VOC.................................                470                392                376                370
NH3.................................               81.1               75.5               74.0               73.3
----------------------------------------------------------------------------------------------------------------
Source: 2016 AQMP, Appendix VI-C, Table VI-C-3.

                               Table 5--Summary of 24-Hour PM2.5 RFP Calculations
                                              [Annual average tpd]
----------------------------------------------------------------------------------------------------------------
     Row       Calculation step        PM2.5            NOX             SO2             VOC             NH3
----------------------------------------------------------------------------------------------------------------
1...........  2012 base year                66.4             540            18.4             470            81.1
               emissions.
2...........  Annual percent                0.55             4.9             1.4             2.9             1.2
               change needed to
               show linear
               progress (%).
3...........  2017 Target Needed            64.6             406            17.1             403            76.0
               to show linear
               progress (tpd).
4...........  2017 Baseline                 63.8             398            17.1             392            75.5
               emissions (tpd).
5...........  Projected                        0               0               0               0               0
               shortfall (tpd).
6...........  Surplus in 2017               0.85             8.6            0.05            10.4            0.48
               (tpd).
7...........  Emissions                     0.36            26.7            0.25            13.5             1.0
               Equivalent to 1
               Year's Worth of
               RFP.
8...........  2019 Baseline                 63.9             353            16.6             376            74.0
               Emissions (tpd).
----------------------------------------------------------------------------------------------------------------
Source: 2016 AQMP, Appendix VI-C, Table VI-C-3A.

    The 2016 PM2.5 Plan documents the State's conclusion
that all BACM and BACT for these pollutants are being implemented as
expeditiously as practicable and identifies projected levels of direct
PM2.5, NOX, VOC, ammonia, and SO2
emissions in 2017 and 2019 that reflect full implementation of the
state, district,

and SCAG's BACM/BACT control strategy for these pollutants.\143\ The
BACM control strategy that provides the basis for these emissions
projections is described in Chapter 4, Appendix IV, and Appendix VI of
the 2016 AQMP.
---------------------------------------------------------------------------

    \143\ 2016 AQMP, Appendix VI-C, pp. VI-C-5 to VI-C-11; see also
evaluation of BACM/BACT in section V.C 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.\144\ For example, Rule 444 (Open Burning) achieved
reductions of direct PM2.5 from the base year of 2012 to the
2017 RFP year. In addition, Rule 445 (Wood-Burning Devices) was amended
in 2013 by lowering the mandatory winter burning curtailment program
threshold for residential wood burning and extending the curtailment to
the entire South Coast air basin, thereby further limiting emissions
from one of the largest combustion sources of direct PM2.5
in the South Coast nonattainment area.\145\ These rule amendments
provide part of the incremental emission reductions of direct
PM2.5 from the 2012 base year to the 2017 RFP milestone
year.\146\ Measures to control sources of direct PM2.5 are
also presented in the Plan's BACM analyses and reflected in the Plan's
baseline emission projections.
---------------------------------------------------------------------------

    \144\ 2016 AQMP, Appendix VI-A, p. VI-A-34.
    \145\ 2016 AQMP, Appendix III; see also 78 FR 59249 (September
26, 2013).
    \146\ 2016 AQMP, Appendix VI-C, p. VI-C-1, 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 (referred to in the Plan as the ``On-Road Heavy-Duty Diesel
Vehicles (In-Use) Regulation'') achieved PM2.5 emissions
reductions beginning in 2012.\147\ Lighter trucks and buses were
required to replace 1995 and older engines with a 2010 MY by 2015. The
2010 MY engines include particulate filters. CARB's LEV II program
includes particulate matter emissions limits by MY for 2016, and the
LEV III 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.\148\ These indices reflect a fleet's overall emissions rate 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.\149\ CARB implemented a similar ban on Tier 1 engines between
January 1, 2014 (large fleets) and January 1, 2016 (small fleets).
---------------------------------------------------------------------------

    \147\ The State's quantitative milestone report for the 2017
milestone indicates that the requirement for heavier trucks to
install diesel particulate filters was fully implemented by 2016.
See SCAQMD, ``2017 Quantitative Milestone Report for 2006 24-hour
PM2.5 National Ambient Air Quality Standard,'' March 2018
(``2017 QM Report''), p. 11.
    \148\ A fleet average index is an indicator of a fleet's overall
emissions rate of particulate matter and NOx based on the horsepower
and model year of each engine in the fleet.
    \149\ Tier 0 engines meet 1995 to 1999 emission standards,
depending on engine size and horsepower. See https://www.assocpower.com/eqdata/tech/US-EPA-Tier-Chart_1995-2004.php.
---------------------------------------------------------------------------

