Document ID: EPA-R08-OAR-2021-0809-0001
Agency: epa
Document Type: Proposed Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: Montana; Thompson Falls PM10 Nonattainment Area Limited Maintenance Plan and Redesignation Request
Posted Date: 2022-03-08T05:00Z

[Federal Register Volume 87, Number 45 (Tuesday, March 8, 2022)]
[Proposed Rules]
[Pages 12905-12912]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-04759]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 52 and 81

[EPA-R08-OAR-2021-0809; FRL-9579-01-R8]

Air Plan Approval; Montana; Thompson Falls PM10 Nonattainment 
Area Limited Maintenance Plan and Redesignation Request

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
fully approve the Limited Maintenance Plan (LMP) submitted by the State 
of Montana to EPA on November 4, 2021, for the Thompson Falls Moderate 
nonattainment area (NAA) for particulate matter with an aerodynamic 
diameter less than or equal to a nominal 10 micrometers 
(PM10) and concurrently redesignate the NAA to attainment 
for the 24-hour PM10 National Ambient Air Quality Standard 
(NAAQS). In order to approve the LMP and redesignation, EPA is 
proposing to determine that the Thompson Falls NAA has attained the 
1987 24-hour PM10 NAAQS of 150 [micro]g/m\3\. This 
determination is based upon monitored air quality data for the 
PM10 NAAQS during the years 2015-2020. EPA is taking this 
action pursuant to the Clean Air Act (CAA).

DATES: Written comments must be received on or before April 7, 2022.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R08-
OAR-2021-0809 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. The EPA may publish any comment received to its 
public docket. Do not submit electronically any information you 
consider to be Confidential Business Information (CBI) or other 
information whose disclosure is restricted by statute. Multimedia 
submissions (audio, video, etc.) must be accompanied by a written 
comment. The written comment is considered the official comment and 
should include discussion of all points you wish to make. The EPA will 
generally not consider comments or

[[Page 12906]]

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 https://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: Kate Gregory, Air and Radiation 
Division, U.S. Environmental Protection Agency (EPA), Region 8, Mail 
Code 8P-ARD-QP, 1595 Wynkoop Street, Denver, Colorado 80202-1129, 
telephone number: (303) 312-6175, email address: [email protected].

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

I. Background

Description of the Thompson Falls NAA

    The Thompson Falls NAA is in Sanders County and is on the north 
side of the Clark Fork River Valley in northwestern Montana. The Clark 
Fork River has been dammed at the center of the small town of Thompson 
Falls to form the Thompson Falls Reservoir and the configuration of the 
nearby mountains and valley create temperature inversions in the fall 
and winter months. The EPA promulgated the PM10 NAAQS on 
July 1, 1987 (52 FR 24634). The Thompson Falls NAA was originally 
designated as a Group III area on July 1, 1987 (52 FR 24634), meaning, 
at that time, there was a strong likelihood the Thompson Falls NAA 
would attain the PM10 NAAQS and, therefore, needed only 
adjustments to their preconstruction permit review program and 
monitoring network. However, multiple exceedances of the 1987 24-hour 
PM10 NAAQS resulted in nonattainment and subsequently the 
Thompson Falls NAA was classified as Moderate for the 1987 24-hour 
PM10 NAAQS, effective January 20, 1994 (58 FR 67334). Within 
18 months of this Moderate designation, by May 18, 1995, Montana was 
required to submit to EPA a Moderate NAA State Implementation Plan 
(SIP) for the Thompson Falls NAA containing, among other requirements, 
provisions to assure that reasonably available control measures (RACM), 
including reasonably available control technologies (RACT) and 
demonstrated whether it was practicable to attain the PM10 
NAAQS by December 31, 2000 (57 FR 13498 (April 16, 1992).\1\
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    \1\ see also 57 FR 18070 (April 28, 1992) and 66 FR 55102 
(November 1, 2001).
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    The State of Montana submitted an initial PM10 SIP to 
EPA on June 26, 1997, and a subsequent submission on June 13, 2000. EPA 
approved both the June 26, 1997 and the June 13, 2000 p.m.10 
SIP submissions for the Thompson Falls initial control plan on April 
24, 2008 (73 FR 22057). The State of Montana's SIP for the Thompson 
Falls Moderate NAA included, but was not limited to, a comprehensive 
emissions inventory, RACM (implemented by November 18, 1997), a 
demonstration that attainment of the PM10 NAAQS would be 
achieved in Thompson Falls by December 31, 2000; Reasonable Further 
Progress (RFP) requirements and control measures that satisfy the 
contingency measures requirement of section 172(c)(9) of the CAA. The 
EPA fully approved the Thompson Falls NAA PM10 attainment 
plan on January 22, 2004 (69 FR 3011).

