\163\ 15 [micro]g/m\3\ SIP Revision, Appendix K, Section 5.7
(``PM2.5 Precursor Sensitivity Analysis''); and West,
J.J., Ansari, A.S., Pandis, S.N., 1999, Marginal PM2.5:
Nonlinear aerosol mass response to sulfate reductions in the eastern
United States, Journal of the Air & Waste Management Association,
49, 1415-1424. https://doi.org/10.1080/10473289.1999.10463973.
    \164\ CARB's June 2019 Precursor Clarification.
---------------------------------------------------------------------------

    The State also provides an emissions trend chart that shows that
SOX emissions are approximately constant at 8 tpd from 2013
through 2024. Given that the relative levels of estimated
SOX and ammonia emissions over the timeframe remain similar,
the State concludes that 2013 sensitivities are also representative of
future years.\165\
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    \165\ 2018 PM2.5 Plan, Appendix G, p. 15. The State
includes modeling of 30 percent and 70 percent reductions of
SOX for 2013 only, finding that the sensitivity of
ambient PM2.5 to such changes were below the EPA's
recommended threshold, and that the 2020 and 2024 results would
differ little from 2013 due to the similarity of emissions
conditions over time. Appendix G, p. 17. CARB's September 2019
Precursor Clarification provides the 2020 and 2024 sensitivity
results, which are indeed very close to those for 2013.
---------------------------------------------------------------------------

    Based on the small modeled response of ambient PM2.5 to
SOX emissions reductions, the constant SOX
emissions over time, and its scientific understanding of sulfate
interactions with other molecules in the air, the State concludes that
SOX does not contribute significantly to ambient
PM2.5 levels that exceed the 1997 annual

PM2.5 NAAQS in the San Joaquin Valley.
c. VOC
    For VOC, CARB compared the annual precursor contributions to the
EPA's recommended contribution threshold for the 2012 PM2.5
NAAQS of 0.2 [micro]g/m\3\. For a modeled 30 percent VOC emissions
reduction, the ambient PM2.5 responses in 2013 ranged from
0.01 [micro]g/m\3\ to 0.16 [micro]g/m\3\ across 15 monitoring sites,
with all sites below the 0.2 [micro]g/m\3\ contribution threshold.\166\
The 2020 and 2024 responses ranged from -0.07 [micro]g/m\3\ to 0.06
[micro]g/m\3\, with all monitoring sites below the 0.2 [micro]g/m\3\
contribution threshold for both years. For a modeled 70 percent VOC
emissions reduction, the PM2.5 responses in 2013 ranged from
0.05 [micro]g/m\3\ to 0.40 [micro]g/m\3\, including responses at or
above the 0.2 [micro]g/m\3\ contribution threshold at 8 of the 15
sites. However, for 2020 and 2024 all responses were below the 0.2
[micro]g/m\3\ contribution threshold; 2020 responses ranged from -0.10
[micro]g/m\3\ to 0.16 [micro]g/m\3\ and the 2024 responses ranged from
-0.18 [micro]g/m\3\ to 0.08 [micro]g/m\3\. The negative responses to
VOC reductions represent an increase in PM2.5 levels, i.e.,
a disbenefit. The 2024 results show a disbenefit at 11 of the 15 sites
for both the 30 percent and the 70 percent VOC emissions reductions
scenarios.
---------------------------------------------------------------------------

    \166\ 2018 PM2.5 Plan, Appendix G, Table 10.
---------------------------------------------------------------------------

    CARB then considered additional information to assess whether these
PM2.5 responses constituted a significant contribution to
ambient PM2.5 in the San Joaquin Valley, including emissions
trends and an assessment of the modeled disbenefit of VOC emissions
reductions. VOC emissions are projected to decrease approximately 30
tpd (or 9 percent) from 2013 to 2024, with approximately 28 out of the
30 tpd reduction taking place by 2020.\167\ The State concludes that
the formation of ambient PM2.5 from VOC may therefore differ
in base and future years and that the sensitivity analysis for 2013,
which showed some contributions above 0.2 [micro]g/m\3\, is not
representative of current or future conditions.
---------------------------------------------------------------------------

    \167\ Id. at p. 19 and Figure 5.
---------------------------------------------------------------------------

    CARB explained the modeled disbenefit of VOC reductions as follows:
emissions of VOC and NOX react in the atmosphere to form
organic nitrate species, such as peroxyacetyl nitrate, meaning that
some portion of the NOX emissions is not available to react
with ammonia to form ammonium nitrate particulate matter. In other
words, VOC emissions can be a ``sink'' for NOX emissions.
Reducing VOC emissions therefore reduces the formation of organic
nitrates, so the sink is smaller and nitrate molecules are freed to
react with ammonia to form particulate ammonium nitrate.\168\ The State
further explored the VOC disbenefit based on a 2016 CARB modeling
assessment provided in Appendix A (``Air Quality Modeling'') of the
``2016 Moderate Area Plan for the 2012 PM2.5 Standard'' for
the San Joaquin Valley (``2016 PM2.5 Plan''), which CARB
submitted to the EPA as a SIP revision on May 10, 2019.\169\
---------------------------------------------------------------------------

    \168\ 15 [micro]g/m\3\ SIP Revision, Appendix K, pp. 81-82
(citing Meng, Z., D. Dabdub, D., Seinfeld, J.H., Chemical Coupling
Between Atmospheric Ozone and Particulate Matter, Science 277, 116
(1997). DOI: 10.1126/science.277.5322.116).
    \169\ 2016 PM2.5 Plan, Appendix A, p. A-57. See also
15 [micro]g/m\3\ SIP Revision, Appendix K, Section 5.7
(``PM2.5 Precursor Sensitivity Analysis'').
---------------------------------------------------------------------------

    Based on its sensitivity-based analysis of VOC emissions
reductions, VOC emissions trends, and the scientific understanding of
VOC chemistry in the San Joaquin Valley, CARB concludes that VOC
emissions do not contribute significantly to PM2.5 levels
that exceed the 1997 annual PM2.5 NAAQS in the San Joaquin
Valley.
3. The EPA's Review of the State's Submission
    The EPA has evaluated the State's precursor demonstration in the
SJV PM2.5 Plan, consistent with the PM2.5 SIP
Requirements Rule and the recommendations in the PM2.5
Precursor Guidance. The State did not present a precursor demonstration
for NOX, and indeed stated that controlling it is essential
for the attainment strategy; \170\ NOX emission sources,
therefore, remain subject to control requirements under subparts 1 and
4 of part D, title I of the Act. For the reasons provided in the
following paragraphs, the EPA proposes to approve the State's
comprehensive demonstrations for ammonia, SOX, and VOC based
on a conclusion that emissions of these precursor pollutants do not
contribute significantly to ambient PM2.5 levels that exceed
the 1997 annual PM2.5 NAAQS in the San Joaquin Valley. For
further discussion of the EPA's evaluation of the precursor
demonstration, please see the EPA's February 2020 Precursor TSD, which
provides the EPA's summary of the State's precursor analyses for all
four PM2.5 precursors.\171\
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    \170\ 2018 Plan Appendix G, p. 2.
    \171\ Much of the analysis in the EPA's February 2020 Precursor
TSD is applicable to SJV PM2.5 Plan for the 1997 annual
PM2.5 NAAQS. For example, the State's precursor
demonstration used 2015 annual average concentration data for its
concentration-based analysis, examined annual average sensitivities
of ambient PM2.5 concentrations to reductions in each
precursor in 2013, 2020, and 2024, and presented information on
research studies and emission trends that are relevant for assessing
the sensitivity of annual average ambient PM2.5
concentrations to emission reductions of each PM2.5
precursor. Our evaluation of such factors is similarly applicable
for the 1997 annual PM2.5 NAAQS and we expand on such
evaluation for purposes of those NAAQS specifically herein.
---------------------------------------------------------------------------

    The State based its analyses on the latest available data and
studies concerning ambient PM2.5 formation in the San
Joaquin Valley from precursor emissions. For the required
concentration-based analysis, the State assessed the absolute annual
average contribution of each precursor to ambient PM2.5 in
2015. Given that the absolute concentrations in 2015 were above the
EPA's recommended contribution thresholds for both the 2006 24-hour and
2012 annual average NAAQS, the State proceeded with a sensitivity-based
analysis, consistent with the recommendations in the PM2.5
SIP Requirements Rule.
    For the sensitivity-based analysis, the State performed its
analyses based on the EPA's recommended approach--i.e., for each
modeled year and level of precursor emissions reduction (in
percentages), the State estimated the ambient PM2.5 response
using the procedure recommended in the PM2.5 Precursor
Guidance. In particular, the State considered the EPA's recommended
range of emissions reductions (30 percent to 70 percent) for the 2013
base year, 2020 interim year, and 2024 future year, and quantified the
estimated response of ambient PM2.5 concentrations to
precursor emission changes in the San Joaquin Valley.
    The State's emissions projections in the 2018 PM2.5 Plan
show that baseline emissions of each of these precursors will decrease
from the 2013 base year to the 2023 attainment year. These decreases
are included in the State's modeled projections of ambient
PM2.5 levels in the San Joaquin Valley for purposes of
demonstrating attainment and RFP. The State's sensitivity analyses are
consistent with these projections, in accordance with the EPA's
recommendations in the PM2.5 Precursor Guidance.\172\
---------------------------------------------------------------------------

    \172\ PM2.5 Precursor Guidance, p. 35.
---------------------------------------------------------------------------

    The EPA is proposing to find that such quantification and CARB's
consideration of additional information provide an informed basis on
which to make a determination as to whether ammonia, SOX,
and VOC contribute significantly to ambient PM2.5 levels
that exceed the 1997 annual PM2.5 NAAQS in the San Joaquin
Valley.\173\ If we

finalize this proposal to approve the State's precursor demonstrations,
the State will not be required to implement BACM/BACT level controls
for sources of ammonia, SOX, and VOC for purposes of the SJV
PM2.5 Plan for 1997 annual PM2.5 NAAQS that is
the subject of this proposed action. Under 40 CFR 51.1006(b), such
precursor demonstration approval would apply only to this attainment
plan. For any new PM2.5 attainment plan that the State is
required to submit in accordance with 40 CFR 51.1003 for purposes of
any PM2.5 NAAQS, the State will be required to submit an
updated precursor demonstration if it seeks to exempt sources of a
particular precursor from control requirements in that attainment plan.
In the subsections that follow, we summarize our evaluation of the
State's precursor demonstrations for each of these three precursor
pollutants.
---------------------------------------------------------------------------

    \173\ The State did not evaluate the 2015 Serious area
attainment year. Because the year has passed and the area failed to
attain by the Serious area attainment date, we will evaluate the
precursor analysis for the Serious area plan based on the current
section 189(d) projected attainment date of December 31, 2023.
---------------------------------------------------------------------------

a. Ammonia
    We have evaluated CARB's sensitivity-based contribution analyses
for 2013, 2020, and 2024 in the 2018 PM2.5 Plan and
supplemental materials provided by the State, as well as CARB's
determination that the 2024 results are representative of conditions in
the San Joaquin Valley for purposes of a sensitivity-based analysis for
the 1997 annual PM2.5 NAAQS. The EPA's PM2.5
Precursor Guidance explicitly provides for consideration of a future
year, and we are proposing to find that the State provided sufficient
justification for relying on modeling results for 2024.\174\
---------------------------------------------------------------------------

    \174\ PM2.5 Precursor Guidance, p. 35.
---------------------------------------------------------------------------

