[Federal Register Volume 86, Number 183 (Friday, September 24, 2021)]
[Proposed Rules]
[Pages 53150-53184]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-20613]



[[Page 53149]]

Vol. 86

Friday,

No. 183

September 24, 2021

Part II





 Environmental Protection Agency





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40 CFR Part 52





Partial Approval and Partial Disapproval of Air Quality Implementation 
Plans and Determination of Attainment by the Attainment Date; 
California; San Joaquin Valley Serious Area and Section 189(d) Plan for 
Attainment of the 1997 24-Hour PM2.5 NAAQS; Proposed Rule

  Federal Register / Vol. 86 , No. 183 / Friday, September 24, 2021 / 
Proposed Rules  

[[Page 53150]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2021-0261; FRL-8969-01-R9]


Partial Approval and Partial Disapproval of Air Quality 
Implementation Plans and Determination of Attainment by the Attainment 
Date; California; San Joaquin Valley Serious Area and Section 189(d) 
Plan for Attainment of the 1997 24-Hour 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 24-
hour fine particulate matter (PM2.5) national ambient air 
quality standards (NAAQS) in the San Joaquin Valley nonattainment area. 
Specifically, the EPA is proposing to approve all but the contingency 
measure element of the submitted SIP revision as meeting all applicable 
Serious area and CAA section 189(d) requirements for the 1997 24-hour 
PM2.5 NAAQS and is proposing disapproval of the contingency 
measure element. The EPA is also proposing to determine that the San 
Joaquin Valley air quality planning area has attained the 1997 24-hour 
PM2.5 NAAQS. This determination is based on sufficient, 
quality-assured, and certified data for 2018-2020. Based on our 
proposed finding that the San Joaquin Valley nonattainment area has 
attained the 1997 24-hour PM2.5 NAAQS, we are proposing to 
determine that the requirement for contingency measures will no longer 
apply to the San Joaquin Valley nonattainment area for these NAAQS. 
Thus, the EPA is proposing to issue a protective finding for 
transportation conformity determinations for this proposed disapproval.

DATES: Any comments on this proposal must be received by October 25, 
2021.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2021-0261 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 protected].

SUPPLEMENTARY INFORMATION: Throughout this document, ``we,'' ``us,'' or 
``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
III. Clean Air Act Requirements for PM2.5 Serious Area 
Plans and for Serious PM2.5 Areas That Fail To Attain
    A. Requirements for PM2.5 Serious Area Plans
    B. Requirements for Serious PM2.5 Areas That Fail To 
Attain
IV. Review of the San Joaquin Valley PM2.5 Plan for the 
1997 24-Hour PM2.5 NAAQS
    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. Determination of Attainment by the Attainment Date
    A. Requirements for Attainment Determinations
    B. Monitoring Network Considerations
    C. Data Considerations and Proposed Determination
VI. Summary of Proposed Action and Request for Public Comment
VII. 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 24-hour and annual 
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 lowered the 24-hour and 
annual PM2.5 NAAQS, the 1997 24-hour PM2.5 NAAQS 
remain in effect and the 1997 primary annual PM2.5 NAAQS 
remains in effect in areas designated nonattainment for that NAAQS.\6\
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    \4\ 71 FR 61144.
    \5\ 78 FR 3086.
    \6\ 40 CFR 50.13(d).
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    The EPA established the 1997 PM2.5 NAAQS after 
considering substantial

[[Page 53151]]

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.\7\
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    \7\ 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, and ammonia.\8\
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    \8\ 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 24-hour and annual PM2.5 NAAQS, using air quality 
monitoring data for the three-year periods of 2001-2003 and 2002-
2004.\9\ The EPA designated the San Joaquin Valley as nonattainment for 
both the 1997 24-hour PM2.5 NAAQS (65 [mu]g/m\3\) and the 
1997 annual PM2.5 NAAQS (15.0 [mu]g/m\3\).\10\
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    \9\ 70 FR 944 (January 5, 2005).
    \10\ 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.\11\ 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 generally has 
responsibility for regulating stationary and area sources, and CARB, 
which generally has responsibility for regulating mobile sources.
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    \11\ For a precise description of the geographic boundaries of 
the San Joaquin Valley nonattainment area, see 40 CFR 81.305.
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    At the time of the initial designations for the 1997 
PM2.5 NAAQS, the EPA interpreted the CAA to require 
implementation of the NAAQS under the general nonattainment plan 
requirements of subpart 1.\12\ Under subpart 1, states were required to 
submit nonattainment plan SIP submissions within three years of the 
effective date of designations, that, among other things, provided for 
implementation of reasonably available control measures (RACM), 
reasonable further progress (RFP), contingency measures, and a modeled 
attainment demonstration showing attainment of the NAAQS as 
expeditiously as practicable but no later than five years from the 
designation (in this instance, no later than April 5, 2010) unless the 
state justified an attainment date extension of up to five years.\13\
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    \12\ 72 FR 20586.
    \13\ 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 24-hour 
and annual PM2.5 NAAQS in the San Joaquin Valley,\14\ 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 24-hour and annual PM2.5 NAAQS in the 
San Joaquin Valley PM2.5 nonattainment area, except for the 
attainment contingency measures, which we disapproved.\15\ 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.\16\
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    \14\ 76 FR 69896, n. 2 (November 9, 2011).
    \15\ Id. at 69924.
    \16\ 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,\17\ the EPA 
published a final rule on June 2, 2014, classifying the San Joaquin 
Valley as a Moderate nonattainment area for the 1997 24-hour and annual 
PM2.5 NAAQS under subpart 4, part D of title I of the 
Act.\18\ In this action, the EPA acknowledged that states must meet 
both subpart 1 and subpart 4 requirements in nonattainment plan SIP 
submissions for the 1997 24-hour and annual PM2.5 NAAQS and 
provided states with additional time to supplement or withdraw and 
resubmit any pending nonattainment plan SIP submissions.
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    \17\ 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 [micro]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.''
    \18\ 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 the determination that the State could not practicably attain 
these NAAQS in the San Joaquin Valley nonattainment area by the latest 
statutory Moderate area attainment date, i.e., April 5, 2015.\19\ Upon 
reclassification as a Serious area, the State became subject to the 
requirement of CAA section 188(c)(2) to attain the 1997 
PM2.5 NAAQS, as expeditiously as practicable but no later 
than ten years after designation, i.e., by no later than December 31, 
2015. California submitted its 1997 PM2.5 Serious area plan 
for the San Joaquin Valley in two submissions dated June 25, 2015 and 
August 13, 2015, including a request under section 188(e) to extend the 
attainment date for the 1997 24-hour PM2.5 NAAQS by three 
years (to December 31, 2018) and to extend the attainment date for the 
1997 annual PM2.5 NAAQS by five years (to December 31, 
2020). On February 9, 2016, the EPA proposed to approve most of the 
Serious area plan and to

[[Page 53152]]

grant the State's request for extensions of the December 31, 2015 
attainment date.\20\ However, on October 6, 2016, after considering 
public comments, the EPA denied California's request for these 
extensions of the attainment dates.\21\ Consequently, on November 23, 
2016, the EPA determined that the San Joaquin Valley had failed to 
attain the 1997 24-hour and annual PM2.5 NAAQS by the 
December 31, 2015 Serious area attainment date.\22\ This determination 
triggered a requirement for California to submit a new SIP submission 
for the 1997 24-hour and annual PM2.5 NAAQS for the San 
Joaquin Valley that satisfies the requirements of CAA section 189(d). 
The statutory deadline for this additional SIP submission was December 
31, 2016. The EPA did not finalize the actions proposed on February 9, 
2016, with respect to the submitted Serious area plan.\23\
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    \19\ 80 FR 18528 (April 7, 2015).
    \20\ 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.
    \21\ 81 FR 69396.
    \22\ 81 FR 84481.
    \23\ 81 FR 69396, 69400.
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    On December 6, 2018, the EPA determined that California had failed 
to submit a complete section 189(d) attainment plan for the 1997 24-
hour and annual PM2.5 NAAQS, among other required SIP 
submissions for the San Joaquin Valley, by the statutory deadlines.\24\ 
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 6 
months thereafter, unless the EPA affirmatively determined that the 
State has made a complete SIP submission addressing the identified 
failure to submit deficiencies.\25\ The finding also triggered the 
obligation under CAA section 110(c) for 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 
submission.\26\
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    \24\ 83 FR 62720.
    \25\ Id. at 62723.
    \26\ Id.
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    On May 10, 2019, CARB made SIP submissions intended to address the 
Serious area nonattainment plan and CAA section 189(d) requirements for 
the 1997 24-hour and annual PM2.5 NAAQS, among other 
requirements for the 2006 and 2012 PM2.5 NAAQS.\27\ CARB 
clarified in its May 10, 2019 letter that these new SIP submissions 
superseded past submissions to the EPA that the agency had not yet 
acted on for the 1997 PM2.5 NAAQS, including the 2015 
Serious area attainment plan submissions. On June 24, 2020, the EPA 
issued a letter finding these submissions complete and terminating the 
sanctions clocks under CAA section 179(a).\28\ The portions of these 
SIP submissions that pertain to the 1997 24-hour PM2.5 NAAQS 
are the subject of this proposal.
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    \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 PM2.5 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).
    \28\ Letter dated June 24, 2020, from Elizabeth J. Adams, 
Director, Air and Radiation Division, EPA Region IX, to Richard 
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 
PM[bdi2].[bdi5] Plan

    The EPA is proposing action on portions of two SIP submissions made 
by CARB to address nonattainment plan requirements for the 1997 24-hour 
PM2.5 NAAQS in the San Joaquin Valley. Specifically, the EPA 
is proposing to act on those portions of the following two SIP 
submissions that pertain to the 1997 24-hour PM2.5 NAAQS: 
(i) 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''); \29\ and (ii) 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.\30\ We refer to these 
two SIP submissions collectively as the ``SJV PM2.5 Plan'' 
or ``Plan.''
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    \29\ The 2018 PM2.5 Plan was developed jointly by 
CARB and the District.
    \30\ Letter dated May 9, 2019, from Richard Corey, Executive 
Officer, CARB, to Mike Stoker, Regional Administrator, EPA Region 9. 
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 proposed action on those 
portions pertaining to the 1997 annual PM2.5 NAAQS (86 FR 
38652, July 22, 2021) and 2012 annual PM2.5 NAAQS (86 FR 
49100, September 1, 2021). The EPA is not, at this time, taking any 
action on those portions that pertain to the 1997 annual 
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 SJV PM2.5 Plan addresses the Serious area 
nonattainment plan and CAA section 189(d) requirements for the 1997 24-
hour and annual PM2.5 NAAQS in the San Joaquin Valley, 
including the State's demonstration that the area would attain the 1997 
24-hour PM2.5 NAAQS by December 31, 2020. In this proposal, 
the EPA is proposing action only on those portions of the SJV 
PM2.5 Plan that pertain to the 1997 24-hour PM2.5 
NAAQS. The EPA is acting on the portions of the SJV PM2.5 
Plan that pertain to the 1997 annual 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 must include 
evidence that the state provided adequate public notice and an 
opportunity for a public hearing 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 nonattainment 
plan requirements in CAA section 189(b) and the CAA section 189(d) 
requirements for the 1997 24-hour 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''); \31\ (iii) 
numerous appendices to the 2018 PM2.5 Plan; (iv)

[[Page 53153]]

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''); \32\ 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).\33\
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    \31\ 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), and proposed action on those 
portions pertaining to the 2012 annual PM2.5 NAAQS (86 FR 
49100). The EPA intends to take further action on those portions 
that pertain to the 2012 annual PM2.5 NAAQS in separate 
rulemakings.
    \32\ 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.
    \33\ 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 24-hour 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''); \34\ 
(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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    \34\ 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.\35\ 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.\36\ 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.\37\ 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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    \35\ 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.
    \36\ 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.
    \37\ 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.\38\ 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 the SJVUAPCD to identify 
additional reductions from sources under District regulatory authority 
as part of a comprehensive plan to attain all of the PM2.5 
NAAQS in the San Joaquin Valley and to return to the Board with a 
commitment to achieve additional emissions reductions from mobile 
sources.\39\
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    \38\ 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 
(see, e.g., 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).
    \39\ 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.\40\
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    \40\ Letter dated May 9, 2019, from Richard Corey, Executive 
Officer, CARB, to Mike Stoker, Regional Administrator, EPA Region 9.
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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.\41\ 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.\42\
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    \41\ 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.
    \42\ 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.\43\ 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.\44\ 
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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    \43\ 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.
    \44\ 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).
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III. Clean Air Act Requirements for PM[bdi2].[bdi5] Serious 
Area Plans and for Serious PM[bdi2].[bdi5] Areas That Fail 
To Attain

A. Requirements for PM2.5 Serious Area Plans

    Upon reclassification of a Moderate nonattainment area as a Serious 
nonattainment area under subpart 4 of part D, title I of the CAA, the 
Act requires the state to make a SIP submission that addresses the 
following Serious nonattainment area requirements: \45\
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    \45\ 40 CFR 51.1003(b)(1); 81 FR 58010, 58074-58075 (August 24, 
2016).
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    1. A comprehensive, accurate, current inventory of actual emissions 
from all sources of PM2.5 and PM2.5 precursors in 
the area (CAA section 172(c)(3));

[[Page 53154]]

    2. Provisions to assure that the best available control measures 
(BACM), including best available control technology (BACT), for the 
control of direct PM2.5 and PM2.5 precursors 
shall be implemented no later than four years after the area is 
reclassified (CAA section 189(b)(1)(B));
    3. A demonstration (including air quality modeling) that the plan 
provides for attainment as expeditiously as practicable but no later 
than the end of the tenth calendar year after designation as a 
nonattainment area (i.e., December 31, 2015, for the San Joaquin Valley 
for the 1997 PM2.5 NAAQS);
    4. Plan provisions that require RFP (CAA section 172(c)(2));
    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 (CAA section 189(c));
    6. 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 
standard in the area (CAA section 189(e)); \46\
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    \46\ As discussed in section IV.H, California submitted 
nonattainment NSR SIP revisions to address the subpart 4 
requirements for the San Joaquin Valley Serious PM2.5 
nonattainment area on November 20, 2019. We are not proposing any 
action on this submission at this time. We will act on this 
submission through a separate rulemaking, as appropriate.
---------------------------------------------------------------------------

    7. Contingency measures to be implemented if the area fails to meet 
RFP or to attain by the applicable attainment date (CAA section 
172(c)(9)); and
    8. A revision to the nonattainment new source review (NSR) program 
to lower the applicable ``major stationary source'' \47\ thresholds 
from 100 tons per year (tpy) to 70 tpy (CAA section 189(b)(3)).
---------------------------------------------------------------------------

    \47\ For any Serious area, the terms ``major source'' and 
``major stationary source'' include any stationary source that emits 
or has the potential to emit at least 70 tons per year of 
PM2.5. CAA section 189(b)(3) and 40 CFR 
51.165(a)(1)(iv)(A)(1)(vii) and (viii) (defining ``major stationary 
source'' in serious PM2.5 nonattainment areas).
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    Serious area plans must also satisfy the requirements for Moderate 
area plans in CAA section 189(a), to the extent the state has not 
already met those requirements in the Moderate area plan submitted for 
the area.\48\ In addition, the Serious area plan must meet the general 
requirements applicable to all SIP submissions under section 110 of the 
CAA, including the requirement to provide necessary assurances that the 
implementing agencies have adequate personnel, funding, and authority 
under section 110(a)(2)(E); and the requirements concerning enforcement 
provisions in section 110(a)(2)(C).
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    \48\ Because the EPA has not previously approved a SIP 
submission for the San Joaquin Valley as meeting the subpart 4 RACM 
Moderate area planning requirement under CAA section 189 for the 
1997 24-hour 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 sections 189(b) 
and 189(d).
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B. 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.\49\ 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.\50\
---------------------------------------------------------------------------

    \49\ CAA section 189(d), 40 CFR 51.1004(a)(3), 40 CFR 
51.1010(c).
    \50\ 81 FR 58010, 58098.
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    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: \51\
---------------------------------------------------------------------------

    \51\ 40 CFR 51.1003(c)(1).
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    1. A comprehensive, accurate, current inventory of actual emissions 
from all sources of PM2.5 and PM2.5 precursors in 
the area;
    2. A Serious area plan control strategy that ensures that BACM, 
including BACT, for the control of direct PM2.5 and 
PM2.5 precursors are implemented in the area;
    3. Additional measures (beyond those already adopted in previous 
nonattainment plan SIP submissions for the area as RACM/RACT, BACM/
BACT, and most stringent measures (MSM) (if applicable)) \52\ that 
provide for attainment of the NAAQS as expeditiously as practicable 
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;
---------------------------------------------------------------------------

    \52\ MSM is applicable if the EPA has previously granted an 
extension of the attainment date under CAA section 188(e) for the 
nonattainment area and NAAQS at issue.
---------------------------------------------------------------------------

    4. A demonstration (including air quality modeling) that the plan 
provides for attainment of the NAAQS at issue as expeditiously as 
practicable;
    5. Plan provisions that require RFP;
    6. Quantitative milestones that the state is to meet every three 
years until the area is redesignated attainment and that demonstrate 
RFP toward attainment by the applicable date;
    7. Contingency measures to be implemented if the state fails to 
meet any requirement concerning RFP or quantitative milestones or to 
attain the NAAQS at issue by the applicable attainment date; and
    8. 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 
NAAQS at issue in the area.\53\
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    \53\ As discussed in section IV.H, California submitted 
nonattainment NSR SIP revisions to address the subpart 4 
requirements for the San Joaquin Valley Serious PM2.5 
nonattainment area on November 20, 2019. We are not proposing any 
action on this submission at this time. We will act on this 
submission through a separate rulemaking, as appropriate.
---------------------------------------------------------------------------

    A state's section 189(d) plan submission 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.\54\
---------------------------------------------------------------------------

    \54\ 81 FR 84481, 84482.
---------------------------------------------------------------------------

    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.\55\ Because the EPA has not previously approved a SIP 
submission

[[Page 53155]]

for the San Joaquin Valley as meeting the subpart 4 RACM Moderate area 
planning requirements under CAA section 189 for the 1997 24-hour 
PM2.5 NAAQS, the EPA is evaluating relevant portions of the 
SJV PM2.5 Plan for compliance with this requirement. In 
addition, as discussed above, the EPA has not previously approved a SIP 
submission for the San Joaquin Valley as meeting the Serious area 
planning requirements under CAA section 189(b)(1) for the 1997 24-hour 
PM2.5 NAAQS. Some Serious area planning requirements operate 
on a timeline that is based on the outermost statutory Serious area 
attainment date of the end of the tenth calendar year following the 
area's designation to nonattainment. Because section 189(d) requires a 
state to address any applicable Serious area requirements that the 
state has not already met in the area, and the section 189(d) 
obligations do not come into effect until an area has failed to attain 
the NAAQS by the Serious area attainment date, the EPA proposes that it 
should evaluate any previously unmet Serious area planning obligations 
based on the current, applicable attainment date appropriate under 
section 189(d), and not the original Serious area attainment date.
---------------------------------------------------------------------------

    \55\ 81 FR 58010, 58098.
---------------------------------------------------------------------------

    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''); \56\ (2) ``State 
Implementation Plans; General Preamble for the Implementation of Title 
I of the Clean Air Act Amendments of 1990; Supplemental'' (``General 
Preamble Supplement''); \57\ 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'').\58\ 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 NAAQS.\59\ We discuss these 
regulatory requirements and interpretations of the Act as appropriate 
in our evaluation of the SJV PM2.5 Plan that follows.
---------------------------------------------------------------------------

    \56\ 57 FR 13498 (April 16, 1992).
    \57\ 57 FR 18070 (April 28, 1992).
    \58\ 59 FR 41998 (August 16, 1994).
    \59\ 81 FR 58010.
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IV. Review of the San Joaquin Valley PM[bdi2].[bdi5] Plan 
for the 1997 24-Hour PM[bdi2].[bdi5] NAAQS

    The EPA is evaluating the SJV PM2.5 Plan against the 
Serious area requirements for the 1997 24-hour PM2.5 NAAQS 
and the section 189(d) requirements for the 1997 24-hour 
PM2.5 NAAQS, as laid out in section III of this proposal. 
Many requirements for both a Serious area plan and a section 189(d) 
plan are structured around the relevant statutory attainment date. The 
latest statutory Serious area attainment date for the San Joaquin 
Valley area was December 31, 2015.\60\ On November 23, 2016, the EPA 
determined that the area failed to attain by the Serious area 
attainment date.
---------------------------------------------------------------------------

    \60\ As discussed in section I.B, California submitted its 
Serious area plan for the 1997 24-hour PM2.5 NAAQS in two 
submissions dated June 25, 2015 and August 13, 2015, including a 
request under section 188(e) to extend the attainment date for the 
1997 24-hour PM2.5 NAAQS by three years (to December 31, 
2018). On October 6, 2016, the EPA denied the request for an 
extension, but did not finalize action on the Serious area plan 
submissions. Accordingly, the Serious area attainment date remained 
unchanged: As expeditiously as practicable but no later than 
December 31, 2015.
---------------------------------------------------------------------------

    For the purposes of the section 189(d) requirements, the attainment 
date is the date by which a state can attain the NAAQS as expeditiously 
as practicable, but no later than five years from the publication date 
of the final determination of failure to attain.\61\ As discussed in 
section IV.D, the SJV PM2.5 Plan projected that attainment 
could be achieved in fewer than five years, i.e., by December 31, 2020.
---------------------------------------------------------------------------

    \61\ CAA section 179(d)(3); 81 FR 84481, 84482. The 
determination of failure to attain published on November 23, 2016.
---------------------------------------------------------------------------

    When the State submitted the SJV PM2.5 Plan in 2019, the 
State withdrew its previous Serious area plan that it had developed to 
meet the December 31, 2015 Serious area attainment date. Because the 
State submitted the SJV PM2.5 Plan after the EPA's finding 
that the area had failed to attain by the applicable Serious area 
attainment date, the State could not demonstrate in the SJV 
PM2.5 Plan that the area would attain by the Serious area 
attainment date, nor could it address other requirements based on this 
attainment date, such as RFP and quantitative milestones, because many 
of the relevant dates had already passed. As described in section III 
of this document, in a section 189(d) plan, a state must address any 
statutory requirements applicable to Moderate and Serious nonattainment 
area plans to the extent that it has not already met those 
requirements, but the EPA believes that it should base this evaluation 
on the current applicable attainment date under section 189(d). For 
example, it would be illogical to require a state to submit a Serious 
area modeled attainment demonstration that provided for attainment by 
December 31, 2015, after the EPA has already determined based on 
monitoring data that the state failed to attain by such date.
    For the purposes of our evaluation of the Serious area plan 
requirements, although the State is required to submit a Serious area 
plan, and it must structure such a plan based on the Serious area 
attainment date, it would serve no purpose to evaluate the SJV 
PM2.5 Plan against the now-passed Serious area attainment 
date by which the area has already failed to attain. For example, RFP 
and quantitative milestones normally are dependent upon the attainment 
date. Accordingly, because the State must still meet all Serious area 
plan requirements, even if doing so later in conjunction with the 
section 189(d) plan and its later attainment date, we will evaluate the 
State's compliance with the Serious area plan requirements in light of 
the later section 189(d) attainment date, as appropriate. Where the 
State in the SJV PM2.5 Plan applies the section 189(d) 
attainment date to a Serious area requirement, we will note the 
statutory Serious area timeline and accept the submission in 
fulfillment of the State's Serious area plan obligation, but evaluate 
the submission in light of the section 189(d) attainment date.