II. Requirements for Redesignation

A. CAA Requirements for Redesignation of NAAs

    NAAs can be redesignated to attainment after the area has measured 
air quality data showing it has attained the NAAQS and when certain 
planning requirements are met. Section 107(d)(3)(E) of the CAA, and the 
General Preamble to Title I provide the criteria for redesignation. See 
57 FR 13498 (April 16, 1992). These criteria are further clarified in a 
policy and guidance memorandum from John Calcagni, Director, Air 
Quality Management Division, EPA Office of Air Quality Planning and 
Standards dated September 4, 1992, ``Procedures for Processing Requests 
to Redesignate Areas to Attainment.'' \2\ The criteria for 
redesignation are:
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    \2\ The ``Procedures for Processing Requests to Redesignate 
Areas to Attainment'' (Calcagni memo) outlines the criteria for 
redesignation (see docket for memo).
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    (1) The Administrator has determined that the area has attained the 
applicable NAAQS;
    (2) The Administrator has fully approved the applicable SIP for the 
area under section 110(k) of the CAA;
    (3) The state containing the area has met all requirements 
applicable to the area under section 110 and part D of the CAA;
    (4) The Administrator has determined that the improvement in air 
quality is due to permanent and enforceable reductions in emissions; 
and
    (5) The Administrator has fully approved a maintenance plan for the 
area as meeting the requirements of section 175A of the CAA.

B. The LMP Option for PM10 NAAs

    On August 9, 2001, the EPA issued guidance on streamlined 
maintenance plan provisions for certain moderate PM10 NAAs 
seeking redesignation to attainment (Memo from Lydia Wegman, Director, 
Air Quality Standards and Strategies Division, entitled ``Limited 
Maintenance Plan Option for Moderate PM10 Nonattainment 
Areas,'' (hereafter the LMP Option memo)).\3\ The LMP Option memo 
contains a statistical demonstration to show that areas meeting certain 
air quality criteria will, with a high degree of probability, maintain 
the standard 10 years into the future. Thus, the EPA has already 
provided the maintenance demonstration for areas meeting the criteria 
outlined in the LMP Option memo. It follows that future year emission 
inventories for these areas, and some of the standard analyses to 
determine transportation conformity with the SIP are no longer 
necessary.
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    \3\ The ``Limited Maintenance Plan Option for Moderate 
PM10 Nonattainment Areas'' outlines the criteria for 
development of a PM10 limited maintenance plan (see 
docket for memo).
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    To qualify for the LMP Option, the area should have attained the 
1987 24-hour PM10 NAAQS, based upon the most recent 5 years 
of air quality data at all monitors in the area, and the 24-hour design 
concentration should be at or below the ``Critical Design Value'' 
(CDV). The CDV is a calculated design concentration that indicates that 
the area has a low probability (1 in 10) of exceeding the NAAQS in the 
future. For the purposes of qualifying for the LMP option, a 
presumptive CDV of 98 [micro]g/m\3\ is most often employed, but an area 
may elect to use a site-specific CDV should the average design 
concentration (ADC) be above 98 [micro]g/m\3\, while demonstrating that 
the area has a low probability of exceeding the NAAQS in the future. 
The annual PM10 standard was effectively

[[Page 12907]]

revoked on December 18, 2006 (71 FR 61143), and as such will not be 
discussed as a requirement for qualifying for the LMP option. In 
addition, the area should expect only limited growth in on-road motor 
vehicle PM10 emissions (including fugitive dust) and should 
have passed a motor vehicle regional emissions analysis test. The LMP 
Option memo also identifies core provisions that must be included in 
the LMP. These provisions include an attainment year emissions 
inventory, assurance of continued operation of an EPA-approved air 
quality monitoring network, and contingency provisions.

III. Review of Montana's Submittal Addressing the Requirements for 
Redesignation and Limited Maintenance Plan

A. Has the Thompson Falls NAA attained the applicable NAAQS?

    States must demonstrate that an area has attained the 24-hour 
PM10 NAAQS through analysis of ambient air quality data from 
an ambient air monitoring network representing peak PM10 
concentrations. The data should be stored in the EPA Air Quality System 
(AQS) database. The request for redesignation of the Thompson Falls 
PM10 NAA submitted by the State of Montana presented data 
and analyses to demonstrate that the area attained the PM10 
standard using 2015-2019 data. During the review process the EPA 
identified a single 2017 24-hour PM10 data point that was 
inadvertently omitted from the submission, and therefore this datapoint 
was included in the tables and calculations contained in this action. 
In addition to reviewing the 2015-2019 data the EPA included 2020 
p.m.10 data in this action (as it is currently the most 
recent year of certified data present in AQS) to confirm that the area 
is still attaining the 24-hour PM10 NAAQS. Additionally, 
preliminary 2021 data indicates the area continues to attain.
    Today, EPA is proposing to determine that the Thompson Falls NAA 
has attained the 24-hour PM10 NAAQS based on monitoring data 
from calendar years 2015-2020. The 24-hour standard is attained when 
the expected number of days with 24-hour average concentrations above 
150 [micro]g/m\3\ (averaged over a 3-year period) is less than or equal 
to one. See 40 CFR 50.6(a). A minimum of three complete and consecutive 
years of air quality data are generally necessary to show attainment of 
the standard. See 40 CFR part 50, appendix K. A complete year of air 
quality data, as referred to in 40 CFR part 50, appendix K, is 
comprised of all four calendar quarters with each quarter containing 
data from at least 75% of the scheduled sampling days.
    The Thompson Falls NAA has one State and Local Air Monitoring 
Station (SLAMS) PM10 monitor, Thompson Falls High School 
(AQS ID 30-089-0007), operated by the Montana Department of 
Environmental Quality (MDEQ). Table 1 summarizes the PM10 
data collected from 2015-2020 for the Thompson Falls NAA. The EPA deems 
the data collected from these monitors valid, and the data have been 
submitted and certified by the MDEQ to be included in AQS. All years 
are complete except for 2016 which has one incomplete quarter of data. 
Therefore, the State performed data substitution for the missing 2016 
data. Methods and results for the missing 2016 data substitution can be 
found in Appendix E of the State submission in the docket of this 
action.

