31470 Federal Register / Vol. 87, No. 100 / Tuesday, May 24, 2022 / Proposed Rules 

Indian country, the rule does not have 

tribal implications and will not impose 

substantial direct costs on tribal 

governments or preempt tribal law as 

specified by Executive Order 13175 (65 

FR 67249, November 9, 2000). 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Incorporation by 

reference, Intergovernmental relations, 

Nitrogen dioxide, Ozone, Reporting and 

recordkeeping requirements, Volatile 

organic compounds. 

Dated: May 16, 2022. 

Debra Shore, 

Regional Administrator, Region 5. 

[FR Doc. 2022–10819 Filed 5–23–22; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R08–OAR–2022–0315; EPA–HQ– 

OAR–2021–0663; FRL–9806–01–R8] 

Air Plan Disapproval; Utah; 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 federal Clean 

Air Act (CAA or the Act), the 

Environmental Protection Agency (EPA) 

is proposing to disapprove the State 

Implementation Plan (SIP) submittal 

from Utah regarding interstate transport 

for the 2015 8-hour ozone national 

ambient air quality standard (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. If the 

EPA finalizes this disapproval, the EPA 

will continue to be subject to an 

obligation to promulgate a Federal 

Implementation Plan (FIP) to address 

the relevant interstate transport 

requirements, which was triggered by a 

finding of failure to submit issued in 

December of 2019. 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–2022–0315, to the Federal 

eRulemaking Portal at https://

www.regulations.gov following the 

online instructions for submitting 

comments. 

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. 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: 

Adam Clark, Air and Radiation 

Division, EPA, Region 8, Mailcode 

8ARD–IO, 1595 Wynkoop Street, 

Denver, Colorado, 80202–1129, 

telephone number: (303) 312–7104, 

email address: clark.adam@epa.gov. 

SUPPLEMENTARY INFORMATION:

Public participation: Submit your 

comments, identified by Docket ID No. 

EPA–R08–OAR–2022–0315, 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 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–2022–0315 and 

EPA–HQ–OAR–2021–0663. Docket No. 

EPA–R08–OAR–2022–0315 contains 

information specific to Utah, 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– 

0315. For additional submission 

methods, please contact Adam Clark, 

telephone number: (303) 312–7104, 

email address: clark.adam@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 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. 

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 4-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. Utah SIP Submission Addressing Interstate 

Transport of Air Pollution for the 2015 

8-Hour Ozone NAAQS 

III. The EPA’s Evaluation 

A. Evaluation of Information Provided by 

Utah Regarding Step 1 and Step 2 

B. Evaluation of Information Provided 

Regarding Step 3 

C. Evaluation of Information Provided 

Regarding Step 4 

D. 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 ozone 

NAAQS (2015 8-hour ozone NAAQS), 

lowering the level of both the primary 


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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. 

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 at 1735 (January 6, 2017). 

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 (‘‘October 2017 

memorandum’’), 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. 

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 socalled ‘‘prongs’’ within CAA 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 4-Step 

Interstate Transport Regulatory Process 

The EPA is using the 4-step interstate 

transport framework (or 4-step 

framework) to evaluate Utah’s SIP 

submittal 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 

standards,4 and the Cross-State Air 

Pollution Rule Update (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 interstate transport 

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 (VOCs) 

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 interstate 

transport 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 interstate transport 


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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. 

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, www.camx.com. 

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 interstate transport framework, and 

considerations for identifying 

downwind areas that may have 

problems maintaining the standard at 

Step 1 of the 4-step interstate transport 

framework.13

Since the release of the modeling data 

shared in the March 2018 

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 (EGUs) that 

reflect the emissions reductions from 

the Revised CSAPR Update, recent 

information on plant closures, and other 

sector trends. The construct of this 

updated emissions platform, 2016v2, is 

described in an emissions modeling 

technical support document (TSD) 

included in the docket 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. This 

modeling will generally be 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 

document 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 document, 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–R08–OAR–2022–0315. Comments 

are not being accepted in docket ID No. 

EPA–HQ–OAR–2021–0663. 

States may have chosen to rely on the 

results of the 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 Utah 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 


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20March 2018 memorandum, Attachment A. 

21 Id. at A–1. 

22 Id. 

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). 

26See North Carolina v. EPA, 531 F.3d 896, 910– 

11 (D.C. Cir. 2008) (holding that the EPA must give 

‘‘independent significance’’ to each prong of CAA 

section 110(a)(2)(D)(i)(I)). 

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 

contribution threshold, and multifactor 

control strategy assessment. 

1. Selection of Analytic Year 

In general, the 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 303 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 (emphasis added). 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 23054 at 23074; see 

also Wisconsin, 938 F.3d at 322. 

Consequently, in this proposal the EPA 

will use the analytical year of 2023 to 

evaluate Utah’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 interstate transport 

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.26

For the purpose of this proposal, the 

EPA identifies nonattainment receptors 

as those monitoring sites that are 


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27See 81 FR 74504 (October 26, 2016). This same 

concept, relying on both current monitoring data 

and modeling to define nonattainment receptors, 

was also applied in CAIR. See 70 FR 25162 at 

25241, 25249 (January 14, 2005); see also North 

Carolina, 531 F.3d at 913–14 (affirming as 

reasonable EPA’s approach to defining 

nonattainment in CAIR). 

28See 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). 

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).27

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 

in EME Homer City Generation, L.P. v. 

EPA, 795 F.3d 118, 136 (D.C. Cir. 

2015).28 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 

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 

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 the result of the 

collective impacts of contributions from 

multiple 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 at 74518. See also 

86 FR at 23085 (reviewing and 

explaining rationale from CSAPR, 76 FR 

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. 

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 


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29As 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. 

30The EPA’s November 21, 2019 letter to the 

State of Utah is included in docket ID EPA–R08– 

OAR–2022–0315 for this action. 

31The EPA is not proposing any action on the 

2008 ozone portion of Utah’s January 29, 2020 

submittal, or any of the other infrastructure 

elements apart from those portions submitted to 

meet the requirements of CAA section 

110(a)(2)(D)(i)(I) for the 2015 ozone NAAQS. 

32Utah’s SIP submission at C–005, C–013. 

33 Id. at C–007. The EPA notes that the modeling 

released with the March 2018 memorandum used 

2011 base year inventory data. 

34 Id. 

35 Id. 

36 Id. at C–007–C008. 

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. 

