of zero-emission technologies in heavy-duty applications that are
suited to early adoption of ZEV technologies. The 2016 State Strategy
includes a California action to establish new low-NOX
certification requirements, coupled with in-use performance
requirements. The strategy also provides greater certification
flexibility for advanced technologies. The measures could reduce
emissions from today's heavy-duty trucks by up to 90 percent. Because
trucks licensed outside of California account for a large portion of
truck activity in California, the 2016 State Strategy calls for the EPA
to develop a national low-NOX engine standard and cites
formal petitions for such rulemaking that have been submitted by
several California air districts. In response to the petitions, on
November 13, 2018, the EPA announced the Cleaner Trucks Initiative, a
future rulemaking to update NOX standards for highway heavy-
duty trucks and engines.\97\
---------------------------------------------------------------------------

    \97\ See https://www.epa.gov/regulations-emissions-vehicles-and-engines/cleaner-truck-initiative.
---------------------------------------------------------------------------

    The 2016 State Strategy includes similar proposed actions for off-
road sources, with a focus on deployment of ZEV technologies in smaller
equipment types such as forklifts and airport ground support equipment.
A low-emission diesel standard builds upon CARB's existing fuels
framework by requiring that low-emission diesel fuels to be used to
achieve greater criteria pollutant reductions. For sources that are
primarily under federal jurisdiction, such as interstate trucks,
locomotives, and ocean-going vessels, the 2016 State Strategy calls for
EPA action to provide the needed emission reductions from these sources
by setting more stringent engine standards. Lastly, the 2016 State
Strategy contains a measure to address VOC emissions from consumer
products, the largest source category of VOCs in California. Chapter 4
(``State SIP Measures'') of the 2016 State Strategy provides a detailed
description of the various measures included in the 2016 State
Strategy, background and regulatory history for the measures, a
description of the specific proposed actions to be taken and timing for
those actions, an estimate of the related emissions reductions, and the
specific SIP commitment by CARB with respect to each of the measures.
    Through adoption of the 2016 State Strategy, CARB is updating its
previously-approved aggregate emissions reduction commitments made as
part of the attainment demonstration for the 1997 ozone NAAQS (by 2023)
in the 2007 South Coast Ozone SIP, and CARB is adopting aggregate
emissions reduction commitments for the attainment demonstration for
the 2008 ozone NAAQS. CARB's commitments in the 2016 State Strategy are
similar in concept to those that were made in connection with the
previously approved plan.
    More specifically, through adoption of the 2016 State Strategy,
CARB has committed to bring to its Board for consideration the list of
measures contained in Attachment A to CARB Resolution 17-7 according to
the schedule set forth in Attachment A, and to achieve aggregate
emissions reductions of 113 tpd of NOX and 50 to 51 tpd of
VOC by 2023, and 111 tpd of NOX and 59 to 60 tpd of VOC by
2031 in the South Coast.\98\
---------------------------------------------------------------------------

    \98\ CARB, Resolution 17-7 (March 23, 2017), 7.
---------------------------------------------------------------------------

    In Table 4, below, we show CARB's updated aggregate emissions
reduction commitments from the 2016 State Strategy with the
corresponding commitments from the 2007 South Coast Ozone SIP for the
1997 ozone NAAQS and from the 2012 AQMP for the 1-hour ozone NAAQS.
CARB's commitments from the 2016 State Strategy are, in concept,
similar to CARB's commitments that the EPA has approved as part of the
attainment demonstrations in the 2007 South Coast Ozone SIP and 2012
AQMP. As with the earlier plans, the 2016 State Strategy includes
estimates of the emissions reductions from each of the individual new
measures, but CARB's overall commitment is to achieve the total
emission reductions necessary to attain the NAAQS.

                                                 Table 4--CARB Aggregate Emission Reduction Commitments
                                                            [Summer planning inventory, tpd]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                     Year 2022                       Year 2023                       Year 2031
                          Plan                           -----------------------------------------------------------------------------------------------
                                                                NOX             VOC             NOX             VOC             NOX             VOC
--------------------------------------------------------------------------------------------------------------------------------------------------------
2007 South Coast Ozone SIP \a\:
    Defined Measures....................................              --              --             141              54              --              --
    New Technology Measures.............................              --              --             241              40              --              --

2012 AQMP \b\:
    Defined Measures....................................              --              --              --              --              --              --
    New Technology Measures.............................             150              17              --              --              --              --
2016 South Coast Ozone SIP \c\:
    Defined and New Technology Measures.................               0               0             113           50-51             111           59-60
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ 2009 State Strategy Update, 20; also see 76 FR 57872, 57882 (September 16, 2011). Reductions are from the 2002 base year. The double-dash mark (``--
  '') indicates that no commitment was made for a given year in a given plan.
\b\ 2012 AQMP, appendix VII, page VII-46; CARB Resolution 13-3 (January 25, 2013); and letter from Richard W. Cory, Executive Officer, CARB, to Jared
  Blumenfeld, Regional Administrator, EPA Region IX, dated May 2, 2014. Reductions are from the 2008 base year. The double-dash mark (``--'') indicates
  that no commitment was made for a given year in a given plan.
\c\ 2016 State Strategy, Table 4, and CARB Resolution 17-7 (March 23, 2017). Reductions are from the 2012 base year.

    For previous South Coast ozone plans, CARB's aggregate emissions
reduction commitments distinguished between those that were to be
achieved through adoption and implementation of defined measures and
those that were to be achieved through ``new technology'' measures. In
this case, ``new technology'' measures refer to provisions in an ozone
plan for an Extreme area that anticipate development of new control
techniques or improvement of existing control technologies as provided
for in CAA section 182(e)(5). For the 2016 South Coast Ozone SIP,
CARB's aggregate emissions reduction commitments include both types of
measures. However, CARB also identifies new technology measures for
which it is requesting approval by the EPA under CAA section 182(e)(5).
Table 5 below divides CARB's estimates of emissions reductions between
new technology measures (i.e., those identified for approval under CAA
section 182(e)(5) by CARB) and the other measures (which we refer to as
``defined measures.'')

                     Table 5--Estimates of Emissions Reductions From Defined and New Technology Measures in the 2016 State Strategy
                                             [Summer planning inventory, tpd, from 2012 base year emissions]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                     VOC                                                               NOX
                     -----------------------------------------------------------------------------------------------------------------------------------
        Year                                   New technology                                                    New technology
                        Defined measures          measures                Total           Defined measures          measures                Total
--------------------------------------------------------------------------------------------------------------------------------------------------------
              2023                  9-10                    41                 50-51                     5                   108                   113
              2031                 21-22                    37                 59-60                    14                    97                   111
--------------------------------------------------------------------------------------------------------------------------------------------------------
Sources: 2016 State Strategy, Table 4. Tonnage values for defined measures determined by subtracting all the new technology measures from the total
  emission reduction estimate. The sum of the emissions values may not equal the total shown due to rounding of the numbers.

    Table 6 below lists CARB's defined measures and associated
reductions from the 2016 State Strategy. As shown in Table 6, CARB
estimates that the defined measures would reduce emissions of
NOX and VOC by 5 tpd and 9-10 tpd, respectively, by 2023 and
by 14 tpd and 21-22 tpd, respectively, by 2031. Table 6 includes only
those CARB defined measures for which CARB has developed emissions
estimates.\99\ We note that the emissions estimates shown in Table 6
are only estimates and are not binding on CARB under the terms of the
commitments CARB has made for the South Coast as part of the 2016 State
Strategy. Rather, CARB has committed to take certain regulatory and
nonregulatory actions according to the schedule in the 2016 State
Strategy and to achieve aggregate emissions reductions by 2023 and
2031. The reductions from any one measure in Table 6 could be more or
less than the estimates shown.
---------------------------------------------------------------------------

    \99\ The defined measures in the 2016 State Strategy for which
future reductions are not yet quantified include: Lower In-Use
Emission Performance Assessment for on-road light-duty vehicles
(CARB and the California Bureau of Automotive Repair); Medium and
Heavy-Duty GHG Gas Phase 2 (CARB, EPA), Innovative Technology
Certification Flexibility (CARB), and Zero-Emission Airport Shuttle
Buses (CARB) for on-road heavy-duty vehicles; Incentivize Low
Emission Efficient Ship Visits for ocean-going vessels (CARB); Zero-
Emission Off-Road Emission Reduction Assessment (CARB), Zero-
Emission Off-Road Worksite Emission Reduction Assessment (CARB), and
Transport Refrigeration Units Used for Cold Storage for off-road
equipment (CARB).

                                                  Table 6--Defined Measures in the 2016 State Strategy
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Implementation                 NOX emission          VOC emission
                                                                      ---------------------------------------   reductions (tpd)      reductions (tpd)
                 Measure                            Adoption              Time                               -------------------------------------------
                                                                         frame              Agency               2023       2031       2023       2031
--------------------------------------------------------------------------------------------------------------------------------------------------------
On-Road Light-Duty:
    Advanced Clean Cars 2...............  2020-2021..................       2026  CARB......................          -        0.6          -        0.4

On-Road Heavy-Duty:
    Lower In-Use Emission Performance     2017-2020..................      2018+  CARB......................        NYQ        NYQ       <0.1       <0.1
     Level.
    Low-NOX Engine Standard--California   2019.......................       2023  CARB......................          -          5          -          -
     Action.
    Innovative Clean Transit............  2017.......................       2018  CARB......................       <0.1        0.1       <0.1       <0.1
    Last Mile Delivery..................  2018.......................       2020  CARB......................       <0.1        0.4       <0.1       <0.1
    Incentive Funding to Achieve Further  ongoing....................       2016  CARB, SCAQMD..............          3          3        0.4        0.4
     Emission Reductions from On-Road
     Heavy Duty Vehicles \a\.
Ocean-Going Vessels:
    At-Berth Regulation Amendments......  2017-2018..................       2023  CARB......................        0.3          1       <0.1       <0.1
Off-Road Equipment:
    Zero-Emission Off-Road Forklift       2020.......................       2023  CARB......................          -          1          -        0.1
     Regulation Phase 1.
    Zero-Emission Airport Ground Support  2018.......................       2023  CARB......................       <0.1       <0.1       <0.1       <0.1
     Equipment.
    Small Off-Road Engines..............  2018-2020..................       2022  CARB......................        0.7          2          7         16
    Low-Emission Diesel Requirement.....  by 2020....................       2023  CARB......................        0.3          1        NYQ        NYQ
Consumer Products:
    Consumer Products Program...........  2019-2021..................     2020 +  CARB......................          0          0        1-2        4-5
                                         ---------------------------------------------------------------------------------------------------------------
        Total Emission Reductions.......  4..........................         14  9-10......................      21-22
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
\a\ On March 22, 2018, CARB adopted the ``South Coast On-Road Heavy-Duty Vehicle Incentive Measure.'' On April 25, 2019, the EPA proposed to approve the
  measure as achieving 1 tpd of NOX reductions in 2023. See 84 FR 17365.
NYQ means not yet quantified. A dash (-) refers to de minimis reductions.
The sum of the emissions values may not equal the total shown due to rounding of the numbers.
Source: 2016 State Strategy, Table 4; Attachment A to CARB Resolution 17-7 (March 23, 2017).

    As noted above, the 2016 State Strategy identifies certain new
technology measures for which CARB is requesting approval by the EPA
under the provisions of section 182(e)(5) of the CAA. The 2016 AQMP
does not rely on the new technology measures in the 2016 State Strategy
to demonstrate RFP, but it does rely on them for attainment of the 1997
and 2008 ozone NAAQS in the South Coast by the applicable attainment
dates.
    Table 7 below lists CARB's new technology measures and associated
reductions from the 2016 State Strategy. As shown in Table 7, CARB
estimates that the new technology measures would reduce emissions of
NOX and VOC by 108 tpd and 41 tpd by 2023, and 97 tpd and 37
tpd by 2031, respectively. As noted above in connection with CARB's
defined measures, the emissions estimates shown in Table 7 are only
estimates and are not binding on CARB under the terms of the
commitments CARB has made for the South Coast as part of the 2016 State
Strategy. Rather, CARB has committed to take certain regulatory and
nonregulatory actions according to the schedule in the 2016 State
Strategy and to achieve aggregate emissions reductions by 2023 and
2031. CARB's aggregate emissions reduction commitments for years 2023
and 2031 do not distinguish between the defined measures and the new
technology measures. The new technology measures in the 2016 State
Strategy are accompanied by an enforceable commitment by CARB to
develop, adopt and submit contingency measures by 2028 for the 2008
ozone NAAQS if the new technology measures do not achieve planned
reductions, as required under CAA section 182(e)(5).\100\ CARB's
commitment to submit contingency measures for section 182(e)(5)
purposes thus relates to attainment for the 2008 ozone NAAQS. With
respect to attainment for the 1997 ozone NAAQS, CARB is relying on the
previously-submitted and approved commitment to submit contingency
measures for section 182(e)(5) purposes from the 2007 South Coast Ozone
SIP.\101\
---------------------------------------------------------------------------

    \100\ CARB Resolution 17-8, 9.
    \101\ See 76 FR 57872, 57882 (September 16, 2011) referencing
CARB Resolution 11-22, July 21, 2011), and in a letter dated
November 18, 2011, from James N. Goldstene, Executive Officer, CARB,
to Jared Blumenfeld, Regional Administrator, EPA Region IX.

