State correctly notes, the 30 percent to 70 percent range recommended
by the EPA is based on historical NOX and SOX
emissions reductions, and changes in ammonia emissions levels
nationally from 2011 to 2017 ranged from a 9 percent decrease to a 6
percent increase.\141\ The State's descriptions of past research relied
upon to develop existing rules that apply to ammonia emissions sources,
as well as ongoing research, show that it has considered the
availability of ammonia controls both in the past and present context,
and that the State has a basis for its conclusion that 30 percent is a
reasonable upper bound on achievable reductions for ammonia.
---------------------------------------------------------------------------

    \141\ Id. at 30, Table 2.
---------------------------------------------------------------------------

    In sum, we find that the State quantified the sensitivity of
ambient PM2.5 levels to reductions in ammonia using
appropriate modeling techniques that performed well, and that the
State's analysis and use of future year sensitivity data, both 2020 and
2024, is well-supported. We also find that the State adequately
documented its basis for using a 30 percent reduction in ammonia
emissions as an upper bound in the modeling to assess ambient
sensitivity to ammonia emissions reductions. Based on these
considerations, the EPA proposes to approve the State's demonstration
that ammonia emissions do not contribute significantly to ambient
PM2.5 levels that exceed the 1997 24-hour PM2.5
NAAQS in the San Joaquin Valley.
b. SOX
    For SOX, the State found that the ambient
PM2.5 responses to SOX emissions reductions were
below the EPA's recommended contribution threshold of 1.3 [micro]g/m\3\
in the Draft PM2.5 Precursor Guidance (and below the EPA
recommended threshold of 1.5 [micro]g/m\3\ in the final
PM2.5 Precursor Guidance), and that for most sites there
would be an increase in ambient PM2.5 levels in response to
SOX reductions (i.e., a disbenefit). The EPA has evaluated
the State's analysis of this disbenefit and resulting conclusion
regarding significance.
    Because the results of the sensitivity analysis were all below the
EPA's recommended 24-hour contribution thresholds at both the 30
percent and 70

percent emissions reductions, and in both the 2013 base year and 2020
(and 2024) future year, it is not necessary to distinguish between the
timing and scale of emissions reductions with respect to the response
of ambient PM2.5 levels as in the ammonia evaluation where
the results diverged according to scale and timing of modeled emissions
reductions. The EPA's February 2020 Precursor TSD contains additional
detail on the EPA's evaluation of SOX as a PM2.5
precursor, including the disbenefit associated with a reduction in
SOX emissions. Accordingly, we find that the State's
decision to rely on the 2013 sensitivity modeling results for a 30
percent SOX reduction is acceptable.
    Therefore, on the basis of the modeled ambient PM2.5
response to both a 30 percent and 70 percent reduction in
SOX emissions in 2013, and on the facts and circumstances of
the area, the EPA proposes to approve the State's demonstration that
SOX emissions do not contribute significantly to ambient
PM2.5 levels that exceed the 1997 24-hour PM2.5
NAAQS in the San Joaquin Valley.
c. VOC
    For VOC, the State found that the ambient PM2.5 response
to VOC emissions reductions were generally below the EPA's recommended
contribution threshold of 1.3 [micro]g/m\3\ in the Draft
PM2.5 Precursor Guidance and below the EPA's recommended
threshold of 1.5 [micro]g/m\3\ in the final PM2.5 Precursor
Guidance, and often predicted an increase in ambient PM2.5
levels in response to such reductions (i.e., a disbenefit), except for
a 70 percent emissions reduction for the 2013 base year, where the
State predicted the ambient PM2.5 response to be above both
recommended thresholds at a majority of sites. The EPA has evaluated
and agrees with the State's determination that the modeling for future
years is more representative of conditions in the San Joaquin Valley
than the 2013 modeling for sensitivity-based analyses and the State's
resulting conclusion as to whether the contribution from VOC emissions
is significant.
    Regarding emissions trends, the EPA agrees that the 8.6 percent
decrease in VOC emissions from 2013 to 2020 and the 9.2 percent
projected decrease from 2013 to 2024 favors reliance on the future year
modeling results. Furthermore, there is a large decrease in
NOX emissions over this period, as discussed in the EPA's
evaluation of ammonia, which affects the atmospheric chemistry with
respect to ambient PM2.5 formation from VOC emissions. The 9
percent VOC emissions reductions and the NOX emissions
reductions are projected to result from implementation of existing
baseline measures. We therefore find it reasonable to rely on future
year 2020 or 2024 modeled responses to VOC emissions reductions, and
both years show a disbenefit from VOC emissions reductions. The EPA
also finds that the State provided a reasonable explanation for the VOC
reduction disbenefit and evidence that it occurs in the San Joaquin
Valley.
    For these reasons, we propose to approve the State's demonstration
that VOC emissions do not contribute significantly to ambient
PM2.5 levels that exceed the 1997 24-hour PM2.5
NAAQS in the San Joaquin Valley.

C. Attainment Plan Control Strategy

1. Statutory and Regulatory Requirements
    Section 189(b)(1)(B) of the Act requires for any Serious
PM2.5 nonattainment area that the state submit provisions to
assure that BACM for the control of PM2.5 and
PM2.5 precursors shall be implemented no later than four
years after the date the area is reclassified as a Serious area. The
EPA has defined BACM in the PM2.5 SIP Requirements Rule to
mean ``any technologically and economically feasible control measure
that . . . can achieve greater permanent and enforceable emissions
reductions of direct PM2.5 emissions and/or emissions of
PM2.5 plan precursors from sources in the area than can be
achieved through the implementation of RACM on the same source(s). BACM
includes best available control technology (BACT).'' \142\
---------------------------------------------------------------------------

    \142\ 40 CFR 51.1000 (definitions). In longstanding guidance,
the EPA has similarly defined BACM to mean, ``among other things,
the maximum degree of emissions reduction achievable for a source or
source category, which is determined on a case-by-case basis
considering energy, environmental, and economic impacts.'' General
Preamble Addendum, 42010, 42013.
---------------------------------------------------------------------------

    Because the 2015 Serious area attainment date has passed, and the
EPA found that the area failed to attain by the Serious area attainment
date, we are evaluating the submission for compliance with the BACM/
BACT requirements now, in conjunction with the State's SIP submission
intended to meet both the Serious area plan and section 189(d) plan
requirements.
    The EPA generally considers BACM a control level that goes beyond
existing RACM-level controls, for example by expanding the use of RACM
controls or by requiring preventative measures instead of
remediation.\143\ Indeed, as implementation of BACM and BACT is
required when a Moderate nonattainment area is reclassified as Serious
due to its inability to attain the NAAQS through implementation of
``reasonable'' measures, it is logical that ``best'' control measures
should represent a more stringent and potentially more costly level of
control.\144\ If RACM and RACT level controls of emissions have been
insufficient to reach attainment, the CAA contemplates the
implementation of more stringent controls, controls on more sources, or
other adjustments to the control strategy are necessary to attain the
NAAQS in the area.
---------------------------------------------------------------------------

    \143\ 81 FR 58010, 58081 and General Preamble Addendum, 42011,
42013.
    \144\ Id. and General Preamble Addendum, 42009-42010.
---------------------------------------------------------------------------

    Under the PM2.5 SIP Requirements Rule, those control
measures that otherwise meet the definition of BACM/BACT but ``can only
be implemented in whole or in part beginning four years after
reclassification'' are referred to as ``additional feasible measures.''
\145\ In accordance with the requirements of CAA section 172(c)(6), a
Serious area plan must include any additional feasible measures to
control emissions of direct PM2.5 and PM2.5
precursors that are necessary and appropriate to provide for attainment
of the relevant NAAQS as expeditiously as practicable and no later than
the applicable attainment date.\146\
---------------------------------------------------------------------------

    \145\ 40 CFR 51.1000, 40 CFR 51.1010(a)(4)(ii).
    \146\ Because the Serious area attainment year has passed and
the area failed to attain by the Serious area attainment date, we
will evaluate the BACM/BACT and additional feasible measure analysis
for the Serious area plan with respect to the current section 189(d)
projected attainment date of December 31, 2020.
---------------------------------------------------------------------------

    Consistent with longstanding guidance provided in the General
Preamble Addendum, the preamble to the PM2.5 SIP
Requirements Rule discusses the following steps for determining BACM
and BACT and additional feasible measures:
    (1) Develop a comprehensive emissions inventory of the sources of
PM2.5 and PM2.5 precursors;
    (2) Identify potential control measures;
    (3) Determine whether an available control measure or technology is
technologically feasible;
    (4) Determine whether an available control measure or technology is
economically feasible; and
    (5) Determine the earliest date by which a control measure or
technology can be implemented in whole or in part.\147\
---------------------------------------------------------------------------

    \147\ 81 FR 58010, 58083-58085.
---------------------------------------------------------------------------

    The EPA allows consideration of factors such as physical plant
layout,

energy requirements, needed infrastructure, and workforce type and
habits when considering technological feasibility. For purposes of
evaluating economic feasibility, the EPA allows consideration of
factors such as the capital costs, operating and maintenance costs, and
cost effectiveness (i.e., cost per ton of pollutant reduced by a
measure or technology) associated with the measure or control.\148\
---------------------------------------------------------------------------

    \148\ 40 CFR 51.1010(a)(3) and 81 FR 58010, 58041-58042.
---------------------------------------------------------------------------

    Once these analyses are complete, the state must use this
information to develop enforceable control measures and submit them to
the EPA for evaluation as SIP revisions to meet the basic requirements
of CAA section 110 and any other applicable substantive provisions of
the Act. The EPA is using these steps as guidelines in the evaluation
of the BACM and BACT measures and related analyses in the SJV
PM2.5 Plan. Furthermore, because the EPA has not previously
taken action to approve the California SIP as meeting the subpart 4
Moderate area planning requirements under CAA section 189 for the 1997
24-hour PM2.5 NAAQS for the San Joaquin Valley area, the EPA
is reviewing the SJV PM2.5 Plan for compliance with those
requirements.\149\
---------------------------------------------------------------------------

    \149\ The EPA does not normally conduct a separate evaluation to
determine whether a Serious area plan's measures also meet the RACM
requirements. As explained in the General Preamble Addendum, we
interpret the BACM requirement as generally subsuming the RACM
requirement--i.e., if we determine that the measures are indeed the
``best available,'' we have necessarily concluded that they are
``reasonably available.'' (General Preamble Addendum, 42010).
Therefore, a separate analysis to determine if the measures
represent a RACM level of control is not necessary. A proposed
approval of a Plan's provisions concerning implementation of BACM is
also a proposed finding that the Plan provides for the
implementation of RACM.
---------------------------------------------------------------------------

    The overarching requirement for the CAA section 189(d) attainment
control strategy is that it provides for attainment of the NAAQS as
expeditiously as practicable.\150\ The control strategy must include
any additional measures (beyond those already adopted in previous
nonattainment plans for the area as RACM/RACT or BACM/BACT) that are
needed for the area to attain expeditiously. This includes reassessing
any measures previously rejected during the development of any Moderate
area or Serious area attainment plan control strategy.\151\ The state
must also demonstrate that it will, at a minimum, achieve an annual
five percent reduction in emissions of direct PM2.5 or any
PM2.5 plan precursor from sources in the area, based on the
most recent emissions inventory for the area.\152\
---------------------------------------------------------------------------

    \150\ 81 FR 58010, 58100.
    \151\ 40 CFR 50.1010(c)(2)(ii).
    \152\ CAA section 189(d) and 40 CFR 51.1010(c).
---------------------------------------------------------------------------

    In the PM2.5 SIP Requirements Rule, the EPA clarified
its interpretation of the statutory language in CAA section 189(d)
requiring a state to submit a new attainment plan to achieve annual
reductions ``from the date of such submission until attainment,'' to
mean annual reductions beginning from the due date of such submission
until the new projected attainment date for the area based on the new
or additional control measures identified to achieve at least five
percent emissions reductions annually.\153\ This interpretation is
intended to make clear that even if a state is late in submitting its
CAA section 189(d) plan, the area must still achieve its annual five
percent emissions reductions beginning from the date by which the state
was required to make its CAA section 189(d) submission, not by some
later date. Because the deadline for California to submit a section
189(d) plan for the 1997 PM2.5 NAAQS in the San Joaquin
Valley was December 31, 2016, one year after the December 31, 2015
attainment date for these NAAQS under CAA section 188(c)(2), the
starting point for the five percent emissions reduction requirement
under section 189(d) for this area is 2017.
---------------------------------------------------------------------------

    \153\ 81 FR 58010, 58101.
---------------------------------------------------------------------------

2. Summary of the State's Submission and the EPA's Evaluation and
Proposed Action
a. Control Strategy
    For the Serious area and section 189(d) plan requirements for the
1997 24-hour PM2.5 NAAQS the State based the control
strategy in the SJV PM2.5 Plan on ongoing emissions
reductions from baseline control measures.\154\ As we use the term
here, baseline measures are State and District regulations adopted
prior to the development of the SJV PM2.5 Plan that continue
to achieve emissions reductions through the projected 2020 attainment
year for the 1997 24-hour PM2.5 NAAQS and beyond. The State
describes the baseline measures in the 2018 PM2.5 Plan in
Chapter 4,\155\ Appendix C (``Stationary Source Control Measure
Analyses''), and Appendix D (``Mobile Source Control Measure
Analyses''). The State incorporates reductions generated by these
baseline measures into the projected baseline inventories and
reductions resulting from District measures are individually quantified
in Appendix C.
---------------------------------------------------------------------------

