Rule2023-27088
Air Quality State Implementation Plans; Approvals and Promulgations: California; 1997 Annual Fine Particulate Matter Serious and Clean Air Act Section 189(d) Nonattainment Area Requirements; San Joaquin Valley, CA
Primary source
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Published
December 14, 2023
Effective
January 16, 2024
Issuing agencies
Environmental Protection Agency
Abstract
The Environmental Protection Agency (EPA or "Agency") is taking final action to approve portions of state implementation plan (SIP) revisions submitted by the State of California to meet Clean Air Act (CAA or "Act") requirements for the 1997 annual fine particulate matter (PM<INF>2.5</INF>) national ambient air quality standards (NAAQS or "standards") in the San Joaquin Valley PM<INF>2.5</INF> nonattainment area. Specifically, the EPA is approving those portions of the submitted SIP revisions as they pertain to the Serious nonattainment area and CAA section 189(d) requirements for the 1997 annual PM<INF>2.5</INF> NAAQS, except for the requirement for contingency measures which will be addressed in a separate rulemaking. In addition, the EPA is approving the 2020 and 2023 motor vehicle emissions budgets and the trading mechanism for use in transportation conformity analyses for the 1997 annual PM<INF>2.5</INF> NAAQS.
Full Text
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<title>Federal Register, Volume 88 Issue 239 (Thursday, December 14, 2023)</title>
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[Federal Register Volume 88, Number 239 (Thursday, December 14, 2023)]
[Rules and Regulations]
[Pages 86581-86608]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2023-27088]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R09-OAR-2023-0263; FRL-10941-02-R9]
Air Quality State Implementation Plans; Approvals and
Promulgations: California; 1997 Annual Fine Particulate Matter Serious
and Clean Air Act Section 189(d) Nonattainment Area Requirements; San
Joaquin Valley, CA
AGENCY: Environmental Protection Agency (EPA).
ACTION: Final rule.
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SUMMARY: The Environmental Protection Agency (EPA or ``Agency'') is
taking final action to approve portions of state implementation plan
(SIP) revisions submitted by the State of California to meet Clean Air
Act (CAA or ``Act'') requirements for the 1997 annual fine particulate
matter (PM<INF>2.5</INF>) national ambient air quality standards (NAAQS
or ``standards'') in the San Joaquin Valley PM<INF>2.5</INF>
nonattainment area. Specifically, the EPA is approving those portions
of the submitted SIP revisions as they pertain to the Serious
nonattainment area and CAA section 189(d) requirements for the 1997
annual PM<INF>2.5</INF> NAAQS, except for the requirement for
contingency measures which will be addressed in a separate rulemaking.
In addition, the EPA is approving the 2020 and 2023 motor vehicle
emissions budgets and the trading mechanism for use in transportation
conformity analyses for the 1997 annual PM<INF>2.5</INF> NAAQS.
DATES: This rule is effective on January 16, 2024.
ADDRESSES: The EPA has established a docket for this action under
Docket ID No. EPA-R09-OAR-2023-0263. All documents in the docket are
listed on the <a href="https://www.regulations.gov">https://www.regulations.gov</a> website. Although listed in
the index, some information is not publicly available, e.g.,
Confidential Business Information (CBI) or other information whose
disclosure is restricted by statute. Certain other material, such as
copyrighted material, is not placed on the internet and will be
publicly available only in hard copy form. Publicly available docket
materials are available through <a href="https://www.regulations.gov">https://www.regulations.gov</a>, or please
contact the person identified in the FOR FURTHER INFORMATION CONTACT
section for additional availability information. If you need assistance
in a language other than English or if you are a person with a
disability 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, Geographic Strategies
and Modeling Section (AIR-2-2), EPA Region IX, 75 Hawthorne Street, San
Francisco, CA 94105. By phone: (415) 972-3877 or by email at
<a href="/cdn-cgi/l/email-protection#630411020b020e4d02100b0f061a11230613024d040c15"><span class="__cf_email__" data-cfemail="0c6b7e6d646d61226d7f646069757e4c697c6d226b637a">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION: Throughout this document, ``we,'' ``us,''
and ``our'' refer to the EPA.
Table of Contents
I. Summary of the Proposed Action
II. Public Comments and EPA Responses
A. Comments From Central California Environmental Justice
Network (CCEJN)
B. Comments From Central Valley Air Quality Coalition (CVAQ)
C. Comments From a Private Individual
III. Motor Vehicle Emissions Budgets and Transportation Conformity
IV. Environmental Justice Considerations
V. Final Action
VI. Statutory and Executive Order Reviews
I. Summary of the Proposed Action
On July 14, 2023, in accordance with CAA section 110(k)(3), the EPA
proposed to approve portions of SIP revisions submitted by the
California Air Resources Board (CARB) to meet CAA requirements for the
1997 annual PM<INF>2.5</INF> NAAQS in the San Joaquin Valley
PM<INF>2.5</INF> nonattainment area.\1\ The San Joaquin Valley is
classified as a Serious nonattainment area for the 1997 annual
PM<INF>2.5</INF> NAAQS and is also subject to CAA section 189(d)
requirements because of the failure of the area to attain the 1997
annual PM<INF>2.5</INF> NAAQS by the area's original Serious area
attainment date (i.e., December 31, 2015). The EPA's determination that
the area failed to attain by the original December 31, 2015 attainment
date triggered the requirement for the State to submit the SIP
revisions on which the EPA is taking final action in this document.\2\
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\1\ 88 FR 45276.
\2\ 81 FR 84481 (November 23, 2016).
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The SIP revisions on which we proposed action are those portions of
the ``2018 Plan for the 1997, 2006, and 2012 PM<INF>2.5</INF>
Standards'' (``2018 PM<INF>2.5</INF> Plan'') \3\ and the ``San Joaquin
Valley Supplement to the 2016 State Strategy for the State
Implementation Plan'' (``Valley State SIP Strategy'') \4\ that pertain
to the 1997 annual PM<INF>2.5</INF> NAAQS, and the ``Attainment Plan
Revision for the 1997 Annual PM<INF>2.5</INF> Standard'' (``15
[micro]g/m\3\ SIP Revision'').\5\ CARB submitted the 2018
PM<INF>2.5</INF> Plan and Valley State SIP Strategy to the EPA as a
revision to the California SIP on May 10, 2019, and submitted the 15
[micro]g/m\3\ SIP Revision on November 8, 2021. We refer to these three
submissions collectively as the ``SJV PM<INF>2.5</INF> Plan'' or
``Plan.'' The SJV PM<INF>2.5</INF> Plan was developed jointly by the
San Joaquin Valley Unified Air Pollution Control District (SJVUAPCD or
``District'') and CARB and addresses Serious area nonattainment plan
and CAA section 189(d) requirements for the 1997 annual
PM<INF>2.5</INF> NAAQS in the San Joaquin Valley, except for the
requirement for contingency measures. The Plan includes the State's
demonstration that the area will attain the 1997 annual
PM<INF>2.5</INF> NAAQS by December 31, 2023.
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\3\ The 2018 PM<INF>2.5</INF> Plan was adopted by the San
Joaquin Valley Unified Air Pollution Control District on November
15, 2018, and by CARB on January 24, 2019.
\4\ The Valley State SIP Strategy was adopted by CARB on October
25, 2018.
\5\ The ``15 [micro]g/m\3\ SIP Revision'' was adopted by the San
Joaquin Valley Unified Air Pollution Control District on August 19,
2021, and adopted by CARB on September 23, 2021.
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Following submittal of the SJV PM<INF>2.5</INF> Plan, CARB
transmitted to the EPA two technical supplements providing additional
information in support of the Plan. The first supplement, submitted on
March 30, 2023, included documents titled ``Ammonia: Supplemental
Information for EPA in Support of 15 [micro]g/m\3\ Annual
PM<INF>2.5</INF> Standard, March
[[Page 86582]]
2023'' (``March 2023 Ammonia Supplement'') and ``Building
Electrification Technical Supplement for the 1997 Annual
PM<INF>2.5</INF> NAAQS'' (``March 2023 Building Heating Supplement'').
The second supplement was submitted on June 15, 2023, and included
information on the State's consideration of Title VI of the Civil
Rights Act of 1964 (``Title VI'') in the context of SIP development to
provide necessary assurances for purposes of CAA section
110(a)(2)(E)(i) (``Title VI Supplement'').\6\
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\6\ Letter dated June 15, 2023, from Steven S. Cliff, Executive
Officer, CARB, to Martha Guzman, Regional Administrator, EPA Region
IX, with enclosures titled ``Title VI of the Civil Rights Act of
1964: CARB Supplemental Information for EPA in Support of 15
[micro]g/m\3\ Annual PM<INF>2.5</INF> Standard'' (``CARB Title VI
Supplement'') and ``San Joaquin Valley Air Pollution Control
District Write-Up on Title VI of the Civil Rights Act of 1964:
Supplemental Information for EPA in Support of 15 [micro]g/m\3\
Annual PM<INF>2.5</INF> Standard'' (``District Title VI
Supplement'').
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The EPA proposed to approve the best available control measures/
best available control technology (BACM/BACT) demonstration,\7\ the
five percent annual emissions reduction demonstration, the attainment
demonstration (including air quality modeling), the reasonable further
progress (RFP) demonstration, and the quantitative milestones
demonstration in the SJV PM<INF>2.5</INF> Plan as meeting the Serious
nonattainment area and CAA section 189(d) planning requirements for the
1997 annual PM<INF>2.5</INF> NAAQS. We also proposed to find that the
previously approved \8\ 2013 base year emissions inventories continue
to satisfy 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, and to find that the forecasted inventories for the
years 2017, 2018, 2019, 2020, 2023, and 2026 provide an adequate basis
for the BACM, RFP, five percent, and modeled attainment demonstration
analyses. Finally, we proposed to approve the motor vehicle emissions
budgets for 2020 and 2023 and the trading mechanism provided for use in
transportation conformity analyses.\9\
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\7\ As discussed in Section III.B of the proposal, 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 also proposed to approve the
BACM/BACT demonstration in the SJV PM<INF>2.5</INF> Plan as meeting
the subpart 4 RACM/RACT requirement for the area. (88 FR 45276,
45322).
\8\ On November 26, 2021, the EPA finalized a partial approval
and partial disapproval of the 2018 PM<INF>2.5</INF> Plan for the
1997 annual PM<INF>2.5</INF> NAAQS, including approval of the 2013
base year emissions inventory in the Plan. 86 FR 67329.
\9\ An adequacy finding for the 2020 and 2023 motor vehicle
emissions budgets was effective on February 25, 2022. (87 FR 7834,
February 10, 2022).
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Please see our July 14, 2023 proposed rulemaking for additional
background and a detailed explanation of the rationale for our proposed
action.
II. Public Comments and EPA Responses
The public comment period for the proposed rulemaking opened on
July 14, 2023, the date of its publication in the Federal Register, and
closed on August 14, 2023. During this period, the EPA received three
comment submissions from the following entities: (1) a coalition of six
environmental and community organizations (collectively referred to
herein as ``CCEJN''),\10\ (2) a coalition of eight environmental and
community organizations (collectively referred to herein as
``CVAQ''),\11\ and (3) a private citizen commenter.\12\ We respond to
the comments herein.
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\10\ Comment letter dated and received August 11, 2023,
including 36 attachments, addressed to Ashley Graham, EPA Region IX.
The six environmental and community organizations, in order of
appearance in the letter, are the Central California Environmental
Justice Network, the Central Valley Air Quality Coalition,
Earthjustice, the Leadership Counsel for Justice and Accountability,
the National Parks Conservation Association, and Sierra Club--Kern-
Kaweah Chapter.
\11\ Comment letter dated and received August 14, 2023,
addressed to Martha Guzman, Regional Administrator, EPA Region IX.
The eight environmental and community organizations, in order of
appearance in the letter, are the Central Valley Air Quality
Coalition, Earthjustice, Sierra Club--Kern-Kaweah Chapter, the
National Parks Conservation Association, the Central California
Environmental Justice Network, Little Manila Rising, and Valley
Improvement Projects.
\12\ Comment letter dated and received August 14, 2023, from
Richard Grow, to Docket ID No. EPA-R09-OAR-2023-0263.
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A. Comments From Central California Environmental Justice Network
(CCEJN)
1. Necessary Assurances Required by CAA Section 110(a)(2)(E)
Comment 1.A: CCEJN questioned the EPA's proposed approval of the
SJV PM<INF>2.5</INF> Plan because of concerns about the adequacy of the
necessary assurances that the State provided in the Title VI
supplement. The commenter contends that to comply with CAA section
110(a)(2)(E), a state's necessary assurances must relate to a state's
nonattainment plan SIP submission itself, not merely the public
processes carried out while preparing the plan or state laws and
policies outside of the plan. The commenter claims that the Title VI
Supplement fails to do this because it ``has nothing to do with'' the
specific contents of the SJV PM<INF>2.5</INF> Plan. As an example, the
commenter points to the State's lack of a Title VI analysis supporting
its decision to not regulate ammonia as part of its PM<INF>2.5</INF>
reduction strategy and contends that this example indicates that the
State has failed to provide adequate necessary assurances.
Additionally, CCEJN asserts that the EPA's analysis of the Plan must
consider how the Plan itself complies with Title VI and that the EPA
did not do so in its proposal.
Response 1.A: The EPA agrees with the commenter that CAA section
110(a)(2)(E)(i) requires that a state provide necessary assurances that
implementing the SIP submission at issue would not be prohibited by
Title VI. However, the EPA disagrees with the commenter that the
necessary assurances provided by CARB, in conjunction with the
substantive elements of the Plan itself, are insufficient to show that
implementation of the Plan is not prohibited by Title VI, consistent
with CAA section 110(a)(2)(E)(i). The EPA explained its rationale
regarding its evaluation of the necessary assurances and CAA section
110(a)(2)(E)(i) in detail in our proposal.\13\
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\13\ 88 FR 45276, 45319-45321.
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As a point of clarification, the commenter includes references to
``compliance with Title VI'' as the relevant inquiry for purposes of
necessary assurances under CAA section 110(a)(2)(E)(i). The EPA does
not agree with this characterization of its responsibilities under the
CAA.\14\ In the proposal action, the EPA clearly noted that ``[t]he
EPA's proposed SIP approval does not constitute a formal finding of
compliance with Title VI or 40 CFR part 7.'' \15\ The EPA further noted
that ``[a]pproval of this SIP submission for purposes of CAA
110(a)(2)(E)(i) does not affect the EPA's discretion to enforce Title
VI and/or the EPA's civil rights regulations.'' \16\ Without making a
formal finding of compliance with Title VI, the EPA believes the
analysis in the EPA's proposed approval and in this
[[Page 86583]]
final rulemaking is consistent with CAA section 110(a)(2)(E)(i).\17\
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\14\ See El Comit[eacute] para el Bienestar de Earlimart et al.
v. EPA, 786 F.3d 688 (9th Cir. 2015) (``El Comit[eacute] effectively
contends the EPA should have evaluated California's assurances the
same way the EPA would have to deal with a pending Title VI
complaint setting forth allegations of a current violation. El
Comit[eacute]'s argument fails because it misconstrues the EPA's
burden regarding the `necessary assurances' requirement. The EPA has
a duty to provide a reasoned judgment as to whether the state has
provided `necessary assurances,' but what assurances are `necessary'
is left to the EPA's discretion.'').
\15\ 88 FR 45276, 45321.
\16\ Id.
\17\ See El Comit[eacute] para el Bienestar de Earlimart et al.
v. EPA, 786 F.3d 688 (9th Cir. 2015) (``Section 110(a)(2)(E) . . .
does not require a state to `demonstrate' it is not prohibited by
Federal or State law from implementing its proposed SIP revision.
Rather, this section requires a state to provide `necessary
assurances' of this.'')
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With respect to the substance of the State's submission, the EPA
disagrees with the commenter that the public processes surrounding the
development and implementation of an attainment plan have no bearing on
necessary assurances under CAA section 110(a)(2)(E)(i). As stated in
the proposal, ``[w]hat is appropriate for purposes of necessary
assurances can vary depending upon the nature of the issues in a
particular situation. Thus, the EPA evaluates a state's compliance with
CAA 110(a)(2)(E)(i) on a case-by-case basis.'' \18\ Further, the EPA
has discretion to determine what assurances are necessary and may
require more or different information as needed in other SIP
actions.\19\ For example, in other contexts, the EPA has identified
public participation as an established approach for recipients of EPA
assistance to provide meaningful access to programs and activities.\20\
Therefore, the EPA does not agree with the contention that methods of
providing for public participation are not relevant to the analysis of
necessary assurances under CAA section 110(a)(2)(E)(i).
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\18\ 88 FR 45276, 45320.
\19\ See id.
\20\ See, e.g., <a href="https://www.epa.gov/external-civil-rights/external-civil-rights-guidance">https://www.epa.gov/external-civil-rights/external-civil-rights-guidance</a>. Although information on this website
is not specific to CAA section 110(a)(2)(E)(i) necessary assurances,
it provides information regarding public participation and
information provided to recipients of EPA assistance.
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In the Title VI Supplement, the State described the early and
enhanced public engagement processes that CARB and the District
undertook during the development and approval of the 2016 State SIP
Strategy, Valley State SIP Strategy, 2018 PM<INF>2.5</INF> Plan, and 15
[micro]g/m\3\ SIP Revision, all of which formed the basis for the SJV
PM<INF>2.5</INF> Plan for the 1997 annual PM<INF>2.5</INF> NAAQS. It
also described steps the State and District took to solicit and respond
to public input following the local adoption of the Plan and to
implement the control measures and strategy outlined in the Plan. These
approaches are beyond minimum public notice and comment requirements
and provide relevant information and important context of the necessary
assurances under CAA section 110(a)(2)(E)(i) that the Plan was adopted
and will be implemented into the future in a manner that is not
prohibited by Title VI.
Similarly, the descriptions of State measures like Assembly Bill
617 (``AB 617'') and the development of community air monitoring
networks provide relevant context for the regulatory landscape in which
the State will implement the Plan, as well as the intent of the
regulators. The EPA believes the State initiatives to prevent or
diminish potential health-related impacts to communities most impacted
by air pollution also, in part, provide assurances that the
implementation of the Plan is not prohibited by Title VI in a manner
consistent with CAA section 110(a)(2)(E)(i). The State's Civil Rights
Policy, too, provides additional support for the conclusion that
implementation of the Plan would not be prohibited by Title VI. For
example, the policy would allow for members of the public to notify and
file a formal complaint with the State that an alleged violation of
Title VI is occurring ``during the administration of [the State's]
programs.'' \21\ Taken together, these various State processes and
initiatives support the conclusion that the State provided necessary
assurances that implementation of the plan would not be prohibited by
Title VI.
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\21\ Title VI Supplement, p. 8.
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The commenter points to one primary substantive deficiency in the
Plan that they believe indicates the State has not demonstrated
compliance with CAA section 110(a)(2)(E)(i): The commenter claims that
ammonia is a major precursor of PM<INF>2.5</INF> and that the policy
decision ``to decline to regulate ammonia implicates disparate
treatment and/or disparate impact, yet CARB provides no necessary
assurances that this policy decision does not violate Title VI.'' The
EPA's proposed and final actions, based upon the State's SIP
submissions, reflect the EPA's agreement that ammonia is not a
significant precursor of PM<INF>2.5</INF> for the purposes of the 1997
annual PM<INF>2.5</INF> NAAQS in the San Joaquin Valley. As described
in more detail in Section II.A.3 of this document, this final
determination comes following the EPA's review of the State's submittal
and request for additional information to support the State's decision
not to regulate ammonia for this NAAQS, as well as the EPA's review of
the exhibits and attachments from the commenter. Included in the
State's submittal and March 2023 Ammonia Supplement are estimates of
the level of emissions reductions possible with a suite of potential
ammonia control measures, justifications for why many of these measures
are not feasible or are already being implemented in the area, and
ultimately, why the State has chosen to focus on reducing direct
PM<INF>2.5</INF> and NO<INF>X</INF> to reduce PM<INF>2.5</INF>
concentrations in the San Joaquin Valley air basin. The EPA believes
the technical information provided by the State to support its decision
not to regulate ammonia for purposes of the 1997 annual
PM<INF>2.5</INF> NAAQS provides adequate necessary assurances that the
implementation of this Plan will not be prohibited by Title VI.
The EPA recognizes that the San Joaquin Valley area has previously
struggled to attain the 1997 annual PM<INF>2.5</INF> NAAQS and that the
Demographic Index analysis the EPA completed as a part of the proposed
approval indicates the area includes communities of color and low-
income populations above the national average. However, as explained in
this response and in our proposal, the EPA believes the information in
the record contains adequate necessary assurances consistent with CAA
section 110(a)(2)(E)(i). This analysis is based in part on technical
analyses such as that the modeling in the State's and District's Plan
shows attainment for these NAAQS by the applicable attainment date and
that the control strategy for PM<INF>2.5</INF> takes into consideration
the unique atmospheric conditions in the San Joaquin Valley air basin
in which the PM<INF>2.5</INF> response to reductions in ammonia
emissions would be relatively small. Thus, based on the existing
technical record before the EPA, we find that the State has adequately
provided necessary assurances that the implementation of the Plan is
consistent with CAA section 110(a)(2)(E)(i).
Comment 1.B: Next, CCEJN contends that the policies cited by CARB
in its Title VI supplement to support its necessary assurances, e.g.,
AB 617, community air monitoring networks, and CARB's Civil Rights
Policy, are not enforceable parts of the submitted Plan (pursuant to
CAA section 110(a)(2)(A)), cannot lead to credited emissions reductions
for SIP purposes, and thus cannot be relied upon as necessary
assurances.
