AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

The Environmental Protection Agency (EPA) is proposing to approve State Implementation Plan (SIP) revisions submitted by the State of Utah on January 4, 2016, which include revisions to Utah's Division of Administrative Rule (DAR) R307-110-10 and maintenance plans for the Salt Lake County, Utah County, and Ogden City nonattainment areas (NAAs) for particulate matter with an aerodynamic diameter less than or equal to a nominal 10 microns (PM₁₀), and on March 6, 2019, which include PM₁₀ redesignation requests and supplemental information for Salt Lake County, Utah County and Ogden City. These submittals demonstrate that the Salt Lake County, Utah County and Ogden City areas have attained the PM₁₀ National Ambient Air Quality Standards (NAAQS), request redesignation to attainment and include maintenance plans for the areas demonstrating attainment for fifteen years. Also, the EPA is proposing approval of Utah's February 27, 2017 submittal, which includes rule revisions to address our October 19, 2016 conditional approval of Utah's DAR R307-302 revisions that were submitted May 9, 2013, May 20, 2014, and September 8, 2015. Additionally, the EPA is proposing to approve SIP revisions submitted by the State of Utah on February 15, 2019, with additional non-substantive changes submitted on July 1, 2019, August 20, 2019, and October 15, 2019, which includes revisions that are located in DAR R307-110-17 and SIP Subsections IX.H.1-2. The EPA is taking this action pursuant to section 107, 110, and 175A of the Clean Air Act (CAA or the Act).

DATES:

Written comments must be received on or before December 23, 2019.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA-R08-OAR-2019-0276, 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 http://www2.epa.gov/​dockets/​commenting-epa-dockets.

Docket: All documents in the docket are listed in the www.regulations.gov index. Although listed in the index, some information is not publicly available, e.g., CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard copy. Publicly available docket materials are available either electronically in www.regulations.gov or in hard copy at the Air and Radiation Division, Environmental Protection Agency (EPA), Region 8, 1595 Wynkoop Street, Denver, Colorado 80202-1129. The EPA requests that if at all possible, you contact the individual listed in the FOR FURTHER INFORMATION CONTACT section to view the hard copy of the docket. You may view the hard copy of the docket Monday through Friday, 8:00 a.m. to 4:00 p.m., excluding federal holidays.

FOR FURTHER INFORMATION CONTACT:

Crystal Ostigaard, Air and Radiation Division, EPA, Region 8, Mailcode 8ARD-QP, 1595 Wynkoop Street, Denver, Colorado, 80202-1129, (303) 312-6602, ostigaard.crystal@epa.gov.

SUPPLEMENTARY INFORMATION:

Throughout this document wherever “we,” “us,” or “our” is used, we mean the EPA.

I. Background

Under section 109 of the Act, the EPA has promulgated NAAQS for certain pollutants, including PM₁₀ (40 CFR 50.2(b)). Once the EPA promulgates a NAAQS, section 107 of the Act specifies a process for the designation of all areas within a state, generally as either an attainment area (an area attaining the NAAQS) or as a NAA (an area not attaining the NAAQS, or that contributes to nonattainment of the NAAQS in a nearby area). For PM₁₀, certain areas have also been designated “unclassifiable.” These various designations, in turn, trigger certain state planning requirements.

For all areas, regardless of designation, section 110 of the Act requires that each state adopt and submit for EPA approval a plan to provide for implementation, maintenance and enforcement of the NAAQS. This plan is commonly referred to as a SIP. Section 110 contains requirements that a SIP must meet in order to be approved by the EPA.^[1] For NAAs, SIPs must meet additional requirements contained in part D of Title I of the Act. Usually, SIPs include measures to control emissions of air pollutants from various sources, including stationary, mobile and area sources. For example, a SIP may specify emission limits at power plants or other industrial sources.

Under the 1990 amendments to the CAA, Salt Lake and Utah Counties were designated nonattainment for PM₁₀ and classified as Moderate areas by operation of law as of November 15, 1990 (56 FR 56694, 56840; November 6, 1991). The air quality planning requirements for PM₁₀ Moderate NAAs are set out in Title I, part D, subparts 1 and 4 of the Act. As described in section 110 and 172 of the Act, areas designated nonattainment based on a failure to meet the PM₁₀ NAAQS are required to develop SIPs with sufficient control measures to expeditiously attain and maintain the NAAQS.

On July 8, 1994, the EPA approved the PM₁₀ SIP for Salt Lake and Utah Counties (59 FR 35036), including approval of R307-110-10, Section IX, Control Measures for Area and Point Sources, Part A, Fine Particulate Matter. The SIP included a demonstration of attainment and various control measures, including emission limits at stationary sources. Because emissions of sulfur dioxide (SO₂) and nitrogen oxides (NO_X) contribute significantly to the PM₁₀ problem in the area, the SIP included limits on emissions of SO₂ and NO_X in addition to emissions of PM₁₀. Additionally, approval of R307-110-10, incorporated by reference (IBR) the Utah SIP, Section IX, Control Measures for Area and Point Sources, Part A, Fine Particulate Matter and made this section a part of Utah's SIP approved rules.

On December 6, 1999, the EPA approved revisions to the road salting and sanding programs for the two counties (64 FR 68031). On July 1, 2002, the EPA approved a new rule, R307-310, Salt Lake County: Trading of Emission Budgets for Transportation Conformity, to the Salt Lake County PM₁₀ SIP that allowed trading between PM₁₀ and NO_X motor vehicle emissions budgets (MVEBs) for transportation conformity determinations (67 FR 44065). Additionally, on September 2, 2008 (73 FR 51222), the EPA approved updates to R307-310, Salt Lake County: Trading of Emission Budgets for Transportation Conformity.

On June 18, 2001 (66 FR 32752), the EPA approved a one-year attainment date extension for the Salt Lake County NAA to December 31, 1995 and determined that the Salt Lake County NAA attained by this extended attainment date. Additionally, within the June 18, 2001 (66 FR 32752) action, the EPA approved a two-year attainment date extension for the Utah County NAA to December 31, 1996 and determined that the Utah County NAA attained by this extended attainment date.

On December 23, 2002, the EPA approved additional revisions to the Utah County PM₁₀ SIP that updated attainment demonstrations, established new 24-hour emission limits for major stationary sources, established new MVEBs and approved an update to R307-110-10 (67 FR 78181). On May 18, 2015 (80 FR 28193), the EPA approved a new rule, R307-311, Utah County: Trading of Emission Budgets for Transportation Conformity, which is the mechanism for allowing trading from MVEB of PM₁₀ to MVEB for NO_X.

On September 26, 1995, the EPA designated Ogden City as nonattainment for PM₁₀ and classified the area as Moderate under section 107(d)(3) of the Act (60 FR 38726, July 28, 1995). On January 7, 2013 (78 FR 885), the EPA finalized a clean data determination (CDD) for Ogden City which suspended Utah's obligation to make SIP submissions for attainment related requirements which includes an attainment demonstration, reasonably available control measures (RACM)/reasonably available control technology (RACT), reasonable further progress (RFP), contingency measures and milestone reports.

