[Federal Register Volume 85, Number 23 (Tuesday, February 4, 2020)]
[Rules and Regulations]
[Pages 6064-6087]
[FR Doc No: 2020-01108]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2010-0682; FRL 10004-55-OAR]
RIN 2016-AT18

National Emission Standards for Hazardous Air Pollutants:
Petroleum Refinery Sector

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: This action sets forth the U.S. Environmental Protection
Agency's (EPA's) decision on aspects of the Agency's proposed
reconsideration of the December 1, 2015, final rule: Petroleum Refinery
Sector Residual Risk and Technology Review (RTR) and New Source
Performance Standards (NSPS). This action also finalizes proposed
amendments to clarify a compliance issue raised by stakeholders subject
to the rule, to correct referencing errors, and to correct publication
errors associated with amendments to the final rule which were
published on November 26, 2018.

DATES: This final action is effective on February 4, 2020.

ADDRESSES: The EPA has established a docket for this action under
Docket ID No. EPA-HQ-OAR-2010-0682. All documents in the docket are
listed on the https://www.regulations.gov/ website. Although listed in
the index, some information is not publicly available, (e.g.,
confidential business information or other information whose disclosure
is restricted by statute. Certain other material, such as copyrighted
material, is not placed on the internet, and will be publicly available
only in hard copy form. Publicly available docket materials are
available either electronically through https://www.regulations.gov/,
or in hard copy at the EPA Docket Center, WJC West Building, Room
Number 3334, 1301 Constitution Ave. NW, Washington, DC. The Public
Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through
Friday, excluding legal holidays. The telephone number for the EPA
Docket Center is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT: For questions about this final action,
please contact Ms. Brenda Shine, 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>;
email address<EMAIL_ADDRESS>For information about the
applicability of the national emission standards for hazardous air
pollutants (NESHAP) to a particular entity, contact Ms. Maria Malave,
Office of Enforcement and Compliance Assurance, U.S. Environmental
Protection Agency, WJC South Building, 1200 Pennsylvania Ave. NW,
Washington, DC 20460; telephone number:<PHONE_NUMBER>; fax number:
(202) 564-0050; and email address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: Acronyms and abbreviations. A number of
acronyms and abbreviations are used in this preamble. While this list
may not be exhaustive, to ease the reading of this preamble and for
reference purposes, the following terms and acronyms are defined:

AEGL acute exposure guideline level
CAA Clean Air Act
CFR Code of Federal Regulations
DCU delayed coking unit
EPA Environmental Protection Agency
ERPG emergency response planning guideline
FCCU fluid catalytic cracking unit
HAP hazardous air pollutants
ICR information collection request
lb/day pounds per day
LEL lower explosive limit
MACT maximum achievable control technology
MIR maximum individual risk
MPV miscellaneous process vent
NESHAP national emissions standards for hazardous air pollutants
NSPS new source performance standards

NTTAA National Technology Transfer and Advancement Act
OAQPS Office of Air Quality Planning and Standards
OECA Office of Enforcement and Compliance Assurance
OMB Office of Management and Budget
OSHA Occupational Safety and Health Administration
PB-HAP hazardous air pollutants known to be persistent and bio-
accumulative in the environment
PRA Paperwork Reduction Act
PRD pressure relief device
psig pounds per square inch gauge
PSM Process Safety Management
PTE potential to emit
RCA/CAA root cause analysis and corrective action analysis
REL reference exposure level
RFA Regulatory Flexibility Act
RMP Risk Management Plan
RTR residual risk and technology review
SRU sulfur recovery unit
[mu]g/m\3\ micrograms per cubic meter
UMRA Unfunded Mandates Reform Act
VOC volatile organic compounds
[deg]F degrees Fahrenheit

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

I. General Information
    A. What is the source of authority for the reconsideration
action?
    B. Does this action apply to me?
    C. Where can I get a copy of this document and other related
information?
    D. Judicial Review and Administrative Reconsideration
II. Background Information
III. Final Action
    A. Issue 1: Work Practice Standard for PRDs
    B. Issue 2: Work Practice Standard for Emergency Flaring
    C. Issue 3: Assessment of Risk From the Petroleum Refinery
Source Categories After Implementation of the PRD and Emergency
Flaring Work Practice Standards
    D. Issue 4: Alternative Work Practice Standards for DCUs
Employing the Water Overflow Design
    E. Issue 5: Alternative Sampling Frequency for Burden Reduction
for Fenceline Monitoring
    F. Additional Proposed Clarifying Amendments
    G. Corrections to November 2018 Final Rule
IV. Summary of Cost, Environmental, and Economic Impacts
V. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Executive Order 13771: Reducing Regulation and Controlling
Regulatory Costs
    C. Paperwork Reduction Act (PRA)
    D. Regulatory Flexibility Act (RFA)
    E. Unfunded Mandates Reform Act (UMRA)
    F. Executive Order 13132: Federalism
    G. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    H. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
    I. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy, Supply, Distribution, or Use
    J. National Technology Transfer and Advancement Act (NTTAA)
    K. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations
    L. Congressional Review Act (CRA)

I. General Information

A. What is the source of authority for the reconsideration action?

    The statutory authority for this action is provided by sections
112, 301, and 307(d)(7)(B) of the Clean Air Act (CAA) (42 U.S.C. 7412,
7601, and 7607(d)(7)(B)).

B. Does this action apply to me?

    Categories and entities potentially regulated by this action are
shown in Table 1 of this preamble.

   Table 1--Industrial Source Categories Affected by This Final Action
------------------------------------------------------------------------
               NESHAP and source category                 NAICS \1\ code
------------------------------------------------------------------------
Petroleum Refining Industry............................          324110
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\1\ North American Industry Classification System.

    Table 1 of this preamble is not intended to be exhaustive, but
rather to provide a guide for readers regarding entities likely to be
affected by the final action for the source categories listed. To
determine whether your facility is affected, you should examine the
applicability criteria in the appropriate NESHAP. If you have any
questions regarding the applicability of any aspect of these NESHAP,
please contact the appropriate person listed in the preceding FOR
FURTHER INFORMATION CONTACT section of this preamble.

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

    The docket number for this final action regarding the sector rules
for the Petroleum Refinery source category is Docket ID No. EPA-HQ-OAR-
2010-0682.
    In addition to being available in the docket, an electronic copy of
this document will also be available on the internet. Following
signature by the EPA Administrator, the EPA will post a copy of this
final action at https://www.epa.gov/stationary-sources-air-pollution/petroleum-refinery-sector-risk-and-technology-review-and-new-source.
Following publication in the Federal Register, the EPA will post the
Federal Register version and key technical documents on this same
website.

D. Judicial Review and Administrative Reconsideration

    Under CAA section 307(b)(1), judicial review of this final action
is available only by filing a petition for review in the U.S. Court of
Appeals for the District of Columbia Circuit (the Court) by April 6,
2020. Under CAA section 307(d)(7)(B), only an objection to this final
rule that was raised with reasonable specificity during the period for
public comment can be raised during judicial review. Note, under CAA
section 307(b)(2), the requirements established by this final rule may
not be challenged separately in any civil or criminal proceedings
brought by the EPA to enforce these requirements.
    This section also provides a mechanism for the EPA to reconsider
the rule ``[i]f the person raising an objection can demonstrate to the
Administrator that it was impracticable to raise such objection within
[the period for public comment] or if the grounds for such objection
arose after the period for public comment (but within the time
specified for judicial review) and if such objection is of central
relevance to the outcome of the rule.'' Any person seeking to make such
a demonstration should submit a Petition for Reconsideration to the
Office of the Administrator, U.S. EPA, Room 3000, WJC West Building,
1200 Pennsylvania Ave. NW, Washington, DC 20460, with a copy to both
the person(s) listed in the preceding FOR FURTHER INFORMATION CONTACT
section, and the Associate General Counsel for the Air and Radiation
Law Office, Office of General Counsel (Mail Code 2344A), U.S. EPA, 1200
Pennsylvania Ave. NW, Washington, DC 20460.

II. Background Information

    The EPA promulgated NESHAP pursuant to CAA sections 112(d)(2) and
(3) for petroleum refineries located at major sources in three separate
rules. These standards are also referred to as maximum achievable
control technology (MACT) standards. The first rule, promulgated on
August 18, 1995, and codified at 40 CFR part 63, subpart CC (also
referred to as Refinery MACT 1), regulates miscellaneous process vents,
storage vessels, wastewater, equipment leaks, gasoline loading racks,
marine tank vessel loading, and heat

exchange systems. The second rule, promulgated on April 11, 2002, and
codified at 40 CFR part 63, subpart UUU (also referred to as Refinery
MACT 2), regulates process vents on catalytic cracking units (CCUs,
including fluid catalytic cracking units (FCCUs)), catalytic reforming
units, and sulfur recovery units (SRUs). The third rule, promulgated on
October 28, 2009, amended Refinery MACT 1 to include MACT standards for
heat exchange systems, which were not originally addressed in Refinery
MACT 1. This same rulemaking included updating cross-references to the
General Provisions in 40 CFR part 63.
    The EPA conducted a residual risk and technology review (RTR) of
Refinery MACT 1 and 2, publishing proposed amendments on June 30, 2014
(June 2014 proposal). These proposed amendments included technical
corrections and clarifications raised in a 2008 industry petition for
reconsideration of NSPS for Petroleum Refineries (40 CFR part 60,
subpart Ja). After soliciting, receiving, and addressing public
comments, the EPA published final amendments on December 1, 2015. The
December 2015 final rule (December 2015 rule) included a determination
pursuant to CAA section 112(f) that the remaining risk after
promulgation of the revised NESHAP is acceptable and that the standards
provide an ample margin of safety to protect public health and prevent
an adverse environmental effect. The December 2015 rule also finalized
changes to Refinery MACT 1 and 2 pursuant to CAA section 112(d)(2) and
(3), notably revising the requirements for flares and pressure relief
devices (PRDs), removing startup, shutdown, and malfunction exemptions,
and adding requirements for delayed cokers. Additional amendments were
also promulgated pursuant to CAA section 112(d)(6) to require a
fenceline monitoring work practice standard as an advancement in the
way fugitive emissions are managed and mitigated. The December 2015
rule also finalized technical corrections and clarifications to
Refinery NSPS subparts J and Ja to address issues raised by the
American Petroleum Institute (API) in their 2008 petition for
reconsideration of the final NSPS Ja rule that had not been previously
addressed. These included corrections and clarifications to provisions
for sulfur recovery plants, performance testing, and control device
operating parameters.
    The EPA received three separate administrative petitions for
reconsideration of the December 2015 rule. Two petitions were jointly
filed by the API and American Fuel and Petrochemical Manufacturers
(AFPM). The first of these petitions was filed on January 19, 2016, and
requested that the EPA reconsider the maintenance vent provisions in
Refinery MACT 1 for sources constructed on or before June 30, 2014; the
alternate startup, shutdown, or hot standby standards for FCCUs
constructed on or before June 30, 2014, in Refinery MACT 2; the
alternate startup and shutdown for SRUs constructed on or before June
30, 2014, in Refinery MACT 2; and the new CRUs purging limitations in
Refinery MACT 2. The request pertained to providing and/or clarifying
the compliance time for these sources. Based on this request and
additional information received, the EPA issued a proposal on February
9, 2016 (81 FR 6814), and a final rule on July 13, 2016 (81 FR 45232),
fully responding to the January 19, 2016, petition for reconsideration.
    The second petition from API and AFPM was filed on February 1,
2016, and outlined a number of specific issues related to the work
practice standards for PRDs and flares, and the alternative water
overflow provisions for delayed coking units (DCUs), as well as a
number of other specific issues on other aspects of the rule. The third
petition was filed on February 1, 2016, by Earthjustice on behalf of
Air Alliance Houston, California Communities Against Toxics, the Clean
Air Council, the Coalition for a Safe Environment, the Community In-
Power & Development Association, the Del Amo Action Committee, the
Environmental Integrity Project, the Louisiana Bucket Brigade, the
Sierra Club, the Texas Environmental Justice Advocacy Services, and
Utah Physicians for a Healthy Environment. The Earthjustice petition
claimed that several aspects of the revisions to Refinery MACT 1 were
not proposed, and, thus the public was precluded from commenting on
them during the public comment period, including: (1) Work practice
standards for PRDs and flares; (2) alternative water overflow
provisions for DCUs; (3) reduced monitoring provisions for fenceline
monitoring; and (4) adjustments to the risk assessment to account for
these new work practice standards. On June 16, 2016, the EPA sent
letters to petitioners granting reconsideration on issues where
petitioners claimed they had not been provided an opportunity to
comment. These petitions and letters granting reconsideration are
available for review in the rulemaking docket (see Docket ID Item Nos.
EPA-HQ-OAR-2010-0682-0860, EPA-HQ-OAR-2010-0682-0891, and EPA-HQ-OAR-
2010-0682-0892).
    On October 18, 2016 (81 FR 71661), the EPA proposed for public
comment the issues for which reconsideration was granted in the June
16, 2016, letters. The EPA solicited public comment on five issues in
the proposal: (1) The work practice standards for PRDs; (2) the work
practice standards for emergency flaring events; (3) the assessment of
risk as modified based on implementation of these PRD and emergency
flaring work practice standards; (4) the alternative work practice
standards for DCUs employing the water overflow design; and (5) the
provision allowing refineries to reduce the frequency of fenceline
monitoring at sampling locations that consistently record benzene
concentrations below 0.9 micrograms per cubic meter ([mu]g/m\3\). In
that notice, the EPA also proposed two minor clarifying amendments to
correct a cross referencing error and to clarify that facilities
complying with overlapping equipment leak provisions must still comply
with the PRD work practice standards in the December 2015 rule. We
received public comments from 17 parties. Copies of all comments
submitted are available at the EPA Docket Center Public Reading Room.
Comments are also available electronically through https://www.regulations.gov/ by searching Docket ID No. EPA-HQ-OAR-2010-0682.
    In section III of this preamble, the EPA sets forth its final
decisions on each of the five reconsideration items included in the
October 18, 2016 (81 FR 71661), proposed notice of reconsideration
(October 2016 proposed notice of reconsideration). Additionally,
section III of this preamble summarizes the history of each of the five
reconsideration items as well as the two proposed clarifying amendments
included in the proposed notice of reconsideration, summarizes the
public comments received on the proposed notice of reconsideration, and
presents the EPA's responses to these comments.
    As described in section III.D of this preamble, specific to
reconsideration item (4), the alternative work practice standards for
DCUs employing the water overflow design, the EPA proposed and
finalized amendments to the DCU water overflow provisions to address
comments on the October 2016 proposed notice of reconsideration. On
April 10, 2018 (April 2018 proposal) (83 FR 15458), the EPA proposed a
number of technical amendments to Refinery MACT 1 and 2 and the
Refinery NSPS, which included a proposed requirement to use a vapor
disengaging device for

