sector[hyphen]specific standards related to fuels, vehicle fuel
economy, pollution controls, and repair and replacement of the existing
fleet. Programs such as the Tier 3 vehicle emissions standards are
already being phased in between now and 2023. That rule was finalized
in 2014 with a phase-in schedule of 2017-2025 reflecting fleet
turnover. As discussed in more detail later, emission reductions from
stationary sources could likely be implemented more quickly than would
result from any attempt to effect additional reductions from mobile
sources beyond those already being implemented. Thus, the EPA has
focused its analysis of the feasibility of implementing additional
emission controls on stationary sources.
a. EGUs
    The EPA's analysis in the CSAPR Update is of particular relevance
to the agency's assessment of feasible EGU NOX mitigation
strategies in this action because that rule evaluated and implemented
all EGU strategies that were cost-effective and feasible to implement
quickly. Accordingly, as explained in the proposal for this action, the
EPA reasonably focused its current assessment of the feasibility of
implementing further EGU NOX mitigation strategies on
control technologies that require more time to implement and that were
thus not previously evaluated in the CSAPR Update with respect to the
2008 ozone NAAQS.
    In establishing the CSAPR Update EGU ozone season NOX
emissions budgets, the agency quantified the emission reductions
achievable from all NOX control strategies that were
feasible to implement in less than one year and cost-effective at a
marginal cost of $1,400 per ton of NOX removed.\67\ These
EGU NOX control strategies were: Optimizing NOX
removal by existing, operational selective catalytic reduction (SCR)
controls; turning on and optimizing existing, idled SCR controls;
installing state-of-the-art NOX combustion controls; and
shifting generation to existing units with lower NOX
emissions rates within the same state. 81 FR 74541. The agency observes
that the resulting CSAPR Update emissions budgets are being
appropriately implemented under the CSAPR NOX Ozone Season
Group 2 allowance trading program. Data for the 2017 ozone season (the
first CSAPR Update compliance period) indicate that power plant ozone
season NOX emissions across the 22 state CSAPR Update region
fell by 77,512 tons (or 21%) from 2016 to 2017.\68\ As a result, total
2017 ozone season NOX emissions from covered EGUs across the
22 CSAPR Update states were approximately 294,394 tons,\69\ well below
the sum of states' 2017 emissions budgets established in the CSAPR
Update of 316,464 tons.\70\ Further, the EPA is not aware of any
relevant, significant changes in the EGU fleet since promulgation of
the CSAPR Update that would necessitate reevalution of the emission
reduction potential from control strategies already implemented in the
CSAPR Update. Accordingly, for the purposes of this final
determination, the EPA considers optimizing NOX removal by
existing, operational SCR controls, turning on and optimizing of
existing SCR controls, and the installation of combustion controls to
be NOX control strategies that have already been
appropriately evaluated and implemented in the final CSAPR Update for
purposes of addressing the good neighbor provision for the 2008 ozone
NAAQS. The EPA does not believe it would be reasonable to base its
selection of a future analytic year on the timeframe for implementation
of control strategies that the EPA has already evaluated in the CSAPR
Update and that are already being implemented appropriately, according
to the best data available at this time (i.e., recent ozone season
NOX emissions data with CSAPR Update implementation).
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    \67\ The CSAPR Update was signed on September 7, 2016,
approximately 8 months before the beginning of the 2017 ozone season
on May 1.
    \68\ https://ampd.epa.gov/ampd/ (Data current as of October 26,
2018).
    \69\ Id.
    \70\ Preliminary data for the 2018 ozone season (the second
CSAPR Update compliance period), which became available after the
proposal for this action and after the close of the comment period,
continue to indicate that CSAPR Update emissions budgets are being
appropriately implemented under the trading program. Power plant
ozone season NOX emissions across the 22 state CSAPR
Update region fell by 83,084 tons (or 22%) from 2016 to 2018. As a
result, total 2018 ozone season NOX emissions from
covered EGUs across the 22 CSAPR Update states were approximately
288,825 tons, well below the sum of states' 2018 emissions budgets
established in the CSAPR Update of 313,626 tons.
---------------------------------------------------------------------------

    In the CSAPR Update, the EPA also evaluated one EGU NOX
control strategy that was considered feasible to implement within one
year but was not cost-effective relative to other near-term control
strategies at a marginal cost of $1,400 per ton of NOX
removed: Turning on existing idled selective non-catalytic reduction
(SNCR) controls. In the CSAPR Update, the EPA identified

a marginal cost of $3,400 per ton as the level of uniform control
stringency that represents turning on and fully operating idled SNCR
controls.\71\ However, the CSAPR Update finalized emissions budgets
using $1,400 per ton control stringency, finding that this level of
stringency represented the control level at which incremental EGU
NOX reductions and corresponding downwind ozone air quality
improvements were maximized with respect to marginal cost in the
context of the short-term control strategies being considered in that
rulemaking. In finding that the $1,400 per ton control cost level was
appropriate, the EPA determined that, based on the fleet
characteristics of SNCR and their operation at the time of the CSAPR
Update, the more stringent emissions budget level reflecting $3,400 per
ton (representing turning on idled SNCR controls) yielded fewer
additional emission reductions and fewer air quality improvements
relative to the increase in control costs. In other words, based on the
CSAPR Update analysis, establishing emissions budgets at $3,400 per
ton, and therefore developing budgets based on operation of idled SNCR
controls, was not determined to be cost-effective for addressing good
neighbor provision obligations for the 2008 ozone NAAQS. 81 FR 74550.
As explained in our proposed determination, the EPA continues to
believe that the strategy of turning on and fully operating idled SNCR
controls was appropriately evaluated in the CSAPR Update with respect
to other short-term control strategies for addressing interstate ozone
pollution transport for the 2008 ozone NAAQS. Further, the EPA is not
aware of any significant changes in the fleet characteristics of
existing SNCR and their operation since promulgation of the CSAPR
Update and therefore does not find it necessary to reevaluate the cost-
effectiveness of operating idled SNCR in the short term. Based on data
available at this time, the EPA does not believe it would be reasonable
to base its selection of a future analytic year on the timeframe for
implementation of a control strategy that the EPA has already
determined was not cost-effective relative to other short-term control
strategies. Accordingly, in this final action the EPA is not further
assessing this control strategy for purposes of identifying an
appropriate future analytic year.
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    \71\ See EGU NOX Mitigation Strategies Final Rule TSD
(docket ID EPA-HQ-OAR-2015-0500-0554, available at
www.regulations.gov and https://www.epa.gov/sites/production/files/2017-05/documents/egu_nox_mitigation_strategies_final_rule_tsd.pdf)
(NOX Mitigation Strategies TSD).
---------------------------------------------------------------------------

    The remaining control strategy that the EPA evaluated in the CSAPR
Update was the shifting of generation from EGUs with higher
NOX emissions rates to EGUs with lower NOX
emissions rates within the same state as a means of reducing emissions
at costs commensurate with and in support of emission control
technologies to reduce NOX emissions. Shifting generation is
a NOX control strategy that occurs on a time- and cost-
continuum, in contrast to the relatively discrete price-points and
installation timeframes that can be identified for emission control
technologies--i.e., combustion and post-combustion controls. Therefore,
in the CSAPR Update, the EPA identified the discrete cost thresholds
used to evaluate upwind states' good neighbor obligations based on its
evaluation of combustion and post-combustion control technologies, and
secondarily examined the amount of generation shifting that would
result at the same time and cost threshold associated with and in
support of the particular control technology. Quantifying
NOX reductions from shifting generation anticipated at the
same time and cost thresholds relative to the control technologies
being considered (e.g., restarting idled SCR controls) helped ensure
that the emission reductions associated with the control strategies
could be expected to occur in the CSAPR Update's market-based
implementation system. In other words, had the agency excluded
consideration of generation shifting in calculating emissions budgets
in step 3 in the CSAPR Update, generation shifting would have
nonetheless occurred as a compliance strategy in step 4. Although
potential emission reductions resulting from generation shifting were
factored into the final budgets, this compliance strategy did not drive
the EPA's identification of the analytic year or cost thresholds
analyzed in the CSAPR Update.
    Consistent with our explanation at proposal, the EPA does not find
it appropriate to solely evaluate the potential for generation shifting
(e.g., in isolation from viable combustion or post-combustion control
assessments) for purposes of selecting a future analytic year. The EPA
continues to believe that generation shifting is not particularly well
suited to identifying discrete analytic inputs, given its ability to be
phased in on a time- and cost-continuum. Further, given CSAPR Update
implementation as well as current and projected natural gas prices that
are low relative to historical levels, significant shifting from
higher-emitting EGUs to lower-emitting EGUs (relative to historical
generation levels) is already occurring and expected to continue to
occur by 2023 due to market drivers.\72\ Thus, there may only be a
limited opportunity, if any, for the EGUs in CSAPR Update states to
implement as an interstate transport control measure further emission
reductions through generation shifting prior to 2023, beyond that which
is already occurring and reasonably expected to occur as a result of
other factors. Given EPA's historical consideration of this strategy as
a secondary factor in quantifying emissions budgets, the EPA believes
the most reasonable approach for selecting a future analytic year is to
focus on the timeframe in which specific control strategies other than
generation shifting can be implemented.\73\
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    \72\ See Electric Monthly Power. Department of Energy, Energy
Information Administration. Table 1.1 Net Generation by Energy
Sources. September 2018. Also See Total Electricity Supply,
Disposition, Prices, and Emissions, Annual Energy Outlook.
Department of Energy, Energy Information Administration.
    \73\ Because the EPA is not in this final action evaluating
additional generation shifting possibilities, it does not at this
time need to revisit the question whether it is within the EPA's
authority or otherwise proper to consider generation shifting in
implementing the good neighbor provision. The EPA is aware that this
has been an issue of contention in the past, and stakeholders have
raised serious concerns regarding this issue. See, e.g., 81 FR at
74545 (responding to comments); CSAPR Update--Response to Comment,
at 534-50 (EPA-HQ-OAR-2015-0500-0572) (summarizing and responding to
comments).
---------------------------------------------------------------------------

    For these reasons, for purposes of identifying an appropriate
future analytic year, the EPA is focusing its assessment of EGUs in
this action on control technologies that were deemed to be infeasible
to install for the 2017 ozone season rather than reassessing controls
previously analyzed for cost-effective emission reductions in the CSAPR
Update. In establishing the CSAPR Update emissions budgets, the EPA
identified but did not analyze the following two EGU NOX
control strategies in establishing emissions budgets because regional
implementation by 2017 was not considered feasible: (1) Installing new
SCR controls; and (2) installing new SNCR controls. The EPA observed
that EGU SCR post-combustion controls can achieve up to 90 percent
reduction in EGU NOX emissions. The EPA also observed that
SNCR controls can be effective at reducing NOX emissions and
can achieve up to a 25 percent emission reduction from EGUs (so long as
sufficient reagent is employed). In 2017, SCR controls were in
widespread use across the power sector in the east, whereas SNCR
controls are considerably

less prevalent. In the 22-state CSAPR Update region, approximately 62
percent of coal-fired EGU capacity is equipped with SCR controls while
12 percent is equipped with SNCR controls.\74\
---------------------------------------------------------------------------

    \74\ National Electric Energy Data System v6 (NEEDS). EPA
(September 2018). Available at https://www.epa.gov/airmarkets/national-electric-energy-data-system-needs-v6.
---------------------------------------------------------------------------

    The EPA notes that differences between these control technologies
exist with respect to the potential viability of achieving cost-
effective, regional NOX reductions from EGUs. As just
described, SCR controls generally achieve greater EGU NOX
reduction efficiency (up to 90 percent) than SNCR controls (up to 25
percent). Resulting in part from this disparity in NOX
reduction efficiency, the EPA found new SCR controls to be more cost-
effective at regionally removing NOX when considering both
control costs and the NOX reduction potential in developing
its cost-per-ton analysis for the CSAPR Update. Specifically, the EPA
found that new SCR controls could generally reduce EGU emissions at a
marginal cost of $5,000 per ton of NOX removed whereas new
SNCR controls could generally reduce EGU emissions at a higher cost of
$6,400 per ton of NOX removed.\75\ In other words, the
greater NOX reduction efficiency for SCR controls translates
into greater cost-effectiveness of NOX removal relative to
SNCR controls. Simply put, SCR can achieve significantly more regional
NOX reduction at a lower cost per ton than SNCR. The general
NOX mitigation and cost-effectiveness advantage of SCR is
also consistent with observed installation patterns where SCR controls
(62 percent of coal-fired capacity) are more prevalent across the CSAPR
Update states relative to SNCR (12 percent of coal-fired capacity).
Moreover, as discussed in response to a comment later in this section,
installation of SNCR still takes significant time as compared to the
2008 ozone NAAQS attainment dates and SNCR installation at an
individual source would likely make later installation of an SCR cost-
prohibitive and therefore forgo the potential for greater emission
reductions that could be achieved at that source from the latter
technology in the future. Considering these factors, the EPA believes
it is appropriate to give particular weight to the timeframe required
for implementation of SCR across the region as compared to SNCR.
---------------------------------------------------------------------------