Generally the emissions-reducing effects 

of all existing emissions control 

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.29

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. Utah SIP Submission Addressing 

Interstate Transport of Air Pollution for 

the 2015 8-Hour Ozone NAAQS 

On October 24, 2019, the State of Utah 

submitted a SIP revision to the EPA 

addressing the 110(a)(1) and (2) 

infrastructure requirements for the 2015 

ozone NAAQS, including CAA section 

110(a)(2)(D)(i)(I). The EPA evaluated 

this submission for completeness 

pursuant to the criteria in 40 CFR part 

51, appendix V, and concluded that it 

was incomplete because Utah had not 

provided the necessary certification 

under section 2.1(g) of appendix V that 

a public hearing was held or provided 

the opportunity for the public to request 

a public hearing in accordance with 40 

CFR 51.102(a). On November 21, 2019, 

the EPA sent a letter to Utah explaining 

our incompleteness determination.30 On 

December 5, 2019, the EPA issued a 

finding that several states, including 

Utah, had failed to submit SIPs to meet 

the interstate transport requirements of 

CAA section 110(a)(2)(D)(i)(I) for the 

2015 ozone NAAQS. See 84 FR 66612. 

On January 29, 2020, the State 

submitted a new SIP revision addressing 

the infrastructure requirements for the 

2015 ozone NAAQS, including CAA 

section 110(a)(2)(D)(i)(I), as well as CAA 

section 110(a)(2)(D)(i)(I) prong 2 for the 

2008 ozone NAAQS.31

The SIP submission provided an 

analysis by the Utah Division of Air 

Quality (UDAQ) of the State’s impact on 

air quality in downwind states and 

concluded that emissions from Utah 

will not significantly contribute to 

nonattainment or interfere with 

maintenance of the 2015 ozone NAAQS 

in other states in 2023.32 In the SIP 

submittal, UDAQ conducted a weightof-evidence analysis, which sought to 

rely in part on certain outside parties’ 

ideas for ‘‘flexibilities’’ in assessing 

good neighbor obligations that had been 

listed in Attachment A to the March 

2018 memorandum. See section I.D. 

above. UDAQ’s weight-of-evidence 

analysis utilized the EPA’s 4-step 

interstate transport framework 

approach. At Step 1 of the framework, 

UDAQ used EPA modeling released 

with the March 2018 memorandum to 

conclude that the Denver nonattainment 

area was the only area with identified 

nonattainment and maintenance 

receptors in 2023 to which sources in 

Utah could possibly contribute (Step 

1).33 In identifying this area at Step 1, 

UDAQ considered the ‘‘flexibility’’ 

listed in Attachment A of the March 

2018 memo, consideration of ‘‘the 

current and projected local emission 

reductions and whether downwind 

areas have considered and/or used 

available mechanisms for regulatory 

relief.’’ UDAQ considered current and 

projected emissions reductions in the 

Denver nonattainment area.34

Specifically, UDAQ considered recent 

oil and gas control requirements 

Colorado adopted for oil and gas sources 

within the Denver nonattainment area.35

At Step 2 of the 4-step interstate 

transport framework, UDAQ utilized a 

weight of evidence approach.36 As part 

of its weight of evidence, UDAQ 

considered EPA’s modeling from the 

March 2018 memorandum to identify 

which nonattainment and/or 

maintenance receptors were linked to 

emissions from Utah. UDAQ identified 

five nonattainment and maintenance 

receptors to which the State was 

projected to contribute greater than 0.70 

ppb (1 percent) to the 2023 design 

values. Table 1 provides information on 

the five nonattainment and maintenance 

receptors identified by UDAQ in their 

SIP submittal. 


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37Utah’s SIP submission at C–008. 

38 Id. 

39Each of the five receptors apart from Receptor 

ID 80590006 (Jefferson, Colorado). 

40Utah’s SIP submission at C–008. 

41 Id. (quoting 81 FR 15200 (March 22, 2016)). 

42 Id. 

43 Id. at C–009. 

TABLE 1—2023 AVERAGE AND MAXIMUM DESIGN VALUES AT DOWNWIND RECEPTORS WITH UTAH CONTRIBUTIONS EQUAL

TO AND GREATER THAN 0.70 ppb a

Receptor ID State County 

Average 

design value 

(ppb) 

Maximum 

design value 

(ppb) 

Utah modeled 

contribution 

(ppb) 

Nonattainment Receptors: 

80350004 ......................................... CO Douglas ................................................... 71.1 73.2 1.08 

80590006 ......................................... CO Jefferson ................................................. 71.3 73.7 0.83 

80690011 ......................................... CO Larimer .................................................... 71.2 73.0 1.05 

Maintenance Receptors: 

80050002 ......................................... CO Arapahoe ................................................. 69.3 71.3 1.23 

80590011 ......................................... CO Jefferson ................................................. 70.9 73.9 1.04 

a Data according to March 2018 memorandum modeling. 

UDAQ presented all of the monitors 

to which the State was modeled to 

contribute at or above the 1 percent of 

the NAAQS threshold. However, UDAQ 

indicated in their SIP submittal that 

they support the use of a 1 ppb 

threshold and referenced the EPA’s 

August 2018 memorandum, which they 

characterized as the EPA finding 

alternative thresholds as 

‘‘appropriate.’’ 37 UDAQ conducted a 

comparison of the 1 percent and 1 ppb 

thresholds at the five nonattainment or 

maintenance receptor sites shown in 

Table 1, analyzing the differences in 

capture of upwind contribution under 

the two thresholds (60% for 1 percent 

and 47% for 1 ppb) to assert that the 1 

ppb threshold is appropriate because 

the capture rates were comparable.38

UDAQ noted that by using a 1 ppb 

threshold, the State would only be 

linked to four 39 of the five receptors 

listed in Table 1. UDAQ still elected to 

evaluate contributions from the fifth 

receptor (Receptor ID 806590011) ‘‘to 

make a more complete assessment of the 

modeled results.’’ 40 Table 2 provides 

UDAQ’s analysis of the two contribution 

thresholds as presented in its January 

29, 2020 submission. 

TABLE 2—COMPARISON OF 2023 CONTRIBUTION THRESHOLDS AT RECEPTOR SITES IN COLORADO a

Receptor ID County 

Total upwind 

state contr. 

(ppb) 

Sum of upwind 

contr. captured 

with 0.70 ppb 

(1%) threshold 

Sum of upwind 

contr. captured 

with 1 ppb 

threshold 

Percent of 

upwind contr. 

captured using 

a 0.70 ppb 

(1%) threshold 

Percent of 

upwind contr. 

captured using 

a 1 ppb 

threshold 

80050002 ............................ Arapahoe ............................ 5.98 3.47 3.47 58.0 58.0 

80350004 ............................ Douglas .............................. 5.94 3.35 3.35 56.4 56.4 

80590006 ............................ Jefferson ............................. 7.06 4.68 2.34 66.3 33.1 

80590011 ............................ Jefferson ............................. 6.98 4.51 3.57 64.6 51.1 

80690011 ............................ Larimer ............................... 6.33 3.48 2.60 55.0 41.1 

a Data according to March 2018 memorandum modeling. 

