Federal Register / Vol. 87, No. 35 / Tuesday, February 22, 2022 / Proposed Rules 9463 

D. Federalism and Indian Tribal 

Governments 

A rule has implications for federalism 

under Executive Order 13132 

(Federalism), if it has a substantial 

direct effect 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. We have analyzed 

this proposed rule under that Order and 

have determined that it is consistent 

with the fundamental federalism 

principles and preemption requirements 

described in Executive Order 13132. 

Also, this proposed rule does not have 

tribal implications under Executive 

Order 13175 (Consultation and 

Coordination with Indian Tribal 

Governments) because it would not 

have a substantial direct effect on one or 

more Indian tribes, on the relationship 

between the Federal Government and 

Indian tribes, or on the distribution of 

power and responsibilities between the 

Federal Government and Indian tribes. 

If you believe this proposed rule has 

implications for federalism or Indian 

tribes, please call or email the person 

listed in the FOR FURTHER INFORMATION

CONTACT section. 

E. Unfunded Mandates Reform Act 

The Unfunded Mandates Reform Act 

of 1995 (2 U.S.C. 1531–1538) requires 

Federal agencies to assess the effects of 

their discretionary regulatory actions. In 

particular, the Act addresses actions 

that may result in the expenditure by a 

State, local, or tribal government, in the 

aggregate, or by the private sector of 

$100,000,000 (adjusted for inflation) or 

more in any one year. Though this 

proposed rule would not result in such 

an expenditure, we do discuss the 

potential effects of this proposed rule 

elsewhere in this preamble. 

F. Environment 

We have analyzed this proposed rule 

under Department of Homeland 

Security Directive 023–01, Rev. 1, 

associated implementing instructions, 

and Environmental Planning 

COMDTINST 5090.1 (series), which 

guide the Coast Guard in complying 

with the National Environmental Policy 

Act of 1969 (42 U.S.C. 4321–4370f), and 

have made a preliminary determination 

that this action is one of a category of 

actions that do not individually or 

cumulatively have a significant effect on 

the human environment. This proposed 

rule involves disestablishing a security 

zone. Such actions are categorically 

excluded from further review under 

paragraph L60(b) of Appendix A, Table 

1 of DHS Instruction Manual 023–01– 

001–01, Rev. 1. We seek any comments 

or information that may lead to the 

discovery of a significant environmental 

impact from this proposed rule. 

G. Protest Activities 

The Coast Guard respects the First 

Amendment rights of protesters. 

Protesters are asked to call or email the 

person listed in the FOR FURTHER

INFORMATION CONTACT section to 

coordinate protest activities so that your 

message can be received without 

jeopardizing the safety or security of 

people, places, or vessels. 

V. Public Participation and Request for 

Comments 

We view public participation as 

essential to effective rulemaking, and 

will consider all comments and material 

received during the comment period. 

Your comment can help shape the 

outcome of this rulemaking. If you 

submit a comment, please include the 

docket number for this rulemaking, 

indicate the specific section of this 

document to which each comment 

applies, and provide a reason for each 

suggestion or recommendation. 

Submitting comments. We encourage 

you to submit comments through the 

Federal Decision Making Portal at 

https://www.regulations.gov. To do so, 

go to https://www.regulations.gov, type 

USCG–2022–0054 in the search box and 

click ‘‘Search.’’ Next, look for this 

document in the Search Results column, 

and click on it. Then click on the 

Comment option. If you cannot submit 

your material by using https://

www.regulations.gov, call or email the 

person in the FOR FURTHER INFORMATION

CONTACT section of this proposed rule 

for alternate instructions. 

Viewing material in docket. To view 

documents mentioned in this proposed 

rule as being available in the docket, 

find the docket as described in the 

previous paragraph, and then select 

‘‘Supporting & Related Material’’ in the 

Document Type column. Public 

comments will also be placed in our 

online docket and can be viewed by 

following instructions on the https://

www.regulations.gov Frequently Asked 

Questions web page. We review all 

comments received, but we will only 

post comments that address the topic of 

the proposed rule. We may choose not 

to post off-topic, inappropriate, or 

duplicate comments that we receive. 

Personal information. We accept 

anonymous comments. Comments we 

post to https://www.regulations.gov will 

include any personal information you 

have provided. For more about privacy 

and submissions to the docket in 

response to this document, see DHS’s 

eRulemaking System of Records notice 

(85 FR 14226, March 11, 2020). 

List of Subjects in 33 CFR Part 165 

Harbors, Marine safety, Navigation 

(water), Reporting and record keeping 

requirements, Security measures, 

Waterways. 

For the reasons discussed in the 

preamble, the Coast Guard is proposing 

to amend 33 CFR part 165 as follows: 

PART 165—REGULATED NAVIGATION 

AREAS AND LIMITED ACCESS AREAS 

■ 1. The authority citation for part 165 

continues to read as follows: 

Authority: 46 U.S.C. 70034, 70051; 33 CFR 

1.05–1, 6.04–1, 6.04–6, and 160.5; 

Department of Homeland Security Delegation 

No. 00170.1, Revision No. 01.2. 

§ 165.785 [Removed] 

■ 2. Remove § 165.785. 

Dated: February 15, 2022. 

J.F. Burdian, 

Captain, U.S. Coast Guard, Captain of the 

Port Miami. 

[FR Doc. 2022–03600 Filed 2–18–22; 8:45 am] 

BILLING CODE 9110–04–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R03–OAR–2021–0872; EPA–HQ– 

OAR–2021–0663; FRL–9493–01–R3] 

Air Plan Disapproval; Maryland; 

Interstate Transport of Air Pollution for 

the 2015 8-Hour Ozone National 

Ambient Air Quality Standard 

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 a State 

Implementation Plan (SIP) submittal 

from Maryland intended to address 

interstate transport for the 2015 8-hour 

ozone national ambient air quality 

standard (2015 8-hour ozone 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 


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9464 Federal Register / Vol. 87, No. 35 / Tuesday, February 22, 2022 / Proposed Rules 

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). 

each state’s air quality management 

program are adequate to meet the state’s 

responsibilities under the CAA. This 

disapproval, if finalized, will establish a 

2-year deadline for the EPA to 

promulgate a Federal Implementation 

Plan (FIP) to address the relevant 

interstate transport requirements, unless 

the EPA approves a subsequent SIP 

submittal that meets these requirements. 

Disapproval does not start a mandatory 

sanctions clock. 

DATES: Written comments must be 

received on or before April 25, 2022. 

ADDRESSES: You may send comments, 

identified as Docket No. EPA–R03– 

OAR–2021–0872, by any of the 

following methods: Federal 

eRulemaking Portal at https://

www.regulations.gov following the 

online instructions for submitting 

comments or via email to gordon.mike@

epa.gov. Include Docket ID No. EPA– 

R03–OAR–2021–0872 in the subject line 

of the message. For further submission 

methods contact the person in the FOR

FURTHER INFORMATION CONTACT section. 

Include Docket ID No. EPA–R03–OAR– 

2021–0872 in the subject line of the 

message. 

Instructions: All submissions received 

must include the Docket ID No. for this 

rulemaking. Comments received may be 

posted without change to https://

www.regulations.gov/, including any 

personal information provided. For 

detailed instructions on sending 

comments and additional information 

on the rulemaking process, see the 

‘‘Public Participation’’ heading of the 

SUPPLEMENTARY INFORMATION section of 

this document. Out of an abundance of 

caution for members of the public and 

our staff, the EPA Docket Center and 

Reading Room are open to the public by 

appointment only to reduce the risk of 

transmitting COVID–19. Our Docket 

Center staff also continues to provide 

remote customer service via email, 

phone, and webform. For further 

information on EPA Docket Center 

services and the current status, please 

visit us online at https://www.epa.gov/ 

dockets. 

