[Federal Register Volume 86, Number 165 (Monday, August 30, 2021)]
[Proposed Rules]
[Pages 48357-48363]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-18516]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R01-OAR-2021-0353; FRL-8916-01-R1]


Air Plan Approval; Connecticut; 2015 Ozone NAAQS Interstate 
Transport Requirements

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Clean Air Act (CAA) requires each State Implementation 
Plan (SIP) to contain adequate provisions prohibiting emissions that 
will have certain adverse air quality effects in other states. The 
State of Connecticut made a submission to the Environmental Protection 
Agency (EPA) to address these requirements for the 2015 ozone National 
Ambient Air Quality Standards (NAAQS). EPA is proposing to approve the 
submission as meeting the requirement that each SIP contain adequate 
provisions to prohibit emissions that will significantly contribute to 
nonattainment or interfere with maintenance of the 2015 ozone NAAQS in 
any other state.

DATES: Written comments must be received on or before September 29, 
2021.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R01-
OAR-2021-0353 at https://www.regulations.gov, or via email to 
[email protected]. For comments submitted at Regulations.gov, 
follow the online instructions for submitting comments. Once submitted, 
comments cannot be edited or removed from Regulations.gov. For either 
manner of submission, EPA may publish any comment received to its 
public docket. Do not submit electronically any information you 
consider to be Confidential Business Information (CBI) or other 
information whose disclosure is restricted by statute. Multimedia 
submissions (audio, video, etc.) must be

[[Page 48358]]

accompanied by a written comment. The written comment is considered the 
official comment and should include discussion of all points you wish 
to make. EPA will generally not consider comments or comment contents 
located outside of the primary submission (i.e., on the web, cloud, or 
other file sharing system). For additional submission methods, please 
contact the person identified in the FOR FURTHER INFORMATION CONTACT 
section. For the full EPA public comment policy, information about CBI 
or multimedia submissions, and general guidance on making effective 
comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets. Publicly available docket materials are available at https://www.regulations.gov or at the U.S. Environmental Protection Agency, EPA 
Region 1 Regional Office, Air and Radiation Division, 5 Post Office 
Square--Suite 100, Boston, MA. EPA requests that if at all possible, 
you contact the contact listed in the FOR FURTHER INFORMATION CONTACT 
section to schedule your inspection. The Regional Office's official 
hours of business are Monday through Friday, 8:30 a.m. to 4:30 p.m., 
excluding legal holidays and facility closures due to COVID-19.

FOR FURTHER INFORMATION CONTACT: Alison C. Simcox, Air Quality Branch, 
U.S. Environmental Protection Agency, EPA Region 1, 5 Post Office 
Square--Suite 100, (Mail code 05-2), Boston, MA 02109--3912, telephone 
number: (617) 918-1684, email address: [email protected].

SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,'' 
``us,'' or ``our'' is used, we mean EPA.

Table of Contents

I. Background
II. Connecticut Submittal
III. EPA Evaluation of Connecticut's Submittal
IV. Proposed Action
V. Statutory and Executive Order Reviews