  Table 1--Summary of Maximum 24-Hour PM10 Concentrations ([mu]g/m\3\), Design Concentrations ([mu]g/m\3\), and
                               Number of Exceedances for Thompson Falls 2015-2020
            [Based on data from Thompson Falls High School, AQS Identification Number (30-089-0007)]
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                                                                                          Number of exceedances
                                                                  Design concentration     excluding regionally
                 Year                   Maximum concentration             \4\             concurred exceptional
                                                                                                events \5\
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2015.................................                      143                      135                        0
2016.................................                      135                      135                        0
2017.................................                      210                      135                        1
2018.................................                       72                      135                        0
2019.................................                       43                       72                        0
2020.................................                      148                       99                        0
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    The CAA allows for the exclusion of air quality monitoring data 
from design value calculations when there are exceedances caused by 
exceptional events, including for expected number exceedances for 
PM10 averaged over a 3-year period, that meet the criteria 
for an exceptional event identified in the EPA's implementing 
regulations, the Exceptional Events Rule at 40 CFR 50.1, 50.14, and 
51.930. For the purposes of this proposed action, on November 23, 2021, 
the State of Montana submitted exceptional event demonstrations to 
request exclusion of data impacted by wildfires. The EPA evaluated the 
State of Montana's exceptional event demonstrations for the flagged 
values of the 24-hour PM10 listed in Table 3 below in the 
Thompson Falls Moderate NAA, with respect to the requirements of EPA's 
Exceptional Events Rule (40 CFR 50.1, 50.14, and 50.930).
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    \4\ The design concentrations are calculated using three years 
of data and the ``Table Look-up'' method described in the 
``PM10 SIP Development Guideline'', EPA-450/2-86-001, 
June 1987.
    \5\ Exceedances in 2017 and 2020 have been flagged and concurred 
on as exceptional events. Additional information on 2017 data can be 
found in Appendix A, p. a-1, of the submission by the state in the 
docket of this action and additional information on 2020 data can be 
found in the docket for this action, document titled: Montana 2020 
p.m.10 Letter.
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    On January 25, 2022, EPA concurred with the State of Montana's 
requests to exclude event-influenced data listed in Table 3, finding 
that the State of Montana's demonstration met the Exceptional Event 
Rule criteria. As such, the event-influenced data have been removed 
from the data set used for regulatory purposes. For this proposed 
action, EPA relies on the PM10 concentrations reported at 
the Thompson Falls monitoring site which showed only one exceedance 
from 2015-2020 when exceptional events are excluded. Therefore, the 
expected number of days with 24-hour average concentrations above 150 
[micro]g/m\3\ averaged over a 3-year period is less than one, and as 
such, the EPA proposes to determine that the Thompson Falls NAA has 
attained the standard for the 24-hour PM10 NAAQS.\6\
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    \6\ Please see section III(F) of this action for further 
discussion and description of exceptional events in the Thompson 
Falls NAA during the 2015-2020 time period.

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[[Page 12908]]

    Additionally, the EPA concurred on the State of Montana's request 
to exclude PM10 data listed in Table 3 in regulatory 
decisions. For further information, refer to the State of Montana's 
Exceptional Event demonstration packages and the EPA's concurrence and 
analyses located in the docket for this proposed action.

B. Does the Thompson Falls NAA have a fully approved SIP under CAA 
section 110(k)?

    To qualify for redesignation, the SIP for the area must be fully 
approved under CAA section 110(k) and must satisfy all requirements 
that apply to the area. Section 189 of the CAA contains requirements 
and milestones for all initial Moderate NAA SIPs including: (1) 
Provisions to assure that RACM (including such reductions in emissions 
from existing sources in the area as may be obtained through the 
adoption, at a minimum, of RACT shall be implemented no later than 
December 10, 1993; (2) A demonstration (including air quality modeling) 
that the plan will provide for attainment as expeditiously as 
practicable by no later than December 31, 1994, or, where the state is 
seeking an extension of the attainment date under section 188(e), a 
demonstration that attainment by December 31, 1994, is impracticable 
and that the plan provides for attainment by the most expeditious 
alternative date practicable (CAA sections 189(a)(1)(A)); (3) 
Quantitative milestones which are to be achieved every 3 years and 
which demonstrate RFP toward attainment by December 31, 1994, (CAA 
sections 172(c)(2) and 189(c)); and (4) Contingency measures to be 
implemented if the area fails to make RFP or attain by its attainment 
deadline. These contingency measures are to take effect without further 
action by the state or the EPA. (CAA section 172(c)(9)).
    The EPA fully approved the Thompson Falls NAA PM10 
attainment plan on January 22, 2004 (69 FR 3011). The Thompson Falls 
plan included RACM, an attainment demonstration, emissions inventory, 
quantitative milestones, and control and contingency measure 
requirements. As such, the area has a fully approved NAA SIP under 
section 110(k) of the CAA.

