year for purposes of the 2012 PM2.5 Moderate area plan. For
the 2019 milestone year, the plan demonstrates that RFP is achieved by
emission reductions from baseline measures alone, whereas the RFP
demonstration for the 2022 milestone year relies on emission reductions
from new control measures committed to in the 2016 PM2.5
Plan.\125\ As shown in Table 3, of the emission reductions needed to
meet the 2022 RFP milestone for the 2012 PM2.5 NAAQS in the
South Coast nonattainment area, 7 tpd of NOX emission
reductions need to be achieved by new or revised control strategy
measures --that is, State and District baseline measures achieve all
but 7 tpd of the NOX emission reductions necessary to meet
the RFP milestone for 2022. This represents approximately 3 percent of
the NOX reductions needed to meet the 2022 RFP milestone.
Historically, the EPA has approved SIPs with enforceable commitments in
the range of approximately 10 to 13 percent of the total reductions
needed for attainment.\126\ We find that the District's NOX
commitment addresses a limited proportion of the required emission
reductions.
---------------------------------------------------------------------------

    \125\ 2016 PM2.5 Plan, Table VI-C-5A.
    \126\ See, e.g., our approvals of the SJV PM10 plan
at 69 FR 30005 (May 26, 2004), the SJV 1-hour ozone plan at 75 FR
10420 (March 8, 2010), the Houston-Galveston 1-hour ozone plan at 66
FR 57160 (November 14, 2001), the SJV PM2.5 plan at 76 FR
69896 (November 9, 2011), and the South Coast PM2.5 plan
at 76 FR 69928 (November 9, 2011).

          Table 3--Reductions Needed for RFP Remaining as Commitments Based on SIP-Creditable Measures
----------------------------------------------------------------------------------------------------------------
                                       PM2.5            NOX             SOX             VOC           Ammonia
----------------------------------------------------------------------------------------------------------------
A. 2012 baseline emissions level            66.4             540            18.4             470            81.1
B. 2022 RFP target level........            64.6             283            17.6             367            74.4
C. Total reductions needed from              1.8             257             0.8             103             6.7
 2012 baseline levels to
 demonstrate RFP (A-B)..........
D. 2022 RFP baseline emissions                64             290              17             362              73
 level..........................
E. Reductions from baseline                  2.4             250             1.4             108             8.1
 measures (A-D).................
F. Reductions needed from new/                 0               7               0               0               0
 revised control strategy
 measures (D-B).................
G. Percent of reductions needed                0            2.7%               0               0               0
 to meet RFP from new control
 measures (F/C).................
----------------------------------------------------------------------------------------------------------------
Data Source: 2016 PM2.5 Plan, Table 3-4B and Table VI-C-5A.

ii. The State Is Capable of Fulfilling Its Commitment
    For the second factor, we consider whether the District is capable
of fulfilling its commitments.
    The District has made significant progress in meeting its
enforceable commitments for the 2022 post-attainment RFP milestone
year. It has adopted numerous baseline measures that are projected to
achieve additional reductions of NOX in future years as
shown in Table 4. In addition to the measures discussed above, both
CARB and the District have well-funded incentive grant programs to
reduce emissions from the on- and off-road engine fleets. Reductions
from these programs have yet to be quantified and/or credited in the
RFP demonstration.

               Table 4--SCAQMD Control Measure Updates Since the 2016 Air Quality Management Plan
----------------------------------------------------------------------------------------------------------------
                                                                                NOX         VOC
         Control measure                Rule         Adoption    Final  implementation     reduction   reduction
                                                       date             date(s)              (tpd)       (tpd)
----------------------------------------------------------------------------------------------------------------
CMB-02..........................  Rule 1111--          * 3/2/  1/1/2046.................       0.017  ..........
                                   ``Natural-Gas-        2018
                                   Fired, Fan-Type
                                   Central
                                   Furnaces''.
CTS-01 (2012 AQMP)..............  Rule 1113--        2/5/2016  1/1/2019.................  ..........        0.88
                                   ``Architectural
                                   Coatings''.
CMB-03..........................  Rule 1118.1--      1/4/2019  7/1/2024.................         0.2  ..........
                                   ``Non-Refinery
                                   Flares''.
CMB-01, CMB-05..................  Rule 1134--        4/5/2019  12/31/2023...............         2.8  ..........
                                   ``Stationary
                                   Gas Turbines''.
CMB-01, CMB-05..................  Rule 1135--       11/2/2018  1/1/2024.................         1.8       0.014
                                   ``Electricity
                                   Generating
                                   Facilities''.
CMB-01, CMB-05..................  Rule 1146, Rule   12/7/2018  1/1/2023.................        0.27  ..........
                                   1146.1, Rule
                                   1146.2--``Non-
                                   Refinery
                                   Boilers and
                                   Heaters''.
CTS-01..........................  Rule 1168--       10/6/2017  2017, 2019, 2023.........  ..........         1.4
                                   ``Adhesive and
                                   Sealant
                                   Applications''.
----------------------------------------------------------------------------------------------------------------
Source: Email dated September 12, 2019 from Kalam Cheung, SCAQMD, to Ashley Graham, EPA Region IX, attaching
  spreadsheet entitled ``Draft Rule Adoption since 2016 AQMP 20190809.xlsx.''
* SCAQMD further amended Rule 1111 on July 6, 2018 and December 6, 2019.

    Given the District's efforts to date and its continuing efforts to
reduce emissions, we believe it is capable of meeting its enforceable
commitments to achieve the reductions needed to meet its 2022 RFP
milestones for the 2012 PM2.5 NAAQS.
iii. The Commitment Is for a Reasonable and Appropriate Timeframe
    For the third and last factor, we consider whether the commitment
is for a reasonable and appropriate period of time.
    In order to meet the commitments to adopt measures and reduce
emissions to the levels needed to meet the area's 2022 RFP milestones
for the 2012 PM2.5 NAAQS in the South Coast nonattainment
area, the 2016 PM2.5 Plan includes ambitious rule
development, adoption, and implementation schedules for a number of
defined control measures. The District has committed to achieve 20.5
tpd of NOX emission reductions by 2022 through adoption and
implementation of these defined measures or substitute measures that
achieve equivalent emission reductions. We believe that these
timeframes are appropriate given the technological and economic
challenges associated with the control measures that will be needed to
achieve these reductions and the State's and District's required
procedures for development and adoption of these measures. In addition,
these reductions are not needed to meet the earlier 2019 RFP
milestones. Thus, the commitment is for a reasonable and appropriate
period of time.
    Based on our consideration of these three factors, we are proposing
to approve the District's commitments to adopt and implement specific
control measures on the schedule identified in Table 4-7 and Table 4-8
of the 2016 PM2.5 Plan to the extent that these commitments
have not yet been fulfilled, and to achieve specific emission
reductions by 2022, as given in these tables and in the Control
Strategy Updates.

E. Major Stationary Source Control Requirements Under CAA Section
189(e)

    CAA section 189(e) specifically requires that the control
requirements applicable to major stationary sources of direct
PM2.5 also apply to major stationary sources of
PM2.5 precursors, except where the Administrator determines
that such sources do not contribute significantly to PM2.5
levels that exceed the standards in the area.\127\ The control
requirements applicable to major stationary sources of direct
PM2.5 in a Moderate PM2.5 nonattainment area
include, at a minimum, the requirements of a NNSR permit program
meeting the requirements of CAA sections 172(c)(5) and 189(a)(1)(A). In
the PM2.5 SIP Requirements Rule, we established a deadline
for states to

submit NNSR plan revisions to implement the PM2.5 NAAQS 18
months after an area is initially designated and classified as a
Moderate nonattainment area.\128\
---------------------------------------------------------------------------

    \127\ General Preamble, 13539 and 13541-13542.
    \128\ 81 FR 58010, 58115.
---------------------------------------------------------------------------

    California submitted NNSR SIP revisions for the South Coast to
address the subpart 4 requirements for Moderate PM2.5
nonattainment areas on December 29, 2014.\129\ The EPA fully approved
these SIP revisions on May 1, 2015.\130\ California also submitted NNSR
SIP revisions for the South Coast to address the subpart 4 requirements
for Serious PM2.5 nonattainment areas on May 8, 2017, and
the EPA conditionally approved these SIP revisions on November 30,
2018.\131\ The basis for the November 30, 2018 conditional approval was
a commitment by CARB and the SCAQMD to submit a revised version of Rule
1325 by December 30, 2019. CARB submitted a revised version of Rule
1325 to the EPA on April 24, 2019, fulfilling this commitment.\132\
Accordingly, in this action, the EPA is not addressing the NNSR control
requirements that apply to major stationary sources of direct
PM2.5 and PM2.5 precursors in the South Coast
area under CAA section 189(e).
---------------------------------------------------------------------------

    \129\ Letter dated December 29, 2014, from Richard W. Corey,
Executive Officer, CARB, to Jared Blumenfeld, Regional
Administrator, EPA Region 9.
    \130\ 80 FR 24821.
    \131\ 83 FR 61551.
    \132\ Letter dated April 24, 2019, from Richard W. Corey,
Executive Officer, CARB, to Mike Stoker, Regional Administrator, EPA
Region 9.
---------------------------------------------------------------------------

F. Demonstration That Attainment by the Moderate Area Attainment Date
Is Impracticable

1. Requirements for Attainment/Impracticability of Attainment
Demonstrations
    CAA section 189(a)(1)(B) requires that each Moderate area
attainment plan include a demonstration that the plan provides for
attainment by the applicable Moderate area attainment date or,
alternatively, that attainment by such date is impracticable. This
provision explicitly requires that a demonstration of attainment be
based on air quality modeling but does not require such modeling for an
impracticability demonstration. Although the EPA expects that most
impracticability demonstrations will also be supported by air quality
modeling, it may be possible in some cases to support an
impracticability demonstration with ambient PM2.5 data and
other relevant non-modeling information.\133\
---------------------------------------------------------------------------

    \133\ 81 FR 58010, 58048 and 58049.
---------------------------------------------------------------------------

    CAA section 188(c) states, in relevant part, that the Moderate area
attainment date ``shall be as expeditiously as practicable but no later
than the end of the sixth calendar year after the area's designation as
nonattainment . . .'' For the South Coast area, which was initially
designated as nonattainment for the 2012 PM2.5 standard
effective April 15, 2015, the applicable Moderate area attainment date
under section 188(c) for this standard is as expeditiously as
practicable but no later than December 31, 2021.
    In SIP submissions that demonstrate impracticability, the state
should document how its required control strategy in the attainment
plan represents the application of RACM/RACT and additional reasonable
measures, at minimum, to existing sources. The EPA believes it is
appropriate to require adoption of all available control measures that
are reasonable, i.e., technologically and economically feasible, in
areas that do not demonstrate timely attainment, even where those
measures cannot be implemented within the 4-year timeframe for
implementation of RACM/RACT under CAA section 189(a)(1)(C). The
impracticability demonstration will then be based on a showing that the
area cannot attain by the applicable attainment date, notwithstanding
implementation of the required controls.
2. Impracticability Demonstration in the 2016 PM2.5 Plan
    The 2016 PM2.5 Plan includes a demonstration, based on
air quality modeling, that even with the implementation of RACM/RACT
and additional reasonable measures for all appropriate sources,
attainment by December 31, 2021 is not practicable. The
impracticability demonstration is included in Appendix VI-B of the 2016
PM2.5 Plan.
    Modeled annual average PM2.5 concentrations are
presented for five monitoring sites representing high PM2.5
concentrations in the South Coast air basin. Annual PM2.5
concentrations were modeled for the 2012 base year and 2021 attainment
year. For 2021, the District examined both baseline and control
scenarios. The demonstration is summarized in Table 5.

               Table 5--Impracticability Demonstration--Annual Average PM2.5 Design Concentrations
                                                 [[micro]g/m\3\]
----------------------------------------------------------------------------------------------------------------
                                                                                2021
                             Station                                   2012       2021  Baseline    Controlled
----------------------------------------------------------------------------------------------------------------
Los Angeles.....................................................            12.4            10.9            10.6
Anaheim.........................................................            10.6             9.4             9.1
Rubidoux........................................................            13.2            11.2            10.9
Mira Loma.......................................................            14.9            12.6            12.3
Fontana.........................................................            12.6            10.6            10.4
----------------------------------------------------------------------------------------------------------------
Source: 2016 PM2.5 Plan, Table VI-B-2.