I. Background

    On October 1, 2015, EPA promulgated a revision to the ozone NAAQS 
(2015 ozone NAAQS), lowering the level of both the primary and 
secondary standards to 0.070 parts per million (ppm).\1\ Section 
110(a)(1) of the CAA requires states to submit, within 3 years after 
promulgation of a new or revised standard, SIP submissions meeting the 
applicable requirements of section 110(a)(2).\2\ One of these 
applicable requirements is found in section 110(a)(2)(D)(i)(I), 
otherwise known as the good neighbor provision, which generally 
requires SIPs to contain adequate provisions to prohibit in-state 
emissions activities from having certain adverse air quality effects on 
other states due to interstate transport of pollution. There are two 
so-called ``prongs'' within CAA section 110(a)(2)(D)(i)(I). A SIP for a 
new or revised NAAQS must contain adequate provisions prohibiting any 
source or other type of emissions activity within the state from 
emitting air pollutants in amounts that will significantly contribute 
to nonattainment of the NAAQS in another state (prong 1), or interfere 
with maintenance of the NAAQS in another state (prong 2). EPA and 
states must give independent significance to prong 1 and prong 2 when 
evaluating downwind air quality problems under CAA section 
110(a)(2)(D)(i)(I).\3\
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    \1\ National Ambient Air Quality Standards for Ozone, Final 
Rule, 80 FR 65292 (October 26, 2015). Although the level of the 
standard is specified in the units of ppm, ozone concentrations are 
also described in parts per billion (ppb). For example, 0.070 ppm is 
equivalent to 70 ppb.
    \2\ SIP revisions that are intended to meet the applicable 
requirements of section 110(a)(1) and (2) of the CAA are often 
referred to as infrastructure SIPs and the applicable elements under 
section 110(a)(2) are referred to as infrastructure requirements.
    \3\ See North Carolina v. EPA, 531 F.3d 896, 909-911 (D.C. Cir. 
2008).
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    We note that EPA has addressed the interstate transport 
requirements of CAA section 110(a)(2)(D)(i)(I) with respect to prior 
ozone NAAQS in several regional regulatory actions, including the 
Cross-State Air Pollution Rule (CSAPR), which addressed interstate 
transport with respect to the 1997 ozone NAAQS as well as the 1997 and 
2006 fine particulate matter standards,\4\ the Cross-State Air 
Pollution Rule Update (CSAPR Update), and, most recently, the Revised 
CSAPR Update for the 2008 ozone NAAQS.5 6
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    \4\ See 76 FR 48208 (August 8, 2011).
    \5\ In 2019, the D.C. Circuit Court of Appeals remanded the 
CSAPR Update to the extent it failed to require upwind states to 
eliminate their significant contribution by the next applicable 
attainment date by which downwind states must come into compliance 
with the NAAQS, as established under CAA section 181(a). Wisconsin 
v. EPA, 938 F.3d 303, 313 (D.C. Cir. 2019).
    \6\ The Revised Cross-State Air Pollution Rule Update for the 
2008 Ozone NAAQS, 86 FR 23054 (April 30, 2021), was signed by the 
EPA Administrator on March 15, 2021, and responded to the remand of 
the CSAPR Update, 81 FR 74504 (October 26, 2016), and the vacatur of 
a separate rule, the CSAPR Close-Out, 83 FR 65878 (December 21, 
2018), by the D.C. Circuit. Wisconsin v. EPA, 938 F.3d 303 (D.C. 
Cir. 2019); New York v. EPA, 781 F. App'x. 4 (D.C. Cir. 2019).
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    Through the development and implementation of CSAPR and other 
regional rulemakings pursuant to the good neighbor provision,\7\ EPA, 
working in partnership with states, developed the following four-step 
interstate transport framework to address the requirements of the good 
neighbor provision for the ozone NAAQS: (1) Identify downwind air 
quality problems; (2) identify upwind states that impact those downwind 
air quality problems sufficiently such that they are considered 
``linked'' and therefore warrant further review and analysis; (3) 
identify the emissions reductions necessary (if any), applying a multi-
factor analysis, to prevent linked upwind states identified in step 2 
from contributing significantly to nonattainment or interfering with 
maintenance of the NAAQS at the locations of the downwind air quality 
problems; and (4) adopt permanent and enforceable measures needed to 
achieve those emissions reductions.
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    \7\ In addition to the CSAPR rulemakings, other regional 
rulemakings addressing ozone transport include the NOX 
SIP Call, 63 FR 57356 (October 27, 1998), and the Clean Air 
Interstate Rule (CAIR), 70 FR 25162 (May 12, 2005).
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    EPA has released several documents containing information relevant 
to evaluating interstate transport with respect to the 2015 ozone 
NAAQS. First, on January 6, 2017, EPA published a notice of data 
availability (NODA) with preliminary interstate ozone transport 
modeling with projected ozone design values (DVs) for 2023 using a 2011 
base year platform, on which we requested public comment.\8\ In the 
NODA, EPA used the year 2023 as the analytic year for this preliminary 
modeling because that year aligns with the expected attainment year for 
Moderate ozone nonattainment areas for the 2015 ozone NAAQS.\9\ On 
October 27, 2017, we released a memorandum (2017 memo) containing 
updated modeling data for 2023, which incorporated changes made in 
response to comments on the NODA, and noted that the modeling may be 
useful for states developing SIPs to address good neighbor obligations 
for the 2008 ozone NAAQS.\10\ On March 27, 2018, we issued a memorandum 
(March 2018 memo) noting that the same 2023 modeling data released in 
the 2017 memo could also be useful for identifying potential downwind 
air quality problems with respect to the 2015 ozone NAAQS at step 1 of 
the

