[Federal Register Volume 88, Number 243 (Wednesday, December 20, 2023)]
[Proposed Rules]
[Pages 87988-88012]
[FR Doc No: 2023-27686]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2023-0477; FRL-11532-01-R9]

Clean Air Plans; Contingency Measures for the Fine Particulate
Matter Standards; San Joaquin Valley, California

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to
approve two state implementation plan (SIP) submissions under the Clean
Air Act (CAA) that address the contingency measures requirements for
the 1997 annual, 2006 24-hour, and 2012 annual fine particulate matter
(PM2.5) national ambient air quality standards (NAAQS or
``standards'') for the San Joaquin Valley PM2.5
nonattainment area. The two SIP submissions include the area's
contingency measure plan element and two specific contingency measures
that would apply to residential wood burning heaters and fireplaces and
non-agricultural, rural open areas. A third contingency measure,
applicable to light-duty on-road motor vehicles, is the subject of a
separate action by the EPA, but the related emissions reductions from
the third measure are accounted for in this proposed rule. The EPA is
proposing approval of the SIP submissions because the Agency has

determined that they are in accordance with the applicable requirements
for such SIP submissions under the CAA and EPA implementation
regulations for the PM2.5 NAAQS. The proposed approval, if
finalized, would incorporate the two contingency measures into the
federally enforceable SIP. The EPA will accept comments on this
proposed rule during a 30-day public comment period.

DATES: Comments must be received by January 19, 2024.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2023-0477 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 (e.g.,
audio or video) 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 a disability
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: Rory Mays, Planning and Analysis
Branch (AIR-2), Air and Radiation Division, EPA Region IX, 75 Hawthorne
Street, San Francisco, CA 94105. By phone:<PHONE_NUMBER> or by email
at [email protected].

SUPPLEMENTARY INFORMATION: Throughout this document, ``we,'' ``us,''
and ``our'' refer to the EPA.

Table of Contents

I. Background for Proposed Action
    A. Standards, Designations, Classifications, and Plans
    B. Findings and Contingency Measure Disapprovals
II. Summary of SIP Submissions and Evaluation for Compliance With
SIP Revision Procedural Requirements
    A. Summary of SIP Submissions
    B. Evaluation for Compliance With SIP Revision Procedural
Requirements
III. Contingency Measure Requirements, Guidance, and Legal Precedent
    A. Statutory and Regulatory Requirements
    B. Draft Revised Contingency Measure Guidance
IV. EPA Review of San Joaquin Valley Contingency Measures
    A. Residential Wood Burning Contingency Measure
    1. Background and Regulatory History
    2. Summary of State Submission
    3. EPA Evaluation
    B. Rural Open Areas Contingency Measure
    1. Background and Regulatory History
    2. Summary of State Submission
    3. EPA Evaluation
    C. Smog Check Contingency Measure
V. EPA Review of San Joaquin Valley PM2.5 Contingency
Measure Plan Element
    A. Background and Regulatory History
    B. Summary of State Submission
    1. General Considerations
    2. Contingency Measure Feasibility Analyses
    3. Conclusion
    C. EPA Evaluation
    1. General Considerations
    2. Contingency Measure Feasibility Analyses
    3. Conclusion
VI. Environmental Justice Considerations
VII. Proposed Action and Request for Public Comment
VIII. Incorporation by Reference
IX. Statutory and Executive Order Reviews

I. Background for Proposed Action

A. Standards, Designations, Classifications, and Plans

    Under section 109 of the Clean Air Act (CAA or ``Act''), the EPA
has established national ambient air quality standards (NAAQS or
``standards'') for certain pervasive air pollutants (referred to as
``criteria pollutants'') and conducts periodic reviews of the NAAQS to
determine whether they should be revised or whether new NAAQS should be
established. To date, the EPA has established NAAQS for particulate
matter, ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide and
lead. Under CAA section 110, states have primary responsibility for
meeting the NAAQS within the state, and must submit an implementation
plan that specifies the manner in which the state will attain and
maintain the NAAQS. These implementation plans are referred to as
``state implementation plans'' or ``SIPs.''
    Periodically, states must make SIP submissions of different types
to meet additional CAA requirements. For example, after the EPA
promulgates a new or revised NAAQS, under CAA section 110(a)(1) and
(2), states are required to adopt and submit to the EPA a state
implementation plan that provides for implementation, maintenance, and
enforcement of the NAAQS. Such plans are referred to as
``infrastructure SIPs.'' Similarly, after the EPA promulgates
designations for a new or revised NAAQS, states with designated
nonattainment areas must make SIP submissions that meet additional
requirements for such nonattainment areas, under CAA section 172(c)
and, in the case of the PM2.5 NAAQS, CAA sections 188 and
189. This type of SIP submission is referred to as an ``attainment
plan.''
    Under CAA section 110(k), the EPA is charged with evaluation of
each SIP submission submitted by states for compliance with applicable
CAA requirements, and for approval or disapproval (in whole or in part)
of the submission. The EPA evaluates SIP submissions and takes action
to approve, disapprove, or conditionally approve them through notice-
and-comment rulemaking published in the Federal Register. Where
appropriate, the EPA may act on specific parts of a SIP submission in
separate rulemaking actions.
    In 1997, the EPA promulgated new NAAQS for fine particulate matter,
using particles with an aerodynamic diameter less than or equal to a
nominal 2.5 micrometers (``PM2.5'') as the indicator.\1\ The
EPA established primary and secondary annual and 24-hour standards for
PM2.5. The EPA set the 1997 annual PM2.5 NAAQS,
both primary and secondary standards, at 15.0 micrograms per cubic
meter ([mu]g/m\3\), based on a 3-year average of annual mean
PM2.5 concentrations. The EPA set the 1997 24-hour
PM2.5 NAAQS, both primary and secondary standards, at 65
[mu]g/m\3\, based on the 3-year average of the 98th percentile of 24-
hour PM2.5 concentrations. Collectively, we refer herein to
the 1997 24-hour and annual PM2.5 NAAQS as the ``1997
PM2.5 NAAQS.'' In 2006, the EPA promulgated a new, more
stringent 24-hour NAAQS for PM2.5 by lowering the primary
and secondary standards level from 65 [mu]g/m\3\ to 35 [mu]g/m\3\
(referred to herein as the ``2006 24-hour PM2.5 NAAQS'').\2\
In 2012, the EPA promulgated a new, more stringent annual NAAQS for
PM2.5 by lowering the primary standards level from 15.0
[mu]g/m\3\ to 12.0 [mu]g/m\3\ (herein referred to as the ``2012 annual
PM2.5

NAAQS'').\3\ Each iteration of the PM2.5 NAAQS remains in
effect, and states with designated nonattainment areas for each of them
are obligated to meet applicable attainment plan requirements for them.
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    \1\ 62 FR 38652 (July 18, 1997) and 40 CFR 50.7.
    \2\ 71 FR 61144 (October 17, 2006) and 40 CFR 50.13.
    \3\ 78 FR 3086 (January 15, 2013) and 40 CFR 50.18.
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    The EPA established each of these NAAQS after considering
substantial evidence from numerous health studies demonstrating that
serious health effects are associated with exposures to
PM2.5 concentrations above these levels. Epidemiological
studies have shown statistically significant correlations between
elevated PM2.5 levels and premature mortality. Other
important health effects associated with PM2.5 exposure
include aggravation of respiratory and cardiovascular disease (as
indicated by increased hospital admissions, emergency room visits,
absences from school or work, and restricted activity days), changes in
lung function, and increased respiratory symptoms. Individuals
particularly sensitive to PM2.5 exposure include older
adults, people with heart and lung disease, and children.\4\
PM2.5 can be particles emitted by sources directly into the
atmosphere as a solid or liquid particle (``primary PM2.5''
or ``direct PM2.5''), or can be particles that form in the
atmosphere as a result of various chemical reactions involving
PM2.5 precursor emissions emitted by sources (``secondary
PM2.5''). The EPA has identified the precursors of
PM2.5 to be oxides of nitrogen (``NOX''), sulfur
oxides (``SOX''), volatile organic compounds (VOCs), and
ammonia.\5\
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    \4\ 78 FR 3086, 3088.
    \5\ EPA, Air Quality Criteria for Particulate Matter, No. EPA/
600/P-99/002aF and EPA/600/P-99/002bF, October 2004.
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    Following promulgation of a new or revised NAAQS, the EPA is
required under CAA section 107(d) to designate areas throughout the
Nation as attaining or not attaining the NAAQS. As noted previously,
for areas the EPA has designated nonattainment, states are required
under the CAA to submit attainment plan SIP submissions. These SIP
submissions must provide for, among other elements, reasonable further
progress (RFP) towards attainment of the NAAQS, attainment of the NAAQS
no later than the applicable attainment date, and implementation of
contingency measures to take effect if the state fails to meet RFP or
to attain the NAAQS by the applicable attainment date.
    The San Joaquin Valley is located in the southern half of
California's Central Valley and includes all of San Joaquin,
Stanislaus, Merced, Madera, Fresno, Tulare, and Kings Counties, and the
valley portion of Kern County.\6\ The area is home to four million
people and is the Nation's leading agricultural region. Stretching over
250 miles from north to south and averaging 80 miles wide, it is
partially enclosed by the Coast Mountain range to the west, the
Tehachapi Mountains to the south, and the Sierra Nevada range to the
east. In 2005, the EPA designated the San Joaquin Valley as
nonattainment for the 1997 annual PM2.5 NAAQS and
nonattainment for the 1997 24-hour PM2.5 NAAQS.\7\
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    \6\ For a precise description of the geographic boundaries of
the San Joaquin Valley nonattainment area, see 40 CFR 81.305.
    \7\ 70 FR 944 (January 5, 2005), codified at 40 CFR 81.305.
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    The local air district with primary responsibility for developing
attainment plan SIP submissions for the PM2.5 NAAQS in this
area is the San Joaquin Valley Unified Air Pollution Control District
(SJVUAPCD or ``District''). Once the District adopts the regional plan,
the District submits the plan to the California Air Resources Board
(CARB) for adoption as part of the California SIP. CARB is the State
agency responsible for adopting and revising the California SIP and for
submitting the SIP and SIP revisions to the EPA. Generally speaking,
under California law, CARB is responsible for regulation of mobile
sources while the local air districts are responsible for regulation of
stationary sources.
    Originally, the EPA designated areas for the 1997 annual and 24-
hour PM2.5 NAAQS under subpart 1 (of part D of title I of
the CAA), i.e., without specifying the classifications of nonattainment
required by subpart 4. Later, in response to a court decision,\8\ the
EPA classified nonattainment areas for the 1997 annual and 24-hour
PM2.5 NAAQS, consistent with the classifications set forth
in subpart 4. With respect to San Joaquin Valley, in 2014, the EPA
classified the San Joaquin Valley as a ``Moderate'' nonattainment
area,\9\ and then in 2015, reclassified the area as a ``Serious''
nonattainment area for the 1997 annual and 24-hour PM2.5
NAAQS.\10\
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    \8\ In Natural Resources Defense Council v. EPA, 706 F.3d 428
(D.C. Cir. 2013), the U.S. Court of Appeals for D.C. Circuit
concluded that the EPA erred in implementing the 1997
PM2.5 NAAQS solely pursuant to the general implementation
requirements of subpart 1, without also considering the requirements
specific to PM10 nonattainment areas in subpart 4, part D
of title I of the CAA.
    \9\ 79 FR 31566 (June 2, 2014).
    \10\ 80 FR 18528 (April 7, 2015).
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    In 2016, the EPA determined that the San Joaquin Valley had failed
to attain the 1997 annual and 24-hour PM2.5 NAAQS by the
applicable ``Serious'' area attainment date.\11\ As a result, the State
of California was required, under CAA section 189(d), to submit a new
SIP submission that, among other elements, provides for expeditious
attainment of the 1997 annual and 24-hour PM2.5 NAAQS and
for a minimum five percent annual reduction in the emissions of direct
PM2.5 or a PM2.5 plan precursor pollutant in the
San Joaquin Valley (herein, referred to as a ``Five Percent Plan'').
The Five Percent Plan for the 1997 annual and 24-hour PM2.5
NAAQS was due no later than December 31, 2016.\12\
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    \11\ 81 FR 84481 (November 23, 2016).
    \12\ Id. at 84482.
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    With respect to the 2006 24-hour PM2.5 NAAQS, the EPA
initially designated San Joaquin Valley as nonattainment under subpart
1 (i.e., without classification) \13\ but, in 2014, in response to the
court decision referred to previously, the EPA classified the area as
Moderate.\14\ In 2016, the EPA reclassified San Joaquin Valley as a
Serious nonattainment area for the 2006 24-hour PM2.5 NAAQS
based on the EPA's determination that the area could not practicably
attain these NAAQS by the applicable attainment date of December 31,
2015.\15\ The EPA established an August 21, 2017 deadline for
California to adopt and submit a SIP submission addressing the Serious
nonattainment area requirements for the 2006 24-hour PM2.5
NAAQS.\16\
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    \13\ 74 FR 58688 (November 13, 2009).
    \14\ 79 FR 31566.
    \15\ 81 FR 2993 (January 20, 2016).
    \16\ Id. at 3000.
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    With respect to the 2012 annual PM2.5 NAAQS, the EPA
designated San Joaquin Valley as a Moderate nonattainment area in
2015.\17\ Under CAA section 189 and the EPA's PM2.5 SIP
Requirements Rule,\18\ the deadline for the state to submit an
attainment plan SIP submission addressing the Moderate nonattainment
area requirements for the 2012 annual PM2.5 NAAQS is 18
months from the effective date of the designation of the area.\19\ The
effective date of the designation of the San Joaquin Valley as a
Moderate nonattainment area for the 2012 annual PM2.5 NAAQS
was April 15, 2015, and thus, the deadline for a SIP submission
addressing the Moderate area requirements was October 15, 2016.
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    \17\ 80 FR 2206 (January 15, 2015).
    \18\ 81 FR 58010 (August 24, 2016); codified at 40 CFR part 51,
subpart Z.
    \19\ 40 CFR 51.1003(a).

