Proposed Rule2025-15458
Air Plan Approval; Michigan; Detroit 2010 Sulfur Dioxide Redesignation and Maintenance Plan
Primary source
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Published
August 14, 2025
Issuing agencies
Environmental Protection Agency
Abstract
The Environmental Protection Agency (EPA) is proposing to find that the Detroit, Michigan area is attaining the 2010 sulfur dioxide (SO<INF>2</INF>) National Ambient Air Quality Standard (NAAQS) and to act in accordance with a request from Michigan to redesignate the area to attainment for the 2010 SO<INF>2</INF> NAAQS, because the request meets the statutory requirements for redesignation under the Clean Air Act (CAA). EPA is also proposing to approve Michigan's maintenance plan for the Detroit area. Michigan submitted the request for approval of the Detroit nonattainment area's redesignation and maintenance plan on May 5, 2025. EPA approved Michigan's attainment plan for the Detroit area on May 19, 2025.
Full Text
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<title>Federal Register, Volume 90 Issue 155 (Thursday, August 14, 2025)</title>
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[Federal Register Volume 90, Number 155 (Thursday, August 14, 2025)]
[Proposed Rules]
[Pages 39148-39155]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2025-15458]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 52 and 81
[EPA-R05-OAR-2025-0238; FRL-12841-01-R5]
Air Plan Approval; Michigan; Detroit 2010 Sulfur Dioxide
Redesignation and Maintenance Plan
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
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SUMMARY: The Environmental Protection Agency (EPA) is proposing to find
that the Detroit, Michigan area is attaining the 2010 sulfur dioxide
(SO<INF>2</INF>) National Ambient Air Quality Standard (NAAQS) and to
act in accordance with a request from Michigan to redesignate the area
to attainment for the 2010 SO<INF>2</INF> NAAQS, because the request
meets the statutory requirements for redesignation under the Clean Air
Act (CAA). EPA is also proposing to approve Michigan's maintenance plan
for the Detroit area. Michigan submitted the request for approval of
the Detroit nonattainment area's redesignation and maintenance plan on
May 5, 2025. EPA approved Michigan's attainment plan for the Detroit
area on May 19, 2025.
DATES: Comments must be received on or before September 15, 2025.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R05-
OAR-2025-0238 at <a href="https://www.regulations.gov">https://www.regulations.gov</a>, or via email to
<a href="/cdn-cgi/l/email-protection#a6c7d4d4c788d5c7d4c7cee6c3d6c788c1c9d0"><span class="__cf_email__" data-cfemail="6e0f1c1c0f401d0f1c0f062e0b1e0f40090118">[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. EPA may publish
any comment received to its public docket. Do not submit to 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. 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
[[Page 39149]]
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: Abigail Teener, Air and Radiation
Division (AR-18J), Environmental Protection Agency, Region 5, 77 West
Jackson Boulevard, Chicago, Illinois 60604, (312) 353-7314,
<a href="/cdn-cgi/l/email-protection#a6d2c3c3c8c3d488c7c4cfc1c7cfcae6c3d6c788c1c9d0"><span class="__cf_email__" data-cfemail="b2c6d7d7dcd7c09cd3d0dbd5d3dbdef2d7c2d39cd5ddc4">[email protected]</span></a>. The EPA Region 5 office is open from 8:30 a.m.
to 4:30 p.m., Monday through Friday, excluding Federal holidays.
SUPPLEMENTARY INFORMATION:
I. Background and Redesignation Requirements
On June 22, 2010 (75 FR 35520), EPA published a new SO<INF>2</INF>
NAAQS of 75 parts per billion (ppb), which is met at an ambient air
quality monitoring site when the 3-year average of the annual 99th
percentile of daily maximum 1-hour average concentrations does not
exceed 75 ppb, as determined in accordance with appendix T of 40 CFR
part 50.
Upon promulgation of a new or revised NAAQS, section 107(d)(1)(B)
of the CAA requires EPA to designate as nonattainment any areas that
are violating the NAAQS. On August 5, 2013 (78 FR 47191), EPA
designated the Detroit area, a portion of Wayne County, Michigan, as
nonattainment for the 2010 SO<INF>2</INF> NAAQS based on ambient air
quality data collected at the Detroit SW monitoring site (AQS ID 26-
163-0015) from 2009 to 2011. The nonattainment area designation became
effective on October 4, 2013. 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 EPA within 18 months
of the effective date of the designation, i.e., by no later than April
4, 2015, in this case. The SIP must demonstrate attainment of the NAAQS
as expeditiously as practicable, but no later than five years from the
effective date of designation, which was October 4, 2018, for the
Detroit nonattainment area.
On March 18, 2016 (81 FR 14736), EPA published an action finding
that Michigan had failed to submit the required SO<INF>2</INF>
nonattainment plan by the submittal deadline. This finding initiated
deadlines under CAA section 179(a) for the potential imposition of 2-
to-1 New Source Review (NSR) offset and Federal highway funding
sanctions. Additionally, 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.
