Document ID: EPA-R08-OAR-2021-0678-0001
Agency: epa
Document Type: Proposed Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: Montana; 2015 Ozone National Ambient Air Quality Standards Interstate Transport Requirements
Posted Date: 2022-02-03T05:00Z

[Federal Register Volume 87, Number 23 (Thursday, February 3, 2022)]
[Proposed Rules]
[Pages 6095-6100]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-02111]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2021-0678; FRL-9299-01-R8]

Air Plan Approval; Montana; 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 significantly contribute to nonattainment or interfere with 
maintenance of air quality in other states. The State of Montana made a 
submission to the Environmental Protection Agency (EPA or Agency) to 
address these requirements for the 2015 ozone National Ambient Air 
Quality Standards (NAAQS). EPA is proposing to approve the submission 
for Montana as meeting the requirement that the SIP contains 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 March 7, 2022.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R08-
OAR-2021-0678, to the Federal Rulemaking Portal: https://www.regulations.gov. Follow the online instructions for submitting 
comments. Once submitted, comments cannot be edited or removed from 
www.regulations.gov. 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

[[Page 6096]]

restricted by statute. Multimedia submissions (audio, video, etc.) must 
be accompanied by a written comment. The written comment is considered 
the official comment and should include discussion of all points you 
wish to make. 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, the full EPA public comment policy, information about CBI or 
multimedia submissions, and general guidance on making effective 
comments, please visit http://www2.epa.gov/dockets/commenting-epa-dockets.
    Docket: All documents in the docket are listed in the 
www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available electronically in 
www.regulations.gov. To reduce the risk of COVID-19 transmission, for 
this action we do not plan to offer hard copy review of the docket. 
Please email or call the person listed in the FOR FURTHER INFORMATION 
CONTACT section if you need to make alternative arrangements for access 
to the docket.

FOR FURTHER INFORMATION CONTACT: Ellen Schmitt, Air and Radiation 
Division, EPA, Region 8, Mailcode 8ARD-IO, 1595 Wynkoop Street, Denver, 
Colorado 80202-1129, telephone number: (303) 312-6728, email address: 
[email protected].

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

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 four 
so-called ``prongs'' within CAA section 110(a)(2)(D)(i); section 
110(a)(2)(D)(i)(I) contains prongs 1 and 2. Under prongs 1 and 2 of the 
good neighbor provision, 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 (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) with respect to the 2008 ozone 
NAAQS, 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), considering air-
quality and cost factors, 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 modeling 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 
memorandum) containing updated modeling data for 2023, which 
incorporated changes made in response to comments on the NODA, and 
noted that the modeling may be useful for states developing SIPs to 
address good neighbor obligations for the 2008 ozone NAAQS.\10\ On 
March 27, 2018, we issued a memorandum (March 2018 memorandum) noting 
that the same 2023 modeling data released in the 2017 memorandum could 
also be useful for identifying potential downwind air

[[Page 6097]]