                                               Table 7--New Technology Measures in 2016 State Strategy \a\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Implementation                 NOX emission          VOC emission
                                                                      ---------------------------------------   reductions (tpd)      reductions (tpd)
                  Title                             Adoption              Time                               -------------------------------------------
                                                                         frame              Agency               2023       2031       2023       2031
--------------------------------------------------------------------------------------------------------------------------------------------------------
On-Road Light-Duty:
    Further Deployment of Cleaner         ongoing....................       2016  CARB, SCAQMD, EPA.........          7          5         16         16
     Technologies \b\.
On-Road Heavy-Duty:
    Low-NOX Engine Standard--Federal      2019.......................       2024  EPA.......................          -          7          -          -
     Action.
    Further Deployment of Cleaner         ongoing....................       2016  CARB, SCAQMD, EPA.........         34         11          4          1
     Technologies.
Aircraft:
    Further Deployment of Cleaner         ongoing....................       2016  CARB, SCAQMD, EPA.........          9         13        NYQ        NYQ
     Technologies.
Locomotives:
    More Stringent National Locomotive    2017.......................       2023  EPA.......................      < 0.1          2      < 0.1      < 0.1
     Emission Standards.
    Further Deployment of Cleaner         ongoing....................       2016  CARB, SCAQMD, EPA.........          7          3        0.3        0.3
     Technologies.
Ocean-Going Vessels:
    Tier 4 Vessel Standards.............  2016-2018..................       2025  CARB, IMO.................          -        NYQ          -        NYQ

    Further Deployment of Cleaner         ongoing....................       2016  CARB, SCAQMD, EPA.........         30         38        NYQ        NYQ
     Technologies.
Off-Road Equipment:
    Further Deployment of Cleaner         ongoing....................       2016  CARB, SCAQMD, EPA.........         21         18         21         20
     Technologies.
                                                                                -------------------------------------------
        Total Emission Reductions.......  -..........................          -  -.........................        108         97         41         37
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
\a\ CARB requested the EPA approve these measures under the provisions of section 182(e)(5) of the CAA.
\b\ In today's action we also refer to these as new technology measures.
NYQ means not yet quantified. A dash (-) refers to de minimis reductions.
The sum of the emissions values may not equal the total shown due to rounding of the numbers.
Source: 2016 State Strategy, Table 4; Attachment A to CARB Resolution 17-7 (March 23, 2017).

    In its 2016 State Strategy, CARB commits to achieving the aggregate
emissions reductions needed in the South Coast for attaining the 1997
and 2008 ozone NAAQS from the defined and new technology measures. Even
though the District does not have a new technology emissions reduction
commitment in the 2016 AQMP, its numerous incentive programs in tables
4-2 and 4-4 of the 2016 AQMP will help advance new control technologies
that will achieve long-term reductions and ultimately reduce CARB's
remaining commitment for reductions in 2023 and 2031.
    SCAQMD's Technology Advancement Office (TAO) is responsible for
expediting the development, demonstration and commercialization of
cleaner technologies and clean-burning fuels in the South Coast. TAO's
mobile source projects have included development and demonstration of
less-polluting automobiles, buses, trucks, construction equipment,
boats, locomotives and other off-road vehicles involving advancements
in engine design, improved batteries, fuel cells, and improved
powertrains for electric vehicles. Other projects involve adapting or
designing vehicles to run on clean fuels and developing the
infrastructure needed to produce and deliver those fuels.\102\ TAO's
projects for stationary sources have included a wide array of low-
NOX combustion systems, low-VOC coatings and processes, and
clean energy production systems including fuel cells, solar power, and
other renewable energy systems.\103\ The technical areas currently
identified by TAO as the highest priority include fuel cells for
transportation and power generation; diesel alternatives; electric and
hybrid-electric technologies; off-road applications of alternative fuel
technologies; VOC reduction technologies for stationary sources; and
infrastructure development.\104\
---------------------------------------------------------------------------

    \102\ SCAQMD technology advancement web page at http://yourstory.aqmd.gov/home/technology, February 6, 2019.
    \103\ Id.
    \104\ Id.
---------------------------------------------------------------------------

    In its 2016 State Strategy, CARB builds on and updates the new
technology measures in prior state strategies (e.g., the 2007 State
Strategy as revised in 2009 and 2011). To implement the long-term
strategy, CARB has committed to a process that will help ensure that
the long-term measures are adopted and that reductions are achieved by
the beginning of the last full ozone season before the attainment date.
CARB is coordinating a government, private, and public effort to
establish emission goals for critical mobile and stationary emission
source categories. The effort includes periodic assessment of
technology advancement opportunities and updates to its Board and the
public regarding new emission control opportunities and progress in
achieving the long-term measure reductions. CARB's commitment for
implementing the long-term strategy also includes reporting back to its
Board within one year of adoption of the 2016 State Strategy, and
yearly thereafter.\105\ This report will include:
---------------------------------------------------------------------------

    \105\ 2016 State Strategy, 46.
---------------------------------------------------------------------------

    1. The status of partnerships with the South Coast, San Joaquin
Valley, the EPA, other government agencies, and the private sector to
pursue research, demonstration, and pilot projects for further
advancement of zero and near-zero emission technologies;
    2. The status of the Financial Incentives Funding Action Plan,
progress in identifying and implementing funding mechanisms, and status
of State level incentive programs and allocation of funding to the
South Coast and San Joaquin Valley regions;
    3. The status of technology assessments, emerging technologies and
emissions reduction opportunities. CARB staff will also report on
implementation of actions identified by the SCAQMD and San Joaquin
Valley Air Pollution Control District as well as actions contained in
the California Sustainable Freight Action Plan, the 2030 Target Scoping
Plan Update, SB 375, and other complementary efforts and the criteria
pollutant benefits that result from these actions; and
    4. Recommendations on the development of further regulatory
measures and schedules for development for inclusion in the SIP.\106\
---------------------------------------------------------------------------

    \106\ E.g., On March 22, 2018, CARB staff conducted a public
meeting to brief the Board on substantial progress made in
implementing various elements of the 2016 State Strategy and 2016
AQMP. The staff presentation can be viewed at https://www.arb.ca.gov/board/books/2018/032218/18-2-5pres.pdf?utm_medium=email&utm_source=govdelivery.
---------------------------------------------------------------------------

    Approximately 70 percent of the reductions needed to meet the ozone
standard in the South Coast in 2031 comes from existing or proposed
regulatory actions. This includes ongoing implementation of the
existing control program, combined with new regulatory measures
identified in the 2016 State Strategy. The regulatory approach forms
the core of the strategy. The remaining 30 percent of reductions is
from additional efforts to enhance the deployment of cleaner
technologies through new incentive or new regulatory actions. These
actions will be implemented through the cleaner technologies measures
for each mobile sector to provide further emissions reductions from the
deployment of technologies necessary to meet the South Coast's Extreme
ozone nonattainment area needs. The approaches contained in the cleaner
technology measures include:
     Incentive programs to further accelerate technology
penetration;
     Identification of additional regulatory approaches based
on further technology assessments;
     Increased efficiency in moving people and freight;

     Use of emerging transportation technologies, such as
intelligent transportation systems and autonomous and connected
vehicles; and
     Further federal actions, including support for
demonstration programs, and supporting policies to achieve reductions
from sources under federal and international regulatory authority.
    The specific combination of approaches to achieve reductions under
these cleaner technologies concepts will vary by source sector and the
timing of needed reductions. Further details regarding the approach for
each sector and identification of technologies are available in the
measure descriptions in Chapter 4 (``State SIP Measures'') of the 2016
State Strategy.
    To achieve the emission reductions from the cleaner technology
measures included in the 2016 State Strategy, the South Coast is also
identifying mechanisms under its local authority to achieve emission
reductions from mobile sources within the region. Given the need for
emissions reductions, significant investments to support incentive
programs will be critical to accelerate the penetration of the cleanest
technologies in the South Coast. CARB staff has been working with
SCAQMD and the EPA to identify funding strategies and ensure
appropriate mechanisms are in place for an approvable SIP.
c. Attainment Demonstration
    The 2016 AQMP includes a new attainment demonstration for the 2008
ozone NAAQS and updated attainment demonstrations for the 1-hour and
1997 ozone NAAQS. In December 2018, CARB submitted the 1-Hour Ozone
Update, which revises the 1-hour ozone attainment demonstration in the
2016 AQMP. Each of the attainment demonstrations includes enforceable
commitments for additional reductions necessary for attainment as
discussed in the previous sections. To determine the additional
NOX reductions needed, the State and District evaluated
scenarios for a controlled emissions level of NOX necessary
for attainment of the ozone standards. The ``controlled emissions
level'' represents, based on modeling scenarios and implementation of
adequate control measures, the remaining attainment year NOX
inventory consistent with the modeling used to demonstrate attainment.
Table 8 below summarizes the controlled emissions level of
NOX selected by the District and CARB as necessary for
attainment of the ozone standards.

                          Table 8--NOX Controlled Emissions Level for Ozone Attainment
----------------------------------------------------------------------------------------------------------------
          Attainment year                     2022                      2023                      2031
----------------------------------------------------------------------------------------------------------------
Standard..........................  1-hour Ozone............  1997 Ozone..............  2008 Ozone.
Controlled Emissions Level (tpd)..  269.....................  141.....................  96.
----------------------------------------------------------------------------------------------------------------

i. Updated Attainment Demonstration for the 1-Hour Ozone NAAQS
    The 2016 AQMP updates the EPA-approved 1-hour ozone attainment
demonstration from the 2012 AQMP to reflect updated emissions
inventories, photochemical models and modeling techniques. In December
2018, CARB submitted to the EPA the 1-Hour Ozone Update, which revises
the 1-hour ozone attainment demonstration in the 2016 AQMP to account
for updated emissions inventories that were not available at the time
the 1-hour ozone attainment demonstration was completed for the 2016
AQMP.
    Table 9 below summarizes the updated attainment demonstration for
the 1-hour ozone NAAQS by listing the base year (2012) emissions level,
the modeled attainment emissions level, and the reductions that the
District has committed to achieve through adoption of the 2016 AQMP.
The updated 1-hour ozone attainment demonstration does not rely on
emissions reductions from the 2016 State Strategy. Also, unlike the
approved 1-hour ozone attainment demonstration from the 2012 AQMP, the
updated attainment demonstration does not rely on new technology
measures.
    As shown in Table 9, the majority of emission reductions needed for
attaining the 1-hour ozone NAAQS by 2022 comes from baseline measures.
These account for approximately 92 percent of the NOX (233
tpd) and 95 percent of the VOC (113 tpd) reductions needed for
attainment of the 1-hour ozone NAAQS. The baseline measures reflect
CARB rules adopted by November 2015 and District rules adopted by
December 2015.\107\ Based on the modeling analysis in the 1-Hour Ozone
Update, the District determined that additional reductions of 21 tpd of
NOX and 6 tpd of VOC would be sufficient for demonstrating
attainment of the 1-hour ozone NAAQS by 2022. The 2016 South Coast
Ozone SIP relies on the District's enforceable commitments to achieve
aggregate emissions reductions through implementation of the measures
described above in section III.D.2.b.i of this document to provide the
reductions necessary to achieve the 1-hour ozone NAAQS by 2022.
---------------------------------------------------------------------------

    \107\ See the TSD for this proposed action for a list of
District rules with post-2012 compliance dates affecting future
baseline emissions projections. Also see 2016 AQMP, Appendix VI-C,
Attachment VI-C-1 for a list of CARB rules adopted post-2012.

     Table 9--Summary of 1-Hour Ozone NAAQS Attainment Demonstration
                    [Summer planning inventory, tpd]
------------------------------------------------------------------------
                                                NOX           VOC \a\
------------------------------------------------------------------------
A. 2012 Base Year Emissions Level \b\...           522.5           499.7
B. 2022 Attainment Year Baseline                   286.8           382.7
 Emissions Level \c\....................
C. Set-Aside (Phase-Out of Toxics,                   3.1             4.5
 General Conformity, SIP Reserve) \c\...
D. 2022 Adjusted Baseline (i.e.,                   289.9           387.2
 includes Set-Aside) (B + C)............
E. 2022 Modeled Attainment Emissions               269.3           381.2
 Level \c\..............................
F. Total Reductions Needed from 2012               253.2           118.5
 Base Year Levels to Demonstrate
 Attainment (A-E).......................
G. Reductions from Baseline (i.e.,                 232.6           112.5
 adopted) Measures, as adjusted to
 account for Set-Aside (A-D)............
H. Reductions from District's Aggregate             21.0             6.1
 Emission Reduction Commitments from
 2016 AQMP \d\..........................
I. Reductions from CARB's Aggregate                    0               0
 Emission Reduction Commitments from
 2016 State Strategy--Defined Measures..

