[Federal Register Volume 87, Number 156 (Monday, August 15, 2022)]
[Proposed Rules]
[Pages 50030-50041]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-17190]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 52 and 81
[EPA-R9-OAR-2022-0501; FRL-10106-01-R9]
Determination of Attainment by the Attainment Date but for
International Emissions for the 2015 Ozone National Ambient Air Quality
Standard; Imperial County, California
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
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SUMMARY: The Environmental Protection Agency (EPA or ``Agency'') is
proposing to determine that the Imperial County nonattainment area
would have attained the 2015 ozone national ambient air quality
standard (NAAQS) by the August 3, 2021 ``Marginal'' area attainment
date, but for emissions emanating from outside the United States. If we
finalize this proposed action, the Imperial County nonattainment area
would no longer be subject to the Clean Air Act (CAA) requirements
pertaining to reclassification upon failure to attain and therefore
would remain classified as a Marginal nonattainment area for the 2015
ozone NAAQS. This action, when finalized, will fulfill the EPA's
statutory obligation to determine whether the Imperial County ozone
nonattainment area attained the NAAQS by the attainment date.
DATES: Comments must be received on or before September 14, 2022.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2022- 0501 at https://www.regulations.gov. For comments submitted
at Regulations.gov, follow the online instructions for submitting
comments. Once submitted, comments cannot be edited or removed from
Regulations.gov. The EPA may publish any comment received to its public
docket. Do not submit electronically any information you consider to be
Confidential Business Information (CBI) or other information whose
disclosure is restricted by statute. Multimedia submissions (audio,
video, etc.) must be accompanied by a written comment. The written
comment is considered the official comment and should include
discussion of all points you wish to make. The EPA will generally not
consider comments or comment contents located outside of the primary
submission (i.e., on the web, cloud, or other file sharing system). For
additional submission methods, please contact the person identified in
the FOR FURTHER INFORMATION CONTACT section. For the full EPA public
comment policy, information about CBI or multimedia submissions, and
general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. If you need assistance in a
language other than English or if you are a person with disabilities
who needs a reasonable accommodation at no cost to you, please contact
the person identified in the FOR FURTHER INFORMATION CONTACT section.
FOR FURTHER INFORMATION CONTACT: Ginger Vagenas, EPA Region IX, 75
Hawthorne Street, San Francisco, CA 94105; telephone number: (415) 972-
3964; email address: [email protected].
SUPPLEMENTARY INFORMATION: Throughout this document ``we,'' ``us,'' or
``our'' refer to the EPA.
Table of Contents
I. Background
A. 2015 Ozone National Ambient Air Quality Standard and Area
Designations
B. Clean Air Act Requirements for Marginal Ozone Nonattainment
Areas
C. Requirement for Determination of Attainment of the 2015 Ozone
National Ambient Air Quality Standard
D. International Transport and Requirements for Clean Air Act
Section 179B
II. Imperial County Ozone Determination of Attainment but for
International Emissions
A. Imperial County Ozone Nonattainment Area
B. Ozone Monitoring Sites in Imperial County
C. Summary of the State's Submission
D. EPA Review of the State's Submission
III. Environmental Justice Considerations
IV. Proposed Action
V. Statutory and Executive Order Reviews
I. Background
A. 2015 Ozone National Ambient Air Quality Standard and Area
Designations
Ground-level ozone pollution is formed from the reaction of
volatile organic compounds (VOC) and oxides of nitrogen
(NOX) in the presence of sunlight. These two pollutants,
referred to as ozone precursors, are emitted by many types of sources,
including on- and non-road motor vehicles and engines, power plants and
industrial facilities, and smaller area sources such as lawn and garden
equipment and paints. Scientific evidence indicates that adverse public
health effects occur following exposure to ground-level ozone
pollution. Exposure to ozone can harm the respiratory system (the upper
airways and lungs), can aggravate asthma and other lung diseases, and
is linked to premature death from respiratory causes. People most at
risk from breathing air containing ozone include people with asthma,
children, older adults, and people who are active outdoors, especially
outdoor workers.\1\
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\1\ EPA Fact Sheet--Ozone and Health, available at https://www.epa.gov/sites/default/files/2016-04/documents/20151001healthfs.pdf and in the docket for this action.
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Under CAA section 109, the EPA promulgates NAAQS (or ``standards'')
for pervasive air pollutants, such as ozone. The EPA has previously
promulgated NAAQS for ozone in 1979, 1997, and 2008.\2\ On October 26,
2015, the EPA revised the NAAQS for ozone to establish a new 8-hour
standard.\3\ In that action, the EPA promulgated identical revised
primary and secondary ozone standards designed to protect public health
and welfare that specified an 8-hour ozone level of 0.070 parts per
million (ppm).\4\ Specifically, the standard requires that the 3-year
average of the annual fourth highest daily maximum 8-hour average ozone
concentration (i.e., the design value) may not exceed 0.070 ppm.\5\
When the design value does not exceed 0.070 ppm at each ambient air
quality monitoring
[[Page 50031]]
site within the area, the area is deemed to be attaining the ozone
NAAQS.\6\
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\2\ 44 FR 8202 (February 8, 1979), 62 FR 38856 (July 18, 1997),
and 73 FR 16436 (March 27, 2008).
\3\ 80 FR 65452.
\4\ Because the 2015 primary and secondary NAAQS for ozone are
identical, for convenience, the EPA refers to them in the singular
as ``the 2015 ozone NAAQS'' or as ``the standard.''
\5\ A design value is a statistic used to compare data collected
at an ambient air quality monitoring site to the applicable NAAQS to
determine compliance with the standard. The design value for the
2015 ozone NAAQS is the 3-year average of the annual fourth highest
daily maximum 8-hour average ozone concentration. The design value
is calculated for each air quality monitor in an area and the area's
design value is the highest design value among the individual
monitoring sites in the area.
\6\ The data handling convention in 40 CFR 50, appendix U
dictates that concentrations shall be reported in ``ppm'' to the
third decimal place, with additional digits to the right being
truncated. Thus, a computed 3-year average ozone concentration of
0.071 ppm is greater than 0.070 ppm and would exceed the standard,
but a design value of 0.0709 is truncated to 0.070 and attains the
2015 ozone NAAQS.
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Section 107(d) of the CAA provides that when the EPA promulgates a
new or revised NAAQS, the Agency must designate areas of the country as
nonattainment, attainment, or unclassifiable based on whether an area
is not meeting (or is contributing to air quality in a nearby area that
is not meeting) the NAAQS, meeting the NAAQS, or cannot be classified
as meeting or not meeting the NAAQS, respectively. Subpart 2 of part D
of title I of the CAA governs the classification, state planning, and
emissions control requirements for any areas designated as
nonattainment for a revised primary ozone NAAQS. In particular, CAA
section 181(a)(1) also requires the EPA to classify each ozone
nonattainment area at the time of designation, based on the extent of
the ozone problem in the area (based on the area's design value).
Classifications for ozone nonattainment areas range from ``Marginal''
to ``Extreme.'' CAA section 182 provides the specific attainment
planning and additional requirements that apply to each ozone
nonattainment area based on its classification. CAA section 182, as
interpreted in the EPA's implementing regulations at 40 CFR 51.1308
through 51.1317, also establishes the timeframes by which air agencies
must submit and implement SIP revisions to satisfy the applicable
attainment planning elements, and the timeframes by which nonattainment
areas must attain the 2015 ozone NAAQS.
Effective on August 3, 2018, the EPA designated 52 areas throughout
the country, including Imperial County, California, nonattainment for
the 2015 ozone NAAQS.\7\ In a separate action, the EPA assigned
classification thresholds and attainment dates based on the severity of
each nonattainment area's ozone problem, determined by the area's
design values and classified the Imperial County nonattainment area as
Marginal.\8\ The EPA established the attainment date for Marginal ozone
nonattainment areas as three years from the effective date of the final
designations. Thus, the attainment date for Marginal nonattainment
areas for the 2015 ozone NAAQS was August 3, 2021.
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\7\ 83 FR 25776 (June 4, 2018). The EPA later designated the San
Antonio area as a 2015 ozone NAAQS nonattainment area effective
September 24, 2018. 83 FR 35136 (July 25, 2018).
\8\ 83 FR 10376 (March 9, 2018), effective May 8, 2018.
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B. Clean Air Act Requirements for Marginal Ozone Nonattainment Areas
The list of applicable requirements for ozone nonattainment areas
classified as Marginal includes a submission that meets the baseline
emissions inventory, source emission statements, and nonattainment new
source review program requirements. The California Air Resources Board
(CARB) has provided submittals to the EPA for the Imperial County
nonattainment area addressing these requirements for the 2015 ozone
NAAQS, and the EPA has proposed to approve them.\9\
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\9\ Our proposed approvals of the District's baseline emissions
inventory, emissions statement rule, and nonattainment new source
review certification for the 2015 ozone NAAQS are at 86 FR 54887
(October 5, 2021), 86 FR 70996 (December 14, 2021), and 87 FR 22163
(April 14, 2022), respectively. We finalized our approval of the
emissions statement rule on July 29, 2022 (87 FR 45657).
