[Federal Register Volume 86, Number 88 (Monday, May 10, 2021)]
[Proposed Rules]
[Pages 24809-24829]
[FR Doc No: 2021-09842]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2020-0254; FRL-10023-52-Region 9]

Clean Air Plans; 2008 8-Hour Ozone Nonattainment Area
Requirements; West Mojave Desert, California

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to
approve, or conditionally approve, all or portions of the state
implementation plan (SIP) revision submitted by the State of California
to meet Clean Air Act requirements for the 2008 8-hour ozone national
ambient air quality standards (NAAQS or ``standards'') in the West
Mojave Desert ozone nonattainment area. The SIP revision addresses the
nonattainment area requirements for the

2008 8-hour ozone NAAQS, including the requirements for an emissions
inventory, emissions statements, attainment demonstration, reasonable
further progress, reasonably available control measures, contingency
measures, and motor vehicle emissions budgets. The EPA is proposing to
approve the SIP revision as meeting all the applicable ozone
nonattainment area requirements, except for contingency measures, for
which we are proposing conditional approval.

DATES: Written comments must arrive on or before June 9, 2021.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2020-0254 at https://www.regulations.gov. For comments submitted at
Regulations.gov, follow the online instructions for submitting
comments. Once submitted, comments cannot be edited or removed from
Regulations.gov. The EPA may publish any comment received to its public
docket. Do not submit electronically any information you consider to be
Confidential Business Information (CBI) or other information whose
disclosure is restricted by statute. Multimedia submissions (audio,
video, etc.) must be accompanied by a written comment. The written
comment is considered the official comment and should include
discussion of all points you wish to make. The EPA will generally not
consider comments or comment contents located outside of the primary
submission (i.e., on the web, cloud, or other file sharing system). For
additional submission methods, please contact the person identified in
the FOR FURTHER INFORMATION CONTACT section. For the full EPA public
comment policy, information about CBI or multimedia submissions, and
general guidance on making effective comments, please visit http://www.epa.gov/dockets/commenting-epa-dockets. If you need assistance in a
language other than English or if you are a person with disabilities
who needs a reasonable accommodation at no cost to you, please contact
the person identified in the FOR FURTHER INFORMATION CONTACT section.

FOR FURTHER INFORMATION CONTACT: Tom Kelly, EPA Region IX, (415) 972-
3856<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:  Throughout this document, ``we,'' ``us,''
and ``our'' refer to the EPA.

Table of Contents

I. Regulatory Context
    A. Ozone Standards, Area Designations, and SIPs
    B. The West Mojave Desert Ozone Nonattainment Area
    C. CAA and Regulatory Requirements for 2008 Ozone Nonattainment
Area SIPs
II. Submissions From the State of California To Address 2008 Ozone
Standards Requirements in the West Mojave Desert
    A. Summary of Submissions
    B. Clean Air Act Procedural Requirements for Adoption and
Submission of SIP Revisions
III. Evaluation of the 2016 WMD Attainment Plan and the 2018 SIP
Update
    A. Emissions Inventories
    B. Emissions Statements
    C. Reasonably Available Control Measures Demonstration
    D. Attainment Demonstration
    E. Rate of Progress Plan and Reasonable Further Progress
Demonstration
    F. Transportation Control Strategies and Measures To Offset
Emissions Increases From Vehicle Miles Traveled
    G. Contingency Measures
    H. Motor Vehicle Emissions Budgets for Transportation Conformity
    I. Other Clean Air Act Requirements Applicable to Severe Ozone
Nonattainment Areas
IV. Proposed Action
V. Statutory and Executive Order Reviews

I. Regulatory Context

A. Ozone Standards, Area Designations, and SIPs

    Ground-level ozone pollution is formed from the reaction of
volatile organic compounds (VOC) and oxides of nitrogen
(NOX) in the presence of sunlight.\1\ These two pollutants,
referred to as ozone precursors, are emitted by many types of sources,
including on-and off-road motor vehicles and engines, power plants and
industrial facilities, and smaller area sources such as lawn and garden
equipment and paints.
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    \1\ The State of California typically refers to reactive organic
gases (ROG) in its ozone-related submissions since VOC in general
can include both reactive and unreactive gases. However, since ROG
and VOC inventories pertain to common chemical species (e.g.,
benzene, xylene, etc.), we refer to this set of gases as VOC in this
proposed rule.
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    Scientific evidence indicates that adverse public health effects
occur following exposure to ozone, particularly in children and adults
with lung disease. Breathing air containing ozone can reduce lung
function and inflame airways, which can increase respiratory symptoms
and aggravate asthma or other lung diseases.\2\
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    \2\ See ``Fact Sheet--2008 Final Revisions to the National
Ambient Air Quality Standards for Ozone'' dated March 2008.
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    Under section 109 of the Clean Air Act (CAA or ``Act''), the EPA
promulgates NAAQS for pervasive air pollutants, such as ozone. The EPA
has previously promulgated NAAQS for ozone in 1979 and 1997.\3\ In
2008, the EPA revised and further strengthened the ozone NAAQS by
setting the acceptable level of ozone in the ambient air at 0.075 parts
per million (ppm) averaged over an 8-hour period.\4\ Although the EPA
further tightened the 8-hour ozone NAAQS to 0.070 ppm in 2015, this
action relates to the requirements for the 2008 ozone NAAQS.\5\
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    \3\ The ozone NAAQS promulgated in 1979 was 0.12 parts per
million (ppm) averaged over a 1-hour period. See 44 FR 8202
(February 8, 1979). The ozone NAAQS promulgated in 1997 was 0.08 ppm
averaged over an 8-hour period. See 62 FR 38856 (July 18, 1997).
    \4\ 73 FR 16436 (March 27, 2008).
    \5\ Information on the 2015 ozone NAAQS is available at 80 FR
65292 (October 26, 2015).
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    Following promulgation of a new or revised NAAQS, the EPA is
required under CAA section 107(d) to designate areas throughout the
country as attaining or not attaining the NAAQS. The ``Los Angeles-San
Bernardino Counties (West Mojave Desert), CA'' area (``West Mojave
Desert'' or WMD) was designated as nonattainment for the 2008 ozone
standards on May 21, 2012 and classified as ``Severe-15.'' \6\
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    \6\ 77 FR 30088 (May 21, 2012).
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    Under the CAA, after the EPA designates areas as nonattainment for
a NAAQS, states with nonattainment areas are required to submit SIP
revisions that provide for, among other things, attainment of the NAAQS
within certain prescribed periods that vary depending on the severity
of nonattainment. Areas classified as Severe-15 must attain the NAAQS
within 15 years of the effective date of the nonattainment
designation.\7\
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    \7\ CAA section 181(a)(1), 40 CFR 51.1102 and 51.1103(a).
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    In California, the California Air Resources Board (CARB) is the
agency responsible for the adoption and submission to the EPA of
California SIPs and SIP revisions, and it has broad authority to
establish emissions standards and other requirements for mobile
sources. Local and regional air pollution control districts in
California are responsible for the regulation of stationary sources and
are generally responsible for the development of regional air quality
plans. In the West Mojave Desert, two agencies develop and adopt air
quality management plans to address CAA planning requirements
applicable to that region, the Antelope Valley Air Quality Management
District (AVAQMD) and the Mojave Desert Air Quality Management District
(MDAQMD) (collectively, ``Districts''). Such plans are then submitted
to CARB for adoption and submittal to the EPA as revisions to the
California SIP.

B. The West Mojave Desert Ozone Nonattainment Area

    The West Mojave Desert is located in northeast Los Angeles County
and southwest San Bernardino County. For a precise description of the
geographic boundaries of the area, see 40 CFR 81.305. The Los Angeles
County portion of the WMD area is under the jurisdiction of the AVAQMD,
and the San Bernardino County portion of the area is under the
jurisdiction of the MDAQMD.
    The population of the West Mojave Desert is approximately
868,380.\8\ Ambient 8-hour ozone concentrations in the WMD are above
the level of the 2008 8-hour ozone NAAQS. The area's maximum design
value for the 2017-2019 period, based on certified data at the Phalen
monitor (Air Quality System ID: 06-071-0012), is 0.096 ppm.\9\
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    \8\ 8-Hour Ozone (2008) Designated Area/State Information, Green
Book, EPA, accessed on November 19, 2020, Population Data from 2010,
https://www3.epa.gov/airquality/greenbook/hbtc.html.
    \9\ Air Quality System (AQS) Design Value Report,
O3_designvalues_2017_2019_final_5_26_20.pdf, in the docket for this
proposed action. The AQS is a database containing ambient air
pollution data collected by the EPA and state, local, and tribal air
pollution control agencies from over thousands of monitors. Design
values, defined to be consistent with the individual NAAQS as
described in 40 CFR part 50, are typically used to designate and
classify nonattainment areas, as well as to assess progress towards
meeting the NAAQS.
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    The West Mojave Desert receives significant transport of ozone and
ozone precursors from the South Coast Air Basin, and to a lesser
extent, the San Joaquin Valley. To attain the 2008 ozone NAAQS, the WMD
will depend on continued emissions reductions in those areas.\10\
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    \10\ See CARB, Staff Report, ``CARB Review of the Mojave Desert
AQMD and Antelope Valley AQMD Federal 75 ppb Ozone Attainment Plans
for the Western Mojave Desert Nonattainment Area,'' April 21, 2017
(``CARB Staff Report''), Appendix B, ``Weight of Evidence
Analysis,'' B-28.
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C. CAA and Regulatory Requirements for 2008 8-Hour Ozone Nonattainment
Area SIPs

    States must implement the 2008 ozone standards under title I, part
D of the CAA, which includes sections 171-179B of subpart 1,
``Nonattainment Areas in General,'' and sections 181-185 of subpart 2,
``Additional Provisions for Ozone Nonattainment Areas.'' To assist
states in developing effective plans to address ozone nonattainment
problems, in 2015 the EPA issued a SIP Requirements Rule (SRR) for the
2008 ozone standards (``2008 Ozone SRR'') that addresses requirements
for nonattainment areas, such as attainment dates, emissions
inventories, attainment and reasonable further progress (RFP)
demonstrations, and the transition from the 1997 8-hour ozone standards
to the 2008 8-hour ozone standards and associated anti-backsliding
requirements.\11\ The 2008 Ozone SRR is codified at 40 CFR part 51,
subpart AA. We discuss each of the CAA statutory and regulatory
requirements for 2008 8-hour ozone plans in more detail in Section III
of this document.
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    \11\ 80 FR 12264 (March 6, 2015).
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    The EPA's 2008 Ozone SRR was challenged, and on February 16, 2018,
the U.S. Court of Appeals for the D.C. Circuit (``D.C. Circuit'')
published its decision in South Coast Air Quality Management District
v. EPA (``South Coast II'') \12\ vacating portions of the 2008 Ozone
SRR. The only aspect of the South Coast II decision that affects this
proposed action is the vacatur of the alternative baseline year for RFP
plans. More specifically, the 2008 Ozone SRR required states to develop
the baseline emissions inventory for RFP plans using the emissions
inventory for the most recent calendar year for which states submit a
triennial inventory to the EPA under subpart A of 40 CFR part 51, ``Air
Emissions Reporting Requirements,'' which was 2011. The 2008 Ozone SRR,
however, allowed states to use an alternative year, between 2008 and
2012, for the baseline emissions inventory, provided the state
demonstrated why the alternative baseline year was appropriate. In the
South Coast II decision, the D.C. Circuit vacated the provisions of the
2008 Ozone SRR that allowed states to use an alternative baseline year
for demonstrating RFP.
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    \12\ South Coast Air Quality Management District v. EPA, 882
F.3d 1138 (D.C. Cir. 2018). The term ``South Coast II'' is used in
reference to the 2018 court decision to distinguish it from a
decision published in 2006 also referred to as ``South Coast.'' The
earlier decision involved a challenge to the EPA's Phase 1
implementation rule for the 1997 ozone NAAQS. South Coast Air
Quality Management Dist. v. EPA, 472 F.3d 882 (D.C. Cir. 2006).
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II. Submissions From the State of California To Address 2008 Ozone
Standards Requirements in the West Mojave Desert

