65878 Federal Register / Vol. 83, No. 245 / Friday, December 21, 2018 / Rules and Regulations 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–HQ–OAR–2018–0225; FRL–9987–86– 

OAR] 

RIN 2060–AT92 

Determination Regarding Good 

Neighbor Obligations for the 2008 

Ozone National Ambient Air Quality 

Standard 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Final rule. 

SUMMARY: This action finalizes the 

Environmental Protection Agency’s 

(EPA) determination that the existing 

Cross-State Air Pollution Rule Update 

for the 2008 Ozone National Ambient 

Air Quality Standards (NAAQS) 

(CSAPR Update) fully addresses certain 

states’ obligations under the good 

neighbor provision of the Clean Air Act 

(CAA) regarding interstate pollution 

transport for the 2008 ozone NAAQS. 

The CSAPR Update, published on 

October 26, 2016, promulgated Federal 

Implementation Plans (FIPs) for 22 

states in the eastern U.S. In the final 

CSAPR Update, based on information 

available at that time, the EPA could not 

conclude that the rule fully addressed 

these CAA section obligations for 21 of 

the 22 CSAPR Update states. As a result, 

the EPA has an outstanding obligation 

to fully address the requirements of this 

Clean Air Act provision for these states. 

Based on information and analysis that 

became available after the CSAPR 

Update was finalized, this action 

finalizes a determination that the 

existing CSAPR Update fully addresses 

the CAA’s good neighbor provision for 

the 2008 ozone NAAQS for all 

remaining CSAPR Update states. 

Specifically, EPA is finalizing a 

determination that 2023 is an 

appropriate future analytic year to 

evaluate remaining good neighbor 

obligations and that, for the purposes of 

addressing good neighbor obligations, 

there will be no remaining 

nonattainment or maintenance receptors 

with respect to the 2008 ozone NAAQS 

in the eastern U.S. in that year. 

Therefore, with the CSAPR Update fully 

implemented, these remaining CSAPR 

Update states are not expected to 

contribute significantly to 

nonattainment in, or interfere with 

maintenance of, any other state with 

regard to the 2008 ozone NAAQS. In 

accord with this finding, the EPA has no 

outstanding, unfulfilled obligation to 

establish additional requirements for 

emission sources in these states to 

further reduce transported ozone 

pollution under the good neighbor 

provision for the 2008 ozone NAAQS. 

As a result of this finding, this action 

finalizes minor revisions to the existing 

CSAPR Update regulations to reflect 

that the CSAPR Update FIPs fully 

address this CAA provision. This 

determination applies to states currently 

subject to CSAPR Update FIPs as well 

as any states for which EPA has 

approved replacement of CSAPR Update 

FIPs with CSAPR Update state 

implementation plans (SIPs). 

DATES: This final rule is effective on 

February 19, 2019. 

ADDRESSES: The EPA has established a 

docket for this action under Docket ID 

No. EPA–HQ–OAR–2018–0225. All 

documents in the docket are listed on 

the www.regulations.gov website. 

Although listed in the index, some 

information may not be publicly 

available, e.g., CBI or other information 

whose disclosure is restricted by statute. 

Certain other material, such as 

copyrighted material, is not placed on 

the internet and will be publicly 

available only in hard copy form. 

Publicly available docket materials are 

available either electronically through 

www.regulations.gov. 

FOR FURTHER INFORMATION CONTACT: 

David Risley, Clean Air Markets 

Division, Office of Atmospheric 

Programs, U.S. Environmental 

Protection Agency, MC 6204M, 1200 

Pennsylvania Avenue NW, Washington, 

DC 20460; telephone number: (202) 

343–9177; email address: Risley.David@

epa.gov. 

SUPPLEMENTARY INFORMATION:

Regulated Entities. Entities regulated 

under the CSAPR Update are fossil fuelfired boilers and stationary combustion 

turbines that serve generators producing 

electricity for sale, including combined 

cycle units and units operating as part 

of systems that cogenerate electricity 

and other useful energy output. 

Regulated categories and entities 

include: 

Category NAICS* 

code 

Examples of 

potentially regulated 

industries 

Industry .... 221112 Fossil fuel-fired 

electric power 

generation 

* North American Industry Classification 

System. 

This table is not intended to be 

exhaustive, but rather provides a guide 

for readers regarding entities likely to be 

regulated. To determine whether your 

facility is affected by this action, you 

should carefully examine the 

applicability provisions in 40 CFR 

97.804. If you have questions regarding 

the applicability of the CSAPR Update 

to a particular entity, consult the person 

listed in the FOR FURTHER INFORMATION

CONTACT section above. 

Outline. The following outline is 

provided to aid in locating information 

in this preamble. 

I. General Information 

A. Summary of Proposal in Relation to the 

Final Determination 

B. States Covered by This Action 

II. Background and Legal Authority 

A. Ground-level Ozone Pollution and 

Public Health 

B. The EPA’s Statutory Authority for This 

Final Action 

C. Good Neighbor Obligations for the 2008 

Ozone NAAQS 

D. Summary of the CSAPR Update 

III. Final Determination Regarding Good 

Neighbor Obligations for the 2008 Ozone 

NAAQS 

A. Analytic Approach 

B. Selection of a Future Analytic Year 

1. Attainment Dates for the 2008 Ozone 

NAAQS 

2. Feasibility of Control Strategies to 

Further Reduce Ozone Season NOX

Emissions 

3. Focusing on 2023 for Analysis 

C. Air Quality Analysis 

1. Overview of Air Quality Modeling 

Platform 

2. Emission Inventories 

3. Definition of Nonattainment and 

Maintenance Receptors 

4. Air Quality Modeling to Identify 

Nonattainment and Maintenance 

Receptors 

5. Pollutant Transport from Upwind States 

D. Final Determination 

IV. Statutory Authority and Executive Order 

Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review, and Executive 

Order 13563: Improving Regulation and 

Regulatory Review 

B. Executive Order 13771: Reducing 

Regulations and Controlling Regulatory 

Costs 

C. Paperwork Reduction Act 

D. Regulatory Flexibility Act 

E. Unfunded Mandates Reform Act 

F. Executive Order 13132: Federalism 

G. Executive Order 13175: Consultation 

and Coordination with Indian Tribal 

Governments 

H. Executive Order 13045: Protection of 

Children from Environmental Health and 

Safety Risks 

I. Executive Order 13211: Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use 

J. National Technology Transfer 

Advancement Act 

K. Executive Order 12898: Federal Actions 

To Address Environmental Justice in 

Minority Populations and Low-Income 

Populations 

L. Congressional Review Act 

M. Determinations Under CAA Section 

307(b)(1) and (d) 


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Federal Register / Vol. 83, No. 245 / Friday, December 21, 2018 / Rules and Regulations 65879 

1The EPA determined in the final CSAPR Update 

that implementation of the emissions budget for 

Tennessee would fully eliminate the state’s 

significant contribution to downwind 

nonattainment and interference with maintenance 

of the 2008 ozone NAAQS because the downwind 

air quality problems to which the state was linked 

were projected to be resolved after implementation 

of the CSAPR Update. 81 FR 74540. 

2For more information on the human health and 

welfare and ecosystem effects associated with 

ambient ozone exposure, see the EPA’s October 

2015 Regulatory Impact Analysis of the Final 

Revisions to the National Ambient Air Quality 

Standards for Ground-Level Ozone (EPA–452/R– 

15–007) in the docket for this action and also found 

in the docket for the 2015 ozone NAAQS, Docket 

No. EPA–HQ–OAR–2013–0169–0057. 

3Rasmussen, D.J. et al. (2011). Ground-level 

ozone-temperature relationships in the eastern US: 

A monthly climatology for evaluating chemistryclimate models. Atmospheric Environment 47: 142– 

153. 

4High ozone concentrations have also been 

observed in cold months, where a few areas in the 

western U.S. have experienced high levels of local 

VOC and NOX emissions that have formed ozone 

when snow is on the ground and temperatures are 

near or below freezing. 

5Bloomer, B.J., J.W. Stehr, C.A. Piety, R.J. 

Salawitch, and R.R. Dickerson (2009). Observed 

relationships of ozone air pollution with 

temperature and emissions, Geophys. Res. Lett., 36, 

L09803. 

I. General Information 

Within this document ‘‘we,’’ ‘‘us,’’ or 

‘‘our’’ should be interpreted to mean the 

U.S. EPA. 

Where can I get a copy of this 

document and other related 

information? 

The EPA has established a docket for 

this action under Docket ID No. EPA– 

HQ–OAR–2018–0225 (available at 

http://www.regulations.gov). 

Information related to this final action is 

available at the website: https://

www.epa.gov/airtransport. 

A. Summary of Proposal in Relation to 

the Final Determination 

On July 10, 2018, the EPA issued its 

proposed Determination Regarding 

Good Neighbor Obligations for the 2008 

Ozone National Ambient Air Quality 

Standard. 83 FR 31915 (July 10, 2018). 

In that action, the agency proposed to 

determine that the existing CSAPR 

Update fully addressed certain states’ 

obligations under CAA section 

110(a)(2)(D)(i)(I) with respect to the 

2008 ozone NAAQS. The proposed 

determination was based upon a finding 

that 2023 was a reasonable future 

analytic year in which to further 

evaluate air quality with respect to 

remaining good neighbor obligations, 

considering relevant attainment dates 

for the 2008 ozone NAAQS and the time 

necessary to further mitigate nitrogen 

oxide (NOX) emissions through regional 

assessment of state-of-the-art postcombustion controls within the CSAPR 

Update region. The agency’s analysis of 

projected 2023 ozone concentrations 

indicated that there would be no 

remaining monitors expected to have 

difficulty attaining or maintaining the 

2008 ozone NAAQS, and the EPA 

therefore proposed to determine that the 

existing regulation—the CSAPR 

Update—fully addressed states’ 

obligations under this Clean Air Act 

provision for this NAAQS. The agency 

solicited comment on that proposal with 

the comment period ending on August 

31, 2018. The agency also held a public 

hearing on August 1, 2018. This final 

action was developed considering 

comments received on the proposal. 

Generally, the agency’s final action 

herein remains consistent with the 

proposal with respect to its 

determination regarding good neighbor 

obligations for the 2008 ozone NAAQS 

and its underlying rationale. 

B. States Covered by This Action 

In the CSAPR Update, 81 FR 74504 

(Oct. 26, 2016), the EPA promulgated 

FIPs affecting 22 eastern states that at 

least partially addressed obligations 

under CAA section 110(a)(2)(D)(i)(I), 

also known as the ‘‘good neighbor 

provision,’’ with respect to the 2008 

ozone NAAQS. The good neighbor 

provision requires upwind states to 

control their emissions that significantly 

contribute to air quality problems in 

downwind states. Based on information 

available when the CSAPR Update was 

finalized, the EPA was unable to 

determine at that time that the FIPs fully 

addressed good neighbor obligations 

under this NAAQS for 21 of the 22 

states.1 The EPA has subsequently 

finalized approval of a SIP that fully 

addresses the good neighbor obligation 

for one of these states—Kentucky. 83 FR 

33730 (July 17, 2018). Consistent with 

the EPA’s July 2018 proposed 

determination, in this action, the EPA 

finalizes a determination that with 

CSAPR Update implementation the 20 

remaining states’ good neighbor 

obligations for the 2008 ozone NAAQS 

are fully addressed. In accord with this 

determination, the EPA has no further 

obligation under CAA section 110(c) to 

establish requirements for power plants 

or any other emission sources in these 

states to further reduce transported 

ozone pollution under CAA section 

110(a)(2)(D)(i)(I) with regard to this 

NAAQS. See Table I.A–1 for a list of 

states covered by this final action. 

TABLE I.A–1—STATES COVERED BY

THIS FINAL DETERMINATION REGARDING GOOD NEIGHBOR OBLIGATIONS FOR THE 2008 OZONE

NAAQS 

State 

Alabama Missouri 

Arkansas New Jersey 

Illinois New York 

Indiana Ohio 

Iowa Oklahoma 

Kansas Pennsylvania 

Louisiana Texas 

Maryland Virginia 

Michigan West Virginia 

Mississippi Wisconsin 

II. Background and Legal Authority 

A. Ground-level Ozone Pollution and 

Public Health 

Ground-level ozone causes a variety 

of negative effects on human health, 

vegetation, and ecosystems. In humans, 

acute and chronic exposure to ozone is 

associated with premature mortality and 

a number of morbidity effects, such as 

asthma exacerbation. In ecosystems, 

ozone exposure causes visible foliar 

injury in some plants, decreases growth 

in some plants, and affects ecosystem 

community composition.2

In this final action, consistent with 

EPA’s proposal and with previous 

rulemakings described in section II.B, 

the EPA relies on analysis that reflects 

the regional nature of transported 

ground-level ozone pollution. Groundlevel ozone is not emitted directly into 

the air, but is a secondary air pollutant 

created by chemical reactions between 

NOX, carbon monoxide (CO), methane 

(CH4), and non-methane volatile organic 

compounds (VOCs) in the presence of 

sunlight. Emissions from mobile 

sources, electric generating units 

(EGUs), industrial facilities, gasoline 

vapors, and chemical solvents are some 

of the major anthropogenic sources of 

ozone precursors. The potential for 

ground-level ozone formation increases 

during periods with warmer 

temperatures and stagnant air masses. 

Therefore, ozone levels are generally 

higher during the summer months.3 4

Ground-level ozone concentrations and 

temperature are highly correlated in the 

eastern U.S., with observed ozone 

increases of 2–3 parts per billion (ppb) 

per degree Celsius reported.5

Precursor emissions can be 

transported downwind directly or, after 

transformation in the atmosphere, as 

ozone. Studies have established that 

ozone formation, atmospheric residence, 

and transport occur on a regional scale 

(i.e., hundreds of miles) over much of 

the eastern U.S. As a result of ozone 

transport, in any given location, ozone 

pollution levels are affected by a 

combination of local emissions and 


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65880 Federal Register / Vol. 83, No. 245 / Friday, December 21, 2018 / Rules and Regulations 

6For example, Bergin, M.S. et al. (2007). Regional 

air quality: local and interstate impacts of NOX and 

SO2 emissions on ozone and fine particulate matter 

in the eastern United States. Environmental Sci & 

Tech. 41: 4677–4689. 

7 Jiang, G.; Fast, J.D. (2004). Modeling the effects 

of VOC and NOX emission sources on ozone 

formation in Houston during the TexAQS 2000 field 

campaign. Atmospheric Environment 38: 5071– 

5085. 

8Liao, K. et al. (2013) Impacts of interstate 

transport of pollutants on high ozone events over 

the Mid-Atlantic United States. Atmospheric 

Environment 84, 100–112. 

9Hidy, G.M. and Blanchard C.L. (2015). Precursor 

reductions and ground-level ozone in the 

Continental United States. J. of Air & Waste 

Management Assn. 65, 10. 

10Simon, H. et al. (2015). Ozone trends across the 

United States over a period of decreasing NOX and 

VOC emissions. Environmental Science & 

Technology 49, 186–195. 

11 Gilliland, A.B. et al. (2008). Dynamic 

evaluation of regional air quality models: Assessing 

changes in O3 stemming from changes in emissions 

and meteorology. Atmospheric Environment 42: 

5110–5123. 

12CASTNET is the EPA’s Clean Air Status and 

Trends Network. AQS is the EPA’s Air Quality 

System. 

13Hou, Strickland & Liao. ‘‘Contributions of 

regional air pollutant emissions to ozone and fine 

particulate matter-related mortalities in eastern U.S. 

urban areas’’. Environmental Research, Feb. 2015. 

Available at https://ac.els-cdn.com/ 

S0013935114004113/1-s2.0–S0013935114004113- 

main.pdf?_tid=78c88101-fa6e-4e75-a65cf56746905e7d&acdnat=1525175812_

0e62553b83c9ffa1105aa306a478e8bb. 

14 Ge ́go et al. (2007). Observation-based 

assessment of the impact of nitrogen oxides 

emission reductions on O3 air quality over the 

eastern United States. J. of Applied Meteorology 

and Climatology 46: 994–1008. 

15 42 U.S.C. 7410(a)(1). 

16See EPA v. EME Homer City Generation, L.P., 

134 S. Ct. 1584, 1601 (2014). 

17The EPA’s general approach to infrastructure 

SIP submissions is explained in greater detail in 

individual notices acting or proposing to act on 

state infrastructure SIP submissions and in 

guidance. See, e.g., Memorandum from Stephen D. 

Page on Guidance on Infrastructure State 

Implementation Plan (SIP) Elements under Clean 

Air Act Sections 110(a)(1) and 110(a)(2) (Sept. 13, 

2013). 

18 42 U.S.C. 7410(c)(1). 

19 42 U.S.C. 7410(a)(2)(D)(i)(I). 

emissions from upwind sources. 

Numerous observational studies have 

demonstrated the transport of ozone and 

its precursors and the impact of upwind 

emissions on high concentrations of 

ozone pollution. 6

The EPA concluded in several 

previous rulemakings (summarized in 

section II.B) that interstate ozone 

transport can be an important 

component of peak ozone 

concentrations during the summer 

ozone season and that NOX control 

strategies are effective for reducing 

regional-scale ozone transport. Model 

assessments have looked at impacts on 

peak ozone concentrations after 

potential emission reduction scenarios 

for NOX and VOCs for NOX-limited and 

VOC-limited areas. For example, Jiang 

and Fast concluded that NOX emission 

reduction strategies are effective in 

lowering ozone mixing ratios in urban 

areas and Liao et al. showed that NOX

reductions result in lower peak ozone 

concentrations in non-attainment areas 

in the Mid-Atlantic.7 8 Assessments of 

ozone conducted for the October 2015 

Regulatory Impact Analysis of the Final 

Revisions to the National Ambient Air 

Quality Standards for Ground-Level 

Ozone (EPA–452/R–15–007) also show 

the importance of NOX emissions on 

ozone formation. This analysis is in the 

docket for this action and also can be 

found in the docket for the 2015 ozone 

NAAQS regulatory impact analysis, 

Docket No. EPA–HQ–OAR–2013–0169 

(document ID EPA–HQ–OAR–2013– 

0169–0057). 

Studies have found that NOX

emission reductions can be effective in 

reducing ozone pollution as quantified 

by the form of the 2008 ozone standard, 

8-hour peak concentrations. 

Specifically, studies have found that 

NOX emission reductions from EGUs, 

mobile sources, and other source 

categories can be effective in reducing 

the upper-end of the cumulative ozone 

distribution in the summer on a regional 

scale.9 Analysis of air quality 

monitoring data trends shows 

reductions in summertime ozone 

concurrent with implementation of NOX

reduction programs.10 Gilliland et al. 

examined the NOX SIP Call, discussed 

in more detail later, and presented 

reductions in observed versus modeled 

ozone concentrations in the eastern U.S. 

downwind from major NOX sources.11

The results showed significant 

reductions in ozone concentrations (10– 

25 percent) from observed 

measurements (CASTNET and AQS) 12

between 2002 and 2005, linking 

reductions in EGU NOX emissions from 

upwind states with ozone reductions 

downwind of the major source areas.13

Additionally, Ge ́go et al. showed that 

ground-level ozone concentrations were 

significantly reduced after 

implementation of the NOX SIP Call.14

Thus, these studies support the EPA’s 

continued focus on regional and 

seasonal NOx control strategies to 

address regional interstate ozone 

pollution transport. 

B. The EPA’s Statutory Authority for 

This Final Action 

The statutory authority for this final 

action is provided by the CAA as 

amended (42 U.S.C. 7401 et seq.). 

Specifically, sections 110 and 301 of the 

CAA provide the primary statutory 

underpinnings for this action. The most 

relevant portions of section 110 are 

subsections 110(a)(1), 110(a)(2) 

(including 110(a)(2)(D)(i)(I)), and 

110(c)(1). 

Section 110(a)(1) provides that states 

must make SIP submissions ‘‘within 3 

years (or such shorter period as the 

Administrator may prescribe) after the 

promulgation of a national primary 

ambient air quality standard (or any 

revision thereof),’’ and that these SIP 

submissions are to provide for the 

‘‘implementation, maintenance, and 

enforcement’’ of such NAAQS.15 The 

statute directly imposes on states the 

duty to make these SIP submissions, 

and the requirement to make the 

submissions is not conditioned upon 

the EPA taking any action other than 

promulgating a new or revised 

NAAQS.16

The EPA has historically referred to 

SIP submissions made for the purpose 

of satisfying the applicable requirements 

of CAA sections 110(a)(1) and 110(a)(2) 

as ‘‘infrastructure SIP’’ submissions. 

Section 110(a)(1) addresses the timing 

and general requirements for 

infrastructure SIP submissions, and 

section 110(a)(2) provides more details 

concerning the required content of these 

submissions. It includes a list of specific 

elements that ‘‘[e]ach such plan’’ 

submission must address.17 All states, 

regardless of whether the state includes 

areas designated as nonattainment for 

the relevant NAAQS, must have SIPs 

that meet the applicable requirements of 

section 110(a)(2), including provisions 

of section 110(a)(2)(D)(i)(I), described 

later, that are the focus of this action. 

Section 110(c)(1) requires the 

Administrator to promulgate a FIP at 

any time within two years after the 

Administrator: (1) Finds that a state has 

failed to make a required SIP 

submission; (2) finds a SIP submission 

to be incomplete pursuant to CAA 

section 110(k)(1)(C); or (3) disapproves 

a SIP submission. This obligation 

applies unless the state corrects the 

deficiency through a SIP revision that 

the Administrator approves before the 

FIP is promulgated.18

Section 110(a)(2)(D)(i)(I), also known 

as the ‘‘good neighbor provision,’’ 

provides the primary basis for this 

action. It requires that each state SIP 

include provisions sufficient to 

‘‘prohibit[ ], consistent with the 

provisions of this subchapter, any 

source or other type of emissions 

activity within the State from emitting 

any air pollutant in amounts which 

will—(I) contribute significantly to 

nonattainment in, or interfere with 

maintenance by, any other State with 

respect to any [NAAQS].’’ 19 The EPA 


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20 63 FR 57356 (Oct. 27, 1998). As originally 

promulgated, the NOX SIP Call also addressed good 

neighbor obligations under the 1997 8-hour ozone 

NAAQS, but the EPA subsequently stayed the rule’s 

provisions with respect to that standard. 40 CFR 

51.121(q). 

21 ‘‘Allowance Trading’’ sometimes referred to as 

‘‘cap and trade’’ is an approach to reducing 

pollution that has been used successfully to protect 

human health and the environment. Allowance 

trading programs have two key components: 

Emissions budgets (the sum of which provide a cap 

on emissions), and tradable allowances equal to the 

budgets that authorize allowance holders to emit a 

specific quantity (e.g., one ton) of the pollutant. 

This approach ensures that the environmental goal 

is met while the tradable allowances provide 

flexibility for individual participants to establish 

and follow their own compliance path. Because 

allowances can be bought and sold in an allowance 

market, these programs are often referred to as 

‘‘market-based.’’ 

22 70 FR 25162 (May 12, 2005). 

23 70 FR 21147 (April 25, 2005). 24See n.14 and main text, supra. 25See n.17 and main text, supra. 26 71 FR 25328 (April 28, 2006). 27 76 FR 48208, 48217 (Aug. 8, 2011). 28 76 FR 48208. 29CSAPR was revised by several rulemakings 

after its initial promulgation in order to revise 

certain states’ budgets and to promulgate FIPs for 

five additional states addressing the good neighbor 

obligation for the 1997 ozone NAAQS. 76 FR 80760 

(Dec. 27, 2011); 77 FR 10324 (Feb. 21, 2012); 77 FR 

34830 (June 12, 2012). 

30The EPA has already approved SIPs fully 

replacing the original CSAPR FIPs for Alabama, 81 

FR 59869 (Aug. 31, 2016); Georgia, 82 FR 47930 

(Oct. 13, 2017); South Carolina, 82 FR 47936 (Oct. 

13, 2017); and Indiana (signed Nov. 27, 2018; 

publication in the Federal Register forthcoming). 

31On August 21, 2012, the D.C. Circuit issued a 

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

EPA, 696 F.3d 7 (D.C. Cir. 2012) (EME Homer City 

I), vacating CSAPR. The EPA sought review with 

the D.C. Circuit en banc and the D.C. Circuit 

declined to consider the EPA’s appeal en banc. EME 

Homer City Generation, L.P. v. EPA, No. 11–1302 

(D.C. Cir. January 24, 2013), ECF No. 1417012 

(denying the EPA’s motion for rehearing en banc). 

32On January 23, 2013, the Supreme Court 

granted the EPA’s petition for certiorari. EPA v. 

EME Homer City Generation, L.P., 133 S. Ct. 2857 

(2013) (granting the EPA’s and other parties’ 

petitions for certiorari). 

33 81 FR 74511. 

34 81 FR 74504. 

35One state, Kansas, was made newly subject to 

a CSAPR ozone season NOX requirement by the 

CSAPR Update. All other CSAPR Update states 

were already subject to ozone season NOX

requirements under the original CSAPR. 

often refers to the emission reduction 

requirements under this provision as 

‘‘good neighbor obligations’’ and 

submissions addressing these 

requirements as ‘‘good neighbor SIPs.’’ 

The EPA has previously issued four 

rules interpreting and clarifying the 

requirements of section 110(a)(2)(D)(i)(I) 

for states in the eastern United States. 

These rules, and the associated court 

decisions addressing these rules, 

summarized here, provide important 

direction regarding the requirements of 

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

The NOX SIP Call, promulgated in 

1998, addressed the good neighbor 

provision for the 1979 1-hour ozone 

NAAQS.20 The rule required 22 states 

and the District of Columbia to amend 

their SIPs to reduce NOX emissions that 

contribute to ozone nonattainment in 

downwind states. The EPA set ozone 

season NOX budgets for each state, and 

the states were given the option to 

participate in a regional allowance 

trading program, known as the NOX

Budget Trading Program (NBP), to 

achieve all or most of the required 

emission reductions.21 The United 

States Court of Appeals for the District 

of Columbia Circuit (D.C. Circuit) 

largely upheld the NOX SIP Call in 

Michigan v. EPA, 213 F.3d 663 (D.C. cir. 

2000), cert. denied, 532 U.S. 904 (2001). 

The EPA’s next rule addressing the 

good neighbor provision, the Clean Air 

Interstate Rule (CAIR), was promulgated 

in 2005 and addressed both the 1997 

fine particulate matter (PM2.5) NAAQS 

and 1997 ozone NAAQS.22 CAIR 

required SIP revisions in 28 states and 

the District of Columbia to reduce 

emissions of sulfur dioxide (SO2) and/ 

or NOX—important precursors of 

regionally transported PM2.5 (SO2 and 

annual NOX) and ozone (summer-time 

NOX). As in the NOX SIP Call, states 

were given the option to participate in 

regional allowance trading programs to 

achieve the reductions. When the EPA 

promulgated the final CAIR in 2005, the 

EPA also issued findings that states 

nationwide had failed to submit SIPs to 

address the requirements of CAA 

section 110(a)(2)(D)(i) with respect to 

the 1997 PM2.5 and 1997 ozone 

NAAQS.23 The states were required by 

the CAA to have submitted good 

neighbor SIPs for those standards by 

July 2000 (i.e., three years after the 

standards were finalized).24 These 

findings of failure to submit triggered a 

two-year clock for the EPA to issue FIPs 

to address interstate transport,25 and on 

March 15, 2006, the EPA promulgated 

FIPs to implement the emission 

reductions required by CAIR.26 CAIR 

was remanded to the EPA by the D.C. 

Circuit in North Carolina v. EPA, 531 

F.3d 896 (D.C. Cir. 2008), modified on 

reh’g, 550 F.3d 1176. For more 

information on the legal issues 

underlying CAIR and the D.C. Circuit’s 

holding in North Carolina, refer to the 

preamble of the original CSAPR.27

In 2011, the EPA promulgated the 

original CSAPR to address the issues 

raised by the remand of CAIR. CSAPR 

addressed the two NAAQS at issue in 

CAIR and additionally addressed the 

good neighbor provision for the 2006 

PM2.5 NAAQS.28 CSAPR, as revised, 

required 28 states to reduce SO2

emissions, annual NOX emissions, and/ 

or ozone season NOX emissions that 

significantly contribute to other states’ 

nonattainment or interfere with other 

states’ abilities to maintain these air 

quality standards.29 To align 

implementation with the applicable 

attainment deadlines, the EPA 

promulgated FIPs for each of the 28 

states covered by CSAPR. The FIPs 

implement regional allowance trading 

programs to achieve the necessary 

emission reductions. Each state can 

submit a good neighbor SIP at any time 

that, if approved by the EPA, would 

replace the CSAPR FIP for that state.30

CSAPR was the subject of an adverse 

decision by the D.C. Circuit in August 

2012.31 However, this decision was 

reversed in April 2014 by the Supreme 

Court,32 which largely upheld the rule, 

including EPA’s approach to addressing 

interstate transport in CSAPR. The rule 

was remanded to the D.C. Circuit to 

consider other claims not addressed by 

the Supreme Court. EPA v. EME Homer 

City Generation, L.P., 134 S. Ct. 1584 

(2014) (EME Homer City). In July 2015 

the D.C. Circuit affirmed the EPA’s 

interpretation of various statutory 

provisions and the EPA’s technical 

decisions. EME Homer City Generation, 

L.P. v. EPA, 795 F.3d 118 (2015) (EME 

Homer City II). However, the court also 

remanded the rule without vacatur for 

reconsideration of the EPA’s emissions 

budgets for certain states, which the 

court found may over-control those 

states’ emissions with respect to the 

downwind air quality problems to 

which the states were linked. Id. at 129– 

30, 138. For more information on the 

legal considerations of CSAPR and the 

court’s decisions in the EME Homer City 

litigation, refer to the preamble of the 

CSAPR Update.33

In 2016, the EPA promulgated the 

CSAPR Update to address interstate 

transport of ozone pollution with 

respect to the 2008 ozone NAAQS.34

The final rule generally updated the 

CSAPR ozone season NOX emissions 

budgets for 22 states to achieve costeffective and immediately feasible NOX

emission reductions from EGUs within 

those states.35 To align implementation 

with relevant attainment dates, the 

CSAPR Update implemented these 

budgets through FIPs requiring sources 

to participate in a revised CSAPR ozone 

season NOX allowance trading program 

beginning with the 2017 ozone season. 

As discussed in more detail later in this 

preamble, the 2017 deadline was 

intended to ensure that the emission 

reductions from the rule would be made 

prior to the July 20, 2018 moderate 

attainment deadline. As under the 


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36EPA has already approved SIPs fully replacing 

the CSAPR Update FIPs for Alabama, 82 FR 46674 

(Oct. 6, 2017), and Indiana (signed Nov. 27, 2018; 

publication in the Federal Register forthcoming). 37 42 U.S.C. 7601(a)(1). 

38These events are described in detail in section 

IV.A.2 of the CSAPR Update. 81 FR 74515. 

39This section of the preamble focuses on SIP and 

FIP actions for those states addressed in the CSAPR 

Update. The EPA has also acted on SIPs for other 

states not mentioned in this action. The 

memorandum, ‘‘Final Action, Status of 

110(a)(2)(D)(i)(I) SIPs for the 2008 Ozone NAAQS,’’ 

more fully describes the good neighbor SIP status 

for the 2008 ozone NAAQS and is available in the 

docket for this action. 

40The nine states were Florida, Georgia, Maine, 

Massachusetts, Minnesota, New Hampshire, North 

Carolina, South Carolina, and Vermont. 

41The two remaining states addressed in the 

findings of failure to submit (California and New 

Mexico) were not part of the CSAPR Update 

analysis and are not addressed in this action. 

42See the following actions: Indiana (81 FR 

38957, June 15, 2016); Kentucky (78 FR 14681, 

March 7, 2013); Louisiana (81 FR 53308, August 12, 

2016); New York (81 FR 58849, August 26, 2016); 

Ohio (81 FR 38957, June 15, 2016); Texas (81 FR 

53284, August 12, 2016); and Wisconsin (81 FR 

53309, August 12, 2016). 

original CSAPR, each state can submit a 

good neighbor SIP at any time that, if 

approved by the EPA, would replace the 

CSAPR Update FIP for that state.36 The 

final CSAPR Update also addressed the 

remand by the D.C. Circuit of certain 

states’ original CSAPR phase 2 ozone 

season NOX emissions budgets in EME 

Homer City II. The CSAPR Update is 

subject to pending legal challenges in 

the D.C. Circuit. Wisconsin v. EPA, No. 

16–1406 (D.C. Cir. argued Oct. 3, 2018). 

Further information about the CSAPR 

Update can be found in section II.D of 

this notice. 

Section 301(a)(1) of the CAA also 

gives the Administrator the general 

authority to prescribe such regulations 

as are necessary to carry out functions 

under the Act.37 Pursuant to this 

section, the EPA has authority to clarify 

the applicability of CAA requirements. 

In this action, among other things, the 

EPA is clarifying the applicability of 

section 110(a)(2)(D)(i)(I) with respect to 

the 2008 ozone NAAQS. In particular, 

the EPA is using its authority under 

sections 110 and 301 to make a 

determination that no further 

enforceable reductions in emissions of 

NOX are required under this provision 

with respect to the 2008 ozone NAAQS 

for the states covered by this rule. The 

EPA is making minor revisions to the 

existing state-specific sections of the 

CSAPR Update regulations for all states 

covered by this action. 

C. Good Neighbor Obligations for the 

2008 Ozone NAAQS 

On March 12, 2008, the EPA 

promulgated a revision to the NAAQS, 

lowering both the primary and 

secondary standards to 75 ppb. See 

National Ambient Air Quality Standards 

for Ozone, Final Rule, 73 FR 16436 

(March 27, 2008). Specifically, the 

standards require that an area may not 

exceed 0.075 ppm (75 ppb) using the 3- 

year average of the fourth highest 24- 

hour maximum 8-hour rolling average 

ozone concentration. These revisions of 

the NAAQS, in turn, triggered a 3-year 

deadline for states to submit SIP 

revisions addressing infrastructure 

requirements under CAA sections 

110(a)(1) and 110(a)(2), including the 

good neighbor provision. Several events 

affected the timely application of the 

good neighbor provision for the 2008 

ozone NAAQS, including 

reconsideration of the 2008 ozone 

NAAQS and legal developments 

pertaining to the EPA’s original CSAPR, 

which created uncertainty surrounding 

the EPA’s statutory interpretation and 

implementation of the good neighbor 

provision.38 Notwithstanding these 

events, the EPA ultimately affirmed that 

states’ good neighbor SIPs were due on 

March 12, 2011. 

The EPA subsequently took several 

actions that triggered the EPA’s 

obligation under CAA section 110(c) to 

promulgate FIPs addressing the good 

neighbor provision for several states.39

First, on July 13, 2015, the EPA 

published a rule finding that 24 states 

failed to make complete submissions 

that address the requirements of section 

110(a)(2)(D)(i)(I) related to the interstate 

transport of pollution as to the 2008 

ozone NAAQS. See 80 FR 39961 

(effective August 12, 2015). This finding 

triggered a two-year deadline for the 

EPA to issue FIPs to address the good 

neighbor provision for these states by 

August 12, 2017. The CSAPR Update 

finalized FIPs for 13 of these states 

(Alabama, Arkansas, Illinois, Iowa, 

Kansas, Michigan, Mississippi, 

Missouri, Oklahoma, Pennsylvania, 

Tennessee, Virginia, and West Virginia), 

requiring their participation in a NOX

emission trading program. The EPA also 

determined in the CSAPR Update that 

the agency had no further FIP obligation 

as to nine additional states identified in 

the finding of failure to submit because 

these states did not contribute 

significantly to nonattainment in, or 

interfere with maintenance by, any 

other state with respect to the 2008 

ozone NAAQS. 81 FR 74506.40 41 On 

June 15, 2016, and July 20, 2016, the 

EPA published additional rules finding 

that New Jersey and Maryland, 

respectively, also failed to submit 

transport SIPs for the 2008 ozone 

NAAQS. See 81 FR 38963 (June 15, 

2016) (New Jersey, effective July 15, 

2016); 81 FR 47040 (July 20, 2016) 

(Maryland, effective August 19, 2016). 

The finding actions triggered two-year 

deadlines for the EPA to issue FIPs to 

address the good neighbor provision for 

Maryland by August 19, 2018, and for 

New Jersey by July 15, 2018. The 

CSAPR Update also finalized FIPs for 

these two states. 

In addition to these findings, the EPA 

finalized disapproval or partial 

disapproval actions for good neighbor 

SIPs submitted by Indiana, Kentucky, 

Louisiana, New York, Ohio, Texas, and 

Wisconsin.42 These disapprovals 

triggered the EPA’s obligation to 

promulgate FIPs to implement the 

requirements of the good neighbor 

provision for those states within two 

years of the effective date of each 

disapproval. The EPA promulgated 

CSAPR Update FIPs for each of these 

states. 

As discussed in more detail in the 

next section, in issuing the CSAPR 

Update, the EPA did not determine that 

it had entirely addressed the EPA’s 

outstanding CAA obligations to 

implement the good neighbor provision 

with respect to the 2008 ozone NAAQS 

for 21 of 22 states covered by that rule. 

Accordingly, the CSAPR Update did not 

fully satisfy the EPA’s obligation under 

section 110(c) to address the good 

neighbor provision requirements for 

those states by approving SIPs, issuing 

FIPs, or some combination of those two 

actions. The EPA found that the CSAPR 

Update FIP fully addressed the good 

neighbor provision for the 2008 ozone 

NAAQS only with respect to Tennessee. 

The EPA notes that it has separately 

finalized an action to fully address 

Kentucky’s good neighbor obligation for 

the 2008 ozone NAAQS. On May 23, 

2017, the U.S. District Court for the 

Northern District of California issued an 

order requiring the EPA to take a final 

action fully addressing the good 

neighbor obligation for the 2008 ozone 

NAAQS for Kentucky by June 30, 2018. 

See Order, Sierra Club v. Pruitt, No. 

3:15–cv–04328 (N.D. Cal.), ECF No. 73. 

On May 10, 2018, Kentucky submitted 

a final SIP to EPA, which the agency 

finalized approval of consistent with the 

court-ordered deadline. 83 FR 33730 

(July 17, 2018). 

Subsequent to the promulgation of the 

CSAPR Update, the EPA approved SIPs 

fully replacing the CSAPR Update FIPs 

for Alabama, 82 FR 46674 (October 6, 

2017), and Indiana (signed November 

27, 2018; publication in the Federal 

Register forthcoming). In those SIP 

approvals and consistent with the 

conclusions of the CSAPR Update, the 

EPA found that the SIPs partially satisfy 


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43The FIP deadline is two years from the effective 

date of the SIP disapproval or Finding of Failure to 

Submit, which generally trails the publication date 

by 30 days. 

44Order, New York v. Pruitt, No. 1:18–cv–00406– 

JGK (S.D.N.Y. June 12, 2018), ECF No. 34. The five 

states are Illinois, Michigan, Pennsylvania, Virginia, 

and West Virginia. 

45Alabama, Arkansas, Illinois, Indiana, Iowa, 

Kansas, Kentucky, Louisiana, Maryland, Michigan, 

Mississippi, Missouri, New Jersey, New York, Ohio, 

Oklahoma, Pennsylvania, Tennessee, Texas, 

Virginia, West Virginia, and Wisconsin. 

Alabama’s and Indiana’s good neighbor 

obligations for the 2008 ozone NAAQS. 

Thus, the EPA continues to have an 

obligation to fully address the good 

neighbor provision requirements for the 

2008 NAAQS with respect to Alabama, 

stemming from the July 13, 2015 

findings notice, and Indiana, due to the 

June 15, 2016 disapproval of the state’s 

good neighbor SIP. Other states have 

also submitted SIPs, some of which the 

EPA has approved and some of which 

still remain pending. However, these 

states are not the subject of this 

rulemaking and these actions are 

therefore not described in detail in this 

section. 

Table II.C–1 summarizes the statutory 

deadline for the EPA to address its FIP 

obligation under CAA section 110(c) 

and the event that activated the EPA’s 

obligation for each of the 20 CSAPR 

Update states that are the subject of this 

final action. For more information 

regarding the actions triggering the 

EPA’s FIP obligation and the EPA’s 

action on SIPs addressing the good 

neighbor provision for the 2008 ozone 

NAAQS, see the memorandum, ‘‘Final 

Action, Status of 110(a)(2)(D)(i)(I) SIPs 

for the 2008 Ozone NAAQS,’’ in the 

docket for this action. 

