Rule2026-22887
Air Plan Approval; Michigan; Determination of Attainment by the Attainment Date for the 2015 Ozone Standards
Primary source
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Published
November 10, 2026
Effective
November 10, 2026
Issuing agencies
Environmental Protection Agency
Abstract
The U.S. Environmental Protection Agency (EPA) is determining under the Clean Air Act (CAA) that the Detroit, Michigan Moderate 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 taking final agency action on Michigan's exceptional events request. This action fulfills 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 216 (Tuesday, November 10, 2026)</title>
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[Federal Register Volume 91, Number 216 (Tuesday, November 10, 2026)]
[Rules and Regulations]
[Pages 72427-72433]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-22887]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R05-OAR-2026-3070; FRL-13352-02-R5]
Air Plan Approval; Michigan; Determination of Attainment by the
Attainment Date for the 2015 Ozone Standards
AGENCY: Environmental Protection Agency (EPA).
ACTION: Final rule.
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SUMMARY: The U.S. Environmental Protection Agency (EPA) is determining
under the Clean Air Act (CAA) that the Detroit, Michigan Moderate
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 taking
final agency action on Michigan's exceptional events request. This
action fulfills 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: This final rule is effective on November 10, 2026.
ADDRESSES: The EPA has established a docket for this action under
Docket ID No. EPA-R05-OAR-2026-3070. All documents in the docket are
listed on the <a href="https://www.regulations.gov">https://www.regulations.gov</a> website. Although listed in
the index, some information is not publicly available, i.e.,
Confidential Business Information (CBI), Proprietary Business
Information (PBI), or other information whose disclosure is restricted
by statute. Certain other material, such as copyrighted material, is
not placed on the internet and will be publicly available only in hard
copy form. Publicly available docket materials are available either
through <a href="https://www.regulations.gov">https://www.regulations.gov</a> or please contact the person
identified in the FOR FURTHER INFORMATION CONTACT section for
additional information.
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#f380859a9d94969ddd96819a90b3968392dd949c85"><span class="__cf_email__" data-cfemail="186b6e71767f7d76367d6a717b587d6879367f776e">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,''
``us,'' or ``our'' is used, we mean the EPA. We use multiple
abbreviations and terms in this proposed rule. While this list may not
be exhaustive, for ease of reading and for reference purposes, the EPA
defines the following terms and acronyms here:
AQI--Air Quality Index
CAA--Clean Air Act
CO--Carbon Monoxide
DV--Design Value
EGLE--Michigan Department of Environment, Great Lakes, and Energy
EMBER--Expedited Modeling of Burn Events Results
EPA--United States Environmental Protection Agency
GAM--Generalized Additive Model
MSA--Metropolitan Statistical Area
NAAQS--National Ambient Air Quality Standards
ppm--Parts Per Million
TSD--Technical Support Document
Table of Contents
I. Background
II. The EPA's Responses to Comments
A. Exceptional Events Demonstration
B. Timing and Deadlines
III. What action is the EPA taking?
IV. Statutory and Executive Order Reviews
I. Background
On October 26, 2015,\1\ 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.
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\1\ 80 FR 65292 (October 26, 2015).
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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, based on the most recent three years of
quality assured ozone monitoring data. Effective August 3, 2018, EPA
designated the Detroit area, consisting of Livingston, Macomb, Monroe,
Oakland, St. Clair, Washtenaw, and Wayne Counties, as a Marginal
nonattainment area for the 2015 ozone NAAQS.\2\ 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).\3\ 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.
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\2\ 83 FR 25776 (June 4, 2018).
\3\ 83 FR 10376 (May 8, 2018).
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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.\4\
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\4\ CAA section 181(b)(2)(A).
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On February 1, 2023, EPA determined based on 2018-2020 monitoring
data that the Detroit area had failed to attain by its Marginal
attainment date of August 3, 2021, and by operation of law the Detroit
area was reclassified the area to Moderate.\5\
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\5\ 88 FR 6633 (February 1, 2023).
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On May 29, 2026, EPA proposed to determine that the Detroit area
attained the 2015 ozone NAAQS by the Moderate attainment date of August
3, 2024, based upon complete, quality-assured, and
[[Page 72428]]
certified ambient air monitoring data for the 2021-2023 design
period.\6\
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\6\ 91 FR 31993 (May 29, 2026).
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EPA's proposed determination relied upon EPA's concurrence on an
exceptional events demonstration submitted by EGLE on February 19,
2026, which requested exclusion of 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.
In the May 29, 2026, proposed determination of attainment by the
attainment date, EPA proposed to take final agency action on the
exceptional events concurrence, which removed the event-influenced data
from the design value, and opened an opportunity for public comment on
the EPA's concurrence.