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.\62\ The EPA has also issued guidance concerning emissions

[[Page 53156]]

inventories for PM2.5 nonattainment areas.\63\
---------------------------------------------------------------------------

    \62\ Id. at 58098-58099.
    \63\ ``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 for a Serious area attainment 
plan or a CAA section 189(d) plan must 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,\64\ and emissions of all chemical precursors to the 
formation of secondary PM2.5, i.e., nitrogen oxides 
(NOX), sulfur dioxide (SO2), volatile organic 
compounds (VOC), and ammonia.\65\
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    \64\ 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.
    \65\ 40 CFR 51.1008(b)(1) and (c)(1).
---------------------------------------------------------------------------

    The emissions inventory base year for a Serious area attainment 
plan must be one of the three years for which monitoring data were used 
to reclassify the area to Serious, or another technically appropriate 
year justified by the state in its Serious area SIP submission.\66\ 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 the EPA used monitored data 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.\67\
---------------------------------------------------------------------------

    \66\ 40 CFR 51.1008(b)(1).
    \67\ 40 CFR 51.1008(c)(1).
---------------------------------------------------------------------------

    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.\68\ Following CARB's submission of the Plan, the EPA 
approved EMFAC2017, the latest revision to this mobile source emissions 
model. 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.\69\ \70\
---------------------------------------------------------------------------

    \68\ 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.
    \69\ 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 emissions tests 
results. 76 FR 6328 (February 4, 2011). CARB used the revised 2011 
AP-42 methodology in developing on-road mobile source emissions; see 
https://www.arb.ca.gov/ei/areasrc/fullpdf/full7-9_2016.pdf.
    \70\ 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.\71\ These future emissions projections are 
necessary components of the attainment demonstrations required under 
CAA sections 189(b)(1) and 189(d) and the demonstration of RFP required 
under section 172(c)(2).\72\ 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 state calculated the 
emissions projections. Where a state chooses to allow new major 
stationary sources or major modifications to use emissions 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.\73\
---------------------------------------------------------------------------

    \71\ 40 CFR 51.1008 and 51.1012. See also Emissions Inventory 
Guidance, section 3 (``SIP Inventory Requirements and 
Recommendations'').
    \72\ 40 CFR 51.1004, 51.1008, 51.1011, and 51.1012.
    \73\ 40 CFR 51.165(a)(3)(ii)(C)(1).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    The State included summaries of the planning emissions inventories 
for direct PM2.5 and PM2.5 precursors 
(NOX, SOX,\74\ VOC,\75\ and ammonia) and the 
documentation for the inventories for the San Joaquin Valley 
PM2.5 nonattainment area in Appendix B (``Emissions 
Inventory'') and Appendix I (``New Source Review and Emission Reduction 
Credits'') of the 2018 PM2.5 Plan.
---------------------------------------------------------------------------

    \74\ 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 
document.
    \75\ 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 document.
---------------------------------------------------------------------------

    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.\76\
---------------------------------------------------------------------------

    \76\ 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 
emissions inventories for the 2013 base year, which CARB derived 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.\77\ In this 
proposal, we are proposing action on those winter average and annual 
average emissions inventories necessary to support the Serious area and 
CAA section 189(d) nonattainment plans for the 1997 24-

[[Page 53157]]

hour 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 emissions inventories for 2018 and 2019 to 
support the five percent annual emissions reduction demonstration as 
required by CAA section 189(d). Each inventory includes emissions from 
stationary, area, on-road, and non-road sources.
---------------------------------------------------------------------------

    \77\ 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 and future year inventories were estimated using the 
California Emission Projection Analysis Model (CEPAM), 2016 SIP 
Baseline Emission Projections, version 1.05.
---------------------------------------------------------------------------

    CARB developed the base year inventories for stationary sources 
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.\78\ 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.\79\ 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.\80\ Re-entrained paved 
road dust emissions were calculated using a CARB methodology consistent 
with the EPA's AP-42 road dust methodology.\81\
---------------------------------------------------------------------------

    \78\ 2018 PM2.5 Plan, Appendix B, section B.2 
(``Emissions Inventory Summary and Methodology'').
    \79\ Id. at B-42 to B-44.
    \80\ Id. at B-37.
    \81\ 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.\82\ 
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.\83\ 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.\84\
---------------------------------------------------------------------------

    \82\ Id. at B-18 and B-19.
    \83\ 2018 PM2.5 Plan, Appendix I, I-1 to I-5.
    \84\ 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)
----------------------------------------------------------------------------------------------------------------
            Category               Direct 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 PM2.5
            Category                                    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 Review of the State's Submission
    We have reviewed the emissions inventories in the SJV 
PM2.5 Plan that pertain to the 1997 24-hour PM2.5 
NAAQS and the 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(b)(1), the 2013 base year is one 
of the three years of monitored data with which the EPA reclassified 
the San Joaquin Valley area to Serious. Furthermore, in accordance with 
40 CFR 51.1008(c)(1), the 2013 base year is one of the three years of 
monitored data with which the EPA determined that the San Joaquin 
Valley area failed to attain the PM2.5 NAAQS by the 
applicable Serious area attainment date for the

[[Page 53158]]

1997 24-hour PM2.5 NAAQS.\85\ The 2013 base year emissions 
inventories represent 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.
---------------------------------------------------------------------------

    \85\ 81 FR 84481, 84482.
---------------------------------------------------------------------------

    With respect to future year emissions projections, we have reviewed 
the growth and control factors and find them acceptable and thus 
conclude that the future baseline emissions projections, which reflect 
ongoing emissions reductions from existing (i.e., ``baseline'') control 
measures as discussed in section IV.C.2.a, in the SJV PM2.5 
Plan reflect appropriate calculation methods and the latest planning 
assumptions. Also, as a general matter, the EPA will approve a SIP 
submission that takes emissions reduction credit for a control measure 
only where the EPA has approved the measure as part of the SIP. Thus, 
for example, to take credit for the emissions reductions from newly 
adopted or amended District rules for stationary sources, the related 
rules must be approved by the EPA into the SIP. Table 1 of the EPA's 
``Technical Support Document, San Joaquin Valley PM2.5 Plan 
for the 1997 24-hour PM2.5 NAAQS,'' August 2021 (``EPA's 
1997 24-hour PM2.5 TSD'') shows District rules with post-
2013 compliance dates that are reflected in the future year baseline 
inventories, along with information on the EPA's approval of these 
rules, and shows that stationary source emissions reductions assumed by 
the SJV PM2.5 Plan for future years are supported by rules 
approved as part of the California SIP for the San Joaquin Valley. With 
respect to mobile sources, the EPA has taken action in recent years to 
approve CARB mobile source regulations into the state-wide portion of 
the California SIP. We therefore find that the future year baseline 
projections in the SJV PM2.5 Plan are properly supported by 
SIP-approved stationary and mobile source measures.\86\
---------------------------------------------------------------------------

    \86\ The baseline emissions projections in the 2018 
PM2.5 Plan assume implementation of CARB's Zero Emissions 
Vehicle (ZEV) sales mandate and greenhouse gas (GHG) standards. On 
September 27, 2019, the U.S. Department of Transportation and the 
EPA (the Agencies) issued a notice of final rulemaking for the Safer 
Affordable Fuel-Efficient (SAFE) Vehicles Rule Part One: One 
National Program (SAFE I) that, among other things, withdrew the 
EPA's 2013 waiver of preemption for the ZEV sales mandate and 
vehicle GHG standards. 84 FR 51310. See also proposed SAFE rule at 
83 FR 42986 (August 24, 2018). In response to SAFE I, CARB developed 
EMFAC off-model adjustment factors to account for anticipated 
changes in on-road emissions. On March 12, 2020, the EPA informed 
CARB that the EPA considers these adjustment factors to be 
acceptable for future use. See letter dated March 12, 2020 from 
Elizabeth J. Adams, EPA Region IX, to Steven Cliff, CARB. On April 
30, 2020 (85 FR 24174), the Agencies issued a notice of final 
rulemaking titled: The Safer Affordable Fuel-Efficient (SAFE) 
Vehicles Rule for Model Years 2021-2026 Passenger Cars and Light 
Trucks (SAFE II), establishing the federal fuel economy and GHG 
vehicle emissions standards based on the August 2018 SAFE proposal. 
The effect of both SAFE final rules (SAFE I and SAFE II) on the on-
road vehicle mix in the San Joaquin Valley nonattainment area and on 
the resulting vehicular emissions is expected to be minimal during 
the timeframe addressed in this SIP revision. Therefore, we 
anticipate the SAFE final rules would not materially change the 
attainment, RFP, or five percent reductions demonstrations for the 
1997 24-hour PM2.5 NAAQS in the SJV PM2.5 
Plan.
---------------------------------------------------------------------------

    For these reasons, we are proposing to approve the 2013 base year 
emissions inventories in the SJV PM2.5 Plan for the 1997 24-
hour PM2.5 NAAQS as meeting the requirements of CAA section 
172(c)(3) and 40 CFR 51.1008 for purposes of both the Serious area and 
the CAA section 189(d) attainment plans. We are also proposing to find 
that the forecasted inventories in the Plan for the years 2017, 2018, 
2019, 2020, and 2023 provide an adequate basis for the BACM, RFP, and 
the modeled attainment demonstration analyses in the SJV 
PM2.5 Plan.

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.\87\ 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.\88\
---------------------------------------------------------------------------

    \87\ ``Air Quality Criteria for Particulate Matter'' (EPA/600/P-
99/002aF), EPA, October 2004, Chapter 3.
    \88\ ``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.\89\ 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.'' \90\ The EPA has identified NOX, 
SO2, VOC, and ammonia as precursors to the formation of 
PM2.5.\91\ 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)).
---------------------------------------------------------------------------

    \89\ 81 FR 58010, 58017-58020.
    \90\ CAA section 302(g).
    \91\ 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, MSM, and new source review (NSR)). 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.\92\ 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,\93\ a 
state may demonstrate in a SIP submission that control of a certain 
precursor pollutant is not necessary because it does not contribute 
significantly to ambient PM10 levels in the nonattainment 
area and is not needed for attainment.\94\
---------------------------------------------------------------------------

    \92\ Id. at 58018-58019.
    \93\ General Preamble, 13539-13542.
    \94\ 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

[[Page 53159]]

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 
standard in the area.\95\ If the EPA determines that the contribution 
of the precursor to PM2.5 levels in the area is not 
significant and approves the demonstration, then the state is not 
required to control emissions of the relevant precursor from sources in 
the attainment plan.\96\
---------------------------------------------------------------------------

    \95\ 40 CFR 51.1006(a)(1).
    \96\ Id.
---------------------------------------------------------------------------

    In addition, in May 2019, the EPA issued the ``Fine Particulate 
Matter (PM2.5) Precursor Demonstration Guidance'' 
(``PM2.5 Precursor Guidance''),\97\ 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.\98\ The EPA's recommendations in the PM2.5 Precursor 
Guidance are generally consistent with those in the Draft 
PM2.5 Precursor Guidance, with some exceptions, including 
that the EPA's recommended contribution threshold for the 24-hour 
PM2.5 NAAQS changed from 1.3 [micro]g/m\3\ in the draft 
guidance to 1.5 [micro]g/m\3\ in the final guidance.\99\
---------------------------------------------------------------------------

    \97\ ``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.
    \98\ ``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.
    \99\ For the 24-hour PM2.5 NAAQS, the EPA generally 
expects that a precursor demonstration showing that the air quality 
impact of a given precursor at all relevant locations does not 
exceed a contribution threshold of 1.5 [mu]g/m\3\ will be adequate 
to exempt sources of that precursor from control requirements. 
PM2.5 Precursor Guidance, 17.
---------------------------------------------------------------------------

    We are evaluating the 1997 24-hour PM2.5 NAAQS portion 
of the SJV PM2.5 Plan in accordance with the presumption 
embodied within subpart 4, that states address all PM2.5 
precursors in the 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 and are not necessary for attainment. In reviewing 
any determination by a 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 brief 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.\100\ CARB presents 
additional modeling results 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 \101\ and further clarifications 
in five email transmittals.\102\ 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.\103\
---------------------------------------------------------------------------

    \100\ A copy of the contents of Appendix G appears in the CARB 
Staff Report, Appendix C4 (``Precursor Demonstrations for Ammonia, 
SOX, and ROG'').
    \101\ 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'').
    \102\ 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'').
    \103\ 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 2018 PM2.5 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 emissions trends, the 
appropriateness of future year versus base year sensitivity, available 
emissions controls, and the severity of nonattainment.\104\ These 
analyses led CARB 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.\105\ 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 February 2020 
Precursor TSD'').
---------------------------------------------------------------------------

    \104\ PM2.5 Precursor Guidance, 18-19 (consideration 
of additional information), 31 (available emissions controls), and 
35-36 (appropriateness of future year versus base year sensitivity).
    \105\ 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 direct PM2.5 and NOX, CARB modeled the 
sensitivity of ambient PM2.5 in the San Joaquin Valley to a 
30 percent reduction in anthropogenic emissions of each pollutant in 
2013, 2020, and 2024.\106\ The State concluded that direct 
PM2.5 and NOX emissions reductions will continue 
to have a significant impact on 24-hour PM2.5 design values 
in the San Joaquin Valley, with NOX reductions being 
particularly important.\107\ Consistent with this conclusion, the State 
focused the control strategy and attainment demonstration on these two 
pollutants,

[[Page 53160]]

as described in section IV.C of this preamble.
---------------------------------------------------------------------------

    \106\ 2018 PM2.5 Plan, Chapter 5, 5-7 to 5-8. CARB 
modeled the effects of both NOX reductions and direct 
PM2.5 reductions but the direct PM2.5 results 
were used only as a point of comparison, as direct PM2.5 
emissions must be regulated in all PM2.5 nonattainment 
areas.
    \107\ Id. at 5-8; and 2018 PM2.5 Plan, Appendix G, 2. 
CARB presents its sensitivity analysis for emissions reductions in 
direct PM2.5 and NOX in the Plan's attainment 
demonstration appendix. 2018 PM2.5 Plan, Appendix K, 
Table 47 (annual average design values) and Table 48 (24-hour 
average design values).
---------------------------------------------------------------------------

    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 [micro]g/m\3\ 
from the Draft PM2.5 Precursor Guidance, which was available 
at the time the State developed the SIP.\108\ The contributions of 
ammonia, SOX, and VOC were 5.2 [micro]g/m\3\, 1.6 [micro]g/
m\3\, and 6.2 [micro]g/m\3\, respectively. Given that these levels are 
well above the EPA's 0.2 [micro]g/m\3\ recommended contribution 
threshold, the State proceeded with a sensitivity-based analysis.
---------------------------------------------------------------------------

    \108\ 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.
---------------------------------------------------------------------------

    CARB'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.\109\
---------------------------------------------------------------------------

    \109\ This procedure is the procedure recommended by the EPA. 
PM2.5 Precursor Guidance, 37.
---------------------------------------------------------------------------

    We summarize the State's sensitivity-based analysis and additional 
information in the sections that follow for ammonia, SOX, 
and VOC.
a. Ammonia
    For ammonia, the State compared the 24-hour precursor contributions 
to 1.3 [micro]g/m\3\, the recommended contribution threshold in the 
Draft PM2.5 Precursor Guidance. For a modeled 30 percent 
ammonia emissions reduction, the ambient PM2.5 responses in 
2013 ranged from 0.9 to 3.3 [micro]g/m\3\ across 15 monitoring sites, 
with a majority of sites above the 1.3 [micro]g/m\3\ contribution 
threshold (and also above the 1.5 [micro]g/m\3\ contribution threshold 
in the final PM2.5 Precursor Guidance). PM2.5 
responses in 2020 ranged from 0.5 to 1.9 [micro]g/m\3\, with four sites 
at or above the 1.3 [micro]g/m\3\ contribution threshold, including one 
site above the 1.5 [micro]g/m\3\ contribution threshold in the final 
PM2.5 Precursor Guidance. In 2024, all modeled responses 
were below both recommended contribution thresholds. For a modeled 70 
percent ammonia emissions reduction, the ambient PM2.5 
responses in 2013 ranged from 3.5 to 12.4 [micro]g/m\3\, with all 
monitoring sites above the 1.3 [micro]g/m\3\ threshold (and above the 
1.5 [micro]g/m\3\ threshold), the PM2.5 responses in 2020 
ranged from 1.6 to 6.4 [micro]g/m\3\, and the PM2.5 
responses in 2024 ranged from 1.2 to 3.0 [micro]g/m\3\, with most sites 
above both recommended thresholds. For further detail, please see the 
EPA's February 2020 Precursor TSD, Table 2, and the 2018 
PM2.5 Plan, Appendix G, tables 2 through 7. In summary, for 
a 30 percent ammonia reduction, a majority of sites have 
PM2.5 responses above the contribution threshold in the 2013 
modeling, decreasing to a single site above the contribution threshold 
for 2020, and no sites above the contribution threshold for 2024. For a 
70 percent reduction, all sites are above the contribution threshold in 
the 2013 and 2020 modeling, and a majority of sites are above the 
contribution threshold in 2024.
    The State based its ammonia precursor determination on the 
sensitivity analysis for the future years, using a 30 percent ammonia 
emissions reduction. These choices respectively reflect its assessment 
of research studies and the Plan's projected emissions reductions, and 
on its assessment of available emissions controls. As explained in the 
PM2.5 Precursor Guidance, precursor responses may be above 
the recommended contribution threshold and yet not contribute 
significantly to levels that exceed the standard in the area. 
Therefore, as recommended by the EPA, the State considered additional 
information to examine whether the identified PM2.5 
responses constituted a significant contribution to ambient 
PM2.5 in the San Joaquin Valley. The additional information 
included research studies, emissions trends, and information to support 
the State's conclusion that a 30 percent ammonia emissions reduction 
represented a reasonable upper bound on the ammonia emissions 
reductions to model in estimating its contribution to ambient 
PM2.5 levels. We summarize this additional information below 
and provide a more detailed evaluation in the EPA's February 2020 
Precursor TSD.
    The State describes previous research that supports its finding 
that ammonium nitrate PM2.5 formation is the San Joaquin 
Valley is NOX-limited rather than ammonia-limited.\110\ 
Essentially, ammonia is so abundant in the San Joaquin Valley that even 
with large ammonia emissions reductions there would still be enough 
ammonia to combine with the available NOX to readily form 
particulate ammonium nitrate. Therefore, ammonia emissions reductions 
would lead to only small decreases in PM2.5 concentrations. 
In contrast, because emissions of NOX are less abundant in 
the San Joaquin Valley (i.e., more limited relative to emissions of 
ammonia after normalizing for their differing molecular weights), the 
PM2.5 concentrations in the atmosphere are more responsive 
to reductions in NOX than to reductions of ammonia. Thus, 
these analyses indicate that the area is NOX-limited.
---------------------------------------------------------------------------

    \110\ 2018 PM2.5 Plan, Appendix G, 9-10; CARB Staff 
Report, Appendix C, 12-15; and Attachment A to CARB's May 9, 2019 
submittal letter.
---------------------------------------------------------------------------

    The State also points to the conclusions of a study conducted by 
Lurmann et al., based on ambient measurements during the winter 2000-
2001 California Regional Particulate Air Quality Study intensive field 
study.\111\ That study found that most areas of the San Joaquin Valley 
were NOX-limited with respect to ammonium nitrate formation. 
Since that time, large additional NOX emissions reductions 
have occurred, which would increase the degree to which ammonium 
nitrate formation in the San Joaquin Valley is NOX-limited. 
Based on more recent aircraft-borne measurements during the 2013 
DISCOVER-AQ campaign,\112\ the State similarly concluded that ammonium 
nitrate formation is NOX-limited based on the large amount 
of ``excess ammonia,'' which is defined as the amount of measured 
ammonia left over if all the nitrate and sulfate present

[[Page 53161]]

were to combine with available ammonia to form particulate.\113\ The 
CARB Staff Report describes these conclusions in more detail and lists 
results from multiple other recent studies with similar 
conclusions.\114\ Finally, in a supplemental submittal, CARB described 
the results of two analyses confirming the likely underestimation of 
ammonia emissions in the modeled emissions inventory inputs.\115\ CARB 
compared CMAQ model predictions of ammonia with the 2013 DISCOVER-AQ 
aircraft measurements and found ammonia was underpredicted, and noted 
that this would result in the response to ammonia reductions being 
overpredicted. CARB also compared 2017 satellite measurements of 
ammonia with CMAQ model predictions and found that modeled ammonia 
concentrations were half of the magnitude of the satellite observations 
at some locations, and the modeled valley-wide average was about 25 
percent less than observed. Because the modeling performs well for the 
various PM2.5 components, as well as for ozone and 
NO2,\116\ the CARB finding of CMAQ model underpredictions 
for ammonia is consistent with an underestimation of ammonia emissions 
inventory input to the model.
---------------------------------------------------------------------------

    \111\ Frederick W. Lurmann, Steven G. Brown, Michael C. 
McCarthy, and Paul T. Roberts, ``Processes Influencing Secondary 
Aerosol Formation in the San Joaquin Valley during Winter,'' Journal 
of the Air & Waste Management Association, (2006), 56:12, 1679-1693, 
DOI: 10.1080/10473289.2006.10464573.
    \112\ Deriving Information on Surface conditions from COlumn and 
VERtically Resolved Observations Relevant to Air Quality,'' https://www.nasa.gov/mission_pages/discover-aq/index.html.
    \113\ 2018 PM2.5 Plan, Appendix G, Figure 2.
    \114\ CARB Staff Report, Appendix C, 12.
    \115\ CARB's April 26, 2021 Precursor Clarification.
    \116\ EPA's February 2020 Modeling TSD, 21.
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    Regarding emissions trends, the CARB Staff Report presents an 
emissions inventory-based argument on the relative insensitivity of 
PM2.5 to ammonia reductions.\117\ CARB compared the size of 
the ammonia and NOX emissions inventories in tons per day, 
after normalizing for their differing molecular weights, and found that 
ammonia was roughly three times as abundant as NOX in 2013 
and is projected to be about six times as abundant in 2025, due to the 
continuing decline in NOX emissions (while ammonia emissions 
are generally constant into the future).\118\ While the State 
recognized that this is only a ``first-level assessment,'' it provides 
additional support for the State's conclusion that NOX, and 
not ammonia, is the limiting precursor for ammonium nitrate formation, 
and that the ammonium nitrate portion of ambient PM2.5 would 
be expected to be relatively insensitive to ammonia emissions 
reductions. This is also consistent with the ammonia sensitivity 
modeling for the San Joaquin Valley, which showed that PM2.5 
concentrations will be less sensitive to ammonia reductions as 
NOX emissions go down in the future (i.e., the 
PM2.5 impacts were much smaller in the 2020 and 2024 future 
modeled cases compared to the 2013 base year).
---------------------------------------------------------------------------

    \117\ CARB Staff Report, Appendix C, 15.
    \118\ Annual average ammonia emissions are projected to decrease 
4.6 tpd (1.4 percent) from 2013 to 2024. 2018 PM2.5 Plan, 
Appendix B, Table B-5.
---------------------------------------------------------------------------

    The State projected that NOX emissions in the San 
Joaquin Valley would decrease by 36 percent from 2013 to 2020, and by 
53 percent from 2013 to 2024, while ammonia emissions would remain 
relatively flat, thereby increasing the relative abundance of 
ammonia.\119\ Based on the Plan's emissions reduction projections 
combined with the research study conclusions, the State relies on the 
modeled responses for the future years, rather than the 2013 base year, 
stating that the future year NOX emissions are more 
representative of San Joaquin Valley emissions conditions.\120\ The 
State references the Draft PM2.5 Precursor Guidance, which 
notes that it may be appropriate to model future conditions that are 
more representative of current atmospheric conditions and those 
conditions expected closer to the attainment date. The State concludes 
that this in fact applies to the San Joaquin Valley.\121\
---------------------------------------------------------------------------

    \119\ 2018 PM2.5 Plan, Appendix G, 8-9.
    \120\ Id. at 9.
    \121\ Id (referencing Draft PM2.5 Precursor Guidance, 
33). See also PM2.5 Precursor Guidance, 35.
---------------------------------------------------------------------------

    With respect to the State's selection of 30 percent as an upper 
bound on the ammonia reductions to model, the State described its 
review of the most important ammonia source categories in the San 
Joaquin Valley, existing control measures that affect ammonia emissions 
from these sources, additional mitigation options for these sources, 
and information provided in the PM2.5 Precursor Guidance 
about ammonia reductions achieved nationwide from 2011 to 2017.\122\ 
The primary sources of ammonia emissions identified in the 2018 
PM2.5 Plan are: (1) Confined animal facilities (CAFs); (2) 
agricultural fertilizer; (3) biosolids, animal manure, and poultry 
litter operations; and (4) organic material composting operations.\123\ 
CAFs are subject to District Rule 4570; biosolids, animal manure, and 
poultry litter operations are subject to District Rule 4565; and 
organic material composting operations are subject to District Rule 
4566. Although these District rules explicitly apply only to VOC 
emissions from these sources, the State concludes that these rules also 
reduce ammonia emissions. Appendix C of the 2018 PM2.5 Plan 
cites several scientific studies that address the correlation between 
VOC and ammonia emissions from these emissions sources.\124\ Based on 
these evaluations, the State concludes that ammonia control measures 
achieving even the low end of the range (30 percent) are not feasible 
for implementation in the San Joaquin Valley and that it is therefore 
reasonable to treat a 30 percent ammonia reduction as an upper bound 
for modeling in the precursor demonstration.
---------------------------------------------------------------------------