TABLE II.C–1—ACTIONS THAT ACTIVATED EPA’S STATUTORY FIP DEADLINES

State Type of action 

(Federal Register citation, publication date) 

Statutory FIP 

deadline 43

Alabama .................................. Finding of Failure to Submit (80 FR 39961, 7/13/2015) .......................................................... 8/12/2017 

Arkansas ................................. Finding of Failure to Submit (80 FR 39961, 7/13/2015) .......................................................... 8/12/2017 

Illinois ...................................... Finding of Failure to Submit (80 FR 39961, 7/13/2015) .......................................................... 8/12/2017 

Indiana .................................... SIP disapproval (81 FR 38957, 6/15/2016) ............................................................................. 7/15/2018 

Iowa ........................................ Finding of Failure to Submit (80 FR 39961, 7/13/2015) .......................................................... 8/12/2017 

Kansas .................................... Finding of Failure to Submit (80 FR 39961, 7/13/2015) .......................................................... 8/12/2017 

Louisiana ................................. SIP disapproval (81 FR 53308, 8/12/2016) ............................................................................. 9/12/2018 

Maryland ................................. Finding of Failure to Submit (81 FR 47040, 7/20/2016) .......................................................... 8/19/2018 

Michigan .................................. Finding of Failure to Submit (80 FR 39961, 7/13/2015) .......................................................... 8/12/2017 

Mississippi ............................... Finding of Failure to Submit (80 FR 39961, 7/13/2015) .......................................................... 8/12/2017 

Missouri ................................... Finding of Failure to Submit (80 FR 39961, 7/13/2015) .......................................................... 8/12/2017 

New Jersey ............................. Finding of Failure to Submit (81 FR 38963, 6/15/2016) .......................................................... 7/15/2018 

New York ................................ SIP disapproval (81 FR 58849, 8/26/2016) ............................................................................. 9/26/2018 

Ohio ........................................ SIP disapproval (81 FR 38957, 6/15/2016) ............................................................................. 7/15/2018 

Oklahoma ................................ Finding of Failure to Submit (80 FR 39961, 7/13/2015) .......................................................... 8/12/2017 

Pennsylvania ........................... Finding of Failure to Submit (80 FR 39961, 7/13/2015) .......................................................... 8/12/2017 

Texas ...................................... SIP disapproval (81 FR 53284, 8/12/2016) ............................................................................. 9/12/2018 

Virginia .................................... Finding of Failure to Submit (80 FR 39961, 7/13/2015) .......................................................... 8/12/2017 

West Virginia ........................... Finding of Failure to Submit (80 FR 39961, 7/13/2015) .......................................................... 8/12/2017 

Wisconsin ................................ Partial SIP disapproval as to prong 2 (81 FR 53309, 8/12/2016) ........................................... 9/12/2018 

An August 12, 2017 statutory 

deadline has passed for the EPA to act 

with respect to good neighbor 

obligations under the 2008 ozone 

NAAQS for 12 CSAPR Update states. 

The EPA is subject to a court-ordered 

deadline to promulgate a final action 

fully addressing the good neighbor 

obligations under the 2008 ozone 

NAAQS for five of these states by no 

later than December 6, 2018.44 The 

statutory deadlines for the EPA to act 

with respect to good neighbor 

obligations under the 2008 ozone 

NAAQS for eight other CSAPR Update 

states passed between July 15, 2018, and 

September 26, 2018. 

D. Summary of the CSAPR Update 

On October 16, 2016, the EPA 

finalized the CSAPR Update. The 

purpose of the CSAPR Update was to 

protect public health and welfare by 

reducing interstate pollution transport 

that will significantly contribute to 

nonattainment, or interfere with 

maintenance, of the 2008 ozone NAAQS 

in the eastern U.S. As discussed in 

section II.C, the EPA finalized a FIP for 

each of the 22 states subject to the 

rule,45 either having previously found 

that those states failed to submit a 

complete good neighbor SIP (15 states) 

or having issued a final rule 

disapproving their good neighbor SIP 

submittals (seven states). For the 22 

states covered by the CSAPR Update, 

the EPA promulgated EGU ozone season 

NOX emissions budgets, implemented 

through a regional allowance trading 

program, to reduce interstate ozone 

transport for the 2008 ozone NAAQS 

during the ozone season (May– 

September), beginning with the 2017 

ozone season. 

To establish and implement the 

CSAPR Update emissions budgets, the 

EPA followed a four-step analytic 

process that has been used in each of 

the agency’s regional interstate transport 

rulemakings. The four-step interstate 

transport framework is described in 

more detail in section III.A. To 

summarize, in step 1, the agency 

identified downwind locations, referred 

to as receptors, that were expected to 

have problems attaining or maintaining 

the NAAQS. In step 2, the EPA 

examined, using a contribution 

threshold of one percent of the NAAQS, 

which upwind states contributed to the 

nonattainment or maintenance receptors 

identified in step 1. In step 3, the EPA 

quantified the upwind emissions that 

significantly contributed to 

nonattainment or interfered with 

maintenance and established emission 

budgets that reflected removal of those 

emissions. Finally, in step 4, the agency 

provided for implementation of the 

budgets through an allowance trading 

program. 

The EPA aligned its analysis of air 

quality and upwind state contributions 

in steps 1 and 2, as well as 

implementation of the trading program 

in step 4 with relevant attainment dates 

for the 2008 ozone NAAQS. The EPA’s 

final 2008 Ozone NAAQS SIP 

Requirements Rule established the 

attainment deadline of July 20, 2018, for 

ozone nonattainment areas classified as 


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46 80 FR 12264, 12268 (Mar. 6, 2015); 40 CFR 

51.1103. Ozone nonattainment areas are classified 

as either Marginal, Moderate, Serious, Severe, or 

Extreme, based on the severity of the air quality 

problem in the area. Areas with more acute air 

quality problems are required to implement more 

stringent control requirements and are provided 

additional time to attain the NAAQS. See CAA 

sections 181 and 182, 42 U.S.C. 7511, 7511a. 

47The ozone season NOX allowance trading 

program created under the original CSAPR was 

renamed the CSAPR NOX Ozone Season Group 1 

Trading Program and now applies only to sources 

in Georgia. In the CSAPR Update, the EPA found 

that Georgia did not contribute to interstate 

transport with respect to the 2008 ozone NAAQS, 

but the state has an ongoing ozone season NOX

requirement under the original CSAPR with respect 

to the 1997 ozone NAAQS. 

48Projected AQAT design values for the $1400/ 

ton policy case are available in Tables D–6 and D– 

7 of the CSAPR Update ‘‘Ozone Transport Policy 

Analysis Final Rule TSD’’ (August 2016), Docket ID 

No. EPA–HQ–OAR–2015–0500–0555. 

Moderate.46 Because the attainment date 

fell during the 2018 ozone season, the 

2017 ozone season was the last full 

season from which data could be used 

to determine attainment of the NAAQS 

by that date. Therefore, consistent with 

the court’s instruction in North Carolina 

to harmonize implementation of 

emission reductions under the good 

neighbor provision with downwind 

attainment dates, 531 F.3d at 912, the 

EPA established and implemented 

emissions budgets starting with the 

2017 ozone season. 81 FR 74507. The 

establishment of 2017 as the CSAPR 

Update’s analytic year and compliance 

timeframe was further supported by an 

assessment that certain control 

strategies to mitigate ozone pollution 

transport were feasible in that 

timeframe. 

As to step 3, in particular, the EPA 

quantified emissions from upwind 

states that would significantly 

contribute to nonattainment or interfere 

with maintenance by first evaluating 

various levels of uniform NOX control 

stringency, each represented by an 

estimated marginal cost per ton of NOX

reduced. The EPA then applied a multifactor test to evaluate cost, available 

emission reductions, and downwind air 

quality impacts to determine the 

appropriate level of uniform NOX

control stringency that addressed the 

impacts of interstate transport on 

downwind nonattainment or 

maintenance receptors. The EPA used 

this multi-factor assessment to gauge the 

extent to which emission reductions 

should be implemented in the future 

compliance year (i.e., 2017) and to 

evaluate the potential for over- and 

under-control of upwind state 

emissions. 

Within the multi-factor test, the EPA 

identified a ‘‘knee in the curve,’’ i.e., a 

point at which the cost-effectiveness of 

the emission reductions was 

maximized, so named for the 

discernable turning point observable in 

a multi-factor (i.e., multi-variable) 

curve. See 81 FR 74550. The EPA 

concluded that this was at the point 

where emissions budgets reflected a 

uniform NOX control stringency 

represented by an estimated marginal 

cost of $1,400 per ton of NOX reduced. 

In light of this multi-factor test, EPA 

determined this level of stringency in 

emissions budgets represented the level 

at which incremental EGU NOX

reduction potential and corresponding 

downwind ozone air quality 

improvements were maximized— 

relative to other control stringencies 

evaluated—with respect to marginal 

cost. That is, the ratio of emission 

reductions to marginal cost and the ratio 

of ozone improvements to marginal cost 

were maximized relative to the other 

levels of control stringency evaluated. 

The EPA found that feasible and costeffective EGU NOX reductions were 

available to make meaningful and 

timely improvements in downwind 

ozone air quality to address interstate 

ozone transport for the 2008 ozone 

NAAQS for the 2017 ozone season. 81 

FR 74508. Further, the agency’s 

evaluation showed that emissions 

budgets reflecting the $1,400 per ton 

cost threshold did not over-control 

upwind states’ emissions relative to 

either the downwind air quality 

problems to which they were linked or 

the one percent contribution threshold 

in step 2 that triggered their further 

evaluation in step 3. Id. at 74551–52. As 

a result, the EPA finalized EGU ozone 

season NOX emissions budgets 

developed using uniform control 

stringency represented by $1,400 per 

ton. These budgets represented 

emissions remaining in each state after 

elimination of the amounts of emissions 

that the EPA identified would 

significantly contribute to 

nonattainment or interfere with 

maintenance of the 2008 ozone NAAQS 

in downwind states. 

To implement the CSAPR Update’s 

emission budgets, the EPA promulgated 

FIPs requiring power plants in covered 

states to participate in the CSAPR NOX

Ozone Season Group 2 allowance 

trading program starting in 2017.47

CSAPR’s trading programs and the 

EPA’s prior emissions trading programs 

(e.g., CAIR and the NOX Budget Trading 

Program) have provided a proven 

implementation framework for 

achieving emission reductions. In 

addition to providing environmental 

certainty (i.e., a cap on emissions), these 

programs also provide regulated sources 

with flexibility in choosing compliance 

strategies. By using the CSAPR 

allowance trading programs, the EPA 

applied an implementation framework 

that was shaped by notice and comment 

in previous rulemakings and reflected 

the evolution of these programs in 

response to court decisions and 

practical experience gained by states, 

industry, and the EPA. 

Based on information available at the 

time of its promulgation, the EPA was 

unable to conclude that the CSAPR 

Update fully addressed most of the 

covered states’ good neighbor 

obligations for the 2008 ozone NAAQS. 

81 FR 74521. Information available at 

the time indicated that, even with 

CSAPR Update implementation, several 

downwind receptors were expected to 

continue having problems attaining and 

maintaining this NAAQS and that 

emissions from upwind states were 

expected to continue to contribute 

greater than or equal to one percent of 

the NAAQS to these areas during the 

2017 ozone season. Id. at 74551–52. 

Further, the EPA could not conclude at 

that time whether additional EGU and 

non-EGU reductions implemented on a 

longer timeframe than 2017 would be 

necessary, feasible, and cost-effective to 

address states’ good neighbor 

obligations for this NAAQS. 

As noted, the EPA premised its 

conclusion that the CSAPR Update may 

not fully address states’ good neighbor 

obligations in part on the agency’s 

assessment that air quality problems 

would persist at downwind receptors in 

2017 even with CSAPR Update 

implementation. The EPA’s assessment 

of CSAPR Update implementation using 

the Air Quality Assessment Tool 

(AQAT) indicated that certain eastern 

air quality monitors would continue to 

have problems attaining and 

maintaining the 2008 ozone NAAQS in 

2017. 81 FR 74550–52. Specifically, 

projected nonattainment receptors 

remained in Connecticut, Texas, and 

Wisconsin, while projected 

maintenance-only receptors remained in 

Connecticut, Maryland, Michigan, New 

York, and Texas.48 See Table II.D–1 for 

a list of remaining nonattainment 

receptors and Table II.D–2 for a list of 

remaining maintenance-only receptors. 

(The EPA’s approach to defining 

nonattainment and maintenance-only 

receptors is explained in section III.C.1 

below.) 


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49See EPA’s Air Quality Assessment Tool from 

the CSAPR Update in the docket for this action. 50 83 FR 33730 (July 17, 2018). 

TABLE II.D–1—REMAINING 2017 PROJECTED NONATTAINMENT RECEPTORS IN THE EASTERN U.S. 

Monitor ID State County 

090019003 Connecticut ......... Fairfield. 

090099002 Connecticut ......... New Haven. 

480391004 Texas .................. Brazoria. 

484392003 Texas .................. Tarrant. 

484393009 Texas .................. Tarrant. 

551170006 Wisconsin ............ Sheboygan. 

TABLE II.D–2—REMAINING 2017 PROJECTED MAINTENANCE-ONLY RECEPTORS IN THE EASTERN U.S. 

Monitor ID State County 

090010017 Connecticut ......... Fairfield. 

090013007 Connecticut ......... Fairfield. 

240251001 Maryland ............. Harford 

260050003 Michigan .............. Allegan. 

360850067 New York ............ Richmond. 

361030002 New York ............ Suffolk. 

481210034 Texas .................. Denton. 

482010024 Texas .................. Harris. 

482011034 Texas .................. Harris. 

482011039 Texas .................. Harris. 

The EPA’s analysis also showed that 

21 of the 22 CSAPR Update states would 

continue to contribute equal to or 

greater than one percent of the 2008 

ozone NAAQS to at least one remaining 

nonattainment or maintenance receptor 

in 2017.49 The EPA did not, at that time, 

evaluate whether the projected air 

quality problems would persist and 

whether upwind states would continue 

to contribute to these receptors in years 

beyond 2017. Thus, for those 21 states, 

the EPA could not, based on 

information available in the CSAPR 

Update rulemaking, make an air qualitybased conclusion that the CSAPR 

Update would fully resolve states’ good 

neighbor obligations with respect to the 

2008 ozone NAAQS. (For one state, 

Tennessee, the EPA determined that the 

CSAPR Update fully resolved its good 

neighbor obligation.) 

Further, it was not feasible for the 

EPA to complete an emissions control 

analysis that may otherwise have been 

necessary to evaluate full elimination of 

each state’s significant contribution to 

nonattainment or interference with 

maintenance and also ensure that 

emission reductions already quantified 

in the rule would be achieved by 2017. 

81 FR at 74522. Specifically, the EPA 

was unable to fully consider both nonEGU ozone season NOX reductions and 

further EGU reductions that may have 

been achievable after 2017. Id. at 74521. 

The EPA did not quantify non-EGU 

stationary source emission reductions to 

address interstate ozone transport for 

the 2008 ozone NAAQS in the CSAPR 

Update for two reasons. First, the EPA 

explained that there was greater 

uncertainty in the EPA’s assessment of 

non-EGU NOX mitigation potential, and 

that more time would be required for 

states and the EPA to improve non-EGU 

point source data and pollution control 

assumptions before we could develop 

emission reduction obligations based on 

that data. Id. at 74542. Second, the EPA 

explained that we did not believe that 

significant, certain, and meaningful 

non-EGU NOX reductions were feasible 

for the 2017 ozone season. Id. Many 

commenters on the CSAPR Update 

generally agreed with the EPA that nonEGU emission reductions were not 

readily available for the 2017 ozone 

season, but some advocated that such 

reductions should be included as 

appropriate in future mitigation actions. 

Id. at 74521–22. With respect to EGUs, 

the EPA concluded that additional 

control strategies, such as the 

implementation of new post-combustion 

controls, would take several years to 

implement, which was beyond the 2017 

ozone season targeted in the CSAPR 

Update. Id. at 74541. Thus, the EPA also 

could not make an emission reductionbased conclusion that the CSAPR 

Update would fully resolve states’ good 

neighbor obligations with respect to the 

2008 ozone NAAQS because the 

reductions evaluated and required by 

the CSAPR Update were limited in 

scope (both by technology and sector). 

Specifically, EPA focused the policy 

analysis for the CSAPR Update on 

reductions available by the beginning of 

the 2017 ozone season from EGUs. 

Regardless of these limitations, in 

promulgating the CSAPR Update the 

EPA stated its belief that it was 

beneficial to implement, without further 

delay, EGU NOX reductions that were 

achievable in the near term, particularly 

before the Moderate area attainment 

date of July 20, 2018. Notwithstanding 

that additional reductions may be 

required to fully address the states’ 

interstate transport obligations, the EPA 

concluded that the EGU NOX emission 

reductions implemented by the final 

rule were needed for upwind states to 

eliminate their significant contribution 

to nonattainment or interference with 

maintenance of the 2008 ozone NAAQS 

and to assist downwind states with 

ozone nonattainment areas that were 

required to attain the standard by July 

20, 2018. 

As a result of the remaining air 

quality problems and the limitations on 

the EPA’s analysis, for all but one of the 

22 affected states, the EPA did not 

determine in the CSAPR Update that the 

rule fully addressed those states’ 

downwind air quality impacts under the 

good neighbor provision for the 2008 

ozone NAAQS. Id. at 74521. For one 

state, Tennessee, the EPA determined in 

the final CSAPR Update that 

Tennessee’s emissions budget fully 

eliminated the state’s significant 

contribution to downwind 

nonattainment and interference with 

maintenance of the 2008 ozone NAAQS 

because the downwind air quality 

problems to which the state was linked 

were projected to be resolved with 

implementation of the CSAPR Update. 

Id. at 74552. 

III. Final Determination Regarding 

Good Neighbor Obligations for the 2008 

Ozone NAAQS 

As described in section II.D, in the 

CSAPR Update the EPA promulgated 

FIPs intended to address the good 

neighbor provision for the 2008 ozone 

NAAQS, but could not at that time 

determine, based on information 

available when the rule was finalized, 

that those FIPs would fully address 

2008 ozone NAAQS good neighbor 

obligations for 21 of the 22 CSAPR 

Update states. As a result, the EPA 

could not conclude that the CSAPR 

Update fully satisfied its obligation to 

issue FIPs, nor had the agency otherwise 

approved SIPs at that time, to address 

those states’ good neighbor obligations 

for the 2008 ozone NAAQS. Since the 

CSAPR Update, the EPA has approved 

a SIP revision fully resolving the 

remaining 2008 ozone NAAQS good 

neighbor obligations for Kentucky.50 In 

this notice, the EPA finalizes a 

determination that, based on additional 

information and analysis that has 

subsequently become available, the 

CSAPR Update fully addresses the 

remaining 20 affected states’ good 

neighbor obligations for the 2008 ozone 

NAAQS. 

In particular, the EPA is finalizing a 

determination that 2023 is an 

appropriate future analytic year 

considering relevant attainment dates 

and the time necessary to implement 

further NOX controls. This rationale is 

described within this section, starting 

with Section III.A, which provides the 

EPA’s analytic approach. Section III.B 

discusses the agency’s selection of 2023 

as its future analytic year and Sections 

III.B.2 provides the EPA’s assessment of 

feasibility (e.g., timing) to implement 

further regional NOX control strategies 

for EGUs (Section III.B.2.a) and nonEGUs (Section III.B.2.b). Further, based 

on the EPA’s analysis of projected air 


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51See Finding of Significant Contribution and 

Rulemaking for Certain States in the Ozone 

Transport Assessment Group Region for Purposes of 

Reducing Regional Transport of Ozone (also known 

as the NOX SIP Call), 63 FR 57356 (October 27, 

1998); Clean Air Interstate Rule (CAIR) Final Rule, 

70 FR 25162 (May 12, 2005); CSAPR Final Rule, 76 

FR 48208 (August 8, 2011); CSAPR Update for the 

2008 Ozone NAAQS Final Rule, 81 FR 74504 

(October 26, 2016). 

52With respect to the 2015 ozone NAAQS, which 

is not addressed in this action, the EPA recently 

provided information to states to inform their 

development of SIPs to address CAA section 

110(a)(2)(D)(i)(I). In a memorandum dated March 

27, 2018, the agency noted that, in developing their 

own plans, states have flexibility to follow the 

familiar four-step transport framework (using the 

EPA’s analytical approach or somewhat different 

analytical approaches within these steps) or 

alternative frameworks, so long as their chosen 

approach has adequate technical justification and is 

consistent with the requirements of the CAA. 

53Affected sources have participated in EPAadministered allowance trading programs under 

both SIPs and FIPs. 

quality in that year, the EPA has 

determined that, for the purposes of 

addressing good neighbor obligations for 

the 2008 ozone NAAQS, there will be 

no remaining nonattainment or 

maintenance receptors in the eastern 

U.S. in the future analytic year of 2023. 

The agency’s analysis is described in 

Section III.C. As a result of these 

determinations, the EPA finds that, with 

CSAPR Update implementation, these 

states will no longer contribute 

significantly to nonattainment in, or 

interfere with maintenance by, any 

other state with respect to the 2008 

ozone NAAQS. This rationale is 

described in Section III.D. The agency 

includes a summary of comments and 

the EPA’s response to those comments 

at the conclusion of certain sections and 

subsections therein. The comments 

summarized in these sections and the 

EPA’s responses are further 

supplemented by the EPA’s Response to 

Comment document in the docket for 

this action. 

A. Analytic Approach 

Through the development and 

implementation of several previous 

rulemakings, including most recently 

the CSAPR Update, the EPA, working in 

partnership with states, established the 

following four-step framework to 

address regional interstate transport of 

ozone pollution under the Clean Air 

Act’s good neighbor provision.51 The 

agency is evaluating its determination 

regarding CSAPR Update states’ 

remaining good neighbor obligations for 

the 2008 ozone NAAQS by applying this 

same approach.52 The steps are 

summarized in the following four 

paragraphs. 

Step 1: Identify downwind air quality 

problems relative to the 2008 ozone 

NAAQS. The EPA historically 

(including in the CSAPR Update) 

identified downwind areas with air 

quality problems, or receptors, using air 

quality modeling projections for a future 

analytic year and, where appropriate, 

considering monitored ozone data. In 

the CSAPR Update, the agency relied on 

modeled and monitored data to identify 

receptors expected to be in 

nonattainment with the ozone NAAQS 

in the future analytic year, and relied on 

modeled data to identify additional 

receptors that may have difficulty 

maintaining the NAAQS in the future 

analytic year, notwithstanding clean 

monitored data or projected attainment. 

Step 2: Determine which upwind 

states contribute to these identified 

downwind air quality problems 

sufficiently to warrant further analysis 

to determine whether their emissions 

violate the good neighbor provision. 

These states are referred to as ‘‘linked’’ 

states. In the CSAPR Update, the EPA 

identified such upwind states as those 

modeled to impact a downwind 

receptor in the future analytic year at or 

above an air quality threshold 

equivalent to one percent of the 2008 

ozone NAAQS. 

Step 3: For states linked to downwind 

air quality problems, identify upwind 

emissions on a statewide basis that will 

significantly contribute to 

nonattainment or interfere with 

maintenance of a standard at a receptor 

in another state. In all of the EPA’s prior 

rulemakings addressing interstate ozone 

pollution transport, the agency 

identified and apportioned emission 

reduction responsibility among multiple 

upwind states linked to downwind air 

quality problems considering multiple 

factors consistently across the region. 

Specifically, the agency considered 

feasible NOX control strategies and used 

cost-based and air quality-based criteria 

to evaluate regionally uniform NOX

control strategies that were then used to 

quantify the amount of a linked upwind 

state’s emissions, if any, that will 

significantly contribute to 

nonattainment or interfere with 

maintenance in another state in the 

future analytic year. The agency then 

established emission budgets reflecting 

remaining emission levels following the 

reduction of emissions that significantly 

contribute to nonattainment or interfere 

with maintenance of the NAAQS 

downwind. 

Step 4: For upwind states that are 

found to have emissions that will 

significantly contribute to 

nonattainment or interfere with 

maintenance of the NAAQS downwind, 

implement the necessary emission 

reductions within the state. In the 

CSAPR Update, the EPA implemented 

the emission budgets for upwind states 

found to have good neighbor obligations 

by requiring EGUs in those states to 

participate in the CSAPR NOX Ozone 

Season Group 2 Trading Program. In 

virtually all respects other than the 

budgets and the starting year, the 

program is identical to allowance 

trading programs used to implement the 

emission reductions quantified in the 

original CSAPR, and it builds on the 

experience of both the EPA and states 

using emission trading programs to 

implement other earlier rules.53

Because this framework provides a 

reasonable and logical structuring of the 

key elements that should be considered 

in addressing the requirements of the 

good neighbor provision and because 

this action is evaluating outstanding 

obligations that remain following the 

EPA’s application of this framework 

with respect to the 2008 ozone NAAQS 

in the CSAPR Update, the agency 

believes it is reasonable to apply the 

same framework in this final action. 

Within this four-step interstate 

transport framework, the EPA would 

only proceed to higher enumerated (i.e., 

downstream) steps if states meet the 

criteria applied in lower enumerated 

(i.e., upstream) steps. For example, the 

EPA would only proceed to step 4, in 

which sources in upwind states are 

subject to enforceable emissions 

limitations, if downwind air quality 

problems are identified at step 1, an 

upwind state is found to be linked to a 

downwind air quality problem at step 2, 

and sources in the linked upwind state 

are identified at step 3 as having 

emissions that significantly contribute 

to nonattainment or interfere with 

maintenance of the NAAQS considering 

multiple cost, emissions, and air-quality 

factors. For the reasons described in the 

following paragraphs, the EPA believes 

this approach is a reasonable 

interpretation of the good neighbor 

provision. 

The good neighbor provision instructs 

the EPA and states to apply its 

requirements ‘‘consistent with the 

provisions of’’ title I of the CAA. The 

EPA is therefore interpreting the 

requirements of the good neighbor 

provision, and the elements of its fourstep interstate transport framework, to 

apply in a manner consistent with the 

designation and planning requirements 

in title I that apply in downwind states. 

See North Carolina, 531 F.3d at 912 

(holding that the good neighbor 

provision’s reference to title I requires 

consideration of both procedural and 

substantive provisions in title I). The 

EPA notes that this consistency 


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54Policy tools are available to apply to areas 

experiencing exceedances of ozone NAAQS that are 

appreciably impacted by U.S. background ozone. 

The tools available for each affected location will 

depend on the specific nature of U.S. background 

ozone in each area. Some tools would provide relief 

from a nonattainment designation; others would 

only provide relief from some of the CAAprescribed nonattainment area requirements. 

55Areas classified as Marginal nonattainment 

areas are required to submit emission inventories 

and implement a nonattainment new source review 

permitting program, but are not generally required 

to implement controls at existing sources. See CAA 

section 182(a), 42 U.S.C. 7511a(a). 

56Clean Air Act section 184 contains the 

exception to this general rule: States that are part 

of the Ozone Transport Region are required to 

provide SIPs that include specific enforceable 

control measures, similar to those for 

nonattainment areas, that apply to the whole state, 

even for areas designated attainment for the ozone 

NAAQS. See generally 42 U.S.C. 7511c. 

57See Attachment 2 to Area Designations for the 

2008 Ozone National Ambient Air Quality 

Standards. Memorandum from Robert J. Meyers, 

Principal Deputy Assistant Administrator, U.S. EPA 

to Regional Administrators. December 4, 2008. 

Available at https://archive.epa.gov/ 

ozonedesignations/web/pdf/area_designations_for_

the_2008_revised_ozone_naaqs.pdf. 

instruction follows the requirement that 

plans ‘‘contain adequate provisions 

prohibiting’’ certain emissions in the 

good neighbor provision. The following 

paragraphs will therefore explain how 

the EPA’s interpretation of the 

circumstances under which the good 

neighbor provision requires that plans 

‘‘prohibit’’ emissions through 

enforceable measures is consistent with 

the circumstances under which 

downwind states are required to 

implement emissions control measures 

in nonattainment areas. 

For purposes of this analysis, the EPA 

notes specific aspects of the title I 

designations process and attainment 

planning requirements for the ozone 

NAAQS that provide relevant context 

for evaluating the consistency of the 

EPA’s approach to implementing the 

good neighbor provision in upwind 

states. The EPA notes that this 

discussion is not intended to suggest 

that the specific requirements of 

designations and attainment planning 

for downwind states apply to upwind 

states pursuant to the good neighbor 

provision, but rather to explain why the 

EPA’s approach to interpreting the good 

neighbor provision is reasonable in light 

of relevant, analogous provisions found 

elsewhere in title I. Cf. EDF v. EPA, 82 

F.3d 451, 457 (D.C. Cir. 1996) (per 

curiam) (describing the phrase 

‘‘consistent with’’ as ‘‘flexible statutory 

language’’ which does not require 

‘‘exact correspondence . . . but only 

congruity or compatibility,’’ thus 

requiring a court to defer to reasonable 

agency determinations), amended by 92 

F.3d 1209 (D.C. Cir. 1996). In particular, 

these provisions demonstrate that the 

EPA’s approach is consistent with other 

relevant provisions of title I with respect 

to what data is considered in the EPA’s 

analysis and when states are required to 

implement enforceable measures. 

First, areas are initially designated 

attainment or nonattainment for the 

ozone NAAQS based on actual 

measured ozone concentrations. See 

CAA section 107(d), 42 U.S.C. 7407(d) 

(noting that an area shall be designated 

attainment where it ‘‘meets’’ the 

NAAQS and nonattainment where it 

‘‘does not meet’’ the NAAQS (including 

certain ‘‘nearby’’ areas, as explained 

below)). If an area measures a violation 

of the relevant ozone NAAQS, then the 

area is generally designated 

nonattainment, regardless of what 

specific factors have influenced the 

measured ozone concentrations or 

whether such levels are due to 

enforceable emissions limits.54 In such 

cases where the an ozone nonattainment 

area is classified as Moderate or higher, 

the state is then required to develop an 

attainment plan, which generally 

includes the application of various 

enforceable control measures to sources 

of emissions located in the 

nonattainment area, consistent with the 

requirements in Part D of title I of the 

Act.55 See generally CAA section 182, 42 

U.S.C. 7511a. If, however, an area 

measures compliance with the ozone 

NAAQS, the area is designated 

attainment (unless it is included in the 

boundaries of a nearby nonattainment 

area due to its contribution to that area’s 

nonattainment, as discussed below), and 

sources in that area generally are not 

subject to any new enforceable control 

measures under Part D.56

In determining the boundaries of an 

ozone nonattainment area, the CAA 

requires the EPA to consider whether 

‘‘nearby’’ areas ‘‘contribute’’ to ambient 

air quality in the area that does not meet 

the NAAQS. 42 U.S.C. 7407(d). For each 

monitor or group of monitors indicating 

a violation of the ozone NAAQS, the 

EPA assesses information related to 

various factors, including current 

emissions and emissions-related data 

from the areas near the monitor(s), for 

the purpose of establishing the 

appropriate geographic boundaries for 

the designated ozone nonattainment 

areas. A nearby area may be included 

within the boundary of the ozone 

nonattainment area only after assessing 

area-specific information, including an 

assessment of whether current 

emissions from that area contribute to 

the air quality problem identified at the 

violating monitor.57 If such a 

determination is made, sources in the 

nearby area are also subject to the 

applicable Part D control requirements. 

However, if the EPA determines that the 

nearby area does not contribute to the 

measured nonattainment problem, then 

the nearby area is not part of the 

designated nonattainment area and 

sources in that area are not subject to 

such control requirements. 

The EPA’s historical approach to 

addressing the good neighbor provision 

via the four-step interstate transport 

framework, and the approach the EPA 

continues to apply here, is consistent 

with these title I requirements. That is, 

in steps 1 and 2 of the framework, the 

EPA evaluates whether there is a 

downwind air quality problem (either 

nonattainment or maintenance), and 

whether an upwind state impacts the 

downwind area such that it contributes 

to and is therefore ‘‘linked’’ to the 

downwind area. The EPA’s 

determination at step 1 of the good 

neighbor analysis (that it has not 

identified any downwind air quality 

problems to which an upwind state 

could contribute) is analogous to the 

EPA’s determination in the designation 

analysis that an area should be 

designated attainment. Similarly, EPA’s 

determination at step 2 of the good 

neighbor analysis (that, while it has at 

step 1 identified downwind air quality 

problems, an upwind state does not 

sufficiently impact the downwind area 

such that the state contributes to that 

area’s air quality problems and is 

therefore linked to that area) is 

analogous to the EPA’s determination in 

the designation analysis that a nearby 

area does not contribute to a NAAQS 

violation in another area. Under the 

good neighbor provision, the EPA can 

determine at either step 1 or 2, as 

appropriate, that the upwind state will 

not contribute to air quality problems in 

downwind areas and, thus, that the 

upwind state does not significantly 

contribute to nonattainment or interfere 

with maintenance of the NAAQS in 

other states. See, e.g., CSAPR Update, 81 

FR 74506 (determining that emissions 

from 14 states do not significantly 

contribute to nonattainment or interfere 

with maintenance of the 2008 ozone 

NAAQS); CSAPR, 76 FR 48236 (finding 

that states whose impacts on downwind 

receptors are below the air quality 

threshold do not significantly contribute 

to nonattainment or interfere with 

maintenance of the relevant NAAQS). 

Under such circumstances, sources in 

the upwind state are not required to 

implement any control measures under 

the good neighbor provision, which is 

analogous to the fact that under the 

designation and attainment regime, 


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58The EPA notes that the consideration of 

projected actual emissions in the future analytic 

year—as opposed to allowable levels—is also 

consistent with the statute’s instruction that states 

in their SIPs (or the EPA when promulgating a FIP) 

prohibit emissions that ‘‘will’’ impermissibly 

impact downwind air quality. This term is 

reasonably interpreted to mean that the EPA should 

evaluate anticipated emissions (based on what 

sources will emit) rather than potential emissions 

(based on what sources could emit). 

sources located in areas that are 

designated attainment (because the area 

is attaining the NAAQS and not 

contributing to any nearby 

nonattainment areas) generally are not 

required to implement the control 

measures found in Part D of the Act. Cf. 

EME Homer City II, 795 F.3d at 130 

(determining that CSAPR ozone-season 

NOX budgets for 10 states were invalid 

based on determination that modeling 

showed no future air quality problems); 

CSAPR Update, 81 FR 74523–24 

(removing three states from CSAPR 

ozone season NOX program based on 

determination that states are not linked 

to any remaining air quality problems 

for the 1997 ozone NAAQS). 

The EPA acknowledges one 

distinction between the good neighbor 

and designation analyses: The good 

neighbor analysis relies on future-year 

projections of emissions to calculate 

ozone concentrations and upwind state 

contributions, compared to the use of 

current measured data in the 

designation analysis. As described in 

more detail in section III.B, this 

approach is a reasonable interpretation 

of the term ‘‘will’’ in the good neighbor 

provision, see North Carolina, 531 F.3d 

at 913–14, and interpreting language 

specific to that provision does not create 

an impermissible inconsistency with 

other provisions of title I. Moreover, the 

EPA’s approach to conducting futureyear modeling in the good neighbor 

analysis to identify downwind air 

quality problems and linked states is 

consistent with its use of current 

measured data in the designations 

process. The EPA’s future-year air 

quality projections consider a variety of 

factors, including current emissions 

data, anticipated future control 

measures, economic market influences, 

and meteorology. These same factors, 

e.g., current control measures, economic 

market influences, and meteorology, can 

affect the NOX emissions levels and 

consequent measured ozone 

concentrations that inform the 

designations process. Like the factors 

that affect measured ozone 

concentrations used in the designations 

process, not all of the factors 

influencing the EPA’s modeling 

projections are or can be subject to 

enforceable limitations on emissions or 

ozone concentrations. However, the 

EPA believes that consideration of these 

factors contributes to a reasonable 

estimate of anticipated future ozone 

concentrations. See EME Homer City II, 

795 F.3d at 135 (declining to invalidate 

the EPA’s modeling projections ‘‘solely 

because there might be discrepancies 

between those predictions and the real 

world’’); Chemical Manufacturers 

Association v. EPA, 28 F.3d 1259, 1264 

(D.C. Cir. 1994) (‘‘a model is meant to 

simplify reality in order to make it 

tractable’’). Thus, the EPA’s 

consideration of these factors in its 

future-year modeling projections used at 

steps 1 and 2 of the good neighbor 

analysis is reasonable and consistent 

with the use of measured data in the 

designation analysis.58

The EPA notes that there is a further 

distinction between the section 107(d) 

designations provision and the section 

110(a)(2)(D)(i) good neighbor provision 

in that the latter provision uses different 

terms to describe the threshold for 

determining whether emissions in an 

upwind state should be regulated 

(‘‘contribute significantly’’) as compared 

to the standard for evaluating the impact 

of nearby areas in the designations 

process (‘‘contribute’’). Thus, at step 3 of 

the good neighbor analysis the EPA 

evaluates additional factors, including 

cost and air-quality considerations, to 

determine whether emissions from a 

linked upwind state would violate the 

good neighbor provision. Only if the 

EPA at step 3 determines that the 

upwind state’s emissions would violate 

the good neighbor provision will it 

proceed to step 4 to require emissions 

in the upwind state to be controlled so 

as to address the identified violation. 

This approach to steps 3 and 4 is 

analogous to the trigger for the 

application of Part D requirements to 

sources upon designation of an area to 

nonattainment. Thus, the EPA 

reasonably interprets the good neighbor 

provision to not require it or the upwind 

state to proceed to step 4 and implement 

any enforceable measures to ‘‘prohibit’’ 

emissions unless it identifies a violation 

of the provision at step 3. See, e.g., 76 

FR 48262 (finding at step 3 that the 

District of Columbia is not violating the 

good neighbor provision, and therefore 

will not at step 4 be subject to any 

control requirements in CSAPR, because 

no cost-effective emission reduction 

opportunities were identified in the 

District). 

Comment: Several comments received 

on the EPA’s proposal addressed the 

EPA’s approach to identifying 

downwind air quality problems at step 

1 of the framework. These comments 

contend that the agency’s analysis relies 

on projected future emission levels that 

are not based on enforceable 

mechanisms that ensure those emission 

levels will actually occur or remain in 

place in a future year and thus improve 

air quality as modeled. The commenters 

contend that the Act requires that these 

emission levels be enforceable in order 

for modeling relying on such 

assumptions to be used to support any 

determination under the good neighbor 

provision. 

One commenter states that the EPA’s 

approach is contrary to the fundamental 

principle behind the statutory obligation 

that SIPs must ‘‘include enforceable 

emission limitations’’ and ‘‘contain 

adequate provisions prohibiting’’ 

emissions that unlawfully impact other 

states, citing CAA sections 110(a)(2)(A) 

and (D). The commenter contends that 

the EPA subverts the text and meaning 

of section 110(a)(2) by declaring that 

future air quality will attain the NAAQS 

without ensuring that the emission 

levels that informed that prediction are 

enforceable. The commenter further 

contends that enforceability of control 

measures is a consistent requirement 

throughout the CAA, including for 

redesignation to attainment under 

section 107(d)(3)(E)(iii) and for 

attainment SIPs under section 172(c)(6). 

In support of this argument, another 

commenter cites CAA section 

110(a)(2)(A), which indicates that SIPs 

must ‘‘include enforceable emission 

limitations and other control measures, 

means, or techniques . . . as well as 

schedules and timetables for 

compliance.’’ The commenter further 

cites CAA section 110(a)(2)(C), which 

indicates that SIPs must ‘‘include a 

program to provide for the enforcement 

of the measures described in 

subparagraph (A), and regulation of the 

modification and construction of any 

stationary source within the areas 

covered by the plan as necessary to 

assure that national ambient air quality 

standards are achieved, including a 

permit program. . . .’’ 

Response: As explained in this 

section, the EPA does not agree that all 

assumptions in a model that inform 

future-year projections must be subject 

to enforceable commitments before the 

EPA can rely on the modeling for 

purposes of identifying downwind air 

quality problems. 

As discussed earlier, within the fourstep framework, the EPA interprets the 

good neighbor provision to require 

sources in upwind states to implement 

enforceable emission limitations only if: 

(1) Downwind air quality problems are 

identified at step 1, (2) emissions from 

an upwind state are linked to a 


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downwind air quality problem at step 2, 

and (3) sources in the linked upwind 

state are identified at step 3 as having 

emissions that significantly contribute 

to nonattainment and interfere with 

maintenance of the NAAQS, 

considering cost- and air-quality-based 

factors. If all three of these steps are not 

satisfied, then the state is not required 

at step 4 to include provisions in its SIP 

prohibiting any level of reductions 

because the EPA has determined that 

emissions from the state will not 

significantly contribute to 

nonattainment or interfere with 

maintenance of the NAAQS downwind 

and accordingly there are no emissions 

the state is obligated to ‘‘prohibit’’ under 

the good neighbor provision. Thus, the 

EPA does not agree that modeling used 

to evaluate ozone concentrations at step 

1 must only consider enforceable 

emission levels. Rather, as explained in 

detail earlier, the EPA’s approach is 

consistent with other applicable 

provisions of title I regarding the 

designations and planning requirements 

applicable in nonattainment areas. 

