[Federal Register Volume 87, Number 100 (Tuesday, May 24, 2022)]
[Proposed Rules]
[Pages 31485-31495]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-11151]



[[Page 31485]]

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

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2022-0138; EPA-HQ-OAR-2021-0663; FRL-9799-01-R9]


Air Plan Disapproval; Nevada; Interstate Transport of Air 
Pollution for the 2015 8-Hour Ozone National Ambient Air Quality 
Standards

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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

SUMMARY: Pursuant to the Clean Air Act (CAA or ``Act''), the 
Environmental Protection Agency (EPA) is proposing to disapprove a 
state implementation plan (SIP) submittal from Nevada addressing 
interstate transport for the 2015 8-hour ozone national ambient air 
quality standards (NAAQS). The ``good neighbor'' or ``interstate 
transport'' provision of the Act requires that each state's SIP contain 
adequate provisions to prohibit emissions from within the state from 
significantly contributing to nonattainment or interfering with 
maintenance of the NAAQS in other states. This requirement is part of 
the broader set of ``infrastructure'' requirements, which are designed 
to ensure that the structural components of each state's air quality 
management program are adequate to meet the state's responsibilities 
under the CAA. This disapproval, if finalized, will establish a 2-year 
deadline for the EPA to promulgate a federal implementation plan (FIP) 
to address the relevant interstate transport requirements, unless the 
EPA approves a subsequent SIP submittal that meets these requirements. 
Disapproval does not start a mandatory sanctions clock.

DATES: Comments: Written comments must be received on or before July 
25, 2022.

ADDRESSES: You may send comments, identified as Docket No. EPA-R09-OAR-
2022-0138, by any of the following methods: Federal eRulemaking Portal 
at https://www.regulations.gov following the online instructions for 
submitting comments or via email to [email protected]. Include 
Docket ID No. EPA-R09-OAR-2022-0138 in the subject line of the message.
    Instructions: All submissions received must include the Docket ID 
No. for this rulemaking. Comments received may be posted without change 
to https://www.regulations.gov, including any personal information 
provided. For detailed instructions on sending comments and additional 
information on the rulemaking process, see the ``Public Participation'' 
heading of the SUPPLEMENTARY INFORMATION section of this document.

FOR FURTHER INFORMATION CONTACT: Tom Kelly, Air Planning Office (AIR-
2), U.S. Environmental Protection Agency, Region IX, (415) 972-3856, 
[email protected].

SUPPLEMENTARY INFORMATION: Public Participation: Submit your comments, 
identified by Docket ID No. EPA-R09-OAR-2022-0138, at https://www.regulations.gov (our preferred method), or the other methods 
identified in the ADDRESSES section. Once submitted, comments cannot be 
edited or removed from the docket. The EPA may publish any comment 
received to its public docket. Do not submit to EPA's docket at https://www.regulations.gov any information you consider to be Confidential 
Business Information (CBI) or other information whose disclosure is 
restricted by statute. Multimedia submissions (audio, video, etc.) must 
be accompanied by a written comment. The written comment is considered 
the official comment and should include discussion of all points you 
wish to make. The EPA will generally not consider comments or comment 
contents located outside of the primary submission (i.e., on the web, 
cloud, or other file sharing system).
    There are two dockets supporting this action, EPA-R09-OAR-2022-0138 
and EPA-HQ-OAR-2021-0663. Docket No. EPA-R09-OAR-2022-0138 contains 
information specific to Nevada, including the notice of proposed 
rulemaking. Docket No. EPA-HQ-OAR-2021-0663 contains additional 
modeling files, emissions inventory files, technical support documents, 
and other relevant supporting documentation regarding interstate 
transport of emissions for the 2015 8-hour ozone NAAQS that are being 
used to support this action. All comments regarding information in 
either of these dockets are to be made in Docket No. EPA-R09-OAR-2022-
0138. For additional submission methods, if you need assistance in a 
language other than English, or if you are a person with disabilities 
who needs a reasonable accommodation at no cost to you, please contact 
Tom Kelly, (415) 972-3856, [email protected]. For the full EPA 
public comment policy, information about CBI or multimedia submissions, 
and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
    The index to the docket for this action, Docket No. EPA-R09-OAR-
2022-0138, is available electronically at https://www.regulations.gov. 
While all documents in the docket are listed in the index, some 
information may not be publicly available due to docket file size 
restrictions or content (e.g., CBI).
    Throughout this document, ``we,'' ``us,'' and ``our'' means the 
EPA.

Table of Contents

I. Background
    A. Description of Statutory Background
    B. Description of the EPA's Four Step Interstate Transport 
Regulatory Process
    C. Background on the EPA's Ozone Transport Modeling Information
    D. The EPA's Approach To Evaluating Interstate Transport SIPs 
for the 2015 8-Hour Ozone NAAQS
II. SIP Submission Addressing Interstate Transport of Air Pollution 
for the 2015 8-Hour Ozone NAAQS
III. EPA Evaluation
    A. Evaluation of Information Provided by Nevada Regarding Steps 
1 and 2
    B. Results of the EPA's Step 1 and Step 2 Modeling and Findings 
for Nevada
    C. Evaluation of Information Provided Regarding Step 3
    D. Evaluation of Information Provided Regarding Step 4
    E. Conclusion
IV. Proposed Action
V. Statutory and Executive Order Reviews

I. Background

A. Description of Statutory Background

    On October 1, 2015, the EPA promulgated a revision to the 2015 8-
hour ozone NAAQS, lowering the level of both the primary and secondary 
standards to 0.070 parts per million (ppm).\1\ Section 110(a)(1) of the 
CAA requires states to submit, within 3 years after promulgation of a 
new or revised standard, SIP submissions meeting the applicable 
requirements of section 110(a)(2).\2\ One of these applicable 
requirements is found in CAA section 110(a)(2)(D)(i)(I), otherwise 
known as the ``interstate transport'' or ``good neighbor'' provision, 
which generally requires SIPs to contain adequate provisions to 
prohibit in-state emissions activities from having certain adverse air 
quality effects on other states due to interstate transport of 
pollution. There are two so-called ``prongs'' within CAA

[[Page 31486]]

section 110(a)(2)(D)(i)(I). A SIP for a new or revised NAAQS must 
contain adequate provisions prohibiting any source or other type of 
emissions activity within the state from emitting air pollutants in 
amounts that will significantly contribute to nonattainment of the 
NAAQS in another state (prong 1) or interfere with maintenance of the 
NAAQS in another state (prong 2). The EPA and states must give 
independent significance to prong 1 and prong 2 when evaluating 
downwind air quality problems under CAA section 110(a)(2)(D)(i)(I).\3\
---------------------------------------------------------------------------

    \1\ National Ambient Air Quality Standards for Ozone, Final 
Rule, 80 FR 65292 (October 26, 2015). Although the level of the 
standard is specified in the units of ppm, ozone concentrations are 
also described in parts per billion (ppb). For example, 0.070 ppm is 
equivalent to 70 ppb.
    \2\ SIP revisions that are intended to meet the applicable 
requirements of section 110(a)(1) and (2) of the CAA are often 
referred to as infrastructure SIPs, and the applicable elements 
under section 110(a)(2) are referred to as infrastructure 
requirements.
    \3\ See North Carolina v. EPA, 531 F.3d 896, 909-11 (D.C. Cir. 
2008).
---------------------------------------------------------------------------

B. Description of the EPA's Four Step Interstate Transport Regulatory 
Process

    The EPA is using the 4-step interstate transport framework (or ``4-
step framework'') to evaluate the states' SIP submittals addressing the 
interstate transport provision for the 2015 8-hour ozone NAAQS. The EPA 
has addressed the interstate transport requirements of CAA section 
110(a)(2)(D)(i)(I) with respect to prior ozone NAAQS in several 
regional regulatory actions, including the Cross-State Air Pollution 
Rule (CSAPR), which addressed interstate transport with respect to the 
1997 ozone NAAQS as well as the 1997 and 2006 fine particulate matter 
(``PM2.5'') standards,\4\ and the CSAPR Update \5\ and the 
Revised CSAPR Update, both of which addressed the 2008 ozone NAAQS.\6\ 
Through the development and implementation of the CSAPR rulemakings and 
prior regional rulemakings pursuant to the interstate transport 
provision,\7\ the EPA, working in partnership with states, developed 
the following 4-step framework to evaluate a state's obligations to 
eliminate interstate transport emissions under the interstate transport 
provision for the ozone NAAQS: (1) Identify monitoring sites that are 
projected to have problems attaining and/or maintaining the NAAQS 
(i.e., nonattainment and/or maintenance receptors); (2) identify states 
that impact those air quality problems in other (i.e., downwind) states 
sufficiently such that the states are considered ``linked'' and 
therefore warrant further review and analysis; (3) identify the 
emissions reductions necessary (if any), applying a multifactor 
analysis, to eliminate each linked upwind state's significant 
contribution to nonattainment or interference with maintenance of the 
NAAQS at the locations identified in Step 1; and (4) adopt permanent 
and enforceable measures needed to achieve those emissions reductions.
---------------------------------------------------------------------------

