and shutdown, such as a startup and shutdown 
plan, there is no reason to retain additional recordkeeping for startup 
and shutdown periods. See section IV.E.1.a of this preamble for further 
discussion of this proposed language removal.
    Furthermore, in lieu of the requirements applicable to malfunctions 
in 40 CFR 63.1111(b), we are proposing new recordkeeping requirements 
at 40 CFR 63.1111(c)(1). The regulatory text we are proposing to add at 
40 CFR 63.1111(c)(1)(i) differs from 40 CFR 63.1111(b) in that 40 CFR 
63.1111(b) requires the creation and retention of a record for each 
malfunction during which excess emissions occurred, including total 
duration of all malfunctions for a reporting period. The EPA is 
proposing that this requirement

[[Page 54323]]

apply to any failure to meet an applicable standard and is requiring 
that the source record the date, time, and duration of the failure 
rather than the total duration of all malfunctions with which excess 
emissions occurred. For each failure to meet an applicable standard, 
the EPA is also proposing to add to 40 CFR 63.1111(c)(1)(ii) a 
provision that sources keep records that include a list of the affected 
source or equipment, an estimate of the quantity of each regulated 
pollutant emitted over the standard for which the source failed to meet 
the standard, and a description of the method used to estimate the 
emissions. Examples of such methods would include product-loss 
calculations, mass balance calculations, measurements when available, 
or engineering judgment based on known process parameters. Furthermore, 
the EPA is proposing to add 40 CFR 63.1111(c)(1)(iii) requiring sources 
keep records of any corrective actions taken to return the affected 
unit to its normal or usual manner of operations, and actions taken to 
minimize emissions in accordance with the general duty regulatory text 
at 40 CFR 63.1108(a)(4)(ii). The EPA is proposing to require that 
sources keep records of this information to ensure that there is 
adequate information to allow the EPA to determine the severity of any 
failure to meet a standard, and to provide data that may document how 
the source met the general duty to minimize emissions when the source 
has failed to meet an applicable standard.
g. Reporting
    We are proposing to completely remove 40 CFR 63.1111(b) which 
describes the reporting requirements for SSM. When applicable, 40 CFR 
63.1111(b)(1) requires sources to report actions taken during SSM 
events to show that actions taken were consistent with their SSM plan. 
When applicable, 40 CFR 63.1111(b)(2) requires sources to report 
actions taken during SSM events when actions were inconsistent with 
their SSM plan. To replace the 40 CFR 63.1111(b) reporting requirement, 
the EPA is proposing to add reporting requirements to 40 CFR 
63.1111(c)(2). The replacement language differs from the 40 CFR 
63.1111(b) language in that it eliminates periodic SSM reports as a 
stand-alone report. We are proposing language that requires sources 
that fail to meet an applicable standard at any time to report the 
information concerning such events in the periodic report already 
required under this rule. We are proposing that the report contain the 
number, date, time, and duration of such events (including unknown 
cause, if applicable), a list of the affected source or equipment, an 
estimate of the quantity of each regulated pollutant emitted over any 
emission limit, and a description of the method used to estimate the 
emissions.
    Regarding the proposed new requirement, discussed above, to 
estimate the quantity of each regulated pollutant emitted over any 
emission limit for which the source failed to meet the standard, and a 
description of the method used to estimate the emissions, examples of 
such methods would include product-loss calculations, mass balance 
calculations, measurements when available, or engineering judgment 
based on known process parameters (e.g., ethylene production rates and 
control efficiencies). The EPA is proposing this provision to ensure 
that there is adequate information to determine compliance, to allow 
the EPA to determine the severity of the failure to meet an applicable 
standard, and to provide data that may document how the source met the 
general duty to minimize emissions during a failure to meet an 
applicable standard.
    We will no longer require owners or operators to determine whether 
actions taken to correct a malfunction are consistent with an SSM plan, 
because plans would no longer be required. The proposed amendments, 
therefore, eliminate 40 CFR 63.1111(b)(2) that requires reporting of 
whether the source deviated from its SSM plan, including required 
actions to communicate with the Administrator, and the cross-reference 
to 40 CFR 63.1111(b)(1) that contains the description of the previously 
required SSM report format and submittal schedule from this section. 
These specifications are no longer necessary because the events will be 
reported in otherwise required reports with similar format and 
submittal requirements.
    We are proposing to completely remove 40 CFR 63.1111(b)(2) for 
reasons discussed above and because 40 CFR 63.1111(b)(2) describes an 
immediate report for startups, shutdown, and malfunctions when a source 
failed to meet an applicable standard but did not follow the SSM plan. 
We will no longer require owners and operators to report when actions 
taken during a startup, shutdown, or malfunction were not consistent 
with an SSM plan, because plans would no longer be required.
h. Waste
    The BWON provisions that are applicable to waste generated by 
sources in the Ethylene Production source category are set forth in 40 
CFR part 63, subpart XX, and are cross-referenced in Table 7 to 40 CFR 
63.1103(e)(3). With the elimination of the SSM exemption, we are 
proposing to remove the exemption language at 40 CFR 63.1095(a)(3) and 
(b)(1) that exempts an owner or operator of continuous butadiene waste 
streams and waste streams that contain benzene at a facility with a TAB 
less than 10 Mg/yr from the BWON requirements during periods of SSM. 
(For more information on how BWON applies to these streams, refer to 
section IV.D.5 of this preamble.) This exemption does not apply to 
facilities with a TAB of 10 Mg/yr or greater. An owner or operator of a 
facility with a TAB less than 10 Mg/yr would be required to comply with 
BWON at all times, including during periods of SSM for continuous 
butadiene waste streams and waste streams that contain benzene. As part 
of these proposed revisions, we are also proposing to remove language 
from the definitions of ``dilution steam blowdown waste stream'' and 
``spent caustic waste stream'' at 40 CFR 63.1082(b) such that the 
definitions no longer exclude streams generated from sampling, 
maintenance activities, or shutdown purges.
    We estimate that there would be no impact on any facility for 
making these changes. In reviewing the data submitted to us from the 
facilities who responded to our CAA section 114 survey, we determined 
that there was only one facility with a TAB less than 10 Mg/yr; 
however, this facility recently went through an expansion and we 
believe their TAB has likely changed to 10 Mg/yr or greater such that 
they are already complying with the BWON requirements at all times for 
continuous butadiene waste streams and waste streams that contain 
benzene. We solicit comment on whether there are any ethylene 
production facilities that operate with a TAB less than 10 Mg/yr; and 
if so, how this proposed change would impact them.
2. Electronic Reporting Requirements
    Through this proposal, the EPA is proposing that owners and 
operators of ethylene production facilities submit electronic copies of 
required performance test results and reports and NOCS reports through 
the EPA's Central Data Exchange (CDX) using the Compliance and 
Emissions Data Reporting Interface (CEDRI). A description of the 
electronic data submission process is provided in the memorandum, 
Electronic Reporting Requirements for New Source Performance Standards 
(NSPS) and National Emission Standards for Hazardous Air Pollutants 
(NESHAP)

[[Page 54324]]

Rules, available in Docket ID No. EPA-HQ-OAR-2017-0357. The proposed 
rule requires that performance test results collected using test 
methods that are supported by the EPA's Electronic Reporting Tool (ERT) 
as listed on the ERT website \36\ at the time of the test be submitted 
in the format generated through the use of the ERT and that other 
performance test results be submitted in portable document format (PDF) 
using the attachment module of the ERT. The proposed rule requires that 
NOCS reports be submitted as a PDF upload in CEDRI.
---------------------------------------------------------------------------

    \36\ https://www.epa.gov/electronic-reporting-air-emissions/electronic-reporting-tool-ert.
---------------------------------------------------------------------------

    Additionally, the EPA has identified two broad circumstances in 
which electronic reporting extensions may be provided. In both 
circumstances, the decision to accept the claim of needing additional 
time to report is within the discretion of the Administrator, and 
reporting should occur as soon as possible. The EPA is providing these 
potential extensions to protect owners and operators from noncompliance 
in cases where they cannot successfully submit a report by the 
reporting deadline for reasons outside of their control. The situation 
where an extension may be warranted due to outages of the EPA's CDX or 
CEDRI which precludes an owner or operator from accessing the system 
and submitting required reports is addressed in 40 CFR 
63.1110(a)(10)(iv). The situation where an extension may be warranted 
due to a force majeure event, which is defined as an event that will be 
or has been caused by circumstances beyond the control of the affected 
facility, its contractors, or any entity controlled by the affected 
facility that prevents an owner or operator from complying with the 
requirement to submit a report electronically as required by this rule 
is addressed in 40 CFR 63.1110(a)(10)(v). Examples of such events are 
acts of nature, acts of war or terrorism, or equipment failure or 
safety hazards beyond the control of the facility.
    The electronic submittal of the reports addressed in this proposed 
rulemaking will increase the usefulness of the data contained in those 
reports, is in keeping with current trends in data availability and 
transparency, will further assist in the protection of public health 
and the environment, will improve compliance by facilitating the 
ability of regulated facilities to demonstrate compliance with 
requirements and by facilitating the ability of delegated state, local, 
tribal, and territorial air agencies and the EPA to assess and 
determine compliance, and will ultimately reduce burden on regulated 
facilities, delegated air agencies, and the EPA. Electronic reporting 
also eliminates paper-based, manual processes, thereby saving time and 
resources, simplifying data entry, eliminating redundancies, minimizing 
data reporting errors, and providing data quickly and accurately to the 
affected facilities, air agencies, the EPA, and the public. Moreover, 
electronic reporting is consistent with the EPA's plan \37\ to 
implement Executive Order 13563 and is in keeping with the EPA's 
Agency-wide policy \38\ developed in response to the White House's 
Digital Government Strategy.\39\ For more information on the benefits 
of electronic reporting, see the memorandum, Electronic Reporting 
Requirements for New Source Performance Standards (NSPS) and National 
Emission Standards for Hazardous Air Pollutants (NESHAP) Rules, 
available in Docket ID No. EPA-HQ-OAR-2017-0357.
---------------------------------------------------------------------------

    \37\ The EPA's Final Plan for Periodic Retrospective Reviews, 
August 2011. Available at: https://www.regulations.gov/document?D=EPA-HQ-OA-2011-0156-0154.
    \38\ E-Reporting Policy Statement for EPA Regulations, September 
2013. Available at: https://www.epa.gov/sites/production/files/2016-03/documents/epa-ereporting-policy-statement-2013-09-30.pdf.
    \39\ Digital Government: Building a 21st Century Platform to 
Better Serve the American People, May 2012. Available at: https://obamawhitehouse.archives.gov/sites/default/files/omb/egov/digital-government/digital-government.html.
---------------------------------------------------------------------------

3. Exemptions for Heat Exchange Systems
    Heat exchange systems that meet any one of the criteria specified 
in 40 CFR 63.1084 are exempt from the LDAR requirements in the EMACT 
standards. We have also reviewed these criteria to see if the 
exemptions were still reasonable to maintain. In addition, we compared 
these exemptions to those requirements for heat exchangers that are 
subject to the Petroleum Refinery Sector Rule given that this MACT 
standard was more recently promulgated in 2009, relative to the EMACT 
standard promulgated in 2002.\40\ Based upon this review, we are 
proposing to remove the exemptions at 40 CFR 63.1084(c) and (d) for 
once-through heat exchange systems and instead, proposing that 
facilities comply with 40 CFR 63.1085 and 40 CFR 63.1086.
---------------------------------------------------------------------------

    \40\ The Refinery MACT standards for heat exchange systems were 
promulgated on October 28, 2009 (see 74 FR 55685) and further 
amended on June 30, 2010 (see 75 FR 37731) and June 20, 2013 (see 78 
FR 37146).
---------------------------------------------------------------------------

    We identified two criteria in 40 CFR 63.1084 that are applicable to 
once-through heat exchange systems meeting certain National Pollutant 
Discharge Elimination System (NPDES) permit conditions (i.e., 40 CFR 
63.1084(c) and (d)) that warranted further assessment. As discussed in 
section IV.D.6 of this preamble, once-through heat exchange systems at 
a petrochemical plant have systems open to the air (e.g., open sewer 
lines, trenches, and ponds) that are utilized to transport used cooling 
water to a discharge point (e.g., an outfall) of a facility. This 
cooling water can also be mixed with other sources of water (e.g., 
cooling water used in once-through heat exchange systems in non-
ethylene source categories, stormwater, treated wastewater, etc.) in 
sewers, trenches, and ponds prior to discharge from the plant. If this 
point of discharge from the plant is into a ``water of the United 
States,'' then the facility is required to have a NPDES permit and to 
meet certain pollutant discharge limits. In reviewing the requirements 
of 40 CFR 63.1084(c), we find that there is a disconnect between having 
a NPDES permit that meets certain allowable discharge limits (i.e., 1 
ppmv) or less above influent concentration, or 10 percent or less above 
influent concentration, whichever is greater) at the discharge point of 
a facility (e.g., outfall) as compared to being able to adequately 
identify a leak from a once-through heat exchange system given that 
these systems are open to the atmosphere prior to this discharge point 
and, therefore, any volatile HAP leaking from a once-through heat 
exchange system would likely be emitted to the atmosphere prior to the 
NPDES outfall. Similarly, while the requirements of 40 CFR 63.1084(d) 
allow facilities with once-through heat exchange systems that have 
certain requirements (i.e., the requirements of 40 CFR 63.1084(d)(1) 
through (4)) incorporated into their NPDES permit not to comply with 
the EMACT standards for heat exchange systems, we find this exemption 
to be problematic. Specifically, the NPDES requirements at 40 CFR 
63.1084(d) lack the specificity of where a sample must be taken to 
adequately find and quantify a leak from a once-through heat exchange 
system. These include, for example, just prior to the outfall from the 
plant versus from the exit of the once-through heat exchange system 
prior to being open to atmosphere, what concentration and/or mass 
emissions rate constitutes a leak that must be fixed, how quickly a 
leak must be fixed, what pollutants must be adequately accounted for, 
and what test method(s)/surrogate(s) facilities can use to demonstrate 
compliance. As such, we

[[Page 54325]]

find 40 CFR 63.1084(d) to be inadequate for purposes of LDAR for leaks 
that are at least as equivalent to those that would be identified if 
once-through heat exchange systems were complying with 40 CFR 63.1085 
and 40 CFR 63.1086 instead.
    Further, in reviewing the data submitted to us from the facilities 
who responded to our CAA section 114 survey, we determined that there 
are no facilities with once-through heat exchange systems complying 
with the NPDES compliance options at 40 CFR 63.1084(c) and (d). 
Accordingly, we are removing the exemption for once-through exchange 
systems that are specified in 40 CFR 63.1084(c) and (d) and are 
proposing that facilities that previously used either of these 
exemptions comply with 40 CFR 63.1085 and 40 CFR 63.1086. Therefore, we 
estimate that there would be no cumulative nationwide costs or emission 
reductions associated with this change. We solicit comment on our 
proposed decision.
4. Equipment Leak Overlap Provisions With Subpart VVa
    When an emission point is subject to multiple regulations, the 
EMACT standards include overlap provisions at 40 CFR 63.1100(g) that 
specify which regulations owners or operators must comply with. For 
equipment leaks, overlap provisions are specified for 40 CFR part 60, 
subpart VV; 40 CFR part 61, subpart J or subpart V; and 40 CFR part 63, 
subpart H. However, since the promulgation of the EMACT standards in 
2002, equipment leak regulations were finalized at 40 CFR part 60, 
subpart VVa, in 2007 and did not address overlap with the EMACT 
standards (or 40 CFR part 63, subpart UU, generally). As such, certain 
equipment at newly constructed ethylene production facilities must 
currently comply with both the EMACT standards and subpart VVa. Except 
for calibration drift assessments required by subpart VVa, we are 
proposing at 40 CFR 63.1100(g)(4)(iii) that equipment controlled 
according to the EMACT standards and subpart VVa are required only to 
comply with the EMACT standards. We believe this compliance option will 
provide flexibility and reduce the burden on ethylene production 
facilities. We are proposing that where equipment at ethylene 
production facilities is subject to both the EMACT standards and 
subpart VVa, an owner or operator that chooses to comply with the EMACT 
standards only (instead of complying with both standards), must also 
still comply with the calibration drift assessment provisions at 40 CFR 
60.485a(b)(2). The calibration drift assessment helps ensure that the 
EPA Method 21 monitoring results are accurate when demonstrating 
compliance.
5. Other Corrections
    There are several additional revisions that we are proposing to 40 
CFR part 63, subpart YY to clarify text or correct typographical 
errors, grammatical errors, and cross-reference errors. These proposed 
editorial corrections and clarifications are summarized in Table 9 of 
this preamble.

 Table 9--Summary of Proposed Editorial and Minor Corrections to 40 CFR
                           Part 63, Subpart YY
------------------------------------------------------------------------
             Provision                        Proposed revision
------------------------------------------------------------------------
Table 1 to 40 CFR 63.1100(a)......  Format footnote ``a''; remove
                                     unnecessary periods; and correct
                                     reference to definition of heat
                                     exchange systems in footnote ``c.''
40 CFR 63.1100(b).................  Clarify applicability of General
                                     Provisions for ethylene production
                                     affected sources.
40 CFR 63.1100(g)(5)..............  Correct spelling of the word
                                     ``collocated.''
40 CFR 63.1100(g)(7)..............  Add paragraph to clarify flares that
                                     are subject to the provisions of 40
                                     CFR 60.18 or 40 CFR 63.11 and used
                                     as a control device for an emission
                                     point subject to the requirements
                                     in Table 7 to 40 CFR 63.1103(e) are
                                     only required to comply with the
                                     provisions specified in 40 CFR
                                     63.1103(e)(4).
40 CFR 63.1101....................  Clarify that the definition of
                                     ``pressure relief device or valve''
                                     does not apply to ethylene
                                     production affected sources (see
                                     section IV.A.2.a of this preamble
                                     for further details). Change
                                     ``ethylene production unit
                                     furnaces'' to ``ethylene cracking
                                     furnaces'' in the definition of
                                     ``shutdown'' for consistency.
40 CFR 63.1103(b)(2)..............  Change the word ``contracts'' to
                                     ``contacts'' in definition of ``in
                                     organic hazardous air pollutant or
                                     in organic HAP service.''
40 CFR 63.1103(e)(1)(F) and Table   Correct the reference to the
 7 at 40 CFR 63.1103(e)(3)(h).       definition of ``heat exchange
                                     systems.''
Table 7 at 40 CFR                   Correct typo by changing ``<='' to
 63.1103(e)(3)(a)(1).                ``<''.
Table 7 at 40 CFR                   Clarify concentration applicability
 63.1103(e)(3)(d)(1).                for ethylene process vents is on a
                                     dry basis based on original MACT
                                     floor determination.
Table 7 at 40 CFR                   Clarify concentration emission
 63.1103(e)(3)(d)(1)(i) and (ii),    limitation for ethylene process
 and (e)(1)(i) and (ii).             vents and transfer racks is on a
                                     dry basis corrected to 3.0-percent
                                     oxygen based on original MACT floor
                                     determination.
40 CFR 63.1107(a).................  Clarify how EPA Method 18 can be
                                     used when determining the percent
                                     organic HAP content of the process
                                     fluid that is contained in or
                                     contacts equipment for the ethylene
                                     production affected sources.
40 CFR 63.1108(a)(4)(ii)..........  Change ``which'' to ``that'' and
                                     clarify inspection of the
                                     ``affected'' source when
                                     determining whether a source is
                                     operating in compliance with
                                     operation and maintenance
                                     requirements.
40 CFR 63.1108(b)(4)(i)...........  Correct reference to paragraphs
                                     (b)(4)(i)(A) through (D).
------------------------------------------------------------------------

F. What compliance dates are we proposing?

    Amendments to the EMACT standards proposed in this rulemaking for 
adoption under CAA section 112(d)(2) and (3) and CAA section 112(d)(6) 
are subject to the compliance deadlines outlined in the CAA under CAA 
section 112(i). For all of the requirements we are proposing under CAA 
sections 112(d)(2) and (3), and CAA section 112 (d)(6), we are 
proposing that all existing affected sources, and all new affected 
source that commence construction or reconstruction after December 6, 
2000 and on or before October 9, 2019, must comply with all of the 
amendments no later than 3 years after the effective date of the final 
rule, or upon startup, whichever is later. For existing sources, CAA 
section 112(i) provides that the compliance date shall provide for 
compliance as expeditiously as practicable, but no later than 3 years 
after the effective date of the standard. (``Section 112(i)(3)'s three-
year maximum compliance period applies generally to any emission 
standard . . .

