Document ID: EPA-R09-OAR-2021-0135-0003
Agency: epa
Document Type: Proposed Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: California; San Diego County; 2008 and 2015 8-Hour Ozone Nonattainment Area Requirements
Posted Date: 2023-12-19T05:00Z

[Federal Register Volume 88, Number 242 (Tuesday, December 19, 2023)]
[Proposed Rules]
[Pages 87850-87888]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-27513]

[[Page 87849]]

Vol. 88

Tuesday,

No. 242

December 19, 2023

Part II

Environmental Protection Agency

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40 CFR Part 52

Air Quality Implementation Plans; California; San Diego County; 2008 
and 2015 8-Hour Ozone Nonattainment Area Requirements; Proposed Rule

  Federal Register / Vol. 88, No. 242 / Tuesday, December 19, 2023 / 
Proposed Rules  

[[Page 87850]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2021-0135; FRL-9538-02-R9]

Air Quality Implementation Plans; California; San Diego County; 
2008 and 2015 8-Hour Ozone Nonattainment Area Requirements

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve portions of two state implementation plan (SIP) revisions 
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'') and the 2015 8-hour ozone NAAQS in the San Diego 
County ozone nonattainment area (``San Diego County area'' or 
``area''). The first SIP revision, ``2020 Plan for Attaining the 
National Ambient Air Quality Standards for Ozone in San Diego County'' 
(``2020 San Diego County Ozone SIP'' or ``2020 Plan''), addresses most 
of the SIP requirements for the area. The second SIP revision, referred 
to as the ``Smog Check Certification,'' supplements the motor vehicle 
inspection and maintenance program portion of the 2020 Plan. The EPA is 
proposing to approve the 2020 Plan, and the San Diego County portion of 
the Smog Check Certification, as meeting all the applicable ozone 
nonattainment area requirements for the 2008 and 2015 8-hour ozone 
NAAQS addressed by the plan except for the emissions statement 
requirement that the EPA previously found to have been met and the 
contingency measure requirements, for which the EPA is deferring 
action.

DATES: Comments must be received on or before January 18, 2024.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2021-0135 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 https://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: John J. Kelly, Air Planning Office 
(AIR-2-1), EPA Region IX, 75 Hawthorne Street, San Francisco, CA 94105. 
By phone at (415) 947-4151, or by email at [email protected].

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 San Diego County Ozone Nonattainment Area
    C. Clean Air Act and Regulatory Requirements for 2008 and 2015 
Ozone Nonattainment Area SIPs
II. Submission From the State of California To Address Ozone 
Requirements in San Diego County
    A. Summary of State Submissions
    B. Clean Air Act Procedural Requirements for Adoption and 
Submission of SIP Revisions
III. Evaluation of the 2020 San Diego County Ozone SIP
    A. Emissions Inventories
    B. Reasonably Available Control Measures Demonstration and 
Control Strategy
    C. Attainment Demonstration
    D. Rate of Progress Plan and Reasonable Further Progress 
Demonstration
    E. Transportation Control Strategies and Measures To Offset 
Emissions Increases From Vehicle Miles Traveled
    F. Contingency Measures
    G. Motor Vehicle Emissions Budgets for Transportation Conformity
    H. General Conformity Budgets
    I. Other Clean Air Act Requirements Applicable to Severe Ozone 
Nonattainment Areas
IV. Environmental Justice Considerations
V. Proposed Action
VI. 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 refers to reactive organic gases 
(ROG) in some of its ozone-related SIP submissions. As a practical 
matter, ROG and VOC refer to the same set of chemical constituents, 
and for the sake of simplicity, 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\ ``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 ``the Act''), the 
EPA promulgates NAAQS for pervasive air pollutants, such as ozone, to 
protect public health and welfare. Under CAA section 110, following 
promulgation of a new or revised NAAQS, states are required to adopt 
and submit plans that provide for implementation, maintenance, and 
enforcement of the NAAQS (referred to as State Implementation Plans or 
SIPs). Under CAA section 107(d), the EPA is required to designate areas 
throughout the nation as either attaining or not attaining the NAAQS, 
and states with designated nonattainment areas are required to submit 
SIP revisions to, among other things, provide for attainment as 
expeditiously as practicable but not later than the applicable 
attainment dates.
    In 1979, the EPA established primary and secondary NAAQS for ozone 
at 0.12 parts per million (ppm) averaged over a 1-hour period (``1979 
ozone NAAQS'').\3\ In 1997, the EPA revised the primary

[[Page 87851]]

and secondary standards for ozone in the ambient air to 0.08 ppm 
averaged over an 8-hour period (``1997 ozone NAAQS'').\4\
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    \3\ 44 FR 8202 (February 8, 1979). When the CAA was amended in 
1990, each area of the country that was designated nonattainment for 
the 1979 ozone NAAQS, including the San Diego area, was classified 
by operation of law as nonattainment and classified as Marginal, 
Moderate, Serious, Severe, or Extreme depending on the severity of 
the area's air quality problem. The EPA redesignated the San Diego 
County area from Serious nonattainment to attainment for the 1979 
ozone NAAQS, effective July 28, 2003. 68 FR 37976 (June 26, 2003).
    \4\ 62 FR 38856 (July 18, 1997). In 2004, the EPA designated 
areas of the country with respect to the 1997 ozone NAAQS. See 69 FR 
23858 (April 30, 2004). The EPA redesignated the San Diego County 
area from Moderate nonattainment to attainment for the 1997 ozone 
NAAQS, effective July 5, 2013. 78 FR 33230 (June 4, 2013).
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    In 2008, the EPA lowered the 8-hour ozone NAAQS to 0.075 ppm 
(``2008 ozone NAAQS'').\5\ Then in 2015, the EPA further lowered the 8-
hour ozone NAAQS to 0.070 ppm (``2015 ozone NAAQS'').\6\ On December 
31, 2020, the EPA finalized its most recent periodic review of the 
ozone NAAQS, retaining the form and level of the standards.\7\ The EPA 
has revoked both the 1979 ozone NAAQS and the 1997 ozone NAAQS but not 
the 2008 ozone NAAQS.\8\
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    \5\ 73 FR 16436 (March 27, 2008).
    \6\ 80 FR 65292 (October 26, 2015).
    \7\ 85 FR 87256. The SIP revision that is the subject of this 
proposed action relates to the requirements for the 2008 and 2015 
ozone standards.
    \8\ 40 CFR 50.9(b) and 40 CFR 50.10(c).
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    In 2012, the EPA designated San Diego County as nonattainment for 
the 2008 ozone NAAQS and classified the area as ``Marginal.'' \9\ Areas 
classified as Marginal must attain the NAAQS within three years of the 
effective date of the nonattainment designation.\10\ Following this 
initial classification as Marginal, the EPA found in 2016 that the area 
did not attain the 2008 ozone standards by the Marginal attainment 
deadline of July 20, 2015.\11\ As a result of our finding, the area was 
reclassified by operation of law to Moderate nonattainment.\12\ 
Moderate nonattainment areas have six years to attain the standard. 
Following the Moderate attainment deadline of July 20, 2018, the EPA 
found that the area did not attain the 2008 ozone standards.\13\ As a 
result of our finding, the area was reclassified by operation of law to 
Serious nonattainment, with a Serious attainment deadline of July 20, 
2021, nine years after the effective date of designation as a 
nonattainment area for the 2008 ozone NAAQS. In response to a letter to 
the EPA dated January 8, 2021 from the California Air Resources Board 
(CARB), the EPA reclassified the area to Severe for the 2008 ozone 
NAAQS.\14\ In the same letter, CARB requested that the EPA also 
reclassify the area as Severe for the 2015 ozone NAAQS. The EPA's 
initial designation for the San Diego County area for the 2015 ozone 
NAAQS was nonattainment, with a Moderate classification.\15\ The San 
Diego County area is now classified as Severe for both the 2008 and the 
2015 ozone NAAQS.\16\
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    \9\ 77 FR 30087 (May 21, 2012), effective July 20, 2012.
    \10\ CAA section 181(a)(1); 40 CFR 51.1102 and 51.1103(a).
    \11\ 81 FR 26697 (May 4, 2016).
    \12\ The State of California submitted the San Diego County 
area's 2016 Moderate ozone attainment plan and the 2016 Moderate 
ozone RACT demonstration to the EPA as a SIP revision on April 12, 
2017. The State withdrew the 2016 Moderate ozone attainment plan by 
letter dated December 16, 2021, following submittal of the 2020 plan 
and the EPA's grant of the State's request to reclassify San Diego 
County to Severe for the 2008 ozone NAAQS. The EPA approved the 2016 
Moderate ozone RACT demonstration at 85 FR 77996 (December 3, 2020), 
87 FR 38665 (June 29, 2022) and 88 FR 2538 (January 17, 2023).
    \13\ 84 FR 44238 (August 23, 2019).
    \14\ Letter dated January 8, 2021 from Richard Corey, Executive 
Officer, California Air Resources Board, to John Busterud, Regional 
Administrator, U.S. EPA Region IX; 86 FR 29522 (June 2, 2021), 
effective July 2, 2021.
    \15\ 83 FR 25776 (June 4, 2018). Severe areas must attain the 
standard as expeditiously as practicable, but not later than 15 
years after the effective date of designation. For the 2008 ozone 
NAAQS, the Severe attainment deadline is July 20, 2027. However, 
note that for attainment modeling purposes we refer to the 
attainment year as 2026. For the 2015 ozone NAAQS, the Severe 
attainment deadline is August 3, 2033, with a 2032 attainment year.
    \16\ 86 FR 29522 (June 2, 2021), effective July 2, 2021.
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    Designations of nonattainment for a given NAAQS trigger 
requirements under the CAA to prepare and submit SIP revisions. The SIP 
revision that is the subject of this proposed action addresses the 
Severe nonattainment area requirements that apply to the San Diego 
County area for the 2008 and the 2015 ozone NAAQS.
    Under California law, CARB is the state agency that is 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 and certain area sources, 
such as consumer products. 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 management plans (``plans''). In the San Diego 
County area, the San Diego County Air Pollution Control District 
(SDCAPCD or ``District'') develops and adopts plans to address CAA 
planning requirements applicable to that area. Such plans are then 
submitted to CARB for adoption and submittal to the EPA as revisions to 
the California SIP.

B. The San Diego County Ozone Nonattainment Area

    The San Diego County area is located in the southwestern-most 
portion of the State of California, and its boundaries generally align 
with those of San Diego County. For a precise description of the 
geographic boundaries of the San Diego County area for both the 2008 
and 2015 ozone NAAQS, see 40 CFR 81.305.
    Prior plans and state control measures developed by the District 
and CARB have produced significant emissions reductions over the years 
and improved air quality in the area. For instance, the 8-hour ozone 
design value for the San Diego County area decreased from 0.095 ppm to 
0.079 ppm from 2002 to 2022,\17\ despite increases in population and 
vehicular activity.
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    \17\ Three design value reports (EPA, Air Quality Design Value 
Report, July 12, 2011; San Diego 2008 Ozone Trends Report, U.S. EPA 
Air Quality System, May 8, 2023; and San Diego 2015 Ozone Trends 
Report, U.S. EPA Air Quality System, May 8, 2023), are included in 
the docket for this action. For the 2008 and 2015 ozone NAAQS, the 
design value at any given monitoring site is the 3-year average of 
the annual fourth highest daily maximum 8-hour average ambient air 
quality ozone concentration. The maximum design value among the 
various ozone monitoring sites is the design value for the area.
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    Under certain weather conditions, the San Diego County area is 
downwind from the Los Angeles-South Coast Air Basin (``South Coast'') 
and, under certain other weather conditions, from Mexico, and is 
subject to transport of ozone from those areas. The South Coast is 
regulated by the South Coast Air Quality Management District (SCAQMD). 
The 2020 Plan describes ozone transport from these areas as follows:

. . . air pollution from both regions significantly contribute to 
ozone levels in the San Diego region under certain weather 
conditions. This impact is acknowledged in State documentation and 
regulation. Importantly . . . SCAQMD has implemented effective 
emissions control programs, resulting in a trend of emission 
reductions and air quality improvements in the South Coast region. 
Though the region is designated as an Extreme Nonattainment Area for 
the 2008 and 2015 ozone NAAQS, SCAQMD predicts continued ozone 
reductions through at least 2031 as shown in their SIP for the 2008 
ozone NAAQS. In turn, air pollution transported to San Diego County 
is expected to decrease as a result of their actions.\18\
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    \18\ 2020 Plan, p. 13.

    Because of the transport from the South Coast into the San Diego 
County area, continued progress in the South Coast towards meeting the 
2008 and 2015 ozone NAAQS is expected to help the San Diego County area 
attain these ozone NAAQS.

C. Clean Air Act and Regulatory Requirements for 2008 and 2015 Ozone 
Nonattainment Area SIPs

    States must implement the 2008 and 2015 ozone NAAQS under title I, 
part D

[[Page 87852]]

of the CAA, including 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) that addresses 
implementation of various aspects of the 2008 ozone NAAQS (``2008 Ozone 
SRR''), including attainment dates, requirements for emissions 
inventories, attainment demonstrations, and reasonable further progress 
(RFP) demonstrations, among other SIP elements. The 2008 Ozone SRR also 
addresses the transition from the 1997 ozone NAAQS to the 2008 ozone 
NAAQS and associated anti-backsliding requirements.\19\ In 2018, the 
EPA also issued an SRR for the 2015 ozone NAAQS (``2015 Ozone SRR'') 
that addresses implementation of the 2015 standards.\20\ The regulatory 
requirements of the 2008 Ozone SRR are codified at 40 CFR part 51, 
subpart AA; those for the 2015 Ozone SRR are codified in 40 CFR part 
51, subpart CC. We discuss the CAA and regulatory planning requirements 
for the elements of 2008 and 2015 ozone plans relevant to this proposed 
action in more detail in Section III of this document.
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    \19\ 80 FR 12264 (March 6, 2015). Anti-backsliding requirements 
are the provisions applicable to revoked NAAQS (including the 1979 
1-hour ozone NAAQS and the 1997 ozone NAAQS).
    \20\ 83 FR 62998 (December 6, 2018).
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II. Submission From the State of California To Address Ozone 
Requirements in San Diego County

A. Summary of State Submissions

1. SDCAPCD's 2020 Attainment Plan
    On January 12, 2021, CARB submitted the 2020 Plan to the EPA as a 
revision to the California SIP.\21\ The 2020 Plan addresses many of the 
nonattainment area requirements for the San Diego County area for both 
the 2008 and the 2015 8-hour ozone NAAQS. In this document, we are 
proposing action on the 2020 Plan that addresses both the 2008 and 2015 
8-hour ozone NAAQS for the San Diego County area.
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    \21\ Letter (with enclosures) dated January 8, 2021, from 
Richard Corey, Executive Officer, CARB, to John Busterud, Regional 
Administrator, EPA Region IX (submitted electronically January 12, 
2021).
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    The 2020 Plan SIP submittal includes the various sections and 
attachments of the plan, plus the District's resolution of approval for 
the plan (District Resolution 20-166) and CARB's resolution of adoption 
of the plan as a revision to the California SIP (CARB Resolution 20-
29).\22\ The 2020 Plan includes a District commitment to achieve 
additional emissions reductions beyond those expected to occur from 
already-implemented control measures and relies on a similar commitment 
by CARB. More specifically, the 2020 Plan includes a commitment by the 
District to achieve an additional 1.7 tons per day (tpd) reduction in 
NOX by 2032 \23\ and relies on CARB's commitment to achieve 
aggregate emissions reductions in San Diego County of 4 tpd of 
NOX by 2032.\24\ Both commitments are part of the 2020 
Plan's attainment demonstration for the 2015 ozone NAAQS. With respect 
to both the 2008 and the 2015 ozone NAAQS, the 2020 Plan addresses the 
CAA requirements for emissions inventories, air quality modeling 
demonstrating attainment, reasonably available control measures (RACM), 
RFP, transportation control strategies and measures, new source review 
(NSR), contingency measures for failure to make RFP or to timely attain 
the relevant standards, and motor vehicle inspection and maintenance 
(I/M) programs (also referred to as ``smog check'' programs), among 
other requirements. The 2020 Plan also addresses the emissions 
statement requirement, and in separate action, the EPA approved the 
emissions statement portion of the 2020 Plan as meeting the applicable 
requirements for emissions statements for the 2008 and 2015 ozone 
NAAQS.\25\
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    \22\ SDCAPCD Board Resolution 20-166, October 14, 2020; CARB 
Board Resolution 20-29, Proposed San Diego 8-Hour Ozone State 
Implementation Plan Submittal, November 19, 2020 (``CARB Board 
Resolution 20-29'').
    \23\ 2020 Plan, at 58, 81-82.
    \24\ CARB Board Resolution 20-29, at 6.
    \25\ 87 FR 45657 (July 29, 2022).
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    The 2020 Plan is organized into an executive summary, five 
sections, and attachments lettered A through Q. Section 1, 
``Introduction and Overview,'' introduces the 2020 Plan, including its 
purpose, the two ozone NAAQS it addresses, current air quality in the 
area in comparison with those NAAQS, historical air quality progress in 
San Diego County, and the District's approach to air quality planning. 
Section 2, ``General Attainment Plan Requirements,'' addresses CAA 
requirements that apply to the area as nonattainment for both the 2008 
and the 2015 ozone NAAQS. Section 3, ``2008 Eight Hour Ozone NAAQS 
Attainment Plan Requirements,'' addresses CAA requirements that apply 
to the area as nonattainment specifically for the 2008 ozone NAAQS, 
including anti-backsliding requirements for the revoked 1979 and 1997 
ozone standards. Section 4, ``2015 Eight Hour Ozone NAAQS Attainment 
Plan Requirements,'' addresses CAA requirements that apply to the area 
as nonattainment specifically for the 2015 ozone NAAQS, including anti-
backsliding requirements for revoked standards. Section 5, 
``Conclusions,'' presents the District's conclusions regarding whether 
the 2020 Plan meets applicable Clean Air Act requirements.
    The 2020 Plan also includes technical attachments:
     Attachment A (``Emissions Inventories and Documentation 
for Baseline, RFP, and Attainment Years'') presents tables, analysis, 
and documentation for the emissions inventories included in the plan.
     Attachment B (``Planned Military Projects Subject to 
General Conformity'') contains annual data compiled by the United 
States Marine Corps (USMC) and Department of the Navy (DoN) for 
emissions changes resulting from USMC and DoN projects out to year 
2037, for the purpose of demonstrating general conformity for USMC and 
DoN facilities in the area.
     Attachment C (``Planned San Diego International Airport 
Projects Subject to General Conformity'') is a report that provides an 
emissions inventory for the San Diego International Airport, for the 
purpose of demonstrating general conformity for the airport.
     Attachment D (``CARB Control Measures, 1985 to 2019'') is 
a listing of CARB control measures from 1985 to 2019.
     Attachment E (``CARB Analyses of Key Mobile Source 
Regulations and Programs Providing Emission Reductions'') describes 
CARB's mobile source regulations and programs that provide emissions 
reductions in the San Diego County area.
     Attachment F (``Pre-Baseline Banked Emission Reduction 
Credits'') describes emission reduction credits that were banked before 
the baseline year.
     Attachment G (``Analyses of Potential Additional 
Stationary Source Control Measures'') provides the District's analysis 
of the feasibility of additional stationary source control measures 
that could be pursued in the area.
     Attachment H (``Implementation Status of Transportation 
Control Measures'') provides the implementation status of 
transportation control measures by the San Diego Association of 
Governments (SANDAG) and other transportation agencies.
     Attachment I (``CARB Analyses of Potential Additional 
Mobile Source and Consumer Products Control Measures'')

[[Page 87853]]

analyzes the potential for further mobile source and consumer products 
controls in the area.
     Attachment J (``Calculation of Cumulative Potential 
Emission Reductions for Possible Reasonably Available Control Measures 
(RACM)'') calculates the cumulative potential emissions reductions in 
the area in support of the plan's RACM demonstration.
     Attachment K (``Modeling Protocol & Attainment 
Demonstration for the 2020 San Diego Ozone SIP'') provides the modeling 
protocol and attainment demonstration for the San Diego County area as 
Severe nonattainment for both the 2008 and the 2015 ozone NAAQS.
     Attachment L (``Modeling Emission Inventory for the Ozone 
State Implementation Plan in San Diego County'') describes the modeled 
or ``gridded'' emissions inventories for the area, in support of the 
area's two modeled attainment demonstrations.
     Attachment M (``Weight of Evidence Demonstration for San 
Diego County'') provides a weight-of-evidence demonstration for the 
area, in support of the area's modeled attainment demonstrations.
     Attachment N (``VMT Offset Demonstration for San Diego 
County'') provides the area's VMT offset demonstration.
     Attachment O (``Contingency Measures for San Diego 
County'') represents the District's assessment of compliance with the 
contingency measure requirements for the area.
     Attachment P (``Federal Clean Air Act Requirements and 
References in Attainment Plan'') provides a summary of CAA requirements 
that apply to the area with specific citations to locations in the plan 
that address those requirements.
     Attachment Q (``Endnotes'') contains the text of all 
endnotes found in the plan.
    Attainment of the 2008 and the 2015 ozone NAAQS in the San Diego 
County area is dependent on emissions reductions occurring in the 
adjacent South Coast nonattainment area. The 2016 South Coast Ozone SIP 
documents baseline emissions reductions from already-adopted control 
measures and provides for new emissions reductions to be achieved 
through fulfillment of SCAQMD and CARB commitments for further 
reductions, and through new technology measures.\26\ More specifically, 
as discussed in Section III.D, ``Attainment Demonstration,'' of the 
EPA's proposed approval of the 2016 South Coast Ozone SIP,\27\ the 
ozone attainment demonstrations for South Coast for the 1997 and 2008 
ozone NAAQS include emissions reduction commitments made by the SCAQMD 
in the 2016 AQMP and by CARB in the ``Revised Proposed 2016 State 
Strategy for the State Implementation Plan'' (``2016 State Strategy'').
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    \26\ 84 FR 28132 (June 17, 2019), at 28134-28134, tables 10 and 
11. The EPA finalized its approval of the 2016 South Coast Ozone SIP 
at 84 FR 52005 (October 1, 2019).
    \27\ 84 FR 28132, 28143-28157 (June 17, 2019),
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    The 2016 State Strategy focuses on two areas: the South Coast and 
the San Joaquin Valley. Although it did not include specific emissions 
reduction commitments for San Diego County, CARB states that, 
``[s]hould additional areas require emission reductions to meet the 
current ozone and PM2.5 standards, ARB will quantify area 
and year specific reductions as part of individual attainment plans.'' 
\28\ The 2020 Plan for the 2015 ozone NAAQS relies on CARB's commitment 
to achieve 4 tpd of NOX emissions reductions in 2032 from 
mobile sources to demonstrate attainment of this standard in San Diego 
County.\29\
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    \28\ 2016 State Strategy, 35.
    \29\ CARB Review of the 2020 Plan for Attaining the National 
Ambient Air Quality Standards for Ozone in San Diego County, Release 
Date: October 16, 2020, at 11; CARB Board Resolution 20-29, at 6.
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2. Smog Check Certification
    On April 26, 2023, CARB submitted the ``California Smog Check 
Performance Standard Modeling and Program Certification for the 70 
Parts Per Billion (ppb) 8-Hour Ozone Standard'' (``Smog Check 
Certification'') to supplement the motor vehicle I/M portion of the 
2020 Plan.\30\ The Smog Check Certification includes CARB's evaluation 
of the California Smog Check program for compliance with the applicable 
I/M performance standard as defined in EPA's regulations for certain 
nonattainment areas for the 2008 and 2015 ozone NAAQS, including San 
Diego County.
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    \30\ Letter (with enclosures) dated April 26, 2023, from Steven 
S. Cliff, Ph.D., Executive Officer, CARB, to Martha Guzman, Regional 
Administrator, EPA Region IX (submitted electronically April 26, 
2023).
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    CARB's SIP submittal package for the Smog Check Certification 
includes CARB Resolution 23-9, through which CARB adopted the Smog 
Check Certification as part of the California SIP,\31\ public notice of 
CARB's hearing on the proposed SIP revision, public comments and 
responses, and MOVES \32\ input and output data sheets. In this 
document, we are proposing action on the San Diego County portion of 
the Smog Check Certification as a supplement to the vehicle I/M portion 
of the 2020 Plan.
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    \31\ CARB Board Resolution 23-9, March 23, 2023.
    \32\ MOVES is the acronym for the EPA's Motor Vehicle Emission 
Simulator model.
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B. Clean Air Act Procedural Requirements for Adoption and Submission of 
SIP Revisions

    CAA sections 110(a) 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 to submit written comments 
and request a public hearing was provided consistent with the EPA's 
implementing regulations in 40 CFR 51.102.
    Both the District and CARB have satisfied the applicable statutory 
and regulatory requirements for reasonable public notice and hearing 
prior to the adoption and submittal of the 2020 Plan. The District held 
two public webinars, one in July and another in August, 2020, and held 
a hearing on October 14, 2020, to discuss the plan and solicit public 
input.\33\ On September 14, 2020, the District published a notice in a 
local newspaper of the public hearing to be held on October 14, 2020, 
to consider approval of the 2020 Plan.\34\ On October 14, 2020, the 
District held the public hearing, and on that same date, through 
Resolution 20-166, the District board approved the 2020 Plan and 
directed the Air Pollution Control Officer to forward its resolution 
and the 2020 Plan to CARB for submittal to the EPA for inclusion in the 
California SIP.
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    \33\ Letter dated October 20, 2020,from Robert Reider, Interim 
Director, SDCAPCD, to Richard Corey, CARB Executive Officer. See the 
letter's response to comments document regarding the two webinars 
and its ``Minute Order'' document regarding the public hearing.
    \34\ Id. See the October 20, 2020 letter's proof of publication 
document regarding public notice for the October 14, 2020 public 
hearing.
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    Upon receipt of the 2020 Plan from the District, CARB also provided 
public notice and opportunity for public comment on the plan. On 
October 16, 2020, CARB released for public review its staff report for 
the 2020 Plan (``CARB Staff Report'') \35\ and published a notice of 
public meeting to be held on November 19, 2020, to consider

[[Page 87854]]

adoption of the 2020 Plan as a revision to the California SIP.\36\ On 
November 19, 2020, CARB held the hearing and adopted the 2020 Plan as a 
revision to the California SIP and directed the Executive Officer to 
submit the 2020 Plan to the EPA for approval into the California 
SIP.\37\ On January 12, 2021, the Executive Officer of CARB submitted 
the 2020 Plan to the EPA. Six months after submittal, on July 12, 2021, 
the 2020 Plan became complete by operation of law.\38\
---------------------------------------------------------------------------

    \35\ CARB Review of the 2020 Plan for Attaining the National 
Ambient Air Quality Standards for Ozone in San Diego County, Release 
Date: October 16, 2020.
    \36\ Notice of Public Meeting to Consider Approval of the 
Proposed San Diego 8-Hour Ozone State Implementation Plan Submittal, 
signed by Richard Corey, Executive Officer, CARB, October 16, 2020.
    \37\ CARB Resolution 20-29, 6.
    \38\ CAA section 110(k)(1)(B).
---------------------------------------------------------------------------

    CARB has also satisfied the applicable statutory and regulatory 
requirements for reasonable public notice and hearing prior to the 
adoption and submittal of the Smog Check Certification. On February 10, 
2023, CARB released for public review the draft Smog Check 
Certification and published a notice of public meeting to be held on 
March 23, 2023, to consider adoption of the Smog Check Certification as 
a revision to the California SIP.\39\ On March 23, 2023, CARB held the 
hearing and adopted the Smog Check Certification as a revision to the 
California SIP and directed the Executive Officer to submit the Smog 
Check Certification to the EPA for approval into the California 
SIP.\40\ On April 26, 2023, the Executive Officer of CARB submitted the 
Smog Check Certification to the EPA.
---------------------------------------------------------------------------

    \39\ Notice of Public Meeting to Consider the Proposed 
California Smog Check Performance Standard Modeling and Program 
Certification for the 70 parts per billion 8-hour Ozone Standard, 
signed by Steven S. Cliff, Ph.D., Executive Officer, CARB, February 
10, 2023.
    \40\ CARB Resolution 23-9, 6.
---------------------------------------------------------------------------

    Based on information provided in the SIP revisions submitted on 
January 12, 2021 and April 26, 2023, and summarized in Section II.A 
this document, the EPA has determined that all hearings were properly 
noticed and that a reasonable opportunity to submit written comments 
was provided. Therefore, we find that the submittal of the 2020 Plan 
and the Smog Check Certification meets 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 2020 San Diego County Ozone SIP

A. Emissions Inventories

1. Statutory and Regulatory Requirements
    CAA sections 172(c)(3) and 182(a)(1) 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 and the 2015 Ozone SRR require that the 
inventory year be selected consistent with the baseline year for the 
RFP demonstration, which is 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 (AERR) at the time of 
designation for the ozone NAAQS.\41\ For the 2008 ozone NAAQS, the 
baseline year for the RFP demonstration is 2011, and for the 2015 ozone 
NAAQS, the base year for the RFP demonstration is 2017.
---------------------------------------------------------------------------

    \41\ 2008 Ozone SRR at 40 CFR 51.1115(a) and 40 CFR 51.1110(b), 
2015 Ozone SRR at 40 CFR 51.1315(a) and 40 CFR 51.1310(b), and the 
Air Emissions Reporting Requirements at 40 CFR part 51, subpart A.
---------------------------------------------------------------------------

    The EPA has issued guidance on the development of base year and 
future year emissions inventories for 8-hour ozone and other 
pollutants.\42\ Emissions inventories for ozone must include emissions 
of VOC and NOX and represent emissions for a typical ozone 
season weekday.\43\ 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.\44\
---------------------------------------------------------------------------