On May 31, 2016, Michigan submitted a Detroit SO<INF>2</INF>
attainment plan and on June 30, 2016, submitted associated final
enforceable measures. Michigan's submission of a complete attainment
plan terminated the deadlines for imposing sanctions, pursuant to 40
CFR 52.31(d)(5), but it did not terminate EPA's FIP obligation. On
March 19, 2021 (86 FR 14827), EPA partially approved and partially
disapproved Michigan's SO<INF>2</INF> plan as submitted in 2016. EPA's
March 19, 2021, action approved the enforceable control measures for
two facilities, approved the base-year emissions inventory, and
affirmed that the NSR requirements for the area had previously been
met. In the same March 19, 2021, action, EPA disapproved the attainment
demonstration, as well as the requirements for meeting reasonable
further progress (RFP) toward attainment of the NAAQS, reasonably
available control measures/reasonably available control technology
(RACM/RACT), and contingency measures. Additionally, EPA disapproved
the plan's control measures for two facilities as insufficient to
demonstrate attainment. These disapprovals started a new sanctions
clock under CAA section 179(a).
On January 28, 2022 (87 FR 4501), EPA issued a finding of failure
to attain for the Detroit SO<INF>2</INF> nonattainment area,
determining that the area failed to attain the 2010 SO<INF>2</INF>
NAAQS by the applicable attainment date of October 4, 2018, and
established a requirement that Michigan submit a revised SIP by January
30, 2023, that would provide for expeditious attainment of the NAAQS
within the time period specified in CAA sections 179(d)(3) and
172(a)(2).
On October 12, 2022 (87 FR 61514), EPA promulgated a FIP for the
Detroit SO<INF>2</INF> nonattainment area, which satisfied EPA's duty
to promulgate a FIP for the area under CAA section 110(c) that resulted
from the March 18, 2016, finding of failure to submit. While EPA's FIP
for the Detroit area met the requirements for SO<INF>2</INF>
nonattainment area plans, the FIP did not relieve Michigan of the
previously discussed CAA requirement to submit a plan that provides for
attainment of the 2010 SO<INF>2</INF> NAAQS for the Detroit
nonattainment area. On December 20, 2022, Michigan submitted a revised
attainment plan for the Detroit SO<INF>2</INF> nonattainment area
mirroring EPA's FIP to remedy Michigan's 2016 plan deficiencies
specified in EPA's March 19, 2021, rulemaking partially approving and
partially disapproving Michigan's SIP.
Michigan's revised plan, as submitted on December 20, 2022,
depended, in part, upon permits that had not yet been issued but would
include limits and associated requirements for the United States Steel
Corporation (U.S. Steel), EES Coke Battery (EES Coke), and Dearborn
Industrial Generation (DIG) facilities containing emission limits and
associated requirements no less stringent than those set forth in EPA's
FIP, codified at 40 CFR 52.1189. On February 21, 2023, Michigan
submitted a clarification letter committing to submit the necessary
permits by April 30, 2024. On March 23, 2023 (88 FR 17488), EPA
proposed to conditionally approve Michigan's plan, conditioned upon the
issuance of and submission for incorporation into the SIP the
applicable permits for the U.S. Steel, EES Coke, and DIG facilities.
Also, on March 23, 2023 (88 FR 17376), EPA issued an interim final
determination to stay and defer sanctions in the Detroit SO<INF>2</INF>
nonattainment area based on EPA's proposed conditional approval.
On December 14, 2023, Michigan submitted three applicable permits
for the U.S. Steel, EES Coke, and DIG facilities. On April 2, 2024, the
State submitted the final applicable permit for the DIG facility, along
with a request that EPA approve its revised plan. On April 29, 2024,
EPA issued a completeness letter, included in the docket for this
action, determining that Michigan's submittal had satisfied the
completeness criteria set forth at 40 CFR part 51, appendix V and met
the requirement for a SIP submittal that provides for expeditious
attainment set forth in EPA's January 28, 2022, finding of failure to
attain.
On May 19, 2025 (90 FR 21228), EPA approved Michigan's revised SIP
submission, which the State submitted to EPA on December 20, 2022, and
supplemented on February 21, 2023, December 14, 2023, and April 2,
2024, for attaining the 2010 SO<INF>2</INF> NAAQS for the Detroit area
and for meeting other nonattainment area planning requirements of CAA
sections 110, 172, 179 and 192. EPA approved Michigan's demonstration
that these requirements provide for attainment of the 2010
SO<INF>2</INF> NAAQS in Detroit and concluded that Michigan had
satisfied the other applicable requirements for nonattainment areas. In
the same action, EPA determined that the conditions articulated in 40
CFR 52.31(d) had been met, thereby terminating the sanctions clock
resulting from EPA's March 19,
[[Page 39150]]
2021, partial disapproval of the prior SIP.
On May 5, 2025, Michigan submitted a redesignation request and
maintenance plan for the Detroit nonattainment area for the 2010
SO<INF>2</INF> NAAQS. Under section 107(d)(3)(E) of the CAA, EPA may
promulgate a redesignation of a nonattainment area provided that:
1. EPA has determined that the area has attained the NAAQS;
2. EPA has fully approved the applicable implementation plan for
the area under section 110(k) of the CAA;
3. 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. 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.