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B. Findings and Contingency Measure Disapprovals

    In the wake of these EPA actions, CARB and the District worked
together to prepare a comprehensive SIP submission to address the
nonattainment area requirements for the 1997, 2006, and 2012
PM2.5 NAAQS for San Joaquin Valley, but did not meet the
various SIP submission deadlines. In late 2018, the EPA issued a
finding of failure to submit to the State for the required attainment
plan SIP submissions for the 1997 annual and 24-hour PM2.5
NAAQS, the 2006 24-hour PM2.5 NAAQS, and the 2012 annual
PM2.5 NAAQS for the San Joaquin Valley.\20\ The EPA's
finding of failure to submit was effective January 7, 2019. Under CAA
section 110(c), the EPA is obligated to promulgate a Federal
Implementation Plan (FIP) within two years of a finding that a state
has failed to make a required SIP submission, unless the state submits
a SIP submission that corrects the deficiency, and the EPA approves
that SIP submission, before the EPA promulgates such FIP.\21\ In this
case, the finding of failure to submit established a deadline of
January 7, 2021, for the EPA to promulgate a FIP to address all
applicable attainment plan requirements for the 1997 annual and 24-hour
PM2.5 NAAQS, the 2006 24-hour PM2.5 NAAQS, and
2012 annual PM2.5 NAAQS for San Joaquin Valley, for which
the EPA had not received and approved an adequate SIP submission from
the State.
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    \20\ 83 FR 62720 (December 6, 2018).
    \21\ The finding of failure to submit also started an 18-month
new source review (NSR) offset sanction clock and a 24-month highway
sanction clock for the State of California. CAA section 179(a) and
40 CFR 52.31.
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    To address a portion of current FIP obligation, the EPA recently
proposed a FIP to address the contingency measures requirements for the
San Joaquin Valley for the 1997 annual, 2006 24-hour, and 2012 annual
PM2.5 NAAQS.\22\ In short, the proposed contingency measure
FIP includes two specific contingency measures, one of which would
extend certain wood-burning curtailment restrictions Valley-wide and
another which would extend certain fugitive dust requirements to
certain open areas that are not currently subject to control
requirements.
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    \22\ 88 FR 53431 (August 8, 2023).
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    On May 10, 2019, CARB submitted two SIP submissions to address the
nonattainment area requirements for all four of the relevant
PM2.5 NAAQS for the San Joaquin Valley, including the
contingency measure requirement.\23\ On November 8, 2021, CARB
submitted a third SIP submission to amend the portions of the May 10,
2019 SIP submissions that pertain to the 1997 annual PM2.5
NAAQS.\24\ As discussed in the following paragraph, the EPA has
previously taken a series of actions on these SIP submissions to
address different nonattainment area requirements for each of the
NAAQS. In this proposed action, we are focused only on the contingency
measure requirements.
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    \23\ The SIP revisions submitted on May 10, 2019, include the
``2016 Moderate Area Plan for the 2012 PM2.5 Standard''
(``2016 PM2.5 Plan'') and the ``2018 Plan for the 1997,
2006, and 2012 PM2.5 Standards'' (``2018 PM2.5
Plan''), which incorporates by reference the ``San Joaquin Valley
Supplement to the 2016 State Strategy for the State Implementation
Plan'' (``Valley State SIP Strategy''). On February 11, 2020, CARB
submitted a revised version of Appendix H (``RFP, Quantitative
Milestones, and Contingency'') that replaces the version submitted
with the 2018 PM2.5 Plan on May 10, 2019. The EPA found
the SIP submissions complete in a letter dated June 24, 2020, from
Elizabeth J. Adams, Director, EPA Region IX, to Richard W. Corey,
Executive Officer, CARB. The EPA's completeness determination
terminated the NSR offsets and highway sanctions started by the
December 6, 2018 finding of failure to submit but did not affect the
FIP obligation.
    \24\ The SIP revision submitted on November 8, 2021, is titled
``Attainment Plan Revision for the 1997 Annual PM2.5
Standard'' (``15 [mu]g/m\3\ SIP Revision'').
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    In 2020, the EPA approved the portion of the SIP submissions
related to the 2006 24-hour PM2.5 NAAQS, but deferred action
on the contingency measure element.\25\ In 2021, the EPA approved the
portion of the SIP submissions related to the Moderate area
requirements for the 2012 annual PM2.5 NAAQS except for the
contingency measure element, which the EPA disapproved.\26\ The EPA
also disapproved the previously-deferred contingency measure element
for the 2006 24-hour PM2.5 NAAQS.\27\ In another 2021
action, the EPA disapproved the portion of the SIP submissions related
to the 1997 annual PM2.5 NAAQS except for the emissions
inventory, which the Agency approved.\28\ In 2022, the EPA approved the
portion of the SIP submission related to the 1997 24-hour
PM2.5 NAAQS, with the exception of the contingency measure
element.\29\ In our action on the SIP submission related to the 1997
24-hour PM2.5 NAAQS, we disapproved the contingency measure
element, but also found that the contingency measure requirement was
moot for that particular PM2.5 NAAQS because of the EPA's
concurrent determination of attainment by the applicable attainment
date for San Joaquin Valley for the 1997 24-hour PM2.5
NAAQS.\30\
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    \25\ 85 FR 44192 (July 22, 2020).
    \26\ 86 FR 67343 (November 26, 2021).
    \27\ Id.
    \28\ 86 FR 67329 (November 26, 2021).
    \29\ 87 FR 4503 (January 28, 2022).
    \30\ Id.
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    In July 2023, the EPA proposed approval of the portions of the
three SIP submissions that pertain to the 1997 annual PM2.5
NAAQS in the San Joaquin Valley nonattainment area.\31\ More recently,
we took action to finalize our approval of the SIP submissions for the
1997 annual PM2.5 NAAQS, as proposed; however, our recent
action on various elements of the San Joaquin Valley PM2.5
plan for the 1997 annual PM2.5 NAAQS did not address the
contingency measures requirements for that particular PM2.5
NAAQS.\32\
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    \31\ 88 FR 45276 (July 14, 2023).
    \32\ EPA, ``Air Quality State Implementation Plans; Approvals
and Promulgations: California; 1997 Annual Fine Particulate Matter
Serious and Clean Air Act Section 189(d) Nonattainment Area
Requirements; San Joaquin Valley, CA,'' Final rule, signed December
5, 2023.
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    With respect to contingency measure elements, the State's May 10,
2019 PM2.5 SIP submissions for San Joaquin Valley relied
upon contingency provisions included in District Rule 4901 (``Wood
Burning Fireplaces and Wood Burning Heaters''), specifically section
5.7.3 of the rule, and a demonstration that the emissions reductions
from the contingency measure would be sufficient to meet the
contingency measure SIP requirements of CAA section 172(c)(9) if the
reductions were viewed together with ``surplus'' \33\ emissions
reductions from already-implemented measures.\34\ We disapproved the
contingency measure elements for San Joaquin Valley for the 1997
annual, 2006 24-hour, and 2012 annual PM2.5 NAAQS because
the contingency provision (i.e., section 5.7.3) in Rule 4901 did not
address the potential for State failures to meet RFP, to meet a
quantitative milestone, or to submit a quantitative milestone report.
In addition, the contingency measure provision of Rule 4901 was not
structured to achieve any additional emissions reductions if the EPA
were to find that the monitoring locations in the ``hot spot'' counties
(i.e., Fresno, Kern, or Madera) are the only counties in the San
Joaquin Valley that are violating the PM2.5 NAAQS as of the
attainment date.\35\ In addition, the contingency

measure elements did not provide sufficient justification as to why the
one adopted contingency measure (in Rule 4901) would suffice to meet
the CAA requirements for contingency measures for the PM2.5
NAAQS for San Joaquin Valley notwithstanding the fact that the one
measure would not achieve one year's worth of RFP, as recommended in
longstanding EPA guidance.36 37
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    \33\ In this context, ``surplus'' refers to emissions reductions
not otherwise relied upon for RFP or attainment demonstrations.
    \34\ See 86 FR 38652, 38668-38669 (July 22, 2021); 86 FR 49100,
49123-49124 and 49132-49133 (September 1, 2021).
    \35\ See 86 FR 38652, 38669-38670 (proposed disapproval of the
contingency measure element for the 1997 annual PM2.5
NAAQS); and 86 FR 49100, 49124-49125 (proposed disapproval of the
contingency measure element for the 2012 annual PM2.5
NAAQS) and 49133-49134 (proposed disapproval of the contingency
measure element for the 2006 24-hour PM2.5 NAAQS)
(September 1, 2021). The proposed disapprovals were finalized at 86
FR 67329 (1997 annual PM2.5 NAAQS); 86 FR 67343 (2012
annual PM2.5 NAAQS and 2006 24-hour PM2.5
NAAQS).
    \36\ Id.
    \37\ 81 FR 58010, 58066. See also 57 FR 13498, 13511, 13543-
13544 (April 16, 1992), and 59 FR 41998, 42014-42015 (August 16,
1994).
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    In our final rules disapproving the contingency measure elements
for San Joaquin Valley for the 1997 annual, 2006 24-hour, and 2012
annual PM2.5 NAAQS, we indicated that the disapprovals would
begin an 18-month clock for imposition of the offset sanction in CAA
section 179(b)(2) and a 24-month clock for imposition of the highway
funding sanction in CAA section 179(b)(1) unless the State submits, and
the EPA approves, a SIP revision that corrects the deficiencies that we
identified in our final actions prior to implementation of the
sanctions.\38\
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    \38\ 86 FR 67329, 67341 (1997 annual PM2.5 NAAQS); 86
FR 67343, 67346-67347 (2012 annual PM2.5 NAAQS and 2006
24-hour PM2.5 NAAQS).
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II. Summary of SIP Submissions and Evaluation for Compliance With SIP
Revision Procedural Requirements

A. Summary of SIP Submissions

    On June 8, 2023, CARB submitted the ``PM2.5 Contingency
Measure State Implementation Plan Revision (May 18, 2023)'' (herein
referred to as the ``SJV PM2.5 Contingency Measure SIP'') to
the EPA as a revision to the California SIP.\39\ Also on June 8, 2023,
CARB submitted revisions to Rule 4901 that add PM2.5 NAAQS
contingency provisions that we refer to herein as the ``Residential
Wood Burning Contingency Measure.'' The District adopted the SJV
PM2.5 Contingency Measure SIP and Residential Wood Burning
Contingency Measure on May 18, 2023, and submitted them to CARB for
adoption and submission to the EPA as SIP revisions. The District
adopted the SJV PM2.5 Contingency Measure SIP and
Residential Wood Burning Contingency Measure to correct the
deficiencies identified by the EPA in the November 26, 2021
disapprovals of the contingency measure elements for the 1997 annual,
2006 24-hour, and 2012 annual PM2.5 NAAQS and the previously
adopted contingency provisions of Rule 4901. In this document, we are
proposing action on both the SJV PM2.5 Contingency Measure
SIP and the Residential Wood Burning Contingency Measure.
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    \39\ CARB adopted the SJV PM2.5 Contingency Measure
SIP and Residential Wood Burning Contingency Measure as SIP
revisions on June 7, 2023, through Executive Order S-23-010 and
submitted the SIP revisions to the EPA electronically on June 8,
2023, as attachments to a letter dated June 7, 2023, from Steven S.
Cliff, Ph.D., Executive Officer, CARB to Martha Guzman, Regional
Administrator, EPA Region IX.
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    The June 8, 2023 SIP submission includes the two specific SIP
revisions (i.e., the SJV PM2.5 Contingency Measure SIP and
the Residential Wood Burning Contingency Measure), as well as
supporting material including the resolutions of adoption, CARB
evaluation and completeness forms, and evidence of public notice and
hearing. The SJV PM2.5 Contingency Measure SIP includes a
general discussion of contingency measures and related requirements and
guidance, context for this particular SIP revision, and feasibility
analyses developed by the District and CARB to identify potential
contingency measures for the PM2.5 NAAQS for the San Joaquin
Valley. (In our evaluation of the latter, we refer to the State's
feasibility analyses herein as infeasibility demonstrations.) The SJV
PM2.5 Contingency Measure SIP includes appendices that
provide further detailed information and documentation for, among other
things, the emissions reductions estimated for the Residential Wood
Burning Contingency Measure. The District also attached excerpts from
certain previously submitted SIPs to provide support for the
conclusions drawn by the District and CARB with respect to the
infeasibility of adopting additional contingency measures for the San
Joaquin Valley. The June 8, 2023 SIP submission of the SJV
PM2.5 Contingency Measure SIP and Residential Wood Burning
Contingency Measure was deemed administratively complete by operation
of law on December 8, 2023, consistent with CAA section 110(k)(1).\40\
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    \40\ In addition, see EPA Region IX SIP Completeness Checklist,
October 13, 2023.
---------------------------------------------------------------------------

