[Federal Register Volume 91, Number 1 (Friday, January 2, 2026)]
[Proposed Rules]
[Pages 98-104]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-24200]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 52 and Part 81
[EPA-R03-OAR-2025-1872; FRL-12994-01-R3]
Proposed Revisions of the Nonattainment Designation for the 2008
and 2015 Ozone Standards and Clean Data Determinations for the 2008 and
2015 Ozone Standards: Cecil County, MD and New Castle County, DE
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
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SUMMARY: The Environmental Protection Agency (EPA) is proposing to
approve two separate requests from Maryland and Delaware to revise the
designation for the Philadelphia-Wilmington-Atlantic City, PA-NJ-MD-DE
nonattainment area (hereafter referred to as the Philadelphia
nonattainment area) for the 2008 primary and secondary ozone national
ambient air quality standards (NAAQS) and the 2015 primary and
secondary ozone NAAQS. Due to the concurrent requests from Maryland and
Delaware, the EPA is proposing to revise the existing Philadelphia
nonattainment area boundary into three distinct nonattainment areas
that together cover the identical geographic area of the existing area.
The EPA is also proposing to issue clean data determinations (CDDs) for
the revised Maryland and Delaware nonattainment areas for both the 2008
and 2015 ozone NAAQS. The EPA is taking this action pursuant to Clean
Air Act (CAA) sections 107, 110, 172, and 182.
DATES: Written comments must be received on or before February 2, 2026.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R03-
OAR-2025-1872 at www.regulations.gov, or via email to
[email protected]. For comments submitted at Regulations.gov, follow
the online instructions for submitting comments. Once submitted,
comments cannot be edited or removed from Regulations.gov. For either
manner of submission, the EPA may publish any comment received to its
public docket. Do not submit electronically any information you
consider to be confidential business information (CBI) or other
information whose disclosure is restricted by statute. Multimedia
submissions (audio, video, etc.) must be accompanied by a written
comment. The written comment is considered the official comment and
should include discussion of all points you wish to make. The EPA will
generally not consider comments or comment contents located outside of
the primary submission (i.e., on the web, cloud, or other file sharing
system). For additional submission methods, please contact the person
identified in the FOR FURTHER INFORMATION CONTACT section. For the full
EPA public comment policy, information about CBI or multimedia
submissions, and general guidance on making effective comments, please
visit www.epa.gov/dockets/commenting-epa-dockets.
FOR FURTHER INFORMATION CONTACT: Sarah McCabe, Planning &
Implementation Branch (3AD30), Air & Radiation Division, U.S.
Environmental Protection Agency, Region III, 1600 John F. Kennedy
Boulevard, Philadelphia, Pennsylvania 19103. The telephone number is
(215) 814-5786. Ms. McCabe can also be reached via electronic mail at
[email protected].
SUPPLEMENTARY INFORMATION: On February 13, 2025, Maryland submitted a
request to revise the Philadelphia nonattainment area into two separate
nonattainment areas, covering the identical geographic area of the
existing Philadelphia nonattainment area, and creating a smaller stand-
alone nonattainment area for Cecil County, MD and a larger
nonattainment area consisting of the remainder of the counties in the
existing Philadelphia nonattainment area. On August 15, 2025, Delaware
also submitted a request to revise the boundaries for the existing
Philadelphia nonattainment area and create a stand-alone nonattainment
area for New Castle County, DE. However, considering both requests, the
EPA is proposing to act on these separate requests in the same notice
to streamline the changes to the Philadelphia nonattainment area
boundaries. Thus, the EPA is proposing to split the identical
geographic area of the existing Philadelphia nonattainment area into
three nonattainment areas: the Cecil County, MD nonattainment area, the
New Castle County, DE nonattainment area, and the revised Philadelphia-
Atlantic City, PA-NJ nonattainment area. These proposed revised
designations are supported by an analysis of air quality data,
emissions and emissions-related data, meteorology, geography/
topography, and jurisdictional boundaries. If finalized, all areas
would retain their current designation statuses and classifications for
each respective ozone NAAQS. Additionally, if the revised designations
and CDDs are finalized, the proposed CDDs would suspend the obligations
of Maryland and Delaware to submit certain attainment planning
requirements for their respective nonattainment areas for as long as
each area continues to attain the 2008 and 2015 ozone NAAQS.
Nonetheless, the EPA views each state's request as separable
redesignation requests and may take separate final action on each
request and adjust the area boundaries accordingly.