II. Evaluation of Michigan's Redesignation Request and Maintenance Plan
On May 5, 2025, Michigan submitted a request that EPA redesignate
the Detroit 2010 SO<INF>2</INF> nonattainment area to attainment and a
SIP revision containing a maintenance plan for the area.
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. Criteria (1)--The Detroit SO2 Nonattainment Area Has Attained the
2010 SO2 NAAQS
In accordance with CAA section 107(d)(3)(E)(i), for redesignation
of a nonattainment area to attainment, the CAA requires EPA to
determine that the area has attained the applicable NAAQS. As stated in
EPA's April 23, 2014, ``Guidance for 1-Hour SO<INF>2</INF>
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 located in the area of maximum concentration; and (2) a further
analysis, 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 May 5, 2025, redesignation
request addresses both components, as described below.
1. Air Quality Monitoring Data
Under 40 CFR 50.17(b), the 2010 SO<INF>2</INF> NAAQS is met at an
ambient air quality monitoring site when the three-year average of the
annual (99th percentile) 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, at all relevant monitoring sites in the subject
area. In a year with 365 days of valid monitoring data, the 99th
percentile would be the fourth highest daily maximum 1-hour value.
Michigan operates five SO<INF>2</INF> monitors in the Detroit
nonattainment area: Detroit SW (AQS ID 26-163-0015; 150 Waterman
Street), NMH 48217 (AQS ID 26-163-0097; 3225 South Deacon Street),
DP4th (AQS ID 26-163-0098; 4700 West Fort Street), Trinity (AQS ID 26-
163-0099; 9191 West Fort Street), and Military Park (AQS ID 26-163-
0100; 1238 Military Street). Tables 1 and 2 below show the 99th
percentile results and three-year average design values, respectively,
for the five monitors in the Detroit SO<INF>2</INF> nonattainment area
for 2019-2023. The design values for 2019-2021 range from 14-37 ppb,
the design values for 2020-2022 range from 16-41 ppb, and the design
values for 2021-2023 range from 15-38, which are all below the
SO<INF>2</INF> NAAQS. Furthermore, Michigan's redesignation request
states that the originally violating monitor, Detroit SW, has shown
attainment since 2014, and all other monitors in the nonattainment area
have shown attainment since they began monitoring in 2016 and 2018.
Documentation of the monitoring data is included as appendix A of
Michigan's redesignation request. Therefore, EPA finds that Michigan
has demonstrated that the SO<INF>2</INF> monitors in the Detroit area
show attainment.
Table 1--Michigan's Monitoring Data for the Detroit SO2 Nonattainment Area for 2019-2023--Annual 99th Percentile Values
[ppb]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Site name Site ID 2019 2020 2021 2022 2023
--------------------------------------------------------------------------------------------------------------------------------------------------------
Detroit SW.............................................. 26-163-0015 61 43 37 43 35
NMH 48217............................................... 26-163-0097 27 17 14 17 18
DP4th................................................... 26-163-0098 19 17 16 16 14
Trinity................................................. 26-163-0099 26 16 20 20 15
Military Park........................................... 26-163-0100 32 33 25 31 30
--------------------------------------------------------------------------------------------------------------------------------------------------------
Table 2--Michigan's Monitoring Data for the Detroit SO2 Nonattainment Area for 2019-2023--Design Values
[ppb]
----------------------------------------------------------------------------------------------------------------
Site name Site ID 2019-2021 2020-2022 2021-2023
----------------------------------------------------------------------------------------------------------------
Detroit SW...................................... 26-163-0015 47 41 38
NMH 48217....................................... 26-163-0097 19 16 16
DP4th........................................... 26-163-0098 17 16 15
Trinity......................................... 26-163-0099 21 19 18
Military Park................................... 26-163-0100 30 29 29
----------------------------------------------------------------------------------------------------------------
[[Page 39151]]
2. Air Quality Dispersion Modeling
The April 2014 SO<INF>2</INF> Guidance states that EPA may make
determinations of attainment based on the modeling, using allowable
emissions, from the attainment demonstrations for the applicable SIP
for the affected area. Attainment demonstrations for the 2010
SO<INF>2</INF> NAAQS should demonstrate future attainment and
maintenance of the NAAQS in the entire area designated as nonattainment
(i.e., not just at the violating monitor) by using air quality
dispersion modeling (see appendix W to 40 CFR part 51) to show that the
mix of sources and enforceable control measures and emission rates in
an identified area will not lead to a violation of the 2010
SO<INF>2</INF> NAAQS. For a short-term (i.e., 1-hour) standard, EPA
believes that dispersion modeling, using allowable emissions and
addressing stationary sources in the affected area (and in some cases
those sources located outside the nonattainment area which may affect
attainment in the area) is technically appropriate, efficient and
effective in demonstrating attainment in nonattainment areas because it
takes into consideration combinations of meteorological and emission
source operating conditions that may contribute to peak ground-level
concentrations of SO<INF>2.</INF>
Preferred air quality models for use in regulatory applications are
described in appendix A of EPA's Guideline on Air Quality Models (40
CFR part 51, appendix W). In 2005, EPA promulgated the AERMOD model as
the Agency's preferred near-field dispersion modeling for a wide range
of regulatory applications addressing stationary sources (for example
in estimating SO<INF>2</INF> concentrations) in all types of terrain
based on extensive developmental and performance evaluation.