The fact that certain statutory 

provisions require imposition of 

enforceable measures does not 

contradict the EPA’s interpretation 

regarding when the good neighbor 

provision requires such measures. In 

fact, the requirement at section 

172(c)(6), which commenters cite, that 

attainment plans for designated 

nonattainment areas include enforceable 

measures to bring the area into 

attainment is consistent with the EPA’s 

interpretation of the good neighbor 

provision, because that requirement 

only applies once an area has been 

designated nonattainment. Similarly, in 

the EPA’s four-step framework, if the 

EPA identifies a downwind air quality 

problem and determines that an upwind 

state significantly contributes to 

nonattainment or interferes with 

maintenance of the NAAQS in that 

downwind area, the EPA would also 

require, at step 4, the imposition of 

enforceable measures to address the 

upwind state’s impact on the downwind 

area. Thus, consistent with the terms of 

the good neighbor provision, the EPA 

requires states to ‘‘prohibit’’ emissions 

upon a determination that such 

emissions are having the requisite 

impact on downwind areas. However, 

the requirement of section 172(c)(6) is 

not a predicate for an attainment 

designation, as would be the case by 

analogy to commenters’ suggestion that 

enforceable limits are a required 

predicate for a determination that 

sources do not violate the good neighbor 

provision. 

The citation to the requirements for 

the redesignation of areas to attainment 

under section 107(d)(3) is inapposite. 

Such requirements only apply in areas 

that have at one point been designated 

nonattainment under section 107(d)(1). 

The commenter has not explained why 

the requirements for redesignation, 

which apply at the end of a process for 

nonattainment areas that is well after 

initial area designations, should be 

considered relevant to interpreting 

initial obligations under the good 

neighbor provision. For the reasons 

described earlier, the EPA believes it is 

more reasonable to liken the process for 

identifying downwind air quality 

problems under the good neighbor 

provision to initial designations, which 

do not turn on evaluations of whether 

or not the measured emission levels 

informing the designation are due to 

enforceable reductions. 

The EPA also does not agree that 

either section 110(a)(2)(A) or section 

110(a)(2)(C) require the state to include 

measures to make the projected 

emission limitations enforceable in 

order to address the good neighbor 

provision. Section 110(a)(2)(A) states 

that a SIP should ‘‘include enforceable 

emission limitations and other control 

measures, means, or techniques . . . as 

may be necessary or appropriate to meet 

the applicable requirements’’ of the 

CAA (emphasis added). As described 

earlier, a finding at step 1 that there is 

no downwind air quality problem 

supports a conclusion that a state 

simply will not contribute significantly 

or interfere with maintenance of the 

NAAQS in another state, and thus that 

the state need not prohibit any 

particular level of emissions under the 

good neighbor provision. Accordingly, 

under section 110(a)(2)(A), no emission 

limitations would be ‘‘necessary or 

appropriate’’ to meet the good neighbor 

provision. Section 110(a)(2)(C) similarly 

indicates that SIPs should provide for 

the enforcement of measures cited to 

support the requirements of section 

110(a)(2)(A), but it does not 

independently require the imposition of 

additional control measures. 

For these reasons, the EPA does not 

agree with the commenters’ conclusion 

that the statute requires the imposition 

of enforceable emission limitations even 

where the agency has determined that 

an upwind state does not significantly 

contribute to nonattainment or interfere 

with maintenance of the NAAQS in a 

downwind state. See section III.C.2 of 

this notice for further discussion 

regarding the EPA’s air quality analysis 

used to support this final determination. 

B. Selection of a Future Analytic Year 

In this action, consistent with its 

practice in previous rulemakings 

addressing ozone transport, the EPA 

focuses its analysis on a future analytic 

year in light of the forward-looking 

nature of the good neighbor obligation 

in section 110(a)(2)(D)(i)(I) and in 

consideration of prior court decisions. 

With respect to the statutory language of 

the good neighbor provision, the statute 

requires that states prohibit emissions 

that ‘‘will’’ significantly contribute to 

nonattainment or interfere with 

maintenance of the NAAQS in any other 

state. The EPA reasonably interprets this 

language as permitting states and the 

EPA in implementing the good neighbor 

provision to prospectively evaluate 

downwind air quality problems and the 

need for further upwind emission 

reductions. In the EPA’s prior regional 

transport rulemakings, the agency 

generally evaluated whether upwind 

states ‘‘will’’ significantly contribute to 

nonattainment or interfere with 

maintenance based on projections of air 

quality in the future year in which any 

emission reductions would be expected 

to go into effect. For the 1998 NOX SIP 

Call, it used an analytic year of 2007, 

and for the 2005 CAIR, it used analytic 

years of 2009 and 2010 for ozone and 

PM2.5, respectively. 63 FR 57450; 70 FR 

25241. The D.C. Circuit affirmed the 

EPA’s interpretation of ‘‘will’’ in CAIR, 

finding the EPA’s consideration of 

future projected air quality (in addition 

to current measured data) to be a 

reasonable interpretation of an 

ambiguous term. North Carolina, 531 

F.3d at 913–14. The EPA applied the 

same approach in finalizing CSAPR in 

2011 and the CSAPR Update in 2016 by 

evaluating air quality in 2012 and 2017, 

respectively. 76 FR 48211; 81 FR 74537. 

Consistent with this approach, a key 

decision that informs the application of 

the interstate transport framework is the 

selection of a future analytic year. 

Several court decisions guide the factors 

that the EPA considers in selecting an 

appropriate future analytic year for this 

action. First, in North Carolina, the D.C. 

Circuit held that the timeframe for 

implementation of emission reductions 

required by the good neighbor provision 

should be selected by considering the 

relevant attainment dates of downwind 

nonattainment areas affected by 

interstate transport of air pollution. 531 

F.3d at 911–12. Moreover, the U.S. 

Supreme Court and the D.C. Circuit 

have both held that the EPA may not 

over-control upwind state emissions 

relative to the downwind air quality 

problems to which the upwind 

emissions contribute. Specifically, the 


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59The Supreme Court also held that the agency 

may not over-control upwind state emissions such 

that the impact from an upwind state to all 

downwind air quality problems is below the 

contribution threshold applied at step 2 that 

‘‘linked’’ the upwind state in the first place, EME 

Homer City, 134 S. Ct. at 1600–01, but CSAPR was 

not found in EME Homer City II to have violated 

the prohibition on this type of over-control. 

60Annual Energy Outlook 2018. Electricity 

Supply, Disposition, Prices, and Emissions. 

Reference Case. Department of Energy, Energy 

Information Administration. Available at https://

www.eia.gov/outlooks/aeo/data/browser/#/?id=8- 

AEO2018&cases=ref2018&sourcekey=0. 

courts found that the agency may not 

require emission reductions (at steps 3 

and 4 of the good neighbor framework) 

from a state that are greater than 

necessary to achieve attainment and 

maintenance of the NAAQS in all of the 

downwind areas to which that state is 

linked. See EME Homer City, 134 S. Ct. 

at 1600–01; EME Homer City II, 795 F.3d 

at 127. In particular, in EME Homer City 

II, the D.C. Circuit determined that the 

CSAPR phase 2 ozone-season NOX

budgets for ten states were invalid 

because the EPA’s modeling showed 

that the downwind air quality problems 

to which these states were linked would 

be resolved by 2014, when the phase 2 

budgets were scheduled to be 

implemented. 795 F.3d at 129–30.59

These court decisions therefore support 

the agency’s choice to use a future 

analytic year in order to help ensure 

that the EPA does not over- or undercontrol upwind state emissions at the 

time that controls will be implemented. 

Generally, NOX emissions levels are 

expected to decline in the future 

through the combination of the 

implementation of existing local, state, 

and federal emission reduction 

programs (e.g., fleet penetration of 

mobile source programs through fleet 

turnover) and changing market 

conditions for electricity generation 

technologies and fuels.60 As a result of 

expected emission reductions and 

resulting lower ozone concentrations in 

the future, the agency is relatively more 

at risk of over-controlling emissions 

were it not to identify an appropriate 

future year in which controls could be 

feasibly implemented to further reduce 

emissions and ozone concentrations. 

Therefore, because further controls 

cannot be implemented feasibly for 

several years, as discussed further 

below, and emissions, upwind 

contributions, and downwind ozone 

concentrations will likely be lower at 

that later point in time due to continued 

phase-in of existing regulatory 

programs, changing market conditions, 

and fleet turnover, it is reasonable for 

the EPA to evaluate air quality (at steps 

1 and 2 of the good neighbor framework) 

in a future analytic year. In other words, 

it is appropriate for the EPA’s 

evaluation of air quality to focus on a 

future analytic year that is aligned with 

feasible timing for installation of 

controls in order to ensure that 

downwind air quality problems exist (at 

step 1) and that upwind states continue 

(at step 2) to be linked to downwind air 

quality problems at a time when any 

cost-effective emission reductions 

(identified at step 3) would be 

implemented (at step 4) and to ensure 

that such reductions do not over-control 

relative to the identified ozone 

problems. Cf. EME Homer City, 134 S. 

Ct. at 1600–01; EME Homer City II, 795 

F.3d at 127. 

Thus, in determining the appropriate 

future analytic year for purposes of 

assessing remaining interstate transport 

obligations for the 2008 ozone NAAQS, 

the EPA considered two primary factors: 

(1) The applicable attainment dates for 

this NAAQS; and (2) the timing to 

feasibly implement new NOX control 

strategies. These factors are discussed in 

the following two sections. The EPA is 

finalizing its proposed determination 

that these factors collectively support 

the identification of 2023 as the future 

analytic year for evaluating whether 

further unfulfilled good neighbor 

obligations for the 2008 ozone NAAQS 

will remain after implementation of the 

CSAPR Update. 

Comment: Several commenters 

challenge the EPA’s interpretation of the 

term ‘‘will’’ in the good neighbor 

provision to permit the identification of 

downwind air quality problems based 

on evaluating air quality in a future 

year. The commenters contend that the 

EPA’s interpretation is inconsistent with 

the Clean Air Act for various reasons. 

One commenter contends that the 

word ‘‘will’’ merely reflects the 

temporal dimension of interstate 

transport of pollutants—i.e., the fact that 

an upwind state ‘‘will’’ significantly 

contribute to nonattainment or interfere 

with maintenance as soon as its ozone 

pollutants are transported in significant 

amounts into a downwind area 

measuring nonattainment or struggling 

to maintain the NAAQS. The 

commenter concedes that the term 

‘‘will’’ also contemplates impacts in 

relevant future compliance years but 

contends it is not limited to the distant 

future. The commenter asserts that 

section 110’s prohibition against 

‘‘emitting’’ pollutants that will 

significantly contribute to downwind 

nonattainment (or interfere with 

downwind maintenance) plainly 

indicates that the phrase ‘‘will 

contribute’’ must be read to include 

both current and future emissions, 

citing North Carolina, 531 F.3d at 914. 

The commenter contends that the EPA’s 

interpretation of ‘‘will’’ to encompass 

future air quality, as affirmed by the 

D.C. Circuit in the CAIR litigation, was 

reasonable only in light of the agency’s 

complementary consideration of present 

measured data. The commenter states 

that the EPA’s proposed interpretation 

would grant the agency unfettered 

discretion, permitting it to find that 

‘‘will’’ refers to any future time that the 

EPA selects, even one only in the 

distant future. The commenter contends 

that the interpretation of ‘‘will’’ to refer 

to a future year when ‘‘any emission 

reductions would be expected to go into 

effect’’ is circular, meaningless, and 

irrational where the EPA finds that no 

further emission reductions are 

required. 

Another commenter states that 

Congress specified that implementation 

plans must prohibit ‘‘any’’ pollution 

from ‘‘any’’ source that will contribute 

significantly to nonattainment and 

interfere with maintenance, and this 

includes pollution that will contibute 

between now and 2023. The commenter 

states that the fact that other pollution 

emitted at some other time allegedly 

will not contribute significantly to 

nonattainment and interfere with 

maintenance does not excuse the EPA’s 

failure to prohibit the pollution that will 

do so between now and 2023. 

A further commenter contends that 

the use of the word ‘‘emitting’’ in 

section 110(a)(2)(D)(i) includes 

protection against current emissions 

from upwind sources that are 

significantly contributing to downwind 

areas’ inability to attain a NAAQS. The 

commenter cites CAA section 126(b), 

which provides that a state ‘‘may 

petition the Administrator for a finding 

that any major source or group of 

stationary sources emits or would emit 

any air pollutant in violation of the 

prohibition of’’ section 110(a)(2)(D)(i) 

(emphasis added). The commenter 

states that this clause confirms that 

current air pollution transport cannot be 

ignored. Similarly, one commenter 

asserts that, when interpreting the term 

‘‘emit’’ in other provisions of the Act, 

the D.C. Circuit has held that it refers to 

actual, present emissions, as opposed to 

mere potential or future emissions, 

citing New York v. EPA, 413 F.3d 3, 39– 

40 (D.C. cir. 2005). 

Response: These commenters are 

incorrect, for five reasons. 

First, the commenters misconstrue 

both the facts and the holding of the 

D.C. Circuit’s decision in North 

Carolina. In that case, the court was 

reviewing a challenge to the EPA’s 

approach to identifying downwind 


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61 In compliance with a separate holding of the 

North Carolina decision, the EPA further evaluates 

receptors in areas currently attaining the standard 

based on projected future air quality in order to 

ensure that the ‘‘interfere with maintenance’’ clause 

of the good neighbor provision is given 

independent effect. See 531 F.3d at 910–11. 

62The text of CAA section 126 as codified in the 

U.S. Code cross-references CAA section 

110(a)(2)(D)(ii) instead of CAA section 

110(a)(2)(D)(i). The courts have confirmed that this 

is a scrivener’s error and the correct cross-reference 

is to CAA section 110(a)(2)(D)(i). See Appalachian 

Power Co. v. EPA, 249 F.3d 1032, 1040–44 (D.C. Cir. 

2001). 

receptors in CAIR wherein the agency 

considered only those areas projected to 

be in nonattainment in a future year to 

be downwind receptors, but not areas 

projected to be in attainment that were 

currently measuring nonattainment. 531 

F.3d at 913. The court explained that 

the EPA had consistently interpreted 

‘‘will’’ in both the NOX SIP Call and 

CAIR to ‘‘indicate sources that presently 

and at some point in the future ‘will’ 

contribute to nonattainment,’’ and noted 

that both rules relied on projections of 

nonattainment in the future year in 

which the rule would go into effect. Id. 

at 914. Thus, contrary to the 

commenters’ assertions, the EPA did not 

identify downwind air quality problems 

in CAIR based on either a current 

measured violation or a projected 

violation of the NAAQS. Rather, in 

CAIR the EPA determined that a 

downwind air quality problem was 

required to be addressed under the good 

neighbor provision only if both the 

current measured data and the projected 

future data demonstrated there would 

be an air quality problem in a 

downwind area. 

The court affirmed the EPA’s 

interpretation, explaining that ‘‘will’’ 

‘‘can mean either certainty or indicate 

the future tense’’ and held that it is 

reasonable for the EPA to give effect to 

both potential meanings of the word. Id. 

Thus, although the court acknowledged 

that the term ‘‘will’’ could refer to the 

certainty of an upwind state’s impact on 

a downwind state (i.e., based on current 

measured nonattainment), as one 

commenter contends it should, the court 

also clearly acknowledged the 

ambiguity of this term and indicated 

this was not the only reasonable 

interpretation. In light of this ambiguity, 

the D.C. Circuit affirmed that the EPA’s 

approach, which gives effect to both 

meanings, is permissible under the Act. 

Here, as explained in more detail later 

in section III.C.3, the EPA is identifying 

downwind nonattainment receptors 

based on both current measured data 

and projected future air quality, just as 

the EPA did in the CSAPR Update, as 

well as CAIR and the NOX SIP Call.61

Second, the EPA also does not agree 

that the term ‘‘emitting’’ precludes its 

interpretation of ‘‘will’’ in the good 

neighbor provision. The relevant clause 

of the CAA section 110(a)(2)(D)(i) 

requires state plans (or federal plans, 

where the agency is acting in the state’s 

stead) to ‘‘contain adequate provisions 

. . . prohibiting . . . any source or other 

type of emissions activity within the 

State from emitting any air pollution in 

amounts which will’’ improperly impact 

downwind areas under the remaining 

terms of the provision (emphasis 

added). Thus, the term ‘‘emitting’’ 

should be read in concert with the 

prohibition required in this clause to 

refer to the limitation that should be 

imposed on sources otherwise found to 

be in violation of section 

110(a)(2)(D)(i)(I); the term ‘‘emitting’’ in 

its statutory context does not clearly 

define the temporal requirements for 

determining whether such a violation 

exists in the first instance. Rather, the 

good neighbor provision indicates that 

sources should be ‘‘prohibit[ed] . . . 

from emitting,’’ which is a forwardlooking phrase intended to address 

limitations on a source’s future activity. 

The introduction of the phrase ‘‘which 

will’’ at the end of the clause further 

serves as a transition from the general 

obligation to impose a prohibition to the 

specific circumstances under which the 

prohibition will apply. 

The commenter’s reference to the 

court’s interpretation of ‘‘emit’’ in New 

York is therefore an inapt citation for 

purposes of interpreting the good 

neighbor provision requirements. In that 

case, the court was evaluating whether 

the use of the term ‘‘emit’’ in certain 

nonattainment new source review 

provisions (a program imposing a 

permitting requirement on the 

construction of new major sources of air 

pollutants and major modifications of 

existing sources) was intended to refer 

to actual or allowable emissions when 

determining whether modifications to 

the source trigger a permitting 

requirement. 413 F.3d 3, 39–40 (D.C. 

Cir. 2005). The court noted that the 

statutory provisions governing new 

source review use different language to 

distinguish between actual emissions 

(‘‘emit’’ or ‘‘emitted’’) and potential 

emissions (‘‘potential to emit’’ or 

‘‘emission limitations’’). Id. In the case 

of the good neighbor provision, the 

phrase ‘‘prohibiting . . . sources . . . 

from emitting’’ certain amounts of 

pollution is more consistent with the 

terminology used to indicate potential 

emissions, and therefore more 

reasonably refers to the emission 

limitation that would be imposed under 

the good neighbor provision if the 

requisite finding of significant 

contribution or interference with 

maintenance is made. Thus, the statute’s 

use of the term ‘‘emit’’ does not clearly 

preclude the EPA’s interpretation of 

‘‘will’’ as permitting the analysis of 

downwind air quality in a future year to 

evaluate interstate transport. The new 

source review preconstruction 

permitting program expressly lays out 

the predicate trigger for the permitting 

requirement (and the D.C. Circuit in 

New York was considering whether 

EPA’s interpretation and application of 

those statutory terms was permissible); 

the good neighbor provision does not 

expressly lay out the methodology 

(including the termporal frame of 

reference) for determining what 

constitutes a good neighbor violation 

(and the D.C. Circuit in North Carolina 

affirmed EPA’s construction of the 

governing statutory provision). 

Third, the commenters err in 

suggesting that the standard for granting 

a section 126(b) petition is incorporated 

into the good neighbor provision. While 

section 126(b) cross-references the 

prohibition in section 110(a)(2)(D)(i),62

the cross-reference is unidirectional. 

There is no indication that Congress 

intended for the ‘‘emits or would emits’’ 

language from section 126(b) to be 

conversely incorporated into section 

110, and section 110(a)(2)(D)(i) does not 

contain any reference to section 126(b). 

In any event, the commenters have not 

offered any explanation regarding how 

any relevant interpretation of section 

126(b) should inform the EPA’s 

interpretation of section 110 with 

respect to current emissions data or 

projections of future air quality. 

Fourth, while the EPA agrees that the 

references to ‘‘any’’ in section 

110(a)(2)(D)(i) means that any source of 

emissions of any air pollutant having 

the requisite impact may be subject to 

control under that provision, the 

commenter does not explain how this 

term imposes an obligation to select a 

specific analytic year when evaluating 

whether such emissions are improperly 

impacting downwind areas and 

therefore whether such control is 

necessary or authorized. Rather, as the 

commenters fail to acknowledge, the 

EPA is only authorized under the good 

neighbor provision to require the 

prohibition of such emissions in 

‘‘amounts which will’’ improperly 

impact another state with respect to the 

NAAQS. The Supreme Court has held 

that this language means that any 

emission reductions imposed under the 

good neighbor provision be no greater 

than necessary to address downwind 


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63As discussed in Section II.D, emission 

reductions that were feasible and cost-effective for 

the 2017 ozone season were the focus of the CSAPR 

Update. 

64While there are no areas (outside of California) 

that are currently designated as Serious or Severe 

for the 2008 ozone NAAQS, the CAA requires that 

the EPA reclassify to Serious any Moderate 

nonattainment areas that fail to attain by their 

attainment date of July 20, 2018. See CAA section 

181(b)(2), 42 U.S.C. 7511(b)(2). Similarly, if any 

area fails to attain by the Serious area attainment 

date, the CAA requires that the EPA reclassify the 

area to Severe. 

nonattainment and maintenance of the 

NAAQS, i.e., that the EPA avoid 

unnecessary ‘‘over-control’’ of emissions 

from upwind states. See EME Homer 

City, 134 S. Ct. at 1608. In interpreting 

that decision, the D.C. Circuit declared 

EPA’s emission reduction requirements 

for certain states to be invalid under the 

good neighbor provision where the EPA 

had information indicating that there 

will be no downwind air quality 

problems by the time the emission 

reductions would have been 

implemented. See EME Homer City II, 

795 F.3d at 130. Thus, the EPA does not 

agree that information indicating a 

current violation necessarily obligates 

the EPA to impose additional emission 

reductions, especially if additional 

information indicates there will be no 

downwind air quality issues to address 

by the time such reductions could be in 

place. On the contrary, the D.C. Circuit 

has already spoken to both the temporal 

flexibilities and the temporal obligations 

imposed by the good neighbor 

provision. The court has both affirmed 

the EPA’s interpretation of ‘‘will’’ as 

permitting consideration of projected 

future air quality and instructed the 

EPA to consider relevant downwind 

attainment dates in establishing future 

compliance timeframes. North Carolina, 

531 F.3d at 910–11, 913. The EPA has 

reasonably aligned these two 

considerations to ensure that emission 

reductions required from ‘‘any source’’ 

within the anticipated compliance 

timeframes are in fact necessary to 

address downwind air quality problems 

at that time, in order to avoid potential 

over-control in contradiction of EME 

Homer City. 

Fifth and finally, the EPA does not 

agree that its interpretation of ‘‘will’’ to 

permit consideration of projected future 

air quality grants the agency unfettered 

discretion to choose any future analytic 

year, however distant, to justify its 

conclusions. While the EPA does 

contend that the statute permits the 

consideration of air quality in a future 

year aligned with anticipated 

compliance, the EPA concedes that it 

must both comply with the holding in 

North Carolina to appropriately 

consider relevant downwind attainment 

dates and provide a reasonable, nonarbitrary justification for selecting an 

appropriate future analytic year. The 

EPA provides such an explanation for 

the selection of the 2023 analytic year 

in the following sections of this notice. 

1. Attainment Dates for the 2008 Ozone 

NAAQS 

As previously noted, in determining 

the appropriate future analytic year for 

purposes of assessing remaining 

interstate transport obligations for the 

2008 ozone NAAQS, the EPA first 

considers the downwind attainment 

dates for the 2008 ozone NAAQS. Many 

areas currently have attainment dates of 

July 20, 2018 for areas classified as 

Moderate. However, as noted earlier, the 

2017 ozone season was the last full 

season from which data could be used 

to determine attainment of the NAAQS 

by that date.63 Given that the 2017 

ozone season has now passed, it is not 

possible to achieve additional emission 

reductions by the Moderate area 

attainment date. It is therefore necessary 

to consider what subsequent attainment 

dates should inform the EPA’s analysis. 

The next attainment dates for the 2008 

ozone NAAQS will be July 20, 2021, for 

nonattainment areas classified as 

Serious, and July 20, 2027, for 

nonattainment areas classified as 

Severe.64 Because the various 

attainment deadlines are in July, which 

is in the middle of the ozone monitoring 

season for all states, data from the 

calendar year prior to the attainment 

date—e.g., data from 2020 for the 2021 

attainment date and from 2026 for the 

2027 attainment date—are the last data 

that can be used to demonstrate 

attainment with the NAAQS by the 

relevant attainment date. Therefore, the 

EPA considers the control strategies that 

could be implemented by 2020 and 

2026 in assessing the 2021 and 2027 

attainment dates in its subsequent 

analysis. The EPA has also considered 

that, in all cases, the statute provides 

that areas should attain as expeditiously 

as practicable. See CAA section 

181(a)(1). 

Comment: One commenter notes that 

all of the states burdened by the 

interstate pollution addressed by the 

proposed action are currently subject to 

attainment deadlines in 2015, 2016, or 

2018, and it is likely that some states 

will be determined to have failed to 

attain and become subject to more 

stringent requirements and a new 

deadline of July 20, 2021. The 

commenter notes that no relevant states 

are subject to a deadline of 2027, nor 

will any be subject to a 2027 deadline 

in the future unless they fail yet again 

to attain by 2021. The commenter 

therefore contends that the EPA’s 

decision to consider the 2027 

attainment deadline is illegal, 

unexplained, and arbitrary. 

Response: The EPA does not agree 

that it may not consider any later 

attainment dates simply because there 

are no states currently subject to that 

deadline. As the commenter concedes, 

there are also currently no areas in the 

east subject to the 2021 Serious area 

attainment date, yet the EPA 

nonetheless believes it is appropriate to 

consider both future attainment dates in 

selecting a future analytic year, 

especially in light of the limitations on 

additional control strategies available in 

the near term, as discussed in more 

detail later. Moreover, the EPA was 

required to select an analytic year before 

the Moderate area attainment date had 

passed in order to provide sufficient 

time to conduct air quality modeling 

before issuing a proposal for the state of 

Kentucky by the court-ordered deadline 

in June 2018. See Order, Sierra Club v. 

Pruitt, No. 3:15-cv-04328 (N.D. Cal. May 

23, 2017), ECF No. 73. Because the 

Kentucky action addressed the same 

problem of regional interstate ozone 

transport for the 2008 ozone NAAQS at 

issue in this action, it was necessary to 

complete the modeling in time for the 

EPA to issue a proposed action for 

Kentucky in advance of that deadline. 

At that time, as the commenter notes, all 

areas were subject to attainment dates in 

2015, 2016, or 2018, and emission 

reductions intended to assist with 

attainment by those dates would need to 

be achieved by the prior year’s ozone 

season. Since all of these dates were 

effectively in the past (including one 

date that fell less than two weeks after 

the date of the proposal of this action), 

the EPA reasonably looked forward to 

the next potential attainment dates for 

purposes of this analysis. 

2. Feasibility of Control Strategies To 

Further Reduce Ozone Season NOX

Emissions 

The EPA’s analysis of the feasibility of 

NOX control strategies reflects the time 

needed to plan for, install, test, and 

place into operation EGU and non-EGU 

NOX reduction strategies regionally— 

i.e., across multiple states. This regional 

analytic approach is consistent with the 

regional nature of interstate ozone 

pollution transport as described in 

section II.A. As proposed, the agency 

adopted this approach for this final 

action based on previous interstate 

ozone transport analyses showing that 

where eastern downwind ozone 

problems are identified, multiple 

upwind states typically are linked to 


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65 81 FR 74538. 66See Assessment of Non-EGU NOX Emission 

Controls, Cost of Controls, and Time for 

Compliance Final TSD from the CSAPR Update 

(U.S. EPA, August 2016) in the docket for this 

action. 

67The CSAPR Update was signed on September 

7, 2016, approximately 8 months before the 

beginning of the 2017 ozone season on May 1. 

68https://ampd.epa.gov/ampd/ (Data current as of 

October 26, 2018). 

69 Id. 

70Preliminary data for the 2018 ozone season (the 

second CSAPR Update compliance period), which 

became available after the proposal for this action 

and after the close of the comment period, continue 

to indicate that CSAPR Update emissions budgets 

are being appropriately implemented under the 

trading program. Power plant ozone season NOX

emissions across the 22 state CSAPR Update region 

fell by 83,084 tons (or 22%) from 2016 to 2018. As 

a result, total 2018 ozone season NOX emissions 

from covered EGUs across the 22 CSAPR Update 

states were approximately 288,825 tons, well below 

the sum of states’ 2018 emissions budgets 

established in the CSAPR Update of 313,626 tons. 

these problems.65 Specifically of 

relevance to this action, as discussed in 

section II.C, the EPA’s prospective air 

quality assessment of CSAPR Update 

implementation found that 21 states 

each continued to contribute greater 

than or equal to one percent of the 2008 

ozone NAAQS (i.e., 0.75 ppb) to 

identified downwind nonattainment or 

maintenance receptors in multiple 

downwind states in 2017. Thus, to 

reasonably address any remaining ozone 

transport problems, the EPA must 

identify and apportion emission 

reduction responsibility across multiple 

upwind states. In other words, given the 

breadth of the ozone transport problem 

identified in the CSAPR Update and the 

breadth of the remaining CAA 

obligations (i.e., for 20 states), it is 

reasonable for the EPA’s analysis to be 

regional. Where such an analysis is 

needed for multiple states, the inquiry 

into the availability and feasibility of 

control options is considerably more 

time-consuming than it would be for a 

single facility or state or sector. 

Further, the feasibility of new 

emissions controls should be considered 

with regard to multiple upwind source 

categories to ensure that the agency 

properly evaluates NOX reduction 

potential and cost-effectiveness from all 

reasonable control measures. NOX

emissions come from multiple 

anthropogenic source categories, such as 

mobile sources, electric utilities, and 

stationary non-EGU sources (e.g., 

resource extraction industries and 

industrial and commercial facilities). 

Among stationary sources, EGUs in the 

eastern U.S. have been the primary 

subject of regulation to address 

interstate ozone pollution transport and 

have made significant financial 

investments to achieve emission 

reductions. While the EPA continues to 

evaluate control feasibility for EGUs in 

its analysis, the EPA’s recent analyses 

indicate that non-EGU source categories, 

which the EPA has not made subject to 

new regulations to address interstate 

ozone transport since the NOX SIP Call, 

may also warrant further assessment of 

their potential to cost-effectively reduce 

NOX relative to EGUs.66 Accordingly, 

the EPA’s assessment of control 

feasibility focuses on both EGU and 

non-EGU sources. 

Although mobile source emissions 

also influence ozone formation, 

transport, and ambient concentrations, 

the EPA has historically addressed 

mobile source emissions through 

national rulemakings. As a result, 

mobile source emissions are already 

decreasing because of sector-specific 

standards related to fuels, vehicle fuel 

economy, pollution controls, and repair 

and replacement of the existing fleet. 

Programs such as the Tier 3 vehicle 

emissions standards are already being 

phased in between now and 2023. That 

rule was finalized in 2014 with a phasein schedule of 2017–2025 reflecting fleet 

turnover. As discussed in more detail 

later, emission reductions from 

stationary sources could likely be 

implemented more quickly than would 

result from any attempt to effect 

additional reductions from mobile 

sources beyond those already being 

implemented. Thus, the EPA has 

focused its analysis of the feasibility of 

implementing additional emission 

controls on stationary sources. 

a. EGUs 

The EPA’s analysis in the CSAPR 

Update is of particular relevance to the 

agency’s assessment of feasible EGU 

NOX mitigation strategies in this action 

because that rule evaluated and 

implemented all EGU strategies that 

were cost-effective and feasible to 

implement quickly. Accordingly, as 

explained in the proposal for this 

action, the EPA reasonably focused its 

current assessment of the feasibility of 

implementing further EGU NOX

mitigation strategies on control 

technologies that require more time to 

implement and that were thus not 

previously evaluated in the CSAPR 

Update with respect to the 2008 ozone 

NAAQS. 

In establishing the CSAPR Update 

EGU ozone season NOX emissions 

budgets, the agency quantified the 

emission reductions achievable from all 

NOX control strategies that were feasible 

to implement in less than one year and 

cost-effective at a marginal cost of 

$1,400 per ton of NOX removed.67 These 

EGU NOX control strategies were: 

Optimizing NOX removal by existing, 

operational selective catalytic reduction 

(SCR) controls; turning on and 

optimizing existing, idled SCR controls; 

installing state-of-the-art NOX

combustion controls; and shifting 

generation to existing units with lower 

NOX emissions rates within the same 

state. 81 FR 74541. The agency observes 

that the resulting CSAPR Update 

emissions budgets are being 

appropriately implemented under the 

CSAPR NOX Ozone Season Group 2 

allowance trading program. Data for the 

2017 ozone season (the first CSAPR 

Update compliance period) indicate that 

power plant ozone season NOX

emissions across the 22 state CSAPR 

Update region fell by 77,512 tons (or 

21%) from 2016 to 2017.68 As a result, 

total 2017 ozone season NOX emissions 

from covered EGUs across the 22 

CSAPR Update states were 

approximately 294,394 tons,69 well 

below the sum of states’ 2017 emissions 

budgets established in the CSAPR 

Update of 316,464 tons.70 Further, the 

EPA is not aware of any relevant, 

significant changes in the EGU fleet 

since promulgation of the CSAPR 

Update that would necessitate 

reevalution of the emission reduction 

potential from control strategies already 

implemented in the CSAPR Update. 

Accordingly, for the purposes of this 

final determination, the EPA considers 

optimizing NOX removal by existing, 

operational SCR controls, turning on 

and optimizing of existing SCR controls, 

and the installation of combustion 

controls to be NOX control strategies 

that have already been appropriately 

evaluated and implemented in the final 

CSAPR Update for purposes of 

addressing the good neighbor provision 

for the 2008 ozone NAAQS. The EPA 

does not believe it would be reasonable 

to base its selection of a future analytic 

year on the timeframe for 

implementation of control strategies that 

the EPA has already evaluated in the 

CSAPR Update and that are already 

being implemented appropriately, 

according to the best data available at 

this time (i.e., recent ozone season NOX

emissions data with CSAPR Update 

implementation). 

In the CSAPR Update, the EPA also 

evaluated one EGU NOX control strategy 

that was considered feasible to 

implement within one year but was not 

cost-effective relative to other near-term 

control strategies at a marginal cost of 

$1,400 per ton of NOX removed: 

Turning on existing idled selective noncatalytic reduction (SNCR) controls. In 

the CSAPR Update, the EPA identified 


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65894 Federal Register / Vol. 83, No. 245 / Friday, December 21, 2018 / Rules and Regulations 

71See EGU NOX Mitigation Strategies Final Rule 

TSD (docket ID EPA–HQ–OAR–2015–0500–0554, 

available at www.regulations.gov and https://

www.epa.gov/sites/production/files/2017–05/ 

documents/egu_nox_mitigation_strategies_final_

rule_tsd.pdf) (NOX Mitigation Strategies TSD). 

72See Electric Monthly Power. Department of 

Energy, Energy Information Administration. Table 

1.1 Net Generation by Energy Sources. September 

2018. Also See Total Electricity Supply, Disposition, 

Prices, and Emissions, Annual Energy Outlook. 

Department of Energy, Energy Information 

Administration. 

73Because the EPA is not in this final action 

evaluating additional generation shifting 

possibilities, it does not at this time need to revisit 

the question whether it is within the EPA’s 

authority or otherwise proper to consider 

generation shifting in implementing the good 

neighbor provision. The EPA is aware that this has 

been an issue of contention in the past, and 

stakeholders have raised serious concerns regarding 

this issue. See, e.g., 81 FR at 74545 (responding to 

comments); CSAPR Update—Response to 

Comment, at 534–50 (EPA–HQ–OAR–2015–0500– 

0572) (summarizing and responding to comments). 

a marginal cost of $3,400 per ton as the 

level of uniform control stringency that 

represents turning on and fully 

operating idled SNCR controls.71

However, the CSAPR Update finalized 

emissions budgets using $1,400 per ton 

control stringency, finding that this 

level of stringency represented the 

control level at which incremental EGU 

NOX reductions and corresponding 

downwind ozone air quality 

improvements were maximized with 

respect to marginal cost in the context 

of the short-term control strategies being 

considered in that rulemaking. In 

finding that the $1,400 per ton control 

cost level was appropriate, the EPA 

determined that, based on the fleet 

characteristics of SNCR and their 

operation at the time of the CSAPR 

Update, the more stringent emissions 

budget level reflecting $3,400 per ton 

(representing turning on idled SNCR 

controls) yielded fewer additional 

emission reductions and fewer air 

quality improvements relative to the 

increase in control costs. In other words, 

based on the CSAPR Update analysis, 

establishing emissions budgets at $3,400 

per ton, and therefore developing 

budgets based on operation of idled 

SNCR controls, was not determined to 

be cost-effective for addressing good 

neighbor provision obligations for the 

2008 ozone NAAQS. 81 FR 74550. As 

explained in our proposed 

determination, the EPA continues to 

believe that the strategy of turning on 

and fully operating idled SNCR controls 

was appropriately evaluated in the 

CSAPR Update with respect to other 

short-term control strategies for 

addressing interstate ozone pollution 

transport for the 2008 ozone NAAQS. 

Further, the EPA is not aware of any 

significant changes in the fleet 

characteristics of existing SNCR and 

their operation since promulgation of 

the CSAPR Update and therefore does 

not find it necessary to reevaluate the 

cost-effectiveness of operating idled 

SNCR in the short term. Based on data 

available at this time, the EPA does not 

believe it would be reasonable to base 

its selection of a future analytic year on 

the timeframe for implementation of a 

control strategy that the EPA has already 

determined was not cost-effective 

relative to other short-term control 

strategies. Accordingly, in this final 

action the EPA is not further assessing 

this control strategy for purposes of 

identifying an appropriate future 

analytic year. 

The remaining control strategy that 

the EPA evaluated in the CSAPR Update 

was the shifting of generation from 

EGUs with higher NOX emissions rates 

to EGUs with lower NOX emissions rates 

within the same state as a means of 

reducing emissions at costs 

commensurate with and in support of 

emission control technologies to reduce 

NOX emissions. Shifting generation is a 

NOX control strategy that occurs on a 

time- and cost-continuum, in contrast to 

the relatively discrete price-points and 

installation timeframes that can be 

identified for emission control 

technologies—i.e., combustion and postcombustion controls. Therefore, in the 

CSAPR Update, the EPA identified the 

discrete cost thresholds used to evaluate 

upwind states’ good neighbor 

obligations based on its evaluation of 

combustion and post-combustion 

control technologies, and secondarily 

examined the amount of generation 

shifting that would result at the same 

time and cost threshold associated with 

and in support of the particular control 

technology. Quantifying NOX reductions 

from shifting generation anticipated at 

the same time and cost thresholds 

relative to the control technologies 

being considered (e.g., restarting idled 

SCR controls) helped ensure that the 

emission reductions associated with the 

control strategies could be expected to 

occur in the CSAPR Update’s marketbased implementation system. In other 

words, had the agency excluded 

consideration of generation shifting in 

calculating emissions budgets in step 3 

in the CSAPR Update, generation 

shifting would have nonetheless 

occurred as a compliance strategy in 

step 4. Although potential emission 

reductions resulting from generation 

shifting were factored into the final 

budgets, this compliance strategy did 

not drive the EPA’s identification of the 

analytic year or cost thresholds 

analyzed in the CSAPR Update. 

Consistent with our explanation at 

proposal, the EPA does not find it 

appropriate to solely evaluate the 

potential for generation shifting (e.g., in 

isolation from viable combustion or 

post-combustion control assessments) 

for purposes of selecting a future 

analytic year. The EPA continues to 

believe that generation shifting is not 

particularly well suited to identifying 

discrete analytic inputs, given its ability 

to be phased in on a time- and costcontinuum. Further, given CSAPR 

Update implementation as well as 

current and projected natural gas prices 

that are low relative to historical levels, 

significant shifting from higher-emitting 

EGUs to lower-emitting EGUs (relative 

to historical generation levels) is already 

occurring and expected to continue to 

occur by 2023 due to market drivers.72

Thus, there may only be a limited 

opportunity, if any, for the EGUs in 

CSAPR Update states to implement as 

an interstate transport control measure 

further emission reductions through 

generation shifting prior to 2023, 

beyond that which is already occurring 

and reasonably expected to occur as a 

result of other factors. Given EPA’s 

historical consideration of this strategy 

as a secondary factor in quantifying 

emissions budgets, the EPA believes the 

most reasonable approach for selecting 

a future analytic year is to focus on the 

timeframe in which specific control 

strategies other than generation shifting 

can be implemented.73

For these reasons, for purposes of 

identifying an appropriate future 

analytic year, the EPA is focusing its 

assessment of EGUs in this action on 

control technologies that were deemed 

to be infeasible to install for the 2017 

ozone season rather than reassessing 

controls previously analyzed for costeffective emission reductions in the 

CSAPR Update. In establishing the 

CSAPR Update emissions budgets, the 

EPA identified but did not analyze the 

following two EGU NOX control 

strategies in establishing emissions 

budgets because regional 

implementation by 2017 was not 

considered feasible: (1) Installing new 

SCR controls; and (2) installing new 

SNCR controls. The EPA observed that 

EGU SCR post-combustion controls can 

achieve up to 90 percent reduction in 

EGU NOX emissions. The EPA also 

observed that SNCR controls can be 

effective at reducing NOX emissions and 

can achieve up to a 25 percent emission 

reduction from EGUs (so long as 

sufficient reagent is employed). In 2017, 

SCR controls were in widespread use 

across the power sector in the east, 

whereas SNCR controls are considerably 


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74National Electric Energy Data System v6 

(NEEDS). EPA (September 2018). Available at 

https://www.epa.gov/airmarkets/national-electricenergy-data-system-needs-v6. 

