[Federal Register Volume 83, Number 194 (Friday, October 5, 2018)]
[Notices]
[Pages 50444-50473]
[FR Doc No: 2018-20854]

Vol. 83

Friday,

No. 194

October 5, 2018

Part II

 Environmental Protection Agency

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Response to Clean Air Act Section 126(b) Petitions From Delaware and
Maryland; Notice

Federal Register / Vol. 83 , No. 194 / Friday, October 5, 2018 /
Notices

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ENVIRONMENTAL PROTECTION AGENCY

[EPA-HQ-OAR-2018-0295; FRL-9984-32-OAR]
RIN 2060-AT40, 2060-AT39, 2060-AT38, 2060-AT37, 2060-AT36

Response to Clean Air Act Section 126(b) Petitions From Delaware
and Maryland

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of final action on petition.

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SUMMARY: The Environmental Protection Agency (EPA) is denying four
petitions submitted by the state of Delaware and one petition submitted
by the state of Maryland under Clean Air Act (CAA or Act) section
126(b). The petitions were submitted between July and November 2016.
Each of Delaware's four petitions requested that the EPA make a finding
that emissions from individual sources in Pennsylvania or West Virginia
are significantly contributing to Delaware's nonattainment of the 2008
and 2015 8-hour ozone national ambient air quality standards (NAAQS).
Maryland's petition requested that the EPA make a finding that
emissions from 36 electric generating units in Indiana, Kentucky, Ohio,
Pennsylvania, and West Virginia are significantly contributing to ozone
levels that exceed the 2008 8-hour ozone NAAQS in Maryland, and,
therefore, are interfering with nonattainment and maintenance of the
2008 ozone NAAQS. The EPA is denying the petitions based on the best
information available to the agency at this time, and particularly in
light of an existing regulation already addressing emissions from these
facilities: The Cross-State Air Pollution Rule Update for the 2008
ozone NAAQS (CSAPR Update). The EPA's denial finds that Delaware has
not demonstrated that the named sources emit or would emit in violation
of the CAA's ``good neighbor'' provision. Further, the agency's
independent analysis indicates that the identified sources in
Delaware's and Maryland's petitions do not currently emit and are not
expected to emit pollution in violation of the good neighbor provision
for either the 2008 or 2015 ozone NAAQS.

DATES: This final action is effective on October 5, 2018.

ADDRESSES: The EPA has established a docket for this action under
Docket ID No. EPA-HQ-OAR-2018-0295. All documents in the docket are
listed and publicly available at http://www.regulations.gov. Although
listed in the index, some information is not publicly available, i.e.,
Confidential Business Information or other information whose disclosure
is restricted by statute. Certain other material, such as copyrighted
material, is not placed on the internet and will be publicly available
only in hard copy form. Publicly available docket materials are
available either electronically in the docket or in hard copy at the
EPA Docket Center, William Jefferson Clinton (WJC) West Building, Room
3334, 1301 Constitution Avenue NW, Washington, DC. The Public Reading
Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday,
excluding legal holidays. The telephone number for the Public Reading
Room is<PHONE_NUMBER>, and the telephone number for the Office of Air
and Radiation Docket and Information Center is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT: Questions concerning this final action
should be directed to Mr. Lev Gabrilovich, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Air
Quality Policy Division, Mail Code C539-01, Research Triangle Park, NC
27711, telephone<PHONE_NUMBER>; email at [email protected].

SUPPLEMENTARY INFORMATION: The information in this document is
organized as follows:

I. Executive Summary of the EPA's Decision on CAA Section 126(b)
Petitions From Delaware and Maryland
II. Background
    A. Ozone and Public Health
    B. The CAA Section 126(b) Petitions From Delaware
    C. The CAA Section 126(b) Petition From Maryland
    D. Summary of the EPA's May 31, 2018, Proposal
    E. Historical Regional Analyses of Good Neighbor Obligations
Related to Ozone
III. CAA Sections 126 and 110 and Standard of Review for This Action
    A. Statutory Authority Under CAA Sections 126 and
110(a)(2)(D)(i)(I)
    B. Reasonableness of Applying the Four-Step Transport Framework
for This Action
IV. The EPA's Final Response to Delaware's and Maryland's CAA
Section 126(b) Petitions
    A. The EPA's Evaluation of Whether the Petitions Are Sufficient
To Support a CAA Section 126(b) Finding
    B. The EPA's Independent Analysis of the Petitions Consistent
With the CSAPR Update
V. Determinations Under CAA Section 307(b)(1)
VI. Statutory Authority

I. Executive Summary of the EPA's Decision on CAA Section 126(b)
Petitions From Delaware and Maryland

    In 2016, the states of Delaware and Maryland submitted a total of
five petitions requesting that the EPA make findings pursuant to CAA
section 126(b) that emissions from numerous upwind sources
significantly contribute to nonattainment and/or interfere with
maintenance of the ozone NAAQS in violation of CAA section
110(a)(2)(D)(i)(I), otherwise known as the ``good neighbor'' provision.
Delaware submitted four petitions, each alleging good neighbor
violations by individual sources located in Pennsylvania or West
Virginia with respect to the 2008 and 2015 ozone NAAQS. Maryland
submitted a single petition alleging good neighbor violations by 36
electric generating units (EGUs) in five states with respect to the
2008 ozone NAAQS. On May 31, 2018, the EPA issued a proposal to deny
all five CAA section 126(b) petitions. 83 FR 26666 (June 8, 2018). The
agency solicited comments on the proposal and hosted a public hearing
on June 22, 2018, where nine speakers testified. The EPA also received
117 written comments submitted to the docket on the proposed denial.
This Federal Register notice addresses certain significant comments the
agency received. The remaining comments are addressed in the Response
to Comments (RTC) document available in the docket for this action.
    As described in further detail in this notice, the EPA is
finalizing the denial of the CAA section 126(b) petitions submitted by
the states of Delaware and Maryland. Generally, the Delaware and
Maryland petitions (and commenters who were supportive of the EPA's
granting these petitions) suggest that Delaware and Maryland residents
are exposed to unhealthy levels of ground-level ozone pollution. They
identify certain EGUs in upwind states, most with post-combustion
nitrogen oxides (NOX) controls,\1\ that historically were
not optimally operating for pollution abatement. The petitions ask EPA
to impose federally enforceable short-term, rate-based emissions limits
on these EGUs to ensure that the NOX controls are optimally
operated. The EPA proposed to deny these petitions in May of 2018, and
has considered public

comments on that proposal in crafting this final action.
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    \1\ In the case of one facility, Brunner Island Steam Generating
Station in Pennsylvania, Delaware cites, the facility's ability to
combust natural gas in electricity generation and thereby reduce
NOX relative to combusting coal at the facility.
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    Consistent with the EPA's proposal and based on the best data
available to the agency at this time, the agency is finalizing its
denial of these petitions. The EPA's denial for Delaware is based on
its findings that air quality modeling of ozone levels in 2017 from the
Cross-State Air Pollution Rule Update for the 2008 Ozone NAAQS \2\
(CSAPR Update) and more recent air quality modeling of ozone levels in
2023 show no air quality problems in the state with regard to the 2008
and 2015 ozone NAAQS, respectively. For both the Delaware and Maryland
petitions, the EPA's denial is also based on the fact that the agency
has already evaluated the ozone transport issues and NOX
control strategies raised in the petitions and finalized the CSAPR
Update to implement the NOX control strategies achievable in
states upwind of Delaware and Maryland, including at the specific EGUs
named in both Delaware's and Maryland's petitions. 81 FR 74504.
Although the CSAPR Update only explicitly addressed the 2008 ozone
NAAQS, the EPA's conclusion in that action as to the control strategies
available at the named sources is relevant to its analysis of
Delaware's and Maryland's petitions with regard to both the 2008 ozone
NAAQS (addressed in all five petitions) and the 2015 ozone NAAQS
(addressed in the Delaware petitions) because the EPA's determination
that the cost-effective control strategy is already being implemented
at the named sources in the context of the CSAPR allowance trading
program applies regardless of which NAAQS is being addressed, as
explained below.
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    \2\ 81 FR 74504 (October 26, 2016).
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    Because the CSAPR Update is a final rule in which the EPA has
evaluated substantially the same environmental issues and concerns as
those that Delaware and Maryland raise in their CAA section 126(b)
petitions, the agency has reviewed those petitions in light of, among
other factors, the CSAPR Update record analysis and the findings made
therein. In doing so, the EPA found that the named EGUs do not have
further cost-effective \3\ NOX reduction potential beyond
the level of NOX control stringency already finalized in the
CSAPR Update emissions budgets. In other words, the agency determines
that the CSAPR Update appropriately quantified the cost-effective
NOX reduction potential from the EGUs named in the CAA
section 126(b) petitions and the EPA does not find any further
NOX reductions that may be available from these EGUs at more
stringent levels of NOX control to be cost effective
considering additional relevant factors such as NOX
reduction potential and air quality impacts.
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    \3\ In the CSAPR Update, the EPA evaluated several levels of EGU
NOX control stringency and represented those levels using
an estimated marginal cost per ton of NOX reduced. The
final CSAPR Update action selected the level of control stringency
that included operating and optimizing existing SCR post-combustion
controls, installing state-of-the-art NOX combustion
controls, and shifting generation to existing units with lower
NOX emission rates within the same state. This level of
NOX control stringency was represented by a marginal cost
of $1,400 per ton. In other words, the agency considered these
NOX reduction strategies to be cost effective at marginal
cost of $1,400 per ton. The EPA selected this level of control
stringency by applying a multi-factor test, which indicated that
this level of control stringency maximized NOX reductions
and air quality improvement relative to cost, as compared to the
other control levels evaluated.
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    Further, the EPA finds that the CSAPR Update is, in fact,
controlling emissions from the named EGUs specifically and from all
EGUs collectively in the named upwind states that impact ozone
concentrations in Delaware and Maryland. Based on the 2017 ozone season
emissions data, the CSAPR Update reduced regional ozone season
NOX emissions by approximately 77,000 tons (21 percent) from
2016 levels. Additionally, the average 2017 ozone season NOX
emissions rate across the EGUs named in the Delaware or Maryland
petitions was 0.116 pounds/one million British thermal units (lbs/
mmBtu) compared with average rates of 0.257 and 0.208 lbs/mmBtu in 2015
and 2016, respectively. Thus, the best data that the agency has
available at this time--2017 emissions data--indicate that the CSAPR
Update ozone season allowance trading program is reducing summer-time
NOX emissions and these data suggest that the units named in
the CAA section 126(b) petitions are collectively controlling their
NOX emissions consistent with the NOX control
strategies identified in the petitions.
    The agency does not at this time find adequate technical or legal
grounds for granting the Delaware or Maryland CAA section 126(b)
petitions in light of the existing and effective CSAPR Update
regulation. The agency, therefore, denies these petitions due to the
lack of further cost-effective controls relative to the emissions
reductions already required by the CSAPR Update and based on the best
available information--2017 emissions data--indicating that the CSAPR
Update is being appropriately implemented to reduce NOX
emissions regionally and from the named EGUs. The EPA also notes
several technical deficiencies in the Delaware analyses. As further
described in this notice, the EPA is, therefore, denying Delaware's
petitions based on the petitioner's failure to meet its burden under
CAA section 126(b) to establish a basis for the finding requested. The
EPA additionally is denying both Delaware's and Maryland's petitions
based on the agency's own independent analysis of the interstate
transport of ozone pollution conducted for the CSAPR Update, which
rebuts several assertions in these petitions, as well as additional
technical analysis regarding current unit operations. Finally, the EPA
is also denying Delaware's petitions for the 2015 ozone NAAQS based on
its own recent analyses projecting emissions levels to a relevant
future year, which found no expected nonattainment or maintenance
problems in Delaware for that NAAQS. In making this final decision, the
EPA reviewed the incoming petitions, the public comments received, the
relevant statutory authorities, and other relevant materials.
Accordingly, the EPA denies the CAA section 126(b) petitions from
Delaware and Maryland.
    The remainder of this notice is organized as follows: Section II of
this notice provides background information, a summary of the relevant
issues raised in Delaware's and Maryland's CAA section 126(b)
petitions, and a summary of the EPA's May 31, 2018, proposed action;
Section III of this notice provides information regarding the EPA's
approach to addressing the interstate transport of ozone and the
statutory authority under CAA sections 110(a)(2)(D)(i) and 126(b); and
Section IV of this notice details the basis for the EPA's final action
to deny these petitions, including responses to significant comments
received on the proposal.

II. Background

A. Ozone and Public Health

    Ground-level ozone is not emitted directly into the air but is a
secondary air pollutant created by chemical reactions between
NOX and volatile organic compounds (VOCs) in the presence of
sunlight. These precursor emissions can be transported downwind
directly or, after transformation in the atmosphere, as ozone. As a
result, ozone formation, atmospheric residence, and transport can occur
on a regional scale (i.e., hundreds of miles). For further discussion
of ozone-formation chemistry, the regional nature of interstate
transport of ozone pollution, and health effects, see the CSAPR Update,
81 FR 74513-14.