    \4\ See Federal Implementation Plans: Interstate Transport of 
Fine Particulate Matter and Ozone and Correction of SIP Approvals, 
76 FR 48208 (August 8, 2011).
    \5\ Cross-State Air Pollution Rule Update for the 2008 Ozone 
NAAQS, 81 FR 74504 (October 26, 2016).
    \6\ In 2019, the D.C. Circuit Court of Appeals remanded the 
CSAPR Update to the extent it failed to require upwind states to 
eliminate their significant contribution by the next applicable 
attainment date by which downwind states must come into compliance 
with the NAAQS, as established under CAA section 181(a). Wisconsin 
v. EPA, 938 F.3d 303, 313 (D.C. Cir. 2019). The Revised CSAPR Update 
for the 2008 Ozone NAAQS, 86 FR 23054 (April 30, 2021), responded to 
the remand of the CSAPR Update in Wisconsin and the vacatur of a 
separate rule, the ``CSAPR Close-Out,'' 83 FR 65878 (December 21, 
2018), in New York v. EPA, 781 F. App'x. 4 (D.C. Cir. 2019).
    \7\ In addition to the CSAPR rulemakings, other regional 
rulemakings addressing ozone transport include the ``NOX 
SIP Call,'' 63 FR 57356 (October 27, 1998), and the ``Clean Air 
Interstate Rule'' (CAIR), 70 FR 25162 (May 12, 2005).
---------------------------------------------------------------------------

C. Background on the EPA's Ozone Transport Modeling Information

    In general, the EPA has performed nationwide air quality modeling 
to project ozone design values which are used in combination with 
measured data to identify nonattainment and maintenance receptors. To 
quantify the contribution of emissions from specific upwind states on 
2023 ozone design values for the identified downwind nonattainment and 
maintenance receptors, the EPA performed nationwide, state-level ozone 
source apportionment modeling for 2023. The source apportionment 
modeling provided contributions to ozone at receptors from precursor 
emissions of anthropogenic nitrogen oxides (NOX) and 
volatile organic compounds in individual upwind states.
    The EPA has released several documents containing projected ozone 
design values, contributions, and information relevant to evaluating 
interstate transport with respect to the 2015 8-hour ozone NAAQS. 
First, on January 6, 2017, the EPA published a notice of data 
availability (NODA) in which we requested comment on preliminary 
interstate ozone transport data including projected ozone design values 
and interstate contributions for 2023 using a 2011 base year 
platform.\8\ In the NODA, the EPA used the year 2023 as the analytic 
year for this preliminary modeling because that year aligns with the 
expected attainment year for ``Moderate'' ozone nonattainment areas for 
the 2015 8-hour ozone NAAQS.\9\ On October 27, 2017, we released a 
memorandum (``October 2017 memorandum'') containing updated modeling 
data for 2023, which incorporated changes made in response to comments 
on the NODA, and noted that the modeling may be useful for states 
developing SIPs to address interstate transport obligations for the 
2008 ozone NAAQS.\10\ On March 27, 2018, we issued a memorandum 
(``March 2018 memorandum'') noting that the same 2023 modeling data 
released in the October 2017 memorandum could also be useful for 
identifying potential downwind air quality problems with respect to the 
2015 8-hour ozone NAAQS at Step 1 of the 4-step framework.\11\ The 
March 2018 memorandum also included the then newly available 
contribution modeling data for 2023 to assist states in evaluating 
their impact on potential downwind air quality problems for the 2015 8-
hour ozone NAAQS under Step 2 of the 4-step framework.\12\ The EPA 
subsequently issued two more memoranda in August and October 2018, 
providing additional information to states developing interstate 
transport SIP submissions for the 2015 8-hour ozone NAAQS concerning, 
respectively, potential contribution thresholds that may be appropriate 
to apply in Step 2 of the 4-step framework, and considerations for 
identifying downwind areas that may have problems maintaining the 
standard at Step 1 of the 4-step framework.\13\
---------------------------------------------------------------------------

    \8\ See Notice of Availability of the Environmental Protection 
Agency's Preliminary Interstate Ozone Transport Modeling Data for 
the 2015 8-hour Ozone National Ambient Air Quality Standard (NAAQS), 
82 FR 1733 (January 6, 2017).
    \9\ 82 FR 1733, 1735.
    \10\ See Information on the Interstate Transport State 
Implementation Plan Submissions for the 2008 Ozone National Ambient 
Air Quality Standards under Clean Air Act Section 
110(a)(2)(D)(i)(I), October 27, 2017, available in docket ID No. 
EPA-HQ-OAR-2021-0663.
    \11\ See Information on the Interstate Transport State 
Implementation Plan Submissions for the 2015 Ozone National Ambient 
Air Quality Standards under Clean Air Act Section 
110(a)(2)(D)(i)(I), March 27, 2018 (``March 2018 memorandum''), 
available in docket ID No. EPA-HQ-OAR-2021-0663.
    \12\ The March 2018 memorandum, however, provided, ``While the 
information in this memorandum and the associated air quality 
analysis data could be used to inform the development of these SIPs, 
the information is not a final determination regarding states' 
obligations under the good neighbor provision. Any such 
determination would be made through notice-and-comment rulemaking.''
    \13\ See Analysis of Contribution Thresholds for Use in Clean 
Air Act Section 110(a)(2)(D)(i)(I) Interstate Transport State 
Implementation Plan Submissions for the 2015 Ozone National Ambient 
Air Quality Standards, August 31, 2018 (``August 2018 memorandum''), 
and Considerations for Identifying Maintenance Receptors for Use in 
Clean Air Act Section 110(a)(2)(D)(i)(I) Interstate Transport State 
Implementation Plan Submissions for the 2015 Ozone National Ambient 
Air Quality Standards, October 19, 2018, available in docket ID No. 
EPA-HQ-OAR-2021-0663.
---------------------------------------------------------------------------

    Since the release of the modeling data shared in the March 2018

[[Page 31487]]

memorandum, the EPA performed updated modeling using a 2016-based 
emissions modeling platform (i.e., 2016v1). This emissions platform was 
developed under the EPA/Multi-Jurisdictional Organization (MJO)/state 
collaborative project.\14\ This collaborative project was a multi-year 
joint effort by the EPA, MJOs, and states to develop a new, more recent 
emissions platform for use by the EPA and states in regulatory modeling 
as an improvement over the dated 2011-based platform that the EPA had 
used to project ozone design values and contribution data provided in 
the 2017 and 2018 memoranda. The EPA used the 2016v1 emissions to 
project ozone design values and contributions for 2023. On October 30, 
2020, in the notice of proposed rulemaking for the Revised CSAPR 
Update, the EPA released and accepted public comment on 2023 modeling 
that used the 2016v1 emissions platform.\15\ Although the Revised CSPAR 
Update addressed transport for the 2008 ozone NAAQS, the projected 
design values and contributions from the 2016v1 platform are also 
useful for identifying downwind ozone problems and linkages with 
respect to the 2015 ozone NAAQS.\16\
---------------------------------------------------------------------------

    \14\ The results of this modeling, as well as the underlying 
modeling files, are included in docket ID No. EPA-HQ-OAR-2021-0663.
    \15\ See 85 FR 68964, 68981.
    \16\ See the Air Quality Modeling Technical Support Document for 
the Final Revised Cross-State Air Pollution Rule Update, included in 
the Headquarters docket ID No. EPA-HQ-OAR-2021-0663.
---------------------------------------------------------------------------

    Following the final Revised CSAPR Update, the EPA made further 
updates to the 2016 emissions platform to include mobile emissions from 
the EPA's Motor Vehicle Emission Simulator MOVES3 model \17\ and 
updated emissions projections for electric generating units that 
reflect the emissions reductions from the Revised CSAPR Update, recent 
information on plant closures, and other sector trends. The construct 
of the updated emissions platform, 2016v2, is described in the 
emissions modeling technical support document (TSD) for this proposed 
rule.\18\ The EPA performed air quality modeling of the 2016v2 
emissions using the most recent public release version of the 
Comprehensive Air-quality Model with extensions (CAMx) photochemical 
modeling, version 7.10.\19\ The EPA now proposes to primarily rely on 
modeling based on the updated and newly available 2016v2 emissions 
platform in evaluating these submissions with respect to Steps 1 and 2 
of the 4-step interstate transport framework and generally referenced 
within this action as 2016v2 modeling for 2023. By using the updated 
modeling results, the EPA is using the most current and technically 
appropriate information for this proposed rulemaking. Section III of 
this notice and the Air Quality Modeling TSD for 2015 Ozone NAAQS 
Transport SIP Proposed Actions, included in Docket ID No. EPA-HQ-OAR-
2021-0663 for this proposal, contain additional detail on the EPA's 
2016v2 modeling. In this notice, the EPA is accepting public comment on 
this updated 2023 modeling, which uses a 2016v2 emissions platform. 
Comments on the EPA's air quality modeling should be submitted in the 
regional docket for this action, docket ID No. EPA-R09-OAR-2022-0138. 
Comments are not being accepted in docket ID No. EPA-HQ-OAR-2021-0663.
---------------------------------------------------------------------------

    \17\ Additional details and documentation related to the MOVES3 
model can be found at https://www.epa.gov/moves/latest-version-motor-vehicle-emission-simulator-moves.
    \18\ See Technical Support Document (TSD) Preparation of 
Emissions Inventories for the 2016v2 North American Emissions 
Modeling Platform included in the Headquarters docket ID No. EPA-HQ-
OAR-2021-0663.
    \19\ Ramboll Environment and Health, January 2021, https://www.camx.com.
---------------------------------------------------------------------------

    States may have chosen to rely on the results of EPA modeling and/
or alternative modeling performed by states or MJOs to evaluate 
downwind air quality problems and contributions as part of their 
submissions. In Section III we evaluate how Nevada used air quality 
modeling information in their submission.

