[Federal Register Volume 85, Number 210 (Thursday, October 29, 2020)]
[Proposed Rules]
[Pages 68509-68533]
[FR Doc No: 2020-23032]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2020-0425; FRL-10015-07-Region 9]

Approval of Air Quality Implementation Plans; California;
Sacramento Metro Area; 2008 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, or conditionally approve, all or portions of two state
implementation plan (SIP) revisions submitted by California to meet
Clean Air Act (CAA or ``Act'') requirements for the 2008 8-hour ozone
national ambient air quality standards (NAAQS or ``standards'') in the
Sacramento Metro ozone nonattainment area. These SIP revisions include
the ``Sacramento Regional 2008 NAAQS 8-hour Attainment and Reasonable
Further Progress Plan'' and the Sacramento Metro portion of the ``2018
Updates to the California State Implementation Plan.'' Collectively,
the EPA refers to these submittals as the ``Sacramento Metro Area Ozone
SIP.'' The Sacramento Metro Area Ozone SIP addresses the CAA
nonattainment area requirements for the 2008 ozone NAAQS, such as the
requirements for an emissions inventory, an attainment demonstration,
reasonable further progress, reasonably available control measures, and
contingency measures, and it establishes motor vehicle emissions
budgets. The EPA is proposing to approve the Sacramento Metro Area
Ozone SIP as meeting all the applicable ozone nonattainment area
requirements, except for the contingency measure requirement where the
EPA is proposing a conditional approval. Also, the EPA is beginning the
adequacy process for the 2023 and 2024 motor vehicle emissions budgets
in the Sacramento Metro Area Ozone SIP via this proposed rule.

DATES: Written comments must arrive on or before November 30, 2020.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2020-0425 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, or 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 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.

FOR FURTHER INFORMATION CONTACT: Jerry Wamsley, Air Planning Office
(ARD-2), EPA Region IX, 75 Hawthorne Street, San Francisco, CA 94105,
(415) 947-4111, or by email at<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: Throughout this document, ``we,'' ``us,''
and ``our'' refer to the EPA.

Table of Contents

I. Regulatory Context
    A. Ozone Standards, Area Designations, and SIPs
    B. The Sacramento Metro Ozone Nonattainment Area
    C. CAA and Regulatory Requirements for 2008 Ozone Nonattainment
Area SIPs
II. Submissions from the State of California To Address 2008 Ozone
Standard Requirements in the Sacramento Metro Area
    A. Summary of State Submissions
    B. Clean Air Act Procedural Requirements for Adoption and
Submission of SIP Revisions
III. Evaluation of the Sacramento Metro Area Ozone SIP
    A. Emissions Inventories
    B. Emissions Statement
    C. Reasonably Available Control Measures Demonstration
    D. Attainment Demonstration
    E. Rate of Progress Plan and Reasonable Further Progress
Demonstration
    F. Transportation Control Strategies and Measures to Offset
Emissions Increases From Vehicle Miles Traveled
    G. Contingency Measures
    H. Motor Vehicle Emissions Budgets for Transportation Conformity
    I. Other Clean Air Act Requirements Applicable to Severe Ozone
Nonattainment Areas

IV. Proposed Action
V. Statutory and Executive Order Reviews

I. Regulatory Context

A. Ozone Standards, Area Designations, and SIPs

    Ground-level ozone pollution is formed from the reaction of
volatile organic compounds (VOC) and oxides of nitrogen
(NOX) in the presence of sunlight.\1\ These two pollutants,
referred to as ozone precursors, are emitted by many types of sources,
including on-and off-road motor vehicles and engines, power plants and
industrial facilities, and smaller area sources such as lawn and garden
equipment and paints. 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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    \1\ The State of California refers to reactive organic gases
(ROG) rather than VOC 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.
    \2\ ``Fact Sheet--2008 Final Revisions to the National Ambient
Air Quality Standards for Ozone'' dated March 2008.
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    In 1979, under section 109 of the CAA, the EPA established primary
and secondary national ambient air quality standards for ozone at 0.12
parts per million (ppm) averaged over a 1-hour period (``1-hour ozone
standard'').\3\
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    \3\ 44 FR 8202 (February 8, 1979).
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    With the CAA Amendments of 1990, the Sacramento Metro ozone
nonattainment area (``Sacramento Metro Area'') was designated as
``Serious'' for the 1979 1-hour ozone standard and was required to
submit an attainment plan designed to meet this NAAQS by 1999. The
California Air Resources Board (CARB) submitted such an attainment plan
to the EPA on November 15, 1994, and we approved this attainment plan
on January 8, 1997.\4\ When subsequent air quality modeling studies
from the State showed that the control strategy in the 1994 attainment
plan would not meet the 1-hour ozone standard, the State requested and
the EPA approved a voluntary reclassification from Serious to ``Severe-
15.'' \5\ This reclassification extended the deadline for attaining the
1-hour ozone standard from 1999 to November 2005. Based on the air
quality data collected from 2007 through 2009, the EPA determined that
the Sacramento Metro Area met the 1979 1-hour ozone standard on October
18, 2012.\6\
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    \4\ 62 FR 1150 (January 8, 1997).
    \5\ 60 FR 20237 (April 25, 1995).
    \6\ 77 FR 64036 (October 18, 2012).
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    On July 18, 1997, the EPA revised the primary and secondary NAAQS
for ozone to set the acceptable level of ozone in the ambient air at
0.08 ppm, averaged over an 8-hour period (``1997 8-hour ozone
standard'').\7\ The EPA set the 1997 8-hour ozone standard based on
scientific evidence demonstrating that ozone causes adverse health
effects at lower concentrations and over longer periods of time than
was understood when the previous 1-hour ozone standard was set. The EPA
determined that the 1997 8-hour standard would be more protective of
human health, especially children and adults who are active outdoors,
and individuals with a pre-existing respiratory disease, such as
asthma.
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    \7\ 62 FR 38856 (July 18, 1997).
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    In 2004, the Sacramento Metro Area was designated as nonattainment
for the 1997 8-hour ozone standard and classified as Serious.\8\
Subsequently, CARB requested that the EPA reclassify the Sacramento
Metro Area, under CAA section 181(b)(3), from Serious to ``Severe-15.''
\9\ The EPA then finalized the reclassification of the Sacramento Metro
Area to Severe-15 on May 5, 2010.\10\ The State and local air districts
developed an attainment plan, along with state-wide and local control
measures, for the 1997 8-hour ozone standard and submitted the plan and
related components to the EPA over the course of several years from
2006 to 2013.\11\ The EPA approved the ``Sacramento 8-Hour Ozone
Attainment Plan'' on January 29, 2015.\12\
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    \8\ 69 FR 23858 (April 30, 2004).
    \9\ Letter dated February 14, 2008, from James N. Goldstene,
Executive Officer, CARB, to Wayne Nastri, Regional Administrator,
EPA Region IX.
    \10\ 75 FR 24409 (May 5, 2010).
    \11\ See Table 4 of our proposed rule for a listing of state and
local submittals composing the attainment plan for the 1997 8-hour
ozone standard; 79 FR 61803 (October 15, 2014).
    \12\ 80 FR 4795 (January 29, 2015). Please see our proposed rule
for this final action for a complete description of the attainment
plan and state and local control measures; 79 FR 61799 (October 15,
2014).
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    On March 27, 2008, the EPA revised and further strengthened the
primary and secondary NAAQS for ozone by setting the acceptable level
of ozone in the ambient air at 0.075 ppm, averaged over an 8-hour
period (``2008 8-hour ozone standard'').\13\ On May 21, 2012, we
designated nonattainment areas for the 2008 8-hour ozone NAAQS.\14\ At
the same time, we assigned classifications to many of these areas based
upon their ozone design value, in accordance with the structure of part
D, subpart 2 of Title I of the CAA.\15\ We designated the Sacramento
Metro Area as nonattainment for the 2008 ozone standards, and at the
request of CARB retained the Severe-15 classification, consistent with
previous ozone NAAQS.\16\ The Sacramento Metro Area's outermost
attainment date for the 2008 8-hour ozone standard is as expeditious as
practicable but no later than July 20, 2027. As a practical matter, the
Sacramento Metro Area would be required to demonstrate attainment of
the 2008 NAAQS no later than the previous ozone season, 2026. As
discussed further below, the EPA has determined that expeditious
attainment for the Sacramento Metro Area can be achieved in 2024.
Accordingly, the effective attainment date for the area is December 31,
2024.
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    \13\ 73 FR 16436 (March 27, 2008).
    \14\ 77 FR 30088 (May 21, 2012) and 40 CFR 81.330.
    \15\ 69 FR 23858 (April 30, 2004) and 40 CFR 51.903(a). The
designations and classifications for the 2008 8-hour ozone standard
for California nonattainment areas are codified at 40 CFR 81.305. A
design value is an ambient concentration calculated using a specific
methodology to evaluate monitored air quality data and is used to
determine whether an area's air quality is meeting a NAAQS. The
methodology for calculating design values for the 8-hour ozone NAAQS
is found in 40 CFR part 50, Appendix I.
    \16\ 77 FR 30088 (May 21, 2012).
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B. The Sacramento Metro Ozone Nonattainment Area

    The Sacramento Metro Area consists of Sacramento and Yolo counties
and portions of El Dorado, Placer, Solano and Sutter counties.\17\
Several local air agencies have jurisdiction in this area. Sacramento
County is under the jurisdiction of the Sacramento Metropolitan Air
Quality Management District (SMAQMD). Yolo County and the eastern
portion of Solano County comprise the Yolo-Solano AQMD (YSAQMD). The
southern portion of Sutter County is part of the Feather River AQMD
(FRAQMD). The western portion of Placer County is part of the Placer
County Air Pollution Control District (PCAPCD). Lastly, the western
portion of El Dorado County is part of the El Dorado County AQMD
(EDCAQMD). In this action, we refer to these five districts
collectively as the ``Districts.'' Under California law, each air
district is responsible for adopting and implementing stationary source
rules, while CARB adopts and

implements consumer products and mobile source rules. The Districts'
and State's rules are submitted to the EPA by CARB.
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    \17\ For a precise description of the geographic boundaries of
the Sacramento Metro Area for the 2008 ozone standards, see 40 CFR
81.305. Specifically included portions are the eastern portion of
Solano County, the western portions of Placer and El Dorado counties
outside of the Lake Tahoe Basin, and the southern portion of Sutter
County.
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    Current ambient 8-hour ozone levels in the Sacramento Metro Area
are well above the 2008 8-hour ozone NAAQS. For the 2014-2016 period,
the design value for the area, based on monitored readings at the
Placerville monitor in El Dorado County, is 0.085 ppm. Since 2010, the
highest design values have been found at the Folsom monitor in
Sacramento County and the Placerville monitor in El Dorado County,
ranging from 0.085 ppm to 0.102 ppm.\18\
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    \18\ Sacramento Regional 2008 NAAQS 8-hour Attainment and
Reasonable Further Progress Plan, Table 4-2.
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C. CAA and Regulatory Requirements for 2008 Ozone Nonattainment Area
SIPs

    States must implement the 2008 ozone NAAQS under Title 1, part D 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) for the 2008 ozone
NAAQS (``2008 Ozone SRR'') that addressed implementation of the 2008
standards, including attainment dates, requirements for emissions
inventories, attainment and reasonable further progress (RFP)
demonstrations, among other SIP elements, as well as the transition
from the 1997 ozone NAAQS to the 2008 ozone NAAQS and associated anti-
backsliding requirements.\19\ The 2008 Ozone SRR is codified at 40 CFR
part 51, subpart AA. In section III below, we discuss in more detail
the CAA and regulatory requirements for the air quality plans required
to meet the 2008 ozone standard.
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    \19\ 80 FR 12264 (March 6, 2015).
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    The EPA's 2008 Ozone SRR was challenged, and on February 16, 2018,
the U.S. Court of Appeals for the D.C. Circuit (``D.C. Circuit'')
published its decision in South Coast Air Quality Management District
v. EPA (``South Coast II'') \20\ vacating portions of the 2008 Ozone
SRR. The only aspect of the South Coast II decision that affects this
proposed action is the vacatur of the alternative baseline year for RFP
plans. More specifically, the 2008 Ozone SRR required states to develop
the baseline emissions inventory for RFP plans using the emissions for
the most recent calendar year for which states submit a triennial
inventory to the EPA under subpart A (``Air Emissions Reporting
Requirements'') of 40 CFR part 51, which was 2011. The 2008 Ozone SRR,
however, allowed states to use an alternative year, between 2008 and
2012, for the baseline emissions inventory provided that the state
demonstrated why the alternative baseline year was appropriate. In the
South Coast II decision, the D.C. Circuit vacated the provisions of the
2008 Ozone SRR that allowed states to use an alternative baseline year
for demonstrating RFP.
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    \20\ South Coast Air Quality Management District v. EPA, 882
F.3d 1138 (D.C. Cir. 2018). The term ``South Coast II'' is used in
reference to the 2018 court decision to distinguish it from a
decision published in 2006 also referred to as ``South Coast.'' The
earlier decision involved a challenge to the EPA's Phase 1
implementation rule for the 1997 ozone NAAQS. South Coast Air
Quality Management Dist. v. EPA, 472 F.3d 882 (D.C. Cir. 2006).
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II. Submissions From the State of California To Address 2008 Ozone
Standard Requirements in the Sacramento Metro Area