    \42\ ``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, 
available in the docket for this action and at https://www.epa.gov/air-emissions-inventories/air-emissions-inventory-guidance-implementation-ozone-and-particulate.
    \43\ For 2008 ozone, 40 CFR 51.1115(a) and (c), and 40 CFR 
51.1100(bb) and (cc). For 2015 ozone, 40 CFR 51.1315(a) and (c), and 
40 CFR 51.1300(p) and (q).
    \44\ 80 FR 12264, 12290 (March 6, 2015); 83 FR 62998, 63022 
(December 6, 2018).
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    Future 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 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 2020 Plan includes three sets of base year and future year 
average summer day baseline inventories for NOX and VOC for 
the San Diego County area, for both the 2008 and 2015 ozone NAAQS.\45\ 
One set of base year and future year baseline emissions inventories 
reflects emissions within the San Diego County area and includes marine 
emissions out to 100 nautical miles (NM) from the coast. A second set 
of emissions inventories adds emissions from the South Coast Air Basin 
to those generated within the San Diego County area (plus marine 
emissions out to 100 NM from the coast) to produce combined 
inventories. A third set of emissions inventories reflects San Diego 
County area emissions including marine emissions but only out to three 
NM from the coast. All three sets of inventories include the years 
2011, 2017, 2020, 2023, 2026, 2029 and 2032.
---------------------------------------------------------------------------

    \45\ 2020 Plan, Attachment A.
---------------------------------------------------------------------------

    Documentation for the inventories is found in Sections 3 and 4 of 
the 2020 Plan, addressing the 2008 and 2015 ozone NAAQS, respectively, 
as well as in the Plan's Attachment A. Because ozone levels in the area 
are typically highest during the summer months, the inventories 
provided in the 2020 Plan represent average summer day emissions from 
May through October. The inventories in the 2020 Plan reflect District 
rules adopted through the end of calendar year 2019 and CARB rules 
adopted through the end of calendar year 2017. For estimating on-road 
motor vehicle emissions, these inventories use EMFAC2017, the EPA-
approved version of California's mobile source emissions model 
available at the time the 2020 Plan was developed.\46\
---------------------------------------------------------------------------

    \46\ EMFAC is short for EMission FACtor. The EPA announced the 
availability of the EMFAC2017 model for use in state implementation 
plan development and transportation conformity in California on 
August 15, 2019. 84 FR 41717. The EPA's approval of the EMFAC2017 
emissions model for SIP and conformity purposes was effective on the 
date of publication of the notice in the Federal Register.
---------------------------------------------------------------------------

    The VOC and NOX emissions estimates are grouped into two 
general categories, stationary sources and mobile sources. Stationary 
sources are further divided into ``point'' and ``area'' sources. Point 
sources typically refer to stationary sources that are permitted 
facilities and have one or more identified and fixed pieces of 
equipment and emissions points. Area sources consist of widespread and 
numerous smaller emissions sources, such as consumer products, 
fireplaces and agricultural burning.\47\ The mobile

[[Page 87855]]

sources category is divided into two major subcategories, ``on-road'' 
and ``off-road'' mobile sources. On-road mobile sources include light-
duty automobiles, light-, medium-, and heavy-duty trucks, and 
motorcycles. Off-road mobile sources include aircraft, locomotives, 
construction equipment, mobile equipment, and recreational vehicles.
---------------------------------------------------------------------------

    \47\ 2020 Plan, p. A-30.
---------------------------------------------------------------------------

    Point source (also referred to as ``stationary source'') emissions 
for the 2011 and 2017 base year emissions inventories are calculated 
using reported data from facilities using the District's annual 
emissions reporting program, which applies under District Rule 19.3 to 
stationary sources in the San Diego County area that emit 25 tons per 
year (tpy) or more of VOC or NOX. Area sources include 
smaller emissions sources distributed across the nonattainment area. 
CARB and the District estimate emissions for numerous area source 
categories using established inventory methods, including publicly 
available emissions factors and activity information. Specific 
estimates are included in the 2020 Plan for area source categories: 
consumer products, architectural coatings and related process solvent 
use, pesticides and fertilizers, asphalt paving and roofing, 
residential fuel combustion, farming operations, fires, managed burning 
and disposal, and cooking.
    On-road emissions inventories in the 2020 Plan are calculated using 
CARB's EMFAC2017 model and the travel activity data provided by SANDAG 
in SANDAG's 2018 adopted Regional Transportation Improvement 
Program.\48\ CARB provided emissions inventories for off-road 
equipment, including construction and mining equipment, industrial and 
commercial equipment, lawn and garden equipment, agricultural 
equipment, ocean-going vessels, commercial harbor craft, locomotives, 
cargo handling equipment, pleasure craft, and recreational vehicles. 
CARB used several models to estimate emissions for off-road equipment 
categories.\49\ Aircraft emissions inventories are developed in 
conjunction with the airports in the region. In particular, an 
emissions analysis was included in the 2020 Plan for the San Diego 
International Airport.\50\
---------------------------------------------------------------------------

    \48\ Id. at A-35. SANDAG is the metropolitan planning 
organization (MPO) for San Diego County.
    \49\ Id. at A-36.
    \50\ Id., Attachment C, ``Planned San Diego International 
Airport Projects Subject to General Conformity.''
---------------------------------------------------------------------------

    The 2020 Plan distinguishes between emissions sources within San 
Diego County, which includes coastal emissions (including marine vessel 
emissions) within three NM of the coastline, and emissions sources 
operating outside the county but within 100 NM of the coastline. The 
base year emissions inventory reflects only those emissions sources 
that operate within the nonattainment area (i.e., within three NM of 
the coastline), but offshore emissions sources affect ozone 
concentrations in the nonattainment area and thus are included in the 
emissions inventories used for the attainment demonstrations in the 
2020 Plan.
    The calendar year 2017 is the base year in the 2020 Plan for both 
the 2008 and 2015 ozone NAAQS because 2017 the most recent calendar 
year for which a complete triennial inventory was required to be 
submitted to the EPA under the provisions of 40 CFR part 51, subpart A 
at the time of plan development. The 2020 Plan includes an emissions 
inventory for an earlier year, i.e., calendar year 2011, because that 
year is the RFP baseline year for the 2008 ozone NAAQS. The 2017 base 
year inventory was used to forecast all future years for area and 
mobile sources and to ``backcast'' such sources for 2011.\51\
---------------------------------------------------------------------------

    \51\ Id. at Q-2, footnote 29.
---------------------------------------------------------------------------

    To develop the 2011 inventory, CARB relied on actual emissions 
reported from industrial point sources for 2011 and backcast emissions 
from 2017 for smaller stationary and certain area sources.\52\ Area 
source emissions from pesticide were developed by CARB based on actual 
emissions reported for 2011, while those from agricultural burning were 
developed by CARB based on actual emissions reported for 2008 that were 
``grown'' (that is, projected forward from 2008, based on estimated 
changes in agricultural burning) to 2011. CARB produced 2011 on-road 
emissions estimates using EMFAC2017. Non-road emissions were either 
backcast from 2017 (commercial aircraft and military ocean-going 
vessels) or were estimated using CARB's OFFROAD2007 model.\53\
---------------------------------------------------------------------------

    \52\ Id.
    \53\ Email dated March 21, 2023, from Nick Cormier, SDCAPCD to 
John J. Kelly, EPA, Subject: ``FW: 2011 emission inventory in SD's 
2020 ozone plan.''
---------------------------------------------------------------------------

    For the 2020 Plan, CARB used the California Emission Projection 
Analysis Model (CEPAM), 2019 SIP Baseline Emission Projections, Version 
1.00 to develop future year emissions forecasts (i.e., 2020, 2023, 
2026, 2029 and 2032).\54\ In doing so, CARB reviewed the growth and 
control factors for each category and relevant year along with the 
resulting emissions projections.\55\ CARB compared year-to-year trends 
to similar and past datasets to ensure general consistency, checked 
emissions for specific categories to confirm they reflect the 
anticipated effects of applicable control measures, and verified mobile 
source categories with CARB mobile source staff for consistency with 
the on-road and off-road emission models.\56\
---------------------------------------------------------------------------

    \54\ 2020 Plan, Attachment A, Section A.8.
    \55\ Id.
    \56\ Id.
---------------------------------------------------------------------------

    In developing the 2020 Plan, the District worked with the 
Department of the Navy and the United States Marine Corps to identify 
specific growth increments from future anticipated actions to include 
in the baseline emissions forecasts for use by the military to comply 
with the applicable general conformity regulations. The District then 
coordinated with CARB to include the growth increments or ``budgets'' 
in the applicable source categories in the CEPAM model used by CARB to 
develop the future year emissions inventories. More specifically, the 
CEPAM model runs used for the future year emissions estimates in the 
2020 Plan reflect a military growth increment of 1.08 tpd of VOC and 
8.34 tpd of NOX for all future years addressed in the 
plan.\57\ Similarly, the District worked with the San Diego County 
Regional Airport Authority to identify a growth increment for future 
anticipated actions at San Diego International Airport (SDIA) for use 
in connection with the general conformity regulations. The growth 
increment for SDIA for all future year emissions estimates in the 2020 
Plan is 0.141 tpd of VOC and 1.756 tpd for NOX.\58\ Section 
III.H of this document provides further information on the military and 
SDIA growth increments reflected in the 2020 Plan.
---------------------------------------------------------------------------

    \57\ 2020 Plan, Section 2.1.3.1 and Attachment B.
    \58\ Id., Section 2.1.3.2 and Attachment C.
---------------------------------------------------------------------------

    The future year emissions estimates in the 2020 Plan include two 
additional specific adjustments--one to account for pre-base year 
emissions reduction credits (ERCs) and one to account for the EPA's 
rescission, in a final action referred to as ``SAFE 1,'' of a waiver of 
preemption of CARB's light-duty vehicle zero emission vehicle (ZEV) 
sales mandate and greenhouse gas (GHG) standards.\59\
---------------------------------------------------------------------------

    \59\ ``The Safer Affordable Fuel-Efficient (SAFE) Vehicles Rule 
Part One: One National Program'' (SAFE 1), 84 FR 51310 (September 
27, 2019).
---------------------------------------------------------------------------

    Under the EPA's SIP regulations for nonattainment new source review 
(NSR) programs, a state may allow new major stationary sources or major 
modifications to use as offsets ERCs that were generated through 
shutdown or

[[Page 87856]]

curtailed emissions units occuring before the base year of an 
attainment plan. However, to use such ERCs, the projected emissions 
inventories used to develop the RFP and attainment demonstration must 
explicitly include the emissions from such previously shutdown or 
curtailed emissions units.\60\ The District has elected to provide for 
use of pre-base year ERCs as offsets by explicitly including such ERCs 
in the future year emissions estimates in the 2020 Plan. The ERC set-
aside in the 2020 Plan amounts to 0.71 tpd of VOC and 0.56 tpd of 
NOX.\61\
---------------------------------------------------------------------------

    \60\ 40 CFR part 51, Appendix S, section IV.C.5.
    \61\ 2020 Plan, section 2.1.3.3 and Attachment F.
---------------------------------------------------------------------------

    The ``EMFAC2017 Adjustment Factors'' refers to adjustment factors 
that CARB developed for EMFAC2017 to account for the EPA's SAFE 1 final 
action that, among other things, withdrew the EPA's waiver of 
preemption for CARB's Advanced Clean Car (ACC) regulation as it 
pertained to CARB's ZEV sales mandate and GHG standards.\62\ EMFAC2017 
reflected emissions reductions that were estimated to be achieved 
through implementation of the ACC regulation, including the ZEV sales 
mandate. In response to the EPA's SAFE 1 action, CARB developed 
correction factors to be used to account for the foregone emissions 
reductions (EMFAC2017 Adjustment Factors).\63\ In 2020, the EPA 
concurred on the use of CARB's EMFAC2017 Adjustment Factors for the 
purposes of SIP development in California,\64\ and the 2020 Plan takes 
them into account as an adjustment to the EMFAC2017-derived motor 
vehicle emissions estimates included in the future year emissions 
inventories. For the 2020 Plan, the EMFAC2017 Adjustment Factor is 
generally 0.1 tpd or less for VOC and NOX in all future 
years expected to be affected by the SAFE 1 action.
---------------------------------------------------------------------------

    \62\ The EPA issued the ACC waiver on January 9, 2013 (78 FR 
2112).
    \63\ Letter and enclosures dated March 5, 2020 from Steven S. 
Cliff, Ph.D., Deputy Executive Officer, CARB, to Elizabeth Adams, 
Director, Air and Radiation Division, EPA Region IX.
    \64\ Letter dated March 12, 2020, from Elizabeth J. Adams, 
Director, Air and Radiation Division, EPA Region IX, to Steven S. 
Cliff, Ph.D., Deputy Executive Officer, CARB.
---------------------------------------------------------------------------

    Table 1 of this document provides a summary of the baseline 
emissions inventories for the base year and future years in tpd 
(average summer day) for VOC and NOX for the 2008 ozone 
NAAQS.\65\ The inventories summarized in Table 1 distinguish between 
emissions generated within the nonattainment area and emissions that 
are generated offshore between three NM and 100 NM from the coastline 
of San Diego County. Table 1 also shows the adjustments made to account 
for ERCs and the EMFAC2017 Adjustment Factors. Table 2 of this document 
provides the same type of summary information as Table 1, but presents 
the base year and future years that are relevant for the 2015 ozone 
NAAQS.
---------------------------------------------------------------------------

    \65\ Tables 1 and 2 summarize anthropogenic emissions sources 
only, which is consistent with the EPA's ``Emissions Inventory 
Guidance for Implementation of Ozone and Particulate Matter National 
Ambient Air Quality Standards (NAAQS) and Regional Haze 
Regulations'' (May 2017). Anthropogenic emissions sources are 
distinguishable from natural sources, which include biogenic, 
geogenic and wildfire emissions sources. Both anthropogenic and 
natural sources of emissions are, however, included in emissions 
inventories used for attainment demonstration modeling purposes.
---------------------------------------------------------------------------

    Based on the emissions inventory for 2017, stationary, area, and 
mobile sources (on-road and off-road) contribute roughly equally to 
county-wide VOC emissions, whereas mobile sources (on-road and off-
road) are the predominant sources of NOX emissions. The 
inventory for 2017 also shows the magnitude of marine offshore (3 NM to 
100 NM) emissions sources relative to those within the nonattainment 
area. A comparison of the base years with the future years shows the 
significant decrease that is expected to be achieved through CARB's 
regulations for new on-road and off-road mobile sources together with 
vehicle turnover (i.e., the rate of replacement of older, more 
polluting models with new models manufactured to meet tighter emissions 
standards). For a more detailed discussion of the methodologies used to 
develop the inventories, see Attachment A of the 2020 Plan.

                       Table 1--San Diego County Base Year and Future Year Baseline Emissions Inventories for the 2008 Ozone NAAQS
                                                            [Summer planning inventory, tpd]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                    2011                  2017                  2020                  2023                  2026
                                           -------------------------------------------------------------------------------------------------------------
                                               NOX        VOC        NOX        VOC        NOX        VOC        NOX        VOC        NOX        VOC
--------------------------------------------------------------------------------------------------------------------------------------------------------
Stationary Sources........................        4.4       27.4        4.1       27.6        4.0       26.9        3.9       26.3        4.0       26.3
Area Sources..............................        1.9       36.8        1.7       33.6        1.5       34.3        1.4       34.8        1.2       35.2
On-Road Mobile Sources....................       71.2       34.4       37.7       20.5       28.5       16.5       19.7       13.8       17.5       12.3
Off-Road Mobile Sources...................       33.2       38.0       33.5       31.1       32.6       28.5       31.2       26.7       30.3       25.2
Emission Reduction Credits adjustment.....  .........  .........  .........  .........        0.6        0.7        0.6        0.7        0.6        0.7
EMFAC2017 Adjustment Factor...............  .........  .........  .........  .........  .........  .........       <0.1        0.1       <0.1       <0.1
                                           -------------------------------------------------------------------------------------------------------------
    Total--San Diego County Nonattainment       110.7      136.6       77.0      112.9       67.1      107.0       56.8      102.4       53.6       99.7
     Area.................................
--------------------------------------------------------------------------------------------------------------------------------------------------------
Marine Emissions (3 NM-100 NM)............       15.8        0.8       17.5        1.0       17.5        1.0       18.1        1.0       18.6        1.1
                                           -------------------------------------------------------------------------------------------------------------

[[Page 87857]]

 
    Total--Nonattainment Area plus Marine       126.5      137.5       94.5      113.8       84.7      108.0       74.8      103.4       72.2      100.8
     Emissions (3 NM-100 NM)..............
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: 2020 Plan, Attachment A, Tables A-1 and A-3. The sum of the emissions values may not equal the total due to rounding of the numbers.

                       Table 2--San Diego County Base Year and Future Year Baseline Emissions Inventories for the 2015 Ozone NAAQS
                                                           [summer planning inventory, (tpd)]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                    2017                  2023                  2026                  2029                  2032
                                           -------------------------------------------------------------------------------------------------------------
                                               NOX        VOC        NOX        VOC        NOX        VOC        NOX        VOC        NOX        VOC
--------------------------------------------------------------------------------------------------------------------------------------------------------
Stationary Sources........................        4.1       27.6        3.9       26.3        4.0       26.3        4.0       26.6        4.1       27.2
Area Sources..............................        1.7       33.6        1.4       34.8        1.2       35.2        1.0       35.6        1.0       36.1
On-Road Mobile Sources....................       37.7       20.5       19.7       13.8       17.5       12.3       16.0       11.1       15.1       10.0
Off-Road Mobile Sources...................       33.5       31.1       31.2       26.7       30.3       25.2       29.7       24.2       28.9       23.2
Emission Reduction Credits adjustment.....  .........  .........        0.6        0.7        0.6        0.7        0.6        0.7        0.6        0.7
EMFAC2017 Adjustment Factor...............  .........  .........       <0.1        0.1       <0.1       <0.1       <0.1       <0.1       <0.1        0.1
                                           -------------------------------------------------------------------------------------------------------------
    Total--San Diego County Nonattainment        77.0      112.9       56.8      102.4       53.6       99.7       51.3       98.2       49.7       97.2
     Area.................................
--------------------------------------------------------------------------------------------------------------------------------------------------------
Marine Emissions (3 NM-100 NM)............       17.5        1.0       18.1        1.0       18.6        1.1       19.0        1.0       19.3        1.1
                                           -------------------------------------------------------------------------------------------------------------
    Total--Nonattainment Area plus Marine        94.5      113.8       74.8      103.4       72.2      100.8       70.0       99.3       69.0       98.3
     Emissions (3 NM-100 NM)..............
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: 2020 Plan, Attachment A, Tables A-1 and A-3. The sum of the emissions values may not equal the total due to rounding of the numbers.

3. The EPA's Review of the State's Submission
    The 2020 Plan refers to year 2017 as the base year inventory for 
both the 2008 and 2015 ozone NAAQS but also includes an inventory of 
actual emissions in calendar year 2011, which we have reviewed for the 
purpose of evaluating compliance with the base year emissions inventory 
SIP requirement for the 2008 ozone NAAQS. Year 2017 is the appropriate 
base year for the emissions inventory SIP requirement for the 2015 
ozone NAAQS.
    We have reviewed the 2011 and 2017 base year emissions inventories 
in the 2020 Plan and the inventory methodologies used by the District 
and CARB for consistency with CAA requirements and EPA guidance. First, 
we find that the 2011 and 2017 inventories include 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 2011 and 2017 base year emissions 
inventories in the 2020 Plan reflect appropriate emissions models and 
methodologies, and, therefore, represent comprehensive, accurate, and 
current inventories of actual emissions during those years in the San 
Diego County area. Therefore, the EPA is proposing to approve the 2011 
and 2017 emissions inventories in the 2020 Plan as meeting the 
requirements for base year inventories for 2008 and 2015 ozone set 
forth in CAA sections 172(c)(3) and 182(a)(1), and 40 CFR 51.1115 and 
40 CFR 51.1315. In addition, although the requirement for a base year 
emissions inventory applies to the nonattainment area, we find that the 
District's estimates of marine emissions out to 100 NM (i.e., beyond 
the nonattainment area boundary that extends three NM offshore) are 
reasonable and appropriate to include in the 2020 Plan given that such 
emissions must be accounted for in

[[Page 87858]]

the ozone attainment demonstrations for this nonattainment area.
    With respect to the future year emissions baseline projections, we 
have reviewed the growth and control factors and find them acceptable 
and conclude that the future baseline emissions projections in the 2020 
Plan reflect appropriate calculation methods and the latest planning 
assumptions. We have also reviewed the documentation concerning the 
growth increments for the military and for SDIA and the documentation 
for the ERCs and find that they are appropriately accounted for in the 
future year baseline emissions inventories or, in the case of the ERCs, 
as an off-model adjustment to the inventories.\66\ With respect to the 
EMFAC2017 Adjustment Factors, we note that, since adoption of the 2020 
Plan, the EPA has rescinded SAFE 1 (the withdrawal of the waiver of 
CARB's ZEV sales mandate and GHG standards),\67\ which calls into 
question the use of the EMFAC2017 Adjustment Factor, as it may affect 
projections, particularly over the long term. However, as shown in 
Tables 1 and 2, the EMFAC2017 Adjustment Factor adjustment in the 
future year emissions inventories is insignificant (0.1 tpd or less for 
both VOC and NOX), and thus the change in circumstances 
regarding the status of CARB's ZEV sales mandate does not affect the 
emissions projections used for the RFP and attainment demonstrations in 
the 2020 Plan.
---------------------------------------------------------------------------

    \66\ See Section III.H of this document for our full evaluation, 
and proposed approval, of the growth increments for the military and 
SDIA.
    \67\ 87 FR 14332 (March 14, 2022).
---------------------------------------------------------------------------

    Also, as a general matter, the EPA will approve a SIP revision that 
takes emissions reduction credit for a control measure only where the 
EPA has approved the measure as part of the SIP. Thus, to take credit 
for the emissions reductions from District rules for stationary sources 
and CARB rules for mobile sources, the related rules must be approved 
by the EPA into the SIP.\68\ The EPA performed a review of District 
rules relied upon in developing the future baseline emissions 
inventories for the 2020 Plan.\69\ Based on our review, we find that, 
with only one exception that does not implicate the RFP or attainment 
demonstrations of the 2020 Plan,\70\ District rules relied upon in 
developing the future baseline emissions inventories are approved as 
part of the SIP. With respect to mobile sources, the EPA has taken 
action in recent years to approve CARB mobile source regulations into 
the California SIP.\71\ We therefore find that the future year baseline 
projections in the 2020 Plan are properly supported by SIP-approved 
stationary and mobile source measures.
---------------------------------------------------------------------------

    \68\ See generally Committee for a Better Arvin v. EPA, 786 F.3d 
1169, 1175-1177 (9th Cir. 2015).
    \69\ The EPA's review of District rules relied upon in 
developing the future baseline emissions inventories is presented in 
Memorandum to Docket EPA-R09-OAR-2021-0135 from Jeff Wehling, Office 
of Regional Counsel, EPA Region IX, August 25, 2023.
    \70\ District Rule 61.4.1 should be submitted for approval as 
part of the SIP; however, the related emissions reductions are not 
of a magnitude as to implicate the RFP or attainment demonstrations.
    \71\ See 81 FR 39424 (June 16, 2016), 82 FR 14446 (March 21, 
2017), and 83 FR 23232 (May 18, 2018).
---------------------------------------------------------------------------

B. Reasonably Available Control Measures Demonstration and Control 
Strategy

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 to provide for attainment of the NAAQS. 
The 2008 Ozone SRR and the 2015 Ozone SRR require 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.\72\
---------------------------------------------------------------------------

    \72\ 40 CFR 51.1112(c); 40 CFR 51.1312(c). The ``San Diego 
County area'' is shorthand for two nonattainment areas, one for each 
of two ozone NAAQS: the 2008 and the 2015 ozone NAAQS. The boundary 
is the same for both areas. Accordingly, the District submitted two 
attainment demonstrations in the 2020 Plan, one for each of the two 
standards.
---------------------------------------------------------------------------

    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 
Measure Requirement and Attainment Demonstration Submissions for Ozone 
Nonattainment Areas.'' \73\ In short, to address the requirement to 
adopt all RACM, states should consider all potentially reasonable 
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.\74\ Any 
measures that are necessary to meet these requirements that are not 
already either federally promulgated, or part of the state's SIP, must 
be submitted in enforceable form as part of the state's attainment plan 
for the area.
---------------------------------------------------------------------------

    \73\ See General Preamble, 57 FR 13498, 13560 (April 16, 1992) 
and memorandum dated November 30, 1999, from John S. Seitz, 
Director, OAQPS, to Regional Air Directors, Subject: ``Guidance on 
the Reasonably Available Control Measure Requirement and Attainment 
Demonstration Submissions for Ozone Nonattainment Areas.''
    \74\ 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, Subject: ``Additional Submission on RACM 
From States with Severe One-Hour Ozone Nonattainment Area SIPs.''
---------------------------------------------------------------------------

    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. CAA section 182(f) requires that 
RACT under section 182(b)(2) also apply to major stationary sources of 
NOX. In Severe areas, a major source is a stationary source 
that emits or has the potential to emit at least 25 tpy of VOC or 
NOX (CAA sections 182(d) and (f)). Under the 2008 Ozone SRR 
and the 2015 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 the 2015 ozone NAAQS, respectively. Implementation 
of the required RACT measures is required as expeditiously as 
practicable but no later than January 1 of the 5th year after the 
effective date of designation for the 2008 ozone NAAQS (see 40 CFR 
51.1112(a)) and for the 2015 ozone NAAQS (see 40 CFR 51.1312(a)).\75\
---------------------------------------------------------------------------

    \75\ California submitted the CAA section 182 RACT SIP for the 
San Diego County area for both the 2008 and 2015 ozone NAAQS, as a 
Severe nonattainment area with a 25 tpy major source threshold, on 
December 29, 2020. To date, the EPA has taken several actions on the 
San Diego County RACT SIP. We are not taking action on the RACT SIP 
in this rulemaking but will be completing action on it in a separate 
rulemaking(s).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    The 2020 Plan presents two RACM demonstrations. The first is 
included in Section 3.2.1 and addresses the 2008 ozone NAAQS. The 
second is presented in Section 4.2.1 for the 2015 ozone NAAQS. Within 
each Section, the 2020 Plan presents a RACM analysis organized by 
several emissions source groups. The District and CARB each undertook a 
process to identify and evaluate potential RACM that could contribute 
to expeditious attainment of the 2008 ozone NAAQS and the 2015

[[Page 87859]]

ozone NAAQS in the San Diego County area. In addition, the District 
presented a ``RACM Cumulative Analysis'' for each standard as an 
overarching analysis of all source categories covered by CARB, the 
District and SANDAG.\76\
---------------------------------------------------------------------------

    \76\ 2020 Plan, Sections 3.2.1 and 4.2.1.
---------------------------------------------------------------------------

    The 2020 Plan's RACM section for the 2008 ozone NAAQS begins by 
determining the magnitude of emissions reductions that would be needed 
to advance the area's attainment date by one year. As noted in Section 
I.B of this document, air pollutants transported from the South Coast 
region contribute to higher ozone levels in San Diego County under 
certain weather conditions. Accordingly, the RACM analysis in the 2020 
Plan for the 2008 ozone NAAQS accounts for projected emissions from the 
San Diego County-South Coast transport couplet.\77\
---------------------------------------------------------------------------

    \77\ 2020 Plan, p. 38. In this context, ``transport couplet'' 
refers to a ``transport couple,'' a term that refers to two air 
basins, one of which has an impact on ambient air pollutant 
concentrations in the other air basin due to transport of pollutants 
and precursors by prevailing wind patterns. See ``Assessment of the 
Impacts of Transported Pollutants on Ozone Concentrations in 
California,'' CARB, March 2001.
---------------------------------------------------------------------------

    Using emissions levels of the District's chosen 2026 attainment 
demonstration year as a basis for comparison, the District compared 
emissions levels from 2026 to what the levels are projected to be one 
year earlier, that is, 2025. The lower levels in 2026 were then 
subtracted from the higher levels of emissions in 2025, providing a 
difference in emissions levels that could then be compared against the 
2020 Plan's RACM, that is, emissions reductions from reasonably 
available control measures, to determine if enough RACM reductions 
would be available to advance the 2026 attainment year to 2025. These 
levels are provided in Table 3 of this document.

 Table 3--Emissions Reductions Needed To Advance Attainment by One Year,
                            2008 Ozone NAAQS
------------------------------------------------------------------------
                                                             Emissions
                    Emissions totals                           (tpd)
------------------------------------------------------------------------
2026 VOC Emissions Inventory............................           471.0
2025 VOC Emissions Inventory............................           473.8
VOC Emissions Reductions Needed in 2025 to Demonstrate               2.8
 Attainment.............................................
2026 NOX Emissions Inventory............................           344.0
2025 NOX Emissions Inventory............................           347.4
NOX Emissions Reductions Needed in 2025 to Demonstrate               3.4
 Attainment.............................................
------------------------------------------------------------------------
Source: 2020 Plan, Table 3-2 and Table A-2.