    On March 12, 2008, the EPA promulgated a revision to the ozone
NAAQS, lowering both the primary and secondary standards to 75 parts
per billion (ppb).\4\ On October 1, 2015, the EPA further revised the
ground-level ozone NAAQS to 70 ppb.\5\
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    \4\ See National Ambient Air Quality Standards for Ozone, Final
Rule, 73 FR 16436 (March 27, 2008).
    \5\ See National Ambient Air Quality Standards for Ozone, Final
Rule, 80 FR 65292 (October 26, 2015).
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B. The CAA Section 126(b) Petitions From Delaware

    In 2016, the state of Delaware, through the Delaware Department of
Natural Resources and Environmental Control (Delaware), submitted four
petitions alleging that emissions from the Conemaugh Generating Station
(Conemaugh), the Homer City Generating Station (Homer City), and the
Brunner Island Steam Generating Station (Brunner Island) in
Pennsylvania, and the Harrison Power Station (Harrison) in West
Virginia, significantly contribute to exceedances of the 2008 and 2015
8-hour ozone NAAQS in the state of Delaware.\6\
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    \6\ See Petitions from the state of Delaware under CAA section
126(b) requesting that the EPA find that Conemaugh, Homer City,
Brunner Island, and Harrison are emitting air pollutants in
violation of the provisions of CAA section 110(a)(2)(D)(i) of the
CAA with respect to the 2008 and the 2015 ozone NAAQS, available in
the docket for this action.
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    The petitions identify a total of 59 exceedance days in Delaware
for the 2008 ozone NAAQS in the six ozone seasons between 2010 and
2015. Furthermore, Delaware contends that if the 2015 8-hour ozone
NAAQS had been in effect during this period, Delaware would have
experienced a total of 113 exceedance days in those ozone seasons. As
discussed in Section III.D of the proposal, each of the Delaware
petitions alleges that an individual source significantly contributes
to nonattainment of the 2008 and 2015 8-hour ozone NAAQS in Delaware
based on two common arguments. First, all four petitions allege that
the EPA's modeling conducted in support of the CSAPR Update shows that
the states in which these sources are located contribute one percent or
more of the 2008 8-hour ozone NAAQS to ozone concentrations in
Delaware. Second, all four petitions point to additional modeling to
support these same claims. The Brunner Island and Harrison petitions
cite an August 6, 2015 technical memorandum from Sonoma Technology,
Inc. (STI), which describes contribution modeling results. The
Conemaugh and Homer City petitions cite to October 24, 2016 modeling
documentation from the Comprehensive Air Quality Model with Extensions
(CAMx), but Delaware did not submit this documentation with its
petitions or otherwise provide it to the EPA. Based on the August 6,
2015 technical memorandum from STI and the October 24, 2016 CAMx
modeling documentation, the petitions claim that all four named sources
had modeled contributions above one percent of the 2008 8-hour ozone
NAAQS to locations in Delaware on select days during the 2011 ozone
season.\7\
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    \7\ See 83 FR 26670.
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    All four petitions contend that the absence of short-term
NOX emissions limits cause the named sources to
significantly contribute to Delaware's nonattainment of the 2008 and
2015 ozone NAAQS. The petitions ask the EPA to implement short-term
NOX emissions limits as a remedy under CAA section 126(c) to
ensure optimal operation at these units. The petitions identify
existing regulatory programs aimed at limiting NOX emissions
at the sources but argue that these programs are not effective at
preventing emissions from significantly contributing to downwind air
quality problems in Delaware. In the case of Brunner Island, Homer
City, and Conemaugh, Delaware argues that the Pennsylvania regulations
addressing the reasonable available control technology (RACT)
requirements for NOX \8\ include a 30-day averaging period
for determining compliance with emissions rates, which will allow the
facilities to emit above the rate limit on specific days while still
meeting the 30-day average limit. Furthermore, the state argues that,
although all four facilities named in their petitions have been subject
to several NOX emissions allowance trading programs that
effectively put a seasonal NOX emissions mass cap on the
fleet of subject units, the subject units are not required to limit
their NOX emissions over any particular portion of the ozone
season as long as they are able to obtain sufficient NOX
allowances to cover each unit's actual ozone season NOX mass
emissions. The state alleges that the sources have, therefore, been
able to comply with the allowance trading program requirements without
having to make any significant reductions in their ozone season average
NOX emissions rates.
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    \8\ Additional RACT Requirements for Major Sources of NOX and
VOC; 25 Pa Code 129.96-100 (also known as the ``RACT II rule'').
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    Notably, each of the facilities is equipped with combustion and/or
post-combustion controls. Harrison is equipped with low NOX
burners (LNBs), overfire air (OFA), and selective catalytic reduction
(SCR) for control of NOX emissions at all three coal-fired
units. Homer City is equipped with LNBs, OFA, and SCR for control of
NOX emissions at all three coal-fired units. Conemaugh is
equipped with LNBs, close-coupled and separated overfire air (CC/SOFA),
and SCR for control of NOX emissions at both coal-fired
units. Brunner Island is equipped with LNBs and combustion air controls
and has the ability to burn coal, gas, or both to provide steam to its
generators. Delaware acknowledges that Brunner Island can use natural
gas as fuel at all three units, lowering the units' NOX
emissions, but argues that Brunner Island's ability to also use coal
indicates that, without a short-term NOX emissions limit,
the units will continue to significantly contribute to nonattainment or
interfere with maintenance of the ozone NAAQS in Delaware. In the case
of Conemaugh, Harrison, and Homer City, Delaware similarly contends
that current NOX emissions regulations applicable to sources
in Pennsylvania and West Virginia do not prevent significant
contribution to Delaware's nonattainment of the ozone NAAQS. As
indicated in this notice, these EGUs all have SCR to control
NOX emissions. Delaware argues that a review of emissions
rates since the SCRs were installed indicates that the SCRs were at
times turned off or operated at reduced levels of effectiveness in the
ozone season. Thus, in Delaware's view, these sources also need a
short-term NOX emissions limit to implement effective and
consistent NOX control operation. For more information on
the sources identified in the petitions, see Sections III.D and III.E
of the proposal.
    Subsequent to receiving the petitions, the EPA published notices
extending the statutory deadline for the agency to take final action on
all four of Delaware's CAA section 126(b) petitions. CAA section 126(b)
of the Act requires the EPA to either make a finding or deny a petition
within 60 days of receipt of the petition and after holding a public
hearing. However, any action taken by the EPA under CAA section 126(b)
is subject to the procedural requirements of CAA section 307(d). See
CAA section 307(d)(1)(N). CAA section 307(d) requires the EPA to
conduct notice-and-comment rulemaking, including issuance of a notice
of proposed action, a period for public comment, and a public hearing
before making a final determination whether to make the requested
finding. In light of the time required for notice-and-comment
rulemaking, CAA section 307(d)(10) provides for a time extension,

under certain circumstances, for rulemakings subject to the CAA section
307(d) procedural requirements. In accordance with CAA section
307(d)(10), the EPA determined that the 60-day period for action on
Delaware's petitions would be insufficient for the EPA to complete the
necessary technical review, develop an adequate proposal, and allow
time for notice and comment, including an opportunity for public
hearing. In 2016, the EPA published notices extending the deadlines to
act on all four of Delaware's petitions by 6 months. The notices
extending these deadlines can be found in the docket for this
rulemaking.

C. The CAA Section 126(b) Petition From Maryland

    On November 16, 2016, the state of Maryland, through the Maryland
Department of the Environment, submitted a CAA section 126(b) petition
alleging that emissions from 36 EGUs significantly contribute to ozone
levels that exceed the 2008 ozone NAAQS in Maryland and, therefore,
significantly contribute to nonattainment and interfere with
maintenance of the NAAQS.\9\ These sources are coal-fired EGUs located
in Indiana, Kentucky, Ohio, Pennsylvania, and West Virginia, which
Maryland notes are states that EPA has already determined are
significantly contributing to nonattainment in Maryland under the 2008
ozone NAAQS. Maryland indicates that all of these sources have SCR or
selective non-catalytic reduction (SNCR) to control NOX
emissions. In addition, Maryland's technical support document discusses
modeling conducted by the University of Maryland, which claims to show
that ozone concentrations would be reduced if these EGUs were to
optimize running their SCR and SNCR controls. Maryland argues that
these projected reductions in ozone concentrations at Maryland monitors
demonstrate that optimizing the post-combustion controls at the 36
units with SCR or SNCR would allow Maryland to attain, or come very
close to attaining, the 2008 8-hour ozone NAAQS. Maryland also provides
the results of control optimization modeling scenarios which project
the ozone impacts of optimizing emissions controls in 2018. Maryland
suggests, by way of using its own state regulation as an example, that
optimizing controls means operating controls consistent with
technological limitations, manufacturers' specifications, good
engineering and maintenance practices, and good air pollution control
practices for minimizing emissions.
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    \9\ See Petition to the United States Environmental Protection
Agency Pursuant to Section 126 of the Clean Air Act for Abatement of
Emissions from 36 Coal-Fired Electric Generating Units at 19 Plants
in Five States that Significantly Contribute to Nonattainment of,
and Interfere with Maintenance of, the 2008 Ozone National Ambient
Air Quality Standard in the State of Maryland, available in the
docket for this action.
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    The petition further alleges that Maryland's proposed remedy--
discussed further below--will influence how areas in Maryland and other
Mid-Atlantic states are designated under the new 2015 ozone NAAQS.
According to Maryland, the proposed remedy, if implemented in 2017,
would most likely allow the Baltimore area and the Washington, DC,
multi-state area, which includes portions of Maryland, to both be
designated attainment for the 2015 ozone NAAQS.
    Maryland alleges that, although the 36 named EGUs have existing
post-combustion control mechanisms that should prevent significant
contribution, the facilities have either ceased to operate the controls
regularly during the ozone season or have chosen to operate them in a
sub-optimal manner. Maryland presents an analysis based on 2005-2015
ozone-season data to support this contention.\10\ Maryland argues that
whether controls are optimally run can be determined by comparing
current ozone season average emissions rates to the lowest ozone season
average emissions rate achieved either after 2005 or after the unit
installed SCR or SNCR, whichever is later. Maryland further alleges
that NOX emissions rates at the 36 EGUs have increased
significantly since the SCR and SNCR installation and initial testing,
indicating that these EGUs are not operating their post-combustion
controls efficiently on each day of the ozone season.
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    \10\ Maryland Petition, Appendix A, Part 2, available in the
docket for this action.
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    Maryland also submitted a number of technical memoranda to support
its argument. Maryland submitted analyses of control technology
optimization for coal-fired EGUs in eastern states, which they contend
demonstrate that NOX emissions rates at specific EGUs are
well above what is considered representative of an EGU running post-
combustion controls efficiently; that 2015 and 2016 EPA data show that
many EGUs have not been running their post combustion controls as
efficiently as they have in the past during the ozone season; and that
the EPA should, therefore, ensure these controls are operating during
the 2017 ozone season by including requirements that each named EGU to
minimize emissions by optimizing existing control technologies,
enforced through use of a 30-day rolling average rate.\11\
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    \11\ See id.
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    Maryland also submitted the following documents: A review of its
own NOX regulations for coal fired EGUs; \12\ a study
conducted by Maryland and the University of Maryland regarding regional
ozone transport research and analysis efforts in Maryland; \13\ an
August 6, 2015 STI report alleging that source apportionment modeling
indicates that emissions from Brunner Island (a source not specifically
addressed in Maryland's petition) contribute significantly to ozone
formation in Pennsylvania and neighboring states during the modeled
ozone season; \14\ a list of recommended language for the EPA to
include in federal orders related to the named EGUs to remedy
significant contribution; \15\ and an evaluation of cost savings
Maryland alleges the units have incurred in 2014 by not fully running
their controls compared with the cost of running their controls at full
efficiency.\16\
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    \12\ Id. Appendix B.
    \13\ Id. Appendix C.
    \14\ Id. Appendix D.
    \15\ Id. Appendix E.
    \16\ Id. Appendix F.
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    Maryland supplemented its petition with several further appendices
submitted in 2017. Maryland submitted an additional optimization
analysis comparing NOX emissions rates in 2006, 2015, and
2016 for EGUs listed in its petition; \17\ an analysis comparing 2016
ozone season average emissions rates to the lowest demonstrated ozone
season average emissions rates between 2005 and 2015 at 369 coal-fired
EGUs in 29 states identified as the Eastern Modeling Domain; \18\ an
analysis comparing of average emissions data at 21 units in
Pennsylvania in the first quarter of 2017 to the lowest demonstrated
ozone season average emissions rate between 2005-2016; \19\ and
additional photochemical modeling conducted by the University of
Maryland regarding the impact of the 36 named EGUs in the five upwind
states on ozone concentrations in Maryland, which concludes that
emissions from these units significantly contribute to ozone
concentrations in Maryland and, therefore, contribute to nonattainment
and interfere with the maintenance of the 8-hour ozone NAAQS.\20\
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    \17\ Id. Supplemental Appendix A.
    \18\ Id. Supplemental Appendix B.
    \19\ Id. Supplemental Appendix C.
    \20\ Id. Supplemental Appendix D.
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    Maryland's petition requests a remedy that will compel the named
EGUs to