    \122\ 2018 PM2.5 Plan, Appendix G and Appendix C, 
section C-25, and CARB's October 2019 Precursor Clarification.
    \123\ 2018 PM2.5 Plan, Appendix C, section C-25.
    \124\ Id. at C-314 and following.
---------------------------------------------------------------------------

    In summary, the State's sensitivity analysis presents a range of 
PM2.5 responses to ammonia emissions reductions depending on 
base year versus future year, and on the scale of emissions reductions 
that may be possible. The Plan provides the State's bases for finding 
that the future year sensitivity results better represent conditions in 
the San Joaquin Valley than the 2013 base year and for finding a 30 
percent ammonia reduction to be a reasonable upper bound for modeled 
ammonia emissions reductions in assessing the ammonia contribution. 
Based on these analyses, the State concludes that ammonia does not 
contribute significantly to ambient PM2.5 levels above the 
1997 24-hour PM2.5 NAAQS in the San Joaquin Valley.
b. SOX
    For SOX, the State compared the 24-hour precursor 
contributions to the recommended draft contribution threshold of 1.3 
[micro]g/m\3\ in the Draft PM2.5 Precursor Guidance. For 
modeled SOX emissions reductions of 30 percent and 70 
percent, the ambient PM2.5 responses in 2013 ranged from -
1.4 to 0.5 [micro]g/m\3\ across 15 monitoring sites, which all fall 
below the 1.3 [micro]g/m\3\ draft contribution threshold, and hence 
also below the contribution threshold of 1.5 [micro]g/m\3\ in the final 
version of the PM2.5 Precursor Guidance.\125\ The response 
was below zero at most monitoring sites, indicating an increase, rather 
than a decrease, in ambient PM2.5 in response to 
SOX emissions reductions (i.e., a disbenefit). Only the 
Stockton and Manteca sites had slightly positive responses to 30 
percent and 70 percent emissions reductions, and the Tranquillity site 
also had a slightly positive response only to a 30 percent reduction. 
For the 15 sites, in 2020, the responses to 30 percent and 70 percent 
emissions reductions ranged from -1.3 [micro]g/m\3\ to

[[Page 53162]]

0.5 [micro]g/m\3\ while for 2024, the responses ranged from -1.1 
[micro]g/m\3\ to 0.6 [micro]g/m\3\; these are also all below the 
contribution threshold, with most sites showing a disbenefit from 
SOX reductions.\126\ The Stockton, Manteca, and Tranquillity 
sites showed the same pattern of slight benefits as for 2013.\127\ For 
further detail, please see the EPA's February 2020 Precursor TSD, Table 
3 and the 2018 PM2.5 Plan, Appendix G, tables 8 and 9 and 
Appendix K, tables 46, 48, and 50.
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    \125\ 2018 PM2.5 Plan, Appendix G, Table 8 and Table 
9.
    \126\ CARB's September 2019 Precursor Clarification, 2020 
analysis tables 15 and 16, and 2024 analysis tables 15 and 16.
    \127\ 2018 PM2.5 Plan, Appendix K, Table 48 and Table 
50.
---------------------------------------------------------------------------

    CARB also included additional information regarding emissions 
trends and an evaluation of the SOX emissions reduction 
disbenefit. We summarize this additional information below and provide 
a more detailed evaluation in the EPA's February 2020 Precursor TSD.
    In terms of emissions trends, the State found that SOX 
emissions decreased from 2013 to 2014 and then were expected to very 
gradually rise to 7.8 tpd in 2020 and 8.0 tpd in 2024.\128\ Given that 
projected SOX emissions are very similar in 2020 and 2024, 
the State concluded that the 2020 and 2024 sensitivity results were 
redundant. Comparing the ambient responses in 2013 and 2024, the State 
found that the responses were slightly less negative or, for a small 
number of sites, slightly higher in 2024, but still no more than 0.6 
[micro]g/m\3\ in response to a 70 percent SOX emissions 
reduction.\129\ This supports the State's conclusion as to the overall 
disbenefit of reducing SOX emissions.
---------------------------------------------------------------------------

    \128\ 2018 PM2.5 Plan, Appendix G, Figure 4.
    \129\ CARB's September 2019 Precursor Clarification, 2013 
analysis Table 16 and 2024 analysis Table 16.
---------------------------------------------------------------------------

    To explain the SOX emissions reduction disbenefit that 
is observed in some cases, CARB refers to the non-linearity of 
inorganic aerosol thermodynamics, as described in a study by West et 
al.\130\ That paper discusses how, under certain conditions, reducing 
SOX could free ammonia to combine with nitrate, increasing 
overall PM2.5 mass. To investigate this issue further, CARB 
conducted simulations with the ISORROPIA inorganic aerosol 
thermodynamic equilibrium model used within the CMAQ model and provided 
clarifications to the EPA.\131\ In essence, CARB states that for some 
conditions typical of San Joaquin Valley, ISORROPIA switches to a 
different chemical regime in which the disbenefit occurs. CARB states 
that it is not known how well this model behavior reflects the actual 
atmosphere, but CARB accepts the results because it is a well-known and 
widely used chemical model.
---------------------------------------------------------------------------

    \130\ 2018 PM2.5 Plan, Appendix K, section 5.6 
(``PM2.5 Precursor Sensitivity Analysis''); and West, 
J.J., Ansari, A.S., Pandis, S.N., 1999, Marginal PM2.5: 
Nonlinear aerosol mass response to sulfate reductions in the eastern 
United States, Journal of the Air & Waste Management Association, 
49, 1415-1424. https://doi.org/10.1080/10473289.1999.10463973.
    \131\ CARB's June 2019 Precursor Clarification.
---------------------------------------------------------------------------

    Based on the small and mostly negative modeled response of ambient 
PM2.5 to SOX emissions reductions, and based on 
its scientific understanding of sulfate interactions with other 
molecules in the air, the State concludes that SOX does not 
contribute significantly to ambient PM2.5 levels that exceed 
the 1997 24-hour PM2.5 NAAQS in the San Joaquin Valley.
c. VOC
    For VOC, CARB compared the 24-hour precursor contributions to the 
EPA's recommended draft contribution threshold of 1.3 [micro]g/m\3\. 
For a modeled 30 percent VOC emissions reduction, the ambient 
PM2.5 responses in 2013 ranged from 0.1 to 1.9 [micro]g/m\3\ 
across 15 monitoring sites, with two sites above the 1.3 [micro]g/m\3\ 
draft contribution threshold.\132\ \133\ The 2020 responses ranged from 
-0.1 to 0.6 [micro]g/m\3\, with all monitoring sites below the 1.3 
[micro]g/m\3\ draft contribution threshold, and hence also below the 
contribution threshold of 1.5 [micro]g/m\3\ that was finalized in the 
final PM2.5 Precursor Guidance. The 2024 responses ranged 
from -0.4 to 0.0 [micro]g/m\3\, with all monitoring sites below both 
the draft and final contribution thresholds. For a 70 percent VOC 
emissions reduction, the PM2.5 responses in 2013 ranged from 
0.2 to 4.8 [micro]g/m\3\, including responses above both contribution 
thresholds at a majority of sites. The 2020 response ranged from -0.2 
to 1.5 [micro]g/m\3\, with one site at the final contribution 
threshold. The 2024 response ranged from -1.0 to 0.0 [micro]g/m\3\ with 
monitoring sites below both the contribution thresholds. In other 
words, in response to either a 30 percent or a 70 percent reduction in 
VOC emissions, CARB models a decrease in ambient PM2.5 
levels at all sites for 2013, whereas for 2020, there were just small 
decreases in ambient PM2.5 levels at most sites and an 
increase at one site, and for 2024 there were increases in 
PM2.5 at all sites, i.e., a disbenefit. For further detail, 
please see the EPA's February 2020 Precursor TSD, Table 4, and the 2018 
PM2.5 Plan, Appendix G, tables 10 through 15.
---------------------------------------------------------------------------

    \132\ 2018 PM2.5 Plan, Appendix G, Table 10.
    \133\ We note that one site (Visalia) has a modeled response 
above the EPA's final recommended contribution threshold of 1.5 
[micro]g/m\3\ and one additional site (Bakersfield-California 
Avenue) has a modeled response below the 1.5 [micro]g/m\3\ threshold 
but above the EPA's draft threshold of 1.3 [micro]g/m\3\.
---------------------------------------------------------------------------

    CARB then considered additional information to assess whether these 
PM2.5 responses constituted a significant contribution to 
ambient PM2.5 in the San Joaquin Valley, including emissions 
trends and an assessment of the modeled disbenefit of VOC emissions 
reductions. Regarding emissions trends, CARB found that VOC emissions 
would decrease approximately 30 tpd (or 9 percent) from 2013 to 2024, 
with approximately 28 out of the 30 tpd reduction taking place by 
2020.\134\ The State concludes that the formation of ambient 
PM2.5 from VOC may therefore differ in base and future years 
and that the sensitivity analysis for 2013 is not representative of 
current or future conditions.
---------------------------------------------------------------------------

    \134\ 2018 PM2.5 Plan, Appendix G, 19 and Figure 5.
---------------------------------------------------------------------------

    CARB explained the modeled disbenefit of VOC reductions as follows: 
Emissions of VOC and NOX react in the atmosphere to form 
organic nitrate species, such as peroxyacetyl nitrate (PAN), meaning 
that some portion of the NOX emissions is not available to 
react with ammonia to form ammonium nitrate. In other words, VOC 
emissions are a ``sink'' for NOX emissions. Reducing VOC 
emissions therefore reduces the formation of organic nitrates, so the 
sink is smaller and nitrate molecules are freed to react with ammonia 
to form particulate ammonium nitrate.\135\ The State further explored 
the VOC disbenefit based on a 2016 CARB modeling assessment provided in 
Appendix A (``Air Quality Modeling'') of the ``2016 Moderate Area Plan 
for the 2012 PM2.5 Standard'' for the San Joaquin Valley 
(``2016 PM2.5 Plan''), which CARB submitted to the EPA as a 
SIP revision on May 10, 2019.\136\
---------------------------------------------------------------------------

    \135\ 2018 PM2.5 Plan, Appendix K, 72 (citing Meng, 
Z., D. Dabdub, D., Seinfeld, J.H., Chemical Coupling Between 
Atmospheric Ozone and Particulate Matter, Science 277, 116 (1997). 
DOI: 10.1126/science.277.5322.116).
    \136\ 2016 PM2.5 Plan, Appendix A, A-57. See also 
2018 PM2.5 Plan, Appendix K, section 5.6 
(``PM2.5 Precursor Sensitivity Analysis''), 71-72.
---------------------------------------------------------------------------

    Based on its sensitivity-based analysis of VOC emissions 
reductions, VOC emissions trends, and the scientific understanding of 
VOC chemistry in the San Joaquin Valley, CARB concludes that VOC 
emissions do not contribute significantly to PM2.5 levels 
that exceed the 1997 24-hour PM2.5 NAAQS in the San Joaquin 
Valley.

[[Page 53163]]

3. The EPA's Review of the State's Submission
    The EPA has evaluated the State's precursor demonstration 
consistent with the PM2.5 SIP Requirements Rule and the 
recommendations in the PM2.5 Precursor Guidance. Based on 
this evaluation, the EPA agrees that NOX emissions 
contribute significantly to ambient PM2.5 levels that exceed 
the 1997 24-hour PM2.5 NAAQS in the San Joaquin Valley and 
that NOX emissions sources, therefore, remain subject to 
control requirements under subparts 1 and 4 of the part D, title I of 
the Act. For the reasons provided below, the EPA proposes to approve 
the State's demonstration that ammonia, SOX, and VOC 
emissions do not contribute significantly to ambient PM2.5 
levels that exceed the 1997 24-hour PM2.5 NAAQS in the San 
Joaquin Valley.
    Regarding the State's analytical approach, the EPA finds that the 
State based its analyses on the latest available data and studies 
concerning ambient PM2.5 formation in the San Joaquin Valley 
from precursor emissions. Regarding the required concentration-based 
analysis, the EPA finds that the State assessed the absolute annual 
average contribution of each precursor in ambient PM2.5 
(i.e., in 2015). On the basis of the absolute concentrations being well 
above the EPA's recommended contribution thresholds for both the 24-
hour and annual average NAAQS, the State proceeded with its 
sensitivity-based analysis, which is the recommended sequence under the 
final PM2.5 Precursor Guidance.\137\
---------------------------------------------------------------------------

    \137\ For further discussion of the EPA's evaluation of the 
State's concentration-based analysis, see the EPA's February 2020 
Precursor TSD, sections entitled ``Concentration-based analysis'' 
within the EPA's evaluation for each of ammonia, SOX, and 
VOC.
---------------------------------------------------------------------------

    With respect to the sensitivity-based analysis, we find that the 
State performed its analyses following the steps of the EPA's 
recommended approach--i.e., for each modeled year and percent precursor 
emissions reduction, the State estimated the ambient PM2.5 
response using the procedure recommended in the PM2.5 
Precursor Guidance and compared the result to the recommended 
contribution threshold. The EPA also finds that the performance of the 
photochemical model was adequate for use in estimating the ambient 
PM2.5 responses, as discussed in section J (``Air Quality 
Model Performance'') of the EPA's ``Technical Support Document, EPA 
Evaluation of Air Quality Modeling, San Joaquin Valley PM2.5 
Plan for the 2006 PM2.5 NAAQS,'' February 2020 (``EPA's 
February 2020 Modeling TSD''). The State considered the EPA's 
recommended range of emissions reductions (30 percent to 70 percent) 
for the 2013 base year, the projected 2020 attainment year for the 1997 
24-hour PM2.5 NAAQS, and the projected 2024 attainment year 
for the 2006 PM2.5 NAAQS, and quantified the estimated 
response of ambient PM2.5 concentrations to precursor 
emissions changes for the first time in a PM2.5 SIP 
submission for the San Joaquin Valley. The EPA finds that such 
quantification and CARB's consideration of additional information 
provide an informed basis on which to make a determination as to 
whether ammonia, SOX, and VOC do or do not contribute 
significantly to ambient PM2.5 levels that exceed the 1997 
24-hour PM2.5 NAAQS in the San Joaquin Valley.\138\ 
Therefore, we turn to our evaluation of the State's determination for 
each of these three precursor pollutants.
---------------------------------------------------------------------------

    \138\ The State did not evaluate the 2015 Serious area 
attainment year. Because the year has passed and the area failed to 
attain by the Serious area attainment date, we will evaluate the 
precursor analysis for the Serious area plan based on the current 
section 189(d) projected attainment date of December 31, 2020.
---------------------------------------------------------------------------

a. Ammonia
    For ammonia, as detailed above, CARB estimated the ambient 
PM2.5 response to both a 30 percent and a 70 percent 
emissions reduction. We find that it was appropriate for the State to 
consider additional information to interpret those results to determine 
whether the ammonia contribution is significant. The primary conclusion 
demonstrated by the State's analysis of additional information is that 
ammonium nitrate formation is NOX-limited. As discussed in 
more detail below, we agree with this conclusion. We have evaluated 
CARB's determination that a projected future year is more 
representative of conditions in the San Joaquin Valley for sensitivity-
based analyses and that 30 percent is a reasonable upper bound for 
ammonia emissions reductions to assess the precursor contribution, as 
discussed below.
    The State provided ample information from scientific studies based 
on ambient measurements to help assess the estimated sensitivity of 
ambient PM2.5 to ammonia reductions. Conclusions based on 
ambient data are particularly relevant because they provide direct 
evidence of the chemical state of the atmosphere and are not dependent 
on modeled estimates of emissions or modeled ambient PM2.5 
concentrations. Measurements represent the ``real world'' result of the 
pollutants' differing geographic distributions, the various 
meteorological and chemical factors influencing their conversion to 
particulate, and their removal from the atmosphere by deposition and 
other processes. The observed abundance of ammonia relative to nitric 
acid, and the positive amount of chemically excess ammonia, both 
provide strong evidence that ammonia is not the limiting pollutant for 
particulate ammonium nitrate formation. They also support the State's 
conclusion that PM2.5 concentrations are insensitive to 
ammonia emissions reductions.
    The relative amount of ammonia and NOX emissions is one 
of the most critical factors in determining the sensitivity of ambient 
PM2.5 to ammonia reductions. We note that the model response 
to precursor reductions may be unrealistically large due to the 
underestimation of ammonia emissions and therefore of the ratio of 
ammonia to NOX emissions. There is evidence that ammonia 
emissions may be underestimated based on direct measurements of ammonia 
emissions flux during two measurement campaigns, as discussed in the 
EPA's February 2020 Precursor TSD. If ammonia emissions were higher in 
the modeling, then ammonia would be more abundant relative to nitrate 
and particulate nitrate formation would be more NOX-limited 
and less sensitive to ammonia reductions. This would make the model 
response more consistent with the ambient measurement studies, which 
suggest a very low sensitivity to ammonia. This evidence indicates that 
ammonia contribution to PM2.5 levels above the standard is 
likely to be less than estimated by the State's modeling in each of the 
three years. In comparison to the 2013 and 2020 modeling, the modeling 
for the year 2024 incorporates lower NOX emissions and so 
has a larger abundance of ammonia relative to nitrate, more similar to 
the studies' ambient measurements. Thus, the 2024 response to ammonia 
reductions is likely to be more reliable than the 2013 and 2020 
responses and appears to be more representative of current atmospheric 
conditions despite the use of emissions projections for a future year.
    The relative sizes of the ammonia and NOX precursor 
emissions inventories after accounting for their differing molecular 
weights are a rough indicator of which pollutant is the limiting 
pollutant for production of ammonium nitrate because ammonium nitrate 
forms from a one-to-one ratio of molecules derived from each precursor 
(i.e., one ammonium nitrate forms from one

[[Page 53164]]

ammonium and one nitrate). However, unlike measurements and 
photochemical modeling, a simple emissions ratio does not account for 
various processes mentioned above; it assumes all the emitted molecules 
find one another and react. The State found ammonia to be roughly three 
times as abundant as NOX in 2013 after accounting for their 
differing molecular weights, and even more abundant in future years. 
The EPA repeated the exercise to account for SOX and found 
that the ratio of total ammonia to the ammonia needed to react with 
both nitrate and sulfate ranged from 2.7 in 2013 to 5.6 in 2028. These 
results are approximately the same as the CARB NOX-only 
results because SOX emissions are very small relative to 
NOX and ammonia emissions (e.g., in 2013, winter daily 
emissions were 8.4 tpd of SOX versus 300.5 tpd of 
NOX and 309.8 tpd of ammonia).\139\ These observations 
support the State's finding that PM2.5 is expected to be 
relatively insensitive to ammonia reductions, though they are not 
definitive on their own.
---------------------------------------------------------------------------

    \139\ 2018 PM2.5 Plan, Appendix B, tables B-2, B-3, 
and B-4.
---------------------------------------------------------------------------

    The State also points to large decreases or projected decreases in 
NOX emissions in the San Joaquin Valley from 2013 to 2024, 
including a 36 percent reduction from baseline measures by 2020, and a 
53 percent reduction by 2024, while CARB projects that ammonia 
emissions will remain roughly constant (i.e., decreasing 1-2 percent). 
In conjunction with the ambient evidence that ammonia is already 
chemically overabundant relative to NOX in the San Joaquin 
Valley, this indicates that the overabundance will become even greater 
in the future, and thus ambient PM2.5 is expected to be even 
less responsive to ammonia reductions. This adds conservatism to the 
State's conclusions about ammonia sensitivity based on the scientific 
studies.
    While the base year for an attainment plan for a given 
nonattainment area is generally more representative of current 
conditions, there can be situations in which is it more appropriate to 
use future conditions representative of when sources will operate, and 
the EPA believes that states may use either a base year or a future 
year for modeling an ambient PM2.5 response to precursor 
emissions reductions, provided the state explains how the choice of 
analysis year and associated assumptions are appropriate.\140\ The 2013 
modeled responses cannot be considered current at the present time, in 
comparison to the 2020 results. Large NOX emissions 
reductions have occurred from 2013-2020 and are projected to continue 
to occur on through 2024, continuing to decrease the ratio of 
NOX to ammonia. In light of this ongoing trend, and the 
ambient data indicating that models underestimate ammonia, the EPA 
believes that future year results, which more accurately reflect the 
expected NOX to ammonia ratio, will continue to be 
representative, unlike the 2013 base year. These reductions are the 
result of regulations put in place by past air quality planning 
decisions and they will occur regardless of the actions that are being 
proposed herein. In assessing the effect of potential ammonia 
reductions, the EPA believes it is reasonable to account for these 
NOX reductions. In addition, as noted above, the greater 
abundance of ammonia relative to NOX in the 2024 year 
modeling is more consistent with recent ambient measurements, which 
suggest that the 2024 responses are more representative of current 
atmospheric conditions than the other model years for assessing 
sensitivity to ammonia reductions. Therefore, in consideration of the 
scientific studies and emissions trends, including the projected large 
amount of NOX emissions reductions through the attainment 
period, the EPA agrees that use of a future year is appropriate. Given 
the available research and ambient data, we conclude that the modeled 
2024 year is the most representative of conditions in the San Joaquin 
Valley.
---------------------------------------------------------------------------

    \140\ PM2.5 Precursor Guidance, 35-36.
---------------------------------------------------------------------------

    Even if we were to set aside the more representative 2024 modeling, 
in the 2020 modeled responses, only the Bakersfield-Planz site is above 
the contribution threshold, at 1.9 [micro]g/m\3\. A single value above 
the threshold is not determinative, particularly in light of the 
additional information provided above, indicating that the modeled 
values overestimate the contribution of ammonia to ambient 
PM2.5 levels, and that the trend continues toward less 
contribution in the future as the ratio of NOX to ammonia 
continues to drop. Moreover, the monitored 2020 design value is 
attaining the 1997 24-hour PM2.5 NAAQS because, as discussed 
above and in section V of this proposal, at the current time there are 
not PM2.5 levels above the NAAQS. This is further evidence 
that the single 2020 modeled response above the contribution threshold 
is not a significant contribution to PM2.5 levels in excess 
of the NAAQS, even if the 2020 modeling were considered representative.
    In the context of interpreting the full set of modeling results for 
ammonia emissions reductions, the EPA also considered the State's 
conclusion that the absence of available ammonia controls for sources 
in the San Joaquin Valley supports its decision to treat a 30 percent 
reduction as a reasonable upper bound on the ammonia emissions 
reductions to model in estimating the precursor contribution. As the 
State correctly notes, the 30 percent to 70 percent range recommended 
by the EPA is based on historical NOX and SOX 
emissions reductions, and changes in ammonia emissions levels 
nationally from 2011 to 2017 ranged from a 9 percent decrease to a 6 
percent increase.\141\ The State's descriptions of past research relied 
upon to develop existing rules that apply to ammonia emissions sources, 
as well as ongoing research, show that it has considered the 
availability of ammonia controls both in the past and present context, 
and that the State has a basis for its conclusion that 30 percent is a 
reasonable upper bound on achievable reductions for ammonia.
---------------------------------------------------------------------------

    \141\ Id. at 30, Table 2.
---------------------------------------------------------------------------