I. Background
Under section 109 of the CAA, the EPA has established primary and
secondary NAAQS for certain air pollutants (referred to as ``criteria
pollutants'') and conducts periodic reviews of the NAAQS to determine
whether they should be revised or whether new NAAQS should be
established. The primary NAAQS represent ambient air quality standards
which the EPA has determined are necessary to protect the public health
with an adequate margin of safety. The
[[Page 99]]
secondary NAAQS represent ambient air quality standards which the EPA
has determined are requisite to protect the public welfare from any
known or anticipated adverse effects associated with the presence of
such air pollutant in the ambient air.
Ground-level ozone is one such NAAQS. Ozone forms from complex
chemical reactions in ambient air between nitrogen oxides
(NOX) and volatile organic compounds (VOCs). Cars, trucks,
buses, engines, industries, power plants and products such as solvents
and paints are among the major manmade sources of ozone-forming
emissions. Exposure to ozone can harm the respiratory system, aggravate
asthma and other lung diseases, and is linked to premature death from
respiratory causes.
Following promulgation of a new or revised NAAQS, the EPA is
required by section 107(d)(1) of the CAA to designate areas throughout
the United States as attainment, nonattainment, or unclassifiable for
the NAAQS.
On March 27, 2008 (73 FR 16436), the EPA revised the 8-hour ozone
NAAQS by lowering the level of the primary and secondary standards from
0.08 parts per million (ppm) to 0.075 ppm (75 parts per billion (ppb))
(40 CFR 50.15). The standards are based on the annual 4th highest daily
maximum 8-hour average ozone concentration, averaged over three
consecutive years.\1\ This average is referred to as the design value
for each 3-year period.\2\ Only ozone measurement data collected in
accordance with the quality assurance (QA) requirements using approved
Federal Reference Method (FRM) or Federal Equivalent Method (FEM)
monitors are used for NAAQS compliance determinations.\3\ The EPA uses
FRM/FEM measurement data residing in the EPA's Air Quality System (AQS)
database to calculate the ozone design values. On May 21, 2012 (77 FR
30088), the EPA designated the Philadelphia nonattainment area as
nonattainment for the 2008 ozone NAAQS, based on air quality data from
the 2008-2010 monitoring period that showed a design value of 83
ppb.\4\ Cecil County, MD and New Castle County, DE were included in the
Philadelphia nonattainment area based on air quality data from the
2008-2010 monitoring period that showed design values of 80 ppb and 76
ppb for each county, respectively.
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\1\ See 40 CFR 50.15(b) and 50.19(b).
\2\ The specific methodology for calculating the ozone design
values, including computational formulas and data completeness
requirements, is described in 40 CFR part 50, appendix U.
\3\ The QA requirements for ozone monitoring data are specified
in 40 CFR part 58, appendix A. The performance test requirements for
candidate FEMs are provided in 40 CFR part 53, subpart B.
\4\ The Philadelphia nonattainment area consists of the
following counties: New Castle County in Delaware; Cecil County in
Maryland; Atlantic County, Burlington County, Camden County, Cape
May County, Cumberland County, Gloucester County, Mercer County,
Ocean County, and Salem County in New Jersey; and Bucks County,
Chester County, Delaware County, Montgomery County, and Philadelphia
County in Pennsylvania. See 40 CFR 81.308, 81.321, 81.331, and
81.339.
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At the time of designation, the Philadelphia nonattainment area was
initially classified as Marginal with an attainment date of July 20,
2015, for the 2008 ozone NAAQS. On May 4, 2016, the EPA determined that
the area qualified for a one-year attainment date extension to July 20,
2016 (81 FR 26697).
On November 2, 2017, the EPA determined that the Philadelphia
nonattainment area had attained the standard by its extended attainment
date of July 20, 2016, effective December 4, 2017 (82 FR 50814). This
determination was based on complete, certified, and quality assured
ambient air quality monitoring data for the Philadelphia nonattainment
area for the 2013-2015 monitoring period. The determination of
attainment of the 2008 ozone NAAQS is not equivalent to a redesignation
to attainment or a CDD; the states in the Philadelphia nonattainment
area must still meet the statutory requirements for redesignation in
order to be redesignated to attainment.
On October 26, 2015, the EPA further revised the 8-hour ozone NAAQS
by lowering the level of the primary and secondary standards from 75
ppb to 70 ppb (40 CFR 50.19). Effective August 3, 2018, the EPA
designated 52 areas throughout the country as nonattainment for the
2015 ozone NAAQS, including the Philadelphia nonattainment area, which
was initially classified as a Marginal nonattainment area based on
certified air quality monitoring data from calendar years 2014 to 2016
(83 FR 25776, June 4, 2018). The design value for the Philadelphia
nonattainment area for the 2014-2016 monitoring period was 77 ppb.