D. The EPA's Approach To Evaluating Interstate Transport SIPs for the 
2015 8-Hour Ozone NAAQS

    The EPA proposes to apply a consistent set of policy judgments 
across all states for purposes of evaluating interstate transport 
obligations and the approvability of interstate transport SIP 
submittals for the 2015 8-hour ozone NAAQS. These policy judgments 
reflect consistency with relevant case law and past agency practice as 
reflected in the CSAPR and related rulemakings. Nationwide consistency 
in approach is particularly important in the context of interstate 
ozone transport, which is a regional-scale pollution problem involving 
many smaller contributors. Effective policy solutions to the problem of 
interstate ozone transport going back to the NOX SIP Call 
have necessitated the application of a uniform framework of policy 
judgments in order to ensure an ``efficient and equitable'' approach. 
See EME Homer City Generation, LP v. EPA, 572 U.S. 489, 519 (2014).
    In the March, August, and October 2018 memoranda, the EPA 
recognized that states may be able to establish alternative approaches 
to addressing their interstate transport obligations for the 2015 8-
hour ozone NAAQS that vary from a nationally uniform framework. The EPA 
emphasized in these memoranda, however, that such alternative 
approaches must be technically justified and appropriate in light of 
the facts and circumstances of each particular state's submittal. In 
general, the EPA continues to believe that deviation from a nationally 
consistent approach to ozone transport must be substantially justified 
and have a well-documented technical basis that is consistent with 
relevant case law. Where states submitted SIPs that rely on any such 
potential ``flexibilities'' as may have been identified or suggested in 
the past, the EPA will evaluate whether the state adequately justified 
the technical and legal basis for doing so.
    The EPA notes that certain concepts included in an attachment to 
the March 2018 memorandum require unique consideration, and these ideas 
do not constitute agency guidance with respect to transport obligations 
for the 2015 ozone NAAQS. Attachment A to the March 2018 memorandum 
identified a ``Preliminary List of Potential Flexibilities'' that could 
potentially inform SIP development.\20\ However, the EPA made clear in 
that Attachment that the list of ideas were not suggestions endorsed by 
the Agency but rather ``comments provided in various forums'' on which 
the EPA sought ``feedback from interested stakeholders.'' \21\ Further, 
Attachment A stated, ``EPA is not at this time making any determination 
that the ideas discussed below are consistent with the requirements of 
the CAA, nor are we specifically recommending that states use these 
approaches.'' \22\ Attachment A to the March 2018 memorandum, 
therefore, does not constitute agency guidance, but was intended to 
generate further discussion around potential approaches to addressing 
ozone transport among interested stakeholders. To the extent states 
sought to develop or rely on these ideas in support of their SIP 
submittals, the EPA will thoroughly review the technical and legal 
justifications for doing so.
---------------------------------------------------------------------------

    \20\ March 2018 memorandum, Attachment A.
    \21\ Id. at A-1.
    \22\ Id.
---------------------------------------------------------------------------

    The remainder of this section describes the EPA's proposed 
framework with respect to analytic year, definition of nonattainment 
and maintenance receptors, selection of

[[Page 31488]]

contribution threshold, and multifactor control strategy assessment.
1. Selection of Analytic Year
    In general, states and the EPA must implement the interstate 
transport provision in a manner ``consistent with the provisions of 
[title I of the CAA.]'' CAA section 110(a)(2)(D)(i). This requires, 
among other things, that these obligations are addressed consistently 
with the timeframes for downwind areas to meet their CAA obligations. 
With respect to ozone NAAQS, under CAA section 181(a), this means 
obligations must be addressed ``as expeditiously as practicable'' and 
no later than the schedule of attainment dates provided in CAA section 
181(a)(1).\23\ Several D.C. Circuit court decisions address the issue 
of the relevant analytic year for the purposes of evaluating ozone 
transport air quality problems. On September 13, 2019, the D.C. Circuit 
issued a decision in Wisconsin v. EPA, remanding the CSAPR Update to 
the extent that it failed to require upwind states to eliminate their 
significant contribution by the next applicable attainment date by 
which downwind states must come into compliance with the NAAQS, as 
established under CAA section 181(a). 938 F.3d at 313.
---------------------------------------------------------------------------

    \23\ For attainment dates for the 2015 8-hour ozone NAAQS, refer 
to CAA section 181(a), 40 CFR 51.1303, and Additional Air Quality 
Designations for the 2015 Ozone National Ambient Air Quality 
Standards, 83 FR 25776 (June 4, 2018, effective August 3, 2018).
---------------------------------------------------------------------------

    On May 19, 2020, the D.C. Circuit issued a decision in Maryland v. 
EPA that cited the Wisconsin decision in holding that the EPA must 
assess the impact of interstate transport on air quality at the next 
downwind attainment date, including ``Marginal'' area attainment dates, 
in evaluating the basis for the EPA's denial of a petition under CAA 
section 126(b). Maryland v. EPA, 958 F.3d 1185, 1203-04 (D.C. Cir. 
2020). The court noted that ``section 126(b) incorporates the Good 
Neighbor Provision,'' and, therefore, ``EPA must find a violation [of 
section 126] if an upwind source will significantly contribute to 
downwind nonattainment at the next downwind attainment deadline. 
Therefore, the agency must evaluate downwind air quality at that 
deadline, not at some later date.'' Id. at 1204. The EPA interprets the 
court's holding in Maryland as requiring the states and the Agency, 
under the good neighbor provision, to assess downwind air quality as 
expeditiously as practicable and no later than the next applicable 
attainment date,\24\ which is now the Moderate area attainment date 
under CAA section 181 for ozone nonattainment. The Moderate area 
attainment date for the 2015 8-hour ozone NAAQS is August 3, 2024.\25\ 
The EPA believes that 2023 is now the appropriate year for analysis of 
interstate transport obligations for the 2015 8-hour ozone NAAQS, 
because the 2023 ozone season is the last relevant ozone season during 
which achieved emissions reductions in linked upwind states could 
assist downwind states with meeting the August 3, 2024 Moderate area 
attainment date for the 2015 8-hour ozone NAAQS.
---------------------------------------------------------------------------

    \24\ We note that the court in Maryland did not have occasion to 
evaluate circumstances in which the EPA may determine that an upwind 
linkage to a downwind air quality problem exists at steps 1 and 2 of 
the interstate transport framework by a particular attainment date, 
but for reasons of impossibility or profound uncertainty the Agency 
is unable to mandate upwind pollution controls by that date. See 
Wisconsin, 938 F.3d at 320. The D.C. Circuit noted in Wisconsin that 
upon a sufficient showing, these circumstances may warrant 
flexibility in effectuating the purpose of the interstate transport 
provision.
    \25\ See CAA section 181(a); 40 CFR 51.1303; Additional Air 
Quality Designations for the 2015 Ozone National Ambient Air Quality 
Standards, 83 FR 25776 (June 4, 2018, effective August 3, 2018).
---------------------------------------------------------------------------

    The EPA recognizes that the attainment date for nonattainment areas 
classified as Marginal for the 2015 8-hour ozone NAAQS was August 3, 
2021. Under the Maryland holding, any necessary emissions reductions to 
satisfy interstate transport obligations should have been implemented 
by no later than this date. At the time of the statutory deadline to 
submit interstate transport SIPs (October 1, 2018), many states relied 
upon the EPA modeling of the year 2023, and no state provided an 
alternative analysis using a 2021 analytic year (or the prior 2020 
ozone season). However, the EPA must act on SIP submittals using the 
information available at the time it takes such action. In this 
circumstance, the EPA does not believe it would be appropriate to 
evaluate states' obligations under CAA section 110(a)(2)(D)(i)(I) as of 
an attainment date that is wholly in the past, because the Agency 
interprets the interstate transport provision as forward looking. See 
86 FR at 23074; see also Wisconsin, 938 F.3d at 322. It would not make 
sense to analyze air quality, contribution levels, or emissions control 
strategies for the 2021 attainment date, for purposes of interstate 
transport obligations, when no emissions reductions, if shown to be 
needed, could be implemented by that date anyway.\26\ Consequently, in 
this proposal the EPA will use the analytical year of 2023 to evaluate 
each state's CAA section 110(a)(2)(D)(i)(I) SIP submission with respect 
to the 2015 8-hour ozone NAAQS.
---------------------------------------------------------------------------