FOR FURTHER INFORMATION CONTACT: 

Michael Gordon, Planning & 

Implementation Branch (3AD30), Air & 

Radiation Division, U.S. Environmental 

Protection Agency, Region III, 1650 

Arch Street, Philadelphia, Pennsylvania 

19103. The telephone number is (215) 

814–2039. Mr. Gordon can also be 

reached via electronic mail at 

gordon.mike@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Public Participation: Submit your 

comments, identified by Docket ID No. 

EPA–R03–OAR–2021–0872, at https://

www.regulations.gov (our preferred 

method), or the other method identified 

in the ADDRESSES section. Once 

submitted, comments cannot be edited 

or removed from the docket. The EPA 

may publish any comment received to 

its public docket. Do not submit to 

EPA’s docket at https://

www.regulations.gov any information 

you consider to be Confidential 

Business Information (CBI) or other 

information whose disclosure is 

restricted by statute. Multimedia 

submissions (audio, video, etc.) must be 

accompanied by a written comment. 

The written comment is considered the 

official comment and should include 

discussion of all points you wish to 

make. The EPA will generally not 

consider comments or comment 

contents located outside of the primary 

submission (i.e., on the web, cloud, or 

other file sharing system). 

There are two dockets supporting this 

action, EPA–R03–OAR–2021–0872 and 

EPA–HQ–OAR–2021–0663. Docket No. 

EPA–R03–OAR–2021–0872 contains 

information specific to Maryland, 

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–R03–OAR–2021– 

0872 only. For additional submission 

methods, please contact Mike Gordon, 

215–814–2039, gordon.mike@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. Due to public 

health concerns related to COVID–19, 

the EPA Docket Center and Reading 

Room are open to the public by 

appointment only. Our Docket Center 

staff also continues to provide remote 

customer service via email, phone, and 

webform. For further information and 

updates on EPA Docket Center services, 

please visit us online at https://

www.epa.gov/dockets. 

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. 

The index to the docket for this 

action, Docket No. EPA–R03–OAR– 

2021–0872, 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 via the online docket 

due to docket file size restrictions, such 

as certain modeling files, or content 

(e.g., CBI). Please contact the EPA 

Docket Center Services for further 

information. 

Throughout this document, ‘‘we,’’ 

‘‘us,’’ and ‘‘our’’ means the EPA. 

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 

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 NAAQS, 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


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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). 

9See 82 FR 1733, 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, available in 

docket ID No. EPA–HQ–OAR–2021–0663. 

11See Information on the Interstate Transport 

State Implementation Plan Submissions for the 

2015 Ozone National Ambient Air Quality 

Standards under Clean Air Act Section 

110(a)(2)(D)(i)(I), March 27, 2018 (March 2018 

memorandum), available in docket ID No. EPA– 

HQ–OAR–2021–0663. 

12The March 2018 memorandum, however, 

provided, ‘‘While the information in this 

memorandum and the associated air quality 

analysis data could be used to inform the 

development of these SIPs, the information is not 

a final determination regarding states’ obligations 

under the good neighbor provision. Any such 

determination would be made through notice-andcomment rulemaking.’’ 

13See Analysis of Contribution Thresholds for 

Use in Clean Air Act Section 110(a)(2)(D)(i)(I) 

Interstate Transport State Implementation Plan 

Submissions for the 2015 Ozone National Ambient 

Air Quality Standards, August 31, 2018 (August 

2018 memorandum), and Considerations for 

Identifying Maintenance Receptors for Use in Clean 

Air Act Section 110(a)(2)(D)(i)(I) Interstate 

Transport State Implementation Plan Submissions 

for the 2015 Ozone National Ambient Air Quality 

Standards, October 19, 2018, available in docket ID 

No. EPA–HQ–OAR–2021–0663. 

14The results of this modeling, as well as the 

underlying modeling files, are included in docket 

ID No. EPA–HQ–OAR–2021–0663. 

B. Description of the EPA’s Four-Step 

Interstate Transport Regulatory Process 

The EPA is using the 4-step interstate 

transport framework (or 4-step 

framework) to evaluate all of the states’ 

SIP submittals addressing the interstate 

transport provision for the 2015 8-hour 

ozone NAAQS. The EPA has addressed 

the interstate transport requirements of 

CAA section 110(a)(2)(D)(i)(I) with 

respect to prior ozone NAAQS in 

several regional regulatory actions, 

including the Cross-State Air Pollution 

Rule (CSAPR), which addressed 

interstate transport with respect to the 

1997 ozone NAAQS, as well as the 1997 

and 2006 fine particulate matter 

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 the EPA requested comment on 

preliminary interstate ozone transport 

data, including projected ozone design 

values and interstate contributions for 

2023 using a 2011 emissions 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, the EPA 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, the EPA 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 

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 

emissions platform (i.e., 2016v1). This 

emissions platform was developed 

under the EPA/Multi-Jurisdictional 

Organization (MJO)/state collaborative 

project.14 This collaborative project was 

a multi-year joint effort by the EPA, 

MJOs, and states to develop a new, more 


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9466 Federal Register / Vol. 87, No. 35 / Tuesday, February 22, 2022 / Proposed Rules 

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. 

20March 2018 memorandum, Attachment A. 

21 Id. at A–1. 

22 Id. 

recent emissions platform for use by the 

EPA and states in regulatory modeling 

as an improvement over the dated 2011 

emissions platform 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 

emissions platform are also useful for 

identifying downwind ozone problems 

and linkages with respect to the 2015 8- 

hour ozone NAAQS.16

Following the final Revised CSAPR 

Update, the EPA made further updates 

to the 2016v1 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 the 

updated emissions platform, 2016v2 

(2016v2 emissions platform), is 

described in the Emissions Modeling 

technical support document (TSD) for 

this proposed rulemaking.18 The EPA 

performed air quality modeling of the 

2016v2 emissions platform using the 

most recent public release version of the 

Comprehensive Air-quality Model with 

extensions (CAMx) photochemical 

modeling, version 7.10 19 in evaluating 

these submissions with respect to Steps 

1 and 2 of the 4-step interstate transport 

framework and generally referenced 

within this action as 2016v2 modeling 

for 2023. By using the updated 

modeling results, the EPA is using the 

most recent available and technically 

appropriate information for this 

proposed rulemaking. Section III of this 

document and the Air Quality Modeling 

TSD for the 2015 8-hour 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 

the 2016v2 emissions platform. 

Comments on the EPA’s air quality 

modeling should only be submitted in 

the Regional docket for this action, 

docket ID No. EPA–R03–OAR–2021– 

0872. No comments on any topic are 

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 

of this document, the EPA evaluates 

how Maryland 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’s 

proposed framework with respect to 

analytic year, definition of 

nonattainment and maintenance 

receptors, selection of contribution 

threshold, and multifactor control 

strategy assessment is described in this 

section. 

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 8- 

hour ozone NAAQS. Attachment A to 

the March 2018 memorandum identified 

a ‘‘Preliminary List of Potential 

Flexibilities’’ that could potentially 

inform SIP development.20 However, 

the EPA made clear in Attachment A 

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 is the EPA 

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 


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23For attainment dates for the 2015 8-hour ozone 

NAAQS, refer to CAA section 181(a), 40 CFR 

51.1303, and Additional Air Quality Designations 

for the 2015 Ozone National Ambient Air Quality 

Standards, 83 FR 25776 (June 4, 2018, effective 

August 3, 2018). 