In its weight-of-evidence analysis, 

UDAQ also referenced the EPA’s 

proposed approval of Arizona’s 

interstate transport SIP for the 2008 

ozone NAAQS as providing an 

administrative precedent for its 

conclusions regarding Utah.41 UDAQ 

stated that in that proposal, the EPA 

considered ‘‘the magnitude of ozone 

attributable to transport from all upwind 

states collectively contributing to the air 

quality problem’’ and, after considering 

the total contributions from all states 

that contributed to the same receptors 

linked to Arizona, determined the 

collective contribution of emissions to 

those downwind receptors was 

negligible ‘‘particularly when compared 

to the relatively large contributions from 

upwind states in the East.’’ To support 

the applicability of the Arizona action, 

UDAQ again pointed to the March 2018 

memorandum modeling to illustrate 

‘‘the disparity between upwind 

contributions from states in the East 

versus the West.’’ 42 Specifically, UDAQ 

cited modeled collective upwind state 

contributions to receptors in 

Connecticut (44.24 ppb to Receptor ID 

900190003) and New York (30.68 ppb to 

Receptor ID 360810124) in comparison 

to the lesser in-state contributions (3.71 

ppb to Receptor ID 900190003 and 13.55 

ppb to Receptor ID 360810124) to these 

receptors. UDAQ then compared these 

ratios against the highest collective 

contributions from upwind states to any 

of the Colorado nonattainment or 

maintenance receptors (7.06 ppb to 

Receptor ID 80590006) and the in-state 

(Colorado) contribution to this receptor 

(25.52 ppb). Table 3 provides UDAQ’s 

summary of in-state and upwind state 

contributions using the March 2018 

memorandum modeling. UDAQ asserted 

that the difference in magnitude 

between Colorado’s modeled in-state 

contributions to its nonattainment and 

maintenance receptors and Utah’s 

modeled contributions, especially when 

compared to receptors in the eastern 

U.S., led the State to conclude that their 

interstate contributions to these 

receptors are negligible.43


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44 Id. 

45 Id. 

46 Id. at C–011. 

47 Id. 

48 Id. 

49 Id. 

50 Id. at C–013. 

TABLE 3—IN-STATE VS. COLLECTIVE UPWIND STATE CONTRIBUTIONS a

Receptor ID County State 

Average 

design value 

(ppb) 

Maximum 

design value 

(ppb) 

In-state 

contribution 

(ppb) 

Total contribution from 

upwind states 

(ppb) 

80050002 ................................... Arapahoe .................................. CO 69.3 71.3 22.94 5.98 

80350004 ................................... Douglas ..................................... CO 71.1 73.2 24.71 5.94 

80590006 ................................... Jefferson ................................... CO 71.3 73.7 25.52 7.06 

80590011 ................................... Jefferson ................................... CO 70.9 73.9 24.72 6.98 

80690011 ................................... Larimer ...................................... CO 71.2 73.0 21.74 6.33 

a Data according to March 2018 memorandum modeling. 

As part of its weight of evidence 

analysis, UDAQ also considered the 

impacts of non-anthropogenic and 

international contributions on the 

Denver area receptors to which it was 

linked by the March 2018 memorandum 

modeling, claiming that this was 

identified as a flexibility under Step 3 

in the March 2018 memorandum.44

UDAQ included the information 

provided in Table 4 to support this 

point and asserted that the high level of 

‘‘[u]ncontrollable’’ emissions made it 

unnecessary for the State to consider 

Step 3 of the 4-step interstate transport 

framework in its analysis.45

TABLE 4—CONTRIBUTIONS FROM CANADA/MEXICO, OFFSHORE, FIRE, AND BIOGENIC EMISSIONS AND THE INITIAL/ 

BOUNDARY CONDITIONS TO COLORADO RECEPTOR SITES a

Receptor ID County 

2023 

Maximum 

design value 

(ppb) 

Non-U.S./non 

anthro b

(ppb) 

Initial and 

Boundary 

conditions 

Total 

uncontrollable 

contribution 

(ppb) 

Percent of 

max DV 

80050002 ......................... Arapahoe ......................... 71.3 5.39 34.84 40.23 56 

80350004 ......................... Douglas ............................ 73.2 5.53 34.74 40.27 55 

80590006 ......................... Jefferson .......................... 73.7 7.13 31.41 38.54 52 

80590011 ......................... Jefferson .......................... 73.9 6.05 32.96 39.01 53 

80690011 ......................... Larimer ............................. 73.0 8.42 34.54 42.96 59 

a Data according to March 2018 memorandum modeling. 

b Includes contributions from Canada/Mexico, Offshore, Fire, and Biogenic sources. 

Lastly, UDAQ’s weight-of-evidence 

argument points to reductions in ozone 

precursor pollutants nitrogen oxides 

(NOX) and volatile organic compounds 

(VOC) that have taken place in the State 

since 2011, the base year for the March 

2018 memorandum modeling.46 UDAQ 

asserted that their statewide emissions 

inventory had decreased by 37% (NOX) 

and 30% (VOC), respectively, between 

2011 and 2017.47 UDAQ also pointed to 

then-forthcoming Best Available Control 

Technology (BACT) requirements for 

the Salt Lake City, UT PM2.5

Nonattainment Area, estimating these 

would result in projected further 

reductions of 1,440 tons/year of NOX

and 5,624 tons/year of VOC within the 

nonattainment area by 2020.48 UDAQ 

also discussed the anticipated reduction 

in mobile source emissions due to the 

national Tier 3 Vehicle Emissions and 

Fuel Standards, as well as increased 

inspection and compliance 

requirements for the oil and gas sector, 

though they did not quantify either of 

these reductions.49 UDAQ concluded 

that it would not be necessary to require 

additional reductions at Steps 3 and 4 

given the amount of reductions already 

achieved.50

Overall, Utah’s SIP submittal asserts 

that: (1) A 1 ppb threshold is 

appropriate for states contributing to the 

Denver area receptors, including Utah; 

(2) contributions from Utah to linked 

nonattainment and maintenance 

receptors are not significant when 

considering in-state contributions from 

Colorado and total collective 

contributions from all upwind states; (3) 

contributions from Utah should not be 

controlled at Step 3 due to the amount 

of uncontrollable international and nonanthropogenic emissions contributing to 

the downwind nonattainment and 

maintenance receptors, and; (4) 

emissions of VOCs and NOX in Utah are 

declining or have declined such that it 

is unnecessary to require further 

reductions at Steps 3 and 4. UDAQ 

asserted that the combined information 

in its weight of evidence analysis 

demonstrates that emissions from the 

State do not significantly contribute to 

nonattainment or interfere with the 

maintenance of the 2015 ozone NAAQS 

in any downwind state. 