On October 19, 2016 (81 FR 71988), the EPA conditionally approved revisions to R307-302, Solid Fuel Burning Devices in Box Elder, Cache, Davis, Salt Lake, Tooele, Utah and Weber Counties based on Utah's commitment letter dated May 19, 2016. On February 27, 2017, Utah submitted revisions to R307-302 in accordance with that conditional approval. When the EPA takes final action on today's proposal, it will complete the action on the revisions described in the conditional approval.

On October 11, 2017 (82 FR 47149), the EPA approved revisions to R307-11-17 titled “Section IX, Control Measures for Area and Point Sources, Part H, Emission Limits” and SIP Subsection IX. H.1-4, which established emissions limits for PM₁₀, NO_X, and SO₂ for certain stationary sources in the NAAs.

II. The EPA's Evaluation

A. EPA's Evaluation of Utah's SIP Revisions

(i) R307-302, Solid Fuel Burning Devices in Box Elder, Cache, Davis, Salt Lake, Tooele, Utah and Weber Counties

The EPA conditionally approved rule revisions to R307-302—Solid Fuel Burning Devices in Box Elder, Cache, Davis, Salt Lake, Tooele, Utah and Weber Counties, and the rule's RACM analysis in our October 19, 2016 (81 FR 71988) final rule based on a May 19, 2016 commitment letter from the Utah Division of Air Quality (UDAQ). Rule R307-302 is an existing rule that was approved by the EPA on February 14, 2006 (71 FR 7679). This rule establishes emission standards for fireplaces and solid fuel burning devices used in residential, commercial, institutional and industrial facilities and associated outbuilding used to provide comfort heating.

On February 27, 2017, the State of Utah submitted revisions to R307-302, based on the commitment letter and made additional revisions to provide further clarification and remove redundancies within the rule. The revisions contained in the February 27, 2017 submission include: (1) Shortening the title of the rule to “R307-302. Solid Fuel Burning Devices”; (2) updating the Purpose of the rule for better clarification; (3) updating the Definitions to include “Seasoned wood means wood that has a moisture content of less than or equal to 25%.”; (4) revising the Applicability to include clarification on the solid fuel burning device and where this rule is applicable; (5) revised terminology throughout the rule to provide better alignment; (6) revised to include “Prohibited Fuels” and additional language to support this revision; and (7) removal of the term “Phase 2” in the Prohibition section to be consistent with the 2015 New Source Performance Standard.

The Utah Air Quality Board proposed revisions to R307-302 for public comment on August 3, 2016, with the public comment period held from October 1 to October 31, 2016. UDAQ received comments from one commenter; which included cursory questions about R307-302.^[2] UDAQ summarizes these comments and responded within the February 1, 2017 submittal. There were no requests for a public hearing. The Utah Air Quality Board adopted the revision to R307-302 on December 7, 2016, and it became effective on February 1, 2017.

(ii) R307-110-10

Section R307-110-10 incorporates the amendments to Section IX.A into state rules, thereby making them effective as a matter of state law. This is a ministerial provision and does not by itself include any SIP measures.

(iii) R307-110-17

Section R307-110-17 incorporates the amendments to Section IX.H into state rules, thereby making them effective as a matter of state law. This is a ministerial provision and does not by itself include any control measures.

(iv) Subsection IX.H.1-2

1. Subsection IX.H.1. General Requirements: Control Measures for Area and Point Sources, Emission Limits and Operating Practices, PM₁₀ Requirements. This section establishes general requirements for record keeping, reporting and monitoring for the stationary sources subject to emissions limits under subsections IX.H.2-4. Additionally, this section establishes general refinery requirements, addressing limitations on emitting units common to the refineries in the NAAs. These general refinery requirements include limits at fluid catalytic cracking units, limits on refinery fuel gas, restrictions on liquid fuel oil consumption, requirement for sulfur removal units and requirements for hydrocarbon flares.

Revisions that were submitted on February 15, 2019, for Subsection IX.H.1. provided clarifications, removed implementation dates that have passed and cleaned up other aspects of this section. These revisions are generally non-substantive and do not affect the stringency of the SIP; thus, the EPA is proposing to approve these revisions.

2. Subsection IX.H.2. Source Specific Emission Limitations in Salt Lake County PM₁₀ Nonattainment/Maintenance Area. This section establishes specific emission limitations for 13 sources. Major stationary sources were identified based on their potential to emit (PTE) of 100 tons per year (tpy) or more of PM₁₀, NO_X, or SO₂. Revisions for Subsection IX.H.2. were submitted on February 15, 2019, and with non-substantive revisions submitted on July 1, 2019, August 20, 2019, and October 15, 2019. A summary of the current emission limits for retained sources, are outlined in Table 1, below, and a summary of the proposed new emission limits are outlined in Table 2 below. We are proposing to approve the revisions specified in the below tables.

Additional revisions within Subsection IX.H.2. include tables that directs the owner/operator to install specified control emissions from the equipment listed in the tables by January 1, 2019. The specific point sources, along with the emission units and the specific control equipment are included in Table 3, below. We are proposing to approve the inclusion of these tables within each specified source section.

Additional revisions are found within Subsection IX.H.2.h. Kennecott Utah Copper (KUC): Power Plant and Tailings Impoundment. Table 4, below, provides the current emission limits and the updated emissions limits, including for start-up/shut-down limits. We are proposing to approve these limits and the additional start-up/shut-down limitations found in the Natural Gas and Coal sections.

Other revisions are contained in Subsection IX.H.2.k.; (1) Subsection IX.H.2.k.ii.A., where the natural gas/refinery fuel gas combustion using: Low NO_X burners (LNB): Is revised from 41 lbs/MMbtu to 0.051 lbs/MMbtu; (2) Subsection IX.H.2.k.ii.B., which includes new language “Stack testing is not required for natural gas/refinery fuel gas combustion equipment with a NO_X CEMS”; (3) Subsection IX.H.2.k.iii.B., new language includes “SRUs: The emission rate shall be determined by multiplying the sulfur dioxide concentration in the flue gas by the flow rate of the flue gas. The sulfur dioxide concentration in the flue gas shall be determined by CEM as outlined in IX.H.1.f.”; and (4) new sections are added: Subsection IX.H.2.k.iii.C. and Subsection IX.H.2.k.iv. We are proposing approval of these revisions.

Other revisions are contained in Subsection IX.H.2.l.i. and ii. where the emission point Boiler numbers were updated; Boiler #4 will be de-commissioned, and Boiler #9 will be installed and operational by December 31, 2019; and the initial test dates were updated for the renumbered Boilers. Additionally, Subsection IX.H.2.l.iii. was removed since the facility completed the requirement by the specified date of January 1, 2019. Subsection IX.H.2.m. was updated with the new facility name of “Utah Municipal Power Association: West Valley Power Plant.” We are proposing to approve these revisions.

Additional revisions were submitted on February 15, 2019, July 1, 2019, August 20, 2019, and October 15, 2019, that included clarifications, stack test requirements, updating specific calculations, corrections, and non-substantive changes. We are proposing to approve the remaining revisions within Subsection IX.H.1. and 2. that was not specifically discussed in the tables and paragraphs above.

