[Federal Register Volume 88, Number 97 (Friday, May 19, 2023)]
[Rules and Regulations]
[Pages 32594-32615]
[FR Doc No: 2023-10563]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 52 and 81

[EPA-R05-OAR-2022-0004; FRL-9629-04-R5]

Air Plan Approval; Michigan; Redesignation of the Detroit, MI
Area to Attainment of the 2015 Ozone Standards

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) is finalizing its
redesignation of the Detroit, Michigan area to attainment for the 2015
ozone National Ambient Air Quality Standards (NAAQS) in accordance with
a request from the Michigan Department of Environment, Great Lakes, and
Energy (EGLE). EGLE submitted this request on January 3, 2022. EPA is
approving, as a revision to the Michigan State Implementation Plan
(SIP), the State's plan for maintaining the 2015 ozone NAAQS through
2035 in the Detroit area. EPA is also finding adequate and approving
Michigan's 2025 and 2035 volatile organic compound (VOC) and oxides of
nitrogen (NOX) motor vehicle emissions budgets (budgets) for
the Detroit area. The Detroit area includes Livingston, Macomb, Monroe,
Oakland, St. Clair, Washtenaw, and Wayne Counties.

DATES: This final rule is effective on May 19, 2023.

ADDRESSES: EPA has established a docket for this action under Docket ID
No. EPA-R05-OAR-2022-0004. All documents in the docket are listed on
the www.regulations.gov website. Although listed in the index, some
information is not publicly available, i.e., Confidential Business
Information (CBI) 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 www.regulations.gov or at the Environmental Protection Agency,
Region 5, Air and Radiation Division, 77 West Jackson Boulevard,
Chicago, Illinois 60604. This facility is open from 8:30 a.m. to 4:30
p.m., Monday through Friday, excluding Federal holidays and facility
closures due to COVID-19. We recommend that you telephone Eric Svingen,
Environmental Engineer, at<PHONE_NUMBER> before visiting the Region 5
office.

FOR FURTHER INFORMATION CONTACT: Eric Svingen, Environmental Engineer,
Attainment Planning and Maintenance Section, Air Programs Branch (AR-
18J), Environmental Protection Agency, Region 5, 77 West Jackson
Boulevard, Chicago, Illinois 60604,<PHONE_NUMBER>,
[email protected].

SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,''
``us,'' or ``our'' is used, we mean EPA.

I. Background

    EPA is redesignating the Detroit area to attainment of the 2015
ozone standard, in accordance with EGLE's January 3, 2022, submission.
The background for this action is discussed in detail in EPA's
proposal, dated March 14, 2022 (87 FR 14210). In that proposal, we
noted that, under EPA's regulations at 40 CFR part 50, the 2015 ozone
NAAQS is attained in an area when the 3-year average of the annual
fourth highest daily maximum 8-hour average concentration (i.e., the
design value) is equal to or less than 0.070 parts per million (ppm),
when truncated after the thousandth decimal place, at all of the ozone
monitoring sites in the area. (See 40 CFR 50.19 and appendix U to 40
CFR part 50.) Under the Clean Air Act (CAA), EPA may redesignate
nonattainment areas to attainment if complete, quality-assured data
show that the area has attained the standard and the area meets the
other CAA redesignation requirements in section 107(d)(3)(E). The
proposed rule provides a detailed discussion of how Michigan has met
these CAA requirements and EPA's rationale for approving the
redesignation request.
    As discussed in the proposed rule, quality-assured and certified
monitoring data for 2019-2021 show that the area has attained the 2015
ozone standard, and EPA has determined that the

attainment is due to permanent and enforceable measures. In the
maintenance plan submitted for the area, Michigan has demonstrated that
compliance with the ozone standard will be maintained in the area
through 2035. As also discussed in the proposed rule, Michigan has
adopted 2025 and 2035 VOC and NOX motor vehicle emissions
budgets for the area that are supported by Michigan's maintenance
demonstration.
    Michigan has met the requirements applicable to redesignations
through various SIP submittals. On July 6, 2022 (87 FR 40097),
consistent with conditions identified in our proposed rulemaking, EPA
approved portions of separate December 18, 2020, submittals as meeting
the applicable requirements for a base year emissions inventory and an
emissions statement program. In this rulemaking EPA is also approving,
as a revision to the Michigan SIP, the State's maintenance plan for the
area. The maintenance plan is designed to keep the Detroit area in
attainment of the 2015 ozone NAAQS through 2035. Additionally, EPA is
finding adequate and approving Michigan's newly established 2025 and
2035 motor vehicle emissions budgets for NOX and VOCs for
the area. With these approvals of Michigan's SIP submissions, all SIP
requirements applicable to redesignation are fully approved.
    After publication of the proposed rule, EPA finalized two
additional rulemakings related to the attainment status of the Detroit
nonattainment area. First, on February 1, 2023, EPA found 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 design value 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, with SIP submissions associated with the Moderate area
classification due March 1, 2023 (88 FR 6633). As described below in
EPA's response to comments, consistent with EPA's longstanding
interpretation of CAA section 107(d)(3)(E)(ii) and (v), and as
described in the final determination and classification, EPA's role is
to assess whether Michigan adequately addressed all requirements
applicable to redesignation that applied to Detroit on the date of
EGLE's submittal (88 FR 6633, 6635). Because EGLE submitted a complete
and approvable redesignation request on January 3, 2022, the Moderate
area requirements that became due on March 1, 2023, are not applicable
for purposes of this redesignation. Second, EPA has issued a
determination that the area is attaining the 2015 ozone NAAQS based on
air quality monitoring data from 2020-2022, i.e., a clean data
determination. In issuing the clean data determination, EPA took notice
and comment on its concurrence on a January 26, 2023, exceptional
events demonstration submitted by EGLE. The demonstration requested
exclusion of wildfire event-influenced data from the 2020-2022 design
value period for the 2015 ozone NAAQS for the Detroit nonattainment
area.

II. Motor Vehicle Emission Budgets

    Under section 176(c) of the CAA, new transportation plans,
programs, or projects that receive Federal funding or support, such as
the construction of new highways, must ``conform'' to (i.e., be
consistent with) the SIP. Conformity to the SIP means that
transportation activities will not cause or contribute to any new air
quality violations, increase the frequency or severity of any existing
air quality violations, or delay timely attainment or any required
interim emissions reductions or any other milestones. Transportation
conformity continues to apply in areas redesignated to attainment with
a maintenance plan, so the Detroit area will continue to be subject to
transportation conformity requirements.
    As shown in Table 1, Michigan's maintenance plan includes
NOX and VOC motor vehicle emission budgets (``budgets'') for
the Detroit area for 2025, the interim year, and 2035, the last year of
the maintenance period. The budgets are the portion of the total
allowable emissions that are allocated to highway and transit vehicle
use that, together with emissions from other sources in the Detroit
area, are projected to result in air quality that either attains or
maintains the NAAQS. These budgets represent the projected 2025 and
2035 on-road emissions plus a safety margin allocation and are
consistent with the State's demonstration of maintenance of the 2015
ozone NAAQS. The safety margin and the allocation of a portion of it to
the motor vehicle emissions budgets are described below. Detailed
information on the transportation conformity program can be found in
our March 14, 2022, proposed approval of Michigan's redesignation
request (87 FR 14210).

          Table 1--2025 and 2035 Budgets for the Detroit Area for the 2015 Ozone NAAQS Maintenance Plan
                                              [Tons per summer day]
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                                              2025 Interim year                    2035 Maintenance year
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                                     Projected      Safety                  Projected      Safety
                                      on-road       margin       Total       on-road       margin       Total
                                     emissions    allocation     budget     emissions    allocation     budget
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NOX...............................        61.20        43.15       104.35        40.30        62.11       102.41
VOCs..............................        34.40        13.46        47.86        22.00        22.67        44.67
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    A ``safety margin'' is the difference between the attainment level
of emissions (from all sources) and the projected level of emissions
(from all sources) in the maintenance plan. Further, the transportation
conformity regulations allow states to allocate all or a portion of a
documented safety margin to the motor vehicle emissions budgets for an
area (40 CFR 93.124(a)). Michigan is allocating a considerable portion
of that safety margin to the mobile source sector. Specifically, in
2025, Michigan is allocating 43.15 tons per summer day (TPSD) and 13.46
TPSD of the NOX and VOC safety margins, respectively,
representing approximately 65 percent of the available safety margins,
to the motor vehicle emissions budgets. In 2035, Michigan is allocating
62.11 TPSD and 22.67 TPSD of the NOX and VOC safety margins,
respectively, representing approximately 65 percent of the available
safety margins, to the motor vehicle emissions budgets. Since only a
part of the safety margin is being used for this purpose, maintenance
requirements are still met. Once allocated to mobile sources, these
portions of the safety margins will not be available for use by other
sources.

III. Environmental Justice (EJ) Considerations

    To identify environmental burdens and susceptible populations in
communities in the Detroit area, EPA performed a screening-level
analysis using EPA's EJ screening and mapping tool (``EJSCREEN'').\1\
EPA utilized EJSCREEN to evaluate environmental and demographic
indicators at the county level for each county within the area
(Livingston, Macomb, Monroe, Oakland, St. Clair, Washtenaw, and Wayne
Counties).
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    \1\ See documentation on EPA's Environmental Justice Screening
and Mapping Tool at https://www.epa.gov/ejscreen.
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    EJSCREEN provides environmental indicators for 12 pollutants or
sources, which include fine particulate matter (PM2.5),
ozone, air toxics cancer risk, traffic proximity, lead paint, Superfund
site proximity, underground storage tanks, and wastewater discharge. Of
the seven counties in the Detroit area, all but St. Clair County score
at or above the 80th percentile nationally for at least one indicator:
Livingston County for Superfund site proximity and wastewater; Macomb
County for PM2.5, traffic proximity, Superfund site
proximity, and underground storage tanks; Monroe County for ozone;
Oakland County for traffic proximity, underground storage tanks, and
wastewater; Washtenaw County for underground storage tanks; and Wayne
County for PM2.5, air toxics cancer risk, traffic proximity,
lead paint, underground storage tanks, and wastewater discharge.
    EPA's screening-level analysis indicates that, of the seven
counties in the Detroit area, only Wayne County scores above the
national average for the EJSCREEN ``Demographic Index'', which is the
average of an area's percent minority and percent low-income
populations, i.e., the two demographic indicators explicitly named in
Executive Order 12898. As discussed in EPA's EJ technical guidance,
people of color and low-income populations often experience greater
exposure and disease burdens than the general population, which can
increase their susceptibility to adverse health effects from
environmental stressors.\2\ As a function in part of its relatively
high demographic index, Wayne County is the only county in the Detroit
area scoring at or above the 80th percentile in at least one EJ Index,
which is derived by combining a single environmental factor with the
demographic indicator. Specifically, Wayne County has EJ Indexes above
the 80th percentile in PM2.5, ozone, traffic proximity, lead
paint, and underground storage tanks. EPA has provided that if any of
the EJ indexes for the areas under consideration are at or above the
80th percentile nationally, then further review may be appropriate.\3\
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    \2\ EPA, ``Technical Guidance for Assessing Environmental
Justice in Regulatory Analysis,'' section 4 (June 2016).
    \3\ EPA, ``EJSCREEN Technical Documentation,'' appendix H
(September 2019).
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    For further review, EPA has evaluated the ozone monitor trends and
determined that all the monitors in the nonattainment area are
similarly demonstrating attainment and therefore, there is no evidence
that any one community is experiencing different air quality for this
NAAQS from another. To consider whether the improvement in air quality
has been observed throughout the area, including the portions of the
area containing communities that are pollution-burdened and
underserved, EPA conducted an additional analysis of historical ozone
design values in the Detroit area. Specifically, EPA reviewed data from
the seven monitors in the area that have been operating since the 2001-
2003 design value period: the Macomb County monitor at New Haven with
Site ID 26-099-0009, the Macomb County monitor at Warren with Site ID
26-099-1003, the Oakland County monitor at Oak Park with Site ID 26-
125-0001, the St. Clair County monitor at Port Huron with Site ID 26-
147-0005, the Washtenaw County monitor at Ypsilanti with Site ID 26-
161-0008, the Wayne County monitor at Allen Park with Site ID 26-163-
0001, and the Wayne County monitor at East 7 Mile with Site ID 26-163-
0019. Ozone design values in the Detroit area have declined
significantly from 0.097 ppm in 2001-2003 to 0.070 ppm in 2019-2021. As
shown in Table 2, the improvement in air quality has been observed at
every monitor in the Detroit area. Specifically, ozone design values at
each monitor have improved by between 20% and 31%.

