[Federal Register Volume 84, Number 203 (Monday, October 21, 2019)]
[Proposed Rules]
[Pages 56288-56365]
[FR Doc No: 2019-21690]

Vol. 84

Monday,

No. 203

October 21, 2019

Part II

Environmental Protection Agency

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40 CFR Part 63

National Emission Standards for Hazardous Air Pollutants: Organic
Liquids Distribution (Non-Gasoline) Residual Risk and Technology
Review; Proposed Rule

Federal Register / Vol. 84 , No. 203 / Monday, October 21, 2019 /
Proposed Rules

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2018-0074; FRL-10000-80-OAR]
RIN 2060-AT86

National Emission Standards for Hazardous Air Pollutants: Organic
Liquids Distribution (Non-Gasoline) Residual Risk and Technology Review

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) for the Organic Liquids Distribution (Non-Gasoline)
(OLD) source category. The EPA is proposing amendments to the storage
tank and equipment leak requirements as a result of the residual risk
and technology review (RTR). The EPA is also proposing amendments to
allow terminals the option to implement a fenceline monitoring program
in lieu of the enhancements to the storage tank and equipment leak
requirements; correct and clarify regulatory provisions related to
emissions during periods of startup, shutdown, and malfunction (SSM);
add requirements for electronic reporting of performance test results
and reports, performance evaluation reports, compliance reports, and
Notification of Compliance Status (NOCS) reports; add operational
requirements for flares; and make other minor technical improvements.
We estimate that these proposed amendments would reduce emissions of
hazardous air pollutants (HAP) from this source category by 386 tons
per year (tpy), which represents an approximate 16-percent reduction of
HAP emissions from the source category.

DATES:
    Comments. Comments must be received on or before December 5, 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 20, 2019.
    Public hearing. If anyone contacts us requesting a public hearing
on or before October 28, 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/organic-liquids-distribution-national-emission-standards-hazardous. See SUPPLEMENTARY INFORMATION for
information on requesting and registering for a public hearing.

ADDRESSES: You may send comments, identified by Docket ID No. EPA-HQ-
OAR-2018-0074, 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_ADDRESS>Include Docket ID No. EPA-
HQ-OAR-2018-0074 in the subject line of the message.
     Fax:<PHONE_NUMBER>. Attention Docket ID No. EPA-HQ-OAR-
2018-0074.
     Mail: U.S. Environmental Protection Agency, EPA Docket
Center, Docket ID No. EPA-HQ-OAR-2018-0074, 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 Docket ID No.
EPA-HQ-OAR-2018-0074. 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 Mr. Art Diem, Sector Policies and Programs Division
(E143-01), Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina
27711; telephone number:<PHONE_NUMBER>; fax number:<PHONE_NUMBER>;
and email address<EMAIL_ADDRESS>For specific information regarding
the risk assessment, contact Mr. Ted Palma, Health and Environmental
Impacts Division (C539-02), Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina 27711; telephone number:<PHONE_NUMBER>; fax
number:<PHONE_NUMBER>; and email address<EMAIL_ADDRESS>For
questions about monitoring and testing requirements, contact Ms. Gerri
Garwood, Sector Policies and Programs Division (D243-05), Office of Air
Quality Planning and Standards, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina 27711; telephone number: (919)
541-2406; fax number:<PHONE_NUMBER>; and email address:
<EMAIL_ADDRESS>For information about the applicability of the
NESHAP to a particular entity, contact Mr. John Cox, Office of
Enforcement and Compliance Assurance, U.S. Environmental Protection
Agency, WJC South Building (Mail Code 2227A), 1200 Pennsylvania Avenue
NW, Washington DC 20460; telephone number:<PHONE_NUMBER>; and email
address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:
    Public hearing. Please contact Ms. Virginia Hunt at<PHONE_NUMBER>
or by email at<EMAIL_ADDRESS>to request a public hearing, to
register to speak at the public hearing, or to inquire as to whether a
public hearing will be held.
    Docket. The EPA has established a docket for this action under
Docket ID No. EPA-HQ-OAR-2018-0074. 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<PHONE_NUMBER>, and the telephone number for the EPA
Docket Center is<PHONE_NUMBER>.
    Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2018-0074. The EPA's policy is that all comments received will be
included in the public docket without change and may be made available
online at https://www.regulations.gov/, including any personal
information provided, unless the comment includes information claimed
to be CBI or other information whose disclosure is restricted by
statute. Do not submit information that you consider to be CBI or
otherwise protected through https://www.regulations.gov/ or email. This

type of information should be submitted by mail as discussed below.
    The EPA may publish any comment received to its public docket.
Multimedia submissions (audio, video, etc.) must be accompanied by a
written comment. The written comment is considered the official comment
and should include discussion of all points you wish to make. The EPA
will generally not consider comments or comment contents located
outside of the primary submission (i.e., on the Web, cloud, or other
file sharing system). For additional submission methods, the full EPA
public comment policy, information about CBI or multimedia submissions,
and general guidance on making effective comments, please visit https://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-2018-0074.
    Preamble acronyms and abbreviations. We use multiple acronyms and
terms in this preamble. While this list may not be exhaustive, to ease
the reading of this preamble and for reference purposes, the EPA
defines the following terms and acronyms here:

AEGL acute exposure guideline level
AERMOD air dispersion model used by the HEM-3 model
APCD air pollution control device
API American Petroleum Institute
ASTM American Society for Testing and Materials
ATSDR Agency For Toxic Substances and Disease Registry
Btu/scf British thermal units per standard cubic foot
CAA Clean Air Act
CalEPA California EPA
CBI Confidential Business Information
CDX Central Data Exchange
CEDRI Compliance and Emissions Data Reporting Interface
CFR Code of Federal Regulations
CMS continuous monitoring system
EIA Energy Information Administration
EPA Environmental Protection Agency
ERPG Emergency Response Planning Guideline
ERT Electronic Reporting Tool
FTIR Fourier transform infrared spectroscopy
GACT generally available control technology
HAP hazardous air pollutant(s)
HCl hydrochloric acid
HEM-3 Human Exposure Model, Version 1.5.5
HF hydrogen fluoride
HI hazard index
HON National Emission Standards for Organic Hazardous Air Pollutants
from the Synthetic Organic Chemical Manufacturing Industry, also
known as the hazardous organic NESHAP
HQ hazard quotient
ICR Information Collection Request
IFR internal floating roof
IRIS Integrated Risk Information System
km kilometer
LDAR leak detection and repair
MACT maximum achievable control technology
MIR maximum individual risk
NAAQS National Ambient Air Quality Standards
NAICS North American Industry Classification System
NATA National Air Toxics Assessment
NEI National Emissions Inventory
NESHAP national emission standards for hazardous air pollutants
NHVcz net heating value in the combustion zone gas
NHVvg net heating value of the flare vent gas
NOCS Notification of Compliance Status
OAQPS Office of Air Quality Planning and Standards
OLD Organic Liquids Distribution (Non-Gasoline)
OMB Office of Management and Budget
PB-HAP hazardous air pollutants known to be persistent and bio-
accumulative in the environment
PDF portable document format
POM polycyclic organic matter
ppm parts per million
ppmv parts per million by volume
PRA Paperwork Reduction Act
PRD pressure relief device
psia pounds per square inch absolute
REL reference exposure level
RfC reference concentration
RfD reference dose
RTR residual risk and technology review
SAB Science Advisory Board
SSM startup, shutdown, and malfunction
TOSHI target organ-specific hazard index
tpy tons per year
TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport, and
Ecological Exposure model
UF uncertainty factor
UMRA Unfunded Mandates Reform Act
URE unit risk estimate
USGS U.S. Geological Survey
UV-DOAS ultraviolet differential optical absorption spectroscopy
VCS voluntary consensus standard
VOC volatile organic compound(s)

