[Federal Register Volume 86, Number 138 (Thursday, July 22, 2021)]
[Proposed Rules]
[Pages 38652-38674]
[FR Doc No: 2021-15551]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2021-0260; FRL-8644-02-R9]

Partial Approval and Partial Disapproval of Air Quality
Implementation Plans; California; San Joaquin Valley Serious Area and
Section 189(d) Plan for Attainment of the 1997 Annual PM2.5 NAAQS

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to
approve in part and disapprove in part portions of a state
implementation plan (SIP) revision submitted by the State of California
to meet Clean Air Act (CAA or ``Act'') requirements for the 1997 annual
fine particulate matter (PM2.5) national ambient air quality
standards (NAAQS or ``standards'') in the San Joaquin Valley
PM2.5 nonattainment area. Specifically, the EPA is proposing
to approve the 2013 base year emissions inventories in the submitted
SIP revisions. Because the area did not attain by the State's projected
attainment date of December 31, 2020, the EPA is proposing to
disapprove the attainment demonstration and related elements, including
the comprehensive precursor demonstration, five percent annual emission
reductions demonstration, best available control measures (BACM)
demonstration, reasonable further progress (RFP) demonstration,
quantitative milestone demonstration, and contingency measures. The EPA
is also proposing to disapprove the motor vehicle emission budgets in
the plan as not meeting the requirements of the CAA and EPA
regulations.

DATES: Any comments on this proposal must be received by August 23,
2021.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2021-0260 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 (e.g.,
audio or video) must be accompanied by a written comment. The written
comment is considered the official comment and should include
discussion of all points you wish to make. The EPA will generally not
consider comments or comment contents located outside of the primary
submission (i.e., on the web, cloud, or other file sharing system). For
additional submission methods, please contact the person identified in
the FOR FURTHER INFORMATION CONTACT section. For the full EPA public
comment policy, information about CBI or multimedia submissions, and
general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. If you need assistance in a
language other than English or if you are a person with disabilities
who needs a reasonable accommodation at no cost to you, please contact
the person identified in the FOR FURTHER INFORMATION CONTACT section.

FOR FURTHER INFORMATION CONTACT: Ashley Graham, Air Planning Office
(ARD-2), EPA Region IX, 75 Hawthorne Street, San Francisco, CA 94105,
(415) 972-3877, or by email at<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: Throughout this document, ``we,'' ``us,''
and ``our'' refer to the EPA.

Table of Contents

I. Background for Proposed Action
    A. PM2.5 NAAQS
    B. San Joaquin Valley PM2.5 Designations,
Classifications, and SIP Revisions
II. Summary and Completeness Review of the San Joaquin Valley PM2.5
Plan
    A. 2018 PM2.5 Plan
    B. Valley State SIP Strategy
    C. District Rule 4901
III. Clean Air Act Requirements for Serious PM2.5 Areas That Fail To
Attain
IV. Review of the San Joaquin Valley PM2.5 Plan
    A. Emissions Inventories
    B. PM2.5 Precursors
    C. Attainment Plan Control Strategy
    D. Attainment Demonstration and Modeling
    E. Reasonable Further Progress and Quantitative Milestones
    F. Contingency Measures
    G. Motor Vehicle Emission Budgets
    H. Nonattainment New Source Review Requirements Under CAA
Section 189(e)
V. Proposed Action
    A. Effect of Finalizing the Proposed Disapproval Actions
VI. Statutory and Executive Order Reviews

I. Background for Proposed Action

A. PM2.5 NAAQS

    Under section 109 of the CAA, the EPA has established NAAQS for
certain pervasive air pollutants (referred to as ``criteria
pollutants'') and conducts periodic reviews of the NAAQS to determine
whether they should be revised or whether new NAAQS should be
established.
    On July 18, 1997, the EPA revised the NAAQS for particulate matter
by establishing new NAAQS for particles with an aerodynamic diameter
less than or equal to a nominal 2.5 micrometers (PM2.5).\1\
The EPA established primary and secondary annual and 24-hour standards
for PM2.5.\2\ The annual primary and secondary standards
were set at 15.0 micrograms per cubic meter ([mu]g/m\3\), based on a
three-year average of annual mean PM2.5 concentrations, and
the 24-hour primary and secondary standards were set at 65 [mu]g/m\3\,
based on the three-year average of the 98th percentile of 24-hour
PM2.5 concentrations at each monitoring site within an
area.\3\ Collectively, we refer herein to the 1997 annual and 24-hour
PM2.5 NAAQS as the ``1997 PM2.5 NAAQS'' or ``1997
PM2.5 standards.''
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    \1\ 62 FR 38652.
    \2\ For a given air pollutant, ``primary'' NAAQS are those
determined by the EPA as requisite to protect the public health,
allowing an adequate margin of safety, and ``secondary'' standards
are those determined by the EPA as requisite to protect the public
welfare from any known or anticipated adverse effects associated
with the presence of such air pollutant in the ambient air. See CAA
section 109(b).
    \3\ 40 CFR 50.7.
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    On October 17, 2006, the EPA revised the level of the 24-hour
PM2.5 NAAQS to 35 [mu]g/m\3\,\4\ and on January 15, 2013,
the EPA revised the level of the primary annual PM2.5 NAAQS
to 12.0 [mu]g/m\3\.\5\ Even though the EPA has lowered the 24-hour and
annual PM2.5 standards, the 1997 PM2.5 standards
remain in effect.
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    \4\ 71 FR 61144.
    \5\ 78 FR 3086.
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    The EPA established these standards after considering substantial
evidence from numerous health studies demonstrating that serious health
effects are associated with exposures to PM2.5
concentrations above these levels. Epidemiological studies have shown
statistically significant correlations between elevated
PM2.5 levels and premature mortality. Other important health
effects associated with PM2.5 exposure include aggravation
of respiratory and cardiovascular disease (as indicated by increased
hospital admissions, emergency room visits, absences from school or
work, and restricted activity dates), changes in lung function and
increased respiratory symptoms, and new evidence for more subtle
indicators of cardiovascular health. Individuals particularly sensitive
to PM2.5 exposure include

older adults, people with heart and lung disease, and children.\6\
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    \6\ EPA, Air Quality Criteria for Particulate Matter, No. EPA/
600/P-99/002aF and EPA/600/P-99/002bF, October 2004.
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    Sources can emit PM2.5 directly into the atmosphere as a
solid or liquid particle (primary PM2.5 or direct
PM2.5), or PM2.5 can form in the atmosphere
(secondary PM2.5) as a result of various chemical reactions
from precursor emissions of nitrogen oxides (NOX), sulfur
oxides (SOX), volatile organic compounds (VOC), and
ammonia.\7\
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    \7\ For example, see 72 FR 20586, 20589 (April 25, 2007).
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B. San Joaquin Valley PM2.5 Designations, Classifications, and SIP
Revisions

    Following promulgation of a new or revised NAAQS, the EPA is
required under CAA section 107(d) to designate areas throughout the
nation as attaining or not attaining the NAAQS. Effective April 5,
2005, the EPA established the initial air quality designations for the
1997 annual and 24-hour PM2.5 NAAQS, using air quality
monitoring data for the three-year periods of 2001-2003 and 2002-
2004.\8\ The EPA designated the San Joaquin Valley as nonattainment for
both the 1997 annual PM2.5 NAAQS (15.0 [mu]g/m\3\) and the
1997 24-hour PM2.5 NAAQS (65 [mu]g/m\3\).\9\
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    \8\ 70 FR 944 (January 5, 2005).
    \9\ 40 CFR 81.305.
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    The San Joaquin Valley PM2.5 nonattainment area
encompasses over 23,000 square miles and includes all or part of eight
counties: San Joaquin, Stanislaus, Merced, Madera, Fresno, Tulare,
Kings, and the valley portion of Kern.\10\ The area is home to four
million people and is one of the nation's leading agricultural regions.
Stretching over 250 miles from north to south and averaging 80 miles
wide, it is partially enclosed by the Coast Mountain range to the west,
the Tehachapi Mountains to the south, and the Sierra Nevada range to
the east. Under State law, the San Joaquin Valley Unified Air Pollution
Control District (SJVUAPCD or ``District'') has primary responsibility
for developing plans to provide for attainment of the NAAQS in this
area. The District works cooperatively with the California Air
Resources Board (CARB) in preparing attainment plans. Authority for
regulating sources under state jurisdiction in the San Joaquin Valley
is split under State law between the District, which has responsibility
for regulating stationary and most area sources, and CARB, which has
responsibility for regulating most mobile sources.
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    \10\ For a precise description of the geographic boundaries of
the San Joaquin Valley nonattainment area, see 40 CFR 81.305.
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    Within three years of the effective date of designations, states
with areas designated as nonattainment for the 1997 PM2.5
NAAQS were required to submit SIP revisions that, among other things,
provided for implementation of reasonably available control measures
(RACM), RFP, attainment of the standards as expeditiously as
practicable but no later than five years from the nonattainment
designation (in this instance, no later than April 5, 2010) unless the
state justified an attainment date extension of up to five years, and
contingency measures.\11\
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    \11\ CAA sections 172(a)(2), 172(c)(1), 172(c)(2), and
172(c)(9).
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    Between 2007 and 2011, California submitted six SIP revisions to
address nonattainment area planning requirements for the 1997
PM2.5 NAAQS in the San Joaquin Valley,\12\ which we refer to
collectively as the ``2008 PM2.5 Plan.'' On November 9,
2011, the EPA approved the portions of the 2008 PM2.5 Plan,
as revised in 2009 and 2011, that addressed attainment of the 1997
PM2.5 NAAQS in the San Joaquin Valley PM2.5
nonattainment area, except for the attainment contingency measures,
which we disapproved.\13\ We also granted the State's request to extend
the attainment deadline for the 1997 PM2.5 NAAQS in the San
Joaquin Valley to April 5, 2015.\14\
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    \12\ 76 FR 69896, n. 2 (November 9, 2011).
    \13\ Id. at 69924.
    \14\ Id.
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    Following a January 4, 2013 decision of the U.S. Court of Appeals
for the D.C. Circuit (``D.C. Circuit'') remanding the EPA's 2007
implementation rule for the 1997 PM2.5 NAAQS,\15\ the EPA
published a final rule on June 2, 2014, classifying the San Joaquin
Valley, among other areas, as a Moderate nonattainment area for the
1997 PM2.5 NAAQS under subpart 4, part D of title I of the
Act.\16\
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    \15\ Natural Resources Defense Council v. EPA, 706 F.3d. 428
(D.C. Cir. 2013) (``NRDC''). In NRDC, the court held that the EPA
erred in implementing the 1997 PM2.5 standards solely
pursuant to the general implementation requirements of subpart 1,
without also considering the requirements specific to nonattainment
areas for particles less than or equal to 10 [mu]m in diameter
(PM10) in subpart 4, part D of title I of the CAA. The
court reasoned that the plain meaning of the CAA requires
implementation of the 1997 PM2.5 standards under subpart
4 because PM2.5 falls within the statutory definition of
PM10 and is thus subject to the same statutory
requirements as PM10. The court remanded the rule,
without vacatur, and instructed the EPA ``to repromulgate these
rules pursuant to Subpart 4 consistent with this opinion.''
    \16\ 79 FR 31566.
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    Effective May 7, 2015, the EPA reclassified the San Joaquin Valley
as a Serious nonattainment area for the 1997 PM2.5 NAAQS
based on our determination that the area could not practicably attain
these NAAQS by the April 5, 2015 attainment date.\17\ Upon
reclassification as a Serious area, the San Joaquin Valley became
subject to a December 31, 2015 deadline under CAA section 188(c)(2) to
attain the 1997 PM2.5 NAAQS. On February 9, 2016, the EPA
proposed to grant the State's request for extensions of the December
31, 2015 attainment date under CAA section 188(e), to December 31,
2018, for the 1997 24-hour PM2.5 NAAQS, and to December 31,
2020, for the 1997 annual PM2.5 NAAQS in the San Joaquin
Valley.\18\ However, on October 6, 2016, after considering public
comments, the EPA denied California's request for these extensions of
the attainment dates.\19\ Consequently, on November 23, 2016, the EPA
determined that the San Joaquin Valley had failed to attain the 1997
PM2.5 NAAQS by the December 31, 2015 Serious area attainment
date.\20\ This determination triggered a requirement for California to
submit, by December 31, 2016, a revised PM2.5 attainment
plan for the 1997 PM2.5 NAAQS for the San Joaquin Valley
that satisfies the requirements of CAA section 189(d).
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    \17\ 80 FR 18528 (April 7, 2015).
    \18\ 81 FR 6936. California's request for extension of the
Serious Area attainment date for the San Joaquin Valley accompanied
its Serious Area attainment plan for the 1997 PM2.5 NAAQS
and related motor vehicle emission budgets, submitted June 25, 2015
and August 13, 2015, respectively.
    \19\ 81 FR 69396. The EPA did not finalize the actions proposed
on February 9, 2016, with respect to the submitted Serious area
plan. Id. at 69400.
    \20\ 81 FR 84481.
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    On December 6, 2018, the EPA determined that California had failed
to submit a complete Serious area and section 189(d) attainment plan
for the 1997 PM2.5 NAAQS, among other required SIP
submissions for the San Joaquin Valley, by the submittal deadline.\21\
This finding, which became effective on January 7, 2019, triggered
clocks under CAA section 179(a) for the application of emissions offset
sanctions 18 months after the finding and highway funding sanctions six
months thereafter, unless the EPA affirmatively determines that the
State has submitted a complete SIP addressing the identified
deficiencies.\22\ The finding also triggered the obligation under CAA
section 110(c) on the EPA to promulgate a federal implementation plan
no later than two years after the finding, unless the State has
submitted, and the EPA has approved, the required SIP

submittal.\23\ CARB submitted a revised attainment plan for the 1997
PM2.5 NAAQS, among other submissions, on May 10, 2019.\24\
This SIP revision is the subject of this proposal. On June 24, 2020,
the EPA issued a letter finding the submittal complete and terminating
the sanctions clocks under CAA section 179(a).\25\
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    \21\ 83 FR 62720.
    \22\ Id. at 62723.
    \23\ Id.
    \24\ Letter dated May 9, 2019, from Richard Corey, Executive
Officer, CARB, to Mike Stoker, Regional Administrator, EPA Region 9.
    \25\ Letter dated June 24, 2020, from Elizabeth J. Adams,
Director, Air and Radiation Division, EPA Region IX, to Richard W.
Corey, Executive Officer, CARB, Subject: ``RE: Completeness Finding
for State Implementation Plan (SIP) Submissions for San Joaquin
Valley for the 1997, 2006, and 2012 Fine Particulate Matter
(PM2.5) National Ambient Air Quality Standards (NAAQS)
and Termination of Clean Air Act (CAA) Sanction Clocks.''
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II. Summary and Completeness Review of the San Joaquin Valley PM2.5
Plan

