AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

The Environmental Protection Agency (EPA) is proposing to approve the remaining portion of a state implementation plan (SIP) revision submitted by the State of Nevada. This revision addresses the interstate transport requirements of the Clean Air Act (CAA) with respect to the 2010 1-hour sulfur dioxide (SO₂) primary national ambient air quality standard (NAAQS). In this action, the EPA is proposing to determine that Nevada will not contribute significantly to nonattainment or interfere with maintenance of the 2010 1-hour SO₂ NAAQS in any other state. We are taking comments on this proposal and plan to follow with a final action.

DATES:

Comments must be received on or before April 30, 2020.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA-R09-OAR-2014-0812 at http://www.regulations.gov, or via email to kelly.thomasp@epa.gov. For comments submitted at Regulations.gov, follow the online instructions for submitting comments. Once submitted, comments cannot be removed or edited from Regulations.gov. For either manner of submission, 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, please contact the person identified in the FOR FURTHER INFORMATION CONTACT section. For the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit http://www.epa.gov/​dockets/​commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT:

Tom Kelly, EPA Region IX, (415) 972-3856, kelly.thomasp@epa.gov.

SUPPLEMENTARY INFORMATION:

Throughout this document, “we,” “us,” or “our” refer to the EPA.

Table of Contents

I. Background

II. Section 110(a)(2)(D)(i)(I)—Interstate Transport

A. General Requirements and Historical Approaches for Criteria Pollutants

B. Nevada's SIP Submittal

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

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

III. Proposed Action

IV. Statutory and Executive Order Reviews

I. Background

On June 22, 2010, the EPA promulgated a revised primary NAAQS for SO₂ at 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.^[1] Pursuant to section 110(a)(1) of the CAA, states are required to submit SIPs meeting the applicable requirements of section 110(a)(2) within three years after promulgation of a new or revised NAAQS or a shorter period as the EPA may prescribe. These SIPs, which the EPA has historically referred to as “infrastructure SIPs,” are to provide for the “implementation, maintenance, and enforcement” of such NAAQS, and the requirements are designed to ensure that the structural components of each state's air quality management program are adequate to meet the state's responsibility under the CAA. Section 110(a) of the CAA imposes the obligation upon states to make a SIP submission to the EPA for a new or revised NAAQS, but the contents of individual state submissions may vary depending upon the facts and circumstances. The content of the revisions proposed in SIP submissions may also vary depending upon what provisions are already contained in the state's approved SIP.

On June 3, 2013, the State of Nevada submitted a revision to its SIP addressing the requirements of section 110(a)(2) of the CAA with respect to the 2010 SO₂ NAAQS (“2013 Nevada SIP revision”). On November 3, 2015, the EPA partially approved and partially disapproved portions of the 2013 Nevada SIP revision for the 2010 SO₂ NAAQS.^[2] However, at that time, the EPA did not take action on the section 110(a)(2)(D)(i)(I), interstate transport portion of the 2013 Nevada SIP revision.^[3] The EPA is now proposing to act on that portion of the 2013 Nevada SIP revision for the 2010 SO₂ NAAQS.

II. Section 110(a)(2)(D)(i)(I)—Interstate Transport

A. General Requirements and Historical Approaches for Criteria Pollutants

Section 110(a)(2)(D)(i)(I) requires states to include in their SIPs 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). The EPA commonly refers to SIP revisions addressing the requirements of section 110(a)(2)(D)(i)(I) as “good neighbor SIPs” or “interstate transport SIPs.”

