Federal Register / Vol. 87, No. 100 / Tuesday, May 24, 2022 / Proposed Rules 31485 

1National 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. 

2SIP 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. 

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 

kelly.thomasp@epa.gov. 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, 

kelly.thomasp@epa.gov. 

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, 

kelly.thomasp@epa.gov. 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 


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3See North Carolina v. EPA, 531 F.3d 896, 909– 

11 (D.C. Cir. 2008). 

4See Federal Implementation Plans: Interstate 

Transport of Fine Particulate Matter and Ozone and 

Correction of SIP Approvals, 76 FR 48208 (August 

8, 2011). 

5Cross-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). 

8See 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. 

10See 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. 

11See 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. 

12The 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-andcomment rulemaking.’’ 

13See 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. 

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

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. 

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

Since the release of the modeling data 

shared in the March 2018 


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14The results of this modeling, as well as the 

underlying modeling files, are included in docket 

ID No. EPA–HQ–OAR–2021–0663. 

15See 85 FR 68964, 68981. 

16See 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. 

17Additional details and documentation related 

to the MOVES3 model can be found at https://

www.epa.gov/moves/latest-version-motor-vehicleemission-simulator-moves. 

18See 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. 

19Ramboll Environment and Health, January 

2021, https://www.camx.com. 

20March 2018 memorandum, Attachment A. 

21 Id. at A–1. 

22 Id. 

memorandum, the EPA performed 

updated modeling using a 2016-based 

emissions modeling platform (i.e., 

2016v1). This emissions platform was 

developed under the EPA/MultiJurisdictional 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

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. 

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 regionalscale 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. 

The remainder of this section 

describes the EPA’s proposed 

framework with respect to analytic year, 

definition of nonattainment and 

maintenance receptors, selection of 


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23For 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). 

24We 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. 

25See 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). 

26Nor 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. 

27See 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)). 

28See 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). 

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. 

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. 

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. 

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

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

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 


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29See 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). 30See August 2018 memorandum at 4. 

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. 

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 


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31Air 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). 

32The 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. 33See August 2018 memorandum at 4. 

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. 

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. 

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. 

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. 

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 


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34As 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. 

35Letter 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. 

36Letter 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. 

37Letter 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). 

38The Nevada Division of Environmental 

Protection Portion of the Nevada State 

Implementation Plan for the 2015 Ozone NAAQS: 

Demonstration of Adequacy, dated October 1, 2018. 

39See (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. 

40Nevada’s 2018 SIP submission, 9. 

41NDEP used the terms nonattainment and 

maintenance receptors as the EPA defines those 

terms. See Appendix E, E–2, E–3, and E–4. 

42Appendix E at E–2 and E–3. 

43NDEP Portion of the 2018 Nevada Submittal, E– 

5. 

44Memorandum 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. 

45Appendix E, E–5. 

46 Id. at E–10. 

47 Id. 

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 welldocumented 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

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

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.’’ 

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

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

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

Whilethe 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 


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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). 

49 Id. at E–11. 

50 Id. 

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

52 Id. at E–11. 

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). 

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. 

55These 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. 

maintenance receptors in another state 

in 2023 was 0.9 percent of the 2015 

ozone NAAQS.48

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

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

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. 

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. 

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


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56Submittal, E–11. 57Nevada’s 2018 SIP submission, 9. 58 Id. at E–11. 

59Letter 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. 

TABLE 1—NEVADA LINKAGE RESULTS BASED ON EPA UPDATED 2023 MODELING

Receptor ID Location Nonattainment/maintenance 

2023 Average 

design value 

(ppb) 

2023 

Maximum 

design value 

(ppb) 

Nevada 

contribution 

(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’’ 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. 

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). 

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: 

• 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 


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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. 

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

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 


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61A 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. 

62The 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. 

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

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 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R08–OAR–2022–0268; EPA–HQ– 

OAR–2021–0663; FRL–9805–01–R8] 

Air Plan Disapproval; Wyoming; 

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 the Act), the Environmental 

Protection Agency (EPA) is proposing to 

disapprove the State Implementation 

Plan (SIP) submittal from Wyoming 

regarding interstate transport for the 

2015 8-hour ozone national ambient air 

quality standards (NAAQS). The ‘‘good 

neighbor’’ or ‘‘interstate transport’’ 

provision 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 

CAA 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–R08– 

OAR–2022–0268, to the Federal 

eRulemaking Portal at https://

www.regulations.gov following the 

online instructions for submitting 

comments. 

Instructions: All submissions received 

must include Docket No. EPA–R08– 

OAR–2022–0268. 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. The EPA Docket Office 

can be contacted at (202) 566–1744, and 

is located at EPA Docket Center Reading 

Room, WJC West Building, Room 3334, 

1301 Constitution Avenue NW, 

Washington, DC 20004. For further 

information on EPA Docket Center 

services and the current hours of 

operation at the EPA Docket Center, 

please visit us online at https://

www.epa.gov/dockets. 

FOR FURTHER INFORMATION CONTACT: 

Ellen Schmitt, Air and Radiation 

Division, EPA, Region 8, Mailcode 

8ARD–IO, 1595 Wynkoop Street, 

Denver, Colorado, 80202–1129, 

telephone number: (303) 312–6728, 

email address: schmitt.ellen@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Public participation: Submit your 

comments, identified by Docket No. 

EPA–R08–OAR–2022–0268, at https://

www.regulations.gov. 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 the 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–R08–OAR–2022–0268 and 

EPA–HQ–OAR–2021–0663. Docket No. 

EPA–R08–OAR–2022–0268 contains 

information specific to Wyoming, 

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 which are being 

used to support this action. All 

comments regarding information in 

either of these dockets are to be made 

in Docket No. EPA–R08–OAR–2022– 

0268. For additional submission 

methods, please contact Ellen Schmitt, 

telephone number: (303) 312–6728, 

email address: schmitt.ellen@epa.gov. 

For the EPA’s full public comment 

policy, information about CBI or 

multimedia submissions, and general 

guidance on making effective 

comments, please visit https://

www.epa.gov/dockets/commenting-epadockets. 

The index for Docket No. EPA–HQ– 

OAR–2021–0663, is available 

electronically at 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). 

The EPA continues to carefully and 

continuously monitor information from 

the Centers for Disease Control and 

Prevention (CDC), local area health 

departments, and our federal partners so 

that we can respond rapidly as 

conditions change regarding COVID–19. 


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