Proposed Rule2026-10767
Air Plan Approval; Michigan; Determination of Attainment by the Attainment Date for the 2015 Ozone Standards
Primary source
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Published
May 29, 2026
Issuing agencies
Environmental Protection Agency
Abstract
The Environmental Protection Agency (EPA) is proposing to determine under the Clean Air Act (CAA) that the Detroit, Michigan nonattainment area ("Detroit area" or "area") attained the 2015 ozone National Ambient Air Quality Standards (NAAQS) by the applicable attainment date. This determination relies on the EPA's concurrence on an exceptional events request submitted by the Michigan Department of Environment, Great Lakes, and Energy (EGLE) on February 19, 2026, and concurred on by the EPA on March 24, 2026. Therefore, the EPA is proposing to take final agency action on Michigan's exceptional events request. This action, if finalized, will fulfill the EPA's statutory obligation to determine whether the Detroit area attained the 2015 ozone NAAQS by the Moderate attainment date of August 3, 2024.
Full Text
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<title>Federal Register, Volume 91 Issue 103 (Friday, May 29, 2026)</title>
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[Federal Register Volume 91, Number 103 (Friday, May 29, 2026)]
[Proposed Rules]
[Pages 31993-31995]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-10767]
[[Page 31993]]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R05-OAR-2026-3070; FRL-13352-01-R5]
Air Plan Approval; Michigan; Determination of Attainment by the
Attainment Date for the 2015 Ozone Standards
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
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SUMMARY: The Environmental Protection Agency (EPA) is proposing to
determine under the Clean Air Act (CAA) that the Detroit, Michigan
nonattainment area (``Detroit area'' or ``area'') attained the 2015
ozone National Ambient Air Quality Standards (NAAQS) by the applicable
attainment date. This determination relies on the EPA's concurrence on
an exceptional events request submitted by the Michigan Department of
Environment, Great Lakes, and Energy (EGLE) on February 19, 2026, and
concurred on by the EPA on March 24, 2026. Therefore, the EPA is
proposing to take final agency action on Michigan's exceptional events
request. This action, if finalized, will fulfill the EPA's statutory
obligation to determine whether the Detroit area attained the 2015
ozone NAAQS by the Moderate attainment date of August 3, 2024.
DATES: Comments must be received on or before June 29, 2026.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R05-
OAR-2026-3070 at <a href="https://www.regulations.gov">https://www.regulations.gov</a>, or via email to
<a href="/cdn-cgi/l/email-protection#0e6f7c7c6f207d6f7c6f664e6b7e6f20696178"><span class="__cf_email__" data-cfemail="b6d7c4c4d798c5d7c4d7def6d3c6d798d1d9c0">[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: Eric Svingen, Air and Radiation
Division (AR-18J), Environmental Protection Agency, Region 5, 77 West
Jackson Boulevard, Chicago, Illinois 60604, telephone number: (312)
353-4489, email address: <a href="/cdn-cgi/l/email-protection#5f2c293631383a31713a2d363c1f3a2f3e71383029"><span class="__cf_email__" data-cfemail="5625203f383133387833243f351633263778313920">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,''
``us,'' or ``our'' is used, we mean the EPA.
I. Background
A. 2015 Ozone NAAQS
On October 26, 2015 (80 FR 65452), the EPA issued its final action
to revise the NAAQS for ozone to establish a new 8-hour standard. In
that action, the EPA promulgated identical tighter primary and
secondary ozone standards designed to protect public health and welfare
that specified an 8-hour ozone level of 0.070 parts per million (ppm).
Specifically, the standards require that the 3-year average of the
annual fourth highest daily maximum 8-hour average ozone concentration
may not exceed 0.070 ppm.
Effective August 3, 2018, the EPA designated 52 areas throughout
the country as nonattainment for the 2015 ozone NAAQS (see 83 FR 25776,
June 4, 2018). In a separate action, the EPA assigned classification
thresholds and attainment dates based on the severity of an area's
ozone problem, determined by the area's design value (DV) (see 83 FR
10376, May 8, 2018). The EPA established the attainment date for
Marginal, Moderate, and Serious nonattainment areas as 3 years, 6
years, and 9 years, respectively, from the effective date of the final
designations. Thus, the attainment date for Marginal nonattainment
areas for the 2015 ozone NAAQS was August 3, 2021, the attainment date
for Moderate areas was August 3, 2024, and the attainment date for
Serious areas is August 3, 2027.
B. Determination of Attainment
Section 181(b)(2)(A) of the CAA requires that within 6 months
following the applicable attainment date, the EPA shall determine
whether an ozone nonattainment area attained the ozone standard based
on the area's DV as of that date. Under CAA section 181(a)(5) as
interpreted by the EPA in 40 CFR 51.1307, upon application by any
State, the EPA may grant a 1-year extension to the attainment date when
certain criteria are met.