The EPA's most recent infrastructure SIP guidance, the September 13, 2013 “Guidance on Infrastructure State Implementation Plan (SIP) Elements under Clean Air Act Sections 110(a)(1) and 110(a)(2),” did not explicitly include criteria for how the Agency would evaluate infrastructure SIP submissions intended to address section 110(a)(2)(D)(i)(I).^[4] With respect to certain pollutants, such as ozone and particulate matter, the EPA has addressed interstate transport in eastern states in the context of regional rulemaking actions that quantify state emissions reduction obligations.^[5] In other actions, such as the EPA actions on western interstate transport SIPs addressing ozone and particulate matter, the EPA has considered a variety of factors on a case-by-case basis to make a weight of evidence determination as to whether emissions from one state interfere with the attainment and maintenance of the NAAQS in another state. In such actions, the EPA has considered available information such as current air quality, emissions data and trends, meteorology, and topography.^[6]

1. The EPA's Approach for Addressing the Interstate Transport Requirements of the 2010 Primary SO₂ NAAQS in Nevada

As previously noted, section 110(a)(2)(D)(i)(I) requires an evaluation of any source or other type of emissions activity in one state and how emissions from these source categories may impact air quality in other states. The EPA believes that a reasonable starting point for determining which sources and emissions activities in Nevada are likely to impact downwind air quality with respect to the 2010 SO₂ NAAQS is to use information in the National Emissions Inventory (NEI).^[7] The NEI is a comprehensive and detailed estimate of air emissions of 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. At the time of this proposed rulemaking, the most recently available complete dataset is the 2014 NEI. The analysis in this proposed rulemaking also relies on facility-reported emissions data, the most recent of which is for 2017.^[8] In addition, our analysis uses trends data, which the EPA prepares annually.^[9] Trends data include facility reported emissions data and data extrapolated by the EPA from the most recent NEI year.

Although SO₂ is emitted from similar point and nonpoint sources, as is directly emitted fine particulate matter (PM_2.5) ^[10] and the precursors to both ozone and PM_2.5, interstate transport of SO₂ is unlike the transport of PM_2.5 or ozone because SO₂ emissions sources usually do not have long range SO₂ impacts. The transport of SO₂ relative to the 1-hour 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 its 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 would be too regionally focused for SO₂, the approach for Pb transport would be too tightly circumscribed to the source. SO₂ transport is therefore a unique case and requires a different approach.

In this proposed rulemaking, as in prior SO₂ transport analyses, we focus on a 50 kilometer (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, the EPA selected a spatial scale with dimensions from four to 50 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, the 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. The EPA's selection of this transport distance for SO₂ is based upon 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 is the EPA's preferred modeling platform for regulatory purposes for near-field dispersion of emissions for distances up to 50 km. (Appendix W of 40 CFR part 51).^[12] Thus, the EPA has applied the 50-km zone as a reasonable distance to evaluate emissions source impacts into neighboring states and to assess air quality monitors within 50 km of the State's border.

Current implementation strategies for the 2010 primary SO₂ NAAQS include the flexibility to characterize air quality for stationary sources via either data collected at ambient air quality monitors sited to capture the points of maximum concentration, or air dispersion modeling.^[13] The EPA's assessment of SO₂ emissions from fuel combustion categories in Nevada and their potential on neighboring states is informed by all available data at the time of this rulemaking and include: SO₂ ambient air quality; SO₂ emissions and emissions trends; SIP-approved regulations that directly address SO₂; and other SIP-approved regulations, which may yield reductions of SO₂. This notice describes the EPA's weight of evidence evaluation of the 2013 Nevada SIP revision to satisfy the requirements of CAA section 110(a)(2)(D)(i)(I).^[14]

B. Nevada's SIP Submittal

1. Administrative Requirements

On June 3, 2013, the Nevada Division of Environmental Protection (NDEP) submitted to the EPA the 2013 Nevada SIP revision.^[15] The submittal includes the following:

• The Nevada Division of Environmental Protection Portion of the Nevada State Implementation Plan for the 2010 Sulfur Dioxide Primary NAAQS, and appendices, June 3, 2013;
• State Implementation Plan Revision to Meet the Sulfur Dioxide Infrastructure SIP Requirements of the Clean Air Act § 110(a)(2), and attachments Clark County, Nevada, May 29, 2013;
• The Washoe County Portion of the Nevada State Implementation Plan to Meet the Sulfur Dioxide Infrastructure SIP Requirements of Clean Air Act § 110(a)(2), and attachments, March 28, 2013

The submittal was deemed complete by operation of law on December 3, 2013.