    \26\ Nor does the EPA view 2022 as a reasonable analytic year 
for a similar reason: It would be impossible to finalize this action 
and implement any emissions reductions measures that could be shown 
to be needed by the 2022 ozone season. Thus, 2023 is the appropriate 
analytic year and also aligns with the next attainment date.
---------------------------------------------------------------------------

2. Step 1 of the 4-Step Interstate Transport Framework
    In Step 1, the EPA identifies monitoring sites that are projected 
to have problems attaining and/or maintaining the NAAQS in the 2023 
analytic year. Where the EPA's analysis shows that a site does not fall 
under the definition of a nonattainment or maintenance receptor, that 
site is excluded from further analysis under the EPA's 4-step 
interstate transport framework. For sites that are identified as a 
nonattainment or maintenance receptor in 2023, we proceed to the next 
step of our 4-step framework by identifying the upwind state's 
contribution to those receptors.
    The EPA's approach to identifying ozone nonattainment and 
maintenance receptors in this action is consistent with the approach 
used in previous transport rulemakings. The EPA's approach gives 
independent consideration to both the ``contribute significantly to 
nonattainment'' and the ``interfere with maintenance'' prongs of CAA 
section 110(a)(2)(D)(i)(I), consistent with the D.C. Circuit's 
direction in North Carolina v. EPA.\27\
---------------------------------------------------------------------------

    \27\ See North Carolina v. EPA, 531 F.3d at 910-11 (holding that 
the EPA must give ``independent significance'' to each prong of CAA 
section 110(a)(2)(D)(i)(I)).
---------------------------------------------------------------------------

    For the purpose of this proposal, the EPA identifies nonattainment 
receptors as those monitoring sites that are projected to have average 
design values that exceed the NAAQS and that are also measuring 
nonattainment based on the most recent monitored design values. This 
approach is consistent with prior transport rulemakings, such as the 
CSAPR Update, where the EPA defined nonattainment receptors as those 
areas that both currently measure nonattainment and that the EPA 
projects will be in nonattainment in the future analytic year (i.e., 
2023).\28\
---------------------------------------------------------------------------

    \28\ See 81 FR 74504 (October 26, 2016). This same concept, 
relying on both current monitoring data and modeling to define 
nonattainment receptor, was also applied in CAIR. See 70 FR at 
25162, 25249 (May 12, 2005); see also North Carolina, 531 F.3d at 
913-14 (affirming as reasonable EPA's approach to defining 
nonattainment in CAIR).
---------------------------------------------------------------------------

    In addition, in this proposal, the EPA identifies a receptor to be 
a ``maintenance'' receptor for purposes of defining interference with 
maintenance, consistent with the method used in the CSAPR and upheld by 
the D.C. Circuit

[[Page 31489]]

in EME Homer City Generation, L.P. v. EPA, 795 F.3d 118, 136 (D.C. Cir. 
2015).\29\ Specifically, the EPA identified maintenance receptors as 
those receptors that would have difficulty maintaining the relevant 
NAAQS in a scenario that takes into account historical variability in 
air quality at that receptor. The variability in air quality was 
determined by evaluating the ``maximum'' future design value at each 
receptor based on a projection of the maximum measured design value 
over the relevant base period. The EPA interprets the projected maximum 
future design value to be a potential future air quality outcome 
consistent with the meteorology that yielded maximum measured 
concentrations in the ambient data set analyzed for that receptor 
(i.e., ozone conducive meteorology). The EPA also recognizes that 
previously experienced meteorological conditions (e.g., dominant wind 
direction, temperatures, vertical mixing, insolation, and air mass 
patterns) promoting ozone formation that led to maximum concentrations 
in the measured data may reoccur in the future. The maximum design 
value gives a reasonable projection of future air quality at the 
receptor under a scenario in which such conditions do, in fact, 
reoccur. The projected maximum design value is used to identify upwind 
emissions that, under those circumstances, could interfere with the 
downwind area's ability to maintain the NAAQS.
---------------------------------------------------------------------------

    \29\ See 76 FR 48208 (August 8, 2011). CSAPR Update and Revised 
CSAPR Update also used this approach. See 81 FR 74504 (October 26, 
2016) and 86 FR 23054 (April 30, 2021).
---------------------------------------------------------------------------

    Recognizing that nonattainment receptors are also, by definition, 
maintenance receptors, the EPA often uses the term ``maintenance-only'' 
to refer to those receptors that are not nonattainment receptors. 
Consistent with the concepts for maintenance receptors, as described 
above, the EPA identifies ``maintenance-only'' receptors as those 
monitoring sites that have projected average design values above the 
level of the applicable NAAQS, but that are not currently measuring 
nonattainment based on the most recent official design values. In 
addition, those monitoring sites with projected average design values 
below the NAAQS, but with projected maximum design values above the 
NAAQS are also identified as ``maintenance only'' receptors, even if 
they are currently measuring nonattainment based on the most recent 
official design values.
3. Step 2 of the 4-Step Interstate Transport Framework
    In Step 2 the EPA quantifies the contribution of each upwind state 
to each receptor in the 2023 analytic year. The contribution metric 
used in Step 2 is defined as the average impact from each state to each 
receptor on the days with the highest ozone concentrations at the 
receptor based on the 2023 modeling. If a state's contribution value 
does not equal or exceed the threshold of 1 percent of the NAAQS (i.e., 
0.70 parts per billion (ppb) for the 2015 8-hour ozone NAAQS), the 
upwind state is not ``linked'' to a downwind air quality problem, and 
the EPA, therefore, concludes that the state does not significantly 
contribute to nonattainment or interfere with maintenance of the NAAQS 
in the downwind states. However, if a state's contribution equals or 
exceeds the 1 percent threshold, the state's emissions are further 
evaluated in Step 3, considering both air quality and cost as part of a 
multi-factor analysis, to determine what, if any, emissions might be 
deemed ``significant'' and, thus, must be eliminated under CAA section 
110(a)(2)(D)(i)(I). The EPA is proposing to rely in the first instance 
on the 1 percent threshold for the purpose of evaluating a state's 
contribution to nonattainment or maintenance of the 2015 8-hour ozone 
NAAQS (i.e., 0.70 ppb) at downwind receptors. This is consistent with 
the Step 2 approach that the EPA applied in CSAPR for the 1997 ozone 
NAAQS, which has subsequently been applied in the CSAPR Update when 
evaluating interstate transport obligations for the 2008 ozone NAAQS. 
The EPA continues to find 1 percent to be an appropriate threshold. For 
ozone, as the EPA found in the Clean Air Interstate Rule (CAIR), CSAPR, 
and CSAPR Update, a portion of the nonattainment problems from 
anthropogenic sources in the U.S. results from the combined impact of 
relatively small contributions from many upwind states, along with 
contributions from in-state sources and, in some cases, substantially 
larger contributions from a subset of particular upwind states. The 
EPA's analysis shows that much of the ozone transport problem being 
analyzed in this proposed rule is still the result of the collective 
impacts of contributions from many upwind states. Therefore, 
application of a consistent contribution threshold is necessary to 
identify those upwind states that should have responsibility for 
addressing their contribution to the downwind nonattainment and 
maintenance problems to which they collectively contribute. Continuing 
to use 1 percent of the NAAQS as the screening metric to evaluate 
collective contribution from many upwind states also allows the EPA 
(and states) to apply a consistent framework to evaluate interstate 
emissions transport under the interstate transport provision from one 
NAAQS to the next. See 81 FR 74504 at 74518. See also 86 FR 23054 at 
23085, reviewing and explaining rationale from CSAPR, 76 FR 48208 at 
48237-38, for selection of 1 percent threshold.
    The EPA's August 2018 memorandum recognized that in certain 
circumstances, a state may be able to establish that an alternative 
contribution threshold of 1 ppb is justifiable. Where a state relies on 
this alternative threshold, and where that state determined that it was 
not linked at Step 2 using the alternative threshold, the EPA will 
evaluate whether the state provided a technically sound assessment of 
the appropriateness of using this alternative threshold based on the 
facts and circumstances underlying its application in the particular 
SIP submission.
a. EPA's Experience With Alternative Step 2 Thresholds
    The EPA's August 2018 memorandum recognized that in certain 
circumstances, a state may be able to establish that an alternative 
contribution threshold of 1 ppb is justifiable. Where a state relies on 
this alternative threshold, and where that state determined that it was 
not linked at Step 2 using the alternative threshold, the EPA will 
evaluate whether the state provided a technically sound assessment of 
the appropriateness of using this alternative threshold based on the 
facts and circumstances underlying its application in the particular 
SIP submission.
    The EPA here shares further evaluation of its experience since the 
issuance of the August 2018 memorandum regarding use of alternative 
thresholds at Step 2. This experience leads the Agency to now believe 
it may not be appropriate to continue to attempt to recognize 
alternative contribution thresholds at Step 2. The August 2018 
memorandum stated that ``it may be reasonable and appropriate'' for 
states to rely on an alternative threshold of 1 ppb threshold at Step 
2.\30\ (The memorandum also indicated that any higher alternative 
threshold, such as 2 ppb, would likely not be appropriate.) However, 
the EPA also provided that ``air agencies should