[[Page 48359]]

four-step interstate transport framework. The March 2018 memo also 
included the then newly available contribution modeling results to 
assist states in evaluating their impact on potential downwind air 
quality problems for the 2015 ozone NAAQS under step 2 of the 
interstate transport framework. EPA subsequently issued two more 
memoranda in August and October 2018, providing additional information 
to states developing good neighbor SIP submissions for the 2015 ozone 
NAAQS concerning, respectively, potential contribution thresholds that 
may be appropriate to apply in step 2 of the framework, and 
considerations for identifying downwind areas that may have problems 
maintaining the standard at step 1 of the framework.\11\
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    \8\ See Notice of Availability of the Environmental Protection 
Agency's Preliminary Interstate Ozone Transport Modeling Data for 
the 2015 Ozone National Ambient Air Quality Standard (NAAQS), 82 FR 
1733 (January 6, 2017).
    \9\ 82 FR 1733, 1735 (January 6, 2017).
    \10\ See Information on the Interstate Transport State 
Implementation Plan Submissions for the 2008 Ozone National Ambient 
Air Quality Standards under Clean Air Act Section 
110(a)(2)(D)(i)(I), October 27, 2017, available in the docket for 
this action or at https://www.epa.gov/interstate-air-pollution-transport/interstate-air-pollution-transport-memos-and-notices.
    \11\ See Analysis of Contribution Thresholds for Use in Clean 
Air Act Section 110(a)(2)(D)(i)(I) Interstate Transport State 
Implementation Plan Submissions for the 2015 Ozone National Ambient 
Air Quality Standards, August 31, 2018) (``August 2018 memo''), and 
Considerations for Identifying Maintenance Receptors for Use in 
Clean Air Act Section 110(a)(2)(D)(i)(I) Interstate Transport State 
Implementation Plan Submissions for the 2015 Ozone National Ambient 
Air Quality Standards, October 19, 2018, available in the docket for 
this action or at https://www.epa.gov/airmarkets/memo-and-supplemental-information-regarding-interstate-transport-sips-2015-ozone-naaqs.
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    On October 30, 2020, in the Notice of Proposed Rulemaking for the 
Revised CSAPR Update, EPA released and accepted public comment on 
updated 2023 modeling that used a 2016 emissions platform developed 
under the EPA/Multi-Jurisdictional Organization (MJO)/state 
collaborative project as the primary source for the base year and 
future year emissions data.\12\ On March 15, 2021, EPA signed the final 
Revised CSAPR Update using the same modeling released at proposal.\13\ 
Although Connecticut relied on the modeling included in the March 2018 
memo to develop its SIP submission as EPA had suggested, EPA now 
proposes to primarily rely on the updated and newly available 2016 base 
year modeling in evaluating these submissions. By using the updated 
modeling results, EPA is using the most current and technically 
appropriate information as the primary basis for this proposed 
rulemaking. EPA's independent analysis, which also evaluated historical 
monitoring data, recent DVs, and emissions trends, found that such 
information provides additional support and further substantiates the 
results of the 2016 base year modeling as the basis for this proposed 
rulemaking. Section III of this document and the Air Quality Modeling 
technical support document (TSD) included in the docket for this 
proposal contain additional detail on this modeling.\14\
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    \12\ See 85 FR 68964, 68981. The results of this modeling are 
included in a spreadsheet in the docket for this action. The 
underlying modeling files are available for public review in the 
docket for the Revised CSAPR Update (EPA-HQ-OAR-2020-0272).
    \13\ See 86 FR 23054 at 23075, 23164 (April 30, 2021).
    \14\ See ``Air Quality Modeling Technical Support Document for 
the Revised Cross-State Air Pollution Rule Update,'' 86 FR 23054 
(April 30, 2021), available in the docket for this action. This TSD 
was originally developed to support EPA's action in the Revised 
CSAPR Update, as relating to outstanding good neighbor obligations 
under the 2008 ozone NAAQS. While developed in this separate 
context, the data and modeling outputs, including interpolated 
design values for 2021, may be evaluated with respect to the 2015 
ozone NAAQS and used in support of this proposal.
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    In the CSAPR, CSAPR Update, and the Revised CSAPR Update, EPA used 
a threshold of one percent of the NAAQS to determine whether a given 
upwind state was ``linked'' at step 2 of the interstate transport 
framework and would, therefore, contribute to downwind nonattainment 
and maintenance sites identified in step 1. If a state's impact did not 
equal or exceed the one percent threshold, the upwind state was not 
``linked'' to a downwind air quality problem, and EPA, therefore, 
concluded the state would not significantly contribute to nonattainment 
or interfere with maintenance of the NAAQS in the downwind states. 
However, if a state's impact equaled or exceeded the one percent 
threshold, the state's emissions were further evaluated in step 3, 
considering both air quality and cost considerations, to determine 
what, if any, emissions might be deemed ``significant'' and, thus, must 
be eliminated under the good neighbor provision. EPA is proposing to 
rely on the one percent threshold (which is 0.70 ppb) for the purpose 
of evaluating Connecticut's contribution to nonattainment or 
maintenance of the 2015 ozone NAAQS in downwind areas.
    Several D.C. Circuit court decisions address the issue of the 
relevant analytic year for the purposes of evaluating ozone transport 
air-quality problems. On September 13, 2019, the D.C. Circuit issued a 
decision in Wisconsin v. EPA, remanding the CSAPR Update to the extent 
that it failed to require upwind states to eliminate their significant 
contribution by the next applicable attainment date by which downwind 
states must come into compliance with the NAAQS, as established under 
CAA section 181(a). 938 F.3d 303, 313.
    On May 19, 2020, the D.C. Circuit issued a decision in Maryland v. 
EPA that cited the Wisconsin decision in holding that EPA must assess 
the impact of interstate transport on air quality at the next downwind 
attainment date, including Marginal area attainment dates, in 
evaluating the basis for EPA's denial of a petition under CAA section 
126(b). Maryland v. EPA, 958 F.3d 1185, 1203-04 (D.C. Cir. 2020). The 
court noted that ``section 126(b) incorporates the Good Neighbor 
Provision,'' and, therefore, ``EPA must find a violation [of section 
126] if an upwind source will significantly contribute to downwind 
nonattainment at the next downwind attainment deadline. Therefore, the 
agency must evaluate downwind air quality at that deadline, not at some 
later date.'' Id. at 1204 (emphasis added). EPA interprets the court's 
holding in Maryland as requiring the Agency, under the good neighbor 
provision, to assess downwind air quality by the next applicable 
attainment date, including a Marginal area attainment date under CAA 
section 181 for ozone nonattainment.\15\ The Marginal area attainment 
date for the 2015 ozone NAAQS is August 3, 2021.\16\ Historically, EPA 
has considered the full ozone season prior to the attainment date as 
supplying an appropriate analytic year for assessing good neighbor 
obligations. While this would be 2020 for an August 2021 attainment 
date (which falls within the 2021 ozone season running from May 1 to 
September 30), in this circumstance, when the 2020 ozone season is 
wholly in the past, it is appropriate to focus on 2021 to address good 
neighbor obligations to the extent possible by the 2021 attainment 
date. EPA does not believe it would be appropriate to select an 
analytical year that is wholly in the past, because the agency 
interprets the good neighbor provision as forward looking. See 86 FR 
23054 at 23074; see also Wisconsin, 938 F.3d at 322. Consequently, in 
this proposal EPA will use the analytical year of 2021 to evaluate 
Connecticut's good neighbor