3. The EPA's Evaluation and Proposed Action
    The impracticability demonstration in the 2016 PM2.5
Plan is based on air quality modeling that is generally consistent with
applicable EPA guidance. We find the modeling adequate to support the
impracticability demonstration in the plan. See section V.C of this
notice.
    We have also evaluated the RACM/RACT and additional reasonable
measures demonstration and find that it provides for the expeditious
implementation of all RACM/RACT and additional reasonable measures that
may feasibly be implemented at this time, consistent with the
requirements of CAA sections 172(c)(1) and 189(a)(1)(C) for the 2012
PM2.5 NAAQS in the South Coast. See section V.D of this
notice.
    Finally, we have evaluated the demonstration in the 2016
PM2.5 Plan that the implementation of the State/District's
SIP control strategy, including

RACM/RACT and additional reasonable measures, is insufficient to bring
the South Coast into attainment by December 31, 2021. In addition to
the information in the 2016 PM2.5 Plan, we have reviewed
recent PM2.5 monitoring data from the South Coast. These
data show that annual PM2.5 levels in the South Coast, with
a current design value (2016-2018) of 14.7 [micro]g/m\3\, continue to
be well above the 12.0 [micro]g/m\3\ level of the 2012 PM2.5
standard, and the recent trends in annual PM2.5 levels in
the South Coast are not consistent with a projection of attainment by
the end of 2021.\134\
---------------------------------------------------------------------------

    \134\ EPA, Design Value Spreadsheets,
``20200306_SouthCoastPM25Annual.xlsx'' and
``pm25_designvalues_20162018_final_12_03_19.xlsx.''
---------------------------------------------------------------------------

    Based on this evaluation, we propose to approve the State's
demonstration in the 2016 PM2.5 Plan that attainment of the
2012 PM2.5 NAAQS in the South Coast by the Moderate area
attainment date of December 31, 2021, is impracticable, consistent with
the requirements of CAA section 189(a)(1)(B)(ii). On this basis, we
also propose to reclassify the South Coast as a Serious nonattainment
area, which would trigger requirements for the State to submit a
Serious area plan consistent with the requirements of subparts 1 and 4
of part D, title I of the Act (see section VI of this notice).

G. Reasonable Further Progress and Quantitative Milestones

1. Requirements for Reasonable Further Progress and Quantitative
Milestones
    CAA section 172(c)(2) states that all nonattainment area plans
shall require RFP. In addition, CAA section 189(c) requires that all
PM2.5 nonattainment area SIPs include quantitative
milestones to be achieved every three years until the area is
redesignated to attainment and which demonstrate RFP. Section 171(1)
defines RFP as ``such annual incremental reductions in emissions of the
relevant air pollutant as are required by [Part D] or may reasonably be
required by the Administrator for the purpose of ensuring attainment of
the applicable [NAAQS] by the applicable date.'' Neither subpart 1 nor
subpart 4 of part D, title I of the Act requires that a set percentage
of emission reductions be achieved in any given year for purposes of
satisfying the RFP requirement.
    For purposes of the PM2.5 NAAQS, the EPA has interpreted
the RFP requirement to require that nonattainment area plans show
annual incremental emission reductions sufficient to maintain generally
linear progress toward attainment by the applicable deadline.\135\ As
discussed in EPA guidance in the Addendum to the General Preamble
(``Addendum''),\136\ requiring linear progress in reductions of direct
PM2.5 and any individual precursor in a PM2.5
plan may be appropriate in situations where:
---------------------------------------------------------------------------

    \135\ Addendum to the General Preamble, 59 FR 41998, 42015
(August 16, 1994).
    \136\ Id.
---------------------------------------------------------------------------

     The pollutant is emitted by a large number and range of
sources,
     the relationship between any individual source or source
category and overall air quality is not well known,
     a chemical transformation is involved (e.g., secondary
particulate significantly contributes to PM2.5 levels over
the standard), and/or
     the emission reductions necessary to attain the
PM2.5 standard are inventory-wide.\137\
---------------------------------------------------------------------------

    \137\ Id.
---------------------------------------------------------------------------

    The Addendum indicates that requiring linear progress may be less
appropriate in other situations, such as:
     Where there are a limited number of sources of direct
PM2.5 or a precursor,
     where the relationships between individual sources and air
quality are relatively well defined, and/or
     where the emission control systems utilized (e.g., at
major point sources) will result in a swift and dramatic emission
reductions.
    In nonattainment areas characterized by any of these latter
conditions, RFP may be better represented as step-wise progress as
controls are implemented and achieve significant reductions soon
thereafter. For example, if an area's nonattainment problem can be
attributed to a few major sources, EPA guidance indicates that ``RFP
should be met by `adherence to an ambitious compliance schedule' which
is likely to periodically yield significant emission reductions of
direct PM2.5 or a PM2.5 precursor.'' \138\
---------------------------------------------------------------------------

    \138\ Id.
---------------------------------------------------------------------------

    Attainment plans for PM2.5 nonattainment areas should
include detailed schedules for compliance with emission regulations in
the area and provide corresponding annual emission reductions to be
achieved by each milestone in the schedule.\139\ In reviewing an
attainment plan under subpart 4, the EPA considers whether the annual
incremental emission reductions to be achieved are reasonable in light
of the statutory objective of timely attainment. Although early
implementation of the most cost-effective control measures is often
appropriate, states should consider both cost-effectiveness and
pollution reduction effectiveness when developing implementation
schedules for control measures and may implement measures that are more
effective at reducing PM2.5 earlier, to provide greater
public health benefits.\140\
---------------------------------------------------------------------------

    \139\ Id. at 42016.
    \140\ Id.
---------------------------------------------------------------------------

    The PM2.5 SIP Requirements Rule establishes specific
regulatory requirements for purposes of satisfying the Act's RFP
requirements and provides related guidance in the preamble to the rule.
Specifically, under the PM2.5 SIP Requirements Rule, each
PM2.5 attainment plan must contain an RFP analysis that
includes, at a minimum, the following four components: (1) An
implementation schedule for control measures; (2) RFP projected
emissions for direct PM2.5 and all PM2.5 plan
precursors for each applicable milestone year, based on the anticipated
control measure implementation schedule; (3) a demonstration that the
control strategy and implementation schedule will achieve reasonable
progress toward attainment between the base year and the attainment
year; and (4) a demonstration that by the end of the calendar year for
each milestone date for the area, pollutant emissions will be at levels
that reflect either generally linear progress or stepwise progress in
reducing emissions on an annual basis between the base year and the
attainment year.\141\ States should estimate the RFP projected
emissions for each quantitative milestone year by sector on a
pollutant-by-pollutant basis.\142\ In an area that cannot practicably
attain the PM2.5 standard by the applicable Moderate area
attainment date, full implementation of a control strategy that
satisfies the Moderate area control requirements represents RFP towards
attainment.\143\
---------------------------------------------------------------------------

    \141\ 40 CFR 51.1012(a).
    \142\ 81 FR 58010, 58056.
    \143\ Id. at 58056, 58057.
---------------------------------------------------------------------------

    Section 189(c) requires that attainment plans include quantitative
milestones that demonstrate RFP. The purpose of the quantitative
milestones is to allow for periodic evaluation of the area's progress
towards attainment of the NAAQS consistent with RFP requirements.
Because RFP is an annual emission reduction requirement and the
quantitative milestones are to be achieved every three years, when a
state demonstrates compliance with the quantitative milestone
requirement, it will demonstrate that RFP has been achieved during each
of the relevant three years. Quantitative milestones

should provide an objective means to evaluate progress toward
attainment meaningfully, e.g., through imposition of emission controls
in the attainment plan and the requirement to quantify those required
emission reductions. The CAA also requires states to submit milestone
reports (due 90 days after each milestone), and these reports should
include calculations and any assumptions made by the state concerning
how RFP has been met, e.g., through quantification of emission
reductions to date.\144\ The Act requires states to include RFP and
quantitative milestones even for areas that cannot practicably attain.
---------------------------------------------------------------------------

    \144\ Addendum, 42016-42017.
---------------------------------------------------------------------------

    The CAA does not specify the starting point for counting the three-
year periods for quantitative milestones under CAA section 189(c). In
the General Preamble and Addendum, the EPA interpreted the CAA to
require that the starting point for the first three-year period be the
due date for the Moderate area plan submission.\145\ Consistent with
this longstanding interpretation of the Act, the PM2.5 SIP
Requirements Rule requires that each plan for a Moderate
PM2.5 nonattainment area contain quantitative milestones to
be achieved no later than milestone dates 4.5 years and 7.5 years from
the date of designation of the area.\146\ Because the EPA designated
the South Coast area nonattainment for the 2012 PM2.5 NAAQS
effective April 15, 2015,\147\ the applicable quantitative milestone
dates for purposes of this NAAQS in the South Coast are October 15,
2019 and October 15, 2022. Following reclassification of the South
Coast area as Serious for the 2012 PM2.5 standard, later
milestones would be addressed by the Serious area plan.\148\
---------------------------------------------------------------------------

    \145\ General Preamble, 13539, and Addendum, 42016.
    \146\ 40 CFR 51.1013(a)(1).
    \147\ 80 FR 2206.
    \148\ Addendum, 42016.
---------------------------------------------------------------------------

2. Reasonable Further Progress Demonstration and Quantitative
Milestones in the 2016 PM2.5 Plan
    The RFP plan and quantitative milestones are discussed in section
VI-C of Appendix VI of the 2016 PM2.5 Plan. The Plan
estimates that emissions of direct PM2.5, NOX,
SOX, VOC, and ammonia will generally decline from the 2012
base year and states that emissions of each of these pollutants will
remain below the levels needed to show ``generally linear progress''
through 2022, the Moderate area post-attainment milestone year for the
2012 PM2.5 NAAQS.\149\ The Plan's emissions inventory shows
that direct PM2.5, NOX, SOX, VOC, and
ammonia are emitted by a large number and range of sources in the South
Coast and that the emission reductions needed for each of these
pollutants are inventory-wide.\150\ Table VI-C-4 of the 2016
PM2.5 Plan contains an implementation schedule for adopted
District control measures,\151\ Table VI-C-6 contains emission
reduction commitments to be achieved each year from 2016 to 2025, and
Table VI-C-5 (reproduced, in part,\152\ in Table 6) contains RFP
projected emissions for each quantitative milestone year. Based on
these analyses, the District concludes that its adopted control
strategy will achieve, for each pollutant, projected emission levels at
or below the RFP and quantitative milestone target emission levels for
2019 and 2022 (see Table 7).\153\
---------------------------------------------------------------------------

    \149\ 2016 PM2.5 Plan, Table VI-C-5 and Table VI-C-
5A.
    \150\ Id., Chapter 4 and appendices IV-A, VI-B, and VI-C.
    \151\ See also email dated September 12, 2019 from Kalam Cheung,
SCAQMD, to Ashley Graham, EPA Region IX, attaching spreadsheet
entitled ``Draft Rule Adoption since 2016 AQMP 20190809.xlsx.''
    \152\ Table 6 identifies only emission levels for milestone
years that must be addressed by the Moderate area plan.
    \153\ 2016 PM2.5 Plan, VI-C-9.

          Table 6--Annual PM2.5 Baseline Emissions for Base Year and Moderate Area Plan Milestone Years
                                              [Annual average tpd]
----------------------------------------------------------------------------------------------------------------
                                                                                2019            2022
                            Pollutant                             2012  Baseline   (Quantitative   (Quantitative
                                                                                milestone)      milestone)
----------------------------------------------------------------------------------------------------------------
PM2.5...........................................................            66.4            63.9            64.1
NOX.............................................................             540             353             275
SOX.............................................................            18.4            16.6            17.0
VOC.............................................................             470             376             348
Ammonia.........................................................            81.1            74.0            72.6
----------------------------------------------------------------------------------------------------------------
Source: 2016 PM2.5 Plan, Table VI-C-5.

                                Table 7--Summary of Annual PM2.5 RFP Calculations
----------------------------------------------------------------------------------------------------------------
         Row               Calculation step         PM2.5         NOX          SOX          VOC        Ammonia
----------------------------------------------------------------------------------------------------------------
1....................  2012 base year emissions         66.4          540         18.4          470         81.1
                        (tpd).
2....................  Annual percent change            0.27          4.8         0.43          2.2         0.83
                        needed to show linear
                        progress (%).
3....................  2019 target needed to            65.2          360         17.8          398         76.4
                        show linear progress
                        (tpd).
4....................  2019 baseline emissions          63.9          353         16.6          376         74.0
                        (tpd).
5....................  Projected shortfall                 0            0            0            0            0
                        (tpd).
6....................  Surplus in 2019 (tpd)...          1.3          6.8          1.2         22.2          2.4
7....................  2022 target needed to            64.6          283         17.6          367         74.4
                        show linear progress
                        (%).
8....................  2022 emissions (tpd) *..         64.1          275         17.0          348         72.6
9....................  Projected shortfall                 0            0            0            0            0
                        (tpd).
10...................  Surplus in 2022 (tpd)...         0.56          8.0         0.59         18.5          1.7
----------------------------------------------------------------------------------------------------------------
* Based on controlled emissions with emission reductions committed to in the 2016 PM2.5 Plan.
Source: 2016 PM2.5 Plan, Table VI-C-5A.