Supplemental guidance on modeling for purposes of demonstrating
attainment of the SO<INF>2</INF> standard is provided in appendix A to
the April 23, 2014, SO<INF>2</INF> nonattainment area SIP guidance
document referenced above. Appendix A provides extensive guidance on
the modeling domain, the source inputs, assorted types of
meteorological data, and background concentrations. Consistency with
the recommendations in this guidance is generally necessary for the
attainment demonstration to offer adequately reliable assurance that
the plan provides for attainment.
The meteorological data used in the analysis should generally be
processed with the most recent version of the AERMET data preprocessor.
Estimated concentrations should include ambient background
concentrations, should follow the form of the standard, and should be
calculated as described in section 2.6.1.2 of the August 23, 2010,
clarification memo on ``Applicability of Appendix W Modeling Guidance
for the 1-hr SO<INF>2</INF> National Ambient Air Quality Standard''
(U.S. EPA, 2010).
Michigan's redesignation request relies upon the air dispersion
modeling analysis EPA conducted while developing its FIP to demonstrate
attainment of the 2010 SO<INF>2</INF> NAAQS. A more in-depth discussion
of EPA's modeling requirements and analysis, including the use of
longer-term average limits, may be found in EPA's proposed FIP (87 FR
33095, June 1, 2022) and the associated technical support document,
which is included as appendix C of Michigan's May 5, 2025,
redesignation request.
In its modeling analysis, EPA explicitly modeled maximum allowable
or maximum uncontrolled emissions from the following sources: U.S.
Steel, EES Coke, DTE Energy (DTE) Trenton Channel, Carmeuse Lime, DTE
Monroe, Cleveland-Cliffs Steel Corporation (formerly known as AK or
Severstal Steel), DIG, and Marathon Refinery. The emission limits and
associated requirements, including the construction of a 170-foot stack
for U.S. Steel Boilerhouse 2, that Michigan's attainment demonstration
rely upon are contained in permits specified in Table 3 below.
Table 3--Emission Limits Included in Michigan's Detroit SO2 Nonattainment Area Plan
----------------------------------------------------------------------------------------------------------------
SO2 emission
Unit limit (lb/hr) Permit No. and date SIP incorporation date
----------------------------------------------------------------------------------------------------------------
U.S. Steel--Zug Island
----------------------------------------------------------------------------------------------------------------
Boilerhouse 1 (all stacks combined)..... 55.00 Permit to Install 110-23, Incorporated into
A1 Blast Furnace........................ 0.00 effective September 26, Michigan's SIP as part of
B2 Blast Furnace........................ 40.18 2023. May 19, 2025, action (90
D4 Blast Furnace........................ 40.18 FR 21228).
A/B Blast Furnace Flares................ 60.19
D Furnace Flare......................... 60.19
Boilerhouse 2........................... * 750.00/81.00 Permit to Install 108-23,
effective November 14,
2024.
----------------------------------------------------------------------------------------------------------------
U.S. Steel--Ecorse
----------------------------------------------------------------------------------------------------------------
Hot Strip Mill--Slab Reheat Furnace 1... 0.31 Permit to Install 110-23, Incorporated into
Hot Strip Mill--Slab Reheat Furnace 2... 0.31 effective September 26, Michigan's SIP as part of
Hot Strip Mill--Slab Reheat Furnace 3... 0.31 2023. May 19, 2025, action (90
FR 21228).
Hot Strip Mill--Slab Reheat Furnace 4... 0.31
Hot Strip Mill--Slab Reheat Furnace 5... 0.31
No. 2 Baghouse.......................... 3.30
Main Plant Boiler No. 8................. 0.07
Main Plant Boiler No. 9................. 0.07
----------------------------------------------------------------------------------------------------------------
EES Coke
----------------------------------------------------------------------------------------------------------------
Combustion Stack........................ 544.6 Permit to Install 51-08C, Incorporated into
effective November 21, Michigan's SIP as part of
2014. May 19, 2025, action (90
FR 21228).
----------------------------------------------------------------------------------------------------------------
[[Page 39152]]
DTE Trenton Channel **
----------------------------------------------------------------------------------------------------------------
Trenton Channel Unit 9.................. 5,907 Permit to Install 125-11C, Incorporated into
effective January 1, 2017. Michigan's SIP as part of
March 19, 2021, action
(86 FR 14827). However,
the source has since shut
down, and any restart
would require a revision
to the source's Title V
permit, subject to EPA
review and possible
objection if a permit
revision would not ensure
compliance with all
applicable CAA
requirements.