A. Summary of Submissions

1. 2016 WMD Attainment Plan
    On June 2, 2017, CARB submitted a SIP revision to address the WMD's
planning obligations as a Severe-15 nonattainment area for the 2008
ozone NAAQS.\13\ The June 2, 2017 submittal includes attainment plans
prepared by the AVAQMD (``AVAQMD Attainment Plan'') \14\ and the MDAQMD
(``MDAQMD Attainment Plan''),\15\ an accompanying staff report prepared
by CARB (``CARB Staff Report''),\16\ and other supporting documents. We
refer to the AVAQMD Attainment Plan and the MDAQMD Attainment Plan
collectively as the Districts' ``Attainment Plans,'' and we refer to
all the documents submitted to the EPA on June 2, 2017 as the ``2016
WMD Attainment Plan.'' The 2016 WMD Attainment Plan addresses the
requirements for base year and projected future year emissions
inventories, air quality modeling demonstrating attainment of the 2008
ozone NAAQS by the applicable attainment year, provisions demonstrating
implementation of reasonably available control measures (RACM),
provisions for transportation control strategies and measures, a
demonstration of RFP, and contingency measures for failure to make RFP
or to attain, among other requirements.
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    \13\ Letter dated June 2, 2017, from Richard Corey, CARB, to
Alexis Strauss, EPA Region IX.
    \14\ AVAQMD, ``AVAQMD Federal 75 ppb Ozone Attainment Plan
(Western Mojave Desert Nonattainment Area),'' adopted on March 21,
2017.
    \15\ MDAQMD, ``MDAQMD Federal 75 ppb Ozone Attainment Plan
(Western Mojave Desert Nonattainment Area),'' adopted on February
27, 2017.
    \16\ CARB, Staff Report, ``CARB Review of the Mojave Desert AQMD
and Antelope Valley AQMD Federal 75 ppb Ozone Attainment Plans for
the Western Mojave Desert Nonattainment Area,'' released April 21,
2017.
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2. CARB's 2018 Updates to the California State Implementation Plan
    On December 11, 2018, CARB submitted the ``2018 Updates to the
California State Implementation Plan'' (``2018 SIP Update'') to the EPA
as a revision to the California SIP.\17\ CARB adopted the 2018 SIP
Update on October 25, 2018. CARB developed the 2018 SIP Update in
response to the court's decision in South Coast II vacating the 2008
Ozone SRR with respect to the use of an alternate baseline year for
demonstrating RFP, and to address contingency measure requirements in
the wake of the court decision in Bahr v. EPA.\18\ The 2018 SIP Update
includes updates for 8 different California ozone nonattainment areas.
We have previously approved portions of the 2018 SIP Update related to
other

nonattainment areas.\19\ For the West Mojave Desert, the 2018 SIP
Update includes an RFP demonstration using the required 2011 baseline
year and revised motor vehicle emission budgets for the 2008 ozone
NAAQS.\20\
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    \17\ Letter dated December 5, 2018, from Richard Corey, CARB, to
Mike Stoker, EPA Region IX.
    \18\ Bahr v. EPA, 836 F.3d 1218 (9th Cir. 2016). In this case,
the court rejected the EPA's longstanding interpretation of CAA
section 172(c)(9) as allowing for early implementation of
contingency measures. The court concluded that a contingency measure
must take effect at the time the area fails to make RFP or attain by
the applicable attainment date, not before. See also Sierra Club v.
EPA, 985 F.3d 1055 (D.C. Cir. 2021), reaching a similar decision.
These cases are addressed below in Section III.G of this document.
    \19\ See, e.g., 84 FR 11198 (March 25, 2019) (final approval of
the San Joaquin Valley portion of the 2018 SIP Update) and 84 FR
52005 (October 1, 2019) (final approval of the South Coast portion
of the 2018 SIP Update).
    \20\ CARB withdrew the 2016 WMD Attainment Plan RFP
demonstration in a letter dated December 18, 2019, from Richard
Corey, CARB, to Michael Stoker, EPA Region IX.
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B. Clean Air Act Procedural Requirements for Adoption and Submission of
SIP Revisions

1. Requirements
    CAA sections 110(a)(1) and (2) and 110(l) require a state to
provide reasonable public notice and opportunity for public hearing
prior to the adoption and submission of a SIP or SIP revision. To meet
this requirement, every SIP submittal should include evidence that
adequate public notice was given and an opportunity for a public
hearing was provided consistent with the EPA's implementing regulations
in 40 CFR 51.102.
2. Summary of the State's Documentation
a. 2016 WMD Attainment Plan
    On February 17, 2017, the AVAQMD published notice in a local
newspaper of a public hearing to be held on March 21, 2017, for
adoption of the AVAQMD Attainment Plan.\21\ The District held the
public hearing on March 21, 2017,\22\ and signed a Board resolution
adopting the plan that same day.\23\ The District sent the plan to CARB
on April 18, 2017.\24\
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    \21\ Appendix B of Final Staff Report, Adoption of AVAQMD
Attainment Plan.
    \22\ Minutes of the Governing Board of the Antelope Valley Air
Quality Management District, Lancaster, California, March 21, 2017.
    \23\ Resolution 17-01, March 21, 2017.
    \24\ Letter dated April 18, 2017, from Alan J. De Salvio,
AVAQMD, to Richard Corey, CARB.
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    On January 27, 2017, the MDAQMD published notice in a local
newspaper of a public hearing to be held on February 27, 2017, for
adoption of the MDAQMD Attainment Plan.\25\ The District held the
public hearing on February 27, 2017,\26\ and signed a Board resolution
adopting the plan the same day.\27\ The District sent the plan to CARB
on April 3, 2017.\28\
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    \25\ Appendix B of Final Staff Report, MDAQMD Attainment Plan.
    \26\ Minutes of the Governing Board of the Mojave Desert Air
Quality Management District, Victorville, California, February 27,
2017.
    \27\ Resolution 17-05, dated February 27, 2017.
    \28\ Letter dated April 3, 2017, from Alan J. De Salvio, MDAQMD,
to Richard Corey, CARB.
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    On April 20, 2017, CARB provided notice of a public comment period
and public hearing to be held on May 25, 2017, for the 2016 WMD
Attainment Plan.\29\ CARB adopted the 2016 WMD Attainment Plan by
resolution at the May 25, 2017 hearing,\30\ and submitted it to the EPA
on June 2, 2017.\31\ The EPA notified CARB the submittal was complete
on November 22, 2017.\32\
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    \29\ Notice of Public Meeting to Consider the 2016 Ozone State
Implementation Plan for the Western Mojave Desert Nonattainment
Area, California Air Resources Board, April 20, 2017.
    \30\ Board Resolution 17-12, May 25, 2017.
    \31\ Letter dated June 2, 2017, from Richard Corey, CARB, to
Alexis Strauss, EPA Region IX.
    \32\ Letter dated November 22, 2017, from Matt Lakin, EPA Region
IX, to Richard Corey, CARB.
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b. 2018 SIP Update
    On September 21, 2018, CARB provided notice of a public comment
period and public hearing to be held on October 25, 2018, for the 2018
SIP Update.\33\ CARB adopted the 2018 SIP Update by resolution at the
October 25, 2018 hearing,\34\ and submitted it the to the EPA in a
letter dated December 5, 2018, which was electronically transmitted to
the EPA's State Planning Electronic Collaboration System on December
11, 2018.\35\
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    \33\ Notice of Public Meeting to Consider the 2018 Updates to
the California State Implementation Plan, September 21, 2018.
    \34\ Board Resolution 18-50, October 25, 2018.
    \35\ Letter dated December 5, 2018, from Richard Corey, CARB, to
Mike Stoker, EPA Region IX.
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c. The EPA's Conclusions on the Submission Requirements for the WMD
2016 Attainment Plan
    CARB has satisfied the applicable statutory and regulatory
requirements for reasonable public notice and hearing prior to the
adoption and submittal of the elements of the 2016 WMD Attainment Plan.
Based on information provided in each SIP revision and summarized
above, the EPA has determined that all hearings were properly noticed.
Therefore, we find that the submittals of the 2016 WMD Attainment Plan
meet the procedural requirements for public notice and hearing in CAA
sections 110(a) and 110(l) and 40 CFR 51.102.

III. Evaluation of the 2016 WMD Attainment Plan and 2018 SIP Update

A. Emission Inventories

1. Statutory and Regulatory Requirements
    Sections 172(c)(3) and 182(a)(1) of the CAA require states to
submit for each ozone nonattainment area a ``base year inventory'' that
is a comprehensive, accurate, current inventory of actual emissions
from all sources of the relevant pollutant or pollutants in the area.
In addition, the 2008 Ozone SRR requires that the inventory year be
selected consistent with the baseline year for the RFP demonstration,
which is usually the most recent calendar year for which a complete
triennial inventory is required to be submitted to the EPA under the
Air Emissions Reporting Requirements.\36\ The EPA has issued guidance
on the development of base year and future year emissions inventories
for 8-hour ozone and other pollutants.\37\ Emissions inventories for
ozone must include emissions of VOC and NOX and represent
emissions for a typical ozone season weekday.\38\ States should include
documentation explaining how the emissions data were calculated. In
estimating mobile source emissions, states should use the latest
emissions models and planning assumptions available at the time the SIP
is developed.\39\
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    \36\ 2008 Ozone SRR at 40 CFR 51.1115(a) and the Air Emissions
Reporting Requirements at 40 CFR part 51 subpart A.
    \37\ ``Emissions Inventory Guidance for Implementation of Ozone
and Particulate Matter National Ambient Air Quality Standards
(NAAQS) and Regional Haze Regulations,'' EPA-454/B-17-002, May 2017.
At the time the 2016 WMD Attainment Plan was developed, the
following EPA emissions inventory guidance applied: ``Emissions
Inventory Guidance for Implementation of Ozone and Particulate
Matter National Ambient Air Quality Standards (NAAQS) and Regional
Haze Regulations,'' EPA-454/R-05-001, August 2005.
    \38\ 40 CFR 51.1115(a) and (c), and 40 CFR 51.1100(bb) and (cc).
    \39\ 80 FR 12264, 12290 (March 6, 2015).
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    Future year baseline emissions inventories must reflect the most
recent population, employment, travel, and congestion estimates for the
area. In this context, ``baseline'' emissions inventories refer to
emissions estimates for a given year and area that reflect rules and
regulations and other measures that are already adopted. Future year
baseline emissions inventories are necessary to show the projected
effectiveness of SIP control measures. Both the base year and future
year inventories are necessary for photochemical modeling to
demonstrate attainment.
2. Summary of State's Submission
    The 2016 WMD Attainment Plan includes base year (2012) and future
year baseline inventories for NOX and VOC for the West
Mojave Desert.\40\