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

I. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document and other related
information?
II. Background
    A. What is the statutory authority for this action?
    B. What is this source category and how does the current NESHAP
regulate its HAP emissions?
    C. What data collection activities were conducted to support
this action?
    D. What other relevant background information and data are
available?
III. Analytical Procedures and Decision Making
    A. How do we consider risk in our decision-making?
    B. How do we perform the technology review?
    C. How do we estimate post-MACT risk posed by the source
category?
IV. Analytical Results and Proposed Decisions

    A. What actions are we taking pursuant to CAA sections 112(d)(2)
and 112(d)(3)?
    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?
    E. What are the benefits?
VI. Request for Comments
VII. Submitting Data Corrections
VIII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Executive Order 13771: Reducing Regulation and Controlling
Regulatory Costs
    C. Paperwork Reduction Act (PRA)
    D. Regulatory Flexibility Act (RFA)
    E. Unfunded Mandates Reform Act (UMRA)
    F. Executive Order 13132: Federalism
    G. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    H. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
    I. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
    J. National Technology Transfer and Advancement Act (NTTAA) 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 Initial List of Categories of Sources Under Section
112(c)(1) of the Clean Air Act Amendments of 1990 (see 57 FR 31576,
July 16, 1992) and Documentation for Developing the Initial Source
Category List, Final Report (see EPA-450/3-91-030, July, 1992), the OLD
source category includes, but is not limited to, those activities
associated with the storage and distribution of organic liquids other
than gasoline, at sites which serve as distribution points from which
organic liquids may be obtained for further use and processing.
    The OLD source category involves the distribution of organic
liquids into, out of, or within a source. The distribution activities
include the storage of organic liquids in storage tanks not subject to
other 40 CFR part 63 standards and transfers into or out of the tanks
from or to cargo tanks, containers, and pipelines. The OLD NESHAP is
codified at 40 CFR part 63, subpart EEEE. Organic liquids are any crude
oils downstream of the first point of custody transfer and any non-
crude oil liquid that contains at least 5 percent by weight of any
combination of the 98 HAP listed in Table 1 of 40 CFR part 63 subpart
EEEE. For the purposes of the OLD NESHAP, organic liquids do not
include gasoline, kerosene (No. 1 distillate oil), diesel (No. 2
distillate oil), asphalt, and heavier distillate oil and fuel oil, fuel
that is consumed or dispensed on the plant site, hazardous waste,
wastewater, ballast water, or any non-crude liquid with an annual
average true vapor pressure less than 0.7 kilopascals (0.1 pound per
square inch absolute (psia)). Emission sources controlled by the OLD
NESHAP are storage tanks, transfer operations, transport vehicles while
being loaded, and equipment leak components (valves, pumps, and
sampling connections) that have the potential to leak.
    The types of organic liquids and emission sources covered by the
OLD NESHAP are frequently found at many types of facilities that are
already subject to other NESHAP. If equipment is in organic liquids
distribution service and is subject to another 40 CFR part 63 NESHAP,
then that equipment is not subject to the corresponding requirements in
the OLD NESHAP.

    Table 1--NESHAP and Industrial Source Categories Affected by This
                             Proposed Action
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                                              North American Industry
        Source category and NESHAP         Classification System (NAICS)
                                                        Code
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Organic Liquids Distribution (Non-         3222, 3241, 3251, 3252, 3259,
 Gasoline).                                 3261, 3361, 3362, 3399,
                                            4247, 4861, 4869, 4931,
                                            5622.
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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/organic-liquids-distribution-national-emission-standards-hazardous. Following
publication in the Federal Register, the EPA will post the Federal
Register version of the proposal and key technical documents at this
same website. Information on the overall RTR program is available at
https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html.
    A redline version of the regulatory language that incorporates the
proposed changes in this action is available in the docket for this
action (Docket ID No. EPA-HQ-OAR-2018-0074).

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 action.
    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
Natural Resources Defense Council v. EPA, 529 F.3d 1077, 1083 (D.C.
Cir. 2008).
    The approach incorporated into the CAA and used by the EPA to
evaluate residual risk and to develop standards under CAA section
112(f)(2) is a two-step approach. In the first step, the EPA determines
whether risks are acceptable. This determination ``considers all health
information, including risk estimation uncertainty, and includes a
presumptive limit on maximum individual lifetime [cancer] risk (MIR)\1\
of approximately 1-in-10 thousand.'' 54 FR 38045, September 14, 1989.
If risks are unacceptable, the EPA must determine the emissions
standards necessary to reduce risk to an acceptable level without
considering costs. In the second step of the approach, the EPA
considers whether the emissions standards provide an ample margin of
safety to protect public health ``in consideration of all health
information, including the number of persons at risk levels higher than
approximately 1-in-1 million, as well as other relevant factors,
including costs and economic impacts, technological feasibility, and
other factors relevant to each particular decision.'' Id. The EPA must
promulgate emission standards necessary to provide an ample margin of
safety to protect public health or determine that the standards being
reviewed provide an ample margin of safety without any revisions. After
conducting the ample margin of safety analysis, we consider whether a
more stringent standard is necessary to prevent, taking into
consideration costs, energy, safety, and other relevant factors, an
adverse environmental effect.
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    \1\ Although defined as ``maximum individual risk,'' MIR refers
only to cancer risk. MIR, one metric for assessing cancer risk, is
the estimated risk if an individual were exposed to the maximum
level of a pollutant for a lifetime.
---------------------------------------------------------------------------

    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 v. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008).
Association of Battery Recyclers, Inc. v. EPA, 716 F.3d 667 (D.C. Cir.
2013). The EPA may consider cost in deciding whether to revise the
standards pursuant to CAA section 112(d)(6).

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

    As defined in the Initial List of Categories of Sources Under
Section 112(c)(1) of the Clean Air Act Amendments of 1990 (see 57 FR
31576, July 16, 1992) and Documentation for Developing the Initial
Source Category List, Final Report (see EPA-450/3-91-030, July, 1992),
the OLD source category includes, but is not limited to, those
activities associated with the storage and distribution of organic
liquids other than gasoline, at sites that serve as distribution points
from which organic liquids may be obtained for further use and
processing.
    The OLD source category involves the distribution of organic
liquids into, out of, or within a source. The distribution activities
include the storage of organic liquids in storage tanks not subject to
other 40 CFR part 63 standards and transfers into or out of the tanks
from or to cargo tanks, containers, and pipelines. Organic liquids are
any crude oils downstream of the first point of custody transfer and
any non-crude oil liquid that contains at least 5 percent by weight of
any combination of the 98 HAP listed in Table 1 of 40 CFR part 63,
subpart EEEE. For the purposes of the OLD NESHAP, organic liquids do
not include gasoline, kerosene (No. 1 distillate oil), diesel (No. 2
distillate oil), asphalt, and heavier distillate oil and