    The EPA is proposing action on portions of three SIP revisions
submitted by CARB to meet CAA requirements for the 1997 annual
PM2.5 NAAQS in the San Joaquin Valley. Specifically, the EPA
is proposing to act on those portions of the following two plan
submissions that pertain to the 1997 annual PM2.5 NAAQS: The
``2018 Plan for the 1997, 2006, and 2012 PM2.5 Standards,''
adopted by the SJVUAPCD on November 15, 2018, and by CARB on January
24, 2019 (``2018 PM2.5 Plan''); \26\ and the ``San Joaquin
Valley Supplement to the 2016 State Strategy for the State
Implementation Plan,'' adopted by CARB on October 25, 2018 (``Valley
State SIP Strategy''). CARB submitted the 2018 PM2.5 Plan
and Valley State SIP Strategy to the EPA as a revision to the
California SIP on May 10, 2019.\27\ We refer to these two SIP
submissions collectively as the ``SJV PM2.5 Plan'' or
``Plan.''
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    \26\ The 2018 PM2.5 Plan was developed jointly by
CARB and the District.
    \27\ Letter dated May 9, 2019, from Richard Corey, Executive
Officer, CARB, to Mike Stoker, Regional Administrator, EPA Region 9.
The letter clarifies that the 2018 PM2.5 Plan supersedes
past submittals to the EPA that the agency has not yet acted on for
the 1997 standards, including the 2015 Plan for the 1997 Standard
(submitted by CARB on June 25, 2015) and motor vehicle emission
budgets (submitted by CARB August 13, 2015). The EPA previously
acted on those portions of the ``2018 Plan for the 1997, 2006, and
2012 PM2.5 Standards'' and the ``San Joaquin Valley
Supplement to the 2016 State Strategy for the State Implementation
Plan'' that pertain to the 2006 PM2.5 NAAQS (85 FR 44192,
July 22, 2020), and is not, at this time, proposing to act on those
portions that pertain to the 1997 24-hour PM2.5 NAAQS or
the 2012 annual PM2.5 NAAQS. We intend to act on these
portions of the submitted SIP revisions in subsequent rulemakings.
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    The EPA is also proposing action on 2019 amendments to the regional
air district residential wood-burning rule, SJVUAPCD Rule 4901, ``Wood
Burning Fireplaces and Wood Burning Heaters'' (``Rule 4901''), adopted
by the SJVUAPCD on June 20, 2019, and by CARB on July 19, 2019.\28\
These amendments include a contingency measure (in section 5.7.3 of the
amended rule) that applies to the 1997 annual PM2.5 NAAQS.
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    \28\ Letter dated July 19, 2019, from Richard W. Corey,
Executive Officer, CARB, to Mike Stoker, Regional Administrator, EPA
Region 9.
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    The SJV PM2.5 Plan addresses the Serious area and CAA
section 189(d) requirements for the 1997 PM2.5 NAAQS in the
San Joaquin Valley, including the State's demonstration that the area
will attain the 1997 annual PM2.5 NAAQS by December 31,
2020. In this proposal, the EPA is proposing to act only on those
portions of the SJV PM2.5 Plan that pertain to the 1997
annual PM2.5 NAAQS. The EPA intends to act on the portions
of the SJV PM2.5 Plan that pertain to the 1997 24-hour
PM2.5 NAAQS and subsequent PM2.5 NAAQS in
separate rulemakings.
    CAA sections 110(a)(1) and (2) and 110(l) require each state to
provide reasonable public notice and opportunity for public hearing
prior to the adoption and submission of a SIP or SIP revision to the
EPA. To meet this requirement, every SIP submission should include
evidence that adequate public notice was given and that an opportunity
for a public hearing was provided consistent with the EPA's
implementing regulations in 40 CFR 51.102.
    CAA section 110(k)(1)(B) requires the EPA to determine whether a
SIP submission is complete within 60 days of receipt. This section also
provides that any plan that the EPA has not affirmatively determined to
be complete or incomplete will become complete by operation of law six
months after the date of submission. The EPA's SIP completeness
criteria are found in 40 CFR part 51, Appendix V.

A. 2018 PM2.5 Plan

    The following portions of the 2018 PM2.5 Plan and
related support documents address both the Serious area requirements in
CAA section 189(b) and the CAA section 189(d) requirements for the 1997
annual PM2.5 NAAQS in the San Joaquin Valley: (i) Chapter 4
(``Attainment Strategy for PM2.5''), (ii) Chapter 5
(``Demonstration of Federal Requirements for 1997 PM2.5
Standards''); \29\ (iii) numerous appendices to the 2018
PM2.5 Plan; (iv) CARB's ``Staff Report, Review of the San
Joaquin Valley 2018 Plan for the 1997, 2006, and 2012 PM2.5
Standards,'' release date December 21, 2018 (``CARB Staff Report'');
\30\ and (v) the State's and District's board resolutions adopting the
2018 PM2.5 Plan (CARB Resolution 19-1 and SJVUAPCD Governing
Board Resolution 18-11-16).\31\
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    \29\ Chapter 6 (``Demonstration of Federal Requirements for the
2006 PM2.5 Standard: Serious Plan and Extension
Request'') and Chapter 7 (``Demonstration of Federal Requirements
for the 2012 PM2.5 Standard'') of the 2018
PM2.5 Plan pertain to the 2006 PM2.5 NAAQS and
the 2012 PM2.5 NAAQS, respectively. The EPA previously
acted on those portions of the Plan that pertain to the 2006
PM2.5 NAAQS (85 FR 44192, July 22, 2020) and intends to
act on those portions that pertain to the 1997 24-hour
PM2.5 NAAQS and 2012 PM2.5 NAAQS in separate
rulemakings.
    \30\ Letter dated December 11, 2019, from Richard Corey,
Executive Officer, CARB, to Mike Stoker, Regional Administrator, EPA
Region 9, transmitting the CARB Staff Report [on the 2018
PM2.5 Plan]. The CARB Staff Report includes CARB's review
of, among other things, the 2018 PM2.5 Plan's control
strategy and attainment demonstration.
    \31\ CARB Resolution 19-1, ``2018 PM2.5 State
Implementation Plan for the San Joaquin Valley,'' January 24, 2019,
and SJVUAPCD Governing Board Resolution 18-11-16, ``Adopting the
[SJVUAPCD] 2018 Plan for the 1997, 2006, and 2012 PM2.5
Standards,'' November 15, 2018.
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    The appendices to the 2018 PM2.5 Plan that address the
requirements for the 1997 annual PM2.5 NAAQS include: (i)
Appendix A (``Ambient PM2.5 Data Analysis''); (ii) Appendix
B (``Emissions Inventory''); (iii) Appendix C (``Stationary Source
Control Measure Analyses''); (iv) Appendix D (``Mobile Source Control
Measure Analyses''); (v) Appendix G (``Precursor Demonstration''); (vi)
Appendix H (``RFP, Quantitative Milestones, and Contingency''); \32\
(vii) Appendix I (``New Source Review and Emission Reduction
Credits''); (viii) Appendix J (``Modeling Emission Inventory''); (ix)
Appendix K (``Modeling Attainment Demonstration''); and (x) Appendix L
(``Modeling Protocol'').
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    \32\ Appendix H to 2018 PM2.5 Plan, submitted
February 11, 2020 via the EPA State Planning Electronic
Collaboration System. Following the identification of a
transcription error in the RFP tables of Appendix H, on February 11,
2020, the State submitted a revised version of Appendix H that
corrects the transcription error and provides additional information
on the RFP demonstration. All references to Appendix H in this
proposed rule are to the revised version submitted on February 11,
2020, which replaces the version submitted with the 2018
PM2.5 Plan on May 10, 2019.
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    The District provided public notice and opportunity for public
comment prior to its November 15, 2018 public hearing on and adoption
of the 2018 PM2.5 Plan.\33\ CARB also provided public notice
and opportunity for public comment prior to its January 24, 2019 public
hearing on and adoption of the

2018 PM2.5 Plan.\34\ The SIP submission includes proof of
publication of notices for the respective public hearings. It also
includes copies of the written and oral comments received during the
State's and District's public review processes and the agencies'
responses thereto.\35\ Therefore, we find that the 2018
PM2.5 Plan meets the procedural requirements for public
notice and hearing in CAA sections 110(a) and 110(l) and 40 CFR 51.102.
The 2018 PM2.5 Plan became complete by operation of law on
November 10, 2019.
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    \33\ SJVUAPCD, ``Notice of Public Hearing for Adoption of
Proposed 2018 PM2.5 Plan for the 1997, 2006, and 2012
Standards,'' October 16, 2018, and SJVUAPCD Governing Board
Resolution 18-11-16.
    \34\ CARB, ``Notice of Public Meeting to Consider the 2018
PM2.5 State Implementation Plan for the San Joaquin
Valley,'' December 21, 2018, and CARB Resolution 19-1.
    \35\ CARB, ``Board Meeting Comments Log,'' March 29, 2019; J&K
Court Reporting, LLC, ``Meeting, State of California Air Resources
Board,'' January 24, 2019 (transcript of CARB's public hearing), and
2018 PM2.5 Plan, Appendix M (``Summary of Significant
Comments and Responses'').
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B. Valley State SIP Strategy

    CARB developed the ``Revised Proposed 2016 State Strategy for the
State Implementation Plan'' (``2016 State Strategy'') to support
attainment planning in the San Joaquin Valley and Los Angeles-South
Coast Air Basin (``South Coast'') ozone nonattainment areas.\36\ In its
resolution adopting the 2016 State Strategy (CARB Resolution 17-7), the
Board found that the 2016 State Strategy would achieve 6 tons per day
(tpd) of NOX emissions reductions and 0.1 tpd of direct
PM2.5 emissions reductions in the San Joaquin Valley by 2025
and directed CARB staff to work with SJVUAPCD to identify additional
reductions from sources under District regulatory authority as part of
a comprehensive plan to attain the PM2.5 standards for the
San Joaquin Valley and to return to the Board with a commitment to
achieve additional emission reductions from mobile sources.\37\
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    \36\ The EPA has approved certain commitments made by CARB in
the 2016 State Strategy for purposes of attaining the ozone NAAQS in
the San Joaquin Valley and South Coast ozone nonattainment areas
(for example, see 84 FR 3302 (February 12, 2019) and 84 FR 52005
(October 1, 2019)) and for attaining the 2006 PM2.5 NAAQS
in the San Joaquin Valley (85 FR 44192 (July 22, 2020)).
    \37\ CARB Resolution 17-7, ``2016 State Strategy for the State
Implementation Plan,'' March 23, 2017, 6-7.
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    CARB responded to this resolution by developing and adopting the
``San Joaquin Valley Supplement to the 2016 State Strategy for the
State Implementation Plan'' (``Valley State SIP Strategy'') to support
the 2018 PM2.5 Plan. The State's May 10, 2019 SIP submission
incorporates by reference the Valley State SIP Strategy as adopted by
CARB on October 25, 2018 and submitted to the EPA on November 16,
2018.\38\
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    \38\ Letter dated May 9, 2019, from Richard Corey, Executive
Officer, CARB, to Mike Stoker, Regional Administrator, EPA Region 9,
2.
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    The Valley State SIP Strategy includes an ``Introduction'' (Chapter
1), a chapter on ``Measures'' (Chapter 2), and a ``Supplemental State
Commitment from the Proposed State Measures for the Valley'' (Chapter
3). Much of the content of the Valley State SIP Strategy is reproduced
in Chapter 4 (``Attainment Strategy for PM2.5'') of the 2018
PM2.5 Plan.\39\ The Valley State SIP Strategy also includes
CARB Resolution 18-49, which, among other things, commits CARB to
achieve specific amounts of NOX and PM2.5
emissions reductions by specific years, for purposes of attaining the
PM2.5 NAAQS in the San Joaquin Valley.\40\
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    \39\ For example, Table 2 (proposed mobile source measures and
schedule), Table 3 (emissions reductions from proposed mobile source
measures), and Table 4 (summary of emission reduction measures) of
the Valley State SIP Strategy correspond to tables 4-8, 4-9, and 4-
7, respectively, of the 2018 PM2.5 Plan, Chapter 4.
    \40\ CARB Resolution 18-49, ``San Joaquin Valley Supplement to
the 2016 State Strategy for the State Implementation Plan,'' October
25, 2018, 5.
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    CARB provided the required public notice and opportunity for public
comment prior to its October 25, 2018 public hearing on and adoption of
the Valley State SIP Strategy.\41\ The SIP submission includes proof of
publication of the public notice for this public hearing. It also
includes copies of the written and oral comments received during the
State's public review process and CARB's responses thereto.\42\
Therefore, we find that the Valley State SIP Strategy meets the
procedural requirements for public notice and hearing in CAA sections
110(a) and 110(l) and 40 CFR 51.102. The Valley State SIP Strategy
became complete by operation of law on November 10, 2019.
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    \41\ CARB, ``Notice of Public Meeting to Consider the San
Joaquin Valley Supplement to the 2016 State Strategy for the State
Implementation Plan,'' September 21, 2018, and CARB Resolution 18-
49.
    \42\ CARB, ``Board Meeting Comments Log,'' November 2, 2018 and
compilation of written comments; and J&K Court Reporting, LLC,
``Meeting, State of California Air Resources Board,'' October 25,
2018 (transcript of CARB's public hearing).
---------------------------------------------------------------------------