75EGU NOX Mitigation Strategies Final Rule TSD. 

76Engineering and Economic Factors Affecting 

the Installation of Control Technologies for 

Multipollutant Strategies. EPA Final Report. Table 

3–1. Available at https://archive.epa.gov/clearskies/ 

web/pdf/multi102902.pdf. 77A month-by-month evaluation of SNCR 

installation is discussed in EPA’s ‘‘Engineering and 

Economic Factors Affecting the Installation of 

Control Technologies for Mulitpollutant Strategies’’ 

at Exhibit A–6 and in EPA’s NOX Mitigation 

Strategies TSD. As noted at proposal, the analysis 

in this exhibit estimates the installation period from 

contract award as within a 10–13 month timeframe. 

The exhibit also indicates a 16-month timeframe 

from start to finish, inclusive of pre-contract award 

steps of the engineering assessment of technologies 

and bid request development. The timeframe cited 

for installation of SNCR at an individual source in 

this final action is consistent with this more 

complete timeframe estimated by the analysis in the 

exhibit. 

78Final Report: Engineering and Economic 

Factors Affecting the Installation of Control 

Technologies for Multipollutant Strategies, EPA– 

600/R–02/073 (Oct. 2002), available at https://

nepis.epa.gov/Adobe/PDF/P1001G0O.pdf. 

79 Id. 

80Occupational Outlook Handbook. Bureau of 

Labor Statistics. Available at https://www.bls.gov/ 

ooh/construction-and-extraction/boilermakers.htm. 

81Union Craft Labor Supply Survey. The 

Association of Union Constructors. Exhibit 4–2 at 

page 29. Available at https://www.tauc.org/files/ 

2017_TAUC_UNION_CRAFT_LABOR_SUPPLY_

REVISEDBC_FINAL.pdf. 

less prevalent. In the 22-state CSAPR 

Update region, approximately 62 

percent of coal-fired EGU capacity is 

equipped with SCR controls while 12 

percent is equipped with SNCR 

controls.74

The EPA notes that differences 

between these control technologies exist 

with respect to the potential viability of 

achieving cost-effective, regional NOX

reductions from EGUs. As just 

described, SCR controls generally 

achieve greater EGU NOX reduction 

efficiency (up to 90 percent) than SNCR 

controls (up to 25 percent). Resulting in 

part from this disparity in NOX

reduction efficiency, the EPA found 

new SCR controls to be more costeffective at regionally removing NOX

when considering both control costs and 

the NOX reduction potential in 

developing its cost-per-ton analysis for 

the CSAPR Update. Specifically, the 

EPA found that new SCR controls could 

generally reduce EGU emissions at a 

marginal cost of $5,000 per ton of NOX

removed whereas new SNCR controls 

could generally reduce EGU emissions 

at a higher cost of $6,400 per ton of NOX

removed.75 In other words, the greater 

NOX reduction efficiency for SCR 

controls translates into greater costeffectiveness of NOX removal relative to 

SNCR controls. Simply put, SCR can 

achieve significantly more regional NOX

reduction at a lower cost per ton than 

SNCR. The general NOX mitigation and 

cost-effectiveness advantage of SCR is 

also consistent with observed 

installation patterns where SCR controls 

(62 percent of coal-fired capacity) are 

more prevalent across the CSAPR 

Update states relative to SNCR (12 

percent of coal-fired capacity). 

Moreover, as discussed in response to a 

comment later in this section, 

installation of SNCR still takes 

significant time as compared to the 2008 

ozone NAAQS attainment dates and 

SNCR installation at an individual 

source would likely make later 

installation of an SCR cost-prohibitive 

and therefore forgo the potential for 

greater emission reductions that could 

be achieved at that source from the 

latter technology in the future. 

Considering these factors, the EPA 

believes it is appropriate to give 

particular weight to the timeframe 

required for implementation of SCR 

across the region as compared to SNCR. 

For SCR, the total time associated 

with project development is estimated 

to be up to 39 months for an individual 

power plant installing controls on more 

than one boiler.76 However, more time 

is needed when considering installation 

timing for new SCR controls regionally, 

for CSAPR Update states. As described 

in the subsequent paragraphs, the EPA 

has determined that a minimum of 48 

months (4 years) is a reasonable time 

period to allow to complete all 

necessary steps of SCR projects at EGUs 

on a regional scale. This timeframe 

would allow for regional 

implementation of these controls (i.e., at 

multiple power plants with multiple 

boilers) considering the necessary stages 

of post-combustion control project 

planning, shepherding of labor and 

material supply, installation, 

coordination of outages, testing, and 

operation. SNCR installations, while 

generally having shorter project 

timeframes (i.e., up to 16 months for an 

individual power plant installing 

controls on more than one boiler), share 

similar implementation steps with and 

also need to account for the same 

regional factors as SCR installations.77

Therefore, the EPA finds that more than 

16 months would be needed to complete 

all necessary steps of SNCR 

development at EGUs on a regional 

scale. Despite EPA’s prioritization of 

SCR as compared to SNCR in 

identifying the timeframe for installing 

new controls, the EPA notes that 

installing these post-combustion 

controls (SCR or SNCR) involve very 

similar steps and many of the same 

considerations. The timing of their 

feasible regional development is 

therefore described together in the 

following paragraphs. 

Installing new SCR or SNCR controls 

for EGUs generally involves the 

following steps: Conducting an 

engineering review of the facility to 

determine suitability and project scope; 

advertising and awarding a procurement 

contract; obtaining a construction 

permit; installing the control 

technology; testing the control 

technology; and obtaining or modifying 

an operating permit.78 These timeframes 

are intended to accommodate a plant’s 

need to conduct an engineering 

assessment of the possible NOX

mitigation technologies necessary to 

then develop and send a bid request to 

potential suppliers. Control 

specifications are variable based on 

individual plant configuration and 

operating details (e.g., operating 

temperatures, location restrictions, and 

ash loads). Before making potential large 

capital investments, plants need to 

complete these careful reviews of their 

system to inform and develop the 

control design they request. They then 

need to solicit bids, review bid 

submissions, and award a procurement 

contract—all before construction can 

begin. 

An appropriate regional control 

implementation timeframe should also 

accommodate the additional 

coordination of labor and material 

supply necessary for any regional NOX

mitigation efforts. For example, the total 

construction labor for a SCR system 

associated with a 500-megawatt (MW) 

EGU is in the range of 330,000 to 

350,000 person-hours, with 

boilermakers accounting for 

approximately half of this time.79 In a 

2017 industry survey, one of the largest 

shortages of union craft workers was for 

boilermakers. This shortage of skilled 

boilermakers is expected to rise due to 

an anticipated nine percent increase in 

boilermaker labor demand growth by 

2026, coupled with expected 

professional retirements and 

comparatively low numbers of 

apprentices joining the workforce.80 The 

shortage of and demand for skilled 

labor, including other craft workers 

critical to pollution control installation, 

is pronounced in the manufacturing 

industry. The Association of Union 

Constructors conducted a survey of 

identified labor shortages and found 

that boilermakers were the second-most 

frequently reported skilled labor market 

with a labor shortage.81 Moreover, 

recovery efforts from the natural 

disasters of recent hurricanes (e.g., 


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82Skilled Wage Growth Less Robust, Worker 

Shortage Still an Issue. Industry Week. October 23, 

2017. Available at http://www.industryweek.com/ 

talent/skilled-wage-growth-less-robust-workershortage-still-issue. 83Union Craft Labor Supply Survey. The 

Association of Union Constructors. Exhibit 4–2 at 

page 29. Available at https://www.tauc.org/files/ 

2017_TAUC_UNION_CRAFT_LABOR_SUPPLY_

REVISEDBC_FINAL.pdf. 84Worldsteel Short Range Outlook. October 16, 

2017. Available at https://www.worldsteel.org/ 

media-centre/press-releases/2017/worldsteel-ShortRange-Outlook-2017-2018.html. 

85See, e.g., Seattle Has Most Cranes in the 

Country for 2nd Year in a Row—and Lead is 

Growing. Seattle Times. July 11, 2017. Available at 

https://www.seattletimes.com/business/real-estate/ 

seattle-has-most-cranes-in-the-country-for-2ndyear-in-a-row-and-lead-is-growing/. 

86See RLB Crane Index, January 2018 in the 

docket for this action. 

87 2014 EIA Form 860. Schedule 6. Environmental 

Control Equipment. 

88 2013 EIA Form 860, Schedule 6, Environmental 

Control Equipment. 

89Big Bend’s Multi-Unit SCR Retrofit. Power 

Magazine. March 1, 2010. Available at http://

www.powermag.com/big-bends-multi-unit-scrretrofit/. 

Harvey, Irma, Florence, and Michael) 

and wildfires in 2017 are expected to 

further tighten the labor supply market 

in manufacturing in the near term.82

The EPA determined that these tight 

labor market conditions within the 

relevant manufacturing sectors, 

combined with regional NOX mitigation 

initiatives, would likely lead to some 

sequencing and staging of labor pool 

usage in implementing control 

technologies, rather than simultaneous 

construction across all efforts. This 

sector-wide trend supports SCR and 

SNCR installation timeframes for a 

regional program that exceed the 

demonstrated single-facility installation 

timeframe. 

In addition to labor supply, NOX postcombustion control projects also require 

materials and equipment such as steel 

and cranes. Sheet metal workers, 

necessary for steel production, are 

reported as having a well-above-average 

supply-side shortage of labor.83 This, 

coupled with growth in steel demand 

estimated at three percent in 2018 

suggests that there may be a constricted 

supply of steel needed for installation of 

new post-combustion controls.84

Similarly, cranes are critical for 

installation of SCRs, components of 

which must be lifted hundreds of feet in 

the air during construction. Cranes are 

also facing higher demand during this 

period of economic growth, with 

companies reporting a shortage in both 

equipment and available labor.85 86 The 

tightening markets in relevant skilled 

labor, materials, and equipment, 

combined with the large number of 

installations that could be required 

under a regional air pollution transport 

program, necessitates longer installation 

timetables relative to what has been 

historically demonstrated at the facility 

level. 

Further, scheduled curtailment, or 

planned outage, for pollution control 

installation would be necessary to 

complete SCR or SNCR projects on a 

regional scale. Given that peak demand 

and rule compliance would both fall in 

the ozone season, sources would likely 

need to schedule installation projects 

for the ‘‘shoulder’’ seasons (i.e., the 

spring and/or fall seasons), when 

electricity demand is lower than in the 

summer, reserves are higher, and ozone 

season compliance requirements are not 

in effect. If multiple units were under 

the same timeline to complete the 

retrofit projects as soon as feasible from 

an engineering perspective, this could 

lead to bottlenecks of scheduled outages 

as each unit attempts to start and finish 

its installation in roughly the same 

compressed time period. Thus, any 

compliance timeframe that would 

assume installation of new SCR or 

SNCR controls should be developed to 

reasonably encompass multiple 

shoulder seasons to accommodate 

scheduling of curtailment for control 

installation purposes and better 

accommodate the regional nature of the 

program. 

Finally, the time lag observed 

between the planning phase and inservice date of SCR operations in certain 

cases also illustrates that site-specific 

conditions can lead to installation times 

of four years or longer—even for 

individual power plants. For instance, 

SCR projects for units at the Ottumwa 

power plant (Iowa), Columbia power 

plant (Wisconsin), and Oakley power 

plant (California) were all in the 

planning phase in 2014. By 2016, these 

projects were under construction with 

estimated in-service dates of 2018.87

Similarly, individual SNCR projects can 

exceed their estimated 16-month 

construction timeframe. For example, 

the SNCR installation at the Jeffrey 

power plant (Kansas) was in the 

planning phase in 2013 but not in 

service until 2015.88 Further, large-scale 

projects also illustrate that timelines can 

extend beyond the general estimate for 

a single power plant when the project is 

part of a larger, multifaceted air 

pollution reduction goal. For instance, 

the Big Bend power plant in Florida 

completed a multifaceted project that 

involved adding SCRs to all four units 

as well as converting furnaces, over-fire 

air changes, and making windbox 

modifications. A decade elapsed 

between the initial planning stages and 

completion.89

In summary, while facility-level SCR 

and SNCR projects can themselves take 

up to 39 and 16 months, respectively, a 

comprehensive and regional emission 

reduction effort requires more time to 

accommodate the labor, materials, and 

outage coordination for these two types 

of control strategies. Given the extra 

weight given to SCR controls due to 

their greater NOX reduction efficiency 

and cost-effectiveness as well as the 

time to regionally develop and 

implement SCRs as a control strategy for 

CSAPR Update states, the EPA 

concludes that 48 months would be a 

reasonable and expeditious timeframe to 

coordinate the planning and completion 

of further regional NOX mitigation 

efforts. 

Comment: Several commenters 

contend that the EPA’s assessment of 

emission reductions available from 

existing EGU NOX controls in the 

CSAPR Update is insufficient. These 

comments suggested that additional 

reductions are available from existing 

SCR NOX controls before 2023 because 

the EPA’s use of a 0.10 lb/mmBtu 

emission rate in its calculation of 

emission budgets was not reflective of 

the total reduction potential from SCR 

optimization. The commenters provide 

analysis using the unit-level ozoneseason emission rates between 2005– 

2016 and suggest that the EPA should 

have relied on each unit’s best 

performing ozone-season emission rate 

from a given year in that period to 

determine the emission rate at which 

each unit’s SCR is fully optimized. The 

commenters suggest that because the 

optimization of SCRs at a lower rate can 

be achieved prior to 2023, the EPA 

should examine air quality in an earlier 

analytic year. 

Response: The EPA does not agree 

that it is necessary to consider any 

further emission reductions ostensibly 

available from the optimization of 

existing SCRs. As described in the 

following paragraphs, the agency’s 

assessment of NOX reduction potential 

from existing SCR controls used in 

establishing CSAPR Update emission 

budgets remains appropriate. Moreover, 

as discussed later in this notice, the best 

data available at this time—2017 EGU 

emission data reflecting CSAPR Update 

implementation—indicate that in 

general these controls are optimally 

operating to mitigate NOX emissions 

across the CSAPR Update region. Thus, 

control optimization for existing SCRs 

has already been addressed in the 

CSAPR Update and emission reductions 

associated with the ‘‘additional’’ control 

technology proposed by commenters are 

being commensurately realized through 

implementation of the CSAPR Update’s 


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90 83 FR 31937 (indicating that EPA is not 

reconsidering or reopening any analyses conducted 

or determinations made in the CSAPR Update). 

allowance trading program. The EPA 

therefore does not agree that a control 

strategy that is already being 

appropriately implemented should 

guide its selection of a future analytic 

year. 

In the CSAPR Update, the EPA 

determined that, based on an 

aggregation of unit-level emission rates, 

an average fleet-wide emission rate of 

0.10 lb/mmBtu would represent the 

optimized operation of SCR controls 

that were not already being operated 

and optimized. 81 FR 74543. In 

concluding that this rate would be 

appropriate for calculating emission 

reduction potential from 

implementation of this control strategy, 

the EPA recognized that some units 

would have optimized rates above that 

level and some below that level. 81 FR 

74543. The EPA explained that it used 

data from 2009 through 2015 and 

calculated an average NOX ozone-season 

emission rate across the fleet of coalfired EGUs with SCR for each of those 

years. It then selected the third-best (i.e., 

third-lowest) yearly rate for each unit, 

noting that it did not find it prudent to 

use the first- and second-best yearly rate 

because the best-performing data from 

those years is likely to reflect the 

utilization of new SCR systems, all of 

whose components were new in that 

year (e.g., new layers of catalyst), and 

may not be representative of an ongoing, 

achievable NOX rate once one or more 

SCR components have begun to degrade 

with age. Id. The third-to-lowest year 

average was 0.10 lb/mmBtu. In the 

CSAPR Update, the EPA applied that 

fleet-wide average to units with SCR 

that were not already emitting at or 

below that NOX emission rate. For units 

operating at or below that level in 2015 

(the starting year from EPA’s budgetsetting methodology), the EPA 

continued to utilize that lower rate. The 

EPA in the CSAPR Update already 

addressed comments regarding the 

reasonableness of its approach to 

calculating an appropriate emission rate 

and did not, in this action, request 

additional comment on the EPA’s 

determination finalized in the CSAPR 

Update that 0.10 lb/mmBtu was a 

reasonable rate to represent optimized 

SCR controls.90 81 FR 74544. The issue 

is also currently the subject of litigation 

before the D.C. Circuit in Wisconsin v. 

EPA, No. 16–1406. Accordingly, the 

EPA does not believe this issue is 

properly within the scope of this action. 

The EPA continues to believe its 

approach in the CSAPR update was 

prudent and reasonable for purposes of 

calculating emission reductions 

achievable from the optimization of 

existing SCR controls and is not 

changing its approach in this action. 

While commenters suggest alternative 

emission rates would have been more 

appropriate, they have not demonstrated 

that the EPA’s approach is 

unreasonable. In particular, the EPA 

does not agree with commenters that 

suggest that the EPA should have used 

a value derived by relying on a 2005– 

2016 baseline (as opposed to the 2009– 

2015 baseline years used by EPA) and 

selecting the single best year (i.e., the 

lowest average ozone-season rate for 

SCR-controlled units in any given year) 

rather than the third-best year. The EPA 

continues to find, as it did in the CSAPR 

Update, that using a baseline starting in 

2009 is more appropriate because that 

year coincided with the onset of annual 

operation for most SCR controls under 

the CAIR annual NOX program. Prior to 

2009, these controls operated 

seasonally, which allowed substantial 

time during the fall, winter, and spring 

for routine maintenance and repair of 

the SCR, as well as replacement of 

catalyst. This seasonal operation is not 

representative of current or reasonably 

anticipated future operation of these 

units that have been and continue to be 

subject to annual NOX requirements, 

first under CAIR and now under 

CSAPR. Further, the agency notes that 

the power sector has undergone 

significant changes in recent years due 

to economic factors and technological 

advances (e.g., natural gas production 

from horizontal fracking technology 

advancements). As a result, the agency 

believes that it is more appropriate to 

focus its analysis on relatively more 

recent years of data, rather than to 

include a significant number of years 

that preceded the set of current 

economic and technological conditions 

affecting and driving outcomes in the 

sector. In other words, the agency is 

more confident that recent data are an 

appropriate basis to reasonably project 

future economic and technological 

conditions with respect to operation of 

EGUs and their NOX controls. The 

agency is not confident that older (i.e., 

pre-2009 data) would be an appropriate 

basis to reasonably project future 

economic and technological conditions 

with respect to operation of EGUs and 

their NOX controls. The EPA therefore 

believes its approach in the CSAPR 

Update was reasonable and preferable 

for the 2008 ozone NAAQS compliance 

assumptions, and retains that approach 

in this action. 

The EPA also believes that its 

decision to rely on the third-best 

seasonal emission rate was more 

appropriate than the commenter’s 

suggestion that the EPA select the 

emission rate from the best performing 

year. By selecting the third-best seasonal 

rate, the EPA avoided selecting times 

when SCR controls were newly 

constructed for most units or may have 

been recently refreshed/replaced with 

all-new catalyst. Complete catalyst 

change may have occurred at the onset 

of major NOX reduction programs or at 

a time when the purpose of the catalyst 

use changed (such as simultaneously 

optimizing for mercury (Hg) removal 

under the Mercury and Air Toxic 

Standards (MATS) program). By 

selecting the third-best seasonal rate out 

of the 2009–2015 time period, the 

agency evaluated repeatable, low-NOX

control operation consistent with 

ongoing operation and maintenance of 

SCR controls. 

Comment: A commenter asserts that 

the EPA should consider operation of 

existing SNCR controls for purposes of 

selecting a future analytic year, rather 

than considering cost-effectiveness to 

eliminate utilization of some potentially 

feasible controls. The commenter 

contends that the EPA’s use of costeffectiveness as a bright line for 

determining what measures are 

appropriate for fully meeting the good 

neighbor SIP obligations for upwind 

states is both erroneous and, as applied 

here, arbitrary and capricious. The 

commenter states that, even if the 

CSAPR Update could be read to 

conclude that operation of SNCR was 

not cost-effective at that time, this 

conclusion was limited to the purposes 

of the partial solution in that rule. The 

commenter claims that the CSAPR 

Update did not deem operation of SNCR 

to never be cost-effective, particularly in 

circumstances where the EPA has found 

no other less-expensive way to reduce 

emissions. The commenter concludes 

that, if EPA is using cost to eliminate 

potentially available solutions, it must 

reevaluate these costs, not merely rest 

on cost data from the CSAPR Update 

that are now several years old. 

Response: The EPA does not agree 

that the timeframe for operating existing 

SNCR should influence its selection of 

a future analytic year. As discussed 

earlier, the EPA’s assessment in the 

CSAPR Update indicated that the $3,400 

per ton NOX control stringency 

(representing turning on idled SNCR) 

was not cost-effective relative to other 

short-term control strategies considered 

in that rulemaking. This conclusion was 

based on the fact that EGUs with idled 

SNCR in the CSAPR Update analysis 


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91Preliminary data for the 2018 ozone season, 

which became available after the proposal for this 

action and after the close of the comment period, 

continue to support this conclusion by showing that 

there were 48 coal units operating in the CSAPR 

Update region with SNCR installed with a weighted 

average ozone-season emission rate of 0.148 lb/ 

mmBtu. 

92CSAPR Update—Response to Comment (EPA– 

HQ–OAR–2015–0500–0572). 

93 83 FR 31937 (indicating that EPA is not 

reconsidering or reopening any analyses conducted 

or determinations made in the CSAPR Update). 

94Preliminary data for the 2018 ozone season, 

which became available after the proposal for this 

action and after the close of the comment period, 

continue to support this conclusion. The average 

emission rate for the 73 SCR-controlled units in the 

CSAPR Update region that were not previously 

emitting with a NOX rate at or below 0.10 lb/mmBtu 

in 2016 and are still operating in 2018 dropped by 

40% from 0.201 lb/mmBtu to 0.121 lb/mmBtu 

between 2016 and 2018—the second ozone season 

of CSAPR Update implementation. Additionally, 

preliminary 2018 data indicate that the 192 coal 

units operating in the CSAPR Update region with 

SCR installed had a weighted average ozone-season 

NOX emission rate of 0.086 lb/mmBtu. 

95Source: AMPD (ampd.epa.gov), EPA, 2018. 

were relatively few and relatively small, 

such that few NOX reductions were 

incrementally achievable from operation 

of idled SNCR compared to other nearterm control strategies available, while 

the difference in cost per ton compared 

to the other strategies was relatively 

large. Accordingly, the EPA found that 

the level of NOX control stringency 

reflecting operation of idled SNCR did 

not maximize NOX reduction potential 

and air quality improvement relative to 

cost. Although the commenters suggest 

that the EPA should reevaluate the costeffectiveness of operating idled SNCR, 

the commenters have not provided any 

data to the agency that would indicate 

the agency’s analysis would 

significantly change. Rather, the EPA’s 

conclusion in the CSAPR Update is 

further supported by reported 2017 data 

which show that there were 55 coal 

units operating in the CSAPR Update 

region with SNCR installed with a 

weighted average ozone-season 

emission rate of 0.14 lb/mmBtu, 

indicating that existing SNCR-controlled 

units are already widely operating and 

would likely provide little opportunity 

for additional reductions.91

The EPA notes that the agency’s 

analysis in the CSAPR Update was 

specific to the conditions evaluated 

therein. Thus, the EPA’s conclusion that 

the feasibility of implementing SNCR 

should not inform the potential 

compliance timeframe and the 

identification of the future analytic year 

would not have precluded the EPA from 

considering whether the operation of 

SNCR would be cost-effective relative to 

the installation of the post-combustion 

controls discussed earlier in this 

section. Had the EPA, at step 1 of the 

four-step framework, identified 

continued downwind air quality 

problems in the future analytic year, the 

EPA could have considered at step 3 

whether it would be cost-effective to 

require upwind states linked at step 2 to 

make emission reductions consistent 

with operation of existing SNCR relative 

to other longer-term control strategies 

like the implementation of new postcombustion controls. However, because 

EPA has already concluded that 

operation of existing SNCR is not costeffective in the near term, the EPA does 

not agree that it would be reasonable for 

EPA to select an earlier analytic year 

that would only be consistent with the 

timeframe for implementing that 

particular compliance strategy. 

Comment: Several commenters 

contend that the EPA’s implementation 

of emission reductions via an allowance 

trading program is not sufficient to 

guarantee that existing SCRs will 

continue to run in the future (especially 

in light of low allowance prices). The 

commenters therefore contend that 

further reductions are available from 

existing EGU controls. The commenters 

suggest that EPA needs to ensure daily 

operation of SCR controls and that the 

seasonal nature of the trading program 

does not do so. 

Response: The EPA begins by 

pointing out that the commenter 

appears to be attempting to reopen a 

determination made in the CSAPR 

Update regarding how best to 

implement the emission reductions 

required by that rule. The question of 

whether an allowance trading program 

is sufficient to ensure emission 

reductions, relative to other forms of 

emission limitations, was raised by 

commenters and addressed in the 

CSAPR Update.92 The EPA did not, in 

this action, request additional comment 

on the appropriateness of an allowance 

trading program to ensure the CSAPR 

Update emission reductions would be 

achieved,93 and it is therefore not reopening the issue in this action. 

Moreover, even if this issue were within 

the scope of this action, the commenters 

have not explained how this concern 

should influence the EPA’s selection of 

the future analytic year used in this 

action. Accordingly, the relative 

effectiveness of the CSAPR Update 

allowance trading program to ensure 

emission reductions commensurate with 

optimizing SCR, as compared to daily 

limits, is outside the scope of this 

action. 

Nonetheless, the EPA notes that 

current data refute commenters’ 

assertion that allowance trading has 

been insufficient to achieve the 

emission reductions associated with the 

operation and optimization of existing 

SCRs. The best currently available data 

indicate that sources in in CSAPR 

Update states are indeed operating SCRs 

in order to comply with the CSAPR 

Update allowance trading program. Data 

from 2017, the first year of ozone-season 

data that would be influenced by the 

CSAPR Update compliance 

requirements, are consistent with the 

EPA’s assumption that the allowance 

trading program would incentivize SCR 

operation on a fleet-wide level. The 

average emission rate for the 83 SCRcontrolled units in the CSAPR Update 

region that were not previously emitting 

with a NOX rate at or below 0.10 lb/ 

mmBtu in 2016 and are still operating 

in 2017 dropped by 45% from 0.22 lb/ 

mmBtu to 0.12 lb/mmBtu between 2016 

and 2017—the first ozone season of 

CSAPR Update implementation.94 Not 

only is the program effective at 

encouraging these particular units to 

achieve a better performance rate, it also 

encourages the wider universe of SCRcontrolled units to keep operating their 

controls. In 2017, 261 of 274 EGUs with 

SCR in the U.S. had ozone-season 

emission rates below 0.20 lb/mmBtu 

(194 of 202 in CSAPR Update states), 

indicating that they were likely 

operating their post-combustion 

controls throughout most of the ozone 

season. The 274 units were operating at 

an average emission rate of 

approximately 0.088 lb/mmBtu. Of the 

13 units with 2017 emission rates above 

0.20 lb/mmBtu, five are located in states 

outside of the CSAPR Update region, 

five have preliminary 2018 ozone 

season NOX emission rates below 0.20 

lb/mmBtu, and one has retired (Killen 

unit 2 in Ohio).95 Consequently, the 

EPA finds that on average, SCRcontrolled units appear to be operating 

their SCRs throughout the season, and 

that the petitioner’s assertion regarding 

the likelihood of not operating controls 

is therefore not supported by the most 

recently available data. The EPA has not 

identified a basis for reevaluating 

emission reductions available from 

optimizing SCRs and it therefore does 

not believe it would be reasonable in 

light of this data to select an earlier 

analytic year on the basis of this control 

strategy. 

Notwithstanding the EPA’s finding 

that SCRs are currently operating 

consistent with optimizing NOX

reduction potential, the EPA notes that 

SCR operation is not the sole metric 

with which to gauge success of a capand-trade program. Rather, the success 

of the program is ultimately indicated 


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96Source: AMPD (ampd.epa.gov), EPA, 2018. 

97Source: AMPD (ampd.epa.gov), EPA, 2018. 

98 83 FR 31937 (indicating that EPA is not 

reconsidering or reopening any analyses conducted 

or determinations made in the CSAPR Update). 

not by the employment of any particular 

control strategy, but rather by 

regionwide and state-level emission 

reductions. The CSAPR Update has 

contributed to a 21 percent reduction in 

regionwide NOX emissions in its first 

year, below the cumulative level of the 

budgets, and all states operated well 

below their assurance levels.96 If some 

SCRs are not performing at lower rates, 

but commensurate reductions are 

achieved elsewhere in the state, this 

demonstrates one of the benefits of a 

market-based trading program: It helps 

participants identify and make the leastcost reductions. The EPA does not agree 

that such a result, even accepting the 

commenter’s analysis for the sake of 

argument, demonstrates that the 

allowance trading program is ineffective 

at achieving the intended emission 

reductions simply because the covered 

sources chose an alternative pathway to 

comply with the program’s 

requirements. 

The EPA has also not identified a 

need to supplement the allowance 

trading program established in the 

CSAPR Update with additional 

emission limits in order to promote the 

daily operation of controls. The EPA 

examined the hourly NOX emissions 

data reported to the EPA and did not 

observe a significant number of 

instances of units selectively turning 

down or turning off their emission 

control equipment during hours with 

high generation. SCR-controlled units 

generally operated with lower emission 

rates during high generation hours, 

suggesting SCRs generally were in better 

operating condition—not worse 

condition, let alone idling—during 

those days/hours. In other words, the 

EPA compared NOX rates for EGUs from 

hours with high energy demand, 

compared them with seasonal average 

NOX rates, and found very little 

difference. Thus, the data do not 

support the notion that units are 

reducing SCR operation on high 

demand days and that consequently a 

narrower compliance timeframe is 

needed to incentivize them to run on a 

daily basis. An examination of average 

daily NOX emission rates for SCRcontrolled units in the CSAPR Update 

region shows that 2017 emission rates 

were significantly lower than 2016 and 

2015. The seasonal decline in emission 

rate was also observed on a daily basis 

in the CSAPR Update region: Out of 153 

days in the ozone season in 2017, all 

153 days had lower average emissions 

rates among SCR-controlled sources 

than the same day in 2016.97 Moreover, 

the auxiliary power used for control 

operation is small—typically less than 

one percent of the generation at the 

facility—and it is therefore unlikely that 

sources would cease operation of 

controls for such a limited energy 

savings. Instead, the data indicate that 

increases in total emissions on days 

with high generation are generally the 

result of additional units that do not 

normally operate coming online to 

satisfy increased energy demand and 

units that do regularly operate 

increasing hourly utilization, rather 

than reduced functioning of control 

equipment. Thus, the EPA does not 

agree that there are additional 

limitations that should be implemented 

to achieve emission reductions from the 

optimization of existing SCRs. 

Comment: One commenter suggests 

that the EPA can achieve additional 

emission reductions in the short term by 

reducing budgets to account for the 

accumulation of banked allowances. 

The commenter contends that this 

would support higher allowance prices 

under the CSAPR NOX Ozone Season 

Group 2 program, thereby incentivizing 

continued SCR operation and further 

cost-effective reductions in NOX

emissions. 

Response: The EPA first notes that, to 

the extent the commenter is challenging 

the EPA’s decision in the CSAPR 

Update permit the continued use of 

certain banked allowances, the agency 

already addressed comments regarding 

this issue in that rulemaking, 81 FR 

74557, and did not, in this action, 

request additional comment on its 

determination with regard to this issue 

as finalized in the CSAPR Update.98 The 

issue is also currently the subject of 

litigation before the D.C. Circuit in 

Wisconsin v. EPA. Accordingly, the EPA 

does not believe concerns regarding the 

bank of allowances that were carried 

over in the CSAPR Update are properly 

within the scope of this action. To the 

extent the commenter suggests that the 

EPA eliminate the current bank of 

allowances to achieve further NOX

emission reductions in the future, the 

EPA does not believe that the mere 

presence of a bank of allowances 

indicates that such additional emission 

reductions are actually achievable in 

practice. Current program design 

elements, specifically the assurance 

provisions, are already in place to 

incentivize the control operation 

referred to by the commenter and ensure 

emission reductions. Moreover, the 

most recently observed historical data 

suggest these controls are widely 

operating in the compliance period and 

that their operation is not undermined 

by the existence of the bank as 

suggested by the commenter. 

First, the CSAPR Update includes 

assurance provisions that help ensure 

that EGUs in each covered state 

collectively limit their emissions. These 

provisions include an assurance level 

for each state that serves as a statewide 

emissions limit that cannot be exceeded 

without penalty. This assurance level is 

the sum of the state emission budget 

plus a variability limit equal to 21 

percent of the state’s ozone-season 

budget. This means that collective EGU 

emissions in each state cannot exceed 

121 percent of the state budget level 

without incurring penalties. The 

assurance levels are designed to help 

ensure that emissions are reduced in 

each covered state of a region-wide 

trading program while acknowledging 

and accommodating the inherent 

variability in electricity generation and 

NOX emissions due to year-to-year 

changes in power sector market 

conditions. These assurance levels help 

ensure that emission reductions, 

including those associated with the 

optimization of existing controls on 

which the CSAPR Update budgets were 

based, continue to be implemented. 

Therefore, even with fleet turnover and 

a growing allowance bank, EPA 

anticipates that the assurance limit will 

maintain downward pressure on statelevel emissions. 

Second, the commenter misconstrues 

the emissions impact of an allowance 

bank and does not provide further 

evidence that would be needed to show 

that real-world emission reductions are 

available. A bank of allowances, first 

and foremost, represents emission 

reductions and not an emissions 

liability. Specifically, an allowance 

bank represents allowable emissions 

that have not been emitted into the 

atmosphere, converted into ozone, or 

transported downwind to impact the 

ability of downwind areas to attain or 

maintain the NAAQS. The commenter 

essentially asserts that an allowance 

bank will necessarily undermine the 

operation of NOX controls. However, as 

described previously, the best currently 

available data (i.e., recent EGU 

emissions data with CSAPR Update 

implementation) indicate that existing 

controls are being operated consistent 

with optimizing for NOX mitigation. As 

such, the agency finds that, at this time, 

the accumulation of the allowance bank 

primarily represents emission 

reductions, and is not creating the 

incentive for controls to be idled. 

Because the emission reductions sought 


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by the commenter (via operation of 

existing SCRs) are in fact already being 

implemented across the region, the EPA 

has no reason to believe that additional 

emission reductions could be achieved 

by either eliminating the banked 

allowances or adjusting the budgets in 

some manner commensurate with the 

current level of banked allowances. As 

such, the emission reduction potential 

asserted by commenters is hypothetical 

and the EPA has no reason to believe at 

this time that the adjustments to the 

bank would lead to significant realworld NOX reductions. 

Comment: The EPA received several 

comments on the proposed 

determination regarding its assessment 

of new EGU NOX control strategies, 

suggesting that new NOX emission 

mitigation technologies are available 

prior to 2023 and that the EPA’s reliance 

on the feasibility of regional installation 

of SCRs for selection of a future analytic 

year is arbitrary and capricious. The 

commenter further questions the EPA’s 

estimate for installation of SCRs and 

suggests they can be installed at a faster 

pace, noting that the EPA allowed for 

just 30 months under the initial CSAPR 

promulgated in 2011. They assert that 

the EPA has not adequately 

demonstrated that the market for labor 

and materials, while observed to be 

strained, is more strained than previous 

environments. The EPA notes that other 

commenters agreed with the EPA’s 

timeline for implementation of new 

mitigation technologies and asserted 

that that it would be infeasible for EGUs 

to install new SCRs or SNCRs in less 

than four years. The commenters 

observe that in many cases it may take 

longer due to planning and the outage 

window required for implementation of 

such controls. They suggest that the 

EPA should consider a later analytic 

year because not doing so puts the EPA 

at risk of over-controlling as some plants 

that could not install controls by 2023 

would install them at a later date when 

those reductions are no longer needed. 

Response: For the reasons discussed 

earlier in this notice, the EPA believes 

that conducting a regional analysis 

ensures that the Agency can fully 

evaluate remaining obligations pursuant 

to the good neighbor provision with 

respect to the 2008 ozone NAAQS. As 

the EPA has routinely found throughout 

nearly 20 years of interstate transport 

rulemakings, the ozone transport 

problem is regional in nature, in that 

downwind states’ problems attaining 

and maintaining the ozone NAAQS 

result from the contribution of pollution 

from multiple upwind states, with 

multiple upwind states routinely 

contributing to multiple downwind 

states’ air quality problems in varying 

amounts. With respect to the 2008 

ozone NAAQS, the EPA determined in 

the CSAPR Update rulemaking that, 

collectively, 22 upwind states 

contributed at or above the 1 percent 

threshold to downwind air quality 

problems at one or more of 19 different 

receptor locations in the eastern United 

States. Individual upwind states 

contributed to between 1 and 8 

downwind nonattainment or 

maintenance receptors and, in a number 

of cases, upwind states also contained at 

least one receptor indicating a 

downwind air quality problem to which 

other states contributed. Given the 

multi-faceted nature of ozone transport, 

the Supreme Court has acknowledged 

that the EPA is faced with the burden 

to determine ‘‘how to differentiate 

among otherwise like contributions of 

multiple upwind states.’’ EME Homer 

City, 134 S. Ct. at 1607. As the Supreme 

Court acknowledged, the statute is silent 

as to which metric the EPA should use 

to decide the apportionment of the 

shared obligation to address a 

downwind air quality problem among 

multiple upwind states—what the Court 

referred to as the ‘‘thorny causation 

problem.’’ Id. at 1603–04. 

Accordingly, because ozone air 

quality problems (and in particular 

interstate transport) are regional in 

nature, the EPA has developed—and the 

Supreme Court has endorsed—a 

regional approach for quantifying 

individual states’ emission reduction 

obligation. In particular, the EPA has 

developed a two-pronged metric 

(constituting steps 2 and 3 of the fourstep transport framework) to identify the 

amounts of an upwind state’s emissions 

that ‘‘contribute significantly to 

nonattainment’’ or ‘‘interfere with 

maintenance’’ of the ozone NAAQS in a 

downwind state to which it is linked. 

The EPA identifies those emissions that 

both: (1) Contribute 1 percent or more 

of the NAAQS to an identified 

downwind air quality problem (i.e., the 

identification of linkage at CSAPR 

framework step 2); and (2) can be 

eliminated through implementation of 

cost-effective control strategies, applied 

uniformly to all states linked to an air 

quality problem (i.e., the quantification 

of emission reductions at CSAPR 

framework step 3). When evaluating at 

step 3 whether a control strategy is costeffective for this purpose, the EPA 

considers the incremental cost per ton 

of emissions reduced, the magnitude of 

emissions that can be reduced using a 

particular control strategy, and the 

downwind air quality benefits of 

implementing such emission 

reductions. 81 FR at 74519. The 

Supreme Court found this approach, as 

applied in the original CSAPR 

rulemaking, to be ‘‘an efficient and 

equitable solution to the allocation 

problem the Good Neighbor Provision 

requires the Agency to address.’’ Id. at 

1607. The Court held that this approach 

is: ‘‘[e]fficient because EPA can achieve 

the levels of attainment, i.e., of emission 

reductions, the proportional approach 

[urged by respondants in EME Homer 

City] aims to achieve, but at a much 

lower overall cost. Equitable because, by 

imposing uniform cost thresholds on 

regulated States, EPA’s rule subjects to 

stricter regulation those States that have 

done relatively less in the past to 

control their pollution. Upwind States 

that have not yet implemented pollution 

controls of the same stringency as their 

neighbors will be stopped from free 

riding on their neighbors’ efforts to 

reduce pollution. They will have to 

bring down their emissions by installing 

devices of the kind in which 

neighboring States have already 

invested.’’ Id. 