fuel oil, fuel that is consumed or dispensed on the plant site,
hazardous waste, wastewater, ballast water, or any non-crude liquid
with an annual average true vapor pressure less than 0.7 kilopascals
(0.1 psia). The OLD NESHAP applies only to major sources of HAP (i.e.,
sources that have the potential to emit 10 tpy of any single HAP or 25
tpy of combined HAP). Facilities subject to this NESHAP fall into two
types, either (1) petrochemical terminals primarily in the business of
storing and distributing organic liquids or (2) chemical production
facilities or other manufacturing facilities that have either a
distribution terminal not subject to another major source NESHAP or
have a few miscellaneous storage tanks or transfer racks that are not
otherwise subject to another major source NESHAP.
    Equipment controlled by the OLD NESHAP are storage tanks, transfer
operations, transport vehicles while being loaded, and equipment leak
components (valves, pumps, and sampling connections) that have the
potential to leak. Table 2 to subpart EEEE of part 63 contains the
criteria for control of storage tanks and transfer racks. If a storage
tank of a certain threshold capacity stores crude oil or a non-crude
organic liquid having a threshold sum of partial pressures of HAP, then
compliance options are either to (1) route emissions through a closed
vent system to a control device that achieves a 95-percent control
efficiency or (2) comply with work practice standards of 40 CFR part 63
subpart WW (i.e., operate the tank with a compliant internal floating
roof (IFR) or a compliant external floating roof), route emissions
through a closed vent system to a fuel gas system of a process, or
route emissions through a vapor balancing system that meets
requirements specified in 40 CFR 63.2346(a)(4). Storage tanks storing
non-crude organic liquids having a sum of partial pressures of HAP of
at least 11.1 psia do not have the option to comply using an internal
or external floating roof tank. Table 2 to subpart EEEE of part 63
contains the criteria for control of transfer racks, which are based on
the facility-wide organic liquid loading volume for organic liquids
having threshold HAP content expressed in percent HAP by weight of the
organic liquid. For transfer racks required to control HAP emissions,
the standards are either to (1) route emissions through a closed vent
system to a control device that achieves 98-percent control efficiency
or (2) operate a compliant vapor balancing system. Transfer rack
systems that fill containers of 55 gallons or greater are required to
comply with specific provisions of 40 CFR part 63, subpart PP or
operate a vapor balancing system.
    The NESHAP requires leak detection and repair for certain equipment
components associated with storage tanks and transfer racks subject to
this subpart and for certain equipment components associated with
pipelines between such storage tanks and transfer racks. The components
are specified in the definition of ``equipment leak components'' at 40
CFR 63.2406 and include pumps, valves, and sampling connection systems
in organic liquid service. The owner or operator is required to comply
with the requirements for pumps, valves, and sampling connections in 40
CFR part 63, subpart TT (control level 1), subpart UU (control level
2), or subpart H. This requires the use of Method 21 of appendix A-7 to
40 CFR part 60 (``Method 21'') to determine the concentration of any
detected leaks and to repair the component if the measured
concentration exceeds the definition of a leak within the applicable
subpart.
    Pressure relief devices on vapor balancing systems are required to
be monitored quarterly for leaks. An instrument reading of 500 parts
per million (ppm) or greater defines a leak. Leaks must be repaired
within 5 days.
    The types of organic liquids and emission sources covered by the
OLD NESHAP are frequently found at many types of facilities that are
already subject to other NESHAP. If equipment is in organic liquids
distribution service and is subject to another 40 CFR part 63 NESHAP,
then that equipment is not subject to the corresponding requirements in
the OLD NESHAP.

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

    The EPA used several sources to develop the list of existing
facilities subject to the OLD NESHAP. All facilities in the 2014
National Emissions Inventory (NEI) and the Toxics Release Inventory
having a facility source type as petroleum storage facility or with a
primary facility NAICS code beginning with 325, representing the
chemical manufacturing sector, were queried to create a comprehensive
base facility list. We supplemented this list with facility lists from
the original OLD NESHAP rule, the Marine Vessel Loading NESHAP, a list
of petrochemical storage facilities from the Internal Revenue Service,
and from the Office of Enforcement and Compliance Assurance's
Enforcement and Compliance History Online (ECHO) tool (https://echo.epa.gov). The EPA reviewed title V air permits to determine which
facilities on the comprehensive list were subject to the OLD NESHAP.
The current facility list consists of 177 facilities subject to the OLD
NESHAP.

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

    We are relying on technical reports and memoranda that the EPA
developed for flares used as air pollution control devices (APCDs) in
the Petroleum Refinery Sector RTR and New Source Performance Standards
rulemaking (80 FR 75178, December 1, 2015). These technical reports and
memoranda can be found in the Petroleum Refinery Sector Docket for that
action, Docket ID No. EPA-HQ-OAR-2010-0682. The Petroleum Refinery
Sector Docket contains a number of flare-related technical reports and
memoranda documenting numerous analyses the EPA conducted to develop
the final suite of operational and monitoring requirements for refinery
flares. We are incorporating this docket by reference in this rule.
Even though we are incorporating the Petroleum Refinery Sector Docket
by reference, for completeness of the rulemaking record for this action
and for ease of reference in finding these items, we are including a
list of specific technical support documents in Table 1 of the
memorandum, Control Option Impacts for Flares Located in the Organic
Liquids Distribution (Non-Gasoline) Source Category, in this docket for
this action.
    Also related to the enhancements we are proposing for flares, we
are citing the Flare Operational Requirements in the Vopak Terminal
Deer Park consent decree, available at https://www.epa.gov/enforcement/vopak-north-america-inc-clean-air-act-settlement-agreement and included
in the docket for this action.
    We are also relying on background information about the fenceline
monitoring program established for the Petroleum Refinery Sector rule,
Docket ID No. EPA-HQ-OAR-2010-0682. We are incorporating this docket by
reference in this rule. Even though we are incorporating the docket by
reference, for completeness of the rulemaking record for this action
and for ease of reference in finding these items, we are including the
following document in the docket for this action memorandum, Fenceline
Monitoring Impact Estimates for Final Rule.
    Lastly, we are incorporating by reference into this action all the
information associated with the

development of the current OLD NESHAP standards at Docket ID No. EPA-
HQ-OAR-2003-0138. This docket includes the materials from the legacy
Docket ID No. A-98-13 associated with the development of the original
OLD NESHAP.

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, the 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.\2\ 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 the policy
chosen by the Administrator permits consideration of multiple measures
of health risk. Not only can the MIR figure be considered, but also
incidence, the presence of non-cancer health effects, and the
uncertainties of the risk estimates. In this way, the effect on the
most exposed individuals can be reviewed as well as the impact on the
general public. These factors can then be weighed in each individual
case. This approach complies with the Vinyl Chloride mandate that the
Administrator ascertain an acceptable level of risk to the public by
employing his expertise to assess available data. It also complies with
the Congressional intent behind the CAA, which did not exclude the use
of any particular measure of public health risk from the EPA's
consideration with respect to CAA section 112 regulations, and thereby
implicitly permits consideration of any and all measures of health risk
which the Administrator, in his judgment, believes are appropriate to
determining what will protect the public health. 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.
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    \2\ The MIR is defined as the cancer risk associated with a
lifetime of exposure at the highest concentration of HAP where
people are likely to live. The HQ is the ratio of the potential HAP
exposure concentration to the noncancer dose-response value; the HI
is the sum of HQs for HAP that affect the same target organ or organ
system.
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    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. In other words, risks that include
an MIR above 100-in-1 million may be determined to be acceptable, and
risk with an MIR below that level may be determined to be unacceptable,
depending on all of the available health information. Similarly, with
regard to the ample margin of safety analysis, the EPA stated in the
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.'' \3\
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    \3\ Recommendations of the SAB Risk and Technology Review
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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    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 emission 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 eight sections
that follow this paragraph describe how we estimated emissions and
conducted the risk assessment. The docket for this action contains the
following document which provides more information on the risk
assessment inputs and models: Residual Risk Assessment for the Organic
Liquids Distribution (Non-Gasoline) Source Category in Support of the
2019 Risk and Technology Review Proposed Rule. The methods used to
assess risk (as described in the eight primary steps below) are
consistent with those described by the EPA in the document reviewed by
a panel of the EPA's SAB in 2009,\4\ and described in the SAB review
report issued in 2010.\5\ They are also consistent with the key
recommendations contained in that report.
---------------------------------------------------------------------------

    \4\ 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.
    \5\ U.S. EPA SAB. Review of EPA's draft, 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'' May 2010. https://
yosemite.epa.gov/sab/sabproduct.nsf/
4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf.
---------------------------------------------------------------------------