    Through adoption of the SJV PM2.5 Contingency Measure
SIP, the District committed to evaluating revisions to a specific
fugitive dust rule, District Rule 8051 (``Open Areas''), for potential
as a second contingency measure for the PM2.5 NAAQS for the
SJV.\41\ On September 21, 2023, the District adopted revisions to Rule
8051 to add contingency provisions that we refer to herein as the
``Rural Open Areas Contingency Measure.'' The District adopted the
Rural Open Areas Contingency Measure to supplement the SJV
PM2.5 Contingency Measure SIP by providing additional
emissions reductions for the San Joaquin Valley if triggered by one of
the contingency events. On October 16, 2023, CARB submitted the Rural
Open Areas Contingency Measure to the EPA as a revision to the
California SIP.\42\ In this document, we are also proposing action on
the Rural Open Areas Contingency Measure.
---------------------------------------------------------------------------

    \41\ SJV PM2.5 Contingency Measure SIP, pp. 31-32.
    \42\ CARB adopted the Rural Open Areas Contingency Measure as a
SIP revision on October 13, 2023, through Executive Order S-23-014
and submitted the SIP revision to the EPA electronically on October
16, 2023, as an attachment to a letter dated October 13, 2023, from
Steven S. Cliff, Ph.D., Executive Officer, CARB to Martha Guzman,
Regional Administrator, EPA Region IX.
---------------------------------------------------------------------------

    The October 16, 2023 SIP submission includes the SIP revision
itself (i.e., the Rural Open Areas Contingency Measure) as well as
supporting material including the resolutions of adoption, CARB
evaluation and completeness forms, and evidence of public notice and
hearing. The EPA has reviewed the October 16, 2023 SIP submission of
the Rural Open Areas Contingency Measure and finds it to be
administratively complete for the purposes of CAA section 110(k)(1),
effective upon publication of this proposed rule.\43\
---------------------------------------------------------------------------

    \43\ EPA Region IX SIP Completeness Checklist, October 18, 2023.
---------------------------------------------------------------------------

B. Evaluation for Compliance With SIP Revision Procedural Requirements

    Under CAA section 110(l), SIP revisions must be adopted by the
state, and the state must provide for reasonable public notice and
hearing prior to adoption. Pursuant to 40 CFR 51.102, states must
provide at least 30-days' notice of any public hearing to be held on a
proposed SIP revision. States must provide the opportunity to submit
written comments and allow the public the opportunity to request a
public hearing within that period.\44\
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    \44\ In addition to establishing procedural requirements for SIP
revisions, CAA section 110(l) prohibits the EPA from approving any
SIP revision that would interfere with any applicable requirement
for reasonable further progress (RFP) or attainment or any other
applicable requirement of the CAA. In this instance, the Residential
Wood Burning Contingency Measure and the Rural Open Areas
Contingency Measure would provide emissions reductions beyond those
needed for RFP and attainment of the NAAQS in San Joaquin Valley
and, thus, would not interfere with the RFP and attainment
demonstrations for the area.

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

    The District adopted the SJV PM2.5 Contingency Measure
SIP and the Residential Wood Burning Contingency Measure on May 18,
2023, through Resolution No. 2023-5-7, following a public hearing held
on the same day. Prior to adoption, the District published notice of
the May 18, 2023 public hearing in newspapers of general circulation in
each of the eight counties that comprise the San Joaquin Valley, and
provided more than 30 days for submission of written comments. CARB
subsequently adopted the SJV PM2.5 Contingency Measure SIP
and the Residential Wood Burning Contingency Measure as a revision to
the SIP on June 7, 2023, through Executive Order S-23-010. CARB then
submitted the SJV PM2.5 Contingency Measure SIP and the
Residential Wood Burning Contingency Measure to the EPA on June 8,
2023, as an attachment to a transmittal letter dated June 7, 2023.
    The District adopted the Rural Open Areas Contingency Measure on
September 21, 2023, through Resolution No. 2023-9-9, following a public
hearing held on the same day. Prior to adoption, the District published
notice of the September 21, 2023 public hearing in newspapers of
general circulation in each of the eight counties that comprise the San
Joaquin Valley, and provided more than 30 days for submission of
written comments. CARB subsequently adopted the Rural Open Areas
Contingency Measure as a revision to the SIP on October 13, 2023,
through Executive Order S-23-014. CARB then submitted the Rural Open
Areas Contingency Measure to the EPA on October 16, 2023, as an
attachment to a transmittal letter dated October 13, 2023.
    Based on the materials provided in the June 8, 2023 and October 16,
2023 SIP submissions, we propose to find that the District and the CARB
have met the procedural requirements for adoption and submission of SIP
revisions under CAA section 110(l) and 40 CFR 51.102.

III. Contingency Measure Requirements, Guidance, and Legal Precedent

    The EPA first provided its views on the CAA's requirements for
particulate matter plans under part D, title I of the Act in the
following guidance documents: (1) ``State Implementation Plans; General
Preamble for the Implementation of Title I of the Clean Air Act
Amendments of 1990'' (``General Preamble''); \45\ (2) ``State
Implementation Plans; General Preamble for the Implementation of Title
I of the Clean Air Act Amendments of 1990; Supplemental''; \46\ and (3)
``State Implementation Plans for Serious PM-10 Nonattainment Areas, and
Attainment Date Waivers for PM-10 Nonattainment Areas Generally;
Addendum to the General Preamble for the Implementation of Title I of
the Clean Air Act Amendments of 1990'' (``General Preamble
Addendum'').\47\ More recently, in the PM2.5 SIP
Requirements Rule, the EPA established regulatory requirements and
provided further interpretive guidance on the statutory SIP
requirements that apply to areas designated nonattainment for all
PM2.5 NAAQS.\48\
---------------------------------------------------------------------------

    \45\ 57 FR 13498 (April 16, 1992).
    \46\ 57 FR 18070 (April 28, 1992).
    \47\ 59 FR 41998 (August 16, 1994).
    \48\ 81 FR 58010.
---------------------------------------------------------------------------

A. Statutory and Regulatory Requirements

    Under CAA section 172(c)(9), states required to make an attainment
plan SIP submission must include contingency measures to be implemented
if the area fails to meet RFP (``RFP contingency measures'') or fails
to attain the NAAQS by the applicable attainment date (``attainment
contingency measures''). Under the PM2.5 SIP Requirements
Rule, states must include contingency measures that provide that the
state will implement them following a determination by the EPA that the
state has failed: (1) to meet any RFP requirement in the approved SIP;
(2) to meet any quantitative milestone (QM) in the approved SIP; (3) to
submit a required QM report; or (4) to attain the applicable
PM2.5 NAAQS by the applicable attainment date.\49\
Contingency measures must be fully adopted rules or control measures
that are ready to be implemented quickly upon failure to meet RFP or
failure of the area to meet the relevant NAAQS by the applicable
attainment date.\50\ In general, we expect all actions needed to effect
full implementation of the measures to occur within 60 days after the
EPA notifies the state of a failure to meet RFP or to attain.\51\
Moreover, we expect the additional emissions reductions from the
contingency measures to be achieved within a year of the triggering
event.\52\
---------------------------------------------------------------------------

    \49\ 40 CFR 51.1014(a).
    \50\ 81 FR 58010, 58066 and General Preamble Addendum, 42015.
    \51\ 81 FR 58010, 58066. See also General Preamble 13512, 13543-
13544, and General Preamble Addendum, 42014-42015.
    \52\ General Preamble, 13511.
---------------------------------------------------------------------------

    The purpose of contingency measures is to continue progress in
reducing emissions while a state revises its SIP to meet the missed RFP
requirement or to correct ongoing nonattainment. Neither the CAA nor
the EPA's implementing regulations establish a specific level of
emission reductions that implementation of contingency measures must
achieve, but the EPA recommends that contingency measures should
provide for emission reductions equivalent to approximately one year of
reductions needed for RFP in the nonattainment area.\53\ For
PM2.5 NAAQS SIP planning purposes, the EPA recommends that
RFP should be calculated as the overall level of reductions needed to
demonstrate attainment divided by the number of years from the base
year to the attainment year.\54\ As part of the attainment plan SIP
submission, the EPA expects states to explain the amount of anticipated
emissions reductions that the contingency measures will achieve. In the
event that a state is unable to identify and adopt contingency measures
that will provide for approximately one year's worth of emissions
reductions, then EPA recommends that the state provide a reasoned
justification why the smaller amount of emissions reductions is
appropriate.\55\
---------------------------------------------------------------------------

    \53\ 81 FR 58010, 58066. See also General Preamble, 13511,
13543-13544, and General Preamble Addendum, 42014-42015.
    \54\ 81 FR 58010, 58066.
    \55\ 81 FR 58010, 58067.
---------------------------------------------------------------------------

    To satisfy the contingency measure requirements of 40 CFR 51.1014,
the contingency measures adopted as part of a PM2.5 NAAQS
attainment plan must consist of control measures for the area that are
not otherwise required to meet other attainment plan requirements
(e.g., to meet reasonably available control measure (RACM)/reasonably
available control technology (RACT) requirements). By definition,
contingency measures are measures that are over and above what a state
must adopt and impose to meet RFP and to provide for attainment by the
applicable attainment date.
    Contingency measures serve the purpose of providing additional
emission reductions during the period after a failure to meet RFP or
failure to attain as the state prepares a new SIP submission to rectify
the problem. Accordingly, contingency measures must provide such
additional emission reductions during an appropriate period and must
specify the timeframe within which their requirements would become
effective following any of the EPA determinations specified in 40 CFR
51.1014(a).

    In addition, to comply with CAA section 172(c)(9), contingency
measures must be both conditional and prospective, so that they will go
into effect and achieve emission reductions only in the event of a
future triggering event such as a failure to meet RFP or a failure to
attain. In a 2016 decision called Bahr v. EPA,\56\ the Ninth Circuit
Court of Appeals held that CAA section 172(c)(9) does not allow EPA
approval of already-implemented control measures as contingency
measures. Thus, already-implemented measures cannot serve as
contingency measures under CAA section 172(c)(9). For purposes of the
PM2.5 NAAQS, a state must develop, adopt, and submit one or
more contingency measures to be triggered upon a failure to meet any
RFP requirement, failure to meet a quantitative milestone requirement,
or failure to attain the NAAQS by the applicable attainment date,
regardless of the extent to which already-implemented measures would
achieve surplus emission reductions beyond those necessary to meet RFP
or quantitative milestone requirements and beyond those predicted to
achieve attainment of the NAAQS.
---------------------------------------------------------------------------

    \56\ Bahr v. EPA, 836 F.3d 1218, 1235-1237 (9th Cir. 2016). See
also Sierra Club v. EPA, 21 F.4th 815, 827-28 (D.C. Cir. 2021).
---------------------------------------------------------------------------

    In a recent decision on the EPA's approval of a SIP contingency
measure element for the ozone NAAQS, the Ninth Circuit Court of Appeals
held that, under the EPA's current guidance, the surplus emissions
reductions from already-implemented measures cannot be relied upon to
justify the approval of a contingency measure that would achieve far
less than one year's worth of RFP as sufficient by itself to meet the
contingency measure requirements of CAA sections 172(c)(9) and
182(c)(9) for the nonattainment area.\57\
---------------------------------------------------------------------------

    \57\ Assoc. of Irritated Residents v. EPA, 10 F.4th 937, 946-47
(9th Cir. 2021) (``AIR v. EPA'' or ``AIR'').
---------------------------------------------------------------------------

B. Draft Revised Contingency Measure Guidance

    In March 2023, the EPA published notice of availability announcing
a new draft guidance addressing the contingency measures requirement of
section 172(c)(9), entitled ``Draft: Guidance on the Preparation of
State Implementation Plan Provisions that Address the Nonattainment
Area Contingency Measure Requirements for Ozone and Particulate Matter
(DRAFT--3/17/23--Public Review Version)'' (herein referred to as the
``Draft Revised Contingency Measure Guidance'') and opportunity for
public comment.\58\ The principal differences between the draft revised
guidance and existing guidance on contingency measures relate to the
EPA's recommendations concerning the specific amount of emission
reductions that implementation of contingency measures should achieve,
and the timing for when the emissions reductions from the contingency
measures should occur. The Draft Revised Contingency Measure Guidance
also provides recommended procedures for developing a demonstration, if
applicable, that the area lacks sufficient feasible measures to achieve
one year's worth of reductions, building on existing guidance that the
state provide a reasoned justification why the smaller amount of
emissions reductions is appropriate.
---------------------------------------------------------------------------

    \58\ 88 FR 17571 (March 23, 2023). The Draft Revised Contingency
Measure Guidance is available at https://www.epa.gov/air-quality-implementation-plans/draft-contingency-measures-guidance.
---------------------------------------------------------------------------

    Under the Draft Revised Contingency Measure Guidance, the
recommended level of emissions reductions that contingency measures
should achieve would represent one year's worth of ``progress'' as
opposed to one year's worth of RFP.\59\ One year's worth of
``progress'' is calculated by determining the average annual reductions
between the base year emissions inventory and the projected attainment
year emissions inventory, determining what percentage of the base year
emissions inventory this amount represents, then applying that
percentage to the projected attainment year emissions inventory to
determine the amount of reductions needed to ensure ongoing progress if
contingency measures are triggered.
---------------------------------------------------------------------------

    \59\ Draft Revised Contingency Measure Guidance, p. 22.
---------------------------------------------------------------------------

