SUPPLEMENTARY INFORMATION:

Throughout this proposed rule, the use of “we,” “us,” or “our” is intended to refer to the EPA. We use multiple abbreviations and terms in this proposed rule. While this list may not be exhaustive, for ease of reading and for reference purposes, the EPA defines the following terms and acronyms here:

CAA Clean Air Act

CBI Confidential Business Information

CFR Code of Federal Regulations

DRR Data Requirements Rule

DV Design Value

EGU Electric Generating Unit

EIS Emissions Inventory System

EPA Environmental Protection Agency

FR Federal Register

km Kilometer

MDEQ Mississippi Department of Environmental Quality

MS Mississippi

NAAQS National Ambient Air Quality Standard

NEI National Emissions Inventory

NPRM Notice of Proposed Rulemaking

NSR New Source Review

Pb Lead

PM_2.5  Particulate Matter less than 2.5 µm in diameter

ppb Parts Per Billion

SIP State Implementation Plan

SO₂  Sulfur Dioxide

tpy Tons per year

TSD Technical Support Document

WOE Weight of Evidence

Table of Contents

I. Background

A. Infrastructure SIPs

B. 2010 1-Hour SO₂ NAAQS Designations Background

II. Relevant Factors Used To Evaluate 2010 1-Hour SO₂ Interstate Transport SIPs

III. Mississippi's SIP Submission and the EPA's Analysis

A. State Submission

B. The EPA's Evaluation Methodology

1. The EPA's Prong 1 Evaluation—Contribute Significantly to Nonattainment

2. The EPA's Prong 2 Evaluation—Interference With Maintenance

IV. Proposed Action

V. Statutory and Executive Order Reviews

I. Background

A. Infrastructure SIPs

On June 2, 2010, the EPA established a revised primary 1-hour SO₂ NAAQS with a level of 75 parts per billion (ppb), based on a 3-year average of the annual 99th percentile of daily maximum 1-hour average concentrations.^[1] CAA section 110(a)(1) requires all States to submit, within three years after promulgation of a new or revised NAAQS, SIP submissions to provide for the implementation, maintenance, and enforcement of the NAAQS.^[2] The EPA has historically referred to these SIPs as “infrastructure SIPs.” Specifically, CAA section 110(a)(1) provides the procedural and timing requirements for SIP submissions. CAA section 110(a)(2) lists specific elements that all States must meet related to a newly established or revised NAAQS, such as requirements for monitoring, basic program requirements, and legal authority that are designed to assure attainment and maintenance of the NAAQS.

CAA section 110(a)(2)(D)(i)(I), also known as the “good neighbor” provision, requires a State's implementation plan to include adequate provisions prohibiting any source or other type of emissions activity in the State from emitting any air pollutant in amounts that will contribute significantly to nonattainment, or interfere with maintenance, of the NAAQS in any other State. The EPA has long interpreted this language to enact a “functional prohibition” on certain emissions from upwind States, necessitating the EPA's independent assessment whether those emissions will occur or have been adequately controlled in the State where they originate.^[3] The EPA often refers to these requirements as prong 1 (significant contribution to nonattainment of the NAAQS) and prong 2 (interference with maintenance of the NAAQS).^[4] This notice of proposed rulemaking (NPRM) addresses Mississippi's good neighbor obligations pursuant to prongs 1 and 2. All other applicable infrastructure SIP requirements of CAA section 110(a)(2) for the 2010 1-hour SO₂ NAAQS for Mississippi, except for prong 4, have been addressed in separate rulemakings.^[5]

B. 2010 1-Hour SO₂ NAAQS Designations Background

In this proposed rulemaking, the EPA has considered information from the 2010 1-hour SO₂ NAAQS designations process, as discussed in more detail in the Technical Support Document (TSD) for this rulemaking. For this reason, a summary of the EPA's designations process for the 2010 1-hour SO₂ NAAQS is included here.^[6]