[[Page 54326]]

promulgated under [section 112].'' Association of Battery Recyclers v. 
EPA, 716 F.3d 667, 672 (D.C. Cir. 2013).) In determining what 
compliance period is as expeditious as practicable, we consider the 
amount of time needed to plan and construct projects and change 
operating procedures by affected sources. As provided in CAA section 
112(i), all ethylene production new affected sources that commenced 
construction or reconstruction after October 9, 2019 would be required 
to comply with these requirements by the effective date of the final 
amendments to the EMACT standards or startup, whichever is later.
    We are proposing new operating and monitoring requirements for 
flares under CAA section 112(d)(2) and (3). We anticipate that these 
requirements would require the installation of new flare monitoring 
equipment and we project that most ethylene production units would 
install new control systems to monitor and adjust assist gas (air or 
steam) addition rates. Similar to the addition of new control 
equipment, these new monitoring requirements for flares would require 
engineering evaluations, solicitation and review of vendor quotes, 
contracting and installation of the equipment, and operator training. 
Installation of new monitoring and control equipment on flares will 
require the flare to be taken out of service. Depending on the 
configuration of the flares and flare header system, taking the flare 
out of service may also require a significant portion of the ethylene 
production unit to be shutdown. Therefore, for all existing affected 
sources, and all new affected source that commence construction or 
reconstruction after December 6, 2000 and on or before October 9, 2019, 
we are proposing that it is necessary to provide 3 years after the 
effective date of the final rule (or upon startup, whichever is later) 
for owners or operators to comply with the new operating and monitoring 
requirements for flares. For all ethylene production new affected 
sources that commenced construction or reconstruction after October 9, 
2019, we are proposing owners or operators comply with the new 
operating and monitoring requirements for flares by the effective date 
of the final rule (or upon startup, whichever is later).
    Under CAA section 112(d)(2) and (3), we are proposing new vent 
control requirements for bypasses. These requirements would typically 
require the addition of piping and potentially new control 
requirements. As these vent controls would most likely be routed to the 
flare, we are proposing to provide 3 years after the effective date of 
the final rule for owners or operators to install additional piping, 
monitoring, and/or controls to correct any vent control bypasses. For 
atmospheric PRDs in organic HAP service, we are establishing a work 
practice standard that requires a process hazard analysis and 
implementation of a minimum of three redundant measures to prevent 
atmospheric releases. Alternately, owners or operators may elect to 
install closed vent systems to route these PRDs to a flare, drain (for 
liquid thermal relief valves) or other control system. We anticipate 
that sources will need to identify the most appropriate preventive 
measures or control approach; design, install, and test the system; 
install necessary process instrumentation and safety systems; and may 
need to time installations with equipment shutdown or maintenance 
outages. Therefore, all existing affected sources, and all new affected 
source that commence construction or reconstruction after December 6, 
2000 and on or before October 9, 2019, we are proposing a compliance 
date of 3 years from the effective date of the final rule (or upon 
startup, whichever is later) for owners or operators to comply with the 
work practice standards for atmospheric PRD releases. For all ethylene 
production new affected sources that commenced construction or 
reconstruction after October 9, 2019, we are proposing owners or 
operators comply with the work practice standards for atmospheric PRD 
releases by the effective date of the final rule (or upon startup, 
whichever is later).
    Under CAA section 112(d)(2) and (3), we are also proposing work 
practice standards for decoking operations that would require owners 
and operators to institute procedures to reduce coke formation and coke 
combustion emissions, and prevent non-coke combustion HAP emissions 
from escaping to the atmosphere due to leaks in the transfer line and 
decoking valves. We anticipate that most, if not all owners and 
operators already have procedures in place that meet the proposed 
criteria; however, the EPA recognizes the confusion that multiple 
different compliance dates for individual requirements would create and 
the additional burden such an assortment of dates would impose. Also, 
facilities will still need some time to read and understand the amended 
rule requirements, update standard operating procedures, and install 
monitoring equipment; therefore, we are proposing that all existing 
affected sources, and all new affected source that commence 
construction or reconstruction after December 6, 2000 and on or before 
October 9, 2019 must comply with the decoking work practice standards 
no later than 3 years after the effective date of the final rule, or 
upon startup, whichever is later. For all ethylene production new 
affected sources that commenced construction or reconstruction after 
October 9, 2019, we are proposing owners or operators comply with the 
decoking work practice standards by the effective date of the final 
rule (or upon startup, whichever is later).
    Under our technology review for storage vessels under CAA section 
112(d)(6), we are revising the EMACT standards to reflect more 
stringent storage vessel capacity and MTVP thresholds. We project that 
some owners and operators will need to install new control equipment on 
certain storage vessels because of the proposed applicability 
revisions. The addition of new control equipment would require 
engineering design, solicitation, and review of vendor quotes, and 
contracting and installation of the equipment, which would need to be 
timed with process unit outage and operator training. Therefore, we are 
proposing a compliance date of 3 years after the effective date of the 
final rule, or upon startup, whichever is later for all existing 
affected sources, and all new affected source that commence 
construction or reconstruction after December 6, 2000 and on or before 
October 9, 2019 to comply with the proposed storage vessel 
requirements. For all ethylene production new affected sources that 
commenced construction or reconstruction after October 9, 2019, we are 
proposing owners or operators comply with the proposed storage vessel 
requirements by the effective date of the final rule (or upon startup, 
whichever is later).
    As a result of our technology review for heat exchange systems, we 
are proposing to replace the existing leak definition and monitoring 
method with a new leak definition and monitoring method. We project 
some owners and operators would require engineering evaluations, 
solicitation, and review of vendor quotes, contracting and installation 
of monitoring equipment, and operator training. In addition, facilities 
will need time to read and understand the amended rule requirements and 
update standard operating procedures. Therefore, we are proposing that 
all existing affected sources, and all new affected source that 
commence construction or reconstruction after December 6, 2000 and on 
or before October 9, 2019 must

[[Page 54327]]

comply with the new monitoring requirements for heat exchange systems 
no later than 3 years after the effective date of the final rule, or 
upon startup, whichever is later. For all ethylene production new 
affected sources that commenced construction or reconstruction after 
October 9, 2019, we are proposing owners or operators comply with the 
new monitoring requirements for heat exchange systems by the effective 
date of the final rule (or upon startup, whichever is later).
    Finally, we are proposing to change the requirements for SSM by 
removing both the exemption from the requirements to meet the standard 
during SSM periods and the requirement to develop and implement an SSM 
plan. We are also proposing electronic reporting requirements. We are 
positing that facilities would need some time to successfully 
accomplish these revisions, including time to read and understand the 
amended rule requirements, to evaluate their operations to ensure that 
they can meet the standards during periods of startup and shutdown, as 
defined in the rule, and make any necessary adjustments, including 
making adjustments to standard operating procedures, and to convert 
reporting mechanisms to install necessary hardware and software. The 
EPA recognizes the confusion that multiple different compliance dates 
for individual requirements would create and the additional burden such 
an assortment of dates would impose. From our assessment of the 
timeframe needed for compliance with the entirety of the revised 
requirements, the EPA considers a period of 3 years after the effective 
date of the final rule to be the most expeditious compliance period 
practicable and, thus, is proposing at 40 CFR 63.1102(c) and 40 CFR 
63.1081 that all affected sources should be in compliance with all of 
this regulation's revised requirements upon initial startup or within 3 
years of the effective date of the final rule, whichever is later.

V. Summary of Cost, Environmental, and Economic Impacts

A. What are the affected sources?

    As of January 1, 2017, there were 26 ethylene production facilities 
currently operating that are major sources of HAP, and the EPA is aware 
of five ethylene production facilities under construction. As such, 31 
ethylene production facilities will be subject to the proposed 
amendments. A complete list of facilities that are currently subject, 
or will be subject, to the EMACT standards is available in Appendix A 
of the memorandum titled Review of the RACT/BACT/LAER Clearinghouse 
Database for the Ethylene Production Source Category, in Docket ID No. 
EPA-HQ-OAR-2017-0357.

B. What are the air quality impacts?

    At the current level of control, estimated HAP emissions were 
approximately 4,040 tpy. We estimated HAP emissions reductions of 62 
tpy and VOC emissions reductions of 540 tpy as a result of the proposed 
amendments for storage vessels, heat exchange systems, and decoking 
operations for ethylene cracking furnaces. We note that these emissions 
reductions do not consider the potential excess emissions reductions 
from flares that could result from the proposed monitoring 
requirements; we estimated flare excess emissions reductions of 1,430 
tpy HAP and 13,020 tpy VOC. When considering the flare excess 
emissions, the total emissions reductions as a result of the proposed 
amendments were estimated at 1,492 tpy HAP and 13,560 tpy VOC. These 
emissions reductions are documented in the following memoranda, which 
are available in Docket ID No. EPA-HQ-OAR-2017-0357: Assessment of Work 
Practice Standards for Ethylene Cracking Furnace Decoking Operations 
Located in the Ethylene Production Source Category, Clean Air Act 
Section 112(d)(6) Technology Review for Storage Vessels Located in the 
Ethylene Production Source Category, Clean Air Act Section 112(d)(6) 
Technology Review for Heat Exchange Systems in the Ethylene Production 
Source Category, and Control Option Impacts for Flares Located in the 
Ethylene Production Source Category.

C. What are the cost impacts?

    We estimated the total capital costs of the proposed amendments to 
be $48.0 million and the total annualized costs to be about $10.3 
million in 2016 dollars (annualized costs include annual recovery 
credits of $290,000). The present value in 2016 of the costs is $87.2 
million at a discount rate of 3 percent and $ 71.8 million at 7 
percent. Calculated as an equivalent annualized value, which is 
consistent with the present value of costs in 2016, the costs are $12.0 
million at a discount rate of 7 percent and $12.4 million at a discount 
rate of 3 percent. The costs are associated with the proposed 
amendments for flares, pressure relief devices, maintenance (equipment 
openings), storage vessels, heat exchange systems, and decoking 
operations for ethylene cracking furnaces. Costs for flares include 
purchasing analyzers, monitors, natural gas and steam, developing a 
flare management plan, and performing root cause analysis and 
corrective action (details are available in section IV.A.1.h of this 
preamble and the memorandum titled Control Option Impacts for Flares 
Located in the Ethylene Production Source Category, in Docket ID No. 
EPA-HQ-OAR-2017-0357). Costs for pressure relief devices were developed 
based on compliance with the proposed work practice standard and 
include implementation of three prevention measures, performing root 
cause analysis and corrective action, and purchasing pressure relief 
device monitors (details are available in section IV.A.2.a of this 
preamble and the memorandum titled Review of Regulatory Alternatives 
for Certain Vent Streams in the Ethylene Production Source Category, in 
Docket ID No. EPA-HQ-OAR-2017-0357). Maintenance costs were estimated 
to document equipment opening procedures and to document circumstances 
under which the alternative maintenance vent limit is used (details are 
available in section IV.A.2.d of this preamble and the memorandum 
titled Review of Regulatory Alternatives for Certain Vent Streams in 
the Ethylene Production Source Category, in Docket ID No. EPA-HQ-OAR-
2017-0357). Costs for storage vessels include installing IFRs and 
upgrading deck fittings (details are available in section IV.D.1 of 
this preamble and the memorandum titled Clean Air Act Section 112(d)(6) 
Technology Review for Storage Vessels Located in the Ethylene 
Production Source Category, in Docket ID No. EPA-HQ-OAR-2017-0357). 
Heat exchange systems costs include the use of the Modified El Paso 
Method to monitor for leaks (details are available in section IV.D.6 of 
this preamble and the memorandum titled Clean Air Act Section 112(d)(6) 
Technology Review for Heat Exchange Systems in the Ethylene Production 
Source Category, in Docket ID No. EPA-HQ-OAR-2017-0357). The costs 
associated with decoking operations for ethylene cracking furnaces 
include conducting isolation valve inspections and conducting flame 
impingement firebox inspections (details are available in section 
IV.A.3 of this preamble and the memorandum titled Assessment of Work 
Practice Standards for Ethylene Cracking Furnace Decoking Operations 
Located in the Ethylene Production Source Category, in Docket ID No. 
EPA-HQ-OAR-2017-0357).

D. What are the economic impacts?

    The EPA conducted economic impact analyses for this proposal, as 
detailed in

[[Page 54328]]

the memorandum titled Economic Impact Analysis for the Proposed 
Ethylene Production Risk and Technology Review (RTR) NESHAP, which is 
available in the docket for this action. The economic impacts of the 
proposal are calculated as the percentage of total annualized costs 
incurred by affected parent owners to their annual revenues. This ratio 
of total annualized costs to annual revenues provides a measure of the 
direct economic impact to parent owners of ethylene production 
facilities while presuming no passthrough of costs to ethylene 
consumers. We estimate that none of the 16 parent owners affected by 
this proposal will incur total annualized costs of 0.02 percent or 
greater of their revenues. Product recovery, which is estimated as an 
impact of the proposed rule, is included in the estimate of total 
annualized costs that is an input to the economic impact analysis. 
Thus, these economic impacts are quite low for affected companies and 
the ethylene production industry, and consumers of ethylene should 
experience minimal price changes.

VI. Request for Comments

    We solicit comments on this proposed action. In addition to general 
comments on this proposed action, we are also interested in additional 
data that may improve the risk assessments and other analyses. We are 
specifically interested in receiving any improvements to the data used 
in the site-specific emissions profiles used for risk modeling. Such 
data should include supporting documentation in sufficient detail to 
allow characterization of the quality and representativeness of the 
data or information. Section VII of this preamble provides more 
information on submitting data.

VII. Submitting Data Corrections

    The site-specific emissions profiles used in the source category 
risk and demographic analyses and instructions are available for 
download on the RTR website at https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html. The data files include detailed information for each HAP 
emissions release point for the facilities in the source category.
    If you believe that the data are not representative or are 
inaccurate, please identify the data in question, provide your reason 
for concern, and provide any ``improved'' data that you have, if 
available. When you submit data, we request that you provide 
documentation of the basis for the revised values to support your 
suggested changes. To submit comments on the data downloaded from the 
RTR website, complete the following steps:
    1. Within this downloaded file, enter suggested revisions to the 
data fields appropriate for that information.
    2. Fill in the commenter information fields for each suggested 
revision (i.e., commenter name, commenter organization, commenter email 
address, commenter phone number, and revision comments).
    3. Gather documentation for any suggested emissions revisions 
(e.g., performance test reports, material balance calculations).
    4. Send the entire downloaded file with suggested revisions in 
Microsoft[supreg] Access format and all accompanying documentation to 
Docket ID No. EPA-HQ-OAR-2017-0357 (through the method described in the 
ADDRESSES section of this preamble).
    5. If you are providing comments on a single facility or multiple 
facilities, you need only submit one file for all facilities. The file 
should contain all suggested changes for all sources at that facility 
(or facilities). We request that all data revision comments be 
submitted in the form of updated Microsoft[supreg] Excel files that are 
generated by the Microsoft[supreg] Access file. These files are 
provided on the RTR website at https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html.

VIII. Statutory and Executive Order Reviews

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

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

    This action is a significant regulatory action that was submitted 
to OMB for review because it raises novel legal or policy issues. Any 
changes made in response to OMB recommendations have been documented in 
the docket. The EPA prepared an analysis of the potential costs and 
benefits associated with this action. This analysis, Economic Impact 
Analysis for the Proposed Ethylene Production Risk and Technology 
Review (RTR) NESHAP, is available in the docket for this rule.

B. Executive Order 13771: Reducing Regulations and Controlling 
Regulatory Costs

    This action is expected to be an Executive Order 13771 regulatory 
action. Details on the estimated costs of this proposed rule can be 
found in section V of this preamble.

C. Paperwork Reduction Act (PRA)

    The information collection activities in this proposed rule have 
been submitted for approval to OMB under the PRA. The Information 
Collection Request (ICR) document that the EPA prepared has been 
assigned EPA ICR number 1983.09. You can find a copy of the ICR in the 
docket for this rule, and it is briefly summarized here.
    We are proposing amendments that change the reporting and 
recordkeeping requirements for several emission sources at ethylene 
production facilities (e.g., flares, decoking operations for ethylene 
cracking furnaces, heat exchangers, PRDs, storage vessels). The 
proposed amendments also require electronic reporting, remove the 
malfunction exemption, and impose other revisions that affect reporting 
and recordkeeping. This information would be collected to assure 
compliance with 40 CFR part 63, subparts XX and YY.
    Respondents/affected entities: Owners or operators of ethylene 
production facilities.
    Respondent's obligation to respond: Mandatory (40 CFR part 63, 
subparts XX and YY).
    Estimated number of respondents: 31 facilities.
    Frequency of response: Semiannual or annual. Responses include 
performance evaluation notifications and reports, NOCS, and semiannual 
compliance reports.
    Total estimated burden: 8,500 hours (per year). Burden is defined 
at 5 CFR 1320.3(b).
    Total estimated cost: $4,410,000 (per year), which includes 
$3,660,000 annualized capital and operation and maintenance costs for 
the responding facilities.
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for the 
EPA's regulations in 40 CFR are listed in 40 CFR part 9.
    Submit your comments on the Agency's need for this information, the 
accuracy of the provided burden estimates, and any suggested methods 
for minimizing respondent burden to the EPA using the docket identified 
at the beginning of this rule. You may also send your ICR-related 
comments to OMB's Office of Information and Regulatory Affairs via 
email to [email protected], Attention: Desk Officer for EPA. 
Because OMB is required to make a decision concerning the ICR between 
30 and 60 days after receipt, OMB must receive comments no later than 
November 8, 2019. The EPA

[[Page 54329]]

will respond to any ICR-related comments in the final rule.

D. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA as 
amended by the Small Business Regulatory Enforcement Fairness Act 
(SBREFA). This action will not impose any requirements on small 
entities. This action is projected to affect 31 facilities, and none of 
these facilities is owned by a small entity. Details of the associated 
analysis are presented in the memorandum, Economic Impact Analysis for 
the Proposed Ethylene Production Risk and Technology Review (RTR) 
NESHAP, which is available in the docket for this action.

E. Unfunded Mandates Reform Act (UMRA)

    This action does not contain an unfunded mandate of $100 million or 
more as described in UMRA, 2 U.S.C. 1531-1538, and does not 
significantly or uniquely affect small governments. The action imposes 
no enforceable duty on any state, local, or tribal governments.

F. Executive Order 13132: Federalism

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

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

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

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

    This action is not subject to Executive Order 13045 because it is 
not economically significant as defined in Executive Order 12866, and 
because the EPA does not believe the environmental health or safety 
risks addressed by this action present a disproportionate risk to 
children. This action's health and risk assessments are contained in 
sections III.A and C and sections IV.B and C of this preamble.

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

    This action is not a ``significant energy action'' because it is 
not likely to have a significant adverse effect on the supply, 
distribution, or use of energy. The overall economic impact of this 
proposed rule should be minimal for ethylene production facilities and 
their parent companies (which are engaged in the energy sector).

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

    This action involves technical standards. Therefore, the EPA 
conducted searches for the Ethylene Production NESHAP through the 
Enhanced National Standards Systems Network (NSSN) Database managed by 
the American National Standards Institute (ANSI). We also contacted 
voluntary consensus standards (VCS) organizations and accessed and 
searched their databases. We conducted searches for EPA Methods 1, 1A, 
2, 2A, 2C, 2D, 2F, 2G, 3B, 4, 5, 18, 21, 22, 25, 25A, 27, and 29 of 40 
CFR part 60, appendix A, 301, 316, and 320 of 40 CFR part 63, appendix 
A, and 602 and 624 of 40 CFR part 136, appendix A. During the EPA's VCS 
search, if the title or abstract (if provided) of the VCS described 
technical sampling and analytical procedures that are similar to the 
EPA's reference method, the EPA ordered a copy of the standard and 
reviewed it as a potential equivalent method. We reviewed all potential 
standards to determine the practicality of the VCS for this rule. This 
review requires significant method validation data that meet the 
requirements of EPA Method 301 for accepting alternative methods or 
scientific, engineering, and policy equivalence to procedures in the 
EPA reference methods. The EPA may reconsider determinations of 
impracticality when additional information is available for particular 
VCS.
    No applicable voluntary consensus standards were identified for EPA 
Methods 1A, 2A, 2D, 2F, 2G, 21, 22, 27, 316, 602, and 624. The 
following VCS were identified as acceptable alternatives to the EPA 
test methods for the purpose of this rule.
    The EPA proposes to use the VCS ANSI/ASME PTC 19-10-1981--Part 10, 
``Flue and Exhaust Gas Analyses'' as an acceptable alternative to EPA 
Methods 3A and 3B for the manual procedures only and not the 
instrumental procedures. The ANSI/ASME PTC 19-10-1981--Part 10 method 
incorporates both manual and instrumental methodologies for the 
determination of oxygen content. The manual method segment of the 
oxygen determination is performed through the absorption of oxygen. 
This method is available at the American National Standards Institute 
(ANSI), 1899 L Street NW, 11th Floor, Washington, DC 20036 and the 
American Society of Mechanical Engineers (ASME), Three Park Avenue, New 
York, NY 10016-5990. See https://wwww.ansi.org and https://www.asme.org.
    Also, the EPA proposes to use the VCS ASTM D6420-18, ``Standard 
Test Method for Determination of Gaseous Organic Compounds by Direct 
Interface Gas Chromatography-Mass Spectrometry'' as an acceptable 
alternative to EPA Method 18 with the following caveats. This ASTM 
procedure has been approved by the EPA as an alternative to EPA Method 
18 only when the target compounds are all known and the target 
compounds are all listed in ASTM D6420 as measurable. We are proposing 
that ASTM D6420-18 should not be used for methane and ethane because 
the atomic mass is less than 35; and ASTM D6420 should never be 
specified as a total VOC method. The ASTM D6420-18 test method employs 
a direct interface gas chromatograph/mass spectrometer to measure 36 
VOC. The test method provides on-site analysis of extracted, 
unconditioned, and unsaturated (at the instrument) gas samples from 
stationary sources.
    In addition, the EPA proposes to use the VCS ASTM D6348-12e1, 
``Determination of Gaseous Compounds by Extractive Direct Interface 
Fourier Transform (FTIR) Spectroscopy'' as an acceptable alternative to 
EPA Method 320 with caveats requiring inclusion of selected annexes to 
the standard as mandatory. The ASTM D6348-12e1 method is an extractive 
FTIR Spectroscopy-based field test method and is used to quantify gas 
phase concentrations of multiple target compounds in emission streams 
from stationary sources. We are proposing the test plan preparation and 
implementation in the Annexes to ASTM D 6348-03, Sections Al through A8 
are mandatory; and in ASTM D6348-03 Annex A5 (Analyte Spiking 
Technique), the percent (%) R must be determined for each target 
analyte (Equation A5.5). We are proposing that in order for the test 
data to be acceptable for a compound, %R must be 70% >= R <= 130%. If 
the %R value does not meet this criterion for a target compound, the 
test data is not acceptable for that compound and the test must be 
repeated

[[Page 54330]]

for that analyte (i.e., the sampling and/or analytical procedure should 
be adjusted before a retest). We are proposing that the %R value for 
each compound must be reported in the test report, and all field 
measurements must be corrected with the calculated %R value for that 
compound by using the following equation:

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

    The two ASTM methods (ASTM D6420-18 and ASTM D6348-12e1) are 
available at ASTM International, 1850 M Street NW, Suite 1030, 
Washington, DC 20036. See https://www.astm.org/.
    The search identified 17 other VCS that were potentially applicable 
for this rule in lieu of the EPA reference methods. After reviewing the 
available standards, the EPA determined that 17 candidate VCS 
identified for measuring emissions of pollutants or their surrogates 
subject to emission standards in the rule would not be practical due to 
lack of equivalency, documentation, validation data and other important 
technical and policy considerations. Additional information for the VCS 
search and determinations can be found in the memorandum, Voluntary 
Consensus Standard Results for National Emission Standards for 
Hazardous Air Pollutants for Ethylene Production RTR, which is 
available in the docket for this action.
    Finally, we are proposing at 40 CFR 63.1107(a) to incorporate by 
reference SW-846-8260B, Volatile Organic Compounds by Gas 
Chromatography/Mass Spectrometry (GC/MS), Revision 2, December 1996, in 
EPA Publication No. SW-846, Test Methods for Evaluating Solid Waste, 
Physical/Chemical Methods, Third Edition; and SW-846-8270D, 
Semivolatile Organic Compounds by Gas Chromatography/Mass Spectrometry 
(GC/MS), Revision 4, February 2007, in EPA Publication No. SW-846, Test 
Methods for Evaluating Solid Waste, Physical/Chemical Methods, Third 
Edition. Method SW-846-8260B is used to determine VOC in a variety of 
solid waste matrices with gas chromatography/mass spectrometry. Method 
SW-846-8260 can be used to quantitate most VOC that have boiling points 
below 200 degrees Celsius, including low molecular weight halogenated 
hydrocarbons, aromatics, ketones, nitriles, acetates, acrylates, 
ethers, and sulfides. Method SW-846-8270D is used to determine the 
concentration of semivolatile organic compounds in a variety of solid 
waste matrices with gas chromatography/mass spectrometry. Method SW-
846-8270D can be used to quantitate semivolatile compounds such as 
polyaromatic hydrocarbons, chlorinated hydrocarbons, pesticides, 
phthalate esters, organophosphate esters, nitrosamines, haloethers, 
aldehydes, ethers, ketones, anilines, pyridines, quinolines, aromatic 
nitro compounds, and phenols, including nitrophenols. The two SW-846 
methods (Method SW-846-8260B and Method SW-846-8270D) are available in 
the docket for this rulemaking and on EPA's website. See https://www.epa.gov/hw-sw846.
    The EPA welcomes comments on this aspect of the proposed rulemaking 
given that these proposed changes are being made in 40 CFR part 63, 
subpart SS, and, specifically, invites the public to identify 
potentially applicable VCS, and to explain why the EPA should use such 
standards in this regulation.