Documentation for the inventories is found in Appendix A-2 of the CARB
Staff Report.\41\ The emissions inventories represent average summer
day emissions, consistent with the observation that ozone levels in
West Mojave Desert are typically higher from May through October.\42\
For stationary and area sources, the 2012 base year and future year
inventories considered several of the Districts' rules, specifically
including MDAQMD Rule 1461, ``Portland Cement Kilns'' (covering mineral
processing), and rules from both Districts based on CARB's rules for
consumer products, aerosol coatings,\43\ and architectural
coatings.\44\ The inventory also specifically notes the incorporation
of CARB's performance standards for gasoline dispensing hose
permeation,\45\ and revised vehicle refueling emission factors.\46\
These District and CARB rules are noted in Table 5, ``Stationary Source
Control Rules and Regulations Included in the Inventory,'' of Appendix
A-1 of the CARB Staff Report. The mobile source portions of both base
year and projected future year inventories were developed using
California's EPA-approved mobile source emissions model, EMFAC2014, for
estimating on-road motor vehicle emissions.\47\
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    \40\ The 2012 base year and future year baseline emissions
inventories in the CARB Staff Report exclude non-anthropogenic
``natural sources'' emissions such as biogenics and geogenics.
However, emissions from such natural sources are included in the
emissions inventories used for the attainment demonstration because
they affect ozone formation.
    \41\ The 2012 base year emissions inventory included in the CARB
Staff Report supersedes and replaces a previous submittal of the
2012 base year emissions inventory for the West Mojave Desert in the
``8-Hour Ozone State Implementation Plan Emission Inventory
Submittal'' (the ``Multi-Area Emission Inventory''). The Multi-Area
Emission Inventory was submitted by CARB on July 17, 2014 and later
withdrawn on December 18, 2019. The Multi-Area Inventory included
2012 base year emissions inventories for 16 nonattainment areas,
including the West Mojave Desert. Relative to the corresponding
inventory for the West Mojave Desert in the Multi-Area Emission
Inventory, the 2012 base year emissions inventory in the 2016 WMD
Attainment Plan reflects updated stationary, area, and nonroad
source calculations as well as an updated version of the EMFAC model
for on-road motor vehicle estimates.
    \42\ Appendix A-2 of the CARB Staff Report. In contrast, the
emissions inventory and projections in Appendix A and B of the
Districts' Attainment Plans contain average daily emissions, not
average summer day emissions.
    \43\ See California Code of Regulations 94522, ``Limits and
Requirements for Aerosol Coating Products,'' incorporated into the
SIP on November 4, 2009 (74 FR 57074).
    \44\ As stated on the CARB website (https://ww2.arb.ca.gov/our-work/programs/coatings/architectural-coatings/scm-district-rulemaking-schedule, accessed on August 25, 2020), AVAQMD Rule 1113,
adopted locally on June 18, 2013 and MDAQMD Rule 1113, adopted
locally on April 23, 2012, implement California's 2007 suggested
control measures for architectural coatings. These rules were
incorporated into the SIP on December 8, 2015 (80 FR 76222) and
December 8, 2015 (80 FR 76222), respectively.
    \45\ See https://ww3.arb.ca.gov/vapor/gdf-emisfactor/attachment5.pdf.
    \46\ See https://ww2.arb.ca.gov/gasoline-dispensing-facility-emission-factors.
    \47\ EMFAC is short for EMission FACtor.
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    The 2016 WMD Attainment Plan includes emissions inventories for
stationary sources, area sources, and on-road and off-road mobile
sources.\48\ Stationary sources refer to larger ``point'' sources that
have a fixed geographic location. The 2018 SIP Update explains that
2012 ``stationary source emissions reflect actual emissions reported
from industrial point sources'' and include stationary aggregate
sources, such as gasoline dispensing facilities.\49\ AVAQMD Rule 107,
``Certification of Submissions and Emission Statements,'' and MDAQMD
Rule 107, ``Certification and Emission Statements,'' require all
stationary sources within the nonattainment area that emit more than 25
tons per year (tpy) or more of VOC or NOX to report and
certify annual emissions. For the 2012 base year, CARB developed a list
of stationary sources in Los Angeles and San Bernardino counties and
their associated emissions. AVAQMD and MDAQMD separated the stationary
sources within the WMD from those within their respective counties but
outside the WMD.
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    \48\ CARB Staff Report, Appendix A-2.
    \49\ 2018 SIP Update, Appendix A, A-1.
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    Area sources include smaller emissions sources distributed across
the nonattainment area, such as consumer products, architectural
coatings, pesticides and herbicides, farming operations, and cooking.
CARB and the District estimate emissions for area sources using surveys
and information from other state and federal agencies. These estimates
are updated with relevant factors such as population changes,
demographic factors, and agency specific growth factors (e.g., for
farming operations and use of herbicides and pesticides).\50\
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    \50\ CARB Staff Report, see the discussion of areawide sources
beginning on page A1-8.
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    On-road emissions inventories in the CARB Staff Report are
calculated using CARB's EMFAC2014 model \51\ and the travel activity
data provided by the area's metropolitan planning organization, the
Southern California Association of Governments (SCAG), in the ``2016-
2040 Regional Transportation Plan/Sustainable Communities Strategy.''
\52\ CARB consulted with MDAQMD staff to estimate emissions from off-
road equipment and area sources occurring in the nonattainment area,
most often using human population as default surrogate for the quantity
of emissions occurring in the WMD.\53\ Future emissions forecasts are
primarily based on population and economic growth projections provided
by SCAG; growth estimates from government agencies such as the U.S.
Bureau of Labor Statistics, the U.S. Department of Agriculture, and
CARB; forecasts from the Districts; and research studies. The growth
factors for each emissions category are discussed in Appendix A-1 of
the CARB Staff Report.
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    \51\ In December 2015, the EPA approved EMFAC2014 for SIP
development and transportation conformity purposes in California. 80
FR 77337 (December 14, 2015). EMFAC2014 was the most recently
approved version of the EMFAC model that was available at the time
of preparation of the 2016 Attainment Plan. The EPA approved an
updated version of the EMFAC model, EMFAC2017, for future SIP
development and transportation purposes in California. 84 FR 41717
(August 15, 2019).
    \52\ CARB Staff Report, Appendix A-1.
    \53\ Id. at A1-3.
---------------------------------------------------------------------------

    Table 1 below provides a summary of the CARB Staff Report's 2012
base year and future attainment year VOC and NOX emissions
estimates within the West Mojave Desert (average summer day). These
inventories provide the basis for the control measure analysis and the
attainment demonstration in the 2016 WMD Attainment Plan. Based on the
inventory for 2012, stationary and area sources of VOC emissions are
roughly equivalent to the combined on-road and off-road mobile source
emissions. For NOX emissions in 2012, on-road mobile sources
contribute the highest fraction of emissions (37.11 tons per day (tpd)
or 37.5 percent) followed by off-road (32.53 tpd or 32.9 percent),
stationary (28.27 tpd or 28.6 percent), and area sources (1.05 tpd or
1.1 percent).

     Table 1--West Mojave Desert Nonattainment Area Base Year and Attainment Year Emissions Inventory Summary
                                           [Summer season average tpd]
----------------------------------------------------------------------------------------------------------------
                                                    NOX  (2012)     NOX  (2026)
                     Category                                                       VOC  (2012)     VOC  (2026)
----------------------------------------------------------------------------------------------------------------
Stationary Sources..............................           28.27           42.08           13.16           17.35
Area Sources....................................            1.05            0.92           11.32           12.15
On-road Mobile..................................           37.11            9.84           15.21            5.98
Off-road Mobile.................................           32.53           25.53            7.09            4.99
                                                 ---------------------------------------------------------------
    Total.......................................           98.95           68.56           46.78           40.47
----------------------------------------------------------------------------------------------------------------
Source: Appendix A-2, CARB Staff Report. Due to rounding, the totals may not agree to the hundredth of a tpd.

3. The EPA's Review of the State's Submission
    We have reviewed the 2012 base year emissions inventory in the 2016
WMD Attainment Plan and the inventory methodologies used by CARB and
the District for consistency with CAA requirements and EPA guidance.
First, as required by EPA regulations, we find that the 2012 inventory
includes estimates for VOC and NOX for a typical ozone
season weekday, and that CARB has provided adequate documentation
explaining how the emissions are calculated. Second, we find that the
2012 base year emissions inventory in the 2016 WMD Attainment Plan
reflects appropriate emissions models and methodologies, and,
therefore, represents a comprehensive, accurate, and current inventory
of actual emissions during that year in the WMD. Third, we find that
selection of year 2012 for the base year emissions inventory is
appropriate because it is consistent with the 2011 RFP baseline year
(from the 2018 SIP Update) because both inventories are derived from a
common set of models and methods. Therefore, the EPA is proposing to
approve the 2012 emissions inventory in the 2016 WMD Attainment Plan as
meeting the requirements for a base year inventory set forth in CAA
section 182(a)(1) and 40 CFR 51.1115.
    With respect to future year baseline projections, we have reviewed
the growth and control factors and find them acceptable, and conclude
that the future baseline emissions projections in the 2016 WMD
Attainment Plan reflect appropriate calculation methods and the latest
planning assumptions.
    Furthermore, we note that the future year baseline projections
account for emissions reductions from control measures in adopted state
and local rules and regulations. As a general matter, the EPA will
approve a SIP revision that takes emissions reduction credit for such
control measures only where the EPA has approved the control measures
as part of the SIP. Tables 1 and 2 in the technical support document
(TSD) supporting this action document the approval of all rules within
the West Mojave Desert. Table 5 of the CARB Staff Report documents the
specific rules considered in the development of the emissions
inventory.
    With respect to mobile sources, the EPA has taken action in recent
years to approve CARB mobile source regulations into the California
SIP.\54\ We therefore find that the future year baseline projections in
the 2016 WMD Attainment Plan are properly supported by SIP-approved
stationary and mobile source control measures.
---------------------------------------------------------------------------

    \54\ See 81 FR 39424 (June 16, 2016), 82 FR 14446 (March 21,
2017), and 83 FR 23232 (May 18, 2018).
---------------------------------------------------------------------------

B. Emissions Statements

1. Statutory and Regulatory Requirements
    Section 182(a)(3)(B)(i) of the Act requires each state to submit a
SIP revision requiring owners or operators of stationary sources of VOC
or NOX to provide the state with statements of actual
emissions from such sources. Statements must be submitted at least
every year and must contain a certification that the information
contained in the statement is accurate to the best knowledge of the
individual certifying the statement. Section 182(a)(3)(B)(ii) of the
Act allows states to waive the emission statement requirement for any
class or category of stationary sources that emit less than 25 tpy of
VOC or NOX, if the state provides an inventory of emissions
from such class or category of sources as part of the base year or
periodic inventories required under CAA sections 182(a)(1) and
182(a)(3)(A), based on the use of emission factors established by the
EPA or other methods acceptable to the EPA.
    The preamble of the 2008 Ozone SRR states that if an area has a
previously approved emissions statement rule for the 1997 ozone NAAQS
or the 1-hour ozone NAAQS that covers all portions of the nonattainment
area for the 2008 ozone NAAQS, such rule should be sufficient for
purposes of the emissions statement requirement for the 2008 ozone
NAAQS.\55\ The state should review the existing rule to ensure it is
adequate and, if so, may rely on it to meet the emissions statement
requirement for the 2008 ozone NAAQS. Where an existing emissions
statement requirement is still adequate to meet the requirements of
this rule, states can provide the rationale for that determination to
the EPA in a written statement in the SIP to meet this requirement.
States should identify the various requirements and how each is met by
the existing emissions statement program. Where an emissions statement
requirement is modified for any reason, the state must provide the
revisions to the emissions statement as part of its SIP.
---------------------------------------------------------------------------

    \55\ 80 FR 12264, at 12291 (March 6, 2015).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    The 2016 WMD Attainment Plan addresses compliance with the
emissions statement requirement in CAA section 182(a)(3)(B) for the
2008 ozone NAAQS by reference to AVAQMD Rule 107 and MDAQMD Rule
107.\56\ These rules require, among other things, emissions reporting
within the West Mojave Desert from all stationary sources of
NOX and VOC with emissions over 25 tpy.\57\ The EPA approved
AVAQMD Rule 107 on April 11, 2013 (78 FR 21545) and MDAQMD Rule 107 on
May 26, 2004 (69 FR 29880) as revisions to each District's portion of
the California SIP. AVAQMD and MDAQMD letters to CARB state that these
rules continue to meet the emission statement requirements of CAA
section 182(a)(3)(B) and that the Districts rely on these rules to meet
the

emissions statement requirements for the 2008 ozone standards.\58\
---------------------------------------------------------------------------

    \56\ Addendum A to Appendix D and Addendum A to Appendix E of
the CARB Staff Report.
    \57\ Id.
    \58\ Appendix D1 and D2 and Appendix E1 and E1 of the CARB Staff
Report.
---------------------------------------------------------------------------

3. The EPA's Review of the State's Submission
    For this action, we have reviewed AVAQMD Rule 107 and MDAQMD Rule
107 for compliance with the specific requirements for emissions
statement rules under CAA section 182(a)(3)(B). We agree with the
Districts' findings: That these rules apply within the entire ozone
nonattainment area and that the nonattainment area is the same for both
the 1997 Ozone NAAQS and the 2008 ozone NAAQS; that the rules apply to
all stationary sources of VOC and NOX, except those emitting
less than 25 tpy for which the Districts have waived the requirement
(consistent with CAA section 182(a)(3)(B)(ii)); and that the rules
require reporting, on an annual basis, of total emissions of VOC and
NOX. We also find that AVAQMD Rule 107 and MDAQMD Rule 107
require certification that the information provided to the Districts is
accurate to the best knowledge of the individual certifying the
emissions data, as required under CAA section 182(a)(3)(B).
    Therefore, we propose to approve the emissions statement element of
the 2016 WMD Attainment Plan as meeting the requirements of CAA section
182(a)(3)(B) and the 40 CFR 51.1102.