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obligation with respect to the 2015 ozone NAAQS.\17\
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    \15\ We note that the court in Maryland did not have occasion to 
evaluate circumstances in which EPA may determine that an upwind 
linkage to a downwind air quality problem exists at steps 1 and 2 of 
the interstate transport framework by a particular attainment date, 
but for reasons of impossibility or profound uncertainty the Agency 
is unable to mandate upwind pollution controls by that date. See 
Wisconsin, 938 F.3d at 320. The D.C. Circuit noted in Wisconsin that 
upon a sufficient showing, these circumstances may warrant 
flexibility in effectuating the purpose of the good neighbor 
provision. Such circumstances are not at issue in the present 
proposal.
    \16\ CAA section 181(a); 40 CFR 51.1303; Additional Air Quality 
Designations for the 2015 Ozone National Ambient Air Quality 
Standards, 83 FR 25776 (June 4, 2018, effective Aug. 3, 2018).
    \17\ EPA recognizes that by the time final action is taken with 
respect to this SIP submission, the 2021 ozone season will be wholly 
in the past. As discussed below, the available modeling information 
indicates that our analysis would not change even using 2023 as the 
analytic year. The 2023 modeling results are included in the ``Ozone 
Design Values and Contributions Revised CSAPR Update.xlsx'', 
included in the docket for this action.
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II. Connecticut Submittal

