SUPPLEMENTARY INFORMATION:

I. Background

A. Infrastructure SIPs

On June 2, 2010, EPA promulgated a revised primary SO₂ NAAQS with a level of 75 parts per billion (ppb), based on a 3-year average of the annual 99th percentile of 1-hour daily maximum concentrations. See75 FR 35520 (June 22, 2010). Whenever EPA promulgates a new or revised NAAQS, CAA section 110(a)(1) requires states to make SIP ( printed page 72279) submissions to provide for the implementation, maintenance, and enforcement of the NAAQS. This particular type of SIP submission is commonly referred to as an “infrastructure SIP.” These submissions must meet the various requirements of CAA section 110(a)(2), as applicable.

Section 110(a)(2)(D)(i)(I) of the CAA requires SIPs to include provisions prohibiting any source or other type of emissions activity in one state from emitting any air pollutant in amounts that will contribute significantly to nonattainment, or interfere with maintenance, of the NAAQS in another state. The two clauses of this section are referred to as prong 1 (significant contribution to nonattainment) and prong 2 (interference with maintenance of the NAAQS).

In a letter dated August 20, 2018,^[1] the Alabama Department of Environmental Management (ADEM) submitted a revision to the Alabama SIP only addressing prongs 1 and 2 of CAA section 110(a)(2)(D)(i)(I) for the 2010 1-hour SO₂ NAAQS.^[2] EPA is proposing to approve ADEM's August 20, 2018, SIP submission because the State demonstrated that Alabama will not contribute significantly to nonattainment, or interfere with maintenance, of the 2010 1-hour SO₂ NAAQS in any other state. All other elements related to the infrastructure requirements of section 110(a)(2) for the 2010 1-hour SO₂ NAAQS for Alabama have been addressed in separate rulemakings.^[3]

B. 2010 1-Hour SO₂ NAAQS Designations Background

In this action, EPA has considered information from the 2010 1-hour SO₂ NAAQS designations process, as discussed in more detail in section III.C of this notice. For this reason, a brief summary of EPA's designations process for the 2010 1-hour SO₂ NAAQS is included here.^[4]

After the promulgation of a new or revised NAAQS, EPA is required to designate areas as “nonattainment,” “attainment,” or “unclassifiable” pursuant to section 107(d)(1) of the CAA. The process for designating areas following promulgation of a new or revised NAAQS is contained in section 107(d) of the CAA. The CAA requires EPA to complete the initial designations process within two years of promulgating a new or revised standard. If the Administrator has insufficient information to make these designations by that deadline, EPA has the authority to extend the deadline for completing designations by up to one year.

EPA promulgated the 2010 1-hour SO₂ NAAQS on June 2, 2010. See75 FR 35520 (June 22, 2010). EPA completed the first round of designations (“round 1”) ^[5] for the 2010 1-hour SO₂ NAAQS on July 25, 2013, designating 29 areas in 16 states as nonattainment for the 2010 1-hour SO₂ NAAQS. See78 FR 47191 (August 5, 2013). EPA signed Federal Register notices of promulgation for round 2 designations ^[6] on June 30, 2016 (81 FR 45039 (July 12, 2016)) and on November 29, 2016 (81 FR 89870 (December 13, 2016)), and round 3 designations ^[7] on December 21, 2017 (83 FR 1098 (January 9, 2018)).^[8]

On August 21, 2015 (80 FR 51052), EPA separately promulgated air quality characterization requirements for the 2010 1-hour SO₂ NAAQS in the Data Requirements Rule (DRR). The DRR requires state air agencies to characterize air quality, through air dispersion modeling or monitoring, in areas associated with sources that emitted 2,000 tons per year (tpy) or more of SO₂, or that have otherwise been listed under the DRR by EPA or state air agencies. In lieu of modeling or monitoring, state air agencies, by specified dates, could elect to impose federally-enforceable emissions limitations on those sources restricting their annual SO₂ emissions to less than 2,000 tpy, or provide documentation that the sources have been shut down. EPA expected that the information generated by implementation of the DRR would help inform designations for the 2010 1-hour SO₂ NAAQS that must be completed by December 31, 2020 (“round 4”).

For Alabama, EPA designated all counties as attainment/unclassifiable or unclassifiable in round 3 except for a portion of Shelby County around the Lhoist North America of Alabama—Montevallo Plant (LNA—Montevallo) that is currently conducting monitoring to inform round 4 designations.^[9] There are no nonattainment areas in Alabama for the 2010 1-hour SO₂ NAAQS based on rounds 1, 2, and 3 of EPA's designations process.^[10]

II. Relevant Factors Used To Evaluate the 2010 1-Hour SO₂ 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 because SO₂ emissions ( printed page 72280) sources usually do not have long range SO₂ impacts. 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 possible concern only 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 and because SO₂ typically has a higher emissions release height than Pb. Emitted SO₂ has wider ranging impacts than emitted Pb, but it does not have such wide-ranging impacts that treatment in a manner similar to ozone or PM_2.5 would be appropriate. Accordingly, while the approaches that the EPA has adopted for ozone or PM_2.5 transport are too regionally focused, the approach for Pb transport is too tightly circumscribed to the source. SO₂ transport is therefore a unique case and requires a different approach.

