2022-04759. Air Plan Approval; Montana; Thompson Falls PM10

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

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 µg/m³ . 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 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: [phone], email address: [e-mail].

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]

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:

(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.

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 µg/m³ is most often employed, but an area may elect to use a site-specific CDV should the average design concentration (ADC) be above 98 µg/m³ , while demonstrating that the area has a low probability of exceeding the NAAQS in the future. The annual PM₁₀ standard was effectively 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 µg/m³ (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 PM ₁₀ Concentrations (μ g / m³ ), Design Concentrations (μ g / m³ ), and Number of Exceedances for Thompson Falls 2015-2020

[Based on data from Thompson Falls High School, AQS Identification Number (30-089-0007)]

Year	Maximum concentration	Design concentration 4	Number of exceedances excluding regionally concurred exceptional events 5
2015	143	135	0
2016	135	135	0
2017	210	135	1
2018	72	135	0
2019	43	72	0
2020	148	99	0

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).

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 µg/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]

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]

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 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]

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 µg/m³ 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 μg/m^[3] and 155 μg/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 μg/m^[3] and 155 μg/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 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 μg/m^[3] and 155 μg/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]

Table 2—Summary of 24-Hour PM ₁₀ Design Concentrations (μ g / m³ ) for Thompson Falls

[Based on data from Thompson Falls HS Site, AQS Identification Number (30-089-0007)]

Design concentration years	Design concentration (μg/m3 )
2015-2017	100
2016-2018	88
2017-2019	70
2018-2020	66
Average Design Concentration (of Most Recent 3 Design Concentrations) 75 μg/m3 .

Table 3—Thompson Falls 24-Hour PM ₁₀ 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)]

Date	24-hour value (μg/m3 )
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 µg/m3 and 155 µg/m3 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 μg/m³ . This value falls below the presumptive 24-hour CDV of 98 μg/m³ 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 μg/m^[3] after 10 years, attributable to motor vehicle emission growth. This value is below the presumptive 24-hour CDV of 98 μg/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]

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 μg/m³ . 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).

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 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.

Footnotes

1.   see also 57 FR 18070 (April 28, 1992) and 66 FR 55102 (November 1, 2001).

2.  The “Procedures for Processing Requests to Redesignate Areas to Attainment” (Calcagni memo) outlines the criteria for redesignation (see docket for memo).

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).

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.

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.

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.

8.  See Thompson Falls, MT submission in docket, Table 2.4—Thompson Falls, MT—PM₁₀ Emission Summary, p. 2-5.

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 (PM_2.5) 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.

12.  See memo to file in docket dated January 10, 2022 titled “Memo to File—Thompson Falls, MT Motor Vehicle Regional Emissions Analysis.”