C. District Rule 4901

    With respect to the District contingency measure, the District
states in Appendix H of the 2018 PM2.5 Plan that it will
amend Rule 4901 to include a requirement to be triggered upon a
determination by the EPA that the San Joaquin Valley failed to meet a
regulatory requirement necessitating implementation of a contingency
measure.\43\ On June 20, 2019, the District adopted amendments to Rule
4901 including a contingency measure (in section 5.7.3 of the amended
rule), and, as an attachment to a letter dated July 19, 2019, CARB
submitted the amended rule to the EPA for approval.\44\ On July 22,
2020, we approved Rule 4901, as amended June 20, 2019, into the SIP
based on our conclusion that the rule meets the requirements for
enforceability and for SIP revisions in CAA sections 110(a)(2)(A),
110(l), and 193 but we did not evaluate section 5.7.3 of the amended
rule for compliance with CAA requirements for contingency measures.\45\
As part of that rulemaking, we stated that we would determine in future
actions whether section 5.7.3 of Rule 4901, in conjunction with other
submitted provisions, meets the statutory and regulatory requirements
for contingency measures.\46\ We are now evaluating section 5.7.3 of
Rule 4901, as amended June 20, 2019, for compliance with the
requirements for contingency measures for purposes of the 1997 annual
PM2.5 NAAQS.
---------------------------------------------------------------------------

    \43\ 2018 PM2.5 Plan, Appendix H, H-25.
    \44\ Letter dated July 19, 2019 from Richard W. Corey, Executive
Officer, CARB, to Mike Stoker, Regional Administrator, EPA Region 9.
    \45\ 85 FR 44206 (July 22, 2020) (final approval of Rule 4901);
85 FR 1131, 1132-33 (January 9, 2020) (proposed approval of Rule
4901).
    \46\ 85 FR 1131, 1132-33.
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    Consistent with the requirements of 40 CFR part 51, Appendix V, we
previously determined that CARB's submittal of the June 20, 2019
revisions to Rule 4901 satisfied the procedural requirements for SIP
revisions under CAA section 110 and the EPA's implementing
regulations.\47\
---------------------------------------------------------------------------

    \47\ 85 FR 1131 (January 9, 2020) (proposed approval of revised
Rule 4901) and 85 FR 44206 (July 22, 2020) (final approval of
revised Rule 4901).
---------------------------------------------------------------------------

III. Clean Air Act Requirements for Serious PM2.5 Areas That Fail To
Attain

    In the event that a Serious area fails to attain the
PM2.5 NAAQS by the applicable attainment date, CAA section
189(d) requires that ``the State in which such area is located shall,
after notice and opportunity for public comment, submit within 12
months after the applicable attainment date, plan revisions which
provide for attainment of the . . . standard. . .'' An attainment plan
under section 189(d) must, among other things, demonstrate expeditious
attainment of the NAAQS within the time period provided under CAA
section 179(d)(3) and provide for annual reductions in emissions of
direct PM2.5 or a PM2.5 plan precursor pollutant
within the area of not less than five

percent per year from the most recent emissions inventory for the area
until attainment.\48\ In addition to the requirement to submit control
measures providing for a five percent reduction in emissions of certain
pollutants on an annual basis, the EPA interprets CAA section 189(d) as
requiring a state to submit an attainment plan that includes the same
basic statutory plan elements that are required for other attainment
plans.\49\ Specifically, a state must submit to the EPA its plan to
meet the requirements of CAA section 189(d) in the form of a complete
attainment plan submission that includes the following elements:
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    \48\ CAA section 189(d) and 40 CFR 51.1010(c).
    \49\ 81 FR 58010, 58098 (August 24, 2016).
---------------------------------------------------------------------------

    1. A comprehensive, accurate, current inventory of actual emissions
from all sources of PM2.5 and PM2.5 precursors in
the area;
    2. A control strategy that includes additional measures (beyond
those already adopted in previous SIPs for the area as RACM/RACT, best
available control measures/best available control technology (BACM/
BACT), and most stringent measures (if applicable)) that provide for
attainment of the standards and, from the date of such submission until
attainment, demonstrate that the plan will at a minimum achieve an
annual five percent reduction in emissions of direct PM2.5
or any PM2.5 plan precursor;
    3. A demonstration (including air quality modeling) that the plan
provides for attainment as expeditiously as practicable;
    4. Plan provisions that require RFP;
    5. Quantitative milestones that are to be achieved every three
years until the area is redesignated attainment and that demonstrate
RFP toward attainment by the applicable date;
    6. Contingency measures to be implemented if the area fails to meet
any requirement concerning RFP or quantitative milestones or to attain
by the applicable attainment date; and
    7. Provisions to assure that control requirements applicable to
major stationary sources of PM2.5 also apply to major
stationary sources of PM2.5 precursors, except where the
state demonstrates to the EPA's satisfaction that such sources do not
contribute significantly to PM2.5 levels that exceed the
standards in the area.
    A state with a Serious PM2.5 nonattainment area that
fails to attain the NAAQS by the applicable Serious area attainment
date must also address any statutory requirements applicable to
Moderate and Serious nonattainment area plans under CAA sections 172
and 189 of the CAA to the extent that those requirements have not
already been met.\50\
---------------------------------------------------------------------------

    \50\ Id. Because the EPA has not previously approved a SIP
submission for the San Joaquin Valley as meeting the Serious area
planning requirements under CAA sections 172 and 189 for the 1997
annual PM2.5 NAAQS, the EPA is evaluating relevant
portions of the SJV PM2.5 Plan for compliance with these
requirements, in addition to the requirements of CAA section 189(d).
---------------------------------------------------------------------------

    A section 189(d) plan must demonstrate attainment as expeditiously
as practicable, and no later than five years from the date of the EPA's
determination that the area failed to attain, consistent with sections
179(d)(3) and 172(a)(2) of the CAA.\51\ Pursuant to those provisions,
the Administrator may also extend the attainment date to the extent the
Administrator deems appropriate, for a period no greater than 10 years
from the effective date of the EPA's determination that the area failed
to attain, considering the severity of nonattainment and the
availability and feasibility of pollution control measures.
---------------------------------------------------------------------------

    \51\ 81 FR 84481, 84482.
---------------------------------------------------------------------------

    The EPA provided its preliminary views on the CAA's requirements
for particulate matter plans under part D, title I of the Act in the
following guidance documents: (1) ``State Implementation Plans; General
Preamble for the Implementation of Title I of the Clean Air Act
Amendments of 1990'' (``General Preamble''); \52\ (2) ``State
Implementation Plans; General Preamble for the Implementation of Title
I of the Clean Air Act Amendments of 1990; Supplemental'' (``General
Preamble Supplement''); \53\ and (3) ``State Implementation Plans for
Serious PM-10 Nonattainment Areas, and Attainment Date Waivers for PM-
10 Nonattainment Areas Generally; Addendum to the General Preamble for
the Implementation of Title I of the Clean Air Act Amendments of 1990''
(``General Preamble Addendum'').\54\ More recently, in an August 24,
2016 final rule entitled, ``Fine Particulate Matter National Ambient
Air Quality Standards: State Implementation Plan Requirements''
(``PM2.5 SIP Requirements Rule''), the EPA established
regulatory requirements and provided further interpretive guidance on
the statutory SIP requirements that apply to areas designated
nonattainment for the PM2.5 standards.\55\ We discuss these
regulatory requirements and interpretations of the Act as appropriate
in our evaluation of the SJV PM2.5 Plan that follows.
---------------------------------------------------------------------------

    \52\ 57 FR 13498 (April 16, 1992).
    \53\ 57 FR 18070 (April 28, 1992).
    \54\ 59 FR 41998 (August 16, 1994).
    \55\ 81 FR 58010.
---------------------------------------------------------------------------

IV. Review of the San Joaquin Valley PM2.5 Plan

A. Emissions Inventories

1. Statutory and Regulatory Requirements
    CAA section 172(c)(3) requires that each SIP include a
comprehensive, accurate, current inventory of actual emissions from all
sources of the relevant pollutant or pollutants in the nonattainment
area. The EPA discussed the emissions inventory requirements that apply
to PM2.5 nonattainment areas in the PM2.5 SIP
Requirements Rule and codified these requirements in 40 CFR
51.1008.\56\ The EPA has also issued guidance concerning emissions
inventories for PM2.5 nonattainment areas.\57\
---------------------------------------------------------------------------

    \56\ Id. at 58098-58099.
    \57\ ``Emissions Inventory Guidance for Implementation of Ozone
and Particulate Matter National Ambient Air Quality Standards
(NAAQS) and Regional Haze Regulations,'' U.S. EPA, May 2017
(``Emissions Inventory Guidance''), available at https://www.epa.gov/air-emissions-inventories/air-emissions-inventory-guidance-implementation-ozone-and-particulate.
---------------------------------------------------------------------------

    The base year emissions inventory should provide a state's best
estimate of actual emissions from all sources of the relevant
pollutants in the area, i.e., all emissions that contribute to the
formation of a particular NAAQS pollutant. For the PM2.5
NAAQS, the base year inventory must include direct PM2.5
emissions, separately reported filterable and condensable
PM2.5 emissions,\58\ and emissions of all chemical
precursors to the formation of secondary PM2.5: nitrogen
oxides (NOX), sulfur dioxide (SO2), volatile
organic compounds (VOC), and ammonia.\59\ In addition, the emissions
inventory base year for a Serious PM2.5 nonattainment area
subject to CAA section 189(d) must be one of the three years for which
monitored data were used to determine that the area failed to attain
the PM2.5 NAAQS by the applicable Serious area attainment
date, or another technically appropriate year justified by the state in
its Serious area SIP submission.\60\ A state's SIP submission must
include documentation explaining how it calculated emissions data for
the inventory. In estimating mobile source emissions, a state should
use the latest emissions models and planning assumptions available at
the time the SIP is developed. The latest EPA-approved version of
California's mobile

source emission factor model for estimating tailpipe, brake, and tire
wear emissions from on-road mobile sources that was available during
the State's and District's development of the SJV PM2.5 Plan
was EMFAC2014.\61\ Following CARB's submission of the Plan, the EPA
approved EMFAC2017, the latest revision to this mobile source emissions
model, and established grace periods during which EMFAC2014 may
continue to be used for transportation conformity purposes (i.e., new
regional emissions analyses and CO, PM10, and
PM2.5 hot-spot analyses).\62\ States are also required to
use the EPA's ``Compilation of Air Pollutant Emission Factors'' (``AP-
42'') road dust method for calculating re-entrained road dust emissions
from paved roads.63 64
---------------------------------------------------------------------------

    \58\ The Emissions Inventory Guidance identifies the types of
sources for which the EPA expects states to provide condensable PM
emissions inventories. Emissions Inventory Guidance, section 4.2.1
(``Condensable PM Emissions''), 63-65.
    \59\ 40 CFR 51.1008(c)(1).
    \60\ Id.
    \61\ 80 FR 77337 (December 14, 2015). EMFAC is short for
EMission FACtor. The EPA announced the availability of the EMFAC2014
model, effective on the date of publication in the Federal Register,
for use in state implementation plan development and transportation
conformity in California. Upon that action, EMFAC2014 was required
to be used for all new regional emissions analyses and CO,
PM10, and PM2.5 hot-spot analyses that were
started on or after December 14, 2017, which was the end of the
grace period for using the prior mobile source emissions model,
EMFAC2011.
    \62\ 84 FR 41717 (August 15, 2019). The grace period for new
regional emissions analyses begins on August 15, 2019 and ends on
August 16, 2021, while the grace period for hot-spot analyses begins
on August 15, 2019 and ends on August 17, 2020. 84 FR 41717, 41720.
    \63\ The EPA released an update to AP-42 in January 2011 that
revised the equation for estimating paved road dust emissions based
on an updated data regression that included new emission tests
results. 76 FR 6328 (February 4, 2011). CARB used the revised 2011
AP-42 methodology in developing on-road mobile source emissions; see
http://www.arb.ca.gov/ei/areasrc/fullpdf/full7-9_2016.pdf.
    \64\ AP-42 has been published since 1972 as the primary source
of the EPA's emission factor information and is available at https://www.epa.gov/air-emissions-factors-and-quantification/ap-42-compilation-air-emissions-factors. It contains emission factors and
process information for more than 200 air pollution source
categories. A source category is a specific industry sector or group
of similar emitting sources. The emission factors have been
developed and compiled from source test data, material balance
studies, and engineering estimates.
---------------------------------------------------------------------------