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Transportation and general conformity apply within the Imperial
County 2015 ozone NAAQS nonattainment area under section 176(c) of the
CAA and the federal regulations for transportation conformity (40 CFR
93 subpart A) and general federal actions (40 CFR 93 subpart B). This
action, if finalized, would not affect the applicability of these
regulations within Imperial County.
As described in the 2015 Ozone NAAQS Implementation Rule, section
182(a) of the CAA does not require states to implement reasonably
available control measures (RACM) or reasonably available control
technology (RACT) in Marginal ozone nonattainment areas, and nothing in
section 179B alters the statutory requirements with respect to RACM/
RACT obligations in subpart 2.\10\
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\10\ 83 FR 62998, 63010 (December 6, 2018).
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C. Requirement for Determination of Attainment of the 2015 Ozone
National Ambient Air Quality Standard
Section 181(b)(2)(A) of the CAA requires that within 6 months
following the applicable attainment date, the EPA shall determine
whether an ozone nonattainment area attained the ozone standard based
on the area's design value as of that date. If the EPA determines that
an area failed to attain, CAA section 181(b)(2)(A) requires the area to
be reclassified by operation of law to the higher of: (1) the next
higher classification for the area, or (2) the classification
applicable to the area's design value as of the determination of
failure to attain.\11\ Section 181(b)(2)(B) of the CAA requires the EPA
to publish the determination of failure to attain and accompanying
reclassification in the Federal Register no later than 6 months after
the attainment date, which in the case of the Imperial County
nonattainment area, was February 3, 2022.
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\11\ If the EPA were to determine that the Imperial County
nonattainment area failed to attain by the attainment date, it would
be classified to the next highest classification of Moderate. The
reclassified area would then be subject to the Moderate area
requirement to attain the 2015 ozone NAAQS as expeditiously as
practicable, but not later than August 3, 2024.
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The EPA's proposed determination that Imperial County would have
attained the 2015 ozone standard but for international emissions is
based in part upon data that have been collected and quality-assured by
CARB and the Imperial County Air Pollution Control District (APCD) in
accordance with 40 CFR part 58 and recorded in the EPA's Air Quality
System (AQS) database.\12\ Ambient air quality monitoring data for the
3-year period preceding the attainment date (2018-2020 for the 2015
ozone NAAQS Marginal areas) must meet the data completeness
requirements in Appendix U.\13\ The completeness requirements are met
for the 3-year period at a monitoring site if daily maximum 8-hour
average concentrations of ozone are available for at least 90 percent
of the days within the ozone monitoring season, on average, for the 3-
year period, and no single year has less than 75 percent data
completeness.
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\12\ The EPA maintains the AQS, a database that contains ambient
air pollution data collected by the EPA, state, local, and tribal
air pollution control agencies. The AQS also contains meteorological
data, descriptive information about each monitoring station
(including its geographic location and its operator) and data
quality assurance/quality control information. The AQS data are used
to (1) assess air quality, (2) assist in attainment/non-attainment
designations, (3) evaluate SIPs for non-attainment areas, (4)
perform modeling for permit review analysis, and (5) prepare reports
for Congress as mandated by the CAA. Access is through the website
at https://www.epa.gov/aqs.
\13\ 40 CFR part 50, appendix U, Sec. 4(b).
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For areas such as Imperial County classified as Marginal
nonattainment for the 2015 ozone NAAQS, the attainment date was August
3, 2021.\14\ Because the design value is based on the three most
recent, complete calendar years of data, attainment must occur no later
than December 31st of the year prior to the attainment date (i.e.,
December 31, 2020, in the case of Marginal nonattainment areas for the
2015 ozone NAAQS). Consequently, the EPA's proposed action for the
Imperial County
[[Page 50032]]
nonattainment area is based upon the complete, quality-assured, and
certified ozone monitoring data from calendar years 2018, 2019, and
2020. The design value for this period is 0.078 ppm, indicating that
the Imperial County nonattainment area did not attain the 2015 ozone
NAAQS by its August 3, 2021 attainment date.\15\
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\14\ The San Antonio, Texas area has an attainment date of
September 24, 2021.
\15\ ``EPA Evaluation of the Clean Air Act Section 179B(b)
Demonstration for the Imperial County Marginal Ozone Nonattainment
Area,'' available in the docket for this rulemaking.
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D. International Transport and Requirements for Clean Air Act Section
179B
CAA section 179B(b) provides that where a state demonstrates to the
Administrator's satisfaction that an ozone nonattainment area would
have attained the NAAQS by the applicable attainment date but for
emissions emanating from outside the United States (U.S.), that area
shall not be subject to the mandatory reclassification provision of CAA
section 181(b)(2).\16\ In the event an air agency does not demonstrate
to the EPA's satisfaction that it would have attained the NAAQS but for
international emissions, it will be reclassified to the next higher
classification.
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\16\ Note that the statute cites 42 U.S.C. 7511(a)(2), but that
provision establishes ozone attainment deadlines for severe areas
under the 1-hour standard. The EPA has long interpreted the citation
in CAA section 179B(b) to be a scrivener's error that was supposed
to refer to 42 U.S.C. 7511(b)(2), which refers to consequences for
failure to attain by the attainment date.
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Anthropogenic emissions sources outside of the U.S. can affect to
varying degrees the ability of some air agencies to attain and maintain
the 2015 ozone NAAQS in areas within their jurisdiction. In a
nonattainment area affected by international emissions, an air agency
may elect under CAA section 179B to develop and submit to the EPA a
demonstration intended to show that a nonattainment area would attain,
or would have attained, the relevant NAAQS by the applicable statutory
attainment date ``but for'' emissions emanating from outside the
U.S.\17\ Under CAA section 179B, the EPA evaluates such demonstrations,
and if it agrees with the air agency's demonstration, the EPA considers
the impacts of international emissions in taking specific regulatory
actions.
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\17\ All references to CAA section 179B are to 42 U.S.C. 7509a.
International border areas, as added Public Law 101-549, title VIII,
Sec. 818, 104 Stat. 2697 (November 15, 1990).
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CAA section 179B provides the EPA with authority to consider
impacts from international emissions in two contexts: (1) a
``prospective'' state demonstration submitted as part of an attainment
plan, which the EPA considers when determining whether the SIP
adequately demonstrates that a nonattainment area will attain the NAAQS
by its future attainment date (CAA section 179B(a)); or (2) a
``retrospective'' state demonstration, which the EPA considers after
the attainment date in determining whether a nonattainment area
attained the NAAQS by the attainment date (CAA section 179B(b)-(d)).
First, CAA section 179B(a) provides that, ``[N]otwithstanding any
other provision of law, an implementation plan or plan revision
required under this chapter shall be approved by the Administrator if
(1) such plan or revision meets all the requirements applicable to it .
. . other than a requirement that such plan or revision demonstrate
attainment and maintenance of the relevant national ambient air quality
standards by the attainment date specified under the applicable
provision of this chapter, or in a regulation promulgated under such
provision, and (2) the submitting state establishes to the satisfaction
of the Administrator that the implementation plan of such state would
be adequate to attain and maintain the relevant national ambient air
quality standards by the attainment date . . . but for emissions
emanating from outside of the United States,'' (emphasis added). The
EPA refers to CAA section 179B(a) demonstrations as ``prospective''
demonstrations because they are intended to assess future air quality,
taking into consideration the impact of international emissions. Thus,
if the EPA approves a prospective demonstration, the state is relieved
from the requirement to demonstrate that the nonattainment area will
attain the NAAQS by the applicable attainment date.\18\
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\18\ Section 182(a) of the CAA, which describes nonattainment
area requirements for ozone Marginal areas, states that the
requirements of section 182(a) ``shall apply in lieu of any
requirement that the State submit a demonstration that the
applicable implementation plan provides for attainment of the ozone
standard by the applicable attainment date in any Marginal Area.''
In other words, there is no prospective relief that can be granted
by the EPA under section 179B(a) for ozone nonattainment areas
classified as Marginal.
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Second, CAA section 179B(b) provides that, for ozone nonattainment
areas, ``[n]otwithstanding any other provision of law, any State that
establishes to the satisfaction of the Administrator that . . . such
State would have attained the national ambient air quality standard . .
. by the applicable attainment date but for emissions emanating from
outside of the United States,'' (emphasis added) shall not be subject
to reclassification to a higher classification category by operation of
law, as otherwise required in CAA section 181(b)(2).\19\ The EPA refers
to demonstrations developed under CAA section 179B(b) as
``retrospective'' demonstrations because they involve analyses of past
air quality (e.g., air quality data from the yearsevaluated for
determining whether an area attained by the attainment date). Thus, an
EPA-approved retrospective demonstration provides relief from
reclassification that would have resulted from the EPA determining that
the area failed to attain the NAAQS by the relevant attainment date.