DCUs using the water overflow provisions. On November 26, 2018,
(November 2018 rule) (83 FR 60696), the EPA finalized the technical
amendments from the April 2018 proposal, including requirements for
DCUs using the water overflow provisions, after considering public
comments received on the April 2018 proposal.

III. Final Action

A. Issue 1: Work Practice Standard for PRDs

1. What is the history of work practice standards for PRDs?
    In the June 2014 proposal, the EPA proposed to revise Refinery MACT
1 to establish operating and pressure release requirements that apply
to all PRDs and to prohibit atmospheric releases of hazardous air
pollutants (HAP) from PRDs. To ensure compliance, we proposed to
require that sources monitor PRDs using a system that is capable of
recording the time and duration of each pressure release and notifying
operators that a pressure release has occurred. Many commenters
suggested that a prohibition on atmospheric PRD releases did not
reflect the manner in which the best performing facilities operate, was
unachievable and/or very costly, and would have negative environmental
impacts due to additional flares that would need to be installed and
operated in standby mode to accept the PRD releases. Some commenters
suggested that we should instead consider as MACT the rules on PRDs
that apply to refineries in the South Coast Air Quality Management
District (SCAQMD) and the Bay Area Air Quality Management District
(BAAQMD).
    The two California district rules are similar in that they both
establish comprehensive regulatory programs to address the group or
system of PRDs at refineries by requiring monitoring, root cause
analysis, and corrective action, and by applying only to those PRD with
the greatest emissions potential through a combination of applicability
thresholds. Based on these comments, pursuant to CAA section 112(d)(2)
and (3), we identified the SCAQMD rule as representing the requirements
applicable to the best performers for PRDs. Consistent with the
requirements of the SCAQMD rule and considering additional measures
included in the BAAQMD rule, we established work practice standards for
PRDs in the December 2015 rule (see 40 CFR 63.648(j)(3)) for new and
existing sources. The work practice standard is a comprehensive set of
requirements that apply to PRDs at refineries and focuses on reducing
the size and frequency of atmospheric releases of HAP from PRDs, with
an emphasis on prevention, monitoring, correction, and limitations on
the frequency of release events. For further details on our analysis of
the SCAQMD and BAAQMD rules and our use of those rules to establish a
work practice standard for PRDs that is representative of the
requirements that apply at best performing refineries, refer to the
December 1, 2015, document at 80 FR 75216-18 and the memorandum in the
docket titled ``Pressure Relief Device Control Option Impacts for Final
Refinery Sector Rule,'' July 30, 2015 (Docket ID Item No. EPA-HQ-OAR-
2010-0682-0750).
    The work practice standard included in the December 2015 rule is
comprised of four parts. The first component of the work practice
standard requires that owners or operators monitor PRDs using a system
that is capable of recording the time and duration of each pressure
release and notifying operators that a pressure release has occurred.
Second, the work practice standard requires refinery owners or
operators to establish preventative measures for each affected PRD to
minimize the likelihood of a direct release of HAP to the atmosphere as
a result of pressure release events. Third, in the event of an
atmospheric release, the work practice standard requires refinery
owners or operators to conduct a root cause analysis to determine the
cause of a PRD release event. If the root cause was due to operator
error or negligence, then the release would be a violation of the work
practice standard. A second release due to the same root cause for the
same equipment in a 3-year period would be a violation of the work
practice standard. A third release in a 3-year period would be a
violation of the work practice standard, regardless of the root cause--
although force majeure events, as defined in the December 2015 rule,
would not count in determining whether there has been a second or third
event. The fourth component of the work practice standard is a
requirement for corrective action. For any event other than a force
majeure event, the owner or operator would be required to conduct a
corrective action analysis and implement corrective action. Refiners
have 45 days to complete the root cause analysis and implement
corrective action after the release event. The results of the root
cause analysis and identification of the corrective action are required
to be included in the periodic reports which are due on a semi-annual
basis.
    Consistent with the District rules, the work practice standard does
not apply to the following PRDs that have very low potential to emit
(PTE) based on their type of service, size, and pressure (40 CFR
63.648(j)(5)): PRDs that only release material that is liquid at
standard temperature and pressure and that is hard-piped to a
controlled drain system, PRDs that do not have a PTE of 72 pounds per
day (lbs/day) or more of volatile organic compounds (VOC), PRDs with
design release pressure of less than 2.5 pounds per square inch gauge
(psig), PRDs on mobile equipment, PRDs in heavy liquid service, and
PRDs that are designed solely to release due to liquid thermal
expansion. These PRDs are subject to the operating and pressure release
requirements in 40 CFR 63.648(j)(1) and (2), which apply to all PRDs,
but not the pressure release management requirements in 40 CFR
63.648(j)(3).
    We requested public comment on the work practice standard for PRDs
as provided in 40 CFR 63.648(j)(3) and (5) through (7), including the
number and type of release/event allowances; the type of PRDs subject
to the work practice standard; and the definition of ``force majeure
event'' in 40 CFR 63.641. We also requested public comment on the
recordkeeping and reporting requirements associated with the work
practice standard in 40 CFR 63.655(g)(10)(iii) and (i)(11).
    The following is a summary of the comments received in response to
our October 2016 proposed notice of reconsideration and our responses
to these comments.
2. What comments were received on the work practice standards for PRDs?
    Comment A.1: Some commenters were generally supportive of the final
work practice standards for PRDs while other commenters disagreed with
numerous aspects of the final work practice standards. The commenters
who did not support the work practice standards claimed that they are
unlawful because they do not provide for standards that are continuous
and that apply at all times, pursuant to section 112 of the CAA as
construed by the Court in the 2008 vacatur of the malfunction
exemptions in the MACT General Provisions. Sierra Club v. EPA, 551 F.3d
1019, 1027-28 (D.C. Cir. 2008). (``Congress has required that there
must be continuous section 112-compliant standards.''). The commenter
also noted that Congress in H.R. Rep. No. 95-294, at 92 (1977),
reprinted in 1977 U.S.C.C.A.N. 1077, 1170 also provided

that the term ``continuous'' emission standard requirement does not
allow merely ``temporary, periodic, or limited systems of control.''
The commenters believe that because the work practice standards do not
limit emissions to an amount certain during a PRD release event, there
is effectively no emission limitation that applies during these times.
Additionally, commenters do not believe that the work practice
standards are justified under CAA section 112(h) because they believe
the EPA erred in determining that the application of measurement
methodology was not feasible in the case of PRDs and cited available
wireless technology or monitoring of PRD releases.
    Response A.1: We disagree that the standards do not apply at all
times. The work practice standards for PRDs require a number of
preventative measures that operators must undertake to prevent PRD
release events, and the installation and operation of continuous
monitoring device(s) to identify when a PRD release has occurred. These
measures must be complied with at all times. The monitoring technology
suggested by the commenters is in fact best suited to this application
and is one of the acceptable methods that facility owners or operators
may use to comply with the continuous monitoring requirement. Although
that technology is adequate for identifying PRD releases, we disagree
that it is adequate for accurately measuring emissions for purposes of
determining compliance with a numeric emission standard. The technology
cited is a wireless monitor that provides an indication that the PRD
released, but it does not provide information on release quantity or
composition. PRD release events are characterized by short, high
pressure non-steady state conditions which make such releases difficult
to quantitatively measure. As detailed in the preamble to the December
2015 rule (80 FR 75218), we specifically considered the issues related
to constructing a conveyance and quantitatively measuring PRD releases
and concluded that these measures were not practicable. Refinery
operators can estimate emissions based on vessel operating conditions
(temperature and pressure) and vessel contents when a release occurs,
but these estimates do not constitute a measurement of emissions or
emission rate within the meaning of CAA section 112(h). As such, we
maintain our position that the application of a work practice standard
is appropriate for PRDs.
    Comment A.2: Commenters indicated that another reason they believe
that the PRD work practice standard is illegal is that PRDs are not
independent emission points and instead function in venting emissions
from other emission points during a malfunction. For example,
commenters pointed out that some equipment that vents to the atmosphere
and, therefore, must meet the miscellaneous process vent standard, may
also contain PRDs that vent HAP emissions to the atmosphere, bypassing
the requirements established for miscellaneous process vents. The
commenters believe that the EPA has simply created an exemption
allowing equipment connected to PRDs to violate their emission
standards without triggering a violation or potential enforcement and
penalty liability. Finally, the commenters indicated that the EPA
should retain the work practice standards for PRD on top of the
existing emission standards for connected equipment to assure
compliance and attempt to prevent fugitive emissions.
    Response A.2: The commenters incorrectly suggest that the PRD work
practice standard replaces the existing emission standards for
``connected equipment.'' The amendments to the NESHAP addressing PRDs
do not affect requirements in the NESHAP that apply to equipment
associated with the PRD. For example, compliance with the PRD
requirements apply in addition to requirements for miscellaneous
process vents for the same equipment, which addresses the commenter's
suggestion.
    We disagree that PRDs are simply bypasses for emissions that are
subject to emission limits and controls and that they, thus, allow for
uncontrolled emissions without violation or penalty. The PRDs are
generally safety devices that are used to prevent equipment failures
that could pose a danger to the facility and facility workers. The PRD
releases are triggered by equipment or process malfunction. As such,
they do not occur frequently or routinely and do not have the same
emissions or release characteristics that routine emission sources
have, even if the PRD and the vent are on the same equipment. This is
because conditions during a PRD release (temperature, pressure, and
vessel contents) differ from those that occur that result in routine
emissions as miscellaneous process vents. In contrast, emissions from
miscellaneous process vents are predictable and must be characterized
for emission potential and applicable control requirements prior to
operation in the facility's notification of compliance status report.
In addition, PRDs must operate in a closed position and, as discussed
earlier, must be continuously monitored to identify when releases have
occurred. If an affected pressure relief device releases to the
atmosphere, the owner and operator is required to perform root cause
analysis and corrective action analysis (RCA/CAA) as well as implement
corrective actions and comply with the specified reporting
requirements. The work practice standard also includes criteria for
releases from affected PRD which would result in a violation at 40 CFR
63.648(j)(3)(v).
    Comment A.3: Commenters indicated that, even if the work practice
standards for PRDs are justified, the work practice standards do not
comply with the CAA requirements to assure both the average limitation
achieved by the relevant best-performing sources and the maximum degree
of emission reduction that is achievable. The commenters asserted that
there is no discussion in the record or analysis that allowing 1-2
uncontrolled releases every 3 years reflects, at minimum, the average
of the best performers' reductions and indicated that the EPA cannot
simply replicate rules in place that specify PRD requirements. The
commenters indicated that the EPA should have reviewed data, such as
the 2007 SCAQMD Staff Report (Docket ID Item No. EPA-HQ-OAR-2010-0869-
0024) which shows releases from Los Angeles area refineries ranged from
0.4-0.89 tons of VOC per year, to establish that no source has done
better or cannot do better than those rules allow. The commenters also
asserted that the EPA's promulgated work practice standards for PRDs
are not as stringent as the SCAQMD and BAAQMD requirements that they
are modelled after.
    Response A.3: Section 112 of the CAA requires MACT for existing
sources to be no less stringent than ``the average emission limitation
achieved by the best performing 12 percent of the existing sources (for
which the Administrator has emissions information). . .'' [(CAA section
112(d)(3)(A)]. ``Emission limitation'' is defined in the CAA as ``. . .
a requirement established by the State or Administrator which limits
the quantity, rate, or concentration of emissions of air pollutants on
a continuous basis, including any requirement relating to operation or
maintenance of a source to assure continuous emission reduction, and
any design, equipment, work practice, or operational standard
promulgated under this chapter'' [CAA section 302(k)]. The EPA
specifically considers existing rules from state and local authorities
in identifying the ``emission limitations'' for a given source. We then
identify the best performers to identify the MACT floor (the no less
stringent than level) for that source. The EPA identified the