    We also consider it appropriate for the State to take into account
additional information as part of its evaluation of whether the ammonia
contribution is significant and to rely on the responses to the 30
percent modeled ammonia emissions reduction in its precursor
demonstration for ammonia. The modeled PM2.5 response to the
30 percent reduction is only marginally above the contribution
threshold at a single monitoring site in 2024, and the EPA has evidence
from the State and elsewhere that the response was overestimated, as
discussed below. Together these suggest that ammonia does not
contribute significantly to ambient PM2.5 levels. However,
because the response is so close to the threshold at a 30 percent
reduction, such a conclusion strongly depends on the emission reduction
benefit of potential controls being 30 percent or less; larger
reductions could give responses above the threshold. Therefore, per 40
CFR 51.1010(a)(2)(ii), the EPA required an analysis of potential
controls to aid the EPA in its evaluation of the precursor
demonstration, which the State provided in the March 2023 Ammonia
Supplement. The response of ambient PM2.5 to an actual
assessment of the benefit from potential controls could then be used by
the State to determine whether controlling ammonia would significantly
affect PM2.5 levels.
    The State relied on the 2024 modeled ambient PM2.5
responses to a 30 percent reduction in ammonia after concluding that 30
percent was a reasonable upper bound on potential ammonia reductions,
based on past research on ammonia emissions and its evaluation of
potential control options. Based on the EPA's review of the State's
rationale, including its ammonia control measure analysis, the EPA
agrees that the reductions that the State could achieve through
additional available BACM/BACT level controls on ammonia sources would
be below 30 percent, and thus that the PM2.5 response to the
ammonia emission reductions available would be below the contribution
threshold at all sites for purposes of this plan, as discussed in the
following paragraphs.\175\
---------------------------------------------------------------------------

    \175\ Note that the task for the State is not to show whether
controls could reduce ammonia by 30 percent, though that is the
focus of the State's March 2023 Ammonia Supplement. The SIP
requirements rule and the PM2.5 Precursor Guidance do not
establish potential reductions of 30 percent as a ``bright line''
test for determining precursor significance. Rather, information
from the control evaluation is to be used in conjunction with other
information to determine whether ammonia reductions are effective in
reducing PM2.5 levels, and so whether ammonia contributes
significantly to PM2.5.
---------------------------------------------------------------------------

    The State compared the ammonia modeled sensitivity results in
Appendix G of the 2018 PM2.5 Plan to the 0.2 [micro]g/m\3\
contribution threshold recommended by the EPA for the 2012 annual
PM2.5 NAAQS in the PM2.5 Precursor Guidance.
However, in the March 2023 Ammonia Supplement, the State also compared
the model results against the 0.25 [micro]g/m\3\ contribution threshold
it calculated based on the level of the 1997 annual PM2.5
NAAQS. We find that the State's use of a 0.25 [micro]g/m\3\ threshold
is consistent with the recommendations in the PM2.5
Precursor Guidance,\176\ and is appropriate for purposes of evaluating
the modeling results for the 1997 annual PM2.5 NAAQS, given
the EPA's method of calculating the threshold and the level of the 1997
annual PM2.5 NAAQS (15.0 [micro]g/m\3\).
---------------------------------------------------------------------------

    \176\ PM2.5 Precursor Guidance, fn. 20.
---------------------------------------------------------------------------

    The precursor demonstration in the SJV PM2.5 Plan
indicates that the ambient response to a 30 percent ammonia emission
reduction would exceed the 0.25 [micro]g/m\3\ contribution threshold
for 13 out of 15 monitoring sites in the 2013 analysis year, and at 4
out of 15 for the 2020 analysis year. For the 2024 analysis year, 1 of
the 15 sites (Hanford) would exceed the contribution threshold. In
absolute terms, the ambient PM2.5 response declines from
0.24 [micro]g/m\3\ in 2020 to 0.12 [micro]g/m\3\ in 2024 at
Bakersfield-Planz, the highest concentration site. The Hanford
responses decline from 0.42 [micro]g/m\3\ in 2020 to 0.26 [micro]g/m\3\
in 2024. The average response over all monitoring sites declines from
0.23 [micro]g/m\3\ to 0.14 [micro]g/m\3\, with the decline being
generally larger for the sites with the highest projected
PM2.5 levels.
    While the 2024 Hanford modeled response to a 30 percent ammonia
reduction is above the contribution threshold, additional information
about this location leads the EPA to give the response lower weight in
the overall assessment of whether ammonia contributes significantly to
PM2.5 levels. An independent study using aircraft and
surface data from the winter 2013 DISCOVER-AQ \177\ campaign, a key
period in the SJV PM2.5 Plan's 2013 model base case, found
that the CMAQ model underestimated ammonia at Hanford by roughly a
factor of five; Hanford is just outside a region with high ammonia
emissions in the model (western Tulare County).\178\ If the modeled
ammonia concentrations were higher to better match observations, there
would be relatively more ammonia per NOX and the model
response to ammonia reductions would be lower. This is consistent with
CARB's conclusions regarding ammonia as described earlier.
---------------------------------------------------------------------------

    \177\ NASA, ``Deriving Information on Surface conditions from
Column and VERtically Resolved Observations Relevant to Air
Quality,'' described at https://www.nasa.gov/mission_pages/discover-aq/index.html.
    \178\ Kelly, J.T. et al. 2018, ``Modeling
NH4NO3 over the San Joaquin Valley during the
2013 DISCOVER-AQ campaign,'' Journal of Geophysical Research:
Atmospheres, 123, pp. 4727-4745, https://doi.org/10.1029/2018JD028290 at 4733. The paper notes that, despite the ammonia
underestimation, model performance was good for particulate ammonium
nitrate and the ammonium nitrate was not sensitive to the ammonia
underestimate since its formation was NOX-limited.
---------------------------------------------------------------------------

    In choosing which year's modeled response to ammonia to rely on,
the EPA considered the State's point that the PM2.5 benefit
of ammonia emission reductions is projected to decline steeply over
time. We believe it is appropriate to consider changes in

atmospheric chemistry that may occur between the base or current year
and the attainment year because the changes may ultimately affect the
nonattainment area's progress toward expeditious attainment. The
PM2.5 Precursor Guidance explicitly states that a future
year may be used, and that there are a multitude of considerations in
choosing the analysis year.\179\ The ``anticipated growth or loss of
sources . . . or trends in ambient speciation data and precursor
emissions'' \180\ are among the ``facts and circumstances of the area''
\181\ to consider in determining the significance of a precursor. The
Guidance states that a future year could be more appropriate if it
better represents the period that sources will operate in. As discussed
in more detail below, the 2024 model results better represent the
period that ammonia sources will operate in than 2013 and 2020 because
of the steep decline in NOX emissions projected to occur by
2023 and 2024. We consider it reasonable for the State to focus on the
ambient PM2.5 response to ammonia emission reductions in
2024, rather than 2013 or 2020, as the modeled response in 2024 in the
San Joaquin Valley better reflects the potential benefit of ammonia
control measures for purposes of expeditious attainment of the 1997
annual PM2.5 NAAQS.
---------------------------------------------------------------------------

    \179\ PM2.5 Precursor Guidance, p. 35.
    \180\ Id. at 18.
    \181\ PM2.5 SIP Requirements Rule, 40 CFR
51.1006(a)(1)(ii).
---------------------------------------------------------------------------

    The State's precursor demonstration in the SJV PM2.5
Plan shows that ambient sensitivity to ammonia emissions reductions in
the San Joaquin Valley declines steeply over time. Between 2020 and
2024, the modeled response to a 30 percent ammonia emissions reduction
declines by 50 percent at the Bakersfield-Planz monitoring site, which
has the highest projected PM2.5 level, and by 37 percent
averaged over all monitoring sites. As noted above, in absolute terms,
the ambient PM2.5 response declines from 0.24 [micro]g/m\3\
in 2020 to 0.12 [micro]g/m\3\ in 2024 at Bakersfield-Planz, and from
0.23 [micro]g/m\3\ to 0.14 [micro]g/m\3\ as averaged over all
monitoring sites, with the decline being generally larger for the sites
with the highest projected PM2.5 levels. Thus, between 2020
and 2024, the number of sites at which modeled sensitivity exceeds the
0.25 [micro]g/m\3\ threshold for the 1997 annual PM2.5 NAAQS
declines from 4 out of 15 down to 1 out of 15.\182\ As discussed
earlier, ammonia sensitivity declines because of the shifting
atmospheric chemistry caused by NOX emissions decreases.
NOX emissions are projected to decrease by 27 percent
between 2020 and 2024 due to baseline measures (e.g., existing motor
vehicle controls), with 91 percent of those emissions reductions
occurring between 2020 and 2023.\183\ That is, NOX emissions
in 2023 are 24 percent lower than NOX emissions in 2020 and
3 percent higher than NOX emissions in 2024. Thus,
conditions in 2024 are anticipated to be much more similar to those in
2023 compared to 2020. The decreased NOX emissions will make
ammonia more abundant relative to NOX, and even less of a
limiting factor on PM2.5 formation. In other words, the
model response in the future year 2024 gives a more realistic
assessment of the potential effect of ammonia controls than past
conditions.\184\
---------------------------------------------------------------------------

    \182\ 2018 PM2.5 Plan, Appendix G, tables 4 and 5.
    \183\ NOX emissions in 2020, 2023, and 2024 are 203.3
tpd, 153.6 tpd, and 148.9 tpd, respectively.
    \184\ Since precursor sensitivity modeling results were not
available for the specific year of 2023, the EPA estimated the 2023
PM2.5 response to a 30 percent ammonia reduction using
the modeling results for 2020 and 2024. As for the 2024 modeled
sensitivities, we found that Hanford was the only site that would be
above the 0.25 [micro]g/m\3\ contribution threshold for 2023, with a
response of 0.27 [micro]g/m\3\. Thus, the results of this exercise
do not change our conclusions. Spreadsheet ``Estimated 2023 annual
PM2.5 sensitivity to ammonia reductions.xlsx,'' EPA
Region IX, June 26, 2023.
---------------------------------------------------------------------------

    Additionally, the ambient studies described by the State and in
independent research studies provide strong evidence that
PM2.5 would respond only weakly to ammonia emissions
reductions. As described above, those include a large measured excess
of ammonia relative to the amount of nitrate available to interact with
it to form PM2.5, and satellite and aircraft measurements
indicating a larger amount of ammonia than is derived in model
predictions. This evidence reflects actual measurements of the
atmosphere, independent of uncertainties in the modeling and
independent of estimates of ammonia and other emissions that are input
to the model.
    Finally, the EPA has reviewed the additional information provided
by the State to support its assertion that 30 percent is a reasonable
upper bound on the ammonia reductions that could be achieved in the San
Joaquin Valley and the State's reliance on the 30 percent sensitivity
modeling results for the precursor demonstration for the 1997 annual
PM2.5 NAAQS. The EPA proposes to find that the additional
information adequately supports the conclusion that potential ammonia
controls would yield less than a 30 percent reduction, such that the
resulting decrease in ambient PM2.5 concentration would be
below the contribution threshold. As discussed in Section IV.B.1 of
this document, the PM2.5 Precursor Guidance indicates that
the EPA may require air agencies to identify and evaluate potential
emissions controls in support of a precursor demonstration that relies
on a sensitivity analysis, particularly for an area in which the
PM2.5 response to a 30 percent reduction in precursor
emissions is close to the contribution threshold. For the San Joaquin
Valley, the modeled response to a single site, Hanford, is just above
the 0.25 [micro]g/m\3\ threshold for the 1997 annual PM2.5
NAAQS at 0.26 [micro]g/m\3\. Furthermore, several analyses show ambient
ammonia concentrations are underestimated at Hanford and so we believe
that the 2024 modeled response of 0.26 [micro]g/m\3\ is likely
overestimated. Supporting that conclusion is the evidence of the large
ambient excess of ammonia relative to nitrate, which suggests that the
actual PM2.5 response to reductions in ammonia emissions
would be very small, and less than the response seen in the modeling.
Thus, we conclude that in the San Joaquin Valley, the PM2.5
response to a 30 percent reduction in ammonia emissions is close to the
contribution threshold and that the State's approach to evaluate
additional information in support of the precursor demonstration
sensitivity analysis, including additional potential ammonia control
measures, is consistent with the EPA's recommendations in the
PM2.5 Precursor Guidance and responsive to the EPA's request
for such additional information and analysis.
    As discussed in Section IV.B.2.a of this document, the State began
its analysis to identify and evaluate potential emissions controls for
ammonia by characterizing key ammonia source categories in the Valley
(i.e., CAFs, agricultural fertilizers, and composting operations), and
identifying existing rules that have resulted in ammonia emission
reductions from these sources. Specifically, the State discusses the
ammonia control effectiveness of a number of existing rules designed to
reduce VOC emissions from these sources.\185\ While there are no
ammonia-specific controls in place for these source categories, the EPA
agrees with the District's information indicating that some of the
management practices in the District's rules to reduce VOC emissions
also reduce ammonia

emissions by limiting ammonia formation and volatilization.\186\
---------------------------------------------------------------------------

