[Federal Register Volume 86, Number 205 (Wednesday, October 27, 2021)]
[Proposed Rules]
[Pages 59327-59333]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-23274]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R05-OAR-2021-0451; FRL-9166-01-R5]


Air Plan Approval; Michigan and Wisconsin; Finding of Failure To 
Attain the 2010 Sulfur Dioxide Primary National Ambient Air Quality 
Standard for the Detroit and Rhinelander Nonattainment Areas

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
determine that the Detroit and Rhinelander sulfur dioxide 
(SO2) nonattainment areas failed to attain the 2010 primary 
1-hour SO2 national ambient air quality standard (NAAQS or 
``standard'') by the applicable attainment date of October 4, 2018. 
This proposed determination is based upon air quality modeling using 
actual and allowable emissions for the Detroit area and monitored air 
quality data from January 2015 to December 2017 for the Rhinelander 
area. If EPA finalizes these determinations as proposed, within one 
year after EPA publishes a final rule the States of Michigan and 
Wisconsin will be required to submit revisions to their State 
Implementation Plans (SIPs) that, among other elements, provide for 
expeditious attainment of the 2010 SO2 standard. However, 
for the Rhinelander area, if EPA approves the recent revised SIP 
submission submitted by the State of Wisconsin, EPA is proposing to 
treat that submission as satisfying the requirement to submit revisions 
to the SIP to address the failure to timely attain the 2010 
SO2 NAAQS.

DATES: Comments must be received on or before November 26, 2021.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R05-
OAR-2021-0451 at https://www.regulations.gov, or via email to 
[email protected]. For comments submitted at Regulations.gov, 
follow the online instructions for submitting comments. Once submitted, 
comments cannot be edited or removed from Regulations.gov. For either 
manner of submission, 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. EPA will 
generally not consider comments or comment contents located outside of 
the primary submission (i.e., on the web, cloud, or other file sharing 
system). For additional submission methods, please contact the person 
identified in the FOR FURTHER INFORMATION CONTACT section. For the full 
EPA public comment policy, information about CBI or multimedia 
submissions, and general guidance on making effective comments, please 
visit https://www2.epa.gov/dockets/commenting-epa-dockets.

FOR FURTHER INFORMATION CONTACT: Melissa Sheffer, Meteorologist, 
Control Strategies Section, Air Programs Branch (AR-18J), Environmental 
Protection Agency, Region 5, 77 West Jackson Boulevard, Chicago, 
Illinois 60604, (312) 353-1027, [email protected]. The EPA Region 
5 office is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, 
excluding Federal holidays and facility closures due to COVID-19.

SUPPLEMENTARY INFORMATION:

[[Page 59328]]

I. Background

A. The 2010 SO2 NAAQS

    Under section 109 of the Clean Air Act (CAA), EPA has established 
NAAQS for certain pervasive air pollutants (referred to as ``criteria 
pollutants'') and conducts periodic reviews of the NAAQS to determine 
whether they should be revised or whether new NAAQS should be 
established.
    Under the CAA, EPA must establish a NAAQS for SO2. 
SO2 is primarily released to the atmosphere through the 
burning of fossil fuels by power plants and other industrial 
facilities. SO2 is also emitted from industrial processes 
including metal extraction from ore and heavy equipment that burn fuel 
with a high sulfur content. Short-term exposure to SO2 can 
damage the human respiratory system and increase breathing 
difficulties. Small children and people with respiratory conditions, 
such as asthma, are more sensitive to the effects of SO2. 
Sulfur oxides at high concentrations can also react with compounds to 
form small particulates that can penetrate deeply into the lungs and 
cause health problems.
    EPA first established primary, health-based SO2 
standards in 1971 at 0.14 parts per million (ppm) over a 24-hour 
averaging period and 0.3 ppm over an annual averaging period (36 FR 
8186, April 30, 1971). In June 2010, EPA revised the NAAQS for 
SO2 to provide increased protection of public health, 
providing for revocation of the 1971 primary annual and 24-hour 
SO2 standards for most areas of the country following area 
designations under the new NAAQS.\1\ The 2010 NAAQS is 75 parts per 
billion (ppb) (equivalent to 0.075 ppm) over a 1-hour averaging period 
(75 FR 35520, June 22, 2010). A violation of the 2010 1-hour 
SO2 NAAQS occurs when the annual 99th percentile of ambient 
daily maximum 1-hour average SO2 concentrations, averaged 
over a 3-year period, exceeds 75 ppb.\2\
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    \1\ 40 CFR 50.4(e).
    \2\ 40 CFR 50.17.
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B. Designations, Classifications, and Attainment Dates for the 2010 SO2 
NAAQS

