Proposed Rule2026-06941
Air Plan Approval; Michigan; Redesignation and Maintenance Plan for the Partial St. Clair 2010 1-Hour Sulfur Dioxide (SO2) NAAQS Nonattainment Area
Primary source
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Published
April 10, 2026
Issuing agencies
Environmental Protection Agency
Abstract
The Environmental Protection Agency (EPA) is proposing to redesignate the St. Clair nonattainment area in southeast Michigan to attainment for the 2010 sulfur dioxide (SO<INF>2</INF>) National Ambient Air Quality Standard (NAAQS). The EPA is also proposing to approve Michigan's maintenance plan for the St. Clair SO<INF>2</INF> nonattainment area and emissions limits for the DTE Belle River Power Plant. Michigan submitted the request for approval of the St. Clair area redesignation and maintenance plan on December 15, 2023, with a supplement to the request on July 24, 2025.
Full Text
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<title>Federal Register, Volume 91 Issue 69 (Friday, April 10, 2026)</title>
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[Federal Register Volume 91, Number 69 (Friday, April 10, 2026)]
[Proposed Rules]
[Pages 18383-18388]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-06941]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 52 and 81
[EPA-R05-OAR-2023-0635; FRL-13222-01-R5]
Air Plan Approval; Michigan; Redesignation and Maintenance Plan
for the Partial St. Clair 2010 1-Hour Sulfur Dioxide (SO2) NAAQS
Nonattainment Area
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
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SUMMARY: The Environmental Protection Agency (EPA) is proposing to
redesignate the St. Clair nonattainment area in southeast Michigan to
attainment for the 2010 sulfur dioxide (SO<INF>2</INF>) National
Ambient Air Quality Standard (NAAQS). The EPA is also proposing to
approve Michigan's maintenance plan for the St. Clair SO<INF>2</INF>
nonattainment area and emissions limits for the DTE Belle River Power
Plant. Michigan submitted the request for approval of the St. Clair
area redesignation and maintenance plan on December 15, 2023, with a
supplement to the request on July 24, 2025.
DATES: Comments must be received on or before May 11, 2026.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R05-
OAR-2023-0635 at <a href="https://www.regulations.gov">https://www.regulations.gov</a>, or via email to
<a href="/cdn-cgi/l/email-protection#eb8a99998ac5988a998a83ab8e9b8ac58c849d"><span class="__cf_email__" data-cfemail="04657676652a776576656c446174652a636b72">[email protected]</span></a>. For comments submitted at <a href="http://Regulations.gov">Regulations.gov</a>, follow
the online instructions for submitting comments. Once submitted,
comments cannot be edited or removed from the docket. The EPA may
publish any comment received to its public docket. Do not submit to the
EPA's docket at <a href="https://www.regulations.gov">https://www.regulations.gov</a> any information you
consider to be Confidential Business Information (CBI), Proprietary
Business Information (PBI), or other information whose disclosure is
restricted by statute. Multimedia submissions (audio, video, etc.) must
be accompanied by a written comment. The written comment is considered
the official comment and should include discussion of all points you
wish to make. The EPA will generally not consider comments or comment
contents located outside of the primary submission (i.e., on the web,
cloud, or other file sharing system). For additional submission
methods, please contact the person identified in the FOR FURTHER
INFORMATION CONTACT section. For the full EPA public comment policy,
information about CBI, PBI, or multimedia submissions, and general
guidance on making effective comments, please visit <a href="https://www.epa.gov/dockets/commenting-epa-dockets">https://www.epa.gov/dockets/commenting-epa-dockets</a>.
FOR FURTHER INFORMATION CONTACT: Alexis Bender, Attainment Planning and
Maintenance Section, Air and Radiation Division (AR18J), Environmental
Protection Agency, Region 5, 77 West Jackson Boulevard, Chicago,
Illinois 60604, telephone number: (312) 886-9497, email address:
<a href="/cdn-cgi/l/email-protection#c0a2a5aea4a5b2eea1aca5b8a9b380a5b0a1eea7afb6"><span class="__cf_email__" data-cfemail="bad8dfd4dedfc894dbd6dfc2d3c9fadfcadb94ddd5cc">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,''
``us,'' or ``our'' is used, we mean the EPA.
I. Background
On June 22, 2010 (75 FR 35520), the EPA established a new 1-hour
SO<INF>2</INF> NAAQS of 75 parts per billion (ppb), which can be met at
an ambient air quality monitoring site (or in the case of dispersion
modeling, at an ambient air quality receptor location) when the 3-year
average of the annual 99th percentile of daily maximum 1-hour average
concentrations is less than or equal to 75 ppb, as determined in
accordance with appendix T of 40 CFR part 50. 40 CFR 50.17(a)-(b).