    On December 6, 2018, Connecticut submitted a SIP revision 
addressing the CAA section 110(a)(2)(D)(i)(I) interstate transport 
requirements for the 2015 ozone NAAQS. Connecticut relied on the 
results of EPA's modeling for the 2015 ozone NAAQS contained in the 
March 2018 memo to identify downwind nonattainment and maintenance 
receptors that may be impacted by emissions from sources in Connecticut 
in the year 2023. These results indicate Connecticut's greatest impact 
on any potential downwind nonattainment or maintenance receptor would 
be 0.83 ppb in Suffolk County, New York.\18\ Based on the March 2018 
memo, this was the only nonattainment or maintenance receptor for which 
Connecticut was projected in 2023 to contribute above the screening 
threshold of 0.70 ppb (one percent of the 2015 ozone NAAQS).
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    \18\ EPA notes that the monitoring site ID for Suffolk County, 
New York is 361030002.
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    Connecticut noted in its December 2018 good neighbor submittal that 
``EPA had considered cost-effective only reductions that are available 
at a cost of less than $1,400 per ton of emissions reduced. 
Connecticut's emitters are currently required to adopt control measures 
at costs exceeding $13,000 per ton (of NOX).'' \19\ 
Connecticut states that as it requires this high level of control of 
ozone precursor emissions, it has exhausted lower-cost emission 
reduction measures.
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    \19\ EPA notes that the $1,400 ton per year threshold stated by 
Connecticut is in reference to the cost per ton threshold used in 
the CSAPR Update, which was used to evaluate available cost-
effective EGU controls under the 2008 ozone NAAQS of 0.075 ppm. See 
81 FR 74504 (October 26, 2016).
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    As evidence of this, Connecticut points to Regulations of 
Connecticut Agencies section 22a-174-22e(g) and its ozone attainment 
plan technical support document for the 2008 ozone NAAQS, which was 
submitted to EPA in August 2017 and documents the State's ozone 
precursor emission reduction measures.
    Connecticut concludes that it has met its good neighbor obligations 
for the 2015 ozone NAAQS because of the existing control measures that 
are in place.

III. EPA Evaluation of Connecticut's Submittal

    Connecticut's SIP submission relies on analysis of the year 2023 to 
show whether it contributes to nonattainment or interferes with 
maintenance of the 2015 ozone NAAQS in any other state.\20\ As 
explained in Section I of this proposal, EPA has conducted an updated 
analysis for the 2021 analytical year that is being used to evaluate 
Connecticut's transport SIP submittal. Significantly, this new analysis 
shows that, in 2021, Connecticut is not projected to contribute to any 
potential downwind nonattainment or maintenance receptor, including the 
monitor in Suffolk County, New York, above the screening threshold of 
0.70 ppb (one percent of the 2015 ozone NAAQS). While EPA has focused 
its analysis in this document on the year 2021, modeling data in the 
record for years 2023 and 2028 confirm that no new linkages to downwind 
receptors are projected for Connecticut in later years. This is not 
surprising as it is consistent with an overall, long-term downward 
trend in emissions from this state.
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    \20\ We recognize that Connecticut and other states may have 
been influenced by EPA's 2018 guidance memos (issued prior to the 
Wisconsin and Maryland decisions) in making good neighbor 
submissions that relied on EPA's modeling of 2023. When there are 
intervening changes in relevant law or legal interpretation of CAA 
requirements, states are generally free to withdraw, supplement, 
and/or re-submit their SIP submissions with new analysis (in 
compliance with CAA procedures for SIP submissions). While 
Connecticut has not done this, as explained in this section, the 
independent analysis EPA has conducted at its discretion confirms 
that the state's submission in this instance is ultimately 
approvable.
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    As explained in Section I of this document, in consideration of the 
holdings in Wisconsin and Maryland, EPA's analysis relies on 2021 as 
the relevant attainment year for evaluating Connecticut's good neighbor 
obligations with respect to the 2015 ozone NAAQS using the four-step 
interstate transport framework. In step 1, we identify locations where 
the Agency expects there to be nonattainment or maintenance receptors 
for the 2015 8-hour ozone NAAQS in the 2021 analytic year. Where EPA's 
analysis shows that an area or site does not fall under the definition 
of a nonattainment or maintenance receptor, that site is excluded from 
further analysis under EPA's four step interstate transport framework. 
For areas that are identified as a nonattainment or maintenance 
receptor in 2021, we proceed to the next step of our four-step 
framework by identifying the upwind state's contribution to those 
receptors.
    EPA's approach to identifying ozone nonattainment and maintenance 
receptors in this action is consistent with the approach used in 
previous transport rulemakings. EPA's approach gives independent 
consideration to both the ``contribute significantly to nonattainment'' 
and the ``interfere with maintenance'' prongs of CAA section 
110(a)(2)(D)(i)(I), consistent with the D.C. Circuit's direction in 
North Carolina v. EPA.\21\
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    \21\ See North Carolina v. EPA, 531 F.3d 896, 910-11 (D.C. Cir. 
2008) (holding that EPA must give ``independent significance'' to 
each prong of CAA section 110(a)(2)(D)(i)(I)).
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    For the purpose of this proposal, EPA identifies nonattainment 
receptors as those monitoring sites that are projected to have average 
design values that exceed the NAAQS and that are also measuring 
nonattainment based on the most recent monitored design values. This 
approach is consistent with prior transport rulemakings, such as CSAPR 
Update, where EPA defined nonattainment receptors as those areas that 
both currently monitor nonattainment and that EPA projects will be in 
nonattainment in the future analytic year.\22\
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    \22\ See 81 FR 74504 (October 26, 2016). Revised CSAPR Update 
also used this approach. See 86 FR 23054 (April 30, 2021). This same 
concept, relying on both current monitoring data and modeling to 
define nonattainment receptor, was also applied in CAIR. See 70 FR 
25241 (January 14, 2005); see also North Carolina, 531 F.3d at 913-
14 (affirming as reasonable EPA's approach to defining nonattainment 
in CAIR).
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    In addition, in this proposal, EPA identifies a receptor to be a 
``maintenance'' receptor for purposes of defining interference with 
maintenance, consistent with the method used in the CSAPR and upheld by 
the D.C. Circuit in EME Homer City Generation, L.P. v. EPA, 795 F.3d 
118, 136 (D.C. Cir. 2015).\23\ Specifically, monitoring sites with a 
projected maximum design value in 2021 that exceeds the NAAQS are 
considered maintenance receptors. EPA's method of defining these 
receptors takes into account both measured data and reasonable 
projections based on modeling analysis.
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    \23\ See 76 FR 48208 (August 8, 2011). CSAPR Update and Revised 
CSAPR Update also used this approach. See 81 FR 74504 (October 26, 
2016) and 86 FR 23054 (April 30, 2021).
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    Recognizing that nonattainment receptors are also, by definition, 
maintenance receptors, EPA often uses the term ``maintenance-only'' to 
refer to receptors that are not also nonattainment receptors. 
Consistent with the methodology described above, monitoring sites with 
a projected maximum design value that exceeds the NAAQS, but with a 
projected average design value that is below the NAAQS,