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\19\ The EPA's longstanding view is that CAA section 179B(b)
contains an erroneous reference to section 181(a)(2), and that
Congress actually intended to refer here to section 181(b)(2), which
addresses reclassification requirements for ozone nonattainment
areas. See ``State Implementation Plans; General Preamble for the
Implementation of Title I of the Clean Air Act Amendments of 1990,''
57 FR 13498, 13569, footnote 41 (April 16, 1992).
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Irrespective of whether developing and submitting a prospective or
retrospective demonstration, states still must meet all nonattainment
area requirements applicable for the relevant NAAQS and area
classification. The 2015 Ozone NAAQS Implementation Rule did not
include regulatory requirements specific to CAA section 179B but did
provide guidance on certain points. In the preamble to the rule, the
EPA confirmed that: (1) only areas classified Moderate and higher must
show that they have implemented reasonably available control measures
and reasonably available control technology (RACM/RACT); (2) CAA
section 179B demonstrations are not geographically limited to
nonattainment areas adjoining an international border; and, (3) a state
demonstration prepared under CAA section 179B can consider emissions
emanating from sources in North America (i.e., Canada or Mexico) or
sources on other continents.\20\ In the preamble to that rule, the EPA
encouraged air agencies to consult with the appropriate EPA regional
office to determine technical requirements for the CAA section 179B
demonstrations. In addition, the EPA noted its development of
supplementary technical information and guidance to assist air agencies
in preparing demonstrations that meet the requirements of CAA section
179B.
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\20\ 83 FR 62998, 63009.
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The EPA issued more detailed guidance regarding CAA section 179B on
December 18, 2020, that includes recommendations to assist state,
local, and tribal air agencies that intend to
[[Page 50033]]
develop a CAA section 179B demonstration (``179B Guidance'').\21\ The
179B Guidance describes and provides examples of the kinds of
information and analyses that the EPA recommends air agencies consider
for inclusion in a CAA section 179B demonstration.
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\21\ ``Guidance on the Preparation of Clean Air Act Section 179B
Demonstrations for Nonattainment Areas Affected by International
Transport of Emissions'' issued on December 18, 2020; available at
https://www.epa.gov/sites/default/files/2020-12/documents/final_caa_179b_guidance_december_2020_with_disclaimer_ogc.pdf. The
EPA also issued a notice of availability in the Federal Register on
January 7, 2021 (86 FR 1107).
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In the 179B Guidance, the EPA confirmed that while approval of a
CAA section 179B demonstration provides specific forms of regulatory
relief for air agencies, the EPA's approval does not relieve air
agencies from obligations to meet the remaining applicable planning or
emission reduction requirements in the CAA. It also does not provide a
basis either for excluding air monitoring data influenced by
international transport from regulatory determinations related to
attainment and nonattainment, or for redesignating an area to
attainment. If an air agency is contemplating a CAA section 179B
demonstration in either the CAA section 179B(a) ``prospective'' context
or the CAA section 179B(b) ``retrospective'' context, the EPA
encourages communication throughout the demonstration development and
submission process, along the lines of these basic steps: (1) the air
agency contacts its EPA Regional office to discuss CAA section 179B
regulatory interests and conceptual model; (2) the air agency begins
gathering information and developing analyses for a demonstration; (3)
the air agency submits a draft CAA section 179B demonstration to its
EPA Regional office for review and discussion; and (4) the air agency
submits its final CAA section 179B demonstration to the EPA. After that
process is complete, the EPA makes a determination as to the
sufficiency of the demonstration after a public notice and comment
process. The EPA may act on a prospective demonstration when taking
action on an area's attainment plan. For a retrospective demonstration,
the EPA may determine its adequacy when taking action to determine
whether the area attained by the attainment date and is subject to
reclassification.
The EPA's consideration of the CAA section 179B demonstrations
submitted by states in connection with reclassification of ozone
nonattainment areas is governed by CAA section 179B(b).\22\ Pursuant to
that provision, the state must establish ``to the satisfaction of the
Administrator that, with respect to [the relevant] ozone nonattainment
area in such State, such State would have attained the [2015 ozone
NAAQS] by the applicable attainment date, but for emissions emanating
from outside of the United States . . .'' Because the wording in CAA
section 179B(b) is in the past tense, it is reasonable for the EPA to
conclude that such demonstrations should be retrospective in nature. In
other words, the demonstration should include analyses showing that the
air quality data on specific days in the time period used to assess
attainment were affected by international emissions to an extent that
prevented the area from attaining the standard by the attainment
date.\23\ By definition, states can only make such a demonstration
after air quality data collected pursuant to federal reference or
equivalent monitoring methods are certified and indicate that the area
failed to attain by the attainment date. Where the EPA approves a
state's CAA section 179B(b) retrospective demonstration, the area
retains its nonattainment designation and is still subject to all
applicable requirements for the area's current classification, but is
not subject to the applicable requirements for any higher
classification.24 25
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\22\ The regulatory relief a state would receive from a
satisfactory prospective CAA section 179B(a) demonstration is
limited to approval of an attainment plan that does not demonstrate
attainment and maintenance of the relevant NAAQS, but meets all
other applicable requirements. CAA section 179B(a) is not germane to
this proposal.
\23\ 179B Guidance, 15-16.
\24\ Id. at 3.
\25\ As we noted in our 179B Guidance, an air agency with a
Marginal ozone nonattainment area that is affected by international
emissions may wish to evaluate whether implementing emission
reduction measures on domestic sources in the nonattainment area can
bring the area into attainment because, until the area attains the
NAAQS and the EPA approves an air agency submission addressing the
redesignation criteria of CAA section 107(d)(3)(E), the area will
continue to be subject to nonattainment area requirements, including
nonattainment new source review. Id. at 17.
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The CAA does not specify what technical analyses would be
sufficient to demonstrate ``to the satisfaction of the Administrator''
that a ``State would have attained the [NAAQS for the pollutant in
question] by the applicable attainment date, but for'' international
emissions. The EPA recognizes that the relationship between certain
NAAQS exceedances and associated international transport is clearer in
some cases than in others. The following characteristics would suggest
the need for a more detailed demonstration with additional evidence:
(1) affected monitors are not located near an international border; (2)
specific international sources and/or their contributing emissions are
not identified or are difficult to identify; (3) exceedances on
internationally influenced days are in the range of typical exceedances
attributable to local sources; and (4) exceedances occurred in
association with other processes and sources of pollutants, or on days
where meteorological conditions were conducive to local pollutant
formation (e.g., for ozone, clear skies and elevated temperatures).
Therefore, CAA section 179B demonstrations for non-border areas may
involve additional technical rigor, analyses and resources compared to
demonstrations for border areas.
Given the extensive number of technical factors and meteorological
conditions that can affect international transport of air pollution,
and the lack of specific guidance in the Act, the EPA evaluates CAA
section 179B demonstrations based on the weight of evidence of all
information and analyses provided by the air agency. The appropriate
level of supporting documentation will vary on a case-by-case basis
depending on the nature and severity of international influence, as
well as the factors identified above. The EPA considers and
qualitatively weighs all evidence based on its relevance to CAA section
179B and the nature of international contributions as described in the
demonstration's conceptual model. Every demonstration should include
fact-specific analyses tailored to the nonattainment area in question.
When a CAA section 179B demonstration shows that international
contributions are larger than domestic contributions, the weight of
evidence will be more compelling than if the demonstration shows
domestic contributions exceeding international contributions. In
contrast, when a CAA section 179B demonstration shows that
international emissions have a lower contribution to ozone
concentrations than domestic emissions, and/or international transport
is not significantly different on local exceedance days compared to
non-exceedance days, then the weight of evidence will not be supportive
of a conclusion that a nonattainment area would attain or would have
attained the relevant NAAQS by the statutory attainment date ``but
for'' emissions emanating from outside the U.S.
In evaluating a CAA section 179B demonstration the EPA also
considers what measures an air agency has implemented to control local
emissions.
[[Page 50034]]
At a minimum, states are still subject to all requirements applicable
to the area based on its nonattainment classification. For the EPA to
concur with a state's CAA section 179B retrospective demonstration, the
weight of evidence should show the area could not attain with on-the-
books measures and and potential reductions associated with controls
required for that particular NAAQS that are to be implemented by the
attainment date. Because CAA section 179B does not relieve an air
agency of its planning or control obligations, the air agency should
show that it has implemented all required emissions controls at the
local level as part of its demonstration.
II. Imperial County Ozone Determination of Attainment but for
International Emissions
A. Imperial County Ozone Nonattainment Area
The Imperial County nonattainment area for the 2015 ozone standard
includes the whole County, including lands of the Quechan Tribe of the
Fort Yuma Indian Reservation and the Torres Martinez Desert Cahuilla
Indians within the geographic boundary of Imperial County.\26\ The
County encompasses over 4,000 square miles in southeastern California.
Its population is estimated to be approximately 180,000 people,\27\ and
its principal industries are farming and retail trade. It is bordered
by Riverside County to the north, Arizona to the east, Mexico to the
south, and San Diego County to the west. The Imperial Valley runs
north-south through the central part of the County and includes the
County's three most populated cities: Brawley, El Centro, and Calexico.
Most of the County's population and industries exist within this
relatively narrow land area that extends about one-fourth the width of
the County. The rest of Imperial County is primarily desert, with
little or no human population.\28\
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\26\ 40 CFR 81.305.
\27\ U.S. Census Bureau, Population Estimates, July 1 2021,
(V2021), https://www.census.gov/quickfacts/imperialcountycalifornia,
accessed April 6, 2021.
