Proposed Rule2025-20418
Air Plan Approval; Delaware; 2006 24-Hour Fine Particulate Matter Limited Maintenance Plan for the Philadelphia Nonattainment Area
Primary source
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Published
November 20, 2025
Issuing agencies
Environmental Protection Agency
Abstract
The Environmental Protection Agency (EPA) is proposing to approve a limited maintenance plan (LMP) submitted by the Delaware Department of Natural Resources and Environmental Control (DNREC). This LMP is a revision to Delaware's state implementation plan (SIP) and addresses the New Castle County portion of the Philadelphia-Wilmington, PA-NJ-DE area (Philadelphia Area). The EPA is proposing to approve the New Castle County portion of the Philadelphia Area LMP because it provides for the maintenance of the 2006 24-hour fine particulate matter (PM<INF>2.5</INF>) national ambient air quality standard (NAAQS) through the end of the second 10-year maintenance period. In addition, the EPA is initiating the process to find the LMP adequate for transportation conformity purposes. This action is being taken under the Clean Air Act (CAA).
Full Text
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<title>Federal Register, Volume 90 Issue 222 (Thursday, November 20, 2025)</title>
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[Federal Register Volume 90, Number 222 (Thursday, November 20, 2025)]
[Proposed Rules]
[Pages 52290-52297]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2025-20418]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R03-OAR-2025-0205; FRL-11969-01-R3]
Air Plan Approval; Delaware; 2006 24-Hour Fine Particulate Matter
Limited Maintenance Plan for the Philadelphia Nonattainment Area
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
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SUMMARY: The Environmental Protection Agency (EPA) is proposing to
approve a limited maintenance plan (LMP) submitted by the Delaware
Department of Natural Resources and Environmental Control (DNREC). This
LMP is a revision to Delaware's state implementation plan (SIP) and
addresses the New Castle County portion of the Philadelphia-Wilmington,
PA-NJ-DE area (Philadelphia Area). The EPA is proposing to approve the
New Castle County portion of the Philadelphia Area LMP because it
provides for the maintenance of the 2006 24-hour fine particulate
matter (PM<INF>2.5</INF>) national ambient air quality standard (NAAQS)
through the end of the second 10-year maintenance period. In addition,
the EPA is initiating the process to find the LMP adequate for
transportation conformity purposes. This action is being taken under
the Clean Air Act (CAA).
DATES: Written comments must be received on or before December 22,
2025.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R03-
OAR-2025-0205 at <a href="http://www.regulations.gov">www.regulations.gov</a>, or via email to
<a href="/cdn-cgi/l/email-protection#b4d3dbc6d0dbda9ad9dddfd1f4d1c4d59ad3dbc2"><span class="__cf_email__" data-cfemail="ee89819c8a8180c08387858bae8b9e8fc0898198">[email protected]</span></a>. For comments submitted at <a href="http://Regulations.gov">Regulations.gov</a>, follow
the online instructions for submitting comments. Once submitted,
comments
[[Page 52291]]
cannot be edited or removed from <a href="http://Regulations.gov">Regulations.gov</a>. 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
<a href="http://www.epa.gov/dockets/commenting-epa-dockets">www.epa.gov/dockets/commenting-epa-dockets</a>.
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
<a href="/cdn-cgi/l/email-protection#c2afa1a1a3a0a7ecb1a3b0a3aa82a7b2a3eca5adb4"><span class="__cf_email__" data-cfemail="7f121c1c1e1d1a510c1e0d1e173f1a0f1e51181009">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION: On April 15, 2024, DNREC submitted a
revision to the State's SIP. This revision is a LMP for the second 10-
year maintenance period for the 2006 24-hour PM<INF>2.5</INF> NAAQS for
the New Castle County portion of the Philadelphia-Wilmington, PA-NJ-DE
area. The Philadelphia Area is comprised of New Castle County in
Delaware; Burlington, Camden, and Gloucester Counties in New Jersey;
and Bucks, Chester, Delaware, Montgomery, and Philadelphia Counties in
Pennsylvania. This action is expected to ensure that the State of
Delaware meets CAA requirements.
I. Background
A. The PM2.5 NAAQS
Under section 109 of the CAA, the EPA has established NAAQS for
certain pervasive 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 EPA sets the NAAQS for criteria pollutants at levels
required to protect public health and welfare.\1\ The EPA's particulate
matter standards address particles with diameters that are generally
two and half micrometers or smaller (fine particulate matter or
PM<INF>2.5</INF>) and particles with diameters that are generally 10
micrometers or smaller (PM<INF>10</INF>). PM<INF>2.5</INF> is one of
the ambient pollutants for which the EPA has established health-based
standards.
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\1\ For a given air pollutant, ``primary'' national ambient air
quality standards are those determined by the EPA as requisite to
protect the public health. ``Secondary'' standards are those
determined by the EPA as 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. CAA section
109(b).
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Fine particulate matter contributes to effects that are harmful to
human health and the environment, including premature mortality,
aggravation of respiratory and cardiovascular disease, decreased lung
function, visibility impairment, and damage to vegetation and
ecosystems. Individuals particularly sensitive to PM<INF>2.5</INF>
exposure include older adults, people with heart and lung disease, and
children. See 78 FR 3086 at 3088 (January 15, 2013). PM<INF>2.5</INF>
can be emitted directly into the atmosphere as a solid or liquid
particle (primary PM<INF>2.5</INF> or direct PM<INF>2.5</INF>) or can
be formed in the atmosphere (secondary PM<INF>2.5</INF>) as a result of
various chemical reactions among precursor pollutants such as nitrogen
oxides (NO<INF>X</INF>), sulfur dioxide (SO<INF>2</INF>), volatile
organic compounds (VOCs), and ammonia (NH<INF>3</INF>).\2\
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\2\ EPA, Air Quality Criteria for Particulate Matter, No. EPA/
600/P-99/002aF and EPA/600/P-99/002bF, October 2004.