Given the regional nature of the ozone 

pollution problem and the requirement 

that the EPA determine the remainder of 

its good neighbor FIP obligation with 

respect to the 2008 ozone NAAQS for 21 

states in the CSAPR Update region, the 

EPA reasonably applied the regional 

framework endorsed by the Supreme 

Court as an ‘‘efficient and equitable’’ 

approach to resolving the remaining 

good neighbor obligations interstate 

transport problem. Id. at 1607. 

Accordingly, the EPA evaluated the 

contributions of all upwind states that 

are linked to a given downwind air 

quality problem, rather than quantifying 

the significant contributions of single 

states or sectors in a vacuum. Similarly, 

the EPA evaluated potential control 

strategies to address that contribution 

on a regional, rather than facility- or 

state-specific, basis. Such an approach 

also ensures that each state’s 

contributions to downwind air quality 

problems are quantified relative to the 

contribution of the other contributing 

states. 

The commenters are also incorrect to 

assert that the agency’s conclusion that 

48 months should be provided for the 

implementation of new SCR is in 

conflict with its position in the original 

CSAPR rulemaking. In the original 

CSAPR, the EPA established NOX

emission budgets in CSAPR based on a 

cost threshold of $500 per ton, which 

was not anticipated to drive any new 

SCR installation in either compliance 

phase. See Table VII.C.2–1, 76 FR 48279 

and discussion at 76 FR 48302. As such, 


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99Labor Availability for the Installation of Air 

Pollution Control Systems at Coal-Fired Power 

Plants. Andover Technology Partners. October 18, 

2011. Available at http://

www.andovertechnology.com/images/ 

boilermaker%20labor%20availability%20final_jes_

%2010%2018%202011.pdf. 

100Based on 2017 ozone-season NOX data. 

Applying SCR reduction potential of 90 percent (up 

to a 0.07 lb/mmBtu floor) as opposed to 25 percent 

reduction for SNCR to 2017 emission levels for 

uncontrolled coal sources emitting at 0.15 lb/ 

mmBtu or greater. 

this control strategy was not central to 

CSAPR Update implementation. 

Notwithstanding that SCR postcombustion controls were omitted from 

the EPA’s CSAPR emissions budgets at 

the time, to the extent labor and supply 

markets were a consideration for 

installation timing requirements for 

scrubbers in CSAPR in 2011, those 

variables have changed over the last 

seven years. For instance, the EPA noted 

a sharp drop in boilermaker personhours worked between 2008 and 2010, 

suggesting that the market at that time 

had substantial underutilized capacity 

whereas today’s industry surveys 

identify labor shortages.99 The EPA also 

disagrees with the commenter’s 

assertion that these observations 

regarding crane and steel markets are 

not reasonable and thus should not 

influence the EPA’s analysis. While not 

the sole reason for the EPA’s conclusion 

that a 48-month timeframe would be 

necessary for region-wide control 

installation, the EPA believes the market 

for labor and materials is a relevant 

weight-of-evidence consideration in 

light of reports from companies that 

supply the tower cranes that there is a 

shortage of both equipment and 

available labor. The crane index and 

quarterly construction costs reports are 

metrics regularly used to evaluate 

construction activity by construction 

consultants and provide a sense of 

equipment demand. Moreover, the 

commenter provides no evidence to 

refute the EPA’s finding that these 

equipment markets are facing periods of 

higher demand. 

Thus, while the EPA does not agree 

that it is reasonable to consider a 

timeframe longer than four years for the 

expeditious, region-wide 

implementation of SCR controls, neither 

does the EPA agree that it would be 

reasonable to assume any shorter 

timeframe under the circumstances. 

Comment: Some commenters assert 

that the EPA could identify an earlier 

analytic year based on the installation of 

new SNCRs because the controls can be 

implemented more quickly than SCRs. 

Response: As explained above, the 

EPA does not agree that that the regional 

installation of SNCRs should drive 

EPA’s selection of an appropriate future 

analytic year, primarily because SCR 

controls are more effective at reducing 

NOX emissions and because SCR 

controls are more regionally costeffective at mitigating NOX. Specifically, 

the EPA estimates the amount of 

reductions available by SCR installation 

at uncontrolled sources is nearly triple 

that available from SNCR installation.100

This difference is significant because 

the agency is tasked with issuing FIPs 

that fully resolve good neighbor 

obligations and therefore the agency 

finds it reasonable to focus its analysis 

on the timeframe for installing controls 

that would be best suited to achieve that 

goal in terms of NOX mitigation, 

downwind air quality improvement, 

and cost—i.e., SCR controls. Further, as 

described in the subsequent paragraphs, 

the EPA finds that the regionally 

implementing NOX reductions from 

SNCR would still take a significant 

amount of time and would significantly 

hamper the ability of these EGUs to 

obtain further emission reductions from 

installation of SCRs in the future. 

First, the EPA noted above that the 

estimated timing to install SNCR for 

multiple boilers at one power plant is 

approximately 16 months—and can take 

even longer in practice. Accounting for 

the regional factors that must be 

considered (described previously), it 

would take more than 16 months for 

this control strategy to be regionally 

implemented. Starting with 

promulgation of this action in December 

of 2018, the agency believes it would 

take well into 2020 for these controls to 

be feasibly implemented, regionally. As 

a result, it is very unlikely that these 

controls could affect ozone season NOX

attainment demonstrations made in July 

2021 for areas designated serious for the 

2008 ozone NAAQS. 

Finally, the agency notes the potential 

for inefficiency in effectively controlling 

NOX emissions in the long term by 

prioritizing SNCR controls now to the 

detriment of future NOX mitigation 

potential from SCR controls. Installing 

an SNCR at a unit in the near term and 

then upgrading or retrofitting the unit to 

an SCR a few years down the road 

would effectively increase the cost per 

ton of that eventual SCR installation as 

compared to installing the SCR in the 

first place. The main difference between 

the two systems is the temperature 

window at which the reaction takes 

place. With an SNCR, that window is 

900–1050 degrees Celsius, whereas it 

drops to a range of 160 to 350 degrees 

Celsius for an SCR. These differentials 

in optimal temperatures influence the 

location and modifications necessary for 

each retrofit technology and therefore 

complicate any transition from SNCR to 

SCR. SNCR can be described as 

including a silo or tank (for reagent), a 

conveyance system for the reagent, and 

a properly placed injection lance in the 

furnace. In terms of volume occupied, 

over 90 percent of the system exists 

outside the flue gas path. The SCR 

system, on the other hand, requires a 

catalytic reactor and is placed 

downstream of the economizer. An SCR 

occupies a significant space as the 

catalytic reactor resides in a dedicated 

multi-story structure elevated above 

ground elevation. Over 90 percent of an 

SCR’s volume exists within the flue and 

duct work. 

The two systems are unique and 

distinct from one another in their 

approach to reducing NOX and the 

equipment cannot be shared or dualpurposed due to the size differences, 

conversion rates, and reagent material 

flows based on the application (namely, 

the location within the flue gas stream). 

Consequently, almost none of the 

capital cost incurred for an SNCR 

system can be credited towards 

installation of an SCR system. This 

would result—in most cases—in a 

higher overall cost to get to the same 

level of emission reductions if a source 

first installed an SNCR and then 

upgraded to an SCR as opposed to the 

initial installation of an SCR. Such a 

retrofit would also likely increase the 

amount of work, and therefore time, to 

complete the SCR installation. 

Thus, selecting an analytic year and 

imposing emission reductions focused 

on installation of SNCR alone at an 

earlier date (if this could even occur on 

an earlier timeframe regionwide) would 

potentially obviate a source’s ability to 

cost-effectively install SCR, a more 

effective NOX control, at a later date. 

The EPA’s obligation in this action was 

to fully address states’ good neighbor 

obligation for the 2008 ozone NAAQS. 

Therefore, it was reasonable for the EPA 

to select a future analytic year that 

would allow for advanced control 

installation which would deliver 

significant reductions, if they were 

determined to be necessary. Choosing 

an earlier analytic year based on the 

installation of a SNCR alone would 

potentially be counterproductive to 

EPA’s objective to address states’ full 

obligations and severely limit sources’ 

ability to obtain more significant 

emission reductions from SCR in the 

future to address other control 

obligations. 

b. Non-EGU Control Technologies 

The EPA is also evaluating the 

feasibility of implementing NOX control 


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101 Institute of Clean Air Companies. Typical 

Installation Timelines for NOX Emissions Control 

Technologies on Industrial Sources, December 

2006. Available at https://c.ymcdn.com/sites/ 

icac.site-ym.com/resource/resmgr/ICAC_NOx_

Control_Installatio.pdf. 

102U.S. EPA. Cement Kilns Technical Support 

Document for the NOX FIP. January 2001. Available 

at https://www.regulations.gov/document?D=EPAHQ-OAR-2015-0500-0094. 

103 INGAA Foundation. Availability and 

Limitations of NOX Emission Control Resources for 

Natural Gas-Fired Reciprocating Engine Prime 

Movers Used in the Interstate Natural Gas 

Transmission Industry, Innovative Environmental 

Solutions Inc., July 2014. Available at http://

www.ingaa.org/Foundation/Foundation-Reports/ 

NOx.aspx. 

104 In particular, this document presents different 

installation time estimates for SCRs for EGUs and 

non-EGUs. However, these installation times are not 

necessarily inconsistent, because the EGU time 

estimate of 39 months mentioned above is based on 

multi-boiler installation and factors in a pre-vendor 

bid engineering study consideration, whereas the 

non-EGU SCR installation time estimates are based 

on single-unit installation and do not factor in prevendor bid evaluation. Consideration of these 

additional factors might extend the time estimate 

for installation of SCRs for non-EGUs. 

technologies for non-EGUs stationary 

sources as part of its identification of an 

appropriate future analytic year. While 

the EPA did not regulate non-EGUs in 

the CSAPR Update, the rule did 

evaluate the feasibility of NOX controls 

on non-EGUs in the eastern United 

States to assess whether any such 

controls could be implemented in time 

for the 2017 ozone season. In the CSAPR 

Update, the EPA noted that there was 

greater uncertainty in the assessment of 

non-EGU point-source NOX mitigation 

potential as compared to EGUs, and 

therefore explained that more time was 

required for states and the EPA to 

improve non-EGU point source data, 

including data on existing control 

efficiencies, additional applicable 

pollution control technologies, and 

installation times for those control 

technologies. 81 FR 74542. A significant 

factor influencing uncertainty was that 

the EPA lacked sufficient information 

on the capacity and experience of 

suppliers and major engineering firms’ 

supply chains to determine if they 

would be able to install the pollution 

controls on non-EGU sources in time for 

the 2017 ozone season. Further, using 

the best information available to the 

EPA at that time, the EPA found that 

there were more non-EGU point sources 

than EGU sources and that these sources 

on average emit less NOX than EGUs. 

The implication was that there were 

more individual sources that could be 

controlled, but relatively fewer emission 

reductions available from each source 

when compared to the number of EGUs 

and emission reductions available from 

EGUs. Considering these factors, the 

EPA found that it was substantially 

uncertain whether significant aggregate 

NOX mitigation would be achievable 

from non-EGU point sources to address 

the 2008 ozone NAAQS by the 2017 

ozone season. Id. 

Although the EPA determined that 

there were limited achievable emission 

reductions available from non-EGUs by 

the 2017 ozone season, the EPA 

acknowledged that it may be 

appropriate to evaluate potential nonEGU emission reductions achievable on 

a timeframe after the 2017 ozone season 

to assess whether upwind states 

continued to have outstanding good 

neighbor obligations for the 2008 ozone 

NAAQS. 81 FR 74522. In particular, the 

EPA’s preliminary assessment in the 

CSAPR Update indicated that there may 

be emission reductions achievable from 

non-EGUs at marginal costs lower than 

the costs of remaining NOX control 

strategies available for EGUs. In 

evaluating potential non-EGU emission 

reductions in the CSAPR Update, the 

EPA included preliminary estimates of 

installation times for some non-EGU 

NOX control technologies in a technical 

support document entitled Assessment 

of Non-EGU NOX Emission Controls, 

Cost of Controls, and Time for 

Compliance Final Technical Support 

Document (henceforth, ‘‘Final Non-EGU 

TSD’’). These preliminary estimates 

were based on research from a variety of 

information sources, including: 

• Typical Installation Timelines for 

NOX Emissions Control Technologies on 

Industrial Sources, Institute of Clean Air 

Companies, December 2006 (all sources 

except cement kilns and reciprocating 

internal combustion engines (RICE)); 101

• Cement Kilns Technical Support 

Document for the NOX FIP, U.S. EPA, 

January 2001; 102 and 

• Availability and Limitations of NOX

Emission Control Resources for Natural 

Gas-Fired Reciprocating Engine Prime 

Movers Used in the Interstate Natural 

Gas Transmission Industry, Innovative 

Environmental Solutions Inc., July 

2014—prepared for the Interstate 

Natural Gas Association of America 

(INGAA Foundation).103

In assessing an appropriate future 

analytic year for this action, the EPA has 

looked to the information compiled in 

the Final Non-EGU TSD for the CSAPR 

Update to evaluate what timeframe 

might be appropriate for installing 

sector- or region-wide controls on nonEGU sources. 

Among the control technologies that 

were evaluated in the Final Non-EGU 

TSD, the EPA identified six categories of 

common control technologies available 

for different non-EGU emission source 

categories. Final Non-EGU TSD at 19. 

For four of the technology categories 

(SNCR, SCR, low-NOX burners (LNB), 

and mid-kiln firing), the EPA 

preliminarily estimated that such 

controls for non-EGUs could be 

installed in approximately one year or 

less in some unit-specific cases. 

Installation time estimates presented in 

the Final Non-EGU TSD considered a 

timeline that begins with control 

technology bid evaluation (bids from 

vendors) and ends with the startup of 

the control technology. See id. at 20. For 

the other two technology categories 

(biosolid injection technology (BSI) and 

OXY-firing), as well as one emission 

source category (RICE), the EPA had no 

installation time estimates or uncertain 

installation time estimates. For example, 

the EPA found that the use of BSI is not 

widespread, and therefore the EPA does 

not have reliable information regarding 

the time required to install the 

technology on cement kilns. The 

installation timing for OXY-firing is 

similarly uncertain because the control 

technology is installed only at the time 

of a furnace rebuild, and such rebuilds 

occur at infrequent intervals of a decade 

or more. For those categories for which 

preliminary estimates were available, as 

noted in the Final Non-EGU TSD, the 

single-unit installation time estimates 

provided do not account for additional 

important considerations in assessing 

the full amount of time needed for 

installation of NOX control measures at 

non-EGUs, including additional time 

likely necessary for permitting or 

installation of monitoring equipment. 

See id. at 19–21. These preliminary 

installation estimates also do not 

account for factors such as multi-boiler 

installations at a particular source and 

pre-vendor bid engineering studies.104

In particular, the preliminary 

estimates of installation times of 

approximately a year or less shown in 

the Final Non-EGU TSD are for 

installation at a single source and do not 

account for the time required for 

installing controls to achieve sectorwide compliance. Thus, the preliminary 

estimates do not consider time, labor, 

and materials needed for programmatic 

adoption of measures and time required 

for installing controls on multiple 

sources in a few to several non-EGU 

sectors across the region. When 

considering installation of control 

measures on sources regionally and 

across non-EGU sectors, the time for full 

sector-wide compliance is uncertain, 

but it is likely longer than the 

installation times shown for control 

measures for individual sources in the 

Final Non-EGU TSD. As discussed 

earlier with respect to EGUs, regional, 


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sector-wide compliance could be 

slowed down by limited vendor 

capacity, limited available skilled labor 

for manufacturers such as boilermakers 

(who produce steel fabrications, 

including those for pollution control 

equipment), availability of raw materials 

and equipment (e.g., cranes) for control 

technology construction, and 

bottlenecks in delivery and installation 

of control technologies. Some of the 

difficulties with control technology 

installation as part of regional, sectorwide compliance at non-EGUs, such as 

availability of skilled labor and 

materials, could also have an impact on 

monitor installation at such sources. 

The EPA currently has insufficient 

information on vendor capacity and 

limited experience with suppliers of 

control technologies and major 

engineering firms, which results in 

additional uncertainty in the overall 

installation time estimates for non-EGU 

sectors. 

The EPA notes that its analysis in the 

Final Non-EGU TSD focused on 

potential control technologies within 

the range of costs considered for EGUs 

in the final CSAPR Update, i.e., those 

controls available at a marginal cost of 

$3,400 per ton (2011 dollars) of NOX

reduced or less. The EPA’s analysis did 

not evaluate implementation timeframes 

or potential emission reductions 

available from controls at higher cost 

thresholds. See Final Non-EGU TSD at 

18. This focus excluded some emission 

source groups with emission reduction 

potential at a marginal cost greater than 

$3,400 per ton, including: Industrial/ 

commercial/institutional boilers using 

SCR and LNB; and catalytic cracking 

units, process heaters, and coke ovens 

using LNB and flue gas recirculation. 

However, while emission reduction 

potential from these source groups is 

uncertain, the timeframe for these 

control technologies would be subject to 

considerations and limitations similar to 

those discussed in the preceding 

paragraphs. 

In summary, there is significant 

uncertainty regarding the 

implementation timeframes for various 

NOX control technologies for non-EGUs. 

While the EPA has developed 

preliminary estimates for some potential 

control technologies, these estimates 

only account for the time between bid 

evaluation and startup but do not 

account for additional considerations 

such as pre-bid evaluation studies, 

permitting, and installation of 

monitoring equipment. Moreover, these 

preliminary estimates do not account for 

the impacts of sector- and region-wide 

compliance, which may be complex 

considering the diversity of non-EGU 

sources as well as the greater number 

and smaller size of the individual 

sources. The EPA did not receive any 

comments on its proposal that would 

contradict the importance of these 

considerations. Accordingly, in light of 

these considerations, the EPA believes 

that it is reasonable to assume for 

purposes of this action that an 

expeditious timeframe for installing 

sector- or region-wide controls on nonEGU sources may be four years or more. 

Comment: One commenter suggests 

that the EPA’s assessment of feasibility 

of control strategies for non-EGU 

sources rests on a need for further 

information gathering, when the agency 

has had ample time to do this work 

already, citing U.S. Sugar Corp. v. EPA, 

830 F.3d 579, 644 (D.C. cir. 2016) (‘‘The 

Agency was obligated to collect the data 

it needed, and Congress gave it the 

authority to do so.’’). The commenter 

asserts that the EPA cited this same 

basis for deferring a full remedy in the 

CSAPR Update and that the EPA has 

been invoking an alleged need to gather 

more information on these sources for 

more than a decade, citing the original 

CSAPR rulemaking and CAIR. The 

commenter states that it is unlawful and 

arbitrary for the EPA to rely on a need 

for information that it has failed to 

collect or analyze despite its own 

longstanding recognition that the 

information is needed, citing Sierra 

Club v. Johnson, 444 F. Supp. 2d 46, 53 

(D.D.C. 2006) (explaining that statutory 

deadlines in the Clean Air Act indicate 

that Congress intended agencies to 

prioritize timeliness over perfection). 

Another commenter notes that the 

EPA indicated in separate litigation that 

it intended to take steps to improve its 

data on non-EGU controls by November 

2017, citing Opposition and CrossMotion for Summary Judgment, Sierra 

Club v. Pruitt, No. 3:15–cv–04328 (N.D. 

Cal. Dec. 15, 2016) ECF No. 63., but that 

it has never completed these steps. The 

commenter asserts that the 

determination is therefore based on 

speculation. The commenter continues 

that the EPA does not explain why the 

information that was previously found 

to be insufficient is now sufficient for 

purposes of this action, nor does the 

EPA explain why it still has not 

quantified or analyzed the potential for 

cost-effective emission reductions from 

non-EGU sources. Thus, the commenter 

asserts that the EPA ignores its own 

framework for determining the 

availability and cost-effectiveness of 

non-EGU controls. The commenter 

claims that this is a change in position 

from the CSAPR Update where the EPA 

stated that a final determination of 

whether the emission reductions from 

that rule would be sufficient to address 

the good neighbor obligation would 

depend upon an evaluation of non-EGU 

sources. 

Response: The commenter is incorrect 

in asserting that the EPA’s basis for its 

conclusion in this action regarding the 

implementation timeframe for control 

strategies for non-EGU sources rests on 

the assumption that more information 

gathering is necessary. While the EPA 

has discussed the uncertainties 

associated with determining appropriate 

implementation timeframes for a 

number of control measures and 

technologies that could be applied to a 

large number and variety of non-EGU 

sources, as discussed above the EPA has 

evaluated the information known to the 

agency regarding various control 

measures and technologies and the 

factors affecting the installation of 

various control technologies. 

Considering the information known to 

the agency, as outlined in the Final 

Non-EGU TSD, the EPA has reasonably 

concluded that expeditious 

implementation of additional controls 

for non-EGU sources may be four years 

or more. The commenter is thus 

incorrect to suggest that the EPA has 

further deferred its evaluation of nonEGU sources. This is the same 

information that the EPA relied upon to 

determine that significant and 

meaningful non-EGU emission 

reductions could not feasibly be 

implemented by the 2017 ozone season 

in the CSAPR Update. 81 FR 74542. The 

commenter has not provided 

information that would contradict the 

EPA’s conclusion that it is appropriate 

to assume, based on the information 

known to the agency, that four years or 

more should be provided for the 

installation of controls for non-EGU 

sources. 

This approach is not a change in 

policy. In the CSAPR Update, the EPA 

only stated that it could not conclude, 

at that time, whether additional 

reductions from NOX sources (including 

non-EGUs) would be necessary to fully 

resolve these obligations. In the CSAPR 

Update, the EPA did indicate that it 

anticipated the need to evaluate nonEGUs to evaluate the full scope of 

upwind states’ good neighbor 

obligations, and the agency has done so 

here in so far as evaluating control 

feasibility. Specifically, in selecting the 

appropriate future analytic year in 

which to evaluate air quality, 

contributions, and NOX reduction 

potential, as necessary, the EPA 

considered the implementation 

timeframes for controls at EGUs as well 

as non-EGUs. As discussed in more 

detail later, the EPA’s analysis showed 


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105Order, New York v. Pruitt, No. 1:18–cv– 

00406–JGK (S.D.N.Y. June 12, 2018), ECF No. 34. 

The five states are Illinois, Michigan, Pennsylvania, 

Virginia, and West Virginia. 

that there would be no remaining air 

quality problems in 2023 in the eastern 

U.S., and thus the EPA has concluded 

that no such additional reductions 

beyond those on-the-books or on-theway controls are necessary, whether 

from non-EGUs or otherwise, to bring 

downwind areas into attainment and 

maintenance of the 2008 ozone NAAQS. 

Because the air quality modeling results 

for 2023 show that air quality problems 

in the eastern U.S. would be resolved by 

2023, the EPA has not further evaluated 

the cost-effectiveness of the control 

options considered for the feasibility 

analysis. This approach is consistent 

with the EPA’s four-step framework and 

does not rely on the relative costeffectiveness of controls for non-EGU 

sources. 

The commenter’s reliance on U.S. 

Sugar and Sierra Club is therefore 

inapposite. In U.S. Sugar, the court was 

reviewing the EPA’s decision not to 

regulate certain sources under a 

different provision of the CAA based on 

a lack of information. 830 F.3d at 642– 

43. The court, however, found that the 

agency’s duty to regulate these sources 

was nondiscretionary and that the 

statute provided the agency with 

explicit authority to gather information 

from the affected sources for this 

purpose. Id. at 644. Here, the EPA is not 

deferring a nondiscretionary duty to 

issue a regulation addressing controls at 

non-EGU sources, but has evaluated the 

potential NOX control measures and 

technologies at non-EGU sources using 

all information known to the agency, as 

described in the Final Non-EGU TSD, in 

order to inform its further analysis of 

upwind state obligations under the good 

neighbor provision. In Sierra Club, the 

court laid out the standard for 

determining the time needed to 

promulgate regulations under the CAA 

after the EPA fails to perform the 

mandatory duties within the statutorily 

prescribed timeframe. 444 F. Supp. 2d 

at 52. As the commenters note, the court 

stated, among other things, that courts 

will generally not provide additional 

time to promulgate a regulation ‘‘simply 

to improve the quality or soundness of 

the regulations to be enacted.’’ Id. at 53. 

However, the court in that case 

addressed a mandatory deadline set by 

the statute to promulgate a plan; it was 

not evaluating the EPA’s interpretation 

of a statutory provision like the good 

neighbor provision that does not set an 

express deadline for implementation of 

emission reductions. 

Notably, the court in Sierra Club did 

find that the statutory deadlines in the 

Clean Air Act indicate that Congress 

intended agencies to prioritize 

timeliness over perfection. 444 F. Supp. 

2d at 53. Thus, to the extent another 

commenter chides the EPA for acting 

based on the information before the 

agency, even if it has not completed all 

steps to improve its data for non-EGU 

sources, the Sierra Club decision 

supports the agency’s approach. 

Moreover, because the EPA did not need 

to evaluate either the cost-effectiveness 

or NOX reduction potential of either 

EGU or non-EGU sources, the 

commenter’s concern with whether the 

EPA has completed steps to improve its 

data on these issues is irrelevant. 

Nonetheless, the EPA notes that the 

particular efforts outlined in the court 

filing referred to by the commenter were 

taken in support of the EPA’s request in 

a mandatory duty suit that the court 

permit the agency several years to 

develop a rulemaking to address the 

good neighbor obligations with respect 

to the 2008 ozone NAAQS for Kentucky 

and 20 other states. In that filing, the 

EPA outlined steps that the agency 

believed would be necessary to 

promulgate a rulemaking if the EPA’s 

analysis demonstrated that additional 

emission reductions would be required 

from sources in upwind states, 

including what the EPA viewed as 

necessary analysis regarding non-EGU 

sources. The EPA acknowledged in that 

same declaration that one possible 

result of the EPA’s analysis could be a 

determination that downwind air 

quality problems would be resolved, in 

which case a cost-effectiveness analysis 

would be unnecessary. See Opposition 

and Cross-Motion for Summary 

Judgment, Exhibit 1 (Decl. of Janet G. 

McCabe) para. 98, Sierra Club v. Pruitt, 

No. 3:15–cv–04328–JD (N.D. Cal. Dec. 

15, 2016), ECF No. 63. As the EPA could 

not know the results of any future air 

quality modeling before it was 

performed, the EPA’s proposed timeline 

assumed that such an analysis might be 

required. Id. para. 170. Ultimately, the 

court disagreed with the EPA’s 

proposed timeline and provided only 

one year from its order—until June 30, 

2018—for promulgation of a rulemaking 

addressing Kentucky’s good neighbor 

obligation, which was insufficient time 

to complete all of the steps outlined in 

the EPA’s declaration, thereby requiring 

the EPA to prioritize certain steps and 

eliminate others, including the 

additional efforts intended to improve 

data regarding the feasibility and costeffectiveness of controls. Nonetheless, 

because the first step of the EPA’s 

analysis demonstrated that there would 

be no remaining air quality problems in 

2023 in the eastern U.S., it turned out 

to be unnecessary for the EPA to finalize 

the efforts to improve its data regarding 

the cost-effectiveness of controls before 

finalizing this action. Thus, the 

representations that the EPA made to 

the court regarding the steps necessary 

to take this action no longer apply under 

the present circumstances. 

3. Focusing on 2023 for Analysis 

As discussed in section III.B, the EPA 

weighed several factors to identify an 

appropriate future analytic year for 

evaluating interstate transport 

obligations for the 2008 ozone NAAQS. 

First, the EPA identified the relevant 

attainment dates to guide the EPA’s 

consideration as 2021 and 2027, 

respectively the Serious and Severe area 

attainment dates for the 2008 ozone 

NAAQS. 

Second, the EPA identified and 

analyzed the feasibility and timing 

needed for installing additional NOX

emissions controls. As discussed in 

section III.B.2, the EPA believes it is 

appropriate to assume that planning for, 

installing, and commencing operation of 

new controls, regionally, for EGUs and 

non-EGUs would take up to 48 months, 

and possibly more in some cases, 

following promulgation of a final rule 

requiring appropriate emission 

reductions. This period of time reflects, 

among other considerations, the time 

needed to regionally develop new postcombustion SCR projects—systems that 

continue to represent the engineering 

gold-standard in terms of reducing NOX

from the U.S. power sector. 

To determine how this feasibility 

assessment should influence potential 

compliance timeframes, the EPA 

believes it is appropriate to consider the 

date of promulgation of the rule that 

would establish emission reduction 

requirements if necessary and thereby 

provide notice to potentially regulated 

entities that actions will be required for 

compliance. The EPA, therefore, 

considered the timeframe in which this 

rulemaking would be finalized. As 

discussed previously, the EPA is subject 

to several statutory and court-ordered 

deadlines to issue FIPs to address any 

outstanding requirements under the 

good neighbor provision for the 2008 

ozone NAAQS for several states. The 

agency is issuing this final action in 

light of those obligations. This action 

will be signed no later than December 

6, 2018, consistent with a court order to 

take action addressing the FIP obligation 

for five states.105 Considering the EPA’s 

conclusion that 48 months is a 

reasonable, and potentially expeditious, 


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timeframe for implementation of 

substantial regional control strategies 

considered herein, emission reductions 

from these control strategies would not 

be feasible until the 2023 ozone season. 

In other words, 48 months from a final 

rule promulgated in December 2018 

would be December 2022, after which 

the next ozone season begins in May 

2023. Considering the time necessary to 

implement the controls calculated from 

a realistic timeframe in which EPA 

would expect to promulgate a final rule 

requiring such controls, the EPA 

believes that such reductions on a 

variety of sources across the region are 

unlikely to be feasibly implemented for 

a full ozone season until 2023. 

Consistent with the court’s holding in 

North Carolina, the agency considers 

this timing in light of upcoming 

attainment dates for the 2008 ozone 

NAAQS. While 2023 is later than the 

next attainment date for nonattainment 

areas classified as Serious (i.e., July 20, 

2021), for the reasons discussed above 

the EPA does not believe it is reasonable 

to expect that additional regional 

emissions control requirements could be 

developed and implemented by the 

Serious area attainment date. Rather, the 

most expeditious timeframe in which 

additional regional control strategies 

could be implemented at both EGUs and 

non-EGUs is 48 months after 

promulgation of a final rule requiring 

appropriate emission reductions. At the 

same time, the EPA does not believe 

that it should generally take longer than 

2023 to install emissions controls on a 

regional basis, based on the analysis 

above. Therefore, there is no basis to 

postpone any potentially needed 

emission reductions to the next 

attainment date after 2023, which is for 

nonattainment areas classified as Severe 

(i.e., July 20, 2027). Accordingly, the 

EPA believes implementation of 

additional emission reductions by 2023 

is the earliest feasible timeframe that 

could be reasonably required of EGU 

and non-EGU sources that would be 

potentially subject to control 

requirements. Although this year does 

not precisely align with a particular 

attainment date, it reflects the year that 

is as expeditious as practicable for 

regionwide implementation, while also 

taking into account the relevant 

attainment dates. 

Given the current stage of the 2008 

ozone implementation cycle, the EPA’s 

feasibility analysis set forth above, the 

relevant attainment dates, and the 

courts’ holdings in North Carolina and 

EME Homer City, the EPA believes that 

2023 is the most appropriate year for it 

to assess downwind air quality and to 

evaluate any remaining requirements 

under the good neighbor provision for 

the 2008 ozone NAAQS with regard to 

all states covered in this action. 

Comment: Several commenters 

contend that the EPA’s selection of a 

2023 analytic year is inappropriate 

because it does not address downwind 

states’ obligations to attain the 2008 

Ozone NAAQS by the July 20, 2021 

attainment date for nonattainment areas 

classified as Serious. The commenters 

generally cite North Carolina for the 

proposition that EPA must esatablish 

interstate transport compliance 

deadlines under the good neighbor 

provision that are identical to deadlines 

for downwind states to achieve 

attainment with the NAAQS. The 

commenters note that, in that decision, 

the D.C. Circuit rejected portions of 

CAIR on the grounds that it did not 

require upwind contributors to 

eliminate their significant contributions 

in time for downwind areas to meet 

their impending attainment deadlines. 

The commenters state that the 

attainment date for areas classified as 

Moderate nonattainment for the 2008 

ozone NAAQS passed on July 20, 2018, 

and the next attainment dates for the 

2008 ozone NAAQS will be Serious area 

attainment date. Because July 20, 2021 

falls during the 2021 ozone season, the 

2020 ozone season will be the last full 

ozone season from which data can be 

used to demonstrate attainment of the 

NAAQS by the July 2021 attainment 

date. The commenters contend that 

North Carolina compels the EPA to 

identify upwind reductions and 

implementation programs to achieve 

these reductions, to the extent possible, 

during or before the 2020 ozone season. 

One commenter further notes that 

CAA sections 110(a)(2)(D) and 182 

require the EPA to implement the good 

neighbor provision ‘‘consistent with’’ 

applicable attainment deadlines, and 

notes that the D.C. Circuit held in North 

Carolina that this requirement is 

unambiguous. The commenter states 

that the attainment deadlines in section 

182 are fixed dates with which the EPA 

must comply, citing Sierra Club v. 

Johnson, 294 F.3d 155, 161 (D.C. cir. 

2002) (‘‘[Section] 181(a)(1)[ ] as written 

sets a deadline without an exception.’’), 

and Train v. Natural Resources Defense 

Council, 421 U.S. 60, 64–65 (1975) 

(Congress ‘‘required’’ attainment of air 

quality standards ‘‘within a specified 

period of time’’). The commenter further 

states that the EPA is bound by the 

requirement to eliminate significant 

contributions ‘‘as expeditiously as 

practicable’’ but further notes that the 

use of the words ‘‘but not later than’’ the 

dates listed in section 182 established 

the attainment deadlines as an express 

limit on the EPA’s discretion. The 

commenter therefore contends that the 

EPA’s claim of authority to fully 

implement the good neighbor provision 

‘‘as expeditiously as practicable’’ and 

later than the Serious attainment dates 

is an exercise in rewriting the statute. 

Commenters also contend that the 

EPA’s consideration of feasibility cannot 

justify delaying action or analysis until 

2023. One commenter contends that the 

D.C. Circuit’s decision in North Carolina 

rejected compliance deadlines in CAIR 

that were based on ‘‘feasibility restraints 

such as the difficulty of securing project 

financing and the limited amount of 

specialized boilermaker labor to install 

controls’’ but were not ‘‘consistent with 

. . . compliance deadlines for 

downwind states.’’ 531 F.3d at 911–12. 

The commenter asserts that the Clean 

Air Act’s attainment deadlines ‘‘leave[ ] 

no room for claims of technological or 

economic infeasibility,’’ citing Union 

Elec. Co. v. EPA, 427 U.S. 246, 258 

(1976) (deadlines are ‘‘intended to 

foreclose the claims of emission sources 

that it would be economically or 

technologically infeasible for them to 

achieve emission limitations sufficient 

to protect the public health within the 

specified time’’); id. at 259 (Congress 

‘‘determined that existing sources of 

pollutants either should meet the 

standard of the law or be closed down’’) 

(quoting S. Rep. No. 91–1196, pp. 2–3 

(1970)). 

Response: The EPA does not agree 

that either the text of the statute or the 

court’s holding in North Carolina 

dictates that there can only be one 

appropriate future analytic year and that 

this year must be identical to an 

attainment deadline or forecloses 

consideration of the feasibility of 

implementing emission reductions in 

determining the appropriate future 

analytic year. 

First, as to the statute, the good 

neighbor provision does not set forth 

any timeframe for the analysis of 

downwind air quality or the 

implementation of upwind emission 

reductions. On its face, the good 

neighbor provision is therefore 

ambiguous as to when the upwind 

emission reductions it calls for must be 

in place. The EPA acknowledges that 

the good neighbor provision does 

indicate that the prohibition of upwind 

state emissions must be ‘‘consistent 

with the provisions of [title I],’’ and that 

the D.C. Circuit held in its North 

Carolina decision that the other 

provisions with which the 

implementation of the good neighbor 

provision must be consistent include 

the attainment dates in part D of title I 

of the Act. However, the good neighbor 


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106 It is worth noting that the statutory text of 

CAA section 181(a) does not itself establish the 

attainment dates for the 2008 ozone NAAQS. 

Rather, the EPA undertakes rulemakings to 

establish the appropriate deadlines after a new or 

revised ozone NAAQS is promulgated. See, e.g., 

2008 Ozone NAAQS SIP Requirements Rule, 80 FR 

12264, 12268 (Mar. 6, 2015); 40 CFR 51.1103. 

107For example, in the CSAPR Update, two 

maintenance receptors (in Allegan County, 

Michigan, and Jefferson County, Kentucky) were 

located in areas designated attainment for the 2008 

ozone NAAQS. 40 CFR 81.318 (Kentucky), 81.323 

(Michigan). 

108See, e.g., 80 FR 30941 (June 1, 2015) 

(determination of attainment of Baltimore, MD 

(Harford receptor)); 81 FR 26697 (May 4, 2016) 

(determination of attainment by the attainment date 

of Cincinnati-Hamilton OH–KY–IN (Hamilton 

receptor)); 82 FR 50814 (November 2, 2017) 

(determination of attainment by attainment date of 

Philadelphia PA–NJ–MD–DE (Philadelphia 

receptor)). 

provision does not specify what it 

means to be ‘‘consistent with’’ the other 

provisions of the Act, and courts have 

routinely held that this phrase is 

ambiguous See, e.g., EDF, 82 F.3d at 457 

(holding the requirement that 

implemention of transportation control 

measures be ‘‘consistent with’’ the 

applicable implementation plan under 

section 176 of the CAA is ‘‘flexible 

statutory language’’ which does not 

require ‘‘exact correspondence . . . but 

only congruity or compatibility,’’ thus 

requiring a court to defer to reasonable 

agency determinations); Natural 

Resources Defense Council v. Daley, 209 

F.3d 747, 754 (D.C. cir. 2000) (finding 

that statute requiring fishing quotas be 

‘‘consistent with’’ a fishery management 

plan was ambiguous); NL Indus. v. 

Kaplan, 792 F.2d 896, 898–99 (9th Cir. 

1986) (statutory phrase ‘‘consistent with 

the national contingency plan’’ in 42 

U.S.C. 9607(a)(2)(B) ‘‘does not 

necessitate strict compliance with 

[national contingency plan’s] 

provisions’’). Moreover, while CAA 

section 181 identifies timeframes for 

attaining ozone standards in downwind 

states, it does not specify deadlines for 

good neighbor emission reductions.106

Therefore, Congress has left a gap for 

EPA to fill. See Chevron v. NRDC, 467 

U.S. 837, 843 (1984). In light of this 

ambiguity, the good neighbor provision 

cannot be read to require 

implementation of upwind emission 

reductions on a specific timeframe, and 

a compliance timeframe imposed 

pursuant to a good neighbor plan should 

be considered reasonable so long as the 

EPA has demonstrated that it is chosen 

in consideration of and is not 

inconsistent with downwind attainment 

dates and other relevant attainment 

planning requirements in title I. 

Moreover, the statute does not impose 

inflexible deadlines for attainment. The 

general planning requirements that 

apply to nonattainment areas under 

subpart 1 of part D provide that the 

Administrator may extend the default 

five-year attainment date by up to 10 

years ‘‘considering the severity of 

nonattainment and the availability and 

feasibility of pollution control 

measures.’’ CAA section 172(a)(2)(A). In 

the case of the ozone NAAQS, this 

provision is overridden by the more 

specific attainment date provisions of 

subpart 2. The general timeframes 

provided for attainment in ozone 

nonattainment areas in the section 

181(a)(1) table may be (and often are) 

modified pursuant to other provisions 

in section 182, considering factors such 

as measured ozone concentrations and 

the feasibility of implementing 

additional emission reductions. For 

example, the six-year timeframe for 

attainment of the 2008 ozone NAAQS in 

Moderate areas (the July 2018 

attainment date) could be extended 

under certain circumstances to 2020, 

pursuant to section 181(a)(5). And 

pursuant to section 181(b)(2), when 

downwind areas are unable to 

implement sufficient reductions via 

feasible control technologies by one 

attainment date, those areas will be 

reclassified, or ‘‘bumped up’’ in 

classification, and given a new 

attainment date with additional time to 

attain. With ‘‘bump-ups’’ like this, the 

date for an area to attain the 2008 ozone 

NAAQS could be extended to 2021, 

2027, and 2032, and each of these 

deadlines could be subject to further 

extensions of up to two years pursuant 

to section 181(a)(5). Part D further 

defines what control strategies states 

must implement by sources in 

nonattainment areas by each of the 

applicable attainment dates, 

incorporating considerations of 

technological feasibility at each stage. 