A. Summary of Submissions

    The EPA's designation of an area as nonattainment for a NAAQS
starts the process for a state to develop and submit to the EPA a plan
providing for attainment of the given NAAQS under title 1, part D of
the CAA. For 8-hour ozone areas designated as nonattainment under the
2008 ozone NAAQS, effective July 20, 2012, the Sacramento Metro Area's
attainment plan was due by July 20, 2016.\21\ The State did not meet
this July 20, 2016 deadline to submit an attainment plan and the EPA
issued a finding of failure to submit an attainment SIP and several of
its required elements on September 26, 2017.\22\ This finding of
failure to submit an attainment plan and other required elements was
addressed by the submittals discussed below.
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    \21\ 40 CFR 51.1108(b) and 40 CFR 51.1110.
    \22\ 82 FR 44736 (September 26, 2017), effective on October 26,
2017.
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    California has submitted two SIP revisions to address the
Sacramento Metro Area's CAA planning obligations for attaining the 2008
8-hour ozone standard. The principal submittals are as follows:
     ``Sacramento Regional 2008 NAAQS 8-Hour Ozone Attainment
Plan and Reasonable Further Progress Plan,'' dated July 25, 2017
(``2017 Sacramento Regional Ozone Plan'' or ``Plan''); and
     The Sacramento Metro portion of CARB's ``2018 Updates to
the California State Implementation Plan'' (``2018 SIP Update'').
    In this document, we are proposing action on all or portions of
these SIP revisions, which are summarized below. Collectively, we refer
to the relevant portions of these SIP revisions as the ``Sacramento
Metro Area Ozone SIP.''
1. 2017 Sacramento Regional Ozone Plan
    On December 18, 2017, CARB submitted the 2017 Sacramento Regional
Ozone Plan to the EPA as a revision to the California SIP.\23\ The 2017
Sacramento Regional Ozone Plan addresses the nonattainment area
requirements for the Sacramento Metro Area concerning the 2008 ozone
NAAQS. The SIP revision for the 2017 Sacramento Regional Ozone Plan
includes the Plan itself with its chapters and appendices, plus the
Districts' resolutions of adoption for the plan, and CARB's resolution
of adoption for the 2017 Sacramento Regional Ozone Plan. The 2017
Sacramento Regional Ozone Plan was adopted by the Districts' governing
boards beginning in late August through October 2017, and then by CARB,
via Resolution 17-40, on November 16, 2017. See Table 1 for the
Districts' adoption dates and board resolution or order numbers.
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    \23\ Letter dated December 18, 2017, from Richard Corey,
Executive Officer, CARB, to Alexis Strauss, Acting Regional
Administrator, EPA Region IX.

Table 1--Districts and Adoption Dates for 2017 Sacramento Regional Ozone
                                  Plan
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                                                                Board
           District             Hearing and  adoption dates  resolution/
                                                                 order
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SMAQMD.......................  August 24, 2017.............     2017-015
EDCAQMD......................  September 12, 2017..........     141-2017
FRAQMD.......................  October 2, 2017.............      2017-10
YSAQMD.......................  October 11, 2017............        17-06
PCAPCD.......................  October 12, 2017............        17-08
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    The 2017 Sacramento Regional Ozone Plan is organized into thirteen
chapters and six technical appendices addressing the CAA requirements
for VOC and NOX emissions inventories, air quality and
photochemical modeling to demonstrate attainment of the 2008 ozone
standard, reasonably available control measures (RACM) for each of the
Districts along with the overall control strategy for the Sacramento
Metro Area, RFP, adoption and implementation of transportation control
strategies and measures, and contingency measures for failure to meet
RFP or attain, among other requirements. Submittal of the 2017
Sacramento Regional Ozone Plan and the EPA's completeness determination
for the Plan set aside our September 26,

2017 finding of failure to submit.\24\ In addition to the 2017
Sacramento Regional Ozone Plan, CARB submitted its Staff Report
reviewing the plan and discussing the photochemical modeling supporting
its attainment demonstration and referred to herein as the ``CARB Staff
Report.'' \25\
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    \24\ Letter dated June 14, 2018, from Elizabeth Adams, Acting
Director, Air Division, EPA Region IX, to Richard Corey, Executive
Officer, CARB.
    \25\ ``Staff Report, ARB Review of the Sacramento Regional 2008
NAAQS 8-Hour Ozone Attainment and Reasonable Further Progress Plan''
(``CARB Staff Report''), release date October 13, 2017.
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2. 2018 SIP Update
    On December 5, 2018, CARB submitted the 2018 SIP Update to the EPA
as a revision to the California SIP.\26\ CARB developed the 2018 SIP
Update in response to the court's decision in South Coast II vacating
the 2008 Ozone SRR with respect to the use of an alternate baseline
year for demonstrating RFP and to address contingency measure
requirements in the wake of the court decision in Bahr v. EPA.\27\ The
2018 SIP Update includes an RFP demonstration using the required 2011
baseline year for the Sacramento Metro Area for the 2008 ozone NAAQS.
The 2018 SIP Update also includes updated motor vehicle emission
budgets and information to support the contingency measure element of
the 2017 Sacramento Regional Ozone Plan. The 2018 SIP Update includes
updates for 8 different California ozone nonattainment areas. We have
already acted to approve portions of the 2018 SIP Update related to
other nonattainment areas.\28\ In this action, we are proposing action
on the Sacramento Metropolitan Area portion of the 2018 SIP Update,
specifically, Section V--SIP Elements for the Sacramento Metropolitan
Area.
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    \26\ Letter dated December 5, 2018, from Richard Corey,
Executive Officer, CARB, to Mike Stoker, Regional Administrator, EPA
Region IX. CARB adopted the 2018 SIP Update on October 25, 2018.
    \27\ Bahr v. EPA, 836 F.3d 1218 (9th Cir. 2016) (``Bahr v.
EPA''). In Bahr v. EPA, the court rejected the EPA's longstanding
interpretation of CAA section 172(c)(9) as allowing for early
implementation of contingency measures. The court concluded that a
contingency measure must take effect at the time the area fails to
make RFP or attain by the applicable attainment date, not before.
    \28\ See, e.g., 84 FR 11198 (March 25, 2019) (final approval of
the San Joaquin Valley portion of the 2018 SIP Update), 84 FR 52005
(October 1, 2019) (final approval of the South Coast portion of the
2018 SIP Update), and 85 FR 38081 (June 25, 2020) (final approval of
the Ventura County portion of the 2018 SIP Update).
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    To supplement the contingency measure element of the 2017
Sacramento Regional Ozone Plan, in a letter dated July 7, 2020, CARB
forwarded to the EPA a May 26, 2020 letter of commitment from the
Districts.\29\ In this letter, the Districts commit to modify their
existing architectural coatings rules, and the SMAQMD also commits to
adopt a VOC rule that would serve as contingency measures that will be
triggered if the area fails to meet an RFP milestone or fails to attain
the 2008 ozone NAAQS.\30\ In the July 7, 2020 letter, CARB commits to
submit the Districts' revised rules to the EPA as a SIP revision within
12 months of the EPA's final conditional approval of the contingency
measures element of the Sacramento Metro Area Ozone SIP.\31\
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    \29\ Letter dated July 7, 2020, from Richard Corey, Executive
Officer, CARB, to John Busterud, Regional Administrator, EPA Region
IX.
    \30\ Letter dated May 26, 2020, from the Districts' respective
Executive Officer or Air Pollution Control Officer, Alberto Ayala-
SMAQMD, Dave Johnston-EDCAQMD, Christopher Brown-FRAQMD, Erik White-
PCAPCD, Mat Ehrhardt-YSAQMD to Richard Corey, Executive Officer,
CARB.
    \31\ Letter dated July 7, 2020, from Richard Corey, Executive
Officer, CARB, to John Busterud, Regional Administrator, EPA Region
IX.
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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 for a public hearing was
provided consistent with the EPA's implementing regulations in 40 CFR
51.102.
    The Districts, collectively, and CARB have satisfied the applicable
statutory and regulatory requirements for reasonable public notice and
hearing prior to the adoption and submittal of the SIP revisions that
comprise the Sacramento Metro Area Ozone SIP. With respect to the 2017
Sacramento Regional Ozone Plan, the Districts held hearings prior to
adoption to discuss the plan and solicit public input. Prior to these
adoption hearings, the Districts published notices of public hearing
for the adoption of the 2017 Sacramento Regional Ozone Plan in local
newspapers within the Districts.\32\ As noted in Table 1 above, the
Districts adopted the 2017 Sacramento Regional Ozone Plan and each
directed their respective Executive Officer or Air Pollution Control
Officer to forward the plan to CARB for inclusion in the California
SIP.
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    \32\ Please refer to the EPA's Completeness Determination and
supporting information included in the docket for this proposal
concerning the specific notices of public hearing, their evidence of
publication in local newspapers, and the Districts' public hearings.
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    CARB also provided public notice and opportunity for public comment
on the 2017 Sacramento Regional Ozone Plan. On October 12, 2017, CARB
released for public review its Staff Report for the 2017 Sacramento
Regional Ozone Plan and published a notice of public meeting to be held
on November 16, 2017, to consider adoption of the 2017 Sacramento
Regional Ozone Plan.\33\ On November 16, 2017, CARB held the public
hearing and adopted the 2017 Sacramento Regional Ozone Plan as a
revision to the California SIP, and directed the Executive Officer to
submit the 2017 Sacramento Regional Ozone Plan to the EPA for approval
into the California SIP.\34\ On December 18, 2017, the Executive
Officer of CARB submitted the 2017 Sacramento Regional Ozone Plan to
the EPA and included the transcript of the hearing held on November 16,
2017.\35\ On June 14, 2018, the EPA determined that this submittal
addressing the 2008 ozone NAAQS was complete.\36\
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    \33\ ``Notice of Public Meeting to Consider the Ozone State
Implementation Plan for the Sacramento Nonattainment Region,''
signed by Richard W. Corey, CARB Executive Officer, October 12,
2017. The Notice was made available on CARB's website.
    \34\ CARB Resolution 17-40.
    \35\ Compilation of Public Comments and Response for the
November 16, 2017 Meeting of the State of California Air Resources
Board.
    \36\ Letter dated June 14, 2018, from Elizabeth Adams, Acting
Director, Air Division, EPA Region IX to Richard Corey, Executive
Officer, CARB.
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    With respect to the 2018 SIP Update, CARB also provided public
notice and opportunity for public comment. On September 21, 2018, CARB
released for public review the 2018 SIP Update and published a notice
of a public meeting to be held on October 23, 2018, to consider
adoption of the 2018 SIP Update.\37\ On October 23, 2018, through
Resolution 18-50, CARB adopted the 2018 SIP Update. On December 5,
2018, CARB submitted the 2018 SIP Update to the EPA.
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    \37\ Notice of Public Meeting to Consider the 2018 Updates to
the California State Implementation Plan signed by Richard Corey,
Executive Officer, CARB, September 21, 2018.
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    Based on information provided in each of the SIP revisions
summarized above, the EPA has determined that all hearings were
properly noticed. Therefore, we find that the submittals of the 2017
Sacramento Regional Ozone Plan and the 2018 SIP Update meet the
procedural requirements for public notice and hearing in CAA sections
110(a) and 110(l) and 40 CFR 51.102.