    Because the District's attainment demonstration relies on specific 
levels of emissions of both VOC and NOX, the reductions of 
emissions to advance that attainment date one year would require 
reductions in both VOC and NOX at the levels shown in Table 
3, that is, 2.8 tpd of VOC and 3.4 tpd of NOX (``2008 ozone 
NAAQS RACM targets''). These amounts of reductions are then viewed as 
targets to see if they can be met or exceeded, and if so, then the 
attainment year for the 2008 ozone NAAQS would be moved up one year, to 
2025. The 2020 Plan groups emissions sources into several large 
categories and assesses each one to identify potential RACM and to 
determine their potential collectively to provide emissions reductions 
equal to or greater than these targets.
a. 2008 Ozone NAAQS, District's RACM Analysis
    The District provides a comprehensive evaluation of its 2008 ozone 
NAAQS RACM control strategy in Section 3.2.1 (``Reasonably Available 
Control Measures (RACM) Demonstration'') and Attachments A, D, G, H, I 
and J of the 2020 Plan. The evaluation includes: source descriptions; 
base year and projected baseline year emissions for the source category 
affected by the rule; discussion of the current requirements of the 
rule; and discussion of potential additional control measures, 
including, in many cases, a discussion of the technological and 
economic feasibility of the additional control measures. This includes 
a comparison of each District rule to analogous control measures 
adopted by other agencies.
    The District's RACM demonstration for the 2008 ozone NAAQS begins 
with an analysis of stationary source controls, described in Section 
3.2.1.2 (``Identifying Potential RACM for Stationary Sources'') of the 
2020 Plan. This section of the 2020 Plan identifies potential control 
measures and analyzes these measures for emissions reduction 
opportunities, as well as economic and technological feasibility. The 
District's comprehensive demonstration considers potential control 
measures for stationary sources located throughout the area under its 
jurisdiction, that is, the entirety of San Diego County.
    As a first step in the RACM analysis, the District prepared a 
detailed inventory of emissions sources of VOC and NOX to 
identify source categories from which emissions reductions would 
effectively contribute to attainment. Details on the methodology and 
development of the emissions inventory are discussed in Section 3 and 
Attachment A of the 2020 Plan. Because the San Diego County area 
airshed is coupled with the South Coast Air Basin, which was used in 
the attainment demonstration modeling in the 2020 Plan, the District 
prepared a ``couplet'' emissions inventory that includes the two areas' 
combined emissions. A total of 75 source categories are included in the 
couplet emissions inventory: 45 for stationary and area sources and 30 
for mobile sources.\78\ Although the couplet emissions inventory 
includes South Coast and is therefore used in calculating the 2008 
ozone NAAQS RACM targets (2.8 tpd VOC, 3.4 tpd NOX), only 
sources of emissions within San Diego County were evaluated for their 
potential to either meet the 2008 ozone NAAQS RACM targets or to 
contribute to a collective reduction to meet those targets.
---------------------------------------------------------------------------

    \78\ 2020 Plan, Table A-2.
---------------------------------------------------------------------------

    The District compared the 45 source categories to its rules for 
stationary and area sources. This analysis builds upon a foundation of 
District rules developed for earlier ozone plans and approved as part 
of the SIP. These rules establish emissions limits or other types of 
emissions controls for a wide range of sources, including VOC storage 
and handling, use of solvents, gasoline storage, gasoline transfer, dry 
cleaning with petroleum-based solvent, architectural coatings, surface 
coating operations, marine, wood products and aerospace coating 
operations, degreasing operations, cutback and emulsified asphalts, 
kelp processing and

[[Page 87860]]

biopolymer manufacturing operations, pharmaceutical and cosmetic 
manufacturing, and bakery ovens, among others. These rules have already 
provided significant reductions toward attainment of the 2008 ozone 
NAAQS by 2026.
    The District excluded RACT rules from their stationary source RACM 
analysis because those rules are already required by federal law to be 
included in the SIP and are therefore not ``potential'' RACM control 
measures. Likewise, the District excluded stationary and area sources 
it regulates under the State's requirement to adopt ``all feasible 
measures,'' as these measures are also already implemented and 
incorporated into the area's attainment demonstration, and are 
therefore also not potential RACM. In addition, California state law 
requires ``Best Available Retrofit Control Technology'' or BARCT.\79\ 
Because BARCT is an ongoing requirement for the District, BARCT rules 
are already implemented, would provide no new emissions reductions, and 
are therefore not potential RACM.
---------------------------------------------------------------------------

    \79\ California Health & Safety Code sections 40918, 40919, 
40920 and 40920.5.
---------------------------------------------------------------------------

    To demonstrate that the SDCAPCD considered all candidate measures 
that are available and technologically and economically feasible for 
stationary sources, the District conducted several steps in their 
analysis.
Step 1. Stakeholder Outreach
    As part of a previous planning effort for the 2008 ozone NAAQS (the 
2016 Moderate Plan),\80\ and again as part of the SIP development 
effort for the (Severe) 2020 Plan, the District held multiple 
stakeholder outreach sessions. These sessions were intended to solicit 
stakeholder input on the full array of control measures that might be 
available for emissions sources in the area. Two public workshops were 
held in July 2020, in addition to other individual stakeholder meetings 
that were held for feedback on the entire draft 2020 Plan before and 
after each public workshop. These meetings built upon similar outreach 
the District conducted for prior federal and state air quality plans, 
including the 2016 Moderate Plan.
---------------------------------------------------------------------------

    \80\ The State of California submitted the San Diego County 
area's 2016 Moderate ozone attainment plan to the EPA as a SIP 
revision on April 12, 2017. At the time, the area was a Moderate 
nonattainment area for the 2008 ozone NAAQS. The State withdrew the 
2016 Moderate ozone attainment plan by letter dated December 16, 
2021 following submittal of the 2020 Plan and the EPA's grant of the 
State's request to reclassify San Diego County to Severe for the 
2008 ozone NAAQS.
---------------------------------------------------------------------------

Step 2. Reasonably Available Control Technology Analysis
    The District then considered Reasonably Available Control 
Technology (RACT) stationary source categories and found 11 existing 
District control measures that could be further controlled when 
compared to existing rules in other California air districts.\81\ These 
11 control measures apply to specific types of emissions sources: 
Receiving and Storing Volatile Organic Compounds at Bulk Plants and 
Bulk Terminals, Transfer of Organic Compounds into Mobile Transport 
Tanks, Metal Parts and Product Coating Operations, Paper, Film, and 
Fabric Coatings, Aerospace Coating Operations, Graphic Arts Operations, 
Marine Coating Operations, Adhesive Materials Application Operations, 
Industrial and Commercial Boilers, Process Heaters and Steam 
Generators, Natural Gas-Fired Fan-Type Central Furnaces, and Stationary 
Gas Turbine Engines. The SDCAPCD compared its rules to the analogous 
rules for the same stationary source types in other California air 
districts, as candidate potential measures, and estimated the potential 
emissions reductions associated with each control measure if it were 
modified to reflect the other district's rule.
---------------------------------------------------------------------------

    \81\ 2020 Plan, Table G-1, items G.1 to G.11.
---------------------------------------------------------------------------

Step 3. EPA Technical Support Documents (TSDs)
    The District researched TSDs from recent EPA rulemakings but did 
not find any potential additional stationary source controls beyond 
what its RACT analysis found.\82\
---------------------------------------------------------------------------

    \82\ Email dated August 31, 2023, from Nick Cormier, SDCAPCD, to 
John J. Kelly, EPA.
---------------------------------------------------------------------------

Step 4. Control Measures in Other Areas
    The District reviewed stationary source control measures in other 
areas (i.e., San Francisco Bay Area, Sacramento, San Joaquin Valley, 
Santa Barbara, South Coast, and Ventura County) to evaluate whether 
control technologies available and cost-effective within other areas 
would be available and cost-effective for use in the San Diego County 
area.\83\ These include six control measures: Vacuum Truck Operations, 
Miscellaneous NOX Sources, Equipment Leaks, Restaurant 
Cooking Operations, Food Products Manufacturing/Processing, and 
Metalworking Fluids and Direct-Contact Lubricants.
---------------------------------------------------------------------------

    \83\ 2020 Plan, Table G-1, items G.12 to G.17.
---------------------------------------------------------------------------

Step 5. EPA Menu of Control Measures
    The Menu of Control Measures (MCM) \84\ compiled by the EPA's 
Office of Air Quality Planning and Standards was created to provide 
information useful in the development of emissions reduction strategies 
and to identify and evaluate potential control measures. District staff 
reviewed the EPA's MCM for stationary source point and nonpoint sources 
of NOX and VOC.
---------------------------------------------------------------------------

    \84\ EPA, MCM, April 12, 2012.
---------------------------------------------------------------------------

    Based on its evaluation of all available stationary source control 
measures, the District concluded that its existing rules are generally 
as stringent as analogous rules in other districts, and where they were 
not, quantified the difference. In all, the District estimated that the 
total possible emissions reductions from further control of stationary 
sources subject to existing District rules and control of additional 
source categories would be approximately 0.4 tpd for VOC and 0.4 tpd 
for NOX.\85\
---------------------------------------------------------------------------

    \85\ 2020 Plan, Attachment G, Table G-1.
---------------------------------------------------------------------------

b. 2008 Ozone NAAQS, RACM Analysis for Transportation Control Measures
    Attachment H of the 2020 Plan contains the District's 
transportation control measure (TCM) RACM evaluation. The implemented 
TCMs in Attachment H are applicable in San Diego County. The District 
conducted the TCM RACM analysis on behalf of SANDAG and local 
jurisdictions in San Diego County, based on SANDAG's regional 
transportation plan (RTP), specifically, ``San Diego Forward: The 2019 
Federal Regional Transportation Plan'' (``2019 RTP'').\86\ The 2019 RTP 
was developed in consultation with federal, state and local 
transportation and air quality planning agencies and other 
stakeholders.
---------------------------------------------------------------------------

    \86\ The 2019 RTP was adopted by SANDAG's Board on October 25, 
2019. The 2019 RTP was approved by the Federal Highway 
Administration on November 15, 2019.
---------------------------------------------------------------------------

    As described in Attachment H of the 2020 Plan, for the TCM RACM 
analysis, the District listed all TCMs that are included in CAA section 
108(f) and their implementation status in San Diego County.\87\ Of the 
16 TCMs listed in CAA section 108(f), 13 are implemented in San Diego 
County. Of these implemented TCMs, five were included in the area's 
1982 SIP.
---------------------------------------------------------------------------

    \87\ 2020 Plan, Attachment H, ``Implementation Status of 
Transportation Control Measures,'' Table H-1.
---------------------------------------------------------------------------

    Of the three TCMs that are not implemented in San Diego County, one 
(``Trip Reduction Ordinances'') was adopted in 1994, but was then 
rescinded in 1995 when federal and State laws were amended eliminating 
the mandate

[[Page 87861]]

for such measures.\88\ Another (``Programs to limit or restrict vehicle 
use in downtown areas or other areas of emission concentration 
particularly during periods of peak use'' or ``Peak Use Restriction 
Programs'') was found to be infeasible due to San Diego's low-density 
land use pattern and accompanying longer transit travel times. However, 
the District notes that SANDAG's Smart Growth Incentive Program 
provides funding to cities in San Diego County for infrastructure 
projects that enhance alternatives to driving in higher density areas.
---------------------------------------------------------------------------

    \88\ As amended in 1990, CAA section 182(d)(1)(B) required 
states with Severe ozone nonattainment areas to adopt and submit SIP 
revisions requiring employers in such areas to implement programs to 
reduce work-related vehicle trips and miles traveled by employees, 
commonly referred to as ``trip reduction ordinances.'' Amendments to 
the CAA promulgated in 1995 revised CAA section 182(d)(1)(B) such 
that trip reduction ordinances are no longer required but may be 
adopted and submitted as SIP revisions at the state's discretion.
---------------------------------------------------------------------------

    Finally, one TCM, (``Programs to reduce motor vehicle emissions, 
consistent with Title II, which are caused by extreme cold start 
conditions'' or ``Cold Weather Start Programs'') was found to be not 
applicable to San Diego County due to its mild climate.
    Based on its review of TCM projects implemented in San Diego 
County, the District determined that 13 of the 16 TCMs listed in CAA 
section 108(f) are being implemented in the county and are therefore 
ineligible for consideration as potential RACM. To determine if the 
three unimplemented TCMs could be required as RACM, the District 
estimated the maximum emissions reductions to be attributed to those 
TCMs.
    The 2020 Plan estimates the maximum emissions reduction potential 
of the three unimplemented TCMs, citing a 1992 SANDAG study that 
estimated maximum emissions reductions for Trip Reduction Ordinances 
alone at less than 2 percent of on-road vehicle emissions.\89\ The 1992 
SANDAG study also found that potential reductions of all 15 of the 
other TCMs combined do not equal the Trip Reduction Ordinances TCM 
alone. Therefore, the 2020 Plan estimates the maximum potential 
emissions reduction potential of the three unimplemented TCMs as 2 
percent of on-road vehicle emissions in a given year. For the modeled 
attainment year, 2026, projected on-road motor vehicle emissions in San 
Diego County are 12.2 tpd VOC and 17.5 tpd NOX. Two percent 
of these projected emissions is 0.2 tpd VOC and 0.4 tpd NOX.
---------------------------------------------------------------------------

    \89\ ``Transportation Control Measures for the Air Quality 
Plan,'' SANDAG, 1992.
---------------------------------------------------------------------------

c. 2008 Ozone NAAQS, CARB's RACM Analysis
    CARB's RACM analysis is contained in Attachment I (``CARB Analyses 
of Potential Additional Mobile Source and Consumer Products Control 
Measures'') (``CARB RACM assessment'') of the 2020 Plan. The CARB RACM 
analysis provides a general description of CARB's existing mobile 
source programs. In its analysis, CARB includes mobile source control 
measures described in CARB's ``2016 State Strategy for the State 
Implementation Plan'' (2016 State Strategy).\90\ A more detailed 
description of CARB's mobile source control program, including a 
comprehensive table listing on- and off-road mobile source regulatory 
actions taken by CARB from 1985 to 2019, is contained in Attachment D 
of the 2020 Plan (``CARB Control Measures, 1985 to 2019 (March 
2020)''). CARB's RACM analysis and 2016 State Strategy collectively 
contain CARB's evaluation of mobile source and other statewide control 
measures that reduce emissions of NOX and VOC in California, 
including San Diego County.
---------------------------------------------------------------------------

    \90\ CARB's 2016 State Strategy is available in the docket for 
this action and at https://ww3.arb.ca.gov/planning/sip/2016sip/rev2016statesip.pdf.
---------------------------------------------------------------------------

    Source categories for which CARB has primary responsibility for 
reducing emissions in California include most new and existing on- and 
off-road engines and vehicles, motor vehicle fuels, and consumer 
products. CARB developed its 2016 State Strategy through a multi-step 
measure development process, including extensive public consultation, 
to develop and evaluate potential strategies for mobile source 
categories under CARB's regulatory authority that could contribute to 
expeditious attainment of the standard.\91\ Through the process of 
developing the 2016 State Strategy, CARB identified certain defined 
measures as available to achieve additional VOC and NOX 
emissions reductions from sources under CARB jurisdiction, including 
tighter requirements for new light- and medium-duty vehicles (referred 
to as the ``Advanced Clean Cars 2'' measure), a low-NOX 
engine standard for vehicles with new heavy-duty engines, tighter 
emissions standards for small off-road engines, and more stringent 
requirements for consumer products, among others.\92\ In adopting the 
2016 State Strategy, CARB committed to bringing the defined measures to 
the CARB Board for action according to the specific schedule included 
as part of the strategy.\93\
---------------------------------------------------------------------------

    \91\ 2020 Plan, p. I-2.
    \92\ 2016 State Strategy, Chapter 4 (``State SIP Measures'').
    \93\ CARB Resolution 17-7 (dated March 23, 2017), p. 7. CARB's 
resolution is available in the docket for this action and at https://ww3.arb.ca.gov/planning/sip/2016sip/res17-7.pdf.
---------------------------------------------------------------------------

    Given the need for substantial emissions reductions from mobile and 
area sources to meet the NAAQS in California nonattainment areas, CARB 
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.\94\
---------------------------------------------------------------------------

    \94\ 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).
---------------------------------------------------------------------------

    In their RACM analysis, CARB concludes that, in light of the 
extensive public process culminating in the 2016 State Strategy, with 
the current mobile source program and proposed measures included in the 
2016 State Strategy, there are no additional mobile source RACM that 
would advance attainment of the 2008 ozone NAAQS in San Diego County. 
As a result, CARB concludes that California's mobile source programs 
fully meet the RACM requirement.\95\
---------------------------------------------------------------------------

    \95\ 2020 Plan, p. I-6.
---------------------------------------------------------------------------

    Attachment I of the 2020 Plan describes CARB's current consumer 
products program and commitments in the 2016 State Strategy to achieve 
additional VOC reductions from consumer products.\96\ As described in 
Attachment I, CARB's current consumer products program limits VOC 
emissions from 129 consumer product categories, including product 
categories such as

[[Page 87862]]

antiperspirants and deodorants and aerosol coatings.\97\ The EPA has 
approved these measures into the California SIP as VOC emissions 
controls for a wide array of consumer products.\98\
---------------------------------------------------------------------------

    \96\ Id., pp. I-6, I-7. CARB's consumer product measures are 
found in the California Code of Regulations, Title 17 (``Public 
Health''), Division 3 (``Air Resources''), Chapter 1 (``Air 
Resources Board''), Subchapter 8.5 (``Consumer Products'').
    \97\ Id., p. D-34.
    \98\ The compilation of such measures that have been approved 
into the California SIP, including Federal Register citations, is 
available at: https://www.epa.gov/sips-ca/epa-approved-regulations-california-sip. EPA's most recent approval of amendments to 
California's consumer products regulations was in 2020. 85 FR 57703 
(September 16, 2020).
---------------------------------------------------------------------------

d. 2008 Ozone NAAQS, the District's RACM Conclusion
    In addition to evaluating a number of stationary, area, and mobile 
sources, as well as consumer products, in the separate groups as 
described in Section III.B.a. to Section III.B.c. in this document, the 
District presents a ``cumulative analysis'' to assess whether all 
potential RACM combined could result in advancement of the modeled 2026 
attainment year to 2025.\99\ Attachment J (``Calculation of Cumulative 
Potential Emission Reductions for Possible Reasonably Available Control 
Measures (RACM)'') of the 2020 Plan presents the cumulative potential 
RACM.\100\ When taken together, all potential RACM reductions of VOC 
and NOX that the District and CARB evaluated amount to 
approximately 0.7 tpd VOC and 0.7 tpd NOX. These amounts 
fall far short of the 2008 ozone RACM targets of 2.8 tpd VOC and 3.4 
tpd NOX.\101\ The District therefore concludes that, 
collectively, there are not enough potential RACM reductions to advance 
the attainment date.
---------------------------------------------------------------------------

    \99\ 2020 Plan, Section 3.2.1.6, ``RACM Cumulative Analysis,'' 
pp. 41-42.
    \100\ Id., Table J-1.
    \101\ Although the District based its RACM analysis for the 2008 
ozone NAAQS on emissions reductions in the San Diego County-South 
Coast transport couplet, the District also analyzed emissions 
reductions from the District alone and also concluded that the 
attainment year could not be advanced one year with RACM emissions 
reductions. See email dated August 9, 2023, from Nick Cormier, 
SDCAPCD, to Jefferson Wehling, EPA.
---------------------------------------------------------------------------

e. 2015 Ozone NAAQS, RACM
    In addition to addressing RACM for the 2008 ozone NAAQS, the 2020 
Plan addresses RACM for the 2015 NAAQS. Section 4.2.1, ``Reasonably 
Available Control Measures (RACM) Demonstration,'' of the 2020 Plan 
contains the plan's RACM demonstration for the 2015 ozone NAAQS. The 
demonstration reflects much of what the 2020 Plan presents for 
demonstrating RACM for the 2008 ozone NAAQS and relies on the same 
attachments described in Section III.B.2.a.-d. of this document, that 
is, Attachments A (``Emissions Inventories and Documentation for 
Baseline, RFP, and Attainment Years''), D (``CARB Control Measures, 
1985 to 2019''), G (``Analyses of Potential Additional Stationary 
Source Control Measures''), H (``Implementation Status of 
Transportation Control Measures''), I (``CARB Analyses of Potential 
Additional Mobile Source and Consumer Products Control Measures''), and 
J (``Calculation of Cumulative Potential Emission Reductions for 
Possible Reasonably Available Control Measures (RACM'').
    In the 2020 Plan, the District compares 2032 projected emissions of 
the ozone precursors VOC and NOX to those of the year prior, 
2031, to determine the amount of emissions reductions that would be 
necessary in order to advance attainment by one year, to 2031, 
providing a 2015 ozone NAAQS RACM target. These levels are provided in 
Table 4 of this document. Unlike the emissions projections used to 
determine the magnitude of emissions reductions that would be necessary 
to advance attainment by one year for the RACM demonstration for the 
2008 ozone NAAQS, the emissions projections used to determine the 
magnitude of emissions reductions necessary to advance attainment by 
one year for the RACM demonstration for the 2015 ozone NAAQS reflect 
emissions only for San Diego County (i.e., including marine emissions 3 
to 100 NM off the County coastline) rather than those for the South 
Coast-San Diego couplet. Using this more conservative approach, the 
District determined that VOC reductions of 0.1 tpd and NOX 
reductions of 5.9 tpd would advance the attainment date for the 2015 
ozone NAAQS by one year.\102\
---------------------------------------------------------------------------

    \102\ 2020 Plan, Table 4-2, p. 58.

 Table 4--Emissions Reductions Needed To Advance Attainment by One Year,
                            2015 Ozone NAAQS
------------------------------------------------------------------------
                                                             Emissions
                    Emissions totals                           (tpd)
------------------------------------------------------------------------
2032 VOC Emissions Inventory............................            98.3
2031 VOC Emissions Inventory............................            98.4
VOC Emissions Reductions Needed in 2031 to Demonstrate               0.1
 Attainment.............................................
2032 NOX Emissions Inventory............................          * 63.3
2031 NOX Emissions Inventory............................            69.2
NOX Emissions Reductions Needed in 2025 to Demonstrate               5.9
 Attainment.............................................
------------------------------------------------------------------------
Source: 2020 Plan, Table 4-2, ``Emissions Reductions Required to Advance
  Attainment By One Year, 2015 Ozone NAAQS (tons per day).''
* Adjusted for RACM. The unadjusted 2032 NOX emissions inventory for San
  Diego County is 69.0 tpd. However, for attainment purposes, CARB has
  committed to obtain additional emissions reductions, in the amount of
  4 tpd NOX, as described in Section 4.3.5 of the 2020 Plan, and 1.7 tpd
  NOX, as described in Section 4.3.4 of the 2020 Plan and in Attachment
  L, Section L.3.9. These commitments add up to 5.7 tpd NOX, leaving a
  total emissions inventory of NOX in 2032 of 63.3 tpd.

    Once the District identifies 2015 ozone NAAQS RACM targets (0.1 tpd 
VOC, 5.9 tpd NOX) in the 2020 Plan, the District assesses 
all potential RACM reductions to determine if, collectively, they could 
equal or exceed the targets. The District analyzes these potential RACM 
reductions in essentially the same steps as those taken to assess 
potential RACM for the 2008 ozone NAAQS, starting with stationary 
sources. As described in Section III.B.2.a. of this document, for the 
stationary source portion of the RACM demonstration for the 2008 ozone 
NAAQS, if all potential stationary source RACM were adopted in the 
area, stationary source emissions would be reduced an additional 0.41 
tpd for VOC and 0.40 tpd for NOX.\103\ With respect to TCMs, 
the District estimates that if all unimplemented TCMs were to be 
adopted, transportation-related emissions sources in San Diego County 
would be reduced by 2 percent of the on-road motor vehicle emissions 
inventory for year 2032, or

[[Page 87863]]

approximately 0.2 tpd VOC and 0.3 tpd NOX. For mobile 
sources and consumer products, the District concludes in the 2020 Plan 
that there are no potential RACM reductions available since all 
reasonable rules regulating both are currently being implemented.\104\ 
In the 2020 Plan, the District bases this conclusion on analysis 
performed by CARB in Attachment I, which we describe in Section 
III.B.2.c. of this document regarding 2008 ozone NAAQS RACM.
---------------------------------------------------------------------------

    \103\ 2020 Plan, Attachment G, Table G-1, ``Stationary Source 
Categories for Which More Stringent Control Requirements Have Been 
Adopted by Another Air District,'' p. G-1.
    \104\ Id., Section 4.2.1.5, ``Identifying Potential RACM for 
Mobile Sources and Consumer Products,'' 61, and Attachment I, ``CARB 
Analyses of Potential Additional Mobile Source and Consumer Products 
Control Measures.''
---------------------------------------------------------------------------

    The District included an additional step in its RACM analysis for 
the 2015 ozone NAAQS, which was not performed for the 2008 ozone NAAQS. 
The purpose was to determine whether further reductions would be 
possible, given that the area's 2032 modeled attainment year was 
further in the future for the 2015 ozone NAAQS than for the 2008 ozone 
NAAQS (2026). The District assessed the top ten non-mobile source 
categories of VOC and NOX in San Diego County's emissions 
inventory.\105\
---------------------------------------------------------------------------

    \105\ Id., Attachment A-1, Table A-1.
---------------------------------------------------------------------------

    For each of these categories, the District estimates the percentage 
of the county's 2032 emissions of VOC and NOX.\106\ In each 
of two tables in the 2020 Plan (Table 4-3 and Table 4-4), the District 
provides, for each category: the numerical ranking from 1 to 10, with 1 
representing the category with the highest emissions of all ten 
categories; the source category name; the emission inventory code or 
EIC; \107\ 2017 base year and 2032 projected attainment year emissions 
of VOC or NOX; the percentage of the County's projected 2032 
total emissions of VOC or NOX; a description of applicable 
regulations for the category; and whether there are potential RACM 
reductions, with an accompanying justification. The purpose of this 
last item, potential RACM and justification, is to determine first if 
there are RACM reductions available. A ``yes'' in this column indicates 
that the category has further reductions that are not being 
implemented. A ``no'' indicates that the category has no potential RACM 
reductions. Justifications for a ``no'' in this column vary. For 
example, the number 1 category of VOC non-mobile emissions is Consumer 
Products. These were discussed in both the 2008 and 2015 ozone NAAQS 
RACM sections in the 2020 Plan. In both instances, the conclusions, 
based on the analyses provided, are that there are no further CARB 
Consumer Products regulations to put in place.
---------------------------------------------------------------------------

    \106\ Id., Table 4-3, ``Top Ten Categories of VOC Emissions in 
2032 (Non-Mobile),'' and Table 4-4, ``Top Ten Categories of 
NOX Emissions in 2032 (Non-Mobile).''
    \107\ Emissions inventory source categories are represented by a 
14-digit emission inventory code (EIC) for area and mobile sources.
---------------------------------------------------------------------------

    In the 2020 Plan, text accompanying each of these two tables (that 
is, Tables 4-3 and 4-4) provides further assessment of each category. 
To continue the example for Consumer Products, the text explains that 
CARB has been developing regulations for this category for thirty 
years, developing regulations for over 100 consumer product categories. 
These regulations have been amended frequently, with increasing levels 
of stringency for VOC limits and reactivity limits.
    In each of these two tables, the District demonstrates that the top 
ten categories of VOC and NOX are addressed in the 2020 
Plan. Where a potential for RACM exists, each category is addressed in 
the 2020 Plan in Sections 3.2.1.1 and 4.2.1.1 regarding RACM for the 
2008 and 2015 ozone NAAQS, respectively, and in Attachment G.
f. 2015 Ozone NAAQS, the District's RACM Conclusion
    After evaluating the emissions reduction potentials of stationary, 
area, and mobile sources, as well as consumer products, by themselves, 
the District presents a ``cumulative analysis'' to assess whether all 
potential RACM combined could result in advancement of the modeled 2032 
attainment year to 2031.\108\ Attachment J (``Calculation of Cumulative 
Potential Emission Reductions for Possible Reasonably Available Control 
Measures (RACM)'') of the 2020 Plan presents the cumulative potential 
RACM reductions in Table J-1, ``Calculation of Cumulative Potential 
Emission Reductions for Possible Reasonably Available Control Measures 
(RACM).'' When taken together, all potential RACM reductions of VOC and 
NOX that the District and CARB evaluated amount to 
approximately 0.6 tpd VOC and 0.7 tpd NOX. The potential 
RACM for combined VOC and NOX, 1.3 tpd potential RACM 
reduction falls far short of the 2015 ozone RACM target (for combined 
VOC and NOX), 6.0 tpd. The District therefore concludes that 
collectively, there is not enough potential RACM reductions to advance 
the attainment date for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \108\ 2020 Plan, Section 4.2.1.7, ``RACM Cumulative Analysis,'' 
p. 74.
---------------------------------------------------------------------------

3. The EPA's Review of the State's Submission
    As described in Section III.B.2.a. of this document, the District 
already implements many rules to reduce VOC and NOX 
emissions from stationary and area sources in the San Diego County 
area. For the 2020 Plan, the District evaluated a range of potentially 
available measures. We find that the process followed by the District 
in the 2020 Plan to identify additional stationary and area source RACM 
is generally consistent with the EPA's recommendations in the General 
Preamble, that the District's evaluation of potential measures is 
appropriate, and that the District has provided reasoned justifications 
for rejection of measures deemed not reasonably available.
    With respect to mobile sources, CARB's current program addresses 
the full range of mobile sources in the San Diego County area through 
regulatory programs for both new and in-use vehicles. With respect to 
TCMs, we find that the District's process for identifying additional 
TCM RACM and its conclusion that the TCMs being implemented in the San 
Diego County area (i.e., the TCMs listed in Attachment H of the 2020 
Plan) represents all TCM RACM to be reasonably justified and supported. 
Further, we find that the District's cumulative analyses appropriately 
sum the various sources of potential RACM, and we agree with the 
District's conclusion that, taken together, all potential RACM would 
advance neither the 2026 modeled attainment year for the 2008 ozone 
NAAQS, nor the 2032 modeled attainment year for the 2015 ozone NAAQS. 
Based on our review of these RACM analyses and the District's and 
CARB's adopted rules, we propose to find that there are currently no 
additional RACM that would advance attainment of either the 2008 ozone 
NAAQS or the 2015 ozone NAAQS in the San Diego County area, and that 
the 2020 Plan provides for the implementation of all RACM as required 
by CAA section 172(c)(1), 40 CFR 51.1112(c) and 40 CFR 51.1312(c).