In SO₂ transport analyses, EPA focuses on a 50 km-wide zone because the physical properties of SO₂ result in relatively localized pollutant impacts near an emissions source that drop off with distance. Given the properties of SO₂ , EPA selected a spatial scale with dimensions from four to 50 kilometers (km) from point sources—the “urban scale”—to assess trends in area-wide air quality that might impact downwind states.^[11] As discussed further in section III.B, EPA selected the urban scale as appropriate for assessing trends in both area-wide air quality and the effectiveness of large-scale pollution control strategies at SO₂ point sources. EPA's selection of this transport distance for SO₂ is consistent with 40 CFR 58, Appendix D, Section 4.4.4(4) “Urban scale,” which states that measurements in this scale would be used to estimate SO₂ concentrations over large portions of an urban area with dimensions from four to 50 km. The American Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD) is EPA's preferred modeling platform for regulatory purposes for near-field dispersion of emissions for distances up to 50 km. See Appendix W of 40 CFR part 51. Thus, EPA applied the 50-km threshold as a reasonable distance to evaluate emission source impacts into neighboring states and to assess air quality monitors within 50 km of the State's border, which is discussed further in section III.C.

As discussed in sections III.C and III.D, EPA first reviewed Alabama's analysis to assess how the State evaluated the transport of SO₂ to other states, the types of information used in the analysis, and the conclusions drawn by the State. EPA then conducted a weight of evidence analysis based on a review of the State's submission and other available information, including SO₂ air quality and available source modeling for other states' sources within 50 km of the Alabama border.^[12]

III. Alabama's SIP Submission and EPA's Analysis

A. State Submission

Through a letter dated August 20, 2018, ADEM submitted a revision to the Alabama SIP addressing prongs 1 and 2 of CAA section 110(a)(2)(D)(i)(I) for the 2010 1-hour SO₂ NAAQS.^[13] Alabama conducted a weight of evidence analysis to examine whether SO₂ emissions from the State adversely affect attainment or maintenance of the 2010 1-hour SO₂ NAAQS in downwind states.

ADEM based its conclusions for prongs 1 and 2 on attaining 2015-2017 SO₂ design values (DVs) ^[14] in Alabama and adjacent states; the lack of 2010 1-hour SO₂ NAAQS nonattainment areas in Alabama or within close proximity to Alabama; the existence of DRR modeling for Alabama SO₂ sources; and established federal and State control measures which address SO₂ emissions. EPA's evaluation of Alabama's August 20, 2018, SIP submission is detailed in sections III.B, C, and D.

B. EPA's Evaluation Methodology

EPA believes that a reasonable starting point for determining which sources and emissions activities in Alabama are likely to impact downwind air quality in other states with respect to the 2010 1-hour SO₂ NAAQS is by using information in EPA's National Emissions Inventory (NEI).^[15] The NEI is a comprehensive and detailed estimate of air emissions for criteria pollutants, criteria pollutant precursors, and hazardous air pollutants from air emissions sources, that is updated every three years using information provided by the states and other information available to EPA. EPA evaluated data from the 2014 NEI (version 2), the most recently available, complete, and quality assured dataset of the NEI.

As shown in Table 1, the majority of SO₂ emissions in Alabama originate from point sources.^[16] In 2014, the total SO₂ emissions from point sources in Alabama comprised approximately 96 percent of the total SO₂ emissions in the State. Further analysis of these data show that SO₂ emissions from fuel combustion from point sources make up approximately 74 percent of the total SO₂ emissions in the State. Because emissions from the other listed source categories are more dispersed throughout the State, those categories are less likely to cause high ambient concentrations when compared to a point source on a ton-for-ton basis. Based on EPA's analysis of the 2014 NEI, EPA believes that it is appropriate to focus the analysis on SO₂ emissions from Alabama's larger point sources ( i.e., emitting over 100 tpy of SO₂ in 2017), which are located within the “urban scale,” i.e., within 50 km of one or more state borders.

( printed page 72281)

As explained in Section II, because the physical properties of SO₂ result in relatively localized pollutant impacts near an emissions source that drop off with distance, in SO₂ transport analyses, EPA focuses on a 50 km-wide zone. Thus, EPA focused its evaluation on Alabama's point sources of SO₂ emissions located within approximately 50 km of another state and their potential impact on neighboring states.

