2022-09254. Air Plan Approval; OR; Oakridge PM10

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

The Environmental Protection Agency (EPA) proposes to redesignate the Oakridge, Oregon nonattainment area (Oakridge NAA or Oakridge area) to attainment for the 1987 National Ambient Air Quality Standard for particulate matter of 10 microns or less (PM₁₀ NAAQS). EPA also proposes to approve the Oakridge PM₁₀ maintenance plan for the area demonstrating continued compliance with the PM₁₀ NAAQS through with the Lane Regional Clean Air Agency (LRAPA), submitted to EPA on January 13, 2022, along with the redesignation request for inclusion into the Oregon State Implementation Plan (SIP). EPA also proposes to approve revisions to LRAPA's rules to reflect the redesignation. Additionally, EPA proposes to approve the PM₁₀ motor vehicle emissions budgets included in the maintenance plan and inform the public that we are starting the adequacy process for the proposed motor vehicle emissions budgets, including a public comment period. Finally, EPA proposes to take final agency action on the wildfire exceptional event request submitted by ODEQ on July 22, 2021 and concurred on by EPA on April 1, 2022. EPA proposes these actions pursuant to the Clean Air Act (CAA or the Act).

DATES:

Comments must be received on or before June 8, 2022.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA-R10-OAR-2022-0125, at https://www.regulations.gov. Follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from Regulations.gov . EPA may publish any comment received to its public docket. Do not electronically submit any information you consider to be Confidential Business Information (CBI) or other information the disclosure of which 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. 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://www.epa.gov/​dockets/​commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT:

Christi Duboiski (15-H13), EPA Region 10, 1200 Sixth Avenue (Suite 155), Seattle WA, 98101, at [phone], or [e-mail] .

SUPPLEMENTARY INFORMATION:

Throughout this document whenever “we,” or “our,” is used, it refers to EPA.

Table of Contents

I. Background

II. Clean Air Act Requirements for Redesignation to Attainment

III. EPA's Analysis of Oregon's Submittal

A. Attainment Determination

B. Applicable Requirements Under Section 110 and Part D of the CAA

1. CAA Section 110 General SIP Requirements

2. Part D of Title I Requirements

3. Fully Approved SIP Under CAA Section 110(k)

C. Improvement in Air Quality Due to Permanent and Enforceable Measures

D. Fully Approved Maintenance Plan

1. Attainment Inventory

2. Maintenance Demonstration

3. Monitoring Network and Verification of Continued Attainment

4. Contingency Plan

E. Transportation Conformity and Motor Vehicle Emissions Budgets

F. State Rule Changes To Reflect the Redesignation

IV. Proposed Action

V. Incorporation by Reference

VI. Statutory and Executive Orders Review

I. Background

EPA revised the NAAQS for particulate matter on July 1, 1987, replacing standards for total suspended particulates, particulate less than 30 microns in diameter, with new standards applying only to PM₁₀ (52 FR 24634). In 1987, EPA established two PM₁₀ standards, an annual standard and a 24-hour standard. In 2006, the 24-hour PM₁₀ standards were retained but the annual standards were revoked, effective December 18, 2006 (71 FR 61144, October 17, 2006). On January 15, 2013 and December 18, 2020, EPA announced that it was again retaining the PM₁₀ NAAQS as a 24-hour standard of 150 micrograms per cubic meter (μg/m³ ) (78 FR 3086 and 85 FR 82684). An area attains the 24-hour PM₁₀ standard when the expected number of days per calendar year with a 24-hour concentration exceeding the standard (referred to as an exceedance), is equal to or less than one. Oregon's January 13, 2022, submittal of the Oakridge PM₁₀ maintenance plan addresses the 1987 24-hour PM₁₀ standard, as originally promulgated, and as reaffirmed on December 18, 2020.

On December 21, 1993, EPA designated the Oakridge, Oregon urban growth boundary as nonattainment for PM₁₀ and classified it as moderate under section 107(d)(3) of the CAA (58 FR 67334). The nonattainment area designation and classification became effective on January 20, 1994, with an attainment date for the area of December 31, 2000.

The nonattainment designation of the Oakridge NAA required Oregon to prepare and submit an attainment plan to meet statutory and regulatory requirements. On December 9, 1996, ODEQ submitted an attainment plan (1996 attainment plan) to EPA, and on March 15, 1999, EPA approved the attainment plan (64 FR 12751). The 1996 attainment plan consisted of an attainment year emission inventory, control measures that meet reasonably available control measures/technology (RACM/RACT), attainment demonstration, motor vehicle emission budgets (MVEBs), demonstration of reasonable further progress (RFP), quantitative milestones and contingency measures. In addition, on July 26, 2001, EPA finalized a determination that the Oakridge NAA attained the PM₁₀ NAAQS (Determination of Attainment) by the December 31, 2000, attainment date (66 FR 38947).

II. Clean Air Act Requirements for Redesignation to Attainment

The CAA provides the requirements for redesignating a nonattainment area to attainment. Specifically, section 107(d)(3)(E) of the CAA allows for redesignation provided that: (1) EPA determines that the area has attained the applicable NAAQS; (2) EPA has fully approved the applicable implementation plan for the area under section 110(k) of the CAA; (3) EPA determines that the improvement in air quality is due to permanent and enforceable reductions in emissions resulting from implementation of the applicable SIP and applicable Federal air pollutant control regulations and other permanent and enforceable reductions; (4) EPA has fully approved a maintenance plan for the area as meeting the requirements of section 175A of the CAA; and (5) the state has met all requirements applicable to the area under section 110 and part D of the CAA. In this proposed action, EPA will review CAA section 107(d)(3)(E) requirements (2) and (5) together as part of our evaluation of Oregon's redesignation request.

EPA has provided guidance on redesignation in the “General Preamble,” ^[1] and has provided further guidance on processing redesignation requests in the following documents: (1) “Procedures for Processing Requests to Redesignate Areas to Attainment,” Memorandum from John Calcagni, Director, Air Quality Management Division, September 4, 1992 (hereafter the “Calcagni Memo”); (2) “State Implementation Plan (SIP) Actions Submitted in Response to Clean Air Act (CAA) Deadlines,” Memorandum from John Calcagni, Director, Air Quality Management Division, October 28, 1992; and (3) “Part D New Source Review (Part D NSR) Requirements for Areas Requesting Redesignation to Attainment,” Memorandum from Mary D. Nichols, Assistant Administrator for Air and Radiation, October 14, 1994. These documents are included in the Docket for this proposed action.