----------------------------------------------------------------------------------------------------------------
Carmeuse Lime
----------------------------------------------------------------------------------------------------------------
Carmeuse Lime Stack..................... 470 Permit to Install 193-14A, Incorporated into
effective October 1, 2018. Michigan's SIP as part of
March 19, 2021, action
(86 FR 14827).
----------------------------------------------------------------------------------------------------------------
Cleveland-Cliffs Steel Corporation **
----------------------------------------------------------------------------------------------------------------
Furnace B Baghouse Stack................ 71.9 Permit MI-ROP-A8640-2016a, Incorporated into
Furnace B Stove Stack................... 38.75 modified January 19, 2017. Michigan's SIP as part of
Furnace B Baghouse and Stove Stacks 77.8 May 19, 2025, action (90
(combined). .............. FR 21228).
Furnace C Baghouse Stack................ 179.65
Furnace C Stove Stack................... 193.6
Furnace C Baghouse and Stove Stacks 271.4
(combined).
----------------------------------------------------------------------------------------------------------------
DIG **
----------------------------------------------------------------------------------------------------------------
Boilers 1, 2, and 3 (combined).......... 420 Permit 253-02A, effective Incorporated into
September 25, 2003. Michigan's SIP as part of
May 19, 2025, action (90
FR 21228).
Boilers 1, 2, and 3 and Flares 1 and 2 840 Permit to Install 109-23, Incorporated into
(combined). effective September 26, Michigan's SIP as part of
2023. May 19, 2025, action (90
FR 21228).
----------------------------------------------------------------------------------------------------------------
* U.S. Steel--Zug Island Boilerhouse 2 shall emit less than 750.00 lbs/hr unless Boilerhouse 1, A1 Blast
Furnace, B2 Blast Furnace, D4 Blast Furnace, A/B Blast Furnace Flares, or D Furnace Flare is operating, in
which case it shall emit less than 81.00 lbs/hr. In addition to the limit, this permit required a new 170-foot
stack to be constructed for Boilerhouse 2 by November 14, 2024.
** The limit for Trenton Channel is expressed as a 30-day average limit, and the limits for Cleveland-Cliffs
Steel Corporation and DIG are expressed as daily average limits. EPA's FIP proposal addresses the use of these
longer-term average limits, both with respect to the general suitability of using such limits for
demonstrating attainment and with respect to whether the particular limits included in the plan have been
suitably demonstrated to provide for attainment.
EPA evaluated two separate operating scenarios as part of its
modeling analysis based on the separate limits for U.S. Steel
Boilerhouse 2. In both scenarios, the modeling for the Detroit area
showed a maximum concentration of 73.6 ppb (192.7 micrograms per cubic
meter ([mu]g/m\3\)), which is below the NAAQS of 75 ppb. This maximum
concentration resulted from modeling all units at maximum permitted
levels now incorporated into Michigan's SIP or maximum uncontrolled
emissions and the background concentration determined using monitoring
data from the Allen Park monitor (AQS ID 26-163-0001).
The April 2014 SO<INF>2</INF> Guidance states that a demonstration
that the control strategy in the SIP has been fully implemented would
be relevant for making a determination of attainment based on modeling
from the attainment demonstration of the applicable SIP. All compliance
dates included in Michigan's plan have passed. The latest compliance
date was for U.S. Steel Boilerhouse 2 on November 14, 2024. Michigan
has confirmed that the facilities included in the modeling analysis are
currently in full compliance with their emission limits and that the
U.S. Steel Boilerhouse 2 stack construction was completed and commenced
operation on October 25, 2024, ahead of the November 14, 2024,
deadline. Compliance documentation is included as appendix D of
Michigan's May 5, 2025, redesignation request.
The modeling analysis was discussed in detail in EPA's proposed FIP
(87 FR 33095, June 1, 2022). In this action, EPA proposes to find that
this modeling analysis and the monitored air quality data demonstrate
that the Detroit area has attained the 2010 SO<INF>2</INF> NAAQS.
B. Criteria (2) and Criteria (5)--Michigan Has Met All Applicable
Requirements Under CAA Section 110 and Part D of the CAA, and EPA Has
Fully Approved the Applicable Implementation Plan Under CAA Section
110(k)
For redesignating a nonattainment area to attainment under a NAAQS,
a State must have met all applicable requirements (CAA section
107(d)(3)(E)(v)), and EPA must have
[[Page 39153]]
fully approved the applicable implementation plan (CAA section
107(d)(3)(E)(ii)). EPA's long-standing interpretation of the CAA is
that not every requirement under CAA section 110 and part D are
applicable for purposes of CAA section 107(d)(3)(E)(ii) and (v). EPA's
interpretation of the statute limiting evaluation of section 110 and
part D requirements to only those that are applicable for purposes of
redesignation was first articulated shortly after the passage of the
1990 CAA Amendments in Agency guidance documents and has been
consistently applied in notice-and-comment redesignation actions over
the last three decades.
