Document ID: EPA-R07-OAR-2021-0365-0001
Agency: epa
Document Type: Proposed Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: Kansas and Nebraska; Interstate Transport Prongs 1 and 2 for the 2010 Sulfur Dioxide Standard
Posted Date: 2021-06-15T04:00Z

[Federal Register Volume 86, Number 113 (Tuesday, June 15, 2021)]
[Proposed Rules]
[Pages 31645-31659]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-12501]

 ========================================================================
 Proposed Rules
                                                 Federal Register
 ________________________________________________________________________
 
 This section of the FEDERAL REGISTER contains notices to the public of 
 the proposed issuance of rules and regulations. The purpose of these 
 notices is to give interested persons an opportunity to participate in 
 the rule making prior to the adoption of the final rules.
 
 ========================================================================
 

  Federal Register / Vol. 86, No. 113 / Tuesday, June 15, 2021 / 
Proposed Rules  

[[Page 31645]]

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R07-OAR-2021-0365; FRL-10024-81-Region 7]

Interstate Transport Prongs 1 and 2 for the 2010 Sulfur Dioxide 
(SO2) Standard for Kansas and Nebraska

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve State Implementation Plan (SIP) submissions from Kansas and 
Nebraska addressing the Clean Air Act (CAA or Act) interstate transport 
SIP requirements for the 2010 Sulfur Dioxide (SO2) National 
Ambient Air Quality Standards (NAAQS). These submissions address the 
requirement that each SIP contain adequate provisions prohibiting air 
emissions that will have certain adverse air quality effects in other 
states. The EPA is proposing to approve portions of these 
infrastructure SIPs for the aforementioned states as containing 
adequate provisions to ensure that air emissions in the states will not 
significantly contribute to nonattainment or interfere with maintenance 
of the 2010 SO2 NAAQS in any other state.

DATES: Comments must be received on or before July 15, 2021.

ADDRESSES: The EPA has established a docket for this action under 
Docket ID No. EPA-R07-OAR-2021-0365. All documents in the docket are 
listed on the https://www.regulations.gov website. Although listed in 
the index, some information may not be publicly available, i.e., 
Confidential Business Information or other information whose disclosure 
is restricted by statute. Certain other material, such as copyrighted 
material, is not placed on the internet and will be publicly available 
only in hard copy form. Publicly available docket materials are 
available either electronically through www.regulations.gov or in hard 
copy at the Atmospheric Programs Section, Air Quality Planning Branch, 
Air and Radiation Division, U.S. Environmental Protection Agency, 
Region 7, 11201 Renner Boulevard, Lenexa, Kansas 66219. The EPA 
requests that if at all possible, you contact the person listed in the 
FOR FURTHER INFORMATION CONTACT section to schedule your inspection. 
The Regional Office's official hours of business are Monday through 
Friday 8:30 a.m. to 4:30 p.m., excluding federal holidays.

FOR FURTHER INFORMATION CONTACT: Ashley Keas, Environmental Protection 
Agency, Region 7 Office, Air Quality Planning Branch, 11201 Renner 
Boulevard, Lenexa, Kansas 66219 at (913) 551-7629, or by email at 
keas.ashley@epa.gov.

SUPPLEMENTARY INFORMATION: Throughout this document ``we,'' ``us,'' and 
``our'' refer to the EPA.

Table of Contents

I. Written Comments
II. Background
    A. Infrastructure SIPs
    B. 2010 1-Hour SO2 NAAQS Designations
III. Relevant Factors To Evaluate 2010 SO2 Interstate 
Transport SIPs
IV. States' Submissions and the EPA's Analysis
    A. Kansas
    1. State's Analysis
    2. The EPA's Prong 1 Evaluation
    3. The EPA's Prong 2 Evaluation
    B. Nebraska
    1. State's Analysis
    2. The EPA's Prong 1 Evaluation
    3. The EPA's Prong 2 Evaluation
V. Requirements for Approval of a SIP Revision
VI. Proposed Action
VII. Statutory and Executive Order Reviews

I. Written Comments

    Submit your comments, identified by Docket ID No. EPA-R07-OAR-2021-
0365 at https://www.regulations.gov. Once submitted, comments cannot be 
edited or removed from Regulations.gov. The EPA may publish any comment 
received to its public docket. Do not submit electronically any 
information you consider to be Confidential Business Information (CBI) 
or other information whose disclosure is restricted by statute. 
Multimedia submissions (audio, video, etc.) must be accompanied by a 
written comment. The written comment is considered the official comment 
and should include discussion of all points you wish to make. The EPA 
will generally not consider comments or comment contents located 
outside of the primary submission (i.e. on the web, cloud, or other 
file sharing system). For additional submission methods, the full EPA 
public comment policy, information about CBI or multimedia submissions, 
and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.

II. Background

A. Infrastructure SIPs

    On June 2, 2010, the EPA established a new primary 1-hour 
SO2 NAAQS of 75 parts per billion (ppb), based on a three-
year average of the annual 99th percentile of 1-hour daily maximum 
concentrations.\1\ The CAA requires states to submit, within three 
years after promulgation of a new or revised NAAQS, SIPs meeting the 
applicable ``infrastructure'' elements of sections 110(a)(1) and (2). 
One of these applicable infrastructure elements, CAA section 
110(a)(2)(D)(i), requires SIPs to contain ``good neighbor'' provisions 
to prohibit certain adverse air quality effects on neighboring states 
due to interstate transport of pollution.
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    \1\ 75 FR 35520 (June 22, 2010).
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    Section 110(a)(2)(D)(i) includes four distinct components, commonly 
referred to as ``prongs,'' that must be addressed in infrastructure SIP 
submissions. The first two prongs, which are codified in section 
110(a)(2)(D)(i)(I), require SIPs to contain adequate provisions that 
prohibit any source or other type of emissions activity in one state 
from contributing significantly to nonattainment of the NAAQS in 
another state (prong 1) and from interfering with maintenance of the 
NAAQS in another state (prong 2). The third and fourth prongs, which 
are codified in section 110(a)(2)(D)(i)(II), require SIPs to contain 
adequate provisions that prohibit emissions activity in one state from 
interfering with measures required to prevent significant deterioration 
of air quality in another state (prong 3) or from interfering with 
measures to protect visibility in another state (prong 4).

[[Page 31646]]

    In this action, the EPA is proposing to approve the prong 1 and 
prong 2 portions of infrastructure SIP submissions submitted by Kansas 
on April 7, 2020, and Nebraska on October 27, 2020, as demonstrating 
that the SIP contains adequate provisions to ensure that air emissions 
from sources in these states will not significantly contribute to 
nonattainment or interfere with maintenance of the 2010 SO2 
NAAQS in any other state or each other. All other applicable 
infrastructure SIP requirements for these SIP submissions are addressed 
in separate rulemakings.

B. 2010 1-Hour SO2 NAAQS Designations

    In this action, the EPA has considered information from the 2010 1-
hour SO2 NAAQS designations process, as discussed in more 
detail in Section IV of this document. For this reason, a brief summary 
of the EPA's designations process for the 2010 1-hour SO2 
NAAQS is included here.\2\ All technical support documents referenced 
throughout this document are also included in the docket for this 
action.
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    \2\ While designations may provide useful information for 
purposes of analyzing transport, the EPA notes that designations 
themselves are not dispositive of whether or not upwind emissions 
are impacting areas in downwind states. The EPA has consistently 
taken the position that CAA section 110(a)(2)(D) requires 
elimination of significant contribution and interference with 
maintenance in other states, and this analysis is not limited to 
designated nonattainment areas. Nor must designations for 
nonattainment areas have first occurred before states or the EPA can 
act under section 110(a)(2)(D). See e.g., Clean Air Interstate Rule, 
70 FR 25162, 25265 (May 12, 2005); Cross-State Air Pollution Rule, 
76 FR 48208, 48211 (Aug. 8, 2011); Final Response to Petition from 
New Jersey Regarding SO2 Emissions From the Portland 
Generating Station, 76 FR 69052 (Nov. 7, 2011) (finding facility in 
violation of the prohibitions of CAA section 110(a)(2)(D)(i)(I) with 
respect to the 2010 1-hour SO2 NAAQS prior to issuance of 
designations for that standard).
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    After the EPA establishes a new or revised NAAQS, the 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 the 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, the EPA has the authority to extend the deadline for 
completing designations by up to one year.
    The EPA Administrator signed the first round of designations 
(``round 1'') \3\ 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. See 78 FR 47191 (August 5, 2013). The EPA 
Administrator signed Federal Register documents for round 2 
designations \4\ on June 30, 2016 (81 FR 45039 (July 12, 2016)), and on 
November 29, 2016 (81 FR 89870 (December 13, 2016)), round 3 
designations \5\ on December 21, 2017 (83 FR 1098 (January 9, 2018)), 
and round 4 designations \6\ on December 21, 2020 (86 FR 16055 (March 
26, 2021)) and on April 8, 2021 (86 FR 19576 (April 14, 2021)).\7\
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    \3\ The term ``round'' in this instance refers to which ``round 
of designations.''
    \4\ EPA and state documents and public comments related to the 
round 2 final designations are in the docket at regulations.gov with 
Docket ID No. EPA-HQ-OAR-2014-0464 and at the EPA's website for 
SO2 designations at https://www.epa.gov/sulfur-dioxide-designations.
    \5\ EPA and state documents and public comments related to round 
3 final designations are in the docket at regulations.gov with 
Docket ID No. EPA-HQ-OAR-2017-0003 and at the EPA's website for 
SO2 designations at https://www.epa.gov/sulfur-dioxide-designations.
    \6\ EPA and state documents and public comments related to round 
4 final designations are in the docket at regulations.gov with 
Docket ID No. EPA-HQ-OAR-2020-0037 and at the EPA's website for 
SO2 designations at https://www.epa.gov/sulfur-dioxide-designations.
    \7\ The Round 4 2010 SO2 NAAQS designations action 
was signed by then EPA Administrator, Andrew Wheeler, on December 
21, 2020, pursuant to a court-ordered deadline of December 31, 2020. 
For administrative purposes only, and in compliance with 
requirements of the Office of the Federal Register, Acting 
Administrator Jane Nishida re-signed the same action on March 10, 
2021 for publication in the Federal Register.
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    At the time of this proposed action, there are no nonattainment 
areas for the 2010 1-hour SO2 NAAQS in Kansas or Nebraska. 
There are two areas designated as unclassifiable, one in Kansas and one 
in Nebraska, the remaining areas in these states are designated as 
attainment/unclassifiable.

