Document ID: EPA-R10-OAR-2016-0001-0001
Agency: epa
Document Type: Proposed Rule
Title: Air Quality State Implementation Plans; Approvals and Promulgations: Idaho; 2010 Sulfur Dioxide National Ambient Air Quality Standards Infrastructure Requirements
Posted Date: 2020-10-05T04:00Z

[Federal Register Volume 85, Number 193 (Monday, October 5, 2020)]
[Proposed Rules]
[Pages 62679-62686]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-21741]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R10-OAR-2016-0001; FRL-10014-83-Region 10]

Air Plan Approval; ID; 2010 Sulfur Dioxide NAAQS Infrastructure 
Requirements

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve a State Implementation Plan (SIP) submission from the State of 
Idaho (Idaho or the State) that addresses the

[[Page 62680]]

Clean Air Act (CAA or Act) interstate transport requirements for the 
2010 1-hour Sulfur Dioxide (SO2) National Ambient Air 
Quality Standards (NAAQS). In this action, the EPA is proposing to 
determine that Idaho will not contribute significantly to nonattainment 
or interfere with maintenance of the 2010 1-hour SO2 NAAQS 
in any other state or the Fort Hall Reservation. Therefore, the EPA is 
proposing to approve Idaho's December 24, 2015, SIP submission as 
meeting the interstate transport requirements for the 2010 1-hour 
SO2 NAAQS.

DATES: Written comments must be received on or before November 4, 2020.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R10-
OAR-2016-0001 at https://www.regulations.gov. Follow the online 
instructions for submitting comments. Once submitted, comments cannot 
be edited or removed from Regulations.gov. The EPA may publish any 
comment received to its public docket. Do not electronically submit any 
information you consider to be Confidential Business Information (CBI) 
or other information the disclosure of which 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.

FOR FURTHER INFORMATION CONTACT: Claudia Vaupel at (206) 553-6121, or 
vaupel.claudia@epa.gov.

SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,'' 
``us,'' or ``our'' is used, it is intended to refer to the EPA.

Table of Contents:

I. Background
II. Relevant Factors To Evaluate 2010 SO2 Interstate 
Transport SIPs
III. State Submission and EPA Analysis
    A. State Submission
    B. EPA Analysis
    1. The EPA's Prong 1 Evaluation
    2. The EPA's Prong 2 Evaluation
IV. Proposed Action
V. Statutory and Executive Order Reviews

I. Background

    On June 2, 2010, the EPA established a new primary 1-hour 
SO2 NAAQS of 75 parts per billion (ppb), based on a 3-year 
average of the annual 99th percentile of 1-hour daily maximum 
concentrations.\1\ The CAA requires states to submit, within 3 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).
---------------------------------------------------------------------------

    CAA 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 CAA 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 CAA 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 the State of Idaho's December 24, 2015 SIP 
submission because, based on the information available at the time of 
this rulemaking, the State demonstrated that Idaho will not contribute 
significantly to nonattainment or interfere with maintenance of the 
2010 SO2 NAAQS in any other state or the Fort Hall 
Reservation. All other applicable infrastructure SIP requirements for 
this SIP submission have been addressed in separate actions. See 79 FR 
46707 (August 11, 2014).

II. 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 to serve as a model for SO2 transport. 
SO2 transport is therefore a unique case and requires a 
different approach.
    In this proposed rulemaking, as in prior SO2 transport 
analyses, the EPA focuses on a 50 km-wide zone because the physical 
properties of SO2 result in relatively localized pollutant 
impacts near an emissions source that drop off with distance. Given the 
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.\2\ 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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    \2\ For the definition of spatial scales for SO2, 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 III of this this document, the EPA reviewed 
Idaho's analysis to assess how it evaluated SO2 transport to 
other states, the types of information used in the analysis and the 
conclusions drawn. The EPA then conducted a weight of evidence 
analysis, reviewing the submission and other available information, 
including air quality monitor data, emission sources and emission 
trends within Idaho and in bordering states to which it could 
potentially contribute or interfere with attainment or maintenance of 
the 2010 SO2 NAAQS.\3\
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    \3\ 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 Data 
Requirements Rule for the 2010 1-Hour SO2 NAAQS (80 FR 
51052, August 21, 2015) and information submitted to the EPA by 
states, air agencies, and third party stakeholders such as citizen 
groups and industry representatives.

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[[Page 62681]]

III. State Submission and EPA Analysis

    On December 24, 2015, Idaho submitted a SIP revision to the EPA 
documenting that its SIP contains provisions that address CAA section 
110(a)(2)(D)(i)(I) interstate transport requirements for the 2010 
SO2 NAAQS. In this section, we provide an overview of 
Idaho's 2010 SO2 interstate transport analysis, as well as 
the EPA's evaluation of prongs 1 and 2.