II. The EPA's Responses to Comments
Upon publication of the May 29, 2026, proposed rulemaking, the EPA
opened a 30-day comment period, ending June 29, 2026.\7\ During the
comment period the EPA received three comments. Two of the comments
were adverse, and the remaining comment raised several recommendations.
In this final rulemaking the EPA is responding to all three comments.
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\7\ 91 FR 31993 (May 29, 2026).
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A. Exceptional Events Demonstration
Comment: A commenter states that removing data points from the
sample is not in the public interest and requests that the proposal be
withdrawn.
Response: CAA section 319(b) allows exclusion of data under the
2016 Exceptional Events Rule because the emissions from these events
are not reasonably controllable or preventable. Air agencies can
request the exclusion of data affected by exceptional events from
regulatory determinations through the exceptional events process. The
requirements that must be met for EPA's concurrence on an exceptional
events demonstration are set forth at 40 CFR 50.14. The EPA's Technical
Support Document (TSD), included in the docket of this rulemaking,
illustrates how EGLE made a justifiable request for excluding the
event-impacted data from regulatory decisions in the Detroit area. For
these reasons, the EPA believes it is appropriate to finalize the
determination that the area attained by the attainment date.
Comment: A commenter requests that the EPA create a plain language
summary explaining what data were excluded, why the exclusions were
justified, what the unadjusted and adjusted data show, and what
obligations or monitoring requirements remain.
Response: The EPA agrees with the commenter that the exclusion of
data for regulatory purposes through the 2016 Exceptional Events Rule
should be transparent, reproducible, and verifiable. The EPA's TSD,
provided in the publicly available docket for this rulemaking, explains
which data was excluded, how EGLE's demonstration met the requirements
in 40 CFR 50.14, and the design values before and after exclusion.
The State of Michigan will continue to operate several monitoring
sites that measure ozone. The EPA has specific design criteria for
ozone monitoring networks described in 40 CFR part 58 appendix D.
According to this criteria, EGLE is required to operate three ozone
monitoring sites in the Detroit metropolitan statistical area (MSA).
Currently, EGLE operates six ozone monitoring sites in the Detroit MSA,
and none of these ozone monitors are eligible for shutdown. The ozone
monitoring network in the Detroit area has historically monitored ozone
at more than the minimum required number of monitoring sites, and
according to EGLE's Annual Ambient Air Monitoring Network Review Plan
for 2027, there are no changes expected to the ozone monitoring network
in Detroit.
The EPA's action is focused on assessing whether the Detroit area
attained the 2015 ozone NAAQS by the Moderate attainment date, as
required by CAA section 181. Excluding data for purposes of calculating
the design value does not remove the data from the EPA's Air Quality
System database. Other data users may decide for themselves if it makes
sense to exclude or include this data for their own evaluations.
Comment: Commenters state, ``EPA's `weight of the evidence'
approach is insufficient to establish the statutorily required
``clear'' evidentiary standard.''
Response: The EPA disagrees that the weight of evidence approach is
insufficient for establishing the ``clear'' evidentiary standard.
Section 319(b)(3)(B) of the CAA requires the causal relationship to be
``clear,'' and as explained in the preamble to the 2016 Exceptional
Events Rule, ``it is appropriate for the EPA to consider all relevant
evidence and qualitatively 'weigh' it based on its relevance to the
2016 Exceptional Events Rule criterion being addressed, the degree of
certainty, its persuasiveness, and other considerations appropriate to
the individual pollutant and the nature and type of event.'' \8\ Courts
have confirmed that it is reasonable for the EPA to use a ``weight of
evidence'' analysis when implementing the CAA.\9\ The weight of
evidence method is an appropriate and reasonable approach, which has
been used historically and successfully under key CAA programs. The
weight of evidence approach is the EPA's process for assessing whether
an exceptional events demonstration meets the requirement for a clear
causal relationship at CAA section 319(b)(3)(B)(ii). Broadly, the
commenter's concerns are not properly raised in this rulemaking and
should have been submitted within the comment period of the 2016
Exceptional Events Rule.
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\8\ 81 FR 68216, 68230 (October 3, 2016).
\9\ See, e.g., Envtl. Def. v. EPA, 369 F.3d 193 (2d Cir. 2004)
(upholding the EPA's approval of a State's attainment demonstration
using photochemical grid modeling and a weight of evidence
analysis), BCCA Appeal Group v. EPA, 355 F.3d 817 (5th Cir. 2003)
(finding that the EPA's conclusion that the weight of evidence
approach to approving attainment demonstrations was consistent with
the CAA, reasonable and entitled to deference).