After the promulgation of a new or revised NAAQS, the EPA is required to designate areas as “nonattainment,” “attainment,” or “unclassifiable” pursuant to CAA section 107(d)(1)-(2). The process for designating areas following promulgation of a new or revised NAAQS is contained in section 107(d) of the CAA. The EPA promulgated the 2010 1-hour SO₂ NAAQS on June 2, 2010.^[7] The EPA Administrator signed the first round ^[8] of designations (Round 1) ^[9] for the 2010 1- ( printed page 55307) hour SO₂ NAAQS on July 25, 2013, designating 29 areas in 16 States as nonattainment for the 2010 1-hour SO₂ NAAQS.^[10] The Federal Register final rules of promulgation for Round 2 designations ^[11] published on July 12, 2016 and on December 13, 2016.^[12 13] Round 3 designations ^[14] were published on January 9, 2018 and April 5, 2018.^[15 16] Round 4 designations ^[17] were published on March 26, 2021 and April 14, 2021.^{[18 19 20]} The Agency published the Data Requirements Rule (DRR) on August 21, 2015 to provide expectations for collection of data, either monitoring or modeling, for the remaining designations.^[21 22] In the DRR, the EPA identified six sources in Mississippi for which the State was required to characterize air quality through modeling or monitoring or impose federally enforceable controls. In Round 2 designations, the EPA designated Lamar County as attainment/unclassifiable based on modeling, effective August 12, 2016.^[23] In Round 3, the EPA designated Choctaw and Jackson Counties as attainment/unclassifiable based on modeling, effective April 9, 2018.^[24] Also, during Round 3, the EPA designated the remaining counties without DRR sources as attainment/unclassifiable, completing the area designations for the 2010 1-hour SO₂ NAAQS in Mississippi effective April 9, 2018. Thus, no areas in the State were designated in Round 4. Currently, there are no nonattainment areas in Mississippi for the 2010 1-hour SO₂ NAAQS based on Rounds 1 through 4.

II. Relevant Factors Used To Evaluate 2010 1-Hour SO 2 Interstate Transport SIPs

Although SO₂ is emitted from a similar universe of point and nonpoint sources as is directly emitted fine particulate matter (PM_2.5) and the precursors to ozone and PM_2.5, interstate transport of SO₂ is unlike the transport of PM_2.5 or ozone, which disperse over a wide area and can contribute to nonattainment or maintenance issues hundreds of miles from precursor-emitting sources or activities. SO₂ emissions usually do not undergo long-range transport in the atmosphere. The transport of SO₂ relative to the 2010 1-hour SO₂ NAAQS is more analogous to the transport of lead (Pb) relative to the Pb NAAQS in that emissions of SO₂ typically result in 1-hour pollutant impacts of greatest concern near the emissions source. However, ambient 1-hour concentrations of SO₂ do not decrease as quickly with distance from the source as do 3-month average concentrations of Pb, because SO₂ gas is not removed by deposition as rapidly as are Pb particles. Emitted SO₂ has wider-ranging impacts than emitted Pb, but it does not have such wide-ranging (far downwind) impacts that treatment in a manner similar to ozone or PM_2.5 would be appropriate. Accordingly, the approaches that the EPA has adopted for ozone or PM_2.5 transport are too regionally focused, and the approach for Pb transport is too tightly circumscribed to the source, to be appropriate for assessing SO₂ transport. SO₂ transport is therefore a unique case and necessitates an approach that lies between these other approaches to assessing pollutant transport.

In this NPRM, and consistent with prior SO₂ transport analyses, the EPA focused on a 50 kilometer (km)-wide zone around sources of interest because the physical properties of SO₂ result in relatively localized pollutant impacts near an emission source that drop off with distance. Given the properties of SO₂, the EPA believes that significant impacts in a downwind State are unlikely at distances greater than 50 km from a source and thus, the EPA's review focused on areas within 50 km of the State lines. This scale of analysis is consistent with the “urban scale” which is the largest appropriate spatial scale for SO₂ monitors and is useful for assessing SO₂ transport and trends in area-wide air quality.^[25]

As discussed in section III of this document, and in further detail in the TSD for this proposed rulemaking, the EPA reviewed Mississippi's January 27, 2022, SO₂ SIP submission. Mississippi's submission did not provide enough data to completely assess whether the State was meeting its CAA good neighbor requirements for the 2010 SO₂ NAAQS. Therefore, the EPA elected to review and assess other available information regarding SO₂ emissions and air quality for sources in Mississippi to assist in this evaluation given the availability of more recent emissions, air quality data, and air dispersion modeling that was not available at the time of Mississippi's submittal. The EPA independently analyzed such information to determine whether Mississippi meets the interstate transport requirements described in the CAA.^[26]