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On July 18, 1997 (62 FR 38652), the EPA revised the NAAQS for
particulate matter to add new standards for PM<INF>2.5</INF>. The
Agency established primary and secondary annual and 24-hour standards
for PM<INF>2.5</INF>. The annual standard was set at 15.0 micrograms
per cubic meter ([micro]g/m\3\) based on a 3-year average of annual
mean PM<INF>2.5</INF> concentrations, and the 24-hour (daily) standard
was set at 65 [micro]g/m\3\ based on the 3-year average of the annual
98th percentile values of 24-hour PM<INF>2.5</INF> concentrations at
each population-oriented monitor within an area.\3\
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\3\ The primary and secondary standards were set at the same
level for both the 24-hour and the annual PM<INF>2.5</INF>
standards.
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On October 17, 2006 (71 FR 61144), the EPA promulgated the 2006
PM<INF>2.5</INF> NAAQS. It retained the annual average NAAQS at 15.0
[micro]g/m\3\ but lowered the level of the 24-hour PM<INF>2.5</INF>
NAAQS to 35 [micro]g/m\3\ based on a 3-year average of the annual 98th
percentile values of 24-hour concentrations.\4\
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\4\ Under EPA regulations at 40 CFR part 50, the primary and
secondary 2006 24-hour PM<INF>2.5</INF> NAAQS are attained when the
annual arithmetic mean concentration, as determined in accordance
with 40 CFR part 50, appendix N, is less than or equal to 35
[micro]g/m\3\ at all relevant monitoring sites in the subject area,
averaged over a 3-year period.
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On December 14, 2012, the EPA promulgated the 2012 PM<INF>2.5</INF>
NAAQS, including lowering the annual standard to 12.0 [micro]g/m\3\
based on a 3-year average of annual mean PM<INF>2.5</INF>
concentrations. The EPA maintained the 24-hour standard of 35 [micro]g/
m\3\ based on a 3-year average of the 98th percentile of 24-hour
concentrations. See 78 FR 3086 (January 15, 2013).
On February 7, 2024, the EPA revised the NAAQS for particulate
matter to add new standards for PM<INF>2.5</INF>. The EPA strengthened
the level of the annual primary PM<INF>2.5</INF> standard from 12.0
[micro]g/m\3\ to 9.0 [micro]g/m\3\. The EPA retained the primary and
secondary 24-hour PM<INF>2.5</INF> standards, secondary annual
PM<INF>2.5</INF> standard, and primary and secondary PM<INF>10</INF>
standards. See 89 FR 16202 (March 6, 2024).
B. Designation of PM2.5 NAAQS Nonattainment Areas and Subsequent
Actions
Following promulgation of a new or revised NAAQS, the EPA is
required by CAA section 107(d) to designate areas throughout the nation
as attaining or not attaining the NAAQS. On November 13, 2009 (74 FR
58688), the EPA designated the Philadelphia Area as nonattainment for
the 2006 24-hour PM<INF>2.5</INF> NAAQS.
Initially, the EPA did not assign classifications for
PM<INF>2.5</INF> for the 2006 24-hour NAAQS (e.g. marginal, moderate,
etc.). Subsequently, on January 4, 2013, the Court of Appeals for the
District of Columbia remanded the EPA's implementation rule as a result
of Natural Resources Defense Council v. EPA, 706 F.3d 428 (D.C. Cir.
2013), regarding the failure of the EPA to assign classifications for
PM<INF>2.5</INF> for the 2006 24-hour NAAQS. The Court concluded that
the EPA had improperly based the 2007 implementation rule for the 2006
24-hour PM<INF>2.5</INF> NAAQS solely upon the requirements of Title I,
part D, subpart 1 of the CAA, and had failed to address the
requirements of part D, subpart 4. In response to the court decision,
the EPA subsequently assigned classifications to the applicable areas.
On April 25, 2014, the EPA finalized a rule identifying the
classification of all PM<INF>2.5</INF> areas currently designated
nonattainment for the 2006 24-hour PM<INF>2.5</INF> NAAQS as
``Moderate'' (79 FR 31566, June 2, 2014).
On November 27, 2012, the State of Delaware submitted to the EPA a
redesignation request and maintenance plan for the New Castle County
portion
[[Page 52292]]
of the Philadelphia Area. The EPA redesignated the New Castle County
portion of the Philadelphia Area from nonattainment to attainment for
the 2006 24-hour PM<INF>2.5</INF> NAAQS and approved the maintenance
plan for the first 10-year maintenance period effective September 4,
2014 (79 FR 45350, August 5, 2014). The first 10-year maintenance
period for the New Castle County portion of the Philadelphia Area ended
on September 4, 2024, and the Area's second 10-year maintenance period,
which is the subject of this proposed rulemaking, extends through
September 4, 2034.
C. Limited Maintenance Plans
Section 107(d)(3)(E) of the CAA sets out the requirements for
redesignating a nonattainment area to attainment. One of the criteria
for redesignation is to have an approved maintenance plan under section
175A of the Act. Section 175A requires that nonattainment areas seeking
redesignation to attainment submit ``a revision of the applicable state
implementation plan to provide for the maintenance of the [NAAQS] for
such air pollutant in the area concerned for at least 10 years after
the redesignation.'' Pursuant to section 175A(b), eight years into the
first maintenance period, the applicable state or local agency must
submit a second maintenance plan demonstrating that the area will
continue to attain for the following 10-year period. On September 4,
1992, the EPA issued guidance on the content of a maintenance plan
(Memorandum from John Calcagni, Director, Air Quality Management
Division, entitled ``Procedures for Processing Requests to Redesignate
Areas to Attainment,'' (hereinafter referred to as the ``Calcagni
Memorandum'')) \5\ which explained that states may meet this
requirement to ``provide for the maintenance of the NAAQS'' by using
projected emissions inventories or air quality modeling showing
continued maintenance until the end of the relevant maintenance period.