A. State Submission

    Idaho conducted a weight of evidence analysis to examine whether 
SO2 emissions from Idaho will adversely affect attainment or 
maintenance of the 2010 SO2 NAAQS in downwind states. In the 
submission, Idaho identified one 2010 SO2 nonattainment area 
in Billings, Montana, within Yellowstone County, which has since been 
redesignated to attainment.\4\ Idaho reviewed 2014 SO2 
emissions data from the largest SO2 emissions sources in the 
State and determined that emissions from those sources were hundreds of 
miles from the SO2 nonattainment/maintenance areas. Idaho 
also reviewed 2012-2014 monitoring data from the 3 SO2 
monitoring sites in its monitoring network and from the 14 
SO2 monitoring sites in neighboring states for years 2011-
2013. Idaho determined that all design values were below the 2010 
SO2 NAAQS.\5\ In addition, Idaho provided 2009-2011 
regional-scale modeling for the State and found that areas of increased 
SO2 concentrations were localized in nature.
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    \4\ The Billings, Montana 2010 SO2 nonattainment area 
was redesignated to attainment on May 10, 2016 following the state's 
SIP submission (81 FR 28718).
    \5\ The design value is the annual 99th percentile of the daily 
maximum 1-hour concentration values, averaged over three consecutive 
years. (See 75 FR 35520, June 22, 2010).
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    Based on the weight of evidence analysis, Idaho concluded that 
emissions within the State will not contribute significantly to 
nonattainment or interfere with maintenance of the 2010 1-hour 
SO2 NAAQS in any other state.

B. EPA Analysis

    The EPA proposes to find that Idaho's SIP meets the interstate 
transport requirements of CAA section 110(a)(2)(D)(i)(I), prong 1 for 
the 2010 SO2 NAAQS. We have analyzed the air quality, 
emission sources and emission trends in Idaho and neighboring states, 
i.e., Montana, Nevada, Oregon, Utah, Washington, Wyoming, and the Fort 
Hall Reservation. Based on our analysis, we propose to find that Idaho 
will not contribute significantly to nonattainment of the 2010 
SO2 NAAQS in any other state or the Fort Hall Reservation.
1. The EPA's Prong 1 Evaluation
    The EPA reviewed SO2 emission data from 2005 to 2017 for 
Idaho and the six neighboring states.\6\ As shown in Table 1 of this 
document, SO2 emissions from Idaho and neighboring states 
have decreased substantially over time, ranging from 37 to 89 percent. 
Specifically, over this 13-year period, Idaho's statewide 
SO2 emissions decreased by 72 percent.
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    \6\ We derived the emissions trends information from the EPA's 
web page https://www.epa.gov/air-emissions-inventories/air-pollutant-emissions-trends-data.

                          Table 1--SO2 Emission Trends in Idaho and Neighboring States
                                               [In tons per year]
----------------------------------------------------------------------------------------------------------------
                                                                                                 SO2 reduction,
            State                  2005         2008         2011         2014         2017       2005-2017 (%)
 
----------------------------------------------------------------------------------------------------------------
Idaho........................       35,452       20,149       13,791       10,062       10,007                72
Montana......................       42,085       29,354       29,452       25,046       18,580                56
Nevada.......................       72,474       20,951       13,578       16,178        7,793                89
Oregon.......................       37,204       25,671       30,285       23,606       19,325                48
Utah.........................       52,999       31,609       27,839       26,964       15,442                71
Washington...................       59,651       34,826       30,492       38,973       37,488                37
Wyoming......................      122,454      112,791     83,256.1       56,772       52,354                57
----------------------------------------------------------------------------------------------------------------

    We also reviewed the most recent certified air quality data 
available for 1-hour SO2 design value concentrations at 
monitors in Idaho and neighboring states. In Table 2 of this document, 
we have included the most recent 2017-2019 design values for (1) all 
monitors in Idaho; (2) the monitor with the highest design value in 
each neighboring state; and (3) the monitor in each neighboring state 
located closest to the Idaho border. The EPA notes that no neighboring 
state has an SO2 monitor within 50 km of the Idaho border. 
To assess how air quality has changed over time, we also reviewed 2014-
2016, 2015-2017, and 2016-2018 SO2 design values for these 
monitors, as shown in Table 2.