Consistent with our prior evaluations of other States' SO₂ transport obligations, the EPA conducted a weight of evidence (WOE) analysis evaluating ( printed page 55308) several sources of information, including current air quality data from monitors as well as available emissions and/or source modeling for sources in Mississippi and neighboring States within 50 km of the State border. A WOE approach can be appropriate in instances, such as in this case, to determine whether or not SO₂ emissions from Mississippi contribute to nonattainment or maintenance issues in adjoining States. A WOE analysis that is based strictly on available data may not be sufficient in all instances for evaluating interstate SO₂ transport, and additional analysis may be necessary. Further, the term “WOE” does not establish the legal or technical meaning for what constitutes significant contribution to nonattainment or interference with maintenance for the 2010 SO₂ NAAQS. Rather, the term refers to the gathering and consideration of a wide range of information, on a case-by-case basis, to determine whether a statutory or regulatory standard is met.

In other SO₂ transport SIP actions, the EPA has generally been able to use a WOE analysis of available information to reach a conclusion that there are no SO₂ nonattainment or maintenance issues in the relevant areas of other States, or that no sources in the upwind State are contributing to those issues. If the available evidence indicated, however, that an upwind source, sources, or emissions activities were contributing to an out-of-State SO₂ nonattainment or maintenance problem, then further analysis and a regulatory determination would be necessary concerning what amount of those emissions, if any, constituted “significant contribution” under prong 1 or prong 2 of the good neighbor provision.

The EPA finds there is sufficient information to allow the EPA to make a determination that no Mississippi sources are contributing to any out-of-State SO₂ nonattainment or maintenance concerns under current and likely future conditions and emissions scenarios; therefore, it is not necessary for purposes of this action to render a determination concerning what amount of emissions would be “significant” and therefore subject to prohibition under the good neighbor provision.^[27]

III. Mississippi's SIP Submission and the EPA's Analysis

A. State Submission

Mississippi's January 27, 2022, SIP submission addresses the requirements of CAA section 110(a)(2)(D)(i)(I) for the 2010 1-hour SO₂ primary NAAQS. Mississippi conducted an analysis to examine whether SO₂ emissions from Mississippi contribute significantly to nonattainment, or interfere with maintenance of, the 2010 1-hour SO₂ NAAQS in downwind States.

Mississippi based its conclusions for prongs 1 and 2 on the following information: SO₂ design values (DVs) ^[28] for the years 2012-2014 at monitors in Mississippi and in the neighboring States (Alabama, Tennessee, and Louisiana); statewide SO₂ actual emissions from 2008 and 2011 and emission trends in this data; stationary source (electric generating units) actual SO₂ emissions from 2002-2017 and emissions trends in this data; Mississippi's initial work to meet the DRR requirements; State and Federal measures that establish requirements for sources of SO₂ emissions; monitored ambient air data in Mississippi and neighboring States based on a 50 km spatial distance; available DRR air dispersion modeling associated with relevant SO₂ sources in Mississippi and in neighboring States within 50 km of Mississippi's border; and an SO₂ source specific emission analysis from stationary sources in Mississippi and neighboring States that were not subject to the DRR that emitted over 100 tons per year (tpy) of SO₂ emissions in 2018 or 2019 within 50 km of the State's border ( i.e., an analyses of non-DRR sources' current emissions relative to the distance to the State's border).

Based on this analysis, MDEQ concluded that no sources in the State are significantly contributing to nonattainment or interfering with maintenance of the 2010 SO₂ NAAQS in a neighboring State. Thus, Mississippi determined that the SIP contains adequate provisions to address the State's CAA good neighbor obligations.

The EPA's evaluation of Mississippi's submission is detailed in section III.B of this document below. The EPA may elect to consider additional information to assist in reaching a conclusion as to whether the submission may be approved, in whole or in part, as satisfying the Act's requirements, or does not meet the Act's requirements. Here, the EPA may consider all relevant information, or generate new data and analysis, to make an independent judgment in evaluating States' compliance with the good neighbor provision, which concerns the effects of States' emissions in other States. Therefore, the EPA elected to supplement Mississippi's transport SIP analysis with a review and assessment of other available information, as described below and in more detail in the TSD for this proposed rulemaking, regarding SO₂ emissions and air quality for sources in Mississippi to assist in the EPA's evaluation and to fully assess whether Mississippi is meeting its CAA good neighbor obligations for the 2010 SO₂ NAAQS.