The EPA clarified in subsequent guidance memoranda that rather than
using air quality modeling or an emission inventory projection, certain
areas could meet the CAA section 175A requirement to provide for
maintenance by demonstrating that the area's design value was well
below the NAAQS and that the historical stability of the area's air
quality levels showed that the area was unlikely to violate the NAAQS
in the future.\6\ Design values (DV) for the 2006 24-hour
PM<INF>2.5</INF> NAAQS are calculated using the 3-year average of
annual 98th percentile 24-hour average PM<INF>2.5</INF> mass
concentration values recorded at each eligible monitoring site.
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\5\ See Calcagni, John, Director, Air Quality Management
Division, EPA Office of Air Quality Planning and Standards,
``Procedures for Processing Requests to Redesignate Areas to
Attainment,'' September 4, 1992 (Calcagni Memorandum). A copy of
this memorandum can be found in the docket for this proposed
rulemaking.
\6\ See ``Limited Maintenance Plan Option for Nonclassifiable
Ozone Nonattainment Areas'' from Sally L. Shaver, Office of Air
Quality Planning and Standards (OAQPS), dated November 16, 1994;
``Limited Maintenance Plan Option for Nonclassifiable CO
Nonattainment Areas'' from Joseph Paisie, OAQPS, dated October 6,
1995; and
``Limited Maintenance Plan Option for Moderate PM<INF>10</INF>
Nonattainment Areas'' from Lydia Wegman, OAQPS, dated August 9,
2001(hereinafter referred to as the ``Wegman Memorandum''). Copies
of these guidance memoranda can be found in the docket for this
proposed rulemaking.
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Most recently, in October 2022, the EPA released guidance extending
this streamlined option for demonstrating maintenance under CAA section
175A to certain PM<INF>2.5</INF> areas, titled ``Guidance on the
Limited Maintenance Plan Option for Moderate PM<INF>2.5</INF>
Nonattainment Areas and PM<INF>2.5</INF> Maintenance Areas''
(PM<INF>2.5</INF> LMP Guidance).\7\
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\7\ The guidance document titled ``Guidance on the Limited
Maintenance Plan Option for Moderate PM<INF>2.5</INF> Nonattainment
Areas and PM<INF>2.5</INF> Maintenance Areas'' can be found at
<a href="https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P1015UL4.pdf">https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P1015UL4.pdf</a>. A copy of
the guidance is in the docket for this proposed rulemaking.
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The EPA refers to this streamlined demonstration of maintenance as
a limited maintenance plan or LMP. The EPA has interpreted CAA section
175A as permitting this option because section 175A does not define how
areas may demonstrate maintenance, and in the EPA's experience with
implementing the various NAAQS, areas that qualify for an LMP and have
approved LMPs, have rarely, if ever, experienced subsequent violations
of the NAAQS. As noted in the PM<INF>2.5</INF> LMP Guidance, states
seeking an LMP must still submit the other maintenance plan elements
outlined in the Calcagni Memorandum, including an attainment emissions
inventory, provisions for the continued operation of the ambient air
quality monitoring network, verification of continued attainment, and a
contingency plan in the event of a future violation of the NAAQS.
The PM<INF>2.5</INF> LMP Guidance describes a process for states to
demonstrate that an area qualifies for an LMP by showing that, based on
recent measured air quality, the area is unlikely to violate the NAAQS
in the future. The PM<INF>2.5</INF> LMP Guidance relies on the critical
design value (CDV) concept. This guidance describes a process for a
PM<INF>2.5</INF> area to qualify for an LMP by showing that the area's
average design value (ADV) for each site in the area (based upon the
most recent five design values as calculated) \8\ is at or below the
CDV. The CDV is an indicator of the likelihood of future violations of
the NAAQS in an area given the area's current ADV and its historical
variability. The PM<INF>2.5</INF> LMP Guidance provides a means for
calculating the CDV for an area (or monitoring site). The CDV
calculation for a monitoring site involves parameters including: (1)
the level of the relevant NAAQS; \9\ (2) the coefficient of variation
(CV) of recent design values measured at that site; and (3) a
statistical parameter t<INF>c</INF> (critical t-value) corresponding to
a 10 percent probability of exceedance, such that sites with
historically high variability in design values result in a lower (or
more stringent) CDV.\10\ The CDV is the highest average design value an
area could have before it may experience a future exceedance of the
NAAQS with a certain probability--in the case of the PM<INF>2.5</INF>
LMP Guidance, a probability of one in ten.\11\ Therefore, if an area's
current ADV is less than the area's CDV, that area has less than a ten
percent probability of exceeding the NAAQS in the future. The
eligibility calculations for the CDV demonstration are shown in table 1
in this document.
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\8\ The EPA recommends that the ADV be calculated using at least
five years of design values, each representing a three-year period,
because this approach would rely on a more robust dataset. However,
we acknowledge that an alternative interpretation may be acceptable,
where these variables could be calculated using three years of
design values, collectively representing five years of air quality
data. See PM<INF>2.5</INF> LMP Guidance at 7.
\9\ As noted in Attachment A of the Wegman Memorandum, the CDV
calculation was designed to apply for any NAAQS pollutant and is not
specific to PM<INF>10</INF>.
\10\ PM<INF>2.5</INF> LMP Guidance at 7.
\11\ The PM<INF>2.5</INF> Guidance directs states to calculate a
site-specific CDV for the monitoring site in an area with the
highest design value, and also for all other active monitoring sites
in the area with complete data.
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[GRAPHIC] [TIFF OMITTED] TP20NO25.005
Per the EPA's transportation conformity regulations, a LMP must
also ``demonstrate that it would be unreasonable to expect that such an
area would experience enough motor vehicle emissions growth for a NAAQS
violation to occur.'' \12\ For further discussion of transportation
conformity, see section III of this document.
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\12\ See 40 CFR 93.109(e).
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II. Summary of SIP Revision and EPA Analysis
On April 15, 2024, the EPA received Delaware's second 10-year
maintenance plan SIP submission for the 2006 24-hour PM<INF>2.5</INF>
NAAQS for the New Castle County portion of the Philadelphia Area.