24The EPA notes 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 at 910– 

11 (holding that the EPA must give ‘‘independent 

significance’’ to each prong of CAA section 

110(a)(2)(D)(i)(I)). 27See 81 FR 74504 (October 26, 2016). This same 

concept, relying on both current monitoring data 

and modeling to define nonattainment receptor, 

was also applied in CAIR. See 70 FR at 25241, 

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

531 F.3d at 913–14 (affirming as reasonable the 

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). 

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 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 each state’s CAA section 

110(a)(2)(D)(i)(I) SIP submission with 

respect to the 2015 8-hour ozone 

NAAQS. 

2. Step 1 of the 4-Step Interstate 

Transport Framework 

In Step 1, the EPA identifies 

monitoring sites that are projected to 

have problems attaining and/or 

maintaining the NAAQS in the 2023 

analytic year. Where the EPA’s analysis 

shows that a site does not fall under the 

definition of a nonattainment or 

maintenance receptor, that site is 

excluded from further analysis under 

the EPA’s 4-step interstate transport 

framework. For sites that are identified 

as a nonattainment or maintenance 

receptor in 2023, the EPA proceeds 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 

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 period. The EPA 

interprets the projected maximum 

future design value to be a potential 

future air quality outcome consistent 


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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 (October 26, 2016); CSAPR, 76 

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, 

air mass patterns) promoting ozone 

formation that led to maximum 

concentrations in the measured data 

may reoccur in the future. The 

maximum design value gives a 

reasonable projection of future air 

quality at the receptor under a scenario 

in which such conditions do, in fact, 

reoccur. The projected maximum design 

value is used to identify upwind 

emissions that, under those 

circumstances, could interfere with the 

downwind area’s ability to maintain the 

NAAQS. 

Recognizing that nonattainment 

receptors are also, by definition, 

maintenance receptors, the EPA often 

uses the term ‘‘maintenance-only’’ to 

refer to those receptors that are not 

nonattainment receptors. Consistent 

with the concepts for maintenance 

receptors, as described above, the EPA 

identifies ‘‘maintenance-only’’ receptors 

as those monitoring sites that have 

projected average design values above 

the level of the applicable NAAQS, but 

that are not currently measuring 

nonattainment based on the most recent 

official design values. In addition, those 

monitoring sites with projected average 

design values below the NAAQS, but 

with projected maximum design values 

above the NAAQS are also identified as 

‘‘maintenance only’’ receptors, even if 

they are currently measuring 

nonattainment based on the most recent 

official design values. 

3. Step 2 of the 4-Step Interstate 

Transport Framework 

In Step 2, the EPA quantifies the 

contribution of each upwind state to 

each receptor in the 2023 analytic year. 

The contribution metric used in Step 2 

is defined as the average impact from 

each state to each receptor on the days 

with the highest ozone concentrations at 

the receptor based on the 2023 

modeling. If a state’s contribution value 

does not equal or exceed the threshold 

of 1 percent of the NAAQS (i.e., 0.70 

parts per billion (ppb) for the 2015 8- 

hour ozone NAAQS), the upwind state 

is not ‘‘linked’’ to a downwind air 

quality problem, and the EPA, therefore, 

concludes that the state does not 

significantly contribute to 

nonattainment or interfere with 

maintenance of the NAAQS in the 

downwind states. However, if a state’s 

contribution equals or exceeds the 1 

percent threshold, the state’s emissions 

are further evaluated in Step 3, 

considering both air quality and cost as 

part of a multi-factor analysis, to 

determine what, if any, emissions might 

be deemed ‘‘significant’’ and, thus, must 

be eliminated under CAA section 

110(a)(2)(D)(i)(I). The EPA is proposing 

to rely in the first instance on the 1 

percent threshold for the purpose of 

evaluating a state’s contribution to 

nonattainment or maintenance of the 

2015 8-hour ozone NAAQS (i.e., 0.70 

ppb) at downwind receptors. This is 

consistent with the Step 2 approach that 

the EPA applied in CSAPR for the 1997 

ozone NAAQS, which has subsequently 

been applied in the CSAPR Update 

when evaluating interstate transport 

obligations for the 2008 ozone NAAQS. 

The EPA continues to find 1 percent to 

be an appropriate threshold. For ozone, 

as the EPA found in the Clean Air 

Interstate Rule (CAIR), CSAPR, and 

CSAPR Update, a portion of the 

nonattainment problems from 

anthropogenic sources in the U.S. result 

from the combined impact of 

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 rulemaking is still the 

result of the collective impacts of 

contributions from many upwind states. 

Therefore, application of a consistent 

contribution threshold is necessary to 

identify those upwind states that should 

have responsibility for addressing their 

contribution to the downwind 

nonattainment and maintenance 

problems to which they collectively 

contribute. Continuing to use 1 percent 

of the NAAQS as the screening metric 

to evaluate collective contribution from 

many upwind states also allows the EPA 

(and states) to apply a consistent 

framework to evaluate interstate 

emissions transport under the interstate 

transport provision from one NAAQS to 

the next. See 81 FR 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 

that may be achieved by requiring such 

controls (if applied across all linked 

upwind states), and an evaluation of the 

air quality impacts such emissions 

reductions would have on the 

downwind receptors to which a state is 

linked; other factors may potentially be 

relevant if adequately supported. In 

general, where the EPA’s or alternative 

air quality and contribution modeling 

establishes that a state is linked at Steps 

1 and 2, it will be insufficient at Step 

3 for a state merely to point to its 

existing rules requiring control 

measures as a basis for approval. In 

general, the emissions-reducing effects 

of all existing emissions control 

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


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FR 48208, 48246–63 (August 8, 2011); CAIR, 70 FR 

25162, 25195–229 (May 12, 2005); or the NOX SIP 

Call, 63 FR 57356, 57399–405 (October 27, 1998). 

See also Revised CSAPR Update, 86 FR 23054, 

23086–23116 (April 30, 2021). 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. 

30See the October 16, 2019 SIP submittal 

included in docket ID No. EPA–R03–OAR–2021– 

0872. 

31Analysis of Contribution Thresholds Memo, 

August 2018, https://www.epa.gov/sites/ 

production/files/2018-09/documents/contrib_

thresholds_transport_sip_subm_2015_ozone_

memo_08_31_18.pdf. 

32See the October 16, 2019 SIP submittal at 2 

included in docket ID No. EPA–R03–OAR–2021– 

0872. 

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. Maryland’s SIP Submission 

Addressing Interstate Transport of Air 

Pollution for the 2015 8-Hour Ozone 

NAAQS 

On October 11, 2018, the Maryland 

Department of the Environment (MDE), 

on behalf of the State of Maryland, made 

a SIP submission to address most of the 

2015 8-hour ozone NAAQS i-SIP 

requirements under CAA section 

110(a)(2), except for the CAA section 

110(a)(2)(D)(i)(I) (the ‘‘Good Neighbor’’ 

or ‘‘interstate transport’’) requirements, 

which Maryland proposed to address in 

a separate SIP submittal. The EPA 

published a final approval of this SIP 

submission on September 18, 2019, 84 

FR 49062. On October 16, 2019, MDE 

then submitted a separate, supplemental 

SIP revision addressing only the CAA 

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

transport requirements for the 2015 8- 

hour ozone NAAQS (the 2019 SIP).30

Maryland’s 2019 SIP submittal provided 

an analysis of ozone monitoring data 

and emission trends, as well as a list of 

already-enacted Federal and State air 

pollution control measures, before 

concluding that Maryland satisfied its 

section 110(a)(2)(D)(i)(I) Good Neighbor 

obligations for purposes of the 2015 8- 

hour ozone NAAQS. 

Maryland’s SIP submittal roughly 

followed the 4-step interstate transport 

framework recommended by the EPA. 

