Thus, this portion of our analysis did not involve wholly new sources,
but focused instead on projects involving the addition of new emissions
units at an existing major source. Since GHG BACT review can only apply
to a modification in cases where a pollutant other than GHGs is
increased in significant amounts and is thus subject to BACT review for
that pollutant, we used the existing PSD NOX SER value of 40
tpy to calculate an equivalent level of increase in GHG emissions that
we would expect to be associated with the combustion unit types most
likely to be part of future modification projects that trigger the
requirement to obtain a PSD permit. Using this approach, the GHG
equivalency results simply provide an approximate measure of the
theoretical minimum level of GHG emissions increase that could be
associated with a project that adds a particular type of combustion
unit that increases NOX by just more than the NOX
SER level of 40 tpy. We then examined this equivalency level in
relation to both the findings from our first technical review (the past
actual permitting actions) and our fourth technical review, which
evaluated the degree of reductions found to be achievable in GHG BACT
reviews for these unit types.
    The results of our equivalency analysis ranged from 17,529 tpy
CO2e for certain types of stationary IC engines, upwards to
425,665 tpy CO2e for large power plant turbines. The average
result across unit types was 98,333 tpy CO2e. The analysis
confirmed that, for some unit types, GHG emissions increases would
clearly exceed the current 75,000 tpy CO2e level if that
unit increased NOX emissions over the NOX 40 tpy
SER level. For example, a natural-gas fired combustion turbine,
commonly added as part of a modification project at existing power
plants, would have GHG emissions well in excess of 75,000 tpy
CO2e. In projects involving a large power plant turbine unit
such as this, a single unit can trigger the requirement to obtain a PSD
permit.
    However, for other types of emissions units that might be added as
part of a PSD triggering modification, we found it necessary to
consider the results in light of the actual permitting experience. For
example, our analysis showed equivalent GHG emissions increases below a
20,000 tpy CO2e level for adding a stationary IC engine. In
other words, an IC engine that just increases NOX emissions
by 40 tpy or more could be expected to increase GHGs by less than
20,000 tpy CO2e. However, addition of a single IC engine is
not commonly a PSD triggering event. Our permitting review showed that
most of the IC engines addressed in ``anyway source'' PSD permits are
present for one of the following two reasons: (1) As associated
equipment (e.g., emergency backup generator or fire pump engine) when
the source is adding a large combustion unit (such as a turbine or
boiler) that is principally responsible for triggering the requirement
to obtain a permit; or (2) in multiple-unit configuration generator
sets (e.g., 10 or more large IC engines linked together for electricity
production). Also, in practice, there is a low likelihood that a PSD
project involving the addition of a single unit, of any type, will just
exceed the 40 tpy NOX SER level because, in such cases, the
permit applicant very often accepts PTE emission limits to avoid
triggering PSD if the project's NOX emission increase is
close to the NOX SER level.
    Therefore, while our equivalency analysis resulted in possible
theoretical occurrences of ``anyway source'' projects involving
combustion units that may have emissions less than 75,000 tpy
CO2e, we found very few actual PSD-triggering modification
projects that involved adding a single combustion unit that would have
total GHG emissions less than 75,000 tpy CO2e. We found it
is much more likely that a PSD-permitted project would have
NOX emissions well in excess of the 40 tpy NOX
SER level due to the addition of multiple combustion units or the sheer
size of the primary unit itself, such as a power plant turbine or
steam-generating unit. Such projects will have GHG emissions multiple
times greater than our theoretical equivalency results.
    Our third category of data review looked to identify any additional
GHG emission sources, particularly non-combustion related units or
processes that might be part of ``anyway sources'' PSD modification
projects, which could potentially be subject to the BACT requirement
for GHGs at applicability levels below 75,000 tpy CO2e. Our
review of past PSD permits showed that the large majority of PSD
permitted projects that involved GHG emission increases triggered PSD
because of the addition of combustion units. In addition, most of these
combustion unit projects had GHG emission increases in excess of 75,000
tpy CO2e. Nevertheless, we also assessed the coverage of
non-combustion related GHG sources that might trigger PSD to ensure
that we did not miss meaningful reductions of GHGs that could be
achieved by applying BACT to GHG at modification projects that increase
GHGs in amounts less than the 75,000 tpy CO2e level that
were used in prior permits. Using information from the EPA's GHGRP, we
identified and evaluated emissions from GHG-emitting processes and
units associated with non-combustion related GHG source categories
relative to different GHG emission threshold levels.
    One main finding from this evaluation was that a high percentage of
GHG emissions from non-combustion units or processes triggering PSD
would be covered by the BACT requirement at a level of 75,000 tpy
CO2e on a PTE basis. We found that at a 75,000 tpy
CO2e PTE-based emission threshold level, non-combustion
related units and processes responsible for approximately 89 percent of
the GHG emissions, on a CO2e basis, all the non-combustion
``anyway source'' categories included in our analysis would be
captured, and thus conceivably subject to GHG BACT review if the GHG
SER was set at a 75,000 tpy CO2e level. A construction
project at a municipal waste landfill, for example, can trigger PSD
applicability if its increased emissions exceed the PSD SER level of 50
tpy for non-methane organic compounds (NMOC), the regulated NSR
pollutant most commonly emitted from municipal waste landfills. A
landfill increasing its emissions by just over 50 tpy NMOC would add
over 190,000 tpy CO2e of GHG emissions (CH4
expressed on a CO2e basis), which is well in excess of
75,000 tpy CO2e.\51\ We found significant GHG emission
source coverage at a 75,000 tpy CO2e level for other
important source categories containing non-combustion related GHG-
emitting units and processes, including cement production, nitric acid
production, refineries, and underground coal mines. The non-combustion
related units and processes in these categories that emit GHGs in
amounts greater than 75,000 tpy CO2e are responsible for
over 90 percent of the non-combustion related GHG emissions from each
of these source categories.
---------------------------------------------------------------------------