    \185\ 2018 PM2.5 Plan, Appendix C, pp. C-311 to C-
358.
    \186\ For example, see 2018 PM2.5 Plan, Appendix C,
p. C-313 (for CAFs).
---------------------------------------------------------------------------

    Regarding the analysis for CAFs, we find that the District provided
a thorough evaluation of potential ammonia mitigation measures by CAF
type and activity through its comparison of the applicability and
requirements of Rule 4570 with comparable rules that are being
implemented in other air districts and its review of scientific
research studies. In considering the technical feasibility of each
identified measure, the District assessed factors such as how the
measure compares with requirements already being implemented under
District Rule 4570, the compatibility of the measure with the types of
CAFs operating in the Valley (considering, for example, CAF size and
common practices employed), compatibility of the measure with the
climate conditions in the Valley, and any cobenefits and/or undesirable
consequences of implementing the measure.
    Based on its evaluation, the District determined that several
measures identified in the literature are already required in the San
Joaquin Valley by Rule 4570 (e.g., washing floors and other soiled
areas in livestock facilities), or by other State regulations (e.g.,
requirements to carefully time manure application as required by the
California Regional Water Quality Control Board).187 188 For
measures that the District identified as feasible for implementation in
the San Joaquin Valley, the District provided information detailing how
it estimated the potential ammonia emission reductions that could be
achieved based on control efficiencies cited in the literature. For
measures that the State determined to be infeasible in the San Joaquin
Valley, the District provided a narrative justification for its
conclusion.
---------------------------------------------------------------------------

    \187\ March 2023 Ammonia Supplement, pp. 47-49.
    \188\ Id. at 77.
---------------------------------------------------------------------------

    Reasons for concluding that a particular measure is infeasible
included that the measure is not conducive to the type, size, or
standard practices of CAFs operating in the Valley; the measure is not
compatible with the hot, dry, drought climate conditions in the Valley;
the measure is not economically feasible; or that the measure would
have undesirable consequences (e.g., adverse effects on water quality,
reduced dairy cattle milk production). The District also concluded that
more research is needed to examine the technical and/or economic
feasibility of implementing some of the measures in the Valley
specifically. For those measures that the District found to be
economically infeasible (e.g., biofilters and wet scrubbers,
oxygenation of liquid manure lagoons), it provided detailed cost
analyses to support its assertion.\189\ Based on our review of the
District's controls analysis for CAFs, we find that the District
provided a robust analysis of its Rule 4570 and a thorough review of 46
possible mitigation measures for reducing ammonia emissions from CAFs
in the San Joaquin Valley.
---------------------------------------------------------------------------

    \189\ Id. at 59-60 and Appendix B.
---------------------------------------------------------------------------

    For fertilizer application, the State emphasizes that it has not
identified any SIP-approved requirements that are being implemented in
other areas. Thus, it describes regulations adopted by other California
State agencies to control fertilizer application, such as regulations
adopted by the California Water Resources Board, and otherwise focuses
its review on several research studies on reducing ammonia emissions
from synthetic fertilizer application. Based on its review of
mitigation options in the literature, the State concludes that some of
the mitigation strategies are already required by current State
regulations, and that further research is needed to explore the
feasibility and effectiveness of those measures that are not currently
in practice.
    Regarding State regulations that are currently in place to control
fertilizer application, we generally agree with the State that those
regulations are likely to enhance the retention of nitrogen from manure
and nitrogen-based chemical fertilizers in the San Joaquin Valley and
to limit the loss of nitrogen as pollution to water and air, thereby
potentially reducing ammonia emissions. Additionally, as discussed
earlier, District Rules 4570 and 4565 have provisions that reduce
ammonia emissions by addressing the land application of manure from
CAFs and of biosolids, animal manure, and poultry litter from
composting operations. The EPA believes that the State's review of both
existing ammonia mitigation measures and the research literature is an
appropriate and thorough method for identifying potential measures. We
also believe it reasonable that the State concludes that several of the
specific mitigation strategies identified in the literature, such as
optimizing fertilizer use, are already being implemented in the San
Joaquin Valley due to these current State regulations and co-benefits
such as reduced cost to farmers, and that more research is needed to
assess the feasibility of other additional measures identified. Based
on our review, and the fact that the State did not identify any ammonia
mitigation measures for fertilizer application being implemented in
other areas, we conclude that the State's overall conclusions are
reasonable.
    For composting and other sources, the District notes that
significant ammonia reductions are already being achieved by existing
rules, including a 44 percent reduction from composting operations from
Rules 4565 and 4566, and reductions from mobile source and fuel
combustion measures. As discussed earlier, the EPA agrees that Rules
4565 and 4566 have reduced ammonia emissions in the Valley. We also
agree that the State's stringent controls for on-road mobile sources
have resulted in ammonia reductions from those sources. While the State
continues to work to reduce emissions from mobile sources to reduce
NOX and other pollutants in the Valley, since on-road mobile
sources account for approximately one percent of the ammonia emissions
inventory,\190\ any ammonia reductions achievable through additional
on-road mobile source controls would be small. The District states that
it did not identify any additional potential mitigation measures for
these source categories.
---------------------------------------------------------------------------

    \190\ 2018 PM2.5 Plan, Appendix B, Table B-5.
---------------------------------------------------------------------------

    While we generally find that the State provided a robust review of
existing regulations and potential additional mitigation measures in
the research literature, we note that a limitation of the District's
analysis is that there remains some uncertainty as to how much
reduction is currently being achieved by State and District rules and
thus if some incremental additional reduction may be available. For
fertilizer application specifically, the District does not attempt to
quantify or otherwise substantiate the scale of ammonia emission
reductions from existing regulations, nor their enforceability, which
confounds the prospects for quantifying how much additional reductions
may be available. Furthermore, while the District provides a detailed
controls analysis for CAFs, with regard to Rule 4570, as the EPA has
previously noted,\191\ the State has not sufficiently substantiated its
calculation of the 100 tpd of ammonia emission reductions attributed to
Rule 4570. In the 2018 PM2.5 Plan, the State references an
analysis from 2006 that relied on a different baseline emissions
inventory, but has not supplemented this analysis, or reconciled it
with more recent

emissions inventory data.\192\ While the EPA agrees that meaningful
ammonia reductions have been achieved from Rule 4570, there remains
some uncertainty as to the precise magnitude of those reductions.
Notwithstanding this uncertainty, as discussed in more detail below,
given the scarcity of additional feasible measures identified by the
State, and the scale of potential additional emissions reductions
available in the context of the sensitivity of PM2.5 to
ammonia reductions in the nonattainment area for the 1997 annual
PM2.5 NAAQS, we find that the controls analysis provided by
the State is sufficient to support its conclusion that that ammonia
emissions do not contribute significantly to ambient PM2.5
levels that exceed the 1997 annual PM2.5 NAAQS in the San
Joaquin Valley.
---------------------------------------------------------------------------

    \191\ 81 FR 69396, 69397-69398 (October 6, 2016) and 87 FR
60494, 60503-60504 (October 5, 2022).
    \192\ 2018 PM2.5 Plan, Appendix C, pp. C-311 to C-339
and SJVUAPCD, ``Final Draft Staff Report, Proposed Re-Adoption of
Rule 4570 (Confined Animal Facilities),'' June 18, 2009, at Appendix
F, ``Ammonia Reductions Analysis for Proposed Rule 4570 (Confined
Animal Facilities),'' June 15, 2006 (discussing various assumptions
underlying the District's calculation of ammonia emission factors
without identifying relevant emissions inventories).
---------------------------------------------------------------------------

    Based on its analysis, the State concludes that significant ammonia
reductions have already been achieved in the San Joaquin Valley through
existing State regulations and standard practices, and that the
potential additional ammonia emissions reductions achievable through
the implementation of additional best available controls is two percent
of the total ammonia emissions in the San Joaquin Valley. This value is
well below the lower end (i.e., 30 percent) of the ammonia reductions
that the State modeled for analytical purposes for its sensitivity-
based analysis. While there remains some uncertainty as to the ammonia
reductions that are currently being achieved by existing rules and
standard practices, and thus the additional reductions that could be
achieved by those rules and practices, we believe the State has
provided sufficient evidence to support its assertion that the
additional available reductions are less than 30 percent.
    Specifically, the District has made a convincing case that
significant ammonia reductions have already been achieved through
District Rule 4570 and that few additional mitigation measures could
provide only modest further reductions from CAFs, which account for 58
percent of the total ammonia inventory. Similarly, the State has
provided support for its assertion that additional reductions are not
feasible from the fertilizer, composting, and other smaller source
categories through its analysis of potential fertilizer controls, in
particular, in addition to information regarding controls that are
already in place for these source categories.\193\ Based on our review
of the analysis, we conclude that the potential reduction from
available controls would be well below 30 percent. Given that the
State's modeled sensitivities of PM2.5 concentrations to a
30 percent ammonia reduction are approximately at or below the
threshold used for identifying an impact that is significant for the
1997 annual PM2.5 NAAQS, and that potential reductions would
be below 30 percent, the EPA agrees that the response of
PM2.5 to an ammonia reduction of a percentage smaller than
30 percent would be below the contribution threshold, indicating that
ammonia does not contribute significantly to ambient PM2.5
concentrations for purposes of the SJV PM2.5 Plan for the
1997 annual PM2.5 NAAQS.
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    \193\ The State has not provided an estimate of the reductions
that are currently being achieved for the fertilizer category, which
accounts for 34 percent of the total ammonia emissions inventory.
Nevertheless, even if ammonia emissions from fertilizers could be
reduced by a very high percentage (e.g., 70 percent), that would
correspond to a smaller percentage reduction of the total ammonia
emissions. Such conservatively high reductions from fertilizers
added to the potential ammonia reductions from CAFs identified by
the State would still amount to less than a 30 percent reduction of
the total ammonia emissions.
---------------------------------------------------------------------------