    The 2016 PM2.5 Plan documents the State's conclusion
that all RACM/RACT and additional reasonable measures for these
pollutants are being implemented as expeditiously as practicable and
identifies projected levels of direct

PM2.5, NOX, SOX, VOC, and ammonia
emissions that reflect full implementation of the State, District, and
SCAG's RACM/RACT and additional reasonable measure control strategy for
these pollutants.\154\ The control strategy that provides the basis for
these emission projections is described in Chapter 4, Appendix IV, and
Appendix VI of the 2016 PM2.5 Plan.
---------------------------------------------------------------------------

    \154\ Id. at VI-C-5 to VI-C-12; see also evaluation of RACM/RACT
in section V.D of this proposed rule.
---------------------------------------------------------------------------

Direct PM2.5
    The District has several stationary and area source rules that are
projected to contribute to RFP and attainment of the PM2.5
standards.\155\ For example, Rule 444 (``Open Burning'') and Rule 445
(``Residential Wood Burning Devices'') were amended in 2013 to achieve
PM2.5 reductions during winter episodic conditions. The 2013
amendments to Rule 445 lowered the mandatory winter burning curtailment
program threshold for residential wood burning and, in certain cases,
extended the curtailment to the entire South Coast air basin, thereby
further limiting emissions from one of the largest direct
PM2.5 combustion sources in the South Coast nonattainment
area.\156\ These rule amendments provide part of the incremental
reductions in emissions of direct PM2.5 needed from the 2012
base year to meet RFP requirements.\157\ Measures to control sources of
direct PM2.5 are also presented in the Plan's RACM analyses
and are reflected in the Plan's baseline emission projections.
---------------------------------------------------------------------------

    \155\ Id., Table III-2-2B and Table 4-8.
    \156\ Id., Table III-1-2. See also 78 FR 59249 (September 26,
2013).
    \157\ Id., Table VI-C-4.
---------------------------------------------------------------------------

    The Plan highlights on-road and other mobile source control
measures as the primary means for achieving direct PM2.5
emission reductions. CARB's implementation of the Truck and Bus
Regulation achieved PM2.5 emission reductions beginning in
2012.\158\ Lighter trucks and buses were required to replace 1995 and
older engines with a 2010 model year by 2015. The 2010 model year
engines include particulate filters. CARB's LEV II program includes PM
emission limits by model year for 2016, and the LEV II program has
stricter emission limits for 2017 and beyond. For off-road vehicles,
CARB adopted the In-Use Off Road Diesel-Fueled Fleets Regulation
(``Off-Road Regulation'') in 2007. The Off-Road Regulation requires
owners to replace older vehicles or engines with newer, cleaner models
to either (1) retire older vehicles or reduce their use, or (2) to
apply retrofit exhaust controls. Off-road fleets are required to meet
increasingly strict fleet average indices over time.\159\ These indices
reflect a fleet's overall emission rates of PM and NOX for
model year and horsepower combinations. Fleets were also banned from
adding Tier 0 off-road engines as of January 1, 2014.\160\ CARB
implemented a similar ban on Tier 1 engines between January 1, 2014
(large fleets) and January 1, 2016 (small fleets).
---------------------------------------------------------------------------

    \158\ The State's quantitative milestone report for the 2017
milestone for the 2006 PM2.5 standards indicates that the
requirement for heavier trucks to install diesel particulate filters
was fully implemented by 2016. See SCAQMD, ``2017 Quantitative
Milestone Report for the 2006 24-hour PM2.5 National
Ambient Air Quality Standard,'' March 2018 (``2017 QM Report''), 11.
    \159\ A fleet average index is an indicator of a fleet's overall
emissions rate of PM and NOX based on the horsepower and
model year of each engine in the fleet.
    \160\ Tier 0 engines meet 1995 to 1999 emission standards,
depending on engine size and horsepower. See http://www.assocpower.com/eqdata/tech/US-EPA-Tier-Chart_1995-2004.php.
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Nitrogen Oxides
    The District regulates numerous NOX emission sources
such as residential space and water heating devices, stationary
internal combustion engines, and various sizes of boilers, steam
generators, and process heaters used in industrial settings. The 2016
PM2.5 Plan identifies the following South Coast regulations
as measures that achieve ongoing NOX reductions with
compliance dates during the RFP years of the Plan: Rule 1111
(``Reductions of NOX from Natural Gas-Fired, Fan-Type
Central Furnaces''), Rule 1146.2 (``Emission of Oxides of Nitrogen from
Large Water Heaters and Small Boilers and Process Heaters''), and Rule
1147 (``NOX Reductions from Miscellaneous
Sources'').161 162
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    \161\ 2016 PM2.5 Plan, Table VI-C-4. See also email
dated September 12, 2019 from Kalam Cheung, SCAQMD, to Ashley
Graham, EPA Region IX, attaching spreadsheet entitled ``Draft Rule
Adoption since 2016 AQMP 20190809.xlsx.''
    \162\ Rule 1111 was mistakenly listed as Rule 1110 in the 2016
PM2.5 Plan, Table VI-C-4. See 2017 QM Report, 6, footnote
1.
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    In addition to these baseline measures, the District has committed
to adopt and implement several new measures to reduce NOX
emissions and ensure RFP toward attainment of the 2012 PM2.5
NAAQS in the South Coast air basin. These measures may include CMB-01
(``Transition to Zero and Near-Zero Emission Technologies for
Stationary Sources''), CMB-02 (``Emission Reductions from Replacement
with Zero or Near-Zero NOX Appliances in Commercial and
Residential Applications''), CMB-03 (``Emission Reductions from Non-
Refinery Flares''), CMB-04 (``Emission Reductions from Restaurant
Burners and Residential Cooking''), ECC-02 (``Co-Benefits from Existing
Residential and Commercial Building Energy Efficiency Measures''), ECC-
03 (``Additional Enhancements in Reducing Residential Building Energy
Use''), MOB-10 (``Extension of the SOON Provision for Construction/
Industrial Equipment''), MOB-11 (``Extended Exchange Program''), and
MOB-14 (``Emission Reductions from Incentive Programs'').\163\
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    \163\ 2016 PM2.5 Plan, Table VI-C-6.
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    For on-road and non-road mobile sources, which represent the
largest sources of NOX emissions in the nonattainment area,
the 2016 PM2.5 Plan lists numerous CARB regulations and
discusses the key regulations that limit emissions of direct
PM2.5 as well as NOX, SO2, VOC, and
ammonia from these sources.\164\ For example, the regulations that
apply to the three largest sources of NOX in the South
Coast--heavy-duty diesel trucks, light- and medium-duty passenger
vehicles, and off-road equipment--are discussed in the 2016
PM2.5 Plan at Appendix VI-C, Attachment VI-C-1, ``California
Existing Mobile Source Control Program,'' and CARB's emission
projections for these sources are presented in the Plan's emissions
inventory.\165\ The Plan also shows that NOX emission levels
in the 2019 and 2022 milestone years are projected to be below the
levels needed to show generally linear progress toward attainment in
2025.\166\
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    \164\ Id., Appendix VI-C, Attachment VI-C-1.
    \165\ Id., Appendix III.
    \166\ Id., Table VI-C-5A.
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    The Truck and Bus Regulation and Drayage Truck Regulation became
effective in 2011 and have rolling compliance deadlines based on truck
engine model year. These and other regulations applicable to heavy-duty
diesel trucks will continue to reduce emissions of diesel PM and
NOX through the RFP planning years.\167\ For example, model
year 1994 and 1995 heavy-duty diesel truck engines were required to be
upgraded to meet the 2010 model year truck engine emission standards by
2016, and model year 1996-1999 engines must be upgraded by January 1,
2020.\168\
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    \167\ Id. at VI-C-20.
    \168\ Title 13, California Code of Regulations, Section 2025
(``Regulation to Reduce Emissions of Diesel Particulate Matter,
Oxides of Nitrogen and Other Criteria Pollutants, from In-Use Heavy-
Duty Diesel-Fueled Vehicles''), paragraphs (e), (f), and (g),
effective December 14, 2011. See also 77 FR 20308, 20309-20310
(April 4, 2012) (final rule approving CARB's Truck and Bus Rule into
California SIP).

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    CARB's Cleaner In-Use Off-road Equipment regulation was first
approved in 2007 to reduce PM2.5 and NOX
emissions from in-use off-road heavy-duty diesel vehicles in California
such as those used in construction, mining, and industrial operations.
The regulation reduces emissions of PM2.5 and NOX
by targeting the existing fleet and imposing idling limits,
restrictions on use of older vehicles, and requirements to retrofit or
replace the oldest engines. For example, Tier 0 engines could not be
added to fleets after January 1, 2014, and Tier 1 engines could not be
added after January 1, 2016. The regulation was phased in between
January 1, 2014 and January 1, 2019.\169\
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    \169\ 2016 PM2.5 Plan, Appendix VI-C, Attachment VI-
C-1, VI-C-23 and VI-C-24.
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Volatile Organic Compounds
    As with other precursors, the District regulates stationary and
area sources of VOCs, and CARB is largely responsible for regulating
emissions from both on-road and off-road mobile sources. The 2016
PM2.5 Plan highlights one adopted stationary source VOC rule
that contributes to RFP: Rule 1114 (``Petroleum Refinery Coking
Operations'').\170\
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    \170\ Id., Table VI-C-4. See also, email dated September 12,
2019 from Kalam Cheung, SCAQMD, to Ashley Graham, EPA Region IX,
attaching spreadsheet entitled ``Draft Rule Adoption since 2016 AQMP
20190809.xlsx.''
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    In addition to the baseline measures discussed above, the District
intends to adopt and implement several measures to reduce
NOX emissions that may also result in VOC emission
reductions and help ensure RFP toward attainment of the 2012
PM2.5 NAAQS in the South Coast air basin. These measures
include CMB-01 (``Transition to Zero and Near-Zero Emission
Technologies for Stationary Sources''), CMB-03 (``Emission Reductions
from Non-Refinery Flares''), ECC-02 (``Co-Benefits from Existing
Residential and Commercial Building Energy Efficiency Measures''), ECC-
03 (``Additional Enhancements in Reducing Residential Building Energy
Use'').\171\
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    \171\ Id.
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    As with NOX, the majority of VOC emission reductions
that occur between the 2012 base year and the 2022 RFP year come from
on-road mobile sources and other mobile sources that are under the
State's jurisdiction.
Ammonia
    Control measures for ammonia sources are described in Appendix VI
of the 2016 PM2.5 Plan. For example, South Coast Rule 223
and Rule 1127, which regulate confined animal facilities and manure
waste from these facilities, control ammonia, as do the District's
composting measures (i.e., Rule 1133, Rule 1133.1, Rule 1133.2 and Rule
1133.3). These rules and the methods they use to control ammonia
emissions are discussed at length in Appendix IV-A of the Plan, and
their emission projections are presented collectively under farming
operations (for confined animal feeding operations and manure) or waste
disposal (for composting categories) in the Plan's emissions
inventory.\172\ We discuss our evaluation of these rules for purposes
of satisfying RACM requirements in section V.D of this proposed rule.
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    \172\ 2016 PM2.5 Plan, IV-A-98 to IV-A-103.
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    As part of the control strategy for the 2016 PM2.5 Plan,
the District has committed to adopt and implement new or revised
control measures to reduce ammonia emissions in the South Coast air
basin. Potential measures include: (1) BCM-04 (``Emission Reductions
from Manure Management Strategies''), which would reduce ammonia from
fresh manure through acidifier application, dietary manipulation, feed
additives, and other manure control strategies, including potentially
lowering the threshold for large confined animal facilities under Rule
223; and (2) BCM-10 (``Emission Reductions from Greenwaste
Composting''), which would reduce ammonia through emerging organic
waste processing technology and potential restrictions on direct land
application of uncomposted greenwaste.\173\
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    \173\ SCAQMD, Governing Board Resolution No. 17-2 (March 3,
2017), 9 and 2016 PM2.5 Plan, Table 4-7, identifying BCM-
04 and BCM-10 as new control measures to be implemented by 2020 for
PM2.5 purposes.
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    The District ascribes the projected reductions in ammonia during
the period from 2012 to 2022 to decreases in farming operations in the
South Coast air basin, reductions in emissions from mobile sources
largely achieved by State regulations for on-road motor vehicles, and
the District's commitments to adopt and implement new control measures
such as BCM-04 and BCM-10.\174\
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    \174\ 2016 PM2.5 Plan, Appendix III, Attachment A.
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Sulfur Dioxide
    Reductions of SO2 in the South Coast nonattainment area
during the period from 2012 to 2022 are mainly from mobile source
reductions. The majority of the SO2 reductions come from
non-road mobile sources, primarily reductions from state regulation of
ocean-going vessels.
Quantitative Milestones
    The 2016 PM2.5 Plan identifies a milestone year of 2019,
which is 4.5 years after the effective date of the EPA's designation
and classification of the South Coast as a Moderate nonattainment area
for the 2012 PM2.5 NAAQS, and a second milestone year of
2022, which is 7.5 years after the effective date of the designation.
The Plan also identifies target RFP emission levels for direct
PM2.5, NOX, SO2, VOC, and ammonia for
the 2019 milestone year and the 2022 post-attainment milestone
year,\175\ and emission reduction commitments to be achieved through
2022 in accordance with the control strategy in the Plan.\176\
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    \175\ 2016 PM2.5 Plan, VI-C-9 and VI-C-10.
    \176\ Id., Table VI-C-6.
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3. The EPA's Evaluation and Proposed Action
    The 2016 PM2.5 Plan describes the adopted control
measures for direct PM2.5, NOX, SO2,
VOC, and ammonia implemented during each year of the plan and
demonstrates that these measures are being implemented as expeditiously
as practicable. Additionally, the Plan presents basin-wide emission
reduction commitments to attain the 2012 PM2.5 NAAQS. The
Plan contains projected RFP emission levels for direct PM2.5
and all PM2.5 precursors for the 2019 and 2022 milestone
years based on the anticipated implementation schedule for the control
strategy. Finally, the 2016 PM2.5 Plan demonstrates that, by
the end of the calendar year for each milestone date for the area,
emissions of direct PM2.5 and all PM2.5
precursors will be reduced at rates representing generally linear
progress towards attainment.\177\ We agree with the State and
District's conclusion that generally linear progress is an appropriate
measure of RFP for the 2012 PM2.5 NAAQS in the South Coast
area given that PM2.5 and its precursors are emitted by a
large number and range of sources in the South Coast, the emission
reductions needed for these