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are identified as maintenance-only receptors. In addition, those sites 
that are currently measuring ozone concentrations below the level of 
the applicable NAAQS but are projected to be 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.
    To evaluate future air quality in steps 1 and 2 of the interstate 
transport framework, EPA is using the 2016 and 2023 base case emissions 
developed under the EPA/MJO/state collaborative emissions modeling 
platform project as the primary source for base year and 2023 future 
year emissions data for this proposal.\24\ Because this platform does 
not include emissions for 2021, EPA developed an interpolation 
technique based on modeling for 2023 and measured ozone data to 
determine ozone concentrations for 2021. To estimate average and 
maximum design values for 2021, EPA first performed air quality 
modeling for 2016 and 2023 to obtain design values in 2023. The 2023 
design values were then coupled with the corresponding 2016 measured 
design values to estimate design values in 2021. Details on the 
modeling, including the interpolation methodology, can be found in the 
Air Quality Modeling TSD, found in the docket for this proposal.
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    \24\ See 86 FR 23054 (April 30, 2021). The results of this 
modeling are included in a spreadsheet in the docket for this 
action. The underlying modeling files are available for public 
access in the docket for the Revised CSAPR Update (EPA-HQ-OAR-2020-
0272).
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    To quantify the contribution of emissions from specific upwind 
states on 2021 8-hour design values for the identified downwind 
nonattainment and maintenance receptors, EPA first performed 
nationwide, state-level ozone source apportionment modeling for 2023. 
The source apportionment modeling provided contributions to ozone from 
precursor emissions of anthropogenic nitrogen oxides (NOX) 
and volatile organic compounds (VOCs) in each state, individually. The 
modeled contributions were then applied in a relative sense to the 2021 
average design value to estimate the contributions in 2021 from each 
state to each receptor. Details on the source apportionment modeling 
and the methods for determining contributions in 2021 are in the Air 
Quality Modeling TSD in the docket.
    The 2021 design values and contributions were examined to determine 
if Connecticut contributes at or above the threshold of one percent of 
the 2015 ozone NAAQS (0.70 ppb) to any downwind nonattainment or 
maintenance receptor. The data \25\ indicate that the highest 
contribution in 2021 from Connecticut to a downwind nonattainment or 
maintenance receptor is 0.44 ppb to a nonattainment receptor in 
Richmond County, New York (monitoring site 360850067). The data also 
show modeled ozone contributions from Connecticut to the design values 
of a larger set of monitoring sites (independent of attainment status) 
and indicate that the highest projected contribution in 2021 from 
Connecticut to any of these sites is 3.51 ppb to Kent County in Rhode 
Island (monitoring site 440030002; #378 on the Design Values and 
Contributions spreadsheet). While Connecticut's modeled contribution to 
the Kent County monitor exceeds one percent of the 2015 ozone NAAQS, 
EPA's analysis at step 1 does not identify the Kent County monitor as a 
downwind area that may have problems maintaining the 2015 ozone NAAQS. 
The Kent County monitor's projected average design value in 2021 is 
65.5 ppb. The updated modeling for 2021 also shows that Connecticut is 
no longer projected to be linked to the Suffolk County monitoring site, 
since this monitor is no longer projected to be a nonattainment or 
maintenance receptor.
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    \25\ The data are given in the ``Air Quality Modeling Technical 
Support Document for the Revised Cross-State Air Pollution Rule 
Update'' and ``Ozone Design Values and Contributions Revised CSAPR 
Update.xlsx,'' which are included in the docket for this action.
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    EPA also analyzed ozone precursor emissions trends in Connecticut 
to support the findings from the air quality analysis. In evaluating 
emissions trends, we first reviewed the information submitted by the 
state and then reviewed additional information available to the Agency. 
We focused on state-wide emissions of NOX and VOCs.\26\ 
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. This evaluation 
looks at both past emissions trends, as well as projected trends.
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    \26\ This is because ground-level ozone is not emitted directly 
into the air but is formed by chemical reactions between ozone 
precursors, chiefly NOX and VOCs, in the presence of 
sunlight. See 86 FR 23054, 23063.
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    As shown in Table 1, for Connecticut, annual total NOX 
and VOC emissions are projected to decline between 2016 and 2023 by 31 
percent and 2 percent, respectively. The projected reductions are a 
result of the implementation of existing control programs that will 
continue to decrease NOX and VOC emissions in Connecticut, 
as indicated by EPA's most recent 2021 and 2023 projected emissions.
    As shown in Table 2, on-road and nonroad mobile source emissions 
collectively comprise a large portion of Connecticut's total 
anthropogenic NOX and VOCs. For example, in 2019, 
NOX emissions from mobile sources in Connecticut comprised 
62 percent of total NOX emissions and 38 percent of total 
VOC emissions.
    The large decrease in NOX emissions between 2016 
emissions and projected 2023 emissions in Connecticut is primarily 
driven by reductions in emissions from on-road and nonroad mobile 
sources. EPA projects that both VOC and NOX emissions will 
continue declining to 2023 as newer vehicles and engines that are 
subject to the most recent, stringent mobile source standards replace 
older vehicles and engines.\27\
---------------------------------------------------------------------------