    In summary, we conclude that the State quantified the sensitivity
of ambient PM2.5 levels to reductions in ammonia emissions
using appropriate modeling techniques, the modeled response to ammonia
reductions is likely lower than reported, and the State's choice of
2024 as the reference point for purposes of evaluating the sensitivity
of ambient PM2.5 levels to ammonia emissions reductions is
well-supported. The State also provided strong evidence to support its
conclusion that additional controls on ammonia sources would achieve
ammonia emissions reductions well below 30 percent, including its
estimate, following review of the measures the State and District
consider feasible, that the reductions available are approximately 2
percent. Since the modeled ambient PM2.5 response to a 30
percent ammonia reduction is only marginally above the contribution
threshold at a single monitoring site, that response may be
overestimated, and potential reductions are below 30 percent, the
PM2.5 response to additional ammonia controls would be below
the contribution threshold. 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 annual PM2.5 NAAQS in the San Joaquin
Valley.
    We note that this proposed determination is specific to the facts
and circumstances of this particular plan--including but not limited to
the specific level of the 1997 annual PM2.5 NAAQS and the
proportional modeling response needed to be considered significant, the
State's modeling indicating that ammonia levels the San Joaquin Valley
are at or below the contribution threshold for the 1997 annual
PM2.5 NAAQS, the unique atmospheric conditions in the Valley
in which the PM2.5 response to reductions in ammonia
emissions would be relatively small, the demonstration that
the potential reductions from additional control measures that are not
currently being implemented would be below 30 percent, and the current
limited research in key areas of ammonia controls--and that it does not
pre-determine the outcome of significance determinations of precursors
in the future.
b. SOX
    For SOX, the 2018 PM2.5 Plan's sensitivity
estimates for 2013 are well below the EPA's recommended threshold for
both the 30 percent and 70 percent emission reduction scenarios and are
even negative for some monitoring sites. Given those results and the
steady SOX emission levels over 2013 to 2023 (as opposed to
increases), the EPA agrees with the State's conclusion that the 2013
modeled sensitivities provide a sufficient basis for the SOX
precursor demonstration. The supplemental results provided by the State
for 2020 and 2024 support this conclusion.
    Therefore, based on these modeled ambient PM2.5
responses to SOX emissions reductions in the San Joaquin
Valley, 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 annual PM2.5 NAAQS in the San
Joaquin Valley. We note that this proposed determination is specific to
the facts and circumstances of this particular plan and that it does
not pre-determine the outcome of significance determinations of
precursors in the future.
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 0.2 [mu]g/m\3\,
and predicted an increase in ambient PM2.5 levels in
response to VOC reductions (i.e., a disbenefit) at 2 out of 15
monitoring sites in 2020, and at 11 out 15 sites in 2024. Only for a 70
percent emissions reduction for the 2013 base year did the State
predict the ambient PM2.5 response to be above the threshold
at a majority of sites.\194\
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    \194\ 2018 PM2.5 Plan, Appendix G, tables 10 and 11.
---------------------------------------------------------------------------

    The EPA has evaluated and agrees with the State's determination in
the 2018 PM2.5 Plan 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 that the contribution from VOC emissions is not significant.
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 Section IV.B.2 of this proposed rule, that affects the
atmospheric chemistry with respect to ambient PM2.5
formation from VOC emissions. The 9.2 percent VOC emissions reductions
and the vast majority of NOX emissions reductions are
expected to result from baseline measures already in effect. Therefore,
we conclude that it is reasonable to rely on future year 2020 or 2024
modeled responses to VOC emissions reductions. The EPA also concludes
that the State provided a reasonable explanation for the VOC emissions
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 annual PM2.5
NAAQS in the San Joaquin Valley. We note that this proposed
determination is specific to the facts and circumstances of this
particular plan and that it does not pre-determine the outcome of
significance determinations of precursors in the future.

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 best available control measures (BACM), including controls
that reflect best available control technology (BACT), 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 be implemented in
whole or in part within four years after the date of reclassification
of a Moderate PM2.5 nonattainment area to Serious and that
generally can achieve greater permanent and enforceable emissions
reductions in 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).'' \195\
---------------------------------------------------------------------------

    \195\ 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 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.\196\ Indeed, because states are required to implement BACM
and BACT 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 technologically
advanced or more costly level of control.\197\ If RACM and RACT level
controls of emissions have been insufficient to reach attainment, then
the CAA title I, part D, subpart 4 provisions for PM2.5
nonattainment plans contemplate 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. Thus, BACM/BACT
determinations are to be ``generally independent'' of attainment for
purposes of implementing the PM2.5 NAAQS.\198\
---------------------------------------------------------------------------

    \196\ 81 FR 58010, 58081 and General Preamble Addendum, 42011,
42013.
    \197\ Id. and General Preamble Addendum, 42009-42010.
    \198\ PM2.5 SIP Requirements Rule, 58081-58082. See
also, General Preamble Addendum, 42011.
---------------------------------------------------------------------------

    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.''
\199\ 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.\200\
---------------------------------------------------------------------------

    \199\ 40 CFR 51.1000, 40 CFR 51.1010(a)(4)(ii).
    \200\ 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, 2023.
---------------------------------------------------------------------------

    Consistent with longstanding guidance provided in the General
Preamble Addendum, the preamble to the PM2.5 SIP
Requirements Rule discusses the following steps for states to follow to
identify and select emission controls needed to meet the BACM/BACT and
additional feasible measures requirements of 40 CFR 51.1010:
    (1) Develop a comprehensive emissions inventory of all sources of
PM2.5 and PM2.5 precursors from major and non-
major stationary point sources, area sources, and mobile sources;
    (2) Identify potential control measures for all sources or source
categories of emissions of PM2.5 and relevant
PM2.5 plan precursors;
    (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.\201\
---------------------------------------------------------------------------

    \201\ 81 FR 58010, 58083-58085.
---------------------------------------------------------------------------

    The EPA allows states to consider factors such as a source's
processes and operating procedures, raw materials, physical plant
layout, and potential environmental effects such as increased water
pollution, waste disposal, and energy requirements when considering
technological feasibility.\202\ For purposes of evaluating economic

feasibility, the EPA allows states to consider 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.\203\ For any potential control
measure identified through the process described above that is
eliminated from consideration, states are required to provide detailed
written justification for doing so on the basis of technological or
economic feasibility, including how its criteria for determining such
feasibility are more stringent than those used for determining RACM/
RACT.\204\
---------------------------------------------------------------------------

    \202\ 40 CFR 51.1010(a)(3)(i).
    \203\ 40 CFR 51.1010(a)(3)(ii).
    \204\ 40 CFR 51.1010(a)(3)(iii).
---------------------------------------------------------------------------

    Once these analyses are complete, the state must use this
information to develop enforceable control measures for all relevant
source categories in the nonattainment area and submit them to the EPA
for evaluation as SIP provisions 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 annual
PM2.5 NAAQS for the San Joaquin Valley area, the EPA is
reviewing the SJV PM2.5 Plan for compliance with those
requirements.\205\
---------------------------------------------------------------------------

    \205\ 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.\206\ 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.\207\ 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.\208\
---------------------------------------------------------------------------

    \206\ 81 FR 58010, 58100.
    \207\ 40 CFR 50.1010(c)(2)(ii).
    \208\ 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.\209\ 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 annual 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.
---------------------------------------------------------------------------

    \209\ 81 FR 58010, 58101.
---------------------------------------------------------------------------

2. Summary of the State's Submission and the EPA's Evaluation and
Proposed Action
a. Control Strategy
i. Baseline Measures
    The control strategy in the SJV PM2.5 Plan is based
largely on ongoing emissions reductions from baseline control measures,
which amount to approximately 98.2 percent of total NOX
emissions reductions and 93.3 percent of total direct PM2.5
emissions reductions modeled to result in attainment of the 1997 annual
PM2.5 NAAQS in the San Joaquin Valley.210 211 As
we use the term here, baseline measures are State and District
regulations adopted prior to the development of the 2018
PM2.5 Plan that continue to achieve emissions reductions
through the projected 2023 attainment year for the 1997 annual
PM2.5 NAAQS and beyond. The State describes these baseline
measures in the 15 [mu]g/m\3\ SIP Revision in Chapter 4 (``Attainment
Strategy for PM2.5'') \212\ and Appendix D (``Mobile Source
Control Measure Analyses''), and in Appendix C (``Stationary Source
Control Measure Analyses'') of the 2018 PM2.5 Plan. 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. Table 4
provides a summary of the 2013 base year emissions and the reductions
from baseline measures, additional State measures, and additional
District measures that the Plan projects will result in attainment of
the 1997 annual PM2.5 NAAQS in the San Joaquin Valley by
December 31, 2023.
---------------------------------------------------------------------------

    \210\ 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,
2023.
    \211\ The EPA calculated these percentages as follows: annual
average baseline NOX reductions from 2013 to 2023 are
163.6 tpd of 166.6 tpd modeled to result in attainment (98.2
percent) and annual average baseline direct PM2.5
reductions are 4.2 tpd of 4.5 tpd modeled to result in attainment
(93.3 percent). 2018 PM2.5 Plan, Appendix B; and 15
[mu]g/m\3\ SIP Revision, Chapter 4 and Appendix K.
    \212\ 15 [mu]g/m\3\ SIP Revision, Chapter 4, Table 4-2.

   Table 4--Summary of the SJV PM2.5 Plan's Annual Average Emission Reductions To Attain the 1997 Annual PM2.5
                                           NAAQS by December 31, 2023
----------------------------------------------------------------------------------------------------------------
                                                                  % of 2013 base   Direct PM2.5   % of 2013 base
                                                    NOX  (tpd)       year NOX          (tpd)        year PM2.5
                                                                     emissions                       emissions
----------------------------------------------------------------------------------------------------------------
A.............................  2013 Base Year             317.2  ..............            62.5  ..............
                                 Emissions.
B.............................  Baseline Measure           163.6            51.6             4.2             6.7
                                 Emissions
                                 Reductions
                                 (2013-2023).
C.............................  Additional CARB              3.0             0.9             0.1             0.2
                                 Measures.

D.............................  Additional                   0.0             0.0             0.2             0.3
                                 District
                                 Measures.
E.............................  Total 2013-2023            166.6            52.5             4.5             7.2
                                 Emissions
                                 Reductions
                                 (B+C+D).
----------------------------------------------------------------------------------------------------------------
Source: 2018 PM2.5 Plan, Appendix B, tables B-1 and B-2; and 15 [mu]g/m\3\ SIP Revision, Appendix K, Table 32.

    In the SJV PM2.5 Plan, the State explains 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 emissions from diesel vehicles and engines,
which include 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.'' \213\
---------------------------------------------------------------------------

    \213\ 15 [mu]g/m\3\ SIP Revision, Chapter 4, p. 4-9. For CARB's
BACM analysis for mobile source measures, see 15 [mu]g/m\3\ SIP
Revision, 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 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 issued numerous waivers and
authorizations for California's mobile source regulations and has
approved many such mobile source regulations as revisions to the
California SIP.\214\
---------------------------------------------------------------------------

    \214\ For example, see 81 FR 39424 (June 16, 2016); 82 FR 14446
(March 21, 2017); 83 FR 23232 (May 18, 2018); and 88 FR 20688 (April
6, 2023).
---------------------------------------------------------------------------

    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 by the State and approved by
the EPA as revisions to the California SIP.\215\
---------------------------------------------------------------------------

    \215\ 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) and revisions to the California
on-road reformulated gasoline and diesel fuel regulations (75 FR
26653, May 12, 2010).
---------------------------------------------------------------------------

    As to stationary and area sources, the State asserts in the SJV
PM2.5 Plan that stringent regulations adopted for prior
attainment plans continue to reduce emissions of NOX and
direct PM2.5.\216\ Specifically, Table 4-1 of the 15 [mu]g/
m\3\ SIP Revision identifies 33 District measures that limit
NOX and direct PM2.5 emissions.\217\ The EPA has
approved each of the identified measures into the California SIP,\218\
with two exceptions.
---------------------------------------------------------------------------

    \216\ 15 [mu]g/m\3\ SIP Revision, Chapter 4, p. 4-3. For the
District's BACM analysis of stationary and area source measures, see
2018 PM2.5 Plan, Appendix C.
    \217\ 15 [mu]g/m\3\ SIP Revision, Chapter 4, Table 4-1.
    \218\ 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 June 21, 2018, to extend the
period during which manufacturers may pay emissions fees in lieu of
meeting the rule's NOX emissions limits.\219\ CARB submitted
the amended rule to the EPA on November 21, 2018. However, the District
amended Rule 4905 again on October 15, 2020, to further extend the
period during which manufacturers of weatherized furnaces must pay
emission fees in lieu of meeting the rule's NOX emissions
limits.\220\ CARB submitted the rule as amended on October 15, 2020, to
the EPA on December 30, 2020, and simultaneously withdrew the rule as
amended June 21, 2018.\221\ The District amended Rule 4905 once more on
December 16, 2021, to further extend the implementation period and CARB
submitted the amended version to the EPA on March, 9, 2022.\222\ The
EPA has not yet proposed any action on either the December 30, 2020 or
the March 9, 2022 versions.
---------------------------------------------------------------------------