pollutants are inventory-wide,\178\ and secondary particulates
contribute significantly to ambient PM2.5 levels in the
South Coast area.\179\
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    \177\ In addition to the Moderate area plan and request for
reclassification to Serious, the 2016 PM2.5 Plan includes
a Serious area attainment demonstration for the 2012
PM2.5 NAAQS with a December 31, 2025 attainment date. The
RFP demonstration in the 2016 PM2.5 Plan represents
generally linear progress between the 2012 base year and projected
2025 attainment year in the Serious area plan. Given that the Plan
identifies December 31, 2025 as the most expeditious attainment date
for the area, we find this date to be an appropriate end point for
the RFP demonstration.
    \178\ 2016 PM2.5 Plan, Appendix IV-A, Appendix IV-B,
and Appendix VI-A.
    \179\ Id. at V-6-61.
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    Additionally, the 2016 PM2.5 Plan identifies
quantitative milestone dates that are consistent with the requirements
of 40 CFR 51.1013(a)(4) and target emission levels for direct
PM2.5 and all PM2.5 precursors to be achieved by
these milestone dates through implementation of the control strategy.
These target emission levels and associated control requirements
provide for objective evaluation of the area's progress towards
attainment of the 2012 PM2.5 NAAQS.
    For all of these reasons, we propose to approve the RFP
demonstration in the 2016 PM2.5 Plan as meeting the
requirements of CAA section 172(c)(2) and 40 CFR 51.1012(a) and to
determine that the quantitative milestones in the Plan satisfy the
requirements of CAA section 189(c) and 40 CFR 51.1013.
    On January 13, 2020, CARB submitted the ``2019 Quantitative
Milestone Report for the 2012 annual PM2.5 National Ambient
Air Qualtiy Standard (January 2020)'' (``2019 QM Report'') to the
EPA.\180\ The 2019 QM Report includes a certification from the
Governor's designee that the 2019 quantitative milestones for the South
Coast PM2.5 nonattainment area have been achieved and a
demonstration that the adopted control strategy has been fully
implemented. The 2019 QM Report also contains a demonstration of how
the emission reductions achieved to date compare to those required or
scheduled to meet RFP. The State and District conclude in the 2019 QM
Report that the emission reductions needed to demonstrate RFP have been
achieved and that the 2019 quantitative milestone has been met in the
South Coast. On March 30, 2020, the EPA determined that the South Coast
2019 QM Report was adequate.\181\ We invite the public to comment on
this determination of adequacy.
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    \180\ Letter dated January 13, 2020, from Richard W. Corey,
Executive Officer, CARB, to Mike Stoker, Regional Administrator, EPA
Region IX, with enclosure.
    \181\ Letter dated March 30, 2020, from Andrew R. Wheeler,
Administrator, EPA, to Richard W. Corey, Executive Officer, CARB,
regarding 2019 Quantitative Milestone Report for the 2012 annual
PM2.5 National Ambient Air Quality Standards.
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H. Contingency Measures

1. Requirements for Contingency Measures
    Under CAA section 172(c)(9), each SIP for a nonattainment area must
include contingency measures to be implemented if an area fails to meet
RFP (``RFP contingency measures'') or fails to attain the NAAQS by the
applicable attainment date (``attainment contingency measures''). Under
the PM2.5 SIP Requirements Rule, PM2.5 attainment
plans must include contingency measures to be implemented following a
determination by the EPA that the state has failed: (1) To meet any RFP
requirement in the approved SIP; (2) to meet any quantitative milestone
in the approved SIP; (3) to submit a required quantitative milestone
report; or (4) to attain the applicable PM2.5 NAAQS by the
applicable attainment date.\182\ Section 189(b)(1)(A) of the CAA,
however, differentiates between attainment plans that provide for
timely attainment and those that demonstrate that attainment is
impracticable. Where a SIP includes a demonstration that attainment by
the applicable attainment date is impracticable, the state need only
submit contingency measures to be implemented if an area fails to meet
RFP, to meet a SIP-approved quantitative milestone, or to submit a
required quantitative milestone report.\183\ Contingency measures must
be fully adopted rules or control measures that are ready to be
implemented quickly upon failure to meet RFP or failure of the area to
meet the relevant NAAQS by the applicable attainment date.\184\
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    \182\ 40 CFR 51.1014(a).
    \183\ The EPA does not interpret the requirement for failure-to-
attain contingency measures to apply to a Moderate PM2.5
nonattainment area that a state demonstrates cannot practicably
attain the NAAQS by the statutory attainment date. Rather, the EPA
believes it is appropriate for the state to identify and adopt
attainment contingency measures as part of the Serious area
attainment plan. 81 FR 58010, 58067 and Addendum, 42015.
    \184\ 81 FR 58010, 58066 and Addendum, 42015.
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    The purpose of contingency measures is to continue progress in
reducing emissions while a state revises its SIP to meet the missed RFP
requirement or to correct ongoing nonattainment. Neither the CAA nor
the EPA's implementing regulations establish a specific level of
emission reductions that implementation of contingency measures must
achieve, but the EPA recommends that contingency measures should
provide for emission reductions equivalent to approximately one year of
reductions needed for RFP, calculated as the overall level of
reductions needed to demonstrate attainment divided by the number of
years from the base year to the attainment year. In general, we expect
all actions needed to effect full implementation of the measures to
occur within 60 days after the EPA notifies the state of a failure to
meet RFP or to attain.\185\
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    \185\ 81 FR 58010, 58066. See also General Preamble, 13512,
13543-13544, and Addendum, 42014-42015.
---------------------------------------------------------------------------

    To satisfy the requirements of 40 CFR 51.1014, the contingency
measures adopted as part of a PM2.5 attainment plan must
consist of control measures for the area that are not otherwise
required to meet other nonattainment plan requirements (e.g., to meet
RACM/RACT requirements) and must specify the timeframe within which
their requirements become effective following any of the EPA
determinations specified in 40 CFR 51.1014(a).
    In a 2016 decision called Bahr v. EPA (``Bahr''),\186\ the Ninth
Circuit Court of Appeals rejected the EPA's interpretation of CAA
section 172(c)(9) to allow approval of already implemented control
measures as contingency measures. In Bahr, the Ninth Circuit concluded
that contingency measures must be measures that are triggered only
after the EPA determines that an area fails to meet RFP requirements or
to attain by the applicable attainment date, not before. Thus, within
the geographic jurisdiction of the Ninth Circuit, already implemented
measures cannot serve as contingency measures under CAA section
172(c)(9).
---------------------------------------------------------------------------

    \186\ Bahr v. EPA, 836 F.3d 1218, 1235-1237 (9th Cir. 2016).
---------------------------------------------------------------------------

    To comply with section 172(c)(9), as interpreted in the Bahr
decision, a state must develop, adopt, and submit a contingency measure
to be triggered upon a failure to meet an RFP milestone, failure to
meet a quantitative milestone requirement, or failure to attain the
NAAQS by the applicable attainment date regardless of the extent to
which already-implemented measures would achieve surplus emission
reductions beyond those necessary to meet RFP or quantitative milestone
requirements and beyond those predicted to achieve attainment of the
NAAQS.
2. Contingency Measures in the 2016 PM2.5 Plan
    The 2016 PM2.5 Plan addresses the contingency measure
requirement in Chapter 4 of the Plan and in section H of the CARB Staff
Report. Chapter 4 of the 2016 PM2.5 Plan addresses
contingency measures for failure to attain the 2006 PM2.5
NAAQS by

describing emission reductions to be achieved by an adopted measure,
South Coast Rule 445 (``Wood-Burning Devices).\187\ The 2016
PM2.5 Plan does not specifically address contingency
measures for failure to meet RFP or quantitative milestone
requirements. The CARB Staff Report provides a brief statement
acknowledging the Bahr decision and committing to work with the EPA and
the District to provide additional documentation or develop any needed
SIP revisions consistent with that decision.\188\
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    \187\ 2016 PM2.5 Plan, 4-51 to 4-52.
    \188\ The SCAQMD and CARB adopted the 2016 PM2.5 Plan
in March and April 2017, shortly after the Ninth Circuit issued its
decision in Bahr.
---------------------------------------------------------------------------

    To supplement the contingency measure element of the 2016
PM2.5 Plan, CARB submitted a letter dated January 29, 2019
enclosing the District's commitment to adopt a control measure by a
date certain for purposes of satisfying CAA contingency measure
requirements for the 2006 and 2012 PM2.5 NAAQS.\189\ By
letter dated February 12, 2020, the District clarified its commitment
by committing to develop, adopt, and submit to CARB, for submission to
the EPA, a revised rule containing specific contingency provisions that
would become effective if the EPA determines: (1) That the area failed
to attain the 2006 24-hour PM2.5 NAAQS or the 2012 annual
PM2.5 NAAQS by the applicable attainment date; (2) that the
area failed to meet any RFP requirement; (3) that the area failed to
meet any quantitative milestone; or (4) that the State failed to submit
a required quantitative milestone report for the area.\190\ The
District submitted this clarified commitment, accompanied by a
technical analysis of the emission reductions to be achieved by the
contingency measure (``Technical Clarification''), to satisfy the
attainment contingency measure requirement for the 2006
PM2.5 NAAQS and the RFP contingency measure requirement for
the 2012 PM2.5 NAAQS in the South Coast nonattainment
area.\191\
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    \189\ Letter dated February 13, 2019, from Michael Benjamin, Air
Quality Planning and Science Division, CARB, to Mike Stoker,
Regional Administrator, EPA Region IX (transmitting letter dated
January 29, 2019, from Wayne Nastri, Executive Officer, SCAQMD, to
Richard Corey, Executive Officer, CARB). In its January 29, 2019
letter, the District committed to modify an existing rule or adopt a
new rule to create a contingency measure that would be triggered if
the area fails to meet an RFP requirement, to submit a quantitative
milestone report, to meet a quantitative milestone, or to attain the
2006 24-hour or 2012 annual PM2.5 NAAQS.
    \190\ Letter dated February 12, 2020, from Wayne Nastri,
Executive Officer, SCAQMD, to Richard Corey, Executive Officer, CARB
(attaching ``Technical clarification regarding emission reductions
associated with contingency measures for the 2006 24-hour
PM2.5 standard attainment and 2012 annual
PM2.5 standard Reasonable Further Progress,'' February
2020) (``Technical Clarification'').
    \191\ Id.
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    Specifically, the District has committed to revise an existing
rule, Rule 445 (``Wood Burning Devices''), to establish more stringent
requirements that would become effective if the EPA makes any of the
four determinations (i.e., ``findings of failure'') listed in 40 CFR
51.1014(a). The revisions are to lower the PM wood burning curtailment
threshold to 29 [micro]g/m\3\ upon the first EPA finding of failure,
and to lower the threshold to 28, 27, and 26 [micro]g/m\3\ upon a
second, third, and fourth finding of failure, respectively. Under the
revised rule, the mandatory winter burning curtailment would apply to
the entire South Coast air basin. The District estimates that lowering
the curtailment threshold to 29, 28, 27, and 26 [micro]g/m\3\ upon each
finding of failure would achieve reductions in PM2.5
emissions of 20.9, 20.9, 13.9, and 19.1 tpy, respectively.\192\
---------------------------------------------------------------------------

    \192\ Technical Clarification, 2.
---------------------------------------------------------------------------

    The District has committed to adopt this revised rule and submit it
to CARB in time for CARB to submit the revised rule to the EPA by the
earlier of the following dates: (1) One year after the date of the
EPA's conditional approval of the contingency measures for the 2012
annual PM2.5 standard, or (2) 60 days after the date the EPA
makes a determination that the South Coast area has failed to attain
the 2006 24-hour PM2.5 standards but no later than one year
after the date of the EPA's conditional approval of the contingency
measures for these standards.\193\ In its March 3, 2020 letter
submitting the District's commitment to the EPA, CARB also committed to
submit the revised rule to the EPA by the earlier of these two
dates.\194\
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    \193\ Letter dated February 12, 2020, from Wayne Nastri,
Executive Officer, SCAQMD, to Richard Corey, Executive Officer,
CARB.
    \194\ Letter dated March 3, 2020, from Michael T. Benjamin,
Chief, Air Quality Planning and Science Division, CARB, to Amy
Zimpfer, Associate Director, Air Division, EPA Region IX
(transmitting letter dated February 12, 2020, from Wayne Nastri,
Executive Officer, SCAQMD, to Richard Corey, Executive Officer,
CARB).
---------------------------------------------------------------------------