optimize their SCR and SNCR. Maryland indicates that its petition is
focused on ensuring controls are run at the units every day of the
ozone season. According to Maryland, the CSAPR Update, earlier federal
allowance trading programs, and many state regulations allow for longer
compliance periods, which means that controls do not necessarily need
to be run effectively every day to comply with these requirements.
Maryland claims that this has resulted in situations where sources in
the five upwind states have not run their controls efficiently on many
days with high ozone, and, therefore, these sources are impacting
Maryland in violation of CAA section 110(a)(2)(D)(i)(I). Maryland also
claims that, on some of those days, the 36 EGUs in these states emitted
in the aggregate over 300 more tons of NOX than they would
have if they had run their control technologies efficiently.
Additionally, Maryland states that these days are often the same days
where downwind ozone levels are likely to be highest because of hot,
ozone-conducive weather. Maryland supports its claim by alleging that
over the entire ozone season, the relief requested in its petition
could result in very large reductions. Maryland contends that in 2015,
approximately 39,000 tons of NOX reductions could have been
achieved in the ozone season if the 36 EGUs had simply run their
controls efficiently. Therefore, Maryland states that, based on the
EPA's past approaches to establishing significant contributions based
on cost-effective controls, the NOX emissions from these 36
EGUs must be abated on each day of the ozone season starting in May of
2017.
    Maryland contends that emissions at the 36 named EGUs can be
reduced at reasonable cost, or with potentially no actual new costs to
the EGUs at all,\21\ because this requested remedy rests on the use of
existing control equipment. Maryland suggests two methods to ensure
optimized use of controls at these sources. First, Maryland requests
that the EPA include language in federal and state regulations or
operating permits requiring the owners or operators of the relevant
EGUs to use all installed pollution control technology consistent with
technological limitations, manufacturers' specifications, good
engineering and maintenance practices, and good air pollution control
practices. Second, Maryland requests that the EPA enforce this
requirement by comparing each unit's maximum 30-day rolling average
emissions rate to the unit's lowest reported ozone emissions rate.
Maryland also requests that this remedy be implemented by 2017 to help
areas in Maryland achieve attainment in time to inform area
designations in the state for the 2015 ozone NAAQS.
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    \21\ Although Maryland suggests emissions could potentially be
reduced with no actual new costs to the EGUs, Maryland does not
provide further information supporting its suggestion that zero-cost
reductions may be available. To the contrary, Maryland states that
the cost per ton range would be from $670 to $1,000, depending on
whether the SCR systems are in partial operation or totally idled.
See Maryland Petition Appendix F, available in the docket for this
action.
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    Consistent with CAA section 307(d), as discussed in Section III.D
of the proposal, the EPA determined that the 60-day period for
responding to Maryland's petition is insufficient for the EPA to
complete the necessary technical review, develop an adequate proposal,
and allow time for notice and comment, including an opportunity for
public hearing, on a proposed finding regarding whether the 36 EGUs
identified in the petition significantly contribute to nonattainment or
interfere with maintenance of the 2008 ozone NAAQS in Maryland. On
January 3, 2017, the EPA published a notice extending the deadline for
acting on Maryland's CAA section 126(b) petition to July 15, 2017.\22\
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    \22\ 82 FR 22 (January 3, 2017).
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D. Summary of the EPA's May 31, 2018, Proposal

    In Section IV of the proposal, the EPA explained its bases for
proposing to deny the CAA section 126(b) petitions from Delaware and
Maryland. Given that ozone is a regional pollutant and that the EPA had
recently evaluated regional ozone pollution in the CSAPR Update, the
EPA proposed to evaluate the petition consistent with the same four-
step regional analytic framework--described in more detail in the
following section--that the EPA has used in previous regulatory actions
to evaluate regional interstate ozone transport. Within this framework,
the EPA also proposed to evaluate whether the sources named in the
petitions emit or would emit in violation of the good neighbor
provision based on both current and future anticipated emissions
levels. The EPA identified multiple bases for the proposed denial.
    The EPA noted that the agency's historical approach to evaluating
CAA section 126(b) petitions looks first to see whether a petition,
standing alone, identifies or establishes a technical basis for the
requested CAA section 126(b) finding. 83 FR 26674. In this regard, the
agency proposed to find that several aspects of Delaware's analyses are
insufficient to support Delaware's conclusion that the four sources
named in the petitions emit or would emit in violation of the good
neighbor provision. First, the EPA proposed to find that Delaware does
not provide sufficient information to indicate that there is a current
or expected future downwind air quality problem in the state with
respect to either the 2008 and 2015 ozone NAAQS. Id. at 26676. Second,
the EPA proposed to find that the emissions information Delaware relies
upon for its air quality modeling is not representative of current or
future projected emissions levels at the named EGUs. Id. Third, the EPA
proposed to find that Delaware's analyses regarding ozone contributions
to modeled and/or measured ozone levels are unclear and, therefore,
insufficient to support Delaware's position that the named sources are
significantly contributing to nonattainment or interfering with
maintenance of the NAAQS on specific days. Id. The EPA also proposed to
find that material elements of the analysis provided in Maryland's
petition are technically deficient. Id. at 26677.
    The EPA further proposed to rely on its own independent analysis to
evaluate the requested CAA section 126(b) findings. Id. First, the EPA
proposed to find that its independent analysis provides no basis to
conclude that any of the sources named by Delaware are linked to a
downwind air quality problem with regard to the 2008 ozone NAAQS in
steps one and two of the four-step framework. The EPA explained that,
based on the modeling conducted in support of the CSAPR Update,
Delaware was not projected to have any nonattainment or maintenance
receptors in 2017 with respect to the 2008 ozone NAAQS, and, therefore,
the states named in Delaware's petitions are not linked to a downwind
air quality problem in the state under that standard. Id. at 26678.
Furthermore, both to confirm the projections in the CSAPR Update
modeling and in response to the petition's assertion that current air
quality data show that Delaware has a downwind problem for the 2008
ozone NAAQS, the EPA examined Delaware's 2014-2016 design values and
found that no monitors were violating the 2008 ozone NAAQS. Id. The EPA
also proposed to find that available future year modeling data do not
suggest that Delaware will have air quality problems by the relevant
attainment date for the 2015 ozone NAAQS.
    Second, the EPA evaluated whether there are further cost-effective
NOX emissions reductions available at the specific sources
named in the petitions,

consistent with step three of the four-step framework. For units in the
Delaware and Maryland petitions already equipped with SCRs, the EPA
proposed to determine that the CSAPR Update emissions budgets already
reflect emissions reductions associated with the turning on and
optimizing of existing SCR controls at the EGUs that are the subject of
the petitions for the 2008 ozone NAAQS, which is the same control
strategy identified in the petitions as being both feasible and cost
effective. Id. at 26679. Therefore, the EPA proposed to determine that
all identified cost-effective emission reductions have already been
implemented with respect to these sources, and therefore that those
sources neither emit nor would emit in violation of the good neighbor
provision for the 2008 NAAQS. The EPA proposed to determine that this
conclusion is also appropriate with regard to the 2015 ozone NAAQS for
those sources addressed in the Delaware petitions because the EPA's
determination that the cost-effective control strategy is already being
implemented applies regardless of which NAAQS is being addressed. In
other words, because the strategy of optimizing existing controls
relative to the 2008 ozone NAAQS has already been implemented via the
CSAPR Update for the sources Delaware named for the 2015 NAAQS, the EPA
proposed there are no additional control strategies available to
further reduce NOX emissions at these sources to address
this standard. Id.
    To the extent that the Delaware and Maryland petitions also
identify sources without SCR, the EPA also proposed to deny the
petitions. Maryland cited two sources operating selective non-catalytic
reduction post-combustion controls (SNCR). The EPA proposed to deny
Maryland's petition with respect to these sources based on its
conclusion in the CSAPR Update that fully operating with SNCR is not a
cost-effective NOX emission reduction strategy with respect
to addressing transport obligations for the 2008 ozone NAAQS. The EPA,
therefore, proposed to find that these sources do not emit and would
not emit in violation of the good neighbor provision with respect to
the 2008 ozone NAAQS. Additionally, one of Delaware's petitions alleges
significant contribution from the Brunner Island facility, which
currently has neither SCR nor SNCR installed. The EPA proposed to
determine that an independent step three analysis still provides a
basis for denying Delaware's Brunner Island petition. The EPA explained
that the facility primarily burned natural gas with a low
NOX emission rate in the 2017 ozone season and that the EPA
reasonably expects the facility to continue operating primarily by
burning natural gas in future ozone seasons. Id. at 26680. As such, the
EPA proposed to deny the Brunner Island petition because the agency
found that there are no additional feasible and cost-effective
NOX emission reductions available at Brunner Island.

E. Historical Regional Analyses of Good Neighbor Obligations Related to
Ozone

    As explained in the proposal, given that formation, atmospheric
residence, and transport of ozone occur on a regional scale (i.e.,
hundreds of miles) over much of the eastern United States, the states
and the EPA have historically addressed interstate transport of ozone
pursuant to the good neighbor provision through a series of regional
rulemakings focused on the reduction of NOX emissions. These
rulemakings have included findings that downwind states' problems
attaining and maintaining the ozone NAAQS result, in part, from the
contribution of pollution from multiple upwind sources located in
different upwind states. Specifically, to support each historical
action, an evaluation of the extent of the ozone transport problem
(i.e., the breadth of downwind ozone problems and the contributions
from upwind states) was performed. Historically, these assessments have
found interstate ozone transport to be an interconnected system of
upwind and downwind ozone transport such that a regional trading
program would be effective at implementing the CAA's good neighbor
requirements.\23\
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    \23\ The Supreme Court has also concurred with the EPA's
assessment regarding the complexity and interconnectivity
underpinning ozone transport. See EPA v. EME Homer City Generation,
L.P., 134 S. Ct. 1584, 1593-94 (2014).
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1. Description of the Four-Step Transport Framework
    The EPA has promulgated several transport rulemakings that have
addressed the good neighbor provision, including four addressing
interstate transport with respect to various ozone NAAQS. Each of these
rulemakings essentially followed the same four-step transport framework
to quantify and implement emission reductions necessary to address the
interstate transport requirements of the good neighbor provision. These
steps are:
    (1) Identifying downwind air quality problems relative to the
NAAQS. The EPA has identified downwind areas with air quality problems
(referred to as ``receptors'') considering monitored air quality data,
where appropriate, and air quality modeling projections to a future
compliance year. The EPA has focused its analysis on a future year in
light of the forward-looking nature of the good neighbor obligation in
CAA section 110(a)(2)(D)(i)(I). Specifically, the statute requires that
states prohibit emissions that ``will'' significantly contribute to
nonattainment or interfere with maintenance of the NAAQS in any other
state. The EPA has reasonably interpreted this language as permitting
states and the EPA in implementing the good neighbor provision to
prospectively evaluate downwind air quality problems and the need for
further upwind emissions reductions. See North Carolina v. EPA, 531
F.3d 896, 913-14 (D.C. Cir. 2008) (affirming as reasonable the EPA's
interpretation of ``will'' to refer to future, projected ozone
concentrations). The agency has thus identified areas expected to be in
nonattainment with the NAAQS and those areas that may struggle to
maintain the NAAQS;
    (2) Determining which upwind states are linked to these identified
downwind air quality problems and warrant further analysis to determine
whether their emissions violate the good neighbor provision. In the
EPA's most recent transport rulemakings for the 2008 ozone NAAQS, the
agency identified such upwind states to be those modeled to contribute
at or above a threshold equivalent to one percent of the applicable
NAAQS;
    (3) For upwind states linked to downwind air quality problems,
identifying on a statewide basis emissions (if any) that will
significantly contribute to nonattainment or interfere with maintenance
of a standard, based on cost and air quality factors evaluated in a
multi-factor test. In all four of the EPA's prior rulemakings for
ozone, the agency apportioned emission reduction responsibility among
multiple upwind states linked to downwind air quality problems using
several particular cost- and air quality-based factors to quantify the
reduction in a linked upwind state's emissions that the rulemaking
would require pursuant to the good neighbor provision; and
    (4) For states that are found to have emissions that significantly
contribute to nonattainment or interfere with maintenance of the NAAQS
downwind, implementing the necessary emission reductions within the
state. When the EPA has promulgated federal implementation plans (FIPs)
addressing the good neighbor provision for the ozone NAAQS in prior
transport rulemakings, the EPA has typically required affected sources
in upwind states to participate in allowance trading