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

    The EPA believes that this action does not have disproportionately 
high and adverse human health or environmental effects on minority 
populations, low-income populations, and/or indigenous peoples, as 
specified in Executive Order 12898 (58 FR 7629, February 16, 1994). Our 
analysis of the demographics of the population with estimated risks 
greater than 1-in-1 million indicates potential disparities in risks 
between demographic groups, including the African American, Hispanic or 
Latino, Over 25 Without a High School Diploma, and Below the Poverty 
Level groups. In addition, the population living within 50 km of the 
ethylene production facilities has a higher percentage of minority, 
lower income, and lower education people when compared to the 
nationwide percentages of those groups. However, acknowledging these 
potential disparities, the risks for the source category were 
determined to be acceptable, and emissions reductions from the proposed 
revisions will benefit these groups the most.
    The documentation for this decision is contained in section IV.B 
and C of this preamble, and the technical report, Risk and Technology 
Review--Analysis of Demographic Factors for Populations Living Near 
Ethylene Production Source Category Operations, which is available in 
the docket for this action.

List of Subjects in 40 CFR Part 63

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

    Dated: September 5, 2019.
Andrew R. Wheeler,
Administrator.

    For the reasons set forth in the preamble, the EPA proposes to 
amend 40 CFR part 63 as follows:

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

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

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

Subpart A--[Amended]

0
2. Section 63.14 is amended by:
0
a. Revising paragraphs (e)(1) and (h)(18) and (85);
0
b. Redesignating paragraphs (h)(92) through (111) as paragraphs (h)(93) 
through (112);
0
c. Adding new paragraph (h)(92);
0
d. Revising paragraphs (n)(12) and (13); and
0
e. Revising paragraph (t)(1).
    The revisions and addition read as follows:


Sec.  63.14   Incorporations by reference.

* * * * *
    (e) * * *
    (1) ANSI/ASME PTC 19.10-1981, Flue and Exhaust Gas Analyses [Part 
10, Instruments and Apparatus], issued August 31, 1981, IBR approved 
for Sec. Sec.  63.309(k), 63.457(k), 63.772(e) and (h), 63.865(b), 
63.997(e), 63.1282(d) and (g), 63.1625(b), 63.3166(a), 63.3360(e), 
63.3545(a), 63.3555(a), 63.4166(a), 63.4362(a), 63.4766(a), 63.4965(a), 
63.5160(d), table 4 to subpart UUUU, 63.9307(c), 63.9323(a), 
63.11148(e), 63.11155(e), 63.11162(f), 63.11163(g), 63.11410(j), 
63.11551(a), 63.11646(a), and 63.11945, table 5 to subpart DDDDD, table 
4 to subpart JJJJJ, table 4 to subpart KKKKK, tables 4 and 5 of subpart 
UUUUU, table 1 to subpart ZZZZZ, and table 4 to subpart JJJJJJ.
* * * * *
    (h) * * *
    (18) ASTM D1946-90 (Reapproved 1994), Standard Method for Analysis 
of Reformed Gas by Gas Chromatography, IBR approved for Sec. Sec.  
63.11(b), 63.987(b), and 63.1412.
* * * * *
    (85) ASTM D6348-12e1, Standard Test Method for Determination of 
Gaseous Compounds by Extractive Direct Interface Fourier Transform 
Infrared (FTIR) Spectroscopy, Approved

[[Page 54331]]

February 1, 2012, IBR approved for Sec. Sec.  63.997(e) and 63.1571(a).
* * * * *
    (92) ASTM D6420-18, Standard Test Method for Determination of 
Gaseous Organic Compounds by Direct Interface Gas Chromatography-Mass 
Spectrometry, IBR approved for Sec.  63.987(b) and Sec.  63.997(e).
* * * * *
    (n) * * *
    (12) SW-846-8260B, Volatile Organic Compounds by Gas 
Chromatography/Mass Spectrometry (GC/MS), Revision 2, December 1996, in 
EPA Publication No. SW-846, Test Methods for Evaluating Solid Waste, 
Physical/Chemical Methods, Third Edition, IBR approved for Sec. Sec.  
63.1107(a), 63.11960, 63.11980, and table 10 to subpart HHHHHHH.
    (13) SW-846-8270D, Semivolatile Organic Compounds by Gas 
Chromatography/Mass Spectrometry (GC/MS), Revision 4, February 2007, in 
EPA Publication No. SW-846, Test Methods for Evaluating Solid Waste, 
Physical/Chemical Methods, Third Edition, IBR approved for Sec. Sec.  
63.1107(a), 63.11960, 63.11980, and table 10 to subpart HHHHHHH.
* * * * *
    (t) * * *
    (1) ``Air Stripping Method (Modified El Paso Method) for 
Determination of Volatile Organic Compound Emissions from Water 
Sources,'' Revision Number One, dated January 2003, Sampling Procedures 
Manual, Appendix P: Cooling Tower Monitoring, January 31, 2003, IBR 
approved for Sec. Sec.  63.654(c) and (g), 63.655(i), 63.1086(e), 
63.1089(d), and 63.11920.
* * * * *

Subpart SS--[Amended]

0
3. Section 63.987 is amended by revising parameter ``Dj'' of Equation 1 
in paragraph (b)(3)(ii) to read as follows:


Sec.  63.987   Flare requirements.

* * * * *
    (b) * * *
    (3) * * *
    (ii) * * *
* * * * *
    Dj = Concentration of sample component j, in parts per million by 
volume on a wet basis, as measured for organics by Method 18 of 40 CFR 
part 60, appendix A, or by American Society for Testing and Materials 
(ASTM) D6420-18 (Incorporated by reference in Sec.  63.14)) under the 
conditions specified in Sec.  63.997(e)(2)(iii)(D)(1) through (3). 
Hydrogen and carbon monoxide are measured by ASTM D1946-90 
(Incorporated by reference, see Sec.  63.14); and
* * * * *
0
4. Section 63.997 is amended by revising paragraphs (e)(2)(iii) 
introductory text, (e)(2)(iii)(C)(1), (e)(2)(iii)(D), (e)(2)(iv) 
introductory text, (e)(2)(iv)(F) and (I) to read as follows:


Sec.  63.997   Performance test and compliance assessment requirements 
for control devices.

* * * * *
    (e) * * *
    (2) * * *
    (iii) To determine compliance with a parts per million by volume 
total organic regulated material or TOC limit, the owner or operator 
shall use Method 18 or 25A of 40 CFR part 60, appendix A, as 
applicable. The ASTM D6420-18 (Incorporated by reference, see Sec.  
63.14) may be used in lieu of Method 18 of 40 CFR part 60, appendix A, 
under the conditions specified in paragraphs (e)(2)(iii)(D)(1) through 
(3) of this section. Alternatively, any other method or data that have 
been validated according to the applicable procedures in Method 301 of 
appendix A of 40 CFR part 63 may be used. The procedures specified in 
paragraphs (e)(2)(iii)(A), (B), (D), and (E) of this section shall be 
used to calculate parts per million by volume concentration. The 
calculated concentration shall be corrected to 3 percent oxygen using 
the procedures specified in paragraph (e)(2)(iii)(C) of this section if 
a combustion device is the control device and supplemental combustion 
air is used to combust the emissions.
* * * * *
    (C) * * *
    (1) The emission rate correction factor (or excess air), integrated 
sampling and analysis procedures of Method 3B of 40 CFR part 60, 
appendix A, or the manual method in ANSI/ASME PTC 19-10-1981--Part 10 
(Incorporated by reference, see Sec.  63.14)), shall be used to 
determine the oxygen concentration. The sampling site shall be the same 
as that of the organic regulated material or organic compound samples, 
and the samples shall be taken during the same time that the organic 
regulated material or organic compound samples are taken.
* * * * *
    (D) To measure the total organic regulated material concentration 
at the outlet of a control device, use Method 18 of 40 CFR part 60, 
appendix A, or ASTM D6420-18. If you have a combustion control device, 
you must first determine which regulated material compounds are present 
in the inlet gas stream using process knowledge or the screening 
procedure described in Method 18. In conducting the performance test, 
analyze samples collected at the outlet of the combustion control 
device as specified in Method 18 or ASTM D6420-18 for the regulated 
material compounds present at the inlet of the control device. The 
method ASTM D6420-18 may be used only under the conditions specified in 
paragraphs (e)(2)(iii)(D)(1) through (3) of this section.
    (1) If the target compounds are all known and are all listed in 
Section 1.1 of ASTM D6420-18 as measurable.
    (2) ASTM D6420-18 may not be used for methane and ethane.
    (3) ASTM D6420-18 may not be used as a total VOC method.
* * * * *
    (iv) Percent reduction calculation. To determine compliance with a 
percent reduction requirement, the owner or operator shall use Method 
18, 25, or 25A of 40 CFR part 60, appendix A, as applicable. The method 
ASTM D6420-18 may be used in lieu of Method 18 of 40 CFR part 60, 
appendix A, under the conditions specified in paragraphs 
(e)(2)(iii)(D)(1) through (3) of this section. Alternatively, any other 
method or data that have been validated according to the applicable 
procedures in Method 301 of appendix A of 40 CFR part 63 may be used. 
The procedures specified in paragraphs (e)(2)(iv)(A) through (I) of 
this section shall be used to calculate percent reduction efficiency.
* * * * *
    (F) To measure inlet and outlet concentrations of total organic 
regulated material, use Method 18 of 40 CFR part 60, appendix A, or 
ASTM D6420-18, under the conditions specified in paragraphs 
(e)(2)(iii)(D)(1) through (3) of this section. In conducting the 
performance test, collect and analyze samples as specified in Method 18 
or ASTM D6420-18. You must collect samples simultaneously at the inlet 
and outlet of the control device. If the performance test is for a 
combustion control device, you must first determine which regulated 
material compounds are present in the inlet gas stream (i.e., 
uncontrolled emissions) using process knowledge or the screening 
procedure described in Method 18. Quantify the emissions for the 
regulated material compounds present in the inlet gas stream for both 
the inlet and outlet gas streams for the combustion device.
* * * * *
    (I) If the uncontrolled or inlet gas stream to the control device 
contains formaldehyde, you must conduct emissions testing according to

[[Page 54332]]

paragraphs (e)(2)(iv)(I)(1) through (3) of this section.
    (1) Except as specified in paragraph (e)(2)(iv)(I)(3) of this 
section, if you elect to comply with a percent reduction requirement 
and formaldehyde is the principal regulated material compound (i.e., 
greater than 50 percent of the regulated material compounds in the 
stream by volume), you must use Method 316 or 320 of 40 CFR part 63, 
appendix A, to measure formaldehyde at the inlet and outlet of the 
control device. Use the percent reduction in formaldehyde as a 
surrogate for the percent reduction in total regulated material 
emissions.
    (2) Except as specified in paragraph (e)(2)(iv)(I)(3) of this 
section, if you elect to comply with an outlet total organic regulated 
material concentration or TOC concentration limit, and the uncontrolled 
or inlet gas stream to the control device contains greater than 10 
percent (by volume) formaldehyde, you must use Method 316 or 320 of 40 
CFR part 63, appendix A, to separately determine the formaldehyde 
concentration. Calculate the total organic regulated material 
concentration or TOC concentration by totaling the formaldehyde 
emissions measured using Method 316 or 320 and the other regulated 
material compound emissions measured using Method 18 or 25/25A.
    (3) You may elect to use ASTM D6348-12e1 (Incorporated by 
reference, Sec.  63.14) in lieu of Method 316 or 320 of 40 CFR part 63, 
appendix A as specified in paragraph (e)(2)(iv)(I)(1) or (2) of this 
section. To comply with this paragraph, the test plan preparation and 
implementation in the Annexes to ASTM D 6348-03 (Incorporated by 
reference, see Sec.  63.14) Sections A1 through A8 are mandatory; the 
percent (%) R must be determined for each target analyte using Equation 
A5.5 of ASTM D6348-03 Annex A5 (Analyte Spiking Technique); and in 
order for the test data to be acceptable for a compound, the %R must be 
70% >= R <= 130%. If the %R value does not meet this criterion for a 
target compound, then the test data is not acceptable for that compound 
and the test must be repeated for that analyte (i.e., the sampling and/
or analytical procedure should be adjusted before a retest). The %R 
value for each compound must be reported in the test report, and all 
field measurements must be corrected with the calculated %R value for 
that compound by using the following equation:
    Reported Results = (Measured Concentration in the Stack x 100)/%R.

Subpart XX--[Amended]

0
5. Section 63.1081 is revised to read as follows:


Sec.  63.1081   When must I comply with the requirements of this 
subpart?

    Except as specified in paragraphs (a) and (b) of this section, you 
must comply with the requirements of this subpart according to the 
schedule specified in Sec.  63.1102(a).
    (a) Each heat exchange system at an ethylene production affected 
source that commenced construction or reconstruction on or before 
October 9, 2019, must be in compliance with the heat exchange system 
requirements specified in Sec.  63.1084(f), Sec.  63.1085(e) and (f), 
Sec.  63.1086(e), Sec.  63.1087(c) and (d), Sec.  63.1088(d), and Sec.  
63.1089(d) and (e) upon initial startup or [date 3 years after date of 
publication of final rule in the Federal Register], whichever is later. 
Each heat exchange system at an ethylene production affected source 
that commences construction or reconstruction after October 9, 2019, 
must be in compliance with the heat exchange system requirements 
specified in Sec. Sec.  63.1084(f), 63.1085(e) and (f), 63.1086(e), 
63.1087(c) and (d), 63.1088(d), and 63.1089(d) and (e) upon initial 
startup, or [date of publication of final rule in the Federal 
Register], whichever is later.
    (b) Each waste stream at an ethylene production affected source 
that commenced construction or reconstruction on or before October 9, 
2019, must be in compliance with the flare requirements specified in 
Sec.  63.1095(a)(1)(vi) and (b)(3) upon initial startup or [date 3 
years after date of publication of final rule in the Federal Register], 
whichever is later. Each waste stream at an ethylene production 
affected source that commences construction or reconstruction after 
October 9, 2019, must be in compliance with the flare requirements 
specified in Sec.  63.1095(a)(1)(vi) and (b)(3) upon initial startup, 
or [date of publication of final rule in the Federal Register], 
whichever is later.
0
6. Section 63.1082 is amended by revising definitions for ``Dilution 
steam blowdown waste stream,'' and ``Spent caustic waste stream'' to 
read as follows:


Sec.  63.1082   What definitions do I need to know?

* * * * *
    Dilution steam blowdown waste stream means any continuously flowing 
process wastewater stream resulting from the quench and compression of 
cracked gas (the cracking furnace effluent) at an ethylene production 
unit and is discharged from the unit. This stream typically includes 
the aqueous or oily-water stream that results from condensation of 
dilution steam (in the cracking furnace quench system), blowdown from 
dilution steam generation systems, and aqueous streams separated from 
the process between the cracking furnace and the cracked gas 
dehydrators. Before [date 3 years after date of publication of final 
rule in the Federal Register], the dilution steam blowdown waste stream 
does not include dilution steam blowdown streams generated from 
sampling, maintenance activities, or shutdown purges. Beginning on 
[date 3 years after date of publication of final rule in the Federal 
Register], the dilution steam blowdown streams generated from sampling, 
maintenance activities, or shutdown purges are included in the 
definition of dilution steam blowdown waste stream. The dilution steam 
blowdown waste stream also does not include blowdown that has not 
contacted HAP-containing process materials.
* * * * *
    Spent caustic waste stream means the continuously flowing process 
wastewater stream that results from the use of a caustic wash system in 
an ethylene production unit. A caustic wash system is commonly used at 
ethylene production units to remove acid gases and sulfur compounds 
from process streams, typically cracked gas. Before [date 3 years after 
date of publication of final rule in the Federal Register], the spent 
caustic waste stream does not include spent caustic streams generated 
from sampling, maintenance activities, or shutdown purges. Beginning on 
[date 3 years after date of publication of final rule in the Federal 
Register], the spent caustic streams generated from sampling, 
maintenance activities, or shutdown purges are included in the 
definition of spent caustic waste stream.
* * * * *
0
7. Section 63.1084 is amended by revising the introductory text and 
adding paragraph (f) to read as follows:


Sec.  63.1084   What heat exchange systems are exempt from the 
requirements of this subpart?

    Except as specified in paragraph (f) of this section, your heat 
exchange system is exempt from the requirements in Sec. Sec.  63.1085 
and 63.1086 if it meets any one of the criteria in paragraphs (a) 
through (e) of this section.
* * * * *
    (f) Beginning no later than the compliance dates specified in

[[Page 54333]]

Sec.  63.1081(a), your heat exchange system is no longer exempt from 
the requirements in Sec. Sec.  63.1085 and 63.1086 if it meets the 
criteria in paragraphs (c) or (d) of this section; instead, your heat 
exchange system is exempt from the requirements in Sec. Sec.  63.1085 
and 63.1086 if it meets any one of the criteria in paragraphs (a), (b), 
or (e) of this section.
0
8. Section 63.1085 is amended by revising the introductory text and 
paragraphs (a) and (b), and by adding paragraphs (e) and (f) to read as 
follows:


Sec.  63.1085   What are the general requirements for heat exchange 
systems?

    Unless you meet one of the requirements for exemptions in Sec.  
63.1084, you must meet the requirements in paragraphs (a) through (f) 
of this section.
    (a) Except as specified in paragraph (e) of this section, you must 
monitor the cooling water for the presence of substances that indicate 
a leak according to Sec.  63.1086(a) through (d).
    (b) Except as specified in paragraph (f) of this section, if you 
detect a leak, then you must repair it according to Sec.  63.1087(a) 
and (b) unless repair is delayed according to Sec.  63.1088(a) through 
(c).
* * * * *
    (e) Beginning no later than the compliance dates specified in Sec.  
63.1081(a), the requirements specified in Sec.  63.1086(a) through (d) 
no longer apply; instead, you must monitor the cooling water for the 
presence of total strippable hydrocarbon concentration (as methane) 
that indicate a leak according to Sec.  63.1086(e). At any time before 
the compliance dates specified in Sec.  63.1081(a), you may choose to 
comply with the requirements in this paragraph in lieu of the 
requirements in paragraph (a) of this section.
    (f) Beginning no later than the compliance dates specified in Sec.  
63.1081(a), the requirements specified in Sec.  63.1087(a) and (b), and 
Sec.  63.1088(a) through (c), no longer apply; instead, if you detect a 
leak, then you must repair it according to Sec.  63.1087(c) and (d), 
unless repair is delayed according to Sec.  63.1088(d). At any time 
before the compliance dates specified in Sec.  63.1081(a), you may 
choose to comply with the requirements in this paragraph in lieu of the 
requirements in paragraph (b) of this section.
0
9. Section 63.1086 is amended by revising the introductory text and by 
adding paragraph (e) to read as follows:


Sec.  63.1086   How must I monitor for leaks to cooling water?

    Except as specified in Sec.  63.1085(e) and paragraph (e) of this 
section, you must monitor for leaks to cooling water by monitoring each 
heat exchange system according to the requirements of paragraph (a) of 
this section, monitoring each heat exchanger according to the 
requirements of paragraph (b) of this section, or monitoring a 
surrogate parameter according to the requirements of paragraph (c) of 
this section. Except as specified in Sec.  63.1085(e) and paragraph (e) 
of this section, if you elect to comply with the requirements of 
paragraph (a) or (b) of this section, you may use alternatives in 
paragraph (d)(1) or (2) of this section for determining the mean 
entrance concentration.
* * * * *
    (e) Beginning no later than the compliance dates specified in Sec.  
63.1081(a), you must perform monitoring to identify leaks of total 
strippable hydrocarbon concentration (as methane) from each heat 
exchange system subject to the requirements of this subpart according 
to the procedures in paragraphs (e)(1) through (5) of this section.
    (1) Monitoring locations for closed-loop recirculation heat 
exchange systems. For each closed loop recirculating heat exchange 
system, you must collect and analyze a sample from the location(s) 
described in either paragraph (e)(1)(i) or (ii) of this section.
    (i) Each cooling tower return line or any representative riser 
within the cooling tower prior to exposure to air for each heat 
exchange system.
    (ii) Selected heat exchanger exit line(s), so that each heat 
exchanger or group of heat exchangers within a heat exchange system is 
covered by the selected monitoring location(s).
    (2) Monitoring locations for once-through heat exchange systems. 
For each once-through heat exchange system, you must collect and 
analyze a sample from the location(s) described in paragraph (e)(2)(i) 
of this section. You may also elect to collect and analyze an 
additional sample from the location(s) described in paragraph 
(e)(2)(ii) of this section.
    (i) Selected heat exchanger exit line(s), so that each heat 
exchanger or group of heat exchangers within a heat exchange system is 
covered by the selected monitoring location(s). The selected monitoring 
location may be at a point where discharges from multiple heat exchange 
systems are combined provided that the combined cooling water flow rate 
at the monitoring location does not exceed 40,000 gallons per minute.
    (ii) The inlet water feed line for a once-through heat exchange 
system prior to any heat exchanger. If multiple heat exchange systems 
use the same water feed (i.e., inlet water from the same primary water 
source), you may monitor at one representative location and use the 
monitoring results for that sampling location for all heat exchange 
systems that use that same water feed.
    (3) Monitoring method. You must determine the total strippable 
hydrocarbon concentration (in parts per million by volume (ppmv) as 
methane) at each monitoring location using the ``Air Stripping Method 
(Modified El Paso Method) for Determination of Volatile Organic 
Compound Emissions from Water Sources'' (incorporated by reference, see 
Sec.  63.14) using a flame ionization detector (FID) analyzer for on-
site determination as described in Section 6.1 of the Modified El Paso 
Method.
    (4) Monitoring frequency and leak action level. For each heat 
exchange system, you must comply with the applicable monitoring 
frequency and leak action level, as defined in paragraphs (e)(4)(i) 
through (iii) of this section. The monitoring frequencies specified in 
paragraphs (e)(4)(i) through (iii) of this section also apply to the 
inlet water feed line for a once-through heat exchange system, if you 
elect to monitor the inlet water feed as provided in paragraph 
(e)(2)(ii) of this section.
    (i) For each heat exchange system at an ethylene production 
affected source that commenced construction or reconstruction on or 
before December 6, 2000, you must monitor quarterly using a leak action 
level defined as a total strippable hydrocarbon concentration (as 
methane) in the stripping gas of 6.2 ppmv. If a leak is detected as 
specified in paragraph (e)(5) of this section, then you must monitor 
monthly until the leak has been repaired according to the requirements 
in Sec.  63.1087(c) or (d). Once the leak has been repaired according 
to the requirements in Sec.  63.1087(c) or (d), quarterly monitoring 
for the heat exchange system may resume.
    (ii) For each heat exchange system at an ethylene production 
affected source that commences construction or reconstruction after 
December 6, 2000 and on or before October 9, 2019, you must monitor at 
the applicable frequency specified in paragraph (e)(4)(ii)(A) or (B) of 
this section using a leak action level defined as a total strippable 
hydrocarbon concentration (as methane) in the stripping gas of 6.2 
ppmv.
    (A) If you have completed the initial weekly monitoring for 6-
months of the heat exchange system as specified in Sec.  
63.1086(a)(2)(ii) or (b)(1)(ii) then you must monitor monthly. If a 
leak is

[[Page 54334]]

detected as specified in paragraph (e)(5) of this section, then you 
must monitor weekly until the leak has been repaired according to the 
requirements in Sec.  63.1087(c) or (d). Once the leak has been 
repaired according to the requirements in Sec.  63.1087(c) or (d), 
monthly monitoring for the heat exchange system may resume.
    (B) If you have not completed the initial weekly monitoring for 6-
months of the heat exchange system as specified in Sec.  
63.1086(a)(2)(ii) or (b)(1)(ii), or if you elect to comply with 
paragraph (e) of this section rather than paragraphs (a) through (d) of 
this section upon startup, then you must initially monitor weekly for 
6-months beginning upon startup and monitor monthly thereafter. If a 
leak is detected as specified in paragraph (e)(5) of this section, then 
you must monitor weekly until the leak has been repaired according to 
the requirements in Sec.  63.1087(c) or (d). Once the leak has been 
repaired according to the requirements in Sec.  63.1087(c) or (d), 
monthly monitoring for the heat exchange system may resume.
    (iii) For each heat exchange system at an ethylene production 
affected source that commences construction or reconstruction after 
October 9, 2019, you must initially monitor weekly for 6-months 
beginning upon startup and monitor monthly thereafter using a leak 
action level defined as a total strippable hydrocarbon concentration 
(as methane) in the stripping gas of 6.2 ppmv. If a leak is detected as 
specified in paragraph (e)(5) of this section, then you must monitor 
weekly until the leak has been repaired according to the requirements 
in Sec.  63.1087(c) or (d). Once the leak has been repaired according 
to the requirements in Sec.  63.1087(c) or (d), monthly monitoring for 
the heat exchange system may resume.
    (5) Leak definition. A leak is defined as described in paragraph 
(e)(5)(i) or (ii) of this section, as applicable.
    (i) For once-through heat exchange systems for which the inlet 
water feed is monitored as described in paragraph (e)(2)(ii) of this 
section, a leak is detected if the difference in the measurement value 
of the sample taken from a location specified in paragraph (e)(2)(i) of 
this section and the measurement value of the corresponding sample 
taken from the location specified in paragraph (e)(2)(ii) of this 
section equals or exceeds the leak action level.
    (ii) For all other heat exchange systems, a leak is detected if a 
measurement value of the sample taken from a location specified in 
paragraph (e)(1)(i), (ii), or (e)(2)(i) of this section equals or 
exceeds the leak action level.
0
10. Section 63.1087 is amended by revising the introductory text and by 
adding paragraphs (c) and (d) to read as follows:


Sec.  63.1087   What actions must I take if a leak is detected?