3. The EPA's Evaluation and Proposed Action
    Section 172(c)(9) requires contingency measures to address
potential failure to achieve RFP milestones, failure to meet
requirements concerning quantitative milestones, and failure to attain
the NAAQS by the applicable attainment date. For purposes of evaluating
the contingency measure element of the 2016 PM2.5 Plan, we
find it useful to distinguish between contingency measures to address
potential failure to achieve RFP milestones or to meet quantitative
milestone requirements (``RFP contingency measures'') and contingency
measures to address potential failure to attain the NAAQS (``attainment
contingency measures'').
2006 PM2.5 Serious Area Contingency Measure Requirements
    The EPA previously approved those portions of the 2016
PM2.5 Plan that pertain to the requirements for implementing
the 2006 PM2.5 NAAQS in the South Coast, except for the
contingency measure component of the Plan.\195\ As part of that action,
the EPA found that, for purposes of the 2006 PM2.5 NAAQS,
the requirement for RFP contingency measures was moot as applied to the
2017 milestone year because CARB and the District had demonstrated to
the EPA's satisfaction that the 2017 quantitative milestones in the
plan had been met.\196\ The EPA took no action, however, with respect
to RFP contingency measures for the 2020 milestone year or attainment
contingency measures for the 2006 PM2.5 NAAQS. Thus, the EPA
is now proposing to act on these outstanding components of the 2016
PM2.5 Plan for purposes of the 2006 PM2.5 NAAQS.
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    \195\ 84 FR 3305 (February 12, 2019).
    \196\ Id. and 83 FR 49872, 49890 (October 3, 2018) (referencing
the EPA's September 7, 2018 adequacy determination).
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    The applicable quantitative milestone dates for the Serious area
plan for the 2006 PM2.5 NAAQS are December 31, 2017 and
December 31, 2020.\197\ We discuss below our evaluation of the 2016
PM2.5 Plan and related State and District commitments for
compliance with the 2020 RFP and attainment contingency measure
requirements for the 2006 PM2.5 NAAQS.
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    \197\ 40 CFR 51.1013(a)(4).
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2012 PM2.5 Moderate Area Contingency Measure Requirements
    Because we are proposing to approve the State's demonstration that
the South Coast area cannot practicably attain the 2012
PM2.5 NAAQS by the applicable Moderate area attainment date
of December 31, 2021, and to reclassify the area to Serious on this
basis, attainment contingency measures are not required as part of the
Moderate area plan for the 2012 PM2.5 NAAQS. Upon
reclassification of the South Coast area as a Serious area, California
will be required to adopt attainment contingency measures as part of
the Serious area attainment plan for the 2012 PM2.5 NAAQS.

    With respect to the RFP contingency measure requirement for the
2012 PM2.5 NAAQS, the applicable quantitative milestone
dates are October 15, 2019 and October 15, 2022. As explained in
section V.G.3 of this proposed rule, on January 13, 2020, CARB
submitted a quantitative milestone report demonstrating that the 2019
quantitative milestones in the 2016 PM2.5 Plan have been
achieved, and the EPA has determined that this milestone report is
adequate. Because the State and District have demonstrated that the
South Coast area has met its 2019 quantitative milestones, RFP
contingency measures for the 2019 milestone year are no longer needed.
The sole purpose of RFP contingency measures is to provide continued
progress if an area fails to meet its RFP or quantitative milestone
requirements. Failure to meet RFP or quantitative milestone
requirements for 2019 would have required California to implement RFP
contingency measures and, in certain cases, to revise the 2016
PM2.5 Plan to assure that the area would achieve the next
quantitative milestone (i.e., for 2022).\198\ In this case, however,
the 2019 QM Report demonstrates that actual emission levels in 2019
were consistent with the approved 2019 RFP milestone year targets for
direct PM2.5 and all precursor pollutants (NOX,
SO2, VOC, and ammonia) regulated in the 2016
PM2.5 Plan. Accordingly, RFP contingency measures for 2019
no longer have meaning or purpose, and the EPA proposes to find that
the requirement for them is now moot as applied to the South Coast. We
discuss below our evaluation of the 2016 PM2.5 Plan and
related State and District commitments for compliance with the 2022 RFP
contingency measure requirement for the 2012 PM2.5 NAAQS.
---------------------------------------------------------------------------

    \198\ Under section 189(c)(3) of the CAA, if a state fails to
submit a required quantitative milestone report or the EPA
determines that the area has not met an applicable milestone, the
EPA must require the state, within nine months after such failure or
determination, to submit a plan revision that assures that the state
will achieve the next milestone (or attain the NAAQS, if there is no
next milestone) by the applicable date.
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The State's Contingency Measure Commitment
    The District and CARB have committed to develop, adopt, and submit
a revised District rule (Rule 445, ``Wood-Burning Devices'') to meet
the attainment contingency measure requirement for the 2006
PM2.5 NAAQS and the RFP contingency measure requirement for
the 2012 PM2.5 NAAQS. The specific revisions the District
has committed to make (i.e., increasing the stringency of the existing
wood burning curtailment provisions in Rule 445) would satisfy the
requirements in CAA section 172(c)(9) because they would be undertaken
if the area fails to attain or fails to meet an RFP or quantitative
milestone requirement, and would take effect without significant
further action by the State or the EPA. The revised rule would also
comply with the regulatory requirements in 40 CFR 51.1014 because it
would contain contingency provisions that take effect if the EPA makes
any of the four determinations listed in 40 CFR 51.1014(a), would
consist of control requirements not otherwise included in the control
strategy, and would specify the timeframe within which its contingency
provisions become effective following any of the determinations listed
in 40 CFR 51.1014(a).
    We also considered the adequacy of the contingency measure (once
adopted and submitted) from the standpoint of the magnitude of emission
reductions the measure would provide (if triggered). Neither the CAA
nor the EPA's implementing regulations for the PM2.5 NAAQS
establish a specific amount of emission reductions that implementation
of contingency measures must achieve, but we generally expect that
contingency measures should provide for emission reductions
approximately equivalent to one year's worth of RFP. For the 2006
PM2.5 NAAQS in the South Coast, one year's worth of
reductions is approximately 0.36 of direct PM2.5 reductions,
26.68 tpd of NOX reductions, 0.26 tpd of SOX
reductions, 13.50 tpd of VOC reductions, and 1.02 tpd of ammonia
reductions.\199\ For the 2012 PM2.5 NAAQS, one year's worth
of reductions needed for RFP is approximately 0.18 tpd of direct
PM2.5 reductions, 25.71 tpd of NOX reductions,
0.08 tpd of SOX reductions, 10.33 tpd of VOC reductions, and
0.67 tpd of ammonia reductions.\200\
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    \199\ Technical Clarification, Table 1.
    \200\ 2016 PM2.5 Plan, Appendix III, Attachment A.
---------------------------------------------------------------------------

    With respect to attainment contingency measures for the 2006
PM2.5 NAAQS, the Technical Clarification contains the
District's quantification of the expected emission reductions from the
strengthened requirements to be adopted as contingency measures in Rule
445. The District estimates that lowering the curtailment threshold in
Rule 445 by 1 [micro]g/m\3\ for each finding of failure (i.e., to 29,
28, 27, and 26 [micro]g/m\3\) would achieve additional reductions in
PM2.5 emissions of 20.9, 20.9, 13.9, and 19.1 tpy (0.06,
0.06, 0.04, and 0.05 tpd), respectively, in 2020, the year after the
attainment year for the 2006 PM2.5 NAAQS.\201\ Each of these
reduction levels alone do not achieve one year's worth of RFP. However,
the District's submittal provides the larger SIP planning context in
which to judge the adequacy of the to-be-submitted District contingency
measure by identifying surplus direct PM2.5, NOX,
VOC, and ammonia emission reductions estimated to be achieved in
2020.\202\ The surplus reflects already implemented regulations,
including vehicle turnover, which refers to the ongoing replacement by
individuals, companies, and government agencies of older, more
polluting vehicles and engines with newer vehicles and engines designed
to meet more stringent CARB mobile source emissions standards. The
surplus also reflects additional emission reductions from regulations
and programs that were adopted after the development of the 2016
PM2.5 Plan. These include CARB's Heavy-Duty Vehicle
Inspection Program, Periodic Smoke Inspection Program, and efforts to
reduce emissions from Ocean-Going Vessels At-Berth, and the District's
Airports Memorandum of Understanding, Metrolink Locomotives, Low Carbon
Fuel Standard and Alternative Diesel Fuels Regulation, and Airborne
Toxic Control Measure (ATCM) for Portable Engines and the Statewide
Portable Equipment Registration Program.\203\
---------------------------------------------------------------------------

    \201\ Technical Clarification, 2-3.
    \202\ These emission reductions are surplus to those relied upon
in the control strategy for attaining the 2006 PM2.5
NAAQS in the 2016 PM2.5 Plan because they occur after the
December 31, 2019 attainment date and/or will be achieved through
implementation of measures adopted after the Plan's adoption.
    \203\ Technical Clarification, 2-4.
---------------------------------------------------------------------------

    We have reviewed the surplus emissions estimates for 2020, as shown
in the Technical Clarification, and find the calculations reasonable.
We therefore agree with the District's conclusion that the 2016
PM2.5 Plan provides surplus emission reductions beyond those
necessary to demonstrate attainment by the December 31, 2019 Serious
area attainment date for the 2006 PM2.5 NAAQS in the South
Coast. While such surplus emission reductions in the year after the
2019 attainment year do not represent contingency measures themselves,
we consider them relevant in evaluating the adequacy of the contingency
measures that the State has committed to in order to meet the
requirements of section 172(c)(9). In light of the ongoing reductions
in emissions of direct PM2.5, NOX, VOC, and
ammonia achieved by the State and District measures identified in the
Technical Clarification, the emission

reductions from the District contingency measure (revised Rule 445)
would be sufficient to meet the attainment contingency measure
requirement for the 2006 PM2.5 NAAQS, even though the
measure would achieve emission reductions lower than the EPA normally
recommends for reductions from such a measure.
    With respect to RFP contingency measures for the 2022 milestone
year in the Moderate area plan for the 2012 PM2.5 NAAQS, the
District similarly explains in the Technical Clarification that
continuing implementation of existing regulations and turn-over of
older vehicles and equipment to cleaner vehicles and equipment will
result in surplus emission reductions in the 2022 RFP milestone
year.\204\ In light of these ongoing reductions in emissions of direct
PM2.5, NOX, VOC, and ammonia, the District
contingency measure (revised Rule 445) would be sufficient to meet the
2022 RFP contingency measure requirement for the 2012 PM2.5
NAAQS, even though the measure would not by itself achieve emission
reductions equivalent to one year's worth of RFP. For the same reasons,
the District contingency measure (revised Rule 445) would be sufficient
to meet the 2020 RFP contingency measure requirement for the 2006
PM2.5 NAAQS. We note that under the proposed revisions to
Rule 445, if the EPA determines that the South Coast area has failed to
attain the 2006 PM2.5 NAAQS by the December 31, 2019
attainment date and thereby triggers the contingency measure provision
to lower the mandatory burning curtailment to 29 [micro]g/m\3\, the
State would not be required to submit a new contingency measure because
the additional provisions to lower the curtailment threshold to 28, 27,
and 26 [micro]g/m\3\ could be triggered upon subsequent failures and
therefore would satisfy RFP contingency measure requirements for both
the 2006 PM2.5 NAAQS and the 2012 PM2.5 NAAQS.
---------------------------------------------------------------------------

    \204\ Id. at 4-6.
---------------------------------------------------------------------------

    Finally, CARB has committed to submit the revised rule to the EPA
within one year after a final action conditionally approving the
contingency measure element of the 2016 PM2.5 Plan, or
within 60 days of a determination by the EPA that the South Coast area
failed to attain the 2006 PM2.5 NAAQS by the applicable
attainment date, whichever occurs sooner. Section 110(k)(4) of the Act
authorizes the EPA to conditionally approve a plan revision based on a
commitment by the state to adopt specific enforceable measures by a
date certain, but not later than one year after the date of approval of
the plan revision. The outermost deadline in CARB's commitment (one
year following conditional approval of the plan revision) is consistent
with the submission deadline in CAA section 110(k)(4). If, however, the
EPA determines that the South Coast area failed to attain the 2006
PM2.5 NAAQS by the applicable attainment date (December 31,
2019), and the date 60 days after this determination is earlier than
the 1-year deadline under section 110(k)(4), then CARB would be
obligated under its commitment to submit the revised rule to the EPA by
the earlier date. These deadlines ensure that, should the EPA determine
that the South Coast area failed to timely attain the 2006
PM2.5 NAAQS, contingency provisions will take effect within
60 days of the determination, consistent with longstanding EPA
guidance.
    For these reasons, we propose to conditionally approve the
contingency measure element of the 2016 PM2.5 Plan for the
2006 PM2.5 NAAQS and the 2012 PM2.5 NAAQS, as
supplemented by commitments from the District and CARB to adopt and
submit an additional contingency measure to meet the attainment and RFP
contingency measure requirements of CAA section 172(c)(9) for these
NAAQS. Our proposed approval is conditional because it relies upon
commitments to adopt and submit a specific enforceable contingency
measure (i.e., a revised District rule with contingent provisions).