(v) Consideration of Section 110(l) of the CAA

Under section 110(l) of the CAA, the EPA cannot approve a SIP revision if the revision would interfere with any applicable requirements concerning attainment and RFP toward attainment of the NAAQS, or any other applicable requirement of the Act. In addition, section 110(l) requires that each revision to an implementation plan submitted by a state be adopted by the state after reasonable notice and public comment.

The Utah SIP revisions at Subsection IX.H.2 required additional analysis to satisfy CAA 110(l) requirements due to a modification of the source-wide caps for NO_X and SO₂ at the Tesoro Refining and Marketing Company. For Tesoro, Utah increased the allowable daily emissions caps for both NO_X and SO₂ but has added a rolling 12-month cap for both pollutants. The inclusion of a 12-month rolling cap effectively lowers the allowable annual emissions, as outlined in Table 5 and Table 6 below. From Table 5 and Table 6, we see that while the daily emissions cap for NO_X and SO₂ are slightly increased, and the rolling allowable 12-month average emissions decreased by 250.62 tons and 831.5 tons, respectively. Monitoring data from the Salt Lake City area for both NO₂ and SO₂ are shown in Table 7 below. As shown in Table 7, the current design values for SO₂ are an order of magnitude lower than their respective standards, and the NO₂ design values are 40%-50% lower than their respective standards. Due to Salt Lake City's low NO₂ and SO₂ monitored values, the minimal increase in NO_X and SO₂ allowable daily emissions in combination with the overall decrease in allowable NO_X and SO₂ annual emissions from the Tesoro facility will not interfere with the areas ability to attain and maintain the NO₂ and SO₂ NAAQS.

Within the PM₁₀ maintenance plan, Utah used the revised annual PTE limit when projecting the 2019, 2024, 2028 and 2030 emissions inventory.^[3] The inclusion of the PTE did not prevent the area from demonstrating continued maintenance of the PM₁₀ NAAQS. Similarly, Utah used the annual PTE values for the modeled attainment demonstration of fine particulate matter (PM_2.5), submitted on February 15, 2019. With the inclusion of Tesoro's revised limits, Utah demonstrated that the Salt Lake City PM_2.5 NAA was still able to model attainment of the PM_2.5 NAAQS. We are not acting on any aspect of the Salt Lake City PM_2.5 Serious SIP within this proposed rule; the reference above is only being used as a support to our CAA section 110(l) analysis.

The Utah SIP revisions that the EPA is proposing to approve do not interfere with any applicable requirements of the Act, including attainment or RFP. The DAR section R307-110-10, R307-110-17, and Subsection IX.H.1-2, submitted on January 4, 2016, February 15, 2019, July 1, 2019, August 20, 2019, and October 15, 2019, are intended to strengthen the SIP. Therefore, CAA section 110(l) requirements are satisfied.

B. What requirements must be followed for redesignation to attainment?

In order for a NAA to be redesignated to attainment, the following conditions in section 107(d)(3)(E) of the CAA must be met:

(i) We must determine that the area has attained the NAAQS;

(ii) The applicable implementation plan for the area must be fully approved under section 110(k) of the Act;

(iii) We must determine that the improvement in air quality is due to permanent and enforceable reductions in emissions resulting from implementation of the applicable implementation plan and applicable Federal air pollutant control regulations and other permanent and enforceable reductions;

(iv) We must fully approve a maintenance plan for the area as meeting the requirements of CAA section 175A; and,

(v) The State containing such area must meet all requirements applicable to the area under section 110 and part D of the CAA.

Our September 4, 1992 guidance entitled “Procedures for Processing Requests to Redesignate Areas to Attainment” (referred to in this action as the Calcagni Memorandum) outlines how to assess the adequacy of redesignation requests against the conditions listed above.

On January 4, 2016, and on March 6, 2019, the Governor of Utah submitted revisions to the SIP for the Salt Lake County, Utah County and Ogden City NAAs and requested that the EPA redesignate the areas to attainment for PM₁₀. The following is a brief discussion of how Utah's redesignation request and maintenance plans meet the requirements of the Act for redesignation of the Salt Lake County, Utah County, and Ogden City areas to attainment for PM₁₀.

C. Do the redesignation requests and maintenance plans meet the CAA requirements?

(i) Attainment of PM₁₀ NAAQS

Whether an area has attained the PM₁₀ NAAQS is based exclusively upon measured air quality levels over the most recent and complete three calendar year period. See 40 CFR part 50 and 40 CFR part 50, appendix K. 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 representing maximum PM₁₀ concentrations. The data, which must be quality assured and recorded in the EPA's Air Quality System (AQS), must show that the average annual number of expected exceedances for the area is less than or equal to 1.0, pursuant to 40 CFR 50.6. In making this showing, three consecutive years of complete air quality data must be used.

Between 2016 and 2018, Utah operated six PM₁₀ monitors, which were either State and Local Air Monitoring Stations (SLAMS) or National Air Monitoring Sites (NAMS), in the Salt Lake County, Utah County and Ogden City NAAs. Of this total, three are in the Salt Lake County NAA, two are in the Utah County NAA and one is in the Ogden City NAA. As part of the redesignation request for Salt Lake County, Utah County and Ogden City, Utah submitted ambient air quality data from the monitoring sites which demonstrates that the area has attained the PM₁₀ NAAQS. This air quality data had been quality-assured and placed in AQS on a quarterly basis. Table 8 below shows expected exceedances for 2016-2018 for all monitors in the PM₁₀ NAAs.

The three-year averages were either 0 or less than 1.0, which indicates the Salt Lake County, Utah County and Ogden City areas attained the 24-hour PM₁₀ NAAQS. In addition, there have been no reported exceedances of the PM₁₀ NAAQS so far in 2019. Further information on PM₁₀ monitoring is presented in Subsections IX.A.11.b(1), IX.A.12.b(1), and IX.A.13.b(1) of the Salt Lake County, Utah County and Ogden City maintenance plans, respectively. We have evaluated the ambient air quality data and Utah has adequately demonstrated that the PM₁₀ NAAQS has been attained in the Salt Lake County, Utah County and Ogden City areas.

(ii) Fully Approved State Implementation Plan

Section 107(d)(3)(E)(ii) of the CAA states that for an area to be redesignated to attainment, it must be determined that the Administrator has fully approved the applicable implementation plan for the area under section 110(k).

Those states containing initial Moderate PM₁₀ NAAs were required to submit a SIP by November 15, 1991, which demonstrated attainment of the PM₁₀ NAAQS by December 31, 1994. However, under section 188(d) of the CAA, Moderate PM₁₀ NAAs are eligible for up to two one-year extensions of their attainment dates if they meet certain requirements of the Act. On June 8, 2001 (66 FR 32752), the EPA finalized a one-year extension for the Salt Lake County NAA and two one-year extensions for the Utah County NAA. The Salt Lake and Utah Counties Moderate attainment date of December 31, 1994 was extended to December 31, 1995, and December 31, 1996, respectively. Within the June 8, 2001 (66 FR 32752) final action, the EPA also determined that the Salt Lake and Utah Counties attained by these extended attainment dates.