[[Page 31490]]

consider whether the recommendations in this guidance are appropriate 
for each situation.'' Following receipt and review of 49 good neighbor 
SIP submittals for the 2015 8-hour ozone NAAQS, the EPA's experience 
has been that nearly every state that attempted to rely on a 1 ppb 
threshold did not provide sufficient information and analysis to 
support a determination that an alternative threshold was reasonable or 
appropriate for that state.
---------------------------------------------------------------------------

    \30\ See August 2018 memorandum at 4.
---------------------------------------------------------------------------

    For instance, in nearly all submittals, the states did not provide 
the EPA with analysis specific to their state or the receptors to which 
its emissions are potentially linked. In one case, the proposed 
approval of Iowa's SIP submittal, the EPA expended its own resources to 
attempt to supplement the information submitted by the state, in order 
to more thoroughly evaluate the state-specific circumstances that could 
support approval.\31\ It was at the EPA's sole discretion to perform 
this analysis in support of the state's submittal, and the Agency is 
not obligated to conduct supplemental analysis to fill the gaps 
whenever it believes a state's analysis is insufficient. The Agency no 
longer intends to undertake supplemental analysis of SIP submittals 
with respect to alternative thresholds at Step 2 for purposes of the 
2015 8-hour ozone NAAQS.
---------------------------------------------------------------------------

    \31\ Air Plan Approval; Iowa; Infrastructure State 
Implementation Plan Requirements for the 2015 Ozone National Ambient 
Air Quality Standard, 85 FR 12232 (March 2, 2020). The Agency 
received adverse comment on this proposed approval and has 
subsequently formally withdrawn the proposed approval. 87 FR 9477 
(Feb. 22, 2022).
---------------------------------------------------------------------------

    Furthermore, the EPA's experience since 2018 is that allowing for 
alternative Step 2 thresholds may be impractical or otherwise 
inadvisable for a number of additional policy reasons. For a regional 
air pollutant such as ozone, consistency in requirements and 
expectations across all states is essential. Based on its review of 
submittals to date and after further consideration of the policy 
implications of attempting to recognize an alternative Step 2 threshold 
for certain states, the Agency now believes the attempted use of 
different thresholds at Step 2 with respect to the 2015 8-hour ozone 
NAAQS raises substantial policy consistency and practical 
implementation concerns.\32\ The availability of different thresholds 
at Step 2 has the potential to result in inconsistent application of 
good neighbor obligations based solely on the strength of a state's 
implementation plan submittal at Step 2 of the 4-step interstate 
transport framework. From the perspective of ensuring effective 
regional implementation of good neighbor obligations, the more 
important analysis is the evaluation of the emissions reductions 
needed, if any, to address a state's significant contribution after 
consideration of a multifactor analysis at Step 3, including a detailed 
evaluation that considers air quality factors and cost. Where 
alternative thresholds for purposes of Step 2 may be ``similar'' in 
terms of capturing the relative amount of upwind contribution (as 
described in the August 2018 memorandum), nonetheless, use of an 
alternative threshold would allow certain states to avoid further 
evaluation of potential emission controls while other states must 
proceed to a Step 3 analysis. This can create significant equity and 
consistency problems among states.
---------------------------------------------------------------------------

    \32\ The EPA notes that Congress has placed on the EPA a general 
obligation to ensure the requirements of the CAA are implemented 
consistently across states and regions. See CAA section 301(a)(2). 
Where the management and regulation of interstate pollution levels 
spanning many states is at stake, consistency in application of CAA 
requirements is paramount.
---------------------------------------------------------------------------

    Further, it is not clear that national ozone transport policy is 
best served by allowing for less stringent thresholds at Step 2. The 
EPA recognized in the August 2018 memorandum that there was some 
similarity in the amount of total upwind contribution captured (on a 
nationwide basis) between 1 percent and 1 ppb. However, the EPA notes 
that while this may be true in some sense, that is hardly a compelling 
basis to move to a 1 ppb threshold. Indeed, the 1 ppb threshold has the 
disadvantage of losing a certain amount of total upwind contribution 
for further evaluation at Step 3 (e.g., roughly 7 percent of total 
upwind state contribution was lost according to the modeling underlying 
the August 2018 memorandum; \33\ in the EPA's updated modeling, the 
amount lost is 5 percent). Considering the core statutory objective of 
ensuring elimination of all significant contribution to nonattainment 
or interference of the NAAQS in other states and the broad, regional 
nature of the collective contribution problem with respect to ozone, 
there does not appear to be a compelling policy imperative in allowing 
some states to use a 1 ppb threshold while others rely on a 1 percent 
of the NAAQS threshold.
---------------------------------------------------------------------------

    \33\ See August 2018 memorandum at 4.
---------------------------------------------------------------------------

    Consistency with past interstate transport actions such as CSAPR, 
and the CSAPR Update and Revised CSAPR Update rulemakings (which used a 
Step 2 threshold of 1 percent of the NAAQS for two less stringent ozone 
NAAQS), is also important. Continuing to use a 1 percent of NAAQS 
approach ensures that as the NAAQS are revised and made more stringent, 
an appropriate increase in stringency at Step 2 occurs, so as to ensure 
an appropriately larger amount of total upwind-state contribution is 
captured for purposes of fully addressing interstate transport. See 76 
FR 48208, 48237-38 (August 8, 2011).
    Therefore, notwithstanding the August 2018 memorandum's recognition 
of the potential viability of alternative Step 2 thresholds, and in 
particular, a potentially applicable 1 ppb threshold, the EPA's 
experience since the issuance of that memorandum has revealed 
substantial programmatic and policy difficulties in attempting to 
implement this approach. Nonetheless, the EPA is not at this time 
rescinding the August 2018 memorandum. As discussed further below in 
Section III, the basis for disapproval of the Nevada SIP submission 
with respect to the Step 2 analysis is, in the Agency's view, warranted 
even under the terms of the August 2018 memorandum. The EPA invites 
comment on this broader discussion of issues associated with 
alternative thresholds at Step 2. Depending on comment and further 
evaluation of this issue, the EPA may determine to rescind the August 
2018 memorandum in the future.
4. Step 3 of the 4-Step Interstate Transport Framework
    Consistent with the EPA's longstanding approach to eliminating 
significant contribution or interference with maintenance, at Step 3, 
states linked at Steps 1 and 2 are generally expected to prepare a 
multifactor assessment of potential emissions controls. The EPA's 
analysis at Step 3 in prior federal actions addressing interstate 
transport requirements has primarily focused on an evaluation of cost-
effectiveness of potential emissions controls (on a marginal cost-per-
ton basis), the total emissions reductions that may be achieved by 
requiring such controls (if applied across all linked upwind states), 
and an evaluation of the air quality impacts such emissions reductions 
would have on the downwind receptors to which a state is linked; other 
factors may potentially be relevant if adequately supported. In 
general, where the EPA's or alternative air quality and contribution 
modeling establishes that a state is linked at Steps 1 and 2, it will 
be insufficient at Step 3 for a state merely to point to its existing 
rules requiring control measures as a basis for approval. In general, 
the emissions-reducing effects of all existing emissions control

[[Page 31491]]

requirements are already reflected in the air quality results of the 
modeling for Steps 1 and 2. If the state is shown to still be linked to 
one or more downwind receptor(s), states must provide a well-documented 
evaluation determining whether their emissions constitute significant 
contribution or interference with maintenance by evaluating additional 
available control opportunities by preparing a multifactor assessment. 
While the EPA has not prescribed a particular method for this 
assessment, the EPA expects states at a minimum to present a sufficient 
technical evaluation. This would typically include information on 
emissions sources, applicable control technologies, emissions 
reductions, costs, cost effectiveness, and downwind air quality impacts 
of the estimated reductions, before concluding that no additional 
emissions controls should be required.\34\
---------------------------------------------------------------------------

    \34\ As examples of general approaches for how such an analysis 
could be conducted for their sources, states could look to the CSAPR 
Update, 81 FR 74504, 74539-51; CSAPR, 76 FR 48208, 48246-63; CAIR, 
70 FR 25162, 25195-229; or the NOX SIP Call, 63 FR 57356, 
57399-405. See also Revised CSAPR Update, 86 FR 23054, 23086-23116. 
Consistently across these rulemakings, the EPA has developed 
emissions inventories, analyzed different levels of control 
stringency at different cost thresholds, and assessed resulting 
downwind air quality improvements.
---------------------------------------------------------------------------

5. Step 4 of the 4-Step Interstate Transport Framework
    At Step 4, states (or the EPA) develop permanent and federally 
enforceable control strategies to achieve the emissions reductions 
determined to be necessary at Step 3 to eliminate significant 
contribution to nonattainment or interference with maintenance of the 
NAAQS. For a state linked at Steps 1 and 2 to rely on an emissions 
control measure at Step 3 to address its interstate transport 
obligations, that measure must be included in the state's SIP so that 
it is permanent and federally enforceable. See CAA section 110(a)(2)(D) 
(``Each such [SIP] shall . . . contain adequate provisions . . . .''). 
See also CAA 110(a)(2)(A); Committee for a Better Arvin v. U.S. E.P.A., 
786 F.3d 1169, 1175-76 (9th Cir. 2015) (holding that measures relied on 
by state to meet CAA requirements must be included in the SIP).