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
AQMP identifies the following South Coast regulations as measures that
achieve ongoing NOX reductions with compliance dates during
the RFP and attainment years of the Plan: Rule 1111 (Reductions of
NOX from Natural Gas-Fired, Fan-Type Central Furnaces), Rule
1110.2 (Emissions from Gaseous- and Liquid-Fueled Engines), Rule 1121
(Control of Nitrogen Oxides from Residential-Type, Natural Gas-Fired
Water Heaters), Rule 1146 (Emission of Oxides of Nitrogen from
Industrial, Institutional, Commercial Boilers, Steam Generators, and
Process Heaters), Rule 1146.1 (Emission of Oxides of Nitrogen from
Small Industrial, Institutional, Commercial Boilers, Steam Generators,
and Process Heaters), 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).\150\ \151\
---------------------------------------------------------------------------

    \150\ 2016 AQMP, Appendix VI-C, Table VI-C-4 and p. VI-C-8.
    \151\ Rule 1111 was mistakenly listed as Rule 1110 in the 2016
AQMP, Appendix VI, Table VI-C-4. See 2017 QM Report at p. 6,
footnote 1.
---------------------------------------------------------------------------

    For on-road and non-road mobile sources, which represent the
largest sources of NOX emissions in the nonattainment area,
the 2016 AQMP lists numerous CARB regulations and discusses the key
regulations that limit emissions of direct PM2.5 as well as
NOX, VOC, SO2 and ammonia from these
sources.\152\ 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 AQMP 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.\153\ The Plan also shows that
NOX emission levels in each milestone year and the
attainment year are projected to be well below the levels needed to
show generally linear progress toward attainment.
---------------------------------------------------------------------------

    \152\ 2016 AQMP, Appendix IV-C, Attachment VI-C-1.
    \153\ 2016 AQMP, Appendix IV-C, Attachment VI-C-1, pp. VI-C-19-
21.
---------------------------------------------------------------------------

    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 particulate
matter and NOX through the RFP and attainment planning
years.\154\ For example, MY 1994 and 1995 heavy-duty diesel truck
engines were required to be upgraded to meet the 2010 MY truck engine
emission standards by 2016, and MY 1996-1999 engines must be upgraded
by January 1, 2020.\155\ The emission reductions from these rules
represent the largest portion of the NOX emission reductions
upon which the 2016 PM2.5 Plan's attainment and RFP
demonstrations rely.\156\ Emission reductions between 2012 and 2017
were achieved through the requirements for particulate filters and
cleaner engine standards.
---------------------------------------------------------------------------

    \154\ 2016 AQMP, Appendix IV-C, p. VI-C-20.
    \155\ 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 at 20309-20310
(April 4, 2012) (final rule approving CARB's Truck and Bus Rule into
California SIP).
    \156\ 2016 AQMP, Appendix III, Attachment B.
---------------------------------------------------------------------------

    California also has the authority under the CAA to regulate light-
and medium-duty vehicle engines. A key control program for these
vehicles is the ACC program.\157\ The ACC program implements a variety
of regulations including the LEV III program, with criteria pollutant
emission limits for non-methane organic gases (NMOG) \158\

and NOX as well as particulate matter, which phased in
starting in 2014 and continues through the RFP year of 2017 and beyond.
---------------------------------------------------------------------------

    \157\ See 81 FR 39424, June 16, 2016.
    \158\ NMOG means the combination of organic gases other than
methane as calculated in 40 CFR 1066.635. Note that for this part,
the organic gases are summed on a mass basis without any adjustment
for photochemical reactivity.
---------------------------------------------------------------------------

    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 is phased in between
January 1, 2014 and January 1, 2019.\159\
---------------------------------------------------------------------------

    \159\ 2016 AQMP, Appendix VI-C, Attachment VI-C-1, p. VI-C-23
and VI-C-24.
---------------------------------------------------------------------------

Volatile Organic Compounds
    As with other precursors, the District regulates stationary and
area sources of VOC, and CARB is largely responsible for both on-road
and off-road mobile sources. The 2016 AQMP highlights three stationary
source VOC rules that contribute to RFP: Rule 1114 (Petroleum Refinery
Coking Operations), Rule 1177 (Liquified Petroleum Gas Transfer and
Dispensing), and Rule 1113 (Architectural Coatings).\160\
---------------------------------------------------------------------------

    \160\ The District projects that revisions to Rule 1113 that it
adopted after submitting the 2016 AQMP are projected to result in an
additional 0.88 tpd of VOC reductions by 2019. See 2017 QM Report,
p. 8.
---------------------------------------------------------------------------

    As with NOX, the majority of VOC emissions reductions
that occur between the base year of 2012 and the 2017 RFP year come
from on-road mobile sources and other mobile sources that are under the
State's jurisdiction. CARB highlights its ACC program, which reduces
emission from light- and medium-duty vehicles. The ACC program has a
combined NMOG plus NOx fleet average requirement that began in 2014.
Ammonia
    With respect to ammonia, the Plan states that, while both
NOX and ammonia participate in forming ammonium nitrate
(i.e., secondary PM2.5), NOX emission reductions
are more effective at reducing ambient PM2.5 than ammonia
reductions.\161\ Control measures for ammonia sources are described in
Appendix VI of the Plan. For example, South Coast Rules 223 and 1127,
which regulate confined animal facilities and manure waste from these
facilities, control ammonia, as do the District's composting measures
(i.e., Rules 1133, 1133.1, 1133.2 and 1133.3). These rules and the
methods they use to control ammonia emissions are discussed at length
in Appendix VI-B of the 2016 AQMP, 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.\162\ We discuss our
evaluation of these rules for purposes of satisfying BACM requirements
in section V.C of this proposed rule.
---------------------------------------------------------------------------