The Washoe and the NDEP portions of the submittal state that they are not required to make submittals addressing the requirements of CAA section 110(a)(2)(D)(i)(I) and cite to a November 19, 2012 memo from EPA Administrator Gina McCarthy, which outlined the EPA's intention to abide by a 2012 D.C. Circuit decision.^[16]

Despite stating in the NDEP portion of the submittal that it was not obligated to address the requirements of CAA section 110(a)(2)(D)(i)(I), the NDEP included Appendix C “Interstate Transport Analysis for the 2010 Sulfur Dioxide Primary National Ambient Air Quality Standard” (“Appendix C” or “transport analysis”) to address the aforementioned CAA requirements.

2. The NDEP's Transport Analysis

As the NDEP's portion of the submittal explains, the Clark County Department of Air Quality (Clark County) and Washoe County Board of Health (Washoe County) regulate air pollution within their respective counties, with the exception of fossil-fuel-fired steam generators. The NDEP regulates air pollution in all other counties of the State as well as fossil-fuel-fired steam generators throughout the State, including Clark County and Washoe County.

The following summarizes the NDEP's rationale for concluding that transport of SO₂ from Nevada would not significantly contribute to nonattainment, or interfere with maintenance, of the 2010 SO₂ NAAQS in other states.^[17]

a. Summary of Nevada's transport analysis regarding nonattainment receptors in contiguous states: Arizona and Utah.

The NDEP's transport analysis cites Clean Air Status and Trends Network (CASTNET) monitoring data in Nevada, Utah, Montana, Colorado, and Arizona. CASTNET data measure air quality in areas where urban influences are minimal, and, thus, are representative of regional background levels of air pollution.^[18] According to the NDEP, average weekly and seasonal SO₂ concentrations from six national parks and one national monument in Nevada, Utah, Montana, Colorado, and Arizona were below 2 ppb from 2007 to 2012, “indicating that the regional SO₂ background concentrations are relatively low, which in turn implies that the bulk of the SO₂ in the urban receptor areas is locally generated and not a regional or transport phenomenon.”

The Nevada transport analysis further explains that Arizona's only nonattainment receptors are the Hayden and Miami SO₂ nonattainment planning areas, located in Gila County and Pinal County, respectively. Total SO₂ emissions from Gila and Pinal counties were 29,470 tons from the 2008 NEI. The NDEP notes that Nevada's nearest SO₂ source, the recently closed Reid Gardner Generating Station,^[19] is 305 miles (490 km) from the Miami nonattainment area and 330 miles (530 km) from the Hayden nonattainment area and emitted only 941 tons of SO₂ in 2008, which, for illustrative purposes, was about three percent of the SO₂ emissions originating from the Miami and Hayden copper smelters.^[20] Additionally, the NDEP states that meteorological data show the prevailing wind direction in the southern part of the State is from the south-southwest blowing mainly north-northeast (indicating that winds in Nevada are generally not blowing south-southeast from Nevada toward Hayden and Miami in Arizona).^[21]

For Utah, the NDEP states that Salt Lake and Tooele counties are classified as nonattainment for the 24-hour and annual 1971 SO₂ NAAQS, but that the counties have not violated those NAAQS since 1981.^[22] The Nevada transport analysis concludes that no areas in Utah are likely to exceed the 2010 NAAQS based on monitoring data indicating that elevated SO₂ levels in Salt Lake and Tooele counties ceased decades ago, and CASTNET data demonstrating low levels of regional background SO₂.

b. Summary of Nevada's transport analysis regarding attainment areas in one contiguous western state: Arizona.

Nevada's transport analysis identifies four maintenance areas for the 1971 SO₂ NAAQS in Arizona: The Ajo, Douglas, Morenci, and San Manuel SO₂ planning areas. In its analysis, Nevada summarizes the approved maintenance plans for the areas and states that copper smelters were historically the primary source of SO₂ emissions. The transport analysis states that only one smelter, located in the San Manuel SO₂ maintenance area, remains operational and that there have been no recorded monitoring violations of the SO₂ NAAQS in any of these areas since the mid-1980s.

c. Summary of Nevada's transport analysis regarding nonattainment and maintenance receptor areas in non-contiguous states: Missouri, Montana, and New Mexico.