    \219\ SJVUAPCD, Final Draft Staff Report, ``Proposed Amendments
to Rule 4905 (Natural Gas-fired, Fan-type Central Furnaces),'' June
21, 2018, p. 2.
    \220\ SJVUAPCD, ``Item Number X: Adopt Proposed Amendments to
Rule 4905 (Natural Gas-Fired, Fan-Type Furnaces),'' October 15,
2020, p. 3, including Final Draft Staff Report, ``Proposed
Amendments to Rule 4905 (Natural Gas-Fired, Fan-Type Furnaces).''
    \221\ Letter dated December 28, 2020, from Richard W. Corey,
Executive Officer, CARB, to John Busterud, Regional Administrator,
EPA Region 9.
    \222\ Letter dated March 9, 2022, from Richard W. Corey,
Executive Officer, CARB, to Martha Guzman, Regional Administrator,
EPA Region IX.
---------------------------------------------------------------------------

    The EPA approved a prior version of Rule 4905 into the California
SIP on March 29, 2016.\223\ 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.\224\ 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 annual average emission reductions of 0.2 tpd
of NOX reductions between 2013 and 2023 to Rule 4905.\225\
These emissions reductions would not materially affect the attainment
demonstration for the 1997 annual PM2.5 NAAQS in the SJV
PM2.5 Plan.
---------------------------------------------------------------------------

    \223\ 81 FR 17390 (March 29, 2016) (approving Rule 4905 as
amended January 22, 2015).
    \224\ 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.
    \225\ 2018 PM2.5 Plan, Appendix C, p. C-290.
---------------------------------------------------------------------------

    Second, the SJV 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.\226\ 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 tpd direct
PM2.5 from 2013 through 2023.\227\ 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.
---------------------------------------------------------------------------

    \226\ The EPA does not have any pending SIP submission for Rule
4203.
    \227\ 2018 PM2.5 Plan, Appendix C, p. C-46.
---------------------------------------------------------------------------

    In sum, although Table 4-1 of the 15 [mu]g/m\3\ SIP Revision
identifies two baseline measures that are not creditable for SIP
purposes at this time, we conclude that the total emissions reductions
attributed to these two measures in the future baseline inventories
would not materially affect the attainment demonstration in the Plan.
ii. Additional Measures and CARB Commitment
    In addition to baseline control measures, the SJV PM2.5
Plan identifies several additional control measures that will
contribute to expeditious attainment of the 1997 annual
PM2.5 NAAQS. These measures include three regulatory
measures adopted by CARB or the District following development of the
2018 PM2.5 Plan, and a commitment by CARB to adopt and
implement an additional regulatory measure to meet an enforceable
commitment. The three regulatory measures adopted following development
of the 2018 PM2.5 Plan include CARB's ``Lower Opacity Limits
for Heavy-Duty Vehicles'' regulation,\228\ CARB's ``Amended Warranty
Requirements for Heavy-Duty Vehicles'' regulation,\229\ and the
District's 2019 amendments to Rule 4901 (``Wood Burning Fireplaces and
Wood Burning Heaters'').\230\ In addition to these three adopted
measures, the 15 [mu]g/m\3\ SIP Revision includes a commitment by CARB
to achieve aggregate emissions reductions of 3.0 tpd of NOX
and 0.04 tpd of direct PM2.5 (referred to as an ``aggregate
tonnage commitment'') through adoption of CARB's ``Heavy-Duty Vehicle
Inspection and Maintenance Program'' (``Heavy-Duty I/M'') (referred to
as a ``control measure commitment'') and/or substitute measures.\231\
Table 5 summarizes the NOX and direct PM2.5
emissions reductions associated with these additional measures in the
15 [mu]g/m\3\ SIP Revision.
---------------------------------------------------------------------------

    \228\ Initially adopted via CARB Resolution 18-20 (May 25,
2018). CARB Resolution 18-20 was repealed on July 26, 2018 via CARB
Resolution 18-28, which included a modified version of the
regulation to address public comments. Per direction from CARB
Resolution 18-28, the regulation was adopted via Executive Order
R19-001 (March 12, 2019).
    \229\ CARB Resolution 18-24, June 28, 2018.
    \230\ SJVUAPCD Resolution 19-06-22, June 20, 2019.
    \231\ CARB Resolution 21-21, September 23, 2021, p. 6; and
August 2021 Staff Report, pp. 4-5.

      Table 5--Additional NOX and Direct PM2.5 Emission Reductions
------------------------------------------------------------------------
                                          NOX  emissions       PM2.5
   Additional measures relied upon for     reductions in     emissions
 attainment  (beyond baseline measures)     2023  (tpd)    reductions in
                                                            2023  (tpd)
------------------------------------------------------------------------
District's 2019 Revisions to Rule 4901..  ..............             0.2
CARB's Lower Opacity Limits for Heavy-    ..............            0.09
 Duty Vehicles..........................
CARB's Warranty Requirements for Heavy-             0.01  ..............
 Duty Vehicles..........................
CARB's Heavy-Duty I/M...................  ..............            0.04
------------------------------------------------------------------------
Source: 15 [mu]g/m\3\ SIP Revision, Appendix K, Table 32.

    Following CARB's submission of the 15 [mu]g/m\3\ SIP Revision, on
October 20, 2021, CARB and the District submitted to the EPA the
``Progress Report and Technical Submittal for the 2012 PM2.5
Standard San Joaquin Valley'' (2021 Progress Report).\232\ The 2021
Progress Report describes the State's progress to date in developing
and adopting the additional measures identified in their control
measure commitments in the 2018 PM2.5 Plan for purpose of
attaining the 2012 annual PM2.5 NAAQS.\233\ These measures
include the additional measures identified in the 15 [mu]g/m\3\ SIP
Revision (i.e., the measures in Table 5 of this proposal). The 2021
Progress Report provides status updates on the substance of each
measure and the timing of board consideration for both adopted and
remaining control measure commitments. The report also provides a side-
by-side comparison of the original emission reduction estimates in the
2018 PM2.5 Plan for each control measure commitment and
updated emission reduction estimates for each measure based on
technical analyses for adopted measures and draft measures and/or
documentation in development for forthcoming regulations.\234\ Although
the purpose of the 2021 Progress Report was to provide an update on the
progress that CARB and the District have made towards implementing the
attainment strategy for the 2012 annual PM2.5 NAAQS, some of
the information provided in the report is relevant to the State's
progress towards attaining the 1997 annual PM2.5 NAAQS, as
discussed below.
---------------------------------------------------------------------------

    \232\ ``Progress Report and Technical Submittal for the 2012
PM2.5 Standard San Joaquin Valley,'' October 19, 2021.
Transmitted to the EPA by letter dated October 20, 2021, from
Richard W. Corey, Executive Officer, CARB, to Deborah Jordan, Acting
Regional Administrator, EPA Region IX. See sections of 2021 Progress
Report entitled ``Progress in Implementing District Measures'' and
``Progress in Implementing CARB Measures.''
    \233\ As discussed in fn. 28 of this document, the Serious area
plan for the 2012 PM2.5 NAAQS has since been withdrawn by
the State.
    \234\ 2021 Progress Report, tables 2 and 3.
---------------------------------------------------------------------------

    First, on July 22, 2020, the EPA published its final approval of
the District's 2019 amendment to Rule 4901 \235\ and concurrently
credited this measure with annual average emission reductions of 0.2
tpd direct PM2.5 towards the District's PM2.5
tonnage commitment in the 2018 PM2.5 Plan for 2024.\236\ As
described in the EPA's March 27, 2020 proposed rule, this amount of SIP
credit corresponded to a 75 percent compliance rate (referred to as a
``rule effectiveness rate''), consistent with EPA guidance on wood
burning curtailment programs,\237\ rather than a higher 100 percent
rule effectiveness rate used in the District's original
calculations.\238\ In the 2021 Progress Report, the State notes this
conclusion in the EPA's July 22, 2020 final rule approving this measure
into the SIP and now estimates emission reductions of 0.2 tpd direct
PM2.5 from this measure, both in the report \239\ and in the
15 [mu]g/m\3\ SIP Revision.\240\ Consistent with the EPA's July 22,
2020 final rule, we propose to credit this measure with annual average
emission reductions of 0.2 tpd direct PM2.5 for purposes of
attaining the 1997 annual PM2.5 NAAQS by December 31, 2023.
---------------------------------------------------------------------------

    \235\ 85 FR 44206.
    \236\ 85 FR 44192, 44204.
    \237\ Strategies for Reducing Wood Smoke, EPA-456/B-13-01, March
2013, p. 42.
    \238\ 85 FR 17382, 17415.
    \239\ 2021 Progress Report, p. 7 and Table 3.
    \240\ 15 [mu]g/m\3\ SIP Revision, Appendix K, Table 32.
---------------------------------------------------------------------------

    Second, in 2018, CARB adopted the Lower Opacity Limits for Heavy-
Duty Vehicles regulation as a revision to the

Heavy-Duty Vehicle Inspection Program (HDVIP) and Periodic Smoke
Inspection Program (PSIP). CARB submitted the measure to the EPA on
February 13, 2020, and on May 10, 2022, the EPA approved the measure
into the California SIP.\241\ CARB initially estimated in its staff
report for the measure that it would achieve 1,170 tons of PM emissions
benefits from the heavy-duty trucking transportation sector from 2019
to 2025.\242\ In the 15 [mu]g/m\3\ SIP Revision, CARB estimates that
the Lower Opacity Limits for Heavy-Duty Vehicles regulation will
achieve 0.09 tpd direct PM2.5 reductions in 2023. CARB later
clarified via email that it derived this estimate using EMFAC2017 and
that if it instead used EMFAC2014, consistent with the 15 [mu]g/m\3\
SIP Revision, the estimated reductions are 0.01 tpd of direct
PM2.5 by 2023.\243\ However, CARB has not yet provided its
analysis of the basis for this emissions reduction estimate for the San
Joaquin Valley. Therefore, the EPA is not proposing at this time to
credit this measure with any particular amount of emissions reductions
toward attainment of the 1997 annual PM2.5 NAAQS in the San
Joaquin Valley. While the Plan indicates that the State attributed
annual average emission reductions of 0.09 tpd of PM2.5
reductions between 2013 and 2023 to the Lower Opacity Limits for Heavy-
Duty Vehicles regulation, these emissions reductions would not
materially affect the attainment demonstration for the 1997 annual
PM2.5 NAAQS in the SJV PM2.5 Plan.
---------------------------------------------------------------------------

    \241\ 87 FR 27949.
    \242\ CARB, ``Proposed Amendments to the Heavy-Duty Vehicle
Inspection Program and Periodic Smoke Inspection Program, Staff
Report: Initial Statement of Reasons,'' release date April 3, 2018,
p. 15. See also, EPA Region IX, ``Technical Support Document for
EPA's Rulemaking for the California State Implementation Plan,
California Air Resources Board--Title 13, Division 3, Chapter 3.5;
Opacity Testing of Heavy-Duty Diesel Vehicles,'' July 2021, p. 4.
    \243\ Email dated March 3, 2022, from Laura Carr, CARB, to
Ashley Graham, EPA Region IX, Subject: ``Lower Opacity regulation
reductions.'' This email is in the docket for this proposed action,
---------------------------------------------------------------------------

    Third, CARB adopted the Amended Warranty Requirements for Heavy-
Duty Vehicles regulation on June 28, 2018 (``2018 HD Warranty
Amendments''). CARB estimates that the measure will achieve 0.01 tpd of
NOX emissions reductions in 2023. By letter dated October
22, 2021, CARB submitted a request that the EPA determine that the 2018
HD Warranty Amendments are within the scope of the previously-granted
waiver for California's emissions standards and associated test
procedures for 2007 and subsequent model year heavy-duty diesel vehicle
engines. Alternatively, CARB requested that the EPA grant California a
new waiver of preemption for the 2018 HD Warranty Amendments. The EPA
published a notice of opportunity for public hearing and comment
concerning CARB's request on June 13, 2022, and the EPA held a public
hearing on June 29, 2022.\244\ On April 5, 2023, the EPA determined
that the 2018 HD Warranty Amendments meet the criteria for a new waiver
under section 209(b) of the CAA.\245\ However, because the measure has
not been approved into the California SIP, the EPA is not proposing at
this time to credit this measure with any particular amount of
emissions reductions toward attainment of the 1997 annual
PM2.5 NAAQS in the San Joaquin Valley. Given the relatively
small quantity of reductions from this measure, these emissions
reductions would not materially affect the attainment demonstration for
the 1997 annual PM2.5 NAAQS in the SJV PM2.5
Plan.
---------------------------------------------------------------------------