Response 1.B: The EPA disagrees that necessary assurances must
themselves be enforceable parts of a plan. While in some instances a
state may submit additional enforceable measures as a component of
necessary assurances, the EPA believes that this is not a requirement.
The commenter cites the CAA section 110(a)(2)(A) requirement that plans
include enforceable emissions limitations and other control measures as
a basis for the assertion that necessary assurances must be enforceable
and part of the plan. The EPA agrees that nonattainment plans
[[Page 86584]]
must contain enforceable emissions limitations and other control
measures--but this does not mean that CAA section 110(a)(2)(E)(i)
necessary assurances must themselves be emissions limitations or
control measures. The EPA interprets section 110(a)(2)(E)(i) as
allowing an ``assurance'' to include an analysis of the plan. In this
context, a state providing adequate information to the EPA to provide
necessary assurances that the state is not prohibited by Title VI from
carrying out the plan in the SIP submission is sufficient. In the
proposal action, the EPA explained the rationale for this approach,
including citing to relevant case law finding that ``what assurances
are `necessary' is left to the EPA's discretion.'' \22\ This is
consistent with necessary assurances that the EPA requires when needed
for other issues related to section 110(a)(2)(E)(i). For example,
states also provide necessary assurances concerning the adequacy of
personnel, funding, and state law authority to implement a SIP
submission, and the EPA generally relies on facts, analyses, and other
forms of assurances from the state for these purposes--not enforceable
measures (that is, the EPA generally does not require SIP-approved
rules that are incorporated by reference into the Code of Federal
Regulations to provide such necessary assurances). There may be
circumstances under which the EPA would expect a state to provide a
state law provision for inclusion into the SIP in order to provide such
necessary assurances for these other requirements, but this is not
generally the case.
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\22\ 88 FR 45276, 45320. See also, El Comit[eacute] para el
Bienestar de Earlimart et al. v. EPA, 786 F.3d 688 (9th Cir. 2015).
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Where a necessary assurances analysis concludes that additional
enforceable measures are needed, a state would also include such new
measures in the SIP submission, but necessary assurances need not
necessarily themselves constitute such measures, as the commenter
suggests. In this case, the EPA has concluded that the information
provided by the State concerning its existing policies and programs
provides adequate necessary assurances that the State's implementation
of the SIP submissions at issue would not be prohibited by Title VI.
2. Emissions Inventory
Comment 2.A: CCEJN states that the soil NO<INF>X</INF> emissions
estimate of approximately 10 tons per day (tpd) used in the modeling
emissions inventory was dubious when the State submitted the Plan in
2018 and that the estimate is clearly inaccurate based on more recent
studies, which the commenter claims suggest soil NO<INF>X</INF> may
contribute as much as 100 tpd to total NO<INF>X</INF> emissions. The
commenter also asserts that studies suggest that soil NO<INF>X</INF>
emissions are likely driven primarily by agriculture and therefore
should be considered anthropogenic. To support these assertions, the
commenter references Exhibit A to the letter (``Exhibit A''), which
summarizes 10 studies from 2015-2023, from which the author concludes
that 9 of the studies indicate that standard soil NO<INF>X</INF>
parameterizations underestimate agricultural soil NO<INF>X</INF>
emissions by a factor of 2 to 10.
CCEJN further states that ``[t]he state has acknowledged that its
existing inventory may be outdated, and it has begun the process of
studying NO<INF>X</INF> emissions from soil in order to update the
inventory for future submissions to EPA,'' but that its use of the
existing inventory in the interim ``. . . is unlawful because it is
based exclusively on inertia, and `the EPA cannot simply recite
``scientific uncertainty'' to evade its statutory duty to update
regulations' '' (citing A Cmty. Voice v. EPA, 997 F.3d 983, 994 (9th
Cir. 2021)). The commenter suggests that ``[i]nstead, the state must
make an updated good faith estimate--if not a perfect estimate--of
emissions, taking into account that the Clean Air Act is `preventative'
and `precautionary' in nature,'' and asserts that such estimate would
undoubtedly be higher than the estimate in the current inventory and
would identify significant anthropogenic soil NO<INF>X</INF> emissions.
Based on its analysis, CCEJN concludes that the EPA must disapprove
the inventory because it is neither ``current'' nor ``accurate'' and
that failure to do so is arbitrary and capricious.
Response 2.A: The EPA acknowledges the information provided by
CCEJN in its comments and in the studies described in Exhibit A
suggesting that soil NO<INF>X</INF> emissions may be higher than have
typically been estimated in the past. The studies cited by the
commenter rely on variants of several emissions estimation approaches,
including efforts to achieve better agreement between air quality
models and satellite measurements, and to correlate satellite
measurements over croplands with the expected soil temperature and
moisture dependence of soil NO<INF>X</INF> emissions. While most of the
studies cited by the commenter were published after the State developed
the emissions and conducted the modeling for the 2018 PM<INF>2.5</INF>
Plan upon which the 15 [micro]g/m\3\ SIP Revision is based, the EPA
would not characterize the studies as providing ``updated'' emissions
that would make the estimates in the 2018 PM<INF>2.5</INF> Plan
obsolete, as suggested by the commenter. Rather, as discussed further
in the remainder of this response, we find that some recent studies
provide evidence that soils are an important NO<INF>X</INF> source, and
several provide alternative estimates of soil NO<INF>X</INF> emissions
using various approaches.
The EPA agrees that there is evidence suggesting soil
NO<INF>X</INF> emissions may be higher than previously estimated but
disagrees with the characterization in Exhibit A that 9 out of the 10
studies conclude that California soil NO<INF>X</INF> is underestimated
by a factor of 2 or more. That was the conclusion of two of the
studies, those described in Almaraz et al. (2018) \23\ and Sha et al.
(2021).\24\ Luo et al. (2022) \25\ did not opine on how their estimate
compares with prior estimates, though the authors did provide an
estimate that the author of Exhibit A notes implies that prior
estimates are largely underestimated. The other studies provide
evidence consistent with soil NO<INF>X</INF> as an important source or
suggest a stronger temperature dependence for soil NO<INF>X</INF>
emissions compared to previous approaches.
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\23\ Almaraz et al. (2018), Agriculture is a major source of
NO<INF>X</INF> pollution in California, Science Advances, 4(1),
2018, doi:10.1126/sciadv.aao3477.
\24\ Sha et al. (2021), Impacts of soil NO<INF>X</INF> emission
on O<INF>3</INF> air quality in rural California, Environmental
Science & Technology, 55(10), 7113-7122, doi:10.1021/
acs.est.0c06834.
\25\ Luo et al. (2022), Integrated Modeling of U.S. Agricultural
Soil Emissions of Reactive Nitrogen and Associated Impacts on Air
Pollution, Health, and Climate, Environmental Science & Technology,
56 (13), 9265-9276. doi:10.1021/acs.est.1c08660.
---------------------------------------------------------------------------
While there is evidence suggesting soil NO<INF>X</INF> emissions
may be higher than previously estimated, there are conflicting
conclusions in the literature. Because the inventories in the SJV
PM<INF>2.5</INF> Plan reflect the State's best estimate based on the
information available at the time the Plan was developed, the EPA does
not believe a change in the soil NO<INF>X</INF> emissions estimation
approach relied on in the SJV PM<INF>2.5</INF> Plan is warranted at
this time. There is a need to reconcile the disagreement among studies
by examining the differing assumptions, techniques, data sources,
locations, and time periods covered. Such further examination may also
help resolve the substantial uncertainty and variability of the
proportion of soil NO<INF>X</INF> emissions that can be attributed to
anthropogenic sources such as agricultural fertilizer application.
The EPA further disagrees with CCEJN's assertion that the State
relies
[[Page 86585]]
on the soil NO<INF>X</INF> emissions estimates in its existing
inventory due to ``inertia.'' As noted by the commenter, the State has
effectively acknowledged that its methodology for estimating soil
NO<INF>X</INF> emissions may need to be updated when it shared its
plans to convene a subject matter expert review panel to assess the
state of the science on soil NO<INF>X</INF> emissions and make
recommendations for future estimates.\26\ These efforts indicate that
the State is taking the issue seriously and attempting to address it,
as acknowledged by the commenter. However, in exploring possible
improvements to its soil NO<INF>X</INF> estimation approach, the State
is not disavowing the approach used in the SJV PM<INF>2.5</INF> Plan,
nor is there a widely accepted soil NO<INF>X</INF> emissions inventory
approach that the State is willfully refusing to use. Depending on the
outcomes of the review panel's work, the State may find that its
current approach provides the best estimate and retain such approach,
or the State may determine that an alternative approach would provide a
more accurate estimate and use such approach moving forward.
---------------------------------------------------------------------------
\26\ SJVUAPCD, 2023 PM<INF>2.5</INF> Plan for Attainment of the
Federal 2012 Annual PM<INF>2.5</INF> Standard, Public Workshop,
slide 16, <a href="http://www.valleyair.org/Workshops/postings/2023/05-11-23_PM25/presentation.pdf">http://www.valleyair.org/Workshops/postings/2023/05-11-23_PM25/presentation.pdf</a>. (A recording of the workshop is also cited
in the comment letter in fn. 39).
---------------------------------------------------------------------------
For the SJV PM<INF>2.5</INF> Plan, the State used the
DeNitrification[hyphen]DeComposition model (DNDC) to estimate the 10
tpd of soil NO<INF>X</INF> emissions used in the modeling.\27\ The
approach is supported by research conducted in the same time frame as
studies cited by the commenter and therefore the EPA does not consider
the State's approach to be outdated. The emissions inventory in the
Plan was among the work that led to the paper by Guo et al. (2020),\28\
which was cited in Exhibit A as among the recent research on soil
NO<INF>X</INF>. Guo et al. (2020) did not find that soil NO<INF>X</INF>
emissions are significantly underestimated in the State's emissions
inventory. Rather, the study examined evidence from satellite
retrievals and ground-based measurements that indicate that the State's
approach provides an accurate emissions inventory for the San Joaquin
Valley. The EPA believes that the DNDC-based soil NO<INF>X</INF>
emissions used in the modeling are a good faith estimate consistent
with the State's current view of the state of the science, and that the
State's estimate is acceptable for use in the modeling emissions
inventory in the SJV PM<INF>2.5</INF> Plan for the 1997 annual
PM<INF>2.5</INF> NAAQS.
---------------------------------------------------------------------------
\27\ Email dated May 26, 2020, from Jeremy Avise, CARB, to Scott
Bohning, EPA Region IX, Subject: ``Soil NO<INF>X</INF> in ARB's
modeling'', with attached poster ``Preliminary Assessment of Soil
NO<INF>X</INF> Emissions from Agricultural Cropland in the San
Joaquin Valley''; ``Estimating Nitrogen Emissions from California's
Agricultural Lands'', March 5, 2019, presentation by Mike
Fitzgibbon, CARB, at 2019 California Climate & Agriculture Summit,
<a href="https://calclimateag.org/2019summit/">https://calclimateag.org/2019summit/</a>.
\28\ Guo et al. (2020), Assessment of Nitrogen Oxide Emissions
and San Joaquin Valley PM<INF>2.5</INF> Impacts From Soils in
California, Journal of Geophysical Research: Atmospheres, 125(24),
doi:10.1029/2020JD033304. Note that a web document with a DOI or
Digital Object Identifier, such as 10.1029/2020JD033304, may be
found via prefixing <a href="http://doi.org/">doi.org/</a> to the doi, as in: <a href="https://doi.org/10.1029/2020JD033304">https://doi.org/10.1029/2020JD033304</a>.
---------------------------------------------------------------------------
The EPA acknowledges that there is evidence that soil
NO<INF>X</INF> emissions have historically been underestimated,
including evidence from some studies finding that satellite
observations of column NO<INF>2</INF> (total amount of NO<INF>2</INF>
in a vertical column of the atmosphere) indicate that soil
NO<INF>X</INF> emissions are higher than predictions by photochemical
models using emissions estimates from older soil NO<INF>X</INF>
parameterizations. The commenter describes some of such evidence in
Exhibit A. However, the case for soil NO<INF>X</INF> emissions being
significantly underestimated in the San Joaquin Valley is not as
settled as CCEJN's comment implies. The studies cited by the commenter
differ in the questions they attempt to address, their assumptions and
analytical approaches, their data analysis techniques and metrics, and
in the differing environmental conditions in the locations and time
periods they cover.
In the remainder of this response, we identify statements from the
ten research papers listed in Exhibit A to show that their support for
a substantially greater soil NO<INF>X</INF> emissions for the San
Joaquin Valley is not definitive, and that there is not an agreed upon
method to estimate a missing increment of emissions if one is in fact
needed. Note that these points are not meant to discredit the work of
the respective authors but rather to illustrate that there are varying
factors that require greater investigation to determine the magnitude
of soil NO<INF>X</INF> emissions in the San Joaquin Valley. Given these
complicating factors and uncertainties, the EPA requests that CARB and
the District continue their work to examine their current methodology
for estimating soil NO<INF>X</INF> emissions, and as appropriate,
revise their methodology based on the findings of the expert review
panel and the latest available research.
Oikawa et al. (2015) \29\ measured NO<INF>X</INF> emissions from
sorghum plots after applying fertilizer, and explored the effect of
higher soil NO<INF>X</INF> emissions on the performance of an air
quality model by comparing the model results with satellite
NO<INF>2</INF> column observations and surface measurements. The study
authors concluded that soil NO<INF>X</INF> emissions would need to be
10 or more times higher to match observations. However, surface
measurements were not consistently underestimated in the model, and
increasing emissions in the model to match the satellite retrievals led
to overestimates in emissions at the surface derived from measurements
of soil NO<INF>X</INF> emissions fluxes. The paper also noted that
global estimates of soil NO<INF>X</INF> emissions from other studies
vary by a factor of three (ranging from 9 to 27 Tg per year),
indicating a high level of uncertainty. The study conclusions suggest
that soil NO<INF>X</INF> emissions are largely underestimated but the
magnitude of the underestimate is not quantified.
---------------------------------------------------------------------------
\29\ Oikawa et al. (2015), Unusually high soil nitrogen oxide
emissions influence air quality in a high-temperature agricultural
region. Nat. Commun., 6:8753, doi:10.1038/ncomms9753.
---------------------------------------------------------------------------
Parrish et al. (2017) \30\ focuses on understanding trends in ozone
design values, noting a difference in the San Joaquin Valley trend in
comparison with other California air basins. The authors note that the
difference may partially be accounted for by the higher agricultural
activity in the Valley, for which controls have not been implemented as
extensively as for other anthropogenic sources. While this explanation
could also hold for agricultural soil NO<INF>X</INF>, that particular
issue is not explored.
---------------------------------------------------------------------------
\30\ Parrish et al. (2017), Ozone Design Values in Southern
California's Air Basins: Temporal Evolution and U.S. Background
Contribution. J. Geophys. Res. Atmos., 122, 11166-11182,
doi:10.1002/2016JD026329.
---------------------------------------------------------------------------
Exhibit A cites Kleeman et al. (2019) \31\ as providing evidence of
a missing source of NO<INF>X</INF> emissions that could help correct a
``consistent underprediction'' in nitrate concentrations. The EPA
believes this underprediction was overstated. For the January average
of the three model years reported, there was a modest underprediction
of nitrate in the model base cases without soil NO<INF>X</INF> compared
to a somewhat larger overprediction when soil NO<INF>X</INF> emissions
were added; whereas for the 2010 model year, nitrate was overpredicted
in the base case and the overprediction was worsened in the
[[Page 86586]]
soil NO<INF>X</INF> case.\32\ In the conclusion, the authors state that
``further research is required to more accurately estimate winter
emissions rates of soil NO<INF>X</INF> and to account for year-to-year
variations driven by changes in meteorological conditions, fertilizer
application rates, and irrigation practices,'' and that the tests
conducted ``do not definitely prove that the missing emissions source
is indeed fertilized agricultural soils. Future measurements should be
made in the rural portions of the SJV to further test the hypothesis
that soil NO<INF>X</INF> emissions are a significant factor in the air
quality cycles within the region.'' \33\ The EPA interprets such
conclusions as an acknowledgement that additional research is needed,
with a focus on wintertime conditions when San Joaquin Valley
PM<INF>2.5</INF> concentrations are highest.
---------------------------------------------------------------------------
\31\ Kleeman, M., A. Kumar, and A. Dhiman, ``Investigative
Modeling of PM<INF>2.5</INF> Episodes in the San Joaquin Valley Air
Basin during Recent Years'' (CARB Contract No. 15-301, 2019),
available at <a href="https://ww2.arb.ca.gov/sites/default/files/classic/research/apr/past/15-301.pdf">https://ww2.arb.ca.gov/sites/default/files/classic/research/apr/past/15-301.pdf</a>.
\32\ Id. at 60 and 63.
\33\ Id. at 77.
---------------------------------------------------------------------------
The author of Exhibit A summarizes a result from Chen et al.
(2020),\34\ noting acceptable PM<INF>2.5</INF> model performance
despite overly low atmospheric mixing heights. But the author goes on
to suggest that overly low mixing heights should have led to
PM<INF>2.5</INF> overpredictions; the good performance therefore may
imply that the PM<INF>2.5</INF> precursor emissions were too low. The
study also found that rural site column NO<INF>2</INF> was
underpredicted by 25 percent relative to NO<INF>2</INF> columns derived
from surface-based measurements, suggesting that soil NO<INF>X</INF>
emissions are underestimated. Thus, the study authors acknowledge that
soil NO<INF>X</INF> emissions may need to be further examined. However,
they also note good agreement between modeled column NO<INF>2</INF> and
the NO<INF>2</INF> columns derived from surface-based measurements at
the urban sites of Fresno and Bakersfield, where NO<INF>2</INF> is
double that of the rural sites, and state that ``it is unlikely that
NO<INF>X</INF> emissions from croplands are comparable to mobile
sources'' (the main source of NO<INF>X</INF> emissions). That is, the
NO<INF>X</INF> emissions increase that would be needed to increase the
model predictions by 25 percent for the low-NO<INF>2</INF> rural sites
is unlikely to be comparable to the NO<INF>X</INF> emissions driving
the high NO<INF>2</INF> urban sites. This finding supports further
exploration of soil NO<INF>X</INF> emissions, and a possible
underestimate, but does not imply a large underestimate in soil
NO<INF>X</INF> emissions.
---------------------------------------------------------------------------
\34\ Chen et al. (2020), Modeling air quality in the San Joaquin
valley of California during the 2013 Discover-AQ field campaign,
Atmospheric Environment: X, Volume 5, January 2020, 100067,
doi:10.1016/j.aeaoa.2020.100067.
---------------------------------------------------------------------------
Wang et al. (2021) \35\ explored the relatively modest downward
trend in satellite column NO<INF>2</INF> measurements after 2009, as
compared to the steady decrease in anthropogenic NO<INF>X</INF>
emissions, and the role of soil NO<INF>X</INF> emissions in this
apparent discrepancy. They found better model agreement with satellite
column NO<INF>2</INF> when they increased the temperature
responsiveness of their soil NO<INF>X</INF> emissions estimates,
especially at high temperatures. This change also improved the
correlation between modeled column NO<INF>2</INF> and satellite column
NO<INF>2</INF> in the central United States. This correlation is an
important finding, implying soil NO<INF>X</INF> emissions may be
underestimated. However, it should be noted that in absolute terms,
even without soil NO<INF>X</INF>, the model simulation overpredicted
the NO<INF>2</INF> concentration relative to the satellite retrieval.
The authors acknowledge that there are many reasons why the predictions
might not match the observations. The authors cite an uncertainty of 35
percent in the satellite NO<INF>2</INF> columns, and the uncertainty in
the satellite retrieval encompasses all of the results, from the zero
soil NO<INF>X</INF> scenario to the increased soil NO<INF>X</INF>
scenario.\36\ The EPA views this as a large enough uncertainty to limit
confidence in at least some of the study conclusions.
---------------------------------------------------------------------------
\35\ Wang et al (2021), Improved modelling of soil
NO<INF>X</INF> emissions in a high temperature agricultural region:
role of background emissions on NO<INF>2</INF> trend over the US,
Environ. Res. Lett., 16, doi:10.1088/1748-9326/ac16a3.
\36\ Id. at Figure 3.
---------------------------------------------------------------------------
Wang et al. (2021) states that the downward trend in the satellite
column NO<INF>2</INF> is smaller than the downward trend in
anthropogenic NO<INF>X</INF> emissions, and that the discrepancy is
greater for the central U.S. than for the eastern or western U.S. Since
the San Joaquin Valley is in the west, the EPA interprets this result
as indicating that there is less of a potential need for increases in
soil NO<INF>X</INF> emissions estimates in the San Joaquin Valley
relative to the central U.S. to resolve the discrepancy. The authors
also cited another study in which the apparent discrepancy between the
trends in modeled versus surface-level ambient measurements (as opposed
to the satellite retrieval) was found to be within the bounds of the
uncertainty of the ambient measurements. The study provides a strong
impetus for exploring soil NO<INF>X</INF> emissions and their potential
increased rate at higher temperatures but does not provide evidence
that soil NO<INF>X</INF> emissions are significantly underestimated in
the San Joaquin Valley.