programs to achieve the necessary emission reductions.\24\ In addition,
the EPA has also offered states the opportunity to participate in
similar EPA-operated allowance trading programs to achieve the
necessary emission reductions through state implementation plans
(SIPs).
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    \24\ While the EPA has chosen to implement emission reductions
through allowance trading programs for states found to have a
downwind impact, upwind states can choose to submit a SIP that
implements such reductions through other enforceable mechanisms that
meets the requirements of the good neighbor provision, such as the
enforceable mechanisms that petitioners apparently favor and argue
for in their petition.
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2. Prior Regional Rulemakings Under the Good Neighbor Provision
    The EPA's first regional rulemaking regarding interstate transport,
the NOX SIP Call, addressed the 1979 ozone NAAQS. 63 FR
57356 (October 27, 1998). The NOX SIP Call was the result of
the analytic work and recommendations of the Ozone Transport Assessment
Group (OTAG), which was organized by and led by states in consultation
with the EPA and other stakeholders. The EPA used this collaboratively
developed analysis to conclude in the NOX SIP Call that
``[t]he fact that virtually every nonattainment problem is caused by
numerous sources over a wide geographic area is a factor suggesting
that the solution to the problem is the implementation over a wide area
of controls on many sources, each of which may have a small or
unmeasurable ambient impact by itself.'' 63 FR 57356, 57377 (October
27, 1998). The NOX SIP Call promulgated statewide emission
budgets and required upwind states to adopt SIPs that would decrease
their NOX emissions by a sufficient amount to meet these
budgets, thereby prohibiting the emissions that significantly
contribute to nonattainment or interfere with maintenance of the ozone
NAAQS in downwind states. The EPA also promulgated a model rule for a
regional allowance trading program called the NOX Budget
Trading Program that states could adopt in their SIPs as a mechanism to
achieve some or all of the required emission reductions. All of the
jurisdictions covered by the NOX SIP Call ultimately chose
to adopt the NOX Budget Trading Program into their SIPs. The
NOX SIP Call was upheld by the U.S. Court of Appeals for the
District of Columbia Circuit (D.C. Circuit) in all pertinent respects.
See Michigan v. EPA, 213 F.3d 663 (2000).
    In coordination with the NOX SIP Call rulemaking under
CAA section 110(a)(2)(D)(i)(I), the EPA also addressed several pending
CAA section 126(b) petitions submitted by eight northeastern states
regarding the same air quality issues addressed by the NOX
SIP Call (i.e., interstate ozone transport for the 1979 ozone NAAQS).
These CAA section 126(b) petitions asked the EPA to find that ozone
emissions from numerous sources located in 22 states and the District
of Columbia had adverse air quality impacts on the petitioning downwind
states. Half of the petitioning states requested that the
NOX reductions to address regional interstate ozone
pollution transport be implemented using an allowance trading
program.\25\ Based on analysis conducted for the NOX SIP
Call regarding upwind state impacts on downwind air quality, the EPA in
May 1999 made technical determinations regarding the claims in the
petitions, but did not at that time make the CAA section 126(b)
findings requested by the petitions. 64 FR 28250 (May 25, 1999). In
making these technical determinations, the EPA concluded that the
NOX SIP Call would fully address and remediate the claims
raised in these petitions, and that the EPA would, therefore, not need
to take separate action to remedy any potential violations of the CAA
section 110(a)(2)(D)(i) prohibition. 64 FR 28252. However, subsequent
litigation over the NOX SIP Call led the EPA to ``de-link''
the CAA section 126(b) petition response from the NOX SIP
Call, and the EPA made final CAA section 126(b) findings for 12 states
named in the petitions and the District of Columbia. The EPA found that
sources in these states emitted in violation of the prohibition in the
good neighbor provision with respect to the 1979 ozone NAAQS based on
the affirmative technical determinations made in the May 1999
rulemaking. In order to remedy the violation under CAA section 126(c),
the EPA required affected sources in the upwind states to participate
in a regional allowance trading program whose requirements were
designed to be interchangeable with the requirements of the optional
NOX Budget Trading Program model rule provided under the
NOX SIP Call. 65 FR 2674 (January 18, 2000). The EPA's
action on these CAA section 126(b) petitions was upheld by the D.C.
Circuit. See Appalachian Power Co. v. EPA, 249 F.3d 1032 (D.C. Cir.
2001).
---------------------------------------------------------------------------

    \25\ Connecticut, Maine, New York, and Pennsylvania requested an
allowance trading program to reduce NOX emissions and
remedy regional interstate ozone transport. 63 FR 56297.
---------------------------------------------------------------------------

    The EPA next promulgated the Clean Air Interstate Rule (CAIR), 70
FR 25162 (May 12, 2005) to address interstate transport under the good
neighbor provision with respect to the 1997 ozone NAAQS, as well as the
1997 fine particulate matter (PM2.5) NAAQS. 70 FR 25172. The
EPA adopted the same framework for quantifying the level of states'
significant contribution to downwind nonattainment in CAIR as it used
in the NOX SIP Call, based on the determination in the
NOX SIP Call that downwind ozone nonattainment is due to the
impact of emissions from numerous upwind sources and states. 70 FR
25162, 25172 (May 12, 2005). The EPA explained that ``[t]ypically, two
or more States contribute transported pollution to a single downwind
area, so that the `collective contribution' is much larger than the
contribution of any single State.'' 70 FR 25186. CAIR included two
distinct regulatory processes: (1) A rulemaking to define significant
contribution (i.e., the emission reduction obligation) under the good
neighbor provision and provide for submission of SIPs eliminating that
contribution, 70 FR 25162 (May 12, 2005); and (2) a rulemaking to
promulgate, where necessary, FIPs imposing emission limitations in the
event states did not submit SIPs. 71 FR 25328 (April 28, 2006). The
FIPs required EGUs in affected states to participate in regional
allowance trading programs, which replaced the previous NOX
Budget Trading Program.
    In conjunction with the second CAIR rulemaking, which promulgated
backstop FIPs, the EPA acted on a CAA section 126(b) petition received
from the state of North Carolina on March 19, 2004, seeking a finding
that large EGUs located in 13 states were significantly contributing to
nonattainment and/or interfering with maintenance of the 1997 ozone
NAAQS and the 1997 PM2.5 NAAQS in North Carolina. Citing the
analyses conducted to support the promulgation of CAIR, the EPA denied
North Carolina's CAA section 126(b) petition in full based on
determinations either that the named states were not adversely
impacting downwind air quality in violation of the good neighbor
provision, or that such impacts were fully remedied by implementation
of the emission reductions required by the CAIR FIPs. 71 FR 25328,
25330 (April 28, 2006).
    The D.C. Circuit found that EPA's approach to CAA section
110(a)(2)(D)(i)(I) in CAIR was ``fundamentally flawed'' in several
respects, and the rule was remanded in July 2008 with the instruction
that the EPA replace the rule ``from the ground up.'' North Carolina,
531 F.3d at 929.

The decision did not find fault with the EPA's general multi-step
framework for addressing interstate ozone transport, but rather
concluded the EPA's analysis and compliance mechanisms did not address
all elements required by the statute. The EPA's separate action denying
North Carolina's CAA section 126(b) petition was not challenged.
    On August 8, 2011, the EPA promulgated CSAPR to replace CAIR. 76 FR
48208 (August 8, 2011). CSAPR addressed the same (1997) ozone and
PM2.5 NAAQS as CAIR and, in addition, addressed interstate
transport for the 2006 PM2.5 NAAQS by requiring 28 states to
reduce sulfur dioxide (SO2) emissions, annual NOX
emissions, and/or ozone season NOX emissions that would
significantly contribute to other states' nonattainment or interfere
with other states' ability to maintain these air quality standards.
Consistent with prior determinations made in the NOX SIP
Call and CAIR, the EPA again found that multiple upwind states
contributed to downwind ozone nonattainment in multiple downwind
states. Specifically, the EPA found ``that the total `collective
contribution' from upwind sources represents a large portion of
PM2.5 and ozone at downwind locations and that the total
amount of transport is composed of the individual contribution from
numerous upwind states.'' 76 FR 48237. Accordingly, the EPA conducted a
regional analysis, calculated emission budgets for affected states, and
required EGUs in these states to participate in new regional allowance
trading programs to reduce statewide emission levels.\26\ CSAPR was
subject to nearly 4 years of litigation. Ultimately, the Supreme Court
upheld the EPA's approach to calculating emission reduction obligations
and apportioning upwind state responsibility under the good neighbor
provision, but also held that the EPA was precluded from requiring more
emission reductions than necessary to address downwind air quality
problems, or ``over-controlling'' upwind state emissions. See EPA v.
EME Homer City Generation, L.P., 134 S. Ct. 1584, 1607-09 (2014) (EME
Homer City).\27\
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    \26\ The CSAPR trading programs included assurance provisions to
ensure that emissions are reduced within each individual state, in
accordance with North Carolina, 531 F.3d at 907-08 (holding the EPA
must actually require elimination of emissions from sources that
contribute significantly to nonattainment and interfere with
maintenance in downwind areas). Those provisions were also included
in the CSAPR Update and went into effect with the 2017 CSAPR
compliance periods.
    \27\ On remand from the Supreme Court, the D.C. Circuit further
affirmed various aspects of the CSAPR, while remanding the rule
without vacatur for reconsideration of certain states' emissions
budgets where it found those budgets may over-control emissions
beyond what was necessary to address the good neighbor requirements.
EME Homer City Generation, L.P. v. EPA, 795 F.3d 118 (2015) (EME
Homer City II). The EPA addressed the remand in several rulemaking
actions in 2016 and 2017.
---------------------------------------------------------------------------

    Most recently, the EPA promulgated the CSAPR Update to address the
good neighbor provision requirements for the 2008 ozone NAAQS. 81 FR
74504 (October 26, 2016). The CSAPR Update built upon previous
regulatory efforts in order to address the collective contributions of
ozone pollution from 22 states in the eastern United States to
widespread downwind air quality problems. As was also the case for the
previous rulemakings, the EPA evaluated the nature (i.e., breadth and
interconnectedness) of the ozone problem and NOX reduction
potential from EGUs, including those sources named in the Delaware and
Maryland CAA section 126(b) petitions. The CSAPR Update is described in
more detail in Section IV.B of this final action.
    In finalizing the CSAPR Update, the EPA found that it was at that
time unable to determine whether the rule fully resolved good neighbor
obligations for most of the states subject to that action, including
those addressed in Delaware's and Maryland's petitions (Indiana,
Kentucky, Ohio, Pennsylvania and West Virginia), and noted that, based
on its analysis at that time, the emission reductions required by the
rule ``may not be all that is needed'' to address transported
emissions.\28\ 81 FR 74521 through 74522. The EPA noted that the
information available at that time suggested that downwind air quality
problems would remain in 2017 after implementation of the CSAPR Update
and that upwind states continued to be linked to those downwind
problems at or above the one-percent threshold. However, in the CSAPR
Update the EPA could not determine whether, in step three of the four-
step framework, the EPA had quantified all emission reductions that may
be considered cost effective because the rule did not evaluate non-EGU
ozone season NOX reductions and further EGU control
strategies (i.e., the implementation of new post-combustion controls)
that were achievable on timeframes extending beyond the 2017 analytic
year.
---------------------------------------------------------------------------

    \28\ The EPA determined that the emission reductions required by
the CSAPR Update satisfied the full scope of the good neighbor
obligation for Tennessee with respect to the 2008 ozone NAAQS. 81 FR
74551-22.
---------------------------------------------------------------------------

    On July 10, 2018, the EPA proposed to find that, based on the
latest available emissions inventory and air quality modeling data for
a 2023 analytic year, the CSAPR Update fully addresses the good
neighbor provision requirements for the 2008 ozone NAAQS for the 20
eastern states (among the 22) previously addressed in the CSAPR Update.
83 FR 31915. The EPA's proposed determination was premised on the
finding that there would be no remaining nonattainment or maintenance
receptors for the 2008 ozone NAAQS in the eastern U.S. in 2023. The
proposed determination applied the four-step CSAPR framework but did
not progress past step one since no air quality receptors were
identified. Therefore, with the CSAPR Update fully implemented, the EPA
has proposed to find that states are not expected to contribute
significantly to nonattainment in, or interfere with maintenance by,
any other state with regard to the 2008 ozone NAAQS. EPA is currently
reviewing comments on the proposed rule and anticipates taking final
action by December 2018. The remaining two states were determined to
have no remaining good neighbor obligation for the 2008 ozone NAAQS in
the CSAPR Update (Tennessee), 81 FR 74540 (October 26, 2016), and in a
separate SIP approval (Kentucky), 81 FR 33730 (July 17, 2018).

III. CAA Sections 126 and 110 and Standard of Review for This Action

    The following subsections describe both the statutory authority and
the EPA's standard of review for the final action on Delaware's and
Maryland's CAA section 126(b) petitions. Section III.A of this notice
describes the EPA's authority and interpretation of key terms under
both CAA sections 126 and 110(a)(2)(D)(i)(I), including the
relationship between the good neighbor provision and CAA section
126(b). Section III.B of this notice describes the reasonableness of
applying the four-step framework and certain prior findings under the
CSAPR Update as the standard of review in evaluating Delaware's and
Maryland's CAA section 126(b) petitions.