1. How did we estimate actual emissions and identify the emissions
release characteristics?
    The OLD facility list was developed as described in section II.C of
this preamble and currently consists of 177 facilities identified as
being subject to the OLD NESHAP. The emissions modeling input files
were developed using the EPA's 2014 NEI. The complete OLD facility list
is available in Appendix 1 of the memorandum, Residual Risk Assessment
for the Organic Liquids Distribution (Non-Gasoline) Source Category in
Support of the 2019 Risk and Technology Review Proposed Rule, which is
available in the docket for this action.
    The EPA used the 2014 NEI data for these facilities to create the
risk assessment model input files using all available HAP emissions
records and other emission release parameters. From the whole facility
risk assessment model input file, the EPA identified emission sources
within the OLD source category from the 2014 NEI data such as source
classification codes (SCCs) and SCC descriptions, emission unit
descriptions, and process descriptions to identify emissions that are
subject to OLD and those that are not. For example, emission units that
were described as chemical production process vents were marked as
being out of the source category. For many facilities in the source
category, the EPA used information in the title V permit to relate
emissions in the 2014 NEI and to assign whether the emissions are
within the OLD source category. In several cases, in the absence of
definitive information that would place the emissions out of the OLD
source category, if the 2014 NEI data indicated

the emissions were associated with a storage tank, a transfer rack or
equipment leaks, the emissions are presumed to be in the OLD source
category. For 21 sources, there were no HAP emissions in the 2014 NEI
that were able to be attributed to OLD equipment.
    The EPA reviewed emissions release point information such as
release point location; emission release point type (stack verses
fugitive); temperature; and the correlation between stack diameter,
velocity, and volumetric flow. In some cases, we corrected release
point locations where the original location was outside of the apparent
facility boundary. During the process of quality assuring the modeling
file input data, for some cases, we obtained specific information from
facility contacts. On November 6, 2018, we also posted a draft of the
model input file on the EPA's website at https://www.epa.gov/stationary-sources-air-pollution/organic-liquids-distribution-national-emission-standards-hazardous. We received feedback from two companies
and included those comments in the docket for this action. Except for
removing facilities having no OLD applicability, the EPA did not make
any of the changes to the modeling file in response to these comments
after posting the draft model input file on the EPA's website because
none of the changes would impact the conclusions of the source category
risk results.
    A record of all changes made to the risk assessment model input
file throughout the quality assurance process is provided in Appendix 1
of the memorandum, Residual Risk Assessment for the Organic Liquids
Distribution (Non-Gasoline) Source Category in Support of the 2019 Risk
and Technology Review Proposed Rule, which is available in the docket
for this action.
2. How did we estimate MACT-allowable emissions?
    The available emissions data in the RTR emissions dataset include
estimates of the mass of HAP emitted during a specified annual 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.)
    For the risk assessment modeling purposes, we modeled 2014 NEI
reported actual emissions for the OLD source category. In preparation
of this RTR, we did not conduct an information collection of the
equipment in this source category. Instead, we relied primarily upon
the 2014 NEI emissions data and readily available title V permit
information to characterize the actual emissions from the source
category. We consider the use of 2014 NEI actual emissions as the best
available reasonable approximation of allowable emissions for the risk
assessment model.
3. How do we conduct dispersion modeling, determine inhalation
exposures, and estimate individual and population inhalation risk?
    Both long-term and short-term inhalation exposure concentrations
and health risk from the source category addressed in this proposal
were estimated using the Human Exposure Model (HEM-3).\6\ The HEM-3
performs three primary risk assessment activities: (1) Conducting
dispersion modeling to estimate the concentrations of HAP in ambient
air, (2) estimating long-term and short-term inhalation exposures to
individuals residing within 50 kilometers (km) of the modeled sources,
and (3) estimating individual and population-level inhalation risk
using the exposure estimates and quantitative dose-response
information.
---------------------------------------------------------------------------

    \6\ For more information about HEM-3, go to https://www.epa.gov/fera/risk-assessment-and-modeling-human-exposure-model-hem.
---------------------------------------------------------------------------

a. Dispersion Modeling
    The air dispersion model AERMOD, used by the HEM-3 model, is one of
the EPA's preferred models for assessing air pollutant concentrations
from industrial facilities.\7\ To perform the dispersion modeling and
to develop the preliminary risk estimates, HEM-3 draws on three data
libraries. The first is a library of meteorological data, which is used
for dispersion calculations. This library includes 1 year (2016) of
hourly surface and upper air observations from 824 meteorological
stations, selected to provide coverage of the United States and Puerto
Rico. A second library of United States Census Bureau census block \8\
internal point locations and populations provides the basis of human
exposure calculations (U.S. Census, 2010). In addition, for each census
block, the census library includes the elevation and controlling hill
height, which are also used in dispersion calculations. A third library
of pollutant-specific dose-response values is used to estimate health
risk. These values are discussed below.
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    \7\ U.S. EPA. Revision to the Guideline on Air Quality Models:
Adoption of a Preferred General Purpose (Flat and Complex Terrain)
Dispersion Model and Other Revisions (70 FR 68218, November 9,
2005).
    \8\ A census block is the smallest geographic area for which
census statistics are tabulated.
---------------------------------------------------------------------------

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) by its unit risk estimate (URE). The URE is an upper-bound
estimate of an individual's incremental risk of contracting cancer over
a lifetime of exposure to a concentration of 1 microgram of the
pollutant per cubic meter of air. For residual risk assessments, we
generally use UREs from the EPA's Integrated Risk Information System
(IRIS). For carcinogenic pollutants without IRIS values, we look to
other reputable sources of cancer dose-response values, often using
California EPA (CalEPA) UREs, where available. In cases where new,
scientifically credible dose-response values have been developed in a
manner consistent with EPA guidelines and have undergone a peer

review process similar to that used by the EPA, we may use such dose-
response values in place of, or in addition to, other values, if
appropriate. The pollutant-specific dose-response values used to
estimate health risk are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants.
    To estimate individual lifetime cancer risks associated with
exposure to HAP emissions from each facility in the source category, we
sum the risks for each of the carcinogenic HAP \9\ emitted by the
modeled facility. We estimate cancer risk at every census block within
50 km of every facility in the source category. The MIR is the highest
individual lifetime cancer risk estimated for any of those census
blocks. In addition to calculating the MIR, we estimate the
distribution of individual cancer risks for the source category by
summing the number of individuals within 50 km of the sources whose
estimated risk falls within a specified risk range. We also estimate
annual cancer incidence by multiplying the estimated lifetime cancer
risk at each census block by the number of people residing in that
block, summing results for all of the census blocks, and then dividing
this result by a 70-year lifetime.
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    \9\ The EPA's 2005 Guidelines for Carcinogen Risk Assessment
classifies carcinogens as: ``carcinogenic to humans,'' ``likely to
be carcinogenic to humans,'' and ``suggestive evidence of
carcinogenic potential.'' These classifications also coincide with
the terms ``known carcinogen, probable carcinogen, and possible
carcinogen,'' respectively, which are the terms advocated in the
EPA's Guidelines for Carcinogen Risk Assessment, published in 1986
(51 FR 33992, September 24, 1986). In August 2000, the document,
Supplemental Guidance for Conducting Health Risk Assessment of
Chemical Mixtures (EPA/630/R-00/002), was published as a supplement
to the 1986 document. Copies of both documents can be obtained from
https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=20533&CFID=70315376&CFTOKEN=71597944. Summing
the risks of these individual compounds to obtain the cumulative
cancer risks is an approach that was recommended by the EPA's SAB in
their 2002 peer review of the EPA's National Air Toxics Assessment
(NATA) titled, NATA--Evaluating the National-scale Air Toxics
Assessment 1996 Data--an SAB Advisory, available at http://
yosemite.epa.gov/sab/sabproduct.nsf/
214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf.
---------------------------------------------------------------------------