To evaluate the human health and climate benefits of reducing
reactive nitrogen emissions, Luo et al. (2022) \37\ used the Fertilizer
Emission Scenario Tool for CMAQ (FEST-C) to generate soil
NO<INF>X</INF> emissions estimates for every U.S. county, including
those counties in the San Joaquin Valley. Exhibit A notes that the
FEST-C-derived San Joaquin Valley county total emissions of soil
NO<INF>X</INF> is 100 tpd compared to CARB's emissions inventory for
all anthropogenic NO<INF>X</INF> which amounts to roughly 200 tpd. The
study used a different emissions model than the model used by CARB,
underscoring the need to explore why emissions models yield such
different results. The study did not validate the model-derived
NO<INF>2</INF> predictions using satellite retrievals or ground-based
measurements, so it does not provide direct evidence that soil
NO<INF>X</INF> emissions are underestimated for the San Joaquin Valley.
---------------------------------------------------------------------------
\37\ Luo et al. (2022), Integrated Modeling of U.S. Agricultural
Soil Emissions of Reactive Nitrogen and Associated Impacts on Air
Pollution, Health, and Climate, Environmental Science & Technology,
2022, 56 (13), 9265-9276. doi:10.1021/acs.est.1c08660.
---------------------------------------------------------------------------
Wang et al. (2023) \38\ explored trends in satellite column
NO<INF>2</INF> and ground level measurements, and the role of lightning
and soil NO<INF>X</INF> in explaining spatial and temporal
distributions of NO<INF>2</INF>. Among other results, they found that
temperature and soil moisture, which are important drivers of soil
NO<INF>X</INF> emissions, were highly correlated with satellite column
NO<INF>2</INF> in rural areas of California, including crop lands. This
suggests soil NO<INF>X</INF> is an important source of NO<INF>X</INF>
near crop lands. The study examined trends in NO<INF>X</INF> over time
rather than attempting to quantify soil NO<INF>X</INF> emissions and
therefore does not provide direct evidence that soil NO<INF>X</INF>
emissions are underestimated for the San Joaquin Valley.
---------------------------------------------------------------------------
\38\ Wang et al (2023), Satellite NO<INF>2</INF> trends reveal
pervasive impacts of wildfire and soil emissions across California
landscapes, Environ. Res. Lett., 18, doi:10.1088/1748-9326/acec5f.
---------------------------------------------------------------------------
Finally, three studies cited in Exhibit A, Almaraz et al. (2018),
Guo et al. (2020), and Sha et al. (2021), provided estimates of soil
NO<INF>X</INF> emissions in California. Almaraz et al. (2018) \39\
estimated soil NO<INF>X</INF> emissions using a top-down approach based
on aircraft measurements as well as the Integrated Model for the
Assessment of the Global Environment (IMAGE) soil model. Guo et al.
(2020) \40\ compared satellite measurements of NO<INF>2</INF> with CMAQ
air quality model predictions using soil
[[Page 86587]]
NO<INF>X</INF> emissions from the DNDC soil model. Sha et al. (2021)
\41\ conducted a similar measurement-model comparison but using the
Weather Research and Forecasting model coupled with Chemistry (WRF-
Chem) air quality model and the Berkeley Dalhousie Iowa Soil NO
Parameterization (BDISNP) soil model. The IMAGE and BDISNP models are
empirical or parametric models. They rely on emissions factors that are
derived from empirical measurements and that may vary by land use,
precipitation, and temperature, but do not incorporate algorithms that
reflect the underlying physical principles. The DNDC model used in Guo
at al. (2020) and in the State's emissions inventory is a
biogeochemical or mechanistic model. It also uses measurements for
validation but includes detailed consideration of the individual
physical and biological processes in soils that lead to NO<INF>X</INF>
emissions and their dependence on factors like the soil's various
nitrogen- and carbon-containing species, moisture, and temperature.
---------------------------------------------------------------------------
\39\ Almaraz et al. (2018), Agriculture is a major source of
NO<INF>X</INF> pollution in California, Science Advances, 4(1),
2018, doi:10.1126/sciadv.aao3477.
\40\ Guo et al. (2020), op. cit.
\41\ Sha et al. (2021), Impacts of soil NO<INF>X</INF> emission
on O<INF>3</INF> air quality in rural California, Environmental
Science & Technology, 55(10), 7113-7122, doi:10.1021/
acs.est.0c06834.
---------------------------------------------------------------------------
Comparisons between the results described in Almaraz et al. (2018),
Guo et al. (2020), and Sha et al. (2021) show large disagreements.\42\
Almaraz et al. (2018) estimated that soil NO<INF>X</INF> emissions from
fertilized croplands account for 32 percent of California
NO<INF>X</INF> emissions, Sha et al. (2021) estimated soil
NO<INF>X</INF> emissions comprise 40.1 percent of California's total
NO<INF>X</INF> emissions, while Guo et al. (2020) estimate that soil
NO<INF>X</INF> emissions are only 1.1 percent of California
anthropogenic NO<INF>X</INF> emissions. (As noted earlier in this
response, the DNDC model emissions estimation work performed for the
Guo et al. (2020) study was also the basis for the State's soil
NO<INF>X</INF> emissions estimate.) The fraction of nitrogen applied as
fertilizer released as NO<INF>X</INF> to the atmosphere was estimated
by Almaraz et al. (2018) to be 15 percent, while 7 other studies
reviewed by Guo et al. (2020) estimate it to be 2 percent or less.
Furthermore, there is an additional possible discrepancy between the
work described in Wang et al. (2021) \43\ and Wang et al. (2023),\44\
and the results in Guo et al. (2020). The former two found correlations
between satellite-derived column NO<INF>2</INF> over agricultural areas
and modeled soil emissions, suggesting soil NO<INF>X</INF> as a driver
of NO<INF>2</INF> there. However, using correlations and ratios of
NO<INF>X</INF> to CO among monitoring sites, and satellite column
NO<INF>2</INF> retrievals, Guo et al. (2020) found little difference
between the diurnal and seasonal temporal variation at rural sites
compared to urban sites, consistent with a larger contribution of
emissions from urban sources rather than rural soils. Higher soil
NO<INF>X</INF> emissions would increase summer emissions more in rural
areas than in urban areas.
---------------------------------------------------------------------------
\42\ The EPA also compared these studies in approving
California's 2020 emissions inventory submittal. 87 FR 59015, 59017-
59019 (February 9, 2022).
\43\ Wang et al. (2021), op. cit.
\44\ Wang et al. (2023), op. cit.
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Despite widely differing estimates of the relative portion of
California's NO<INF>X</INF> emissions inventories attributable to soil
NO<INF>X</INF> in Almaraz et al. (2018), Sha et al. (2021), and Guo et
al. (2020), each study reported high agreement between its modeled and
its observed soil NO<INF>X</INF> emissions. Reconciling the differences
in input data used in the models, such as fertilizer and irrigation
amounts and timing; other inputs to the air quality models; and data
analysis techniques would be necessary for a process-based
understanding of the differences in the contribution and magnitude of
soil NO<INF>X</INF> emissions estimates between models. There is also a
need for additional measurements of soil NO<INF>X</INF> emissions
fluxes for various locations and conditions to help develop and
validate soil models.
The various authors acknowledge considerable uncertainty in their
work. While Almaraz et al. (2018) suggest that soil NO<INF>X</INF>
emissions may be significantly underestimated using current techniques,
the study acknowledges the limited number of surface measurements that
were available for purposes of validating the model results and that,
where observations exist, there is a large range in observed values due
to varying soil conditions (e.g., relating to temperature, moisture,
and fertilizer application). The ``top-down'' NO<INF>X</INF> emissions
estimates derived from aircraft measurements relied upon in the study
also reflect a significant degree of uncertainty, reported at 190 tpd
plus or minus 130 tpd, i.e., plus or minus 68 percent. The authors
acknowledge the limited number of surface measurements that were
available for purposes of comparing with the model results, the
difficulty in comparing the model results with the observations, and
the need for more field measurements. Guo et al. (2020) stated that
obtaining an emissions factor correlating NO<INF>X</INF> emissions to
fertilizer application from the presently available data in various
studies (including Almaraz et al. (2018)) would be ``difficult or
impossible'' due to the sparseness of data collected in terms of
sampling length, sampling frequency, and the episodic nature of
nitrogen gases from soil.
Most of the discussion herein concerns the varying estimates of
overall total soil NO<INF>X</INF> emissions. However, how those
emissions are distributed in time and space are also of great
importance for understanding the effect of NO<INF>X</INF> emissions on
ambient PM<INF>2.5</INF> concentrations. PM<INF>2.5</INF>
concentrations in the San Joaquin Valley are highest in the cool, moist
winter, whereas soil NO<INF>X</INF> emissions are highest in the warm,
dry summer. For modeling PM<INF>2.5</INF> concentrations, it is
especially important that the soil NO<INF>X</INF> approach that is used
performs well under wintertime conditions. Also important is how the
approach reflects soil composition, soil management practices, and
fertilizer application, each of which vary in time and space. Adopting
a different soil NO<INF>X</INF> emissions estimation approach is not a
matter of simply replacing one estimate of total soil NO<INF>X</INF>
with another. Rather, it requires ensuring that the approach accurately
reflects the spatial and temporal variation of the many factors
affecting emissions and of the emissions themselves.
In light of the uncertainties and disagreements among studies, the
EPA does not believe that the available research provides sufficient
certainty about the magnitude and proportion of soil NO<INF>X</INF>
emissions to warrant a revision to the State's inventory for purposes
of the SJV PM<INF>2.5</INF> Plan.\45\ The EPA is not convinced that any
revised estimate developed by the State at this time would be
verifiably more accurate than the inventory in the Plan. A revision to
the State's inventory approach may be warranted in the future pending
the State's ongoing work in this area and the most up-to-date
understanding of soil NO<INF>X</INF> emissions, as discussed earlier in
this response. The EPA encourages the State to continue its ongoing
work to convene a subject matter expert review panel to assess the
state of the science on soil NO<INF>X</INF> emissions, to keep abreast
of the latest research, and to update its estimation methodologies, as
appropriate. However, for purposes of the SJV PM<INF>2.5</INF> Plan for
the 1997 annual PM<INF>2.5</INF> NAAQS that is the subject of this
action, we find that the State relied on a reasonable methodology that
is supported by the research literature. Thus, we conclude that the
State
[[Page 86588]]
provided an accurate, up-to-date emissions inventory for
NO<INF>X</INF>.
---------------------------------------------------------------------------
\45\ The EPA reached a similar conclusion in approving
California's 2020 emissions inventory submittal. 87 FR 59015, 59017-
59019 (February 9, 2022).
---------------------------------------------------------------------------
Comment 2.B: Regarding the motor vehicle emissions modeling, CCEJN
points to a previous statement from the EPA, saying that ``it could
approve an outdated inventory so long as the inventory was built using
the `latest EPA-approved' emission model `at the time [the State]
developed the submission.' '' The commenter asserts that the EPA now
``proposes to abandon both the statutory text and the already-lax
requirement to use the most recent EPA-approved model,'' by allowing
the State to rely on a model that is a decade old when two more recent
models are available, one of which (EMFAC2017) shows higher attainment-
year emissions of both NO<INF>X</INF> and PM<INF>2.5.</INF> CCEJN
contends that the State and the EPA speculate that the higher values
would not affect the attainment demonstration. However, CCEJN asserts
that the effect on the attainment demonstration is unknown and that it
is also unknown what the effects would be on the precursor
demonstration, which the commenter claims relies on low estimates of
NO<INF>X</INF> in 2023 to conclude that the State need not regulate
ammonia.
Finally, the commenter states that the ``EPA's decision to abandon
its recently adopted standard that inventories should be built using
the `latest EPA-approved' emission model is arbitrary and capricious,''
asserting that the EPA is ``simply resistant to the idea that a current
inventory must be used'' and has lost litigation over this issue
(citing Sierra Club v. EPA, 671 F.3d 955 (9th Cir. 2012)), and claiming
that ``. . .the agency is therefore bending over backwards to adopt
whatever standard will allow the state to continue to use the outdated
inventory.''
Response 2.B: The EPA disagrees with CCEJN's claims that we are
resistant to require, or have changed our position, that inventories
must be developed using the latest EPA-approved emissions model
available at the time the State developed the SIP submission and that
our proposed action to reaffirm the base year inventory is arbitrary
and capricious. As discussed in our proposal, the SJV PM<INF>2.5</INF>
Plan relies on much of the same technical information and analyses from
the 2018 PM<INF>2.5</INF> Plan, including the emissions
inventories.\46\ The EPA previously found, for purposes of the 1997
annual PM<INF>2.5</INF> NAAQS as well as other PM<INF>2.5</INF>
standards, that these inventories were based on the most current and
accurate information available to the State and District at the time
they were developing the 2018 PM<INF>2.5</INF> 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.\47\
Thus, as part of our prior action on the 2018 PM<INF>2.5</INF> Plan for
the 1997 annual PM<INF>2.5</INF> NAAQS, we approved the emissions
inventories as meeting the Serious area and CAA section 189(d)
requirements for the 1997 annual PM<INF>2.5</INF> NAAQS.\48\
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\46\ 88 FR 45276, 45279.
\47\ The EPA previously approved the emissions inventories in
the 2018 PM<INF>2.5</INF> Plan as they pertain to the Serious area
and 189(d) requirements for the 1997 annual PM<INF>2.5</INF> NAAQS
(86 FR 67329, November 26, 2021), the Serious area and 189(d)
requirements for the 1997 24-hour PM<INF>2.5</INF> NAAQS (87 FR
4503, January 28, 2022), the Serious area requirements for the 2006
24-hour PM<INF>2.5</INF> NAAQS (85 FR 44192, July 22, 2020), and the
Moderate area planning requirements for the 2012 annual
PM<INF>2.5</INF> NAAQS (86 FR 67343, November 26, 2021).
\48\ 86 FR 67329.
---------------------------------------------------------------------------
In the EPA's final action approving the base year inventories in
the 2018 PM<INF>2.5</INF> Plan for the 1997 annual PM<INF>2.5</INF>
NAAQS, the EPA addressed concerns raised by a commenter about the use
of EMFAC2014.\49\ The EPA discussed the timeline for the State's
submittal of the emissions inventories in the 2018 PM<INF>2.5</INF>
Plan relative to the EPA's approval of EMFAC2014 and EMFAC2017,
explaining that EMFAC2014 was the most current mobile source model
available for emissions inventory development purposes at the time the
State was developing the plan. Nevertheless, at that time, we
considered comparisons between EMFAC2014 and EMFAC2017 in the 2013 base
year as provided by CARB in its ``Staff Report, Proposed SIP Revision
for the 15 [micro]g/m\3\ Annual PM<INF>2.5</INF> Standard for the San
Joaquin Valley'' (``CARB Staff Report'').\50\ Based on our review of
the State's analysis, we concluded that the 2013 base year emissions
inventories in the 2018 PM<INF>2.5</INF> Plan were comprehensive,
accurate, and current, consistent with the requirements of CAA section
172(c)(3) and 40 CFR 51.1008.
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\49\ Id. at 67332-67334.
\50\ CARB, ``Staff Report, Proposed SIP Revision for the 15
[micro]g/m\3\ Annual PM<INF>2.5</INF> Standard for the San Joaquin
Valley,'' release date August 13, 2021.
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Given that the 15 [micro]g/m\3\ SIP Revision was submitted to the
EPA by the State as an ``administrative revision'' to the 2018
PM<INF>2.5</INF> Plan and relies on much of the same technical
information that was developed for the 2018 PM<INF>2.5</INF> Plan, the
State continued to rely on the previously approved emissions
inventories from the 2018 PM<INF>2.5</INF> Plan. However, to address
the most up-to-date information available, in addition to the EMFAC2017
model results noted earlier in this response, the State provided to the
EPA comparisons between the estimated annual NO<INF>X</INF> and
PM<INF>2.5</INF> emissions developed for the 2018 PM<INF>2.5</INF> Plan
using EMFAC2014 with those developed using the most recent EPA-approved
version of EMFAC, EMFAC2021.\51\ CARB's analysis included comparisons
between all three EMFAC models for both the 2020 RFP year and the 2023
attainment year.\52\ As the commenter correctly notes, model results
from EMFAC2017 indicate higher NO<INF>X</INF> and PM<INF>2.5</INF>
emissions in the 2023 attainment year than those derived for the same
year using EMFAC2014. However, EMFAC2021, which was the most recent
EPA-approved model at the time of the EPA's proposal,\53\ indicates
that NO<INF>X</INF> and PM<INF>2.5</INF> emissions in the 2023
attainment year are lower than those derived for the same year using
EMFAC2014.
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\51\ 88 FR 45276, 45284-45285.
\52\ Id.
\53\ The EPA approved the use of EMFAC2021 for use in SIP
development on November 15, 2022 (87 FR 68483).
---------------------------------------------------------------------------
As discussed in the EPA's technical support document (TSD) for our
proposal,\54\ the differences in emissions estimates for mobile sources
between the three EMFAC model versions correspond to differences of
approximately two percent or less of the regional emissions inventories
for PM<INF>2.5</INF> and NO<INF>X</INF> for the 2023 attainment
year.\55\ Using the sensitivity of the PM<INF>2.5</INF> design value
per tpd of emissions modeled by the State, the EPA assessed the effects
of the various EMFAC model version results on the attainment
demonstration in the Plan.\56\ Based on our technical analysis, we
determined that although the NO<INF>X</INF> and PM<INF>2.5</INF>
emissions estimates in the 2023 attainment year are higher in EMFAC2017
than in EMFAC2014, the effect on the PM<INF>2.5</INF> concentrations of
0.07 [micro]g/m\3\ is sufficiently small that the attainment
demonstration remains valid.\57\ Furthermore, more up-to-date emissions
data from EMFAC2021 show lower emissions of NO<INF>X</INF> and
PM<INF>2.5</INF> in the attainment year, indicating that the attainment
modeling results in the Plan derived using EMFAC2014 are conservative.
The same is true for the modeling for the precursor demonstration--the
lower NO<INF>X</INF> estimates derived using EMFAC2021 would produce
lower sensitivities of PM<INF>2.5</INF> to ammonia, since they would
increase the abundance of ammonia
[[Page 86589]]
relative to NO<INF>X</INF> (since particulate ammonium nitrate
formation would be less limited by, and so less sensitive to, the
amount of ammonia)<INF>.</INF> Therefore, the State's conclusions based
on their use of EMFAC2014 are conservative relative to if it had used
the most up-to-date EPA-approved model, EMFAC2021. Thus, we disagree
with the assertions that the effects of the various EMFAC versions on
the attainment demonstration and precursor demonstration are unknown
and find that reliance on the previously approved emissions inventories
is acceptable.
---------------------------------------------------------------------------
\54\ EPA, ``Technical Support Document, San Joaquin Valley
PM<INF>2.5</INF> Plan Revision for the 1997 Annual PM<INF>2.5</INF>
NAAQS,'' April 2023.
\55\ Id. at 53.
\56\ Spreadsheet ``EMFAC update effect on annual 1997 p.m.2.5
NAAQS attainment demonstration.xlsx,'' EPA Region IX, May 1, 2023.
\57\ Id.
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Finally, we also disagree with the commenter's assertion (citing
Sierra Club) \58\ that the EPA has lost litigation over the issue that
a current inventory must be used. In Sierra Club, the Ninth Circuit
remanded the EPA's March 2010 approval of an ozone attainment plan for
the San Joaquin Valley submitted in 2004, holding that the EPA's
failure to consider new emissions data that the State had submitted in
2007 as part of a separate ozone plan rendered the EPA's action
arbitrary and capricious under the Administrative Procedure Act.\59\
The decision in that case rested on the unreasonableness of the EPA's
failure to address the new emissions data. The court found the EPA's
action arbitrary and capricious because of its ``reliance on old data
without meaningful comment on the significance of more current compiled
data'' and concluded that ``it was unreasonable for EPA summarily to
rely on the point of view taken [in longstanding policy] without
advancing an explanation for its action based on `the facts found and
the choice made.' '' \60\
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\58\ Sierra Club v. EPA, 671 F.3d 955 (9th Cir. 2012).
\59\ Id. The court also noted that the EPA's action was
inconsistent with the court's holding in Ass'n of Irritated
Residents (AIR) v. EPA, 632 F.3d 584 (9th Cir. 2011) (amended and
superseded by Ass'n of Irritated Residents v. U.S. EPA, 686 F.3d
668, 671 (9th Cir. 2012)), which ``supports the proposition that if
new information indicates to EPA that an existing SIP or SIP
awaiting approval is inaccurate or not current, then, viewing air
quality and scope of emissions with public interest in mind, EPA
should properly evaluate the new information and may not simply
ignore it without reasoned explanation of its choice.'' Id. at 967.
\60\ Id. at 968 (citing Burlington Truck Lines v. United States,
371 U.S. 156, 168 (1962)).
---------------------------------------------------------------------------
For purposes of this action, the EPA has reviewed the emissions
data derived using more recent versions of the EMFAC model provided by
CARB, consistent with the holding in Sierra Club. Based on our
technical analysis of the latest information available described
earlier in this response, we determined that the precursor and
attainment demonstrations are valid. Thus, we continue to find that the
2013 base year inventories in the SJV PM<INF>2.5</INF> Plan for the
1997 annual PM<INF>2.5</INF> NAAQS satisfy 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 plan requirements, and to
find that the forecasted inventories provide an adequate basis for the
BACM, RFP, and the modeled attainment demonstration analyses in the
Plan.