Many of the 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
SO<INF>2</INF> NAAQS. For example, the CAA section 110(a)(2)(D)
interstate transport requirements for a State are not linked with a
nonattainment area's designation and classification in that State and
continue to apply to States regardless of the designation status of
areas within that State. However, even though many of the section 110
requirements are not applicable for purposes of redesignation, EPA in
any case approved Michigan's section 110 infrastructure SIP on November
12, 2015 (80 FR 61311).
EPA proposes to determine that Michigan has met, and EPA has fully
approved, those part D requirements that are applicable for purposes of
redesignation. Part D is comprised of the general nonattainment area
plan requirements in subpart 1 (section 172) as well as pollutant-
specific subparts, including section 191 (or subpart 5), which applies
to areas designated nonattainment for SO<INF>2</INF>, nitrogen dioxide,
or lead. While some nonattainment planning requirements are not
applicable for purposes of CAA section 107(d)(3)(E)(ii) and (v) for
areas that are attaining the NAAQS, Michigan has in any case submitted
a complete attainment plan and EPA has fully approved that plan,
including emissions inventories, RACT/RACM, RFP, and contingency
measures.
On May 19, 2025 (90 FR 21228), EPA fully approved Michigan's
attainment SIP, mirroring EPA's FIP, for the Detroit area including the
operation of a new stack at U.S. Steel Boilerhouse 2 and emission
limits and associated requirements for U.S. Steel, EES Coke, Carmeuse
Lime, Cleveland-Cliffs Steel Corporation, and DIG. In that action, EPA
found that Michigan had satisfied requirements for providing for
attainment of the 2010 SO<INF>2</INF> NAAQS in the Detroit area. The
adopted SO<INF>2</INF> SIP regulations for U.S. Steel, EES Coke,
Carmeuse Lime, Cleveland-Cliffs Steel Corporation, and DIG are
contained in the permits specified above in Table 3. Michigan has shown
that it maintains an active enforcement program to ensure ongoing
compliance with these requirements. Michigan's program for NSR, which
includes provisions for the Prevention of Significant Deterioration
program, will address emissions from potential new sources in the area
(78 FR 76064, December 16, 2013).
Section 176(c) of the CAA requires States to establish criteria and
procedures to ensure that federally supported or funded projects
conform to the air quality planning goals in the applicable SIP. The
requirement to determine conformity applies to transportation plans,
programs, and projects that are developed, funded, or approved under
title 23 of the United States Code (U.S.C.) or the Federal Transit Act
(49 U.S.C. 1601) (transportation conformity) as well as to all other
federally supported or funded projects (general conformity). State
transportation conformity SIP revisions must be consistent with Federal
conformity regulations relating to consultation, enforcement, and
enforceability that EPA promulgated pursuant to its authority under the
CAA. EPA's longstanding interpretation of the CAA is that because CAA
section 176(c) conformity requirements continue to apply after areas
are redesignated to attainment, meeting those requirements is not a
prerequisite to redesignating an area. In addition, based on EPA's
April 2014 SO<INF>2</INF> Guidance, transportation conformity only
applies to SO<INF>2</INF> SIPs if transportation-related emissions of
SO<INF>2</INF> as a precursor are a significant contributor to a fine
particulate matter (PM<INF>2.5</INF>) nonattainment problem or if the
SIP has established an approved or adequate budget for such emissions
as part of the RFP, attainment, or maintenance strategy, neither of
which applies to the Detroit area. EPA concluded that highway and
transit vehicles are not significant sources of SO<INF>2</INF> in this
area. As a result, transportation conformity determinations are not
required in the Detroit SO<INF>2</INF> maintenance area. Therefore,
transportation plans, improvement programs, and projects are presumed
to conform to applicable implementation plans for SO<INF>2</INF>.
Federal agencies are still required to address general conformity in
the Detroit SO<INF>2</INF> maintenance area. EPA approved Michigan's
general conformity SIP on December 18, 1996 (61 FR 66607).
Based on the above findings, EPA is proposing to find that Michigan
has met the applicable requirements of section 110 and part D of title
I of the CAA for purposes of the redesignation of the Detroit
nonattainment area. Furthermore, EPA has fully approved the applicable
implementation plan for the Detroit area.
C. Criteria (3)--The Air Quality Improvement in the Detroit SO2
Nonattainment Area Is Due to Permanent and Enforceable Emission
Reductions
To redesignate an area from nonattainment to attainment, section
107(d)(3)(E)(iii) of the CAA requires 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.
Michigan's attainment plan (90 FR 21228, May 19, 2025) incorporates
the permits for U.S. Steel, EES Coke, DTE Trenton Channel, Carmeuse
Lime, Cleveland-Cliffs Steel Corporation, and DIG specified above in
Table 3, which include SO<INF>2</INF> emission limits and associated
requirements, including the construction of a 170-foot stack for U.S.