    \154\ Because the 2015 Serious area attainment date has passed,
and the EPA found that the area failed to attain by the Serious area
attainment date, we are evaluating the control strategy for the
Serious area requirements based on the timeline associated with the
current section 189(d) projected attainment date of December 31,
2020.
    \155\ 2018 PM2.5 Plan, Chapter 4, Table 4-2.
---------------------------------------------------------------------------

    In the 2018 PM2.5 Plan, CARB indicates that mobile
sources emit over 85 percent of the NOX emissions in the San
Joaquin Valley and that CARB has adopted and amended regulations to
reduce public exposure to diesel particulate matter, which includes
direct PM2.5 and NOX, from ``fuel sources,
freight transport sources like heavy-duty diesel trucks, transportation
sources like passenger cars and buses, and non-road sources like large
construction equipment.'' \156\
---------------------------------------------------------------------------

    \156\ 2018 PM2.5 Plan, Chapter 4, 4-9. For CARB's
BACM analysis for mobile source measures, see 2018 PM2.5
Plan, Appendix D, including analyses for on-road light-duty vehicles
and fuels (starting on page D-17), on-road heavy-duty vehicles and
fuels (starting on page D-35), and non-road sources (starting on
page D-64).
---------------------------------------------------------------------------

    Given the need for substantial emissions reductions from mobile and
area sources to meet the NAAQS in California nonattainment areas, the
State of California has developed stringent control measures for on-
road and non-road mobile sources and the fuels that power them.
California has unique authority under CAA section 209 (subject to a
waiver or authorization as applicable by the EPA) to adopt and
implement new emissions standards for many categories of on-road
vehicles and engines and new and in-use non-road vehicles and engines.
The EPA has approved many such mobile source regulations for which it
has issued waiver authorizations as revisions to the California
SIP.\157\
---------------------------------------------------------------------------

    \157\ For example, see 81 FR 39424 (June 16, 2016); 82 FR 14446
(March 21, 2017); and 83 FR 23232 (May 18, 2018).
---------------------------------------------------------------------------

    CARB's mobile source program extends beyond regulations that are
subject to the waiver or authorization process set forth in CAA section
209 to include standards and other requirements to control emissions
from in-use heavy-duty trucks and buses, gasoline and diesel fuel
specifications, and many other types of mobile sources. Generally,
these regulations have also been submitted and approved as revisions to
the California SIP.\158\
---------------------------------------------------------------------------

    \158\ For example, see the EPA's approval of standards and other
requirements to control emissions from in-use heavy-duty diesel
trucks (77 FR 20308, April 4, 2012), revisions to the California on-
road reformulated gasoline and diesel fuel regulations (75 FR 26653,
May 12, 2010), and revisions to the California motor vehicle
inspection and maintenance program (75 FR 38023, July 1, 2010).
---------------------------------------------------------------------------

    As to stationary and area sources, the SJV PM2.5 Plan
indicates that regulations adopted for prior attainment plans

continue to reduce emissions of NOX and direct
PM2.5.\159\ Specifically, Table 4-1 of the 2018
PM2.5 Plan identifies 33 District measures that limit
NOX and direct PM2.5 emissions.\160\ The EPA has
approved each of the identified measures into the California SIP,\161\
with two exceptions.
---------------------------------------------------------------------------

    \159\ 2018 PM2.5 Plan, Chapter 4, 4-3. For the
District's BACM analysis of stationary and area source measures, see
2018 PM2.5 Plan, Appendix C.
    \160\ 2018 PM2.5 Plan, Chapter 4, Table 4-1.
    \161\ See EPA Region IX's website for information on District
control measures that have been approved into the California SIP,
available at: https://www.epa.gov/sips-ca/epa-approved-san-joaquin-valley-unified-air-district-regulations-california-sip.
---------------------------------------------------------------------------

    First, the District amended Rule 4905 (``Natural Gas-fired, Fan-
type, Residential Central Furnaces'') on October 15, 2020, to extend
the period during which manufacturers may pay emissions fees in lieu of
meeting the rule's NOX emissions limits.\162\ CARB submitted
the amended rule to the EPA on December 30, 2020,\163\ and the EPA has
not yet proposed any action on this submission. The EPA approved a
prior version of Rule 4905 into the California SIP on March 29,
2016.\164\ As part of that rulemaking, the EPA noted that because of
the option in Rule 4905 to pay mitigation fees in lieu of compliance
with emissions limits, emissions reductions associated with the rule's
emissions limits would not be creditable in any attainment plan without
additional documentation.\165\ Until the District submits the necessary
documentation to credit emissions reductions achieved by Rule 4905
toward an attainment control strategy, this rule is not creditable for
SIP purposes. The Plan indicates that the District attributed 0.06 tpd
of NOX reductions between 2013 and 2020 to Rule 4905.\166\
These emissions reductions have de minimis impacts on the attainment
demonstration for the 1997 24-hour PM2.5 NAAQS in the SJV
PM2.5 Plan.
---------------------------------------------------------------------------

    \162\ SJVUAPCD, Final Draft Staff Report with Appendix for
Proposed Amendments to Rule 4905, ``Adopt Proposed Amendments to
Rule 4905 (Natural Gas-fired, Fan-type Central Furnaces),'' 2.
    \163\ Letter dated December 28, 2020, from Richard W. Corey,
Executive Officer, CARB, to John Busterud, Regional Administrator,
EPA Region 9. CARB's submittal letter formally withdrew a previously
amended version of Rule 4905 adopted by the District on June 21,
2018 and submitted to the EPA by CARB on November 21, 2018.
    \164\ 81 FR 17390 (March 29, 2016) (approving Rule 4905 as
amended January 22, 2015).
    \165\ EPA, Region IX Air Division, ``Technical Support Document
for EPA's Proposed Rulemaking for the California State
Implementation Plan (SIP), San Joaquin Valley Unified Air Pollution
Control District's Rule 4905, Natural Gas-Fired, Fan-Type Central
Furnaces,'' October 5, 2015, n. 8.
    \166\ 2018 PM2.5 Plan, Appendix C, C-290.
---------------------------------------------------------------------------

    Second, the 2018 PM2.5 Plan lists Rule 4203
(``Particulate Matter Emissions from Incineration of Combustible
Refuse'') as a baseline measure. This rule has not been approved into
the California SIP.\167\ Appendix C of the 2018 PM2.5 Plan
indicates, however, that the emissions inventory for incineration of
combustible refuse is 0.00 tpd of NOX and 0.00 direct
PM2.5 from 2013 through 2020.\168\ Thus, although the
District included this rule as a baseline measure, there are no
meaningful reductions associated with this rule that would affect the
attainment demonstration in the SJV PM2.5 Plan.
---------------------------------------------------------------------------

    \167\ The EPA does not have any pending SIP submission for Rule
4203.
    \168\ 2018 PM2.5 Plan, Appendix C, C-46.
---------------------------------------------------------------------------

    In sum, although Table 4-1 of the 2018 PM2.5 Plan
identifies two baseline measures that are not creditable for SIP
purposes at this time, we find that the total emissions reductions
attributed to these measures in the future baseline inventories have de
minimis effects on the attainment demonstration in the Plan.
b. Best Available Control Measures
    We are evaluating the State's BACM demonstration for the 1997 24-
hour PM2.5 NAAQS against the section 189(b)(1)(B) Serious
area plan BACM requirement, and the section 189(d) plan requirement to
address all Serious area plan requirements that the State has not
already met. Because we have already found that the State failed to
attain the 1997 24-hour PM2.5 NAAQS in the San Joaquin
Valley area by the Serious area attainment date, and because we have
not previously found that the state has met the BACM requirement for
purposes of the 1997 24-hour PM2.5 NAAQS, we are evaluating
the State's submission against the Serious area BACM requirement in
light of the section 189(d) control plan timeline. The State's BACM
demonstration is presented in Appendix C (``Stationary Source
Controls'') and Appendix D (``Mobile Source Control Measure Analyses'')
of the 2018 PM2.5 Plan.\169\ As discussed in section IV.A of
this proposed rule, Appendix B (``Emissions Inventory'') of the 2018
PM2.5 Plan contains the planning inventories for direct
PM2.5 and all PM2.5 precursors (NOX,
SOX, VOC, and ammonia) for the San Joaquin Valley
nonattainment area together with documentation to support these
inventories. Each inventory includes emissions from stationary, area,
on-road, and non-road emissions sources, and the State specifically
identifies the condensable component of direct PM2.5 for
relevant stationary source and area source categories. As discussed in
section IV.B of this proposed rule, the State concludes that the Plan
should control emissions of PM2.5 and NOX to
reach attainment. Accordingly, the BACM and BACT evaluation in the Plan
addresses potential controls for sources of those pollutants.
---------------------------------------------------------------------------

    \169\ Appendices C and D also present an MSM analysis for the
purposes of meeting a precondition for an extension of the Serious
area attainment date under CAA section 188(e) for the 2006
PM2.5 NAAQS. The San Joaquin Valley area is not subject
to the MSM requirement for the 1997 24-hour PM2.5 NAAQS.
Thus, the EPA is evaluating the Plan's control strategy for
implementation of BACM and BACT only.
---------------------------------------------------------------------------

    For stationary and area sources, the District identifies the
sources of direct PM2.5 and NOX in the San
Joaquin Valley that are subject to District emissions control measures
and provides its evaluation of these regulations for compliance with
BACM requirements in Appendix C of the 2018 PM2.5 Plan. As
part of its process for identifying candidate BACM and considering the
technical and economic feasibility of additional control measures, the
District reviewed the EPA's guidance documents on BACM, additional
guidance documents on control measures for direct PM2.5 and
NOX emissions sources, and control measures implemented in
other ozone and PM2.5 nonattainment areas in California and
other states.\170\ The District also provides an analysis of several
SIP-approved VOC regulations that, according to the District, also
provide ammonia co-benefits.\171\ Based on these analyses, the District
concludes that all best available control measures for stationary and
area sources are in place in the San Joaquin Valley for NOX
and directly emitted PM2.5 for purposes of meeting the BACM/
BACT requirement for the 1997 24-hour PM2.5 NAAQS. We
provide an evaluation of many of the District's control measures for
stationary sources and area sources in section III of the EPA's 1997
24-hour PM2.5 TSD together with recommendations for possible
future improvements to these rules.
---------------------------------------------------------------------------

    \170\ 2018 PM2.5 Plan, Chapter 4, section 4.3.1.
    \171\ 2018 PM2.5 Plan, Appendix C., section C.25.
---------------------------------------------------------------------------

    For mobile sources, CARB identifies the sources of direct
PM2.5 and NOX in the San Joaquin Valley that are
subject to the State's emissions control measures and provides its
evaluation of these regulations for compliance with BACM requirements
in Appendix D of the 2018 PM2.5 Plan. Appendix D describes
CARB's process for determining BACM, including identification of the
sources of direct PM2.5 and NOX in the San
Joaquin

Valley, identification of potential control measures for such sources,
assessment of the stringency and feasibility of the potential control
measures, and adoption and implementation of feasible control
measures.\172\
---------------------------------------------------------------------------

    \172\ 2018 PM2.5 Plan, Appendix D, Chapter II.
---------------------------------------------------------------------------

    Mobile source categories for which CARB has primary responsibility
for reducing emissions in California include most new and existing on-
and non-road engines and vehicles and motor vehicle fuels. The SJV
PM2.5 Plan's BACM demonstration provides a general
description of CARB's key mobile source programs and regulations and a
comprehensive table listing on-road and non-road mobile source
regulatory actions taken by CARB since 1985.\173\
---------------------------------------------------------------------------

    \173\ Id. at Table 17.
---------------------------------------------------------------------------

    Appendix D of the 2018 PM2.5 Plan also describes the
current efforts of the eight local jurisdiction metropolitan planning
organizations (MPOs) to implement cost-effective transportation control
measures (TCMs) in the San Joaquin Valley.\174\ TCMs are projects that
reduce air pollutants from transportation sources by reducing vehicle
use, traffic congestion, or vehicle miles traveled. TCMs are currently
being implemented in the San Joaquin Valley as part of the Congestion
Mitigation and Air Quality cost effectiveness policy adopted by the
eight local jurisdiction MPOs and in the development of each Regional
Transportation Plan (RTP). The Congestion Mitigation and Air Quality
policy, which is included in a number of the District's prior
attainment plan submissions for the ozone and PM2.5 NAAQS,
provides a standardized process for distributing 20 percent of the
Congestion Mitigation and Air Quality funds to projects that meet a
minimum cost effectiveness threshold beginning in fiscal year 2011. The
MPOs revisited the minimum cost effectiveness standard during the
development of their 2018 RTPs and 2019 Federal Transportation
Improvement Program and concluded that they were implementing all
reasonable transportation control measures.\175\ Appendix D of the
District's ``2016 Ozone Plan for 2008 8-Hour Ozone Standard,'' adopted
June 16, 2016, contains a listing of adopted TCMs for the San Joaquin
Valley.\176\
---------------------------------------------------------------------------