II. SIP Submission Addressing Interstate Transport of Air Pollution for 
the 2015 8-Hour Ozone NAAQS

    In Nevada, the Nevada Division of Environmental Protection (NDEP or 
``State'') is the state agency responsible for the adoption and 
submission to the EPA of Nevada SIPs and SIP revisions. NDEP submitted 
Nevada's infrastructure SIP revision for the 2015 ozone NAAQS on 
October 1, 2018 (``Nevada's 2018 SIP submission'' or 
``submittal'').\35\ We find this submittal meets the applicable 
completeness criteria in Appendix V to 40 CFR part 51. We are proposing 
to act on Nevada's Infrastructure SIP Submittals. Nevada's 2018 SIP 
submission included information from the two other agencies that 
regulate air quality in Nevada: The Clark County Department of Air 
Quality \36\ and the Washoe County Health District Air Quality 
Management Division.\37\
---------------------------------------------------------------------------

    \35\ Letter dated October 1, 2018, from Greg Lovato, 
Administrator, NDEP, to Mike Stoker, Regional Administrator, EPA 
Region IX, regarding: The Nevada State Implementation Plan for the 
2015 Primary and Secondary Ozone NAAQS.
    \36\ Letter dated September 18, 2018, from Mike Sword for Marci 
Henson, Director of the Clark County Department of Air Quality, 
regarding: Clark County Portion of the Nevada Infrastructure State 
Implementation Plan for the 2015 Ozone NAAQS. See Appendix C for the 
NDEP Ozone Interstate Transport Analysis.
    \37\ Letter dated August 28, 2018, from Charlene Albee, Director 
Air Quality Management Division, to Greg Lovato, Administrator, 
NDEP, 2015 regarding: Ozone National Ambient Air Quality Standard 
Infrastructure State Implementation Plan (SIP).
---------------------------------------------------------------------------

    The NDEP portion of Nevada's 2018 SIP submission addressed the good 
neighbor provisions of the CAA on page 9 of the submittal and in 
Appendix E.\38\ The NDEP analysis is reiterated in the Clark County and 
Washoe County portions of Nevada's 2018 SIP submission, which did not 
include a separate transport evaluation but instead includes NDEP's 
analysis verbatim.\39\ We refer to the collective information on good 
neighbor provisions as the ``the NDEP analysis.''
---------------------------------------------------------------------------

    \38\ The Nevada Division of Environmental Protection Portion of 
the Nevada State Implementation Plan for the 2015 Ozone NAAQS: 
Demonstration of Adequacy, dated October 1, 2018.
    \39\ See (1) Appendix C of the Clark County Portion of the 
Nevada State Implementation Plan to Meet the Ozone Infrastructure 
SIP Requirements of Clean Air Act Section 110(a)(2), Clark County 
Department of Air Quality, August 2018; and (2) Attachment C of the 
Washoe County Portion of the Nevada State Implementation Plan to 
Meet the Ozone Infrastructure SIP Requirements of Clean Air Act 
Section 110(a)(2), adopted by the Washoe County District Board of 
Health on July 26, 2018.
---------------------------------------------------------------------------

    The NDEP analysis concludes the state does not contribute to 
nonattainment or interfere with maintenance of the 2015 ozone NAAQS in 
any other state. This determination is based on the modeling results 
contained in EPA's March 2018 memorandum. The NDEP analysis further 
states, ``Nevada commits to continue to review new air quality 
information as it becomes available to ensure that this negative 
declaration is still supported by such information.'' \40\
---------------------------------------------------------------------------

    \40\ Nevada's 2018 SIP submission, 9.
---------------------------------------------------------------------------

    The NDEP analysis follows the 4-step framework to analyze its 
impact on other states. In Step 1, NDEP identified the nonattainment 
and maintenance monitors identified in the modeling results for 2023 
released with the March 2018 memorandum, which included a total of 
forty-five nonattainment monitors and twenty maintenance receptors.\41\
---------------------------------------------------------------------------

    \41\ NDEP used the terms nonattainment and maintenance receptors 
as the EPA defines those terms. See Appendix E, E-2, E-3, and E-4.
---------------------------------------------------------------------------

    In conducting Step 2, the NDEP analysis relied on the contribution 
modeling released with the March 2018 memorandum.\42\ NDEP also states 
that the State does not support the use of a 1 percent of the NAAQS 
screening level to determine potentially significant contributions in 
the CSAPR for western states. However, the NDEP analysis described the 
screening threshold as a ``very conservative approach since interstate 
contributions in the West are relatively small, especially given the 
large contributions from background and intrastate emissions.'' \43\ 
The NDEP analysis cited an EPA memorandum on significant impact levels 
for ozone and PM2.5 in prevention of significant 
deterioration (PSD) permitting \44\ as ``further evidence that the 
CSAPR screening threshold is a conservative approach to identify 
contributing upwind states.'' \45\ Despite this, the 2018 Nevada 
submittal utilized a 1 percent of the NAAQS threshold at Step 2.\46\
---------------------------------------------------------------------------

    \42\ Appendix E at E-2 and E-3.
    \43\ NDEP Portion of the 2018 Nevada Submittal, E-5.
    \44\ Memorandum dated April 17, 2018, from Peter Tsirigotis, 
Director, EPA Office of Air Quality Planning and Standards, to 
Regional Air Division Directors, Regions 1-10, regarding: Guidance 
on Significant Impact Levels for Ozone and Fine Particles in the 
Prevention of Significant Deterioration Permitting Program.
    \45\ Appendix E, E-5.
    \46\ Id. at E-10.
---------------------------------------------------------------------------

    While the NDEP analysis contained concerns about the use of the 
CSAPR screening level (1 percent of the NAAQS) in western states, it 
expressed confidence in the EPA's contribution modeling, stating, 
``contribution modeling is the best available data with which to 
conduct Nevada's transport analysis,'' and contribution modeling ``is 
state-of-the-science given the USEPA's constraints.'' \47\ Based on the 
EPA's contribution modeling results released in the March 2018 
memorandum, Nevada's 2018 submittal concluded that the largest 
contribution from Nevada to a nonattainment or

[[Page 31492]]

maintenance receptors in another state in 2023 was 0.9 percent of the 
2015 ozone NAAQS.\48\
---------------------------------------------------------------------------

    \47\ Id.
    \48\ Id. at E-6 and Attachment A. Specific contributions to 
nonattainment and maintenance monitors are contained in Table E-A3 
(Nevada's Contributions to 2023 Ozone Design Values for 
Nonattainment and Maintenance Monitors Outside of Nevada).
---------------------------------------------------------------------------

    Nevada's 2018 SIP submission also referenced its own comment 
letters and those of the Western States Air Resources Council on the 
EPA ozone transport proposed rules, proposed changes to modeling 
guidance, modeling white papers, and interstate transport models.
    Based on its conclusion that emissions sources in Nevada do not 
contribute above 1 percent of the NAAQS to any nonattainment and 
maintenance receptors, according to the modeling results contained in 
the EPA's March 2018 memorandum, NDEP, Washoe County, and Clark County 
determined that identification of necessary emissions reductions at 
Step 3 of the EPA's 4-step interstate transport framework is not 
needed.\49\ Accordingly, NDEP, Washoe County, and Clark County did not 
address reduction of upwind emissions at Step 4 of the interstate 
transport framework.\50\
---------------------------------------------------------------------------

    \49\ Id. at E-11.
    \50\ Id.
---------------------------------------------------------------------------

III. EPA Evaluation

    The EPA is proposing to find that Nevada's 2018 SIP submission does 
not meet the State's obligations with respect to prohibiting emissions 
that contribute significantly to nonattainment or interfere with 
maintenance of the 2015 8-hour ozone NAAQS in any other state based on 
the EPA's evaluation of the SIP submission using the 4-step interstate 
transport framework. The EPA is therefore proposing to disapprove 
Nevada's 2018 SIP submission.