    To assess the risk of noncancer health effects from chronic
exposure to HAP, we calculate either an HQ or a target organ-specific
hazard index (TOSHI). We calculate an HQ when a single noncancer HAP is
emitted. Where more than one noncancer HAP is emitted, we sum the HQ
for each of the HAP that affects a common target organ or target organ
system to obtain a TOSHI. The HQ is the estimated exposure divided by
the chronic noncancer dose-response value, which is a value selected
from one of several sources. The preferred chronic noncancer dose-
response value is the EPA RfC, defined as ``an estimate (with
uncertainty spanning perhaps an order of magnitude) of a continuous
inhalation exposure to the human population (including sensitive
subgroups) that is likely to be without an appreciable risk of
deleterious effects during a lifetime'' (https://iaspub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&vocabName=IRIS%20Glossary). In cases where an RfC
from the EPA's IRIS is not available or where the EPA determines that
using a value other than the RfC is appropriate, the chronic noncancer
dose-response value can be a value from the following prioritized
sources, which define their dose-response values similarly to the EPA:
(1) The Agency for Toxic Substances and Disease Registry (ATSDR)
Minimum Risk Level (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,\10\ 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 the Organic Liquids Distribution (Non-Gasoline) 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 have been applying this revision in
RTR rulemakings proposed on or after June 3, 2019.
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    \10\ 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 (i.e., 99th
percentile),\11\ and the point of highest off-site exposure.
Specifically, we assume that peak emissions from the source category
and reasonable worst-case air dispersion conditions co-occur and that a
person is present at the point of maximum exposure. These assumptions
represent a reasonable worst-case exposure scenario and, although less
conservative than our previous approach, is still sufficiently
conservative given that 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.
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    \11\ In the absence of hourly emission data, we develop
estimates of maximum hourly emission rates by multiplying the
average actual annual emissions rates by a factor (either a
category-specific factor or a default factor of 10) to account for
variability. This is documented in Residual Risk Assessment for the
Organic Liquids Distribution (Non-Gasoline) 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. Both are available in the docket for this
action.
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    To characterize the potential health risks associated with
estimated acute inhalation exposures to a HAP, we generally use
multiple acute dose-response values, including acute RELs, acute
exposure guideline levels (AEGLs), and emergency response planning
guidelines (ERPG) for 1-hour exposure durations, if available, to
calculate acute HQs. The acute HQ is calculated by dividing the
estimated acute exposure concentration by the acute dose-response
value. For each HAP for which acute dose-response values are available,
the EPA calculates acute HQs.
    An acute REL is defined as ``the concentration level at or below
which no adverse health effects are anticipated

for a specified exposure duration.'' \12\ 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.\13\ 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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    \12\ CalEPA issues acute RELs as part of its Air Toxics Hot
Spots Program, and the 1-hour and 8-hour values are documented in
Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The
Determination of Acute Reference Exposure Levels for Airborne
Toxicants, which is available at http://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-rel-summary.
    \13\ 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.'' \14\ 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 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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    \14\ ERPGS Procedures and Responsibilities. March 2014. American
Industrial Hygiene Association. Available at: https://www.aiha.org/get-involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Documents/ERPG%20Committee%20Standard%20Operating%20Procedures%20%20-%20March%202014%20Revision%20%28Updated%2010-2-2014%29.pdf.
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    An acute REL for 1-hour exposure durations is typically lower than
its corresponding AEGL-1 and ERPG-1. Even though their definitions are
slightly different, AEGL-1s are often the same as the corresponding
ERPG-1s, and AEGL-2s are often equal to ERPG-2s. The maximum HQs from
our acute inhalation screening risk assessment typically result when we
use the acute REL for a HAP. In cases where the maximum acute HQ
exceeds 1, we also report the HQ based on the next highest acute dose-
response value (usually the AEGL-1 and/or the ERPG-1).
    For this source category, we used the default acute emissions
multiplier of 10 to conservatively estimate maximum hourly rates.
    In our acute inhalation screening risk assessment, acute impacts
are deemed negligible for HAP where acute HQs are less than or equal to
1, and no further analysis is performed for these HAP. In cases for
which an acute HQ from the screening step is greater than 1, we assess
the site-specific data to ensure that the acute HQ is at an off-site
location. For this source category, the data refinements employed
consisted of determining the maximum off-site acute HQ for each
facility that had an initial HQ greater than 1. These refinements are
discussed more fully in the Residual Risk Assessment for the Organic
Liquids Distribution (Non-Gasoline) Source Category in Support of the
2019 Risk and Technology Review Proposed Rule, which is available in
the docket for this action.
4. How do we conduct the multipathway exposure and risk screening
assessment?
    The EPA conducts a tiered screening assessment examining the
potential for significant human health risks due to exposures via
routes other than inhalation (i.e., ingestion). We first determine
whether any sources in the source category emit any HAP known to be
persistent and bioaccumulative in the environment, as identified in the
EPA's Air Toxics Risk Assessment Library (see Volume 1, Appendix D, at
https://www.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library).
    For the OLD source category, we identified PB-HAP emissions of
arsenic, cadmium, lead, mercury, and polycyclic organic matter (POM).
Therefore, we proceeded to the next step of the evaluation. Except for
lead, the human health risk screening assessment for PB-HAP consists of
three progressive tiers. In a Tier 1 screening assessment, we determine
whether the magnitude of the facility-specific emissions of PB-HAP
warrants further evaluation to characterize human health risk through
ingestion exposure. To facilitate this step, we evaluate emissions
against previously developed screening threshold emission rates for
several PB-HAP that are based on a hypothetical upper-end screening
exposure scenario developed for use in conjunction with the EPA's Total
Risk Integrated Methodology.Fate, Transport, and Ecological Exposure
(TRIM.FaTE) model. The PB-HAP with screening threshold emission rates
are arsenic compounds, cadmium compounds, chlorinated dibenzodioxins
and furans, mercury compounds, and POM. Based on the EPA estimates of
toxicity and bioaccumulation potential, these pollutants represent a
conservative list for inclusion in multipathway risk assessments for
RTR rules. (See Volume 1, Appendix D at https://www.epa.gov/sites/production/files/2013-08/documents/volume_1_reflibrary.pdf). In this
assessment, we compare the facility-specific emission rates of these
PB-HAP to the screening threshold emission rates for each PB-HAP to
assess the potential for significant human health risks via the
ingestion pathway. We call this application of the TRIM.FaTE model the
Tier 1 screening assessment. The ratio of a facility's actual emission
rate to the Tier 1 screening threshold emission rate is a ``screening
value.''
    We derive the Tier 1 screening threshold emission rates for these
PB-HAP (other than lead compounds) to