III. The EPA’s Evaluation 

The EPA is proposing to find that 

Utah’s January 29, 2020 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. The 

Agency’s decision to propose 

disapproval of Utah’s SIP submission is 

based on our evaluation of the SIP using 

the 4-step interstate transport 

framework. 

A. Evaluation of Information Provided 

by Utah Regarding Step 1 and Step 2 

At Step 1 and Step 2 of the 4-step 

interstate transport framework, UDAQ 

relied on EPA modeling released in the 

March 2018 memorandum to identify 

nonattainment and maintenance 

receptors and upwind state linkages to 

those nonattainment and maintenance 

receptors in 2023. In this proposal, the 


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51We note the explanation for how the 1 percent 

contribution threshold was originally derived is 

available in the 2011 CSAPR rulemaking. See 76 FR 

48208, 48237–38. Further, in the CSAPR Update, 

the EPA re-analyzed the threshold for purposes of 

the 2008 ozone NAAQS and determined it was 

appropriate to continue to apply this threshold. See 

81 FR 74504, 74518–19. 

52See August 2018 memorandum at 4. 

53 Id. 

54See 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). 

55We note 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. 

EPA relies on the Agency’s most 

recently available modeling (2016v2) to 

identify upwind contributions and 

linkages to downwind air quality 

problems in 2023. The earlier modeling 

relied on by UDAQ identified a number 

of nonattainment and maintenance 

receptor sites in 2023 as did the more 

recent 2023 modeling. Thus, EPA agrees 

with UDAQ that for Step 1 under the 4- 

step interstate transport framework, a 

number of nonattainment and 

maintenance receptors for the 2015 

ozone NAAQS were projected for 2023 

in the Denver area. 

In their January 2020 SIP submittal, 

UDAQ stated that a 1 ppb threshold is 

appropriate for the Denver area 

receptors to which it is linked. As noted 

in Section II of this proposed action, 

UDAQ cited the EPA’s August 2018 

memorandum to justify using a 1 ppb 

alternative contribution threshold at 

Step 2 as a basis to assert that Utah 

would not be linked to some projected 

downwind nonattainment or 

maintenance receptors. UDAQ did not 

appear to argue in its submittal that 1 

percent of the NAAQS would not be an 

appropriate threshold for upwind 

contribution to the Denver area 

receptors, and purported to evaluate 

contribution even at a fifth receptor to 

which it contributed less than 1 ppb 

(See Submittal at C–009). The EPA 

views the 1 percent of NAAQS 

threshold as the more appropriate 

threshold, as explained elsewhere in 

this document.51

As discussed in the August 2018 

memorandum, the EPA suggested that, 

with appropriate additional analysis, it 

may be reasonable for states to use a 1 

ppb contribution threshold, as an 

alternative to a 1 percent threshold, at 

Step 2 of the 4-step interstate transport 

framework, for the purposes of 

identifying linkages to downwind 

receptors. Utah conducted an analysis 

comparing the 1 ppb and 1 percent 

thresholds, as shown in Table 2 of this 

document and asserted that the 1 ppb 

threshold is appropriate because the 

capture rates are generally comparable 

in the March 2018 memorandum 

modeling. However, UDAQ did not 

adequately explain how a 1 ppb 

threshold would be justified with 

respect to all the receptors to which 

Utah is linked. While the EPA agrees 

that the capture rate is comparable with 

regard to some of the listed Denver area 

receptors, the use of the alternative 1 

ppb threshold would have the result of 

reducing the amount of cumulative 

upwind state contributions that would 

be captured for other receptors. 

Specifically, the two Jefferson Country 

receptors (sites 80590006 and 80590011) 

captured 33.2% and 13.5% less upwind 

contribution, respectively, at 1 ppb than 

at 1 percent using the March 2018 

memorandum modeling UDAQ relied 

on (see Table 2). This far exceeds the 

roughly 7 percent loss in total upwind 

state contributions the EPA found 

would occur at 1 ppb on a nationwide 

basis in its August 2018 memorandum, 

but UDAQ offered no further 

explanation why that level of loss in 

cumulative upwind state contribution 

would be approvable with respect to the 

receptors to which it was linked. 

Indeed, this degree of loss in cumulative 

upwind state contribution appears more 

comparable to what would occur at a 

threshold of 2 ppb, which the EPA 

indicated in its August 2018 

memorandum would generally not be 

approvable.52 While the EPA does not, 

in this action, approve of UDAQ’s 

application of the 1 ppb threshold, 

because all of Utah’s linkages based on 

the EPA’s updated 2016v2 modeling 

(See Table 5 below) are greater than 1 

ppb to projected downwind 

nonattainment or maintenance 

receptors, UDAQ’s use of this 

alternative threshold at Step 2 of the 4- 

step interstate framework would not 

alter our review and proposed 

disapproval of this SIP submittal. 

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 2.53 (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 

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 that state, in order to more 

thoroughly evaluate the state-specific 

circumstances that could support 

approval.54 It was at the EPA’s sole 

discretion to perform this analysis in 

support of Iowa’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 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 ozone NAAQS raises 

substantial policy consistency and 

practical implementation concerns.55

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 SIP 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 


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56See August 2018 memorandum, at 4. 

57These 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 Utah had a maximum 

contribution equal to or greater than 0.70 ppb to 

multiple 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. 

58Partial Approval and Partial Disapproval of Air 

Quality State Implementation Plans; Arizona; 

Infrastructure Requirements To Address Interstate 

Transport for the 2008 Ozone NAAQS. 81 FR 31513 

(May 19, 2016). 

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 seven percent of 

total upwind state contribution was lost 

according to the modeling underlying 

the August 2018 memorandum; 56 in the 

EPA’s updated modeling, the amount 

lost is five 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 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. 

Accord 76 FR 48237–38. 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. The basis for 

disapproval of Utah’s 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. 

As described in Section I of this 

preamble, the EPA recently performed 

air quality modeling using the 2016v2 

emissions platform to project design 

values and contributions for 2023. 

These data were examined to determine 

if Utah 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 5, the EPA’s 2016v2 modeling 

projects that in 2023, emissions from 

Utah will contribute greater than 1 

percent of the standard to 

nonattainment receptors in both 

Douglas and Jefferson Counties, 

Colorado.57

TABLE 5—UTAH LINKAGE RESULTS BASED ON EPA UPDATED 2023 MODELING a

Receptor ID Location Nonattainment/maintenance 

2023 Average 

design value 

(ppb) 

2023 

Maximum 

design value 

(ppb) 

Utah 

contribution 

(ppb) 

80350004 ............................... Douglas County, CO ............ Nonattainment ...................... 71.7 72.3 1.37 

80590006 ............................... Jefferson County, CO ........... Nonattainment ...................... 72.6 73.3 1.10 

80590011 ............................... Jefferson County, CO ........... Nonattainment ...................... 73.8 74.4 1.06 

aAccording to data from 2016v2 platform modeling. 