A. Statutory Authority Under CAA Sections 126 and 110(a)(2)(D)(i)(I)

    The statutory authority for this action is provided by CAA sections
126 and 110(a)(2)(D)(i). Section 126(b) of the CAA provides that any
state or political subdivision may petition the Administrator of the
EPA to find that any major source or group of stationary sources in an
upwind state emits or would emit any air pollutant in violation of the
prohibition of CAA

section 110(a)(2)(D)(i).\29\ Petitions submitted pursuant to this
section are commonly referred to as CAA section 126(b) petitions.
Similarly, findings by the Administrator, pursuant to this section,
that a source or group of sources emits air pollutants in violation of
the CAA section 110(a)(2)(D)(i) prohibition are commonly referred to as
CAA section 126(b) findings.
---------------------------------------------------------------------------

    \29\ The text of CAA section 126 as codified in the U.S. Code
cross-references CAA section 110(a)(2)(D)(ii) instead of CAA section
110(a)(2)(D)(i). The courts have confirmed that this is a
scrivener's error and the correct cross-reference is to CAA section
110(a)(2)(D)(i). See Appalachian Power Co. v. EPA, 249 F.3d 1032,
1040-44 (D.C. Cir. 2001).
---------------------------------------------------------------------------

    CAA section 126(c) explains the effect of a CAA section 126(b)
finding and establishes the conditions under which continued operation
of a source subject to such a finding may be permitted. Specifically,
CAA section 126(c) provides that it is a violation of section 126 of
the Act and of the applicable SIP: (1) For any major proposed new or
modified source subject to a CAA section 126(b) finding to be
constructed or operate in violation of the prohibition of CAA section
110(a)(2)(D)(i); or (2) for any major existing source for which such a
finding has been made to stay in operation more than 3 months after the
date of the finding. The statute, however, also gives the Administrator
discretion to permit the continued operation of a source beyond 3
months if the source complies with emission limitations and compliance
schedules provided by the EPA to bring about compliance with the
requirements contained in CAA sections 110(a)(2)(D)(i) and 126 as
expeditiously as practicable, but in any event no later than 3 years
from the date of the finding.
    Section 110(a)(2)(D)(i) of the CAA, referred to as the good
neighbor provision of the Act, requires states to prohibit certain
emissions from in-state sources if such emissions impact the air
quality in downwind states. Specifically, CAA sections 110(a)(1) and
110(a)(2)(D)(i)(I) require all states, within 3 years of promulgation
of a new or revised NAAQS, to submit SIPs that contain adequate
provisions prohibiting any source or other type of emissions activity
within the state from emitting any air pollutant in amounts which will
contribute significantly to nonattainment in, or interfere with
maintenance by, any other state with respect to that NAAQS. As
described in the prior section, the EPA has developed a number of
regional rulemakings to address CAA section 110(a)(2)(D)(i)(I) for the
various ozone NAAQS. Notably, the EPA's most recent rulemaking, the
CSAPR Update, was promulgated to address interstate transport under
section 110(a)(2)(D)(i)(I) for the 2008 ozone NAAQS and required
implementation of specific emission budgets starting in 2017. 81 FR
74504.
    The EPA's historical approach to evaluating CAA section 126(b)
petitions evaluates whether a petition establishes a sufficient basis
for the requested CAA section 126(b) finding. See, e.g., 76 FR 19662,
19666 (April 7, 2011) (proposed response to petition from New Jersey
regarding SO2 emissions from the Portland Generating
Station); 83 FR 16064, 16070 (April 13, 2018) (final response to
petition from Connecticut regarding ozone emissions from Brunner
Island). The EPA first evaluates the technical analysis in the petition
to see if that analysis, standing alone, is sufficient to support a CAA
section 126(b) finding. The EPA focuses on the analysis in the petition
because the statute does not require the EPA to conduct an independent
technical analysis to evaluate claims made in CAA section 126(b)
petitions. The petitioner, thus, bears the burden of establishing, as
an initial matter, a technical basis for the specific finding
requested. The EPA has no obligation to prepare an analysis to
supplement a petition that fails, on its face, to include an initial
technical demonstration. Such a petition, or a petition that fails to
identify the specific finding requested, can be denied as insufficient.
Nonetheless, the EPA has the discretion to conduct independent analyses
when helpful in evaluating the basis for a potential CAA section 126(b)
finding or developing a remedy if a finding is made.
    With respect to the statutory requirements of both section
110(a)(2)(D)(i) and section 126 of the CAA, the EPA has consistently
acknowledged that Congress created these provisions as two independent
statutory processes to address the problem of interstate pollution
transport. See, e.g., 76 FR 69052, 69054 (November 7, 2011). Congress
provided two separate statutory processes without indicating any
preference for one over the other, suggesting it viewed either approach
as a legitimate means to produce the desired result. While either
provision may be applied to address interstate transport, they are also
closely linked in that a violation of the prohibition in CAA section
110(a)(2)(D)(i) is a condition precedent for action under CAA section
126(b) and, critically, significant contribution to nonattainment and
interference with maintenance are construed identically for purposes of
both provisions (since the identical terms are naturally interpreted as
meaning the same thing in the two linked provisions). See Appalachian
Power, 249 F.3d at 1049-50.
    While section 126(b) of the CAA provides a mechanism for states and
other political subdivisions to seek abatement of pollution in other
states that may affect their air quality, it does not identify specific
criteria or a specific methodology for the Administrator to apply when
deciding whether to make a CAA section 126(b) finding or deny a
petition. Therefore, the EPA has discretion to identify relevant
criteria and develop a reasonable methodology for determining whether a
CAA section 126(b) finding should be made. Thus, in addressing a CAA
section 126(b) petition that addresses ozone transport, the EPA
believes it is appropriate to interpret these ambiguous terms
consistent with the EPA's historical approach to evaluating interstate
ozone pollution transport under the good neighbor provision, and its
interpretation and application of that related provision of the
statute. This approach is particularly applicable to the Delaware and
Maryland petitions because the EPA recently finalized and began
implementation of the CSAPR Update, which evaluated and addresses
interstate ozone pollution transport, inclusive of the named states'
impacts on Delaware and Maryland. As described further in Section II of
this notice, ozone is a regional air pollutant and previous EPA
analyses and regulatory actions have evaluated the regional interstate
ozone transport problem using a four-step analytic framework. The EPA
most recently applied this four-step framework in promulgating the
CSAPR Update to address interstate transport with respect to the 2008
ozone NAAQS under CAA section 110(a)(2)(D)(i)(I) and believes it may be
generally useful in analyzing the 2015 ozone NAAQS. Given the specific
cross-reference in CAA section 126(b) to the substantive prohibition in
CAA section 110(a)(2)(D)(i), the EPA believes any prior findings made
under the good neighbor provision are informative--if not
determinative--for a CAA section 126(b) action. Therefore, in this
instance, the EPA's decision whether to grant or deny the CAA section
126(b) petitions regarding both the 2008 8-hour ozone and 2015 ozone
NAAQS depends on application of the four-step framework. The
application of the four-step framework to the EPA's analysis of
Maryland's and Delaware's CAA section 126(b) petitions regarding the
2008

ozone NAAQS is, therefore, legally appropriate given the EPA has
previously interpreted (and addressed) significant contribution and
interference with maintenance under CAA section 110(a)(2)(D)(i) under
this framework via the CSAPR Update.
    Unlike the 2008 ozone NAAQS, the EPA has not to date engaged in a
rulemaking action regarding the good neighbor provision for the 2015
ozone NAAQS. However, the EPA has recently released technical
information intended to assist states' efforts in development of SIPs
to address this standard.\30\ As part of the memo releasing the
technical information, the EPA acknowledged that states have
flexibility to pursue approaches that may differ from the EPA's
historical approach to evaluating interstate transport in developing
their good neighbor SIPs. Nonetheless, the EPA's technical analysis and
the potential flexibilities identified in the memo generally followed
the basic elements of the EPA's historical four-step framework. Thus,
in light of the EPA's discretion to identify relevant criteria and
develop a reasonable methodology for determining whether a CAA section
126(b) finding should be made, the EPA continues to evaluate the claims
regarding the 2015 ozone NAAQS for the specific sources named in in
Delaware's CAA section 126(b) petitions consistent with the EPA's four-
step framework. To the extent that the EPA made determinations in
either the CSAPR Update or other analytic exercises that are pertinent
to the evaluation of the 2015 ozone NAAQS under the four-step framework
for the sources named in the petitions, it is appropriate to consider
that relevant information as well.\31\
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    \30\ See ``Information on the Interstate Transport State
Implementation Plan Submissions for the 2015 Ozone National Ambient
Air Quality Standards under Clean Air Act Section
110(a)(2)(D)(i)(I)'' (March 27, 2018), available in the docket for
this proposed action. By operation of statute, states are required
to submit to the EPA their SIPs to address the good neighbor
provision for the 2015 ozone NAAQS in October 2018.
    \31\ As discussed further in Section IV.B.1 of this notice, in
the CSAPR Update the EPA found that it was not at that time able to
determine whether the Update fully resolved good neighbor
obligations for the 2008 ozone NAAQS for most of the states subject
to that action, including those addressed in Delaware's and
Maryland's petitions (Indiana, Kentucky, Ohio, Pennsylvania, and
West Virginia), and noted that the emission reductions required by
the rule may not be all that is needed to address transported
emissions. 81 FR 74521. The EPA is not making a final determination
regarding any remaining good neighbor obligation for those states as
part of this action, other than with respect to emissions from the
sources named in the petition with respect to the particular NAAQS
at issue. (Any determination made in this final rule is only with
respect to the sources specifically named in Delaware's and
Maryland's petitions for the applicable NAAQS.) However, the EPA
notes that in a separate, pending action, the EPA has proposed to
determine that the CSAPR Update fully addresses certain states' good
neighbor obligations regarding the 2008 ozone NAAQS. See 83 FR 31915
(July 10, 2018).
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    The EPA notes that Congress did not specify how the EPA should
determine that a major source or group of stationary sources ``emits or
would emit'' any air pollutant in violation of the prohibition of CAA
section 110(a)(2)(D)(i)(I) under the terms of CAA section 126(b). The
EPA also believes, given the more regional, rather than localized,
impact of NOX emissions on downwind ozone concentrations, it
is reasonable and appropriate at each step to consider whether the
facility ``emits or would emit'' in light of the facility's current or
reasonably anticipated future operating conditions. Therefore, the EPA
interprets the phrase ``emits or would emit'' in the context of acting
on Delaware's and Maryland's petitions to mean that a source may
``emit'' in violation of the good neighbor provision if, based on
current emission levels, the upwind state in which the source is
located contributes to downwind air quality problems and the individual
source may be further controlled as determined through a multi-factor
test that includes consideration of cost-effective controls, technical
feasibility, and air quality factors. Similarly, in evaluating the
sources named under these petitions, a source ``would emit'' in
violation of the good neighbor provision if, based on reasonably
anticipated future emission levels (accounting for existing
conditions), the upwind state in which the source is located
contributes to downwind air quality problems and the individual source
could be further controlled as determined through a multi-factor test
that includes consideration of cost-effective controls, technical
feasibility, and air quality factors. Consistent with this
interpretation, the EPA has, therefore, evaluated, in this notice,
whether the sources cited in the petitions emit or would emit in
violation of the good neighbor provision based on both current and
anticipated future emission levels.
    In interpreting the phrase ``emits or would emit in violation of
the prohibition of section [110(a)(2)(D)(i)],'' if the EPA or a state
has already adopted adequate provisions that eliminate the significant
contribution to nonattainment or interference with maintenance of the
NAAQS in downwind states, then there simply is no violation of the CAA
section 110(a)(2)(D)(i)(I) prohibition, and, hence, no grounds to grant
a CAA section 126(b) petition. Put another way, requiring additional
reductions would result in eliminating emissions that do not contribute
significantly to nonattainment or interfere with maintenance of the
NAAQS, an action beyond the scope of the prohibition in CAA section
110(a)(2)(D)(i)(I) and, therefore, beyond the scope of the EPA's
authority to make the requested finding under CAA section 126(b). See
EME Homer City, 134 S. Ct. at 1604 n.18, 1608-09 (holding the EPA may
not over-control by requiring sources in upwind states to reduce
emissions by more than necessary to eliminate significant contribution
to nonattainment or interference with maintenance of the NAAQS in
downwind states under the good neighbor provision).
    Thus, for example, if the EPA has already approved a state's SIP as
adequate to meet the requirements of CAA section 110(a)(2)(D)(i)(I),
the EPA has no basis to find that a source in that state emits or would
emit in violation of the prohibition of CAA section 110(a)(2)(D)(i)(I)
absent new information demonstrating that the SIP is now insufficient
to address the prohibition. Similarly, if the EPA has promulgated a FIP
that it has determined fully eliminates emissions that significantly
contribute to nonattainment or interfere with maintenance in a downwind
state, the EPA has no basis to find that sources in the upwind state
are emitting or would emit in violation of the CAA section
110(a)(2)(D)(i)(I) prohibition, absent new information to the contrary.
    The EPA notes that the approval of a SIP or promulgation of a FIP
implementing CAA section 110(a)(2)(D)(i)(I) means that a state's
emissions are adequately prohibited for the particular set of facts
analyzed under approval of a SIP or promulgation of a FIP. If a
petitioner produces new data or information showing a different level
of contribution or other facts not considered when the SIP or FIP was
promulgated, compliance with a SIP or FIP may not be determinative
regarding whether the upwind sources would emit in violation of the
prohibition of CAA section 110(a)(2)(D)(i)(I). See 64 FR 28274 n.15; 71
FR 25336 n.6; Appalachian Power, 249 F.3d at 1067 (later developments
can provide the basis for another CAA section 126(b) petition). Thus,
in circumstances where a SIP or FIP addressing CAA section
110(a)(2)(D)(i)(I) is being implemented, the EPA will evaluate the CAA
section 126(b) petition to determine if it raises new information that
merits further consideration.
    Several commenters disagreed with the EPA's interpretation of the