For Steps 1 and 2, Maryland relied on 

the EPA’s modeling in the March 2018 

memorandum to demonstrate that it 

complies with the requirements of CAA 

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

hour ozone NAAQS. As part of Step 1, 

Maryland’s SIP submittal identified the 

downwind nonattainment and 

maintenance receptors for which the 

EPA’s modeling projected impacts from 

Maryland emissions, and thus linkage in 

2023. The State examined historical 

ozone design values based on past 

monitoring data from 2015 to 2018 at 

key linked monitors to evaluate the 

likelihood of future compliance with the 

NAAQS at those locations. As part of 

Step 2, Maryland’s SIP submission 

specified that even though the EPA’s 

August 31, 2018 31 memorandum 

concluded that it may be reasonable and 

appropriate for states to use a 1 ppb 

contribution threshold, as an alternative 

to a 1-percent threshold, Maryland 

chose to use the one-percent threshold 

as it captured a greater contribution 

from upwind states. 

In the 2019 SIP submittal, Maryland 

also asserted that it does not agree with 

the results of the EPA’s 2023 projection 

modeling outlined in the March 2018 

memorandum, because in their opinion 

the air quality modeling accompanying 

the March 2018 memorandum was 

‘‘based on flawed, unenforceable 

inventory assumptions and modeling 

methodology’’ that resulted in lower 

projected 2023 design values and state 

contributions that differ from the 

expected reality.32 Maryland further 

explained that even though that was the 

most current modeling available at the 

time, states should not solely rely on it 

to fulfill their interstate transport 

obligations, and for that reason, the 

State identified four items that, in its 

opinion, need to be included in a SIP 

submission to address section 

110(a)(2)(D)(i)(I) for the EPA to approve 

it. These four items include the 

following: (i) Completion of the entire 4- 

step interstate transport framework; (ii) 

requiring optimization of postcombustion controls at EGUs as a costeffective strategy for NOx reduction; (iii) 

requiring that reductions included in 

the modeling for interstate transport SIP 

submittals be permanent, enforceable 

and implemented as expeditiously as 

possible; and (iv) requiring that the 

optimization of post-combustion 

controls at EGUs happen on a daily 

basis, consistent with the way peak days 

are used to demonstrate attainment with 

the standards using measured ozone 

data. Even though Maryland did not 

agree with the results of the EPA’s 

March 2018 memorandum modeling on 

the basis that it contains unenforceable 

control measures, the State did use that 

modeling analysis to fulfill Step 2 of the 

4-step interstate transport framework. 

For Step 3 of the 4-step interstate 

transport framework, Maryland’s SIP 

submittal highlighted the EPA’s CSAPR 

Update rule. In particular, the State 

focused on the determination of the 

necessary level of NOX emission control 

and the state budgets for NOX emissions 

for EGUs, corresponding to emission 

levels after accounting for operation of 

existing pollution controls, emission 

reductions available at a certain cost 

threshold, and any additional 

reductions required to address interstate 

ozone transport. Maryland 

acknowledged that the CSAPR Update 

rule aids in the reduction of interstate 

transport through the implementation of 

NOX emissions limits for EGUs in 22 

eastern states, including Maryland, 

during the ozone season. 

Lastly, with regard to Step 4 of the 4- 

step interstate transport framework, the 

State’s SIP submittal described why it 

believed that Maryland’s NOX Rule met 

and exceeded the CSAPR Update 

requirements. Maryland claims that 

Maryland’s NOX Rule controls EGU 

NOX emissions at levels more stringent 

than required by the CSAPR Update 

rule. The submittal notes that Maryland 

has implemented its NOX Rule in two 

phases, with Phase 1 satisfying the 

CSAPR Update requirements, while 

Phase 2, which took effect in 2020, 

could be considered as additional 

emission reductions eliminating 

Maryland’s significant contributions to 

downwind states. As part of Step 4, 

Maryland’s submittal also provided a 

list of state regulations and voluntary 

control measures for a variety of other 

source categories for both NOX and VOC 

emissions that the State has adopted to 

demonstrate how Maryland complies 

and will continue to comply with the 

good neighbor provisions of the 2015 8- 

hour ozone NAAQS. 

III. EPA Evaluation 

The EPA is proposing to find that 

Maryland’s October 16, 2019 SIP 

submission does not meet the state’s 

obligations with respect to prohibiting 


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33Page 2 of Maryland’s 2019 SIP submission 

notes that Maryland does not agree with the 2023 

modeling assessment included with the March 2018 

memorandum because it is ‘‘based on flawed, 

unenforceable inventory assumptions and modeling 

assumptions’’ that result in lower projected 2023 

design values and state contributions that differ 

from reality. However, Maryland does not elaborate 

further on these ‘‘flaws,’’ nor does Maryland 

explain how or why these flaws, if corrected, would 

either change the status of any receptor or show that 

Maryland is not linked to any downwind 

nonattainment or maintenance receptors. 34 Design values and contributions at individual 

monitoring sites nationwide are provide in the file: 

2016v2_DVs_state_contributions.xlsx which is 

included in docket ID No. EPA–HQ–OAR–2021– 

0663. 

35These 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 of this 

document. That modeling showed that Maryland 

had a maximum contribution greater than 0.70 ppb 

to at least one nonattainment or maintenance-only 

receptor in 2023. These modeling results are 

included in the file ‘‘Ozone Design Values and 

Contributions Revised CSAPR Update.xlsx’’ in 

docket ID No. EPA–HQ–OAR–2021–0663. 

emissions that contribute significantly 

to nonattainment or interfere with 

maintenance of the 2015 8-hour ozone 

NAAQS in any other state, and the EPA 

is therefore proposing to disapprove 

Maryland’s SIP submission. This 

proposed disapproval is based on 

newer, updated modeling performed by 

the EPA which was not available when 

Maryland submitted its supplemental 

SIP, and the EPA’s evaluation of the SIP 

submission using the 4-step interstate 

transport framework. 

A. Maryland 

1. Evaluation of Information Provided 

by Maryland Regarding Steps 1 and 2 

As noted in Section II of this 

document, at Steps 1 and 2 of the 4-step 

interstate transport framework, 

Maryland used the EPA modeling 

released in the March 2018 

memorandum 33 to identify 

nonattainment and maintenance 

receptors in 2023 and to determine 

whether the State was linked to any of 

these receptors in 2023. The March 2018 

memorandum modeling was the latest 

modeling available when Maryland 

submitted its SIP revision in October 

2019. As described previously in this 

document, the EPA has since released 

air quality modeling using the most 

recent available and technically 

appropriate emissions data (i.e., 2016v2 

emissions platform). Therefore, the EPA 

proposes to primarily rely on the EPA’s 

most recent modeling to identify 

nonattainment and maintenance 

receptors and identify upwind state 

linkages to these receptors 2023. 

In Maryland’s 2019 SIP submission, 

the State used the modeling in the 

EPA’s March 2018 memorandum to 

identify six downwind monitors to 

which Maryland sources contributed to 

nonattainment or interfered with 

maintenance. The EPA’s air quality 

modeling for 2023 using the 2016v2 

emissions platform shows 

nonattainment or interference at five of 

the same six monitors, as shown in 

Table 1 of this document in the 

following subsection, although in 

slightly differing amounts. As noted in 

Section II of this document, Maryland 

objected to the modeling attached to the 

March 2018 memorandum by claiming 

that it relied on outdated information 

and flawed inventory assumptions that 

would tend to lessen downwind 

contributions from upwind sources. The 

EPA’s air quality modeling using the 

2016v2 emissions platform would 

presumably address some of Maryland’s 

concerns regarding the March 2018 

memorandum modeling. As stated in 

Section I of this document, the EPA is 

accepting comment on this more recent 

modeling data used to support this 

action. Regardless, both sets of modeling 

show that Maryland is linked to 

nonattainment or interfering with 

maintenance at downwind out-of-state 

monitors, and the State did not provide 

any alternative modeling analysis that 

showed an alternative set of 

nonattainment or maintenance receptors 

in 2023, nor did Maryland provide an 

alternative analysis to demonstrate that 

they were not linked to nonattainment 

or interfering with maintenance at 

downwind monitors. Therefore, both 

the EPA and Maryland agree that 

Maryland’s sources are contributing to 

nonattainment or interfering with 

maintenance at downwind monitors. 