Section 107(d)(3)(E)(ii) of the CAA states that for NAAs to be redesignated to attainment, it must be determined that the Administrator has fully approved the applicable implementation plan for the areas under section 110(k). We approved the Salt Lake County and Utah County PM₁₀ attainment plans on July 8, 1994 (59 FR 35036). The SIP included a demonstration of attainment and various control measures, including emission limits at stationary sources. Because emissions of SO₂ and NO_X contribute significantly to the PM₁₀ problem in the areas, the SIPs included limits on emissions of SO₂ and NO_X in addition to emissions of PM₁₀.

The EPA's prior actions on Salt Lake and Utah Counties PM₁₀ SIPs, along with Ogden City PM₁₀ CDD, Utah SIP section Part H, and R307-403 are discussed in Section I: Background above.

(iii) Improvement in Air Quality Due to Permanent and Enforceable Measures

Section 107(d)(3)(E)(iii) of the CAA provides that for an area to be redesignated to attainment, the Administrator must determine that the improvement in air quality is due to permanent and enforceable reductions in emissions resulting from implementation of the applicable implementation plan, implementation of applicable Federal air pollutant control regulations, and other permanent and enforceable reductions.

The Salt Lake County area plan was adopted in June 1991 and approved by the EPA on July 8, 1994 (59 FR 35036). The Utah County area plan was adopted in September 1990, modified in June 1991, and approved by the EPA on July 8, 1994 (59 FR 35036). The Utah County area plan was revised and adopted on June 5, 2002 and July 3, 2002, and the EPA approved these revisions on December 23, 2002 (67 FR 78181). The SIP's emission control plans were based on emission reductions from stationary sources, re-entrained road dust controls, woodburning restrictions, and mobile source emission control programs. These permanent and enforceable control measures are explained below.

As part of the PM₁₀ SIP, Utah has been implementing emission limits found in Subsection IX.H.1-4. The titles for Subsection IX.H.1-4 include: (1) General Requirements: Control Measures for Area and Point Sources, Emission Limits and Operating Practices, PM₁₀ Requirements; (2) Source Specific Emission Limitations in Salt Lake County PM₁₀ Nonattainment/Maintenance Area; (3) Source Specific Emission Limitations in Utah County PM₁₀ Nonattainment/Maintenance Area; and (4) Interim Emission Limits and Operating Practices. The revisions approved on October 11, 2017 (82 FR 47149), established emission limitations and related requirements for certain stationary sources of PM₁₀, NO_X and SO₂, as well as updates of the inventory of major stationary sources to accurately reflect the current sources in both the Salt Lake County and Utah County areas.

Utah has also implemented multiple area source rules in the Salt Lake County, Utah County and Ogden City areas. Some area source rules that would impact PM₁₀ NAAs include controls on solid fuel burning devices (R307-302), road salting/sanding (R307-307), fugitive emissions/dust (R307-309) and aggregate processing (R307-312).^[5] On February 25, 2016 (81 FR 9343), October 19, 2016 (81 FR 71988), and October 2, 2019 (84 FR 52368) the EPA approved revisions to several area source rules and approved new rules for PM_2.5 NAAs into the Utah SIP, which provide direct and indirect benefits to PM₁₀ NAAs.

Additionally, on October 19, 2016 (81 FR 71988), the EPA finalized a conditional approval of certain revisions to R307-302-5 (Solid Fuel Burning Devices) based on a commitment letter from the director of UDAQ. In that letter, Utah committed to “establishing a prohibition on fuel types that can't be burned in a solid fuel burning device at any time.” With UDAQ's February 27, 2017 submittal, R307-302-5 was revised to represent what was in the commitment letter, which satisfied the condition specified in the conditional approval. Accordingly, when the EPA takes final action on today's proposal, it will complete the EPA's action on the May 9, 2013, May 20, 2014, and September 8, 2015 submittals for R307-302.

The mobile source control measures implemented in the PM₁₀ SIP include inspection and maintenance (I/M) programs in Salt Lake, Utah and Weber Counties. On August 1, 2005 (70 FR 44055) and November 2, 2005 (70 FR 66264), the EPA approved the I/M programs for Salt Lake County and Utah County, respectively. On September 14, 2005, the EPA approved the I/M program in Weber county (70 FR 54267).

We have evaluated the various State and Federal control measures and historical emissions inventories and believe that the improvement in air quality in the Salt Lake and Utah Counties NAAs have resulted from emission reductions that are permanent and enforceable.

(iv) Fully Approved Maintenance Plan Under Section 175A of the Act

Section 107(d)(3)(E) of the Act requires that, for a NAA to be redesignated to attainment, we must fully approve a maintenance plan which meets the requirements of section 175A of the Act. The 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 our approval of a redesignation, a 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. See sections 175A(b) and (d). The Calcagni Memorandum outlines five core elements that are necessary to ensure maintenance of the relevant NAAQS in an area seeking redesignation from nonattainment to attainment. Those elements, as well as guidelines for subsequent maintenance plan revisions, are explained in detail below.

a. Attainment Inventory

The EPA's interpretations of the CAA section 175A maintenance plan requirements are generally provided in the General Preamble (see 57 FR 13498, April 16, 1992) and the Calcagni Memorandum referenced above. Under our interpretations, PM₁₀ maintenance plans should include an attainment emission inventory to identify the level of emissions in the area which is sufficient to maintain the NAAQS.

An emissions inventory was developed and submitted with the PM₁₀ maintenance plan for the Salt Lake County, Utah County and Ogden City areas on December 4, 2015. This submittal contains a base year of 2011, interim-year projection inventories for 2019, 2024 and 2028, and projected maintenance inventory of 2030. The emissions contained in the inventories include sources of PM₁₀ and PM₁₀ precursor emissions located within a regional area called a modeling domain. The modeling domain encompasses all three areas within the state that were designated as nonattainment for PM₁₀: Salt Lake County, Utah County and Ogden City, as well as a bordering region.^[6]

Since this bordering region is so large (the modeling domain was used for the larger region of PM_2.5 nonattainment), a “core area” within this domain was identified wherein a higher degree of accuracy was included. Within this core area (which includes Weber, Davis, Salt Lake and Utah Counties), SIP-specific inventories were prepared to include seasonal adjustments and forecasting to represent each of the projection years. In the bordering regions, outside the core area, the 2011 National Emissions Inventory (NEI) was used in the analysis. There were four general categories of sources included in these inventories: Large stationary sources, smaller area sources, on-road mobile sources and off-road mobile sources.

For each of these source categories, the pollutants that were inventoried included: PM₁₀, SO₂, NO_X, volatile organic compounds (VOC) and ammonia (NH₃). SO₂ and NO_X are specifically defined as PM₁₀ precursors, and the Community Multi-scale Air Quality Model (CMAQ) model also considers ammonia and VOC to be contributing factors in the formation of secondary aerosol. More detailed descriptions of the 2011 base-year inventory and the 2019, 2024, 2028 and 2030 projection inventories can be found in section IX.A.11.c, IX.A.12.c, and IX.A.13.c, Maintenance Plan, subsection (2) Attainment Inventory of the Salt Lake County, Utah County, and Ogden City Maintenance Plans, and in the technical support document (TSD). Utah's submittal contains detailed emission inventory information that was prepared in accordance with the EPA emission inventory guidance.^[7] Summary of emission figures from 2011 base year and the projected inventories are provided in Table 9, 10 and 11, below.