III. EPA's Analysis of Oregon's Submittal

EPA proposes to redesignate the Oakridge NAA to attainment for the 1987 24-hour PM₁₀ NAAQS and proposes to approve into the Oregon SIP the associated Oakridge PM₁₀ maintenance plan. EPA's proposed approval of the redesignation request and maintenance plan is based upon EPA's determination that the area continues to attain the 1987 24-hour PM₁₀ NAAQS and that all other redesignation criteria have been met for the area. Sections III.A through D of this document describe how Oregon's January 13, 2022, submittal satisfies the requirements of section 107(d)(3)(E) of the CAA for the 1987 24-hour PM₁₀ standard. In addition, EPA proposes to approve revisions to LRAPA's rules to reflect the redesignation of the Oakridge PM₁₀ and fine particulate matter (PM_2.5 ) nonattainment areas.^[2]

Oregon's submittal also addresses transportation conformity, MVEBs and emissions from wildfire-influenced PM₁₀ concentrations recorded in the Oakridge NAA in 2020. EPA proposes to approve the MVEBs and proposes to approve the exclusion of data associated with the wildfire exceptional events that affected data in September of 2020 for purposes of showing continued attainment of the PM₁₀ NAAQS.

A. Attainment Determination

To redesignate an area from nonattainment to attainment, the CAA requires EPA to determine that the area has attained the applicable NAAQS (CAA section 107(d)(3)(E)(i)). An area has attained the 1987 24-hour PM₁₀ NAAQS if the average number of expected exceedances per year is less than or equal to one, when averaged over a three-year period.^[3] A state must demonstrate that an area has attained the PM₁₀ NAAQS through submittal of ambient air quality data from an ambient air monitoring network for PM₁₀ to EPA's Air Quality System (AQS) (40 CFR 58.15 and 58.16(a)). Three years of representative data should be used (40 CFR part 50, Appendix K, 2.3(b)).

The Exceptional Events Rule

Congress has recognized that it may not be appropriate for EPA to use certain monitoring data collected by the ambient air quality monitoring network and maintained in EPA's AQS database ^[4] in certain regulatory determinations. Thus, in 2005, Congress provided the statutory authority for the exclusion of data influenced by “exceptional events” meeting specific criteria by adding section 319(b) to the CAA.^[5] To implement this 2005 CAA amendment, EPA promulgated the 2007 Exceptional Events Rule.^[6] The 2007 Exceptional Events Rule created a regulatory process codified at 40 CFR parts 50 and 51 (§§ 50.1, 50.14 and 51.930). These regulatory sections, which superseded EPA's previous guidance on handling data influenced by events, contain definitions, procedural requirements, requirements for air agency demonstrations, criteria for EPA's approval of the exclusion of event-affected air quality data from the data set used for regulatory decisions, and requirements for air agencies to take appropriate and reasonable actions to protect public health from exceedances or violations of the NAAQS. In 2016, EPA promulgated a comprehensive revision to the 2007 Exceptional Events Rule.^[7] Under the Exceptional Events Rule, for example, if a state demonstrates to EPA's satisfaction that emissions from a wildfire smoke event caused a specific air pollution concentration in excess of the PM₁₀ NAAQS at a particular air quality monitoring location and otherwise satisfies the requirements of 40 CFR 50.14, EPA must exclude that data from use in determinations of exceedances and violations.^[8]

The Oakridge NAA Exceptional Event Demonstrations and Concurrences

The CAA allows for the exclusion of air quality monitoring data from design value calculations when there are NAAQS exceedances caused by events, such as wildfires, that meet the criteria for an exceptional event identified in EPA's Exceptional Events Rule at 40 CFR 50.1, 50.14 and 51.930. For the purposes of this proposed action, on July 22, 2021, ODEQ submitted an exceptional events demonstration for the purpose of showing that PM₁₀ concentrations recorded at the Oakridge Willamette Center monitor from September 11, 2020 through September 16, 2020 were influenced by wildfires. EPA concurred on this request on April 1, 2022.

EPA found that Oregon's demonstration met the Exceptional Events Rule criteria and determined that the wildfire event had regulatory significance for purposes of calculating the area's most recent design value to demonstrate the area continues to attain the standard in order to redesignate the area to attainment for the PM₁₀ NAAQS. As such, EPA proposes to take final regulatory action on the concurred dates, as detailed in the docket for this action, as exceptional events to be removed from the data set used for regulatory purposes. For this proposed action, EPA will rely on the calculated values that exclude the event-influenced data for the purpose of demonstrating continued attainment of the 1987 24-hour PM₁₀ NAAQS. Further details on Oregon's analyses and EPA's concurrences can be found in the docket for this regulatory action.

While EPA may agree with Oregon's request to exclude event influenced air quality monitoring data from regulatory decisions, these regulatory actions require EPA to provide an opportunity for public comment on the claimed exceptional event and all supporting data prior to EPA taking final agency action. This proposed action provides the public with an opportunity to comment on the claimed exceptional event, all supporting documents and EPA's concurrence with Oregon's request.

Evaluation of Current Attainment

As noted previously, on July 26, 2001, EPA finalized a Determination of Attainment for the Oakridge NAA based upon quality-assured and certified ambient air quality monitoring data for the 1998-2000 design value period (66 FR 38947). There were no exceedances of the 24-hour PM₁₀ standard during this period. Therefore, the expected exceedance rate was 0.0, which demonstrates attainment of the 24-hour PM₁₀ NAAQS.

For this proposed action, EPA reviewed the most recent PM₁₀ ambient air monitoring data in the Oakridge area for the monitoring design value period of 2018-2020. Consistent with the requirements at 40 CFR part 50, this ambient monitoring data in EPA's AQS has been quality-assured, quality-controlled and certified by ODEQ. The 24-hour PM₁₀ design value for 2020 was 0.7, therefore, the average number of expected exceedances averaged over a three-year period is less than or equal to one.^[9] Thus, EPA concludes that the Oakridge area continues to demonstrate continued attainment of the 1987 24-hour PM₁₀ NAAQS during the three-year period ending on December 31, 2020.

B. Applicable Requirements Under Section 110 and Part D of the CAA

Section 107(d)(3)(E)(ii) and (v) of the CAA require EPA to determine that the area has a fully approved applicable SIP under section 110(k) that meets all applicable requirements under section 110 (general SIP requirements) and part D (SIP requirements for nonattainment areas) for the purposes of redesignation. We interpret this to mean that, for a redesignation request to be approved, the state must have met all requirements that applied to the subject area prior to, or at the time of, submitting a complete redesignation request. EPA may rely on prior SIP approvals in approving a redesignation request ^[10] as well as any additional measure it may approve in conjunction with a redesignation action.