III. Relevant Factors To Evaluate 2010 SO2 Interstate Transport SIPs

    Although SO2 is emitted from a similar universe of point 
and nonpoint sources, interstate transport of SO2 is unlike 
the transport of fine particulate matter (PM2.5) or ozone, 
in that SO2 is not a regional pollutant and does not 
commonly contribute to widespread nonattainment over a large (and often 
multi-state) area. The transport of SO2 is more analogous to 
the transport of lead (Pb) because its physical properties result in 
localized pollutant impacts very near the emissions source. However, 
ambient concentrations of SO2 do not decrease as quickly 
with distance from the source as Pb because of the physical properties 
and typical release heights of SO2. Emissions of 
SO2 travel farther and have wider ranging impacts than 
emissions of Pb but do not travel far enough to be treated in a manner 
similar to ozone or PM2.5. The approaches that the EPA has 
adopted for ozone or PM2.5 transport are too regionally 
focused and the approach for Pb transport is too tightly circumscribed 
to the source. SO2 transport is therefore a unique case and 
requires a different approach.
    Given the physical properties of SO2, the EPA selected 
the ``urban scale''--a spatial scale with dimensions from 4 to 50 
kilometers (km) from point sources--given the usefulness of that range 
in assessing trends in both area-wide air quality and the effectiveness 
of large-scale pollution control strategies at such point sources.\8\ 
The EPA's selection of this transport distance for SO2 is 
based upon 40 CFR part 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 
the 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. As such, the EPA utilized an assessment up to 50 km 
from point sources in order to assess trends in area-wide air quality 
that might impact downwind states.
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    \8\ For the definition of spatial scales for SO2, 
please see 40 CFR part 58, appendix D, section 4.4 (``Sulfur Dioxide 
(SO2) Design Criteria''). For further discussion on how 
the EPA is applying these definitions with respect to interstate 
transport of SO2, see the EPA's proposal on Connecticut's 
SO2 transport SIP. 82 FR 21351, 21352, 21354 (May 8, 
2017).
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    As discussed in Section IV of this proposed action, the EPA first 
reviewed each state'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. The EPA 
then conducted a weight of evidence analysis, including review of each 
state's submission and other available information, including air 
quality, emission sources and emission trends within the state and in 
bordering states to which it could potentially contribute or 
interfere.\9\
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    \9\ This proposed approval action is based on the information 
contained in the administrative record for this action and does not 
prejudge any other future EPA action that may make other 
determinations regarding any of the subject state's air quality 
status. Any such future actions, such as area designations under any 
NAAQS, will be based on their own administrative records and the 
EPA's analyses of information that becomes available at those times. 
Future available information may include, and is not limited to, 
monitoring data and modeling analyses conducted pursuant to the 
EPA's SO2 Data Requirements Rule (80 FR 51052, August 21, 
2015) and information submitted to the EPA by states, air agencies, 
and third party stakeholders such as citizen groups and industry 
representatives.

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[[Page 31647]]

IV. States' Submissions and EPA's Analysis

    In this section, we provide an overview of each state's 2010 
SO2 transport analysis, as well as the EPA's evaluation of 
prongs 1 and 2 for each state. Table 1 shows emission trends for the 
states addressed in this document along with their neighboring 
states.\10\ Table 2 shows ambient air monitoring data for monitors 
located within 50 km of the borders of either Kansas or Nebraska. Table 
3 shows emissions trends for sources in Kansas and Nebraska emitting 
over 100 tons per year (tpy) located within 50 km of the border with 
another state. Tables 1, 2 and 3 will be referenced as part of the 
EPA's analysis for each state.
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    \10\ This emissions trends information was derived from the 
EPA's web page https://www.epa.gov/air-emissions-inventories/air-pollutant-emissions-trends-data.

                                                         Table 1--Statewide SO2 Emission Trends
                                                                   [In tons per year]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                          SO2 reduction,
                          State                                2000            2005            2010            2015            2019        2000-2019 (%)
 
--------------------------------------------------------------------------------------------------------------------------------------------------------
Colorado................................................         115,122          80,468          60,459          28,860          17,045              85
Iowa....................................................         265,005         222,419         142,738          84,932          64,294              76
Kansas..................................................         148,416         199,006          80,267          36,828          24,855              83
Missouri................................................         401,287         425,167         321,059         158,998         110,888              72
Nebraska................................................          86,894         121,785          77,898          63,237          51,886              40
Oklahoma................................................         145,862         169,464         136,348          99,095          45,996              68
South Dakota............................................          41,120          28,579          16,202          11,975           5,093              88
Wyoming.................................................         141,439         122,453          91,022          53,335          42,191              70
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                    Table 2--SO2 Monitor Values Within 50 km of the Nebraska or Kansas Border
----------------------------------------------------------------------------------------------------------------
                                                 Distance to  Kansas      Distance to  Nebraska
                                               border (km) * (nearest    border (km) * (nearest      2017-2019
         State/area               Site ID         state listed for          state listed for       design value
                                                monitors in  Kansas)     monitors in  Nebraska)     (ppb) \11\
----------------------------------------------------------------------------------------------------------------
South Dakota/Sioux City.....       461270001  305.....................  10......................               3
Kansas/Wyandotte County.....       202090021  2 (Missouri)............  114.....................               6
Nebraska/Omaha..............       310550053  147.....................  0.5 (Iowa)..............              41
Nebraska/Omaha..............       310550019  138.....................  4.5 (Iowa)..............              24
Nebraska/Omaha..............       310550057  146.....................  1.5 (Iowa)..............              34
Missouri/Jackson County.....       290950034  3.......................  118.....................              10
Oklahoma/Ponca City.........       400710604  33......................  367.....................              28
Oklahoma/Enid...............       400470555  54......................  387.....................              48
----------------------------------------------------------------------------------------------------------------
* All distances throughout this document are approximations.

                               Table 3--SO2 Emission Trends for Kansas and Nebraska Sources Within 50 km of a State Border
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                                                                                                        SO2 emissions (tons)                   % change
          State/county              Facility name        EIS       Distance to  nearest ----------------------------------------------------------------
                                                     facility ID        state (km)           2011         2014         2017         2019      2011-2019
--------------------------------------------------------------------------------------------------------------------------------------------------------
Kansas/Johnson.................  AGC Flat Glass....      4538011  18, Missouri.........       243.83       154.51       157.42       133.06       -45.43
Kansas/Linn....................  Evergy--La Cygne..      5367811  3, Missouri..........    17,872.15    12,639.08       619.07       719.98       -95.97
Kansas/Douglas.................  Evergy--Lawrence..      4827111  44, Missouri.........     2,792.76     1,845.46       295.11       471.72       -83.11
Kansas/Wyandotte...............  Kansas City BPU--       4633811  0.5, Missouri........     5,989.47     5,332.61       904.01     1,203.00       -79.91
                                  Nearman.
Nebraska/Otoe..................  Nebraska City           7303711  0.3, Iowa............    17,334.65    16,134.40    15,950.20    10,386.51       -40.08
                                  Station.
Nebraska/Douglas...............  North Omaha             6732411  0.3, Iowa............    14,069.34    11,244.90     7,896.85     5,792.82       -58.83
                                  Station.
Nebraska/Cass..................  Ash Grove Cement        7287311  24, Iowa.............     1,067.12     1,250.77       694.12       681.44       -36.14
                                  Company.
Nebraska/Dodge.................  Lon D Wright Power      7766111  33, Iowa.............     1,399.76     2,231.52       926.23       985.08       -29.63
                                  Plant.
Nebraska/Kimball...............  Clean Harbors           7768011  17, Colorado.........         0.62       222.81       221.36       205.93         \12\
                                  Environmental                                                                                                  33114.1
                                  Services.
Nebraska/Scotts Bluff..........  Western Sugar           7767911  35, Wyoming..........       151.66       149.08       176.80       144.71        -4.58
                                  Cooperative.
Nebraska/Douglas...............  Douglas County          7699311  25, Iowa.............       111.98       102.53       131.04       164.59        46.98
                                  Recycling
                                  Landfill.
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 31648]]

A. Kansas
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    \11\ Data retrieved from the EPA's https://www.epa.gov/air-trends/air-quality-design-values#report.
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1. State's Analysis
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    \12\ The EPA notes that emissions for Clean Harbors 
Environmental Services decreased by 7.5% from 2014 to 2019.
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    In its SIP submittal, Kansas conducted a weight of evidence 
analysis to examine whether SO2 emissions from Kansas 
adversely affect attainment or maintenance of the 2010 SO2 
NAAQS in downwind states.\13\ Kansas evaluated potential air quality 
impacts on areas outside the state through an assessment of whether 
SO2 emissions from sources located within 50 km of Kansas' 
borders may have associated interstate transport impacts. The State's 
analysis included SO2 emissions information in the state, 
with specific focus on sources and counties located within 50 km of 
Kansas' borders. Of the 11 facilities in Kansas with SO2 
emissions greater than 100 tpy, only four facilities are located within 
50 km of Kansas' borders: AGC Flat Glass (18 km from Missouri), 
Evergy--La Cygne (3 km from Missouri), Evergy--Lawrence (44 km from 
Missouri), and Kansas City BPU--Nearman (0.6 km from Missouri). Kansas 
provided an in-depth analysis for these four facilities by assessing 
current permitted emissions rates and existing control technologies. 
Kansas also evaluated an additional six facilities with SO2 
emissions greater than 10 tpy but less than 100 tpy, located within 50 
km of Kansas' borders. Kansas also reviewed meteorological conditions 
representative of SO2 sources near the state's border, and 
the distances from identified SO2 sources in Kansas to the 
nearest area that is not attaining the NAAQS or may have trouble 
maintaining the NAAQS in another state. Kansas also reviewed statewide 
emissions and ambient air monitoring trends. Finally, Kansas reviewed 
mobile source emissions data from highway and off-highway vehicles and 
population data in all of the Kansas counties which border other 
states. Based on this weight of evidence analysis, Kansas concluded 
that emissions from sources within the state will not contribute to 
nonattainment or interfere with maintenance of the 2010 SO2 
NAAQS in neighboring states.
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    \13\ See Kansas' SO2 interstate transport SIP as 
submitted in January 2020 in the docket for this action.
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2. The EPA's Prong 1 Evaluation
    The EPA proposes to find that Kansas' SIP meets the interstate 
transport requirements of CAA section 110(a)(2)(D)(i)(I), prong 1 for 
the 2010 SO2 NAAQS, as discussed below. To support our 
proposal, we completed a weight of evidence analysis which considers an 
evaluation of ambient air quality data and of available information for 
certain emission sources near the Kansas border, as well as available 
modeling results for sources in Kansas or neighboring states within 50 
km of Kansas' borders. Based on that analysis, we propose to find that 
Kansas will not significantly contribute to nonattainment of the 2010 
SO2 NAAQS in any other state.
    To assess ambient air quality, the EPA reviewed monitoring data in 
Kansas and neighboring states to see whether there were any monitoring 
sites, particularly near the Kansas border, with elevated 
SO2 concentrations that might warrant further investigation 
with respect to interstate transport of SO2 from emission 
sources in Kansas to a neighboring state near any given monitor. We 
reviewed 2017-2019 SO2 design value concentrations at 
monitors with data sufficient to produce valid 1-hour SO2 
design values for Kansas and neighboring states.\14\ In Table 2, we 
have included all monitors in each neighboring state and in Kansas 
within 50 km of the Kansas border. As shown, there are no violating 
design values in Kansas or neighboring states within 50 km of the state 
border. In Kansas' analysis, the state reviewed its potential impact on 
the existing 2010 SO2 nonattainment area in Jackson County, 
Missouri, which is the only designated nonattainment area within 50 km 
of Kansas' borders.
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    \14\ Id.
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    The data presented in Table 2 shows that Kansas has one 
SO2 monitor within 50 km of its borders, in Wyandotte 
County. The 2017-2019 design value for this monitor is 6 ppb, or 8% of 
the 75 ppb level of the NAAQS. Two monitors in neighboring states are 
located within 50 km of the Kansas border, and these monitors recorded 
SO2 design values ranging between 13% and 37% of the level 
of the 2010 SO2 NAAQS. Thus, these air quality data do not, 
by themselves, indicate any particular location that would warrant 
further investigation with respect to SO2 emission sources 
that might significantly contribute to nonattainment in the bordering 
states. However, because the monitoring network is not necessarily 
designed \15\ to find all locations of high SO2 
concentrations, this observation indicates an absence of evidence of 
impact at these locations but is not sufficient evidence by itself of 
an absence of impact at all locations in the neighboring states. We 
have therefore considered additional evidence to support our conclusion 
that Kansas will not significantly contribute to nonattainment of the 
2010 SO2 NAAQS in any other state.
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    \15\ State monitoring networks must meet the minimum monitoring 
requirements contained in appendix D to 40 CFR part 58. 
Specifically, section 4.4 of appendix D outlines the minimum 
monitoring requirements for SO2 monitoring based on 
population weighted emissions. Monitors sited to meet the minimum 
monitoring requirements are sited for a number of reasons (e.g. 
measuring a source's maximum contribution, measuring background 
concentrations, monitoring population exposure, etc.) and may not 
necessarily capture maximum impacts from specific sources. However, 
data from these monitors may still provide useful evidence in the 
context of interstate transport.
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    In the next step of our weight of evidence analysis, the EPA 
evaluated available modeling results for sources in Kansas and in the 
adjacent states that are within 50 km of the Kansas border. The purpose 
for evaluating modeling for sources in Kansas within 50 km of the 
Kansas border is to determine whether these sources are, either on 
their own or in conjunction with other sources near the border, 
impacting a violation of the 2010 1-hour SO2 NAAQS in 
another state. The purpose of evaluating modeling results in adjacent 
states within 50 km of the Kansas border is to ascertain whether there 
are any modeled violations in neighboring states to which sources in 
Kansas could potentially be contributing.
    Table 4 provides a summary of the modeling results for two sources 
in Kansas which have available modeling information and are located 
within 50 km of another state: Evergy--La Cygne Generating Station (La 
Cygne) and the Board of Public Utilities Nearman Creek Station 
(Nearman). The modeling analyses resulted in no modeled violations of 
the 2010 1-hour SO2 NAAQS within the modeling domain for 
each facility. The emission trends for these facilities are also 
provided in Table 3, and the EPA has verified that the most recent 
annual emissions are below the annual emissions from the years modeled 
at each modeled source. The modeling submitted by Kansas in September 
2015 for La Cygne was based on allowable emissions and resulted in a 
maximum impact of 52.6 ppb or 70% of the level of the NAAQS.\16\ Kansas