    Following promulgation of any new or revised NAAQS, EPA is required 
by CAA section 107(d) to designate areas throughout the nation as 
attaining or not attaining the NAAQS. On August 5, 2013, EPA finalized 
its first round of designations for the 2010 primary SO2 
NAAQS (78 FR 47191). In the 2013 action, EPA designated 29 areas in 16 
states as nonattainment for the 2010 SO2 NAAQS, including 
the Detroit area in Michigan and the Rhinelander area in Wisconsin.\3\ 
EPA's initial round of designations for the 2010 SO2 NAAQS, 
including the Detroit and Rhinelander areas, became effective on 
October 4, 2013. Pursuant to CAA sections 172(a)(2) and 192(a), the 
maximum attainment date for the Detroit and Rhinelander areas was 
October 4, 2018, five years after the effective date of the final 
action designating each area as nonattainment for the 2010 
SO2 NAAQS.
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    \3\ For exact descriptions of the Detroit and Rhinelander areas, 
refer to 40 CFR 81.303.
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    For a number of nonattainment areas, including the Detroit area, 
EPA published an action on March 18, 2016, effective April 18, 2016, 
finding that Michigan and other pertinent states had failed to submit 
the required SO2 nonattainment plan by the submittal 
deadline (81 FR 14736). Under CAA section 110(c), the finding triggered 
a requirement that EPA promulgate a Federal implementation plan (FIP) 
within two years of the finding unless, by that time (a) the state had 
made the necessary complete submittal and (b) EPA had approved the 
submittal as meeting applicable requirements. Michigan submitted a 
complete nonattainment plan on May 31, 2016 and submitted associated 
final enforceable measures on June 30, 2016. However, on March 19, 
2021, EPA partially approved and partially disapproved Michigan's 
SO2 plan as submitted in 2016 (86 FR 14827). Therefore, the 
FIP clock was not stopped. EPA disapproved the attainment 
demonstration, in part because it relied on an invalidated rule 
(Michigan Administrative Code 336.1430) that was no longer enforceable. 
EPA also disapproved the plan for failing to meet the requirements for 
meeting reasonable further progress (RFP) toward attainment of the 
NAAQS, reasonably available control measures and reasonably available 
control technology (RACM/RACT), and contingency measures. To date, 
Michigan has not submitted an approvable plan for the Detroit area, and 
EPA is currently working on a FIP.
    For the Rhinelander area, Wisconsin submitted a nonattainment plan 
on January 22, 2016, and supplemented it on July 18, 2016, and November 
29, 2016. On March 23, 2021, EPA partially approved and partially 
disapproved Wisconsin's Rhinelander SO2 plan as submitted 
and supplemented in 2016 (86 FR 15418). EPA disapproved the attainment 
demonstration for failing to comply with EPA's stack height 
regulations. Additionally, EPA disapproved the plan for failing to meet 
the requirements for meeting RFP toward attainment of the NAAQS, RACM/
RACT, emission limitations and control measures as necessary to attain 
the NAAQS, and contingency measures. Under CAA section 110(c), the 
partial disapproval triggered a requirement that EPA promulgate a FIP 
within two years of the finding unless, by that time (a) the state had 
made the necessary complete submittal and (b) EPA had approved the 
submittal as meeting applicable requirements. On March 29, 2021, 
Wisconsin submitted a permit containing a more stringent emission limit 
for Ahlstrom-Munksj[ouml]'s Rhinelander facility, the main 
SO2 source in the area, along with supplemental information 
in order to remedy the plan's deficiencies specified in EPA's March 23, 
2021 rulemaking. EPA proposed to approve Wisconsin's revised plan for 
the Rhinelander SO2 nonattainment area on July 22, 2021 (86 
FR 38643).
    On August 6, 2020, the Center for Biological Diversity, the Center 
for Environmental Health, and the Sierra Club filed a complaint in the 
United States District Court (amended October 29, 2020), alleging that 
EPA failed to perform certain non-discretionary duties in accordance 
with the CAA, including to make timely findings that the Detroit and 
Rhinelander areas attained the 2010 SO2 NAAQS by the 
attainment date. Under court order, EPA must determine whether Detroit 
and Rhinelander areas have attained the SO2 NAAQS by January 
31, 2022. The court order provides that if a covered nonattainment area 
is redesignated to attainment before the applicable deadline for EPA's 
determination, then EPA's duty to make the determination for that area 
is automatically terminated. Therefore, EPA may not finalize this 
action if either area is redesignated to attainment of the 2010 
SO2 NAAQS before January 31, 2022.