In regard to UDAQ’s argument that 

contributions from Utah are not 

significant when considering total 

collective contributions from all upwind 

states to the same receptors, as well as 

UDAQ’s argument that ozone transport 

is somehow fundamentally different in 

the west than the east, the EPA 

disagrees. The EPA’s recent air quality 

modeling shows that multiple upwind 

states collectively contributed to 

projected downwind nonattainment or 

maintenance receptors in Colorado. In 

particular, the EPA found that the total 

upwind states’ contribution to ozone 

concentrations (from linked and 

unlinked states) to identified downwind 

air quality problems in Colorado is 

between 6 and 7 percent, as shown in 

Table 6. The EPA has found that the 

collective contribution of emissions 

from upwind states represents a 

significant portion of the ozone 

concentrations at projected 

nonattainment and maintenance 

receptors in Colorado. 

In its SIP submittal, UDAQ pointed to 

the EPA’s approval of an Arizona 

interstate transport SIP for the 2008 

ozone NAAQS based on collective 

transport contributions.58 However, for 

that SIP, Arizona was the only state 

linked to the downwind monitoring 

sites at issue and the range of total 

upwind-state contributions to those 

sites identified in the Arizona case were 


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59See 81 FR 15200 (March 22, 2016) (proposal); 

81 FR 31513 (May 19, 2016) (final rule; no 

comments received). 

very low as well, in the range of 2.5 to 

4.4 percent of the design value for all 

upwind states, including both linked 

(above 1 percent) and unlinked (below 

1 percent) state contributions. 

TABLE 6—ALL UPWIND STATE CONTRIBUTIONS TO NONATTAINMENT RECEPTORS IN COLORADO a

Site ID State County 2023 Avg 

(ppb) 

2023 Max 

(ppb) 

Contribution of 

all upwind 

states 

combined 

(ppb) b

Percent 

contribution of 

all 

upwind states 

combined c

80350004 ...................... Colorado ...................... Douglas ....................... 71.7 72.3 5.17 7.21 

80590006 ...................... Colorado ...................... Jefferson ..................... 72.6 73.3 4.23 5.83 

80590011 ...................... Colorado ...................... Jefferson ..................... 73.8 74.4 4.34 5.88 

aAccording to data from 2016v2 platform modeling. 

bThe contribution from all upwind states and percent contribution are based on individual upwind contributions that are truncated to two digits 

to the right of the decimal, as provided in regulations.gov at document EPA–HQ–OAR–2021–0668–0069. c Calculated using the projected 2023 average design values for the applicable receptors. 

As noted, the EPA has consistently 

found that the 1 percent threshold is 

appropriate for identifying interstate 

transport linkages for states collectively 

contributing to downwind ozone 

nonattainment or maintenance problems 

because that threshold captures a high 

percentage of the total pollution 

transport affecting downwind receptors. 

The EPA believes contribution from an 

individual state equal to or above 1 

percent of the NAAQS could be 

considered significant where the 

collective contribution of emissions 

from one or more upwind states is 

responsible for a considerable portion of 

the downwind air quality problem 

regardless of where the receptor is 

geographically located. In the case of the 

two Jefferson County, Colorado 

nonattainment receptors listed in Table 

6, two states, including Utah, contribute 

emissions greater than or equal to 1 

percent of the 2015 ozone NAAQS. 

Three states, also including Utah, 

contribute above 1 percent to the 

nonattainment receptor located in 

Douglas County, CO. Given the 2016v2 

modeling results and the EPA’s 

consistent application of the 1 percent 

threshold to establish linkages, the EPA 

is proposing to determine that Utah 

contributes to nonattainment and 

interferes with maintenance of the 2015 

ozone NAAQS in the Denver, Colorado 

area. 

Further, the EPA has explained in 

prior actions on western states’ ozone 

transport SIPs that a 1 percent threshold 

may be appropriate in the west just as 

much as in the east. When the EPA took 

action on Utah’s SIP submittal as to 

prong 2 for the 2008 ozone NAAQS, the 

EPA addressed the basis for applying a 

1 percent threshold at least as to 

Colorado receptors and rejected 

comments advocating for a higher 

threshold. 81 FR 71991, 71994–95 (Oct. 

19, 2016). The EPA explained the basis 

for the 1 percent threshold as derived in 

the CSAPR and CSAPR Update 

rulemakings, and then explained that 

the same reasoning would hold true 

with respect to the Colorado receptors to 

which Utah was linked. Id. The EPA 

noted that Utah’s advocacy for a higher 

contribution threshold of 2 percent of 

the NAAQS was not technically 

supported and ‘‘appears to only be 

justified by the conclusion that Utah 

would not have been linked to Denver 

receptors at this level.’’ Id. at 71995. 

Similarly, in acting on Wyoming’s 

interstate transport submittals for the 

2008 ozone NAAQS, the EPA 

consistently applied the 1 percent 

threshold and rejected use of a higher 

threshold. The EPA explained that a 1 

percent threshold was appropriate to 

apply for a Colorado receptor ‘‘because 

the air quality problem in that area 

resulted in part from the relatively small 

individual contribution of upwind 

states that collectively contribute a 

larger portion of the ozone contributions 

(9.7%), comparable to some eastern 

receptors . . . .’’ See 84 FR 3389, 3391 

(Feb. 12, 2019). 

When the EPA approved Arizona’s 

2008 ozone NAAQS transport SIP 

submittal, it found the 1 percent 

threshold appropriate to apply as to that 

western state. 81 FR 15200, 15202–03 

(March 22, 2016). We stated that we 

disagreed with Arizona’s contention 

that it is unclear what screening 

threshold is significant for southwestern 

states when addressing interstate 

transport contributions. We explained 

that we believe contribution from an 

individual state equal to or above 1 

percent of the NAAQS could be 

considered significant where the 

collective contribution of emissions 

from one or more upwind states is 

responsible for a considerable portion of 

the downwind air quality problem 

regardless of where the receptor is 

geographically located. See id. 15202. 

As discussed in further detail below, 

the EPA found based on an analysis of 

the California monitoring sites at issue 

in that action that Arizona was not 

contributing to downwind 

nonattainment or maintenance 

problems. 

UDAQ relies on the EPA’s approval of 

Arizona’s 2008 ozone NAAQS transport 

SIP as a basis for the claim that its 

contributions to Colorado are 

‘‘negligible.’’ 59 In that action the EPA 

made an assessment of the nature of 

certain monitoring sites in California. 