See, e.g., CAA section 172(c)(1), (2) 

(requiring implementation of reasonably 

available control measures and 

reasonable further progress in 

designated nonattainment areas); 

section 182(b)(1)(A), (c)(2)(B) (setting 

explicit reasonable further progress 

targets for ozone precursors, and 

providing an exception when the SIP 

includes ‘‘all measures that can feasibly 

be implemented in the area, in light of 

technological achievability’’ (emphasis 

added)). 

Thus, while the statute indicates that 

downwind areas should attain as 

expeditiously as practicable, but no later 

than the attainment dates specified in 

sections 172(a)(2) and 181(a)(1), 

implementation provisions for 

nonattainment planning lay out myriad 

exceptions to those deadlines, including 

for circumstances when attainment is 

simply infeasible. See Whitman v. Am. 

Trucking Ass’ns, Inc., 531 U.S. 457, 

493–94 (2001) (Breyer, J., concurring) 

(considerations of costs and 

technological feasibility may affect 

deadlines established for attainment by 

the EPA). Thus, the EPA’s approach to 

evaluating upwind emission reductions 

based on technological feasibility is 

consistent with the requirements 

imposed on downwind nonattainment 

areas required to implement certain 

‘‘reasonable’’ controls within the 

targeted timeframe. By contrast, the 

commenters’ premise that all upwind 

emission reductions must occur before 

the earliest downwind attainment date, 

without regard to feasibility, is 

inconsistent with the framework of 

section part D as it applies to downwind 

states. 

The ambiguity in the good neighbor 

provision regarding the relationship of 

upwind state emission reductions to 

attainment dates is further heightened 

with respect to downwind areas that the 

EPA anticipates are likely to be in 

attainment in a future year, some of 

which are already currently attaining 

the standard (or even designated 

attainment) 107 but which may have 

problems maintaining the standard in 

the future (i.e., maintenance receptors). 

In the EPA’s 2017 air quality modeling 

performed for the CSAPR Update, the 

EPA identified six nonattainment 

receptors and thirteen maintenance 

receptors. 81 FR 74533. The 

maintenance receptors were areas that 

the EPA expected were likely to be in 

attainment based either on the modeling 

projections or current monitored data, 

but which EPA expected may have 

problems maintaining attainment of the 

standard under certain circumstances. 

While many of the maintenance 

receptors are in areas currently 

designated nonattainment, the EPA’s 

analysis suggests that these areas will be 

able to demonstrate (and in many cases 

have in fact demonstrated) 108

attainment of the NAAQS by the 

attainment date or otherwise receive a 

clean data determination that relieves 

the state of further planning obligations. 

While the good neighbor provision 

requires states to prohibit emissions that 

will ‘‘interfere with maintenance’’ of the 

NAAQS in these areas, there is no 

deadline for maintenance of the 

standard comparable to an attainment 

date for downwind areas that are in 

nonattainment of the standard. The 

commenters present no argument as to 

why upwind obligations for states 

linked to downwind maintenance areas 


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109Commenters also cite Union Electric for the 

proposition that economic and technological 

feasibility may not be considered, but the Court was 

also reviewing an earlier version of the Clean Air 

Act that has since been amended to add the specific 

provisions for ozone nonattainment areas discussed 

in this section which allow for consideration of 

economic and technological feasibility. 427 U.S. at 

249–50. 

must be pegged to future analytic years 

identical to attainment dates which may 

not themselves be relevant to 

maintenance receptors. 

The EPA further disagrees that the 

D.C. Circuit’s North Carolina decision 

requires the EPA to only use the next 

relevant attainment date in selecting its 

future analytic year. The North Carolina 

decision faulted the EPA for not giving 

any consideration to upcoming 

attainment dates in downwind states 

when setting compliance deadlines for 

upwind emission reductions in CAIR: 

There, the EPA had evaluated only the 

feasibility of implementing upwind 

controls. 531 F.3d at 911–12. But the 

court did not hold that the CAA requires 

that compliance deadlines for good 

neighbor emission reductions be 

identical to any attainment date, let 

alone the next upcoming one. Nor did 

the court opine that the EPA would 

never be justified in setting compliance 

dates that fall after the next upcoming 

downwind attainment date (but, as with 

the future analytic year selected in this 

action, well before the next date after 

that one) or that are based, in part, on 

the feasibility of implementing upwind 

emission reductions. Indeed, in 

remanding the rule, the D.C. Circuit 

acknowledged that upwind compliance 

dates may, in some circumstances, come 

after attainment dates. Id. at 930 (where 

the attainment date relevant to the 

discussion was 2010, instructing EPA to 

‘‘decide what date, whether 2015 or 

earlier, is as expeditious as practicable 

for states to eliminate their significant 

contributions to downwind 

nonattainment’’). Accordingly, the 

EPA’s consideration of anticipated 

compliance timeframes for 

implementation of NOX control 

strategies in selecting a future analytic 

year is not inconsistent with North 

Carolina. 

The commenter’s citations to Sierra 

Club and Train also do not contradict 

the EPA’s interpretation. At issue in 

Sierra Club was whether the EPA could 

extend the deadline for attainment 

without reclassifying the area as a 

‘‘Severe’’ nonattainment area and 

suspend other planning requirements 

based on the conclusion that continued 

nonattainment would be caused by 

emissions transported from other states. 

294 F.3d at 159. Thus, although the 

court indicated that the attainment dates 

are ‘‘without exception,’’ it specifically 

stated that this was with respect to 

‘‘setbacks owing to ozone transport.’’ Id. 

at 161. The court did not contradict the 

conclusion that states are only required 

to implement measures that are 

‘‘reasonably available’’ in downwind 

areas, deferring to the EPA’s 

interpretation of section 172(c) as not 

requiring measures that ‘‘would not 

advance the attainment date, would 

cause substantial widespread and longterm adverse impacts, or would be 

economically or technologically 

infeasible.’’ Id. at 162–63, quoting 66 FR 

608. Sierra Club therefore supports 

EPA’s position that it is appropriate to 

consider the feasibility of implementing 

control strategies when evaluating 

appropriate compliance timeframes 

under the good neighbor provision. And 

although the Supreme Court in Train 

stated that the Act requires states to 

attain the air quality standards ‘‘within 

a specified period of time,’’ the court 

pointed this out in a background 

discussion describing the evolution of 

the CAA from a prior period when the 

statute included no attainment dates. 

421 U.S. at 65. Moreover, the decision 

was issued in 1975, before the 1990 

amendments added the complicated set 

of provisions governing the timing 

concerns and control obligations 

imposed on states with ozone 

nonattainment areas. Thus, this decision 

cannot be relied upon to read out the 

flexibilities subsequently provided in 

the Act.109 (And, of course, in any event 

it does not address requirements such as 

the good neighbor provision, which 

contains no express deadlines or other 

timeframes.) 

CAA section 110(a)(2)(D)(i) (the good 

neighbor provision) and part D 

(governing nonattainment 

requirements), when read together, do 

not unambiguously require good 

neighbor emission reductions by a 

particular deadline. And in North 

Carolina the court simply found that 

EPA must make an effort to 

‘‘harmonize’’ its upwind good neighbor 

reductions with downwind attainment 

dates. 531 F.3d at 911–12. The EPA has 

reasonably harmonized these provisions 

to require good neighbor emission 

reductions as expeditiously as 

practicable to benefit downwind areas, 

taking into account their attainment 

dates as well as how expeditiously 

upwind controls could feasibly be 

implemented. Thus, where the EPA was 

able to identify substantial upwind 

emission reductions available by the 

upcoming attainment date, as in the 

CSAPR Update, the EPA implemented 

those reductions. However, where 

additional controls could not be feasibly 

implemented by the next immediate 

attainment date, the EPA has instead 

reasonably determined it was 

appropriate to analyze air quality in the 

future year that represents the most 

expeditious timeframe for 

implementation of such controls after 

that date, but before the following 

attainment date. The EPA reasonably 

reads the good neighbor provision and 

the gaps left in the statutory scheme by 

Congress to allocate responsibility 

between the upwind and downwind 

states in a manner that aligns with the 

overall structure of CAA Title I. See, 

e.g., 81 FR at 74515–16, 74535–36. 

Notably, the consequence of reading the 

statute as the commenters suggest 

would be profound: Emission 

reductions would be required even if 

such reductions could be achieved only 

by the use of manifestly infeasible 

upwind control measures, an obligation 

not imposed on downwind 

nonattainment areas due to the 

availability of extensions and 

reclassifications, described earlier, 

which provide more time for such areas 

to implement reductions to attain the 

relevant NAAQS. Cf. S. Rep. No. 95– 

127, at 42 (1977) (the good neighbor 

provision is intended to ‘‘mak[e] a 

source at least as responsible for 

polluting another State as it would be 

for polluting its own State’’—not more 

responsible) (emphasis added). Nothing 

in the CAA or judicial precedents 

requires this result. 

Comment: One commenter suggests 

that EPA cannot rely on the need to 

avoid over-control to justify the choice 

of the 2023 analytic year. The 

commenter states that, in EME Homer 

City, the Supreme Court made clear that, 

while EPA should strive to avoid overcontrol, ‘‘the Agency also has a statutory 

obligation to avoid ‘under-control.’’’ 134 

S. Ct. at 1609. The commenter suggests 

that, should over-control become an 

issue at some future time, such as in 

2023, the EPA can address that issue 

when it arises. 

Response: The EPA disagrees with the 

commenter’s assertion that the EPA has 

inappropriately weighted concerns 

about over-control of upwind state 

emissions. The Supreme Court and the 

D.C. Circuit have both held that EPA 

may not require emission reductions 

that are greater than necessary to 

achieve attainment and maintenance of 

the NAAQS in downwind areas. See 

EME Homer City, 134 S. Ct. at 1608; 

EME Homer City II, 795 F.3d at 127. 

While the Supreme Court indicated that 

‘‘EPA must have leeway’’ to balance the 

possibilities of under-control and overcontrol and that ‘‘some amount of overVerDate Sep<11>2014 00:31 Dec 21, 2018 Jkt 247001 PO 00000 Frm 00031 Fmt 4701 Sfmt 4700 E:\FR\FM\21DER3.SGM 21DER3

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110For instance, based on 2017 heat input, SNCR 

coal-fired operation reflected a small portion (8 

percent) of the total coal-fired fleet operation. Not 

only is it a small inventory of units, but the 

additional reductions from these sources would be 

small as the SNCR fleet was already averaging a 

nationwide ozone-season emission rate of 0.16 lb/ 

mmBtu and most SNCR-controlled units were 

emitting at levels consistent with control operation. 

Less than 1 percent of the 2017 coal-fleet heat input 

had a SNCR and was operating at emission rates 

(greater than 0.3 lb/mmBtu) that would suggest 

additional reductions would be available from 

better SNCR operation. 

control . . . would not be surprising,’’ 

the Court did not indicate that the EPA 

should ignore the risk of over-control. 

134 S. Ct. at 1609. Rather, the Court 

held, ‘‘If EPA requires an upwind State 

to reduce emissions by more than the 

amount necessary to achieve attainment 

in every downwind State to which it is 

linked, the Agency will have 

overstepped its authority, under the 

Good Neighbor Provision.’’ Id. at 1608. 

On remand in EME Homer City II, the 

D.C. Circuit gave that holding further 

meaning when it determined that the 

CSAPR phase 2 ozone season NOX

budgets for 10 states were invalid 

because EPA’s modeling showed that 

the downwind air quality problems to 

which these states were linked when 

EPA projected air quality to 2012 would 

be entirely resolved by 2014, when the 

phase 2 budgets were scheduled to be 

implemented. 795 F.3d at 129–30. Thus, 

the Court did not hold that over-control 

was a secondary consideration or an 

issue that could be deferred to some 

indefinite future course correction, but 

rather that it was a primary constraint 

on the EPA’s authority. 

Under the current circumstances, the 

EPA is determining that substantial 

additional emission reductions cannot 

be achieved until 2023 because the 

implementation of additional control 

strategies not already considered and 

implemented in the CSAPR Update 

would take at least four years to 

accomplish. Thus, in order to ensure 

that the emission reductions that might 

be achieved from the implementation of 

such controls would not be more than 

necessary to address downwind air 

quality problems, the EPA reasonably 

evaluated air quality in the future year 

when implementation of such controls 

could reasonably and feasibly be 

expected to occur. Had the EPA instead 

evaluated air quality in an earlier year 

(e.g., the 2021 Serious area attainment 

date), even though emission reductions 

from these control strategies could not 

be implemented for several more years, 

the EPA could not have ensured that the 

emission reductions would still be 

necessary by the time of 

implementation. Here, where the EPA 

has information indicating that such 

emission reductions would likely not be 

necessary to address downwind air 

quality problems by the time they could 

feasibly and expeditiously be 

implemented, the D.C. Circuit’s holding 

in EME Homer City II suggests that the 

EPA may not have the authority under 

the good neighbor provision to require 

such additional emission reductions. In 

any event, the court’s holding suggests 

that it is prudent for the EPA to exercise 

its discretion taking into consideration, 

among other factors, the prohibition 

against over-control as one of multiple 

scientific, policy, and legal 

considerations informing the selection 

of a future analytic year for projection 

of air quality at step 1 of the four-step 

framework. Thus, it is reasonable for the 

EPA to harmonize this consideration 

with the EPA’s reasonable anticipation 

of how long it would take to accomplish 

substantial additional emission 

reductions. 

Comment: One commenter contends 

that North Carolina required that the 

EPA model nonattainment and 

maintenance in the earliest compliance 

year that would align with the next 

attainment deadline, which is 

effectively the 2020 ozone season for the 

July 2021 Moderate area attainment 

date. Under the four-step framework, 

the commenter asserts that the EPA 

must first identify whether any 

downwind receptors are expected to 

have problems attaining or maintaining 

the 2008 ozone NAAQS in 2020 and 

then identify the upwind states that are 

contributing to those downwind 

problems. The commenter then 

contends that EPA should evaluate 

whether those unlawful contributions 

could be reduced through compliance 

with state budgets established using the 

next most cost-effective NOX control 

technology that EPA has not yet relied 

upon to establish a good neighbor 

provision rule, in this case, starting up 

and operating idled SNCR controls. 

Another commenter states that the 

Ozone Transport Commission (OTC) has 

already conducted modeling for 2020, 

which shows that a number of receptor 

sites will exceed the 2008 ozone 

standard in 2020. In light of this 

modeling, the commenter asserts that it 

would be arbitrary for the EPA to 

dismiss the likelihood of continued 

attainment and maintenance difficulties 

through and in 2020 or to fail to conduct 

comprehensive modeling for the years 

before 2023. 

Response: As discussed earlier, the 

EPA does not agree that it is obligated 

to review air quality only in a year 

associated with the next attainment 

date, particularly under the present 

circumstances where its analysis of 

potential control strategies shows that 

new control strategies cannot be feasibly 

implemented within that timeframe. 

Further, the EPA does not believe it 

would be reasonable to implement the 

next most costly control technology 

simply to achieve any amount of 

additional reductions in the near term. 

As discussed in section III.B.2 earlier, 

the EPA has already determined in the 

CSAPR Update that the operation of 

idled SNCR is not a cost-effective 

control strategy as compared to other 

available short term control strategies 

because the operation of such controls 

would result in small emission 

reductions and small downwind air 

quality improvements relative to the 

cost and relative to the much more 

significant emission reductions and 

ozone improvements the EPA 

determined were available from lesscostly control strategies.110 Thus, it is 

incorrect to refer to the operation of 

SNCR as the ‘‘next most cost-effective’’ 

control strategy because the EPA 

concluded the control strategy was 

simply not cost-effective relative to 

other near-term control strategies. 

The EPA notes that it would have 

been difficult under the circumstances 

to conduct air quality modeling for both 

the 2020 attainment date suggested by 

the commenters and the 2023 

compliance timeframe associated with 

the additional control strategies 

discussed earlier. Air quality modeling 

is a resource- and time-consuming 

process, as described in more detail in 

Section III.C and in the technical 

support documents in the record. Air 

quality modeling for a future year 

requires more than three months to 

develop detailed emission projection 

inventories for each emissions sector for 

the future year (with many of the 

inventories themselves derived from 

running other models) and to preprocess these emissions data for input to 

the air quality model. Once the inputs 

are prepared, a month or more is 

required to run the air quality model 

and post-process the outputs in order to 

produce results, followed by additional 

analysis to interpret the results. 

Producing contribution data, if 

necessary, also requires additional time 

to run a different, more complex 

modeling tool (i.e., modeling with 

source apportionment) and to interpret 

the results. All told, preparing for, 

completing, and interpreting air quality 

modeling data for a future year generally 

takes on the order of 6 months. Thus, 

modeling more than one future year 

would have required significant 

additional time beyond that available to 


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111Order, New York v. Pruitt, No. 1:18–cv– 

00406–JGK (S.D.N.Y. June 12, 2018), ECF No. 34 

(setting deadline for EPA to address FIP obligation 

for Illinois, Michigan, Pennsylvania, Virginia, and 

West Virginia). The EPA’s time to conduct the 

modeling was additionally constrained by the 

court-ordered deadline to take final action 

addressing the good neighbor obligation for 

Kentucky by June 30, 2018. See Order, Sierra Club 

v. Pruitt, No. 3:15–cv–04328 (N.D. Cal. May 23, 

2017), ECF No. 73. Because the Kentucky action 

addressed the same problem of regional interstate 

ozone transport for the 2008 ozone NAAQS, it was 

necessary to complete the modeling in time for the 

EPA to issue a proposed action for Kentucky in 

advance of that deadline. 

112Annual Energy Outlook 2018. Electricity 

Supply, Disposition, Prices, and Emissions. 

Reference Case. Department of Energy, Energy 

Information Administration. 

the agency in light of the court-ordered 

deadline to propose an action fully 

addressing the good neighbor obligation 

for the 2008 ozone NAAQS for several 

states by June 30, 2018, and to take final 

action by December 6, 2018.111 In light 

of the resource and time constraints, the 

EPA determined that it was appropriate 

to select a single future analytic year 

that was most likely to permit the 

agency to fulfill its obligation to 

determine whether any good neighbor 

requirements remain unfulfilled for the 

2008 ozone NAAQS. Accordingly, the 

EPA reasonably chose to only model air 

quality in 2023 in order to target the 

control strategies that were most likely 

to impact downwind air quality. Cf. 

Sierra Club v. Johnson, 444 F. Supp. 2d 

46, 53 (D.D.C. 2006) (explaining that 

statutory deadlines in the Clean Air Act 

indicate that Congress intended 

agencies to prioritize timeliness over 

perfection). 

If the EPA had analyzed air quality in 

2020 instead of 2023, in order to strictly 

adhere to the attainment dates under the 

Act, as the commenters suggest, and 

identified downwind air quality 

problems in that year, the agency would 

not have been able to identify any costeffective emission reductions that could 

be implemented in that year. As 

explained earlier, the EPA has already 

addressed control strategies that could 

be implemented in the short term and 

that were considered to be costeffective. If the EPA issued a rule that 

focused instead only on the limited 

amount of emission reductions 

potentially achievable from additional 

control strategies feasible to implement 

by 2020—i.e., from the optimization of 

SNCR—the EPA is not aware of any 

information that would change its 

analysis of the cost-effectiveness of 

those controls, and accordingly believes 

that those controls would be unlikely to 

be implemented. Under these 

circumstances, any downwind air 

quality problems projected in 2020 

would remain. 

The EPA believes that a more 

substantial amount of emission 

reductions is likely achievable from the 

implementation of new controls (SCR 

and SNCR) at EGUs or from the 

implementation of various control 

strategies at non-EGUs, but its analysis 

shows that such control strategies could 

not be feasibly implemented by the 2020 

attainment date (or, indeed, for several 

years thereafter). Thus, if the EPA had 

relied on modeling for 2020 to identify 

downwind air quality issues, as the 

commenter urges, the EPA could not 

ensure that implementation of the 

emission reductions achievable with 

these control strategies several years 

later would be justified by continued 

downwind air quality problems (a 

concern justified by the results of the 

2023 modeling cited in this action). 

NOX emissions levels are expected to 

decline in the future through the 

combination of the implementation of 

existing local, state, and federal 

emission reduction programs and 

changing market conditions for 

generation technologies and fuels.112

Therefore, were the EPA to evaluate 

downwind ozone concentrations and 

upwind state linkages in a future year 

that precedes the date when actual 

compliance is anticipated (i.e., the 

timeframe within which additional 

control strategies can feasibly be 

implemented), the EPA could not 

ensure that the emission reductions will 

be ‘‘necessary to achieve attainment’’ in 

any downwind area by the time they 

were implemented. EME Homer City, 

134 S. Ct. at 1608. While the Supreme 

Court indicated that the EPA was 

entitled to ‘‘leeway,’’ id. at 1609, the 

EPA does not believe it would have 

been consistent with the EME Homer 

City decisions to impose substantially 

greater emission reductions several 

years after the modeling year used to 

identify downwind air quality problems 

without ensuring that such reductions 

would be necessary by the time that 

they can reasonably be anticipated to be 

implemented, i.e., without ensuring that 

they would not over-control relative to 

downwind air quality. Such an 

approach would only replicate the 

circumstances the D.C. Circuit found 

impermissible in CSAPR in EME Homer 

City II. 

Thus, if the EPA were to rely on only 

air quality modeling for 2020, the EPA 

would be faced with a choice between 

the possibility of under-control if it 

promulgated a rule focusing only on the 

cost-effective emission reductions 

achievable by the 2020 ozone season, 

and the potential for a significant 

amount of over-control if it promulgated 

a rule requiring substantial emission 

reductions to be implemented several 

years after any downwind ozone 

problems projected in 2020. Given the 

limited availability of potential 

emission reductions by the 2020 

attainment date, the EPA instead has 

reasonably chosen to model downwind 

air quality in a year associated with a 

compliance timeframe consistent with 

the NOX control strategies anticipated to 

result in more meaningful 

improvements in downwind areas. 

While the EPA is aware of the 

modeling conducted by the OTC for 

2020, the EPA does not believe that this 

information demonstrates that the EPA’s 

decision to model 2023 was 

unreasonable. As already noted, the 

EPA has already implemented all costeffective control strategies that could be 

implemented in the near term under the 

CSAPR Update, and does not believe 

additional cost-effective control 

strategies can be implemented by the 

2020 ozone season, even if the modeling 

did appropriately identify downwind 

air quality problems in that year. 

Moreover, despite asserting that the 

OTC used ‘‘EPA-approved methods’’ for 

the modeling, the commenter did not 

provide sufficient information regarding 

the inputs and methodology for the 

modeling such that the EPA could rely 

on the OTC modeling for purposes of 

this action. For the same reasons 

described more fully below in section 

III.C.4 with regard to the OTC’s 2023 

projections, the EPA also cannot 

conclude that the projections are 

reliable for all of the areas identified as 

having apparent projected air quality 

problems in 2020. Without reliable 

projected design values, the EPA cannot 

appropriately determine whether 

emission reductions implemented in 

that year (even assuming, contrary to 

EPA’s conclusions in this action, that 

any additional control strategies that 

could be implemented in that year 

would be both feasible and costeffective) would under- or over-control 

upwind state emissions. 

It is worth noting that the EPA was 

not aware at the time that it selected the 

2023 modeling year that the results 

would show no remaining air quality 

problems in the East. The EPA certainly 

anticipated that ozone concentrations 

would improve over time relative to the 

2017 modeling conducted for the 

CSAPR Update. However, the EPA had 

previously conducted modeling for 

2023, released in Janaury 2017 and 

discussed further in section III.C, that 

showed at least one potential 

maintenance receptor in Tarrant 

County, Texas. See Notice of Data 


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113Although the modeling was conducted to 

evaluate air quality relative to the more stringent 

2015 ozone NAAQS, the data show that the 

maximum design value for the Tarrant County, 

Texas monitor was also expected to exceed the 2008 

ozone NAAQS. 

Availability, 82 FR 1733, 1737.113 The 

EPA accepted comments on this 

modeling and made adjustments to the 

emission inventories and other 

modeling inputs before running the 

model for 2023 again for purposes of 

this action after determining that 2023 

would also be an appropriate year to 

evaluate for purposes of the remaining 

good neighbor obligations for the 2008 

ozone NAAQS. It was only upon 

completing this additional modeling run 

that the EPA could conclude that, for 

the purposes of these good neighbor 

obligations, it projected no further air 

quality problems in 2023. 

Comment: One commenter contends 

that the EPA’s approach to determining 

that 2023 is the appropriate analytic 

year is a reversal of past agency 

interpretation regarding the four-step 

CSAPR framework. The commenter 

states that the CSAPR Update, though 

only a partial remedy under the good 

neighbor provision, acknowledged the 

2018 attainment deadline for Moderate 

nonattainment areas. The commenter 

asserts that here, in contrast, the EPA 

has begun by assessing the feasibility of 

installing an arbitrarily narrow set of 

new controls without regard to the next 

attainment date. The commenter 

contends that this approach turns the 

CSAPR framework on its head, 

unreasonably changing agency 

interpretation without explanation and 

in violation of the Act. 

The commenter notes that control 

feasibility has played a role in the past 

regional ozone rules, but contends that 

it cannot override the obligation to 

prohibit pollution that prevents 

attainment and maintenance of the 

standards, nor can it displace the 

attainment deadlines. The commenter 

further asserts that when the EPA has 

considered feasibility in analyzing 

ozone-related good neighbor obligations 

since the North Carolina decision, it has 

not done so in the context of selecting 

an analytic year, but in apportioning the 

necessary emission reductions. The 

commenter explains that, in the original 

CSAPR, feasibility of installing SO2

controls did contribute to selecting two 

future analytic years, but contends that 

the rule linked both analytic years to 

attainment deadlines, including analysis 

of the next upcoming attainment year. 

Response: In the CSAPR Update, the 

EPA focused its analysis on the 

upcoming attainment date and the 

limited control strategies that could be 

implemented within that timeframe 

with the explicit understanding that 

such a limited analysis was unlikely to 

provide a sufficient basis to determine 

that the good neighbor obligation was 

fully addressed for all states for the 2008 

ozone NAAQS. Here, the EPA is 

obligated to conduct an analysis that 

fully addresses the good neighbor 

provision and thus has selected a future 

analytic year to coincide with the 

timeframe in which emission reductions 

most likely to address that obligation 

could be implemented, rather than 

selecting a year in which few emission 

reductions could be implemented. 

Selection of an analytic year associated 

with anticipated future compliance is 

entirely consistent with the EPA’s fourstep framework as applied in prior 

rulemakings. See, e.g., NOX SIP Call, 63 

FR 57450 (using the anticipated 2007 

compliance year for its analysis); CAIR, 

70 FR 25241 (using the years 2009 and 

2010, the anticipated compliance years 

for the ozone and PM2.5 NAAQS, 

respectively); CSAPR, 76 FR 48211 

(using the 2012 compliance year); 

CSAPR Update, 81 FR 74537 (using the 

2017 compliance year). 

The commenter is also incorrect to 

suggest that the EPA’s approach is 

inconsistent with the original CSAPR 

rulemaking, which addressed good 

neighbor obligations for the 1997 ozone 

NAAQS. While it is true that the EPA 

considered attainment dates in its 

CSAPR analysis, the commenter fails to 

acknowledge that the EPA considered 

the entire suite of attainment dates for 

the relevant NAAQS, including the 

‘‘maximum’’ future attainment dates 

that CSAPR’s later compliance phase 

was intended to address. 76 FR 48277– 

78. Thus, in establishing two phases of 

compliance in 2012 and 2014, the EPA 

considered attainment dates for the 

ozone NAAQS between 2007 and 2024, 

and for the PM2.5 NAAQS, the EPA 

considered attainment dates ranging 

from 2010 to 2019. Id. Moreover, as the 

commenter acknowledges, the EPA 

established two compliance phases in 

CSAPR based on the feasibility of 

implementing certain control strategies. 

Id. at 48278. In the earlier phase, the 

EPA anticipated that the covered EGUs 

would undertake more easily 

implemented control strategies that 

could be implemented in the short term, 

including optimization of existing 

controls, installation of relatively simple 

NOX controls, and generation shifting, 

see id. at 48279, the same control 

strategies already considered and 

implemented for the 2008 ozone 

NAAQS in the CSAPR Update. The EPA 

determined that a later compliance 

phase was justified based on the need 

for more time to feasibly implement 

other controls strategies. Id. at 48278 

(‘‘Given the time needed to design and 

construct scrubbers at a large number of 

facilities, EPA believes the 2014 

compliance date is as expeditious as 

practicable for the full quantity of SO2

reductions necessary to fully address 

the significant contribution to 

nonattainment and interference with 

maintenance.’’). The EPA’s approach to 

the 2008 ozone NAAQS has been 

consistent with ths earlier approach, 

except that the EPA has evaluated these 

two categories of control strategies in 

two separate actions (i.e., the CSAPR 

Update and this action) rather than in a 

single rulemaking specifically to ensure 

that the first phase of reductions could 

be implemented as soon as possible. 

To the extent that the commenters 

suggest that the EPA chose an earlier 

analytic year in prior rulemakings, the 

EPA notes that it has not done so in all 

rulemakings. In the NOX SIP Call, the 

EPA evaluated air quality in 2007, nine 

years after the rule was promulgated. 63 

FR 57377 (October 27, 1998). In CAIR, 

which was promulgated in 2005, the 

EPA evaluated air quality in 2009 and 

2010, for the ozone and PM2.5 NAAQS, 

respectively. 70 FR 25241 (May 12, 

2005). Thus, the EPA’s approach in this 

action is not inconsistent with these 

prior actions. Although the EPA 

evaluated relatively more near-term air 

quality in CSAPR and CSAPR Update, 

the EPA expected that certain costeffective control strategies could be 

implemented in the near term in those 

actions. Here, the EPA has already 

analyzed and implemented those costeffective control strategies that could be 

implemented quickly to address the 

2008 ozone NAAQS through the CSAPR 

Update. Accordingly, any further 

emission reductions that may be 

required to address the 2008 ozone 

NAAQS would necessarily be 

implemented through control strategies 

that cannot be implemented in the near 

term and require a longer period for 

implementation. 

C. Air Quality Analysis 

In this section, the agency describes 

the air quality modeling performed, 

consistent with step 1 of the framework 

described in section III.A, to identify 

locations where it expects 

nonattainment or maintenance problems 

with respect to the 2008 ozone NAAQS 

in the 2023 analytic year. This section 

includes information on the air quality 

modeling platform used in support of 

the final determination with a focus on 

the base year and future base case 

emission inventories. The June 2018 Air 


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114And available online at https://www.epa.gov/ 

airmarkets/proposed-csapr-close-out. 

115Memorandum from Stephen D. Page, Director, 

Office of Air Quality Planning and Standards, to 

Regional Air Division Directors, Regions 1–10, 

Supplemental 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) (Oct. 27, 2017), available at https:// 

www.epa.gov/airmarkets/october-2017-memo-andsupplemental-information-interstate-transport-sips2008-ozone-naaqs. 

116U.S. Environmental Protection Agency, 2014. 

Modeling Guidance for Demonstrating Attainment 

of Air Quality Goals for Ozone, PM2.5, and Regional 

Haze, Research Triangle Park, NC, available at 

http://www.epa.gov/ttn/scram/guidance/guide/ 

Draft_O3-PM-RH_Modeling_Guidance-2014.pdf. 

117CAMx v6.40 was the most recent public 

release version of CAMx at the time the EPA 

updated its modeling in fall 2017. Comprehensive 

Air Quality Model with Extensions version 6.40 

User’s Guide. Ramboll Environ, December 2016, 

available at http://www.camx.com/. 

118As recommended in the modeling guidance, 

the acceptability of model performance was judged 

by considering the 2011 CAMx performance results 

in light of the range of performance found in recent 

regional ozone model applications. These other 

modeling studies represent a wide range of 

modeling analyses that cover various models, 

model configurations, domains, years and/or 

episodes, and chemical mechanisms. Overall, the 

ozone model performance results for the 2011 

CAMx simulations are within the range found in 

other recent peer-reviewed and regulatory 

applications. The model performance results, as 

described in the AQM TSD, demonstrate that the 

predictions from the 2011 modeling platform 

correspond to measured data in terms of the 

magnitude, temporal fluctuations, and spatial 

differences for 8-hour daily maximum ozone. 

Quality Modeling Technical Support 

Document (AQM TSD) in the docket for 

this action contains more detailed 

information on the air quality modeling 

for 2023 used to support the final 

determination.114

In addition to the proposal, 83 FR 

31915 (July 10, 2018), the EPA provided 

an additional opportunity to comment 

on the air quality modeling platform 

and air quality modeling results that are 

used in this determination when it 

published a Notice of Data Availability 

(82 FR 1733) on January 6, 2017, which 

provided the preliminary modeling 

results for the 2023 analytic year. 

Specifically, in the NODA the EPA 

requested comment on the data and 

methodologies related to the 2011 and 

2023 emission inventories and the air 

quality modeling to project 2023 ozone 

concentrations and ozone contributions. 

While the EPA issued this NODA to 

provide information to assist state 

interstate transport planning for the 

2015 ozone NAAQS (which is set at 70 

ppb), the modeling approaches and 

future year projection methods were 

also applicable to the 2008 ozone 

NAAQS (set at 75 ppb). In fact, 

commenters explicitly commented on 

these methods with respect to the 2008 

ozone NAAQS. The EPA considered 

comments received on the NODA in the 

development of the air quality modeling 

analysis used for proposal. As discussed 

below and in the Response to Comments 

(RTC) in the docket for this action, we 

have considered additional comments 

on emission inventories and air quality 

modeling submitted in response to the 

proposal for this action for this final 

determination. However, the EPA did 

not find that any of these comments 

raised concerns with the modeling 

discussed at proposal such that 

additional air quality modeling was 

merited. Accordingly, the emission 

inventories and modeling discussed in 

the following sections is the same 

information discussed in the EPA’s 

proposed action. 

1. Overview of Air Quality Modeling 

Platform 

The EPA performed nationwide 

photochemical modeling for 2023 to 

identify nonattainment and 

maintenance receptors relevant for the 

2008 ozone NAAQS. For this action, the 

EPA performed air quality modeling for 

two emissions scenarios: (1) A 2011 

base year; and (2) the 2023 analytic year 

(i.e., a business-as-usual scenario in 

2023: One without any additional 

interstate ozone transport requirements 

beyond those imposed by the CSAPR 

Update). The modeling results for 2023 

presented here were originally released 

to the public with an accompanying 

memorandum on October 27, 2017.115

The 2011 base year has previously 

been used to support the CSAPR Update 

proposal and final rule. The EPA chose 

to continue using 2011 as the base year 

because when EPA’s analyses 

commenced, 2011 was the most recent 

emissions modeling platform available 

that included future year projected 

inventories needed for transport 

analyses. Using 2011 as a base year also 

remains appropriate from the standpoint 

of good modeling practice. The 

meteorological conditions during the 

summer of 2011 were generally 

conducive for ozone formation across 

much of the U.S., particularly the 

eastern U.S. As described in the AQM 

TSD, the EPA’s guidance for ozone 

attainment demonstration modeling, 

hereafter referred to as the modeling 

guidance, recommends modeling a time 

period with meteorology conducive to 

ozone formation for purposes of 

projecting future year design values.116

The EPA therefore believes that 

meteorological conditions and 

emissions during the summer of 2011 

provide an appropriate basis for 

projecting 2023 ozone concentrations. 

For this rule, the EPA used the 

Comprehensive Air Quality Model with 

Extensions (CAMx) version 6.40 117 to 

simulate pollutant concentrations for 

the 2011 base year and the 2023 future 

year scenarios. This version of CAMx 

was the most recent publicly available 

version of this model at the time that the 

EPA performed air quality modeling for 

this final rule. CAMx is a grid cellbased, multi-pollutant photochemical 

model that simulates the formation and 

fate of ozone and fine particles in the 

atmosphere. The CAMx model 

applications were performed for a 

modeling region (i.e., modeling domain) 

that covers the contiguous 48 United 

States, the District of Columbia, and 

adjacent portions of Canada and Mexico 

using grid cells with a horizontal 

resolution of 12 km x 12 km. A map of 

the air quality modeling domain is 

provided in the AQM TSD. 

The 2011-based air quality modeling 

platform includes 2011 base year 

emissions, 2023 future year projections 

of these emissions, and 2011 

meteorology for air quality modeling 

with CAMx. In the remainder of this 

section, the EPA provides an overview 

of the 2011 and 2023 emission 

inventories and the methods for 

identifying nonattainment and 

maintenance receptors along with a list 

of the receptors in the U.S. that EPA 

projected would have nonattainment 

and maintenance air quality problems in 

2023 (in the business-as-usual scenario). 

To ensure the reliability of its 

modeling results, the EPA conducted an 

operational model performance 

evaluation of the 2011 modeling 

platform by comparing the 8-hour daily 

maximum ozone concentrations 

predicted during the May through 

September ozone season to the 

corresponding measured concentrations 

in 2011. This evaluation generally 

followed the approach described in the 

modeling guidance. Details of the model 

performance evaluation are described in 

the AQM TSD. The model performance 

results indicate that the 8-hour daily 

maximum ozone concentrations 

predicted by the 2011 CAMx modeling 

platform generally reflect the 

corresponding magnitude of observed 8- 

hour ozone concentrations on high 

ozone days in the 12-km U.S. modeling 

domain. These results provide 

confidence in the ability of the 

modeling platform to provide a 

reasonable projection of expected future 

year ozone concentrations and 

contributions.118


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119This TSD is also available in the docket for 

this final action and at https://www.epa.gov/airemissions-modeling/additional-updates-2011-and2023-emissions-version-63-platform-technical. 

120The initial modeling platform based on the 

2011 National Emissions Inventory (NEI) was first 

released for public comment in November 2013 

through a NODA (78 FR 70935). In developing the 

CSAPR Update, the EPA subsequently updated the 

base year 2011 emission inventory as well as future 

year inventories for that rulemaking and took 

comment on those updates. Notice of Data 

Availability, 79 FR 2437 (January 2014); CSAPR 

Update proposal, 80 FR 46271 (August 2015); 

CSAPR Update final, 81 FR 74527 (September 

2016). Technical support documents are available 

for each iteration of the inventories on EPA’s 

emissions modeling website: https://www.epa.gov/ 

air-emissions-modeling/2011-version-6-airemissions-modeling-platforms. 

121Biogenic emissions and emissions from 

wildfires and prescribed fires were held constant 

between 2011 and 2023 because: (1) These 

emissions are tied to 2011 meteorological 

conditions and (2) the focus of this action is on the 

contribution from anthropogenic emissions to 

projected ozone nonattainment and maintenance. 

122The EPA uses the U.S. EIA Form 860 as a 

source for upcoming controls, retirements, and new 

units. 

123Available at https://www.epa.gov/airemissions-modeling/2011-version-63-platform. 

124Also see the Ozone Transport Policy Analysis 

Final Rule Technical Support Document. EPA. 

August 2016. Available at https://www.epa.gov/ 

sites/production/files/2017-05/documents/ozone_

transport_policy_analysis_final_rule_tsd.pdf. 

125For more information on the 2011 National 

Emissions Inventory version 2, see https://

www.epa.gov/air-emissions-inventories/2011- 

national-emissions-inventory-nei-technical-supportdocument. 

2. Emission Inventories 

The EPA developed emission 

inventories for this rule, including 

emissions estimates for EGUs, non-EGU 

point sources, stationary nonpoint 

sources, onroad mobile sources, 

nonroad mobile sources, wildfires, 

prescribed fires, and biogenic emissions. 

The EPA’s air quality modeling relies on 

this comprehensive set of emission 

inventories because emissions from 

multiple source categories are needed to 

model ambient air quality and to 

facilitate comparison of model outputs 

with ambient measurements. 