    In sum, we find that the State quantified the sensitivity of 
ambient PM2.5 levels to reductions in ammonia using 
appropriate modeling techniques that performed well, and that the 
State's analysis and use of future year sensitivity data, both 2020 and 
2024, is well-supported. We also find that the State adequately 
documented its basis for using a 30 percent reduction in ammonia 
emissions as an upper bound in the modeling to assess ambient 
sensitivity to ammonia emissions reductions. Based on these 
considerations, the EPA proposes to approve the State's demonstration 
that ammonia emissions do not contribute significantly to ambient 
PM2.5 levels that exceed the 1997 24-hour PM2.5 
NAAQS in the San Joaquin Valley.
b. SOX
    For SOX, the State found that the ambient 
PM2.5 responses to SOX emissions reductions were 
below the EPA's recommended contribution threshold of 1.3 [micro]g/m\3\ 
in the Draft PM2.5 Precursor Guidance (and below the EPA 
recommended threshold of 1.5 [micro]g/m\3\ in the final 
PM2.5 Precursor Guidance), and that for most sites there 
would be an increase in ambient PM2.5 levels in response to 
SOX reductions (i.e., a disbenefit). The EPA has evaluated 
the State's analysis of this disbenefit and resulting conclusion 
regarding significance.
    Because the results of the sensitivity analysis were all below the 
EPA's recommended 24-hour contribution thresholds at both the 30 
percent and 70

[[Page 53165]]

percent emissions reductions, and in both the 2013 base year and 2020 
(and 2024) future year, it is not necessary to distinguish between the 
timing and scale of emissions reductions with respect to the response 
of ambient PM2.5 levels as in the ammonia evaluation where 
the results diverged according to scale and timing of modeled emissions 
reductions. The EPA's February 2020 Precursor TSD contains additional 
detail on the EPA's evaluation of SOX as a PM2.5 
precursor, including the disbenefit associated with a reduction in 
SOX emissions. Accordingly, we find that the State's 
decision to rely on the 2013 sensitivity modeling results for a 30 
percent SOX reduction is acceptable.
    Therefore, on the basis of the modeled ambient PM2.5 
response to both a 30 percent and 70 percent reduction in 
SOX emissions in 2013, and on the facts and circumstances of 
the area, the EPA proposes to approve the State's demonstration that 
SOX emissions do not contribute significantly to ambient 
PM2.5 levels that exceed the 1997 24-hour PM2.5 
NAAQS in the San Joaquin Valley.
c. VOC
    For VOC, the State found that the ambient PM2.5 response 
to VOC emissions reductions were generally below the EPA's recommended 
contribution threshold of 1.3 [micro]g/m\3\ in the Draft 
PM2.5 Precursor Guidance and below the EPA's recommended 
threshold of 1.5 [micro]g/m\3\ in the final PM2.5 Precursor 
Guidance, and often predicted an increase in ambient PM2.5 
levels in response to such reductions (i.e., a disbenefit), except for 
a 70 percent emissions reduction for the 2013 base year, where the 
State predicted the ambient PM2.5 response to be above both 
recommended thresholds at a majority of sites. The EPA has evaluated 
and agrees with the State's determination that the modeling for future 
years is more representative of conditions in the San Joaquin Valley 
than the 2013 modeling for sensitivity-based analyses and the State's 
resulting conclusion as to whether the contribution from VOC emissions 
is significant.
    Regarding emissions trends, the EPA agrees that the 8.6 percent 
decrease in VOC emissions from 2013 to 2020 and the 9.2 percent 
projected decrease from 2013 to 2024 favors reliance on the future year 
modeling results. Furthermore, there is a large decrease in 
NOX emissions over this period, as discussed in the EPA's 
evaluation of ammonia, which affects the atmospheric chemistry with 
respect to ambient PM2.5 formation from VOC emissions. The 9 
percent VOC emissions reductions and the NOX emissions 
reductions are projected to result from implementation of existing 
baseline measures. We therefore find it reasonable to rely on future 
year 2020 or 2024 modeled responses to VOC emissions reductions, and 
both years show a disbenefit from VOC emissions reductions. The EPA 
also finds that the State provided a reasonable explanation for the VOC 
reduction disbenefit and evidence that it occurs in the San Joaquin 
Valley.
    For these reasons, we propose to approve the State's demonstration 
that VOC emissions do not contribute significantly to ambient 
PM2.5 levels that exceed the 1997 24-hour PM2.5 
NAAQS in the San Joaquin Valley.

C. Attainment Plan Control Strategy

1. Statutory and Regulatory Requirements
    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).'' \142\
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    \142\ 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.
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    Because the 2015 Serious area attainment date has passed, and the 
EPA found that the area failed to attain by the Serious area attainment 
date, we are evaluating the submission for compliance with the BACM/
BACT requirements now, in conjunction with the State's SIP submission 
intended to meet both the Serious area plan and section 189(d) plan 
requirements.
    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.\143\ 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.\144\ 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 are necessary to attain the 
NAAQS in the area.
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    \143\ 81 FR 58010, 58081 and General Preamble Addendum, 42011, 
42013.
    \144\ Id. and General Preamble Addendum, 42009-42010.
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    Under the PM2.5 SIP Requirements Rule, those control 
measures that otherwise meet the definition of BACM/BACT but ``can only 
be implemented in whole or in part beginning four years after 
reclassification'' are referred to as ``additional feasible measures.'' 
\145\ In accordance with the requirements of CAA section 172(c)(6), a 
Serious area plan must include any additional feasible measures to 
control emissions of direct PM2.5 and PM2.5 
precursors that are necessary and appropriate to provide for attainment 
of the relevant NAAQS as expeditiously as practicable and no later than 
the applicable attainment date.\146\
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    \145\ 40 CFR 51.1000, 40 CFR 51.1010(a)(4)(ii).
    \146\ Because the Serious area attainment year has passed and 
the area failed to attain by the Serious area attainment date, we 
will evaluate the BACM/BACT and additional feasible measure analysis 
for the Serious area plan with respect to the current section 189(d) 
projected attainment date of December 31, 2020.
---------------------------------------------------------------------------

    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 and additional feasible measures:
    (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.\147\
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    \147\ 81 FR 58010, 58083-58085.
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    The EPA allows consideration of factors such as physical plant 
layout,

[[Page 53166]]

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.\148\
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    \148\ 40 CFR 51.1010(a)(3) and 81 FR 58010, 58041-58042.
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    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 revisions to meet the basic requirements 
of CAA section 110 and any other applicable substantive provisions of 
the Act. The EPA is using these steps as guidelines in the evaluation 
of the BACM and BACT measures and related analyses in the SJV 
PM2.5 Plan. Furthermore, because the EPA has not previously 
taken action to approve the California SIP as meeting the subpart 4 
Moderate area planning requirements under CAA section 189 for the 1997 
24-hour PM2.5 NAAQS for the San Joaquin Valley area, the EPA 
is reviewing the SJV PM2.5 Plan for compliance with those 
requirements.\149\
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    \149\ The EPA does not normally conduct a separate evaluation to 
determine whether a Serious area plan's measures also meet the RACM 
requirements. As explained in the General Preamble Addendum, we 
interpret the BACM requirement as generally subsuming the RACM 
requirement--i.e., if we determine that the measures are indeed the 
``best available,'' we have necessarily concluded that they are 
``reasonably available.'' (General Preamble Addendum, 42010). 
Therefore, a separate analysis to determine if the measures 
represent a RACM level of control is not necessary. A proposed 
approval of a Plan's provisions concerning implementation of BACM is 
also a proposed finding that the Plan provides for the 
implementation of RACM.
---------------------------------------------------------------------------

    The overarching requirement for the CAA section 189(d) attainment 
control strategy is that it provides for attainment of the NAAQS as 
expeditiously as practicable.\150\ The control strategy must include 
any additional measures (beyond those already adopted in previous 
nonattainment plans 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.\151\ The state 
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, based on the 
most recent emissions inventory for the area.\152\
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    \150\ 81 FR 58010, 58100.
    \151\ 40 CFR 50.1010(c)(2)(ii).
    \152\ CAA section 189(d) and 40 CFR 51.1010(c).
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    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.\153\ 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 emissions 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 emissions reduction requirement 
under section 189(d) for this area is 2017.
---------------------------------------------------------------------------

    \153\ 81 FR 58010, 58101.
---------------------------------------------------------------------------

2. Summary of the State's Submission and the EPA's Evaluation and 
Proposed Action
a. Control Strategy
    For the Serious area and section 189(d) plan requirements for the 
1997 24-hour PM2.5 NAAQS the State based the control 
strategy in the SJV PM2.5 Plan on ongoing emissions 
reductions from baseline control measures.\154\ As we use the term 
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 for the 1997 24-hour PM2.5 NAAQS and beyond. The State 
describes the baseline measures in the 2018 PM2.5 Plan in 
Chapter 4,\155\ Appendix C (``Stationary Source Control Measure 
Analyses''), and Appendix D (``Mobile Source Control Measure 
Analyses''). The State incorporates reductions generated by these 
baseline measures into the projected baseline inventories and 
reductions resulting from District measures are individually quantified 
in Appendix C.
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    \154\ Because the 2015 Serious area attainment date has passed, 
and the EPA found that the area failed to attain by the Serious area 
attainment date, we are evaluating the control strategy for the 
Serious area requirements based on the timeline associated with the 
current section 189(d) projected attainment date of December 31, 
2020.
    \155\ 2018 PM2.5 Plan, Chapter 4, Table 4-2.
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    In the 2018 PM2.5 Plan, CARB indicates that mobile 
sources emit over 85 percent of the NOX emissions 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.'' \156\
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    \156\ 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 many such mobile source regulations for which it 
has issued waiver authorizations as revisions to the California 
SIP.\157\
---------------------------------------------------------------------------

    \157\ 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.\158\
---------------------------------------------------------------------------

    \158\ 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), revisions to the California on-
road reformulated gasoline and diesel fuel regulations (75 FR 26653, 
May 12, 2010), and revisions to the California motor vehicle 
inspection and maintenance program (75 FR 38023, July 1, 2010).
---------------------------------------------------------------------------

    As to stationary and area sources, the SJV PM2.5 Plan 
indicates that regulations adopted for prior attainment plans

[[Page 53167]]

continue to reduce emissions of NOX and direct 
PM2.5.\159\ Specifically, Table 4-1 of the 2018 
PM2.5 Plan identifies 33 District measures that limit 
NOX and direct PM2.5 emissions.\160\ The EPA has 
approved each of the identified measures into the California SIP,\161\ 
with two exceptions.
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    \159\ 2018 PM2.5 Plan, Chapter 4, 4-3. For the 
District's BACM analysis of stationary and area source measures, see 
2018 PM2.5 Plan, Appendix C.
    \160\ 2018 PM2.5 Plan, Chapter 4, Table 4-1.
    \161\ See EPA Region IX's website for information on District 
control measures that have been approved into the California SIP, 
available at: https://www.epa.gov/sips-ca/epa-approved-san-joaquin-valley-unified-air-district-regulations-california-sip.
---------------------------------------------------------------------------

    First, the District amended Rule 4905 (``Natural Gas-fired, Fan-
type, Residential Central Furnaces'') on October 15, 2020, to extend 
the period during which manufacturers may pay emissions fees in lieu of 
meeting the rule's NOX emissions limits.\162\ CARB submitted 
the amended rule to the EPA on December 30, 2020,\163\ and the EPA has 
not yet proposed any action on this submission. The EPA approved a 
prior version of Rule 4905 into the California SIP on March 29, 
2016.\164\ As part of that rulemaking, the EPA noted that because of 
the option in Rule 4905 to pay mitigation fees in lieu of compliance 
with emissions limits, emissions reductions associated with the rule's 
emissions limits would not be creditable in any attainment plan without 
additional documentation.\165\ Until the District submits the necessary 
documentation to credit emissions reductions achieved by Rule 4905 
toward an attainment control strategy, this rule is not creditable for 
SIP purposes. The Plan indicates that the District attributed 0.06 tpd 
of NOX reductions between 2013 and 2020 to Rule 4905.\166\ 
These emissions reductions have de minimis impacts on the attainment 
demonstration for the 1997 24-hour PM2.5 NAAQS in the SJV 
PM2.5 Plan.
---------------------------------------------------------------------------

    \162\ SJVUAPCD, Final Draft Staff Report with Appendix for 
Proposed Amendments to Rule 4905, ``Adopt Proposed Amendments to 
Rule 4905 (Natural Gas-fired, Fan-type Central Furnaces),'' 2.
    \163\ Letter dated December 28, 2020, from Richard W. Corey, 
Executive Officer, CARB, to John Busterud, Regional Administrator, 
EPA Region 9. CARB's submittal letter formally withdrew a previously 
amended version of Rule 4905 adopted by the District on June 21, 
2018 and submitted to the EPA by CARB on November 21, 2018.
    \164\ 81 FR 17390 (March 29, 2016) (approving Rule 4905 as 
amended January 22, 2015).
    \165\ EPA, Region IX Air Division, ``Technical Support Document 
for EPA's Proposed Rulemaking for the California State 
Implementation Plan (SIP), San Joaquin Valley Unified Air Pollution 
Control District's Rule 4905, Natural Gas-Fired, Fan-Type Central 
Furnaces,'' October 5, 2015, n. 8.
    \166\ 2018 PM2.5 Plan, Appendix C, C-290.
---------------------------------------------------------------------------

    Second, the 2018 PM2.5 Plan lists Rule 4203 
(``Particulate Matter Emissions from Incineration of Combustible 
Refuse'') as a baseline measure. This rule has not been approved into 
the California SIP.\167\ Appendix C of the 2018 PM2.5 Plan 
indicates, however, that the emissions inventory for incineration of 
combustible refuse is 0.00 tpd of NOX and 0.00 direct 
PM2.5 from 2013 through 2020.\168\ Thus, although the 
District included this rule as a baseline measure, there are no 
meaningful reductions associated with this rule that would affect the 
attainment demonstration in the SJV PM2.5 Plan.
---------------------------------------------------------------------------

    \167\ The EPA does not have any pending SIP submission for Rule 
4203.
    \168\ 2018 PM2.5 Plan, Appendix C, C-46.
---------------------------------------------------------------------------

    In sum, although Table 4-1 of the 2018 PM2.5 Plan 
identifies two baseline measures that are not creditable for SIP 
purposes at this time, we find that the total emissions reductions 
attributed to these measures in the future baseline inventories have de 
minimis effects on the attainment demonstration in the Plan.
b. Best Available Control Measures
    We are evaluating the State's BACM demonstration for the 1997 24-
hour PM2.5 NAAQS against the section 189(b)(1)(B) Serious 
area plan BACM requirement, and the section 189(d) plan requirement to 
address all Serious area plan requirements that the State has not 
already met. Because we have already found that the State failed to 
attain the 1997 24-hour PM2.5 NAAQS in the San Joaquin 
Valley area by the Serious area attainment date, and because we have 
not previously found that the state has met the BACM requirement for 
purposes of the 1997 24-hour PM2.5 NAAQS, we are evaluating 
the State's submission against the Serious area BACM requirement in 
light of the section 189(d) control plan timeline. 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.\169\ 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 emissions 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.
---------------------------------------------------------------------------

    \169\ Appendices C and D also present an MSM analysis for the 
purposes of meeting a precondition for an extension of the Serious 
area attainment date under CAA section 188(e) for the 2006 
PM2.5 NAAQS. The San Joaquin Valley area is not subject 
to the MSM requirement for the 1997 24-hour PM2.5 NAAQS. 
Thus, the EPA is evaluating the Plan's control strategy for 
implementation of BACM and BACT only.
---------------------------------------------------------------------------

    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 emissions 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 emissions sources, and control measures implemented in 
other ozone and PM2.5 nonattainment areas in California and 
other states.\170\ The District also provides an analysis of several 
SIP-approved VOC regulations that, according to the District, also 
provide ammonia co-benefits.\171\ Based on these analyses, the District 
concludes that all best available control measures for stationary and 
area sources are in place in the San Joaquin Valley for NOX 
and directly emitted PM2.5 for purposes of meeting the BACM/
BACT requirement for the 1997 24-hour PM2.5 NAAQS. We 
provide an evaluation of many of the District's control measures for 
stationary sources and area sources in section III of the EPA's 1997 
24-hour PM2.5 TSD together with recommendations for possible 
future improvements to these rules.
---------------------------------------------------------------------------

    \170\ 2018 PM2.5 Plan, Chapter 4, section 4.3.1.
    \171\ 2018 PM2.5 Plan, 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 emissions 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

[[Page 53168]]

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.\172\
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    \172\ 2018 PM2.5 Plan, Appendix D, Chapter II.
---------------------------------------------------------------------------

    Mobile source categories for which CARB has primary responsibility 
for reducing emissions in California include most new and existing on- 
and non-road engines and vehicles and motor vehicle fuels. The SJV 
PM2.5 Plan's BACM demonstration provides a general 
description of CARB's key mobile source programs and regulations and a 
comprehensive table listing on-road and non-road mobile source 
regulatory actions taken by CARB since 1985.\173\
---------------------------------------------------------------------------

    \173\ Id. at Table 17.
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    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.\174\ TCMs are projects that 
reduce air pollutants from transportation sources by reducing vehicle 
use, traffic congestion, or vehicle miles traveled. TCMs are currently 
being implemented in the San Joaquin Valley as part of the Congestion 
Mitigation and Air Quality cost effectiveness policy adopted by the 
eight local jurisdiction MPOs and in the development of each Regional 
Transportation Plan (RTP). The Congestion Mitigation and Air Quality 
policy, which is included in a number of the District's prior 
attainment plan submissions for the ozone and PM2.5 NAAQS, 
provides a standardized process for distributing 20 percent of the 
Congestion Mitigation and Air Quality funds to projects that meet a 
minimum cost effectiveness threshold beginning in fiscal year 2011. The 
MPOs revisited the minimum cost effectiveness standard during the 
development of their 2018 RTPs and 2019 Federal Transportation 
Improvement Program and concluded that they were implementing all 
reasonable transportation control measures.\175\ Appendix D of the 
District's ``2016 Ozone Plan for 2008 8-Hour Ozone Standard,'' adopted 
June 16, 2016, contains a listing of adopted TCMs for the San Joaquin 
Valley.\176\
---------------------------------------------------------------------------

    \174\ Id. at D-127 and D-128.
    \175\ Id. at D-127.
    \176\ Id. and SJVUAPCD, ``2016 Ozone Plan for 2008 8-Hour Ozone 
Standard'' (adopted June 16, 2016), Appendix D, Attachment D, tables 
D-10 to D-17.
---------------------------------------------------------------------------

    We have reviewed the State's and District's analysis and 
determination in the SJV PM2.5 Plan that their baseline 
mobile, stationary, and area source control measures meet the 
requirements for BACM for sources of direct PM2.5 and 
applicable PM2.5 plan precursors (i.e., NOX) for 
purposes of the 1997 24-hour PM2.5 NAAQS. In our review, we 
considered our evaluation of the State's and District's rules in 
connection with our approval of the demonstrations for BACM (including 
BACT) and MSM for the 2006 PM2.5 NAAQS.\177\ We find that 
the evaluation processes followed by CARB and the District in the SJV 
PM2.5 Plan to identify potential BACM were generally 
consistent with the requirements of the PM2.5 SIP 
Requirements Rule, the State's and District's evaluation of potential 
measures is appropriate, and the State and District have provided 
reasoned justifications for their rejection of potential measures based 
on technological or economic infeasibility. We also agree with the 
District's conclusion that all reasonable TCMs are being implemented in 
the San Joaquin Valley and propose to find that these TCMs implement 
BACM for transportation sources.
---------------------------------------------------------------------------

    \177\ 85 FR 44192.
---------------------------------------------------------------------------

    For the foregoing reasons, we propose to find that the SJV 
PM2.5 Plan provides for the implementation of BACM for 
sources of direct PM2.5 and NOX as expeditiously 
as practicable in accordance with the requirements of CAA section 
189(b)(1)(B), and in satisfaction of both the Serious area and section 
189(d) plan requirements.
c. Section 189(d) Five Percent 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 emissions 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 a 
reduction of approximately 15.9 tpd of NOX, and the targets 
for subsequent years are additional reductions of five percent per 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 Emissions 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 EPA proposes to find that the State's use of 2017 as the 
starting point from which the five percent per year emissions 
reductions should begin is reasonable and consistent with the CAA. As 
discussed in section IV.C.1 of this document, the EPA interprets the 
language under CAA section 189(d) to require a state to submit a new 
attainment plan to achieve annual reductions ``from the date of such 
submission until attainment.'' The 2018 PM2.5 Plan was not 
submitted until May 10, 2019. However, the Serious area attainment 
deadline for the San Joaquin Valley nonattainment area for the 1997 
PM2.5 NAAQS was December 31, 2015.\178\ Accordingly, a plan 
submittal

[[Page 53169]]

to meet the requirements under section 189(d) was due by December 31, 
2016, and reductions were required to occur as of that date. The 
decline in emissions from 2017 to 2020 shows that reductions did, in 
fact, occur within the required timeframe. Furthermore, the State's 
demonstration shows that NOX emissions reductions from 2017 
to 2020 are greater than the required five percent per year. Thus, the 
EPA proposes to find that the SJV PM2.5 Plan meets the CAA 
189(d) requirement to provide for an annual reduction in 
PM2.5 or PM2.5 precursor emissions of not less 
than five percent of the amount of such emissions reported in the most 
recent inventory prepared for the area.
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    \178\ 80 FR 18528.
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D. Attainment Demonstration and Modeling

1. Statutory and Regulatory Requirements
    Section 189(b)(1)(A) of the CAA requires that each Serious area 
plan include a demonstration (including air quality modeling) that the 
plan provides for attainment of the PM2.5 NAAQS by the 
applicable attainment date. As discussed in section IV of this 
proposal, given that the outermost statutory Serious area attainment 
date for the San Joaquin Valley area (i.e., December 31, 2015) has 
passed and that the EPA has already found that the SJV area failed to 
attain by that date, the EPA must evaluate the State's plan for 
attainment by a later attainment date. Given that the finding of 
failure to attain triggered the State's obligation to submit a new plan 
meeting the requirements of section 189(d), the EPA is evaluating the 
SJV PM2.5 Plan in light of the outermost attainment date 
required in section 189(d). That section requires that the attainment 
date be as expeditious as practicable, but not later than five years 
following the EPA's finding that the area failed to attain the NAAQS by 
the applicable Serious area attainment date. In this case, the State 
projected such attainment by December 31, 2020, i.e., by the relevant 
statutory date.
    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.\179\ 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.
---------------------------------------------------------------------------

    \179\ 40 CFR 51.1011(b)(1); 81 FR 58010, 58102.
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    The EPA's PM2.5 modeling guidance \180\ (``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 
future year.\181\ The modeled response to the emissions changes between 
those years is used to calculate relative response factors (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 should 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.\182\
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    \180\ 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, Office of Air Quality Planning and Standards, EPA, to 
Regional Air Program Managers, EPA, Subject: ``Update to the 24 Hour 
PM2.5 NAAQS Modeled Attainment Test,'' (``Modeling 
Guidance Update'').
    \181\ 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.
    \182\ Modeling Guidance, section 4.5, ``What is the Recommended 
Modeled Attainment Test for the 24-Hour NAAQS.''
---------------------------------------------------------------------------

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 24-hour 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.\183\ 
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 
emissions 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.
---------------------------------------------------------------------------

    \183\ 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

[[Page 53170]]

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. CARB's supplemental weight of evidence 
analysis further supports the Plan's demonstration of attainment by the 
end of 2020. 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 70 percent decrease between 1999 and 2017 in the 
number of days above the 1997 24-hour PM2.5 NAAQS.\184\ The 
analysis also shows decreases in daily PM2.5 concentrations 
during winter, and in the frequency of high PM2.5 
concentrations generally.\185\ 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.\186\ These trends show that there has been an improvement in air 
quality due to emissions reductions in the San Joaquin Valley, although 
that point is not fully reflected in the 98th percentile statistic, 
which is the basis for the regulatory design value.
---------------------------------------------------------------------------

    \184\ Weight of Evidence Analysis, 27-28, Figure 14, and Figure 
24.
    \185\ Id. at Figure 16 and Figure 17.
    \186\ Id. at Figure 21.
---------------------------------------------------------------------------

    The State conducted three CMAQ \187\ 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.\188\
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    \187\ CMAQ Version 5.0.2.
    \188\ 2018 PM2.5 Plan, 5-5.
---------------------------------------------------------------------------

    Table 4 shows the 2013 base year and 2020 projected future year 24-
hour PM2.5 design values at monitoring sites in the San 
Joaquin Valley. As recommended by the EPA's guidance, the 2013 base 
year design value for modeling purposes is a weighted average of three 
monitored design values, to minimize the influence of year-to-year 
variability. The highest 2020 projected design value is 47.6 [micro]g/
m\3\ at the Bakersfield-California monitoring site, which is below the 
65 [micro]g/m\3\ level of the 1997 24-hour PM2.5 NAAQS.