J. Reductions from CARB's Aggregate                    0               0
 Emission Reduction Commitments from
 2016 State Strategy--New Technology
 Measures...............................
K. Total Reductions from District and               21.0             6.1
 CARB Commitments in 2016 AQMP and 2016
 State Strategy (H + I + J).............
L. Total Reductions from Baseline                  253.6           118.6
 Measures plus District and CARB
 Commitments in 2016 AQMP and 2016 State
 Strategy (G + K).......................
M. 2022 Emissions with Reductions from             268.9           381.1
 Control Strategy (A-L).................
                                         -------------------------------
Attainment demonstrated?................                Yes
------------------------------------------------------------------------
Notes and sources:
\a\ While attainment of the 8-hour ozone NAAQS in the South Coast is
  dependent almost exclusively on NOX reductions, both NOX and VOC
  emissions reductions reduce 1-hour ozone levels.
\b\ 2016 AQMP, Appendix III, Attachment B.
\c\ 1-Hour Ozone Update, 7.
\d\ 2016 AQMP, Table 4-9.

ii. Updated Attainment Demonstration for the 1997 Ozone NAAQS
    In the 2016 AQMP and 2016 State Strategy, the District and State
collectively update the attainment demonstration for the 1997 ozone
NAAQS. The 2016 AQMP and 2016 State Strategy update the EPA-approved
1997 ozone NAAQS ozone attainment demonstration from the 2007 South
Coast Ozone SIP to reflect updated emissions inventories, photochemical
models and modeling techniques. Table 10 below summarizes the updated
attainment demonstration for the 1997 ozone NAAQS by listing the base
year (2012) emissions level, the modeled attainment emissions level,
and the reductions that the District and CARB have committed to achieve
through adoption of the 2016 AQMP and 2016 State Strategy.
    As shown in Table 10, the majority of emission reductions needed
for attaining the 1997 ozone NAAQS by 2023 comes from baseline
measures. These account for approximately 66 percent of the
NOX (251 tpd) reductions needed for attainment of the 1997
ozone NAAQS. The 2016 South Coast Ozone SIP relies on the District's
and CARB's enforceable commitments to achieve aggregate emission
reductions through implementation of the measures described above in
section III.D.2.b.i and III.D.2.b.ii of this document to provide the
reductions (beyond those from baseline measures) that are necessary to
achieve the 1997 ozone NAAQS by 2023.

     Table 10--Summary of 1997 Ozone NAAQS Attainment Demonstration
                    [Summer planning inventory, tpd]
------------------------------------------------------------------------
                                                              NOX \a\
------------------------------------------------------------------------
A. 2012 Base Year Emissions Level \b\...................             522
B. 2023 Attainment Year Baseline Emissions Level \b\....             269
C. Set-Aside (Phase-Out of Toxics, General Conformity,                 3
 SIP Reserve) \c\.......................................
D. 2023 Adjusted Baseline (i.e., includes Set-Aside) (B              272
 + C)...................................................
E. 2023 Modeled Attainment Emissions Level \d\..........             141
F. Total Reductions Needed from 2012 Base Year Levels to             381
 Demonstrate Attainment (A-E)...........................
G. Reductions from Baseline (i.e., adopted) Measures, as             250
 adjusted to account for Set-Aside (A-D)................
H. Reductions from District's Aggregate Emission                      23
 Reduction Commitments from 2016 AQMP \e\...............
I. Reductions from CARB's Aggregate Emission Reduction                 5
 Commitments from 2016 State Strategy--Defined Measures
 \f\....................................................
J. Reductions from CARB's Aggregate Emission Reduction               108
 Commitments from 2016 State Strategy--New Technology
 Measures \f\...........................................
K. Total Reductions from District and CARB Commitments               136
 in 2016 AQMP and 2016 State Strategy (H + I + J).......
L. Total Reductions from Baseline Measures plus District             386
 and CARB Commitments in 2016 AQMP and 2016 State
 Strategy (G + K).......................................
M. 2023 Emissions with Reductions from Control Strategy              136
 (A-L)..................................................
Attainment demonstrated?................................             Yes
------------------------------------------------------------------------
Notes and sources:
\a\ VOC emissions are not included in this table because attainment of
  the 8-hour ozone NAAQS in the South Coast is dependent almost
  exclusively on NOX reductions.
\b\ 2016 AQMP, Appendix III, Attachment B; Year 2023 baseline estimates
  for aircraft, oceangoing vessels, and commercial harbor craft have
  been updated based on information contained in the 2018 SIP Update,
  page A-35.
\c\ 2016 AQMP, Appendix III, pages II-2-90 through III-2-92.
\d\ 2016 AQMP, Appendix V, page V-4-2.
\e\ 2016 AQMP, Table 4-10.
\f\ 2016 State Strategy, Table 4; CARB's aggregate emission reduction
  commitment is for 113 tpd of NOX reductions by 2023; for analytical
  purposes only, we have distinguished the estimated emissions
  reductions for defined measures from those for new technology
  measures.

iii. Attainment Demonstration for the 2008 Ozone NAAQS
    In the 2016 AQMP and 2016 State Strategy, the District and State
collectively demonstrate attainment of the 2008 ozone NAAQS. Table 11
below summarizes the attainment demonstration for the 2008 ozone NAAQS
by listing the base year (2012) emissions level, the modeled attainment
emissions level, and the reductions that the District and CARB have
committed

to achieve through adoption of the 2016 AQMP and 2016 State Strategy.
    As shown in Table 11, the majority of emission reductions needed
for attaining the 2008 ozone NAAQS by 2031 comes from baseline
measures. These account for approximately 66 percent of the
NOX (283 tpd) reductions needed for attainment of the 2008
ozone NAAQS. The 2016 South Coast Ozone SIP relies on the District's
and CARB's enforceable commitments to achieve aggregate emission
reductions through implementation of the measures described above in
section III.D.2.b.i and III.D.2.b.ii of this document to provide the
reductions (beyond those from baseline measures) that are necessary to
achieve the 2008 ozone NAAQS by 2031.

     Table 11--Summary of 2008 Ozone NAAQS Attainment Demonstration
                    [Summer planning inventory, tpd]
------------------------------------------------------------------------
                                                              NOX \a\
------------------------------------------------------------------------
A. 2012 Base Year Emissions Level \b\...................             522
B. 2031 Attainment Year Baseline Emissions Level \b\....             238
C. Set-Aside (Phase-Out of Toxics, General Conformity,                 1
 SIP Reserve) \c\.......................................
D. 2031 Adjusted Baseline (i.e., includes Set-Aside) (B              239
 + C)...................................................
E. 2031 Modeled Attainment Emissions Level \d\..........              96
F. Total Reductions Needed from 2012 Base Year Levels to             426
 Demonstrate Attainment (A-E)...........................
G. Reductions from Baseline (i.e., adopted) Measures, as             283
 adjusted to account for Set-Aside (A-D)................
H. Reductions from District's Aggregate Emission                      31
 Reduction Commitments from 2016 AQMP \e\...............
I. Reductions from CARB's Aggregate Emission Reduction                14
 Commitments from 2016 State Strategy--Defined Measures
 \f\....................................................
J. Reductions from CARB's Aggregate Emission Reduction                97
 Commitments from 2016 State Strategy--New Technology
 Measures \f\...........................................
K. Total Reductions from District and CARB Commitments               142
 in 2016 AQMP and 2016 State Strategy (H + I + J).......
L. Total Reductions from Baseline Measures plus District             425
 and CARB Commitments in 2016 AQMP and 2016 State
 Strategy (G + K).......................................
M. 2031 Emissions with Reductions from Control Strategy               97
 (A-L)..................................................
Attainment demonstrated?................................             Yes
------------------------------------------------------------------------
Notes and sources:
\a\ VOC emissions are not included in this table because attainment of
  the 8-hour ozone NAAQS in the South Coast is dependent almost
  exclusively on NOX reductions.
\b\ 2016 AQMP, Appendix III, Attachment B; Year 2031 baseline estimates
  for aircraft, oceangoing vessels, and commercial harbor craft have
  been updated based on information contained in the 2018 SIP Update,
  page A-35.
\c\ 2016 AQMP, Appendix III, pages II-2-90 through III-2-92.
\d\ 2016 AQMP, Appendix V, page V-4-2.
\e\ 2016 AQMP, Table 4-11.
\f\ 2016 State Strategy, Table 4; CARB's aggregate emission reduction
  commitment is for 111 tpd of NOX reductions by 2031; for analytical
  purposes only, we have distinguished the estimated emissions
  reductions for defined measures from those for new technology
  measures.

3. The EPA's Review of the State's Submission
a. Photochemical Modeling
    To approve a SIP's attainment demonstration, the EPA must make
several findings. First, we must find that the demonstration's
technical bases, including the emissions inventories and air quality
modeling, are adequate. As discussed above in section III.A of this
action, we are proposing to approve the base year emissions inventory
and to find that the future year emissions projections in the 2016 AQMP
reflect appropriate calculation methods and that the latest planning
assumptions are properly supported by SIP-approved stationary and
mobile source measures.
    With respect to the photochemical modeling in the 2016 AQMP and 1-
Hour Ozone Update, based on our review of appendix V of the 2016 AQMP
and the 1-Hour Ozone Update, the EPA finds that the modeling is
adequate for purposes of supporting the attainment demonstration.\108\
First, we note the extensive discussion of modeling procedures, tests,
and performance analyses called for in the Modeling Protocol (i.e.,
chapter 2 of Appendix V of the 2016 AQMP) and the good model
performance. Second, we find the WRF meteorological model results and
performance statistics including hourly time series graphs of wind
speed, direction, and temperature for the South Coast, to be
satisfactory and consistent with our Modeling Guidance.\109\
Performance was evaluated for each month in each zone for the entire
year of 2012.\110\ Diurnal variation of temperature, humidity and
surface wind are well represented by WRF. Geographically, winds are
predicted most accurately at the inland urban receptor sites. Accurate
wind predictions in this region of elevated ozone concentrations is one
of the most critical factors to simulate chemical transport. Overall,
the daily WRF simulation for 2012 provided representative
meteorological fields that characterized the observed conditions well.
---------------------------------------------------------------------------

    \108\ The EPA's review of the modeling and attainment
demonstration is discussed in greater detail in section V. Modeling
and Attainment Demonstration of the TSD.
    \109\ Modeling Guidance, 30.
    \110\ Temperature, water vapor mixing ratio, and wind speed were
evaluated in terms of normalized gross bias and normalized gross
error.
---------------------------------------------------------------------------

    The model performance statistics for ozone are described in
chapters 5 and 8 of Appendix V and are based on the statistical
evaluation recommended in the Modeling Guidance. Model performance was
provided for 8-hour and 1-hour daily maximum ozone for each of the
South Coast sub-regions.\111\ The model performance varied by zone,
with over-prediction in the ``Coastal zone'' and under-prediction in
the ``San Fernando,'' and ``Foothills'' zones. The model ozone
predictions in the ``Urban Receptor'' zone, where the design site
station is located, agree reasonably well with the measurements.\112\
The 2016

AQMP also presents ozone frequency distributions, scatter plots, and
plots of bias against concentration. The scatter and density scatter
plots show low bias at high concentrations, and higher bias at low
concentrations. The modeling guidance requires the use of only the top
10 days in the RRF calculation, indicating that the modeling capability
to predict high concentrations is more important than the prediction of
low concentrations. The supplemental hourly time series show generally
good performance, though many individual daily ozone peaks are
underpredicted. Note that, because only relative changes are used from
the modeling, the underprediction of absolute ozone concentrations does
not mean that future concentrations will be underestimated. The 2016
AQMP's unmonitored area analysis showed concentrations below 1997 and
2008 ozone NAAQS for all locations.\113\ This analysis adds assurance
to the attainment demonstrations that all locations in the South Coast
will attain the 1997 ozone NAAQS by 2023 and the 2008 ozone NAAQS by
2031. In addition, the weight of evidence analyses presented in the
2016 AQMP and 1-Hour Update provide additional information with respect
to the sensitivity to emission changes and improve the understanding of
the model performance. We are proposing to find the air quality
modeling adequate to support the updated attainment demonstrations for
the 1-hour ozone and 1997 ozone NAAQS and the attainment demonstration
for the 2008 ozone NAAQS, based on reasonable meteorological and ozone
modeling performance, supported by the unmonitored area and weight of
evidence analyses.
---------------------------------------------------------------------------