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Furthermore, and more recently, the EPA's concurrence based on a
weight of evidence approach for evaluating exceptional events was
upheld in Sierra Club v. EPA, 161 F.4th 934 (6th Cir. 2025). The
Court's opinion states, ``Thus, the EPA met the requirement to
demonstrate that it 'reasonably considered the relevant issues and
reasonably explained the decision.' '' Even if the monitored data and/
or technical analyses may not unequivocally support the clear causal
relationship, agencies should submit available information regarding
the event and the monitored exceedances or violations. It may still be
possible, with a weight of evidence approach, to clearly establish the
existence of a causal connection between the data or analyses and the
event causing elevated ozone concentrations. Under that approach, each
piece of information or analysis--favorable or unfavorable--is
considered, but by itself is not conclusive.
Comment: The commenters state, for EGLE to satisfy CAA section
319(b)(3)(B)(iv), ``it must show that exceptional events, here wildfire
smoke, were the proximate and foreseeable cause of the monitored
exceedance. EGLE must have demonstrated in their proposal that there
was a direct relationship between the claimed wildfire contributions
and the ozone exceedance, showing that the two were very intricately
connected.''
[[Page 72429]]
Response: The EPA evaluates exceptional event demonstrations on a
case-by-case basis using a weight of evidence approach to assess
whether a clear causal relationship exists between the event and the
exceedance. The ``EPA Guidance on the Preparation of Exceptional Events
Demonstrations for Wildfire Events that May Influence Ozone
Concentrations'' uses a three-tier approach for addressing the clear
causal relationship element with a wildfire ozone demonstration,
recognizing that some events require more evidence to demonstrate the
clear causal relationship. Tier 3 demonstrations include additional
evidence beyond what is required for Tier 1 and Tier 2 demonstrations
because these events are more complex. EGLE submitted a Tier 3
demonstration, requiring the highest level of supporting evidence,
consistent with this guidance. The record includes multiple lines of
evidence showing wildfire smoke transport and ground level impacts at
the Detroit area monitors, including: photographic evidence, regional
ozone and PM<INF>2.5</INF> Air Quality Index maps, National Oceanic and
Atmospheric Administration Hazard Mapping System Fire and Smoke maps,
Hybrid Single-Particle Lagrangian Integrated Trajectory analyses, local
and regional meteorological evidence, the presence of elevated surface
level PM<INF>2.5</INF> concentrations, the EPA's Expedited Modeling of
Burn Events Results (EMBER) screening-level photochemical modeling
analysis, the General Additive Model statistical model, and the EPA's
Met-Adjusted Ozone Trends statistical model. Across these independent
methods, results collectively show wildfire smoke caused elevated ozone
concentrations on the event days. Using a weight of evidence approach,
the EPA concluded that EGLE met the burden of proof and successfully
demonstrated a clear causal relationship between the wildfire events
and the monitored exceedances at the Detroit area monitors.
Comment: The commenters note that EGLE did not adequately
demonstrate the wildfire smoke was the ``proximate cause'' of the ozone
exceedances or that the ozone exceedances were ``directly due'' to
wildfire smoke and therefore do not satisfy the clear causal
connection. The commenters assertions are that the models demonstrate
that local pollution sources made up the bulk of the ozone
concentrations, that wildfire smoke-influenced ozone was present in
minimal concentrations on the event days, and thus, do not meet the
CAA's causation standard for exceptional event demonstrations.
Response: For the EPA to concur on an exceptional events
demonstration and exclude data from regulatory use, CAA section 319(b)
and 40 CFR 50.14 require a clear causal relationship between the event
and the monitored exceedance. The EPA evaluates the clear causal
connection between the exceptional events and the monitored exceedances
using a weight of evidence approach and not the ``but for'' or
``proximate cause'' methods. The weight of evidence approach looks at
all the information available and evaluates how supportive and relevant
each line of evidence is to the overall clear causal relationship.
Before the 2016 Exceptional Events Rule revision, the 2007 Exceptional
Events Rule required agencies to show that there would have been no
exceedance or violation ``but for'' the event. This was known as the
``but for'' test. In the most recent revisions to the EPA's Exceptional
Event Rule in 2016, the EPA removed the ``but for'' test and no longer
requires quantitative analyses intended to subtract estimated wildfire
smoke contributions from reported monitoring concentrations.
Accordingly, there is no requirement in the EPA's current Exceptional
Event Rule to (1) quantify exact wildfire contributions, (2) show the
event was the ``predominant cause,'' or (3) rule out all other sources.