B. The EPA's Evaluation Methodology

For this CAA section 110(a)(2)(D)(i)(I) evaluation of the 2010 SO₂ NAAQS, the EPA conducted a WOE analysis for prong 1 and prong 2 separately,^[29] evaluating available information such as SO₂ ambient air data, emission inventory trends, modeling, and emission trends in Mississippi and the States that border Mississippi. The EPA has evaluated this information and further supplements Mississippi's analysis here to ensure there are no further SO₂ emissions controls needed for meeting CAA interstate transport requirements. To identify which sources and emissions activities in Mississippi could potentially impact downwind air quality in other States with respect to the 2010 1-hour SO₂ NAAQS, the EPA used information in the EPA's National Emissions Inventory (NEI) ^[30] and Emissions Inventory System (EIS).^[31] The NEI is a comprehensive and detailed estimate of air emissions for criteria pollutants, criteria pollutant precursors, and hazardous air pollutants ( printed page 55309) from air emissions sources, updated every three years using information provided by the States and other information available to the EPA. For the identification of sources and emissions activities, the EPA largely relied on data from the 2020 NEI because it is the most recently available, complete, and quality assured dataset. However, in evaluating emissions trends, both State-wide and at the facility level, the EPA also considered data from prior NEI reports and EIS queries as part of the overall WOE analysis.

As shown in table 1 below, the majority of SO₂ emissions in Mississippi originate from point sources. In 2020, total SO₂ emissions from point sources in Mississippi comprised approximately 56 percent of the total SO₂ emissions in the State. Nonpoint sources, on road, and nonroad emissions sources are individually much smaller and more dispersed throughout the State and are therefore unlikely to contribute to high ambient concentrations when compared to point source contributions. Further analysis ^[32] shows that facilities with reported emissions greater than 100 tpy represent approximately 4 percent of the total number of Mississippi SO₂ point sources but are responsible 5,411 tons of SO₂, or 84 percent of the total 2020 reported SO₂ emissions originating from point sources in Mississippi.^[33] Based on this analysis, the EPA's WOE analysis focused on SO₂ emissions from Mississippi's point sources ( i.e., sources emitting over 100 tpy of SO₂ ) that are located within 50 km of one or more State borders.^[34] The EPA's WOE analysis includes some of the same sources included in Mississippi's non-DRR source specific analysis.

As described in this section III of this document, the EPA proposes that an assessment of Mississippi's satisfaction of the prong 1 and 2 requirements under CAA section 110(a)(2)(D)(i)(I) for the 2010 1-hour SO₂ NAAQS may be reasonably based upon several factors. These factors include 2020-2022 through 2022-2024 ambient air quality SO₂ design value concentrations in Mississippi and surrounding States, 2022 SO₂ emission trends data for sources in Mississippi and neighboring States (assessing sources' current emissions relative to distance from the border), assessment of Mississippi's SO₂ point source 2022 emissions of more than 100 tpy of SO₂ per facility that are located within approximately 50 km of another State, assessment of other States' point sources emitting more than 100 tpy of SO₂ located within approximately 50 km of Mississippi, evaluation of the predicted downwind impacts projected in previous relevant modeling studies that have been conducted for certain sources, review of wind and topographic data to evaluate the likely direction of transport and magnitude of SO₂ emissions from relevant sources, and assessment of Federal regulations and SIP-approved regulations affecting Mississippi's SO₂ sources. The EPA's evaluation is informed by all available data at the time of this proposed rulemaking, including the analysis Mississippi provided in its January 27, 2022, SIP submission.^[35]

The EPA notes that if this information were insufficient to draw a reasonable conclusion concerning whether Mississippi is “significantly contributing” or not, then it would not be possible to propose approval based only on this information. In other words, in general, the absence of information concerning whether interstate transport is occurring is not in itself sufficient justification for approving a good neighbor SIP submission. For example, if there were inadequate monitoring or modeling information to characterize the effects of a large, near-border source of SO₂ emissions, it may be appropriate to conduct, or ask the State to conduct, further analysis to better characterize that source and its effects, in order to reach a determination concerning whether the good neighbor provision is being met.^[36] In this case, the information available to the EPA, as analyzed in the accompanying TSD and summarized below, is fully sufficient to conclude that under current and likely future conditions and emissions scenarios Mississippi is not emitting and will not emit SO₂ pollution in violation of the good neighbor provision for the 2010 SO₂ NAAQS.