    \111\ These zones are represented by the following ozone
monitoring sites: ``Coastal''(Costa Mesa, LAX, Long Beach, Mission
Viejo, West Los Angeles); ``Urban Source''(Anaheim, Central Los
Angeles, Compton, La Habra, Pico Rivera, Pomona) ''San
Fernando''(Reseda, Santa Clarita, Burbank); ``Foothills''(Azusa,
Glendora, Pasadena); and ``Urban Receptor''(Crestline, Fontana, Lake
Elsinore, Mira Loma, Redlands, Rubidoux, San Bernardino, Upland).
    \112\ Table V-5-7; 2012 Base Year 8-Hour Average Ozone
Performance for Days When Regional 8-Hour Maximum >= 60 parts per
billion in the ``Urban Receptor'' region. Appendix V of the 2016
AQMP, page V-5-13.
    \113\ Appendix V of the 2016 AQMP, Unmonitored Area Analysis, V-
5-28 to V-5-35. Spatial projections of the 8-hour and 1-hour design
values were also provided. See Appendix V of the 2016 AQMP, Spatial
Projections of 8-Hour Ozone Design Values, pages V-5-25 to V-5-28,
and 1-Hour Ozone Update, Spatial Projections of 1-Hour Ozone Design
Values, p. 10-11.
---------------------------------------------------------------------------

b. Control Strategy for Attainment
    Second, we must find that the emissions reductions that are relied
on for attainment are creditable and are sufficient to provide for
attainment. As shown in tables 9, 10, and 11 above, the 2016 South
Coast Ozone SIP relies on adopted measures to achieve a significant
portion of the emissions reductions needed to attain the 1-hour ozone
NAAQS by 2022, the 1997 ozone NAAQS by 2023, and the 2008 ozone NAAQS
by 2031. The balance of the reductions needed for attainment is in the
form of enforceable commitments to take certain specific regulatory and
nonregulatory actions within prescribed periods and to achieve
aggregate tonnage reductions of VOC or NOX by specific years
in the South Coast. The enforceable commitments made by the District
and CARB through adoption of the 2016 AQMP and 2016 State Strategy are
similar to the enforceable commitments that the EPA has approved as
part of attainment demonstrations in previous California air quality
plans and that have withstood legal challenge.\114\
---------------------------------------------------------------------------

    \114\ See Committee for a Better Arvin v. EPA, 786 F.3d 1169
(9th Cir. 2015) (approval of state commitments to propose and adopt
emissions control measures and to achieve aggregate emissions
reductions for San Joaquin Valley ozone and particulate matter plans
upheld); Physicians for Social Responsibility--Los Angeles v. EPA,
9th Cir., memorandum opinion issued July 25, 2016 (approval of air
district commitments to propose and adopt measures and to achieve
aggregate emissions reductions for South Coast 1-hour ozone plan
upheld).
---------------------------------------------------------------------------

    As noted in the preceding paragraph the EPA has previously accepted
enforceable commitments in lieu of adopted control measures in
attainment demonstrations when the circumstances warrant them and when
the commitments meet specific criteria. We believe that, with respect
to all three ozone NAAQS, circumstances warrant the consideration of
enforceable commitments as part of the attainment demonstrations for
the South Coast. First, as shown in tables 9, 10 and 11 above, a
substantial portion of the emission reductions needed to demonstrate
attainment in the South Coast come from measures adopted prior to
adoption and submittal of the 2016 AQMP and 2016 State Strategy. As a
result of these State and District efforts, most emissions sources in
the South Coast are currently subject to stringent emission limitations
and other requirements, leaving few opportunities to further reduce
emissions. In the 2016 AQMP and 2016 State Strategy, the District and
CARB identified potential control measures that could provide many of
the additional emissions reductions needed for attainment. These are
described above in sections III.D.2.b.i and III.D.2.b.ii of this
action. However, the timeline needed to develop, adopt, and implement
these measures went beyond the required submittal date for the
attainment demonstration for the South Coast for the 2008 ozone NAAQS.
These circumstances warrant the District's and CARB's reliance on
enforceable commitments as part of the attainment demonstrations for
the 1-hour, 1997, and 2008 ozone NAAQS.
    Given the State's demonstrated need for reliance on enforceable
commitments, we now consider the three factors the EPA uses to
determine whether the use of enforceable commitments in lieu of adopted
measures to meet CAA planning requirements is approvable: (a) Does the
commitment address a limited portion of the statutorily-required
program; (b) is the state capable of fulfilling its commitment; and (c)
is the commitment for a reasonable and appropriate period of time.
i. Commitments are a Limited Portion of Required Reductions
    For the first factor, we look to see if the commitment addresses a
limited portion of a statutory requirement and review the amount of
emissions reductions needed to demonstrate attainment in a
nonattainment area. For this calculation, reductions assigned to the
new technologies provision (i.e., CAA section 182(e)(5) new technology
measures) are not counted as commitments.\115\
---------------------------------------------------------------------------

    \115\ CAA section 182(e)(5) specifically allows EPA to approve
an attainment demonstration that relies on reductions from new
technologies. This provision is separate from the requirement in CAA
section 172(c)(6) for enforceable emissions limitations under which
enforceable commitments are considered. As a result, reductions
attributed in the attainment demonstration to new technologies are
not considered part of the State's enforceable commitments for
purposes of determining the percentage of reductions needed for
attainment that remain as commitments.
---------------------------------------------------------------------------

    Tables 9, 10, and 11 above show emission reductions needed to
demonstrate attainment of the 1-hour, 1997, and 2008 8-hour NAAQS in
the South Coast and the aggregate emissions reductions commitments by
the District and CARB. Based on these values, we have calculated the
percent of required reductions that would come from enforceable
commitments by the District and CARB (other than new technology
measures). See Table 12 below.

              Table 12--Enforceable Aggregate Commitments as a Percentage of Required Reductions a
----------------------------------------------------------------------------------------------------------------
                                                               2022                    2023            2031
                 Attainment year                 ---------------------------------------------------------------
                                                        NOX             VOC             NOX             NOX
----------------------------------------------------------------------------------------------------------------
Tons per day....................................              21               6              28              45
Percentage of Required Reductions \b\...........              8%              5%              7%             11%
----------------------------------------------------------------------------------------------------------------
Notes and sources:
\a\ CAA section 182(e)(5) reductions are not included below.
\b\ The percentage of required emissions from enforceable commitments is calculated by dividing the sum of Rows
  H and I in tables 9, 10, and 11 above by Row F.

    As shown in Table 12, when compared to the total reductions needed
to demonstrate attainment (not including the CAA section 182(e)(5)
reductions in the attainment demonstration), the remaining portion of
the enforceable commitments represents a small fraction of the
reductions needed. Historically, the EPA has approved SIPs with
enforceable commitments in the range of approximately 10 percent of the
total needed reductions for attainment.\116\ Thus, we find that the
District's and CARB commitments in the 2016 AQMP and 2016 State
Strategy for the South Coast address a limited proportion of the
required emission reductions.
---------------------------------------------------------------------------

    \116\ See our approval of the following plans: San Joaquin
Valley (SJV) PM10 Plan at 69 FR 30005 (May 26, 2004); SJV
1-hour ozone plan at 75 FR 10420 (March 8, 2010); Houston-Galveston
1-hour ozone plan at 66 FR 57160 (November 14, 2001); South Coast
1997 8-hour ozone plan at 77 FR 12674 (March 1, 2012); and South
Coast 1-hour ozone plan at 79 FR 52526 (September 3, 2014).
---------------------------------------------------------------------------

ii. The State Is Capable of Fulfilling its Commitment
    For the second factor, we consider whether the District and CARB
are capable of fulfilling their commitments. CARB adopted and submitted
the 2016 State Strategy to achieve the reductions necessary from mobile
sources, fuels, and consumer products to meet ozone and
PM2.5 NAAQS over the next 15 years. The 2016 State Strategy
builds on the 2007 State Strategy and its revisions. The 2016 State
Strategy shows that CARB has made significant progress in fulfilling
its enforceable commitments from the 2007 South Coast Ozone SIP. The
District has also made significant progress in meeting its enforceable
commitments in its prior AQMPs.
    The District and CARB also have a history of funding incentive
grant programs to reduce emissions from the on- and off-road engine
fleets. CARB has also continued to work with the District on defining
funding needs and mechanisms for implementing the 2016 State Strategy.
Working with CARB, the District has estimated that sustained funding
levels of approximately $1 billion per year through 2031 will be needed
to support the necessary scale of technology transformation. The
District developed a Draft Financial Incentives Funding Action Plan
(``Funding Action Plan'') \117\ that describes existing sources of
funding, new funding opportunities, activities that will be undertaken
to pursue each potential funding mechanism, as well as a schedule and
reporting process. As part of this effort, the District has identified
a broad spectrum of potential funding mechanisms that could meet the
region's funding needs. The District established a stakeholder-based
2016 AQMP Funding Working Group that began meeting in August 2017 to
help further develop and implement the Funding Action Plan. CARB will
continue to collaborate with the District on the Funding Action Plan,
as well as play a key role in implementing state-level efforts that are
facilitating the transition to cleaner technologies, such as the
California Sustainable Freight Action Plan, the ZEV Action Plan, and
the Transformative Climate Communities program.
---------------------------------------------------------------------------

    \117\ See http://www.aqmd.gov/docs/default-source/clean-air-plans/air-quality-management-plans/2016-air-quality-management-plan/draftfinancialincentivefunddec2016.pdf.
---------------------------------------------------------------------------

    Given CARB's and the District's efforts to date to reduce
emissions, we believe that the State and District are capable of
meeting their enforceable commitments to adopt measures that will
reduce emissions to the levels needed to attain the 1-hour, 1997, and
2008 ozone NAAQS in the South Coast by the 2022, 2023, and 2031
attainment years, respectively.
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. To meet the
commitments to adopt measures to reduce emissions to the levels needed
to attain the 1-hour, 1997, and 2008 ozone NAAQS in the South Coast,
the 2016 AQMP and 2016 State Strategy includes ambitious rule
development, adoption, and implementation schedules. The District and
CARB have committed to take the necessary actions and to achieve the
remaining reductions by 2022, 2023, and 2031. We believe that this
period is appropriate given the technological and economic challenges
associated with the control measures that will be needed to achieve
these reductions and given the procedures under state law for
development and adoption of these measures. In addition, these
reductions are not needed to meet RFP targets for the 2008 ozone NAAQS,
and the adoption and submission timeframe ensures adequate time for
implementation by the beginning of the last full ozone season
applicable to each of the three ozone standards addressed in the 2016
South Coast Ozone SIP. Thus, the commitments are for a reasonable and
appropriate period of time.
iv. CAA Section 182(e)(5) New Technology Provisions
    For ozone nonattainment areas classified as Extreme, the CAA
recognizes that an attainment demonstration may need to rely to a
certain extent on new or evolving technologies, given the long time
period between developing the initial plan and attaining the standard,
and the degree of emissions reductions needed to attain. To address
these needs, CAA section 182(e)(5) authorizes the EPA to approve
provisions in an Extreme area plan which ``anticipate development of
new control techniques or improvement of existing control
technologies,'' and to approve an attainment demonstration based on
such provisions, if the state demonstrates that: (1) Such provisions
are not necessary to achieve the incremental emission reductions
required during the first 10 years after November 15, 1990; and (2) the
state has submitted enforceable commitments to develop and adopt
contingency measures to be implemented if the anticipated technologies
do not achieve the planned reductions. The state must submit these
contingency measures to the EPA no later than 3 years before

proposed implementation of these long-term measures, and the
contingency measures must be ``adequate to produce emissions reductions
sufficient, in conjunction with other approved plan provisions, to
achieve the periodic emissions reductions required by [CAA sections
182(b)(1) or (c)(2)] and attainment by the applicable dates.'' \118\
---------------------------------------------------------------------------

    \118\ Id.
---------------------------------------------------------------------------

    The General Preamble further provides that the new technology
measures contemplated by section 182(e)(5) may include those that
anticipate future technological developments as well as those that
require complex analyses, decision making, and coordination among a
number of government agencies.\119\ An attainment demonstration that
relies on long-term new technology measures under section 182(e)(5)
must identify any such measures and contain a schedule outlining the
steps leading to final development and adoption of the measures.\120\
---------------------------------------------------------------------------

    \119\ General Preamble, 13524.
    \120\ Id.
---------------------------------------------------------------------------