Cecil County, MD and New Castle County, DE were included in the
Philadelphia nonattainment area based on air quality data from the
2014-2016 monitoring period that showed design values of 74 ppb for
each county. As established by the EPA's March 2018 ``Classifications
Rule'', the attainment date for Marginal nonattainment areas as three
years from the effective date of the final designations.\5\ Thus, the
attainment date for the Philadelphia nonattainment area for the 2015
ozone NAAQS was August 3, 2021.
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\5\ See 40 CFR 51.1303(a) and 83 FR 10376 (March 9, 2018).
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Effective November 7, 2022, the EPA determined that the
Philadelphia nonattainment area failed to attain by the Marginal area
attainment date and the area was reclassified by operation of law to
Moderate.\6\ This finding was based on certified air quality monitoring
data from calendar years 2018 to 2020. The design value for the
Philadelphia nonattainment area for the 2018-2020 monitoring period was
74 ppb. For that same period, the design value for Cecil County, MD was
68 ppb, and the design value for New Castle County, DE was 65 ppb. As
established by the March 2018 ``Classifications Rule'', the Moderate
area attainment date for the 2015 ozone NAAQS was August 3, 2024, six
years from the effective date of designation.
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\6\ 87 FR 60897 (October 7, 2022).
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On July 30, 2024 (89 FR 61025), the EPA granted a request from the
Commonwealth of Pennsylvania (Pennsylvania) and the States of New
Jersey, Maryland, and Delaware to voluntarily reclassify the
Philadelphia nonattainment area from Moderate to Serious for the 2015
ozone NAAQS under CAA section 181(b)(3). The attainment date for 2015
ozone NAAQS Serious areas is August 3, 2027, nine years from the
effective date of designation.\7\ Accordingly, each state in the
Philadelphia nonattainment area must provide a Serious nonattainment
plan to the EPA by January 1, 2026, demonstrating how the area will
come into attainment with the standard by the attainment date.\8\
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\7\ March 2018 Classifications Rule (n 5).
\8\ See 40 CFR 51.1402(b)(1), 40 CFR 51.1400, and 90 FR 5651
(January 17, 2025).
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II. Summary of Maryland's Redesignation Request and EPA Analysis
On February 13, 2025, Governor Wes Moore and the Maryland
Department of the Environment (MDE) submitted a request and
accompanying five-factor analysis for the EPA to revise the boundary of
the Philadelphia nonattainment area for the 2008 ozone NAAQS and 2015
ozone NAAQS.\9\ Maryland requested, under CAA section 107(d)(3)(D), to
revise the boundary for the existing Philadelphia nonattainment area by
splitting it into two distinct nonattainment areas for the 2008 ozone
NAAQS and 2015 ozone NAAQS: a
[[Page 100]]
Southern Philadelphia nonattainment area encompassing all of Cecil
County, MD and a Central Philadelphia nonattainment area encompassing
the existing nonattainment area counties in Delaware, New Jersey, and
Pennsylvania. As discussed in section IV of this proposal, due to
Delaware's similar concurrent proposal, the EPA is proposing to revise
the Philadelphia nonattainment area into three distinct nonattainment
areas.
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\9\ Maryland's submittal can be found in the docket of this
rulemaking using Docket ID No. EPA-R03-OAR-2025-1872.
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There are 20 FRM/FEM ozone monitors throughout the existing
Philadelphia nonattainment area. The data from these monitors
demonstrate a decrease in ozone levels in the Philadelphia
nonattainment area from 2014 to 2024. The design values from the Fair
Hill monitor in Cecil County, MD have remained below the 2015 NAAQS
since the 2018-2020 monitoring period.\10\
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\10\ See Table 1 of the EPA's Technical Support Document (TSD)
at page 9.
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The EPA is using the technical information contained in Maryland's
February 13, 2025 submittal and the most recent complete, quality-
assured, and certified air quality data for the 2022-2024 monitoring
period to support the record for this proposed rulemaking.
III. Summary of Delaware's Redesignation Request and EPA Analysis
On August 15, 2025, Governor Matt Meyer and the Delaware Department
of Natural Resources and Environmental Control (DNREC) submitted a
request and accompanying five-factor analysis for the EPA to revise the
boundary of the Philadelphia nonattainment area for the 2008 ozone
NAAQS and 2015 ozone NAAQS.\11\ Delaware requested, under CAA section
107(d)(3)(D), to revise the boundary for the existing Philadelphia
nonattainment area for the 2008 ozone NAAQS and the 2015 ozone NAAQS to
create a stand-alone nonattainment area for New Castle County,
Delaware.
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\11\ Delaware's submittal can be found in the docket of this
rulemaking using Docket ID No. EPA-R03-OAR-2025-1872.