    \174\ Id. at D-127 and D-128.
    \175\ Id. at D-127.
    \176\ Id. and SJVUAPCD, ``2016 Ozone Plan for 2008 8-Hour Ozone
Standard'' (adopted June 16, 2016), Appendix D, Attachment D, tables
D-10 to D-17.
---------------------------------------------------------------------------

    We have reviewed the State's and District's analysis and
determination in the SJV PM2.5 Plan that their baseline
mobile, stationary, and area source control measures meet the
requirements for BACM for sources of direct PM2.5 and
applicable PM2.5 plan precursors (i.e., NOX) for
purposes of the 1997 24-hour PM2.5 NAAQS. In our review, we
considered our evaluation of the State's and District's rules in
connection with our approval of the demonstrations for BACM (including
BACT) and MSM for the 2006 PM2.5 NAAQS.\177\ We find that
the evaluation processes followed by CARB and the District in the SJV
PM2.5 Plan to identify potential BACM were generally
consistent with the requirements of the PM2.5 SIP
Requirements Rule, the State's and District's evaluation of potential
measures is appropriate, and the State and District have provided
reasoned justifications for their rejection of potential measures based
on technological or economic infeasibility. We also agree with the
District's conclusion that all reasonable TCMs are being implemented in
the San Joaquin Valley and propose to find that these TCMs implement
BACM for transportation sources.
---------------------------------------------------------------------------

    \177\ 85 FR 44192.
---------------------------------------------------------------------------

    For the foregoing reasons, we propose to find that the SJV
PM2.5 Plan provides for the implementation of BACM for
sources of direct PM2.5 and NOX as expeditiously
as practicable in accordance with the requirements of CAA section
189(b)(1)(B), and in satisfaction of both the Serious area and section
189(d) plan requirements.
c. Section 189(d) Five Percent Requirement
    The SJV PM2.5 Plan's demonstration of annual five
percent reductions in NOX emissions is in section 5.2 of the
2018 PM2.5 Plan. As shown in Table 3, the demonstration uses
the 2013 base year inventory as the starting point from which the five
percent per year emissions reductions are calculated and uses 2017 as
the year from which the reductions start. The target required reduction
in 2017 is five percent of the base year (2013) inventory, which is a
reduction of approximately 15.9 tpd of NOX, and the targets
for subsequent years are additional reductions of five percent per year
until the 2020 attainment year. The projected emissions inventories
reflect NOX emissions reductions achieved by baseline
control measures and the demonstration shows that these NOX
emissions reductions are greater than the required five percent per
year.

      Table 3--2017-2020 Annual Five Percent Emissions Reductions Demonstration for the San Joaquin Valley
----------------------------------------------------------------------------------------------------------------
                                                                           CEPAM
                                        % Reduction   5% Target (tpd     inventory
                Year                  from 2013 base       NOX)         v1.05 (tpd             Meets 5%?
                                           year                            NOX)
----------------------------------------------------------------------------------------------------------------
2013 (base year)....................  ..............  ..............           317.3  ..........................
2017................................               5           301.3           233.4  Yes.
2018................................              10           285.5           221.5  Yes.
2019................................              15           269.6           214.5  Yes.
2020................................              20           253.8           203.3  Yes.
----------------------------------------------------------------------------------------------------------------
Source: 2018 PM2.5 Plan, Table 5-2.

    The EPA proposes to find that the State's use of 2017 as the
starting point from which the five percent per year emissions
reductions should begin is reasonable and consistent with the CAA. As
discussed in section IV.C.1 of this document, the EPA interprets the
language under CAA section 189(d) to require a state to submit a new
attainment plan to achieve annual reductions ``from the date of such
submission until attainment.'' The 2018 PM2.5 Plan was not
submitted until May 10, 2019. However, the Serious area attainment
deadline for the San Joaquin Valley nonattainment area for the 1997
PM2.5 NAAQS was December 31, 2015.\178\ Accordingly, a plan
submittal

to meet the requirements under section 189(d) was due by December 31,
2016, and reductions were required to occur as of that date. The
decline in emissions from 2017 to 2020 shows that reductions did, in
fact, occur within the required timeframe. Furthermore, the State's
demonstration shows that NOX emissions reductions from 2017
to 2020 are greater than the required five percent per year. Thus, the
EPA proposes to find that the SJV PM2.5 Plan meets the CAA
189(d) requirement to provide for an annual reduction in
PM2.5 or PM2.5 precursor emissions of not less
than five percent of the amount of such emissions reported in the most
recent inventory prepared for the area.
---------------------------------------------------------------------------

    \178\ 80 FR 18528.
---------------------------------------------------------------------------

D. Attainment Demonstration and Modeling

1. Statutory and Regulatory Requirements
    Section 189(b)(1)(A) of the CAA requires that each Serious area
plan include a demonstration (including air quality modeling) that the
plan provides for attainment of the PM2.5 NAAQS by the
applicable attainment date. As discussed in section IV of this
proposal, given that the outermost statutory Serious area attainment
date for the San Joaquin Valley area (i.e., December 31, 2015) has
passed and that the EPA has already found that the SJV area failed to
attain by that date, the EPA must evaluate the State's plan for
attainment by a later attainment date. Given that the finding of
failure to attain triggered the State's obligation to submit a new plan
meeting the requirements of section 189(d), the EPA is evaluating the
SJV PM2.5 Plan in light of the outermost attainment date
required in section 189(d). That section requires that the attainment
date be as expeditious as practicable, but not later than five years
following the EPA's finding that the area failed to attain the NAAQS by
the applicable Serious area attainment date. In this case, the State
projected such attainment by December 31, 2020, i.e., by the relevant
statutory date.
    The PM2.5 SIP Requirements Rule explains that the same
general requirements that apply to Moderate and Serious area plans
under CAA sections 189(a) and 189(b) should apply to plans developed
pursuant to CAA section 189(d)--i.e., the plan must include a
demonstration (including air quality modeling) that the control
strategy provides for attainment of the PM2.5 NAAQS as
expeditiously as practicable.\179\ For purposes of determining the
attainment date that is as expeditious as practicable, the state must
conduct future year modeling that takes into account emissions growth,
known controls (including any controls that were previously determined
to be RACM/RACT or BACM/BACT), the five percent per year emissions
reductions required by CAA section 189(d), and any other emissions
controls that are needed for expeditious attainment of the NAAQS.
---------------------------------------------------------------------------

    \179\ 40 CFR 51.1011(b)(1); 81 FR 58010, 58102.
---------------------------------------------------------------------------

    The EPA's PM2.5 modeling guidance \180\ (``Modeling
Guidance'' and ``Modeling Guidance Update'') recommends that a
photochemical model, such as the Comprehensive Air Quality Model with
Extensions (CAMx) or Community Multiscale Air Quality Model (CMAQ), be
used to simulate a base case, with meteorological and emissions inputs
reflecting a base case year, to replicate concentrations monitored in
that year. The model application to the base year undergoes a
performance evaluation to ensure that it satisfactorily corroborates
the concentrations monitored in that year. The model may then be used
to simulate emissions occurring in other years required for a plan,
namely the base year (which may differ from the base case year) and
future year.\181\ The modeled response to the emissions changes between
those years is used to calculate relative response factors (RRFs) that
are applied to the design value in the base year to estimate the
projected design value in the future year for comparison against the
NAAQS. Separate RRFs are estimated for each chemical species component
of PM2.5, and for each quarter of the year, to reflect their
differing responses to seasonal meteorological conditions and
emissions. Because each species is handled separately, before applying
an RRF, the base year design value should be speciated using available
chemical species measurements--that is, each day's measured
PM2.5 design value must be split into its species
components. The Modeling Guidance provides additional detail on the
recommended approach.\182\
---------------------------------------------------------------------------

    \180\ Memorandum dated November 29, 2018, from Richard Wayland,
Air Quality Assessment Division, Office of Air Quality Planning and
Standards, EPA, to Regional Air Division Directors, EPA, Subject:
``Modeling Guidance for Demonstrating Air Quality Goals for Ozone,
PM2.5, and Regional Haze,'' (``Modeling Guidance''), and
memorandum dated June 28, 2011 from Tyler Fox, Air Quality Modeling
Group, Office of Air Quality Planning and Standards, EPA, to
Regional Air Program Managers, EPA, Subject: ``Update to the 24 Hour
PM2.5 NAAQS Modeled Attainment Test,'' (``Modeling
Guidance Update'').
    \181\ In this section, we use the terms ``base case,'' ``base
year'' or ``baseline,'' and ``future year'' as described in section
2.3 of the EPA's Modeling Guidance. The ``base case'' modeling
simulates measured concentrations for a given time period, using
emissions and meteorology for that same year. The modeling ``base
year'' (which can be the same as the base case year) is the
emissions starting point for the plan and for projections to the
future year, both of which are modeled for the attainment
demonstration. Modeling Guidance, 37-38.
    \182\ Modeling Guidance, section 4.5, ``What is the Recommended
Modeled Attainment Test for the 24-Hour NAAQS.''
---------------------------------------------------------------------------

2. Summary of the State's Submission
    As discussed in section IV.C, the SJV PM2.5 Plan
includes a modeled demonstration projecting that the San Joaquin Valley
would attain the 1997 24-hour PM2.5 NAAQS by December 31,
2020, based on ongoing emissions reductions from baseline control
measures. CARB conducted photochemical modeling with the CMAQ model
using inputs developed from routinely available meteorological and air
quality data, as well as more detailed and extensive data from the
DISCOVER-AQ field study conducted in January and February of 2013.\183\
The Plan's primary discussion of the photochemical modeling appears in
Appendix K (``Modeling Attainment Demonstration'') of the 2018
PM2.5 Plan. The State briefly summarizes the area's air
quality problem in Chapter 2 (``Air Quality Challenges and Trends'')
and the modeling results in Chapter 5.3 (``Attainment Demonstration and
Modeling'') of the 2018 PM2.5 Plan. The State provides a
conceptual model of PM2.5 formation in the San Joaquin
Valley as part of the modeling protocol in Appendix L (``Modeling
Protocol''). Appendix J (``Modeling Emission Inventory'') describes
emissions input preparation procedures. The State presents additional
relevant information in Appendix C (``Weight of Evidence Analysis'') of
the CARB Staff Report, which includes ambient trends and other data in
support of the attainment demonstration.
---------------------------------------------------------------------------

    \183\ NASA, ``Deriving Information on Surface conditions from
COlumn and VERtically Resolved Observations Relevant to Air
Quality,'' available at https://www.nasa.gov/mission_pages/discover-aq/index.html.
---------------------------------------------------------------------------

    CARB's air quality modeling approach investigated the many inter-
connected facets of modeling ambient PM2.5 in the San
Joaquin Valley, including model input preparation, model performance
evaluation, use of the model output for the numerical NAAQS attainment
test, and modeling documentation. Specifically, this required the
development and evaluation of a conceptual model, modeling protocol,
episode (i.e., base year) selection, modeling domain, CMAQ model
selection, initial and boundary condition procedures, meteorological

model choice and performance, modeling emissions inventory preparation
procedures, model performance, attainment test procedure, adjustments
to baseline air quality for modeling, the 2020 attainment test, and an
unmonitored area analysis. CARB's supplemental weight of evidence
analysis further supports the Plan's demonstration of attainment by the
end of 2020. These analyses are generally consistent with the EPA's
recommendations in the Modeling Guidance.
    The model performance evaluation in Appendix K includes statistical
and graphical measures of model performance. The magnitude and timing
of predicted concentrations of total PM2.5, as well as of
its ammonium and nitrate components, generally match the occurrence of
elevated PM2.5 levels in the measured observations. A
comparison to other recent modeling efforts shows good model
performance on bias, error, and correlation with measurements, for
total PM2.5 and for most of its chemical components. The
Weight of Evidence Analysis shows the downward trend in NOX
emissions along with a 70 percent decrease between 1999 and 2017 in the
number of days above the 1997 24-hour PM2.5 NAAQS.\184\ The
analysis also shows decreases in daily PM2.5 concentrations
during winter, and in the frequency of high PM2.5
concentrations generally.\185\ Available ambient air quality data show
that total PM2.5 and ammonium nitrate concentrations have
declined over the 2004-2017 period, despite some increases from time to
time.\186\ These trends show that there has been an improvement in air
quality due to emissions reductions in the San Joaquin Valley, although
that point is not fully reflected in the 98th percentile statistic,
which is the basis for the regulatory design value.
---------------------------------------------------------------------------

    \184\ Weight of Evidence Analysis, 27-28, Figure 14, and Figure
24.
    \185\ Id. at Figure 16 and Figure 17.
    \186\ Id. at Figure 21.
---------------------------------------------------------------------------

    The State conducted three CMAQ \187\ simulations: (1) A 2013 base
year simulation to demonstrate that the model reasonably reproduced the
observed PM2.5 concentrations in the San Joaquin Valley; (2)
a 2013 baseline year simulation that was the same as the 2013 base year
simulation but excluded exceptional event emissions, such as wildfire
emissions; and (3) a 2020 future year simulation that reflects
projected emissions growth and reductions due to controls that have
already been adopted and implemented.\188\
---------------------------------------------------------------------------

    \187\ CMAQ Version 5.0.2.
    \188\ 2018 PM2.5 Plan, 5-5.
---------------------------------------------------------------------------

    Table 4 shows the 2013 base year and 2020 projected future year 24-
hour PM2.5 design values at monitoring sites in the San
Joaquin Valley. As recommended by the EPA's guidance, the 2013 base
year design value for modeling purposes is a weighted average of three
monitored design values, to minimize the influence of year-to-year
variability. The highest 2020 projected design value is 47.6 [micro]g/
m\3\ at the Bakersfield-California monitoring site, which is below the
65 [micro]g/m\3\ level of the 1997 24-hour PM2.5 NAAQS.