On September 12, 2016 (81 FR 45039), the EPA designated part of St.
Clair County, Michigan as nonattainment for the 2010 SO<INF>2</INF>
NAAQS based on computer modeling that incorporated SO<INF>2</INF> data
from Continuous Emissions Monitors (CEM) at the DTE Belle River and St.
Clair power plants.
Section 191 of the CAA directs States to submit a State
Implementation Plan (SIP) for an area designated as nonattainment for
the 2010 SO<INF>2</INF> NAAQS to the EPA within 18 months of the
effective date of the designation. The SIP must demonstrate that the
State will achieve the NAAQS for the nonattainment area as
expeditiously as practicable, but no later than five years from the
effective date of designation. As a result, Michigan was required to
submit a nonattainment SIP to the EPA by March 12, 2018, to bring the
St. Clair area into attainment by the attainment date of September 12,
2021. Michigan did not submit a nonattainment SIP for the St. Clair
area by the March 12, 2018, deadline, instead relying on the EPA's
Clean Data Policy, described in more detail below, to address the
requirement.
On July 24, 2020, Michigan submitted a request that the EPA make a
Clean Data Determination (CDD) under the CAA and the EPA's Clean Data
Policy, based on both local monitored air quality data and a new
dispersion modeling analysis, demonstrating that the St. Clair
nonattainment area attained the 2010 SO<INF>2</INF> NAAQS. When a
nonattainment area is attaining the 2010 SO<INF>2</INF> NAAQS based on
the most recent available data, the EPA may issue a CDD suspending
certain planning requirements for as long as the area continues to
attain the NAAQS. On June 30, 2021, Michigan submitted the St. Clair
area's emissions inventory and nonattainment new source review (NNSR)
verification required by CAA section 172 to the EPA. The EPA issued a
CDD for the St. Clair area on December 7, 2021 (86 FR 69173), and
approved Michigan's submittal of the emissions inventory and NNSR
elements on February 9, 2022 (87 FR 7387). Additionally, to address
requirements under CAA section 179(c), the EPA made a determination of
attainment by the attainment date, finding that the St. Clair
nonattainment area attained the 2010 SO<INF>2</INF> NAAQS for the
relevant period associated with the attainment date of September 12,
2021 (89 FR 104884, December 26, 2024).
II. Evaluation of Michigan's Redesignation Request and Maintenance Plan
Michigan submitted a request for redesignation and a maintenance
plan for the St. Clair nonattainment area on December 15, 2023, and
supplemented the request on July 24, 2025. In addition to information
addressing CAA redesignation and maintenance plan requirements, the
submittal addresses the DTE Energy St. Clair Power Plant closure and
the reduction of SO<INF>2</INF> emissions from the DTE Belle River
Power Plant.
Under section 107(d)(3)(E) of the CAA, the EPA may not promulgate a
[[Page 18384]]
redesignation of a nonattainment area (or portion thereof) unless:
1. The EPA has determined that the area has attained the NAAQS;
2. The EPA has fully approved the applicable implementation plan
for the area under section 110(k) of the CAA;
3. The EPA has determined that improvement in air quality is due to
permanent and enforceable reductions in emissions resulting from
implementation of the applicable implementation plan and applicable
Federal air pollution control regulations and other permanent and
enforceable reductions;
4. The EPA has fully approved a maintenance plan for the area under
section 175A of the CAA; and
5. The State containing such area has met all requirements
applicable to the area under section 110 of the CAA and part D.
The EPA's evaluation of Michigan's redesignation request and
maintenance plan was based on consideration of the five redesignation
criteria provided under CAA section 107(d)(3)(E) and is described in
the remainder of this section.
A. Criterion (1)--The St. Clair SO2 Nonattainment Area Has Attained the
2010 SO2 NAAQS
In accordance with CAA section 107(d)(3)(E)(i), to redesignate a
nonattainment area to attainment, the EPA must determine that the area
has attained the applicable NAAQS. An area is attaining the 2010
SO<INF>2</INF> standard when the three-year average of the annual 99th
percentile of daily maximum 1-hour average concentrations is less than
or equal to 75 ppb consistent with 40 CFR 50.17 and appendix T of Part
50. If dispersion modeling is used to make this determination, an area
is attaining the 2010 SO<INF>2</INF> NAAQS when the modeled
concentration is at or below the one-hour SO<INF>2</INF> NAAQS of 196.4
micrograms per cubic meter (or 75 ppb).