A. Evaluation of Information provided by Nevada Regarding Steps 1 and 2

    At Step 1 of the 4-Step interstate transport framework, Nevada 
relied on EPA modeling released in the March 2018 memorandum to 
identify nonattainment and maintenance receptors in 2023. Since new 
modeling has been performed by the EPA with updated emissions data, the 
EPA proposes to primarily rely on the most recent modeling to identify 
nonattainment and maintenance receptors in 2023. Nonetheless, the NDEP 
analysis also identified a number of nonattainment and maintenance 
receptor sites in 2023 using the EPA's older modeling.\51\
---------------------------------------------------------------------------

    \51\ Id. at E-3 (Table E1) and E-4 (Table E2).
---------------------------------------------------------------------------

    At Step 2 of the 4-step interstate transport framework, Nevada 
relied on EPA modeling released in the March 2018 memorandum to 
identify upwind state linkages to nonattainment and maintenance 
receptors in 2023. Based on this, the analysis concluded that Nevada 
would contribute below 1 percent of the NAAQS to receptors in 2023 and 
was therefore not ``linked'' to any other state.\52\ However, in this 
proposal, the EPA relies on the Agency's most recently available 
modeling, which uses a more recent base year and more up-to-date 
emissions inventories, to identify upwind contributions and 
``linkages'' to downwind air quality problems in 2023 using a threshold 
of 1 percent of the NAAQS. As shown in Table 1 (and explained in III.B 
below), the updated EPA modeling identifies Nevada's maximum 
contribution to a downwind nonattainment or maintenance receptor to be 
greater than 1 percent of the standard (i.e., greater than 0.70 ppb). 
Because the entire technical basis for the State's submittal is that 
the State is not linked at Step 2, the EPA proposes to disapprove the 
SIP submission based on the EPA's finding that such a linkage does 
exist.
---------------------------------------------------------------------------

    \52\ Id. at E-11.
---------------------------------------------------------------------------

    Although the State did not rely on the 1 ppb threshold in its SIP 
submittal, the EPA recognizes that the most recently available EPA 
modeling at the time the State submitted its SIP submittal indicated 
the State did not contribute above 1 percent of the NAAQS to a 
projected downwind nonattainment or maintenance receptor. Therefore, 
the State may not have considered analyzing the reasonableness and 
appropriateness of a 1 ppb threshold at Step 2 of the 4-step interstate 
transport framework per the August 2018 memorandum. However, the EPA's 
August 2018 memorandum provided that whether use of a 1 ppb threshold 
is appropriate must be based on an evaluation of state-specific 
circumstances, and no such evaluation was included in the State's 
submittal. The EPA's experience with the alternative Step 2 threshold 
is discussed in Section I.D.3. As discussed there, the EPA is 
considering withdrawing the August 2018 memorandum.
    The NDEP analysis mentions the EPA's memorandum titled ``Guidance 
on Significant Impact Levels for Ozone and Fine Particles in the 
Prevention of Significant Deterioration Permitting Program'' (``SILs 
Guidance'') without specifically proposing the replacement of the 
screening threshold for interstate transport (1 percent of the NAAQS) 
with the screening level in the guidance (1 ppb).\53\ Even so, because 
the SILs Guidance is mentioned, we wish to clarify that it relates to a 
different provision of the CAA regarding implementation of the 
Prevention of Significant Deterioration (PSD) permitting program, i.e., 
a program that applies in areas that have been designated attainment of 
the NAAQS, and it is not applicable to the good neighbor provision, 
which requires states to eliminate significant contribution or 
interference with maintenance of the NAAQS at known and ongoing air 
quality problem areas in other states.
---------------------------------------------------------------------------

    \53\ Id. at E-4 and E-5 (citing Guidance on Significant Impact 
Levels for Ozone and Fine Particles in the Prevention of Significant 
Deterioration Permitting Program. Memorandum from Peter Tsirigotis, 
Director, EPA Office of Air Quality Planning and Standards, to 
Regional Air Division Directors, Regions 1-10. April 17, 2018).
---------------------------------------------------------------------------

B. Results of the EPA's Step 1 and Step 2 Modeling and Findings for 
Nevada

    As described in section I.B, the EPA performed air quality modeling 
using the 2016v2 emissions platform to project design values and 
contributions for 2023. These data were examined to determine if Nevada 
contributes at or above the threshold of 1 percent of the 2015 8-hour 
ozone NAAQS (0.70 ppb) to any downwind nonattainment or maintenance 
receptor. As shown in Table 1, the data \54\ indicate that in 2023, 
emissions from Nevada contribute greater than 1 percent of the standard 
to nonattainment or maintenance-only receptors in Salt Lake County and 
Davis County, Utah.\55\
---------------------------------------------------------------------------

    \54\ Design values and contributions at individual monitoring 
sites nationwide are provided in the file: 
2016v2_DVs_state_contributions.xlsx which is included in docket ID 
No. EPA-HQ-OAR-2021-0663.
    \55\ These modeling results are consistent with the results of a 
prior round of 2023 modeling using the 2016v1 emissions platform 
which became available to the public in the fall of 2020 in the 
Revised CSAPR Update, as noted in Section I. That modeling showed 
that Nevada had a maximum contribution greater than 0.70 ppb to at 
least one nonattainment or maintenance-only receptor in 2023. These 
modeling results are included in the file ``Ozone Design Values and 
Contributions Revised CSAPR Update.xlsx'' in docket EPA-HQ-OAR-2021-
0663.

[[Page 31493]]



                       Table 1--Nevada Linkage Results Based on EPA Updated 2023 Modeling
----------------------------------------------------------------------------------------------------------------
                                                                   2023 Average    2023 Maximum       Nevada
         Receptor ID               Location       Nonattainment/   design value    design value    contribution
                                                   maintenance         (ppb)           (ppb)           (ppb)
----------------------------------------------------------------------------------------------------------------
490353006....................  Salt Lake County  Nonattainment..            73.6            75.3            0.89
490110004....................  Davis County....  Nonattainment..            72.9            75.1            0.86
----------------------------------------------------------------------------------------------------------------

    Therefore, based on the EPA's evaluation of the information 
submitted by Nevada, and based on the EPA's most recent modeling 
results for 2023 using the 2016v2 emission platform, the EPA proposes 
to find that Nevada is linked at Steps 1 and 2 and has an obligation to 
assess potential emissions reductions from sources or other emissions 
activity at Step 3 of the 4-step framework.

C. Evaluation of Information Provided Regarding Step 3

    At Step 3 of the 4-step interstate transport framework, a state's 
emissions are further evaluated, in light of multiple factors, 
including air quality and cost considerations, to determine what, if 
any, emissions significantly contribute to nonattainment or interfere 
with maintenance and, thus, must be eliminated under CAA section 
110(a)(2)(D)(i)(I).
    To effectively evaluate which emissions in the state should be 
deemed ``significant'' and therefore prohibited, states generally 
should prepare an accounting of sources and other emissions activity 
for relevant pollutants and assess potential, additional emissions 
reduction opportunities and resulting downwind air quality 
improvements. The EPA has consistently applied this general approach 
(i.e., Step 3 of the 4-step interstate transport framework) when 
identifying emissions contributions that the Agency has determined to 
be ``significant'' (or interfere with maintenance) in each of its prior 
federal, regional ozone transport rulemakings, and this interpretation 
of the statute has been upheld by the Supreme Court. See EME Homer 
City, 572 U.S. 489, 519 (2014). While the EPA has not directed states 
that they must conduct a Step 3 analysis in precisely the manner the 
EPA has done in its prior regional transport rulemakings, SIPs 
addressing the obligations in CAA section 110(a)(2)(D)(i)(I) must 
prohibit ``any source or other type of emissions activity within the 
State'' from emitting air pollutants which will contribute 
significantly to downwind air quality problems. Thus, states must 
complete something similar to the EPA's analysis (or an alternative 
approach to defining ``significance'' that comports with the statute's 
objectives) to determine whether and to what degree emissions from a 
state should be ``prohibited'' to eliminate emissions that will 
``contribute significantly to nonattainment in, or interfere with 
maintenance of[hairsp]'' the NAAQS in any other state. Nevada did not 
conduct such an analysis in its SIP submission.
    The EPA modeling results released with the March 2018 memorandum 
indicated Nevada would not contribute above 1 percent of the NAAQS to 
any downwind receptor. Therefore, the NDEP analysis stated it 
``determined the identification of emissions reductions necessary to 
prevent Nevada from contributing significantly to downwind air quality 
problems is moot.'' \56\ Furthermore, NDEP ``commit[ed] to continue to 
review new air quality information as it becomes available to ensure 
that this negative declaration is still supported by such 
information.'' \57\ However, as mentioned above, the EPA has newly 
available information that indicates that sources in Nevada are linked 
to downwind air quality problems for the 2015 ozone standards. We 
therefore propose that Nevada was required to assess additional 
emissions control opportunities, and we propose to disapprove its 
submission because Nevada did not do so.
---------------------------------------------------------------------------

    \56\ Submittal, E-11.
    \57\ Nevada's 2018 SIP submission, 9.
---------------------------------------------------------------------------

D. Evaluation of Information Provided Regarding Step 4

    Step 4 of the 4-step interstate transport framework calls for 
development of permanent and federally enforceable control strategies 
to achieve the emissions reductions determined to be necessary at Step 
3 to eliminate significant contribution to nonattainment or 
interference with maintenance of the NAAQS. As mentioned previously, 
Nevada's SIP submission did not contain an evaluation of additional 
emissions control opportunities (or establish that no additional 
controls are required), and in fact NDEP analysis explicitly declined 
to address Step 4.\58\ As a result, the EPA proposes to disapprove 
Nevada's submittal on the separate, additional basis that the State has 
not developed permanent and enforceable emissions reductions necessary 
to meet the obligations of CAA section 110(a)(2)(d)(i)(I).
---------------------------------------------------------------------------

    \58\ Id. at E-11.
---------------------------------------------------------------------------

E. Conclusion

    Based on the EPA's evaluation of Nevada's SIP submission, the EPA 
is proposing to find that Nevada's 2018 SIP submission addressing CAA 
section 110(a)(2)(D)(i)(I) does not meet the State's interstate 
transport obligations, because it fails to contain the necessary 
provisions to eliminate emissions that will contribute significantly to 
nonattainment or interfere with maintenance of the 2015 8-hour ozone 
NAAQS in any other state.