             Table 2--SO2 Design Values \7\ in ppb for AQS Monitors in Idaho and Neighboring States
----------------------------------------------------------------------------------------------------------------
                                                Distance to                      Design value
           State/area            AQS site ID   nearest Idaho ---------------------------------------------------
                                               border (km) *   2014-2016    2015-2017    2016-2018    2017-2019
----------------------------------------------------------------------------------------------------------------
Idaho/Boise....................    160010010              55            4            3            3            3
Idaho/Pocatello................    160050004             102           39           38           38           40
Idaho/Caribou County...........    160290031              45           26           30           31           35
Montana/Helena.................    300490004             180            2            3            5            5

[[Page 62682]]

 
Montana/Billings...............    301110066             256           53           33           24           24
Nevada/Las Vegas...............    320030540             644            7            6            6            5
Nevada/Reno....................    320310016             362            5            5            5            4
Oregon/Portland................    410510080             447            3            3            3            3
Washington/Anacortes...........    530570011             412            5            4            3            3
Wyoming/Casper.................    560252601             393           25           20           19           19
Wyoming/Rock Springs...........    560370300             108           21           21           20           12
----------------------------------------------------------------------------------------------------------------
* All distances throughout this notice are approximations.

    We reviewed ambient air quality data in Idaho and neighboring 
states to see whether there were any monitoring sites, particularly 
near the Idaho border, with elevated SO2 concentrations that 
might warrant further investigation with respect to interstate 
transport of SO2 from emission sources near any given 
monitor. As shown in Table 2 of this document, there are no monitors 
with violating design values in Idaho or neighboring states. 
Additionally, the highest monitored 2017-2019 design value in Idaho or 
neighboring states is 40 ppb, or approximately 54 percent of the level 
of the 2010 SO2 NAAQS.
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    \7\ Design values are from monitors with sufficient data 
available in the EPA's Air Quality System (AQS) to produce valid 
design values. Data retrieved from the EPA's https://www.epa.gov/air-trends/air-quality-design-values#report.
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    As discussed previously, Idaho analyzed potential impacts to the 
Billings, Montana area, which was still designated nonattainment at the 
time of Idaho's submission. The EPA redesignated the former Billings 
2010 SO2 nonattainment area to attainment following the 
permanent closure of the PPL Corette Plant. See 81 FR 28718 (May 10, 
2016). As noted by Idaho, the Billings, Montana area is located far 
from the nearest Idaho border (256 km). Table 2 of this document also 
shows that recent monitoring data in the Billings area do not approach 
the level of the 2010 SO2 NAAQS. For these reasons, the EPA 
agrees with Idaho's conclusion that the emissions from Idaho will not 
contribute significantly to nonattainment in the Billings, Montana 
area.
    The data presented in Table 2 of this document show that 2017-2019 
1-hour SO2 design values in Idaho are between 4 and 54 
percent of the 75-ppb level of the NAAQS. The Caribou County 
SO2 monitor (AQS Site ID 160290031) is the only Idaho 
SO2 monitor that is located within 50 km of a state border--
the Idaho-Wyoming border. The 2017-2019 design value at the Caribou 
County SO2 monitor is 35 ppb or 47% of the NAAQS. However, 
these air quality data do not, by themselves, indicate any particular 
location that would warrant further investigation with respect to 
SO2 emission sources in Idaho that might contribute 
significantly to nonattainment in the bordering states. Because the 
monitoring network is not necessarily designed 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.
    As noted, the EPA finds that it is appropriate to examine the 
impacts of emissions from stationary sources in Idaho 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. Therefore, we assessed Idaho and neighboring state point sources 
that emit 100 tons per year (tpy) of SO2 \8\ or more that 
are located up to 50 km from an Idaho border.
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    \8\ We have limited our analysis to sources emitting at least 
100 tpy of SO2 because in the absence of special factors, 
for example the presence of a nearby larger source or unusual 
physical factors, Idaho sources emitting less than 100 tpy can 
appropriately be presumed to not be causing or contributing to 
SO2 concentrations above the NAAQS.
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    There are four sources in Idaho that emit 100 tpy of SO2 
or more. These sources are located in southeastern Idaho and are listed 
in Table 3 of this document. Two of the sources, P4 Production and 
Itafos Conda, are less than 50 km from the Idaho-Wyoming border, 45 km 
and 40 km, respectively.

                       Table 3--Idaho SO2 Sources
                            [SO2 >= 100 tpy]
------------------------------------------------------------------------
                                         2017       Distance to nearest
          Idaho SO2 Source            Emissions     state border (km)/
                                       (tpy) 9         state border
------------------------------------------------------------------------
J.R. Simplot Company--Don Siding             748  101/ID-NV.
 Pocatello (Pocatello, ID).
The Amalgamated Sugar Company (Twin          635  61/ID-NV.
 Falls, ID).
P4 Production (Soda Springs, ID)...          488  45/ID-WY.
Itafos Conda (Conda, ID)...........          387  40/ID-WY.
------------------------------------------------------------------------