There are many factors that contribute to regional ozone
concentrations in the Midwest, such as natural emissions of precursors,
transport of ozone and precursors from distant locations, local
precursor emissions, and meteorology. On these event days, wildfire
smoke was also a contributor to elevated ozone concentrations, causing
the exceedance. The presence of routine local emissions does not
preclude a finding that wildfire smoke was the cause of the monitor
exceedance where the evidence shows a clear causal connection between
the event and the exceedance. An exceptional event may still be the
cause of an exceedance even in the presence of other sources.
The ``directly due'' concept is satisfied by the totality of
evidence showing a clear causal connection. Typically, a single
analysis may not conclusively link an exceptional event to a monitored
exceedance. The EPA therefore applies a weight of evidence approach,
evaluating multiple, independent lines of evidence collectively to
determine a clear causal relationship. This approach is reflected in
the ``EPA Guidance on the Preparation of Exceptional Events
Demonstrations for Wildfire Events that May Influence Ozone
Concentrations'' \10\ and has been upheld by the Sixth Circuit in
Sierra Club v. EPA, 161 F.4th 934 (2025).
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\10\ <a href="https://www.epa.gov/system/files/documents/2023-12/guidance-on-the-preparation-of-ee-wf-ozone.pdf">https://www.epa.gov/system/files/documents/2023-12/guidance-on-the-preparation-of-ee-wf-ozone.pdf</a>.
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The meteorological, photochemical, and statistical models and
analyses have uncertainty. Differences among model outputs do not
invalidate the demonstration because such differences are expected
given that the models use different methodologies, inputs, and
parameters. As described in the EPA's EMBER Overview document,
there is uncertainty in photochemical model estimates of fire
impacts as is true of all available methods for attributing ozone
concentrations to fire emissions. As noted in the 2016 Wildfire
Guidance, `predictions of fire impacts on air quality are complex
due to uncertainties in emissions, height of emissions, plume
temperature, and plume chemistry (including radiative impacts on
chemistry). However, with proper set-up, application, and
evaluation, air quality models can be used to indicate fire impacts
on [ozone] concentrations. Combining multiple types of analysis,
including photochemical modeling, air quality monitoring data, and
meteorological analyses, offers a comprehensive approach for
understanding wildfire effects on ozone exceedances.' \11\
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\11\ <a href="https://www.epa.gov/system/files/documents/2026-06/expedited-modeling-of-burn-events-results-ember-overview-document-for-data-years-of-2021-2025.pdf">https://www.epa.gov/system/files/documents/2026-06/expedited-modeling-of-burn-events-results-ember-overview-document-for-data-years-of-2021-2025.pdf</a>.
The models are meant to estimate the magnitude of the event's
impact on the ozone exceedances, plume timing, and spatial extent. The
2016 Exceptional Events Rule does not require the exact wildfire smoke
contribution to be quantified and instead uses a weight of evidence
approach.
The results of the Generalized Additive Model (GAM), EMBER, and
Met-Adjusted Ozone Trends models on the event days for the Detroit
area, coupled with the additional evidence provided in EGLE's
demonstration, are supportive of wildfire smoke impacts. Although the
models estimate different levels of wildfire smoke impacts at the
monitors, they consistently confirm wildfire smoke elevated ozone
concentrations and are supportive to the overall weight of evidence.
The EPA's TSD on pages 19-20 explains how EMBER's modeled wildfire
smoke impact on ozone concentrations of 3 parts per billion on June 30,
2023, underestimated the smoke contribution to ozone concentrations due
to premature clearing of smoke emissions in EMBER versus what occurred.
EMBER's clean out of the fire plume over Detroit on this day was too
strong
[[Page 72430]]
and early compared to the ambient air monitoring concentrations and
Tropospheric Monitoring Instrument satellite-based data products, using
enhancements of the carbon monoxide (CO) vertical column as an
indicator of the location of the fire plume. While the EMBER clean out
on June 30, 2023, appears too drastic and too early compared to ambient
data, this modeling clearly indicated a substantial impact of fires on
ozone during the prior day of this episode (June 29, 2023), and
combined with the ambient data, also contributes to the weight of
evidence supporting the clear causal connection for June 30, 2023.
The preamble to the 2016 Exceptional Events Rule notes that the EPA
``do[es] not expect nor would all air agencies necessarily need to
include all of the evidence and analyses identified in Table 1 [Example
Clear Causal Relationship Evidence and Analyses], but rather to use
available information to build a weight of evidence showing.'' \12\
Similarly, the 2016 Wildfire Guidance states ``The EPA does not expect
an air agency to prepare all identified analyses but only those that
add to their weight of evidence supporting the clear causal
relationship.'' In this instance, EGLE provided the appropriate level
of evidence including both a statistical regression modeling analysis
and a photochemical modeling analysis, and the EPA determined that
EGLE's demonstration included sufficient evidence to demonstrate a
clear causal relationship between the fire and the monitored ozone
exceedances.