C. Reasonably Available Control Measures Demonstration

1. Statutory and Regulatory Requirements
    CAA section 172(c)(1) requires that each attainment plan provide
for the implementation of all RACM as expeditiously as practicable
(including such reductions in emissions from existing sources in the
area as may be obtained through implementation of reasonably available
control technology (RACT)), and also provide for attainment of the
NAAQS. The 2008 Ozone SRR requires that, for each nonattainment area
required to submit an attainment demonstration, the state concurrently
submit a SIP revision demonstrating that it has adopted all RACM
necessary to demonstrate attainment as expeditiously as practicable and
to meet any RFP requirements.\59\
---------------------------------------------------------------------------

    \59\ 40 CFR 51.1112(c).
---------------------------------------------------------------------------

    The EPA has previously provided guidance interpreting the RACM
requirement in the General Preamble for the Implementation of the Clean
Air Act Amendments of 1990 (``General Preamble'') and in a memorandum
entitled ``Guidance on the Reasonably Available Control Measures (RACM)
Requirement and Attainment Demonstration Submissions for Ozone
Nonattainment Areas.'' \60\ In summary, to address the requirement to
adopt all RACM, states should consider all potentially reasonable
control measures for source categories in the nonattainment area to
determine whether they are reasonably available for implementation in
that area and whether they would, if implemented individually or
collectively, advance the area's attainment date by one year or
more.\61\ Any measures that are necessary to meet these requirements
that are not already either federally promulgated, or part of the
state's SIP, or otherwise creditable in the SIP, must be submitted in
enforceable form as part of the state's attainment plan for the
area.\62\
---------------------------------------------------------------------------

    \60\ General Preamble, 57 FR 13498 at 13560 (April 16, 1992);
memorandum dated November 30, 1999, from John Seitz, Director,
OAQPS, to EPA Regional Air Directors, Regions I-X, Subject:
``Guidance on the Reasonably Available Control Measures (RACM)
Requirement and Attainment Demonstration Submissions for Ozone
Nonattainment Areas.''
    \61\ Id. See also 44 FR 20372 (April 4, 1979), and memorandum
dated December 14, 2000, from John S. Seitz, Director, OAQPS, to
Regional Air Directors, titled ``Additional Submission on RACM From
States with Severe One-Hour Ozone Nonattainment Area SIPs.''
    \62\ For ozone nonattainment areas classified as Moderate or
above, CAA section 182(b)(2) also requires implementation of RACT
for all major sources of VOC and for each VOC source category for
which the EPA has issued a Control Techniques Guideline (CTG). CAA
section 182(f) requires that RACT under section 182(b)(2) also apply
to major stationary sources of NOX. In Extreme areas, a
major source is a stationary source that emits or has the potential
to emit at least 10 tpy of VOC or NOX (see CAA section
182(e) and (f)). Under the 2008 Ozone SRR, states were required to
submit SIP revisions meeting the RACT requirements of CAA sections
182(b)(2) and 182(f) no later than 24 months after the effective
date of designation for the 2008 Ozone NAAQS and to implement the
required RACT measures as expeditiously as practicable but no later
than January 1 of the 5th year after the effective date of
designation (see 40 CFR 51.1112(a)). California submitted the CAA
section 182 RACT SIP for AVAQMD and MDAQMD on October 23, 2015 and
September 9, 2015, respectively. The EPA conditionally approved
these submissions at 82 FR 46923 (October 10, 2017) and 83 FR 5921
(February 12, 2018).
---------------------------------------------------------------------------

    CAA section 172(c)(6) requires that nonattainment area plans
include enforceable emission limitations, and such other control
measures, means or techniques (including economic incentives such as
fees, marketable permits, and auctions of emission rights), as well as
schedules and timetables for compliance, as may be necessary or
appropriate to provide for timely attainment of the NAAQS.\63\ Under
the 2008 Ozone SRR, all control measures needed for attainment must be
implemented no later than the beginning of the attainment year ozone
season.\64\ The attainment year ozone season is defined as the ozone
season immediately preceding a nonattainment area's outermost
attainment date.\65\
---------------------------------------------------------------------------

    \63\ See also CAA section 110(a)(2)(A).
    \64\ 40 CFR 51.1108(d).
    \65\ 40 CFR 51.1100(h).
---------------------------------------------------------------------------

2. Summary of the State's Submission
a. The Districts' RACM Analysis
    The AVAQMD and MDAQMD Attainment Plans explain that they
incorporate all RACM, and that the Districts have adopted or committed
in the Attainment Plans to adopt all such measures.\66\ The Plans note
the Districts' reviews of stationary source rules conducted during the
development of the RACT SIPs submitted to the EPA in 2015,\67\ and set
out the Districts' schedules for adoption of rules identified in those
reviews.\68\ The CARB Staff Report includes a further RACM assessment
from each District confirming that the Districts have examined existing
control measures and determined that no additional RACT or mobile
source controls will advance the attainment date for the West Mojave
Desert for the 2008 ozone standard.\69\ These assessments also note
that photochemical modeling shows the WMD would attain the ozone NAAQS
if not for upwind emissions from the South Coast Air Basin and San
Joaquin Valley.\70\
---------------------------------------------------------------------------

    \66\ AVAQMD Attainment Plan, 6-7, and MDAQMD Attainment Plan, 7.
    \67\ ``2015 8-Hour Ozone Reasonably Available Control Technology
(RACT) SIP Analysis: Antelope Valley Air Quality Management
District'' and ``2015 8-Hour Ozone Reasonably Available Control
Technology (RACT) SIP Analysis: Mojave Desert Air Quality Management
District.'' The EPA conditionally approved these submissions at 82
FR 46923 (October 10, 2017) and 83 FR 5921 (February 12, 2018),
respectively.
    \68\ AVAQMD Attainment Plan, 17, and MDAQMD Attainment Plan, 19.
    \69\ CARB Staff Report, Appendix D-3 and E-3. See also CARB
Staff Report, 10.
    \70\ CARB Staff Report, Appendix D-3 and E-3. This finding is
supported by Appendix B of the CARB Staff Report, which contains a
conceptual model explaining the formation of ozone in the WMD, and
the heavy influence of transport from the South Coast Air Basin.
---------------------------------------------------------------------------

b. CARB'S RACM Analysis
    Source categories for which CARB has primary jurisdiction for
reducing emissions in California include most new and existing on- and
off-road engines and vehicles, motor vehicle fuels, and consumer
products. CARB's RACM assessment is contained in the Appendix E,
``Ozone RACM Assessment,'' of both the AVAQMD and MDAQMD Attainment
Plans. Appendix

F, ``CARB Adopted Mobile Source Programs,'' of these attainment plans
also includes a general description of CARB's key mobile source
regulations and programs and a comprehensive table listing on- and off-
road mobile source regulatory actions taken by CARB from 1985 through
2016. The RACM assessment contains CARB's evaluation of mobile source
and other statewide control measures that reduce emissions of
NOX and VOC in the WMD.
    Given the need for substantial emissions reductions from mobile and
area sources to meet the NAAQS in California nonattainment areas, CARB
has established stringent control measures for on-road and off-road
mobile sources and the fuels that power them. California has unique
authority under CAA section 209 (subject to a waiver by the EPA) to
adopt and implement new emission standards for many categories of on-
road vehicles and engines, and new and in-use off-road vehicles and
engines.
    CARB's mobile source program extends beyond regulations that are
subject to the waiver or authorization process set forth in CAA section
209, to include standards and other requirements to control emissions
from in-use heavy-duty trucks and buses, gasoline and diesel fuel
specifications, and many other types of mobile sources. Generally,
these regulations have been submitted and approved as revisions to the
California SIP.\71\
---------------------------------------------------------------------------

    \71\ See, e.g., the EPA's approval of standards and other
requirements to control emissions from in-use heavy-duty diesel-
powered trucks, at 77 FR 20308 (April 4, 2012), revisions to the
California on-road reformulated gasoline and diesel fuel regulations
at 75 FR 26653 (May 12, 2010), and revisions to the California motor
vehicle inspection and maintenance program at 75 FR 38023 (July 1,
2010).
---------------------------------------------------------------------------

    The Districts' Attainment Plans include CARB's RACM analysis for
mobile source measures in the West Mojave Desert. In this analysis,
CARB concludes:

    There are no reasonable regulatory control measures excluded
from use in this plan; therefore, there are no emissions reductions
associated with unused regulatory control measures. As a result,
California's mobile source control programs fully meet the
requirements for RACM.\72\
---------------------------------------------------------------------------

    \72\ AVAQMD Attainment Plan, Appendix E-7; MDAQMD Attainment
Plan, Appendix E-7.
---------------------------------------------------------------------------

c. Local Jurisdictions' RACM Analysis and Transportation Control
Measures
    The supplemental RACM assessments included as addendums to
appendices D and E of the CARB Staff Report address the Districts' RACM
findings, including for transportation control measures (TCMs). These
addendums state that the Districts examined existing control measures
and determined that controls from RACT and mobile source emission
control programs will not advance the West Mojave Desert's attainment
year for the 2008 ozone standards.\73\
---------------------------------------------------------------------------

    \73\ CARB Staff Report, Appendix D-3 and E-3.
---------------------------------------------------------------------------

3. The EPA's Review of the State's Submission
    The TSD for this action includes additional analysis to evaluate
the Districts' and CARB's RACM assessments.\74\ In that analysis, we
estimate that a 1.2 tpd reduction of NOX emissions would be
necessary to advance attainment by one year from 2026 to 2025, and
conservatively identify no more than 1.04 tpd of additional reductions
that could be achieved through implementation of potential RACM for
stationary sources. Based on this analysis, we agree with the
Districts' and CARB's conclusion that there are no additional RACM that
would advance attainment of the 2008 ozone standards in the WMD by at
least one year.
---------------------------------------------------------------------------

    \74\ Technical Support Document, Clean Air Plans; 2008 8-Hour
Ozone Nonattainment Area Requirements; West Mojave Desert,
California, U.S. EPA Region IX, September 2020.
---------------------------------------------------------------------------

    We also find that CARB's consumer products program comprehensively
addresses emissions from consumer products in the WMD. CARB measures
are more stringent than the EPA's consumer products regulation
promulgated in 1998,\75\ and generally exceed the controls in place
throughout other areas of the country. We agree with CARB's conclusion
that its mobile source regulations include all reasonably available
controls.
---------------------------------------------------------------------------

    \75\ 63 FR 48819 (September 11, 1998).
---------------------------------------------------------------------------

    For the WMD, given the significant influence of pollutant transport
from the South Coast Air Basin and the minimal and diminishing
emissions benefits generally associated with TCMs, no new TCMs
implemented in the WMD, alone or in combination with potential
additional rules, would contribute to advancing the attainment date in
the WMD by one year. Therefore, no new TCMs are required to satisfy the
RACM requirement in the WMD.
    For the foregoing reasons, and as addressed more fully in the TSD
for this action, we propose to find that the 2016 Attainment Plan
provides for the implementation of all RACM as required by CAA section
172(c)(1) and 40 CFR 51.1112(c).