3. Ammonia Precursor Demonstration
Comment 3: CCEJN states that the EPA must disapprove the ammonia
precursor demonstration based on considerations outlined in several
specific comments (summarized in Comments 3.A through 3.D that follow),
but also in several introductory remarks. In the introductory remarks,
the commenter appears to refer to the precursor demonstration's modeled
PM<INF>2.5</INF> responses to ammonia reductions for the 2020 analysis
year, some of which are above the 0.2 [micro]g/m\3\ EPA-recommended
contribution threshold for the 2012 annual PM<INF>2.5</INF> NAAQS in
the EPA's ``PM<INF>2.5</INF> Precursor Demonstration Guidance''
(``PM<INF>2.5</INF> Precursor Demonstration Guidance'').\61\ Based on
these model results, the commenter asserts that the State tacitly
acknowledges that ammonia assessments in previous PM<INF>2.5</INF>
plans, finding that ammonia does not contribute significantly to
PM<INF>2.5</INF> levels that exceed the 1997 annual PM<INF>2.5</INF>
NAAQS, were incorrect. The commenter concludes that these results
indicate that the State should have been regulating ammonia in the
recent past, and also that the State should err on the side of caution
and regulate ammonia now. Finally, CCEJN contends that not regulating
ammonia has led to greater ammonium nitrate PM<INF>2.5,</INF> thereby
implicating disparate treatment and disparate impacts, and that the
State has failed to provide necessary assurances that the policy
decision not to regulate ammonia complies with Title VI.
---------------------------------------------------------------------------
\61\ ``PM<INF>2.5</INF> 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.
---------------------------------------------------------------------------
Response 3: The EPA disagrees with the commenter's premise that the
modeled PM<INF>2.5</INF> responses for the 2020 analysis year indicate
that ammonia contributed significantly to PM<INF>2.5</INF> levels in
the past. Under the EPA's PM<INF>2.5</INF> Precursor Demonstration
Guidance, a response above the recommended contribution threshold
indicates a ``contribution,'' but additional information can be
considered in determining whether that response ``contributes
significantly.'' \62\ Such information may include, but is not limited
to, the amount by which the threshold is exceeded, studies to evaluate
specific atmospheric chemistry in the area, trends in ambient
speciation data and precursor emissions,\63\ and the general facts and
circumstances of the nonattainment area.\64\ In concluding that ammonia
does not contribute significantly, the State considered model responses
for the 2024 analysis year in addition to 2020, as well as other
additional information, as summarized in the EPA's February 2020
Precursor Technical Support Document.\65\ We do not believe that
viewing modeled responses to ammonia for specific years in isolation or
out of context is an adequate method for determining whether a
precursor contributes significantly to PM<INF>2.5</INF> levels.
---------------------------------------------------------------------------
\62\ PM<INF>2.5</INF> Precursor Demonstration Guidance, pp. 17-
19.
\63\ Id.
\64\ Id. at 14; 40 CFR 51.1006(a)(1)(ii).
\65\ ``Technical Support Document, EPA Evaluation of
PM<INF>2.5</INF> Precursor Demonstration, San Joaquin Valley
PM<INF>2.5</INF> Plan for the 2006 PM<INF>2.5</INF> NAAQS,''
February 2020.
---------------------------------------------------------------------------
Additionally, the EPA does not agree that prior precursor
assessments should be considered erroneous based on the analysis in a
newer plan, particularly when the more recent plan uses different
criteria for assessing precursor significance. Previous plans for the
1997 annual PM<INF>2.5</INF> NAAQS in the San Joaquin Valley, like the
ones mentioned by the commenter, predated the 2016 ``Fine Particulate
Matter National Ambient Air Quality Standards: State Implementation
Plan Requirements'' (``PM<INF>2.5</INF> SIP Requirements Rule'') \66\
and the 2019 PM<INF>2.5</INF> Precursor Demonstration Guidance;
therefore, they did not assess a modeled ammonia response relative to a
contribution threshold but rather relied on the conclusions from
modeling performed at the time and from past studies indicating that
ammonium nitrate PM<INF>2.5</INF> is far more responsive to
NO<INF>X</INF> reductions than to ammonia reductions. Following
promulgation of the PM<INF>2.5</INF> SIP Requirements Rule, the EPA now
requires that each precursor be evaluated individually by comparing
modeled responses to the contribution threshold and considering
additional information.\67\ The State conducted its precursor analysis
for the SJV PM<INF>2.5</INF>
[[Page 86590]]
Plan in accordance with these requirements.
---------------------------------------------------------------------------
\66\ 81 FR 58010 (August 24, 2016).
\67\ 40 CFR 51.1006; EPA's PM<INF>2.5</INF> Precursor
Demonstration Guidance.
---------------------------------------------------------------------------
Regarding CCEJN's Title VI-related concerns, we address the
comments regarding Title VI in Responses 1.A, 1.B, 5, and 7, which rely
on supporting information discussed in Responses 3.A, 3.B.1 through
3.B.4, 3.C, and 3.D.
Comment 3.A: CCEJN's first specific stated concern with the
precursor demonstration is that the State's conclusion that the San
Joaquin Valley is NO<INF>X</INF>-limited relies on low NO<INF>X</INF>
estimates based on soil NO<INF>X</INF> emissions that are biased low.
The commenter asserts that ``. . .the state's estimates of soil
NO<INF>X</INF> emissions are on the extreme low-end of those reported
in the academic literature, and the state has acknowledged that it is
unsure how much NO<INF>X</INF> is actually emitted from soil in the
Valley.'' The commenter asserts that the State's only rationale for
maintaining the current estimate is that it will take time to develop a
new estimate, even though including anthropogenic soil NO<INF>X</INF>
emissions has been a longstanding request by Valley advocates.
Additionally, CCEJN asserts that ``[t]he state's reliance on very
low estimates of soil NO<INF>X</INF> emissions is contrary to the
presumption that precursors should be regulated and to the overall
`preventative' and `precautionary' tenor of the Act.'' The commenter
asserts that even if there was not sufficient time to fully evaluate
the scientific literature, a key question is what assumptions the State
should rely on in the interim. The commenter proposes that the State
should base its decision of whether to regulate ammonia on a median
reasonable estimate of soil NO<INF>X</INF> emissions, if not the high-
end estimate.
Response 3.A: We do not agree that the information provided by the
commenter on soil NO<INF>X</INF> emissions undermines the State's
conclusion that PM<INF>2.5</INF> formation in the San Joaquin Valley is
NO<INF>X</INF>-limited (i.e., much more sensitive to NO<INF>X</INF>
emissions reductions than to ammonia emissions reductions). Three lines
of evidence support the EPA's agreement with the State's conclusion.
First, at this time, it is not clear that soil NO<INF>X</INF> emissions
estimates are largely underestimated as the commenter suggests. Second,
ammonia emissions are likely underestimated and so the response to an
ammonia reduction is likely overestimated in the modeling. Third,
ambient measurements strongly suggest that PM<INF>2.5</INF>
concentrations would respond relatively little to ammonia emissions
reductions. We discuss each of these lines of evidence in the
paragraphs that follow.
We do not dispute that increasing NO<INF>X</INF> emissions in the
model would be expected to decrease the modeled amount of ammonia
relative to NO<INF>X</INF> and increase the modeled sensitivity of
PM<INF>2.5</INF> concentrations to ammonia reductions. However, as
discussed in detail in Response 2.A, further investigation is needed
and merited regarding whether soil NO<INF>X</INF> emissions are
underestimated or the magnitude of such underestimation. The magnitude
of the difference, if any, could have an important effect on whether
the model responses to ammonia reductions would be above the
contribution threshold. Additionally, even if it is determined that
soil NO<INF>X</INF> emissions are underestimated, proper updating of
the model emissions inventory to address the relative abundance of
ammonia and NO<INF>X</INF> could require updates to both the
NO<INF>X</INF> and ammonia emissions inventories, and there is ample
evidence that ammonia emissions are underestimated. Furthermore,
independent of any emissions estimates or modeling, evidence from
ambient measurements imply that PM<INF>2.5</INF> concentrations would
respond very little to ammonia reductions, and that the model responses
in the precursor demonstration may be overestimated, as discussed
further in the remainder of this response. Thus, the EPA disagrees with
the commenter's assertions that the State's conclusion that the San
Joaquin Valley is NO<INF>X</INF>-limited (in the sense that it is much
more sensitive to NO<INF>X</INF> reductions than to ammonia reductions)
is based on biased soil NO<INF>X</INF> emissions estimates that compel
the EPA to disapprove the ammonia precursor demonstration.
A second line of evidence is that multiple studies have suggested
that ammonia emissions are underestimated in the San Joaquin Valley.
These studies reached this conclusion by comparing ambient measurements
and satellite retrievals to model results that incorporate estimates of
ammonia emissions, and by comparing monitoring or modeling results to
what would be expected based on the size(s) of the ammonia and
NO<INF>X</INF> emissions inventories. For example, in a summary report
for the CalNex air quality study, the authors concluded based on direct
measurements of ammonia emissions flux that ``[p]reliminary results
indicate that within the San Joaquin Valley, [ammonia] emissions could
be underestimated in inventories by about a factor of three.'' \68\
This finding was confirmed in later modeling using monitored data from
the DISCOVER-AQ field study.\69\ Other studies identified in a
literature search also suggest that ammonia emissions are
underestimated, as discussed in the remainder of this response. If
higher ammonia emissions were used in the modeling to correct the
underestimation, then modeled ammonia would be more abundant relative
to nitrate, and particulate nitrate formation would be more
NO<INF>X</INF>-limited. Thus, the modeled response to ammonia
reductions would be lower than reported in the precursor demonstration
in the SJV PM<INF>2.5</INF> Plan, and below the contribution threshold.
---------------------------------------------------------------------------
\68\ Parrish, D. (2014), Synthesis of Policy Relevant Findings
from the CalNex 2010 Field Study, Final Report to the Research
Division of the California Air Resources Board, 2014, p. 63;
available at <a href="https://csl.noaa.gov/projects/calnex/synthesisreport.pdf">https://csl.noaa.gov/projects/calnex/synthesisreport.pdf</a>.
\69\ Kelly, J.T. et al. (2018), Modeling
NH<INF>4</INF>NO<INF>3</INF> over the San Joaquin Valley during the
2013 DISCOVER-AQ campaign, Journal of Geophysical Research:
Atmospheres, 123, 4727-4745, doi:10.1029/2018JD028290.
---------------------------------------------------------------------------
A literature search conducted by the EPA found ample evidence that
ammonia emissions may be underestimated in the San Joaquin Valley.\70\
Most studies compared air quality model results with satellite
retrievals; a few compared model results to measurements from aircraft.
All of the studies reviewed concluded that ammonia emissions are
underestimated by a factor of two to five. A factor of two is greater
than the 20-51 percent increase in total NO<INF>X</INF> emissions
estimated by Almaraz et al. (2018) and would more than offset the
effect of an increase in soil NO<INF>X</INF> on the sensitivity of
PM<INF>2.5</INF> concentrations to ammonia reductions. These studies
collectively suggest that ammonia emissions are underestimated in the
San Joaquin Valley. In turn, that implies that model estimates of the
sensitivity in the precursor demonstration may be overestimated.
---------------------------------------------------------------------------
\70\ Memorandum dated October 12, 2023, from Scott Bohning, EPA
Region IX, to Docket EPA-R09-OAR-2023-0263, Subject: ``Literature
search finds evidence that ammonia emissions are underestimated.''
---------------------------------------------------------------------------
Note that such an underestimate does not imply that the emissions
inventories in the SJV PM<INF>2.5</INF> Plan do not meet the
requirements of CAA section 172(c)(3); rather it reflects that more
work is needed to continue to improve ammonia emissions estimates.
Studies may deduce that there is underestimation using a ``top down''
approach relying on ambient measurements or satellite observations; the
measurements reflect the atmospheric sum of the contribution of many
sources, possibly over an extended area. On the other hand, an
emissions inventory developed for regulatory purposes is typically a
``bottom-up'' estimate, derived from
[[Page 86591]]
compiling an inventory of stationary, area, mobile, and biogenic
sources, with their associated emissions factors and activity rates.
The emissions inventory is based on detailed knowledge and measurements
of specific source types under particular conditions. It is impractical
to measure every source under all environmental conditions or under all
possible variations, and to know the exact mix of source types and of
management practices in place. Thus, the emissions inventory depends on
the basic assumption that information compiled for the subset of
sources that it is practical to measure can be generalized to the full
population of sources in an area. Characterizing ammonia emissions from
the bottom up requires spatially and temporally resolved data, such as
detailed farming practices including irrigation and fertilizer
application, and how they affect emissions, which may vary depending on
multiple factors. Such detailed data may not be available except at an
enormous, impractical cost. A bottom-up emissions inventory may use the
best available data and techniques, yet not match estimates made via
top-down approaches. The discrepancy between the estimates from top-
down and bottom-up approaches indicates the need for further research
to better characterize the specific source types that contribute to the
total.
In 2021, CARB reported comparisons between its own model
predictions of ammonia to ambient data.\71\ The SJV PM<INF>2.5</INF>
Plan did not include an evaluation of model performance for ammonia per
se (just for particulate ammonium), but in a supplemental transmittal,
CARB described the results of two analyses confirming the likely
underestimation of ammonia. CARB compared CMAQ model predictions of
ammonia with the 2013 DISCOVER-AQ \72\ aircraft measurements and found
that near-ground ammonia was underpredicted by 50 percent at Fresno and
200 percent at Porterville. CARB also compared 2017 satellite
observations of ammonia from the Infrared Atmospheric Sounding
Interferometer to CMAQ model predictions and found that modeled ammonia
concentrations were half of the magnitude of the satellite retrievals
at some locations, and that the modeled average in the San Joaquin
Valley was about 25 percent less than observed. CARB also noted that
underprediction of ammonia would result in the modeled PM<INF>2.5</INF>
response to ammonia reductions being overpredicted.
---------------------------------------------------------------------------
\71\ 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''.
\72\ DISCOVER-AQ: ``Deriving Information on Surface conditions
from COlumn and VERtically Resolved Observations Relevant to Air
Quality,'' <a href="https://science.nasa.gov/mission/discover-aq">https://science.nasa.gov/mission/discover-aq</a>.
---------------------------------------------------------------------------
Finally, a third line of evidence supports the conclusion that
PM<INF>2.5</INF> in the San Joaquin Valley is relatively insensitive to
ammonia reductions. Evidence from ambient data is especially strong
since it is independent of uncertainties in the emissions estimates and
the modeling exercises. Appendix G (``Precursor Demonstration'') of the
2018 PM<INF>2.5</INF> Plan and Appendix C (``Weight of Evidence
Analysis'') of the CARB Staff Report on the 2018 PM<INF>2.5</INF> Plan
\73\ describe previous research in support of the claim that ammonium
nitrate PM<INF>2.5</INF> formation is NO<INF>X</INF>-limited rather
than ammonia-limited. That is, PM<INF>2.5</INF> concentrations in the
San Joaquin Valley are expected to be sensitive to reductions in
NO<INF>X</INF> emissions but much less sensitive to reductions in
ammonia. Essentially, due to the abundance of ammonia, even with
ammonia emissions reductions there would still be enough available
ammonia to combine with NO<INF>X</INF> (in the form of nitric acid) to
form about the same amount of particulate ammonium nitrate. This was
the conclusion of Lurmann et al. (2006) \74\ based on ambient
measurements during the California Regional Particulate Air Quality
Study (CRPAQS), an intensive field study during winter 2000-2001.
Ammonia was almost always abundant relative to the amount of nitric
acid \75\ (derived from NO<INF>X</INF> and the immediate precursor to
particulate nitrate), so the authors concluded that ammonium nitrate
formation in the San Joaquin Valley was NO<INF>X</INF>-limited. This
conclusion was based on ambient data collected before the additional 60
percent reduction in NO<INF>X</INF> emissions that has occurred in the
interim, which would be expected to have increased the degree of
NO<INF>X</INF>-limitation (i.e., particulate ammonium nitrate formation
would be more limited by, and so more sensitive to, the amount of
NO<INF>X</INF>).
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\73\ CARB's ``Staff Report, Review of the San Joaquin Valley
2018 Plan for the 1997, 2006, and 2012 PM<INF>2.5</INF> Standards,''
release date December 21, 2018.
\74\ Lurmann et al. (2006) Processes Influencing Secondary
Aerosol Formation in the San Joaquin Valley during Winter, Journal
of the Air & Waste Management Association, 56(12):1679-1693, doi:
10.1080/10473289.2006.10464573.
\75\ Nitric acid (HNO<INF>3</INF>) is formed from NO<INF>X</INF>
emissions; it combines with ammonium to form particulate ammonium
nitrate. The relative amounts of nitric acid and ammonium indicate
which is the limiting factor in ammonium nitrate formation.
---------------------------------------------------------------------------
Consistent with CRPAQS, aircraft-borne measurements during the more
recent 2013 DISCOVER-AQ \76\ study led CARB to a similar conclusion,
based on the large amount of ``excess ammonia''. This is defined as the
amount of measured ammonia left over if all the nitrate and sulfate
present combined with available ammonia to form particulate. The CARB
December 2018 Staff Report describes this in more detail,\77\ and also
lists results from multiple other recent studies with similar
conclusions. Two studies with chemical modeling,<SUP>78 79</SUP> at
temperature and humidity levels typical for the San Joaquin Valley and
with ammonia and nitrate concentrations observed during DISCOVER-AQ,
showed that over 90 percent of the nitrate is present as particulate
rather than gas, consistent with abundance of ammonia and with low
sensitivity to ammonia changes. Two other studies, one using data from
DISCOVER-AQ \80\ and one using data from the 2010 CalNex field
campaign, \81\ found measured ammonia to be 50-100 times as abundant as
nitric acid, implying low sensitivity to ammonia emissions changes.\82\
In summary, the
[[Page 86592]]
ambient field study data that the EPA is aware of is consistent with a
conclusion that PM<INF>2.5</INF> concentrations in the Valley are much
more sensitive to NO<INF>X</INF> emissions reductions than to ammonia
emissions reductions. This evidence is independent of the State's soil
NO<INF>X</INF> emissions estimate and is an important basis for the
EPA's determination that the responses to ammonia reductions for the
1997 annual PM<INF>2.5</INF> NAAQS that are slightly above the
recommended contribution threshold are likely overestimated. Thus, the
ambient evidence supports the EPA's determination that ammonia does not
contribute significantly to PM<INF>2.5</INF> levels above the 1997
annual PM<INF>2.5</INF> NAAQS.
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\76\ DISCOVER-AQ: ``Deriving Information on Surface conditions
from COlumn and VERtically Resolved Observations Relevant to Air
Quality,'' <a href="https://science.nasa.gov/mission/discover-aq">https://science.nasa.gov/mission/discover-aq</a>.
\77\ CARB, ``Staff Report: Review of the San Joaquin Valley 2018
Plan for the 1997, 2006, and 2012 PM<INF>2.5</INF> Standards,''
December 21, 2018, Appendix C, 12ff.; available at <a href="https://ww2.arb.ca.gov/resources/documents/2018-san-joaquin-valley-pm25-plan">https://ww2.arb.ca.gov/resources/documents/2018-san-joaquin-valley-pm25-plan</a>.
\78\ Id. at 12 (presenting CARB analysis of ammonia impacts in
the San Joaquin Valley).
\79\ Prabhakar et al. (2017) Observational assessment of the
role of nocturnal residual-layer chemistry in determining daytime
surface particulate nitrate concentrations, Atmospheric Chemistry
Physics, 17, 14747-14770. doi:10.5194/acp-17-14747-2017.
\80\ Parworth et al. (2017) Wintertime water-soluble aerosol
composition and particle water content in Fresno, California,
Journal of Geophysical Research, Atmosphere., 122, 3155-3170. doi:
10.1002/2016JD026173, p. 3165. (noting that ``The average mixing
ratio of NH<INF>3</INF> was 49 times greater than HNO<INF>3</INF> .
. . . These results highlight that NH<INF>3</INF> was in excess, and
NH<INF>4</INF>NO<INF>3</INF> [ammonium nitrate] formation is likely
limited by HNO<INF>3</INF> availability in Fresno,'' i.e., about a
factor of 50).
\81\ CalNex, or California Research at the Nexus of Air Quality
and Climate Change, was a NOAA-sponsored field study during summer
2010; <a href="https://www.esrl.noaa.gov/csd/projects/calnex/">https://www.esrl.noaa.gov/csd/projects/calnex/</a>. Markovic et
al., (2014), Measurements and modeling of the inorganic chemical
composition of fine particulate matter and associated precursor
gases in California's San Joaquin Valley during CalNex 2010, Journal
of Geophysical Research--Atmospheres, 119, 6853-6866, doi:10.1002/
2013JD021408, p. 6863 (noting that `` . . . the observed
NH<INF>3</INF> (g) mixing ratios were elevated . . . the observed
HNO<INF>3</INF> (g) mixing ratios were 2 orders of magnitude
lower,'' i.e., about a factor of 100).
\82\ The CARB December 2018 Staff Report explains (in Appendix
C, p. 14) that NO<INF>X</INF> is the limiting pollutant as shown by
this relative abundance of ammonia, but that the expected low
sensitivity to ammonia reductions does not mean zero response; the
reduction necessarily shifts nitrate from particulate to gas to
maintain chemical equilibrium. Thus, NO<INF>X</INF> being the
limited pollutant does not contradict the modeled responses to 30-70
percent reductions.