2. Results of the EPA’s Step 1 and Step 

2 Modeling and Findings for Maryland 

As described in Section I of this 

document, the EPA performed air 

quality modeling using the 2016v2 

emissions platform to project design 

values and contributions for 2023. The 

EPA examined these data to determine 

if emissions from Maryland sources 

contribute at or above the threshold of 

1 percent of the 2015 8-hour ozone 

NAAQS (0.70 ppb) to any downwind 

nonattainment or maintenance receptor. 

As shown in Table 1 of this document, 

the data 34 indicate that in 2023, 

emissions from Maryland contribute 

greater than 1 percent of the NAAQS to 

nonattainment or maintenance-only 

receptors in Fairfield County and New 

Haven County, Connecticut; and in 

Queens County and Suffolk County, 

New York.35

Therefore, based on the EPA’s 

evaluation of the information submitted 

by Maryland, and based on the EPA’s 

most recent modeling results for 2023, 

the EPA proposes to find that Maryland 

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. 

TABLE 1—MARYLAND LINKAGE RESULTS BASED ON EPA’S UPDATED 2016V2-BASED MODELING

Receptor ID Location Nonattainment/maintenance 

2023 average 

design value 

(ppb) 

2023 maximum 

design value 

(ppb) 

Maryland 

contribution 

(ppb) 

090013007 .............. Fairfield County—Stratford, CT ...... Nonattainment .................... 74.3 75.2 1.18 

090019003 .............. Fairfield County—Westfield, CT ..... Nonattainment .................... 76.9 77.2 1.18 

090010017 .............. Fairfield County—Greenwich, CT ... Maintenance ....................... 73.4 74.0 0.67 

090099002 .............. New Haven—Madison, CT ............. Maintenance ....................... 71.7 73.8 1.51 

360810124 .............. Queens County, NY ........................ Maintenance ....................... 66.2 67.8 1.10 

361030002 .............. Suffolk County—Babylon, NY ......... Nonattainment .................... 67.0 68.8 1.12 

3. 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). 


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36See Maryland’s October 16, 2019 SIP submittal 

included in docket ID No. EPA–R03–OAR–2021– 

0872. 

37See Maryland’s October 16, 2019 SIP submittal 

at 7 included in docket ID No. EPA–R03–OAR– 

2021–0872. 38The Maryland NOX rule is codified at COMAR 

26.11.38 (Control of NOX Emissions from Coal-Fired 

Electric Generating Units). 

To evaluate effectively 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 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. At Step 3 of the 4-step 

interstate transport framework, 

Maryland did not include an accounting 

of all of the NOX emitting facilities in 

the state along with an analysis of 

potential NOX emissions control 

technologies, their associated costs, 

estimated emissions reductions, and 

downwind air quality improvements. 

Maryland’s analysis instead focused 

on the CSAPR Update rule and 

described how, as of May 2017, that rule 

has reduced ozone season NOX

emissions from power plants in 22 

eastern states, including Maryland. 

Maryland referenced the EPA’s finding 

in the CSAPR Update that for the 

updated NOX ozone season budgets for 

EGUs, an increased cost threshold of 

$1,400 per ton of NOX reduced was 

appropriate, because it represented the 

level of maximum marginal NOX

reduction with respect to cost, while not 

over-controlling upwind states’ 

emissions. Maryland’s SIP submittal 

included a table with the 22 states’ 

updated ozone season NOX budgets. 

That table shows that for Maryland, the 

CSAPR Update NOX ozone season 

budget, at the $1,400 per ton threshold, 

was 3,238 tons.36

Maryland’s focus on the CSAPR 

Update (which reflected a stringency at 

the nominal marginal cost threshold of 

$1400/ton (2011$) for the 2008 ozone 

NAAQS) rule to satisfy their obligations 

for the 2015 8-hour ozone NAAQS is 

unpersuasive. First, the CSAPR Update 

did not regulate non-electric generating 

units (non-EGU), so Maryland’s reliance 

on only the CSAPR Update analysis is 

incomplete because Maryland did not 

analyze non-EGU sources. See 

Wisconsin, 938 F.3d at 318–20. Second, 

relying on the CSAPR Update’s (or any 

other CAA program’s) determination of 

cost-effectiveness without further Step 3 

analysis by Maryland is not approvable. 

Cost-effectiveness must be assessed in 

the context of the specific CAA 

program; assessing cost-effectiveness in 

the context of ozone transport should 

reflect a more comprehensive evaluation 

of the nature of the interstate transport 

problem, the total emissions reductions 

available at several cost thresholds, and 

the air quality impacts of the reductions 

at downwind receptors. While the EPA 

has not established a benchmark costeffectiveness value for the 2015 8-hour 

ozone NAAQS interstate transport 

obligations, because the 2015 8-hour 

ozone NAAQS is a more stringent and 

more protective air quality standard, it 

is reasonable to expect control measures 

or strategies to address interstate 

transport under this NAAQS to reflect 

higher marginal control costs. As such, 

the marginal cost threshold of $1,400/ 

ton for the CSAPR Update (which 

addresses the 2008 ozone NAAQS and 

is in 2011$) is not an appropriate cost 

threshold and cannot be approved as a 

benchmark to use for interstate transport 

SIP submissions for the 2015 8-hour 

ozone NAAQS. Furthermore, Maryland 

did not explain how the ozone season 

NOX emission budget for Maryland’s 

EGUs set by the CSAPR Update, which 

was intended to address ozone transport 

nonattainment and maintenance issues 

for the less-stringent 2008 ozone 

NAAQS, eliminates Maryland’s 

significant contribution to the 

downwind nonattainment and 

maintenance receptors to which 

Maryland is linked for purposes of the 

more stringent 2015 8-hour ozone 

NAAQS. 

In addition, the updated 2023 EPA 

modeling using the 2016v2 emissions 

platform captures all existing CSAPR 

trading programs in the baseline, and 

that modeling confirms that these 

control programs were not sufficient to 

eliminate Maryland’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. 

Finally, relying on a FIP at Step 3 is 

per se not approvable if the state has not 

adopted that program into its SIP and 

instead continues to rely on the FIP. 

States may not rely on non-SIP 

measures to meet SIP requirements. See 

CAA section 110(a)(2)(D) (‘‘Each such 

[SIP] shall . . . contain adequate 

provisions . . .’’). See also CAA section 

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). 