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\12\ 81 FR 68216 at 68242 (October 3, 2016).
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Comment: The commenters state, ``EPA's application of the
regulatory presumption that wildfire exceedances are per se not
reasonably controllable or preventable is contrary to the act and the
evidence.'' The commenters also state that if control measures for the
relevant pollutant ``were not in place but would have prevented the
exceedance, then the exceedance was preventable.''
Response: The not reasonably controllable or preventable criterion
for wildfire events applies to the event and not the exceedance. At CAA
section 319(b)(1)(A), the term ``exceptional event'' is defined as an
event that affects air quality, is not reasonably controllable or
preventable, is an event caused by human activity that is unlikely to
recur at a particular location or a natural event, and is determined by
the Administrator through the process established in the regulations
promulgated under CAA section 319(b)(2) to be an exceptional event.
Under the regulations promulgated by the EPA at 40 CFR 50.14(b)(4),
the Administrator will determine every wildfire occurring predominantly
on wildland has met the requirement regarding the not reasonably
controllable or preventable criterion, so long there is no compelling
evidence to the contrary in the record. Further, at 40 CFR
50.14(b)(8)(vii), the Administrator shall not require a State to
provide case-specific justification regarding the not reasonably
controllable or preventable criterion in instances where emissions-
generating activity occurred outside the State's boundaries.
The preamble to the 2016 Exceptional Events Rule clarifies that the
EPA interprets the not reasonably controllable or preventable criterion
to contain two factors: the event must be both not reasonably
controllable and not reasonably preventable at the time the event
occurred. This requirement applies to both natural events and events
caused by human activities. However, it is presumptively assumed that
wildfires on wildland will satisfy both factors of the ``not reasonably
controllable or preventable'' element unless evidence in the record
clearly demonstrates otherwise.
Though a State might have the ability to adopt reasonably available
control measures of anthropogenic sources, that does not imply a
naturally occurring event was reasonably controllable. Similarly, it is
not relevant whether anthropogenic control measures might have
prevented an exceedance during the days of a wildfire exceptional
event. In the statute, the term ``not reasonably controllable or
preventable'' describes the wildfire event itself.
Comment: The commenters state, ``EGLE failed to comply with the
Clean Air Act's notification requirements regarding exceptional
events.''
Response: The 2016 Exceptional Events Rule does not specify how
States must provide public notification. EGLE has demonstrated that
they have processes in place to notify the public when there is high
confidence of adverse air quality impacts. EGLE's air quality forecasts
and near real-time continuous data provided the public notice of ozone
concentrations meeting an Air Quality Index (AQI) rating of ``Unhealthy
for Sensitive Groups'' or worse on the event days, after ambient
concentrations of ozone rose quickly due to the distant Canadian fires.
Data from the air monitors are provided, in near real-time, to the
EPA's AirNow website as well as EGLE's MiAir website.\13\ Additionally,
AirNow's EnviroFlash is a system that sends emails to subscribers about
their daily air quality forecast and current conditions. Air agencies
issue air quality forecasts based on measured near real-time air
quality levels and weather information. The forecast is then provided
to local media, posted online, and sent out to EnviroFlash subscribers.
Furthermore, EnviroFlash allows subscribers to opt in to receive
notifications at the Unhealthy for Sensitive Groups and higher AQI
categories. EGLE maintains a robust forecasting program and issues
alerts when elevated PM<INF>2.5</INF> or ozone are expected. Even when
forecasts don't fully capture an unfolding air quality event, AirNow,
MiAir, and EnviroFlash alert the public in near real-time when air
quality does become Unhealthy for Sensitive Groups or greater.
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\13\ <a href="http://www.deqmiair.org">http://www.deqmiair.org</a>.
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B. Timing and Deadlines
Comment: The commenters state, ``EGLE's obligation to promptly
provide EPA with its intent to request data exclusions started the
summer of 2023, after the exceptional events occurred. By submitting
its exceptional event demonstration two and half years later, EGLE has
failed this basic requirement.'' The commenters cite a court decision
finding that a delay of ``one or two years is clearly too long'' when
compared to deadlines under the Clean Water Act.