[[Page 31649]]

indicated in its SIP that Evergy La Cygne is comprised of two coal-
fired boilers, one of which is equipped with a wet lime scrubber with a 
95% efficiency for controlling SO2 emissions.\17\ The 
emissions limits associated with these controls were modeled by Kansas 
and resulted in a concentration gradient within the domain that does 
not lead the EPA to believe that there would be substantial impacts 
beyond the modeling domain. There are no SO2 sources in 
Missouri within 50 km of La Cygne around which the EPA would expect 
elevated concentrations to which La Cygne could contribute.
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    \16\ See the EPA's Technical Support Document for its Intended 
Round 2 Designations for the 2010 SO2 NAAQS for Kansas 
available at: https://www.epa.gov/sites/production/files/2016-03/documents/ks-epa-tsd-r2.pdf and the EPA's Technical Support Document 
for its Final Round 2 Designations for the 2010 SO2 NAAQS 
for Kansas available at: https://www.epa.gov/sites/production/files/2016-07/documents/r7_ks_final_designation_tsd_06302016.pdf.
    \17\ Pursuant to La Cygne's operating permit No. O-11952 issued 
on May 14, 2018, units 1 and 2 are subject to an emissions limit of 
0.10 pounds per Million British Thermal Units (lb/MMBtu) on a 30-day 
rolling average.
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    For Nearman, the EPA evaluated two sets of available modeling 
results. The first, depicted in Table 4, includes modeling submitted by 
the State of Kansas.\18\ That modeling was based on actual emissions 
from 2012-2014 and resulted in a maximum impact of 49.2 ppb, or 66% of 
the level of the NAAQS. The second set of modeling results was 
submitted by the State of Missouri and was the basis of the clean data 
determination for the Jackson County, Missouri 1-hour SO2 
nonattainment area. That modeling, depicted in Table 5 as associated 
with nearby sources in Missouri, included actual emissions for Nearman 
from 2016-2018.\19\ This modeling demonstrates that there are no 
violations in the designated Jackson County nonattainment area to which 
Kansas sources could contribute. Kansas explicitly reviewed the Jackson 
County, Missouri, 2010 1-hour SO2 nonattainment area, as 
part of its analysis and concluded that Kansas sources do not 
contribute to violations in the area as it is no longer experiencing 
violations of the NAAQS. Further, the EPA previously determined that 
the Jackson County, Missouri nonattainment area has attained the 
standard and thereby the EPA agrees with Kansas' conclusion that there 
are no violations in this area to which Kansas sources could 
contribute.\20\ Additionally, as shown in Table 2, the monitor in the 
Jackson County, Missouri nonattainment area is currently monitoring 
concentrations well below the level of the standard. Kansas indicated 
in its SIP that BPU-Nearman is comprised of two units, one of which is 
equipped with a circulating dry scrubber for SO2 
control.\21\ BPU-Nearman is also subject to the acid gas emissions 
limit of the Mercury and Air Toxics Standard (MATS) and opts to meet 
this limit by complying with the SO2 emissions limits 
spelled out in 40 CFR part 63, subpart UUUUU. Based on the downward 
trend in emissions since the modeled time period, specifically 
emissions from BPU-Nearman have decreased by approximately 80% from 
2011 to 2019, the EPA finds the available modeling to be a conservative 
estimate of current actual air quality and an indicator that the 
Jackson County, Missouri area is not likely to experience issues 
maintaining the standard in the future. Additionally, it is unlikely 
that the emissions from these facilities could increase in the future 
to such a degree as to significantly contribute to nonattainment in any 
other state.
---------------------------------------------------------------------------

    \18\ See the EPA's Technical Support Document for its Intended 
Round 2 Designations for the 2010 SO2 NAAQS for Kansas 
available at: https://www.epa.gov/sites/production/files/2016-03/documents/ks-epa-tsd-r2.pdf and the EPA's Technical Support Document 
for its Final Round 2 Designations for the 2010 SO2 NAAQS 
for Kansas available at: https://www.epa.gov/sites/production/files/2016-07/documents/r7_ks_final_designation_tsd_06302016.pdf.
    \19\ For more details on the modeling demonstration for Nearman 
and the nearby sources (i.e. sources in nearby Missouri) included in 
the modeling, see Determination of Attainment for the Jackson 
County, Missouri 1-Hour SO2 NAAQS and Redesignation of 
the Wyandotte County, Kansas Unclassifiable Area to Attainment/
Unclassifiable, 85 FR 41193, July 9, 2020.
    \20\ See Id.
    \21\ Pursuant to Nearman's operating permit No. O-14125, Unit 
001 is subject to an annual SO2 emission limit of 3 lb/
MMBtu [K.A.R. 28-19-31(c) and 40 CFR 60.45(g)(2)]; 0.8 lb/MMBtu 
derived from liquid fossil fuel [NSPS Subpart D40 CFR 60.43(a)(2)]; 
1.2 lb/MMBtu derived from solid fossil fuel [NSPS Subpart D40 CFR 
60.43(a)(1)].

                Table 4--Kansas Sources With Modeling Data Located Within 50 km of Another State
----------------------------------------------------------------------------------------------------------------
                                                                                 Modeled 99th
                                              Distance from                     percentile  1-
                                    2020        source to    Other facilities  hour SO2 maximum     Model grid
 Kansas source      County       emissions    Kansas border    included  in      concentration     extends into
                                  (tons) *        (km)           modeling            (ppb)        another state?
 
----------------------------------------------------------------------------------------------------------------
La Cygne......  Linn..........          725             2.8  None............  52.60 (based on   No.
                                                                                allowable
                                                                                emissions).
Nearman.......  Wyandotte.....        1,211            0.77  Numerous          49.24 (based on   Yes (into
                                                              facilities        2012-2014         Jackson and
                                                              located in        actual            Platte County,
                                                              Jackson County,   emissions for     Missouri).
                                                              Missouri.         all sources).
----------------------------------------------------------------------------------------------------------------
* Emissions data throughout this document were obtained using the EPA's Emissions Inventory System (EIS)
  Gateway.

    Table 5 provides a summary of the available modeling results for 
sources with annual emissions of greater than 100 tons per year based 
on the latest available emissions inventory in neighboring states which 
are located within 50 km of Kansas: Evergy Hawthorn Generating Station 
(Hawthorn), Audubon Materials (Audubon), and Empire Asbury in Missouri, 
and Continental Carbon Black Production Facility in Ponca City, 
Oklahoma. As stated above, we consider the air quality near these 
sources in our analysis because, as a result of the localized nature of 
SO2 as a pollutant, it is near these sources that sources in 
Kansas are more likely to contribute to a violation of the standard.
    For Hawthorn and Audubon, the EPA similarly evaluated the modeling 
results of the clean data determination modeling for the Jackson 
County, Missouri 1-hour SO2 nonattainment area, in which 
actual emissions for Hawthorn and Audubon were explicitly included. 
This modeling demonstrates that there are no violations in the 
designated Jackson County nonattainment area to which Kansas sources 
could contribute.\22\
---------------------------------------------------------------------------

    \22\ See Determination of Attainment for the Jackson County, 
Missouri 1-Hour SO2 NAAQS and Redesignation of the 
Wyandotte County, Kansas Unclassifiable Area to Attainment/
Unclassifiable, 85 FR 41193, July 9, 2020.
---------------------------------------------------------------------------

    The modeling submitted by Missouri for the Empire Asbury facility 
was based on actual emissions and resulted in a maximum impact of 39 
ppb, or 52% of the level of the NAAQS.\23\ The Empire Asbury facility, 
located 2.5 km from the Kansas border, reported zero emissions in 2020 
and officially retired in March

[[Page 31650]]

2020.\24\ Additionally, there are no Kansas sources located within 50 
km of the Empire Asbury facility. The modeling submitted by Oklahoma 
for the Continental Carbon facility in Kay, Oklahoma was based on 
actual emissions and resulted in a maximum impact of 65.1 ppb, or 87% 
of the level of the NAAQS.\25\ However, the emissions for this facility 
have decreased from 5,893 tons in 2014 (the highest year in the modeled 
period) to 2,995 tons in 2019. Additionally, the Continental Carbon 
facility is located 37 km from the Kansas border and there are no 
sources in Kansas within 50 km of the Continental Carbon facility. The 
most recent available annual emissions for each source are also 
provided in Table 5, and the EPA has verified that the most recent 
annual emissions are below the annual emissions from the years modeled 
at each modeled source. For these reasons, the EPA finds there are no 
areas with modeled violations within 50 km of the Kansas border to 
which Kansas sources could be contributing.
---------------------------------------------------------------------------

    \23\ See the EPA's Technical Support Document for its Intended 
Round 3 Designations for the 2010 SO2 NAAQS for Missouri 
available at: https://www.epa.gov/sites/production/files/2017-08/documents/22_mo_so2_rd3-final.pdf and the EPA's Technical Support 
Document for its Final Round 3 Designations for the 2010 
SO2 NAAQS for Missouri available at: https://www.epa.gov/sites/production/files/2017-12/documents/22-mo-so2-rd3-final.pdf.
    \24\ In a letter dated December 3, 2019, from Liberty Utilities 
to the State of Missouri, Liberty Utilities requested that all air 
permits for the Empire Asbury facility become void on the permanent 
retirement date of March 1, 2020. This letter is included in the 
docket for this action.
    \25\ See the EPA's Technical Support Document for its Intended 
Round 3 Designations for the 2010 SO2 NAAQS for Oklahoma 
available at: https://www.epa.gov/sites/production/files/2017-12/documents/33-ok-so2-rd3-final.pdf and the EPA's Technical Support 
Document for its Final Round 3 Designations for the 2010 
SO2 NAAQS for Oklahoma available at: https://www.epa.gov/sites/production/files/2017-12/documents/33-ok-so2-rd3-final.pdf.