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There are 20 ozone monitors throughout the existing Philadelphia
nonattainment area. The data from these monitors demonstrate a decrease
in ozone levels in the Philadelphia nonattainment area from 2014 to
2024. The design values from the four monitors in New Castle County, DE
have remained below the 2015 NAAQS since the 2017-2019 monitoring
period.\12\
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\12\ See Table 7 of EPA's TSD at page 19 for this rulemaking.
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The EPA is using the technical information contained in Delaware's
August 15, 2025 submittal, the EPA's supplemental analyses, and the
most recent complete, quality-assured, and certified air quality data
for the 2022-2024 monitoring period to support the record for this
proposed rulemaking.
IV. Proposed Actions
In this rulemaking, the EPA is proposing to take six actions. In
two separate actions, under the authority of CAA section 107(d)(3)(D),
the EPA is proposing to approve Maryland and Delaware's separate
requested revisions to the Philadelphia nonattainment area. To take
both requests into consideration, the EPA is proposing to revise the
original Philadelphia-Wilmington-Atlantic City, PA-NJ-MD-DE
nonattainment area for the 2008 ozone NAAQS and 2015 ozone NAAQS into
three separate nonattainment areas that together cover the identical
geographic area of the original nonattainment area. Second, pursuant to
regulations at 40 CFR 51.1118 and 51.1318, the EPA is proposing to
issue four CDDs for the proposed Cecil County, MD nonattainment area
and proposed New Castle County, DE nonattainment area for the 2008 and
2015 ozone NAAQS.
Maryland's redesignation request is separable from Delaware's
redesignation request. Each redesignation request is also separable
from its associated CDDs, such that the EPA may take final action on
the redesignation request separate from the associated CDDs, so long as
action on the redesignation request precedes that area's CDDs. A CDD
for the 2015 ozone NAAQS is separable from a CDD for the 2008 ozone
NAAQS. The proposed Cecil County, MD nonattainment area CDDs are also
separable from the proposed New Castle County, DE nonattainment area
CDDs. Thus, final action on the CDDs for the Cecil County, MD
nonattainment area will not impact final action on the CDDs for the New
Castle County, DE nonattainment area. The proposed revisions to the
Philadelphia nonattainment area boundary for the 2008 and 2015 ozone
NAAQS does not affect the boundary of the Philadelphia-Wilmington, PA-
NJ-DE maintenance area for the 2006 24-hour fine particulate matter
NAAQS.
A. Revisions to the Philadelphia Nonattainment Area Boundary
In determining whether to approve or deny a state's request for a
revision to the designation of an area under CAA section 107(d)(3)(D),
the EPA considers the same factors when the EPA initiates a revision to
a designation of an area on its own motion under CAA section
107(d)(3)(A). These, CAA section 107(d)(3)(A), factors include ``air
quality data, planning and control considerations, or any other air
quality-related considerations the Administrator deems appropriate.''
Using CAA section 107(d)(3)(A) as a framework, the EPA considers 5
factors when issuing initial area designations and when evaluating
requests under CAA section 107(d)(3)(D): air quality data, emissions
and emissions-related data, meteorology, geography/topography, and
jurisdictional boundaries.\13\
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\13\ The March 28, 2000, memorandum entitled ``Boundary Guidance
on Air Quality Designations for the 8-Hour Ozone National Ambient
Air Quality Standards,'' the December 4, 2008, memorandum entitled
``Area Designations for the 2008 Revised Ozone National Ambient Air
Quality Standards,'' and the February 25, 2016, memorandum entitled
``Area Designations for the 2015 Ozone National Ambient Air Quality
Standards'' can be found in the docket of this rulemaking using
Docket ID No. EPA-R03-OAR-2025-1872.
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If the EPA finalizes this rulemaking as proposed, the current
Philadelphia nonattainment area for the 2008 ozone NAAQS and the 2015
ozone NAAQS would be split into three distinct nonattainment areas that
together cover the identical geographic area of the current area. One
of the proposed separate areas, to be called the ``Cecil County, MD
Nonattainment Area,'' would consist of Cecil County, MD. The other
proposed separate area, to be called the ``New Castle County, DE
Nonattainment Area,'' would consist of New Castle County, DE. The
revised Philadelphia nonattainment area would consist of the remaining
existing nonattainment area counties in New Jersey and Pennsylvania,
and be called the ``Philadelphia-Atlantic City, PA-NJ'' nonattainment
area.\14\ All areas would continue to be designated nonattainment and
classified as Marginal for the 2008 ozone NAAQS and classified as
Serious for the 2015 ozone NAAQS.
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\14\ If, for example, the EPA takes final action on Maryland's
redesignation request separate from Delaware's redesignation
request, the EPA proposes that it would first create two separate
nonattainment areas consisting of the ``Cecil County, MD
nonattainment area'' and the ``Philadelphia-Atlantic City, PA-NJ-DE
nonattainment area.''