C. Has the state met all applicable requirements under section 110 and 
Part D of the CAA?

    Section 107(d)(3)(E) of the CAA requires that a state containing a 
NAA must meet all applicable requirements under section 110 and Part D 
of the CAA for an area to be redesignated to attainment. The EPA 
interprets this to mean that the state must meet all requirements that 
applied to the area prior to, and at the time of, the submission of a 
complete redesignation request. The following is a summary of how 
Montana meets these requirements.
1. CAA Section 110 Requirements
    Section 110(a)(2) of the CAA contains general requirements for 
SIPs. These requirements include, but are not limited to, submittal of 
a SIP that has been adopted by the state after reasonable notice and 
public hearing, provisions for establishment and operation of 
appropriate apparatus, methods, systems and procedures necessary to 
monitor ambient air quality, implementation of a permit program, 
provisions for Part C--Prevention of Significant Deterioration (PSD) 
and Part D--New Source Review (NSR) permit programs, criteria for 
stationary source emission control measures, monitoring and reporting, 
provisions for modeling and provisions for public and local agency 
participation. See the General Preamble for further explanation of 
these requirements. See 57 FR 13498 (April 16, 1992).
    For purposes of redesignation, the EPA's review of the Montana SIP 
shows that the State has satisfied all requirements under section 
110(a)(2) of the CAA. Further, in 40 CFR 52.1372, the EPA has approved 
Montana's plan for the attainment and maintenance of the national 
standards under section 110.
2. Part D Requirements
    Part D contains general requirements applicable to all areas 
designated nonattainment. The general requirements are followed by a 
series of subparts specific to each pollutant. All PM10 NAAs 
must meet the general provisions of Subpart 1 and the specific 
PM10 provisions in Subpart 4, ``Additional Provisions for 
Particulate Matter Nonattainment Areas.'' The following paragraphs 
discuss these requirements as they apply to the Thompson Falls NAA.
3. Subpart 1, Section 172(c)
    Subpart 1, section 172(c) contains general requirements for NAA 
plans. A thorough discussion of these requirements may be found in the 
General Preamble. See 57 FR 13538 (April 16, 1992). CAA section 
172(c)(2) requires nonattainment plans to provide for RFP. Section 
171(1) of the CAA defines RFP as ``such annual incremental reductions 
in emissions of the relevant air pollutant as are required by this part 
(part D of title I) or may reasonably be required by the Administrator 
for the purpose of ensuring attainment of the applicable national 
ambient air quality standard by the applicable date.'' Since EPA is 
proposing to determine that the Thompson Falls NAA is in attainment of 
the PM10 NAAQS, we believe that no further showing of RFP or 
quantitative milestones is necessary.
4. Section 172(c)(3)--Emissions Inventory Section
    Section 172(c)(3) of the CAA requires a comprehensive, accurate, 
current inventory of actual emissions from all sources in the Thompson 
Falls PM10 NAA. Montana included an emissions inventory for 
the calendar year 2017 with the November 4, 2021submittal of the LMP 
for the NAA. The LMP Option memo states that an attainment inventory 
should represent emissions during the same 5-year period associated 
with the air quality data used to determine that the area meets the 
applicability requirements of the LMP option. The Thompson Falls LMP 
includes an emission inventory from 2017, representative of the 2015-
2019 5-year period which served as the 5-year period relied upon in the 
LMPs as meeting the air quality data requirements of the LMP option 
memo.\7\
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    \7\ The emissions inventory included in the Thompson Falls MT 
submission is the 2017 National Emissions Inventory (NEI). The NEI 
is a composite of data from many different sources, with PM data 
coming primarily from EPA models as well as from state, tribal, and 
local air quality management agencies. Different data sources use 
different data collection methods, and many of the emissions data 
are based on estimates rather than actual measurements. The EPA 
considers the 2017 NEI representative of the period from 2015--2019 
because MT provided comparable vehicle miles traveled (VMT) data in 
their submission. See Thompson Falls, MT Submission, Appendix C, 
Montana Department of Transportation Future VMT Projections, p.C-1 
in docket.
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5. Section 172(c)(5)--NSR
    The 1990 CAA Amendments contained revisions to the NSR program 
requirements for the construction and operation of new and modified 
major stationary sources located in NAAs. The CAA requires states to 
amend their SIPs to reflect these revisions but does not require 
submittal of this element along with the other SIP elements. The CAA 
established June 30, 1992, as the submittal date for the revised NSR 
programs (section 189 of the CAA).
    Montana has a fully approved nonattainment NSR program, approved on 
August 30, 1995 (60 FR 45051). Montana also has a fully approved PSD

[[Page 12909]]