SCAQMD rule requirements as the MACT floor because it represented the
requirements applicable to the best performing sources. The commenters
appear to suggest that the EPA should identify an emissions level
achieved in practice through implementation of the work practices in
the two California rules and that the EPA is obligated to require
sources to meet that emissions level. However, this is contrary to the
predicate for the EPA establishing work practice standards. Work
practice standards are established in place of a numeric limit where it
is not feasible to establish such limits. Thus, in a case such as this,
where the EPA has determined that it is appropriate to establish work
practice standards (because it is infeasible to establish numeric
limits), it was reasonable for the EPA to identify the work practice
standards that impose the most stringent requirements and, thus,
represent what applies to the best performers and then to require those
work practice standards as MACT.
    We recognize that the final standards for PRDs do not exactly
mirror the SCAQMD provisions, but this is because, having established
the MACT floor, we consider options for going beyond the MACT floor. As
noted in the memorandum in the docket titled ``Pressure Relief Device
Control Option Impacts for Final Refinery Sector Rule,'' July 30, 2015
(Docket ID Item No. EPA-HQ-OAR-2010-0682-0750), we looked at the BAAQMD
standard as a more stringent work practice standard, and while we did
not directly adopt the BAAQMD rule requirements, we did adopt several
aspects of that rule. Specifically, we adopted the three prevention
measures requirements in the BAAQMD with limited modifications. We also
did not include a provision similar to that in the SCAQMD rule that
excludes releases less than 500 lbs/day from the requirement to perform
a root cause analysis; that provision in the SCAQMD rule does not
include any other obligation to reduce the number of these events.
Rather than allowing unlimited releases less than 500 lbs/day, we
require a root cause analysis for releases of any size. We considered
these to be reasonable and cost-effective enhancements to the SCAQMD
rule. However, because we count small releases that the SCAQMD rule
does not regulate at all, we considered it reasonable to provide a
higher number of releases prior to considering the owner or operator to
be in violation of the work practice standard. After considering the
PRD release event limits in both the SCAQMD and BAAQMD rules, we
determined it was reasonable and appropriate to establish PRD
requirements consistent with those provisions in the SCAQMD and BAAQMD
rules that provide flare work practice standards. Therefore, the final
requirements provide that three events from the same PRD in a 3-
calendar-year period is a violation of the work practice standard. We
also note that a facility cannot simply choose to release pollutants
from a PRD; any release that is caused willfully or caused by
negligence or operator error is considered a violation. Additionally, a
second PRD release event in a 3-calendar-year period for the same root
cause is a violation.
    With the implementation of the three prevention measures and the
elimination of the 500 lbs/day applicability threshold, we specifically
evaluated and adopted requirements beyond the MACT floor (i.e., more
stringent than the SCAQMD rule) and established requirements that we
deemed to be cost effective and that we determined would achieve
emission reductions equivalent to or better than the SCAQMD
requirements.
    The EPA further notes that the reported emissions the commenters
claim the EPA should rely on are not actually measured emissions but
rather engineering calculations of release quantities. As such, even if
it were possible to establish a numeric emissions limit, there would be
concerns about relying on the information cited by the commenters.
Finally, we note that the commenter's summary of PRD release data from
the 2007 SCAQMD Staff Report (Docket ID Item No. EPA-HQ-OAR-2010-0869-
0024) suggests that the SCAQMD PRD requirements appear to be effective
at reducing PRD emissions compared to states that do not have similar
work practice standards.
    In summary, the work practice standard we finalized provides a
comprehensive program to manage entire populations of PRDs and includes
prevention measures, continuous monitoring, root cause analysis, and
corrective actions, and addresses the potential for violations for
multiple releases over a 3-year period. We followed the requirements of
section 112 of the CAA, including CAA section 112(h), in establishing
what work practice constituted the MACT floor; we then identified
certain additional provisions which were more stringent than the MACT
floor requirements that we determined were cost effective, and we
finalized the work practice standards, as enhanced by those additional
provisions, as MACT.
    Comment A.4: Commenters claimed that the EPA's malfunction
exemptions are arbitrary and capricious under the CAA because the EPA
did not finalize the prohibition on atmospheric releases from PRDs, as
included in the June 2014 proposal. The commenters noted that the EPA
finalized similar provisions prohibiting PRD releases in MACT standards
for Group IV Polymers and Resins, Pesticide Active Ingredient
Manufacturing, and Polyether Polyols Production. The commenters further
stated that the Court recently upheld this type of prohibition
[Mexichem Specialty Resins, Inc. v EPA, 787 F.3d 544, 560-61 (D.C. Cir.
2015)] and urged the EPA to finalize the standards for PRD as proposed.
The commenters also suggested that the EPA's justification for not
finalizing a prohibition on atmospheric PRDs was based on environmental
disbenefits of having additional flare capacity on standby to control
these unpredictable and infrequent events. According to the commenters,
flares can be operated with spark ignition systems that would only
operate when triggered by a flare event, and, therefore, the commenters
suggested that the EPA overestimated the environmental disbenefits.
    Response A.4: During the comment period on the June 2014 proposal,
comments both from industry and environmental advocacy groups suggested
we consider requiring the work practice standards established in
regulations adopted by the BAAQMD and SCAQMD rules for PRD releases. In
light of those comments and the statutory requirement that the EPA
evaluate the best performing facilities in determining the appropriate
MACT standard, the Agency considered whether the work practice
standards established in the SCAQMD and BAAQMD rules represented what
was achieved by the best performers. The BAAQMD and SCAQMD rules are
the only rules we are aware of that have been established to address
the infrequent and unpredictable nature of PRD releases for petroleum
refineries. As noted in the previous response, the EPA established a
MACT standard based on the SCAQMD rule and incorporated several of the
key elements of the BAAQMD standard into the PRD requirements
promulgated for new and existing sources in the December 2015 rule.
    After determining a standard based on the best performing sources,
we examined whether to establish a more stringent standard (requiring
all PRD releases to be routed to a control

device). We rejected such an approach based on the economic impacts. We
estimated that requiring control of all atmospheric PRDs would cost
approximately 41 million dollars per year (annually) compared to the
estimated economic impact of the work practice standards of 3.3 million
dollars per year. (Cost is not a consideration in setting the MACT
floor, but it is relevant to our determination whether to establish
additional requirements more stringent than that floor.) We also
estimated that secondary emissions for additional flaring in the event
all PRDs were routed to a control device would increase greenhouse gas
emissions by 104,000 megagrams of carbon dioxide equivalents per year
and increase nitrogen oxide emissions by 85 tons per year (see
memorandum in the docket titled ``Pressure Relief Device Control Option
Impacts for Final Refinery Sector Rule,'' July 30, 2015, Docket ID Item
No. EPA-HQ-OAR-2010-0682-0750).
    Regarding the comment that flares could be equipped with spark
ignition systems, we note that such systems are not compliant with the
long-standing requirements in 40 CFR 60.18 and 63.11 or the new
requirements in 40 CFR 63.670 that flares be operated with a pilot
present at all times. The EPA has previously rejected the use of spark
ignition systems because these systems may not reliably ignite on
demand which would result in an atmospheric release of the pollutants
routed to the flare.
    Comment A.5: Commenters stated that the EPA's malfunction exemption
for force majeure events in the PRD work practice standard is arbitrary
and capricious under CAA section 112 because it creates periods of time
when no emissions standard applies. Further, commenters added that
force majeure is a term defined by contracts law to provide a defense
to avoid meeting a party's responsibility under a contract and applies
only where a party has specifically negotiated and agreed to its use.
As such, commenters claimed that the concept of force majeure does not
exist or belong in the context of compliance with a non-contractual
federal law, such as the CAA. Refineries should not be able to decide
when to comply with the CAA requirements.
    Commenters stated that it is unlawful and arbitrary to promulgate a
definition of force majeure that does not codify criteria for
determining whether a force majeure event or a violation has occurred
(i.e., the determination is left to the Administrator). The commenters
added that the EPA does not have the authority to decide when such an
event has occurred, rather the Court must decide whether a violation
warranting a penalty has occurred with the burden of proof resting on
the refinery.
    Response A.5: The PRD work practice standard requires redundant
prevention measures, which are designed to limit the duration and
quantity of releases from all atmospheric PRDs regardless of the cause.
These requirements apply at all times; thus, the final work practice
standards do have requirements that apply to PRDs at all times and they
are not contrary to the CAA requirements in CAA section 112. We also
note that facilities are also required to initiate a root cause
analysis to assess the cause of the release, including releases
determined to be caused by a force majeure event.
    We disagree that because force majeure is a term typically used in
contract law that it cannot or should not be used in the context of
regulations establishing standards under the CAA. We have determined
that a force majeure provision is part of the MACT floor for regulating
PRDs at refineries and, as such, should be included as part of the MACT
standard. The definition of force majeure event in the December 2015
final rule is based specifically on a clause included in the SCAQMD
rule, which served as the basis for the MACT standard. Rather than
repeating this clause at each instance, we determined that is was
preferential to use and define the term force majeure event. We find
that the December 2015 final rule's definition of force majeure event
has adequate specificity to allow determination of whether a PRD
release event was caused by a force majeure event. The definition
specifies events that are beyond the control of the operator, including
natural disasters, acts of war or terrorism, external power
curtailments (excluding curtailments due to interruptible service
agreements), and fire or explosions originating at near or adjoining
facilities outside of the refinery owner or operator's control that
impact the refinery's ability to operate. The commenters suggest that
criteria are needed for determining whether a force majeure event has
occurred. We disagree; the examples provided in the definition provide
sufficient specificity to help guide a decisionmaker in deciding
whether to pursue an enforcement action because they believe a
violation has occurred that was not caused by a force majeure event and
for a court or other arbiter to rule on any claim. Regarding the
comment that the Court, not the Administrator, should determine when a
force majeure event has occurred, we note that the regulations do not
specify that the Administrator would make a binding determination of
whether a force majeure event has occurred, and the issue could be
argued and resolved by the Court in the context of a citizen suit.
    Comment A.6: One commenter supported the work practices for PRD and
emergency flaring with the exception of the additional backstop
measures in 40 CFR 63.648(j)(3)(iv) and (v) and 40 CFR
63.670(o)(7)(iv), respectively. The commenter explained that these
backstops arbitrarily limit the number of release events for PRD and
emergency flaring events and are not needed to demonstrate continuous
compliance with the work practice standards.
    Response A.6: For PRDs, these are the applicable standards that
were determined to be MACT and are modeled after the backstop within
the SCAQMD rule. With respect to the flare work practice requirements,
our goal is to ensure continuous compliance with the emission limits
applicable to the gas streams that are discharged to the flare. We
determined that optimal HAP destruction occurs under specific
conditions, which include limited periods of visible emissions.
Therefore, we established these requirements in parallel with the PRD
requirements to help limit the size and duration of these emergency
flaring events and optimize flare performance. We consider these
backstop measures for PRD and emergency flaring to be critical to
ensure that the prevention measures implemented are effective, that the
root-cause analyses conducted are thorough, and that the corrective
action measures implemented are effective.
    Comment A.7: Commenters stated the final rule provided criteria for
releases that will be considered a violation of the pressure release
management work practices in 40 CFR 63.648(j)(v)(B) and (C) based on a
``3 calendar year period,'' but the Agency did not explain how this
time period runs nor how it will be assessed or reported to the EPA and
to the public. The commenter noted that the EPA stated in the preamble
(80 FR 75212) relative to the flare work practice provisions, the
violation criteria is based on a ``rolling 3-year period,'' but a
rolling 3-year period is not in the regulatory text for either the
flare or PRD work practice.
    Response A.7: The regulatory text at 40 CFR 63.648(j)(3)(B) and (C)
clearly states that the time period is based on a 3-calendar-year
period. We consider 2020 to be one calendar year. A 3-calendar-year
period in 2020 would include events that occurred in 2018, 2019, and
2020. It is a rolling average to the extent that, in 2021, one would
consider events that occurred in 2019,