To prepare the emission inventories 

for air quality modeling, the EPA 

processed the emission inventories 

using the Sparse Matrix Operator Kernel 

Emissions (SMOKE) Modeling System 

version 3.7 to produce the gridded, 

hourly, speciated, model-ready 

emissions for input to the CAMx air 

quality model. Additional information 

on the development of the emission 

inventories and on datasets used during 

the emissions modeling process for this 

final rule is provided in the October 

2017 Technical Support Document 

‘‘Additional Updates to Emission 

Inventories for the Version 6.3, 2011 

Emissions Modeling Platform for the 

Year 2023’’ (Emissions Modeling 

TSD).119

As noted earlier, the emission 

inventories, methodologies, and data 

used for the air quality modeling 

discussed in this final rule are the same 

as the inventories discussed at proposal 

as no new modeling was performed 

following the proposal. The inventories 

incorporate comments received on the 

January 2017 NODA along with 

improved data and methods that became 

available after the NODA modeling was 

completed. The inventories are 

documented in the Emissions Modeling 

TSD. The January 2017 NODA itself was 

developed after taking into account the 

several iterations of comments on the 

data and methods used in the 2011 

emissions modeling platform.120

As noted above, the EPA uses 

emissions data from the year 2011 in its 

base year air quality modeling. The 2011 

NOX and SO2 EGU emissions are based 

primarily on reported data from 

continuous emissions monitoring 

systems (CEMS). Other EGU pollutants 

in the 2011 emission inventories are 

estimated using emissions factors and 

annual heat input data reported to the 

EPA. For EGUs without CEMS, the EPA 

used data submitted to the National 

Emissions Inventory (NEI) by the states. 

The 2011 inventories also include some 

updates to 2011 EGU stack parameters 

and emissions made in response to 

comments on the January 2017 NODA. 

For more information on the details of 

how the 2011 EGU emissions were 

developed and prepared for air quality 

modeling, see the Emissions Modeling 

TSD. 

In developing the 2023 emission 

inventory, the EPA did not incorporate 

any new interstate transport emission 

reductions beyond the CSAPR Update, 

but the 2023 projected emission 

inventory does reflect expected changes 

in activity and emission reductions from 

on-the-books actions, including planned 

emission control installations and 

promulgated federal measures that affect 

anthropogenic emissions. The emission 

inventories for air quality modeling 

include some emissions categories that 

are held constant between the base and 

future years, such as biogenic emissions 

and emissions from agricultural, wild, 

and prescribed fires.121 The emission 

inventories used for Canada were 

received from Environment and Climate 

Change Canada in April 2017 and were 

provided for the years 2013 and 2025. 

This was the first time that future year 

projected inventories for Canada were 

provided directly by Environment and 

Climate Change Canada and the new 

inventories are thought to be an 

improvement over inventories projected 

by EPA. The EPA used the Canadian 

emission inventories without adjusting 

the emissions to the represented year 

because the EPA lacks specific 

knowledge regarding Canadian 

emissions trends and because the 

interval of years (i.e., 12) was the same 

as that used for the U.S. modeling 

which relied on a 2011 to 2023 interval. 

For Mexico, onroad mobile source 

inventory data were based on 2011 and 

2023 runs of MOVES-Mexico. For area, 

nonroad, and point source emissions in 

Mexico, EPA used the Inventario 

Nacional de Emisiones de Mexico using 

2018 and 2025 data projections to 

interpolate 2023 estimates. 

As noted in the October memo, the 

EPA projected EGU emissions for the 

2023 emission inventory based on an 

approach that combines the latest 

reported operational data with known 

and anticipated fleet and pollution 

controls changes. The EPA begins with 

the most recent reported ozone season 

data available at the time of the EPA’s 

analysis—in this case, 2016 SO2 and 

NOX data from units reporting under the 

Acid Rain and CSAPR programs under 

40 CFR part 75. The EPA then updated 

the 2016 reported emissions with unitspecific adjustments to account for 

upcoming announced retirements, postcombustion control retrofits, coal-to-gas 

conversions, combustion controls 

upgrades, new units, and on-the-books 

reductions such as CSAPR Update 

compliance, state rules, and Best 

Available Retrofit Technology (BART) 

requirements under the regional haze 

program of the CAA.122 The EPA 

implemented reductions associated with 

the CSAPR Update in its emission 

projection, because the 2016 reported 

data did not reflect the implementation 

of this rule, by assuming each SCRcontrolled unit in the CSAPR Update 

region not already emitting at or below 

0.10 lb/mmBtu would do so beginning 

in 2017. For emissions from EGUs not 

reporting under 40 CFR part 75, the EPA 

largely relied on unadjusted 2011 NEI 

data for its 2023 assumptions.123 We 

note that the EPA’s approach to 

projecting 2023 EGU emissions is 

consistent with the approach the EPA 

used in the CSAPR Update to project the 

future EGU emissions baseline from 

which to estimate reduction potential. 

81 FR 74543.124 Additional details 

about the EPA’s future year EGU 

emissions projections are provided in 

the Emissions Modeling TSD. 

Non-EGU point source emissions in 

the 2011 inventory are generally based 

on the 2011 NEI version 2.125 However, 


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the NEI emission inventories must be 

processed into a format that is 

appropriate for the air quality model to 

use. Details on the development and 

processing of the emissions for 2011 are 

available in the Emissions Modeling 

TSD. The TSD also describes the EPA’s 

methodology for developing the nonEGU emissions for the 2023 emission 

inventory. Projection factors and 

percent reductions used to estimate 

2023 emissions in this final rule reflect 

comments received through the January 

2017 NODA, along with emission 

reductions due to national and local 

rules, control programs, plant closures, 

consent decrees, and settlements. The 

Emissions Modeling TSD contains 

details on the factors used and on their 

respective impacts on the emission 

inventories. 

As noted in the proposal, the EPA 

updated its methodology for estimating 

point and nonpoint 2023 emissions 

from the oil and gas sector after the 

release of the January 2017 NODA. The 

projection factors used in the updated 

2023 oil and gas emission inventory 

incorporate state-level factors based on 

historical growth from 2011–2015 and 

region-specific factors that represent 

projected growth from 2015 to 2023. 

The 2011–2015 state-level factors were 

based on historical state oil and gas 

production data published by the U.S. 

Department of Energy’s Energy 

Information Administration (EIA), while 

the 2015–2023 factors are based on 

projected oil and gas production in 

EIA’s 2017 Annual Energy Outlook 

(AEO) Reference Case without the Clean 

Power Plan for the six EIA supply 

regions. The 2017 AEO was the latest 

available at the time the modeling was 

performed. Details on the revised 

methodology that the EPA used to 

project oil and gas emissions to 2023, as 

well as changes to the base year 2011 

and future year 2023 emission 

inventories for other sectors, can be 

found in the Emissions Modeling TSD. 

The EPA developed the onroad 

mobile source emissions for both the 

2011 and 2023 inventories using the 

EPA’s Motor Vehicle Emissions 

Simulator, version 2014a 

(MOVES2014a). The agency computed 

these emissions within SMOKE by 

multiplying the MOVES-based 

emissions factors with activity data 

appropriate to each inventory year. 

MOVES2014a reflects projected changes 

to fuel usage and onroad mobile control 

programs finalized as of March 2014, 

which include emission reductions 

expected to occur into the future. 

Therefore, for the 2011 inventory, those 

rules that were in effect in 2011 are 

reflected at a level that corresponds to 

the extent to which each rule had 

penetrated the fleet and fuel supply by 

that year, and similarly for the 2023 

inventory. Local control programs such 

as the California Low Emission Vehicle 

(LEV) III program, also implemented in 

states other than California that have 

adopted California’s program pursuant 

to CAA section 177, are included in the 

onroad mobile source emissions. 

Activity data for onroad mobile sources, 

such as the expected vehicle miles 

traveled in 2023, were projected for 

future year using trends identified in 

AEO 2016. 

The commercial marine category 3 

vessel (‘‘C3 marine’’) emissions in the 

2011 emission inventory for this rule are 

equivalent to those in the 2011NEIv2 

with the inclusion of updated emissions 

for California. These emissions reflect 

reductions associated with the 

Emissions Control Area proposal to the 

International Maritime Organization 

control strategy (EPA–420–F–10–041, 

August 2010); reductions of NOX, VOC, 

and CO emissions for new C3 engines 

that went into effect in 2011; and fuel 

sulfur limits that went into effect as 

early as 2010. The cumulative impacts 

of these rules, which will achieve 

additional reductions through 2023, are 

incorporated in the 2023 projected 

emissions for C3 marine sources. For 

this modeling, the larger C3 marine 

sources are treated with plume rise, 

thereby putting the emissions into 

model layers higher than ground-level. 

This was done because the ships have 

stacks that release emissions higher than 

the 20-meter threshold for the groundlevel layer in the air quality model. The 

height at which the emissions are 

inserted into the model impacts how the 

emissions are transported within the 

model. The emissions from the smaller 

category 1 (C1) and category 2 (C2) 

vessels are still released into the 

ground-level layer of the model. 

To develop the nonroad mobile 

source emission inventories other than 

C3 marine for the modeling platform, 

the EPA used monthly, county, and 

process-level emissions output from the 

National Mobile Inventory Model 

(NMIM) (http://www.epa.gov/otaq/ 

nmim.htm). The nonroad mobile 

emissions control programs include 

reductions in emissions from 

locomotives, diesel engines, and marine 

engines, along with standards for fuel 

sulfur content and evaporative 

emissions. A comprehensive list of 

control programs included for mobile 

sources is available in the Emissions 

Modeling TSD. 

The emissions for stationary nonpoint 

sources in the 2011 emission inventory 

are generally derived from the 2011 NEI 

version 2. For more information on 

nonpoint source emissions in the 2011 

emission inventory, see the Emissions 

Modeling TSD and the 2011NEIv2 TSD. 

2023 emissions for stationary nonpoint 

sources were projected using a variety of 

factors, including AEO 2017 projections 

for 2023 and state projection factors 

using EIA data from 2011–2015. The 

2023 emission inventory in the EPA’s 

proposal and this final rule also 

incorporate information from states 

about projected control measures or 

changes in nonpoint source emissions 

provided in comments to the January 

2017 NODA. These changes were 

limited and are discussed in the 

Emissions Modeling TSD. 

Comment: While some commenters 

agreed with the reasonableness of the 

EPA’s projections, others contend that 

the EPA’s EGU emission projections are 

unreasonable for a variety of reasons. 

These commenters assert that actual 

2023 emissions may be higher than 

modeled due to low CSAPR Update 

allowance prices or natural gas price 

uncertainty. They suggest that the 0.10 

lb/mmBtu average used by EPA for SCRcontrolled units covered by the CSAPR 

Update is not reasonable because some 

units may operate at higher levels in the 

future, and they also suggest that EPA 

should have incorporated impacts of the 

proposed repeal of the Clean Power Plan 

and the proposed Affordable Clean 

Energy (ACE) rule into its emissions 

projections. 

Response: The EPA disagrees with the 

suggestion that its 2023 EGU emission 

projections and the underlying 

methodology to generate those 

projections are unreasonable. As with 

all projections, there is inherent 

uncertainty, but with respect to EGU 

NOX emissions, the EPA’s 2023 

projections likely reflect a more 

conservative (i.e., higher) NOX

emissions estimate than comparable 

alternative methods for projecting future 

EGU emissions. As explained above, the 

EPA’s 2023 EGU emissions projections 

used reported 2016 data, adjusting that 

data based only on currently known 

changes in the power sector and a 

change in emission rate to reflect 

implementation of the CSAPR Update 

after 2017. As such, the EPA’s approach 

does not account for changes that would 

be estimated to occur due to economic 

and other environmental policy factors. 

Trends in historic emissions data and 

emission projections using a variety of 

methods and models suggest that 

inclusion of these factors would likely 

further reduce future NOX emission 

projections. To illustrate the potential 

for additional NOX reductions when 

considering further factors, we note that 


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126EIA 2018 Annual Energy Outlook, Reference 

Case and High Oil and Gas Resource and 

Technology side case. Table 8 ‘‘Electricity Supply, 

Disposition, Prices, and Emissions,’’ available at 

https://www.eia.gov/outlooks/aeo/. 

127 IPM Version 6—Initial Run, available at 

https://www.epa.gov/airmarkets/clean-air-marketspower-sector-modeling. 

128EPA–HQ–OAR–2018–0225–0042 at 98; EPA– 

HQ–OAR–2009–0491–4512 (RTC at 4). 

129See 2016 Program Progress—Cross-State Air 

Pollution Rule and Acid Rain Program available at 

https://www3.epa.gov/airmarkets/progress/reports/ 

index.html. 

nationwide 2023 EGU NOX emission 

projections using various modeling 

approaches estimate lower NOX

emission futures than the methodology 

EPA applied here. The EPA’s EGU 

emissions projection methodology 

estimates that 2023 NOX emissions will 

be 20% below 2016 levels whereas EIA 

estimates that 2023 NOX emissions will 

be 21% to 32% below 2016 levels and 

EPA’s Integrated Planning Model 

estimates that 2023 NOX emissions will 

be 28% below 2016 levels.126 127

The EPA neither intends nor expects 

to be able to predict future emissions 

from each of thousands of EGUs.128 And 

it does not expect each of these SCRcontrolled units to emit at the fleet-wide 

technology-specific average emission 

rate that it uses in its EGU emissions 

projections. Some of the units will overperform and some of the units will 

under-perform in comparison to this 

average rate, but the average rate 

nevertheless reflects both a reasonable 

compliance pathway in response to the 

CSAPR Update and a reasonable fleet 

average for that compliance pathway. 

Predicting each unit’s individual 

emission rate is an exercise in increased 

uncertainty, and the use of an average 

technology-specific fleet emission rate 

for each unit reduces that uncertainty. 

Moreover, in a trading program with 

state-specific caps, sources are 

permitted the flexibility to emit in a 

variety of ways provided the state and 

regional caps are met. The compliance 

success is not gauged on unit-level 

operation and emissions, but rather state 

and regional operation and emission 

levels. (The same holds true for gauging 

the reasonableness and accuracy of 

projections for such programs.) This 

compliance mechanism promotes more 

cost-effective attainment of the 

emissions and air quality goals. 

Therefore, it is plausible—and entirely 

consistent with EPA projections—that 

sources in each state would find an 

alternative compliance pathway that 

achieves commensurate emission 

reductions in equally relevant parts of 

the upwind airshed. 

The EPA’s EGU assumptions for 2023 

reflected ozone-season emission levels 

that were approximately 10 percent 

lower than the CSAPR Update budgets. 

2017 ozone-season data reflected 

emissions that were already 7 percent 

below the CSAPR Update budgets, 

reflecting a 21 percent drop from the 

prior year, a pace of reduction that 

would, if continued, put actual 

emissions well below 2023 

assumptions. Preliminary 2018 data 

suggest continuing reductions, and 

indicate that the CSAPR Update region 

is already in 2018 emitting at or near the 

EPA-assumed 2023 emission level. In 

other words, the emission levels that 

commenters suggest are unreasonable 

for 2023 may well already have been 

achieved or nearly achieved in 2018— 

five years ahead of the analytic year. In 

order for emissions in 2023 to be at the 

levels commenters prefer that the EPA 

model (e.g., only emission levels that 

can be ensured via enforceable limits), 

a decade-long decline in ozone-season 

emissions would have to not only cease 

but reverse. Moreover, this would have 

to occur during a time period where 

significantly more high-emitting coal 

generation capacity has announced 

plans to retire and significantly more 

zero- or lower-emitting generation 

capacity is expected to come online. In 

particular, since the EPA in 2017 made 

EGU projections for 2023 (in which the 

EPA only assumed retirements that had 

already been planned and announced at 

the time it made the projections), many 

additional high emitting coal units have 

announced their plans to retire by 2023. 

5.9 gigawatts (GW) of coal capacity 

retirements were announced and 

planned for 2019–2022 based on the 

June 2017 EIA 860m Form, but that 

same form a year later (June 2018 EIA 

Form 860m) shows 10.2 GW of coal 

retirements for that same period, 

reflecting a near doubling of coal 

retirement announcements occurring 

over a one-year period. For instance, 

Conesville Units 4, 5, and 6 in Ohio 

have announced their retirement prior 

to 2023. The EPA in its 2017 projections 

had assumed these units would be 

operating and collectively emitting 

1,502 tons of NOX in the 2023 ozone 

season. These additional retirements 

announced subsequent to the EPA’s 

analysis further bolster the conclusion 

that the EPA’s emission estimates are 

conservative (i.e., that they may 

overpredict 2023 emissions). The 

magnitude of coal retirements like this, 

announced after the EPA’s analysis, but 

scheduled to occur prior to 2023, 

suggests the emissions trend will 

continue downward. Moreover, the 

commenters’ assertion that an assumed 

increase would be a more reasonable 

projection is not supported by 

compelling analysis or economic 

modeling: It contradicts the recent 

historical data, the most recent 

announcements on retirements and 

newly built capacity, and the widely 

used power sector models’ outlook for 

2023. The EPA believes, supported by 

the most recent reported data, that its 

2023 EGU projections are reasonable 

and conservative. To the extent that 

actual 2023 emissions may differ from 

these projections, they are more likely to 

be even lower than the assumptions 

used in the EPA’s modeling. 

The utility and the reasonableness of 

the EPA’s EGU projections hinge on 

state-level and regional-level EGU 

emission projections, not projections for 

individual units or groups of units 

within a state. Nonetheless, the EPA 

notes that the assumed average emission 

rate for units with SCR optimization 

potential was quite consistent with the 

observed compliance measures. That is, 

the most recent historical data reported 

by unit operation, discussed in more 

detail in section III.B.2, bears out EPA 

assumptions in the CSAPR Update that 

these units would lower their emission 

rates in response to that rule, as they did 

in fact lower their emission rate 45 

percent in the first year of the program. 

The EPA also disagrees with the 

assertion that that low allowance prices 

necessarily mean that emissions will be 

higher than the EPA’s EGU projections. 

In a scenario where all other elements 

of the power sector and allowance 

market are held constant, the 

commenters observation would likely be 

realized. However, it is the EPA’s 

experience with trading programs that 

those other variables do not remain 

constant over time. In most cases, lower 

allowance prices reflect the market’s 

expectation that future emissions will 

be lower than anticipated, rather than 

higher, as other market forces continue 

to drive down emissions, thus 

decreasing demand for allowances 

authorizing those emissions. The 

commenters’ claim is therefore not 

consistent with observed historical 

emission patterns over successive years 

of an allowance trading program’s 

implementation. For example, regional 

emissions under the Acid Rain Program 

and CSAPR have consistently been 

below the sum of emission budgets, 

despite relatively low allowance 

prices.129 The commenters’ claim is also 

not consistent with forward-looking 

emissions projections in power sector 

models. There are a variety of policy 

and market forces at work beyond 

CSAPR Update allowance prices that are 


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130Regulatory Impact Analysis for the Proposed 

Emission Guidelines for Greenhouse Gas Emissions 

from Existing Electric Utility Generating Units; 

Revisions to Emission Guideline Implementing 

Regulations; Revisions to New Source Review 

Program. EPA. Table ES–8. August 2018. Available 

at https://www.epa.gov/sites/production/files/2018- 

08/documents/utilities_ria_proposed_ace_2018- 

08.pdf. 

131Regulatory Impact Analysis for the Proposed 

Emission Guidelines for Greenhouse Gas Emissions 

from Existing Electric Utility Generating Units; 

Revisions to Emission. Table ES–8. Available at 

https://www.epa.gov/sites/production/files/2018- 

08/documents/utilities_ria_proposed_ace_2018- 

08.pdf. 

132See Table 4.3–19 in EPA Regulatory Impact 

Analysis for EPA’s Final Rulemaking for 2017–2025 

Light-Duty Vehicle Greenhouse Gas Emission 

Standards and Corporate Average Fuel Economy 

Standards (EPA–420–R–12–016, August 2012). 

anticipated to continue to drive 

generation shifting from higher-emitting 

to lower-emitting sources. These 

include changes such as: Sustained, 

lower natural gas prices that make 

lower-emitting natural gas combined 

cycle units more economic to build and 

dispatch; state energy policy and 

technology advancements which have 

made renewable energy (e.g., solar and 

wind) more competitive compared to 

higher-emitting fossil-fuel fired 

generation; and the aging of the coal 

fleet which is leading many companies 

to conclude that a significant number of 

higher-emitting plants are reaching the 

end of their useful economic life. The 

EPA’s experience implementing prior 

allowance trading programs shows that 

emissions from covered sources 

generally trend downwards (regardless 

of allowance price) as time extends 

further from the initial compliance year. 

Both the Acid Rain Program and CSAPR 

SO2 allowance banks grew in 2017 from 

their 2016 levels, indicating that sources 

are collectively adding to the bank by 

emitting below state budgets rather than 

drawing down the bank because of the 

availability of low-cost allowances. This 

supports the EPA’s belief that the 

assumptions underlying its projection of 

2023 ozone-season NOX levels for EGUs 

are reasonable and appropriate. 

To the extent that commenters assert 

that the EPA cannot in its projections 

perfectly predict future natural gas 

prices, the EPA agrees. Projections are 

inherently uncertain, and the EPA 

believes it has made reasonable and 

conservative estimates regarding the 

role of natural gas prices in generation 

shifting and lower future emission 

reductions. The EPA’s EGU projection 

method for this action started with 

existing data and only assumed 

generation shifting in instances where 

retirements were scheduled to occur 

and newly built capacity was scheduled 

to come online. In other words, the 

generation shifting assumed for 2023 

reflects concrete, planned actions. The 

agency’s applied projection method 

would suggest that the EPA’s 2023 

projections are conservative and that 

more, not less, generation shifting is 

likely to occur as we remain in a low 

natural gas price environment that is 

complemented by debottlenecking of 

Marcellus region natural gas production 

through significant new pipeline and 

pipeline capacity expansion in the 

2017–2023 timeframe. 

With regard to comments stating that 

the EPA should factor the proposed ACE 

rule into its 2023 outlook, the EPA notes 

it has not done so as the ACE rule is not 

final. Moreover, it has not factored the 

Clean Power Plan into its projections 

given the stay of that rule issued by the 

Supreme Court. Both of these 

assumptions are reasonable and 

consistent with EPA analytic precedents 

and OMB Circular A–4 guidance 

(requiring that regulatory baselines 

should reflect the future effect of current 

government programs and 

policies).130 131

Comment: For mobile source and nonEGU emissions, commenters suggest 

that emissions projections for these 

sectors could be unreliable due to the 

EPA’s planned rulemaking actions 

including the proposed repeal of 

regulations with respect to so-called 

‘‘glider’’ vehicles, engines, and kits, 82 

FR 53442 (Nov. 16, 2017) (proposing to 

repeal the Greenhouse Gas Emissions 

and Fuel Efficiency Standards for 

Medium- and Heavy-Duty Engines and 

Vehicles—Phase 2); the proposed Safer 

Affordable Fuel Efficient (SAFE) 

Vehicles Rule for Model Years 2021– 

2026 Passenger Cars and Light Trucks, 

83 FR 42986 (Aug. 24, 2018) (proposing 

to repeal the Corporate Average Fuel 

Economy (CAFE) standards); and the 

proposed withdrawal of Control 

Techniques Guidelines (CTG) for the Oil 

and Natural Gas Industry, 83 FR 10478 

(Mar. 9, 2018). 

Response: The EPA disagrees that its 

2023 projections are unreliable because 

of potential changes to other 

regulations. The EPA first notes any 

potential regulatory changes to the 

‘‘glider’’ regulations, the SAFE vehicle 

rules, and the oil and gas CTG have not 

been finalized. In general, the mobile 

source and non-EGU emission 

inventories do not reflect rulemakings 

finalized in calendar year 2016 or later, 

nor do they reflect any rules proposed 

but not yet finalized since 2016, as only 

finalized rules are reflected in modeling 

inventories. The EPA’s normal practice 

is to only include changes in emissions 

from final regulatory actions in its 

modeling because, until such rules are 

finalized, any potential changes in NOX

or VOC emissions are speculative. 

In addition, even if emissions were to 

change as a result of any such final 

rules, commenters have not indicated 

how and whether these additional 

emissions would affect downwind 

ozone concentrations. The model year 

2017–2025 GHG regulations for cars and 

light trucks were projected to yield 

small but measurable criteria and toxic 

emission reductions from vehicles.132

Because the vehicles affected by the 

2017–2025 GHG standards would still 

need to meet applicable criteria 

pollutant emissions standards (e.g., the 

Tier 3 emissions standards; 79 FR 

23414), the regulatory impact analysis 

that accompanied the proposed revision 

to the GHG standards estimated a very 

limited impact on criteria and toxic 

pollutant emissions (increases in 

upstream emissions and decreases in 

tailpipe emissions). Moreover, the 

proposed SAFE Vehicles Rule 

specifically notes that none of the 

regulatory alternatives considered 

‘‘would noticeably impact net emissions 

of smog-forming or other ‘criteria’ or 

toxic air pollutants.’’ 83 FR 42996. As to 

glider kits in particular, we note that the 

‘‘no action assurance’’ provided by thenAdministrator Pruitt via memorandum 

of July 6, 2018, was subsequently 

rescinded via a memorandum signed by 

Acting Administrator Wheeler on July 

26, 2018, and that the EPA has not taken 

any further final action that would 

change any requirements for glider 

vehicles, glider engines, or glider kits. 

Finally, with regard to the proposed 

withdrawal of the oil and gas CTG, we 

also note that impacts of the CTGs were 

not included in the modeled 

inventories, so their withdrawal would 

not change the results of the modeling. 

3. Definition of Nonattainment and 

Maintenance Receptors 

In this action, the EPA is continuing 

to apply the CSAPR Update approach to 

identifying nonattainment and 

maintenance receptors for the 2008 

ozone NAAQS in the 2023 analytic year. 

The EPA here describes the analytical 

approach pursued in the CSAPR Update 

with regard to the good neighbor 

requirements for the 2008 ozone 

NAAQS. For consistency’s sake, the 

analysis and discussion underlying and 

presented in this action adheres to that 

analytical approach. 

To give independent effect to both the 

‘‘contribute significantly to 

nonattainment’’ and the ‘‘interfere with 

maintenance’’ prongs of section 

110(a)(2)(D)(i)(I) for the 2008 ozone 

NAAQS, consistent with the D.C. 

Circuit’s opinion in North Carolina, 531 


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133See 795 F.3d at 136. 

134From 40 CFR 50.15(b): ‘‘The 8-hour primary 

and secondary ambient air quality standards are 

met at an ambient air quality monitoring site when 

the 3-year average of the annual fourth-highest daily 

maximum 8-hour average O3 concentration is less 

than or equal to 0.075 ppm, as determined in 

accordance with appendix P to this part.’’ The 

agency’s use of 76.0 ppb (or 0.076 parts per million) 

to identify violations of the 2008 Ozone NAAQS in 

this action is consistent the 2008 ozone NAAQS 

regulation. From section 2.2 of appendix P to 40 

CFR part 50: ‘‘The computed 3-year average of the 

annual fourth-highest daily maximum 8-hour 

average O3 concentrations shall be reported to three 

decimal places (the digits to the right of the third 

decimal place are truncated, consistent with the 

data handling procedures for the reported data).’’ 

F.3d at 910–11, the EPA has separately 

identified downwind areas expected to 

be in nonattainment of the 2008 ozone 

NAAQS and downwind areas expected 

to have problems maintaining the 2008 

ozone NAAQS. 

Specifically, the EPA has identified as 

nonattainment receptors those monitors 

that both currently measure 

nonattainment based on measured 

2014–2016 design values and that the 

EPA projects will be in nonattainment 

for the 2008 ozone NAAQS in 2023 (i.e., 

are projected to have average design 

values that exceed the NAAQS). 

The EPA has identified maintenance 

receptors as those receptors that would 

have difficulty maintaining the relevant 

NAAQS in a scenario that accounts for 

historical variability in air quality at 

that receptor. The variability in air 

quality was determined by evaluating 

the ‘‘maximum’’ future design value at 

each receptor based on a projection of 

the maximum measured design value 

over the relevant base-year period. The 

EPA defines the projected maximum 

future design value as a potential future 

air quality outcome consistent with the 

meteorology that yielded maximum 

measured concentrations in the ambient 

data set analyzed for that receptor. 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. Therefore, 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 downwind areas where 

emissions from upwind states could 

therefore interfere with the area’s ability 

to maintain the NAAQS. The EPA 

therefore assessed the magnitude of the 

maximum projected design value for 

2023 at each receptor in relation to the 

2008 ozone NAAQS. Where that value 

exceeded the NAAQS, the EPA 

determined that receptor to be a 

‘‘maintenance’’ receptor for purposes of 

defining interference with maintenance, 

consistent with the method used in 

CSAPR and upheld by the D.C. Circuit 

in EME Homer City II.133 That is, 

monitoring sites with a maximum 

projected design value that exceeds the 

NAAQS in 2023 are considered to have 

a maintenance problem in 2023. 

All nonattainment receptors also, by 

definition, meet EPA’s criteria for 

identifying maintenance receptors—i.e., 

in addition to currently measuring 

nonattainment and having projected 

average design values that exceed the 

NAAQS, the receptors also would have 

difficulty maintaining the NAAQS 

accounting for variability in air quality 

at the receptor. The EPA refers to 

maintenance receptors that are not also 

nonattainment receptors as 

‘‘maintenance-only’’ receptors. 

Maintenance-only receptors therefore 

include those sites where the projected 

maximum design value exceeds the 

NAAQS, but the projected average 

design value is at or below the NAAQS. 

In addition, those sites that are currently 

measuring clean data (i.e., are at or 

below the 2008 ozone NAAQS), but are 

projected to be in nonattainment based 

on the average design value (and that, 

by definition, are projected to have a 

maximum design value above the 

standard) are also identified as 

maintenance-only receptors. Unlike 

nonattainment receptors, the EPA did 

not disqualify potential maintenance 

receptors based on current clean 

monitored data in order to account for 

the possibility that certain areas would 

fail to maintain the NAAQS in the 

future, even though they may be 

currently attaining the NAAQS. See 

North Carolina, 531 F.3d at 910–11 

(finding that failure to give independent 

significance to the maintenance prong 

‘‘provides no protection for downwind 

areas that, despite EPA’s predictions, 

still find themselves struggling to meet 

NAAQS due to upwind interference’’). 

For further details regarding the EPA’s 

identification of receptors in the CSAPR 

Update, see 81 FR 74526. 

4. Air Quality Modeling To Identify 

Nonattainment and Maintenance 

Receptors 

The following summarizes the 

procedures for projecting future-year 8- 

hour ozone average and maximum 

design values to 2023 to determine 

nonattainment and maintenance 

receptors. Consistent with the EPA’s 

modeling guidance, the agency uses the 

air quality modeling results in a 

‘‘relative’’ sense to project future 

concentrations. That is, the ratios of 

future year model predictions to base 

year model predictions, i.e., the 

‘‘relative response factor’’ or relative 

(percent) change in model predictions 

for each location, are used to adjust 

monitored ambient ozone design values 

to generate future year projected design 

values. The modeling guidance 

recommends using measured ozone 

concentrations for the 5-year period 

centered on the base year as the air 

quality data starting point for future 

year projections. This average design 

value is used to dampen the effects of 

inter-annual variability in meteorology 

on ozone concentrations and to provide 

a reasonable projection of future air 

quality at the receptor under ‘‘average’’ 

conditions. In addition, the EPA uses 

the projection of the maximum base 

period design value to provide a 

projection of future year air quality 

during meteorological conditions more 

favorable for ozone formation than on 

average. Because the base year for this 

analysis is 2011, the EPA is using the 

base period 2009–2013 ambient ozone 

design value data to project 2023 

average and maximum design values in 

a manner consistent with the modeling 

guidance. 

The approach for projecting future 

ozone design values involved the 

projection of an average of up to three 

design value periods, which include the 

years 2009–2013 (design values for 

2009–2011, 2010–2012, and 2011– 

2013). The 2009–2011, 2010–2012, and 

2011–2013 design values are accessible 

at www.epa.gov/airtrends/values.html. 

The average of the three design values 

creates a ‘‘5-year weighted average’’ 

value. The 5-year weighted average 

values were then projected to 2023. To 

project 8-hour ozone design values, the 

agency used the 2011 base year and 

2023 future base-case model-predicted 

ozone concentrations to calculate 

relative response factors (RRFs) for the 

location of each monitoring site. The 

RRFs were then applied to actual 

monitored data, i.e., the 2009–2013 

average ozone design values (to generate 

the projected average design values) and 

the individual design values for 2009– 

2011, 2010–2012, and 2011–2013 (to 

generate potential maximum design 

values). Details of this approach are 

provided in the AQM TSD. 

The EPA considers projected design 

values that are greater than or equal to 

76.0 ppb to be violating the 2008 ozone 

NAAQS in 2023.134 As noted 

previously, nonattainment receptors are 

those sites that both have projected 

average design values greater than the 

2008 ozone NAAQS and are also 


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135U.S. Environmental Protection Agency, 2014. 

Modeling Guidance for Demonstrating Attainment 

of Air Quality Goals for Ozone, PM2.5, and Regional 

Haze. http://www.epa.gov/ttn/scram/guidance/ 

guide/Draft_O3-PM-RH_Modeling_Guidance2014.pdf. 

136A model grid cell is identified as a ‘‘water’’ 

cell if more than 50 percent of the grid cell is water 

based on the 2006 National Land Cover Database. 

Grid cells that meet this criterion are treated as 

entirely over water in the Weather Research 

Forecast (WRF) modeling used to develop the 2011 

meteorology for EPA’s air quality modeling. 

137The EPA recognizes that the modeling results 

indicate a substantial projected improvement in 

ozone air quality (compared to current measured 

ozone levels) at several locations, including three 

monitors in Connecticut located near the sea—i.e., 

on the order of 10–12 ppb. 

violating the NAAQS based on the most 

recent measured air quality data. 

Therefore, as an additional step, for 

those sites that are projected to be 

violating the NAAQS based on the 

average design values in 2023, the EPA 

examined the most recent measured 

design value data to determine if the site 

was currently violating the NAAQS. For 

the proposal, the agency examined 

ambient data for the 2014–2016 period, 

which form the basis for the most recent 

available, certified measured design 

values at the time of proposal. Certified 

measured design value data for 2015– 

2017 are now available and have been 

included in the analysis of projected 

receptor. The 2015–2017 design values 

can be found in a spreadsheet file in the 

docket for this rule. Considering the 

2015–2017 measured design values does 

not change the determination regarding 

nonattainment and maintenance 

receptors in 2023 for the 2008 NAAQS. 

As discussed above, maintenanceonly receptors include both: (1) Those 

sites with projected average and 

maximum design values above the 

NAAQS that are currently measuring 

clean data; and (2) those sites with 

projected average design values below 

the level of the NAAQS, but with 

projected maximum design values of 

76.0 ppb or greater. 

In projecting these future year design 

values, the EPA applied its own 

modeling guidance,135 which 

recommends using model predictions 

from the ‘‘3 x 3’’ array of grid cells 

surrounding the location of the 

monitoring site to calculate the relative 

response factors and identify future 

areas of nonattainment. In addition, in 

light of comments on the January 2017 

NODA and other analyses, the EPA also 

projected 2023 design values based on 

a modified version of this approach for 

those monitoring sites located in coastal 

areas. In brief, in the alternative 

approach, the EPA eliminated from the 

design value calculations those 

modeling data in grid cells not 

containing a monitoring site that are 

dominated by water (i.e., more than 50 

percent of the land use in the grid cell 

is water).136 For each individual 

monitoring site, the EPA is providing 

the base period 2009–2013 average and 

maximum design values, 2023 projected 

average and maximum design values 

based on both the 3 x 3 approach and 

the alternative approach affecting 

coastal sites, and 2014–2016 measured 

design values. 

Tables III.C–1 and III.C–2 contain the 

ambient 2009–2013 base period average 

and maximum 8-hour ozone design 

values, the 2023 projected baseline 

average and maximum design values, 

and the ambient 2014–2016 design 

values for the air quality monitors that 

were identified in the CSAPR Update as 

having remaining problems attaining or 

maintaining the 2008 ozone NAAQS in 

2017, even with CSAPR Update 

implementation. The tables present the 

projected design values under both the 

3x3 approach and the alternative 

approach. Table III.C–1 contains data for 

the monitors identified as remaining 

nonattainment receptors in 2017 in the 

CSAPR Update and Table III.C–2 

contains data for the monitors identified 

as remaining maintenance-only 

receptors in 2017 in the CSAPR 

Update.137 The design values for all 

monitoring sites in the contiguous U.S. 

are provided in the docket. According to 

the EPA’s modeling, there are no 

remaining nonattainment or 

maintenance receptors in the eastern 

U.S. in 2023 regardless of which 

approach to projecting design values is 

used. 

TABLE III.C–1—BASE PERIOD, CURRENT (2014–2016), AND 2023 PROJECTED DESIGN VALUES (ppb) FOR MONITORS

IDENTIFIED AS REMAINING NONATTAINMENT RECEPTORS IN 2017 IN THE CSAPR UPDATE

Monitor ID State County 2009–2013 

Avg 

2009–2013 

Max 2014–2016 

2023en 

‘‘3x3’’ 

Avg 

2023en 

‘‘3x3’’ 

Max 

2023en 

‘‘No Water’’ 

Avg 

2023en 

‘‘No Water’’ 

Max 

090019003 ....... Connecticut ............ Fairfield ................... 83.7 87 85 72.7 75.6 73.0 75.9 

090099002 ....... Connecticut ............ New Haven ............. 85.7 89 76 71.2 73.9 69.9 72.6 

480391004 ....... Texas ...................... Brazoria .................. 88.0 89 75 74.0 74.9 74.0 74.9 

484392003 ....... Texas ...................... Tarrant .................... 87.3 90 73 72.5 74.8 72.5 74.8 

484393009 ....... Texas ...................... Tarrant .................... 86.0 86 75 70.6 70.6 70.6 70.6 

551170006 ....... Wisconsin ............... Sheboygan ............. 84.3 87 79 70.8 73.1 72.8 75.1 

TABLE III.C–2—BASE PERIOD, CURRENT (2014–2016), AND 2023 PROJECTED DESIGN VALUES (ppb) FOR MONITORS

IDENTIFIED AS REMAINING MAINTENANCE-ONLY RECEPTORS IN 2017 IN THE CSAPR UPDATE

Monitor ID State County 2009–2013 

Avg 

2009–2013 

Max 2014–2016 

2023en 

‘‘3x3’’ 

Avg 

2023en 

‘‘3x3’’ 

Max 

2023en 

‘‘No Water’’ 

Avg 

2023en 

‘‘No Water’’ 

Max 

090010017 ....... Connecticut ............ Fairfield ................... 80.3 83 80 69.8 72.1 68.9 71.2 

090013007 ....... Connecticut ............ Fairfield ................... 84.3 89 81 71.2 75.2 71.0 75.0 

240251001 ....... Maryland ................. Harford ................... 90.0 93 73 71.4 73.8 70.9 73.3 

260050003 ....... Michigan ................. Allegan ................... 82.7 86 75 69.0 71.8 69.0 71.7 

360850067 ....... New York ................ Richmond ............... 81.3 83 76 71.9 73.4 67.1 68.5 

361030002 ....... New York ................ Suffolk .................... 83.3 85 72 72.5 74.0 74.0 75.5 

481210034 ....... Texas ...................... Denton .................... 84.3 87 80 69.7 72.0 69.7 72.0 

482010024 ....... Texas ...................... Harris ...................... 80.3 83 79 70.4 72.8 70.4 72.8 

482011034 ....... Texas ...................... Harris ...................... 81.0 82 73 70.8 71.6 70.8 71.6 

482011039 ....... Texas ...................... Harris ...................... 82.0 84 67 71.8 73.6 71.8 73.5 


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138Note that the analysis of modeled ozone 

design values described in this response are based 

on the ‘‘3x3’’ method to be consistent with the 

modeling data submitted by the commenter. 

139See the Appendix in to the Considerations for 

Identifying Maintenance Receptors Memo (signed 

on October 19, 2018). 

140The OTC did not provide data on projected 

future year maximum design values based on their 

modeling. 

Comment: The EPA received several 

comments regarding its projection of 

2023 ozone design values. The 

commenters suggest that certain 

monitoring sites in the New York City 

area will continue to have 

nonattainment and/or maintenance 

problems for the 2008 NAAQS in 2023, 

a claim which is contrary to the results 

of the EPA’s modeling which shows that 

nonattainment and maintenance 

problems will be resolved in all areas 

outside of California by 2023. The 

assertion by the commenters is based on 

their examination of measured design 

values for 2017 and modeling-based 

projected design values for 2017 and 

2023. First, some commenters compared 

the projected design values for 2017 

based on modeling by the OTC using the 

Community Multi-scale Air Quality 

Model (CMAQ) to the 2017 design 

values projected by the EPA using the 

CAMx model. Those commenters point 

out that the 2017 CMAQ-based design 

values are higher than the EPA CAMx 

design values by up to 9.2 ppb at certain 

sites in the Northeast. Commenters also 

point to data showing that the greatest 

difference between the OTC CMAQ and 

EPA CAMx 2017 design values is at 

coastal monitoring sites, such as the 

Susan Wagner site in New York and the 

Westport site in Connecticut. Second, 

commenters compared the 2017 OTC 

CMAQ and EPA CAMx design values to 

the corresponding 2017 measured 

design values and contend that the 

CMAQ-based 2017 design values 

compare favorably to the measured data 

and that the CAMx-based design values 

under-predict the measured data. One 

commenter identified eight sites in 

Connecticut that are currently 

measuring nonattainment based on 

2015–2017 design values which the 

EPA’s CAMx modeling predicts will be 

in attainment in 2017. Third, 

commenters point to OTC CMAQ-based 

design values for 2023 which indicate 

that there will be two monitoring sites 

in Connecticut with design values that 

exceed the 2008 NAAQS in that year. 