1. CAA Section 110 General SIP Requirements

Section 110(a)(2) of Title I of the CAA delineates the general requirements for a SIP. These requirements include, but are not limited to the following: (1) Submittal of a SIP that has been adopted by the state after reasonable public notice and hearing; (2) provisions for establishment and operation of appropriate procedures needed to monitor ambient air quality; (3) implementation of a source permit program; (4) provisions for the implementation of part C requirements (PSD); (5) provisions for the implementation of part D requirements for NSR permit programs; (6) provisions for air pollution modeling; and (7) provisions for public and local agency participation in planning and emission control rule development.^[11]

We note that SIPs must be fully approved only with respect to applicable requirements for purposes of redesignation in accordance with section 107(d)(3)(E)(ii). Similarly, EPA believes that the other CAA section 110(a)(2) (and part D) requirements that are not connected with nonattainment plan submittals and not linked with an area's attainment status are not applicable requirements for purposes of redesignation because the area will still be subject to these requirements after it is redesignated. EPA considers the CAA section 110(a)(2) (and part D) requirements that relate to a particular nonattainment area's designation and classification as the relevant measures to evaluate in reviewing a redesignation request. This approach is consistent with EPA's existing policy on applicability of the conformity SIP requirement for redesignations.^[12]

EPA has reviewed the Oregon SIP and concludes that it meets the general SIP requirements under section 110(a)(2) of the CAA to the extent they are applicable for the purposes of redesignation.^[13] On several occasions, Oregon has submitted, and EPA has approved, provisions of Oregon's SIP as demonstrating compliance with CAA section 110(a)(2) requirements.^[14] These requirements are, however, statewide requirements that are not linked to the PM₁₀ nonattainment status of the Oakridge NAA. In addition, there are no outstanding or disapproved applicable SIP submittals with respect to the Oakridge portion of the SIP that would prevent redesignation of the Oakridge NAA for the PM₁₀ NAAQS. Therefore, we conclude that ODEQ and LRAPA have met all general SIP requirements for the Oakridge NAA that are applicable for purposes of redesignating the area to attainment of the PM₁₀ NAAQS.

2. Part D of Title I Requirements

Before a PM₁₀ nonattainment area may be redesignated to attainment, the state must have fulfilled the applicable requirements of part D of Title I of the CAA, which sets forth the basic nonattainment plan requirements applicable to all areas designated nonattainment. The general requirements are followed by a series of subparts specific to each pollutant. Subpart 1 of part D establishes the general requirements applicable to all NAAs, while subpart 4 of part D establishes specific requirements applicable to PM₁₀ NAAs. The General Preamble provides that the applicable requirements of subpart 1 (CAA section 172) are, in relevant part, 172(c)(3) (emissions inventory), 172(c)(5) (new source review permitting program), 172(c)(7) (the applicable provisions of section 110(a)(2)), and 172(c)(9) (contingency measures). It is also worth noting that we interpreted the requirements of section 172(c)(2) (RFP) and 172(c)(6) (other measures) as being irrelevant to a redesignation request because they only have meaning for an area that is not attaining the standard. See Calcagni Memo and the General Preamble, 57 FR 13530, 13564, dated April 16, 1992. Finally, Oregon has not sought to exercise the options that would trigger CAA section 172(c)(8) (equivalent techniques). Thus, these provisions are also not relevant to this redesignation request.

The requirements of CAA section 172(c) and 189(a) regarding attainment of the PM₁₀ NAAQS, and the requirements of section 172(c) regarding RFP, imposition of RACM, the adoption of contingency measures, and the submittal of an emission inventory have been satisfied through our March 15, 1999, approval of the Oakridge PM₁₀ SIP (64 FR 12751). Additionally, on July 26, 2001, EPA published a finding of attainment for the Oakridge PM₁₀ area (66 FR 38947). EPA found that the Oakridge NAA attained the 24-hour PM₁₀ NAAQS by the moderate PM₁₀ attainment date of December 31, 2000.

CAA section 172(c)(4) requires the identification and quantification of allowable emissions for major new and modified stationary sources in an area, and CAA section 172(c)(5) requires source permits for the construction and operation of new and modified major stationary sources anywhere in the nonattainment area. EPA first approved the requirements of the part D, subpart 1 NSR permit program for LRAPA on December 27, 2011 (76 FR 80747, 80748). Subsequently, LRAPA revised its rules to meet additional part D, subpart 4 NSR requirements promulgated by EPA (81 FR 58010, August 24, 2016) and to align with ODEQ's rules.^[15] EPA approved LRAPA's rules on October 5, 2018 (83 FR 50274).

Once the Oakridge NAA is redesignated to attainment, the prevention of significant deterioration (PSD) requirements of part C of the Act will apply. LRAPA's PSD regulations are codified in Title 29 (Designation of Air Quality Areas), Title 38 (New Source Review) and Title 50 (Ambient Air Standards and PSD Increments) in conjunction with other provisions including but not limited to LRAPA's rules in Titles 12, 31, 34, 35, 40, and 42. We most recently approved revisions to LRAPA's PSD program on October 5, 2018 (83 FR 50274). EPA finds that LRAPA's PSD provisions meet all applicable Federal requirements for any area designated unclassifiable or attainment, and these provisions will become fully effective in the Oakridge area upon redesignation to attainment.

CAA section 172(c)(7) requires the SIP to meet the applicable provisions of CAA section 110(a)(2). As noted above, we find that the Oregon SIP meets the CAA section 110(a)(2) applicable requirements. For purposes of redesignation to attainment for the 1987 24-hour PM₁₀ NAAQS, EPA proposes to find that LRAPA has met all the applicable SIP requirements under part D of Title I of the CAA in accordance with section 107(d)(3)(E)(v) of the CAA.

3. Fully Approved SIP Under CAA Section 110(k)

Section 110(k) of the CAA sets out provisions governing EPA's review of SIP submittals. In order for an area to qualify for redesignation, the SIP for the area must be fully approved under section 110(k) of the CAA. As discussed in Sections III.B.1 and III.B.2 of this document, for purposes of redesignation to attainment for the 1987 24-hour PM₁₀ NAAQS, EPA has fully approved all applicable requirements of Oregon's SIP for the Oakridge area in accordance with CAA section 110(k). Therefore, the criterion for redesignation, set forth at CAA section 107(d)(3)(E)(ii), is satisfied.

C. Improvement in Air Quality Due to Permanent and Enforceable Measures

In order to approve a redesignation to attainment, section 107(d)(3)(E)(iii) of the CAA requires EPA to determine that the improvement in air quality is due to emissions reductions that are permanent and enforceable, and that the improvement is from the implementation of the applicable SIP, implementation of applicable Federal air pollution control regulations, and other permanent and enforceable reductions.

The Oakridge 1996 attainment plan addressed attainment planning requirements for the Oakridge moderate NAA, including control measures to satisfy the RACM requirement and a demonstration that attainment of the PM₁₀ NAAQS would be achieved by the required dates. The federally-approved 1996 attainment plan included woodstove change-outs, a voluntary residential woodsmoke curtailment program, commitment to reduce winter road sanding, and the paving of unpaved roads to reduce emissions of PM₁₀ in the Oakridge NAA. EPA's approval of this SIP made these control strategies federally enforceable.