Response: CAA section 319(b)(2)(A) directs the EPA to promulgate
regulations governing ``the review and handling of air quality
monitoring data influenced by exceptional events,'' and CAA section
319(b)(3)(B)(i) requires that these regulations provide that ``the
occurrence of an exceptional event must be demonstrated by reliable,
accurate data that is promptly produced and provided by Federal, State,
or local government agencies.'' The EPA has fulfilled its obligations
under CAA section 319(b)(2)(A) by promulgating several final rules,
including the 2007 Exceptional Events Rule \14\ and the 2016
Exceptional Events Rule.\15\
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\14\ 72 FR 13560 (March 22, 2007).
\15\ 81 FR 68216 (October 3, 2016).
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In the 2007 Exceptional Events Rule, the EPA finalized a provision
at 40 CFR 50.14(c)(3)(i) requiring air agencies to submit a
demonstration ``not later than the lesser of, 3 years following the end
of the calendar quarter in which the flagged concentration was recorded
or, 12 months prior to the date that a regulatory decision must be made
by EPA.''
[[Page 72431]]
In the 2016 Exceptional Events Rule, the EPA revisited that
provision, noting that ``air agencies have previously expressed concern
that the timelines for event flagging and demonstration submittal are
not always appropriate because an air agency may not know that data
influenced by an exceptional event caused the design value exceedance
until 3 years after the event occurred.'' \16\ The EPA acknowledged
that this scenario can and does occur, particularly for annual
standards and when a regulatory decision is based on a design value
that is averaged over three years. Such a regulatory decision would
include a determination of attainment by the attainment date for the
2015 ozone NAAQS. Within the 2016 rulemaking, the EPA proposed to
remove the general schedule demonstration submittal deadlines contained
within 40 CFR 50.14(c)(3)(i). The overwhelming majority of commenters
supported this proposal, and in the final rule the EPA revised the CFR
to remove fixed deadlines.\17\ The 2016 Exceptional Events Rule instead
set forth a case-by-case approach to timing of demonstrations, in which
the EPA shall respond to a State's initial notification of a potential
exceptional event with a due date for demonstration submittal that
considers the nature of the event and the anticipated timing of the
associated regulatory decision, except that the EPA may waive the
initial notification process under 40 CFR 50.14(c)(2)(i)(C). In the
final rule, the EPA noted that the EPA was not changing the timing of
the regulatory actions in which the affected data may be used. Many of
these deadlines are statutorily established and cannot be changed by
regulation. Because the EPA is also accountable for these statutory
deadlines, the effect of the scheduling revision in the 2016
Exceptional Events Rule is compression of the timeline for the EPA's
review.
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\16\ 81 FR 68216 at 68266 (October 3, 2016).
\17\ 81 FR 68216 at 68267 (October 3, 2016).
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The EPA disagrees with the commenter that, regarding the maximum
reasonable amount of time between an event and the submission of a
demonstration, one or two years is too long. The EPA has addressed the
timing of demonstrations in both the 2007 Exceptional Events Rule,
which took an approach with fixed three-year deadlines, and in the 2016
Exceptional Events Rule, which considered the comments of affected air
agencies and adopted a case-by-case approach. The timing of EGLE's
February 19, 2026, demonstration would fit within the requirements of
either approach. Broadly, the commenter's concerns are not properly
raised in this rulemaking and should have been submitted within the
comment period of the 2016 Exceptional Events Rule.
Further, regardless of the demonstration timing that might
generally be appropriate, the EPA believes it is important to consider
timing considerations specific to the Detroit area.
On May 19, 2023, the EPA published a final rule redesignating the
Detroit area to attainment of the 2015 ozone NAAQS.\18\ Later that
year, on June 19, June 29, June 30, and July 25, 2023, air quality in
the area was impacted by Canadian wildfires. More than two years later,
on December 5, 2025, the EPA's 2023 final redesignation was vacated by
the United States Court of Appeals for the Sixth Circuit. EGLE
submitted its demonstration on February 19, 2026, less than three
months after the date of the Sixth Circuit decision.
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\18\ 88 FR 32594 (May 19, 2023).
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In its decision regarding the 2023 final redesignation, the Sixth
Circuit concluded that the EPA erred only with respect to its legal
interpretation of CAA section 107(d)(3)(E)(v). The court held that
Michigan was required to have met all requirements due at the time of
the EPA's redesignation action, not just the requirements that had been
due as of the time of submittal of the redesignation request, which had
been the EPA's interpretation of CAA section 107(d)(3)(E)(v) for more
than three decades. During the years when the redesignation had been
effective, Michigan had understandably believed that the area was a
maintenance area, and therefore not subject to the EPA's obligation
under CAA section 181 to make a determination of attainment by the
attainment date for Moderate nonattainment areas.