correspond to a maximum excess lifetime cancer risk of 1-in-1 million
(i.e., for arsenic compounds, polychlorinated dibenzodioxins and furans
and POM) or, for HAP that cause noncancer health effects (i.e., cadmium
compounds and mercury compounds), a maximum HQ of 1. If the emission
rate of any one PB-HAP or combination of carcinogenic PB-HAP in the
Tier 1 screening assessment exceeds the Tier 1 screening threshold
emission rate for any facility (i.e., the screening value is greater
than 1), we conduct a second screening assessment, which we call the
Tier 2 screening assessment. The Tier 2 screening assessment separates
the Tier 1 combined fisher and farmer exposure scenario into fisher,
farmer, and gardener scenarios that retain upper-bound ingestion rates.
    In the Tier 2 screening assessment, the location of each facility
that exceeds a Tier 1 screening threshold emission rate is used to
refine the assumptions associated with the Tier 1 fisher scenario and
farmer exposure scenarios at that facility. A key assumption in the
Tier 1 screening assessment is that a lake and/or farm is located near
the facility. As part of the Tier 2 screening assessment, we use a U.S.
Geological Survey (USGS) database to identify actual waterbodies within
50 km of each facility and assume the fisher only consumes fish from
lakes within that 50 km zone. We also examine the differences between
local meteorology near the facility and the meteorology used in the
Tier 1 screening assessment. We then adjust the previously-developed
Tier 1 screening threshold emission rates for each PB-HAP for each
facility based on an understanding of how exposure concentrations
estimated for the screening scenario change with the use of local
meteorology and USGS lakes database.
    In the Tier 2 farmer scenario, we maintain an assumption that the
farm is located within 0.5 km of the facility and that the farmer
consumes meat, eggs, dairy, vegetables, and fruit produced near the
facility. We may further refine the Tier 2 screening analysis by
assessing a gardener scenario to characterize a range of exposures with
the gardener scenario being more plausible in RTR evaluations. Under
the gardener scenario, we assume the gardener consumes home-produced
eggs, vegetables, and fruit products at the same ingestion rate as the
farmer. The Tier 2 screen continues to rely on the high-end food intake
assumptions that were applied in Tier 1 for local fish (adult female
angler at 99th percentile fish consumption \15\) and locally grown or
raised foods (90th percentile consumption of locally grown or raised
foods for the farmer and gardener scenarios \16\). If PB-HAP emission
rates do not result in a Tier 2 screening value greater than 1, we
consider those PB-HAP emissions to pose risks below a level of concern.
If the PB-HAP emission rates for a facility exceed the Tier 2 screening
threshold emission rates, we may conduct a Tier 3 screening assessment.
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    \15\ Burger, J. 2002. Daily consumption of wild fish and game:
Exposures of high end recreationists. International Journal of
Environmental Health Research 12:343-354.
    \16\ U.S. EPA. Exposure Factors Handbook 2011 Edition (Final).
U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/
052F, 2011.
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    There are several analyses that can be included in a Tier 3
screening assessment, depending upon the extent of refinement
warranted, including validating that the lakes are fishable, locating
residential/garden locations for urban and/or rural settings,
considering plume-rise to estimate emissions lost above the mixing
layer, and considering hourly effects of meteorology and plume rise on
chemical fate and transport (a time-series analysis). If necessary, the
EPA may further refine the screening assessment through a site-specific
assessment.
    In evaluating the potential multipathway risk from emissions of
lead compounds, rather than developing a screening threshold emission
rate, we compare maximum estimated chronic inhalation exposure
concentrations to the level of the current National Ambient Air Quality
Standard (NAAQS) for lead.\17\ Values below the level of the primary
(health-based) lead NAAQS are considered to have a low potential for
multipathway risk. For further information on the multipathway
assessment approach, see the Residual Risk Assessment for the Organic
Liquids Distribution (Non-Gasoline) Source Category in Support of the
Risk and Technology Review 2019 Proposed Rule, which is available in
the docket for this action.
---------------------------------------------------------------------------

    \17\ 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'').
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.
---------------------------------------------------------------------------

5. How do we assess risks considering emissions control options?
    In addition to assessing baseline inhalation risks and screening
for potential multipathway risks, we also estimate risks considering
the potential emission reductions that would be achieved by the control
options under consideration. In these cases, the expected emission
reductions are applied to the specific HAP and emission points in the
RTR emissions dataset to develop corresponding estimates of risk and
incremental risk reductions.
6. How do we conduct the environmental risk screening assessment?
a. Adverse Environmental Effect, Environmental HAP, and Ecological
Benchmarks
    The EPA conducts a screening assessment to examine the potential
for an adverse environmental effect as required under section
112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA defines ``adverse
environmental effect'' as ``any significant and widespread adverse
effect, which may reasonably be anticipated, to wildlife, aquatic life,
or other natural resources, including adverse impacts on populations of
endangered or threatened species or significant degradation of
environmental quality over broad areas.''
    The EPA focuses on eight HAP, which are referred to as
``environmental HAP,'' in its screening assessment: Six PB-HAP and two
acid gases. The PB-HAP included in the screening assessment are arsenic
compounds, cadmium compounds, dioxins/furans, POM, mercury (both
inorganic mercury and methyl mercury), and lead compounds. The acid
gases included in the screening assessment are hydrochloric acid (HCl)
and hydrogen fluoride (HF).
    HAP that persist and bioaccumulate are of particular environmental
concern because they accumulate in the soil, sediment, and water. The
acid gases, HCl and HF, are included due to their well-documented
potential to cause direct damage to terrestrial plants. In the
environmental risk screening assessment, we evaluate the following four
exposure media: Terrestrial soils, surface water bodies (includes
water-column and benthic sediments), fish consumed by wildlife, and
air. Within these four exposure media, we evaluate nine ecological
assessment endpoints, which are defined by the ecological

entity and its attributes. For PB-HAP (other than lead), both
community-level and population-level endpoints are included. For acid
gases, the ecological assessment evaluated is terrestrial plant
communities.
    An ecological benchmark represents a concentration of HAP that has
been linked to a particular environmental effect level. For each
environmental HAP, we identified the available ecological benchmarks
for each assessment endpoint. We identified, where possible, ecological
benchmarks at the following effect levels: Probable effect levels,
lowest-observed-adverse-effect level, and no-observed-adverse-effect
level. In cases where multiple effect levels were available for a
particular PB-HAP and assessment endpoint, we use all of the available
effect levels to help us to determine whether ecological risks exist
and, if so, whether the risks could be considered significant and
widespread.
    For further information on how the environmental risk screening
assessment was conducted, including a discussion of the risk metrics
used, how the environmental HAP were identified, and how the ecological
benchmarks were selected, see Appendix 9 of the Residual Risk
Assessment for the Organic Liquids Distribution (Non-Gasoline) Source
Category in Support of the Risk and Technology Review 2019 Proposed
Rule, which is available in the docket for this action.
b. Environmental Risk Screening Methodology
    For the environmental risk screening assessment, the EPA first
determined whether any facilities in the OLD source category emitted
any of the environmental HAP. For the OLD source category, we
identified emissions of arsenic compounds, cadmium compounds, dioxins/
furans, POM, mercury (both inorganic mercury and methyl mercury), lead
compounds, HCl, and HF. 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 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
Residual Risk Assessment for the Organic Liquids Distribution (Non-
Gasoline) Source Category in Support of the Risk and Technology Review
2019 Proposed Rule, which is available in the docket for this action.
7. How do we conduct facility-wide assessments?
    To put the source category risks in context, we typically examine
the risks from the entire ``facility,'' where the facility includes all
HAP-emitting operations within a contiguous area and under common
control. In other words,