   Table 4--Projected Future 24-Hour PM2.5 Design Values at Monitoring
            Sites in the San Joaquin Valley ([micro]g/m \3\)
------------------------------------------------------------------------
                                             2013 Base    2020 Projected
             Monitoring site               design value    design value
------------------------------------------------------------------------
Bakersfield--California.................            64.1            47.6
Fresno-Garland..........................            60.0            44.3
Hanford.................................            60.0            43.7
Fresno-Hamilton & Winery................            59.3            45.6
Clovis..................................            55.8            41.1
Visalia.................................            55.5            42.8
Bakersfield-Planz.......................            55.5            41.2
Madera..................................            51.0            38.9
Turlock.................................            50.7            37.8
Modesto.................................            47.9            35.8
Merced-M. Street........................            46.9            32.9
Stockton................................            42.0            33.5
Merced-S Coffee.........................            41.1            30.0
Manteca.................................            36.9            30.1
Tranquility.............................            29.5            21.5
------------------------------------------------------------------------
Source: 2018 PM2.5 Plan, Table 5-5.

3. The EPA's Review of the State's Submission
    The EPA must make several findings in order to approve the modeled 
attainment demonstration in an attainment plan SIP submission. First, 
we must find that the attainment demonstration's technical bases, 
including the emissions inventories and air quality modeling, are 
adequate. As discussed in section IV.A of this preamble, we are 
proposing to approve the emissions inventories on which the SJV 
PM2.5 Plan's attainment demonstration and related provisions 
are based. Furthermore, the EPA has evaluated the State's choice of 
model and the extensive discussion in the Modeling Protocol about 
modeling procedures, tests, and performance analyses. We find that the 
analyses are consistent with the EPA's guidance on modeling for 
PM2.5 attainment planning purposes. Based on these reviews, 
we find that the modeling in the Plan is adequate for the purposes of 
supporting the RFP demonstration and demonstration of attainment by 
2020 and are proposing to approve the air quality modeling. For further 
detail, see the EPA's February 2020 Modeling TSD.
    Second, we must find that the SIP submittal provides for 
expeditious attainment through the timely implementation of the control 
strategy. As discussed in section IV.C of this preamble, we are 
proposing to approve the control strategy in the SJV PM2.5 
Plan, including the BACM/BACT demonstration and the five percent 
emissions reduction requirement under CAA sections 189(b)(1)(B) and 
189(d), respectively.

[[Page 53171]]

    Third, the EPA must find that the emissions reductions that are 
relied on for attainment in the SIP submission are creditable. As 
discussed in section IV.C.2.a, the SJV PM2.5 Plan relies 
principally on rules that have already been adopted and approved by the 
EPA to achieve the emissions reductions needed to attain the 1997 24-
hour PM2.5 NAAQS in the San Joaquin Valley. We present our 
evaluation of the rules in section IV.C.2.a and in sections II and III 
of the EPA's 1997 24-hour PM2.5 TSD. We find that all but 
two of these rules are SIP-creditable and that the total emissions 
reductions attributed to the two measures that are not SIP-creditable 
have de minimis impacts on the attainment demonstration in the Plan.
    The EPA has also reviewed ambient monitoring data recorded at air 
quality monitors throughout the San Joaquin Valley PM2.5 
nonattainment area during the three years leading up to the projected 
December 31, 2020 attainment date (i.e., 2018-2020). As discussed in 
section V of this proposal, based on these data, we are proposing to 
find that the San Joaquin Valley area attained the 1997 24-hour 
PM2.5 NAAQS by the December 31, 2020 attainment date.
    Based on these evaluations, we propose to determine that the SJV 
PM2.5 Plan provides for attainment of the 1997 24-hour 
PM2.5 NAAQS by the most expeditious date practicable, 
consistent with the requirements of CAA section 189(d). Furthermore, 
because the 2015 Serious area attainment date has passed, and the EPA 
found that the area failed to attain by the Serious area attainment 
date, we are evaluating the State's compliance with the Serious area 
plan requirements in light of the attainment date required under CAA 
section 189(d).\189\ Thus, we are also proposing to determine that the 
Plan meets the Serious area attainment plan requirement under CAA 
section 189(b)(1)(A).
---------------------------------------------------------------------------

    \189\ See CAA section 179(d); 40 CFR 51.1004(a)(3).
---------------------------------------------------------------------------

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 emissions 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 emissions reductions sufficient to maintain generally 
linear progress toward attainment by the applicable deadline.\190\
---------------------------------------------------------------------------

    \190\ General Preamble Addendum, 42015.
---------------------------------------------------------------------------

    Attainment plans for PM2.5 nonattainment areas should 
include detailed schedules for compliance with emissions regulations in 
the area and provide corresponding annual emissions reductions to be 
achieved by each milestone in the schedule.\191\ In reviewing an 
attainment plan under subpart 4, the EPA considers whether the annual 
incremental emissions 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.\192\
---------------------------------------------------------------------------

    \191\ Id. at 42016.
    \192\ 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.\193\ Additionally, states should estimate the RFP 
projected emissions for each quantitative milestone year by sector on a 
pollutant-by-pollutant basis.\194\
---------------------------------------------------------------------------

    \193\ 40 CFR 51.1012(a).
    \194\ 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 emissions 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 emissions controls in the 
attainment plan and the requirement to quantify those required 
emissions 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 emissions 
reductions to date.\195\
---------------------------------------------------------------------------

    \195\ 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.\196\ 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.\197\
---------------------------------------------------------------------------

    \196\ General Preamble, 13539, and General Preamble Addendum, 
42016.
    \197\ 79 FR 31566 (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.

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[[Page 53172]]

    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.\198\ 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.\199\ 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.\200\
---------------------------------------------------------------------------

    \198\ 40 CFR 51.1013(a)(4).
    \199\ 81 FR 58010, 58064.
    \200\ Id. at 58064 and 58092.
---------------------------------------------------------------------------

    Because the EPA designated the San Joaquin Valley area as 
nonattainment for the 1997 24-hour PM2.5 NAAQS effective 
April 5, 2005,\201\ 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.\202\ For a Serious area attainment plan 
with a statutory attainment date of December 31, 2015, the relevant 
quantitative milestone year is December 31, 2017. However, as discussed 
in section III, the area did not attain by the statutory Serious area 
attainment date and evaluating reasonable further progress toward that 
date does not make sense. We are therefore evaluating the Serious area 
obligations based on the attainment date the State must meet in a plan 
required under CAA section 189(d).\203\ To meet CAA section 189(d), the 
SJV PM2.5 Plan includes a demonstration that the area will 
attain by December 31, 2020. Therefore, in accordance with 40 CFR 
51.1013(a)(4), the attainment plan for this area must contain 
quantitative milestones to be achieved no later than December 31, 2017, 
December 31, 2020, and December 31, 2023.
---------------------------------------------------------------------------

    \201\ 70 FR 944.
    \202\ 40 CFR 51.1013(a)(4).
    \203\ See CAA section 179(d); 40 CFR 51.1004(a)(3).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    Appendix H (``RFP, Quantitative Milestones, and Contingency'') of 
the 2018 PM2.5 Plan contains the State's RFP demonstration 
and quantitative milestones for the 1997 24-hour PM2.5 
NAAQS,\204\ and the Valley State SIP Strategy contains the control 
measure commitments that CARB has identified as mobile source 
quantitative milestones for the 2020 milestone date.\205\ Given the 
State's conclusions that ammonia, SOX, and VOC emissions do 
not contribute significantly to PM2.5 levels that exceed the 
1997 24-hour PM2.5 NAAQS in the San Joaquin Valley, as 
discussed in section IV.B of this proposed rule, the RFP demonstration 
provided by the State addresses emissions of direct PM2.5 
and NOX.\206\ Similarly, the State developed quantitative 
milestones based upon implementation of control strategy measures in 
the adopted SIP and in the SJV PM2.5 Plan that achieve 
reductions in emissions of direct PM2.5 and 
NOX.\207\ For the 1997 24-hour PM2.5 NAAQS, the 
RFP analysis in the Plan shows generally linear progress toward 
attainment.
---------------------------------------------------------------------------

    \204\ As discussed in footnote 34, 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.
    \205\ Valley State SIP Strategy, Table 7 (identifying State 
measures scheduled for action between 2017 and 2020, inter alia) and 
CARB Resolution 18-49, ``San Joaquin Valley Supplement to the 2016 
State Strategy for the State Implementation Plan'' (October 25, 
2018), 5 (adopting State commitment to begin public processes and 
propose for Board consideration the list of proposed SIP measures 
outlined in the Valley State SIP Strategy and included in Attachment 
A, according to the schedule set forth therein).
    \206\ SJV PM2.5 Plan, Appendix H, H-1.
    \207\ Id. at H-18 and H-19 (District milestones) and H-21 and H-
22 (State milestones).
---------------------------------------------------------------------------

    We describe the RFP analysis and quantitative milestones in the SJV 
PM2.5 Plan in greater detail below.
Reasonable Further Progress
    The State addresses the RFP and quantitative milestone requirements 
in Appendix H to the 2018 PM2.5 Plan submitted in February 
2020. The State estimates that emissions of direct PM2.5 and 
NOX will generally decline from the 2013 base year to the 
projected 2020 attainment year, and beyond to the 2023 post-attainment 
quantitative milestone year. The Plan's emissions inventory shows that 
direct PM2.5 and NOX are emitted by a large 
number and range of sources in the San Joaquin Valley. Table H-2 in 
Appendix H contains an anticipated implementation schedule for District 
regulatory control measures and Table 4-8 in Chapter 4 of the 2018 
PM2.5 Plan contains an anticipated implementation schedule 
for CARB control measures in the San Joaquin Valley. Table H-5 in 
Appendix H contains projected emissions for each quantitative milestone 
year. These emissions levels reflect baseline emissions projections 
through the 2023 post-attainment milestone year.\208\
---------------------------------------------------------------------------

    \208\ Id. at tables H-3 to H-5.
---------------------------------------------------------------------------

    The SJV PM2.5 Plan identifies emissions reductions 
needed for attainment of the 1997 24-hour PM2.5 NAAQS by 
2020,\209\ and identifies San Joaquin Valley's progress toward 
attainment in each milestone year.\210\ The State and District set RFP 
targets for each of the quantitative milestone years as shown in Table 
H-8 of Appendix H of the 2018 PM2.5 Plan.
---------------------------------------------------------------------------

    \209\ Id. at Table H-6.
    \210\ Id. at Table H-7.
---------------------------------------------------------------------------

    According to the Plan, reductions in both direct PM2.5 
and NOX emissions from 2013 base year levels result in 
emissions levels consistent with attainment in the 2020 attainment 
year. Based on these analyses, the State and District conclude that the 
adopted control strategy is adequate to meet the RFP requirement for 
the 1997 24-hour PM2.5 NAAQS.
Quantitative Milestones
    Appendix H of the 2018 PM2.5 Plan identifies the 
milestone dates of December 31, 2017, December 31, 2020, and December 
31, 2023, for the 1997 PM2.5 NAAQS.\211\ Appendix H also 
identifies target emissions levels to meet the RFP requirement for 
direct PM2.5 and NOX emissions for each of these 
milestone years,\212\ and State and District control measures that will 
achieve emissions reductions in the years leading up to each of the 
milestones, in accordance with the control strategy in the Plan.\213\
---------------------------------------------------------------------------

    \211\ Id. at Table H-12.
    \212\ Id. at Table H-8.
    \213\ Id. at H-18 and H-19 (District milestones) and H-21 and H-
22 (State milestones).
---------------------------------------------------------------------------

    The Plan includes quantitative milestones for mobile, stationary, 
and area sources. For mobile sources, CARB has developed quantitative 
milestones that provide for an evaluation of RFP based on the 
implementation of specific control measures by the relevant three-year 
milestones. For each quantitative milestone year, the Plan provides for 
evaluating RFP by tracking State and District implementation of 
regulatory measures and SIP commitments during the three-year period 
leading to each

[[Page 53173]]

milestone date, consistent with the control strategy in the SJV 
PM2.5 Plan.\214\ The identified regulatory measures include 
State measures for light-duty vehicles and non-road vehicles and 
several District measures for stationary and area sources.\215\
---------------------------------------------------------------------------

    \214\ Id. We note that the District's identified quantitative 
milestones for 2023 appear to contain a typographical error, as they 
include a District report on ``[t]he status of SIP measures adopted 
between 2017 and 2020 as per the schedule included in the adopted 
Plan.'' Id. at H-18 and H-19. We understand that the District 
intended to refer here to the status of SIP measures adopted between 
2020 and 2023, consistent with the schedule in the 2018 
PM2.5 Plan.
    \215\ Id. at H-18 and H-19 (District milestones), and H-21 and 
H-22 (State milestones).
---------------------------------------------------------------------------

    CARB submitted its 2017 Quantitative Milestone Report for the San 
Joaquin Valley to the EPA on December 20, 2018.\216\ The report 
includes a certification that CARB and the District met the 2017 
quantitative milestones identified in the SJV PM2.5 Plan for 
the 1997 PM2.5 NAAQS and discusses the State's and 
District's progress on implementing the three CARB measures and six 
District measures identified in Appendix H as quantitative milestones 
for the 2017 milestone year. On February 15, 2021, the EPA determined 
that the 2017 Quantitative Milestone Report was adequate.\217\ In our 
evaluation of the 2017 Quantitative Milestone Report, we found that the 
control measures in the Plan are in effect, consistent with the RFP 
demonstration in the SJV PM2.5 Plan for the 1997 24-hour 
PM2.5 NAAQS, but we noted that the determination of adequacy 
did not constitute approval of any component of the SJV 
PM2.5 Plan.\218\
---------------------------------------------------------------------------

    \216\ Letter dated December 20, 2018, from Richard W. Corey, 
Executive Officer, CARB, to Michael Stoker, Regional Administrator, 
EPA Region IX, with attachment ``2017 Quantitative Milestone Report 
for the 1997 and 2006 NAAQS.''
    \217\ Letter dated February 15, 2021, from Deborah Jordan, 
Acting Regional Administrator, EPA Region IX, to Richard W. Corey, 
Executive Officer, CARB, with enclosure titled ``EPA Evaluation of 
2017 Quantitative Milestone Report.''
    \218\ Id.
---------------------------------------------------------------------------

3. The EPA's Review of the State's Submission
    The RFP demonstration in the SJV PM2.5 Plan identifies 
quantitative milestone dates (i.e., December 31 of 2017, 2020, and 
2023) that are consistent with the requirements of 40 CFR 51.1013(a)(4) 
and presents projected RFP emissions levels for direct PM2.5 
and NOX to be achieved by these milestone dates based on the 
implementation schedule for existing control measures in the area 
(i.e., baseline measures). The projected emissions levels based on the 
implementation schedule in the Plan demonstrate that the control 
strategy will achieve direct PM2.5 and NOX 
emissions reductions at rates representing generally linear progress 
towards attainment between the 2013 baseline year and the 2020 
attainment year. The target emissions levels and associated control 
requirements provide for objective evaluation of the area's progress 
towards attainment of the 1997 24-hour PM2.5 NAAQS.
    The State's quantitative milestones in Appendix H are to implement 
specific measures listed in the State's control measure commitments 
that apply to heavy-duty trucks and buses, light-duty vehicles, and 
non-road equipment sources and may provide substantial reductions in 
emissions of direct PM2.5 and NOX from mobile 
sources in the San Joaquin Valley. Similarly, the District's 
quantitative milestones in Appendix H are to implement specific 
measures listed in the District's control measure commitments that 
apply to sources such as residential wood burning, commercial 
charbroiling, glass melting furnaces, and internal combustion engines, 
and that may provide substantial reductions in emissions of direct 
PM2.5 and NOX from stationary sources. These 
milestones provide an objective means for tracking the State's and 
District's progress in implementing their respective control strategies 
and, thus, provide for objective evaluation of the San Joaquin Valley's 
progress toward timely attainment.
    For these reasons, we propose to determine that the SJV 
PM2.5 Plan satisfies the requirements for RFP in CAA section 
172(c)(2) and 40 CFR 51.1012 and for quantitative milestones in CAA 
section 189(c) and 40 CFR 51.1013 for the 1997 24-hour PM2.5 
NAAQS in the San Joaquin Valley for purposes of both the Serious area 
and CAA section 189(d) attainment plans. Because we are proposing to 
determine that the San Joaquin Valley has attained the 1997 24-hour 
PM2.5 NAAQS by the December 31, 2020 attainment date, as 
discussed in section V of this proposed rule, we are also proposing to 
determine that the requirement for a post-attainment milestone will no 
longer apply in the San Joaquin Valley nonattainment area for these 
NAAQS. As described in section IV.E.1 above, the purpose of the post-
attainment quantitative milestone is to provide the EPA with the tools 
necessary to monitor the area's continued progress toward attainment in 
the event the area fails to attain by the attainment date.\219\ Once an 
area has attained the NAAQS, ``no further milestones are necessary or 
meaningful.'' \220\ Similarly, the section 189(c)(2) requirement to 
submit a quantitative milestone report no longer applies when the area 
has attained the standard.\221\ Accordingly, upon a final determination 
that the San Joaquin Valley area has attained the 1997 24-hour 
PM2.5 NAAQS by the attainment date, the post-attainment RFP 
milestone will no longer have purpose and the EPA is proposing to find 
that the requirement will no longer apply to the San Joaquin Valley. If 
we finalize this action as proposed, the State will no longer be 
required to submit a quantitative milestone report for the San Joaquin 
Valley under 40 CFR 51.1013(b) for the purposes of the 2023 post-
attainment milestone year identified in the Plan for the 1997 24-hour 
PM2.5 NAAQS.
---------------------------------------------------------------------------

    \219\ 81 FR 58010, 58064.
    \220\ 75 FR 13710, 13713 (March 23, 2010).
    \221\ Id.
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F. Contingency Measures

1. Requirements for Contingency Measures
    Under CAA section 172(c)(9), each state required to make a 
nonattainment plan SIP submission must include, in such plan, 
contingency measures to be implemented if an area fails to meet RFP 
(``RFP contingency measures'') or fails to attain the NAAQS by the 
applicable attainment date (``attainment contingency measures''). Under 
the PM2.5 SIP Requirements Rule, states must include 
contingency measures that will be implemented following a determination 
by the EPA that the state has failed: (1) To meet any RFP requirement 
in the approved SIP; (2) to meet any quantitative milestone in the 
approved SIP; (3) to submit a required quantitative milestone report; 
or (4) to attain the applicable PM2.5 NAAQS by the 
applicable attainment date.\222\ Contingency measures must be fully 
adopted rules or control measures that are ready to be implemented 
quickly upon failure to meet RFP or failure of the area to meet the 
relevant NAAQS by the applicable attainment date.\223\
---------------------------------------------------------------------------

    \222\ 40 CFR 51.1014(a).
    \223\ 81 FR 58010, 58066 and General Preamble Addendum, 42015.
---------------------------------------------------------------------------

    The purpose of contingency measures is to continue progress in 
reducing emissions while a state revises its SIP to meet the missed RFP 
requirement or to correct ongoing nonattainment. Neither the CAA nor 
the EPA's implementing regulations establish a specific level of 
emissions reductions that implementation of contingency measures must 
achieve, but the EPA recommends that contingency measures provide for 
emissions reductions

[[Page 53174]]

equivalent to approximately one year of reductions needed for RFP in 
the nonattainment area at issue, calculated as the overall level of 
reductions needed to demonstrate attainment divided by the number of 
years from the base year to the attainment year. In general, we expect 
all actions needed to effect full implementation of the measures to 
occur within 60 days after the EPA notifies the state of a failure to 
meet RFP or to attain.\224\
---------------------------------------------------------------------------

    \224\ 81 FR 58010, 58066. See also General Preamble, 13512, 
13543-13544, and General Preamble Addendum, 42014-42015.
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    To satisfy the requirements of 40 CFR 51.1014, the contingency 
measures adopted as part of a PM2.5 attainment plan must 
consist of control measures for the area that are not otherwise 
required to meet other nonattainment plan requirements (e.g., to meet 
RACM/RACT requirements) and must specify the timeframe within which 
their requirements become effective following any of the EPA 
determinations specified in 40 CFR 51.1014(a). In a 2016 decision 
called Bahr v. EPA (``Bahr''),\225\ the Ninth Circuit Court of Appeals 
rejected the EPA's interpretation of CAA section 172(c)(9) to allow 
approval of already-implemented control measures as contingency 
measures. In Bahr, the Ninth Circuit concluded that contingency 
measures must be measures that are triggered and implemented only after 
the EPA determines that an area failed to meet RFP requirements or to 
attain by the applicable attainment date. Thus, within the geographic 
jurisdiction of the Ninth Circuit, already implemented measures cannot 
serve as contingency measures under CAA section 172(c)(9).\226\ To 
comply with section 172(c)(9), a state must develop, adopt, and submit 
a contingency measure to be triggered upon a failure to meet an RFP 
milestone, failure to meet a quantitative milestone requirement, or 
failure to attain the NAAQS by the applicable attainment date.
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    \225\ Bahr v. EPA, 836 F.3d 1218, 1235-1237 (9th Cir. 2016).
    \226\ See also Sierra Club v. EPA, 985 F.3d 1055 (D.C. Cir. 
2021) and Assoc. of Irritated Residents v. EPA, No. 19-71223, slip 
op. (9th Cir. Aug 26, 2021).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    The SJV PM2.5 Plan addresses the contingency measure 
requirement for the 1997 24-hour PM2.5 NAAQS in section 5.6 
and Appendix H (specifically, section H.3 (``Contingency Measures'')) 
of the 2018 PM2.5 Plan. The Plan relies on revisions to the 
District's wood-burning rule (Rule 4901) and refers to a SIP revision 
submitted by CARB on October 23, 2017, titled ``State Implementation 
Plan Attainment Contingency Measures for the San Joaquin Valley 15 
[mu]g/m\3\ Annual PM2.5 NAAQS'' (``2017 Contingency Measure 
SIP'').\227\ On March 19, 2021, CARB withdrew the 2017 Contingency 
Measure SIP submission.\228\ Therefore, we are not evaluating the 2017 
Contingency Measure SIP as part of this action.
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    \227\ Letter dated October 23, 2017, from Richard W. Corey, 
Executive Officer, CARB, to Alexis Strauss, Acting Regional 
Administrator, EPA Region 9.
    \228\ Letter dated March 19, 2021, from Richard W. Corey, 
Executive Officer, CARB, to Deborah Jordan, Acting Regional 
Administrator, EPA Region 9, transmitting CARB Executive Order S-21-
004.
---------------------------------------------------------------------------