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Section 107(d)(1)(A)(i) of the CAA defines ``nonattainment'' as
``any area that does not meet (or that contributes to ambient air
quality in a nearby area that does not meet)'' the NAAQS. Therefore,
consistent with the statute the EPA will not redraw the boundaries of
nonattainment areas where one portion of the area contributes to the
nonattainment of another portion of the area.
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1. Proposed Cecil County, MD Nonattainment Area for the 2008 and 2015
Ozone NAAQS
Based on a consideration of the information submitted by Maryland
and other available information discussed in the EPA's TSD included in
the docket for this rulemaking, the EPA is proposing to find that the
air quality data, emissions and emissions-related data, meteorology,
geography/topography, jurisdictional boundaries, other air quality
related considerations, as well as planning and control considerations,
support the state's request to revise the Philadelphia nonattainment
area boundary.
Maryland's February 13, 2025, submittal requested that the EPA
split the Philadelphia nonattainment area for the 2008 ozone NAAQS and
2015 ozone NAAQS and create a stand-alone nonattainment area for Cecil
County, MD. In this rulemaking, the EPA is proposing to revise the
existing nonattainment area boundary into three separate nonattainment
areas, acknowledging the differences in the factors contributing to
ozone levels in the separate areas, and thus providing Maryland with
additional flexibility in meeting the CAA's nonattainment area planning
and emissions control requirements. This includes the ability to
account for differences in air quality in the separate areas in the
event that one of the new, separate areas attains the ozone standards
faster than the other.
The EPA proposes in this rulemaking that the available information
demonstrates that the proposed new Cecil County, MD nonattainment area
does not contribute to a violation of the 2015 ozone NAAQS in the
proposed Philadelphia nonattainment area or the proposed New Castle
County, DE nonattainment area (there is no violation in this area), and
thus it is appropriate that the three areas be considered separate for
implementation and planning purposes. An analysis of the five
recommended factors and a weight-of-evidence approach supports this
conclusion. The air quality data in Cecil County, MD show that there
have been no violations of the 2015 ozone standard since 2020. An
analysis of emissions data, considering meteorological and
geographical/topographical factors, support the conclusion that the
emissions from this area are not contributing to the violations in the
proposed Philadelphia nonattainment area. Additionally, to take
jurisdictional boundaries into consideration, the proposed Cecil
County, MD nonattainment area follows the county boundary. A detailed
analysis supporting this demonstration can be found in the TSD
contained in the docket for this rulemaking.
Because this rulemaking also proposes to find that the proposed
Cecil County, MD nonattainment area is attaining the 2015 ozone NAAQS,
it is not necessary to consider whether the proposed Philadelphia-
Atlantic City, PA-NJ nonattainment area or the proposed New Castle
County, DE nonattainment area contributes to a violation of the 2015
ozone NAAQS in the proposed Cecil County, MD nonattainment area, as no
such violation exists. Because the 2015 ozone NAAQS retains the same
general form and averaging time as the 2008 ozone NAAQS, but is set at
a more protective level, the EPA's analysis for the 2015 ozone NAAQS
suffices as a demonstration for an identical nonattainment area
boundary revision for the less stringent 2008 ozone NAAQS.
2. Proposed New Castle County, DE Nonattainment Area for the 2008 and
2015 Ozone NAAQS
Based on a consideration of the information submitted by Delaware
and other available information discussed in the EPA's TSD included in
the docket for this rulemaking, the EPA is proposing to find that the
air quality data, emissions and emissions-related data, meteorology,
geography/topography, and jurisdictional boundaries, as well as
planning and control considerations, support the state's request to
revise the Philadelphia nonattainment area boundary.
Delaware's August 15, 2025, submittal requested that the EPA revise
the boundary for the existing Philadelphia nonattainment area for the
2008 ozone NAAQS and the 2015 ozone NAAQS and create a stand-alone
nonattainment area for New Castle County, DE. To this end, the EPA
proposes to revise the existing nonattainment area boundary into three
separate nonattainment areas, acknowledging the differences in the
factors contributing to ozone levels in the separate areas, thus
providing Delaware with additional flexibility in meeting the CAA's
nonattainment area planning and emissions control requirements. This
includes the ability to account for differences in air quality in the
separate areas in the event that one of the new, separate areas attains
the ozone standards faster than the other.