As stated in the EPA's April 23, 2014, Guidance for 1-Hour SO2
Nonattainment Area SIP Submissions (April 2014 SO<INF>2</INF>
Guidance), there are two components needed to support an attainment
determination: (1) a review of representative air quality monitoring
data; and (2) a further analysis, where there are no monitors, or the
monitors are not located in the area of maximum concentration, using
air quality dispersion modeling, which will generally be needed to
estimate SO<INF>2</INF> concentrations throughout the nonattainment
area to demonstrate that the entire area is attaining the applicable
NAAQS, based on current actual emissions or the fully implemented
control strategy. Michigan's redesignation request submission for the
St. Clair nonattainment area provides a demonstration that the area is
attaining based on ambient air monitoring data and a dispersion
modeling analysis for the nonattainment area.
Per component (1), ambient air monitoring data was collected from
2017 to 2021 by two SO<INF>2</INF> monitors located in the
nonattainment area: the Remer monitor near the St. Clair Power Plant
and the Mills monitor near the Belle River Power Plant. Because of the
nonattainment designation, DTE installed these two on-site
SO<INF>2</INF> monitoring and meteorology stations in late 2016. A
Michigan Air Quality Division SO<INF>2</INF> monitor, known as the Port
Huron monitor, is located approximately 12 miles north of the power
plants but is outside the nonattainment area; this monitor is addressed
in the Technical Support Document (TSD) accompanying this action.
Monitoring data at the two DTE SO<INF>2</INF> monitors for the
period from 2017 through 2019 showed attainment of the SO<INF>2</INF>
NAAQS and served as justification for Michigan's July 24, 2020, CDD
submittal to the EPA. The DTE monitors continued to collect
SO<INF>2</INF> data through the end of 2022 showing that the NAAQS
continued to be met. Table 1 details the attaining values of ambient
air monitoring data in the St. Clair area in accordance with 40 CFR
50.17(b).
Table 1--Monitoring Data for the SO Nonattainment Area
[Annual 99th percentile and design values in ppb]
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99th Percentile values 3-Year design values
Site ID Power plant Monitor site name -------------------------------------------------------------------------------
2017 2018 2019 2020 2021 2017-2019 2018-2020 2019-2021
--------------------------------------------------------------------------------------------------------------------------------------------------------
DTE..................... Belle River........... Mills................. 46 50 40 28.8 62.2 45 39.6 43.6
DTE..................... St. Clair............. Remer................. 51 65 45 24.5 41.1 53.6 44.8 46.8
--------------------------------------------------------------------------------------------------------------------------------------------------------
Per component (2), Michigan conducted air quality dispersion
modeling in accordance with 40 CFR part 51, appendix W to demonstrate
attainment of the 2010 SO<INF>2</INF> NAAQS for the St. Clair
nonattainment area based on the fully implemented control strategy. A
more in-depth discussion of the EPA's modeling requirements, including
an assessment of longer-term average limits, as well as Michigan's
modeling analysis is included in the TSD for this action.
Michigan's modeled demonstration of attainment of the
SO<INF>2</INF> NAAQS relies upon the permanent and enforceable
SO<INF>2</INF> emission limits for the Belle River Power Plant
established in Permit to Install 51-22 and the shutdown of the St.
Clair Power Plant, which ceased operation in 2022. Permit to Install
51-22, which implemented revised lower emissions limits for the Belle
River facility in April 2022, includes limits for each of the Belle
River Power Plant boilers of 0.680 pounds per million British thermal
units (lbs/MMBtu) for a 30-day rolling average emission rate and 1.2
pounds per lbs/MMBtu based upon any 3-hour average. The EPA is
proposing to incorporate Permit to Install 51-22 into Michigan's SIP in
this action.
The April 2014 SO<INF>2</INF> Guidance states that a demonstration
that the control strategy in the SIP has been fully implemented is
relevant when making an attainment determination based on modeling.
Pursuant to the Belle River Renewable Operating Permit, (ROP) MI-ROP-
B2796-2024, the facility submitted quarterly Opacity Excess Emissions
Reports containing monthly SO<INF>2</INF> emission rate averages for
2023-2024 to Michigan. These monthly emission rate averages are all
within the SO<INF>2</INF> emission limits set forth in Permit to
Install 51-22.
Michigan's modeling analysis demonstrates that the SO<INF>2</INF>
emission limits contained in Permit to Install 51-22, governing Belle
River Power Plant SO<INF>2</INF> emissions, in combination with the St.
Clair Power Plant shutdown and background concentrations, yield a
maximum SO<INF>2</INF> concentration of 62.8 ppb, which is below the
2010 SO<INF>2</INF> NAAQS of 75 ppb. Therefore, the EPA proposes to
conclude that the dispersion modeling analysis demonstrates that the
[[Page 18385]]
St. Clair nonattainment area has attained the 2010 SO<INF>2</INF>
NAAQS.