The EPA noted that a ‘‘factor [. . .] 

relevant to determining the nature of a 

projected receptor’s interstate transport 

problem is the magnitude of ozone 

attributable to transport from all upwind 

states collectively contributing to the air 

quality problem.’’ 81 FR at 15203. The 

EPA observed that only one upwind 

state (Arizona) was linked above 1 

percent of the 2008 ozone NAAQS to 

the two relevant monitoring sites in 

California, and the cumulative ozone 

contribution from all upwind states to 

those sites was 2.5 percent and 4.4 

percent of the total ozone concentration, 

respectively. The EPA determined the 

size of those cumulative upwind 

contributions was ‘‘negligible, 

particularly when compared to the 

relatively large contributions from 

upwind states in the East or in certain 

other areas of the West.’’ Id. (emphasis 

added). In that action, the EPA 

concluded the two California sites to 

which Arizona was linked should not be 

treated as receptors for the purposes of 

determining Good Neighbor obligations 

for the 2008 ozone NAAQS. Id. 

As an initial matter, we note that this 

analysis is properly considered at Step 


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60While EPA ultimately approved Wyoming’s 

transport SIP submittal as proposed in this 2019 

action, this was on the basis of a unique air quality 

demonstration developed by Colorado itself to 

establish that there would be no air quality problem 

in Colorado with respect to the 2008 ozone NAAQS 

once air quality monitoring data influenced by 

‘‘atypical events’’ were removed (assuming 2023 

was the correct analytical year). See 84 FR 3392– 

94; 84 FR 14270 (April 10, 2019) (final action; no 

comments received). 

61As noted in that action, because Utah was 

found to still be linked to Colorado’s maintenance 

receptors under the 2008 ozone NAAQS, EPA’s 

disapproval of the SIP as to prong 2 remained in 

place. See id. at 9156. 

1 of the 4-step framework rather than at 

Step 2, as it is a determination of 

whether an interstate-pollution 

transport problem should be considered 

to exist at all, before reaching a 

determination as to which states 

contribute to that problem. As the EPA 

explained in its Arizona action, it 

considered the 1 percent of NAAQS 

threshold appropriate to apply at Step 2. 

Id. at 15202. See also id. at 15203 (‘‘EPA 

believes the emissions that result in 

transported ozone from upwind states 

have limited impacts on the projected 

air quality problems in El Centro, 

California and Los Angeles, California, 

and therefore should not be treated as 

receptors for purposes of determining 

the interstate transport obligations of 

upwind states.’’). However, because 

UDAQ has presented this argument as a 

part of its weight of evidence analysis at 

Step 2, we present this analysis in turn 

here, as related to UDAQ’s Step 2 

arguments. 

Turning to the substance of UDAQ’s 

argument that the EPA’s Arizona action 

supports an approval here: The 

conclusions the EPA reached regarding 

El Centro and Los Angeles California 

cannot be reached with respect to the 

receptors in Colorado, and the EPA has 

consistently taken this same position 

across several prior actions addressing 

Wyoming’s and Utah’s interstate 

transport obligations, where we have 

concluded that the receptors in 

Colorado are ‘‘substantially’’ influenced 

by upwind-state emissions. See 82 FR 

9155, 9157 (Feb. 3, 2017). The EPA’s 

view in acting on Wyoming and Utah’s 

2008 ozone NAAQS SIP submittals was 

that ‘‘the air quality problem in [the 

Denver nonattainment area of Colorado] 

resulted in part from the relatively small 

individual contribution of upwind 

states that collectively contribute a 

larger portion of the ozone contributions 

(9.7%), comparable to some eastern 

receptors . . . .’’ See 84 FR 3389, 3391 

(Feb. 12, 2019).60 See also 81 FR 71991, 

71994–95 (Oct. 19, 2016); 81 FR 28807, 

28810 (May 10, 2016) (Colorado 

receptors are impacted by interstate 

transport where total upwind state 

contribution is about 11 percent of the 

total ozone concentration, and five 

states were projected to be linked). 

Indeed, the EPA has specifically 

addressed this precise comparison 

between the circumstances of Arizona’s 

approval and the nature of the receptors 

in Colorado. In approving Utah’s 

transport SIP as to prong 1 for the 2008 

ozone NAAQS, the EPA found its 

analysis as to Arizona’s impact on 

California sites did not apply to Utah’s 

impact on Colorado’s sites (which the 

EPA found remained at least 

maintenance receptors as to the 2008 

ozone NAAQS). See 82 FR 9155, 9157 

(Feb. 3, 2017) (‘‘The EPA’s assessment 

concluded that emissions reductions 

from Arizona are not necessary to 

address interstate transport because the 

total collective upwind state ozone 

contribution to these receptors is 

relatively low compared to the air 

quality problems typically addressed by 

the good neighbor provision. As 

discussed previously, the EPA similarly 

evaluated collective contribution to the 

Douglas County, Colorado monitor and 

finds the collective contribution of 

transported pollution to be substantial’’) 

(emphasis added).61

The modeling data on which UDAQ 

relied in its SIP submittal (from the 

EPA’s March 2018 memorandum) 

continue to bear out these conclusions 

(see Table 3 of UDAQ’s submittal). That 

modeling showed contributions from 

more than one upwind state above 1 

percent of the NAAQS at all Colorado 

receptors, and it showed total upwindstate contribution to be between 8 and 

10 percent of the total ozone 

concentrations at those receptors. The 

EPA disagrees that that degree of 

upwind state contribution can be 

characterized as ‘‘negligible.’’ 

The EPA acknowledges that in its 

most recent modeling of 2023 (using the 

2016v2 platform), the degree of the 

interstate transport problem to Colorado 

is now projected to lessen somewhat 

compared to previous projections of 

2023. However, these projected 

improvements are still not sufficient to 

draw a conclusion that Colorado is not 

impacted to a considerable degree by 

out of state emissions. The EPA’s recent 

air quality modeling continues to show 

that multiple upwind states collectively 

contribute to projected downwind 

nonattainment or maintenance receptors 

in Colorado—specifically, California, 

Utah, and Wyoming all contribute above 

1 percent of the NAAQS to at least one 

of Colorado’s receptors in 2023. (In 

contrast, at the time EPA approved 

Arizona’s 2008 ozone NAAQS good 

neighbor SIP, Arizona was the only state 

linked above 1 percent at the relevant 

California monitoring sites.) Further, 

our most recent modeling shows that 

the total upwind state contribution to 

ozone concentrations at identified 

downwind air quality problems in 

Colorado is approximately 6 to 7 

percent, as shown in Table 6. That 

remains higher than the 2 to 4% range 

of total upwind contribution the EPA 

found to be negligible with respect to 

the California sites analyzed in the 

Arizona action. Therefore, the EPA 

continues to find that the collective 

contribution of emissions from upwind 

states represents a significant portion of 

the ozone concentrations at projected 

nonattainment and maintenance 

receptors in Colorado. 