    \75\ EGU NOX Mitigation Strategies Final Rule TSD.
---------------------------------------------------------------------------

    For SCR, the total time associated with project development is
estimated to be up to 39 months for an individual power plant
installing controls on more than one boiler.\76\ However, more time is
needed when considering installation timing for new SCR controls
regionally, for CSAPR Update states. As described in the subsequent
paragraphs, the EPA has determined that a minimum of 48 months (4
years) is a reasonable time period to allow to complete all necessary
steps of SCR projects at EGUs on a regional scale. This timeframe would
allow for regional implementation of these controls (i.e., at multiple
power plants with multiple boilers) considering the necessary stages of
post-combustion control project planning, shepherding of labor and
material supply, installation, coordination of outages, testing, and
operation. SNCR installations, while generally having shorter project
timeframes (i.e., up to 16 months for an individual power plant
installing controls on more than one boiler), share similar
implementation steps with and also need to account for the same
regional factors as SCR installations.\77\ Therefore, the EPA finds
that more than 16 months would be needed to complete all necessary
steps of SNCR development at EGUs on a regional scale. Despite EPA's
prioritization of SCR as compared to SNCR in identifying the timeframe
for installing new controls, the EPA notes that installing these post-
combustion controls (SCR or SNCR) involve very similar steps and many
of the same considerations. The timing of their feasible regional
development is therefore described together in the following
paragraphs.
---------------------------------------------------------------------------

    \76\ Engineering and Economic Factors Affecting the Installation
of Control Technologies for Multipollutant Strategies. EPA Final
Report. Table 3-1. Available at https://archive.epa.gov/clearskies/web/pdf/multi102902.pdf.
    \77\ A month-by-month evaluation of SNCR installation is
discussed in EPA's ``Engineering and Economic Factors Affecting the
Installation of Control Technologies for Mulitpollutant Strategies''
at Exhibit A-6 and in EPA's NOX Mitigation Strategies
TSD. As noted at proposal, the analysis in this exhibit estimates
the installation period from contract award as within a 10-13 month
timeframe. The exhibit also indicates a 16-month timeframe from
start to finish, inclusive of pre-contract award steps of the
engineering assessment of technologies and bid request development.
The timeframe cited for installation of SNCR at an individual source
in this final action is consistent with this more complete timeframe
estimated by the analysis in the exhibit.
---------------------------------------------------------------------------

    Installing new SCR or SNCR controls for EGUs generally involves the
following steps: Conducting an engineering review of the facility to
determine suitability and project scope; advertising and awarding a
procurement contract; obtaining a construction permit; installing the
control technology; testing the control technology; and obtaining or
modifying an operating permit.\78\ These timeframes are intended to
accommodate a plant's need to conduct an engineering assessment of the
possible NOX mitigation technologies necessary to then
develop and send a bid request to potential suppliers. Control
specifications are variable based on individual plant configuration and
operating details (e.g., operating temperatures, location restrictions,
and ash loads). Before making potential large capital investments,
plants need to complete these careful reviews of their system to inform
and develop the control design they request. They then need to solicit
bids, review bid submissions, and award a procurement contract--all
before construction can begin.
---------------------------------------------------------------------------

    \78\ Final Report: Engineering and Economic Factors Affecting
the Installation of Control Technologies for Multipollutant
Strategies, EPA-600/R-02/073 (Oct. 2002), available at https://nepis.epa.gov/Adobe/PDF/P1001G0O.pdf.
---------------------------------------------------------------------------

    An appropriate regional control implementation timeframe should
also accommodate the additional coordination of labor and material
supply necessary for any regional NOX mitigation efforts.
For example, the total construction labor for a SCR system associated
with a 500-megawatt (MW) EGU is in the range of 330,000 to 350,000
person-hours, with boilermakers accounting for approximately half of
this time.\79\ In a 2017 industry survey, one of the largest shortages
of union craft workers was for boilermakers. This shortage of skilled
boilermakers is expected to rise due to an anticipated nine percent
increase in boilermaker labor demand growth by 2026, coupled with
expected professional retirements and comparatively low numbers of
apprentices joining the workforce.\80\ The shortage of and demand for
skilled labor, including other craft workers critical to pollution
control installation, is pronounced in the manufacturing industry. The
Association of Union Constructors conducted a survey of identified
labor shortages and found that boilermakers were the second-most
frequently reported skilled labor market with a labor shortage.\81\
Moreover, recovery efforts from the natural disasters of recent
hurricanes (e.g.,

Harvey, Irma, Florence, and Michael) and wildfires in 2017 are expected
to further tighten the labor supply market in manufacturing in the near
term.\82\ The EPA determined that these tight labor market conditions
within the relevant manufacturing sectors, combined with regional
NOX mitigation initiatives, would likely lead to some
sequencing and staging of labor pool usage in implementing control
technologies, rather than simultaneous construction across all efforts.
This sector-wide trend supports SCR and SNCR installation timeframes
for a regional program that exceed the demonstrated single-facility
installation timeframe.
---------------------------------------------------------------------------

    \79\ Id.
    \80\ Occupational Outlook Handbook. Bureau of Labor Statistics.
Available at https://www.bls.gov/ooh/construction-and-extraction/boilermakers.htm.
    \81\ Union Craft Labor Supply Survey. The Association of Union
Constructors. Exhibit 4-2 at page 29. Available at https://www.tauc.org/files/2017_TAUC_UNION_CRAFT_LABOR_SUPPLY_REVISEDBC_FINAL.pdf.
    \82\ Skilled Wage Growth Less Robust, Worker Shortage Still an
Issue. Industry Week. October 23, 2017. Available at http://www.industryweek.com/talent/skilled-wage-growth-less-robust-worker-shortage-still-issue.
---------------------------------------------------------------------------

    In addition to labor supply, NOX post-combustion control
projects also require materials and equipment such as steel and cranes.
Sheet metal workers, necessary for steel production, are reported as
having a well-above-average supply-side shortage of labor.\83\ This,
coupled with growth in steel demand estimated at three percent in 2018
suggests that there may be a constricted supply of steel needed for
installation of new post-combustion controls.\84\ Similarly, cranes are
critical for installation of SCRs, components of which must be lifted
hundreds of feet in the air during construction. Cranes are also facing
higher demand during this period of economic growth, with companies
reporting a shortage in both equipment and available labor.\85\ \86\
The tightening markets in relevant skilled labor, materials, and
equipment, combined with the large number of installations that could
be required under a regional air pollution transport program,
necessitates longer installation timetables relative to what has been
historically demonstrated at the facility level.
---------------------------------------------------------------------------

    \83\ Union Craft Labor Supply Survey. The Association of Union
Constructors. Exhibit 4-2 at page 29. Available at https://www.tauc.org/files/2017_TAUC_UNION_CRAFT_LABOR_SUPPLY_REVISEDBC_FINAL.pdf.
    \84\ Worldsteel Short Range Outlook. October 16, 2017. Available
at https://www.worldsteel.org/media-centre/press-releases/2017/worldsteel-Short-Range-Outlook-2017-2018.html.
    \85\ See, e.g., Seattle Has Most Cranes in the Country for 2nd
Year in a Row--and Lead is Growing. Seattle Times. July 11, 2017.
Available at https://www.seattletimes.com/business/real-estate/seattle-has-most-cranes-in-the-country-for-2nd-year-in-a-row-and-lead-is-growing/.
    \86\ See RLB Crane Index, January 2018 in the docket for this
action.
---------------------------------------------------------------------------

    Further, scheduled curtailment, or planned outage, for pollution
control installation would be necessary to complete SCR or SNCR
projects on a regional scale. Given that peak demand and rule
compliance would both fall in the ozone season, sources would likely
need to schedule installation projects for the ``shoulder'' seasons
(i.e., the spring and/or fall seasons), when electricity demand is
lower than in the summer, reserves are higher, and ozone season
compliance requirements are not in effect. If multiple units were under
the same timeline to complete the retrofit projects as soon as feasible
from an engineering perspective, this could lead to bottlenecks of
scheduled outages as each unit attempts to start and finish its
installation in roughly the same compressed time period. Thus, any
compliance timeframe that would assume installation of new SCR or SNCR
controls should be developed to reasonably encompass multiple shoulder
seasons to accommodate scheduling of curtailment for control
installation purposes and better accommodate the regional nature of the
program.
    Finally, the time lag observed between the planning phase and in-
service date of SCR operations in certain cases also illustrates that
site-specific conditions can lead to installation times of four years
or longer--even for individual power plants. For instance, SCR projects
for units at the Ottumwa power plant (Iowa), Columbia power plant
(Wisconsin), and Oakley power plant (California) were all in the
planning phase in 2014. By 2016, these projects were under construction
with estimated in-service dates of 2018.\87\ Similarly, individual SNCR
projects can exceed their estimated 16-month construction timeframe.
For example, the SNCR installation at the Jeffrey power plant (Kansas)
was in the planning phase in 2013 but not in service until 2015.\88\
Further, large-scale projects also illustrate that timelines can extend
beyond the general estimate for a single power plant when the project
is part of a larger, multifaceted air pollution reduction goal. For
instance, the Big Bend power plant in Florida completed a multifaceted
project that involved adding SCRs to all four units as well as
converting furnaces, over-fire air changes, and making windbox
modifications. A decade elapsed between the initial planning stages and
completion.\89\
---------------------------------------------------------------------------

    \87\ 2014 EIA Form 860. Schedule 6. Environmental Control
Equipment.
    \88\ 2013 EIA Form 860, Schedule 6, Environmental Control
Equipment.
    \89\ Big Bend's Multi-Unit SCR Retrofit. Power Magazine. March
1, 2010. Available at http://www.powermag.com/big-bends-multi-unit-scr-retrofit/.
---------------------------------------------------------------------------

    In summary, while facility-level SCR and SNCR projects can
themselves take up to 39 and 16 months, respectively, a comprehensive
and regional emission reduction effort requires more time to
accommodate the labor, materials, and outage coordination for these two
types of control strategies. Given the extra weight given to SCR
controls due to their greater NOX reduction efficiency and
cost-effectiveness as well as the time to regionally develop and
implement SCRs as a control strategy for CSAPR Update states, the EPA
concludes that 48 months would be a reasonable and expeditious
timeframe to coordinate the planning and completion of further regional
NOX mitigation efforts.
    Comment: Several commenters contend that the EPA's assessment of
emission reductions available from existing EGU NOX controls
in the CSAPR Update is insufficient. These comments suggested that
additional reductions are available from existing SCR NOX
controls before 2023 because the EPA's use of a 0.10 lb/mmBtu emission
rate in its calculation of emission budgets was not reflective of the
total reduction potential from SCR optimization. The commenters provide
analysis using the unit-level ozone-season emission rates between 2005-
2016 and suggest that the EPA should have relied on each unit's best
performing ozone-season emission rate from a given year in that period
to determine the emission rate at which each unit's SCR is fully
optimized. The commenters suggest that because the optimization of SCRs
at a lower rate can be achieved prior to 2023, the EPA should examine
air quality in an earlier analytic year.
    Response: The EPA does not agree that it is necessary to consider
any further emission reductions ostensibly available from the
optimization of existing SCRs. As described in the following
paragraphs, the agency's assessment of NOX reduction
potential from existing SCR controls used in establishing CSAPR Update
emission budgets remains appropriate. Moreover, as discussed later in
this notice, the best data available at this time--2017 EGU emission
data reflecting CSAPR Update implementation--indicate that in general
these controls are optimally operating to mitigate NOX
emissions across the CSAPR Update region. Thus, control optimization
for existing SCRs has already been addressed in the CSAPR Update and
emission reductions associated with the ``additional'' control
technology proposed by commenters are being commensurately realized
through implementation of the CSAPR Update's

allowance trading program. The EPA therefore does not agree that a
control strategy that is already being appropriately implemented should
guide its selection of a future analytic year.
    In the CSAPR Update, the EPA determined that, based on an
aggregation of unit-level emission rates, an average fleet-wide
emission rate of 0.10 lb/mmBtu would represent the optimized operation
of SCR controls that were not already being operated and optimized. 81
FR 74543. In concluding that this rate would be appropriate for
calculating emission reduction potential from implementation of this
control strategy, the EPA recognized that some units would have
optimized rates above that level and some below that level. 81 FR
74543. The EPA explained that it used data from 2009 through 2015 and
calculated an average NOX ozone-season emission rate across
the fleet of coal-fired EGUs with SCR for each of those years. It then
selected the third-best (i.e., third-lowest) yearly rate for each unit,
noting that it did not find it prudent to use the first- and second-
best yearly rate because the best-performing data from those years is
likely to reflect the utilization of new SCR systems, all of whose
components were new in that year (e.g., new layers of catalyst), and
may not be representative of an ongoing, achievable NOX rate
once one or more SCR components have begun to degrade with age. Id. The
third-to-lowest year average was 0.10 lb/mmBtu. In the CSAPR Update,
the EPA applied that fleet-wide average to units with SCR that were not
already emitting at or below that NOX emission rate. For
units operating at or below that level in 2015 (the starting year from
EPA's budget-setting methodology), the EPA continued to utilize that
lower rate. The EPA in the CSAPR Update already addressed comments
regarding the reasonableness of its approach to calculating an
appropriate emission rate and did not, in this action, request
additional comment on the EPA's determination finalized in the CSAPR
Update that 0.10 lb/mmBtu was a reasonable rate to represent optimized
SCR controls.\90\ 81 FR 74544. The issue is also currently the subject
of litigation before the D.C. Circuit in Wisconsin v. EPA, No. 16-1406.
Accordingly, the EPA does not believe this issue is properly within the
scope of this action.
---------------------------------------------------------------------------