    The Naughton Generating Plant in Lincoln, Wyoming, is the closest 
neighboring state source to P4 Production and Itafos Conda. The EPA has 
therefore assessed potential SO2 impacts from these Idaho 
sources to the Lincoln, Wyoming area. Table 4 of this document shows 
SO2 emissions and approximate distances between the sources. 
The EPA finds that the 131 to 134 km distance between the two Idaho 
sources and the Wyoming source, more than twice the 50-km distance the 
EPA has focused on for this analysis, makes it very unlikely that 
SO2 emissions from

[[Page 62683]]

the Idaho sources will interact with SO2 emissions from the 
Wyoming source in such a way as to contribute significantly 
nonattainment in the Lincoln, Wyoming area.\10\
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    \9\ Point source emissions data throughout this document were 
obtained through the EPA's Emissions Inventory System (EIS) Gateway 
at https://www.epa.gov/air-emissions-inventories/emissions-inventory-system-eis-gateway.
    \10\ In round 3 of 2010 SO2 designations, the EPA 
designated Lincoln County in Wyoming as attainment/unclassifiable 
for the 2010 1-hour SO2 NAAQS based on modeling of the 
Naughton source area. See ``Technical Support Document: Chapter 45 
Final Round 3 Area Designations for the 2010 1-Hour SO2 
Primary National Ambient Air Quality Standard for Wyoming'' at 
https://www.epa.gov/sites/production/files/2017-12/documents/45-wy-so2-rd3-final.pdf. See also ``Technical Support Document: Chapter 45 
Intended Round 3 Area Designations for the 2010 1-Hour 
SO2 Primary National Ambient Air Quality Standard for 
Wyoming'' at https://www.epa.gov/sites/production/files/2017-08/documents/45_wy_so2_rd3-final.pdf.

                            Table 4--Idaho SO2 Sources Within 50 km of a State Border
                                                [SO2 >= 100 tpy]
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                                                                                                    Neighboring
                                                  2017 SO2                                         state source
               Idaho SO2 source                   emissions     Distance to nearest neighboring      2017 SO2
                                                    (tpy)         state SO2 source (km)/source       emissions
                                                                                                       (tpy)
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Itafos Conda (Conda, Idaho)..................             387  134/Naughton Generating Plant,              4,048
                                                                Lincoln, WY.
P4 Production (Soda Springs, Idaho)..........             488  131/Naughton Generating Plant,              4,048
                                                                Lincoln, WY.
----------------------------------------------------------------------------------------------------------------

    The EPA also reviewed the location of neighboring state sources 
that emit 100 tpy of SO2 or more and are located within 50 
km of the Idaho border. This is because SO2 emitted by 
sources in Idaho are most likely to impact elevated levels of 
SO2 in neighboring states near such sources. As shown in 
Table 5 of this document, there are two sources in neighboring states 
that are located within 50 km of an Idaho border, the previously 
mentioned Naughton Generating Plant in Lincoln, Wyoming, located in 
southeastern Idaho, and EP Minerals in Vale, Oregon, located in 
southwestern Idaho. The shortest distance between any pair of these 
sources is 131 km, between the Naughton Generating Plant and P4 
Production. As just explained, this distance makes it unlikely that 
SO2 emissions from the Idaho source will interact with 
SO2 emissions from the Wyoming source. This indicates that 
there is no location in any neighboring state that would warrant 
further investigation with respect to Idaho SO2 emission 
sources that might contribute to problems with attainment of the 2010 
SO2 NAAQS.