    Except as specified in Sec.  63.1085(f) and paragraphs (c) and (d) 
of this section, if a leak is detected, you must comply with the 
requirements in paragraphs (a) and (b) of this section unless repair is 
delayed according to Sec.  63.1088.
* * * * *
    (c) Beginning no later than the compliance dates specified in Sec.  
63.1081(a), if a leak is detected using the methods described in Sec.  
63.1086(e), you must repair the leak to reduce the measured 
concentration to below the applicable leak action level as soon as 
practicable, but no later than 45 days after identifying the leak, 
except as specified in Sec.  63.1088(d). Repair must include re-
monitoring at the monitoring location where the leak was identified 
according to the method specified in Sec.  63.1086(e)(3) to verify that 
the measured total strippable hydrocarbon concentration is below the 
applicable leak action level. Repair may also include performing the 
additional monitoring in paragraph (d) of this section to verify that 
the total strippable hydrocarbon concentration is below the applicable 
leak action level. Actions that can be taken to achieve repair include 
but are not limited to:
    (1) Physical modifications to the leaking heat exchanger, such as 
welding the leak or replacing a tube;
    (2) Blocking the leaking tube within the heat exchanger;
    (3) Changing the pressure so that water flows into the process 
fluid;
    (4) Replacing the heat exchanger or heat exchanger bundle; or
    (5) Isolating, bypassing, or otherwise removing the leaking heat 
exchanger from service until it is otherwise repaired.
    (d) Beginning no later than the compliance dates specified in Sec.  
63.1081(a), if you detect a leak when monitoring a cooling tower return 
line according to Sec.  63.1086(e)(1)(i), you may conduct additional 
monitoring of each heat exchanger or group of heat exchangers 
associated with the heat exchange system for which the leak was 
detected, as provided in Sec.  63.1086(e)(1)(ii). If no leaks are 
detected when monitoring according to the requirements of Sec.  
63.1086(e)(1)(ii), the heat exchange system is considered to have met 
the repair requirements through re-monitoring of the heat exchange 
system, as provided in paragraph (c) of this section.
0
11. Section 63.1088 is amended by revising the introductory text and by 
adding paragraph (d) to read as follows:


Sec.  63.1088   In what situations may I delay leak repair, and what 
actions must I take for delay of repair?

    You may delay the repair of heat exchange systems if the leaking 
equipment is isolated from the process. At any time before the 
compliance dates specified in Sec.  63.1081(a), you may also delay 
repair if repair is technically infeasible without a shutdown, and you 
meet one of the conditions in paragraphs (a) through (c) of this 
section. Beginning no later than the compliance dates specified in 
Sec.  63.1081(a), paragraphs (a) through (c) of this section no longer 
apply; instead, you may delay repair if the conditions in paragraph (d) 
of this section are met.
* * * * *
    (d) Beginning no later than the compliance dates specified in Sec.  
63.1081(a), you may delay repair when one of the conditions in 
paragraph (d)(1) or (2) of this section is met and the leak is less 
than the delay of repair action level specified in paragraph (d)(3) of 
this section. You must determine if a delay of repair is necessary as 
soon as practicable, but no later than 45 days after first identifying 
the leak.
    (1) If the repair is technically infeasible without a shutdown and 
the total strippable hydrocarbon concentration is initially and remains 
less than the delay of repair action level for all monitoring periods 
during the delay of repair, then you may delay repair until the next 
scheduled shutdown of the heat exchange system. If, during subsequent 
monitoring, the delay of repair action level is exceeded, then you must 
repair the leak within 30 days of the monitoring event in which the 
leak was equal to or exceeded the delay of repair action level.
    (2) If the necessary equipment, parts, or personnel are not 
available and the total strippable hydrocarbon concentration is 
initially and remains less than the delay of repair action level for 
all monitoring periods during the delay of repair, then you may delay 
the repair for a maximum of 120 calendar days. You must demonstrate 
that the necessary equipment, parts, or personnel were not available. 
If, during subsequent monitoring, the delay of repair action level is 
exceeded, then you must repair the leak within 30 days of the 
monitoring event in which the leak was equal to or exceeded the delay 
of repair action level.

[[Page 54335]]

    (3) The delay of repair action level is a total strippable 
hydrocarbon concentration (as methane) in the stripping gas of 62 ppmv. 
The delay of repair action level is assessed as described in paragraph 
(d)(3)(i) or (ii) of this section, as applicable.
    (i) For once-through heat exchange systems for which the inlet 
water feed is monitored as described in Sec.  63.1086(e)(2)(ii), the 
delay of repair action level is exceeded if the difference in the 
measurement value of the sample taken from a location specified in 
Sec.  63.1086(e)(2)(i) and the measurement value of the corresponding 
sample taken from the location specified in Sec.  63.1086(e)(2)(ii) 
equals or exceeds the delay of repair action level.
    (ii) For all other heat exchange systems, the delay of repair 
action level is exceeded if a measurement value of the sample taken 
from a location specified in Sec.  63.1086(e)(1)(i) and (ii) or Sec.  
63.1086(e)(2)(i) equals or exceeds the delay of repair action level.
0
12. Section 63.1089 is amended by revising paragraphs (d) and (e) to 
read as follows:


Sec.  63.1089   What records must I keep?

* * * * *
    (d) At any time before the compliance dates specified in Sec.  
63.1081(a), you must keep documentation of delay of repair as specified 
in Sec.  63.1088(a) through (c). Beginning no later than the compliance 
dates specified in Sec.  63.1081(a), the requirement to keep 
documentation of delay of repair as specified in Sec.  63.1088(a) 
through (c) no longer applies; instead, you must keep documentation of 
delay of repair as specified in paragraphs (d)(1) through (4) of this 
section.
    (1) The reason(s) for delaying repair.
    (2) A schedule for completing the repair as soon as practical.
    (3) The date and concentration of the leak as first identified and 
the results of all subsequent monitoring events during the delay of 
repair.
    (4) An estimate of the potential strippable hydrocarbon emissions 
from the leaking heat exchange system or heat exchanger for each 
required delay of repair monitoring interval following the procedures 
in paragraphs (d)(4)(i) through (iv) of this section.
    (i) Determine the leak concentration as specified in Sec.  
63.1086(e) and convert the stripping gas leak concentration (in ppmv as 
methane) to an equivalent liquid concentration, in parts per million by 
weight (ppmw), using equation 7-1 from ``Air Stripping Method (Modified 
El Paso Method) for Determination of Volatile Organic Compound 
Emissions from Water Sources'' (incorporated by reference--see Sec.  
63.14) and the molecular weight of 16 grams per mole (g/mol) for 
methane.
    (ii) Determine the mass flow rate of the cooling water at the 
monitoring location where the leak was detected. If the monitoring 
location is an individual cooling tower riser, determine the total 
cooling water mass flow rate to the cooling tower. Cooling water mass 
flow rates may be determined using direct measurement, pump curves, 
heat balance calculations, or other engineering methods. Volumetric 
flow measurements may be used and converted to mass flow rates using 
the density of water at the specific monitoring location temperature or 
using the default density of water at 25 degrees Celsius, which is 997 
kilograms per cubic meter or 8.32 pounds per gallon.
    (iii) For delay of repair monitoring intervals prior to repair of 
the leak, calculate the potential strippable hydrocarbon emissions for 
the leaking heat exchange system or heat exchanger for the monitoring 
interval by multiplying the leak concentration in the cooling water, 
ppmw, determined in (d)(4)(i) of this section, by the mass flow rate of 
the cooling water determined in (d)(4)(ii) of this section and by the 
duration of the delay of repair monitoring interval. The duration of 
the delay of repair monitoring interval is the time period starting at 
midnight on the day of the previous monitoring event or at midnight on 
the day the repair would have been completed if the repair had not been 
delayed, whichever is later, and ending at midnight of the day the of 
the current monitoring event.
    (iv) For delay of repair monitoring intervals ending with a 
repaired leak, calculate the potential strippable hydrocarbon emissions 
for the leaking heat exchange system or heat exchanger for the final 
delay of repair monitoring interval by multiplying the duration of the 
final delay of repair monitoring interval by the leak concentration and 
cooling water flow rates determined for the last monitoring event prior 
to the re-monitoring event used to verify the leak was repaired. The 
duration of the final delay of repair monitoring interval is the time 
period starting at midnight of the day of the last monitoring event 
prior to re-monitoring to verify the leak was repaired and ending at 
the time of the re-monitoring event that verified that the leak was 
repaired.
    (e) At any time before the compliance dates specified in Sec.  
63.1081(a), if you validate a 40 CFR part 136 method for the HAP listed 
in Table 1 to this subpart according to the procedures in appendix D to 
this part, then you must keep a record of the test data and 
calculations used in the validation. On the compliance dates specified 
in Sec.  63.1081(a), this requirement no longer applies.
0
13. Section 63.1090 is amended by revising the introductory text and by 
adding paragraph (f) to read as follows:


Sec.  63.1090   What reports must I submit?

    If you delay repair for your heat exchange system, you must report 
the delay of repair in the semiannual report required by Sec.  
63.1110(e). If the leak remains unrepaired, you must continue to report 
the delay of repair in semiannual reports until you repair the leak. 
Except as provided in paragraph (f) of this section, you must include 
the information in paragraphs (a) through (e) of this section in the 
semiannual report.
* * * * *
    (f) For heat exchange systems subject to Sec.  63.1085(e) and (f), 
Periodic Reports must include the information specified in paragraphs 
(f)(1) through (5) of this section, in lieu of the information 
specified in paragraphs (a) through (e) of this section.
    (1) The number of heat exchange systems at the plant site subject 
to the monitoring requirements in Sec.  63.1085(e) and (f).
    (2) The number of heat exchange systems at the plant site found to 
be leaking.
    (3) For each monitoring location where the total strippable 
hydrocarbon concentration was determined to be equal to or greater than 
the applicable leak definitions specified in Sec.  63.1086(e)(5), 
identification of the monitoring location (e.g., unique monitoring 
location or heat exchange system ID number), the measured total 
strippable hydrocarbon concentration, the date the leak was first 
identified, and, if applicable, the date the source of the leak was 
identified;
    (4) For leaks that were repaired during the reporting period 
(including delayed repairs), identification of the monitoring location 
associated with the repaired leak, the total strippable hydrocarbon 
concentration measured during re-monitoring to verify repair, and the 
re-monitoring date (i.e., the effective date of repair); and
    (5) For each delayed repair, identification of the monitoring 
location associated with the leak for which repair is delayed, the date 
when the delay of repair began, the date the repair is expected to be 
completed (if the leak is not repaired during the reporting period), 
the total strippable hydrocarbon concentration and date of each 
monitoring event conducted on the

[[Page 54336]]

delayed repair during the reporting period, and an estimate of the 
potential strippable hydrocarbon emissions over the reporting period 
associated with the delayed repair.
0
14. Section 63.1095 is amended by:
0
a. Revising paragraphs (a)(1) introductory text;
0
b. Adding paragraph (a)(1)(vi);
0
c. Revising paragraphs (a)(3), (b) introductory text, and (b)(1); and
0
d. Adding paragraph (b)(3).
    The revisions and additions read as follows:


Sec.  63.1095   What specific requirements must I comply with?

* * * * *
    (a) * * *
    (1) Route the continuous butadiene stream to a treatment process or 
wastewater treatment system used to treat benzene waste streams that 
complies with the standards specified in 40 CFR 61.348. Comply with the 
requirements of 40 CFR part 61, subpart FF; with the changes in Table 2 
to this subpart, and as specified in paragraphs (a)(1)(i) through (vi) 
of this section.
* * * * *
    (vi) Beginning no later than the compliance dates specified in 
Sec.  63.1081(b), if you use a steam-assisted, air-assisted, non-
assisted, or pressure-assisted multi-point flare to comply with 40 CFR 
part 61, subpart FF, then you must comply with the requirements of 40 
CFR 63.1103(e)(4) in lieu of 40 CFR 61.349(a)(2)(iii) and (d), 40 CFR 
61.354(c)(3), 40 CFR 61.356(f)(2)(i)(D) and (j)(7), and 40 CFR 
61.357(d)(7)(iv)(F).
* * * * *
    (3) Before [date 3 years after date of publication of final rule in 
the Federal Register], if the total annual benzene quantity from waste 
at your facility is less than 10 Mg/yr, as determined according to 40 
CFR 61.342(a), comply with the requirements of this section at all 
times except during periods of startup, shutdown, and malfunction, if 
the startup, shutdown, or malfunction precludes the ability of the 
affected source to comply with the requirements of this section and the 
owner or operator follows the provisions for periods of startup, 
shutdown, and malfunction, as specified in Sec.  63.1111. Beginning on 
[date 3 years after date of publication of final rule in the Federal 
Register], if the total annual benzene quantity from waste at your 
facility is less than 10 Mg/yr, as determined according to 40 CFR 
61.342(a), you must comply with the requirements of this section at all 
times.
    (b) Waste streams that contain benzene. For waste streams that 
contain benzene, you must comply with the requirements of 40 CFR part 
61, subpart FF, except as specified in Table 2 to this subpart and 
paragraph (b)(3) of this section. You must manage and treat waste 
streams that contain benzene as specified in either paragraph (b)(1) or 
(2) of this section.
    (1) If the total annual benzene quantity from waste at your 
facility is less than 10 Mg/yr, as determined according to 40 CFR 
61.342(a), manage and treat spent caustic waste streams and dilution 
steam blowdown waste streams according to 40 CFR 61.342(c)(1) through 
(c)(3)(i). Before [date 3 years after date of publication of final rule 
in the Federal Register], the requirements of this paragraph (b)(1) 
shall apply at all times except during periods of startup, shutdown, 
and malfunction, if the startup, shutdown, or malfunction precludes the 
ability of the affected source to comply with the requirements of this 
section and the owner or operator follows the provisions for periods of 
startup, shutdown, and malfunction, as specified in Sec.  63.1111. 
Beginning on [date 3 years after date of publication of final rule in 
the Federal Register], the requirements of this paragraph (b)(1) shall 
apply at all times.
* * * * *
    (3) Beginning no later than the compliance dates specified in Sec.  
63.1081(b), if you use a steam-assisted, air-assisted, non-assisted, or 
pressure-assisted multi-point flare to comply with 40 CFR part 61, 
subpart FF, then you must comply with the requirements of 40 CFR 
63.1103(e)(4) in lieu of 40 CFR 61.349(a)(2)(iii) and (d), 40 CFR 
61.354(c)(3), 40 CFR 61.356(f)(2)(i)(D) and (j)(7), and 40 CFR 
61.357(d)(7)(iv)(F).
0
15. Table 2 to subpart XX of part 63 is amended by revising the first 
column heading, third entry to row 1, and the first two entries to row 
2 to read as follows:

    Table 2 to Subpart XX of Part 63--Requirements of 40 CFR Part 61,
    Subpart FF, Not Included in the Requirements for This Subpart and
                         Alternate Requirements
------------------------------------------------------------------------
 If the total annual benzene
quantity for waste from your   Do not comply with:     Instead, comply
      facility is * * *                                     with:
------------------------------------------------------------------------
1. Less than 10 Mg/yr.......  40 CFR 61.340.......  Sec.   63.1093.
                              40 CFR                There is no
                               61.342(c)(3)(ii),     equivalent
                               (d), and (e).         requirement.
                              40 CFR 61.342(f)....  Sec.   63.1096.
 
                              * * * * * * *
2. Greater than or equal to   40 CFR 61.340.......  Sec.   63.1093.
 10 Mg/yr.
                              40 CFR 61.342(f)....  Sec.   63.1096.
 
                              * * * * * * *
------------------------------------------------------------------------

0
16. Section 63.1100 is amended by:
0
a. Revising the heading to Table 1 to Sec.  63.1100(a);
0
b. Revising the rows ``Carbon Black Production,'' ``Cyanide Chemicals 
Manufacturing,'' ``Ethylene Production,'' and ``Spandex Production''; 
and revising footnote c to Table 1 to Sec.  63.1100(a);
0
c. Revising paragraphs (b), (g) introductory text, and (g)(4)(ii);
0
d. Adding paragraph (g)(4)(iii);
0
e. Revising paragraph (g)(5); and
0
f. Adding paragraph (g)(7).
    The revisions and additions read as follows:


Sec.  63.1100   Applicability.

    (a) * * *

[[Page 54337]]



                                                              Table 1 to Sec.   63.1100(a)--Source Category MACT \a\ Applicability
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                                                               Source category
         Source category              Storage vessels        Process vents        Transfer racks         Equipment leaks         Wastewater streams            Other          MACT requirements
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 
                                                                                          * * * * * * *
Carbon Black Production..........  No..................  Yes.................  No..................  No.....................  No.....................  No..................  Sec.   63.1103(f).
Cyanide Chemicals Manufacturing..  Yes.................  Yes.................  Yes.................  Yes....................  Yes....................  No..................  Sec.   63.1103(g).
Ethylene Production..............  Yes.................  Yes.................  Yes.................  Yes....................  Yes....................  Yes \c\.............  Sec.   63.1103(e).
 
                                                                                          * * * * * * *
Spandex Production...............  Yes.................  Yes.................  No..................  No.....................  No.....................  Yes \d\.............  Sec.   63.1103(h).
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Maximum achievable control technology.
\b\ Fiber spinning lines using spinning solution or suspension containing acrylonitrile.
\c\ Heat exchange systems as defined in Sec.   63.1082(b).
\d\ Fiber spinning lines.

    (b) Subpart A requirements. The following provisions of subpart A 
of this part (General Provisions), Sec. Sec.  63.1 through 63.5, and 
Sec. Sec.  63.12 through 63.15, apply to owners or operators of 
affected sources subject to this subpart. Beginning no later than the 
compliance dates specified in Sec.  63.1102(c), for ethylene production 
affected sources, Sec. Sec.  63.7, 63.8, 63.10(c), and 63.10(e) also 
apply, except for Sec.  63.8(c)(1)(iii).
* * * * *
    (g) Overlap with other regulations. Paragraphs (g)(1) through (7) 
of this section specify the applicability of this subpart YY emission 
point requirements when other rules may apply. Where subpart YY of this 
part allows an owner or operator an option to comply with one or 
another regulation to comply with subpart YY of this part, an owner or 
operator must report which regulation they choose to comply with in the 
Notification of Compliance Status report required by Sec.  
63.1110(a)(4).
    (4) * * *
    (ii) After the compliance dates specified in Sec.  63.1102, 
equipment that must be controlled according to this subpart and subpart 
H of this part is in compliance with the equipment leak requirements of 
this subpart if it complies with either set of requirements. For 
ethylene production affected sources, the requirement in Sec.  
63.1103(e)(9)(i) also applies. The owner or operator must specify the 
rule with which they will comply in the Notification of Compliance 
Status report required by Sec.  63.1110(a)(4).
    (iii) Beginning no later than the compliance dates specified in 
Sec.  63.1102(c), for ethylene production affected sources, equipment 
that must be controlled according to this subpart and subpart VVa of 40 
CFR part 60 is required only to comply with the equipment leak 
requirements of this subpart, except the owner or operator must also 
comply with the calibration drift assessment requirements specified at 
Sec.  60.485a(b)(2). When complying with the calibration drift 
assessment requirements at Sec.  60.485a(b)(2), the requirement at 
Sec.  60.486a(e)(8)(v) to record the instrument reading for each scale 
used applies.
    (5) Overlap of subpart YY with other regulations for wastewater for 
source categories other than ethylene production. (i) After the 
compliance dates specified in Sec.  63.1102 for an affected source 
subject to this subpart, a wastewater stream that is subject to the 
wastewater requirements of this subpart and the wastewater requirements 
of subparts F, G, and H of this part (collectively known as the 
``HON'') shall be deemed to be in compliance with the requirements of 
this subpart if it complies with either set of requirements. In any 
instance where a source subject to this subpart is collocated with a 
Synthetic Organic Chemical Manufacturing Industry (SOCMI) source, and a 
single wastewater treatment facility treats both Group 1 wastewaters 
and wastewater residuals from the source subject to this subpart and 
wastewaters from the SOCMI source, a certification by the treatment 
facility that they will manage and treat the waste in conformity with 
the specific control requirements set forth in 40 CFR 63.133 through 
63.147 will also be deemed sufficient to satisfy the certification 
requirements for wastewater treatment under this subpart.
* * * * *
    (7) Overlap of subpart YY with other regulations for flares for the 
ethylene production source category. (i) Beginning no later than the 
compliance dates specified in Sec.  63.1102(c), flares that are subject 
to the provisions of 40 CFR 60.18 or 63.11 and used as a control device 
for an emission point subject to the requirements in Table 7 to Sec.  
63.1103(e) are required to comply only with the provisions specified in 
Sec.  63.1103(e)(4). At any time before the compliance dates specified 
in Sec.  63.1102(c), flares that are subject to the provisions of 40 
CFR 60.18 or 63.11 and elect to comply with the requirements in Sec.  
63.1103(e)(4) are required to comply only with the provisions specified 
in this subpart.
0
17. Section 63.1101 is amended by revising the definitions of 
``Pressure relief device or value'' and ``Shutdown'' to read as 
follows:


Sec.  63.1101   Definitions.