In the event an area fails to attain the ozone NAAQS by the
applicable attainment date and is not granted a 1-year attainment date
extension, CAA section 181(b)(2)(A) requires the EPA to make the
determination that an ozone nonattainment area failed to attain the
ozone standard by the applicable attainment date, and requires the area
to be reclassified by operation of law to the higher of: (1) The next
higher classification for the area, or (2) the classification
applicable to the area's DV as of the determination of failure to
attain.
The level of the 2015 ozone NAAQS is 0.070 ppm.\1\ Under the EPA
regulations at 40 CFR part 50, appendix U, the 2015 ozone NAAQS is
attained at a site when the 3-year average of the annual fourth highest
daily maximum 8-hour average ambient ozone concentration (i.e., DV)
does not exceed 0.070 ppm. When the DV does not exceed 0.070 ppm at
each ambient air quality monitoring site within the area, the area is
deemed to be attaining the ozone NAAQS. Each area's DV is determined by
the highest DV among monitors with valid DVs.\2\ The data handling
convention in appendix P dictates that concentrations shall be reported
in ``ppm'' to the third decimal place, with additional digits to the
right being truncated. Thus, a computed 3-year average ozone
concentration of 0.071 ppm is greater than 0.070 ppm and would exceed
the standard, but a computed 3-year average ozone concentration of
0.0709 ppm is truncated to 0.070 ppm and attains the 2015 ozone NAAQS.
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\1\ See 40 CFR 50.19.
\2\ According to appendix U to 40 CFR part 50, ambient
monitoring sites with a DV of 0.070 ppm or less must meet minimum
data completeness requirements in order to be considered valid.
These requirements are met for a 3-year period at a site if daily
maximum 8-hour average ozone concentrations are available for at
least 90% of the days within the ozone monitoring season, on
average, for the 3-year period, with a minimum of at least 75% of
the days within the ozone monitoring season in any one year. Ozone
monitoring seasons are defined for each State in appendix D to 40
CFR part 58. DVs greater than 0.070 ppm are considered to be valid
regardless of the data completeness.
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C. The Detroit Area
The EPA designated the Detroit area as Marginal nonattainment for
the 2015 ozone NAAQS on June 4, 2018 (83 FR 25776) (effective August 3,
2018). On February 1, 2023 (88 FR 6633), the EPA determined that the
Detroit area failed
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to attain the 2015 ozone NAAQS by its Marginal attainment date of
August 3, 2021, based on the area's DV as of the attainment date (i.e.,
monitoring data from 2018-2020). As a result of that determination, the
area was reclassified by operation of law to Moderate nonattainment. On
January 3, 2022, EGLE submitted a request to redesignate the Detroit
area to attainment of the 2015 ozone NAAQS based on monitored
attainment of the NAAQS for the 2019-2021 time period. On May 19, 2023
(88 FR 32584 and 32594), the EPA issued a determination that the
Detroit area was attaining the 2015 ozone NAAQS based on air quality
monitoring data from 2020-2022 (clean data determination) and finalized
redesignation of the Detroit area to attainment of the 2015 ozone
NAAQS.
On December 5, 2025, the United States Court of Appeals for the
Sixth Circuit upheld the EPA's clean data determination but vacated the
EPA's redesignation of the Detroit area. The Court issued its mandate
in the case on February 24, 2026. See Sierra Club v. EPA, 161 F.4th 934
(6th Cir. 2025). Therefore, the Detroit area is currently designated as
nonattainment for the 2015 ozone NAAQS, with a classification of
Moderate.
On March 10, 2026, EGLE submitted a request that EPA initiate
parallel processing of a supplement to its January 3, 2022,
redesignation request. EGLE held a public comment period on the
supplemental submittal, which closed on April 22, 2026. In its request
for parallel processing EGLE stated that it would address all public
comments received and, if appropriate, submit the supplement to EPA in
May 2026. EPA will take action on this request in a separate
rulemaking.
II. Exceptional Events Demonstration
Congress has recognized that it may not be appropriate for the EPA
to use certain monitoring data collected by the ambient air quality
monitoring network and maintained in the EPA's Air Quality System (AQS)
database in certain regulatory determinations. Thus, in 2005, Congress
provided the statutory authority for the exclusion of data influenced
by ``exceptional events'' meeting specific criteria by adding section
319(b) to the CAA.\3\
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\3\ Under CAA section 319(b), an exceptional event means an
event that (i) affects air quality; (ii) is not reasonably
controllable or preventable; (iii) is an event caused by human
activity that is unlikely to recur at a particular location or a
natural event; and (iv) is determined by the EPA under the process
established in regulations promulgated by the EPA in accordance with
section 319(b)(2) to be an exceptional event. For the purposes of
section 319(b), an exceptional event does not include (i) stagnation
of air masses or meteorological inversions; (ii) a meteorological
event involving high temperatures or lack of precipitation; or (iii)
air pollution relating to source noncompliance.