          Table 2--Improvement in Ozone Design Values Between the 2001-2003 Period and 2019-2021 Period
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                                                                                Improvement
                                              2001-2003         2010-2012         2019-2021      between  2001-
                 Monitor                    Design value      Design value      Design value     2003 and 2019-
                                                (ppm)             (ppm)             (ppm)           2021 (%)
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New Haven...............................             0.097             0.078             0.068                30
Warren..................................             0.095             0.079             0.066                31
Oak Park................................             0.091             0.078             0.069                24
Port Huron..............................             0.090             0.077             0.070                22
Ypsilanti...............................             0.091             0.076             0.066                27
Allen Park..............................             0.084             0.074             0.067                20
East 7 Mile.............................             0.091             0.081             0.070                23
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    Not only have ozone design values at all monitors improved by the
relatively consistent margin of 20% to 31%, but the design values at
all monitors have been relatively consistent within each 3-year period.

IV. Response to Comments

    Upon publication of the March 14, 2022, proposed rulemaking, EPA
opened a 30-day comment period, ending April 13, 2022 (87 FR 14210). On
April 4, 2022, in response to a request from Sierra Club, EPA extended
the comment period by an additional 14 days through April 27, 2022 (87
FR 19414). During the comment period EPA received three supportive
comment letters and three adverse comment letters. Two adverse comment
letters were submitted by students at the University of Michigan. The
third adverse comment letter was submitted by Sierra Club and Great
Lakes Environmental Law Center (GLELC), on behalf of themselves and 19
other groups based in Michigan. On March 14, 2023, after the close of
the comment period for this rulemaking or any rulemaking relating to
the Detroit area,

GLELC and Sierra Club sent what they described as ``supplemental
comments'' regarding the proposed redesignation. EPA is exercising its
discretion to respond to these comments herein. Summaries of the
adverse comments and EPA's responses are provided below.
    Comment: Two students at the University of Michigan raised concerns
with EPA's proposed approval of EGLE's redesignation request. One
student shared their fear that redesignating the Detroit area could
increase ground-level ozone and suggested that deregulation in the past
has ``worsened our fight against climate change.'' The second student
raised concerns about Detroit's air quality, given the existence of
power plants and other facilities in the area. Given EPA's April 13,
2022, proposed determination that the Detroit area failed to attain the
2015 ozone NAAQS by its attainment date based on 2018-2020 data, this
student believes it is inappropriate to reevaluate the area's legal
designation at this time. This student suggested that ``legal status
should only be considered when changes have been made and have been
upheld over a substantial period of time.''
    Response: These commenters raise issues that are similar to the
concerns of Sierra Club and GLELC, which we discuss more extensively
below.
    A redesignation to attainment does not remove any emission control
measures for existing sources that are already adopted into the EPA
approved SIP for Michigan. As we discuss below and in the March 14,
2022, proposal, EGLE's redesignation request includes a demonstration
that attainment of the 2015 ozone NAAQS was attributable to permanent
and enforceable emissions reductions. Further, EGLE's January 3, 2022,
submission includes a plan to maintain the NAAQS through 2035 in the
Detroit area, as well as a contingency plan that would be triggered if
the area were to violate the 2015 ozone NAAQS in the future. While EPA
agrees that climate change is an important issue, this rulemaking
addresses the separate issue of the Detroit area's designation for the
2015 ozone NAAQS.
    Regarding concerns about the existence of power plants and other
industrial facilities in the area, we refer the commenter to Table 2 in
EPA's March 14, 2022, proposal, which shows significant emissions
decreases in the Detroit area from 2014 to 2019. Specifically,
NOX and VOC emissions from point, nonpoint, on-road, and
nonroad sources in the Detroit area declined by 203.21 tons per ozone
season day and 104.33 tons per ozone season day, respectively, between
2014 and 2019. Decreases in NOX and VOC emissions from point
sources, which is the category including power plants, account for
69.85 TPSD and 18.50 TPSD, respectively, of the total decrease. These
emissions decreases have contributed to the gradual reductions in ozone
concentrations in the Detroit area. Further discussion of the
commenter's suggestion that EPA should delay action on Michigan's
redesignation request is found below.

A. Monitoring Data

    Comment: Sierra Club and GLELC observe that the Detroit area
attained the 2015 ozone NAAQS, but they raise concerns that the
``margin for NAAQS compliance is particularly thin'' at two monitors in
the Detroit area. The commenters predict future values at which the
NAAQS would be exceeded at four monitors in the area, and raise
additional concerns that the area may violate the NAAQS during the 2022
ozone season. The commenters contend that, in order to approve a
redesignation request, EPA must find that the improvement in air
quality is ``permanent'' and the result of ``enforceable reductions to
emissions,'' and that, in this case, neither of those conditions has
been met.
    Response: The 2015 ozone NAAQS is defined at 40 CFR 50.19, and
appendix U to 40 CFR part 50 contains the data handling conventions and
computations necessary for determining whether the NAAQS has been met
at a monitoring site. To attain the 2015 ozone NAAQS, the 3-year
average of the annual fourth-highest daily maximum 8-hour average ozone
concentrations (ozone design values) at each monitor must not exceed
0.070 ppm. As described in appendix U, design values are reported in
ppm to three decimal places, with additional digits to the right of the
third decimal place truncated.
    The commenters conflate two separate demonstrations that are
required under the statutory criteria for redesignation. CAA section
107(d)(3)(E)(i) provides that EPA may not promulgate a redesignation to
attainment unless the Administrator ``determines that the area has
attained the national ambient air quality standard.'' In finding that
an area has met the first criterion, the statute does not require EPA
to assess how long that attainment has been occurring for or by what
margin the area is attaining. Therefore, the margin by which an area
(or monitor) attains the NAAQS is not relevant to the question of
whether or not the area is attaining the NAAQS. Separately, CAA section
107(d)(3)(E)(iii) provides that the Administrator must also determine
``that the 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 pollutant
control regulations and other permanent and enforceable reductions.''
As used in CAA section 107(d)(3)(E), the term ``permanent'' does not
describe the improvement in air quality, as commenters suggest, but
instead describes the emissions reductions to which attainment must be
attributable.
    Michigan's plan for maintaining the NAAQS is relevant under CAA
section 107(d)(3)(E)(iv), which provides that the Administrator must
fully approve ``a maintenance plan for the area as meeting the
requirements of section 175A.'' The requirement for a maintenance plan
includes the requirement for contingency provisions to be triggered
should an area violate the NAAQS after redesignation, which illustrates
that the CAA anticipates some possibility that areas may in the future
violate the NAAQS despite meeting all requirements under CAA section
107(d)(3)(E). In this final rule EPA is approving EGLE's plan for
maintaining the NAAQS through 2035, as described below and in the
proposed rule.

B. Planning Requirements

    Comment: Sierra Club and GLELC raise concerns that redesignation
``could jeopardize public health by unnecessarily delaying needed air
quality planning requirements.'' The commenters note EPA's separate
proposal to reclassify the Detroit area as Moderate, which would
trigger new requirements for SIP submissions. The commenters allege
that redesignation would ``prematurely halt ongoing planning efforts to
reduce NOX and VOCs'' and without a nonattainment
designation the State will face ``no obligation to select or implement
any of these control measures to assure ozone levels are maintained
below the NAAQS.'' The commenters allege that although ``similar
discussions and planning might resume upon redesignation to
nonattainment, there could be several years of delay in the meantime
while excess ozone levels endanger public health.'' The commenters
reference requirements for Reasonably Available Control Technology
(RACT), and the potential for reductions in NOX emissions
from the Monroe power plant, claiming that this facility emitted 15,219
tons of NOX in 2014.

    Response: In a separate rulemaking published April 13, 2022, EPA
proposed to reclassify the Detroit area as Moderate, based on air
quality data from 2018-2020 showing the Detroit area failed to attain
the 2015 ozone NAAQS by its Marginal attainment date. EPA finalized the
reclassification as Moderate on February 1, 2023, and established a
deadline of March 1, 2023, for most SIP revisions associated with
Moderate area requirements, including requirements for an attainment
plan and RACT. However, upon the effective date of this redesignation
to attainment, nonattainment requirements, including Moderate area
requirements, will no longer apply to the Detroit area.
    As described below, if the Detroit area violates the 2015 ozone
NAAQS after this redesignation, then Michigan would be required to
implement its contingency plan to bring the area back into attainment.
The contingency provisions submitted by EGLE include adoption or
expansion of NOX RACT rules and/or VOC RACT rules for
existing stationary sources. This is the construct of the CAA with
regard to redesignated attainment areas to provide for protections
associated with air quality in designated attainment areas. It should
be noted that many sources that would be subject to VOC RACT under the
2015 ozone NAAQS have implemented VOC controls as required by the rules
Michigan adopted to meet VOC RACT requirements under the 1979 ozone
NAAQS. See 59 FR 46182, September 7, 1994.
    To illustrate the example of a facility with high NOX
emissions which could be subject to additional control requirements,
the commenters reference the Monroe power plant, and incorrectly claim
this facility emitted 15,219 tons of NOX in 2014. According
to EPA's 2014 National Emissions Inventory (NEI), the Monroe power
plant emitted 8,320 tons of NOX in 2014.\4\ A separate data
source, EPA's Clean Air Markets Program Data (CAMPD), shows a similar
result of 8,296 tons of NOX in 2014.\5\ However, as shown in
the CAMPD database, more recent emissions data indicate reduced
NOX emissions and improved control efficiency at this
facility. NOX emissions from the Monroe facility declined by
45% between 2014 and 2021, even though heat input declined by only 5%
over the same period.\6\ Because heat input corresponds to power
generation, these data show that the significant decrease in
NOX emissions was not due to significantly decreased
operation of the facility. Rather, the decrease in NOX
emissions is attributable to increased efficacy of pollution control
equipment that was installed and operated to reduce NOX
emissions. Specifically, Monroe power plant has Selective Catalytic
Reduction (SCR) NOX controls on all four units. The most
recent installation of SCR was in November of 2014, and therefore would
have been minimally represented in the 2014 emissions data. As
discussed in more detail further below, these significant reductions in
NOX emissions from Electric Generating Units (EGUs) such as
the Monroe facility can be attributed to permanent and enforceable
measures such as the Cross-State Air Pollution Rule (CSAPR), which is a
Federal rule that established emissions budgets designed to incentivize
the installation and operation of emissions controls.
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    \4\ https://www.epa.gov/air-emissions-inventories/2014-national-emissions-inventory-nei-data.
    \5\ https://campd.epa.gov/.
    \6\ In 2014, heat input was 157,824,072 Metric Million British
Thermal Units (MMBtu) and NOX emissions were 8,296 tons.
In 2021, heat input was 149,865,102 MMBtu and NOX
emissions were 4,544 tons.
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    The commenters also raise concerns that implementation of Moderate
area requirements could be delayed by a violation of the 2015 ozone
NAAQS subsequent to redesignation. The commenters speculate that under
this scenario EPA would redesignate the area to nonattainment in 2023
and set a new attainment date for three years later, which would be
2026. As discussed below, under the CAA, a violation of the NAAQS after
redesignation to attainment does not trigger an automatic redesignation
to nonattainment. Rather, as discussed above, the initial required
action under such circumstances would be the State's implementation of
the contingency provisions in a State's approved maintenance plan for
the relevant NAAQS, and Michigan's maintenance plan here would require
the State to implement the contingency provisions more quickly than the
three-year timeline identified by the commenters. The redesignation of
an area to nonattainment under section 107(d)(3) is discretionary, and
could take significantly longer whether initiated at the request of the
State or by EPA itself.