    \90\ 83 FR 31937 (indicating that EPA is not reconsidering or
reopening any analyses conducted or determinations made in the CSAPR
Update).
---------------------------------------------------------------------------

    The EPA continues to believe its approach in the CSAPR update was
prudent and reasonable for purposes of calculating emission reductions
achievable from the optimization of existing SCR controls and is not
changing its approach in this action. While commenters suggest
alternative emission rates would have been more appropriate, they have
not demonstrated that the EPA's approach is unreasonable. In
particular, the EPA does not agree with commenters that suggest that
the EPA should have used a value derived by relying on a 2005-2016
baseline (as opposed to the 2009-2015 baseline years used by EPA) and
selecting the single best year (i.e., the lowest average ozone-season
rate for SCR-controlled units in any given year) rather than the third-
best year. The EPA continues to find, as it did in the CSAPR Update,
that using a baseline starting in 2009 is more appropriate because that
year coincided with the onset of annual operation for most SCR controls
under the CAIR annual NOX program. Prior to 2009, these
controls operated seasonally, which allowed substantial time during the
fall, winter, and spring for routine maintenance and repair of the SCR,
as well as replacement of catalyst. This seasonal operation is not
representative of current or reasonably anticipated future operation of
these units that have been and continue to be subject to annual
NOX requirements, first under CAIR and now under CSAPR.
Further, the agency notes that the power sector has undergone
significant changes in recent years due to economic factors and
technological advances (e.g., natural gas production from horizontal
fracking technology advancements). As a result, the agency believes
that it is more appropriate to focus its analysis on relatively more
recent years of data, rather than to include a significant number of
years that preceded the set of current economic and technological
conditions affecting and driving outcomes in the sector. In other
words, the agency is more confident that recent data are an appropriate
basis to reasonably project future economic and technological
conditions with respect to operation of EGUs and their NOX
controls. The agency is not confident that older (i.e., pre-2009 data)
would be an appropriate basis to reasonably project future economic and
technological conditions with respect to operation of EGUs and their
NOX controls. The EPA therefore believes its approach in the
CSAPR Update was reasonable and preferable for the 2008 ozone NAAQS
compliance assumptions, and retains that approach in this action.
    The EPA also believes that its decision to rely on the third-best
seasonal emission rate was more appropriate than the commenter's
suggestion that the EPA select the emission rate from the best
performing year. By selecting the third-best seasonal rate, the EPA
avoided selecting times when SCR controls were newly constructed for
most units or may have been recently refreshed/replaced with all-new
catalyst. Complete catalyst change may have occurred at the onset of
major NOX reduction programs or at a time when the purpose
of the catalyst use changed (such as simultaneously optimizing for
mercury (Hg) removal under the Mercury and Air Toxic Standards (MATS)
program). By selecting the third-best seasonal rate out of the 2009-
2015 time period, the agency evaluated repeatable, low-NOX
control operation consistent with ongoing operation and maintenance of
SCR controls.
    Comment: A commenter asserts that the EPA should consider operation
of existing SNCR controls for purposes of selecting a future analytic
year, rather than considering cost-effectiveness to eliminate
utilization of some potentially feasible controls. The commenter
contends that the EPA's use of cost-effectiveness as a bright line for
determining what measures are appropriate for fully meeting the good
neighbor SIP obligations for upwind states is both erroneous and, as
applied here, arbitrary and capricious. The commenter states that, even
if the CSAPR Update could be read to conclude that operation of SNCR
was not cost-effective at that time, this conclusion was limited to the
purposes of the partial solution in that rule. The commenter claims
that the CSAPR Update did not deem operation of SNCR to never be cost-
effective, particularly in circumstances where the EPA has found no
other less-expensive way to reduce emissions. The commenter concludes
that, if EPA is using cost to eliminate potentially available
solutions, it must reevaluate these costs, not merely rest on cost data
from the CSAPR Update that are now several years old.
    Response: The EPA does not agree that the timeframe for operating
existing SNCR should influence its selection of a future analytic year.
As discussed earlier, the EPA's assessment in the CSAPR Update
indicated that the $3,400 per ton NOX control stringency
(representing turning on idled SNCR) was not cost-effective relative to
other short-term control strategies considered in that rulemaking. This
conclusion was based on the fact that EGUs with idled SNCR in the CSAPR
Update analysis

were relatively few and relatively small, such that few NOX
reductions were incrementally achievable from operation of idled SNCR
compared to other near-term control strategies available, while the
difference in cost per ton compared to the other strategies was
relatively large. Accordingly, the EPA found that the level of
NOX control stringency reflecting operation of idled SNCR
did not maximize NOX reduction potential and air quality
improvement relative to cost. Although the commenters suggest that the
EPA should reevaluate the cost-effectiveness of operating idled SNCR,
the commenters have not provided any data to the agency that would
indicate the agency's analysis would significantly change. Rather, the
EPA's conclusion in the CSAPR Update is further supported by reported
2017 data which show that there were 55 coal units operating in the
CSAPR Update region with SNCR installed with a weighted average ozone-
season emission rate of 0.14 lb/mmBtu, indicating that existing SNCR-
controlled units are already widely operating and would likely provide
little opportunity for additional reductions.\91\
---------------------------------------------------------------------------

    \91\ Preliminary data for the 2018 ozone season, which became
available after the proposal for this action and after the close of
the comment period, continue to support this conclusion by showing
that there were 48 coal units operating in the CSAPR Update region
with SNCR installed with a weighted average ozone-season emission
rate of 0.148 lb/mmBtu.
---------------------------------------------------------------------------

    The EPA notes that the agency's analysis in the CSAPR Update was
specific to the conditions evaluated therein. Thus, the EPA's
conclusion that the feasibility of implementing SNCR should not inform
the potential compliance timeframe and the identification of the future
analytic year would not have precluded the EPA from considering whether
the operation of SNCR would be cost-effective relative to the
installation of the post-combustion controls discussed earlier in this
section. Had the EPA, at step 1 of the four-step framework, identified
continued downwind air quality problems in the future analytic year,
the EPA could have considered at step 3 whether it would be cost-
effective to require upwind states linked at step 2 to make emission
reductions consistent with operation of existing SNCR relative to other
longer-term control strategies like the implementation of new post-
combustion controls. However, because EPA has already concluded that
operation of existing SNCR is not cost-effective in the near term, the
EPA does not agree that it would be reasonable for EPA to select an
earlier analytic year that would only be consistent with the timeframe
for implementing that particular compliance strategy.
    Comment: Several commenters contend that the EPA's implementation
of emission reductions via an allowance trading program is not
sufficient to guarantee that existing SCRs will continue to run in the
future (especially in light of low allowance prices). The commenters
therefore contend that further reductions are available from existing
EGU controls. The commenters suggest that EPA needs to ensure daily
operation of SCR controls and that the seasonal nature of the trading
program does not do so.
    Response: The EPA begins by pointing out that the commenter appears
to be attempting to reopen a determination made in the CSAPR Update
regarding how best to implement the emission reductions required by
that rule. The question of whether an allowance trading program is
sufficient to ensure emission reductions, relative to other forms of
emission limitations, was raised by commenters and addressed in the
CSAPR Update.\92\ The EPA did not, in this action, request additional
comment on the appropriateness of an allowance trading program to
ensure the CSAPR Update emission reductions would be achieved,\93\ and
it is therefore not re-opening the issue in this action. Moreover, even
if this issue were within the scope of this action, the commenters have
not explained how this concern should influence the EPA's selection of
the future analytic year used in this action. Accordingly, the relative
effectiveness of the CSAPR Update allowance trading program to ensure
emission reductions commensurate with optimizing SCR, as compared to
daily limits, is outside the scope of this action.
---------------------------------------------------------------------------

    \92\ CSAPR Update--Response to Comment (EPA-HQ-OAR-2015-0500-
0572).
    \93\ 83 FR 31937 (indicating that EPA is not reconsidering or
reopening any analyses conducted or determinations made in the CSAPR
Update).
---------------------------------------------------------------------------

    Nonetheless, the EPA notes that current data refute commenters'
assertion that allowance trading has been insufficient to achieve the
emission reductions associated with the operation and optimization of
existing SCRs. The best currently available data indicate that sources
in in CSAPR Update states are indeed operating SCRs in order to comply
with the CSAPR Update allowance trading program. Data from 2017, the
first year of ozone-season data that would be influenced by the CSAPR
Update compliance requirements, are consistent with the EPA's
assumption that the allowance trading program would incentivize SCR
operation on a fleet-wide level. The average emission rate for the 83
SCR-controlled units in the CSAPR Update region that were not
previously emitting with a NOX rate at or below 0.10 lb/
mmBtu in 2016 and are still operating in 2017 dropped by 45% from 0.22
lb/mmBtu to 0.12 lb/mmBtu between 2016 and 2017--the first ozone season
of CSAPR Update implementation.\94\ Not only is the program effective
at encouraging these particular units to achieve a better performance
rate, it also encourages the wider universe of SCR-controlled units to
keep operating their controls. In 2017, 261 of 274 EGUs with SCR in the
U.S. had ozone-season emission rates below 0.20 lb/mmBtu (194 of 202 in
CSAPR Update states), indicating that they were likely operating their
post-combustion controls throughout most of the ozone season. The 274
units were operating at an average emission rate of approximately 0.088
lb/mmBtu. Of the 13 units with 2017 emission rates above 0.20 lb/mmBtu,
five are located in states outside of the CSAPR Update region, five
have preliminary 2018 ozone season NOX emission rates below
0.20 lb/mmBtu, and one has retired (Killen unit 2 in Ohio).\95\
Consequently, the EPA finds that on average, SCR-controlled units
appear to be operating their SCRs throughout the season, and that the
petitioner's assertion regarding the likelihood of not operating
controls is therefore not supported by the most recently available
data. The EPA has not identified a basis for reevaluating emission
reductions available from optimizing SCRs and it therefore does not
believe it would be reasonable in light of this data to select an
earlier analytic year on the basis of this control strategy.
---------------------------------------------------------------------------

    \94\ Preliminary data for the 2018 ozone season, which became
available after the proposal for this action and after the close of
the comment period, continue to support this conclusion. The average
emission rate for the 73 SCR-controlled units in the CSAPR Update
region that were not previously emitting with a NOX rate
at or below 0.10 lb/mmBtu in 2016 and are still operating in 2018
dropped by 40% from 0.201 lb/mmBtu to 0.121 lb/mmBtu between 2016
and 2018--the second ozone season of CSAPR Update implementation.
Additionally, preliminary 2018 data indicate that the 192 coal units
operating in the CSAPR Update region with SCR installed had a
weighted average ozone-season NOX emission rate of 0.086
lb/mmBtu.
    \95\ Source: AMPD (ampd.epa.gov), EPA, 2018.
---------------------------------------------------------------------------

    Notwithstanding the EPA's finding that SCRs are currently operating
consistent with optimizing NOX reduction potential, the EPA
notes that SCR operation is not the sole metric with which to gauge
success of a cap-and-trade program. Rather, the success of the program
is ultimately indicated

not by the employment of any particular control strategy, but rather by
regionwide and state-level emission reductions. The CSAPR Update has
contributed to a 21 percent reduction in regionwide NOX
emissions in its first year, below the cumulative level of the budgets,
and all states operated well below their assurance levels.\96\ If some
SCRs are not performing at lower rates, but commensurate reductions are
achieved elsewhere in the state, this demonstrates one of the benefits
of a market-based trading program: It helps participants identify and
make the least-cost reductions. The EPA does not agree that such a
result, even accepting the commenter's analysis for the sake of
argument, demonstrates that the allowance trading program is
ineffective at achieving the intended emission reductions simply
because the covered sources chose an alternative pathway to comply with
the program's requirements.
---------------------------------------------------------------------------