A. Qualifying for the Limited Maintenance Plan Option
As discussed in section I.C. of this document, one way for an area
to qualify for an LMP is to show that the area's ADV (based upon the
most recent five years of monitoring data) is at or below the CDV. The
New Castle County portion of the Philadelphia Area includes five
ambient air monitoring sites for the 24-hour PM<INF>2.5</INF> NAAQS:
the Bellefonte I site (AQS 10-003-1003), the Lums Pond site (AQS 10-
003-1007), the RT 9 site (AQS 10-003-1008), the Newark site (AQS 10-
003-1012), and the MLK site (AQS 10-003-2004). Due to multiple
technical and operational issues from 2014-2020, four out of the five
PM<INF>2.5</INF> monitors were unable to meet the data completeness
requirement \13\ for multiple years (Bellefonte, RT 9, Newark, and Lums
Pond). For the New Castle County portion of the Philadelphia Area,
Delaware calculated the ADV by averaging the most recent five
consecutive 3-year averages (design values) of monitoring data at the
time of submission, from 2014 to 2020.\14\ Delaware is in the process
of transitioning from manual to continuous monitors, which are expected
to reduce monitor downtime due to technical/mechanical issues.\15\ The
MLK monitoring station meets the EPA's PM<INF>2.5</INF> design value
completeness rules for 2014-2020 as the EPA allows the collocated
Federal equivalent methods (FEM) to fill in when the primary monitor is
down.\16\ Collocated refers to two or more air samplers, analyzers, or
other instruments that are operated simultaneously while located side
by side, separated by a distance that is large enough to preclude the
air sampled by any of the devices from being affected by any of the
other devices, but small enough so that all devices obtain identical or
uniform ambient air samples that are equally representative of the
general area in which the group of devices is located. Additionally,
FEM is a method of measuring the concentration of an air pollutant in
the ambient air that has been designated as an equivalent method in
accordance with 40 CFR part 53. A Federal reference method (FRM) is a
method of sampling and analyzing the ambient air for an air pollutant
that is specified as a reference method in an appendix to 40 CFR part
50, or a method that has been designated as a reference method in
accordance with 40 CFR part 53. Data from these monitors are measured
using the EPA approved methods including FEM and FRM.
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\13\ In accordance with 40 CFR part 50, appendix N, each quarter
of a three-year period must be >75% complete for the entire three-
year Design Value to be considered >75% complete.
\14\ Delaware provided data for this LMP demonstration from the
time period according to the timeline in CAA section 175A(b), i.e.,
2022, 8 years after initial redesignation. The most recent DVs for
the MLK site are 19 [micro]g/m\3\ (2019-2021), 17 [micro]g/m\3\
(2020-2022), 20 [micro]g/m\3\ (2021-2023), and 19 [micro]g/m\3\
(2022-2024). The ADV for the MLK site from 2019-2024 (18.75
[micro]g/m\3\) is consistent with the data provided in this
demonstration and qualifies for an LMP as it falls below the
calculated MLK CDV of 32.14 [micro]g/m\3\.
\15\ See Division of Air Quality, Delaware Department of Natural
Resources and Environmental Control, ``2024 Delaware Ambient Air
Monitoring Network Plan for Criteria Pollutants'' May 2024.
<a href="http://documents.dnrec.delaware.gov/Air/monitoring/delaware-air-monitoring-network-plan.pdf">documents.dnrec.delaware.gov/Air/monitoring/delaware-air-monitoring-network-plan.pdf</a>. A copy of this memorandum can be found in the
docket for this proposed rulemaking.
\16\ See Wayland, Richard A., Director, Air Quality Assessment
Division, EPA Office of Air Quality Planning and Standards,
``Implementing Continuous PM<INF>2.5</INF> Federal Equivalent
Methods (FEMs) and Approved Regional Methods (ARMs) in State or
Local Air Monitoring Station (SLAMS) Networks,'' July 24, 2008.
<a href="http://www.epa.gov/sites/default/files/2015-09/documents/use_of_pm2_5_fems_and_arms_in_slams_network.pdf">www.epa.gov/sites/default/files/2015-09/documents/use_of_pm2_5_fems_and_arms_in_slams_network.pdf</a>.
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Since each design value is calculated by averaging three years of
the 98th percentile of 24-hour average, the average of the five
consecutive 3-year design values includes data from a seven-year period
(2014-2020).\17\ Table 2 in this document presents five 3-year design
values for the 24-hour PM<INF>2.5</INF> NAAQS for the New Castle County
portion of the Philadelphia Area that were available to Delaware while
developing the LMP. Due to incomplete data, only the MLK monitoring
site is used to calculate eligibility for the LMP. This is consistent
with the PM<INF>2.5</INF> LMP Guidance, however, ADVs and CDVs were
calculated for the monitors with incomplete data for reference. The ADV
of the MLK site is 20 [micro]g/m\3\.
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\17\ See footnote 14. The average of the most recent 3-year
design values from 2019-2024 are 18 [micro]g/m\3\ (Bellefonte-DVs do
not meet completeness rules), 18 [micro]g/m\3\ (Lums Pond), 18
[micro]g/m\3\ (RT 9), 16.5 [micro]g/m\3\ (Newark- DVs do not meet
completeness rules), and 18.75 [micro]g/m\3\ (MLK). These design
value averages are equal to or lower than the 2014-2020 design value
averages, thus indicating that the LMP approach is still
appropriate.
[[Page 52294]]
Table 2--New Castle County 24-Hour PM2.5 NAAQS Design Values
[[micro]g/m\3\] \a\
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Design value period Bellefonte I Lums Pond RT 9 Newark MLK
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2014-2016....................... * 22 * 19 * 23 23 23
2015-2017....................... * 21 * 18 * 18 * 22 21
2016-2018....................... * 18 * 16 * 16 * 18 19
2017-2019....................... 19 18 17 * 19 20
2018-2020....................... * 17 17 17 * 17 19
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Average of 3-year design 19 18 18 20 20
values.....................