C. Environmental Justice Concerns

    Comment: The commenters state that EPA must consider environmental
justice in this action, as much of the nonattainment area contains
already overburdened communities facing disproportionate environmental
impacts. The commenters reference various rates of asthma incidence
across demographic or geographic groups, including asthma rates in
Detroit that are higher than rates in the rest of Michigan, and rates
of asthma hospitalizations within both Wayne and Washtenaw counties
that are higher for Black children relative to white children. The
commenters also raise concerns that ``the asthma burden in Detroit
appears to be worsening'' and reference statistics showing that asthma
rates for adults in Detroit increased from 15.5% in 2016 to 16.2% in
2021. In support of their comments, the commenters reference a peer-
reviewed study from 2009 associating ozone exposure with health effects
on adults with asthma in Atlanta. Additionally, the commenters contend
that EPA has not followed the portion of Executive Order 12898 that
calls for ``meaningful involvement'' from impacted communities beyond
the minimum requirements for a rulemaking. The commenters further
contend that EPA ``must also consider Title VI of the Civil Rights Act
in evaluating the disproportionate consequences of prematurely
approving'' the redesignation request. Commenters cite 40 CFR 7.35(b)
to state that EGLE cannot use ``criteria or methods of administering
its program which have the effect of subjecting individuals to
discrimination because of their race, color, [or] national origin''.
Commenters then state that ``[g]iven the links between ozone pollution
and asthma as well as the racial disparities regarding asthma burdens
in Michigan, there is significant risk of EPA's decision violating
Title VI's prohibition'' against administering programs in a manner
that has a discriminatory effect. Commenters end this portion of the
comments by stating, ``It's unclear how, if at all, EGLE or EPA
accounted for the Title VI requirements and ensured compliance in
regards to this proposal.''
    Response: EPA is committed to the meaningful involvement and fair
treatment of vulnerable populations disproportionately affected by
pollution. EPA does not agree with all of the commenters'
characterizations in this letter. EPA has considered both environmental
justice and title VI of the Civil Rights Act in the context of this
action, and an overview of EPA's considerations of both are described
below. Further, EPA has complied with public notice and comment
requirements for this action.
    With regard to EPA's consideration of environmental justice, EPA is
aware of the demographic data for the Detroit nonattainment area that
is the subject of this final action. EPA acknowledges that the Detroit
area includes communities that are pollution-burdened and underserved.
As described above, EPA considered this information as it

pertains to actions being taken in this action, and further discussion
on this consideration is below in this response.
    Consistent with regulatory obligations associated with this action,
EPA held a public notice and comment period for this action. In
addition, EPA conducted related outreach with Detroit community
members, advocacy groups, and local government officials, regarding air
quality issues that have been identified as priorities by these
stakeholders. In a meeting EPA held with representatives from the City
of Detroit, Michigan Environmental Council, GLELC, Southwest Detroit
Environmental Vision, and the Ecology Center regarding a separate
regulatory action, following a presentation by EPA and a roundtable
discussion with these stakeholders, EPA solicited opinions from these
stakeholders regarding topics for future meetings.\7\ EPA suggested
three topics: permitting, enforcement and inspections, and ground-level
ozone, which we explained included our proposed redesignation. Of those
stakeholders who shared an opinion, all voiced interest in topics other
than ozone, and no stakeholders indicated an interest in future
engagement on ozone. Through community engagement, EPA took steps to
understand different levels of public interest for different
rulemakings that were impacting the Detroit, MI area on more than one
topic around the same time (which was in addition to public notice and
comment requirements).
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    \7\ See Appendix A to May 11, 2023, memorandum entitled
``Memorandum to the Docket: Technical Support Document for the
Detroit Redesignation to Attainment for the 2015 Ozone National
Ambient Air Quality Standard'' (hereafter referred to as May 11,
2023, TSD).
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    In addition to communicating directly with stakeholders, EPA went
beyond the obligations of notice-and-comment rulemaking by issuing a
press release on the day the proposed redesignation was published in
the Federal Register.\8\ The press release was picked up by The Detroit
News, one of the area's two major newspapers.\9\ In its article, The
Detroit News noted that EPA would be accepting public comments on the
proposed redesignation. Additionally, on April 4, 2022, EPA extended
the comment period on the proposed redesignation by 14 days, in
response to a request from Sierra Club for additional time to ``fully
review the basis for EPA's proposal and confer with local partners''
given Sierra Club's suggestion that the proposed action was a
``consequential decision impacting environmental justice communities.''
---------------------------------------------------------------------------

    \8\ https://www.epa.gov/newsreleases/epa-and-michigan-propose-detroit-now-meets-federal-air-quality-standard-ozone.
    \9\ https://www.detroitnews.com/story/news/environment/2022/03/14/pollution-reduction-prompts-epa-improve-metro-detroits-air-quality-rating/7041856001.
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    With regard to the comments concerning the demographics of the
community and asthma burdens in the area, EPA considered a variety of
relevant factors in its determination to propose approval of the
Detroit area redesignation and maintenance plan. Importantly, the
comment letter indicates that EPA is now ``prematurely'' approving the
request for redesignation. As is explained throughout this action, this
action is not premature. Rather, it is consistent with the applicable
requirements of the CAA for an area to qualify for a redesignation.
This redesignation request recognizes that the area has achieved a
national ambient air quality standard and alters the designation of the
area; however, applicable emission reduction measures remain in effect,
as do contingency provisions in the maintenance plan now being approved
that will be triggered if the area fails to continue to attain the
standards. Additional information is provided below in this response to
comment.
    Further, under section 109 of the CAA, EPA sets primary, or health-
based, NAAQS for all criteria pollutants to provide requisite
protection of public health, including the health of at-risk
populations, with an adequate margin of safety. It establishes
secondary, or welfare-based, standards to provide requisite protection
of public welfare from any known or anticipated adverse effects of the
criteria pollutant in ambient air. In EPA's October 26, 2015,
rulemaking strengthening the ozone NAAQS to the level of 0.070 ppm, we
provided a detailed rationale for the Administrator's determination
that the 2015 ozone NAAQS would be protective of public health (80 FR
65292). This rationale included explicit consideration of protection
for people, including children, with asthma.
    EPA considered commenters' concerns regarding asthma rates and
considered that information in light of the action being finalized. As
we explained in the October 26, 2015, rulemaking, asthma is a multi-
etiologic disease, and air pollutants, including ozone, represent only
one potential factor that may trigger an asthma exacerbation.
    Importantly, as is explained throughout this action, if, following
redesignation, there are increases in ozone that result in a violation
of the 2015 ozone standard, the contingency provisions of the
maintenance plan would trigger additional actions by EGLE.
    In support of their comments, the commenters reference a peer-
reviewed study from 2009 associating ozone exposure with health effects
on adults with asthma in Atlanta.
    As we noted in a Technical Support Document in the docket folder
for the June 4, 2018, rulemaking designating the Detroit area as
nonattainment for the 2015 ozone standard, the 2014-2016 design value
for the area was 0.073 ppm (83 FR 25776). As noted above, the 2019-2021
design value is 0.070 ppm. The commenters do not clarify how the ozone
levels in the area might be a primary cause or primary contributor to
the increase in asthma rates they cite as occurring over that same
period (between 2016 and 2021).
    As discussed above, the entire Detroit area is attaining the 2015
ozone NAAQS, which EPA established to provide requisite protection of
public health, including the health of at-risk populations, with an
adequate margin of safety.
    EPA also reviewed current and upcoming emission reduction measures
that are anticipated to further mitigate pollution issues in the
Detroit area. Existing Federal mobile source and point source emission
reduction programs will result in ongoing NOX and VOC
emissions reductions in the Detroit area. For example, NOX
cap and trade programs such as CSAPR continue to achieve emissions
reductions that are protective of human health regardless of whether
EPA redesignates downwind areas for any NAAQS. In addition, the Federal
Good Neighbor Plan for the 2015 ozone NAAQS is projected to achieve
emissions reductions that will provide health benefits to populations
living in proximity to covered facilities beginning in the 2023 ozone
season. Further, Michigan has submitted a maintenance plan that
projects continuing reductions in NOX and VOC emissions
through 2035 from the point, nonpoint, on-road, and nonroad categories,
based on outputs from EPA's MOVES3 and 2016v2 modeling platforms.
    In addition, EPA is now approving the contingency provisions in
Michigan's maintenance plan for the Detroit area. As noted elsewhere in
this rulemaking if the Detroit area were to violate the 2015 ozone
NAAQS after redesignation, then Michigan would be required to correct
the violation by expeditiously implementing the contingency provisions
in its maintenance plan. EPA reviewed the contingency provisions
submitted by EGLE, and found that many of these actions would benefit

pollution-burdened and underserved communities that may be located near
heavily industrial areas (i.e., fuel and diesel retrofit programs,
which may have significant impacts around truck corridors and rail
yards).
    Turning to the issues raised regarding title VI of the Civil Rights
Act of 1964 (title VI), EPA does not agree with commenters'
characterization of potential concerns raised under title VI. Title VI
prohibits discrimination by recipients of EPA financial assistance on
the basis of race, color, or national origin. Under EPA's
nondiscrimination regulations, which implement title VI and other civil
rights laws,\10\ recipients of EPA financial assistance are prohibited
from taking actions in their programs or activities that are
intentionally discriminatory and/or have an unjustified disparate
impact.\11\ Because EPA is not a recipient of Federal financial
assistance, title VI does not apply to EPA itself. EPA carries out its
mandate to ensure that recipients of EPA financial assistance comply
with their nondiscrimination obligations by investigating
administrative complaints filed with EPA alleging discrimination
prohibited by title VI and the other civil rights laws; \12\ initiating
affirmative compliance reviews; \13\ and providing technical assistance
to recipients to assist them in meeting their title VI obligations.
Importantly, compliance with the CAA does not constitute compliance
with title VI.
---------------------------------------------------------------------------

    \10\ 40 CFR part 7 and part 5.
    \11\ 40 CFR 7.30 and 7.35.
    \12\ 40 CFR 7.120.
    \13\ 40 CFR 7.115.
---------------------------------------------------------------------------

    As part of this redesignation, EPA is approving the maintenance
plan for the area, including contingency provisions, which will be
incorporated into the SIP. Title VI does apply to EGLE as a recipient
of Federal financial assistance.
    In the context of SIP actions, EPA has evaluated issues similar to
the title VI comments through CAA section 110(a)(2)(E)(i). See, e.g.,
77 FR 65294 (October 26, 2012); 87 FR 60494 (October 5, 2022). EPA has
previously acknowledged that it has not issued national guidance or
regulations concerning implementation of section 110(a)(2)(E) as it
pertains to consideration of title VI and disparate impacts on the
basis of race, color, or national origin in the context of the SIP
program. 87 FR at 60530. Such guidance is forthcoming and will address
CAA section 110(a)(2)(E)'s necessary assurance requirements as they
relate to title VI.
    In the context of a SIP action, however, section 110(a)(2)(E)
requires that a State provide ``necessary assurances'' that the SIP
submission at issue would not result in violations of any State or
Federal law. Thus, as the commenters suggest, a relevant inquiry for
EPA in this rulemaking is whether the air agency has provided adequate
necessary assurances that implementation of the content of the SIP
submission at issue is not prohibited by title VI (i.e., implementation
of the SIP would not result in an unjustified adverse disparate impact
on the basis of race, color, or national origin). See, e.g., CAA
section 110(a)(2)(E)(i).
    This redesignation action, at its core, recognizes that an area is
meeting the NAAQS and has all the required CAA measures in place,
including the required maintenance plan with contingency provisions.
The contingency provisions of the maintenance plan would require
additional control measures in the event that a future design value for
the area exceeds the level of the ozone standard, or if the fourth-
highest monitored value, averaged over two years, is 0.071 ppm or
higher.\14\ In this action, the plan being finalized includes required
contingency provisions (as was described above) as well as additional
ozone related measures already approved into the SIP due to prior ozone
standards (also described earlier in this action).
---------------------------------------------------------------------------

    \14\ The list of potential contingency provisions is provided in
EGLE's submittal dated January 3, 2022. They include: Adoption of or
updating of VOC or NOX Reasonable Available Control
Technology (RACT) rules for existing sources covered by USEPA
Control Technique Guidelines, Alternative Control Guidelines, or
other appropriate guidance issued after the 1990 CAA, such as VOC
RACT for increased methane leak monitoring and repair at oil and gas
compressor stations, automobile and light-duty truck assembly
coatings, miscellaneous metal and plastic parts coatings, paper,
film, and foil coatings, miscellaneous industrial adhesives, or
industrial cleaning solvents, or NOX RACT for stationary
internal combustion sources, utility boilers, process heaters, iron
and steel mills, or glass manufacturing; Applying VOC RACT on
existing smaller sources; Implementing alternative fuel and diesel
retrofit programs for fleet vehicle Operations; Requiring VOC or
NOX control on new minor sources (less than 100 tons per
year); Increasing the VOC or NOX emission offsets for new
and modified major sources; Reducing idling programs; Trip reduction
programs; Traffic flow and transit improvements; Working with the
Michigan Department of Licensing and Regulatory Affairs to encourage
natural gas utilities to increase turnover of legacy distribution
pipelines; Stationary engine controls to reduce formaldehyde and
NOX Emissions; Phase 2 AIM rules; Phase 5 Consumer
Products rules; and additional measures as identified by EGLE.
---------------------------------------------------------------------------

    For all these reasons, there is no information to support a
conclusion that EGLE's implementation of this SIP submittal, including
the maintenance plan now being approved (including contingency
provisions), would result in an unjustified disparate impact or is
otherwise prohibited by title VI of the Civil Rights Act. Thus, EPA is
not requiring any further necessary assurances at this time for
purposes of compliance with section 110(a)(2)(E)(i).