Following our review, we have determined that Utah prepared an adequate attainment inventory for the Salt Lake County, Utah County and Ogden City areas.

b. Maintenance Demonstration

The Calcagni Memorandum states that where modeling was relied on to demonstrate maintenance, the plan should contain a summary of the air quality concentrations expected to result from the application of the control strategies. Also, the plan should identify and describe the dispersion model or other air quality model used to project ambient concentrations. The maintenance demonstrations for the Salt Lake County, Utah County and Ogden City areas used a regional photochemical model.

Prior to the development of the PM₁₀ maintenance plans, UDAQ conducted a technical analysis to support the development of Utah's 24-hour SIP for PM_2.5. That analysis included preparation of emissions inventories and meteorological data, and the evaluation and application of a regional photochemical model. Outside of the springtime high wind events and wildfires, the Wasatch Front experiences high 24-hour PM₁₀ concentrations under stable meteorological conditions in the winter during cold air pool temperature inversions. These are the same episodes where the Wasatch Front sees its highest concentrations of PM_2.5 that sometimes exceed the 24-hour PM_2.5 NAAQS. Most (60% to 90%) of the PM₁₀ observed during high wintertime pollution days consists of PM_2.5. The dominant species of the wintertime PM₁₀ is secondarily formed particulate nitrate, which is also the dominant species of PM_2.5. Given these similarities, the PM_2.5 modeling analysis was utilized as the foundation for the PM₁₀ maintenance plans.

The CMAQ model performance evaluation for the PM₁₀ maintenance plans builds on the detailed model performance evaluation that was part of the UDAQ's previous PM_2.5 SIP process. UDAQ used the same modeling episode that was used in the PM_2.5 SIP, which is the 45-day modeling episode from the winter of 2009-2010. The modeled meteorological datasets from the Weather Research and Forecasting (WRF) model for the PM₁₀ Plans are the same datasets used for the PM_2.5 SIP. Also, the CMAQ version (4.7.1) and CMAQ model setup for the PM₁₀ modeling matches the PM_2.5 SIP setup.

For these reasons, much of the information presented in the PM₁₀ maintenance plans pertains specifically to the PM_2.5 evaluation. The information was supplemented with information pertaining to PM₁₀, most notably with respect to the PM₁₀ model performance evaluation.

For PM₁₀, the CMAQ model performance was acceptable at all locations in northern Utah. CMAQ was able to reproduce the multiday buildup and washout of the pollution episodes during the 2009-2010 winter and was able to reproduce the peak PM₁₀ concentrations during most of the other two episodes modeled, January 11-20, 2007, and February 14-18, 2008. However, the model simulation for the 2010 January 8-14 episode failed to build to the high PM₁₀ concentration (>80 micrograms per cubic meter (µg/m³)) observed at the monitors. This episode featured an “early model washout,” which had similar results for PM_2.5.

After determining that the model had acceptable performance for the 2009-2010 inversion episodes, the model was utilized to make future-year attainment projections. The first step in projecting future PM₁₀ concentrations is to quantify current pollution levels which are expressed as a Baseline Design Value (BDV). The BDV is consistent with the form of the 24-hour PM₁₀ NAAQS where the probability of exceeding the standard should be no greater than once per calendar year. Thus, the BDV is calculated as the 3-year average of second highest measured 24-hour average PM₁₀ concentration each year. Table 12 below, provides the BDV for the five monitors that span the three NAAs: Salt Lake County, Utah County and Ogden City. These values were calculated based on data collected during the 2011-2014 time-period.

For each future year, an attainment projection is made by calculating a concentration termed the Future Design Value (FDV). This calculation is made for each monitor included in the analysis, and then compared to the NAAQS (150 µg/m³). When the FDV is smaller than the NAAQS at every monitor in the NAA, this would demonstrate attainment for the area in that specific future year. In making future-year projections, the output from the CMAQ model is not considered the final answer; rather the model is used in a relative sense. In doing this, a comparison is made using the predicted concentrations for both the year in question and a pre-selected base-year, which is 2011. This comparison results in a Relative Response Factor (RRF) which is calculated as the ratio of the model predicted PM₁₀ concentration in the future year to the modeled PM₁₀ concentration in the 2011 base year. Finally, the FDV is calculated by multiplying the BDV with the RRF. Additional discussions pertaining to the RRF can be found in the maintenance plans for the three NAAs: Salt Lake County, Utah County and Ogden City. The FDV's are compared to the NAAQs in order to determine whether attainment is predicted at each monitoring location. An RRF greater than one indicates the model predicted PM₁₀ is greater in the future year than in the 2011 base year, and typically is a result of increased emissions in the future year associated with projected population growth. Table 13 below provides FDV results for each monitor and projection year and shows that no FDV exceeds the NAAQS. Therefore, continued attainment is demonstrated in all three NAAs.

According to the Calcagni Memorandum, any assumptions concerning emission rates must reflect permanent, enforceable measures. A state cannot take credit in the maintenance demonstration for reductions unless there are regulations in place requiring those reductions or the reductions are otherwise shown to be permanent. States are expected to maintain implemented control strategies despite redesignation to attainment, unless such measures that achieve equivalent reductions. Emission reductions from source shutdowns can be considered permanent and enforceable to the extent that those shutdowns have been reflected in the SIP and all applicable permits have been modified accordingly.

In preparing the Salt Lake County, Utah County and Ogden City maintenance plans, Utah made revisions to their control strategies found in Section IX.H.1, 2, 3 and 4. These revisions were approved by the EPA on October 11, 2017 (82 FR 47149). Additionally, on February 15, 2019, and with non-substantive changes submitted on July 1, 2019, August 20, 2019, and on October 15, 2019, the State of Utah submitted revisions to Section IX.H.1-2. We are acting on these revisions within this action and our analysis of the revisions are discussed above in section II.A of this proposed rule.

As discussed above in section II.C.iii. of this proposed rule, Utah has also implemented multiple area source rules in the Salt Lake County, Utah County and Ogden City areas. Some area source rules that would impact PM₁₀ NAAs include controls on solid fuel burning devices, road salting/sanding, fugitive emissions/dust, and aggregate processing. On February 25, 2016 (81 FR 9343), October 19, 2016 (81 FR 71988) and October 2, 2019 (84 FR 52368) the EPA acted on area source rules for PM_2.5 NAAs which would provide direct and indirect benefits to PM₁₀ NAAs. As discussed above, we are also acting on revisions to the state's solid fuel burning devices rule within this action.