    \27\ Tier 3 Motor Vehicle Emission and Fuel Standards (79 FR 
23414, April 28, 2014); Mobile Source Air Toxics Rule (MSAT2) (72 FR 
8428, February 26, 2007), Heavy-Duty Engine and Vehicle Standards 
and Highway Diesel Fuel Sulfur Control Requirements (66 FR 5002, 
January 18, 2001); Clean Air Nonroad Diesel Rule (69 FR 38957, June 
29, 2004); Locomotive and Marine Rule (73 FR 25098, May 6, 2008); 
Marine Spark-Ignition and Small Spark-Ignition Engine Rule (73 FR 
59034, October 8, 2008); New Marine Compression-Ignition Engines at 
or Above 30 Liters per Cylinder Rule (75 FR 22895, April 30, 2010); 
and Aircraft and Aircraft Engine Emissions Standards (77 FR 36342, 
June 18, 2012).
---------------------------------------------------------------------------

    In summary, based on the projected downward trend in projected 
future emissions trends, in combination with the historical decline in 
actual emissions, there is no evidence to suggest that the overall 
emissions trend demonstrated in Table 2 would suddenly reverse or spike 
in 2021 compared to historical emissions levels or those projected for 
2023. Further, there is no evidence that the projected ozone precursor 
emissions trends beyond 2021 would not continue to show a decline in 
emissions. In addition, EPA followed its normal practice of including 
in our modeling only changes in NOX or VOC emissions that 
result from final regulatory actions. Any potential changes in 
NOX or VOC emissions that may result from possible future or 
proposed regulatory actions are speculative.
    This downward trend in emissions in Connecticut adds support to the 
air quality analyses presented above for the state and indicates that 
the contributions from emissions from sources in Connecticut to ozone 
receptors in downwind states will

[[Page 48362]]

continue to decline and remain below one percent of the NAAQS.
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    \28\ The annual emissions data for the years 2011 through 2019 
were obtained from EPA's National Emissions Inventory website: 
https://www.epa.gov/air-emissions-inventories/air-pollutant-emissions-trends-data. Note that emissions from miscellaneous 
sources are not included in the state totals. The emissions for 2021 
and 2023 are based on the 2016 emissions modeling platform. See 
``2005 thru 2019 + 2021_2023_2028 Annual State Tier 1 Emissions_v3'' 
and the Emissions Modeling TSD in the docket for this action.