\28\ Maps showing stationary NOX and VOC emission
sources, vehicle traffic, and population density in Imperial County
are included as Figures A-1-A-3 in the EPA's technical support
document, which is included in the docket for this rulemaking.
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B. Ozone Monitoring Sites in Imperial County
There are currently four ozone monitoring sites in Imperial County.
Listed from south to north, the Imperial ozone monitoring sites are:
Calexico-Ethel Street, El Centro-9th Street, Westmorland, and
Niland.\29\ The maximum 2020 design value for the County, based on
certified monitoring data at the monitor located closest to the Mexico
border (the Calexico-Ethel Street monitor), was 0.078 ppm. Calexico-
Ethel Street is the only ozone monitor in Imperial County violating the
2015 ozone NAAQS of 0.070 ppm. The 2020 design value for the El Centro-
9th Street monitor was 0.068 ppm, i.e., attaining the 2015 ozone NAAQS.
The design values for monitors farther from the border, Westmorland
(0.058 ppm) and Niland (0.049 ppm), are invalid due to less than 90
percent data completeness for the three-year period and less than 75
percent completeness in calendar year 2020.\30\
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\29\ A map showing the ozone monitoring sites in Imperial County
is included as Figure 4 in the EPA's technical support document,
which is included in the docket for this rulemaking.
\30\ We note that the 2020 design values at Westmorland of 58
ppb and at Niland of 49 ppb are invalid because the average data
completeness of 84 percent and 86 percent for the 2018-2020 period
and 72 percent and 67 percent in 2020, respectively. These
percentages are below the minimum completeness thresholds of 90
percent for the three-year period and 75 percent for an individual
year, respectively. Air Quality System (AQS) Design Value Report
(AMP480), pulled December 3, 2021, and 40 CFR part 50, App. U,
section 4(b).
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Tables 1 and 2 of this document list the 2016-2020 annual fourth
highest daily maximum 8-hour average (``4th max'') and design values at
the Imperial County ozone monitors. The Calexico-Ethel Street monitor,
which is one mile from the border, consistently measures the highest
4th max concentration in each year; concentrations decrease as each
monitor's distance from the border increases. The 2019 design value,
which is valid for all four sites, shows a similar relationship between
concentration and distance from the border: 0.079 ppm at Calexico-Ethel
Street, 0.072 ppm at El Centro-9th Street (9 miles from border), 0.061
ppm at Westmorland (26 miles from border), and 0.054 ppm at Niland (38
miles from border).
The Niland monitor design value has been consistently below 0.070
ppm since 2016. In addition, the valid design values and complete
yearly 4th maxes at Niland have been consistently lower than the El
Centro-9th Street and Calexico-Ethel Street monitors in the past five
years. The Westmorland monitor started operation in July 2015; the only
valid Westmorland monitor design value, in 2019, was 0.061 ppm, below
the 2015 ozone NAAQS of 0.070 ppm. In addition, the complete yearly 4th
maxes at Westmorland have been consistently lower than the El Centro-
9th Street and Calexico-Ethel Street monitors in the past five years.
Table 1--2015 Ozone NAAQS: 2016-2020 Yearly 4th Max Imperial County Ozone Monitors
--------------------------------------------------------------------------------------------------------------------------------------------------------
Distance from 4th max (ppm)
Site name AQS site ID border -------------------------------------------------------------------------------
(miles) 2016 2017 2018 2019 2020
--------------------------------------------------------------------------------------------------------------------------------------------------------
Calexico-Ethel Street................... 06-025-0005 1 0.074 0.082 0.076 0.080 0.080
El Centro-9th Street.................... 06-025-1003 9 \a\ 0.074 0.079 0.075 0.062 0.069
Westmorland............................. 06-025-4003 26 0.063 0.063 0.061 0.059 \a\ 0.054
Niland.................................. 06-025-4004 38 0.062 0.057 0.051 0.054 \a\ 0.043
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: Air Quality System (AQS) Design Value Report (AMP480), pulled December 3, 2021.
\a\ Incomplete; did not meet completeness threshold of 75% for an individual year.
Table 2--2015 Ozone NAAQS Design Values Imperial County Ozone Monitors
--------------------------------------------------------------------------------------------------------------------------------------------------------
Design value (ppm)
Site name AQS site ID -------------------------------------------------------------------------------
2016 2017 2018 2019 2020
--------------------------------------------------------------------------------------------------------------------------------------------------------
Calexico-Ethel Street................................... 06-025-0005 0.076 0.077 0.077 0.079 0.078
El Centro-9th Street.................................... 06-025-1003 0.076 0.076 0.076 0.072 0.068
Westmorland............................................. 06-025-4003 \a\ 0.060 \a\ 0.061 \a\ 0.062 0.061 \a\ 0.058
[[Page 50035]]
Niland.................................................. 06-025-4004 0.067 0.063 0.056 0.054 \a\ 0.049
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source:AQS Design Value Report (AMP480), pulled December 3, 2021.
\a\ Invalid because data are incomplete (did not meet minimum completeness thresholds of 90% for the three-year period).
C. Summary of the State's Submission
On August 16, 2021, CARB submitted to the EPA for review its
``Imperial County Clean Air Act Section 179B(b) Analysis for the 70 ppb
8-Hour Ozone Standard'' (``Demonstration''). CARB submitted additional
information on November 24, 2021. Using several lines of evidence, CARB
evaluated whether, and the extent to which, ambient ozone levels in
Imperial County would be affected by emissions emanating from northern
Mexico. This evaluation includes a conceptual model of ozone formation
in Imperial County including a discussion of the meteorological and
topographic conditions that influence ozone formation; an analysis of
the ozone design value trends in the County from 2000 to 2020; an
emissions inventory analysis comparing ozone precursor emissions in
Imperial County, California to those in the Mexicali Municipality in
Mexico; an ambient observational analysis of back-trajectories
examining whether there is an internationally influenced source-
receptor relationship on ozone exceedance days in Imperial County; and
a photochemical air quality modeling exercise estimating the
contribution of cross-border, northern Mexico emissions to ozone design
values in Imperial County.
1. Conceptual Model
CARB provided a conceptual model describing ozone formation in the
Imperial County ozone nonattainment area, which is located on the
border of the United States and Mexico and encompasses all of Imperial
County. Imperial County includes the northern portion of the Imperial
Valley, which extends from the southern end of the Salton Sea southward
into Mexico, where it becomes known as the Mexicali Valley. The valleys
are bordered by mountains to the west and east, and on the south side
by mountains south of the border to the southwest of Mexicali. These
ranges channel airflow within the Imperial and Mexicali Valleys,
without topographic features between, creating a shared binational air
shed for the region. Imperial County experiences hot, dry weather and
stagnation in the summer, which are conducive to ozone formation.
Highest ozone concentrations are experienced between May through
September and generally peak in the late afternoon. Ozone and ozone
precursors are often transported to Imperial County by prevailing winds
from Mexicali to the south, and to a lesser extent from other
surrounding air basins.\31\
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\31\ Demonstration, 2-5.
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CARB provided trends in the ozone design values for the Calexico-
Ethel Street, El Centro-9th Street, and Niland monitors, number of days
with maximum daily 8-hour ozone values greater than 70 ppb within the
nonattainment area, and Imperial County ozone precursor emissions from
2000-2020.\32\ The County's maximum ozone design value across all
monitors has decreased over the past two decades, along with a 60
percent reduction in oxides of nitrogen (NOX) and a 45%
reduction in anthropogenic VOC emissions within Imperial County over
that period.\33\ The Calexico monitor's design value trend, however,
has been relatively flat when compared to the downward trend at the
Niland and, more recently, at the El Centro monitors, which are farther
from the border. From 2003 through 2015, El Centro had the highest
design value of the three monitors for all design value periods except
for two: Calexico and El Centro had the same design value in 2016, and
from 2017-2020 Calexico had the highest design value.
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\32\ Id. at 4-6. CARB often states ozone concentrations in units
of parts per billion (ppb). The form of the NAAQS in 40 CFR 50.15 is
in ppm (parts per million). To convert from ppm to ppb, multiply ppm
by 1000. Thus, e.g., 0.070 ppm becomes 70 ppb. While those values
are numerically equal, for comparison of concentrations to the NAAQS
care must be used in applying the data handling requirements of 40
CFR 50, appendix P, e.g., truncation after the third digit of a ppm
value is equivalent to dropping digits after the decimal point in a
ppb value.
\33\ CARB refers to reactive organic gases (ROG) in some of its
ozone-related submittals. The CAA and the EPA's regulations refer to
VOC, rather than ROG, but both terms cover essentially the same set
of gases. In this document, we use the term VOC to refer to this set
of gases.
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2. Emissions Analysis for Imperial County and the Mexicali Municipality
CARB provided a table of 2018 ozone precursor emissions, shown in
Table 3 of this document.\34\ The emissions of both NOX and
VOC in the Mexicali Municipality are approximately four times larger
than Imperial County emissions. These emissions do not include
emissions originating in other parts of Mexico or elsewhere that could
also affect ozone levels in Imperial County. CARB notes that while
domestic emissions have decreased, the Mexicali emissions have
increased. CARB also notes that the population of Mexicali Municipality
grew from around 600,000 in the early 1990s to over 1.1 million in 2019
and that it has become an economic center for the region with a
corresponding increase in emissions for the area.