    In addition to the base year inventory submitted to meet the
requirements of CAA section 172(c)(3), the state must also submit a
projected attainment year inventory and emissions projections for each
RFP milestone year.\65\ These future emissions projections are
necessary components of the attainment demonstration required under CAA
section 189(d) and the demonstration of RFP required under section
172(c)(2).\66\ Emissions projections for future years (referred to in
the Plan as ``forecasted inventories'') should account for, among other
things, the ongoing effects of economic growth and adopted emissions
control requirements. The state's SIP submission should include
documentation to explain how the emissions projections were calculated.
Where a state chooses to allow new major stationary sources or major
modifications to use emission reduction credits (ERCs) that were
generated through shutdown or curtailed emissions units occuring before
the base year of an attainment plan, the projected emissions inventory
used to develop the attainment demonstration must explicitly include
the emissions from such previously shutdown or curtailed emissions
units.\67\
---------------------------------------------------------------------------

    \65\ 40 CFR 51.1008 and 51.1012. See also Emissions Inventory
Guidance, section 3 (``SIP Inventory Requirements and
Recommendations'').
    \66\ 40 CFR 51.1004, 51.1008, 51.1011, and 51.1012.
    \67\ 40 CFR 51.165(a)(3)(ii)(C)(1).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    Summaries of the planning emissions inventories for direct
PM2.5 and PM2.5 precursors (NOX,
SOX,\68\ VOC,\69\ and ammonia) and the documentation for the
inventories for the San Joaquin Valley PM2.5 nonattainment
area are included in Appendix B (``Emissions Inventory'') and Appendix
I (``New Source Review and Emission Reduction Credits'') of the 2018
PM2.5 Plan.
---------------------------------------------------------------------------

    \68\ The SJV PM2.5 Plan generally uses ``sulfur
oxides'' or ``SOX'' in reference to SO2 as a
precursor to the formation of PM2.5. We use
SOX and SO2 interchangeably throughout this
notice.
    \69\ The SJV PM2.5 Plan generally uses ``reactive
organic gasses'' or ``ROG'' in reference to VOC as a precursor to
the formation of PM2.5. We use ROG and VOC
interchangeably throughout this notice.
---------------------------------------------------------------------------

    CARB and District staff worked together to develop the emissions
inventories for the San Joaquin Valley PM2.5 nonattainment
area. The District worked with operators of the stationary facilities
in the nonattainment area to develop the stationary source emissions
estimates. The responsibility for developing emissions estimates for
area sources such as agricultural burning and paved road dust was
shared by the District and CARB. CARB staff developed the emissions
inventories for both on-road and non-road mobile sources.\70\
---------------------------------------------------------------------------

    \70\ The EPA regulations refer to ``non-road'' vehicles and
engines whereas CARB regulations refer to ``Other Mobile Sources''
or ``off-road'' vehicles and engines. These terms refer to the same
types of vehicles and engines. We refer herein to such vehicles and
engines as ``non-road'' sources.
---------------------------------------------------------------------------

    The Plan includes winter (24-hour) average and annual average daily
planning inventories for the 2013 base year, which were modeled from
the 2012 emissions inventory, and estimated emissions for forecasted
years from 2017 through 2028 for the attainment and RFP demonstrations
for the 1997, 2006, and 2012 PM2.5 NAAQS.\71\ In this
proposal, we are proposing action on those winter average and annual
average emissions inventories necessary to support the attainment plan
for the 1997 annual PM2.5 NAAQS--i.e., the 2013 base year
inventory, forecasted inventories for the RFP milestone years of 2017,
2020 (attainment year), and 2023 (post-attainment milestone year), and
additional forecasted inventories for 2018 and 2019 to support the five
percent annual emission reduction demonstration. Each inventory
includes emissions from stationary, area, on-road, and non-road
sources.
---------------------------------------------------------------------------

    \71\ 2018 PM2.5 Plan, Appendix B, B-18 to B-19. The
winter average daily planning inventory corresponds to the months of
November through April when daily ambient PM2.5
concentrations are typically highest. The base year inventory is
from the California Emissions Inventory Development and Reporting
System (CEIDARS) and future year inventories were estimated using
the California Emission Projection Analysis Model (CEPAM), 2016 SIP
Baseline Emission Projections, version 1.05.
---------------------------------------------------------------------------

    The base year inventories for stationary sources were developed
using actual emissions reports from facility operators. The State
developed the base year emissions inventory for area sources using the
most recent models and methodologies available at the time the State
was developing the Plan.\72\ The Plan also includes background,
methodology, and inventories of condensable and filterable
PM2.5 emissions from stationary point and non-point
combustion sources that are expected to generate condensable
PM2.5.\73\ CARB used EMFAC2014 to estimate on-road motor
vehicle emissions based on transportation activity data from the 2014
Regional Transportation Plan (2014 RTP) adopted by the transportation
planning agencies in the San Joaquin Valley.\74\ Re-entrained paved
road dust emissions were calculated using a CARB methodology consistent
with the EPA's AP-42 road dust methodology.\75\
---------------------------------------------------------------------------

    \72\ 2018 PM2.5 Plan, Appendix B, section B.2
(``Emissions Inventory Summary and Methodology'').
    \73\ Id. at B-42 to B-44.
    \74\ Id. at B-37.
    \75\ Id. at B-28.
---------------------------------------------------------------------------

    CARB developed the emissions forecasts by applying growth and
control profiles to the base year inventory. CARB's mobile source
emissions projections take into account predicted activity rates and
vehicle fleet turnover by vehicle model year and adopted controls.\76\
In addition, the Plan states that the District is providing for use of
pre-base year ERCs as offsets by accounting for such ERCs in the

projected 2025 emissions inventory.\77\ The 2018 PM2.5 Plan
identifies growth factors, control factors, and estimated offset use
between 2013 and 2025 for direct PM2.5, NOX,
SOX, and VOC emissions by source category and lists all pre-
base year ERCs issued by the District for PM10,
NOX, SOX, and VOC emissions, by facility.\78\
---------------------------------------------------------------------------

    \76\ Id. at B-18 and B-19.
    \77\ 2018 PM2.5 Plan, Appendix I, I-1 to I-5.
    \78\ Id. at tables I-1 to I-5.
---------------------------------------------------------------------------

    Table 1 provides a summary of the winter (24-hour) average
inventories in tons per day (tpd) of direct PM2.5 and
PM2.5 precursors for the 2013 base year. Table 2 provides a
summary of annual average inventories of direct PM2.5 and
PM2.5 precursors for the 2013 base year. These annual
average inventories provide the basis for the control measure analysis
and the RFP and attainment demonstrations in the SJV PM2.5
Plan.

  Table 1--San Joaquin Valley Winter Average Emissions Inventory for Direct PM2.5 and PM2.5 Precursors for the
                                                 2013 Base Year
                                                      [tpd]
----------------------------------------------------------------------------------------------------------------
                                                    Direct
                    Category                        PM2.5         NOX          SOX          VOC        Ammonia
----------------------------------------------------------------------------------------------------------------
Stationary Sources.............................          8.5         35.0          6.9         86.6         13.9
Area Sources...................................         41.4         11.5          0.5        156.8        291.5
On-Road Mobile Sources.........................          6.4        188.7          0.6         51.1          4.4
Non-Road Mobile Sources........................          4.4         65.3          0.3         27.4          0.0
                                                ----------------------------------------------------------------
    Totals a...................................         60.8        300.5          8.4        321.9        309.8
----------------------------------------------------------------------------------------------------------------
Source: 2018 PM2.5 Plan, Appendix B, tables B-1 to B-5.
a Totals reflect disaggregated emissions and may not add exactly as shown here due to rounding.

  Table 2--San Joaquin Valley Annual Average Emissions Inventory for Direct PM2.5 and PM2.5 Precursors for the
                                                 2013 Base Year
                                                      [tpd]
----------------------------------------------------------------------------------------------------------------
                                                    Direct
                    Category                        PM2.5         NOX          SOX          VOC        Ammonia
----------------------------------------------------------------------------------------------------------------
Stationary Sources.............................          8.8         38.6          7.2         87.1         13.9
Area Sources...................................         41.5          8.1          0.3        153.4        310.9
On-Road Mobile Sources.........................          6.4        183.1          0.6         49.8          4.4
Non-Road Mobile Sources........................          5.8         87.4          0.3         33.8          0.0
                                                ----------------------------------------------------------------
    Totals a...................................         62.5        317.2          8.5        324.1        329.2
----------------------------------------------------------------------------------------------------------------
Source: 2018 PM2.5 Plan, Appendix B, tables B-1 to B-5.
a Totals reflect disaggregated emissions and may not add exactly as shown here due to rounding.

3. The EPA's Evaluation and Proposed Action
    We have reviewed the 2013 base year emissions inventories in the
SJV PM2.5 Plan and emissions inventory estimation
methodologies used by California for consistency with CAA requirements
and the EPA's guidance. We find that the inventories are based on the
most current and accurate information available to the State and
District at the time they were developing the Plan and inventories,
including the latest version of California's mobile source emissions
model that had been approved by the EPA at the time, EMFAC2014. The
inventories comprehensively address all source categories in the San
Joaquin Valley PM2.5 nonattainment area and are consistent
with the EPA's inventory guidance.
    In accordance with 40 CFR 51.1008(c)(1), the 2013 base year is one
of the three years for which monitored data were used to determine that
the San Joaquin Valley area failed to attain the PM2.5 NAAQS
by the applicable Serious area attainment date for the 1997 annual
PM2.5 NAAQS,\79\ and it represents actual annual average
emissions of all sources within the nonattainment area. Direct
PM2.5 and PM2.5 precursors are included in the
inventories, and filterable and condensable direct PM2.5
emissions are identified separately.
---------------------------------------------------------------------------

    \79\ 81 FR 84481, 84482 (November 23, 2016).
---------------------------------------------------------------------------

    For these reasons, we are proposing to approve the 2013 base year
emissions inventories in the SJV PM2.5 Plan for the 1997
annual PM2.5 NAAQS as meeting the requirements of CAA
section 172(c)(3) and 40 CFR 51.1008.

B. PM2.5 Precursors

1. Statutory and Regulatory Requirements
    The composition of PM2.5 is complex and highly variable
due in part to the large contribution of secondary PM2.5 to
total fine particle mass in most locations, and to the complexity of
secondary particle formation processes. A large number of possible
chemical reactions, often non-linear in nature, can convert gaseous
NOX, SO2, VOC, and ammonia to PM2.5,
making them precursors to PM2.5.\80\ Formation of secondary
PM2.5 may also depend on atmospheric conditions, including
solar radiation, temperature, and relative humidity, and the
interactions of precursors with preexisting particles and with cloud or
fog droplets.\81\
---------------------------------------------------------------------------

    \80\ ``Air Quality Criteria for Particulate Matter'' (EPA/600/P-
99/002aF), EPA, October 2004, Chapter 3.
    \81\ ``Regulatory Impact Analysis for the Final Revisions to the
National Ambient Air Quality Standards for Particulate Matter''
(EPA/452/R-12-005), EPA, December 2012), 2-1.
---------------------------------------------------------------------------

    Under subpart 4 of part D, title I of the CAA and the
PM2.5 SIP Requirements Rule, each state containing a
PM2.5 nonattainment area must evaluate all PM2.5
precursors for regulation unless, for any given PM2.5
precursor, the state demonstrates to the Administrator's satisfaction
that such precursor does not contribute significantly to
PM2.5 levels that exceed the NAAQS in the nonattainment
area.\82\ The provisions of

subpart 4 do not define the term ``precursor'' for purposes of
PM2.5, nor do they explicitly require the control of any
specifically identified PM2.5 precursor. The statutory
definition of ``air pollutant,'' however, provides that the term
``includes any precursors to the formation of any air pollutant, to the
extent the Administrator has identified such precursor or precursors
for the particular purpose for which the term `air pollutant' is
used.'' \83\ The EPA has identified NOX, SO2,
VOC, and ammonia as precursors to the formation of
PM2.5.\84\ Accordingly, the attainment plan requirements of
subpart 4 apply to emissions of all four precursor pollutants and
direct PM2.5 from all types of stationary, area, and mobile
sources, except as otherwise provided in the Act (e.g., CAA section
189(e)).
---------------------------------------------------------------------------

    \82\ 81 FR 58010, 58017-58020.
    \83\ CAA section 302(g).
    \84\ 81 FR 58010, 58015.
---------------------------------------------------------------------------