    With respect to the time period within which reductions from
contingency measures should occur, the EPA previously recommended that
contingency measures take effect within 60 days of being triggered, and
that the resulting emission reductions generally occur within one year
of the triggering event. Under the Draft Revised Contingency Measure
Guidance, in instances where there are insufficient contingency
measures available to achieve the recommended amount of emissions
reductions within one year of the triggering event, the EPA believes
that contingency measures that provide reductions within up to two
years of the triggering event would be appropriate to consider towards
achieving the recommended amount of emissions reductions. The Draft
Revised Contingency Measure Guidance does not alter the 60-day
recommendation for the contingency measures to take initial effect.
    If, after adequately evaluating additional control measures, the
state is unable to identify contingency measures that would provide
approximately one year's worth of emissions reductions, the Draft
Revised Contingency Measure Guidance recommends that the state should
provide a reasoned justification (referred to herein as an
``infeasibility demonstration'') that explains and documents how it has
evaluated all existing and potential control measures relevant to the
appropriate source categories and pollutants in the nonattainment area
and has reached reasonable conclusions regarding whether such measures
are feasible.\60\
---------------------------------------------------------------------------

    \60\ Draft Revised Contingency Measure Guidance, p. 29.
---------------------------------------------------------------------------

    As explained in the Draft Revised Contingency Measure Guidance,
while the EPA notes that CAA section 172(c)(9) and section 182(c)(9) do
not explicitly provide for consideration of whether specific measures
are feasible, the Agency believes that it is reasonable to infer that
the statute does not require control measures regardless of any
technological or cost constraints whatsoever.\61\ It is more reasonable
to interpret the contingency measure requirement not to require air
agencies to adopt and impose infeasible measures. The statutory
provisions applicable to other nonattainment area plan control measure
requirements, including RACM/RACT (for ozone and PM), best available
control measure (BACM)/best available control technology (BACT) (for
PM), and most stringent measures (MSM) (for PM), allow air agencies to
exclude certain control measures that are deemed unreasonable or
infeasible (depending on the requirement). For example, the MSM
provision in CAA section 188(e) requires plans to include ``the most
stringent measures that are included in the implementation plan of any
state or are achieved in practice in any state, and can feasibly be
implemented in the area.'' The EPA considers it reasonable to conclude
that Congress similarly did not expect air agencies to satisfy the
contingency measure requirement with infeasible measures. Thus, the EPA
anticipates that a demonstrated lack of feasible measures would be a
reasoned justification for adopting contingency measures that only
achieve a lesser amount of emission reductions.
---------------------------------------------------------------------------

    \61\ Id.

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

IV. EPA Review of San Joaquin Valley Contingency Measures

    We provide our review of two specific contingency measures--the
Residential Wood Burning Contingency Measure and the Rural Open Areas
Contingency Measure--in sections IV.A and IV.B of this document,
respectively. As noted previously, we are reviewing and proposing
approval of a third contingency measure, the Smog Check Contingency
Measure,\62\ in a separate rulemaking; \63\ however, we provide a
summary of the Smog Check Contingency Measure in section IV.C for
informational purposes. Because we are proposing approval of the
contingency measures, we take into account the measures' anticipated
emission reductions in our evaluation of the SJV PM2.5
Contingency Measure SIP, which we present in section V of this proposed
rule.
---------------------------------------------------------------------------

    \62\ CARB, ``California Smog Check Contingency Measure State
Implementation Plan Revision,'' release date September 15, 2023,
(``Smog Check Contingency Measure'').
    \63\ EPA, ``Air Plan Revision; California; Motor Vehicle
Inspection and Maintenance Program Contingency Measure,'' Proposed
rule, published in this Federal Register.
---------------------------------------------------------------------------

A. Residential Wood Burning Contingency Measure

1. Background and Regulatory History
    Residential wood burning includes wood-burning heaters (i.e.,
woodstoves, pellet stoves, and wood-burning fireplace inserts), which
are used primarily for heat generation, and wood-burning fireplaces,
which are used primarily for aesthetic purposes. All of these devices
emit direct PM2.5 and NOX. However, wood-burning
heaters, that are certified under the EPA's New Source Performance
Standards (NSPS) emit lower levels of PM2.5 compared to
wood-burning fireplaces and non-certified heaters when properly
installed, operated, and maintained.
    Residential wood-burning is included within the ``Residential Fuel
Combustion'' emissions inventory category within the 2018
PM2.5 Plan's emissions inventories. In the 2018
PM2.5 Plan, the District estimates emissions of 2.82 tons
per day (tpd) of PM2.5 and 0.42 tpd NOX (annual
average) specifically from residential wood burning for each year from
2017 onward. However, these estimates do not account for the effect of
2019 amendments to Rule 4901, discussed in the following section of
this document.
    Rule 4901 (``Wood Burning Fireplaces and Wood Burning Heaters'')
establishes requirements for the sale/transfer, operation, and
installation of wood-burning devices and on the advertising of wood for
sale intended for burning in a wood-burning fireplace, wood-burning
heater, or outdoor wood-burning device within the San Joaquin Valley.
One of the most effective ways to reduce wintertime smoke is a
curtailment program that restricts use of wood-burning heaters and
fireplaces on days that are conducive to buildup of PM concentrations
(i.e., days where ambient PM2.5 and/or PM10
concentrations are forecast to be above a particular level, known as a
``curtailment threshold'').
    Rule 4901 includes a tiered mandatory curtailment program that
establishes different curtailment thresholds based on the type of
devices (i.e., registered clean-burning devices \64\ vs. unregistered
devices) and different counties (i.e., hot spot vs. non-hot spot).
During a Level One Episodic Wood Burning Curtailment, operation of
wood-burning fireplaces and other unregistered wood-burning heaters or
devices is prohibited, but properly operated, registered wood-burning
heaters may be used.\65\ During a Level Two Episodic Wood Burning
Curtailment, operation of any wood-burning device is prohibited.\66\
However, the rule includes an exemption from the curtailment provisions
for (1) locations where piped natural gas service is not available and
(2) residences for which a wood-burning fireplace or wood-burning
heater is the sole available source of heat.\67\
---------------------------------------------------------------------------

    \64\ In order to be registered, a device must either be
certified under the NSPS at time of purchase or installation and at
least as stringent as Phase II requirements or be a pellet-fueled
wood burning heater exempt from EPA certification requirements at
the time of purchase or installation (Rule 4901, section 5.9.1). The
rule includes requirements for documentation and inspection to
verify compliance with these standards (Rule 4901, sections 5.9.2
and 5.10).
    \65\ Rule 4901, section 5.7.1.
    \66\ Rule 4901, section 5.7.2.
    \67\ Rule 4901, section 5.7.4.
---------------------------------------------------------------------------

    In order to implement the curtailment program under Rule 4901, the
District develops daily air quality forecasts, based on EPA and CARB
guidance, which include a projection of the maximum PM2.5
concentration in each county for the following day.\68\ District staff
then compare this maximum county PM2.5 concentration
forecast with the curtailment thresholds in Rule 4901. If a county's
PM2.5 forecast exceeds the applicable threshold, then the
District's Air Pollution Control Officer declares a curtailment for the
county for the following day.
---------------------------------------------------------------------------

    \68\ Email dated October 9, 2019, from Jon Klassen, SJVUAPCD to
Meredith Kurpius, EPA Region IX, Subject: ``RE: Info to support Rule
4901.''
---------------------------------------------------------------------------

    In 2019, the District lowered the curtailment thresholds in Madera,
Fresno, and Kern counties, which the District identified as ``hot
spot'' counties, because they were ``either new areas of gas utility or
areas deemed to have persistently poor air quality.'' \69\ Table 1
presents the residential curtailment thresholds in Rule 4901, as
revised in 2019.
---------------------------------------------------------------------------

    \69\ 2018 PM2.5 Plan, Appendix J, 60.

  Table 1--Residential Wood Burning Curtailment Thresholds in Rule 4901
                          [As amended in 2019]
------------------------------------------------------------------------
                                                         Non-hot spot
                                                         counties (San
      Episodic wood burning        Hot spot counties       Joaquin,
       curtailment levels          (Madera, Fresno,       Stanislaus,
                                       and Kern)      Merced, Kings, and
                                                            Tulare)
------------------------------------------------------------------------
Level One (No Burning Unless      12 [mu]g/m\3\.....  20 [mu]g/m\3\.
 Registered).
Level Two (No Burning for All)..  35 [mu]g/m\3\.....  65 [mu]g/m\3\.
------------------------------------------------------------------------

    The 2019 revision by the District also added a provision to the
rule to operate as a contingency measure, which would lower the
curtailment thresholds for any county that failed to attain the
applicable standards to levels consistent with current thresholds for
hot spot counties. However, the EPA disapproved this provision because
it did not meet all of the CAA requirements for contingency
measures.\70\ Specifically, it did not address three of the four
required triggers for contingency measures in 40 CFR 51.1014(a) and was
not structured to achieve any additional emissions reductions if the
EPA found that the monitoring locations in the ``hot spot''

counties (i.e., Fresno, Kern, or Madera) were the only counties in the
San Joaquin Valley that are violating the applicable PM2.5
NAAQS as of the attainment date.\71\ In addition, with respect to the
1997 annual PM2.5 NAAQS in particular, the EPA also
disapproved the contingency provision in Rule 4901 because the EPA was
concurrently disapproving the RFP and attainment demonstrations and,
thus, was unable to determine whether the emissions reductions from the
contingency provision were in fact surplus to the reductions that would
be needed to provide for RFP and attainment for the 1997 annual
PM2.5 NAAQS in the SJV.\72\ Accordingly, the SIP-approved
version of Rule 4901 does not include any contingency provision.
---------------------------------------------------------------------------

    \70\ 86 FR 67329, 67338 (for the 1997 annual PM2.5
NAAQS) and 86 FR 67343, 67345 (for the 2006 24-hour PM2.5
NAAQS and 2012 annual PM2.5 NAAQS).
    \71\ Id. See also 86 FR 38652, 38669 (proposed rule on
contingency measures element for the 1997 annual PM2.5
NAAQS) and 86 FR 49100, 49125 and 49133-49134 (proposed rule on
contingency measures element for the 2012 annual PM2.5
NAAQS and 2006 24-hour PM2.5 NAAQS, respectively).
    \72\ 86 FR 67329, 67338.
---------------------------------------------------------------------------

2. Summary of State Submission
    On May 18, 2023, the District amended the contingency measure in
section 5.7.3 of Rule 4901, and CARB submitted the amended rule as part
of the June 8, 2023 SIP Submission. The contingency measure would be
triggered by a final determination by the EPA that the District failed
to meet one or more of the following triggering events for the
applicable PM2.5 NAAQS:
    (1) Any Reasonable Further Progress requirement;
    (2) Any quantitative milestone;
    (3) Submission of a quantitative milestone report; or
    (4) Attainment of the applicable PM2.5 NAAQS by the
applicable attainment date.
    Following the first such triggering event, the measure would lower
the thresholds for the non-hot spot counties to the current thresholds
for hot spot counties (i.e., from 20 [mu]g/m\3\ to 12 [mu]g/m\3\ for
unregistered devices; and from 65 [mu]g/m\3\ to 35 [mu]g/m\3\ for
registered devices). Following the second such event, the measure would
further lower the threshold for unregistered devices in all counties of
the San Joaquin Valley from 12 [mu]g/m\3\ to 11 [mu]g/m\3\.
    The District estimates that the Residential Wood Burning
Contingency Measure for the first triggering event would achieve annual
average emissions reductions of 0.5793 tpd direct PM2.5 and
0.0817 tpd NOX in the SJV and the second triggering event
would achieve additional reductions of 0.1078 tpd direct
PM2.5 and 0.0148 tpd NOX.\73\
---------------------------------------------------------------------------

    \73\ SJV PM2.5 Contingency Measure SIP, p. C-15.
---------------------------------------------------------------------------

3. EPA Evaluation
    Through the revisions adopted by the District to Rule 4901 on May
18, 2023, the District has corrected the deficiencies in the
contingency provision of Rule 4901 that we identified in our November
26, 2021 final actions. Namely, the contingency provision in the rule
(section 5.7.3) has been revised to address all the determinations for
which contingency measures are required under 40 CFR 51.1014(a) and has
been revised to achieve emissions reductions under all circumstances,
i.e., if triggered by one of the specific EPA determinations. In
addition, we find that the contingency provision in section 5.7.3 of
Rule 4901 is surplus to the RFP and attainment demonstrations for the
annual 1997 PM2.5 NAAQS based on the conclusions in our
recent final action approving the RFP and attainment demonstrations in
the State's 15 [mu]g/m\3\ SIP Revision.\74\
---------------------------------------------------------------------------

    \74\ EPA, ``Air Quality State Implementation Plans; Approvals
and Promulgations: California; 1997 Annual Fine Particulate Matter
Serious and Clean Air Act Section 189(d) Nonattainment Area
Requirements; San Joaquin Valley, CA,'' Final rule, signed December
5, 2023.
---------------------------------------------------------------------------

    In our previous actions, we found that the contingency provision in
Rule 4901 met the other specific criteria used to evaluate contingency
measures.\75\ Specifically, the contingency provision in Rule 4901 (the
Residential Wood Burning Contingency Measure) is structured to be both
conditional and prospective, to be implemented quickly following a
triggering event (i.e., within 60 days) and to be implemented without
significant further action by the State or the EPA. The revisions to
section 5.7.3 of Rule 4901 that were adopted on May 18, 2023 do not
affect those features of the contingency provision, and thus we propose
to re-affirm those findings in this proposed rule.
---------------------------------------------------------------------------

    \75\ See, e.g., 86 FR 38652, 38669.
---------------------------------------------------------------------------