D. Attainment Demonstration

1. Statutory and Regulatory Requirements
    An attainment demonstration consists of the following: (1)
Technical analyses, such as base year and future year modeling, to
locate and identify sources of emissions that are contributing to
violations of the ozone NAAQS within the nonattainment area (i.e.,
analyses related to the emissions inventory for the nonattainment area
and the emissions reductions necessary to attain the standard); (2) a
list of adopted measures (including RACT controls) with schedules for
implementation and other means and techniques necessary and appropriate
for demonstrating RFP and attainment as expeditiously as practicable
but no later than the outside attainment date for the area's
classification; (3) a RACM analysis; and (4) contingency measures
required under sections 172(c)(9) and 182(c)(9) of the CAA that can be
implemented without further action by the state or the EPA to cover
emissions shortfalls in RFP plans and failures to attain.\76\ This
subsection of this proposed rule addresses the first two components of
the attainment demonstration--the technical analyses and a review of
adopted measures. Section III.C of this document, ``Reasonably
Available Control Measures Demonstration,'' addresses the RACM
component, and section III.G, ``Contingency Measures,'' addresses the
contingency measures component of the attainment demonstration in the
Attainment Plans.
---------------------------------------------------------------------------

    \76\ 78 FR 34178, 34184 (June 6, 2013), the EPA's proposed rule
for implementing the 2008 ozone NAAQS.
---------------------------------------------------------------------------

    With respect to the technical analyses, section 182(c)(2)(A) of the
CAA requires that a plan for an ozone nonattainment area classified
``Serious'' or above include a ``demonstration that the plan . . . will
provide for attainment of the ozone [NAAQS] by the applicable
attainment date. This attainment demonstration must be based on
photochemical grid modeling or any other analytical method determined .
. . to be at least as effective.'' The attainment demonstration
predicts future ambient concentrations for comparison to the NAAQS,
making use of available information on measured concentrations,
meteorology, and current and projected emissions inventories of ozone
precursors, including the effect of control measures in the plan. Areas
classified Severe-15 for the 2008 ozone NAAQS must demonstrate
attainment as expeditiously as practicable, but no later than 15 years

after the effective date of designation as nonattainment. The WMD was
designated nonattainment for the 2008 ozone NAAQS effective July 20,
2012,\77\ and accordingly must demonstrate attainment of the standards
by no later than July 20, 2027.\78\ An attainment demonstration must
show attainment of the standards for a full calendar year before the
attainment date, so in practice, Severe-15 nonattainment areas must
demonstrate attainment no later than 2026.
---------------------------------------------------------------------------

    \77\ 77 FR 30088 (May 21, 2012).
    \78\ 80 FR 12264 (March 6, 2015).
---------------------------------------------------------------------------

    The EPA's recommended procedures for modeling ozone as part of an
attainment demonstration are contained in ``Modeling Guidance for
Demonstrating Attainment of Air Quality Goals for Ozone,
PM2.5, and Regional Haze'' (``Modeling Guidance'').\79\ The
Modeling Guidance includes recommendations for a modeling protocol,
model input preparation, model performance evaluation, use of model
output for the numerical NAAQS attainment test, and modeling
documentation. Air quality modeling is performed using meteorology and
emissions from a base year, and the predicted concentrations from this
base case modeling are compared to air quality monitoring data from
that year to evaluate model performance. Once the model performance is
determined to be acceptable, future year emissions are simulated with
the model. The relative (or percent) change in modeled concentration
due to future emissions reductions provides a relative response factor
(RRF). Each monitoring site's RRF is applied to its monitored base year
design value to provide the future design value for comparison to the
NAAQS. The Modeling Guidance also recommends supplemental air quality
analyses, which may be used as part of a weight of evidence (WOE)
analysis. A WOE analysis corroborates the attainment demonstration by
considering evidence other than the main air quality modeling
attainment test, such as trends and additional monitoring and modeling
analyses.
---------------------------------------------------------------------------

    \79\ ``Modeling Guidance for Demonstrating Attainment of Air
Quality Goals for Ozone, PM2.5, and Regional Haze,'' EPA
454/R-18-009 (November 2018); available at https://www.epa.gov/scram/state-implementation-plan-sip-attainment-demonstration-guidance. See also December 2014 draft of this guidance, available
at the same website. The December 2014 draft guidance was available
during development of the Plan; the final version differs mainly in
organization, and in updates to the regional haze portion and to
other document references. Additional EPA modeling guidance can be
found in 40 CFR 51 Appendix W, Guideline on Air Quality Models, 82
FR 5182 (January 17, 2017); available at https://www.epa.gov/scram/clean-air-act-permit-modeling-guidance.
---------------------------------------------------------------------------

    The Modeling Guidance also does not require a particular year to be
used as the base year for 8-hour ozone plans.\80\ The Modeling Guidance
states that the most recent year of the National Emissions Inventory
may be appropriate for use as the base year for modeling, but that
other years may be more appropriate when considering meteorology,
transport patterns, exceptional events, or other factors that may vary
from year to year.\81\ Therefore, the base year used for the attainment
demonstration need not be the same year used to meet the requirements
for emissions inventories and RFP.
---------------------------------------------------------------------------

    \80\ Modeling Guidance at section 2.7.1, 35.
    \81\ Id.
---------------------------------------------------------------------------

    With respect to the list of adopted measures, CAA section 172(c)(6)
requires that nonattainment area plans include enforceable emissions
limitations, and such other control measures, means or techniques
(including economic incentives such as fees, marketable permits, and
auctions of emission rights), as well as schedules and timetables for
compliance, as may be necessary or appropriate to provide for timely
attainment of the NAAQS.\82\ Under the 2008 Ozone SRR, all control
measures needed for attainment must be implemented no later than the
beginning of the attainment year ozone season.\83\ The attainment year
ozone season is defined as the ozone season immediately preceding a
nonattainment area's outermost attainment date.\84\ For the West Mojave
Desert, the outermost attainment year is 2026.
---------------------------------------------------------------------------

    \82\ See also CAA section 110(a)(2)(A).
    \83\ 40 CFR 51.1108(d).
    \84\ 40 CFR 51.1100(h).
---------------------------------------------------------------------------

2. Summary of the State's Submission
a. Photochemical Modeling
    The 2016 WMD Attainment Plan includes photochemical modeling for
the 2008 ozone NAAQS. The South Coast Air Quality Management District
(SCAQMD) performed the air quality modeling for the 2016 WMD Attainment
Plan, as part of the Final 2016 Air Quality Management Plan for the
South Coast Air Quality Management District (``SCAQMD 2016 AQMP'').\85\
The modeling relies on a 2012 base year and demonstrates attainment of
the 2008 ozone NAAQS by the applicable Severe-15 area attainment year
(i.e., 2026).
---------------------------------------------------------------------------

    \85\ Appendix V, Final 2016 Air Quality Management Plan, March
2017, SCAQMD. See AVAQMD Attainment Plan, 31, and MDAQMD Attainment
Plan, 33.
---------------------------------------------------------------------------

    The modeling and modeled attainment demonstration are described in
Chapter 4, ``Attainment Demonstration,'' of the 2016 WMD Attainment
Plan and in Appendix D, ``Western Mojave Desert Modeling Analysis.''
The AVAQMD Attainment Plan and the MDAQMD Attainment Plan also
reference Appendix V of the SCAQMD 2016 AQMP for additional information
on the modeled attainment demonstration.
    The modeling protocol is in Chapter 2, ``Modeling Protocol,'' of
Appendix V of the SCAQMD 2016 AQMP and contains all the elements
recommended in the Modeling Guidance. Those include the following:
Selection of model, time period to model, modeling domain, and model
boundary conditions and initialization procedures; a discussion of
emissions inventory development and other model input preparation
procedures; model performance evaluation procedures; selection of days;
and other details for calculating RRFs. Appendix V of the SCAQMD 2016
AQMP also provides the coordinates of the modeling domain and
thoroughly describes the development of the modeling emissions
inventory, its spatial and temporal allocation, its temperature
dependence, and quality assurance procedures.
    The modeling analysis uses version 5.0.2 of the Community
Multiscale Air Quality (CMAQ) photochemical model, developed by the
EPA. To prepare meteorological input for CMAQ, the modeling analysis
uses the Weather and Research Forecasting model version 3.6 (WRF) from
the National Center for Atmospheric Research. CMAQ and WRF are both
recognized in the Modeling Guidance as technically sound, state-of-the-
art models. The areal extent and the horizontal and vertical resolution
used in these models are adequate for modeling West Mojave Desert
ozone.
    The SCAQMD assessed the performance of the WRF meteorological model
through a series of simulations, and the SCAQMD concluded that the
daily WRF simulation for 2012 provided representative meteorological
fields that characterized the observed conditions well. The SCAQMD's
conclusions are supported by hourly time series graphs of wind speed,
direction, and temperature.\86\
---------------------------------------------------------------------------

    \86\ Attachment 1 (``WRF Model Performance Time Series''),
Chapter 3 (``Meteorological Modeling and Sensitivity Analyses''),
Appendix V (``Modeling and Attainment Demonstration'') of the 2016
SCAQMD AQMP.
---------------------------------------------------------------------------

    Ozone model performance statistics are described in Appendix D,
``West Mojave Desert Community Multiscale Air Quality Model Performance
Analysis,'' of both the AVAQMD and MDAQMD Attainment Plans, which
include tables of statistics

recommended in the Modeling Guidance for 8-hour daily maximum ozone for
the WMD. This section presents hourly time series, as well as density
scatter plots and plots of bias against concentration. Note that
because only relative changes are used from the modeling, the
overprediction or underprediction of absolute ozone concentrations does
not mean that future concentrations will be overestimated or
underestimated.
    After model performance for the 2012 base case was accepted, the
model was applied to develop RRFs for the attainment demonstration.
This entailed running the model with the same meteorological inputs as
before, but with adjusted emissions inventories to reflect the expected
changes between 2012 and the 2026 attainment year. The base year or
``reference year'' modeling inventory was the same as the inventory for
the modeling base case. The 2026 inventory projects the base year into
the future by including the effect of economic growth and emissions
control measures. The set of 153 days from May 1 through September 30,
2012, was simulated and analyzed to determine daily 8-hour average
maximum ozone concentrations for the 2020 emissions inventory. To
develop the RRFs for the 2008 ozone NAAQS, only the top 10 days were
used.
    The Modeling Guidance addresses attainment demonstrations with
ozone NAAQS based on 8-hour averages. For the 2008 ozone NAAQS,
Appendix D of the 2016 WMD Attainment Plan includes the attainment test
procedure consistent with the Modeling Guidance. The RRFs were
calculated as the ratio of future to base year concentrations. The
resulting RRFs were then applied to 2012 weighted base year design
values \87\ for each monitor to arrive at a 2026 future year design
value.\88\ The 2016 WMD Attainment Plan narrowly projects that the West
Mojave Desert will reach modeled attainment in 2023, with the highest
ozone design value of 0.0759 ppm at the Phelan monitor site (station
number: 06-071-0012); this value demonstrates attainment of the
corresponding 2008 ozone NAAQS of 0.075 ppm.\89\
---------------------------------------------------------------------------