The EPA proposes in this document that the available information
demonstrates that the proposed New Castle County, DE nonattainment area
does not contribute to a violation of the 2015 ozone NAAQS in the
proposed Philadelphia nonattainment area or the proposed Cecil County
MD, nonattainment area (there is no violation in this area), and thus
it is appropriate that the three areas be considered separate for
implementation and planning purposes. An analysis of the five
recommended factors and a weight-of-evidence approach supports this
conclusion. The air quality data in New Castle County, DE show that
there have been no violations of the 2015 ozone standard since 2019. An
analysis of emissions data, considering meteorological and
geographical/topographical factors, support the conclusion that the
emissions from this area are not contributing to the violations in the
proposed Philadelphia nonattainment area. The EPA supplemented
Delaware's meteorological data by analyzing monitors that violated the
standard in 2023 and 2024 using HYSPLIT (HYbrid Single-Particle
Lagrangian Integrated Trajectory) modeling and TROPOMI (Tropospheric
Monitoring Instrument) satellite images. Additionally, to take
jurisdictional boundaries into consideration, the proposed New Castle
County, DE nonattainment area follows the county boundary. A detailed
analysis supporting this demonstration can be found in the TSD
contained in the docket for this rulemaking.
Because this rulemaking also proposes to find that the proposed New
Castle County, DE nonattainment area is attaining the 2015 ozone NAAQS,
it is not necessary to consider whether the proposed Philadelphia-
Atlantic City, PA-NJ nonattainment area or the proposed Cecil County,
MD nonattainment area contributes to a violation of the 2015 ozone
NAAQS in the proposed New Castle County, DE nonattainment area, as no
such violation exists. Because the 2015 ozone NAAQS retains the same
general form and averaging time as the 2008 ozone NAAQS, but is set at
a more protective level, the EPA's analysis for the 2015 ozone NAAQS
suffices as a demonstration for an identical nonattainment area
boundary revision for the less stringent 2008 ozone NAAQS.
B. Clean Data Determinations
An area is attaining the 2015 ozone NAAQS if it meets the 2015
ozone NAAQS, as determined in accordance with 40 CFR 50.19 and appendix
U of part 50, based on three complete, consecutive calendar years of
quality-assured air quality data for all monitoring sites in the area.
To attain
[[Page 102]]
the 2015 ozone NAAQS, the three-year average of the annual fourth-
highest daily maximum 8-hour average ozone concentrations (ozone design
values) at each monitor must not exceed 70 ppb. The air quality data
must be collected and quality-assured in accordance with 40 CFR part 58
and recorded in the EPA's AQS. Ambient air quality monitoring data for
the three-year period must also meet data completeness requirements. An
ozone design value is valid if daily maximum 8-hour average
concentrations are available for at least 90% of the days within the
ozone monitoring seasons,\15\ on average, for the three-year period,
with a minimum data completeness of 75% during the ozone monitoring
season of any year during the three-year period. See section 4 of
appendix U to 40 CFR part 50.
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\15\ Per 40 CFR 51.1300(j), the ozone season is varied by state
as defined in 40 CFR part 58 appendix D, section 4.1(i). The ozone
season for Maryland and Delaware runs from March 1 to October 31.
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1. Clean Data Determinations for the Cecil County, MD Nonattainment
Area for the 2008 and 2015 Ozone NAAQS
In accordance with 40 CFR 51.1118 and 51.1318, the EPA proposes to
determine that the proposed Cecil County, MD nonattainment area is
attaining the 2015 ozone NAAQS. Because the 2015 ozone NAAQS retains
the same general form and averaging time as the 2008 ozone NAAQS, but
is set at a more protective level, the EPA's analysis for the 2015
ozone NAAQS CDD suffices as a CDD analysis for the less stringent 2008
ozone NAAQS. This determination is based upon two three-year periods of
complete, quality-assured and certified data for the 2021-2023 and
2022-2024 monitoring periods. The Fair Hill monitor with site ID 24-
015-0003 is the only FRM ozone monitor within the proposed separate
Cecil County, MD nonattainment area; the annual fourth-highest 8-hour
ozone concentrations and the three-year average of these concentrations
(monitoring site ozone design values) for this monitoring site are
summarized in Table 1 in this document.
Table 1--Annual 4th Highest Daily Maximum 8-Hour Ozone Concentrations and Three-Year Average of the 4th Highest Daily Maximum 8-Hour Ozone
Concentrations for the Proposed Cecil County, MD Nonattainment Area
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AQS Site 2021 4th 2022 4th 2023 4th 2024 4th 2021-2023 2022-2024
County, State ID Site name high (ppb) high (ppb) high (ppb) high (ppb) DV (ppb) DV (ppb)
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Cecil, MD.............................. 240150003 Fair Hill................ 70 63 70 70 67 67
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The most recent three-year ozone design value for the proposed
Cecil County, MD nonattainment area is 67 ppb, which meets the 2015
ozone NAAQS. Therefore, in this rulemaking, the EPA proposes to
determine that the proposed separate Cecil County, MD nonattainment
area is attaining the 2008 and 2015 ozone NAAQS.