As discussed in section I.B., EPA's current implementation strategy for the 2010 1-hour SO₂ NAAQS includes the flexibility to characterize air quality for stationary sources subject to the DRR via either data collected at ambient air quality monitors sited to capture the points of maximum concentration, or air dispersion modeling (hereinafter referred to as “DRR monitors” or “DRR modeling,” respectively). EPA's assessment of SO₂ emissions from Alabama's point sources located within approximately 50 km of another state and their potential impacts on neighboring states (see sections III.C.1. and II.C.2 of this notice) and SO₂ air quality data at monitors within 50 km of the Alabama border (see section III.C.3. of this notice) is informed by all available data at the time of this proposed rulemaking.^[17]

As described in Section III, EPA proposes to conclude that an assessment of Alabama's satisfaction of the prong 1 and 2 requirements under section 110(a)(2)(D)(i)(I) of the CAA for the 2010 1-hour SO₂ NAAQS may be reasonably based upon evaluating the downwind impacts via modeling and an assessment of SO₂ emissions from Alabama's point sources emitting more than 100 tpy of SO₂ (including fuel combustion sources) that are located within approximately 50 km of another state and upon any regulations intended to address Alabama's SO₂ point sources.

C. EPA's Prong 1 Evaluation—Significant Contribution to Nonattainment

Prong 1 of the good neighbor provision requires states' plans to prohibit emissions that will contribute significantly to nonattainment of a NAAQS in another state. ADEM states in its submission that Alabama does not contribute significantly to nonattainment of the 2010 1-hour SO₂ NAAQS in another state based on the information provided therein. To evaluate Alabama's satisfaction of prong 1, EPA assessed Alabama's SIP submission with respect to the following factors: (1) Potential ambient air quality impacts of SO₂ emissions from certain facilities in Alabama on neighboring states based on available air dispersion modeling results; (2) SO₂ emissions from Alabama sources; (3) SO₂ ambient air quality for Alabama and neighboring states; (4) SIP-approved Alabama regulations that address SO₂ emissions; and (5) federal regulations that reduce SO₂ emissions at Alabama sources. A detailed discussion of Alabama's SIP submission with respect to each of these factors follows. EPA proposes that these factors, taken together, support the Agency's proposed determination that Alabama will not contribute significantly to nonattainment of the 2010 1-hour SO₂ NAAQS in another state. EPA's proposed conclusion is based, in part, on the fact that adjacent states with modeled DRR sources located within 50 km of the Alabama border do not have areas that are violating or that model violations of the 2010 1-hour SO₂ NAAQS and the fact that the valid SO₂ 2016-2018 DVs for monitors in adjacent states show attainment of the 2010 1-hour SO₂ NAAQS.^[18] Also, 2017 SO₂ emissions for Alabama's non-DRR sources emitting over 100 tons of SO₂ within 50 km of another state are at distances or emit levels of SO₂ that make it unlikely that these SO₂ emissions could interact with SO₂ emissions from the neighboring states' sources in such a way as to contribute significantly to nonattainment in these neighboring states. In addition, the downward trends in statewide SO₂ emissions, combined with federal and SIP-approved State regulations affecting SO₂ emissions from Alabama's sources, further support EPA's proposed conclusion.

1. SO₂ Designations Air Dispersion Modeling

a. State Submission

( printed page 72282)

In its August 20, 2018, SIP submission, ADEM referenced a January 14, 2016, letter ^[19] that the State submitted to EPA identifying the facilities in Alabama with SO₂ emissions subject to the DRR.^[20] ADEM explained that the DRR modeling data is contained in EPA's technical support document (TSD) for the SO₂ round 3 area designations.^[21]

b. EPA Analysis

EPA evaluated available DRR modeling data for sources in Alabama within 50 km of another state, including the Big Escambia Supplement, and available DRR modeling data for sources in the adjacent states of Florida, Georgia, Mississippi, and Tennessee that are within 50 km of the Alabama border.^[22] The purpose of evaluating DRR modeling results in adjacent states within 50 km of the Alabama border is to ascertain whether any nearby sources in Alabama are impacting a violation of the 2010 1-hour SO₂ NAAQS in another state.