The historical PM₁₀ air pollution problem in the Oakridge area has been emissions from residential wood combustion. Since 1993, as funding allowed, the Oakridge area has experienced emission reduction benefits from changing-out uncertified woodstoves for cleaner burning and more efficient home heating units. More recently, EPA approved the Oregon Heat Smart Program ^[16] and the Oakridge City Air Pollution Control Ordinance 920 (Oakridge Ordinance 920) ^[17] into the Oregon SIP. Both prohibit the installation and ban the sale of non-EPA-certified devices in new or existing buildings. In addition to the initial woodstove change-outs provided for in the 1996 attainment plan, these SIP strengthening control strategies provide for permanent and enforceable PM₁₀ reductions in the Oakridge NAA.

Since 1989, LRAPA, in cooperation with the City of Oakridge, has implemented a residential woodsmoke curtailment program in the Oakridge NAA. Oakridge Ordinance 815, State effective August 26, 1996 and federally-approved in the 1999 attainment plan, prohibited visible emission from a solid fuel burning device during a Red Advisory (when the PM₁₀ levels are forecast by LRAPA to be greater than or equal to 120 µg/m³ ) unless granted a sole source or economic need exemption. Oakridge Ordinance 815 is superseded by the federally-approved Oakridge Ordinance 920, which is more protective of the PM₁₀ NAAQS. In addition to the existing residential woodsmoke curtailment program, Oakridge Ordinance 920 provides further strengthening of the control measures while maintaining the integrity of the prior ordinance.

Oakridge Ordinance 920 strengthens the SIP by prohibiting the burning of any fuel other than “seasoned wood,” which is defined as any species of wood that has been sufficiently dried to contain 20 percent or less moisture by weight, and prohibiting the burning of specified materials such as plastic, rubber products, petroleum-treated materials and other materials which normally emit dense smoke, noxious odors, or hazardous air contaminants in a solid fuel burning device. EPA proposes to remove the City of Oakridge Ordinance 815 from the Oregon SIP because it is superseded by the federally-approved Oakridge Ordinance 920, which strengthens the PM₁₀ SIP and ensures the woodstove curtailment program continues to be permanent and enforceable.

The second largest source of PM₁₀ emissions in the Oakridge NAA is road dust, of which winter road sanding and unpaved road dust are contributors. To reduce road sanding emissions the Oregon Department of Transportation (ODOT) has been using an anti-icing chemical, calcium magnesium acetate (CMA), instead of grit, within the City of Oakridge since 1995. ODOT continues to commit to using these chemicals into the future ( See the September 20, 2021, letter from Jim Gamble, District 5 Manager, ODOT, included in the docket for this action). In addition, between 1991 and 1995 all of Oakridge's unpaved roads, approximately 2.5 miles, and numerous unpaved commercial driveways and parking lots were paved.^[18]

Based on the foregoing evaluation of these control measures, EPA proposes to determine that the improvement in air quality is reasonably attributable to permanent and enforceable reductions in emissions resulting from implementation of the applicable implementation plan and other permanent and enforceable reductions. Therefore, the criterion for redesignation set forth at CAA section 107(d)(3)(E)(iii) is satisfied.

D. Fully Approved Maintenance Plan

CAA section 107(d)(3)(E)(iv) requires that, for a nonattainment area to be redesignated to attainment, EPA must fully approve a maintenance plan for the area as meeting the requirements of CAA section 175A. The maintenance plan must demonstrate continued attainment of the relevant NAAQS in the area for at least 10 years after our approval of the redesignation. Eight years after redesignation, the state must submit a revised maintenance plan demonstrating attainment for the 10 years following the initial 10-year period. The maintenance plan must also contain a contingency plan to ensure prompt correction of any violation of the NAAQS that occurs after redesignation of the area. See CAA sections 175A(a), (b) and (d). The Calcagni Memo provides additional guidance on the content of a maintenance plan, stating that a maintenance plan should include the following elements: (1) An attainment emissions inventory; (2) a maintenance demonstration showing attainment for 10 years following redesignation; (3) a commitment to maintain and operate an appropriate air quality monitoring network; (4) verification of continued attainment; and (5) a contingency plan to prevent or correct future violations of the NAAQS. In this proposed action, EPA will review requirements (3) and (4) together as part of our evaluation of LRAPA's maintenance plan for the Oakridge area.

In conjunction with Oregon's request to redesignate the Oakridge area to attainment, Oregon submitted a SIP revision to provide for maintenance of the 1987 24-hour PM₁₀ NAAQS through 2035. EPA proposes to approve LRAPA's PM₁₀ maintenance plan for the Oakridge area. The following paragraphs describe how each of the maintenance plan elements are addressed in the maintenance plan.

1. Attainment Inventory

As discussed in the General Preamble ( See 57 FR 13498, April 16, 1992) and the Calcagni Memo, PM₁₀ maintenance plans should include an attainment emission inventory to identify the level of emissions in the area sufficient to maintain the PM₁₀ NAAQS. The maintenance plan attainment inventory should be consistent with EPA's emissions inventory requirements and most recent guidance on emissions inventories for nonattainment areas available at the time and should represent emissions during the time period associated with the monitoring data showing attainment.^[19] The inventory must also be comprehensive, including emissions from stationary point sources, area sources, mobile sources, and must be based on actual emissions during the appropriate season, if applicable.

The Oakridge PM₁₀ maintenance plan includes a 2015 PM₁₀ attainment emission inventory (2015 attainment inventory) based on typical season and worst-case day actual emissions from all direct primary PM₁₀ sources (point, area, on-road mobile and nonroad mobile sources.^{[20]  [21]} The year 2015 is representative of the level of emissions during the time period when the Oakridge area's monitoring data shows attainment of the 1987 24-hour PM₁₀ NAAQS. The 2015 maintenance plan attainment inventory is based on emission reduction strategies that were implemented as of 2015. These are summarized in Table 1, along with future year projected emissions for a 2035 “horizon year” (a future year at least 10 years from the approval date of the maintenance plan), and two interim years of 2025 and 2030.

Oregon's 2015 attainment inventory relies on methods and assumptions presented in detail in Appendix II of the Oakridge PM₁₀ maintenance plan (“Emision Inventory for 2015 Base Year”). The 2015 attainment inventory is based on typical season and worst-case day (episodic) emissions. The typical season day emissions represent an average daily emission value occurring from November 1 through the end of February. This four-month time period is considered to be the particulate matter season and is when the PM₁₀ standard has historically been exceeded. EPA considers the preparation of the typical season day inventory and worst-case day inventory, as opposed to an annual average daily inventory, appropriate given that the elevated PM₁₀ concentrations in Oakridge exhibit clear seasonal or episodic patterns. The worst-case day emissions represent a day during the PM season when emissions generating activity is at its highest due to meteorological factors like temperature. However, residential woodburning and other area source emissions on worst-case days are lower than on typical season days in the inventory due to woodburning curtailments and outdoor burning bans.