Nevada's transport analysis also examined transport to nonattainment receptors in Missouri and Montana and determined that SO₂ emissions from Nevada do not contribute to nonattainment in those areas based on a comparison of the emissions inventories in those states and Nevada, wind patterns, and the distance between those states and Nevada.

In addition, the Nevada transport analysis evaluated maintenance receptors in New Mexico and determined that Nevada does not interfere with maintenance in that state based on comparison of the emissions inventories in New Mexico and Nevada, overall regional background levels of SO₂, and the distance between New Mexico and Nevada.

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

Prong 1 of the good neighbor provision requires state plans to prohibit emissions that will significantly contribute to nonattainment of a NAAQS in another state. In order to evaluate whether Nevada met prong 1 for the 2010 SO₂ NAAQS, the EPA evaluated the 2013 Nevada SIP revision with respect to the following two factors: (1) SO₂ ambient air quality in Nevada and neighboring states; and (2) SO₂ emissions sources in Nevada and neighboring states. Based on the detailed discussion of these factors below, the EPA proposes to find that Nevada's SIP meets the interstate transport requirements of CAA Section 110(a)(2)(D)(i)(I), prong 1, for the 2010 SO₂ NAAQS.

1. SO₂ Ambient Air Quality in Nevada and Neighboring States

First, the EPA reviewed ambient air quality data in Nevada and neighboring states to see whether there were any monitoring sites with elevated SO₂ concentrations that might warrant further investigation with respect to interstate transport of SO₂ from emissions sources near any given monitor. As shown in Table 1, there are no violating design values ^[23] between 2014 and 2018 in Nevada or neighboring states apart from monitors located in the Hayden and Miami nonattainment areas in Arizona.^[24]

Table 2 lists the annual 99th percentiles for SO₂ monitors that collected either three or four complete quarters of data in the specified year but lacked three consecutive years of complete data (i.e., a design value) like the monitors in Table 1. Again, the only monitor exceeding the 2010 SO₂ NAAQS is located in the Miami nonattainment area.

In concluding that Nevada would not impact receptors in the Hayden or Miami nonattainment areas in Arizona, Nevada's submittal noted several factors, including the prevailing wind direction in Las Vegas to the south and southwest and the significant distance, more than 300 miles (482 km), between the nonattainment areas and the nearest large generator of SO₂ emissions in southern Nevada, the now closed Reid Gardner Generating Station. At the closest point at Nevada's southern tip, the Hayden and Miami nonattainment areas are 350 km from the Nevada border, far outside the range within which we might expect a potential impact from SO₂ sources located in Nevada, given the localized range of potential 1-hour SO₂ emissions.

The data presented in Table 1 show that Nevada's SO₂ monitors, with sufficient data to produce valid 1-hour SO₂ design values, indicate that monitored 1-hour SO₂ concentrations in Nevada are between 5 percent (%) and 9% of the 75 ppb 1-hour SO₂ NAAQS. The Reno monitor is located within 50 km of the California border and the Las Vegas monitor is located within 50 km of the Arizona border. The highest SO₂ concentration within 300 km of Nevada is the Pocatello Idaho monitor, which is 59% of the NAAQS based on the 2018 design value and 162 km from the Nevada border. The low level of SO₂ at these air quality monitors in and near Nevada do not, by themselves, indicate any particular location that would warrant further investigation with respect to SO₂ emissions sources that might significantly contribute to nonattainment in neighboring states. However, because the monitoring network is not necessarily designed to find all locations of high SO₂ concentrations, this observation is not sufficient evidence by itself of an absence of impact at all locations in the neighboring states. We have therefore also conducted a source-oriented analysis.