                     Table 5--Neighboring State SO2 Sources Within 50 km of an Idaho Border
                                                [SO2 >= 100 tpy]
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                                                                                                   Idaho Source
                                          2017 SO2       Distance to   Distance to nearest Idaho     2017 SO2
     Neighboring state SO2 source         emissions     Idaho border        SO2 source (km)          Emissions
                                            (tpy)           (km)                                       (tpy)
----------------------------------------------------------------------------------------------------------------
Naughton Generating Station, Lincoln,           4,048              46  131 (P4 Production, Soda              488
 WY.                                                                    Springs, ID).
EP Minerals, Vale, OR................             182              32  286/The Amalgamated Sugar             635
                                                                        Company, Twin Falls, ID.
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The Fort Hall Reservation
    On January 19, 2017, the EPA determined that the Shoshone-Bannock 
Tribes of the Fort Hall Reservation were eligible to be treated in the 
same manner as an affected downwind state for purposes of CAA sections 
110(a)(2)(D) and 126.\11\ Idaho submitted the SO2 interstate 
transport SIP before this determination and the submission did not 
analyze SO2 transport to the Fort Hall Reservation. 
Therefore, the EPA has conducted the following weight of evidence 
analysis for potential Idaho SO2 transport to the Fort Hall 
Reservation.
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    \11\ The EPA's determination that the Shoshone-Bannock Tribes 
are eligible for treatment in the same manner as a state for CAA 
sections 110(a)(2)(D) and 126 is available in the docket for this 
action. See also https://www.epa.gov/tribal/tribes-approved-treatment-state-tas.
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    The Fort Hall Reservation is located in southeastern Idaho, mostly 
on the high, flat, cultivated east banks of the Snake River Plain which 
average around 4,500 feet above sea level. The east portion of the 
Reservation rests on the northern reaches of the Pocatello range of 
mountains. The Fort Hall Reservation is bordered on the east and south 
by the rugged rocky hills of the Pocatello, Chesterfield, and Caribou 
mountain ranges. These ranges run north-south with peaks rising from 
6,000 to 9,000 feet above sea level, generally east and south of the 
Reservation.
    The EPA reviewed ambient air quality data, particularly near the 
Fort Hall Reservation borders, for any monitoring sites with elevated 
SO2 concentrations that might warrant further investigation 
with respect to interstate transport of SO2 from Idaho 
sources. The nearest SO2 monitor to the Fort Hall 
Reservation is in Pocatello, Idaho (AQS Site ID 160050004) and is 
approximately 2 km from the nearest Reservation border. Another 
SO2 monitor is located in Caribou County, Idaho (AQS Site ID 
160290031) and is approximately 37 km from the southeastern border of 
the Fort Hall Reservation. Although these monitors are not sited to 
determine maximum impacts at the Fort Hall Reservation, monitoring data 
listed in Table 6 of this document, indicate that SO2 levels 
in those areas are relatively low. The 2017-2019 design values at the 
Pocatello and Caribou County monitor

[[Page 62684]]

sites were 53 at 47 and percent of the 75-ppb level of the NAAQS, 
respectively.

                               Table 6--Idaho SO2 Design Values 12 in ppb for AQS Monitors Near the Fort Hall Reservation
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                             Approximate                                    Design value
                                                             distance to   -----------------------------------------------------------------------------
           AQS monitor location  (AQS site ID)                Fort Hall
                                                             Reservation     2012-2014    2013-2015    2014-2016    2015-2017    2016-2018    2017-2019
                                                                 (km)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pocatello (160050004)....................................                2           51           41           39           38           38           40
Caribou County (160290031)...............................               37           30           26           26           30           31           35
--------------------------------------------------------------------------------------------------------------------------------------------------------

    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 contribute 
significantly to nonattainment at the Fort Hall Reservation. However, 
data from this monitoring network is not necessarily representative of 
SO2 levels throughout the Fort Hall Reservation and we have 
therefore also conducted a source-oriented analysis.
---------------------------------------------------------------------------

    \12\ Design values are from monitors with sufficient data 
available in the EPA's Air Quality System (AQS) to produce valid 
design values. Data retrieved from https://www.epa.gov/air-trends/air-quality-design-values#report.
---------------------------------------------------------------------------

    As discussed previously, the EPA finds that it is appropriate to 
examine the impacts of emissions from stationary sources in Idaho 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. Therefore, we assessed point sources with SO2 
emissions of 100 tpy \13\ or more within 50 km of the Fort Hall 
Reservation to evaluate trends and SO2 concentrations in 
areawide air quality. We identified three such sources, listed in Table 
7 of this document. We note that there are no sources within the Fort 
Hall Reservation that emit more than 2 tpy of SO2.
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    \13\ We have limited our analysis to Idaho sources emitting at 
least 100 tpy of SO2 because in the absence of special 
factors, for example the presence of a nearby larger source or 
unusual physical factors, Idaho sources emitting less than 100 tpy 
can appropriately be presumed to not be causing or contributing to 
SO2 concentrations above the NAAQS.

                    Table 7--SO2 Emissions Sources Within 50 km of the Fort Hall Reservation
                                                [SO2 >= 100 tpy]
----------------------------------------------------------------------------------------------------------------
                                                 2017 SO2     Distance to      Distance to        Distance to
                                                emissions      Fort Hall      Pocatello site     Caribou County
               SO2 Source 14 15                   (tpy)       Reservation      (AQS site ID     site  (AQS Site
                                                                 (km)           160050004)       ID 160290031)
----------------------------------------------------------------------------------------------------------------
J.R. Simplot Company--Don Siding Pocatello             748              <1                  1                 80
 (Pocatello, ID).............................
P4 Production (Soda Springs, ID).............          488              38                 80                  1
Itafos Conda (Conda, ID).....................          387              38                 82                  7
----------------------------------------------------------------------------------------------------------------