Notwithstanding the above 

deficiencies, Maryland asserts at Step 3 

of its analysis that ‘‘Maryland’s NOX

Rule controls EGU NOX emissions at 

levels more stringent than what is 

required by the CSAPR Update and it 

will achieve the necessary reductions to 

meet the State’s good neighbor 

obligations under the 2015 8-hour ozone 

NAAQS.’’ 37 Maryland’s submittal 

provided, among other things, a 

description of the Maryland NOX Rule 

to control NOX emissions from CoalFired EGUs, and the following 

description of the NOX Rule is taken 

largely from Maryland’s submittal.38

Maryland’s NOX Rule took effect in May 

2015 and contains two phases. Phase I, 

found at COMAR 26.11.38.3, became 

effective on May 1, 2015 and required 

owners and operators of affected EGUs 

(coal-fired EGUs in Maryland) to 

comply with several measures meant to 

optimize their emission controls. These 

measures included: (i) The submission 

of a plan for approval by MDE and the 

EPA demonstrating how the EGU will 

operate installed pollution control 

technology and combustion controls 

during the ozone season to minimize 

emissions (COMAR 26.11.38.03A(1)); 

(ii) beginning May 1, 2015, and during 

the entire ozone season, requiring the 

owners and operators to operate and 

optimize the use of all installed 

pollution and combustion controls 


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39COMAR 28.11.38(D) does not specify that CFBs 

must meet the 0.10 lb/MMBtu 24-hour block 

average rate on an ‘‘annual basis,’’ so EPA has not 

been able to verify that this rate applies outside of 

ozone season. 

40See Maryland’s October 16, 2019 SIP submittal 

at 7 included in docket ID No. EPA–R03–OAR– 

2021–0872. 

41 Id. at 8. 

42 Detailed information and documentation of 

EPA’s Base Case, including all the underlying 

assumptions, data sources, architecture parameters, 

and IPM comments form can be found on EPA’s 

website at: https://www.epa.gov/airmarkets/epaspower-sector-modeling-platform-v6-using-ipmsummer-2021-reference-case. 

43The ‘‘Capacity Dropped’’ and the ‘‘Retired 

Through 2023’’ worksheets in NEEDS lists all units 

that are removed from the NEEDS v6 inventory— 

NEEDS v6 Summer 2021 Reference Case. This data 

can be found on EPA’s website at: https://

www.epa.gov/airmarkets/national-electric-energydata-system-needs-v6. 

44Phase II is codified at COMAR 26.11.38.04 

(Additional NOX Emission Control Requirements). 

consistent with the technological 

limitations, manufacturers’ 

specifications, good engineering, 

maintenance practices, and air pollution 

control practices to minimize emissions 

(COMAR 26.11.38.03A(2)); (iii) setting 

an ozone season system-wide NOX

emission rate of 0.15 pounds per million 

British units (lbs/MMBtu) as a 30-day 

rolling average for affected EGUs 

(COMAR 26.11.38.03B(1)); (iv) 

exempting EGUs that are the only 

facility in Maryland directly or 

indirectly owned, operated, or 

controlled by the owner, operator, or 

controller of the facility from the 0.15 

lbs/MMBtu system-wide emission rate 

specified in COMAR 26.11.38.03B(1) 

(COMAR 26.11.38.03B(3)); and (v) 

setting a NOX emission rate for EGUs 

using fluidized bed combustors of 0.10 

lbs/MMBtu as a 24-hour block average 

on an annual basis while exempting 

these units from meeting COMAR 

26.11.38.03A, B(1) and (2), and (C) 

(COMAR 26.11.38.03D).39 Sources 

subject to Phase I must also continue 

meeting annual NOX reductions in 

COMAR 26.11.27, Maryland’s Healthy 

Air Act. Maryland claims that for 

owners and operators to meet the limits 

set by Maryland’s NOX Rule, the sources 

are required to run their controls 

‘‘continuously.’’ 40

In addition, Maryland’s 2019 SIP 

Submission contains a table (Table 5) 41

which the State describes as listing 

‘‘NOX indicator rates’’ which 

demonstrate compliance with the 

optimization requirement in COMAR 

26.11.38.03A(1). These rates, found in 

COMAR 26.11.38.05, are described as 

‘‘Required 24-Hour Block Average Unit 

Level NOX Emission Rates.’’ The rates 

can vary from unit to unit at each 

affected source (and at the unit level 

based on heat input at Brandon Shores 

Unit 2) and between affected sources. 

These limits range from 0.07 lbs/MMBtu 

to 0.34 lbs/MMBtu. The effect of 

meeting these indicator rates is that ‘‘(2) 

An affected electric generating unit shall 

not be required to submit a unit-specific 

report consistent with § A(3) of this 

regulation when the unit emits at levels 

that are at or below the . . .’’ rates in 

the table. COMAR 26.11.38.05A(2). If 

the affected EGU does not meet its 

prescribed emission rate, it must submit 

a report to MDE for that day explaining 

the circumstances of the exceedance. 

COMAR 26.11.38.05A(3). As specified 

in COMAR 26.11.38.05A(4), such 

exceedance shall not be a violation if it 

was caused by certain events and was in 

accordance with the plan submitted 

under COMAR 26.11.38.03A(1). 

Regarding Phase I of Maryland’s NOX

Rule, the EPA notes that the Phase I 

NOX Rule emission reductions took 

effect in 2017 and are captured in the 

EPA’s updated 2023 modeling using the 

2016v2 emissions platform, but that 

emissions modeling still shows that 

Maryland is contributing to 

nonattainment or interfering with 

maintenance at downwind receptors in 

other states. The EPA’s latest projections 

of the baseline EGU emissions uses the 

version 6—Summer 2021 Reference 

Case of the Integrated Planning Model 

(IPM). IPM is a multi-regional, dynamic, 

and deterministic linear programming 

model of the U.S. electric power sector. 

The model provides forecasts of least 

cost capacity expansion, electricity 

dispatch, and emission control 

strategies, while meeting energy 

demand, environmental, transmission, 

dispatch, and reliability constraints. 

The IPM version 6—Summer 2021 

Reference Case incorporated recent 

updates through the Summer of 2021 to 

account for updated Federal and State 

environmental regulations for EGUs. 

This projected base case accounts for 

the effects of the finalized Mercury and 

Air Toxics Standards rule, CSAPR, the 

CSAPR Update, the Revised CSAPR 

Update, New Source Review 

settlements, the final effluent limitation 

guidelines (ELG) Rule, the coal 

combustion residual (CCR) Rule, and 

other on-the-books Federal and State 

rules (including renewable energy tax 

credit extensions from the Consolidated 

Appropriations Act of 2021) through 

early 2021 impacting SO2, NOX, directly 

emitted particulate matter, CO2, and 

power plant operations. It also includes 

final actions the EPA has taken to 

implement the Regional Haze Rule and 

the best available retrofit technology 

(BART) requirements. Further, the IPM 

Platform version 6 uses demand 

projections from the Energy Information 

Agency’s (EIA) annual energy outlook 

(AEO) 2020.42

The IPM version 6—Summer 2021 

Reference Case uses the national electric 

energy data system (NEEDS) v6 database 

as its source for data on all existing and 

planned-committed units. Units are 

removed from the NEEDS inventory 

only if a high degree of certainty could 

be assigned to future implementation of 

the announced future closure or 

retirement.43 The available retirementrelated information was reviewed for 

each unit, and the following rules are 

applied to remove: 

(i) Units that are listed as retired in 

the December 2020 EIA Form 860M; 

(ii) Units that have a planned 

retirement year prior to June 30, 2023 in 

the December 2020 EIA Form 860M; 

(iii) Units that have been cleared by 

a regional transmission operator (RTO) 

or independent system operator (ISO) to 

retire before 2023, or whose RTO/ISO 

clearance to retire is contingent on 

actions that can be completed before 

2023; 

(iv) Units that have committed 

specifically to retire before 2023 under 

Federal or state enforcement actions or 

regulatory requirements; and 

(v) Finally, units for which a 

retirement announcement can be 

corroborated by other available 

information. Units required to retire 

pursuant to enforcement actions or state 

rules on July 1, 2023 or later are 

retained in NEEDS v6. 

Retirements or closures taking place 

on or after July 1, 2023 are captured as 

constraints on those units in the IPM 

modeling, and the units are retired in 

future year projections per the terms of 

the related requirements. 