                                    Table 5--Other States' Sources With Modeling Data Located Within 50 km of Kansas
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         Distance from                            Modeled 99th
                                                               2019        source to      Other facilities      percentile 1-hour    Model grid extends
              Source                        County          emissions    Kansas border      included  in           SO2 maximum       into another state?
                                                              (tons)         (km)             modeling         concentration (ppb)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Evergy Hawthorn...................  Jackson, Missouri....  [caret] 929             9.7  Nearman (Wyandotte    43.47 (based on 2016- No.
                                                                                         County, Kansas);      2018 actual
                                                                                         other sources <100    emissions for all
                                                                                         tons per year.        sources).
Audubon Materials, LLC Sugar Creek  Jackson, Missouri....          229              15  Nearman (Wyandotte    43.47 (based on 2016- No.
 Plant.                                                                                  County, Kansas);      2018 actual
                                                                                         other sources <100    emissions for all
                                                                                         tons per year of      sources).
                                                                                         SO2.
Empire Asbury.....................  Jasper/Barton            [caret] 0             2.5  Other Missouri        39.0 (based on 2012-  Yes (into Crawford
                                     Counties, Missouri.                                 sources <100 tons     2014 actual           and Cherokee
                                                                                         per year of SO2.      emissions for all     Counties in
                                                                                                               sources).             Kansas).
Continental Carbon Black            Kay, Oklahoma........        2,995              37  Oklahoma Gas &        65.1 (based on 2012-  No.
 Production Facility--Ponca City                                                         Electric, Sooner      2014 actual
 Plant.                                                                                  Generating Station    emissions for all
                                                                                         (Noble County,        sources).
                                                                                         Oklahoma), Phillips
                                                                                         66 Company--Ponca
                                                                                         City Refinery (Kay
                                                                                         County, Oklahoma),
                                                                                         2 other Kay County,
                                                                                         Oklahoma sources
                                                                                         <100 tons per year
                                                                                         of SO2.
--------------------------------------------------------------------------------------------------------------------------------------------------------
[caret] Based on 2020 emissions.

    The EPA proposes to find that the modeling results summarized in 
Tables 4 and 5, which provide evidence that air quality near certain 
larger sources in other states is attaining the NAAQS, when weighed 
along with the other factors in this document, support the EPA's 
proposed conclusion that sources in Kansas will not significantly 
contribute to nonattainment of the 2010 1-hour SO2 NAAQS in 
any other state.
    The next step in our weight of evidence analysis is to assess 
certain other sources near the border for which we do not have 
available modeling or monitoring data. As noted in Section III of this 
document, the EPA finds that it is appropriate to examine the impacts 
of emissions from stationary sources in Kansas in distances ranging 
from 0 km to 50 km from the facility, based on the ``urban scale'' 
definition contained in appendix D to 40 CFR part 58, section 4.4. 
Kansas assessed point sources up to 50 km from state borders to 
evaluate trends and SO2 concentrations in area-wide air 
quality. The list of sources emitting 100 tpy \26\ or more of 
SO2 within 50 km from state borders without available 
modeling data, is shown in Table 6.
---------------------------------------------------------------------------

    \26\ Kansas limited its analysis to Kansas sources of 
SO2 emitting at least 100 tpy. We agree with Kansas' 
choice to limit its analysis in this way, because in the absence of 
special factors, for example the presence of a nearby larger source, 
a high concentration of smaller sources in an area, or unusual 
physical factors, Kansas sources emitting less than 100 tpy can 
appropriately be presumed to not be causing or contributing to 
SO2 concentrations above the NAAQS.

               Table 6--Kansas SO2 Sources With No Available Modeling Data Near Neighboring States
----------------------------------------------------------------------------------------------------------------
                                                                                                    Neighboring
                                                                                   Distance to     state source
                                                   2019 SO2       Distance to        nearest           2019
         Kansas source            Facility ID      emissions     Kansas border     neighboring       emissions
                                                    (tons)           (km)       state SO2 source  (tons) [caret]
                                                                                      (km)
----------------------------------------------------------------------------------------------------------------
AGC Flat Glass................         4538011           133.1              19  50 (Evergy           [caret] 929
                                                                                 Hawthorn).
Evergy Lawrence...............         4827111   [caret] 225.5              44  55 (Evergy           [caret] 812
                                                                                 Iatan).
----------------------------------------------------------------------------------------------------------------
[caret] Based on 2020 emissions.

    Table 6 shows the distance from the sources listed therein to the 
nearest out-of-state source emitting above 100 tpy of SO2, 
because elevated levels of SO2, to which SO2 
emitted in Kansas may have a downwind impact, are most likely to be 
found near such sources. As shown in Table 6, the distance between the 
sources in Kansas and the nearest

[[Page 31651]]

sources emitting over 100 tpy in Missouri is greater than or equal to 
50 km. Additionally, Kansas evaluated the current operations and 
control equipment at the AGC Flat Glass and Evergy Lawrence facilities. 
In its SIP, Kansas indicated that the AGC Flat Glass facility operates 
a glass melting furnace which is equipped with dry sorbent injection 
for control of SO2.\27\ The Evergy Lawrence facility is 
comprised of two units which are both equipped with high-efficiency 
scrubbers for SO2 control.\28\ Kansas evaluated available 
meteorological data to determine the wind patterns near AGC Flat Glass 
and Evergy Lawrence. Kansas included wind roses for the Olathe Johnson 
County airport that depict the predominant wind pattern in the area as 
being from the South-Southwest blowing emissions from AGC Flat Glass 
away from Missouri.\29\ Kansas included wind roses for the Lawrence 
Municipal airport that depict the predominant wind pattern in the area 
as being from the South-Southeast blowing emissions from Evergy 
Lawrence away from the Jackson County nonattainment area.\30\
---------------------------------------------------------------------------

    \27\ Pursuant to AGC's operating permit No. O-10871, unit EU-001 
is subject to an SO2 emission limit of 2.2 lb of 
SO2 per ton of glass produced on a 30-day rolling 
average, and 262.8 tons of SO2 emissions per rolling 
consecutive 12-month period.
    \28\ Pursuant to Evergy Lawrence's operating permit No. O-11856 
issued on February 14, 2018, units 4 and 5 are subject to an 
emissions limit of 0.15 lb/MMBtu on a 30-day rolling average.
    \29\ See Chapter 3 of Kansas' SO2 Transport SIP 
Submittal included in the docket for this action for the wind rose 
graphics referenced by Kansas.
    \30\ See id.
---------------------------------------------------------------------------

    Given the large distance between the cross-state sources, the 
localized nature of SO2, and the wind rose analysis provided 
by Kansas, the EPA agrees it is unlikely that emissions from AGC Flat 
Glass or Evergy Lawrence in Kansas could interact with emissions from 
Evergy Hawthorn or Evergy Iatan in Missouri in such a way as to cause a 
violation of the NAAQS in Missouri. Additionally, based on the distance 
from the Kansas sources to the border and the overall wind patterns in 
the area, the EPA finds it unlikely that the sources in Kansas could on 
their own cause a violation in Missouri.
    The EPA also reviewed the location of sources for which modeling 
information was not available in neighboring states emitting more than 
100 tpy of SO2 and located within 50 km of the Kansas 
border, as shown in Table 7. This is because elevated levels of 
SO2, to which SO2 emitted in Kansas may have a 
downwind impact, are most likely to be found near such sources.

              Table 7--Neighboring State SO2 Sources With No Available Modeling Data Near Kansas *
----------------------------------------------------------------------------------------------------------------
                                                                                  Distance to
                                                  2019 SO2       Distance to    nearest Kansas    Kansas source
            Source               Facility ID      emissions     Kansas border   SO2 source (km)   2020 emissions
                                                   (tons)           (km)                              (tons)
----------------------------------------------------------------------------------------------------------------
Evergy Iatan Generating               6795111   [caret] 811.6             0.7  39 (Kansas City             1,211
 Station (Missouri).                                                            BPU-Nearman).
Exide Technologies Canon               331492           158.5             7.1  106 (Kansas City            1,211
 Hollow (Missouri).                                                             BPU-Nearman).
----------------------------------------------------------------------------------------------------------------
* We have not included sources that are duplicative of those in Table 6.
[caret] Based on 2020 emissions.

    As shown in Table 7, the shortest distance between any pair of 
these sources is 39 km (between Evergy Iatan in Missouri and Nearman in 
Kansas). The available modeling data for the Nearman facility, 
referenced in Tables 4 and 5, indicates that Nearman does not 
significantly contribute to violations in nearby areas in Missouri as 
there are no modeled violations in Missouri. Kansas evaluated available 
meteorological data to determine the wind patterns near Nearman. Kansas 
included wind roses for the Kansas City downtown airport that depict 
the predominant wind pattern in the area around Nearman as being from 
the South-Southwest blowing emissions from Nearman away from the 
Jackson County nonattainment area.\31\ Additionally, based on the 
distance between cross-state sources as well as the overall wind 
patterns in the area as referenced by Kansas, the EPA agrees that it is 
unlikely that emissions from Nearman could interact with emissions from 
Every Iatan or Exide Technologies in such a way as to cause a violation 
in Missouri.
---------------------------------------------------------------------------

    \31\ See Id.
---------------------------------------------------------------------------

    Kansas also evaluated two sources located within 50 km of its 
borders that emitted above 80 tpy but below 100 tpy. The CRNF-
Coffeyville and CRRM-Refinery facilities are each located 5 km from the 
Kansas border with Oklahoma. CRNF-Coffeyville emitted 83 tons of 
SO2 in 2018. CRRM-Refinery emitted 93 tons of SO2 
in 2018. There are no sources in Oklahoma within 50 km of these sources 
such that their emissions could interact to impact a violation of the 
NAAQS. Kansas also included wind roses for the Coffeyville Municipal 
airport that depict the predominant wind pattern in the area as being 
from the South blowing emissions from the Kansas sources away from 
Oklahoma and further into Kansas.\32\ Given the localized nature of 
SO2 and the overall wind pattern in the area as referenced 
by Kansas, the EPA agrees it is unlikely that the CRNF-Coffeyville and 
CRRM-Refinery facilities could on their own cause or contribute to a 
violation in the nearby State of Oklahoma.
---------------------------------------------------------------------------

    \32\ See Id.
---------------------------------------------------------------------------

    This information together with the localized range of potential 1-
hour SO2 impacts indicates that there are no additional 
locations in neighboring states that would warrant further 
investigation with respect to Kansas SO2 emission sources 
that might contribute to problems with attainment of the 2010 
SO2 NAAQS.
    Kansas also included information on mobile source emissions and 
population in its border counties. Kansas indicated that SO2 
emissions from mobile sources are controlled through federally mandated 
fuel standards which limit sulfur concentrations at the refinery level. 
Kansas notes that mobile emissions are disbursed in small quantities 
over large geographic areas leading to greater dispersion before 
crossing state borders. Additionally, Kansas expects further reductions 
in SO2 emissions from this sector as the EPA continues to 
regulate emissions from mobile sources along with regular fleet 
turnover to cleaner vehicles. The EPA agrees that because emissions 
from non-point sources in other source categories such as mobile 
emissions are more dispersed throughout the State, emissions from other 
source categories such as mobile sources are less likely to cause high 
ambient concentrations when compared to a point source on a ton-for-ton 
basis.
    In conclusion, for interstate transport prong 1, we reviewed 
ambient SO2 monitoring data and available information for 
SO2 emission sources within 50 km of the Kansas border, as 
well as available modeling results for

