[Federal Register Volume 86, Number 113 (Tuesday, June 15, 2021)]
[Proposed Rules]
[Pages 31645-31659]
[FR Doc No: 2021-12501]

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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.

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

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<PHONE_NUMBER>, or by email at
<EMAIL_ADDRESS>
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).

    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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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]
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                                                                                SO2 reduction,
                          State                                2000            2005            2010            2015            2019        2000-2019 (%)

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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
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                                                 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\
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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
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* 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
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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.
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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

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

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

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

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

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;

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).
--------------------------------------------------------------------------------------------------------------------------------------------------------

    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

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

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

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.
----------------------------------------------------------------------------------------------------------------

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