   Table 4--Projected Future 24-Hour PM2.5 Design Values at Monitoring
            Sites in the San Joaquin Valley ([micro]g/m \3\)
------------------------------------------------------------------------
                                             2013 Base    2020 Projected
             Monitoring site               design value    design value
------------------------------------------------------------------------
Bakersfield--California.................            64.1            47.6
Fresno-Garland..........................            60.0            44.3
Hanford.................................            60.0            43.7
Fresno-Hamilton & Winery................            59.3            45.6
Clovis..................................            55.8            41.1
Visalia.................................            55.5            42.8
Bakersfield-Planz.......................            55.5            41.2
Madera..................................            51.0            38.9
Turlock.................................            50.7            37.8
Modesto.................................            47.9            35.8
Merced-M. Street........................            46.9            32.9
Stockton................................            42.0            33.5
Merced-S Coffee.........................            41.1            30.0
Manteca.................................            36.9            30.1
Tranquility.............................            29.5            21.5
------------------------------------------------------------------------
Source: 2018 PM2.5 Plan, Table 5-5.

3. The EPA's Review of the State's Submission
    The EPA must make several findings in order to approve the modeled
attainment demonstration in an attainment plan SIP submission. First,
we must find that the attainment demonstration's technical bases,
including the emissions inventories and air quality modeling, are
adequate. As discussed in section IV.A of this preamble, we are
proposing to approve the emissions inventories on which the SJV
PM2.5 Plan's attainment demonstration and related provisions
are based. Furthermore, the EPA has evaluated the State's choice of
model and the extensive discussion in the Modeling Protocol about
modeling procedures, tests, and performance analyses. We find that the
analyses are consistent with the EPA's guidance on modeling for
PM2.5 attainment planning purposes. Based on these reviews,
we find that the modeling in the Plan is adequate for the purposes of
supporting the RFP demonstration and demonstration of attainment by
2020 and are proposing to approve the air quality modeling. For further
detail, see the EPA's February 2020 Modeling TSD.
    Second, we must find that the SIP submittal provides for
expeditious attainment through the timely implementation of the control
strategy. As discussed in section IV.C of this preamble, we are
proposing to approve the control strategy in the SJV PM2.5
Plan, including the BACM/BACT demonstration and the five percent
emissions reduction requirement under CAA sections 189(b)(1)(B) and
189(d), respectively.

    Third, the EPA must find that the emissions reductions that are
relied on for attainment in the SIP submission are creditable. As
discussed in section IV.C.2.a, the SJV PM2.5 Plan relies
principally on rules that have already been adopted and approved by the
EPA to achieve the emissions reductions needed to attain the 1997 24-
hour PM2.5 NAAQS in the San Joaquin Valley. We present our
evaluation of the rules in section IV.C.2.a and in sections II and III
of the EPA's 1997 24-hour PM2.5 TSD. We find that all but
two of these rules are SIP-creditable and that the total emissions
reductions attributed to the two measures that are not SIP-creditable
have de minimis impacts on the attainment demonstration in the Plan.
    The EPA has also reviewed ambient monitoring data recorded at air
quality monitors throughout the San Joaquin Valley PM2.5
nonattainment area during the three years leading up to the projected
December 31, 2020 attainment date (i.e., 2018-2020). As discussed in
section V of this proposal, based on these data, we are proposing to
find that the San Joaquin Valley area attained the 1997 24-hour
PM2.5 NAAQS by the December 31, 2020 attainment date.
    Based on these evaluations, we propose to determine that the SJV
PM2.5 Plan provides for attainment of the 1997 24-hour
PM2.5 NAAQS by the most expeditious date practicable,
consistent with the requirements of CAA section 189(d). Furthermore,
because the 2015 Serious area attainment date has passed, and the EPA
found that the area failed to attain by the Serious area attainment
date, we are evaluating the State's compliance with the Serious area
plan requirements in light of the attainment date required under CAA
section 189(d).\189\ Thus, we are also proposing to determine that the
Plan meets the Serious area attainment plan requirement under CAA
section 189(b)(1)(A).
---------------------------------------------------------------------------

    \189\ See CAA section 179(d); 40 CFR 51.1004(a)(3).
---------------------------------------------------------------------------

E. Reasonable Further Progress and Quantitative Milestones

1. Statutory and Regulatory Requirements
    CAA section 172(c)(2) provides that all nonattainment area plans
shall require RFP toward attainment. In addition, CAA section 189(c)
requires that all PM2.5 nonattainment area SIPs include
quantitative milestones to be achieved every three years until the area
is redesignated to attainment and that demonstrate RFP. Section 171(l)
of the Act defines RFP as ``such annual incremental reductions in
emissions of the relevant air pollutant as are required by [Part D] or
may reasonably be required by the Administrator for the purpose of
ensuring attainment of the applicable [NAAQS] by the applicable date.''
Neither subpart 1 nor subpart 4 of part D, title I of the Act requires
that states achieve a set percentage of emissions reductions in any
given year for purposes of satisfying the RFP requirement. For purposes
of the PM2.5 NAAQS, the EPA has interpreted the RFP
requirement to require that the nonattainment area plans show annual
incremental emissions reductions sufficient to maintain generally
linear progress toward attainment by the applicable deadline.\190\
---------------------------------------------------------------------------

    \190\ General Preamble Addendum, 42015.
---------------------------------------------------------------------------

    Attainment plans for PM2.5 nonattainment areas should
include detailed schedules for compliance with emissions regulations in
the area and provide corresponding annual emissions reductions to be
achieved by each milestone in the schedule.\191\ In reviewing an
attainment plan under subpart 4, the EPA considers whether the annual
incremental emissions reductions to be achieved are reasonable in light
of the statutory objective of timely attainment. Although early
implementation of the most cost-effective control measures is often
appropriate, states should consider both cost-effectiveness and
pollution reduction effectiveness when developing implementation
schedules for control measures and may implement measures that are more
effective at reducing PM2.5 earlier to provide greater
public health benefits.\192\
---------------------------------------------------------------------------

    \191\ Id. at 42016.
    \192\ Id.
---------------------------------------------------------------------------

    The PM2.5 SIP Requirements Rule establishes specific
regulatory requirements for purposes of satisfying the Act's RFP
requirements and provides related guidance in the preamble to the rule.
Specifically, under the PM2.5 SIP Requirements Rule, each
PM2.5 attainment plan must contain an RFP analysis that
includes, at minimum, the following four components: (1) An
implementation schedule for control measures; (2) RFP projected
emissions for direct PM2.5 and all PM2.5 plan
precursors for each applicable milestone year, based on the anticipated
control measure implementation schedule; (3) a demonstration that the
control strategy and implementation schedule will achieve reasonable
progress toward attainment between the base year and the attainment
year; and (4) a demonstration that by the end of the calendar year for
each milestone date for the area, pollutant emissions will be at levels
that reflect either generally linear progress or stepwise progress in
reducing emissions on an annual basis between the base year and the
attainment year.\193\ Additionally, states should estimate the RFP
projected emissions for each quantitative milestone year by sector on a
pollutant-by-pollutant basis.\194\
---------------------------------------------------------------------------

    \193\ 40 CFR 51.1012(a).
    \194\ 81 FR 58010, 58056.
---------------------------------------------------------------------------

    Section 189(c) of the Act requires that PM2.5 attainment
plans include quantitative milestones that demonstrate RFP. The purpose
of the quantitative milestones is to allow periodic evaluation of the
area's progress towards attainment of the NAAQS consistent with RFP
requirements. Because RFP is an annual emissions reduction requirement
and the quantitative milestones are to be achieved every three years,
when a state demonstrates compliance with the quantitative milestone
requirement, it should also demonstrate that RFP has been achieved
during each of the relevant three years. Quantitative milestones should
provide an objective means to evaluate progress toward attainment
meaningfully, e.g., through imposition of emissions controls in the
attainment plan and the requirement to quantify those required
emissions reductions. The CAA also requires states to submit milestone
reports (due 90 days after each milestone), and these reports should
include calculations and any assumptions made by the state concerning
how RFP has been met, e.g., through quantification of emissions
reductions to date.\195\
---------------------------------------------------------------------------

    \195\ General Preamble Addendum, 42016-42017.
---------------------------------------------------------------------------

    The CAA does not specify the starting point for counting the three-
year periods for quantitative milestones under CAA section 189(c). In
the General Preamble and General Preamble Addendum, the EPA interpreted
the CAA to require that the starting point for the first three-year
period be the due date for the Moderate area plan submission.\196\ In
keeping with this historical approach, the EPA established December 31,
2014, the deadline that the EPA established for a state's submission of
any additional attainment-related SIP elements necessary to satisfy the
subpart 4 Moderate area requirements for the 1997 PM2.5
NAAQS, as the starting point for the first three-year period under CAA
section 189(c) for the 1997 PM2.5 NAAQS in the San Joaquin
Valley.\197\
---------------------------------------------------------------------------

    \196\ General Preamble, 13539, and General Preamble Addendum,
42016.
    \197\ 79 FR 31566 (final rule establishing subpart 4 moderate
area classifications and deadline for related SIP submissions).
Although this final rule did not affect any action that the EPA had
previously taken under CAA section 110(k) on a SIP for a
PM2.5 nonattainment area, the EPA noted that states may
need to submit additional SIP elements to fully comply with the
applicable requirements of subpart 4, even for areas with previously
approved PM2.5 attainment plans, and that the deadline
for any such additional plan submissions was December 31, 2014. Id.
at 31569.

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

    Under the PM2.5 SIP Requirements Rule, each attainment
plan submission for an area designated nonattainment for the 1997
PM2.5 NAAQS before January 15, 2015, must contain
quantitative milestones to be achieved no later than three years after
December 31, 2014, and every three years thereafter until the milestone
date that falls within three years after the applicable attainment
date.\198\ If the area fails to attain, this post-attainment date
milestone provides the EPA with the tools necessary to monitor the
area's continued progress toward attainment while the state develops a
new attainment plan.\199\ Quantitative milestones must provide for
objective evaluation of RFP toward timely attainment of the
PM2.5 NAAQS in the area and include, at minimum, a metric
for tracking progress achieved in implementing SIP control measures,
including BACM and BACT, by each milestone date.\200\
---------------------------------------------------------------------------

    \198\ 40 CFR 51.1013(a)(4).
    \199\ 81 FR 58010, 58064.
    \200\ Id. at 58064 and 58092.
---------------------------------------------------------------------------

    Because the EPA designated the San Joaquin Valley area as
nonattainment for the 1997 24-hour PM2.5 NAAQS effective
April 5, 2005,\201\ the plan for this area must contain quantitative
milestones to be achieved no later than three years after December 31,
2014 (i.e., by December 31, 2017), and every three years thereafter
until the milestone date that falls within three years after the
applicable attainment date.\202\ For a Serious area attainment plan
with a statutory attainment date of December 31, 2015, the relevant
quantitative milestone year is December 31, 2017. However, as discussed
in section III, the area did not attain by the statutory Serious area
attainment date and evaluating reasonable further progress toward that
date does not make sense. We are therefore evaluating the Serious area
obligations based on the attainment date the State must meet in a plan
required under CAA section 189(d).\203\ To meet CAA section 189(d), the
SJV PM2.5 Plan includes a demonstration that the area will
attain by December 31, 2020. Therefore, in accordance with 40 CFR
51.1013(a)(4), the attainment plan for this area must contain
quantitative milestones to be achieved no later than December 31, 2017,
December 31, 2020, and December 31, 2023.
---------------------------------------------------------------------------

    \201\ 70 FR 944.
    \202\ 40 CFR 51.1013(a)(4).
    \203\ See CAA section 179(d); 40 CFR 51.1004(a)(3).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    Appendix H (``RFP, Quantitative Milestones, and Contingency'') of
the 2018 PM2.5 Plan contains the State's RFP demonstration
and quantitative milestones for the 1997 24-hour PM2.5
NAAQS,\204\ and the Valley State SIP Strategy contains the control
measure commitments that CARB has identified as mobile source
quantitative milestones for the 2020 milestone date.\205\ Given the
State's conclusions that ammonia, SOX, and VOC emissions do
not contribute significantly to PM2.5 levels that exceed the
1997 24-hour PM2.5 NAAQS in the San Joaquin Valley, as
discussed in section IV.B of this proposed rule, the RFP demonstration
provided by the State addresses emissions of direct PM2.5
and NOX.\206\ Similarly, the State developed quantitative
milestones based upon implementation of control strategy measures in
the adopted SIP and in the SJV PM2.5 Plan that achieve
reductions in emissions of direct PM2.5 and
NOX.\207\ For the 1997 24-hour PM2.5 NAAQS, the
RFP analysis in the Plan shows generally linear progress toward
attainment.
---------------------------------------------------------------------------