2020, and 2021. As indicated in 40 CFR 63.655(g)(10)(iii), each
pressure release to the atmosphere, including the duration of the
release, the estimated quantity of each organic HAP released, and the
results of the RCA/CAA completed during the reporting period must be
included as part of the reporting obligation.
    Comment A.8: Commenters stated that the EPA should add to the
reporting requirements for the PRD and flare work practice standards by
requiring an initial report to the EPA, state, and local regulators
within 1 hour of the start of a release event or within 1 hour of the
operator reasonably knowing of its occurrence. They maintained that the
initial report should include the process unit the flare or PRD is
associated with and initial identification of the cause of the event.
The initial report should be followed by a report containing the
contents of 40 CFR 63.655(g)(10) and (11) within 30 days after the
event and additionally include whether the PRD or flare has had an
emissions release or smoking event in the past 3 years, including
references or copies of previously submitted reports. Commenters added
that this would be consistent with the Agency's attempt to match the
SCAQMD requirements for PRDs. Finally, commenters suggested that the
EPA should require all malfunction reports be made publicly available
online at the same time they are submitted to the EPA.
    Response A.8: The SCAQMD rule has notification and reporting
requirements for atmospheric PRD releases in excess of the reportable
quantity limits in 40 CFR part 117, part 302, and part 355, including
releases in excess of 100 pounds of VOC (Rule 1173(i)(3)). The
notification must occur within 1 hour of the release or within 1 hour
of the time a person should have reasonably known of its occurrence. A
written report must be submitted within 30 days of the atmospheric
release. These requirements closely mirror those under other EPA
programs, such as the Superfund Amendments and Reauthorization Act 313
(SARA 313). We note that refinery owners or operators are already
required to report emissions events through various state and federal
requirements, including immediate notifications of releases exceeding
reportable quantities under SARA 313, and while we acknowledge that
these reports would be submitted to a different branch within the EPA,
we believe any additional reporting requirements would be redundant,
unnecessary, and inefficient. Therefore, we are not revising the
recordkeeping and reporting requirements in the December 2015 rule as
requested by the commenter.
    Comment A.9: Commenters stated that the exemptions for specific
types of pressure relief devices are unlawful and arbitrary. Commenters
contended that the only justification the EPA has made for providing
these PRD exemptions is that the emissions are expected to be small.
Commenters asserted that there is no de minimis threshold for
regulating emission points within a source category and, thus, the
EPA's attempt to exempt certain types of PRDs is illegal.
    Response A.9: We modeled the applicability of the PRD provisions
after the SCAQMD rule, based on a MACT floor analysis and considering
the appropriate requirements for these types of PRDs. It is likely that
the SCAQMD rule did not apply the PRD-specific requirements to certain
PRDs due to their low emissions release potential. As part of our
``beyond the floor'' analysis, we determined that it was not cost
effective to include control of these PRDs as part of the work practice
standard for PRDs. However, these PRDs are regulated under other
provisions of the MACT. We note that, if the PRD is in gas or vapor
service, refinery owners and operators are still required to monitor
the PRD after the release to verify the device is operating with an
instrument reading of less than 500 parts per million. Liquid PRDs are
still subject to repair if a leak is found during visual inspection.
3. What is the EPA's final decision on the work practice standards for
PRDs?
    The PRD work practice standards were developed in accordance with
the CAA, establishing a MACT floor based on consideration of the SCAQMD
and BAAQMD work practice standards. The sources complying with these
requirements are the best performing sources. It was necessary to
establish these requirements as work practice standards under CAA
section 112(h) because quantitative measurement of flow rates during
PRD release events is not practicable due to technological and economic
limitations with measuring highly transient flows. The inclusion of
force majeure event allowances and restrictions of the applicability of
the pressure release management requirements to specified types of PRDs
are consistent with the MACT floor and are necessary components of the
work practice standards. We consider a complete prohibition of
atmospheric PRD to be ``beyond the MACT floor'' and we are declining to
set a ``beyond the floor'' requirement on the basis of cost and
environmental disbenefits. We have not been presented with any comments
and/or information received in response to the October 2016 proposed
notice of reconsideration relative to the PRD work practice standards
which will result in any changes to the December 2015 rule.

B. Issue 2: Work Practice Standard for Emergency Flaring

1. What is the history of work practice standards for emergency
flaring?
    In the June 2014 proposal, the EPA proposed to amend the operating
and monitoring requirements for petroleum refinery flares. As discussed
in the proposal at 79 FR 36904, we determined that the requirements for
flares in the General Provisions at 40 CFR 63.18 were not adequate to
ensure compliance with the Refinery MACT standards. In general, at the
time the MACT standards were promulgated, flares used as air pollution
control devices were expected to achieve a 98-percent HAP destruction
efficiency. However, because flows of waste gases to the flares had
diminished based on reductions achieved by the increased use of flare
gas recovery systems, there have been times when the waste gas to the
flare contained insufficient heat content to adequately combust and,
thus, a 98-percent HAP destruction efficiency was not being achieved.
In addition, the practice of applying assist media to the flare
(particularly steam to prevent smoking of the flare tip) had led to a
decrease in the combustion efficiency of flares.
    To ensure that a 98-percent HAP destruction efficiency was being
met, as contemplated at the time the MACT standard was promulgated, we
proposed revisions to Refinery MACT 1 that required flares to operate
with a continuously-lit pilot flame at all times when gases are sent to
the flare, with no visible emissions except for periods not to exceed 5
minutes during any 2 consecutive hours, and to meet flare tip velocity
limits and combustion zone operating limits at all times when gases are
flared.
    During the comment period on the June 2014 proposal, we received
comments that the EPA's concern over insufficient heat content of the
waste gas or over-assisting flares is less problematic in attaining a
high level of destruction efficiency at the flare in emergency
situations, where the flow in the flare exceeds the smokeless capacity
of the flare. The commenters suggested that better combustion was
assured closer to the incipient smoke point of the flare and that flow
velocity limits and limits on visible emissions should not apply during
emergency flaring events.

    In the December 2015 rule, we determined that it was appropriate to
set different standards for when a flare is operating below its
smokeless capacity and when it is operating above its smokeless
capacity. We finalized the proposed requirements (with minor revisions)
to apply when a flare is operating below its smokeless capacity.
    In the December 2015 rule, we established a work practice standard
that applies to each affected flare with a potential to exceed its
smokeless capacity. The work practice standard requires owners or
operators to develop flare management plans to identify the flare
system smokeless capacity and flare components, waste gas streams that
are flared, monitoring systems and their locations, procedures that
will be followed to limit discharges to the flare that cause the flare
to exceed its smokeless capacity, and prevention measures implemented
for PRDs that discharge to the flare header. The work practice standard
requires a continuously-lit pilot flame, combustion-zone operating
limits, and the monitoring, recordkeeping, and reporting requirements
apply at all times--whether the flare is operating below, at, or above
its smokeless capacity, including during a force majeure event. These
requirements are the most critical in ensuring that a 98-percent
destruction efficiency is being met during emergency release events.
    In addition, where a flare exceeds its smokeless capacity, a work
practice standard requires refinery owners or operators to conduct a
root cause analysis and take corrective action for any flaring event
that exceeds the flare's smokeless capacity and that also exceeds the
flare tip velocity and/or visible emissions limit. Refiners have 45
days to complete the root cause analysis and implement corrective
action after an event. The results of the root cause analysis and
corrective action are due with the periodic reports on a semi-annual
basis. If the root cause analysis indicates that the exceedance of the
flare tip velocity and/or the visible emissions limit is caused by
operator error or poor maintenance, the exceedance is a violation of
the work practice standard. A second event causing an exceedance of
either the flare tip velocity or the visible emissions limit within a
rolling 3-year period from the same root cause on the same equipment is
a violation of the standard. A third exceedance of the velocity or
visible emissions limit occurring from the same flare in a rolling 3-
year period is a violation of the work practice standard, regardless of
the root cause. However, force majeure events are excluded from the
event count.
    We requested public comment on the above smokeless capacity work
practice standard in 40 CFR 63.670(o), including the requirements to
maintain records of prevention measures in 40 CFR 63.670(o)(1)(ii)(B)
and (iv); the requirement to establish a single smokeless design
capacity in 40 CFR 63.670(o)(1)(iii)(B); the number and type of
releases/events that constitute a violation; the phrase ``. . . and the
flare vent gas flow rate is less than the smokeless design capacity of
the flare'' in 40 CFR 63.670(c) and (d); the proposed correction to
paragraph 40 CFR 63.670(o)(1)(ii)(B); and other provisions in 40 CFR
63.670(o)(3) through (7). We also requested public comment on the
recordkeeping and reporting requirements associated with these work
practice standards in 40 CFR 63.655(g)(11)(iv) and (i)(9)(x) through
(xii).
    In reviewing the regulatory text for this proposed action, we also
determined that 40 CFR 63.670(o)(1)(ii)(B) contains an incorrect
reference to pressure relief devices for which preventative measures
must be implemented. The correct reference is paragraph 40 CFR
63.648(j)(3)(ii), not 40 CFR 63.648(j)(5). We proposed to correct this
referencing error.
2. What comments were received on the work practice standards for
emergency flaring?
    Comment B.1: Some commenters were generally supportive of the final
work practice standards for emergency flares, while other commenters
disagreed with numerous aspects of the final work practice standards.
The commenters who disagree indicated that establishing these work
practice standards for emergency flaring is unlawful because they do
not provide for standards that are continuous and that apply at all
times, as directed by section 112 of the CAA and as upheld by the Court
in the 2008 vacatur of the malfunction exemptions in the MACT General
Provisions. Sierra Club v. EPA, 551 F.3d 1019, 1027-28 (D.C. Cir. 2008)
(``Congress has required that there must be continuous section 112-
compliant standards.''); see also H.R. Rep. No. 95-294, at 92 (1977),
reprinted in 1977 U.S.C.C.A.N. 1077, 1170 (``continuous'' emission
standard requirement does not allow merely ``temporary, periodic, or
limited systems of control''). The commenters state that because the
work practice standards do not limit emissions to any certain amount
during an emergency flaring event, there is effectively no emission
limitation that applies during these times. Additionally, the
commenters do not believe that the work practice standards are
justified under CAA section 112(h) for emergency flaring because
measurement technology is available to measure what is sent to the
flare.
    Response B.1: We disagree that the standards do not apply at all
times. The work practice combustion efficiency standards (specifically
limits on the net heating value in combustion zone) apply at all times,
including during periods of emergency flaring. With respect to setting
work practice standards under CAA section 112(h), we note that the
combustion efficiency standards were established as work practice
standards. In the case of flaring, emissions are not conveyed through a
stack and are difficult to measure. The EPA's practice has been to
establish work practice standards for regulating flares (see, e.g.,
General Provisions in 40 CFR parts 60 and 63, the combustion efficiency
requirements in this rule, and flaring work practice standards in the
Petroleum Refinery NSPS, subpart Ja). These work practice standards do
take advantage of upstream measurement systems, but we do not agree
that upstream measurement systems are the same as measuring emissions
from the flare following combustion nor are they, standing alone, a
sufficient emissions limitation or standard.
    Comment B.2: Commenters stated that, even if the work practice
standards for flares operating above the smokeless capacity are
justified, the work practice standards do not comply with the CAA
requirements that the emissions limitation is as stringent as the
average emission limitation achieved by the best-performing sources,
and the maximum degree of emission reduction that is achievable.
Commenters explained that the EPA provided an allowance for up to two
smoking flare events per flare in a 3-year period based on API-supplied
information reporting that the average refinery flare experiences an
event every 4.4 years and an assumption that the best performing flares
have one smoking event every 6 years. The commenters contended that
these figures are based on unverified data submitted in an API/AFPM
survey and its use is arbitrary and capricious. The commenters
maintained that instead of using the API/AFPM survey data, the EPA
should have reviewed data including emissions data from their own
studies as well as emissions data available from Texas Commission on
Environmental Quality (TCEQ), SCAQMD, or BAAQMD when developing these
standards. The commenters suggested that the EPA