program, approved on August 30, 1995 (60 FR 45051). Upon the effective 
date of redesignation of an area from nonattainment to attainment, the 
requirements of the Part D NSR program will be replaced by the PSD 
program and the maintenance area NSR program.
6. Section 172(c)(7)--Compliance With CAA Section 110(a)(2): Air 
Quality Monitoring Requirements
    Once an area is redesignated, the state must continue to operate an 
appropriate air monitoring network in accordance with 40 CFR part 58 to 
verify attainment status of the area. The State of Montana operates one 
PM10 SLAMS in each of the NAAs. The Thompson Falls 
monitoring site meets EPA SLAMS network design and siting requirements 
set forth at 40 CFR part 58, appendices D and E. In section 3.5 of the 
LMP that we are proposing to approve, the State commits to continued 
operation of the monitoring network.
7. Section 172(c)(9)--Contingency Measures
    The CAA requires that contingency measures take effect if the area 
fails to meet RFP requirements or fails to attain the NAAQS by the 
applicable attainment date. Since the Thompson Falls NAA has attained 
the 1987 24-hour PM10 NAAQS, contingency measures are no 
longer required under section 172(c)(9) of the CAA. However, 
contingency provisions are required for maintenance plans under section 
175(a)(d). We describe the contingency provisions Montana provided in 
the LMP section below.
8. Part D, Subpart 4
    Part D, subpart 4, section 189(a), (c) and (e) requirements apply 
to any Moderate NAA before the area can be redesignated to attainment. 
The requirements which were applicable prior to the submission of the 
request to redesignate the area must be fully approved into the SIP 
before redesignating the area to attainment. These requirements 
include: (a) Provisions to assure that RACM was implemented by December 
10, 1993; (b) Either a demonstration that the plan provided for 
attainment as expeditiously as practicable but not later than December 
31, 1994, or a demonstration that attainment by that date was 
impracticable; (c) Quantitative milestones which were achieved every 3 
years and which demonstrate RFP toward attainment by December 31, 1994; 
and (d) Provisions to assure that the control requirements applicable 
to major stationary sources of PM10 also apply to major 
stationary sources of PM10 precursors except where the 
Administrator determined that such sources do not contribute 
significantly to PM10 levels which exceed the NAAQS in the 
area. These provisions were fully approved into the SIP upon the EPA's 
approval of the PM10 Moderate area plan for the Thompson 
Falls NAA on January 22, 2004 (69 FR 3011).

D. Has the state demonstrated that the air quality improvement is due 
to permanent and enforceable reductions?

    A state must be able to reasonably attribute the improvement in air 
quality to permanent and enforceable emission reductions. In making 
this showing, a state must demonstrate that air quality improvements 
are the result of actual enforceable emission reductions. This showing 
should consider emission rates, production capacities, and other 
related information. The analysis should assume that sources are 
operating at permitted levels (or historic peak levels) unless evidence 
is presented that such an assumption is unrealistic. Permanent and 
enforceable control measures in the Thompson Falls NAA SIP includes 
RACM. Emission sources in the NAA have been implementing RACM for at 
least 10 years.
    Areas that qualify for the LMP will meet the NAAQS, even under 
worst case meteorological conditions. Under the LMP option, the 
maintenance demonstration is presumed to be satisfied if an area meets 
the qualifying criteria. Thus, by qualifying for the LMP, Montana has 
demonstrated that the air quality improvements in the Thompson Falls 
NAA is the result of permanent emission reductions and not a result of 
either economic trends or meteorology. A description of the LMP 
qualifying criteria and how the Thompson Falls area meets these 
criteria is provided in the following section.
    Permanent and enforceable emission reductions in the Thompson Falls 
NAA have reduced emissions 29% since the 1991 baseline. The primary 
controls incorporated into the SIP included rules focused on reducing 
fugitive dust emissions from roads and parking lots. Additionally, the 
approved control plan satisfied the requirements for RACM of area 
sources. Based on the 2017 national emissions inventory, 
PM10 emissions in all source areas are below the levels 
approved in the original control plan.\8\
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    \8\ See Thompson Falls, MT submission in docket, Table 2.4--
Thompson Falls, MT--PM10 Emission Summary, p. 2-5.
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E. Does the area have a fully approved maintenance plan pursuant to 
section 175A of the CAA?

    In this action, we are proposing to approve the LMP for the 
Thompson Falls NAA in accordance with the principles outlined in the 
LMP Option.

F. Has the state demonstrated that the Thompson Falls NAA qualifies for 
the LMP Option?

    The LMP Option memo outlines the requirements for an area to 
qualify for the LMP Option. First, the area should be attaining the 
NAAQS. As stated above in section III. A., the EPA has determined that 
the Thompson Falls NAA is attaining the PM10 NAAQS.
    Second, the ADC for the past 5 years of monitoring data must be at 
or below the CDV. As noted in section II.B., the CDV is a margin of 
safety value and is the value at which an area has been determined to 
have a 1 in 10 probability of exceeding the NAAQS. The LMP Option memo 
provides two methods for review of monitoring data for the purpose of 
qualifying for the LMP option. The first method is a comparison of a 
site's ADC with the CDV of 98 [micro]g/m\3\ for the 24-hour 
PM10 NAAQS. A second method that applies to the 24-hour 
PM10 NAAQS is the calculation of a site-specific CDV and a 
comparison of the site-specific CDV with the ADC for the past 5 years 
of monitoring data. Table 2 below outlines the design concentrations 
for the years 2015-2020 and presents the ADC.
    Table 3 summarizes the wildfire related events that were excluded 
from the calculated design concentrations in Table 2. Table 3 includes 
all regionally concurred exceptional events, as well as values between 
98 [mu]g/m\3\ and 155 [mu]g/m\3\, which were treated in a manner 
analogous to exceedance data under the Exceptional Events Rule for the 
purpose of determining the LMP option eligibility. The values between 
98 [mu]g/m\3\ and 155 [mu]g/m\3\ remain in the AQS database for use in 
calculating design concentrations for every purpose besides determining 
LMP eligibility.\9\ The Exceptional Events Rule can be found in 40 CFR 
50.14 and 40 CFR 51.930, and outlines the requirements for the 
treatment of monitored air quality data that has been heavily 
influenced by an exceptional event. 40 CFR 50.1(j) defines an 
exceptional event as an event which affects air quality, is not 
reasonably controllable or preventable, is an event caused by