III. Evaluation of the Sacramento Metro Area 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 requires 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.\38\
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    \38\ 2008 Ozone SRR at 40 CFR 51.1115(a) and the Air Emissions
Reporting Requirements at 40 CFR part 51 subpart A.
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    The EPA has issued guidance on the development of base year and
future year emissions inventories for 8-hour ozone and other
pollutants.\39\ Emissions inventories for ozone must include emissions
of VOC and NOX and represent emissions for a typical ozone
season weekday.\40\ States should include documentation explaining how
the emissions data were calculated. When estimating mobile source
emissions, states should use the latest emissions models and planning
assumptions available at the time the SIP is developed.\41\
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    \39\ ``Emissions Inventory Guidance for Implementation of Ozone
and Particulate Matter National Ambient Air Quality Standards
(NAAQS) and Regional Haze Regulations,'' EPA-454/B-17-002, May 2017.
At the time the 2017 Sacramento Regional Ozone Plan was developed,
the following EPA emissions inventory guidance applied: ``Emissions
Inventory Guidance for Implementation of Ozone and Particulate
Matter National Ambient Air Quality Standards (NAAQS) and Regional
Haze Regulations'' EPA-454-R-05-001, August 2005.
    \40\ 40 CFR 51.1115(a) and (c), and 40 CFR 51.1100(bb) and (cc).
    \41\ 80 FR 12264, 12290 (March 6, 2015).
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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 2017 Sacramento Regional Ozone Plan includes base year (2012)
and future year baseline inventories for NOX and VOC for the
Sacramento Metro Area. Documentation for the inventories is found in
Chapter 5 (``Emissions Inventory'') and Appendix A (``Emission
Inventory'') of the 2017 Sacramento Regional Ozone Plan.\42\ The
emissions inventories represent average summer day emissions,
consistent with the observation that ozone levels in the Sacramento
Metro Area are typically higher from May through October.
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    \42\ Appendix A-4 contains detailed source category and
emissions inventory projections from CARB's California Emission
Projection Analysis Model. This detailed information is consolidated
and presented in Chapter 5 of the plan.
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    The 2012 base year and future year inventories in the 2017
Sacramento Regional Ozone Plan reflect District and CARB rules adopted
prior to the plan in late 2015.\43\ The plan's emission reductions are
based on continuing implementation of existing federal, state and local
control measures. Both base year and projected future year inventories
use the most recent EPA-approved version of California's mobile source
emissions model at the time the plan was developed, EMFAC2014, for
estimating on-road motor vehicle emissions.\44\
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    \43\ 2017 Sacramento Regional Ozone Plan, 5-11 and 7-12 to 7-14.
    \44\ 80 FR 77337 (December 14, 2015). EMFAC is short for
EMission FACtor. The EPA announced the availability of the EMFAC2014
model for use in state implementation plan development and
transportation conformity in California on December 14, 2015. The
EPA's approval of the EMFAC2014 emissions model for SIP and
conformity purposes was effective on the date of publication of the
notice in the Federal Register. EMFAC2014 was the most recently
approved version of the EMFAC model that was available at the time
of preparation of the 2017 Sacramento Regional Ozone Plan. Recently,
the EPA approved an updated version of the EMFAC model, EMFAC2017,
for future SIP development and transportation purposes in
California; 84 FR 41717 (August 15, 2019).
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    VOC and NOX emissions estimates in the 2017 Sacramento
Regional Ozone Plan 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
permitted facilities and have one or more identified and fixed pieces
of equipment and emissions points. Area sources consist of widespread
and numerous smaller emission sources, such as small permitted
facilities and households. The mobile 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.
    For the 2017 Sacramento Regional Ozone Plan, point source emissions
for the 2012 base year emissions inventory are based on reported data
from facilities using the Districts' annual emissions reporting
programs. Area sources include smaller emissions sources distributed
across the nonattainment area. CARB and the Districts estimate
emissions for area sources using established inventory methods,
including publicly available emission factors and activity information.
Activity data are derived from national survey data such as the Energy
Information Administration or from local sources such as public
utilities, paint suppliers, and Districts' databases. Emission factors
used for the estimates come from many sources, such as facility and
equipment source tests, compliance reports, and the EPA's compilation
of emissions factors document known as ``AP-42.''
    CARB calculated the on-road emissions inventories in the 2017
Sacramento Regional Ozone Plan and the 2018 SIP Update using the
EMFAC2014 model and the vehicle travel activity data provided by the
Sacramento Council of Governments (SACOG) in its ``2016 Metropolitan
Transportation Plan/Sustainable Communities Strategy'' (``2016 MTP/
SCS'') \45\ as updated in the ``2017-20 Metropolitan Transportation
Improvement Program'' (``2017 MTIP'') \46\ and the Metropolitan
Transportation Commission (MTC) in its 2012 ``Bay Area Plan--Preferred
Land Use and Transportation and Investment Strategy.'' \47\ 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 uses several
models to estimate emissions for more than one hundred off-road
equipment categories.\48\ Aircraft emissions are developed in
conjunction with the airports in the region.
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    \45\ SACOG, ``2016 Metropolitan Transportation Plan/Sustainable
Communities Strategy,'' February 2016. Available at http://www.sacog.org/general-information/2016-mtpscs.
    \46\ SACOG, ``2017-20 Metropolitan Transportation Improvement
Program,'' September 15, 2016, Appendix A-6, ``Amendment #1 to the
2016 Metropolitan Transportation Plan/Sustainable Communities
Strategy,'' available at https://www.sacog.org/post/2017-20-mtip.
    \47\ 2017 Sacramento Regional Ozone Plan, Sections 10-2--10-6.
2018 SIP Update, 31. SACOG is the regional transportation planning
agency for the greater Sacramento area and covers Sacramento and
Yolo counties, and portions of El Dorado, Placer, and Sutter
counties. MTC is the regional transportation planning agency for the
San Francisco Bay area, including portions of Solano County within
the Sacramento Metro Area.
    \48\ 2017 Sacramento Regional Ozone Plan, 5-4.
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    Table 2 provides a summary of the Sacramento Metro Area's 2012 base
year, interim, and future attainment year baseline emissions estimates
in tons per average summer day for NOX and VOC. These
inventories provide the basis for the control measure analysis and the
attainment demonstrations in the 2017 Sacramento Regional Ozone Plan.
This emissions inventory includes emissions throughout the Sacramento
Metro Area. In the 2012 emissions inventory, stationary and area
sources account for roughly 45 percent of VOC emissions and 10 percent
of the NOX emissions in the Sacramento Metro Area while
mobile sources account for roughly 55 percent of the VOC emissions and
90 percent of the NOX emissions. For a more detailed
discussion of the inventories, see Chapter 5 and Appendix A-4 of the
2017 Sacramento Regional Ozone Plan.

                          Table 2--Sacramento Metro Area Base Year, Interim, and Attainment Year Baseline Emissions Inventories
                                                     [Summer planning inventory, tons per day (tpd)]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                   2012                    2018                    2021                    2024
                     Source category                     -----------------------------------------------------------------------------------------------
                                                              NOX         VOC         NOX         VOC         NOX         VOC         NOX         VOC
--------------------------------------------------------------------------------------------------------------------------------------------------------
Stationary Sources......................................           8          22           7          22           7          23           7          23
Area Sources............................................           3          29           2          29           2          30           2          31
On-Road Mobile Sources..................................          61          34          35          20          26          16          19          14
Off-Road Mobile Sources.................................          30          26          26          20          23          18          21          17
                                                         -----------------------------------------------------------------------------------------------
    Total...............................................         101         110          69          91          58          87          49          84
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: 2017 Sacramento Regional Ozone Plan, Chapter 5, tables 5-1 and 5-2. The sum of the emissions values may not equal the total shown due to
  rounding of the numbers.

    Future emissions forecasts in the 2017 Sacramento Regional Ozone
Plan, particularly on-road mobile source emissions, are based primarily
on demographic and economic growth projections provided by SACOG, the
metropolitan planning organization (MPO) for the Sacramento Metro Area,
and the MTC, the MPO for Solano County. The Districts and CARB
developed stationary and area source control factors in reference to
the 2012 base year, and then used the California Emission Projection
Analysis Model to project these 2012 baseline inventories to future
years.\49\
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    \49\ 2017 Sacramento Regional Ozone Plan, Chapter 5, and
Appendices A-2 and A-4.
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    Following the South Coast II decision, CARB submitted the 2018 SIP
Update to the EPA to revise, among other things, the RFP demonstration
in the 2017 Sacramento Regional Ozone Plan based on a 2011 RFP baseline
year (i.e., rather than 2012).\50\ Our analysis of the emissions
inventories for the 2011 RFP baseline year and RFP milestone years 2017
and 2020 can be found in section III.E below.
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    \50\ 2018 SIP Update, Section V (``SIP Elements for the
Sacramento Metropolitan Area''), 27-34; and Appendix A, A-15 through
A-18.
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3. The EPA's Review of the State's Submission
    We have reviewed the 2012 base year emissions inventory in the 2017
Sacramento Regional Ozone Plan, and the inventory methodologies used by
the District and CARB, for consistency with CAA requirements and EPA
guidance. First, as required by EPA regulation, we find that the 2012
inventory includes estimates of VOC and NOX for a typical
ozone season weekday and that CARB has provided adequate documentation
explaining how the emissions are calculated. Second, we find that the
2012 base year emissions inventory in the 2017 Sacramento Regional
Ozone Plan reflects appropriate emissions models and methodologies;
therefore, the submitted emissions inventory represents a
comprehensive, accurate, and current inventory of actual emissions
during that year in the Sacramento Metro Area. Third, we find that
selection of year 2012 for the base year emissions inventory is
appropriate because it is consistent with the 2011 RFP baseline year
(from the 2018 SIP Update) that is derived from a common set of models
and methods. Consequently, the EPA is proposing to approve the 2012
emissions inventory in the 2017 Sacramento Regional Ozone Plan as
meeting the requirements for a base year inventory set forth in CAA
section 182(a)(1) and 40 CFR 51.1115.
    With respect to future year baseline projections, we have reviewed
the growth and control factors and find them acceptable and conclude
that the future baseline emissions projections in the 2017 Sacramento
Regional Ozone Plan reflect appropriate calculation methods and the
latest planning assumptions. 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 newly
adopted or amended District rules for stationary sources, the related
rules must be approved by the EPA into the SIP. The 2017 Sacramento
Regional Ozone Plan emissions inventories reflect credit for local VOC
and NOX control measures adopted and submitted to CARB
through late 2015 and for the future effects of these currently adopted
control measures; no new future local stationary or area source control
measures were submitted or credited within the Plan. With respect to
mobile sources, the EPA has acted in recent years to approve CARB
mobile source regulations into the California SIP.\51\ CARB mobile
source control measures are reviewed in more detail in Sections III.C
and III.D of this action. Based on our review, we find that the future
year baseline projections in the 2017 Sacramento Regional Ozone Plan
are properly supported by SIP-approved stationary and mobile source
measures.
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    \51\ 81 FR 39424 (June 16, 2016), 82 FR 14446 (March 21, 2017),
and 83 FR 23232 (May 18, 2018).
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    In September 2019 and April 2020, the U.S. Department of
Transportation and the EPA published separate final actions concerning
the ``Safer Affordable Fuel-Efficient (SAFE) Vehicles Rule'' (``SAFE
rule'') that, among other things, withdrew the EPA's