    CARB and the SCAQMD have demonstrated a clear need for emissions
reductions from new and improved control technologies to reduce air
pollution in the South Coast. The adopted control measures and
enforceable commitments, discussed above, provide the majority, but not
all, of the balance of the emissions reductions needed to attain the
1997 and 2008 ozone NAAQS by 2023, and 2031, respectively. (The updated
attainment demonstration in the 2016 South Coast Ozone SIP for the 1-
hour ozone NAAQS does not rely on CAA section 182(e)(5) new technology
provisions.)
    Through adoption of the 2016 State Strategy, CARB is updating its
previously-approved commitments from the 2007 South Coast Ozone SIP to
achieve aggregate emissions reductions from defined and new technology
measures for the 1997 ozone NAAQS. More specifically, CARB is replacing
its commitments to achieve 141 tpd of NOX reductions and 54
tpd of VOC reductions from defined measures and to achieve 241 tpd of
NOX reductions and 40 tpd of VOC reductions from new
technology measures by 2023 with a combined (i.e., defined and new
technology measures together in a single commitment) commitment to
achieve 113 tpd of NOX reductions and 50-51 tpd of VOC
reductions by 2023.
    We find that CARB's updated commitment \121\ for the 1997 ozone
NAAQS in the 2016 State Strategy satisfies the criteria in CAA section
182(e)(5) for the following reasons: (1) The 2016 South Coast Ozone SIP
does not rely on the new technology measure reductions until the
attainment year (2023); (2) it does not rely on new technology measure
reductions to achieve RFP milestones for the first 10 years after
designation (for the 1997 ozone NAAQS); and (3) the previously-approved
commitment by CARB to submit contingency measures by 2020 (as necessary
to cover any shortfall from new technology measures) remains in effect.
Moreover, we find that the 2016 State Strategy adequately describes the
new technology measures by, among other things, identifying a schedule
outlining the specific actions to be taken to develop and adopt the
measures and achieve the related reductions.
---------------------------------------------------------------------------

    \121\ We approved CARB's commitment for contingency measures to
cover any new technology measures shortfall as part of our approval
of the 2007 South Coast Ozone SIP. 77 FR 12674, at 12695 (March 1,
2012) (approval of section 182(e)(5) contingency measure commitment
in CARB Resolution 11-22 (July 21, 2011).
---------------------------------------------------------------------------

    With respect to attainment of the 2008 ozone NAAQS for the South
Coast, through adoption of the 2016 State Strategy, CARB commits to
achieve aggregate emissions reductions from a combination of defined
and new technology measures of 111 tpd of NOX and 59-60 tpd
of VOC by 2031. As described above with respect to CARB's updated
commitment for the 1997 ozone NAAQS, we recognize that the 2016 State
Strategy does not rely on the new technology measure reductions until
the attainment year (2031) and thus, does not rely on them to achieve
RFP milestones for the first 10 years after designation (for the 2008
ozone NAAQS). Also, we find that CARB's description of the new
technology measures in the 2016 State Strategy to be adequate. For the
2008 ozone NAAQS, CARB has submitted a new commitment to develop, adopt
and submit contingency measures by 2028 if new technology measures do
not achieve planned reductions.\122\ We find that CARB's new commitment
complies with the criterion in CAA section 182(e)(5) that requires
submittal of such contingency measures no later than 3 years prior to
implementation of the new technology measures.
---------------------------------------------------------------------------

    \122\ CARB Resolution 17-8, 9 (March 23, 2017) (CARB resolution
adopting the 2016 AQMP as a revision to the California SIP).
---------------------------------------------------------------------------

v. Proposed Action on Measures in the Attainment Strategy
    As discussed above, we believe that circumstances here warrant the
consideration of enforceable commitments, and that the three criteria
are met: (1) The commitments constitute a limited portion of the
required emissions reductions; (2) both CARB and the District are
capable of meeting their commitments; and (3) the commitments are for
an appropriate timeframe. Based on these evaluations, we are proposing
to approve the enforceable commitments as part of the attainment
demonstration.
    More specifically, we propose to approve the SCAQMD's updated
commitments for the 1-hour and 1997 ozone NAAQS and new commitment for
the 2008 ozone NAAQS: (1) To develop, adopt, submit, and implement the
ozone measures in tables 4-2 and 4-4 of Chapter 4 in the 2016 AQMP
(main document); and (2) to meet or exceed the aggregate emissions
reduction commitments identified in tables 4-9 through 4-11 of the 2016
AQMP (main document); and (3) to substitute any other measures as
necessary to make up any emissions reduction shortfall following the
procedures set forth for such substitution in Chapter 4 (pages 4-54 and
4-55) of the 2016 AQMP.
    We also propose to approve CARB's updated commitment for the 1997
ozone NAAQS and new commitment for the 2008 ozone NAAQS: (1) To bring
to its Board for consideration the list of proposed SIP measures
outlined in Chapter 4 of the 2016 State Strategy and included in
Attachment A (``Proposed New SIP Measures and Schedule'') of CARB Board
Resolution 17-7 according to the schedule set forth therein; and (2) to
achieve the aggregate emission reductions from defined and new
technology measures for the South Coast outlined in the 2016 State
Strategy of 113 tpd of NOX and 50-51 tpd of VOC by 2023 and
111 tpd of NOX and 59-60 tpd of VOC by 2031. In connection
with the new technology measures, we propose to find that the 2016
South Coast Ozone SIP meets the criteria for reliance on new technology
measures in CAA section 182(e)(5) for the 1997 and 2008 ozone NAAQS.
Our proposed finding in this regard is based on the proposed approval
herein of CARB's commitment in Resolution 17-8 (March 23, 2017) to
develop, adopt, and submit contingency measures by 2028 (for the
purposes of attaining the 2008 ozone NAAQS in the South Coast) if new
technology measures do not achieve planned reductions. (As noted
previously, CARB has already submitted as part of the 2007 South Coast
Ozone SIP, and the EPA has approved, a commitment to submit such
measures by 2020 for the purposes of attaining the 1997 ozone NAAQS in
the South Coast if new technology measures do not achieve planned
reductions.)

c. Attainment Demonstration
    Based on our proposed determinations that the photochemical
modeling and control strategy are acceptable, and our proposed approval
of the aggregate emissions reduction commitments by the District and
CARB, including the commitment by CARB to submit contingency measures
to cover the reductions from new technology measures if needed, we
propose to approve the updated attainment demonstrations for the 1-hour
ozone NAAQS and the 1997 ozone NAAQS, and the attainment demonstration
for the 2008 ozone NAAQS in the 2016 South Coast Ozone SIP as meeting
the requirements of CAA section 182(c)(2)(A) and 40 CFR 51.1108.\123\
---------------------------------------------------------------------------

    \123\ We recognize that in Table 11 the control strategy is
expected to achieve a NOX emissions level of 97 tpd by
2031 in the South Coast whereas the modeled attainment demonstration
for the 2008 ozone NAAQS is based on a NOX emissions
level of 96 tpd. However, we believe that the control strategy will
suffice to attain the NAAQS because a shortfall of 1 tpd of
NOX is unlikely to have a 0.001 ppm or greater impact on
the 0.075 ppm model-predicted 8-hour ozone concentration in 2031
(controlled case) at the highest site (Fontana) as shown in Table 5-
2 of the 2016 AQMP based on the isopleth map for the Fontana site
shown on page 7 of Attachment 4 to Appendix V of the 2016 AQMP.
(Note that under the control strategy in the 2016 AQMP and 2016
State Strategy, South Coast VOC emissions in 2031 are expected to be
approximately 292-293 tpd based on the 2031 baseline value (362 tpd)
minus the District's and CARB's aggregate emission reduction
commitments by 2031.)
---------------------------------------------------------------------------

E. Rate of Progress Plan and Reasonable Further Progress Demonstration

1. Statutory and Regulatory Requirements
    Requirements for RFP for ozone nonattainment areas are specified in
CAA sections 172(c)(2), 182(b)(1), and 182(c)(2)(B). Under CAA section
171(1), RFP is defined as meaning such annual incremental reductions in
emissions of the relevant air pollutant as are required under part D
(``Plan Requirements for Nonattainment Areas'') or may reasonably be
required by the EPA for the purpose of ensuring attainment of the
applicable NAAQS by the applicable date. CAA section 182(b)(1)
specifically requires that ozone nonattainment areas that are
classified as Moderate or above demonstrate a 15 percent reduction in
VOC between the years of 1990 and 1996. The EPA has typically referred
to section 182(b)(1) as the Rate of Progress (ROP) requirement. For
ozone nonattainment areas classified as Serious or higher, section
182(c)(2)(B) requires reductions averaged over each consecutive 3-year
period, beginning 6 years after the baseline year until the attainment
date, of at least 3 percent of baseline emissions per year. The
provisions in CAA section 182(c)(2)(B)(ii) allow an amount less than 3
percent of such baseline emissions each year if the state demonstrates
to the EPA that the plan includes all measures that can feasibly be
implemented in the area in light of technological achievability.
    In the 2008 Ozone SRR, the EPA provides that areas classified
Moderate or higher will have met the ROP requirements of CAA section
182(b)(1) if the area has a fully approved 15 percent ROP plan for the
1-hour or 1997 8-hour ozone standards, provided the boundaries of the
ozone nonattainment areas are the same.\124\ For such areas, the EPA
interprets the RFP requirements of CAA section 172(c)(2) to require
areas classified as Moderate to provide a 15 percent emission reduction
of ozone precursors within 6 years of the baseline year. Areas
classified as Serious or higher must meet the RFP requirements of CAA
section 182(c)(2)(B) by providing an 18 percent reduction of ozone
precursors in the first 6-year period, and an average ozone precursor
emission reduction of 3 percent per year for all remaining 3-year
periods thereafter.\125\ To meet CAA sections 172(c)(2) and
182(c)(2)(B) RFP requirements, the state may substitute NOX
emissions reductions for VOC reductions.\126\
---------------------------------------------------------------------------

    \124\ 70 FR 12264, at 12271 (March 6, 2015).
    \125\ Id.
    \126\ 40 CFR 51.1110(a)(2)(i)(C) and 40 CFR
51.1110(a)(2)(ii)(B); and 70 FR 12264, at 12271 (March 6, 2015).
---------------------------------------------------------------------------

    Except as specifically provided in CAA section 182(b)(1)(C),
emissions reductions from all SIP-approved, federally promulgated, or
otherwise SIP-creditable measures that occur after the baseline year
are creditable for purposes of demonstrating that the RFP targets are
met. Because the EPA has determined that the passage of time has caused
the effect of certain exclusions to be de minimis, the RFP
demonstration is no longer required to calculate and specifically
exclude reductions from measures related to motor vehicle exhaust or
evaporative emissions promulgated by January 1, 1990; regulations
concerning Reid vapor pressure promulgated by November 15, 1990;
measures to correct previous RACT requirements; and, measures required
to correct previous inspection and maintenance (I/M) programs.\127\
---------------------------------------------------------------------------

    \127\ 40 CFR 51.1110(a)(7).
---------------------------------------------------------------------------

    The 2008 Ozone SRR requires the RFP baseline year to be the most
recent calendar year for which a complete triennial inventory was
required to be submitted to the EPA. For the purposes of developing RFP
demonstrations for the 2008 ozone NAAQS, the applicable triennial
inventory year is 2011. As discussed previously, the 2008 Ozone SRR
provided states with the opportunity to use an alternative baseline
year for RFP,\128\ but that provision of the 2008 Ozone SRR was vacated
by the D.C. Circuit in the South Coast II decision.
---------------------------------------------------------------------------

    \128\ 40 CFR 51.1110(b).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    In response to the South Coast II decision, CARB developed the 2018
SIP Update, which replaces the RFP portion of the 2016 AQMP and
includes updated emissions estimates for the RFP baseline year,
subsequent milestone years, and the attainment year, and an updated RFP
demonstration relying on a 2011 RFP baseline year.\129\ To develop the
2011 RFP baseline inventory, CARB relied on actual emissions reported
from industrial point sources for year 2011 and backcast emissions from
smaller stationary sources and area sources from 2012 to 2011 using the
same growth and control factors as was used for the 2016 AQMP. To
develop the emissions inventories for the RFP milestone years (i.e.,
2017, 2020, 2023, 2026, 2029) and attainment year (2031), CARB also
relied upon the same growth and control factors as the 2016 AQMP.
---------------------------------------------------------------------------

    \129\ 2018 SIP Update, RFP demonstration, section IX-B, 64 and
65.
---------------------------------------------------------------------------

    Documentation for the South Coast RFP baseline and milestone
emissions inventories is found in the 2018 SIP Update on pages 4-5, 63-
65, and appendix A, pages A-31--A-35. For both sets of baseline
emissions inventories (those in the 2016 AQMP and those in the 2018 SIP
Update), emissions estimates reflect District rules adopted through
December 2015 and CARB rules adopted through November 2015. Unlike the
emissions inventories for the base year (2012) and for the attainment
demonstrations in the 2016 AQMP, the RFP baseline and milestone
emissions inventories only include emissions within the South Coast
ozone nonattainment area and thus do not include marine emissions
(e.g., emissions from ocean-going vessels) beyond three nautical miles
from the coastline. In contrast, the base year (2012) and attainment
demonstration inventories include emissions from marine vessels out to
100 miles from the coastline.