D. Trend in Design Values

    Comment: The commenters contend that EPA does not have sufficient
data to determine that the 2021 emission reductions were part of a
downward trend, as the fourth highest recorded concentration increased
at all monitor locations except St. Clair County between the years of
2019 and 2020. As the 2018-2020 design values show nonattainment at
half of the monitor locations in the area, the commenters contend that
there is no reason to believe that the 2019-2021 design values will be
representative of future ozone concentrations.
    Response: Attainment of the 2015 ozone NAAQS, like the 1997 ozone
NAAQS and 2008 ozone NAAQS before it, is measured by averaging the
annual fourth-highest daily maximum 8-hour average concentrations over
a 3-year period. In our rulemaking promulgating the 1997 ozone NAAQS,
EPA noted the ``lack of year-to-year stability'' inherent to the prior
1979 ozone NAAQS, and determined that a form including a 3-year average
would ``provide some insulation from the impacts of extreme
meteorological events that are conducive to ozone formation.'' (62 FR
38856, July 18, 1997). Similarly, when EPA revised the NAAQS in 2008,
we recognized ``that it is important to have a form that is stable and
insulated from the impacts of extreme meteorological events that are
conducive to ozone formation. Such instability can have the effect of
reducing public health protection, because frequent shifting in and out
of attainment due of meteorological conditions can disrupt an area's
ongoing implementation plans and associated control programs. Providing
more stability is one of the reasons that EPA moved to a concentration-
based form in 1997.'' (73 FR 16435, March 27, 2008). In our October 26,
2015, rulemaking which retained the form of the 1997 ozone NAAQS and
2008 ozone NAAQS but strengthened the NAAQS to the level of 0.070 ppm,
EPA found that the three-year average ``provides an appropriate balance
between public health protection and a stable target for implementing
programs to improve air quality.'' We therefore observe that as a
general matter, EPA designed the form of the 2015 ozone NAAQS to
accommodate some year-to-year variation in ozone concentrations. The

design value is intended to be the simple average of the annual fourth-
highest daily maximum 8-hour average concentrations over the 3-year
period, with no special consideration given to any of those three
years. When we structured the form of the 2015 ozone NAAQS, EPA created
no requirement that for a monitor or an area to attain the standard, a
downward trend must be observed within the 3-year period.
    Over a longer period, however, EPA has observed a clear downward
trend in ozone design values in the Detroit area. In evaluating the
commenters' claims regarding trends in ozone concentrations, EPA
reviewed past data from all monitors in the Detroit area. These data
cover the period ending with the most recent design value period, which
is 2020-2022, and starting with the design value period that was the
basis of our nonattainment designation for the 1997 ozone NAAQS, which
was 2001-2003 (69 FR 56697, September 22, 2004). The historic ozone
design values for the seven-county Detroit area are summarized in Table
3. For each 3-year period, the design value is determined by the
monitor or monitors with the highest 3-year averaged concentration. For
all 3-year periods, the highest design value was observed at one or
more of the following five monitors: Port Huron, East 7 Mile, New
Haven, Allen Park, or Warren.

Table 3--3-Year Average of the Fourth-Highest Daily Maximum 8-Hour Ozone
        Concentrations (Ozone Design Values) for the Detroit Area
------------------------------------------------------------------------
                                                Average fourth-highest
               3-Year period                 daily maximum  8-hour ozone
                                                 concentration (ppm)
------------------------------------------------------------------------
2001-2003..................................                        0.097
2002-2004..................................                        0.092
2003-2005..................................                        0.090
2004-2006..................................                        0.082
2005-2007..................................                        0.086
2006-2008..................................                        0.082
2007-2009..................................                        0.080
2008-2010..................................                        0.075
2009-2011..................................                        0.078
2010-2012..................................                        0.081
2011-2013..................................                        0.077
2012-2014..................................                        0.074
2013-2015..................................                        0.072
2014-2016..................................                        0.073
2015-2017..................................                        0.073
2016-2018..................................                        0.074
2017-2019..................................                        0.072
2018-2020..................................                        0.071
2019-2021..................................                        0.070
2020-2022..................................                        0.070
------------------------------------------------------------------------

    As shown in Table 3, ozone design values in the Detroit area have
declined significantly from 0.097 ppm in 2001-2003 to 0.070 ppm in
2019-2021, and 2020-2022. On this point, we agree with the commenters'
statement that ``there is no doubt that, in general, ozone precursor
emissions have decreased over the past two decades as noted by the
studies and that, as a result, ozone concentrations have decreased.''
This decrease is clear across the overall time period presented in
Table 3.
    However, as also shown in Table 3, EPA has sometimes observed an
increase in ozone design values, such as the increase from 0.073 ppm in
2015-2017 to 0.074 ppm in 2016-2018. In EPA's view, fluctuation in
design values over a shorter period does not detract from the overall
trend in air quality improvements over a longer period. On three
occasions, at the 2004-2006, 2008-2010, and 2013-2015 3-year periods,
the design value reached a new low, before experiencing an increase in
the subsequent 3-year period. However, after each of these occasions,
the design value returned to its low point within several years and did
not exceed that low point for a second time. This is consistent with
national decreasing trends in ozone concentrations which face some
year-to-year variability in measured concentrations.\15\ Interannual
variability is expected even when there are longer-term downward trends
driven by emissions reductions (Strode et al., 2015; \16\ Simon et al.,
2015 \17\). This suggests that, despite variability within a 3-year
period and occasionally across several 3-year periods, historic
permanent and enforceable emissions reductions have been effective in
reducing ozone concentrations in the area, and these reduced ozone
concentrations have become more durable as the associated control
programs have progressed through implementation. As we discuss below,
if a future design value in the Detroit area exceeds the level of the
2015 ozone NAAQS, then implementation of Michigan's contingency
provisions, combined with the ongoing implementation of State and
Federal control measures documented in EGLE's maintenance plan, would
be the appropriate remedy.
---------------------------------------------------------------------------

    \15\ https://www.epa.gov/air-trends/trends-ozone-adjusted-weather-conditions.
    \16\ Strode, S.A., Rodriguez, J.M., Logan, J.A., Cooper, O.R.,
Witte, J.C., Lamsal, L.N., Damon, M., Van Aartsen, B., Steenrod,
S.D., and Strahan, S.E.: Trends and variability in surface ozone
over the United States, J. Geophys. Res.-Atmos., 120, 9020-9042,
https://doi.org/10.1002/2014JD022784, 2015.
    \17\ Heather Simon, Adam Reff, Benjamin Wells, Jia Xing, and
Neil Frank, Ozone Trends Across the United States over a Period of
Decreasing NOX and VOC Emissions, Environmental Science &
Technology, 2015 49(1), 186-195.
---------------------------------------------------------------------------

E. Timeline

    Comment: The commenters suggest that EPA should wait until the end
of the 2022 ozone season to act upon the redesignation request.
    Response: EPA is finalizing this action after considering the
additional year of monitoring data from 2022. In our separate
rulemaking finalizing a

clean data determination for the Detroit area, EPA has found that the
area continued to attain the standard for the 2020-2022 period, which
is one year beyond the 2019-2021 period which is the basis of the
State's redesignation request.

F. Meteorology

    Comment: The commenters stated that EPA did not fully consider
unusually favorable meteorological conditions as the cause for
decreased ozone concentrations, since EPA relies on temperature studies
done by EGLE and the Lake Michigan Air Directors Consortium (LADCO)
that consider long-term ozone concentrations rather than concentrations
during the design value years. Additionally, the commenters contend
that although temperature is a large factor in the creation of ozone,
there are other factors that should be considered. While factors
besides temperature were considered for the LADCO study, they were only
considered through 2019 and did not include 2020 or 2021, and the
commenters stated that the higher 2021 humidity levels could have
contributed to decreased ozone concentrations. Lastly, the commenters
also claim that EPA did not account for ``how lower than average
temperatures and fewer days above 80 degrees Fahrenheit have impacted
ozone concentrations'' and that ``2019 appears to have been a year with
exceptionally few high temperature days. In that year, there were only
76 days with a maximum temperature equal to or above 80 degrees
Fahrenheit, which is the lowest total since 2009.'' Broadly, the
commenters question if EGLE and EPA have appropriately considered
whether temperature and other meteorological conditions, as opposed to
emissions reductions, were the cause of lower ozone concentrations.
    Response: The analyses of long-term meteorological trends including
both Michigan's meteorological analysis and LADCO's classification and
regression tree (CART) analysis helps to illustrate the cause for
decreasing ozone concentrations over time in the Detroit area.
Additionally, EPA's Trends in Ozone Adjusted for Weather Conditions
show that while the Detroit area benefited from unconducive meteorology
in 2019, the weather adjusted ozone trends show that meteorological
conditions were more conducive than average in 2020. Thus, the area did
not experience three consecutive years of unconducive meteorology in
2019-2021, therefore the meteorology for the 3-year period as a whole
was not ``unusual''.\18\
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    \18\ https://www.epa.gov/air-trends/trends-ozone-adjusted-weather-conditions.
---------------------------------------------------------------------------

    Michigan's January 3, 2022, submittal presents LADCO's CART
analysis for years 2005 through 2019, which evaluates 21 separate
meteorological factors that can influence ozone formation in Detroit.
This analysis ranks each variable by its relative importance. The most
important factor in ozone formation in Detroit is Average PM
Temperature, which is assigned a relative importance level of 1.000.
Closely following Average PM Temperature are Max Daily Temperature, Max
Apparent Temperature, and Average AM Temperature which are all assigned
relatively high variable importance to ozone formation. The last of
these four, Average AM Temperature, has a relative importance level of
0.9273. After this variable, there is a steep drop-off before arriving
at the importance of the fifth variable, which is Average Wind South
Vector with a relative importance level of 0.5763. In other words, the
top four variables all relate to temperature, and these temperature
variables are much more important than any other variable. As shown in
LADCO's CART analysis for 2005 through 2019, temperature is the peak
driving meteorological factor determining ozone formation in the
Detroit area. Additionally, EPA's weather adjusted ozone trends, which
go through 2021, also have daily max temperature as the most important
variable at every site in the Detroit area. The next five are PM wind
direction, AM wind speed, mid-day relative humidity and 24-hour
transport direction, in varying orders of importance for individual
ozone sites.
    In evaluating the commenters' concerns that LADCO's CART analysis
included data only through 2019, EPA reviewed a CART analysis which
LADCO prepared more recently, and which analyzes data for 2005 through
2020. Inclusion of the more recent year does not support commenters'
broader claims regarding meteorological impacts during the design value
period. Rather, inclusion of the more recent year only reinforces the
finding that variables relating to temperature are more important than
any other meteorological variable in determining ozone formation in the
Detroit area. In the newer analysis, LADCO evaluated a new variable,
Average Apparent Temperature, which is grouped with the other four
variables relating to temperature as the most important variables
affecting ozone formation in Detroit, ahead of the variable for Average
Wind South Vector and other less-important variables relating to
factors such as precipitation and humidity.
    Michigan's analysis for the years 2000-2021 considered temperature
during the ozone season and its relationship with ozone concentrations.
The State found that ozone concentrations declined over this period,
even though temperatures increased over the same period. It is
important to keep in mind that high ozone cannot form in the absence of
precursor emissions. Michigan's finding is consistent with LADCO's CART
analysis for the 2005-2019 period in the Detroit area, which shows that
when the influence of meteorological variability is largely removed,
ozone concentrations declined regardless, indicating that the downward
trend in ozone levels is attributable to reductions in precursor
emissions.
    However, the commenters raise the concern that the State did not
consider a wider breadth of meteorological factors besides temperature
in 2020 and 2021. The commenters suggest that there may have been
unanalyzed unusual meteorological conditions that might have affected
ozone concentrations. The commenters state that there may have been
higher levels of humidity in Detroit during the ozone season which may
have depressed ozone formation in the area. To support this claim, the
commenters present a graph of Hourly Humidity Comfort Levels
Categorized by Dew Point for summers 2020 and 2021 in Detroit.\19\
However, a presentation of dew point data does not illustrate anything
useful about humidity levels, because dew point values are a function
not only of humidity data but also of temperature data. In other words,
a high dew point value may be caused by high temperatures, even if
relative humidity is held constant. The commenters also fail to provide
an analysis of humidity levels for previous years to back up their
claim that humidity levels in 2020 and 2021 were unusual relative to
historical levels. Regardless, meteorologically adjusted trends always
show negative relationships between both relative humidity (RH) and
ozone and dewpoint and ozone (meaning higher RH and dewpoint are
associated with lower ozone), while temperature and ozone always have a
positive relationship (higher temperature is associated with

higher ozone). As explained above, other meteorological factors had a
greater influence on Detroit ozone as evidenced by Michigan's, LADCO's
and EPA's analyses.
---------------------------------------------------------------------------

    \19\ In the narrative section of their comment letter, the
commenters include the incorrect chart for summer 2021. However, in
a footnote, the commenters include a URL to the correct chart.
---------------------------------------------------------------------------

    EPA does not agree that we failed to provide significant evidence
that the improvement in air quality is not attributed to unusual
meteorological circumstances. EPA relied on Michigan's analysis and the
LADCO CART analysis to conclude that air quality improvement has been a
constant trend when meteorology is controlled for variance. The
commenters have not presented any compelling evidence that the 2019-
2021 design value period had unusual meteorology. Additionally, EPA's
Trends in Ozone Adjusted for Weather Conditions corroborates these
analyses.
    As exhibited in LADCO's CART analysis, Detroit has seen decreasing
ozone concentrations even when controlling for meteorological variance
between 2005-2019. As presented in Michigan's analysis, ozone
concentrations have been decreasing between 2000-2021 despite
increasing temperatures in Detroit. This helps us conclude that the
long-term trend of decreasing ozone concentrations can be attributed to
decreases in ozone precursors and not because of meteorological
factors. Additionally, EPA's Trends in Ozone Adjusted for Weather
Conditions corroborates these analyses. EPA agrees with Michigan's
conclusion that the air quality improvement in the Detroit area was
caused by reductions in ozone precursors and not unusually favorable
meteorological conditions.