Of the 15 sources in Alabama initially subject to the DRR, 10 sources conducted dispersion modeling.^[23] Six of the 10 modeled sources are within 50 km of another state: Akzo Nobel Functional Chemicals—Lemoyne Site (AkzoNobel); Alabama Power Company—James M. Barry Electric Generating Plant (Plant Barry); Ascend Performance Materials—Decatur Plant (Ascend); Big Escambia; PowerSouth Energy Cooperative—Charles R. Lowman Power Plant (Lowman); and Continental Carbon Company—Phenix City Plant (Continental Carbon).^[24] With respect to Continental Carbon, EPA previously determined that the modeling and supporting information provided to meet DRR requirements was acceptable.^[25] With respect to the modeling and other information submitted by the State for the remaining five modeled Alabama sources within 50 km of another state ( i.e., AkzoNobel, Ascend, Big Escambia, Lowman, and Plant Barry), EPA previously determined that the Agency does not have sufficient information to demonstrate whether the areas around these sources meet or do not meet the 2010 1-hour SO₂ NAAQS or contribute to an area that does not meet the standard, and thus designated these areas as unclassifiable.^[26] Although EPA does not have any indications that there are violations of the 2010 1-hour SO₂ NAAQS in these areas, the Agency assessed AkzoNobel, Ascend, Lowman, and Plant Barry in section III.C.2.b. of this proposed action with respect to interstate transport for the 2010 1-hour SO₂ NAAQS. Regarding Big Escambia, ADEM provided supplemental information in September and December of 2019 that addresses the issues with the original modeling for this source performed under the DRR for the purposes of evaluating interstate transport of SO₂ from Alabama into Florida.^[27] EPA's TSD for Big Escambia summarizes the issues with the original DRR modeling and how ADEM has now addressed these issues for the purpose of evaluating potential ambient air impacts in the neighboring state of Florida.^[28] Table 2 provides a summary of the 99th percentile daily maximum 1-hour average concentrations estimated by the modeling for Big Escambia and Continental Carbon, which are based on actual emissions for Big Escambia and potential to emit (PTE) emissions for Continental Carbon. Alabama's modeling analyses for Big Escambia and Continental Carbon indicate that the maximum impacts did not exceed the level of the 2010 1-hour SO₂ NAAQS in neighboring states. Based on the modeling results indicating that the maximum impacts did not exceed the level of the 2010 1-hour SO₂ NAAQS in neighboring states, no further analysis is necessary for assessing the potential impacts of the interstate transport of SO₂ emissions from these facilities.

( printed page 72283)

Table 3 provides a summary of the modeling results for the four DRR sources in neighboring states which are located within 50 km of Alabama and which elected to provide air dispersion modeling under the DRR: Gulf Power Company—Crist Electric Generating Station (Crist) in Florida; Georgia Power—Plant Bowen (Plant Bowen) and Georgia Power—Plant Wansley (Plant Wansley) in Georgia; and Mississippi Power Company's Victor J. Daniel Steam Electric Generating Plant (Plant Daniel) in Mississippi. The modeling results for all four sources indicated that the maximum impacts did not exceed the level of the 2010 1-hour SO₂ NAAQS.^[30]

EPA believes that the modeling results in Tables 2 and 3, weighed along with other factors in this notice, support EPA's proposed conclusion that sources in Alabama will not contribute significantly to nonattainment of the 2010 1-hour SO₂ NAAQS in any other state.

2. SO₂ Emissions Analysis

a. State Submission

With respect to emissions trends, ADEM states that significant SO₂ emissions reductions have resulted from the implementation of several federal programs in Alabama. These federal programs are identified in section III.C.5 of this notice.

b. EPA Analysis

EPA reviewed statewide and EGU SO₂ emissions in Alabama from the NEI for the years 2005, 2008, 2011, and 2014 to examine any trends in SO₂ emissions over this period. As shown in Table 4, Alabama's statewide SO₂ emissions have declined by 66 percent from 592,670 tons in 2002 to 201,418 tons in 2014. Alabama EGU SO₂ emissions decreased by 74 percent from 461,634 tons in 2005 to 119,976 tons in 2014. ( printed page 72284)

As discussed in section III.B., EPA also finds that it is appropriate to examine the impacts of SO₂ emissions from stationary sources emitting greater than 100 tons of SO₂ in Alabama at distances ranging from zero km to 50 km from a neighboring state's border. Therefore, in addition to those sources addressed in section III.C.1.b. of this notice, EPA also assessed the potential impacts of SO₂ emissions from stationary sources not subject to the DRR that emitted over 100 tons of SO₂ in 2017 and are located in Alabama within 50 km from the border.^[31] EPA assessed this information to evaluate whether the SO₂ emissions from these sources could interact with SO₂ emissions from the nearest source in a neighboring state in such a way as to impact a violation of the 2010 1-hour SO₂ NAAQS in that state. Table 5 lists sources in Alabama not subject to the DRR that emitted greater than 100 tpy of SO₂ in 2017 within 50 km of the State's border.

Currently, EPA does not have monitoring or modeling data suggesting that Florida, Georgia, North Carolina, and Tennessee are impacted by SO₂ emissions from the 14 Alabama sources not subject to the DRR listed in Table 5. Of these 14 Alabama sources, 10 are located over 50 km from the nearest source in another state emitting over 100 tons of SO₂ . EPA believes that the distances greater than 50 km between sources make it unlikely that SO₂ emissions from the 10 Alabama sources could interact with SO₂ emissions from the neighboring states' nearest sources in Table 5 in such a way as to contribute significantly to nonattainment in Florida, Georgia, Mississippi, and Tennessee.