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To implement this 2005 CAA amendment, on March 22, 2007 (72 FR
13560), the EPA promulgated the 2007 Exceptional Events Rule. The 2007
Exceptional Events Rule created a regulatory process codified at 40 CFR
parts 50 and 51 (sections 50.1, 50.14 and 51.930). These regulatory
sections, which superseded the EPA's previous guidance on handling data
influenced by events, contain definitions, procedural requirements,
requirements for air agency demonstrations, criteria for the EPA's
approval of the exclusion of event-affected air quality data from the
data set used for regulatory decisions, and requirements for air
agencies to take appropriate and reasonable actions to protect public
health from exceedances or violations of the NAAQS. On October 3, 2016
(81 FR 68216), the EPA promulgated a comprehensive revision to the 2007
Exceptional Events Rule. The 2016 Exceptional Events Rule revision
included the requirement that, if a State demonstrates that emissions
from a wildfire smoke event caused a specific air pollution
concentration in excess of the NAAQS at a particular air quality
monitoring location and otherwise satisfies the requirements of 40 CFR
50.14, the EPA must exclude that data from use in determinations of
exceedances and violations.\4\
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\4\ 40 CFR 50.14(b)(4).
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The CAA provides for the exclusion of air quality monitoring data
from design value calculations when there are NAAQS exceedances caused
by events, such as wildfires, that meet the criteria for an exceptional
event identified in the EPA's Exceptional Events Rule at 40 CFR 50.1,
50.14 and 51.930. For the purposes of this proposed action, on February
19, 2026, EGLE submitted an exceptional events demonstration to show
that ozone concentrations recorded at the Allen Park monitor in Wayne
County with Site ID 26-163-0001 on June 29 and June 30, 2023, and the
East 7 Mile monitor in Wayne County with Site ID 26-163-0019 on June
19, June 29, June 30, and July 25, 2023, were influenced by wildfires.
The EPA concurred on this request on March 24, 2026.
The EPA found that Michigan's demonstration met the Exceptional
Events Rule criteria and determined that these wildfire events had
regulatory significance for purposes of calculating the area's most
recent design value to determine if the area attained the standard by
the Moderate attainment date. For this proposed action, the EPA will
rely on the calculated values that exclude the event-influenced data
for the purpose of demonstrating attainment of the 2015 ozone NAAQS by
the Moderate attainment date. Further details on EGLE's analyses and
the EPA's concurrence can be found in the docket for this regulatory
action.
While the EPA has concurred with Michigan's request to exclude
event-influenced air quality monitoring data from regulatory decisions,
the EPA is providing an opportunity for public comment on the claimed
exceptional events and all supporting data prior to the EPA taking
final agency action that relies on the revised data set. This proposed
action provides the public with an opportunity to comment on the
claimed exceptional events, all supporting documents, and the EPA's
concurrence with Michigan's request. As such, the EPA proposes to take
final regulatory action on the request from Michigan to remove the
claimed exceptional events from the data set used for regulatory
purposes.
III. Determination of Attainment by the Attainment Date
For areas classified as Moderate nonattainment for the 2015 ozone
NAAQS, the attainment date was August 3, 2024. Because the DV is based
on the three most recent, complete calendar years of data, attainment
must occur no later than December 31 of the year prior to the
attainment date, i.e., December 31, 2023, in the case of Moderate
nonattainment areas for the 2015 ozone NAAQS. Therefore, the EPA's
proposed determination of attainment for the Detroit area is based upon
hourly ozone concentration data for calendar years 2021, 2022 and 2023
that have been collected and quality-assured in accordance with 40 CFR
part 58 and reported to the EPA's AQS database.\5\ These data
demonstrate that the Detroit area attained the 2015 ozone NAAQS by the
Moderate attainment deadline. As discussed in section II above, in
making this proposed determination, the EPA is relying on
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calculated values that exclude the event-influenced data. The annual
fourth-highest 8-hour ozone concentrations and the 3-year average of
these concentrations (monitoring site ozone DVs) for all monitoring
sites are summarized in Table 1.
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\5\ The EPA maintains the AQS, a database that contains ambient
air pollution data collected by the EPA, State, local, and Tribal
air pollution control agencies. The AQS also contains meteorological
data, descriptive information about each monitoring station
(including its geographic location and its operator) and data
quality assurance/quality control information. The AQS data is used
to (1) assess air quality, (2) assist in attainment/non-attainment
designations, (3) evaluate SIPs for nonattainment areas, (4) perform
modeling for permit review analysis, and (5) prepare reports for
Congress as mandated by the CAA. Access is through the website at
<a href="https://www.epa.gov/aqs">https://www.epa.gov/aqs</a>.