    The updated RFP demonstration for the South Coast for the 2008
ozone NAAQS is shown in Table 13. The updated RFP demonstration
calculates future year VOC targets from the 2011 baseline, consistent
with CAA 182(c)(2)(B)(i), which requires reductions of ``at least 3
percent of baseline emissions each year;'' and it substitutes
NOX reductions for VOC reductions beginning in milestone
year 2020 to meet VOC emission targets.\130\ For the South Coast, CARB
concludes that the RFP demonstration meets the applicable requirements
for each milestone year as well as the attainment year.
---------------------------------------------------------------------------

    \130\ NOX substitution is permitted under EPA
regulations. See 40 CFR 51.1110(a)(2)(i)(C) and 40 CFR
51.1110(a)(2)(ii)(B); and 70 FR 12264, at 12271 (March 6, 2015).

                                        Table 13--RFP Demonstration for the South Coast for the 2008 Ozone NAAQS
                                                       [Summer planning inventory, tpd or percent]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                   2011         2017         2020         2023         2026         2029         2031
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                           VOC
--------------------------------------------------------------------------------------------------------------------------------------------------------
Baseline VOC.................................................        522.0        413.7        388.6        376.0        367.5        362.5        358.3
Required change since 2011 (VOC or NOX), %...................  ...........          18%          27%          36%          45%          54%          60%
Required reductions since 2011, tpd..........................  ...........         94.0        140.9        187.9        234.9        281.9        313.2
Target VOC level.............................................  ...........        428.0        381.1        334.1        287.1        240.1        208.8
Apparent shortfall (-)/surplus (+) in VOC....................  ...........         14.3         -7.5        -41.9        -80.4       -122.4       -149.5
Apparent shortfall (-)/surplus (+) in VOC, %.................  ...........         2.8%        -1.4%        -8.0%       -15.4%       -23.4%       -28.6%
VOC shortfall previously provided by NOX substitution, %.....  ...........         0.0%         0.0%         1.4%         8.0%        15.4%        23.4%
Actual VOC shortfall (-)/surplus (+), %......................  ...........         2.8%        -1.4%        -6.6%        -7.4%        -8.1%        -5.2%
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                           NO
--------------------------------------------------------------------------------------------------------------------------------------------------------
Baseline NOX.................................................        534.3        366.2        306.5        239.0        220.9        209.9        204.9
Change in NOX since 2011, tpd................................  ...........        168.1        227.9        295.3        313.4        324.4        329.4
Change in NOX since 2011, %..................................  ...........        31.5%        42.6%        55.3%        58.7%        60.7%        61.7%
NOX reductions used for VOC substitution through last          ...........           0%           0%         1.4%         8.0%        15.4%        23.4%
 milestone year, %...........................................
NOX reductions since 2011 available for VOC substitution in    ...........        31.5%        42.6%        53.8%        50.6%        45.3%        38.2%
 this milestone year, %......................................
NOX reductions since 2011 used for VOC substitution in this    ...........           0%         1.4%         6.6%         7.4%         8.1%         5.2%
 milestone year, %...........................................
NOX reductions since 2011 surplus after meeting VOC            ...........        31.5%        41.2%        47.2%        43.3%        37.3%        33.0%
 substitution needs in this milestone year, %................
Total shortfall for RFP......................................  ...........           0%           0%           0%           0%           0%           0%
RFP met?.....................................................  ...........          Yes          Yes          Yes          Yes          Yes          Yes
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: Table IX-2 of the 2018 SIP Update.

3. The EPA's Review of the State's Submission
    In 1997, the EPA approved a 15 percent ROP plan for the South Coast
ozone nonattainment area for the 1-hour ozone NAAQS, and the South
Coast nonattainment area for the 2008 ozone NAAQS is the same as the
South Coast nonattainment area for the 1-hour ozone NAAQS.\131\ As a
result, the District and CARB have met the ROP requirements of CAA
section 182(b)(1) for the South Coast and do not need to demonstrate
another 15 percent reduction in VOC for this area.
---------------------------------------------------------------------------

    \131\ 62 FR 1150, at 1183 (January 8, 1997).
---------------------------------------------------------------------------

    Based on our review of the emissions inventory documentation in the
2016 AQMP and 2018 SIP Update, we find that CARB and the District have
used the most recent planning and activity assumptions, emissions
models, and methodologies in developing the RFP baseline and milestone
year emissions inventories. We have also have reviewed the calculations
in Table IX-2 of the 2018 SIP Update and presented in Table 13 above
and find that the District and CARB have used an appropriate
calculation method to demonstrate RFP. For these reasons, we have
determined that the 2016 South Coast Ozone SIP demonstrates RFP in each
milestone year and the attainment year, consistent with applicable CAA
requirements and EPA guidance. We therefore propose to approve the RFP
demonstrations for the South Coast for the 2008 ozone NAAQS under
sections 172(c)(2), 182(b)(1) and 182(c)(2)(B) of the CAA and 40 CFR
51.1110(a)(2)(ii).

F. Transportation Control Strategies and Measures to Offset Emissions
Increases From Vehicle Miles Traveled

1. Stationary and Regulatory Requirements
    Section 182(d)(1)(A) of the Act requires, in relevant part, the
state, if subject to its requirements for a given area, to ``submit a
revision that identifies and adopts specific enforceable transportation
control strategies and transportation control measures to offset any
growth in emissions from growth in vehicle miles traveled or number of
vehicle trips in such area.'' \132\ Herein, we use ``VMT'' to refer to
vehicle miles traveled and refer to the related SIP requirement as the
``VMT emissions offset requirement.'' In addition, we refer to the SIP
revision intended to demonstrate compliance with the VMT emissions
offset requirement as the ``VMT emissions offset demonstration.''
---------------------------------------------------------------------------

    \132\ CAA section 182(d)(1)(A) includes three separate elements.
In short, under section 182(d)(1)(A), states are required to adopt
transportation control strategies and measures to offset growth in
emissions from growth in VMT, and, as necessary, in combination with
other emission reduction requirements, to demonstrate RFP and
attainment. For more information on the EPA's interpretation of the
three elements of section 182(d)(1)(A). See 77 FR 58067, at 58068
(September 19, 2012) (proposed withdrawal of approval of South Coast
VMT emissions offset demonstrations). In section III.F of this
document, we are addressing the first element of CAA section
182(d)(1)(A) (i.e., the VMT emissions offset requirement). In
sections III.E and D of this document, we are proposing to approve
the RFP and attainment demonstrations, respectively, for the 2008
ozone NAAQS in the South Coast, and compliance with the second and
third elements of section 182(d)(1)(A) is predicated on final
approval of the RFP and attainment demonstrations.
---------------------------------------------------------------------------

    In Association of Irritated Residents v. EPA, the United States
Court of Appeals for the Ninth Circuit (``Court'') ruled that
additional transportation control measures are required whenever
vehicle emissions are projected to be higher than they would have been
had VMT not increased, even when aggregate

vehicle emissions are actually decreasing.\133\ In response to the
Court's decision, in August 2012, the EPA issued a memorandum titled
``Guidance on Implementing Clean Air Act Section 182(d)(1)(A):
Transportation Control Measures and Transportation Control Strategies
to Offset Growth in Emissions Due to Growth in Vehicle Miles
Travelled'' (herein referred to as the ``August 2012 guidance'').\134\
---------------------------------------------------------------------------

    \133\ See Association of Irritated Residents v. EPA, 632 F.3d.
584, at 596-597 (9th Cir. 2011), reprinted as amended on January 27,
2012, 686 F.3d 668, further amended February 13, 2012 (``Association
of Irritated Residents'').
    \134\ Memorandum dated August 30, 2012, Karl Simon, Director,
Transportation and Climate Division, Office of Transportation and
Air Quality, to Carl Edland, Director, Multimedia Planning and
Permitting Division, EPA Region 6, and Deborah Jordan, Director, Air
Division, EPA Region 9.
---------------------------------------------------------------------------

    The August 2012 guidance discusses the meaning of ``transportation
control strategies'' (TCSs) and ``transportation control measures''
(TCMs) and recommends that both TCSs and TCMs be included in the
calculations made for the purpose of determining the degree to which
any hypothetical growth in emissions due to growth in VMT should be
offset. Generally, TCSs is a broad term that encompasses many types of
controls including, for example, motor vehicle emission limitations, I/
M programs, alternative fuel programs, other technology-based measures,
and TCMs, that would fit within the regulatory definition of ``control
strategy.'' \135\ TCMs are defined at 40 CFR 51.100(r) as meaning ``any
measure that is directed toward reducing emissions of air pollutants
from transportation sources. Such measures include, but are not limited
to those listed in section 108(f) of the Clean Air Act[,].'' TCMs
generally refer to programs intended to reduce the VMT, the number of
vehicle trips, or traffic congestion, such as programs for improved
public transit, designation of certain lanes for passenger buses and
high-occupancy vehicles, and trip reduction ordinances.
---------------------------------------------------------------------------

    \135\ See, e.g., 40 CFR 51.100(n).
---------------------------------------------------------------------------

    The August 2012 guidance explains how states may demonstrate that
the VMT emissions offset requirement is satisfied in conformance with
the Court's ruling. States are recommended to estimate emissions for
the nonattainment area's base year and the attainment year. One
emission inventory is developed for the base year, and three different
emissions inventory scenarios are developed for the attainment year.
For the attainment year, the state would present three emissions
estimates, two of which would represent hypothetical emissions
scenarios that would provide the basis to identify the ``growth in
emissions'' due solely to the growth in VMT, and one that would
represent projected actual motor vehicle emissions after fully
accounting for projected VMT growth and offsetting emissions reductions
obtained by all creditable TCSs and TCMs. See the August 2012 guidance
for specific details on how states might conduct the calculations.
    The base year on-road VOC emissions should be calculated using VMT
in that year, and it should reflect all enforceable TCSs and TCMs in
place in the base year. This would include vehicle emissions standards,
state and local control programs, such as I/M programs or fuel rules,
and any additional implemented TCSs and TCMs that were already required
by or credited in the SIP as of that base year.
    The first of the emissions calculations for the attainment year
would be based on the projected VMT and trips for that year and assume
that no new TCSs or TCMs beyond those already credited in the base year
inventory have been put in place since the base year. This calculation
demonstrates how emissions would hypothetically change if no new TCSs
or TCMs were implemented, and VMT and trips were allowed to grow at the
projected rate from the base year. This estimate would show the
potential for an increase in emissions due solely to growth in VMT and
trips. This represents a ``no action'' taken scenario. Emissions in the
attainment year in this scenario may be lower than those in the base
year due to the fleet that was on the road in the base year gradually
being replaced through fleet turnover; however, provided VMT and/or
numbers of vehicle trips will in fact increase by the attainment year,
they would still likely be higher than they would have been assuming
VMT had held constant.
    The second of the attainment year's emissions calculations would
assume that no new TCSs or TCMs beyond those already credited have been
put in place since the base year, but it would also assume that there
was no growth in VMT and trips between the base year and attainment
year. This estimate reflects the hypothetical emissions level that
would have occurred if no further TCMs or TCSs had been put in place
and if VMT and trip levels had held constant since the base year. Like
the ``no action'' attainment year estimate described above, emissions
in the attainment year may be lower than those in the base year due to
the fleet that was on the road in the base year gradually being
replaced by cleaner vehicles through fleet turnover, but in this case
they would not be influenced by any growth in VMT or trips. This
emissions estimate would reflect a ceiling on the attainment emissions
that should be allowed to occur under the statute as interpreted by the
Court because it shows what would happen under a scenario in which no
offsetting TCSs or TCMs have yet been put in place and VMT and trips
are held constant during the period from the area's base year to its
attainment year. This represents a ``VMT offset ceiling'' scenario.
These two hypothetical status quo estimates are necessary steps in
identifying the target level of emissions from which states would
determine whether further TCMs or TCSs, beyond those that have been
adopted and implemented in reality, would need to be adopted and
implemented in order to fully offset any increase in emissions due
solely to VMT and trips identified in the ``no action'' scenario.
    Finally, the state would present the emissions that are actually
expected to occur in the area's attainment year after taking into
account reductions from all enforceable TCSs and TCMs that in reality
were put in place after the baseline year. This estimate would be based
on the VMT and trip levels expected to occur in the attainment year
(i.e., the VMT and trip levels from the first estimate) and all of the
TCSs and TCMs expected to be in place and for which the SIP will take
credit in the area's attainment year, including any TCMs and TCSs put
in place since the base year. This represents the ``projected actual''
attainment year scenario. If this emissions estimate is less than or
equal to the emissions ceiling that was established in the second of
the attainment year calculations, the TCSs or TCMs for the attainment
year would be sufficient to fully offset the identified hypothetical
growth in emissions.
    If, instead, the estimated projected actual attainment year
emissions are still greater than the ceiling which was established in
the second of the attainment year emissions calculations, even after
accounting for post-baseline year TCSs and TCMs, the state would need
to adopt and implement additional TCSs or TCMs to further offset the
growth in emissions. The additional TCSs or TCMs would need to bring
the actual emissions down to at least the ``had VMT and trips held
constant'' ceiling estimated in the second of the attainment year
calculations, in order to meet the VMT offset requirement of section
182(d)(1)(A) as interpreted by the Court.