II. Proposed Determinations and Consequences

    Section 179(c)(1) of the CAA requires EPA to determine whether a 
nonattainment area attained an applicable standard by the applicable 
attainment date based on the area's air quality as of the attainment 
date. In determining the attainment status of SO2 
nonattainment areas, EPA may consider ambient monitoring data, air 
quality dispersion modeling, and/or a

[[Page 59329]]

demonstration that the control strategy in the SIP has been fully 
implemented.\4\
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    \4\ EPA, Guidance for 1-Hour SO2 Nonattainment Area 
SIP Submissions (April 2014) (``2014 SO2 Guidance''), 49.
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    Under EPA regulations in 40 CFR 50.17 and in accordance with 40 CFR 
part 50, appendix T, the 2010 1-hour annual SO2 standard is 
met at a monitoring site when the design value is less than or equal to 
75 ppb. Design values are calculated by computing the three-year 
average of the annual 99th percentile daily maximum 1-hour average 
concentrations.\5\ When calculating 1-hour primary standard design 
values, the calculated design values are rounded to the nearest whole 
number or 1 ppb by convention. A SO2 1-hour primary standard 
design value is valid if it encompasses three consecutive calendar 
years of complete monitoring data or modeling data.
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    \5\ As defined in 40 CFR part 50, appendix T, section 1(c), 
daily maximum 1-hour values refer to the maximum 1-hour 
SO2 concentration values measured from midnight to 
midnight that are used in the NAAQS computations.
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A. Detroit Area Determination

    The determination of failure to attain for the Detroit area was 
based on air quality dispersion modeling, using actual and allowable 
emissions from the most recent three complete calendar years, prior to 
the attainment date of October 4, 2018 (i.e., from 2015-2017).
    As previously noted, EPA may consider air quality dispersion 
modeling in addition to monitoring data when determining the attainment 
status of SO2 nonattainment areas. EPA's 2014 SO2 
Guidance states that ``[i]f the EPA determines that the air quality 
monitors located in the affected area are located in the area of 
maximum concentration, the EPA may be able to use the data from these 
monitors to make the determination of attainment without the use of air 
quality modeling data.'' \6\ Although all the monitors in the Detroit 
area are showing values below the NAAQS, EPA may not use the monitoring 
data for this proposed determination of failure to attain because the 
modeling results show that the monitors are not in the area of maximum 
ambient SO2 concentration. The modeling data show that 
SO2 concentrations near the monitors are below the NAAQS 
while showing concentrations that violate the NAAQS at other modeling 
receptors in the Detroit area.
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    \6\ Id., 50.
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    EPA's modeling requirements to support SIP attainment 
demonstrations are specified by regulation in appendix W of 40 CFR part 
51 (Guideline on Air Quality Models), as referenced by 40 CFR 51.112. 
Additionally, specific SO2 modeling guidance can be found in 
EPA's document titled, ``SO2 NAAQS Designations Modeling 
Technical Assistance Document'' (Modeling TAD), which was most recently 
updated in August 2016. EPA conducted a modeling demonstration, based 
on guidelines from appendix W and the Modeling TAD, that contained an 
assessment of the air quality impacts from the following sources: U.S. 
Steel Ecorse, U.S. Steel Zug Island, EES Coke, DTE Energy (DTE) River 
Rouge, DTE Trenton Channel, Carmeuse Lime, DTE Monroe, Severstal Steel, 
Dearborn Industrial Generation (DIG), and Marathon Refinery.
1. Model Selection and Modeling Components
    EPA's Modeling TAD notes that for area designations under the 2010 
SO2 NAAQS, the American Meteorological Society/Environmental 
Protection Agency Regulatory Model (AERMOD) modeling system should be 
used, unless use of an alternative model can be justified. In some 
instances, the recommended model may be a model other than AERMOD, such 
as the BLP model for buoyant line sources. The AERMOD modeling system 
contains the following components: AERMOD (the dispersion model), 
AERMAP (the terrain processor for AERMOD), AERMET (the meteorological 
data processor for AERMOD), BPIPPRIME (the building input processor), 
AERMINUTE (a pre-processor to AERMET incorporating 1-minute automated 
surface observation system (ASOS) wind data), AERSURFACE (the surface 
characteristics processor for AERMET), and AERSCREEN (a screening 
version of AERMOD).
    EPA conducted its air dispersion modeling demonstration with 
AERMOD, the preferred model for this application. EPA used version 
19191 of AERMOD, which was the most recent version at that time.
2. Modeling Parameter: Rural or Urban Dispersion
    EPA's recommended procedure for characterizing an area by prevalent 
land use is based on evaluating the dispersion environment within 3 
kilometers of the facility. According to EPA's modeling guidelines 
contained in documents such as the Modeling TAD, rural dispersion 
coefficients are to be used in the dispersion modeling analysis if more 
than 50% of the area within a 3 kilometer radius of the facility is 
classified as rural. Conversely, if more than 50% of the area is urban, 
urban dispersion coefficients should be used in the modeling analysis.
    Although EPA's modeling guidelines recommend that areas such as 
Detroit should be modeled using urban dispersion coefficients, it was 
found that using urban dispersion coefficients caused the model to 
overpredict monitored concentrations by 2-3 times due to emissions from 
the tall stacks becoming trapped in the nighttime boundary layer. 
Section 5.1 of the AERMOD Implementation Guide \7\ describes how prior 
to AERMOD version 15181, the application of the urban option on tall 
stacks in small to moderate size urban areas may have limited the plume 
height resulting in high concentrations. While this issue was mitigated 
beginning with bug fixes in version 15181 of AERMOD, a model to monitor 
comparison conducted by EPA determined that modeled concentrations at 
the monitor receptor locations correlated with monitoring 
concentrations when the tall stacks were modeled with the rural 
dispersion option instead of urban. In addition, peak monitored 
concentrations occur during the daytime. When modeling the tall stacks 
with the rural dispersion option the peak modeled concentrations 
occurred during the daytime hours, while using the urban option 
resulted in peak modeled concentrations during the nighttime hours. 
Therefore, the rural dispersion option was used for the tall stacks at 
EES Coke, DTE River Rouge, DTE Trenton Channel, and DTE Monroe, and the 
urban dispersion option was used for the remaining modeled sources with 
a population of 1,000,000.
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    \7\ U.S. Environmental Protection Agency, 2021. AERMOD 
Implementation Guide, section 5.1. Publication No. 454-B-21-002. 
Office of Air Quality Planning and Standards, Research Triangle 
Park, NC. https://gaftp.epa.gov/Air/aqmg/SCRAM/models/preferred/aermod/aermod_implementation_guide.pdf.
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3. Modeling Parameter: Area of Analysis (Receptor Grid)
    EPA believes that a reasonable first step towards characterization 
of air quality in the Detroit area is to determine the extent of the 
area of analysis, i.e., receptor grid. Considerations presented in the 
Modeling TAD include but are not limited to: The location of the 
SO2 emission sources or facilities considered for modeling; 
the extent of significant concentration gradients of nearby sources; 
and sufficient receptor coverage and density to adequately capture and 
resolve the model predicted maximum SO2 concentrations.