As highlighted in previous 

rulemakings, the IPM documentation 

and the EPA’s Power Sector Modeling 

website, the EPA’s goal is to explain and 

document the use of IPM in a 

transparent and publicly accessible 

manner, while also providing for 

concurrent channels for improving the 

model’s assumptions and representation 

by soliciting constructive feedback to 

improve the model. This includes 

making all inputs and assumptions to 

the model, output files from the model, 

and IPM feedback form publicly 

available on the EPA’s website. 

Phase II 44 of Maryland’s NOX Rule 

took effect on June 1, 2020 and applies 

only to owners or operators of EGUs 

without SCR controls, which consists of 

seven units at four facilities. These 

EGUs were required to choose between 

four options by June 1, 2020. The 


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45 Deeper reductions include meeting a 30-day 

system-wide rolling average NOX emission rate of 

0.13 lbs/MMBtu in May 2016, 0.11 lbs/MMBtu in 

May 2018, and 0.09 lbs/MMBtu in May 2020 during 

the ozone season. 

46Pointing to anticipated upcoming emission 

reductions, even if they were not included in the 

analysis at Steps 1 and 2, is not sufficient as a Step 

3 analysis, for the reasons discussed in Section 

III.A.3 of this document. In this section, the EPA 

explains that to the extent such anticipated 

reductions are not included in the SIP and rendered 

permanent and enforceable, reliance on such 

anticipated reductions is also insufficient at Step 4. 

options include: (i) Installation and 

operation of an SCR control system by 

June 1, 2020 that can meet a NOX

emission rate of 0.09 lbs/MMBtu during 

the ozone season based on a 30-day 

rolling average; (ii) permanently retiring 

the unit; (iii) switching fuel 

permanently from coal to natural gas 

and operating the unit on natural gas; or 

(iv) meeting a system-wide, daily NOX

tonnage cap of 21 tons per day for every 

day of the ozone season or meeting a 

system-wide NOX emission rate of 0.13 

lbs/MMBtu as a 24-hour block average. 

Option 4, if selected by the source, 

included additional measures requiring 

a series of greater emission reductions 

beginning in May 2016, 2018, and 

2020.45 If the owner or operator did not 

select option 4, then the allowable 30- 

day system-wide rolling average NOX

emission rate was set at 0.15 lbs/MMBtu 

during the ozone season. In addition, 

option 4 included provisions to ensure 

that the reliability of the electrical 

system is maintained. There are 

additional provisions in the NOX Rule 

which addressed the options and limits 

applicable if a unit or units included in 

a ‘‘system’’ as of May 1, 2015 were no 

longer owned, operated or controlled by 

the ‘‘system.’’ 

For Phase II, the 2019 SIP Submission 

notes that Chalk Point, Dickerson and 

Morgantown generating stations 

selected option 4, that Brandon Shores 

and Herbert A. Wagner generating 

stations chose the optimization 

requirement in COMAR 26.11.38.03A, 

and that pursuant to a May 23, 2018 

settlement agreement, C.P. Crane agreed 

to cease, and has ceased, the burning of 

coal in Units 1 and 2 by no later than 

June 15, 2018, and that the coal-fired 

boilers have been disabled. Maryland 

predicted that the implementation of 

both the Phase I and II requirements 

would result in ozone season NOX

emission reductions of 2,507 to 2,627 

tons from the base year 2011 emissions. 

The SIP submission did not specify the 

amount of reduction that would occur 

on any specific date, or the amount of 

reduction attributable to any specific 

element of the NOX Rule. As noted 

earlier, these reductions are likely 

included in the 2016v2 emission 

platform, and that modeling continues 

to show that Maryland is contributing to 

downwind nonattainment and 

maintenance receptors for the 2015 8- 

hour ozone NAAQS. 

The SIP submission also listed several 

control measures, including regulation 

of emissions from the mobile sector, 

pursuing significant regulation of 

industrial sources, and implementing 

VOC rules that regulate emissions from 

other source categories that Maryland 

has implemented to address the control 

of VOC and NOX emissions from various 

point, mobile, and area sources. 

Maryland’s submission also described 

additional voluntary or innovative 

control measures that the State has 

implemented in attainment plan SIP 

provisions and stated that even though 

they do not rely on any emission 

reductions projected as a result of the 

implementation of these voluntary 

programs to demonstrate attainment, 

these strategies assist in the overall 

clean air goals across the State. 

Unfortunately, Maryland failed to 

provide any analysis as to how these 

many provisions cited in its 2019 SIP 

Submittal would eliminate the 

significant contribution of Maryland’s 

emission sources to downwind 

nonattainment or maintenance receptors 

to which Maryland’s emissions are 

linked by the EPA’s 2016v2 emissions 

platform. As noted in Section D–4 of 

this proposal, ‘‘[i]n general, where the 

EPA’s or alternative air quality and 

contribution modeling establishes that a 

state is linked at Steps 1 and 2, it will 

be insufficient at Step 3 for a state 

merely to point to its existing rules 

requiring control measures as a basis for 

approval. In general, the emissionsreducing 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 well-documented evaluation 

determining whether their emissions 

constitute significant contribution or 

interference with maintenance by 

evaluating additional available control 

opportunities by preparing a multifactor 

assessment.’’ Maryland provided no 

such multifactor assessment, and 

instead claims, without any modeling to 

support this claim, that its existing, 

already adopted control measures for 

EGUs and other sources will keep 

Maryland from contributing 

significantly to nonattainment or 

interfere with maintenance at 

downwind receptors to which it is 

linked. As such, it does not rise to the 

level of a ‘‘well-documented 

evaluation.’’ 

Maryland’s SIP submittal also 

included a weight of evidence analysis 

which analyzed various scenarios. 

These scenarios evaluated various 

iterations of controls, including SCR 

controls and emission limits comparable 

to those under the 2015 Maryland NOX

Rule, and applied these SCR controls 

and limits to emissions sources in other 

states (IL, IN, KY, MI, NC, OH, WV, VA, 

NY and PA). This is the same weight of 

evidence analysis that Maryland 

included with its transport SIP 

submittal for the 2008 ozone NAAQS. 

This modeling analysis only addressed 

the impact that installation of these 

controls and imposition of these limits 

in other states would have on 

Maryland’s monitors. There is no 

analysis in this weight of evidence 

portion addressing Maryland’s 

contribution to downwind receptors. It 

therefore does not change the EPA’s 

evaluation of Maryland’s obligations to 

address its own contributions. 

The EPA acknowledges that 

Maryland’s efforts to reduce NOX

emissions from EGUs, and other 

requirements to reduce NOX and VOC 

emissions from other source categories, 

have helped reduce the interstate 

transport impacts of emissions from 

Maryland’s sources on other states’ 

receptors. In addition to addressing 

ambient ozone levels in nonattainment 

areas in Maryland, these state specific 

requirements should also help reduce 

the level of NOX emissions reductions 

that Maryland needs to obtain in order 

to meet the section 110(a)(2)(D)(i)(I) 

requirements for the 2015 8-hour ozone 

NAAQS. 

Based on the EPA’s evaluation of 

Maryland’s SIP submittal at Step 3, 

however, the EPA proposes that 

Maryland was required to analyze 

emissions from the sources and other 

emissions activity from within the state 

to determine whether its contributions 

were significant, and therefore the EPA 

proposes to base part of its disapproval 

on Maryland’s failure to do so. 

4. 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. Maryland 

identified a number of measures that 

were either in development or 

anticipated to occur in the future.46 As 


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47See Maryland’s October 16, 2019 SIP submittal 

at pages 8–9, included in docket ID No. EPA–R03– 

OAR–2021–0872. 