    \161\ 2016 AQMP, Appendix V, p. V-6-61.
    \162\ 2016 AQMP, Appendix IV-A, p. IV-A-98-103.
---------------------------------------------------------------------------

    The District ascribes the reductions in ammonia during the period
from 2012 to 2017 to decreases in farming operations in the South Coast
air basin, as well as reductions in emissions from mobile sources
largely achieved by state regulations for on-road motor vehicles.
Sulfur Dioxide
    Reductions of SO2 in the South Coast nonattainment area
during the period from 2012 to 2017 were 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 AQMP identifies a milestone date of December 31, 2017,
which is the date 3 years after December 31, 2014, and a second
milestone date of December 31, 2020, which is the milestone date that
falls within 3 years after the applicable attainment date (December 31,
2019). The 2016 AQMP also identifies target RFP emissions levels for
direct PM2.5, NOX, VOC, NH3, and
SO2 for the 2017 milestone year, the 2019 attainment year,
and the 2020 post-attainment year milestone, and adopted control
measures to be implemented by each of these years in accordance with
the control strategy in the Plan.\163\
---------------------------------------------------------------------------

    \163\ 2016 AQMP, Appendix VI-C, pp. VI-C-6 and VI-C-7.
---------------------------------------------------------------------------

3. Evaluation and Proposed Actions
    The 2016 PM2.5 Plan describes the control measures for
direct PM2.5, NOX, SO2, VOC and
ammonia implemented during each year of the attainment plan and
demonstrates that these measures, which provide the bases for the
emissions projections in the RFP plan, are being implemented as
expeditiously as practicable. Additionally, the Plan contains projected
RFP emission levels for direct PM2.5 and all
PM2.5 precursors for the 2017 and 2020 milestone years and
for the 2019 attainment year, based on the anticipated implementation
schedule for the attainment control strategy. The Plan also
demonstrates that the control strategy will achieve RFP toward
attainment between the 2012 base year and the 2019 attainment year.
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 toward
attainment. We agree with the State and District's conclusion that
generally linear progress is an appropriate measure of RFP for the 2006
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,\164\ and secondary particulates
contribute significantly to ambient PM2.5 levels in the
South Coast area.\165\
---------------------------------------------------------------------------

    \164\ See generally 2016 AQMP, Appendix IV-A and B and Appendix
VI-A.
    \165\ See 2016 AQMP, Appendix V, p. V-6-61.
---------------------------------------------------------------------------

    Accordingly, we propose to determine that the 2016 PM2.5
Plan requires the annual incremental reductions in emissions of direct
PM2.5 and PM2.5 precursors that are necessary for
ensuring attainment of the 2006 24-hour PM2.5 NAAQS by
December 31, 2019, in accordance with the requirements of CAA sections
171(1) and 172(c)(2) and 40 CFR 51.1012.
    Additionally, the 2016 PM2.5 Plan identifies milestone
dates that are consistent with the requirements of 40 CFR 51.1013(a)(4)
and target emissions levels for direct PM2.5 and all
PM2.5 precursors to be achieved by these milestone dates
through implementation of the attainment control strategy. These target
emission levels and associated control requirements provide for
objective evaluation of the area's progress towards attainment of the
2006 PM2.5 NAAQS. We propose to determine that these
quantitative milestones satisfy the requirements of CAA section 189(c)
and 40 CFR 51.1013.
    On April 2, 2018, CARB submitted the ``2017 Quantitative Milestone
Report for the 2006 24-Hour PM2.5 National Ambient Air
Quality Standards (March 2018)'' (``2017 QM Report'') to the EPA.\166\
The 2017 QM report includes a

certification from the Governor's designee that the 2017 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 2017 QM Report also contains a
demonstration of how the emissions reductions achieved to date compare
to those required or scheduled to meet RFP. The State and District
conclude in the 2017 QM Report that the South Coast area is on track to
attain the 2006 p.m.2.5 NAAQS by the projected attainment
date for the area, which is December 31, 2019. On September 7, 2018,
the EPA determined that the South Coast 2017 QM Report was
adequate.\167\
---------------------------------------------------------------------------

    \166\ Letter from Richard W. Corey, Executive Officer, CARB, to
Alexis Strauss, Acting Regional Administrator, EPA Region IX, with
attachment, April 2, 2018.
    \167\ Letter from Andrew R. Wheeler EPA, Acting Administrator,
to Richard W. Corey, Executive Officer, CARB, regarding 2017
Quantitative Milestone Report for 2006 24-hour PM2.5
National Ambient Air Quality Standards, September 7, 2018.
---------------------------------------------------------------------------