    \51\ Memorandum from H. Ward, EPA/SPPD, to J. Mangino, EPA/AQPD,
re: Methane to NMOC ratio at landfills. June 17, 2014.
---------------------------------------------------------------------------

    Another important finding from our review of non-combustion sources
that emit GHGs was that there is evidence that smaller GHG-emitting
units that would not otherwise trigger PSD independently can be pulled
into PSD when other emissions units are added in the same project. Once
the BACT requirement is applicable to a given pollutant based on
emissions in excess of the significance levels, the BACT review covers
any associated processes emitting the same pollutants as the main units
that are the principal reason for triggering PSD review. Because of the

definition of the GHG pollutant as the ``sum-of-six'' constituent
gases, ancillary units that emit relatively small amounts of GHGs other
than CO2 could become subject to GHG BACT requirement if a
combustion unit added to the source at the same time emits GHGs in
excess of the significance level that the EPA promulgates. Based on the
actual experience of permitted sources using a 75,000 tpy
CO2e level under Step 1 of the Tailoring Rule to determine
GHG BACT applicability, we have seen smaller GHG-emitting units get
pulled into PSD permits involving larger units at oil and gas
production, processing and transmission facilities. At these
facilities, projects that have triggered PSD involved addition of a
large single or multiple smaller combustion units (such as large gas
compressor turbines and engines that trigger PSD because of emissions
of NOX or another pollutant besides GHG). These projects
also had associated CH4 leaks from piping, valves, and gas
storage equipment. The combustion unit(s) involved in such projects
that triggered PSD had GHG emission increases exceeding 75,000 tpy
CO2e, and thus subjecting the project to GHG BACT review
under previous PSD regulations. In addition to evaluating controls for
GHG emission from the combustion units, the GHG BACT review
accompanying these projects included measures directed at the fugitive
CH4 sources associated with the project because the GHG
pollutant includes both CO2 and CH4 gases. By
themselves, the CH4 emissions fell below the 75,000 tpy
CO2e level, and the fugitive sources alone would not have
triggered PSD based on pollutants other than GHGs. However, based on
the definition of the GHG pollutant, because other emissions units at
these sources triggered PSD and then also triggered BACT for GHGs based
on emission in excess of 75,000 tpy CO2e, these ancillary
units were pulled into the overall GHG BACT review.
    This finding explains in part why we did not find evidence of many
``anyway source'' PSD permits with emission units that emit less than
75,000 tpy CO2e. Our review of prior ``anyway source'' PSD
permitting actions showed that a large majority of PSD permits for
projects that would be most likely to involve GHG emission increases
are triggered by the addition of large combustion units. In addition,
we found that most of these larger combustion units would have GHG
emission increases in excess of a 75,000 tpy CO2e GHG SER
level. Thus, we can anticipate that setting a GHG SER below the 75,000
tpy CO2e level would be unlikely to subject additional non-
combustion emissions to the GHG BACT review. If these non-combustion
units are constructed independently, they will generally not emit
regulated NSR pollutants other than GHGs in amounts that are high
enough to trigger PSD review, or they will not involve GHG emissions at
all. So establishing a GHG SER lower than 75,000 tpy CO2e
would not likely cause these non-combustion sources to become subject
to the GHG BACT requirement. Non-combustion GHG-emitting processes that
are part of a project generally are not brought into the GHG BACT
review without the contemporaneous addition of a combustion unit that
serves as the PSD-triggering event. A GHG SER of 75,000 tpy
CO2e would ensure that such projects will be subject to the
GHG BACT requirement.
    Our fourth category of data review looked at the degree of GHG
emissions reductions that one could expect to achieve by applying
energy efficiency measures as BACT for GHGs at projects involving
certain types and sizes of combustion units. Although we reviewed a
variety of GHG reduction techniques focused on energy efficiency
measures applied to combustion units since, as noted in our review of
``anyway source'' permitting, the addition or modification of
combustion units is, and likely will continue to be, the principal
triggering event for most PSD permits involving GHGs. The EPA's GHG
permitting experience has been that BACT for such sources will usually
be energy efficiency measures. Therefore, in evaluating a possible GHG
SER option, we focused on the implementation, effectiveness and value
of energy efficiency measures at combustion sources that may be
expected to trigger PSD.
    Our main finding from reviewing these energy efficiency measures is
that the degree of emissions reductions achieved is greater at larger
combustion units that would be subject to GHG BACT review at or above a
75,000 tpy CO2e SER. We found that the maximum reduction
potential from energy efficiency measures is approximately 7 percent
\52\ from a baseline industrial boiler configuration. Emissions
reductions on this scale are generally only obtainable where site-
specific design and construction criteria can be part of the combustion
unit design and manufacture. Large industrial boilers, process heaters
and furnaces of the size typically seen as part of ``anyway source''
PSD projects are custom-built and thus not generally purchased as
``off-the-shelf'' items. Thus, these units can be site-designed and
constructed in a way that considers and incorporates a combination of
energy efficiency measures.\53\ The application of BACT review is thus
particularly relevant to these types of units as it involves case-by-
case review of technology implementation and cost considerations.
---------------------------------------------------------------------------