---------------------------------------------------------------------------
Comment 3.B.1: CCEJN's second concern with the precursor
demonstration relates to the State's conclusions regarding the level of
ammonia reductions that could be achieved through potential control
measures. The commenter asserts that ``. . . the state repeatedly uses
a lack of certainty about emission reduction potential to justify no
regulation at all.'' As an example, they argue that the State
acknowledges that research shows that ammonia emissions from manure-
based fertilizer can be reduced by 50-90 percent through quick mixing
or injection but that it declines to consider the measure feasible for
synthetic fertilizers merely because the State does not know how
effective it will be.
Response 3.B.1: We disagree with CCEJN's claim that the State
relies primarily on a lack of certainty about potential emissions
reductions to justify not regulating ammonia in the San Joaquin Valley.
Rather, the State based its decision not to regulate ammonia for
purposes of meeting the 1997 annual PM<INF>2.5</INF> NAAQS on the
technical analyses it performed indicating that ammonia does not
contribute significantly to PM<INF>2.5</INF> concentrations that exceed
the 1997 annual PM<INF>2.5</INF> NAAQS.
Where the State identifies uncertainties about potential ammonia
emissions reductions, it does so in the context of its controls
analysis to support the ammonia precursor demonstration, which it
conducted at the request of the EPA and in accordance with EPA
guidance. As acknowledged by the commenter, under the PM<INF>2.5</INF>
SIP Requirements Rule, a state may submit an optional precursor
demonstration showing that a particular PM<INF>2.5</INF> precursor
chemical species does not contribute significantly to PM<INF>2.5</INF>
levels above the standard in the area.\83\ If the EPA approves a
precursor demonstration for a particular chemical species, the state is
not required to control emissions of that precursor from existing
sources in the relevant attainment plan.\84\
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\83\ 81 FR 58010, 58021 (August 24, 2016); 40 CFR 51.1006
(``Optional PM<INF>2.5</INF> precursor demonstrations'').
\84\ 40 CFR 51.1006(a)(1)(iii) and 51.1010(a)(2)(ii).
---------------------------------------------------------------------------
The EPA's July 2023 proposal includes a detailed summary of the
precursor demonstration in the SJV PM<INF>2.5</INF> Plan and supporting
March 2023 Ammonia Supplement, and of the EPA's evaluation. We will not
reiterate all of the State's conclusions herein except to highlight the
key finding that modeled sensitivities for the 1997 annual
PM<INF>2.5</INF> NAAQS of PM<INF>2.5</INF> concentrations to a 30
percent ammonia reduction are approximately at or below the
contribution threshold used to determine significance. The
PM<INF>2.5</INF> Precursor Guidance explains that in cases where the
PM<INF>2.5</INF> response to a 30 percent reduction in precursor
emissions is close to the contribution threshold, the EPA may require
air agencies to identify and evaluate potential emissions controls in
support of a precursor demonstration that relies on a sensitivity
analysis. The response of ambient PM<INF>2.5</INF> to an actual
assessment of the benefit from potential controls can be used to
determine whether controlling ammonia would significantly affect
PM<INF>2.5</INF> levels. In accordance with 40 CFR 51.1010(a)(2)(ii),
the EPA required the State to provide an analysis of potential controls
to aid the EPA in its evaluation of the precursor demonstration. The
State provided such controls analysis in the March 2023 Ammonia
Supplement, which built upon information previously provided in the
2018 PM<INF>2.5</INF> Plan.
As discussed in our proposal, the State's controls analysis
included a review of ammonia emissions reductions achieved nationwide
from 2011 to 2017, an evaluation of the main ammonia source categories
in the San Joaquin Valley, a summary of existing control measures in
the San Joaquin Valley that affect ammonia from these sources, a review
of existing control measures implemented by other air districts, and an
evaluation of additional mitigation options for ammonia sources in the
Valley.\85\ Based on the State's and District's analyses, they
determined that significant ammonia emissions reductions are already
being achieved by measures targeting VOC emissions and that the ammonia
reductions achievable from additional controls are well below 30
percent.
---------------------------------------------------------------------------
\85\ 88 FR 45276, 45288-45290.
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In this action, we are finalizing our determination that the State
has provided adequate support for its conclusion that available
additional ammonia controls would yield less than a 30 percent
reduction in ammonia emissions. We are finding that the District made a
convincing case that significant ammonia reductions have already been
achieved through District Rule 4570 and that few additional mitigation
measures could provide only modest further reductions from confined
animal facilities (CAFs), which account for 58 percent of the total
ammonia inventory. Similarly, the State has provided support for its
assertion that additional reductions are not feasible from the
fertilizer, composting, and other smaller source categories through its
analysis of potential fertilizer controls and information regarding
controls that are already in place for these source categories. As
discussed in our proposal, we acknowledge the uncertainty in the
reductions that are currently being achieved from the fertilizer source
category but are finalizing our determination that even if ammonia
reductions could be reduced by a very high percentage, such reductions
added to the potential reductions from CAFs would amount to less than a
30 percent reduction in total ammonia emissions.
Given that the State's modeled sensitivities of PM<INF>2.5</INF>
concentrations to a 30 percent ammonia reduction are approximately at
or below the threshold used for identifying an impact that is
significant for the 1997 annual PM<INF>2.5</INF> NAAQS, and that the
potential additional reductions would be well below 30 percent, the
response of PM<INF>2.5</INF> to an ammonia reduction of a percentage
smaller than 30 percent would be below the contribution threshold,
indicating that ammonia does not contribute significantly to ambient
PM<INF>2.5</INF> concentrations for purposes of the SJV
PM<INF>2.5</INF> Plan for the 1997 annual PM<INF>2.5</INF> NAAQS. Based
on these results, the State excluded ammonia controls from the SIP
submission. Because the EPA is finalizing approval of the State's
precursor demonstration as proposed, the State is not required to
regulate ammonia for purposes of meeting the CAA requirements for the
1997 annual PM<INF>2.5</INF> NAAQS.
Regarding the example cited by the commenter of quickly mixing or
injecting fertilizer into the soil, we do not disagree that research
literature indicates that quick mixing or injection
[[Page 86593]]
can reduce ammonia emissions from manure-based fertilizer. The State
acknowledges in the March 2023 Technical Supplement that applying
manure to the soil surface without incorporation can lead to
significant ammonia emissions and includes an extensive discussion of
the various methods of incorporation as well as the related
requirements for injection and incorporation of manure-based fertilizer
in District Rule 4570. We disagree, however, with the commenter's
assertions that because the measure is effective at reducing ammonia
from manure-based fertilizers, the State should infer a similar
magnitude of effectiveness for synthetic fertilizers. The studies cited
by the commenter acknowledge uncertainties and highlight the importance
of additional research to adapt a potential measure to local
conditions.\86\ For example, Ti et al. (2019), in a global meta-
analysis of measures to reduce ammonia emissions from livestock and
cropping systems, found that the effects of fertilizer application
processes are highly dependent on crop type.\87\ The paper further
concludes that mitigation needs to be carefully planned and adapted to
local conditions because ammonia emissions are dependent on
environmental factors such as weather and soil conditions, that the
applicability of measures depends strongly on farm structures, and that
studies examining economic feasibility and the effects of combinations
of measures are needed.\88\ The State's March 2023 Ammonia Supplement
draws similar conclusions about the need for additional research to
assess the potential for ammonia emissions reductions, specifically as
they relate to quick mixing and injection, under conditions
representative of those in the San Joaquin Valley.\89\ Given these
uncertainties, we agree with the State's conclusion that additional
research is needed and find that the State's decision not to assign
ammonia reductions to such measure at this time to be reasonable.
---------------------------------------------------------------------------
\86\ Pan, B. et al. (2016). Ammonia volatilization from
synthetic fertilizers and its mitigation strategies: A global
synthesis. Agriculture, Ecosystems & Environment, Vol. 232, 283-289,
doi:10.1016/j.agee.2016.08.019; Ti, C. et al. (2019). Potential for
mitigating global agricultural ammonia emission: A meta-analysis.
Environmental Pollution, Vol. 245, 141-148, doi:10.1016/
j.envpol.2018.10.124.
\87\ Ti et al. (2019) op cit., p. 146. For example, the paper
notes that the effects of fertilizer application practices on
reducing ammonia emissions from vegetable production are lower than
in wheat and fruit production due in part to the smaller reduction
in ammonia emissions from vegetable fields associated with more
intensive irrigation.
\88\ Id. at 147.
\89\ March 2023 Ammonia Supplement, p. 94.
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In addition to helping to resolve the uncertainties related to the
effectiveness of mitigation measures, additional research would also be
beneficial for improving understanding of any potential disbenefits
that may be specific to the area. The commenter appears to acknowledge
the potential for disbenefits in a footnote to their comment, which
notes that CCEJN does not endorse any specific approach for reducing
ammonia emissions, including quick mixing or injection, and that
``regulation of ammonia emissions cannot be permitted to exacerbate
degradation of groundwater quality.'' These expressed concerns about
the potential for adverse effects on water quality seem to align with
the State's position that more research is needed. Such research may
also inform other important considerations, such as the effects on
greenhouse gas emissions.
Comment 3.B.2: CCEJN asserts that the State's evaluation of
emissions from fertilizers is limited in that it is seemingly based on
just two studies, and does not consider additional mitigation options
identified in the literature such as using non-urea based fertilizers;
using controlled release fertilizers; using fertilizers with
nitrification inhibitors; irrigating immediately after fertilizer
placement; or adding amendments to fertilizers, such as zeolite,
pyrite, or organic acids. The commenter also points to a study on the
field of precision agriculture as a resource on mechanisms to minimize
fertilizer use,\90\ as well as two studies examining how modeling can
be used to predict ammonia volatilization, claiming that such studies
undermine the State's position that emissions reductions cannot be
calculated.\91\
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\90\ Association of Equipment Manufacturers, The Environmental
Benefits of Precision Agriculture in the United States, <a href="https://newsroom.aem.org/download/977839/environmentalbenefitsofprecisionagriculture-2.pdf">https://newsroom.aem.org/download/977839/environmentalbenefitsofprecisionagriculture-2.pdf</a>.
\91\ Gurung, R.B. et al. (2021) Modeling ammonia volatilization
from urea application to agricultural soils in the DayCent model.
Nutr Cycl Agroecosyst, 119, 259-273. doi:10.1007/s10705-021-10122-z;
Yang, Y. et al. (2022) Comprehensive quantification of global
cropland ammonia emissions and potential abatement. Science of The
Total Environment, 812, 151450, doi:10.1016/j.scitotenv.2021.151450.
---------------------------------------------------------------------------
Response 3.B.2: We disagree with CCEJN's characterization of the
State's analysis of emissions from fertilizer as ``extremely narrow.''
We infer that the commenter is referring to the State's analyses for
synthetic fertilizer specifically, based on the numerous studies cited
in the State's discussion of manure application-related measures,\92\
and the commenter's assertion that the State's evaluation of
fertilizers is seemingly based on the findings from just two studies
and that Table 13 of the March 2023 Ammonia Supplement lists references
for Guthrie et al. (2018) \93\ and Eory et al. (2016) only.\94\
However, we note that both Guthrie et al. (2018) and Eory et al. (2016)
are compilation studies covering a range of mitigation options for
organic and synthetic fertilizer application and that the State's March
2023 Ammonia Supplement cites numerous studies in addition to these two
compilation studies. Furthermore, the State turned to the research
literature only after reviewing how other California State agencies are
engaged in fertilizer use and attempting to identify any existing rules
or regulations in the nation controlling ammonia emissions from this
source category.
---------------------------------------------------------------------------
\92\ E.g., see March 2023 Ammonia Supplement pp. 74-75.
\93\ Guthrie, S. et al. (2018). Impact of ammonia emissions from
agriculture on biodiversity: An evidence synthesis. Rand Europe, The
Royal Society. <a href="https://www.rand.org/pubs/research_reports/RR2695.html">https://www.rand.org/pubs/research_reports/RR2695.html</a>.
\94\ Eory, V. et al. (2016) ClimateXChange, On-farm technologies
for the reduction of greenhouse gas emissions in Scotland. <a href="https://www.climatexchange.org.uk/media/1927/on-farm_technology_report.pdf">https://www.climatexchange.org.uk/media/1927/on-farm_technology_report.pdf</a>.
---------------------------------------------------------------------------
Regarding the additional mitigation options identified by CCEJN, we
appreciate that the commenter raises these potential strategies. We
acknowledge the studies cited by the commenter finding that
implementation of some of these strategies may help minimize ammonia
emissions from agricultural systems around the globe. We encourage CARB
and the District to keep abreast of research examining mitigation
options for minimizing ammonia emissions from fertilizer application in
support of future policy and management decisions, particularly as they
may relate to reducing PM<INF>2.5</INF> exposure in the San Joaquin
Valley. However, as discussed in the following paragraphs, in light of
the absence of any SIP-approved requirements elsewhere in the nation,
the regulations adopted by other California State agencies to control
fertilizer application, and the uncertainties discussed in the studies
cited by CARB and the commenters, the EPA continues to agree with the
State's overall conclusions that more research is needed on potential
mitigation measures to reduce ammonia emissions from fertilizer
application in the San Joaquin Valley. We also agree that based on the
information currently available, the additional reductions achievable
are sufficiently low that the PM<INF>2.5</INF> response to such
reduction would
[[Page 86594]]
be below the contribution threshold, indicating that ammonia does not
contribute significantly to ambient PM<INF>2.5</INF> concentrations for
purposes of the SJV PM<INF>2.5</INF> Plan for the 1997 annual
PM<INF>2.5</INF> NAAQS. As we emphasized in our proposal, this finding
is specific to the facts and circumstances of this particular plan and
does not pre-determine the outcome of significance determinations of
precursors in the future.
In the March 2023 Ammonia Supplement, the State describes its
efforts to identify any SIP-approved requirements limiting ammonia
emissions from fertilizers that are being implemented in any other
areas of the United States and explains that it has not identified any
rules or regulations being implemented elsewhere. Thus, it describes
regulations in place adopted by other California State agencies to
control fertilizer application and its review of research studies
examining techniques for reducing ammonia emissions from synthetic
fertilizer application.
The State describes in Appendix C (``Stationary Source Control
Measure Analyses'') of the 2018 PM<INF>2.5</INF> Plan and in the March
2023 Ammonia Supplement the various State agencies responsible for
ensuring environmentally safe use of fertilizer material. It describes
requirements for commercial irrigated lands in the San Joaquin Valley
to prepare a farm management plan (including an irrigation nitrogen
management plan) that complies with waste discharge requirements in
accordance with the Central Valley Irrigated Lands Regulatory Program
established by the California State Water Resources Control Board. The
nitrogen management plan is designed to ensure that the amount of
nitrogen applied to agricultural lands is in reasonable balance with
the needs of crops that are being grown. The State explains that the
``4 R's'' of nitrogen management (``Right source'' of nitrogen at the
``right rate,'' ``right time,'' and ``right place'') \95\ serve as
guiding nitrogen efficiencies principles that growers are recommended
to follow when developing their management plans, and that growers are
required to employ enhanced strategies if it is determined that they
are not optimizing fertilizer use, as determined by the fraction of
nitrogen applied to nitrogen used.
---------------------------------------------------------------------------
\95\ March 2023 Ammonia Supplement, p. 92.
---------------------------------------------------------------------------
Next, CARB discusses measures identified in the literature for
reducing ammonia emissions from fertilizer application, which include
optimizing fertilizer use, adding a urease inhibitor, mixing and
injecting fertilizer into the soil quickly, and applying fertilizer
during optimal weather conditions. Based on its review, the State finds
that several of the strategies align with the 4 R's of nitrogen
management but that more research is needed to determine the
feasibility and effectiveness of such strategies in California due to
the unique climate conditions and farming practices in the San Joaquin
Valley, and to explore any potential adverse consequences. CARB cites
studies linking weather conditions with ammonia emissions,\96\ and
states that it is unclear which environmental factors are the most
important for different fertilizer types.
---------------------------------------------------------------------------
\96\ Venterea, R.T. et al. (2012) Challenges and opportunities
for mitigating nitrous oxide emissions from fertilized cropping
systems. Frontiers in Ecology and the Environment, 10:10, 562-570.
doi:10.1890/120062; Grahmann, K., et al. (2013) Nitrogen use
efficiency and optimization of nitrogen fertilization in
conservation agriculture. Cabi Reviews, 8:053. doi:10.1079/
PAVSNNR20138053.
---------------------------------------------------------------------------
As discussed in Response 3.B.1, the studies cited by CCEJN
similarly highlight the need for additional research to examine how the
potential for ammonia emissions reductions varies with local
conditions. These studies largely focused on the United Kingdom or were
global in scale and none of them appear to address mitigation
potentials in the western United States or San Joaquin Valley
specifically. Thus, none of the studies reflect climate conditions or
farming practices in the San Joaquin Valley, and likely also do not
reflect efficiencies already achieved through local regulations in the
Valley. Furthermore, several of the studies suggest that some of the
measures have already been adopted in many areas, adding to the
uncertainty about whether and where there are opportunities for
significant reductions in ammonia. For example, Pan et al. (2016),
notes that ``[e]nhanced efficiency fertilizers have been widely adopted
to minimize N[itrogen] loss, including NH<INF>3</INF> volatilization
from agricultural systems.'' \97\ Similarly, Gu et al. (2023), in a
study examining the potential to mitigate nitrogen pollution from
global cropland, concluded that the largest reduction of reactive
nitrogen input and losses available were in East and South Asia and
Southeast Asia, which they attribute to an overuse of fertilizer in
those areas.\98\ They calculated a much lower reduction potential in
the European Union, Australia, and North America, where they concluded
that nitrogen use in croplands is ``closer to the estimated optimal
level.''
---------------------------------------------------------------------------
\97\ Pan et al. (2016) op. cit., p. 288.
\98\ Gu, B. et al. (2023) Cost-effective mitigation of nitrogen
pollution from global croplands. Nature, Vol. 613, pp. 77-84.
---------------------------------------------------------------------------
In addition to the uncertainty in emissions reduction potentials,
we note that studies suggest that one of the five mitigation options
identified by CCEJN, using fertilizers with nitrification inhibitors,
may lead to an increase in ammonia emissions. For example, Pan et al.
(2016) noted that ``[a]lthough nitrification inhibitors are designed to
target N<INF>2</INF>O emissions, the use of these inhibitors may
prolong the retention of NH<INF>4</INF> in the soil resulting in
[ammonia] volatilization (Kim et al., 2012; Lam et al., 2016; Ni et
al., 2014).'' \99\ Pan et al. (2016) concluded that nitrification
inhibitors increase ammonia volatilization by 38.0 percent.\100\
Similarly, Ti et al. (2019) found that nitrification inhibitors
increased ammonia emissions by 42.6 percent,\101\ whereas Newell Price
et al. (2011) found that ``[ammonia] emissions to air and ammonium/
nitrite losses to water may be increased by a small amount.'' \102\
While studies specific the San Joaquin Valley may show different
results, based on the studies cited by the commenter, the research
currently available does not indicate that use of fertilizers with
nitrification inhibitors would reduce ammonia emissions in the San
Joaquin Valley.
---------------------------------------------------------------------------
\99\ Pan et al. (2016) op. cit., p. 284.
\100\ Id. at p. 286.
\101\ Ti et al. (2019) op. cit., p. 143.
\102\ J. Newell Price, et al., (2011) An inventory of mitigation
methods and guide to their effects on diffuse water pollution,
greenhouse gas emissions and ammonia emissions from agriculture
(Defra Project WQ0106). <a href="http://randd.defra.gov.uk/Document.aspx?Document=MitigationMethodsUserGuideDecember2011FINAL.pdf">http://randd.defra.gov.uk/Document.aspx?Document=MitigationMethodsUserGuideDecember2011FINAL.pdf</a>, p. 52.
---------------------------------------------------------------------------
The studies that CCEJN points to on precision agriculture also note
wide adoption of such practices while acknowledging some potential for
additional environmental benefits. For example, in a 2021 report on the
benefits of precision agriculture in the United States, the Association
of Equipment Manufacturers discusses environmental improvements that
have already been achieved through adoption of precision agriculture
technologies.\103\ Whitmore (2019) notes that larger farms have been
quicker to adopt precision agriculture techniques due to greater
resources,\104\ and Lowenberg-Deboer
[[Page 86595]]
and Erickson (2019) note that ``[t]he biggest gap in [precision
agriculture] adoption is for medium and small farms in the developing
world that do not use motorized mechanization,'' which they attribute
to cost-effectiveness challenges.\105\ Lowenberg-Deboer and Erickson
(2019) also highlight the perception that adoption of precision
agriculture has been slow, but state that ``[s]ome aspects of
[precision agriculture] were adopted as quickly and as widely as any
technology in history, while others have lagged behind for technical
and economic reasons.'' \106\
---------------------------------------------------------------------------
\103\ Association of Equipment Manufacturers, The Environmental
Benefits of Precision Agriculture in the United States, <a href="https://newsroom.aem.org/download/977839/environmentalbenefitsofprecisionagriculture-2.pdf">https://newsroom.aem.org/download/977839/environmentalbenefitsofprecisionagriculture-2.pdf</a>.
\104\ Whitmore J. (2019) Precision Farming Comes into Its Own,
Mich. St. Univ., <a href="https://www.canr.msu.edu/news/precision-farming-comes-into-its-own">https://www.canr.msu.edu/news/precision-farming-comes-into-its-own</a>.
\105\ Lowenberg-DeBoer, J. and Erickson, B. (2019) Setting the
Record Straight on Precision Agriculture Adoption, Agronomy J., p.
1565.
\106\ Id. at 1552.