There are four Alabama sources not subject to the DRR that are located at or less than 50 km from the nearest source in another state which emit greater than 100 tons of SO₂: American Midstream Chatom, LLC; Evonik Corporation; ExxonMobil Production Company; and Georgia-Pacific Brewton LLC. EPA believes that the relatively low SO₂ emissions of each of these four Alabama sources combined with the emissions from the nearest sources emitting greater than 100 tons of SO₂ in neighboring states make it unlikely that the SO₂ emissions from these four Alabama ( printed page 72285) sources could interact with SO₂ emissions from the neighboring states' sources in such a way as to contribute significantly to nonattainment in the neighboring states of Florida, Georgia, Mississippi, and Tennessee.

In addition, EPA evaluated 2017 SO₂ emissions data for four of the five DRR sources for which EPA could not rely on existing DRR modeling to assess their impacts for interstate transport for the 2010 1-hour SO₂ NAAQS on other states: AkzoNobel, Ascend, Lowman, and Plant Barry. Table 6 provides annual 2017 SO₂ emissions data along with the distances to the closest neighboring state's sources emitting over 100 tpy of SO₂ .^[32] Table 7 shows the SO₂ emissions trends for these sources from 2012-2017 (and 2018 if data is available).^[33]

Table 6 shows that the distances between the four Alabama DRR sources without valid DRR modeling and the nearest state's source emitting over 100 tpy of SO₂ exceed 50 km. EPA believes that the distances greater than 50 km between sources make it unlikely that SO₂ emissions from the four Alabama DRR sources could interact with SO₂ emissions from the neighboring states' nearest sources in Table 6 in such a way as to contribute significantly to nonattainment in Mississippi and Tennessee. Table 7 shows that 2017 SO₂ emissions have declined below 2012 levels for Ascend and Akzo Nobel) and that 2018 SO₂ emissions have declined below 2012 levels for Lowman and Plant Barry.

EPA also considered whether any changes in controls or operations had occurred at AkzoNobel, Ascend, Lowman, and Plant Barry. AkzoNobel entered into a consent decree with EPA that has reduced SO₂ emissions.^[34] According to June 6, 2019, and December 2, 2019, emails from ADEM to EPA, Ascend ceased operating Boiler 5, Boiler 6 is set to cease operations in 2020, and Cokers 1 and 2 are set to cease operations in 2021.^[35] At Loman, three coal-fired boilers are set to be shut down in 2020. Plant Barry has retired Unit 3, and Units 1 and 2 are restricted to burn only natural gas as of January 1, 2017.

EPA also evaluated data in EPA's Air Quality System (AQS) ^[36] from the SO₂ monitors in the surrounding areas of AkzoNobel, Ascend, Lowman, and Plant Barry. The only monitor within 50 km of these sources is located in Mobile County, Alabama (AQS ID: 01-097-0003) and is approximately 23 km from AkzoNobel. The 2018 DV for this monitor is 11 ppb.

Based on the declining SO₂ emissions trends in Alabama shown in Table 4, and the Agency's analysis of the Alabama sources and respective data in Tables 5, 6, and 7, EPA believes that Alabama's potential for contributing significantly to nonattainment in a nearby state is reduced substantially.

3. SO₂ Ambient Air Quality

a. State Submission

In its August 20, 2018, SIP submission, ADEM indicated that there is one SO₂ monitor located in the State with complete data.^[37] This monitor (AQS ID: 01-073-1003) is located in Jefferson County, Alabama, and has a 2015-2017 DV of 13 ppb. The monitor is well over 50 km from the State's border. ADEM also asserts that there are no monitors located in Florida, Georgia, Louisiana, Mississippi, or Tennessee that are violating the 2010 1-hour SO₂ NAAQS for the 2015-2017 monitoring period based on the DVs in EPA's AQS for these monitors.

b. EPA Analysis

EPA reviewed monitoring data for AQS monitors in Alabama within 50 km ( printed page 72286) of another state and for AQS monitors within 50 km of Alabama in adjacent states using relevant data from EPA's AQS DV reports. The 2010 1-hour SO₂ standard is violated at an ambient air quality monitoring site (or in the case of dispersion modeling, at an ambient air quality receptor location) when the 3-year average of the annual 99th percentile of the daily maximum 1-hour average concentrations exceeds 75 ppb, as determined in accordance with Appendix T of 40 CFR part 50. The only AQS monitors in Alabama within 50 km of another state are the Mobile County monitor (AQS ID: 01-097-0003), and the Sumter County monitor (AQS ID: 01-119-0003). The Mobile County monitor is approximately 30 km from Mississippi and 45 km from Florida, and the Sumter County monitor is approximately 13 km from Mississippi. The Mobile County monitor began operation on January 1, 2016. The monitor has a complete, quality-assured 2016-2018 DV of 11 ppb, which is 85 percent below the level of the 2010 1-hour SO₂ NAAQS. The Sumter County monitor began operation on January 1, 2018. Since the monitor has not operated for three years, it has not yet collected a valid DV. During 2018, the Sumter County monitor recorded a 99th percentile daily maximum 1-hour SO₂ concentration of approximately 4 ppb. Neither the Mobile County nor Sumter County monitor has measured any daily exceedances of the 2010 1-hour SO₂ NAAQS during their respective years of operation.