    \96\ Source: AMPD (ampd.epa.gov), EPA, 2018.
---------------------------------------------------------------------------

    The EPA has also not identified a need to supplement the allowance
trading program established in the CSAPR Update with additional
emission limits in order to promote the daily operation of controls.
The EPA examined the hourly NOX emissions data reported to
the EPA and did not observe a significant number of instances of units
selectively turning down or turning off their emission control
equipment during hours with high generation. SCR-controlled units
generally operated with lower emission rates during high generation
hours, suggesting SCRs generally were in better operating condition--
not worse condition, let alone idling--during those days/hours. In
other words, the EPA compared NOX rates for EGUs from hours
with high energy demand, compared them with seasonal average
NOX rates, and found very little difference. Thus, the data
do not support the notion that units are reducing SCR operation on high
demand days and that consequently a narrower compliance timeframe is
needed to incentivize them to run on a daily basis. An examination of
average daily NOX emission rates for SCR-controlled units in
the CSAPR Update region shows that 2017 emission rates were
significantly lower than 2016 and 2015. The seasonal decline in
emission rate was also observed on a daily basis in the CSAPR Update
region: Out of 153 days in the ozone season in 2017, all 153 days had
lower average emissions rates among SCR-controlled sources than the
same day in 2016.\97\ Moreover, the auxiliary power used for control
operation is small--typically less than one percent of the generation
at the facility--and it is therefore unlikely that sources would cease
operation of controls for such a limited energy savings. Instead, the
data indicate that increases in total emissions on days with high
generation are generally the result of additional units that do not
normally operate coming online to satisfy increased energy demand and
units that do regularly operate increasing hourly utilization, rather
than reduced functioning of control equipment. Thus, the EPA does not
agree that there are additional limitations that should be implemented
to achieve emission reductions from the optimization of existing SCRs.
---------------------------------------------------------------------------

    \97\ Source: AMPD (ampd.epa.gov), EPA, 2018.
---------------------------------------------------------------------------

    Comment: One commenter suggests that the EPA can achieve additional
emission reductions in the short term by reducing budgets to account
for the accumulation of banked allowances. The commenter contends that
this would support higher allowance prices under the CSAPR
NOX Ozone Season Group 2 program, thereby incentivizing
continued SCR operation and further cost-effective reductions in
NOX emissions.
    Response: The EPA first notes that, to the extent the commenter is
challenging the EPA's decision in the CSAPR Update permit the continued
use of certain banked allowances, the agency already addressed comments
regarding this issue in that rulemaking, 81 FR 74557, and did not, in
this action, request additional comment on its determination with
regard to this issue as finalized in the CSAPR Update.\98\ The issue is
also currently the subject of litigation before the D.C. Circuit in
Wisconsin v. EPA. Accordingly, the EPA does not believe concerns
regarding the bank of allowances that were carried over in the CSAPR
Update are properly within the scope of this action. To the extent the
commenter suggests that the EPA eliminate the current bank of
allowances to achieve further NOX emission reductions in the
future, the EPA does not believe that the mere presence of a bank of
allowances indicates that such additional emission reductions are
actually achievable in practice. Current program design elements,
specifically the assurance provisions, are already in place to
incentivize the control operation referred to by the commenter and
ensure emission reductions. Moreover, the most recently observed
historical data suggest these controls are widely operating in the
compliance period and that their operation is not undermined by the
existence of the bank as suggested by the commenter.
---------------------------------------------------------------------------

    \98\ 83 FR 31937 (indicating that EPA is not reconsidering or
reopening any analyses conducted or determinations made in the CSAPR
Update).
---------------------------------------------------------------------------

    First, the CSAPR Update includes assurance provisions that help
ensure that EGUs in each covered state collectively limit their
emissions. These provisions include an assurance level for each state
that serves as a statewide emissions limit that cannot be exceeded
without penalty. This assurance level is the sum of the state emission
budget plus a variability limit equal to 21 percent of the state's
ozone-season budget. This means that collective EGU emissions in each
state cannot exceed 121 percent of the state budget level without
incurring penalties. The assurance levels are designed to help ensure
that emissions are reduced in each covered state of a region-wide
trading program while acknowledging and accommodating the inherent
variability in electricity generation and NOX emissions due
to year-to-year changes in power sector market conditions. These
assurance levels help ensure that emission reductions, including those
associated with the optimization of existing controls on which the
CSAPR Update budgets were based, continue to be implemented. Therefore,
even with fleet turnover and a growing allowance bank, EPA anticipates
that the assurance limit will maintain downward pressure on state-level
emissions.
    Second, the commenter misconstrues the emissions impact of an
allowance bank and does not provide further evidence that would be
needed to show that real-world emission reductions are available. A
bank of allowances, first and foremost, represents emission reductions
and not an emissions liability. Specifically, an allowance bank
represents allowable emissions that have not been emitted into the
atmosphere, converted into ozone, or transported downwind to impact the
ability of downwind areas to attain or maintain the NAAQS. The
commenter essentially asserts that an allowance bank will necessarily
undermine the operation of NOX controls. However, as
described previously, the best currently available data (i.e., recent
EGU emissions data with CSAPR Update implementation) indicate that
existing controls are being operated consistent with optimizing for
NOX mitigation. As such, the agency finds that, at this
time, the accumulation of the allowance bank primarily represents
emission reductions, and is not creating the incentive for controls to
be idled. Because the emission reductions sought

by the commenter (via operation of existing SCRs) are in fact already
being implemented across the region, the EPA has no reason to believe
that additional emission reductions could be achieved by either
eliminating the banked allowances or adjusting the budgets in some
manner commensurate with the current level of banked allowances. As
such, the emission reduction potential asserted by commenters is
hypothetical and the EPA has no reason to believe at this time that the
adjustments to the bank would lead to significant real-world
NOX reductions.
    Comment: The EPA received several comments on the proposed
determination regarding its assessment of new EGU NOX
control strategies, suggesting that new NOX emission
mitigation technologies are available prior to 2023 and that the EPA's
reliance on the feasibility of regional installation of SCRs for
selection of a future analytic year is arbitrary and capricious. The
commenter further questions the EPA's estimate for installation of SCRs
and suggests they can be installed at a faster pace, noting that the
EPA allowed for just 30 months under the initial CSAPR promulgated in
2011. They assert that the EPA has not adequately demonstrated that the
market for labor and materials, while observed to be strained, is more
strained than previous environments. The EPA notes that other
commenters agreed with the EPA's timeline for implementation of new
mitigation technologies and asserted that that it would be infeasible
for EGUs to install new SCRs or SNCRs in less than four years. The
commenters observe that in many cases it may take longer due to
planning and the outage window required for implementation of such
controls. They suggest that the EPA should consider a later analytic
year because not doing so puts the EPA at risk of over-controlling as
some plants that could not install controls by 2023 would install them
at a later date when those reductions are no longer needed.
    Response: For the reasons discussed earlier in this notice, the EPA
believes that conducting a regional analysis ensures that the Agency
can fully evaluate remaining obligations pursuant to the good neighbor
provision with respect to the 2008 ozone NAAQS. As the EPA has
routinely found throughout nearly 20 years of interstate transport
rulemakings, the ozone transport problem is regional in nature, in that
downwind states' problems attaining and maintaining the ozone NAAQS
result from the contribution of pollution from multiple upwind states,
with multiple upwind states routinely contributing to multiple downwind
states' air quality problems in varying amounts. With respect to the
2008 ozone NAAQS, the EPA determined in the CSAPR Update rulemaking
that, collectively, 22 upwind states contributed at or above the 1
percent threshold to downwind air quality problems at one or more of 19
different receptor locations in the eastern United States. Individual
upwind states contributed to between 1 and 8 downwind nonattainment or
maintenance receptors and, in a number of cases, upwind states also
contained at least one receptor indicating a downwind air quality
problem to which other states contributed. Given the multi-faceted
nature of ozone transport, the Supreme Court has acknowledged that the
EPA is faced with the burden to determine ``how to differentiate among
otherwise like contributions of multiple upwind states.'' EME Homer
City, 134 S. Ct. at 1607. As the Supreme Court acknowledged, the
statute is silent as to which metric the EPA should use to decide the
apportionment of the shared obligation to address a downwind air
quality problem among multiple upwind states--what the Court referred
to as the ``thorny causation problem.'' Id. at 1603-04.
    Accordingly, because ozone air quality problems (and in particular
interstate transport) are regional in nature, the EPA has developed--
and the Supreme Court has endorsed--a regional approach for quantifying
individual states' emission reduction obligation. In particular, the
EPA has developed a two-pronged metric (constituting steps 2 and 3 of
the four-step transport framework) to identify the amounts of an upwind
state's emissions that ``contribute significantly to nonattainment'' or
``interfere with maintenance'' of the ozone NAAQS in a downwind state
to which it is linked. The EPA identifies those emissions that both:
(1) Contribute 1 percent or more of the NAAQS to an identified downwind
air quality problem (i.e., the identification of linkage at CSAPR
framework step 2); and (2) can be eliminated through implementation of
cost-effective control strategies, applied uniformly to all states
linked to an air quality problem (i.e., the quantification of emission
reductions at CSAPR framework step 3). When evaluating at step 3
whether a control strategy is cost-effective for this purpose, the EPA
considers the incremental cost per ton of emissions reduced, the
magnitude of emissions that can be reduced using a particular control
strategy, and the downwind air quality benefits of implementing such
emission reductions. 81 FR at 74519. The Supreme Court found this
approach, as applied in the original CSAPR rulemaking, to be ``an
efficient and equitable solution to the allocation problem the Good
Neighbor Provision requires the Agency to address.'' Id. at 1607. The
Court held that this approach is: ``[e]fficient because EPA can achieve
the levels of attainment, i.e., of emission reductions, the
proportional approach [urged by respondants in EME Homer City] aims to
achieve, but at a much lower overall cost. Equitable because, by
imposing uniform cost thresholds on regulated States, EPA's rule
subjects to stricter regulation those States that have done relatively
less in the past to control their pollution. Upwind States that have
not yet implemented pollution controls of the same stringency as their
neighbors will be stopped from free riding on their neighbors' efforts
to reduce pollution. They will have to bring down their emissions by
installing devices of the kind in which neighboring States have already
invested.'' Id.
    Given the regional nature of the ozone pollution problem and the
requirement that the EPA determine the remainder of its good neighbor
FIP obligation with respect to the 2008 ozone NAAQS for 21 states in
the CSAPR Update region, the EPA reasonably applied the regional
framework endorsed by the Supreme Court as an ``efficient and
equitable'' approach to resolving the remaining good neighbor
obligations interstate transport problem. Id. at 1607. Accordingly, the
EPA evaluated the contributions of all upwind states that are linked to
a given downwind air quality problem, rather than quantifying the
significant contributions of single states or sectors in a vacuum.
Similarly, the EPA evaluated potential control strategies to address
that contribution on a regional, rather than facility- or state-
specific, basis. Such an approach also ensures that each state's
contributions to downwind air quality problems are quantified relative
to the contribution of the other contributing states.
    The commenters are also incorrect to assert that the agency's
conclusion that 48 months should be provided for the implementation of
new SCR is in conflict with its position in the original CSAPR
rulemaking. In the original CSAPR, the EPA established NOX
emission budgets in CSAPR based on a cost threshold of $500 per ton,
which was not anticipated to drive any new SCR installation in either
compliance phase. See Table VII.C.2-1, 76 FR 48279 and discussion at 76
FR 48302. As such,

this control strategy was not central to CSAPR Update implementation.
    Notwithstanding that SCR post-combustion controls were omitted from
the EPA's CSAPR emissions budgets at the time, to the extent labor and
supply markets were a consideration for installation timing
requirements for scrubbers in CSAPR in 2011, those variables have
changed over the last seven years. For instance, the EPA noted a sharp
drop in boilermaker person-hours worked between 2008 and 2010,
suggesting that the market at that time had substantial underutilized
capacity whereas today's industry surveys identify labor shortages.\99\
The EPA also disagrees with the commenter's assertion that these
observations regarding crane and steel markets are not reasonable and
thus should not influence the EPA's analysis. While not the sole reason
for the EPA's conclusion that a 48-month timeframe would be necessary
for region-wide control installation, the EPA believes the market for
labor and materials is a relevant weight-of-evidence consideration in
light of reports from companies that supply the tower cranes that there
is a shortage of both equipment and available labor. The crane index
and quarterly construction costs reports are metrics regularly used to
evaluate construction activity by construction consultants and provide
a sense of equipment demand. Moreover, the commenter provides no
evidence to refute the EPA's finding that these equipment markets are
facing periods of higher demand.
---------------------------------------------------------------------------

    \99\ Labor Availability for the Installation of Air Pollution
Control Systems at Coal-Fired Power Plants. Andover Technology
Partners. October 18, 2011. Available at http://www.andovertechnology.com/images/boilermaker%20labor%20availability%20final_jes_%2010%2018%202011.pdf.