The EPA believes Utah has adequately demonstrated that the Salt Lake County, Utah County and Ogden City areas will maintain the PM₁₀ NAAQS to 2030.

c. Monitoring Network

Once a NAA 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 plans should contain provisions for continued operation of air quality monitors that will provide such verification. We approve these monitoring sites annually, and any future change would require discussion and approval from the EPA. In its January 4, 2016 submittal, Utah commits to maintaining an ambient monitoring network for PM₁₀ in Salt Lake County, Utah County and Ogden City, in accordance with 40 CFR part 58 and the Utah SIP.

d. Verification of Continued Attainment

Utah's maintenance plan submittal for Salt Lake County, Utah County and Ogden City, indicates how the State will track the progress of the maintenance plans. This is necessary due to the fact that the emissions projections made for the maintenance demonstrations depend on assumptions of point and area source growth. In Sections IX.A.11.c.(9), IX.A.12.c.(9) and IX.A.13.c.(9), Utah commits to track and document measured mobile source parameters (e.g., vehicle miles traveled, congestion, fleet mix, etc.) and changes in new and modified stationary source permits. If these and the resulting emissions change significantly over time, the State will perform appropriate studies to determine: (1) Whether additional and/or re-sited monitors are necessary and (2) whether mobile and stationary source emission projections are on target.

e. Contingency Plan

Section 175A(d) of the Act 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. For the purposes of section 175A, the 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 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.

As stated in Sections IX.A.11.c.(10), IX.A.12.c.(10), and IX.A.13.c.(10) of the Salt Lake County, Utah County and Ogden City maintenance plans, triggering the contingency plan does not automatically require a revision to the SIP, nor does it necessarily mean the area will be redesignated once again to nonattainment. Instead, the State will normally have an appropriate timeframe to correct the potential violation with implementation of one or more adopted contingency measures. In the event that violations continue to occur, additional contingency measures will be adopted until the violations are corrected.

Upon notification of a potential violation of the PM₁₀ NAAQS, the State will develop appropriate contingency measures intended to prevent or correct a violation of the PM₁₀ standard. Information about historical exceedances of the standard, the meteorological conditions related to the recent exceedances, and the most recent estimates of growth and emissions will be reviewed. The possibility that an exceptional event occurred will also be evaluated.

Upon monitoring a potential violation of the PM₁₀ NAAQS, including exceedances flagged as exceptional events but not concurred with by the EPA, the State will take the following actions: (1) The State will identify the source(s) of PM₁₀ causing the potential violation, and report the situation to EPA Region 8 within four months of the potential violation; and (2) The State will identify a means of corrective action within six months after a potential violation.

The Salt Lake County maintenance plan list of contingency measures includes: (1) Re-evaluate the thresholds at which a red or yellow burn day is triggered, as established in R307-302; and (2) Further controls on stationary sources to include the controls previously approved into the PM₁₀ SIP by the EPA (effective August 8, 1994). The sources are listed in Section IX.A.11.c.(10)(b).

The Utah County maintenance plan list of contingency measures includes: (1) Re-evaluate the thresholds at which a red or yellow burn day is triggered, as established in R307-302; and (2) Further controls on stationary sources.

The Ogden City maintenance plan list of contingency measures includes: (1) Re-evaluate the thresholds at which red or yellow burn day is triggered, as established in R307-302; and (2) Expand the road salting and sanding program in R307-307 to include Weber County.

The State will then hold a public hearing to consider the contingency measures identified to address the potential violation. The State will require implementation of such corrective action no later than one year after a violation is confirmed. Any contingency measure adopted and implemented will become part of the next revised maintenance plan submitted to the EPA for approval.

Based on the above, we find that the contingency measures provided in the Salt Lake County, Utah County and Ogden City PM₁₀ maintenance plans are sufficient and meet the requirements of section 175A(d) of the CAA.

f. Subsequent Maintenance Plan Revisions

In accordance with section 175A(b) of the Act, Utah is required to submit a revision to the maintenance plans eight years after the redesignation of the Salt Lake County, Utah County and Ogden City areas to attainment for PM₁₀. This revision is to provide for maintenance of the NAAQS for an additional ten years following the first ten-year period. In the Salt Lake County, Utah County and Ogden City maintenance plans, Utah committed to submit a revised maintenance plan eight years after the approval of the redesignation request and maintenance plan.

(v) Meeting Applicable Requirements of Section 110 and Part D of the Act

In order for an area to be redesignated to attainment, section 107(d)(3)(E) requires that it must have met all applicable requirements of section 110 and part D of the Act. 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. In our evaluation of a redesignation request, we do not need to consider other requirements of the CAA that became due after the date of the submission of a complete redesignation request.

a. Section 110 Requirements

Section 110(a)(2) contains general requirements for nonattainment plans. For purposes of redesignation, the Utah SIP was reviewed to ensure that all applicable requirements under the amended Act were satisfied. These requirements were met with Utah's November 15, 1991, February 1, 1995, May 13, 2002, and July 3, 2002 submittals for the Salt Lake County and Utah County PM₁₀ NAAs. We approved these submittals on July 8, 1994 (59 FR 35036), December 6, 1999 (64 FR 68031), July 1, 2002 (67 FR 44065), and December 23, 2002 (67 FR 78181). Ogden City PM₁₀ NAA satisfied section 110(a)(2) when the EPA finalized a CDD on January 7, 2013 (78 FR 885).

b. Part D Requirements

Before a PM₁₀ NAA may be redesignated to attainment, the state must have fulfilled the applicable requirements of part D. 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 (see 57 FR 13530, et seq.) provides that the applicable requirements of CAA section 172 are 172(c)(3) (emissions inventory), 172(c)(5) (new source review permitting program), 172(c)(7) (the section 110(a)(2) air quality monitoring requirements), 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 Memorandum and the General Preamble, 57 FR at 13564, dated April 16, 1992. Finally, the State has not sought to exercise the options that would trigger sections 172(c)(8) (equivalent techniques). Thus, these provisions are also not relevant to this redesignation request.

The requirements of 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 submission of an emission inventory, have been satisfied through our July 8, 1994 (59 FR 35036), December 6, 1999 (64 FR 68031), June 8, 2001 (66 FR 32752), July 1, 2002 (67 FR 44065), December 23, 2002 (67 FR 78181), February 25, 2016 (81 FR 9343), October 19, 2016 (81 FR 71988), October 11, 2017 (82 FR 47149) and October 2, 2019 (84 FR 52368) approvals of the Salt Lake County and Utah County PM₁₀ SIPs and the demonstration that the area is attaining the NAAQS. These requirements for the Ogden City PM₁₀ NAA were satisfied with our January 7, 2013 (78 FR 885) CDD which suspended Utah's obligation to make a SIP submission for attainment related requirements which includes: An attainment demonstration, RACM/RACT, RFP, contingency measures, and milestone reports. With this action we will satisfy Utah's obligation to submit an emissions inventory for the Ogden City PM₁₀ NAA. Additionally, the Ogden City PM₁₀ NAA attained by the Moderate PM₁₀ attainment date of December 31, 2000.^[8] The expected exceedances for 1998-2000 was 0.^[9]

We approved the requirements of the part D new source review permit program for Utah on July 25, 2019 (84 FR 35831). Once the Salt Lake County, Utah County and Ogden City areas are redesignated to attainment, the prevention of significant deterioration (PSD) requirements of part C of the Act will apply. We must ensure that the State has made any needed modifications to its PSD regulations so that Utah's PSD regulations will apply in the Salt Lake County, Utah County and Ogden City areas after redesignation. Utah's PSD regulations, R307-405 Permits: Major Sources in Attainment or Unclassified Areas (PSD), which we approved as meeting all applicable Federal requirements on July 15, 2011 (76 FR 41712) and January 29, 2016 (81 FR 4957), apply to any area designated unclassifiable or attainment and, thus, will become fully effective in the Salt Lake County, Utah County and Ogden City areas upon redesignation of the areas to attainment.