I. Motor Vehicle Emissions Budgets

1. Requirements for Motor Vehicle Emissions Budgets
    Section 176(c) of the CAA requires federal actions in nonattainment
and maintenance areas to conform to the SIP's goals of eliminating or
reducing the severity and number of violations of the NAAQS and
achieving timely attainment of the standards. Conformity to the SIP's
goals means that such actions will not: (1) Cause or contribute to
violations of a NAAQS, (2) worsen the severity of an existing
violation, or (3) delay timely attainment of any NAAQS or any interim
milestone.
    Actions involving Federal Highway Administration (FHWA) or Federal
Transit Administration (FTA) funding or approval are subject to the
EPA's transportation conformity rule, codified at 40 CFR part 93,
subpart A. Under this rule, metropolitan planning organizations (MPOs)
in nonattainment and maintenance areas coordinate with state and local
air quality and transportation agencies, the EPA, the FHWA, and the FTA
to demonstrate that an area's regional transportation plans and
transportation improvement programs conform to the applicable SIP. This
demonstration is typically done by showing that estimated emissions
from existing and planned highway and transit systems are less than or
equal to the motor vehicle emissions budgets (MVEBs or ``budgets'')
contained in all control strategy SIPs. An attainment, maintenance, or
RFP SIP should include budgets for the attainment year, each required
RFP milestone year, and the last year of the maintenance plan, as
appropriate. Budgets are generally established for specific years and
specific pollutants or precursors and must reflect all of the motor
vehicle control measures contained in the attainment and RFP
demonstrations.\205\
---------------------------------------------------------------------------

    \205\ 40 CFR 93.118(e)(4)(v).
---------------------------------------------------------------------------

    Under the PM2.5 SIP Requirements Rule, each attainment
plan submittal for a Moderate PM2.5 nonattainment area must
contain quantitative milestones to be achieved no later than 4.5 years
and 7.5 years after the date the area was designated
nonattainment.\206\ The second of these milestone dates, October 15,
2022,\207\ falls after the attainment date for the South Coast area,
which is December 31, 2021. As the EPA explained in the preamble to the
PM2.5 SIP Requirements Rule, it is important to include a
post-attainment year quantitative milestone to ensure that, if the area
fails to attain by the attainment date, the EPA can continue to monitor
the area's progress toward attainment while the state develops a new
attainment plan.\208\ Moderate area plans demonstrating that attainment
by the Moderate area attainment date is impracticable must, therefore,
include budgets for both of the milestone dates. States that submit
impracticability demonstrations for Moderate areas under CAA section
189(a)(1)(B)(ii), however, are not required to submit budgets for the
attainment year because the submitted SIP does not demonstrate
attainment.\209\
---------------------------------------------------------------------------

    \206\ 40 CFR 51.1013(a)(1).
    \207\ Because the South Coast area was designated nonattainment
effective April 15, 2015, the first milestone date is October 15,
2019, and the second milestone date is October 15, 2022. 80 FR 2206.
    \208\ 81 FR 58010, 58058 and 58063-58064.
    \209\ Id. at 58055.
---------------------------------------------------------------------------

    PM2.5 plans should identify budgets for direct
PM2.5, NOX, and all other PM2.5
precursors for which on-road emissions are determined to significantly
contribute to PM2.5 levels in the area for each RFP
milestone year and the attainment year, if the plan demonstrates
attainment. All direct PM2.5 SIP budgets should include
direct PM2.5 motor vehicle emissions from

tailpipes, brake wear, and tire wear. With respect to PM2.5
from re-entrained road dust and emissions of VOC, SO2, and/
or ammonia, the transportation conformity provisions of 40 CFR part 93,
subpart A, apply only if the EPA Regional Administrator or the director
of the state air agency has made a finding that emissions of these
pollutants within the area are a significant contributor to the
PM2.5 nonattainment problem and has so notified the MPO and
Department of Transportation (DOT), or if the applicable implementation
plan (or implementation plan submission) includes any of these
pollutants in the approved (or adequate) budget as part of the RFP,
attainment, or maintenance strategy.\210\ Additionally, as the EPA
explained in its May 6, 2005 transportation conformity rule amendments
for the PM2.5 NAAQS, it is not necessary for a SIP to
explicitly state that VOC, SO2, and/or ammonia are
insignificant precursors. Instead, states should consider the on-road
contribution of all four precursors to the PM2.5 problem as
they develop their SIPs and establish emissions budgets for those
precursors for which on-road emissions need to be addressed in order to
attain the PM2.5 standard as expeditiously as practicable.
Conformity determinations must address all precursors for which the SIP
establishes a budget and need not address those precursors for which
the state has not established a budget because the emissions of that
precursor are insignificant.\211\
---------------------------------------------------------------------------

    \210\ 40 CFR 93.102(b)(3), 93.102(b)(2)(v), and 93.122(f); see
also Conformity Rule preambles at 69 FR 40004, 40031-40036 (July 1,
2004), 70 FR 24280, 24283-24285 (May 6, 2005) and 70 FR 31354 (June
1, 2005).
    \211\ 70 FR 24280, 24287 (May 6, 2005).
---------------------------------------------------------------------------

    By contrast, transportation conformity requirements apply with
respect to emissions of NOX unless both the EPA Regional
Administrator and the director of the state air agency have made a
finding that transportation-related emissions of NOX within
the nonattainment area are not a significant contributor to the
PM2.5 nonattainment problem and have so notified the MPO and
DOT, or the applicable implementation plan (or implementation plan
submission) does not establish an approved (or adequate) budget for
such emissions as part of the RFP, attainment, or maintenance
strategy.\212\
---------------------------------------------------------------------------

    \212\ 40 CFR 93.102(b)(2)(iv).
---------------------------------------------------------------------------

    The criteria for insignificance determinations are provided in 40
CFR 93.109(f). In order for a pollutant or precursor to be considered
an insignificant contributor, the control strategy SIP must demonstrate
that it would be unreasonable to expect that such an area would
experience enough motor vehicle emissions growth in that pollutant/
precursor for a NAAQS violation to occur. Insignificance determinations
are based on factors such as air quality, SIP motor vehicle control
measures, trends and projections of motor vehicle emissions, and the
percentage of the total SIP inventory that is comprised of motor
vehicle emissions. The EPA's rationale for providing for insignificance
determinations is described in the July 1, 2004 revision to the
Transportation Conformity Rule.\213\
---------------------------------------------------------------------------

    \213\ 69 FR 40004 (July 1, 2004).
---------------------------------------------------------------------------

    The EPA's process for determining the adequacy of a budget consists
of three basic steps: (1) Notifying the public of a SIP submittal; (2)
providing the public the opportunity to comment on the budget during a
public comment period; and, (3) making a finding of adequacy or
inadequacy. The EPA can notify the public by either posting an
announcement that the EPA has received SIP budgets on the EPA's
adequacy website (40 CFR 93.118(f)(1)), or through a Federal Register
notice of proposed rulemaking when the EPA reviews the adequacy of an
implementation plan budget simultaneously with its review and action on
the SIP itself (40 CFR 93.118(f)(2)).
    For budgets to be approvable, they must meet, at a minimum, the
EPA's adequacy criteria (40 CFR 93.118(e)(4)). To meet these
requirements, the budgets must be consistent with the attainment and
RFP requirements and reflect all of the motor vehicle control measures
contained in the attainment and RFP demonstrations.\214\
---------------------------------------------------------------------------

    \214\ 40 CFR 93.118(e)(4)(iii), (iv) and (v). For more
information on the transportation conformity requirements and
applicable policies on MVEBs, please visit our transportation
conformity website at: http://www.epa.gov/otaq/stateresources/transconf/index.htm.
---------------------------------------------------------------------------

2. Motor Vehicle Emissions Budgets in the 2016 PM2.5 Plan
    The 2016 PM2.5 Plan includes budgets for direct
PM2.5, NOx, and VOC for 2019 and 2022 (RFP milestone year
and post-attainment quantitative milestone year, respectively).\215\
The budgets were calculated using EMFAC2014, the latest approved
version of the EMFAC model for estimating emissions from on-road
vehicles operating in California that was available at the time the
plan was prepared, and SCAG's latest modeled VMT and speed
distributions from the ``2016 Regional Transportation Plan/Sustainable
Communities Strategy (RTP/SCS)'' adopted in April 2016.\216\ The
budgets reflect annual average emissions because those emissions are
linked with the District's RFP demonstration for the 2012
PM2.5 NAAQS.
---------------------------------------------------------------------------

    \215\ 2016 PM2.5 Plan, Appendix VI-D and Table VI-D-
3.
    \216\ See footnote 30, supra.
---------------------------------------------------------------------------

    The direct PM2.5 budgets include tailpipe, brake wear,
and tire wear emissions as well as paved road dust, unpaved road dust,
and road construction dust emissions.\217\ The Plan includes budgets
for NOx and VOC because they are regulated precursors under the Plan,
but the Plan does not include budgets for SO2 or ammonia.
The budgets included in the 2016 PM2.5 Plan are shown in
Table 8.
---------------------------------------------------------------------------

    \217\ 2016 PM2.5 Plan, Table VI-D-3.

                         Table 8--MVEBs for the South Coast for the 2012 PM2.5 Standard
                                              [Annual average tpd]
----------------------------------------------------------------------------------------------------------------
                                               2019  (RFP year)                 2022  (post attainment year)
                                   -----------------------------------------------------------------------------
                                       PM2.5         NOX          VOC         PM2.5         NOX          VOC
----------------------------------------------------------------------------------------------------------------
Baseline emissions: Exhaust, brake        10.82       168.13        82.52        10.25       126.26        68.22
 and tire wear....................
Paved road dust...................         8.15  ...........  ...........         8.38  ...........  ...........
Unpaved road dust.................         0.59  ...........  ...........         0.59  ...........  ...........
Road construction.................         0.25  ...........  ...........         0.27  ...........  ...........
                                   -----------------------------------------------------------------------------
    Total.........................        19.81       168.13        82.52        19.48       126.26        68.22

Conformity budget.................           20          169           83           20          127           69
----------------------------------------------------------------------------------------------------------------
Source: 2016 PM2.5 Plan, Table VI-D-3. Budgets are rounded up to the nearest whole number.

    In the submittal letter for the 2016 PM2.5 Plan, CARB
requested that we limit the duration of our approval of the budgets to
the period before the effective date of the EPA's adequacy finding for
any subsequently submitted budgets.\218\
---------------------------------------------------------------------------

    \218\ Letter dated April 27, 2017, from Richard W. Corey,
Executive Officer, CARB, to Alexis Strauss, Acting Regional
Administrator, EPA Region IX, 3.
---------------------------------------------------------------------------

3. The EPA's Evaluation and Proposed Action
    We have evaluated the budgets in the 2016 PM2.5 Plan
against our adequacy criteria in 40 CFR 93.118(e)(4) as part of our
review of the budgets' approvability (see Table 10 in section IV of the
EPA's TSD for this proposal) and will complete the adequacy review
concurrent with our final action on the 2016 PM2.5 Plan. The
EPA is not required under its transportation conformity rule to find
budgets adequate prior to proposing approval of them.\219\
---------------------------------------------------------------------------

    \219\ Under the Transportation Conformity regulations, the EPA
may review the adequacy of submitted MVEBs simultaneously with the
EPA's approval or disapproval of the submitted implementation plan.
40 CFR 93.118(f)(2).
---------------------------------------------------------------------------

    Based on the information about SO2 and ammonia emissions
in the 2016 PM2.5 Plan, we propose to find that it is not
necessary to establish MVEBs for transportation-related emissions of
SO2 and ammonia to attain the 2012 PM2.5 standard
in the South Coast. As discussed in the May 6, 2005 final
transportation conformity rule that addresses the requirements for
PM2.5 precursors,\220\ on-road emissions of SO2
and ammonia typically are a small portion of the total emissions for
these precursors. In the May 6, 2005 final rule, the EPA stated that
with adopted fuel regulations, projections of on-road emissions of
SO2 would be less than one percent of total SO2
emissions in 2020. This was based on an analysis of projected on-road
SO2 emissions in 372 counties that potentially could have
been designated as nonattainment for the 1997 annual PM2.5
NAAQS based on 1999-2001 air quality data.\221\ In the South Coast, on-
road emissions of SO2 and ammonia are projected to account
for approximately 10 and 18 percent of total SO2 and ammonia
emissions, respectively, in 2020.\222\ The projected contribution of
total SO2 emissions to PM2.5 concentrations in
the South Coast is in the range of 10 to 13 percent, and the projected
contribution of total ammonia emissions to PM2.5
concentrations in the area is in the range of 6 to 8 percent, in
2021.\223\ CARB implements stringent standards for sulfur content in
reformulated gasoline and diesel fuel,\224\ both of which effectively
limit the SO2 contribution from motor vehicles in the South
Coast. Given that transportation-related emissions of SO2 or
ammonia are not significant contributors to the nonattainment problem
in this area, it is not necessary for the 2016 PM2.5 Plan to
include SO2 or ammonia budgets.
---------------------------------------------------------------------------