2013 waiver of preemption for CARB's Zero Emissions Vehicle (ZEV) sales
mandate and Greenhouse Gas (GHG) standards that are applicable to new
model year 2021 through 2025 light-duty vehicles (``SAFE Part 1''), and
relaxed federal GHG emissions and fuel economy standards (``SAFE Part
2'').\52\ The future year emissions projections in the 2017 Sacramento
Regional Ozone Plan assume implementation of CARB's entire Advanced
Clean Cars (ACC) program including the third generation of Low-Emission
Vehicle (``LEV III'') criteria pollutant standards, but also including
the ZEV sales mandate and GHG standards. The Plan's on-road emissions
projections for NOX and VOCs are based on EMFAC2014, the
EPA-approved model at the time the Plan was developed, and assumptions
concerning implementation of the ACC program. Calculations for other
portions of the future year emissions inventories (e.g., the point and
area source portions of the inventories) also include assumptions about
the continued implementation of the ACC program, which were appropriate
when the plan was submitted in 2017.
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    \52\ 84 FR 51310 (September 27, 2019) and 85 FR 24174 (April 30,
2020).
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    In response to the EPA's final action on SAFE Part 1, CARB
developed adjustment factors for EMFAC to account for criteria
pollutant emissions increases associated with the revocation of the ZEV
sales mandate waiver.\53\ CARB's EMFAC off-model adjustment factors are
multipliers that are to be applied to gasoline-powered light-duty
automobiles, light-duty trucks and medium-duty vehicles modeled by
EMFAC2014 (and its more recent EPA-approved update, EMFAC2017). The EPA
reviewed CARB's EMFAC off-model adjustment factors and concluded that
they are acceptable for use because the effect of their application is
more conservative than necessary, and that, therefore, the factors may
be used in transportation conformity determinations and SIP
development.\54\ We applied the adjustment factors to the relevant
light duty gasoline motor vehicle source categories in the relevant
years, 2023--RFP year and 2024--attainment year, to estimate the VOC
and NOX increases in the Sacramento Metro Area relative to
those included in the Plan and found that the emissions increases were
so small as to be negligible.\55\
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    \53\ Letter dated March 5, 2020, from Steven S. Cliff, Deputy
Executive Officer, CARB, to Elizabeth Adams, Director, Air and
Radiation Division, EPA, Region IX; includes enclosure, ``EMFAC Off-
Model Adjustment Factors to Account for the SAFE Vehicles Rule Part
One,'' November 20, 2019. CARB has determined that additional EMFAC
adjustment factors for criteria pollutants are not needed in
response to SAFE Part 2; CARB, ``EMFAC Off-Model Adjustment Factors
for Carbon Dioxide (CO2) Emissions to Account for the
SAFE Vehicles Rule Part One and the Final SAFE Rule,'' June 26,
2020.
    \54\ Letter dated March 12, 2020, from Elizabeth J. Adams,
Director, Air and Radiation Division, EPA Region IX, to Steven
Cliff, Deputy Executive Officer, CARB.
    \55\ We estimated SAFE rule effects as follows: 2023 VOC and
NOX emissions increase 0.0115 and 0.0026 tons per day,
respectively; 2024 VOC and NOX emissions increase 0.0189
and 0.0047 tons per day, respectively.
---------------------------------------------------------------------------

    SAFE Parts 1 and 2 could result in a higher level of gasoline
production, transport, and usage, with associated upstream emissions,
than had been assumed for the Plan. We believe, however, that the
incremental increase in upstream impacts would be limited between now
and 2024, the last year addressed in this Plan. Moreover, the relevant
source categories that may be affected by increased gasoline
production, transport, and usage: Oil and gas production (combustion),
and petroleum production and marketing, collectively represent only 5.6
percent of the area's projected VOC emissions estimates and 0.02
percent of the area's projected NOX emissions estimates for
the relevant years.\56\ As such, the anticipated small incremental
increase in emissions from these upstream sources due to higher-than-
expected gasoline consumption in the wake of SAFE Part 1 and SAFE Part
2 would be inconsequential from the standpoint of the RFP and
attainment demonstrations in the Plan. Therefore, we find that the
regulatory changes established by the SAFE Part 1 and Part 2 final
rules do not undermine the RFP and attainment demonstrations in the
Sacramento Metro Area Ozone SIP.
---------------------------------------------------------------------------

    \56\ Total petroleum production and marketing VOC and
NOX emissions in the Sacramento Metro Area are estimated
as follows: 4.72 tpd and 0.01 tpd in 2023, respectively; and, 4.62
tpd and 0.01 tpd in 2024, respectively. Total VOC and NOX
emissions in the Sacramento Metro Area are estimated as follows:
83.46 and 48.25 in 2023, respectively; and, 82.86 and 46.53,
respectively. 2018 SIP Update, A-15 to A-18.
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B. Emissions Statement

1. Statutory and Regulatory Requirements
    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 tons per year
(tpy) of VOC or NOX, if the state provides an inventory of
emissions from such class or category of sources as part of the base
year or periodic inventories required under CAA sections 182(a)(1) and
182(a)(3)(A), based on the use of emission factors established by the
EPA or other methods acceptable to the EPA.
    The preamble of the 2008 Ozone SRR states that if an area has a
previously approved emissions statement rule for the 1997 ozone NAAQS
or the 1-hour ozone NAAQS that covers all portions of the nonattainment
area for the 2008 ozone NAAQS, such rule should be sufficient for
purposes of the emissions statement requirement for the 2008 ozone
NAAQS.\57\ The state should review the existing rule to ensure it is
adequate and, if so, may rely on it to meet the emissions statement
requirement for the 2008 ozone NAAQS. Where an existing emissions
statement requirement is still adequate to meet the requirements of
this rule, states can provide the rationale for that determination to
the EPA in a written statement in the SIP to meet this requirement.
States should identify the various requirements and how each is met by
the existing emissions statement program. Where an emissions statement
requirement is modified for any reason, a state must provide the
revision to the emissions statement as part of its SIP.
---------------------------------------------------------------------------

    \57\ 80 FR 12264, 12291 (March 6, 2015).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    The Districts in the Sacramento Metro Area have adopted and CARB
has submitted emissions statement rules for incorporation into the
California SIP. The EPA has reviewed and approved into the SIP the
rules listed in Table 3.

Table 3--EPA-Approved Emissions Statement Rules for the Sacramento Metro
                                  Area
------------------------------------------------------------------------
                                                      EPA approval date
          District              Rule No. and name         and cite
------------------------------------------------------------------------
SMAQMD......................  Rule 105, Emission    73 FR 32240, June 6,
                               Statements.           2008.
EDCAQMD.....................  Rule 1000, Emission   69 FR 29880, May 26,
                               Statement.            2004.
FRAQMD......................  Rule 4.8, Further     69 FR 29880, May 26,
                               Information.          2004.
YSAQMD......................  Rule 3.18, Emission   69 FR 29880, May 26,
                               Statements.           2004.
PCAPCD......................  Rule 503, Emission    77 FR 72968,
                               Statement.            December 7, 2012.
------------------------------------------------------------------------

    The CARB Staff Report submitted with the 2017 Sacramento Regional
Ozone Plan certified the submittal and EPA approval of the Districts'
emissions statement rules and their applicability to the area.\58\ CARB
certified that these emissions statement rules are applicable to the
area and the 75 ppb ozone standard because the nonattainment area
boundaries have not changed since the EPA's approval of these rules and
the reporting thresholds within the rules are appropriate.
---------------------------------------------------------------------------

    \58\ CARB Staff Report, 7. The CARB Staff Report cites a June 6,
2006 rulemaking for SMAQMD Rule 105; while the Federal Register
citation is correct, the correct date is June 6, 2008. The EPA's
2012 approval of PCAPCD Rule 503 provided in Table 3 is not cited by
CARB.
---------------------------------------------------------------------------

3. The EPA's Review of the State's Submission
    As noted above, the EPA has reviewed and approved the Districts'
emissions statement rules as meeting the requirements of section
182(a)(3)(B) and incorporated them into the SIP. Also, although the
emissions reporting requirements in these rules do not apply to
permitted sources of emissions less than 10 or 25 tpy (depending on the
subject rule), we note that such an exclusion is allowed under CAA
section 182(a)(3)(B)(ii), so long as the state includes estimates of
such class or category of stationary sources in base year emissions
inventories and periodic inventories, submitted under CAA sections
182(a)(1) and 182(a)(3)(A), based on EPA emission factors or other
methods acceptable to the EPA. The EPA has routinely approved emissions
inventories developed by the Districts and CARB for the Sacramento
Metro Area that include actual emissions estimates for all stationary
sources or classes or categories of such sources, including those
emitting less than the reporting thresholds within these emissions
statement rules, and that such inventories provide the basis for
inventories submitted to meet the requirements of CAA sections
182(a)(1) and 182(a)(3)(A). Most recently, we approved the base year
emissions inventory for the 1997 8-hour ozone NAAQS on January 29,
2015.\59\ Similarly, we are proposing approval of the base year
inventory for the 2008 ozone NAAQS, as noted in the previous section.
Therefore, for the reasons described above, we propose to approve the
2017 Sacramento Regional Ozone Plan as meeting the emissions statement
requirements under CAA section 182(a)(3)(B).
---------------------------------------------------------------------------

    \59\ 80 FR 4795.
---------------------------------------------------------------------------

C. Reasonably Available Control Measures Demonstration

1. Statutory and Regulatory Requirements
    CAA section 172(c)(1) requires that each attainment plan provide
for the implementation of all RACM as expeditiously as practicable
(including such reductions in emissions from existing sources in the
area as may be obtained through implementation of reasonably available
control technology (RACT)) and for attainment of the NAAQS. For each
nonattainment area required to submit an attainment demonstration, the
2008 Ozone SRR requires that the state concurrently submit a SIP
revision showing that it has adopted all RACM necessary to demonstrate
attainment as expeditiously as practicable and to meet any RFP
requirements.\60\
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    \60\ 40 CFR 51.1112(c).
---------------------------------------------------------------------------

    The EPA has 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.''
\61\ In short, to address the requirement to adopt all RACM, states
should consider all potentially reasonable control measures for source
categories in the nonattainment area to determine whether they are
reasonably available for implementation in that area and whether they
would, if implemented individually or collectively, advance the area's
attainment date by one year or more.\62\ Any measures that are
necessary to meet these requirements that are not 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.
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    \61\ General Preamble, 57 FR 13498, 13560 (April 16, 1992) and
memorandum dated November 30, 1999, from John Seitz, Director,
OAQPS, to Regional Air Directors, titled ``Guidance on the
Reasonably Available Control Measure Requirement and Attainment
Demonstration Submissions for Ozone Nonattainment Areas.''
    \62\ Id. 44 FR 20372 (April 4, 1979), and memorandum dated
December 14, 2000, from John S. Seitz, Director, OAQPS, to Regional
Air Directors, titled ``Additional Submission on RACM from States
with Severe 1-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 (CTG). CAA section 182(f)
requires that RACT under section 182(b)(2) also apply to major
stationary sources of NOX. In Severe-15 areas, a major
source is a stationary source that emits or has the potential to emit
at least 25 tpy of VOC or NOX (see CAA section 182(d) and
(f)). CARB has submitted separate SIP revisions to address these
requirements for each of the Districts.\63\ We are not addressing the
section 182 RACT requirements in today's proposed rule.
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    \63\ The EPA fully approved the submissions for EDCAQMD (83 FR
67696, December 31, 2018), FRAQMD (80 FR 38959, July 18, 2015), and
PCAPCD (82 FR 38604, August 15, 2017). The EPA has not yet acted on
the SMAQMD and YSAQMD submissions.
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2. Summary of the State's Submission
    For the 2017 Sacramento Regional Ozone Plan, the Districts, SACOG,
and CARB undertook collective and individual processes to identify and
evaluate potential RACM that could contribute to expeditious attainment
of the 2008 ozone NAAQS in the Sacramento Metro Area. We describe each
agency's evaluation below.
a. The Districts' RACM Analysis
    The Districts' RACM demonstration for the 2008 ozone NAAQS focuses
on stationary and area source controls, and is described in Appendix E
(``Reasonably Available Control

Measures (RACM) Analysis'') of the 2017 Sacramento Regional Ozone Plan.
Appendix E contains summary analyses of all potential control measures
for emissions reduction opportunities, as well as their economic and
technological feasibility. As a first step in the RACM analysis, the
Districts prepared a detailed inventory of emissions sources that emit
VOC and NOX to identify source categories from which
emissions reductions would effectively contribute to attainment.
Details on the methodology and development of this source category and
control measure review are discussed in chapter 7 and appendix E of the
2017 Sacramento Regional Ozone Plan.\64\
---------------------------------------------------------------------------

    \64\ 2017 Sacramento Regional Ozone Plan, Appendix E provides
the overall discussion, while tables E-1 through E-5 list the
Districts' rules that were reviewed for RACM.
---------------------------------------------------------------------------