D. Have the transportation conformity requirements been met?

Transportation conformity is required by section 176(c) of the CAA. 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 (CAA section 176(c)(1)(B)). The EPA's conformity rule at 40 CFR part 93, subpart A (sections 93.100 to 93.129) requires that transportation plans, programs and projects conform to SIPs and establishes the criteria and procedures for determining whether or not they conform. To effectuate its purpose, the EPA's conformity rule typically requires a demonstration that emissions from the Regional Transportation Plan (RTP), as applicable, and the Transportation Improvement Program (TIP) are consistent with the MVEB contained in the control strategy SIP revision or maintenance plan (40 CFR 93.101, 93.118, and 93.124). The EPA notes that a MVEB is usually defined as 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 areas.

According to 40 CFR 93.118(b)(2), when a maintenance plan has been submitted, mobile source emissions from an RTP or TIP must be less than or equal to the MVEB established for the last year of the maintenance plan, and for any other years for which the maintenance plan establishes MVEBs. If the maintenance plan does not establish MVEBs for any years other than the last year of the maintenance plan, the demonstration of consistency with the MVEBs must be accompanied by a qualitative finding that there are no factors which would cause or contribute to a new violation or exacerbate an existing violation in the years before the last year of the maintenance plan. For analysis years after the last year of the maintenance plan, emissions must be less than or equal to the MVEBs established for the last year of the maintenance plan. In addition, we note that if an EPA-approved NAA control strategy implementation plan has established MVEBs for years in the timeframe of the transportation plan, then mobile source emissions in these years must be less than or equal to the NAA's control strategy implementation plan's MVEBs for these years.

With respect to previously established MVEBs, we note for the Salt Lake County nonattainment plan, Utah had previously adopted MVEBs for 2003. These budgets were 40.3 tons per day of primary PM₁₀ and 32.3 tons per day of NO_X. These budgets were derived by the Wasatch Front Regional Council (WFRC), a local Metropolitan Planning Organization (MPO) for the Salt Lake City and Ogden urban areas, in conjunction with the EPA, by using the Salt Lake County PM₁₀ SIP element attainment year (2003) emission inventories and adjusted for winter weekday vehicle miles traveled (VMT) rates. The above noted PM₁₀ and NO_X MVEBs have continued to apply for the WFRC's RTP and TIP conformity determinations since 2003.

In the Utah County nonattainment plan, the State had previously adopted MVEBs for 2003 and two future horizon years which were used in transportation planning, 2010 and 2020. On December 23, 2002 (67 FR 78181), the EPA approved the Utah County MVEBs as presented in Table 14 below.

In addition to the above On July 1, 2002 (67 FR 44065) the EPA approved the State's rule R307-310 for Salt Lake County: “Trading of Emission Budgets for Transportation Conformity.” R307-310 allows trading between the PM₁₀ and NO_X MVEBs for purposes of demonstrating transportation conformity by the WFRC. Similarly, on May 18, 2015 (80 FR 28193), the EPA approved the State's rule R307-311 for Utah County: “Trading of Emission Budgets for Transportation Conformity.” R307-311 also allows trading between the PM₁₀ and NO_X MVEBs for purposes of demonstrating transportation conformity by the Mountainland Association of Governments (MAG) who is the MPO for Utah County.

For the Ogden City PM₁₀ NAA, we designated Ogden City as nonattainment on July 28, 1995 (60 FR 38726). Using our CDD approach, on July 30, 2012, the EPA proposed to determine that the Ogden City NAA was currently attaining the 24-hour NAAQS for PM₁₀, based on certified, quality assured data for the years 2009 through 2011, and that Utah's obligation to submit certain CAA requirements would be suspended for so long as the area continued to attain the PM₁₀ NAAQS (77 FR 44544). We finalized our proposal with our final rule dated January 7, 2013 (78 FR 885). PM₁₀ NAAs like Ogden City, that have an approved CDD, are required to use the interim emissions test, described in 40 CFR 93.119, to demonstrate conformity (see 40 CFR 93.109(c)(5) and (6)). As applicable, the WFRC, which is the applicable MPO for Ogden City, has been performing conformity determinations for the Ogden City PM₁₀ NAA using the 40 CFR 93.119 interim emissions test. The WFRC demonstrates that RTP and TIP conformity determinations show that projected future year PM₁₀ and NO_X emissions will be at or below the established and updated 1990 level of PM₁₀ and NO_X emissions.

For the Ogden City, Salt Lake County and Utah County maintenance plans, the State is establishing transportation conformity MVEBs for direct PM₁₀ and NO_X for 2030. The derivation of these 2030 MVEBs is provided as follows:

a. Ogden City

The Ogden City maintenance area and the corresponding 2030 MVEBs are presented in Table 15 below:

We note that the originally modeled 2030 maintenance year had mobile sources emissions levels of 0.71 tons per winter-weekday of direct PM₁₀ and 0.70 tons per winter-weekday of NO_X. These levels of 2030 mobile sources direct PM₁₀ and NO_X would typically become the MVEBs for 2030. However, our conformity rule does allow the implementation plan to quantify explicitly the amount by which motor vehicle emissions could be higher while still demonstrating compliance with the maintenance requirement (see 40 CFR 93.124(a)). These additional emissions that can be allocated to the applicable MVEB are considered the “safety margin.” As defined in 40 CFR 93.101, safety margin represents the amount of emissions by which the total projected emissions from all sources of a given pollutant are less than the total emissions that would satisfy the applicable requirement for demonstrating maintenance. The implementation plan can then allocate some or all of this “safety margin” to the applicable MVEBs for transportation conformity purposes. The State performed additional modeling for 2030 and established that the PM₁₀ and NO_X mobile source emissions could be increased to arrive at those MVEB figures presented in Table 15 above.

b. Salt Lake County

The Salt Lake County maintenance area and the corresponding 2030 MVEBs are presented in Table 16 below:

We note that the originally modeled 2030 maintenance year had mobile sources emissions levels of 12.07 tons per winter-weekday of direct PM₁₀ and 12.59 tons per winter-weekday of NO_X. These levels of 2030 mobile sources direct PM₁₀ and NO_X would typically become the MVEBs for 2030. As with the Ogden City maintenance area noted above, the State elected to also use the above described safety margin modeling procedure to arrive at the applicable 2030 MVEBs for the Salt Lake County maintenance area. As such, the State performed additional modeling for 2030 and established that the PM₁₀ and NO_X mobile source emissions could be increased to arrive at those MVEB figures presented in Table 16 above.

c. Utah County

The Utah County maintenance area and the corresponding 2030 MVEBs are presented in Table 17 below:

We note that the originally modeled 2030 maintenance year had mobile sources emissions levels of 7.66 tons per winter-weekday of direct PM₁₀ and 6.81 tons per winter-weekday of NO_X. These levels of 2030 mobile sources direct PM₁₀ and NO_X would typically become the MVEBs for 2030. As with the Ogden City maintenance area noted above, the State elected to also use the above described safety margin modeling procedure to arrive at the applicable 2030 MVEBs for the Utah County maintenance area. As such, the State performed additional modeling for 2030 and established that the PM₁₀ and NO_X mobile source emissions could be increased to arrive at those MVEB figures presented in Table 17 above.