quality problems with respect to the 2015 ozone NAAQS at step 1 of the 
four-step interstate transport framework.\11\ The March 2018 memorandum 
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.\12\
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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 as ``October 2017 Memorandum'' or at https://www.epa.gov/interstate-air-pollution-transport/interstate-air-pollution-transport-memos-and-notices.
    \11\ See Information on the Interstate Transport State 
Implementation Plan Submissions for the 2015 Ozone National Ambient 
Air Quality Standards under Clean Air Act Section 
110(a)(2)(D)(i)(I), March 27, 2018, available in the docket for this 
action as ``March 2018 Memorandum.''
    \12\ 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 
memorandum''), and Considerations for Identifying Maintenance 
Receptors for Use in Clean Air Act Section 110(a)(2)(D)(i)(I) 
Interstate Transport State Implementation Plan Submissions for the 
2015 Ozone National Ambient Air Quality Standards, October 19, 2018, 
available in the docket for this action as ``Maintenance Receptors 
Memo_Oct2018'' 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.\13\ On March 15, 2021, EPA signed the final 
Revised CSAPR Update using the same modeling released at proposal.\14\ 
Although Montana relied on the modeling included in the March 2018 memo 
to develop their 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 Revised CSAPR 
Update modeling results, EPA is using the most current and technically 
appropriate information as the primary basis for this proposed 
rulemaking.\15\ EPA's independent analysis, which evaluated historical 
monitoring data, recent DVs, and emissions trends, in addition to the 
Revised CSAPR Update modeling, provides support and further 
substantiates the results of the 2011 platform modeling relied on my 
Montana. 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 Revised CSAPR Update 
modeling.\16\
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    \13\ See 85 FR 68964, 68981. The underlying modeling files are 
available for public review in the docket for the Revised CSAPR 
Update (EPA-HQ-OAR-2020-0272).
    \14\ See 86 FR 23054 at 23075, 23164 (April 30, 2021).
    \15\ EPA recently made available updated modeling results on its 
website but was not able to incorporate those results into this 
proposal prior to signature. See https://www.epa.gov/air-emissions-modeling/2016v2-platform. In any case, these results corroborate the 
prior EPA modeling on which this proposal relies with respect to 
Montana.
    \16\ See ``Air Quality Modeling Technical Support Document for 
the Final 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 relying on the 
one percent threshold for the purpose of evaluating Montana'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).\17\
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    \17\ 938 F.3d 303, 313.
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    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).\18\ 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 no 
later than the next applicable attainment date, including a Marginal 
area attainment date under CAA section 181 for ozone nonattainment.\19\
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    \18\ Maryland v. EPA, 958 F.3d 1185, 1203-04 (D.C. Cir. 2020).
    \19\ 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.
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    However, the Marginal area attainment date for the 2015 ozone NAAQS 
was August 3, 2021.\20\ EPA does not believe it would be appropriate to 
focus its analysis on an attainment date 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, as this action is being proposed after the 2021 
attainment date (as well as after the end of the 2021 ozone season), 
EPA proposes to use 2023 as an appropriate

[[Page 6098]]

analytic year in this action. The year 2023 contains the last full 
ozone season before the next downwind attainment date, which is the 
August 3, 2024, Moderate area attainment date. (Historically, EPA has 
considered the full ozone season prior to the attainment date as 
supplying an appropriate analytic year for assessing Montana's good 
neighbor obligations.) EPA acknowledges that the first order directive 
for the timing of good neighbor compliance is ``as expeditiously as 
practicable.'' See CAA section 181(a)(1); 938 F.3d at 313. EPA believes 
that an assessment of future air quality in the 2023 analytic year is 
as expeditiously as practicable. Should any emission reductions be 
required under the four-step interstate transport framework (though, to 
be clear, none are found to be necessary for Montana in this proposal), 
EPA believes 2023 is the earliest ozone season by which such reductions 
would be possible. Therefore, EPA has analyzed projected ozone air 
quality and Montana's emissions for purposes of the good neighbor 
provision using the 2023 analytic year.
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    \20\ 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).
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II. Montana Submission

    On October 1, 2018, EPA received a SIP revision from the State of 
Montana addressing the CAA section 110(a)(2)(D)(i)(I) interstate 
transport requirements for the 2015 ozone NAAQS. Montana relied on the 
results of EPA's modeling for the 2015 ozone NAAQS contained in the 
March 2018 memorandum to identify downwind nonattainment and 
maintenance receptors that may be impacted by emissions from sources in 
Montana in the year 2023. These results indicated the State's greatest 
impact on any potential downwind nonattainment or maintenance receptor 
would be 0.10 ppb. Referencing the March 2018 memorandum modeling, this 
level of impact from Montana was found in Brazoria, Texas (monitoring 
site 480391004), Tarrant, Texas (monitoring site 484392003), and 
Milwaukee, Wisconsin (monitoring site 550790085). Montana compared this 
value to a screening threshold of 0.70 ppb, representing one percent of 
the 2015 ozone NAAQS. Because Montana's impacts to receptors in 
downwind states are projected to be less than 0.70 ppb in 2023, the 
State concluded that emissions from sources within Montana will not 
significantly contribute to nonattainment or interfere with maintenance 
of the 2015 ozone NAAQS in any other state.
    Montana's October 2018 good neighbor SIP submission also lists the 
State's regulations for controlling ozone precursors. These rules and 
regulations are included in ARM Title 17, Chapter 8, subchapters 7, 8, 
9, 10, 16, and 17.