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\34\ CARB's Demonstration, Appendix A, 17-19 describes the
emissions used in the photochemical modeling exercise and summarized
in Table 3 of this document. Updated Mexico emissions were developed
as part of a project prepared for CARB by the Eastern Research
Group, Inc. (ERG). ERG, Final Report, ``2014 Northern Baja
California Emissions Inventory Project,'' September 30, 2019.
Table 3--CARB's 2018 Imperial County and Mexicali Municipality Emissions Inventory
[tons per day (tpd), summer planning inventory] \a\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Imperial county City of Mexicali
-------------------------------------------------------------------------------------------------------
Source NOX (tpd) NOX (tpd)
NOX (%) VOC (tpd) VOC (%) NOX (%) VOC (tpd) VOC (%)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Stationary...................................... 1.4 9 1.3 10 3.3 5 12.8 21
Area-wide....................................... 0.2 1 6.6 49 1.0 1 29.6 50
[[Page 50036]]
Off-Road Mobile................................. 8.8 55 3.0 22 8.0 12 0.8 1
On-Road Mobile.................................. 5.6 35 2.5 19 54.4 82 16.4 28
-------------------------------------------------------------------------------------------------------
Total....................................... 16.0 100 13.5 100 66.6 100 59.6 100
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: The EPA calculated percentages using information from Demonstration, Appendix A, Table 3, 19.
\a\ CARB modeled April-October and refers to this period as the ``modeled ozone season'' and the emission inventory used as the ``summer planning
inventory''. For calendar years 2018-2020 all max daily 8-hour ozone values above 70 ppb at Calexico-Ethel Street and El Centro-9th Street occurred
between April-September. These months represent peak ozone for the area.
3. Ambient Observational Analysis--Back Trajectories
CARB's Demonstration includes an analysis of back trajectories
created using the National Oceanic and Atmospheric Administration's
(NOAA) Hybrid Single Particle Lagrangian Integrated Trajectory
(HYSPLIT) model.\35\ The analysis includes trajectories for each
exceedance day in 2018, 2019, and 2020 (when the daily maximum eight-
hour average ozone level was above 70 ppb) at the two Imperial County
monitors with the highest 2020 design values, Calexico-Ethel Street (42
exceedance days) and El Centro-9th Street (17 exceedance days). CARB
identified the hours contributing to the daily maximum 8-hour average
ozone value for each exceedance day and then used HYSPLIT to generate
8-hour back-trajectories for each of the eight hours that contributed
to the maximum 8-hour average ozone value for each exceedance day at
each monitor. CARB generated back-trajectories for three starting
altitudes (100, 500, and 1000 meters (m)) at each monitor using
meteorological data from the North American Mesoscale Forecast System
(NAM) 12 kilometer (km) pressure coordinate system dataset.
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\35\ Demonstration, Appendix B. National Oceanic and Atmospheric
Administration's Hybrid Single Particle Lagrangian Integrated Model
(HYSPLIT), https://www.ready.noaa.gov/HYSPLIT.php.
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CARB's analysis flagged an exceedance day as having likely
influence from emissions emanating from Mexico if the majority of back-
trajectories (at least five out of eight) for that day originated from
or passed over Mexico. CARB then removed those flagged days and
recalculated the 2020 design values for the Calexico-Ethel Street and
El Centro-9th Street monitors. Using this analysis, CARB asserts that
when days with likely influence from emissions emanating from Mexico
are excluded based on the HYSPLIT analysis, the estimated design values
for the monitors would meet the 0.070 ppm (70 ppb) 8-hour ozone
standard.
4. Modeling To Quantify International Contribution--CARB Photochemical
Modeling
Appendix A to CARB's Demonstration describes CARB's photochemical
modeling. CARB simulated conditions between April 2018 and October 2018
using the Community Multiscale Air Quality model (CMAQ) driven by
meteorological fields from the Weather Research and Forecasting (WRF)
prognostic model.\36\ The overall CMAQ air quality modeling domain
covers the entire State of California, and has a horizontal grid size
resolution of 12 kilometer (km) with 107 x 97 lateral grid cells for
each vertical layer. It extends from the Pacific Ocean in the west to
eastern Nevada in the east, and from the northern Mexico in the south
to the California-Oregon border in the north. The smaller nested domain
used to model the Imperial County nonattainment area covers southern
California (including the South Coast, San Diego, and Salton Sea air
basins) and northern Mexico, has a finer scale 4 km grid resolution,
and includes 156 x 102 lateral grid cells.
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\36\ CMAQ model version 5.3.2, released by the EPA in October
2020. Further information on CMAQ is available at: https://www.cmascenter.org/cmaq/. WRF model version 4.2.1. Further
information on WRF is available at https://www.mmm.ucar.edu/weather-research-and-forecasting-model.
---------------------------------------------------------------------------
CARB included a performance analysis for the meteorological model
(WRF) and the ozone model (CMAQ) simulations including statistics
recommended in the EPA's ``Modeling Guidance for Demonstrating Air
Quality Goals for Ozone, PM2.5 and Regional Haze,''
(``Modeling Guidance'').\37\ CARB validated the WRF-simulated surface
wind speed, temperature, and relative humidity from the 4 km domain
against hourly observations at 13 surface stations in Imperial County
and included detailed hourly time-series together with spatial
distributions of the mean bias and mean error.\38\ CARB also included a
phenomenological analysis showing the model captures the general
meteorological patterns affecting the region on exceedance days.\39\
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\37\ EPA 454/R-18-009, November 2018.
\38\ Demonstration, 24-27 and 46-58.
\39\ Id. at 28-32.
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CARB provided an operational evaluation of the ozone model
performance including tables of statistics for elevated ozone periods
(greater than 60 ppb) as recommended in the Modeling Guidance for 1-
hour ozone, daily maximum 1-hour ozone, and daily maximum 8-hour
modeled ozone compared to observations at the Calexico-Ethel Street and
El Centro-9th Street ozone monitoring locations.\40\ CARB also provided
scatter plots, time series and additional performance statistics and
compared these results to those from similar studies in other
areas.\41\
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\40\ Id. at 34-36.
\41\ Id. at 37-39 and 59-64.
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After confirming the model performance for the 2018 base case using
2018 anthropogenic emissions for both the U.S. and Mexico, CARB
performed a ``brute-force'' or ``zero-out'' sensitivity case. The only
difference from the base case is that anthropogenic, near-source
northern Mexico emissions (those within the CMAQ 4 and 12 km modeling
domains \42\) were excluded from the simulation. CARB then used the
modeled zero-out and base case results to apply a pseudo-Relative
Reduction Factor (RRF) to observations and to predict the contribution
of near-source northern Mexico emissions to the average of Imperial
County 2018, 2019, and 2020 ozone design values.\43\ Here, the RRF
represents the fractional change
[[Page 50037]]
in modeled peak ozone between the base and zero-out simulations. The
Modeling Guidance recommends calculating an RRF based on the highest 10
modeled days in the simulated period (at each monitoring site). CARB
used the top 10 days from the base case simulation and then the same
corresponding days from the zero-out simulation. These values are based
on the maximum simulated ozone within a 3x3 array of grid cells
surrounding the grid cell in which the monitor is located. The
predicted design values were then calculated by multiplying the average
of Imperial County 2018, 2019, and 2020 design values by the pseudo-
RRFs. The change in design value represents the contribution of near-
source, northern Mexico emissions to the design value.
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\42\ See Demonstration, Appendix A, Figure 6 and email dated
March 3, 2022, from Chenxia Cai (CARB) to Rynda Kay (EPA), Subject:
``RE: Imperial 179B(b) demo: quick clarification question on model
set-up.''
\43\ The Modeling Guidance recommends using three 3-year design
value periods when doing an attainment test as part of a SIP
demonstration for ozone in order to account for meteorological
variability. CARB applied this approach to its 179B(b) modeling
demonstration and calculated design values for the 3 three-year
periods ending in 2018, 2019, and 2020 and then averaged them.
---------------------------------------------------------------------------
As shown in Table 4 of this document, with the removal of
anthropogenic northern Mexico emissions in the 4 km and 12 km modeling
domains, the average of the 2018-2020 design values for Calexico-Ethel
Street is predicted to be reduced from 78.0 to 69.2 ppb, and for El
Centro-9th Street is reduced from 72.0 to 61.3 ppb. These calculations
indicate that emissions from northern Mexico contribute approximately 9
ppb to the design value at the Calexico-Ethel Street monitor and
approximately 11 ppb to the design value at the El Centro-9th Street
monitor. The contribution from the rest of Mexico and other
international sources outside of the modeling domain were not removed.
Had the contribution from the rest of Mexico and other international
sources also been removed, the modeling would have predicted a larger
contribution to the design values from international emissions.