---------------------------------------------------------------------------

    Thus, while the EPA does not agree that it is reasonable to
consider a timeframe longer than four years for the expeditious,
region-wide implementation of SCR controls, neither does the EPA agree
that it would be reasonable to assume any shorter timeframe under the
circumstances.
    Comment: Some commenters assert that the EPA could identify an
earlier analytic year based on the installation of new SNCRs because
the controls can be implemented more quickly than SCRs.
    Response: As explained above, the EPA does not agree that that the
regional installation of SNCRs should drive EPA's selection of an
appropriate future analytic year, primarily because SCR controls are
more effective at reducing NOX emissions and because SCR
controls are more regionally cost-effective at mitigating
NOX. Specifically, the EPA estimates the amount of
reductions available by SCR installation at uncontrolled sources is
nearly triple that available from SNCR installation.\100\ This
difference is significant because the agency is tasked with issuing
FIPs that fully resolve good neighbor obligations and therefore the
agency finds it reasonable to focus its analysis on the timeframe for
installing controls that would be best suited to achieve that goal in
terms of NOX mitigation, downwind air quality improvement,
and cost--i.e., SCR controls. Further, as described in the subsequent
paragraphs, the EPA finds that the regionally implementing
NOX reductions from SNCR would still take a significant
amount of time and would significantly hamper the ability of these EGUs
to obtain further emission reductions from installation of SCRs in the
future.
---------------------------------------------------------------------------

    \100\ Based on 2017 ozone-season NOX data. Applying
SCR reduction potential of 90 percent (up to a 0.07 lb/mmBtu floor)
as opposed to 25 percent reduction for SNCR to 2017 emission levels
for uncontrolled coal sources emitting at 0.15 lb/mmBtu or greater.
---------------------------------------------------------------------------

    First, the EPA noted above that the estimated timing to install
SNCR for multiple boilers at one power plant is approximately 16
months--and can take even longer in practice. Accounting for the
regional factors that must be considered (described previously), it
would take more than 16 months for this control strategy to be
regionally implemented. Starting with promulgation of this action in
December of 2018, the agency believes it would take well into 2020 for
these controls to be feasibly implemented, regionally. As a result, it
is very unlikely that these controls could affect ozone season
NOX attainment demonstrations made in July 2021 for areas
designated serious for the 2008 ozone NAAQS.
    Finally, the agency notes the potential for inefficiency in
effectively controlling NOX emissions in the long term by
prioritizing SNCR controls now to the detriment of future
NOX mitigation potential from SCR controls. Installing an
SNCR at a unit in the near term and then upgrading or retrofitting the
unit to an SCR a few years down the road would effectively increase the
cost per ton of that eventual SCR installation as compared to
installing the SCR in the first place. The main difference between the
two systems is the temperature window at which the reaction takes
place. With an SNCR, that window is 900-1050 degrees Celsius, whereas
it drops to a range of 160 to 350 degrees Celsius for an SCR. These
differentials in optimal temperatures influence the location and
modifications necessary for each retrofit technology and therefore
complicate any transition from SNCR to SCR. SNCR can be described as
including a silo or tank (for reagent), a conveyance system for the
reagent, and a properly placed injection lance in the furnace. In terms
of volume occupied, over 90 percent of the system exists outside the
flue gas path. The SCR system, on the other hand, requires a catalytic
reactor and is placed downstream of the economizer. An SCR occupies a
significant space as the catalytic reactor resides in a dedicated
multi-story structure elevated above ground elevation. Over 90 percent
of an SCR's volume exists within the flue and duct work.
    The two systems are unique and distinct from one another in their
approach to reducing NOX and the equipment cannot be shared
or dual-purposed due to the size differences, conversion rates, and
reagent material flows based on the application (namely, the location
within the flue gas stream). Consequently, almost none of the capital
cost incurred for an SNCR system can be credited towards installation
of an SCR system. This would result--in most cases--in a higher overall
cost to get to the same level of emission reductions if a source first
installed an SNCR and then upgraded to an SCR as opposed to the initial
installation of an SCR. Such a retrofit would also likely increase the
amount of work, and therefore time, to complete the SCR installation.
    Thus, selecting an analytic year and imposing emission reductions
focused on installation of SNCR alone at an earlier date (if this could
even occur on an earlier timeframe regionwide) would potentially
obviate a source's ability to cost-effectively install SCR, a more
effective NOX control, at a later date. The EPA's obligation
in this action was to fully address states' good neighbor obligation
for the 2008 ozone NAAQS. Therefore, it was reasonable for the EPA to
select a future analytic year that would allow for advanced control
installation which would deliver significant reductions, if they were
determined to be necessary. Choosing an earlier analytic year based on
the installation of a SNCR alone would potentially be counterproductive
to EPA's objective to address states' full obligations and severely
limit sources' ability to obtain more significant emission reductions
from SCR in the future to address other control obligations.
b. Non-EGU Control Technologies
    The EPA is also evaluating the feasibility of implementing
NOX control

technologies for non-EGUs stationary sources as part of its
identification of an appropriate future analytic year. While the EPA
did not regulate non-EGUs in the CSAPR Update, the rule did evaluate
the feasibility of NOX controls on non-EGUs in the eastern
United States to assess whether any such controls could be implemented
in time for the 2017 ozone season. In the CSAPR Update, the EPA noted
that there was greater uncertainty in the assessment of non-EGU point-
source NOX mitigation potential as compared to EGUs, and
therefore explained that more time was required for states and the EPA
to improve non-EGU point source data, including data on existing
control efficiencies, additional applicable pollution control
technologies, and installation times for those control technologies. 81
FR 74542. A significant factor influencing uncertainty was that the EPA
lacked sufficient information on the capacity and experience of
suppliers and major engineering firms' supply chains to determine if
they would be able to install the pollution controls on non-EGU sources
in time for the 2017 ozone season. Further, using the best information
available to the EPA at that time, the EPA found that there were more
non-EGU point sources than EGU sources and that these sources on
average emit less NOX than EGUs. The implication was that
there were more individual sources that could be controlled, but
relatively fewer emission reductions available from each source when
compared to the number of EGUs and emission reductions available from
EGUs. Considering these factors, the EPA found that it was
substantially uncertain whether significant aggregate NOX
mitigation would be achievable from non-EGU point sources to address
the 2008 ozone NAAQS by the 2017 ozone season. Id.
    Although the EPA determined that there were limited achievable
emission reductions available from non-EGUs by the 2017 ozone season,
the EPA acknowledged that it may be appropriate to evaluate potential
non-EGU emission reductions achievable on a timeframe after the 2017
ozone season to assess whether upwind states continued to have
outstanding good neighbor obligations for the 2008 ozone NAAQS. 81 FR
74522. In particular, the EPA's preliminary assessment in the CSAPR
Update indicated that there may be emission reductions achievable from
non-EGUs at marginal costs lower than the costs of remaining
NOX control strategies available for EGUs. In evaluating
potential non-EGU emission reductions in the CSAPR Update, the EPA
included preliminary estimates of installation times for some non-EGU
NOX control technologies in a technical support document
entitled Assessment of Non-EGU NOX Emission Controls, Cost
of Controls, and Time for Compliance Final Technical Support Document
(henceforth, ``Final Non-EGU TSD''). These preliminary estimates were
based on research from a variety of information sources, including:
     Typical Installation Timelines for NOX
Emissions Control Technologies on Industrial Sources, Institute of
Clean Air Companies, December 2006 (all sources except cement kilns and
reciprocating internal combustion engines (RICE)); \101\
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    \101\ Institute of Clean Air Companies. Typical Installation
Timelines for NOX Emissions Control Technologies on
Industrial Sources, December 2006. Available at https://c.ymcdn.com/sites/icac.site-ym.com/resource/resmgr/ICAC_NOx_Control_Installatio.pdf.
---------------------------------------------------------------------------

     Cement Kilns Technical Support Document for the NOX FIP,
U.S. EPA, January 2001; \102\ and
---------------------------------------------------------------------------

    \102\ U.S. EPA. Cement Kilns Technical Support Document for the
NOX FIP. January 2001. Available at https://www.regulations.gov/document?D=EPA-HQ-OAR-2015-0500-0094.
---------------------------------------------------------------------------

     Availability and Limitations of NOX Emission Control
Resources for Natural Gas-Fired Reciprocating Engine Prime Movers Used
in the Interstate Natural Gas Transmission Industry, Innovative
Environmental Solutions Inc., July 2014--prepared for the Interstate
Natural Gas Association of America (INGAA Foundation).\103\
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    \103\ INGAA Foundation. Availability and Limitations of
NOX Emission Control Resources for Natural Gas-Fired
Reciprocating Engine Prime Movers Used in the Interstate Natural Gas
Transmission Industry, Innovative Environmental Solutions Inc., July
2014. Available at http://www.ingaa.org/Foundation/Foundation-Reports/NOx.aspx.
---------------------------------------------------------------------------

    In assessing an appropriate future analytic year for this action,
the EPA has looked to the information compiled in the Final Non-EGU TSD
for the CSAPR Update to evaluate what timeframe might be appropriate
for installing sector- or region-wide controls on non-EGU sources.
    Among the control technologies that were evaluated in the Final
Non-EGU TSD, the EPA identified six categories of common control
technologies available for different non-EGU emission source
categories. Final Non-EGU TSD at 19. For four of the technology
categories (SNCR, SCR, low-NOX burners (LNB), and mid-kiln
firing), the EPA preliminarily estimated that such controls for non-
EGUs could be installed in approximately one year or less in some unit-
specific cases. Installation time estimates presented in the Final Non-
EGU TSD considered a timeline that begins with control technology bid
evaluation (bids from vendors) and ends with the startup of the control
technology. See id. at 20. For the other two technology categories
(biosolid injection technology (BSI) and OXY-firing), as well as one
emission source category (RICE), the EPA had no installation time
estimates or uncertain installation time estimates. For example, the
EPA found that the use of BSI is not widespread, and therefore the EPA
does not have reliable information regarding the time required to
install the technology on cement kilns. The installation timing for
OXY-firing is similarly uncertain because the control technology is
installed only at the time of a furnace rebuild, and such rebuilds
occur at infrequent intervals of a decade or more. For those categories
for which preliminary estimates were available, as noted in the Final
Non-EGU TSD, the single-unit installation time estimates provided do
not account for additional important considerations in assessing the
full amount of time needed for installation of NOX control
measures at non-EGUs, including additional time likely necessary for
permitting or installation of monitoring equipment. See id. at 19-21.
These preliminary installation estimates also do not account for
factors such as multi-boiler installations at a particular source and
pre-vendor bid engineering studies.\104\
---------------------------------------------------------------------------

    \104\ In particular, this document presents different
installation time estimates for SCRs for EGUs and non-EGUs. However,
these installation times are not necessarily inconsistent, because
the EGU time estimate of 39 months mentioned above is based on
multi-boiler installation and factors in a pre-vendor bid
engineering study consideration, whereas the non-EGU SCR
installation time estimates are based on single-unit installation
and do not factor in pre-vendor bid evaluation. Consideration of
these additional factors might extend the time estimate for
installation of SCRs for non-EGUs.
---------------------------------------------------------------------------