we examine the HAP emissions not only from the source category emission
points of interest, but also emissions of HAP from all other emission
sources at the facility for which we have data. For this source
category, we conducted the facility-wide assessment using a dataset
compiled from the 2014 NEI. We flagged source category records of that
NEI dataset as described in section II.C of this preamble. We performed
quality assurance and quality control on the whole facility dataset,
including the source category records. The facility-wide file was then
used to analyze risks due to the inhalation of HAP that are emitted
``facility-wide'' for the populations residing within 50 km of each
facility, consistent with the methods used for the source category
analysis described above. For these facility-wide risk analyses, the
modeled source category risks were compared to the facility-wide risks
to determine the portion of the facility-wide risks that could be
attributed to the source category addressed in this proposal. We also
specifically examined the facility that was associated with the highest
estimate of risk and determined the percentage of that risk
attributable to the source category of interest. The Residual Risk
Assessment for the Organic Liquids Distribution (Non-Gasoline) Source
Category in Support of the Risk and Technology Review 2019 Proposed
Rule, available through the docket for this action, provides the
methodology and results of the facility-wide analyses, including all
facility-wide risks and the percentage of source category contribution
to facility-wide risks.
8. How do we consider uncertainties in risk assessment?
    Uncertainty and the potential for bias are inherent in all risk
assessments, including those performed for this proposal. Although
uncertainty exists, we believe that our approach, which used
conservative tools and assumptions, ensures that our decisions are
health and environmentally protective. A brief discussion of the
uncertainties in the RTR emissions dataset, dispersion modeling,
inhalation exposure estimates, and dose-response relationships follows
below. Also included are those uncertainties specific to our acute
screening assessments, multipathway screening assessments, and our
environmental risk screening assessments. A more thorough discussion of
these uncertainties is included in the Residual Risk Assessment for the
Organic Liquids Distribution (Non-Gasoline) Source Category in Support
of the Risk and Technology Review 2019 Proposed Rule, which is
available in the docket for this action. If a multipathway site-
specific assessment was performed for this source category, a full
discussion of the uncertainties associated with that assessment can be
found in Appendix 11 of that document, Site-Specific Human Health
Multipathway Residual Risk Assessment Report.
a. Uncertainties in the RTR Emissions Dataset
    Although the development of the RTR emissions dataset involved
quality assurance/quality control processes, the accuracy of emissions
values will vary depending on the source of the data, the degree to
which data are incomplete or missing, the degree to which assumptions
made to complete the datasets are accurate, errors in emission
estimates, and other factors. The emission estimates considered in this
analysis generally are annual totals for certain years, and they do not
reflect short-term fluctuations during the course of a year or
variations from year to year. The estimates of peak hourly emission
rates for the acute effects screening assessment were based on an
emission adjustment factor applied to the average annual hourly
emission rates, which are intended to account for emission fluctuations
due to normal facility operations.
b. Uncertainties in Dispersion Modeling
    We recognize there is uncertainty in ambient concentration
estimates associated with any model, including the EPA's recommended
regulatory dispersion model, AERMOD. In using a model to estimate
ambient pollutant concentrations, the user chooses certain options to
apply. For RTR assessments, we select some model options that have the
potential to overestimate ambient air concentrations (e.g., not
including plume depletion or pollutant transformation). We select other
model options that have the potential to underestimate ambient impacts
(e.g., not including building downwash). Other options that we select
have the potential to either under- or overestimate ambient levels
(e.g., meteorology and receptor locations). On balance, considering the
directional nature of the uncertainties commonly present in ambient
concentrations estimated by dispersion models, the approach we apply in
the RTR assessments should yield unbiased estimates of ambient HAP
concentrations. We also note that the selection of meteorology dataset
location could have an impact on the risk estimates. As we continue to
update and expand our library of meteorological station data used in
our risk assessments, we expect to reduce this variability.
c. Uncertainties in Inhalation Exposure Assessment
    Although every effort is made to identify all of the relevant
facilities and emission points, as well as to develop accurate
estimates of the annual emission rates for all relevant HAP, the
uncertainties in our emission inventory likely dominate the
uncertainties in the exposure assessment. Some uncertainties in our
exposure assessment include human mobility, using the centroid of each
census block, assuming lifetime exposure, and assuming only outdoor
exposures. For most of these factors, there is neither an under nor
overestimate when looking at the maximum individual risk or the
incidence, but the shape of the distribution of risks may be affected.
With respect to outdoor exposures, actual exposures may not be as high
if people spend time indoors, especially for very reactive pollutants
or larger particles. For all factors, we reduce uncertainty when
possible. For example, with respect to census-block centroids, we
analyze large blocks using aerial imagery and adjust locations of the
block centroids to better represent the population in the blocks. We
also add additional receptor locations where the population of a block
is not well represented by a single location.
d. Uncertainties in Dose-Response Relationships
    There are uncertainties inherent in the development of the dose-
response values used in our risk assessments for cancer effects from
chronic exposures and noncancer effects from both chronic and acute
exposures. Some uncertainties are generally expressed quantitatively,
and others are generally expressed in qualitative terms. We note, as a
preface to this discussion, a point on dose-response uncertainty that
is stated in the EPA's 2005 Guidelines for Carcinogen Risk Assessment;
namely, that ``the primary goal of EPA actions is protection of human
health; accordingly, as an Agency policy, risk assessment procedures,
including default options that are used in the absence of scientific
data to the contrary, should be health protective'' (the EPA's 2005
Guidelines for Carcinogen Risk Assessment, page 1-7). This is the
approach followed here as summarized in the next paragraphs.
    Cancer UREs used in our risk assessments are those that have been
developed to generally provide an upper

bound estimate of risk.\18\ 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.\19\ 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,\20\ 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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    \18\ IRIS glossary (https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary).
    \19\ 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.
    \20\ 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 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 HCl). For
lead, we use AERMOD to determine ambient air concentrations, which are
then compared to the secondary NAAQS standard for lead. Two important
types of uncertainty associated with the use of these models in RTR
risk assessments and inherent to any assessment that relies on
environmental modeling are model uncertainty and input uncertainty.\21\
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    \21\ 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 the
previous EPA SAB reviews and other reviews, we are confident that the
models used in the

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

IV. Analytical Results and Proposed Decisions

A. What actions are we taking pursuant to CAA sections 112(d)(2) and
112(d)(3)?

    In this action, we are proposing the following pursuant to CAA
section 112(d)(2) and (3): \22\ (1) Adding monitoring and operational
requirements for flares used as an APCD and (2) requesting comment on
whether the EPA should add requirements and clarifications for pressure
relief devices (PRD). The results and proposed decisions based on the
analyses performed pursuant to CAA section 112(d)(2) and (3) are
presented below.
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    \22\ The EPA has authority under CAA section 112(d)(2) and (3)
to set MACT standards for previously unregulated emission points.
The EPA also retains the discretion to revise a MACT standard under
the authority of CAA section 112(d)(2) and (3) (see Portland Cement
Ass'n v. EPA, 665 F.3d 177, 189 (D.C. Cir. 2011), such as when it
identifies an error in the original standard. See also Medical Waste
Institute v. EPA, 645 F. 3d at 426 (upholding the EPA action
establishing MACT floors, based on post-compliance data, when
originally-established floors were improperly established).
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1. Flares
    The EPA is proposing under CAA section 112(d)(2) and (3) to amend
the operating and monitoring requirements for flares used as APCDs in
the OLD source category because we have determined that the current
requirements for flares are not adequate to ensure the level of
destruction efficiency needed to conform with the MACT standards for
the OLD source category. A flare is a type of APCD used in the OLD
source category to control emissions from a single emission source
(i.e., a storage tank or a transfer rack) or multiple emission sources
(i.e., a combination of several storage tanks and/or transfer racks).
We have determined that 27 flares at 16 OLD facilities would be
affected by these proposed operating and monitoring requirements (see
the memorandum, Control Option Impacts for Flares Located in the
Organic Liquids Distribution Source Category, in the docket for this
action).
    The requirements applicable to flares in the OLD NESHAP are set
forth in the General Provisions to 40 CFR part 63 and are cross-
referenced in 40 CFR part 63, subpart SS. The OLD NESHAP allows storage
tanks and transfer racks to vent through a closed vent system and flare
that meet the requirements of 40 CFR part 63, subpart SS. In general,
flares used as APCDs at OLD facilities are expected to achieve a
minimum destruction efficiency of at least 98 percent by weight, when
designed and operated according to the General Provisions. Studies on
flare performance, however, indicate that these General Provision
requirements are inadequate to ensure proper performance of flares at
refineries and other petrochemical facilities (including chemical
manufacturing facilities), particularly when either assist steam or
assist air is used, but also when no assist is used.\23\ The data from
the recent