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\a\ Taken from Delaware's 2006 24-hour PM2.5 LMP SIP submission for the New Castle County portion of the
Philadelphia Area
* Fails to meet PM2.5 design value data completeness rules.\18\
To calculate the CDV for each area, the EPA used the recent five
years of design values and their variability with the equation
presented in the PM<INF>2.5</INF> LMP Guidance, replicated in table 1
in this document.
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\18\ In accordance with 40 CFR part 50, appendix N, each quarter
of a three-year period must be >75% complete for the entire three-
year Design Value to be considered >75% complete.
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Table 3 in this document shows the input and results of the LMP
eligibility calculations.\19\ The resulting CDV for the New Castle
County portion of the Philadelphia Area is calculated to be 31.1
[micro]g/m\3\. The New Castle County portion of the Philadelphia Area's
ADV (20 [micro]g/m\3\) falls below the site-specific CDV of 31.1
[micro]g/m\3\ and thus meets the first criterion for LMP
eligibility.\20\ While this calculation is based solely on the MLK
monitor, it is notable that the ADV and CDV calculations for each of
the four monitors with incomplete data are also consistent with LMP
eligibility.
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\19\ See ``LMP Criteria Data Analysis'' spreadsheet in the
docket for this proposed rulemaking.
\20\ The ADV for the MLK site from 2019-2024 (18.75 [micro]g/
m\3\) aligns with the data provided in this demonstration and
qualifies for an LMP as it falls below the calculated MLK CDV of
32.14 [micro]g/m\3\. Additionally, the 2019-2024 ADVs and CDVs for
the monitors that do not meet data completeness rules are consistent
with LMP eligibility.
Table 3--LMP Eligibility Calculations and Inputs of CDVs at New Castle County Monitors for the 24-Hour PM2.5 NAAQS \a\
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ADV (2014-
Standard 2020) CDV [[micro]g/
Site Monitor deviation CV [[micro]g/ m\3\] Qualify for an LMP?
m\3\]
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Bellefonte I *.......................... 10-003-1003 2.073644135 0.106888873 19 30.1 Yes.
MLK..................................... 10-003-2004 1.67332 0.082025 20 31.1 Yes.
RT 9 *.................................. 10-003-1008 2.774887 0.152466 18 28.4 Yes.
Newark *................................ 10-003-1012 2.588436 0.130729 20 29.2 Yes.
Lums Pond *............................. 10-003-1007 1.1401754 0.0647827 18 31.8 Yes.
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\a\ Taken from ``EPA_DE LMP Criteria Data Analysis (Site Specific)'' spreadsheet found in the docket of this rulemaking.
NAAQS = 35 [micro]g/m\3\.
tc = 1.533.
* Fails to meet PM2.5-design value data completeness rules.\21\
As discussed in section III in this document below, due to the air
quality and VMT trends, the EPA is proposing to conclude that it would
be unreasonable to expect that the area will experience growth in motor
vehicle emissions sufficient to cause a violation of the 2006 24-hour
PM<INF>2.5</INF> NAAQS over the second maintenance period. As discussed
in further sections of this document, the EPA proposes to find that
Delaware's LMP for the New Castle County portion of the Philadelphia
Area includes all the necessary components, so we are proposing to
approve the second LMP as a revision to the Delaware SIP.
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\21\ In accordance with 40 CFR part 50, appendix N, each quarter
of a three-year period must be >75% complete for the entire three-
year Design Value to be considered >75% complete.
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B. Attainment Emissions Inventories
States that qualify for an LMP must still meet the other elements
of a maintenance plan, as articulated in the Calcagni Memorandum. This
includes an attainment year emissions inventory consistent with the
EPA's most recent guidance on emission inventories for nonattainment
areas.\22\ Delaware has developed emission inventories that meet the
criterion of 172(c)(3) every three years since 1990. For the second 10-
year maintenance plan for the New Castle County portion of the
Philadelphia Area, Delaware provided an emissions inventory consistent
with the EPA's most recent guidance from the latest comprehensive,
accurate inventory of actual emissions from all sources of
NO<INF>X</INF>, PM<INF>2.5</INF>, and SO<INF>2</INF> in the calendar
year 2017, which was the latest inventory at the time of development of
the LMP. Delaware postponed proposal of their second maintenance plan,
originally scheduled for September 2, 2022, due to the EPA's
development of the PM<INF>2.5</INF> LMP guidance. On October 27, 2022,
the EPA released the PM<INF>2.5</INF> LMP guidance, so Delaware updated
their original LMP draft to align with the guidance. Meanwhile, the
2020 National Emissions Inventory (NEI) was released on July 31, 2023.
Delaware proposed the LMP for approval at the state level on January
23, 2024, and finalized their approval on March 12, 2024. On April 15,
2024, Delaware submitted the LMP to the EPA. This timeline indicates
that
[[Page 52295]]
for the majority of the development of the LMP, Delaware was using the
most recently available emissions data, the 2017 NEI, originally
released in April 2020, with an updated final release in January 2021.
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\22\ The guidance document titled ``Emissions Inventory Guidance
for Implementation of Ozone and Particulate Matter National Ambient
Air Quality Standards (NAAQS) and Regional Haze Regulations'' can be
found at <a href="http://www.epa.gov/sites/default/files/2017-07/documents/ei_guidance_may_2017_final_rev.pdf">www.epa.gov/sites/default/files/2017-07/documents/ei_guidance_may_2017_final_rev.pdf</a>.
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Table 4 in this document includes the following four categories
from the 2008 and 2017 inventories for direct PM<INF>2.5</INF> and its
precursors (NO<INF>X</INF> and SO<INF>2</INF>): point sources, nonpoint
(area) sources, on-road mobile sources, and nonroad mobile sources.
Table 4--New Castle County 2008 and 2017 Annual Emissions Inventory (tpy) Comparison for PM2.5 \a\, NOX, and SO2 \b\
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Source 2008 Annual (tpy) 2017 Annual (tpy) Percent decrease/increase
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Sector NOX PM2.5 SO2 NOX PM2.5 SO2 NOX PM2.5 SO2
--------------------------------------------------------------------------------------------------------------------------------------------------------
Point.................................................... 5,657 1,109 10,576 2,582 566 551 -54 -49 -95
Nonpoint................................................. 1,287 1,191 402 1,443 1,500 41 12 26 -90
Nonroad.................................................. 4,317 312 1,067 3,074 162 44 -29 -48 -96
Onroad................................................... 9,311 282 94 5,136 150 23 -45 -47 -76
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All Sectors.......................................... 20,572 2,894 12,139 12,235 2,378 659 -41 -18 -95
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\a\ Total primary PM2.5.