Steel Boilerhouse 2 by November 14, 2024. Michigan has confirmed that
the facilities are currently in full compliance with their emission
limits and associated requirements contained in the permits specified
in Table 3 and that the U.S. Steel Boilerhouse 2 stack construction has
been completed. Compliance documentation is included as appendix D of
Michigan's May 5, 2025, redesignation request. EPA has included these
emission limits and associated requirements in the March 19, 2021,
partial approval of Michigan's SIP (86 FR 14827) and the May 19, 2025,
approval of Michigan's SIP (90 FR 21228), which also renders them
federally enforceable.
The EPA modeling that Michigan's attainment plan relies upon
includes the emission limits for U.S. Steel, EES Coke, DTE Trenton
Channel, Carmeuse Lime, Cleveland-Cliffs Steel Corporation, and DIG and
shows attainment of the 2010 SO<INF>2</INF> NAAQS throughout the
Detroit area. A more in-depth discussion of EPA's modeling may be found
in EPA's proposed FIP (87 FR 33095, June 1, 2022) and the associated
technical support document, which is included as appendix C of
Michigan's May 5, 2025,
[[Page 39154]]
redesignation request. EPA is proposing to find, consistent with the
FIP and the approval of the State's attainment plan, that the modeling
results demonstrate attainment and continued maintenance of the 2010
SO<INF>2</INF> NAAQS and that the air quality improvement in the
Detroit nonattainment area is due to permanent and enforceable
reductions in emissions.
D. Criteria (4)--The Detroit SO2 Nonattainment Area Has a Fully
Approved Maintenance Plan Pursuant to Section 175A
To redesignate an area from nonattainment to attainment, section
107(d)(3)(E)(iv) of the CAA requires EPA to determine that the area has
a fully approved maintenance plan pursuant to 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 maintenance plan must demonstrate continued
attainment of the NAAQS for at least 10 years after EPA approves a
redesignation to attainment. Eight years after the redesignation, the
State must submit a revised maintenance plan which demonstrates that
attainment of the NAAQS will continue for an additional 10 years beyond
the initial 10-year maintenance period. To address the possibility of
future NAAQS violations, the maintenance plan must contain contingency
measures, as EPA deems necessary, to ensure prompt correction of any
future NAAQS violation.
Specifically, the maintenance plan should address five
requirements: an attainment emissions inventory, a maintenance
demonstration, a commitment for continued air quality monitoring, a
process for verification of continued attainment, and a contingency
plan. EPA is proposing to determine that Michigan's May 5, 2025,
redesignation request contains its maintenance plan and all the
necessary components, which Michigan has committed to review eight
years after the redesignation.
As a part of a State's maintenance plan, the air agency should
develop an attainment emissions inventory to identify the level of
emissions in the affected area which is sufficient to attain and
maintain the SO<INF>2</INF> NAAQS.\1\ In its redesignation request,
Michigan provided an emissions inventory for SO<INF>2</INF> in the
nonattainment area for 2025, the first year after the latest compliance
date included in Michigan's attainment plan and the U.S. Steel
Boilerhouse 2 stack construction was completed. Total allowable
emissions in the Detroit area for the 2025 attainment year are 11,890
tons. This level of emissions, in combination with the new stack
construction at the U.S. Steel facility, is sufficient to maintain the
NAAQS, and Michigan has confirmed that the facilities are in full
compliance with their emission limits. Compliance documentation is
included as appendix D of Michigan's May 5, 2025, redesignation
request. In its attainment plan, Michigan reported that total actual
SO<INF>2</INF> emissions for the nonattainment area from 2012, a year
during which the area was not attaining the NAAQS, were 37,378 tons.
The SO<INF>2</INF> emission limits for U.S. Steel, EES Coke, Carmeuse
Lime, Cleveland-Cliffs Steel Corporation, and DIG specified in Table 3
above, as well as the shutdown of the DTE Trenton Channel and DTE River
Rouge facilities, led to a more than 25,000-ton, or 68 percent,
decrease between actual emissions in 2012 and maximum allowable
emissions in 2025 in the Detroit area. EPA's modeling that Michigan
relied upon for its redesignation request for the Detroit area, based
on maximum uncontrolled emissions or SO<INF>2</INF> emission limits now
incorporated into Michigan's SIP, resulted in a design value of 73.6
ppb, below the SO<INF>2</INF> NAAQS. See Detroit SO<INF>2</INF> FIP
technical support document (87 FR 61514, October 12, 2022).
---------------------------------------------------------------------------
\1\ See April 2014 SO<INF>2</INF> Guidance, page 66.
---------------------------------------------------------------------------
EPA's ``Procedures for Processing Requests to Redesignate Areas to
Attainment'' (Calcagni Memo) \2\ 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
where modeling is relied upon to demonstrate maintenance. Michigan's
maintenance demonstration consists of the attainment plan air quality
modeling analysis showing that the emissions reductions now in effect
in the Detroit area will provide for attainment of the 2010
SO<INF>2</INF> NAAQS. The permanent and enforceable SO<INF>2</INF>
emission reductions described above ensure that the area emissions will
be equal to or less than the emission levels that were evaluated in the
air quality modeling analysis, and Michigan's enforceable emission
requirements will ensure that the Detroit area SO<INF>2</INF> emission
limits are met continuously. Michigan's redesignation request contains
an emissions inventory for 2036, the maintenance year, which does not
show any increases in maximum allowable emissions from the attainment
year. Additionally, Michigan has a fully approved New Source Review
(NSR) program (78 FR 76064, December 16, 2013), including requirements
to assess the impacts of any plans to construct or resume operations of
an emission unit on maintaining NAAQS attainment.