    Section 189(e) of the Act requires that the control requirements
for major stationary sources of direct PM10 also apply to
major stationary sources of PM10 precursors, except where
the Administrator determines that such sources do not contribute
significantly to PM10 levels that exceed the standard in the
area. Section 189(e) contains the only express exception to the control
requirements under subpart 4 (e.g., requirements for RACM and RACT,
BACM and BACT, most stringent measures, and new source review (NSR))
for sources of direct PM2.5 and PM2.5 precursor
emissions. Although section 189(e) explicitly addresses only major
stationary sources, the EPA interprets the Act as authorizing it also
to determine, under appropriate circumstances, that regulation of
specific PM2.5 precursors from other source categories in a
given nonattainment area is not necessary.\85\ For example, under the
EPA's longstanding interpretation of the control requirements that
apply to stationary, area, and mobile sources of PM10
precursors in the nonattainment area under CAA section 172(c)(1) and
subpart 4,\86\ a state may demonstrate in a SIP submission that control
of a certain precursor pollutant is not necessary in light of its
insignificant contribution to ambient PM10 levels in the
nonattainment area.\87\
---------------------------------------------------------------------------

    \85\ Id. at 58018-58019.
    \86\ General Preamble, 57 FR 13498, 13539-13542.
    \87\ Courts have upheld this approach to the requirements of
subpart 4 for PM10. See, e.g., Assoc. of Irritated
Residents v. EPA, et al., 423 F.3d 989 (9th Cir. 2005).
---------------------------------------------------------------------------

    Under the PM2.5 SIP Requirements Rule, a state may elect
to submit to the EPA a ``comprehensive precursor demonstration'' for a
specific nonattainment area to show that emissions of a particular
precursor from all existing sources located in the nonattainment area
do not contribute significantly to PM2.5 levels that exceed
the standards in the area.\88\ If the EPA determines that the
contribution of the precursor to PM2.5 levels in the area is
not significant and approves the demonstration, the state is not
required to control emissions of the relevant precursor from existing
sources in the attainment plan.\89\
---------------------------------------------------------------------------

    \88\ 40 CFR 51.1006(a)(1).
    \89\ Id.
---------------------------------------------------------------------------

    In addition, in May 2019, the EPA issued the ``Fine Particulate
Matter (PM2.5) Precursor Demonstration Guidance''
(``PM2.5 Precursor Guidance''),\90\ which provides
recommendations to states for analyzing nonattainment area
PM2.5 emissions and developing such optional precursor
demonstrations, consistent with the PM2.5 SIP Requirements
Rule. The PM2.5 Precursor Guidance builds upon the draft
version of the guidance, released on November 17, 2016 (``Draft
PM2.5 Precursor Guidance''), which CARB referenced in
developing its precursor demonstration in the SJV PM2.5
Plan.\91\ The EPA's recommendations in the PM2.5 Precursor
Guidance are essentially the same as those in the Draft
PM2.5 Precursor Guidance, including the recommended annual
contribution threshold of 0.2 [mu]g/m\3\.
---------------------------------------------------------------------------

    \90\ ``PM2.5 Precursor Demonstration Guidance,'' EPA-
454/R-19-004, May 2019, including memorandum dated May 30, 2019 from
Scott Mathias, Acting Director, Air Quality Policy Division and
Richard Wayland, Director, Air Quality Assessment Division, Office
of Air Quality Planning and Standards (OAQPS), EPA to Regional Air
Division Directors, Regions 1-10, EPA.
    \91\ ``PM2.5 Precursor Demonstration Guidance, Draft
for Public Review and Comments,'' EPA-454/P-16-001, November 17,
2016, including memorandum dated November 17, 2016 from Stephen D.
Page, Director, OAQPS, EPA to Regional Air Division Directors,
Regions 1-10, EPA.
---------------------------------------------------------------------------

    We are evaluating the SJV PM2.5 Plan in accordance with
the presumption embodied within subpart 4 that all PM2.5
precursors must be addressed in the State's evaluation of potential
control measures, unless the State adequately demonstrates that
emissions of a particular precursor or precursors do not contribute
significantly to ambient PM2.5 levels that exceed the
PM2.5 NAAQS in the nonattainment area. In reviewing any
determination by the State to exclude a PM2.5 precursor from
the required evaluation of potential control measures, we consider both
the magnitude of the precursor's contribution to ambient
PM2.5 concentrations in the nonattainment area and the
sensitivity of ambient PM2.5 concentrations in the area to
reductions in emissions of that precursor.
2. Summary of the State's Submission
    The State presents a summary of its PM2.5 precursor
analysis in Chapter 5 of the 2018 PM2.5 Plan and the full
precursor demonstration in Appendix G (``Precursor Demonstration'') of
the 2018 PM2.5 Plan.\92\ Additional modeling results are
presented in Appendix K (``Modeling Attainment Demonstration''),
section 5.6 (``PM2.5 Precursor Sensitivity Analysis''). CARB
also provided clarifying information on its precursor assessment,
including an Attachment A to its letter transmitting the 2018
PM2.5 Plan to the EPA \93\ and further clarifications in
five email transmittals.\94\ The CARB Staff Report contains additional
discussion of the role of ammonia in the formation of ammonium nitrate
and the role of VOC in the formation of ammonium nitrate and secondary
organic aerosol.\95\
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    \92\ A copy of the contents of Appendix G appears in the CARB
Staff Report, Appendix C4 (``Precursor Demonstrations for Ammonia,
SOX, and ROG'').
    \93\ Letter dated May 9, 2019, from Richard Corey, Executive
Officer, CARB, to Michael Stoker, Regional Administrator, EPA Region
9, Attachment A (``Clarifying information for the San Joaquin Valley
2018 Plan regarding model sensitivity related to ammonia and ammonia
controls'').
    \94\ Email dated June 20, 2019, from Jeremy Avise, CARB, to
Scott Bohning, EPA Region IX, Subject: ``RE: SJV model disbenefit
from SOX reduction,'' with attachment (``CARB's June 2019
Precursor Clarification''); email dated September 19, 2019, from
Jeremy Avise, CARB, to Scott Bohning, EPA Region IX, Subject: ``FW:
SJV species responses,'' with attachments (``CARB's September 2019
Precursor Clarification''); email dated October 18, 2019, from Laura
Carr, CARB, to Scott Bohning, Jeanhee Hong, and Rory Mays, EPA
Region IX, Subject: ``Clarifying information on ammonia,'' with
attachment ``Clarifying Information on Ammonia'' (``CARB's October
2019 Precursor Clarification''); email dated April 19, 2021, from
Laura Carr, CARB, to Rory Mays, EPA Region IX, Subject: ``Ammonia
update,'' with attachment ``Update on Ammonia in the San Joaquin
Valley'' (``CARB's April 19, 2021 Precursor Clarification''); and
email dated April 26, 2021, from Laura Carr, CARB, to Scott Bohning,
EPA Region IX, Subject: ``RE: Ammonia update,'' with attachment
``Ammonia in San Joaquin Valley'' (``CARB's April 26, 2021 Precursor
Clarification'').
    \95\ CARB Staff Report, Appendix C, 9-16. The CARB Staff Report,
Appendix C4 (``Precursor Demonstrations for Ammonia, SOX,
and ROG'') is very similar to the contents of Appendix G of the 2018
PM2.5 Plan.
---------------------------------------------------------------------------

    The Plan provides both concentration-based and sensitivity-based
analyses of precursor contributions to ambient PM2.5
concentrations in the San Joaquin Valley. The State supplemented the
sensitivity analysis, particularly for ammonia, with additional
information, including factors identified in the PM2.5
Precursor Guidance, such as emission trends, the appropriateness of
future year versus base year sensitivity, available emission controls,
and the

severity of nonattainment.\96\ These analyses led the State to conclude
that direct PM2.5 and NOX emissions contribute
significantly to ambient PM2.5 levels that exceed the
PM2.5 NAAQS in the San Joaquin Valley while ammonia,
SOX, and VOC do not contribute significantly to such
exceedances.\97\ We summarize the State's analysis and conclusions
below. For a more detailed summary of the precursor demonstration in
the Plan, please refer to the EPA's ``Technical Support Document, EPA
Evaluation of PM2.5 Precursor Demonstration, San Joaquin
Valley PM2.5 Plan for the 2006 PM2.5 NAAQS,''
February 2020 (``EPA's PM2.5 Precursor TSD'').
---------------------------------------------------------------------------

    \96\ PM2.5 Precursor Guidance, 18-19 (consideration
of additional information), 31 (available emission controls), and
35-36 (appropriateness of future year versus base year sensitivity).
    \97\ Direct PM2.5 emissions are considered a primary
source of ambient PM2.5 (i.e., no further formation in
the atmosphere is required), and therefore is not considered a
precursor pollutant under subpart 4, which may differ from a more
generalized understanding of what contributes to ambient
PM2.5.
---------------------------------------------------------------------------

    For ammonia, SOX, and VOC, CARB assessed the 2015 annual
average concentration of each precursor in ambient PM2.5 at
Bakersfield, for which the necessary speciated PM2.5 data
are available and where the highest PM2.5 design values have
been recorded in most years, and compared those concentrations to the
recommended annual average contribution threshold of 0.2 [mu]g/m\3\
from the Draft PM2.5 Precursor Guidance, which was available
at the time the State developed the SIP.\98\ The contributions of
ammonia, SOX, and VOC were 5.2 [mu]g/m\3\, 1.6 [mu]g/m\3\,
and 6.2 [mu]g/m\3\, respectively. Given that these levels are well
above the EPA's 0.2 [mu]g/m\3\ recommended contribution threshold, the
State proceeded with a sensitivity-based analysis.
---------------------------------------------------------------------------

    \98\ 2018 PM2.5 Plan, Appendix G, 3. The Plan does
not present a concentration-based analysis for the 24-hour average
concentrations in the San Joaquin Valley. Instead, CARB relied on
the annual average concentration-based analysis as an interim step
to the sensitivity-based analysis, for which CARB assessed the
sensitivity of both 24-hour average and annual average ambient
PM2.5 concentrations to precursor emissions reductions.
Separately, the Plan presents a graphical representation of annual
average ambient PM2.5 components (i.e., crustal
particulate matter, elemental carbon, organic matter, ammonium
sulfate, and ammonium nitrate) for 2011-2013 for Bakersfield,
Fresno, and Modesto. 2018 PM2.5 Plan, Chapter 3, 3-3 to
3-4.
---------------------------------------------------------------------------

    The State's sensitivity-based analysis used the same Community
Multiscale Air Quality (CMAQ) modeling platform as that used for the
Plan's attainment demonstration. The State modeled the sensitivity of
ambient PM2.5 concentration in the San Joaquin Valley to 30
percent and 70 percent emissions reductions in 2013, 2020, and 2024 for
each of ammonia, SOX, and VOC. The State estimated baseline
(2013, 2020, and 2024) design values for PM2.5 using
relative response factors (RRFs) and calculated the ammonia,
SOX, and VOC precursor contribution for a given year and for
each sensitivity scenario (30 percent and 70 percent emissions
reductions) as the difference between its baseline design value and the
design value for each sensitivity scenario.\99\ Based on these analyses
and supporting information, the State concludes that ammonia,
SOX, and VOC emissions do not contribute significantly to
PM2.5 levels that exceed the 1997 annual PM2.5
NAAQS in the San Joaquin Valley.
---------------------------------------------------------------------------

    \99\ This procedure is the procedure recommended by the EPA.
PM2.5 Precursor Guidance, 37.
---------------------------------------------------------------------------

3. The EPA's Evaluation and Proposed Action
    As discussed in section IV of this proposal, the EPA is proposing
to disapprove the attainment demonstration and related elements in the
SJV PM2.5 Plan for the 1997 annual PM2.5 NAAQS,
including the five percent annual emission reductions demonstration,
reasonable further progress (RFP) demonstration, and quantitative
milestones, based on ambient monitoring data that show that the Plan
was insufficient to achieve attainment of the 1997 annual
PM2.5 NAAQS by December 31, 2020, the State's projected
attainment date. Given that we are proposing to disapprove the
attainment demonstration, and given that the precursor demonstration
for the 1997 annual PM2.5 NAAQS largely relies on the
technical analyses and assumptions that provide the basis for the
attainment demonstration, we are also proposing to disapprove the
precursor demonstration in the SJV PM2.5 Plan for the 1997
annual PM2.5 NAAQS. Therefore, all precursors to the
formation of PM2.5 in the San Joaquin Valley (i.e.,
NOX, ammonia, SOX, and VOC) remain
``PM2.5 plan precursors'' as defined in 40 CFR 51.1000 for
purposes of the 1997 annual PM2.5 NAAQS for the Plan that is
the subject of this proposal.
    If the EPA takes final action on the SJV PM2.5 Plan as
proposed, California will be required to develop and submit a revised
plan for the San Joaquin Valley area that addresses the applicable CAA
requirements, including the requirements of CAA section 189(d). Under
40 CFR 51.1006, the State will be required to submit an updated
precursor demonstration if it seeks to exempt sources of a particular
precursor from control requirements in the new Serious area attainment
demonstration. For these reasons, and because we are proposing to
disapprove the precursor demonstration on the basis of our proposed
disapproval of the attainment demonstration, we are not providing a
full evaluation of the precursor demonstration for the 1997 annual
PM2.5 NAAQS in the SJV PM2.5 Plan at this time.