establish standards based on the duration and amount of gas routed to a
flare during a malfunction event that causes the flare to operate above
its smokeless capacity, in addition to the cap on the number of
exceptions.
    Response B.2: First, one must recognize that the flare is not a
specific emission source within Refinery MACT 1 standards and, thus, we
did not seek to establish a MACT floor for flares at the time that we
promulgated Refinery MACT 1. Rather, we identified flares as an
acceptable means for meeting otherwise applicable requirements and we
established flare operational standards that we believed would achieve
a 98-percent destruction efficiency on a continual basis. Recognizing
that flares were not achieving the 98-percent reduction efficiency in
practice, we proposed additional requirements in the June 2014 proposal
to ensure that flares operate as intended at the time we promulgated
Refinery MACT 1.
    Regarding the operational standards for flares operating above the
smokeless capacity, we note that these flare emissions are emissions
due to a sudden increase in waste gas entering the flare, typically
resulting from a malfunction or an emergency shutdown at one or more
pieces of equipment that vents emissions to the flare. The commenter's
suggestion that the EPA should establish standards on the duration and
amount of gas discharged to a flare during malfunction events misses
the mark. Flares are associated with a wide variety of process
equipment and the emissions routed to a flare during a malfunction can
vary widely based on the cause of the malfunction and the type of
associated equipment. Thus, it is not feasible to establish a one-size-
fits-all standard on the amount of gas allowed to be routed to flares
during a malfunction. Moreover, we note that routing emissions to the
flare will result in less pollution than the other alternative, which
would be to emit directly to the atmosphere. We note that we do not set
similar limits for thermal oxidizers, baghouses, or other control
devices that we desire to remain operational during malfunction events
to limit pollutant emissions to the extent practicable. However, we did
establish work practice standards that we believe will be effective in
reducing the size and duration of flaring events that exceed the
smokeless capacity of the flare to improve overall flare performance.
We are establishing these work practice standards for flares in order
to ensure 98-percent destruction of HAP discharged to the flare (as
contemplated at the time Refinery MACT 1 was promulgated) during both
normal operating conditions when the flare is used solely as a control
device and malfunction releases where the flare acts both as a safety
device and a control device.
    Comment B.3: Commenters stated that the EPA's malfunction exemption
for force majeure events for emergency flaring is arbitrary and
capricious under CAA section 112 because it creates periods of time
when no emissions standard applies.
    Response B.3: As noted in Response A.5 to similar comments
regarding PRD release events, it is very difficult to guard perfectly
against acts of God and acts of terrorism. The EPA does not believe it
can develop measures that would effectively limit emissions during all
such acts. Regardless, we disagree that force majeure events are exempt
from regulation. Several of the work practice standards apply during
these events. Specifically, flares are required to comply with the
requirements for a continuously lit pilot flame and combustion
efficiency standards (i.e., limits on the net heating value in
combustion zone) at all times, including during periods of emergency
flaring caused by a force majeure event.
    Comment B.4: Commenters requested that the EPA delete from the rule
the requirements at 40 CFR 63.670(o)(1)(ii)(B) and (o)(1)(iv), claiming
the requirements are highly burdensome. These requirements require an
owner or operator to include as part of the flare management plan (FMP)
records of prevention measures and design and operating details for
PRDs that are routed to flares. Alternatively, commenters recommended
that the rule only require this information be included in the FMP for
those PRDs (i.e., a single PRD or a single set of PRDs which protect a
single piece of equipment) whose potential for release is great enough
to exceed the smokeless capacity of the flare.
    Response B.4: Because PRDs are expected to be the primary source of
a release that might cause a flaring event that could exceed the
smokeless capacity of the flare, we determined that the identification
of the PRDs that are vented to the flare is a critical component of the
FMP. We also recognize that consideration of prevention measures for
PRDs that can discharge to a flare will help to reduce the number of
flaring events that exceed the smokeless capacity of the flare.
Consequently, we include consideration of prevention measures for PRDs
as one of three critical items, listed in 40 CFR 63.670(o)(1)(ii)(A)
through (C), that each owner or operator of a flare must consider
within the flare minimization assessment requirement of the FMP. While
submission of the FMP is primarily a one-time event, we expect that
these prevention measures for PRDs discharged to the flare will be an
active and growing list as owners and operators implement corrective
actions after a release event exceeding the smokeless capacity of the
flare and exceeding the visible emissions limit and/or the flare tip
velocity limit. As noted in 40 CFR 63.670(o)(2)(ii), the plan must be
updated periodically to account for changes in the operation of the
flare, but we do not consider new prevention measures implemented for
PRDs that discharge to the flare to constitute a change in the
operation of the flare. Thus, this updated listing can be in an
electronic database and it is not required to be updated in the FMP
unless the FMP is otherwise required to be updated or re-submitted
according to the provisions in 40 CFR 63.670(o)(2)(ii). We do not
consider this effort to be a significant burden beyond what is already
required for hazards analysis and the commenter did not provide any
data to quantify or substantiate the claims that this effort is
``highly burdensome.''
    We considered the suggestion to limit this requirement to PRDs with
high potential release rates. However, many flares may receive
discharges from dozens of PRDs across multiple process units. In an
emergency event, it is possible that several of these PRDs associated
with different equipment can relieve at the same time. While any one
PRD may not exceed the flare's smokeless capacity, the combination of
PRD releases may. Thus, we determined that it is appropriate to require
all PRDs discharged to the flare to be identified and applicable
prevention measures should be evaluated regardless of the release
potential of an individual PRD.
3. What is the EPA's final decision on the work practice standards for
emergency flaring?
    The emergency flaring work practice standards were developed to
ensure that flares achieve the 98-percent reduction assumed at the time
MACT 1 was promulgated. In determining the means to ensure that flares
achieve the 98-percent reduction, the EPA considered available data for
best performing flare sources. The inclusion of the force majeure
provisions in the work practice standard do not alter the work practice
requirements for a continuously lit pilot flame and combustion
efficiency standards, which apply at all times. The flare requirements
in Refinery MACT 1 were established as work practice

standards and the operational standards established in the December
2015 final rule and affirmed in this action are also work practice
standards under CAA section 112(h). Work practice standards are
appropriate for flares because pollutants emitted from the flare cannot
be emitted through a conveyance designed and constructed to emit or
capture such pollutants. We have not been presented with any comments
and/or information received in response to the proposed notice of
reconsideration relative to the emergency flaring work practice
standards which will result in any changes to these requirements as
promulgated in the December 2015 rule.

C. Issue 3: Assessment of Risk From the Petroleum Refinery Source
Categories After Implementation of the PRD and Emergency Flaring Work
Practice Standards

1. What is the history of the assessment of risk from the Petroleum
Refinery source categories after implementation of the PRD and
emergency flaring work practice standards?
    The results of our residual risk review for the Petroleum Refinery
source categories were published in the June 2014 proposal (79 FR 36934
through 36942), and included assessment of chronic and acute inhalation
risk, as well as multipathway and environmental risk, to inform our
decisions regarding acceptability and ample margin of safety. The
results indicated that the cancer risk to the individual most exposed
(maximum individual risk or ``MIR'') based on allowable HAP emissions
is no greater than approximately 100-in-1 million, which is the
presumptive limit of risk acceptability, and that the MIR based on
actual HAP emissions is no greater than 60-in-1 million, but may be
closer to 40-in-1 million. In addition, the maximum chronic noncancer
target organ-specific hazard index (TOSHI) due to inhalation exposures
was less than 1. The evaluation of acute noncancer risks, which was
conservative, showed the potential for adverse health effects from
acute exposures is unlikely. Based on the results of a refined site-
specific multipathway analysis, we also concluded that the cancer risk
to the individual most exposed through ingestion is considerably less
than 100-in-1 million.
    In the December 2015 rule, we established work practice standards
for PRD releases and emergency flaring events, which under the June
2014 proposal would not have been allowed. Because we did not consider
such non-routine emissions under our risk assessment for the June 2014
proposal, we performed a screening level analysis of risk associated
with these emissions for the December 2015 rule as discussed in detail
in ``Final Residual Risk Assessment for the Petroleum Refining Source
Sector'' in Docket ID Item No. EPA-HQ-OAR-2010-0682-0800. Our analysis
showed that HAP emissions could increase the MIR based on actual
emissions by as much as 2-in-1 million, which is not substantially
different than the level of risk estimated at proposal. We also
estimated that chronic noncancer TOSHIs attributable to the additional
exposures from non-routine flaring and PRD HAP emissions are well below
1. When the additional chronic noncancer TOSHI from the screening
analysis are added to the TOSHI estimated in the June 2014 proposal,
all chronic noncancer TOSHIs remain below 1. Further, our screening
analysis also projected that maximum acute exposure to non-routine PRD
and flare emissions would result in a maximum hazard quotient (HQ) of
14 from benzene emissions based on a reference exposure level (REL). An
exceedance of an REL value does not necessarily indicate that an
adverse health effect will occur. Because of the infrequent occurrence
of such events and the probability that someone would be at the exact
most highly impacted exposure locations at the time of the elevated
ambient levels, the EPA risk assessors believe there is a very low
probability of any adverse exposure. Based on the risk analysis
performed for the June 2014 proposal and the screening assessment to
consider how conclusions from that analysis would be affected by the
additional non-routine flare and PRD emissions allowed under the
December 2015 rule, we determined that the risk posed after
implementation of the revisions to the MACT standards is acceptable and
that the standards as promulgated provide an ample margin of safety to
protect public health.
    We requested public comment on the screening analysis and the
conclusions reached based on that analysis in conjunction with the risk
analysis performed for the June 2014 proposal.
2. What comments were received on the assessment of risk from the
Petroleum Refinery source categories after implementation of the PRD
and emergency flaring work practice standards?
    Comment C.1: Commenters explained that the EPA performed a
screening level risk assessment to account for the additional risk from
the PRD and emergency flare work practice standards based on
``approximately 430 records of PRD and flare HAP pollutant release
events'' from 25 facilities, as reported in response to the detailed
Petroleum Refinery information collection request (ICR), and that this
assessment resulted in an additional 2-in-1 million lifetime cancer
risk and an acute risk that is 14 times higher than what the Agency
considers safe. The commenters contended that these risks were based on
biased-low industry-estimated emissions data when they should have been
based on a true maximum additional cancer or acute risk from a serious
fire, explosion, or force majeure event, or even from one of the
largest historical leaks or emergency flaring events. Commenters
referenced numerous malfunction events which they asserted demonstrate
the long history of these types of releases from refineries that could
have been prevented by advanced planning, inspections, upgrades, and
maintenance and claimed these events could have been used for the
purpose of estimating additional risks from PRD releases and smoking
flare events. In addition to not basing the risks on a worst-case
scenario, the commenters said the EPA did not explain how the risk
model predicted worst case 1-hour and annual average concentrations for
PRDs and flares or whether the concentrations presented in the final
risk assessment were total HAP or benzene. In any case, the commenters
asserted that these concentrations are higher than what the California
EPA has deemed health protective for acute and chronic exposure, and
while they are lower than the EPA's 2003 Integrated Risk Information
System values, the EPA should consider that these exposures occur in
combination with other emissions from refineries.
    Response C.1: The December 2015 rule established work practice
standards that require advanced planning, inspections, upgrades, and
maintenance of equipment through the implementation of prevention
measures, root cause analysis, and corrective action. Under CAA section
112(f)(2), the EPA is required to estimate the risk remaining after the
implementation of the MACT, which for this emissions source is the
promulgated work practice standards. This approach is consistent with
the way that EPA has performed its risk analysis for all previously
promulgated risk reviews under CAA section 112(f)(2). In the screening
analysis, we used release information collected under the authority of
CAA section 114 which represents annual releases occurring prior to the
implementation of these work practice