    In particular, the preliminary estimates of installation times of
approximately a year or less shown in the Final Non-EGU TSD are for
installation at a single source and do not account for the time
required for installing controls to achieve sector-wide compliance.
Thus, the preliminary estimates do not consider time, labor, and
materials needed for programmatic adoption of measures and time
required for installing controls on multiple sources in a few to
several non-EGU sectors across the region. When considering
installation of control measures on sources regionally and across non-
EGU sectors, the time for full sector-wide compliance is uncertain, but
it is likely longer than the installation times shown for control
measures for individual sources in the Final Non-EGU TSD. As discussed
earlier with respect to EGUs, regional,

sector-wide compliance could be slowed down by limited vendor capacity,
limited available skilled labor for manufacturers such as boilermakers
(who produce steel fabrications, including those for pollution control
equipment), availability of raw materials and equipment (e.g., cranes)
for control technology construction, and bottlenecks in delivery and
installation of control technologies. Some of the difficulties with
control technology installation as part of regional, sector-wide
compliance at non-EGUs, such as availability of skilled labor and
materials, could also have an impact on monitor installation at such
sources. The EPA currently has insufficient information on vendor
capacity and limited experience with suppliers of control technologies
and major engineering firms, which results in additional uncertainty in
the overall installation time estimates for non-EGU sectors.
    The EPA notes that its analysis in the Final Non-EGU TSD focused on
potential control technologies within the range of costs considered for
EGUs in the final CSAPR Update, i.e., those controls available at a
marginal cost of $3,400 per ton (2011 dollars) of NOX
reduced or less. The EPA's analysis did not evaluate implementation
timeframes or potential emission reductions available from controls at
higher cost thresholds. See Final Non-EGU TSD at 18. This focus
excluded some emission source groups with emission reduction potential
at a marginal cost greater than $3,400 per ton, including: Industrial/
commercial/institutional boilers using SCR and LNB; and catalytic
cracking units, process heaters, and coke ovens using LNB and flue gas
recirculation. However, while emission reduction potential from these
source groups is uncertain, the timeframe for these control
technologies would be subject to considerations and limitations similar
to those discussed in the preceding paragraphs.
    In summary, there is significant uncertainty regarding the
implementation timeframes for various NOX control
technologies for non-EGUs. While the EPA has developed preliminary
estimates for some potential control technologies, these estimates only
account for the time between bid evaluation and startup but do not
account for additional considerations such as pre-bid evaluation
studies, permitting, and installation of monitoring equipment.
Moreover, these preliminary estimates do not account for the impacts of
sector- and region-wide compliance, which may be complex considering
the diversity of non-EGU sources as well as the greater number and
smaller size of the individual sources. The EPA did not receive any
comments on its proposal that would contradict the importance of these
considerations. Accordingly, in light of these considerations, the EPA
believes that it is reasonable to assume for purposes of this action
that an expeditious timeframe for installing sector- or region-wide
controls on non-EGU sources may be four years or more.
    Comment: One commenter suggests that the EPA's assessment of
feasibility of control strategies for non-EGU sources rests on a need
for further information gathering, when the agency has had ample time
to do this work already, citing U.S. Sugar Corp. v. EPA, 830 F.3d 579,
644 (D.C. cir. 2016) (``The Agency was obligated to collect the data it
needed, and Congress gave it the authority to do so.''). The commenter
asserts that the EPA cited this same basis for deferring a full remedy
in the CSAPR Update and that the EPA has been invoking an alleged need
to gather more information on these sources for more than a decade,
citing the original CSAPR rulemaking and CAIR. The commenter states
that it is unlawful and arbitrary for the EPA to rely on a need for
information that it has failed to collect or analyze despite its own
longstanding recognition that the information is needed, citing Sierra
Club v. Johnson, 444 F. Supp. 2d 46, 53 (D.D.C. 2006) (explaining that
statutory deadlines in the Clean Air Act indicate that Congress
intended agencies to prioritize timeliness over perfection).
    Another commenter notes that the EPA indicated in separate
litigation that it intended to take steps to improve its data on non-
EGU controls by November 2017, citing Opposition and Cross-Motion for
Summary Judgment, Sierra Club v. Pruitt, No. 3:15-cv-04328 (N.D. Cal.
Dec. 15, 2016) ECF No. 63., but that it has never completed these
steps. The commenter asserts that the determination is therefore based
on speculation. The commenter continues that the EPA does not explain
why the information that was previously found to be insufficient is now
sufficient for purposes of this action, nor does the EPA explain why it
still has not quantified or analyzed the potential for cost-effective
emission reductions from non-EGU sources. Thus, the commenter asserts
that the EPA ignores its own framework for determining the availability
and cost-effectiveness of non-EGU controls. The commenter claims that
this is a change in position from the CSAPR Update where the EPA stated
that a final determination of whether the emission reductions from that
rule would be sufficient to address the good neighbor obligation would
depend upon an evaluation of non-EGU sources.
    Response: The commenter is incorrect in asserting that the EPA's
basis for its conclusion in this action regarding the implementation
timeframe for control strategies for non-EGU sources rests on the
assumption that more information gathering is necessary. While the EPA
has discussed the uncertainties associated with determining appropriate
implementation timeframes for a number of control measures and
technologies that could be applied to a large number and variety of
non-EGU sources, as discussed above the EPA has evaluated the
information known to the agency regarding various control measures and
technologies and the factors affecting the installation of various
control technologies. Considering the information known to the agency,
as outlined in the Final Non-EGU TSD, the EPA has reasonably concluded
that expeditious implementation of additional controls for non-EGU
sources may be four years or more. The commenter is thus incorrect to
suggest that the EPA has further deferred its evaluation of non-EGU
sources. This is the same information that the EPA relied upon to
determine that significant and meaningful non-EGU emission reductions
could not feasibly be implemented by the 2017 ozone season in the CSAPR
Update. 81 FR 74542. The commenter has not provided information that
would contradict the EPA's conclusion that it is appropriate to assume,
based on the information known to the agency, that four years or more
should be provided for the installation of controls for non-EGU
sources.
    This approach is not a change in policy. In the CSAPR Update, the
EPA only stated that it could not conclude, at that time, whether
additional reductions from NOX sources (including non-EGUs)
would be necessary to fully resolve these obligations. In the CSAPR
Update, the EPA did indicate that it anticipated the need to evaluate
non-EGUs to evaluate the full scope of upwind states' good neighbor
obligations, and the agency has done so here in so far as evaluating
control feasibility. Specifically, in selecting the appropriate future
analytic year in which to evaluate air quality, contributions, and
NOX reduction potential, as necessary, the EPA considered
the implementation timeframes for controls at EGUs as well as non-EGUs.
As discussed in more detail later, the EPA's analysis showed

that there would be no remaining air quality problems in 2023 in the
eastern U.S., and thus the EPA has concluded that no such additional
reductions beyond those on-the-books or on-the-way controls are
necessary, whether from non-EGUs or otherwise, to bring downwind areas
into attainment and maintenance of the 2008 ozone NAAQS. Because the
air quality modeling results for 2023 show that air quality problems in
the eastern U.S. would be resolved by 2023, the EPA has not further
evaluated the cost-effectiveness of the control options considered for
the feasibility analysis. This approach is consistent with the EPA's
four-step framework and does not rely on the relative cost-
effectiveness of controls for non-EGU sources.
    The commenter's reliance on U.S. Sugar and Sierra Club is therefore
inapposite. In U.S. Sugar, the court was reviewing the EPA's decision
not to regulate certain sources under a different provision of the CAA
based on a lack of information. 830 F.3d at 642-43. The court, however,
found that the agency's duty to regulate these sources was
nondiscretionary and that the statute provided the agency with explicit
authority to gather information from the affected sources for this
purpose. Id. at 644. Here, the EPA is not deferring a nondiscretionary
duty to issue a regulation addressing controls at non-EGU sources, but
has evaluated the potential NOX control measures and
technologies at non-EGU sources using all information known to the
agency, as described in the Final Non-EGU TSD, in order to inform its
further analysis of upwind state obligations under the good neighbor
provision. In Sierra Club, the court laid out the standard for
determining the time needed to promulgate regulations under the CAA
after the EPA fails to perform the mandatory duties within the
statutorily prescribed timeframe. 444 F. Supp. 2d at 52. As the
commenters note, the court stated, among other things, that courts will
generally not provide additional time to promulgate a regulation
``simply to improve the quality or soundness of the regulations to be
enacted.'' Id. at 53. However, the court in that case addressed a
mandatory deadline set by the statute to promulgate a plan; it was not
evaluating the EPA's interpretation of a statutory provision like the
good neighbor provision that does not set an express deadline for
implementation of emission reductions.
    Notably, the court in Sierra Club did find that the statutory
deadlines in the Clean Air Act indicate that Congress intended agencies
to prioritize timeliness over perfection. 444 F. Supp. 2d at 53. Thus,
to the extent another commenter chides the EPA for acting based on the
information before the agency, even if it has not completed all steps
to improve its data for non-EGU sources, the Sierra Club decision
supports the agency's approach. Moreover, because the EPA did not need
to evaluate either the cost-effectiveness or NOX reduction
potential of either EGU or non-EGU sources, the commenter's concern
with whether the EPA has completed steps to improve its data on these
issues is irrelevant. Nonetheless, the EPA notes that the particular
efforts outlined in the court filing referred to by the commenter were
taken in support of the EPA's request in a mandatory duty suit that the
court permit the agency several years to develop a rulemaking to
address the good neighbor obligations with respect to the 2008 ozone
NAAQS for Kentucky and 20 other states. In that filing, the EPA
outlined steps that the agency believed would be necessary to
promulgate a rulemaking if the EPA's analysis demonstrated that
additional emission reductions would be required from sources in upwind
states, including what the EPA viewed as necessary analysis regarding
non-EGU sources. The EPA acknowledged in that same declaration that one
possible result of the EPA's analysis could be a determination that
downwind air quality problems would be resolved, in which case a cost-
effectiveness analysis would be unnecessary. See Opposition and Cross-
Motion for Summary Judgment, Exhibit 1 (Decl. of Janet G. McCabe) para.
98, Sierra Club v. Pruitt, No. 3:15-cv-04328-JD (N.D. Cal. Dec. 15,
2016), ECF No. 63. As the EPA could not know the results of any future
air quality modeling before it was performed, the EPA's proposed
timeline assumed that such an analysis might be required. Id. para.
170. Ultimately, the court disagreed with the EPA's proposed timeline
and provided only one year from its order--until June 30, 2018--for
promulgation of a rulemaking addressing Kentucky's good neighbor
obligation, which was insufficient time to complete all of the steps
outlined in the EPA's declaration, thereby requiring the EPA to
prioritize certain steps and eliminate others, including the additional
efforts intended to improve data regarding the feasibility and cost-
effectiveness of controls. Nonetheless, because the first step of the
EPA's analysis demonstrated that there would be no remaining air
quality problems in 2023 in the eastern U.S., it turned out to be
unnecessary for the EPA to finalize the efforts to improve its data
regarding the cost-effectiveness of controls before finalizing this
action. Thus, the representations that the EPA made to the court
regarding the steps necessary to take this action no longer apply under
the present circumstances.
3. Focusing on 2023 for Analysis
    As discussed in section III.B, the EPA weighed several factors to
identify an appropriate future analytic year for evaluating interstate
transport obligations for the 2008 ozone NAAQS. First, the EPA
identified the relevant attainment dates to guide the EPA's
consideration as 2021 and 2027, respectively the Serious and Severe
area attainment dates for the 2008 ozone NAAQS.
    Second, the EPA identified and analyzed the feasibility and timing
needed for installing additional NOX emissions controls. As
discussed in section III.B.2, the EPA believes it is appropriate to
assume that planning for, installing, and commencing operation of new
controls, regionally, for EGUs and non-EGUs would take up to 48 months,
and possibly more in some cases, following promulgation of a final rule
requiring appropriate emission reductions. This period of time
reflects, among other considerations, the time needed to regionally
develop new post-combustion SCR projects--systems that continue to
represent the engineering gold-standard in terms of reducing
NOX from the U.S. power sector.
    To determine how this feasibility assessment should influence
potential compliance timeframes, the EPA believes it is appropriate to
consider the date of promulgation of the rule that would establish
emission reduction requirements if necessary and thereby provide notice
to potentially regulated entities that actions will be required for
compliance. The EPA, therefore, considered the timeframe in which this
rulemaking would be finalized. As discussed previously, the EPA is
subject to several statutory and court-ordered deadlines to issue FIPs
to address any outstanding requirements under the good neighbor
provision for the 2008 ozone NAAQS for several states. The agency is
issuing this final action in light of those obligations. This action
will be signed no later than December 6, 2018, consistent with a court
order to take action addressing the FIP obligation for five
states.\105\ Considering the EPA's conclusion that 48 months is a
reasonable, and potentially expeditious,

timeframe for implementation of substantial regional control strategies
considered herein, emission reductions from these control strategies
would not be feasible until the 2023 ozone season. In other words, 48
months from a final rule promulgated in December 2018 would be December
2022, after which the next ozone season begins in May 2023. Considering
the time necessary to implement the controls calculated from a
realistic timeframe in which EPA would expect to promulgate a final
rule requiring such controls, the EPA believes that such reductions on
a variety of sources across the region are unlikely to be feasibly
implemented for a full ozone season until 2023.
---------------------------------------------------------------------------

    \105\ Order, New York v. Pruitt, No. 1:18-cv-00406-JGK (S.D.N.Y.
June 12, 2018), ECF No. 34. The five states are Illinois, Michigan,
Pennsylvania, Virginia, and West Virginia.
---------------------------------------------------------------------------