* * * * *
    Pressure relief device or valve means a safety device used to 
prevent operating pressures from exceeding the maximum allowable 
working pressure of the process equipment. A common pressure relief 
device is a spring-loaded pressure relief valve. Devices that are 
actuated either by a pressure of less than or equal to 2.5 pounds per 
square inch gauge or by a vacuum are not pressure relief devices. This 
definition does not apply to ethylene production affected sources.
* * * * *
    Shutdown means the cessation of operation of an affected source or 
equipment that is used to comply with this subpart, or the emptying and 
degassing of a storage vessel. For the purposes of this subpart, 
shutdown includes, but is not limited to, periodic maintenance, 
replacement of equipment, or repair. Shutdown does not include the 
routine rinsing or washing of equipment in batch operation between 
batches. Shutdown includes the decoking of ethylene cracking furnaces.
* * * * *
0
18. Section 63.1102 is amended by revising paragraph (a) introductory 
text and adding paragraph (c) to read as follows:

[[Page 54338]]

Sec.  63.1102   Compliance schedule.

    (a) General requirements. Affected sources, as defined in Sec.  
63.1103(a)(1)(i) for acetyl resins production, Sec.  63.1103(b)(1)(i) 
for acrylic and modacrylic fiber production, Sec.  63.1103(c)(1)(i) for 
hydrogen fluoride production, Sec.  63.1103(d)(1)(i) for polycarbonate 
production, Sec.  63.1103(e)(1)(i) for ethylene production, Sec.  
63.1103(f)(1)(i) for carbon black production, Sec.  63.1103(g)(1)(i) 
for cyanide chemicals manufacturing, or Sec.  63.1103(h)(1)(i) for 
spandex production shall comply with the appropriate provisions of this 
subpart and the subparts referenced by this subpart according to the 
schedule in paragraphs (a)(1) or (2) of this section, as appropriate, 
except as provided in paragraphs (b) and (c) of this section. Proposal 
and effective dates are specified in Table 1 to this section.
* * * * *
    (c) All ethylene production affected sources that commenced 
construction or reconstruction on or before October 9, 2019, must be in 
compliance with the requirements listed in paragraphs (c)(1) through 
(13) of this section upon initial startup or [date 3 years after date 
of publication of final rule in the Federal Register], whichever is 
later. All ethylene production affected sources that commenced 
construction or reconstruction after October 9, 2019, must be in 
compliance with the requirements listed in paragraphs (c)(1) through 
(13) of this section upon initial startup, or [date of publication of 
final rule in the Federal Register], whichever is later.
    (1) Overlap requirements specified in Sec.  63.1100(g)(4)(iii) and 
(7), if applicable.
    (2) The storage vessel requirements specified in paragraphs (a)(2), 
(b)(2), and (c)(1)(ii) of Table 7 to Sec.  63.1103(e).
    (3) The ethylene process vent requirements specified in paragraph 
(d)(1)(ii) of Table 7 to Sec.  63.1103(e).
    (4) The transfer rack requirements specified in Sec.  
63.1105(a)(5).
    (5) The equipment requirements specified in paragraph (f)(1)(ii) of 
Table 7 to Sec.  63.1103(e), and Sec.  63.1107(h).
    (6) The bypass line requirements specified in paragraph (i) of 
Table 7 to Sec.  63.1103(e), and Sec.  63.1103(e)(6).
    (7) The decoking requirements for ethylene cracking furnaces 
specified in paragraph (j) of Table 7 to Sec.  63.1103(e), and Sec.  
63.1103(e)(7) and (8).
    (8) The flare requirements specified in Sec.  63.1103(e)(4).
    (9) The maintenance vent requirements specified in Sec.  
63.1103(e)(5).
    (10) The requirements specified in Sec.  63.1103(e)(9).
    (11) The requirements in Sec.  63.1108(a)(4)(i), (b)(1)(ii), 
(b)(2), and (b)(4)(ii)(B).
    (12) The recordkeeping requirements specified in Sec.  63.1109(e) 
through (i).
    (13) The reporting requirements specified in Sec.  63.1110(a)(10), 
(d)(1)(iv) and (v), and (e)(4) through (8).
* * * * *
0
19. Section 63.1103 is amended:
0
a. By revising the definition of ``In organic hazardous air pollutant 
or in organic HAP service'' in paragraph (b)(2);
0
b. By revising paragraphs (e)(1)(i) introductory text, (e)(1)(i)(F), 
and (e)(1)(ii)(J);
0
c. In paragraph (e)(2) by;
0
i. Adding in alphabetical order a definition for ``Decoking 
operation'';
0
ii. Revising the definition of ``Ethylene process vent'';
0
iii. Adding in alphabetical order a definition for ``Force majeure 
event'';
0
iv. Removing the definition of ``Heat exchange system'';
0
v. Adding in alphabetical order, a definition for ``Periodically 
discharged,'' ``Pressure-assisted multi-point flare,'' ``Pressure 
relief device,'' ``Radiant tube(s),'' and ``Relief valve'';
0
d. By revising paragraph (e)(3);
0
e. By revising Table 7 to Sec.  63.1103(e); and
0
f. By adding paragraphs (e)(4) through (9).
    The revisions and additions read as follows:


Sec.  63.1103   Source category-specific applicability, definitions, 
and requirements.

* * * * *
    (b) * * *
    (2) * * *
* * * * *
    In organic hazardous air pollutant or in organic HAP service means, 
for acrylic and modacrylic fiber production affected sources, that a 
piece of equipment either contains or contacts a fluid (liquid or gas) 
that is at least 10 percent by weight of total organic HAP as 
determined according to the provisions of Sec.  63.180(d). The 
provisions of Sec.  63.180(d) also specify how to determine that a 
piece of equipment is not in organic HAP service.
* * * * *
    (e) Ethylene production applicability, definitions, and 
requirements--(1) Applicability--(i) Affected source. For the ethylene 
production (as defined in paragraph (e)(2) of this section) source 
category, the affected source comprises all emission points listed in 
paragraphs (e)(1)(i)(A) through (G) of this section that are associated 
with an ethylene production unit that is located at a major source, as 
defined in section 112(a) of the Act.
* * * * *
    (F) All heat exchange systems (as defined in Sec.  63.1082(b)) 
associated with an ethylene production unit.
* * * * *
    (ii) * * *
    (J) Air emissions from all ethylene cracking furnaces.
* * * * *
    (2) Definitions.
    Decoking operation means the coke combustion activity that occurs 
inside the radiant tube(s) in the ethylene cracking furnace firebox.
    Ethylene process vent means a gas stream with a flow rate greater 
than 0.005 standard cubic meters per minute containing greater than 20 
parts per million by volume HAP that is continuously discharged, or 
periodically discharged on and after [date 3 years after date of 
publication of final rule in the Federal Register], during operation of 
an ethylene production unit. Ethylene process vents are gas streams 
that are discharged to the atmosphere (or the point of entry into a 
control device, if any) either directly or after passing through one or 
more recovery devices. Ethylene process vents do not include:
    (A) Pressure relief device discharges;
    (B) Gaseous streams routed to a fuel gas system, including any 
flares using fuel gas, of which less than 50 percent of the fuel gas is 
derived from an ethylene production unit;
    (C) Gaseous streams routed to a fuel gas system whereby any flares 
using fuel gas, of which 50 percent or more of the fuel gas is derived 
from an ethylene production unit, comply with Sec.  63.1103(e)(4) 
beginning no later than the compliance dates specified in Sec.  
63.1102(c);
    (D) Leaks from equipment regulated under this subpart;
    (E) Episodic or nonroutine releases such as those associated with 
startup, shutdown, and malfunction until [date 3 years after date of 
publication of final rule in the Federal Register]; and
    (F) In situ sampling systems (online analyzers) until [date 3 years 
after date of publication of final rule in the Federal Register].
* * * * *
    Force majeure event means a release of HAP, either directly to the 
atmosphere from a pressure relief device or discharged via a flare, 
that is demonstrated to the satisfaction of the Administrator to result 
from an event beyond the owner or operator's control, such as natural 
disasters; acts of war or terrorism; loss of a utility external to the

[[Page 54339]]

ethylene production unit (e.g., external power curtailment), excluding 
power curtailment due to an interruptible service agreement; and fire 
or explosion originating at a near or adjoining facility outside of the 
ethylene production unit that impacts the ethylene production unit's 
ability to operate.
* * * * *
    Periodically discharged means gas stream discharges that are 
intermittent for which the total organic HAP concentration is greater 
than 20 parts per million by volume and total volatile organic compound 
emissions are 50 pounds per day or more. These intermittent discharges 
are associated with routine operations, maintenance activities, 
startups, shutdowns, malfunctions, or process upsets and do not include 
pressure relief device discharges or discharges classified as 
maintenance vents.
    Pressure-assisted multi-point flare means a flare system consisting 
of multiple flare burners in staged arrays whereby the vent stream 
pressure is used to promote mixing and smokeless operation at the flare 
burner tips. Pressure-assisted multi-point flares are designed for 
smokeless operation at velocities up to Mach = 1 conditions (i.e., 
sonic conditions), can be elevated or at ground level, and typically 
use cross-lighting for flame propagation to combust any flare vent 
gases sent to a particular stage of flare burners.
    Pressure relief device means a valve, rupture disk, or similar 
device used only to release an unplanned, nonroutine discharge of gas 
from process equipment in order to avoid safety hazards or equipment 
damage. A pressure relief device discharge can result from an operator 
error, a malfunction such as a power failure or equipment failure, or 
other unexpected cause. Such devices include conventional, spring-
actuated relief valves, balanced bellows relief valves, pilot-operated 
relief valves, rupture disks, and breaking, buckling, or shearing pin 
devices.
    Radiant tube(s) means any portion of the tube coil assembly located 
within the ethylene cracking furnace firebox whereby a thermal cracking 
reaction of hydrocarbons (in the presence of steam) occurs. 
Hydrocarbons and steam pass through the radiant tube(s) of the ethylene 
cracking furnace during normal operation and coke is removed from the 
inside of the radiant tube(s) during decoking operation.
    Relief valve means a type of pressure relief device that is 
designed to re-close after the pressure relief.
* * * * *
    (3) Requirements. The owner or operator must control organic HAP 
emissions from each affected source emission point by meeting the 
applicable requirements specified in Table 7 to this section. An owner 
or operator must perform the applicability assessment procedures and 
methods for process vents specified in Sec.  63.1104, except for 
paragraphs (d), (g), (h) through (j), (l)(1), and (n). An owner or 
operator must perform the applicability assessment procedures and 
methods for equipment leaks specified in Sec.  63.1107. General 
compliance, recordkeeping, and reporting requirements are specified in 
Sec.  Sec.  63.1108 through 63.1112. Before [date 3 years after date of 
publication of final rule in the Federal Register], minimization of 
emissions from startup, shutdown, and malfunctions must be addressed in 
the startup, shutdown, and malfunction plan required by Sec.  63.1111; 
the plan must also establish reporting and recordkeeping of such 
events. A startup, shutdown, and malfunction plan is not required on 
and after [date 3 years after date of publication of final rule in the 
Federal Register] and the requirements specified in Sec.  63.1111 no 
longer apply; however, for historical compliance purposes, a copy of 
the plan must be retained and available on-site for five years after 
[date 3 years after date of publication of final rule in the Federal 
Register]. Except as specified in paragraph (e)(4)(i) of this section, 
procedures for approval of alternate means of emission limitations are 
specified in Sec.  63.1113.

   Table 7 to Sec.   63.1103(e)--What Are My Requirements if I Own or
     Operate an Ethylene Production Existing or New Affected Source?
------------------------------------------------------------------------
 If you own or operate . . .      And if . . .       Then you must . . .
------------------------------------------------------------------------
(a) A storage vessel (as      (1) Except as         (i) Fill the vessel
 defined in Sec.   63.1101)    specified in          through a submerged
 that stores liquid            paragraph (a)(2) of   pipe; or
 containing organic HAP.       this table, the      (ii) Comply with the
                               maximum true vapor    requirements in
                               pressure of total     paragraph (b)(1)(i)
                               organic HAP is        or (ii) of this
                               >=3.4 kilopascals     table.
                               but <76.6
                               kilopascals; and
                               the capacity of the
                               vessel is >=4 cubic
                               meters but <95
                               cubic meters.
                              (2) Beginning no      (i) Fill the vessel
                               later than the        through a submerged
                               compliance dates      pipe; or
                               specified in Sec.    (ii) Comply with the
                               63.1102(c), the       requirements in
                               maximum true vapor    paragraph (b)(2)(i)
                               pressure of total     or (ii) of this
                               organic HAP is        table.
                               >=0.69 kilopascals
                               but <76.6
                               kilopascals; and
                               the capacity of the
                               vessel is >=4 cubic
                               meters but <59
                               cubic meters.
(b) A storage vessel (as      (1) Except as         (i) Comply with the
 defined in Sec.   63.1101)    specified in          requirements of
 that stores liquid            paragraph (b)(2) of   subpart WW of this
 containing organic HAP.       this table, the       part; or
                               maximum true vapor   (ii) Reduce
                               pressure of total     emissions of total
                               organic HAP is        organic HAP by 98
                               >=3.4 kilopascals     weight-percent by
                               but <76.6             venting emissions
                               kilopascals; and      through a closed
                               the capacity of the   vent system to any
                               vessel is >=95        combination of
                               cubic meters.         control devices and
                                                     meet the
                                                     requirements of
                                                     Sec.
                                                     63.982(a)(1).

[[Page 54340]]

 
                              (2) Beginning no      (i) Comply with the
                               later than the        requirements of
                               compliance dates      subpart WW of this
                               specified in Sec.     part; \a\ or (ii)
                               63.1102(c), the       Reduce emissions of
                               maximum true vapor    total organic HAP
                               pressure of total     by 98 weight-
                               organic HAP is        percent by venting
                               >=0.69 kilopascals    emissions through a
                               but <76.6             closed vent system
                               kilopascals; and      to a flare and meet
                               the capacity of the   the requirements of
                               vessel is >=59        Sec.   63.983 and
                               cubic meters.         paragraphs (e)(4)
                                                     and (9) of this
                                                     section; or (iii)
                                                     Reduce emissions of
                                                     total organic HAP
                                                     by 98 weight-
                                                     percent by venting
                                                     emissions through a
                                                     closed vent system
                                                     to any combination
                                                     of non-flare
                                                     control devices and
                                                     meet the
                                                     requirements
                                                     specified in Sec.
                                                     63.982(c)(1) and
                                                     (e)(9) of this
                                                     section; or (iv)
                                                     Reduce emissions of
                                                     total organic HAP
                                                     by 98 weight-
                                                     percent by routing
                                                     emissions to a fuel
                                                     gas system \b\ or
                                                     process and meet
                                                     the requirements
                                                     specified in Sec.
                                                     63.982(d) and
                                                     (e)(9) of this
                                                     section.
(c) A storage vessel (as      (1) The maximum true  (i) Except as
 defined in Sec.   63.1101)    vapor pressure of     specified in
 that stores liquid            total organic HAP     paragraph
 containing organic HAP.       is >=76.6             (c)(1)(ii) of this
                               kilopascals.          table, reduce
                                                     emissions of total
                                                     organic HAP by 98
                                                     weight-percent by
                                                     venting emissions
                                                     through a closed
                                                     vent system to any
                                                     combination of
                                                     control devices and
                                                     meet the
                                                     requirements of
                                                     Sec.
                                                     63.982(a)(1). (ii)
                                                     Beginning no later
                                                     than the compliance
                                                     dates specified in
                                                     Sec.   63.1102(c),
                                                     comply with
                                                     paragraph
                                                     (c)(1)(ii)(A), (B),
                                                     or (C) of this
                                                     section. (A) Reduce
                                                     emissions of total
                                                     organic HAP by 98
                                                     weight-percent by
                                                     venting emissions
                                                     through a closed
                                                     vent system to a
                                                     flare and meet the
                                                     requirements of
                                                     Sec.   63.983 and
                                                     paragraphs (e)(4)
                                                     and (9) of this
                                                     section; or (B)
                                                     Reduce emissions of
                                                     total organic HAP
                                                     by 98 weight-
                                                     percent by venting
                                                     emissions through a
                                                     closed vent system
                                                     to any combination
                                                     of non-flare
                                                     control devices and
                                                     meet the
                                                     requirements
                                                     specified in Sec.
                                                     63.982(c)(1) and
                                                     (e)(9) of this
                                                     section; or (C)
                                                     Reduce emissions of
                                                     total organic HAP
                                                     by 98 weight-
                                                     percent by routing
                                                     emissions to a fuel
                                                     gas system \b\ or
                                                     process and meet
                                                     the requirements
                                                     specified in Sec.
                                                     63.982(d) and
                                                     (e)(9) of this
                                                     section.
(d) An ethylene process vent  (1) The process vent  (i) Except as
 (as defined in paragraph      is at an existing     specified in
 (e)(2) of this section).      source and the vent   paragraph
                               stream has a flow     (d)(1)(ii) of this
                               rate >=0.011 scmm     table, reduce
                               and a total organic   emissions of
                               HAP concentration     organic HAP by 98
                               >=50 parts per        weight-percent; or
                               million by volume     reduce organic HAP
                               on a dry basis; or    or TOC to a
                               the process vent is   concentration of 20
                               at a new source and   parts per million
                               the vent stream has   by volume on a dry
                               a flow rate >=0.008   basis corrected to
                               scmm and a total      3% oxygen;
                               organic HAP           whichever is less
                               concentration >=30    stringent, by
                               parts per million     venting emissions
                               by volume on a dry    through a closed
                               basis.                vent system to any
                                                     combination of
                                                     control devices and
                                                     meet the
                                                     requirements
                                                     specified in Sec.
                                                     63.982(b) and
                                                     (c)(2). (ii)
                                                     Beginning no later
                                                     than the compliance
                                                     dates specified in
                                                     Sec.   63.1102(c),
                                                     comply with the
                                                     maintenance vent
                                                     requirements
                                                     specified in
                                                     paragraph (e)(5) of
                                                     this section and
                                                     either paragraph
                                                     (d)(1)(ii)(A) or
                                                     (B) of this table.
                                                     (A) Reduce
                                                     emissions of
                                                     organic HAP by 98
                                                     weight-percent; or
                                                     reduce organic HAP
                                                     or TOC to a
                                                     concentration of 20
                                                     parts per million
                                                     by volume on a dry
                                                     basis corrected to
                                                     3% oxygen;
                                                     whichever is less
                                                     stringent, by
                                                     venting emissions
                                                     through a closed
                                                     vent system to a
                                                     flare and meet the
                                                     requirements of
                                                     Sec.   63.983 and
                                                     paragraphs (e)(4)
                                                     and (9) of this
                                                     section; or (B)
                                                     Reduce emissions of
                                                     organic HAP by 98
                                                     weight-percent; or
                                                     reduce organic HAP
                                                     or TOC to a
                                                     concentration of 20
                                                     parts per million
                                                     by volume on a dry
                                                     basis corrected to
                                                     3% oxygen;
                                                     whichever is less
                                                     stringent, by
                                                     venting emissions
                                                     through a closed
                                                     vent system to any
                                                     combination of non-
                                                     flare control
                                                     devices and meet
                                                     the requirements
                                                     specified in Sec.
                                                     63.982(c)(2) and
                                                     (e)(9) of this
                                                     section.

[[Page 54341]]

 
(e) A transfer rack (as       (1) Materials loaded  (i) Reduce emissions
 defined in paragraph (e)(2)   have a true vapor     of organic HAP by
 of this section).             pressure of total     98 weight-percent;
                               organic HAP >=3.4     or reduce organic
                               kilopascals and       HAP or TOC to a
                               >=76 cubic meters     concentration of 20
                               per day (averaged     parts per million
                               over any              by volume on a dry
                               consecutive 30-day    basis corrected to
                               period) of HAP-       3% oxygen;
                               containing material   whichever is less
                               is loaded.            stringent, by
                                                     venting emissions
                                                     through a closed
                                                     vent system to any
                                                     combination of
                                                     control devices as
                                                     specified in Sec.
                                                     63.1105 and meet
                                                     the requirements
                                                     specified in
                                                     paragraph (e)(9) of
                                                     this section.; or
                                                    (ii) Install process
                                                     piping designed to
                                                     collect the HAP-
                                                     containing vapors
                                                     displaced from tank
                                                     trucks or railcars
                                                     during loading and
                                                     to route it to a
                                                     process, a fuel gas
                                                     system, or a vapor
                                                     balance system, as
                                                     specified in Sec.
                                                     63.1105 and meet
                                                     the requirements
                                                     specified in
                                                     paragraph (e)(9) of
                                                     this section.\b\
(f) Equipment (as defined in  (1) The equipment     (i) Except as
 Sec.   63.1101) that          contains or           specified in
 contains or contacts          contacts >=5 weight-  paragraph
 organic HAP.                  percent organic       (f)(1)(ii) of this
                               HAP; and the          table, comply with
                               equipment is not in   the requirements of
                               vacuum service.       subpart UU of this
                                                     part. (ii)
                                                     Beginning no later
                                                     than the compliance
                                                     dates specified in
                                                     Sec.   63.1102(c),
                                                     comply with the
                                                     requirements of
                                                     paragraph (e)(9) of
                                                     this section and
                                                     subpart UU of this
                                                     part, except
                                                     instead of
                                                     complying with the
                                                     pressure relief
                                                     device requirements
                                                     of Sec.   63.1030
                                                     of subpart UU, meet
                                                     the requirements of
                                                     Sec.   63.1107(h),
                                                     and in lieu of the
                                                     flare requirement
                                                     of Sec.
                                                     63.1034(b)(2)(iii),
                                                     comply with the
                                                     requirements
                                                     specified in
                                                     paragraph (e)(4) of
                                                     this section.\b\
(g) Processes that generate   (1) The waste stream  (i) Comply with the
 waste (as defined in          contains any of the   waste requirements
 paragraph (e)(2) of this      following HAP:        of subpart XX of
 section.                      Benzene, cumene,      this part. For
                               ethyl benzene,        ethylene production
                               hexane,               unit waste stream
                               naphthalene,          requirements, terms
                               styrene, toluene, o-  have the meanings
                               xylene, m-xylene, p-  specified in
                               xylene, or 1,3-       subpart XX.
                               butadiene.
(h) A heat exchange system    ....................  Comply with the heat
 (as defined in Sec.                                 exchange system
 63.1082(b)).                                        requirements of
                                                     subpart XX of this
                                                     part.
(i) A closed vent system      (1) The bypass line   (i) Beginning no
 that contains one or more     could divert a vent   later than the
 bypass lines.                 stream directly to    compliance dates
                               the atmosphere or     specified in Sec.
                               to a control device   63.1102(c), comply
                               not meeting the       with the
                               requirements in       requirements
                               this table.           specified in
                                                     paragraphs (e)(6)
                                                     and (9) of this
                                                     section.
(j) A decoking operation      ....................  Beginning no later
 associated with an ethylene                         than the compliance
 cracking furnace.                                   dates specified in
                                                     Sec.   63.1102(c),
                                                     comply with the
                                                     requirements
                                                     specified in
                                                     paragraphs (e)(7)
                                                     and (8) of this
                                                     section.
------------------------------------------------------------------------
\a\ For owners or operators that choose to comply with the requirements
  of subpart WW of this part for storage vessels with a capacity >=59
  cubic meters, the timing for installation of the required controls is
  specified within subpart WW of this part. All references to
  ``promulgation of the referencing subpart'' and ``the promulgation
  date of the referencing subpart'' in subpart WW of this part means
  [date of publication of final rule in the Federal Register].
\b\ Beginning no later than the compliance dates specified in Sec.
  63.1102(c), any flare using fuel gas from a fuel gas system, of which
  50 percent or more of the fuel gas is derived from an ethylene
  production unit, must be in compliance with paragraph (e)(4) of this
  section.