    The Districts' RACM analysis builds upon a foundation of the
respective rules developed for earlier ozone plans and approved as part
of the SIP, e.g., the Sacramento 8-Hour Ozone Attainment Plan for the
1997 8-hour ozone standard. The Districts' rules listed in Tables E-1
to E-5 of the 2017 Sacramento Regional Ozone Plan establish emissions
limits or other types of emissions controls for a wide range of
sources, including use of solvents, refineries, gasoline storage,
architectural coatings, spray booths, various types of commercial
coatings, boilers, steam generators and process heaters, oil and gas
production wells, and many more. These rules have already provided
significant and ongoing reductions toward attainment of the 2008 ozone
NAAQS by 2024.
    To identify all potential RACM, staff from the Districts reviewed
multiple sources of control measure information. These sources included
past regional ozone plans, rules adopted between January 2006 and July
2013 by other California air quality management districts, the EPA's
``RACT/BACT/LAER Clearinghouse,'' \65\ CARB's BACT Clearinghouse, the
Bay Area AQMD's 2010 Clean Air Plan, the South Coast AQMD's 2012 Air
Quality Management Plan, and rules from ozone nonattainment areas in
other states, such as Houston-Galveston-Brazoria (Texas), Dallas-Fort
Worth (Texas), and Baltimore (Maryland). Next, the Districts performed
the RACM analyses for the stationary and areawide sources within their
jurisdictions. For each potential RACM measure, Districts' staff
estimated the emissions inventory, emissions reductions, and cost
effectiveness. With this process, the Districts evaluated and analyzed
all reasonable control measures that were available to include within
the 2017 Sacramento Regional Ozone Plan. The Districts determined that
emissions reductions associated with the evaluated control measures
would not advance the area's attainment date or RFP because the
emission reductions, in total, were either too small or
unquantifiable.\66\
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    \65\ LAER means lowest achievable emission rate. For more
information on the RACT/BACT/LAER Clearinghouse, see https://cfpub.epa.gov/RBLC/index.cfm?action=Home.Home⟨=en.
    \66\ 2017 Sacramento Regional Ozone Plan, Appendix E and Tables
E-1 through Table E-5. These tables present a list of the individual
district rules and control measures evaluated by the Districts and a
brief discussion of their respective conclusions for each district
rule or source category.
---------------------------------------------------------------------------

    As discussed above, the Districts are required to make submittals
addressing the CAA section 182(b)(2) requirement to implement RACT for
all major sources of VOC and for each VOC source category for which the
EPA has issued control techniques guidelines. CAA section 182(f)
requires that RACT under section 182(b)(2) also apply to major
stationary sources of NOX. California has submitted the CAA
section 182 RACT SIPs from the Districts, and the EPA has approved the
submittals from EDCAQMD, FRAQMD, and PCAPCD. The CARB Staff Report,
submitted with the 2017 Sacramento Regional Ozone Plan, identified
commitments by SMAQMD and YSAQMD to submit or amend rules for several
source categories to address the RACT SIP requirement.\67\ As a result,
the SMAQMD and YSAQMD adopted or amended the following stationary
source rules: SMAQMD Rule 419 (``Miscellaneous Combustion Units'');
SMAQMD Rule 468 (``Plastic Parts''); and YSAQMD Rule 2.29 (``Graphic
Arts''). Subsequently, the State submitted these rules to the EPA in
2018 and 2019.\68\ Within the 2017 Sacramento Regional Ozone Plan, the
SMAQMD and YSAQMD evaluated these rules and/or the relevant source
categories for RACM and found that controls applied to these sources
would not individually or collectively advance the attainment date.\69\
The control strategy for the Sacramento Metro Area Ozone SIP, overall,
takes credit for emissions reductions from the Districts' stationary or
area source rules adopted or amended before late 2015.\70\
Consequently, any emission reductions after 2015 and associated with
the later 2018 amendments to or adoption of these SMAQMD and YSAQMD
rules to meet the CAA section 182(b)(2) requirement are not credited or
incorporated within the attainment demonstration of the Sacramento
Metro Area Ozone SIP. Accordingly, the EPA's approval of these three
rules, submitted in 2018 and 2019, are not required for our proposed
action on the Sacramento Metro Area Ozone SIP; however, our review and
approval into the SIP of these local rules remain relevant for our
action on the submitted RACT SIPs, in accordance with CAA section
182(b)(2).
---------------------------------------------------------------------------

    \67\ CARB Staff Report, 9.
    \68\ California submitted these rules to the EPA on the
following dates: SMAQMD Rule 419 on August 15, 2018 and January 23,
2019; SMAQMD Rule 468 on May 18, 2018; and YSAQMD Rule 2.29 on
August 15, 2018.
    \69\ 2017 Sacramento Regional Ozone Plan, Appendix E.4, Table E-
1, and Appendix E.8, Table E-5.
    \70\ 2017 Sacramento Regional Ozone Plan, 5-11 and 7-12 to 7-14.
---------------------------------------------------------------------------

b. Local Jurisdictions' RACM Analysis and Transportation Control
Measures
    The 2017 Sacramento Regional Ozone Plan's Appendix E-9
(``Sacramento Area Council of Governments (SACOG) Transportation
Control Measures Considered''), contains the transportation control
measures (TCMs) RACM component for the plan. This analysis was
conducted by SACOG, the MPO for the Sacramento Metro Area region. In
its initial analysis, SACOG conducted a comprehensive review of
implemented TCMs in California and other states, measures and
strategies from the Sacramento Region's 2009 Ozone SIP, and statewide
and mobile source emissions reduction strategies, and identified almost
100 potential TCM measures. Of these, SACOG selected and analyzed 22
measures that were not already implemented in Sacramento Metro Area.
These measures were assessed based on the criteria specified in the
2015 Ozone SRR and the EPA's RACT guidance, such as technical and
economic feasibility, enforceability, local applicability, and the
measures' ability to provide emission reductions before 2026 to advance
attainment of the ozone standard. A summary of SACOG's findings for
each measure is provided in Table E-6 of the 2017 Sacramento Regional
Ozone Plan. Using the assessment criteria, SACOG concluded that none of
the additional 22 measures that they identified were appropriate for
implementation. Individual measures were economically infeasible, and
when considered together, the 22 measures did not advance attainment of
the ozone standard by one year. Based on this comprehensive review of
TCM projects, SACOG determined that the TCMs being

implemented in the Sacramento Metro Area are inclusive of all RACM.\71\
---------------------------------------------------------------------------

    \71\ 2017 Sacramento Regional Ozone Plan, 7-16 and Appendix E-9,
E-33.
---------------------------------------------------------------------------

c. CARB's RACM Analysis
    CARB's RACM analysis is contained in Appendix E-10 (``California
Mobile Source Reasonably Available Control Measures Assessment'') of
the 2017 Sacramento Regional Ozone Plan. This analysis provides a
general description of CARB's existing mobile source programs. A more
detailed description of these mobile source control programs, including
comprehensive tables listing on- and off-road mobile source regulatory
actions taken by CARB since as early as 1985, is contained in Section
7.2 of the 2017 Sacramento Regional Ozone Plan. Collectively, the
Appendix E.10 RACM analysis and Section 7.2 contain CARB's evaluation
of mobile source and other statewide control measures that reduce
emissions of NOX and VOC in the Sacramento Metro Area.
    Within California, CARB has primary responsibility for reducing
emissions in several state-wide source categories, including most new
and existing on- and off-road engines and vehicles, motor vehicle
fuels, and consumer products. Given the need for substantial emissions
reductions from mobile and area sources to meet the NAAQS in California
nonattainment areas, CARB has developed stringent control measures for
on-road and off-road mobile sources and their related fuels. California
has 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 engine standards, gasoline and diesel fuel
specifications, and other requirements to control emissions from in-use
heavy-duty trucks and buses and many other types of mobile sources.
Generally, these regulations have been submitted and approved as
revisions to the California SIP.\72\
---------------------------------------------------------------------------

    \72\ See, e.g., 77 FR 20308 (April 4, 2012), the EPA's approval
of standards and other requirements to control emissions from in-use
heavy-duty diesel-powered trucks; 75 FR 26653 (May 12, 2010),
revisions to the California on-road reformulated gasoline and diesel
fuel regulations; and, 75 FR 38023 (July 1, 2010), revisions to the
California motor vehicle inspection and maintenance program.
---------------------------------------------------------------------------

    Based on the strength of the measures included in the current
statewide mobile source program, and the extensive public process
involved in developing that program, CARB concluded that there are no
additional RACM that would further advance attainment of the 2008 ozone
NAAQS in the Sacramento Metro Area, and as a result, that California's
mobile source programs fully meet the RACM requirement.\73\
---------------------------------------------------------------------------

    \73\ 2017 Sacramento Regional Ozone Plan, Appendix E.10, E-37.
CARB's 2016 Mobile Source Strategy and the public process they
conducted for this submittal is referenced in the appendix at
footnote 2, E-34.
---------------------------------------------------------------------------

3. The EPA's Review of the State's Submission
    As described above, collectively, the Districts already implement
many rules to reduce VOC and NOX emissions from stationary
and area sources in the Sacramento Metro Area. For the Sacramento Metro
Area Ozone SIP, the Districts evaluated a wide range of potentially
available measures. We find that the process followed by the Districts
and described in the 2017 Sacramento Regional Ozone Plan to identify
additional RACM is generally consistent with the EPA's recommendations
in the General Preamble, that the Districts' evaluation of potential
measures to be appropriate, and that the Districts have provided
reasoned justifications that additional measures would not advance
attainment. Regarding TCMs, we find that SACOG's process for
identifying additional TCM RACM and conclusion that the TCMs being
implemented in the Sacramento Metro Area (identified in Section 7.7 and
Table E-6 of the 2017 Sacramento Regional Ozone Plan), are inclusive of
all TCM RACM that are reasonably justified and supported.
    With respect to mobile sources, CARB's current program addresses
the full range of mobile sources in the Sacramento Metro Area through
regulatory programs for both new and in-use vehicles. We find that the
process conducted by CARB, as described in Appendix E.10, was
reasonably designed to identify additional available measures within
CARB's jurisdiction, and that CARB has adopted those measures that are
reasonably available.
    Based on our review of these RACM analyses and the Districts' and
CARB's adopted rules, we propose to find that there are, at this time,
no additional RACM that would further advance attainment of the 2008
ozone NAAQS in the Sacramento Metro Area. For the foregoing reasons, we
propose to find that the Sacramento Metro Area Ozone SIP provides for
the implementation of all RACM as required by CAA section 172(c)(1) and
40 CFR 51.1112(c).
    If finalized, this finding under CAA section 172(c)(1) does not
affect the State's and the EPA's continuing obligation under CAA
sections 182(b)(2) and (f) and 40 CFR 51.905(a)(1)(ii) to implement
RACT on all major sources and all CTG source categories.

D. Attainment Demonstration

1. Statutory and Regulatory Requirements
    An attainment demonstration consists of the following: (1)
Technical analyses, such as base year and future year modeling, to
locate and identify sources of emissions that are contributing to
violations of the ozone NAAQS within the nonattainment area (i.e.,
analyses related to the emissions inventory for the nonattainment area
and the emissions reductions necessary to attain the standard); (2) a
list of adopted measures (including RACT controls) with schedules for
implementation and other means and techniques necessary and appropriate
for demonstrating RFP and attainment as expeditiously as practicable
but no later than the outside attainment date for the area's
classification; (3) a RACM analysis; and, (4) contingency measures
required under sections 172(c)(9) and 182(c)(9) of the CAA that can be
implemented without further action by the state or the EPA to cover
emissions shortfalls in RFP plans and failures to attain.\74\ This
subsection of today's proposed rule addresses the first two components
of the attainment demonstration--the technical analyses and a review of
adopted measures. Section III.C (``Reasonably Available Control
Measures Demonstration'') of this document addresses the RACM
component, and section III.G (``Contingency Measures'') addresses the
contingency measures component of the attainment demonstration in the
Sacramento Metro Area Ozone SIP.
---------------------------------------------------------------------------

    \74\ 78 FR 34178, 34184 (June 6, 2013), the EPA's proposed rule
for implementing the 2008 ozone NAAQS.
---------------------------------------------------------------------------