    With respect to the District contingency measure, the 2018 
PM2.5 Plan states that the District will amend Rule 4901 to 
include a requirement that would 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.\229\ 
The District adopted amendments to Rule 4901 on June 20, 2019, 
including a contingency measure in section 5.7.3 of the amended rule 
(more details below). In the EPA's July 22, 2020 final action to 
approve Rule 4901, as amended June 20, 2019, we did not evaluate 
section 5.7.3 of the amended rule for compliance with CAA requirements 
for contingency measures.\230\ On July 22, 2021, the EPA proposed to 
find that the contingency provision of Rule 4901 (section 5.7.3) does 
not satisfy the CAA requirements for contingency measures for the 1997 
annual PM2.5 NAAQS and proposed to remove the provision from 
the SIP because it is severable from the remainder of Rule 4901.\231\ 
In this action, we evaluate section 5.7.3 of Rule 4901 for compliance 
with the contingency measures requirements for purposes of the 1997 24-
hour PM2.5 NAAQS.
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    \229\ 2018 PM2.5 Plan, Appendix H, H-25.
    \230\ 85 FR 44206 (final approval of Rule 4901); 85 FR 1131, 
1132-1133 (January 9, 2020) (proposed approval of Rule 4901).
    \231\ 86 FR 38652.
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    Rule 4901 is designed to limit emissions generated by the use of 
wood burning fireplaces, wood burning heaters, and outdoor wood burning 
devices. The rule establishes requirements for the sale/transfer, 
operation, and installation of wood burning devices and for advertising 
the sale of seasoned wood consistent with a moisture content limit 
within the San Joaquin Valley. The rule includes a two-tiered, episodic 
wood burning curtailment requirement that applies during four winter 
months, November through February. During a level one episodic wood 
burning curtailment, section 5.7.1 prohibits any person from operating 
a wood burning fireplace or unregistered wood burning heater, but 
permits the use of a properly operated wood burning heater that meets 
certification requirements and has a current registration with the 
District. Sections 5.9 through 5.11 impose specific registration 
requirements on any person operating a wood burning fireplace or wood 
burning heater and section 5.12 imposes specific certification 
requirements on wood burning heater professionals. During a level two 
episodic wood burning curtailment, operation of any wood burning device 
is prohibited by section 5.7.2.
    Prior to the 2019-2020 wood burning season, the District imposed a 
level one curtailment when the PM2.5 concentration was 
forecasted to be between 20 [mu]g/m\3\ and 65 [mu]g/m\3\ and imposed a 
level two curtailment when the PM2.5 concentration was 
forecasted to be above 65 [mu]g/m\3\ or the PM10 
concentration was forecasted to be above 135 [mu]g/m\3\. In 2019 the 
District adopted revisions to Rule 4901 to lower the wood burning 
curtailment thresholds in the ``hot spot'' counties of Madera, Fresno, 
and Kern. The District lowered the level one PM2.5 threshold 
for these three counties from 20 [mu]g/m\3\ to 12 [mu]g/m\3\, and the 
level two PM2.5 threshold from 65 [mu]g/m\3\ to 35 [mu]g/
m\3\. The District did not modify the curtailment thresholds for other 
counties in the San Joaquin Valley--those levels remain at 20 [mu]g/
m\3\ for level one and 65 [mu]g/m\3\ for level two.
    The District's 2019 revision to Rule 4901 also included the 
addition of a contingency measure in section 5.7.3 of the rule, 
requiring that 60 days following the effective date of an EPA 
determination that the San Joaquin Valley has failed to attain the 
1997, 2006, or 2012 PM2.5 NAAQS by the applicable attainment 
date, the PM2.5 curtailment levels of any county that has 
failed to attain the applicable standard will be lowered to the 
curtailment levels in place for hot spot counties. The District 
estimates that the potential emissions reduction of direct 
PM2.5 would be in the range of 0.014 tpd (if the contingency 
measure is triggered in Kings County but not the other non-hot spot 
counties) to 0.387 tpd (if the contingency measure is triggered in all 
five of the non-hot spot counties), but there would be no emissions 
reduction if, at the time of the determination of failure to attain the 
1997 24-hour PM2.5 NAAQS by the attainment date, violations 
of the 1997 24-hour PM2.5

[[Page 53175]]

NAAQS are observed only at monitors in the hot spot counties.\232\ The 
corresponding potential NOX emissions reduction would be in 
the range of 0.002 tpd to 0.060 tpd, respectively, but once again, 
there would be no emissions reduction if the violations are monitored 
in the hot spot counties only.\233\ The EPA has already approved Rule 
4901, as amended in 2019, as a revision to the California SIP.\234\
---------------------------------------------------------------------------

    \232\ See Table B-13 in Appendix B from the District's Final 
Staff Report (June 20, 2019) for revisions to Rule 4901.
    \233\ NOX emissions reductions from the contingency 
measure are based on the District's estimates for direct 
PM2.5 emissions using the ratio of direct 
PM2.5 to NOX in Table 1, page 8, of the 
District's Final Staff Report (June 20, 2019) for revisions to Rule 
4901.
    \234\ 85 FR 44206.
---------------------------------------------------------------------------

3. The EPA's Review of the State's Submission
    As noted above, the EPA previously proposed to find that the 
contingency provision of Rule 4901 (section 5.7.3) does not satisfy the 
CAA requirements for contingency measures for the 1997 annual 
PM2.5 NAAQS.\235\ As part of that proposal, the EPA found 
that the measure meets some, but not all, of the applicable 
requirements for contingency measures under CAA section 172(c)(9) and 
40 CFR 51.1014. One of the deficiencies outlined in our proposal was 
that the contingency provisions of Rule 4901 do not address the 
potential for State failures to meet RFP, to meet a quantitative 
milestone, or to submit a quantitative milestone report. In addition, 
the contingency measure provisions of Rule 4901 are not structured to 
achieve any additional emissions reductions if the EPA were to find 
that the monitoring locations in the ``hot spot'' counties (i.e., 
Fresno, Kern, or Madera) are the only counties in the San Joaquin 
Valley that are violating the 1997 24-hour PM2.5 NAAQS as of 
the attainment date. To qualify as a contingency measure, a measure 
must be structured to achieve emissions reductions if triggered; 
however, the contingency provisions of Rule 4901 provide for such 
reductions only under certain circumstances.
---------------------------------------------------------------------------

    \235\ 86 FR 38652.
---------------------------------------------------------------------------

    Consistent with our proposal for the 1997 annual PM2.5 
NAAQS and for these same reasons, we are proposing to disapprove the 
contingency measure element of the SJV PM2.5 Plan for the 
1997 24-hour PM2.5 NAAQS as not meeting the requirements of 
172(c)(9) and 40 CFR 51.1014 for Serious area and section 189(d) 
attainment plans. However, the EPA is also proposing to find that the 
contingency measures are no longer required for the San Joaquin Valley 
nonattainment area for the 1997 24-hour PM2.5 NAAQS, for the 
reasons discussed below.
    Attainment contingency measures under 172(c)(9) are triggered upon 
the EPA's determination that an area failed to attain a given NAAQS by 
its applicable attainment date. CAA section 179(c) requires the EPA to 
determine whether the area attained the NAAQS by its applicable 
attainment date. As part of this proposed action, we are proposing to 
determine that the San Joaquin Valley nonattainment area attained the 
1997 24-hour PM2.5 NAAQS by the December 31, 2020 attainment 
date projected by the Plan. Based on our proposed finding of attainment 
by the applicable attainment date, we are also proposing to determine 
that the CAA requirement for the SIP to provide for attainment 
contingency measures will no longer apply to the San Joaquin Valley for 
the 1997 24-hour PM2.5 NAAQS. Under CAA section 172(c)(9), 
attainment contingency measures are implemented only if the area fails 
to attain by the attainment date. Therefore, if we finalize the 
determination that the San Joaquin Valley nonattainment area has 
attained the 1997 24-hour PM2.5 NAAQS, attainment 
contingency measures for this NAAQS would never be required to be 
implemented. Because there are no circumstances under which CAA section 
172(c)(9) attainment contingency measures could ever be triggered, we 
think it is a reasonable interpretation of the CAA that these measures 
are no longer required to be submitted.\236\
---------------------------------------------------------------------------

    \236\ See Bahr v. Regan, No. 20-70092, (9th Cir. July 28, 2021), 
slip op. 45-51.
---------------------------------------------------------------------------

    Similarly, we are proposing to find that, upon finalization of the 
determination of attainment by the attainment date, the RFP related 
contingency measure requirement (i.e., for failure to meet RFP, to 
submit a quantitative milestone report, or to meet the quantitative 
milestone) would also no longer apply to the San Joaquin Valley 
nonattainment area for the 1997 24-hour PM2.5 NAAQS. The 
purpose of the RFP and related quantitative milestone requirements 
under the CAA is to ``ensure[e] attainment of the applicable [NAAQS] by 
the applicable date.'' \237\ Because the sole purpose of RFP 
contingency measures is to provide continued progress if an area fails 
to meet its RFP or quantitative milestone requirements, a final 
determination of attainment by the attainment date serves as 
demonstration that RFP requirements for the area have been met, and 
that there is no need for any later quantitative milestone or milestone 
report, and thus the RFP related contingency measures are no longer 
needed. Accordingly, because we are proposing to determine that the San 
Joaquin Valley has attained the 1997 24-hour PM2.5 NAAQS by 
the December 31, 2020 attainment date, and that therefore the RFP and 
quantitative milestone requirements would no longer apply, we are now 
also proposing to determine that RFP contingency measures are no longer 
required for this area.\238\
---------------------------------------------------------------------------

    \237\ CAA section 171(c).
    \238\ With respect to the 2017 RFP contingency measure 
requirement specifically, we note that, as explained in section 
IV.E.2 of this proposed rule, on December 20, 2018, CARB submitted a 
quantitative milestone report demonstrating that the 2017 
quantitative milestones in the SJV PM2.5 Plan have been 
achieved, and the EPA has determined that this milestone report is 
adequate. Because the State and District have demonstrated that the 
San Joaquin Valley area has met its 2017 quantitative milestones, 
RFP contingency measures for the 2017 milestone year would never be 
triggered.
---------------------------------------------------------------------------

    Under section 179(a) of the CAA, final disapproval of a SIP 
submission that addresses a requirement of part D, title I of the CAA, 
or is required in response to a finding of substantial inadequacy as 
described in CAA section 110(k)(5) (SIP Call), starts sanctions clocks. 
The SJV PM2.5 Plan, including the contingency measure 
element, does address requirements of part D. However, if we finalize 
our determinations that the requirements for contingency measures no 
longer apply to the San Joaquin Valley nonattainment area for the 1997 
24-hour PM2.5 NAAQS, then the contingency measure element of 
the SJV PM2.5 Plan would no longer be required to address 
any part D requirement for the 1997 24-hour PM2.5 NAAQS. 
Therefore, final disapproval of the contingency measure element of the 
SJV PM2.5 Plan would not trigger sanctions clocks. 
Similarly, final disapproval would not trigger any obligation for the 
EPA to promulgate a federal implementation plan (FIP) under CAA section 
110(c) because there would be no deficiency for such a FIP to 
correct.\239\
---------------------------------------------------------------------------

    \239\ This is the case for both the Serious area plan and the 
section 189(d) plan. Because the purpose of contingency measures is 
to ensure continued progress toward attainment in the event that an 
area fails to attain the NAAQS or meet RFP requirements, and we are 
proposing to find that the area has meet the 1997 24-hour 
PM2.5 NAAQS, there is no purpose to triggering sanction 
and FIP obligations for the State to submit measures to achieve the 
goal of attaining the 1997 24-hour PM2.5 NAAQS when this 
goal has already been met.
---------------------------------------------------------------------------

    Because we are proposing to approve the RFP analysis, the modeled 
attainment demonstration, and the motor vehicle emissions budgets, we 
are also proposing to issue a protective finding under 40 CFR 
93.120(a)(3) in the event we finalize the disapproval of the

[[Page 53176]]

contingency measures. Without a protective finding, the final 
disapproval would result in a conformity freeze, under which only 
projects in the first four years of the most recent conforming Regional 
Transportation Plan (RTP) and Transportation Improvement Programs 
(TIPs) can proceed. During a freeze, no new RTPs, TIPs, or RTP/TIP 
amendments can be found to conform.\240\ Under this protective finding, 
however, the final disapproval of the contingency measures does not 
result in a transportation conformity freeze in the San Joaquin Valley 
PM2.5 nonattainment area.
---------------------------------------------------------------------------

    \240\ 40 CFR 93.120(a)(2).
---------------------------------------------------------------------------

    If the State chooses to withdraw the contingency measure element 
with respect to the 1997 24-hour PM2.5 NAAQS prior to our 
final action on the SJV PM2.5 Plan for that NAAQS, we would 
take no final action either to approve or to disapprove that element.

G. Motor Vehicle Emission Budgets

1. Statutory and Regulatory Requirements
    Section 176(c) of the CAA requires federal actions in nonattainment 
and maintenance areas to conform to the goals of the state's SIP to 
eliminate or reduce the severity and number of violations of the NAAQS 
and achieve timely attainment of the NAAQS. Conformity to the SIP's 
goals means that such actions will not: (1) Cause or contribute to 
violations of a NAAQS, (2) worsen the severity of an existing 
violation, or (3) delay timely attainment of any NAAQS or any interim 
milestone.
    Actions involving Federal Highway Administration (FHWA) or Federal 
Transit Administration (FTA) funding or approval are subject to the 
EPA's transportation conformity rule, codified at 40 CFR part 93, 
subpart A. Under this rule, metropolitan planning organizations (MPOs) 
in nonattainment and maintenance areas coordinate with state and local 
air quality and transportation agencies, the EPA, the FHWA, and the FTA 
to demonstrate that an area's regional transportation plans (RTPs) and 
transportation improvement programs conform to the applicable SIP. This 
demonstration is typically done by showing that estimated emissions 
from existing and planned highway and transit systems are less than or 
equal to the motor vehicle emission budgets (MVEBs or ``budgets'') 
contained in all control strategy SIPs. Budgets are generally 
established for specific years and specific pollutants or precursors 
and must reflect all of the motor vehicle control measures contained in 
the attainment and RFP demonstrations.\241\
---------------------------------------------------------------------------

    \241\ 40 CFR 93.118(e)(4)(v).
---------------------------------------------------------------------------

    Under the PM2.5 SIP Requirements Rule, Serious area 
PM2.5 attainment plans must include appropriate quantitative 
milestones and projected RFP emissions levels for direct 
PM2.5 and all PM2.5 plan precursors in each 
milestone year.\242\ For an area designated nonattainment for the 1997 
PM2.5 NAAQS before January 15, 2015, the attainment plan 
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.\243\ As the EPA explained in the preamble to the 
PM2.5 SIP Requirements Rule, it is important to include a 
post-attainment year quantitative milestone to ensure that, if the area 
fails to attain by the attainment date, the EPA can continue to monitor 
the area's progress toward attainment while the state develops a new 
attainment plan.\244\ Although the post-attainment year quantitative 
milestone is a required element of a Serious area plan, it is not 
necessary to demonstrate transportation conformity for 2023 or to use 
the 2023 budgets in transportation conformity determinations until such 
time as the area fails to attain the 1997 24-hour PM2.5 
NAAQS.
---------------------------------------------------------------------------

    \242\ 40 CFR 51.1012(a), 51.1013(a)(1).
    \243\ 40 CFR 51.1013(a)(4) and 81 FR 58010, 58058 and 58063-
58064. Because the area has failed to attain the 1997 24-hour 
PM2.5 NAAQS by the Serious area attainment date, and it 
would serve no purpose for the plan to include budgets for the EPA 
to evaluate conformity for the dates associated with the Serious 
area attainment date, the applicable attainment date for the 
purposes of our evaluation is the section 189(d) projected 
attainment date of December 31, 2020.
    \244\ 81 FR 58010, 58063-58064.
---------------------------------------------------------------------------

    PM2.5 plans should identify budgets for direct 
PM2.5, NOX, and all other PM2.5 
precursors for which on-road emissions are determined to significantly 
contribute to PM2.5 levels in the area for each RFP 
milestone year and the attainment year, if the plan demonstrates 
attainment. All direct PM2.5 SIP budgets should include 
direct PM2.5 motor vehicle emissions from tailpipes, brake 
wear, and tire wear. With respect to PM2.5 from re-entrained 
road dust and emissions of VOC, SO2, and/or ammonia, the 
transportation conformity provisions of 40 CFR part 93, subpart A, 
apply only if the EPA Regional Administrator or the director of the 
state air agency has made a finding that emissions of these pollutants 
within the area are a significant contributor to the PM2.5 
nonattainment problem and has so notified the MPO and Department of 
Transportation (DOT), or if the applicable implementation plan (or 
implementation plan submission) includes any of these pollutants in the 
approved (or adequate) budget as part of the RFP, attainment, or 
maintenance strategy.\245\
---------------------------------------------------------------------------

    \245\ 40 CFR 93.102(b)(3), 93.102(b)(2)(v), and 93.122(f); see 
also Conformity Rule preambles at 69 FR 40004, 40031-40036 (July 1, 
2004), 70 FR 24280, 24283-24285 (May 6, 2005) and 70 FR 31354 (June 
1, 2005).
---------------------------------------------------------------------------

    By contrast, transportation conformity requirements apply with 
respect to emissions of NOX unless both the EPA Regional 
Administrator and the director of the state air agency have made a 
finding that transportation-related emissions of NOX within 
the nonattainment area are not a significant contributor to the 
PM2.5 nonattainment problem and have so notified the MPO and 
DOT, or the applicable implementation plan (or implementation plan 
submission) does not establish an approved (or adequate) budget for 
such emissions as part of the RFP, attainment, or maintenance 
strategy.\246\
---------------------------------------------------------------------------

    \246\ 40 CFR 93.102(b)(2)(iv).
---------------------------------------------------------------------------

    It is not always necessary for states to establish motor vehicle 
emissions budgets for all PM2.5 precursors. The 
PM2.5 SIP Requirements Rule allows a state to demonstrate 
that emissions of certain precursors do not contribute significantly to 
PM2.5 levels that exceed the NAAQS in a nonattainment area, 
in which case the state may exclude such precursor(s) from its control 
evaluations for the specific NAAQS at issue. If a state successfully 
demonstrates that the emissions of one or more of the PM2.5 
precursors from all sources do not contribute significantly to 
PM2.5 levels in the subject area, then it is not necessary 
to establish motor vehicle emissions budgets for such precursor(s).
    Alternatively, the transportation conformity regulations contain 
criteria for determining whether emissions of one or more 
PM2.5 precursors are insignificant for transportation 
conformity purposes.\247\ For a pollutant or precursor to be considered 
an insignificant contributor based on the transportation conformity 
rule's criteria, the control strategy SIP must demonstrate that it 
would be unreasonable to expect that such an area would experience 
enough motor vehicle emissions growth in that pollutant and/or 
precursor for a NAAQS violation to occur. Insignificance determinations 
are based on factors such as air quality, SIP motor vehicle control 
measures, trends

[[Page 53177]]

and projections of motor vehicle emissions, and the percentage of the 
total attainment plan emissions inventory for the NAAQS at issue that 
is comprised of motor vehicle emissions. The EPA's rationale for 
providing for insignificance determinations is described in the July 1, 
2004 revision to the Transportation Conformity Rule.\248\
---------------------------------------------------------------------------

    \247\ 40 CFR 93.109(f).
    \248\ 69 FR 40004.
---------------------------------------------------------------------------

    Transportation conformity trading mechanisms are allowed under 40 
CFR 93.124 where a state establishes appropriate mechanisms for such 
trades. The basis for the trading mechanism is the SIP attainment 
modeling that establishes the relative contribution of each 
PM2.5 precursor pollutant. The applicability of emissions 
trading between conformity budgets for conformity purposes is described 
in 40 CFR 93.124(c).
    The EPA's process for determining the adequacy of a budget consists 
of three basic steps: (1) Notifying the public of a SIP submittal; (2) 
providing the public the opportunity to comment on the budget during a 
public comment period; and (3) making a finding of adequacy or 
inadequacy. The EPA can notify the public by either posting an 
announcement that the EPA has received SIP budgets on the EPA's 
adequacy website,\249\ or through a Federal Register notice of proposed 
rulemaking when the EPA reviews the adequacy of an implementation plan 
budget simultaneously with its review and action on the SIP 
itself.\250\
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    \249\ 40 CFR 93.118(f)(1).
    \250\ 40 CFR 93.118(f)(2).
---------------------------------------------------------------------------

2. Summary of the State's Submission
    The 2018 PM2.5 Plan includes budgets for direct 
PM2.5 and NOX emissions, calculated using annual 
average daily emissions, for 2017, 2020, and 2023 (RFP milestone year, 
attainment year, and post-attainment quantitative milestone year, 
respectively).\251\ The Plan establishes separate direct 
PM2.5 and NOX subarea budgets for each county, 
and partial county (for Kern County), in the San Joaquin Valley.\252\ 
CARB calculated the budgets using EMFAC2014, CARB's latest version of 
the EMFAC model for estimating emissions from on-road vehicles 
operating in California that was available at the time of Plan 
development, and the latest modeled vehicle miles traveled and speed 
distributions from the San Joaquin Valley MPOs from the Final 2017 
Federal Transportation Improvement Program, adopted in September 2016. 
The budgets reflect annual average emissions because those emissions 
are linked with the District's attainment demonstration for the 1997 
24-hour PM2.5 NAAQS.
---------------------------------------------------------------------------

    \251\ 2018 PM2.5 Plan, Appendix D, Table 3-1.
    \252\ 40 CFR 93.124(c) and (d).
---------------------------------------------------------------------------

    The direct PM2.5 budgets include tailpipe, brake wear, 
and tire wear emissions but do not include paved road dust, unpaved 
road dust, and road construction dust emissions.\253\ The State is not 
required to include re-entrained road dust in the budgets under section 
93.103(b)(3) unless the EPA or the State has made a finding that these 
emissions are significant. Neither the State nor the EPA has made such 
a finding, but the Plan does include a discussion of the significance/
insignificance factors for re-entrained road dust.\254\ The budgets 
included in the 2018 PM2.5 Plan for purposes of the 1997 24-
hour PM2.5 NAAQS are shown in Table 8.
---------------------------------------------------------------------------

    \253\ 2018 PM2.5 Plan, Appendix D, D-122 and D-123.
    \254\ Id. at D-121 and D-122.

                           Table 8--Motor Vehicle Emission Budgets for the San Joaquin Valley for the 1997 24-Hour PM2.5 NAAQS
                                                                  [Annual average, tpd]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                 2017  (RFP year)             2020  (Attainment year)      2023  (Post-attainment year)
                         County                          -----------------------------------------------------------------------------------------------
                                                               PM2.5            NOX            PM2.5            NOX            PM2.5            NOX
--------------------------------------------------------------------------------------------------------------------------------------------------------
Fresno..................................................             0.9            28.5             0.9            25.3             0.8            15.1
Kern....................................................             0.8            28.0             0.8            23.3             0.7            13.3
Kings...................................................             0.2             5.8             0.2             4.8             0.2             2.8
Madera..................................................             0.2             5.3             0.2             4.2             0.2             2.5
Merced..................................................             0.3            10.7             0.3             8.9             0.3             5.3
San Joaquin.............................................             0.7            14.9             0.6            11.9             0.6             7.6
Stanislaus..............................................             0.4            11.9             0.4             9.6             0.4             6.1
Tulare..................................................             0.4            10.8             0.4             8.5             0.4             5.2
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: 2018 PM2.5 Plan, Appendix D, Table 3-1. Budgets are rounded to the nearest tenth of a ton.