    (4) Flares. Beginning no later than the compliance dates specified 
in Sec.  63.1102(c), if a steam-assisted, air-assisted, non-assisted, 
or pressure-assisted multi-point flare is used as a control device for 
an emission point subject to the requirements in Table 7 to this 
section, then the owner or operator must meet the applicable 
requirements for flares as specified in Sec. Sec.  63.670 and 63.671 of 
subpart CC, including the provisions in Tables 12 and 13 to subpart CC 
of this part, except as specified in paragraphs (e)(4)(i) through (xi) 
of this section. This requirement also applies to any flare using fuel 
gas from a fuel gas system, of which 50 percent or more of the fuel gas 
is derived from an ethylene production unit, being used to control an 
emission point subject to the requirements in Table 7 of this section. 
For purposes of compliance with this paragraph, the following terms are 
defined in Sec.  63.641 of subpart CC: Assist air, assist steam, center 
steam, combustion zone, combustion zone gas, flare, flare purge gas, 
flare supplemental gas, flare sweep gas, flare vent gas, lower steam, 
net heating value, perimeter assist air, pilot gas, premix assist air, 
total steam, and upper steam.
    (i) The owner or operator may elect to comply with the alternative 
means of emissions limitation requirements specified in of Sec.  
63.670(r) of subpart CC in lieu of the requirements in Sec.  63.670(d) 
through (f) of subpart CC, as applicable. However, instead of complying 
with Sec.  63.670(r)(3) of subpart CC, the owner or operator must 
submit the alternative means of emissions limitation request following 
the requirements in Sec.  63.1113.
    (ii) Instead of complying with Sec.  63.670(o)(2)(i) of subpart CC, 
the owner or operator must develop and implement the flare management 
plan no later than the compliance dates specified in Sec.  63.1102(c).

[[Page 54342]]

    (iii) Instead of complying with Sec.  63.670(o)(2)(iii) of subpart 
CC, if required to develop a flare management plan and submit it to the 
Administrator, then the owner or operator must also submit all versions 
of the plan in portable document format (PDF) to the EPA via the 
Compliance and Emissions Data Reporting Interface (CEDRI), which can be 
accessed through the EPA's Central Data Exchange (CDX) (https://cdx.epa.gov/). If you claim some of the information in your flare 
management plan is confidential business information (CBI), submit a 
version with the CBI omitted via CEDRI. A complete plan, including 
information claimed to be CBI and clearly marked as CBI, must be mailed 
to the following address: U.S. Environmental Protection Agency, Office 
of Air Quality Planning and Standards, Sector Policies and Programs 
Division, U.S. EPA Mailroom (E143-01), Attention: Ethylene Production 
Sector Lead, 109 T.W. Alexander Drive, Research Triangle Park, NC 
27711.
    (iv) Substitute ``ethylene production unit'' for each occurrence of 
``petroleum refinery.''
    (v) Each occurrence of ``refinery'' does not apply.
    (vi) If a pressure-assisted multi-point flare is used as a control 
device for an emission point subject to the requirements in Table 7 to 
this section, then the following conditions apply:
    (A) The owner or operator is not required to comply with the flare 
tip velocity requirements in Sec.  63.670(d) and (k) of subpart CC;
    (B) The owner or operator must substitute ``800'' for each 
occurrence of ``270'' in Sec.  63.670(e) of subpart CC;
    (C) The owner or operator must determine the 15-minute block 
average NHVvg using only the direct calculation method specified in 
Sec.  63.670(l)(5)(ii) of subpart CC;
    (D) Instead of complying with Sec.  63.670(b) and (g) of subpart 
CC, if a pressure-assisted multi-point flare uses cross-lighting on a 
stage of burners rather than having an individual pilot flame on each 
burner, the owner or operator must operate each stage of the pressure-
assisted multi-point flare with a flame present at all times when 
regulated material is routed to that stage of burners. Each stage of 
burners that cross-lights in the pressure-assisted multi-point flare 
must have at least two pilots with a continuously lit pilot flame 
capable of igniting all regulated material that is routed to that stage 
of burners. Each 15-minute block during which there is at least one 
minute where no pilot flame is present on a stage of burners when 
regulated material is routed to the flare is a deviation of the 
standard. Deviations in different 15-minute blocks from the same event 
are considered separate deviations. The pilot flame(s) on each stage of 
burners that use cross-lighting must be continuously monitored by a 
thermocouple or any other equivalent device used to detect the presence 
of a flame;
    (E) The owner or operator of a pressure-assisted multi-point flare 
must ensure that if a stage of burners on the flare uses cross-
lighting, that the distance between any two burners in series on that 
stage is no more than 6 feet; and
    (F) The owner or operator of a pressure-assisted multi-point flare 
must install and operate pressure monitor(s) on the main flare header, 
as well as a valve position indicator monitoring system for each 
staging valve to ensure that the flare operates within the proper range 
of conditions as specified by the manufacturer. The pressure monitor 
must meet the requirements in Table 13 of subpart CC of this part.
    (vii) If an owner or operator chooses to determine compositional 
analysis for net heating value with a continuous process mass 
spectrometer, the owner or operator must comply with the requirements 
specified in paragraphs (e)(4)(vii)(A) through (G) of this section.
    (A) The owner or operator must meet the requirements in Sec.  
63.671(e)(2). The owner or operator may augment the minimum list of 
calibration gas components found in Sec.  63.671(e)(2) with compounds 
found during a pre-survey or known to be in the gas through process 
knowledge.
    (B) Calibration gas cylinders must be certified to an accuracy of 2 
percent and traceable to National Institute of Standards and Technology 
(NIST) standards.
    (C) For unknown gas components that have similar analytical mass 
fragments to calibration compounds, the owner or operator may report 
the unknowns as an increase in the overlapped calibration gas compound. 
For unknown compounds that produce mass fragments that do not overlap 
calibration compounds, the owner or operator may use the response 
factor for the nearest molecular weight hydrocarbon in the calibration 
mix to quantify the unknown component's NHVvg.
    (D) The owner or operator may use the response factor for n-pentane 
to quantify any unknown components detected with a higher molecular 
weight than n-pentane.
    (E) The owner or operator must perform an initial calibration to 
identify mass fragment overlap and response factors for the target 
compounds.
    (F) The owner or operator must meet applicable requirements in 
Performance Specification 9 of 40 CFR part 60, appendix B, for 
continuous monitoring system acceptance including, but not limited to, 
performing an initial multi-point calibration check at three 
concentrations following the procedure in Section 10.1 and performing 
the periodic calibration requirements listed for gas chromatographs in 
Table 13 of 40 CFR part 63, subpart CC, for the process mass 
spectrometer. The owner or operator may use the alternative sampling 
line temperature allowed under Net Heating Value by Gas Chromatograph 
in Table 13 of 40 CFR part 63, subpart CC.
    (G) The average instrument calibration error (CE) for each 
calibration compound at any calibration concentration must not differ 
by more than 10 percent from the certified cylinder gas value. The CE 
for each component in the calibration blend must be calculated using 
the following equation:
[GRAPHIC] [TIFF OMITTED] TP09OC19.000

Where:

Cm = Average instrument response (ppm)
Ca = Certified cylinder gas value (ppm)

    (viii) An owner or operator using a gas chromatograph or mass 
spectrometer for compositional analysis for net heating value may 
choose to use the CE of NHVmeasured versus the cylinder tag 
value NHV as the measure of agreement for daily calibration and 
quarterly audits in lieu of determining the compound-specific CE. The 
CE for NHV at any calibration level must not differ by more than 10 
percent from the certified cylinder gas value. The CE for must be 
calculated using the following equation:
[GRAPHIC] [TIFF OMITTED] TP09OC19.001


[[Page 54343]]


Where:

NHVmeasured = Average instrument response (Btu/scf)
NHVa = Certified cylinder gas value (Btu/scf)

    (ix) Instead of complying with Sec.  63.670(p) of subpart CC, the 
owner or operator must keep the flare monitoring records specified in 
Sec.  63.1109(e).
    (x) Instead of complying with Sec.  63.670(q) of subpart CC, the 
owner or operator must comply with the reporting requirements specified 
in Sec.  63.1110(d) and (e)(4).
    (xi) When determining compliance with the flare tip velocity and 
combustion zone operating limits specified in Sec.  63.670(d) and (e), 
the initial 15-minute block period starts with the 15-minute block that 
includes a full 15 minutes of the flaring event.
    (5) Maintenance vents. Beginning no later than the compliance dates 
specified in Sec.  63.1102(c), an owner or operator may designate a 
process vent as a maintenance vent if the vent is only used as a result 
of startup, shutdown, maintenance, or inspection of equipment where 
equipment is emptied, depressurized, degassed, or placed into service. 
The owner or operator must comply with the applicable requirements in 
paragraphs (e)(5)(i) through (iii) of this section for each maintenance 
vent, unless an extension is requested in accordance with the 
provisions in Sec.  63.6(i) of subpart A.
    (i) Prior to venting to the atmosphere, remove process liquids from 
the equipment as much as practical and depressurize the equipment to 
either: A flare meeting the requirements specified in paragraph (e)(4) 
of this section, or a non-flare control device meeting the requirements 
specified in Sec.  63.982(c)(2) of subpart SS, until one of the 
following conditions, as applicable, is met.
    (A) The vapor in the equipment served by the maintenance vent has a 
lower explosive limit (LEL) of less than 10 percent.
    (B) If there is no ability to measure the LEL of the vapor in the 
equipment based on the design of the equipment, the pressure in the 
equipment served by the maintenance vent is reduced to 5 pounds per 
square inch gauge (psig) or less. Upon opening the maintenance vent, 
active purging of the equipment cannot be used until the LEL of the 
vapors in the maintenance vent (or inside the equipment if the 
maintenance is a hatch or similar type of opening) is less than 10 
percent.
    (C) The equipment served by the maintenance vent contains less than 
50 pounds of total volatile organic compounds (VOC).
    (D) If, after applying best practices to isolate and purge 
equipment served by a maintenance vent, none of the applicable 
criterion in paragraphs (e)(5)(i)(A) through (C) of this section can be 
met prior to installing or removing a blind flange or similar equipment 
blind, then the pressure in the equipment served by the maintenance 
vent must be reduced to 2 psig or less before installing or removing 
the equipment blind. During installation or removal of the equipment 
blind, active purging of the equipment may be used provided the 
equipment pressure at the location where purge gas is introduced 
remains at 2 psig or less.
    (ii) Except for maintenance vents complying with the alternative in 
paragraph (e)(5)(i)(C) of this section, the owner or operator must 
determine the LEL or, if applicable, equipment pressure using process 
instrumentation or portable measurement devices and follow procedures 
for calibration and maintenance according to manufacturer's 
specifications.
    (iii) For maintenance vents complying with the alternative in 
paragraph (e)(5)(i)(C) of this section, the owner or operator must 
determine mass of VOC in the equipment served by the maintenance vent 
based on the equipment size and contents after considering any contents 
drained or purged from the equipment. Equipment size may be determined 
from equipment design specifications. Equipment contents may be 
determined using process knowledge.
    (6) Bypass lines. Beginning on the compliance dates specified in 
Sec.  63.1102(c), the use of a bypass line at any time on a closed vent 
system to divert a vent stream to the atmosphere or to a control device 
not meeting the requirements specified in Table 7 of this subpart is an 
emissions standards violation. Equipment such as low leg drains and 
equipment subject to the requirements specified in paragraph (f) of 
Table 7 to Sec.  63.1103(e) are not subject to this paragraph (e)(6). 
Open-ended valves or lines that use a cap, blind flange, plug, or 
second valve and follow the requirements specified in Sec.  60.482-
6(a)(2), (b), and (c) are also not subject to this paragraph (e)(6). If 
the owner or operator is subject to the bypass monitoring requirements 
of Sec.  63.983(a)(3) of subpart SS, then the owner or operator must 
continue to comply with the requirements in Sec.  63.983(a)(3) of 
subpart SS and the recordkeeping and reporting requirements in 
Sec. Sec.  63.998(d)(1)(ii) and 63.999(c)(2) of subpart SS, in addition 
to paragraph (e)(9) of this section, the recordkeeping requirements 
specified in Sec.  63.1109(g), and the reporting requirements specified 
in Sec.  63.1110(e)(6).
    (7) Decoking operation standards for ethylene cracking furnaces. 
Beginning no later than the compliance dates specified in Sec.  
63.1102(c), the owner or operator must comply with paragraph (e)(7)(i) 
of this section and also use at least two of the control measures 
specified in paragraphs (e)(7)(ii) through (v) of this section to 
minimize coke combustion emissions from the decoking of the radiant 
tube(s) in each ethylene cracking furnace.
    (i) During normal operations, conduct daily inspections of the 
firebox burners and repair all burners that are impinging on the 
radiant tube(s) as soon as practical, but not later than 1 calendar day 
after the flame impingement is found. An inspection may include, but is 
not limited to: Visual inspection of the radiant tube(s) for localized 
bright spots (this may be confirmed with a temperature gun), use of 
luminescent powders injected into the burner to illuminate the flame 
pattern, or identifying continued localized coke build-up that causes 
short runtimes between decoking cycles. A repair may include, but is 
not limited to: Taking the burner out of service, replacing the burner, 
adjusting the alignment of the burner, adjusting burner configuration, 
making burner air corrections, repairing a malfunction of the fuel 
liquid removal equipment, or adding insulation around the radiant 
tube(s).
    (ii) During decoking operations, continuously monitor (or use a gas 
detection tube every hour to monitor) the CO2 concentration 
at the radiant tube(s) outlet for indication that the coke combustion 
in the ethylene cracking furnace radiant tube(s) is complete. The owner 
or operator must immediately initiate procedures to stop the decoking 
cycle once the CO2 concentration at the radiant tube(s) 
outlet consistently reaches a level that indicates combustion of coke 
inside the radiant tube(s) is slowing or stopping.
    (iii) During decoking operations, continuously monitor the 
temperature at the radiant tube(s) outlet to ensure the coke combustion 
occurring inside the radiant tube(s) is not so aggressive (i.e., too 
hot) that it damages either the radiant tube(s) or ethylene cracking 
furnace isolation valve(s). The owner or operator must immediately 
initiate procedures to reduce the temperature at the radiant tube(s) 
outlet once the temperature reaches a level that indicates combustion 
of coke inside the radiant tube(s) is too aggressive.
    (iv) After decoking, but before returning the ethylene cracking 
furnace back to normal operations, purge the

[[Page 54344]]

radiant tube(s) with steam and verify that all air is removed.
    (v) After decoking, but before returning the ethylene cracking 
furnace back to normal operations, apply a coating material to the 
interior of the radiant tube(s) to protect against coke formation 
inside the radiant tube during normal operation.
    (8) Ethylene cracking furnace isolation valve inspections. 
Beginning no later than the compliance dates specified in Sec.  
63.1102(c), the owner or operator must conduct ethylene cracking 
furnace isolation valve inspections as specified in paragraphs 
(e)(8)(i) and (ii) of this section.
    (i) Prior to decoking operation, inspect the applicable ethylene 
cracking furnace isolation valve(s) to confirm that the radiant tube(s) 
being decoked is completely isolated from the ethylene production 
process so that no emissions generated from decoking operations are 
sent to the ethylene production process. If poor isolation is 
identified, then the owner or operator must rectify the isolation issue 
prior to continuing decoking operations to prevent leaks into the 
ethylene production process.
    (ii) Prior to returning the ethylene cracking furnace to normal 
operations after a decoking operation, inspect the applicable ethylene 
cracking furnace isolation valve(s) to confirm that the radiant tube(s) 
that was decoked is completely isolated from the decoking pot or 
furnace firebox such that no emissions are sent from the radiant 
tube(s) to the decoking pot or furnace firebox once the ethylene 
cracking furnace returns to normal operation. If poor isolation is 
identified, then the owner or operator must rectify the isolation issue 
prior to continuing normal operations to prevent product from escaping 
to the atmosphere through the decoking pot or furnace firebox.
    (9) Startup, shutdown, and malfunction referenced provisions. 
Beginning no later than the compliance dates specified in Sec.  
63.1102(c), the referenced provisions specified in paragraphs (e)(9)(i) 
through (xv) of this section do not apply when demonstrating compliance 
with paragraph (e)(3) of this section.
    (i) The second sentence of Sec.  63.181(d)(5)(i) of subpart H.
    (ii) Section 63.983(a)(5) of subpart SS.
    (iii) The phrase ``except during periods of start-up, shutdown and 
malfunction as specified in the referencing subpart'' in Sec.  
63.984(a) of subpart SS.
    (iv) The phrase ``except during periods of start-up, shutdown and 
malfunction as specified in the referencing subpart'' in Sec.  
63.985(a) of subpart SS.
    (v) The phrase ``other than start-ups, shutdowns, or malfunctions'' 
in Sec.  63.994(c)(1)(ii)(D) of subpart SS.
    (vi) Section 63.996(c)(2)(ii) of subpart SS.
    (vii) Section 63.997(e)(1)(i) of subpart SS.
    (viii) The term ``breakdowns'' from Sec.  63.998(b)(2)(i) of 
subpart SS.
    (ix) Section 63.998(b)(2)(iii) of subpart SS.
    (x) The phrase ``other than periods of startups, shutdowns, and 
malfunctions'' from Sec.  63.998(b)(5)(i)(A) of subpart SS.
    (xi) The phrase ``other than periods of startups, shutdowns, and 
malfunctions'' from Sec.  63.998(b)(5)(i)(C) of subpart SS.
    (xii) The phrase ``except as provided in paragraphs (b)(6)(i)(A) 
and (B) of this section'' from Sec.  63.998(b)(6)(i) of subpart SS.
    (xiii) The second sentence of Sec.  63.998(b)(6)(ii) of subpart SS.
    (xiv) Section 63.998(c)(1)(ii)(D) through (G) of subpart SS.
    (xv) Section 63.998(d)(1)(ii) of subpart SS.
    (xvi) Section 63.998(d)(3)(i) and (ii) of subpart SS.
    (xvii) The phrase ``(except periods of startup, shutdown, or 
malfunction)'' from Sec.  63.1026(e)(1)(ii)(A) of subpart UU.
    (xviii) The phrase ``(except periods of startup, shutdown, or 
malfunction)'' from Sec.  63.1028(e)(1)(i)(A) of subpart UU.
    (xix) The phrase ``(except periods of startup, shutdown, or 
malfunction)'' from Sec.  63.1031(b)(1) of subpart UU.
* * * * *
0
20. Section 63.1104 is amended by revising paragraph (c) to read as 
follows:


Sec.  63.1104   Process vents from continuous unit operations: 
Applicability assessment procedures and methods.

* * * * *
    (c) Applicability assessment requirement. The TOC or organic HAP 
concentrations, process vent volumetric flow rates, process vent 
heating values, process vent TOC or organic HAP emission rates, 
halogenated process vent determinations, process vent TRE index values, 
and engineering assessments for process vent control applicability 
assessment requirements are to be determined during maximum 
representative operating conditions for the process, except as provided 
in paragraph (d) of this section, or unless the Administrator specifies 
or approves alternate operating conditions. For acrylic and modacrylic 
fiber production affected sources, polycarbonate production affected 
sources, and ethylene production affected sources, operations during 
periods of malfunction shall not constitute representative conditions 
for the purpose of an applicability test. For all other affected 
sources, operations during periods of startup, shutdown, and 
malfunction shall not constitute representative conditions for the 
purpose of an applicability test.
* * * * *
0
21. Section 63.1105 is amended by revising paragraph (a) introductory 
text and adding paragraph (a)(5).


Sec.  63.1105   Transfer racks.

    (a) Design requirements. Except as specified in paragraph (a)(5) of 
this section, the owner or operator shall equip each transfer rack with 
one of the control options listed in paragraphs (a)(1) through (5) of 
this section.
* * * * *
    (5) Beginning no later than the compliance dates specified in Sec.  
63.1102(c), if emissions are vented through a closed vent system to a 
flare at an ethylene production affected source, then the owner or 
operator must comply with the requirements specified in Sec.  
63.1103(e)(4) instead of the requirements in Sec.  63.987 and the 
provisions regarding flare compliance assessments at Sec.  63.997(a) 
through (c).
* * * * *
0
22. Section 63.1107 is amended by revising paragraph (a) and adding 
paragraph (h) to read as follows:


Sec.  63.1107   Equipment leaks.