[[Page 59330]]

    For the Detroit area modeling analysis, a uniform Cartesian 
receptor grid was used with receptor spacing of 100 meters throughout 
the modeled domain. The receptor network contained 5,432 receptors and 
covered 12 kilometers by 12 kilometers area over the city of Detroit. 
EPA determined that this was the appropriate distance in order to 
adequately characterize air quality from the sources in the Detroit 
area which may have a potential impact in the area of analysis where 
maximum concentrations of SO2 are expected.
4. Modeling Parameter: Source Characterization
    EPA characterized the sources within the area of analysis in 
accordance with practices outlined as acceptable in the Modeling TAD. 
Specifically, EPA used actual stack heights in conjunction with actual 
or allowable emissions. EPA also adequately characterized the sources' 
building layouts and locations, as well as the stack parameters, e.g., 
exit temperature, exit velocity, location, and diameter.
5. Modeling Parameter: Emissions
    Guidance on modeling SO2 actual emissions is provided in 
section 5.2 of EPA's Modeling TSD. EPA believes that continuous 
emissions monitoring systems (CEMS) data provide acceptable historical 
emissions information when it is available and that these data are 
available for many electric generating units. The Modeling TAD also 
provides for the flexibility of using allowable emissions.
    EPA ran AERMOD using 2015-2017 actual average CEMS emissions data 
for DTE River Rouge and Trenton Channel, and 2016 actual emissions data 
for U.S. Steel, the source with the most significant contribution to 
the maximum NAAQS violations in the area, from Michigan's annual 
emissions database. Table 1 shows the actual emissions used for this 
analysis.

       Table 1--Actual SO2 Emissions Used in the Modeling Analysis
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                                                          SO2 emissions
                     Facility name                       (tons per year)
 
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DTE River Rouge........................................            4,383
DTE Trenton Channel....................................           11,303
U.S. Steel.............................................            1,480
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    For EES Coke, Carmeuse Lime, DTE Monroe, Severstal Steel, DIG, and 
Marathon Refinery in the area of analysis, EPA modeled the facilities 
using the most recent federally enforceable allowable limits for 
SO2. The facilities in EPA's area of analysis and their 
associated allowable rates are summarized in Table 2 below.

     Table 2--Allowable SO2 Emissions Used in the Modeling Analysis
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                                                          SO2 allowable
                                                         emissions (tons
                     Facility name                          per year)
 