    \220\ 70 FR 24280, 24283-24285.
    \221\ Id. at 24283.
    \222\ 2016 PM2.5 Plan, Appendix III, Attachment A
(identifying 2020 total SOX emissions estimate of 16.67
tpd in the South Coast, of which 1.75 tpd (approximately 10 percent)
is attributed to on-road motor vehicles, and 2020 total ammonia
emissions estimate of 73.25 tpd, of which 13.21 tpd (approximately
18 percent) is attributed to on-road motor vehicles).
    \223\ Id., Table V-6-6 (identifying projected 2021
PM2.5 annual design values by component species,
including SO4 and NH4).
    \224\ California Code of Regulations, title 13, sections 2262
and 2282, 74 FR 33196, 33199 (July 10, 2009) (noting that CARB's
sulfur content standard for diesel fuel is more stringent than the
requirements of the federal ultra-low sulfur diesel program at 40
CFR 80.29), and 75 FR 26653 (May 12, 2010) (final rule approving
revisions to the California reformulated gasoline and diesel fuel
regulations).
---------------------------------------------------------------------------

    For the reasons discussed in section V.F of this proposed rule, we
are proposing to approve the State's demonstration that it is
impracticable to attain the 2012 PM2.5 standard in the South
Coast by the applicable Moderate area attainment date of December 31,
2021 and are proposing to reclassify the area as Serious. Because the
2016 PM2.5 Plan does not demonstrate attainment, we do not
address in this proposal any budgets for the Moderate area attainment
year of 2021.
    For the reasons discussed in section V.G of this proposed rule, we
are proposing to approve the RFP demonstration in the 2016
PM2.5 Plan. The 2019 and 2022 budgets, as shown in Table 8
of this proposed rule, are consistent with applicable requirements for
RFP, are clearly identified and precisely quantified, and meet all
other applicable statutory and regulatory requirements including the
adequacy criteria in 93.118(e)(4) and (5). For these reasons, the EPA
proposes to approve the budgets listed in Table 8. We provide a more
detailed discussion in section IV of the TSD, which can be found in the
docket for today's action.
    We have previously approved MVEBs for the 1997 and 2006 annual and
24-hour PM2.5 NAAQS.\225\ The budgets that the EPA is
proposing to approve apply only for purposes of the 2012
PM2.5 NAAQS and would not affect the status of the
previously-approved budgets for the 1997 or 2006 PM2.5 NAAQS
and related trading mechanisms, which remain in effect for those
PM2.5 NAAQS.
---------------------------------------------------------------------------

    \225\ 76 FR 69928, 69951 (November 9, 2011) and 84 FR 3305, 3307
(February 12, 2019).
---------------------------------------------------------------------------

    In general, only budgets in approved SIPs can be used for
transportation conformity purposes. However, section 93.118(e) of the
transportation conformity rule allows budgets in a SIP submission to
apply for conformity purposes before the SIP submission is approved
under certain circumstances. First, there must not be any other
approved SIP budgets that have been established for the same year,
pollutant, and CAA requirement. Second, the EPA must find that the
submitted SIP budgets are adequate for transportation conformity
purposes. To be found adequate, the submission must meet the conformity
adequacy requirements of 40 CFR 93.118(e)(4) and (5).
    The transportation conformity rule allows for replacement of
previously approved budgets by submitted MVEBs that the EPA has found
adequate, if the EPA has limited the duration of its prior approval to
the period before it finds replacement budgets adequate.\226\ However,
the EPA will consider a state's request to limit the duration of an
MVEB approval only if the request includes the following elements:
---------------------------------------------------------------------------

    \226\ 40 CFR 93.118(e)(1).
---------------------------------------------------------------------------

     An acknowledgement and explanation as to why the budgets
under

consideration have become outdated or deficient;
     A commitment to update the budgets as part of a
comprehensive SIP update; and
     A request that the EPA limit the duration of its approval
to the period before the EPA finds new budgets to be adequate for
transportation conformity purposes.\227\
---------------------------------------------------------------------------

    \227\ See, e.g., 67 FR 69139 (November 15, 2002), limiting our
prior approval of MVEBs in certain California SIPs.
---------------------------------------------------------------------------

    In the submittal letter for the 2016 PM2.5 Plan, CARB
requested that we limit the duration of our approval of the budgets to
the period before the effective date of the EPA's adequacy finding for
any subsequently submitted budgets.\228\ In a letter dated March 3,
2020, CARB clarified their request to limit the budgets and included an
explanation as to why the budgets under consideration will become
outdated. In short, CARB has requested that we limit the duration of
the approval of the budgets because the EPA's approval of EMFAC2017
\229\ on August 15, 2019 has rendered the budgets outdated. CARB
explains that the budgets from the 2016 PM2.5 Plan, for
which we are proposing approval in today's action, will need to be
revised using EMFAC2017 within the transportation conformity grace
period established in our approval of EMFAC2017 to provide for a new
conformity determination for the South Coast regional transportation
plan and program. In addition, CARB states that, without the ability to
replace the budgets using the budget adequacy process, the benefits of
using the updated data may not be realized for a year or more after the
updated SIP (with the EMFAC2017-derived budgets) is submitted, due to
the length of the SIP approval process. We find that CARB's explanation
for limiting the duration of the approval of the budgets is appropriate
and provides us with a reasonable basis on which to limit the duration
of the approval of the budgets.
---------------------------------------------------------------------------

    \228\ See letter dated April 27, 2017, from Richard W. Corey,
Executive Officer, CARB, to Alexis Strauss, Acting Regional
Administrator, EPA Region IX, 3.
    \229\ EMFAC2017 updates vehicle mix and emissions data of the
previously approved version of the model, EMFAC2014.
---------------------------------------------------------------------------

    We note that CARB has not committed to update the budgets as part
of a comprehensive SIP update, but as a practical matter, CARB must
submit a SIP revision that includes updated demonstrations as well as
the updated budgets to meet the adequacy criteria in 40 CFR
93.118(e)(4); \230\ and thus, we do not need a specific commitment for
such a plan at this time. For the reasons provided above, and in light
of CARB's explanation for why the budgets will become outdated and
should be replaced upon an adequacy finding for updated budgets, we
propose to limit the duration of our approval of the budgets in the
2016 PM2.5 Plan until new budgets have been found adequate.
---------------------------------------------------------------------------

    \230\ Under 40 CFR 93.118(e)(4), the EPA will not find a budget
in a submitted SIP to be adequate unless, among other criteria, the
budgets, when considered together with all other emission sources,
are consistent with applicable requirements for RFP and attainment.
40 CFR 93.118(e)(4)(iv).
---------------------------------------------------------------------------

VI. Reclassification as Serious Nonattainment and Serious Area SIP
Requirements

A. Reclassification as Serious and Applicable Attainment Date

    Section 188 of the Act outlines the process for classification of
PM2.5 nonattainment areas and establishes the applicable
attainment dates. Under the plain meaning of the terms of section
188(b)(1) of the Act, the EPA has general authority to reclassify at
any time before the applicable attainment date any area that the EPA
determines cannot practicably attain the standard by such date.
Accordingly, section 188(b)(1) of the Act is a general expression of
delegated rulemaking authority. In addition, subparagraphs (A) and (B)
of section 188(b)(1) mandate that the EPA reclassify ``appropriate''
PM10 nonattainment areas at specified time frames (i.e., by
December 31, 1991 for the initial PM10 nonattainment areas,
and within 18 months after the SIP submittal due date for subsequent
nonattainment areas). These subparagraphs do not restrict the EPA's
general authority but simply specify that, at a minimum, it must be
exercised at certain times.\231\
---------------------------------------------------------------------------

    \231\ For a general discussion of the EPA's interpretation of
the reclassification provisions in section 188(b)(1) of the Act, see
the General Preamble, 13537-13538.
---------------------------------------------------------------------------

    We have reviewed the air quality modeling and impracticability
demonstration in the 2016 PM2.5 Plan and, based on our
review, agree with the District's conclusion that implementation of the
State/District's SIP control strategy, including RACM/RACT and
additional reasonable measures, is insufficient to bring the South
Coast into attainment by the December 31, 2021 Moderate area attainment
deadline. See sections V.C and V.F of this notice. In addition, we have
reviewed recent PM2.5 monitoring data for the South Coast
available in the EPA's Air Quality System (AQS) database. These data
show that 24-hour PM2.5 levels in the South Coast continue
to be above 12 [micro]g/m\3\, the level of the 2012 PM2.5
standard, and the recent trends in the South Coast's annual
PM2.5 levels are not consistent with a projection of
attainment by the end of 2021.\232\
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    \232\ EPA, Design Value Spreadsheets,
``20200306_SouthCoastPM25Annual.xlsx'' and
``pm25_designvalues_20162018_final_12_03_19.xlsx.''
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    In accordance with section 188(b)(1) of the Act, the EPA is
proposing to reclassify the South Coast area from Moderate to Serious
nonattainment for the 2012 PM2.5 standard of 12 [micro]g/
m\3\, based on the EPA's determination that the South Coast area cannot
practicably attain the standard by the applicable attainment date of
December 31, 2021.
    Under section 188(c)(2) of the Act, the attainment date for a
Serious area ``shall be as expeditiously as practicable but no later
than the end of the tenth calendar year beginning after the area's
designation as nonattainment . . .'' The EPA designated the South Coast
area as nonattainment for the 2012 PM2.5 standard effective
April 15, 2015.\233\ Therefore, upon final reclassification of the
South Coast area as a Serious nonattainment area, the latest
permissible attainment date under section 188(c)(2) of the Act, for
purposes of the 2012 PM2.5 standard in this area, will be
December 31, 2025.
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    \233\ 80 FR 2206.
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    Under section 188(e) of the Act, a state may apply to the EPA for a
single extension of the Serious area attainment date by up to 5 years,
which the EPA may grant if the state satisfies certain conditions.
Before the EPA may extend the attainment date for a Serious area under
section 188(e), the state must: (1) Apply for an extension of the
attainment date beyond the statutory attainment date; (2) demonstrate
that attainment by the statutory attainment date is impracticable; (3)
demonstrate that it has complied with all requirements and commitments
pertaining to the area in the implementation plan; (4) demonstrate to
the satisfaction of the Administrator that the plan for the area
includes the most stringent measures that are included in the
implementation plan of any state or are achieved in practice in any
state, and can feasibly be implemented in the area; and (5) submit a
demonstration of attainment by the most expeditious alternative date
practicable.\234\
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    \234\ For a discussion of the EPA's interpretation of the
requirements of section 188(e), see Addendum, 42002; 65 FR 19964
(April 13, 2000) (proposed action on PM10 Plan for
Maricopa County, Arizona); 67 FR 48718 (July 25, 2002) (final action
on PM10 Plan for Maricopa County, Arizona); and Vigil v.
EPA, 366 F.3d 1025, amended at 381 F.3d 826 (9th Cir. 2004)
(remanding EPA action on PM10 Plan for Maricopa County,
Arizona but generally upholding the EPA's interpretation of CAA
section 188(e)).

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B. Clean Air Act Requirements for Serious PM2.5 Nonattainment Area
Plans