    With respect to the technical analyses, section 182(c)(2)(A) of the
CAA requires that a plan for an ozone nonattainment area classified
Serious or above include a ``demonstration that the plan . . . will
provide for attainment of the ozone [NAAQS] by the applicable
attainment date. This attainment demonstration must be based on
photochemical grid modeling or any other analytical method determined .
. . to be at least as effective.'' The attainment demonstration
predicts future ambient concentrations for comparison to the NAAQS,
making use of available information on measured

concentrations, meteorology, and current and projected emissions
inventories of ozone precursors, including the effect of control
measures in the plan. Areas classified Severe-15 for the 2008 ozone
NAAQS must demonstrate attainment as expeditiously as practicable, but
no later than 15 years after the effective date of designation as
nonattainment. The Sacramento Metro Area was designated nonattainment
for the 2008 ozone NAAQS effective July 20, 2012,\75\ and accordingly
must demonstrate attainment of the standards by no later than July 20,
2027.\76\ An attainment demonstration must show attainment of the
standards for a full calendar year before the attainment date, so in
practice, Severe-15 nonattainment areas must demonstrate attainment no
later than 2026.
---------------------------------------------------------------------------

    \75\ 77 FR 30088 (May 21, 2012).
    \76\ 80 FR 12264 (March 6, 2015).
---------------------------------------------------------------------------

    The EPA's recommended procedures for modeling ozone as part of an
attainment demonstration are contained in ``Modeling Guidance for
Demonstrating Attainment of Air Quality Goals for Ozone,
PM2.5, and Regional Haze'' (``Modeling Guidance'').\77\ The
Modeling Guidance includes recommendations for a modeling protocol,
model input preparation, model performance evaluation, use of model
output for the numerical NAAQS attainment test, and modeling
documentation. Air quality modeling is performed using meteorology and
emissions from a base year, and the predicted concentrations from this
base case modeling are compared to air quality monitoring data from
that year to evaluate model performance. Once the model performance is
determined to be acceptable, future year emissions are simulated with
the model. The relative (or percent) change in modeled concentration
due to future emissions reductions provides a relative response factor
(RRF). Each monitoring site's RRF is applied to its monitored base year
design value to provide the future design value for comparison to the
NAAQS. The Modeling Guidance also recommends supplemental air quality
analyses, which may be used as part of a weight of evidence (WOE)
analysis. A WOE analysis corroborates the attainment demonstration by
considering evidence other than the main air quality modeling
attainment test, such as trends and additional monitoring and modeling
analyses.
---------------------------------------------------------------------------

    \77\ ``Modeling Guidance for Demonstrating Attainment of Air
Quality Goals for Ozone, PM2.5, and Regional Haze,'' EPA
454/R-18-009; available at https://www.epa.gov/scram/state-implementation-plan-sip-attainment-demonstration-guidance. See also
December 2014 draft of this guidance, available at https://www3.epa.gov/ttn/scram/guidance/guide/Draft-O3-PM-RH-Modeling_Guidance-2014.pdf. The December 2014 draft guidance was
available during development of the Plan; the final version differs
mainly in organization, and in updates to the regional haze portion
and to other document references. Additional EPA modeling guidance
can be found in 40 CFR 51 Appendix W, Guideline on Air Quality
Models, 82 FR 5182 (January 17, 2017); available at https://www.epa.gov/scram/clean-air-act-permit-modeling-guidance.
---------------------------------------------------------------------------

    The Modeling Guidance also does not require a particular year to be
used as the base year for 8-hour ozone plans.\78\ The Modeling Guidance
states that the most recent year of the National Emissions Inventory
may be appropriate for use as the base year for modeling, but that
other years may be more appropriate when considering meteorology,
transport patterns, exceptional events, or other factors that may vary
from year to year.\79\ 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.
---------------------------------------------------------------------------

    \78\ Modeling Guidance at section 2.7.1, 35.
    \79\ Id.
---------------------------------------------------------------------------

    For a more detailed discussion of photochemical modeling guidance
recommendations, please see the technical support document (TSD)
provided in the docket for this proposal.
    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.\80\ Under the 2008 Ozone SRR, all control
measures needed for attainment must be implemented no later than the
beginning of the attainment year ozone season.\81\ The attainment year
ozone season is defined as the ozone season immediately preceding a
nonattainment area's maximum attainment date; in the case of the
Sacramento Metro area, the attainment year is 2026.\82\
---------------------------------------------------------------------------

    \80\ See also CAA section 110(a)(2)(A).
    \81\ 40 CFR 51.1108(d).
    \82\ 40 CFR 51.1100(h).
---------------------------------------------------------------------------

2. Summary of the State's Submission
a. Photochemical Modeling
    CARB performed the air quality modeling for the Sacramento Metro
Area Ozone SIP with assistance from the Districts and has included
documentation of this modeling within the 2017 Sacramento Regional
Ozone Plan and the CARB Staff Report. The modeling relies on a 2012
base year and projects design values for 2022 and 2026. As discussed
below, CARB also included an interpolation of NOX emissions
to estimate the design value in the attainment year 2024. The
attainment plan's modeling protocol is in Appendix B-3 of the 2017
Sacramento Regional Ozone Plan and contains all the elements
recommended in the Modeling Guidance.
    The modeling and modeled attainment demonstration are described in
Chapter 6 of the 2017 Sacramento Regional Ozone Plan and in more detail
in Appendix B-4, which provides a description of model input
preparation procedures and various model configuration options.
Appendix B-5 of the 2017 Sacramento Regional Ozone Plan provides the
coordinates of the modeling domain and 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 modeling analysis
used version 5 of the Community Multiscale Air Quality (CMAQ)
photochemical model developed by the EPA. To prepare meteorological
input for CMAQ, CARB used the Weather and Research Forecasting model
version 3.6 (WRF) from the National Center for Atmospheric Research.
The WRF modeling uses routinely available meteorological and air
quality data collected during 2012. Those data cover May through
September, a period that spans the period of highest ozone
concentrations in the Sacramento Metro Area. 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 were adequate for modeling Sacramento Metro Area
ozone.
    The WRF meteorological model results and performance statistics are
described in Appendix B-4.\83\ There is a slight underprediction of
wind speeds and overprediction of temperatures in the eastern portion
of the nonattainment area; but overall, modeled wind speed, temperature
and relative humidity all track observations well, as shown in scatter
and time series plots. The modeling was able to replicate some
important meteorological features such as the bifurcation of the delta
breeze from the ocean into northern and

southern branches, and afternoon upslope flows in the Sierra Nevada
foothills. The 2017 Sacramento Regional Ozone Plan states that the bias
and error are relatively small and are comparable to those seen in
previous meteorological modeling of central California and cited in the
2017 Sacramento Regional Ozone Plan. In summary, the 2017 Sacramento
Regional Ozone Plan's meteorological modeling performance statistics
appear satisfactory.
---------------------------------------------------------------------------

    \83\ Appendix B-4, section 3.2, B-125; also, refer to
supplemental figures S.1-S.15 at B-166.
---------------------------------------------------------------------------

    Ozone model performance statistics are described in the 2017
Sacramento Regional Ozone Plan at Appendix B-4.\84\ It includes tables
of statistics recommended in the Modeling Guidance for 8-hour and 1-
hour daily maximum ozone concentrations, for the whole nonattainment
area and for three Sacramento Metro Area subregions (i.e., western,
central, and eastern. There is a slight negative bias (underprediction)
for the central and eastern subregions. Because only the relative
response to emissions changes from the modeling is used, note that the
underprediction of absolute ozone concentrations does not mean that
future concentrations will be underestimated. The 2017 Sacramento
Regional Ozone Plan found the statistics to be within the ranges for
other modeling applications, at the low end of the distribution for
error and bias. The Plan's supplemental figures with hourly time series
show generally good performance; although some individual daily ozone
peaks are missed, for each site there are days for which the modeled
highest concentration is close to the value of the highest observed
concentration.
---------------------------------------------------------------------------

    \84\ Appendix B-4, section 5.2, B-139; also, refer to
supplemental figures S.16-S.69, B-182.
---------------------------------------------------------------------------

    As noted in the 2017 Sacramento Regional Ozone Plan's modeling
protocol, the Modeling Guidance recognizes that limited time and
resources can constrain the extent of the diagnostic and dynamic
evaluation of model performance undertaken.\85\ The 2017 Sacramento
Regional Ozone Plan describes a dynamic evaluation \86\ in which model
predictions of ozone concentrations for weekdays and weekends were
compared to each other and to observed concentrations. This evaluation
provides useful information on how well the model simulates the effect
of emissions changes, since NOX emissions are lower on
weekends than on weekdays, but otherwise similar. The model-predicted
ozone reduction on weekends tends to match the observed ozone
reduction; this match lends confidence to the modeling. The modeled
weekend response is also consistent with an independent study \87\ that
examined the frequency of ozone exceedance days over 2001-2007 and the
NOX emission reductions during the same period. The study
concluded the NOX reductions were effective at reducing
ozone throughout the entire Sacramento urban ozone plume (i.e.,
downwind and northeast of urban Sacramento, within the nonattainment
area), which exhibits ``NOX-limited'' ozone chemistry except
in the urban core, and is expected to transition to NOX-
limited conditions everywhere in the nonattainment area as
NOX emissions continue to decline.\88\ The Plan also
contains results of an analysis of weekday and weekend ozone
concentrations during the 2000-2014 period. It notes a shift over the
years toward lower ozone on weekends, especially after 2010, showing
that lower NOX emissions lead to lower ozone
concentrations.\89\ Both the modeling and the observed weekday-weekend
trends throughout the Sacramento Metro Area show that ozone responds to
NOX emission reductions, i.e., that ozone formation is
NOX-limited.
---------------------------------------------------------------------------

    \85\ 2017 Sacramento Regional Ozone Plan, Appendix B-3
(``Modeling Protocol''), B-76; Modeling Guidance, 63.
    \86\ See ``Diagnostic Evaluation'' in Appendix B-4 section
5.2.1, B-146.
    \87\ La Franchi et al., ``Observations of the temperature
dependent response of ozone to NOX reductions in the
Sacramento, CA urban plume,'' Atmospheric Chemistry and Physics, 11,
6945-6960, doi:10.5194/acp-11-6945-2011, 2011; described in Appendix
B, B-150.
    \88\ The term ``NOX-limited'' can mean either that
reducing NOX emissions decrease ozone (as opposed to
increasing it); or that reducing NOX is much more
effective at decreasing ozone than is reducing VOC. Both are true in
this case; as discussed below, ambient Sacramento Metro Area ozone
responds only weakly to VOC reductions. The NOX-limited
ozone regime in the Sacramento Metro Area is discussed in Plan
Appendix B. See, e.g., B-147 through B-150 (comparing weekend-
weekday concentrations); B-150 through B-152; B-157 through B-158.
The issue is also discussed in the CARB Staff Report Appendix B, B-
17 and B-36.
    \89\ 2017 Sacramento Regional Ozone Plan, Appendix B, B-149.
---------------------------------------------------------------------------

    After model performance for the 2012 base case was accepted, the
model was applied to develop RRFs for the attainment demonstration.\90\
This entailed running the model with the same meteorological inputs as
before, but with adjusted emissions inventories to reflect the expected
changes between the 2012 base year and the 2022 and 2026 future years.
These modeling inventories excluded ``emissions events which are either
random and/or cannot be projected to the future . . . wildfires, and
events such as the [San Francisco Bay Area] Chevron refinery fire.''
\91\ The future inventories project the base year with these exclusions
into the future by including the effect of economic growth and
emissions control measures.
---------------------------------------------------------------------------

    \90\ 2017 Sacramento Regional Ozone Plan, section 6.8, 6-10, and
Appendix B-4, section 5.3, B-150.
    \91\ 2017 Sacramento Regional Ozone Plan, Appendix B-3
(``Modeling Protocol''), B-78; and, Appendix B-5 (``Modeling
Emissions Inventory''), B-259. To include the fires in the base year
but not the future year would effectively credit the Plan's control
measures with eliminating emissions from the fire.
---------------------------------------------------------------------------

    The 2017 Sacramento Regional Ozone 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; these
were then applied to 2012 weighted base year design values for each
monitor to arrive at future year design values.\92\ The highest 2022
ozone design value is 75.2 ppb, which occurs at the Folsom Natoma
Street site, and just barely meets the level of the 2008 8-hour ozone
NAAQS of 0.075 ppm.\93\ The highest 2026 ozone design value is 70.7 ppb
at the same monitoring site, and is well below the NAAQS.
---------------------------------------------------------------------------