Considering together the statutory requirements at CAA section
319(b), the history of the 2007 Exceptional Events Rule and 2016
Exceptional Events Rule, and the facts of the Detroit area, the EPA is
finding that the Agency is not prohibited from reaching a concurrence
decision on the exceptional events demonstration submitted by EGLE on
February 19, 2026, regarding wildfire impacts observed in the Detroit
area in June and July of 2023.
Comment: The commenters state that EPA must evaluate the conditions
of the Detroit area ``as they existed at the attainment deadline, not
the date of any belated determination'' and that the EPA may not rely
on a post hoc ``revision of the ozone design value based on an
exceptional event determination made long after the attainment deadline
had passed.'' The commenters cite a court decision regarding the
``snapshot rule'' under the Bankruptcy Code.
Response: The CAA was first enacted in 1955, and Congress enacted
major revisions in 1970, 1977, and 1990. In a major departure from the
prior law, the 101st U.S. Congress amended the CAA in 1990 by grouping
ozone nonattainment areas into six classifications based on the extent
to which the NAAQS was exceeded, and established specific pollution
controls and attainment dates for each classification. These
requirements are spelled out in CAA sections 181 through CAA section
193. Under CAA section 181(b)(2), following the applicable attainment
date for an ozone nonattainment area, the EPA shall determine whether
the area attained the standard ``based on the area's design value (as
of the attainment date).''
When making determinations of attainment by the attainment date,
EPA has consistently applied this language as restricting its analysis
to the years of data that constitute the basis for an area's DV as of
the specific attainment deadline.\19\ The DV ``as of'' the attainment
date is the one that applies on that date--i.e., the most recent three-
year average of concentrations of certified data. The maximum
attainment date applicable to Moderate 2015 ozone areas was August 3,
2024.\20\ The EPA's determination of attainment is based upon the
area's design value as of August 3, 2024, which in turn is calculated
using 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 Air Quality System (AQS)
database.
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\19\ See 82 FR 50814, 50817 (November 2, 2017).
\20\ See CAA section 181(a)(1); 40 CFR 51.1303.
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In 2005, the 109th U.S. Congress provided the statutory authority
for the exclusion of data influenced by exceptional events by adding
section 319(b) to the CAA. Aside from CAA section 319(b)(3)(B),
discussed above, the commenter has not identified any language within
CAA section 319 that suggests the 109th U.S. Congress intended to
restrict the EPA from evaluating a state's demonstration if that
demonstration were submitted past a certain deadline. Regarding the
requirement at CAA section 181(b)(2)(A) that EPA reach a determination
``based on the area's design value (as of the attainment date),'' as
discussed above, the EPA believes the best interpretation
[[Page 72432]]
of this language is that the 101st U.S. Congress was directing the EPA
to constrain its analysis to the years of data that constitute the
basis for an area's DV as of the specific attainment deadline. In
enacting the language ``based on the area's design value (as of the
attainment date),'' it was plainly not the intent of Congress to
describe the exceptional events process, because the authority for the
exceptional events process at CAA section 319 had not yet been enacted.
Though the EPA is required under CAA section 181(b)(2) to reach its
determination within six months following the applicable attainment
date, the EPA does not believe that the EPA must ignore relevant data
in an instance where the EPA is delayed in finalizing its action. For
example, if there had been a quality assurance issue that incorrectly
showed attaining data in a nonattainment area, and if the EPA was
delayed in reaching a determination while it researched the quality
assurance issue, and if the quality assurance process was belatedly
resolved to show violating data, then under a ``snapshot rule'' the EPA
would be required to reach an incorrect decision that an area with
violating data had attained the standard. Rather, it is the EPA's view
that it may be in the best interest of the public for the EPA to
consider the full record of information at the time of the EPA's
decision, even in instances where the EPA is delayed in reaching that
decision.
Turning to the specific facts of the Detroit area, the EPA's 2023
final reclassification action is an example of the EPA's consistent
interpretation of CAA section 181(b)(2) as constraining the EPA's
analysis to the years of data that constitute the basis for an area's
DV as of the specific attainment deadline. The EPA designated the
Detroit area as Marginal nonattainment for the 2015 ozone NAAQS on June
4, 2018, effective August 3, 2018.\21\ On February 1, 2023, the EPA
determined that the Detroit area failed 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).\22\ At the time of the EPA's 2023 final reclassification action,
the EPA had already reviewed certified monitoring data for the more
recent 2019-2021 design value period showing that the area had attained
the standard, and in fact the EPA had already proposed to redesignate
the area to attainment under CAA section 107(d)(3)(E) based on the more
recent attaining data.\23\ However, consistent with the EPA's
longstanding interpretation of CAA section 181(b)(2), on February 1,
2023, the EPA finalized its determination that the Detroit area had
failed to attain the standard by the applicable attainment date.