During the development of the Salt Lake County and Utah County PM₁₀ maintenance plans, the EPA became aware of a potential inconsistency regarding the VMT being used. The MAG and WFRC MPOs initially used elevated 2030 VMT numbers, for the development of the Salt Lake County and Utah County PM₁₀ SIP maintenance plans, that exceeded the actual MPO's own projected VMT numbers for 2030. Our understanding was the MPOs intention was to secure sufficient PM₁₀ and NO_X 2030 MVEBs, for RTP/TIP transportation conformity determinations, that would take into consideration the rate of brisk growth within Utah and to also protect air quality for the duration of the respective PM₁₀ maintenance plan. The UDAQ advised that as demonstrated through air quality modeling, used to develop the maintenance plans, it was established that in using the 2030 PM₁₀ and NO_X mobile source emissions derived with the elevated VMT, both maintenance plans were still able to demonstrate maintenance of the PM₁₀ NAAQS. In addition, the UDAQ further advised that the derived PM₁₀ and NO_X MVEBs also contained an added “safety margin” of additional mobile sources emissions as described in 40 CFR 93.124(a).

During our review of both PM₁₀ maintenance plans, we noted that the elevated VMT numbers, used in part to develop the 2030 MVEBs, were not explicitly identified and quantified in the maintenance plans or the associated TSD. This is necessary as per 40 CFR 93.118(e)(4)(iii) and 40 CFR 93.124(a). Based on a recommendation from the EPA, the TSDs for each maintenance plan were subsequently supplemented by the UDAQ to appropriately detail the derivation of the 2030 VMT figures, the associated PM₁₀ and NO_X mobile source emissions, and the 2030 MVEBs. This additional, supplemental TSD information was included with a submittal letter from the Governor dated February 21, 2019, which is provided in the docket.

Based on our above evaluation and our review of the submitted additional TSD supplemental technical information, we have determined that the three maintenance plans appropriately address the applicable transportation conformity requirements in 40 CFR 93, Subpart A and we are proposing approval of the 2030 PM₁₀ and NO_X MVEBs as described above.

E. Did Utah follow the proper procedures for adopting this action?

Section 110(k) of the CAA addresses our actions on submissions of revisions to a SIP. The Act also requires states to observe certain procedural requirements in developing implementation plans and plan revisions for submission. Section 110(a)(2) of the Act provides that each implementation plan submitted by a state must be adopted after reasonable notice and public hearing. Section 110(l) of the Act similarly provides that each revision to an implementation plan submitted by a state under the Act must be adopted by such state after reasonable notice and public hearing.

We also must determine whether a submittal is complete and therefore warrants further review and action (see section 110(k)(1) of the Act and 57 FR 13565, April 16, 1992). Our completeness criteria for SIP submittals are set out at 40 CFR part 51, appendix V. We attempt to make completeness determinations within 60 days of receiving a submission. However, a submittal is deemed complete by operation of law under section 110(k)(1)(B) of the Act if a completeness determination is not made within six months after receipt of the submission.

On September 2, 2015, the Utah Air Quality Board proposed for public comment for the Salt Lake County, Utah County and Ogden City maintenance plans and redesignation requests. The public comment period was held from October 1, 2015, to November 2, 2015. Comments were submitted by industry, environmental associates, and the EPA. The EPA submitted written comments dated November 2, 2015, on Utah's draft PM₁₀ maintenance plans and TSD. On December 2, 2015, the Utah Air Quality Board adopted R307-110-10, Utah SIP Subsections IX.A.11, IX.A.12, and IX.A.13 and it became effective on December 3, 2015. UDAQ submitted these revisions to the EPA on January 4, 2016. Additionally, on March 6, 2019, the Governor of Utah submitted a redesignation request for the Salt Lake County, Utah County and Ogden City PM₁₀ NAAs and included supplemental information. This information was necessary in order to complete our review of the maintenance plans and technical support information.

III. Proposed Action

We are proposing to approve the Governor of Utah's submittal of January 4, 2016, that contains revisions to R307-110-10 and the PM₁₀ maintenance plans for Salt Lake County, Utah County and Ogden City PM₁₀ NAAs. We are also proposing to approve the Governor of Utah's submittal of March 6, 2019, that contains the redesignation requests for the Salt Lake County, Utah County and Ogden City PM₁₀ NAAs to attainment for the 1987 PM₁₀ standards and provided supplemental information. We are using 2016-2018 ambient air quality data from Salt Lake County, Utah County and Ogden City NAAs as the basis for our decision. In addition, we are approving the emissions inventories found within the maintenance plans to cover the one element of the Moderate PM₁₀ nonattainment SIP that was not suspended with the CDD for the Ogden City NAA.

We are proposing to approve this redesignation request, the maintenance plans, and R307-110-10 revisions because UDAQ has adequately addressed all of the requirements of the Act for redesignation to attainment applicable to the Salt Lake County, Utah County and Ogden City PM₁₀ NAAs. Upon the effective date of a subsequent final action, the Salt Lake County, Utah County and Ogden City areas designation status under 40 CFR part 81 will be revised to attainment.

We are also proposing to approve R307-110-17 and revisions for Section IX.H.1 and 2 that were submitted on February 15, 2019, and with non-substantive changes submitted on July 1, 2019, August 20, 2019, and on October 15, 2019. Additionally, we are proposing approval of the revisions in R307-302 for incorporation into the Utah SIP as submitted by the State of Utah on May 9, 2013, May 20, 2014, September 8, 2015 and February 27, 2017. This proposal will complete the EPA's October 19, 2016 (81 FR 71988) conditional approval action on the May 9, 2013, May 20, 2014 and September 8, 2015 submittals for R307-302 from UDAQ.

IV. Incorporation by Reference

In this document, the EPA is proposing to include regulatory text in an EPA final rule that includes incorporation by reference. In accordance with requirements of 1 CFR 51.5, the EPA is proposing to incorporate by reference revisions to R307-110-10; R307-110-17; R307-302; Section IX.H.1 and 2; maintenance plans for Salt Lake County, Utah County and Ogden City PM₁₀ NAAs; and the Governor of Utah's redesignation requests for Salt Lake County, Utah County and Ogden City PM₁₀ NAAs to attainment. The EPA has made, and will continue to make, these materials generally available through www.regulations.gov and at the EPA Region 8 Office (please contact the person identified in the For Further Information Contact section of this preamble for more information).

V. 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);
• Is not an Executive Order 13771 (82 FR 9339, February 2, 2017) regulatory action because SIP approvals are exempted under Executive Order 12866;
• 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
• Incorporation by reference
• Intergovernmental relations
• Greenhouse gases
• 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.

Footnotes