[[Page 31652]]

sources in Kansas and in adjacent states within 50 km of the Kansas 
border. Based on this analysis, we propose to determine that Kansas 
will not significantly contribute to nonattainment of the 2010 
SO2 NAAQS in any other state, per the requirements of CAA 
section 110(a)(2)(D)(i)(I).
3. The EPA's Prong 2 Evaluation
    In its prong 2 analysis, Kansas reviewed potential SO2 
impacts on designated maintenance areas. The EPA interprets CAA section 
110(a)(2)(D)(i)(I) 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, 
rather than only former nonattainment, and thus current maintenance, 
areas. Kansas also performed a prong 2 analysis based on the EPA's 
interpretation, noting that monitors located near Kansas in neighboring 
states showed very low levels of SO2, emissions in Kansas 
and neighboring states have decreased indicating they should not be 
considered to have maintenance issues for this NAAQS. Kansas also 
referenced federal regulations which have resulted in and will continue 
to result in SO2 emissions decreases in Kansas and 
neighboring states.
    The EPA has reviewed Kansas' analysis and other available 
information on SO2 air quality, including federally 
enforceable regulations and emission trends to evaluate the state's 
conclusion that Kansas will not interfere with maintenance of the 2010 
SO2 NAAQS in downwind states. This evaluation builds on the 
analysis regarding significant contribution to nonattainment (prong 1), 
which evaluated monitored ambient concentrations of SO2 in 
Kansas and neighboring states, available modeling results, and the 
large distances between cross-state SO2 sources, the EPA is 
proposing to find that SO2 levels in neighboring states near 
the Kansas border do not indicate any inability to maintain the 
SO2 NAAQS that could be attributed in part to sources in 
Kansas. As shown in Table 1, the statewide SO2 emissions 
from Kansas and neighboring states have decreased substantially over 
time, per our review of the EPA's emissions trends data.\33\ From 2000 
to 2019, total statewide SO2 emissions decreased by the 
following proportions: Colorado (85% decrease), Kansas (83% decrease), 
Missouri (72% decrease), Nebraska (40% decrease), and Oklahoma (68% 
decrease). This trend of decreasing SO2 emissions does not 
by itself demonstrate that areas in Kansas and neighboring states will 
not have issues maintaining the 2010 SO2 NAAQS. However, as 
a piece of this weight of evidence analysis for prong 2, it provides 
further indication (when considered alongside low monitor values in 
neighboring states as depicted in Table 2) that such maintenance issues 
are unlikely. This is because the geographic scope of these reductions 
and their large sizes strongly suggest that they are not transient 
effects from reversible causes, and thus these reductions suggest that 
there is very low likelihood that a strong upward trend in emissions 
will occur that might cause areas presently in attainment to violate 
the NAAQS. These reductions have been caused by regulatory requirements 
in Kansas and the downwind states and by economic factors, such as low 
natural gas prices and the increasing supply of renewable energy, that 
are not likely to be reversed.\34\
---------------------------------------------------------------------------

    \33\ Additional emissions trends data are available at: https://www.epa.gov/air-emissions-inventories/air-pollutant-emissions-trends-data.
    \34\ Kansas provided information on emission reductions and 
control equipment for certain sources in its SIP and the EPA 
summarized this information in its prong 1 analysis.
---------------------------------------------------------------------------

    Kansas also identified EPA programs which, either directly or 
indirectly, have significantly reduced SO2 emissions in 
Kansas. These programs include: The Acid Rain program; the Cross-State 
Air Pollution Rule (CSAPR); Prevention of Significant Deterioration 
(PSD)/New Source Review (NSR) Permitting Programs; Heavy-Duty Diesel 
Rule; Mercury and Air Toxic Standards Rule (MATS); \35\ Regional Haze; 
\36\ Nonroad Diesel Rule; and the EPA's Tier 2 Motor Vehicle Emissions 
Standards and Gasoline Sulfur Control Requirements Rule. The EPA agrees 
that the federal regulations identified by Kansas have helped to reduce 
SO2 emissions from various sources in Kansas in addition to 
other federal regulations as detailed here. The EPA's Acid Rain Program 
set a permanent cap on the total amount of SO2 that may be 
emitted by electric generating units (EGUs) in the contiguous United 
States.\37\ CSAPR requires significant reductions in SO2 
emissions from power plants in the eastern half of the United States, 
including Kansas and neighboring states.\38\ MATS requires reductions 
of emissions of heavy metals which, as a co-benefit, reduce emissions 
of SO2, and establishes alternative numeric emission 
standards, including SO2 (as an alternate to hydrochloric 
acid).\39\ The EPA's Nonroad Diesel Rule will reduce sulfur levels from 
about 3,000 parts per million (ppm) to 15 ppm when fully 
implemented.\40\ The EPA's Heavy-Duty Engine and Vehicle Standards and 
Highway Diesel Fuel Sulfur Control Requirements (Heavy-Duty Diesel 
Rule) required refiners to start producing diesel fuel for use in 
highway vehicles with a sulfur content of no more than 15 ppm as of 
June 1, 2006.\41\ NSPS for various source categories, including but not 
limited to Industrial-Commercial-Institutional Steam Generating Units; 
\42\ Sulfuric Acid Plants; \43\ Stationary Gas and Combustion Turbines; 
\44\ Portland Cement Manufacturing; \45\ Electric Utility Steam 
Generating Units (Boilers); \46\ and Onshore Natural Gas 
Processing,\47\ establish standards which reduce SO2 
emissions.
---------------------------------------------------------------------------

    \35\ See 77 FR 9304.
    \36\ See 64 FR 35714.
    \37\ See 40 CFR parts 72 through 78.
    \38\ See 40 CFR part 97. See also 76 FR 48208.
    \39\ See 40 CFR parts 60 and 63. See also 77 FR 9304.
    \40\ See 40 CFR parts 9, 69, 80, 86, 89, 94, 1039, 1048, 1051, 
1065, and 1068. See also 69 FR 38958.
    \41\ See 40 CFR parts 69, 80, and 86. See also 66 FR 5002.
    \42\ See 40 40 CFR part 60, subpart Da and 40 CFR part 63. See 
also 77 FR 9304.
    \43\ See 40 CFR part 60, subparts A, D, E, F, G and H. See also 
36 FR 24876.
    \44\ See 40 CFR part 60, subparts GG and KKKK. See also 71 FR 
38482 and 44 FR 52792
    \45\ See 40 CFR parts 60 and 63. See also 75 FR 54970.
    \46\ See 40 CFR part 60, subpart Da and 40 CFR part 63. See also 
77 FR 9304.
    \47\ See 40 CFR part 60, subpart LLL. See also 77 FR 49490.
---------------------------------------------------------------------------

    In addition, the EPA's Tier 3 Motor Vehicle Emission and Fuel 
Standards Rule \48\ also reduce SO2 emissions by 
establishing gasoline sulfur standards that reduce SO2 
emissions from certain types of mobile sources. The EPA finds that 
these federal measures have and continue to lower SO2 
emissions, which, in turn, are expected to continue to support the 
EPA's proposed conclusion that SO2 emissions from Kansas 
will not contribute significantly to nonattainment or interfere with 
maintenance of the 2010 1-hour SO2 NAAQS in another state.
---------------------------------------------------------------------------

    \48\ See 40 CFR parts 79, 80, 85, 86, 600, 1036, 1037, 1039, 
1042, 1048, 1054, 1065, and 1066. See also 79 FR 23414.
---------------------------------------------------------------------------

    As noted in Kansas' submission, any future large sources of 
SO2 emissions will be addressed by Kansas' SIP-approved 
Prevention of Significant Deterioration (PSD) program.\49\ Future minor 
sources of SO2 emissions will be addressed by Kansas' minor 
new source review permit program.\50\ The permitting regulations 
contained within these programs should help ensure that

[[Page 31653]]

ambient concentrations of SO2 in neighboring states are not 
exceeded as a result of new facility construction or modification 
occurring in Kansas.
---------------------------------------------------------------------------

    \49\ See EPA's final action of the PSD portions of Kansas' SIP, 
at 80 FR 32017, June 4, 2015.
    \50\ Id.
---------------------------------------------------------------------------

    As previously mentioned, Kansas evaluated its potential impacts to 
the Jackson County, Missouri nonattainment area located near the Kansas 
border. As discussed in the EPA's prong 1 analysis, the modeling for 
the Jackson County area's clean data determination included sources in 
Kansas and did not show substantial impacts from Kansas sources to the 
Missouri area. Additionally, the EPA has determined the area attained 
the NAAQS through a clean data determination with the monitor in the 
area still showing values well below the level of the standard. For 
these reasons, the EPA finds that emissions from Kansas do not 
interfere with maintenance of the NAAQS in the Jackson County area as 
the area is not exhibiting difficulties in maintaining the standard.
    In conclusion, for interstate transport prong 2, we reviewed 
additional information about SO2 air quality and emission 
trends and Kansas' permitting regulations, as well as the technical 
information considered for interstate transport prong 1. We find that 
the combination of low ambient concentrations of SO2 in 
Kansas and neighboring states, the available modeling results, the 
large distances between cross-state SO2 sources, the 
downward trend in SO2 emissions from Kansas and neighboring 
states, and state measures that prevent new facility construction or 
modification in Kansas from causing SO2 exceedances in 
downwind states, indicates no interference with maintenance of the 2010 
SO2 NAAQS in other states. Accordingly, we propose to 
determine that Kansas SO2 emission sources will not 
interfere with maintenance of the 2010 SO2 NAAQS in any 
other state, per the requirements of CAA section 110(a)(2)(D)(i)(I).

B. Nebraska

1. State's Analysis
    In its SIP, Nebraska conducted a weight of evidence analysis to 
examine whether SO2 emissions from Nebraska adversely affect 
attainment or maintenance of the 2010 SO2 NAAQS in downwind 
states.\51\ Nebraska evaluated potential air quality impacts on areas 
outside the state through an assessment of whether SO2 
emissions from sources located within 50 km of Nebraska's borders may 
have associated interstate transport impacts. The State's analysis 
included SO2 emissions information in the state, with 
specific focus on sources and counties located within 50 km of 
Nebraska's borders. For the seven sources which emitted greater than 
100 tons per year of SO2 located within 50 km of Nebraska's 
borders, Nebraska provided an in-depth analysis by assessing current 
permitted emissions rates and existing control technologies. Nebraska 
also reviewed meteorological conditions representative of 
SO2 sources near the state's border, and the distances from 
identified SO2 sources in Nebraska to the nearest area that 
is not attaining the NAAQS or may have trouble maintaining the NAAQS in 
another state. Nebraska also reviewed statewide emissions and ambient 
air monitoring trends. Based on this weight of evidence analysis, 
Nebraska concluded that emissions within the state will not contribute 
to nonattainment or interfere with maintenance of the 2010 
SO2 NAAQS in neighboring states. Nebraska also noted that 
SO2 emissions within the state have been steadily decreasing 
over time, specifically noting a 49.7% decrease in point source 
emissions between 2006 and 2019. With regard to the interference with 
maintenance requirement, Nebraska discussed the low monitored ambient 
concentrations of SO2 in neighboring states in the period up 
to and including 2019. Based on this weight of evidence analysis, 
Nebraska concluded that emissions within the state will not 
significantly contribute to nonattainment or interfere with maintenance 
of the 2010 SO2 NAAQS in neighboring states.
---------------------------------------------------------------------------

    \51\ See Nebraska's SO2 interstate transport SIP as 
submitted in October 2020 in the docket for this action.
---------------------------------------------------------------------------