Fourth, the commenters note that the 

design values based on OTC CAMx 

modeling for 2023 are comparable in 

magnitude to the corresponding 2023 

design values based on EPA’s 2023 

CAMx modeling. Commenters use this 

information to contend that the CAMx 

model provides a forecast that is too 

optimistic and that the EPA should rely 

upon the higher projected design values 

for 2023 from the OTC CMAQ modeling. 

Some of the commenters point out 

that the EPA’s 2023 modeling projects a 

maximum design value of 75.9 ppb at 

Westport site and contend that, before 

the EPA can conclude that areas will 

attain by 2023 with only the narrowest 

of margins (i.e., 0.1 ppb), the EPA must 

conduct its own analysis of the emission 

response differences between CMAQ 

and CAMx. Similarly, some commenters 

said that the EPA must address the 

demonstrated tendency of its 

methodology to under-predict realworld ozone levels in many downwind 

locations and that the EPA’s modeling is 

not sufficiently conservative to give 

confidence that attainment is assured 

even as late as 2023. 

Response: The EPA does not agree 

that the modeling provided by 

commenters should affect the EPA’s 

reliance on its own 2023 modeling. 

First, the commenters focused on 

projected average design values and 

completely ignore the EPA’s projected 

maximum design values when 

comparing modeled to measured design 

values for 2017.138 The projected 

maximum design values are intended to 

represent future ozone concentrations 

when meteorological conditions are 

more conducive to ozone formation than 

on average. Analysis of meteorological 

conditions for the summers of 2015, 

2016, and 2017 indicate that 

meteorology was more conducive than 

average for ozone formation during 

these summers in the Northeast.139

Comparing both the 2017 modeled 

average design values and maximum 

projected design values from the EPA’s 

modeling to the 2017 measured design 

values indicates that the projected 

maximum design values are, in most 

cases, closer in magnitude to the 2017 

measured design values than the 2017 

model-projected average design values, 

particularly for the Susan Wagner and 

Westport sites cited by commenters. 

Specifically, the 2017 measured design 

value and the EPA’s modeled maximum 

design value at the Susan Wagner site 

are 76 ppb and 77.8 ppb, respectively. 

At the Westport site the 2017 measured 

design value and the EPA’s modeled 

maximum design value are 83 ppb and 

79.5 ppb, respectively. At the site in 

Philadelphia County, Pennsylvania the 

modeled 2017 maximum design value 

was 1.1 ppb lower than the 

corresponding measured value (78 ppb), 

and at the site in Harford County, 

Maryland, the modeled value was 

higher, not lower, than the measured 

2017 design value (75 ppb). As part of 

our response to the commenters’ 

concerns about the EPA’s modeling we 

also compared the 2017 measured 

design values to the EPA’s projected 

2017 maximum design values for 81 

sites in the Northeast that had both a 

2009 to 2013 base period measured 

maximum design value exceeding the 

2008 NAAQS and valid 2017 measured 

design values. As a result of this 

analysis we found that the 2017 

projected maximum design values are 

only 0.5 ppb higher than the 

corresponding 2017 measured design 

values, on average across these 81 sites, 

and the median difference is ¥0.9 ppb. 

Thus, while the EPA recognizes that 

there are uncertainties in the modeling, 

the results for sites in the Northeast do 

not, on balance, show a notable bias in 

the EPA’s design value projections. It is 

not unreasonable that there may be 

some differences in terms of over- and 

under-estimates between the modelingbased projections for a future year and 

the measured data in part because the 

meteorology of the future year cannot be 

known in advance. For instance, the 

degree of ozone conducive meteorology 

in a particular region can vary from year 

to year such that some years are more 

conducive then others. Since it is not 

possible to forecast meteorology for 

analytic years in the future, the EPA 

chose to model meteorological 

conditions from a historical time-period 

when meteorology was generally 

conducive for ozone formation, as 

recommended in the EPA’s modeling 

guidance. 

For 2023, the modeling results show 

that the EPA and OTC CAMx-based 

2023 average design value projections 

are consistent on an individual site 

basis for all sites in the Northeast.140

Both the EPA and OTC CAMx modeling 

indicate that there will be no sites with 

design values that exceed the 2008 

NAAQS by 2023. 

Moreover, the OTC CMAQ 2023 

design values are, in fact, fairly 

consistent with both the OTC and EPA 

CAMx-based 2023 projections at nearly 

all sites. As an example, the average and 

median differences between the OTC 

CMAQ and EPA CAMx 2023 design 

values for sites in the Northeast are 0.15 

ppb and 0.70 ppb, respectively. 

However, while the EPA and OTC 

CAMx modeling both indicate that all 

sites in the Northeast will be clean for 

the 2008 NAAQS by 2023, the OTC 

CMAQ modeling projects that two sites 

will have average design values above 

the 2008 NAAQS by 2023. The two sites 

projected to exceed the 2008 NAAQS in 


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141Ozone Transport Commission/Mid-Atlantic 

Northeastern Visibility Union 2011 Based Modeling 

Platform Support Document, October 18, 2018. This 

document can be found in the docket for this 

action. 

142 In Figures 6–81 through 6–90 of the OTC TSD 

the highest modeled ozone concentration in the 3 

x 3 array of grid cells is referred to as the ‘‘9-Grid 

8HMX’’ value. 

2023 with OTC CMAQ modeling are the 

Westport and the Susan Wagner site. 

The CMAQ projected design values for 

these two sites are not only inconsistent 

with the CAMx modeling, but they are 

also inconsistent with the CMAQ 

modeling for other nearby sites in 

Connecticut, New York, and New Jersey. 

For example, based on the OTC CMAQ 

modeling, ozone at the Susan Wagner 

site is projected to decline by only 5 

percent between 2011 and 2023, 

whereas at a site in nearby Bayonne, 

New Jersey, ozone is projected to 

decline by 13 percent over this same 

time period. Similarly, ozone at the 

Westport site is projected to decline by 

only 3 percent between 2011 and 2023 

with CMAQ, but at other sites along the 

Connecticut coastline (i.e., sites in 

Greenwich, Stratford, and Madison), 

ozone is projected to decline by 10 to 19 

percent. In addition, the OTC CMAQ 

results for these two sites (i.e., Westport 

and Susan Wagner) are inconsistent 

with ozone reductions predicted by 

CMAQ at other sites in the New York 

City area which range from 11 to 18 

percent. In contrast, the EPA’s 2023 

modeling shows that ozone is projected 

to decline by 13 percent at the Westport 

site which is an amount far greater than 

the 3 percent predicted by OTC’s CMAQ 

modeling. The EPA’s predicted ozone 

reductions at Westport, however, are 

consistent with the predicted reductions 

at other coastal sites in Greenwich, 

Madison, and Stratford, all of which are 

in the range of 13 to 18 percent. 

Similarly, ozone at the Susan Wagner 

site is projected to decline by 12 percent 

between 2011 and 2023 based on the 

EPA’s CAMx modeling which is 

consistent with the 15 percent reduction 

predicted at the nearby site in Bayonne, 

New Jersey. Thus, the change in ozone 

from 2011 to 2023 predicted by the 

EPA’s CAMx modeling is much more 

spatially consistent within the New 

York City area than OTC’s CMAQ 

modeling which predicts spatially 

anomalous results at two sites (i.e., 

Westport and Susan Wagner). 

While it is possible ozone levels in 

2023 at the Westport and/or Susan 

Wagner sites may be higher than at 

other sites in the New York City area, 

the commenter fails to provide any 

explanation regarding the large 

difference in the CMAQ-based model 

response to emission reductions 

compared to the response at nearby sites 

and to other sites in the New York City 

area. Based on the complicated 

photochemistry in this area, it is 

possible that ozone monitoring sites 

closest to the large NOX emissions in 

New York City may be less responsive 

to NOX controls compared to sites 

further downwind. Due to non-linear 

chemistry, sites very close to the city 

may experience increases in ozone or 

less reduction than other nearby sites on 

some days in response to local emission 

reductions in NOX. Thus, we might 

expect that monitoring sites in 

Connecticut that are closer to New York 

City would show less reduction in 

ozone than sites in Connecticut that are 

further downwind. However, as noted 

above, in the OTC CMAQ modeling, the 

closest downwind Connecticut site 

(Greenwich) has a 10-percent modeled 

ozone reduction, while the Westport 

site, which is slightly farther 

downwind, has only a 3-percent 

modeled ozone reduction. The 

commenter did not provide any 

information to explain why the OTC 

CMAQ modeling results for the 

Westport and Susan Wagner monitoring 

sites are dissimilar to other nearby sites 

or why the commenters believe that the 

OTC CMAQ modeling provides a more 

representative ozone projection for these 

two sites compared to the EPA and OTC 

CAMx-based modeling. 

Information in the OTC air quality 

modeling technical support document 

(OTC TSD) provides some insight into 

why their CMAQ and CAMx modeling 

shows a dramatic difference in model 

response in New York City and coastal 

Connecticut.141 First, the OTC’s 

comparison of CMAQ and CAMx 2011 

base year model predictions to the 

corresponding measured data indicate 

that the CAMx 2011 predictions have 

lower error and higher correlation with 

measured data (i.e., better model 

performance) than the CMAQ 2011 

predictions for the 8 monitoring sites in 

Connecticut and New York that are 

included in Table 6–6 of the OTC TSD. 

Second, examining the 2011 modeled 

data for the top-10 days used to 

calculate the site-specific RRF indicates 

that the CMAQ 2011 predictions are not 

representative of ozone concentrations 

at the location of high ozone coastal 

sites in New York City and coastal 

Connecticut for which data are provided 

in the OTC TSD. For example, Figures 

6–81 through 6–90 in the OTC TSD 

provide time series plots of measured 

and CMAQ and CAMx-modeled ozone 

data for the days used to calculate the 

RRF at each of 5 monitoring sites in the 

Northeast (2 sites in coastal 

Connecticut, 2 sites in New York City, 

and 1 site in Maryland). These figures 

show several types of data including (1) 

the 2011 measured and corresponding 

model-predicted hourly ozone 

concentrations at the monitoring site 

and (2) the highest 2011 and 2017 

modeled 8-hour daily maximum ozone 

concentrations in the 3 x 3 array of grid 

cells including and surrounding the 

monitoring site.142 The latter set of data 

are used in the calculation of the RRF 

which, in turn, is used to project the 

future year design value at each site. It 

is expected that the highest modeled 

ozone values based on the 3 x 3 

approach for calculating RRFs will be 

equal to or greater than the modeled 

value in the grid cell containing the 

monitor. However, as evident from the 

figures in the OTC TSD, the 2011 and 

2017 ozone concentrations used for 

projecting design values based on OTC’s 

CMAQ modeling overstate the modeled 

values at the coastal monitoring sites by 

a notably larger amount than the 

corresponding 2011 predictions from 

OTC’s CAMx modeling. The clearest 

example of this is at the Queens College 

site in New York City where the CMAQbased 2011 and 2017 data for the ten 

days used for the RRF calculation 

appear to be 50 to 60 ppb above the 

highest hourly measured concentrations 

at the location of the monitoring site. In 

contrast, the CAMx data used for the 

RRF calculation appear to be within 20 

ppb of the highest hourly measured data 

on all ten days at this site. Overall, the 

OTC CAMx 2011 ozone concentrations 

used to calculate the RRF align closely 

with the model predictions and 

measured data at the monitoring sites 

for which data are provided in the OTC 

TSD. Thus, the CAMx-based projections 

are more likely to be representative than 

OTC’s CMAQ modeling of the expected 

ozone response to emissions reductions 

at the location of the monitoring site. 

Typically, the highest modeled 

concentrations near coastal monitoring 

sites are found in adjacent over-water 

grid cells. Ozone can be higher over 

water than over land because mixing of 

the air is more limited over water and 

titration (i.e., removal) by chemical 

reaction of ozone with fresh NO 

emissions is less prevalent. Thus, it is 

possible that the apparent anomalous 

2017 design values at the Westport and 

Susan Wagner sites derived from OTC’s 

CMAQ modeling may be the result of 

using predicted ozone values in the RRF 

calculations that are not representative 

of concentrations at the monitoring site. 

This hypothesis is supported by the 


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143Baker, K., S. Phillips, and B. Timin. 

‘‘Operational Evaluation and Model Response 

Comparison of CAMx and CMAQ for Ozone and 

PM2.5’’, 7th Annual Community Modeling & 

Analysis System Conference, October 2008. 

144See the Technical Support Document (TSD): 

Preparation of Emissions Inventories for the Version 

6.2, 2011 Emissions Modeling Platform, EPA, 

August 2015. 

145A description of the CAMx modeling can be 

found in the Regulatory Impact Analysis of the 

Final Revisions to the National Ambient Air Quality 

Standards for Ground-Level Ozone, EPA–452/R– 

15–007, September 2015. 

146A description of the EPA CMAQ modeling can 

be found in the docket. 

147An Excel file containing the differences in 

projected design values between EPA’s CMAQ and 

CAMx modeling for sates along the Northeast 

Corridor from Washington, DC to Connecticut can 

be found in the docket for this final action. 

148Final Report: Three-Dimensional Performance 

Comparison of CAMx and CMAQ Using the 2013 

DISCOVER–AQ Field Study Data Base. Prepared by 

Ramboll under contract to the Texas Commission 

on Environmental Quality, August 2015. 

149 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). EPA 

Memorandum to Regional Air Division Directors. 

March 27, 2018. Available at https://www.epa.gov/ 

sites/production/files/2018-03/documents/ 

transport_memo_03_27_18_1.pdf. 

OTC’s own analysis in which the OTC 

applied an approach that limits the use 

of over-water ozone predictions in the 

calculation of projected design values 

(i.e., Land Water Mask or LWMASK). 

When the OTC applied the LWMASK 

approach, the projected 2017 design 

values at the Westport and Susan 

Wagner sites were lowered significantly. 

Specifically, the 2017 OTC CMAQ 

design value at Westport drops from 83 

ppb to 76 ppb and from 78 ppb to 72 

ppb at Susan Wagner by limiting the 

amount of over water grid cells used in 

the projections. Thus, the concerns with 

the OTC’s application of CMAQ for 

2017, as described above, call into 

question the validity of their CMAQ 

modeling for other future years. 

Regarding the comment that the EPA’s 

modeling predicts attainment in 2017 at 

eight monitors in Connecticut that are 

currently measuring nonattainment, it is 

entirely reasonable to project that these 

sites will be in attainment by 2023 as a 

result of the roughly 19 percent 

reduction in aggregate ozone season 

NOX emissions that is expected to occur 

between 2017 and 2023 for the states 

covered by the CSAPR Update. Despite 

large regional and local NOX emission 

reductions, ozone has remained 

stubbornly high at sites in Connecticut. 

Larger ozone reductions are expected at 

these sites in the future as NOX

emissions continue to go down, and the 

local ozone chemistry becomes more 

responsive to NOX reductions. That is, 

because of the high NOX emissions in 

the New York City area and the nonlinear chemistry associated with ozone 

formation, the benefits of NOX emission 

reductions may not have been fully 

realized to date at downwind sites in 

Connecticut. More notable reductions in 

ozone at these sites are expected as NOX

emissions decline further, in response to 

existing control programs and other 

factors influencing emissions. Large, 

short-term reduction in ozone is not 

unprecedented at historically highozone sites in other parts of the 

Northeast Corridor. Specifically, the 

measured design values at the 

Edgewood monitoring site in Harford 

County, Maryland, which is downwind 

of the Baltimore/Washington, DC urban 

area, declined by nearly 20 percent 

between 2012 and 2014 and have been 

below the level of the 2008 NAAQS 

since 2014, as shown by the data in 

Table III.C–3, below. Thus, the EPA 

disagrees that the monitored and OTC 

CMAQ modeling data cited by the 

commenter indicate that the EPA 

modeling projections for 2023 are not 

reliable. 

TABLE III.C–3—DESIGN VALUES (PPB) AT EDGEWOOD SITE IN HARFORD COUNTY, MD, 2007 THROUGH 2017 

Year 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 

Design Value ......................... 94 91 87 89 92 93 85 75 71 73 75 

As the commenters have suggested, 

the EPA did perform an analysis 

comparing model response of ozone to 

emissions between CMAQ and CAMx 

and found that both models give very 

similar responses when both models are 

run with similar inputs (e.g., emissions, 

meteorology, and boundary 

concentrations) and similar technical 

constructs (e.g., vertical layer structure 

and vertical mixing method).143 The 

results of that study are further 

supported by a more recent comparison 

by the EPA of projected CAMx and 

CMAQ ozone design values using the 

EPA’s version 6.2 of the 2011 emissions 

platform 144 with 2025 as the future 

year.145 146 For the two sites in the New 

York City area that are the focus of the 

comments (i.e., Westport and Susan 

Wagner), the EPA’s analysis shows that 

both models predict a comparable 

reduction at each of these sites. 

Specifically, at the Westport site the 

2009 to 2013 base period ozone design 

values were projected to decline by 9 

percent with CMAQ and by 11 percent 

with CAMx. This difference in model 

response equates to only a 1.8 ppb 

difference in projected 2025 design 

values at this site, which is far less than 

the 9.2 ppb difference between CMAQ 

and CAMx seen in the OTC’s analysis of 

2023 modeling results. Similarly, at the 

Susan Wagner site the base period 

ozone design value was projected to 

decline by 11.2 percent with CMAQ and 

11.7 percent with CAMx in EPA’s 

modeling. The difference in model 

response at the Susan Wagner site 

equates to only a 0.4 ppb difference in 

the projected 2025 design, which is far 

less than the 5.8 ppb difference between 

CMAQ and CAMx in OTC’s 2023 

analysis.147 Furthermore, a study 

sponsored by the Texas Commission on 

Environmental Quality also found that 

CAMx and CMAQ provide a comparable 

response to the same amount of NOX

and VOC emission reductions.148 In 

summary, based on the EPA’s analysis 

of its own data and the data available 

from commenters, we disagree with the 

commenter’s contention that the EPA’s 

CAMx-based modeling does not provide 

a credible projection of 2023 ozone 

design values. 

5. Pollutant Transport From Upwind 

States 

Although the EPA has conducted 

nationwide contribution modeling for 

2023, the EPA does not believe this 

information is necessary for evaluating 

remaining good neighbor obligations for 

the 2008 ozone NAAQS because there 

are no ozone monitoring sites in the 

eastern U.S. that are expected to have 

problems attaining or maintaining the 

2008 ozone NAAQS in 2023. 

Nonetheless, the results of the EPA’s 

state-by-state ozone contribution 

modeling were released in a 

memorandum on March 27, 2018, and 

are also available in the docket for this 

action.149 The EPA notes that, while the 

air quality modeling did identify 

potential remaining problem receptors 

in California in 2023, none of the EPA’s 

prior analysis nor its current 

contribution modeling have linked any 

of the CSAPR Update states in the 

eastern U.S., whose good neighbor 

obligations for the 2008 ozone NAAQS 


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150The EPA has also already separately finalized 

an approval of Kentucky’s SIP submittal 

demonstrating that the CSAPR Update is a full 

remedy for Kentucky’s good neighbor obligation for 

the 2008 ozone NAAQS. 83 FR 33730 (July 17, 

2018). 

151 In this action, the EPA proposed to find that 

Alabama’s previously approved CSAPR Update SIP 

would now fully satisfy its good neighbor obligation 

for the 2008 ozone NAAQS. Subsequent to the 

proposal, the EPA finalized its approval of Indiana’s 

CSAPR Update SIP. As discussed earlier, the EPA 

found that Indiana’s SIP approval only partially 

satisfied its good neighbor obligation for the 2008 

ozone NAAQS for the same reasons that the EPA 

found that Alabama’s SIP approval only partially 

satisfied that state’s good neighbor obligation. 

Although the EPA did not propose in this action to 

find that Indiana’s SIP would now fully satisfy its 

good neighbor obligation, the EPA did propose to 

find that the state’s CSAPR Update FIP would fully 

satisfy its obligation. Because Indiana’s approved 

SIP is commensurate with its prior CSAPR Update 

FIP such that Indiana is therefore now situated 

identically to Alabama, the EPA believes it is a 

logical outgrowth of the proposal to finalize a 

finding that Indiana’s approved CSAPR Update SIP 

also now fully satisfies its good neighbor obligation 

for the 2008 ozone NAAQS. 

are the subject of this action, to any of 

those potential remaining problem 

receptors. Therefore, the EPA does not 

believe there is a need to further 

evaluate the contributions of the 20 

CSAPR Update states to any downwind 

receptors identified in the EPA’s 2017 

modeling conducted for the CSAPR 

Update. 

D. Final Determination 

Consistent with the proposed action, 

the EPA has determined that, with 

CSAPR Update implementation, 20 

eastern states’ good neighbor obligations 

for the 2008 ozone NAAQS are fully 

addressed.150 The states covered by this 

action are listed in table III.D–1. The 

EPA’s determination is based on 

findings that: (1) 2023 is a reasonable 

future analytic year for evaluating ozone 

transport problems with respect to the 

2008 ozone NAAQS; and (2) for the 

purposes of interstate ozone transport, 

air quality modeling projections for 

2023 indicate that no further air quality 

problems will remain in the east in 

2023. 

As explained in more detail in section 

III.B, the EPA’s selection of 2023 as a 

reasonable future analytic year is 

supported by an assessment of 

attainment dates for the 2008 ozone 

NAAQS and feasibility of implementing 

control strategies to reduce NOX in 

CSAPR Update states. The EPA’s NOX

control strategy feasibility assessment 

prioritizes NOX control strategies in 

CSAPR Update states that would be 

additional to those strategies that were 

already quantified into CSAPR Update 

emissions budgets. The EPA finds: (1) 

That 2023 is an appropriate future 

analytic year, taking into consideration 

relevant attainment dates, because it is 

the first ozone season for which 

significant new controls to reduce NOX

could be feasibly installed across the 

CSAPR Update region and thus 

represents the timeframe that is as 

expeditious as practicable for upwind 

states to implement additional emission 

reductions. 

Furthermore, as described in section 

III.C, the EPA finds: (2) That its analysis 

of ozone concentrations in step 1 for the 

2023 analytic year indicates that there 

are no monitoring sites in the east that 

are projected to have nonattainment or 

maintenance problems with respect to 

the 2008 ozone NAAQS in 2023. 

Together, these two findings lead to 

EPA’s final determination that—with 

CSAPR Update implementation— 

CSAPR Update states are not expected 

to significantly contribute to 

nonattainment or interfere with 

maintenance of the 2008 ozone NAAQS 

in downwind states in 2023. 

As a result of this final determination, 

the EPA finds that the promulgation of 

the CSAPR Update fully satisfies the 

requirements of the good neighbor 

provision for the 2008 ozone NAAQS 

for these states, and therefore also 

satisfies the agency’s obligation 

pursuant to CAA section 110(c) for these 

states. Accordingly, the EPA has no 

remaining obligation to issue FIPs, nor 

are the states required to submit SIPs, 

that would further reduce transported 

ozone pollution beyond the existing 

CSAPR Update requirements with 

regard to the 2008 ozone NAAQS. 

TABLE III.D–1—STATES COVERED BY

THE FINAL DETERMINATION REGARDING GOOD NEIGHBOR OBLIGATIONS

FOR THE 2008 OZONE NAAQS 

State name 

Alabama 

Arkansas 

Illinois 

Indiana 

Iowa 

Kansas 

Louisiana 

Maryland 

Michigan 

Mississippi 

Missouri 

New Jersey 

New York 

Ohio 

Oklahoma 

Pennsylvania 

Texas 

Virginia 

West Virginia 

Wisconsin 

Consistent with this final 

determination, this action also finalizes 

minor revisions to the existing statespecific sections of the CSAPR Update 

regulations for states other than 

Kentucky and Tennessee. The revisions 

will remove the current statements 

indicating that the CSAPR Update FIP 

for each such state only partially 

addresses the state’s good neighbor 

obligation under CAA section 

110(a)(2)(D)(i)(I) for the 2008 ozone 

NAAQS. Because states can replace the 

CSAPR Update FIPs with SIPs, these 

revisions will also mean that a SIP that 

is approved through notice-andcomment rulemaking to fully replace 

the CSAPR Update FIP for one of these 

states would also fully address the 

state’s good neighbor obligation for this 

NAAQS. In particular, the EPA finalizes 

findings that the agency’s previous 

approvals of CSAPR Update SIPs for 

Alabama (82 FR 46674) and Indiana 

(signed November 27, 2018; publication 

in the Federal Register forthcoming) 151

fully satisfy those states’ good neighbor 

obligations for the 2008 ozone NAAQS. 

Thus, Alabama and Indiana have no 

obligation to submit any additional SIP 

revisions addressing these good 

neighbor obligations. 

IV. Statutory and Executive Order 

Reviews 

Additional information about these 

statutes and Executive Orders can be 

found at http://www2.epa.gov/lawsregulations/laws-and-executive-orders. 

A. Executive Order 12866: Regulatory 

Planning and Review, and Executive 

Order 13563: Improving Regulation and 

Regulatory Review 

This action is a significant regulatory 

action that was submitted to the Office 

of Management and Budget (OMB) for 

review. Any changes made in response 

to OMB recommendations have been 

documented in the docket. 

B. Executive Order 13771: Reducing 

Regulations and Controlling Regulatory 

Costs 

This action is not subject to Executive 

Order 13771 because this final rule is 

expected to result in no more than de 

minimis costs. 

C. Paperwork Reduction Act 

This action does not impose any new 

information collection burden under the 

Paperwork Reduction Act. The OMB has 

previously approved the information 

collection activities contained in the 

existing regulations and has assigned 

OMB control number 2060–0667. The 

minor revisions to the FIP provisions 

finalized in this action have no impact 

on monitoring, recordkeeping, and 

reporting requirements for affected 


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EGUs in the CSAPR NOX Ozone Season 

Group 2 Trading Program. 

D. Regulatory Flexibility Act 

I certify that this action will not have 

a significant economic impact on a 

substantial number of small entities 

under the Regulatory Flexibility Act. In 

making this determination, the impact 

of concern is any significant adverse 

economic impact on small entities. An 

agency may certify that a rule will not 

have a significant economic impact on 

a substantial number of small entities if 

the rule relieves regulatory burden, has 

no net burden, or otherwise has a 

positive economic effect on the small 

entities subject to the rule. This action 

makes a minor modification to existing 

CSAPR Update FIPs and does not 

impose new requirements on any entity. 

The EPA has therefore concluded that 

this action will have no net regulatory 

burden for all directly regulated small 

entities. 

E. Unfunded Mandates Reform Act 

This action does not contain any 

unfunded mandate as described in the 

Unfunded Mandates Reform Act, 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. 

This action simply updates the existing 

CSAPR Update FIPs to establish that no 

further federal regulatory requirements 

are necessary. 

F. 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. This action 

simply updates the existing CSAPR 

Update FIPs to establish that no further 

federal regulatory requirements are 

necessary. 

G. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

This action does not have tribal 

implications as specified in Executive 

Order 13175. It will not have substantial 

direct effects on tribal governments, 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. This 

action simply updates the existing 

CSAPR Update FIPs to establish that no 

further federal regulatory requirements 

are necessary. Thus, Executive Order 

13175 does not apply to this action. 

Consistent with the EPA Policy on 

Consultation and Coordination with 

Indian Tribes, the EPA consulted with 

tribal officials while developing the 

CSAPR Update. A summary of that 

consultation is provided in the 

preamble for the CSAPR Update, 81 FR 

74584 (October 26, 2016). Additionally, 

the EPA provided an overview of its 

proposed determination during a 

National Tribal Air Association—EPA 

Air Policy Update meeting on Thursday 

July 26, 2018. 

H. Executive Order 13045: Protection of 

Children From Environmental Health 

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 simply updates the existing 

CSAPR Update FIPs to establish that no 

further federal regulatory requirements 

are necessary. 

Comment: One commenter contends 

that the EPA has inappropriately failed 

to identify and assess the health risks to 

children from its decision to authorize 

continued interstate ozone pollution 

that contributes to violations of the 2008 

and 2015 ozone air quality standards in 

downwind states. The commenter states 

that the EPA has consistently 

recognized that children are 

disproportionately vulnerable to the 

environmental health risks of ozone and 

asserts that by authorizing continued 

pollution that will harm children, the 

EPA has failed to ensure that its 

policies, programs, activities, and 

standards address these risks. The 

commenter claims that this rule is 

subject to section 2–202 of the Executive 

Order, which provides that ‘‘covered 

regulatory action’’ means ‘‘any 

substantive action in a rulemaking’’ that 

is ‘‘likely to result in a rule that may’’ 

(1) ‘‘adversely affect in a material way 

. . . the environment, public health or 

safety, or State, local, or tribal 

governments or communities’’ and (2) 

‘‘concern an environmental health risk 

or safety risk that an agency has reason 

to believe may disproportionately affect 

children.’’ The commenter asserts that 

ozone pollution above the air quality 

standards the EPA has adopted 

indisputably is a health risk that 

disproportionately affects children. 

Response: According to section 2– 

202, a rulemaking is a ‘‘covered 

regulatory action’’ and thus subject to 

the Executive Order if the action is 

economically significant under 

Executive Order 12866 and involves an 

environmental health risk or safety risk 

that the agency has reason to believe 

may disproportionately affect children. 

This rulemaking does not qualify under 

either criterion. First, although this 

action is considered a significant 

regulatory action under Executive Order 

12866, the EPA has not determined that 

the rule is economically significant 

under that Order, and the commenter 

has not explained whether or why it 

should be considered economically 

significant. To the extent that the 

commenter cites the standard for 

economic significance wherein an 

action ‘‘would adversely affect in a 

material way . . . the environment, 

public health or safety, or State, local, 

or tribal governments or communities,’’ 

the commenter has not explained how 

this action, which concludes that air 

quality problems will be resolved and 

therefore does not either impose or 

repeal any regulatory requirements, 

would have an adverse effect. 

Second, the health-based standard at 

issue in this action has already been set 

in a prior rulemaking to promulgate the 

2008 ozone NAAQS, wherein the EPA 

did consider the effects of the standard 

under the Executive Order. 73 FR 

16436, 16506–07. Therefore, this action 

does not concern an environmental 

health or safety risk because the EPA is 

simply evaluating how to implement an 

existing health standard. Moreover, 

under the good neighbor provision, the 

EPA’s authority to prohibit emissions 

from sources in upwind states is 

constrained by the obligation to 

demonstrate that such reductions are 

necessary to address a downwind 

nonattainment or maintenance problem 

relative to a NAAQS. See EME Homer 

City, 134 S. Ct. at 1608. If the EPA’s 

analysis determines that there are no 

such downwind air quality problems in 

the future, then the EPA cannot 

demonstrate that further emission 

reductions are necessary from an 

upwind state and the EPA lacks the 

authority to prohibit any further 

emissions. See id.; EME Homer City II, 

795 F.3d at 130. Under such 

circumstances, there is no health or 

safety risk which may 

disproportionality affect children. 

I. Executive Order 13211: Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use 

This action is not a ‘‘significant 

energy action’’ because it is not likely to 


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have a significant adverse effect on the 

supply, distribution, or use of energy. 

This action simply updates the existing 

CSAPR Update FIPs to establish that no 

further federal regulatory requirements 

are necessary. 

J. National Technology Transfer 

Advancement Act 

This rulemaking does not involve 

technical standards. 

K. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations 

Consistent with Executive Order 

12898 and the EPA’s environmental 

justice policies, the EPA considered 

effects on low-income populations, 

minority populations, and indigenous 

peoples while developing the CSAPR 

Update. The process and results of that 

consideration are described in the 

preamble for the CSAPR Update, 81 FR 

74585 (October 26, 2016). Because this 

action simply updates the existing 

CSAPR Update FIPs to establish that no 

further federal regulatory requirements 

are necessary and does not establish a 

new environmental health or safety 

standard, the EPA believes that no 

further review of this action under 

Executive Order 12898 is necessary. 

Comment: One commenter asserts 

that the EPA has failed either to identify 

or to address the disproportionately 

high and adverse impact on minority 

communities of continued interstate 

ozone pollution that contributes to 

violations of both the 2008 and 2015 

health-based standards for ozone and 

harms human health, in violation of the 

Executive Order. The commenter notes 

that the EPA’s modeling conducted for 

the CSAPR Update showed that 

interstate ozone pollution contributes 

significantly to downwind states’ failure 

to attain and maintain the 2008 ozone 

standard and identified the downwind 

nonattainment and maintenance areas 

that receive this pollution. However, the 

commenter contends that the EPA 

conceded the CSAPR Update would 

achieve only very small reductions in 

the pollution and that the EPA expected 

air quality problems in downwind areas 

to persist. Data for the 2017 ozone 

season confirms the EPA’s projection 

that these areas would continue to suffer 

poor air quality in violation of the 2008 

standard. The commenter asserts that 

the agency’s claim that all Eastern states 

will be in compliance with the 2008 

ozone standard in 2023 does not negate 

the serious harms that will result from 

unhealthy ozone levels this year, next 

year, and in future years. The 

commenter states that the populations 

in downwind areas that continue to 

experience violations are 

disproportionately members of minority 

racial and ethnic groups, and that the 

EPA’s decision will expose 

communities who live near polluting 

sources, who are also disproportionally 

members of racial and ethnic minorities, 

to continued high levels of pollution. 

The commenter further asserts that 

people most exposed to power plant 

pollution are the least likely to be able 

to afford the health care costs imposed 

by exposure to pollution and are 

otherwise socially disadvantaged. 

The commenter concludes that the 

agency’s attempt to justify its failure to 

identify and address disproportionately 

high and adverse impacts on minority 

populations is contrary to the Executive 

Order and arbitrary. The commenter 

explains that Executive Order 12898 

applies to all ‘‘effects of [EPA’s] 

programs, policies, and activities,’’ 

which includes effects of the EPA’s 

administration of the Clean Air Act’s 

good neighbor provision and the 

decision not to address ongoing air 

pollution that contributes to violations 

of health-based air quality standards. 

The commenter contends that there is 

no basis to conclude that the Executive 

Order creates any exception for EPA 

programs, policies, or activities that 

effectively authorize, rather than curtail 

pollution, concluding that decisions 

that result in greater pollution are most 

likely to have disproportionately high 

and adverse impacts on minority 

populations. 

Response: The health-based standard 

at issue in this action was set in a prior 

rulemaking to promulgate the 2008 

ozone NAAQS, wherein the EPA did 

consider the effects of ozone on 

different populations, including those 

identified by the commenter. 73 FR 

16436, 16507. As discussed earlier, the 

EPA also considered these effects in 

promulgating the emission reduction 

obligations intended to address 

downwind nonattainment and 

maintenance concerns with respect to 

this standard in the CSAPR Update. 

However, under the good neighbor 

provision, the EPA’s authority to 

prohibit emission reductions from 

sources in upwind states is constrained 

by the obligation to demonstrate that 

such reductions are necessary to address 

a downwind nonattainment or 

maintenance problem relative to a 

NAAQS. See EME Homer City, 134 S. 

Ct. at 1608. If the EPA’s analysis 

demonstrates that there are no such 

downwind air quality problems in the 

future, then the EPA cannot 

demonstrate that further emission 

reductions are necessary from an 

upwind state and the EPA therefore 

lacks the authority to prohibit any 

further emissions. See id.; EME Homer 

City II, 795 F.3d at 130. Under such 

circumstances, further review under 

Executive Order 12898 is not warranted. 

L. Congressional Review Act 

This action is subject to the 

Congressional Review Act, and the EPA 

will submit a rule report to each House 

of the Congress and to the Comptroller 

General of the United States. This action 

is not a ‘‘major rule’’ as defined by 5 

U.S.C. 804(2). 

M. Determinations Under CAA Section 

307(b)(1) and (d) 

Section 307(b)(1) of the CAA indicates 

which Federal Courts of Appeal have 

venue for petitions of review of final 

actions by the EPA. This section 

provides, in part, that petitions for 

review must be filed in the Court of 

Appeals for the District of Columbia 

Circuit if: (i) the agency action consists 

of ‘‘nationally applicable regulations 

promulgated, or final action taken, by 

the Administrator’’; or (ii) such action is 

locally or regionally applicable, but 

‘‘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.’’ 

The EPA finds that this action is 

‘‘nationally applicable’’ or, in the 

alternative, is based on a determination 

of ‘‘nationwide scope and effect’’ within 

the meaning of section 307(b)(1). This 

action addresses emissions impacts and 

sources located in 20 States, which are 

located in multiple EPA Regions and 

federal circuits. The final action is also 

based on a common core of factual 

findings and analyses concerning the 

transport of pollutants between the 

different states. Furthermore, the EPA 

intends this interpretation and approach 

to be consistently implemented 

nationwide with respect to section 

110(a)(2)(D)(i)(I) for the 2008 ozone 

NAAQS. 

For these reasons, the Administrator 

determines that this final action is 

nationally applicable or, in the 

alternative, is based on a determination 

of nationwide scope and effect for 

purposes of section 307(b)(1). Thus, 

pursuant to section 307(b), any petitions 

for review of this final action must be 

filed in the Court of Appeals for the 

District of Columbia Circuit within 60 

days from the date this final action is 

published in the Federal Register. 

In addition, pursuant to sections 

307(d)(1)(C) and 307(d)(1)(V) of the 

CAA, the Administrator has determined 


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that this action is subject to the 

provisions of section 307(d). CAA 

section 307(d)(1)(B) provides that 

section 307(d) applies to, among other 

things, ‘‘the promulgation or revision of 

an implementation plan by the 

Administrator under CAA section 

110(c).’’ 42 U.S.C. 7407(d)(1)(B). Under 

section 307(d)(1)(V), the provisions of 

section 307(d) also apply to ‘‘such other 

actions as the Administrator may 

determine.’’ 42 U.S.C. 7407(d)(1)(V). 

The agency has complied with 

procedural requirements of CAA section 

307(d) during the course of this 

rulemaking. 

List of Subjects in 40 CFR Part 52 

Environmental protection, 

Administrative practice and procedure, 

Air pollution control, Incorporation by 

reference, Intergovernmental relations, 

Nitrogen oxides, Ozone, Particulate 

matter, Regional haze, Reporting and 

recordkeeping requirements, Sulfur 

dioxide. 

Dated: December 6, 2018. 

Andrew R. Wheeler, 

Acting Administrator. 

For the reasons stated in the 

preamble, part 52 of chapter I of title 40 

of the Code of Federal Regulations is 

amended as follows: 

PART 52—APPROVAL AND 

PROMULGATION OF 

IMPLEMENTATION PLANS 

■ 1. The authority citation for part 52 

continues to read as follows: 

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

§§ 52.54, 52.184, 52.731, 52.789, 52.840, 

52.882, 52.984, 52.1084, 52.1186, 52.1284, 

52.1326, 52.1584, 52.1684, 52.1882, 52.1930, 

52.2040, 52.2283, 52.2440, 52.2540, and 

52.2587 [Amended] 

■ 2. Part 52 is amended by removing the 

text ‘‘, provided that because the CSAPR 

FIP was promulgated as a partial rather 

than full remedy for an obligation of the 

State to address interstate air pollution, 

the SIP revision likewise will constitute 

a partial rather than full remedy for the 

State’s obligation unless provided 

otherwise in the Administrator’s 

approval of the SIP revision’’ from the 

second sentence in each of the following 

paragraphs: 

■ a. Section 52.54(b)(2); 

■ b. Section 52.184(b); 

■ c. Section 52.731(b)(2); 

■ d. Section 52.789(b)(2); 

■ e. Section 52.840(b)(2); 

■ f. Section 52.882(b)(1); 

■ g. Section 52.984(d)(2); 

■ h. Section 52.1084(b)(2); 

■ i. Section 52.1186(e)(2); 

■ j. Section 52.1284(b); 

■ k. Section 52.1326(b)(2); 

■ l. Section 52.1584(e)(2); 

■ m. Section 52.1684(b)(2); 

■ n. Section 52.1882(b)(2); 

■ o. Section 52.1930(b); 

■ p. Section 52.2040(b)(2); 

■ q. Section 52.2283(d)(2); 

■ r. Section 52.2440(b)(2); 

■ s. Section 52.2540(b)(2); and 

■ t. Section 52.2587(e)(2). 

[FR Doc. 2018–27160 Filed 12–20–18; 8:45 am] 

BILLING CODE 6560–50–P 


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