    \87\ The Modeling Guidance recommends that RRFs be applied to
the average of three three-year design values centered on the base
year, in this case the design values for 2010-2012, 2011-2013, and
2012-2014. This amounts to a 5-year weighted average of individual
year 4th-high concentrations, centered on the base year of 2012, and
so is referred to as a weighted design value.
    \88\ Table 5 of Appendix A-1 of the CARB Staff Report.
    \89\ Appendix P of 40 CFR part 50 for a discussion of reporting
and handling procedures for the primary and secondary ozone
standards that discusses truncating the third digit to the right of
the decimal place.
---------------------------------------------------------------------------

    Appendix B of the CARB Staff Report presents a WOE analysis with
further discussion of the modeling for the area. The WOE analysis
includes the following: An evaluation of ambient ozone trends;
precursor emissions trends for the region (i.e., the South Coast Air
Basin, San Joaquin Valley, and the WMD); an evaluation of diurnal ozone
monitoring trends; and a conceptual model that describes the conditions
that create the exceedances of the 2008 ozone NAAQS. These evaluations
complement the photochemical modeling analysis for the area and show
that the area's timely attainment is dependent on continuing future
reductions from implementation of control measures in neighboring
upwind nonattainment areas. The WOE analysis concludes that, based on
these upwind reductions from neighboring nonattainment areas, the WMD
will attain the 2008 ozone standard by 2026.\90\
---------------------------------------------------------------------------

    \90\ Appendix B, CARB Staff Report, B-30. The TSD for this
action includes additional discussion of the modeled attainment
demonstration and WOE analysis that support this conclusion.
---------------------------------------------------------------------------

    Finally, Appendix D of each of the Districts' Attainment Plans
includes an unmonitored area analysis for the 2008 ozone NAAQS to
assess the attainment status of locations other than monitoring sites.
The unmonitored area analysis in the 2016 WMD Attainment Plan shows
concentrations below the 2008 ozone NAAQS for all locations.\91\
---------------------------------------------------------------------------

    \91\ Figure 3: 2023 Predicted 8-hr Ozone Design Values, Appendix
D, of both districts Attainment Plans.
---------------------------------------------------------------------------

b. Control Strategy
    The control strategy for attainment of the 2008 ozone NAAQS in the
WMD relies on timely attainment in 2023 of the 1997 ozone NAAQS in the
upwind Los Angeles-South Coast Air Basin,\92\ which is the same year
the WMD model shows attainment. The attainment plan for the 2008 ozone
NAAQS for the South Coast Air Basin, which has been previously approved
by the EPA, projects a 277 tpd reduction in NOX and a 121
tpd reduction in VOC from 2012 base year emissions (522 tpd for
NOX and 500 tpd for VOC).\93\ In addition, the 2008 ozone
attainment plan for the San Joaquin Valley, which has also been
previously approved by the EPA, projects a 214.6 tpd reduction of
NOX and 34.4 tpd reduction of VOC in 2023, from 2012 base
year emissions (339.6 tpd for NOX and 337.3 tpd for VOC in
2011).\94\ Both upwind areas continue to show emission reductions
through 2026 and beyond.
---------------------------------------------------------------------------

    \92\ Appendix B, CARB Staff Report, B-2.
    \93\ Approval of Air Quality Implementation Plans; California;
South Coast Air Basin; 1-Hour and 8-Hour Ozone Nonattainment Area
Requirements, Proposed Rule, 84 FR 28132 (June 17, 2019). EPA
finalized approval of the South Coast plan for the 2008 ozone NAAQS
at 84 FR 52005 (October 1, 2019).
    \94\ Air Quality State Implementation Plans; Approvals and
Promulgations: Clean Air Plans; 2008 8-Hour Ozone Nonattainment Area
Requirements; San Joaquin Valley, California, Proposed Rule 83 FR
61346 (November 28, 2018). EPA finalized approval of the San Joaquin
Valley plan for the 2008 ozone NAAQS at 84 FR 3302 (February 12,
2018).
---------------------------------------------------------------------------

    Within the WMD, the control strategy for attainment of the 2008
ozone NAAQS in the 2016 WMD Attainment Plan relies primarily on
emissions reductions from baseline (i.e., already-adopted) measures.
These baseline control measures include the Districts' stationary
source rules,\95\ and CARB's mobile source and consumer product rules
adopted through 2016, as listed in Appendix F of the 2016 WMD
Attainment Plan, ``CARB Adopted Mobile Source Programs.'' The
attainment demonstration and base year emissions inventory use a 2012
base year (101.09 tpd of NOX and 43.69 tpd of VOC), and
consistent with South Coast II, the RFP demonstration relies on a 2011
baseline year.\96\ The attainment year emissions estimate for the
attainment demonstration is the same throughout the 2016 WMD Attainment
Plan and 2018 SIP Update (68.5 tpd of NOX and 40.5 tpd of
VOC) and represents a 30.3 percent NOX reduction and a 13.4
percent VOC reduction from the 2012 emissions inventory base year
emissions.
---------------------------------------------------------------------------

    \95\ Technical Support Document: Clean Air Plans; 2008 8-Hour
Ozone Nonattainment Area Requirements; West Mojave Desert,
California, EPA-R09-OAR-2020-0254, Tables 1 and 2.
    \96\ The modeling base year emissions were taken from Table 1
and Appendix A of the AVAQMD and MDAQMD Attainment Plans. The CARB
Staff Report notes 2012 base year emissions from the Districts'
plans were average day emissions, i.e., averaged over the entire
year, rather than average summer day emissions, which are included
in Appendix A of the CARB Staff Report and were submitted as the
2012 base year emissions.
---------------------------------------------------------------------------

c. Attainment Demonstration
    Chapter 4 of the Districts' Attainment Plans describes the
attainment demonstration in general terms, including photochemical
modeling results. Chapter 4 references Appendix V of the SCAQMD 2016
AQMP, which provides information on the modeling protocol. Appendix D
of the District's Attainment Plans contains model results and
performance for the WMD. The WOE analysis in Appendix B to the CARB
Staff Report includes additional supporting information to complement
the photochemical modeling and to provide context for this attainment

demonstration, such as ambient ozone data, a conceptual model of ozone
formation, anthropogenic emission trends, ozone trends, and a
discussion of the attainment projections. Baseline measures are
expected to reduce 2012 base year emissions of NOX by 30.7
percent and VOC emissions by 13 percent by 2026, and to attain the 2008
ozone NAAQS in the WMD by 2023, three years ahead of the outermost
attainment year, 2026.
3. The EPA's Review of the State's Submission
a. Photochemical Modeling
    The EPA has reviewed the modeling platform and agrees that the CMAQ
(version 5.0.2) modeling platform, and the WRF (version 3.6.1)
meteorological fields are appropriate for the ozone attainment
demonstration. After review, the EPA is satisfied that the
meteorological model, WRF, performed adequately. The diurnal variation
of temperature, humidity and surface wind are well represented by WRF.
The EPA has also reviewed the time series, scatter plots, and ozone
performance, and determined that overall, the CMAQ photochemical
modeling performance for ozone is acceptable.
    We are proposing to find the air quality modeling adequate to
support the attainment demonstrations for the 2008 ozone NAAQS, based
on reasonable meteorological and ozone modeling performance, supported
by the weight of evidence analyses.
b. Control Strategy
    Based on our review of the emissions inventory documentation in the
CARB Staff Report, we find that CARB and the Districts have used the
most recent planning and activity assumptions, emissions models, and
methodologies to estimate the effect of the control strategy on the
baseline and milestone year emissions inventories. The 2016 WMD
Attainment Plan relies on state and locally adopted baseline control
measures, i.e., already-adopted control measures, to achieve the
emissions reductions needed to attain the 2008 ozone NAAQS. The
baseline measures are approved into the SIP and, as such, are fully
creditable within the attainment demonstration analysis. Accordingly,
we propose to find that the emissions reductions that are relied on for
attainment are creditable and sufficient to provide for attainment.
c. Attainment Demonstration
    Based on our review of the 2016 WMD Attainment Plan and our
proposed findings that the photochemical modeling and control strategy
are acceptable and demonstrate attainment by July 20, 2027, we propose
to approve the attainment demonstration for the 2008 ozone NAAQS in the
2016 WMD Attainment Plan as meeting the requirements of CAA section
182(c)(2)(A) and 40 CFR 51.1108. The Districts' Attainment Plans and
the WOE in the CARB Staff Report demonstrate that the ozone design
value in the WMD will meet the 0.075 ppm standard by 2026, and
therefore will meet the attainment date of July 20, 2027, for the 2008
ozone standard. While the submitted modeling projects that attainment
is possible in advance of the 2026 deadline, the EPA is relying on the
modeling, additional information provided in the WOE, and current ozone
trends, to conclude that the WMD will attain the 2008 ozone NAAQS by
2026, consistent with the outermost attainment date of July 20, 2027.
See the TSD for additional information.

E. Rate of Progress Plan and Reasonable Further Progress Demonstration

1. Statutory and Regulatory Requirements
    Requirements for RFP are specified in CAA sections 172(c)(2),
182(b)(1), and 182(c)(2)(B). CAA section 172(c)(2) requires that plans
for nonattainment areas provide for RFP, which is defined at CAA
section 171(1) as 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. CAA section
182(c)(2)(B)(ii) allows 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.
    The 2008 Ozone SRR considers areas classified Moderate or higher to
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.\97\ For such areas, the RFP requirements of CAA
section 172(c)(2) 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.\98\ Under CAA 182(c)(2)(C), a
state may substitute NOX emissions reductions for VOC
emissions reductions.
---------------------------------------------------------------------------

    \97\ 80 FR 12264, 12271 (March 6, 2015).
    \98\ Id.
---------------------------------------------------------------------------

    Except as specifically provided in CAA section 182(b)(1)(C),
emission reductions from all SIP-approved, federally promulgated, or
otherwise SIP-creditable measures that occur after the baseline 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 vehicle
inspection and maintenance (I/M) programs.\99\
---------------------------------------------------------------------------

    \99\ 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 is
required to be submitted to the EPA (i.e., 2011). As discussed above,
the 2008 Ozone SRR provided states with the opportunity to use an
alternative baseline year for RFP,\100\ but this provision was vacated
by the D.C. Circuit in the South Coast II decision.
---------------------------------------------------------------------------

    \100\ 40 CFR 51.1110(b).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    The 2016 WMD Attainment Plan addresses the 15 percent ROP
requirement by noting that the EPA had proposed approval of the 15
percent ROP plan for the 1997 ozone NAAQS for the WMD, and that the
1997 ozone nonattainment area covers the entire

nonattainment area for the 2008 ozone standards.\101\ The EPA approved
the 15 percent ROP demonstration for the 1997 ozone NAAQS, effective
July 24, 2017.\102\
---------------------------------------------------------------------------

    \101\ Chapter 3 of both Districts' Attainment Plans.
    \102\ 82 FR 28560 (June 23, 2017).
---------------------------------------------------------------------------

    With respect to the RFP demonstration requirement, the 2016 WMD
Attainment Plan includes an RFP demonstration derived from a 2012 RFP
baseline year.\103\ In response to the South Coast II decision, CARB
developed the 2018 SIP Update, which includes a section that replaces
the RFP portion of the 2016 WMD Attainment Plan with an updated RFP
demonstration based on a 2011 RFP baseline year.\104\ To develop the
2011 RFP baseline inventory, CARB relied on actual emissions reported
from industrial point sources for year 2011. For emissions from smaller
stationary sources and area sources, CARB backcast emissions from 2012
to 2011 using the same growth and control factors as were used for the
2016 WMD Attainment Plan. To develop the emissions inventories for the
2017, 2020 and 2023 RFP milestone years, CARB also relied upon the same
growth and control factors as the 2016 WMD Attainment Plan. Therefore,
the emissions estimates for the attainment year, 2026, are consistent
in both the 2018 SIP Update and the 2016 WMD Attainment Plan.
---------------------------------------------------------------------------

    \103\ Chapter 3 of both Districts' Attainment Plans.
    \104\ Chapter VI of the 2018 SIP Update.
---------------------------------------------------------------------------

    Documentation for the WMD RFP baseline and milestone emissions
inventories is found in the 2018 SIP Update on pages 36-37 and in
Appendix A of the 2018 SIP Update on pages A-19 through A-22. The RFP
baseline emissions inventories reflect rules identified in Table 5 of
the CARB Staff Report.
    Table 2 provides a summary of CARB's emissions estimates in tpd for
VOC and NOX for the 2011 RFP baseline year, the 2017, 2020,
2023 RFP milestone years, and the 2026 RFP milestone/attainment year,
evaluated relative to the percentage reductions necessary to
demonstrate RFP.