C. Attainment Demonstration

1. Statutory and Regulatory Requirements
    An attainment demonstration consists of: (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

[[Page 87864]]

the nonattainment area and the emissions reductions necessary to attain 
the standards); (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 and failures to attain.\109\ In this section, we address the first 
two components of the attainment demonstration--the technical analyses 
and a list of adopted measures. We address the RACM component of the 
2020 Plan attainment demonstration in Section III.B (Reasonably 
Available Control Measures Demonstration and Control Strategy) of this 
document and the contingency measures component of the attainment 
demonstration in Section III.F (Contingency Measures) of this document.
---------------------------------------------------------------------------

    \109\ 78 FR 34178, 34184 (June 6, 2013) (proposed rule for 
implementing the 2008 ozone NAAQS), codified at 40 CFR 51.1108. For 
the 2015 ozone NAAQS, the EPA finalized modeling requirements at 40 
CFR 51.1308.
---------------------------------------------------------------------------

    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 for the 2008 and 2015 ozone NAAQS must 
demonstrate attainment as expeditiously as practicable, but no later 
than 15 years after the effective date of designation to nonattainment. 
San Diego County was designated nonattainment for the 2008 ozone NAAQS 
effective July 20, 2012, and for the 2015 ozone NAAQS, the area was 
designated nonattainment effective August 3, 2018.\110\ Accordingly the 
area must demonstrate attainment of the 2008 ozone NAAQS by July 20, 
2027; for the 2015 ozone NAAQS, the area must demonstrate attainment by 
August 3, 2033.\111\ An attainment demonstration must show attainment 
of the standards by the ozone season (for San Diego County, the ozone 
season is the entire calendar year) prior to the attainment date, so in 
practice, Severe nonattainment areas must demonstrate attainment in 
2026 for the 2008 ozone NAAQS and in 2032 for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \110\ 77 FR 30087 (May 21, 2012) and 83 FR 25776 (June 4, 2018), 
respectively.
    \111\ 80 FR 12264 and 83 FR 62998, respectively.
---------------------------------------------------------------------------

    The EPA's recommended procedures for modeling ozone as part of an 
attainment demonstration are contained in ``Modeling Guidance for 
Demonstrating Air Quality Goals for Ozone, PM2.5, and 
Regional Haze'' (``Modeling Guidance'').\112\ 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.
---------------------------------------------------------------------------

    \112\ Modeling Guidance, EPA 454/R-18-009, November 2018. 
Additional EPA modeling guidance can be found in 40 CFR 51 Appendix 
W, ``Guideline on Air Quality Models,'' 82 FR 5182 (January 17, 
2017). These documents are available in the docket for this action 
and at https://www.epa.gov/sites/default/files/2020-10/documents/o3-pm-rh-modeling_guidance-2018.pdf and https://www.epa.gov/scram/clean-air-act-permit-modeling-guidance, respectively.
---------------------------------------------------------------------------

    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 analysis. A weight of evidence 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. Lastly, an unmonitored 
area analysis is used to predict areas of high ozone concentrations 
where air quality monitoring data is not available. This analysis 
utilizes interpolated ambient data with modeled outputs to determine 
gradient-adjusted spatial fields. Section 4.7 of the Modeling Guidance 
provides guidelines for estimating design values at unmonitored grid 
cells.
    The Modeling Guidance does not require a particular year to be used 
as the base year for 8-hour ozone plans.\113\ The Modeling Guidance 
states that the most recent year of the National Emissions Inventory 
\114\ 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.\115\ 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.
---------------------------------------------------------------------------

    \113\ Modeling Guidance, Section 2.7.1, p. 35.
    \114\ The National Emissions Inventory (NEI) is an electronic 
database of criteria pollutant and precursor emissions data for the 
United States. State, local and tribal agencies contribute to the 
NEI every three years (2011, 2014, 2017, 2020, etc.). For more 
information about the NEI, see: https://www.epa.gov/air-emissions-inventories/national-emissions-inventory-nei.
    \115\ Modeling Guidance at Section 2.7.1, p 35.
---------------------------------------------------------------------------

    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.\116\ Under the 2008 Ozone SRR and the 2015 
Ozone SRR, all control measures needed for attainment must be 
implemented no later than the beginning of the attainment year ozone 
season.\117\ The attainment year ozone season is defined as the ozone 
season immediately preceding a nonattainment area's maximum attainment 
date.\118\
---------------------------------------------------------------------------

    \116\ See also CAA section 110(a)(2)(A).
    \117\ 40 CFR 51.1108(d) and 40 CFR 51.1308(d), respectively.
    \118\ 40 CFR 51.1100(h) for the 2008 ozone NAAQS and 40 CFR 
51.1300(g), for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

2. Summary of the State's Submission
a. Photochemical Modeling
    The 2020 San Diego County Ozone SIP includes photochemical modeling 
for the 2008 and 2015 ozone NAAQS. CARB performed the air quality 
modeling for the 2020 Plan. The modeling relies on a 2017 base year and 
demonstrates attainment of the 2008 ozone NAAQS in 2026 and attainment 
of the 2015 ozone NAAQS in 2032.

[[Page 87865]]

    As a general matter, the modeling for the 2020 Plan represents the 
most up-to-date photochemical modeling performed for the area, 
accounting for improved chemical gaseous and particulate mechanisms, 
improved computational resources and post-processing utilities, 
enhanced spatial and temporal allocations of the emissions inventory, 
and CARB's latest attainment demonstration methodology. Air quality 
modeling included in the 2020 Plan is described briefly in the plan's 
Sections 3.3 and 4.3 (for 2008 and 2015 ozone NAAQS, respectively) and 
in detail in the plan's Attachment K (``Attachment K'' or ``Modeling 
Protocol'').\119\ The 2020 Plan discusses its modeling emissions 
inventory in Attachment L, ``Modeling Emissions Inventory,'' while 
Attachment M, ``Weight of Evidence Demonstration for San Diego 
County,'' supplements the plan's modeling results with a weight of 
evidence analysis.
---------------------------------------------------------------------------

    \119\ 2020 Plan, Attachment K, ``Modeling Protocol & Attainment 
Demonstration for the 2020 San Diego Ozone SIP'' (March 2020).
---------------------------------------------------------------------------

    Attachment K of the 2020 Plan provides a description of model input 
preparation procedures, various model configuration options, and model 
performance statistics. The Modeling Protocol contains all the elements 
recommended in the Modeling Guidance, including: 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 Relative Response Factors (RRFs). Attachment K also 
provides the coordinates of the modeling domain.
    Attachment L of the 2020 Plan thoroughly describes the development 
of the modeling emissions inventory, including its chemical speciation, 
its spatial and temporal allocation, its temperature dependence, and 
quality assurance procedures.
    The CARB Staff Report for the 2020 Plan provides additional 
information about CAA requirements that apply to the San Diego County 
area, including an attainment demonstration, emissions reductions 
commitments by CARB and the District and the source categories from 
which those reductions are expected to come.\120\
---------------------------------------------------------------------------

    \120\ Emissions reduction commitments are described in the 2020 
Plan (Sections 4.3.4 and 4.3.5; Attachment L, Section 3.9; and Table 
4-9), the CARB Staff Report, and the District's and CARB's Board 
resolutions.
---------------------------------------------------------------------------

    The modeling analysis uses version 5.2.1 of the Community 
Multiscale Air Quality (CMAQ) photochemical model, developed by the 
EPA. To prepare meteorological input for CMAQ, the Weather Research and 
Forecasting model version 3.9.1.1 (WRF) from the National Center for 
Atmospheric Research was used. 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 San Diego County ozone.
    The WRF meteorological model results and performance statistics are 
described in Section K.3.1 (``Meteorological Model Evaluation'') of 
Attachment K. The District and CARB evaluated the performance of the 
WRF model through a series of simulations and concluded that the daily 
WRF simulation for 2017 performed comparably to recent WRF modeling 
studies of ozone formation in California. The District's conclusions 
are supported by hourly time series, with performance statistics 
provided in Table K-7 for wind speed, temperature and relative 
humidity.
    Ozone model performance and related statistics are described in the 
2020 Plan Attachment K, Section K.3.2 (``Air Quality Model 
Evaluation''), which includes tables of statistics recommended in the 
Modeling Guidance for ozone for San Diego County. Model performance 
metrics provided in the 2020 Plan include mean bias, mean error, mean 
fractional bias, mean fractional error, normalized mean bias, 
normalized mean error, root mean square error, and correlation 
coefficient. In addition, plots were provided in evaluating the 
modeling: time-series plots comparing the predictions and observations, 
scatter plots for comparing the magnitude of the simulated and observed 
mixing ratios, box plots to summarize the time series data across 
different regions and averaging times, as well as frequency 
distributions.
    After model performance for the 2017 base case was accepted, the 
model was applied to develop RRFs for the attainment 
demonstration.\121\ This entailed running the model with the same 
meteorological inputs as before, but with adjusted emissions 
inventories to reflect the expected changes between 2017 and the 
attainment years 2026 and 2032. The base year, or ``reference year'' as 
referred to by the District and CARB, modeling inventory was the same 
as the inventory for the modeling base case, except for the exclusion 
of some emissions events that are random or cannot be projected to the 
future.\122\ The 2026 and 2032 inventories project the base year into 
the future by including the effect of economic growth and emissions 
control measures. To develop the RRFs for the 8-hour ozone NAAQS, only 
the top 10 modeled days were used, consistent with the Modeling 
Guidance.\123\
---------------------------------------------------------------------------

    \121\ Modeling TSD, p. 26. Section 4.0 of the Modeling Guidance 
focuses on establishing guidelines for analyzing simulated emissions 
reductions for a future year with the goal of meeting the NAAQS. The 
Modeling Guidance recommends examining relative changes in design 
values through Relative Response Factors instead of absolute values 
to reduce the effect of model biases. In short, the RRF is a 
relative change in concentration with respect to a change in 
emissions between a base and future year, i.e., the ratio of future 
year and base year modeled concentrations, and is multiplied by the 
base design value obtained from monitoring data at a particular site 
to obtain a future year design value at that site.
    \122\ The terms base year and reference year can be used 
interchangeably. To use consistent EPA terminology, the terms ``base 
year'' and ``base case'' are used in this document and correspond to 
the District's and CARB's use of the terms ``reference year'' and 
``base year,'' respectively.
    \123\ See Modeling Guidance at section 4.2.1.
---------------------------------------------------------------------------

    The Modeling Guidance addresses attainment demonstrations with 
ozone NAAQS based on 8-hour averages, and for the 2008 and 2015 ozone 
NAAQS, the 2020 Plan carried out 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 two sets of reference design values. One set is for the 
period 2016-2018. Another set of design values was more current at the 
time of the state and District's analysis, the period 2017-2019. 
However, because that set of design values included data for 2019 that 
was not finalized at the time of the analysis, the earlier 2016-2018 
set was used as an additional reference. The RRFs were applied to five 
monitoring sites in the San Diego County area to obtain future year 
2026 and 2032 design values, summarized in Table K-13 and Table K-14 of 
the 2020 Plan, respectively. The modeled 2026 and 2032 ozone design 
values at the Alpine monitoring site (the highest of the county's 
monitors) are 0.074 ppm and 0.070 ppm, respectively; these values 
demonstrate attainment of the 2008 and the 2015 ozone NAAQS.
    The 2020 Plan modeling demonstration includes a weight of evidence 
demonstration.\124\ The weight of evidence demonstration in Attachment 
M of the 2020 Plan includes ambient ozone data and trends, precursor 
emissions trends and

[[Page 87866]]

reductions, to complement the regional photochemical modeling analyses. 
The CARB Staff Report for the 2020 Plan concludes that the weight of 
evidence analysis supports the conclusions of the photochemical 
modeling.\125\
---------------------------------------------------------------------------

    \124\ 2020 Plan, Attachment M, ``Weight of Evidence 
Demonstration for San Diego County.''
    \125\ CARB Staff Report, 10.
---------------------------------------------------------------------------

b. Control Strategy for the 2008 Ozone NAAQS and for the 2015 Ozone 
NAAQS
    Continued air quality improvement in the San Diego County area is 
expected during the 2017 through 2032 timeframe because of the 
continued implementation of adopted District and CARB control measures 
and ongoing fleet turnover that replaces older more polluting mobile 
sources with newer, cleaner models and the downward emissions trends in 
the upwind South Coast Air Basin.
    The control strategy for the San Diego County area for the 2008 
ozone NAAQS relies on emissions reductions from baseline (already-
implemented) measures. The baseline control measures include the 
District's stationary source rules and CARB's mobile source and 
consumer products regulations adopted at the time of development of the 
2020 Plan.
    The control strategy for the San Diego County area for the 2015 
ozone NAAQS also relies on emissions reductions from baseline (already-
implemented) measures. However, unlike the 2008 ozone NAAQS attainment 
demonstration, the 2020 Plan concludes that baseline measures will not 
by themselves provide sufficient emissions reductions by 2032 to 
demonstrate attainment of the 2015 ozone NAAQS. Thus, the control 
strategy for the attainment demonstration for the 2015 ozone NAAQS 
includes commitments by CARB and the District to adopt and submit new 
control measures to achieve additional emissions reductions that the 
modeling indicates are necessary to attain the 2015 ozone NAAQS in the 
San Diego County area by the attainment year (2032).
    To provide for attainment of the 2015 ozone NAAQS by the attainment 
year (2032), CARB and the District commit in the 2020 Plan to reduce 
NOX emissions by 4.0 tpd \126\ and by 1.7 tpd,\127\ 
respectively. CARB expects to adopt and submit certain mobile source 
control measures developed pursuant to CARB's 2016 State Strategy to 
fulfill the 4.0 tpd NOX aggregate emissions reduction 
commitment for San Diego County by 2032. The specific control measures 
that CARB expects to adopt and submit are listed in Table 5 of this 
document. The District expects to adopt and submit certain stationary 
source control measures to fulfill the 1.7 tpd NOX aggregate 
emissions reduction commitment by 2032, as listed in Table 6 of this 
document.
---------------------------------------------------------------------------

    \126\ CARB Board Resolution 20-29, 6; 2020 Plan, section 4.3.5.
    \127\ 2020 Plan, section 4.3.4.

  Table 5--San Diego County Expected NOX Emissions Reductions From CARB
                    2016 State SIP Strategy Measures
------------------------------------------------------------------------
                                           Control measure/        2032
    2016 State strategy measure(s)            regulation          (tpd)
------------------------------------------------------------------------
On-Road Heavy-Duty Vehicles: Low-NOX   Heavy-Duty Engine and         1.9
 Engine Standard--California Action     Vehicle Omnibus
 and Lower In-Use Emission              Regulation (``Low NOX
 Performance Level.                     Omnibus Regulation'').
On-Road Heavy-Duty Vehicles: Last      Advanced Clean Trucks         0.4
 Mile Delivery.                         Regulation.
On-Road Heavy-Duty Vehicles: Lower In- Heavy Duty Vehicle            1.7
 Use Emission Performance Level.        Inspection and
                                        Maintenance Regulation.
                                                                --------
    Total Aggregate CARB Commitment..  ........................      4.0
------------------------------------------------------------------------
Sources: 2016 State Strategy, Chapters 3 and 4; 2020 Plan, Table 4-9.

Table 6--San Diego County Expected NOX Emissions Reductions From SDCAPCD
                            Control Measures
------------------------------------------------------------------------
                                                                   2032
             Source type                 Control measure/rule     (tpd)
------------------------------------------------------------------------
Stationary Reciprocating Internal      Amended District Rule         0.8
 Combustion Engines.                    69.4.1.
Small and Medium Boilers, Process      New or Amended District       0.9
 Heaters, Steam Generators and Large    Rules 69.2.1 and 69.2.2.
 Water Heaters.
                                                                --------
    Total Aggregate SDCAPCD            ........................      1.7
     Commitment.
------------------------------------------------------------------------
Source: 2020 Plan, Section 4.3.4.

c. Attainment Demonstration
    Table 7 of this document summarizes the attainment demonstration 
for the 2008 ozone NAAQS by listing the 2011 base year emissions level, 
the attainment year (2026) baseline emissions level, the modeled 
attainment (2026) emissions level, and the reductions that the District 
and CARB estimate will be achieved through implementation of baseline 
(i.e., adopted) measures taking into account area-wide growth, the 
growth increments for the military and SDIA, the District's ERC set-
aside and the EMFAC2017 Adjustment Factors adjustment. The District and 
CARB have not made any emissions reductions commitments as part of the 
control strategy for attainment of the 2008 ozone NAAQS in San Diego 
County. The control strategy relies only on baseline measures. As shown 
in Table 7, baseline measures are expected to reduce base year (2011) 
emissions of NOX by 43 percent and VOC emissions by 27 
percent by the 2026 attainment year, notwithstanding area-wide growth, 
the growth increments for the military and SDIA, the District's ERC 
set-aside and the EMFAC2017 Adjustment Factors adjustment, and to 
attain the 2008 ozone NAAQS in San Diego County by that year.

[[Page 87867]]

    Table 7--Summary of San Diego County 2008 Ozone NAAQS Attainment
                              Demonstration
                    [Summer planning inventory, tpd]
------------------------------------------------------------------------
       Row                                          NOX          VOC
------------------------------------------------------------------------
A...............  2011 Base Year Emissions            126.5        137.5
                   Level \a\.
B...............  2026 Attainment Year                 72.2        100.8
                   Baseline Emissions Level
                   \b\.
C...............  2026 Modeled Attainment              72.2        100.8
                   Emissions Level \c\.
D...............  Total Reductions Needed from         54.3         36.7
                   2011 Levels to Demonstrate
                   Attainment (A-C).
E...............  Reductions from Baseline             54.3         36.7
                   (i.e., adopted) Measures,
                   net of growth, growth
                   increment for military and
                   SDIA, ERC set-aside and
                   EMFAC2017 Adjustment
                   Factors adjustment (A-B).
F...............  Reductions from District's              0            0
                   Aggregate Emissions
                   Reduction Commitment from
                   2020 Plan.
G...............  Reductions from CARB's                  0            0
                   Aggregate Emissions
                   Reduction Commitment from
                   2016 State Strategy.
H...............  Total Reductions from                   0            0
                   District's and CARB's
                   Commitments.
I...............  Total Reductions from                54.3         36.7
                   Baseline Measures and the
                   District's and CARB's
                   Commitments (E + H).
J...............  2026 Emissions with                  72.2        100.8
                   Reductions from Control
                   Strategy (A-I).
                  Attainment demonstrated?....          Yes          Yes
------------------------------------------------------------------------
\a\ See Table 1 of this document. Includes emissions out to 100 NM from
  the coast.
\b\ See Table 1 of this document. Includes emissions out to 100 NM from
  the coast. Year 2026 baseline emissions reflect area-wide growth, the
  growth increments for the military and SDIA, the District's ERC set-
  aside and the EMFAC2017 Adjustment Factors adjustment.
\c\ 2020 Plan, Section 3.3.4.

    Table 8 of this document summarizes the attainment demonstration 
for the 2015 ozone NAAQS by listing the 2017 base year emissions level, 
the attainment year (2032) baseline emissions level, the modeled 
attainment (2032) emissions level, and the reductions that the District 
and CARB estimate will be achieved through implementation of baseline 
(i.e., adopted) measures taking into account area-wide growth, the 
growth increments for the military and SDIA, the District's ERC set-
aside and the EMFAC2017 Adjustment Factors adjustment. Table 8 also 
shows the aggregate emissions reductions commitments (for year 2032) 
made by the District and CARB as part of the control strategy for 
attainment of the 2015 ozone NAAQS in San Diego County. As shown in 
Table 8, baseline measures are expected to reduce base year (2017) 
emissions of NOX by 27 percent and VOC emissions by 14 
percent by the 2032 attainment year, notwithstanding area-wide growth, 
the growth increments for the military and SDIA, the District's ERC 
set-aside and the EMFAC2017 Adjustment Factors adjustment. The 
District's and CARB's commitments would further reduce emissions of 
NOX by 2032 by an additional 5.7 tpd. Together, the baseline 
emissions reductions and the NOX emissions reduction 
commitments would provide for attainment of the 2015 ozone NAAQS by the 
attainment year (2032).

    Table 8--Summary of San Diego County 2015 Ozone NAAQS Attainment
                              Demonstration
                    [Summer planning inventory, tpd]
------------------------------------------------------------------------
       Row                                          NOX          VOC
------------------------------------------------------------------------
A...............  2017 Base Year Emissions             94.5        113.8
                   Level \a\.
B...............  2032 Attainment Year                 69.0         98.3
                   Baseline Emissions Level
                   \b\.
C...............  2032 Modeled Attainment              63.3         98.3
                   Emissions Level \c\.
D...............  Total Reductions Needed from         31.0         15.5
                   2017 Levels to Demonstrate
                   Attainment (A-C).
E...............  Reductions from Baseline             25.5         15.5
                   (i.e., adopted) Measures,
                   net of growth, growth
                   increment for military and
                   SDIA, ERC set-aside and
                   EMFAC2017 Adjustment
                   Factors adjustment (A-B).
F...............  Reductions from District's            1.7            0
                   Aggregate Emissions
                   Reduction Commitment from
                   2020 Plan.
G...............  Reductions from CARB's                4.0            0
                   Aggregate Emissions
                   Reduction Commitment from
                   2016 State Strategy.
H...............  Total Reductions from                 5.7            0
                   District's and CARB's
                   Commitments.
I...............  Total Reductions from                31.2         15.5
                   Baseline Measures and the
                   District's and CARB's
                   Commitments (E + H).
J...............  2032 Emissions with                  63.3         98.3
                   Reductions from Control
                   Strategy (A-I).
                  Attainment demonstrated?....          Yes          Yes
------------------------------------------------------------------------
\a\ See Table 1 of this document. Includes emissions out to 100 NM from
  the coast.
\b\ See Table 1 of this document. Includes emissions out to 100 NM from
  the coast. Year 2032 baseline emissions reflect area-wide growth, the
  growth increments for the military and SDIA, the District's ERC set-
  aside and the EMFAC2017 Adjustment Factors adjustment.
\c\ 2020 Plan, Section 4.3.4.

3. The EPA's Review of the State's Submission
a. Photochemical Modeling
    As discussed in Section III.A of this document, we are proposing to 
approve the base year emissions inventory and to find that the future 
year emissions projections in the 2020 San Diego County Ozone SIP 
reflect appropriate calculation methods and that the latest planning 
assumptions are properly supported by SIP-approved stationary and 
mobile source control measures. Here, we address our findings for the 
modeling submitted with the 2020 Plan. Because of the importance of 
ozone transport from the South Coast to attainment in San Diego County, 
and the close interactions of the modeling for each area, we have 
considered the influence of South Coast on the modeling for San Diego 
County. Similar and additional discussion for the South Coast can be 
found in our June 17, 2019 proposed action on the 2016 South Coast 
Ozone SIP.\128\
---------------------------------------------------------------------------

    \128\ 84 FR 28132.
---------------------------------------------------------------------------

    Based on our review of Attachment K \129\ of the 2020 Plan, the EPA 
finds that the photochemical modeling is

[[Page 87868]]

adequate for purposes of supporting the attainment demonstration.\130\ 
First, we note the extensive discussion of modeling procedures, tests, 
and performance analyses in the Methodology section of Attachment K and 
the good model performance. Second, we find the WRF meteorological 
model results and performance statistics, including hourly time series 
graphs of wind speed, direction, and temperature for San Diego County 
to be satisfactory and consistent with our Modeling Guidance.\131\ 
Performance for wind speed, temperature, and relative humidity was 
evaluated from May to September 2017.\132\ Geographically, winds are 
predicted most accurately along the coast. Accurate wind predictions in 
this region are important in simulating chemical transport in the San 
Diego Air Basin. Overall, the WRF simulation provided reasonable 
meteorological fields comparable to other WRF modeling studies and is 
sufficient for the attainment demonstration.
---------------------------------------------------------------------------

    \129\ Attachment K, ``Modeling Protocol & Attainment 
Demonstration for the 2020 San Diego Ozone SIP,'' 2020 Plan.
    \130\ The EPA's review of the modeling and attainment 
demonstration is discussed in greater detail in the Modeling TSD for 
this action.
    \131\ Modeling Guidance, 30.
    \132\ Temperature, water vapor mixing ratio, and wind speed were 
evaluated in terms of normalized gross bias and normalized gross 
error.
---------------------------------------------------------------------------

    The model performance statistics for ozone are described in 
Attachment K Section K.3.2 and are based on the statistical evaluation 
recommended in the Modeling Guidance. Model performance was provided 
for 8-hour daily maximum ozone for San Diego County, separately for the 
Alpine site and the coastal sites. A geographical and temporal bias is 
shown in the time series, which sufficiently captures the variability 
in the maximum daily eight-hour average ozone concentration at the 
Alpine site, but overpredicts this concentration from mid-June to mid-
July at the coastal sites. Through a series of sensitivity tests and 
consideration of other meteorological phenomena, the observed ozone 
concentrations during the overprediction period are likely attributed 
to numerous meteorological factors affecting ozone transport (see, 
``Technical Support Document, Review of Attainment Modeling in the 2020 
San Diego Ozone Plan (July 2022)'' (``Modeling TSD'')).\133\
---------------------------------------------------------------------------

    \133\ These factors are discussed in greater detail in Section 
3.1.2 of the EPA's Modeling TSD, included in the docket to this 
action.
---------------------------------------------------------------------------

    The 2020 Plan presents scatter plots of monitored and modeled ozone 
concentrations that also suggest that the Alpine site has the best 
correspondence between modeled and observed concentrations. This 
correspondence reflects the model's capability of reliably predicting 
the high concentrations that result in exceedances frequently observed 
at the Alpine site, which are important for the top ten days that form 
the basis for the RRF calculation. However, the overprediction of 
absolute ozone concentrations does not mean that future concentrations 
will be overestimated. In addition, the weight of evidence analysis 
presented in Attachment M of the 2020 Plan provides additional 
information with respect to the sensitivity to emissions changes and 
further supports the model performance. We are proposing to find the 
air quality modeling adequate to support the attainment demonstrations 
for the 2008 and 2015 ozone NAAQS, based on reasonable meteorological 
and ozone modeling performance, and supported by the weight of evidence 
analyses. For additional information regarding the EPA's analysis, 
please see the Modeling TSD for this action.
b. Control Strategy
    As part of our evaluation of attainment demonstrations, we must 
find that the emissions reductions that are relied on for attainment 
are creditable and are sufficient to provide for attainment. As shown 
in Table 7 of this document, the 2020 Plan relies on baseline measures 
to achieve all the emissions reductions needed to attain the 2008 ozone 
NAAQS by 2026. The baseline measures are approved into the SIP (with 
only minor exceptions) and, as such, the emissions reductions are fully 
creditable.
    With respect to the attainment demonstration for the 2015 ozone 
NAAQS, we must also find that the emissions reductions that are relied 
on for attainment are creditable and are sufficient to provide for 
attainment. As shown in Table 8, the 2020 Plan relies on baseline 
measures to achieve a significant portion of the emissions reductions 
needed to attain the 2015 ozone NAAQS by 2032. The balance of the 
reductions needed for attainment is in the form of enforceable 
commitments to achieve aggregate tonnage reductions of NOX 
through adoption and implementation of more stringent emissions 
limitations contained in certain new or amended rules and regulations.
    Table 9 of this document provides a summary of the status of the 
commitments made by the District and CARB in connection with the 2020 
Plan. As shown in Table 9, the District and CARB have adopted all six 
of the rules or regulations that the agencies are relying on to meet 
their aggregate emissions reduction commitments. Four of the six rules 
or regulations have been submitted to the EPA for action as revisions 
to the California SIP. The rules or regulations are at various phases 
of implementation and at various stages of the process from adoption to 
approval by the EPA as part of the SIP. The commitments will be 
fulfilled once the EPA approves the rules or regulations as part of the 
SIP, assuming that the rules or regulations, as approved, provide 
NOX emissions reductions equal to or greater than the 
corresponding aggregate emissions reduction commitments by year 2032 in 
the San Diego County area.

          Table 9--Status of District and CARB Aggregate Emissions Reduction Commitments for 2020 Plan
----------------------------------------------------------------------------------------------------------------
                                      Adoption date and
               Rule                  district resolution   Submission date to the EPA as    Most recent EPA SIP
                                         of adoption                SIP revision                   action
----------------------------------------------------------------------------------------------------------------
 District Commitment
    Amendments to Rule 69.2.1       July 8, 2020          September 21, 2020.............  Proposed rule
     (Small Boilers, Process         (Resolution 20-118).                                   published at 88 FR
     Heaters, and Steam Generators                                                          48150 (July 26,
     and Large Water Heaters.                                                               2023).
    New Rule 69.2.2 (Medium         September 9, 2021     March 9, 2022..................  Final rule published
     Boilers, Process Heaters, and   (Resolution 21-005).                                   at 88 FR 57361
     Steam Generators).                                                                     (August 23, 2023).
    Amendments to Rule 69.4.1       July 8, 2020          September 21, 2020.............  No EPA action to
     (Stationary Reciprocating       (Resolution 20-120).                                   date.
     Internal Combustion Engines).
----------------------------------------------------------------------------------------------------------------

 
                                     Adoption date and CARB  CAA Section 209 preemption waiver    Submission date to the EPA as     Most recent EPA SIP
            Regulations              resolution of adoption                status                         SIP revision                    action
--------------------------------------------------------------------------------------------------------------------------------------------------------
 CARB Commitment:

[[Page 87869]]

 
    Low-NOX Omnibus Regulation \a\.  August 27, 2020         Notice of Opportunity for Public   Not yet submitted...............  ......................
                                      (Resolution 20-23).     Hearing and Comment published at
                                                              87 FR 35765 (June 13, 2022).
    Advanced Clean Trucks            June 25, 2020           Notice of Decision published at    Not yet submitted...............  ......................
     Regulation.                      (Resolution 20-19).     88 FR 20688 (April 6, 2023).
    Heavy-Duty Vehicle Inspection    December 9, 2021        Not preempted....................  December 7, 2022................  No EPA action to date.
     and Maintenance Regulation.      (Resolution 21-29).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ In July 2023, CARB proposed amendments to the Low-NOX Omnibus Regulation to provide additional flexibility for manufacturers of model year (MY) 2024-
  2026 heavy-duty engines.