    (a) Each piece of equipment within a process unit that can 
reasonably be expected to contain equipment in organic HAP service is 
presumed to be in organic HAP service unless an owner or operator 
demonstrates that the piece of equipment is not in organic HAP service. 
For a piece of equipment to be considered not in organic HAP service, 
it must be determined that the percent organic HAP content can be 
reasonably expected not to exceed the percent by weight control 
applicability criteria specified in Sec.  63.1103 for an affected 
source on an annual average basis. For purposes of determining the 
percent organic HAP content of the process fluid that is contained in 
or contacts equipment, Method 18 of 40 CFR part 60, appendix A shall be 
used. For purposes of determining the percent organic HAP content of 
the process fluid that is contained in or contacts equipment for the 
ethylene production affected sources, the following methods shall be 
used for equipment: For equipment in gas and vapor service, as that 
term is defined in Subpart UU of this part, shall use Method 18 of 40 
CFR

[[Page 54345]]

part 60, appendix A; for equipment in liquid service, as that term is 
defined in Subpart UU of this part, shall use a combination of Method 
18 of 40 CFR part 60, appendix A, SW-846-8260B (incorporated by 
reference, see Sec.  63.14); and SW-846-8270D (incorporated by 
reference, see Sec.  63.14), as appropriate.
* * * * *
    (h) Ethylene production pressure release requirements. Beginning no 
later than the compliance dates specified in Sec.  63.1102(c), except 
as specified in paragraph (h)(4) of this section, owners or operators 
of ethylene production affected sources must comply with the 
requirements specified in paragraphs (h)(1) and (2) of this section for 
pressure relief devices, such as relief valves or rupture disks, in 
organic HAP gas or vapor service instead of the pressure relief device 
requirements of Sec.  63.1030 of subpart UU or Sec.  63.165 of subpart 
H. Beginning no later than the compliance dates specified in Sec.  
63.1102(c), except as specified in paragraphs (h)(4) and (5) of this 
section, the owner or operator must also comply with the requirements 
specified in paragraphs (h)(3), and (6) through (8) of this section for 
all pressure relief devices.
    (1) Operating requirements. Except during a pressure release, 
operate each pressure relief device in organic HAP gas or vapor service 
with an instrument reading of less than 500 ppm above background as 
measured by the method in Sec.  63.1023(b) of subpart UU or Sec.  
63.180(b) and (c) of subpart H.
    (2) Pressure release requirements. For pressure relief devices in 
organic HAP gas or vapor service, the owner or operator must comply 
with the applicable requirements in paragraphs (h)(2)(i) through (iii) 
of this section following a pressure release.
    (i) If the pressure relief device does not consist of or include a 
rupture disk, conduct instrument monitoring, as specified in Sec.  
63.1023(b) of subpart UU or Sec.  63.180(b) and (c) of subpart H, no 
later than 5 calendar days after the pressure relief device returns to 
organic HAP gas or vapor service following a pressure release to verify 
that the pressure relief device is operating with an instrument reading 
of less than 500 ppm.
    (ii) If the pressure relief device includes a rupture disk, either 
comply with the requirements in paragraph (h)(2)(i) of this section 
(and do not replace the rupture disk) or install a replacement disk as 
soon as practicable after a pressure release, but no later than 5 
calendar days after the pressure release. The owner or operator must 
conduct instrument monitoring, as specified in Sec.  63.1023(b) of 
subpart UU or Sec.  63.180(b) and (c) of subpart H, no later than 5 
calendar days after the pressure relief device returns to organic HAP 
gas or vapor service following a pressure release to verify that the 
pressure relief device is operating with an instrument reading of less 
than 500 ppm.
    (iii) If the pressure relief device consists only of a rupture 
disk, install a replacement disk as soon as practicable after a 
pressure release, but no later than 5 calendar days after the pressure 
release. The owner or operator must not initiate startup of the 
equipment served by the rupture disk until the rupture disc is 
replaced. The owner or operator must conduct instrument monitoring, as 
specified in Sec.  63.1023(b) of subpart UU or Sec.  63.180(b) and (c) 
of subpart H, no later than 5 calendar days after the pressure relief 
device returns to organic HAP gas or vapor service following a pressure 
release to verify that the pressure relief device is operating with an 
instrument reading of less than 500 ppm.
    (3) Pressure release management. Except as specified in paragraphs 
(h)(4) and (5) of this section, the owner or operator must comply with 
the requirements specified in paragraphs (h)(3)(i) through (v) of this 
section for all pressure relief devices in organic HAP service.
    (i) The owner or operator must equip each affected pressure relief 
device with a device(s) or use a monitoring system that is capable of:
    (A) Identifying the pressure release;
    (B) Recording the time and duration of each pressure release; and
    (C) Notifying operators immediately that a pressure release is 
occurring. The device or monitoring system must be either specific to 
the pressure relief device itself or must be associated with the 
process system or piping, sufficient to indicate a pressure release to 
the atmosphere. Examples of these types of devices and systems include, 
but are not limited to, a rupture disk indicator, magnetic sensor, 
motion detector on the pressure relief valve stem, flow monitor, or 
pressure monitor.
    (ii) The owner or operator must apply at least three redundant 
prevention measures to each affected pressure relief device and 
document these measures. Examples of prevention measures include:
    (A) Flow, temperature, liquid level and pressure indicators with 
deadman switches, monitors, or automatic actuators. Independent, non-
duplicative systems within this category count as separate redundant 
prevention measures.
    (B) Documented routine inspection and maintenance programs and/or 
operator training (maintenance programs and operator training may count 
as only one redundant prevention measure).
    (C) Inherently safer designs or safety instrumentation systems.
    (D) Deluge systems.
    (E) Staged relief system where the initial pressure relief device 
(with lower set release pressure) discharges to a flare or other closed 
vent system and control device.
    (iii) If any affected pressure relief device releases to atmosphere 
as a result of a pressure release event, the owner or operator must 
perform root cause analysis and corrective action analysis according to 
the requirement in paragraph (h)(6) of this section and implement 
corrective actions according to the requirements in paragraph (h)(7) of 
this section. The owner or operator must also calculate the quantity of 
organic HAP released during each pressure release event and report this 
quantity as required in Sec.  63.1110(e)(8)(iii). Calculations may be 
based on data from the pressure relief device monitoring alone or in 
combination with process parameter monitoring data and process 
knowledge.
    (iv) The owner or operator must determine the total number of 
release events that occurred during the calendar year for each affected 
pressure relief device separately. The owner or operator must also 
determine the total number of release events for each pressure relief 
device for which the root cause analysis concluded that the root cause 
was a force majeure event, as defined in Sec.  63.1103(e)(2).
    (v) Except for pressure relief devices described in paragraphs 
(h)(4) and (5) of this section, the following release events from an 
affected pressure relief device are a violation of the pressure release 
management work practice standards.
    (A) Any release event for which the root cause of the event was 
determined to be operator error or poor maintenance.
    (B) A second release event not including force majeure events from 
a single pressure relief device in a 3-calendar year period for the 
same root cause for the same equipment.
    (C) A third release event not including force majeure events from a 
single pressure relief device in a 3-calendar year period for any 
reason.
    (4) Pressure relief devices routed to a control device, process, 
fuel gas system, or drain system. (i) If all releases and potential 
leaks from a pressure relief device are routed through a closed vent 
system to a control device, back into the

[[Page 54346]]

process, a fuel gas system, or drain system, then the owner or operator 
is not required to comply with paragraph (h)(1), (2), or (3) of this 
section.
    (ii) Before the compliance dates specified in Sec.  63.1102(c), 
both the closed vent system and control device (if applicable) 
referenced in paragraph (h)(4)(i) of this section must meet the 
applicable requirements specified in Sec.  63.982(b) and (c)(2). 
Beginning no later than the compliance dates specified in Sec.  
63.1102(c), both the closed vent system and control device (if 
applicable) referenced in paragraph (h)(4)(i) of this section must meet 
the applicable requirements specified in Sec.  63.982(c)(2), Sec.  
63.983, and Sec.  63.1103(e)(4).
    (iii) The drain system (if applicable) referenced in paragraph 
(h)(4)(i) of this section must meet the applicable requirements 
specified in Sec.  61.346.
    (5) Pressure relief devices exempted from pressure release 
management requirements. The following types of pressure relief devices 
are not subject to the pressure release management requirements in 
paragraph (h)(3) of this section.
    (i) Pressure relief devices in heavy liquid service, as defined in 
Sec.  63.1020 of subpart UU.
    (ii) Thermal expansion relief valves.
    (iii) Pressure relief devices designed with a set relief pressure 
of less than 2.5 psig.
    (iv) Pilot-operated pressure relief devices where the primary 
release valve is routed through a closed vent system to a control 
device or back into the process, a fuel gas system, or drain system.
    (v) Balanced bellows pressure relief devices where the primary 
release valve is routed through a closed vent system to a control 
device or back into the process, a fuel gas system, or drain system.
    (6) Root cause analysis and corrective action analysis. A root 
cause analysis and corrective action analysis must be completed as soon 
as possible, but no later than 45 days after a release event. Special 
circumstances affecting the number of root cause analyses and/or 
corrective action analyses are provided in paragraphs (h)(6)(i) through 
(iv) of this section.
    (i) You may conduct a single root cause analysis and corrective 
action analysis for a single emergency event that causes two or more 
pressure relief devices that are installed on the same equipment to 
release.
    (ii) You may conduct a single root cause analysis and corrective 
action analysis for a single emergency event that causes two or more 
pressure relief devices to release, regardless of the equipment served, 
if the root cause is reasonably expected to be a force majeure event, 
as defined in Sec.  63.1103(e)(2).
    (iii) Except as provided in paragraphs (h)(6)(i) and (ii) of this 
section, if more than one pressure relief device has a release during 
the same time period, an initial root cause analysis must be conducted 
separately for each pressure relief device that had a release. If the 
initial root cause analysis indicates that the release events have the 
same root cause(s), the initial separate root cause analyses may be 
recorded as a single root cause analysis and a single corrective action 
analysis may be conducted.
    (7) Corrective action implementation. Each owner or operator 
required to conduct a root cause analysis and corrective action 
analysis as specified in paragraphs (h)(3)(iii) and (6) of this 
section, must implement the corrective action(s) identified in the 
corrective action analysis in accordance with the applicable 
requirements in paragraphs (h)(7)(i) through (iii) of this section.
    (i) All corrective action(s) must be implemented within 45 days of 
the event for which the root cause and corrective action analyses were 
required or as soon thereafter as practicable. If an owner or operator 
concludes that no corrective action should be implemented, the owner or 
operator must record and explain the basis for that conclusion no later 
than 45 days following the event.
    (ii) For corrective actions that cannot be fully implemented within 
45 days following the event for which the root cause and corrective 
action analyses were required, the owner or operator must develop an 
implementation schedule to complete the corrective action(s) as soon as 
practicable.
    (iii) No later than 45 days following the event for which a root 
cause and corrective action analyses were required, the owner or 
operator must record the corrective action(s) completed to date, and, 
for action(s) not already completed, a schedule for implementation, 
including proposed commencement and completion dates.
    (8) Flowing pilot-operated pressure relief devices. For ethylene 
production affected sources that commenced construction or 
reconstruction on or before October 9, 2019, owners or operators are 
prohibited from installing a flowing pilot-operated pressure relief 
device or replacing any pressure relief device with a flowing pilot-
operated pressure relief device after [date 3 years after date of 
publication of final rule in the Federal Register]. For ethylene 
production affected sources that commenced construction or 
reconstruction after October 9, 2019, owners or operators are 
prohibited from installing and operating flowing pilot-operated 
pressure relief devices. For purpose of compliance with this paragraph, 
a flowing pilot-operated pressure relief device means the type of 
pilot-operated pressure relief device where the pilot discharge vent 
continuously releases emissions to the atmosphere when the pressure 
relief device is actuated.
0
23. Section 63.1108 is amended by revising paragraphs (a) introductory 
text, (a)(4)(i) and (ii), (b)(1)(ii), (b)(2) introductory text, (b)(3), 
(b)(4)(i) introductory text, and (b)(4)(ii)(B) to read as follows:


Sec.  63.1108   Compliance with standards and operation and maintenance 
requirements.

    (a) Requirements. The requirements of paragraphs (a)(1), (2), and 
(5) of this section apply to all affected sources except acrylic and 
modacrylic fiber production affected sources, polycarbonate production 
affected sources, and beginning no later than the compliance dates 
specified in Sec.  63.1102(c), ethylene production affected sources. 
The requirements of paragraph (a)(4) of this section apply only to 
acrylic and modacrylic fiber production affected sources, polycarbonate 
production affected sources and beginning no later than the compliance 
dates specified in Sec.  63.1102(c), ethylene production affected 
sources. The requirements of paragraphs (a)(3), (6), and (7) of this 
section apply to all affected sources.
* * * * *
    (4) * * *
    (i) For acrylic and modacrylic fiber production affected sources 
and polycarbonate production affected sources, and beginning no later 
than the compliance dates specified in Sec.  63.1102(c), ethylene 
production affected sources, the emission limitations and established 
parameter ranges of this part shall apply at all times except during 
periods of non-operation of the affected source (or specific portion 
thereof) resulting in cessation of the emissions to which this subpart 
applies. Equipment leak requirements shall apply at all times except 
during periods of non-operation of the affected source (or specific 
portion thereof) in which the lines are drained and depressurized 
resulting in cessation of the emissions to which the equipment leak 
requirements apply.
    (ii) General duty. At all times, the owner or operator must operate 
and maintain any affected source, including associated air pollution 
control

[[Page 54347]]

equipment and monitoring equipment, in a manner consistent with safety 
and good air pollution control practices for minimizing emissions. The 
general duty to minimize emissions does not require the owner or 
operator to make any further efforts to reduce emissions if levels 
required by the applicable standard have been achieved. Determination 
of whether a source is operating in compliance with operation and 
maintenance requirements will be based on information available to the 
Administrator that may include, but is not limited to, monitoring 
results, review of operation and maintenance procedures, review of 
operation and maintenance records, and inspection of the affected 
source.
* * * * *
    (b) * * *
    (1) * * *
    (ii) Excused excursions are not allowed for acrylic and modacrylic 
fiber production affected sources, polycarbonate production affected 
sources, and beginning no later than the compliance dates specified in 
Sec.  63.1102(c), ethylene production affected sources. For all other 
affected sources, including ethylene production affected sources prior 
to the compliance dates specified in Sec.  63.1102(c), an excused 
excursion, as described in Sec.  63.998(b)(6)(ii), is not a violation.
    (2) Parameter monitoring: Excursions. An excursion is not a 
violation in cases where continuous monitoring is required and the 
excursion does not count toward the number of excused excursions (as 
described in Sec.  63.998(b)(6)(ii)), if the conditions of paragraphs 
(b)(2)(i) or (ii) of this section are met, except that the conditions 
of paragraph (b)(2)(i) of this section do not apply for acrylic and 
modacrylic fiber production affected sources, polycarbonate production 
affected sources, and beginning no later than the compliance dates 
specified in Sec.  63.1102(c), ethylene production affected sources. 
Nothing in this paragraph shall be construed to allow or excuse a 
monitoring parameter excursion caused by any activity that violates 
other applicable provisions of this subpart or a subpart referenced by 
this subpart.
* * * * *
    (3) Operation and maintenance procedures. Determination of whether 
acceptable operation and maintenance procedures are being used will be 
based on information available to the Administrator. This information 
may include, but is not limited to, monitoring results, review of 
operation and maintenance procedures (including the startup, shutdown, 
and malfunction plan under Sec.  63.1111, if applicable), review of 
operation and maintenance records, and inspection of the affected 
source, and alternatives approved as specified in Sec.  63.1113.
    (4) * * *
    (i) Applicability assessments. Unless otherwise specified in a 
relevant test method required to assess control applicability, each 
test shall consist of three separate runs using the applicable test 
method. Each run shall be conducted for the time and under the 
conditions specified in this subpart. The arithmetic mean of the 
results of the three runs shall apply when assessing applicability. 
Upon receiving approval from the Administrator, results of a test run 
may be replaced with results of an additional test run if it meets the 
criteria specified in paragraphs (b)(4)(i)(A) through (D) of this 
section.
* * * * *
    (ii) * * *
    (B) For acrylic and modacrylic fiber production affected sources, 
polycarbonate production affected sources, and beginning no later than 
the compliance dates specified in Sec.  63.1102(c), ethylene production 
affected sources, performance tests shall be conducted under such 
conditions as the Administrator specifies to the owner or operator 
based on representative performance of the affected source for the 
period being tested. Representative conditions exclude periods of 
startup and shutdown unless specified by the Administrator or an 
applicable subpart. The owner or operator may not conduct performance 
tests during periods of malfunction. The owner or operator must record 
the process information that is necessary to document operating 
conditions during the test and include in such record an explanation to 
support that such conditions represent normal operation. Upon request, 
the owner or operator shall make available to the Administrator such 
records as may be necessary to determine the conditions of performance 
tests.
* * * * *
0
23. Section 63.1109 is amended by adding paragraphs (e) through (i) to 
read as follows:


Sec.  63.1109   Recordkeeping requirements.

* * * * *
    (e) Ethylene production flare records. For each flare subject to 
the requirements in Sec.  63.1103(e)(4), owners or operators must keep 
records specified in paragraphs (e)(1) through (15) of this section in 
lieu of the information required in Sec.  63.998(a)(1) of subpart SS.
    (1) Retain records of the output of the monitoring device used to 
detect the presence of a pilot flame as required in Sec.  63.670(b) of 
subpart CC and Sec.  63.1103(e)(4)(vi)(D) for a minimum of 2 years. 
Retain records of each 15-minute block during which there was at least 
one minute that no pilot flame is present when regulated material is 
routed to a flare for a minimum of 5 years. For each pressure-assisted 
multi-point flare that uses cross-lighting, retain records of each 15-
minute block during which there was at least one minute that no pilot 
flame is present on each stage when regulated material is routed to a 
flare for a minimum of 5 years.
    (2) Retain records of daily visible emissions observations or video 
surveillance images required in Sec.  63.670(h) of subpart CC as 
specified in paragraphs (e)(2)(i) through (iv), as applicable, for a 
minimum of 3 years.
    (i) To determine when visible emissions observations are required, 
the record must identify all periods when regulated material is vented 
to the flare.
    (ii) If visible emissions observations are performed using Method 
22 at 40 CFR part 60, appendix A-7, then the record must identify 
whether the visible emissions observation was performed, the results of 
each observation, total duration of observed visible emissions, and 
whether it was a 5-minute or 2-hour observation. Record the date and 
start time of each visible emissions observation.
    (iii) If a video surveillance camera is used, then the record must 
include all video surveillance images recorded, with time and date 
stamps.
    (iv) For each 2-hour period for which visible emissions are 
observed for more than 5 minutes in 2 consecutive hours, then the 
record must include the date and start and end time of the 2-hour 
period and an estimate of the cumulative number of minutes in the 2-
hour period for which emissions were visible.
    (3) The 15-minute block average cumulative flows for flare vent gas 
and, if applicable, total steam, perimeter assist air, and premix 
assist air specified to be monitored under Sec.  63.670(i) of subpart 
CC, along with the date and time interval for the 15-minute block. If 
multiple monitoring locations are used to determine cumulative vent gas 
flow, total steam, perimeter assist air, and premix assist air, then 
retain records of the 15-minute block average flows for each monitoring 
location for a minimum of 2 years, and retain records of the 15-minute 
block average cumulative flows that are used in subsequent calculations 
for a minimum of 5 years. If pressure and temperature monitoring is 
used, then retain records of the 15-minute

[[Page 54348]]

block average temperature, pressure, and molecular weight of the flare 
vent gas or assist gas stream for each measurement location used to 
determine the 15-minute block average cumulative flows for a minimum of 
2 years, and retain records of the 15-minute block average cumulative 
flows that are used in subsequent calculations for a minimum of 5 
years.
    (4) The flare vent gas compositions specified to be monitored under 
Sec.  63.670(j) of subpart CC. Retain records of individual component 
concentrations from each compositional analysis for a minimum of 2 
years. If an NHVvg analyzer is used, retain records of the 15-minute 
block average values for a minimum of 5 years.
    (5) Each 15-minute block average operating parameter calculated 
following the methods specified in Sec.  63.670(k) through (n) of 
subpart CC, as applicable.
    (6) All periods during which operating values are outside of the 
applicable operating limits specified in Sec.  63.670(d) through (f) of 
subpart CC and Sec.  63.1103(e)(4)(vi) when regulated material is being 
routed to the flare.
    (7) All periods during which the owner or operator does not perform 
flare monitoring according to the procedures in Sec.  63.670(g) through 
(j) of subpart CC.
    (8) For pressure-assisted multi-point flares, if a stage of burners 
on the flare uses cross-lighting, then a record of any changes made to 
the distance between burners.
    (9) For pressure-assisted multi-point flares, all periods when the 
pressure monitor(s) on the main flare header show burners are operating 
outside the range of the manufacturer's specifications. Indicate the 
date and time for each period, the pressure measurement, the stage(s) 
and number of burners affected, and the range of manufacturer's 
specifications.
    (10) For pressure-assisted multi-point flares, all periods when the 
staging valve position indicator monitoring system indicates a stage of 
the pressure-assisted multi-point flare should not be in operation and 
when a stage of the pressure-assisted multi-point flare should be in 
operation and is not. Indicate the date and time for each period, 
whether the stage was supposed to be open, but was closed or vice 
versa, and the stage(s) and number of burners affected.
    (11) Records of periods when there is flow of vent gas to the 
flare, but when there is no flow of regulated material to the flare, 
including the start and stop time and dates of periods of no regulated 
material flow.
    (12) Records when the flow of vent gas exceeds the smokeless 
capacity of the flare, including start and stop time and dates of the 
flaring event.
    (13) Records of the root cause analysis and corrective action 
analysis conducted as required in Sec.  63.670(o)(3) of subpart CC, 
including an identification of the affected flare, the date and 
duration of the event, a statement noting whether the event resulted 
from the same root cause(s) identified in a previous analysis and 
either a description of the recommended corrective action(s) or an 
explanation of why corrective action is not necessary under Sec.  
63.670(o)(5)(i) of subpart CC.
    (14) For any corrective action analysis for which implementation of 
corrective actions are required in Sec.  63.670(o)(5) of subpart CC, a 
description of the corrective action(s) completed within the first 45 
days following the discharge and, for action(s) not already completed, 
a schedule for implementation, including proposed commencement and 
completion dates.
    (15) Records described in Sec.  63.10(b)(2)(vi) and (xi).
    (f) Ethylene production maintenance vent records. For each 
maintenance vent opening subject to the requirements in Sec.  
63.1103(e)(5), the owner or operator must keep the applicable records 
specified in (f)(1) through (5) of this section.
    (1) The owner or operator must maintain standard site procedures 
used to deinventory equipment for safety purposes (e.g., hot work or 
vessel entry procedures) to document the procedures used to meet the 
requirements in Sec.  63.1103(e)(5). The current copy of the procedures 
must be retained and available on-site at all times. Previous versions 
of the standard site procedures, as applicable, must be retained for 
five years.
    (2) If complying with the requirements of Sec.  63.1103(e)(5)(i)(A) 
and the lower explosive limit at the time of the vessel opening exceeds 
10 percent, records that identify the maintenance vent, the process 
units or equipment associated with the maintenance vent, the date of 
maintenance vent opening, and the lower explosive limit at the time of 
the vessel opening.
    (3) If complying with the requirements of Sec.  63.1103(e)(5)(i)(B) 
and either the vessel pressure at the time of the vessel opening 
exceeds 5 psig or the lower explosive limit at the time of the active 
purging was initiated exceeds 10 percent, records that identify the 
maintenance vent, the process units or equipment associated with the 
maintenance vent, the date of maintenance vent opening, the pressure of 
the vessel or equipment at the time of discharge to the atmosphere and, 
if applicable, the lower explosive limit of the vapors in the equipment 
when active purging was initiated.
    (4) If complying with the requirements of Sec.  
63.1103(e)(5)(i)(C), records used to estimate the total quantity of VOC 
in the equipment and the type and size limits of equipment that contain 
less than 50 pounds of VOC at the time of maintenance vent opening. For 
each maintenance vent opening for which the deinventory procedures 
specified in paragraph (f)(1) of this section are not followed or for 
which the equipment opened exceeds the type and size limits established 
in the records specified in this paragraph, records that identify the 
maintenance vent, the process units or equipment associated with the 
maintenance vent, the date of maintenance vent opening, and records 
used to estimate the total quantity of VOC in the equipment at the time 
the maintenance vent was opened to the atmosphere.
    (5) If complying with the requirements of Sec.  
63.1103(e)(5)(i)(D), identification of the maintenance vent, the 
process units or equipment associated with the maintenance vent, 
records documenting actions taken to comply with other applicable 
alternatives and why utilization of this alternative was required, the 
date of maintenance vent opening, the equipment pressure and lower 
explosive limit of the vapors in the equipment at the time of 
discharge, an indication of whether active purging was performed and 
the pressure of the equipment during the installation or removal of the 
blind if active purging was used, the duration the maintenance vent was 
open during the blind installation or removal process, and records used 
to estimate the total quantity of VOC in the equipment at the time the 
maintenance vent was opened to the atmosphere for each applicable 
maintenance vent opening.
    (g) Ethylene production bypass line records. For each flow event 
from a bypass line subject to the requirements in Sec.  63.1103(e)(6), 
the owner or operator must maintain records sufficient to determine 
whether or not the detected flow included flow requiring control. For 
each flow event from a bypass line requiring control that is released 
either directly to the atmosphere or to a control device not meeting 
the requirements specified in Table 7 to Sec.  63.1103(e), the owner or 
operator must include an estimate of the volume of gas, the 
concentration of organic HAP in the gas and the resulting emissions of 
organic HAP that bypassed the control