    \204\ As discussed in footnote 34, all references to Appendix H
in this proposed rule are to the revised version submitted on
February 11, 2020, which replaces the version submitted with the
2018 PM2.5 Plan on May 10, 2019.
    \205\ Valley State SIP Strategy, Table 7 (identifying State
measures scheduled for action between 2017 and 2020, inter alia) and
CARB Resolution 18-49, ``San Joaquin Valley Supplement to the 2016
State Strategy for the State Implementation Plan'' (October 25,
2018), 5 (adopting State commitment to begin public processes and
propose for Board consideration the list of proposed SIP measures
outlined in the Valley State SIP Strategy and included in Attachment
A, according to the schedule set forth therein).
    \206\ SJV PM2.5 Plan, Appendix H, H-1.
    \207\ Id. at H-18 and H-19 (District milestones) and H-21 and H-
22 (State milestones).
---------------------------------------------------------------------------

    We describe the RFP analysis and quantitative milestones in the SJV
PM2.5 Plan in greater detail below.
Reasonable Further Progress
    The State addresses the RFP and quantitative milestone requirements
in Appendix H to the 2018 PM2.5 Plan submitted in February
2020. The State estimates that emissions of direct PM2.5 and
NOX will generally decline from the 2013 base year to the
projected 2020 attainment year, and beyond to the 2023 post-attainment
quantitative milestone year. The Plan's emissions inventory shows that
direct PM2.5 and NOX are emitted by a large
number and range of sources in the San Joaquin Valley. Table H-2 in
Appendix H contains an anticipated implementation schedule for District
regulatory control measures and Table 4-8 in Chapter 4 of the 2018
PM2.5 Plan contains an anticipated implementation schedule
for CARB control measures in the San Joaquin Valley. Table H-5 in
Appendix H contains projected emissions for each quantitative milestone
year. These emissions levels reflect baseline emissions projections
through the 2023 post-attainment milestone year.\208\
---------------------------------------------------------------------------

    \208\ Id. at tables H-3 to H-5.
---------------------------------------------------------------------------

    The SJV PM2.5 Plan identifies emissions reductions
needed for attainment of the 1997 24-hour PM2.5 NAAQS by
2020,\209\ and identifies San Joaquin Valley's progress toward
attainment in each milestone year.\210\ The State and District set RFP
targets for each of the quantitative milestone years as shown in Table
H-8 of Appendix H of the 2018 PM2.5 Plan.
---------------------------------------------------------------------------

    \209\ Id. at Table H-6.
    \210\ Id. at Table H-7.
---------------------------------------------------------------------------

    According to the Plan, reductions in both direct PM2.5
and NOX emissions from 2013 base year levels result in
emissions levels consistent with attainment in the 2020 attainment
year. Based on these analyses, the State and District conclude that the
adopted control strategy is adequate to meet the RFP requirement for
the 1997 24-hour PM2.5 NAAQS.
Quantitative Milestones
    Appendix H of the 2018 PM2.5 Plan identifies the
milestone dates of December 31, 2017, December 31, 2020, and December
31, 2023, for the 1997 PM2.5 NAAQS.\211\ Appendix H also
identifies target emissions levels to meet the RFP requirement for
direct PM2.5 and NOX emissions for each of these
milestone years,\212\ and State and District control measures that will
achieve emissions reductions in the years leading up to each of the
milestones, in accordance with the control strategy in the Plan.\213\
---------------------------------------------------------------------------

    \211\ Id. at Table H-12.
    \212\ Id. at Table H-8.
    \213\ Id. at H-18 and H-19 (District milestones) and H-21 and H-
22 (State milestones).
---------------------------------------------------------------------------

    The Plan includes quantitative milestones for mobile, stationary,
and area sources. For mobile sources, CARB has developed quantitative
milestones that provide for an evaluation of RFP based on the
implementation of specific control measures by the relevant three-year
milestones. For each quantitative milestone year, the Plan provides for
evaluating RFP by tracking State and District implementation of
regulatory measures and SIP commitments during the three-year period
leading to each

milestone date, consistent with the control strategy in the SJV
PM2.5 Plan.\214\ The identified regulatory measures include
State measures for light-duty vehicles and non-road vehicles and
several District measures for stationary and area sources.\215\
---------------------------------------------------------------------------

    \214\ Id. We note that the District's identified quantitative
milestones for 2023 appear to contain a typographical error, as they
include a District report on ``[t]he status of SIP measures adopted
between 2017 and 2020 as per the schedule included in the adopted
Plan.'' Id. at H-18 and H-19. We understand that the District
intended to refer here to the status of SIP measures adopted between
2020 and 2023, consistent with the schedule in the 2018
PM2.5 Plan.
    \215\ Id. at H-18 and H-19 (District milestones), and H-21 and
H-22 (State milestones).
---------------------------------------------------------------------------

    CARB submitted its 2017 Quantitative Milestone Report for the San
Joaquin Valley to the EPA on December 20, 2018.\216\ The report
includes a certification that CARB and the District met the 2017
quantitative milestones identified in the SJV PM2.5 Plan for
the 1997 PM2.5 NAAQS and discusses the State's and
District's progress on implementing the three CARB measures and six
District measures identified in Appendix H as quantitative milestones
for the 2017 milestone year. On February 15, 2021, the EPA determined
that the 2017 Quantitative Milestone Report was adequate.\217\ In our
evaluation of the 2017 Quantitative Milestone Report, we found that the
control measures in the Plan are in effect, consistent with the RFP
demonstration in the SJV PM2.5 Plan for the 1997 24-hour
PM2.5 NAAQS, but we noted that the determination of adequacy
did not constitute approval of any component of the SJV
PM2.5 Plan.\218\
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    \216\ Letter dated December 20, 2018, from Richard W. Corey,
Executive Officer, CARB, to Michael Stoker, Regional Administrator,
EPA Region IX, with attachment ``2017 Quantitative Milestone Report
for the 1997 and 2006 NAAQS.''
    \217\ Letter dated February 15, 2021, from Deborah Jordan,
Acting Regional Administrator, EPA Region IX, to Richard W. Corey,
Executive Officer, CARB, with enclosure titled ``EPA Evaluation of
2017 Quantitative Milestone Report.''
    \218\ Id.
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3. The EPA's Review of the State's Submission
    The RFP demonstration in the SJV PM2.5 Plan identifies
quantitative milestone dates (i.e., December 31 of 2017, 2020, and
2023) that are consistent with the requirements of 40 CFR 51.1013(a)(4)
and presents projected RFP emissions levels for direct PM2.5
and NOX to be achieved by these milestone dates based on the
implementation schedule for existing control measures in the area
(i.e., baseline measures). The projected emissions levels based on the
implementation schedule in the Plan demonstrate that the control
strategy will achieve direct PM2.5 and NOX
emissions reductions at rates representing generally linear progress
towards attainment between the 2013 baseline year and the 2020
attainment year. The target emissions levels and associated control
requirements provide for objective evaluation of the area's progress
towards attainment of the 1997 24-hour PM2.5 NAAQS.
    The State's quantitative milestones in Appendix H are to implement
specific measures listed in the State's control measure commitments
that apply to heavy-duty trucks and buses, light-duty vehicles, and
non-road equipment sources and may provide substantial reductions in
emissions of direct PM2.5 and NOX from mobile
sources in the San Joaquin Valley. Similarly, the District's
quantitative milestones in Appendix H are to implement specific
measures listed in the District's control measure commitments that
apply to sources such as residential wood burning, commercial
charbroiling, glass melting furnaces, and internal combustion engines,
and that may provide substantial reductions in emissions of direct
PM2.5 and NOX from stationary sources. These
milestones provide an objective means for tracking the State's and
District's progress in implementing their respective control strategies
and, thus, provide for objective evaluation of the San Joaquin Valley's
progress toward timely attainment.
    For these reasons, we propose to determine that the SJV
PM2.5 Plan satisfies the requirements for RFP in CAA section
172(c)(2) and 40 CFR 51.1012 and for quantitative milestones in CAA
section 189(c) and 40 CFR 51.1013 for the 1997 24-hour PM2.5
NAAQS in the San Joaquin Valley for purposes of both the Serious area
and CAA section 189(d) attainment plans. Because we are proposing to
determine that the San Joaquin Valley has attained the 1997 24-hour
PM2.5 NAAQS by the December 31, 2020 attainment date, as
discussed in section V of this proposed rule, we are also proposing to
determine that the requirement for a post-attainment milestone will no
longer apply in the San Joaquin Valley nonattainment area for these
NAAQS. As described in section IV.E.1 above, the purpose of the post-
attainment quantitative milestone is to provide the EPA with the tools
necessary to monitor the area's continued progress toward attainment in
the event the area fails to attain by the attainment date.\219\ Once an
area has attained the NAAQS, ``no further milestones are necessary or
meaningful.'' \220\ Similarly, the section 189(c)(2) requirement to
submit a quantitative milestone report no longer applies when the area
has attained the standard.\221\ Accordingly, upon a final determination
that the San Joaquin Valley area has attained the 1997 24-hour
PM2.5 NAAQS by the attainment date, the post-attainment RFP
milestone will no longer have purpose and the EPA is proposing to find
that the requirement will no longer apply to the San Joaquin Valley. If
we finalize this action as proposed, the State will no longer be
required to submit a quantitative milestone report for the San Joaquin
Valley under 40 CFR 51.1013(b) for the purposes of the 2023 post-
attainment milestone year identified in the Plan for the 1997 24-hour
PM2.5 NAAQS.
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    \219\ 81 FR 58010, 58064.
    \220\ 75 FR 13710, 13713 (March 23, 2010).
    \221\ Id.
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F. Contingency Measures

1. Requirements for Contingency Measures
    Under CAA section 172(c)(9), each state required to make a
nonattainment plan SIP submission must include, in such plan,
contingency measures to be implemented if an 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 will be implemented 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 in the
approved SIP; (3) to submit a required quantitative milestone report;
or (4) to attain the applicable PM2.5 NAAQS by the
applicable attainment date.\222\ 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.\223\
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    \222\ 40 CFR 51.1014(a).
    \223\ 81 FR 58010, 58066 and General Preamble Addendum, 42015.
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    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
emissions reductions that implementation of contingency measures must
achieve, but the EPA recommends that contingency measures provide for
emissions reductions

equivalent to approximately one year of reductions needed for RFP in
the nonattainment area at issue, 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. 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.\224\
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    \224\ 81 FR 58010, 58066. See also General Preamble, 13512,
13543-13544, and General Preamble Addendum, 42014-42015.
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    To satisfy the requirements of 40 CFR 51.1014, the contingency
measures adopted as part of a PM2.5 attainment plan must
consist of control measures for the area that are not otherwise
required to meet other nonattainment plan requirements (e.g., to meet
RACM/RACT requirements) and must specify the timeframe within which
their requirements become effective following any of the EPA
determinations specified in 40 CFR 51.1014(a). In a 2016 decision
called Bahr v. EPA (``Bahr''),\225\ the Ninth Circuit Court of Appeals
rejected the EPA's interpretation of CAA section 172(c)(9) to allow
approval of already-implemented control measures as contingency
measures. In Bahr, the Ninth Circuit concluded that contingency
measures must be measures that are triggered and implemented only after
the EPA determines that an area failed to meet RFP requirements or to
attain by the applicable attainment date. Thus, within the geographic
jurisdiction of the Ninth Circuit, already implemented measures cannot
serve as contingency measures under CAA section 172(c)(9).\226\ To
comply with section 172(c)(9), a state must develop, adopt, and submit
a contingency measure to be triggered upon a failure to meet an RFP
milestone, failure to meet a quantitative milestone requirement, or
failure to attain the NAAQS by the applicable attainment date.
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    \225\ Bahr v. EPA, 836 F.3d 1218, 1235-1237 (9th Cir. 2016).
    \226\ See also Sierra Club v. EPA, 985 F.3d 1055 (D.C. Cir.
2021) and Assoc. of Irritated Residents v. EPA, No. 19-71223, slip
op. (9th Cir. Aug 26, 2021).
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2. Summary of the State's Submission
    The SJV PM2.5 Plan addresses the contingency measure
requirement for the 1997 24-hour PM2.5 NAAQS in section 5.6
and Appendix H (specifically, section H.3 (``Contingency Measures''))
of the 2018 PM2.5 Plan. The Plan relies on revisions to the
District's wood-burning rule (Rule 4901) and refers to a SIP revision
submitted by CARB on October 23, 2017, titled ``State Implementation
Plan Attainment Contingency Measures for the San Joaquin Valley 15
[mu]g/m\3\ Annual PM2.5 NAAQS'' (``2017 Contingency Measure
SIP'').\227\ On March 19, 2021, CARB withdrew the 2017 Contingency
Measure SIP submission.\228\ Therefore, we are not evaluating the 2017
Contingency Measure SIP as part of this action.
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    \227\ Letter dated October 23, 2017, from Richard W. Corey,
Executive Officer, CARB, to Alexis Strauss, Acting Regional
Administrator, EPA Region 9.
    \228\ Letter dated March 19, 2021, from Richard W. Corey,
Executive Officer, CARB, to Deborah Jordan, Acting Regional
Administrator, EPA Region 9, transmitting CARB Executive Order S-21-
004.
---------------------------------------------------------------------------