2. Analysis of SO₂ Emissions Sources in Nevada and Neighboring States

To understand the potential for Nevada's emissions to contribute significantly to nonattainment in another state, we begin with a summary of the State's SO₂ emissions in Table 3 from the 2014 NEI.^[25] The EPA believes a reasonable starting point for determining which sources and emissions activities in Nevada are likely to impact downwind air quality in other states with respect to the 2010 1-hour SO₂ NAAQS is by using information in the EPA's 2014 NEI. 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; it is updated every three years using information provided by the states and other information available to the EPA. The 2014 NEI (version 2) is the most recently available complete and quality assured dataset of the NEI that includes all emissions categories.

As shown in Table 3, the majority of SO₂ emissions in Nevada originate from fuel combustion at point sources. In 2014, SO₂ emissions from fuel combustion point sources accounted for approximately 85% of the State's SO₂ emissions.^[26] With the closure of the Reid Gardner Generating Station, which accounted for over 15% of overall SO₂ emissions in the 2014 NEI, the SO₂ state-wide total should be substantially smaller once the 2017 emissions inventory is released. The next largest category of emissions is fire. According to the 2014 NEI, approximately 92% of fire emissions are from wildfires, which vary in location and quantity of emissions from year to year, while most of the other fire emissions come from prescribed burning. Of the remaining emissions (mobile, waste disposal, non-combustion industrial, and other, which make up approximately 9% of the state total), slightly more than half (about 5% of the state-wide total or 880 tons) originate in Clark County, which contains approximately 75% of Nevada's population, and the rest originate elsewhere throughout the State.

Emissions from the other listed source categories are more dispersed throughout the State, with the exception of McCarran Airport and Sunrise Landfill analyzed later in this notice. Due to the dispersed nature of these other source categories, their emissions are less likely to cause high ambient concentrations when compared to a point source on a ton-for-ton basis. Based on the EPA's analysis of the 2014 NEI SO₂ emissions data, the EPA considers it to be appropriate to focus the discussion on SO₂ emissions from Nevada's larger point sources (i.e., those emitting over 50 tons per year (tpy) of SO₂), which are located within the “urban scale,” i.e., within 50 km of one or more state borders.

Specifically, in 2014 60 percent of the statewide SO₂ emissions came from two facilities.^[27] The first, the North Valmy Generating Station, is 124 km from the state border, well beyond the 50-km threshold zone considered to be a reasonable distance to evaluate emissions source impacts to neighboring states for purposes of this analysis. In addition, EPA recently considered a modeling analysis submitted by the NDEP to support its recommendation that the EPA designate the entire State of Nevada as attainment/unclassifiable for the 2010 SO₂ NAAQS.^[28] The modeling was conducted in response to the Final Data Requirements Rule for the 2010 1-Hour SO₂ Primary NAAQS.^[29] As required by the rule, Nevada identified the North Valmy Generating Station as a facility emitting more than 2,000 tpy of SO₂ in 2014.^[30] Based on modeling that shows a maximum SO₂ concentration of 63 ppb, the EPA determined that the North Valmy Generating Station “is not modeled to cause or contribute to violations of the 2010 SO₂ [NAAQS],” and the EPA designated the area around North Valmy Generating Station, along with the rest of the State, as attainment/unclassifiable for the 2010 SO₂ NAAQS.^[31]

The North Valmy Generating Station is located 124 km from the Nevada-Oregon border and 125 km from the Nevada-Idaho border. Based on 2017 facility reported emissions data, Nevada has no other facilities emitting more than 50 tpy of SO₂ within 50 km of the State's border that could potentially combine with the emissions from the North Valmy Generating Station to contribute to nonattainment in the nearby states of Idaho and Oregon. The closest facility to the North Valmy Generating Station is the TS Power Plant, which is slightly more than 50 km from the North Valmy facility and more than 130 km from the Nevada-Idaho and Nevada-Oregon borders. This information supports the EPA's proposed conclusion that the North Valmy facility, in combination with Nevada's other SO₂ emissions sources, will not contribute significantly to nonattainment of the 2010 SO₂ NAAQS in any other state.