    The State did not include budgets for VOC, SO2, or 
ammonia. As discussed in section IV.B of this preamble, the State 
submitted a PM2.5 precursor demonstration documenting its 
conclusion that control of these precursors would not significantly 
contribute to attainment of the 1997 24-hour PM2.5 NAAQS, 
and the EPA is proposing to approve the precursor demonstration. 
Therefore, if the EPA approves the demonstration, the State would not 
be required to submit budgets for these precursors. The State included 
a discussion of the significance/insignificance factors for ammonia, 
SO2, and VOC to demonstrate a finding of insignificance 
under the transportation conformity rule.\255\
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    \255\ 40 CFR 93.109(f).
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    In the submittal letter for the 2018 PM2.5 Plan, CARB 
requested that the EPA limit the duration of the approval of the 
budgets to the period before the effective date of the EPA's adequacy 
finding for any subsequently submitted budgets.\256\
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    \256\ Letter dated May 9, 2019, from Richard W. Corey, Executive 
Officer, CARB, to Mike Stoker, Regional Administrator, EPA Region 9, 
3.
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Conformity Trading Mechanism
    The 2018 PM2.5 Plan also includes a proposed trading 
mechanism for transportation conformity analyses that would allow 
future decreases in NOX emissions from on-road mobile 
sources to offset any on-road increases in direct PM2.5 
emissions. The State is proposing to use a 2 to 1 NOX to 
PM2.5 ratio for the 1997 24-hour PM2.5 NAAQS. 
This ratio was derived by performing a sensitivity analysis based on a 
30 percent reduction of NOX or PM2.5 emissions 
and calculating the corresponding effect on design values at sites in 
Bakersfield and Fresno.
    To ensure that the trading mechanism does not affect the ability of 
the San Joaquin Valley to meet the NOX budget, the 
NOX emissions reductions available to supplement the 
PM2.5 budget would

[[Page 53178]]

only be those remaining after the NOX budget has been 
met.\257\ The Plan also provides that the San Joaquin Valley MPOs shall 
clearly document the calculations used in the trading, along with any 
additional reductions of NOX and PM2.5 emissions 
in the conformity analysis.
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    \257\ 2018 PM2.5 Plan, Appendix D, D-126 and D-127.
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3. The EPA's Review of the State's Submission
    The EPA generally first conducts a preliminary review of budgets 
submitted with an attainment or maintenance plan for PM2.5 
for adequacy, prior to taking action on the plan itself, and did so 
with respect to the PM2.5 budgets in the 2018 
PM2.5 Plan. On June 18, 2019, the EPA announced the 
availability of the 2018 PM2.5 Plan with MVEBs and a 30-day 
public comment period. This announcement was posted on the EPA's 
Adequacy website at: https://www.epa.gov/state-and-local-transportation/state-implementation-plans-sip-submissions-currently-under-epa. The comment period for this notification ended on July 18, 
2019. We did not receive any comments during this comment period.
    Based on our proposal to approve the State's demonstration that 
emissions of ammonia, SO2, and VOCs do not contribute 
significantly to PM2.5 levels that exceed the 1997 24-hour 
PM2.5 NAAQS in the San Joaquin Valley, as discussed in 
section IV.B of this proposal, and the information about ammonia, 
SO2, and VOC emissions in the Plan, the EPA proposes to find 
that it is not necessary to establish motor vehicle emissions budgets 
for transportation-related emissions of ammonia, SO2, and 
VOC to attain the 1997 24-hour PM2.5 NAAQS in the San 
Joaquin Valley. Based on the information about re-entrained road dust 
in the Plan and in accordance with 40 CFR 93.102(b)(3), the EPA 
proposes to find that it is not necessary to include re-entrained road 
dust emissions in the budgets for 1997 24-hour PM2.5 NAAQS 
in the San Joaquin Valley.
    For the reasons discussed in sections IV.D and IV.E of this 
proposed rule, the EPA is proposing to approve the attainment and RFP 
demonstrations, respectively, in the SJV PM2.5 Plan. The 
2017 RFP and 2020 attainment year budgets, as shown in Table 8 of this 
preamble, are consistent with these demonstrations, are clearly 
identified and precisely quantified, and meet all other applicable 
statutory and regulatory requirements including the adequacy criteria 
in 40 CFR 93.118(e)(4). For these reasons, the EPA proposes to approve 
the 2017 and 2020 budgets listed in Table 8.\258\ We provide a more 
detailed discussion in section IV of the EPA's 1997 24-hour 
PM2.5 TSD. The budgets that the EPA is proposing to approve 
relate only to the 1997 24-hour PM2.5 NAAQS, and our 
proposed approval does not affect the status of the budgets for the 
1997 annual PM2.5 NAAQS or the previously-approved MVEBs for 
the 2006 PM2.5 NAAQS and related trading mechanism, which 
remain in effect for that PM2.5 NAAQS.
---------------------------------------------------------------------------

    \258\ Although we are proposing to approve the 2017 budgets, we 
note that these budgets would not be used in any future 
transportation conformity determinations because the Plan contains 
budgets for 2020.
---------------------------------------------------------------------------

    Although the post-attainment year quantitative milestone is a 
required element of the Serious area plan, it is not necessary to 
demonstrate transportation conformity for 2023 or to use the 2023 
budgets in transportation conformity determinations until such time as 
the area fails to attain the 1997 24-hour PM2.5 NAAQS. As 
discussed in section V of this document, the EPA is proposing to find 
that the San Joaquin Valley area has attained the 1997 24-hour 
PM2.5 NAAQS. The EPA does not believe that it is necessary 
to demonstrate conformity using post-attainment year budgets in areas 
that attain by the attainment date. Therefore, if the EPA finalizes the 
determination that the San Joaquin Valley area attained by the December 
31, 2020 attainment date, the requirement for post-attainment year 
budgets will no longer apply in the area for the 1997 24-hour 
PM2.5 NAAQS.
    As noted above, the State included a trading mechanism to be used 
in transportation conformity analyses that would be used in conjunction 
with the budgets in the 2018 PM2.5 Plan, as allowed for 
under 40 CFR 93.124(b). This trading mechanism would allow future 
decreases in NOX emissions from on-road mobile sources to 
offset any on-road increases in PM2.5, using a 2 to 1 
NOX to PM2.5 ratio for the 1997 24-hour 
PM2.5 NAAQS. To ensure that the trading mechanism does not 
affect the ability to meet the NOX budget, the Plan provides 
that the NOX emissions reductions available to supplement 
the PM2.5 budget would only be those remaining after the 
NOX budget has been met. The San Joaquin Valley MPOs will 
have to document clearly the calculations used in the trading when 
demonstrating conformity, along with any additional reductions of 
NOX and PM2.5 emissions in the conformity 
analysis. The trading calculations must be performed prior to the final 
rounding to demonstrate conformity with the budgets.
    The EPA has reviewed the trading mechanism as described on pages D-
125 to D-127 in Appendix D of the 2018 PM2.5 Plan and finds 
it is appropriate for transportation conformity purposes in the San 
Joaquin Valley for the 1997 24-hour PM2.5 NAAQS. The 
methodology for estimating the trading ratio for conformity purposes is 
essentially an update (based on newer modeling) of the approach that 
the EPA previously approved for the 2008 PM2.5 Plan for the 
1997 PM2.5 NAAQS \259\ and the 2012 PM2.5 Plan 
for the 2006 24-hour PM2.5 NAAQS.\260\ The State's approach 
in the previous plans was to model the ambient PM2.5 effect 
of areawide NOX emissions reductions and of areawide direct 
PM2.5 emissions reductions, and to express the ratio of 
these modeled sensitivities as an inter-pollutant trading ratio.
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    \259\ 80 FR 1816, 1841 (January 13, 2015) (noting the EPA's 
prior approval of MVEBs for the 1997 annual and 24-hour 
PM2.5 standards in the 2008 PM2.5 Plan at 76 
FR 69896).
    \260\ 81 FR 59876 (August 31, 2016).
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    In the updated analysis for the 2018 PM2.5 plan, the 
State completed separate sensitivity analyses for the annual and 24-
hour NAAQS and modeled only transportation related sources in the 
nonattainment area. The ratio the State is proposing to use for 
transportation conformity purposes is derived from air quality modeling 
that evaluated the effect of reductions in transportation-related 
NOX and PM2.5 emissions in the San Joaquin Valley 
on ambient concentrations at the Bakersfield-California Avenue, 
Bakersfield-Planz, Fresno-Garland, and Fresno-Hamilton & Winery 
monitoring sites. The modeling that the State performed to evaluate the 
effectiveness of NOX and PM2.5 reductions on 
ambient 24-hour concentrations showed NOX to 
PM2.5 ratios that range from a high of 2.3 at the 
Bakersfield-California Avenue monitor to a low of 1.6 at the Fresno-
Hamilton & Winery monitor.\261\ In our July 22, 2020 action on the 2018 
PM2.5 Plan for the 2006 PM2.5 NAAQS, we found 
that the State's approach is a reasonable method to use to develop 
ratios for transportation conformity purposes and approved the 2 to 1 
NOX to PM2.5 trading mechanism as an enforceable 
component of the transportation conformity program for the San Joaquin 
Valley for the 2006 PM2.5 NAAQS.\262\ Here, we similarly 
find that the State's approach is reasonable and propose to

[[Page 53179]]

approve the 2 to 1 NOX to PM2.5 trading ratio.
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    \261\ 2018 PM2.5 Plan, Appendix D, D-126.
    \262\ 85 FR 44192.
---------------------------------------------------------------------------

    If approved, this trading ratio will replace the 9 to 1 
NOX to PM2.5 trading ratio approved for the San 
Joaquin Valley for analysis years after 2014 for the 1997 24-hour 
PM2.5 NAAQS.\263\
---------------------------------------------------------------------------

    \263\ 76 FR 69896.
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    Under the transportation conformity rule, once budgets are 
approved, they cannot be superseded by revised budgets submitted for 
the same CAA purpose and the same year(s) addressed by the previously 
approved SIP until the EPA approves the revised budgets as a SIP 
revision. In other words, as a general matter, such approved budgets 
cannot be superseded by revised budgets found adequate, but rather only 
through approval of the revised budgets, unless the EPA specifies 
otherwise in its approval of a SIP by limiting the duration of the 
approval to last only until subsequently submitted budgets are found 
adequate.\264\
---------------------------------------------------------------------------

    \264\ 40 CFR 93.118(e)(1).
---------------------------------------------------------------------------

    In the submittal letter for the 2018 PM2.5 Plan, CARB 
requested that we limit the duration of our approval of the budgets to 
the period before the effective date of the EPA's adequacy finding for 
any subsequently submitted budgets.\265\ The transportation conformity 
rule allows us to limit the approval of budgets.\266\ However, we will 
consider a state's request to limit an approval of its budgets only if 
the request includes the following elements: \267\
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    \265\ Letter dated May 9, 2019, from Richard W. Corey, Executive 
Officer, CARB, to Mike Stoker, Regional Administrator, EPA Region 9, 
3.
    \266\ 40 CFR 93.118(e)(1).
    \267\ 67 FR 69139 (November 15, 2002), limiting our prior 
approval of MVEBs in certain California SIPs.
---------------------------------------------------------------------------

    (1) An acknowledgement and explanation as to why the budgets under 
consideration have become outdated or deficient;
    (2) A commitment to update the budgets as part of a comprehensive 
SIP update; and
    (3) A request that the EPA limit the duration of its approval to 
the period before new budgets have been found to be adequate for 
transportation conformity purposes.
    CARB's request includes an explanation for why the budgets have 
become, or will become, outdated or deficient. In short, CARB has 
requested that we limit the duration of the approval of the budgets in 
light of the EPA's approval of EMFAC2017, an updated version of the 
model (EMFAC2014) used for the budgets in the SJV PM2.5 
Plan.\268\ EMFAC2017 updates vehicle mix and emissions data of the 
previously approved version of the model, EMFAC2014.
---------------------------------------------------------------------------

    \268\ On August 15, 2019, the EPA approved and announced the 
availability of EMFAC2017, the latest update to the EMFAC model for 
use by the State and local governments to meet CAA requirements. 84 
FR 41717.
---------------------------------------------------------------------------

    In light of the EPA's approval of EMFAC2017, CARB explains that the 
budgets in the SJV PM2.5 Plan, which we are proposing to 
approve in today's action, will become outdated and will need to be 
revised using EMFAC2017. In addition, CARB states that, without the 
ability to replace the budgets using the budget adequacy process, the 
benefits of using the updated data may not be realized for a year or 
more after the updated SIP (with the EMFAC2017-derived budgets) is 
submitted, due to the length of the SIP approval process. We find that 
CARB's explanation for limiting the duration of the approval of the 
budgets is appropriate and provides us with a reasonable basis for 
limiting the duration of the approval of the budgets.
    We note that CARB has not committed to update the budgets as part 
of a comprehensive SIP update, but as a practical matter, CARB must 
submit a SIP revision that includes updated demonstrations as well as 
the updated budgets to meet the adequacy criteria in 40 CFR 
93.118(e)(4).\269\ Therefore, we do not need a specific commitment for 
such a plan at this time. For the reasons provided above, and in light 
of CARB's explanation for why the budgets will become outdated and 
should be replaced upon an adequacy finding for updated budgets, we 
propose to limit the duration of our approval of the budgets addressed 
in this action to the period before we find revised budgets based on 
EMFAC2017 to be adequate.
---------------------------------------------------------------------------

    \269\ Under 40 CFR 93.118(e)(4), the EPA will not find a budget 
in a submitted SIP to be adequate unless, among other criteria, the 
budgets, when considered together with all other emissions sources, 
are consistent with applicable requirements for RFP and attainment. 
40 CFR 93.118(e)(4)(iv).
---------------------------------------------------------------------------

H. Nonattainment New Source Review Requirements Under CAA Section 
189(e)

    CAA section 189(e) specifically requires that the control 
requirements applicable to major stationary sources of direct 
PM2.5 also apply to major stationary sources of 
PM2.5 precursors, except where the Administrator determines 
that such sources do not contribute significantly to PM2.5 
levels that exceed the NAAQS in the area.\270\ The control requirements 
applicable to major stationary sources of direct PM2.5 in a 
Serious PM2.5 nonattainment area include, at minimum, the 
requirements of a nonattainment NSR permit program meeting the 
requirements of CAA sections 172(c)(5) and 189(b)(3). As part of our 
April 7, 2015 final action to reclassify the San Joaquin Valley area as 
Serious nonattainment for the 1997 PM2.5 standards, we 
established a May 7, 2016 deadline for the State to submit 
nonattainment NSR SIP revisions addressing the requirements of CAA 
sections 189(b)(3) and 189(e) of the Act for the 1997 PM2.5 
NAAQS.\271\
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    \270\ General Preamble, 13539 and 13541-13542.
    \271\ 80 FR 18528, 18533.
---------------------------------------------------------------------------

    California submitted nonattainment NSR SIP revisions to address the 
subpart 4 requirements for the San Joaquin Valley Serious 
PM2.5 nonattainment area on November 20, 2019.\272\ We are 
not proposing any action on this submission at this time. We will act 
on this submission through a separate rulemaking, as appropriate.
---------------------------------------------------------------------------

    \272\ Letter dated November 15, 2019, from Richard W. Corey, 
Executive Officer, CARB, to Michael Stoker, Regional Administrator, 
EPA Region IX.
---------------------------------------------------------------------------

V. Determination of Attainment by the Attainment Date

A. Requirements for Attainment Determinations

    Sections 179(c)(1) and 188(b)(2) of the CAA require the EPA to 
determine whether a state with a PM2.5 nonattainment area 
attained the applicable PM2.5 NAAQS by the applicable 
attainment date, based on the area's air quality as of the attainment 
date. A determination of whether an area's air quality currently meets 
the PM2.5 NAAQS is generally based upon the most recent 
three years of complete, quality-assured data gathered at established 
State and Local Air Monitoring Stations (SLAMS) in a nonattainment area 
and entered into the EPA's Air Quality System (AQS) database. Data from 
ambient air monitors operated by state/local agencies in compliance 
with the EPA monitoring requirements must be submitted to AQS. 
Monitoring agencies annually certify that these data are accurate to 
the best of their knowledge. Accordingly, the EPA relies primarily on 
data in AQS when determining the attainment status of areas.\273\ The 
EPA reviews all data to determine the area's air quality status in 
accordance with 40 CFR part 50, Appendix N.
---------------------------------------------------------------------------

    \273\ See 40 CFR 50.7; 40 CFR part 50, Appendix L; 40 CFR part 
53; 40 CFR part 58, and 40 CFR part 58, appendices A, C, D, and E.
---------------------------------------------------------------------------

    Under EPA regulations in 40 CFR 50.7 and in accordance with 
Appendix N, the 1997 24-hour PM2.5 NAAQS are met when the 
design value is less than or equal to 65 [micro]g/m\3\ (based on the 
rounding convention in 40 CFR part 50,

[[Page 53180]]

Appendix N) at each eligible monitoring site within the area. Data 
completeness requirements for a given year are met when at least 75 
percent of the scheduled sampling days for each quarter have valid 
data.\274\
---------------------------------------------------------------------------

    \274\ 40 CFR part 50, Appendix N, section 4.2(b).
---------------------------------------------------------------------------

B. Monitoring Network Considerations

    Section 110(a)(2)(B)(i) of the CAA requires states to establish and 
operate air monitoring networks to compile data on ambient air quality 
for all criteria pollutants. The monitoring requirements are specified 
in 40 CFR part 58. These requirements are applicable to state, and 
where delegated, local air monitoring agencies that operate criteria 
pollutant monitors. The regulations in 40 CFR part 58 establish 
specific requirements for operating air quality surveillance networks 
to measure ambient concentrations of PM2.5, including 
requirements for measurement methods, network design, quality assurance 
procedures, and in the case of large urban areas, the minimum number of 
monitoring sites designated as SLAMS.
    In section 4.7 of Appendix D to 40 CFR part 58, the EPA specifies 
minimum monitoring requirements for PM2.5 to operate at 
SLAMS. SLAMS produce data comparable to the NAAQS, and therefore, the 
monitor must be an approved federal reference method (FRM), federal 
equivalent method (FEM), or approved regional method (ARM). The minimum 
number of SLAMS required is described in section 4.7.1 and can be met 
by either filter-based or continuous FRMs or FEMs. The monitoring 
regulations also provide that each core-based statistical area (CBSA) 
must operate a minimum number of PM2.5 continuous monitors; 
\275\ however, this requirement can be met by either an FEM or a non-
FEM continuous monitor, and the continuous monitors can be located with 
other SLAMS or at a different location. Consequently, the monitoring 
requirements for PM2.5 can be met with filter-based FRMs/
FEMs, continuous FEMs, continuous non-FEMs, or a combination of 
monitors at each required SLAMS.
---------------------------------------------------------------------------

    \275\ 40 CFR part 58, Appendix D, section 4.7.2.
---------------------------------------------------------------------------

    Under 40 CFR 58.10, states are required to submit annual monitoring 
network plans to the EPA.\276\ Within the San Joaquin Valley, CARB and 
the District are the agencies responsible for assuring that the area 
meets air quality monitoring requirements. CARB and SJVUAPCD submit 
monitoring network plans to the EPA annually. These plans describe and 
discuss the status of the air monitoring network, as required under 40 
CFR 58.10. The EPA reviews these annual network plans for compliance 
with the applicable reporting requirements in 40 CFR part 58. With 
respect to PM2.5, we have found that the CARB and SJVUAPCD 
annual network plans meet the applicable requirements under 40 CFR part 
58.\277\
---------------------------------------------------------------------------

    \276\ 40 CFR 58.10(a)(1).
    \277\ Letter dated November 5, 2018, from Gwen Yoshimura, 
Manager, Air Quality Analysis Office, EPA Region IX, to Sheraz Gill, 
Deputy Air Pollution Control Office, SJVUAPCD; letter dated November 
6, 2019, from Gwen Yoshimura, Manager, Air Quality Analysis Office, 
EPA Region IX, to Jon Klassen, Director of Strategies and 
Incentives, SJVUAPCD; letter dated October 26, 2020, from Gwen 
Yoshimura, Manager, Air Quality Analysis Office, EPA Region IX, to 
Jon Klassen, Director of Strategies and Incentives, SJVUAPCD; letter 
dated November 26, 2018, from Gwen Yoshimura, Manager, Air Quality 
Analysis Office, EPA Region IX, to Ravi Ramalingam, Chief, Consumer 
Products and Air Quality Assessment Branch, CARB; letter dated 
November 26, 2019, from Gwen Yoshimura, Manager, Air Quality 
Analysis Office, EPA Region IX, to Ravi Ramalingam, Chief, Consumer 
Products and Air Quality Assessment Branch, CARB; and letter dated 
November 5, 2020, from Gwen Yoshimura, Manager, Air Quality Analysis 
Office, EPA Region IX, to Ravi Ramalingam, Chief, Consumer Products 
and Air Quality Assessment Branch, CARB.
---------------------------------------------------------------------------

    During the 2018-2020 period, PM2.5 ambient concentration 
data that are eligible for use in determining whether an area has 
attained the PM2.5 NAAQS were collected at a total of 18 
sites within the San Joaquin Valley: 5 sites in Fresno County; 3 sites 
in Kern County; 2 sites each in Kings, Merced, San Joaquin, and 
Stanislaus counties; and 1 site each in Madera and Tulare counties. The 
District operates 12 of these sites while CARB operates 6 of these 
sites. All of the sites are designated SLAMS for PM2.5.\278\ 
The primary monitors are FRMs at 5 of the 18 sites and beta attenuation 
monitor FEMs at 13 of the 18 sites. Overall, the District's 
PM2.5 monitoring network meets, and in several Metropolitan 
Statistical Areas (MSAs) exceeds, the PM2.5 minimum 
monitoring requirements for the San Joaquin Valley.
---------------------------------------------------------------------------

    \278\ There are a number of other PM2.5 monitoring 
sites within the valley, including other sites operated by the 
District, the National Park Service, and certain Indian tribes, but 
the data collected from these sites are non-regulatory and not 
eligible for use in determining whether the San Joaquin Valley has 
attained the PM2.5 NAAQS.
---------------------------------------------------------------------------

    Based on our review of the PM2.5 monitoring network as 
summarized above, we find that the monitoring network in the San 
Joaquin Valley is adequate for the purpose of collecting ambient 
PM2.5 concentration data for use in determining whether the 
San Joaquin Valley attained the 1997 24-hour PM2.5 NAAQS by 
the December 31, 2020 attainment date.

C. Data Considerations and Proposed Determination

    Under 40 CFR 58.15, monitoring agencies must certify, on an annual 
basis, that data collected at all SLAMS and at all FRM, FEM, and ARM 
SPM stations meet the EPA's quality assurance requirements. In doing 
so, monitoring agencies must certify that the previous year of ambient 
concentration and quality assurance data are submitted to AQS and that 
the ambient concentration data are accurate. CARB annually certifies 
that the data the agency submits to AQS are quality assured, including 
the data collected at monitoring sites in the San Joaquin Valley.\279\ 
SJVUAPCD does the same for data submitted to AQS from monitoring sites 
operated by the District.\280\
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    \279\ For example, see letter dated June 21, 2021, from Sylvia 
Vanderspek, Chief, Air Quality Planning Branch, CARB, to Gwen 
Yoshimura, Manager, Air Quality Analysis Office, EPA Region 9, with 
enclosures, certifying calendar year 2020 ambient air quality data 
and quality assurance data.
    \280\ For example, see letter dated June 22, 2021, from Jessica 
Olsen, Program Manager, SJVUAPCD, to Elizabeth Adams, Director, Air 
and Radiation Division, EPA Region IX, with attachments, certifying 
calendar year 2020 ambient air quality data and quality assurance 
data.
---------------------------------------------------------------------------

    As noted above, CAA sections 179(c)(1) and 188(b)(2) require the 
EPA to determine whether a PM2.5 nonattainment area attained 
the applicable PM2.5 NAAQS by the applicable attainment 
date, based on the area's air quality as of the attainment date. The 
SJV PM2.5 Plan includes a modeled demonstration of 
attainment by December 31, 2020, for the 1997 24-hour PM2.5 
NAAQS. Thus, the EPA's evaluation of whether the San Joaquin Valley 
PM2.5 nonattainment area has attained the 1997 24-hour 
PM2.5 NAAQS is based on our review of the monitoring data 
recorded during the three years preceding the attainment date (2018-
2020). Our review also takes into account the adequacy of the 
PM2.5 monitoring network in the nonattainment area and the 
reliability of the data collected by the network as discussed in the 
previous sections of this document.
    With respect to data completeness, we determined that the data 
collected by CARB and the District meet the quarterly completeness 
criterion for all 12 quarters of the three-year period at most of the 
PM2.5 monitoring sites in the San Joaquin Valley. More 
specifically, among the 18 PM2.5 monitoring sites from which 
regulatory data are available, the data from 5 of the sites did not 
meet the 75 percent completeness criterion (for each quarter); however, 
the data from all but 3 sites (Fresno-

[[Page 53181]]

Foundry (AQS ID: 06-019-2016), Manteca (AQS ID: 06-077-2010), and 
Clovis-Villa (AQS ID: 06-019-5001)) are sufficient nonetheless to 
produce a valid design value for the 1997 24-hour PM2.5 
NAAQS pursuant to the rules governing design value validity in 40 CFR 
part 50, Appendix N, section 4.2. We note that monitors with incomplete 
data in one or more quarters may still produce valid design values if 
the conditions for applying the EPA's data substitution test are 
met.\281\ The Bakersfield-Airport (Planz) (AQS ID: 06-029-0016) and 
Hanford-Irwin (AQS ID: 06-031-1004) monitoring sites had incomplete 
data in the 4th quarter and 3rd quarter of 2018, respectively; however, 
both sites had between 50 and 75 percent data completeness for these 
quarters and have valid design values after applying the maximum 
quarterly value data substitution test.
---------------------------------------------------------------------------

    \281\ See 40 CFR part 50, Appendix N, section 4.2(b).
---------------------------------------------------------------------------