B. Criterion (2) and Criterion (5)--Michigan Has Met All Applicable
Requirements Under CAA Section 110 and Part D of the CAA, and the EPA
Has Fully Approved the Applicable Implementation Plan Under CAA Section
110(K)
In order to be redesignate a nonattainment area to attainment under
a NAAQS, a State must have met all applicable requirements of section
110 and part D of the CAA (CAA section 107(d)(3)(E)(v)), and the EPA
must have fully approved the applicable implementation plan (CAA
section 107(d)(3)(E)(ii)). The EPA's long-standing interpretation of
the CAA is that not every requirement under CAA section 110 and part D
is applicable for purposes of CAA section 107(d)(3)(E)(ii) and (v). The
Agency's interpretation of the statute limiting evaluation of section
110 and part D requirements to only those requirements that are
applicable for purposes of redesignation was first articulated shortly
after the passage of the 1990 Amendments to the CAA in Agency guidance
documents, and has been consistently applied in notice-and-comment
redesignation actions over the last three decades.
Many of the CAA section 110 elements that are unrelated to an
area's SO<INF>2</INF> attainment status are not applicable requirements
for purposes of redesignation. The area will still be subject to these
requirements after the area is redesignated to attainment of the 2010
1-hour primary SO<INF>2</INF> NAAQS.
The EPA is proposing to determine that Michigan has met the part D
requirements and the EPA has fully approved those requirements that are
applicable for purposes of redesignation. Part D is comprised of the
general nonattainment area plan requirements in subpart 1 (CAA section
172) as well as pollutant-specific subparts, including CAA section 191
(or subpart 5), which applies to areas designated nonattainment for
SO<INF>2</INF>, nitrogen dioxide, or lead. In lieu of an attainment SIP
for St. Clair, Michigan submitted a CDD consistent with the Clean Data
Policy that determined the nonattainment area has attained the 2010
SO<INF>2</INF> NAAQS. In designated nonattainment areas where monitored
data demonstrate that the NAAQS have been achieved, the EPA interprets
certain requirements of the CAA as no longer applicable for so long a
time as air quality continues to meet the standard. Under the Clean
Data Policy, the EPA may issue a determination of attainment after
notice and comment rulemaking determining that a specific area is
attaining the relevant standard. For such areas, the requirement to
submit to the EPA those SIP elements related to attaining the NAAQS is
suspended for as long as the area continues to attain the standard;
these planning elements include reasonable further progress
requirements, attainment demonstrations, reasonably available control
measures, contingency measures, and other State planning requirements
related to attainment of the NAAQS. In the April 2014 SO<INF>2</INF>
Nonattainment Area Guidance, the EPA provides guidance and a rationale
for the application of the Clean Data Policy to the 2010 SO<INF>2</INF>
NAAQS.
The EPA approved Michigan's CDD request in lieu of an attainment
SIP, and the determination became effective December 7, 2021 (86 FR
69173). The EPA's final determination suspended the requirements for
Michigan to submit an attainment demonstration and other associated
nonattainment planning requirements for the St. Clair nonattainment
area as long as the St. Clair area continues to attain the 2010
SO<INF>2</INF> NAAQS. Michigan was still required to submit an
emissions inventory under CAA section 172(c)(3) and a nonattainment new
source review program under CAA section 172(c)(5). Michigan submitted
the St. Clair area's emissions inventory and NNSR verification to the
EPA on June 30, 2021, which were approved on February 9, 2022 (87 FR
7387).
CAA sections 172(c)(1) and 172(c)(6) direct States with areas
designated as nonattainment to demonstrate that the submitted plan and
its emission limitations and control measures provide for attainment of
the NAAQS. 40 CFR part 51, subpart G further delineates the control
strategy requirements that SIPs must meet, and the EPA has long
required that all SIPs and control strategies reflect the four
fundamental principles of quantification, enforceability,
replicability, and accountability. See ``General Preamble for the
Implementation of Title I of the Clean Air Act Amendments of 1990,''
(General Preamble) published on April 16, 1992 (57 FR 13498), at 13567
through 13568. SO<INF>2</INF> attainment plans must consist of two
components: (1) enforceable emission limits and other control measures
that assure implementation of permanent, enforceable and necessary
emission controls, and (2) a modeling analysis which meets the
requirements of 40 CFR part 51, appendix W. As discussed above in
section II.A., Criterion (1), of this document, Michigan's
redesignation request addresses both components, because it includes
permanent and enforceable emission reductions for the SO<INF>2</INF>
sources in the area and a modeling analysis that demonstrates that
Michigan's control strategy provides for attainment of the 2010
SO<INF>2</INF> NAAQS. The EPA is proposing to incorporate Permit to
Install 51-22, governing Belle River Power Plant SO<INF>2</INF>
emissions, into Michigan's SIP in this action, which will render it
Federally enforceable.