G. Economic Conditions

    Comment: The commenters contend that EPA's determination that
improved air quality during 2019-2021 was caused by permanent and
enforceable emissions reductions program has no basis because EPA did
not fully evaluate whether decreased economic activity from the COVID-
19 pandemic caused improved air quality in the Detroit area. The
commenters suggest that effects of the COVID-19 pandemic on power plant
emissions and automobile travel may be the likely cause of the
reductions rather than the cited enforceable reduction measures.
Specifically, the commenters raise concerns that reductions in vehicle
miles traveled and emissions of ozone precursor emissions occurring in
2020 and 2021 were likely caused by the COVID-19 pandemic. The
commenters conclude that EPA failed to consider an important aspect of
the problem in not fully considering the impact of the pandemic in
EPA's proposed rulemaking to redesignate the Detroit area to attainment
of the 2015 ozone NAAQS.
    Response: EPA recognizes the difficulties in assessing the impacts
of the COVID-19 pandemic on ozone precursor emissions and ozone design
values and the economic disparities from the COVID-19 pandemic, but we
do not agree that the Detroit area's attainment is due to a temporary
economic downturn associated with the COVID-19 pandemic. As discussed
in the March 14, 2022, proposed rulemaking, we think that EGLE's
submission and the rationale provided in EPA's proposal establishes
that the area's attainment is due to the cited permanent and
enforceable reductions and not temporary adverse economic conditions.
    In their January 3, 2022, submittal, EGLE evaluated whether the
improvement in air quality was caused by temporary adverse economic
conditions, especially the economic conditions associated with the
COVID-19 pandemic which first impacted Michigan in 2020. EGLE charted
point source VOC and NOX emissions in the Detroit area from
2012 to 2020. These two charts show the overall downward trend in point
source emissions from 2012 to 2020. EGLE also evaluated both employment
levels and VMT. While employment levels in the Detroit area were
affected by COVID-19 and saw a 27 percent decrease in employment from
March 2020 to April 2020, employment returned to 85 percent of March
2020 levels by June 2020, according to Bureau of Labor and Statistics
(BLS) Quarterly Census of Employment and Wages.\20\ Employment levels
continued to increase through 2022, and as of March 2021 and March
2022, employment levels in the Detroit area were 93 and 99 percent of
the employment in February 2020, before the onset of the COVID-19
pandemic, respectively. As noted by EGLE in their submission, the
analysis performed by the Southeast Michigan Council of Governments
(SEMCOG) indicated a reduction of less than 5 percent of VMT in 2020
based on their travel demand forecasting model.
---------------------------------------------------------------------------

    \20\ See www.bls.gov/cew.
---------------------------------------------------------------------------

    Nevertheless, in response to this comment, EPA has performed
additional analyses that further support our determination.
    The commenters highlight nationally decreased power plant emissions
during the COVID-19 pandemic recession beginning in 2020 and cite point
source reductions that occurred from 2019 to 2020. EPA therefore
analyzed total heat input from EGUs across the State of Michigan from
2018 to 2022 to investigate whether Detroit's attainment of the NAAQS
during the 2020 ozone season could be attributable to economic effects
from the COVID-19 pandemic.\21\ Of the five years of data examined, our
analysis found that April 2020 had the single lowest total monthly heat
input for EGUs located in the seven Southeast Michigan counties in the
Detroit area. This monthly value is correlated with the strongest
economic effects that could be attributable to lockdown orders,
declining employment figures, or decreases in vehicle miles traveled,
as discussed later in this section. However, we note that the total
monthly heat input at these power plants began rebounding in May 2020
and increased to an annual peak in July 2020. This pattern of monthly
total heat inputs increasing from April onwards and peaking in July or
August is consistent with annual trends over the five-year period for
both EGUs in the seven-county Detroit area and across the State as a
whole. The ozone monitoring season runs from March 1 to September 30 in
Michigan, but the meteorology most conductive to conditions that could
result in exceedances of the NAAQS typically occurs in summer months of
May through July. EPA's analysis shows that while there was a
pronounced effect on electricity production at EGU facilities in the
Detroit area in April 2020, emissions activity from these sources
increased in subsequent months following the same monthly patterns that
were observed in 2018 and 2019. Moreover, we note similar annual
patterns of EGU activity peaking in July or August continued again in
2021 and 2022. Therefore, EPA does not agree that economic effects of
the COVID-19 pandemic on power plant emissions are responsible for the
Detroit area's attainment of the NAAQS in 2020 or any year thereafter
rather than the permanent and enforceable emissions reductions
described in the notice of proposed redesignation.
---------------------------------------------------------------------------

    \21\ See Appendix B to May 11, 2023, TSD.
---------------------------------------------------------------------------

    In response to the commenters concerns that 2021 emissions were
still impacted by the pandemic, EPA additionally examined emissions
from EGUs in Michigan subject to the Cross-State Air Pollution Rule
NOX Annual Program, and found that there were similar annual
NOX emissions in 2021 relative to 2019, 31,743 tons per year
(tpy) versus 31,123 tpy, respectively.\22\

EPA further evaluated coal consumption for electric power, which the
commenters note was still lower in 2021 as compared to 2019 likely due
to the pandemic. Calculations show that 2021 consumption was 97 percent
of the level of coal consumption in 2019 in Michigan.\23\ In May 2021,
one of the largest coal-fired EGU facilities in the area, DTE River
Rouge, permanently retired. The shutdown of this facility was estimated
by EGLE to achieve annual reductions of 2,716 tons of NOX.
---------------------------------------------------------------------------

    \22\ See Appendix C to May 11, 2023, TSD.
    \23\ See Energy Information Administration, Coal Data Browser
(Data Set: Total Consumption, Electric Power), https://www.eia.gov/coal/data/browser/.
---------------------------------------------------------------------------

    EPA also analyzed the pandemic's impact on traffic in response to
the commenters' assertion that automobile travel ``plunged'' in 2020 as
a result of the pandemic, using data from StreetLight,\24\ which is an
on-demand mobility analytics platform that uses data from mobile
devices. We found that traffic did decrease during the pandemic, but
largely returned to pre-pandemic levels by the time of year that
meteorological conditions are most conducive to ozone formation. As
shown in the StreetLight data, the seven-county Detroit area
experienced a drop in VMT during the period of the stay-at-home order,
beginning March 23 and ending June 1. However, beginning in June 2020,
VMT was comparable to VMT levels before the start of the pandemic.\25\
This is significant because EPA has found that in the upper Midwest,
the majority of ozone exceedances occur in late May though late
July.\26\ In addition, border crossing information, provided by SEMCOG,
shows that heavy duty truck VMT remained near pre-pandemic levels in
2020. Given the many mobile source reduction measures in place in
Michigan, EPA does not conclude that the reductions achieved are based
on a brief period of decreased VMT in 2020 due to the COVID-19
pandemic.
---------------------------------------------------------------------------

    \24\ See https://www.streetlightdata.com/. EPA would not rely on
StreetLight for the purpose of generating inventories, such as the
inventories submitted by EGLE. However, this data source has a
reasonable accuracy that is sufficient for the purpose of assessing
claims made by the commenters regarding temporal changes in VMT
during the COVID-19 pandemic. EPA believes this source of data is
usable for this analysis in part because StreetLight data has very
good performance when compared against traditional manual traffic
counts, with an R[caret]2 value of 0.9782. StreetLight has been
utilized by many departments of transportation at the State and
Federal level. See https://www.streetlightdata.com/transportation-planning-case-studies/.
    \25\ See Appendix D to May 11, 2023, TSD.
    \26\ See Appendix E to May 11, 2023, TSD.
---------------------------------------------------------------------------

    Another important aspect of the economic changes that occurred
during the COVID-19 pandemic in the Detroit area, which the commenters
do not address, is that manufacturing processes in the Detroit area did
not stop during the pandemic, but rather shifted towards new processes
related to the pandemic. For example, the Oakland County Board of
Commissioners appropriated over 300,000 dollars to six facilities to
begin production on personal protection equipment (PPE) such as face
masks and ventilator equipment.\27\ Ford Motor Company and General
Motors Corporation (GM) worked to reallocate their production to
ventilators, which began training by April 2020. GM also began
producing face masks by March 27, 2020 and worked with a local
automation company to create an assembly line capable of producing
50,000 masks a day.\28\ Several nonprofit groups worked to assist
manufacturing facilities in shifting to production of surgical masks
and gowns, such as the Industrial Sewing and Innovation Center (ISAIC),
working with the City of Detroit, Michigan Economic Development
Corporation, and others to establish efficient and automated production
methods, noting that this effort was ``a way to keep people employed,
and at the same time protecting people that are working on the front
lines.'' \29\ Carhartt worked with ISAIC, and offered one floor of
their Detroit store to the nonprofit for factory space for this
initiative, which received funding to produce 1 million surgical masks
per month. These efforts speak to the rebounding of Detroit's
employment rates post pandemic and highlight nonprofit work that drove
much of the initiative to shift production. While the commenters
highlight the highest single quarterly drop in Gross Domestic Product
(GDP) of 31.4 percent in the second quarter of 2020, it is important to
note the highest single quarterly increase in GDP in the third quarter
of 2020, of 33.1 percent,\30\ noted in the same report by the
Congressional Research Service. Efforts such as those seen in Detroit
have likely aided this rebound.
---------------------------------------------------------------------------

    \27\ See https://www.clickondetroit.com/news/local/2020/05/04/oakland-county-funds-manufacturers-to-switch-production-to-medical-equipment-protective-gear.
    \28\ See https://www.assemblymag.com/articles/95741-manufacturers-shift-to-ppe-production-to-fight-covid-19-pandemic.
    \29\ See https://www.modeldmedia.com/features/detroit-apparel-manufacturers-coalition.aspx.
    \30\ See Congressional Research Service, Covid-19 and the U.S.
Economy, https://crsreports.congress.gov/product/pdf/R/R46606.
---------------------------------------------------------------------------

    EPA does not agree that the Detroit area's attainment is due to a
temporary economic downturn associated with the COVID-19 pandemic, but
rather believes the Federally enforceable emission reduction measures
were the main driving factor in the area coming into attainment.