    \244\ 87 FR 35760.
    \245\ 88 FR 20688.
---------------------------------------------------------------------------

    Finally, the 15 [mu]g/m\3\ SIP Revision includes an aggregate
emissions reduction commitment by CARB to achieve reductions of 3.0 tpd
of NOX and 0.04 tpd of direct PM2.5 through
adoption of CARB's Heavy-Duty I/M program and/or substitute
measures.\246\ These reductions amount to 1.8 percent and 0.9 percent
of the total NOX and direct PM2.5 reductions,
respectively, needed to attain the 1997 annual PM2.5 NAAQS.
CARB adopted the Heavy-Duty I/M measure on December 9, 2021, fulfilling
CARB's control measure commitment in the 15 [mu]g/m\3\ SIP Revision.
Implementation of the program began on January 1, 2023. On December 14,
2022, CARB submitted the measure to the EPA as a revision to the
California SIP.\247\ The EPA is not proposing to credit the emission
reductions from the Heavy-Duty I/M program towards the aggregate
tonnage commitment at this time. The EPA will take such action in a
separate future rulemaking.
---------------------------------------------------------------------------

    \246\ CARB Resolution 21-21, pp. 4-5.
    \247\ Letter dated December 7, 2022, from Steven S. Cliff,
Ph.D., Executive Officer, to Martha Guzman, Regional Administrator,
EPA Region IX, with enclosures.
---------------------------------------------------------------------------

    In addition to the baseline and additional measures discussed
above, CARB notes in its August 2021 Staff Report accompanying the 15
[micro]g/m\3\ SIP Revision that two additional measures are expected to
provide for more emissions reductions by the 2023 attainment year for
the 1997 annual PM2.5 NAAQS.\248\ While the EPA is not
proposing to credit either of these measures at this time towards the
aggregate tonnage commitment for the 1997 annual PM2.5
NAAQS, we agree with the State that they will further reduce ambient
PM2.5 levels and exposure to PM2.5 pollution for
communities in the San Joaquin Valley.
---------------------------------------------------------------------------

    \248\ August 2021 Staff Report, pp. 3-4.
---------------------------------------------------------------------------

    The first measure is the Accelerated Turnover of Agricultural
Equipment Incentive Projects (``Agricultural Equipment Incentive
Measure''), which includes commitments by CARB to monitor, assess, and
report on emission reductions, and to achieve emission reductions of
5.1 tpd NOX and 0.3 tpd direct PM2.5 from the
2025 baseline inventory in the 2018 PM2.5 Plan by December
31, 2024.\249\ The State asserts in the August 2021 Staff Report that a
large portion of those emissions reductions will be achieved by
2023.\250\ The EPA finalized a partial approval of this measure on
December 16, 2021, wherein the EPA credited 4.83 tpd NOX and
0.24 tpd direct PM2.5 towards CARB's tonnage commitments for
2024 (for attaining the 2006 24-hour PM2.5 NAAQS), and
calculated 4.46 tpd NOX and 0.26 tpd direct PM2.5
for 2025 (for attaining the 2012 annual PM2.5 NAAQS).\251\
---------------------------------------------------------------------------

    \249\ EPA Region IX ``Technical Support Document for EPA's
Rulemaking for the California State Implementation Plan California
Air Resources Board Resolution 19-26 San Joaquin Valley Agricultural
Equipment Incentive Measure,'' February 2020, pp. 4-5, 24-25, and
31.
    \250\ CARB's August 2021 Staff Report, p. 3.
    \251\ 86 FR 73106 (December 27, 2021). The EPA deferred action
on the NRCS portion of the Agricultural Equipment Incentive Measure.
---------------------------------------------------------------------------

    The second measure is the Agricultural Burning Phase-out Measure,
which for purposes of state law, was adopted by the District on June
17, 2021,\252\ and concurred on by CARB on June 18, 2021,\253\ and
later adopted by the District on November 18, 2021, as a revision to
the California SIP.\254\ Previously, through Rule 4103 (``Open
Burning''), as amended April 15, 2010, the District restricted the type
of materials that may be burned and established other conditions and
procedures for open burning in conjunction with the District's Smoke
Management Program.\255\ The EPA

approved Rule 4103 and the associated table of the restrictions on open
burning by crop category into the California SIP on January 4,
2012.\256\ The District identifies Rule 4103 as a baseline measure in
the 2018 PM2.5 Plan.\257\ The Agricultural Burning Phase-out
Measure, in turn, includes a schedule to phase-out (i.e., introduce
prohibitions of) agricultural burning for additional crop categories or
materials accounting for a vast majority of the tonnage of agricultural
waste in phases starting January 1, 2022, and becoming fully
implemented by January 1, 2025.\258\ Thus, the State asserts that the
measure will provide for additional reductions in 2023 not accounted
for in the attainment demonstration for the in the 15 [micro]g/m\3\ SIP
Revision for 1997 annual PM2.5 NAAQS.\259\ The EPA approved
the Agricultural Burning Phase-out Measure into the California SIP on
June 16, 2022.\260\
---------------------------------------------------------------------------

    \252\ SJVUAPCD Resolution 21-06-12, June 17, 2021.
    \253\ Letter dated June 18, 2021, from Richard W. Corey,
Executive Officer, CARB, to Samir Sheikh, Executive Director,
SJVUAPCD.
    \254\ SJVUAPCD Resolution 21-11-7, November 18, 2021. See also,
Letter dated October 20, 2021, from Richard W. Corey, Executive
Officer, CARB, to Deborah Jordan, Acting Regional Administrator, EPA
Region IX.
    \255\ SJVUAPCD Rule 4103, as amended April 15, 2010.
    \256\ 77 FR 214 (January 4, 2012). The table of open burning
restrictions by crop category is codified at 40 CFR
52.220(c)(388)(i)(B)(3) Table 9-1, Revised Proposed Staff Report and
Recommendations on Agricultural Burning, approved by the District on
May 20, 2010.
    \257\ 2018 PM2.5 Plan, Chapter 4, tables 4-2 and 4-3,
and Appendix C.
    \258\ 2021 Supplemental Report and Recommendations, Table 2-1
(``Accelerated Reductions by Crop Category'').
    \259\ CARB's August 2021 Staff Report, pp. 3-4.
    \260\ 87 FR 36222.
---------------------------------------------------------------------------

iii. Three Factor Test for Enforceable Commitments
    The EPA interprets the CAA to allow for approval of enforceable
commitments that are limited in scope where circumstances exist that
warrant the use of such commitments in place of adopted and submitted
measures.\261\ Specifically, CAA section 110(a)(2)(A) provides that
each SIP ``shall include enforceable emission limitations and other
control measures, means or techniques. . .as well as schedules and
timetables for compliance, as may be necessary or appropriate to meet
the applicable requirements of [the Act].'' Section 172(c)(6) of the
Act, which applies to nonattainment SIPs, is virtually identical to
section 110(a)(2)(A). The language in these sections of the CAA is
broad, allowing a SIP to contain any ``means or techniques'' that the
EPA determines are ``necessary or appropriate'' to meet CAA
requirements, such that the area will attain as expeditiously as
practicable, but no later than the designated date. Furthermore, the
express allowance for ``schedules and timetables'' demonstrates that
Congress understood that all required controls might not have to be in
place before a SIP could be fully approved.
---------------------------------------------------------------------------

    \261\ Commitments approved by the EPA under CAA section
110(k)(3) are enforceable by the EPA and citizens under CAA sections
113 and 304, respectively. In the past, the EPA has approved
enforceable commitments and courts have enforced these actions
against states that failed to comply with those commitments. See,
e.g., American Lung Ass'n of N.J. v. Kean, 670 F. Supp. 1285 (D.N.J.
1987), aff'd, 871 F.2d 319 (3rd Cir. 1989); NRDC v. N.Y. State Dept.
of Env. Cons., 668 F. Supp. 848 (S.D.N.Y. 1987); Citizens for a
Better Env't v. Deukmejian, 731 F. Supp. 1448, recon. granted in
par, 746 F. Supp. 976 (N.D. Cal. 1990); Coalition for Clean Air v.
South Coast Air Quality Mgt. Dist., No. CV 97-6916-HLH, (C.D. Cal.
Aug. 27, 1999). Further, if a state fails to meet its commitments,
the EPA could make a finding of failure to implement the SIP under
CAA section 179(a), which starts an 18-month period for the State to
correct the non-implementation before mandatory sanctions are
imposed.
---------------------------------------------------------------------------

    Once the EPA determines that circumstances warrant consideration of
an enforceable commitment to satisfy a CAA requirement, it considers
three factors in determining whether to approve the enforceable
commitment: (1) does the commitment address a limited portion of the
CAA requirement; (2) is the state capable of fulfilling its commitment;
and (3) is the commitment for a reasonable and appropriate period of
time.\262\
---------------------------------------------------------------------------

    \262\ The Fifth Circuit Court of Appeals upheld the EPA's
interpretation of CAA sections 110(a)(2)(A) and 172(c)(6) and the
Agency's use and application of the three factor test in approving
enforceable commitments in the 1-hour ozone SIP for Houston-
Galveston. BCCA Appeal Group v. EPA, 355 F.3d 817 (5th Cir. 2003).
More recently, the Ninth Circuit Court of Appeals upheld the EPA's
approval of enforceable commitments in ozone and PM2.5
SIPs for the San Joaquin Valley, based on the same three factor
test. Committee for a Better Arvin v. EPA, 786 F.3d 1169 (9th Cir.
2015). But see, Medical Advocates for Healthy Air v. EPA, Case No.
20-72780, (9th Cir., Apr. 13, 2022) (finding that the EPA did not
adequately show the State was capable of fulfilling its commitment
with respect to incentive-based control measure commitments).
---------------------------------------------------------------------------

    With respect to the SJV PM2.5 Plan, circumstances
warrant the consideration of enforceable commitments as part of the
attainment demonstration for this area. As discussed in Section
IV.C.2.a.i of this proposed rule, the majority of the emissions
reductions needed to demonstrate attainment and RFP in the San Joaquin
Valley are achieved by rules and regulations adopted prior to the
State's development of the SJV PM2.5 Plan, i.e., baseline
measures. As a result of these already-adopted CARB and District
measures, most air pollution sources in the San Joaquin Valley were
already subject to stringent rules prior to the development of the SJV
PM2.5 Plan, leaving fewer and more technologically
challenging opportunities to reduce emissions. Despite these
significant emission reductions, as shown in Table 4 of this proposed
rule, the State needs to reduce NOX and direct
PM2.5 emission levels by a total of 52.5 percent and 7.2
percent, respectively, from 2013 base year levels in order to attain
the 1997 annual PM2.5 NAAQS in the San Joaquin Valley.
    As part of CARBs control measure commitment in the 15 [micro]g/m\3\
SIP Revision, it identifies the control measure (i.e., Heavy-Duty I/M)
that it expects to achieve the additional emissions reductions needed
for attainment. The timeline needed to develop, adopt, and implement
the measure extended beyond the timeline for Plan adoption, with board
consideration scheduled for December 2021 at the time the Plan was
developed.\263\ As discussed in Section IV.C.2.a.ii of this document,
CARB adopted the Heavy-Duty I/M measure on December 9, 2021, fulfilling
CARB's control measure commitment per the schedule in the Plan. Given
these circumstances, we conclude that reliance on enforceable
commitments in the SJV PM2.5 Plan is warranted. Therefore,
we have considered the three factors the EPA uses to determine whether
the use of enforceable commitments in lieu of adopted measures
satisfies CAA planning requirements.
---------------------------------------------------------------------------