    \52\ ``Available and Emerging Technologies for Reducing
Greenhouse Gas Emissions from Industrial, Commercial, and
Institutional Boilers,'' EPA Office of Air Quality Planning and
Standards. October 2010. http://www.epa.gov/sites/production/files/2015-12/documents/iciboilers.pdf.
    \53\ ``Boiler Efficiency Projects-Development of Issues Papers
for GHG Reduction Project Types: Boiler Efficiency Projects,''
Prepared for the California Climate Action Registry, January 7,
2009. http://www.climateactionreserve.org/wp-content/uploads/2009/03/future-protocol-development_boiler-efficiency.pdf.
---------------------------------------------------------------------------

    If carbon capture and sequestration (CCS) is found to be achievable
at such large industrial boilers, process heaters and furnaces, the
degree of emissions reductions that could be achieved is significantly
increased. Thus, whether energy efficiency or more effective controls
are applied, the BACT requirement would be expected to yield a
meaningful degree of GHG emissions reductions when applied to an
individual source or modification that increases GHG emission by 75,000
tpy CO2e or more.
    In contrast, when we consider emissions units that emit GHGs in
amounts below 30,000 tpy CO2e, we generally see smaller
``off-the-shelf'' type units, such as stationary IC engines. The
ability to achieve additional GHG reductions from such units is limited
or non-existent for several reasons. First, implementing the efficiency
measures generally requires site-specific design and construction
criteria, more typically associated with larger scale projects where
these measures can be part of unit design and manufacture. Second,
``off-the-shelf'' units such as IC engines typically cannot be
substantially modified or tampered with in order to be guaranteed to
meet their certified performance standards. Third, there is little
variation, typically within 1 or 2 percentage points, in the efficiency
of these types of engines sold by different vendors. The market demands
that all such engines be highly-efficient across vendors, and thus
offers little opportunity for GHG reductions from the purchase
decision. Finally, given the relatively small capital cost of these
units and the anticipated high cost of CCS, it is unlikely that CCS
will even be found to be achievable when such a unit is installed by
itself without a much