Table 4--CARB's Average 2018-2020 Design Values Estimates Based on Scaling Exercise From CARB Modeling
----------------------------------------------------------------------------------------------------------------
Estimated DVB
without Approximate
Measured anthropogenic northern
average 2018- northern Mexico Change in
Monitoring site 2020 design Mexico contribution design value
values (DVB, emissions to DVB (ppb) (percent)
ppb) (ppb)
----------------------------------------------------------------------------------------------------------------
Calexico-Ethel.................................. 78.0 69.2 8.8 11.3
El Centro-9th................................... 72.0 61.3 10.7 14.9
----------------------------------------------------------------------------------------------------------------
Source: Demonstration, 9. Note that the Demonstration refers to emissions from ``Mexico'' but only emissions
from northern Mexico (those within the 4 and 12 km modeling domains) were excluded.
Note: ``Measured Average 2018-2020 Design Values'' above takes the 2018, 2019, and 2020 design value for the
individual site and averages the three design values together to arrive at the value listed.
D. EPA Review of the State's Submission
As part of meeting its duty to determine whether the Imperial
County area attained the 2015 ozone NAAQS by the applicable attainment
date, the EPA evaluated air quality monitoring data submitted by CARB
to determine the attainment status of the Imperial County nonattainment
area as of its Marginal area attainment date. The Agency has also
evaluated the State's 179B(b) demonstration that the Imperial County
nonattainment area would have attained the 2015 ozone NAAQS by the
attainment date, but for international emissions. Based on our review,
the EPA is proposing to approve the CAA section 179B(b) demonstration.
The EPA is proposing this action to fulfill its statutory obligation
under CAA section 181(b)(2) to determine whether the Imperial County
nonattainment area attained the 2015 ozone NAAQS as of the attainment
date of August 3, 2021. Our rationale supporting the proposed approval
of the State's 179B(b) demonstration and determination is summarized
below. The full rationale is included in the technical support document
provided in the docket for this rulemaking.
CARB's retrospective 179B(b) demonstration includes multiple lines
of evidence consistent with the key types of analyses recommended in
our 179B Guidance.\44\ These analyses appropriately focus on 2018,
2019, and 2020, which are the key years for demonstrating attainment
for a Marginal area for the 2015 ozone NAAQS. We agree that each line
of evidence supports the conclusion that the 2020 ozone design values
at all monitoring sites in Imperial County would be at or below 0.070
ppm (70 ppb) but for the influence of Mexican emissions. CARB's
analyses focus on the influence from near-source northern Mexico
contribution; the EPA notes that this is a narrow, conservative
approach to analyzing ``international contribution.'' Even with this
approach, we find that these analyses support this conclusion. Based on
the evaluation of these analyses as a whole, the EPA agrees that
Imperial County would have attained the 2015 ozone NAAQS by the August
3, 2021 attainment date but for emissions emanating from Mexico.
---------------------------------------------------------------------------
\44\ 179B Guidance, Section 6.
---------------------------------------------------------------------------
CARB provided a conceptual model describing the meteorology and
topography of the area, an evaluation of ozone precursor emissions, and
an analysis of ozone trends at County monitors. We agree that the
following factors support the proposition that the Mexicali
Municipality emissions likely have a substantial influence on Imperial
County ozone levels, particularly at the Calexico-Ethel monitor, which
remains the only monitor with a violating 2020 design value: the
topography and meteorology of the Imperial and Mexicali areas results
in a single, shared binational airshed; Mexicali Municipality ozone
precursor emissions are much larger (currently approximately four times
greater) than Imperial County emissions; ozone concentration trends
over time show that monitors farther from the border have experienced
decreasing concentrations, while at the Calexico-Ethel monitor
concentrations have remained flat; and spatially, ozone concentrations
decrease with increasing distance from the border.
CARB ran the HYSPLIT model to generate 8-hour back-trajectories for
each of the eight hours contributing to each 2018-2020 daily maximum 8-
hour average ozone exceedance (greater than 70 ppb) at the Calexico-
Ethel and El Centro-9th Street monitors at three altitudes (100 m, 500
m, 1000 m). CARB flagged days that had at least 5 of the 8 hours
originating from or traversing through Mexico as having likely
influence from emissions emanating from Mexico. The 179B Guidance
recommends a slightly more stringent
[[Page 50038]]
test for identifying days influenced by international emissions using a
threshold of 75 percent of trajectories (e.g., 6 of 8 trajectories) as
indicating values that are likely influenced by international emissions
for a given day.\45\ CARB notes that for more than 75 percent of
flagged days, six or more of the eight 8-hour back-trajectories
originated from or went through Mexico, with most back-trajectories
passing over the city of Mexicali.\46\ The EPA performed additional
analysis and found that 61-87 percent of the 8-hour back trajectories
(considering all three starting altitudes of 100 m, 500 m, and 1000 m)
passed over Mexico within the 8-hour period prior to arriving at the
monitoring site, with 55-80 percent passing over the Mexicali
Municipality. The remaining trajectories, particularly at lower
elevations, generally come from the northwest, following valley
topography, over the sparsely populated Anza-Borrego desert region. We
conclude that the high percentage of 8-hour back trajectories passing
over Mexicali supports the conclusion that there is a direct
international source-receptor relationship between the Mexicali area
and Imperial County on 2018-2020 exceedance days.
---------------------------------------------------------------------------
\45\ 179B Guidance, 34.
\46\ Demonstration, 11.
---------------------------------------------------------------------------
CARB also recalculated the 2020 design value excluding the days
flagged following the same methodology. The EPA notes that flagged days
on which international emissions are likely to have an impact might
also be affected by domestic emissions, and a simple back-trajectory
analysis cannot distinguish whether ozone levels on that day would have
exceeded the NAAQS without any international contributions. Therefore,
a simple recalculation of the design value excluding days with
influence from Mexico is not a conclusive ``but for'' analysis.
However, the EPA agrees that CARB's 8-hour back trajectory analysis
shows that there is consistent, direct transport from the high-
emissions Mexicali Municipality on high ozone days to violating
Imperial County monitors. This direct transport, in conjunction with
the much larger emissions magnitudes in Mexicali than in Imperial
County, supports an international source-receptor relationship between
the Mexicali area and Imperial County on exceedance days.
CARB used CMAQ (version 5.3.2) driven by WRF (version 4.2.1)
meteorological fields to conduct its photochemical modeling analysis.
The EPA recognizes both CMAQ and WRF as technically sound, state-of-
the-science models applicable for use in regulatory applications.\47\
We find that the areal extent and the horizontal and vertical
resolution CARB used in these models are appropriate for modeling
Imperial County ozone. The diurnal variation of temperature, humidity
and surface wind are well represented by WRF and the model captures the
main meteorological features contributing to high ozone in Imperial
County. We reviewed the scatter plots, time series, and performance
statistics provided and agree that, overall, the CMAQ modeling
performance is acceptable and compares favorably to similar studies in
other areas.
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\47\ Memorandum dated August 4, 2017, from Tyler Fox, EPA,
Office of Air Quality Planning and Standards, Subject: ``Use of
Photochemical Grid Models for Single-Source Ozone and Secondary
PM2.5 Impacts for Permit Program Related Assessments and
for NAAQS Attainment Demonstrations for Ozone, PM2.5 and
Regional Haze.''
---------------------------------------------------------------------------
As previously discussed, CARB used the model results to estimate
the impact of cross-border, northern Mexico emissions on air quality.
The results of this estimate were applied to the average of the 2018,
2019, and 2020 ozone design values at Calexico-Ethel Street and El
Centro-9th Street (78 and 72 ppb, respectively) and indicate near-
source Mexico emissions contribute approximately 9 ppb and 11 ppb to
the design values at Calexico-Ethel Street and El Centro-9th Street,
respectively. The EPA notes that the analysis here conservatively
evaluates only cross-border emissions from northern Mexico, and does
not evaluate effects of international emissions from other parts of
Mexico or elsewhere.
The EPA has performed additional analysis of its 2020 Ozone Policy
Assessment (``2020 PA'') modeling \48\ to provide broad U.S. and
international source attribution for 2015 ozone NAAQS nonattainment
areas in the year 2016.\49\ The 2020 PA modeling predicts that
nationwide, average simulated international anthropogenic ozone
contribution to the top 10 model days over all nonattainment areas is
5.3 4.9 ppb (mean standard deviation) and the
average U.S. anthropogenic ozone contribution is 40.2 13.5
ppb.\50\ This result shows that in most nonattainment areas the U.S.
anthropogenic contribution is much larger than the international
anthropogenic contribution.
---------------------------------------------------------------------------
\48\ U.S. EPA. (2020). Policy Assessment for the Review of the
Ozone National Ambient Air Quality Standards (No. EPA-452/R-20-001).
Research Triangle Park, NC: United States Environmental Protection
Agency. Retrieved from https://www.epa.gov/sites/production/files/2020-05/documents/o3-final_pa-05-29-20compressed.pdf.
\49\ Memorandum dated August 10, 2021, from Barron Henderson and
Heather Simon (EPA, OAQPS), Subject: ``Designated Area Source
Attribution Results Related to the National Determination of
Attainment by the Attainment date (DAAD) Action.''
\50\ The EPA modeling was done for the year 2016.