Based on the EPA’s evaluation of 

Utah’s January 2020 submission and 

consideration of the EPA’s most recent 

(2016v2) modeling results for 2023, the 

EPA proposes to find that Utah 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. 

B. 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, state 

implementation plans addressing the 


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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. 

UDAQ did not conduct such an 

analysis in its SIP submission, 

determining instead that the relatively 

large impact of so-called 

‘‘uncontrollable’’ emissions (i.e., 

international and non-anthropogenic 

emissions) and home state emissions at 

the Colorado receptors, as well as 

emissions reductions already achieved 

as a result of other regulatory programs, 

meant the State had no further 

obligation to assess or implement 

additional emissions control measures 

at Steps 3 or 4. The EPA disagrees with 

these conclusions for the reasons below. 

UDAQ asserted that receptors in the 

western U.S. are much more impacted 

by emissions from non-U.S. sources or 

non-anthropogenic sources (see Table 4) 

than by upwind State contributions, 

especially when compared to such 

impacts in the eastern U.S., making 

Utah’s contributions to Denver area 

receptors comparably negligible. The 

EPA disagrees that contributions from 

other sources, including international or 

non-anthropogenic emissions, in any 

way excuse Utah from addressing its 

own significant contribution to 

nonattainment or interference with 

maintenance at downwind areas under 

CAA section 110(a)(2)(D)(i)(I). The EPA 

acknowledges that the consideration of 

international contributions was among 

the ‘‘Preliminary List of Potential 

Flexibilities’’ provided in the March 

2018 memorandum, as UDAQ noted. 

However, as described in section I.D. of 

this proposed action, the EPA does not 

consider the potential flexibilities 

described in the March 2018 

memorandum as constituting agency 

guidance; rather, the EPA must 

thoroughly review the technical and 

legal merits of invoking the concepts in 

that Appendix. 

UDAQ’s reasoning related to 

international and non-anthropogenic 

emissions is inapplicable to the 

requirements of CAA section 

110(a)(2)(D)(i)(I). The good neighbor 

provision requires states and the EPA to 

address interstate transport of air 

pollution that contributes to downwind 

states’ ability to attain and maintain 

NAAQS. Whether emissions from other 

countries or non-anthropogenic sources 

also contribute to the same downwind 

air quality issue is irrelevant in 

assessing whether a downwind state has 

an air quality problem, or whether an 

upwind state is significantly 

contributing to that problem. States are 

not obligated under CAA section 

110(a)(2)(D)(i)(I) to reduce emissions 

sufficient on their own to resolve 

downwind receptors’ nonattainment or 

maintenance problems. Rather, states 

are obligated to eliminate their own 

‘‘significant contribution’’ or 

‘‘interference’’ with the ability of other 

states to attain or maintain the NAAQS. 

Indeed, the D.C. Circuit in Wisconsin 

specifically rejected petitioner 

arguments suggesting that upwind states 

should be excused from good neighbor 

obligations on the basis that some other 

source of emissions (whether 

international or another upwind state) 

could be considered the ‘‘but-for’’ cause 

of downwind air quality problem. 938 

F.3d 303 at 323–324. The court viewed 

petitioners’ arguments as essentially an 

argument ‘‘that an upwind State 

‘contributes significantly’ to downwind 

nonattainment only when its emissions 

are the sole cause of downwind 

nonattainment.’’ 938 F.3d 303 at 324. 

The court explained that ‘‘an upwind 

State can ‘contribute’ to downwind 

nonattainment even if its emissions are 

not the but-for cause.’’ Id. at 324–325. 

See also Catawba County v. EPA, 571 

F.3d 20, 39 (D.C. Cir. 2009) (rejecting 

the argument ‘‘that ‘significantly 

contribute’ unambiguously means 

‘strictly cause’ ’’ because there is ‘‘no 

reason why the statute precludes EPA 

from determining that [an] addition of 

[pollutant] into the atmosphere is 

significant even though a nearby 

county’s nonattainment problem would 

still persist in its absence’’); Miss. 

Comm’n on Envtl. Quality v. EPA, 790 

F.3d 138, 163 n.12 (D.C. Cir. 2015) 

(observing that the argument that ‘‘there 

likely would have been no violation at 

all . . . if it were not for the emissions 

resulting from [another source]’’ is 

‘‘merely a rephrasing of the but-for 

causation rule that we rejected in 

Catawba County.’’). Therefore, a state is 

not excused from eliminating its 

significant contribution on the basis that 

some amount of ‘‘uncontrollable’’ 

emissions (whether international or 

non-anthropogenic) also contribute 

some amount of pollution to the same 

receptors to which the state is linked. 

Further, the data supplied in UDAQ’s 

SIP submission tends to be self-refuting 

on this point. Table 4 of the submission 

indicates that 52 percent–59 percent 

(depending on receptor) of the total 

ozone concentrations at the Colorado 

receptors are from non-anthropogenic or 

non-U.S. emissions sources. This means 

that between 41 percent–48 percent of 

the ozone levels at the Colorado 

receptors are the result of anthropogenic 

emissions originating in the U.S. Those 

emissions are clearly within the 

authority of states and the EPA to 

redress, and reducing some portion of 

those emissions can be assumed to 

improve air quality at the Colorado 

receptors. While not all of those U.S. 

anthropogenic emissions can be 

attributed to Utah, Utah’s emissions are 

shown by the modeling to contribute to 

Colorado’s air quality problem at levels 

sufficient to warrant evaluation of 

emissions control opportunities at Step 

3 of the EPA’s longstanding analytical 

framework. 

The EPA also disagrees that greater instate emissions, in this case 

anthropogenic emissions generated in 

Colorado, preclude upwind states’ good 

neighbor obligations under CAA section 

110(a)(2)(D)(i)(I). The D.C. Circuit has 

held on five different occasions that the 

timing framework for addressing 

interstate transport obligations must be 

consistent with the downwind areas’ 

attainment schedule. In particular, for 

the ozone NAAQS, the states and the 

EPA are to address interstate transport 

obligations ‘‘as expeditiously as 

practicable’’ and no later than the 

attainment schedule set in accordance 

with CAA section 181(a). See North 

Carolina, 531 F.3d at 911–13; 

Wisconsin, 938 F.3d at 313–20; 

Maryland, 958 F.3d at 1204; New York 

v. EPA, 964 F.3d 1214, 1226 (D.C. Cir. 