                             Table 2--WMD RFP Demonstration for the 2008 Ozone NAAQS
                                   [Summer planning inventory, tpd or percent]
----------------------------------------------------------------------------------------------------------------
                                       2011            2017            2020            2023            2026
----------------------------------------------------------------------------------------------------------------
                                                      VOCs
----------------------------------------------------------------------------------------------------------------
Baseline VOC....................            48.7            41.5            40.4            40.4            40.5
Transportation conformity safety  ..............               0               0               0             0.2
 margin.........................
Baseline VOC + safety margin....            48.7            41.5            40.4            40.4            40.7
Required % change since 2011....  ..............             18%             27%             36%             45%
Target VOC level................  ..............            40.0            35.6            31.2            26.8
Apparent shortfall/surplus, tpd.  ..............            -1.5            -4.8            -9.2           -13.9
Apparent shortfall ( - )/surplus  ..............           -3.1%           -9.9%          -18.8%          -28.4%
 ( + ) in VOC...................
VOC shortfall previously          ..............               0            3.1%            9.9%           18.8%
 provided by NOX substitution, %
Actual VOC shortfall ( - )/       ..............           -3.1%           -6.8%           -8.9%           -9.6%
 surplus ( + ), %...............
----------------------------------------------------------------------------------------------------------------
                                                       NO
----------------------------------------------------------------------------------------------------------------
Baseline NOX....................            98.4            84.5            79.8            72.1            68.5
Transportation conformity safety               0               0               0               0             0.4
 margin.........................
Baseline NOX + safety margin....            98.4            84.5            79.8            72.1            68.9
Change in NOX since 2011, tpd...  ..............            13.8            18.6            26.2            29.4
Change in NOX since 2011, %.....  ..............           14.1%           18.9%           26.7%           29.9%
NOX reductions used for VOC       ..............               0            3.1%            9.9%           18.8%
 substitution through last
 milestone year, %..............
NOX reductions since 2011         ..............           14.1%           15.8%           16.7%           11.1%
 available for VOC substitution
 in this milestone year, %......
NOX reductions since 2011         ..............            3.1%            6.8%            8.9%            9.6%
 available for VOC substitution
 in this milestone year, %......
NOX reductions since 2011         ..............           10.9%            9.0%            7.9%            1.5%
 surplus after meeting VOC
 substitution needs in this
 milestone year, %..............
Total shortfall for RFP.........  ..............              0%              0%              0%              0%
RFP met?........................  ..............             Yes             Yes             Yes             Yes
----------------------------------------------------------------------------------------------------------------
Source: Table VI-2, 2018 SIP Update.

    The revised 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 2017 to meet VOC emission targets.
NOX substitution is permitted under EPA regulations at 40
CFR 51.1110(a)(2)(i)(C) and 40 CFR 51.1110(a)(2)(ii)(B). As stated in
the WOE in the CARB Staff Report, ``given Western Mojave's downwind
location from the only two extreme ozone nonattainment areas in the
country, it is expected that ozone formation would be limited by
available NOX emissions,'' meaning that NOX
reductions would be more effective at reducing ozone concentrations
than VOC reductions. For the WMD, CARB concluded that the revised RFP
demonstration meets the applicable requirements for each milestone year
as well as the attainment year.
3. The EPA's Review of the State's Submission
    Consistent with the 2008 Ozone SRR, the EPA's final approval of the
15 percent ROP demonstration for the 1997 ozone NAAQS fulfills the
requirements of CAA section 182(b)(1) for WMD for the 2008 ozone
NAAQS.\105\
---------------------------------------------------------------------------

    \105\ 82 FR 13086 (March 9, 2017).
---------------------------------------------------------------------------

    With respect to the RFP demonstration requirement, based on

our review of the emissions inventory documentation in the 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 reviewed and verified the calculations in
Table VI-3 of the 2018 SIP Update. Furthermore, we find that
NOX emission reductions are as effective as VOC emission
reductions in reducing levels of ozone within the Western Mojave
Desert.\106\ For these reasons, we have determined that the 2018 SIP
Update demonstrates RFP in the 2017, 2020, and 2023 milestone years as
well as the 2026 milestone/attainment year, consistent with applicable
CAA requirements and EPA guidance. Therefore, we propose to approve the
RFP demonstration for the WMD for the 2008 ozone NAAQS under sections
172(c)(2) and 182(c)(2)(B) of the CAA and 40 CFR 51.1110(a)(2)(ii).
---------------------------------------------------------------------------

    \106\ Additional evaluation of this matter is discussed in
Section V of the TSD supporting this notice.
---------------------------------------------------------------------------

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

1. Statutory and Regulatory Requirements
    Section 182(d)(1)(A) of the Act requires a state to submit a
revision for each area classified as Serious or above that identifies
and adopts specific enforceable transportation control strategies
(TCSs) and transportation control measures (TCMs) to offset any growth
in emissions from growth in vehicle miles traveled (VMT) or number of
vehicle trips in such area.\107\ 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.''
---------------------------------------------------------------------------

    \107\ 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 (1) to offset growth
in emissions from growth in VMT, and, (2) in combination with other
emission reduction requirements, to demonstrate RFP, and (3) to
demonstrate 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 Association of Irritated Residents v. EPA, the United States
Court of Appeals for the Ninth Circuit (``Ninth Circuit'') ruled that
additional TCMs 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.\108\ In response
to the Ninth Circuit's decision, 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'' (``August 2012 Guidance'').\109\
---------------------------------------------------------------------------

    \108\ 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'').
    \109\ Memorandum from Karl Simon, Director, Transportation and
Climate Division, Office of Transportation and Air Quality, to Carl
Edlund, Director, Multimedia Planning and Permitting Division, EPA
Region VI, and Deborah Jordan, Director, Air Division, EPA Region
IX, August 30, 2012.
---------------------------------------------------------------------------

    The August 2012 Guidance discusses the meaning of TCSs and 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 encompass many types of controls (including, for example, motor
vehicle emissions limitations, I/M programs, alternative fuel programs,
other technology-based measures, and TCMs) that would fit within the
regulatory definition of ``control strategy.'' \110\ Such measures
include, but are not limited to, those listed in CAA section 108(f).
TCM is defined at 40 CFR 51.100(r) as meaning ``any measure that is
directed toward reducing emissions of air pollutants from
transportation sources,'' including, but not limited to, those listed
in section 108(f) of the CAA. TCMs generally refer to programs intended
to reduce VMT, the number of vehicle trips, or traffic congestion,
including, e.g., programs for improved public transit, designation of
certain lanes for passenger buses and high-occupancy vehicles, and trip
reduction ordinances.
---------------------------------------------------------------------------

    \110\ See, e.g., 40 CFR 51.100(n). 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.
---------------------------------------------------------------------------

    The August 2012 Guidance explains how states may demonstrate that
the VMT emissions offset requirement is satisfied in conformance with
the Ninth Circuit's ruling. The August 2012 Guidance recommends that
states estimate emissions for the nonattainment area's base year and
attainment year. One emissions 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 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'' scenario. Emissions in the
attainment year in this scenario may be lower than those in the base
year due to fleet turnover; however, if VMT and/or numbers of vehicle
trips are projected to increase in the attainment year, emissions would
still likely be higher than if 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
fleet turnover, but in this case emissions 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 Ninth Circuit 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 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 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.
    Alternatively, if the estimated projected actual attainment year
emissions are still greater than the ceiling that 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 Ninth Circuit.
2. Summary of the State's Submission
    The VMT emissions offset demonstration for the WMD for the 2008
ozone NAAQS is contained in Chapter 3 of the Districts' Attainment
Plans.\111\ For the VMT emissions offset demonstration, CARB used
EMFAC2014, the latest EPA-approved motor vehicle emissions model for
California available at the time the 2016 WMD Attainment Plan was
developed.\112\ 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.
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    \111\ AVAQMD Attainment Plan, 23, and MDAQMD Attainment Plan,
25.
    \112\ On August 15, 2019, the EPA approved and announced the
availability of EMFAC2017, the latest update to the EMFAC model for
use by State and local governments to meet CAA requirements. See 84
FR 41717.
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    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 the analysis included these emissions in the
calculations that provide the basis for the WMD VMT emissions offset
demonstration. The analysis 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 WMD VMT emissions offset demonstration uses a 2012 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 WMD for the purposes of
the 2008 ozone NAAQS, and thus, the selection of 2012 as the base year
for the WMD VMT emissions offset demonstration for the 2008 ozone NAAQS
is appropriate.
    The WMD 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 WMD
Attainment Plan provides a demonstration of attainment of the 2008
ozone NAAQS in the WMD by the applicable attainment date, based on the
controlled 2026 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 WMD, and thus, we find
the selection of year 2026 as the attainment year for the VMT emissions
offset demonstration for the 2008 ozone NAAQS to be acceptable.
    Table 3 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 3--VMT Emissions Offset Inventory Scenarios and Results for 2008 Ozone NAAQS
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                        VMT                           Starts                 Controls      VOC emissions
                                                         -----------------------------------------------------------------------------------------------
                        Scenario                                           1,000 miles/
                                                               Year             day            Year          1,000/day         Year             Tpd
--------------------------------------------------------------------------------------------------------------------------------------------------------
Base Year...............................................            2012          26,536            2012           4,470            2012            12.4
No Action...............................................            2026          34,724            2026           5,238            2012             6.5
VMT Offset Ceiling......................................            2012          26,536            2012           4,470            2012             5.3
Actual Projected........................................            2026          34,724            2026           5,238            2026             4.6
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: AVAQMD Attainment Plan, 23-27, and MDAQMD Attainment Plan, 26-29.

3. The EPA's Review of the State's Submission
    Based on our review of the WMD VMT emissions offset demonstration
in the 2016 WMD Attainment Plan, we find CARB's analysis to be
consistent with our August 2012 Guidance and consistent with the
emissions and vehicle activity estimates provided by CARB in support of
the 2016 AQMP. We agree that the TCSs and TCMs in place for the area
are sufficient to offset the growth in emissions from growth in VMT and
vehicle trips in the WMD for the purposes of the 2008 8-hour ozone
standards. As such, we find that the WMD VMT emissions offset
demonstration complies with the VMT emissions offset requirement in CAA
section 182(d)(1)(A). Therefore, we propose approval of the WMD VMT
emissions offset demonstration portion of the 2016 WMD Attainment Plan.