F. 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. 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.
    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 continuing nonattainment. Neither the CAA nor
the EPA's implementing regulations establish a specific level of
emissions reductions that implementation of contingency measures must
achieve, but the EPA has taken the position that contingency measures
should provide for emissions reductions equivalent to approximately one
year of reductions needed for RFP. In general, we expect all actions
needed to effect full implementation of the measures to occur within 60
days after EPA notifies the state of a failure to meet RFP or to
attain.\168\
---------------------------------------------------------------------------

    \168\ General Preamble at 13512, 13543-44 and Addendum at 42014-
42015.
---------------------------------------------------------------------------

    To satisfy the requirements of 40 CFR 51.1014, the contingency
measures adopted as part of a PM2.5 attainment plan must:
(1) consist of control measures for the area that are not otherwise
included in the control strategy or that achieve emissions reductions
not otherwise relied upon in the control strategy for the area (e.g.,
to meet RACM/RACT, BACM/BACT, or MSM requirements), and (2) specify the
timeframe within which their requirements become effective following
any of the EPA determinations specified in 40 CFR 51.1014(a).
    The Ninth Circuit recently rejected the EPA's interpretation of CAA
section 172(c)(9) as allowing for early implementation of contingency
measures, in a decision called Bahr v. EPA (``Bahr'').\169\ In Bahr,
the Ninth Circuit concluded that contingency measures must take effect
at the time the area fails to make RFP or attain by the applicable
attainment date, not before. Thus, within the geographic jurisdiction
of the Ninth Circuit, states cannot rely on early-implemented measures
to comply with the contingency measure requirements under CAA section
172(c)(9).
---------------------------------------------------------------------------

    \169\ Bahr v. EPA, 836 F.3d 1218, at 1235-1237 (9th Cir. 2016).
---------------------------------------------------------------------------

2. Contingency Measures in the 2016 PM2.5 Plan
    The 2016 PM2.5 Plan addresses the contingency measure
requirement in Chapter 4 of the 2016 AQMP and in section H of the CARB
Staff Report. Chapter 4 of the 2016 AQMP addresses contingency measures
for failure to attain by describing emission reductions to be achieved
by an adopted measure, South Coast Rule 445 (Wood-Burning Devices). The
2016 PM2.5 Plan does not specifically address contingency
measures for failure to meet RFP.
    The CARB Staff Report provides a brief statement acknowledging the
recent 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.
3. EPA's Evaluation and Proposed Action
    As explained above in Section V.E, on April 2, 2018, CARB submitted
a quantitative milestone report demonstrating that the 2017
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 2017 quantitative milestones, RFP
contingency measures for 2017 are no longer needed. Accordingly, we are
proposing to find that the RFP contingency measure requirement for the
2017 RFP milestone year is now moot as applied to the South Coast. 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 milestones for 2017
would have required California to implement RFP contingency measures
and to revise the 2016 PM2.5 Plan to assure that it still
provided for attainment by the applicable attainment date of December
31, 2019. In this case, however, the 2017 QM Report demonstrates that
actual emissions levels in 2017 were consistent with the approved 2017
RFP milestone year targets for direct PM2.5 and all
precursor pollutants (NOX, SO2, VOCs, and
ammonia) regulated in the 2016 PM2.5 Plan. Accordingly, RFP
contingency measures for 2017 no longer have meaning or purpose, and
the EPA proposes to find that the requirement for them is now moot.
    We are not proposing any action at this time on the attainment
contingency measure component of the 2016 PM2.5 Plan and
will act on that component through a subsequent rulemaking, as
appropriate.

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

    Section 189(e) of the Act 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.\170\ The control
requirements applicable to major stationary sources of direct
PM2.5 in a Serious PM2.5 nonattainment area
include, at minimum, the requirements of a NNSR permit program meeting
the requirements of CAA sections 172(c)(5) and 189(b)(3).\171\ As part
of our January 13, 2016 final action to reclassify the

South Coast area as Serious nonattainment for the 2006 PM2.5
standards, we established a deadline 18 months from the effective date
of our reclassification (or August 14, 2017) for the State to submit
NNSR SIP revisions addressing the requirements of CAA sections
189(b)(3) and 189(e) of the Act.\172\
---------------------------------------------------------------------------

    \170\ General Preamble at 13539 and 13541-42.
    \171\ CAA section 189(b)(1) (requiring that Serious area plans
include provisions submitted to meet the requirements for Moderate
areas in section 189(a)(1)).
    \172\ 81 FR 1514, at 1515 (January 13, 2016).
---------------------------------------------------------------------------

    California submitted NNSR SIP revisions to address the subpart 4
requirements for Serious PM2.5 nonattainment areas on May 8,
2017.\173\ We are not proposing any action on this submission at this
time. We will act on this submission through a subsequent rulemaking,
as appropriate.
---------------------------------------------------------------------------