\b\ Taken from ``DE LMP Errata 7-2-25'' spreadsheet, found in the docket for this proposed rulemaking.
The redesignation request and first 10-year maintenance plan for
the New Castle County portion of the Philadelphia Area included a 2008
emissions inventory. The emissions of direct PM<INF>2.5</INF> and its
precursors in the New Castle County portion of Philadelphia Area have
decreased substantially between the 2008 and 2017 inventory (18%
decrease in PM<INF>2.5</INF>, 41% decrease in NO<INF>X</INF>, and a 95%
decrease in SO<INF>2</INF>).
C. Air Quality Monitoring Network
Once an area is redesignated, the applicable state or local agency
must continue to operate an appropriate air monitoring network in
accordance with 40 CFR part 58 to verify the attainment status of the
area over the maintenance period. Delaware operates, in accordance with
the requirements of 40 CFR part 58, five PM<INF>2.5</INF> monitors
within the Philadelphia Area.\23\ On June 30, 2023, DNREC submitted its
2023 Annual Monitoring Plan, which the EPA approved on November 17,
2023. Additionally, on June 25, 2024, DNCREC submitted its 2024 Annual
Monitoring Plan, which the EPA approved on November 27, 2024.
Delaware's annual monitoring network plans and the EPA's approval
letters are included in the docket associated with this action.
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\23\ Delaware is in the process of transitioning from manual to
continuous monitors, which are expected to reduce monitor downtime
due to technical/mechanical issues. See Delaware Ambient Air
Monitoring Network Plan at note 15.
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D. Verification of Continued Attainment
Delaware, through DNREC, has the legal authority to enforce and
implement the requirements of the New Castle County portion of the
Philadelphia Area LMP. This includes the authority to adopt, implement,
and enforce any subsequent emissions control contingency measures
determined to be necessary to correct future PM<INF>2.5</INF>
attainment problems.
In demonstrating maintenance, continued attainment of the NAAQS can
be verified through operation of an appropriate air quality monitoring
network. The Calcagni Memorandum states that the maintenance plan
should contain provisions for continued operation of air quality
monitors that will provide such verification. As discussed previously
in section II.C., PM<INF>2.5</INF> is currently monitored by DNREC
within the New Castle County portion of the Philadelphia Area. In
section 2.7 of Delaware's submitted limited maintenance plan, DNREC
committed to continue to conduct ambient PM<INF>2.5</INF> air quality
monitoring in the New Castle County portion of the Philadelphia Area
throughout the term of the second 10-year maintenance period. Delaware
will also track the progress of the maintenance demonstration by
periodically updating the emissions inventory as required by the Air
Emissions Reporting Requirements Rule (AERR), or as required by Federal
regulation during the maintenance plan period. Tracking will include
annual and periodic evaluations for any significant emission increases
above the 2008 attainment year levels.
E. Contingency Provisions
CAA section 175A(d) states that a maintenance plan must include
contingency provisions, as necessary, to ensure prompt correction of
any violation of the relevant NAAQS which may occur after redesignation
of the area to attainment. As explained in the Calcagni Memorandum,
these contingency provisions are an enforceable part of the federally
approved SIP. The maintenance plan should clearly identify the events
that would ``trigger'' the adoption and implementation of a contingency
provision, the contingency provision(s) that would be adopted and
implemented, and the schedule indicating the timeframe by which the
state would adopt and implement the provision(s). The Calcagni
Memorandum states that the EPA will determine the adequacy of a
contingency plan on a case-by-case basis. At a minimum, the plan must
require that the state implement all measures contained in the CAA part
D nonattainment plan for the area prior to redesignation.
In Delaware's PM<INF>2.5</INF> LMP submission, DNREC included
maintenance plan contingency provisions to ensure the area will
continue to meet the 2006 PM<INF>2.5</INF> NAAQS. The submission
describes a process and a timeline to identify, evaluate, and select
the appropriate contingency measure(s) from a list of measures in the
event of a violation of the PM<INF>2.5</INF> NAAQS. Delaware commits to
two levels of contingency response that may be implemented to reduce
emissions, a ``warning level response'' and an ``action level
response.'' A warning level response is prompted whenever the 98th
percentile 24-hour PM<INF>2.5</INF> concentration of 35.5 [mu]g/m\3\ or
greater occurs in a single calendar year within New Castle County and/
or the New Castle County, Delaware maintenance area total
PM<INF>2.5</INF>, NO<INF>X</INF> and SO<INF>2</INF> emissions increase
more than 10% above the levels in the 2008 attainment year emissions
inventory. An action level response is triggered whenever a three-year
average of the 98th percentile (DV) 24-hour PM<INF>2.5</INF>
concentration of 35.5 [mu]g/m\3\ or greater occurs within New Castle
County.
[[Page 52296]]
Should a warning level response be triggered, measures that can be
implemented in a short time will be selected in order to be in place
within 30 months from the close of the calendar year that prompted the
warning level. Should an action level response be triggered,
implementation of necessary control measures will take place as
expeditiously as possible, but in no event later than 30 months after
the certification of a NAAQS violation. Within three months of
certification, Delaware will identify and quantify the emissions
reductions expected to result in the future from existing and future
state and federal regulatory measures. Within six months of
certification, Delaware will use the best available air quality
modeling to evaluate the air quality improvement expected to result in
New Castle County from the measures and emissions reductions identified
below. Within nine months, Delaware will draft any needed permit
conditions or SIP regulations, and within 12 months, Delaware will
complete the rulemaking or permit revision process and submit to the
EPA.