2. The EPA's Prong 1 Evaluation
    The EPA proposes to find that Nebraska's SIP meets the interstate 
transport requirements of CAA section 110(a)(2)(D)(i)(I), prong 1 for 
the 2010 SO2 NAAQS, as discussed below. To support our 
proposal, we completed a weight of evidence analysis which considers an 
evaluation of ambient air quality data and of available information for 
certain emission sources near the Nebraska border, as well as available 
modeling results for sources in Nebraska or neighboring states within 
50 km of Nebraska's borders. Based on that analysis, we propose to find 
that Nebraska will not significantly contribute to nonattainment of the 
2010 SO2 NAAQS in any other state.
    To assess ambient air quality, the EPA reviewed monitoring data in 
Nebraska and neighboring states to see whether there were any 
monitoring sites, particularly near the Nebraska border, with elevated 
SO2 concentrations that might warrant further investigation 
with respect to interstate transport of SO2 from emission 
sources in Nebraska to a neighboring state near any given monitor. We 
reviewed 2017-2019 SO2 design value concentrations at 
monitors with data sufficient to produce valid 1-hour SO2 
design values for Nebraska and neighboring states.\52\ In Table 2, we 
have included all monitors in each neighboring state and in Nebraska 
within 50 km of the Nebraska border. As shown, there are no violating 
design values at monitors in Nebraska or neighboring states within 50 
km of the state border. One area bordering Nebraska--Woodbury County, 
Iowa--has been designated unclassifiable. Later in this section, the 
EPA discusses modeling available for Woodbury County, Iowa (See Table 
10). There are no other areas designated as unclassifiable located 
within 50 km of Nebraska's borders. For these reasons and for reasons 
discussed later in this section, the EPA is proposing to find that 
emissions from Nebraska will not contribute significantly to 
nonattainment in any other state.
---------------------------------------------------------------------------

    \52\ Id.
---------------------------------------------------------------------------

    The data presented in Table 2 show that there are three Nebraska 
monitors located within 50 km of a neighboring state's border, and 
these monitors indicate design values between 32% to 55% of the NAAQS. 
One SO2 monitor was installed in Nebraska as a source-
oriented monitor (AQS Site ID: 310550057) and was sited to characterize 
the Omaha Public Power District's (OPPD) North Omaha Station (North 
Omaha), which is located in Douglas County, Nebraska and is within 50 
km of the Nebraska border with Iowa. The EPA designated Douglas County 
as attainment/unclassifiable as part of the Round 4 designations for 
the 2010 1-hour NAAQS.\53\ Table 8 provides the 3-year design value 
used to characterize the impacts from North Omaha. The 2017-2019 design 
value is 34 ppb, which is 45% of the 2010 SO2 NAAQS and 
provides evidence that there is not an air quality problem around the 
North Omaha facility. Therefore, it is unlikely that the North Omaha 
facility could significantly contribute to nonattainment of the 2010 1-
hour SO2 NAAQS in the nearby State of Iowa. In its SIP, 
Nebraska noted that the North Omaha facility currently operates two 
coal-fired units, using low-sulfur coal;

[[Page 31654]]

these units are to be converted to natural gas by 2023. Three coal-
fired units were retired in 2016 which resulted in a significant 
SO2 emissions decrease in that year. The emissions trends 
for this source are shown in Table 3. Nebraska also referenced the low 
design values at the monitors located in Omaha (as shown in Table 2) 
between the North Omaha facility and the Walter Scott Jr. facility in 
Iowa that similarly support the claim that the North Omaha facility is 
not causing or contributing to violations of the NAAQS in Iowa.\54\ The 
North Omaha facility was also included in a modeling demonstration for 
a nearby Iowa source. That modeling is discussed later in this section 
and provides further evidence that there are no violations in Iowa to 
which the North Omaha facility could contribute.
---------------------------------------------------------------------------

    \53\ See TSD Chapter 2: Final Round 4 Area Designations for the 
2010 1-Hour SO2 Primary National Ambient Air Quality 
Standard for Areas without Violating Monitors, at https://www.epa.gov/sites/production/files/2020-12/documents/02-rd4_so2d_tsd_for_areas_without_violating_monitors.pdf.
    \54\ For locations of monitors in relation to the sources in 
Nebraska and Iowa, please see map on page 21 of Nebraska's SIP as 
contained in the docket for this action.

                                 Table 8--Nebraska Sources With a Source-Oriented Monitor Within 50 km of Another State
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                        Distance from                       2017-2019
                                                                                      2020  emissions     source to                       monitor 3-year
                 Nebraska source                                County                     (tons)       Nebraska/Iowa       Site ID        design value
                                                                                                         border (km)                          (ppb)
--------------------------------------------------------------------------------------------------------------------------------------------------------
OPPD North Omaha................................  Douglas...........................           5,447               0.3        310550057               34
--------------------------------------------------------------------------------------------------------------------------------------------------------

    There is one monitor in a neighboring state located within 50 km of 
the Nebraska border, in Sioux City, South Dakota, and this monitor 
recorded an SO2 design value of 3 ppb, or 4% of the 2010 
SO2 NAAQS. Thus, these air quality data do not, by 
themselves, indicate any particular location that would warrant further 
investigation with respect to SO2 emission sources that 
might significantly contribute to nonattainment in the bordering 
states. However, because the monitoring network is not necessarily 
designed \55\ to find all locations of high SO2 
concentrations, this observation indicates an absence of evidence of 
impact at these locations but 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.
---------------------------------------------------------------------------

    \55\ State monitoring networks must meet the minimum monitoring 
requirements contained in appendix D to 40 CFR part 58. 
Specifically, section 4.4 of appendix D outlines the minimum 
monitoring requirements for SO2 monitoring based on 
population weighted emissions. Monitors sited to meet the minimum 
monitoring requirements are sited for a number of reasons (e.g., 
measuring a source's maximum contribution, measuring background 
concentrations, monitoring population exposure, etc.) and may not 
necessarily capture maximum impacts from specific sources. However, 
data from these monitors may still provide useful evidence in the 
context of interstate transport.
---------------------------------------------------------------------------

    In the next step of our weight of evidence analysis, the EPA 
evaluated available modeling results for sources in Nebraska and in the 
adjacent states that are within 50 km of the Nebraska border. The 
purpose of evaluating modeling for sources in Nebraska within 50 km of 
the Nebraska border is to determine whether these sources are, either 
on their own or in conjunction with other sources near the border, 
impacting a violation of the 2010 1-hour SO2 NAAQS in 
another state. The purpose of evaluating modeling results in adjacent 
states within 50 km of the Nebraska border is to ascertain whether 
there are any modeled violations in neighboring states to which sources 
in Nebraska could potentially be contributing.
    Table 9 provides a summary of the modeling results for one source 
in Nebraska for which we have available modeling information and is 
located within 50 km of another state: Omaha Public Power District's 
(OPPD) Nebraska City Station (Nebraska City).\56\ The modeling analysis 
for Nebraska City resulted in no modeled violations of the 2010 1-hour 
SO2 NAAQS within the modeling domain. The emissions trends 
for this source are included in Table 3. The most recent available 
annual emissions at Nebraska City are also provided in Table 9, and the 
EPA has verified that the most recent annual emissions are below the 
annual emissions from the years modeled for Nebraska City. The nearest 
source in a neighboring state emitting greater than 100 tpy is the 
Walter Scott Jr., Energy Center, located 66 km North of Nebraska City. 
In its SIP, Nebraska indicated that Nebraska City is comprised of two 
coal-fired units, one of which (Unit 2) is fitted with a dry flue gas 
desulfurization (scrubber) system to control SO2 emissions. 
Emissions at Nebraska City have decreased approximately 36% from 2014. 
Based on the large distance between cross-state sources, the localized 
nature of SO2, and the available modeling information, the 
EPA agrees that Nebraska City is not likely contributing to violations 
in Iowa as there are no modeled air quality violations in Iowa.
---------------------------------------------------------------------------

    \56\ See the EPA's Technical Support Document for its Intended 
Round 2 Designations for the 2010 SO2 NAAQS for Nebraska 
available at: https://www.epa.gov/sites/production/files/2016-03/documents/ne-epa-tsd-r2.pdf and the EPA's Technical Support Document 
for its Final Round 2 Designations for the 2010 SO2 NAAQS 
for Nebraska available at: https://www.epa.gov/sites/production/files/2016-07/documents/r7_ne_final_designation_tsd_06302016.pdf.

                                    Table 9--Nebraska Source With Modeling Data Located Within 50 km of Another State
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         Distance from                              Modeled 99th
                                                              2020         source to       Other  facilities     percentile 1-hour    Model grid extends
         Nebraska source                   County          emissions    Nebraska border  included in  modeling      SO2 maximum      into another state?
                                                             (tons)          (km)                               concentration (ppb)
--------------------------------------------------------------------------------------------------------------------------------------------------------
OPPD Nebraska City...............  Otoe.................       11,480              0.62  None.................  32.7 (based on 2012- Yes (Fremont
                                                                                                                 2014 actual          County, Iowa).
                                                                                                                 emissions).
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 31655]]

    Table 10 provides a summary of the available modeling results for 
the modeled sources in neighboring states which are located within 50 
km of Nebraska: Mid-American Energy--George Neal North (George Neal 
North), Mid-American Energy George Neal South (George Neal South) and 
Mid-American Energy Walter Scott Jr. Energy Center (Walter Scott Jr.) 
in Iowa. The Round 2 1-hour SO2 designations modeling for 
Woodbury County, Iowa explicitly included George Neal North and George 
Neal South and no other SO2 sources in the area, and 
included portions of Nebraska in the modeling domain.\57\ In 2016, the 
EPA designated Woodbury County, Iowa as unclassifiable, because even 
though the modeling demonstrated attainment for the area, some emission 
rates used in the modeling analysis, specifically the emission rates 
for MidAmerican Energy Company's George Neal North Units 1 and 2 were 
not yet federally enforceable at the time of the final Round 2 
designations (in June 2016). In September 2016, Iowa rescinded the 
permits for George Neal North Units 1 and 2 as they were permanently 
retired.\58\ Therefore, the EPA can consider the Round 2 modeling 
demonstration for the purpose of evaluating potential transport as the 
emissions rates assumed in the modeling have since become federally 
enforceable.\59\ The North Omaha Station is located over 100 km from 
the George Neal facilities in Iowa. Specifically, there are no sources 
of SO2 emitting over 10 tpy in Nebraska located within 50 km 
of George Neal North and George Neal South, providing further evidence 
that Nebraska emissions are not causing or contributing to violations 
in Woodbury County, Iowa.
---------------------------------------------------------------------------

    \57\ See the EPA's Technical Support Document for its Intended 
Round 2 Designations for the 2010 SO2 NAAQS for Iowa 
available at: https://www.epa.gov/sites/production/files/2016-03/documents/ia-epa-tsd-r2.pdf and the EPA's Technical Support Document 
for its Final Round 2 Designations for the 2010 SO2 NAAQS 
for Iowa available at: https://www.epa.gov/sites/production/files/2016-07/documents/r7_ia_final_designation_tsd_06302016.pdf.
    \58\ See docket document containing letter from MidAmerican 
Energy dated April 18, 2016, requesting the permits for George Neal 
North Units 1 and 2 be rescinded and Iowa's response letter dated 
September 9, 2016, indicating the permits for these units were 
revoked.
    \59\ The modeling for the George Neal facilities resulted in a 
maximum impact near the level of the NAAQS; however, because this 
modeling was based on maximum allowable emissions prior to the 
shutdown of Units 1 and 2 and included a background concentration, 
the EPA finds this to be a conservative estimate of actual air 
quality in the Woodbury County area not an indication of potential 
air quality issues to which Nebraska sources could contribute.
---------------------------------------------------------------------------