    \263\ August 2021 Staff Report, p. 4.
---------------------------------------------------------------------------

(1) The Commitment Represents a Limited Portion of Required Reductions
    For the first factor, we look to see if the commitment addresses a
limited portion of a statutory requirement, such as the amount of
emissions reductions needed to attain the NAAQS in a nonattainment
area. As discussed in Section IV.C.2.a.i of this proposed rule, most of
the total emission reductions needed to attain the 1997 annual
PM2.5 NAAQS in the San Joaquin Valley by the end of 2023
will be achieved through implementation of baseline measures and
additional measures for which the EPA has finalized approval, leaving
1.8 percent (3 tpd) of the necessary NOX reductions and 0.9
percent (0.04 tpd) of the necessary direct PM2.5 reductions
as aggregate tonnage commitments.
    Given the nature of the PM2.5 challenge in the San
Joaquin Valley, the significant reductions in NOX and direct
PM2.5 emission levels achieved through implementation of
baseline measures over the past several decades, and the difficulty of
identifying additional control measures that are feasible for
implementation in the area, we consider it reasonable for CARB and the
District to seek additional time to develop and adopt the last
increment of emission reductions necessary for attainment by 2023.
Therefore, we conclude that the

emission reductions remaining as enforceable commitments in the SJV
PM2.5 Plan represent a limited portion of the total
emissions reductions needed to demonstrate attainment of the 1997
annual PM2.5 NAAQS by December 31, 2023.
(2) The State Is Capable of Fulfilling Its Commitment
    For the second factor, we consider whether the State is capable of
fulfilling its commitments. As discussed in Section IV.C.2.a.ii of this
document, CARB has already adopted the regulatory measure (i.e., Heavy-
Duty I/M) it committed to in the SJV PM2.5 Plan for the 1997
annual PM2.5 NAAQS. The aggregate tonnage commitments
associated with this measure are 3 tpd of NOX and 0.04 tpd
of direct PM2.5 in 2023, less than 2 percent of the
NOX and direct PM2.5 emissions reductions needed
for attainment by December 31, 2023.\264\
---------------------------------------------------------------------------

    \264\ Unlike the aggregate commitments at issue in the Medical
Advocates case, which relied in-part on incentive-based control
measure commitments, the aggregate commitment the EPA is proposing
to approve in this action consists solely of a regulatory measure
that has already been adopted and submitted by the State and for
which implementation began on January 1, 2023.
---------------------------------------------------------------------------

    Given CARB's progress in adopting the Heavy-Duty I/M measure it
committed to in the 15 [micro]g/m\3\ SIP Revision per the schedule in
the Plan and its continuing efforts to develop additional control
measures to further reduce NOX and PM2.5
emissions in the San Joaquin Valley, we propose that CARB is capable of
fulfilling the remaining increment of NOX emission
reductions necessary to attain the 1997 annual PM2.5 NAAQS
in the San Joaquin Valley by December 31, 2023.
    More broadly, we note that CARB will have to submit to the EPA, for
SIP approval, any control measure that it intends to rely on to satisfy
the aggregate tonnage commitments in the Plan. Furthermore, if CARB
intends to substitute reductions in one pollutant to achieve a tonnage
commitment concerning a different pollutant (e.g., substituting direct
PM2.5 reductions to satisfy a NOX reduction
commitment), it must include an appropriate inter-pollutant trading
(IPT) ratio and the technical basis for such ratio. The EPA will review
any such IPT ratio and its bases before approving or disapproving the
measure.
(3) The Commitment Is for a Reasonable and Appropriate Timeframe
    For the third factor, we consider whether the commitment is for a
reasonable and appropriate period of time. The SJV PM2.5
Plan includes specific rule adoption and implementation schedules for
the Heavy-Duty I/M measure to meet CARB's commitment to reduce
emissions to the levels needed to attain the 1997 annual
PM2.5 NAAQS in the San Joaquin Valley by 2023. CARB has
already met its control measure commitment through its December 2021
adoption of the Heavy-Duty I/M measure and implementation ahead of the
December 31, 2023 projected attainment date. We consider that these
schedules provide a reasonable and appropriate amount of time for CARB
to achieve the remaining emission reductions necessary to attain the
1997 annual PM2.5 NAAQS in the San Joaquin Valley by
December 31, 2023. We therefore propose to conclude that the third
factor is satisfied.
b. Best Available Control Measures
    We are evaluating the State's BACM demonstration for the 1997
annual 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 annual 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 annual 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.
i. Summary of the State's Submission
    The State's BACM demonstration is presented in Appendix C
(``Stationary Source Controls'') of the 2018 PM2.5 Plan and
Appendix D (``Mobile Source Control Measure Analyses'') of the 15
[micro]g/m\3\ SIP Revision.\265\ The State also provided additional
information regarding building heating appliances, including
residential natural gas-fired water heaters and furnaces, in a document
titled ``Building Electrification Technical Supplement for the 1997
Annual PM2.5 NAAQS'' (``March 2023 Building Heating
Supplement''), submitted to the EPA on March 30, 2023.\266\
---------------------------------------------------------------------------

    \265\ 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 annual PM2.5 NAAQS.
Thus, the EPA is evaluating the Plan's control strategy for
implementation of BACM and BACT only.
    \266\ Letter dated March 29, 2023, from Steven S. Cliff,
Executive Officer, CARB, to Martha Guzman, Regional Administrator,
EPA Region 9, with enclosures. This letter is in the docket for this
proposed action.
---------------------------------------------------------------------------

    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 concluded 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.
Stationary and Area Sources
    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.\267\ 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 annual PM2.5 NAAQS. We provide an
evaluation of many of the District's control measures for stationary
sources and area sources in Section IV of the EPA's 1997 Annual
PM2.5 TSD together with recommendations for possible future
improvements to these rules.
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    \267\ 15 [micro]g/m\3\ SIP Revision, Chapter 4, Section 4.3.1.

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

    As noted earlier, the State provided additional information to the
EPA to support its BACM analysis for building heating appliances in its
March 2023 Building Electrification Supplement.\268\ We provide a
summary of the State's BACM analysis for building heating appliances in
the paragraphs that follow.
---------------------------------------------------------------------------

    \268\ Letter dated March 29, 2023, from Steven S. Cliff,
Executive Officer, CARB, to Martha Guzman, Regional Administrator,
EPA Region 9, with enclosures.
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    The State provides a summary of its existing rules governing
building heating appliances, including Rule 4902 (``Residential Water
Heaters'') and Rule 4905 (``Natural Gas-Fired, Fan-Type Central
Furnaces''), in Appendix C of the 2018 PM2.5 Plan.\269\ The
rules are point of sale rules that limit the types of water heaters and
furnaces that may be sold in the San Joaquin Valley.\270\ The District
also provides comparisons of its rules with rules in other California
air districts.\271\ Based on the District's analysis at that time, it
determined that it was implementing the most stringent requirements
feasible for such building heating appliances.
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    \269\ 2018 PM2.5 Plan, Appendix C, sections C.20 and
C.21.
    \270\ SJVUAPCD Rule 4902 (``Residential Water Heaters''),
amended March 19, 2009, and SJVUAPCD Rule 4905 (``Natural Gas-Fired,
Fan-Type Central Furnaces''), amended January 22, 2015.
    \271\ 2018 PM2.5 Plan, Appendix C, sections C.20 and
C.21.
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    The EPA has previously provided our evaluation of the District's
BACM demonstration in the 2018 PM2.5 Plan for stationary and
area sources in general, and several source categories in more detail,
for purposes of other PM2.5 NAAQS in three documents: (1)
the EPA's ``Technical Support Document, EPA Evaluation of BACM/MSM, San
Joaquin Valley PM2.5 Plan for the 2006 PM2.5
NAAQS,'' February 2020 (``EPA's BACM/MSM TSD''); (2) the EPA's
``Response to Comments Document for the EPA's Final Action on the San
Joaquin Valley Serious Area Plan for the 2006 PM2.5 NAAQS,''
June 2020 (``EPA's 2020 Response to Comments''); and (3) Section II of
the EPA's ``Technical Support Document, San Joaquin Valley
PM2.5 Plan for the 1997 24-hour PM2.5 NAAQS,''
August 2021 (``EPA's 1997 24-hour PM2.5 TSD''). In
particular, the EPA's 2020 Response to Comments presented our
evaluation of the District's BACM demonstration for residential water
heaters and residential and commercial, natural gas-fired, fan-type
central furnaces.\272\ At that time we found that the requirements for
residential fuel combustion sources covered by Rules 4902 and 4905
represented BACM.\273\ In addition, the EPA concluded that setting a
zero-NOX standard for heating appliances in new buildings
reasonably requires additional consideration and analysis of
technological and economic feasibility by the District because, per the
2018 PM2.5 Plan, the most common types of residential water
heaters and furnaces are those that use natural gas as fuel.
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    \272\ EPA's 2020 Response to Comments, pp. 142-148, Comment 6.O
and Response 6.O.
    \273\ Id. at 146-147.
---------------------------------------------------------------------------

    We also noted in the EPA's 2020 Response to Comments that the
building codes referenced by commenters at that time appeared to be
green building code ordinances that restrict or prohibit installation
of natural gas or propane appliances in new construction.\274\ Such
ordinances, most of which appeared to have been adopted in late 2019
and early 2020, fell within a category known as ``reach codes,'' which
are city and county building code standards for energy efficiency that
exceed California's statewide standards. We stated that California law
requires local governments to submit proposed ordinances to the
California Energy Commission for a determination that they will be both
cost effective and more energy efficient than statewide standards, and
that compliance with this procedure is necessary for such measures to
be enforceable.\275\ We also noted that ordinances adopted by city
councils and county officials are legally distinct from measures
adopted by the governing boards of the respective air districts and
that it did not appear at the time that California air districts had
adopted similar restrictions.
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    \274\ Id. at 147-148.
    \275\ California 2019 Building Energy Standards, at California
Code of Regulations (CCR), title 24, part 1, article 1, sec. 10-106
(``Locally Adopted Energy Standards''); see also https://ww2.energy.ca.gov/title24/2016standards/ordinances.
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    Since the time of the EPA's actions on the San Joaquin Valley plans
for the 2006 24-hour and 1997 24-hour PM2.5 standards (i.e.,
2020-2021), additional jurisdictions have adopted natural gas bans,
appliance standards, and other strategies to reduce emissions from
building heating devices.\276\ Furthermore, CARB and the Bay Area AQMD
are moving forward in developing measures to set zero-emission
standards for space heaters and water heaters. Given these factors, the
State has supplemented its evaluation of the feasibility of
strengthening its rules for building heating sources for purposes of
the EPA's evaluation of the SJV PM2.5 Plan for the 1997
annual PM2.5 NAAQS.\277\
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    \276\ We note, for awareness only, that the City of Berkeley
introduced an ordinance in 2019 prohibiting the installation of
natural gas infrastructure in most new buildings. In April 2023, the
Ninth Circuit Court of Appeals reversed and remanded the prior
district court's rule that upheld the ordinance on the grounds that
the federal Energy Policy and Conservation Act expressly preempted
the local ordinance's regulation of ``energy use'' of a product
covered by the statute. California Restaurant Association v. City of
Berkeley, No. 21-16278 (9th Cir. 2023).
    \277\ The EPA's evaluation of BACM for NOX emissions
from building heating appliances in its proposed rule on the State's
Serious area plan for the 2012 annual PM2.5 NAAQS was the
subject of adverse comments. (86 FR 74310, December 29, 2021); and
comment letter dated and received January 28, 2022, from Brent
Newell, Public Justice, et al., to Rory Mays, EPA, including
Exhibits 1 through 47. The EPA re-proposed action on portions of
that Serious area plan, including BACM for building heating
appliances based on the record available at the time. (87 FR 60494,
October 5, 2022). However, the State withdrew that original Serious
area plan on October 27, 2022, and has since supplemented its
analysis of BACM for this source category, as described herein.
---------------------------------------------------------------------------