J.R. Simplot Company--Don Siding Pocatello
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    \14\ The Simplot Don Siding Plant, P4 Production, and Itafos 
Conda are title V major stationary sources subject to the applicable 
limits and controls in the Idaho SIP, including Idaho's SIP-approved 
stationary source Permit to Construct program (IDAPA 58.01.01.200 
through 222). The Simplot Don Siding Plant is owned or operated by 
J.R. Simplot Company, which is a party to a Federal Consent Decree 
to resolve CAA violations at the company's sulfuric acid plants. 
(Consent Decree, USA et al. v. J.R. Simplot Company, Case No. 1:15-
cv-00562-CWD (Dist. Idaho 2015). On August 19, 2019, the Idaho 
Department of Environmental Quality issued a revised Permit to 
Construct to incorporate the consent decree requirements into the 
Simplot Don Siding Plant's permit. (P-2016-0055 Project 62103 issued 
pursuant to IDAPA 58.01.01.200 through 222.)
    \15\ A schematic map of the sources and their proximity to the 
Fort Hall Reservation is available in the docket for this action.
---------------------------------------------------------------------------

    The J.R. Simplot Company--Don Siding Pocatello plant (Simplot Don 
Siding Plant), in Pocatello, Idaho, is the closest SO2 
source to the Fort Hall Reservation and has the highest SO2 
emissions in the area with 748 tpy in 2017. The Simplot Don Siding 
Plant is approximately 1 km from the boundary of the Fort Hall 
Reservation and approximately 1 km from the Pocatello SO2 
monitor (AQS Site ID 160050004). The EPA reviewed SO2 
emissions data for the Simplot Don Siding Plant from 2010 through 2017. 
As shown in Table 8 of this document, SO2 emissions have 
decreased considerably over time and are less than half what they were 
in 2010.

                                          Table 8--Simplot Don Siding Plant SO2 Emissions (tpy) From 2010-2017
--------------------------------------------------------------------------------------------------------------------------------------------------------
                         2010                               2011          2012          2013          2014          2015          2016          2017
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1,634.................................................        1,647         1,563           803           795           732           735           748
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    The EPA reviewed data from the meteorological station at the 
Pocatello Regional Airport, which is approximately 6 km west of the 
Simplot Don Siding Plant. Prevailing winds are from the southwest with 
an average speed of 4.2 meters per second. Given the close distance of 
the Pocatello SO2 monitor to the Simplot Don Siding Plant, 
the low monitored SO2 concentrations, and the prevalent wind 
direction, it is likely that SO2 emissions from the Simplot 
Don Siding Plant will be sufficiently dispersed before reaching the 
Fort Hall Reservation.

[[Page 62685]]

    In addition to reviewing the 2009-2011 regional scale 
SO2 modeling in Idaho's submission, the EPA examined more 
recent regional-scale SO2 modeling for the Pocatello area 
using the same tool Idaho used with updated data from July 2014 to June 
2017.\16\ The highest design concentration identified in the area is 
about 6.8 ppb, well under the 1-hour SO2 NAAQS of 75 ppb. On 
the Fort Hall Reservation, the highest design concentration identified 
in the area is 6.3 ppb and occurs west of the Simplot Don Siding Plant. 
This analysis indicates that SO2 emissions impacts from the 
Simplot Don Siding Plant to the vicinity and the Fort Hall Reservation 
are likely minimal. While this regional-scale modeling is not 
dispositive as to the determination of whether impermissible 
SO2 transport is occurring, it provides information that 
along with other factors may be considered in a weight of evidence 
evaluation.
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    \16\ The EPA used a tool developed and operated by Washington 
State University as part of the NW-AIRQUEST consortium. The tool 
estimates design concentrations from a regionally optimized 
photochemical air pollutant transport grid model that uses 
meteorological data and computes air pollutant emissions, transport, 
and chemistry using the EPA's CMAQ photochemical grid model. The 
model simulates industrial source emissions from point sources, 
including the Simplot Don Siding Plant, assuming a constant hourly 
emission rate of air pollutants based on the annual tons-per-year 
emissions provided in the 2014 National Emissions Inventory. The 
technical support document in the docket for this action provides 
additional information on the NW-AIRQUEST consortium's tool and the 
EPA's analysis.
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P4 Production and The Itafos Conda
    The EPA also assessed potential SO2 impacts from other 
point sources near the Fort Hall Reservation, P4 Production and Itafos 
Conda, which are approximately 7 km apart. These sources are located in 
the Soda Springs region on the east side of the high Caribou Valley 
plain, along the west flanks of the Caribou Range of mountains. The 
rugged Blackfoot Lava Fields and high, rocky Chesterfield Range of 
mountains lie between the Fort Hall Reservation and Soda Springs region 
and rise to peaks exceeding 7,000 feet.
    As shown in Table 7 of this document, these sources are 
approximately 38 km from the Fort Hall Reservation. The closest 
SO2 monitor to these sources is the Caribou County monitor 
(AQS Site ID 160290031), which is 1 km from P4 Production and 7 km from 
Itafos Conda. The EPA reviewed SO2 emissions data for P4 
Production and Itafos Conda from 2010 to 2017. As shown in Table 9 of 
this document, SO2 emissions at P4 Production have decreased 
by almost half since 2010. At Itafos Conda, SO2 emissions 
have not changed substantially since 2010.