    We also note that the contingency provisions do not require the
replacement or installation of an emissions control device and can
therefore achieve emission reductions upon the rule taking effect. For
example, if the EPA were to determine that the San Joaquin Valley
failed to attain a given PM2.5 NAAQS, effective in July of a
given year, the more stringent curtailment thresholds would take effect
in September of that year, prior to the seasonal start of the No Burn
Day program on November 1st. Thus, the emission reductions from the
Residential Wood Burning Contingency Measure would be achieved within
one year of the triggering event. Based on our review of the
contingency provisions, as revised, we propose to re-affirm those
findings.
    Contingency measures must also be designed to provide emissions
reductions (if triggered) that are not otherwise required to meet other
attainment plan requirements and not relied upon to demonstrate RFP and
attainment. In this regard, we note that none of the SJV plans for the
1997 annual, 2006 24-hour, and 2012 annual PM2.5 NAAQS
relied upon the contingency provision in Rule 4901 to meet any plan
element (other than the contingency measure element) and that none of
the plans relied on the related emissions reductions from the
contingency provision to provide for RFP or attainment. Based on our
previous approvals of the San Joaquin Valley plans for the 2006 24-hour
PM2.5 NAAQS in 2020 and 2012 annual PM2.5 NAAQS
in 2021,\76\ and the recent approval of the San Joaquin Valley plan for
the 1997 annual PM2.5 NAAQS, including the various plan
elements such as the BACM, RFP, and attainment demonstrations, we find
that the Residential Wood Burning Contingency Measure is not otherwise
required for these PM2.5 NAAQS and that the associated
emissions reductions would be surplus to the PM2.5-related
RFP and attainment needs of the San Joaquin Valley.
---------------------------------------------------------------------------

    \76\ 85 FR 44192 and 86 FR 67343.
---------------------------------------------------------------------------

    Therefore, for the reasons provided in the preceding paragraphs, we
propose to approve Rule 4901, as revised, because we find that the
Residential Wood Burning Contingency Measure set forth in section 5.7.3
of the rule now meets all the applicable requirements for a contingency
measure for the San Joaquin Valley for the 1997 annual, 2006 24-hour,
and 2012 annual PM2.5 NAAQS.
    Lastly, we reviewed the emissions reduction estimates for the
Residential Wood Burning Contingency Measure that were prepared by the
District and included in Appendix C (``Emission Reduction Analysis for
Rule 4901'') of the SJV PM2.5 Contingency Measure SIP and
find the estimates to be reasonable and adequately documented. As
described in Appendix C of the SJV PM2.5 Contingency Measure
SIP, the District has estimated the reductions from the two triggering
events provided for in the Residential Wood Burning Contingency Measure
by taking into account many different factors, such as the number of
fireplaces and wood stoves in the individual counties within

the San Joaquin Valley, the different types of wood stoves (registered
and unregistered, certified and uncertified), and the number of
additional curtailment days under various scenarios, among other
factors. Taking into account these various factors, the District
estimates the Residential Wood Burning Contingency Measure would
achieve annual average emissions reductions of 0.5793 tpd direct
PM2.5 and 0.0817 tpd NOX in the SJV following the
first triggering event and additional reductions of 0.1078 tpd direct
PM2.5 and 0.0148 tpd NOX following the second
triggering event.
    Because we are proposing to find that the Residential Wood Burning
Contingency Measure meets the requirements for individual contingency
measures, the associated emissions reductions can be taken into account
by the EPA when determining whether CARB and the District have met the
requirements for the San Joaquin Valley as a whole with respect to the
contingency measure SIP requirements of CAA section 172(c)(9) and 40
CFR 51.1014 for PM2.5 nonattainment areas. Section V of this
document presents our evaluation of the SJV PM2.5
Contingency Measure SIP for compliance with these requirements for the
San Joaquin Valley for the 1997 annual, 2006 24-hour, and 2012 annual
PM2.5 NAAQS, and, as part of that evaluation, we have taken
into account the District's estimates of emissions reductions from the
Residential Wood Burning Contingency Measure.

B. Rural Open Areas Contingency Measure

1. Background and Regulatory History
    In areas where there is open, uncovered land, a natural crust will
form and minimize dust emissions. However, activities such as
earthmoving activities, material dumping, weed abatement, and vehicle
traffic will disturb otherwise naturally stable land and allow
windblown fugitive dust emissions to occur.
    The District adopted fugitive dust control requirements in
Regulation VIII (containing the 8000 series rules) on November 15,
2001, to address RACM/RACT and BACM/BACT attainment plan requirements
for the 1987 p.m.10 NAAQS.\77\ The EPA found that new
provisions in Regulation VIII ``significantly strengthened'' the prior
existing rules by tightening standards, covering more activities, and
adding more requirements to control dust-producing activities.\78\
Subsequently, the District adopted amendments to Regulation VIII on
August 19, 2004, and September 16, 2004, that the EPA approved into the
San Joaquin Valley portion of the California SIP in 2006.\79\ More
recently the EPA has reviewed Regulation VIII for RACM/RACT, BACM/BACT,
and MSM requirements in acting on the San Joaquin Valley plan for the
2006 24-hour PM2.5 NAAQS.\80\
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    \77\ Regulation VIII includes eight rules. Rule 8011 (``General
Requirements'') provides definitions and the general requirements on
which the seven other rules rely. In turn, those seven rules apply
to different sources of fugitive windblown dust based on activity
type. They include Rule 8021 (``Construction, Demolition,
Excavation, Extraction, and Other Earthmoving Activities''), Rule
8031 (``Bulk Materials''), Rule 8041 (``Carryout and Trackout''),
Rule 8051 (``Open Areas''), Rule 8061 (``Paved and Unpaved Roads''),
Rule 8071 (Unpaved Vehicle/Equipment Traffic Area''), and Rule 8081
(``Agricultural Sources''). In this proposed rule, the EPA proposes
to approve Rule 8051, as amended to include a contingency provision,
as a revision to the California SIP.
    \78\ 67 FR 15345, 15346-15447 (April 1, 2002) (proposed rule on
2001 version of Regulation VIII).
    \79\ 71 FR 8461 (February 17, 2006).
    \80\ See, e.g., 85 FR 17382, 17431 (March 27, 2020) (proposal on
BACM/BACT and MSM for the 2006 24-hour PM2.5 NAAQS); and
EPA Region IX, ``Technical Support Document, EPA Evaluation of BACM/
MSM, San Joaquin Valley PM2.5 Plan for the 2006
PM2.5 NAAQS,'' February 2020.
---------------------------------------------------------------------------

    Among the rules of Regulation VIII, Rule 8051 (``Open Areas'')
applies to vacant portions of residential and commercial lots and
contiguous parcels and the 2004 amendments added applicability
thresholds for rural and urban areas required to meet both the
conditions for a stabilized surface (defined in Rule 8011) and a 20%
opacity standard. Rule 8051 applies to any open area having 0.5 acres
or more within urban areas, or 3.0 acres or more within rural areas,
that contains at least 1,000 square feet of disturbed surface area.\81\
In addition, under Rule 8051, upon evidence of vehicle trespass,
owners/operators must apply a measure(s) that effectively prevents
access to the lot. Rule 8051 does not apply to agricultural areas,
which are subject to other fugitive dust controls such as those under
Rule 4550 (``Conservation Management Practices'') and Rule 8081
(``Agricultural Sources'').
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    \81\ Rule 8051, section 2.1.
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2. Summary of State Submission
    On September 21, 2023, the District adopted a new contingency
measure in section 7.0 of District Rule 8051 (referred to herein as the
``Rural Open Areas Contingency Measure''), and CARB submitted Rule
8051, as amended, to include the Rural Open Areas Contingency Measure,
as a supplement to the SJV PM2.5 Contingency Measure SIP.
The Rural Open Areas Contingency Measure would be triggered by a final
determination by the EPA that the District failed to meet one or more
of the following triggering events for the applicable PM2.5
NAAQS:
    (1) Any Reasonable Further Progress requirement;
    (2) Any quantitative milestone;
    (3) Submission of a quantitative milestone report; or
    (4) Attainment of the applicable PM2.5 NAAQS by the
applicable attainment date.
    The Rural Open Areas Contingency Measure would lower the
applicability threshold for rural open areas from 3.0 acres to 1.0
acres, thereby reducing windblown fugitive dust, including the direct
PM2.5 portion of such dust emissions. The State estimates
that the newly subject total acreage would be 18,816 acres. The Rural
Open Areas Contingency Measure would be effective 60 days after an EPA
determination under 40 CFR 51.1014(a) that triggers contingency
measures. At such time, Rule 8051 would require any rural open area
having 1.0 acre or more and containing at least 1,000 square feet of
disturbed surface area (notwithstanding exemptions in section 4.0 of
the rule) to meet section 5.0 of the rule, which requires that:

    Whenever open areas are disturbed or vehicles are used in open
areas, an owner/operator shall implement one or a combination of
control measures indicated in Table 8051-1 to comply with the
conditions of a stabilized surface at all times and to limit VDE to
20% opacity. In addition to the requirements of this rule, a person
shall comply with all other applicable requirements of Regulation
VIII.\82\
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    \82\ VDE is Visible Dust Emissions.

    Table 8051-1 contains the following control measures for open
---------------------------------------------------------------------------
areas:

    A. Open Areas:
    Implement, apply, maintain, and reapply if necessary, at least
one or a combination of the following control measures to comply at
all times with the conditions for a stabilized surface and limit VDE
to 20% opacity as defined in Rule 8011:
    A1. Apply and maintain water or dust suppressant(s) to all
unvegetated areas; and/or
    A2. Establish vegetation on all previously disturbed areas; and/
or
    A3. Pave, apply and maintain gravel, or apply and maintain
chemical/organic stabilizers/suppressant(s).
    B. Vehicle Use in Open Areas:
    Upon evidence of trespass, prevent unauthorized vehicle access
by:
    Posting `No Trespassing' signs or installing physical barriers
such as fences, gates, posts, and/or other appropriate barriers to
effectively prevent access to the area.

    The Rural Open Areas Contingency Measure is narrowed by the
addition of

a new exemption in section 4.2 of Rule 8051 that exempts owners or
operators of rural parcels between 1.0 acres to 3.0 acres that
implement fire prevention activities required by a Federal, State, or
local agency by mowing or cutting (if three inches or more of stubble
remains after moving or cutting) or discing (if no more than two passes
are made).
    The District estimates that the Rural Open Burning Contingency
Measure would achieve annual average emissions reductions of 0.008 tpd
direct PM2.5.\83\
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    \83\ SJVUAPCD, Final Draft Staff Report, ``Proposed Amendments
to Rule 8051 (Open Areas),'' September 21, 2023, p. B-7.
---------------------------------------------------------------------------

3. EPA Evaluation
    As discussed further in the EPA's technical support document that
documents our evaluation of amended Rule 8051,\84\ we find that the
Rural Open Areas Contingency Measure now included as section 7.0 of
Rule 8051 meets the applicable requirements for contingency measures.
First, we note that the expansion of the control requirements to rural
parcels between one (1.0) to three (3.0) acres under section 7.0 of
Rule 8051 is conditional and prospective by design and is not required
to meet existing control requirements (i.e., RACM or BACM) \85\ nor
relied upon by the area as part of the area's PM2.5 RFP or
attainment demonstrations. Moreover, the exemption for owners or
operators of certain rural parcels of 1.0 to 3.0 acres in size from the
requirements of the rule that would otherwise be included if the Rural
Open Areas Contingency Measure were triggered is narrowly drawn and
limited such that the exemption will have essentially no impact on the
emissions reductions expected from implementation of the Rural Open
Areas Contingency Measure. This is because the exemption applies only
to owners and operators acting in response to a Federal, State, or
local agency that is requiring implementation of fire prevention
activities and is further limited by specifying the methods that must
be followed to be covered by the exemption.
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    \84\ EPA Region IX, ``Technical Support Document for EPA's
Rulemaking for the California State Implementation Plan, San Joaquin
Valley Air Pollution Control District Rule 8051 (`Open Areas'),''
December 2023.
    \85\ As noted previously, the RACM and BACM demonstrations that
the EPA has approved for the 1997 annual, 2006 24-hour, and the 2012
annual PM2.5 NAAQS included review of Regulation VIII,
including Rule 8051. See 85 FR 44192, 86 FR 67343, and EPA, ``Air
Quality State Implementation Plans; Approvals and Promulgations:
California; 1997 Annual Fine Particulate Matter Serious and Clean
Air Act Section 189(d) Nonattainment Area Requirements; San Joaquin
Valley, CA,'' Final rule, signed December 5, 2023.
---------------------------------------------------------------------------

    Second, the Rural Open Areas Contingency Measure includes a trigger
mechanism (``. . . final determination by EPA that the District has
failed to meet any of the following elements for any of the
PM2.5 NAAQS . . .'') that addresses all of the specific
types of determinations listed in 40 CFR 51.1014(a). Third, the Rural
Open Areas Contingency Measure specifies a schedule for timely
implementation (``Upon 60 days after the issuance of a final
determination . . .''). While the extension of the control requirements
to rural parcels between 1.0 to 3.0 acres under section 7.0 is self-
executing (i.e., does not require additional rulemaking), the District
will need as a practical matter to provide notice to the affected
owners/operators that the contingency measure has been triggered.
However, we do not find that providing such notice constitutes
``further action'' by the state for the purposes of CAA section
172(c)(9). Lastly, given the nature of the controls required under Rule
8051 (such as watering, establishing vegetation, applying gravel, or
fencing (if needed)), we find that the associated emissions reductions
from implementation of the Rural Open Areas Contingency Measure can be
achieved within a year of the triggering event.
    Therefore, for the reasons provided in the preceding paragraphs, we
propose to approve Rule 8051, as revised, because we find that the
Rural Open Areas Contingency Measure meets all the applicable
requirements for a contingency measure for the San Joaquin Valley for
the 1997 annual, 2006 24-hour, and 2012 annual PM2.5 NAAQS.
    We have also reviewed the emissions reduction estimates for the
Rural Open Areas Contingency Measure that were prepared by the District
and included in Appendix B (``Emission Reduction and Cost Effectiveness
Analysis for Proposed Amendments to Rule 8051 (Open Areas)'') of the
Final Draft Staff Report and find the estimates to be reasonable and
adequately documented. As documented in Appendix B of the Final Draft
Staff Report, the District took into account county-specific parcel
size data, among other relevant factors to develop the emissions
reduction estimate of 0.008 tpd of direct PM2.5 for the
Rural Open Areas Contingency Measure.\86\
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    \86\ SJVUAPCD, Final Draft Staff Report, ``Proposed Amendments
to Rule 8051 (Open Areas),'' September 21, 2023, p. B-7. The
District's estimate compares favorably with the EPA's own estimate
of 0.01 tpd for essentially the same contingency measure in EPA's
proposed PM2.5 contingency measure FIP for San Joaquin
Valley. 88 FR 53431, 53444.
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    Because we are proposing to find that the Rural Open Areas
Contingency Measure meets the requirements for individual contingency
measures, the associated emissions reductions can be taken into account
by the EPA when determining whether CARB and District have met the
requirements for the San Joaquin Valley as a whole with respect to the
contingency measure requirements of CAA section 172(c)(9) and 40 CFR
51.1014 for PM2.5 nonattainment areas. Section V of this
document presents our evaluation of the SJV PM2.5
Contingency Measure SIP for compliance with these requirements for the
San Joaquin Valley for the 1997 annual, 2006 24-hour, and 2012 annual
PM2.5 NAAQS, and, as part of that evaluation, we have taken
into account the District's estimates of emissions reductions from the
Rural Open Areas Contingency Measure.