---------------------------------------------------------------------------
Taken together, the EPA finds that the studies cited by CCEJN
highlight the uncertainties in the feasibility of the measures
identified in its comment letter and suggest that more research is
needed to estimate the additional reductions achievable in the San
Joaquin Valley. Furthermore, while several studies suggest that there
may be the potential for additional ammonia reductions from synthetic
fertilizer application, they also indicate that such potential is not
quantifiable with the information available at this time and may be
lower in the San Joaquin Valley than in other locations around the
globe.
Finally, regarding CCEJN's comment about the availability of
modeling to predict ammonia volatilization, we acknowledge these
additional studies \107\ identified by the commenter describing models
for estimating ammonia emissions. However, we disagree with the
commenter that the output from these models compel certain policy
decisions in the San Joaquin Valley at this time. Here again the
commenter cites large-scale studies that do not reflect model
performance under conditions representative of those in the Valley.
Both studies cited by the commenter note uncertainties due to crop
type, meteorological conditions, and other factors, suggesting that
research specific to the climate and farming practices in the Valley is
needed. Furthermore, it is not clear that the models discussed in the
studies are ripe for application in a regulatory context. For example,
Gurung et al. (2021) concludes that additional research is needed
before the models could be used to evaluate policy decisions for
mitigating ammonia emissions from soils:
---------------------------------------------------------------------------
\107\ Gurung et al. (2021) op. cit.; Yang et al. (2022) op. cit.
In future research, DayCent can also be used to test ``what if''
scenarios for identifying best management practices (BMPs) given
variation in the soil and climatic conditions. These scenarios could
focus on adopting the 4R nutrient stewardship principles and
identifying regional level BMPs associated with the addition of urea
fertilization. Further model improvement would also allow for a
broader set of options to be evaluated in support of policy and
management decisions associated with mitigating of NH<INF>3</INF>
---------------------------------------------------------------------------
volatilization from agricultural soils.
Thus, based on our review, we find the State's conclusions that
further research is needed to explore ammonia reduction potentials in
the San Joaquin Valley to be reasonable. We encourage the State and
District to perform and keep abreast of research on quantifying the
effects of mitigation measures on ammonia emissions and their
implications for policy and management decisions.
Comment 3.B.3: CCEJN asserts that the State dismisses controls for
fertilizers on the basis that there is no published literature on
control effectiveness in the San Joaquin Valley specifically. The
commenter contends that such justification is ``sometimes absurd'' and
that it cannot be true that studies specific to the Valley are
necessary to determine that minimizing the use of fertilizer will
decrease ammonia emissions. The commenter asserts that ``this bar for
effectiveness makes meaningful regulation impossible, particularly when
the state disincentivizes research in the Central Valley by insisting
that ammonia need not be regulated.'' The commenter further notes that
it is unfortunate that the State never mentions conducting any studies
in the San Joaquin Valley.
Response 3.B.3: We disagree with CCEJN that the State claims that
studies specific to the Valley are needed to discern that reducing
fertilizer use will reduce ammonia emissions. In the 2018
PM<INF>2.5</INF> Plan, the State discusses the link between fertilizer
application and both ammonia emissions and nitrate contamination in
groundwater, and describes current State regulations aimed at
optimizing fertilizer use to minimize emissions of ammonia to the
atmosphere.\108\ Additionally, in its discussion of optimizing or
minimizing fertilizer use in the 2023 Ammonia Supplement, the State
discuss the ``4 R's'' of nitrogen management (i.e., ``applying the
`Right source' of nitrogen at the `Right rate,' `Right time,' and
`Right place' '') and that minimizing fertilizer use is consistent with
the right rate principle. CARB also notes that Guthrie et al. (2018)
describes that minimizing the application of fertilizer to a level
commensurate with optimal crop production can reduce ammonia
emissions.\109\ Thus, the State does acknowledge the potential benefits
of minimizing fertilizer use on ammonia emissions. Where the State
concludes that additional research is needed is in the context of how
optimal fertilizer use can be achieved, which it notes is ``not well
described by both Guthrie et al. (2018) and the publications they
referenced, nor were any specific regulations identified.'' Given that
some level of reduction is already being achieved through existing
regulations and current practices, and the importance of careful
consideration of environmental factors for optimizing fertilizer use,
we find the State's conclusion that additional research specific to the
warm, dry climate conditions of the San Joaquin Valley is needed to
determine whether additional strategies could further optimize
fertilizer use and reduce ammonia emissions to be reasonable.
---------------------------------------------------------------------------
\108\ 2018 PM<INF>2.5</INF> Plan, Appendix C, pp. C-339 to C-
341.
\109\ March 2023 Ammonia Supplement, p. 92.
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Regarding CCEJN's statement that the State dismisses controls for
fertilizers based on a lack of information on control effectiveness in
the Valley, as discussed in Responses 3.B.1 and 3.B.2, studies reviewed
by the State, as well as studies cited by the commenter, emphasize that
strategies to reduce ammonia emissions are highly dependent on local
environmental factors and farm structures, and that more research is
needed to examine these factors, as well as the effects of combinations
of measures. The State concludes that specific mitigation strategies
identified in the literature, such as optimizing fertilizer use, are
already being implemented in the San Joaquin Valley because of
regulations adopted by other California State agencies and co-benefits
such as reduced cost to farmers. Based on the literature study findings
regarding the importance of local information and the need to examine
combinations of measures, the absence of existing rules or regulations
in other areas controlling ammonia emissions directly, and the State's
evaluation of the mitigation strategies already implemented through
regulation by other State agencies, we maintain that it is reasonable
that the State concludes that more research specific to the Valley is
needed to assess the feasibility and effectiveness of additional
measures for synthetic fertilizers.
We also disagree with CCEJN's assertions that needing additional
studies specific to the conditions in the
[[Page 86596]]
Valley makes meaningful regulation impossible and that the State
disincentivizes research by concluding ammonia does not need to be
regulated. Contrary to the commenter's claim that the State does not
discuss any studies that it is conducting to assess the effectiveness
of ammonia controls in the Valley, the State does include a discussion
of recent and ongoing and research in Section 4 of the March 2023
Ammonia Supplement. CARB's work includes the development of a mobile
measurement platform equipped with an ammonia monitor and other
instrumentation to examine ammonia sources. The State notes that in
fall 2018, CARB collaborated with researchers from the University of
California, Davis to measure ammonia and other air pollutants near
dairies in the San Joaquin Valley to evaluate the effectiveness of
alternative manure management practices.\110\ The State also mentions
additional research to evaluate emissions from dairies, to use
satellite and remote sensing data to evaluate ammonia emissions sources
across the Valley, and to identify opportunities to reduce ammonia and
other pollutant emissions from dairy manure lagoons specifically. These
efforts may inform future decision-making regarding the regulation of
ammonia in the San Joaquin Valley.
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\110\ March 2023 Ammonia Supplement, Figure 5 (showing that
dairy cattle account for an estimated 67.2 percent of ammonia
emissions from CAFs).
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Moreover, the EPA's action herein to approve the precursor
demonstration in the SJV PM<INF>2.5</INF> Plan for the 1997 annual
PM<INF>2.5</INF> NAAQS does not preclude the State from adopting
controls for ammonia in the future. As discussed in our proposal, a
consequence of this final action to approve the State's ammonia
precursor demonstration is that the State is not required to implement
BACM/BACT level controls for sources of ammonia for purposes of the SJV
PM<INF>2.5</INF> Plan for 1997 annual PM<INF>2.5</INF> NAAQS. Under 40
CFR 51.1006(b), such precursor demonstration approval applies only to
the SJV PM<INF>2.5</INF> Plan that is the subject of this final action.
For any new PM<INF>2.5</INF> attainment plan that the State is required
to submit in accordance with 40 CFR 51.1003 for purposes of any
PM<INF>2.5</INF> NAAQS, the EPA may determine that ammonia contributes
significantly to PM<INF>2.5</INF> levels that exceed the NAAQS and that
the State is required to implement controls for sources of ammonia for
purposes of such attainment plan.
Comment 3.B.4: Regarding the District's current rules, CCEJN
asserts that the State assumes that farmers are already adopting the
most efficient practices (e.g., feeding the most efficient amount of
protein, incorporating manure quickly) but ``provides little support
for these assumptions, even though it is well established that farmers
do not always adopt the most efficient practices.'' The commenter
proposes that the precursor analysis should err on maintaining the
presumption that precursors should be regulated and thereby err on the
side of high estimates of potential effectiveness and that because the
State does not do so, its analysis is arbitrary and capricious. The
commenter asserts that the State relies on ``biased assumptions,''
assuming low potential effectiveness from measures not being
implemented, high reductions from Rule 4570, and that making optional
measures mandatory would have no impact. The commenter further contends
that if Rule 4570 is effective, the State should make its most
effective requirements mandatory where feasible and possibly increase
the stringency, and that the EPA should require the State to conduct
further analysis of the rule.
Response 3.B.4: We disagree with CCEJN's assertions that the State
provides little support for its estimates of ammonia reductions that
have been achieved by existing regulations and that the assumptions it
makes to arrive at those estimates are biased. As discussed in our
proposal, the District discusses in detail in Appendix C of the 2018
PM<INF>2.5</INF> Plan how Rule 4570 is structured, the control menu
requirements for each of the CAF operations/sources, and research
papers that support its estimates of ammonia emissions reductions from
the measures.\111\ As the District explains, some of the measures in
Rule 4570 are required to be implemented but the rule also requires
that additional measures be selected from a menu of options. The menu-
based approach was developed to allow facilities flexibility to select
measures that are the most practical and effective for their design and
operation.\112\
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\111\ 2018 PM<INF>2.5</INF> Plan, Appendix C, pp. C-312 to C-
323.
\112\ Id.; March 2023 Ammonia Supplement, pp. 25-26.
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For those measures that are required to be selected from a menu of
options, the District presents its rationale in Appendix C of the 2018
PM<INF>2.5</INF> Plan and Appendix F of the staff report for Rule 4570
for its assumptions about which measure a farmer will select and the
resulting effects on ammonia emissions.\113\ The District references
research studies to support many of its assumptions, and where there is
greater uncertainty about which measures may be selected or the
corresponding ammonia reductions that can be achieved, the District
explains how its assumptions are conservative. CCEJN has not provided
any evidence to refute the District's analysis or conclusions.
Therefore, based on the information presented, the EPA believes that
the District relied on its expertise and the best information available
and applied that information reasonably.
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\113\ 2018 PM<INF>2.5</INF> Plan, Appendix C, pp. C-311 to C-
323; SJVUAPCD, ``Final Draft Staff Report, Proposed Re-Adoption of
Rule 4570 (Confined Animal Facilities),'' June 18, 2009, at Appendix
F, ``Ammonia Reductions Analysis for Proposed Rule 4570 (Confined
Animal Facilities),'' June 15, 2006 (discussing various assumptions
underlying the District's calculation of ammonia emissions factors).
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Regarding CCEJN's statement that the State should err on the side
of high estimates of potential reductions from additional measures,
given the uncertainties discussed in Responses 3.B.1 and 3.B.2, we find
that the potential emissions reductions achievable in the San Joaquin
Valley from many of the measures are not quantifiable at this time and
that the State drew reasonable conclusions based on the information it
evaluated. While the EPA appreciates that the commenter raises
additional research studies not identified by the State in its
analysis, as discussed in Responses 3.B.1 and 3.B.2, we have reviewed
the studies and find that they do not contradict the State's
conclusions. Thus, we find that the State's analysis of potential
ammonia emissions reductions is neither arbitrary nor capricious.
We also find that CCEJN's claim that it is well-established that
farmers do not adopt the most efficient practices is not well
supported. To back this claim, the commenter cites two studies
discussing the rates of adoption of precision agriculture
technologies.\114\ However, these studies do not appear to indicate any
reluctance on the part of farmers to adopt the most efficient
practices. As discussed in Response 3.B.2, these papers discuss
widespread adoption of precision agriculture technology while also
acknowledging areas where there are opportunities for increased
adoption, such as for specific crop types or farm sizes and for
specific precision agriculture technologies, such as variable rate
technology.\115\ Where
[[Page 86597]]
adoption has been slower, the studies point to feasibility constraints
and the need for more research. For example, Lowenberg-DeBoer and
Erickson (2019) emphasize that precision agriculture has been widely
adopted and that in cases where technologies have been adopted at a
slower pace, the authors attribute it to technological and economic
feasibility challenges.\116\ The study authors also note that the
studies they reviewed hypothesize that more reliable decision rules
that account for the effects of moisture, temperature, soil organic
matter, and other factors on nitrogen response may be needed to
increase variable rate technology adoption.\117\ Whitmore (2019)
similarly notes the complexity and high cost of new equipment as
barriers to wider adoption of precision technology.\118\ CCEJN does not
provide any evidence related to other measures in its letter or other
measures in the State's analysis to support its claim.
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\114\ Whitmore (2019) op. cit.; Lowenberg-DeBoer and Erickson
(2019) op. cit.
\115\ Variable rate technology refers to the use of data and
automation to optimize application of fertilizer, soil amendments,
seed, or plant protection chemicals to optimize crop performance,
save time and money, and reduce environmental impacts.
\116\ Lowenberg-DeBoer and Erickson (2019) op. cit., p. 1552.
\117\ Id. at 1564-1565.
\118\ Whitmore (2019) op. cit.
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Finally, we disagree with CCEJN's assertion that if Rule 4570 is
effective, the State must consider making its optional requirements
mandatory. As discussed earlier in this response, if the EPA approves a
state's precursor demonstration showing that a particular
PM<INF>2.5</INF> precursor chemical species does not contribute
significantly to PM<INF>2.5</INF> levels above the standard in the
area, the state is relieved of the obligation to control emissions of
that precursor from existing sources in the relevant attainment plan.
Comment 3.C: Regarding the State's reliance on 2024 modeling
results for its precursor analysis, CCEJN asserts that the State should
not have relied on modeling of 2024, which is after the 2023 attainment
deadline, and which nevertheless shows ammonia contributions that are
above the contribution threshold. CCEJN further asserts that the use of
2024 modeling ``violates the Act in three ways.''
First, the commenter asserts that the approach ignores the
requirement to demonstrate attainment as expeditiously as practicable
because it does not consider ammonia reductions that may have resulted
in attainment before 2023. They note that the State claimed it was
close to attaining in 2020 and that meaningful reductions in ammonia
would have most likely resulted in attainment earlier (i.e., in 2021 or
2022).
Second, the commenter notes that the State relies not only on a
future year but a year after the attainment deadline. Because
NO<INF>X</INF> emissions are expected to be lower in 2024 than 2023,
the commenter suggests that the impacts of ammonia reductions would be
less in 2024 than in 2023 and that the impacts of ammonia reductions in
2023 are unknown. The commenter also claims that the EPA makes
assumptions about how the State conducted its analysis and recommends
that the EPA seek clarification from the State about whether the
analysis relied on emissions projected from baseline (i.e., existing)
control measures or baseline measures plus measures committed to in the
plan. If the State did not conduct the analysis ``with numbers that are
comparable to what are expected in 2023,'' the commenter contends that
the EPA must require the State to redo the analysis.
Third, CCEJN asserts that the State's model indicating a design
value of 12.03 [micro]g/m\3\ cannot accurately describe 2023 conditions
given that 2022 data show a design value well above 16 [micro]g/m\3\.
They conclude that the ``EPA's approval of a precursor analysis that
relies on such unrealistic modeling is therefore arbitrary and
capricious and contrary to law.''
Response 3.C: While the State relied on 2024 modeled sensitivities
of PM<INF>2.5</INF> to ammonia reductions, it is important to note that
the EPA also considered the 2023 model responses via a NO<INF>X</INF>-
based interpolation between the State's model results for 2020 and
2024. The highest estimated response was at the Hanford site, 0.26
[micro]g/m\3\ for 2024 and 0.27 [micro]g/m\3\ for 2023, and did not
change the EPA's conclusions regarding the ammonia precursor
demonstration.\119\ In determining that ammonia does not contribute
significantly in the San Joaquin Valley despite the Hanford response
being above the 0.25 [micro]g/m\3\ contribution threshold that the
State derived for the 1997 annual PM<INF>2.5</INF> NAAQS, we continue
to rely on the abundant ambient evidence of excess ammonia relative to
NO<INF>X</INF>. This evidence includes evidence specific to the Hanford
area, where mobile laboratory observations during the DISCOVER-AQ study
showed ambient concentrations of ammonia that were approximately five
times higher than those that were modeled.\120\ These factors led the
EPA to conclude that the model responses were likely overestimated and
did not represent a significant contribution of ammonia to
PM<INF>2.5</INF> levels.
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\119\ 88 FR 45276, 45293, fn. 184.
\120\ Kelly, J.T. et al. (2018), op. cit.
---------------------------------------------------------------------------
We further disagree with the commenter's assertion that the State's
approach ignores the requirement for expeditious attainment. The CAA
requirement for expeditious attainment is not directly relevant for
evaluating a precursor demonstration, which is mainly concerned with
whether PM<INF>2.5</INF> in the atmosphere is sensitive to emissions
reductions of the precursor. For that purpose, the PM<INF>2.5</INF>
Precursor Demonstration Guidance provides for the use of modeled
sensitivities of PM<INF>2.5</INF> to a reduction in precursor emissions
evaluated in the base year or a future year, noting that there are many
considerations in choosing the appropriate year to model.\121\ The key
factor for the State's use of a future year was the fact that sizable
NO<INF>X</INF> emissions reductions were projected to occur over time
and would change the atmospheric chemistry in the San Joaquin Valley.
The reductions are mainly due to the existing motor vehicle control
program and would occur independent of any controls in, or EPA action
on, the Plan.\122\ The sensitivity of PM<INF>2.5</INF> concentrations
to ammonia reductions decreases with decreasing NO<INF>X</INF>
emissions. Between 2020 and 2024, the modeled response to a 30 percent
ammonia emissions reduction declines by 50 percent at the design value
monitoring site, Bakersfield-Planz, from 0.24 [micro]g/m\3\ down to
0.12 [micro]g/m\3\. (The corresponding decline is 37 percent for the
average over all monitoring sites.) Thus, much of the benefit of
ammonia controls applied in 2020 would be lost by 2023 and 2024.
---------------------------------------------------------------------------
\121\ PM<INF>2.5</INF> Precursor Demonstration Guidance, p. 36.
\122\ 2018 PM<INF>2.5</INF> Plan, Appendix B. NO<INF>X</INF>
emissions decrease 27 percent between 2020 and 2024 due to baseline
measures.
---------------------------------------------------------------------------
With regard to whether ammonia emissions reductions could have
resulted in earlier attainment, the EPA used results from the Plan's
attainment demonstration to assess the effect of a 30 percent ammonia
reduction in 2022 and found that it would not have resulted in
attainment in that year.\123\ We estimated the 2022 design value as
15.4 [micro]g/m\3\ by using a NO<INF>X</INF> emissions-based
interpolation between the Plan's 2018 and 2023 design values, 16.3 and
14.7 [micro]g/m\3\, respectively.\124\ Similarly we estimated the 2022
sensitivity to ammonia from the State's modeled sensitivities for 2020
and 2024. Applying a 30 percent ammonia reduction for 2022 resulted in
a design value of 15.2 [micro]g/m\3\, which is above the level of the
1997 annual PM<INF>2.5</INF> NAAQS
[[Page 86598]]
(i.e., 15.0 [micro]g/m\3\). Thus, we conclude that ammonia emissions
reductions would not have resulted in attainment before the Plan's
projected 2023 attainment date.
---------------------------------------------------------------------------
\123\ Spreadsheet ``Estimated 2023 annual PM<INF>2.5</INF>
ammonia sensitivity and 2022 DV.xlsx,'' ``2023 vs. 2024 response to
30% ammonia reduction,'' EPA Region IX, October 20, 2023.
\124\ 15 [micro]g/m\3\ SIP Revision, Appendix K, Table 33.
---------------------------------------------------------------------------
Regarding the use of 2024 modeled sensitivities in lieu of modeled
sensitivities for 2023, the EPA finds that our conclusions would be the
same for the purposes of our evaluation of the precursor demonstration.
We estimated 2023 responses to ammonia emissions reductions by
interpolating between the responses for available 2020 and 2024
modeling; the interpolation used projected NO<INF>X</INF> emissions for
2020, 2023, and 2024 and found the estimated 2023 response to be only
0.01 [micro]g/m\3\ higher than in 2024.\125\ While there are several
differences between 2020 and 2024 modeled emissions for the various
PM<INF>2.5</INF> precursors and direct PM<INF>2.5</INF>, the key
difference for assessing the change in the sensitivity of
PM<INF>2.5</INF> to ammonia reductions is NO<INF>X</INF> emissions
levels. The modeling for 2020 and 2024 represent PM<INF>2.5</INF>
design values for the NO<INF>X</INF> emissions levels in 2020 and 2024,
and their respective responses to a 30 percent ammonia emissions
reduction. To estimate the PM<INF>2.5</INF> response to ammonia
reductions in other years or for other control scenarios, only the
NO<INF>X</INF> emissions level is needed. The estimate does not depend
on NO<INF>X</INF> emissions differences between 2023 and 2024
calculated for baseline, controlled, or other scenarios, only on the
resulting 2023 emissions level being evaluated.
---------------------------------------------------------------------------
\125\ Spreadsheet ``Estimated 2023 annual PM<INF>2.5</INF>
ammonia sensitivity and 2022 DV.xlsx,'' ``Whether 30% ammonia
reduction could attain early,'' EPA Region IX, October 20, 2023.