                                       Table 9--P4 Production and Itafos Conda SO2 Emissions (tpy) From 2010-2017
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                    Facility                          2010         2011         2012         2013         2014         2015         2016         2017
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P4 Production...................................          936         1169          643          615          456          467          478          488
Itafos Conda....................................          341          302          311          410          332          438          364          387
--------------------------------------------------------------------------------------------------------------------------------------------------------

    With a 38 km transport distance over complex, rugged terrain, and 
the low monitored SO2 concentrations, it is likely that 
SO2 emissions from P4 Production and Itafos Conda will be 
sufficiently dispersed before impacting the Fort Hall Reservation, and 
that any impacts to the Reservation from these sources would likely be 
minimal.
    The EPA has reviewed SO2 sources with emissions of 100 
tpy or more within 50 km of the Fort Hall Reservation. Based on the 
available information, the EPA is proposing to find that Idaho will not 
contribute significantly to nonattainment of the 2010 1-hour 
SO2 NAAQS for purposes of CAA section 110(a)(2)(D)(i)(I) in 
the Fort Hall Reservation.
    We are proposing to conclude that, based on our review of the Idaho 
submission and our supplemental evaluation, Idaho's SIP meets the prong 
1 requirements of CAA section 110(a)(2)(D)(i)(I) for purposes of the 
2010 SO2 NAAQS. In summary, for interstate transport prong 
1, we reviewed the Idaho submission and conducted a supplemental 
analysis of ambient SO2 monitoring data and SO2 
emission sources within Idaho, neighboring states, and the Fort Hall 
Reservation. Based on this analysis, we propose to determine that Idaho 
will not contribute significantly to nonattainment of the 2010 
SO2 NAAQS in any other state or the Fort Hall Reservation, 
per the requirements of CAA section 110(a)(2)(D)(i)(I).

2. The EPA's Prong 2 Evaluation

    The EPA has reviewed available information on SO2 air 
quality and emission trends to evaluate Idaho's conclusion that 
emissions from sources in the State will not interfere with maintenance 
of the 2010 SO2 NAAQS in any downwind state. The EPA notes 
that Idaho's analysis does not independently address whether the SIP 
contains adequate provisions prohibiting emissions that will interfere 
with maintenance of the 2010 SO2 NAAQS in any other state, 
or the Fort Hall Reservation. In remanding the Clean Air Interstate 
Rule (CAIR) to the EPA in North Carolina v. EPA, the D.C. Circuit 
explained that the regulating authority must give the ``interfere with 
maintenance'' clause of section 110(a)(2)(D)(i)(I) ``independent 
significance'' by evaluating the impact of upwind state emissions on 
downwind areas that, while currently in attainment, are at risk of 
future nonattainment, considering historic variability.\17\ While Idaho 
did not evaluate the potential impact of its emissions on areas that 
are currently measuring clean data, but that may have issues 
maintaining that air quality, the EPA reviewed additional information, 
which builds on the analysis regarding significant contribution to 
nonattainment (prong 1) to determine potential impacts on areas that 
are measuring clean data. Specifically, because of the relatively low 
monitored ambient concentrations of SO2 in Idaho and 
neighboring states, the levels of SO2 emissions of Idaho 
sources, and the large distances between cross-state SO2 
sources, the EPA's weight of evidence evaluation shows that 
SO2 levels in neighboring states near the Idaho border do 
not indicate any inability to maintain the SO2 NAAQS that 
could be attributed, even in part, to sources in Idaho.
---------------------------------------------------------------------------

    \17\ North Carolina v. EPA, 531 F.3d 896, 910-11 (D.C. Cir. 
2008). The Court held that the EPA must give ``independent 
significance'' to each prong of CAA section 110(a)(2)(D)(i)(I). Id.
---------------------------------------------------------------------------

    Based on our review of the EPA's emissions trends data, as shown in 
Table 1 of this document, SO2 emissions from Idaho and 
neighboring states have decreased substantially over time.\18\ From 
2005 to 2017, total statewide SO2 emissions decreased by the 
following