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EES Coke...............................................            4,067
Carmeuse Lime..........................................            2,059
DTE Monroe.............................................           13,403
Severstal Steel........................................            2,119
DIG....................................................            2,335
Marathon Refinery......................................              401
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6. Modeling Parameter: Meteorology and Surface Characteristics
    As noted in the Modeling TAD, the selection of meteorological data 
should be based on spatial and climatological (temporal) 
representativeness. The representativeness of the data are based on: 
(1) The proximity of the meteorological monitoring site to the area 
under consideration, (2) the complexity of terrain, (3) the exposure of 
the meteorological site, and (4) the period of time during which data 
are collected. Sources of meteorological data include National Weather 
Service stations, site-specific or onsite data, and other sources such 
as universities, the Federal Aviation Administration, and military 
stations.
    EPA used the Detroit Metropolitan Wayne County Airport's 
meteorological surface data and the White Lake meteorological upper air 
data for the years 2013-2017 for modeling the Detroit area. This 
meteorological data set was processed by Michigan and obtained from its 
website.
    Meteorological data from the above surface and upper air stations 
were used in generating AERMOD-ready files with the AERMET processor. 
The output meteorological data created by the AERMET processor is 
suitable for being applied with AERMOD input files for AERMOD modeling 
runs. EPA followed the methodology and settings presented in appendix W 
in the processing of the raw meteorological data into an AERMOD-ready 
format and used AERSURFACE to best represent surface characteristics.
7. Modeling Parameter: Geography and Terrain
    The terrain in the area of analysis is best described as generally 
flat. To account for these terrain changes, the AERMAP terrain program 
within AERMOD was used to specify terrain elevations for all the 
receptors. The source of the elevation data incorporated into the model 
was the U.S. Geological Survey National Elevation Database.
8. Modeling Parameter: Background Concentrations
    The Modeling TAD offers two mechanisms for characterizing 
background concentrations of SO2 that are ultimately added 
to the modeled design values: (1) A ``first tier'' approach, based on 
monitored design values, or (2) a temporally varying approach, based on 
the 99th percentile monitored concentrations by hour of day and season 
or month. For the Detroit area modeling analysis, hourly SO2 
data from 2015-2017 at the Allen Park monitor, which is approximately 
17 kilometers southwest of Detroit, along with Allen Park wind data was 
used to generate Season/Hour-of-Day concentrations. Monitored 
concentrations associated with wind directions between and including 40 
to 205 degrees were excluded to avoid concentrations associated with 
sources explicitly modeled in the demonstration. The Season/Hour-of-Day 
background concentrations for this area of analysis were determined by 
EPA to be between 0.9 and 13.2 ppb, and these values were incorporated 
into the final AERMOD results.
8. Summary of Results and Proposed Determination
    EPA's modeling analysis indicated that the highest predicted 3-year 
average 99th percentile 1-hour average concentration within the chosen 
modeling domain is 139 ppb or 363.3 micrograms per cubic meter. The 
AERMOD analysis included an output unit factor of 381,680 to convert 
the model results from grams per second to ppb. This modeled 
concentration included the background concentration of SO2, 
and is based on actual and allowable emissions from the facilities in 
the Detroit area.
    For an area to attain the 2010 SO2 NAAQS by the October 
4, 2018 attainment date, the design value based upon modeled actual and 
allowable air quality data from 2015-2017 at the area of maximum 
ambient SO2 concentration must be equal to or less than 75 
ppb for the 1-hour standard. EPA's modeling results show that the 
maximum modeled design concentration in the Detroit area exceeds 75 
ppb. Therefore, based on modeled actual and allowable emissions for the 
2015-2017 period, EPA is proposing to determine that the Detroit area 
failed to attain the 2010 1-hour SO2 standard by the October 
4, 2018 attainment date.

B. Rhinelander Area Determination

    The determination of failure to attain for the Rhinelander area was 
based

[[Page 59331]]