The EPA will not take final action to determine that the proposed
separate Cecil County, MD nonattainment area is attaining the 2008 or
2015 ozone NAAQS if the design value of a monitoring site in the area
exceeds the 2008 or 2015 ozone NAAQS respectively after proposal but
prior to final approval of the CDD. Additionally, if after proposal but
prior to final approval, the proposed separate Cecil County, MD
nonattainment area is attaining the 2008 ozone NAAQS but not the 2015
ozone NAAQS, the EPA may finalize a CDD for only the 2008 standard and
not the 2015 standard. The EPA will not finalize any CDD for Cecil
County unless and until the EPA takes final action on the proposed
revision splitting Cecil County, MD nonattainment area from the
Philadelphia nonattainment area.
Should this rulemaking be finalized, the requirements for MDE to
submit attainment demonstrations, and associated reasonably available
control measures (RACM), reasonable further progress (RFP) plans,
contingency measures, and any other planning requirements related to
attainment of the 2008 and 2015 ozone NAAQS for the proposed Cecil
County, MD nonattainment area, would be suspended until the EPA
rescinds the CDD due to the area no longer attaining the 2015 ozone
NAAQS. This rulemaking does not constitute a redesignation of the area
to attainment of the 2008 or 2015 ozone NAAQS under section
107(d)(3)(E) of the CAA, nor does it constitute approval of a
maintenance plan for the area as required under section 175A of the
CAA, nor does it find that the area has met all other requirements for
redesignation. The proposed Cecil County, MD nonattainment area will
remain designated nonattainment for the 2008 and 2015 ozone NAAQS until
such time as the EPA determines that the area meets CAA requirements
for redesignation to attainment and takes a separate action to
redesignate the area.
2. Clean Data Determinations for the New Castle County, DE
Nonattainment Area for the 2008 and 2015 Ozone NAAQS
In accordance with 40 CFR 51.1118 and 51.1318, the EPA proposes to
determine that the proposed New Castle County, DE nonattainment area is
attaining the 2008 and 2015 ozone NAAQS. Because the 2015 ozone NAAQS
retains the same general form and averaging time as the 2008 ozone
NAAQS, but is set at a more protective level, the EPA's analysis for
the 2015 ozone NAAQS CDD suffices as a CDD analysis for the less
stringent 2008 ozone NAAQS. This determination is based upon two three-
year periods of complete, quality-assured and certified data for the
2021-2023 and 2022-2024 monitoring periods. There are four FRM/FEM
monitors within the proposed separate New Castle County, DE
nonattainment area; the annual fourth-highest 8-hour ozone
concentrations and the three-year average of these concentrations
(monitoring site ozone design values) for these monitoring sites are
summarized in Table 2 in this document.
[[Page 103]]
Table 2--Annual 4th Highest Daily Maximum 8-Hour Ozone Concentrations and Three-Year Average of the 4th Highest Daily Maximum 8-Hour Ozone
Concentrations for the Proposed New Castle County, DE Nonattainment Area
--------------------------------------------------------------------------------------------------------------------------------------------------------
AQS Site 2021 4th 2022 4th 2023 4th 2024 4th 2021-2023 2022-2024
County, State ID Site name high (ppb) high (ppb) high (ppb) high (ppb) DV (ppb) DV (ppb)
--------------------------------------------------------------------------------------------------------------------------------------------------------
New Castle, DE......................... 100031007 Lums Pond................ 63 64 72 66 66 67
100031010 BCSP..................... 65 64 70 63 66 65
100031013 Bellevue................. 64 65 69 68 66 67
100032004 MLK...................... 66 65 69 70 66 68
--------------------------------------------------------------------------------------------------------------------------------------------------------
Where several monitors are located in a county (or a designated
nonattainment area or maintenance area), the design value for the
county or area is determined by the monitor with the highest level. The
highest most recent three-year ozone design value for the proposed New
Castle County, DE nonattainment area is 68 ppb, which meets the 2015
ozone NAAQS. Therefore, in this rulemaking, the EPA proposes to
determine that the proposed separate New Castle County, DE
nonattainment area is attaining the 2008 and 2015 ozone NAAQS.
The EPA will not take final action to determine that the proposed
separate New Castle County, DE nonattainment area is attaining the 2008
or 2015 ozone NAAQS if the design value of a monitoring site in the
area exceeds the 2008 or 2015 ozone NAAQS respectively after proposal
but prior to final approval of the CDDs. Additionally, if after
proposal but prior to final approval, the proposed separate New Castle
County, DE nonattainment area is attaining the 2008 ozone NAAQS but not
the 2015 ozone NAAQS, the EPA may finalize a CDD for only the 2008
standard and not the 2015 standard. The EPA will not finalize any CDD
for New Castle County unless and until the EPA takes final action on
the proposed revision splitting New Castle County, DE nonattainment
area from the Philadelphia nonattainment area.