    The modeling submitted by Iowa for Walter Scott Jr. in 
Pottawattamie County based on a set of hybrid (i.e., a mix of allowable 
and 2012-2014 actual) emissions for Walter Scott Jr. and the OPPD North 
Omaha Station located in Nebraska resulted in a maximum impact of 51.1 
ppb, or 68% of the level of the NAAQS.\60\ The modeling demonstrates 
maximum impacts below the level of the NAAQS and thereby provides 
evidence that Nebraska emissions are not causing or contributing to 
violations in the area of Pottawattamie County, Iowa around Walter 
Scott Jr. As depicted in Figure 19 of the EPA's Technical Support 
Document for its Intended Round 3 Designations for the 2010 
SO2 NAAQS for Iowa, the maximum modeled impact is located to 
the Southeast of the Walter Scott Jr. facility.\61\ The North Omaha 
Station is located approximately 19 km from the Walter Scott Jr. 
facility. As previously mentioned, Nebraska also referenced the low 
design values at the monitors located in Omaha (as shown in Table 2) 
between the North Omaha facility and the Walter Scott Jr. facility in 
Iowa that similarly support the claim that the North Omaha facility is 
not causing or contributing to violations of the NAAQS in Iowa.\62\ 
Based on the distance between cross-state sources, the localized nature 
of SO2 and the available modeling and monitoring information 
for the area, the EPA agrees that the North Omaha Station is not likely 
to cause or contribute to violations in Iowa as there are no air 
quality violations in the nearby area in Iowa.
---------------------------------------------------------------------------

    \60\ See the EPA's Technical Support Document for its Intended 
Round 3 Designations for the 2010 SO2 NAAQS for Iowa 
available at: https://www.epa.gov/sites/production/files/2017-08/documents/14_ia_so2_rd3-final.pdf and the EPA's Technical Support 
Document for its Final Round 3 Designations for the 2010 
SO2 NAAQS for Iowa available at: https://www.epa.gov/sites/production/files/2017-12/documents/14-ia-so2-rd3-final.pdf.
    \61\ See Id.
    \62\ For locations of monitors in relation to the sources in 
Nebraska and Iowa, please see map on page 21 of Nebraska's SIP as 
contained in the docket for this action.
---------------------------------------------------------------------------

    The most recent available annual emissions of these identified 
sources in nearby states are also provided in Table 10, and the EPA has 
verified that the most recent annual emissions are below the annual 
emissions from the years modeled at each source.\63\
---------------------------------------------------------------------------

    \63\ Nebraska also included emissions trends for certain sources 
in neighboring states in Table 5 of its SIP which depicts the 
downward trend in emissions at these sources as well. See Nebraska's 
SIP submittal included in the docket for this action.

                                   Table 10--Other States' Sources With Modeling Data Located Within 50 km of Nebraska
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                        Distance from                             Modeled 99th
                                                             2020         source to       Other facilities      percentile 1-hour    Model grid extends
        Other state source                County          emissions    Nebraska border       included in           SO2 maximum       into another state?
                                                            (tons)          (km)              modeling         concentration (ppb)
--------------------------------------------------------------------------------------------------------------------------------------------------------
George Neal North................  Woodbury, Iowa......        1,660               0.2  George Neal South     74.3 (Allowable       Yes (Dakota and
                                                                                         (Iowa).               Emissions).           Thurston Counties,
                                                                                                                                     Nebraska).
George Neal South................  Woodbury, Iowa......        1,203               0.8  George Neal North     74.3 (Allowable       Yes (Dakota and
                                                                                         (Iowa).               Emissions).           Thurston Counties,
                                                                                                                                     Nebraska).
Walter Scott Jr..................  Pottawattamie, Iowa.        5,960               0.1  OPPD North Omaha      51.1 (Hybrid of       Yes (Douglas and
                                                                                         (Nebraska).           Actual and            Sarpy Counties,
                                                                                                               Allowable Emissions   Nebraska).
                                                                                                               for 2012-2014).
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The EPA proposes to find that the modeling results summarized in 
Tables 9 and 10, which provide evidence that air quality near certain 
larger sources in other states is attaining the NAAQS, when weighed 
along with the other factors in this document, support the EPA's 
proposed conclusion that sources in Nebraska will not significantly

[[Page 31656]]

contribute to nonattainment of the 2010 1-hour SO2 NAAQS in 
any other state.
    The next step in our weight of evidence analysis, is to assess 
certain other sources near the border for which we do not have 
available modeling or monitoring data. As noted in section III of this 
document, the EPA finds that it is appropriate to examine the impacts 
of emissions from stationary sources in Nebraska in distances ranging 
from 0 km to 50 km from the facility, based on the ``urban scale'' 
definition contained in appendix D to 40 CFR part 58, section 4.4. 
Nebraska assessed point sources up to 50 km from neighboring state 
borders to evaluate trends and SO2 concentrations in area-
wide air quality The list of sources emitting 100 tpy \64\ or more of 
SO2 within 50 km from state borders without available 
modeling data is shown in Table 11.
---------------------------------------------------------------------------

    \64\ Nebraska limited its analysis to Nebraska sources of 
SO2 emitting at least 100 tpy. We agree with Nebraska's 
choice to limit its analysis in this way, because in the absence of 
special factors, for example the presence of a nearby larger source, 
a high concentration of small sources in an area, or unusual 
physical factors, Nebraska sources emitting less than 100 tpy can 
appropriately be presumed to not be causing or contributing to 
SO2 concentrations above the NAAQS.

             Table 11--Nebraska SO2 Sources Without Available Modeling Data Near Neighboring States
----------------------------------------------------------------------------------------------------------------
                                                                                   Distance to      Neighboring
                                                   2019 SO2       Distance to        nearest       state source
        Nebraska source           Facility ID      emissions       Nebraska        neighboring         2019
                                                    (tons)        border (km)      state  SO2        emissions
                                                                                  source  (km)        (tons)
----------------------------------------------------------------------------------------------------------------
Clean Harbors Environmental            7768011           205.9              15  95                         174.7
 Services, Inc.                                                                  (HollyFrontier
                                                                                 Cheyenne
                                                                                 Refinery,
                                                                                 Wyoming).
Western Sugar Cooperative.....         7767911           144.7              35  107 (Basin           [caret]5261
                                                                                 Electric Power
                                                                                 Cooperative--La
                                                                                 ramie River
                                                                                 Station,
                                                                                 Wyoming).
Ash Grove Cement Co...........         7287311           681.4              24  33 (MidAmerican      [caret]5960
                                                                                 Energy Co.--
                                                                                 Walter Scott
                                                                                 Jr., Iowa).
Douglas Co Recycling Landfill.         7699311           164.6              25  41 (MidAmerican      [caret]5960
                                                                                 Energy Co.--
                                                                                 Walter Scott
                                                                                 Jr., Iowa).
Lon D Wright Power Plant......         7766111    [caret]587.9              33  59 (MidAmerican      [caret]5960
                                                                                 Energy Co.--
                                                                                 Walter Scott
                                                                                 Jr., Iowa).
----------------------------------------------------------------------------------------------------------------
[caret] Based on 2020 emissions.

                             Table 12--Neighboring State SO2 Sources Near Nebraska *
----------------------------------------------------------------------------------------------------------------
                                                                                   Distance to       Nebraska
                                                   2019 SO2       Distance to   nearest Nebraska    source 2020
            Source                Facility ID      emissions       Nebraska      SO2 source (km)     emissions
                                                    (tons)       border  (km)                         (tons)
----------------------------------------------------------------------------------------------------------------
Exide Technologies Canon               8230311           158.5             7.2  80 (OPPD                  11,480
 Hollow (Missouri).                                                              Nebraska City
                                                                                 Station).
----------------------------------------------------------------------------------------------------------------
* Table 12 does not include sources duplicative of Table 11.

    As shown, there are two Nebraska sources (Ash Grove Cement Company 
and Douglas County Recycling Landfill) located within 50 kilometers of 
a cross-state source, MidAmerican Energy Co.--Walter Scott Jr., located 
in the State of Iowa. As previously discussed and shown in Table 10, 
modeling submitted to the EPA by the State of Iowa for the 
Pottawattomie County area, containing Walter Scott Jr., indicates that 
the highest predicted 99th percentile daily maximum 1-hour 
concentration within the modeling domain is 51.1 ppb. Additionally, as 
shown in Table 8, the most recent 3-year design value for Douglas 
County, Nebraska, containing the North Omaha Station is 34 ppb.
    Nebraska evaluated available meteorological data to determine the 
wind patterns near Ash Grove Cement Company and Douglas County 
Recycling Landfill. For the Ash Grove Cement Company, Nebraska included 
a wind rose for the Plattsmouth airport that depicts the predominant 
wind pattern in the area as being in a Southeast-Northwest pattern 
which would blow emissions away from the Walter Scott Jr. facility in 
Iowa.\65\ For the Douglas County Recycling Landfill, Nebraska included 
a wind rose for the Omaha/Eppley airport that depicts the predominant 
wind pattern in the area as being in a South-Southeast and North-
Northwest wind pattern which would keep emissions from Douglas County 
Recycling Landfill in Nebraska.\66\ Nebraska also referenced the low 
design values at the monitors located in Omaha (as shown in Table 2) 
between the Douglas County Recycling Landfill and the Walter Scott Jr. 
facility in Iowa that similarly support the claim that the Douglas 
County Recycling Landfill is not causing or contributing to violations 
of the NAAQS in Iowa. Based on the respective distances from Ash Grove 
Cement Company and Douglas County Recycling Landfill to the Nebraska 
border, the localized nature of SO2, and the general wind 
patterns in the area as referenced by Nebraska, the EPA agrees that it 
is unlikely these Nebraska sources could on their own cause or 
contribute to a violation in the neighboring State of Iowa.
---------------------------------------------------------------------------

    \65\ See page 24 of Nebraska's SO2 Transport SIP 
Submittal included in the docket for this action for the wind rose 
referenced by Nebraska.
    \66\ See page 32 of Nebraska's SO2 Transport SIP 
Submittal included in the docket for this action for the wind rose 
referenced by Nebraska.
---------------------------------------------------------------------------

    For the remaining three Nebraska sources listed in Table 11, there 
are no cross-state sources located within 50 km of the Nebraska source 
meaning it is unlikely there is an air quality problem in the 
neighboring state to which the Nebraska sources could contribute. 
Additionally, based on the distance from each Nebraska source to the 
border along with the localized nature of SO2, the EPA finds 
it unlikely that these sources could on their own cause or contribute 
to a violation in any other state. As shown in Table 12, Exide 
Technologies in Missouri is located 7

[[Page 31657]]

km from the Nebraska border; however, there are no Nebraska sources 
within 50 km which could contribute to a potential air quality problem 
in Missouri near the Exide facility.
    In conclusion, for interstate transport prong 1, we reviewed 
ambient SO2 monitoring data and SO2 emissions 
information as well as available modeling information for sources both 
within Nebraska and in neighboring states within 50 km of Nebraska's 
borders. Based on this analysis, we propose to determine that Nebraska 
will not significantly contribute to nonattainment of the 2010 
SO2 NAAQS in any other state, per the requirements of CAA 
section 110(a)(2)(D)(i)(I).
3. The EPA's Prong 2 Evaluation
    In its prong 2 analysis, Nebraska reviewed potential SO2 
impacts on designated maintenance areas. The EPA interprets CAA section 
110(a)(2)(D)(i)(I) 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, 
rather than only former nonattainment, and thus current maintenance, 
areas. Nebraska also performed a prong 2 analysis based on the EPA's 
interpretation, noting that monitors located near Nebraska in 
neighboring states showed very low levels of SO2 and 
emissions in Nebraska and neighboring states have decreased, indicating 
they should not be considered to have maintenance issues for this 
NAAQS.
    The EPA has reviewed Nebraska's analysis and other available 
information on SO2 air quality and emission trends to 
evaluate the state's conclusion that Nebraska will not interfere with 
maintenance of the 2010 SO2 NAAQS in downwind states. This 
evaluation builds on the analysis regarding significant contribution to 
nonattainment (prong 1), which evaluated monitored ambient 
concentrations of SO2 in Nebraska and neighboring states, 
available modeling results, the distances between cross-state 
SO2 sources, and other factors. The EPA is proposing to find 
that SO2 levels in neighboring states near the Nebraska 
border do not indicate any inability to maintain the SO2 
NAAQS that could be attributed in part to sources in Nebraska.
    As shown in Table 1, the statewide SO2 emissions from 
Nebraska and neighboring states have decreased substantially over time, 
per our review of the EPA's emissions trends data.\67\ From 2000 to 
2019, total statewide SO2 emissions decreased by the 
following proportions: Colorado (85% decrease), Iowa (76% decrease), 
Kansas (83% decrease), Missouri (72% decrease), Nebraska (40% 
decrease), South Dakota (88% decrease) and Wyoming (70% decrease). This 
trend of decreasing SO2 emissions does not by itself 
demonstrate that areas in Nebraska and neighboring states will not have 
issues maintaining the 2010 SO2 NAAQS. However, as a piece 
of this weight of evidence analysis for prong 2, it provides further 
indication (when considered alongside low monitor values in neighboring 
states as depicted in Table 2) that such maintenance issues are 
unlikely. This is because the geographic scope of these reductions and 
their large sizes strongly suggest that they are not transient effects 
from reversible causes, and thus these reductions suggest that there is 
very low likelihood that a strong upward trend in emissions will occur 
that might cause areas presently in attainment to violate the NAAQS. 
These reductions have been caused by regulatory requirements in 
Nebraska and the downwind states and by economic factors, such as low 
natural gas prices and the increasing supply of renewable energy, that 
are not likely to be reversed.\68\
---------------------------------------------------------------------------