    \92\ 2017 Sacramento Regional Ozone Plan, Table 6-2 and Appendix
B-4, Table 13, B-151.
    \93\ The Modeling Guidance recommends that RRFs be applied to
the average of three three-year design values centered on the base
year, in this case the design values for 2010-2012, 2011-2013, and
2012-2015. This amounts to a 5-year weighted average of individual
year 4th high concentrations, centered on the base year of 2012, and
so is referred to as a weighted design value. 75.2 ppb is equivalent
to 0.0752 ppm, which is truncated to 0.075 ppm according to the data
handling conventions of 40 CFR 50 Appendix P.
---------------------------------------------------------------------------

    As discussed in chapter 8 of the 2017 Sacramento Regional Ozone
Plan, the reduction per year needed from the monitored design value of
83 in 2016 to the projected 75 in 2022 was roughly twice the reduction
per year seen during 2010-2016. Given the uncertainty posed by the
magnitude of the reductions necessary to reach this level by 2022
relative to the historic rate of reduction, and the fact that 2022
design values would achieve the standard by only a very small margin,
the Districts determined that a 2024 attainment year would be more
appropriate, while still representing an ambitious target for
expeditious attainment in advance of the statutory outermost deadline
for attainment.\94\ Since modeling was not available for year 2024, the
plan interpolated between the 2022 and 2026 modeling results, on the
basis of projected NOX emissions. The Plan's discussion of
the weekend-weekday

differences, described above, notes that the area's ozone formation is
NOX-limited, so NOX emissions are a reasonable
basis for interpolation. The interpolation is a form of a scaling of
model results and has been done for previous EPA-approved plans.\95\
The interpolation gives a 2024 design value estimate of 72.1 ppb,
corresponding to 0.072 ppm, which is below the 2008 8-hour ozone NAAQS
of 0.075 ppm, and therefore demonstrates attainment in 2024.\96\
---------------------------------------------------------------------------

    \94\ 2017 Sacramento Regional Ozone Plan, 8-2. Here, the year
2024 is discussed for modeling purposes. As noted earlier, the
effective attainment date for a determination of attainment is
December 31, 2024 if we approve this attainment demonstration as we
propose.
    \95\ San Joaquin Valley ``phase 2'' plan for the 2008 ozone
NAAQS, 83 FR 61346 (November 29, 2018), and revisions to the San
Joaquin Valley plan for the 1997 ozone NAAQS, 77 FR 12652 (March 1,
2012).
    \96\ 2017 Sacramento Regional Ozone Plan, 8-4.
---------------------------------------------------------------------------

    Finally, the 2017 Sacramento Regional Ozone Plan modeling includes
an ``Unmonitored Area Analysis'' (UAA) to assess whether locations
without a monitor are able to reach attainment; the standard attainment
test procedure covers only locations with a monitor.\97\ The Modeling
Guidance describes a procedure utilizing ``gradient adjusted spatial
fields,'' as well as the EPA software used to carry it out.\98\ This
procedure uses a form of interpolation, combining monitored
concentrations and modeled gradients (modeled changes in concentration
with distance from a monitor) to estimate future concentrations at
locations without a monitor. The 2017 Sacramento Regional Ozone Plan
describes an UAA carried out using software developed by CARB and
implemented in ``R,'' \99\ using a procedure virtually the same as that
outlined in the Modeling Guidance. The 2017 Sacramento Regional Ozone
Plan states that the 2026 results showed concentrations below 70 ppb
for all locations except for one grid square at Folsom Lake; the Plan
notes that this was likely an artifact of too-low mixing heights, a
known problem over water. Because the results are well below the 2008
ozone NAAQS level of 75 ppb, the UAA supports the demonstration that
all locations in the Sacramento Metro Area will attain the NAAQS by
2024.
---------------------------------------------------------------------------

    \97\ 2017 Sacramento Regional Ozone Plan, Appendix B-4, section
5.4.
    \98\ Modeling Guidance section 4.7.
    \99\ The R Project for Statistical Computing, https://www.r-project.org.
---------------------------------------------------------------------------

    In addition to the formal attainment demonstration, the plan also
contains a WOE analysis within Appendix B to the CARB Staff Report. It
mainly shows the long-term downward trends that continue through 2015,
the latest year available prior to 2017 Sacramento Regional Ozone Plan
development. Downward trends are demonstrated for measured ozone
concentrations, number of days above the ozone NAAQS, geographic area
and population exposed to concentrations above the NAAQS, and emissions
of the ozone precursors NOX and VOC. These all show the
substantial air quality progress made in the Sacramento Metro Area and
add support to the attainment demonstration for 2024.
    The 2017 Sacramento Regional Ozone Plan includes an additional
attainment demonstration using ``banded'' RRFs; the EPA also considers
this to be part of the WOE.\100\ The banded approach is described more
fully in a study cited in the 2017 Sacramento Regional Ozone Plan, and
also cited in the Modeling Guideline as an alternative RRF
approach.\101\ The banded RRF approach divides ozone concentrations
into ranges or bands and computes a specific RRF for each band. This
allows different ozone concentrations to respond differently to
emission changes, a refinement on the standard approach. In this case,
the banded approach increased design values for some monitors and
decreased them for others; for Folsom, the site with the highest 2026
design value, the design value decreased from 75.2 ppb to 69.0 ppb.
This more refined approach provides corroboration for the attainment
demonstration and suggests that the analysis was done conservatively.
---------------------------------------------------------------------------

    \100\ 2017 Sacramento Regional Ozone Plan Appendix B-4, section
5.5, and Appendix B-3, section 8.2.
    \101\ Modeling Guidance, 103.
---------------------------------------------------------------------------

b. Control Strategy for Attainment
    The control strategy for attainment of the 2008 ozone NAAQS in the
2017 Sacramento Regional Ozone Plan relies primarily on emissions
reductions from control measures that have been adopted by the
Districts and CARB prior to the submittal of the plan. Local stationary
and area source emissions reductions come from baseline (i.e., already-
adopted) control measures.\102\ Overall, nearly all of the emissions
reductions that the control strategy relies upon are expected to come
from already-adopted and EPA-approved state on- and off-road mobile
source control measures, which are discussed in section III.C of this
document.\103\ For the 2008 ozone NAAQS, already-adopted control
measures from the Districts and CARB are expected to achieve almost all
of the reductions needed from the 2012 base year to attain the 2008
NAAQS in 2024. As tables 4 and 5 show, the vast majority of emissions
reductions relied upon by the Plan's control strategy are from the on-
and off-road mobile source inventory and can be largely attributed to
control measures adopted by CARB, subsequently approved by the EPA, and
cited in detail in Section III.C.\104\
---------------------------------------------------------------------------

    \102\ 2017 Sacramento Regional Ozone Plan, Sections 7.3, 7.4,
and 7.5, 7-12 to 7-14.
    \103\ 2017 Sacramento Regional Ozone Plan, Section 7.2, 7-1 to
7-14.
    \104\ 2017 Sacramento Regional Ozone Plan, 5-13, Figures 5-8 and
5-9 show VOC and NOX emission reductions by source
category over time.

         Table 4--2012 and 2024 Volatile Organic Compound (VOC) Emissions for the Sacramento Metro Area
                                        [Summer planning inventory, tpd]
----------------------------------------------------------------------------------------------------------------
                                                                                Emissions        Percentage of
              Source category                    2012            2024        difference from     total emission
                                                                               2012 to 2024        reductions
----------------------------------------------------------------------------------------------------------------
Stationary Sources........................              22              23                 +1                 -4
Area Sources..............................              29              31                 +2                 -8
On-Road Mobile Sources....................              34              14                -20                 77
Other Mobile Sources......................              26              17                 -9                 35
                                           ---------------------------------------------------------------------
    Total.................................             110              84                -26                100
----------------------------------------------------------------------------------------------------------------
Source: 2017 Sacramento Regional Ozone Plan, Chapter 5, Table 5-1. The sum of the emissions values may not equal
  the total shown due to rounding. Percentage reductions are calculated against net total of gross reductions.

             Table 5--2012 and 2024 Oxides of Nitrogen (NOX) Emissions for the Sacramento Metro Area
                                        [Summer planning inventory, tpd]
----------------------------------------------------------------------------------------------------------------
                                                                                Emissions        Percentage of
              Source category                    2012            2024        difference from     total emission
                                                                               2012 to 2024        reductions
----------------------------------------------------------------------------------------------------------------
Stationary Sources........................               8               7                 -1                  2
Area Sources..............................               3               2                 -1                  2
On-Road Mobile Sources....................              61              19                -42                 81
Other Mobile Sources......................              30              21                 -9                 17
                                           ---------------------------------------------------------------------
    Total.................................             101              49                -52                100
----------------------------------------------------------------------------------------------------------------
Source: 2017 Sacramento Regional Ozone Plan, Chapter 5, Table 5-2. The sum of the emissions values may not equal
  the total shown due to rounding.

c. Attainment Demonstration
    Chapter 8 of the Plan describes the attainment demonstration in
general terms, including photochemical modeling results, and the
process for selecting and demonstrating a 2024 attainment year, while
Appendix B to the Plan provides more detail concerning photochemical
modeling. Other aspects of this demonstration are included throughout
the Plan, including emissions inventory forecasts included in section
5.5 and the control strategy described in Chapter 7. The WOE analysis
in Appendix B to the CARB Staff Report includes additional supporting
information to complement the photochemical modeling and to provide
context for this attainment demonstration, such as analyses of
anthropogenic emission, ambient ozone data, and meteorological
analyses. Table 6 below summarizes the attainment demonstration for the
2008 ozone NAAQS by listing the base year (2012) emissions level, the
modeled attainment emissions level, and the total reductions that the
District and CARB estimate to achieve through baseline control measures
and accounting for growth. Baseline measures are expected to reduce
base year (2012) emissions of NOX by 51 percent and VOC
emissions by 24 percent by the 2024 attainment year, notwithstanding
growth and the emission reduction credit (ERC) balance, and to attain
the 2008 ozone NAAQS in the Sacramento Metro Area by 2024, two years
ahead of the required attainment year, 2026.

  Table 6--Summary of Sacramento Metro Area 2008 Ozone NAAQS Attainment
                              Demonstration
                    [Summer planning inventory, tpd]
------------------------------------------------------------------------
                                                NOX             VOC
------------------------------------------------------------------------
2012 Base Year Emissions Level (A)......             101             110
2024 Modeled Attainment Emissions Level               49              84
 (B)....................................
                                         -------------------------------
    Total Reductions Needed from 2012                 52              26
     Base Year Levels to Demonstrate
     Attainment (A-B)...................
    Reductions from Baseline (i.e.,                   52              26
     adopted) Measures, net of growth
     and excluding ERC balance..........
------------------------------------------------------------------------
2024 Emissions with Reductions from                   49              84
 Baseline Control Strategy (compare to
 Row B).................................
Attainment demonstrated?................             Yes             Yes
------------------------------------------------------------------------
Notes and sources: 2017 Sacramento Regional Ozone Plan, Figure 5-8 and 5-
  9, 5-3.

3. The EPA's Review of the State's Submission
a. Photochemical Modeling
    The interpolation of 2022 and 2026 modeling results to estimate the
2024 design value assumed that only NOX emissions needed to
be considered; it was assumed that small changes in VOC emissions have
a negligible effect on ozone. That assumption is supported by the ozone
isopleth diagram in the Plan showing the ozone results from modeling
various combinations of NOX and VOC reductions.\105\ Its
lines of constant ozone are nearly parallel to the VOC axis; that is,
ozone is about the same for the whole range of VOC emissions levels,
and ozone changes very little with VOC emissions reductions.
Conversely, the lines are nearly perpendicular to the NOX
axis, indicating ozone varies strongly with NOX emissions
levels. This illustrates the ozone formation is not just
NOX-limited (responsive to NOX emissions
changes), but also far more sensitive to emissions changes in
NOX than VOC. On a percentage basis, ozone is about 14 times
as sensitive to NOX reductions than to VOC reductions; on a
tons per year basis, it is about 24 times as sensitive. Nevertheless,
the isopleth diagram shows there is some modeled sensitivity to VOC
change, so the EPA used it to estimate a 2024 design value, as an
alternative to the Plan's interpolation approach. The methodology used
is discussed in the TSD, which applies the modeled sensitivity from the
2026 isopleth diagram to the NOX and VOC emissions
differences between 2026 and 2024, to arrive at an ozone difference
between 2026 and 2024. The result was a 2024 design value of 72.7 ppb,
about 0.6 ppb higher than the Plan's estimate, but still well below the
75 ppb NAAQS. The difference is due mainly to the different simplifying
assumptions used in the two approaches, rather than to the inclusion of
the effect of VOC, which by itself resulted in an impact of only 0.03
ppb. The results corroborate the Plan's attainment demonstration,
including the assumption that VOC emissions changes have little effect
on ozone concentrations.\106\
---------------------------------------------------------------------------

    \105\ Plan Appendix B-4, Figure 16, p. B-158.
    \106\ The relative sensitivity of ozone to NOX and
VOC and the alternative 2024 design value are discussed in
``Assessment of Sacramento Metro NAA Conformity Motor Vehicle
Emissions Budget Consistency with O3 NAAQS Attainment,''
draft August 7, 2020, EPA Region IX, within the docket for this
proposed rulemaking.