    Consistent with the court's holding in North Carolina, the agency
considers this timing in light of upcoming attainment dates for the
2008 ozone NAAQS. While 2023 is later than the next attainment date for
nonattainment areas classified as Serious (i.e., July 20, 2021), for
the reasons discussed above the EPA does not believe it is reasonable
to expect that additional regional emissions control requirements could
be developed and implemented by the Serious area attainment date.
Rather, the most expeditious timeframe in which additional regional
control strategies could be implemented at both EGUs and non-EGUs is 48
months after promulgation of a final rule requiring appropriate
emission reductions. At the same time, the EPA does not believe that it
should generally take longer than 2023 to install emissions controls on
a regional basis, based on the analysis above. Therefore, there is no
basis to postpone any potentially needed emission reductions to the
next attainment date after 2023, which is for nonattainment areas
classified as Severe (i.e., July 20, 2027). Accordingly, the EPA
believes implementation of additional emission reductions by 2023 is
the earliest feasible timeframe that could be reasonably required of
EGU and non-EGU sources that would be potentially subject to control
requirements. Although this year does not precisely align with a
particular attainment date, it reflects the year that is as expeditious
as practicable for regionwide implementation, while also taking into
account the relevant attainment dates.
    Given the current stage of the 2008 ozone implementation cycle, the
EPA's feasibility analysis set forth above, the relevant attainment
dates, and the courts' holdings in North Carolina and EME Homer City,
the EPA believes that 2023 is the most appropriate year for it to
assess downwind air quality and to evaluate any remaining requirements
under the good neighbor provision for the 2008 ozone NAAQS with regard
to all states covered in this action.
    Comment: Several commenters contend that the EPA's selection of a
2023 analytic year is inappropriate because it does not address
downwind states' obligations to attain the 2008 Ozone NAAQS by the July
20, 2021 attainment date for nonattainment areas classified as Serious.
The commenters generally cite North Carolina for the proposition that
EPA must esatablish interstate transport compliance deadlines under the
good neighbor provision that are identical to deadlines for downwind
states to achieve attainment with the NAAQS. The commenters note that,
in that decision, the D.C. Circuit rejected portions of CAIR on the
grounds that it did not require upwind contributors to eliminate their
significant contributions in time for downwind areas to meet their
impending attainment deadlines. The commenters state that the
attainment date for areas classified as Moderate nonattainment for the
2008 ozone NAAQS passed on July 20, 2018, and the next attainment dates
for the 2008 ozone NAAQS will be Serious area attainment date. Because
July 20, 2021 falls during the 2021 ozone season, the 2020 ozone season
will be the last full ozone season from which data can be used to
demonstrate attainment of the NAAQS by the July 2021 attainment date.
The commenters contend that North Carolina compels the EPA to identify
upwind reductions and implementation programs to achieve these
reductions, to the extent possible, during or before the 2020 ozone
season.
    One commenter further notes that CAA sections 110(a)(2)(D) and 182
require the EPA to implement the good neighbor provision ``consistent
with'' applicable attainment deadlines, and notes that the D.C. Circuit
held in North Carolina that this requirement is unambiguous. The
commenter states that the attainment deadlines in section 182 are fixed
dates with which the EPA must comply, citing Sierra Club v. Johnson,
294 F.3d 155, 161 (D.C. cir. 2002) (``[Section] 181(a)(1)[ ] as written
sets a deadline without an exception.''), and Train v. Natural
Resources Defense Council, 421 U.S. 60, 64-65 (1975) (Congress
``required'' attainment of air quality standards ``within a specified
period of time''). The commenter further states that the EPA is bound
by the requirement to eliminate significant contributions ``as
expeditiously as practicable'' but further notes that the use of the
words ``but not later than'' the dates listed in section 182
established the attainment deadlines as an express limit on the EPA's
discretion. The commenter therefore contends that the EPA's claim of
authority to fully implement the good neighbor provision ``as
expeditiously as practicable'' and later than the Serious attainment
dates is an exercise in rewriting the statute.
    Commenters also contend that the EPA's consideration of feasibility
cannot justify delaying action or analysis until 2023. One commenter
contends that the D.C. Circuit's decision in North Carolina rejected
compliance deadlines in CAIR that were based on ``feasibility
restraints such as the difficulty of securing project financing and the
limited amount of specialized boilermaker labor to install controls''
but were not ``consistent with . . . compliance deadlines for downwind
states.'' 531 F.3d at 911-12. The commenter asserts that the Clean Air
Act's attainment deadlines ``leave[ ] no room for claims of
technological or economic infeasibility,'' citing Union Elec. Co. v.
EPA, 427 U.S. 246, 258 (1976) (deadlines are ``intended to foreclose
the claims of emission sources that it would be economically or
technologically infeasible for them to achieve emission limitations
sufficient to protect the public health within the specified time'');
id. at 259 (Congress ``determined that existing sources of pollutants
either should meet the standard of the law or be closed down'')
(quoting S. Rep. No. 91-1196, pp. 2-3 (1970)).
    Response: The EPA does not agree that either the text of the
statute or the court's holding in North Carolina dictates that there
can only be one appropriate future analytic year and that this year
must be identical to an attainment deadline or forecloses consideration
of the feasibility of implementing emission reductions in determining
the appropriate future analytic year.
    First, as to the statute, the good neighbor provision does not set
forth any timeframe for the analysis of downwind air quality or the
implementation of upwind emission reductions. On its face, the good
neighbor provision is therefore ambiguous as to when the upwind
emission reductions it calls for must be in place. The EPA acknowledges
that the good neighbor provision does indicate that the prohibition of
upwind state emissions must be ``consistent with the provisions of
[title I],'' and that the D.C. Circuit held in its North Carolina
decision that the other provisions with which the implementation of the
good neighbor provision must be consistent include the attainment dates
in part D of title I of the Act. However, the good neighbor

provision does not specify what it means to be ``consistent with'' the
other provisions of the Act, and courts have routinely held that this
phrase is ambiguous See, e.g., EDF, 82 F.3d at 457 (holding the
requirement that implemention of transportation control measures be
``consistent with'' the applicable implementation plan under section
176 of the CAA is ``flexible statutory language'' which does not
require ``exact correspondence . . . but only congruity or
compatibility,'' thus requiring a court to defer to reasonable agency
determinations); Natural Resources Defense Council v. Daley, 209 F.3d
747, 754 (D.C. cir. 2000) (finding that statute requiring fishing
quotas be ``consistent with'' a fishery management plan was ambiguous);
NL Indus. v. Kaplan, 792 F.2d 896, 898-99 (9th Cir. 1986) (statutory
phrase ``consistent with the national contingency plan'' in 42 U.S.C.
9607(a)(2)(B) ``does not necessitate strict compliance with [national
contingency plan's] provisions''). Moreover, while CAA section 181
identifies timeframes for attaining ozone standards in downwind states,
it does not specify deadlines for good neighbor emission
reductions.\106\ Therefore, Congress has left a gap for EPA to fill.
See Chevron v. NRDC, 467 U.S. 837, 843 (1984). In light of this
ambiguity, the good neighbor provision cannot be read to require
implementation of upwind emission reductions on a specific timeframe,
and a compliance timeframe imposed pursuant to a good neighbor plan
should be considered reasonable so long as the EPA has demonstrated
that it is chosen in consideration of and is not inconsistent with
downwind attainment dates and other relevant attainment planning
requirements in title I.
---------------------------------------------------------------------------

    \106\ It is worth noting that the statutory text of CAA section
181(a) does not itself establish the attainment dates for the 2008
ozone NAAQS. Rather, the EPA undertakes rulemakings to establish the
appropriate deadlines after a new or revised ozone NAAQS is
promulgated. See, e.g., 2008 Ozone NAAQS SIP Requirements Rule, 80
FR 12264, 12268 (Mar. 6, 2015); 40 CFR 51.1103.
---------------------------------------------------------------------------

    Moreover, the statute does not impose inflexible deadlines for
attainment. The general planning requirements that apply to
nonattainment areas under subpart 1 of part D provide that the
Administrator may extend the default five-year attainment date by up to
10 years ``considering the severity of nonattainment and the
availability and feasibility of pollution control measures.'' CAA
section 172(a)(2)(A). In the case of the ozone NAAQS, this provision is
overridden by the more specific attainment date provisions of subpart
2. The general timeframes provided for attainment in ozone
nonattainment areas in the section 181(a)(1) table may be (and often
are) modified pursuant to other provisions in section 182, considering
factors such as measured ozone concentrations and the feasibility of
implementing additional emission reductions. For example, the six-year
timeframe for attainment of the 2008 ozone NAAQS in Moderate areas (the
July 2018 attainment date) could be extended under certain
circumstances to 2020, pursuant to section 181(a)(5). And pursuant to
section 181(b)(2), when downwind areas are unable to implement
sufficient reductions via feasible control technologies by one
attainment date, those areas will be reclassified, or ``bumped up'' in
classification, and given a new attainment date with additional time to
attain. With ``bump-ups'' like this, the date for an area to attain the
2008 ozone NAAQS could be extended to 2021, 2027, and 2032, and each of
these deadlines could be subject to further extensions of up to two
years pursuant to section 181(a)(5). Part D further defines what
control strategies states must implement by sources in nonattainment
areas by each of the applicable attainment dates, incorporating
considerations of technological feasibility at each stage. See, e.g.,
CAA section 172(c)(1), (2) (requiring implementation of reasonably
available control measures and reasonable further progress in
designated nonattainment areas); section 182(b)(1)(A), (c)(2)(B)
(setting explicit reasonable further progress targets for ozone
precursors, and providing an exception when the SIP includes ``all
measures that can feasibly be implemented in the area, in light of
technological achievability'' (emphasis added)).
    Thus, while the statute indicates that downwind areas should attain
as expeditiously as practicable, but no later than the attainment dates
specified in sections 172(a)(2) and 181(a)(1), implementation
provisions for nonattainment planning lay out myriad exceptions to
those deadlines, including for circumstances when attainment is simply
infeasible. See Whitman v. Am. Trucking Ass'ns, Inc., 531 U.S. 457,
493-94 (2001) (Breyer, J., concurring) (considerations of costs and
technological feasibility may affect deadlines established for
attainment by the EPA). Thus, the EPA's approach to evaluating upwind
emission reductions based on technological feasibility is consistent
with the requirements imposed on downwind nonattainment areas required
to implement certain ``reasonable'' controls within the targeted
timeframe. By contrast, the commenters' premise that all upwind
emission reductions must occur before the earliest downwind attainment
date, without regard to feasibility, is inconsistent with the framework
of section part D as it applies to downwind states.
    The ambiguity in the good neighbor provision regarding the
relationship of upwind state emission reductions to attainment dates is
further heightened with respect to downwind areas that the EPA
anticipates are likely to be in attainment in a future year, some of
which are already currently attaining the standard (or even designated
attainment) \107\ but which may have problems maintaining the standard
in the future (i.e., maintenance receptors). In the EPA's 2017 air
quality modeling performed for the CSAPR Update, the EPA identified six
nonattainment receptors and thirteen maintenance receptors. 81 FR
74533. The maintenance receptors were areas that the EPA expected were
likely to be in attainment based either on the modeling projections or
current monitored data, but which EPA expected may have problems
maintaining attainment of the standard under certain circumstances.
While many of the maintenance receptors are in areas currently
designated nonattainment, the EPA's analysis suggests that these areas
will be able to demonstrate (and in many cases have in fact
demonstrated) \108\ attainment of the NAAQS by the attainment date or
otherwise receive a clean data determination that relieves the state of
further planning obligations. While the good neighbor provision
requires states to prohibit emissions that will ``interfere with
maintenance'' of the NAAQS in these areas, there is no deadline for
maintenance of the standard comparable to an attainment date for
downwind areas that are in nonattainment of the standard. The
commenters present no argument as to why upwind obligations for states
linked to downwind maintenance areas