[[Page 12910]]

human activity that is unlikely to recur at a particular location or a 
natural event and is determined by the Administrator in accordance with 
40 CFR 50.14 to be an exceptional event. Exceptional events do not 
include stagnation of air masses or meteorological inversions, 
meteorological events involving high temperatures or lack of 
precipitation, or air pollution relating to source noncompliance. 40 
CFR 50.14(b) states that the EPA shall exclude data from use in 
determinations of exceedances and NAAQS violations where a state 
demonstrates to the EPA's satisfaction that an exceptional event caused 
a specific air pollution concentration in excess of one or more NAAQS 
at a particular air quality monitoring location and otherwise satisfies 
the requirements of section 50.14. Table 3 below includes some values 
between 98 [mu]g/m\3\ and 155 [mu]g/m\3\ that were excluded for the 
sole purpose of determining PM10 LMP eligibility in 
accordance with the LMP guidance.\10\ Supporting documentation of EPA's 
concurrence with the wildfire related events can be found in the 
docket.\11\
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    \9\ Update on Application of the Exceptional Events Rule to the 
PM10 Limited Maintenance Plan Option, US EPA, William T. 
Harnett, Director, Air Quality Policy Division, OAQPS, May 7, 2009.
    \10\ See Update on Application of the Exceptional Events Rule to 
the PM10 Limited Maintenance Plan Option, US EPA, William 
T. Harnett, Director, Air Quality Policy Division, OAQPS, May 7, 
2009 and Additional Methods, Determinations, and Analyses to Modify 
Air Quality Data Beyond Exceptional Events, US EPA, Richard Wayland, 
Director, Air Quality Assessment Division and Anna Marie Wood, 
Director, Air Quality Policy Division, April 4, 2019 memos in 
docket.
    \11\ February 8, 2019 letter to MDEQ, Re: Exceptional Events 
Requests Regarding Exceedances of the 24-hour PM10 NAAQS 
and the LMP Eligibility Threshold at Montana Monitoring Sites with 
PM10 Nonattainment Areas; and November 1, 2018 letter to 
MDEQ, Re: Request for EPA concurrence on exceptional event claims 
for fine (PM2.5) and coarse (PM10) particulate 
matter data impacted by wildfires in 2015 and 2016. See Thompson 
Falls, MT submission in docket; and additional information on 2020 
data can be found in the docket for this action, document titled: 
Montana 2020 PM10 Letter.

 Table 2--Summary of 24-Hour PM10 Design Concentrations ([mu]g/m\3\) for
                             Thompson Falls
  [Based on data from Thompson Falls HS Site, AQS Identification Number
                             (30-089-0007)]
------------------------------------------------------------------------
                                                             Design
              Design concentration years                 concentration
                                                          ([mu]g/m\3\)
------------------------------------------------------------------------
2015-2017............................................                100
2016-2018............................................                 88
2017-2019............................................                 70
2018-2020............................................                 66
------------------------------------------------------------------------
Average Design Concentration (of Most Recent 3 Design Concentrations) 75
  [mu]g/m\3\.

 Table 3--Thompson Falls 24-Hour PM10 Events Excluded From the 2015-2020
           Data for the Purpose of Determining LMP Eligibility
  [Based on data from Thompson Falls HS Site, AQS Identification Number
                             (30-089-0007)]
------------------------------------------------------------------------
                                                         24-hour value
                         Date                             ([mu]g/m\3\)
------------------------------------------------------------------------
8-14-2016............................................                105
8-24-2015............................................                117
8-26-2015............................................                135
8-27-2015............................................                122
8-29-2015............................................                143
8-30-2016............................................                135
9-6-2017.............................................                251
9-7-2017.............................................                231
9-8-2017.............................................                249
9-9-2017.............................................                100
9-12-2020............................................                168
9-13-2020............................................                206
9-14-2020............................................                185
9-15-2020............................................                148
9-16-2020............................................                103
9-17-2020............................................                107
9-18-2020............................................                 99
------------------------------------------------------------------------
Values between 98 [micro]g/m\3\ and 155 [micro]g/m\3\ were excluded by
  EPA solely for the purpose of determining limited maintenance plan
  (LMP) eligibility in accordance with LMP guidance. The values remain
  in AQS and are still used for all other purposes (including
  calculating the estimated exceedances and official design
  concentrations).

    The ADC for the 24-hour PM10 NAAQS for Thompson Falls, 
based on data from the SLAMS monitor for the years 2016-2020 is 75 
[mu]g/m\3\. This value falls below the presumptive 24-hour CDV of 98 
[mu]g/m\3\ and would meet the first threshold for LMP eligibility.
    In addition to having an ADC that is below the presumptive or area 
specific CDV, and in order to qualify for the LMP, the area must meet 
the motor vehicle regional emissions analysis test in attachment B of 
the LMP Option memo. Using the methodology outlined in the memo, the 
data presented in the State submission in section 3.2 and based on 
monitoring data for the period 2016-2020, the EPA has determined that 
the Thompson Falls NAA has a projected design concentration of 79 
[mu]g/m\3\ after 10 years, attributable to motor vehicle emission 
growth. This value is below the presumptive 24-hour CDV of 98 [mu]g/
m\3\ and therefore passes the motor vehicle regional emissions analysis 
test. For the detailed calculations used to determine how the Thompson 
Falls NAA passed the motor vehicle regional analysis test, see the 
supporting documents in the docket.\12\
---------------------------------------------------------------------------