---------------------------------------------------------------------------
The commenter states that it is unclear whether the precursor
demonstration analysis relied on a baseline emissions inventory, or an
inventory considering the controls in the plan. While this is not
documented prominently in the submittal materials, the precursor
demonstration modeling performed by the State used baseline
projections,\126\ that is, emissions expected with existing control
measures and without new control measures from the 2018
PM<INF>2.5</INF> Plan or the 15 [micro]g/m\3\ SIP Revision.\127\
Notably, the EPA's conclusions for the precursor demonstration do not
depend on which of the two inventories is used. For the interpolation
to 2023, the EPA relied on controlled NO<INF>X</INF> emissions levels
(150.6 tpd) to estimate the 2023 response to 30 percent reduction to be
0.265 [micro]g/m\3\ (reported as 0.27 [micro]g/m\3\). Using baseline
NO<INF>X</INF> emissions (153.6 tpd), the estimated 2023 response is
0.275 [micro]g/m\3\, which is about 0.01 [micro]g/m\3\ higher. Thus,
the difference between using the baseline or controlled emissions for
assessing the sensitivity to ammonia emissions reductions is
negligible.
---------------------------------------------------------------------------
\126\ 2018 PM<INF>2.5</INF> Plan, Appendix K, Section 5.6
``PM<INF>2.5</INF> Precursor Sensitivity Analysis'', p. 70: ``To
evaluate the impact of reducing emissions of different
PM<INF>2.5</INF> precursors on PM<INF>2.5</INF> DVs, a series of
model sensitivity simulations were performed, for which
anthropogenic emissions of the precursor species were reduced by a
certain percentage from the baseline emissions;'' email dated
September 19, 2019, from Jeremy Avise, CARB, to Scott Bohning, EPA
Region IX, Subject: ``FW: SJV species responses,'' with attachments,
in which the attached tables have titles like ``Difference in Annual
PM<INF>2.5</INF> mass and species between the 2024 baseline run and
the 30% PM reduction precursor run.''
\127\ In comparison to potential modeling of controlled
emissions, the NO<INF>X</INF> emissions for projected baseline years
2020 and 2024 are higher, ammonia would be less abundant relative to
NO<INF>X</INF>, and the responses to ammonia reductions would be
higher. Relying on baseline rather than controlled NO<INF>X</INF>
emissions levels was therefore conservative for purposes of the
ammonia precursor demonstration.
---------------------------------------------------------------------------
Finally, the EPA disagrees that a monitored 2022 design value being
``well above'' the modeled 2023 design value invalidates the modeling
for purposes of the precursor demonstration. As discussed in the EPA's
modeling TSD for the 2018 PM<INF>2.5</INF> Plan,\128\ the State
determined that the model performance was excellent, and the EPA found
the results to be adequate for attainment demonstration modeling. The
modeling used a 2013 base year, i.e., the specific meteorological and
emissions conditions of 2013, not those of 2022 (nor of the 2018
monitored value used in scaling the modeling results from the 2018
PM<INF>2.5</INF> Plan). Even when the modeling itself is valid, the
model-predicted design value can differ from a recent monitored design
value due to different meteorological conditions than in 2013 base
case, emissions variability, and atypical events that affect the
monitored value, but that are not necessarily reflected in the modeling
because they are inherently unpredictable.\129\ The greater uncertainty
in the precursor demonstration, which supports the EPA's conclusion in
this final action, is that the modeling seems to conservatively
overestimate the sensitivity of PM<INF>2.5</INF> concentrations to
ammonia reductions compared to what would be expected based on ambient
measurements of ammonia and nitrate, as discussed in Response 3A.
---------------------------------------------------------------------------
\128\ EPA, ``Technical Support Document, EPA Evaluation of Air
Quality Modeling, San Joaquin Valley PM<INF>2.5</INF> Plan for the
2006 PM<INF>2.5</INF> NAAQS,'' February 2020.
\129\ The issue of how model predictions may not match monitor
observations despite a well-performing model, and how that does not
in itself invalidate the precursor demonstration is discussed in
more detail in the EPA's proposed disapproval of the 2018
PM<INF>2.5</INF> Plan portion addressing the 1997 annual
PM<INF>2.5</INF> NAAQS. 86 FR 67329, 67335 (November 26, 2021).
---------------------------------------------------------------------------
Comment 3.D: CCEJN's fourth concern with the precursor analysis is
that it believes that ``[t]he State improperly adopts a lax
contribution threshold of 0.25 [micro]g/m\3\.'' The commenter
acknowledges that the State's approach of using a 0.25 [micro]g/m\3\
threshold is consistent with the EPA's guidance but contends that the
guidance is arbitrary and capricious and that the EPA should reject it
in this rulemaking. To support their assertion, the commenter reasons
that
[t]he result of the state's approach is that an area, like the
San Joaquin Valley, that is failing to meet multiple successively
rigorous standards for the same measurement of the same pollutant,
may need to regulate a precursor only for purposes of the more
rigorous standard. This is a senseless result because the failure to
meet an already-outdated standard only highlights the necessity of
taking all feasible regulatory steps, including regulating relevant
precursors.
The commenter concludes that there is no advantage of two distinct
thresholds because the area will need to apply the lower threshold
eventually, and states that the ``EPA's failure to grapple with this
arbitrary result means that it has failed to provide a reasoned
explanation for its guidance, and the guidance--or at least its
application in this case--is arbitrary and capricious.'' For areas not
meeting both the 1997 and 2012 annual PM<INF>2.5</INF> NAAQS, the
commenter proposes that the EPA should require states to apply the
threshold for the 2012 NAAQS for purposes of evaluating a precursor
contribution for both NAAQS.
Response 3.D: The EPA disagrees that the same contribution
threshold must be used regardless of the level of the NAAQS being
examined. The EPA believes that applying a threshold that is
proportional to the level of the NAAQS is appropriate and consistent
with the Act; i.e., 0.2 [micro]g/m\3\ is appropriate for the 2012
annual PM<INF>2.5</INF> NAAQS of 12.0 [micro]g/m\3\, and 0.25 [micro]g/
m\3\ is appropriate for the 1997 annual PM<INF>2.5</INF> NAAQS of 15.0
[micro]g/m\3\.
The contribution thresholds the EPA derived in the PM<INF>2.5</INF>
Precursor Demonstration Guidance represent a change in air quality that
is statistically indistinguishable from the inherent variability in the
measured atmospheric concentrations. A contribution threshold that is
proportional to, or scales with, the level of the NAAQS may also be
termed a ``relative'' approach, since the size of the threshold is
relative to the level of the NAAQS. The contribution thresholds in the
PM<INF>2.5</INF>
[[Page 86599]]
Precursor Demonstration Guidance were derived from a relative
variability estimate multiplied by the NAAQS level for the 2006 24-hour
PM<INF>2.5</INF> NAAQS and 2012 annual PM<INF>2.5</INF> NAAQS. Notably,
the PM<INF>2.5</INF> Precursor Demonstration Guidance states: \130\
---------------------------------------------------------------------------
\130\ PM<INF>2.5</INF> Precursor Demonstration Guidance, p. 17,
fn. 20.
As described in the Technical Basis Document, the monitoring
site variability is first calculated as a percentage of the measured
PM<INF>2.5</INF>. Then the median percent variability from all sites
is multiplied by the level of the NAAQS to get the threshold
concentrations. Therefore, these thresholds represent a percentage
of the 2006 24-hour NAAQS (35 [mu]g/m\3\) and the 2012 annual NAAQS
(12 [mu]g/m\3\). Different thresholds may be applicable to other
---------------------------------------------------------------------------
levels and/or forms of the NAAQS (either past or future).
The Technical Basis Document \131\ referred to in the guidance
explains that relative variability (concentration changes as a fraction
of total concentration) was found to be more stable than absolute
variability (concentration changes in [micro]g/m\3\), and notes that
this ``indicates that a central tendency value for the relative
variability in the DV [design value]. Therefore, a representative value
can be multiplied by the level of that NAAQS to obtain a value in
concentration units ([micro]g/m\3\ for PM<INF>2.5</INF>) that is
appropriately used to characterize variability.'' \132\ The Technical
Basis Document also explains that the ``relative variability was fairly
consistent across the range of design values, suggesting a commonality
in the relative variability across a wide range of geographic regions,
chemical regimes, and baseline air quality levels.'' \133\ Thus, a
concentration amount that is relative, or proportional, to the NAAQS
level is a better basis than a fixed concentration number for
determining the size of a concentration change that is within the
inherent variability of monitored concentrations. The superiority of
the relative variability approach that was the basis of the
PM<INF>2.5</INF> Precursor Demonstration Guidance contribution
threshold of 0.2 [micro]g/m\3\ for the 2012 annual PM<INF>2.5</INF>
NAAQS makes it appropriate to scale that value according to the NAAQS
level to arrive at 0.25 [micro]g/m\3\ for the 1997 annual
PM<INF>2.5</INF> NAAQS.
---------------------------------------------------------------------------
\131\ EPA, ``Technical Basis for the EPA's Development of the
Significant Impact Thresholds for PM<INF>2.5</INF> and Ozone,'' EPA-
454/R-18-001R-18-001, EPA OAQPS, April 2018, available at <a href="https://www.epa.gov/nsr/significant-impact-levels-ozone-and-fine-particles">https://www.epa.gov/nsr/significant-impact-levels-ozone-and-fine-particles</a>,
<a href="https://www.epa.gov/sites/default/files/2018-04/documents/ozone_pm2.5_sils_technical_document_final_4-17-18.pdf">https://www.epa.gov/sites/default/files/2018-04/documents/ozone_pm2.5_sils_technical_document_final_4-17-18.pdf</a>.
\132\ Technical Basis Document, p. 26.
\133\ Id. at 39.
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Moreover, the EPA does not agree that it is arbitrary or contrary
to the Act to apply a lower contribution threshold or to potentially
regulate a precursor only for a more stringent NAAQS--it is reasonable
to expect that achieving lower PM<INF>2.5</INF> concentrations may
require regulation of additional sources of direct PM<INF>2.5</INF>
and/or PM<INF>2.5</INF> precursors. This is true even if an area is
nonattainment for both the higher and lower NAAQS and the EPA will
ultimately be applying the lower contribution threshold for a
subsequent plan to attain the more stringent NAAQS. Indeed, the
PM<INF>2.5</INF> SIP Requirements Rule at 40 CFR 51.1000 defines a
precursor demonstration to mean analyses showing that precursor
emissions do not contribute significantly to PM<INF>2.5</INF> levels
that exceed the relevant PM2.5 standard'' [emphasis added]. Applying a
lower threshold for the 1997 annual PM<INF>2.5</INF> NAAQS because the
area is in nonattainment for a more stringent NAAQS could presume that
the modeling and precursor demonstration in a future plan will show
responses to ammonia reductions above the lower threshold and that
ammonia will be determined to be significant, such that ammonia would
need to be controlled. The EPA does not believe it is appropriate to
prejudge the analyses for a potential future plan.
4. BACM/MSM Demonstration
Comment 4: Regarding the BACM demonstration, CCEJN notes that the
EPA's proposed approval does not address the CAA requirement for most
stringent measures (MSM), asserting that such analysis is required for
a 189(d) plan under 40 CFR 51.1010(c)(2)(i) and (c)(4), and 88 FR
45280, 45297, 45322. The commenter claims that it appears that the
State acknowledges that the MSM requirement applies in its submittal
and asserts that the EPA cannot approve the Plan until it reviews the
State's control measures under the MSM standard.
The commenter also states that ``[t]he state's control measures
meet neither the BACM nor MSM standards.'' They note that in previous
letters to the EPA (as summarized in a previous letter attachment
included as Exhibit B), Valley groups have identified numerous
weaknesses and presented ways the District could strengthen its
regulations. The commenter asserts that the EPA's technical support
document accompanying the proposed action addresses few of these
weaknesses, and advises that ``[t]o the extent EPA has not considered
whether the suggestions in the letter constitute BACM or MSM for
purposes of the 1997 annual standard, it should do so.'' Specifically,
the commenter notes that ``[o]ne particularly glaring shortfall in the
state's submission is its failure to contain any analysis of potential
control measures to minimize soil NO<INF>X</INF> emissions,'' and
suggests that the EPA must require the State to analyze the measures in
Exhibit A to CCEJN's comment letter (citing control measures described
on pages 5 and 6), including measures to reduce soil NO<INF>X</INF>
emissions from fertilized farmlands.
Response 4: We disagree with CCEJN's assertion that the EPA must
review the State's control measures analysis under the MSM standard. As
outlined in the PM<INF>2.5</INF> SIP Requirements Rule, the CAA
requirement for MSM is tied to a specific trigger in the act--an
extension of the Serious area deadline under CAA section 188(e).\134\
The EPA addressed the relevance of MSM to a 189(d) plan as part of our
discussion of the control strategy for such plan in the technical
support document accompanying the final rule: \135\
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\134\ 81 FR 58010, 58094.
\135\ EPA, ``Response to Comments on the Fine Particulate Matter
National Ambient Air Quality Standards: State Implementation Plan
Requirements,'' July 29, 2016.
In addition to meeting the 5 percent emission reduction
requirement for PM<INF>2.5</INF> or any PM<INF>2.5</INF> plan
precursor, for any Serious nonattainment area that fails to attain
by the Serious area attainment date, the state is required to update
its control measures analysis in the section 189(d) plan. In the
event the area previously had received an extension of the Serious
area attainment date pursuant to section 188(e), the reevaluation of
control measures referenced in section 51.1010(c)(2) should include
a reevaluation of MSM. (For this reason, section 51.1010(c)(2)(i)
refers to the reevaluation of MSM ``as applicable.'') If, however,
the area did not previously request and receive an extension of the
Serious area attainment date under section 188(e), the MSM
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requirement does not apply.
Thus, we noted in the summary of the requirements for Serious
PM<INF>2.5</INF> areas that fail to attain in our proposed action that
MSM is applicable only if the EPA granted an extension of the
attainment date under CAA section 188(e) for the area for the NAAQS at
issue.\136\
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\136\ 88 FR 45276, 45280, fn. 57.
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As discussed in our proposal, California's Serious area plan for
the 1997 PM<INF>2.5</INF> NAAQS submitted in 2015 included a request
under CAA section 188(e) to extend the attainment date for the 1997
annual PM<INF>2.5</INF> NAAQS by five years to December 31, 2020.\137\
However, after considering public comments, the EPA denied California's
request for an extension of the attainment date and subsequently
determined that the area failed to attain by the December 31, 2015
Serious area
[[Page 86600]]
attainment date, triggering the requirement for the 189(d) plan.
Consequently, because the San Joaquin Valley area did not receive an
extension of the Serious area attainment date under CAA section 188(e),
the MSM requirement does not apply for purposes of the 1997 annual
PM<INF>2.5</INF> NAAQS.
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\137\ Id. at 45277.
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Regarding the commenter's claim that the State appears to
acknowledge in its submission that MSM applies, we note that the
State's controls analysis in the 2018 PM<INF>2.5</INF> Plan was
developed to address multiple PM<INF>2.5</INF> NAAQS, including the
2006 PM<INF>2.5</INF> NAAQS for which the State requested an attainment
date extension under CAA section 188(e), triggering the MSM requirement
for those NAAQS. Any assertion by the State in the SJV PM<INF>2.5</INF>
Plan that a particular measure meets the MSM standard may not
necessarily indicate that the State believes that the requirement
applies for the 1997 annual PM<INF>2.5</INF> NAAQS. Regardless,
regarding CCEJN's comment that the State's control measures do not meet
the BACM or MSM standards, given that the MSM standard does not apply
to the 1997 annual PM<INF>2.5</INF> NAAQS, as discussed earlier in this
response, we are responding only to the commenter's assertion regarding
BACM.
We also disagree with the commenter's assertion that the control
measures in the Plan do not meet the requirement for BACM for the 1997
annual PM<INF>2.5</INF> NAAQS. As discussed in our proposed rule, in
our review of the State's and District's BACM demonstration, we
considered our evaluation of the State's and District's rules,
supporting information provided in the SJV PM<INF>2.5</INF> Plan, and
our prior evaluations of the BACM and MSM demonstrations in the 2018
PM<INF>2.5</INF> Plan for other PM<INF>2.5</INF> NAAQS.\138\ These
prior evaluations include those to support our approval of the
demonstration for BACM (including BACT) for the 1997 24-hour
PM<INF>2.5</INF> NAAQS,\139\ our approval of the demonstrations for
BACM and MSM for the 2006 24-hour PM<INF>2.5</INF> NAAQS,\140\ and our
proposed disapproval of the demonstration for BACM for the 2012 annual
PM<INF>2.5</INF> NAAQS.\141\ The EPA's prior actions for the 1997 24-
hour, 2006 24-hour, and 2012 annual PM<INF>2.5</INF> NAAQS are relevant
to our evaluation for this final rulemaking because the State relied on
a common analysis for each of the PM<INF>2.5</INF> standards. The EPA
conducted a thorough analysis of the State's BACM demonstration for
purposes of these prior actions, and updated the analysis for certain
source categories, as appropriate, for purposes of our proposed
approval of the BACM demonstration in the SJV PM<INF>2.5</INF> Plan for
the 1997 annual PM<INF>2.5</INF> NAAQS.
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\138\ Id. at 45305-45306.
\139\ 87 FR 4503 (January 28, 2022).
\140\ 85 FR 44192 (July 22, 2020).
\141\ 86 FR 74310 (December 29, 2021).
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Regarding the EPA's prior approval of the BACM demonstration in the
2018 PM<INF>2.5</INF> Plan as meeting the CAA requirements for the 2006
24-hour PM<INF>2.5</INF> NAAQS, we note that on September 17, 2020, a
group of five environmental, public health, and community groups
petitioned the Ninth Circuit Court of Appeals (``Ninth Circuit'') for
review of the EPA's final rulemaking approving the 2018
PM<INF>2.5</INF> Plan's demonstration of BACM, BACT, and MSM for
emissions sources of direct PM<INF>2.5</INF> and NO<INF>X</INF> for
purposes of the 2006 PM<INF>2.5</INF> NAAQS.\142\ On April 13, 2022,
the Ninth Circuit denied the petitioners' challenge with respect to the
EPA's approval of the Plan's BACM/MSM demonstration, upholding such
approval for those NAAQS.
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\142\ See Medical Advocates for Healthy Air v. EPA, Case No. 20-
72780, Dkt. #58-1 (9th Cir., April 13, 2022). The five
environmental, public health, and community organizations, in order
of appearance in the petition, are Medical Advocates for Healthy
Air, National Parks Conservation Association, Association of
Irritated Residents, and Sierra Club.
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Following approval of the State's BACM and MSM demonstrations for
the 2006 24-hour PM<INF>2.5</INF> NAAQS, on December 29, 2021, the EPA
proposed to approve portions of the 2018 PM<INF>2.5</INF> Plan as
meeting the Serious area requirements for the San Joaquin Valley for
the 2012 annual PM<INF>2.5</INF> NAAQS, including the requirement that
the plan include BACM. However, after considering public comments, on
October 5, 2022, the EPA proposed to disapprove portions of the
District's BACM demonstration, including the evaluations of ammonia
emissions sources and building heating sources.\143\ We proposed to
disapprove the BACM demonstration for ammonia sources based in part on
our on proposed disapproval of the State's ammonia precursor analysis
for the 2012 annual PM<INF>2.5</INF> NAAQS,\144\ as well as the State's
control measure analysis for ammonia.\145\ We proposed to disapprove
the BACM demonstration for building heating sources based on recent
control measure developments and the time horizon of the 2012 annual
PM<INF>2.5</INF> NAAQS portion of the SJV PM<INF>2.5</INF> Plan, which
raised questions about the feasibility of implementing additional
controls for such sources for BACM purposes in the San Joaquin
Valley.\146\ Notably, we did not re-propose action on any other
portions of the State's and District's BACM demonstration that we had
previously proposed to approve.
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\143\ 87 FR 60494.
\144\ Based on our proposed disapproval of the precursor
demonstration for the 2012 annual PM<INF>2.5</INF> NAAQS, we
proposed to determine that ammonia remained a regulated precursor
for that NAAQS in the San Joaquin Valley.
\145\ 87 FR 60494, 60509.
\146\ Id. at 60511-60512.
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In response to the EPA's proposed disapproval of portions of the
BACM demonstration for the 2012 annual PM<INF>2.5</INF> NAAQS, CARB and
the District developed and submitted additional information to support
the ammonia precursor demonstration and building heating BACM
demonstration for purposes of meeting the Serious area and CAA section
189(d) requirements for the 1997 annual PM<INF>2.5</INF> NAAQS. Our
proposal and accompanying ``Technical Support Document, San Joaquin
Valley PM<INF>2.5</INF> Plan Revision for the 1997 Annual
PM<INF>2.5</INF> NAAQS,'' April 2023 (``EPA's 1997 Annual
PM<INF>2.5</INF> TSD'') summarize the additional information provided
by the State and District and the EPA's evaluation. Based on our
review, we determined that the additional information provided by the
State and District addressed the deficiencies identified in the
proposed disapproval of the 2018 PM<INF>2.5</INF> Plan for the 2012
annual PM<INF>2.5</INF> NAAQS as they pertained to the 1997 annual
PM<INF>2.5</INF> NAAQS. Thus, considering our prior approvals of the
State's and District's BACM analysis for the 1997 24-hour
PM<INF>2.5</INF> NAAQS, BACM and MSM analysis for the 2006
PM<INF>2.5</INF> NAAQS (which was upheld by the Ninth Circuit), and the
supplemental information provided to update the SJV PM<INF>2.5</INF>
Plan based on the latest information available, we proposed to approve
the BACM demonstration for the 1997 annual PM<INF>2.5</INF> NAAQS.