    Upon reclassification as a Serious nonattainment area for the 2012
PM2.5 NAAQS, California will be required to submit
additional SIP revisions to satisfy the statutory requirements that
apply to Serious PM2.5 nonattainment areas, including the
requirements of subpart 4 of part D, title I of the Act.
    The Serious area SIP elements that California will be required to
submit are as follows:
    1. Provisions to assure that the best available control measures
(BACM),\235\ including best available control technology (BACT) for
stationary sources, for the control of direct PM2.5 and
PM2.5 precursors shall be implemented no later than 4 years
after the area is reclassified (CAA section 189(b)(1)(B));
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    \235\ The EPA defines BACM as, among other things, the maximum
degree of emission reduction achievable for a source or source
category, which is determined on a case-by-case basis considering
energy, environmental, and economic impacts. (Addendum, 42010 and
42014). BACM must be implemented for all categories of sources in a
Serious PM2.5 nonattainment area unless the State
adequately demonstrates that a particular source category does not
contribute significantly to nonattainment of the PM2.5
standard. (Id. at 42011, 42012).
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    2. a demonstration (including air quality modeling) that the plan
provides for attainment as expeditiously as practicable but no later
than December 31, 2025, or where the state is seeking an extension of
the attainment date under section 188(e), a demonstration that
attainment by December 31, 2025 is impracticable and that the plan
provides for attainment by the most expeditious alternative date
practicable and no later than December 31, 2030 (CAA sections
189(b)(1)(A), 188(c)(2), and 188(e));
    3. plan provisions that require reasonable further progress (RFP)
(CAA 172(c)(2));
    4. quantitative milestones that are to be achieved every three
years until the area is redesignated attainment and that demonstrate
RFP toward attainment by the applicable date (CAA section 189(c));
    5. provisions to assure that control requirements applicable to
major stationary sources of PM2.5 also apply to major
stationary sources of PM2.5 precursors, except where the
state demonstrates to the EPA's satisfaction that such sources do not
contribute significantly to PM2.5 levels that exceed the
standard in the area (CAA section 189(e));
    6. a comprehensive, accurate, current inventory of actual emissions
from all sources of PM2.5 and PM2.5 precursors in
the area (CAA section 172(c)(3));
    7. contingency measures to be implemented if the area fails to meet
RFP or to attain by the applicable attainment date (CAA section
172(c)(9)); and
    8. a revision to the NNSR program to lower the applicable ``major
stationary source'' \236\ thresholds from 100 tpy to 70 tpy (CAA
section 189(b)(3)) and to satisfy the subpart 4 control requirements
for major stationary sources of PM2.5 precursors (CAA
section 189(e)).
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    \236\ For any Serious area, the terms ``major source'' and
``major stationary source'' include any stationary source that emits
or has the potential to emit at least 70 tpy of PM10 (CAA
sections 189(b)(3)).
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    As discussed in section V.E of this proposed rule, California
submitted NNSR SIP revisions for the South Coast to address the subpart
4 NNSR requirements for Serious PM2.5 nonattainment areas on
May 8, 2017, and the EPA conditionally approved these NNSR SIP
revisions on November 30, 2018.\237\ The State fulfilled the commitment
that provided the basis for the EPA's conditional approval of these
NNSR SIP revisions by submitting a revised version of Rule 1325
(``Federal PM2.5 New Source Review Program'') on April 24,
2019.
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    \237\ 83 FR 61551 (establishing December 30, 2019 deadline for
the State to correct identified rule deficiencies). Previously, the
EPA fully approved NNSR SIP revisions from California to address the
NNSR requirements for Moderate PM2.5 nonattainment areas.
80 FR 24821 (May 1, 2015).
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    Finally, reclassification of the South Coast area as Serious
nonattainment for the 2012 PM2.5 standard would lower the de
minimis threshold under the CAA's General Conformity requirements (40
CFR part 93, subpart B) from 100 tpy to 70 tpy for PM2.5 and
PM2.5 precursors.\238\ In this case, however,
reclassification would have no impact on the applicable General
Conformity de minimis thresholds, because the South Coast area is
already subject to the 70 tpy de minimis threshold for PM2.5
and all PM2.5 precursors as a result of the EPA's previous
action reclassifying the area as Serious nonattainment for the 2006
PM2.5 NAAQS.\239\
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    \238\ 40 CFR 93.153(b), 81 FR 58010, 58126.
    \239\ 81 FR 1514.
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C. Statutory Deadline for Submittal of the Serious Area Plan

    For an area reclassified as a Serious nonattainment area before the
applicable attainment date under CAA section 188(b)(1), section
189(b)(2) requires the state to submit the required BACM provisions
``no later than 18 months after reclassification of the area as a
Serious Area'' and to submit the required attainment demonstration ``no
later than 4 years after reclassification of the area to Serious.''
Section 189(b)(2) establishes outer bounds on the SIP submission
deadlines as necessary or appropriate to assure consistency among the
required submissions and to implement the statutory requirements.
    The Act provides the state with up to 18 months after final
reclassification of an area to Serious to submit the required BACM
provisions. Because an up-to-date emissions inventory serves as the
foundation for a state's BACM/BACT determination, the PM2.5
SIP Requirements Rule requires the state to submit the emissions
inventory required under CAA section 172(c)(3) within 18 months after
the effective date of final reclassification.\240\ Similarly, because
an effective evaluation of BACM/BACT measures requires evaluation of
the precursor pollutants that must be controlled to provide for
expeditious attainment in the area, if the state chooses to submit an
optional precursor insignificance demonstration to support a
determination to exclude a PM2.5 precursor from the required
control measure evaluations for the area, the EPA requires that the
state submit any such demonstration by this same date. An 18-month
timeframe for submission of these plan elements is consistent with both
the timeframe for submission of BACM/BACT provisions under CAA section
189(b)(2) and the timeframe for submission of subpart 1 plan elements
under section 172(b) of the Act.\241\
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    \240\ 81 FR 58010, 58077.
    \241\ Section 172(b) requires the EPA to establish, concurrent
with nonattainment area designations, a schedule extending no later
than 3 years from the date of the nonattainment designation for
states to submit plans or plan revisions meeting the applicable
requirements of sections 110(a)(2) and 172(c) of the CAA.
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    The PM2.5 SIP Requirements Rule also establishes a
specific deadline for submission of the attainment demonstration and
attainment-related plan elements following discretionary
reclassification, which is the earlier of (1) four years from the date
of reclassification, or (2) the end of the eighth calendar year after
designation.\242\ In this case, the earlier of these two dates will be
the end of the eighth calendar year after designation--i.e., December
31, 2023. The attainment-related plan elements required within the same
timeframe as the attainment demonstration are: (1) The RFP
demonstration required under section 172(c)(2); (2) the quantitative
milestones

required under section 189(c); (3) any additional control measures
necessary to meet the requirements of section 172(c)(6); and (4) the
contingency measures required under section 172(c)(9). Although section
189(b)(2) generally provides for up to four years after a discretionary
reclassification for the state to submit the required attainment
demonstration, given the timing of this reclassification action less
than two years before the Moderate area attainment date, it is
appropriate in this case for the EPA to establish an earlier SIP
submission deadline to assure timely implementation of the statutory
requirements.
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    \242\ 81 FR 58010, 58077.
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    Finally, the PM2.5 SIP Requirements Rule establishes a
regulatory requirement that the state submit revised NNSR program
requirements no later than 18 months after final reclassification.\243\
The Act does not specify a deadline for the state's submission of SIP
revisions to meet NNSR program requirements to lower the ``major
stationary source'' threshold from 100 tpy to 70 tpy (CAA section
189(b)(3)) and to address the control requirements for major stationary
sources of PM2.5 precursors (CAA section 189(e)) \244\
following reclassification of a Moderate PM2.5 nonattainment
area as Serious nonattainment under subpart 4. Pursuant to the EPA's
gap-filling authority in CAA section 301(a) and to effectuate the
statutory control requirements in section 189 of the Act, the
PM2.5 SIP Requirements Rule requires the state to submit
these NNSR SIP revisions, as well as any necessary analysis of and
additional control requirements for major stationary sources of
PM2.5 precursors, no later than 18 months after the
effective date of final reclassification of the South Coast area as
Serious nonattainment for the 2012 PM2.5 standard. This due
date will ensure that necessary control requirements for major sources
are established in advance of the required attainment demonstration. An
18-month timeframe for submission of the NNSR SIP revisions also aligns
with the statutory deadline for submission of BACM and BACT provisions
and the broader analysis of PM2.5 precursors for potential
controls on existing sources in the area.
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    \243\ Id. at 58078.
    \244\ Section 189(e) requires that the control requirements
applicable to major stationary sources of PM2.5 also
apply to major stationary sources of PM2.5 precursors,
except where the state demonstrates to the EPA's satisfaction that
such sources do not contribute significantly to PM2.5
levels that exceed the standard in the area.
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    Accordingly, if we finalize our proposal to reclassify the South
Coast as a Serious nonattainment area for the 2012 PM2.5
NAAQS, California will be required to submit the emissions inventory
required under CAA section 172(c)(3), the BACM/BACT provisions required
under CAA section 189(b)(1)(B), and any NNSR SIP revisions required to
satisfy the requirements of CAA sections 189(b)(3) and 189(e) for the
2012 PM2.5 NAAQS no later than 18 months after the effective
date of a final reclassification action. Additionally, California will
be required to submit the Serious area attainment demonstration and all
attainment-related plan elements no later than the end of the eighth
calendar year after designation--i.e., by December 31, 2023. We note
that the 2016 PM2.5 Plan submitted on April 27, 2017,
includes a Serious area attainment demonstration, an emissions
inventory, attainment-related plan elements, and BACM/BACT provisions,
which the EPA intends to evaluate and act on through subsequent
rulemakings, as appropriate.

VII. Reclassification of Areas of Indian Country

    When the South Coast area was designated nonattainment for the 2012
PM2.5 NAAQS, five Indian tribes were located within the
boundaries of the nonattainment area. These tribes include the Cahuilla
Band of Mission Indians of the Cahuilla Reservation, the Morongo Band
of Mission Indians, the Ramona Band of Cahuilla, the San Manuel Band of
Mission Indians, and the Soboba Band of Luiseno Indians. At that time,
the main body of land belonging to the Pechanga Band of Luiseno Mission
Indians of the Pechanga Reservation was expressly excluded from the
South Coast 2012 PM2.5 nonattainment area. However, since
designations, the tribe acquired the Meadowbrook parcel, which is
located approximately 30 miles northwest of the northern boundary of
the Reservation and is located within the 2012 PM2.5
nonattainment area.
    We have considered the relevance of our proposal to reclassify the
South Coast area as Serious nonattainment for the 2012 PM2.5
standard for each tribe located within the South Coast area. We believe
that the same facts and circumstances that support the proposal for the
non-Indian country lands also support the proposal for reservation
areas of Indian country \245\ and any other areas of Indian country
where the EPA or a tribe has demonstrated that the tribe has
jurisdiction located within the South Coast nonattainment area. The EPA
is therefore proposing to exercise our authority under CAA section
188(b)(1) to reclassify areas of Indian country geographically located
in the South Coast nonattainment area. Section 188(b)(1) broadly
authorizes the EPA to reclassify a nonattainment area--including any
Indian country located within such an area--that the EPA determines
cannot practicably attain the relevant standard by the applicable
attainment date.
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    \245\ ``Indian country'' as defined at 18 U.S.C. 1151 refers to:
``(a) all land within the limits of any Indian reservation under the
jurisdiction of the United States Government, notwithstanding the
issuance of any patent, and including rights-of-way running through
the reservation, (b) all dependent Indian communities within the
borders of the United States whether within the original or
subsequently acquired territory thereof, and whether within or
without the limits of a state, and (c) all Indian allotments, the
Indian titles to which have not been extinguished, including rights-
of-way running through the same.''
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    Directly-emitted PM2.5 and its precursor pollutants
(NOX, SO2, VOC, and ammonia) are emitted
throughout a nonattainment area and can be transported throughout that
nonattainment area. Therefore, boundaries for nonattainment areas are
drawn to encompass both areas with direct sources of the pollutant
problem as well as nearby areas in the same airshed. Initial
classifications of nonattainment areas are coterminous with, that is,
they match exactly, their boundaries. The EPA believes this approach
best ensures public health protection from the adverse effects of
PM2.5 pollution. Therefore, it is generally
counterproductive from an air quality and planning perspective to have
a disparate classification for a land area located within the
boundaries of a nonattainment area, such as the reservation areas of
Indian country contained within the South Coast PM2.5
nonattainment area. Violations of the 2012 PM2.5 standard,
which are measured and modeled throughout the nonattainment area, as
well as shared meteorological conditions, would dictate the same
conclusion. Furthermore, emissions increases in portions of a
PM2.5 nonattainment area that are left classified as
Moderate could counteract the effects of efforts to attain the standard
within the overall area because less stringent requirements would apply
in those Moderate portions relative to those that would apply in the
portions of the area reclassified to Serious.
    Uniformity of classification throughout a nonattainment area is
thus a guiding principle and premise when an area is being
reclassified. In this

particular case, we are proposing to determine, based on the State's
demonstration and current ambient air quality trends, that the entire
South Coast nonattainment area, including all reservations areas of
Indian country and any other area located within the South Coast where
a tribe has jurisdiction, cannot practicably attain the 2012
PM2.5 standard by the applicable Moderate area attainment
date of December 31, 2021.
    In light of the considerations outlined above that support
retention of a uniformly-classified PM2.5 nonattainment
area, and our proposal to find that it is impracticable for the area to
attain by the applicable attainment date, we propose to reclassify the
entire South Coast nonattainment area, including reservation areas of
Indian country and any other area of Indian country located within it
where the EPA or a tribe has demonstrated that the tribe has
jurisdiction, as Serious nonattainment for the 2012 PM2.5
standard.
    Generally, the effect of reclassification is to lower the
applicable ``major source'' threshold for purposes of the NNSR program
and the Title V operating permit program from 100 tpy to 70 tpy,\246\
thus subjecting more new or modified stationary sources to these
requirements. Reclassification also lowers the de minimis threshold
under the CAA's General Conformity requirements from 100 tpy to 70
tpy.\247\ In this case, however, reclassification would not change the
``major source'' thresholds because, as a result of the EPA's January
2016 reclassification of the South Coast area as a ``Serious''
nonattainment area for the 2006 PM2.5 NAAQS, the area is
already subject to the 70 tpy major source threshold for Serious
PM2.5 nonattainment areas in CAA section 189(b)(3).\248\
Likewise, reclassification would have no impact on the applicable
General Conformity de minimis thresholds, because the South Coast area
is already subject to the 70 tpy de minimis threshold for
PM2.5 and all PM2.5 precursors as a result of the
EPA's previous reclassification of the area as Serious for the 2006
PM2.5 NAAQS.\249\
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    \246\ CAA sections 189(b)(3) and 501(2)(B).
    \247\ 40 CFR part 93, subpart B.
    \248\ 81 FR 1514.
    \249\ Id. and 40 CFR 93.153(b).
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    The EPA has contacted tribal officials to invite government-to-
government consultation on this rulemaking effort.\250\ The EPA
specifically solicits additional comment on this proposed rule from