    \173\ Letter from Richard W. Corey, Executive Officer, CARB, to
Alexis Strauss, Acting Regional Administrator, EPA Region IX, May 8,
2017. California previously submitted NNSR SIP revisions to address
the subpart 4 requirements for Moderate PM2.5
nonattainment areas, and the EPA approved these SIP revisions on May
1, 2015 (80 FR 24821).
---------------------------------------------------------------------------

H. Motor Vehicle Emission 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 expeditious 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, FHWA, and FTA to
demonstrate that an area's regional transportation plans (RTP) and
transportation improvement programs (TIP) 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 (``budgets''
or ``MVEB'') contained in all control strategy SIPs. An attainment,
maintenance, or RFP SIP should include budgets for the attainment year,
each required RFP milestone year, or the last year of the maintenance
plan, as appropriate, for direct PM2.5 and PM2.5
precursors subject to transportation conformity analyses. 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.\174\ Under the
PM2.5 SIP Requirements Rule, Serious area PM2.5
attainment plans must define appropriate quantitative milestones and
include projected RFP emission levels for direct PM2.5 and
all PM2.5 plan precursors in each milestone year.\175\
---------------------------------------------------------------------------

    \174\ 40 CFR 93.118(e)(4)(v).
    \175\ See 81 FR 58010, 58091-58092.
---------------------------------------------------------------------------

    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. A state must also consider whether re-entrained
paved road dust, unpaved road dust, or highway and transit construction
dust are significant contributors and should be included in the direct
PM2.5 budget.\176\
---------------------------------------------------------------------------

    \176\ 40 CFR 93.102(b) and 93.122(f); see also conformity rule
preamble at 69 FR 40004, 40031-40036 (July 1, 2004).
---------------------------------------------------------------------------

    For an area designated nonattainment for the 2006 PM2.5
NAAQS before January 15, 2015, the attainment plan must contain
quantitative milestones to be achieved no later than 3 years after
December 31, 2014, and every 3 years thereafter until the milestone
date that falls within 3 years after the applicable attainment
date.\177\ 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.\178\
---------------------------------------------------------------------------

    \177\ 40 CFR 51.1013(a)(4), see also 81 FR 58010, 58058 and
58063-58064 (August 24, 2016).
    \178\ See 81 FR 58010, 58063-58064 (August 24, 2016).
---------------------------------------------------------------------------

    Transportation conformity trading mechanisms are allowed under 40
CFR 93.124 where a SIP establishes appropriate mechanisms for such
trades. The basis for the trading mechanism is the SIP attainment
modeling that established the relative contribution of each
PM2.5 precursor pollutant. The applicability of emission
trading between conformity budgets for conformity purposes is described
in 40 CFR 93.124(c).
    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 motor vehicle emissions
budgets 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.\179\ 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:
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    \179\ 40 CFR 93.118(e)(1).
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     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 time when new budgets have been found to be adequate for
transportation conformity purposes.\180\
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    \180\ See, e.g., 67 FR 69139 (November 15, 2002), limiting our
prior approval of budgets in certain California SIPs.
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2. Motor Vehicle Emissions Budgets in the 2016 PM2.5 Plan
    Consistent with the requirements of 40 CFR 51.1013(a)(4), the 2016
PM2.5 Plan identifies December 31, 2017, as the first
quantitative milestone date (i.e., the date 3 years after December 31,
2014). The second quantitative milestone date is December 31, 2020, and
is also the last milestone date identified in the Plan because it falls
within 3 years after the December 31, 2019 attainment date for the
area.\181\
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    \181\ Under CAA section 188(c)(2), a Serious PM2.5
nonattainment area must attain the PM2.5 NAAQS as
expeditiously as practicable but no later than the end of the tenth
calendar year after the area is designated as nonattainment. Because
the South Coast area was designated as nonattainment for the 2006
PM2.5 NAAQS effective December 14, 2009 (74 FR 58688,
November 13, 2009), the latest permissible attainment date for the
area is December 31, 2019.

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    The 2016 PM2.5 Plan includes budgets for direct
PM2.5, NOX, and VOC for 2017 and 2019 (RFP
milestone year and projected attainment year, respectively) and for
2020 (post-attainment year quantitative milestone).\182\ The budgets
were calculated using EMFAC2014, CARB's latest version of the EMFAC
model for estimating emissions from on-road vehicles operating in
California, and SCAG's latest modeled VMT and speed distributions from
the 2016 Regional Transportation Plan/Sustainable Communities Strategy
adopted in April of 2016. The budgets reflect annual average emissions
because those emissions are linked with the District's attainment
demonstration for the 24-hour PM2.5 NAAQS.
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    \182\ 2016 PM2.5 Plan, Appendix VI-D and Table VI-D-4
(for 2017, 2019, and 2020 budgets).
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    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.\183\ The Plan includes budgets
for VOC and NOX because they are regulated precursors under
the Plan. Under 40 CFR 93.102(b)(2)(v), states are not required to
include budgets for SO2 and/or NH3 unless EPA or
the state has made a finding that transportation-related emissions of
any of these precursors within the nonattainment area are significant
contributors to the PM2.5 nonattainment problem. Neither the
State nor the EPA has made such a funding. The budgets included in the
2016 PM2.5 Plan are shown in Table 6 below.
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    \183\ 2016 PM2.5 Plan, Appendix VI-D, Table VI-D-3,
p. VI-D-4.
[GRAPHIC] [TIFF OMITTED] TP03OC18.004