    The commitments made by the District and CARB through adoption of 
the 2020 Plan and 2016 State Strategy are similar to the enforceable 
commitments that the EPA has approved as part of attainment 
demonstrations in previous California air quality plans and that have 
withstood legal challenge.\134\ The EPA has previously accepted 
enforceable commitments in lieu of adopted control measures in 
attainment demonstrations when the circumstances warrant them and when 
the commitments meet specific criteria. We believe that, with respect 
to the 2015 ozone NAAQS, circumstances warrant the consideration of 
enforceable commitments as part of the attainment demonstration for San 
Diego County. First, as shown in Table 8, a substantial portion of the 
emissions reductions needed to demonstrate attainment of the 2015 ozone 
NAAQS in the San Diego County area by 2032 will come from measures 
adopted prior to adoption and submittal of the 2020 Plan. As a result 
of these State and District efforts, most emissions sources in the San 
Diego County area are currently subject to stringent emissions 
limitations and other requirements, leaving few opportunities to 
further reduce emissions. In the 2020 Plan and 2016 State Strategy, the 
District and CARB identified potential control measures that could 
provide many of the additional emissions reductions needed for 
attainment. These are described in Section III.C.2.b of this document. 
However, the timeline needed to develop, adopt, and implement these 
measures went beyond the required submittal date for the attainment 
demonstration for the San Diego County area for the 2015 ozone NAAQS. 
These circumstances warrant the District's and CARB's reliance on 
enforceable commitments as part of the attainment demonstrations for 
the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \134\ See Committee for a Better Arvin v. EPA, 786 F.3d 1169 
(9th Cir. 2015) (approval of state commitments to propose and adopt 
emissions control measures and to achieve aggregate emissions 
reductions for San Joaquin Valley ozone and particulate matter plans 
upheld); Physicians for Social Responsibility--Los Angeles v. EPA, 
9th Cir., memorandum opinion issued July 25, 2016 (approval of air 
district commitments to propose and adopt measures and to achieve 
aggregate emissions reductions for South Coast 1-hour ozone plan 
upheld).
---------------------------------------------------------------------------

    Given the State's demonstrated need for reliance on enforceable 
commitments, we now consider the three factors the EPA uses to 
determine whether the use of enforceable commitments in lieu of adopted 
measures to meet CAA planning requirements is approvable: (i) does the 
commitment address a limited portion of the statutorily-required 
program?; (ii) is the state capable of fulfilling its commitment?; and 
(iii) is the commitment for a reasonable and appropriate period of 
time?
    i. Commitments Are a Limited Portion of Required Reductions
    For the first factor, we look to see if the commitment addresses a 
limited portion of a statutory requirement and review the magnitude of 
emissions reductions needed to demonstrate attainment in a 
nonattainment area. Table 8 of this document shows emissions reductions 
needed to demonstrate attainment of the 2015 ozone NAAQS in San Diego 
County by 2032 and the aggregate emissions reductions commitments by 
the District and CARB. Historically, the EPA has approved SIPs with 
enforceable commitments in the vicinity of 10 percent of the total 
needed reductions for attainment.\135\ Based on the values in Table 8 
of this document, we note that the sum of the aggregate emission 
reductions commitments (5.7 tpd NOX) represents 
approximately 18 percent of the total emissions reductions (31.0 tpd 
NOX) needed for attainment (relative to the 2017 base year). 
(The attainment demonstration for the 2015 ozone NAAQS for the San 
Diego County area does not rely on any commitments with respect to VOC 
emissions reductions.) While the value of 18 percent is higher than the 
EPA has generally found acceptable in the past, we note that all six of 
the rules or regulations that are relied upon to meet the aggregate 
emissions reduction commitments have already been adopted, and four of 
the six have been submitted to the EPA as revisions to the SIP. Taking 
into account the emissions reductions associated with rules or 
regulations already adopted and submitted (3.4 tpd NOX) 
reduces the remaining percentage associated with the commitments from 
18 percent to approximately 7 percent, which is well within historical 
norms for EPA approvals of enforceable commitments. Thus, we find that 
the District's and CARB commitments in the 2020 Plan for San Diego 
County for the 2015 ozone NAAQS address a limited proportion of the 
required emissions reductions.
---------------------------------------------------------------------------

    \135\ See our approval of these plans: San Joaquin Valley (SJV) 
PM10 Plan at 69 FR 30006 (May 26, 2004); SJV 1-hour ozone 
plan at 75 FR 10420 (March 8, 2010); Houston-Galveston 1-hour ozone 
plan at 66 FR 57160 (November 14, 2001); South Coast 1997 8-hour 
ozone plan at 77 FR 12674 (March 1, 2012); and South Coast 1-hour 
ozone plan at 79 FR 52526 (September 3, 2014).
---------------------------------------------------------------------------

ii. The State Is Capable of Fulfilling Its Commitment
    For the second factor, we consider whether the District and CARB 
are capable of fulfilling their commitments. All six rules or 
regulations that the District and CARB are relying on to meet the 
aggregate emissions reduction commitments have been adopted, and four 
have been submitted to the EPA as revisions to the California SIP. The 
emissions reductions associated with the four rules or regulations that 
have been adopted and submitted amount to approximately 3.4 tpd 
NOX, which represents approximately 60 percent of the 
overall aggregate commitment of 5.7 tpd NOX. As such, the 
State and District are well on their way to meeting their commitments. 
Thus, we believe that the State and District are capable of meeting 
their enforceable commitments to adopt and submit control measures that 
will reduce emissions to the levels needed for the 2015 ozone NAAQS in 
the San

[[Page 87870]]

Diego County area by the 2032 attainment year.
iii. The Commitment Is for a Reasonable and Appropriate Timeframe
    For the third and final factor, we consider whether the commitment 
is for a reasonable and appropriate period of time. All six rules or 
regulations that the District and State are relying on to meet the 
commitments have been adopted, and four have been submitted to the EPA 
as revisions to the California SIP. The District and CARB have 
committed to take the necessary actions and to achieve the remaining 
reductions by 2032. We believe that this period is appropriate given 
the technological and economic challenges associated with the rules and 
regulations adopted to achieve these reductions. In addition, these 
reductions are not needed to meet RFP targets for the 2015 ozone NAAQS. 
Thus, the commitments are for a reasonable and appropriate period of 
time.
    The reductions of NOX and VOC in the area, detailed in 
the control strategy in the 2020 Plan, allow for expeditious attainment 
of both the 2008 and 2015 ozone NAAQS in the San Diego County area. The 
attainment years chosen by the District comport with those required by 
the Act for a Severe ozone nonattainment area for the 2008 and 2015 
ozone NAAQS. For the reasons described in this document and based on 
CARB's and the District's demonstration specific to the San Diego 
County area described in the 2020 Plan, we propose to find the 
District's control strategy acceptable for purposes of attaining the 
2008 ozone NAAQS and the 2015 ozone NAAQS in the San Diego County area. 
For additional information, please see the Modeling TSD for this 
action.
c. Attainment Demonstration
    Based on our proposed determinations that the photochemical 
modeling and control strategy are acceptable, we propose to approve the 
attainment demonstrations for the 2008 ozone NAAQS and for the 2015 
ozone NAAQS in the 2020 San Diego County Ozone SIP as meeting the 
requirements of CAA section 182(c)(2)(A), 40 CFR 51.1108 and 40 CFR 
51.1308.

D. Rate of Progress Plan and Reasonable Further Progress Demonstration

1. Statutory and Regulatory Requirements
    Requirements for RFP for ozone nonattainment areas are specified in 
CAA sections 172(c)(2), 182(b)(1), and 182(c)(2)(B). Under CAA section 
171(1), RFP is defined as meaning such annual incremental reductions in 
emissions of the relevant air pollutant as are required under part D 
(``Plan Requirements for Nonattainment Areas'') of the CAA or as 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 
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 VOC reductions of at least 3 percent of baseline 
emissions per year, averaged over each consecutive three-year period, 
beginning six years after the baseline year until the attainment date. 
Under CAA section 182(c)(2)(C), a state may substitute NOX 
emissions reductions for VOC emissions reductions if such reductions 
would result in a reduction in ozone concentrations at least equivalent 
to that which would result from the amount of VOC emissions reductions 
otherwise required. Additionally, CAA section 182(c)(2)(B)(ii) allows 
an amount less than 3 percent of such baseline emissions each year if a 
state demonstrates to the EPA that its plan includes all measures that 
can feasibly be implemented in the area in light of technological 
achievability.
    In the 2008 Ozone SRR, the EPA provides that areas classified 
Moderate or higher will have met the ROP requirements of CAA section 
182(b)(1) if the area has a fully approved 15 percent ROP plan for the 
1-hour or 1997 ozone NAAQS.\136\ For such areas, the EPA interprets the 
RFP requirements of CAA section 172(c)(2) to require areas classified 
as Moderate to provide a 15 percent emissions reduction of ozone 
precursors within six 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 emissions 
reduction of 3 percent per year for all remaining 3-year periods 
thereafter.\137\ The 2008 Ozone SRR allows substitution of 
NOX reductions for VOC reductions to meet the CAA section 
172(c)(2) and 182(c)(2)(B) RFP requirements.\138\
---------------------------------------------------------------------------

    \136\ 80 FR 12264, 12271 (March 6, 2015); 40 CFR 51.1110(a)(2).
    \137\ Id.
    \138\ Id.; 40 CFR 51.1110(a)(2)(i)(C) and 40 CFR 
51.1110(a)(2)(ii)(B).
---------------------------------------------------------------------------

    In the 2015 Ozone SRR, as with the 2008 Ozone SRR, the EPA provides 
that areas classified Moderate or higher will have met the ROP 
requirements of CAA section 182(b)(1) if the area has a prior, fully 
approved 15 percent ROP plan.\139\ For such areas, the EPA interprets 
the RFP requirements of CAA section 172(c)(2) to require areas 
classified as Moderate to provide a 15 percent emissions reduction of 
ozone precursors within six 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 
emissions reduction of 3 percent per year for all remaining 3-year 
periods thereafter.\140\ The 2015 Ozone SRR allows substitution of 
NOX reductions for VOC reductions to meet the CAA section 
172(c)(2) and 182(c)(2)(B) RFP requirements.\141\
---------------------------------------------------------------------------

    \139\ 83 FR 62998, 63004 (December 6, 2018); 51.1310(a)(2).
    \140\ Id.
    \141\ Id.; 40 CFR 51.1310(a)(2)(i)(B) and 40 CFR 
51.1310(a)(2)(ii)(B).
---------------------------------------------------------------------------

    Except as specifically provided in CAA section 182(b)(1)(C), 
emissions reductions from all SIP-approved, federally promulgated, or 
otherwise SIP-creditable measures that occur after the baseline year 
are creditable for purposes of demonstrating that the RFP targets are 
met. Because the EPA has determined that the passage of time has caused 
the effect of certain exclusions to be de minimis, the RFP 
demonstration is no longer required to calculate and specifically 
exclude reductions from measures related to motor vehicle exhaust or 
evaporative emissions promulgated by January 1, 1990; regulations 
concerning Reid vapor pressure promulgated by November 15, 1990; 
measures to correct previous RACT requirements; and measures required 
to correct previous inspection and maintenance (I/M) programs.\142\
---------------------------------------------------------------------------

    \142\ 40 CFR 51.1110(a)(7) and 40 CFR 51.1310(a)(7).
---------------------------------------------------------------------------

    The 2008 Ozone SRR requires the RFP baseline year to be the most 
recent calendar year for which a complete triennial inventory was 
required to be submitted to the EPA. For the purposes of developing RFP 
demonstrations for the 2008 ozone NAAQS, the applicable triennial 
inventory year is 2011.\143\ The 2015 Ozone SRR similarly requires the 
RFP baseline year to be the most recent calendar year for which a 
complete

[[Page 87871]]

triennial inventory was required to be submitted to the EPA.\144\ For 
the purpose of developing RFP demonstrations for the 2015 ozone NAAQS, 
the applicable triennial inventory year is 2017.\145\
---------------------------------------------------------------------------

    \143\ 40 CFR 51.1110(b).
    \144\ 40 CFR 51.1310(b).
    \145\ 2015 Ozone SRR, 63005.
---------------------------------------------------------------------------

2. Summary of the State's Submission
    For both the 2008 and 2015 ozone NAAQS, the 2020 Plan cites the 
EPA's 1997 approval of the 15 percent VOC-only ROP plan for the one-
hour ozone NAAQS as the basis for concluding that the San Diego County 
area had met the 15 percent VOC-only ROP plan SIP requirement.\146\
---------------------------------------------------------------------------

    \146\ 2020 Pan, Sections 3.2.2.1 and 4.2.2.1.
---------------------------------------------------------------------------

    For the RFP demonstration for the 2008 ozone NAAQS, the 2020 Plan 
includes updated inventories of ozone precursor emissions (VOC and 
NOX) for 2017, the first RFP milestone year and the year 
from which future-year inventories are projected. As described further 
in Section III.A (``Emissions Inventories'') of this document, the RFP 
baseline year of 2011 was, for the most part, backcast from the 2017 
emissions inventories except for point sources, which are based on 
actual reported emissions from the individual facilities.
    To develop the emissions inventories for remaining RFP milestone 
years (2020 and 2023) and the attainment year (2026), the District and 
CARB relied upon the same growth and control factors used in the 
attainment demonstration, and included certain growth increments for 
the military and SDIA and certain adjustments (such as ERCs and 
EMFAC2017 Adjustment Factors impacts), as further described in Section 
III.A (``Emissions Inventories'') of this document.
    The RFP demonstration for the San Diego County area for the 2008 
ozone NAAQS is provided in Section 3.2.2.3 of the 2020 Plan and is 
presented in Table 10 of this document. The RFP demonstration 
calculates future year VOC targets from the 2011 baseline, consistent 
with CAA section 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 emissions targets.\147\ As shown in Table 10, the 
2020 Plan provides a demonstration of RFP for each milestone year as 
well as the attainment year for the 2008 ozone NAAQS.
---------------------------------------------------------------------------

    \147\ NOX substitution is permitted under EPA 
regulations for the 2008 ozone NAAQS. See 40 CFR 51.1110(a)(2)(i)(C) 
and 40 CFR 51.1110(a)(2)(ii)(B); and 80 FR 12264, at 12271 (March 6, 
2015).

                    Table 10--RFP Demonstration for San Diego County for the 2008 Ozone NAAQS
                                   [Summer planning inventory, tpd or percent]
----------------------------------------------------------------------------------------------------------------
                                                                                    VOC
                                                          ------------------------------------------------------
                                                              2011       2017       2020       2023       2026
----------------------------------------------------------------------------------------------------------------
Baseline VOC Emissions (tpd).............................      136.6      112.9      107.0      102.4       99.7
Change in VOC since 2011 (tpd)...........................  .........       23.7       29.6       34.2       36.9
Change in VOC since 2011 (percent).......................  .........      17.4%      21.7%      25.1%      27.0%
Required percentage change since 2011....................  .........        18%        27%        36%        45%
Shortfall (-)/Surplus (+) in VOC (percent)...............  .........      -0.6%      -5.3%     -10.9%     -18.0%
----------------------------------------------------------------------------------------------------------------
                                                                                    NOX
                                                          ------------------------------------------------------
                                                                2011       2017       2020       2023       2026
----------------------------------------------------------------------------------------------------------------
Baseline NOX Emissions (tpd).............................      110.7       77.0       67.1       56.8       53.6
Change in NOX since 2011 (tpd)...........................  .........       33.7       43.6       53.9       57.1
Change in NOX since 2011 (percent).......................  .........      30.5%      39.3%      48.7%      51.6%
NOX reductions since 2011 used for VOC substitution in     .........       0.6%       5.3%      10.9%      18.0%
 this milestone year (percent)...........................
NOX reductions since 2011 surplus after meeting VOC        .........      29.8%      34.0%      37.8%      33.6%
 substitution needs in this milestone year (percent).....
RFP shortfall (if any) (percent).........................  .........         0%         0%         0%         0%
RFP met?.................................................  .........        Yes        Yes        Yes        Yes
----------------------------------------------------------------------------------------------------------------
Source: 2020 Plan, Table 3-3.

    For the RFP demonstration for the 2015 ozone NAAQS, the 2020 Plan 
includes updated inventories of ozone precursor emissions for 2017, 
which is the baseline year and the year from which future-year 
inventories are projected. To develop the emissions inventories for RFP 
milestone years (2023, 2026 and 2029) and the attainment year (2032), 
the District and CARB relied upon the same growth and control factors 
as used in the attainment demonstration, and included certain growth 
increments for the military and SDIA and certain adjustments (such as 
ERCs and EMFAC2017 Adjustment Factors impacts), as further described in 
Section III.A (``Emissions Inventories'') of this document.
    The RFP demonstration for the San Diego County area for the 2015 
ozone NAAQS is shown in Table 11 of this document. The RFP 
demonstration calculates future year VOC targets from the 2017 
baseline, consistent with CAA section 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 2023 to meet VOC emission targets.\148\ For 
the San Diego County area, CARB concludes that the RFP demonstration 
meets the applicable requirements for each milestone year as well as 
the attainment year for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \148\ NOX substitution is permitted under EPA 
regulations for the 2015 ozone NAAQS. See 40 CFR 51.1310(a)(2)(i)(B) 
and 40 CFR 51.1310(a)(2)(ii)(B); and 83 FR 62998, at 63004 (December 
6, 2018).

[[Page 87872]]

                    Table 11--RFP Demonstration for San Diego County for the 2015 Ozone NAAQS
                                   [Summer planning inventory, tpd or percent]
----------------------------------------------------------------------------------------------------------------
                                                                                    VOC
                                                          ------------------------------------------------------
                                                              2017       2023       2026       2029       2032
----------------------------------------------------------------------------------------------------------------
Baseline VOC Emissions (tpd).............................      112.9      102.4       99.7       98.2       97.2
Change in VOC since 2017 (tpd)...........................  .........       10.5       13.2       14.6       15.7
Change in VOC since 2017 (percent).......................  .........       9.3%      11.7%      13.0%      13.9%
Required percentage change since 2017....................  .........        18%        27%        36%        45%
Shortfall (-)/Surplus (+) in VOC (percent)...............  .........      -8.7%     -15.3%     -23.0%     -31.1%
----------------------------------------------------------------------------------------------------------------
                                                                                    NOX
                                                          ------------------------------------------------------
                                                                2017       2023       2026       2029       2032
----------------------------------------------------------------------------------------------------------------
Baseline NOX Emissions (tpd).............................       77.0       56.8       53.6       51.3       49.7
Change in NOX since 2017 (tpd)...........................  .........       20.2       23.4       25.6       27.3
Change in NOX since 2017 (percent).......................  .........      26.3%      30.4%      33.3%      35.5%
NOX reductions since 2017 used for VOC substitution in     .........       8.7%      15.3%      23.0%      31.1%
 this milestone year (percent)...........................
NOX reductions since 2017 surplus after meeting VOC        .........      17.6%      15.1%      10.3%       4.3%
 substitution needs in this milestone year (percent).....
RFP shortfall (if any) (percent).........................  .........         0%         0%         0%         0%
RFP met?.................................................  .........        Yes        Yes        Yes        Yes
----------------------------------------------------------------------------------------------------------------
Source: 2020 Plan, Table 4-5.

3. The EPA's Review of the State's Submission
    In 1997, the EPA approved a 15 percent ROP plan for San Diego 
County for the 1-hour ozone NAAQS.\149\ The San Diego County 
nonattainment areas for the 2008 and 2015 ozone NAAQS are essentially 
the same geographic area as the nonattainment area for the 1-hour ozone 
NAAQS, and thus, we agree with the conclusion in the 2020 Plan that the 
ROP requirements of CAA section 182(b)(1) for the San Diego County area 
have been met and that, as a result, there is no need to demonstrate 
another 15 percent reduction in VOC for this area.
---------------------------------------------------------------------------

    \149\ 62 FR 1150, 1183 (January 8, 1997).
---------------------------------------------------------------------------

    The RFP demonstrations in the 2020 Plan derive from the same 
emissions inventories as presented in Section III.A (``Emissions 
Inventories'') of this document. In Section III.A, we are proposing to 
approve the 2011 and 2017 base year emissions inventories for the 2008 
and 2015 ozone NAAQS, respectively. With respect to the future year 
emissions baseline projections, as further explained in Section III.A 
of this document, we have reviewed the growth and control factors and 
find them acceptable and conclude that the future baseline emissions 
projections in the 2020 Plan reflect appropriate calculation methods 
and the latest planning assumptions and appropriately account for the 
growth increments for the military and SDIA as well as the adjustments 
for ERCs and the EMFAC2017 Adjustment Factors. In addition, we have 
reviewed the calculations in Table 3-3 and Table 4-5 of the 2020 Plan 
and find that the District and CARB have used an appropriate 
calculation method to demonstrate RFP.\150\
---------------------------------------------------------------------------

    \150\ We note that the weight of evidence demonstration provided 
in Attachment M to the 2020 Plan generally supports the substitution 
of NOX emissions reductions for VOC emissions reductions 
for the RFP demonstrations for the 2008 and 2015 ozone NAAQS. See 
Modeling TSD, at 32 and 33.
---------------------------------------------------------------------------

    CARB provided support for substituting NOX reductions 
for VOC reductions in the San Diego County area in Attachment K to the 
2020 Plan and supplemented that information in an attachment to an 
email to the EPA dated September 1, 2023.\151\ Combining the 
information from Attachment K in the 2020 Plan with additional 
explanation and analysis in the attachment, CARB presents two 
approaches to understanding the relationship between the two ozone 
precursors, NOX and VOC, in the area. First, CARB presents a 
table comparing emissions of the precursors over time and the modeled 
ozone design value. This table is shown here as Table 12 of this 
document (replacing the term ROG for VOC).
---------------------------------------------------------------------------

    \151\ Email dated September 1, 2023, from Chenxia Cai, CARB, 
with attachment, to John J. Kelly, EPA.

 Table 12--Ozone Design Values in San Diego County and the Corresponding
          Emissions of NOX and VOC in the San Diego County Area
------------------------------------------------------------------------
                                                       Emissions (tpd)
             Scenario                Design value  ---------------------
                                         (ppb)         NOX        VOC
------------------------------------------------------------------------
Base Year (2017)..................            83.0       77.0      116.0
Attainment Year (2032)............            71.1       43.4       96.5
Attainment Year (2032) with a 10              69.9       39.1       96.5
 percent reduction in NOX.........
------------------------------------------------------------------------
Sources: 2020 Plan, Attachment K, Section K.3.5 (``NOX Sensitivity
  Analysis''); Attachment to September 1, 2023 email from CARB to the
  EPA.

[[Page 87873]]

    Table 12 of this document presents CARB's summary data regarding 
NOX sensitivity in the area, including the emissions of 
NOX and VOC for the 2015 ozone NAAQS base year (2017) and 
the future attainment year (2032), as well as the measured 2017 ozone 
design value (83.0 ppb) and the predicted 2032 design value (71.1 ppb) 
with emissions reflecting business-as-usual, that is, without further 
emissions reductions. The fourth row of the table shows the DV 
predicted for the 2032 attainment year if there were an additional 
NOX reduction of ten percent from the business-as-usual 
scenario. When NOX emissions in the area are modeled at 39.1 
tpd, the modeled design value for the area is 69.9 ppb, a design value 
that meets the 2015 ozone NAAQS. DVs are approximately linear with 
respect to the corresponding NOX emissions in Table 12, 
indicating that the reduction of NOX likely plays a dominant 
role in the attainment demonstration in the 2020 Plan.
    Second, CARB presents information from a series of sensitivity 
tests for the area, in order to provide additional insight into the 
relative impact of reducing NOX and VOC on the modeled 
design value for the area. These simulations use different data than 
the 2020 Plan, including a different model year, domain, and a 2018 
emissions inventory base year. However, the (2018) baseline emissions 
used for the simulations are similar enough to the baseline emissions 
(2017) used for the 2020 Plan that the results of the simulations 
provide useful information with which to evaluate the reliance on 
NOX substitution in the 2020 Plan for the RFP demonstrations 
for compliance with CAA section 182(c)(2)(C).\152\
---------------------------------------------------------------------------

    \152\ For example, the 2017 baseline emissions in the 2020 Plan 
for the San Diego County nonattainment area are 77 tpd for 
NOX and 113 tpd for VOC (see Table 1 of this document--
not including emissions beyond three NM from the coast), whereas the 
2018 baseline emissions used for the simulations are 75 tpd for 
NOX and 112 tpd for VOC.
---------------------------------------------------------------------------

    The simulations were run from values of twenty percent to 100 
percent of baseline emissions to produce ``design value isopleths'' at 
the Alpine monitoring site, the long-standing design value monitoring 
site in San Diego County. Such isopleths can be used to predict what 
the effect would be on the design value if either NOX or VOC 
emissions were held constant while the other ozone precursor were 
altered. Based on the isopleths produced by the simulations, a 
reduction of NOX of 40 percent (from 2018 baseline 
emissions) results in a decrease in the design value (from 2018) at the 
Alpine monitoring site to the level of the 2008 ozone NAAQS whereas the 
same decrease in the design value requires a 60 percent decrease in VOC 
emissions (from 2018 baseline emissions). The isopleths that were 
produced by these simulations indicate that the design value in this 
area is more sensitive to decreases in NOX, and that the 
effect is more pronounced at lower NOX emissions. For 
example, if NOX emissions were held constant at 20 percent 
of the 2018 baseline, a change in VOC levels has almost no effect on 
the design value modeled for the area (in this case, around 60 ppb), 
whereas at a design value of 70.9 ppb, the design value is noticeably 
dependent on both pollutants, but still more sensitive to 
NOX. This isopleth indicates that NOX control is 
more effective than VOC control in the area on both a percentage and a 
per ton basis. As such, we find that the reliance on NOX 
substitution for RFP demonstration purposes in the 2020 Plan to be 
consistent with the requirements of CAA section 182(c)(2)(C).
    For these reasons, we have determined that the 2020 Plan 
demonstrates RFP in each milestone year, as well as in each attainment 
year (2026 for the 2008 ozone NAAQS and 2032 for the 2015 ozone NAAQS), 
consistent with applicable CAA requirements and EPA guidance and 
rulemakings. We therefore propose to approve the RFP demonstrations for 
the San Diego County area for the 2008 ozone NAAQS and for the 2015 
ozone NAAQS under sections 172(c)(2), 182(b)(1) and 182(c)(2)(B) of the 
CAA, 40 CFR 51.1110(a)(2), 40 CFR 51.1110(a)(2)(i) and (ii), 40 CFR 
51.1310(a)(2) and 40 CFR 51.1310(a)(2)(ii).

E. 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, in relevant part, a state 
to submit, for each area classified as Severe or above, a SIP revision 
that ``identifies and adopts specific enforceable transportation 
control strategies and transportation control measures to offset any 
growth in emissions from growth in vehicle miles traveled or number of 
vehicle trips in such area.'' \153\ 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.'' The 
2008 and 2015 SRRs extend the VMT emissions offset requirement to 
Severe and above areas for the 2008 and 2015 ozone NAAQS at 40 CFR 
51.1102 and 40 CFR 51.1302, respectively.
---------------------------------------------------------------------------

    \153\ CAA section 182(d)(1)(A) includes three separate elements. 
In short, under section 182(d)(1)(A), states are required to adopt 
transportation control strategies and measures to offset growth in 
emissions from growth in VMT, and, as necessary, in combination with 
other emission reduction requirements, to demonstrate RFP and 
attainment. For more information on the EPA's interpretation of the 
three elements of section 182(d)(1)(A), see 77 FR 58067 at 58068 
(September 19, 2012) (proposed withdrawal of approval of South Coast 
VMT emissions offset demonstrations). In Section III.E of this 
document, we address the first element of CAA section 182(d)(1)(A) 
(i.e., the VMT emissions offset requirement). In Sections III.C and 
III.D of this document, we propose to approve the attainment 
demonstrations and RFP demonstrations, respectively, for the 2008 
ozone NAAQS and for the 2015 ozone NAAQS in the San Diego County 
area. Compliance with the second and third elements of section 
182(d)(1)(A) is predicated on final approval of the attainment and 
RFP demonstrations.
---------------------------------------------------------------------------

    In Association of Irritated Residents v. EPA, the Ninth Circuit 
ruled that additional transportation control measures are required 
whenever vehicle emissions are projected to be higher than they would 
have been had VMT not increased, even when aggregate vehicle emissions 
are actually decreasing.\154\ In response to the court's decision, in 
August 2012, the EPA issued guidance titled ``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'').\155\
---------------------------------------------------------------------------

    \154\ See Association of Irritated Residents v. EPA, 632 F.3d. 
584, at 596-597 (9th Cir. 2011), reprinted as amended on January 27, 
2012, 686 F.3d 668, further amended February 13, 2012 (``Association 
of Irritated Residents'').
    \155\ EPA, ``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,'' EPA-420-B-12-053, August 2012, https://nepis.epa.gov/Exe/ZyPDF.cgi/P100EZ4X.PDF?Dockey=P100EZ4X.PDF.
---------------------------------------------------------------------------

    The August 2012 Guidance discusses the meaning of ``transportation 
control strategies'' (TCSs) and ``transportation control measures'' 
(TCMs) and recommends that both TCSs and TCMs be included in the 
calculations made for the purpose of determining the degree to which 
any hypothetical growth in emissions due to growth in VMT should be 
offset. Generally, TCS is a broad term that encompasses many types of 
controls (including, for example, motor vehicle emissions limitations, 
I/M

[[Page 87874]]

programs, alternative fuel programs, other technology-based measures, 
and TCMs) that would fit within the regulatory definition of ``control 
strategy.'' \156\ A TCM is defined at 40 CFR 51.100(r) as ``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 Clean Air Act. TCMs generally refer to 
programs intended to reduce VMT, number of vehicle trips, or traffic 
congestion, such as programs for improved public transit, designation 
of certain lanes for passenger buses and high-occupancy vehicles, and 
trip reduction ordinances.
---------------------------------------------------------------------------

    \156\ See, e.g., 40 CFR 51.100(n).
---------------------------------------------------------------------------

    The August 2012 Guidance explains how states may demonstrate that 
the VMT emissions offset requirement is satisfied in conformance with 
the Court's ruling in Association of Irritated Residents. Under the 
August 2012 Guidance, states would develop one emissions inventory for 
the base year and three different emissions inventory scenarios for the 
attainment year.\157\ The base year on-road VOC emissions should be 
calculated using VMT in that year, and they 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.
---------------------------------------------------------------------------

    \157\ See the August 2012 Guidance for specific details on how 
states might conduct the calculations.
---------------------------------------------------------------------------