    The March 2023 Building Electrification Supplement includes
analyses from both CARB and the District regarding the stringency of
the District's current rules, recent efforts across the State of
California to further reduce emissions from building heating
appliances, and information supporting the State's assertion that it is
infeasible, and therefore not required for BACM, to implement a zero-
emission regulation for building heating appliances within the
timeframe of the Plan for the 1997 annual PM2.5 NAAQS.
    First, the District asserts that its Rules 4902 (``Residential
Water Heaters''), 4308 (``Boilers, Steam Generators, and Process
Heaters--0.075 MMBtu/HR to Less Than 2.0 MMBtu/HR''), and 4905
(``Natural Gas-Fired, Fan-Type Central Furnaces'') include the most
stringent requirements currently being implemented for water and space
heaters in the nation and are the most stringent measures feasible for
implementation in the San Joaquin Valley as of March 2023.\278\
Specifically, the District notes that its NOX limits of 10
and 14 nanograms of NOX per joule of useful heat (ng/J) for
water and space heaters, respectively, are the same as those
implemented by the South Coast AQMD and are the most stringent in the
country.\279\ The District also points to its efforts to reduce
emissions from home heating through its Fireplace and Woodstove Change-
Out incentive program, which offers support for purchasing and
installing cleaner space heating appliances.\280\ The District notes

that the program has helped replace over 21,000 wood burning appliances
with natural gas inserts, stoves, and fireplaces and that recent
changes to the program are providing larger incentives for electric
space heating and cooling heat pumps in Valley homes.\281\
---------------------------------------------------------------------------

    \278\ March 2023 Building Electrification Supplement, p. 1.
    \279\ Id.
    \280\ Id. at 1-2. The EPA proposed to approve the District's
``Burn Cleaner Fireplace and Woodstove Change-out Incentive
Measure'' into the California SIP on April 14, 2023 (88 FR 22978).
    \281\ March 2023 Building Electrification Supplement, pp. 1-2.
---------------------------------------------------------------------------

    Next, CARB and the District discuss CARB's commitment and ongoing
work to develop a statewide zero-emission space and water heater
regulation. CARB included in its 2022 State SIP Strategy for the State
Implementation Plan (``2022 State SIP Strategy''), among other
measures, a commitment to develop a zero-emission standard for space
and water heaters.\282\ CARB submitted the 2022 State SIP Strategy to
the EPA for approval into the California SIP on February 23, 2023.\283\
CARB reiterated its commitment for a zero-emission standard in the
Final 2022 Scoping Plan for Achieving Carbon Neutrality (``2022 Scoping
Plan'').\284\ The 2022 State SIP Strategy and 2022 Scoping Plan
anticipate implementation of a zero-emission standard for building
heating appliances starting in 2030, pending rule development and CARB
Board approval in 2025.\285\
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    \282\ CARB, 2022 State Strategy for the State Implementation
Plan, pp. 101-103. Available at https://ww2.arb.ca.gov/sites/default/files/2022-08/2022_State_SIP_Strategy.pdf.
    \283\ Letter dated February 22, 2023, from Steven S. Cliff,
Executive Director, CARB, to Martha Guzman, Regional Administrator,
EPA Region IX, with enclosures. The EPA has not yet taken action on
the 2022 State SIP Strategy.
    \284\ CARB, 2022 Scoping Plan, pp. 211-215 and Appendix F.
    \285\ 2022 State SIP Strategy, Table 3.
---------------------------------------------------------------------------

    Third, the State discusses the technical and economic feasibility
challenges of implementing a zero-emission standard for space and water
heaters in the San Joaquin Valley. The State summarizes its position in
the March 2023 Building Electrification Supplement and refers to
technical and economic feasibility considerations outlined in Appendix
F of the 2022 Scoping Plan, which CARB included as an attachment to the
March 2023 Building Electrification Supplement.
    With regard to technical feasibility, CARB acknowledges that
electric alternatives to gas-fueled appliances are currently available
for deployment in some applications but cites various challenges
related to manufacturing capacity, retrofit complications (e.g.,
physical space constraints), consumer awareness/perception, and
decreased performance of some units in colder climates.\286\ The State
asserts that consumer preference for appliance types that they are
already familiar with is a major barrier to building electrification
and discusses the need for increased consumer awareness and adoption,
which would allow manufacturers to take advantage of economies of scale
and increase production capacity.\287\
---------------------------------------------------------------------------

    \286\ 2022 Scoping Plan, pp. 5-10.
    \287\ Id. at Appendix F, p. 22.
---------------------------------------------------------------------------

    With regard to economic feasibility, CARB provides some qualitative
comparisons between capital and energy costs for electric and natural
gas-powered appliances, which vary depending on equipment and
installation needs, climate zones, and energy rate structures.\288\
Costs associated with retrofitting an existing building are expected to
be higher than those for new construction due to the potential for
additional installation costs, which may include electrical panel and
circuit upgrades, rewiring, ductwork modifications, and space
reconfigurations.\289\ Energy costs are expected to vary depending on
the characteristics of the appliances and buildings, climate variation,
consumer use patterns, and utility rate structures.\290\ CARB notes
that higher energy bills after electrification have the potential to
especially burden low-income residents of the State and discusses the
importance of coordinating statewide actions to ensure energy rates are
structured to support electrification.\291\
---------------------------------------------------------------------------

    \288\ Id. at 11-13.
    \289\ Id. at 16-18.
    \290\ Id. at 12.
    \291\ Id. at 13-14.
---------------------------------------------------------------------------

    Additionally, the State posits that low-income customers may be
less likely to adopt electric appliances early on due to capital costs
and could end up paying a larger share of systemwide fossil gas system
costs as other households move away from natural gas use.\292\ With
regard to the San Joaquin Valley specifically, the District notes that
the per capita income of District residents is only 40.5 percent of the
average per capita income of areas in California that have adopted
building electrification ordinances to date, creating additional
challenges for implementation in the Valley.\293\ Furthermore, the
State notes that care must be taken to ensure that vulnerable
communities are not adversely affected. For example, some rural and
tribal areas in California rely on propane or wood burning for heating
because they are not connected to the State's electric grid or natural
gas infrastructure.\294\ CARB emphasizes the need for robust community
engagement to ensure equitable consideration of low-income and
environmental justice communities in the Valley and identifies a need
for increased incentive funding to support a successful transition to
building decarbonization.\295\
---------------------------------------------------------------------------

    \292\ Id. at 15.
    \293\ March 2023 Building Electrification Supplement, pp. 2-3.
The average per capita income of San Joaquin Valley residents is
$24,708 while the average per capita income in cities with building
electrification ordinances is $60,969.
    \294\ Id.
    \295\ Id. at Section 4.
---------------------------------------------------------------------------

    Lastly, the State discusses the anticipated implementation
timelines for zero-NOX building electrification standards in
the context of the San Joaquin Valley Plan for the 1997 annual
PM2.5 NAAQS. CARB asserts that the public process to develop
a rulemaking would take at least two years and that more time would be
needed for implementation.\296\ As discussed earlier, CARB's adoption
and implementation timeline for a statewide zero-NOX measure
involves taking a measure to the CARB Board in 2025 and beginning
implementation in 2030. This timeline was established to allow adequate
time for CARB to collaborate with the U.S. Department of Energy;
California Energy Commission; and California Building Standards
Commission, Department of Housing and Community Development; and to
provide time for robust public engagement with community-based
organizations and other key stakeholders. The State asserts that
emission reductions from building decarbonization are not feasible in
the timeframe of the SJV PM2.5 Plan, given the 2023
attainment date for the 1997 annual PM2.5 NAAQS. The
District has committed in the 2022 Plan for the 2015 8-Hour Ozone
Standard to evaluate current and upcoming work by CARB and other
agencies and to evaluate the feasibility of implementing zero-emission
NOX requirements for building heating sources in the Valley
as part of their ongoing work to attain the 2015 ozone NAAQS.\297\
---------------------------------------------------------------------------

    \296\ March 2023 Building Electrification Supplement, p. 4.
    \297\ 2022 Plan for the 2015 8-Hour Ozone Standard, Section
<IP_ADDRESS>.1. Available at https://ww2.valleyair.org/rules-and-planning/air-quality-plans/ozone-plans/2022-ozone-plan-for-the-san-joaquin-valley/.
---------------------------------------------------------------------------

Mobile Sources
    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 15 [micro]g/m\3\ SIP Revision. 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.\298\
---------------------------------------------------------------------------

    \298\ 15 [micro]g/m\3\ SIP Revision, 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.\299\
---------------------------------------------------------------------------

    \299\ Id. at Table 17.
---------------------------------------------------------------------------

    Appendix D of the 15 [micro]g/m\3\ SIP Revision 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.\300\ 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.\301\ 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.\302\
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    \300\ Id. at D-127 and D-128.
    \301\ Id. at D-127.
    \302\ 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.
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ii. The EPA's Review of the State's Submission
    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 annual PM2.5 NAAQS. In our review, we
considered our evaluation of the State's and District's rules and
supporting information included in the SJV PM2.5 Plan in
connection with our approval of the demonstrations for BACM (including
BACT) and MSM for the 2006 24-hour PM2.5 NAAQS,\303\ our
approval of the demonstration for BACM for the 1997 24-hour
PM2.5 NAAQS,\304\ and our proposed disapproval of the
demonstration for BACM for the 2012 annual PM2.5 NAAQS.\305\
We are proposing to find that the evaluation processes followed by CARB
and the District in the SJV PM2.5 Plan to identify potential
BACM are 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 that additional TCMs
are being considered by the metropolitan transportation agencies as
part of the Congestion Mitigation and Air Quality cost effectiveness
policy, with strategies adopted to meet their SB375 greenhouse gas
reduction targets. Therefore, we propose to find that these TCMs
implement BACM for transportation sources.
---------------------------------------------------------------------------

    \303\ 85 FR 44192.
    \304\ 87 FR 4503 (January 28, 2022).
    \305\ 86 FR 74310.
---------------------------------------------------------------------------

    With regard to building heating appliances, based on the EPA's
review of the additional information provided in the March 2023
Building Electrification Supplement, and for the reasons discussed
below, we are proposing to approve the State's BACM demonstration for
NOX and direct PM2.5 emissions from building
heating appliances for purposes of meeting the CAA requirements for the
1997 annual PM2.5 NAAQS.
    Consistent with the EPA's prior approvals of the State's BACM
demonstration for building heating emission sources with respect to the
2006 24-hour and 1997 24-hour PM2.5 NAAQS, we are proposing
to find that the State provided a thorough review of measures for
building heating sources that were being implemented in other
nonattainment areas at the time the 2018 PM2.5 Plan was
developed, in accordance with 40 CFR 51.1010(a)(2)(i). The State has
since updated the analysis to reflect the current facts and
circumstances for controlling emissions from such sources in 2023 by
providing a feasibility analysis and an updated evaluation of current
measures and ongoing efforts by the State and local air districts to
develop more stringent requirements in the future.
    In accordance with 40 CFR 51.1010(a)(3)(iii), the State has
provided a detailed justification, based on technical and economic
feasibility constraints, for why a zero-emission standard for building
heating appliances is not feasible in the timeframe of the SJV
PM2.5 Plan for the 1997 annual PM2.5 NAAQS (i.e.,
before the projected attainment date). The State summarized various
challenges that must be overcome, ranging from increased manufacturing
to coordination with other State agencies to ensure energy rates are
structured to support electrification. The State emphasized the need
for careful consideration of potential adverse effects on low-income
and environmental justice communities and a robust public process. The
EPA acknowledges the work that is already underway by CARB to develop a
statewide zero-emission NOX measure for this source category
and the recent commitment by the District in its plan for the 2015