C. Smog Check Contingency Measure

    The general purpose of motor vehicle inspection and maintenance (I/
M) programs is to reduce emissions from in-use motor vehicles in need
of repairs and thereby contribute to state and local efforts to improve
air quality and to attain the NAAQS. California has operated an I/M
program, also known as the ``Smog Check'' program, in certain areas of
the state for over 30 years. Under the current California Smog Check
program, certain vehicles are exempt from the biennial inspection
requirement, including vehicles eight or fewer model years old.
    On November 13, 2023, CARB submitted a third contingency measure
for San Joaquin Valley for the PM2.5 NAAQS, which we refer
to herein as the Smog Check Contingency Measure. Under the Smog Check
Contingency Measure, CARB would, within 30 days of the effective date
of an EPA determination that an applicable triggering event has
occurred for San Joaquin Valley for the PM2.5 NAAQS,
transmit a letter to the California Bureau of Automotive Repair and
Department of Motor Vehicles that, in effect, would narrow the newer
vehicle exemption from eight or fewer model years old to seven or fewer
model years old throughout the San Joaquin Valley.\87\ CARB estimates
that the Smog Check Contingency Measure would, after the first
triggering event and adjusting slightly for the effect on foregone
emission reductions from Carl Moyer

funding,\88\ achieve annual average emission reductions of 0.113 tpd
NOX for the 1997 annual PM2.5 NAAQS, 0.116 tpd
NOX for the 2006 24-hour PM2.5 NAAQS, and 0.083
tpd NOX for the 2012 annual PM2.5 NAAQS in the
San Joaquin Valley.\89\
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    \87\ Smog Check Contingency Measure, section 4. The Smog Check
Contingency Measure is structured to further narrow the newer
vehicle exemption by another year upon a second triggering event.
    \88\ The Carl Moyer Program distributes incentive grants to fund
the incremental cost of cleaner-than-required engines, equipment,
and other technology. The slight adjustment to emission reductions
mentioned results from a decrease in funding to the Carl Moyer
program. If the contingency measure were triggered, fewer vehicles
would be exempt from the Smog Check program, and thus fewer vehicles
would be subject to the Smog Check abatement fee (which is only
assessed on vehicles exempted from Smog Check testing). That fee
provides funding to the Carl Moyer Program. For more information on
the program, see https://ww2.arb.ca.gov/carl-moyer-program-apply.
    \89\ Smog Check Contingency Measure, Table 28 and Table 31.
---------------------------------------------------------------------------

    In a separate proposed rule published in this Federal Register, we
are proposing to approve the Smog Check Contingency Measure and,
therefore, its associated emissions reductions can be taken into
account by the EPA when determining whether the State and District have
met the contingency measure requirements of CAA section 172(c)(9) and
40 CFR 51.1014 for PM2.5 nonattainment areas for the San
Joaquin Valley as a whole. Section V of this document presents our
evaluation of the SJV PM2.5 Contingency Measure SIP for
compliance with these requirements for the San Joaquin Valley for the
1997 annual, 2006 24-hour, and 2012 annual PM2.5 NAAQS, and
as part of that evaluation, we have taken into account CARB's estimates
of emissions reductions from the Smog Check Contingency Measure.

V. EPA Review of San Joaquin Valley PM2.5 Contingency Measure Plan
Element

A. Background and Regulatory History

    In light of the nonattainment designation for San Joaquin Valley
for the PM2.5 NAAQS, the State of California was required
under CAA section 172(c)(9) and 40 CFR 51.1014 to adopt and submit a
SIP revision providing for implementation of contingency measures to
take effect in the San Joaquin Valley if the EPA determines that the
area has failed to meet an RFP requirement, failed to submit a
quantitative milestone report, failed to meet a quantitative milestone,
or failed to attain the PM2.5 NAAQS by the applicable
attainment date.
    In 2019, as discussed in section I.B of this document, CARB
submitted a SIP revision that included contingency measure plan
elements for San Joaquin Valley for the 1997 annual and 24-hour, 2006
24-hour, and 2012 annual PM2.5 NAAQS. The contingency
measure plan elements relied on an earlier version of the Residential
Wood Burning Contingency Measure and justified reliance on that single
measure notwithstanding the fact that the measure alone would not
achieve emissions reductions equivalent to one year's worth of RFP by
reference to larger planning context for the area and related surplus
emissions reductions expected to be achieved from already-implemented
control measures.
    In 2021, the EPA disapproved the contingency measure plan elements
for the applicable PM2.5 NAAQS because the plan elements did
not include a contingency measure that addressed all four triggering
events for the PM2.5 NAAQS under 40 CFR 51.1014; that would
ensure that emissions reductions would be achieved, once triggered; or,
for the 1997 annual PM2.5 NAAQS, that would be surplus to
the area's needs for RFP and attainment.\90\ We proposed disapproval of
the contingency measure elements before the Ninth Circuit's Assoc. of
Irritated Residents (AIR) v. EPA decision \91\ was published and, thus,
did not identify the contingency measure elements' reliance on surplus
emissions reductions from already-implemented measures (to justify
adoption of a single contingency measure which would not, on its own,
achieve one year's worth of RFP) as a specific deficiency.
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    \90\ 86 FR 38652, 38669-38670; and 86 FR 49100, 49124-49125 and
49133-49134.
    \91\ In AIR v. EPA, the Ninth Circuit held that, under the EPA's
current guidance, the surplus emissions reductions from already-
implemented measures cannot be relied upon to justify the approval
of a contingency measure that would achieve far less than one year's
worth of RFP as sufficient by itself to meet the contingency measure
requirements of CAA sections 172(c)(9) and 182(c)(9) for the
nonattainment area. 10 F.4th at 946-47.
---------------------------------------------------------------------------

B. Summary of State Submission

    In response to the disapprovals of the previous contingency measure
elements, the District and CARB prepared the SJV PM2.5
Contingency Measure SIP, which CARB adopted as part of the California
SIP and submitted for EPA approval on June 8, 2023. In the SJV
PM2.5 Contingency Measure SIP, the District and CARB present
their evaluation of potential contingency measures, amendments to the
previous contingency provisions in the District's residential wood
burning rule (i.e., the Residential Wood Burning Contingency Measure),
a commitment to evaluate potential contingency provisions for Rule 8051
(``Open Areas''), analysis of one year's worth of emission reductions,
and infeasibility demonstrations for rejecting other potential
contingency measures. In light of the AIR v. EPA decision, the District
and CARB do not justify the selection of the contingency measures on
the basis of surplus emissions reductions from already-implemented
measures, as had been the case previously, but rather ``due to a
scarcity of available, qualifying measures,'' and the time period in
which emission reductions should occur.\92\ Subsequent to the
submission of the SJV PM2.5 Contingency Measure SIP, the
District and CARB have supplemented the contingency measure elements
for the applicable PM2.5 NAAQS with the adoption and
submission of two additional contingency measures--the Rural Open Areas
Contingency Measure and the Smog Check Contingency Measure.
---------------------------------------------------------------------------

    \92\ SJV PM2.5 Contingency Measure SIP, p. 5.
---------------------------------------------------------------------------

1. General Considerations
    ``General Considerations,'' for the purposes of this proposed
action, includes identification of the relevant pollutants, the use of
contingency measures for more than one triggering event and for more
than one NAAQS, and the magnitude of emissions reductions. Contingency
measure feasibility analyses are addressed in a separate subsection.
a. PM2.5 and PM2.5 Precursors
    CARB and the District have concluded, based on CARB modeling, that
sulfur oxides (SOX), volatile organic compounds (VOCs), and
ammonia are not significant precursors for PM2.5 formation
in the San Joaquin Valley. Therefore, their contingency measure
submissions address sources of direct PM2.5 and
NOX emissions.

b. Using Same Contingency Measures for More Than One Triggering Event,
NAAQS

    The contingency measures that CARB and the District rely upon in
the SJV PM2.5 Contingency Measure SIP are not limited to one
PM2.5 NAAQS, but rather cover all three of the 1997 annual,
2006 24-hour, and 2012 annual PM2.5 NAAQS (i.e., the same
set of contingency measures has been submitted to address the
contingency measure requirements for more than one PM2.5
NAAQS).
c. Magnitude of Emissions Reductions
    To evaluate the sufficiency of the Residential Wood Burning
Contingency Measure with respect to the magnitude of emissions
reductions that the contingency measures should achieve, the SJV
PM2.5 Contingency Measure SIP

includes calculations of one year's worth of RFP for the relevant
PM2.5 NAAQS for the San Joaquin Valley. To do this, the
District calculated the change in annual average emission reductions
from the base year to the attainment year for the 1997 annual
PM2.5 NAAQS (from 2013 to 2023) and 2006 24-hour
PM2.5 NAAQS (from 2013 to 2024), and the outermost Moderate
area RFP year for the 2012 annual PM2.5 NAAQS (from 2013 to
2022), and divided those by the number of years between the base year
and applicable attainment or RFP year. The State's estimates of one
year's worth of RFP in the SJV PM2.5 Contingency Measure SIP
are as follows: 0.44 tpd direct PM2.5 and 16.7 tpd
NOX (for the 1997 annual PM2.5 NAAQS); 0.58 tpd
direct PM2.5 and 18.4 tpd NOX (for the 2006 24-
hour PM2.5 NAAQS); and 0.46 tpd direct PM2.5 and
15.3 tpd NOX (for the 2012 annual PM2.5
NAAQS).\93\
---------------------------------------------------------------------------

    \93\ SJV PM2.5 Contingency Measure SIP, pp. 5-6; see
``Step 1b'' emissions estimates in the ``Step 1'' table for one
year's worth of RFP.
---------------------------------------------------------------------------

    Per the EPA's Draft Revised Contingency Measure Guidance, the SJV
PM2.5 Contingency Measure SIP also includes estimates of one
year's worth of progress that were made by calculating one year's worth
of RFP as a percentage of the base year emissions inventory and
applying that percentage to the attainment year emissions inventory for
the 1997 annual and 2006 24-hour PM2.5 NAAQS, and to the
outermost Moderate area RFP year for the 2012 annual PM2.5
NAAQS. The estimates of one year's worth of progress in the SJV
PM2.5 Contingency Measure SIP are as follows: 0.41 tpd
direct PM2.5 and 7.91 tpd NOX (for the 1997
annual PM2.5 NAAQS); 0.52 tpd direct PM2.5 and
6.66 tpd NOX (for the 2006 24-hour PM2.5 NAAQS);
and 0.43 tpd direct PM2.5 and 8.65 tpd NOX (for
the 2012 annual PM2.5 NAAQS).\94\
---------------------------------------------------------------------------

    \94\ SJV PM2.5 Contingency Measure SIP, pp. 5-6; see
the ``Step 3'' table for one year's worth of progress.
---------------------------------------------------------------------------

    CARB and the District present their comparison of emission
reductions from the Residential Wood Burning Contingency Measure to
those needed for one year's worth of progress in Table 17 of the SJV
PM2.5 Contingency Measure SIP.\95\ They conclude that this
contingency measure would achieve emission reductions of 0.69 tpd
direct PM2.5 and 0.1 tpd NOX (including
reductions following both first and second triggering events) and that
such reductions would exceed those needed for one year's worth of
progress for direct PM2.5 but would fall short of those
needed for one year's worth of progress for NOX.
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    \95\ SJV PM2.5 Contingency Measure SIP, Table 17.
---------------------------------------------------------------------------