relationship between the good neighbor provision under CAA section
110(a)(2)(D)(i)(I) and section 126(b), contending that Congress
intended CAA section 126(b) petitions to be a legal tool to address
interstate problems separate and distinct from SIP and FIP actions
under CAA section 110. Commenters cite to legislative history and the
D.C. Circuit's opinion in Appalachian Power in support of their
assertions that CAA section 126 is intended to remedy interstate
transport problems notwithstanding the existence of CAA section 110.
Commenters accordingly assert the EPA is incorrect in determining that
its four-step approach under CAA section 110(a)(2)(D)(i)(I) is
appropriate for evaluating under CAA section 126(b) whether an upwind
source or group of sources will significantly contribute to
nonattainment or interfere with maintenance of the 2008 and the 2015
ozone NAAQS in a petitioning downwind state.
    The EPA has consistently acknowledged in prior actions under CAA
section 126(b) that Congress created the good neighbor provision and
CAA section 126 as two independent statutory processes to address one
problem: Interstate pollution transport. See, e.g., 83 FR 26666, 26675
(June 8, 2018) (proposal for this final action); 76 FR 69052, 69054
(November 7, 2011) (proposed action for the EPA's final action on New
Jersey's CAA section 126(b) petition regarding SO2 emissions
from Portland Generating Station). As the commenters point out, courts
have upheld the EPA's position that CAA sections 110(a)(2)(D)(i) and
126 are two independent statutory processes to address the same problem
of interstate transport. See GenOn REMA, LLC v. EPA, 722 F.3d 513, 520-
23 (3d Cir. 2013); Appalachian Power, 249 F.3d at 1047. However, the
commenters misread the courts' holding regarding the EPA's
interpretation of the interplay between the two provisions. Both the
D.C. Circuit and Third Circuit spoke to the question of the timing of
these processes--specifically, whether the EPA could act on a CAA
section 126(b) petition in instances where the agency had not yet acted
on a CAA section 110 SIP addressing interstate transport for the same
NAAQS. Both courts upheld the EPA's position that it need not wait for
the CAA section 110 process to conclude in order to act on a CAA
section 126(b) petition, thus affirming that both statutory provisions
are independent from one another from a timing perspective. Here, the
agency has not deferred action on Delaware's petitions regarding the
2015 ozone NAAQS, for which good neighbor SIPs are not due until
October 2018, until its action on the good neighbor SIPs (for the named
upwind states) has concluded. Therefore, by taking action in this
instance on Delaware's section 126(b) petitions regarding the 2015
ozone NAAQS before action under section 110 has been concluded, the EPA
believes it has given CAA section 126(b) independent meaning as
intended by Congress and the courts.
    The D.C. Circuit's opinion in Appalachian Power, which commenters
specifically point to, further supports the EPA's interpretation taken
in this action: That while the agency need not wait for the CAA section
110 process to conclude before taking action on a CAA section 126(b)
petition, the EPA reasonably interprets the substantive requirements of
the two provisions to be closely linked. The court in Appalachian Power
specifically considered whether it was appropriate for the EPA to rely
on findings made under the good neighbor provision in the
NOX SIP Call rulemaking in granting several CAA section
126(b) petitions raising similar interstate transport concerns with
regards to the same NAAQS. Petitioners in that case argued that the EPA
should instead make a finding that ``the specified stationary sources
within a given state independently met [the statute's] threshold test
for effect on downwind nonattainment.'' 249 F.3d at 1049. The court
found that by referring to stationary sources that emit pollutants ``in
violation of the prohibition of [CAA section 110(a)(2)(D)(i)],''
Congress ``clearly hinged the meaning of section 126 on that of section
110(a)(2)(D)(i).'' Id. at 1050. The court, therefore, concluded that
given CAA section 126's silence on what it means for a stationary
source to violate CAA section 110(a)(2)(D)(i), the EPA's approach of
relying on findings under CAA section 110(a)(2)(D)(i) was reasonable
and, therefore, entitled to deference under Chevron U.S.A. Inc. v.
Natural Resources Defense Council, Inc., 467 U.S. 837, 843 (1984). Id.
The EPA's approach to addressing the CAA section 126(b) petitions
considered the Appalachian Power case is consistent with the EPA's
application of the four-step framework and consideration of findings
made in the CSAPR Update in acting on Maryland's and Delaware's CAA
section 126(b) petitions.
    Commenters also contend that the EPA is erecting a ``new barrier''
to CAA section 126(b) petitions by requiring a petitioner to disprove
the validity of the SIP or FIP in place for a source. However, the
commenters mischaracterize the EPA's position. As described, where a
SIP or FIP is already in place to address the prohibition in CAA
section 110(a)(2)(D)(i)(I), the EPA has already made a determination
that sources subject to that SIP or FIP have been adequately addressed
for purposes of interstate transport. A petitioner need not demonstrate
that the EPA's original determination underlying the SIP or FIP is
flawed. Rather, the EPA has recognized that circumstances may change
after the EPA makes its determination under CAA section 110, in which
case it is incumbent upon the petitioner in the first instance to
provide information demonstrating that the named sources is unlawfully
impacting the petitioning state in spite of the SIP or FIP, in light of
newly available information. The EPA disagrees that this is a ``new''
position the agency is taking regarding the linkage between good
neighbor SIPs and FIPs and CAA section 126(b) petition. As described
earlier in this section, the EPA has interpreted CAA section 126(b) to
impose this burden on petitioners in each section 126(b) petition
addressed by the agency in the last two decades. See, e.g., 64 FR 28274
n.15 (action on eight states' petitions for the 1979 ozone NAAQS); 71
FR 25336 n.6 (action on North Carolina's petition for the 1997 ozone
NAAQS).

B. Reasonableness of Applying the Four-Step Transport Framework for
This Action

    As discussed in Section II of this notice, the EPA has consistently
analyzed ozone transport with the understanding that nonattainment and
maintenance concerns result from the cumulative air quality impacts of
contributions from numerous anthropogenic sources across several upwind
states (as well as from within the downwind state). Consistent with
this understanding, the EPA has evaluated ozone transport based in part
on the relative contribution of all anthropogenic sources within a
state, as measured against to a screening threshold, and then
identified particular source sectors and units for regulatory
consideration.\32\ This approach to evaluating ozone transport is
reasonable because the statute's use of ``significantly'' as a modifier
to ``contribute'' implies a relationship, e.g.,

the impact a source or collection of sources has relative to other
relevant sources of that pollutant. Therefore, although CAA section
126(b) allows downwind states to petition the EPA regarding specific
sources or groups of sources that they believe are contributing to the
downwind air quality problems, the EPA believes it is reasonable and
appropriate to evaluate the emissions from sources named in a petition
in the context of all relevant anthropogenic sources of that pollutant
to determine whether or not emissions from the named sources are in
violation of the good neighbor provision.
---------------------------------------------------------------------------

    \32\ The EPA has used cost as a factor in its multi-factor
approach for quantifying significant contribution from multiple
contributing states. Cost is used in a relative (i.e., least-cost
abatement) approach that also requires examining individual source
impact and reduction potential in the context of the larger universe
of contributors.
---------------------------------------------------------------------------

    The EPA notes that the four-step framework provides a logical,
consistent, and systematic approach for addressing interstate transport
for a variety of criteria pollutants under a broad array of national,
regional, and local scenarios. Consequently, the EPA finds it
reasonable to apply the same four-step transport framework used to
evaluate regional ozone transport under the good neighbor provision in
considering a CAA section 126(b) petition addressing the impacts of
individual sources on downwind attainment and maintenance of the ozone
NAAQS. As the four-step framework is applied to evaluate a particular
interstate transport problem, the EPA can determine whether upwind
sources are actually contributing to a downwind air quality problem;
whether and which sources can be cost effectively controlled relative
to that downwind air quality problem; what level of emissions should be
eliminated to address the downwind air quality problem; and the means
of implementing corresponding emission limits (i.e., source-specific
rates, or statewide emission budgets in a limited regional allowance
trading program). The outcome of this assessment will vary based on the
scope of the air quality problem, the availably and cost of controls at
sources in upwind states, and the relative impact of upwind emission
reductions on downwind ozone concentrations. For a more localized
pollutant like SO2, the use of the four-step framework could
result in a finding that emissions from a unit were significantly
contributing to nonattainment, or interfering with maintenance, under
the first three steps, which may lead the agency in step four to
require unit-specific compliance requirements (such as an emission
rate).\33\
---------------------------------------------------------------------------

    \33\ For an example of such a case, the EPA's action on a prior
CAA section 126(b) petition regarding SO2 emissions from
the Portland Generating Station in Pennsylvania analyzed similar
factors as those outlined the four-step transport framework to
evaluate whether the identified source was emitting in violation of
the good neighbor provision. The EPA concluded that the petitioning
downwind state had an air quality problem (step one) for the 2010
SO2 NAAQS. The agency determined that emissions from the
named source in the upwind state alone were sufficient not just to
contribute to (step two), but to cause a violation of the NAAQS in
the petitioning state. As such, the agency determined that the
facility should be regulated because of the magnitude of its
contribution and the relative lack of other contributing sources
(step three). To address this impact, the EPA imposed federally
enforceable source-specific rate limits to eliminate the source's
significant contribution (step four). See Final Response to Petition
From New Jersey Regarding SO2 Emissions from the Portland
Generating Station, 76 FR 69052 (November 7, 2011).
---------------------------------------------------------------------------

    The complexity of atmospheric chemistry and the interconnected,
long-distance nature of ozone transport also demonstrates the
appropriateness of the four-step framework. As a result of this
complexity, including domestic and international as well as
anthropogenic and background contributions to ozone and its precursors,
it is less likely that a single source is entirely responsible for
impacts to a downwind area. For example, several commenters assert that
the emissions from all of the sources named in the Maryland petition
contribute 0.656 ppb to the Edgewood receptor in Maryland--an amount
that is insufficient to itself cause nonattainment. Thus, a
determination regarding whether this impact is sufficient to
significantly contribute to nonattainment or interfere with maintenance
of the NAAQS--in light of other anthropogenic emission sources
impacting a downwind area--is necessarily more complicated. However,
the EPA evaluates within step three of the framework whether upwind
sources have emissions that significantly contribute to nonattainment
or interfere with maintenance of the ozone NAAQS based on various
control, cost, and air quality factors, including the magnitude of
emissions from upwind states, the number of potential emission
reductions from upwind sources, the cost of those potential emission
reductions, and the potential air quality impacts of emission
reductions.\34\ The EPA believes it is reasonable to consider these
factors whether evaluating ozone transport in the context of a good
neighbor SIP under CAA section 110 or a section 126(b) petition.
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    \34\ ``We believe it is important to consider both [cost and air
quality] factors because circumstances related to different downwind
receptors can vary and consideration of multiple factors can help
EPA appropriately identify each state's significant contribution
under different circumstances. [. . .] Using both air quality and
cost factors allows EPA to consider the full range of circumstances
and state-specific factors that affect the relationship between
upwind emissions and downwind nonattainment and maintenance
problems. For example, considering cost takes into account the
extent to which existing plants are already controlled as well as
the potential for, and relative difficulty of, additional emissions
reductions. Therefore, EPA believes that it is appropriate to
consider both cost and air quality metrics when quantifying each
state's significant contribution.'' Proposed Federal Implementation
Plans To Reduce Interstate Transport of Fine Particulate Matter and
Ozone, 75 FR 45210, 45271 (August 2, 2010) (CSAPR proposal)
(describing potential disparities between upwind and downwind state
contributions to identified air quality problems and between levels
of controls between states).
---------------------------------------------------------------------------

    The EPA has already conducted such an analysis for all sources
named in Delaware and Maryland's petitions via the CSAPR Update. The
EPA determined that the upwind states named by the petitioners emitted
in violation of the good neighbor provision with respect to downwind
states. The EPA, therefore, found that EGUs in these states, including
the named sources, collectively needed to make reductions at a cost
level commensurate with operating and optimizing existing SCR controls
(among other NOX reduction strategies included in the CSAPR
Update). Based on the nature of ozone formation, the many receptors
throughout the region, the many source sectors and numerous sources,
and because EGUs had readily available low-cost and impactful emission
reductions available, the EPA found that a limited allowance trading
program would achieve emission reductions commensurate with applying
these cost-effective controls. As discussed in more detail in Section
IV of this notice, petitioners and commenters have not demonstrated,
based on information available at this time, either that the particular
sources named by petitioners should be required to make further
emission reductions under the good neighbor provision in light of their
contributions relative to other sources that are not named in the
petitions, or that source-specific unit-level emission rates are
necessary to ensure reductions are being achieved under the CSAPR
Update. As further described in Section IV.B of this notice, the EPA's
independent analysis finds that, contrary to the petitioners' and
commenters' assertions, the CSAPR Update allowance trading program has
been sufficient and successful in reducing regional emissions of ozone
and emissions across the named EGUs.
    For any analysis of a CAA section 126(b) petition regarding
interstate transport of ozone, a regional pollutant with contribution
from a variety of sources, the EPA reviews whether the particular
sources identified by the petitioner should be controlled in light of
the collective impact of emissions on

air quality in the area, including emissions from other anthropogenic
sources. Thus, review of the named sources in the Delaware and Maryland
petitions provides a starting point for the EPA's evaluation, but does
not--as the commenters suggest--complete the evaluation to determine
whether the named sources emit or would emit in violation of the good
neighbor provision.