---------------------------------------------------------------------------
The 2020 PA modeling predicts that the international anthropogenic
ozone contribution to the top 10 model days specifically for Imperial
County is 31.8 ppb, the largest international anthropogenic
contribution of any nonattainment area in the country. In contrast to
the modeling submitted by CARB, which quantifies only the small portion
of the international contribution that comes from near-source
anthropogenic emissions in northern Mexico, the EPA's modeling
quantifies impacts from all international anthropogenic emissions
sources. This international anthropogenic contribution is four times
larger than the U.S. anthropogenic contribution of 8.2 ppb on those
days. The EPA also provided contribution estimates to the average of
the 2018, 2019, and 2020 design values for Imperial County (78 ppb) and
predicted that the international anthropogenic contribution to that
value was 31.8 ppb and U.S. anthropogenic contribution was 8.2 ppb.\51\
The analyses are from different years and different modeling platforms,
which complicates conclusions from direct comparisons. In addition,
CARB did not specifically split out the U.S. anthropogenic
contributions in their modeling. Even so, we note that the U.S.
anthropogenic contribution of 8.2 ppb from the 2020 PA modeling is
smaller than the 9-11 ppb estimated contribution from just northern
Mexico in CARB's modeling and is much smaller than the 31.8 ppb from
all international sources in the EPA's 2020 PA modeling. This
additional modeling indicates that international anthropogenic
emissions contribute significantly to ozone in Imperial County, and
that emissions from northern Mexico, while having a substantial
contribution, are only a portion of the total contribution from all
international anthropogenic sources to Imperial County ozone design
values. CARB and EPA analyses both support the conclusion that Mexican
anthropogenic emissions substantially
[[Page 50039]]
contribute to ozone exceedances in Imperial County.
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\51\ In addition to the international anthropogenic and U.S.
anthropogenic contributions, natural emissions were predicted to
contribute 30.0 ppb. Due to the non-linearity of ozone chemistry,
some portion of the ozone concentration in each area cannot be
attributed solely to U.S. anthropogenic or international
anthropogenic sources. Thus, reducing this fraction of ozone
(referred to as ``Mix Anth'') requires reducing both U.S.
anthropogenic and international anthropogenic sources. The predicted
Mix Anth contribution to this value was 7.9 ppb.
---------------------------------------------------------------------------
In conclusion, the EPA finds that these multiple lines of evidence,
taken together, support the conclusion that Imperial County would have
attained the 2015 ozone NAAQS by the August 3, 2021 attainment date
``but for'' international emissions and support the approval of CARB's
179B(b) demonstration.
III. Environmental Justice Considerations
Executive Order 12898 (59 FR 7629, February 16, 1994) requires that
federal agencies, to the greatest extent practicable and permitted by
law, identify and address disproportionately high and adverse human
health or environmental effects of their actions on minority and low-
income populations. Additionally, Executive Order 13985 (86 FR 7009,
January 25, 2021) directs federal government agencies to assess
whether, and to what extent, their programs and policies perpetuate
systemic barriers to opportunities and benefits for people of color and
other underserved groups, and Executive Order 14008 (86 FR 7619,
February 1, 2021) directs federal agencies to develop programs,
policies, and activities to address the disproportionate health,
environmental, economic, and climate impacts on disadvantaged
communities.
To identify environmental burdens and susceptible populations in
underserved communities in the Imperial County nonattainment area and
to better understand the context of our proposed approval of CARB's
179B(b) demonstration on these communities, we conducted a screening-
level analysis using the EPA's environmental justice (EJ) screening and
mapping tool (``EJSCREEN'').\52\ Our screening-level analysis indicates
that communities affected by this action score above the national
average for the EJSCREEN ``Demographic Index,'' which is the average of
an area's percent minority and percent low income populations, i.e.,
the two demographic indicators explicitly named in Executive Order
12898.\53\ These communities also score above the national average for
the ``linguistically isolated population,'' and ``population with less
than high school education'' indicators. Additionally, these
communities score above the national average for numerous EJ Index
indicators, including the PM2.5 EJ index and the respiratory
hazard EJ Index. We also looked at ozone design values for the 2018-
2020 period as an indicator of potential ozone pollution exposure.\54\
Both the Calexico and the El Centro monitors score above the national
average design value for this period.\55\
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\52\ EJSCREEN provides a nationally consistent dataset and
approach for combining environmental and demographic indicators.
EJSCREEN is available at https://www.epa.gov/ejscreen/what-ejscreen.
The EPA used EJSCREEN to obtain environmental and demographic
indicators representing the City of Calexico, which is located
adjacent to the border with Mexico and measures the highest levels
of ozone in the nonattainment area, and the central portion of
Imperial County, where the overwhelming majority of the population
resides. These indicators are included in EJSCREEN reports that are
available in the rulemaking docket for this action.
\53\ EJSCREEN reports environmental indicators (e.g., air toxics
cancer risk, Pb paint exposure, and traffic proximity and volume)
and demographic indicators (e.g., people of color, low income, and
linguistically isolated populations). The score for a particular
indicator measures how the community of interest compares with the
state, the EPA region, or the national average. For example, if a
given location is at the 95th percentile nationwide, this means that
only five percent of the US population has a higher value than the
average person in the location being analzed. EJSCREEN also reports
EJ indexes, which are combinations of a single environmental
indicator with the EJSCREEN Demographic Index. For additional
information about environmental and demographic indicators and EJ
indexes reported by EJSCREEN, see EPA, ``EJSCREEN Environmental
Justice Mapping and Screening Tool--EJSCREEN Technical
Documentation,'' section 2 (September 2019).
\54\ The ozone metric in EJSCREEN represents the summer seasonal
average of daily maximum 8-hour concentrations (parts per billion,
ppb) and was not used in our EJ analyses because it does not
represent summertime peak ozone concentrations, which are instead
represented here by the design value (DV) metric. Ozone DVs are the
basis of the attainment determination in this proposed action, and
in this case we consider it a more informative indicator of
pollution burden relative to the Imperial nonattainment area and the
U.S. as a whole.
\55\ The 2020 ozone design value for the Calexico monitor (0.078
ppm) is in the 94th percentile and the El Centro monitor (0.068 ppm)
is in the 73rd percentile among 2020 ozone design values nationally.
The percentiles were calculated using data available at https://www.epa.gov/system/files/documents/2022-05/O3_DesignValues_2019_2021_FINAL_05_25_22.xlsx, Table 6. Site Trend,
column T (``2018-2020 Design Value (ppm)'').
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As discussed in the EPA's EJ technical guidance, people of color
and low-income populations, such as those in Imperial County, often
experience greater exposure and disease burdens than the general
population, which can increase their susceptibility to adverse health
effects from environmental stressors.\56\ Underserved communities may
have a compromised ability to cope with or recover from such exposures
due to a range of physical, chemical, biological, social, and cultural
factors.\57\ In addition to the demographic and environmental
indicators identified in our screening level analysis, the proximity of
underserved communities to the border with Mexico and the resulting
exposure to levels of ozone that exceed the NAAQS contributes to the
potential EJ concerns faced by communities in the Imperial
nonattainment area.
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\56\ EPA, ``Technical Guidance for Assessing Environmental
Justice in Regulatory Analysis,'' section 4 (June 2016).
\57\ Id. section 4.1.
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If finalized, this proposed action to approve California's
demonstration that the Imperial County ozone nonattainment area would
have attained the standard by the statutory attainment date, but for
emissions emanating from Mexico, would result in the area retaining its
Marginal classification. The area will retain its designation as
nonattainment and continue to implement nonattainment new source
review, but will not be reclassified as ``Moderate'' and the State will
not be required to submit a plan demonstrating attainment or to adopt
additional control measures, consistent with CAA section 179B(b).\58\
As a result, the EPA will not be requiring the State to impose
additional control measures for purposes of the 2015 ozone NAAQS that
could serve to reduce ozone exposure in the area, even if they would
not result in actual attainment of the NAAQS due to the influx of ozone
and its precursors from Mexico.
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\58\ In light of the overall health and clean air objectives of
the CAA, the EPA encourages the State and District to continue to
evaluate and, where feasible, implement measures that would further
reduce emissions and contribute to improved air quality in the
Imperial nonattainment area.
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However, we note that the Imperial County nonattainment area is
also designated nonattainment, and classified as Moderate, for the 2008
ozone NAAQS. Section 172(c)(1) of the CAA requires states to implement
RACM/RACT level emission controls for ozone nonattainment areas
classified Moderate and above. In 2020, the EPA determined that
California's Moderate area nonattainment plan for the Imperial County
nonattainment area for the 2008 ozone NAAQS provides for the
implementation of all RACM as required by CAA section 172(c)(1) and 40
CFR 51.1112(c).\59\ Because California has already implemented RACM/
RACT level controls for purposes of the 2008 ozone NAAQS in the area,
we think that this will serve to limit potential impacts from the EPA's
approval of the 179(B)(b) demonstration for purposes of the 2015 ozone
NAAQS.
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\59\ 85 FR 11817 (February 27, 2020), 85 FR 8181 (February 13,
2020), and 86 FR 49248 (September 2, 2021).