Based on the above details and the approval of Michigan's CDD, the
EPA is proposing to find that Michigan has met the applicable
requirements of section 110 and part D of the CAA for purposes of the
redesignation of the St. Clair nonattainment area.
C. Criterion (3)--The EPA Has Determined That Improvement in Air
Quality Is Due to Permanent and Enforceable Reductions in Emissions
Resulting From Implementation of the Applicable Implementation Plan and
Applicable Federal Air Pollution Control Regulations and Other
Permanent and Enforceable Reductions
To redesignate an area from nonattainment to attainment, section
107(d)(3)(E)(iii) of the CAA requires the EPA to determine that the air
quality improvement in the area is due to permanent and enforceable
reductions in emissions resulting from the implementation of the SIP
and applicable Federal air pollution control regulations and other
permanent and enforceable emission reductions.
Permanent and enforceable improvements in air quality for the St.
Clair area were focused on the two large sources in the area: the St.
Clair Power Plant, which shut down in 2022, and the Belle River Power
Plant, which implemented lower emission limits that took effect in
April 2022. There are no other sources of significant size emitting
SO<INF>2</INF> in the area. Michigan's redesignation request contains
permanent and enforceable SO<INF>2</INF> strategies for both DTE power
plants. As discussed above in section II.A., Criterion (1), of this
document, the reduced emission limits at the Belle River facility are
contained within Permit to Install 51-22, which the EPA is proposing to
incorporate into Michigan's SIP in this action. The Belle River Power
Plant will be required to operate emissions controls following
redesignation of the area unless such a change is first approved by the
EPA as a revision to Michigan's SIP consistent with section 110(l) of
the CAA. As part of the closure of the St. Clair Power Plant, the Acid
Rain permit for the
[[Page 18386]]
facility was revoked by the State on December 15, 2022.
If the area is redesignated to attainment, CAA Prevention of
Significant Deterioration (PSD) Requirements for permitting any new
sources or modifications to sources in the area will apply.
Michigan's computer modeling analysis assesses nonattainment years
(pre-2022) and the modeled attainment year (2022) for the Belle River
and St. Clair Power Plants. In this analysis, the State modeled
nonattainment (pre-2022) allowable emissions of 38,798 pounds per hour
(lbs/hr) which declined to 9,268 lbs/hr after permanent and enforceable
reductions were put in place for the area. The dispersion modeling
analysis demonstrates that the St. Clair area is attaining the 2010
NAAQS with the closure of the St. Clair Power Plant and implementation
of lower emission limits at the Belle River Power Plant. The TSD, which
is included in the docket for this action, contains further detail on
Michigan's modeling analysis.
The EPA is proposing to find that the St. Clair area modeling
results demonstrate attainment and continued maintenance of the 2010
SO<INF>2</INF> NAAQS and that the air quality improvement in the St.
Clair nonattainment area is due to permanent and enforceable reductions
in emissions.
D. Criterion (4)--The EPA Has Fully Approved a Maintenance Plan for the
Area Under Section 175A of the CAA
Section 175A of the CAA sets forth the elements of a maintenance
plan for areas seeking redesignation from nonattainment to attainment.
Under section 175A, the plan must demonstrate continued attainment of
the applicable NAAQS for at least ten years after the nonattainment
area is redesignated to attainment. Eight years after the
redesignation, the State must submit a revised maintenance plan
demonstrating that attainment will continue to be maintained for the
ten years following the initial ten-year period. To address the
possibility of future NAAQS violations, the maintenance plan must
contain contingency measures as the EPA deems necessary to ensure
prompt correction of any future violations of the 2010 SO<INF>2</INF>
NAAQS.
Specifically, the maintenance plan should address five
requirements: the attainment emissions inventory, maintenance
demonstration, monitoring, verification of continued attainment, and a
contingency plan. The EPA is proposing to determine that Michigan's
redesignation request contains all the necessary components and
commitments. The EPA is further proposing to approve the maintenance
plan as part of Michigan's federally enforceable SIP.