III. EPA Evaluation of Montana's Submission

    Montana's SIP submission relies on analysis of the year 2023 (using 
a 2011 base year platform) to show that the State does not 
significantly contribute to nonattainment or interfere with maintenance 
of the 2015 ozone NAAQS in any other state. As explained in Section I 
of this proposal, EPA has conducted an updated analysis for the 2023 
analytical year (using a 2016 base year platform) and proposed to rely 
primarily on this updated modeling to evaluate Montana's transport SIP 
submission. This updated modeling corroborates Montana's conclusion 
that the State will not significantly contribute to nonattainment or 
interfere with maintenance of the 2015 ozone NAAQS in any other 
state.\21\ While EPA has focused its analysis in this document on the 
year 2023, modeling data in the record for a future analytic year, 
2028, confirm that no new linkages to downwind receptors are projected 
in later years. This is consistent with an overall, long-term downward 
trend in emissions from the State.
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    \21\ 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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    In step 1 of the four-step interstate framework, we identify 
locations where the Agency expects there to be nonattainment or 
maintenance receptors for the 2015 8-hour ozone NAAQS in the 2023 
analytic future year, using the 2016 base year modeling platform. Where 
EPA's analysis shows that an area or site does not fall under the 
definition of a nonattainment or maintenance receptor in 2023, 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 2023, 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 proposal is consistent with the approach used in 
previous transport rulemakings and is consistent with the D.C. 
Circuit's direction in North Carolina to give independent consideration 
to both the ``contribute significantly to nonattainment'' and the 
``interfere with maintenance'' prongs of CAA section 
110(a)(2)(D)(i)(I).\22\
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    \22\ 531 F.3d at 910-911 (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 the 
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.\23\
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    \23\ 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-
914 (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).\24\ Specifically, monitoring sites with a 
projected maximum design value in 2023 that exceeds the NAAQS are 
considered maintenance receptors. EPA's method of defining these 
receptors takes into account both measured data and projections based 
on modeling analysis.
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    \24\ 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 See 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, 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.

[[Page 6099]]

    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.\25\
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    \25\ 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 2023 8-hour design values for the identified downwind 
nonattainment and maintenance receptors, EPA first performed 
nationwide, state-level ozone source apportionment modeling. 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. Details 
on the source apportionment modeling and the methods for determining 
contributions are in the Air Quality Modeling TSD in the docket.
    The design values and contributions were examined to determine if 
Montana 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 \26\ indicate that the highest 
contribution in 2023 from Montana to downwind nonattainment or 
maintenance receptors is 0.08 ppb, well below the one percent of the 
NAAQS screening threshold. Montana contributes 0.08 ppb to two 
nonattainment receptors in Connecticut (monitoring site 90013007 in 
Fairfield County and monitoring site 90099002 in New Haven County) and 
to one maintenance receptor in Illinois (monitoring site 170314201 in 
Cook County).
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    \26\ 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 emissions trends for ozone precursors in Montana 
to support the findings from the air quality analysis. We focused on 
state-wide emissions of NOX and VOC.\27\ 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. EPA notes 
that the projected VOC emissions are greater than historical emissions 
in recent years according to NEI data. However, EPA also notes that 
NOX emissions are the primary contributor to regional ozone 
formation in ozone transport, and for Montana, NOX emissions 
are projected to continue to decline. As a result of these 
NOX emissions reductions, Montana is projected to contribute 
below the one percent threshold in 2023 to projected nonattainment and 
maintenance receptors and is projected to continue to contribute below 
one percent in 2028, despite the greater projected VOC emissions. 
Projected ozone design values and contributions data for 2021, 2023, 
and 2028 can be found in the file ``Ozone Design Values and 
Contributions Revised CSAPR Update.xlsx'' in the docket for this 
action.
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    \27\ 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 VOC, in the presence of 
sunlight. See 86 FR 23054, 23063.
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    As shown in Table 1, for Montana, between 2015 and 2019, annual 
total NOX and VOC emissions have declined by 19 percent and 
21 percent, respectively. Between 2016 and 2023, annual NOX 
emissions are projected to decline by 30 percent as a result of the 
implementation of existing control programs that will continue to 
decrease NOX in Montana as indicated by EPA's most recent 
2023 projected emissions.
    As shown in Table 2, onroad and nonroad mobile source emissions 
collectively comprise a large portion of the State's total 
anthropogenic NOX and VOC. For example, in 2019, 
NOX emissions from mobile sources in Montana comprised 63 
percent of total NOX emissions and 25 percent of total VOC 
emissions.
    The large decrease in NOX emissions between 2016 
emissions and projected 2023 emissions in Montana is primarily driven 
by reductions in emissions from onroad and nonroad mobile sources. EPA 
projects that the total anthropogenic NOX emissions and the 
highway and off highway VOC emissions will continue declining out to 
2023 as newer vehicles and engines that are subject to the most recent, 
stringent mobile source standards replace older vehicles and 
engines.\28\
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    \28\ 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).
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    In summary, there is no evidence to suggest that the overall 
emissions trend for Montana demonstrated in Table 1 will suddenly 
reverse or spike in 2021 or 2022 compared to historical emissions 
levels or those projected for 2023. Further, there is no evidence that 
the projected NOX emissions trend out to 2023 and beyond 
would not continue to show a decline in emissions from Montana. In 
addition, EPA's normal practice is to include 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 general downward trend in emissions in Montana adds support to 
the air quality analyses presented above and indicates that the 
contributions from emissions from sources in the State to ozone 
receptors in downwind states will generally continue to decline and 
remain below one percent of the NAAQS.
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    \29\ 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 presented in Table 1. 
The emissions for 2023 are based on the 2016 emissions modeling 
platform. See ``2005 thru 2019_2021_2023_2028 Annual State Tier1 
Emissions_v3'' and the Emissions Modeling TSD in the docket for this 
action.