    With respect to the District contingency measure, the 2018
PM2.5 Plan states that the District will amend Rule 4901 to
include a requirement that would be triggered upon a determination by
the EPA that the San Joaquin Valley failed to meet a regulatory
requirement necessitating implementation of a contingency measure.\229\
The District adopted amendments to Rule 4901 on June 20, 2019,
including a contingency measure in section 5.7.3 of the amended rule
(more details below). In the EPA's July 22, 2020 final action to
approve Rule 4901, as amended June 20, 2019, we did not evaluate
section 5.7.3 of the amended rule for compliance with CAA requirements
for contingency measures.\230\ On July 22, 2021, the EPA proposed to
find that the contingency provision of Rule 4901 (section 5.7.3) does
not satisfy the CAA requirements for contingency measures for the 1997
annual PM2.5 NAAQS and proposed to remove the provision from
the SIP because it is severable from the remainder of Rule 4901.\231\
In this action, we evaluate section 5.7.3 of Rule 4901 for compliance
with the contingency measures requirements for purposes of the 1997 24-
hour PM2.5 NAAQS.
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    \229\ 2018 PM2.5 Plan, Appendix H, H-25.
    \230\ 85 FR 44206 (final approval of Rule 4901); 85 FR 1131,
1132-1133 (January 9, 2020) (proposed approval of Rule 4901).
    \231\ 86 FR 38652.
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    Rule 4901 is designed to limit emissions generated by the use of
wood burning fireplaces, wood burning heaters, and outdoor wood burning
devices. The rule establishes requirements for the sale/transfer,
operation, and installation of wood burning devices and for advertising
the sale of seasoned wood consistent with a moisture content limit
within the San Joaquin Valley. The rule includes a two-tiered, episodic
wood burning curtailment requirement that applies during four winter
months, November through February. During a level one episodic wood
burning curtailment, section 5.7.1 prohibits any person from operating
a wood burning fireplace or unregistered wood burning heater, but
permits the use of a properly operated wood burning heater that meets
certification requirements and has a current registration with the
District. Sections 5.9 through 5.11 impose specific registration
requirements on any person operating a wood burning fireplace or wood
burning heater and section 5.12 imposes specific certification
requirements on wood burning heater professionals. During a level two
episodic wood burning curtailment, operation of any wood burning device
is prohibited by section 5.7.2.
    Prior to the 2019-2020 wood burning season, the District imposed a
level one curtailment when the PM2.5 concentration was
forecasted to be between 20 [mu]g/m\3\ and 65 [mu]g/m\3\ and imposed a
level two curtailment when the PM2.5 concentration was
forecasted to be above 65 [mu]g/m\3\ or the PM10
concentration was forecasted to be above 135 [mu]g/m\3\. In 2019 the
District adopted revisions to Rule 4901 to lower the wood burning
curtailment thresholds in the ``hot spot'' counties of Madera, Fresno,
and Kern. The District lowered the level one PM2.5 threshold
for these three counties from 20 [mu]g/m\3\ to 12 [mu]g/m\3\, and the
level two PM2.5 threshold from 65 [mu]g/m\3\ to 35 [mu]g/
m\3\. The District did not modify the curtailment thresholds for other
counties in the San Joaquin Valley--those levels remain at 20 [mu]g/
m\3\ for level one and 65 [mu]g/m\3\ for level two.
    The District's 2019 revision to Rule 4901 also included the
addition of a contingency measure in section 5.7.3 of the rule,
requiring that 60 days following the effective date of an EPA
determination that the San Joaquin Valley has failed to attain the
1997, 2006, or 2012 PM2.5 NAAQS by the applicable attainment
date, the PM2.5 curtailment levels of any county that has
failed to attain the applicable standard will be lowered to the
curtailment levels in place for hot spot counties. The District
estimates that the potential emissions reduction of direct
PM2.5 would be in the range of 0.014 tpd (if the contingency
measure is triggered in Kings County but not the other non-hot spot
counties) to 0.387 tpd (if the contingency measure is triggered in all
five of the non-hot spot counties), but there would be no emissions
reduction if, at the time of the determination of failure to attain the
1997 24-hour PM2.5 NAAQS by the attainment date, violations
of the 1997 24-hour PM2.5

NAAQS are observed only at monitors in the hot spot counties.\232\ The
corresponding potential NOX emissions reduction would be in
the range of 0.002 tpd to 0.060 tpd, respectively, but once again,
there would be no emissions reduction if the violations are monitored
in the hot spot counties only.\233\ The EPA has already approved Rule
4901, as amended in 2019, as a revision to the California SIP.\234\
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    \232\ See Table B-13 in Appendix B from the District's Final
Staff Report (June 20, 2019) for revisions to Rule 4901.
    \233\ NOX emissions reductions from the contingency
measure are based on the District's estimates for direct
PM2.5 emissions using the ratio of direct
PM2.5 to NOX in Table 1, page 8, of the
District's Final Staff Report (June 20, 2019) for revisions to Rule
4901.
    \234\ 85 FR 44206.
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3. The EPA's Review of the State's Submission
    As noted above, the EPA previously proposed to find that the
contingency provision of Rule 4901 (section 5.7.3) does not satisfy the
CAA requirements for contingency measures for the 1997 annual
PM2.5 NAAQS.\235\ As part of that proposal, the EPA found
that the measure meets some, but not all, of the applicable
requirements for contingency measures under CAA section 172(c)(9) and
40 CFR 51.1014. One of the deficiencies outlined in our proposal was
that the contingency provisions of Rule 4901 do 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 provisions of Rule 4901 are 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 1997 24-hour PM2.5 NAAQS as of
the attainment date. To qualify as a contingency measure, a measure
must be structured to achieve emissions reductions if triggered;
however, the contingency provisions of Rule 4901 provide for such
reductions only under certain circumstances.
---------------------------------------------------------------------------

    \235\ 86 FR 38652.
---------------------------------------------------------------------------

    Consistent with our proposal for the 1997 annual PM2.5
NAAQS and for these same reasons, we are proposing to disapprove the
contingency measure element of the SJV PM2.5 Plan for the
1997 24-hour PM2.5 NAAQS as not meeting the requirements of
172(c)(9) and 40 CFR 51.1014 for Serious area and section 189(d)
attainment plans. However, the EPA is also proposing to find that the
contingency measures are no longer required for the San Joaquin Valley
nonattainment area for the 1997 24-hour PM2.5 NAAQS, for the
reasons discussed below.
    Attainment contingency measures under 172(c)(9) are triggered upon
the EPA's determination that an area failed to attain a given NAAQS by
its applicable attainment date. CAA section 179(c) requires the EPA to
determine whether the area attained the NAAQS by its applicable
attainment date. As part of this proposed action, we are proposing to
determine that the San Joaquin Valley nonattainment area attained the
1997 24-hour PM2.5 NAAQS by the December 31, 2020 attainment
date projected by the Plan. Based on our proposed finding of attainment
by the applicable attainment date, we are also proposing to determine
that the CAA requirement for the SIP to provide for attainment
contingency measures will no longer apply to the San Joaquin Valley for
the 1997 24-hour PM2.5 NAAQS. Under CAA section 172(c)(9),
attainment contingency measures are implemented only if the area fails
to attain by the attainment date. Therefore, if we finalize the
determination that the San Joaquin Valley nonattainment area has
attained the 1997 24-hour PM2.5 NAAQS, attainment
contingency measures for this NAAQS would never be required to be
implemented. Because there are no circumstances under which CAA section
172(c)(9) attainment contingency measures could ever be triggered, we
think it is a reasonable interpretation of the CAA that these measures
are no longer required to be submitted.\236\
---------------------------------------------------------------------------

    \236\ See Bahr v. Regan, No. 20-70092, (9th Cir. July 28, 2021),
slip op. 45-51.
---------------------------------------------------------------------------

    Similarly, we are proposing to find that, upon finalization of the
determination of attainment by the attainment date, the RFP related
contingency measure requirement (i.e., for failure to meet RFP, to
submit a quantitative milestone report, or to meet the quantitative
milestone) would also no longer apply to the San Joaquin Valley
nonattainment area for the 1997 24-hour PM2.5 NAAQS. The
purpose of the RFP and related quantitative milestone requirements
under the CAA is to ``ensure[e] attainment of the applicable [NAAQS] by
the applicable date.'' \237\ Because the sole purpose of RFP
contingency measures is to provide continued progress if an area fails
to meet its RFP or quantitative milestone requirements, a final
determination of attainment by the attainment date serves as
demonstration that RFP requirements for the area have been met, and
that there is no need for any later quantitative milestone or milestone
report, and thus the RFP related contingency measures are no longer
needed. Accordingly, because we are proposing to determine that the San
Joaquin Valley has attained the 1997 24-hour PM2.5 NAAQS by
the December 31, 2020 attainment date, and that therefore the RFP and
quantitative milestone requirements would no longer apply, we are now
also proposing to determine that RFP contingency measures are no longer
required for this area.\238\
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    \237\ CAA section 171(c).
    \238\ With respect to the 2017 RFP contingency measure
requirement specifically, we note that, as explained in section
IV.E.2 of this proposed rule, on December 20, 2018, CARB submitted a
quantitative milestone report demonstrating that the 2017
quantitative milestones in the SJV PM2.5 Plan have been
achieved, and the EPA has determined that this milestone report is
adequate. Because the State and District have demonstrated that the
San Joaquin Valley area has met its 2017 quantitative milestones,
RFP contingency measures for the 2017 milestone year would never be
triggered.
---------------------------------------------------------------------------

    Under section 179(a) of the CAA, final disapproval of a SIP
submission that addresses a requirement of part D, title I of the CAA,
or is required in response to a finding of substantial inadequacy as
described in CAA section 110(k)(5) (SIP Call), starts sanctions clocks.
The SJV PM2.5 Plan, including the contingency measure
element, does address requirements of part D. However, if we finalize
our determinations that the requirements for contingency measures no
longer apply to the San Joaquin Valley nonattainment area for the 1997
24-hour PM2.5 NAAQS, then the contingency measure element of
the SJV PM2.5 Plan would no longer be required to address
any part D requirement for the 1997 24-hour PM2.5 NAAQS.
Therefore, final disapproval of the contingency measure element of the
SJV PM2.5 Plan would not trigger sanctions clocks.
Similarly, final disapproval would not trigger any obligation for the
EPA to promulgate a federal implementation plan (FIP) under CAA section
110(c) because there would be no deficiency for such a FIP to
correct.\239\
---------------------------------------------------------------------------

    \239\ This is the case for both the Serious area plan and the
section 189(d) plan. Because the purpose of contingency measures is
to ensure continued progress toward attainment in the event that an
area fails to attain the NAAQS or meet RFP requirements, and we are
proposing to find that the area has meet the 1997 24-hour
PM2.5 NAAQS, there is no purpose to triggering sanction
and FIP obligations for the State to submit measures to achieve the
goal of attaining the 1997 24-hour PM2.5 NAAQS when this
goal has already been met.
---------------------------------------------------------------------------

    Because we are proposing to approve the RFP analysis, the modeled
attainment demonstration, and the motor vehicle emissions budgets, we
are also proposing to issue a protective finding under 40 CFR
93.120(a)(3) in the event we finalize the disapproval of the

contingency measures. Without a protective finding, the final
disapproval would result in a conformity freeze, under which only
projects in the first four years of the most recent conforming Regional
Transportation Plan (RTP) and Transportation Improvement Programs
(TIPs) can proceed. During a freeze, no new RTPs, TIPs, or RTP/TIP
amendments can be found to conform.\240\ Under this protective finding,
however, the final disapproval of the contingency measures does not
result in a transportation conformity freeze in the San Joaquin Valley
PM2.5 nonattainment area.
---------------------------------------------------------------------------

    \240\ 40 CFR 93.120(a)(2).
---------------------------------------------------------------------------

    If the State chooses to withdraw the contingency measure element
with respect to the 1997 24-hour PM2.5 NAAQS prior to our
final action on the SJV PM2.5 Plan for that NAAQS, we would
take no final action either to approve or to disapprove that element.