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In addition, the EPA notes that there are other efforts underway to
reduce environmental burden along the U.S.-Mexico border, including
Imperial County. The United States and Mexico
[[Page 50040]]
have long recognized the environmental challenges in the border region
and share the goal of protecting the environment and public health in
the U.S.-Mexico border region. The two nations have been working
together outside the framework of the SIP process to make progress
towards those goals.
The U.S.-Mexico Environmental Program (``Border 2025'') is a five-
year (2021-2025) binational effort designed ``to protect the
environment and public health in the U.S.-Mexico border region,
consistent with the principles of sustainable development.'' \60\
Border 2025 is the latest of a series of cooperative efforts
implemented under the 1983 La Paz Agreement. It builds on previous
binational efforts (i.e., the Border 2012 and Border 2020 Environmental
Programs), emphasizing regional, bottom-up approaches for decision
making, priority setting, and project implementation to address the
environmental and public health problems in the border region. As in
the previous two border programs, Border 2025 encourages meaningful
participation from communities and local stakeholders and establishes
guiding principles that will support the mission statement, ensure
consistency among all aspects of the Border 2025 Program, and continue
successful elements of previous binational environmental programs.
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\60\ ``Border 2025: United States--Mexico Environmental
Program,'' included in this docket and accessible at https://www.epa.gov/sites/default/files/2021-05/documents/final_us_mx_border_2025_final_may_6.pdf.
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Border 2025 sets out four strategic goals, including the reduction
of air pollution and the improvement of water quality, to address
environmental and public health challenges in the border region. Within
the goals are specific objectives that identify actions that will be
taken in support of the program's mission. The goals and objectives
were determined binationally between the EPA and the Ministry of
Environment and Natural Resources of Mexico (SEMARNAT) to address
ongoing environmental challenges, and considered input from state and
tribal partners. The ``California[hyphen]Baja California 2021-2023
Border 2025 Action Plan'' lists and describes the projects that are
being undertaken to achieve the goals and objectives of Border 2025,
along with the target outputs, expected results, and status of each
action.\61\
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\61\ The ``California[hyphen]Baja California 2021-2023 Border
2025 Action Plan'' is included in the docket for this action and is
accessible online at https://www.epa.gov/usmexicoborder/region-9-action-plansplanes-de-accion-de-region-9.
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In addition to the ongoing efforts under the Border 2025 agreement,
in 2020, the EPA awarded the Imperial County APCD $3,350,371 to pave
3.5 miles of residential alleyways in the downtown core of the City of
Calexico to reduce PM2.5 and PM10.\62\ While the
resulting reductions of particulate emissions will not reduce ozone
levels, it should relieve some of the cumulative burden on
disadvantaged communities in the Imperial ozone nonattainment area.
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\62\ A list of the Targeted Airshed Grants the EPA awarded in
fiscal years 2015-2020 is accessible online at https://www.epa.gov/air-quality-implementation-plans/targeted-airshed-grant-recipients.
These EPA grants support projects to reduce emissions in areas
facing the highest levels of ground-level ozone and fine particulate
matter, or PM2.5.
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The EPA is committed to environmental justice for all people, and
we acknowledge that the Imperial County nonattainment area includes
minority and low income populations that could be affected by this
action. As discussed in Section I.B. of this document, the District and
State have met the requirements for ozone nonattainment areas
classified as Marginal. Notwithstanding the purpose of this action
determining that the Imperial ozone nonattainment area would have
attained the 2015 ozone NAAQS but for emissions transported from
Mexico, the EPA is working to reduce disproportionate health,
environmental, economic, and climate change impacts in the Imperial
County nonattainment area by other means, including those described in
this section.
IV. Proposed Action
For the reasons discussed in this document, we are proposing to
determine, consistent with our evaluation of the ``Imperial County
Clean Air Act Section 179B(b) Analysis for the 70 ppb 8-Hour Ozone
Standard,'' that the Imperial County nonattainment area would have
attained the 2015 ozone NAAQS by the Marginal area attainment date of
August 3, 2021, but for emissions emanating from outside the United
States. If finalized, the EPA's obligation under section 181(b)(2)(A)
to determine whether the area attained by its attainment date will no
longer apply and the area will not be reclassified. The area will
remain designated nonattainment and thus the State will continue to
comply with applicable requirements for a Marignal ozone nonattainment
area.
The EPA is soliciting public comments on the issues discussed in
this document. We will accept comments from the public on this proposal
until September 14, 2022 and will consider comments before taking final
action.
V. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review and Executive
Order 13563: Improving Regulation and Regulatory Review
This action is not a significant regulatory action and was
therefore not submitted to the Office of Management and Budget (OMB)
for review.
B. Paperwork Reduction Act (PRA)
This rulemaking does not impose any new information collection
burden under the PRA not already approved by the Office of Management
and Budget. This action proposes to find that the Imperial County
Marginal ozone nonattainment area would have attained the 2015 NAAQS by
the applicable attainment date, but for emissions emanating from
outside the United States. Thus, the proposed action does not establish
any new information collection burden that has not already been
identified and approved in the EPA's information collection
request.\63\
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\63\ On April 30, 2018, the OMB approved the EPA's request for
renewal of the previously approved information collection request
(ICR). The renewed request expired on April 30, 2021, 3 years after
the approval date (see OMB Control Number 2060-0695 and ICR
Reference Number 201801-2060-003 for EPA ICR No. 2347.03). On April
30, 2021, the OMB published the final 30-day Notice (86 FR 22959)
for the ICR renewal titled ``Implementation of the 8-Hour National
Ambient Air Quality Standards for Ozone (Renewal)'' (see OMB Control
Number 2060-0695 and ICR Reference No: 202104-2060-004 for EPA ICR
Number 2347.04). The ICR renewal is pending OMB final approval.
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C. Regulatory Flexibility Act (RFA)
I certify that this action will not have a significant economic
impact on a substantial number of small entities under the RFA. This
action will not impose any requirements on small entities. The proposed
determination that Imperial County would have attained the 2015 ozone
NAAQS but for international emissions does not in and of itself create
any new requirements beyond what is mandated by the CAA. Instead, this
rulemaking only makes factual determinations, and does not directly
regulate any entities.
D. Unfunded Mandates Reform Act (UMRA)
This action does not contain any unfunded mandate as described in
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect
small
[[Page 50041]]
governments. This action imposes no enforceable duty on any state,
local or tribal governments or the private sector.
E. Executive Order 13132: Federalism
This action does not have federalism implications. It will not have
substantial direct effects on the states, on the relationship between
the national government and the states and tribes, or on the
distribution of power and responsibilities among the various levels of
government. The division of responsibility between the Federal
Government and the states for the purposes of implementing the NAAQS is
established under the CAA.
F. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments
This action has tribal implications. However, it will neither
impose substantial direct compliance costs on federally recognized
tribal governments, nor preempt tribal law.
The EPA has identified two tribal areas located within the Imperial
County nonattainment area, which is the subject of this action
proposing to determine the area attained the 2015 ozone NAAQS, but for
emissions emanating from outside the United States. The EPA has invited
the Quechan Tribe of the Fort Yuma Indian Reservation and the Torres
Martinez Desert Cahuilla Indians to engage in government to government
consultation in advance of our proposed action and intends to continue
to communicate with the tribes as the Agency moves forward in
developing a final rule.
G. Executive Order 13045: Protection of Children From Environmental
Health and Safety Risks
The EPA interprets Executive Order 13045 as applying only to those
regulatory actions that concern environmental health or safety risks
that the EPA has reason to believe may disproportionately affect
children, per the definition of ``covered regulatory action'' in
section 2-202 of the Executive Order. This action is not subject to
Executive Order 13045 because it does not concern an environmental
health risk or safety risk.
H. Executive Order 13211: Actions That Significantly Affect Energy
Supply, Distribution, or Use
This action is not subject to Executive Order 13211, because it is
not a significant regulatory action under Executive Order 12866.
I. National Technology Transfer Advancement Act (NTTAA)
This rulemaking does not involve technical standards.
J. Executive Order 12898: Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Populations
Executive Order (E.O.) 12898 (59 FR 7629 (Feb. 16, 1994))
establishes federal executive policy on environmental justice. Its main
provision directs federal agencies, to the greatest extent practicable
and permitted by law, to make environmental justice part of their
mission by identifying and addressing, as appropriate,
disproportionately high and adverse human health or environmental
effects of their programs, policies, and activities on minority
populations and low-income populations in the United States. The EPA's
evaluation of this issue is contained in the section of the preamble
titled ``Environmental Justice Considerations.''
List of Subjects
40 CFR Part 52
Environmental protection, Administrative practice and procedure,
Air pollution control, Designations and classifications, Incorporation
by reference, Intergovernmental relations, Nitrogen oxides, Ozone,
Reporting and recordkeeping requirements, and Volatile organic
compounds.
40 CFR Part 81
Environmental protection, Administrative practice and procedure,
Air pollution control, Designations and classifications,
Intergovernmental relations, Nitrogen oxides, Ozone, Reporting and
recordkeeping requirements, and Volatile organic compounds.
Dated: August 4, 2022.
Martha Guzman Aceves,
Regional Administrator, Region IX.
[FR Doc. 2022-17190 Filed 8-12-22; 8:45 am]
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