IV. The EPA's Final Response to Delaware's and Maryland's CAA Section
126(b) Petitions

    The EPA is finalizing denials of the Maryland petition and all four
of the Delaware petitions. Section IV.A of this notice describes the
EPA's determination that Delaware has not demonstrated that the sources
named in their petitions emit or would emit in violation of the good
neighbor provision such that they will significantly contribute to
nonattainment or interfere with maintenance of the 2008 or 2015 ozone
NAAQS in Delaware. Section IV.B of this notice describes the EPA's
independent analysis of the sources named in both states' petitions and
concludes based on such analysis that there is no basis to find that
the named sources emit or would emit pollution in violation of the good
neighbor provision with respect to the 2008 ozone NAAQS (Delaware and
Maryland) or the 2015 ozone NAAQS (Delaware only). In this section, and
in the RTC document included in the docket for this action, the agency
explains the rationale supporting its final action and provides its
response to significant public comments on the proposed action.

A. The EPA's Evaluation of Whether the Petitions Are Sufficient To
Support a CAA Section 126(b) Finding

1. Delaware's Petition Is Not Sufficient on Its Own Merit To Support a
CAA Section 126(b) Finding
    The EPA finds that Delaware's conclusions are not supported by the
petitions' assessments based on several technical deficiencies. First,
with respect to the 2008 ozone NAAQS, the EPA is finalizing its
conclusion that Delaware does not provide sufficient information to
indicate that there is a current or expected future air quality problem
in the state. While the Delaware petitions identify individual
exceedances of the ozone standard in the state between the 2000 and
2016 ozone seasons, this does not demonstrate that there is a resulting
nonattainment or maintenance problem. Ozone NAAQS violations, as
opposed to exceedances, are determined based on the fourth-highest
daily maximum ozone concentration, averaged across 3 consecutive
years.\35\ In contrast, exceedances represent, in the case of the 2008
and 2015 ozone NAAQS, an 8-hour measurement above the level of the
NAAQS. Violations, rather than exceedances, are the relevant metric for
identifying nonattainment and maintenance problems. A design value is a
statistic that describes the air quality status of a given location
relative to the level of the NAAQS. Thus, individual exceedances at
monitors do not by themselves indicate that a state is not attaining or
maintaining the NAAQS. In prior transport rulemakings, the EPA
identified both nonattainment and maintenance receptors based on air
quality model projections of measured design values. In the CSAPR
Update, the EPA identified nonattainment receptors as those with an
average projected design value above the NAAQS and with current
measured nonattainment. The EPA identified maintenance receptors as
those monitors with a ``maximum'' future design value above the NAAQS
in order to take into account historic variability in air quality at
the monitor. See 81 FR 74531.
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    \35\ See 80 FR 65296 (October 26, 2015) for a detailed
explanation of the calculation of the 3-year 8-hour average and the
methodology set forth in 40 CFR part 50, appendix U.
---------------------------------------------------------------------------

    Several commenters have argued that Delaware is not attaining or
maintaining the 2008 ozone NAAQS because there are areas in Delaware
that are designated nonattainment for that standard. However, a
nonattainment designation, which was first issued for the 2008 ozone
NAAQS in 2012, does not by itself indicate that a state is currently
failing to attain or struggling to maintain the NAAQS, or that it will
have problems attaining or maintaining the standard in the future. The
courts have confirmed that the EPA's authority to find that a source or
state is in violation of the good neighbor provision is constrained to
circumstances where an actual air quality problem has been identified.
See EME Homer City, 134 S. Ct. at 1608-09 (holding the EPA cannot
require more emission reductions than necessary to address downwind air
quality problems); EME Homer City II, 795 F.3d 118 at 129-30 (D.C. Cir.
2015) (holding state emission budgets invalid where air quality
modeling projected no downwind air quality problems). Delaware has not
demonstrated that there is a current or expected future air quality
problem in the state, nor did any commenters provide evidence of a
current or anticipated future violation of the 2008 ozone NAAQS. As
discussed in Section IV.B of this notice, the EPA's review of current
and projected future air quality in Delaware indicates that the state
is attaining and will maintain the 2008 ozone NAAQS. Accordingly,
Delaware's petition provides insufficient evidence of a requisite air
quality problem with respect to the 2008 ozone NAAQS within the state.
    With respect to the 2015 ozone NAAQS, Delaware argues that if that
NAAQS had been in effect from 2011 through 2016, Delaware monitors
would have recorded more exceedances than they did under the 2008 ozone
NAAQS. However, again, the identification of individual exceedances
does not speak to whether there are current violations of the standard.
Additionally, as discussed further in Section II of this notice, the
EPA evaluates downwind ozone air quality problems for purposes of step
one of the four-step framework using modeled future air quality
concentrations for a year that considers the relevant attainment
deadlines for the NAAQS, based on its interpretation of the term
``will'' in the good neighbor provision.\36\ The petitions do not
provide any analysis indicating that Delaware may violate or have
difficulty maintaining 2015 ozone NAAQS in a year associated with the
relevant attainment dates for that standard.
---------------------------------------------------------------------------

    \36\ 81 FR 74517.
---------------------------------------------------------------------------

    Several commenters allege that the EPA incorrectly identified
technical deficiencies in Delaware's petition regarding whether there
is an air quality problem in Delaware. The commenters also submitted
additional data that they contend demonstrates current violations in
the state. However, comments related to the 2008 ozone NAAQS either
identified violating monitors outside of Delaware or identified further
individual exceedances in Delaware without demonstrating that they
contributed to a violating design value. The commenters have not
submitted information that conclusively shows current or future
violations of the 2008 ozone NAAQS within the state of Delaware. For
the 2015 ozone NAAQS, the commenters identified current violating
monitors in Delaware but did not identify any projected air quality
violations in a future year associated with the relevant attainment
dates. Commenters did not correct any of the technical deficiencies the
EPA identified in Delaware's petitions. Thus, the EPA is concluding, as
proposed, that the petition does not adequately identify a relevant air
quality problem related to the 2008 or 2015 ozone NAAQS.
    Second, with respect to step two of the four-step framework,
material

elements of Delaware's analysis regarding the contributions from the
Brunner Island, Harrison, Homer City, and Conemaugh EGUs to air quality
in Delaware are deficient and, therefore, the conclusions that the
petitions draw are not supported by the technical assessment. As noted
earlier, all four petitions rely upon air quality modeling that uses
2011 emissions to quantify the contribution from each of the four named
sources to locations in Delaware on individual days in 2011. However,
2011 emissions are generally much higher than, and therefore not
representative of, current or future projected emissions levels at
these EGUs and in the rest of the region--levels that the EPA believes
are most relevant to determining whether a source ``emits or would
emit'' in violation of the good neighbor provision.\37\ Thus, the 2011
modeling does not provide representative data regarding contributions
that would result from either current or future emission levels from
these EGUs. When evaluating a CAA section 126(b) petition, it is
important and consistent with the language of the section to rely on
current and relevant data known at the time the agency takes action.
Were the EPA to act based on outdated or non-representative information
solely because it was provided in a petition, that action could be
arbitrary and unreasonable and could, for example, impose controls or
emission limitations that are not appropriately tailored to the nature
of the problem at the time of the EPA's final action or at the time
when such controls or limitations would actually be implemented. This
could result in unnecessary over-control (or under-control) of
emissions, beyond (or short of) what is required to address the good
neighbor provision, in violation of the Supreme Court's holding in EME
Homer City, 134 S. Ct. at 1608-09.
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    \37\ As an example of how emissions have changed between 2011
and a recent historical year, the EPA notes that Pennsylvania's 2017
EGU NOX ozone season emissions were 79 percent below 2011
levels. One of the named sources, Brunner Island, is located in
Pennsylvania and reduced its individual ozone season NOX
emissions by 88 percent in 2017 relative to 2011 levels. (https://www.epa.gov/ampd). Additional emissions data from 2011 and a recent
historical year is included in the docket, which also shows that
2011 emissions are generally higher than emissions in recent years.
See 2011 to 2017 NOX Comparisons, Ozone Season, available
in the docket for this action.
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    Further, the analyses provided by Delaware regarding the alleged
impacts of the four sources on downwind air quality include some
information on the frequency and magnitude of ozone impacts, but the
information provided does not account for the form of the 2008 or 2015
ozone standards--which indicates that a NAAQS violation occurs when the
fourth highest daily maximum value in a calendar year at a specific
monitor exceeds the standard--and, thus, is not informative of whether
there is a nonattainment issue in the state. Specifically, Delaware
does not identify the numeric modeled and/or measured ozone levels on
the same days identified in Delaware's petitions with modeled
impacts.\38\ For example, Delaware's Homer City petition identifies
modeled contributions from emissions at that source to three downwind
monitoring sites in Delaware on July 18, 2011. However, the petition
fails to identify whether there were measured and/or modeled
exceedances of the ozone NAAQS on that particular day at those sites.
Delaware's Harrison and Brunner Island petitions identify the days the
contributions were modeled to occur, but not the specific monitoring
sites where Delaware claims emissions from these sources impact air
quality. Moreover, these two petitions do not provide information on
whether the contributions were to design values that actually exceed
the ozone NAAQS. Delaware's Conemaugh petition identifies 2011
contributions on days when some Delaware monitors exceeded the 2008
NAAQS, but the petition does not specify which monitors were impacted
on those days. The petition therefore does not provide information to
show that the modeled contributions occurred at monitoring sites that
were exceeding either the 2008 or 2015 ozone NAAQS. Commenters did not
provide additional information clarifying these deficiencies.
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    \38\ Existing EPA analyses of interstate ozone pollution
transport focus on contributions to high ozone days at the specific
downwind receptor in order to evaluate the impact on nonattainment
and maintenance at the receptor. For example, in the CSAPR Update
modeling, ozone contributions were calculated using data for the
days with the highest future year modeled ozone concentrations. For
the 2008 ozone NAAQS, only the highest measured ozone days from each
year are considered for the calculation of ozone design values (the
values that determine whether there is a measured NAAQS violation).
Measured ozone values that are far below the level of the NAAQS do
not cause an exceedance or violation of the NAAQS. For this reason,
only ozone contributions to days that are among the highest modeled
ozone days at the receptor are relevant to determining if a state or
source is linked to downwind nonattainment or maintenance issues.
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    For the reasons described in this section, Delaware's analyses in
its four petitions do not allow the EPA to conclude that there is a
current or future nonattainment or maintenance problem in Delaware
based on violations of the NAAQS, nor that the named sources are
improperly impacting downwind air quality on days when such violations
would be expected. Therefore, the EPA does not have a basis to grant
Delaware's petition with respect to either the 2008 or 2015 ozone NAAQS
based on data and analyses provided in the petitions.
2. The EPA's Analysis of the Technical Sufficiency of Maryland's
Petition
    The EPA is not finalizing its proposed finding that Maryland's
petitions are technically deficient, but is finalizing the denial based
on the EPA's independent assessment there are no additional cost-
effective reductions relative to the CSAPR Update for the sources named
in Maryland's petition. This topic is discussed in more detail in
Section IV.B of this notice.