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\21\ 83 FR 25776 (June 4, 2018).
\22\ 88 FR 6633 (February 1, 2023).
\23\ 87 FR 14210 (March 14, 2022).
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Even if the EPA were to adapt a requirement that states should
generally submit an exceptional events demonstration before the
applicable attainment date or before the EPA's deadline to reach a
determination of attainment by the attainment date under CAA section
181(b)(2), the EPA believes additional flexibility would be warranted
for the Detroit area. The attainment date for the Detroit area was
August 3, 2024, and the EPA's deadline to make a determination of
attainment by the attainment date was February 3, 2025. As described
above, on both of those dates, Michigan understandably believed that
the area was not subject to the requirements of CAA section 181. The
Sixth Circuit issued its decision vacating the EPA's redesignation on
December 5, 2025, and EGLE submitted its demonstration on February 19,
2026, less than three months after the date of the court decision.
Based on the EPA's longstanding interpretation of the statutory
language at CAA section 181(b)(2), as well as the specific facts of the
Detroit area, the EPA is finding that the EPA is not prohibited from
considering the exceptional events demonstration submitted by EGLE on
February 19, 2026, and the EPA is determining that the area attained
the 2015 ozone NAAQS by the applicable attainment date.
III. What action is the EPA taking?
The EPA is determining that the Detroit area attained the 2015
ozone NAAQS by the Moderate attainment date. This 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
taking 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 fulfills the EPA's statutory obligation to determine
whether the Detroit area attained the 2015 ozone NAAQS by the Moderate
attainment date.
In accordance with 5 U.S.C. 553(d), EPA finds there is good cause
for this action to become effective immediately upon publication. This
is because a delayed effective date is unnecessary due to the nature of
this action, which merely determines that the Detroit area attained the
2015 ozone NAAQS by the Moderate attainment date. The immediate
effective date for this action is authorized under section 553(d)(3),
which allows an effective date less than 30 days after publication ``as
otherwise provided by the agency for good cause found and published
with the rule.'' The purpose of the 30-day waiting period prescribed in
section 553(d) is to give affected parties a reasonable time to adjust
their behavior and prepare before the final rule takes effect. This
rule, however, does not create any new regulatory requirements such
that affected parties would need time to prepare before the rule takes
effect. For this reason, EPA finds good cause under 5 U.S.C. 553(d)(3)
for this action to become effective on the date of publication of this
action.
IV. 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 determines 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 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
[[Page 72433]]
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 determines 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 determines 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.
Under section 307(b)(1) of the CAA, petitions for judicial review
of this action must be filed in the United States Court of Appeals for
the appropriate circuit by January 11, 2027. Filing a petition for
reconsideration by the Administrator of this final rule does not affect
the finality of this action for the purposes of judicial review nor
does it extend the time within which a petition for judicial review may
be filed, and shall not postpone the effectiveness of such rule or
action. This action may not be challenged later in proceedings to
enforce its requirements. (See section 307(b)(2).)
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: October 22, 2026.
Anne Vogel,
Regional Administrator, Region 5.
For the reasons stated in the preamble, 40 CFR part 52 is amended
as follows:
PART 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS
0
1. The authority citation for part 52 continues to read as follows:
Authority: 42 U.S.C. 7401 et seq.
0
2. In Sec. 52.1170, amend the table in paragraph (e) by adding an
entry for ``2015 Ozone Determination of Attainment by the Attainment
Date'' after the entry for ``2015 8-hour ozone Moderate RFP plans and
motor vehicle emission budgets'' to read as follows:
Sec. 52.1170 Identification of plan.
* * * * *
(e) * * *
EPA-Approved Michigan Nonregulatory and Quasi-Regulatory Provisions
----------------------------------------------------------------------------------------------------------------
State
Name of nonregulatory SIP Applicable geographic or submittal EPA approval date Comments
provision nonattainment area date
----------------------------------------------------------------------------------------------------------------
* * * * * * *
2015 Ozone Determination of Detroit area .......... 11/10/2026, 91 FR
Attainment by the Attainment (Livingston, Macomb, [INSERT FEDERAL
Date. Monroe, Oakland, St. REGISTER PAGE WHERE THE
Clair, Washtenaw, and DOCUMENT BEGINS].
Wayne Counties).
* * * * * * *
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* * * * *
[FR Doc. 2026-22887 Filed 11-9-26; 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.