standards and the data and assumptions used as inputs to the screening
analysis are a reasonable representation of the worst-case releases
allowed under the promulgated standard and that may be expected
subsequent to the implementation of the work practice standards.
    In response to the commenters' statement that the EPA did not
explain how the risk model predicted worst case 1-hour and annual
average concentrations for PRDs and flares or whether the
concentrations presented in the final risk assessment were total HAP or
benzene, as noted in the risk report (appendix 13 of Docket ID Item No.
EPA-HQ-OAR-2010-0682-0800), the EPA estimated concentrations using a
conservative (health protective) screening dispersion modeling
approach. Further, the risks were estimated based on all reported
emissions (i.e., not only benzene). Acute risks (HQs) are estimated on
a pollutant-by-pollutant basis.
    With regard to the comment that the EPA should consider the
California Office of Environmental Health Hazard Assessment health
benchmarks, in May 2018, based on examination of the California EPA's
acute (1-hour) REL for benzene, and taking into account aspects of the
methodology used in the derivation of the value and how this assessment
stands in comparison to the Agency for Toxic Substances and Disease
Registry's toxicological assessment, EPA toxicologists decided it is
not appropriate to use the benzene REL value to support the EPA's RTR
rules. In lieu of using the REL in RTR risk assessments, the EPA is now
evaluating acute benzene risks by comparing potential exposure levels
to the emergency response planning guidelines (ERPG)-1 values. In this
case, the acute HQ value from non-routine PRD and flare emissions is
0.07 when comparing ambient levels to the ERPG-1.
    Comment C.2: Commenters asserted that the EPA's risk assessment and
determinations are unlawful and are arbitrary and capricious because
the EPA has not followed its own policy and guidelines in summing
cancer risk and treating a lifetime cancer risk above 100-in-1 million
as showing the need for section CAA section 112(f) standards. The
commenters stated that the EPA found an inhalation-based cancer risk of
100-in-1 million from routine emissions, an additional cancer risk of
2-in-1 million from non-routine PRD and flare emissions, and an
additional cancer risk of 4-in-1 million from non-inhalation or
multipathway emissions. The sum of these risks is 106-in-1 million,
and, therefore, above the presumptive acceptability threshold of 100-
in-1 million, yet the EPA has continued to maintain that risks are
acceptable. The commenters also contended that in addition to never
adding these risks, the EPA has not provided a reasoned justification
in the record for not doing so. The commenters added that the EPA
recognized risks were unacceptable for a similar set of risks (e.g.,
lead smelting and ferroalloys) as those in the Petroleum Refinery RTR,
and, thus, the risk for the Petroleum Refinery RTR should also be found
unacceptable.
    Further, the commenters noted that the EPA's refined multipathway
risk assessment for one refinery, for which the EPA indicates that the
sum of the multipathway and inhalation risks for that facility is less
than 100-in-1 million, conflicts with the fact that the inhalation risk
alone is at least 100-in-1 million; it is unclear how combined risks
would not exceed 100-in-1 million. Finally, the commenters stated that
the EPA has not supported the conclusion based on data in the record
that after performing a refined risk assessment on one refinery that
cancer risk for all facilities can be discounted.
    Response C.2: As an initial matter, it is important to note that a
risk level of 100-in-1 million is a presumptive limit of acceptability,
not a threshold for acceptability or regulatory action. As stated in
the Benzene NESHAP (54 FR 38044, 38061, September 14, 1989), in
determining the need for residual risk standards, we strive to limit to
no higher than approximately 100-in-1 million the estimated cancer risk
that a person living near a plant would have if he or she were exposed
to the maximum pollutant concentrations for 70 years and, in the ample
margin of safety decision, to protect the greatest number of persons
possible to an individual lifetime risk level of no higher than
approximately 1-in-1 million. In determining whether risk is acceptable
under CAA section 112(f), these levels are not rigid lines, and we
weigh the cancer risk values with a series of other health measures and
factors, including the specific uncertainties of the emissions, health
effects, and risk information for the relevant source category, in both
the decision regarding risk acceptability and in the ample margin of
safety determination. The source category-specific decision of what
constitutes an acceptable level of risk and whether it is necessary to
promulgate more stringent standards to provide an ample margin of
safety is a holistic one; that is, the EPA considers all potential
health impacts--chronic and acute, cancer and noncancer, and
multipathway--along with their uncertainties.
    With regard to the analysis performed for the refinery standards at
issue here, the estimated risk of 100-in-1 million is based on a risk
analysis using the MACT-allowable HAP emissions from a model plant,
while the estimated risk based on actual HAP emissions from refineries
is no greater than approximately 60-in-1 million and may be closer to
40-in-1 million based on updated data received during the comment
period. The model plant screening approach used to assess MACT-
allowable HAP emissions used several health protective assumptions
including co-locating all sources at a refinery at a single location.
The screening analysis used to estimate risk from non-routine PRD and
flare emissions is also based on several health protective assumptions.
Because of the conservative nature of these screening analyses, the EPA
does not typically add their results (i.e., risk estimates from the
model plant non-routine PRD and flare emissions to risk estimates from
model plant allowable emissions). Further, we do not add the
multipathway (non-inhalation) risks to inhalation risks because it is
highly unlikely that the person exposed to the highest inhalation risk
is the same person exposed to the highest refined multipathway
(ingestion) risks. Overall risk results are presented to one
significant digit, thus, even if we were to add the non-inhalation risk
of 4-in-1 million to the 100-in-1 million risk from inhalation, we
would still assess the total risk based on allowable emissions as 100-
in-1 million.
    Regarding the refined multipathway analysis performed on a single
facility, as stated in the risk report, the EPA performed the refined
analysis to gain a better understanding of the uncertainty associated
with the multipathway Tier I and II screening analyses. The site,
Marathon Ashland Petroleum facility (NEI6087) near Garyville in St.
John the Baptist Parish, Louisiana, was among those that exceeded the
Tier I screen for any HAP known to be persistent and bio-accumulative
in the environment (PB-HAP), and it was among the refineries that had
the greatest exceedance of a Tier II threshold for any PB-HAP. It also
was selected based on the feasibility, with respect to the modeling
framework, of obtaining model parameters for the region surrounding the
refinery. The exposure estimates (and the risks calculated for those
exposures) are anticipated to be among the highest that might be
encountered for this source category because of the proximity of
waterbodies

as well as agricultural lands. We note that many of the refineries did
not exceed the Tier I screen, and for those that did, the levels of the
exceedances were generally less than the level of exceedance exhibited
by the facility selected for the refined assessment. Because the other
facilities had a similar or lower exceedance of the screening level,
the results of the refined assessment for this facility led us to
conclude that if refined analyses were performed for other sites, the
risk estimates would similarly be reduced from their Tier II estimates.
    Comment C.3: A commenter stated that the EPA acknowledged that
people of color and those with low incomes are disproportionately
exposed to risk from refinery emissions. The commenter asserted that
the EPA has not provided a rational explanation why the unfair
distribution of this risk does not lead to an unacceptable risk finding
or at least require additional protections to assure an ample margin of
safety to protect public health for all exposed persons.
    Response C.3: Following the analysis that CAA section 112(f)(2)
requires, the EPA determined that the risk posed by emissions from the
Petroleum Refinery source category were acceptable. After considering
whether additional standards were required to provide an ample margin
of safety to protect public health, including the health of people of
color and those with low income, the EPA established additional control
requirements for storage vessels. The December 2015 rule reduces risk
for millions of people living near petroleum refineries and provides an
ample margin of safety to protect public health. The NESHAP accordingly
provides an ample margin of safety for all proximate populations,
including people of color and those with low incomes.
    Comment C.4: A commenter stated that the EPA's risk assessment and
determination are unlawful and are arbitrary and capricious because
they are based on internally contradictory findings that, although
acute risk is high (citing an HQ of 14 due to benzene from non-routine
PRD and flare emissions), exposure to these non-routine emissions will
rarely occur. The commenter asserted that the EPA's own record shows
that non-routine emissions occur frequently: Every 4.4 to 6 years at
all refineries, 16.7 percent probability of having an event in any
given year, and that over a long period of time, such as 20 years, half
of the best performers would have two events in a 3-year period. The
commenter added that the December 2015 rule will allow these non-
routine emissions events to happen even more frequently. The commenter
further asserted that the EPA's justification to discount this high
acute risk was by stating that it could have used the acute exposure
guideline level (AEGL) or ERPG level to develop a lower acute risk
value than the value developed for the published risk assessment which
was based on the REL. The commenter stated that the AEGL and ERPG level
are designed to be used in a true emergency and not to set health
protective standards that will generally apply at all times, adding
that the AEGL, unlike the REL, does not incorporate consideration of
vulnerability, such as for children, or community exposure over time.
The commenter stated that the use of the AEGL and ERPG numbers would be
expected to substantially underestimate risk and using them as
justification to discount the high acute risk is arbitrary and
capricious.
    Response C.4: As an initial matter, we disagree with the
characterization that the work practice standards in the December 2015
rule for flares and PRDs will allow non-routine events to occur more
frequently than they do now. Prior to promulgation of the flare
requirements and the PRD provisions, the MACT did not include any
specific regulatory requirements that applied to these events. As noted
in sections III.A and B above, the final work practice standards
include requirements that are designed to reduce the number and
magnitude of these types of releases. The commenters have not explained
why the new requirements would increase the frequency and/or magnitude
of these events.
    In May 2018, based on examination of California EPA's acute (1-
hour) REL for benzene, and considering aspects of the methodology used
in the derivation of the value and how this assessment stands in
comparison to the Agency for Toxic Substances and Disease Registry's
toxicological assessment, EPA toxicologists decided it is not
appropriate to use the benzene REL value to support the EPA's RTR
rules. In lieu of using the REL in RTR risk assessments, the EPA is now
evaluating acute benzene risks by comparing potential exposure levels
to the ERPG-1 values. In this case, the acute HQ value from non-routine
PRD and flare emissions is 0.07 when comparing ambient levels to the
ERPG-1. To better characterize the potential health risks associated
with estimated worst-case acute exposures to HAP, and in response to a
key recommendation from the Science Advisory Board's peer review of the
EPA's RTR risk assessment methodologies, we now examine a wider range
of available acute health metrics than we do for our chronic risk
assessments. This is in acknowledgement that there are generally more
data gaps and uncertainties in acute reference values than there are in
chronic reference values. The acute REL represents a health-protective
level of exposure, with effects not anticipated below those levels,
even for repeated exposures. Although the potential for effects
increases as exposure concentration increases above the acute REL, the
level of exposure greater than the REL that would cause health effects
is not specifically known. Therefore, when an REL is exceeded and an
AEGL-1 or ERPG-1 level is available (i.e., levels at which mild,
reversible effects are anticipated in the general public for a single
exposure), we typically use them as an additional comparative measure,
as they provide an upper bound for exposure levels above which exposed
individuals could experience effects. The worst-case maximum estimated
1-hour exposure to benzene outside the facility fence line is less than
the AEGL-1 or ERPG-1 levels.
3. What is the EPA's final decision on the risk assessment?
    As supported by the screening analysis published with the December
2015 rule, the additional risk from the PRD and emergency flaring work
practice standards did not significantly alter the risk estimates in
the EPA's 2014 analysis. In response to the current proposal, we did
not receive any new information or other basis that would support a
change to the risk analysis and the determination that the risk from
the source category is acceptable and that, as modified by the December
2015 rule, the MACT standards provide an ample margin of safety to
protect public health.

D. Issue 4: Alternative Work Practice Standards for DCUs Employing the
Water Overflow Design

1. What is the history of the alternative work practice standards for
DCUs employing the water overflow design?
    In the December 2015 rule, we finalized MACT standards for DCU
decoking operations. The rule provided that existing DCU-affected
sources must comply with a 2 psig or 220 degrees Fahrenheit ([deg]F)
limit in the drum overhead line determined on a rolling 60-event basis
prior to venting to the atmosphere, draining, or deheading the coke
drum. New DCU-affected sources must comply with a 2.0 psig or 218
[deg]F limit in the drum overhead line on a per-event, not-to-exceed
basis. In the

December 2015 rule, we also finalized an alternative requirement that
we did not propose to address DCU with water overflow design, where
pressure monitoring would not be appropriate. As part of these
provisions, we included a new requirement in the December 2015 rule for
DCU with water overflow design to hard-pipe the overflow drain water to
the receiving tank via a submerged fill pipe (pipe below the existing
liquid level) whenever the overflow water exceeds 220 [deg]F.
    We requested public comment on the alternative work practice
standard for delayed coking units employing a water overflow design
provided in 40 CFR 63.657(e).
    In response to the comments received on the October 2016 proposed
notice of reconsideration regarding the alternative work practice
standards for DCU employing the water overflow design, we proposed
amendments on April 10, 2018 (April 2018 proposal) (see 83 FR 15458),
to the water overflow requirements in 40 CFR 63.657(e). The EPA has
issued a final rule which was promulgated on November 26, 2018
(November 2018 rule) fully addressing this issue and responding to all
of the comments on the proposal for this rule as well as the April 2018
proposal.