    \67\ Additional emissions trends data are available at: https://www.epa.gov/air-emissions-inventories/air-pollutant-emissions-trends-data.
    \68\ Nebraska provided information on emission reductions and 
control equipment for certain sources in its SIP and the EPA 
summarized this information in its prong 1 analysis.
---------------------------------------------------------------------------

    The EPA also evaluated federal regulations which have helped to 
reduce SO2 emissions from various sources in Nebraska and 
neighboring states. The EPA's Acid Rain Program set a permanent cap on 
the total amount of SO2 that may be emitted by EGUs in the 
contiguous United States.\69\ CSAPR requires significant reductions in 
SO2 emissions from power plants in the eastern half of the 
United States, including Nebraska and neighboring states.\70\ MATS 
requires reductions of emissions of heavy metals which, as a co-
benefit, reduce emissions of SO2, and establishes 
alternative numeric emission standards, including SO2 (as an 
alternate to hydrochloric acid).\71\ The EPA's Nonroad Diesel Rule will 
reduce sulfur levels from about 3,000 parts per million (ppm) to 15 ppm 
when fully implemented.\72\ The EPA's Heavy-Duty Engine and Vehicle 
Standards and Highway Diesel Fuel Sulfur Control Requirements (Heavy-
Duty Diesel Rule) required refiners to start producing diesel fuel for 
use in highway vehicles with a sulfur content of no more than 15 ppm as 
of June 1, 2006.\73\ NSPS for various source categories, including but 
not limited to Industrial-Commercial-Institutional Steam Generating 
Units; \74\ Sulfuric Acid Plants; \75\ Stationary Gas and Combustion 
Turbines; \76\ Portland Cement Manufacturing; \77\ Electric Utility 
Steam Generating Units (Boilers); \78\ and Onshore Natural Gas 
Processing,\79\ establish standards which reduce SO2 
emissions.
---------------------------------------------------------------------------

    \69\ See 40 CFR parts 72 through 78.
    \70\ See 40 CFR part 97. See also 76 FR 48208.
    \71\ See 40 CFR parts 60 and 63. See also 77 FR 9304.
    \72\ See 40 CFR parts 9, 69, 80, 86, 89, 94, 1039, 1048, 1051, 
1065, and 1068. See also 69 FR 38958.
    \73\ See 40 CFR parts 69, 80, and 86. See also 66 FR 5002.
    \74\ See 40 CFR part 60, subpart Da and 40 CFR part 63. See also 
77 FR 9304.
    \75\ See 40 CFR part 60, subparts A, D, E, F, G and H. See also 
36 FR 24876.
    \76\ See 40 CFR part 60, subparts GG and KKKK. See also 71 FR 
38482 and 44 FR 52792.
    \77\ See 40 CFR parts 60 and 63. See also 75 FR 54970.
    \78\ See 40 CFR part 60, subpart Da and 40 CFR part 63. See also 
77 FR 9304.
    \79\ See 40 CFR part 60, subpart LLL. See also 77 FR 49490.
---------------------------------------------------------------------------

    In addition, the EPA's Tier 3 Motor Vehicle Emission and Fuel 
Standards Rule \80\ also reduce SO2 emissions by 
establishing gasoline sulfur standards that reduce SO2 
emissions from certain types of mobile sources. The EPA finds that 
these federal measures have and continue to lower SO2 
emissions, which, in turn, are expected to continue to support the 
EPA's proposed conclusion that SO2 emissions from Nebraska 
will not contribute significantly to nonattainment or interfere with 
maintenance of the 2010 1-hour SO2 NAAQS in another state.
---------------------------------------------------------------------------

    \80\ See 40 CFR parts 79, 80, 85, 86, 600, 1036, 1037, 1039, 
1042, 1048, 1054, 1065, and 1066. See also 79 FR 23414.
---------------------------------------------------------------------------

    As noted in Nebraska's submission, any future large sources of 
SO2 emissions will be addressed by Nebraska's SIP-approved 
PSD program.\81\ Future minor sources of SO2 emissions will 
be addressed by Nebraska's minor new source review permit program.\82\ 
The permitting regulations contained within these programs should help 
ensure that ambient concentrations of SO2 in neighboring 
states are not exceeded as a result of new facility construction or 
modification occurring in Nebraska.
---------------------------------------------------------------------------

    \81\ See EPA's final action of the PSD portions of Nebraska's 
SIP, at 83 FR 14179, April 2, 2018.
    \82\ Id.
---------------------------------------------------------------------------

    In conclusion, for interstate transport prong 2, we reviewed 
additional information about SO2 air quality and emission 
trends, federal regulations, and Nebraska's permitting regulations, as 
well as the technical information

[[Page 31658]]

considered for interstate transport prong 1. We find that the 
combination of low ambient concentrations of SO2 in Nebraska 
and neighboring states, available modeling results, the distances 
between cross-state SO2 sources, the downward trend in 
SO2 emissions from Nebraska and surrounding states, and 
state measures that prevent new facility construction or modification 
in Nebraska from causing SO2 exceedances in downwind states, 
indicates no interference with maintenance of the 2010 SO2 
NAAQS from Nebraska in other states. Accordingly, we propose to 
determine that Nebraska SO2 emission sources will not 
interfere with maintenance of the 2010 SO2 NAAQS in any 
other state, per the requirements of CAA section 110(a)(2)(D)(i)(I).

V. Requirements for Approval of a SIP Revision

    The State submissions have met the public notice requirements for 
SIP submissions in accordance with 40 CFR 51.102. The submissions also 
satisfied the completeness criteria of 40 CFR part 51, appendix V. 
Kansas provided public notice on its SIP revision from January 16, 
2020, to February 17, 2020, and received no comments. Nebraska provided 
public notice on its SIP revision from September 14, 2020, to October 
16, 2020, and received no comments. In addition, the revision meets the 
substantive SIP requirements of the CAA, including section 110 and 
implementing regulations.

VI. Proposed Action

    The EPA is proposing to approve the following submittals as meeting 
the interstate transport requirements of CAA section 110(a)(2)(D)(i)(I) 
for the 2010 SO2 NAAQS: Kansas' April 7, 2020 submittal and 
Nebraska's October 27, 2020 submittal. The EPA is proposing this 
approval based on our review of the information and analysis provided 
by each state, as well as additional relevant information, which 
indicates that in-state air emissions will not contribute significantly 
to nonattainment or interfere with maintenance of the 2010 
SO2 NAAQS in any other state. This action is being taken 
under section 110 of the CAA.

VII. 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 CAA. Accordingly, 
these proposed actions merely approve state law as meeting federal 
requirements and do not impose additional requirements beyond those 
imposed by state law. For that reason, these proposed actions:
     Are not significant regulatory actions subject to review 
by the Office of Management and Budget under Executive Order 12866 (58 
FR 51735, October 4, 1993);
     Do not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Are 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.);
     Do 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);
     Do not have Federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Are not economically significant regulatory actions based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Are not significant regulatory actions subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Are 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 this action does not involve technical standards; and
     Do not provide the EPA with the discretionary authority to 
address, as appropriate, disproportionate human health or environmental 
effects, using practicable and legally permissible methods, under 
Executive Order 12898 (59 FR 7629, February 16, 1994).
    In addition, these SIPs are 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, Nitrogen dioxide, Particulate 
matter, Reporting and recordkeeping requirements, Sulfur dioxide, 
Volatile organic compounds.

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

    Dated: June 8, 2021.
Edward H. Chu,
Acting Regional Administrator, Region 7.

    For the reasons stated in the preamble, the EPA proposes to amend 
40 CFR part 52 as set forth below:

PART 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

0
1. The authority citation for part 52 continues to read as follows:

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

Subpart R--Kansas

0
2. In Sec.  52.870, the table in paragraph (e) is amended by adding the 
entry ``(46)'' in numerical order to read as follows:

Sec.  52.870   Identification of plan.

* * * * *
    (e) * * *

                                  EPA-Approved Kansas Nonregulatory Provisions
----------------------------------------------------------------------------------------------------------------
                                                                State
    Name of nonregulatory SIP      Applicable  geographic     submittal    EPA approval date      Explanation
            provision              or  nonattainment area       date
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
(46) Section 110(a)(2)(D)(i)(I)-- Statewide...............     4/7/2020   [Date of            [EPA-R07-OAR-2021-
 significant contribution to                                               publication of      0365; FRL-10024-
 nonattainment (prong 1), and                                              final rule in the   81-Region 7].
 interfering with maintenance of                                           Federal             This action
 the NAAQs (prong 2) (Interstate                                           Register],          addresses the
 Transport) Infrastructure                                                 [Federal Register   following CAA
 Requirements for the 2010 SO2                                             citation of the     elements:
 NAAQS.                                                                    final rule].        110(a)(2)(D)(i)(I
                                                                                               )--prongs 1 and
                                                                                               2.
----------------------------------------------------------------------------------------------------------------

[[Page 31659]]

Subpart CC--Nebraska

0
3. In Sec.  52.1420, the table in paragraph (e) is amended by adding 
the entry ``(37)'' in numerical order to read as follows:

Sec.  52.1420   Identification of plan.

* * * * *
    (e) * * *

                                 EPA-Approved Nebraska Nonregulatory Provisions
----------------------------------------------------------------------------------------------------------------
                                                                State
    Name of nonregulatory SIP     Applicable geographic or    submittal    EPA approval date      Explanation
            provision                nonattainment area         date
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
(37) Section 110(a)(2)(D)(i)(I)-- Statewide...............   10/27/2020   [Date of            [EPA-R07-OAR-2021-
 significant contribution to                                               publication of      0365; FRL-10024-
 nonattainment (prong 1), and                                              final rule in the   81-Region 7].
 interfering with maintenance of                                           Federal             This action
 the NAAQs (prong 2) (Interstate                                           Register],          addresses the
 Transport) Infrastructure                                                 [Federal Register   following CAA
 Requirements for the 2010 SO2                                             citation of the     elements:
 NAAQS.                                                                    final rule].        110(a)(2)(D)(i)(I
                                                                                               )--prongs 1 and
                                                                                               2.
----------------------------------------------------------------------------------------------------------------

[FR Doc. 2021-12501 Filed 6-14-21; 8:45 am]
BILLING CODE 6560-50-P