The second facility contributing 60 percent of statewide SO₂ emissions in 2014 is the Reid Gardner Generating Station that ceased operation in 2017. Consequently, this facility does not warrant further investigation with respect to SO₂ emissions sources that might significantly contribute to nonattainment in neighboring states.^[32]

Table 4 below shows all other Nevada sources that generated more than 50 tpy of SO₂ emissions in 2017 located within 50 km of the state border, including Nevada's second largest active source of SO₂ emissions, the McCarran Airport. Table 4 also lists the nearest out-of-state neighboring sources emitting above 50 tpy of SO₂ because elevated levels of SO₂, to which SO₂ emitted in Nevada may have a downwind impact, are most likely to be found near such sources.^[33] As shown in Table 4, the shortest distance between a Nevada source and a neighboring state source, with both emitting more than 50 tpy of SO₂, is 167 km. Furthermore, neighboring states have no sources of SO₂ emissions greater than 50 tpy located within 50 km of the Nevada border. Given the localized range of potential 1-hour SO₂ impacts, the data indicate that there are no additional locations in neighboring states that would warrant further investigation with respect to individual Nevada SO₂ emissions sources that might contribute to nonattainment of the 2010 SO₂ NAAQS.

3. Conclusion

In order to determine whether Nevada satisfied prong 1 for the 2010 SO₂ NAAQS, the EPA evaluated the State's 2013 SIP revision with respect to the following two factors: (1) SO₂ ambient air quality in Nevada and neighboring states; and (2) SO₂ emissions sources in Nevada and neighboring states. For the first factor, we identified no violating monitors near the Nevada border, and the only violating monitors in neighboring states are well outside the range within which we might expect them to be significantly impacted by interstate transport of SO₂ from Nevada. For the second factor, we identified no SO₂ sources within 50 km of the Nevada border that are likely contributing to a violation of the standard in another state, and we conclude that it is unlikely that sources farther from the border are leading to violations. Therefore, based on the analysis provided by the State in its SIP submission and the factors discussed above, the EPA proposes to find that Nevada will not cause or contribute significantly to nonattainment of the 2010 1-hour SO₂ NAAQS in any other state.

D. The EPA's Evaluation of Prong 2—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 considers that reasonable criteria to ensure that sources or emissions activities originating within Nevada will not interfere with its neighboring states' ability to maintain the NAAQS involves a close examination of the following: (1) Air quality trends in Nevada and neighboring states; (2) SIP-approved state and county measures that limit existing and new facility emissions; and (3) ambient concentrations of SO₂ in Nevada and neighboring states.

1. Air Quality Trends for Nevada and Neighboring States

As shown in Table 5 below, the statewide Tier 1 SO₂ emissions trends for Nevada and neighboring states have substantially decreased over time.^[34] Since 2000, overall SO₂ emissions have decreased by 89% in Nevada, 66% in Arizona, 82% in California, 77% in Idaho, 82% in Oregon, and 74% in Utah. The size and geographic scope of these reductions strongly suggest that the reductions are not transient effects from temporary causes and suggest that a trend of increasing emissions is unlikely to occur in these states.

Table 6 shows the emissions trend since 2008 for all Nevada facilities that emitted more than 100 tpy of SO₂. While some facilities, such as McCarran International Airport, show an increasing trend, the increases are small relative to the decreases at the North Valmy Generating Station and Reid Gardner Generating Station, and the overall downward trend in SO₂ emissions in Nevada is illustrated by the row showing total point source emissions.

While these trends do not by themselves demonstrate that Nevada and neighboring states will not have issues maintaining the 2010 SO₂ NAAQS, when considered alongside low ambient concentrations in Nevada and neighboring states, as illustrated in Table 1, they provide further evidence that emissions of SO₂ from Nevada are unlikely to interfere with maintenance of the SO₂ NAAQS in other states.