Table 8 shows that there are three AQS monitors in the adjacent states of Florida (Escambia County monitor), Georgia (Floyd County monitor), and Mississippi (Jackson County monitor) which are located within 50 km of the Alabama border. Currently, there are no AQS monitors with complete, valid data indicating a violation of the 2010 1-hour SO₂ NAAQS located within 50 km of Alabama in the states of Florida, Georgia, and Mississippi. Further, the DVs from these monitors show a general downward trend in SO₂ concentrations and that the DVs from 2012-2018 have remained below the standard, with the exception of the Floyd County monitor in Georgia which did not have a valid DV for 2015-2017 and 2016-2018.^[38]

EPA notes that the 2014-2016 DV for the Floyd County, Georgia AQS monitor (AQS ID: 13-115-0003) of 42 ppb is 44 percent below the level of the 2010 1-hour SO₂ NAAQS. None of the monitors listed in Table 8 has measured any daily exceedances of the 2010 1-hour SO₂ NAAQS during 2017 or 2018. Thus, based on this assessment, EPA believes that these data support EPA's proposed conclusion that Alabama will not contribute significantly to nonattainment of the 2010 1-hour SO₂ NAAQS in any other state.

EPA also evaluated monitoring data provided to date for AQS monitors located in states adjacent to Alabama within 50 km of the State's border that were established to characterize the air quality around specific sources subject to EPA's DRR to inform the Agency's future round 4 designations for the 2010 1-hour SO₂ NAAQS in lieu of modeling (hereinafter referred to as “DRR monitors”). There is only one DRR monitor—located in Floyd County, Georgia (AQS ID: 13-115-0006)—that is within 50 km of the Alabama border. Although this monitor does not have three or more years of complete data to establish DVs, EPA evaluated the available, annual 99th percentile SO₂ concentration data for 2017 and 2018 (see Table 9). The Floyd County DRR monitor was sited in the vicinity of the International Paper—Rome facility, a DRR source.

Though the annual 99th percentile daily maximum 1-hour SO₂ concentrations shown in Table 9 are not directly comparable to a DV for the 2010 1-hour SO₂ NAAQS, which is in the form of the 3-year average of the 99th percentile of daily maximum 1-hour values, EPA notes that the highest annual 99th percentile daily maximum 1-hour values observed at the Floyd County DRR monitor in 2017 and 2018 were 22 ppb and 15 ppb, respectively. The Floyd County DRR monitor has not measured any daily exceedances of the 2010 1-hour SO₂ NAAQS during 2017 or 2018. After careful review of the State's assessment and all available monitoring data, EPA believes that the AQS monitoring data assessed support EPA's proposed conclusion that Alabama will not contribute significantly to 2010 1-hour SO₂ violations in the neighboring states. ( printed page 72287)

4. SIP-Approved Regulations Addressing SO₂ Emissions

a. State Submission

Alabama's August 20, 2018, SIP submission identifies SIP-approved measures which help ensure that SO₂ emissions in the State will not contribute significantly to nonattainment of the 2010 1-hour SO₂ NAAQS in any other state. Specifically, ADEM lists the following SIP-approved Alabama regulations which establish emission limits and other control measures for SO₂: ADEM Administrative Code Chapter 335-3-5— Control of Sulfur Compound Emissions and Rules 335-3-14-.01— General Provisions; 335-3-14-.02— Permit Procedure; 335-3-14-.03— Standards for Granting Permits; 335-3-14-.04— Air Permits Authorizing Construction in Clean Air Areas (Prevention of Significant Deterioration (PSD)); and 335-3-14-.05— Air Permits Authorizing Construction in or Near Nonattainment Areas.

b. EPA Analysis

EPA believes that Alabama's SIP-approved measures summarized in III.C.4.a. of this notice, which establish emissions limits, permitting requirements, and other control measures for SO₂, effectively address emissions of SO₂ from sources in the State. For the purposes of ensuring that SO₂ emissions at new major sources or major modifications at existing major sources in Alabama do not contribute significantly to nonattainment or interfere with maintenance of the 2010 1-hour SO₂ NAAQS, the State has a SIP-approved major source new source review (NSR) program. Alabama's SIP-approved nonattainment NSR regulation, Rule 335-3-14-.05, applies to the construction of any new major stationary source or major modification at an existing major stationary source in an area designated as nonattainment. Alabama's SIP-approved prevention of significant deterioration (PSD) regulation, Rule 335-3-14-.04, applies to the construction of any new major stationary source or any major modification at an existing major stationary source in an area designated as attainment or unclassifiable or not yet designated. Rules 335-3-14-.01— General Provisions, 335-3-14-.02— Permit Procedure, and 335-3-14-.03— Standards for Granting Permits govern the preconstruction permitting of modifications to and construction of minor stationary sources. These major and minor NSR rules ensure that SO₂ emissions due to major modifications at existing major stationary sources, modifications at minor stationary sources, and the construction of new major and minor sources in Alabama will not contribute significantly to nonattainment of the 2010 1-hour SO₂ NAAQS in neighboring states.