    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.\184\
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    \184\ Letter from Richard W. Corey, Executive Officer, CARB, to
Alexis Strauss, Acting Regional Administrator, EPA Region IX, page
3, April 27, 2017.
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    We found the budgets for the 2017 RFP year and the 2019 attainment
year adequate in a letter dated December 19, 2017.\185\ In today's
action, we are proposing to approve these budgets.
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    \185\ Id.
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Conformity Trading Mechanism
    The 2016 PM2.5 Plan also includes a proposed trading
mechanism for transportation conformity analyses that would allow
future decreases in NOX emissions from on-road mobile
sources to offset any on-road increases in PM2.5, using the
ratios shown in Table 7 below.\186\ For the 2006 24-hour
PM2.5 NAAQS the State is proposing to use the same ratios
that were submitted for use with that NAAQS in the 2012
PM2.5 Plan.\187\
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    \186\ 2016 PM2.5 Plan, Appendix VI-D, Table VI-D-5.
    \187\ 82 FR 22025 (April 14, 2016).

       Table 7--Trading Equivalencies for 2006 24-Hour PM2.5 NAAQS
------------------------------------------------------------------------
                                               NOX      VOC      PM2.5
------------------------------------------------------------------------
NOX........................................        1    3.151     0.067
VOC........................................    0.317        1     0.021
PM2.5......................................   14.833   46.792         1
------------------------------------------------------------------------
Source: 2016 PM2.5 Plan, Appendix VI-D, Table VI-D-5, and letter from
  Phil Fine, Deputy Executive Officer, SCAQMD, to Amy Zimpfer, Associate
  Director, Air Division, EPA Region 9, March 14, 2018.

    To ensure that the trading mechanism does not affect the ability of
the South Coast to meet the NOX budget, the NOX
emission reductions available to supplement the PM2.5 budget
would only be those remaining after the NOX budget has been
met.\188\ SCAG must clearly document the calculations used in the
trading when demonstrating conformity, along with any additional
reductions of NOX, PM2.5 or VOC emissions in the
conformity analysis. It should be noted that the trading calculations
are performed prior to the final rounding to demonstrate conformity
with the budgets.
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    \188\ 2016 PM2.5 Plan, Appendix VI-D, page VI-D-5.
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    The District provided a clarification as to how the trading
mechanism would be implemented in a March 14, 2018 letter.\189\ In that
letter, the District clarified that the trading mechanism identified in
the 2012 AQMP for the 2006 PM2.5 24-hour NAAQS, which the
EPA did not previously act on, is

included in the 2016 AQMP for approval by the EPA for use by SCAG in
conformity determinations for the 2006 PM2.5 NAAQS for
analysis years after the attainment year of 2019. The letter also
explained why these trading ratios are still appropriate for use in
conformity determinations even though they are derived from modeling
conducted for the 2012 AQMP.
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    \189\ Letter from Philip Fine, Deputy Executive Officer,
Planning, Rule Development, and Area Sources, SCAQMD, to Amy
Zimpfer, Associate Director, Air Division, EPA Region IX, regarding
trading ratios among PM2.5 precursors, March 14, 2018.
---------------------------------------------------------------------------