1. The EPA's Prong 1 Evaluation—Contribute Significantly to Nonattainment

Prong 1 of the “good neighbor” provision requires States' plans to prohibit emissions that will contribute significantly to nonattainment of the NAAQS in another State. The EPA's evaluation ^[37] of whether Mississippi has met its prong 1 transport obligations was accomplished by considering all available information including the following: SO₂ ambient air quality in Mississippi and neighboring States; SO₂ emissions trends for Mississippi and neighboring States; potential ambient impacts of SO₂ emissions from certain facilities ^[38] in Mississippi on neighboring States; Mississippi's SIP-approved regulations specific to SO₂ emissions and to permit requirements; ( printed page 55310) and other SIP-approved or federally enforceable regulations which may reduce SO₂ emissions either directly or indirectly.

Based on the EPA's analysis, the Agency proposes to determine that there are no SO₂ nonattainment issues in the relevant areas in other States bordering Mississippi, and as such, the EPA proposes to determine that Mississippi's SIP satisfies the requirements of prong 1 of CAA section 110(a)(2)(D)(i)(I). This proposed determination is based on the following considerations:

• Monitors in neighboring Alabama, Louisiana, and Tennessee within 50 km of Mississippi's border all have DVs below the standard; there are no monitors recording violations of the 2010 1-hour SO₂ NAAQS located in Mississippi within 50 km of its border; and there are only two SO₂ monitors in Mississippi and neither are violating the 2010 SO₂ NAAQS. Only one of the two Mississippi monitors is within 50 km of the State's border, and the current DVs ^[39] at these two monitors are well below the 2010 SO₂ NAAQS and have remained well below the standard for many years;
• Downward SO₂ emission trends in Mississippi and in Alabama, Louisiana, and Tennessee, when considered together with the other factors discussed as part of Mississippi's analysis and the EPA's WOE, support Mississippi's conclusion that sources in the State will not contribute significantly to any other States' nonattainment of the 2010 1-hour SO₂ NAAQS; and
• Source-specific analyses of sources located within 50 km of the State border that emitted 100 tpy or more of SO₂ indicate that these sources do not contribute significantly to nonattainment in other States. These analyses draw upon available emissions data, monitoring data, air dispersion modeling, source retirements, wind rose data, and other relevant information to assess the likelihood of air quality impacts from these sources to areas in surrounding States. A detailed discussion of each source-specific analysis is contained in section IV.B.1.iii of the EPA's TSD accompanying this proposed rulemaking.

Below, the EPA covers some of the principal evidence that confirms that emissions from Mississippi do not contribute significantly to nonattainment in other States.^[40]

a. North Mississippi: The EPA evaluated two sources in north Mississippi—Rockwool (formerly Roxul USA, Inc.) and Mississippi Silicon. Considering the short distance (approximately 2 km) from Rockwool to the Tennessee border, the EPA looked at available wind rose data (2021-2023) at the Olive Branch Airport in DeSoto County, Mississippi (the nearest wind rose west of Rockwool). This data shows predominant wind patterns from the south, southeast, and southwest suggesting that Rockwool emissions are most likely carried north into Tennessee possibly interacting with the Shelby Farms monitor and Memphis Airport. However, the EPA assessed prevention of significant deterioration (PSD) permit modeling for Rockwool performed in 2012 ^[41] and 2016,^[42] including modeling of SO₂ to determine compliance with the 1-hour SO₂ NAAQS. The results showed Rockwool did not cause or contribute to any violations of the 1-hour SO₂ NAAQS in either Mississippi or across the border in Tennessee. Both sets of modeling included cumulative impacts above the 1-hour SO₂ NAAQS, but in both analyses, the contribution from the Rockwool facility to the modeled violations was very small (<0.11 microgram per cubic meter (µg/m³ )), which is well below the 1-hour SO₂ Significant Impact Level (SIL) of 7.8 µg/m³ .