E. Issue 5: Alternative Sampling Frequency for Burden Reduction for
Fenceline Monitoring

1. What is the history of the alternative sampling frequency for burden
reduction for fenceline monitoring?
    In the December 2015 rule, we revised Refinery MACT 1 to establish
a work practice standard requiring refinery owners to monitor benzene
concentrations around the fenceline or perimeter of the refinery. We
promulgated new EPA Methods 325A and B which specify monitor siting and
quantitative sample analysis procedures. The work practice is designed
to improve the management of fugitive emissions at petroleum refineries
through the use of passive monitors by requiring sources to implement
corrective measures if the benzene concentration in air attributable to
emissions from the refinery exceeds a fenceline benzene concentration
action level. The work practice requires refinery owners to maintain
fenceline benzene concentrations at or below the concentration action
level of 9 [mu]g/m\3\. In the December 2015 rule, we included
provisions that were not proposed that would allow for reduced
monitoring frequency (after 2 years of continual monitoring) at
monitoring locations that record concentrations below 0.9 [mu]g/m\3\
[see 40 CFR 63.658(e)(3)].
    We requested public comment on the provision allowing refineries to
reduce the frequency of fenceline monitoring at monitoring locations
that consistently record benzene concentrations below 0.9 [mu]g/m\3\.
2. What comments were received on the alternative sampling frequency
for fenceline monitoring?
    Comment E.1: Commenters asserted that setting the threshold for
reducing the frequency of fenceline monitoring at 0.9 [mu]g/m\3\ is
arbitrary and capricious. The commenters stated that the EPA's modeling
predicted that more than half (81 of 142) of the refineries modeled
would have fenceline concentrations equal to or less than 0.4 [mu]g/
m\3\, and, thus, it is unlikely these facilities will have any monitors
register concentrations in excess of the threshold. Therefore, these
refineries will likely qualify for reduced monitoring, although they
could have malfunctioning equipment causing benzene levels to be double
the EPA's modeled amount.
    The commenter added that while the fenceline concentrations modeled
by the EPA do not include background ambient concentrations of benzene
which will contribute to the benzene concentration measured at each
monitor, it is still likely that the eligibility threshold for reduced
frequency monitoring is too high and will allow operators to reduce the
monitoring frequency at downwind monitors. The commenter supported this
statement by referencing the API Corrected Fenceline Monitoring
Results, Docket ID Item No. EPA-HQ-OAR-2010-0682-0752, which showed
that at least 25 percent of facilities would be eligible for reduced
monitoring at more than half of the monitoring sites based on the 0.9
[mu]g/m\3\ threshold.
    Response E.1: We disagree that entire refineries will be able to
qualify for reduced monitoring frequency. As the commenters themselves
noted, the Agency's modeled concentrations provide only the impact of
refinery emissions on the ambient air concentration (the [Delta]C) and
do not include background concentrations. The modeling does not allow
us to evaluate the total (refinery plus background) concentration level
at any one location. Second, we note that the API study was a 3-month
study that occurred primarily in the winter months when fugitive
emissions are expected to be at their lowest. We also considered the
Corpus Christi year-long study and a comparison of the concentrations
observed throughout the year. That study showed that benzene
concentrations at the fenceline are higher during warmer weather
because most fugitive emission sources, such as storage tanks and
wastewater, have a significant temperature dependency. The reduced
monitoring provisions require 2 full years (52 consecutive 2-week
samples) where the highest single value, not the average concentration
at that location, is less than 0.9 [mu]g/m\3\. Based on the data we
have available, we consider that only a few monitoring locations will
qualify for reduced frequency monitoring based on this 2-year
requirement that all sample concentrations at the location are less
than 0.9 [mu]g/m\3\.
    In addition, we selected this value to be consistent with the
minimum detection limit we required for an alternative monitoring
method. It seemed incongruous to allow an alternative monitoring method
with a detection limit of 0.9 [mu]g/m\3\ to be used to comply with the
rule but then establish a burden reduction alternative that used a
lower concentration level. Ultimately, we are confident that only a
limited number of sampling locations at any petroleum refinery will
meet the burden reduction criteria. We considered it reasonable to
provide incentives for refinery owners or operators to achieve even
greater reductions than are required by the 9 [mu]g/m\3\ [Delta]C
action level, and the final burden reduction provisions provide such an
incentive without compromising the overall objectives of the program.
    Comment E.2: One commenter stated that the provisions allowing
refineries to reduce the frequency of fenceline monitoring are unlawful
and are arbitrary and capricious. To support this statement, the
commenter stated that a reduction in burden to the fenceline monitoring
program will not allow the program to serve its intended purpose: To
enable operators to identify leaks or operating problems at equipment
that cannot practically be monitored, tested, or evaluated for
compliance on a frequent basis. In further support of their argument,
the commenters explained that the risk findings for the December 2015
rule hinge on the frequency of the fenceline monitoring cycle. The
commenter stated that the EPA is on record stating that if the emission
inventories or risk assessment do understate actual emissions, as some
commenters have alleged, the fenceline monitoring and corrective action
requirements will ensure refineries reduce their actual emissions to
levels comparable to their emissions inventories, and that in doing so,
will

ensure communities surrounding petroleum refineries would be protected
to acceptable risk levels. Therefore, the commenter asserted that it is
imperative for the EPA to maintain the 2-week monitoring cycle to
ensure operators are quickly identifying malfunctioning equipment and
to close the gap between actual and reported emissions.
    On the other hand, some commenters stated that the alternative
monitoring provisions did not go far enough at reducing burden. Some
commenters suggested that after 2 years of demonstrating a background-
corrected maximum fenceline annual average concentration ([Delta]C)
below the action level, monitoring frequency be reduced to a 2-week
period every quarter for all monitoring locations. If the background-
corrected annual average benzene concentration based on the quarterly
monitoring exceeds the action level, a return to more frequent
monitoring could be required RCA/CAA requirement. The reduced
monitoring frequency could be available again after 1 year of meeting
the action level. Another commenter recommended that the reduced
monitoring provision be removed in favor of a one-time demonstration
that the annual fenceline benzene [Delta]C concentration is less than
50 percent of the action level during normal operations.
    Response E.2: With respect to the commenter's opposition to the
alternative sampling frequency, it is important to understand that the
alternative sampling frequency provision in the December 2015 rule does
not reduce the frequency by which the [Delta]C values must be
determined. This is because the reduced sampling frequency provision
will impact only selected locations that have monitored benzene
concentrations below 0.9 [mu]g/m\3\ based on 2 full years of data.
Refineries will still collect samples at all other locations during
each 2-week period and will still determine the [Delta]C value for each
sampling interval and include the [Delta]C for the sampling interval in
the annual average [Delta]C value calculation. Therefore, we still
expect the fenceline monitoring program as included in the December
2015 rule to achieve its purpose of more timely detection and
correction of issues that can lead to high fugitive emissions.
    The burden reduction alternatives suggested by some commenters
would significantly limit the effectiveness of the fenceline monitoring
program to identify issues early. A one-time determination completely
defeats this purpose and could not possibly be done in a manner
representative of the variety of circumstances that can occur
throughout the year or the lifetime of a facility. The purpose of the
fenceline monitoring program is to allow for detection and correction
of issues that may cause abnormally high emissions, such as large leaks
in valves, tears in rim seals of floating roof storage vessels, and
other unexpected, difficult to predict events. A one-time determination
does not allow the fenceline monitoring program to timely and
effectively identify these issues on an on-going basis.
    While quarterly determinations would be more effective than a one-
time determination for on-going fugitive management, quarterly
determinations are less effective in improving fugitive emissions
management than continual 2-week sampling. First, for large leak
events, the emissions may continue for months prior to being detected
under quarterly monitoring versus being detected in a week or two under
continual 2-week sampling. Thus, the emission reduction achieved by the
quarterly monitoring would not be as great as by continual 2-week
monitoring. Second, under the quarterly monitoring option, there would
be large periods of time when no monitoring will be performed. The
passive diffusive tubes cannot be deployed over such a long time
period. Thus, we assume that quarterly monitoring would consist of a 2-
week sampling period once every quarter. As such, for more than 80
percent of the time, no monitoring would be conducted at the fenceline.
Consequently, quarterly monitoring would often miss periodic emission
events, such as tank cleaning and/or filling, which can lead to high
short-term emissions. These short-term events can contribute
significantly to a facility's emissions and their contribution would be
captured via the continual 2-week sampling, but likely missed under a
quarterly monitoring approach. In order to effectively manage all
fugitive emission sources, including periodic releases, we determined
that the continual 2-week sampling period should be maintained for the
overall program. By providing a monitoring skip period only to
locations that do not exceed 0.9 [mu]g/m\3\ for any sampling interval
for 2 full years (52 consecutive 2-week sampling periods), we maintain
continual 2-week sampling at all locations that may contribute to an
exceedance of the action level and ensure on-going enhanced management
of fugitive emissions.
    Comment E.3: Commenters stated that the rule does not include
provisions for re-instating the monitoring frequency for those monitors
which may at one time qualify for reduced monitoring.
    Response E.3: We disagree. Section 63.658(e)(v) of the final rule
provides that any location with a value above 0.9 [mu]g/m\3\ while
reduced monitoring is being implemented will subject the owner or
operator to a 3-month ``probationary period'' where samples must be
collected every 2 weeks at that location. If the concentrations during
the probationary period are all at or below 0.9 [mu]g/m\3\, the owner
or operator may continue with the monitoring frequency prior to the
excursion. If any other sample during the probationary period exceeds
0.9 [mu]g/m\3\, then the owner or operator must comply with the more
stringent monitoring requirements and would not be eligible for reduced
monitoring frequency until completion of a new 2-year period at that
more stringent monitoring frequency.
    Comment E.4: A commenter stated that despite the EPA's claims that
it is allowing less frequent monitoring to reduce burden, there is no
quantified or otherwise evaluated data available in the record related
to the actual burden reduction.
    Response E.4: We did not specifically develop burden reduction
estimates associated with this provision for several reasons. First,
fenceline monitoring must be performed for a full 2 years prior to the
burden reduction provisions applying to any monitoring location, so
estimating the burden of the fenceline monitoring provisions without
consideration of the burden reduction provisions provides an accurate
estimate of the annual burden for the first 2 years. Second, we were
uncertain how many monitoring locations would qualify for the burden
reduction provision. Third, with respect to the burden estimate for the
December 2015 rule as provided in the Supporting Statement for the
Office of Management and Budget's (OMB's) ICR, we estimated the costs
of the on-going fenceline monitoring program assuming all samples would
continue to be collected during the 3-year period covered by the ICR.
    Based on the burden estimate detail provided in the attachments to
the memorandum, ``Fenceline Monitoring Impact Estimates for Final
Rule'' (see Docket ID Item No. EPA-HQ-OAR-2010-0682-0749), we estimate
that each time a sample does not need to be collected at a specific
location there will be a burden reduction of 0.3 technical hours (0.25
hours reduced during sample collection and 0.05 hours reduced during
sample analyses). Considering management and clerical hours, the total
burden reduction per sample skipped would be 0.35 hours and
approximately $29. As an example

of potential burden reduction, if a facility could use the monthly
reduced monitoring provisions for two locations in a given year (26
skipped samples, 13 at each site), the burden reduction for that
facility would be 9 hours and $745 each year.
    Comment E.5: One commenter recommended that the EPA reduce burden
by providing a mechanism to use existing HAP ambient monitoring
programs as an acceptable alternative to the EPA fenceline monitoring
program.
    Response E.5: We provided a mechanism and criteria by which a
refinery owner or operator may submit a request for an alternative test
method to the passive diffusive tube fenceline monitoring methods (EPA
Methods 325A and 325B). These provisions are included at 40 CFR
63.658(k) of the final rule.
3. What is EPA's final decision on the alternative sampling frequency
for fenceline monitoring?
    For fenceline monitoring requirements, the alternative sampling
frequency requirements will not alter the effectiveness of the program
as the requirements do not change the facility-level procedures and
frequency for calculating and reporting [Delta]C (see Response E.1).
Furthermore, the 0.9 [mu]g/m\3\ threshold for reducing the frequency of
fenceline monitoring is appropriate based on the available data and it
is consistent with the minimum detection limit required for alternative
monitoring methods. We have not been presented with any comments and/or
information in response to the October 2016 proposed notice of
reconsideration relative to the alternative sampling frequency for
fenceline monitoring which will result in any changes to the December
2015 rule.