---------------------------------------------------------------------------
\2\ Calcagni, John, Director, Air Quality Management Division,
EPA Office of Air Quality Planning and Standards, ``Procedures for
Processing Requests to Redesignate Areas to Attainment,'' September
4, 1992.
---------------------------------------------------------------------------
For verification of continued attainment, Michigan has committed to
track the emissions and compliance status of the major facilities in
the Detroit area so that future emissions will not exceed the allowable
emissions-based attainment inventory. All major sources in Michigan are
required to submit annual emissions data, which the State uses to
update its emission inventories as required by the CAA. Michigan
commits to continue monitoring SO<INF>2</INF> levels in the Detroit
area and consult EPA prior to making changes to the existing monitoring
network, periodically reevaluate assumptions and input data used for
the attainment plan modeling analysis, and monitor contingency plan
indicators as described below.
Section 175A(d) of the CAA provides that a maintenance plan must
contain contingency provisions that will promptly correct any violation
of the 2010 SO<INF>2</INF> NAAQS after the area is redesignated to
attainment (Calcagni Memo). 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 175A of the CAA does not explicitly require that
contingency measures must take effect without further action by the air
agency for the maintenance plan to be approved. However, if this action
is finalized, the contingency plan would
[[Page 39155]]
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.\3\
---------------------------------------------------------------------------
\3\ See April 2014 SO<INF>2</INF> Guidance, page 74.
---------------------------------------------------------------------------
In the ``General Preamble for the Implementation of Title I of the
Clean Air Act Amendments of 1990,'' published on April 16, 1992 (57 FR
13498), 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), 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,\4\ which can quickly
identify and address sources that might be causing exceedances of the
NAAQS.
---------------------------------------------------------------------------
\4\ See April 2014 SO<INF>2</INF> Guidance, page 41-42.
---------------------------------------------------------------------------
Michigan's enforcement program is active and capable of prompt
action to remedy compliance issues. Michigan commits to ongoing
compliance and enforcement of the control measures contained in the
federally enforceable permits specified above in Table 3, which have
already been incorporated into Michigan's attainment SIP approval (90
FR 21228, May 19, 2025). Michigan also has the necessary resources in
the event of violations to enforce its permit provisions and rules.
Michigan has the authority to expeditiously adopt, implement, and
enforce any subsequent emission control measures deemed necessary to
correct any future SO<INF>2</INF> violations. Michigan commits to
adopting and implementing such corrective actions as necessary to
address violations of the 2010 SO<INF>2</INF> NAAQS. Specifically,
Michigan commits to adopt and expeditiously implement necessary
corrective actions in the event of a violation of the standard or an
annual 99th percentile daily maximum 1-hour SO<INF>2</INF>
concentration of 79 ppb or above occurs in a single calendar year in
the Detroit area. Based on the foregoing, EPA proposes to find that
Michigan has addressed the contingency measure requirement.
EPA is proposing to find that Michigan's maintenance plan
adequately addresses the five basic components of a maintenance plan
necessary to maintain the SO<INF>2</INF> NAAQS in the Detroit
nonattainment area. Therefore, EPA proposes to find that the
redesignation and maintenance plan SIP revision submitted by Michigan
for the 2010 SO<INF>2</INF> Detroit nonattainment area meets the
requirements of section 175A of the CAA and proposes to approve this
plan.
III. What action is EPA taking?
EPA is proposing to redesignate the Detroit area from nonattainment
to attainment for the 2010 SO<INF>2</INF> NAAQS in accordance with
Michigan's May 5, 2025, request. EPA has determined that the area is
attaining the 2010 SO<INF>2</INF> NAAQS and that the improvement in air
quality is due to permanent and enforceable SO<INF>2</INF> emission
reductions in the area. 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 2010 SO<INF>2</INF> NAAQS.
IV. Statutory and Executive Order Reviews
Under the CAA, 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, 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 that reason, this action:
<bullet> Is not a significant regulatory action subject to review
by the Office of Management and Budget under Executive Order 12866 (58
FR 51735, October 4, 1993);
<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 EPA or an Indian Tribe has
demonstrated that a Tribe has jurisdiction. In those areas of Indian
country, the rulemaking does not have Tribal implications and will not
impose substantial direct costs on Tribal governments or preempt Tribal
law as specified by Executive Order 13175 (65 FR 67249, November 9,
2000).
List of Subjects in 40 CFR Part 52
Environmental protection, Air pollution control, Incorporation by
reference, Intergovernmental relations, Reporting and recordkeeping
requirements, Sulfur oxides.
Dated: July 31, 2025.
Anne Vogel,
Regional Administrator, Region 5.
[FR Doc. 2025-15458 Filed 8-13-25; 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.