H. Federal Control Programs

    Comment: The commenters contend that EPA did not demonstrate that
the Federal good neighbor rules and mobile source standards were key
elements of the ozone reductions. The commenters assert that most of
these rules were implemented and would have had emissions impacts prior
to 2019, and even prior to 2018, and yet ozone concentrations increased
in 2020 and most of the monitors in the area continued to be in
nonattainment based on design values for the years 2018-2020. The
commenters conclude that these facts undermine EPA's finding that the
reduced ambient concentrations in 2019-2021 are in fact attributable to
regulations that went into effect from 2004-2017. Additionally, the
commenters contend that EPA relied on overall pollution reductions from
the CSAPR Update, which covers areas that are downwind of the Detroit
area. The commenters point out that EPA did not determine whether
reductions in emissions specifically causing nonattainment in Southeast
Michigan will occur, and that, because the CSAPR Update is a cap-and-
trade program, facilities contributing to Detroit's ozone problem could
comply with the rule by purchasing allowances, rather than reducing
emissions. The commenters claim that ``reliance on these rules is
illogical, incomplete, and fails to satisfy the requirements for
redesignation.''
    Response: Regarding EPA's mobile source standards, the commenters
have incorrectly interpreted the timeline by which emissions reductions
are achieved. The full benefit of these programs does not occur in the
first year that a rule is effective, or even within the years that
manufacturers must first begin manufacturing vehicles or engines in
accordance with EPA's rules. These mobile source measures have resulted
in, and continue to result in, large reductions in NOX
emissions over time due to fleet turnover (i.e., the replacement of
older vehicles that predate the standards with newer vehicles that meet
the standards). Emissions reductions from these programs are modeled by
EPA's 2016v2 platform and the MOVES3 mobile source emission modeling
system, which we discuss below in greater detail. In our March 14,
2022, proposed rulemaking, in our discussions of Tier 3 motor vehicle
emission standards as well as rules for heavy-duty diesel engines,
nonroad diesel engines, large

spark-ignition engines, and marine diesel engines, we noted that some
of these emission reductions occurred by the attainment years and
additional emission reductions will occur throughout the maintenance
period, as older vehicles or engines are replaced with newer, compliant
model years. It is incorrect that, by pointing out that the Detroit
area did not attain the standard immediately upon promulgation or
implementation of these rules, the commenters have demonstrated that it
is ``illogical'' or ``incomplete'' for EPA to rely on these rules as
permanent and enforceable emissions reductions as required by CAA
section 107(d)(3)(E).
    We also disagree that it was ``illogical,'' ``incomplete,'' or
otherwise inappropriate for EPA to point to emissions reductions
resulting from the Revised CSAPR Update as contributing to the Detroit
area's attainment. First, we note that EPA did not only cite the
Revised CSAPR Update; we also pointed to the historical and/or ongoing
Federal programs such as the Clean Air Interstate Rule (CAIR), CSAPR,
CSAPR Update, and Revised CSAPR Update, all of which addressed the
interstate transport requirements of CAA section 110(a)(2)(D) and
reduced ozone precursor emissions in the eastern United States over the
relevant time period.
    First, we note that multiple Federal Circuit Courts of Appeal have
reviewed similar arguments challenging whether it is reasonable for EPA
to rely upon regional interstate transport cap-and-trade programs as
part of the cause of an area's attainment, and those courts have upheld
EPA's reliance. See Sierra Club v. EPA, 774 F.3d 383 (7th Cir. 2014);
Sierra Club v. EPA, 793 F.3d 656 (6th Cir. 2015). Arguments raised in
those cases were remarkably similar to commenters' contentions here:
``Sierra Club criticizes EPA's reliance on the NOX SIP Call,
because that program is aimed at reducing pollution in the region as a
whole and permits the twenty-two affected states to purchase pollution
`allowances' from one another. Accordingly, Sierra Club believes that
the effects on any one area in particular are not necessarily permanent
and enforceable.'' Sierra Club v. EPA, 774 F.3d at 397. The Seventh
Circuit noted that the overall structure of the trading program ensured
a regional reduction in emissions, and that ``it is reasonable to rely
on the program as one basis, among many, for concluding that reduced
emissions levels will persist.'' Id. at 399. The Sixth Circuit
similarly upheld challenges to EPA's reliance on interstate transport
trading programs in a redesignation as one of the causes of an area's
attainment. Sierra Club v. EPA, 793 F.3d at 665-68.
    While commenters are correct that sources may comply with the
Revised CSAPR Update by purchasing allowances rather than reducing
emissions, the Revised CSAPR Update trading region (which includes
Michigan and is currently comprised of 12 states in the eastern United
States) is subject to an overall reduction in emissions via the State-
level emissions budgets and assurance levels in that program.
Commenters are not correct that EPA did not analyze whether reductions
are and were required from states upwind of Michigan in the Revised
CSAPR Update. While the Detroit area was not identified as having
receptors in that rule, emission reductions required of Michigan and
other states included in the Revised CSAPR Update will still result in
air quality benefits in the Detroit area, due to the regional nature of
ozone and ozone precursor transport.
    Further, the control of ozone season NOX emissions under
the Good Neighbor Provision of the CAA will be continued and improved
through the more recent final Good Neighbor Plan for the 2015 ozone
NAAQS, which was signed on March 15, 2023.\31\ This rule, as
promulgated, is set to control ozone season NOX emissions
from power plants through a revised trading program beginning in 2023
and through emissions limits on certain other industrial sources
beginning in 2026. The initial control stringency for power plants is
based on the level of reductions achievable through immediately
available measures, including consistently operating already-installed
emissions controls. Power plant emissions budgets then decline over
time based on the level of reductions achievable through phased
installation of state-of-the-art emissions controls starting in 2024.
The Good Neighbor Plan covers sources in Michigan, Ohio, Indiana, and
Illinois, among other states. The final rule includes additional
features to the trading program for power plants that promote
consistent operation of emissions controls to enhance public health and
environmental protection for the affected downwind regions and will
also benefit local communities, including:
---------------------------------------------------------------------------

    \31\ See https://www.epa.gov/csapr/good-neighbor-plan-2015-ozone-naaqs.
---------------------------------------------------------------------------

     A backstop daily emissions rate in the form of a 3-for-1
allowance surrender for emissions from large coal-fired units that
exceed a protective daily NOX emissions rate. This backstop
would take effect in 2024 for units with existing controls and one year
after installation for units installing new controls, but no later than
2030;
     Annually recalibrating the size of the emissions allowance
bank to maintain strong long-term incentives to reduce NOX
pollution;
     Annually updating emissions budgets starting in 2030 to
account for changes in power generation, including new retirements, new
units, and changing operation. Updating budgets may start as early as
2026 if the updated budget amount is higher than the State emissions
budgets established by the final rule for 2026-2029.
    The commenters' concerns about prior NOX cap and trade
programs are misplaced, and these programs, up through the Revised
CSAPR Update, can be counted on to deliver ozone air quality benefits.
We continue to find it reasonable to rely on emissions reductions from
these programs as one of the measures contributing to the attainment of
this area. The more recent Good Neighbor Plan for the 2015 ozone NAAQS
signed in March 2023 builds on these programs and will deliver
continued assurance that permanent and enforceable emissions reductions
providing air quality benefits to Detroit (among many other areas) will
continue to be realized.

I. Maintenance Plan Contingency Provisions

    Comment: The commenters contend that the contingency measure
triggers in Michigan's maintenance plan are insufficient. The
commenters conclude that the warning level response trigger of a 1-year
4th high daily maximum 8-hour average of 74 parts per billion (ppb) and
the action level response trigger of a 4th high daily maximum 8-hour
average monitoring value averaged over two years of 71 ppb or more are
too lenient, and essentially meaningless given the current margin of
attainment in the area. The commenters note that when considering
current monitoring data, even a single monitoring value of 71 ppb in
2022 would result in a violation of the NAAQS and trigger a
nonattainment designation.
    Response: EPA disagrees with the commenters' contention that the
contingency measure triggers are inadequate. Under the CAA, a violation
of the NAAQS subsequent to redesignation to attainment does not trigger
an automatic redesignation to nonattainment. As demonstrated by the
contingency provisions requirement in section 175A(d), the CAA clearly
anticipates and provides for situations where an area might monitor a
violation

of the NAAQS after having been redesignated to attainment. Section
175A(d) of the CAA states that in the event of a NAAQS violation after
an area is redesignated to attainment a State is required to implement
additional contingency provisions. Under this section of the CAA,
states are not obligated to implement additional emission controls if
an area is ``threatened'' with a future ozone standard violation.
However, EPA does encourage the states to take preventative measures to
prevent future ozone standard violations if at all possible, but does
not definitively require the states to implement the identified
contingency provisions unless a violation of the standard has actually
occurred. See September 4, 1992, memorandum from John Calcagni entitled
``Procedures for Processing Requests to Redesignate Areas to
Attainment'' (Calcagni memorandum) at 12. Michigan's commitment to
respond to triggers of a 1-year 4th high daily maximum 8-hour average
of 74 parts per billion (ppb) and a 4th high daily maximum 8-hour
average monitoring value averaged over two years of 71 ppb or more in
addition to responding to a violation of the 2015 ozone NAAQS goes
beyond the minimum requirements of section 175A(d).
    Comment: The commenters contend that the maintenance plan allows
Michigan too much discretion in selecting and implementing contingency
provisions, stating that the language does not commit Michigan to
implementing any control measures and lacks specificity as to which
measures should be implemented in response to different levels of
increasing ozone pollution. The commenters further argue that the 18-
month timeline allowed from the triggering event to implementation of a
contingency measure is too long, stating that a nonattainment
designation for the area would be finalized by the time a contingency
measure is implemented.
    Response: The commenters overlook the provisions of the CAA
applicable to contingency provisions. Section 175A(d) provides that
``[e]ach plan revision submitted under this section shall contain such
contingency provisions as the Administrator deems necessary to assure
that the State will promptly correct any violation of the standard
which occurs after the redesignation of the area as an attainment
area.'' (emphasis added). Thus, Congress gave EPA discretion to
evaluate and determine the contingency provisions EPA ``deems
necessary'' to assure that the State will promptly correct any
subsequent violation. EPA has long exercised this discretion in its
rulemakings on section 175A contingency provisions in redesignation
maintenance plans, allowing as contingency provisions commitments to
adopt and implement in lieu of fully adopted contingency measures, and
finding that implementation within 18 months of a violation complies
with the requirements of section 175A. See past redesignations, e.g.,
Columbus, OH 2015 ozone standard (84 FR 43508, August 21, 2019),
Shoreline Sheboygan County, WI 2008 ozone standard (85 FR 41405, July
10, 2020), Columbus, OH, 2008 ozone standard (81 FR 93631, December 21,
2016), Cincinnati, OH-IN, 2008 ozone standard (81 FR 91035, December
16, 2016, and 82 FR 16940, April 7, 2017), Cleveland, OH 2008 ozone
standard (82 FR 1603, January 6, 2017), St. Louis, MO-IL 2008 ozone
standard (83 FR 8756, March 1, 2018), Chicago-Gary-Lake County, IL-IN
1997 ozone standard (75 FR 26113, May 11, 2010, and 77 FR 48062, August
13, 2012), Milwaukee-Racine, WI 1997 ozone standard (77 FR 45252, July
31, 2012), and Detroit-Ann Arbor, MI 1997 ozone standard (74 FR 30950,
June 29, 2009).
    Section 175A does not establish any specific deadlines for
implementation of contingency provisions after redesignation to
attainment. It also provides far more latitude than does section
172(c)(9), which applies to a different set of contingency measures
applicable to nonattainment areas. Section 172(c)(9) contingency
measures must ``take effect . . . without further action by the State
or [EPA].'' By contrast, section 175A confers upon EPA the discretion
to determine what constitutes adequate assurance, and thus permits EPA
to take into account the need of a State to assess, adopt and implement
contingency provisions if and when a violation occurs after an area's
redesignation to attainment. Therefore, in accordance with the
discretion accorded it by statute, EPA may allow reasonable time for
states to analyze data and address the causes and appropriate means of
remedying a violation. In assessing what ``promptly'' means in this
context, EPA also may take into account time for adopting and
implementation of the appropriate measure. Cf. Greenbaum v. EPA, 370
F.3d 527, 541 (6th Cir. 2004).
    As discussed in the proposed rule at 87 FR 14218, EPA has
determined that Michigan's maintenance plan comports with the
requirements set forth at section 175A of the CAA. The contingency plan
portion of Michigan's maintenance plan delineates the State's planned
actions in the event of future 2015 ozone standard violations or
increasing ozone levels threatening a subsequent violation of the ozone
standard.
    Michigan has developed a contingency plan with two levels of
triggered actions. A warning level response is triggered if a 4th high
daily maximum 8-hour average ozone concentration of 74 ppb or greater
occurs within the maintenance area. If a warning level response is
triggered, Michigan will conduct a study to determine whether the ozone
value indicates a trend toward higher ozone values and whether
emissions appear to be increasing. The study will evaluate whether the
trend, if any, is likely to continue and, if so, the control measures
necessary to reverse the trend. Michigan commits to implementing
necessary controls within 18 months.
    An action level response is triggered if: (1) a two-year average of
the 4th high daily maximum 8-hour average ozone concentration at a
monitor within the maintenance area is 71 ppb or greater; or (2) if a
violation of the 2015 ozone NAAQS is monitored within the maintenance
area. If an action level is triggered and is not found to be due to an
exceptional event,\32\ malfunction, or noncompliance with a permit
condition or rule requirement,\33\ Michigan will determine what
additional control measures are needed to assure future attainment of
the 2015 ozone NAAQS.
---------------------------------------------------------------------------