upon the most recent three complete calendar years, prior to the 
attainment date of October 4, 2018, of complete, quality-assured 
measured data gathered at an established state and local air monitoring 
station (SLAMS) in the nonattainment area and entered into EPA's Air 
Quality System (AQS) database.\8\ A year is considered complete when 
all four quarters are complete, and a quarter is complete when at least 
75 percent of the sampling days are complete. A sampling day is 
considered complete if 75 percent of the hourly concentration values 
are reported; this includes data affected by exceptional events that 
have been approved for exclusion by the Administrator.\9\ Data from 
ambient air monitors operated by state and local agencies in compliance 
with EPA monitoring requirements must be submitted to AQS.\10\ 
Monitoring agencies annually certify that these data are accurate to 
the best of their knowledge.\11\ All data are reviewed to determine the 
area's air quality status in accordance with 40 CFR part 50, appendix 
T.
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    \8\ AQS is EPA's repository of ambient air quality data.
    \9\ See 40 CFR part 50, appendix T, sections 1(c), 3(b), 4(c), 
and 5(a).
    \10\ 40 CFR 58.16.
    \11\ 40 CFR 58.15.
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    With regard to the use of monitoring data for determining the 
attainment status of SO2 nonattainment areas, EPA's 2014 
SO2 Guidance specifically notes that ``[i]f the EPA 
determines that the air quality monitors located in the affected area 
are located in the area of maximum concentration, the EPA may be able 
to use the data from these monitors to make the determination of 
attainment without the use of air quality modeling data.'' \12\ This 
language might be read to suggest that EPA must always assess whether 
the air quality monitors in the affected area are located in the area 
of maximum concentration prior to using monitoring data to determine an 
SO2 nonattainment area's attainment status. However, this 
language was intended to refer to a situation where EPA is considering 
making a determination that the area has attained the NAAQS based on a 
finding that all of the monitoring sites within the affected area had 
an attaining design value for the relevant period. As described in 
section II.B of this action, in this instance, the monitoring site in 
the Rhinelander area did not have attaining design values for the 
relevant period. Consequently, even if the monitoring sites are not 
located in the area of maximum concentration, any monitors that would 
be located in the area of maximum concentration could not record 
concentrations lower than those recorded at the existing monitor at the 
Rhinelander site. Accordingly, since the Rhinelander Tower monitor 
design value for the 2015-2017 period was above the NAAQS, it is not 
necessary to consider whether the monitor is located in the area of 
maximum concentration in order to determine that the Rhinelander area 
did not attain the 2010 SO2 NAAQS by the October 4, 2018 
attainment date.
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    \12\ Id., 50.
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1. Monitoring Network Considerations
    Section 110(a)(2)(B)(i) of the CAA requires states to establish and 
operate air monitoring networks to compile data on ambient air quality 
for all criteria pollutants. EPA's monitoring requirements are 
specified by regulation in 40 CFR part 58. These requirements are 
applicable to state, and where delegated, local air monitoring agencies 
that operate criteria pollutant monitors.
    In section 4.4 of appendix D to 40 CFR part 58, EPA specifies 
minimum monitoring requirements for SO2 to operate at SLAMS. 
SLAMS produce data that are eligible for comparison with the NAAQS, and 
therefore, the monitor must be an approved Federal reference method 
(FRM), Federal equivalent method (FEM), or approved regional method 
(ARM) monitor.
    The minimum number of required SO2 SLAMS is described in 
sections 4.4.2 and 4.4.3 of appendix D to 40 CFR part 58. According to 
section 4.4.2, the minimum number of required SO2 monitoring 
sites is determined by the population weighted emissions index for each 
state's core based statistical area. Section 4.4.3 describes additional 
monitors that may be required by an EPA regional administrator.
    Under 40 CFR 58.10, states are required to submit annual monitoring 
network plans (AMNP) for ambient air monitoring networks for approval 
by EPA. Within the Rhinelander area, Wisconsin is responsible for 
ensuring that the area meets air quality monitoring requirements. 
Wisconsin submits annual monitoring network plans to EPA that describe 
the various monitoring sites that it operates.\13\ Each AMNP discusses 
the status of the air monitoring network as required under 40 CFR 58.10 
and addresses the operation and maintenance of the air monitoring 
network in the previous year. EPA regularly reviews these AMNPs for 
compliance with the applicable reporting requirements in 40 CFR part 
58.\14\
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    \13\ See, e.g., ``Wisconsin Department of Natural Resources 2018 
Air Monitoring Network Plan,'' which is included in the docket for 
this action.
    \14\ See, e.g., letter dated September 1, 2017 from Edward Nam, 
Director, Air and Radiation Division, EPA Region V, to Gail Good, 
Director, Bureau of Air Management, Wisconsin Department of Natural 
Resources, which is included in the docket for this action.
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    EPA also conducts regular ``technical systems audits'' (TSAs) 
during which EPA reviews and inspects ambient air monitoring programs 
to assess compliance with applicable regulations concerning the 
collection, analysis, validation, and reporting of ambient air quality 
data.\15\ As part of its 2018 TSA of Wisconsin, EPA required Wisconsin 
to prepare and submit a corrective action plan, and EPA accepted 
Wisconsin's TSA finding response forms in 2019.\16\
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    \15\ See 40 CFR part 58, appendix A, section 2.5.
    \16\ See letter dated June 24, 2019 from Michael Compher, Chief, 
Air Monitoring and Analysis Section, Air and Radiation Division, EPA 
Region V, to Katie Praedel, Chief, Air Monitoring Section, Bureau of 
Air Management, Wisconsin Department of Natural Resources, which is 
included in the docket for this action.
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    During the 2015-2017 data period, Wisconsin operated one 
SO2 SLAMS in the Rhinelander area: Rhinelander Tower monitor 
(AQS ID 55-085-0996). The Rhinelander Tower monitor site is located at 
434 High Street under the Rhinelander municipal water tower. The 
primary monitor at this site is an FEM monitor.
    Based on EPA's review of Wisconsin's AMNPs for the years 2016-2018 
\17\ and the 2018 TSA of Wisconsin's monitoring program, EPA proposes 
to find that the monitoring network in the Rhinelander area is adequate 
for the purpose of collecting ambient SO2 concentration data 
for use in determining whether the nonattainment area attained the 2010 
SO2 NAAQS by the October 4, 2018 attainment date.
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    \17\ Wisconsin's ANPs for 2016-2018 address the operation and 
maintenance of its air monitoring network for 2015-2017.
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2. SO2 Data Considerations
    Under 40 CFR 58.15, monitoring agencies must certify, on an annual 
basis, data collected at all SLAMS and at all FRM, FEM, and ARM special 
purpose monitor stations that meet EPA quality assurance requirements. 
In doing so, monitoring agencies must certify that the previous year of 
ambient concentration and quality assurance data are completely 
submitted to AQS and that the ambient concentration data are accurate 
to the best of their knowledge. Wisconsin annually certifies that the 
data it submits to AQS are quality assured, including data collected