Residential wood combustion emissions from woodstoves, fireplaces and pellet stoves continue to be the major source of PM₁₀ emissions for both typical season days and worst-case winter days contributing to exceedances of the NAAQS.

Table 1—Oakridge PM ₁₀ Maintenance Plan Emissions Inventories

[In pounds per day]

Source category	2015 Attainment	2025 Interim	2030 Interim	2035 Maintenance	Difference from 2015 and 2035
PM 10 Typical Season Day
Point	0.0	8.0	8.0	8.0	8.0
Area	444.8	364.2	364.0	363.5	−81.3
On-road	142.1	131.0	133.2	132.8	−9.3
Nonroad	2.9	2.9	2.9	2.9	0.0
Total	589.8	506.1	508.1	507.2	−82.6
PM 10 Worst-Case Day
Point	0.0	13.7	13.7	13.7	13.7
Area	334.5	250.9	233.8	216.5	−118.0
On-road	158.5	144.1	146.5	146.0	−12.5
Nonroad	2.9	2.9	2.9	2.9	0
Total	495.9	411.6	396.9	379.1	−116.8

Based on our review of the documentation provided in the maintenance plan, we propose to find that the 2015 direct PM₁₀ attainment emission inventory is based on reasonable assumptions and methodologies, and that the inventory is comprehensive and based on the most accurate and current information available to LRAPA at the time it was developed. Based on our review of the 2015 emissions inventory Oregon provided in its January 13, 2022 submittal, we propose to find that LRAPA prepared an adequate attainment inventory for the Oakridge area.^[22]

2. Maintenance Demonstration

CAA section 175A requires a state seeking redesignation to attainment to submit a SIP revision to provide for maintenance of the NAAQS for a period of at least 10 years following redesignation. A state can make this demonstration by either showing that future emissions of a pollutant or its precursors will not exceed the level of the attainment (base year) inventory, or by modeling to show that the future mix of sources and emission rates will not cause a violation of the NAAQS.^[23]

In its maintenance demonstration for the Oakridge area, LRAPA elected to demonstrate maintenance of the PM₁₀ NAAQS for at least 10 years following redesignation using the attainment year inventory method. LRAPA developed projected inventories, provided in Table 1 of this document, to show that the Oakridge area will remain in attainment through the year 2035. These projected inventories, covering interim years 2025 and 2030 and a horizon year of 2035, show that future emissions of direct PM₁₀ throughout the nonattainment area will remain at or below the 2015 attainment emissions for the 1987 24-hour PM₁₀ NAAQS.

The projected emissions inventories in the Oakridge PM₁₀ maintenance plan address four major source categories: Point, area, on-road mobile and nonroad mobile. Oregon estimated future year emission inventories using the latest socioeconomic growth indictors and applying emissions reduction benefits from adopted control strategies when appropriate. A detailed description of the 2015 attainment year inventory and the 2025, 2030 and 2035 projected inventories can be found in Appendix III of LRAPA's January 13, 2022, PM₁₀ maintenance plan submittal, which is in the docket for this action.

As discussed in the Oakridge PM₁₀ maintenance plan, direct PM₁₀ emissions estimates for stationary point sources reflect actual emissions for both industrial point sources in Oakridge. The Oakridge Sand & Gravel ready-mix concrete plant and rock crusher did not operate in Oakridge in 2015, resulting in actual 2015 emissions that were zero. In addition, the ready-mix concrete plant air discharge permit was terminated on January 24, 2014, resulting in zero emissions in the 2015 and projected year emission inventories. Future year emissions were therefore based on the January 2011 PM₁₀ emissions at this source.

Areawide sources occur over a wide geographic area with the most significant emissions resulting from residential wood combustion sources such as fireplaces, woodstoves and pellet stoves. These residential wood heating devices are commonly used to heat homes in Oakridge since natural gas is not available in this area. The permanent and enforceable residential wood combustion control strategies are discussed in Section III.C. of this document. The only other area source category with potentially significant emissions is outdoor burning, which is banned in Lane County from November-February. Emissions for these categories are derived using various surveys, emission factors and other methodologies.

Emissions from on-road mobile sources (exhaust, brake wear and tire wear), which include passenger vehicles, buses, and trucks, were estimated using MOVES2014a. Traffic growth in Vehicle-Miles Traveled (VMT) was based on transportation modeling by the Lane Council of Governments (LCOG) and ODOT. LRAPA confirmed re-entrained road dust calculations for both paved and unpaved roads using AP-42 protocols. Federal control measures included in the MOVES2014a modeling are all Federal measures that affect the fleets and fuels used in future years once implemented by EPA.

The nonroad emissions from railroads were calculated using the EPA NONROAD2008a emission protocol. The National Emissions Inventories (NEIs) for Lane County indicate a significant decrease in locomotive emissions from 2008 to 2014 (42.63 tons/year and 19.62 tons/year, respectively). The 2015 PM₁₀ railroad emissions have been adjusted to reflect the locomotive emission reductions as seen in the 2014 NEI data. Future year emissions are based on the adjusted 2014 and 2017 NEI data. All other Oakridge nonroad mobile sources are categorized by LRAPA as insignificant during the PM₁₀ winter season.

EPA has reviewed the documentation provided by Oregon for developing the projected 2025, 2030 and 2035 emissions inventories for the Oakridge PM₁₀ NAA. Based on our review, EPA finds that the projected inventories were developed using appropriate procedures, comprehensively address all source categories in the Oakridge area, and sufficiently account for PM₁₀ projected actual emissions. These inventories indicate a decrease in PM₁₀ emissions throughout the maintenance period. Therefore, EPA proposes to determine that the projected emissions inventories in the maintenance plan sufficiently demonstrate that the Oakridge PM₁₀ area will continue to attain the 1987 24-hour PM₁₀ standard throughout the maintenance period.

3. Monitoring Network and Verification of Continued Attainment

Once a nonattainment area has been redesignated to attainment, the state must continue to operate an appropriate air quality monitoring network, in accordance with 40 CFR part 58, to verify the attainment status of the area. The maintenance plan should contain provisions for continued operation of air quality monitors that will provide such verification.

LRAPA notes in the Oakridge PM₁₀ maintenance plan that it currently operates a regulatory monitor (the Willamette Center monitor since 1989) in the Oakridge NAA. LRAPA commits to continue operating a regulatory monitoring network, in accordance with 40 CFR part 58 and the Oregon SIP through the year 2035 in order to verify continued attainment of the PM₁₀ NAAQS and track the progress of the maintenance plan. LRAPA also states that it will continue to operate the PM₁₀ monitoring network in accordance with the approved Annual Monitoring Network Plan (ANP). Any modification to the monitoring network will be done in consultation with ODEQ and with the approval of EPA Region 10 ( See 40 CFR 58.14(b)). EPA will work with ODEQ and LRAPA each year through the air monitoring network review process to determine the adequacy of the monitoring network.^[24]

Oregon remains obligated to continue to quality-assure monitoring data and enter all data into AQS in accordance with Federal guidelines. LRAPA will review the air monitoring results each year to verify continued attainment. LRAPA will determine annually if exceptional events influenced the continued attainment of the 1987 24-hour PM₁₀ NAAQS and need to be documented. If needed, ODEQ and LRAPA will coordinate and provide exceptional events documentation to EPA Region 10 for review.