    The 2016 PM2.5 Plan also provides that SCAG, the MPO
responsible for demonstrating transportation conformity, shall clearly
document the calculations used in the trading, along with any
additional reductions of NOX, PM2.5 or VOC
emissions in the conformity analysis.
3. EPA's Evaluation and Proposed Actions
    The EPA generally first conducts a preliminary review of budgets
submitted with an attainment, RFP, or maintenance plan for adequacy,
prior to acting on the plan itself, and did so with respect to the
replacement PM2.5 budgets in the 2016 PM2.5 Plan.
On October 18, 2017, the EPA announced the availability of the 2016
PM2.5 Plan with budgets and a 30-day public comment period.
This announcement was posted on EPA's Adequacy website at: https://www.epa.gov/state-and-local-transportation/state-implementation-plans-sip-submissions-currently-under-epa. The comment period for this
notification ended on November 17, 2017. We did not receive any
comments during this comment period. We found the budgets adequate on
December 19, 2017.\190\ A notice of the adequacy finding was published
in the Federal Register on January 5, 2018.\191\
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    \190\ Letter from Matthew J. Lakin, Acting Director, Air
Division, EPA Region IX, to Richard W. Corey, Executive Officer,
CARB, December 19, 2017.
    \191\ See 83 FR 679, January 5, 2018.
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    Based on the information about SO2 and ammonia emissions
in the Plan and in accordance with 40 CFR 93.102(b)(2)(v), we propose
to find that it is not necessary to establish motor vehicle emissions
budgets for transportation-related emissions of SO2 and
ammonia to attain the 2006 PM2.5 standards in the South
Coast.
    For the reasons discussed in sections V.D. and V.E. of this
proposed rule, we are proposing to approve the RFP and attainment
demonstrations in the 2016 PM2.5 Plan. The 2017 RFP and 2019
attainment budgets, as given in Table 6 of this proposed rule, are
consistent with these demonstrations, are clearly identified and
precisely quantified, and meet all other applicable statutory and
regulatory requirements including the adequacy criteria in 93.118(e)(4)
and (5). For these reasons, the EPA proposes to approve the budgets
listed in Table 6 above. We provided a more detailed discussion in our
adequacy letter, which can be found in the docket for today's action.
    We are not taking action on the 2020 budgets at this time. Although
the post-attainment year quantitative milestone is a required element
of the Serious area plan, it is not necessary to demonstrate
transportation conformity for 2020 or to use the 2020 budgets in
transportation conformity determinations until such time as the area
fails to attain the 2006 PM2.5 NAAQS. Additionally, the EPA
has not yet started the adequacy process for the 2020 budgets.
Therefore, the EPA is not taking action on the submitted budgets for
2020 in the 2016 PM2.5 Plan at this time.
    If the EPA were to either find adequate or approve the post-
attainment milestone year budgets now, those budgets would have to be
used in transportation conformity determinations that are made after
the effective date of the adequacy finding or approval even if the
South Coast area ultimately attains the PM2.5 NAAQS by the
Serious area attainment date. This would mean that SCAG would be
required to demonstrate conformity for the post-attainment date
milestone year and all later years addressed in the conformity
determination (e.g., the last year of the metropolitan transportation
plan) to the post-attainment date RFP budgets rather than the budgets
associated with the attainment year for the area (i.e., the budgets for
2019). The EPA does not believe that it is necessary to demonstrate
conformity using these post-attainment year budgets in areas that
either the EPA anticipates will attain by the attainment date or in
areas that attain by the attainment date. The EPA has found adequate
the budgets for the first milestone year (2017) and the attainment year
(2019) for the South Coast PM2.5 nonattainment area.\192\
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    \192\ Letter from Matthew J. Lakin, Acting Director, Air
Division, EPA Region IX, to Richard W. Corey, Executive Officer,
CARB, December 19, 2017, and 83 FR 679 (January 5, 2018).
---------------------------------------------------------------------------

    If the EPA determines that the South Coast area has failed to
attain the 2006 PM2.5 NAAQS by the applicable attainment
date, the EPA will begin the budget adequacy and approval processes for
the post-attainment year (2020) budgets. If the EPA finds the 2020
budgets adequate or approves them, those budgets will have to be used
in subsequent transportation conformity determinations. The EPA
believes that initiating the process to act on the submitted post-
attainment year MVEBs following a determination that the area has
failed to attain by the Serious area attainment date ensures that
transportation activities will not cause or contribute to new
violations, increase the frequency or severity of any existing
violations, or delay timely attainment or any required interim emission
reductions or milestones in the South Coast nonattainment area,
consistent with the requirements of CAA section 176(c)(1)(B).
    We have previously approved motor vehicle emissions budgets for the
1997 annual and 24-hour PM2.5 NAAQS.\193\ These budgets will
continue to apply for the 1997 PM2.5 NAAQS in the South
Coast area.
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    \193\ 76 FR 69928, at 69951 (November 9, 2011).
---------------------------------------------------------------------------

    The EPA has reviewed the trading mechanism described on pages VI-D-
5 and VI-D-6 in Appendix VI-D of the 2016 AQMP and, given the
clarification letter submitted to the EPA on March 14, 2018, finds this
trading mechanism appropriate for use in transportation conformity
analyses in the South Coast for the 2006 PM2.5 NAAQS. We
agree with the District that these trading ratios are still appropriate
for use in transportation conformity determinations even though they
are derived from modeling conducted for the 2012 AQMP. We therefore
propose to approve the trading mechanism as an enforceable component of
the transportation conformity program for the South Coast for the 2006
PM2.5 NAAQS.
    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.\194\ The transportation conformity
rule allows us to limit the approval of budgets.\195\ CARB's request
does not, however, contain an acknowledgement and explanation as to why
the budgets under consideration will become outdated or a commitment to
update the budgets as part of a comprehensive SIP update. Therefore, we
are not proposing at this time to limit the duration of our approval of
the submitted budgets. In order to limit the duration of our approval,
we would need the information described above to determine whether such
limitation is reasonable and appropriate in this case. Once CARB has
provided the necessary information, we intend to review it and

take appropriate action. If we propose to limit the duration of our
approval of the budgets in the 2016 PM2.5 Plan, we will
provide the public an opportunity to comment. The duration of our
approval of the submitted budgets will not be limited until we complete
such a rulemaking.
---------------------------------------------------------------------------