2. Summary of State's Submission
    CARB prepared the VMT emissions offset demonstration for the South
Coast for the 2008 ozone NAAQS, and the District included it in 2016
AQMP as appendix VI-E (``VMT Offset Demonstration''). In addition to
the VMT emissions offset demonstration, appendix VI-E of the 2016 AQMP
includes two attachments--one listing the TCSs adopted by CARB since
1990 and another listing the TCMs developed by SCAG (as of September
2014) in the South Coast region that are subject to timely
implementation reporting requirements.
    For the VMT emissions offset demonstration, CARB used EMFAC2014,
the latest EPA-approved motor vehicle emissions model for California.
The EMFAC2014 model estimates the on-road emissions from two combustion
processes (i.e., running exhaust and start exhaust) and four
evaporative processes (i.e., hot soak, running losses, diurnal losses,
and resting losses). The EMFAC2014 model combines trip-based VMT data
from the regional transportation planning agency (i.e., SCAG), starts
data based on household travel surveys, and vehicle population data
from the California Department of Motor Vehicles. These sets of data
are combined with corresponding emission rates to calculate emissions.
    Emissions from running exhaust, start exhaust, hot soak, and
running losses are a function of how much a vehicle is driven.
Emissions from these processes are thus directly related to VMT and
vehicle trips, and CARB included emissions from them in the
calculations that provide the basis for the South Coast VMT emissions
offset demonstration. CARB did not include emissions from resting loss
and diurnal loss processes in the analysis because such emissions are
related to vehicle population, not to VMT or vehicle trips, and thus
are not part of ``any growth in emissions from growth in vehicle miles
traveled or numbers of vehicle trips in such area'' under CAA section
182(d)(1)(A).
    The South Coast VMT emissions offset demonstration uses 2012 as the
``base year.'' The base year for VMT emissions offset demonstration
purposes should generally be the same base year used for nonattainment
planning purposes. In section III.A of this document, the EPA is
proposing to approve the 2012 base year inventory for the South Coast
for the purposes of the 2008 ozone NAAQS, and thus, CARB's selection of
2012 as the base year for the South Coast VMT emissions offset
demonstration for the 2008 ozone NAAQS is appropriate.
    The South Coast VMT emissions offset demonstration also includes
the previously described three different attainment year scenarios
(i.e., no action, VMT offset ceiling, and projected actual). The 2016
AQMP provides a demonstration of attainment of the 2008 ozone NAAQS in
the South Coast by the applicable attainment date, based on the
controlled 2031 emissions inventory. As described in section III.D of
this document, the EPA is proposing to approve the attainment
demonstration for the 2008 ozone NAAQS for the South Coast, and thus,
we find CARB's selection of year 2031 as the attainment year for the
VMT emissions offset demonstration for the 2008 ozone NAAQS to be
acceptable.
    Table 14 summarizes the relevant distinguishing parameters for each
of the emissions scenarios and shows CARB's corresponding VOC emissions
estimates for the demonstration for the 2008 ozone NAAQS.

                                   Table 14--VMT Emissions Offset Inventory Scenarios and Results for 2008 Ozone NAAQS
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                        VMT                           Starts                 Controls      VOC Emissions
                        Scenario                         -----------------------------------------------------------------------------------------------
                                                               Year          1000/day          Year          1000/day          Year             tpd
--------------------------------------------------------------------------------------------------------------------------------------------------------
Base Year...............................................            2012         380,248            2012          69,789            2012             138
No Action...............................................            2031         408,964            2031          78,894            2012              64
VMT Offset Ceiling......................................            2031         380,248            2012          69,789            2012              61
Projected Actual........................................            2031         408,964            2031          78,894            2031              40
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: 2016 AQMP, Appendix VI-E.

    For the base year scenario, CARB ran the EMFAC2014 model for the
applicable base year (i.e., 2012 for the 2008 ozone NAAQS) using VMT
and starts data corresponding to that year. As shown in Table 14, CARB
estimates the South Coast VOC emissions at 138 tpd in 2012.
    For the ``no action'' scenario, CARB first identified the on-road
motor vehicle control programs (i.e., TCSs or TCMs) put in place since
the base year and incorporated into EMFAC2014 and then ran EMFAC2014
with the VMT and starts data corresponding to the applicable attainment
year (i.e., 2031 for the 2008 ozone NAAQS) without the emissions
reductions from the on-road motor vehicle control programs put in place
after the base year. Thus, the no action scenario reflects the
hypothetical VOC emissions that would occur in the attainment year in
the South Coast if the CARB had not put in place any additional TCSs or
TCMs after 2012. As shown in Table 14, CARB estimates the ``no action''
South Coast VOC emissions at 64 tpd in 2031.
    For the ``VMT offset ceiling'' scenario, CARB ran the EMFAC2014
model for the attainment years but with VMT and starts data
corresponding to base year values. Like the no action scenario, the
EMFAC2014 model was adjusted to reflect the VOC emissions levels in the
attainment years without the benefits of the post-base-year on-road
motor vehicle control programs. Thus, the VMT offset ceiling scenario
reflects hypothetical VOC emissions in the South Coast if CARB had not
put in place any TCSs or TCMs after the base year and if there had been
no growth in VMT or vehicle trips between the base year and the
attainment year.
    The hypothetical growth in emissions due to growth in VMT and trips
can be determined from the difference between the VOC emissions
estimates under the ``no action'' scenario and the corresponding
estimates under the ``VMT offset ceiling'' scenario. Based on the
values in Table 14, the hypothetical growth in emissions due to growth
in VMT and trips in the South Coast would have been 3 tpd (i.e., 64 tpd
minus 61 tpd). This hypothetical difference establishes the level of
VMT growth-caused emissions that need to be offset by the combination
of post-baseline year TCMs and TCSs and any necessary additional TCMs
and TCSs.
    For the ``projected actual'' scenario calculation, CARB ran the
EMFAC2014 model for the attainment year with VMT

and starts data at attainment year values and with the full benefits of
the relevant post-baseline year motor vehicle control programs. For
this scenario, CARB included the emissions benefits from TCSs and TCMs
put in place since the base year. The most significant measures
reducing VOC emissions during the 2012 to 2031 timeframe include the
Advanced Clean Cars program, ZEV requirements, and more stringent on-
board diagnostics requirements.\136\
---------------------------------------------------------------------------

    \136\ Attachment V-E-1 to appendix VI of the 2016 AQMP includes
a list of the State's transportation control strategies adopted by
CARB since 1990. Also see EPA final action on CARB mobile source SIP
submittals at 81 FR 39424 (June 16, 2016), 82 FR 14446 (March 21,
2017), and 83 FR 23232 (May 18, 2018).
---------------------------------------------------------------------------

    As shown in Table 14, the projected actual attainment-year VOC
emissions is 40 tpd. CARB then compared this value against the
corresponding VMT offset ceiling value to determine whether additional
TCMs or TCSs would need to be adopted and implemented in order to
offset any increase in emissions due solely to VMT and trips. Because
the projected actual emissions are less than the corresponding VMT
offset ceiling emissions, CARB concluded that the demonstration shows
compliance with the VMT emissions offset requirement and that there are
sufficient adopted TCSs and TCMs to offset the growth in emissions from
the growth in VMT and vehicle trips in the South Coast for the 2008
ozone NAAQS.
3. The EPA's Review of the State's Submission
    Based on our review of revised South Coast VMT emissions offset
demonstration in appendix VI-E of the 2016 AQMP, we find CARB's
analysis to be consistent with our August 2012 guidance and consistent
with the emissions and vehicle activity estimates found elsewhere in
the 2016 AQMP. We agree that CARB and SCAG have adopted sufficient TCSs
and TCMs to offset the growth in emissions from growth in VMT and
vehicle trips in the South Coast for the purposes of the 2008 ozone
NAAQS. As such, we propose to approve the South Coast VMT emissions
offset demonstration element of the 2016 South Coast Ozone SIP as
meeting the requirements of CAA section 182(d)(1)(A).

G. Contingency Measures

1. Statutory and Regulatory Requirements
    Under the CAA, 8-hour ozone nonattainment areas classified under
subpart 2 as Moderate or above must include in their SIPs contingency
measures consistent with sections 172(c)(9) and 182(c)(9). Contingency
measures are additional controls or measures to be implemented in the
event the area fails to make reasonable further progress or to attain
the NAAQS by the attainment date. The SIP should contain trigger
mechanisms for the contingency measures, specify a schedule for
implementation, and indicate that the measure will be implemented
without significant further action by the state or the EPA.\137\
---------------------------------------------------------------------------

    \137\ 70 FR 71612 (November 29, 2005). See also 2008 Ozone SRR,
80 FR 12264, at 12285 (March 6, 2015).
---------------------------------------------------------------------------

    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's 2008 Ozone SRR
reiterates the EPA's policy that contingency measures should provide
for emissions reductions approximately equivalent to one year's worth
progress, amounting to reductions of 3 percent of the baseline
emissions inventory for the nonattainment area.\138\
---------------------------------------------------------------------------

    \138\ 80 FR 12264 at 12285 (March 6, 2015).
---------------------------------------------------------------------------

    It has been the EPA's longstanding interpretation of section
172(c)(9) that states may rely on federal measures (e.g., federal
mobile source measures based on the incremental turnover of the motor
vehicle fleet each year) and local measures already scheduled for
implementation that provide emissions reductions in excess of those
needed to provide for RFP or expeditious attainment. The key is that
the statute requires that contingency measures provide for additional
emissions reductions that are not relied on for RFP or attainment and
that are not included in the RFP or attainment demonstrations as
meeting part or all of the contingency measure requirements. The
purpose of contingency measures is to provide continued emissions
reductions while the plan is being revised to meet the missed milestone
or attainment date.
    The EPA has approved numerous SIPs under this interpretation--i.e.,
SIPs that use as contingency measures one or more federal or local
measures that are in place and provide reductions that are in excess of
the reductions required by the attainment demonstration or RFP
plan,\139\ and there is case law supporting the EPA's interpretation in
this regard.\140\ However, in Bahr v. EPA, the Ninth Circuit rejected
the EPA's interpretation of CAA section 172(c)(9) as allowing for early
implementation of contingency measures.\141\ 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.\142\ 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)
and 182(c)(9).\143\
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    \139\ See, e.g., 62 FR 15844 (April 3, 1997) (direct final rule
approving an Indiana ozone SIP revision); 62 FR 66279 (December 18,
1997) (final rule approving an Illinois ozone SIP revision); 66 FR
30811 (June 8, 2001) (direct final rule approving a Rhode Island
ozone SIP revision); 66 FR 586 (January 3, 2001) (final rule
approving District of Columbia, Maryland, and Virginia ozone SIP
revisions); and 66 FR 634 (January 3, 2001) (final rule approving a
Connecticut ozone SIP revision).
    \140\ See, e.g., LEAN v. EPA, 382 F.3d 575 (5th Cir. 2004)
(upholding contingency measures that were previously required and
implemented where they were in excess of the attainment
demonstration and RFP SIP).
    \141\ Bahr v. EPA, 836 F.3d 1218, at 1235-1237 (9th Cir. 2016).
    \142\ Id. at 1235-1237.
    \143\ The Bahr v. EPA decision involved a challenge to an EPA
approval of contingency measures under the general nonattainment
area plan provisions for contingency measures in CAA section
172(c)(9), but, given the similarity between the statutory language
in section 172(c)(9) and the ozone-specific contingency measure
provision in section 182(c)(9), we find that the decision affects
how both sections of the Act must be interpreted.
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    With respect to Extreme ozone nonattainment areas, CAA section
182(e)(5) allows the agency to exercise discretion in approving Extreme
area attainment plans that rely, in part, on the future development of
new control technologies or improvements of existing control
technologies, where certain conditions are met. Among the conditions to
qualify for reliance on section 182(e)(5) is the requirement that the
state submit enforceable commitments to timely develop and adopt
contingency measures to be implemented if the anticipated future
technologies do not achieve planned reductions. Contingency measures
submitted to comply with commitments made for the purposes of section
182(e)(5) differ in substance from contingency measures submitted to
comply with sections 172(c)(9) and 182(c)(9) in that the former
addresses a potential failure to meet an emissions reduction target
whereas the latter address a potential failure to meet an ambient
concentration target (i.e., in this case, the 2008 ozone NAAQS).
However, in our 2008 Ozone SRR, we recognized the inherent difficulty
in identifying specific contingency measures to be triggered upon a
failure to attain the NAAQS by the applicable attainment date in
Extreme nonattainment areas that rely on the new technology provisions
in section 182(e)(5) to demonstrate attainment, and thus, we allow
states to submit, for such