48 Id. at 16. 

discussed in detail in the Step 3 

analysis above, Phase II of Maryland’s 

NOX Rule (COMAR 26.11.38.04) 

requires coal-fired EGUs that have not 

installed SCR to choose from one of four 

options by June 1, 2020 that should 

result in NOX emission reductions.47

Another measure is the Regional 

Greenhouse Gas Initiative (RGGI), which 

Maryland projects will result in 

Maryland’s and other participating 

states’ regional CO2 emission budgets 

declining by 30% by 2030.48 However, 

the State has not revised its SIP to 

include these emission reductions to 

ensure the reductions are permanent 

and enforceable. As a result, the EPA 

also proposes as an additional ground 

for disapproval of Maryland’s SIP 

submission the fact 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). 

5. Conclusion 

Based on the EPA’s evaluation of 

Maryland’s SIP submission, the EPA is 

proposing to find that Maryland’s 

October 16, 2019 SIP submission does 

not meet the State’s interstate transport 

obligations, because it fails to show that 

the provisions adopted by Maryland to 

reduce NOX and VOC emissions from 

sources within Maryland will reduce 

emissions to levels that will not 

contribute significantly to 

nonattainment or interfere with 

maintenance of the 2015 8-hour ozone 

NAAQS at downwind monitors in other 

states to which it is linked. Maryland’s 

2019 SIP submission lacks an analysis 

of the effect that Maryland’s adopted 

emission reductions would have on the 

specific downwind monitors which the 

EPA’s March 2018 memorandum 

modeling analysis and 2016v2 

emissions platform analysis determined 

that Maryland sources contribute more 

than 1 percent to nonattainment or 

interference with maintenance. 

Maryland’s SIP submission disputes 

neither the significant contribution from 

Maryland nor the ‘‘linkages’’ between 

Maryland emissions and these 

downwind nonattainment or 

maintenance monitors. Further, 

although Maryland objects to the 

modeling assessment included with the 

EPA’s March 2018 Memorandum, it 

does not offer an alternative modeling 

assessment showing that projected 

reductions in Maryland’s emissions, as 

outlined in its 2019 SIP submittal, 

would eliminate the contribution 

Maryland’s emissions make to nonattaining or maintenance monitors 

identified by the EPA’s 2018 

memorandum modeling assessment, or 

to those in the more recent 2016v2 

emissions platform assessment. 

Maryland’s modeling assessment in its 

2019 SIP submittal merely explores the 

varying effects that various emission 

reduction strategies in eastern states 

would have on ozone nonattainment in 

general, rather than the effect 

Maryland’s reductions would have on 

non-attaining or maintenance monitors 

to which it is linked. 

IV. Proposed Action 

The EPA is proposing to disapprove 

Maryland’s October 16, 2019 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 Maryland 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 new 

Maryland SIP submission that meets 

these requirements. Disapproval does 

not start a mandatory sanctions clock for 

Maryland. 

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’’ as defined by 

Executive Order 12866 and was 

therefore not submitted to the Office of 

Management and Budget for review. 

B. Paperwork Reduction Act (PRA) 

This proposed action does not impose 

an information collection burden under 

the PRA because it does not contain any 

information collection activities 

C. Regulatory Flexibility Act (RFA) 

I certify that this action will not have 

a significant economic impact on a 

substantial number of small entities 

under the RFA. This action merely 

proposes to disapprove a SIP 

submission as not meeting the CAA. 

D. Unfunded Mandates Reform Act 

(UMRA) 

This action does not contain any 

unfunded mandate as described in 

UMRA, 2 U.S.C. 1531–1538, and does 

not significantly or uniquely affect small 

governments. The action imposes no 

enforceable duty on any state, local or 

tribal governments or the private sector. 

E. Executive Order 13132: Federalism 

This action does not have federalism 

implications. It will not have substantial 

direct effects on the states, on the 

relationship between the national 

government and the states, or on the 

distribution of power and 

responsibilities among the various 

levels of government. 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

This action does not have tribal 

implications as specified in Executive 

Order 13175. This action does not apply 

on any Indian reservation land, any 

other area where the EPA or an Indian 

tribe has demonstrated that a tribe has 

jurisdiction, or non-reservation areas of 

Indian country. Thus, Executive Order 

13175 does not apply to this action. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

Risks and Safety Risks 

The EPA interprets Executive Order 

13045 as applying only to those 

regulatory actions that concern 

environmental health or safety risks that 

the EPA has reason to believe may 

disproportionately affect children, per 

the definition of ‘‘covered regulatory 

action’’ in section 2–202 of the 

Executive Order. This action is not 

subject to Executive Order 13045 

because it merely proposes to 

disapprove a SIP submission as not 

meeting the CAA. 

H. Executive Order 13211, Actions That 

Significantly Affect Energy Supply, 

Distribution or Use 

This action is not subject to Executive 

Order 13211, because it is not a 

significant regulatory action under 

Executive Order 12866. 

I. National Technology Transfer and 

Advancement Act 

This rulemaking does not involve 

technical standards. 

J. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations 

The EPA believes the human health or 

environmental risk addressed by this 


lotter on DSK11XQN23PROD with PROPOSALS1
Federal Register / Vol. 87, No. 35 / Tuesday, February 22, 2022 / Proposed Rules 9475 

49 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. 

50A 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. 

51The 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 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. 

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).49

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 8-hour 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 8-hour 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 definition of 

nonattainment and maintenance 

receptors at Step 1, and a nationally 

uniform contribution threshold analysis 

at Step 2.50 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).51

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: February 7, 2022. 

Diana Esher, 

Acting Regional Administrator, Region III. 

[FR Doc. 2022–02951 Filed 2–18–22; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R09–OAR–2022–0106; FRL–9527–01– 

R9] 

Air Plan Approval; Nevada; Clark 

County Department of Environment 

and Sustainability 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is proposing to approve 

revisions to the Clark County 

Department of Environment and 

Sustainability (DES) portion of the 

Nevada State Implementation Plan 

(SIP). These revisions concern the title 

change of the Clark County Department 

of Air Quality to the Department of 

Environment and Sustainability. We are 

proposing to approve this title change. 

The ‘‘department of air quality’’ was 

deleted in the air quality regulations 

and replaced with ‘‘department.’’ We 

are taking comments on this proposal 

and plan to follow with a final action. 

DATES: Any comments must arrive by 

March 24, 2022. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–R09– 

OAR–2022–0106 at https://

www.regulations.gov. For comments 

submitted at Regulations.gov, follow the 

online instructions for submitting 

comments. Once submitted, comments 

cannot be edited or removed from 

Regulations.gov. The EPA may publish 

any comment received to its public 

docket. Do not submit electronically any 

information you consider to be 

Confidential Business Information (CBI) 

or other information whose disclosure is 

restricted by statute. Multimedia 

submissions (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). For 

additional submission methods, please 

contact the person identified in the FOR

FURTHER INFORMATION CONTACT section. 

For the full EPA public comment policy, 

information about CBI or multimedia 

submissions, and general guidance on 

making effective comments, please visit 

https://www.epa.gov/dockets/ 

commenting-epa-dockets. If you need 

assistance in a language other than 

English or if you are a person with 

disabilities who needs a reasonable 

accommodation at no cost to you, please 

contact the person identified in the FOR

FURTHER INFORMATION CONTACT section. 

FOR FURTHER INFORMATION CONTACT: 

Christine Vineyard, EPA Region IX, 75 

Hawthorne St., San Francisco, CA 

94105. By phone: (415) 947–4125 or by 

email at vineyard.christine@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Throughout this document, ‘‘we,’’ ‘‘us’’ 

and ‘‘our’’ refer to the EPA. 

Table of Contents 

I. The State’s Submittal 

A. What rules did the State submit? 


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