Should this rulemaking be finalized, the requirements for DNREC to
submit attainment demonstrations, and associated RACM, RFP plans,
contingency measures, and any other planning requirements related to
attainment of the 2008 and 2015 ozone NAAQS for the proposed New Castle
County, DE nonattainment area, would be suspended until the EPA
rescinds the CDD due to the area no longer attaining the 2015 ozone
NAAQS. This rulemaking does not constitute a redesignation of the area
to attainment of the 2008 or 2015 ozone NAAQS under section
107(d)(3)(E) of the CAA, nor does it constitute approval of a
maintenance plan for the area as required under section 175A of the
CAA, nor does it find that the area has met all other requirements for
redesignation. The proposed New Castle County, DE nonattainment area
will remain designated nonattainment for the 2008 and 2015 ozone NAAQS
until such time as the EPA determines that the area meets CAA
requirements for redesignation to attainment and takes a separate
action to redesignate the area.
C. Summary
This rulemaking proposes to revise the boundary of an existing
ozone nonattainment area by splitting it into three separate
nonattainment areas that together cover the identical geographic area
of the original nonattainment area and proposes to make a determination
of attainment of the 2008 and 2015 ozone NAAQS based on air quality
data for two of those proposed areas--the Cecil County, MD
nonattainment area and the New Castle County, DE nonattainment area. If
the EPA finalizes the boundary revision for the Cecil County, MD
nonattainment area, and the CDDs for that proposed revised area, then,
the EPA will suspend requirements to submit certain plan requirements
to attain the 2008 and 2015 ozone NAAQS, so long as the area continues
to attain the standard. Similarly, if the EPA finalizes the boundary
revision for the New Castle County, DE nonattainment area, and the CDDs
for that proposed revised area, then, EPA will suspend requirements to
submit certain plan requirements to attain the 2008 and 2015 ozone
NAAQS, so long as the area continues to attain the standard. These
actions do not impose additional requirements.
V. Statutory and Executive Order Reviews
This rulemaking proposes to revise the boundary of an existing
ozone nonattainment area by splitting it into three separate
nonattainment areas that together cover the identical geographic area
of the original nonattainment area. It also proposes to make CDDs for
the two new areas in Cecil County, MD and New Castle County, DE
resulting from the proposed revisions, which if finalized would suspend
the requirement to submit certain attainment plan requirements for the
2008 and 2015 ozone NAAQS. This proposed rulemaking action does not
impose additional requirements. For that reason, this action:
Is not a significant regulatory action subject to review
by the Office of Management and Budget under Executive Order 12866 (58
FR 51735, October 4, 1993);
Is not subject to Executive Order 14192 (90 FR 9065,
February 6, 2025) because it is not a significant regulatory action
under Executive Order 12866;
Does not impose an information collection burden under the
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
Is certified as not having a significant economic impact
on a substantial number of small entities under the Regulatory
Flexibility Act (5 U.S.C. 601 et seq.);
Does not contain any unfunded mandate or significantly or
uniquely affect small governments, as described in the Unfunded
Mandates Reform Act of 1995 (Pub. L. 104-4);
Does not have federalism implications as specified in
Executive Order 13132 (64 FR 43255, August 10, 1999);
Is not subject to Executive Order 13045 (62 FR 19885,
April 23, 1997) because it is not a significant regulatory action under
Executive Order 12866;
Is not a significant regulatory action subject to
Executive Order 13211 (66 FR 28355, May 22, 2001); and
Is not subject to requirements of section 12(d) of the
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272
note) because application of those requirements would be inconsistent
with the CAA.
In addition, this rulemaking action is not approved to apply on any
Indian reservation land or in any other area where the EPA or an Indian
Tribe has demonstrated that a Tribe has jurisdiction. In those areas of
Indian country, the rule does not have Tribal implications and will not
impose substantial direct costs on Tribal
[[Page 104]]
governments or preempt Tribal law as specified by Executive Order 13175
(65 FR 67249, November 9, 2000).
List of Subjects
40 CFR Part 52
Environmental protection, Air pollution control, Incorporation by
reference, Intergovernmental relations, Nitrogen dioxide, Ozone,
Volatile organic compounds.
40 CFR Part 81
Environmental protection, Air pollution control, Designations,
Intergovernmental relations, Redesignation, Reporting and recordkeeping
requirements, Nitrogen dioxide, Ozone, Volatile organic compounds.
Amy Van Blarcom-Lackey,
Regional Administrator, Region III.
[FR Doc. 2025-24200 Filed 12-31-25; 8:45 am]
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