G. Motor Vehicle Emission Budgets

1. Statutory and Regulatory Requirements
    Section 176(c) of the CAA requires federal actions in nonattainment
and maintenance areas to conform to the goals of the state's SIP to
eliminate or reduce the severity and number of violations of the NAAQS
and achieve timely attainment of the NAAQS. Conformity to the SIP's
goals means that such actions will not: (1) Cause or contribute to
violations of a NAAQS, (2) worsen the severity of an existing
violation, or (3) delay timely attainment of any NAAQS or any interim
milestone.
    Actions involving Federal Highway Administration (FHWA) or Federal
Transit Administration (FTA) funding or approval are subject to the
EPA's transportation conformity rule, codified at 40 CFR part 93,
subpart A. Under this rule, metropolitan planning organizations (MPOs)
in nonattainment and maintenance areas coordinate with state and local
air quality and transportation agencies, the EPA, the FHWA, and the FTA
to demonstrate that an area's regional transportation plans (RTPs) and
transportation improvement programs conform to the applicable SIP. This
demonstration is typically done by showing that estimated emissions
from existing and planned highway and transit systems are less than or
equal to the motor vehicle emission budgets (MVEBs or ``budgets'')
contained in all control strategy SIPs. Budgets are generally
established for specific years and specific pollutants or precursors
and must reflect all of the motor vehicle control measures contained in
the attainment and RFP demonstrations.\241\
---------------------------------------------------------------------------

    \241\ 40 CFR 93.118(e)(4)(v).
---------------------------------------------------------------------------

    Under the PM2.5 SIP Requirements Rule, Serious area
PM2.5 attainment plans must include appropriate quantitative
milestones and projected RFP emissions levels for direct
PM2.5 and all PM2.5 plan precursors in each
milestone year.\242\ For an area designated nonattainment for the 1997
PM2.5 NAAQS before January 15, 2015, the attainment plan
must contain quantitative milestones to be achieved no later than three
years after December 31, 2014, and every three years thereafter until
the milestone date that falls within three years after the applicable
attainment date.\243\ As the EPA explained in the preamble to the
PM2.5 SIP Requirements Rule, it is important to include a
post-attainment year quantitative milestone to ensure that, if the area
fails to attain by the attainment date, the EPA can continue to monitor
the area's progress toward attainment while the state develops a new
attainment plan.\244\ Although the post-attainment year quantitative
milestone is a required element of a Serious area plan, it is not
necessary to demonstrate transportation conformity for 2023 or to use
the 2023 budgets in transportation conformity determinations until such
time as the area fails to attain the 1997 24-hour PM2.5
NAAQS.
---------------------------------------------------------------------------

    \242\ 40 CFR 51.1012(a), 51.1013(a)(1).
    \243\ 40 CFR 51.1013(a)(4) and 81 FR 58010, 58058 and 58063-
58064. Because the area has failed to attain the 1997 24-hour
PM2.5 NAAQS by the Serious area attainment date, and it
would serve no purpose for the plan to include budgets for the EPA
to evaluate conformity for the dates associated with the Serious
area attainment date, the applicable attainment date for the
purposes of our evaluation is the section 189(d) projected
attainment date of December 31, 2020.
    \244\ 81 FR 58010, 58063-58064.
---------------------------------------------------------------------------

    PM2.5 plans should identify budgets for direct
PM2.5, NOX, and all other PM2.5
precursors for which on-road emissions are determined to significantly
contribute to PM2.5 levels in the area for each RFP
milestone year and the attainment year, if the plan demonstrates
attainment. All direct PM2.5 SIP budgets should include
direct PM2.5 motor vehicle emissions from tailpipes, brake
wear, and tire wear. With respect to PM2.5 from re-entrained
road dust and emissions of VOC, SO2, and/or ammonia, the
transportation conformity provisions of 40 CFR part 93, subpart A,
apply only if the EPA Regional Administrator or the director of the
state air agency has made a finding that emissions of these pollutants
within the area are a significant contributor to the PM2.5
nonattainment problem and has so notified the MPO and Department of
Transportation (DOT), or if the applicable implementation plan (or
implementation plan submission) includes any of these pollutants in the
approved (or adequate) budget as part of the RFP, attainment, or
maintenance strategy.\245\
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    \245\ 40 CFR 93.102(b)(3), 93.102(b)(2)(v), and 93.122(f); see
also Conformity Rule preambles at 69 FR 40004, 40031-40036 (July 1,
2004), 70 FR 24280, 24283-24285 (May 6, 2005) and 70 FR 31354 (June
1, 2005).
---------------------------------------------------------------------------

    By contrast, transportation conformity requirements apply with
respect to emissions of NOX unless both the EPA Regional
Administrator and the director of the state air agency have made a
finding that transportation-related emissions of NOX within
the nonattainment area are not a significant contributor to the
PM2.5 nonattainment problem and have so notified the MPO and
DOT, or the applicable implementation plan (or implementation plan
submission) does not establish an approved (or adequate) budget for
such emissions as part of the RFP, attainment, or maintenance
strategy.\246\
---------------------------------------------------------------------------

    \246\ 40 CFR 93.102(b)(2)(iv).
---------------------------------------------------------------------------

    It is not always necessary for states to establish motor vehicle
emissions budgets for all PM2.5 precursors. The
PM2.5 SIP Requirements Rule allows a state to demonstrate
that emissions of certain precursors do not contribute significantly to
PM2.5 levels that exceed the NAAQS in a nonattainment area,
in which case the state may exclude such precursor(s) from its control
evaluations for the specific NAAQS at issue. If a state successfully
demonstrates that the emissions of one or more of the PM2.5
precursors from all sources do not contribute significantly to
PM2.5 levels in the subject area, then it is not necessary
to establish motor vehicle emissions budgets for such precursor(s).
    Alternatively, the transportation conformity regulations contain
criteria for determining whether emissions of one or more
PM2.5 precursors are insignificant for transportation
conformity purposes.\247\ For a pollutant or precursor to be considered
an insignificant contributor based on the transportation conformity
rule's criteria, the control strategy SIP must demonstrate that it
would be unreasonable to expect that such an area would experience
enough motor vehicle emissions growth in that pollutant and/or
precursor for a NAAQS violation to occur. Insignificance determinations
are based on factors such as air quality, SIP motor vehicle control
measures, trends

and projections of motor vehicle emissions, and the percentage of the
total attainment plan emissions inventory for the NAAQS at issue that
is comprised of motor vehicle emissions. The EPA's rationale for
providing for insignificance determinations is described in the July 1,
2004 revision to the Transportation Conformity Rule.\248\
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    \247\ 40 CFR 93.109(f).
    \248\ 69 FR 40004.
---------------------------------------------------------------------------

    Transportation conformity trading mechanisms are allowed under 40
CFR 93.124 where a state establishes appropriate mechanisms for such
trades. The basis for the trading mechanism is the SIP attainment
modeling that establishes the relative contribution of each
PM2.5 precursor pollutant. The applicability of emissions
trading between conformity budgets for conformity purposes is described
in 40 CFR 93.124(c).
    The EPA's process for determining the adequacy of a budget consists
of three basic steps: (1) Notifying the public of a SIP submittal; (2)
providing the public the opportunity to comment on the budget during a
public comment period; and (3) making a finding of adequacy or
inadequacy. The EPA can notify the public by either posting an
announcement that the EPA has received SIP budgets on the EPA's
adequacy website,\249\ or through a Federal Register notice of proposed
rulemaking when the EPA reviews the adequacy of an implementation plan
budget simultaneously with its review and action on the SIP
itself.\250\
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    \249\ 40 CFR 93.118(f)(1).
    \250\ 40 CFR 93.118(f)(2).
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2. Summary of the State's Submission
    The 2018 PM2.5 Plan includes budgets for direct
PM2.5 and NOX emissions, calculated using annual
average daily emissions, for 2017, 2020, and 2023 (RFP milestone year,
attainment year, and post-attainment quantitative milestone year,
respectively).\251\ The Plan establishes separate direct
PM2.5 and NOX subarea budgets for each county,
and partial county (for Kern County), in the San Joaquin Valley.\252\
CARB calculated the budgets using EMFAC2014, CARB's latest version of
the EMFAC model for estimating emissions from on-road vehicles
operating in California that was available at the time of Plan
development, and the latest modeled vehicle miles traveled and speed
distributions from the San Joaquin Valley MPOs from the Final 2017
Federal Transportation Improvement Program, adopted in September 2016.
The budgets reflect annual average emissions because those emissions
are linked with the District's attainment demonstration for the 1997
24-hour PM2.5 NAAQS.
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    \251\ 2018 PM2.5 Plan, Appendix D, Table 3-1.
    \252\ 40 CFR 93.124(c) and (d).
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    The direct PM2.5 budgets include tailpipe, brake wear,
and tire wear emissions but do not include paved road dust, unpaved
road dust, and road construction dust emissions.\253\ The State is not
required to include re-entrained road dust in the budgets under section
93.103(b)(3) unless the EPA or the State has made a finding that these
emissions are significant. Neither the State nor the EPA has made such
a finding, but the Plan does include a discussion of the significance/
insignificance factors for re-entrained road dust.\254\ The budgets
included in the 2018 PM2.5 Plan for purposes of the 1997 24-
hour PM2.5 NAAQS are shown in Table 8.
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    \253\ 2018 PM2.5 Plan, Appendix D, D-122 and D-123.
    \254\ Id. at D-121 and D-122.

                           Table 8--Motor Vehicle Emission Budgets for the San Joaquin Valley for the 1997 24-Hour PM2.5 NAAQS
                                                                  [Annual average, tpd]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                 2017  (RFP year)             2020  (Attainment year)      2023  (Post-attainment year)
                         County                          -----------------------------------------------------------------------------------------------
                                                               PM2.5            NOX            PM2.5            NOX            PM2.5            NOX
--------------------------------------------------------------------------------------------------------------------------------------------------------
Fresno..................................................             0.9            28.5             0.9            25.3             0.8            15.1
Kern....................................................             0.8            28.0             0.8            23.3             0.7            13.3
Kings...................................................             0.2             5.8             0.2             4.8             0.2             2.8
Madera..................................................             0.2             5.3             0.2             4.2             0.2             2.5
Merced..................................................             0.3            10.7             0.3             8.9             0.3             5.3
San Joaquin.............................................             0.7            14.9             0.6            11.9             0.6             7.6
Stanislaus..............................................             0.4            11.9             0.4             9.6             0.4             6.1
Tulare..................................................             0.4            10.8             0.4             8.5             0.4             5.2
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: 2018 PM2.5 Plan, Appendix D, Table 3-1. Budgets are rounded to the nearest tenth of a ton.

    The State did not include budgets for VOC, SO2, or
ammonia. As discussed in section IV.B of this preamble, the State
submitted a PM2.5 precursor demonstration documenting its
conclusion that control of these precursors would not significantly
contribute to attainment of the 1997 24-hour PM2.5 NAAQS,
and the EPA is proposing to approve the precursor demonstration.
Therefore, if the EPA approves the demonstration, the State would not
be required to submit budgets for these precursors. The State included
a discussion of the significance/insignificance factors for ammonia,
SO2, and VOC to demonstrate a finding of insignificance
under the transportation conformity rule.\255\
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    \255\ 40 CFR 93.109(f).
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    In the submittal letter for the 2018 PM2.5 Plan, CARB
requested that the EPA limit the duration of the approval of the
budgets to the period before the effective date of the EPA's adequacy
finding for any subsequently submitted budgets.\256\
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    \256\ Letter dated May 9, 2019, from Richard W. Corey, Executive
Officer, CARB, to Mike Stoker, Regional Administrator, EPA Region 9,
3.
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Conformity Trading Mechanism
    The 2018 PM2.5 Plan also includes a proposed trading
mechanism for transportation conformity analyses that would allow
future decreases in NOX emissions from on-road mobile
sources to offset any on-road increases in direct PM2.5
emissions. The State is proposing to use a 2 to 1 NOX to
PM2.5 ratio for the 1997 24-hour PM2.5 NAAQS.
This ratio was derived by performing a sensitivity analysis based on a
30 percent reduction of NOX or PM2.5 emissions
and calculating the corresponding effect on design values at sites in
Bakersfield and Fresno.
    To ensure that the trading mechanism does not affect the ability of
the San Joaquin Valley to meet the NOX budget, the
NOX emissions reductions available to supplement the
PM2.5 budget would

only be those remaining after the NOX budget has been
met.\257\ The Plan also provides that the San Joaquin Valley MPOs shall
clearly document the calculations used in the trading, along with any
additional reductions of NOX and PM2.5 emissions
in the conformity analysis.
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    \257\ 2018 PM2.5 Plan, Appendix D, D-126 and D-127.
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3. The EPA's Review of the State's Submission
    The EPA generally first conducts a preliminary review of budgets
submitted with an attainment or maintenance plan for PM2.5
for adequacy, prior to taking action on the plan itself, and did so
with respect to the PM2.5 budgets in the 2018
PM2.5 Plan. On June 18, 2019, the EPA announced the
availability of the 2018 PM2.5 Plan with MVEBs and a 30-day
public comment period. This announcement was posted on the EPA's
Adequacy website at: https://www.epa.gov/state-and-local-transportation/state-implementation-plans-sip-submissions-currently-under-epa. The comment period for this notification ended on July 18,
2019. We did not receive any comments during this comment period.
    Based on our proposal to approve the State's demonstration that
emissions of ammonia, SO2, and VOCs do not contribute
significantly to PM2.5 levels that exceed the 1997 24-hour
PM2.5 NAAQS in the San Joaquin Valley, as discussed in
section IV.B of this proposal, and the information about ammonia,
SO2, and VOC emissions in the Plan, the EPA proposes to find
that it is not necessary to establish motor vehicle emissions budgets
for transportation-related emissions of ammonia, SO2, and
VOC to attain the 1997 24-hour PM2.5 NAAQS in the San
Joaquin Valley. Based on the information about re-entrained road dust
in the Plan and in accordance with 40 CFR 93.102(b)(3), the EPA
proposes to find that it is not necessary to include re-entrained road
dust emissions in the budgets for 1997 24-hour PM2.5 NAAQS
in the San Joaquin Valley.
    For the reasons discussed in sections IV.D and IV.E of this
proposed rule, the EPA is proposing to approve the attainment and RFP
demonstrations, respectively, in the SJV PM2.5 Plan. The
2017 RFP and 2020 attainment year budgets, as shown in Table 8 of this
preamble, are consistent with these demonstrations, are clearly
identified and precisely quantified, and meet all other applicable
statutory and regulatory requirements including the adequacy criteria
in 40 CFR 93.118(e)(4). For these reasons, the EPA proposes to approve
the 2017 and 2020 budgets listed in Table 8.\258\ We provide a more
detailed discussion in section IV of the EPA's 1997 24-hour
PM2.5 TSD. The budgets that the EPA is proposing to approve
relate only to the 1997 24-hour PM2.5 NAAQS, and our
proposed approval does not affect the status of the budgets for the
1997 annual PM2.5 NAAQS or the previously-approved MVEBs for
the 2006 PM2.5 NAAQS and related trading mechanism, which
remain in effect for that PM2.5 NAAQS.
---------------------------------------------------------------------------