    \12\ See memo to file in docket dated January 10, 2022 titled 
``Memo to File--Thompson Falls, MT Motor Vehicle Regional Emissions 
Analysis.''
---------------------------------------------------------------------------

    The State's submission demonstrated that the 2015-2019 monitoring 
data shows that Thompson Falls has attained the 24-hour NAAQS for 
PM10, and the 24-hour ADC for the area is less than the 24-
hour PM10 presumptive and area-specific CDV. The data 
presented in this action demonstrates that the 2016-2020 data show that 
Thompson Falls has attained the 24-hour NAAQS for PM10, and 
the 24-hour ADC for the area is less that the 24-hour PM10 
presumptive CDV of 98 [mu]g/m\3\. Finally, the area has met the 
regional vehicle emissions analysis test for both the 2015-2019 and 
2016-2020 periods of monitoring data. Thus, the Thompson Falls NAA 
qualifies for the LMP Option described in the LMP Option memo. The LMP 
Option memo also indicates that once a state selects the LMP Option and 
it is in effect, the state will be expected to determine, on an annual 
basis, that the LMP criteria are still being met. If a state determines 
that the LMP criteria are not being met, it should take action to 
reduce PM10 concentrations enough to requalify for the LMP. 
One possible approach a state could take is to implement contingency 
measures. Please see section 3.6 of the Thompson Falls LMP for a 
description of contingency provisions submitted as part of the State's 
submittal.

G. Does the state have an approved attainment emissions inventory which 
can be used to demonstrate attainment of the NAAQS?

    A state's approved attainment plan should include an emissions 
inventory (attainment inventory) which can be used to demonstrate 
attainment of the NAAQS. The inventory should represent emissions 
during the same 5-year period associated with air quality data used to 
determine whether the area meets the applicability requirements of the 
LMP Option. A state should review its inventory every 3 years to ensure 
emissions growth is incorporated in the attainment inventory if 
necessary. In this instance, Montana completed an attainment year 
inventory for the attainment year 2017 for the Thompson Falls NAA. The 
EPA has reviewed the 2017 emissions inventories and determined that 
they are current, accurate and complete. In addition, the emissions 
inventory submitted with the LMP for the calendar year 2017 is 
representative of the level of emissions during the time period used to 
calculate the ADC since 2017 is included in the 5-year period used to 
calculate the design concentrations (2015-2019).

[[Page 12911]]

H. Does the LMP include an assurance of continued operation of an 
appropriate EPA-approved air quality monitoring network, in accordance 
with 40 CFR Part 58?

    The PM10 monitoring network for the Thompson Falls NAA 
has been developed and maintained in accordance with federal siting and 
design criteria in 40 CFR part 58, appendices D and E and in 
consultation with the EPA Region 8. In section 3.5 of the Thompson 
Falls LMP, Montana states that it will continue to operate its 
monitoring network to meet EPA requirements.

I. Does the plan meet the CAA requirements for contingency provisions 
for maintenance plans?

    Section 175A of the CAA states that a maintenance plan must include 
contingency provisions, as necessary, to promptly correct any violation 
of the NAAQS which may occur after redesignation of the area to 
attainment. As explained in the LMP Option memo, these contingency 
measures do not have to be fully adopted at the time of redesignation. 
As noted above, CAA section 175A requirements are distinct from CAA 
section 172(c)(9) contingency measures. Section 3.6 of the Thompson 
Falls LMP describes a process and timeline to identify and evaluate 
appropriate contingency measures in the event of a quality assured 
violation of the PM10 NAAQS. Upon notification of a 
PM10 exceedance in any of the three areas, the MDEQ and the 
appropriate local government will develop contingency measures designed 
to prevent or correct a violation of the PM10 standard. This 
process will be completed within twelve months of the exceedance 
notification. Upon violating the PM10 standard, the MDEQ and 
local government will determine if the local contingency measures will 
be adequate to prevent further exceedances or violations. If the 
agencies determine that local measures will be inadequate, the MDEQ and 
local government will adopt State-enforceable measures.
    The current and proposed contingency provisions in the Thompson 
Falls LMP meet the requirements for contingency provisions as outlined 
in the LMP Option memo.