    The Manteca monitoring site recorded data amounting to less than 75 
percent completeness during the 1st, 2nd, and 3rd quarters of 2019 (61 
percent, 66 percent, and 67 percent, respectively) due to ongoing 
instrument operational issues. Under Appendix N, section 4.2(b) data 
shall be considered valid, in spite of quarters with incomplete data, 
if the resulting annual 98th percentile value or resulting 24-hour 
NAAQS design value exceeds the standard. Here, the incomplete annual 
98th percentile value, 26.8 [micro]g/m\3\, is well below the standard, 
and the resulting design value for the site, 59 [micro]g/m\3\, is also 
below the standard. Therefore, this provision of section 4.2(b) does 
not validate the 2019 Manteca monitoring site data. Like Bakersfield-
Airport (Planz) and Hanford-Irwin, the data for the Manteca site 
qualify for the maximum quarterly value data substitution test under 40 
CFR part 50, Appendix N, section 4.2(c). However, upon applying the 
data substitution test to the Manteca monitoring site data, we find 
that the data do not pass the test (i.e., after substituting the 
highest reported daily maximum PM2.5 value for a quarter for 
all missing daily data in the matching deficient quarter, the resulting 
test design value was above the 1997 24-hour PM2.5 NAAQS). 
Because the data substitution test results in a test design value above 
the NAAQS, the Manteca monitoring site 2019 design value is considered 
invalid. The EPA then reviewed additional information about the 
monitoring network and air quality data, including historical 24-hour 
PM2.5 design value trends, to assess if the data collection 
deficiency, in the context of data that otherwise show attainment, 
precludes the EPA from determining that the San Joaquin Valley area 
attained the 1997 24-hour PM2.5 NAAQS during the 2018-2020 
period.
    First, although the 2019 data were incomplete, the available data 
that were collected over a substantial amount of the year show zero 
exceedances of the NAAQS.
    Second, the Manteca monitoring site has not historically been the 
24-hour PM2.5 design value site for the San Joaquin Valley 
area. For example, the Bakersfield-California (AQS ID: 06-029-0014) 
monitoring site was the design value site for the 24-hour 
PM2.5 NAAQS for 2011 to 2013, the Bakersfield-Airport 
(Planz) monitoring site was the design value site in 2014, the 
Corcoran-Patterson (AQS ID: 06-031-0004) monitoring site was the design 
value site from 2015 to 2019, and the Modesto-14th Street (AQS ID: 06-
099-0005) monitoring site was the design value site in 2020.
    Third, an assessment of long-term trends at the Manteca monitoring 
site and nearby monitoring sites shows nearby sites have design values 
below the 24-hour PM2.5 NAAQS and the Manteca site typically 
has lower design values compared to nearby sites. For example, during 
the 2013 to 2020 period, the Manteca monitoring site had consistently 
lower design values for the 24-hour PM2.5 NAAQS than the 
Stockton-Hazelton (AQS ID: 06-077-1002) and Modesto-14th Street 
monitoring sites, which are located approximately 11 miles and 18 
miles, respectively, from the Manteca monitoring site. The Stockton-
Hazelton and Modesto-14th Street monitoring sites have complete annual 
24-hour design values that are below the 1997 24-hour PM2.5 
NAAQS (after excluding monitored exceedances associated with the August 
20-24, 2020 wildfire exceptional event, as discussed below) and provide 
an appropriate comparison and characterization of air quality for the 
areas surrounding the Manteca monitoring site. Thus, because the data 
that were collected provide a 98th percentile value below the standard, 
and the Manteca monitoring site has historically lower design value 
concentrations relative to the 24-hour PM2.5 NAAQS and 
design values at nearby locations, we find that the incomplete data 
should not preclude the EPA from determining that the San Joaquin 
Valley area has attained the 1997 24-hour PM2.5 NAAQS.
    The remaining two sites, Fresno-Foundry and Clovis-Villa, recorded 
data amounting to less than 50 percent completeness during multiple 
quarters during the 2018-2020 period. Specifically, the Fresno-Foundry 
monitoring site recorded less than 50 percent data capture during all 
four quarters of 2018 and 2019 and the Clovis-Villa monitoring site 
recorded less than 50 percent data capture during the 2nd and 4th 
quarters of 2019. Thus, the data in these quarters are not eligible for 
the maximum quarterly value data substitution test under the provisions 
in 40 CFR part 50 Appendix N, section 4.2(c)(i), which state that if 
any quarter has less than 50 percent data capture, then the required 
test conditions are not met and the substitution test cannot be used. 
Additionally, the data collected at these sites did not result in an 
98th percentile value or resulting 24-hour NAAQS design value that 
exceeds the standard under the provision of Appendix N section 4.2(b). 
Therefore, the design values at these two sites are considered invalid. 
However, the EPA reviewed historical 24-hour PM2.5 design 
value trends and the causes of the incomplete data in the context of 
data that otherwise show attainment, and found that the data collection 
deficiency should not preclude a determination that the San Joaquin 
Valley area attained the 1997 24-hour PM2.5 NAAQS during the 
2018-2020 period.
    The Fresno-Foundry monitoring site began operation on January 1, 
2020. Although data completeness was 98 percent for year 2020, the data 
completeness requirements for the 2018-2020 period are not met since 
the site was not yet operational and thus data were not collected in 
2018 and 2019. Because the incomplete data at the Fresno-Foundry 
monitoring site is due to the site having only begun operation in 2020, 
the incomplete data should not preclude the EPA from determining 
whether the area has attained the NAAQS. Upon excluding monitored 
exceedances associated with the August 20-24, 2020 wildfire exceptional 
event, as discussed below, the Fresno-Foundry monitoring site has an 
incomplete 2020 design value of 64 [micro]g/m\3\, which is below the 
level of the 1997 24-hour PM2.5 NAAQS.
    The Clovis-Villa monitoring site recorded less than 75 percent data 
capture during the 2nd, 3rd, and 4th quarters of 2019 (48 percent, 66 
percent, and 41 percent, respectively) due to ongoing instrument 
operational issues. Because the data substitution test under 40 CFR 
part 50, Appendix N, section 4.2(c) requires each quarter to have data 
completeness of at least 50 percent, the Clovis-Villa 2019 data do not 
qualify for the data substitution test. Like Manteca, the Clovis-Villa 
site has not historically

[[Page 53182]]

been the 24-hour PM2.5 design value site. An assessment of 
long-term trends at the Clovis-Villa monitoring site and a nearby 
monitoring site shows that the Clovis-Villa site has historically had 
design values below the 24-hour PM2.5 NAAQS and has had 
lower design values compared to the nearby site. During the 2011 to 
2019 period, the Clovis-Villa monitoring site consistently had lower 
design values for the 24-hour PM2.5 NAAQS than the Fresno-
Garland monitoring site, which is located approximately four miles from 
Clovis-Villa.\282\ The Fresno-Garland site has a complete 2020 annual 
24-hour design value below the 1997 24-hour PM2.5 NAAQS and 
provides an appropriate comparison and characterization of air quality 
for the area surrounding the Clovis-Villa monitoring site. Furthermore, 
the District exceeds the PM2.5 minimum monitoring 
requirements for three PM2.5 SLAMs monitors in the Fresno 
MSA as they are currently operating five SLAMs monitors.
---------------------------------------------------------------------------

    \282\ The Clovis-Villa and Fresno-Garland monitoring sites have 
the same 2020 design value of 62 [micro]g/m\3\.
---------------------------------------------------------------------------

    Thus, based on the historical design value concentrations at the 
Clovis-Villa monitoring site relative to the 24-hour PM2.5 
NAAQS and the nearest site, we find that the incomplete data at the 
Clovis-Villa monitoring site should not preclude the EPA from 
determining the San Joaquin Valley area has attained the 1997 24-hour 
PM2.5 NAAQS.
    Table 5 shows the 24-hour 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 indicate that the San Joaquin Valley area likely experienced 
higher than normal PM2.5 concentrations in 2018 and 2020 due 
to wildfire impacts during the summer and fall months.\283\ Table 5 
shows that 98th percentile concentrations at all 18 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, again, 
likely due to the wildfires in those years. Accordingly, the 2018-2020 
design values in Table 5 may also be higher than normal at certain 
monitoring sites due to potential wildfire impacts within the 2018-2020 
data period. Nevertheless, the data show that the 24-hour design value 
for the 2018-2020 period was equal to or less than 65 [micro]g/m\3\ 
(i.e., the level of the 1997 24-hour PM2.5 NAAQS) at all 
monitors after excluding monitored exceedances specifically associated 
with the August 20-24, 2020 wildfire exceptional event, as discussed 
below. Therefore, we are proposing to determine, based on complete (or 
otherwise not inconsistent, as described above), quality-assured, and 
certified data for 2018-2020, that the San Joaquin Valley area has 
attained the 1997 24-hour PM2.5 NAAQS, consistent with 
attainment of the standard projected by the State in the SJV 
PM2.5 Plan.
---------------------------------------------------------------------------

    \283\ EPA, 2020 Raw Data Report, AMP350, accessed July 13, 2021.

                              Table 5--2018-2020 24-Hour PM2.5 Design Values for the San Joaquin Valley Nonattainment Area
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                98th percentile ([micro]g/m\3\)                      2018-2020  24-hour
         County             General location      AQS ID    ----------------------------------------------------------------------     design  values
                                  site                                2018                    2019                   2020             ([micro]g/m\3\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Fresno..................  Fresno--Pacific....   06-019-5025  65.5..................  37.1.................  81.0.................  61.
                          Fresno--Garland....   06-019-0011  63.5..................  36.9.................  85.0.................  62.
                          Fresno--Foundry....   06-019-2016  Inc...................  Inc..................  63.9.................  64 (Inv).\a\
                          Clovis--Villa......   06-019-5001  57.0..................  28.0 (Inc)...........  99.5.................  62 (Inv).\b\
                          Tranquillity.......   06-019-2009  51.4..................  17.1.................  92.5.................  54.
Kern....................  Bakersfield--Airpor   06-029-0016  60.8..................  46.7.................  57.1.................  55.
                           t (Planz).
                          Bakersfield--Califo   06-029-0014  69.2..................  43.4.................  79.2.................  64.
                           rnia Ave.
                          Bakersfield--Golden   06-029-0010  60.9..................  44.3.................  76.9.................  61.
                           State Highway.
Kings...................  Corcoran--Patterson   06-031-0004  78.0..................  45.1.................  69.0.................  64.
                          Hanford--Irwin.....   06-031-1004  78.2..................  41.1.................  72.6.................  64.
Madera..................  Madera--Avenue 14..   06-039-2010  50.2..................  23.9.................  87.7.................  54.
Merced..................  Merced--M Street...   06-047-2510  52.7..................  29.5.................  77.1.................  53.
                          Merced--Coffee.....   06-047-0003  56.0..................  23.4.................  78.3.................  53.
San Joaquin.............  Stockton--Hazelton.   06-077-1002  92.3..................  32.9.................  65.9.................  64.
                          Manteca............   06-077-2010  84.6 \c\..............  26.8 (Inc)...........  66.9.................  59 (Inv).\d\
Stanislaus..............  Modesto--14th         06-099-0005  100.4.................  28.4.................  67.1.................  65.
                           Street.
                          Turlock............   06-099-0006  88.6..................  36.0.................  67.7.................  64.
Tulare..................  Visalia............   06-107-2002  63.4..................  45.5.................  83.4.................  64.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: EPA, 2020 AQS Design Value Report, AMP480, accessed September 1, 2021.The Design Value Report excludes measurements with regionally concurred
  exceptional event flags. AQS reports for 24-hour PM2.5 data are only available for the 2006 24-hour PM2.5 NAAQS as a Pollutant Standard, thus this
  report only reflects the 2006 24-hour PM2.5 NAAQS and does not include the 1997 24-hour PM2.5 NAAQS as a Pollutant Standard. Subsequently, AQS only
  allows the EPA to place concurrence flags on data associated with the 2006 24-hour PM2.5 NAAQS. 40 CFR part 50 Appendix N specifies the data handling
  and design value calculations for both the 2006 24-hour PM2.5 NAAQS and the 1997 24-hour PM2.5 NAAQS. The design values in the Design Value Report for
  the 2006 24-hr PM2.5 NAAQS for the San Joaquin Valley nonattainment area are the same as would be expected for the 1997 24-hr PM2.5 NAAQS if the
  exceptional events for that NAAQS were correctly represented in AQS.
Notes: Inc = Incomplete data. Inv = Invalid design value due to incomplete data.
\a\ The 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 4.2(b), three years of valid annual PM2.5 98th percentile mass concentrations are required to produce a valid 24-hour PM2.5 NAAQS design
  value. Thus, the Fresno-Foundry 2018-2020 design value is considered invalid.
\b\ Based on the design value calculation methodologies described in 40 CFR part 50, Appendix N, section 4.2(b), the Clovis-Villa (AQS ID: 06-019-5001)
  2018-2020 design value is considered invalid due to incomplete data in the 2nd, 3rd, and 4th quarters of 2019.

[[Page 53183]]

 
\c\ Identification of the 98th percentile 24-hour concentration is based on the number of creditable samples in a given year. See 40 CFR part 50,
  appendix N, section 4.5. Specifically, in any year for which there are at least 351 creditable samples, the 98th percentile is the 8th highest
  concentration, and as the number of creditable samples decreases the 98th percentile concentration is represented by a data point closer to the
  maximum concentration. The number of creditable samples in 2018 for Manteca is reflected inaccurately in AQS and results in an inaccurate 2018 98th
  percentile concentration and 2018-2020 design value. Table 5 reflects the 2018 98th percentile concentration and 2018-2020 design value based on the
  corrected number of creditable samples. See memorandum dated August 6, 2021, from Dena Vallano, EPA Region IX, to Docket EPA-R09-OAR-2021-0261,
  Subject: ``San Joaquin Valley, CA 1997 24-hour PM2.5 Nonattainment Area, Manteca Monitoring.''
\d\ Based on the design calculation methodologies described in 40 CFR part 50, Appendix N, section 4.2(b), the Manteca (AQS ID: 06-077-2010) 2018-2020
  design value is considered invalid due to incomplete data in the 1st, 2nd, and 3rd quarters of 2019.

    In the EPA's review of monitoring data for the 1997 24-hour 
PM2.5 NAAQS for the San Joaquin Valley nonattainment area, 
the EPA is excluding certain exceedances of the standard from the 
attainment determination presented herein because they were the result 
of exceptional events. Under the EPA's Exceptional Events Rule 
(EER),\284\ exceedances flagged as exceptional events will only be 
considered for EPA concurrence if the data affect one of the types of 
regulatory actions specified by the EER. The State has submitted a 
demonstration for a wildfire PM2.5 exceptional event 
covering a total of 30 measured exceedances occurring over 5 
consecutive days (August 20-24, 2020) at 8 monitoring sites within the 
San Joaquin Valley nonattainment area that were critical for informing 
this attainment determination.\285\ The State's submission notes that 
additional San Joaquin Valley monitoring sites were affected by 
wildfire smoke during the 2018-2020 period, but that those dates were 
not included in the submission because they did not cause the 2020 
design values to violate the 1997 24-hour PM2.5 NAAQS and 
did not have regulatory significance relevant to this 
determination.\286\ The EPA reviewed the documentation that the State 
provided to demonstrate that these exceedances meet the criteria for 
exceptional events under the EER. The EPA concurred with the State's 
determinations that, based on the weight of evidence, the exceedances 
were caused by an exceptional event.\287\ Accordingly, the EPA has 
determined that the monitored exceedances associated with this 
exceptional event should not be used for regulatory purposes, including 
the evaluation of whether the San Joaquin Valley nonattainment area has 
attained by the attainment date and evaluation of the CAA Serious area 
and section 189(d) plan submission. Excluding these exceedances caused 
by uncontrollable emissions, the EPA proposes to determine that the San 
Joaquin Valley has attained the 1997 24-hour PM2.5 NAAQS, 
consistent with attainment of the standard projected by the State in 
the SJV PM2.5 Plan.
---------------------------------------------------------------------------

    \284\ 40 CFR 50.1(j), (k), (l); 50.14(a)(1)(i); 51.930.
    \285\ The eight monitoring sites covered by the August 20-24, 
2020 wildfire exceptional event demonstration include Fresno-
Foundry, Bakersfield-Airport (Planz), Corcoran-Patterson, Hanford-
Irwin, Stockton-Hazelton, Manteca, Modesto-14th Street, and Turlock.
    \286\ SJVUAPCD, ``Exceptional Event Demonstration for August 
2020 PM2.5 Exceedances due to Wildfires'', May 11, 2021, 
3.
    \287\ Letter dated July 13, 2021, from Elizabeth J. Adams, 
Director, Air and Radiation Division, EPA Region IX, to Michael 
Benjamin, Division Chief, Air Quality Planning and Science Division, 
CARB.
---------------------------------------------------------------------------

VI. Summary of Proposed Action and Request for Public Comment

    The EPA is proposing to determine that the San Joaquin Valley 
nonattainment area has attained the 1997 24-hour PM2.5 
NAAQS, based on complete (or otherwise not inconsistent), quality-
assured, and certified ambient air quality monitoring data for the 
2018-2020 monitoring period. If finalized, this proposed determination 
that the San Joaquin Valley nonattainment area has attained the 1997 
24-hour PM2.5 NAAQS would not constitute a redesignation of 
the area to attainment. Under CAA section 107(d)(3)(E), redesignations 
of nonattainment areas to attainment require states to meet a number of 
additional statutory criteria, including the EPA's approval of a SIP 
revision demonstrating maintenance of the standard for 10 years after 
redesignation. The designation status of the San Joaquin Valley area 
will remain Serious nonattainment for the 1997 24-hour PM2.5 
NAAQS until such time as the EPA determines that the area meets the CAA 
requirements for redesignation to attainment.
    For the reasons discussed in this proposed rule, under CAA section 
110(k)(3), the EPA is also proposing to approve in part and disapprove 
in part portions of the SJV PM2.5 Plan submitted by 
California that pertain to the 1997 24-hour PM2.5 NAAQS in 
the San Joaquin Valley nonattainment area as follows:
    (1) We are proposing to approve the following elements as meeting 
the Serious nonattainment area planning requirements:
    (a) The 2013 base year emissions inventories as meeting the 
requirements of CAA section 172(c)(3) and 40 CFR 51.1008(b);
    (b) the BACM/BACT demonstration as meeting the requirements of CAA 
section 189(b)(1)(B) and 40 CFR 51.1010(a);
    (c) the demonstration (including air quality modeling) that the 
Plan provides for attainment as expeditiously as practicable as meeting 
the requirements of CAA sections 179(d) and 189(b) and 40 CFR 
51.1011(b);
    (d) the RFP demonstration as meeting the requirements of CAA 
sections 172(c)(2) and 171(1) and 40 CFR 51.1012; and
    (e) the quantitative milestone demonstration as meeting the 
requirements of CAA section 189(c) and 40 CFR 51.1013;
    (2) We are proposing to approve the following elements as meeting 
the CAA section 189(d) planning requirements:
    (a) The 2013 base year emissions inventories as meeting the 
requirements of CAA section 172(c)(3) and 40 CFR 51.1008(c);
    (b) the BACM/BACT demonstration as meeting the requirements of CAA 
sections 189(a)(1)(C) \288\ and 189(b)(1)(B) and 40 CFR 51.1010(c);
---------------------------------------------------------------------------

    \288\ As discussed in section III.B of this document, a section 
189(d) plan must address any outstanding Moderate or Serious area 
requirements that have not previously been approved. Because we have 
not previously approved a subpart 4 RACM demonstration for the San 
Joaquin Valley nonattainment area, we are also proposing to approve 
the BACM/BACT demonstration in the SJV PM2.5 Plan as 
meeting the subpart 4 RACM/RACT requirement for the area.
---------------------------------------------------------------------------

    (c) the demonstration that the Plan will, at a minimum, achieve an 
annual five percent reduction in emissions of NOX as meeting 
the requirements of CAA section 189(d) and 40 CFR 51.1010(c);
    (d) the demonstration (including air quality modeling) that the 
Plan provides for attainment as expeditiously as practicable as meeting 
the requirements of CAA sections 179(d) and 189(d) and 40 CFR 
51.1011(b);
    (e) the RFP demonstration as meeting the requirements of CAA 
sections 172(c)(2) and 171(1) and 40 CFR 51.1012; and
    (f) the quantitative milestone demonstration as meeting the 
requirements of CAA section 189(c) and 40 CFR 51.1013;
    (3) We are proposing to approve the motor vehicle emission budgets 
for 2017 and 2020 as shown in Table 8 of this proposed rule because 
they are derived

[[Page 53184]]

from approvable RFP and attainment demonstrations and meet the 
requirements of CAA section 176(c) and 40 CFR part 93, subpart A;
    (4) We are proposing to approve the inter-pollutant trading 
mechanism provided for use in transportation conformity analyses for 
the 1997 24-hour PM2.5 NAAQS, in accordance with 40 CFR 
93.124(b); and
    (5) We are proposing to disapprove the contingency measure element 
of the SJV PM2.5 Plan for the 1997 24-hour PM2.5 
NAAQS for both the Serious area and CAA section 189(d) planning 
requirements for failing to meet the requirements of CAA section 
172(c)(9). However, based on our proposed finding of attainment by the 
applicable attainment date, we are also proposing to determine that the 
contingency measures requirement will no longer apply to the San 
Joaquin Valley area for the 1997 24-hour PM2.5 NAAQS if we 
finalize the determination of attainment by the applicable attainment 
date. Therefore, our proposed disapproval, if finalized, would not 
trigger sanctions or FIP clocks, and we are proposing to issue a 
protective finding for transportation conformity determinations under 
40 CFR 93.120(a)(3) if the proposed disapproval is finalized.
    The EPA is soliciting public comments on the issues discussed in 
this proposed rule. We will accept comments from the public on this 
proposal for the next 30 days.

VII. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive Orders 
can be found at https://www2.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review and Executive 
Order 13563: Improving Regulation and Regulatory Review

    This action is not a significant regulatory action and was 
therefore not submitted to the Office of Management and Budget (OMB) 
for review.

B. Paperwork Reduction Act (PRA)

    This action does not impose an information collection burden under 
the PRA because the proposed partial SIP approval and partial 
disapproval, if finalized, will not in-and-of itself create any new 
information collection burdens but will simply disapprove certain State 
requirements for inclusion in the SIP.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. This 
action will not impose any requirements on small entities. This 
proposed partial SIP approval and partial disapproval, if finalized, 
will not in-and-of itself create any new requirements but will simply 
disapprove certain state requirements for inclusion in the SIP.

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate as described in 
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect 
small governments. This action proposes to partially approve and 
partially disapprove pre-existing requirements under state or local law 
and imposes no new requirements. Accordingly, no additional costs to 
state, local, or tribal governments, or to the private sector, result 
from this action.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have 
substantial direct effects on the states, on the relationship between 
the national government and the states, or on the distribution of power 
and responsibilities among the various levels of government.

F. Executive Order 13175: Coordination With Indian Tribal Governments

    This action does not have tribal implications, as specified in 
Executive Order 13175, because the SIP revision that the EPA is 
proposing to partially approve and partially disapprove would not apply 
on any Indian reservation land or in any other area where the EPA or an 
Indian tribe has demonstrated that a tribe has jurisdiction, and will 
not impose substantial direct costs on tribal governments or preempt 
tribal law. Thus, Executive Order 13175 does not apply to this action.

G. Executive Order 13045: Protection of Children From Environmental 
Health Risks and Safety Risks

    The EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that concern environmental health or safety risks 
that the EPA has reason to believe may disproportionately affect 
children, per the definition of ``covered regulatory action'' in 
section 2-202 of the Executive Order. This action is not subject to 
Executive Order 13045 because this proposed partial SIP approval and 
partial disapproval, if finalized, will not in-and-of itself create any 
new regulations but will simply disapprove certain state requirements 
for inclusion in the SIP.

H. Executive Order 13211: Actions That Significantly Affect Energy 
Supply, Distribution, or Use

    This action is not subject to Executive Order 13211 because it is 
not a significant regulatory action under Executive Order 12866.

I. National Technology Transfer and Advancement Act (NTTAA)

    Section 12(d) of the NTTAA directs the EPA to use voluntary 
consensus standards in its regulatory activities unless to do so would 
be inconsistent with applicable law or otherwise impractical. The EPA 
believes that this action is not subject to the requirements of section 
12(d) of the NTTAA because application of those requirements would be 
inconsistent with the CAA.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Population

    The EPA lacks the discretionary authority to address environmental 
justice in this rulemaking.

List of Subjects in 40 CFR Part 51

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

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

    Dated: September 17, 2021.
Deborah Jordan,
Acting Regional Administrator, Region IX.
[FR Doc. 2021-20613 Filed 9-23-21; 8:45 am]
BILLING CODE 6560-50-P