                                   Table 1--Annual Emissions of NOX and VOCs From Anthropogenic Sources in Connecticut
                                                                   [Tons per year] 28
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                 Projected    Projected
                                        2011      2012      2013      2014      2015      2016      2017      2018      2019        2021         2023
--------------------------------------------------------------------------------------------------------------------------------------------------------
CT NOX..............................    72,815    69,540    66,264    62,989    57,791    48,729    46,285    43,751    40,219       35,033       33,412
CT VOCs.............................    79,806    80,621    81,435    82,250    74,313    62,658    57,777    56,137    54,498       63,354       61,110
--------------------------------------------------------------------------------------------------------------------------------------------------------


                               Table 2--Annual Emissions of NOX and VOCs From On-Road and Nonroad Vehicles in Connecticut
                                                                     [Tons per year]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                 Projected    Projected
                                        2011      2012      2013      2014      2015      2016      2017      2018      2019        2021         2023
--------------------------------------------------------------------------------------------------------------------------------------------------------
CT NOX..............................    54,371    50,956    47,540    44,124    40,040    32,090    30,760    27,878    24,995       19,128       16,935
CT VOCs.............................    38,749    37,166    35,583    33,999    30,837    23,957    23,851    22,212    20,573       17,398       16,229
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Thus, EPA's air quality and emissions analyses indicate that 
emissions from Connecticut will not significantly contribute to 
nonattainment or interfere with maintenance of the 2015 ozone NAAQS in 
any other state in 2021.

IV. Proposed Action

    As discussed in Section II, Connecticut concluded that it has met 
its good neighbor obligations for the 2015 ozone NAAQS based on 
existing control measures that are in place. EPA conducted an 
independent analysis for the analytic year 2021 based on more recent 
data and updated modeling. EPA's evaluation of measured and monitored 
data, including interpolating values to generate a reasonable 
expectation of air quality and contribution values in 2021, is 
discussed in Section III. Based on the updated modeling and analysis, 
EPA concluded that emissions from sources in the state will not 
contribute significantly to nonattainment or interfere with maintenance 
of the 2015 ozone NAAQS in any other state. This conclusion remains 
true for later modeled years 2023 and 2028 in the updated modeling EPA 
is relying on. Therefore, we propose to approve the Connecticut 
submission as meeting the requirements of CAA section 
110(a)(2)(D)(i)(I).
    EPA is soliciting public comments on this document. These comments 
will be considered before taking final action. Interested parties may 
participate in the Federal rulemaking procedure by submitting written 
comments to this proposed rule by following the instructions listed in 
the ADDRESSES section of this Federal Register document.

V. Statutory and Executive Order Reviews

    Under the Clean Air Act, the Administrator is required to approve a 
SIP submission that complies with the provisions of the Act and 
applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). 
Thus, in reviewing SIP submissions, EPA's role is to approve state 
choices, provided that they meet the criteria of the Clean Air Act. 
Accordingly, this proposed action merely approves state law as meeting 
Federal requirements and does not impose additional requirements beyond 
those imposed by state law. For that reason, this proposed action:
     Is not a significant regulatory action subject to review 
by the Office of Management and Budget under Executive Orders 12866 (58 
FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);
     Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because application of those requirements would be inconsistent 
with the Clean Air Act; and
     Does not provide EPA with the discretionary authority to 
address, as appropriate, disproportionate human health or environmental 
effects, using practicable and legally permissible methods, under 
Executive Order 12898 (59 FR 7629, February 16, 1994).
    In addition, the SIP is not approved to apply on any Indian 
reservation land or in any other area where EPA or an Indian tribe has 
demonstrated that a tribe has jurisdiction. In those areas of Indian 
country, the rule does not have tribal implications and will not impose 
substantial direct costs on tribal governments or preempt tribal law as 
specified by Executive Order 13175 (65 FR 67249, November 9, 2000).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Carbon monoxide, 
Incorporation by reference, Intergovernmental relations, Lead, Nitrogen 
dioxide, Ozone, Particulate matter, Reporting and recordkeeping

[[Page 48363]]

requirements, Sulfur oxides, Volatile organic compounds.

    Dated: August 24, 2021.
Deborah Szaro,
Acting Regional Administrator, EPA Region 1.
[FR Doc. 2021-18516 Filed 8-27-21; 8:45 am]
BILLING CODE 6560-50-P