IV. Conformity and the LMP Option

    Section 176(c) of the CAA requires the conformity of federal 
actions to the air quality goals of an NAA or maintenance area. Such 
federal actions include actions on transportation plans, programs and 
projects developed, funded, or approved by federal agencies or by 
recipients of federal funds, as well as more general actions receiving 
federal assistance or approval. Conformity of these two types of 
actions is known, respectively, as ``transportation conformity'' and 
``general conformity.'' The purpose of conformity is to ensure that 
such federal actions will not produce new air quality violations, 
worsen existing violations, or delay timely attainment of the NAAQS. 
The EPA's transportation and general conformity rules are found in 40 
CFR part 93, subparts A and B, respectively.
    The transportation conformity rule generally requires a 
demonstration that emissions from the relevant projects of a 
transportation plan and transportation improvement program covering a 
designated area are consistent with the motor vehicle emissions budget 
(MVEB or `budget') contained in the SIP or maintenance plan for that 
area. The MVEB is the level of mobile source emissions of a pollutant 
relied upon in the attainment or maintenance demonstration to attain or 
maintain the NAAQS in the NAA or maintenance area.
    Under the transportation conformity rule, designated areas meeting 
the criteria for the LMP Option will not be required to satisfy the 
rule's regional emissions analysis requirements (40 CFR 93.109(e)). 
When the EPA approves an LMP, we are concluding that it is unreasonable 
to expect that the qualifying area will experience sufficient growth 
during the maintenance period that a violation of the PM10 
NAAQS would result. Therefore, the EPA is concluding with an LMP 
approval that the area's budget is essentially not constraining for the 
duration of the maintenance period and a regional emissions analysis 
will not be necessary to demonstrate conformity.
    However, because LMP areas are still maintenance areas, approval of 
a Thompson Falls LMP does not remove certain transportation conformity 
rule requirements for transportation plans, programs, and projects. As 
an isolated rural maintenance area, the Thompson Falls area will 
generally be subject to the requirements of 40 CFR 93.109(g), as 
modified by the requirements for LMP areas in 40 CFR 93.109(e). 
Specifically, state transportation plans, transportation improvement 
programs and transportation projects still must demonstrate that they 
are fiscally constrained (30 CFR 93.108), are still subject to 
consultation requirements (40 CFR 93.112), and projects must not 
interfere with the implementation of any transportation control 
measures from the applicable implementation plan (40 CFR 93.113).
    Approval of the LMP option would have similar implications with 
respect to general conformity. Federal actions subject to general 
conformity in an LMP area will not be required to satisfy the budget 
test requirement of the general conformity rule. Such federal actions 
are presumed to conform under the LMP option as emissions budgets in 
such areas are essentially not constraining for the duration of the 
maintenance period.

V. Environmental Justice Concerns

    To identify potential environmental burdens and susceptible 
populations in the Thompson Falls NAA, EPA performed a screening-level 
analysis using the EPA's EJSCREEN tool to evaluate environmental and 
demographic indicators within the area. The tool outputs are contained 
in the docket for this action. The results indicate that within the 
Thompson Falls NAA, the EJ index for the National-Scale Air Toxics 
Assessment (NATA) for diesel particulate matter is at the 81st 
percentile compared to the rest of the State and results indicate a 
low-income population of 58%, as compared to the State average of 34% 
for Montana. These populations may be vulnerable and subject to 
disproportionate impacts within the meaning of the executive orders 
described above. Further, as the EJSCREEN analysis is a screening-level 
assessment and not an in-depth review, it is possible that there are 
other vulnerable groups within the Thompson Falls NAA.
    As to all vulnerable groups within the Thompson Falls NAA, as 
explained above, we believe that this action will be beneficial and 
will tend to reduce impacts as this action, if finalized, addresses a 
plan for continued attainment of the PM10 NAAQS for the 
Thompson Falls NAA. When the EPA establishes a new or revised NAAQS, 
the CAA requires the EPA to designate all areas of the U.S. as either 
nonattainment, attainment, or unclassifiable. If an area is designated 
nonattainment for a NAAQS, the state must develop a plan outlining how 
the area will attain and maintain the standard by reducing air 
pollutant emissions. In this action we are proposing to approve the LMP 
for the Thompson Falls NAA and the State's request to redesignate the 
Thompson Falls NAA from nonattainment to attainment for the 1987 24-
hour PM10 NAAQS. Approval of the LMP will contribute to the 
ongoing protection of those residing, working, attending school, or 
otherwise present in those areas, and we propose to determine that this 
action, if finalized, will not have disproportionately high or adverse

[[Page 12912]]

human health or environmental effects on communities with environmental 
justice concerns.

VI. Proposed Action

    For the reasons explained in section III., we are proposing to 
approve the LMP for the Thompson Falls NAA and the State's request to 
redesignate the Thompson Falls NAA from nonattainment to attainment for 
the 1987 24-hour PM10 NAAQS. Additionally, the EPA is 
proposing to determine that the Thompson Falls NAA has attained the 
NAAQS for PM10. This determination is based upon monitored 
air quality data for the PM10 NAAQS during the years 2014-
2020. The EPA is proposing to approve the Thompson Falls LMP as meeting 
the appropriate transportation conformity requirements found in 40 CFR 
part 93, subpart A.

VII. Statutory and Executive Order Reviews

    Under the CAA, 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, the EPA's role is to approve state choices, 
provided that they meet the criteria of the CAA. Accordingly, this 
action merely proposes to approve state law as meeting Federal 
requirements and does not impose additional requirements beyond those 
imposed by state law. For that reason, this 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 CAA; 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

40 CFR Part 52

    Environmental protection, Air pollution control, Carbon monoxide, 
Greenhouse gases, Incorporation by reference, Intergovernmental 
relations, Lead, Nitrogen dioxide, Ozone, Particulate matter, Reporting 
and recordkeeping requirements, Sulfur oxides, Volatile organic 
compounds.

40 CFR Part 81

    Environmental protection, Air pollution control, National parks, 
and Wilderness areas.

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

    Dated: February 28, 2022.
KC Becker,
Regional Administrator, Region 8.
[FR Doc. 2022-04759 Filed 3-7-22; 8:45 am]
BILLING CODE 6560-50-P