C. Attainment Plan Control Strategy

1. Statutory and Regulatory Requirements
    The overarching requirement for the CAA section 189(d) attainment
control strategy is that it provides for attainment of the standards as
expeditiously as practicable.\100\ The control strategy must include
any additional measures (beyond those already adopted in previous SIPs
for the area as RACM/RACT or BACM/BACT) that are needed for the area to
attain expeditiously. This includes reassessing any measures previously
rejected during the development of any Moderate area or Serious area
attainment plan control strategy.\101\ The plan must also demonstrate
that it will, at a minimum, achieve an annual five percent reduction in
emissions of direct PM2.5 or any PM2.5 plan
precursor from sources in the area until attainment, based on the most
recent emissions inventory for the area.\102\
---------------------------------------------------------------------------

    \100\ 81 FR 58010, 58100.
    \101\ 40 CFR 50.1010(c)(2)(ii).
    \102\ CAA section 189(d) and 40 CFR 51.1010(c).
---------------------------------------------------------------------------

    In the PM2.5 SIP Requirements Rule, the EPA clarified
its interpretation of the statutory language in CAA section 189(d)
requiring a state to submit a new attainment plan to achieve annual
reductions ``from the date of such submission until attainment,'' to
mean annual reductions beginning from the due date of such submission
until the new projected attainment date for the area based on the new
or additional control measures identified to achieve at least five
percent emissions reductions annually.\103\ This interpretation is
intended to make clear that even if a state is late in submitting its
CAA section 189(d) plan, the area must still achieve its annual five
percent emission reductions beginning from the date by

which the state was required to make its CAA section 189(d) submission,
not by some later date. Because the deadline for California to submit a
section 189(d) plan for the 1997 PM2.5 NAAQS in the San
Joaquin Valley was December 31, 2016, one year after the December 31,
2015 attainment date for these NAAQS under CAA section 188(c)(2), the
starting point for the five percent emission reduction requirement
under section 189(d) for this area is 2017.
---------------------------------------------------------------------------

    \103\ 81 FR 58010, 58101. The new projected attainment date is
established by the EPA in accordance with the provisions of CAA
sections 179(d)(3) and 172(a)(2), which require that the new
attainment date be as expeditious as practicable but no later than 5
years from the date of publication in the Federal Register of the
EPA's determination that the area failed to attain the relevant
NAAQS, except that the EPA may extend the attainment date by up to 5
additional years based on the severity of nonattainment and the
availability and feasibility of pollution control measures. Id. at
58103.
---------------------------------------------------------------------------

    As discussed in section III of this proposed rule, a state with a
Serious PM2.5 nonattainment area that fails to attain the
NAAQS by the applicable Serious area attainment date must also address
any statutory requirements applicable to Moderate and Serious
nonattainment area plans under CAA sections 172 and 189 of the CAA to
the extent that those requirements have not already been met. Because
the EPA has not previously taken action to approve the California SIP
as meeting the Serious nonattainment area planning requirements under
CAA sections 172 and 189 for the 1997 annual PM2.5 NAAQS for
the San Joaquin Valley area, the EPA is reviewing the SJV
PM2.5 Plan for compliance with those requirements, including
the requirement for BACM.
    Section 189(b)(1)(B) of the Act requires for any Serious
PM2.5 nonattainment area that the state submit provisions to
assure that BACM for the control of PM2.5 and
PM2.5 precursors shall be implemented no later than four
years after the date the area is reclassified as a Serious area. The
EPA has defined BACM in the PM2.5 SIP Requirements Rule to
mean ``any technologically and economically feasible control measure
that . . . can achieve greater permanent and enforceable emissions
reductions of direct PM2.5 emissions and/or emissions of
PM2.5 plan precursors from sources in the area than can be
achieved through the implementation of RACM on the same source(s). BACM
includes best available control technology (BACT).'' \104\
---------------------------------------------------------------------------

    \104\ 40 CFR 51.1000 (definitions). In longstanding guidance,
the EPA has similarly defined BACM to mean, ``among other things,
the maximum degree of emissions reduction achievable for a source or
source category, which is determined on a case-by-case basis
considering energy, environmental, and economic impacts.'' General
Preamble Addendum, 42010, 42013.
---------------------------------------------------------------------------

    The EPA generally considers BACM a control level that goes beyond
existing RACM-level controls, for example by expanding the use of RACM
controls or by requiring preventative measures instead of
remediation.\105\ Indeed, as implementation of BACM and BACT is
required when a Moderate nonattainment area is reclassified as Serious
due to its inability to attain the NAAQS through implementation of
``reasonable'' measures, it is logical that ``best'' control measures
should represent a more stringent and potentially more costly level of
control.\106\ If RACM and RACT level controls of emissions have been
insufficient to reach attainment, the CAA contemplates the
implementation of more stringent controls, controls on more sources, or
other adjustments to the control strategy necessary to attain the NAAQS
in the area.
---------------------------------------------------------------------------

    \105\ 81 FR 58010, 58081 and General Preamble Addendum, 42011,
42013.
    \106\ Id. and General Preamble Addendum, 42009-42010.
---------------------------------------------------------------------------

    Consistent with longstanding guidance provided in the General
Preamble Addendum, the preamble to the PM2.5 SIP
Requirements Rule discusses the following steps for determining BACM
and BACT:
    (1) Develop a comprehensive emissions inventory of the sources of
PM2.5 and PM2.5 precursors;
    (2) Identify potential control measures;
    (3) Determine whether an available control measure or technology is
technologically feasible;
    (4) Determine whether an available control measure or technology is
economically feasible; and
    (5) Determine the earliest date by which a control measure or
technology can be implemented in whole or in part.\107\
---------------------------------------------------------------------------

    \107\ 81 FR 58010, 58083-58085.
---------------------------------------------------------------------------

    The EPA allows consideration of factors such as physical plant
layout, energy requirements, needed infrastructure, and workforce type
and habits when considering technological feasibility. For purposes of
evaluating economic feasibility, the EPA allows consideration of
factors such as the capital costs, operating and maintenance costs, and
cost effectiveness (i.e., cost per ton of pollutant reduced by a
measure or technology) associated with the measure or control.\108\
---------------------------------------------------------------------------

    \108\ 40 CFR 51.1010(a)(3) and 81 FR 58010, 58041-58042.
---------------------------------------------------------------------------

    Once these analyses are complete, the state must use this
information to develop enforceable control measures and submit them to
the EPA for evaluation as SIP provisions to meet the basic requirements
of CAA section 110 and any other applicable substantive provisions of
the Act.
2. Summary of the State's Submission and the EPA's Evaluation and
Proposed Action
    The control strategy in the SJV PM2.5 Plan is based on
ongoing emissions reductions from baseline control measures. As the
term is used here, baseline measures are State and District regulations
adopted prior to the development of the SJV PM2.5 Plan that
continue to achieve emissions reductions through the projected 2020
attainment year and beyond. The 2018 PM2.5 Plan describes
these measures in Chapter 4,\109\ Appendix C (``Stationary Source
Control Measure Analyses''), and Appendix D (``Mobile Source Control
Measure Analyses''). Reductions from these baseline measures are
incorporated into the projected baseline inventories and reductions
from District measures are individually quantified in Appendix C.
---------------------------------------------------------------------------

    \109\ 2018 PM2.5 Plan, Chapter 4, Table 4-2.
---------------------------------------------------------------------------

    The 2018 PM2.5 Plan states that mobile sources emit over
85 percent of the NOX in the San Joaquin Valley and that
CARB has adopted and amended regulations to reduce public exposure to
diesel particulate matter, which includes direct PM2.5 and
NOX, from ``fuel sources, freight transport sources like
heavy-duty diesel trucks, transportation sources like passenger cars
and buses, and non-road sources like large construction equipment.''
\110\
---------------------------------------------------------------------------

    \110\ 2018 PM2.5 Plan, Chapter 4, 4-9. For CARB's
BACM analysis for mobile source measures, see 2018 PM2.5
Plan, Appendix D, including analyses for on-road light-duty vehicles
and fuels (starting on page D-17), on-road heavy-duty vehicles and
fuels (starting on page D-35), and non-road sources (starting on
page D-64).
---------------------------------------------------------------------------

    Given the need for substantial emissions reductions from mobile and
area sources to meet the NAAQS in California nonattainment areas, the
State of California has developed stringent control measures for on-
road and non-road mobile sources and the fuels that power them.
California has unique authority under CAA section 209 (subject to a
waiver or authorization as applicable by the EPA) to adopt and
implement new emissions standards for many categories of on-road
vehicles and engines and new and in-use non-road vehicles and engines.
The EPA has approved such mobile source regulations for which waiver
authorizations have been issued as revisions to the California
SIP.\111\
---------------------------------------------------------------------------

    \111\ For example, see 81 FR 39424 (June 16, 2016); 82 FR 14446
(March 21, 2017); and 83 FR 23232 (May 18, 2018).
---------------------------------------------------------------------------

    CARB's mobile source program extends beyond regulations that are
subject to the waiver or authorization process set forth in CAA section
209 to

include standards and other requirements to control emissions from in-
use heavy-duty trucks and buses, gasoline and diesel fuel
specifications, and many other types of mobile sources. Generally,
these regulations have also been submitted and approved as revisions to
the California SIP.\112\
---------------------------------------------------------------------------

    \112\ For example, see the EPA's approval of standards and other
requirements to control emissions from in-use heavy-duty diesel
trucks (77 FR 20308, April 4, 2012), and revisions to the California
on-road reformulated gasoline and diesel fuel regulations (75 FR
26653, May 12, 2010).
---------------------------------------------------------------------------

    As to stationary and area sources, the SJV PM2.5 Plan
states that stringent regulations adopted for prior attainment plans
continue to reduce emissions of NOX and direct
PM2.5.\113\ Specifically, Table 4-1 of the 2018
PM2.5 Plan identifies 33 District measures that limit
NOX and direct PM2.5 emissions from stationary
and area sources.\114\
---------------------------------------------------------------------------

    \113\ 2018 PM2.5 Plan, Chapter 4, 4-3. For the
District's BACM analysis for stationary and area source measures,
see 2018 PM2.5 Plan, Appendix C.
    \114\ Id. at Chapter 4, Table 4-1.
---------------------------------------------------------------------------

a. Best Available Control Measures
    The State's BACM demonstration is presented in Appendix C
(``Stationary Source Controls'') and Appendix D (``Mobile Source
Control Measure Analyses'') of the 2018 PM2.5 Plan. As
discussed in section IV.A of this proposed rule, Appendix B
(``Emissions Inventory'') of the 2018 PM2.5 Plan contains
the planning inventories for direct PM2.5 and all
PM2.5 precursors (NOX, SOX, VOC, and
ammonia) for the San Joaquin Valley nonattainment area together with
documentation to support these inventories. Each inventory includes
emissions from stationary, area, on-road, and non-road emission
sources, and the State specifically identifies the condensable
component of direct PM2.5 for relevant stationary source and
area source categories. As discussed in section IV.B of this proposed
rule, the State concludes that the Plan should control emissions of
PM2.5 and NOX to reach attainment. Accordingly,
the BACM and BACT evaluation in the Plan addresses potential controls
for sources of those pollutants.
    For stationary and area sources, the District identifies the
sources of direct PM2.5 and NOX in the San
Joaquin Valley that are subject to District emission control measures
and provides its evaluation of these regulations for compliance with
BACM requirements in Appendix C of the 2018 PM2.5 Plan. As
part of its process for identifying candidate BACM and considering the
technical and economic feasibility of additional control measures, the
District reviewed the EPA's guidance documents on BACM, additional
guidance documents on control measures for direct PM2.5 and
NOX emission sources, and control measures implemented in
other ozone and PM2.5 nonattainment areas in California and
other states.\115\ The District also provides an analysis of several
SIP-approved VOC regulations that, according to the District, also
provide ammonia co-benefits.\116\
---------------------------------------------------------------------------

    \115\ 2018 PM2.5 Plan, Chapter 4, section 4.3.1.
    \116\ Id. at Appendix C., section C.25.
---------------------------------------------------------------------------

    For mobile sources, CARB identifies the sources of direct
PM2.5 and NOX in the San Joaquin Valley that are
subject to the State's emission control measures and provides its
evaluation of these regulations for compliance with BACM requirements
in Appendix D of the 2018 PM2.5 Plan. Appendix D describes
CARB's process for determining BACM, including identification of the
sources of direct PM2.5 and NOX in the San
Joaquin Valley, identification of potential control measures for such
sources, assessment of the stringency and feasibility of the potential
control measures, and adoption and implementation of feasible control
measures.\117\ Appendix D of the 2018 PM2.5 Plan also
describes the current efforts of the eight local jurisdiction
metropolitan planning organizations (MPOs) to implement cost-effective
transportation control measures (TCMs) in the San Joaquin Valley.\118\
---------------------------------------------------------------------------

    \117\ Id. at Appendix D, Chapter II.
    \118\ Id. at Appendix D, D-127 and D-128.
---------------------------------------------------------------------------

    Because we are proposing to disapprove the comprehensive precursor
demonstration in the SJV PM2.5 Plan for purposes of the 1997
annual PM2.5 NAAQS, all precursors to the formation of
PM2.5 (i.e., NOX, ammonia, SOX and
VOC) remain PM2.5 plan precursors subject to control
requirements under subpart 4 of part D, title I of the Act for purposes
of the 1997 annual PM2.5 NAAQS in the San Joaquin Valley.
The SJV PM2.5 Plan contains State and District control
measures and related BACM analyses for sources of direct
PM2.5 and NOX in the San Joaquin Valley but does
not contain such measures or analyses for sources of SOX or
VOC emissions, given the State's assumption that these precursors would
not be subject to controls. Furthermore, while the District provides an
analysis of potential control of ammonia sources, the Plan does not
identify any specific, enforceable requirement to reduce ammonia
emissions in the area and does not demonstrate that the State or
District adequately considered potential control measures for ammonia
sources, given the State's assumption that ammonia would not be subject
to controls. Without an approvable precursor demonstration, the SJV
PM2.5 Plan does not satisfy BACM and BACT requirements for
sources of direct PM2.5 and PM2.5 plan precursors
for purposes of the 1997 annual PM2.5 NAAQS. We therefore
propose to disapprove the BACM/BACT demonstration in the SJV
PM2.5 Plan for failure to meet the requirements of CAA
section 189(b)(1)(B) and 40 CFR 51.1010 for the 1997 annual
PM2.5 NAAQS.
b. Five Percent Emission Reduction Requirement
    The SJV PM2.5 Plan's demonstration of annual five
percent reductions in NOX emissions is in section 5.2 of the
2018 PM2.5 Plan. As shown in Table 3, the demonstration uses
the 2013 base year inventory as the starting point from which the five
percent per year emission reductions are calculated and uses 2017 as
the year from which the reductions start. The target required reduction
in 2017 is five percent of the base year (2013) inventory, which is
approximately 15.9 tpd of NOX, and the targets for
subsequent years are additional reductions of five percent each year
until the 2020 attainment year. The projected emissions inventories
reflect NOX emissions reductions achieved by baseline
control measures and the demonstration shows that these NOX
emissions reductions are greater than the required five percent per
year.