Table 1--2021-2023 Annual Fourth-Highest Daily Maximum 8-hour Ozone Concentrations and Design Values for Monitors in the Detroit Area
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2021 4th high 2022 4th high 2023 4th high 2021-2023 DV
County Monitor ID Site name (ppm) (ppm) (ppm) (ppm)
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Macomb............................... 26-099-0009............. New Haven.............. 0.068 0.066 0.072 0.068
26-099-1003............. Warren FS.............. 0.067 0.068 0.073 0.069
Oakland.............................. 26-125-0001............. Oak Park............... 0.068 0.065 0.075 0.069
St. Clair............................ 26-147-0005............. Port Huron............. 0.072 0.066 0.074 0.070
Washtenaw............................ 26-161-0008............. Towner St.............. 0.066 0.067 0.073 0.068
26-161-9991............. Ann Arbor.............. 0.063 0.066 0.072 0.067
Wayne................................ 26-163-0001............. Allen Park............. 0.069 0.071 0.069 0.069
26-163-0019............. East 7 Mile............ 0.069 0.067 0.071 0.069
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IV. Proposed Action
The EPA is proposing to determine that the Detroit area attained
the 2015 ozone NAAQS by the Moderate attainment date. This proposed
determination is based on complete, quality-assured, and certified
ambient air quality monitoring data for the 2021-2023 design value
period showing that the area achieved attainment of the 2015 ozone
NAAQS. The EPA is also proposing to take final agency action on an
exceptional events request submitted by EGLE on February 19, 2026, and
concurred on by the EPA on March 24, 2026. This action, if finalized,
will fulfill the EPA's statutory obligation to determine whether the
Detroit area attained the 2015 ozone NAAQS by the Moderate attainment
date.
V. Statutory and Executive Order Reviews.
A. Executive Order 12866: Regulatory Planning and Review and Executive
Order 13563: Improving Regulation and Regulatory Review
This action is not a significant regulatory action and was
therefore not submitted to the Office of Management and Budget (OMB)
for review. This action proposed to issue a determination that the
Detroit, Michigan area attained the 2015 ozone NAAQS by the Moderate
attainment date.
B. Executive Order 14192: Unleashing Prosperity Through Deregulation
This action is not an Executive Order 14192 regulatory action
because this action is not significant under Executive Order 12866.
C. Paperwork Reduction Act (PRA)
This rule does not impose an information collection burden under
the provisions of the Paperwork Reduction Act of 1995 (44 U.S.C. 3501
et seq.).
D. Regulatory Flexibility Act (RFA)
I certify that this action will not have a significant economic
impact on a substantial number of small entities under the RFA (5
U.S.C. 601 et seq.). This action will not impose any requirements on
small entities beyond those imposed by State law. The proposed
attainment determination does not create any new requirements and does
not directly regulate any entities.
E. Unfunded Mandates Reform Act (UMRA)
This action does not contain any unfunded mandate as described in
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect
small governments. The action imposes no enforceable duty on any State,
local, or Tribal governments or the private sector.
F. Executive Order 13132: Federalism
This action does not have federalism implications. It will not have
substantial direct effects on the States, on the relationship between
the national government and the States, or on the distribution of power
and responsibilities among the various levels of government. This
action proposed to determine that the Detroit area attained the 2015
ozone NAAQS by the Moderate attainment date, as required by the CAA.
G. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments
This rule does not have Tribal implications, as specified in
Executive Order 13175. It will not have substantial direct effects on
Tribal governments. Thus, Executive Order 13175 does not apply to this
rule.
H. Executive Order 13045: Protection of Children From Environmental
Health and Safety Risks
This action is not subject to Executive Order 13045 because it is
not 3(f)(1) significant as defined in Executive Order 12866, and
because the EPA does not believe the environmental health or safety
risks addressed by this action present a disproportionate risk to
children because it merely proposed to determine that the Detroit area
attained the 2015 ozone NAAQS by the Moderate attainment date.
I. Executive Order 13211: Actions That Significantly Affect Energy
Supply, Distribution, or Use
This action is not subject to Executive Order 13211 because it is
not a significant regulatory action under Executive Order 12866.
J. National Technology Transfer Advancement Act
This rulemaking does not involve technical standards.
List of Subjects in 40 CFR Part 52
Environmental protection, Air pollution control, Incorporation by
reference, Intergovernmental relations, Nitrogen oxides, Ozone,
Reporting and recordkeeping requirements, Volatile organic compounds.
Dated: May 19, 2026.
Anne Vogel,
Regional Administrator, Region 5.
[FR Doc. 2026-10767 Filed 5-28-26; 8:45 am]
BILLING CODE 6560-50-P
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