As part of a State's maintenance plan, the EPA's Redesignation
Guidance requires States to identify the level of emissions in an
affected area sufficient to attain and maintain the NAAQS. In its
redesignation request, Michigan provided modeled SO<INF>2</INF>
emissions of the emission units in the nonattainment area for 2022, a
year in which the permanent and enforceable reductions reduced the
emission rates for the two large facilities in St. Clair. As discussed
above in section II.A., Criterion (1), of this document, the Belle
River facility lowered its allowable limits in revised Permit to
Install 51-22, and the St. Clair Power Plant shut down, causing
allowable emissions in the area to decline heavily. The pre-2022 total
emissions were 39,798 lbs/yr from both large SO<INF>2</INF> emitting
facilities, with 2019-2021 design values from the near monitors of 43.7
ppb at DTE Mills Compressor Station Monitor and 37.0 ppb at DTE Remer
Road Monitor. The emissions then decreased to 9,268 lbs/yr for the
post-2022 modeled rates, summarized in Table 2 of this document below.
Michigan's modeling analysis, based on the post-2022 emission rates in
Table 2, resulted in a design value of 62.8 ppb, below the
SO<INF>2</INF> NAAQS of 75 ppb. Michigan's modeling analysis is
discussed further in the TSD, which is included in the docket for this
action.
Table 2--Modeled SO Emission Rates Before and After Permanent Reductions in 2022
----------------------------------------------------------------------------------------------------------------
Pre-2022 (lbs/ Post-2022 (lbs/
Modeled source Emission unit hr) hr)
----------------------------------------------------------------------------------------------------------------
Belle River Power Plant....................... Boiler 1........................ 8176 4634
Boiler 2........................ 8176 4634
St. Clair Power Plant......................... Unit 1.......................... 2355 0
Unit 2.......................... 2355 0
Unit 3.......................... 2355 0
Unit 4.......................... 2355 0
Unit 6.......................... 5186 0
Unit 7.......................... 7840 0
----------------------------------------------------------------------------------------------------------------
The EPA's ``Procedures for Processing Requests to Redesignate Areas
to Attainment'' describes two ways for a State to demonstrate
maintenance of the NAAQS following the redesignation of the area: (1)
the State can show that future emissions of a pollutant will not exceed
the level of the attainment inventory, or (2) the State can model to
show that the future mix of sources and emission rates will not cause a
violation of the standard. In both instances, the demonstration should
be for a period of 10 years following the redesignation. Furthermore,
the plan should contain a summary of air quality concentrations
resulting from control measures implemented in instances where modeling
is relied upon to demonstrate maintenance. Michigan's maintenance
demonstration consists of modeling showing total 1-hour SO<INF>2</INF>
concentration values (i.e., maximum 1-hour SO<INF>2</INF>
concentrations added to background concentration values) now in effect
in the St. Clair area which meet attainment of the 2010 SO<INF>2</INF>
NAAQS. The modeling was based on maximum allowable rates that are
protective of the SO<INF>2</INF> NAAQS. Because there are no large
sources of SO<INF>2</INF> projected to enter the St. Clair area, the
St. Clair Power Plant closed in 2022, and the Belle River facility
plans to convert from coal to natural gas by 2027, the nonattainment
area can be expected to demonstrate attainment of the standard for the
requisite 10 years and beyond. Table 3 below shows Michigan's base year
inventory and attainment year inventory to demonstrate that the area
will remain in attainment to projected year 2035.
[[Page 18387]]
Table 3--Source Base Year Inventory and Attainment Year Inventory
----------------------------------------------------------------------------------------------------------------
Modeled source Emission unit 2017 (tpy) 2023 (tpy) 2035 (tpy)
----------------------------------------------------------------------------------------------------------------
Belle River facility...................... Boiler 1..................... 12,790.03 8,831.2 0
Boiler 2..................... 9,766.03 7,961.3 0
St. Clair facility........................ Unit 1....................... 2,443.21 0 0
Unit 2....................... 2,294.02 0 0
Unit 3....................... 2,374.14 0 0
Unit 4....................... 0 0 0
Unit 6....................... 5,974.07 0 0
Unit 7....................... 1,274.03 0 0
----------------------------------------------------------------------------------------------------------------
While the State's maintenance plan submission expressly documents
that the area's emissions inventories will remain below the attainment
year inventories through 2035, emissions are projected to continue to
remain below attainment levels into 2036 and beyond due to the 2022
closure of the St. Clair facility and the projected 2027 conversion of
the Belle River facility to natural gas. Along with Table 3 of this
document above, Michigan provides additional support within its Permit
to Install APP-2024-0273, which shows that the conversion to natural
gas from coal will continue to allow the St. Clair area to meet
attainment. Detailed within the permit, the baseline actual emissions
of the highest consecutive 24-month period from the Belle River
facility was calculated at 21,470 tons per year (tpy). After its
conversion to natural gas, the Belle River facility's actual emissions
are projected to decline to 24 tpy. Therefore, even if the
redesignation action is finalized in 2026, the maintenance plan
provides continued maintenance for at least ten years after
redesignation in accordance with the requirements of section 175A.