       Table 3--2017-2020 Annual Five Percent Emission Reductions Demonstration for the San Joaquin Valley
----------------------------------------------------------------------------------------------------------------
                                                                           CEPAM
                                        % Reduction   5% Target (tpd     inventory
                Year                  from 2013 base       NOX)         v1.05 (tpd             Meets 5%?
                                           year                            NOX)
----------------------------------------------------------------------------------------------------------------
2013 (base year)....................                                           317.3

2017................................               5           301.3           233.4  Yes.
2018................................              10           285.5           221.5  Yes.
2019................................              15           269.6           214.5  Yes.
2020................................              20           253.8           203.3  Yes.
----------------------------------------------------------------------------------------------------------------
Source: 2018 PM2.5 Plan, Table 5-2.

    The State's methodology for calculating the five percent emission
reduction targets for the years 2017, 2018, 2019, and 2020 is
consistent with CAA requirements as interpreted in the PM2.5
SIP Requirements Rule, and the Plan shows that NOX emissions
reductions from 2017 to 2020 are greater than the required five percent
per year. However, the language in section 189(d) compels us to
conclude that the five percent demonstration in the Plan does not meet
that section's requirement for the 1997 annual PM2.5 NAAQS.
CAA section 189(d) requires that the plan provide for annual reductions
of PM2.5 or a PM2.5 precursor of not less than
five percent each year from the date of submission of the plan until
the applicable attainment date approved by the EPA.\119\ The Plan
submitted by California does not demonstrate reductions after 2020
because it projects attainment of the 1997 annual PM2.5
NAAQS by December 31, 2020. Because the EPA is proposing to disapprove
the attainment demonstration, as discussed in section IV.D, based on
ambient monitoring data for 2018-2020 indicating that the San Joaquin
Valley did not attain the 1997 annual PM2.5 NAAQS by the
December 31, 2020 attainment date projected by the State in the SJV
PM2.5 Plan, December 31, 2020 is not the applicable
attainment date for purposes of the 1997 annual PM2.5 NAAQS
in this area, and the Plan does not meet the requirement to demonstrate
five percent reductions per year until attainment. Therefore, the EPA
is proposing to disapprove the demonstration of the five percent annual
emission reductions in the SJV PM2.5 Plan for failure to
meet the requirements of CAA section 189(d) and 40 CFR 51.1010(c) for
the 1997 annual PM2.5 NAAQS.
---------------------------------------------------------------------------

    \119\ Under 40 CFR 51.1000, the applicable attainment date is
the latest statutory date by which an area is required to attain a
particular PM2.5 NAAQS or the attainment date approved by
the EPA as part of an attainment plan for the area. For a Serious
nonattainment area subject to the requirements of CAA section
189(d), the EPA establishes the applicable attainment date in
accordance with the provisions of CAA sections 179(d)(3) and
172(a)(2). 81 FR 58010, 58103.
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D. Attainment Demonstration and Modeling

1. Statutory and Regulatory Requirements
    Section 189(d) of the CAA requires a state with a Serious
nonattainment area that failed to attain the NAAQS by the Serious area
attainment date to submit a revised attainment demonstration as part of
a new plan. The PM2.5 SIP Requirements Rule explains that
the same general requirements that apply to Moderate and Serious area
plans under CAA sections 189(a) and 189(b) should apply to plans
developed pursuant to CAA section 189(d)--i.e., the plan must include a
demonstration (including air quality modeling) that the control
strategy provides for attainment of the PM2.5 NAAQS as
expeditiously as practicable.\120\ For purposes of determining the
attainment date that is as expeditious as practicable, the state must
conduct future year modeling that takes into account emissions growth,
known controls (including any controls that were previously determined
to be RACM/RACT or BACM/BACT), the five percent per year emissions
reductions required by CAA section 189(d), and any other emissions
controls that are needed for expeditious attainment of the NAAQS.
---------------------------------------------------------------------------

    \120\ 81 FR 58010, 58102.
---------------------------------------------------------------------------

    The EPA's PM2.5 modeling guidance \121\ (``Modeling
Guidance'' and ``Modeling Guidance Update'') recommends that a
photochemical model, such as the Comprehensive Air Quality Model with
Extensions (CAMx) or Community Multiscale Air Quality Model (CMAQ), be
used to simulate a base case, with meteorological and emissions inputs
reflecting a base case year, to replicate concentrations monitored in
that year. The model application to the base year undergoes a
performance evaluation to ensure that it satisfactorily corroborates
the concentrations monitored in that year. The model may then be used
to simulate emissions occurring in other years required for a plan,
namely the base year (which may differ from the base case year) and a
future year.\122\ The modeled response to the emission changes between
those years is used to calculate RRFs that are applied to the design
value in the base year to estimate the projected design value in the
future year for comparison against the NAAQS. Separate RRFs are
estimated for each chemical species component of PM2.5, and
for each quarter of the year, to reflect their differing responses to
seasonal meteorological conditions and emissions. Because each species
is handled separately, before applying an RRF, the base year design
value must be speciated using available chemical species measurements--
that is, each day's measured PM2.5 design value must be
split into its species components. The Modeling Guidance provides
additional detail on the recommended approach.\123\
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    \121\ Memorandum dated November 29, 2018, from Richard Wayland,
Air Quality Assessment Division, Office of Air Quality Planning and
Standards, EPA, to Regional Air Division Directors, EPA, Subject:
``Modeling Guidance for Demonstrating Air Quality Goals for Ozone,
PM2.5, and Regional Haze,'' (``Modeling Guidance''), and
memorandum dated June 28, 2011, from Tyler Fox, Air Quality Modeling
Group, OAQPS, EPA, to Regional Air Program Managers, EPA, Subject:
``Update to the 24 Hour PM2.5 NAAQS Modeled Attainment
Test,'' (``Modeling Guidance Update'').
    \122\ In this section, we use the terms ``base case,'' ``base
year'' or ``baseline,'' and ``future year'' as described in section
2.3 of the EPA's Modeling Guidance. The ``base case'' modeling
simulates measured concentrations for a given time period, using
emissions and meteorology for that same year. The modeling ``base
year'' (which can be the same as the base case year) is the
emissions starting point for the plan and for projections to the
future year, both of which are modeled for the attainment
demonstration. Modeling Guidance, 37-38.
    \123\ Modeling Guidance, section 4.4, ``What is the Modeled
Attainment Tests for the Annual Average PM2.5 NAAQS.''
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2. Summary of the State's Submission
    As discussed in section IV.C, the SJV PM2.5 Plan
includes a modeled demonstration projecting that the San Joaquin Valley
would attain the 1997

annual PM2.5 NAAQS by December 31, 2020, based on ongoing
emissions reductions from baseline control measures. CARB conducted
photochemical modeling with the CMAQ model using inputs developed from
routinely available meteorological and air quality data, as well as
more detailed and extensive data from the DISCOVER-AQ field study
conducted in January and February of 2013.\124\ The Plan's primary
discussion of the photochemical modeling appears in Appendix K
(``Modeling Attainment Demonstration'') of the 2018 PM2.5
Plan. The State briefly summarizes the area's air quality problem in
Chapter 2 (``Air Quality Challenges and Trends'') and the modeling
results in Chapter 5.3 (``Attainment Demonstration and Modeling'') of
the 2018 PM2.5 Plan. The State provides a conceptual model
of PM2.5 formation in the San Joaquin Valley as part of the
modeling protocol in Appendix L (``Modeling Protocol''). Appendix J
(``Modeling Emission Inventory'') describes emission input preparation
procedures. The State presents additional relevant information in
Appendix C (``Weight of Evidence Analysis'') of the CARB Staff Report,
which includes ambient trends and other data in support of the
attainment demonstration.
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    \124\ NASA, ``Deriving Information on Surface conditions from
COlumn and VERtically Resolved Observations Relevant to Air
Quality,'' available at https://www.nasa.gov/mission_pages/discover-aq/index.html.
---------------------------------------------------------------------------

    CARB's air quality modeling approach investigated the many inter-
connected facets of modeling ambient PM2.5 in the San
Joaquin Valley, including model input preparation, model performance
evaluation, use of the model output for the numerical NAAQS attainment
test, and modeling documentation. Specifically, this required the
development and evaluation of a conceptual model, modeling protocol,
episode (i.e., base year) selection, modeling domain, CMAQ model
selection, initial and boundary condition procedures, meteorological
model choice and performance, modeling emissions inventory preparation
procedures, model performance, attainment test procedure, adjustments
to baseline air quality for modeling, the 2020 attainment test, and an
unmonitored area analysis. These analyses are generally consistent with
the EPA's recommendations in the Modeling Guidance.
    The model performance evaluation in Appendix K includes statistical
and graphical measures of model performance. The magnitude and timing
of predicted concentrations of total PM2.5, as well as of
its ammonium and nitrate components, generally match the occurrence of
elevated PM2.5 levels in the measured observations. A
comparison to other recent modeling efforts shows good model
performance on bias, error, and correlation with measurements, for
total PM2.5 and for most of its chemical components. The
Weight of Evidence Analysis shows the downward trend in NOX
emissions along with a 24 to 44 percent decrease in annual
PM2.5 design values between 1999 and 2017.\125\ The analysis
also shows decreases in daily PM2.5 concentrations during
winter, and in the frequency of high PM2.5 concentrations
generally.\126\ Available ambient air quality data show that total
PM2.5 and ammonium nitrate concentrations have declined over
the 2004-2017 period, despite some increases from time to time.\127\
These trends show that there has been an improvement in air quality due
to emissions reductions in the San Joaquin Valley.
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    \125\ Weight of Evidence Analysis, 26-27, Figure 12, and Figure
24.
    \126\ Id. at Figure 16 and Figure 17.
    \127\ Id. at Figure 21.
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    The State conducted three CMAQ \128\ simulations: (1) A 2013 base
year simulation to demonstrate that the model reasonably reproduced the
observed PM2.5 concentrations in the San Joaquin Valley; (2)
a 2013 baseline year simulation that was the same as the 2013 base year
simulation but excluded exceptional event emissions, such as wildfire
emissions; and (3) a 2020 future year simulation that reflects
projected emissions growth and reductions due to controls that have
already been adopted and implemented.
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    \128\ CMAQ Version 5.0.2.
---------------------------------------------------------------------------

    Table 4 shows the 2013 base year and 2020 projected future year
annual PM2.5 design values at monitoring sites in the San
Joaquin Valley. The highest 2020 projected design value is 14.6 [mu]g/m
\3\ at the Bakersfield--California monitoring site, which is below the
15.0 [mu]g/m \3\ level of the 1997 annual PM2.5 NAAQS.

Table 4--Projected Future Annual PM2.5 Design Values at Monitoring Sites
                        in the San Joaquin Valley
                              [[mu]g/m\3\]
------------------------------------------------------------------------
                                                               2020
             Monitoring site                 2013 Base       Projected
                                           design value    design value
------------------------------------------------------------------------
Bakersfield--California.................            17.2            14.6
Fresno--Garland.........................            16.9            14.2
Hanford.................................            16.5            13.3
Fresno--Hamilton & Winery...............            16.2            13.5
Clovis..................................            16.1            13.4
Visalia.................................            16.0            13.5
Bakersfield--Planz......................            15.0            12.4
Madera..................................            14.9            12.5
Turlock.................................            14.2            11.9
Modesto.................................            13.1            11.4
Merced-M. Street........................            13.1            10.9
Stockton................................            13.0            11.0
Merced--S Coffee........................            11.0             9.3
Manteca.................................            10.1             8.7
Tranquility.............................             7.7             6.4
------------------------------------------------------------------------
Source: 2018 PM2.5 Plan, Table 5-4.