[[Page 54349]]

device using process knowledge and engineering estimates.
    (h) Decoking operation of ethylene cracking furnace records. For 
each decoking operation of an ethylene cracking furnace subject to the 
standards in Sec.  63.1103(e)(7) and (8), the owner or operator must 
keep the records specified in paragraphs (h)(1) through (6) of this 
section.
    (1) Records that document the day and time each inspection 
specified in Sec.  63.1103(e)(7)(i) took place, the results of each 
inspection, and any repairs made to correct the flame impingement.
    (2) If the owner or operator chooses to monitor the CO2 
concentration during decoking as specified in Sec.  63.1103(e)(7)(ii), 
then for each decoking cycle, records must be kept for all measured CO2 
concentration values and the target used to indicate combustion is 
complete.
    (3) If the owner or operator chooses to monitor the temperature at 
the radiant tube(s) outlet during decoking as specified in Sec.  
63.1103(e)(7)(iii), then for each decoking cycle, records must be kept 
for all measured temperature values and the target used to indicate a 
reduction in temperature of the inside of the radiant tube(s) is 
necessary.
    (4) If the owner or operator chooses to purge the radiant tube(s) 
with steam after decoking, but before returning the ethylene cracking 
furnace back to normal operation as specified in Sec.  
63.1103(e)(7)(iv), then records must be kept that document the 
verification that all air is removed after each decoking cycle.
    (5) If the owner or operator chooses to apply a coating material to 
the interior of the radiant tube after decoking, but before returning 
the ethylene cracking furnace back to normal operation as specified in 
Sec.  63.1103(e)(7)(v), then records must be kept that document when 
the coating was applied.
    (6) For each decoking operation of an ethylene cracking furnace 
subject to the requirements in Sec.  63.1103(e)(8), the owner or 
operator must keep records that document the day and time each 
inspection took place, the results of each inspection, and any repairs 
made to correct any isolation issues that were identified.
    (i) Ethylene production pressure relief devices records. For each 
pressure relief device subject to the pressure release management work 
practice standards in Sec.  63.1107(h)(3), the owner or operator must 
keep the records specified in paragraphs (i)(1) through (3) of this 
section.
    (1) Records of the prevention measures implemented as required in 
Sec.  63.1107(h)(3)(ii).
    (2) Records of the number of releases during each calendar year and 
the number of those releases for which the root cause was determined to 
be a force majeure event. Keep these records for the current calendar 
year and the past five calendar years.
    (3) For each release to the atmosphere, the owner or operator must 
keep the records specified in paragraphs (i)(3)(i) through (iv) of this 
section.
    (i) The start and end time and date of each pressure release to the 
atmosphere.
    (ii) Records of any data, assumptions, and calculations used to 
estimate of the mass quantity of each organic HAP released during the 
event.
    (iii) Records of the root cause analysis and corrective action 
analysis conducted as required in Sec.  63.1107(h)(3)(iii), including 
an identification of the affected pressure relief device, a statement 
noting whether the event resulted from the same root cause(s) 
identified in a previous analysis and either a description of the 
recommended corrective action(s) or an explanation of why corrective 
action is not necessary under Sec.  63.1107(h)(7)(i).
    (iv) For any corrective action analysis for which implementation of 
corrective actions are required in Sec.  63.1107(h)(7), a description 
of the corrective action(s) completed within the first 45 days 
following the discharge and, for action(s) not already completed, a 
schedule for implementation, including proposed commencement and 
completion dates.
0
24. Section 63.1110 is amended by:
0
a. Revising paragraphs (a) introductory text and (a)(7) and (9);
0
b. Adding paragraph (a)(10);
0
c. Revising paragraphs (d)(1) introductory text and (d)(1)(i);
0
d. Adding paragraphs (d)(1)(iv) and (v);
0
e. Revising paragraph (e)(1);
0
f. Adding paragraphs (e)(4) through (8); and
0
g. Revising paragraphs (g)(1) and (2).
    The revisions and additions read as follows:


Sec.  63.1110   Reporting requirements.

    (a) Required reports. Each owner or operator of an affected source 
subject to this subpart shall submit the reports listed in paragraphs 
(a)(1) through (8) of this section, as applicable. Each owner or 
operator of an acrylic and modacrylic fiber production affected source 
or polycarbonate production affected source subject to this subpart 
shall also submit the reports listed in paragraph (a)(9) of this 
section in addition to the reports listed in paragraphs (a)(1) through 
(8) of this section, as applicable. Beginning no later than the 
compliance dates specified in Sec.  63.1102(c), each owner or operator 
of an ethylene production affected source subject to this subpart shall 
also submit the reports listed in paragraph (a)(10) of this section in 
addition to the reports listed in paragraphs (a)(1) through (8) of this 
section, as applicable.
* * * * *
    (7) Startup, Shutdown, and Malfunction Reports described in Sec.  
63.1111 (except for acrylic and modacrylic fiber production affected 
sources, ethylene production affected sources, and polycarbonate 
production affected sources).
* * * * *
    (9) Within 60 days after the date of completing each performance 
test (as defined in Sec.  63.2), the owner or operator must submit the 
results of the performance tests, including any associated fuel 
analyses, required by this subpart according to the methods specified 
in paragraph (a)(9)(i) or (ii) of this section.
* * * * *
    (10) (i) Beginning no later than the compliance dates specified in 
Sec.  63.1102(c), within 60 days after the date of completing each 
performance test required by this subpart, the owner or operator must 
submit the results of the performance test following the procedures 
specified in paragraphs (a)(10)(i)(A) through (C) of this section.
    (A) Data collected using test methods supported by the EPA's 
Electronic Reporting Tool (ERT) as listed on the EPA's ERT website 
(https://www.epa.gov/electronic-reporting-air-emissions/electronic-reporting-tool-ert) at the time of the test. Submit the results of the 
performance test to the EPA via CEDRI, which can be accessed through 
the EPA's CDX (https://cdx.epa.gov/). The data must be submitted in a 
file format generated through the use of the EPA's ERT. Alternatively, 
you may submit an electronic file consistent with the extensible markup 
language (XML) schema listed on the EPA's ERT website.
    (B) Data collected using test methods that are not supported by the 
EPA's ERT as listed on the EPA's ERT website at the time of the test. 
The results of the performance test must be included as an attachment 
in the ERT or an alternate electronic file consistent with the XML 
schema listed on the EPA's ERT website. Submit the ERT generated 
package or alternative file to the EPA via CEDRI.
    (C) CBI. If you claim some of the information submitted under 
paragraph (a)(10)(i)(A) or (B) of this section is CBI,

[[Page 54350]]

then the owner or operator must submit a complete file, including 
information claimed to be CBI, to the EPA. The file must be generated 
through the use of the EPA's ERT or an alternate electronic file 
consistent with the XML schema listed on the EPA's ERT website. Submit 
the file on a compact disc, flash drive, or other commonly used 
electronic storage medium and clearly mark the medium as CBI. Mail the 
electronic medium to U.S. EPA/OAQPS/CORE CBI Office, Attention: Group 
Leader, Measurement Policy Group, MD C404-02, 4930 Old Page Rd., 
Durham, NC 27703. The same file with the CBI omitted must be submitted 
to the EPA via EPA's CDX as described in paragraphs (a)(10)(i)(A) and 
(B) of this section.
    (ii) Beginning no later than the compliance dates specified in 
Sec.  63.1102(c), the owner or operator must submit all subsequent 
Notification of Compliance Status reports required under paragraph 
(a)(4) of this section to the EPA via CEDRI, which can be accessed 
through EPA's CDX (https://cdx.epa.gov/). If you claim some of the 
information required to be submitted via CEDRI is CBI, then submit a 
complete report, including information claimed to be CBI, on a compact 
disc, flash drive, or other commonly used electronic storage medium and 
clearly mark the medium as CBI. Mail the electronic medium to U.S. 
Environmental Protection Agency, Office of Air Quality Planning and 
Standards, Sector Policies and Programs Division, U.S. EPA Mailroom 
(E143-01), Attention: Ethylene Production Sector Lead, 109 T.W. 
Alexander Drive, Research Triangle Park, NC 27711. The same file with 
the CBI omitted must be submitted to the EPA via the EPA's CDX as 
described earlier in this paragraph.
    (iii) If you are required to electronically submit a report through 
CEDRI in the EPA's CDX, you may assert a claim of EPA system outage for 
failure to timely comply with the reporting requirement. To assert a 
claim of EPA system outage, the owner or operator must meet the 
requirements outlined in paragraphs (a)(10)(iii)(A) through (G) of this 
section.
    (A) The owner or operator must have been or will be precluded from 
accessing CEDRI and submitting a required report within the time 
prescribed due to an outage of either the EPA's CEDRI or CDX systems.
    (B) The outage must have occurred within the period of time 
beginning five business days prior to the date that the submission is 
due.
    (C) The outage may be planned or unplanned.
    (D) The owner or operator must submit notification to the 
Administrator in writing as soon as possible following the date you 
first knew, or through due diligence should have known, that the event 
may cause or has caused a delay in reporting.
    (E) The owner or operator must provide to the Administrator a 
written description identifying:
    (1) The date(s) and time(s) when CDX or CEDRI was accessed and the 
system was unavailable;
    (2) A rationale for attributing the delay in reporting beyond the 
regulatory deadline to EPA system outage;
    (3) Measures taken or to be taken to minimize the delay in 
reporting; and
    (4) The date by which you propose to report, or if you have already 
met the reporting requirement at the time of the notification, the date 
you reported.
    (F) The decision to accept the claim of EPA system outage and allow 
an extension to the reporting deadline is solely within the discretion 
of the Administrator.
    (G) In any circumstance, the report must be submitted 
electronically as soon as possible after the outage is resolved.
    (iv) If you are required to electronically submit a report through 
CEDRI in the EPA's CDX, you may assert a claim of force majeure for 
failure to timely comply with the reporting requirement. To assert a 
claim of force majeure, the owner or operator must meet the 
requirements outlined in paragraphs (a)(10)(iv)(A) through (E) of this 
section.
    (A) You may submit a claim if a force majeure event is about to 
occur, occurs, or has occurred or there are lingering effects from such 
an event within the period of time beginning five business days prior 
to the date the submission is due. For the purposes of this paragraph, 
a force majeure event is defined as an event that will be or has been 
caused by circumstances beyond the control of the affected facility, 
its contractors, or any entity controlled by the affected facility that 
prevents you from complying with the requirement to submit a report 
electronically within the time period prescribed. Examples of such 
events are acts of nature (e.g., hurricanes, earthquakes, or floods), 
acts of war or terrorism, or equipment failure or safety hazard beyond 
the control of the affected facility (e.g., large scale power outage).
    (B) The owner or operator must submit notification to the 
Administrator in writing as soon as possible following the date you 
first knew, or through due diligence should have known, that the event 
may cause or has caused a delay in reporting.
    (C) The owner or operator must provide to the Administrator:
    (1) A written description of the force majeure event;
    (2) A rationale for attributing the delay in reporting beyond the 
regulatory deadline to the force majeure event;
    (3) Measures taken or to be taken to minimize the delay in 
reporting; and
    (4) The date by which you propose to report, or if you have already 
met the reporting requirement at the time of the notification, the date 
you reported.
    (D) The decision to accept the claim of force majeure and allow an 
extension to the reporting deadline is solely within the discretion of 
the Administrator.
    (E) In any circumstance, the reporting must occur as soon as 
possible after the force majeure event occurs.
* * * * *
    (d) Notification of Compliance Status--(1) Contents. The owner or 
operator shall submit a Notification of Compliance Status for each 
affected source subject to this subpart containing the information 
specified in paragraphs (d)(1)(i) and (ii) of this section. For 
pressure relief devices subject to the requirements of Sec.  
63.1107(e)(3), the owner or operator of an acrylic and modacrylic fiber 
production affected source or polycarbonate production affected source 
shall also submit the information listed in paragraph (d)(1)(iii) of 
this section in a supplement to the Notification of Compliance Status 
within 150 days after the first applicable compliance date for pressure 
relief device monitoring. For flares subject to the requirements of 
Sec.  63.1103(e)(4), the owner or operator of an ethylene production 
affected source shall also submit the information listed in paragraph 
(d)(1)(iv) of this section in a supplement to the Notification of 
Compliance Status within 150 days after the first applicable compliance 
date for flare monitoring. For pressure relief devices subject to the 
pressure release management work practice standards in Sec.  
63.1107(h)(3), the owner or operator of an ethylene production affected 
source shall also submit the information listed in paragraph (d)(1)(v) 
of this section in a supplement to the Notification of Compliance 
Status within 150 days after the first applicable compliance date for 
pressure relief device monitoring.
    (i) Except as specified in paragraphs (d)(1)(iv) and (v) of this 
section, the Notification of Compliance Status shall include the 
information specified in this subpart and the subparts referenced by 
this subpart. Alternatively, this

[[Page 54351]]

information can be submitted as part of a title V permit application or 
amendment.
* * * * *
    (iv) For each flare subject to the requirements in Sec.  
63.1103(e)(4), in lieu of the information required in Sec.  63.987(b) 
of subpart SS, the Notification of Compliance Status shall include 
flare design (e.g., steam-assisted, air-assisted, non-assisted, or 
pressure-assisted multi-point); all visible emission readings, heat 
content determinations, flow rate measurements, and exit velocity 
determinations made during the initial visible emissions demonstration 
required by Sec.  63.670(h) of subpart CC, as applicable; and all 
periods during the compliance determination when the pilot flame is 
absent.
    (v) For pressure relief devices subject to the requirements Sec.  
63.1107(h), the Notification of Compliance Status shall include the 
information specified in paragraphs (d)(1)(v)(A) and (B) of this 
section.
    (A) A description of the monitoring system to be implemented, 
including the relief devices and process parameters to be monitored, 
and a description of the alarms or other methods by which operators 
will be notified of a pressure release.
    (B) A description of the prevention measures to be implemented for 
each affected pressure relief device.
* * * * *
    (e) * * *
    (1) Contents. Except as specified in paragraphs (e)(4) through (8) 
of this section, Periodic Reports shall include all information 
specified in this subpart and subparts referenced by this subpart.
* * * * *
    (4) Ethylene production flare reports. For each flare subject to 
the requirements in Sec.  63.1103(e)(4), the Periodic Report shall 
include the items specified in paragraphs (e)(4)(i) through (vi) of 
this section in lieu of the information required in Sec.  63.999(c)(3) 
of subpart SS.
    (i) Records as specified in Sec.  63.1109(e)(2) for each 15-minute 
block during which there was at least one minute when regulated 
material is routed to a flare and no pilot flame is present. Include 
the start and stop time and date of each 15-minute block.
    (ii) Visible emission records as specified in Sec.  
63.1109(e)(3)(iv) for each period of 2 consecutive hours during which 
visible emissions exceeded a total of 5 minutes.
    (iii) The periods specified in Sec.  63.1109(e)(7). Indicate the 
date and start time for the period, and the net heating value operating 
parameter(s) determined following the methods in Sec.  63.670(k) 
through (n) of subpart CC as applicable.
    (iv) For flaring events meeting the criteria in Sec.  63.670(o)(3) 
of subpart CC:
    (A) The start and stop time and date of the flaring event.
    (B) The length of time that emissions were visible from the flare 
during the event.
    (C) For steam-assisted, air-assisted, and non-assisted flares, the 
periods of time that the flare tip velocity exceeds the maximum flare 
tip velocity determined using the methods in Sec.  63.670(d)(2) of 
subpart CC and the maximum 15-minute block average flare tip velocity 
recorded during the event.
    (D) Results of the root cause and corrective actions analysis 
completed during the reporting period, including the corrective actions 
implemented during the reporting period and, if applicable, the 
implementation schedule for planned corrective actions to be 
implemented subsequent to the reporting period.
    (v) For pressure-assisted multi-point flares, the periods of time 
when the pressure monitor(s) on the main flare header show the burners 
operating outside the range of the manufacturer's specifications.
    (vi) For pressure-assisted multi-point flares, the periods of time 
when the staging valve position indicator monitoring system indicates a 
stage should not be in operation and is or when a stage should be in 
operation and is not.
    (5) Ethylene production maintenance vent reports. For maintenance 
vents subject to the requirements Sec.  63.1103(e)(5), Periodic Reports 
must include the information specified in paragraphs (e)(5)(i) through 
(iv) of this section for any release exceeding the applicable limits in 
Sec.  63.1103(e)(5)(i). For the purposes of this reporting requirement, 
owners or operators complying with Sec.  63.1103(e)(5)(i)(D) must 
report each venting event conducted under those provisions and include 
an explanation for each event as to why utilization of this alternative 
was required.
    (i) Identification of the maintenance vent and the equipment served 
by the maintenance vent.
    (ii) The date and time the maintenance vent was opened to the 
atmosphere.
    (iii) The lower explosive limit, vessel pressure, or mass of VOC in 
the equipment, as applicable, at the start of atmospheric venting. If 
the 5 psig vessel pressure option in Sec.  63.1103(e)(5)(i)(B) was used 
and active purging was initiated while the lower explosive limit was 10 
percent or greater, also include the lower explosive limit of the 
vapors at the time active purging was initiated.
    (iv) An estimate of the mass of organic HAP released during the 
entire atmospheric venting event.
    (6) Bypass line reports. For bypass lines subject to the 
requirements in Sec.  63.1103(e)(6), Periodic Reports must include the 
date, time, duration, estimate of the volume of gas, the concentration 
of organic HAP in the gas and the resulting mass emissions of organic 
HAP that bypass a control device. For periods when the flow indicator 
is not operating, report the date, time, and duration.
    (7) Decoking operation reports. For decoking operations of an 
ethylene cracking furnace subject to the requirements in Sec.  
63.1103(e)(7) and (8), Periodic Reports must include the information 
specified in paragraphs (e)(7)(i) and (ii) of this section.
    (i) For each control measure selected to minimize coke combustion 
emissions as specified in Sec.  63.1103(e)(7)(ii) through (v), report 
instances where the control measures were not followed.
    (ii) Report instances where an isolation valve inspection was not 
conducted according to the procedures specified in Sec.  63.1103(e)(8).
    (8) Ethylene production pressure relief devices reports. For 
pressure relief devices subject to the requirements Sec.  63.1107(h), 
Periodic Reports must include the information specified in paragraphs 
(e)(8)(i) through (iii) of this section.
    (i) For pressure relief devices in organic HAP gas or vapor 
service, pursuant to Sec.  63.1107(h)(1), report any instrument reading 
of 500 ppm or greater.
    (ii) For pressure relief devices in organic HAP gas or vapor 
service subject to Sec.  63.1107(h)(2), report confirmation that any 
monitoring required to be done during the reporting period to show 
compliance was conducted.
    (iii) For pressure relief devices in organic HAP service subject to 
Sec.  63.1107(h)(3), report each pressure release to the atmosphere, 
including duration of the pressure release and estimate of the mass 
quantity of each organic HAP released; the results of any root cause 
analysis and corrective action analysis completed during the reporting 
period, including the corrective actions implemented during the 
reporting period; and, if applicable, the implementation schedule for 
planned corrective actions to be implemented subsequent to the 
reporting period.
* * * * *

[[Page 54352]]

    (g) Report and notification submission--(1) Submission to the 
Environmental Protection Agency. All reports and notifications required 
under this subpart shall be sent to the appropriate EPA Regional Office 
and to the delegated State authority, except that request for 
permission to use an alternative means of emission limitation as 
provided for in Sec.  63.1113 shall be submitted to the Director of the 
EPA Office of Air Quality Planning and Standards, U.S. Environmental 
Protection Agency, MD-10, Research Triangle Park, North Carolina, 
27711. The EPA Regional Office may waive the requirement to submit a 
copy of any reports or notifications at its discretion, except that 
electronic reporting to CEDRI cannot be waived, and as such, compliance 
with the provisions of this paragraph does not relieve owners or 
operators of affected facilities of the requirement to submit 
electronic reports required in this subpart to the EPA.
    (2) Submission of copies. If any State requires a notice that 
contains all the information required in a report or notification 
listed in this subpart, an owner or operator may send the appropriate 
EPA Regional Office a copy of the report or notification sent to the 
State to satisfy the requirements of this subpart for that report or 
notification, except that performance test reports and performance 
evaluation reports required under paragraph (a)(10) of this section 
must be submitted to CEDRI in the format specified in that paragraph.
* * * * *
0
25. Section 63.1111 is amended by revising paragraphs (a) introductory 
text, (b) introductory text, and (c) introductory text to read as 
follows:


Sec.  63.1111   Startup, shutdown, and malfunction.

    (a) Startup, shutdown, and malfunction plan. Before [date 3 years 
after date of publication of final rule in the Federal Register], the 
requirements of this paragraph (a) apply to all affected sources except 
for acrylic and modacrylic fiber production affected sources and 
polycarbonate production affected sources. On and after [date 3 years 
after date of publication of final rule in the Federal Register], the 
requirements of this paragraph (a) apply to all affected sources except 
for acrylic and modacrylic fiber production affected sources, ethylene 
production affected sources, and polycarbonate production affected 
sources.
* * * * *
    (b) Startup, shutdown, and malfunction reporting requirements. 
Before [date 3 years after date of publication of final rule in the 
Federal Register], the requirements of this paragraph (b) apply to all 
affected sources except for acrylic and modacrylic fiber production 
affected sources and polycarbonate production affected sources. On and 
after [date 3 years after date of publication of final rule in the 
Federal Register], the requirements of this paragraph (b) apply to all 
affected sources except for acrylic and modacrylic fiber production 
affected sources, ethylene production affected sources, and 
polycarbonate production affected sources.
* * * * *
    (c) Malfunction recordkeeping and reporting. Before [date 3 years 
after date of publication of final rule in the Federal Register], the 
requirements of this paragraph (c) apply only to acrylic and modacrylic 
fiber production affected sources and polycarbonate production affected 
sources. On and after [date 3 years after date of publication of final 
rule in the Federal Register], the requirements of this paragraph (c) 
apply only to acrylic and modacrylic fiber production affected sources, 
ethylene production affected sources, and polycarbonate production 
affected sources.
* * * * *
0
26. Section 63.1112 is amended by revising paragraph (d)(2) to read as 
follows:


Sec.  63.1112   Extension of compliance, and performance test, 
monitoring, recordkeeping and reporting waivers and alternatives.

* * * * *
    (d) * * *
    (2) Recordkeeping or reporting requirements may be waived upon 
written application to the Administrator if, in the Administrator's 
judgment, the affected source is achieving the relevant standard(s), or 
the source is operating under an extension of compliance, or the owner 
or operator has requested an extension of compliance and the 
Administrator is still considering that request. Electronic reporting 
to the EPA cannot be waived, and as such, compliance with the 
provisions of this paragraph does not relieve owners or operators of 
affected facilities of the requirement to submit electronic reports 
required in this subpart to the EPA.
* * * * *
0
27. Section 63.1113 is amended by revising paragraph (a)(2) to read as 
follows:


Sec.  63.1113   Procedures for approval of alternative means of 
emission limitation.

    (a) * * *
    (2) Any such notice shall be published only after public notice and 
an opportunity for public comment.
* * * * *
0
28. Section 63.1114 is amended by revising paragraph (b) introductory 
text and adding paragraph (b)(6) to read as follows:


Sec.  63.1114   Implementation and enforcement.

* * * * *
    (b) In delegating implementation and enforcement authority of this 
subpart to a State, local, or tribal agency under 40 CFR part 63, 
subpart E, the authorities contained in paragraphs (b)(1) through (6) 
of this section are retained by the EPA Administrator and are not 
transferred to the State, local, or tribal agency.
* * * * *
    (6) Approval of an alternative to any electronic reporting to EPA 
required by this subpart.

[FR Doc. 2019-19875 Filed 10-8-19; 8:45 am]
BILLING CODE 6560-50-P