must be pegged to future analytic years identical to attainment dates
which may not themselves be relevant to maintenance receptors.
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    \107\ For example, in the CSAPR Update, two maintenance
receptors (in Allegan County, Michigan, and Jefferson County,
Kentucky) were located in areas designated attainment for the 2008
ozone NAAQS. 40 CFR 81.318 (Kentucky), 81.323 (Michigan).
    \108\ See, e.g., 80 FR 30941 (June 1, 2015) (determination of
attainment of Baltimore, MD (Harford receptor)); 81 FR 26697 (May 4,
2016) (determination of attainment by the attainment date of
Cincinnati-Hamilton OH-KY-IN (Hamilton receptor)); 82 FR 50814
(November 2, 2017) (determination of attainment by attainment date
of Philadelphia PA-NJ-MD-DE (Philadelphia receptor)).
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    The EPA further disagrees that the D.C. Circuit's North Carolina
decision requires the EPA to only use the next relevant attainment date
in selecting its future analytic year. The North Carolina decision
faulted the EPA for not giving any consideration to upcoming attainment
dates in downwind states when setting compliance deadlines for upwind
emission reductions in CAIR: There, the EPA had evaluated only the
feasibility of implementing upwind controls. 531 F.3d at 911-12. But
the court did not hold that the CAA requires that compliance deadlines
for good neighbor emission reductions be identical to any attainment
date, let alone the next upcoming one. Nor did the court opine that the
EPA would never be justified in setting compliance dates that fall
after the next upcoming downwind attainment date (but, as with the
future analytic year selected in this action, well before the next date
after that one) or that are based, in part, on the feasibility of
implementing upwind emission reductions. Indeed, in remanding the rule,
the D.C. Circuit acknowledged that upwind compliance dates may, in some
circumstances, come after attainment dates. Id. at 930 (where the
attainment date relevant to the discussion was 2010, instructing EPA to
``decide what date, whether 2015 or earlier, is as expeditious as
practicable for states to eliminate their significant contributions to
downwind nonattainment''). Accordingly, the EPA's consideration of
anticipated compliance timeframes for implementation of NOX
control strategies in selecting a future analytic year is not
inconsistent with North Carolina.
    The commenter's citations to Sierra Club and Train also do not
contradict the EPA's interpretation. At issue in Sierra Club was
whether the EPA could extend the deadline for attainment without
reclassifying the area as a ``Severe'' nonattainment area and suspend
other planning requirements based on the conclusion that continued
nonattainment would be caused by emissions transported from other
states. 294 F.3d at 159. Thus, although the court indicated that the
attainment dates are ``without exception,'' it specifically stated that
this was with respect to ``setbacks owing to ozone transport.'' Id. at
161. The court did not contradict the conclusion that states are only
required to implement measures that are ``reasonably available'' in
downwind areas, deferring to the EPA's interpretation of section 172(c)
as not requiring measures that ``would not advance the attainment date,
would cause substantial widespread and long-term adverse impacts, or
would be economically or technologically infeasible.'' Id. at 162-63,
quoting 66 FR 608. Sierra Club therefore supports EPA's position that
it is appropriate to consider the feasibility of implementing control
strategies when evaluating appropriate compliance timeframes under the
good neighbor provision. And although the Supreme Court in Train stated
that the Act requires states to attain the air quality standards
``within a specified period of time,'' the court pointed this out in a
background discussion describing the evolution of the CAA from a prior
period when the statute included no attainment dates. 421 U.S. at 65.
Moreover, the decision was issued in 1975, before the 1990 amendments
added the complicated set of provisions governing the timing concerns
and control obligations imposed on states with ozone nonattainment
areas. Thus, this decision cannot be relied upon to read out the
flexibilities subsequently provided in the Act.\109\ (And, of course,
in any event it does not address requirements such as the good neighbor
provision, which contains no express deadlines or other timeframes.)
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    \109\ Commenters also cite Union Electric for the proposition
that economic and technological feasibility may not be considered,
but the Court was also reviewing an earlier version of the Clean Air
Act that has since been amended to add the specific provisions for
ozone nonattainment areas discussed in this section which allow for
consideration of economic and technological feasibility. 427 U.S. at
249-50.
---------------------------------------------------------------------------

    CAA section 110(a)(2)(D)(i) (the good neighbor provision) and part
D (governing nonattainment requirements), when read together, do not
unambiguously require good neighbor emission reductions by a particular
deadline. And in North Carolina the court simply found that EPA must
make an effort to ``harmonize'' its upwind good neighbor reductions
with downwind attainment dates. 531 F.3d at 911-12. The EPA has
reasonably harmonized these provisions to require good neighbor
emission reductions as expeditiously as practicable to benefit downwind
areas, taking into account their attainment dates as well as how
expeditiously upwind controls could feasibly be implemented. Thus,
where the EPA was able to identify substantial upwind emission
reductions available by the upcoming attainment date, as in the CSAPR
Update, the EPA implemented those reductions. However, where additional
controls could not be feasibly implemented by the next immediate
attainment date, the EPA has instead reasonably determined it was
appropriate to analyze air quality in the future year that represents
the most expeditious timeframe for implementation of such controls
after that date, but before the following attainment date. The EPA
reasonably reads the good neighbor provision and the gaps left in the
statutory scheme by Congress to allocate responsibility between the
upwind and downwind states in a manner that aligns with the overall
structure of CAA Title I. See, e.g., 81 FR at 74515-16, 74535-36.
Notably, the consequence of reading the statute as the commenters
suggest would be profound: Emission reductions would be required even
if such reductions could be achieved only by the use of manifestly
infeasible upwind control measures, an obligation not imposed on
downwind nonattainment areas due to the availability of extensions and
reclassifications, described earlier, which provide more time for such
areas to implement reductions to attain the relevant NAAQS. Cf. S. Rep.
No. 95-127, at 42 (1977) (the good neighbor provision is intended to
``mak[e] a source at least as responsible for polluting another State
as it would be for polluting its own State''--not more responsible)
(emphasis added). Nothing in the CAA or judicial precedents requires
this result.
    Comment: One commenter suggests that EPA cannot rely on the need to
avoid over-control to justify the choice of the 2023 analytic year. The
commenter states that, in EME Homer City, the Supreme Court made clear
that, while EPA should strive to avoid over-control, ``the Agency also
has a statutory obligation to avoid `under-control.''' 134 S. Ct. at
1609. The commenter suggests that, should over-control become an issue
at some future time, such as in 2023, the EPA can address that issue
when it arises.
    Response: The EPA disagrees with the commenter's assertion that the
EPA has inappropriately weighted concerns about over-control of upwind
state emissions. The Supreme Court and the D.C. Circuit have both held
that EPA may not require emission reductions that are greater than
necessary to achieve attainment and maintenance of the NAAQS in
downwind areas. See EME Homer City, 134 S. Ct. at 1608; EME Homer City
II, 795 F.3d at 127. While the Supreme Court indicated that ``EPA must
have leeway'' to balance the possibilities of under-control and over-
control and that ``some amount of over-

control . . . would not be surprising,'' the Court did not indicate
that the EPA should ignore the risk of over-control. 134 S. Ct. at
1609. Rather, the Court held, ``If EPA requires an upwind State to
reduce emissions by more than the amount necessary to achieve
attainment in every downwind State to which it is linked, the Agency
will have overstepped its authority, under the Good Neighbor
Provision.'' Id. at 1608. On remand in EME Homer City II, the D.C.
Circuit gave that holding further meaning when it determined that the
CSAPR phase 2 ozone season NOX budgets for 10 states were
invalid because EPA's modeling showed that the downwind air quality
problems to which these states were linked when EPA projected air
quality to 2012 would be entirely resolved by 2014, when the phase 2
budgets were scheduled to be implemented. 795 F.3d at 129-30. Thus, the
Court did not hold that over-control was a secondary consideration or
an issue that could be deferred to some indefinite future course
correction, but rather that it was a primary constraint on the EPA's
authority.
    Under the current circumstances, the EPA is determining that
substantial additional emission reductions cannot be achieved until
2023 because the implementation of additional control strategies not
already considered and implemented in the CSAPR Update would take at
least four years to accomplish. Thus, in order to ensure that the
emission reductions that might be achieved from the implementation of
such controls would not be more than necessary to address downwind air
quality problems, the EPA reasonably evaluated air quality in the
future year when implementation of such controls could reasonably and
feasibly be expected to occur. Had the EPA instead evaluated air
quality in an earlier year (e.g., the 2021 Serious area attainment
date), even though emission reductions from these control strategies
could not be implemented for several more years, the EPA could not have
ensured that the emission reductions would still be necessary by the
time of implementation. Here, where the EPA has information indicating
that such emission reductions would likely not be necessary to address
downwind air quality problems by the time they could feasibly and
expeditiously be implemented, the D.C. Circuit's holding in EME Homer
City II suggests that the EPA may not have the authority under the good
neighbor provision to require such additional emission reductions. In
any event, the court's holding suggests that it is prudent for the EPA
to exercise its discretion taking into consideration, among other
factors, the prohibition against over-control as one of multiple
scientific, policy, and legal considerations informing the selection of
a future analytic year for projection of air quality at step 1 of the
four-step framework. Thus, it is reasonable for the EPA to harmonize
this consideration with the EPA's reasonable anticipation of how long
it would take to accomplish substantial additional emission reductions.
    Comment: One commenter contends that North Carolina required that
the EPA model nonattainment and maintenance in the earliest compliance
year that would align with the next attainment deadline, which is
effectively the 2020 ozone season for the July 2021 Moderate area
attainment date. Under the four-step framework, the commenter asserts
that the EPA must first identify whether any downwind receptors are
expected to have problems attaining or maintaining the 2008 ozone NAAQS
in 2020 and then identify the upwind states that are contributing to
those downwind problems. The commenter then contends that EPA should
evaluate whether those unlawful contributions could be reduced through
compliance with state budgets established using the next most cost-
effective NOX control technology that EPA has not yet relied
upon to establish a good neighbor provision rule, in this case,
starting up and operating idled SNCR controls.
    Another commenter states that the Ozone Transport Commission (OTC)
has already conducted modeling for 2020, which shows that a number of
receptor sites will exceed the 2008 ozone standard in 2020. In light of
this modeling, the commenter asserts that it would be arbitrary for the
EPA to dismiss the likelihood of continued attainment and maintenance
difficulties through and in 2020 or to fail to conduct comprehensive
modeling for the years before 2023.
    Response: As discussed earlier, the EPA does not agree that it is
obligated to review air quality only in a year associated with the next
attainment date, particularly under the present circumstances where its
analysis of potential control strategies shows that new control
strategies cannot be feasibly implemented within that timeframe.
Further, the EPA does not believe it would be reasonable to implement
the next most costly control technology simply to achieve any amount of
additional reductions in the near term. As discussed in section III.B.2
earlier, the EPA has already determined in the CSAPR Update that the
operation of idled SNCR is not a cost-effective control strategy as
compared to other available short term control strategies because the
operation of such controls would result in small emission reductions
and small downwind air quality improvements relative to the cost and
relative to the much more significant emission reductions and ozone
improvements the EPA determined were available from less-costly control
strategies.\110\ Thus, it is incorrect to refer to the operation of
SNCR as the ``next most cost-effective'' control strategy because the
EPA concluded the control strategy was simply not cost-effective
relative to other near-term control strategies.
---------------------------------------------------------------------------

    \110\ For instance, based on 2017 heat input, SNCR coal-fired
operation reflected a small portion (8 percent) of the total coal-
fired fleet operation. Not only is it a small inventory of units,
but the additional reductions from these sources would be small as
the SNCR fleet was already averaging a nationwide ozone-season
emission rate of 0.16 lb/mmBtu and most SNCR-controlled units were
emitting at levels consistent with control operation. Less than 1
percent of the 2017 coal-fleet heat input had a SNCR and was
operating at emission rates (greater than 0.3 lb/mmBtu) that would
suggest additional reductions would be available from better SNCR
operation.
---------------------------------------------------------------------------

    The EPA notes that it would have been difficult under the
circumstances to conduct air quality modeling for both the 2020
attainment date suggested by the commenters and the 2023 compliance
timeframe associated with the additional control strategies discussed
earlier. Air quality modeling is a resource- and time-consuming
process, as described in more detail in Section III.C and in the
technical support documents in the record. Air quality modeling for a
future year requires more than three months to develop detailed
emission projection inventories for each emissions sector for the
future year (with many of the inventories themselves derived from
running other models) and to pre-process these emissions data for input
to the air quality model. Once the inputs are prepared, a month or more
is required to run the air quality model and post-process the outputs
in order to produce results, followed by additional analysis to
interpret the results. Producing contribution data, if necessary, also
requires additional time to run a different, more complex modeling tool
(i.e., modeling with source apportionment) and to interpret the
results. All told, preparing for, completing, and interpreting air
quality modeling data for a future year generally takes on the order of
6 months. Thus, modeling more than one future year would have required
significant additional time beyond that available to

the agency in light of the court-ordered deadline to propose an action
fully addressing the good neighbor obligation for the 2008 ozone NAAQS
for several states by June 30, 2018, and to take final action by
December 6, 2018.\111\ In light of the resource and time constraints,
the EPA determined that it was appropriate to select a single future
analytic year that was most likely to permit the agency to fulfill its
obligation to determine whether any good neighbor requirements remain
unfulfilled for the 2008 ozone NAAQS. Accordingly, the EPA reasonably
chose to only model air quality in 2023 in order to target the control
strategies that were most likely to impact downwind air quality. Cf.
Sierra Club v. Johnson, 444 F. Supp. 2d 46, 53 (D.D.C. 2006)
(explaining that statutory deadlines in the Clean Air Act indicate that
Congress intended agencies to prioritize timeliness over perfection).
---------------------------------------------------------------------------

    \111\ Order, New York v. Pruitt, No. 1:18-cv-00406-JGK (S.D.N.Y.
June 12, 2018), ECF No. 34 (setting deadline for EPA to address FIP