    Noting the direct PM2.5 surplus, CARB and the District
then trade the surplus direct PM2.5 emission reductions at a
ratio of 6:1 (i.e., 6 tpd NOX for each excess 1 tpd direct
PM2.5),\96\ based on analyses in their 2021 ``Progress
Report and Technical Submittal for the 2012 PM2.5 Standard
San Joaquin Valley'' (``2021 Progress Report'').\97\ CARB and the
District note that direct PM2.5 emission reductions are a
more efficient and cost-effective way to reduce ambient
PM2.5 in the San Joaquin Valley than NOX emission
reductions.\98\ The report presented analysis of the relative effect of
reducing 30% direct PM2.5 (annual average) emissions versus
30% NOX (annual average) emissions on ambient annual average
PM2.5 concentrations (as modeled for 2024) at each
regulatory monitoring site in the San Joaquin Valley using data from
the precursor sensitivity analyses in the 2018 PM2.5
Plan.\99\ CARB and the District examined several methods for
calculating the ratio based on varying combinations of monitoring
sites. They concluded that 6:1 was a conservative ratio as it was less
than the average ratio for the two sites with the highest modeled
(annual average) ambient PM2.5 concentrations in 2025
(6.1:1), the average ratio of sites with modeled 2025 concentrations
over 11.00 [mu]g/m\3\ (6.4:1), and the average ratio of sites with a
2020 design value over 12 [mu]g/m\3\ (6.6:1).\100\ They also conclude
that a ratio of 6:1 would be conservative as it was less than the 8.1:1
ratio for the modeled design value for the Bakersfield-Planz site
(i.e., the site with the highest modeled 2025 concentration).
---------------------------------------------------------------------------

    \96\ SJV PM2.5 Contingency Measure SIP, pp. 73-74.
    \97\ CARB and SJVUAPCD, ``Progress Report and Technical
Submittal for the 2012 PM2.5 Standard San Joaquin
Valley,'' October 19, 2021 (``2021 Progress Report''). See pages 34-
38 for the State's ``PM2.5 Precursor Sensitivity Modeling
Analysis and Trading Ratios.'' Transmitted to the EPA by letter
dated October 20, 2021, from Richard W. Corey, Executive Officer,
CARB, to Deborah Jordan, Acting Regional Administrator, EPA Region
IX.
    \98\ 2021 Progress Report, p. 34.
    \99\ See Appendix K (``Modeling Attainment Demonstration'') of
the 2018 PM2.5 Plan, including Table 14 (annual average
modeled emissions inventory) and Table 49 (precursor sensitivity
analysis for annual average ambient PM2.5 concentration
in 2024).
    \100\ At the time, the modeled 2025 PM2.5
concentrations corresponded to the attainment year in the State's
Serious area plan for the 2012 annual PM2.5 NAAQS, which
was later withdrawn on October 27, 2022. Letter dated October 27,
2022, from Steven S. Cliff, Executive Officer, CARB, to Martha
Guzman, Regional Administrator, EPA Region IX.
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    Applying this 6:1 trading ratio, CARB and the District estimate
that, after achieving the full one year's worth of progress for direct
PM2.5 emission reductions, the shortfall of NOX
emissions for one year's worth of progress would be as follows: 6.13
tpd (compared to 7.91 tpd for the 1997 annual PM2.5 NAAQS),
5.54 tpd (compared to 6.66 tpd for the 2006 24-hour PM2.5
NAAQS), and 6.99 tpd (compared to 8.65 tpd for the 2012 annual
PM2.5 NAAQS).\101\ The NOX equivalent emissions
reductions equate to a range of 17% to 23% of one year's worth of
progress for NOX.
---------------------------------------------------------------------------

    \101\ SJV PM2.5 Contingency Measure SIP, p. 74.
---------------------------------------------------------------------------

    In light of the shortfall of NOX emissions reductions,
the SJV PM2.5 Contingency Measure SIP includes feasibility
analyses by the District for stationary and area sources and by CARB
for mobile sources to justify the reliance on a contingency measure
that would not provide for one year's worth of progress (i.e., for
NOX). We summarize the feasibility analyses prepared by the
District and CARB in the following section of this document.
2. Contingency Measure Feasibility Analyses
    The District states that it has already implemented rules for
sources that meet or go beyond federal requirements and that few
measures remain to explore as contingency measures. The District
describes the relative stringency of their stationary and area source
measures by noting the EPA's 2020 approval of the State's demonstration
of BACM and MSM for the 2006 24-hour PM2.5 NAAQS; highlights
the District's tighter limits for certain industrial sources compared
to the EPA's national emission limits to address the interstate
transport of air pollution; and describes the numerous regulatory
measures and incentive-based measures adopted since and in fulfillment
of the 2018 PM2.5 Plan.\102\
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    \102\ SJV PM2.5 Contingency Measure SIP, section 4.1
(``Stringency of District's Regulatory Program''). See also 87 FR
20036 (April 6, 2022) (proposed rule for the interstate transport
FIP for the 2015 ozone NAAQS); and 88 FR 36654 (June 5, 2023) (final
rule for interstate transport FIP for the 2015 ozone NAAQS).
---------------------------------------------------------------------------

    More specifically, the District analyzed the wide range of
stationary and area sources for contingency measure opportunities,
including identification of potential control measures, analysis of the
technological and economic feasibility of such measures, assessment of
the time required to develop and implement such measures within 60 days
and achieve emission reductions within one to two years, and discussion
of whether the District could adopt such measures

and secure EPA approval prior to the EPA promulgating a contingency
measure FIP for PM2.5 in the San Joaquin Valley. For the
potential control measures identified through this process, the
District further analyzed possible contingency measures for wood
burning fireplaces and wood burning heaters, rural open areas,
commercial charbroiling, almond harvesting, and oil and gas production
combustion equipment. Based on this analysis, the District adopted the
Residential Wood Burning Contingency Measure and concluded that the
other possible contingency measures were infeasible or untimely but
committed to further evaluate the rural open areas rule as a potential
contingency measure. Subsequently, the District fulfilled the Agency's
commitment to further evaluate the rural open areas rule and adopted
the Rural Open Areas Contingency Measure to supplement the SJV
PM2.5 Contingency Measure SIP.
    In turn, CARB states that its mobile source control programs often
set the standard for other states to follow and that more than half of
mobile source NOX emissions in the San Joaquin Valley are
from primarily federally regulated sources, which limit opportunities
for contingency measures that would achieve one year's worth of
progress in emission reductions. CARB further notes that a relatively
limited portion (of NOX) emissions are regulated by local
air districts in California and that, even if discounting the emission
reductions needed for contingency measures by primarily federally
regulated emission sources, additional control measures to achieve the
one year's worth of emission reductions are scarce or nonexistent.
    CARB states that if such measures were identified, they would be
adopted to improve air quality and help attain the NAAQS, rather than
held in reserve as contingency measures, and that control measures to
achieve large emission reductions often take longer than two years to
implement--beyond the one- to two-year timeframe for achieving emission
reductions for contingency purposes. For example, CARB states that the
three largest NOX reduction measures committed to in the
2022 State SIP Strategy \103\ rely on accelerated turnover of engines
and trucks and shifting to zero-emission equipment, which is limited by
infrastructure and equipment options. CARB further states that a
central difficulty in considering contingency measures is that CARB has
already committed to zero emission standards where feasible and as
expeditiously as possible to fulfill goals established in California
Executive Order N-79-20 for mobile sources ranging from light-duty cars
by 2035 to heavy-duty trucks by 2045.\104\
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    \103\ CARB, ``2022 State Strategy for the State Implementation
Plan,'' adopted September 22, 2022, Chapter 5 (``State SIP
Measures'').
    \104\ Executive Department, State of California, Executive Order
N-79-20, September 23, 2020.
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    More specifically, CARB analyzed all sources under its authority to
identify potential contingency measures using three criteria, per CAA
requirements, court decisions, and the EPA's Draft Revised Contingency
Measure Guidance. First, CARB assessed whether the measure could be
implemented within 60 days of a triggering event and emission
reductions achieved within one to two years. Second, CARB assessed the
technological and economic feasibility of implementing the measure,
particularly within the one- to two-year timeframe. Third, CARB
evaluated whether it could adopt the measure and secure EPA approval by
the September 30, 2024 consent decree deadline for the EPA to
promulgate a FIP or alternatively approve contingency measure SIP
submissions meeting the contingency measure requirements.
    Regarding mobile source contingency measures, CARB describes
several challenges that limit the control measure options that would
meet contingency measure requirements. For new engine standards, CARB
states that engine manufacturers need lead time to ``design, plan,
certify, manufacture, and deploy cleaner engines.'' For fleet
regulations, CARB states that manufacturing must be mature to provide
sufficient supply and that owners and operators must ``plan, purchase,
and deploy new, often zero-emission, equipment'' that may involve
changes to business operations and infrastructure. Based on the time
required for implementing such measures, CARB concludes that new engine
standards and fleet regulations are not appropriate for contingency
measures.
    Furthermore, CARB states that its regulations are technology-
forcing, which requires time for industry to plan, develop, and
implement new technologies, and that it is driving mobile sources to
zero-emissions where feasible to achieve criteria, air toxic, and
climate pollutant goals. Similarly, CARB argues that the technology-
forcing and zero-emission-based nature of its mobile source regulations
reduce or eliminate opportunities for contingency measure emission
reductions. Lastly, CARB states that its full rulemaking process for
most mobile source measures takes about five years to develop and
adopt, which would not be possible prior to the September 30, 2024
consent decree deadline for the EPA to promulgate a FIP, or approve
contingency measure SIP submissions meeting the contingency measure
requirements.
    CARB concludes that there are no feasible mobile source contingency
measures for the 1997 annual, 2006 24-hour, and 2012 annual
PM2.5 NAAQS (as of the April 2023 public notice for the SJV
PM2.5 Contingency Measure SIP) yet continued to assess
opportunities for feasible contingency measures. Per a June 2023
commitment letter by CARB's Executive Officer, and as further described
in section IV.C of this proposed rule, CARB has since completed the
development of and adopted the state-wide Smog Check Contingency
Measure that complements the District contingency measures for
residential wood burning and rural open areas.
3. Conclusion
    Based on achieving the full one year's worth of progress for direct
PM2.5 emission reductions, a portion of one year's worth of
progress for NOX emission reductions, and their contingency
measure feasibility analyses, CARB and the District conclude that the
SJV PM2.5 Contingency Measure SIP, and related infeasibility
demonstrations, and the Residential Wood Burning Contingency Measure
fulfill the contingency measure requirements for the PM2.5
NAAQS.\105\
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    \105\ SJV PM2.5 Contingency Measure SIP, p. 74. As
noted previously, the SJV PM2.5 Contingency Measure SIP
has been supplemented with two additional contingency measures
(i.e., the Rural Open Areas Contingency Measure and the Smog Check
Contingency Measure).
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C. EPA Evaluation

    We propose to find that CARB and the District have corrected the
specific deficiencies that we identified in the previously submitted
contingency measure elements for the applicable PM2.5 NAAQS
and that were the bases for our previous disapprovals of the
contingency measure element. Our proposed conclusion in this regard
recognizes that the revised contingency measure plan elements for the
applicable PM2.5 NAAQS (SJV PM2.5 Contingency
Measure SIP) now includes contingency measures (Residential Wood
Burning Contingency Measure, Rural Open Areas Contingency Measure, and
the Smog Check Contingency Measure) that address all four triggering
events for the PM2.5 NAAQS under 40

CFR 51.1014, that have been structured to ensure emissions reductions,
once triggered, and that are surplus to the RFP and attainment needs of
the San Joaquin Valley for the 1997 annual PM2.5 NAAQS.\106\
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    \106\ With respect to the contingency measures being surplus to
the RFP and attainment needs of the San Joaquin Valley for the 1997
annual PM2.5 NAAQS, we are relying on the recent approval
of the RFP and attainment demonstrations in the State's 15 [mu]g/
m\3\ SIP Revision.
---------------------------------------------------------------------------