[[Page 59332]]

by Wisconsin at the monitoring site in the Rhinelander area.
    For the Rhinelander area, for reasons discussed in section I.B of 
this action, the applicable attainment date was October 4, 2018. In 
accordance with appendix T to 40 CFR part 50, determinations of 
SO2 NAAQS compliance are based on three consecutive calendar 
years of data. To determine the air quality as of the attainment date 
in the Rhinelander area, EPA must review the data collected during the 
three calendar years immediately preceding the attainment date, or 
January 1, 2015-December 31, 2017.
    The SO2 data for the Rhinelander area from January 1, 
2015-December 31, 2017, have been certified by Wisconsin. EPA has also 
evaluated the completeness of these data in accordance with the 
requirements of 40 CFR part 50, appendix T. The data collected by 
Wisconsin meet the quarterly completeness criterion for all 12 quarters 
in the three calendar years preceding the attainment date at the 
Rhinelander Tower SO2 monitoring site.
3. Rhinelander SO2 Data and Proposed Determination
    The 1-hour SO2 design values at the Rhinelander Tower 
monitor for the 2015-2017 period are presented in Table 3. Table 3 
demonstrates that the 1-hour SO2 design values for the 2015-
2017 period are greater than 75 ppb at the eligible monitoring site.

                                            Table 3--2015-2017 1-Hour Design Values for the Rhinelander Area
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                        Annual 99th percentile daily maximum 1-hour
                                                                                          average                        1-hour design     Design value
                           Site (AQS ID)                            ---------------------------------------------------   value (ppb)         valid?
                                                                           2015             2016             2017
--------------------------------------------------------------------------------------------------------------------------------------------------------
Rhinelander Tower (55-085-0996)....................................             156              129               38              108              Yes
--------------------------------------------------------------------------------------------------------------------------------------------------------
Source: EPA, Design Value Report, August 26, 2020.

    The data in Table 3 demonstrates that the monitoring site in the 
Rhinelander area failed to attain the 2010 1-hour SO2 NAAQS 
by the applicable attainment date of October 4, 2018. The 3-year design 
value for the Rhinelander Tower monitor was deemed valid due to meeting 
the criteria in 40 CFR part 50, appendix T, section 3(c)(i), which 
requires that ``at least 75 percent of the days in each quarter of each 
of three consecutive years have at least one reported hourly value, and 
the design value calculated according to the procedures specified in 
section 5 is above the level of the primary 1-hour standard.''
    For an area to attain the 2010 SO2 NAAQS by the October 
4, 2018 attainment date, the design value based upon monitored air 
quality data from 2015-2017 at each eligible monitoring site must be 
equal to or less than 75 ppb for the 1-hour standard. Table 3 shows 
that the design value at the monitoring site in the Rhinelander area 
exceeds 75 ppb. Therefore, based on quality-assured and certified data 
for the 2015-2017 data period, EPA is proposing to determine that the 
Rhinelander area failed to attain the 2010 1-hour SO2 
standard by the October 4, 2018 attainment date.

C. Consequences for SO2 Nonattainment Areas Failing To Attain Standards 
by Attainment Dates

    The consequences for SO2 nonattainment areas for failing 
to attain the standards by the applicable attainment date are set forth 
in CAA section 179(d). Under section 179(d), a state must submit a SIP 
revision for the area meeting the requirements of CAA sections 110 and 
172, the latter of which requires, among other elements, a 
demonstration of attainment and reasonable further progress and 
contingency measures. In addition, under CAA section 179(d)(2), the SIP 
revision must include such additional measures as EPA may reasonably 
prescribe, including all measures that can be feasibly implemented in 
the area in light of technological achievability, costs, and any non-
air quality and other air quality-related health and environmental 
impacts. The state is required to submit the SIP revision within one 
year after EPA publishes a final action in the Federal Register 
determining that the nonattainment area failed to attain the 
SO2 NAAQS.
    On March 19, 2021 (86 FR 14827), and March 23, 2021 (86 FR 15418), 
EPA published actions partially disapproving the 2010 SO2 
attainment plans for the Detroit and Rhinelander areas, respectively, 
as submitted and supplemented in 2016. Although final findings of 
failure to attain will not eliminate each state's obligation to address 
the disapproved elements of its prior plan submittal, EPA anticipates 
that the submission of a new, approvable attainment plan in response to 
these findings would also satisfy these obligations for Michigan and 
Wisconsin.
    On July 22, 2021 (86 FR 38643), EPA proposed to approve Wisconsin's 
revised plan, submitted to EPA on March 29, 2021. If EPA takes final 
action to approve that revised SIP submission from Wisconsin, EPA is 
proposing to find that the State has also satisfied the requirement to 
submit a SIP revision to address the finding, if finalized, that the 
area failed to timely attain the 2010 SO2 NAAQS.
    Under CAA sections 179(d)(3) and 172(a)(2), the new attainment date 
for each nonattainment area is the date by which attainment can be 
achieved as expeditiously as practicable, but no later than five years 
after EPA publishes a final action in the Federal Register determining 
that the nonattainment area failed to attain the SO2 NAAQS. 
In the meantime, EPA's FIP obligations for both the Detroit and 
Rhinelander areas remain in force, and this finding, if finalized, 
would not negate EPA's FIP deadlines. For the Detroit area, the 
statutory deadline for EPA to promulgate a FIP has passed, and EPA is 
actively working on a FIP.
    In addition to triggering requirements for a new SIP submittal, a 
final determination that a nonattainment area failed to attain the 
NAAQS by the attainment date would trigger the implementation of 
contingency measures adopted under 172(c)(9).