    \32\ Should Michigan believe an action level response was
triggered by an exceptional event, Michigan would need to submit an
exceptional event demonstration in accordance with EPA's Exceptional
Events Rule codified at 40 CFR 50.1, 50.14, and 51.930. Should EPA
concur with the demonstration, the event-affected air quality data
would be excluded from the data set used for certain regulatory
decisions. Removal of such data would affect the monitoring values
used to determine whether an action level response was triggered.
Should EPA non-concur on the exceptional event demonstration or
should an action level response still be triggered after removal of
the affected data, Michigan would be required to address the action
level trigger with control measures sufficient to return the area to
attainment of the 2015 NAAQS.
    \33\ Should Michigan find that an action level response is
triggered by malfunction or noncompliance with a permit or rule
requirement, enforcement action or other measures to ensure an
expeditious return to compliance may constitute an appropriate
response to the trigger. Note that depending on the circumstances of
the trigger, the appropriate response may be a combination of
compliance assurance and contingency provision implementation.
---------------------------------------------------------------------------

    Michigan's contingency plan for the Detroit area lists a number of
possible contingency provisions. The list of possible contingency
provisions in Michigan's plan include the following: (1) VOC or
NOX RACT rules for existing sources covered by Control
Technique Guidelines, Alternative Control Guidelines, or other
appropriate

guidance; (2) application of VOC RACT on existing smaller sources; (3)
alternative fuel and diesel retrofit programs for fleet vehicle
operations; (4) VOC or NOX control on new minor sources
(less than 100 tons per year); (5) increased VOC or NOX
emission offsets for new and modified major sources; (6) reduced idling
programs; (7) trip reduction programs; (8) traffic flow and transit
improvements; (9) increased turnover of legacy natural gas distribution
pipelines; (10) stationary engine controls to reduce formaldehyde and
NOX emissions; (11) phase 2 architectural and industrial
maintenance coatings (AIM) rules; (12) phase 5 consumer products rules;
and, (13) additional measures as identified by EGLE. EGLE may also
consider the timing of an action level trigger and determine if
additional, significant new regulations not currently included as part
of the maintenance provisions will be implemented in a timely manner
and will constitute the response.
    Upon triggering an action level response, Michigan may find that
choosing a contingency provision from the list included in the
maintenance plan is not necessary because there are significant new
regulations already adopted that will address the elevated ozone
levels. This does not mean that Michigan would be choosing not to
implement control measures in response to a triggering event. A State
can choose as its contingency provision any adopted but not fully
implemented control measure providing that it is not included in the
calculation of the maintenance inventory. The emissions reductions from
these programs are real, not considered in maintenance plan emissions
projections, and can be achieved more quickly since the State has
already gone through the adoption process. To prohibit a State from
using any control measure adopted prior to the actual triggering of a
maintenance plan contingency provision would only penalize states that
are proactive in addressing anticipated air quality problems.
    Michigan's maintenance plan calls for the appropriate contingency
provisions to be implemented within 18 months of a triggering event. In
order to properly deal with potential future ozone standard violations
and to comply with its own internal rulemaking procedure requirements,
Michigan requires time to evaluate potential controls and provide
public notice and public participation in the rulemaking process when
adopting contingency provisions. The commenters provided no rationale
for why a time period shorter than 18 months to adopt and implement
contingency provisions is warranted. EPA finds that 18 months, as
described in Michigan's maintenance plan, is a reasonable time period
for Michigan to meet its regulatory obligations while meeting the
requirement under section 175A to promptly correct a potential
monitored violation. This timeframe also conforms with EPA's many prior
rulemakings on acceptable schedules for implementing section 175A
contingency provisions as noted above.
    Comment: The commenters argue that the maintenance plan should
address the possibility of a violation of the NAAQS by committing
Michigan to an expedited nonattainment designation process if that
occurs.
    Response: Under the CAA, a violation of the NAAQS subsequent to
redesignation to attainment does not trigger an automatic redesignation
to nonattainment. As demonstrated by the contingency provisions
required by section 175A(d), the CAA clearly anticipates and provides
for situations where an area might monitor a violation of the NAAQS
after having been redesignated to attainment, and leaves it to the
Administrator to determine whether redesignation to nonattainment and a
new nonattainment plan SIP submission is necessary in such cases.
Michigan's maintenance plan also accounts for this possibility by
including a violation of the NAAQS as an action level trigger requiring
the implementation of control measures to reduce ozone precursor
emissions and bring the area back into attainment. Finally, EPA retains
its authority under CAA section 107(d)(3)(A) to initiate a
redesignation ``on the basis of air quality data, planning and control
considerations, or any other air quality-related considerations the
Administrator deems appropriate.'' Given this underlying authority, and
the uncertainty of any cause of a potential future violation, we do not
agree that it is necessary or appropriate to include the suggested
commitment in the State's maintenance plan.

J. Maintenance Plan Modeling Platform

    Comment: The commenters argue that because EGLE's 2019 emissions
inventory shows emissions lower than in EPA's Emissions Inventory
System, the 2016v2 model that EGLE used may be underpredicting
emissions, which would impact the future emissions projections.
    Response: The commenters misunderstand how 2016v2 emissions data
are being used in the context of this redesignation. Air emissions
modeling platform development is the process of preparing emission
inventories for use in air quality models. Air quality models typically
require hourly, gridded emissions of specific pollutants. An emissions
modeling platform (hereafter referred to as emissions platform or
platform) is the full set of emissions inventories, other data files,
software tools, and scripts that process the emissions into the form
needed for air quality modeling. Each platform relies on a version of
the NEI for most of its data, although some adjustments are made to
support air quality modeling. The 2016v2 platform incorporates
emissions based on: MOVES3, the 2017 NEI nonpoint inventory (both
anthropogenic and biogenic), the Western Regional Air Partnership oil
and gas inventory, and updated inventories for Canada and Mexico. The
2016v2 platform includes emissions for the years 2016, 2023, 2026, and
2032. Methodologies are documented in the technical support document
for the 2016v2 platform. The commenters have articulated no specific
problems with any of the 2016v2 platform emission inventories or with
the methodologies used to develop them.
    EPA policy, as set forth in the Calcagni memorandum, and
longstanding practice allows states to demonstrate maintenance by
preparing an attainment emissions inventory corresponding to the period
during which the area monitored attainment and to demonstrate
maintenance by showing that future emissions are projected to remain
below this level for ten years following redesignation.
    Following this policy, Michigan selected a 2019 emission inventory
to represent attainment level VOC and NOX emissions, which
is appropriate because it is one of the years in the period used to
demonstrate monitored attainment of the NAAQS. In developing the 2019
attainment inventory for the Detroit area, Michigan interpolated
between the 2016 and 2023 2016v2 platform inventories for point,
nonpoint and nonroad inventories. For on-road emissions estimates,
SEMCOG used EPA's MOVES3 model to generate emissions with local travel
inputs including vehicle population, VMT, speeds, road types, Vehicle
Hours of Travel, and vehicle age, as well as meteorological data. To
demonstrate maintenance through 2035, Michigan developed emission
inventories for 2035 and an interim year of 2025. To estimate point,
nonpoint and nonroad emissions, Michigan used 2016v2 platform
inventories. Specifically, for the 2025 interim year, Michigan
interpolated between 2023 and 2026 2016v2 platform inventories. For the
maintenance year, Michigan extrapolated to 2035 using the

2026 and 2032 2016v2 platform inventories. For on-road emissions in
2025 and 2035 SEMCOG used EPA's MOVES3 model to generate emissions with
local travel inputs as described above. When comparing emissions
between attainment year 2019 and maintenance year 2035, VOC and
NOX emissions decrease by 34.88 TPSD and 99.55 TPSD,
respectively. Michigan's maintenance demonstration clearly follows the
process set forth in the Calcagni memorandum, showing that future
emissions are projected to decrease and remain below the level of the
attainment inventory. Again, the commenters articulated no specific
problems with Michigan's maintenance plan inventories or methodologies
and suggested nothing specific that should have been done to improve
those inventories.
    In questioning the validity of these inventories for demonstrating
maintenance, the commenters pointed to EPA's review of point source
emissions data submitted through EIS. The commenters mistakenly
inferred that EPA found all the inventories Michigan submitted based on
the 2016v2 platform to underestimate emissions in comparison to EIS
data. This is not the case. In reviewing Michigan's submission, EPA
only compared the interpolated point source inventories for 2019
submitted by EGLE against point source emissions information available
to EPA through EIS. EPA converted annual emission totals to a value of
tons per ozone season day using the same conversion factors calculated
by EGLE. Michigan's interpolated inventory estimates 2019
NOX and VOC point source emissions to be 97.01 tons per
ozone season day and 13.74 tons per ozone season day, respectively.
Using EIS reported point source data and conversion factors, EPA
estimated 2019 NOX and VOC point source emissions to be
102.27 tons per ozone season day and 29.42 tons per ozone season day,
respectively. While EIS-based 2019 point source estimates differed from
estimates based upon interpolation between 2016v2 platform years,
Michigan's maintenance demonstration remains valid. Regardless of
whether EGLE had chosen to use point source emissions from EIS or from
the 2016v2 platform in compiling its inventory for the 2019 attainment
year, projected emissions for 2025 and future years would be well below
the attainment inventory, as is demonstrated in Tables 4 and 5.
Further, beyond making the statement that ``the 2016v2 model may be
underpredicting emissions,'' the commenters offer no substantive
evidence to support this conclusion.

   Table 4--Detroit NOX Emissions for 2019 Attainment Year (With EIS and 2016v2 Point Source Emissions), 2025
                                     Interim Year, and 2035 Maintenance Year
                                           [Tons per ozone season day]
----------------------------------------------------------------------------------------------------------------
                                                2019                                    Net change (2019-2035)
                                    ---------------------------                      ---------------------------
              Category                              2016v2         2025       2035                    2016v2
                                     EIS point   interpolated                          EIS point   interpolated
                                       source    point source                           source     point source
----------------------------------------------------------------------------------------------------------------
Point..............................     102.27           97.01       80.8      76.44      -25.83          -20.57
Nonpoint...........................      27.98           27.98      27.39      25.84       -2.14           -2.14
On-road............................     105.80          105.80      61.20      40.30      -65.50          -65.50
Nonroad............................      22.51           22.51      17.49      15.17       -7.34           -7.34
                                    ----------------------------------------------------------------------------
    Total..........................     258.56          253.30     186.91     157.75     -100.81          -95.55
----------------------------------------------------------------------------------------------------------------

   Table 5--Detroit VOC Emissions for 2019 Attainment Year (With EIS and 2016v2 Point Source Emissions), 2025
                                     Interim Year, and 2035 Maintenance Year
                                           [Tons per ozone season day]
----------------------------------------------------------------------------------------------------------------
                                                2019                                    Net change (2019-2035)
                                    ---------------------------                      ---------------------------
              Category                              2016v2         2025       2035                    2016v2
                                     EIS point   interpolated                          EIS point   interpolated
                                       source    point source                           source     point source
----------------------------------------------------------------------------------------------------------------
Point..............................      29.42           13.74       14.1      14.12      -15.30            0.38
Nonpoint...........................     134.77          134.77     134.12     133.11       -1.66           -1.66
On-road............................      51.70           51.70      34.40      22.00      -29.70          -29.70
Nonroad............................      30.46           30.46      27.39      26.56       -3.90           -3.90
                                    ----------------------------------------------------------------------------
    Total..........................     246.35          230.67     209.97     195.79      -50.56          -34.88
----------------------------------------------------------------------------------------------------------------