For Mississippi (MS) Silicon, the EPA looked at available wind rose data (2021-2023). This data shows predominant wind patterns from the south and southeast suggesting that emissions are likely transported northward into Tennessee possibly interacting with the nearest Tennessee source, Package Corporation of America. However, the EPA also considered 2014 ^[43] and 2021 ^[44] PSD permit modeling for MS Silicon where both modeling analyses were performed to demonstrate compliance with the 1-hour SO₂ NAAQS in accordance with PSD permitting requirements. The results of the modeling show that MS Silicon did not cause or contribute to any violations of the 1-hour SO₂ NAAQS in either Mississippi or across the borders in Tennessee and Alabama. The available modeling for MS Silicon, discussed further in the EPA's TSD, supports a determination that the source does not contribute significantly to nonattainment of the NAAQS in Tennessee or Alabama.

b. East Mississippi: For the three Lowndes County sources—Steel Dynamics Columbus (SDI), International Paper Columbus Mill (IP-Columbus Mill), and the Columbus Air Force Base (AFB). These sources are approximately 27 km, 15 km, and 17 km, respectively, from the Alabama State border. In 2022, these sources emitted approximately 370 tpy, 215 tpy, and 239 tpy, respectively. From 2020-2022, these sources collectively emitted 912 tpy or less per year. The distance between the closest Lowndes County source (IP-Columbus Mill) and the nearest Alabama source (Nucor Steel in Tuscaloosa) is 90 km. Wind rose data showing predominant winds from the south, southeast, and north indicate that emissions from these sources will predominately not be transported across the Alabama border. Based on all of this, the EPA believes these three sources in Lowndes County are not interacting in such a way that they will significantly contribute to nonattainment or interfere with maintenance in Alabama.

c. West Mississippi: The low SO₂ emissions (under 100 tpy in 2023) from IP-Vicksburg in Warren County, infrequent winds toward Louisiana, the large distance between the closest Louisiana source, GPI, in Ouachita Parish, and IP-Vicksburg (129 km) (suggesting the respective plumes would be too far apart to interact), and the Mississippi-Louisiana border (98 km), all suggest an unlikely cumulative impact in Louisiana. Thus, the EPA believes it is unlikely that emissions from IP-Vicksburg could contribute significantly to nonattainment of the 2010 SO₂ NAAQS in Louisiana.

d. South Mississippi:

i. Lamar County

There are no nearby SO₂ sources in Mississippi or Louisiana within 50 km of the Rain CII Carbon LLC (Rain-MS) facility in Lamar County that emitted greater than 100 tpy of SO₂ that could interact with the facility and create a potential cumulative downwind transport of SO₂ emissions into Louisiana to cause a violation of the 2010 standard. The closest Louisiana source—International Paper-Bogalusa ( printed page 55311) Mill (IP-Bogalusa Mill)—is approximately 64 km southwest of Rain. Additionally, available 2021-2023 wind rose data shows predominant wind patterns from the south and north and less frequently from the northwest and southeast in the path of Rain-MS suggesting a low frequency of winds blowing from Rain-MS towards Louisiana. With the distance from Rain-MS to the Louisiana border and IP-Bogalusa greater than 50 km, the consistent trend in annual SO₂ emissions at Rain-MS over the past 10 years,^[45] no evidence of modeled cumulative impacts with the nearby R.D. Morrow DRR, and the repowering of emission units at Morrow, the EPA believes it is unlikely that Rain-MS could interact with these sources to contribute significantly to nonattainment of the SO₂ NAAQS in Louisiana. Furthermore, there are no nearby SO₂ sources in Mississippi or Louisiana within 50 km of Rain that emitted greater than 100 tpy of SO₂ that could interact with the facility and create potential cumulative downwind impacts.^[46]

ii. Jackson County

Wind rose data near Chevron Texaco Products (Chevron) petroleum refinery in Jackson County, Mississippi indicates a low frequency of west to east winds in the path of Chevron towards the Alabama border and the W&T Offshore and Evonik sources in southeast Mobile County. The 80 km spatial distance between Chevron and Alabama Power Plant Barry Generating Station and Nouryon in northwest Mobile County is also too far for their respective plumes to interact and contribute significantly to SO₂ NAAQS nonattainment in Alabama. The EPA also believes it is unlikely that emissions from Chevron and the two sources in the St. Bernard Parish SO₂ nonattainment area (Chalmette Refining LLC and Rain CII Carbon-Louisiana) could interact as to contribute significantly to SO₂ NAAQS nonattainment in Louisiana.^[47] Based on this weight of evidence, the EPA concludes that emissions from Chevron are not contributing significantly to SO₂ NAAQS nonattainment in Alabama or Louisiana.

The Pascagoula monitor, located approximately 5 km northwest of Chevron in Jackson County, 13 km west of the Alabama border, and 80 km north of St. Bernard Parrish, Louisiana, measured less than 6 ppb from 2018 through 2024. This monitor was not sited to characterize the maximum SO₂ concentrations from Chevron, however, the EPA believes the low design value provides a good indication that Chevron's SO₂ concentrations near the Alabama border are likely well below the 1-hr SO₂ NAAQS.