2. Nevada's Air Quality Rules

The 2013 Nevada SIP submittal identifies many rules for controlling current and future SO₂ or sulfur oxides (SO_X) emissions.^[35] The rules identified by the NDEP primarily regulate fuel combustion from large power plants as well as smaller stationary combustion sources (e.g., portable generators). The NDEP retains authority over facilities that generate electricity by using steam produced from fossil fuels, even if located within Clark or Washoe counties. Emissions limits for SO_X are set by Nevada Administrative Code (NAC) 445B.22095 and NAC 445.22096. NAC 445B.22095 identifies factors considered in determining best available control technology (BACT) for major sources, and NAC 445B.22096 provides numeric emissions limits for specific sources where BACT has been established for the Nevada Energy Tracy Generating Station and the Nevada Energy Fort Churchill Generating Station.^[36] NAC 445B.22047 and Article 8.2.1 limit SO₂ emissions from the combustion of fuel based on the heat input of the fuel in British Thermal Units (BTUs). NAC 445B.2205 limits SO₂ emissions from other processes. Nevada also identified many supporting regulations, such as rules covering definitions, calculations, and exemptions, including the following: NAC 445B.22043 (“Sulfur emissions: Calculation of total feed sulfur”); NAC 445B.22083 (“Construction, major modification or relocation of plants to generate electricity using steam produced by burning fossil fuels”); NAC 445B.308 (“Prerequisites and conditions for issuance of certain operating permits; compliance with applicable state implementation plan”); NAC 445B.310 (“Environmental evaluation: Applicable sources and other subjects; exemption”); and NAC 445B.311 (“Environmental evaluation: Contents; and consideration of good engineering practice stack height”).^[37]

Clark County broadly identified permitting rules limiting current and future SO₂ and hydrogen sulfide emissions. More specifically, Clark County permits require the following: Reasonably available control technology (RACT) for minor sources (25 tpy for SO₂) and existing sources with significant emissions increases, if a RACT determination has been made; ^[38] BACT for major new sources and existing sources proposing significant increases in attainment areas; ^[39] and a limit on maximum increment increases of SO₂ for areas with a regional haze designation of Class I, Class II, or Class III.^[40]

For limiting SO₂ emissions, Washoe County identified rules that control trace quantities of SO_X emissions from the storage of petroleum products, gasoline loading, gasoline unloading, and the use of organic solvents.^[41] An additional SIP-approved Washoe County regulation that controls SO_X is Section 040.060 (“Sulfur Content of Fuel”). It limits the sulfur content to 0.7% by weight for solid fuels and 1.0% for liquid fuels burned at less than 250 million BTUs of heat input. For fuels burned at more than 250 million BTUs of heat input per hour, Section 040.060 provides a calculation that sets a maximum quantity of sulfur (in pounds per hour).

In conclusion, for interstate transport prong 2, we reviewed SO₂ emissions trends in Nevada and neighboring states, Nevada's SIP-approved rules regulating SO₂ and SO_X, and the technical information related to SO₂ ambient air quality and SO₂ emissions for interstate transport prong 1, as discussed above. Based on (1) the downward trend in SO₂ emissions in Nevada and neighboring states; (2) SIP-approved State and local measures that limit existing and new facility emissions; and (3) the low ambient concentrations of SO₂ in Nevada and neighboring states, we propose to determine that the 2013 Nevada SIP revision demonstrates that SO₂ emissions in the State will not interfere with maintenance of the 2010 SO₂ NAAQS in any other state, per the requirements of prong 2 of CAA section 110(a)(2)(D)(i)(I).

III. Proposed Action

In light of the above analysis, the EPA is proposing to approve Nevada's infrastructure submittal for the 2010 SO₂ NAAQS as it pertains to section 110(a)(2)(D)(i)(I) of the CAA.

We will accept comments from the public on these proposals for the next 30 days and plan to follow with a final action. The deadline and instructions for submission of comments are provided in the DATE and ADDRESSES sections at the beginning of this proposed rule.

IV. Statutory and Executive Order Reviews

Under the Clean Air Act, 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 Clean Air Act. Accordingly, 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 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 Clean Air Act; and
• Does not provide the EPA with the discretionary authority to address disproportionate human health or environmental effects with practical, appropriate, 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 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).

List of Subjects in 40 CFR Part 52

• Environmental protection
• Air pollution control
• Incorporation by reference
• Intergovernmental relations
• Sulfur oxides

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

Footnotes