2020); New York v. EPA, 781 Fed. App’x 

4, 6–7 (D.C. Cir. 2019). The court in 

Wisconsin explained its reasoning in 

part by noting that downwind 

jurisdictions often may need to heavily 

rely on emissions reductions from 

upwind states in order to achieve 

attainment of the NAAQS, 938 F.3d at 

316–17; such states would face 

increased regulatory burdens including 

the risk of bumping up to a higher 

nonattainment classification if 

attainment is not reached by the 

relevant deadline, Maryland, 958 F.3d at 

1204. The statutory framework of the 

CAA and these cases establish clearly 

that states and the EPA must address 

interstate transport obligations in line 

with the attainment schedule provided 

in the CAA in order to timely assist 

downwind states in attaining and 


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Federal Register / Vol. 87, No. 100 / Tuesday, May 24, 2022 / Proposed Rules 31483 

62See, e.g., 86 FR 23054, 23087. 

maintaining the NAAQS, and this 

schedule is ‘‘central to the regulatory 

scheme.’’ Wisconsin, 938 F.3d at 316 

(quoting Sierra Club v. EPA, 294 F.3d 

155, 161 (D.C. Cir. 2002)). Therefore, the 

EPA does not find that it should be the 

sole responsibility of the downwind 

state to resolve its nonattainment, 

especially after having established that 

collective contribution of emissions 

from multiple upwind states is 

responsible for a considerable portion of 

the downwind air quality problem. To 

that end, the EPA does not find UDAQ’s 

arguments regarding the impacts of 

emissions from sources other than 

upwind states to be relevant to the 

analysis of interstate transport to Denver 

area nonattainment receptors. Therefore, 

the EPA finds that Utah has not 

adequately addressed its modeled 

contributions to projected downwind 

nonattainment receptors identified by 

the EPA. 

UDAQ also pointed to reductions in 

emissions of VOCs and NOX in the State 

through a combination of regulatory 

actions. Though the EPA considers the 

measures UDAQ described to be 

beneficial in reducing VOCs and NOX in 

the State, UDAQ’s analysis primarily 

quantifies anticipated reductions from 

area source rules in the Salt Lake City 

2006 PM2.5 nonattainment area. These 

rules all were finalized between 2008 

and 2018 (see UDAQ submittal Table 5). 

UDAQ also cites but does not quantify 

emissions reductions from certain oil 

and gas sector rules which have 

effective dates in March 2019 (Table 6 

in UDAQ’s submittal). However, the 

EPA’s modeling captures the air quality 

effects of existing on-the-books control 

measures in the emissions inventory 

baseline, and that modeling confirms 

that these control programs were not 

sufficient to eliminate Utah’s linkage at 

Steps 1 and 2 under the 2015 8-hour 

ozone NAAQS. The State was therefore 

obligated at Step 3 to assess additional 

control measures using a multifactor 

analysis. 

Further, the emissions reductions 

cited in Table 5 of UDAQ’s submittal are 

predominantly from reductions in VOC 

emissions. The EPA has long recognized 

that the more important ozoneprecursors for purposes of addressing 

regional and long-range interstate ozone 

transport are nitrogen oxides (NOX).62

According to Table 5 of the submittal, 

the existing rules UDAQ cited may 

achieve on the order of roughly 600 tons 

of NOX reductions per ozone season 

(roughly 4 tons per day multiplied by 

the number of days in an ozone season). 

The import of this figure is unclear; 

regardless, UDAQ did not explain the 

baseline from which that amount of 

emissions reductions was derived, nor 

did UDAQ explain how or why that 

amount of emissions reduction is 

sufficient to eliminate significant 

contribution or interference with 

maintenance. For example, UDAQ could 

have but did not conduct a comparative 

assessment of additional emissions 

control opportunities and associated 

costs, develop a regional emissionsreduction assessment, or analyze the air 

quality benefits of those strategies at the 

downwind receptors. All of these are 

factors in the analysis the EPA has 

consistently performed at Step 3 over 

several ozone transport rulemakings 

such as CSAPR and the CSAPR Update. 

In particular, UDAQ’s analysis failed 

to evaluate emissions and emissionsreduction opportunities from most of 

the highest emitting NOx sources in the 

State, including multiple electric 

generating units located further east of 

the Salt Lake City, Utah area and thus 

closer to the Denver area receptors to 

which Utah contributes greater than 1 

percent of the NAAQS. A state 

conducting a Step 3 analysis should 

undertake an evaluation of these kinds 

of substantial and potentially costeffective emissions reduction 

opportunities, and the failure to do so 

is grounds for disapproval. 

For these reasons, the EPA finds that 

the historically-achieved emissions 

reductions listed in Utah’s January 2020 

submission are not a satisfactory Step 3 

analysis and do not demonstrate that the 

Utah SIP contains adequate provisions 

prohibiting emissions that will 

significantly contribute to 

nonattainment or interfere with 

maintenance of the 2015 ozone NAAQS 

in any other state. 

We therefore propose to find that 

Utah was required to analyze emissions 

from the sources and other emissions 

activity from within the State to 

determine whether its contributions 

were significant, and we propose to 

disapprove its submission because the 

State failed to do so. 

C. 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, Utah’s SIP 

submission did not contain an 

evaluation of additional emission 

control opportunities (or establish that 

no additional controls are required), 

thus, no information was provided at 

Step 4. As a result, the EPA proposes to 

disapprove Utah’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). 

D. Conclusion 

Based on the EPA’s evaluation of 

Utah’s SIP submission, the Agency is 

proposing to find that the portion of the 

State’s January 29, 2020 SIP submission 

addressing CAA section 

110(a)(2)(D)(i)(I) for the 2015 8-hour 

ozone NAAQS does not meet Utah’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 this NAAQS in any 

other state. 

IV. Proposed Action 

We are proposing to disapprove 

Utah’s SIP submission pertaining to 

interstate transport of air pollution 

which will significantly contribute to 

nonattainment or interfere with 

maintenance of the 2015 8-hour ozone 

NAAQS in other states. Under CAA 

section 110(c)(1), disapproval would 

establish a 2-year deadline for the EPA 

to promulgate a FIP for Utah 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 CAA sanctions clock for 

Utah. The remaining elements of the 

State’s January 29, 2020 submission are 

not addressed in this action and either 

have been or 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. 


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31484 Federal Register / Vol. 87, No. 100 / Tuesday, May 24, 2022 / Proposed Rules 

63 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. 

64A 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. 

65The 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. 

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).63

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 

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.64 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).65

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. 

KC Becker, 

Regional Administrator, Region 8. 

[FR Doc. 2022–11152 Filed 5–23–22; 8:45 am] 

BILLING CODE 6560–50–P 


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