Based on this evaluation, discussed further in the EPA's TSD, EPA proposes to find that SO₂ sources in Mississippi will not contribute significantly to nonattainment of the 2010 1-hour SO₂ NAAQS in any other State.

2. The EPA's Prong 2 Evaluation—Interference With Maintenance

Prong 2 of the “good neighbor” provision requires State plans to prohibit emissions that will interfere with maintenance of a NAAQS in another State. The EPA's evaluation of whether Mississippi has met its prong 2 transport obligations was accomplished by considering all available information, with a focus on current air quality data, SO₂ emission trends for Mississippi and neighboring States, and how existing and future sources of SO₂ are addressed through existing SIP-approved and other federally enforceable regulations. This evaluation builds upon the analysis conducted for significant contribution to nonattainment (prong 1), which considered SO₂ ambient air quality in Mississippi and neighboring States and potential ambient impacts of SO₂ emissions from certain facilities in Mississippi on neighboring States.

Based on the EPA's analysis, we propose to find that SO₂ levels in neighboring States near the Mississippi border do not indicate an inability to maintain the SO₂ NAAQS that could be attributed in part to sources in Mississippi. As such, the EPA proposes to determine that Mississippi's SIP satisfies the requirements of prong 2 of CAA section 110(a)(2)(D)(i)(I). This determination is based on the following considerations:

• The current 2022-2024 DV for the SO₂ monitor in Mississippi within 50 km of another State's border and in neighboring States within 50 km of Mississippi's border are below the standard, indicating that these areas are all currently in attainment of the 2010 1-hour SO₂ NAAQS;
• State-wide SO₂ emission trends in Mississippi and surrounding States are generally declining thus resulting in declining impacts to neighboring States;
• Source-specific analyses show that Mississippi facility-level emissions are generally decreasing considering Federal and SIP-approved provisions regulating SO₂ emission standards, indicating that emissions are not anticipated to increase relative to baseline emissions;
• Current Mississippi SIP-approved measures and Federal SO₂ emission requirements control SO₂ emissions from specific source sectors within Mississippi; and
• Mississippi's SIP-approved PSD, major New Source Review (NSR), and minor source NSR regulations address future new and modified SO₂ sources above major and minor permitting thresholds with the intent of ensuring that the SO₂ NAAQS will not be exceeded within or outside of the State because of new facility construction or existing facility modification within the State.

Based on this evaluation, as discussed further in the EPA's TSD for this proposed rulemaking, the Agency proposes to find that sources within Mississippi will not interfere with maintenance of the 2010 1-hour SO₂ NAAQS in any other State.

IV. Proposed Action

The EPA is proposing to approve Mississippi's January 27, 2022, prong 1 and prong 2 infrastructure SIP addressing interstate transport for the 2010 1-hour SO₂ NAAQS. Based on the EPA's WOE analysis, and as more thoroughly discussed in the TSD, the Agency proposes to determine that emissions from Mississippi will not contribute significantly to nonattainment in, or interfere with maintenance of, any other State with respect to the 2010 SO₂ NAAQS. The EPA therefore proposes to find that Mississippi's SIP contains adequate provisions consistent with CAA section 110(a)(2)(D)(i)(I).

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 CAA and applicable Federal regulations.^[48] Thus, in reviewing SIP ( printed page 55312) submissions, the EPA's role is to approve State choices, provided that they meet the criteria of the CAA. Accordingly, this proposed rulemaking 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 proposed rulemaking:

• Is not a significant regulatory action subject to review by the Office of Management and Budget underExecutive Order 12866 (58 FR 51735, October 4, 1993);
• Is not anExecutive Order 14192 (90 FR 9065, February 6, 2025) regulatory action because this action is not significant 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 inExecutive Order 13132 (64 FR 43255, August 10, 1999);
• Is not subject toExecutive Order 13045 (62 FR 19885, April 23, 1997) because it approves a State program;
• Is not a significant regulatory action subject toExecutive Order 13211 (66 FR 28355, May 22, 2001); and
• 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.

In addition, the SIP is not approved to apply on any Indian reservation land or in any other area where the EPA or an Indian Tribe has demonstrated that a Tribe has jurisdiction. In those areas of Indian country, the 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).

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

91 FR 55305