DTE voluntarily installed and operated two SO<INF>2</INF> monitors
in the nonattainment area and within the vicinity of the two power
plants in late 2016 until the end of 2022 to determine whether the
modeled violations of SO<INF>2</INF> in fact reflected ambient
SO<INF>2</INF> impacts. In 2022, DTE discontinued its monitors due to
cost, consistent attainment, and the fact that modeling shows NAAQS
attainment will be maintained into the future. The monitoring data
showed that monitored SO<INF>2</INF> consistently stayed well below the
SO<INF>2</INF> NAAQS for the six years that the monitors were in
operation. Additionally, Michigan has long implemented air rules,
including the New Source Review (NSR) and PSD programs that aim to
prevent new sources and major modifications from significantly
contributing to air quality violations and to continue to protect
public health and welfare. Both programs look to safeguard economic
growth in a manner consistent with the preservation of existing clean
air resources. The NSR and PSD programs will ensure attainment of the
SO<INF>2</INF> NAAQS is maintained within the St. Clair area.
For continued verification, Michigan has committed to periodically
reevaluate the modeling assumptions and input data used in the
redesignation SIP development, as well as to monitor contingency plan
indicators and triggers. As Michigan's SO<INF>2</INF> monitoring
network does not include a monitor in the St. Clair County
nonattainment area, Michigan commits to providing the EPA with an
annual emissions report for the Belle River Power Plant in order to
provide ongoing verification of attainment in the manner required by
the EPA's SO<INF>2</INF> Data Requirements Rule (80 FR 51052, August
21, 2015).
Section 175A(d) of the CAA provides that a maintenance plan must
also contain contingency provisions that will promptly correct any
violation of the SO<INF>2</INF> NAAQS after the area is redesignated to
attainment. The maintenance plan should identify the contingency
measures to be adopted, a schedule and procedure for adoption and
implementation, and a time limit for action by the State. A State
should also identify specific indicators to be used to determine when
the contingency measures need to be implemented. The maintenance plan
must also include a requirement that a State will implement all
measures with respect to control of the pollutant that were contained
in the SIP before redesignation of the area to attainment in accordance
with section 175A(d). Unlike CAA section 172(c)(9), section l75A of the
CAA does not explicitly require that contingency measures must take
effect without further action by the air agency in order for the
maintenance plan to be approved. However, the maintenance plan's
contingency plan would become an enforceable part of the SIP and should
ensure that contingency measures are adopted and implemented as
expeditiously as practicable once they are triggered.\1\
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\1\ See April 2014 SO<INF>2</INF> Guidance, page 74.
---------------------------------------------------------------------------
In the General Preamble, the EPA provides further discussion of
contingency measures for SO<INF>2</INF>. This guidance states that in
many cases, attainment revolves around compliance of a single source or
a small set of sources with emission limits shown to provide for
attainment. Although this guidance applies to contingency measures
under section 172(c)(9), the EPA applies a similar policy with respect
to contingency measures for SO<INF>2</INF> required in maintenance
plans under section 175A(d). The requirement to submit contingency
measures in accordance with section 175A of the CAA can be adequately
addressed for SO<INF>2</INF> by the operation of a comprehensive
enforcement program,\2\ which can quickly identify and address sources
that might be causing NAAQS exceedances.
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\2\ See April 2014 SO<INF>2</INF> Guidance, pages 41 and 42.
---------------------------------------------------------------------------
Michigan's enforcement program is active and capable of prompt
action to remedy compliance issues. Additionally, Michigan commits to
the implementation of necessary contingency measures in the event of
future violations of the 2010 SO<INF>2</INF> NAAQS. Michigan will
consider various contingency measures which will be selected from a
comprehensive list of measures deemed appropriate. Listed below are
example measures that may be considered, but not a complete
comprehensive list:
<bullet> Require alternative fuel
<bullet> Require SO<INF>2</INF> emissions add-on control technologies
for existing emission units
<bullet> Require reduced operating hours
<bullet> Require SO<INF>2</INF> emission offsets for new and modified
major sources
<bullet> Require SO<INF>2</INF> emission offsets for new and modified
minor sources
All of the listed contingency measures are potentially effective or
proven methods of obtaining significant reductions of SO<INF>2</INF>
emissions. Because it
[[Page 18388]]
is not possible at this time to determine what control measure(s) will
be appropriate at an unspecified time in the future, the list of
contingency measures outlined is not comprehensive. The selection of
measures will be based upon cost-effectiveness, emission reduction
potential, economic and social considerations, or other factors that
Michigan deems appropriate. Michigan will solicit input from all
interested and affected persons in the maintenance area prior to
selecting appropriate contingency measures. Additionally, no
contingency measure shall be implemented without providing the
opportunity for full public participation during which the relative
costs and benefits of individual measures, at the time they are under
consideration, can be fully evaluated. Based on the foregoing, the EPA
proposes to find that Michigan has addressed the contingency measure
requirement.