G. Contingency Measures

1. Statutory and Regulatory Requirements
    Under the CAA, SIPs for 8-hour ozone nonattainment areas classified
under subpart 2 as Moderate or above must include 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 an
area fails to make RFP 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.\113\
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    \113\ 70 FR 71612 (November 29, 2005). See also 2008 Ozone SRR,
80 FR 12264, 12285 (March 6, 2015).
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    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 generally
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.\114\
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    \114\ 80 FR 12264, 12285 (March 6, 2015).
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    It has been the EPA's longstanding interpretation of CAA section
172(c)(9) that states may meet the contingency measure requirement by
relying 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 Act requires contingency
measures to 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 a 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 in excess of the
reductions required by the attainment demonstration or RFP plan,\115\
and there is case law supporting the EPA's interpretation in this
regard.\116\ 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.\117\ 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.\118\ The D.C. Circuit recently reached a similar conclusion
regarding the contingency measure provisions in CAA sections 172(c)(9)
and 182(c)(9), in Sierra Club v. EPA.\119\ Following these decisions,
states cannot rely on early-implemented measures to comply with the
contingency measure requirements under CAA section 172(c)(9) and
182(c)(9).
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    \115\ 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).
    \116\ 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).
    \117\ Bahr v. EPA, 836 F.3d at 1235-1237 (9th Cir. 2016)
(``Bahr'').
    \118\ Id. at 1235-1237.
    \119\ Sierra Club v. EPA, 985 F.3d 1055 (D.C. Cir. 2021)
(``Sierra Club'').
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2. Summary of the State's Submission
    The Districts and CARB had largely prepared the 2016 WMD Attainment
Plan prior to the Bahr and Sierra Club decisions; therefore, the plan
relies solely upon surplus emissions reductions from already
implemented control measures in the RFP milestone years to demonstrate
compliance with the RFP milestone contingency measures requirements of
CAA sections 172(c)(9) and 182(c)(9).\120\ The plan also demonstrates
compliance with the attainment contingency measures requirements using
surplus emissions reductions (in the year after the attainment year),
and separately identifies use of the State's enhanced I/M program as an
attainment contingency measure.\121\
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    \120\ AQAQMD Attainment Plan, 20; MDAQMD Attainment Plan, 22.
    \121\ Id. AQAQMD Attainment Plan, 18; MDAQMD Attainment Plan,
20.
---------------------------------------------------------------------------

    In the 2018 SIP Update, CARB revised the RFP demonstration for the
2008 ozone NAAQS for the WMD and recalculated the extent of surplus
emission reductions in the milestone years. Consistent with the Bahr
decision (and the later Sierra Club decision), 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 instead documents the extent to which future baseline
emissions would provide surplus emissions reductions beyond those
required to meet applicable contingency measure requirements, to
provide context for determining the magnitude of the contingency
measures needed for the 2008 ozone NAAQS.
    The 2018 SIP Update identifies one year's worth of RFP as
approximately 1.5 tpd of VOC. The 2018 SIP Update estimates surplus
NOX reductions for RFP as ranging from approximately 10.7
tpd in 2017 to 7.8 tpd in 2023, and estimates that implementation of
the state control measures will result in an additional 0.2 tpd VOC and
1.6 tpd of NOX emissions reductions occuring in the year
after the attainment year.\122\
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    \122\ 2018 SIP Update, Chapter VI, Tables VI-4, VI-5, and VI-6.
---------------------------------------------------------------------------

    In subsequent communications, CARB has clarified that the proposed
contingency measure would involve implementation of enhanced I/M
specifically in those areas of the WMD subject to MDAQMD jurisdiction
that are currently subject only to basic I/M requirements.\123\ As
described by the MDAQMD, within 30 days of a finding by the EPA that
the WMD has either failed to meet an RFP milestone for the 2008 ozone
NAAQS or failed to attain the 2008 ozone NAAQS by the

attainment deadline, the MDAQMD Executive Officer will transmit a
formal letter to the California Bureau of Automotive Repair (BAR)
requesting implementation of the enhanced I/M program throughout the
entirety of the portion of the WMD that is subject to the District's
jurisdiction. Upon receiving the District's letter, BAR would initiate
the program and notify the relevant stakeholders of the updated
requirements in the area. This procedure is described in section
44003(c) of the California Health and Safety Code, and no additional
regulations would need to be adopted.\124\ CARB estimates that
implementation of the enhanced I/M program for this region will result
in additional emissions reductions of 0.03 tpd of VOC and 0.04 tpd of
NOX.\125\
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    \123\ Email dated November 20, 2020, from Ariel Fideldy (CARB)
to Tom Kelly (EPA), Subject: West Mojave Desert Contingency
Measures.
    \124\ Letter dated March 29, 2021, from Brad Poiriez, Executive
Officer, MDAQMD, to Richard Corey, Executive Officer, CARB. The EPA
approved California Health and Safety Code section 44003(c) into the
California SIP at 75 FR 38023 (July 1, 2010).
    \125\ Letter dated April 9, 2021, from Michael Benjamin, Chief,
Air Quality Planning and Science Division, CARB, to Deborah Jordan,
Acting Regional Administrator, EPA Region IX. CARB indicates that
these figures represent conservative estimates of the potential
emissions reductions that would result from implementation of the
contingency measure, because they are derived from residential
populations that may underrepresent the actual vehicle populations
located within the zip codes currently subject to basic I/M. See
Attachment A to letter dated April 9, 2021, from Michael Benjamin,
Chief, Air Quality Planning and Science Division, CARB, to Deborah
Jordan, Acting Regional Administrator, EPA Region IX.
---------------------------------------------------------------------------

    The MDAQMD has committed to submit a Board resolution further
detailing the circumstances, timing, and procedure for implementing
this contingency measure, within eleven months of the EPA's final
conditional approval of the contingency measures element of the 2016
WMD Attainment Plan.\126\ CARB, in turn, has committed to submit the
Board resolution to the EPA for SIP approval within 12 months of the
EPA's final conditional approval.\127\
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    \126\ Letter dated March 29, 2021, from Brad Poiriez, Executive
Officer, MDAQMD, to Richard Corey, Executive Officer, CARB.
    \127\ Letter dated April 9, 2021, from Michael Benjamin, Chief,
Air Quality Planning and Science Division, CARB, to Deborah Jordan,
Acting Regional Administrator, EPA Region IX.
---------------------------------------------------------------------------

3. The EPA's Review of the State's Submission
    Sections 172(c)(9) and 182(c)(9) of the CAA require contingency
measures to address potential failure to achieve RFP milestones or
failure to attain the NAAQS by the applicable attainment date. To
evaluate the contingency measure element of the 2016 WMD Attainment
Plan, 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. Therefore, we agree that the emission estimates from the
2018 SIP Update provide surplus reductions well beyond those necessary
to demonstrate RFP in 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 MDAQMD and CARB have committed to develop, adopt,
and submit a Board resolution further detailing the circumstances,
timing, and procedure for implementing enhanced I/M requirements in the
portion of the WMD that is currently subject to basic I/M, should the
WMD fail to meet an RFP milestone. The specific commitment of the
MDAQMD upon an RFP milestone failure (i.e., changing from basic to
enhanced I/M) complies with the requirements in CAA sections 172(c)(9)
and 182(c)(9) because it would be undertaken if the area fails to meet
an RFP milestone and would take effect without further significant
action by the District, the State, or the EPA.\128\
---------------------------------------------------------------------------

    \128\ Section 182(c)(3) of the CAA requires states with ozone
nonattainment areas classified under subpart 2 as Serious or above
to implement an enhanced motor vehicle I/M program in each urbanized
area within the nonattainment area. Section 182(c)(3) further
explains that urbanized areas are ``defined by the Bureau of the
Census, with a 1980 population of 200,000 or more.'' Because parts
of the MDAQMD within the WMD were not considered urbanized areas in
1980, only part of the WMD is subject to enhanced I/M. All of the
area under the jurisdiction of the AVAQMD is subject to enhanced I/
M.
---------------------------------------------------------------------------

    To assess the adequacy of the RFP contingency measure (once adopted
and submitted), we next consider 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 equivalent to
approximately 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 WMD, one year's
worth of RFP is approximately 1.5 tpd of VOC, or 3.0 tpd of
NOX reductions, or a combination of the two calculated on a
percentage basis.\129\ In its commitment letter, CARB conservatively
estimates the potential additional emissions reductions from the
contingency measure commitments at 0.03 tpd of VOC and 0.04 tpd of
NOX. While these amounts collectively reflect less than one
year's worth of RFP, the 2018 SIP Update provides the larger SIP
planning context with which to judge the adequacy of the to-be-
submitted District contingency measures, by calculating the surplus
emissions reductions estimated to be achieved in the RFP milestone
years. The estimates of surplus NOX reductions range from
10.7 to 7.8 tpd, depending on the RFP year, which represents more than
twice one year's worth of progress (3.0 tpd of NOX).\130\
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. In
light of these surplus NOX emissions reductions in the RFP
milestone years, the emissions reductions from the committed
contingency measure are adequate to meet the contingency measure
requirements of the CAA with respect to RFP milestones.
---------------------------------------------------------------------------

    \129\ The 2011 baseline for VOC and NOX is 48.7 tpd
and 98.4 tpd, respectively, as shown in table VI-1 of the 2018 SIP
Update. Three percent of these baselines is 1.5 tpd of VOC and 3.0
tpd of NOX.
    \130\ 2018 SIP Update, Table VI-5.
---------------------------------------------------------------------------

    For attainment contingency measure purposes, we evaluate the
emissions reductions from the District's contingency measures in the
context of the expected reduction in emissions within the WMD in the
year following the attainment year, relative to those occurring in the
attainment year. In 2027, VOC and NOX emissions for the WMD
are expected to be approximately 0.2 and 1.6 tpd, respectively, lower
than the emissions in 2026. Considered together, the continuing
reductions from already-implemented measures and the emissions
reductions from the MDAQMD's contingency measure provide for emissions
reductions near to, but below, one year's worth of progress.\131\
Therefore, we find that the

contingency measures described in the MDAQMD's and CARB's commitment
letters would provide sufficient emissions reductions to satisfy the
attainment contingency measures requirement, even though reductions
from the measures would be lower than one year's worth of RFP.
---------------------------------------------------------------------------

    \131\ Combined reductions (0.23 tpd VOC and 1.64 tpd
NOX) represent 70 percent of one year's RFP (15.3 percent
of 1.5 tpd VOC; 54.7 percent of 3.0 tpd NOX). Further
emissions reductions are projected to occur in upwind areas in the
year following the attainment year (see, e.g., 2016 AQMP, Chapter
3), and we anticipate that these reductions will drive additional
reductions in ozone concentrations in the WMD in this period,
consistent with the strong influence of upwind emissions on
nonattainment in the WMD.
---------------------------------------------------------------------------

    For these reasons, we propose to conditionally approve the
contingency measures element of the 2016 WMD attainment plan, as
supplemented by the commitment from the MDAQMD and CARB to adopt and
submit an MDAQMD Board resolution detailing the circumstances, timing,
and procedure for implementing the contingency measure requirements of
CAA sections 172(c)(9) and 182(c)(9). Our proposed approval is
conditional because it relies upon specific commitments from MDAQMD and
CARB. Conditional approvals are authorized under CAA section 110(k)(4).

H. Motor Vehicle Emissions Budgets for Transportation Conformity

1. Statutory and Regulatory Requirements
    Section 176(c) of the CAA requires federal actions in nonattainment
and maintenance areas to conform to the SIP's goals of eliminating or
reducing the severity and number of violations of the NAAQS and
achieving expeditious attainment of the standards. Conformity to the
SIP's goals means that such actions will not: (1) Cause or contribute
to violations of a NAAQS, (2) worsen the severity of an existing
violation, or (3) delay timely attainment of any NAAQS or any interim
milestone.
    Actions involving Federal Highway Administration (FHWA) or Federal
Transit Administration (FTA) funding or approval are subject to the
EPA's transportation conformity rule, codified at 40 CFR part 93,