It should be noted that LRAPA included in the Oakridge maintenance plan a discussion on the use of PM_2.5 monitoring as a surrogate for PM₁₀ monitoring in the future. See Section 4.2 of the Oakridge maintenance plan. Since any change to the monitoring network would occur in the future, EPA is not proposing to approve LRAPA discontinuing the PM₁₀ monitor, nor is EPA making a determination whether the use of a PM_2.5 surrogate monitor would be appropriate or consistent with 40 CFR part 58 requirements as part of this action.

EPA proposes to determine that the Oakridge PM₁₀ maintenance plan contains adequate provisions for continued operation of an air quality monitoring network and a commitment to annually verify continued attainment of the 1987 24-hour PM₁₀ NAAQS for the Oakridge area.

4. Contingency Plan

CAA section 175A(d) requires that a maintenance plan also include contingency provisions, as necessary, to promptly correct any violation of the NAAQS that occurs after redesignation of the area to attainment. For the purposes of CAA section 175A, a state is not required to have fully adopted contingency measures that will take effect without further action by the state in order for the maintenance plan to be approved. However, the contingency plan is an enforceable part of the SIP and should ensure that contingency measures are adopted expeditiously once they are triggered. The maintenance plan should discuss the measures to be adopted and a schedule and procedure for adoption and implementation. The contingency plan must require that the state will implement all measures contained in the part D nonattainment plan for the area prior to redesignation. The state should also identify the specific indicators, or triggers, which will be used to determine when the contingency plan will be implemented.^[25]

The Oakridge PM₁₀ maintenance plan outlines the procedures for the adoption and implementation of contingency measures to further reduce emissions should a violation of the PM₁₀ NAAQS or the 2006 24-hour PM_2.5 NAAQS (35 μg/m³ ) occur. It is expected that the PM_2.5 NAAQS would be exceeded before the PM₁₀ NAAQS, thus more quickly triggering the implementation of the contingency measures in the maintenance plan. If there is a violation of either standard, after consideration of any exceptional events, the following contingency strategies, or equivalent, will be implemented by LRAPA and the City of Oakridge:

• Stricter green-yellow-red advisory program,^[26] with more red advisory days each winter, by reducing the red advisory thresholds by 3 μg/m³ PM₁₀ . This is projected to increase the average number of potential red advisory days by three to five additional days per year.

• Prohibition of fireplace use on yellow advisory days (in addition to the existing prohibition on red advisory days).

While these measures do not need to be fully adopted by LRAPA prior to the occurrence of a NAAQS violation, LRAPA commits to adopting and implementing the necessary contingency measures as expeditiously as possible, but not later than one year after a violation based on confirmed quality assured data.

LRAPA will evaluate all appropriate data including air quality data, meteorological data, evaluation of wood smoke programs and information on unusual weather events ( e.g., wildfires or winter power outages) and other data to determine the cause of the violation. LRAPA will perform this evaluation within three months of the determination of a violation. Where appropriate, LRAPA will follow EPA's exceptional events rules and guidance if it is determined that an exceptional event contributed to the violation.^[27]

Based on our analysis of Oregon's submittal, we propose to find that the contingency measure provisions provided in the Oakridge PM₁₀ maintenance plan are sufficient and meet the requirements of CAA section 175A(d).

E. Transportation Conformity and Motor Vehicle Emissions Budgets

Transportation conformity is required by CAA section 176(c). EPA's conformity rule at 40 CFR part 93, subpart A requires that transportation plans, programs, and projects conform to SIPs and establishes the criteria and procedures for determining whether or not they conform. Conformity to a SIP means that transportation activities will not produce new air quality violations, worsen existing violations, or delay timely attainment of the NAAQS. Thus, EPA's conformity rule requires a demonstration that emissions from a Metropolitan Planning Organization's (MPO's) Regional Transportation Plan and Transportation Improvement Program, involving Federal Highway Administration (FHWA) or Federal Transit Administration (FTA) funding or approval, are consistent with the MVEB(s) contained in a control strategy SIP revision or maintenance plan (40 CFR 93.101, 93.118, and 93.124). A MVEB is the level of mobile source emissions of a pollutant relied upon in the attainment or maintenance demonstration to attain or maintain compliance with the NAAQS in the nonattainment or maintenance area.

PM₁₀ maintenance plan MVEBs are generally established for specific years and specific pollutants or precursors.^[28] The maintenance plan submittal should identify MVEBs for transportation related PM₁₀ emissions (motor vehicle emissions from tailpipe, brake wear, tire wear and re-entrained road dust) in the last year of the maintenance period. Budgets may also be specified for additional years during the maintenance period.

It should be noted that Oakridge is considered an isolated rural nonattainment area within the meaning of 40 CFR 93.109(g), so transportation conformity determinations are only required when a non-exempt Federal Highway Administration or Federal Transit Administration funded project is funded or approved.^[29]

With respect to previously established MVEBs, we note for the 1996 attainment plan, Oregon had previously adopted PM₁₀ MVEBs for 2003. These budgets were 178.8 pounds per day of direct PM₁₀ . This budget has continued to apply for conformity determinations since 2003. In addition, as determined in the 1996 attainment plan approval, major sources of PM₁₀ precursors do not contribute significantly to PM₁₀ levels in excess of the PM₁₀ NAAQs in the Oakridge NAA. Therefore, the Oakridge PM₁₀ maintenance plan includes direct PM₁₀ MVEBs that reflect the total on-road PM₁₀ emissions for the attainment year (2015), and the projected PM₁₀ emissions for two interim years (2025 and 2030) and the last year of the maintenance plan (2035). See Table 2, below.

The MVEBs reflect the total on-road PM₁₀ worst-case day emissions (a sum of primary exhaust, brake wear, tire wear and re-entrained paved and unpaved road dust), plus a portion of the available safety margin to accommodate technical uncertainties due to model updates and inputs into the EPA MOVES model and travel forecasting models as well as potential changes to regional transportation plans. A safety margin is the amount by which the total projected PM₁₀ emissions from all sources are less than the total emissions that would satisfy the NAAQS for the 2015 base year. With the safety margin applied to the future year MVEB, the budgets still demonstrate maintenance of the 1987 24-hour PM₁₀ NAAQS.