5. Federal Regulations Addressing SO₂ Emissions in Alabama

a. State Submission

ADEM identified EPA programs which, either directly or indirectly, have significantly reduced SO₂ emissions in Alabama. These programs include: 2007 Heavy-Duty Highway Rule; Acid Rain Program; Cross-State Air Pollution Rule; National Emission Standards for Hazardous Air Pollutants; New Source Performance Standards; Nonroad Diesel Rule; and Tier 1 and 2 Mobile Source Rules.

b. EPA Analysis

In addition to the list of federal regulations identified in section III.C.5.a. of this notice which contribute to SO₂ reductions in Alabama, EPA notes that some facilities in the State are also subject to the federal requirements contained in EPA's Mercury Air Toxic Standards (MATS). These regulations reduce acid gases, which also result in reductions of SO₂ emissions. EPA believes that the federal control measures for SO₂ which Alabama lists in the State's SIP submission, along with MATS, may lower SO₂ emissions, which, in turn, are expected to continue to support EPA's proposed conclusion that SO₂ emissions from Alabama will not contribute significantly to nonattainment of the 2010 1-hour SO₂ NAAQS in another state.

6. Conclusion

EPA proposes to determine that Alabama's August 20, 2018, SIP submission satisfies the requirements of prong 1 of CAA section 110(a)(2)(D)(i)(I). This proposed determination is based on the following considerations: Current air quality data for AQS SO₂ monitors located in the states of Florida, Georgia, and Mississippi that are within 50 km of Alabama's border are well below the 2010 1-hour SO₂ NAAQS; modeling for the two Alabama DRR sources whose modeling grids extend into a portion of other states indicate that the maximum impacts did not exceed the level of the 2010 1-hour SO₂ NAAQS in neighboring states; modeling for four DRR sources in the surrounding states of Florida, Georgia, and Mississippi located within 50 km of Alabama indicate that the areas around these sources do not violate the 2010 1-hour SO₂ NAAQS; declining statewide and EGU SO₂ emissions from 2005 to 2014 in Alabama suggest that the State's potential for contributing significantly to nonattainment of the 2010 1-hour SO₂ NAAQS is reduced substantially; SO₂ emissions from Alabama sources not subject to the DRR and which emitted over 100 tons of SO₂ in 2017 are not likely interacting with SO₂ emissions from the nearest sources in bordering states in such a way as to contribute significantly to nonattainment in the surrounding states of Florida, Georgia, Mississippi, and Tennessee; Alabama DRR sources without valid DRR modeling are located over 50 km from the nearest state's SO₂ source and their SO₂ emissions show an overall general downward trend; and the implementation of current Alabama SIP-approved measures and federal emissions control programs help to further reduce and control SO₂ emissions from sources within Alabama. Further, EPA has no information indicating that Alabama sources will contribute significantly to nonattainment of the 2010 1-hour SO₂ NAAQS in another state.

Based on the analysis provided by Alabama in its SIP submission and EPA's analysis of the factors described in section III.C, EPA proposes to find that sources within Alabama will not contribute significantly to nonattainment of the 2010 1-hour SO₂ NAAQS in any other state.

D. EPA's Prong 2 Evaluation—Interference With Maintenance of the NAAQS

Prong 2 of the good neighbor provision requires state plans to prohibit emissions that will interfere with maintenance of a NAAQS in another state.

1. State Submission

In its August 20, 2018, SIP submission, ADEM relied upon the information provided for prong 1 to demonstrate that emissions within Alabama will not interfere with maintenance of the 2010 1-hour SO₂ NAAQS in any neighboring state. Further, ADEM notes that there are no monitors located in the surrounding states of Florida, Georgia, Louisiana, Mississippi, and Tennessee that are violating the 2010 1-hour SO₂ NAAQS for the 2015-2017 monitoring period. ADEM also highlighted the State's PSD regulation (335-3-14-.04) and states that this regulation “will continue to apply to any future, large sources in Alabama, further ensuring that maintenance efforts in neighboring states are addressed.” ( printed page 72288)

2. EPA Analysis

In North Carolina v. EPA, the United States Court of Appeals for the District of Columbia Circuit (D.C. Circuit) explained that the regulating authority must give prong 2 “independent significance” from prong 1 by evaluating the impact of upwind state emissions on downwind areas that, while currently in attainment, are at risk of future nonattainment. North Carolina v. EPA, 531 F.3d 896, 910-11 (D.C. Cir. 2008). EPA interprets prong 2 to require an evaluation of the potential impact of a state's emissions on areas that are currently measuring clean data, but that may have issues maintaining that air quality. Therefore, in addition to the analysis presented by Alabama, EPA has also reviewed additional information on SO₂ air quality and emission trends to evaluate the State's conclusion that Alabama will not interfere with maintenance of the 2010 1-hour SO₂ NAAQS in downwind states. This evaluation builds on the analysis regarding significant contribution to nonattainment (prong 1).