III. What action is EPA taking?

    EPA is proposing under CAA section 179(c)(1) to determine that the 
Detroit and Rhinelander areas failed to attain the 2010 1-hour 
SO2 standard by the applicable attainment date of October 4, 
2018. If finalized as proposed, Michigan and Wisconsin would be 
required under CAA section 179(d) to submit revisions to the SIP for 
the Detroit and Rhinelander SO2 nonattainment areas, 
respectively. The required SIP revision for each area must, among other 
elements, demonstrate expeditious attainment of the standards within 
the time period prescribed by CAA section 179(d). If finalized as 
proposed, the SIP

[[Page 59333]]

revisions required under CAA section 179(d) would be due for submittal 
to EPA no later than one year after the publication date of the final 
action. However, for the Rhinelander area, if EPA approves the recently 
revised SIP submission submitted by the State of Wisconsin, EPA is 
proposing to treat that submission as satisfying the requirement to 
submit revisions to the SIP to address the failure to timely attain the 
2010 SO2 NAAQS.
    EPA is soliciting public comments on the issues discussed in this 
action. EPA will accept comments from the public on this proposal for 
the next 30 days and will consider these comments before taking final 
action.

IV. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive Orders 
can be found at https://www2.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review, and Executive 
Order 13563: Improving Regulation and Regulatory Review

    This action is not a significant regulatory action and therefore 
was not submitted to the Office of Management and Budget (OMB) for 
review.

B. Paperwork Reduction Act (PRA)

    This action does not impose an information collection burden under 
the provisions of the PRA because it does not contain any information 
collection activities.

C. Regulatory Flexibility Act (RFA)

    EPA certifies that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. This 
action will not impose any requirements on small entities. This 
proposed action, if finalized, would require the State to adopt and 
submit SIP revisions to satisfy CAA requirements and would not itself 
directly regulate any small entities.

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate of $100 million 
or more, as described in UMRA (2 U.S.C. 1531-1538) and does not 
significantly or uniquely affect small governments. This action itself 
imposes no enforceable duty on any state, local, or tribal governments, 
or the private sector. This action proposes to determine that the 
Detroit and Rhinelander SO2 nonattainment areas failed to 
attain the NAAQS by the applicable attainment dates. If finalized, this 
determination would trigger existing statutory timeframes for the State 
to submit SIP revisions. Such a determination in and of itself does not 
impose any Federal intergovernmental mandate.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have 
substantial direct effects on the states, on the relationship between 
the National Government and the states, or on the distribution of power 
and responsibilities among the various levels of government.

F. Executive Order 13175, Consultation and Coordination With Indian 
Tribal Governments

    This action does not have tribal implications as specified in 
Executive Order 13175. The proposed finding of failure to attain the 
SO2 NAAQS does not apply to tribal areas, and the proposed 
rule would not impose a burden on Indian reservation lands or other 
areas where EPA or an Indian tribe has demonstrated that a tribe has 
jurisdiction within the Detroit and Rhinelander SO2 
nonattainment areas. Thus, this 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.

G. Executive Order 13045, Protection of Children From Environmental 
Health Risks and Safety Risks

    EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that concern environmental health or safety risks 
that EPA has reason to believe may disproportionately affect children, 
per the definition of ``covered regulatory action'' in section 2-202 of 
the Executive order. This proposed action is not subject to Executive 
Order 13045 because the effect of this proposed action, if finalized, 
would be to trigger additional planning requirements under the CAA. 
This proposed action does not establish an environmental standard 
intended to mitigate health or safety risks.

H. Executive Order 13211, Actions That Significantly Affect Energy 
Supply, Distribution, or Use

    This proposed rule is not subject to Executive Order 13211, because 
it is not a significant regulatory action under Executive Order 12866.

I. National Technology Transfer and Advancement Act (NTTAA)

    This rulemaking does not involve technical standards.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations

    EPA believes that this action does not have disproportionately high 
and adverse human health or environmental effects on minority 
populations, low-income populations and/or indigenous peoples, as 
specified in Executive Order 12898 (59 FR 7629, February 16, 1994). The 
effect of this proposed action, if finalized, would be to trigger 
additional planning requirements under the CAA.

List of Subjects in 40 CFR Part 52

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

    Dated: October 20, 2021.
Cheryl Newton,
Acting Regional Administrator, Region 5.
[FR Doc. 2021-23274 Filed 10-26-21; 8:45 am]
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