IV. Proposed Action

    We are proposing to disapprove the portion of Nevada's 2018 SIP 
submission pertaining to interstate transport of air pollution that 
will significantly contribute to nonattainment or interfere with 
maintenance of the 2015 8-hour ozone NAAQS in other states. The 
following parts of the Nevada SIP submittal, transmitted to the EPA in 
a letter dated October 1, 2018,\59\ comprise the material to be 
disapproved:
---------------------------------------------------------------------------

    \59\ Letter dated October 1, 2018, from Greg Lovato, 
Administrator, NDEP, to Mike Stoker, Regional Administrator, EPA 
Region IX, regarding: The Nevada State Implementation Plan for the 
2015 Primary and Secondary Ozone NAAQS.
---------------------------------------------------------------------------

     The subheading (D)(i) and the text under the subheading on 
page 9 of the Nevada Division of Environmental Protection Portion of 
the Nevada State Implementation Plan for the 2015 Ozone NAAQS: 
Demonstration of Adequacy, dated October 1, 2018;
     Appendix E of the Nevada Division of Environmental 
Protection Portion of the Nevada State Implementation Plan for the 2015 
Ozone NAAQS: Demonstration of Adequacy, dated October 1, 2018;
     The text under the element heading (D)(i)(I) on page 5 of 
the Clark County Portion of the Nevada State Implementation Plan to 
Meet the Ozone Infrastructure SIP Requirements of Clean Air Act Section 
110(a)(2), Clark

[[Page 31494]]

County Department of Air Quality, August 2018;
     Appendix C of the Clark County Portion of the Nevada State 
Implementation Plan to Meet the Ozone Infrastructure SIP Requirements 
of Clean Air Act Section 110(a)(2), Clark County Department of Air 
Quality, August 2018;
     The text under the subheading element (D)(i) on page 4 of 
the Washoe County Portion of the Nevada State Implementation Plan to 
Meet the Ozone Infrastructure SIP Requirements of Clean Air Act Section 
110(a)(2), adopted by the Washoe County District Board of Health on 
July 26, 2018.
     Attachment C of the Washoe County Portion of the Nevada 
State Implementation Plan to Meet the Ozone Infrastructure SIP 
Requirements of Clean Air Act Section 110(a)(2), adopted by the Washoe 
County District Board of Health on July 26, 2018.
    Under CAA section 110(c)(1), disapproval would establish a 2-year 
deadline for the EPA to promulgate a FIP for Nevada to address the CAA 
section 110(a)(2)(D)(i)(I) interstate transport requirements pertaining 
to significant contribution to nonattainment and interference with 
maintenance of the 2015 8-hour ozone NAAQS in other states, unless the 
EPA approves a SIP that meets these requirements. Disapproval does not 
start a mandatory sanctions clock for Nevada. The remaining elements of 
Nevada's 2018 SIP submission are not addressed in this action and will 
be acted on in a separate rulemaking.

V. Statutory and Executive Order Reviews

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

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

B. Paperwork Reduction Act (PRA)

    This proposed action does not impose an information collection 
burden under the PRA because it does not contain any information 
collection activities.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. This 
action merely proposes to disapprove a SIP submission as not meeting 
the CAA.

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate as described in 
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect 
small governments. The action imposes no enforceable duty on any state, 
local or tribal governments or the private sector.

E. Executive Order 13132: Federalism

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

F. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    This action does not have tribal implications as specified in 
Executive Order 13175. This action does not apply on any Indian 
reservation land, any other area where the EPA or an Indian tribe has 
demonstrated that a tribe has jurisdiction, or non-reservation areas of 
Indian country. Thus, Executive Order 13175 does not apply to this 
action.

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

    The EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that concern environmental health or safety risks 
that the EPA has reason to believe may disproportionately affect 
children, per the definition of ``covered regulatory action'' in 
section 2-202 of the Executive Order. This action is not subject to 
Executive Order 13045 because it merely proposes to disapprove a SIP 
submission as not meeting the CAA.

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

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

I. National Technology Transfer and Advancement Act

    This rulemaking does not involve technical standards.

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

    The EPA believes the human health or environmental risk addressed 
by this action will not have potential disproportionately high and 
adverse human health or environmental effects on minority, low-income 
or indigenous populations. This action merely proposes to disapprove a 
SIP submission as not meeting the CAA.

K. CAA Section 307(b)(1)

    Section 307(b)(1) of the CAA governs judicial review of final 
actions by the EPA. This section provides, in part, that petitions for 
review must be filed in the D.C. Circuit: (i) When the agency action 
consists of ``nationally applicable regulations promulgated, or final 
actions taken, by the Administrator,'' or (ii) when such action is 
locally or regionally applicable, if ``such action is based on a 
determination of nationwide scope or effect and if in taking such 
action the Administrator finds and publishes that such action is based 
on such a determination.'' For locally or regionally applicable final 
actions, the CAA reserves to the EPA complete discretion whether to 
invoke the exception in (ii).\60\
---------------------------------------------------------------------------

    \60\ In deciding whether to invoke the exception by making and 
publishing a finding that an action is based on a determination of 
nationwide scope or effect, the Administrator takes into account a 
number of policy considerations, including his judgment balancing 
the benefit of obtaining the D.C. Circuit's authoritative 
centralized review versus allowing development of the issue in other 
contexts and the best use of agency resources.
---------------------------------------------------------------------------

    If the EPA takes final action on this proposed rulemaking the 
Administrator intends to exercise the complete discretion afforded to 
him under the CAA to make and publish a finding that the final action 
(to the extent a court finds the action to be locally or regionally 
applicable) is based on a determination of ``nationwide scope or 
effect'' within the meaning of CAA section 307(b)(1). Through this 
rulemaking action (in conjunction with a series of related actions on 
other SIP submissions for the same CAA obligations), the EPA interprets 
and applies section 110(a)(2)(d)(i)(I) of the CAA for the 2015 ozone 
NAAQS based on a common core of nationwide policy judgments and 
technical analysis concerning the interstate transport of pollutants 
throughout the continental U.S. In particular, the EPA is applying here 
(and in other proposed actions related to the same obligations) the 
same, nationally consistent 4-step framework for assessing good 
neighbor obligations for the 2015 ozone NAAQS. The EPA relies on a 
single set of updated, 2016-base year photochemical grid modeling 
results of the year 2023 as the primary basis for its assessment of air 
quality conditions and

[[Page 31495]]

contributions at steps 1 and 2 of that framework. Further, the EPA 
proposes to determine and apply a set of nationally consistent policy 
judgments to apply the 4-step framework. The EPA has selected a 
nationally uniform analytic year (2023) for this analysis and is 
applying a nationally uniform approach to nonattainment and maintenance 
receptors and a nationally uniform approach to contribution threshold 
analysis.\61\ For these reasons, the Administrator intends, if this 
proposed action is finalized, to exercise the complete discretion 
afforded to him under the CAA to make and publish a finding that this 
action is based on one or more determinations of nationwide scope or 
effect for purposes of CAA section 307(b)(1).\62\
---------------------------------------------------------------------------

    \61\ A finding of nationwide scope or effect is also appropriate 
for actions that cover states in multiple judicial circuits. In the 
report on the 1977 Amendments that revised section 307(b)(1) of the 
CAA, Congress noted that the Administrator's determination that the 
``nationwide scope or effect'' exception applies would be 
appropriate for any action that has a scope or effect beyond a 
single judicial circuit. See H.R. Rep. No. 95-294 at 323, 324, 
reprinted in 1977 U.S.C.C.A.N. 1402-03.
    \62\ The EPA may take a consolidated, single final action on all 
of the proposed SIP disapproval actions with respect to obligations 
under CAA section 110(a)(2)(D)(i)(I) for the 2015 ozone NAAQS. 
Should the EPA take a single final action on all such disapprovals, 
this action would be nationally applicable, and the EPA would also 
anticipate, in the alternative, making and publishing a finding that 
such final action is based on a determination of nationwide scope or 
effect.
---------------------------------------------------------------------------

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Ozone.

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

    Dated: May 16, 2022.
Martha Guzman Aceves,
Regional Administrator, Region IX.
[FR Doc. 2022-11151 Filed 5-23-22; 8:45 am]
BILLING CODE 6560-50-P