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

    The modeling shows that existing control measures from CARB and the
Districts are sufficient to attain the 2008 8-hour ozone NAAQS by 2024
at all monitoring sites in the Sacramento Metro Area. Because the Plan
properly incorporates all modeling and input preparation procedures,
tests, and performance analyses called for in the modeling protocol,
demonstrates good model performance, and responds to emission changes
consistent with observations, the EPA finds that the photochemical
modeling is adequate for purposes of supporting the attainment
demonstration.
b. Control Strategy for Attainment
    As discussed above, the Sacramento Metro Area Ozone SIP relies on
state and locally adopted baseline control measures, i.e., already-
adopted control measures, to achieve the emissions reductions needed to
attain the 2008 ozone NAAQS by 2024. As shown in Tables 4-6 and
discussed in Section III.C, the Sacramento Metro Area Ozone SIP relies
on these measures to achieve all the emissions reductions needed to
attain the 2008 ozone NAAQS by 2024. These baseline measures are
approved into the SIP and, as such, are fully creditable within the
attainment demonstration analysis. Accordingly, we propose to find that
the emissions reductions that are relied on for attainment are
creditable and sufficient to provide for attainment.
c. Attainment Demonstration
    The Plan followed the modeling procedures recommended in the EPA's
Modeling Guidance and showed excellent performance in simulating
observed ozone concentrations in the 2012 base year; the TSD discusses
the modeling in detail. Given the extensive discussion of modeling
procedures, tests, and performance analyses called for in the modeling
protocol, the good model performance, and the model response to
emissions changes consistent with observations, the EPA finds that the
modeling is adequate for purposes of supporting the attainment
demonstration. Based on our review of the Plan and our proposed
findings that the photochemical modeling and control strategy are
acceptable and demonstrate attainment by the applicable attainment
date, we propose to approve the attainment demonstration for the 2008
ozone NAAQS in the Sacramento Metro Area Ozone SIP as meeting the
requirements of CAA section 182(c)(2)(A) and 40 CFR 51.1108.

E. Rate of Progress Plan and Reasonable Further Progress Demonstration

1. Statutory and Regulatory Requirements
    Requirements for RFP for ozone nonattainment areas are specified in
CAA sections 172(c)(2), 182(b)(1), and 182(c)(2)(B). Under CAA section
171(1), RFP is defined as meaning such annual incremental reductions in
emissions of the relevant air pollutant as are required under part D
(``Plan Requirements for Nonattainment Areas'') 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 that are
classified as Moderate or above demonstrate a 15 percent reduction in
VOC between the years of 1990 and 1996. The EPA has typically referred
to section 182(b)(1) as the rate of progress (ROP) requirement. For
ozone nonattainment areas classified as Serious or higher, section
182(c)(2)(B) requires VOC reductions of at least 3 percent of baseline
emissions per year, averaged over each consecutive 3-year period,
beginning 6 years after the baseline year until the attainment date.
CAA section 182(c)(2)(B)(ii) allows an amount less than 3 percent of
such baseline emissions each year if the state demonstrates to the EPA
that the plan includes all measures that can feasibly be implemented in
the area in light of technological achievability. Additionally, under
CAA section 182(c)(2)(C), a state may substitute NOX
emissions reductions for VOC emissions reductions.
    In the 2008 Ozone SRR, the EPA provides that an area classified
Moderate or higher will have met the ROP requirements of CAA section
182(b)(1) if the area has a fully approved 15 percent ROP plan for the
1-hour or 1997 8-hour ozone standards, provided the boundaries of the
ozone nonattainment areas are the same.\107\ 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 6 years of the baseline year.
Areas classified as Serious or higher must meet the RFP requirements of
CAA section 182(c)(2)(B) by providing an 18 percent reduction of ozone
precursors in the first 6-year period, and an average ozone precursor
emissions reduction of 3 percent per year for all remaining 3-year
periods thereafter.\108\ To meet CAA sections 172(c)(2) and
182(c)(2)(B) RFP requirements, a state may substitute NOX
emissions reductions for VOC reductions.\109\
---------------------------------------------------------------------------

    \107\ 80 FR 12264, 12271 (March 6, 2015).
    \108\ Id.
    \109\ 40 CFR 51.1110(a)(2)(i)(C) and 40 CFR
51.1110(a)(2)(ii)(B); 80 FR 12264, 12271 (March 6, 2015).
---------------------------------------------------------------------------

    Except as specifically provided in CAA section 182(b)(1)(C),
emissions reductions from all SIP-approved, federally promulgated, or
otherwise SIP-creditable measures that occur after the baseline year
are creditable for purposes of demonstrating that the RFP targets are
met. Because the EPA has determined that the passage of time has caused
the effect of certain exclusions to be de minimis, the RFP
demonstration is no longer required to calculate and specifically
exclude reductions from measures related to motor vehicle exhaust or
evaporative emissions promulgated by January 1, 1990; regulations
concerning Reid vapor pressure promulgated by November 15, 1990;
measures to correct previous RACT requirements; and, measures required
to correct previous inspection and maintenance (I/M) programs.\110\
---------------------------------------------------------------------------

    \110\ 40 CFR 51.1110(a)(7).
---------------------------------------------------------------------------

    The 2008 Ozone SRR requires the RFP baseline year to be the most
recent calendar year for which a complete triennial inventory was
required to be submitted to the EPA. For the purposes of developing RFP
demonstrations for the 2008 ozone NAAQS, the applicable triennial
inventory year is 2011. As discussed above, the 2008 Ozone SRR provided
states with the opportunity to use an alternative baseline year for
RFP,\111\ but this provision was vacated by the D.C. Circuit in the
South Coast II decision.
---------------------------------------------------------------------------

    \111\ 40 CFR 51.1110(b).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    In response to the South Coast II decision, CARB developed the 2018
SIP Update, which replaces the RFP portion of the 2017 Sacramento
Regional Ozone Plan and includes updated emissions estimates for the
RFP baseline year, subsequent milestone years, and the attainment year,
and an updated RFP demonstration relying on a 2011 RFP baseline
year.\112\ To develop the 2011 RFP baseline inventory, CARB relied on
actual emissions reported from industrial point sources for year 2011
and back-cast emissions from smaller stationary sources and area
sources from 2012 to 2011 using the same growth and

control factors as was used for the 2017 Sacramento Regional Ozone
Plan. To develop the emissions inventories for the RFP milestone years
(i.e., 2017, 2020, 2023) and attainment year (i.e., 2024), CARB also
relied upon the same growth and control factors as the 2017 Sacramento
Regional Ozone Plan. The 2018 SIP Update emissions estimates reflect
District rules adopted and submitted to CARB through November 2015 and
CARB rules adopted through December 2014.\113\
---------------------------------------------------------------------------

    \112\ 2018 SIP Update, Section V.B. Reasonable Further Progress,
28-30.
    \113\ 2018 SIP Update, Appendix A, A-1, A-2.
---------------------------------------------------------------------------

    Documentation for the Sacramento Metro Area RFP baseline and
milestone emissions inventories is found in the 2018 SIP Update.\114\
The updated RFP demonstration for the Sacramento Metro Area for the
2008 ozone NAAQS is shown in Table 7. This demonstration calculates
future year VOC targets from the 2011 baseline, consistent with CAA
182(c)(2)(B)(i), which requires reductions of ``at least 3 percent of
baseline emissions each year,'' and it substitutes NOX
reductions for VOC reductions beginning in milestone year 2020 to meet
VOC emission targets.\115\ For the Sacramento Metro Area, CARB
concludes that the RFP demonstration meets the applicable requirements
for each milestone year as well as the attainment year.\116\
---------------------------------------------------------------------------

    \114\ 2018 SIP Update, 27-30, and Appendix A, A-15 through A-18.
    \115\ NOX substitution is permitted under EPA
regulations. See 40 CFR 51.1110(a)(2)(i)(C) and 40 CFR
51.1110(a)(2)(ii)(B); and 80 FR 12264, 12271 (March 6, 2015).
    \116\ In addition to the RFP demonstration in Table 7, CARB
provided a clarification including the small rounding additions in
the motor vehicle emission budgets to ensure that they are accounted
for and that RFP would still be met; email dated August 11, 2020,
from Webster Tasat, CARB to Anita Lee, USEPA, including attached RFP
demonstration table, in the docket.

  Table 7--RFP Demonstration for the Sacramento Metro Area for the 2008 Ozone NAAQS, Summer Planning Inventory,
                                              tpd or Percentage (%)
----------------------------------------------------------------------------------------------------------------
                                                                        VOC
                                 -------------------------------------------------------------------------------
                                       2011            2017            2020            2023            2024
----------------------------------------------------------------------------------------------------------------
Baseline VOC....................           111.6            91.7            91.3            88.5            87.9
Transportation conformity safety               0               0               0               0             0.5
 margin *.......................
Baseline + safety margin (VOC)..           111.6            91.7            91.3            88.5            88.4
Required change since 2011 (VOC   ..............              18              27              36              39
 or NOX), %.....................
Target VOC level................  ..............            91.5            81.5            71.4            68.1
Apparent shortfall (-)/surplus    ..............            -0.2            -9.9           -17.0           -20.3
 (+) in VOC.....................
Apparent shortfall (-)/surplus    ..............            -0.1            -8.8           -15.3           -18.2
 (+) in VOC, %..................
VOC shortfall previously          ..............               0            -0.1             8.8            15.3
 provided by NOX substitution, %
Actual VOC shortfall (-)/surplus  ..............            -0.1            -8.7            -6.4            -2.9
 (+), %.........................
----------------------------------------------------------------------------------------------------------------

                                                                        NOX
                                 -------------------------------------------------------------------------------
                                       2011            2017            2020            2023            2024
----------------------------------------------------------------------------------------------------------------
Baseline NOX....................           107.7            71.7            63.8            52.2            50.5
Transportation conformity safety               0               0             0.4             0.9             1.2
 margin *.......................
Baseline + safety margin (NOX)..           107.7            71.7            64.2            53.2            51.7
Change in NOX since 2011, tpd...  ..............            36.0            43.4            54.5            56.0
Change in NOX since 2011, %.....  ..............            33.4            40.3            50.6            52.0
NOX reductions used for VOC       ..............               0             0.1             8.8            15.3
 substitution through last
 milestone year, %..............
NOX reductions since 2011         ..............            33.4            40.2            41.8            36.7
 available for VOC substitution
 in this milestone year, %......
NOX reductions since 2011 used    ..............             0.1             8.7             6.4             2.9
 for VOC substitution in this
 milestone year, %..............
NOX reductions since 2011         ..............            33.3            31.5            35.3            33.8
 surplus after meeting VOC
 substitution needs in this
 milestone year, %..............
Total shortfall for RFP.........  ..............               0               0               0               0
RFP met?........................  ..............             Yes             Yes             Yes             Yes
----------------------------------------------------------------------------------------------------------------
Source: 2018 SIP Update, Table V-3, and Appendix A, A-15--A-18. The sum of the emissions values may not equal
  the total shown due to rounding of the numbers. Baseline emissions for 2020, 2023, and 2024 include 5 tpd VOC
  and 4 tpd NOX to account for area ERC banking and accounting.
* We discuss the concept of a safety margin within motor vehicle emissions budgets below in the Section H
  concerning transportation conformity.

3. The EPA's Review of the State's Submission
    In 2015, the EPA approved a 15 percent ROP plan for the Sacramento
Metro Area for the 1-hour ozone NAAQS and 1997 8-hour ozone NAAQS,\117\
and the boundaries of the Sacramento Metro Area for the 2008 ozone
NAAQS are the same as the Sacramento Metro Area for the 1997 8-hour