studies on flare performance \24\ clearly indicate that combustion
efficiencies begin to deteriorate at combustion net heating values
above 200 British thermal units per standard cubic foot (Btu/scf) and
that an operating limit of 200 Btu/scf in the flare vent gas, as
currently provided in the General Provisions for unassisted flares,
does not ensure that these flares will achieve an average destruction
efficiency of 98 percent. Therefore, we believe the proposed amendments
described in this section are necessary to ensure that OLD facilities
that use flares as APCD meet the MACT standards at all times when
controlling HAP emissions. In fact, at least one recent consent decree
addresses inefficient flare operations at a large bulk terminal in the
OLD source category.\25\
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    \23\ Based on review of NEI description fields and a sampling of
air permits, we believe the majority of flares at OLD facilities are
non-assisted.
    \24\ Parameters for Properly Designed and Operated Flares,
Docket ID Item No. EPA-HQ-OAR-2010-0682-0191.
    \25\ See the Flare Operational Requirements in the Vopak
Terminal Deer Park consent decree, available at: https://www.epa.gov/enforcement/vopak-north-america-inc-clean-air-act-settlement-agreement.
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    The General Provisions of 40 CFR 63.11(b) specify that flares are
(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 two 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 requires 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 (see the technical report,
Parameters for Properly Designed and Operated Flares, in Docket ID Item
No. EPA-HQ-OAR-2010-0682-0191, which has been incorporated into the
docket for this action). The EPA submitted the report, along with a
charge statement and a set of charge questions, to an external peer
review panel.\26\ The panel, consisting of individuals representing a
variety of backgrounds and perspectives (i.e., industry, academia,
environmental experts, and industrial flare consultants), concurred
with the EPA's assessment that the following three primary factors
affect flare performance: (1) The flow of the vent gas to the flare;
(2) the amount of assist media (e.g., steam or air) added to the flare;
and (3) the combustibility of the vent gas/assist media mixture in the
combustion zone (i.e., the net heating value, lower flammability limit,
and/or combustibles concentration) at the flare tip. However, 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, Peer Review of Parameters for Properly Designed and
Operated Flares, available in Docket ID Item No. EPA-HQ-OAR-2010-0682-
0193, which has been incorporated into the docket for this action.
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). We are also relying on the same
analyses and proposing the same operating limits for flares used as
APCDs in the OLD source category. The Agency believes, given the
results from the various data analyses conducted for the Petroleum
Refinery Sector rule (see section II.D of this preamble, which states
that the Petroleum Refinery RTR Docket is incorporated by reference
into the docket for this action),\27\ that the operating limits
promulgated for flares used in the Petroleum Refinery Sector are also
appropriate and reasonable and will ensure flares used as APCDs in the
OLD source category meet the HAP removal efficiency at all times.
Therefore, to ensure clarity and consistency in terminology with the
Petroleum Refinery Sector rule (80 FR 75178), we are proposing at 40
CFR 63.2380 to directly apply the Petroleum Refinery Sector rule flare
definitions and requirements in 40 CFR part 63, subpart CC to flares in
the OLD source category with certain clarifications and exemptions as
discussed in this section of the preamble.
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    \26\ These documents can also be found at https://www.epa.gov/stationary-sources-air-pollution/petroleum-refinery-sector-risk-and-technology-review-and-new-source.
    \27\ See technical memorandum, Flare Performance Data: Summary
of Peer Review Comments and Additional Data Analysis for Steam-
Assisted Flares, in Docket ID Item No. EPA-HQ-OAR-2010-0682-0200 for
a more detailed discussion of the data quality and analysis. See
technical memorandum, Petroleum Refinery Sector Rule: Operating
Limits for Flares, in Docket ID Item No. EPA-HQ-OAR-2010-0682-0206
for a more detailed discussion of the failure analysis. See
technical memorandum, Flare Control Option Impacts for Final
Refinery Sector Rule, in Docket ID Item No. EPA-HQ-OAR-2010-0682-
0748 for additional analyses on flare performance standards based on
public comments received on the proposed refinery rule.
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    Currently, the MACT standards in the OLD NESHAP cross-reference the
General Provisions at 40 CFR 63.11(b) for the operational requirements
for flares used as APCD (through reference of 40 CFR part 63, subpart
SS). This proposal specifies all operational and monitoring
requirements that are intended to apply to flares used as APCDs in the
OLD source category. All of the flare requirements in this proposed
rulemaking are intended to ensure compliance with the MACT standards in
the OLD NESHAP when using a flare as an APCD.
a. Pilot Flames
    This action proposes that flares used as APCDs in the OLD source
category operate pilot flame systems continuously when organic HAP
emissions are routed to the flare. The OLD NESHAP references the flare
requirements in 40 CFR 63.11(b) (through reference of 40 CFR part 63,
subpart SS and Table 12 to 40 CFR part 63 subpart EEEE), 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 cross-reference 40 CFR part 63, subpart CC to
include in the OLD NESHAP the existing provisions that flares operate
with a pilot flame at all times and be continuously monitored for a
pilot flame using a thermocouple or any other equivalent device.
    We are also proposing to add a continuous compliance measure that
would consider each 15-minute block when there is at least 1 minute
where no pilot flame is present when regulated material is routed to
the flare as a deviation from the standard. The proposed requirements
are set forth in 40 CFR 63.2380 and 40 CFR 63.670(b) and (g). 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 regarding flare pilot
flames.

b. Visible Emissions
    This action proposes that flares used as APCDs in the OLD source
category operate with no visible emissions (except for periods not to
exceed a total of 5 minutes during any 2 consecutive hours) when
organic HAP emissions are routed to the flare. The OLD NESHAP
references 40 CFR 63.11(b) (through reference of 40 CFR part 63,
subpart SS and Table 12 to 40 CFR part 63, subpart EEEE), 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 Method 22 of appendix A-7 to 40 CFR part 60
(``Method 22''). We are proposing to remove the cross-reference to the
General Provisions and instead cross-reference 40 CFR part 63, subpart
CC to include the limitation on visible emissions. We are also
proposing to clarify that the initial 2-hour visible emissions
demonstration should be conducted the first-time regulated materials
are routed to the flare.
    With regard to continuous compliance with the visible emissions
limitation, we are proposing daily visible emissions monitoring for
whenever regulated material is routed to the flare and visible
emissions are observed from the flare. On days the flare receives
regulated material, we are proposing that owners or operators of flares
monitor visible emissions at a minimum of once per day using an
observation period of 5 minutes and Method 22. Additionally, whenever
regulated material is routed to the flare and there are visible
emissions from the flare, we are proposing that another 5-minute
visible emissions observation period be performed using Method 22, even
if the required daily visible emissions monitoring has already been
performed. If an employee observes visible emissions, then the owner or
operator of the flare would perform a 5-minute Method 22 observation to
check for compliance upon initial observation or notification of such
event. In addition, in lieu of daily visible emissions observations
performed using Method 22, we are proposing that owners and operators
be allowed to use video surveillance cameras. We believe that video
surveillance cameras would be at least as effective as the proposed
daily 5-minute visible emissions observations using Method 22. We are
also proposing to extend the observation period for a flare to 2 hours
whenever visible emissions are observed for greater than 1 continuous
minute during any of the required 5-minute observation periods. Refer
to 40 CFR 63.2380 and 40 CFR 63.670(c) and (h) for these proposed
requirements.
    We solicit comment on the proposed revisions regarding visible
emissions.
c. Flare Tip Velocity
    This action consolidates provisions related to flare tip velocity.
The OLD NESHAP references the flare requirements in 40 CFR 63.11(b)
(through reference of 40 CFR part 63, subpart SS and Table 12 to 40 CFR
part 63, subpart EEEE), 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. 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 instead cross-reference 40 CFR part 63, subpart
CC to consolidate the specification of maximum flare tip velocity into
the OLD NESHAP as a single equation, irrespective of flare type (i.e.,
steam-assisted, air-assisted, or non-assisted). The proposed flare tip