For the prong 2 analysis, EPA evaluated the data discussed in section III.C. of this notice for prong 1, with a specific focus on evaluating emissions trends in Alabama, analyzing air quality data, and assessing how future sources of SO₂ are addressed through existing SIP-approved and federal regulations. Given the continuing trend of decreasing statewide SO₂ emissions from sources within Alabama, and the fact that all areas in other states within 50 km of the Alabama border have DVs attaining the 2010 1-hour SO₂ NAAQS, EPA believes that evaluating whether these decreases in emissions can be maintained over time is a reasonable criterion to ensure that sources within Alabama do not interfere with its neighboring states' ability to maintain the 2010 1-hour SO₂ NAAQS.

With respect to air quality data trends, the valid 2016-2018 DVs for AQS SO₂ monitors both in Alabama within 50 km of another state's border and in adjacent states within 50 km of Alabama's border are below the 2010 1-hour SO₂ NAAQS.^[39] Further, modeling results for DRR sources in the State within 50 km of Alabama's border did not exceed the level of the 2010 1-hour SO₂ NAAQS in neighboring states and modeling results for DRR sources in neighboring states within 50 km of Alabama's border show maximum impacts did not exceed the level of the 2010 1-hour SO₂ NAAQS. Thus, these modeling results demonstrate that Alabama's largest point sources of SO₂ are not expected to interfere with maintenance of the 2010 1-hour SO₂ NAAQS in another state.

As discussed in sections III.C.4 and III.C.5, EPA believes that federal and SIP-approved State regulations that both directly and indirectly reduce emissions of SO₂ in Alabama help ensure that the State does not interfere with maintenance of the NAAQS in another state. SO₂ emissions from future major modifications and new major sources will be addressed by Alabama's SIP-approved major NSR regulations described in section III.C.4. In addition, ADEM Rules 335-3-14-.01— General Provisions, 335-3-14-.02— Permit Procedure, and 335-3-14-.03— Standards for Granting Permits govern the preconstruction permitting of modifications to and construction of minor stationary sources. These major and minor source permitting regulations are designed to ensure that emissions from these activities will not interfere with maintenance of the 2010 1-hour SO₂ NAAQS in the State or in any other state.

3. Conclusion

EPA proposes to determine that Alabama's August 20, 2018, SIP submission satisfies the requirements of prong 2 of CAA section 110(a)(2)(D)(i)(I). This determination is based on the following considerations: Statewide and EGU SO₂ emissions from 2005 to 2014 in Alabama have declined significantly (66 and 74 percent, respectively); current Alabama SIP-approved measures and federal emissions control programs adequately control SO₂ emissions from sources within Alabama; Alabama's SIP-approved PSD and minor source NSR permit programs will address future large and small SO₂ sources; current air quality data for AQS SO₂ monitors in Florida, Georgia, and Mississippi within 50 km of Alabama's border have DVs well below the 2010 1-hour SO₂ NAAQS; and modeling for DRR sources in Alabama indicate that the maximum impacts did not exceed the level of the 2010 1-hour SO₂ NAAQS in neighboring states; modeling for DRR sources within 50 km of Alabama's border located in the states of Florida, Georgia, and Mississippi demonstrate that Alabama's largest point sources of SO₂ will not interfere with maintenance of the 2010 1-hour SO₂ NAAQS in another state. Based on the analysis provided by Alabama in its SIP submission and EPA's analysis of the factors described in section III.C of this notice, EPA proposes to find that emission sources within Alabama will not interfere with maintenance of the 2010 1-hour SO₂ NAAQS in any other state.

IV. Proposed Action

In light of the above analysis, EPA is proposing to approve Alabama's August 20, 2018, SIP submission as demonstrating that emissions from Alabama will not contribute significantly to nonattainment or interfere with maintenance of the 2010 1-hour SO₂ NAAQS in another state.

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. See42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, EPA's role is to approve state choices, provided that they meet the criteria of the CAA. This proposed 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 proposed action:

• Is not a significant regulatory action subject to review by the Office of Management and Budget under Executive Orders 12866 (58 FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);
• Is not anExecutive 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 inExecutive Order 13132 (64 FR 43255, August 10, 1999);
• Is not an economically significant regulatory action based on health or safety risks subject toExecutive Order 13045 (62 FR 19885, April 23, 1997);
• Is not a significant regulatory action subject toExecutive Order 13211 (66 FR 28355, May 22, 2001);
• Is not subject to requirements of Section 12(d) of the National ( printed page 72289) 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, underExecutive Order 12898 (59 FR 7629, February 16, 1994).

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 as specified by Executive Order 13175 (65 FR 67249, November 9, 2000), nor will it impose substantial direct costs on tribal governments or preempt tribal law.

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

84 FR 72278