Oregon used the Motor Vehicle Emissions Simulator model, MOVES2014a, during the development of the maintenance plan and executed it with locally developed inputs representative of wintertime calendar year 2015 conditions and future projections in order to appropriately calculate the budgets. MOVES2014a was the accepted model when this work began. EPA recently released MOVES3, but since sufficient work had taken place on this SIP with MOVES2014a, we are accepting that mobile model in this submittal (86 FR 1106, 1108, January 7, 2021). Traffic growth in VMT for the Oakridge NAA is based on transportation modeling by Lane County, LCOG and ODOT. The mobile source emissions, in total, were modeled to steadily decrease between 2015 and 2035 as a result of cleaner vehicles and cleaner fuels. The MVEBs are based on the control measures in the maintenance plan and consistent with maintaining the PM₁₀ NAAQS.

The mobile source emissions budgets for the years 2015, 2025, 2030 and 2035 are provided in Table 2 of this proposed action. According to EPA's conformity rule, the emissions budget acts as a ceiling on emissions in the year for which it is defined or until a SIP revision modifies the budget.^[30]

Table 2—PM ₁₀ MVEBs for the Oakridge PM ₁₀ NAA

Motor vehicle emissions budgets	Year
	2015	2025	2030	2035
PM 10 (lbs/day)	138.9	147.4	156.8	164.7

For MVEBs to be approvable, they must meet, at a minimum, EPA's adequacy criteria (40 CFR 93.118(e)(4)). EPA's process for determining adequacy of a budget consists of three basic steps: (1) Notifying the public of a SIP submittal; (2) providing the public the opportunity to comment on the budget during a public comment period; and (3) making a finding of adequacy or inadequacy. The process for determining the adequacy of a submitted budget is codified at 40 CFR 93.118(f). EPA can notify the public by either posting an announcement that EPA has received SIP budgets on EPA's adequacy website (40 CFR 93.118(f)(1)), or via a Federal Register notice of proposed rulemaking when EPA reviews the adequacy of an implementation plan budget simultaneously with its review and action on the SIP itself (40 CFR 93.118(f)(2)).

Today, we are notifying the public that EPA will be reviewing the adequacy of the 2015, 2025, 2030 and 2035 budgets in the Oakridge PM₁₀ maintenance plan. The public has a 30-day comment period as described in the DATES section of this notice. After this comment period, EPA will indicate whether the budgets are adequate via the final rulemaking on this proposed action or on the adequacy website, according to 40 CFR 93.118(f)(2)(iii). The details of EPA's evaluation of the budget for compliance with the budget adequacy criteria of 40 CFR 93.118(e) are provided in a separate memorandum included with the docket for this rulemaking.^[31] As noted earlier, the public comment period for EPA's adequacy finding will be concurrent with the public comment period for this proposed action on the Oakridge PM₁₀ maintenance plan.

Based on the information presented in the Oakridge PM₁₀ maintenance plan and our adequacy review to date, we propose to find that Oregon has evaluated the appropriate pollutants and appropriately established MVEBs for direct PM₁₀ emissions. EPA has reviewed the Oakridge PM₁₀ maintenance plan's MVEBs and found them to be consistent with the control measures in the SIP and consistent with maintenance of the 1987 24-hour PM₁₀ NAAQS within the Oakridge area through 2035. We propose to approve the MVEBs in the Oakridge PM₁₀ maintenance plan as meeting the requirements of the CAA and EPA regulations.

F. State Rule Changes To Reflect the Redesignation

Oregon adopted maintenance plans for both the Oakridge PM₁₀ area and Oakridge PM_2.5 area in the same state rulemaking package and submitted them as a single SIP submittal to EPA. This single submittal includes changes to LRAPA rules to reflect the anticipated redesignation of both areas. Today's action addresses the Oakridge PM₁₀ area, and we are addressing the Oakridge PM_2.5 area in a separate action. In today's action EPA is proposing to approve revisions to LRAPA's Title 29 Designation of Air Quality Areas, Section 29-0030(1) Designation of Nonattainment Areas and Section 29-0040(2)(b) Designation of Maintenance Areas. These revisions will remove the Oakridge PM₁₀ nonattainment areas from the list of PM₁₀ nonattainment areas and add them to the list of PM₁₀ maintenance areas within the federally-approved Oregon SIP.^[32]

IV. Proposed Action

EPA proposes to redesignate the Oakridge, Oregon PM₁₀ NAA, and proposes to approve the associated maintenance plan for the area. If this proposal is finalized, the designation status of the Oakridge, Oregon PM₁₀ NAA, under 40 CFR part 81 will be revised to attainment upon the effective date of that final action.

EPA proposes to approve and incorporate by reference into the Oregon SIP, the submitted revisions to LRAPA Title 29 Sections 29-0030(1) and 29-0040(2)(b) state effective November 18, 2021. EPA also proposes to approve the State's request to remove from incorporation by reference City of Oakridge Ordinance 815, state effective August 15, 1996.

In addition, EPA proposes to take final agency action on Oregon's exceptional event demonstration for the Oakridge PM_2.5 monitor as discussed in this action.

Finally, we propose to find that the Oakridge PM₁₀ maintenance plan's MVEBs meet applicable CAA requirements for maintenance plans and transportation conformity requirements. With this action, we are starting the adequacy process for these proposed MVEBs and opening a public comment period.

We note that the January 13, 2022 submittal also includes the Oakridge PM_2.5 redesignation and maintenance plan, revisions to the Lane County Code, and additional revisions to LRAPA's Title 29 rules, which EPA will address in a separate action.

V. Incorporation by Reference

In this document, EPA proposes to include in a final rule, regulatory text that includes incorporation by reference. In accordance with the requirements of 1 CFR 51.5, EPA proposes to incorporate by reference the provisions described in section IV of this preamble. EPA is also proposing to remove regulatory text that includes incorporation by reference. In accordance with requirements of 1 CFR 51.5, EPA proposes to remove the City of Oakridge Ordinance 815, state effective August 15, 1996, from the incorporation by reference as described in section IV of this preamble. EPA has made, and will continue to make, these documents generally available through https://www.regulations.gov and at the EPA Region 10 Office (please contact the person identified in the FOR FURTHER INFORMATION CONTACT section of this preamble for more information).