    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 the fleet that was on the road in the base year gradually 
being replaced through fleet turnover; however, provided VMT and/or 
numbers of vehicle trips in fact increase by the attainment year, they 
would still likely be higher than they would have been assuming VMT had 
held constant.
    The second of the attainment year's emissions calculations would 
assume that no new TCSs or TCMs beyond those already credited have been 
put in place since the base year, but it would also assume that there 
was no growth in VMT and trips between the base year and attainment 
year. This estimate reflects the hypothetical emissions level that 
would have occurred if no further TCMs or TCSs had been put in place 
and if VMT and trip levels had held constant since the base year. Like 
the ``no action'' attainment year estimate, emissions in the attainment 
year may be lower than those in the base year due to the fleet that was 
on the road in the base year gradually being replaced by cleaner 
vehicles through fleet turnover, but in this case they would not be 
influenced by any growth in VMT or trips. This emissions estimate would 
reflect a ceiling on the attainment emissions that should be allowed to 
occur under the statute as interpreted by the Court in Association of 
Irritated Residents because it shows what would happen under a scenario 
in which no offsetting TCSs or TCMs have yet been put in place and VMT 
and trips are held constant during the period from the area's base year 
to its attainment year. This represents a ``VMT offset ceiling'' 
scenario. These two hypothetical status quo estimates are necessary 
steps in identifying the target level of emissions from which states 
would determine whether further TCMs or TCSs, beyond those that have 
been adopted and implemented, 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 expected to 
occur in the area's attainment year after taking into account 
reductions from all enforceable TCSs and TCMs. 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 and TCMs 
implemented by the attainment year would be sufficient to fully offset 
the identified hypothetical growth in emissions.
    If, instead, the estimated projected actual attainment year 
emissions are still greater than the ceiling 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 VMT offset ceiling estimated 
in the second of the attainment year calculations, in order to meet the 
VMT offset requirement of section 182(d)(1)(A) as interpreted by the 
Court.
2. Summary of State's Submission
    CARB prepared the VMT emissions offset demonstration for San Diego 
County for the 2008 ozone NAAQS and for the 2015 ozone NAAQS. The 
District referenced the State's demonstration in Sections 3.1.3 and 
4.1.3 of the 2020 Plan and included the demonstration itself in 
Attachment N (``VMT Offset Demonstration for San Diego County'').\158\ 
In addition to the VMT emissions offset demonstration, Attachment N of 
the 2020 Plan includes two appendices--one listing the TCSs adopted by 
CARB since 1990 and another listing the TCMs adopted by SANDAG (as of 
2018) in San Diego County.\159\ Based on the demonstration included as 
Attachment N of the 2020 Plan, the District concludes that the TCSs and 
TCMs identified in Attachment N offset the growth in emissions due to 
growth in VMT, thus satisfying the VMT emissions offset requirement for 
both the 2008 and 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \158\ 2020 Plan, pp. 37, 57 and N-1.
    \159\ 2020 Plan, Attachment N, Appendix A-1, ``State of 
California Motor Vehicle Control Program (1990-Present); Appendix A-
2, ``Adopted Transportation Control Measures.''
---------------------------------------------------------------------------

    In Attachment N of the 2020 Plan, CARB presents the VMT offset 
demonstration for the area. For this demonstration, CARB used 
EMFAC2017, the latest EPA-approved motor vehicle emissions model for 
California available at the time the 2020 Plan was developed.\160\ The 
EMFAC2017 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 EMFAC2017 model combines trip-based VMT and 
speed distribution data from the regional transportation planning

[[Page 87875]]

agency (i.e., SANDAG), 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 emissions 
rates to calculate emissions.
---------------------------------------------------------------------------

    \160\ 84 FR 41717 (August 15, 2019).
---------------------------------------------------------------------------

    Emissions from running exhaust, start exhaust, hot soak, and 
running losses are a function of how much a vehicle is driven. 
Emissions from these processes are thus directly related to VMT and 
vehicle trips, and CARB included these emissions in the calculations 
that provide the basis for the San Diego County VMT emissions offset 
demonstration. CARB did not include emissions from resting loss and 
diurnal loss processes in the analysis because such emissions are 
related to vehicle population, not to VMT or vehicle trips, and thus 
are not part of ``any growth in emissions from growth in vehicle miles 
traveled or numbers of vehicle trips in such area'' under CAA section 
182(d)(1)(A).
    The San Diego County VMT emissions offset demonstration for the 
2008 ozone NAAQS uses a 2011 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 2011 base year inventory 
for San Diego County for the purposes of the 2008 ozone NAAQS, and 
thus, CARB's selection of 2011 as the base year for the area's VMT 
emissions offset demonstration for the 2008 ozone NAAQS is appropriate.
    The San Diego County VMT emissions offset demonstration for the 
2008 ozone NAAQS also includes the three different attainment year 
scenarios (i.e., no action, VMT offset ceiling, and projected actual) 
described in Section III.E.1 of this document. The 2020 Plan provides a 
demonstration of attainment of the 2008 ozone NAAQS in San Diego County 
by the applicable attainment date, based on the controlled 2026 
emissions inventory. As described in Section III.C of this document, 
the EPA is proposing to approve the attainment demonstration for the 
2008 ozone NAAQS for San Diego County, and thus, we find CARB's 
selection of year 2026 as the attainment year for the VMT emissions 
offset demonstration for the 2008 ozone NAAQS to be acceptable.
    Table 13 of this document 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 13--VMT Emissions Offset Inventory Scenarios and Results for 2008 Ozone NAAQS
----------------------------------------------------------------------------------------------------------------
                                                                VMT (1,000/    Starts (trips)     VOC emissions
                          Scenario                                 day)          (1,000/day)          (tpd)
----------------------------------------------------------------------------------------------------------------
Base Year (2011)............................................          82,640            11,596                33
No Action (2026)............................................          87,279            12,278                12
VMT Offset Ceiling (2026)...................................          82,640            11,625                11
Projected Actual (2026).....................................          87,279            12,008                10
----------------------------------------------------------------------------------------------------------------
Sources: 2020 Plan, Tables N-1 and N-2; supplemental email dated April 27, 2023, from Nesamani Kalandiyur, CARB,
  with attachment to John J. Kelly, EPA.

    For the base year scenario, CARB ran the EMFAC2017 model for the 
2011 base year using VMT and starts data corresponding to that year. As 
shown in Table 13, CARB estimates San Diego County VOC emissions at 33 
tpd in 2011.
    For the ``no action'' scenario, CARB first identified the on-road 
motor vehicle control programs (i.e., TCSs \161\) put in place since 
the base year and incorporated into EMFAC2017, and then ran EMFAC2017 
with the VMT and starts data corresponding to the 2026 attainment year 
without the emissions reductions from the on-road motor vehicle control 
programs put in place after the base year. Thus, the no action scenario 
reflects the hypothetical VOC emissions in the attainment year if CARB 
had not put in place any additional TCSs after 2011. As shown in Table 
13, CARB estimates the ``no action'' San Diego County VOC emissions at 
12 tpd in 2026.
---------------------------------------------------------------------------

    \161\ 2020 Plan, Attachment N, table N-5.
---------------------------------------------------------------------------

    For the ``VMT offset ceiling'' scenario, CARB ran the EMFAC2017 
model for the attainment year but with VMT and starts data 
corresponding to base year values. Like the no action scenario, the 
EMFAC2017 model was adjusted to reflect the VOC emissions levels in the 
attainment years without the benefits of the post-base-year on-road 
motor vehicle control programs. Thus, the VMT offset ceiling scenario 
reflects hypothetical VOC emissions in San Diego County if CARB had not 
put in place any TCSs after the base year and if there had been no 
growth in VMT or vehicle trips between the base year and the attainment 
year.
    The hypothetical growth in emissions due to growth in VMT and trips 
can be determined from the difference between the VOC emissions 
estimates under the ``no action'' scenario and the corresponding 
estimates under the ``VMT offset ceiling'' scenario. Based on the 
values in Table 13, the hypothetical growth in emissions due to growth 
in VMT and trips in San Diego County would have been 1 tpd (i.e., 12 
tpd minus 11 tpd). This hypothetical difference establishes the level 
of VMT growth-caused emissions that need to be offset by the 
combination of post-baseline year TCSs and any necessary additional 
TCSs.
    For the ``projected actual'' scenario calculation, CARB ran the 
EMFAC2017 model for the attainment year with VMT and starts data at 
attainment year values and with the full benefits of the relevant post-
baseline year motor vehicle control programs. For this scenario, CARB 
included the emissions benefits from TCSs put in place since the base 
year. Between 2000 and 2019, annual VOC emissions in San Diego County 
declined 48 percent, approximately 65 percent of which was due to 
reductions from light-duty passenger vehicles.\162\ As shown in Table 
13 of this document, on-road VOC emissions are projected to decline by 
more than two-thirds (from 33 tpd to 10 tpd), from the 2011 base year 
to the 2026 attainment year. The most significant measures reducing VOC 
emissions during this timeframe are the regulations included in the 
Advanced Clean Cars regulatory package, such as the Low Emission 
Vehicle (LEV) III regulations that establish increasingly stringent 
emission standards for both criteria pollutants and greenhouse gases 
for new passenger vehicles through the 2025 model year and the Zero-
Emission

[[Page 87876]]

Vehicle (ZEV) sales mandate regulations.\163\
---------------------------------------------------------------------------

    \162\ 2020 Plan, Attachment M, ``Weight of Evidence 
Demonstration for San Diego County,'' Table M-4.
    \163\ See also 2020 Plan, Attachment N, Table N-5.
---------------------------------------------------------------------------

    As shown in Table 13, the projected actual attainment-year VOC 
emissions are 10 tpd. CARB compared this value against the 
corresponding VMT offset ceiling value to determine whether additional 
TCSs or TCMs would need to be adopted and implemented in order to 
offset any increase in emissions due solely to VMT and trips. Because 
the projected actual emissions are less than the corresponding VMT 
offset ceiling emissions, CARB concluded that the demonstration shows 
compliance with the VMT emissions offset requirement and that the 
adopted TCSs are sufficient to offset the growth in emissions from the 
growth in VMT and vehicle trips in the San Diego County area for the 
2008 ozone NAAQS.
    The San Diego County VMT emissions offset demonstration for the 
2015 ozone NAAQS uses a 2017 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 2017 base year inventory 
for the San Diego County area for the purposes of the 2015 ozone NAAQS, 
and thus, CARB's selection of 2017 as the base year for the area's VMT 
emissions offset demonstration for the 2015 ozone NAAQS is appropriate.
    The San Diego County area VMT emissions offset demonstration for 
the 2015 ozone NAAQS also includes the three different attainment year 
scenarios (i.e., no action, VMT offset ceiling, and projected actual) 
described in Section III.E.1. The 2020 Plan provides a demonstration of 
attainment of the 2015 ozone NAAQS in the San Diego County area by the 
applicable attainment date, based on the controlled 2032 emissions 
inventory. As described in Section III.C of this document, the EPA is 
proposing to approve the attainment demonstration for the 2015 ozone 
NAAQS for the San Diego County area, and thus, we find CARB's selection 
of year 2032 as the attainment year for the VMT emissions offset 
demonstration for the 2015 ozone NAAQS to be acceptable.
    Table 14 of this document summarizes the relevant distinguishing 
parameters for each of the emissions scenarios and shows CARB's 
corresponding VOC emissions estimates for the demonstration for the 
2015 ozone NAAQS.

               Table 14--VMT Emissions Offset Inventory Scenarios and Results for 2015 Ozone NAAQS
----------------------------------------------------------------------------------------------------------------
                                                                VMT (1,000/    Starts (trips)     VOC emissions
                          Scenario                                 day)          (1,000/day)          (tpd)
----------------------------------------------------------------------------------------------------------------
Base Year (2017)............................................          83,217            10,783                18
No Action (2032)............................................          91,751            13,411                10
VMT Offset Ceiling (2032)...................................          83,217            12,164                 9
Projected Actual (2032).....................................          91,751            13,130                 8
----------------------------------------------------------------------------------------------------------------
Sources: 2020 Plan, Tables N-1 and N-2; supplemental email dated April 27, 2023, from Nesamani Kalandiyur, CARB,
  with attachment, to John J. Kelly, EPA.

    For the base year scenario, CARB ran the EMFAC2017 model for the 
2017 base year using VMT and starts data corresponding to that year. As 
shown in Table 14, CARB estimates San Diego County VOC emissions at 18 
tpd in 2017.
    For the ``no action'' scenario, CARB first identified the on-road 
motor vehicle control programs (i.e., TCSs \164\) put in place since 
the base year and incorporated into EMFAC2017, and then ran EMFAC2017 
with the VMT and starts data corresponding to the 2032 attainment year 
without the emissions reductions from the on-road motor vehicle control 
programs put in place after the base year. Thus, the no action scenario 
reflects the hypothetical VOC emissions in the attainment year if CARB 
had not put in place any additional TCSs after 2017. As shown in Table 
14 of this document, CARB estimates the ``no action'' San Diego County 
VOC emissions at 10 tpd in 2032.
---------------------------------------------------------------------------

    \164\ 2020 Plan, Attachment N, Table N-5.
---------------------------------------------------------------------------

    For the ``VMT offset ceiling'' scenario, CARB ran the EMFAC2017 
model for the attainment year but with VMT and starts data 
corresponding to base year values. Like the no action scenario, the 
EMFAC2017 model was adjusted to reflect the VOC emissions levels in the 
attainment years without the benefits of the post-base-year on-road 
motor vehicle control programs. Thus, the VMT offset ceiling scenario 
reflects hypothetical VOC emissions in San Diego County if CARB had not 
put in place any TCSs after the base year and if there had been no 
growth in VMT or vehicle trips between the base year and the attainment 
year.
    The hypothetical growth in emissions due to growth in VMT and trips 
can be determined from the difference between the VOC emissions 
estimates under the ``no action'' scenario and the corresponding 
estimates under the ``VMT offset ceiling'' scenario. Based on the 
values in Table 14 of this document, the hypothetical growth in 
emissions due to growth in VMT and trips in San Diego County would have 
been 1 tpd (i.e., 10 tpd minus 9 tpd). This hypothetical difference 
establishes the level of VMT growth-caused emissions that need to be 
offset by the combination of post-baseline year TCSs and any necessary 
additional TCSs.
    For the ``projected actual'' scenario calculation, CARB ran the 
EMFAC2017 model for the attainment year with VMT and starts data at 
attainment year values and with the full benefits of the relevant post-
baseline year motor vehicle control programs. For this scenario, CARB 
included the emissions benefits from TCSs put in place since the base 
year. Between 2000 and 2019, annual VOC emissions in San Diego County 
declined 48 percent, approximately 65 percent of which was due to 
reductions from light-duty passenger vehicles.\165\ Table 14 of this 
document shows that on-road VOC emissions are projected to decline by 
more than one half (from 18 tpd to 8 tpd), from the 2017 base year to 
the 2032 attainment year. Significant VOC emissions reductions during 
the 2017-2032 timeframe result from the ZEV provisions of the Advanced 
Clean Cars program.
---------------------------------------------------------------------------

    \165\ 2020 Plan, Table M-4.
---------------------------------------------------------------------------

    As shown in Table 14 of this document, the projected actual 
attainment-year VOC emissions are 8 tpd. CARB compared this value 
against the corresponding VMT offset ceiling value to determine whether 
additional TCSs or TCMs would need to be adopted and implemented in 
order to offset any increase in emissions due solely to VMT and trips. 
Because the

[[Page 87877]]

projected actual emissions are less than the corresponding VMT offset 
ceiling emissions, CARB concluded that the demonstration shows 
compliance with the VMT emissions offset requirement and that the 
adopted TCSs are sufficient to offset the growth in emissions from the 
growth in VMT and vehicle trips in the San Diego County area for the 
2015 ozone NAAQS.
3. The EPA's Review of the State's Submission
    Based on our review of the San Diego County VMT emissions offset 
demonstration in Attachment N of the 2020 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 2020 Plan. We agree that CARB and SANDAG have adopted sufficient 
TCSs and TCMs to offset the growth in emissions from growth in VMT and 
vehicle trips in the San Diego County area for the purposes of both the 
2008 ozone NAAQS and the 2015 ozone NAAQS. Therefore, we propose to 
approve the San Diego County area VMT emissions offset demonstration 
element of the 2020 San Diego County Ozone SIP as meeting the 
requirements of CAA section 182(d)(1)(A), 40 CFR 51.1102 and 40 CFR 
51.1302.

F. Contingency Measures

1. Statutory and Regulatory Requirements
    Under the CAA, ozone nonattainment areas classified under subpart 2 
as Serious or above must include in their SIPs contingency measures 
consistent with sections 172(c)(9) and 182(c)(9). CAA section 172(c)(9) 
requires states with nonattainment areas to provide for the 
implementation of specific measures to be undertaken if the area fails 
to make RFP or to attain the NAAQS by the applicable attainment date. 
Such measures must be included in the SIP as contingency measures to 
take effect in any such case without further action by the state or the 
EPA. CAA section 182(c)(9) requires states to provide contingency 
measures in the event that an ozone nonattainment area fails to meet 
any applicable RFP milestone. 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.\166\ Contingency measures must 
be designed so as to be implemented prospectively; already-implemented 
control measures may not serve as contingency measures even if they 
provide emissions reductions beyond those needed for any other CAA 
purpose.\167\
---------------------------------------------------------------------------

    \166\ 70 FR 71612 (November 29, 2005); 2008 Ozone SRR, 80 FR 
12264, 12285 (March 6, 2015); 2015 Ozone SRR, 83 FR 62998, 63026 
(December 6, 2018).
    \167\ See Bahr v. EPA, 836 F.3d 1218, 1235-1237 (9th Cir. 2016) 
(``Bahr'') and Sierra Club v. EPA, 21 F.4th 815, 827-828 (D.C. Cir. 
2021).
---------------------------------------------------------------------------

    The purpose of contingency measures is to continue progress in 
reducing emissions while a state revises its SIP to meet the missed RFP 
requirement or to correct ongoing nonattainment. Neither the CAA nor 
the EPA's implementing regulations establish a specific level of 
emissions reductions that implementation of contingency measures must 
achieve, but the EPA's 2008 Ozone SRR and 2015 Ozone SRR reiterate the 
EPA's policy that contingency measures should provide for emissions 
reductions approximately equivalent to one year's worth of RFP, 
amounting to reductions of 3 percent of the baseline emissions 
inventory for the nonattainment area.\168\ A state cannot rely on 
already-implemented measures to serve as contingency measures, and in 
addition, a state cannot rely on already-implemented measures to 
justify the adoption of a contingency measure or contingency measures 
that would achieve less than one year's worth of RFP to meet the 
contingency measures requirements of CAA sections 172(c)(9) and 
182(c)(9) for the nonattainment area.\169\ As part of the contingency 
measures SIP revision for a given area, the EPA expects states to 
explain the amount of anticipated emissions reductions that the 
contingency measures will achieve. In the event that a state is unable 
to identify and adopt contingency measures that will provide for 
approximately one year's worth of RFP, then the EPA recommends that the 
state provide a reasoned justification why the smaller amount of 
emissions reductions is appropriate.\170\
---------------------------------------------------------------------------

    \168\ 2008 Ozone SRR, 80 FR 12264, 12285 (March 6, 2015); 2015 
Ozone SRR, 83 FR 62998, 63026 (December 6, 2018).
    \169\ See Association of Irritated Residents v. EPA, 10 F.4th 
937 (9th Cir. 2021) (``AIR'').
    \170\ 81 FR 58010, 58067 (August 24, 2016).
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    In March 2023, the EPA published notice of availability announcing 
a new draft guidance addressing the contingency measures requirement of 
section 172(c)(9), entitled: ``DRAFT: Guidance on the Preparation of 
State Implementation Plan Provisions that Address the Nonattainment 
Area Contingency Measure Requirements for Ozone and Particulate Matter 
(DRAFT--3/17/23--Public Review Version)'' (herein referred to as the 
``Draft Revised Contingency Measure Guidance'') and opportunity for 
public comment.\171\ The principal differences between the draft 
revised guidance and existing guidance on contingency measures relate 
to the EPA's recommendations concerning the specific amount of 
emissions reductions that implementation of contingency measures should 
achieve, and the timing for when the emissions reductions from the 
contingency measures should occur.
---------------------------------------------------------------------------

    \171\ 88 FR 17571 (March 23, 2023).
---------------------------------------------------------------------------

    Under the draft revised guidance, the recommended level of 
emissions reductions that contingency measures should achieve would 
represent one year's worth of ``progress'' as opposed to one year's 
worth of RFP. One year's worth of ``progress'' is calculated by 
determining the average annual reductions between the base year 
emissions inventory and the projected attainment year emissions 
inventory, determining what percentage of the base year emissions 
inventory this amount represents, then applying that percentage to the 
projected attainment year emissions inventory to determine the amount 
of reductions needed to ensure ongoing progress if contingency measures 
are triggered.
    With respect to the time period within which reductions from 
contingency measures should occur, the EPA previously recommended that 
contingency measures take effect within 60 days of being triggered, and 
that the resulting emissions reductions generally occur within one year 
of the triggering event. Under the draft revised guidance, in instances 
where there are insufficient contingency measures available to achieve 
the recommended amount of emissions reductions within one year of the 
triggering event, the EPA believes that contingency measures that 
provide reductions within up to two years of the triggering event would 
be appropriate to consider towards achieving the recommended amount of 
emissions reductions. The draft revised guidance does not alter the 60-
day recommendation for the contingency measures to take initial effect.
2. Summary of the State's Submission
    The 2020 Plan addresses the contingency measures requirement in 
Section 3.4 for the 2008 ozone NAAQS, Section 4.4 for the 2015 ozone 
NAAQS and Attachment O (``Contingency Measures for San Diego County'') 
to the plan. For both ozone NAAQS, the 2020 Plan anticipates the 
District's adoption of a revision to the District's architectural 
coatings rule (Rule 67.0.1)

[[Page 87878]]

to include a specific contingency provision that would narrow the small 
container exemption in the rule in the event that the area misses an 
RFP milestone or fails to attain the ozone NAAQS by the applicable 
attainment date. The District estimates that the anticipated 
contingency provision in the architectural rule would achieve 0.72 tpd 
of VOC reductions, i.e., if triggered by the EPA's determination that 
the area failed to meet an RFP milestone or failed to attain the 2008 
or 2015 ozone NAAQS by the applicable attainment date.\172\ The 
estimated emissions reductions from the amended architectural coatings 
rule (0.72 tpd of VOC) represent approximately 18 percent of one year's 
worth of RFP for the 2008 ozone NAAQS and approximately 21 percent of 
one year's worth of RFP for the 2015 ozone NAAQS.\173\
---------------------------------------------------------------------------

    \172\ 2020 Plan, Attachment O, p. O-1.
    \173\ The percentages are based on one year's worth of RFP, 
which is 3 percent of the 2011 VOC baseline emissions.
---------------------------------------------------------------------------

    For both ozone NAAQS, the 2020 Plan demonstrates compliance with 
the contingency measures requirements in CAA sections 172(c)(9) and 
182(c)(9) by coupling the anticipated emissions reductions from the 
contingency provision in the architectural coatings rule with projected 
surplus VOC and NOX emissions reductions that are expected 
to occur due to ongoing State mobile source control programs in San 
Diego County, providing for approximately one year's worth of RFP in 
the years following RFP milestone and attainment years.\174\ In this 
context, ``surplus'' emissions reductions refers to emissions 
reductions that are beyond those required to provide for RFP and 
attainment for the 2008 and 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \174\ 2020 Plan, Attachment O, p. O-7.
---------------------------------------------------------------------------

    Since submission of the 2020 Plan, the District has adopted the 
contingency provision in the District's architectural coatings rule 
(District Rule 67.0.1), and CARB has submitted the amended rule to the 
EPA as a revision to the California SIP. In late 2022, the EPA took 
final action to approve amended Rule 67.0.1.\175\ In our final rule 
approving amended Rule 67.0.1, we concluded that the contingency 
provision in the amended rule (paragraph (b)(6) of the rule) meets the 
requirements for individual contingency measures under CAA sections 
172(c)(9) and 182(c)(9). However, we also indicated that, while the 
amended rule meets the requirements for a stand-alone contingency 
measure, we were not making any determination at that time as to 
whether the individual contingency measure is sufficient in itself for 
San Diego County to fully comply with the contingency measures 
requirements under CAA sections 172(c)(9) and 182(c)(9).\176\
---------------------------------------------------------------------------

    \175\ 87 FR 78544 (December 22, 2022).
    \176\ Id.
---------------------------------------------------------------------------

3. The EPA's Review of the State's Submission
    Sections 172(c)(9) and 182(c)(9) require contingency measures to 
address potential failure to achieve RFP milestones or failure to 
attain the NAAQS by the applicable attainment date. The 2020 Plan was 
prepared and submitted following the Bahr decision and, thus, does not 
rely solely on surplus emissions reductions from already-implemented 
measures to demonstrate compliance with the contingency measures 
requirements, but rather, anticipated the revision of a District rule 
to include a specific contingency provision that would be designed to 
be both prospective and conditional. Since the 2020 Plan was submitted, 
the District has fulfilled the commitment in the 2020 Plan that the 
District amend the District's architectural coatings rule to include 
contingency provisions, and the EPA has approved the amended rule as a 
stand-alone contingency measure.
    The 2020 Plan was, however, prepared and submitted prior to the AIR 
decision and relies on the surplus emissions reductions from already-
implemented measures, not as a contingency measure per se, but as 
justification for adopting a contingency measure that would provide far 
less than the EPA's recommended amount of emissions reductions to meet 
the contingency measures requirements (i.e., one year's worth of RFP). 
In doing so, the 2020 Plan takes an approach to meeting the contingency 
measures requirements that is essentially the same as the approach that 
was rejected in the AIR decision. Also, earlier this year, the EPA has 
published new draft guidance addressing the contingency measures 
requirements. The principal differences between the Draft Revised 
Contingency Measure Guidance and existing guidance on contingency 
measures relate to the EPA's recommendations concerning the specific 
amount of emission reductions that implementation of contingency 
measures should achieve, and the timing for when the emissions 
reductions from the contingency measures should occur.
    In light of the change in circumstances arising from the AIR 
decision and the EPA's Draft Revised Contingency Measure Guidance, we 
are deferring action on the contingency measures portion of the 2020 
Plan at the present time to provide additional time for CARB and the 
District to supplement the contingency measures portion of the 2020 
Plan with additional contingency measures and a reasoned justification 
(if the contingency measures do not provide for the amount of 
reductions recommended by the EPA), as needed, to meet the contingency 
measure requirements of CAA sections 172(c)(9) and 182(c)(9).

G. 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 timely attainment of the standards. Conformity to the SIP's 
goals means that such actions will not: (1) cause or contribute to 
violations of a NAAQS; (2) worsen the severity of an existing 
violation; or (3) delay timely attainment of any NAAQS or any interim 
milestone.
    Actions involving Federal Highway Administration (FHWA) or Federal 
Transit Administration (FTA) funding or approval are subject to the 
EPA's transportation conformity rule, codified at 40 CFR part 93, 
subpart A. Under this rule, metropolitan planning organizations in 
nonattainment and maintenance areas coordinate with state and local air 
quality and transportation agencies, the EPA, the FHWA, and the FTA to 
demonstrate that an area's regional transportation plans and 
transportation improvement programs conform to the applicable SIP. This 
demonstration is typically done by showing that estimated emissions 
from existing and planned highway and transit systems are less than or 
equal to the motor vehicle emissions budgets contained in all control 
strategy SIPs. Motor vehicle emissions budgets are generally 
established for specific years and specific pollutants or precursors. 
Ozone plans should identify motor vehicle emissions budgets for on-road 
emissions of ozone precursors (NOX and VOC) in the area for 
each RFP milestone year and, if the plan demonstrates attainment, the 
attainment year.\177\
---------------------------------------------------------------------------

    \177\ 40 CFR 93.102(b)(2)(i).
---------------------------------------------------------------------------

    For motor vehicle emissions budgets to be approvable, they must 
meet, at a minimum, the EPA's adequacy criteria

[[Page 87879]]

at 40 CFR 93.118(e)(4). To meet these requirements, the motor vehicle 
emissions budgets must be consistent with the attainment and RFP 
requirements and reflect all motor vehicle control measures contained 
in the attainment and RFP demonstrations.\178\
---------------------------------------------------------------------------

    \178\ 40 CFR 93.118(e)(4)(iii), (iv) and (v). For more 
information on the transportation conformity requirements and 
applicable policies on motor vehicle emissions budgets, please visit 
our transportation conformity website at: https://www.epa.gov/state-and-local-transportation.
---------------------------------------------------------------------------

    The EPA's process for determining adequacy of a transportation 
budget consists of three basic steps: (1) providing public notification 
of a SIP submission; (2) providing the public the opportunity to 
comment on the motor vehicle emissions budgets during a public comment 
period; and, (3) making a finding of adequacy or inadequacy.\179\
---------------------------------------------------------------------------

    \179\ 40 CFR 93.118.
---------------------------------------------------------------------------

2. Summary of the State's Submission
    The 2020 Plan includes motor vehicle emissions budgets for both the 
2008 and the 2015 ozone NAAQS. For the 2008 ozone NAAQS, the 2020 Plan 
provides for motor vehicle emissions budgets for 2020 and 2023 RFP 
milestone years, and a 2026 attainment year. For the 2015 ozone NAAQS, 
the plan provides for motor vehicle emissions budgets for 2023, 2026 
and 2029 RFP milestone years and the 2032 attainment year.
    The motor vehicle emissions budgets in the 2020 Plan were 
calculated for an average summer day using EMFAC2017, the version of 
CARB's EMFAC model approved by the EPA for estimating emissions from 
on-road vehicles operating in California at the time the 2020 Plan was 
developed.\180\ The motor vehicle emissions budgets in the 2020 Plan 
reflect the transportation activity data provided by SANDAG including 
updated VMT and speed distribution data developed for the 2019 Federal 
Regional Transportation Plan.\181\ The motor vehicle emissions budgets 
also reflect an upward adjustment to account for the EPA's SAFE 1 
action \182\ and are rounded up to the nearest tenth of a ton per day. 
The 2008 and 2015 ozone NAAQS motor vehicle emissions budgets for 
NOX and VOC in the 2020 Plan for the San Diego County area 
are shown in Table 15 and Table 16 of this document, respectively.
---------------------------------------------------------------------------

    \180\ The EPA approved the use of EMFAC2017 for use in SIP 
development and transportation conformity at 84 FR 41717 (August 15, 
2019).
    \181\ 2020 Plan, endnote 130. SANDAG, San Diego Forward: The 
2019 Federal Regional Transportation Plan (October 2019).
    \182\ 84 FR 51310 (September 27, 2019).

  Table 15--Motor Vehicle Emissions Budgets for the 2008 Ozone NAAQS in
                        the San Diego County Area
                    [Summer planning inventory, tpd]
------------------------------------------------------------------------
               Budget year                      VOC             NOX
------------------------------------------------------------------------
2020....................................            16.3            28.1
2023....................................            13.6            19.3
2026....................................            12.1            17.3
------------------------------------------------------------------------
Source: 2020 Plan, Table 3-1.