Regarding the measures in Exhibit B to CCEJN's comment letter, the
EPA has reviewed and considered the recommendations for improvements to
the District's PM<INF>2.5</INF> control strategy as outlined in the two
letters in Exhibit B sent by environmental groups to the EPA in 2021
\147\ and 2022.\148\ A detailed summary of our evaluation of the
feasibility of these measures, as well as numerous others, is provided
in Sections III and IV of the ``EPA Source Category and Control Measure
Assessment and Reasoned Justification
[[Page 86601]]
Technical Support Document'' (``Control Measure Assessment TSD'') \149\
accompanying our proposed action to promulgate a federal implementation
plan for contingency measures for the 1997 annual PM<INF>2.5</INF>
NAAQS, the 2006 24-hour PM<INF>2.5</INF> NAAQS, and the 2012 annual
PM<INF>2.5</INF> NAAQS.\150\ The EPA determined that the recommended
measures are either not technologically feasible or not economically
feasible within the two year timeframe for implementation as
contingency measures discussed in the EPA's draft guidance.\151\ Given
that by statute, contingency measures are additional requirements that
go beyond attainment planning requirements, and the shorter timeframe
of the attainment plan for the 1997 annual PM<INF>2.5</INF> NAAQS
(i.e., by December 31, 2023), we similarly conclude that these measures
are not feasible for purposes of the BACM requirement for the SJV
PM<INF>2.5</INF> Plan for the 1997 annual PM<INF>2.5</INF> NAAQS.
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\147\ Letter dated October 22, 2021, from environmental
organizations to Michael S. Regan, Administrator, EPA, Subject:
``Meeting Request to Discuss PM-2.5 Crisis in the San Joaquin
Valley.''
\148\ Letter dated May 18, 2022, from environmental
organizations to Michael S. Regan, Administrator, Environmental
Protection Agency, Subject: ``Meeting Request to Discuss PM-2.5
Crisis in the San Joaquin Valley.''
\149\ EPA Region IX, ``EPA Source Category and Control Measure
Assessment and Reasoned Justification Technical Support Document,
Proposed Contingency Measures Federal Implementation Plan for the
Fine Particulate Matter Standards for San Joaquin Valley,
California,'' July 2023.
\150\ 88 FR 53431 (August 8, 2023).
\151\ EPA, Office of Air Quality Planning and Standards, Air
Quality Policy Division, ``DRAFT: Guidance on the Preparation of
State Implementation Plan Provisions that Address the Nonattainment
Area Contingency Measure Requirements for Ozone and Particulate
Matter'' (``Draft Guidance''), March 16, 2023, p. 41.
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Lastly, we disagree with CCEJN's assertion that the EPA must
require the State to analyze the control measures for soil
NO<INF>X</INF> emissions outlined in Exhibit A in order to approve the
BACM demonstration for the 1997 annual PM<INF>2.5</INF> NAAQS. The EPA
previously addressed the issues of soil NO<INF>X</INF> emissions and of
analyzing potential controls for such emissions in the context of the
2018 PM<INF>2.5</INF> Plan in the EPA's ``Response to Comments Document
for the EPA's Final Action on the San Joaquin Valley Serious Area Plan
for the 2006 PM<INF>2.5</INF> NAAQS,'' June 2020 (``EPA's 2020 Response
to Comments'').\152\ More recently, the EPA also addressed the issue of
soil NO<INF>X</INF> emissions from the use of fertilizers and
pesticides in the context of our final rulemaking approving CARB's
submission of emissions inventories for VOC and NO<INF>X</INF> for the
2015 ozone NAAQS for areas in California (``2015 Ozone Inventory Final
Rule'').\153\
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\152\ EPA's 2020 Response to Comments, pp. 148-156, Comments and
responses 6.P-1 and 6.P-2.
\153\ 87 FR 59015 (September 29, 2022).
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In both the EPA's 2020 Response to Comments and the 2015 Ozone
Inventory Final Rule, the EPA acknowledged the studies cited by
commenters finding that soil NO<INF>X</INF> emissions from fertilizer
and pesticide use contribute to atmospheric NO<INF>X</INF> levels in
California.\154\ Particularly, the EPA acknowledged the growing body of
research surrounding the identification and quantification of soil
NO<INF>X</INF> emissions from fertilizer application in agricultural
soils. However, in light of the uncertainties and disagreements among
the studies regarding the contribution of fertilized cropland soils to
NO<INF>X</INF> emissions in California, the EPA found that CARB's
emissions inventories met the applicable requirements of the CAA
notwithstanding the absence of soil NO<INF>X</INF> emissions from
fertilizer or pesticide use.\155\ Furthermore, for purposes of our
final action on the San Joaquin Valley Serious Area Plan for the 2006
PM<INF>2.5</INF> NAAQS, we determined that there was not sufficient
information available to require a controls evaluation for soil
NO<INF>X</INF> emissions for purposes of the BACM analysis for those
NAAQS.\156\
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\154\ Id. at 59018.
\155\ Id. at 59018-59020.
\156\ EPA's 2020 Response to Comments, p. 156.
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Upon reviewing the studies cited by CCEJN in its comment letter, we
similarly find that the information provided is not sufficient to
compel a revision to the emissions inventories in the SJV
PM<INF>2.5</INF> Plan for the 1997 annual PM<INF>2.5</INF> NAAQS, given
the large uncertainties in the emissions estimates. As discussed in
Response 2.A, the magnitude of soil NO<INF>X</INF> emissions varies
based on temperature; agricultural practices, such as the timing and
amount of fertilizer application and irrigation; crop type; and other
factors. Additionally, soil NO<INF>X</INF> is not directly emitted and
involves numerous natural emissions sources and processes. Thus, soil
NO<INF>X</INF> emissions are inherently difficult to estimate and
model. Likewise, given that the production of NO<INF>X</INF> in the
soil is complex, it may also be challenging to estimate the effects of
potential controls. Due to the complexity of estimating soil
NO<INF>X</INF> emissions, the partially natural source of the
emissions, and the uncertainties in the effectiveness of potential
control measures, the EPA concludes that there is not sufficient
information available at this time to warrant an evaluation of
potential controls for soil NO<INF>X</INF> emissions in the San Joaquin
Valley for purposes of the BACM analysis for the 1997 annual
PM<INF>2.5</INF> NAAQS. We encourage CARB and the District to continue
their ongoing efforts to resolve the uncertainties in soil
NO<INF>X</INF> emissions and examine any implications for air quality
modeling and planning.
5. Public Process
Comment 5: CCEJN asserts that the EPA must disapprove portions of
the attainment plan for the 1997 annual PM<INF>2.5</INF> NAAQS because
the State did not provide public notice and the opportunity to comment
on portions of the Plan.
The commenter identifies two submissions made by CARB in March 2023
and June 2023 to provide additional information relevant to the
original SIP submissions comprising the Plan: the March 2023 Ammonia
Supplement and the March 2023 Building Heating Supplement, discussing
the ammonia precursor demonstration and the BACM requirement for
building electrification, and the Title VI Supplement, addressing
necessary assurances under CAA section 110(a)(2)(E). CCEJN notes that
CAA section 110(a)(2) requires ``[e]ach implementation plan submitted
by a State under this chapter shall be adopted by the State after
reasonable notice and public hearing.'' The commenter states that the
supplements are ``required contents of such plans'' and notes that the
EPA's supplemental proposal for the 2012 annual PM<INF>2.5</INF> NAAQS
indicated the EPA's expectation that any Title VI necessary assurances
would go through state-level notice and comment along with the
remainder of the Plan.
Because CARB submitted these supplements directly to the EPA
without first going through additional public process and after CARB
had formally submitted the Plan, the commenter asserts that the EPA
cannot rely upon these supplements to approve the State's precursor
demonstration, BACM demonstration, or necessary assurances under CAA
section 110(a)(2)(E)(i).
Response 5: Generally, the EPA agrees with CCEJN that SIP
submissions must meet the reasonable notice and public hearing
requirements of CAA section 110(a)(2). This is a basic requirement for
SIP submissions that appears in section 110(a)(1), section 110(a)(2),
and section 110(l), as well as EPA regulations pertaining to the
completeness of SIP submissions in 40 CFR part 51, Appendix V. However,
the EPA does not agree that this requirement necessarily applies to all
information of any type that a state may provide to the EPA. This
includes such instances as when the state is providing additional
information to supplement a SIP submission that did previously meet
notice and public hearing process
[[Page 86602]]
requirements, particularly when the EPA has requested that the state
provide such additional information to clarify an ambiguity in the
original SIP submission or to aid the EPA in evaluating adverse
comments raising an issue related to the original SIP submission.\157\
The EPA considers it appropriate to rely on such supplemental
information, even if it is not in the form of a formal SIP submission
that underwent full notice and public hearing process, when it expands
on and confirms information presented in the state's original SIP
submission or addresses potential deficiencies in the pre-existing
data.\158\ In such situations, the EPA considers the relevant question
to be whether the state provided reasonable notice and public hearing
with respect to the issue as part of the original SIP submission. It
would be illogical to require a state to restart the entire SIP
development process and would delay the EPA's action on a SIP
submission, thereby potentially delaying needed emissions reductions,
were the Agency to interpret CAA section 110(a)(2) notice and public
hearing requirements to apply to any and all supplemental information
provided by state. Thus, the EPA disagrees with CCEJN's assertion that
it is inappropriate for the Agency to rely on the additional
information provided by CARB in the two supplements in its analysis of
the SJV PM<INF>2.5</INF> Plan because it would violate the requirement
under section 110(a)(2) that plans submitted to the EPA for inclusion
in the SIP must go through ``reasonable notice and public hearing.''
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\157\ The EPA has previously explained that it may be
appropriate to rely on a supplemental letter from a state to resolve
ambiguities in a SIP submission. See 80 FR 33840, 33888 (June 12,
2015).
\158\ See 80 FR 33840, 33888 (``It is the EPA's practice to
neither require a state to resubmit a SIP submission nor repropose
action on the submission, so long as the clarification provided in
the interpretive letter is a logical outgrowth of the proposed SIP
provision.'').
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With respect to the 2023 Ammonia Supplement and the 2023 Building
Heating Supplement, the EPA believes the information contained therein
falls within the EPA's discretion to accept as a supplement, as it
expands upon and confirms information provided in the State's
previously submitted SIP submissions that did undergo the full notice
and public hearing process. CARB submitted the supplement to ``support
action on the attainment plan'' and the supplement was intended as
``clarifying information'' rather than a formal SIP revision.\159\
Also, CARB submitted this information in reaction to prior comments
related to the EPA's proposed action on the SIP submissions with
respect to the 2012 annual PM<INF>2.5</INF> NAAQS, and in anticipation
of receiving those same comments in this action. In this respect, CARB
provided additional information that it anticipated the EPA would
request to help evaluate the issues raised in such comments.
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\159\ Letter dated March 29, 2023, from Steven S. Cliff,
Executive Officer, CARB, to Martha Guzman, Regional Administrator,
EPA Region 9, with enclosures.
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In the ammonia context, the 2018 PM<INF>2.5</INF> Plan and 15
[micro]g/m\3\ SIP Revision present the fundamental elements of the
State's demonstration that ammonia does not contribute significantly to
exceedances of the 1997 annual PM<INF>2.5</INF> NAAQS, including
research that supports its conclusion that ammonium nitrate
PM<INF>2.5</INF> formation in the San Joaquin Valley is NO<INF>X</INF>-
limited rather than ammonia-limited; \160\ evidence that the area's
measures targeting VOC reductions are already reducing ammonia; \161\
and an analysis of how the District's control measures compare with
other state's rules and regulations.\162\ Upon initial review of the
State's submission, and in light of related comments received on
attainment plans for other PM<INF>2.5</INF> NAAQS for the San Joaquin
Valley, the EPA requested clarifying information and additional
analysis to support the State's conclusions in the SJV PM<INF>2.5</INF>
Plan for the 1997 annual PM<INF>2.5</INF> NAAQS.\163\ The information
and analysis the State provided in the March 2023 Ammonia Supplement
does not deviate from or fundamentally alter the analysis in the SJV
PM<INF>2.5</INF> Plan; rather, it provides a wide array of potential
controls and analyses to support the fundamental conclusions in the
submitted SIP. The EPA believes that CARB provided reasonable notice
and public hearing on its position with respect to the ammonia
precursor issue in the initial SIP submission, and the additional
information in the March 2023 Ammonia Supplement merely expands upon
that position. Moreover, by taking into account the information that
CARB provided in that supplement during this rulemaking action, the EPA
itself has provided the commenters with the opportunity to address that
supplemental information now.
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\160\ 2018 PM<INF>2.5</INF> Plan, Appendix G, pp. 9-10; CARB
December 2018 Staff Report, Appendix C, pp. 12-15; Attachment A to
CARB's May 9, 2019, submittal letter.
\161\ 2018 PM<INF>2.5</INF> Plan, Appendix C, Section C-25.
\162\ Id.
\163\ 40 CFR 51.1010 authorizes the EPA to require supplemental
information on potential controls when the EPA deems it necessary to
evaluate the comprehensive precursor demonstration. The regulations
and EPA guidance do not instruct on what state-level processes this
supplemental information should go through in being submitted to the
EPA. See PM<INF>2.5</INF> Precursor Demonstration Guidance, p. 31.
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Similarly, the building heating BACM demonstration in the 2018
PM<INF>2.5</INF> Plan provides the foundations and analysis for CARB's
conclusions that the State is implementing BACM with respect to
building heating appliances. As discussed in Section II.A.4, in 2020,
the EPA approved this demonstration as meeting BACM for the 2006 24-
hour PM<INF>2.5</INF> NAAQS.\164\ However, given comments concerning
this same issue on an EPA proposal related to the 2018 PM<INF>2.5</INF>
Plan with respect to 2012 annual PM<INF>2.5</INF> NAAQS, the EPA
requested that the State support its conclusion with more up-to-date,
additional analysis.\165\ Like the supplemental information for the
ammonia precursor demonstration, the March 2023 Building Heating
Supplement merely provides additional support for the State's original
analysis and determination that it is implementing BACM for this source
category in the San Joaquin Valley area. The EPA believes that CARB
provided reasonable notice and public hearing on its position with
respect to the building heating and electrification issue during the
development of initial SIP submission, and the additional information
in the March 2023 Building Heating Supplement merely expands upon that
position.
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\164\ 85 FR 44192 (July 22, 2020).
\165\ 87 FR 60494 (October 5, 2022); Comment letter dated and
received January 28, 2022, from Brent Newell, Public Justice, et
al., to Rory Mays, EPA Region IX, including Exhibits 1 through 47.
We note, however, that there is no Exhibit 23; so, there are 46
exhibits in total. Email dated February 1, 2022, from Brent Newell,
Public Justice, to Rory Mays, EPA Region IX. The 13 environmental,
public health, and community organizations are Public Justice,
Central Valley Environmental Justice Network, Association of
Irritated Residents, Central Valley Air Quality Coalition,
Leadership Counsel for Justice and Accountability, Valley
Improvement Projects, The LEAP Institute, Little Manila Rising,
Center for Race, Poverty, and the Environment, Central California
Asthma Collaborative, Animal Legal Defense Fund, National Parks
Conservation Association, and Food and Water Watch.
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Thus, the EPA believes the State provided reasonable notice and
opportunity for public engagement with respect to its conclusions in
the ammonia precursor demonstration and building heating BACM elements
of the SIP and satisfied the reasonable notice and public hearing
requirements of the CAA.\166\
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\166\ The EPA notes that a review of the State's records
submitted with the SIP indicates that the public did identify these
two elements prior to and during the public hearing held on the
State's approval of the SIP in 2021.
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With respect to the Title VI Supplement, the EPA acknowledges that
[[Page 86603]]
it provides additional information related to an issue that the State
did not expressly address during the development of the SJV
PM<INF>2.5</INF> Plan, i.e., the State did not previously engage in
public process specifically with respect to CAA section 110(a)(2)(E)
necessary assurances that implementation of the Plan would not be
prohibited by Title VI. However, in this instance, the issue of
necessary assurances arose in adverse comments on a related EPA
proposed action on the same 2018 PM<INF>2.5</INF> Plan with respect to
the 2012 PM<INF>2.5</INF> NAAQS.\167\ In order to address the concerns
raised by the commenter, the EPA sought additional information from the
State to supplement the SJV PM<INF>2.5</INF> Plan by providing
necessary assurances and CARB provided that information in the Title VI
Supplement to do so.
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\167\ 86 FR 74310 (December 29, 2021). Some of the environmental
and community organizations that contributed to the adverse comments
related to necessary assurances on the EPA's proposed SIP action for
the 2012 annual PM<INF>2.5</INF> NAAQS are among the organizations
that provided the adverse comments on the EPA's proposal for the
1997 annual PM<INF>2.5</INF> NAAQS discussed herein.
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In light of prior comments, and the responsiveness of the Title VI
Supplement to the prior comments, the EPA considers it appropriate to
rely on the additional information provided by CARB in this way. Going
forward, as part of developing new SIP submissions, the EPA requests
that CARB and the District include consideration of issues related to
compliance with Title VI as part of that process, in order to ensure
public awareness and engagement. The public notice and comment process
required for development of SIP submissions provides an opportunity for
an air agency to share its position on necessary assurances publicly,
and to develop the record supporting their analysis of CAA section
110(a)(2)(E)(i) as it pertains to a particular SIP submission. Through
this process, the EPA expects states to develop adequate necessary
assurances so that they can be reviewed during the air agency-level
public comment process and subsequently by the EPA.\168\
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\168\ The EPA notes that the content of the Title VI Supplement
is substantially similar to recent submissions of necessary
assurances from the State on the attainment plan for the 2015 ozone
NAAQS (see ``Staff Report, CARB Review of the San Joaquin Valley
2022 Plan for the 70 ppb 8-Hour Ozone Standard'' (release date:
December 16, 2022), pp. 21-23). The plan for the 2015 ozone NAAQS,
which was submitted after the EPA's supplemental proposal on the
plan for the 2012 annual PM<INF>2.5</INF> NAAQS, was made available
for public review during the State's public comment processes (see
CARB's ``Notice of Public Meeting to Consider Proposed San Joaquin
Valley 70 parts per billion Ozone State Implementation Plan,'' dated
December 16, 2022).
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B. Comments From Central Valley Air Quality Coalition (CVAQ)
Comment 6: CVAQ's comments cover many of the same issues as the
comments from CCEJN. In summary, they assert that the State's plan
``improperly relies upon faulty emission inventories and modeling data,
fails to regulate key PM<INF>2.5</INF> precursors like ammonia and soil
NO<INF>X</INF>, does not analyze the most stringent measures needed for
attainment, and does nothing to prove State compliance with Title VI of
the Civil Rights [Act] (Title VI).'' The commenter also notes that the
two CARB-submitted supplements did not go through the State's public
process, and that the EPA had an obligation to issue a federal
implementation plan in January 2021 and has failed to do so.
Response 6: The EPA has addressed CVAQ's concerns about the
emissions inventory and modeling data in Response 2.B; ammonia in
Responses 3.A through 3.D; soil NO<INF>X</INF> in Responses 2.A and 4;
MSM in Response 4; Title VI in Responses 1.A and 1.B, Response 5, and
in Response 7 that follows; and the State's public process in Response
5 of this document.
Regarding the EPA's federal implementation plan (FIP) obligation,
we do not dispute that the EPA has had an obligation to implement a FIP
for the San Joaquin Valley for the 1997 annual PM<INF>2.5</INF> NAAQS
due to a prior finding of failure to submit the required attainment
plan. As we explained in the proposed rule, as a result of the EPA's
December 6, 2018 determination effective January 7, 2019, that
California had failed to submit the required attainment plan for the
1997 annual PM<INF>2.5</INF> NAAQS, among other required SIP
submissions for the San Joaquin Valley, the EPA became subject to a
statutory deadline to promulgate a FIP for this purpose no later than
two years after the effective date of that determination--i.e., by
January 7, 2021.\169\ However, as a result of this final rulemaking
approving all but the contingency measure requirement of the submitted
Serious area and section 189(d) plan for the 1997 annual
PM<INF>2.5</INF> NAAQS, the only outstanding deficiency for these NAAQS
relates to contingency measures. We note that CARB has submitted three
SIP submissions to address the CAA contingency measure requirements for
the 1997 annual PM<INF>2.5</INF> NAAQS (as well as other
PM<INF>2.5</INF> NAAQS) in the San Joaquin Valley, including (1) the
``PM<INF>2.5</INF> Contingency Measure State Implementation Plan
Revision,'' submitted to the EPA on June 8, 2023; \170\ (2) amendments
to District Rule 8051 (``Open Areas''), submitted to the EPA on October
16, 2023; \171\ and (3) the state-wide ``California Smog Check
Contingency Measure for the State Implementation Plan,'' submitted to
the EPA on November 13, 2023.\172\ The EPA will act on the contingency
measure SIP revisions, and/or promulgate a FIP for the contingency
measure requirement for the 1997 annual PM<INF>2.5</INF> NAAQS and
other NAAQS, in a separate rulemaking.
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\169\ 88 FR 45276, 45278.
\170\ Letter dated June 7, 2023, from Steven S. Cliff, Executive
Officer, CARB, to Martha Guzman, Regional Administrator, EPA Region
IX.
\171\ Letter dated October 13, 2023, from Stev
[…truncated; see source link]Indexed from Federal Register on December 14, 2023.
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