3. The EPA's Evaluation and Proposed Action
    The EPA has reviewed monitoring data recorded at air quality
monitors throughout the San Joaquin Valley PM2.5
nonattainment area to consider whether the area attained the 1997
annual PM2.5 NAAQS by the December 31, 2020 attainment date
projected in the SJV PM2.5 Plan. We based our review on
preliminary but complete and quality-assured ambient air monitoring
data recorded during the three years preceding the State's identified
attainment date (2018-2020).\129\ The EPA has found that the
PM2.5 monitoring network in the San Joaquin Valley currently
meets or exceeds the requirements for the minimum number of monitoring
sites designated as State and Local Air Monitoring Stations (SLAMS) for
PM2.5 and that CARB's and the District's annual network
plans meet the applicable requirements in 40 CFR part 58.\130\
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    \129\ At the time of the EPA's review, the State had not yet
certified the 2020 ambient air monitoring data. We understand that
the State is working to certify the data and anticipate that the
2020 data will be certified prior to our final action. We do not
expect the certified data to differ significantly from the data
reflected in this proposal.
    \130\ Letter dated October 26, 2020, from Gwen Yoshimura,
Manager, EPA Region 9, Air Quality Analysis Office, to Jon Klassen,
Director of Strategies and Incentives, SJVUAPCD, and letter dated
November 5, 2020, from Gwen Yoshimura, Manager, EPA Region 9, Air
Quality Analysis Office, to Ravi Ramalingam, Chief, Consumer
Products and Air Quality Assessment Branch, CARB.
---------------------------------------------------------------------------

    Table 5 shows the annual arithmetic means and preliminary annual
PM2.5 design values at each of the 18 SLAMS monitoring sites
within the San Joaquin Valley nonattainment area for the most recent
three-year period (2018-2020). The data show that the annual design
value for the 2018-2020 period ranged from 9.5 to 17.6 [mu]g/m \3\
across the area at monitors with valid design values, and that the
valid design values exceeded 15.0 [mu]g/m \3\ (i.e., the level of the
1997 annual PM2.5 NAAQS) at eight of the monitoring sites,
indicating that the area did not attain the 1997 annual
PM2.5 NAAQS by the projected December 31, 2020 attainment
date.
    As discussed in section IV.D.2, CARB's Weight of Evidence Analysis
shows a long-term downward trend in annual PM2.5 design
values through 2017, the latest year prior to development of the SJV
PM2.5 Plan for which air quality data were available. As
described in the Weight of Evidence Analysis, the San Joaquin Valley
has shown a general downward trend in measured PM2.5
concentrations despite the effects of extensive wildfires in 2008 and
unusual meteorological conditions during the 2013/2014 winter that
resulted in higher concentrations during those periods. Similarly, the
San Joaquin Valley area may have experienced higher than normal
PM2.5 concentrations in 2018 and 2020 due to wildfires in
the surrounding areas during the summer and fall months. Table 5 shows
that concentrations at all 17 monitors in the San Joaquin Valley area
with data spanning 2018 to 2020 are significantly higher in 2018 and
2020 relative to concentrations in 2019, possibly due to the wildfires
in those years.

                               Table 5--2018-2020 Annual PM2.5 Design Values for the San Joaquin Valley Nonattainment Area
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Annual arithmetic mean ([mu]g/m\3\)          2018-2020
                                                                                ------------------------------------------------ Annual  design
                  County                        General location site         AQS ID                                                      values ([mu]g/
                                                                                2018            2019            2020          m\3\) \a\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Fresno....................................  Fresno--Pacific.............     06-019-5025            17.1            11.2            18.7            15.7
                                            Fresno--Garland.............     06-019-0011            16.2            11.1            19.2            15.5
                                            Fresno--Foundry.............     06-019-2016             Inc             Inc            20.3        \b\ 20.3
                                                                                (Inv)
                                            Clovis......................     06-019-5001            14.3            10.3            18.4            14.4
                                                                                (Inc)                           (Inv)
                                            Tranquility.................     06-019-2009            11.1             5.8            11.5             9.5
Kern......................................  Bakersfield--Planz Road.....     06-029-0016            19.4            13.0            20.3            17.6
                                            Bakersfield--California Ave.     06-029-0014            17.7            11.9            19.7            16.4
                                            Bakersfield--Golden State        06-029-0010            18.1            12.4            20.0            16.8
                                             Highway.
Kings.....................................  Corcoran....................     06-031-0004            17.2            12.1            19.5            16.3
                                            Hanford.....................     06-031-1004            17.7            12.2            19.9            16.6
Madera....................................  Madera--Avenue 14...........     06-039-2010            14.0             9.7            16.9            13.5
Merced....................................  Merced--M Street............     06-047-2510            14.2             9.6            15.5            13.1
                                            Merced--Coffee..............     06-047-0003            15.1             9.1            14.7            13.0
San Joaquin...............................  Stockton....................     06-077-1002            17.6             9.3            14.4            13.8
                                            Manteca.....................     06-077-2010            13.4             8.3            14.8            12.2
                                                                                (Inc)                           (Inv)
Stanislaus................................  Modesto.....................     06-099-0005            15.2             7.7            14.5            12.5
                                            Turlock.....................     06-099-0006            17.2            10.7            15.5            14.5
Tulare....................................  Visalia.....................     06-107-2002            17.3            12.9            19.7            16.7
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: EPA, Preliminary 2020 AQS Design Value Report, AMP480, accessed June 15, 2021.
Notes: Inc = Incomplete data. Inv = Invalid design value due to incomplete data. Design values shown in bold type do not meet the 1997 annual PM2.5
  NAAQS.
\a\ This preliminary design value includes all available data; no data flagged for exceptional events have been excluded.
\b\ The preliminary 2018-2020 design value at Fresno-Foundry (AQS ID: 06-019-2016) is based on concentration data from January 1, 2020 to December 31,
  2020. The site began operation in 2020; therefore, data from January 1, 2018 to December 31, 2019 are not available. Based on 40 CFR part 50, Appendix
  N, section 4.1(b), three years of valid annual means are required to produce a valid annual PM2.5 NAAQS design value. Thus, the Fresno-Foundry 2018-
  2020 preliminary design value is considered invalid.

    Under 40 CFR part 50, appendix N, because the 2018-2020 preliminary
design value exceeded the 15.0 [mu]g/m \3\ level of the 1997 annual
PM2.5 NAAQS, the San Joaquin Valley area did not attain the
1997 annual PM2.5 NAAQS by December 31, 2020, as projected
in the SJV PM2.5 Plan. Therefore, the EPA is proposing to
disapprove the attainment

demonstration in the SJV PM2.5 Plan for the 1997 annual
PM2.5 NAAQS for failure to meet the requirements of CAA
sections 189(d) and 179(d) and 40 CFR 51.1011(b). Because our proposal
is based on ambient monitoring data clearly indicating that the Plan
was insufficient to achieve attainment of the 1997 annual
PM2.5 NAAQS by the December 31, 2020 attainment date, we do
not provide a full evaluation of the attainment demonstration analyses
for these NAAQS at this time.

E. Reasonable Further Progress and Quantitative Milestones

1. Statutory and Regulatory Requirements
    CAA section 172(c)(2) provides that all nonattainment area plans
shall require RFP toward attainment. In addition, CAA section 189(c)
requires that all PM2.5 nonattainment area SIPs include
quantitative milestones to be achieved every three years until the area
is redesignated to attainment and that demonstrate RFP. Section 171(l)
of the Act defines RFP as ``such annual incremental reductions in
emissions of the relevant air pollutant as are required by [Part D] or
may reasonably be required by the Administrator for the purpose of
ensuring attainment of the applicable [NAAQS] by the applicable date.''
Neither subpart 1 nor subpart 4 of part D, title I of the Act requires
that states achieve a set percentage of emission reductions in any
given year for purposes of satisfying the RFP requirement. For purposes
of the PM2.5 NAAQS, the EPA has interpreted the RFP
requirement to require that the nonattainment area plans show annual
incremental emission reductions sufficient to maintain generally linear
progress toward attainment by the applicable deadline.\131\
---------------------------------------------------------------------------

    \131\ General Preamble Addendum, 42015.
---------------------------------------------------------------------------

    Attainment plans for PM2.5 nonattainment areas should
include detailed schedules for compliance with emission regulations in
the area and provide corresponding annual emission reductions to be
achieved by each milestone in the schedule.\132\ In reviewing an
attainment plan under subpart 4, the EPA considers whether the annual
incremental emission reductions to be achieved are reasonable in light
of the statutory objective of timely attainment. Although early
implementation of the most cost-effective control measures is often
appropriate, states should consider both cost-effectiveness and
pollution reduction effectiveness when developing implementation
schedules for control measures and may implement measures that are more
effective at reducing PM2.5 earlier to provide greater
public health benefits.\133\
---------------------------------------------------------------------------

    \132\ Id. at 42016.
    \133\ Id.
---------------------------------------------------------------------------

    The PM2.5 SIP Requirements Rule establishes specific
regulatory requirements for purposes of satisfying the Act's RFP
requirements and provides related guidance in the preamble to the rule.
Specifically, under the PM2.5 SIP Requirements Rule, each
PM2.5 attainment plan must contain an RFP analysis that
includes, at minimum, the following four components: (1) An
implementation schedule for control measures; (2) RFP projected
emissions for direct PM2.5 and all PM2.5 plan
precursors for each applicable milestone year, based on the anticipated
control measure implementation schedule; (3) a demonstration that the
control strategy and implementation schedule will achieve reasonable
progress toward attainment between the base year and the attainment
year; and (4) a demonstration that by the end of the calendar year for
each milestone date for the area, pollutant emissions will be at levels
that reflect either generally linear progress or stepwise progress in
reducing emissions on an annual basis between the base year and the
attainment year.\134\ Additionally, states should estimate the RFP
projected emissions for each quantitative milestone year by sector on a
pollutant-by-pollutant basis.\135\
---------------------------------------------------------------------------

    \134\ 40 CFR 51.1012(a).
    \135\ 81 FR 58010, 58056.
---------------------------------------------------------------------------

    Section 189(c) of the Act requires that PM2.5 attainment
plans include quantitative milestones that demonstrate RFP. The purpose
of the quantitative milestones is to allow periodic evaluation of the
area's progress towards attainment of the NAAQS consistent with RFP
requirements. Because RFP is an annual emission reduction requirement
and the quantitative milestones are to be achieved every three years,
when a state demonstrates compliance with the quantitative milestone
requirement, it should also demonstrate that RFP has been achieved
during each of the relevant three years. Quantitative milestones should
provide an objective means to evaluate progress toward attainment
meaningfully, e.g., through imposition of emission controls in the
attainment plan and the requirement to quantify those required emission
reductions. The CAA also requires states to submit milestone reports
(due 90 days after each milestone), and these reports should include
calculations and any assumptions made by the state concerning how RFP
has been met, e.g., through quantification of emission reductions to
date.\136\
---------------------------------------------------------------------------

    \136\ General Preamble Addendum, 42016-42017.
---------------------------------------------------------------------------

    The CAA does not specify the starting point for counting the three-
year periods for quantitative milestones under CAA section 189(c). In
the General Preamble and General Preamble Addendum, the EPA interpreted
the CAA to require that the starting point for the first three-year
period be the due date for the Moderate area plan submission.\137\ In
keeping with this historical approach, the EPA established December 31,
2014, the deadline that the EPA established for a state's submission of
any additional attainment-related SIP elements necessary to satisfy the
subpart 4 Moderate area requirements for the 1997 PM2.5
NAAQS, as the starting point for the first three-year period under CAA
section 189(c) for the 1997 PM2.5 NAAQS in the San Joaquin
Valley.\138\
---------------------------------------------------------------------------

    \137\ General Preamble, 13539, and General Preamble Addendum,
42016.
    \138\ 79 FR 31566 (June 2, 2014) (final rule establishing
subpart 4 moderate area classifications and deadline for related SIP
submissions). Although this final rule did not affect any action
that the EPA had previously taken under CAA section 110(k) on a SIP
for a PM2.5 nonattainment area, the EPA noted that states
may need to submit additional SIP elements to fully comply with the
applicable requirements of subpart 4, even for areas with previously
approved PM2.5 attainment plans, and that the deadline
for any such additional plan submissions was December 31, 2014. Id.
at 31569.
---------------------------------------------------------------------------

    Under the PM2.5 SIP Requirements Rule, each attainment
plan submission for an area designated nonattainment for the 1997
PM2.5 NAAQS before January 15, 2015, must contain
quantitative milestones to be achieved no later than three years after
December 31, 2014, and every three years thereafter until the milestone
date that falls within three years after the applicable attainment
date.\139\ If the area fails to attain, this post-attainment date
milestone provides the EPA with the tools necessary to monitor the
area's continued progress toward attainment while the state develops a
new attainment plan.\140\ Quantitative milestones must provide for
objective evaluation of RFP toward timely attainment of the
PM2.5 NAAQS in the area and include, at minimum, a metric
for tracking progress achieved in implementing SIP control measures,
including BACM and BACT, by each milestone date.\141\
---------------------------------------------------------------------------

    \139\ 40 CFR 51.1013(a)(4).
    \140\ 81 FR 58010, 58064.
    \141\ Id. at 58064 and 58092.
---------------------------------------------------------------------------

    Because the EPA designated the San Joaquin Valley area as
nonattainment for the 1997 annual PM2.5 NAAQS effective

April 5, 2005,\142\ the plan for this area must contain quantitative
milestones to be achieved no later than three years after December 31,
2014 (i.e., by December 31, 2017), and every three years thereafter
until the milestone date that falls within three years after the
applicable attainment date.\143\
---------------------------------------------------------------------------

    \142\ 70 FR 944 (January 5, 2005).
    \143\ 40 CFR 51.1013(a)(4).
---------------------------------------------------------------------------

2. Summary of the State's Submission