Delaware's potential contingency measures include the following:
(1) working with local metropolitan planning organizations (MPOs) to
implement transportation control measures, (2) vehicle inspection and
maintenance measures enhancements, (3) alternative fuel and additional
diesel retrofit programs for fleet vehicle operations, (4) require
NO<INF>X</INF> or SO<INF>2</INF> emission offsets for new and modified
major sources, (5) increase the ratio of emission offsets required for
new sources, (6) require NO<INF>X</INF> or SO<INF>2</INF> controls on
new minor sources, and (7) require increased recovery efficiency at
sulfur recovery plants.
III. Transportation Conformity
Transportation conformity is required by section 176(c) of the CAA.
Transportation conformity for the purposes of the SIP means that
transportation activities will not cause or contribute to new air
quality violations, worsen existing violations, or delay timely
attainment of the NAAQS or any required interim emission reductions or
other milestones in any area. See CAA 176(c)(1)(A) and (B). While
qualification for the LMP option does not exempt an area from the need
to determine transportation conformity, in an area with an adequate or
approved LMP, transportation conformity may be demonstrated without a
regional emissions analysis for the relevant NAAQS and pollutant (40
CFR 93.109(e)). An LMP must demonstrate that it is unreasonable to
expect that the qualifying areas would experience so much growth in on-
road motor vehicle emissions during the maintenance period that a
violation of the relevant NAAQS would occur. See 40 CFR 93.109(e).
Hence, because no such impact is expected, areas with LMPs are not
required to do a regional emissions analysis as part of a
transportation conformity determination. See 40 CFR 93.109(e).
Therefore, an LMP does not include a motor vehicle emissions budget.
The PM<INF>2.5</INF> LMP Guidance notes that an LMP may be
particularly appropriate for a second maintenance plan, as the area
will have demonstrated attainment of the PM<INF>2.5</INF> NAAQS for at
least 8 years. To demonstrate that it would be unreasonable to expect
that the area would experience enough motor vehicle growth for a NAAQS
violation to occur, the guidance states that an LMP submission for an
area's second maintenance plan should address the area's
PM<INF>2.5</INF> air quality trends and the historical and projected
vehicle miles traveled (VMT). To determine whether it would be
unreasonable to expect that the area would experience sufficient motor
vehicle emissions growth in the remaining maintenance period for a
violation of the NAAQS to occur as required by 40 CFR 93.109(e),
Delaware submitted both air quality data and VMT trend data for the New
Castle County portion of the Philadelphia Area. As shown in table 2 of
this document, design values for the New Castle County portion of the
Philadelphia Area have remained well below the NAAQS since the 2014-
2016 monitoring period. Additionally, as shown in table 4 of this
document, the on-road mobile emissions, when comparing 2008 to 2017,
decreased significantly for NO<INF>X</INF> and PM<INF>2.5</INF> (45%
and 47%).
Delaware's Division of Air Quality also assessed historical and
future projected VMT to determine VMT growth trends. The VMT
projections considered by Delaware were based on transportation models
provided by the Delaware Department of Transportation (DelDOT). DelDOT
used MOVES3 \24\ (Motor Vehicle Emission Simulator) runs using the most
recent 10 years of Highway Performance Monitoring System (HPMS) data
for New Castle County. Delaware's Division of Air Quality used the
annual growth rate from 2013-2019 (pre-COVID) to extrapolate the VMT
for the 10-year period addressed by the LMP (2025-2035). The
extrapolated VMT projects an 18.59 percent increase in VMT over the 10-
year LMP period. \25\ Delaware's Division of Air Quality performed a
motor vehicle analysis to determine whether increased emissions from
on-road mobile sources could, over the 10-year period, increase PM
concentrations in the area and threaten the assumption of maintenance
that underlies the LMP. If the mobile design value (M) is less than or
equal to the margin of safety (MOS), it demonstrates that an increase
in vehicle miles travelled, or other mobile emissions is unlikely to
negatively impact air quality. Based on Delaware's Division of Air
Quality's results, the value of M (8.2 [micro]g/m\3\) is less than the
MOS (13.4 [micro]g/m\3\), which therefore qualifies for the LMP.
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\24\ EPA's MOVES3 Technical Guidance: Using MOVES to Prepare
Emission Inventories for State Implementation Plans and
Transportation Conformity is located in the EPA's guidance portal at
<a href="http://www.epa.gov/state-and-local-transportation/policy-and-technical-guidance-state-and-local-transportation">www.epa.gov/state-and-local-transportation/policy-and-technical-guidance-state-and-local-transportation</a>.
\25\ Taken from ``DE LMP Errata 7-2-25'' found in the docket for
this proposed rulemaking.
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The EPA is proposing to conclude that the VMT growth rate of 18.59
percent between the 10-year LMP period (2025-2035) would not cause an
exceedance of the CDV of 30.3ug/m\3\ in table 3 of this document. Given
the results of the motor vehicle analysis and the downward trend of
PM<INF>2.5</INF> concentrations as shown in table 4 in this document,
the state has adequately demonstrated that it would be unreasonable to
expect that this area will experience growth in motor vehicle emissions
sufficient to cause a violation of the 2006 24-hour PM<INF>2.5</INF>
NAAQS, and therefore, the New Castle County portion of the
Philadelphia-Wilmington, PA-NJ-DE area would qualify for the LMP
option.\26\
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\26\ See table 3 in ``DE LMP Errata 7-2-25'' found in the docket
for this proposed rulemaking.
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For areas with an approved or adequate LMP, transportation plan and
transportation improvement program (TIP) conformity determinations that
meet applicable requirements continue to be required in these areas
(see table 1 in 40 CFR 93.109). Additionally, project-level conformity
determinations must continue to be completed according to all
applicable requirements for federally supported highway and transit
projects, including the hot-spot requirements for projects in
PM<INF>2.5</INF> nonattainment and maintenance areas.