[[Page 62686]]

proportions: Idaho: 72% decrease, Montana: 56% decrease, Nevada: 89% 
decrease, Oregon: 48% decrease, Utah: 71% decrease, Washington: 37% 
Decrease, and Wyoming: 57% decrease. This trend of decreasing 
SO2 emissions does not by itself demonstrate that areas in 
Idaho 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) that such 
maintenance issues are unlikely. This is because the large decrease in 
SO2 emissions covers a large geographic area, which strongly 
suggests that it is not a transient effect from reversible causes and 
that there is low likelihood that a strong upward trend in emissions 
will occur that might cause areas that are presently in attainment to 
violate the NAAQS.
---------------------------------------------------------------------------

    \18\ Additional emissions trends data are available at: https://www.epa.gov/air-emissions-inventories/air-pollutant-emissions-trends-data.
---------------------------------------------------------------------------

    The EPA notes that existing sources are subject to the control 
requirements in the Idaho SIP discussed in our prong 1 evaluation, and 
any future new and modified stationary sources of SO2 
emissions will be subject to Idaho's SIP-approved pre-construction 
permitting (``new source review'' or ``NSR'') program.\19\ The EPA 
believes that the permitting regulations contained within these 
programs will help ensure that ambient concentrations of SO2 
in neighboring states will not be exceeded as a result of new facility 
construction or modification occurring in Idaho.
---------------------------------------------------------------------------

    \19\ The EPA approved a consolidated pre-construction permitting 
program, including both major and minor source NSR, into the Idaho 
SIP on June 23, 1986 (51 FR 22810). Since that time, we have 
approved revisions to the program as consistent with the CAA and 
Federal NSR requirements codified at 40 CFR 51.160 through 40 CFR 
51.166, most recently on August 20, 2018 (83 FR 42033).
---------------------------------------------------------------------------

    In conclusion, for interstate transport prong 2, the EPA has 
incorporated additional information into our evaluation of Idaho's 
submission, which did not include an independent analysis of prong 2. 
In doing so, we have reviewed information about emission trends, as 
well as the technical information considered for our interstate 
transport prong 1 analysis. We find that the combination of low ambient 
concentrations of SO2 in Idaho and neighboring states, 
including near the Fort Hall Reservation, the large distances between 
cross-state SO2 sources, the downward trend in 
SO2 emissions from Idaho and surrounding states, and SIP-
approved control measures designed to limit SO2 emissions 
from new and modified stationary sources in Idaho, indicates that Idaho 
sources will not interfere with maintenance of the 2010 SO2 
NAAQS in any other state or the Fort Hall Reservation. Accordingly, we 
propose to determine that Idaho SO2 emission sources will 
not interfere with maintenance of the 2010 SO2 NAAQS in any 
other state or the Fort Hall Reservation, per the requirements of CAA 
section 110(a)(2)(D)(i)(I).

IV. Proposed Action

    The EPA is proposing to approve the December 24, 2015 Idaho SIP as 
meeting the interstate transport requirements of CAA section 
110(a)(2)(D)(i)(I) for the 2010 SO2 NAAQS. The EPA is 
proposing this approval based on our review of the information and 
analysis provided by Idaho, as well as additional analyses conducted by 
the EPA to verify and supplement the Idaho SIP, which indicates that 
Idaho will not contribute significantly to nonattainment or interfere 
with maintenance of the 2010 SO2 NAAQS in any other state or 
the Fort Hall Reservation. This action is being taken under section 110 
of the CAA.

V. Statutory and Executive Order Reviews

    Under the Clean Air Act, the Administrator is required to approve a 
SIP submission that complies with the provisions of the Act and 
applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). 
Thus, in reviewing SIP submissions, the EPA's role is to approve state 
choices, provided that they meet the criteria of the Clean Air Act. 
Accordingly, this proposed action merely approves state law as meeting 
Federal requirements and does not impose additional requirements beyond 
those imposed by state law. For that reason, this proposed action:
     Is not a ``significant regulatory action'' subject to 
review by the Office of Management and Budget under Executive Orders 
12866 (58 FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 
2011);
     Is not an Executive Order 13771 (82 FR 9339, February 2, 
2017) regulatory action because SIP approvals are exempted under 
Executive Order 12866;
     Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because it does not involve technical standards; and
     Does 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).
    The proposed SIP would not be 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 proposed 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). Consistent with EPA policy, the EPA provided a 
consultation opportunity to the Shoshone-Bannock Tribes concerning the 
EPA's action on this SIP submission in a letter dated March 7, 2018. 
The EPA did not receive a request for consultation.

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: September 25, 2020.
Christopher Hladick,
Regional Administrator, Region 10.
[FR Doc. 2020-21741 Filed 10-2-20; 8:45 am]
 BILLING CODE 6560-50-P