VI. Statutory and Executive Orders Review

Under the CAA, redesignation of an area to attainment and the accompanying approval of a maintenance plan under section 107(d)(3)(E) are actions that affect the status of a geographical area and do not impose any additional regulatory requirements on sources beyond those imposed by state law. A redesignation to attainment does not in and of itself create any new requirements, but rather results in the applicability of requirements contained in the CAA for areas that have been redesignated to attainment. Moreover, the Administrator is required to approve a SIP submittal that complies with the provisions of the CAA and applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submittals, EPA's role is to approve State choices, provided that they meet the criteria of the CAA. Accordingly, this proposed action merely proposes to approve a State plan as meeting Federal requirements and does not impose additional requirements beyond those already imposed by State law. For that reason, this proposed action:

• Is not a “significant regulatory action” subject to review by the Office of Management and Budget under Executive Orders 12866 (58 FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);

• Does not impose an information collection burden under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq. );

• Is certified as not having a significant economic impact on a substantial number of small entities under the Regulatory Flexibility Act (5 U.S.C. 601 et seq. );

• Does not contain any unfunded mandate or significantly or uniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4);
• Does not have federalism implications as specified in Executive Order 13132 (64 FR 43255, August 10, 1999);
• Is not an economically significant regulatory action based on health or safety risks subject to Executive Order 13045 (62 FR 19885, April 23, 1997);
• Is not a significant regulatory action subject to Executive Order 13211 (66 FR 28355, May 22, 2001);
• Is not subject to requirements of Section 12(d) of the National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) because application of those requirements would be inconsistent with the 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, this rule does not have tribal implications 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
• 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
• Wilderness areas

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

Dated: April 25, 2022.

Michelle L. Pirzadeh,

Acting Regional Administrator, Region 10.

Footnotes

1.   See “State Implementation Plans; General Preamble for the Implementation of Title I of the Clean Air Act Amendments of 1990,” 57 FR 13498, April 16, 1992.

2.  We note that the January 13, 2022 submittal also includes the Oakridge PM_2.5 redesignation and maintenance plan and revisions to the Lane County Code, which EPA will address in a separate action.

3.   See 40 CFR part 50 and 40 CFR part 50, appendix K.

4.  AQS is EPA's official repository of ambient air data.

5.  Under CAA section 319(b), an exceptional event means an event that (i) affects air quality; (ii) is not reasonably controllable or preventable; (iii) is an event caused by human activity that is unlikely to recur at a particular location or a natural event; and (iv) is determined by EPA under the process established in regulations promulgated by EPA in accordance with section 319(b)(2) to be an exceptional event. For the purposes of section 319(b), an exceptional event does not include (i) stagnation of air masses or meteorological inversions; (ii) a meteorological event involving high temperatures or lack of precipitation; or (iii) air pollution relating to source noncompliance.

6.  72 FR 13560 (March 22, 2007).

7.  81 FR 68216 (October 3, 2016). We refer herein to the 2016 revision as the “Exceptional Events Rule.”

8.  40 CFR 50.14(b)(4).

9.  As noted above, EPA excluded data for September 11, 2020 through September 16, 2020 from this design value because the Agency determined concentrations recorded on those dates satisfied the requirements of the Exceptional Events Rule.

10.  Calcagni Memo, 3; Wall v. EPA, 265 F.3d 426, 438 (6th Cir. 2001); and Southwestern Pennsylvania Growth Alliance v. Browner, 144 F.3d 984, 989-990 (6th Cir. 1998).

11.   See the General Preamble for further explanation of these requirements. 57 FR 13498 (April 16, 1992).

12.   See 75 FR 36023, 36026 (June 24, 2010) and citations within.

13.  The LRAPA portion of the federally-approved Oregon SIP can be viewed at https://www.epa.gov/​sips-or/​epa-approved-regulations-oregon-sip.

14.   See, e.g., 83 FR 24034 (May 24, 2019) and 84 FR 26347 (June 6, 2019).

15.   See 40 CFR 51.160, 51.161, 51.165, and 51.166. See also EPA's proposed approval of Oregon nonattainment NSR program (March 22, 2017, 82 FR 14654, 14663) and EPA's final approval (October 11, 2017, 82 FR 47122).

16.  A statewide mandate approved by EPA on October 11, 2017 (82 FR 47122).

17.   See 83 FR 5537, February 8, 2018.

18.   See 64 FR 12751 (March 15, 1999).

19.   See Calcagni Memo at 8.

20.  ODEQ's PM₁₀ emission inventory includes emissions within the larger Oakridge-Westfir PM_2.5 nonattainment area boundary (not the smaller Oakridge urban growth boundary). EPA believes this is appropriate in this instance (except for when calculating the motor vehicle emissions) because the Oakridge PM₁₀ nonattainment area encompasses the vast majority of the population and activity within the Oakridge-Westfir PM_2.5 NAA.

21.  PM₁₀ precursor emissions should also be included depending upon the contribution of the secondarily-formed particulate matter to high ambient PM₁₀ concentrations in the area. In this instance, an inventory of PM₁₀ precursor emissions is not required because PM₁₀ precursor controls were not relied upon to achieve attainment of the PM₁₀ NAAQS in the Oakridge planning area (64 FR 12751, March 15, 1999), nor are they relied upon to demonstrate maintenance of the NAAQS. While not required, the maintenance plan includes an inventory of PM₁₀ precursor emissions in Appendix II (“PM₁₀ Emission Inventory for 2015 Base Year”).

22.   See “Emissions Inventory Guidance for Implementation of Ozone and Particulate Matter National Ambient Air Quality Standards (NAAQS) and Regional Haze Regulations,” May 2017, available at https://www.epa.gov/​sites/​default/​files/​2017-07/​documents/​ei_​guidance_​may_​2017_​final_​rev.pdf.

23.   See Calcagni Memo, pages 9-10.

24.   See EPA's February 22, 2022 approval of Oregon's 2021 Annual Monitoring Network Plan, in the docket for this action.

25.   See Calcagni Memo at 12.

26.  LRAPA implements an advisory system that designates days as green, yellow, or red when 24-hour PM levels reach certain designated thresholds. During a red advisory day, LRAPA prohibits the use of any solid fuel space heating device that emits visible emissions into the air outside of the building housing the device unless a specific exemption has been granted.

27.  Treatment of Data Influenced by Exceptional Events, October 3, 2016, 81 FR 68216.

28.  Transportation-related emissions of volatile organic compounds (VOCs) or nitrogen oxides (NO_X) must also be specified in PM₁₀ areas if EPA or the state find that transportation-related emissions of one or both of these precursors within the nonattainment area are a significant contributor to the PM₁₀ nonattainment problem and has so notified the MPO and the U.S. Department of Transportation (DOT), or the applicable SIP revisions or SIP revision submittal establishes an approved or adequate budget for such emissions as part of the reasonable further progress, attainment or maintenance strategy. 40 CFR 93.102(b)(2)(iii). Neither of these conditions apply to the Oakridge PM₁₀ nonattainment area.

29.   See 40 CFR 93.109(g).

30.   See 40 CFR 93.118.

31.   See EPA memorandum titled, “EPA Region 10 Adequacy Review of Motor Vehicle Emissions Budgets in Oakridge PM₁₀ Maintenance Plan”, dated April 6, 2022.

32.  On January 13, 2022, Oregon also submitted LRAPA Title 29 Sections 0020, 0050-0090, 0300 and 0320. Oregon made no changes to these sections, except for the State effective date. EPA has reviewed these rules and approved them in a previous action (83 FR 50274, March 23, 2018).