    \194\ See letter dated April 27, 2017, from Richard W. Corey,
Executive Officer, CARB, to Alexis Strauss, Acting Regional
Administrator, EPA Region IX, page 3.
    \195\ 40 CFR 93.118(e)(1).
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VI. Summary of Proposed Actions and Request for Public Comment

    Under CAA section 110(k)(3), the EPA is proposing to approve SIP
revisions submitted by California to address the Act's Serious area
planning requirements for the 2006 PM2.5 NAAQS in the South
Coast nonattainment area. Specifically, the EPA is proposing to approve
the following elements of the 2016 PM2.5 Plan:
    1. 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));
    2. Provisions to assure that BACM, including BACT, 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));
    3. A demonstration (including air quality modeling) that the plan
provides for attainment as expeditiously as practicable but no later
than December 31, 2019 (CAA sections 188(c)(2) and 189(b)(1)(A));
    4. Plan provisions that require RFP (CAA section 172(c)(2));
    5. Quantitative milestones that are to be achieved every 3 years
until the area is redesignated attainment and which demonstrate RFP
toward attainment by the applicable date (CAA section 189(c)); and
    6. 2017 and 2019 motor vehicle emissions budgets, as shown in Table
6 of this proposed rule, because they are derived from an approvable
RFP plan and attainment demonstration and meet the requirements of CAA
section 176(c) and 40 CFR part 93, subpart A.
    The EPA is also proposing to approve the interpollutant trading
mechanism provided in the 2016 PM2.5 Plan and clarified in a
March 14, 2018 letter from the District for use in transportation
conformity analyses for the 2006 PM2.5 NAAQS, in accordance
with 40 CFR 93.124. We are not proposing any action at this time on the
attainment contingency measure component of the 2016 PM2.5
Plan. Finally, the EPA is proposing to find that the requirement for
contingency measures to be undertaken if the area fails to make
reasonable further progress under CAA section 172(c)(9) is moot as
applied to the 2017 milestone year, because the State and District have
demonstrated to the EPA's satisfaction that the 2017 milestones have
been met.
    We will accept comments from the public on these proposals for the
next 30 days. The deadline and instructions for submission of comments
are provided in the DATES and ADDRESSES sections at the beginning of
this preamble.

VII. Statutory and Executive Order Reviews

    Under the Clean Air Act, the Administrator is required to approve a
SIP submission that complies with the provisions of the Act and
applicable federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a).
Thus, in reviewing SIP submissions, the EPA's role is to approve state
choices, provided that they meet the criteria of the Clean Air Act.
Accordingly, this proposed action merely proposes to approve state law
as meeting federal requirements and does not impose additional
requirements beyond those imposed by state law. For that reason, this
proposed action:
     Is not a ``significant regulatory action'' subject to
review by the Office of Management and Budget under Executive Orders
12866 (58 FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21,
2011);
     is not an Executive Order 13771 (82 FR 9339, February 2,
2017) regulatory action because SIP approvals are exempted under
Executive Order 12866;
     does not impose an information collection burden under the
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     is certified as not having a significant economic impact
on a substantial number of small entities under the Regulatory
Flexibility Act (5 U.S.C. 601 et seq.);
     does not contain any unfunded mandate or significantly or
uniquely affect small governments, as described in the Unfunded
Mandates Reform Act of 1995 (Pub. L. 104-4);
     does not have Federalism implications as specified in
Executive Order 13132 (64 FR 43255, August 10, 1999);
     is not an economically significant regulatory action based
on health or safety risks subject to Executive Order 13045 (62 FR
19885, April 23, 1997);
     is not a significant regulatory action subject to
Executive Order 13211 (66 FR 28355, May 22, 2001);
     is not subject to requirements of Section 12(d) of the
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272
note) because application of those requirements would be inconsistent
with the Clean Air Act; and
     does not provide the EPA with the discretionary authority
to address disproportionate human health or environmental effects with
practical, appropriate, and legally permissible methods under Executive
Order 12898 (59 FR 7629, February 16, 1994).
    In addition, the SIP is not approved to apply on any Indian
reservation land or in any other area where the EPA or an Indian tribe
has demonstrated that a tribe has jurisdiction. In those areas of
Indian country, the rule does not have tribal implications and will not
impose substantial direct costs on tribal governments or preempt tribal
law as specified by Executive Order 13175 (65 FR 67249, November 9,
2000).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Ammonia,
Incorporation by reference, Intergovernmental relations, Oxides of
nitrogen, Particulate matter, Reporting and recordkeeping requirements,
Sulfur oxides, Volatile organic compounds.

    Authority: 42 U.S.C. 7401 et seq.

    Dated: September 24, 2018.
Deborah Jordan,
Acting Regional Administrator, Region 9.
[FR Doc. 2018-21560 Filed 10-2-18; 8:45 am]
 BILLING CODE 6560-50-P