F. Additional Proposed Clarifying Amendments

1. What is the history of the proposed clarifying amendments?
    The EPA proposed to amend provisions related to the overlap
requirements for equipment leaks that are contained in Refinery MACT 1
and in the Refinery Equipment Leak NSPS (40 CFR part 60, subpart GGGa).
The Refinery MACT 1 provision at 40 CFR 63.640(p)(2) states that
equipment leaks that are subject to the provisions in the Refinery
Equipment Leak NSPS (40 CFR part 60, subpart GGGa) are only required to
comply with the provisions in the Refinery Equipment Leak NSPS.
However, the Refinery Equipment Leak NSPS does not include the new work
practice standards finalized in the final Refinery MACT 1 at 40 CFR
63.648(j) which apply to releases from PRDs. We intended that these new
work practice standards would be applicable to all PRDs at refineries,
including those PRDs subject to the requirements in the Refinery
Equipment Leaks NSPS. In order to provide clarity and assure that
refiners subject to these provisions fully understand their compliance
obligations, we proposed to modify the equipment leak requirement to
provide that PRDs in organic HAP service must comply with the
requirements in Refinery MACT 1 at 40 CFR 63.648(j) for PRDs. We also
proposed to amend the introductory text in 40 CFR 63.648(j) to
reference the Refinery Equipment Leaks NSPS at 40 CFR 60.482-4a and
amend paragraphs (j)(2)(i) through (iii) of Refinery MACT 1 to correct
the existing reference to 40 CFR 60.485(b), to instead refer to 40 CFR
60.485(c) and 40 CFR 60.485a(c). As noted in section III.B.1 of this
preamble, we also proposed to revise the incorrect cross-reference to
PRD prevention measures at 40 CFR 63.670(o)(1)(ii)(B) from 40 CFR
63.648(j)(5) to 63.648(j)(3)(ii). However, we concluded it would be
more accurate to cross-reference 40 CFR 63.648(j)(3)(ii)(A) through (E)
rather than the entirety of 40 CFR 63.648(j)(3)(ii). Therefore, in the
April 2018 proposal, we proposed this clarified revision and finalized
this revision as proposed in the November 2018 rule.
2. What comments were received on the proposed clarifying amendments?
    Comment F.1: Commenters asserted that the EPA's proposal to modify
the provisions in 40 CFR 63.640(p)(2) by providing that PRDs in organic
HAP service must comply with the requirements in 40 CFR 63.648(j) is
arbitrary and capricious. Commenters opposed the proposed revisions
claiming they would enshrine exemptions from NSPS equipment leak
standards for new and modified PRD or allow for substitution of NSPS
requirements for the work practice standards in 40 CFR 63.648(j), which
they believe are exemptions from malfunction requirements. They added
that these provisions amend the NSPS for Petroleum Refineries without
satisfying the appropriate procedural and substantive legal tests
required to do so.
    Response F.1: It appears that the commenter misunderstands the
proposed amendment. When we revised Refinery MACT 1 at 40 CFR 63.648(j)
to add PRD requirements, we failed to recognize that the NSPS overlap
provisions in 40 CFR 63.640(p)(2) could be used as a ``loophole'' by
refinery owners and operators to not implement three prevention
measures and to not perform the root cause analysis or implement
corrective actions. This is because the NSPS subpart GGGa does not have
any pressure release management requirements. In the absence of the
proposed amendment, the existing overlap provision states that
``Equipment leaks that are also subject to the provisions of 40 CFR
part 60, subpart GGGa, are required to comply only with the provisions
specified in 40 CFR part 60, subpart GGGa.'' Thus, PRDs subject to 40
CFR part 60, subpart GGGa, were inadvertently exempted from the new PRD
pressure release management requirements. We understand that the
commenter does not support some of the provisions in the pressure
release management requirements in the final Refinery MACT 1 rule, but
these requirements are clearly more stringent than the NSPS subpart
GGGa provisions for PRDs which only require monitoring of the PRD after
a release, and do not have any restrictions or requirements to limit
PRD releases. We note that in addition to the new PRD requirements
established in the December 2015 rule, the Refinery MACT 1 PRD
requirements at 40 CFR 63.648(j)(1) and (2) fully include those
requirements that would apply under 40 CFR part 60, subpart GGGa. In
reviewing standards covering the same pieces of equipment, we look to
identify the overlapping standards and require the owner or operator to
comply only with the most stringent standard. After the revisions to
the PRD requirements in Refinery MACT 1, we determined that the
equipment leak provisions for PRDs in Refinery MACT 1 are more
stringent than those in 40 CFR part 60, subpart GGGa. By revising this
overlap provision, we are requiring equipment leak sources that are
subject to both rules to comply with the 40 CFR part 60, subpart GGGa
for most equipment leak sources but PRDs must comply with the PRD
requirements in Refinery MACT 1. This revision will require PRDs that
are also subject to 40 CFR part 60, subpart GGGa, to implement
prevention measures for PRDs, conduct root cause analyses, and
implement corrective actions to prevent a similar release from
occurring. Because compliance with 40 CFR part 60, subpart GGGa is not
sufficient to demonstrate compliance with Refinery MACT 1 PRD
provisions, revision of the existing overlap provisions was deemed
critical to ensure all Refinery MACT 1 PRDs comply with the new
pressure release management requirements.

    The commenter is also mistaken that this provision amends the NSPS.
Rather, it defines what sources subject to Refinery MACT 1 must do to
comply with Refinery MACT 1. Specifically, for equipment leaks at
facilities subject to both Refinery MACT 1 and 40 CFR part 60, subpart
GGGa, owners and operators must comply with the requirements in
Refinery MACT 1 (40 CFR part 63, subpart CC) for PRDs associated with
the leaking equipment because the requirements in Refinery MACT 1 for
PRDs are more stringent than those in 40 CFR part 60, subpart GGGa. The
NSPS requirements are not modified by this change to 40 CFR part 63,
subpart CC and remain in effect for PRDs associated with equipment
leaks that are not subject to Refinery MACT 1.
    Comment F.2: Commenters supported the clarification to the overlap
provisions for equipment leaks in 40 CFR 63.640(p)(2), but also request
that a delay of repair provision be included in 40 CFR 63.648 because
other equipment leak rules (such as 40 CFR part 60, subparts GGG and
GGGa) potentially applicable to refinery PRDs include such delay of
repair provisions. The commenters noted that PRDs subject to 40 CFR
part 60, subpart GGG, are made subject to 40 CFR 63.648(j) by 40 CFR
63.640(p)(1).
    Response F.2: By proposing a technical correction to 40 CFR
63.640(p)(2), the EPA was not proposing to re-open the substantive
requirements of 40 CFR 63.640 nor of other provisions, such as 40 CFR
63.648 that may be referenced in 40 CFR 63.640. We also disagree that
PRDs are allowed to comply with delay of repair provisions in the NSPS
(subparts GGG/GGGa or VV/Vva) beyond taking the equipment out of VOC
service. In any case, we determined that it was contrary to safety and
good air pollution control practices to continue to operate a process
unit without a properly functioning PRD as PRDs are, primarily, safety
devices.
3. What is the EPA's final decision on the proposed clarifying
amendments?
    We are finalizing the amendment that equipment leaks that are
subject to the provisions of the Refinery Equipment Leak NSPS pursuant
to 40 CFR 63.640(p)(2) must comply with the requirements in Refinery
MACT 1 at 40 CFR 63.648(j) for PRDs, as proposed. We are also
finalizing the amendment to the introductory text in 40 CFR 63.648(j)
to reference Refinery Equipment Leaks NSPS at 40 CFR 60.482-4a and the
amendment to paragraphs (j)(2)(i) through (iii) of Refinery MACT 1 to
correct the existing reference to 40 CFR 60.485(b), which should refer
to 40 CFR 60.485(c) and 40 CFR 60.485a(c), as proposed. Finally, as
noted in the history of these clarifying amendments, we addressed the
proposed amendments at 40 CFR 63.670(o)(1)(ii)(B) in a final rule
issued in November 2018 to more accurately cross-reference 40 CFR
63.648(j)(3)(ii)(A) through (E) rather than the entirety of 40 CFR
63.648(j)(3)(ii).

G. Corrections to November 2018 Final Rule

    There were a number of publication errors associated with the
November 2018 rule. Several of these errors were associated with
inaccurate amendatory instructions or editorial errors in the final
amendment package. We are correcting these errors to finalize the
amendments consistent with the intent of the preamble to the November
2018 final rule (83 FR 60696). Table 2 of this preamble provides a
summary of the publication and editorial errors in the November 2018
rule that we are correcting in this final action.

          Table 2--Summary of Corrections to November 2018 Rule
------------------------------------------------------------------------
           Provision                  Issue            Final revision
------------------------------------------------------------------------
                             Refinery MACT 1
------------------------------------------------------------------------
40 CFR 63.641, definition of    Incorrect          Revise instructions
 ``Reference control             amendatory         and reprint the
 technology for storage          instructions;      entire definition to
 vessels''.                      the Code of        more easily
                                 Federal            implement revisions
                                 Regulations        to the definition of
                                 could not          ``Reference control
                                 implement          technology for
                                 revisions as       storage vessels''
                                 instructed.        consistent with the
                                                    intent of the
                                                    preamble to the
                                                    November 2018 final
                                                    rule.
40 CFR 63.643(c)(1)(v)........  There is a comma   Amend 40 CFR
                                 after the word     63.643(c)(1)(v) to
                                 ``less.'' It       replace the comma
                                 should be a        after the word
                                 period.            ``less'' with a
                                                    period.
40 CFR 63.655(f)(1)(iii)......  Subordinate        Amend 40 CFR
                                 paragraphs (A)     63.655(f)(1)(iii) to
                                 and (B) were       include subordinate
                                 inadvertently      paragraphs (A) and
                                 removed due to     (B) consistent with
                                 incorrect          the intent of the
                                 amendatory         preamble to the
                                 instructions.      November 2018 final
                                                    rule.
40 CFR 63.655(f)(2)...........  Subordinate        Amend 40 CFR
                                 paragraphs (i)     63.655(f)(2) to
                                 through (iii)      include subordinate
                                 were               paragraphs (i)
                                 inadvertently      through (iii)
                                 removed due to     consistent with the
                                 incorrect          intent of the
                                 amendatory         preamble to the
                                 instructions.      November 2018 final
                                                    rule.
40 CFR 63.655(h)(10)..........  The introductory   Amend 40 CFR
                                 text associated    63.655(h)(10)
                                 with this          introductory text to
                                 paragraph was      read as ``Extensions
                                 missing from the   to electronic
                                 regulatory text    reporting
                                 included in the    deadlines.''
                                 rule as
                                 published in the
                                 Federal Register.
40 CFR 63.655(i)(11) ``. . .    Pilot-operated     Amend 40 CFR
 For each pilot-operated         PRDs are not       63.655(i)(11)
 pressure relief device          subject to         introductory text to
 subject to the requirements     requirements at    remove ``or (iii).''
 at 40 CFR 63.648(j)(4)(ii) or   40 CFR
 (iii), . . .''.                 63.648(j)(4)(iii
                                 ) so the
                                 inclusion of
                                 ``or (iii)'' was
                                 incorrect.
40 CFR 63.660(i)(2)(iii).       Use of the plural  Amend 40 CFR
 ``Use a cap, blind flange,      in referencing     63.660(i)(2)(iii) to
 plug, or a second valve for     ``. . . an open-   read ``Use a cap,
 an open-ended valves or line    ended valves . .   blind flange, plug,
 . . .''.                        .'' is incorrect   or a second valve
                                 grammar.           for an open-ended
                                                    valve or line . .
                                                    .''
40 CFR 63.670(d)(2)...........  Equation term      Amend the reference
                                 NHVvg              in the equation term
                                 incorrectly        NHVvg in 40 CFR
                                 references         63.670(d)(2) from
                                 paragraph (l)(4)   (l)(4) to (k)(4).
                                 and should
                                 instead
                                 reference (k)(4).
------------------------------------------------------------------------

                             Refinery MACT 2
------------------------------------------------------------------------
Table 4 to Subpart UUU, Item    The ``1'' should   Amend Item 9.c. of
 9.c. ``XRF procedure in         be superscripted   Table 4 to Subpart
 appendix A to this subpart 1;   as it is           UUU to read. ``XRF
 . . .''.                        intended to        procedure in
                                 identify           appendix A to this
                                 footnote 1.        subpart; \1\ . . .''
------------------------------------------------------------------------

IV. Summary of Cost, Environmental, and Economic Impacts

    As described in section III of this preamble, the EPA is not
revising the 2015 Rule requirements for: (1) The work practice
standards for PRDs; (2) the work practice standards for emergency
flaring events; (3) the assessment of risk as modified based on
implementation of these PRD and emergency flaring work practice
standards; or (4) the provision allowing refineries to reduce the
frequency of fenceline monitoring at sampling locations that
consistently record benzene concentrations below 0.9 [micro]g/m\3\. In
this action, the EPA is finalizing two clarifying amendments which were
included in the proposed notice of reconsideration. These amendments
are not expected to have any cost, environmental, or economic impacts.
Therefore, the burden estimates and economic impact analysis associated
with the December 2015 rule (available in Docket ID No. EPA-HQ-OAR-
2010-0682) have not been altered as a result of this action. We note
that in the November 2018 rule, the EPA revised the requirements for
the alternative water overflow provisions for DCUs. A discussion of the
cost, environmental, and economic impacts of the amendments for the
water overflow provisions for DCUs were included in the April 2018