The EPA is proposing to find that the Michigan maintenance plan
adequately addresses the five components of a maintenance plan
necessary to attain the NAAQS in the St. Clair nonattainment area.
Therefore, the EPA proposes to find that the maintenance plan submitted
by Michigan for the St. Clair SO<INF>2</INF> nonattainment area meet
the requirements of section 175A of the CAA and proposes to approve
this plan.
III. What action is the EPA taking?
The EPA is proposing to take several related actions. The EPA is
proposing to redesignate the St. Clair area from nonattainment to
attainment for the 2010 SO<INF>2</INF> NAAQS in accordance with
Michigan's December 15, 2023, request for redesignation. The EPA has
determined that the area is attaining the 2010 SO<INF>2</INF> NAAQS and
has met the requirements for redesignation under section 107(d)(3)(E)
of the CAA. The EPA is also proposing to approve Michigan's maintenance
plan, which is designed to ensure that the area will continue to
maintain attainment of the SO<INF>2</INF> NAAQS. Additionally, the EPA
is proposing to approve into the Michigan SIP Permit to Install 51-22,
governing Belle River Power Plant SO<INF>2</INF> emissions.
IV. Incorporation by Reference
In this rulemaking, the EPA is proposing to include in a final EPA
rule regulatory text that includes incorporation by reference. In
accordance with requirements of 1 CFR 51.5, the EPA is proposing to
incorporate by reference Michigan Permit to Install 51-22, approved
April 26, 2022 and revised May 25, 2023, discussed in sections II and
III of this preamble. The EPA has made, and will continue to make,
these documents generally available through <a href="http://www.regulations.gov">www.regulations.gov</a> and at
the EPA Region 5 Office (please contact the person identified in the
FOR FURTHER INFORMATION CONTACT section of this preamble for more
information).
V. Statutory and Executive Order Reviews
Under the CAA, redesignation of an area to attainment and the
accompanying approval of a maintenance plan are actions that affect the
status of a geographical area and do not impose any additional
regulatory requirements on sources beyond those imposed by State law. A
redesignation to attainment does not in and of itself create any new
requirements, but rather results in the applicability of requirements
contained in the CAA for areas that have been redesignated to
attainment. Moreover, the Administrator is required to approve a SIP
submission that complies with the provisions of the CAA and applicable
Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in
reviewing SIP submissions, the EPA's role is to approve State choices,
provided that they meet the criteria of the CAA. Accordingly, this
action merely approves State law as meeting Federal requirements and
does not impose additional requirements beyond those imposed by State
law. For these reasons, this action:
<bullet> Is not subject to Executive Order 14192 (90 FR 9065,
February 6, 2025) because SIP actions are exempt from review under
Executive Order 12866;
<bullet> Does not impose an information collection burden under the
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
<bullet> 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.);
<bullet> 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);
<bullet> Does not have federalism implications as specified in
Executive Order 13132 (64 FR 43255, August 10, 1999);
<bullet> Is not subject to Executive Order 13045 (62 FR 19885,
April 23, 1997) because it approves a State program;
<bullet> Is not a significant regulatory action subject to
Executive Order 13211 (66 FR 28355, May 22, 2001); and
<bullet> Is not subject to requirements of section 12(d) of the
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272
note) because application of those requirements would be inconsistent
with the CAA.
In addition, the SIP is not approved to apply on any Indian
reservation land or in any other area where the EPA or an Indian Tribe
has demonstrated that a Tribe has jurisdiction. In those areas of
Indian country, the rule does not have Tribal implications and will not
impose substantial direct costs on Tribal governments or preempt Tribal
law as specified by Executive Order 13175 (65 FR 67249, November 9,
2000).
List of Subjects
40 CFR Part 52
Environmental protection, Air pollution control, Incorporation by
reference, Intergovernmental relations, Reporting and recordkeeping
requirements, Sulfur oxides.
40 CFR Part 81
Environmental protection, Air pollution control, National parks,
Wilderness areas.
Dated: March 31, 2026.
Anne Vogel,
Regional Administrator, Region 5.
[FR Doc. 2026-06941 Filed 4-9-26; 8:45 am]
BILLING CODE 6560-50-P
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This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.