    \258\ Although we are proposing to approve the 2017 budgets, we
note that these budgets would not be used in any future
transportation conformity determinations because the Plan contains
budgets for 2020.
---------------------------------------------------------------------------

    Although the post-attainment year quantitative milestone is a
required element of the Serious area plan, it is not necessary to
demonstrate transportation conformity for 2023 or to use the 2023
budgets in transportation conformity determinations until such time as
the area fails to attain the 1997 24-hour PM2.5 NAAQS. As
discussed in section V of this document, the EPA is proposing to find
that the San Joaquin Valley area has attained the 1997 24-hour
PM2.5 NAAQS. The EPA does not believe that it is necessary
to demonstrate conformity using post-attainment year budgets in areas
that attain by the attainment date. Therefore, if the EPA finalizes the
determination that the San Joaquin Valley area attained by the December
31, 2020 attainment date, the requirement for post-attainment year
budgets will no longer apply in the area for the 1997 24-hour
PM2.5 NAAQS.
    As noted above, the State included a trading mechanism to be used
in transportation conformity analyses that would be used in conjunction
with the budgets in the 2018 PM2.5 Plan, as allowed for
under 40 CFR 93.124(b). This trading mechanism would allow future
decreases in NOX emissions from on-road mobile sources to
offset any on-road increases in PM2.5, using a 2 to 1
NOX to PM2.5 ratio for the 1997 24-hour
PM2.5 NAAQS. To ensure that the trading mechanism does not
affect the ability to meet the NOX budget, the Plan provides
that the NOX emissions reductions available to supplement
the PM2.5 budget would only be those remaining after the
NOX budget has been met. The San Joaquin Valley MPOs will
have to document clearly the calculations used in the trading when
demonstrating conformity, along with any additional reductions of
NOX and PM2.5 emissions in the conformity
analysis. The trading calculations must be performed prior to the final
rounding to demonstrate conformity with the budgets.
    The EPA has reviewed the trading mechanism as described on pages D-
125 to D-127 in Appendix D of the 2018 PM2.5 Plan and finds
it is appropriate for transportation conformity purposes in the San
Joaquin Valley for the 1997 24-hour PM2.5 NAAQS. The
methodology for estimating the trading ratio for conformity purposes is
essentially an update (based on newer modeling) of the approach that
the EPA previously approved for the 2008 PM2.5 Plan for the
1997 PM2.5 NAAQS \259\ and the 2012 PM2.5 Plan
for the 2006 24-hour PM2.5 NAAQS.\260\ The State's approach
in the previous plans was to model the ambient PM2.5 effect
of areawide NOX emissions reductions and of areawide direct
PM2.5 emissions reductions, and to express the ratio of
these modeled sensitivities as an inter-pollutant trading ratio.
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    \259\ 80 FR 1816, 1841 (January 13, 2015) (noting the EPA's
prior approval of MVEBs for the 1997 annual and 24-hour
PM2.5 standards in the 2008 PM2.5 Plan at 76
FR 69896).
    \260\ 81 FR 59876 (August 31, 2016).
---------------------------------------------------------------------------

    In the updated analysis for the 2018 PM2.5 plan, the
State completed separate sensitivity analyses for the annual and 24-
hour NAAQS and modeled only transportation related sources in the
nonattainment area. The ratio the State is proposing to use for
transportation conformity purposes is derived from air quality modeling
that evaluated the effect of reductions in transportation-related
NOX and PM2.5 emissions in the San Joaquin Valley
on ambient concentrations at the Bakersfield-California Avenue,
Bakersfield-Planz, Fresno-Garland, and Fresno-Hamilton & Winery
monitoring sites. The modeling that the State performed to evaluate the
effectiveness of NOX and PM2.5 reductions on
ambient 24-hour concentrations showed NOX to
PM2.5 ratios that range from a high of 2.3 at the
Bakersfield-California Avenue monitor to a low of 1.6 at the Fresno-
Hamilton & Winery monitor.\261\ In our July 22, 2020 action on the 2018
PM2.5 Plan for the 2006 PM2.5 NAAQS, we found
that the State's approach is a reasonable method to use to develop
ratios for transportation conformity purposes and approved the 2 to 1
NOX to PM2.5 trading mechanism as an enforceable
component of the transportation conformity program for the San Joaquin
Valley for the 2006 PM2.5 NAAQS.\262\ Here, we similarly
find that the State's approach is reasonable and propose to

approve the 2 to 1 NOX to PM2.5 trading ratio.
---------------------------------------------------------------------------

    \261\ 2018 PM2.5 Plan, Appendix D, D-126.
    \262\ 85 FR 44192.
---------------------------------------------------------------------------

    If approved, this trading ratio will replace the 9 to 1
NOX to PM2.5 trading ratio approved for the San
Joaquin Valley for analysis years after 2014 for the 1997 24-hour
PM2.5 NAAQS.\263\
---------------------------------------------------------------------------

    \263\ 76 FR 69896.
---------------------------------------------------------------------------

    Under the transportation conformity rule, once budgets are
approved, they cannot be superseded by revised budgets submitted for
the same CAA purpose and the same year(s) addressed by the previously
approved SIP until the EPA approves the revised budgets as a SIP
revision. In other words, as a general matter, such approved budgets
cannot be superseded by revised budgets found adequate, but rather only
through approval of the revised budgets, unless the EPA specifies
otherwise in its approval of a SIP by limiting the duration of the
approval to last only until subsequently submitted budgets are found
adequate.\264\
---------------------------------------------------------------------------

    \264\ 40 CFR 93.118(e)(1).
---------------------------------------------------------------------------

    In the submittal letter for the 2018 PM2.5 Plan, CARB
requested that we limit the duration of our approval of the budgets to
the period before the effective date of the EPA's adequacy finding for
any subsequently submitted budgets.\265\ The transportation conformity
rule allows us to limit the approval of budgets.\266\ However, we will
consider a state's request to limit an approval of its budgets only if
the request includes the following elements: \267\
---------------------------------------------------------------------------

    \265\ Letter dated May 9, 2019, from Richard W. Corey, Executive
Officer, CARB, to Mike Stoker, Regional Administrator, EPA Region 9,
3.
    \266\ 40 CFR 93.118(e)(1).
    \267\ 67 FR 69139 (November 15, 2002), limiting our prior
approval of MVEBs in certain California SIPs.
---------------------------------------------------------------------------

    (1) An acknowledgement and explanation as to why the budgets under
consideration have become outdated or deficient;
    (2) A commitment to update the budgets as part of a comprehensive
SIP update; and
    (3) A request that the EPA limit the duration of its approval to
the period before new budgets have been found to be adequate for
transportation conformity purposes.
    CARB's request includes an explanation for why the budgets have
become, or will become, outdated or deficient. In short, CARB has
requested that we limit the duration of the approval of the budgets in
light of the EPA's approval of EMFAC2017, an updated version of the
model (EMFAC2014) used for the budgets in the SJV PM2.5
Plan.\268\ EMFAC2017 updates vehicle mix and emissions data of the
previously approved version of the model, EMFAC2014.
---------------------------------------------------------------------------

    \268\ On August 15, 2019, the EPA approved and announced the
availability of EMFAC2017, the latest update to the EMFAC model for
use by the State and local governments to meet CAA requirements. 84
FR 41717.
---------------------------------------------------------------------------

    In light of the EPA's approval of EMFAC2017, CARB explains that the
budgets in the SJV PM2.5 Plan, which we are proposing to
approve in today's action, will become outdated and will need to be
revised using EMFAC2017. In addition, CARB states that, without the
ability to replace the budgets using the budget adequacy process, the
benefits of using the updated data may not be realized for a year or
more after the updated SIP (with the EMFAC2017-derived budgets) is
submitted, due to the length of the SIP approval process. We find that
CARB's explanation for limiting the duration of the approval of the
budgets is appropriate and provides us with a reasonable basis for
limiting the duration of the approval of the budgets.
    We note that CARB has not committed to update the budgets as part
of a comprehensive SIP update, but as a practical matter, CARB must
submit a SIP revision that includes updated demonstrations as well as
the updated budgets to meet the adequacy criteria in 40 CFR
93.118(e)(4).\269\ Therefore, we do not need a specific commitment for
such a plan at this time. For the reasons provided above, and in light
of CARB's explanation for why the budgets will become outdated and
should be replaced upon an adequacy finding for updated budgets, we
propose to limit the duration of our approval of the budgets addressed
in this action to the period before we find revised budgets based on
EMFAC2017 to be adequate.
---------------------------------------------------------------------------

    \269\ Under 40 CFR 93.118(e)(4), the EPA will not find a budget
in a submitted SIP to be adequate unless, among other criteria, the
budgets, when considered together with all other emissions sources,
are consistent with applicable requirements for RFP and attainment.
40 CFR 93.118(e)(4)(iv).
---------------------------------------------------------------------------

H. Nonattainment New Source Review Requirements Under CAA Section
189(e)

    CAA section 189(e) specifically requires that the control
requirements applicable to major stationary sources of direct
PM2.5 also apply to major stationary sources of
PM2.5 precursors, except where the Administrator determines
that such sources do not contribute significantly to PM2.5
levels that exceed the NAAQS in the area.\270\ The control requirements
applicable to major stationary sources of direct PM2.5 in a
Serious PM2.5 nonattainment area include, at minimum, the
requirements of a nonattainment NSR permit program meeting the
requirements of CAA sections 172(c)(5) and 189(b)(3). As part of our
April 7, 2015 final action to reclassify the San Joaquin Valley area as
Serious nonattainment for the 1997 PM2.5 standards, we
established a May 7, 2016 deadline for the State to submit
nonattainment NSR SIP revisions addressing the requirements of CAA
sections 189(b)(3) and 189(e) of the Act for the 1997 PM2.5
NAAQS.\271\
---------------------------------------------------------------------------

    \270\ General Preamble, 13539 and 13541-13542.
    \271\ 80 FR 18528, 18533.
---------------------------------------------------------------------------

    California submitted nonattainment NSR SIP revisions to address the
subpart 4 requirements for the San Joaquin Valley Serious
PM2.5 nonattainment area on November 20, 2019.\272\ We are
not proposing any action on this submission at this time. We will act
on this submission through a separate rulemaking, as appropriate.
---------------------------------------------------------------------------

    \272\ Letter dated November 15, 2019, from Richard W. Corey,
Executive Officer, CARB, to Michael Stoker, Regional Administrator,
EPA Region IX.
---------------------------------------------------------------------------

V. Determination of Attainment by the Attainment Date

A. Requirements for Attainment Determinations

    Sections 179(c)(1) and 188(b)(2) of the CAA require the EPA to
determine whether a state with a PM2.5 nonattainment area
attained the applicable PM2.5 NAAQS by the applicable
attainment date, based on the area's air quality as of the attainment
date. A determination of whether an area's air quality currently meets
the PM2.5 NAAQS is generally based upon the most recent
three years of complete, quality-assured data gathered at established
State and Local Air Monitoring Stations (SLAMS) in a nonattainment area
and entered into the EPA's Air Quality System (AQS) database. Data from
ambient air monitors operated by state/local agencies in compliance
with the EPA monitoring requirements must be submitted to AQS.
Monitoring agencies annually certify that these data are accurate to
the best of their knowledge. Accordingly, the EPA relies primarily on
data in AQS when determining the attainment status of areas.\273\ The
EPA reviews all data to determine the area's air quality status in
accordance with 40 CFR part 50, Appendix N.
---------------------------------------------------------------------------

    \273\ See 40 CFR 50.7; 40 CFR part 50, Appendix L; 40 CFR part
53; 40 CFR part 58, and 40 CFR part 58, appendices A, C, D, and E.
---------------------------------------------------------------------------

    Under EPA regulations in 40 CFR 50.7 and in accordance with
Appendix N, the 1997 24-hour PM2.5 NAAQS are met when the