                                     Table 1--Annual Emissions of NOX and VOC From Anthropogenic Sources in Montana
                                                                  [tons per year] \29\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                               Projected
                                              2011       2012       2013       2014       2015       2016       2017       2018       2019       2023
--------------------------------------------------------------------------------------------------------------------------------------------------------
NOX......................................    108,605    108,895    109,184    109,474    103,417     92,623     88,663     85,882     84,040      64,567

[[Page 6100]]

 
VOC......................................    100,778    104,768    108,759    112,750    103,312     91,612     83,660     82,432     81,204      92,076
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                  Table 2--Annual Emissions of NOX and VOC From Onroad and Nonroad Vehicles in Montana
                                                                     [tons per year]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                               Projected
                                              2011       2012       2013       2014       2015       2016       2017       2018       2019       2023
--------------------------------------------------------------------------------------------------------------------------------------------------------
NOX......................................     75,883     75,352     74,821     74,289     69,640     60,254     57,701     55,182     52,662      41,261
VOC......................................     31,108     30,865     30,622     30,379     28,059     23,477     22,644     21,416     20,188      16,631
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Thus, EPA's evaluation of measured and monitored data, and 
contribution values in 2023, as discussed in this section, is 
consistent with conclusions made by Montana that emissions from sources 
in the State will not contribute to nonattainment or interfere with 
maintenance of the 2015 ozone NAAQS in any other state.

IV. Proposed Action

    EPA is proposing to approve the October 1, 2018 SIP submittal as 
meeting the interstate transport requirements of CAA section 
110(a)(2)(D)(i)(I) for the 2015 ozone NAAQS. At this time, EPA is not 
proposing action on the remaining infrastructure elements included in 
Montana's submittal and will act on those elements in a future action.
    The Agency is soliciting public comments on its proposed approval 
of the CAA section 110(a)(2)(D)(i)(I) element of Montana's 
infrastructure SIP submittal for the 2015 ozone NAAQS. Significant 
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.

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 CAA. 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 proposed rule does not have tribal implications and will 
not impose substantial direct costs on tribal governments or preempt 
tribal law as specified by Executive Order 13175 (65 FR 67249, November 
9, 2000).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Nitrogen dioxide, Ozone, 
Reporting and recordkeeping requirements, Volatile organic compounds.

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

    Dated: January 27, 2022.
KC Becker,
Regional Administrator, Region 8.
[FR Doc. 2022-02111 Filed 2-2-22; 8:45 am]
BILLING CODE 6560-50-P