B. The EPA's Independent Analysis of the Petitions Consistent With the
CSAPR Update

    As discussed in Section III.A of this notice, the EPA may decide to
conduct independent analyses when evaluating the basis for a potential
CAA section 126(b) finding or when developing a remedy if a finding is
made. Because the CSAPR Update recently evaluated interstate ozone
pollution transport, including considering the air quality and EGU
emissions described in the Delaware and Maryland 126(b) petitions, the
EPA evaluated the petitions and comments received on the proposal in
light of the agency's existing regulatory program, and the underlying
analysis on which it is based. This constitutes the EPA's independent
analysis for certain aspects of the petitions. The agency also
evaluated additional technical information that became available after
the CSAPR Update was finalized to independently evaluate other aspects
of the petitions.
    This section begins by explaining the relationship between the
CSAPR Update and the EPA's independent analysis of the petitions. The
subsequent subsections discuss the EPA's rationale for denying the
petitions with respect to the named sources.
1. CSAPR Update as Context
    The EPA promulgated the CSAPR Update to address the good neighbor
provision requirements for the 2008 ozone NAAQS. 81 FR 74504. The final
CSAPR Update built upon previous regulatory efforts in order to address
the collective contributions of ozone pollution from 22 states in the
eastern United States to widespread downwind air quality problems. As
was also the case for the previous rulemakings, the EPA evaluated the
nature (i.e., breadth and interconnectedness) of the ozone problem and
NOX reduction potential

from EGUs, including those sources named in the Delaware and Maryland
CAA section 126(b) petitions.
    Of particular relevance to this action, the EPA determined in the
CSAPR Update that emissions from the states identified in Maryland's
petition were linked in steps one and two of the four-step framework to
maintenance receptors for the 2008 ozone NAAQS in Maryland based on air
quality modeling projections to 2017. 81 FR 74538 through 74539. With
respect to Delaware, the CSAPR Update modeling revealed no monitors in
the state with a projected average or maximum design value above the
level of the 2008 ozone NAAQS in 2017.\39\ Thus, the EPA in step one of
the four-step framework did not identify any downwind air quality
problems in Delaware with respect to the 2008 ozone NAAQS and,
therefore, did not determine that emissions from any of the states
identified in the state's four petitions would be linked to Delaware.
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    \39\ See Air Quality Modeling Technical Support Document for the
Final Cross-State Air Pollution Rule Update. Available at https://www.epa.gov/airmarkets/air-quality-modeling-technical-support-document-final-cross-state-air-pollution-rule.
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    For states linked to downwind air quality problems in Maryland, the
agency identified certain emissions from large EGUs as significantly
contributing to nonattainment and/or interfering with maintenance of
the NAAQS based on cost and air-quality factors. Considering these
factors, the EPA found there were cost-effective emission reductions
that could be achieved within upwind states at a level of control
stringency available at a marginal cost of $1,400 per ton of
NOX reduced. This level of control stringency represented
ozone season NOX reductions that could be achieved in the
2017 analytic year and included the potential for operating and
optimizing existing SCR post-combustion controls; installing state-of-
the-art NOX combustion controls; and shifting generation to
existing units with lower NOX emission rates within the same
state. 81 FR 74551. The CSAPR Update quantified an emission budget for
each state based on that level of control potential. The EPA found that
these emission budgets were necessary to achieve the required emission
reductions and mitigate impacts on downwind states' air quality in time
for the July 2018 moderate area attainment date for the 2008 ozone
NAAQS.
    The CSAPR Update finalized enforceable measures necessary to
achieve the emission reductions in each state by requiring power plants
in covered states, including the sources identified in Maryland and
Delaware's petitions, to participate in the CSAPR NOX Ozone
Season Group 2 allowance trading program, with more detailed assurance
provisions applying to each covered state to ensure that they will be
required to collectively limit their emissions, beginning with the 2017
ozone season. The CSAPR trading programs and the EPA's prior emission
trading programs (e.g., the NOX Budget Trading Program
associated with the NOX SIP Call) have provided a proven,
cost-effective implementation framework for achieving emission
reductions. This implementation approach was shaped by previous
rulemakings and reflects the evolution of these programs in response to
court decisions and practical experience gained by states, industry,
and the EPA.
    As discussed in more detail later, the EPA has considered the CSAPR
Update and related technical information in evaluating the section
126(b) petitions. This includes a review of the air quality modeling
conducted for the CSAPR Update to evaluate projected nonattainment and
maintenance concerns in each petitioning states in steps one and two of
the four-step framework. The EPA has also considered the control
strategies evaluated and implemented in the CSAPR Update to conclude,
in step three, that the EPA has already implemented emission reductions
associated with operation of existing SCRs at the named sources and
that the EPA has already concluded that the operation of existing SNCR
at two other named sources is not a cost-effective control strategy
under the good neighbor provision.
2. The EPA's Step One and Two Analyses for Delaware and Maryland
    As part of the EPA's independent analysis, the agency considered
Delaware's and Maryland's petitions in light of recent agency analysis
which applied steps one and two of the four-step framework. The EPA
found that the named sources are not contributing to nonattainment or
interfering with maintenance of Delaware's air quality for either the
2008 or 2015 ozone NAAQS, and that the sources named in Maryland's
petition warranted further analysis of significant contribution to
nonattainment and interference with maintenance for the 2008 ozone
NAAQS in step three.
a. The EPA's Step One Analyses for Delaware
    While the EPA, as discussed in Section IV.A of this notice, finds
that Delaware's petitions do not on their own merits adequately
establish the presence of a current or future nonattainment or
maintenance problem in Delaware, the EPA also independently examined
whether there is an air quality problem under the 2008 and 2015 ozone
NAAQS (step one). As described in the following sections, the EPA finds
that the named sources in Delaware's petitions are not, and will not
be, emitting in violation of the good neighbor provision with respect
to Delaware for either the 2008 or 2015 ozone NAAQS. The EPA also
conducted a further independent assessment of the sources named in
Delaware's petitions with respect to step three of the framework,
discussed later in this notice, which further supports the EPA's denial
of the Delaware petitions.
(1) The EPA's Independent Analysis Regarding Delaware's Step One Claims
With Respect to the 2008 Ozone NAAQS
    The EPA first looked to modeling conducted in 2016 that projects
ozone concentrations at air quality monitoring sites in 2017, which was
conducted for purposes of evaluating step one of the four-step
framework for the 2008 ozone NAAQS as part of the CSAPR Update.\40\
This modeling indicated that Delaware was not projected to have any
nonattainment or maintenance receptors in 2017 with respect to the 2008
ozone NAAQS. See 83 FR 26678. Furthermore, the EPA examined Delaware's
2014-2016 design values, and found that no areas in Delaware had a
design value that violated the 2008 ozone NAAQS. See id. An examination
of the recently released 2015-2017 design values showed the same
result.\41\ Accordingly, the EPA has no basis to conclude that any of
the sources named by Delaware in its petitions are linked to a downwind
air quality problem in the state with regard to the 2008 ozone NAAQS.
In the absence of a downwind air quality problem, the EPA has no
authority to regulate upwind sources to address air quality in Delaware
with respect to the 2008 ozone NAAQS.
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    \40\ Air Quality Modeling Technical Support Document for the
Final Cross-State Air Pollution Rule Update (August 2016). Available
at https://www.epa.gov/sites/production/files/2017-05/documents/aq_modeling_tsd_final_csapr_update.pdf.
    \41\ See 2017 Design Value Reports, available at https://www.epa.gov/sites/production/files/2018-07/ozone_designvalues_20152017_final_07_24_18.xlsx.

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(2) The EPA's Independent Analysis Regarding Delaware's Step One Claims
With Respect to the 2015 Ozone NAAQS
    Additionally, the EPA independently examined whether there will be
a downwind air quality problem in Delaware with regard to the 2015
ozone NAAQS. The modeling conducted in support of the CSAPR Update
shows one monitor--monitor ID 100051003 in Sussex County--with a
maximum 2017 projected design value (which the EPA has typically used
to help identify maintenance receptors) above the 2015 ozone NAAQS.\42\
Measured data show that two monitors exceeded the 2015 ozone NAAQS
based on the 2014-2016 design values,\43\ and three monitors show
exceedances of the 2015 ozone NAAQS based on the 2015-2017 design
values.\44\ However, as described in Section II.B of this notice, the
EPA evaluates downwind ozone air quality problems for the purposes of
Step one of the four-step framework using modeled future air quality
concentrations for a year that EPA selects in consideration of the
relevant attainment deadlines for the NAAQS. Thus, the 2017 modeling
data and the recent measured data are not necessarily indicative of a
downwind air quality problem that would necessitate the control of
upwind sources to address air quality in Delaware with respect to the
2015 ozone NAAQS.
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    \42\ In prior transport rulemakings, the EPA identified both
nonattainment and maintenance receptors based on air quality model
projections of measured design values. In the CSAPR Update, the EPA
identified nonattainment receptors as those with an average
projected design value above the NAAQS and with current measured
nonattainment. The EPA identified maintenance receptors as those
monitors with a ``maximum'' future design value above the NAAQS in
order to take into account historic variability in air quality at
the monitor. See 81 FR 74531.
    \43\ See 2016 Design Value Reports, available at https://www.epa.gov/air-trends/air-quality-design-values#report. The
official designations for these areas and information relied upon
for those designations are contained in the EPA's designation
actions for the 2015 ozone NAAQS. See 82 FR 54232 (November 16,
2017) and the docket for Additional Air Quality Designations for the
2015 Ozone National Ambient Air Quality Standards, EPA-HQ-OAR-2017-
0548, and accompanying technical support documents.
    \44\ See 2017 Design Value Reports, available at https://www.epa.gov/sites/production/files/2018-07/ozone_designvalues_20152017_final_07_24_18.xlsx.
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    Recent analyses projecting emission levels to a future year
indicate that no air quality monitors in Delaware are projected to have
nonattainment or maintenance problems with respect to the 2015 ozone
NAAQS by 2023, which is the last year of ozone season data that will be
considered in order to determine whether downwind nonattainment areas
classified as moderate have attained the standard by the relevant 2024
attainment date.\45\ Therefore, consistent with the EPA's
interpretation of the term ``will'' in the good neighbor provision
discussed in Section III of this notice, available future year
information does not indicate Delaware will have air quality concerns
by the attainment date for the 2015 ozone NAAQS that EPA has determined
is relevant for purposes of this analysis. Accordingly, the EPA does
not have a basis to regulate upwind sources to address air quality in
Delaware with respect to the 2015 ozone NAAQS.
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    \45\ See Information on the Interstate Transport State
Implementation Plan Submissions for the 2015 Ozone National Ambient
Air Quality Standards under Clean Air Act Section 110(a)(2)(D)(i)(I)
(March 27, 2017), available in the docket for this proposed action.
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(3) Responses to Comments Regarding the EPA's Independent Analysis for
Step One Under the 2008 and 2015 Ozone NAAQS
    Commenters asserted that the EPA's conclusion that Delaware does
not have current or future nonattainment or maintenance problems for
the 2008 and 2015 ozone NAAQS is unreasonable in light of technical
information in the record they claim demonstrates otherwise. Commenters
further state that New Castle County, Delaware, was designated
nonattainment as part of the multistate Philadelphia nonattainment area
under both the 2008 and 2015 ozone NAAQS, and that the most recent
design values for three monitors in New Castle County exceeded the 70
ppb 2015 ozone standard.
    As an initial matter, the EPA disagrees with the way the commenters
characterize an air quality problem in relation to CAA section 126(b).
The EPA's statutory authority extends to addressing emissions that
significantly contribute to nonattainment or interfere with maintenance
of the NAAQS. Commenters' focus on individual high ozone days does not
account for the form of the 2008 or 2015 ozone standards (under which a
violation occurs when the fourth-highest reading in a calendar year at
a specific monitor exceeds the NAAQS) and thus is not informative of
whether there is a nonattainment or maintenance issue. Thus, the
petitioners and commenters raise contentions are ultimately misaligned
with the EPA's logical approach of identifying downwind air quality
problems for purposes of CAA sections 110(a)(2)(D)(i)(I) and 126(b) in
a manner that is consistent with the form of the standard.
    As described earlier, the EPA has evaluated air quality monitoring
and modeling data for the 2008 ozone NAAQS, and found no current or
anticipated future violations of the 2008 ozone NAAQS (in the form of
the standard) at receptors within the state of Delaware. While the EPA
evaluated modeling data for future projections of air quality for both
the 2008 and 2015 ozone NAAQS consistent with the forward-looking
nature of the good neighbor provision, monitoring data regarding
current violations is a relevant analytic tool for the 2008 ozone NAAQS
considering the attainment date for the standard has already passed.
However, because the relevant attainment date for the 2015 ozone NAAQS
has not yet passed, it is appropriate to evaluate future anticipated
air quality in step one of determining whether sources must be
controlled under the good neighbor provision. The EPA evaluated air
quality modeling data for receptors located within the state of
Delaware and found that, while there are monitors that are currently