    Michigan's maintenance plan projected that in 2035, the area would
see an overall reduction in NOX and VOC emissions of 95.55
and 34.88 TPSD, relative to the 2019 attainment inventory. More than
half of these reductions are attributable to the on-road sector with
projected decreases of 65.50 and 29.70 TPSD in NOX and VOC,
respectively. The on-road sector was not interpolated or extrapolated.
It was run using EPA's MOVES3 model and area specific data, which was
not called into question by the commenters. The difference between
interpolating point source emissions for 2019 rather than using
emissions reported through EIS does not change the fact that projected
emissions for future years 2025 and 2035 are below the level of the
attainment inventory.
    Comment: The commenters contend that the 2016v2 emissions platform-
based air quality model predictions of ozone concentration decreases
through 2023 appear overly optimistic, as the majority of the
reductions would need to occur in the next two years. The commenters
contend that unrealistic

predictions by the air quality model render suspect Michigan's reliance
on the 2016v2 emissions platform for its attainment projections and
that EPA should explain how it can assure the improvements in air
quality predicted by the air quality model.
    Response: To clarify, Michigan and EPA are not relying on the air
quality modeling's predictions (i.e., the projected future design
values) to meet the CAA's requirement that the maintenance plan provide
for maintenance of the NAAQS for ten years following redesignation.
Michigan only used the emissions inventories generated for the 2016v2
platform and is not relying on the results of the air quality model
(i.e., the modeled future design values that are estimated using the
air quality modeling performed using that emissions platform). We do
not agree that EPA has an obligation to assure the air quality model's
predicted design values come to pass.
    A maintenance demonstration need not be based on modeling. See Wall
v. EPA, 265 F.3d 426 (6th Cir. 2001), Sierra Club v. EPA, 375 F. 3d 537
(7th Cir. 2004). See also 66 FR 53094, 53099-53100 (October 19, 2001),
and 68 FR 25413, 25430-25432 (May 12, 2003). EPA policy and
longstanding practice allows states to demonstrate maintenance by
preparing an attainment emissions inventory corresponding to the period
during which the area monitored attainment and to project maintenance
by showing that future emissions are projected to remain below this
level for the next ten years. See Calcagni memorandum. Holding
emissions at or below the level of attainment is adequate to reasonably
assure continued maintenance of the standard. See 65 FR 37879, 37888
(June 19, 2000).
    Comment: The commenters also express concern that some of the
regulatory actions assumed in the 2016v2 emissions platform may not be
implemented in the event of a change in Administration, causing
emissions to rise.
    Response: As noted above, EPA's longstanding practice is to permit
states to ``provide for the maintenance of the NAAQS'' as required by
CAA 175A by comparing current attainment emission inventories with
projected future inventories. Inherent in the act of projection is some
uncertainty; in order to accurately project future year inventories,
the Agency must make assumptions that cannot be made enforceable, such
as expectations about population growth and energy demand. We would
also note that, as commenters point out, even adopted, enforceable
measures can be revised. For the 2016v2 emissions platform, future year
emissions were projected from the 2016 base case either by running
models to estimate future year emissions from specific types of sources
or by adjusting the base year emissions according to the best estimate
of changes expected to occur in the intervening years. Rules and
specific legal obligations that go into effect in the intervening
years, along with anticipated changes in activity of the sector (e.g.,
source retirements) were incorporated when possible. Documentation of
the specific methodologies used to develop future year emissions for
the 2016 emissions platform can be found in the technical support
document for the 2016v2 platform. EPA contends that the methods used to
develop the 2016v2 emissions platform were appropriate and it was
reasonable for Michigan to use those emissions in developing
inventories for the Detroit maintenance plan.

K. Approval of Infrastructure SIP

    Comment: The commenters state that EPA must find that the State
``has met all requirements applicable to the area for the purposes of
redesignation under section 110 and part D'' of the CAA, which the
commenters allege includes having an approved infrastructure SIP
pursuant to CAA section 110(a)(2). The commenters allege that EPA's
approval of Michigan's infrastructure SIP for the 2015 ozone NAAQS was
entered in error, due to an oversight in failing to review and respond
to comments from Sierra Club. The commenters allege that ``unless and
until EPA reissues an approval that properly considers and responds to
this comment, EPA should not consider Michigan to have an approved
ozone infrastructure SIP for the purposes of redesignation.''
    Response: As we noted in our March 14, 2022, proposed rulemaking,
SIP requirements that are not linked with the area's ozone designation
and classification are not ``applicable'' measures to evaluate when
reviewing a redesignation request for the area under CAA section
107(d)(3)(E)(ii) and (v). We noted that section 110(a)(2)(D)
requirements, like many section 110(a)(2) requirements, continue to
apply to a State regardless of the designation of any one particular
area within the State, and thus are not applicable requirements for
purposes of redesignation. See 65 FR 37890 (June 15, 2000), 66 FR 50399
(October 19, 2001), 68 FR 25418, 25426-27 (May 13, 2003). In addition,
EPA believes that other section 110 elements that are not connected to
an area's ozone nonattainment designation 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 2015 ozone NAAQS. This approach is consistent with
EPA's interpretation of the applicability of conformity requirements
for purposes of CAA section 107(d)(3)(E)(ii) and (v), as well as with
section 184 ozone transport requirements. See Reading, Pennsylvania
proposed and final rulemakings (61 FR 53174-53176, October 10, 1996 and
62 FR 24826, May 7, 1997), Cleveland-Akron-Loraine, Ohio final
rulemaking (61 FR 20458, May 7, 1996), and Tampa, Florida final
rulemaking (60 FR 62748, December 7, 1995). See also the discussion of
this issue in the Cincinnati, Ohio ozone redesignation (65 FR 37890,
June 19, 2000), and the Pittsburgh, Pennsylvania ozone redesignation
(66 FR 50399, October 19, 2001).
    In any case, on May 19, 2022 (87 FR 30420), EPA published a final
rulemaking which corrected the omission of timely comment and response
in our September 28, 2021, rulemaking approving most elements and
disapproving the visibility protection requirements of CAA section
110(a)(2)(D)(i)(II) prong 4.\34\ EPA has reissued the approval in
question after responding to comments on the proposal, addressing
concerns with Michigan's satisfaction of CAA section 110(a)(2)(E)(i)
with respect to adequate resources.
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    \34\ Michigan has a partially approved Regional Haze Plan and is
subject to FIPs for St. Marys Cement, Escanaba Paper Company, and
Tilden Mining, a taconite processing facility. See 81 FR 21671
(April 12, 2016) and 83 FR 25375 (July 2, 2018) for more information
on the FIPs that apply to this area.
---------------------------------------------------------------------------

L. Enforcement Authority

    Comment: The commenters dispute the commitment in Michigan's SIP
stating that the State ``has the authority to implement the requested
SIP revision . . . includ[ing] the authority to adopt, implement, and
enforce any subsequent emission control measures determined to be
necessary to correct future ozone attainment problems.'' The commenters
assert that the State does not have the authority to enforce emission
control measures that may be needed to correct future ozone problems.
The commenters rely on a decision from the Michigan Court of Claims
which invalidated a State administrative rule, Michigan Administrative
Code (MAC) 336.1430 (`Rule 430'), on the basis that the rule failed the
State Administrative Procedures Act ``general applicability''

requirement because of its focus on one particular facility. The
commenters assert that EPA has failed to address the court's holding or
explain why the Agency believes Michigan will have sufficient authority
to impose enforceable emissions limitations as may be necessary when a
particular polluter refuses to limit pollution as needed to bring an
area into attainment with the NAAQS in the event of future violations
of the NAAQS that trigger contingency provisions. The commenters urge
EPA to reexamine whether Michigan has adequate authority to implement
its maintenance plan in light of U.S. Steel Corp. and to disapprove the
plan if the Agency concludes that Michigan does not.
    Response: We do not agree that the U.S. Steel Corp. decision
indicates that Michigan does not have authority to implement and
enforce its maintenance plan. The State listed the following
contingency provisions in its maintenance plan for the Detroit area:
(1) VOC or NOX RACT rules for existing sources covered by
Control Technique Guidelines, Alternative Control Guidelines, or other
appropriate guidance; (2) application of VOC RACT on existing smaller
sources; (3) alternative fuel and diesel retrofit programs for fleet
vehicle operations; (4) VOC or NOX control on new minor
sources (less than 100 tons per year); (5) increased VOC or
NOX emission offsets for new and modified major sources; (6)
reduced idling programs; (7) trip reduction programs; (8) traffic flow
and transit improvements; (9) increased turnover of legacy natural gas
distribution pipelines; (10) stationary engine controls to reduce
formaldehyde and NOX emissions; (11) phase 2 architectural
and industrial maintenance coatings (AIM) rules; (12) phase 5 consumer
products rules; and, (13) additional measures as identified by EGLE.
Given the nature of these provisions, we think it unlikely that these
measures are designed to apply only to a single source, like the State
rule at issue in the U.S. Steel Corp. decision, which the court found
clearly applied to only one entity and could conceivably apply to only
one entity. To the extent that the commenters are asserting that EPA
should disapprove the State's maintenance plan because the State may
need to target emissions from one particular source in the event of a
future violation, and the 2017 Court of Claims decision calls into
question whether the State could do so, we anticipate that the State
will adopt future measures consistent with the applicable procedural
State law requirements at issue in U.S. Steel Corp. The State has
provided in its maintenance plan for twelve contingency provisions that
on their face appear to be generally applicable, and it would be
unreasonable to disapprove the SIP submission based on a measure the
State has not adopted, nor suggested it would adopt, on the speculation
that such a measure might be necessary.
    Moreover, we note that in our May 19, 2022, final rulemaking
correcting the omission in the September 28, 2021, rulemaking, EPA
published a substantive response to Sierra Club's comment regarding
Michigan's authority to enforce control measures. 87 FR 30420. As we
noted then, EPA disagrees with the commenters' concern that the
Michigan Court of Claims decision in United States Steel Corp. v. Dept.
of Environmental Quality, indicates that Michigan lacks legal authority
to regulate sources. EPA concluded that the court only decided that the
State had improperly sought to impose emissions controls on the sources
at issue through a rule that did not meet State law requirements for a
``rule of general applicability'' in violation of relevant State
administrative procedures act requirements. EPA interprets the ruling
to indicate that the State does have authority under Michigan law to
impose necessary emission limitations on sources, as required to meet
CAA requirements, via other legal mechanisms. In our May 19, 2022,
final rulemaking, EPA identified several authorities by which Michigan
may enforce its SIP.

M. Prevention of Significant Deterioration (PSD) Program

    Comment: The commenters argue that EGLE did not properly implement
the preconstruction monitoring requirement for several sources subject
to PSD New Source Review (NSR), and thus the commenters contend that
CAA section 107(d)(3)(E)(v), which requires that EPA determine the
State has met all applicable SIP requirements described in CAA section
110, is not satisfied. The commenters assert that CAA section 110
includes a requirement to include provisions for the proper
implementation of programs including PSD NSR. The commenters
acknowledge that Michigan has adopted provisions meeting CAA
requirements regarding preconstruction monitoring requirements into its
SIP, but the commenters allege that the State has failed to properly
implement those requirements. Specifically, the commenters State that
Michigan has failed to collect air quality data as required from
sources with net emissions increases of 100 tpy or more of VOCs or
NOX. The commenters also call into question the validity of
the significant monitoring concentrations for ozone established in 40
CFR part 51 and 40 CFR part 52 based on a D.C. Circuit decision
regarding Significant Monitoring Concentrations (SMCs) for particulate
matter, and they state that the ozone SMCs are unlawful and must be
vacated.
    Response: CAA section 107(d)(3)(E)(v) states that EPA may not
promulgate a redesignation of a nonattainment area to attainment unless
``the State containing such area has met all requirements applicable to
the area under section 7410 [i.e., section 110] of this title and Part
D of this subchapter.'' Section 110, as it pertains to obligations for
states, sets forth the required contents of the revisions to a State's
implementation plan that must be adopted and submitted to EPA after the
promulgation of a NAAQS. EPA therefore understands its role in
determining whether CAA section 107(d)(3)(E)(v) is satisfied to be an
inquiry into whether a State has adopted and submitted to EPA all those
revisions to its SIP that are required by section 110 and part D. In
this case, Michigan has met its obligations to submit those
requirements applicable to it for purposes of redesignation.
    As we noted in the March 14, 2022, proposed rulemaking, EPA fully
approved Michigan's PSD program on March 25, 2010 (75 FR 14352), and
most recently approved revisions to Michigan's PSD program on May 12,
2021 (86 FR 25954). The SIP-approved PSD program prohibits air quality
from deteriorating beyond the concentration allowed by the applicable
NAAQS. See MAC R 336.2811.
    We do not agree with the commenter that a State's implementation of
its SIP is equivalent to whether the State has met the requirements of
CAA section 110 and part D, which concern whether a State has made
required revisions to its SIP. Any issues with respect to the State's
application of the approved SIP are beyond the scope of this action and
should be raised on a permit specific basis.
    Similarly, comments regarding the lawfulness of EPA's PSD
regulations pertaining to ozone at 40 CFR 51.166(i)(5)(i)(f) or 40 CFR
52.21(i)(5)(i)(f) are outside the scope of this action.

N. Supplemental Comments

    Comment: In their March 14, 2023, supplemental comment, commenters
contend that EPA cannot redesignate the

Detroit area until EPA has approved RACT and reasonably available
control measures (RACM) for the area. Commenters note that under
section 107(d)(3)(E), EPA cannot redesignate an area unless (among
other things) ``the State containing such area has met all requirements
applicable to the area under section [110] and part D of [title I of
the Act].'' Effective March 1, 2023, EPA reclassified the Detroit ozone
nonattainment area as Moderate. This triggered a requirement under
sections 182(b)(2) and 182(f) of the CAA for Michigan to implement RACT
for sources of VOCs and NOX. The commenters, citing Sierra
Club v. U.S. EPA, 793 F.3d 656 (6th Cir. 2015), contend that section
172(c)(1) of the CAA requires Michigan to implement RACM, regardless of
whether the area is attaining the NAAQS.
    The Commenters further contest EPA's position that, for purposes of
redesignation ``all requirements applicable to the area'' are those
that were due prior to the State's submittal of a complete
redesignation request. The commenters cite the decision in Sierra Club