1. General Considerations
    As stated previously, ``General Considerations,'' for the purposes
of this proposed action, includes identification of the relevant
pollutants, the use of contingency measures for more than one
triggering event and for more than one NAAQS, and the magnitude of
emissions reductions. We present our evaluation of the State's
contingency measure feasibility analyses in a separate subsection.
a. PM2.5 and PM2.5 Plan Precursors
    Under the CAA, states are required to regulate not only direct
emissions of PM2.5 in an attainment plan, but also all
PM2.5 precursors. Under the EPA's PM2.5 SIP
Requirements Rule, states must identify, adopt, and implement control
measures, including control technologies, on sources of direct
PM2.5 emissions and sources of emissions of PM2.5
plan precursors located in PM2.5 nonattainment areas.\107\
PM2.5 plan precursors are those PM2.5 precursors
(which are sulfur dioxide (SO2), NOX, VOCs, and
ammonia) that the state must regulate in the applicable attainment
plan.\108\ A state may elect to submit to the EPA precursor
demonstrations for a specific nonattainment area in order to establish
that regulation of one or more precursors is not necessary for
attainment in the nonattainment area at issue.\109\ If the EPA approves
a comprehensive precursor demonstration that shows that emissions of a
particular precursor does not contribute significantly to
PM2.5 levels that exceed the NAAQS in an area, then the
state is not required to control emissions of the relevant precursor
from existing sources in the current attainment plan.\110\ Accordingly,
the state would not need to address the precursor in order to meet
attainment plan requirements, including RFP, in QMs and associated QM
reports, or be required to adopt contingency measures to reduce the
precursor at issue.\111\
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    \107\ See generally 40 CFR 51.1009(a) and 40 CFR 51.1010(a).
    \108\ 40 CFR 51.1000.
    \109\ 40 CFR 51.1006(a).
    \110\ 40 CFR 51.1006(a)(1)(iii).
    \111\ 40 CFR 51.1009(a)(4)(i).
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    For the San Joaquin Valley, as noted in section V.B.1 of this
proposed rule, CARB and the District have concluded, based on CARB
modeling, that SOX, VOCs, and ammonia are not significant
precursors for PM2.5 formation in the San Joaquin
Valley.\112\ The EPA has considered, and approved, the State's
precursor demonstrations with respect to the 1997 annual, 2006 24-hour,
and the 2012 annual PM2.5 NAAQS in taking action on the SIP
submissions applicable to each NAAQS.\113\ Therefore, we agree with
CARB and the District that the contingency measure submissions for the
1997 annual, 2006 24-hour, and 2012 annual PM2.5 NAAQS must
address sources of direct PM2.5 and NOX emissions
but do not need to address sources of SOX, VOCs, or ammonia.
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    \112\ See, e.g., SJV PM2.5 Contingency Measure SIP,
Appendix G (Appendix C from the 2018 PM2.5 Plan), p. C-
12.
    \113\ EPA, ``Air Quality State Implementation Plans; Approvals
and Promulgations: California; 1997 Annual Fine Particulate Matter
Serious and Clean Air Act Section 189(d) Nonattainment Area
Requirements; San Joaquin Valley, CA,'' Final rule, signed December
5, 2023; 85 FR 17382, 17390-17396, finalized at 85 FR 44192; 86 FR
49100, 49107-49112, finalized at 86 FR 67343.
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    For the 2006 24-hour PM2.5 NAAQS, the EPA approved the
comprehensive precursor demonstration that established that
SO2, VOCs, and ammonia emissions do not contribute
significantly to PM2.5 levels that exceed the 2006 24-hour
PM2.5 NAAQS in the San Joaquin Valley.\114\ In 2020, a
petition for review before the Ninth Circuit Court of Appeals
challenged the EPA's approval of the portions of the 2019 SIP
submissions related to the 2006 24-hour PM2.5 NAAQS. In
2021, the Court vacated the approval of aggregate commitments to the
extent such commitments relied on inadequately funded incentive-based
control measures and remanded to the EPA for further consideration of
the aggregate commitments, and for further proceedings consistent with
the decision, but denied the petition in all other respects.\115\ The
EPA's approval of the comprehensive precursor demonstration was not the
subject of the court challenge. In light of the current circumstances
surrounding these precursor demonstrations, the EPA agrees that direct
PM2.5 and NOX are the appropriate pollutants for
which contingency measures are required in the San Joaquin Valley for
the 2006 24-hour PM2.5 NAAQS.
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    \114\ 85 FR 17382, 17390-17396, finalized at 85 FR 44192.
    \115\ Medical Advocates for Healthy Air v. EPA, No. 20-72780,
Memorandum, Dkt. #58-1 (9th Cir. Apr. 13, 2022).
---------------------------------------------------------------------------

b. Using Same Contingency Measures for More Than One Triggering Event,
NAAQS
    Under CAA section 172(c)(9), SIPs must provide for the
implementation of specific contingency measures if the area fails to
meet RFP or to attain the NAAQS by the applicable attainment date. For
PM2.5, there are four potential triggering events: failure
to meet any RFP requirement, failure to submit a QM report, failure to
meet a QM, and failure to attain the NAAQS by the applicable attainment
date.\116\
---------------------------------------------------------------------------

    \116\ 40 CFR 51.1014(a).
---------------------------------------------------------------------------

    To meet the contingency measure requirement, states may adopt
different measures for different triggering events but are not required
to do so. If the state adopts the same set of contingency measures for
all the triggering events, however, then the contingency measures may
all be implemented by earlier-occurring triggering events leaving no
contingency measures for potential later-occuring events. In that case,
if a state has no remaining approved contingency measures, then the EPA
believes that states must adopt and submit additional contingency
measures to be available for potential later-occuring triggering
events. The potential for states to have used all approved contingency
measures, and thus to lack contingency measures for potential later-
triggering events is compounded by the reliance on the same set of
contingency measures for more than one iteration of the
PM2.5 NAAQS. Accordingly, while the EPA might approve a SIP
that relies on the same contingency measures for multiple potential
triggering events, a SIP that does so may be subject to the need for
future revision each time a triggering event occurs.
    As noted previously, CARB and the District have submitted three
contingency measures, each of which covers all three of the 1997
annual, 2006 24-hour, and 2012 annual PM2.5 NAAQS (i.e., the
same set of contingency measures has been submitted to address the
contingency measure requirements for more than one PM2.5
NAAQS). In addition, each of the contingency measures addresses each of
the four potential triggering events: failure to meet any RFP
requirement, failure to submit a QM report, failure to meet a QM, and
failure to attain the NAAQS by the applicable attainment date.\117\ As
noted previously, states may adopt different measures for different
triggering events and different NAAQS, but we do not believe that
states are

required to do so, and thus, we find that the State's reliance on the
same set of contingency measures for more than one triggering event and
more than one NAAQS to be acceptable.
---------------------------------------------------------------------------

    \117\ 40 CFR 51.1014(a).
---------------------------------------------------------------------------

    In this instance, two of the three contingency measures--the
Residential Wood Burning Contingency Measure and the Smog Check
Contingency Measure--include provisions that would separately be
implemented after a second triggering event.\118\ Under section 5.7.3
of Rule 4901, upon a first triggering event, the No Burn (i.e.,
curtailment) thresholds for the five non-hot spot counties (Kings,
Merced, San Joaquin, Stanislaus, and Tulare) would be lowered to match
the tighter No Burn thresholds for the three hot spot counties (Fresno,
Madera, and Kern) (i.e., to 35 [mu]g/m\3\ for registered devices and to
12 [mu]g/m\3\ for unregistered devices). Upon a subsequent triggering
event (i.e., in response to a separate, later determination by the
EPA), the No Burn threshold for unregistered fireplaces and woodstoves
for all eight counties would be lowered from 12 [mu]g/m\3\ to 11 [mu]g/
m\3\.
---------------------------------------------------------------------------

    \118\ We note that the contingency provisions in Rule 8051 would
be fully implemented following a first triggering event.
---------------------------------------------------------------------------

    Similarly, under the Smog Check Contingency Measure, upon a first
triggering event, the Smog Check exemption would be lowered from eight
or fewer model years old to seven or fewer model years old. Upon a
subsequent triggering event (i.e., in response to a separate, later
determination by the EPA), the Smog Check exemption would be lowered
from seven or fewer model years old to six or fewer model years old.
    Therefore, after a first triggering event, the State would have two
remaining SIP-approved contingency measures that are not yet triggered
as it develops a SIP revision to meet the missed RFP requirement or to
correct ongoing nonattainment. The EPA believes that the State would
need to assess whether those two remaining contingency measures were
sufficient to meet the contingency measure requirements in that future
time and, if necessary, adopt and submit additional contingency
measures to be available for potential later-occuring triggering
events.
c. Magnitude of Emissions Reductions
    As noted previously, neither the CAA nor the EPA's implementing
regulations establish a specific level of emission reductions that
implementation of contingency measures must achieve, but the EPA has
recommended in existing guidance that contingency measures should
provide for emission reductions equivalent to approximately one year of
reductions needed for RFP in the nonattainment area.
    Using the longstanding approach, contingency measures should
provide for emissions reductions of approximately one year's worth of
RFP for each of the relevant PM2.5 NAAQS. Under the approach
described in the EPA's Draft Revised Contingency Measure Guidance, the
EPA has suggested that contingency measures provide for emissions
reductions of approximately one year's worth of progress for each of
the relevant PM2.5 NAAQS rather than one year's worth of
RFP.
    We have reviewed the calculations in the SJV PM2.5
Contingency Measure SIP, as summarized in section V.B.1 of this
proposed rule, and find that the State properly calculated one year's
worth of RFP (as an interim step in calculating one year's worth of
progress) and one year's worth of progress for each of the relevant
PM2.5 NAAQS in the San Joaquin Valley.\119\ We have also
reviewed the calculations in the SJV PM2.5 Contingency
Measure SIP used to compare the emissions reductions from the
Residential Wood Burning Contingency Measure with one year's worth of
progress and generally find them to be acceptable with the exception
that the calculation includes the emissions reductions from both
triggering events in the evaluation. Only the emissions reductions from
the first trigger should be used because there is no assurance that the
additional emissions reductions from the second triggering event will
provide emissions reductions in the year or two following the first
triggering event.
---------------------------------------------------------------------------

    \119\ With respect to the 2012 PM2.5 NAAQS, we agree
with the calculation of one year's worth of progress in the SJV
PM2.5 Contingency Measure SIP that is based on the
outermost RFP milestone year, rather than the attainment year,
because, as an area for which an impracticability demonstration has
been approved, the attainment year has not yet been established.
---------------------------------------------------------------------------

    We recognize that the calculations in the SJV PM2.5
Contingency Measure SIP relied upon an interpollutant trading ratio of
6:1 (i.e., 6 tpd NOX for each excess 1 tpd direct
PM2.5) to convert ``excess'' PM2.5 emissions
reductions to equivalent NOX emissions reductions. The
technical basis of the interpollutant trading ratio of 6:1 was provided
in the State's 2021 Progress Report to the EPA to support the State's
Serious area attainment demonstration for the 2012 annual
PM2.5 NAAQS. Specifically, the State analyzed the relative
effect of reducing 30% direct PM2.5 (annual average)
emissions versus 30% NOX (annual average) emissions on
ambient annual average PM2.5 concentrations (as modeled for
2024) at each regulatory monitoring site in the San Joaquin Valley
using data from the precursor sensitivity analyses in the 2018
PM2.5 Plan.\120\ While the 2021 Progress Report was
nominally for only the 2012 annual PM2.5 NAAQS and
corresponded to the modeled 2025 attainment year in the State's Serious
area plan for the 2012 annual PM2.5 NAAQS (later withdrawn
on October 27, 2022), we note that the control strategy in the 2018
PM2.5 Plan was built upon annual average emissions
inventories (e.g., for demonstrating RFP) and applied in common to the
1997, 2006, and 2012 PM2.5 NAAQS. Later, the 15 [mu]g/m\3\
SIP Revision for the 1997 annual PM2.5 NAAQS retained the
annual average emissions inventory basis for the control strategy to
attain that NAAQS and continued to rely on the State's precursor
sensitivity analyses. In other words, there is a common foundation on
which CARB and the District selected the 6:1 ratio.
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    \120\ See Appendix K (``Modeling Attainment Demonstration'') of
the 2018 PM2.5 Plan, including Table 14 (annual average
modeled emissions inventory) and Table 49 (precursor sensitivity
analysis for annual average ambient PM2.5 concentration
in 2024).
---------------------------------------------------------------------------

    As previously discussed, CARB and the District examined several
methods for calculating the ratio based on varying combinations of
monitoring sites. They concluded that 6:1 was a conservative ratio as
it was less than the average ratio for the two sites (in Fresno and
Kern Counties) with the highest modeled (annual average) ambient
PM2.5 concentrations in 2025 (6.1:1), the average ratio of
the six sites (in Fresno, Kern, Stanislaus, and Tulare Counties) with
modeled 2025 concentrations over 11.00 [mu]g/m\3\ (6.4:1), and the
average ratio of the six sites (in Fresno, Kern, Kings, and Tulare
Counties) with a 2020 design value over 12 [mu]g/m\3\ (6.6:1).\121\
---------------------------------------------------------------------------

    \121\ 2021 Progress Report, Table 7 (``Base and Projected 2025
Annual Average Design Values Used to Select/Prioritize Sites for
Calculating an Average Trading Ratio''). At the time, the modeled
2025 concentrations corresponded to the attainment year in the
State's Serious area plan for the 2012 annual PM2.5
NAAQS, which was later withdrawn on October 27, 2022.
---------------------------------------------------------------------------

    We have reviewed the State's technical basis for the 6:1
interpollutant trading ratio and find that it is a reasonable ratio for
purposes of estimating the NOX equivalent of excess direct
PM2.5 emission reductions for purposes of contingency
measures in the San Joaquin Valley for the 1997 annual, 2006 24-hour,
and 2012 annual PM2.5 NAAQS. First, the annual average
emissions inventory and integrated

nature of attainment planning for the three NAAQS provides a common
emissions and control strategy basis for the ratios. Second, the ratios
are based on whole emissions inventories (rather than, for example,
only on-road emissions inventories that might be relevant to motor
vehicle emission budgets) and modeling for a near-term year (2025),
given that these contingency measures would be triggered no sooner than
2024.
    Third, by examining several methods that involve averaging across
two to six sites, including two methods that include both hot spot and
non-hot spot counties, the State provides robustness in the ratio
(i.e., may better reflect the effect of emission reductions from the
three contingency measures across sites in the San Joaquin Valley). The
inclusion of non-hot spot counties in two of the averaging methods is
important in that, upon a first triggering event, the Residential Wood
Burning Contingency Measure--which is the contingency measure that
would achieve emission reductions in excess of one year's worth of
direct PM2.5 emission reductions--would lower the No Burn
(i.e., curtailment) thresholds for the five non-hot spot counties
(Kings, Merced, San Joaquin, Stanislaus, and Tulare) to match the
tighter No Burn thresholds for the three hot spot counties (Fresno,
Madera, and Kern). Fourth, we agree with CARB and the District that the
selected 6:1 ratio is conservative relative to the slightly higher
average ratios of 6.1:1, 6.4:1, and 6.6:1 from the methods that select
sites with relatively high modeled concentrations, and relative to the
ratio of 8.1:1 at the modeled 2025 high site of Bakersfield-Planz.\122\
---------------------------------------------------------------------------

    \122\ We note that the interpollutant trading ratio of 6:1
compares favorably with the interpollutant trading ratios that the
EPA used recently in the Agency's proposed San Joaquin Valley
PM2.5 contingency measure FIP. We provide our evaluation
of the interpollutant trading ratio in the SJV PM2.5