  Table 16--Motor Vehicle Emissions Budgets for the 2015 Ozone NAAQS in
                        the San Diego County Area
                    [Summer planning inventory, tpd]
------------------------------------------------------------------------
               Budget year                      VOC             NOX
------------------------------------------------------------------------
2023....................................            13.6            19.3
2026....................................            12.1            17.3
2029....................................            11.0            15.9
2032....................................            10.0            15.1
------------------------------------------------------------------------
Source: 2020 Plan, Table 4-1.

3. The EPA's Review of the State's Submission
    The EPA previously found the motor vehicle emissions budgets in the 
2020 Plan to be adequate, using our adequacy criteria in 40 CFR 
93.118(e)(4) and (5).\183\ On June 4, 2021, the EPA announced the 
availability of the 2020 Plan and related motor vehicle emissions 
budgets on the EPA's transportation conformity website, requesting 
comments by July 6, 2021. The EPA received no comments from the public. 
By letter dated September 21, 2021, the EPA determined the 2020, 2023, 
2026 motor vehicle emissions budgets for the 2008 ozone NAAQS and the 
2023, 2026, 2029 and 2032 motor vehicle emissions budgets for the 2015 
ozone NAAQS were adequate for transportation conformity purposes.\184\ 
On October 4, 2021, the notice of adequacy was published in the Federal 
Register.\185\ Since the effective date of our adequacy finding, 
October 19, 2021, the U.S. Department of Transportation and the 
applicable metropolitan transportation organization, SANDAG, have been 
using the adequate motor vehicle emissions budgets for transportation 
conformity determinations for the area. The EPA is not required under 
its transportation conformity rule to find motor vehicle emissions 
budgets adequate prior to proposing approval of them, but in this 
instance, we have completed the adequacy review of these motor vehicle 
emissions budgets prior to our proposed action on the 2020 Plan.
---------------------------------------------------------------------------

    \183\ The EPA Office of Transportation and Air Quality (OTAQ) 
maintains a website that lists motor vehicle emissions budgets we 
are reviewing or have reviewed for adequacy. See our OTAQ adequacy 
review web page: https://www.epa.gov/state-and-local-transportation/adequacy-review-state-implementation-plan-sip-submissions-conformity.
    \184\ Letter from Elizabeth J. Adams, Air and Radiation Division 
Director, EPA Region IX to Richard Corey, Executive Officer, CARB, 
dated September 21, 2021.
    \185\ 86 FR 54692, effective October 19, 2021.
---------------------------------------------------------------------------

    The EPA is proposing to approve the motor vehicle emissions budgets 
the 2020 Plan for transportation conformity purposes. The EPA has 
determined through its review of the 2020 Plan that the motor vehicle 
emissions budgets are consistent with emissions control measures in the 
SIP and the RFP and attainment demonstrations for the 2008 ozone NAAQS 
and the 2015 ozone NAAQS. We note that the on-road motor vehicle 
emissions estimates used for the RFP and attainment demonstrations in 
the 2020 Plan are based on

[[Page 87880]]

transportation activity data developed for SANDAG's 2018 Regional 
Transportation Improvement Program whereas the motor vehicle emissions 
budgets are based on updated VMT and speed distribution data from 
SANDAG's 2019 Regional Transportation Plan, and thus the on-road motor 
vehicle estimates are not exactly the same as the corresponding motor 
vehicle emissions budgets. However, we have compared the on-road motor 
vehicle emissions used for the RFP and attainment demonstrations with 
the motor vehicle emissions budgets and find that the latter are 
numerically the same or slightly lower (by 0.1 to 0.4 tpd) for both VOC 
and NOX than the corresponding estimates used for the RFP 
and attainment demonstrations. Thus, the motor vehicle emissions 
budgets are conservative in that they reflect slightly less vehicle 
activity than the level of such activity assumed for the RFP and 
attainment demonstrations that we are proposing to approve in this 
document.
    For the reasons discussed in Sections III.C and III.D of this 
document, we are proposing to approve the RFP and attainment 
demonstrations in the 2020 Plan for the 2008 and 2015 ozone NAAQS. The 
motor vehicle emissions budgets, as listed in Tables 15 and 16 of this 
document, are consistent with the RFP and attainment demonstrations, 
are clearly identified and precisely quantified, and meet all other 
applicable statutory and regulatory requirements, including the 
adequacy criteria in 40 CFR 93.118(e)(4). For these reasons, the EPA 
proposes to approve the motor vehicle emissions budgets in the 2020 
Plan for years 2020, 2023, and 2026 for the 2008 ozone NAAQS (and shown 
in Table 15 of this document), as well as the motor vehicle emissions 
budgets in the 2020 Plan for years 2023, 2026, 2029 and 2032 (shown in 
Table 16 of this document), for the 2015 ozone NAAQS.

H. General Conformity Budgets

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 timely attainment of the standards. Conformity to the SIP's 
goals means that such actions will not: (1) cause or contribute to 
violations of a NAAQS; (2) worsen the severity of an existing 
violation; or (3) delay timely attainment of any NAAQS or any interim 
milestone.
    Section 176(c)(4) of the CAA establishes the framework for general 
conformity. The EPA first promulgated general conformity regulations in 
November 1993.\186\ In 2006, 2010, and again in 2016, the EPA revised 
the general conformity regulations.\187\ The general conformity 
regulations ensure that federal actions not covered by the 
transportation conformity rule will not interfere with the SIP and 
encourage consultation between the federal agency and the state or 
local air pollution control agencies before or during the environmental 
review process, as well as public participation (e.g., notification of 
and access to federal agency conformity determinations and review of 
individual federal actions). In San Diego County, federal actions not 
covered by the transportation conformity rule are subject to the 
general conformity requirements in District Rule 1501 (``Conformity of 
General Federal Actions'') \188\ and in 40 CFR part 93, subpart B, to 
the extent the requirements in 40 CFR part 93, subpart B are not 
contained in District Rule 1501.\189\
---------------------------------------------------------------------------

    \186\ 40 CFR part 51, subpart W, and 40 CFR part 93, subpart B.
    \187\ 71 FR 40420 (July 17, 2006); 75 FR 17254 (April 5, 2010); 
and 81 FR 58010, 58162 (August 24, 2016).
    \188\ SDCAPCD Rule 1501 (``Conformity of General Federal 
Actions''), approved at 64 FR 19916 (April 23, 1999).
    \189\ 40 CFR 93.151.
---------------------------------------------------------------------------

    The general conformity regulations in 40 CFR part 93, subpart B 
provide criteria and procedures for federal agencies to follow in 
determining general conformity for federal actions. The applicability 
analysis under 40 CFR 93.153 is used to find if a federal action 
requires a conformity determination for a specific pollutant. If a 
conformity determination is needed, federal agencies can use one of 
several methods to show that the federal action conforms to the SIP. In 
an area for which the EPA has not approved a revision to the relevant 
SIP since the area was designated or reclassified, a federal action may 
be shown to ``conform'' by demonstrating there will be no net increase 
in emissions in the nonattainment or maintenance area from the federal 
action. In an area with an approved SIP revision, conformity to the 
applicable SIP can be demonstrated in one of several ways. For actions 
where the direct and indirect emissions exceed the rates in 40 CFR 
93.153(b), the federal action can include mitigation measures to offset 
the emissions increases from the federal action or can show that the 
action will conform by meeting any of the following requirements:
     showing that the net emissions increases caused by an 
action are included in the SIP;
     documenting that the state agrees to include the emissions 
increases in the SIP;
     offsetting the action's emissions in the same or nearby 
area of equal or greater classification; or
     providing an air quality modeling demonstration in some 
circumstances.
    The general conformity regulations at 40 CFR 93.161 allow state and 
local air quality agencies working with federal agencies with large 
facilities (e.g., commercial airports, ports, and large military bases) 
that are subject to the general conformity regulations to develop and 
adopt an emissions budget for those facilities in order to facilitate 
future conformity determinations. Such a budget, referred to as a 
facility-wide emissions budget, may be used by federal agencies to 
demonstrate conformity as long as the total facility-wide budget level 
identified in the SIP is not exceeded.
    A state or local agency responsible for implementing and enforcing 
the SIP can develop and adopt an emissions budget to be used for 
demonstrating conformity under 40 CFR 93.158(a)(1) so long as the 
budget meets certain criteria listed in 40 CFR 93.161(a). The 
requirements include: (1) the facility-wide budget must be for a set 
time period; (2) the budget must cover the pollutants or precursors of 
the pollutants for which the area is designated nonattainment or 
maintenance; (3) the budgets must be specific about what can be emitted 
on an annual or seasonal basis; (4) the emissions from the facility 
along with all other emissions in the area must not exceed the total 
SIP emissions budget for the nonattainment or maintenance area; (5) 
specific measures must be included to ensure compliance with the 
facility-wide budget, such as periodic reporting requirements or 
compliance demonstrations when the federal agency is taking an action 
that would otherwise require a conformity determination; (6) the budget 
must be submitted to the EPA as a SIP revision; and (7) the SIP 
revision must be approved by the EPA. Having or using a facility-wide 
emissions budget does not preclude a federal agency from demonstrating 
conformity in any other manner allowed by the conformity rule.
    Once approved by the EPA, total direct and indirect emissions from 
federal actions in conjunction with all other emissions subject to 
general conformity from the facility that do not exceed the facility-
wide budget are ``presumed to conform'' to the SIP and

[[Page 87881]]

do not require a conformity analysis.\190\ However, if the total direct 
and indirect emissions from the federal actions in conjunction with the 
other emissions subject to general conformity from the facility exceed 
the budget, the action must be evaluated for conformity.\191\
---------------------------------------------------------------------------

    \190\ 40 CFR 93.161(c).
    \191\ 40 CFR 93.161(d).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    General conformity requirements are addressed in the 2020 Plan in 
Section 2.1.3, ``Emissions Budgets.'' The 2020 Plan includes facility-
wide emissions budgets (facility-wide budgets) that allow for 
increments of growth for military and airport facilities in the area. 
Further information supporting the military facility-wide budgets is 
included in the 2020 Plan's Attachment B, ``Planned Military Projects 
Subject to General Conformity''; further information supporting airport 
facility-wide budgets is included in Attachment C, ``Planned San Diego 
International Airport Projects Subject to General Conformity.''
    The EPA has reviewed facility-wide budgets for military facilities 
in San Diego County in the past, prior to the 2010 revisions to the 
EPA's general conformity regulations that expressly authorized such 
budgets. In 2003, the EPA proposed to approve the San Diego County 
redesignation request and maintenance plan (RRMP) for the 1979 1-hour 
ozone NAAQS.\192\ We approved the RRMP later that year, redesignating 
the area to attainment for the 1-hour ozone NAAQS and approving a ten-
year maintenance plan for the area.\193\ Although our final action did 
not approve facility-wide budgets explicitly, expected growth of 
military facility emissions in the San Diego County area were included 
in the area's RRMP. In our proposed approval of the RRMP, we indicated 
that the ``military growth [general] conformity increment is 11.4 tpd 
NOX in 2005, 2010, and 2014,'' that is, over the ten-year 
period of the maintenance plan.\194\ Likewise, the EPA approved the San 
Diego County RRMP for the 1997 ozone NAAQS, which included a military 
growth increment for years 2015, 2020 and 2025.\195\
---------------------------------------------------------------------------

    \192\ 68 FR 13653 (March 20, 2003).
    \193\ 68 FR 37976 (June 26, 2003), effective July 28, 2003.
    \194\ 68 FR 13653, 13654.
    \195\ 78 FR 17902, at 17912 (March 25, 2013) (proposed approval 
of San Diego County RRMP for the 1997 ozone NAAQS); finalized at 78 
FR 33230 (June 4, 2013).
---------------------------------------------------------------------------

    In 2018, for the 2020 Plan, the Department of the Navy (DoN) and 
United States Marine Corps (USMC) developed updated projections of 
future annual emissions increases and decreases from anticipated 
military actions in San Diego County from 2018 through 2037.\196\ 
NOX was estimated to increase by 8.34 tpd and VOC was 
expected to increase by 0.86 tpd from 2018 through 2037.\197\ 
Previously, the DoN and USMC had estimated emissions would increase by 
5.91 tpd NOX and 1.08 tpd VOC between 2011 and 2035.\198\ 
For the 2020 Plan, the District conservatively took the higher of both 
pairs of numbers and, again, conservatively assumed that the entire 
anticipated increase through 2037 would occur in 2018. CARB 
incorporated that growth increment into the 2019 CARB CEPAM emissions 
inventories (Version 1.00) that are used to develop the RFP and 
attainment demonstrations in the 2020 Plan.
---------------------------------------------------------------------------

    \196\ DoN and USMC report to SDCAPCD, ``Department of Navy 2017 
Mobile Source Baseline and Emissions Growth Increment Request for 
Submittal to the San Diego Air Pollution Control District,'' Naval 
Facilities Engineering Command Southwest, San Diego, California, 
December 2018.
    \197\ 2020 Plan, Table B-2.
    \198\ 2020 Plan, Table B-1.
---------------------------------------------------------------------------

    Specifically, the District and CARB incorporated a total growth 
projection of 8.34 tpd of NOX and 1.08 tpd of VOC emissions 
into the 2020 Plan and related RFP demonstrations and photochemical 
modeling for the attainment demonstrations. The modeling analysis CARB 
performed for the 2020 Plan indicates that the growth in military 
facility-related emissions is not expected to cause additional ozone 
violations.\199\
---------------------------------------------------------------------------

    \199\ 2020 Plan, p. 18.
---------------------------------------------------------------------------

    In Section 2.1.3.2 of the 2020 Plan, the District also accommodates 
facility-wide budgets (in the form of growth increments) for SDIA in 
San Diego County. The San Diego County Regional Airport Authority 
(Airport Authority) developed an emissions inventory for SDIA that the 
District includes in the 2020 Plan as Attachment C. The SDIA emissions 
inventory includes emissions increases anticipated to occur at the 
airport from 2012 through 2040. As with the military growth increment, 
the District conservatively assumed that all emissions increases at 
SDIA would occur in 2018 and CARB included those emissions in their 
modeling.
3. The EPA's Review of the State's Submission
    The 2020 Plan's facility-wide budgets (i.e., increments of growth) 
are included in Table 17 of this document for both the military and for 
SDIA expected emissions increases (hereafter, the ``facilities''). At 
these levels of growth, CARB air quality modeling predicts that there 
will not be an increase in ozone exceedances.\200\ These budgets 
represent emissions that are in addition to the baseline emissions 
projections in the 2020 Plan and that are built into the 2020 Plan as 
separate line items in the emissions inventories used for the RFP and 
attainment demonstrations. The purpose of the budgets is to accommodate 
anticipated federal actions by the military or by the federal agencies 
that permit, fund or approve actions at SDIA that would cause emissions 
increases greater than de minimis levels under the general conformity 
regulations. The de minimis level used to determine applicability of 
the general conformity requirements to federal actions in San Diego 
County is 25 tons per year of VOC or NOX based on the area's 
Severe classification for the 2008 and 2015 ozone NAAQS.\201\
---------------------------------------------------------------------------

    \200\ 2020 Plan, p. 19.
    \201\ District Rule 1501, section 1551.853(b)(1).

    Table 17--Facility-Wide General Conformity Budgets (Increments of
 Growth) for the Department of the Navy and United States Marine Corps,
     and for the San Diego International Airport in San Diego County
                    [Summer planning inventory, tpd]
------------------------------------------------------------------------
                Facility                        VOC             NOX
------------------------------------------------------------------------
DoN and USMC............................            1.08            8.34
SDIA....................................           0.141           1.756
------------------------------------------------------------------------
Source: 2020 Plan, pp. 18 and 19.

[[Page 87882]]

    The EPA reviewed the facility-wide budgets (i.e., increments of 
growth) for the facilities using the seven criteria listed for 
facility-wide budgets in 40 CFR 93.161(a). Criterion 1 is that the 
facility-wide budgets must be for a set time period. This criterion is 
satisfied by the duration of the growth projected by the military (out 
to 2037) and by the Airport Authority (out to 2040).
    Criterion 2 is that the facility-wide budgets must cover the 
pollutants or precursors of the pollutants for which the area is 
designated nonattainment or maintenance. This criterion is satisfied 
because the area is designated nonattainment for the 2008 and the 2015 
ozone NAAQS and ozone's precursors are VOC and NOX. Both 
precursors are addressed in the facility-wide budgets included in the 
2020 Plan for the facilities, presented in Table 17 of this document. 
Criterion 3 is likewise satisfied in that it requires that facility-
wide budgets include specific quantities allowed to be emitted on an 
annual or seasonal basis. Table 17 of this document includes specific 
quantities allowed to be emitted by the facilities. Criterion 4 is that 
the emissions from the facilities along with all other emissions in the 
area will not exceed the emission budget for the area. This criterion 
will be satisfied if the EPA finalizes the proposed approval of the RFP 
and attainment demonstrations in the 2020 Plan for the 2008 and 2015 
ozone NAAQS because the 2020 Plan includes the facility-wide budgets 
and all other emissions in the area in the future-year emissions 
projections used for the RFP and attainment demonstrations.\202\
---------------------------------------------------------------------------

    \202\ A detailed description of how the facility-based budgets 
were included in the future-year projections used for the RFP and 
attainment demonstrations is contained in an email dated May 22, 
2023, from Nick Cormier, SDCAPCD, to John J. Kelly, EPA Region IX.
---------------------------------------------------------------------------

    Criterion 5 is that there must be specific measures to ensure 
compliance with the budget, such as periodic reporting requirements or 
a compliance demonstration when the federal agency is taking an action 
that would otherwise require a general conformity determination. The 
District requested that the military and San Diego Regional Airport 
Authority each provide a written letter of commitment to track 
compliance with the facility-wide budgets and to make periodic reports 
to the District demonstrating compliance when they are taking actions 
that would otherwise require a general conformity determination. The 
requested letters of commitment have been provided to the 
District.\203\
---------------------------------------------------------------------------

    \203\ Letter dated July 31, 2023, from Ted Anasis, Manager, 
Airport Planning, SDIA, to Nick Cormier, SDCAPCD, and letter dated 
August 16, 2023, from J.C. Golumbfskie-Jones, Fleet Environmental 
Director, Commander Navy Region Southwest, DoN, to Paula Forbis, Air 
Pollution Control Officer, SDCAPCD.
---------------------------------------------------------------------------

    Criterion 6 is that the facility-wide budgets must be submitted to 
the EPA as a SIP revision. The 2020 Plan includes the facility-wide 
budgets shown in Table 17 of this document. The seventh and last 
criterion is that the SIP revision must be approved by the EPA. For the 
reasons stated in this section of this document, we propose to approve 
the general conformity budgets included in the 2020 Plan. If the EPA 
finalizes this action as proposed, criterion 7 will be satisfied.

I. Other Clean Air Act Requirements Applicable to Severe Ozone 
Nonattainment Areas

    In addition to the SIP requirements discussed in Sections III.A--
III.H, of this document, the CAA includes certain other SIP 
requirements applicable to Severe ozone nonattainment areas, such as 
the San Diego County area. In Section III.I., we identify these other 
requirements and evaluate the compliance by the State and District with 
respect to them for the San Diego County area.
1. Enhanced Vehicle Inspection and Maintenance Programs
    Section 182(b)(4) of the CAA requires states with ozone 
nonattainment areas classified under subpart 2 as Moderate to submit 
SIP revisions that provide for the implementation of a ``Basic'' 
vehicle inspection and maintenance (I/M) program in those areas. 
Section 182(c)(3) of the CAA requires states with ozone nonattainment 
areas classified under subpart 2 as Serious or above to submit SIP 
revisions that provide for the implementation of an ``Enhanced'' I/M 
program in certain urbanized portions of those areas.\204\ As a Severe 
ozone nonattainment area for the 2008 and 2015 ozone NAAQS, the State 
of California must implement an Enhanced I/M program in the urbanized 
portions of the San Diego County area.
---------------------------------------------------------------------------

    \204\ The CAA I/M SIP requirements apply to Moderate and above 
nonattainment areas for the 2008 and 2015 ozone NAAQS pursuant to 40 
CFR 51.1102 (for the 2008 ozone NAAQS) and 40 CFR 51.1302 (for the 
2015 ozone NAAQS).
---------------------------------------------------------------------------

    As a general matter, Basic and Enhanced I/M programs both achieve 
their objective by identifying vehicles that have high emissions as a 
result of one or more malfunctions and requiring them to be repaired. 
An Enhanced I/M program covers more of the vehicles in operation, 
employs inspection methods that are better at finding high emitting 
vehicles, and has additional features to better assure that all 
vehicles are tested properly and effectively repaired. The EPA has 
established specific requirements for Basic and Enhanced I/M programs 
in 40 CFR part 51, subpart S (``The EPA's I/M regulation''). The EPA's 
I/M regulation establishes minimum performance standards for Basic and 
Enhanced I/M programs as well as requirements for certain elements of 
the programs, including, among other elements, test frequency, vehicle 
coverage, test procedures and standards, stations and inspectors, and 
data collection, analysis and reporting.\205\
---------------------------------------------------------------------------

    \205\ 40 CFR part 51, subpart S, sections 350-373.
---------------------------------------------------------------------------

    Under 40 CFR 51.351(i), areas required to implement an Enhanced I/M 
program because of being designated and classified under the 8-hour 
ozone standard must meet or exceed the VOC and NOX emissions 
reductions (i.e., performance standard) achieved by the EPA's model 
program for Enhanced I/M. An I/M performance standard is a collection 
of program design elements that defines a benchmark program to which a 
state's proposed program is compared in terms of its potential to 
reduce emissions of the ozone precursors, VOC and NOX. The 
performance standard is expressed as emission levels in area-wide 
average grams per mile (grams/mile), achieved from on-road motor 
vehicles as a result of a specified model I/M program design. The 
emissions levels achieved by the state's program design must be 
calculated using the most current version of the EPA mobile source 
emissions factor model and must meet or exceed the emissions reductions 
achieved by the performance standard program both in operation and for 
SIP approval. The current version of the EPA mobile source emissions 
factor model at the time of CARB's evaluation of the California I/M 
program for compliance with 40 CFR 51.351(i) was the Motor Vehicle 
Emission Simulator model, version 3 (MOVES3).\206\
---------------------------------------------------------------------------

    \206\ 86 FR 1106 (January 7, 2021).
---------------------------------------------------------------------------

    For subject ozone nonattainment areas, the performance standard 
must be met for both VOC and NOX unless a NOX 
waiver has been approved for the area. Enhanced I/M program areas must 
be shown to obtain the same or lower emissions levels as the model 
program described in section 51.351(i) to within +/-0.02 grams/mile and 
must demonstrate through modeling the ability to maintain this level of

[[Page 87883]]

emissions reduction (or better) through their attainment deadline for 
the applicable NAAQS. See 40 CFR 51.351(i)(13).
    The California Bureau of Automotive Repair (BAR) implements the I/M 
program in California. BAR was required to implement an Enhanced I/M 
program in the urbanized portions of San Diego County due to the 
County's classification as a Serious nonattainment area for the 1-hour 
ozone NAAQS.\207\ In 1997, the EPA issued an interim approval of the 
program as meeting the Enhanced I/M requirements for the 1-hour ozone 
NAAQS in California.\208\ Currently, BAR implements an Enhanced I/M 
program in the urbanized areas of the County, a Basic I/M program in 
certain parts of central San Diego County, and a change of ownership I/
M program in the eastern half of the County.\209\
---------------------------------------------------------------------------

    \207\ In 1995, the EPA corrected the design value for San Diego 
County used to establish San Diego County's original nonattainment 
classification for the 1-hour ozone NAAQS and changed the 
classification from Severe to Serious. 60 FR 3771 (January 19, 
1995).
    \208\ 62 FR 1150 (January 8, 1997); see also 74 FR 41818, at 
41820 (August 19, 2009).
    \209\ California Bureau of Automotive Repair, Smog Check 
Reference Guide, revised August 2012, appendix A.
---------------------------------------------------------------------------

    The EPA's most recent approval of California's I/M program occurred 
in 2010, and in that action, the EPA approved the program as meeting 
the applicable I/M requirements for the various nonattainment areas in 
the State.\210\ However, at that time, because San Diego County had 
been redesignated to attainment for the 1-hour ozone NAAQS and had not 
yet been classified for the 1997 ozone NAAQS, San Diego County was no 
longer subject to the Enhanced I/M requirement, and the EPA did not 
review the program as it applies to San Diego County for compliance 
with Enhanced I/M program requirements.\211\
---------------------------------------------------------------------------

    \210\ 75 FR 38023 (July 1, 2010).
    \211\ The EPA did not classify San Diego County for the 1997 
ozone NAAQS until 2012, and, in that rulemaking, classified San 
Diego County as ``Subpart 2/Moderate.'' 77 FR 28424 (May 14, 2012).
---------------------------------------------------------------------------

    The statutory and regulatory foundation for the approved California 
I/M program is set forth in California Health & Safety Code (CH&SC), 
Division 26, Part 5, Chapter 5 (Motor Vehicle Inspection Program), 
Articles 1 through 9 and in Title 16 of the California Code of 
Regulations (16 CCR), Division 33, Chapter 1, Article 5.5 (Motor 
Vehicle Inspection Program).\212\ Additional I/M-related statutory and 
regulatory provisions in the California SIP include CH&SC section 
39032.5; California Business and Professions Code sections 9886 and 
9886.1-9886.4; California Vehicle Code sections 4000.1, 4000.2, 4000.3 
and 4000.6; and 16 CCR sections 3303.1, 3303.2, 3392.1-3392.6 and 
3394.1-3394.6.\213\
---------------------------------------------------------------------------

    \212\ 75 FR 38023, 38025-38026 (July 1, 2010).
    \213\ Id.
---------------------------------------------------------------------------

    For the 2020 San Diego County Ozone SIP, the District reviewed the 
existing I/M program as implemented in the San Diego County area and 
concluded, in light of the EPA's approval of the program with respect 
to the 1-hour and 1997 ozone NAAQS, that the area met all applicable I/
M requirements for the 2008 and 2015 ozone NAAQS.\214\ For this 
proposed action, we reviewed the existing I/M program and confirmed 
that the State implements and enforces an Enhanced I/M program in the 
urbanized areas of San Diego County as required in Severe ozone 
nonattainment areas.\215\ We also note that, since the EPA's most 
recent approval of the California I/M program in 2010, the State has 
taken steps to improve the effectiveness of the Smog Check program by 
requiring the BAR to direct older vehicles to high-performing auto 
technicians and test stations for inspection and certification.\216\ 
Further changes to State law have required the BAR to implement an 
updated protocol for testing 2000 and newer model-year vehicles that 
collects more complete On-Board Diagnostic (OBD) information than had 
been collected under the existing protocol.\217\ The State publishes an 
annual report summarizing the performance of the California smog check 
program.\218\ The State also publishes periodic reports to the 
Legislature on the resources allocated to smog check program 
administration and enforcement.\219\
---------------------------------------------------------------------------

    \214\ 2020 Plan, Section 3.1, pp. 33-34 (2008 ozone NAAQS) and 
Section 4.1, pp. 53-54 (2015 ozone NAAQS).
    \215\ CH&SC section 44003(a)(1) provides: ``An enhanced motor 
vehicle inspection and maintenance program is established in each 
urbanized area of the state, any part of which is classified by the 
Environmental Protection Agency as a serious, severe, or extreme 
nonattainment area for ozone or a moderate or serious nonattainment 
area for carbon monoxide with a design value greater than 12.7 ppm, 
and in other areas of the state as provided in this chapter.'' In 
addition, we used BAR's Smog Check Program Area Lookup tool and a 
list of zip codes for San Diego County to confirm the implementation 
of the Enhanced I/M program in the urbanized areas of San Diego 
County.
    \216\ CARB, Progress Report on Implementation of 
PM2.5 State Implementation Plans (SIP) for the South 
Coast and San Joaquin Valley Air Basins and Proposed SIP Revisions 
(Release Date: March 29, 2011), Table 1.
    \217\ CARB, Revised Proposed 2016 State Strategy for the State 
Implementation Plan (March 7, 2017), pp. 52-53.
    \218\ The most recent performance report is BAR's Smog Check 
Performance Report 2023, July 1, 2023.
    \219\ The most recent periodic report is BAR's Sunset Review 
Report 2022: presented to the Senate Committee on Business, 
Professions and Economic Development and the Assembly Committee on 
Business and Professions.
---------------------------------------------------------------------------

    Additionally, in April 2023, in response to the EPA's clarification 
of I/M SIP requirements for areas designated nonattainment for the 
eight-hour ozone NAAQS,\220\ CARB supplemented the motor vehicle I/M 
portion of the 2020 Plan with the submission of the Smog Check 
Certification as a revision to the California SIP. CARB's Smog Check 
Certification includes Enhanced I/M performance standard evaluations 
for the urbanized areas within certain ozone nonattainment areas, 
including the San Diego County area, for the 2008 and 2015 ozone NAAQS. 
For the Smog Check Certification, CARB relied upon the EPA's MOVES3 
emissions model and the EPA's most recent guidance for I/M performance 
standard modeling \221\ in preparing the Enhanced I/M performance 
standard evaluations for the various nonattainment areas addressed in 
the Smog Check Certification.
---------------------------------------------------------------------------

    \220\ See 87 FR 21842, at 21853 (April 13, 2022) (proposed 
determinations and reclassifications for Marginal areas for 2015 
ozone NAAQS), finalized at 87 FR 60897 (October 7, 2022).
    \221\ EPA, Performance Standard Modeling for New and Existing 
Vehicle Inspection and Maintenance (I/M) Programs Using the MOVES 
Mobile Source Emissions Model, EPA-420-B-22-034, October 2022.
---------------------------------------------------------------------------

    For the San Diego County area, the Smog Check Certification 
presents a comparison of July weekday emissions rates (in grams/mile) 
for VOC and NOX based on the existing California smog check 
program and the Enhanced I/M model program benchmark. The model program 
benchmark ultimately includes a 0.02 grams/mile buffer. The analysis 
was performed for the years 2017, 2026 and 2032. Table 18 of this 
document summarizes the results of the performance standard 
modeling.\222\
---------------------------------------------------------------------------

    \222\ Smog Check Certification, Table 8, p. 20.