areas, enforceable commitments to develop and adopt contingency
measures meeting the requirements of section 182(e)(5) to satisfy the
requirements for both attainment contingency measures in CAA sections
172(c)(9) and 182(c)(9).\144\ These enforceable commitments must
obligate the state to submit the required contingency measures (i.e.,
contingency measures to be triggered if the emissions reduction target
under section 182(e)(5) is not met and contingency measures to be
triggered if the area fails to attain the NAAQS by the applicable
attainment date) to the EPA no later than three years before any
applicable implementation date, in accordance with section
182(e)(5).\145\
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    \144\ 80 FR 12264, at 12285-12286 (March 6, 2015).
    \145\ Id.
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2. Summary of the State's Submission
    The District and CARB had largely prepared the 2016 AQMP prior to
the Bahr v. EPA decision, and thus, it relies solely upon surplus
emissions reductions from already implemented control measures in the
RFP milestone years to demonstrate compliance with the RFP milestone
contingency measure requirements of CAA sections 172(c)(9) and
182(c)(9).\146\ Because the attainment demonstration for the 2008 ozone
NAAQS relies on CAA section 182(e)(5) reductions in the 2016 State
Strategy, CARB has submitted a commitment to develop, adopt, and submit
contingency measures by 2028 if the section 182(e)(5) measures do not
achieve planned reductions.\147\ More recently, in a letter from CARB
dated May 20, 2019, CARB clarified that the commitment to submit
contingency measures as needed to address shortfalls in the emissions
reductions anticipated by new technology measures under section
182(e)(5) also includes a commitment to submit by 2028 contingency
measures to be triggered upon a failure to attain the 2008 ozone NAAQS
in the South Coast by the applicable attainment date as required under
sections 172(c)(9) and 182(c)(9).\148\
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    \146\ 2016 AQMP, 4-51 and 4-52; appendix VI-C, pages V-C-1--V-C-
4.
    \147\ CARB Board Resolution 7-18, 9.
    \148\ Letter dated May 20, 2019, from Michael Benjamin, CARB, to
Amy Zimpfer, EPA Region IX.
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    In the 2018 SIP Update, CARB revises the RFP demonstration for the
2008 ozone NAAQS for the South Coast and recalculates the extent of
surplus emission reductions (i.e., surplus to meeting the RFP milestone
requirement for a given milestone year) in the milestone years. In
light of the Bahr v. EPA decision, however, the 2018 SIP Update does
not rely on the surplus or incremental emissions reductions to comply
with the contingency measures requirements of sections 172(c)(9) and
182(c)(9) but, to provide context in which to review contingency
measures for the 2008 ozone NAAQS, the 2018 SIP Update documents the
extent to which future baseline emissions would provide surplus
emissions reductions beyond those required to meet applicable RFP
milestones.\149\ More specifically, the 2018 SIP Update identifies one
year's worth of RFP as approximately 16 tpd and estimates surplus
NOX reductions as ranging from approximately 170 tpd to 250
tpd depending upon the particular RFP milestone year.
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    \149\ 2018 SIP Update, chapter IX, tables IX-2, IX-5 and IX-6.
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    To comply with sections 172(c)(9) and 182(c)(9), as interpreted in
the Bahr v. EPA decision, the state must develop, adopt and submit a
contingency measure to be triggered upon a failure to meet RFP
milestones or failure to attain the NAAQS by the applicable attainment
date regardless of the extent to which already-implemented measures
would achieve surplus emissions reductions beyond those necessary to
meet RFP milestones and beyond those predicted to achieve attainment of
the NAAQS. Therefore, to fully address the contingency measure
requirement for the 2008 ozone NAAQS in the South Coast, the District
has committed to develop, adopt and submit a contingency measure to
CARB in sufficient time to allow CARB to submit the contingency measure
as a SIP revision to the EPA within 12 months of the EPA's final
conditional approval of the contingency measure element of the 2016
South Coast Ozone SIP.\150\ The District's specific commitment is to
modify one (or more) existing rule, or adopt a new rule or rules, that
would include a more stringent requirement or remove an exemption if
the EPA determines that the South Coast nonattainment area has missed
an RFP milestone for the 2008 ozone NAAQS. More specifically, the
District has identified a list of 12 different rules that the District
is reviewing for inclusion of potential contingency provisions. The
rules and the types of revisions under review for contingency purposes
include: New Rule 1109.1 (NOX Emission Reductions From
Refinery Equipment) (contingency to remove an exemption (e.g., low-use
exemption) for a specific refinery equipment category); existing Rule
1110.2 (Emissions from Gaseous- and Liquid-Fueled Engines) (contingency
to remove exemptions for orchard wind machines powered by internal
combustion engines and agricultural stationary engines); and existing
Rule 1117 (Emissions of Oxides of Nitrogen from Glass Melting Furnaces)
(contingency to remove exemptions for idling furnaces and furnaces used
in the melting of glass for the production of fiberglass exclusively),
among others.
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    \150\ Letters dated January 29, 2019 and May 2, 2019, from Wayne
Nastri, SCAQMD Executive Officer, to Richard Corey, Executive
Officer, CARB.
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    CARB has attached the District's commitment to revise a rule to a
letter committing to adopt and submit the revised rule to the EPA
within one year of the EPA's final action on the contingency measure
element of the 2016 South Coast Ozone Plan.\151\
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    \151\ Letters dated February 13, 2019, from Richard Corey,
Executive Officer, CARB, to Mike Stoker, Regional Administrator, EPA
Region IX, and May 20, 2019, from Michael Benjamin, CARB, to Amy
Zimpfer, EPA Region IX.
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3. The EPA's Review of the State's Submission
    Sections 172(c)(9) and 182(c)(9) require contingency measures to
address potential failure to achieve RFP milestones or failure to
attain the NAAQS by the applicable attainment date. For the purposes of
evaluating the contingency measure element of the 2016 South Coast
Ozone SIP, we find it useful to distinguish between contingency
measures to address potential failure to achieve RFP milestones (``RFP
contingency measures'') and contingency measures to address potential
failure to attain the NAAQS (``attainment contingency measures'').
    With respect to the RFP contingency measure requirement, we have
reviewed the surplus emissions estimates in each of the RFP milestone
years, as shown in the 2018 SIP Update, and find that the calculations
are correct. We therefore agree that the 2016 South Coast Ozone SIP
provides surplus emissions reductions well beyond those necessary to
demonstrate RFP in all of the RFP milestone years. While such surplus
emissions reductions in the RFP milestone years do not represent
contingency measures themselves, we believe they are relevant in
evaluating the adequacy of RFP contingency measures that are submitted
(or will be submitted) to meet the requirements of sections 172(c)(9)
and 182(c)(9).
    In this case, the District and CARB have committed to develop,
adopt and submit a revised District rule or rules, or a new rule or
rules, as an RFP contingency measure within one year of our final
action on the 2016 South Coast Ozone SIP. The specific types of

revisions the District has committed to make, such as increasing the
stringency of an existing requirement or removing an exemption, upon an
RPF milestone failure would comply with the requirements in CAA
sections 172(c)(9) and 182(c)(9) because they would be undertaken if
the area fails to meet an RFP milestone and would take effect without
significant further action by the state or the EPA.
    Next, we considered the adequacy of the RFP contingency measure
(once adopted and submitted) from the standpoint of the magnitude of
emissions reductions the measure would provide (if triggered). Neither
the CAA nor the EPA's implementing regulations for the ozone NAAQS
establish a specific amount of emissions reductions that implementation
of contingency measures must achieve, but we generally expect that
contingency measures should provide for emissions reductions
approximately equivalent to one year's worth of RFP, which, for ozone,
amounts to reductions of 3 percent of the baseline emissions inventory
for the nonattainment area. For the 2008 ozone NAAQS in the South
Coast, one year's worth of RFP is approximately 16 tpd of VOC or
NOX reductions.\152\
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    \152\ The 2011 baseline for NOX and VOC is 534.3 tpd
and 522.0 tpd, respectively, as shown in tables IX-1 and IX-2 of the
2018 SIP Update. Three percent of the baselines is 16.0 tpd of
NOX and 15.7 tpd of VOC, respectively.
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    In this instance, because of the nature of the District's intended
contingency measure (i.e., to modify an existing rule or rules to
increase the stringency or to remove an exemption), the District did
not quantify the potential additional emission reductions from its
contingency measure commitment, but we believe that it is unlikely that
the RFP contingency measure, once adopted and submitted, will achieve
one year's worth of RFP (i.e., 16.0 tpd of NOX or VOC) given
the types of rule revisions under consideration and the magnitude of
emissions reductions constituting one year's worth of RFP. However, the
2018 SIP Update provides the larger SIP planning context in which to
judge the adequacy of the to-be-submitted District contingency measure
by calculating the surplus emissions reductions estimated to be
achieved in the RFP milestone years. More specifically, Table IX-2 in
the 2018 SIP Update identified surplus NOX reductions in the
various RFP milestone years. For the South Coast, the estimates of
surplus NOX reductions vary for each RFP milestone year but
range from a minimum of 31.5 percent in milestone year 2017 to 47.2
percent in milestone year 2023.\153\ These represent values that far
eclipse one year's worth of RFP (approximately 16 tpd or 3 percent) and
that provide the basis to conclude that the risk of any failure to
achieve an RFP milestone for the 2008 ozone NAAQS in the South Coast is
very low. The surplus reflects already implemented regulations and is
primarily the result of 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 emission
standards. In light of the extent of surplus NOX emissions
reductions in the RFP milestone years, the emissions reductions from
the District contingency measure would be sufficient to meet the
contingency measure requirements of the CAA with respect to RFP
milestones, even though the measure would likely achieve emissions
reductions lower than the EPA normally recommends for reductions from
such a measure.
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    \153\ 2018 SIP Update, Table IX-2.
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    With respect to the attainment contingency measure requirement, we
are proposing to approve the attainment demonstration for the 2008
Ozone NAAQS in the 2016 South Coast Ozone SIP that relies in part on
new technology provisions under CAA section 182(e)(5). In connection
with the proposed approval of the attainment demonstration, we are
proposing to approve CARB's commitment to develop, adopt and submit
contingency measures by 2028 (three years prior to the attainment year)
if new technology measures do not achieve planned reductions. CARB has
clarified that the commitment to submit contingency measures as
necessary to address shortfalls in emissions reductions from new
technology measures also includes a commitment to submit attainment
contingency measures.
    The EPA allows states to submit, for Extreme areas, enforceable
commitments to develop and adopt contingency measures meeting the
requirements of section 182(e)(5) to satisfy the requirements for both
attainment contingency measures in CAA sections 172(c)(9) and
182(c)(9).\154\ We find that CARB's commitment, as clarified by CARB to
include attainment contingency measures, provides an adequate basis to
defer submittal of attainment contingency measures for the South Coast
for the 2008 ozone NAAQS until 2028.
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    \154\ 80 FR 12264, at 12285-12286 (March 6, 2015)
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    For the these reasons, we propose to approve conditionally the RFP
contingency measure element of the 2016 South Coast Ozone SIP as
supplemented by commitments from the District and CARB to adopt and
submit an additional contingency measure, to meet the RFP contingency
measure requirements of CAA sections 172(c)(9) and 182(c)(9). Our
proposed approval is conditional because it relies upon commitments to
adopt and submit a specific enforceable contingency measure (i.e., a
revised or new District rule or rules with contingent provisions).
Conditional approvals are authorized under CAA section 110(k)(4) of the
CAA. We also propose to find that CARB's commitment to submit
attainment contingency measures provides an adequate basis to defer
submittal of attainment contingency measures meeting the requirements
in CAA sections 172(c)(9) and 182(c)(9) until 2028.

H. Clean Fuels or Advanced Control Technology for Boilers

1. Statutory and Regulatory Requirements
    Section 182(e)(3) of the CAA provides that SIPs for Extreme
nonattainment areas require each new, modified, and existing electric
utility and industrial and commercial boiler that emits more than 25