In addition to these proposed actions, the EPA is notifying the
public that the Agency is initiating the adequacy process for the New
Castle County portion of the Philadelphia-Wilmington, PA-NJ-DE area
LMP. See 40 CFR 93.118(e)(4) for the criteria the EPA considers, and 40
CFR 93.118(f)(2) for
[[Page 52297]]
the process the EPA follows. Since LMPs do not include motor vehicle
emissions budgets, in the case of an LMP, the EPA's adequacy review is
to assess whether the demonstration required by 40 CFR 93.109(e) is
met. Any comments on the adequacy of the submitted Delaware LMP should
be submitted to the docket established for this rulemaking. It is
important to note that the New Castle County portion of the
Philadelphia Area has approved motor vehicle emission budgets for
NO<INF>X</INF> and direct PM<INF>2.5</INF> for the year 2025 from the
first maintenance plan that must continue to be met in any
transportation conformity determination made through the year 2025.\27\
In addition, project-level conformity requirements as well as the other
transportation conformity criteria continue to apply with respect to
the 2006 PM<INF>2.5</INF> NAAQS for conformity determinations that
occur through the maintenance period, i.e., through 2034.\28\ The EPA
will complete the adequacy determination process either in the final
action on this proposal or by notifying the State in writing,
publishing a notice in the Federal Register and by posting the finding
on the EPA's adequacy web page. See 40 CFR 93.118(f).
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\27\ See 79 FR 45350, August 5, 2014.
\28\ See 40 CFR 93.102(b)(4) and Transportation Conformity
Guidance for Areas Reaching the End of the Maintenance Period
(October 2014, EPA-420-B-14-093).
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IV. General Conformity
The general conformity regulations of November 30, 1993 (58 FR
63214), as amended, apply within nonattainment areas and redesignated
attainment areas operating under maintenance plans (i.e., maintenance
areas). General conformity requires conformity to the purpose of a SIP,
which means that Federal activities not related to transportation
plans, programs, and projects (i.e., general Federal activities) will
not cause or contribute to any new violation of any standard in any
area, increase the frequency or severity of any existing violation of
any standard in any area, or delay timely attainment of any standard or
any required interim emission reductions or other milestones in any
area (CAA section 176(c)(1)(A) and (1)(B)). As noted in the
PM<INF>2.5</INF> LMP Guidance, the EPA's general conformity regulations
do not distinguish between maintenance areas with an approved ``full
maintenance plan'' and those with an approved LMP. Thus, maintenance
areas with an approved LMP are subject to the same general conformity
requirements under 40 CFR part 93 subpart B, as those covered by a
``full maintenance plan.'' Nothing less than full compliance with the
general conformity program is required within an LMP.
V. Proposed Action
The EPA is proposing to approve the second 10-year limited
maintenance plan for the New Castle County Portion of the Philadelphia-
Wilmington, PA-NJ-DE 2006 24-hour PM<INF>2.5</INF> maintenance area
submitted by DNREC on April 15, 2024. The EPA has reviewed the air
quality data for this area and the Agency has determined that: (1) the
area continues to show attainment of the PM<INF>2.5</INF> NAAQS; and
(2) the area qualifies for an LMP, as described in this action, and has
met the CAA's requirement for a second 10-year maintenance plan. The
EPA is soliciting public comments on the issues discussed in this
document. These comments will be considered before taking final action.
If finalized, the EPA's approval of this LMP will satisfy the CAA
section 175A requirements for the second 10-year maintenance period.
The EPA is also initiating the process to determine if the LMP is
adequate for transportation conformity purposes. As discussed in
section III of this document, the EPA may complete that process either
in its final action on the LMP or through a separate process provided
for in the transportation conformity regulations. See 40 CFR 93.118(f).
VI. Statutory and Executive Order Reviews
Under the Clean Air Act, the Administrator is required to approve a
SIP submission that complies with the provisions of the Clean Air Act
and applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a).
Thus, in reviewing SIP submissions, the EPA's role is to approve state
choices, provided that they meet the criteria of the Clean Air Act.
Accordingly, this action merely approves state law as meeting Federal
requirements and does not impose additional requirements beyond those
imposed by state law. For that reason, this action:
<bullet> Is not a significant regulatory action subject to review
by the Office of Management and Budget under Executive Orders 12866 (58
FR 51735, October 4, 1993); and 13563 (76 FR 3821, January 21, 2011);
<bullet> Executive Order 14192 (90 FR 9065, February 6, 2025) does
not apply because SIP actions are exempted from review under Executive
Order 12866.;
<bullet> Is certified as not having a significant economic impact
on a substantial number of small entities under the Regulatory
Flexibility Act (5 U.S.C. 601 et seq.);
<bullet> Does not contain any unfunded mandate or significantly or
uniquely affect small governments, as described in the Unfunded
Mandates Reform Act of 1995 (Pub. L. 104-4);
<bullet> Does not have federalism implications as specified in
Executive Order 13132 (64 FR 43255, August 10, 1999);
<bullet> Is not subject to Executive Order 13045 (62 FR 19885,
April 23, 1997) because it approves a state program;
<bullet> Is not a significant regulatory action subject to
Executive Order 13211 (66 FR 28355, May 22, 2001); and
<bullet> Is not subject to requirements of section 12(d) of the
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272
note) because application of those requirements would be inconsistent
with the Clean Air Act.
In addition, this proposed rulemaking, regarding the second 10-year
PM<INF>2.5</INF> limited maintenance plan for the New Castle County
portion of the Philadelphia-Wilmington, PA-NJ-DE 2006 24-hour
PM<INF>2.5</INF> maintenance area, does not have tribal implications as
specified by Executive Order 13175 (65 FR 67249, November 9, 2000),
because the SIP is not approved to apply in Indian country located in
the State, and the EPA notes that it will not impose substantial direct
costs on tribal governments or preempt tribal law.
List of Subjects in 40 CFR Part 52
Environmental protection, Air pollution control, Incorporation by
reference, Particulate matter, Reporting and recordkeeping
requirements.
Amy Van Blarcom-Lackey,
Regional Administrator, Region III.
[FR Doc. 2025-20418 Filed 11-19-25; 8:45 am]
BILLING CODE 6560-50-P
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This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.