[[Page 87884]]

  Table 18--Summary of July Weekday Emission Rates for San Diego County
------------------------------------------------------------------------
                Scenario                        NOX             VOC
------------------------------------------------------------------------
       Calendar Year 2017 July Weekday Emission Rates (grams/mile)
------------------------------------------------------------------------
CA Existing Program.....................          0.2604          0.2292
Enhanced Performance Standard Benchmark.          0.2831          0.2357
Enhanced Performance Standard Benchmark           0.3031          0.2557
 with 0.02 g/mile Buffer................
------------------------------------------------------------------------
       Calendar Year 2026 July Weekday Emission Rates (grams/mile)
------------------------------------------------------------------------
CA Existing Program.....................          0.0863          0.1284
Enhanced Performance Standard Benchmark.          0.0902          0.1255
Enhanced Performance Standard Benchmark           0.1102          0.1455
 with 0.02 g/mile Buffer................
------------------------------------------------------------------------
       Calendar Year 2032 July Weekday Emission Rates (grams/mile)
------------------------------------------------------------------------
CA Existing Program.....................          0.0374          0.0960
Enhanced Performance Standard Benchmark.          0.0367          0.0921
Enhanced Performance Standard Benchmark           0.0567          0.1121
 with 0.02 g/mile Buffer................
------------------------------------------------------------------------
Source: CARB, Smog Check Certification, Table 8.

    For both VOC and NOX in all analysis years, CARB's 
MOVES3 modeling results indicate that the California Enhanced I/M 
program meets or exceeds the federal Enhanced I/M performance standard 
benchmark program with the 0.02 g/mile buffer in San Diego County.
    We find that CARB used appropriate methods and input data to 
perform the I/M performance standard evaluations for San Diego County, 
analyzed appropriate years consistent with 40 CFR 351(i)(13), and 
included sufficient documentation to support the results. We also find 
that, based on our review of the District's and CARB's certification 
and the results presented in the Smog Check Certification, the 
California smog check program meets the Enhanced I/M program SIP 
requirements under CAA section 182(c)(3), 40 CFR 51.1102 and 40 CFR 
51.1302 for the 2008 and 2015 ozone NAAQS in the San Diego County area. 
Therefore, the EPA proposes to approve the I/M portion of the 2020 
Plan, as supplemented by the San Diego County portion of the Smog Check 
Certification, as revisions to the California SIP.
2. New Source Review Rules
    Section 182(a)(2)(C) of the CAA requires states to submit SIP 
revisions containing permit programs for each of their ozone 
nonattainment areas. The SIP revisions are to include requirements for 
permits in accordance with CAA sections 172(c)(5) and 173 for the 
construction and operation of each new or modified major stationary 
source for VOC or NOX anywhere in the nonattainment 
area.\223\ The 2008 Ozone SRR and 2015 Ozone SRR include provisions and 
guidance for nonattainment new source review (NSR) programs.\224\
---------------------------------------------------------------------------

    \223\ See also CAA section 182(d).
    \224\ 40 CFR 51.1114 and 80 FR 12264 (March 6, 2015) (2008 ozone 
NAAQS); and 40 CFR 51.1314 and 83 FR 62998 (December 6, 2018) (2015 
ozone NAAQS).
---------------------------------------------------------------------------

    In the 2020 San Diego County Ozone SIP, the District certifies 
compliance with NSR requirements for the 2008 and 2015 ozone NAAQS 
through amendments to the District's NSR rules (Rules 20.1-20.4) in 
June 2019.\225\ In 2020, the EPA issued a final limited approval/
limited disapproval of Rule 20.1 and a full approval of Rules 20.2, 
20.3 and 20.4.\226\ In that rulemaking, we found that the rules, with 
one exception not directly related to the ozone NAAQS, met the 
applicable NSR requirements for San Diego County as a Serious 
nonattainment area for the 2008 ozone NAAQS and as a Moderate 
nonattainment area for the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \225\ 2020 Plan, section 2.3, pp. 25-26.
    \226\ 85 FR 57727 (September 16, 2020).
---------------------------------------------------------------------------

    Since our NSR rulemaking in 2020, the San Diego County area has 
been reclassified to Severe for the 2008 and 2015 ozone NAAQS. However, 
the approved NSR rules already include NOX and VOC 
applicability thresholds and offset ratios applicable to Severe ozone 
nonattainment areas that automatically applied upon the July 2, 2021 
effective date of the area's reclassification to Severe.\227\ In 
addition, in 2022, the EPA issued a final full approval of four amended 
District rules, including Rule 20.1.\228\ In our 2022 rulemaking, we 
found that the submitted NSR rules satisfy the applicable NSR 
requirements for both the 2008 and 2015 ozone NAAQS.\229\
---------------------------------------------------------------------------

    \227\ 86 FR 29522 (June 2, 2021).
    \228\ 87 FR 58729 (September 28, 2022).
    \229\ 87 FR 29105, at 29107 (May 12, 2022) (proposed approval of 
amended District NSR rules); finalized at 87 FR 58729 (September 28, 
2022).
---------------------------------------------------------------------------

    Given the recent approval of the NSR program as meeting the 
applicable NSR requirements for the two relevant ozone NAAQS, including 
the applicability of the Severe area applicability threshold and offset 
ratio, we propose to approve the NSR certification in the 2020 Plan 
that the EPA-approved District NSR rules comply with the applicable NSR 
requirements under CAA sections 172(c)(5), 173 and 182(a)(2)(C), and 40 
CFR 51.1114 and 51.1314 for the San Diego County area for the 2008 and 
2015 ozone NAAQS.
3. Clean Fuels Fleet Program
    Sections 182(c)(4)(A) and 246 of the CAA require states to submit 
SIP revisions that establish a clean-fuel vehicle program for fleets 
(referred to herein as a Clean Fuels Fleets Program (CFFP)) in certain 
of their ozone nonattainment areas classified as Serious and above. The 
federal CFFP is specified in part C of title II of the CAA. Section 
182(c)(4)(B) of the CAA allows states to opt out of the federal CFFP by 
submitting a SIP revision consisting of a program or programs that will 
result in at least equivalent long-term reductions in ozone precursors 
and toxic air emissions. The CFFP SIP requirement applies to the San 
Diego County area as an ozone nonattainment area with a 1980 population 
of 200,000 or more and classified as Severe for the 2008 and 2015 ozone 
NAAQS.\230\
---------------------------------------------------------------------------

    \230\ See the definition of ``covered areas'' in CAA section 
246(a)(2). The CFFP SIP requirement applies to the 2008 and 2015 
ozone NAAQS pursuant to 40 CFR 51.1102 and 40 CFR 51.1302.

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

[[Page 87885]]

    In 1994, CARB submitted a SIP revision to the EPA to opt out of the 
federal CFFP. The submittal included a demonstration that California's 
low-emissions vehicle program (now referred to as the low-emissions 
vehicle (LEV I) regulation) achieved emissions reductions at least as 
large as would be achieved by the federal program. The EPA approved the 
SIP revision to opt out of the federal program on August 27, 1999.\231\ 
There have been no changes to the federal CFFP since the EPA approved 
the California SIP revision to opt out of the federal program, and 
thus, no corresponding changes to the SIP are required. In addition, 
California continues to implement its low-emissions vehicle program and 
has tightened the low-emissions vehicle emissions standards through 
adoption of the LEV II and LEV III regulations. The EPA approved the 
LEV II and LEV III regulations as part of the California SIP in 
2016.\232\
---------------------------------------------------------------------------

    \231\ 64 FR 46849 (August 27, 1999).
    \232\ 81 FR 39424 (June 16, 2016).
---------------------------------------------------------------------------

    In the 2020 San Diego County Ozone SIP, the District certified 
that, in light of the EPA's approval of the SIP revision to opt out of 
the federal program, the San Diego County area continues to meet the 
requirements of CAA sections 182(c)(4) and 246 for the 2008 and 2015 
ozone NAAQS.\233\ We agree with the District's conclusion and find that 
the California SIP revision to opt out of the federal program, as 
approved in 1999, continues to meet the requirements of CAA sections 
182(c)(4) and 246, and 40 CFR 51.1102 and 51.1302, for the San Diego 
County area for the 2008 and 2015 ozone NAAQS. For that reason, we 
propose to approve the certification in the 2020 San Diego County Ozone 
SIP that the San Diego County area continues to meet the CFFP SIP 
requirements for the 2008 and 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \233\ 2020 San Diego County Ozone SIP, Section 3.1, pp. 33-34 
and endnote 78 (2008 ozone NAAQS) and Section 4.1, pp. 53-54 and 
endnote 126 (2015 ozone NAAQS).
---------------------------------------------------------------------------

4. Gasoline Vapor Recovery
    Section 182(b)(3) of the CAA requires states to submit SIP 
revisions by November 15, 1992, that require owners or operators of 
gasoline dispensing systems to install and operate gasoline vehicle 
refueling vapor recovery (``Stage II'') systems in ozone nonattainment 
areas classified as Moderate and above. California's ozone 
nonattainment areas implemented Stage II vapor recovery well before the 
passage of the CAA Amendments of 1990.\234\
---------------------------------------------------------------------------

    \234\ General Preamble, 57 FR 13498, 13514 (April 16, 1992).
---------------------------------------------------------------------------

    Section 202(a)(6) of the CAA requires the EPA to promulgate 
standards requiring motor vehicles to be equipped with onboard 
refueling vapor recovery (ORVR) systems. The EPA promulgated the first 
set of ORVR system regulations in 1994 for phased implementation by 
vehicle manufacturers, and since the end of 2006, essentially all new 
gasoline-powered light and medium-duty vehicles are ORVR-equipped.\235\ 
Section 202(a)(6) also authorizes the EPA to waive the SIP requirement 
under CAA section 182(b)(3) for installation of Stage II vapor recovery 
systems after such time as the EPA determines that ORVR systems are in 
widespread use throughout the motor vehicle fleet. Effective May 16, 
2012, the EPA waived the requirement of CAA section 182(b)(3) for Stage 
II vapor recovery systems in ozone nonattainment areas regardless of 
classification.\236\ Thus, a SIP submittal meeting CAA section 
182(b)(3) is not required for the 2008 ozone NAAQS or the 2015 ozone 
NAAQS.
---------------------------------------------------------------------------

    \235\ 77 FR 28772, at 28774 (May 16, 2012).
    \236\ 40 CFR 51.126(b).
---------------------------------------------------------------------------

    While a SIP submittal meeting CAA section 182(b)(3) is not required 
for the 2008 or 2015 ozone NAAQS, under California state law (i.e., 
Health and Safety Code section 41954), CARB is required to adopt 
procedures and performance standards for controlling gasoline emissions 
from gasoline marketing operations, including transfer and storage 
operations. State law also authorizes CARB, in cooperation with local 
air districts, to certify vapor recovery systems, to identify defective 
equipment and to develop test methods. CARB has adopted numerous 
revisions to its vapor recovery program regulations and continues to 
rely on its vapor recovery program to achieve emissions reductions in 
ozone nonattainment areas in California.
    In the San Diego County area, the installation and operation of 
CARB-certified vapor recovery equipment is required and enforced by 
SDCAPCD Rule 61.4 (``Transfer of Volatile Organic Compounds into 
Vehicle Fuel Tanks''). This rule was most recently approved into the 
SIP on January 7, 2013.\237\
---------------------------------------------------------------------------

    \237\ 78 FR 897.
---------------------------------------------------------------------------

5. Enhanced Ambient Air Monitoring
    Section 182(c)(1) of the CAA requires states to submit SIP 
revisions for all ozone nonattainment areas classified as Serious or 
above that contain measures to enhance and improve monitoring for 
ambient concentrations of ozone, NOX, and VOC, and to 
improve monitoring of emissions of NOX and VOC in those 
areas. The enhanced monitoring network for ozone is referred to as the 
photochemical assessment monitoring station (PAMS) network. The EPA 
promulgated final PAMS regulations on February 12, 1993.\238\ San Diego 
County is subject to the CAA PAMS network SIP requirement as a Severe 
nonattainment area for the 2008 and 2015 ozone NAAQS pursuant to 40 CFR 
51.1102 and 51.1302.
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    \238\ 58 FR 8452 (February 12, 1993).
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    On November 10, 1993, CARB submitted to the EPA a SIP revision 
addressing the PAMS network for six ozone nonattainment areas, 
including San Diego County, to meet the enhanced monitoring 
requirements of CAA section 182(c)(1) and the PAMS regulations for the 
1-hour ozone NAAQS. At the time, San Diego County was classified as a 
``Severe-15'' ozone nonattainment area for the 1-hour ozone NAAQS but 
that classification was later corrected to be ``Serious.'' The EPA 
determined that the PAMS SIP revision met all applicable requirements 
for enhanced monitoring and approved the PAMS submittal into the 
California SIP.\239\
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    \239\ 82 FR 45191 (September 28, 2017).
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    Prior to 2006, the EPA's ambient air monitoring regulations in 40 
CFR part 58 (``Ambient Air Quality Surveillance'') set forth specific 
SIP requirements (see former 40 CFR 52.20). In 2006, the EPA 
significantly revised and reorganized 40 CFR part 58.\240\ Under 
revised 40 CFR part 58, SIP revisions are no longer required; rather, 
compliance with EPA monitoring regulations is established through 
review of required annual monitoring network plans.\241\ The 2008 Ozone 
SRR and 2015 Ozone SRR made no changes to these requirements.\242\
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    \240\ 71 FR 61236 (October 17, 2006).
    \241\ 40 CFR 58.2(b) now provides that ``[t]he requirements 
pertaining to provisions for an air quality surveillance system in 
the SIP are contained in this part.''
    \242\ The 2008 and 2015 ozone SRRs address PAMS-related 
requirements. For the 2008 ozone NAAQS, see 80 FR 12264, at 12291 
(March 6, 2015); for the 2015 ozone NAAQS, see 83 FR 62998, at 63008 
(December 6, 2018).
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    The most recent annual monitoring plan for San Diego County that 
the EPA has reviewed is the District's ``Annual Air Quality Monitoring 
Network Report 2021'' (2021 ANP).\243\ The District's 2021 ANP 
describes the steps taken to address the requirements of section 
182(c)(1), includes descriptions of the PAMS program and provides 
additional details about the PAMS network.\244\ The

[[Page 87886]]

EPA approved the District's current PAMS network as part of our 
approval of the District's ANP.\245\
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    \243\ SDCAPCD, Annual Air Quality Monitoring Report 2021, 
submitted for EPA review on June 29, 2022.
    \244\ 2021 ANP, chapter 11 (``Photochemical Assessment 
Monitoring Stations (PAMS)''). Starting in 2007, the EPA's 
monitoring rules at 71 FR 61236 (October 17, 2006) required the 
submittal and EPA action on ANPs. SDCAPCD's 2021 ANP can be found in 
the docket for this action.
    \245\ Letter dated October 31, 2022, from Gwen Yoshimura, EPA 
Region IX to David Sodeman, Chief, Monitoring and Technical 
Services, SDCAPCD, approving the 2021 San Diego ANP with certain 
exceptions unrelated to the PAMS requirements.
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    The 2020 Plan certifies compliance with the CAA section 182(c)(1) 
enhanced ambient monitoring requirement for the 2008 ozone NAAQS and 
2015 ozone NAAQS by reference to the area's approved PAMS SIP revision 
for the 1-hour ozone NAAQS.\246\ We agree that the San Diego County 
area meets the CAA section 182(c)(1) enhanced ambient monitoring 
requirement for the 2008 and 2015 ozone NAAQS based on the District's 
compliance with the EPA's monitoring regulations in 40 CFR part 58 for 
PAMS networks. On that basis, we propose to approve the 2020 Plan's 
certification of compliance with the enhanced monitoring requirements 
for the 2008 and 2015 ozone NAAQS for the San Diego County area under 
CAA section 182(c)(1) and 40 CFR 51.1102 and 51.1302.
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    \246\ 2020 Plan, pp. 33-34 and endnote 80 (2008 ozone NAAQS) and 
pp. 53-54 and endnote 128 (2015 ozone NAAQS).
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6. CAA Section 185 Fee Program
    Sections 182(d)(3) and 185 of the CAA require that the SIP for each 
Severe and Extreme ozone nonattainment area provide that, if the area 
fails to attain by its applicable attainment date, each major 
stationary source of VOC and NOX located in the area shall 
pay a fee to the state as a penalty for such failure for each calendar 
year beginning after the attainment date, until the area is 
redesignated as an attainment area for ozone. These requirements apply 
to the San Diego County area as a Severe nonattainment area for both 
the 2008 and the 2015 ozone NAAQS. States were required to submit to 
the EPA by July 20, 2022, a SIP revision that meets the requirements of 
CAA section 185 for the 2008 ozone NAAQS. The District adopted Rule 45 
to meet those requirements and the state submitted it to the EPA on 
July 20, 2022. The EPA plans to take action on that submittal 
separately from this action. States are not yet required to submit a 
SIP revision that meets the requirements of CAA section 185 for the 
2015 ozone NAAQS.\247\
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    \247\ See 40 CFR 51.1117 (2008 ozone NAAQS) and 51.1317 (2015 
ozone NAAQS). The deadline for submittal to the EPA for the area's 
CAA section 185 SIP revision for the 2015 ozone NAAQS is August 3, 
2028.
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7. Emissions Statement
    Section 182(a)(3)(B)(i) of the Act requires states 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 emissions 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 emissions 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. 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.\248\ The same approach was 
included in the 2015 Ozone SRR.\249\ Where an existing emissions 
statement requirement is still adequate to meet the requirements of 
these rules, 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, states must provide the 
revision to the emissions statement as part of its SIP.
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    \248\ See 80 FR 12264, at 12291 (March 6, 2015).
    \249\ See 83 FR 62998, at 63023 (December 6, 2018).
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    The 2020 Plan addresses compliance with the emissions statement 
requirement in CAA section 182(a)(3)(B) for the San Diego County area 
for the 2008 and 2015 ozone NAAQS in Section 2.2 (``Emissions Statement 
Rule Certification'') of the plan.\250\ In Section 2.2 of the 2020 
Plan, the District evaluates compliance with CAA section 182(a)(3)(B) 
by reference to District Rule 19.3 that, among other things, requires 
emissions reporting from stationary sources of NOX and VOC 
greater than or equal to 5 tpy, as deemed appropriate by the District's 
Air Pollution Control Officer (APCO). In addition, the District reports 
emissions of VOC and NOX from sources that emit less than 25 
tpy via CARB's California Emission Inventory Development and Reporting 
System (CEIDARS). All sources with emissions of VOC or NOX 
greater than or equal to 25 tpy must provide an emissions statement to 
the District. District Rule 19.3 applies throughout the San Diego 
County area. On April 6, 1993, the District adopted District Rule 19.3 
to meet the requirements in CAA section 182(a)(3)(B). The District 
amended District Rule 19.3 on May 15, 1996, and the EPA approved the 
rule into the California SIP, effective May 8, 2000.\251\
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    \250\ 2020 Plan, at 23-25.
    \251\ 65 FR 12472 (March 9, 2000).
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    In a separate action, the EPA approved the ``Emissions Statement 
Rule Certification'' portion of the 2020 Plan that certifies District 
Rule 19.3 as meeting the emissions statement requirement under CAA 
section 182(a)(3)(B) for the San Diego County area for the 2008 and 
2015 ozone NAAQS.\252\
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    \252\ 87 FR 45657 (July 29, 2022).
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IV. Environmental Justice Considerations

    This document proposes to approve certain SIP elements included in 
the 2020 Plan and the San Diego County area portion of the Smog Check 
Certification. Information on ozone and its relationship to negative 
health impacts can be found on the EPA's website.\253\ We expect that 
this proposed action, once approved, will generally be neutral or 
contribute to reduced environmental and health impacts on all 
populations in the San Diego County area, including people of color and 
low-income populations in the area. At a minimum, the approved action 
would not worsen any existing air quality and is expected to ensure the 
area is meeting requirements to attain air quality standards. Further, 
there is no information in the record indicating that this action is 
expected to have disproportionately high or adverse human health or 
environmental effects on a particular group of people. Lastly,

[[Page 87887]]

although the District did not perform an environmental justice review 
specifically for the 2020 Plan, the District does implement the State's 
``Community Air Protection Program'' in San Diego County.\254\ This 
program identifies specific communities based on environmental, health 
and socioeconomic information in order to reduce their pollution 
exposure.
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    \253\ Ozone National Ambient Air Quality Standards (NAAQS): 
https://www.epa.gov/ground-level-ozone-pollution/ozone-national-ambient-air-quality-standards-naaqs; Health Effects of Ozone 
Pollution: https://www.epa.gov/ground-level-ozone-pollution/health-effects-ozone-pollution.
    \254\ See email dated March 2, 2023, from Nick Cormier, SDCAPCD, 
to John J. Kelly, EPA, regarding environmental justice information 
on San Diego County communities. The State's Community Air 
Protection Program was created by passage of the State's Assembly 
Bill (AB) 617. At the time of the email, the District had developed 
a plan to address emissions of air pollutants in one community 
(Portside) that was identified by the program and another community 
(the ``International Border Community,'' that is, the San Ysidro-
Otay Mesa area) had also been identified.
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V. Proposed Action

    For the reasons discussed in this document, under CAA section 
110(k)(3), the EPA is proposing to approve all of the ``2020 Plan for 
Attaining the National Ambient Air Quality Standards for Ozone in San 
Diego County,'' submitted on January 12, 2021, with two exceptions, and 
the San Diego County area I/M SIP revision for the 2008 and 2015 ozone 
NAAQS, i.e., the San Diego County portion of the ``Smog Check 
Performance Standing Modeling and Certification,'' submitted on April 
26, 2023. The portions of the 2020 Plan on that we are not proposing 
action are the portion addressing the emissions statement requirement, 
which we already approved in a separate rulemaking, and the portion 
addressing the contingency measures requirement, for which we are 
deferring action.\255\
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    \255\ Regarding other applicable requirements for the 2008 and 
2015 ozone NAAQS in San Diego County, the EPA has previously 
approved the portion of the 2020 Plan that addresses the emissions 
statement requirement and will be taking action on the San Diego 
RACT submittal in separate rulemakings. See 87 FR 45657 (July 29, 
2022) (approval of emissions statement certification); and 88 FR 
57361(August 23, 2023) (final approval of District Rule 69.2.2), and 
88 FR 48150 (July 26, 2023) (proposed approval of District Rule 
69.2.1). A SIP revision for San Diego County addressing the penalty 
fee requirements under CAA sections 182(d)(3) and 185 for the 2008 
ozone NAAQS was submitted by CARB to the EPA on July 20, 2022, and 
EPA will take action on the July 20, 2022 SIP revision in a separate 
rulemaking. The area's penalty fee SIP revision is not due for the 
2015 ozone NAAQS until August 3, 2028.
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    More specifically, we are proposing approval of the following 
portions of the 2020 Plan, as supplemented by the Smog Check 
Certification, as meeting the following requirements:
     Base year emissions inventory element as meeting the 
requirements of CAA sections 172(c)(3) and 182(a)(1) for the 2008 and 
2015 ozone NAAQS, 40 CFR 51.1115 for the 2008 ozone NAAQS, and 40 CFR 
51.1315 for the 2015 ozone NAAQS;
     RACM demonstration element as meeting the requirements of 
CAA section 172(c)(1) for the 2008 and 2015 ozone NAAQS, 40 CFR 
51.1112(c) for the 2008 ozone NAAQS, and 40 CFR 51.1312(c) for the 2015 
ozone NAAQS;
     Attainment demonstration element for the 2008 ozone NAAQS 
as meeting the requirements of CAA section 182(c)(2)(A) and 40 CFR 
51.1108;
     Attainment demonstration element for the 2015 ozone NAAQS 
as meeting the requirements of CAA section 182(c)(2)(A) and 40 CFR 
51.1308, and the related commitments by CARB (through CARB Resolution 
20-29) to achieve an aggregate emissions reduction of 4 tpd of 
NOX by 2032 in the San Diego County area and by the District 
(through District Resolution 20-166) to achieve emissions reductions of 
1.7 tpd by 2032;
     ROP demonstration element as meeting the requirements of 
CAA section 182(b)(1) for the 2008 and 2015 ozone NAAQS, 40 CFR 
51.1110(a)(2) for the 2008 ozone NAAQS, and 40 CFR 51.1310(a)(2) for 
the 2015 ozone NAAQS;
     RFP demonstration element as meeting the requirements of 
CAA sections 172(c)(2), 182(b)(1), and 182(c)(2)(B) for the 2008 and 
2015 ozone NAAQS, 40 CFR 51.1110(a)(2)(i) and (ii) for the 2008 ozone 
NAAQS, and 40 CFR 51.1310(a)(2)(ii) for the 2015 ozone NAAQS;
     VMT emissions offset demonstration element as meeting the 
requirements of CAA section 182(d)(1)(A) for the 2008 and 2015 ozone 
NAAQS, 40 CFR 51.1102 for the 2008 ozone NAAQS, and 40 CFR 51.1302 for 
the 2015 ozone NAAQS;
     Motor vehicle emissions budgets for the 2020 and 2023 RFP 
milestone years and the 2026 attainment year (see Table 15) because 
they are consistent with the RFP and attainment demonstrations for the 
2008 ozone NAAQS proposed for approval herein and meet the other 
criteria in 40 CFR 93.118(e)(4);
     Motor vehicle emissions budgets for the 2023, 2026 and 
2029 RFP milestone years and the 2032 attainment year (see Table 16) 
because they are consistent with the RFP and attainment demonstrations 
for the 2015 ozone NAAQS proposed for approval herein and meet the 
other criteria in 40 CFR 93.118(e)(4);
     General conformity budgets (or growth increments, in this 
case) for the Department of the Navy and United States Marine Corps, 
and for the San Diego International Airport (see Table 17) as meeting 
the requirements of CAA section 176(c) and 40 CFR 93.161;
     Enhanced vehicle inspection and maintenance program 
element in the 2020 Plan, as supplemented by the San Diego County area 
portion of the Smog Check Certification, as meeting the requirements of 
CAA section 182(c)(3) for the 2008 and 2015 ozone NAAQS, 40 CFR 51.1102 
for the 2008 ozone NAAQS, and 40 CFR 51.1302 for the 2015 ozone NAAQS;
     Clean fuels fleet program element as meeting the 
requirements of CAA sections 182(c)(4)(A) and 246 for the 2008 and 2015 
ozone NAAQS, 40 CFR 51.1102 for the 2008 ozone NAAQS, and 40 CFR 
51.1302 for the 2015 ozone NAAQS;
     New Source Review program element as meeting the 
requirements of CAA sections 172(c)(5), 173 and 182(a)(2)(C) for the 
2008 and 2015 ozone NAAQS, 40 CFR 51.1114 for the 2008 ozone NAAQS, and 
40 CFR 51.1314 for the 2015 ozone NAAQS; and
     Enhanced monitoring element as meeting the requirements of 
CAA section 182(c)(1) for the 2008 and 2015 ozone NAAQS, 40 CFR 51.1102 
for the 2008 ozone NAAQS, and 40 CFR 51.1302 for the 2015 ozone NAAQS.
    The EPA is soliciting public comments on the issues discussed in 
this document. We will accept comments from the public on this proposal 
for the next 30 days and will consider comments before taking final 
action.

VI. Statutory and Executive Order Reviews

    Under the Clean Air Act, the Administrator is required to approve a 
SIP submission that complies with the provisions of the Act and 
applicable federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). 
Thus, in reviewing SIP submissions, the EPA's role is to approve state 
choices, provided that they meet the criteria of the Clean Air Act. 
Accordingly, this proposed action merely proposes to approve state law 
as meeting federal requirements and does not impose additional 
requirements beyond those imposed by state law. For that reason, this 
proposed action:
     Is not a ``significant regulatory action'' subject to 
review by the Office of Management and Budget under Executive Orders 
12866 (58 FR 51735, October 4, 1993), 13563 (76 FR 3821, January 21, 
2011) and 14094 (88 FR 21879, April 11, 2023);
     Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);

[[Page 87888]]

     Is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have Federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001); and
     Is not subject to requirements of Section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because application of those requirements would be inconsistent 
with the Clean Air Act.
    In addition, the SIP is not approved to apply on any Indian 
reservation land or in any other area where the EPA or an Indian tribe 
has demonstrated that a tribe has jurisdiction. In those areas of 
Indian country, the proposed action does not have tribal implications 
and will not impose substantial direct costs on tribal governments or 
preempt tribal law as specified by Executive Order 13175 (65 FR 67249, 
November 9, 2000).
    Furthermore, Executive Order 12898, ``Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations,'' (59 FR 7629, February 16, 1994), directs Federal 
agencies to identify and address ``disproportionately high and adverse 
human health or environmental effects'' of their actions on minority 
populations and low-income populations to the greatest extent 
practicable and permitted by law. The EPA defines environmental justice 
(EJ) as ``the fair treatment and meaningful involvement of all people 
regardless of race, color, national origin, or income with respect to 
the development, implementation, and enforcement of environmental laws, 
regulations, and policies.'' The EPA further defines the term fair 
treatment to mean that ``no group of people should bear a 
disproportionate burden of environmental harms and risks, including 
those resulting from the negative environmental consequences of 
industrial, governmental, and commercial operations or programs and 
policies.''
    The State did not evaluate environmental justice considerations as 
part of its SIP submittal; the CAA and applicable implementing 
regulations neither prohibit nor require such an evaluation. However, 
as described in Section IV (Environmental Justice Considerations) of 
this document, the District does participate in the State's 
environmental justice program. The EPA did not perform an EJ analysis 
and did not consider EJ in this proposed action. Due to the nature of 
this proposed action, if finalized, this action is expected to have a 
neutral to positive impact on the air quality of San Diego County. 
Consideration of EJ is not required as part of this action, and there 
is no information in the record inconsistent with the stated goal of 
Executive Order 12898, to achieve environmental justice for people of 
color, low-income populations, and Indigenous peoples.

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Nitrogen dioxide, Ozone, 
Reporting and recordkeeping requirements, Volatile organic compounds.

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

    Dated: December 8, 2023.
Martha Guzman Aceves,
Regional Administrator, Region IX.
[FR Doc. 2023-27513 Filed 12-18-23; 8:45 am]
BILLING CODE 6560-50-P