larger combustion unit that will trigger the PSD BACT requirement.
    It is worth recalling the definition of the word ``meaningful,'' as
described earlier in Section V.C of this preamble where we discuss the
historical background for de minimis levels under PSD. In the preamble
to its 1980 PSD rule, the EPA defined ``meaningful'' reductions as
greater emission reductions than one would expect to be achieved from
otherwise-applicable regulatory requirements such as an NSPS or NESHAP.
45 FR 52706. The EPA does not expect that BACT review for IC engines
would produce any reductions for GHGs beyond that resulting from the
NSPS compliance standards that already exist for these new units. Given
the nature of these units, the EPA and permitting authorities have not
identified controls at this time that can be added to these engines to
further reduce their GHG emissions. Where IC engines have been part of
``anyway source'' PSD projects to date, typically in association with a
larger turbine or boiler units, the selection of high-efficiency
engines that meet the requirements of the applicable NSPS has qualified
as BACT. Therefore, the value for site-specific GHG BACT review on
projects involving only one or two smaller combustion units of the type
that might be implicated at GHG SER values less than 30,000 tpy
CO2e is likely to be virtually non-existent. The EPA
therefore does not view potential emission reductions from the BACT
requirement at projects that increase GHG emissions by less than 30,000
tpy CO2e as meaningful in the context of setting a de
minimis level under PSD.
    For modifications at ``anyway sources'' that trigger PSD and
increase GHG emissions by 30,000 tpy to 75,000 tpy CO2e, we
found that it may be possible to apply energy efficiency measures to
achieve some reductions in emissions, but there is reason to question
whether the degree of reduction achieved would be meaningful. For
example, we found that the current maximum reduction potential from
energy efficiency measures for combustion units, mainly at boiler
configurations, is around 7 percent.\54\ At smaller combustion units,
there are reasons to question whether this maximum reduction potential
could be achieved. However, assuming this percentage of reduction could
be achieved by applying the most aggressive energy efficiency measures
on an additional unit that emits at or near the current 75,000 tpy
CO2e permitting threshold, the total amount of GHG emissions
avoided would be limited considering the total amount of increased GHG
emissions from such a unit. A 7 percent improvement in a baseline
boiler unit efficiency could reduce a 74,999 tpy CO2e boiler
unit's GHG emissions by approximately 5,500 tons CO2e per
year. Another way to view this is that exempting such a source from the
BACT requirement for GHGs would result in a marginal increase of 5,500
tpy CO2e in GHG emissions. The modification would still
increase GHG emissions by 69,500 tpy CO2e even after
applying the most aggressive energy efficiency measures through the
BACT requirement. In reality, the marginal emissions increase from not
applying BACT to GHGs at such a source would likely be less than 5,500
tpy CO2e because that increase is based on a PTE
scenario.\55\
---------------------------------------------------------------------------

    \54\ ``Available and Emerging Technologies for Reducing
Greenhouse Gas Emissions from Industrial, Commercial, and
Institutional Boilers,'' EPA Office of Air Quality Planning and
Standards. October 2010. http://www.epa.gov/nsr/ghgdocs/iciboilers.pdf.
    \55\ As this summary of our technical review demonstrates, our
findings are based on an analysis of currently available
information. The information considered as part of our analysis,
such as the average GHG emissions reduction that can be achieved
from the application of energy efficiency or the availability of CCS
for smaller sources, may change in the future. Thus, after this rule
is finalized, EPA may need to periodically consider if there are
significant changes to the information considered in our analysis.
---------------------------------------------------------------------------

    In addition to considering the findings from the four categories of
analysis described earlier, we also considered the GHGRP's reporting
threshold for GHG emissions, which is 25,000 metric tpy CO2e
for most reporting sources, based on actual emissions. Depending on
utilization, the PTE-based emissions can be significantly greater than
25,000 metric tpy CO2e. For example, a source actually
emitting 25,000 tpy CO2e would have a PTE of 50,000 tpy
CO2e if it were run at a 50 percent utilization rate over
the course of the year. Also, the reporting rule does not require that
those facilities above the reporting threshold take measures to control
their GHG emissions; rather it only requires that sources monitor and
report their emissions. So while the GHGRP illustrates a comparative
level of GHG emissions associated with industrial type GHG-emitting
facilities deemed significant for monitoring and reporting purposes, we
did not see this threshold as a directly transferrable GHG metric for
setting a GHG SER because of the different end-uses and requirements.
However, the GHGRP reporting threshold did provide us a quantified GHG
emission level for a relative frame of reference in evaluating our
proposed GHG SER option as described in the sections of this preamble
that follow.
    Sections V.D.2 to V.D.5 of this preamble provide more detail on
each of the individual technical reviews and analyses and the findings
obtained from each.
2. Review of PSD Permitting and GHG Emission Sources
    Under our first technical review, we examined existing PSD
permitting information to determine the types and size of GHG emission
sources that are likely to be part of PSD ``anyway sources.'' We looked
at two sources of information for this review. First, we looked at GHG
permitting information from the EPA Regional offices and states as part
of an effort under the Tailoring Rule to collect information on actual
PSD permits issued that included GHG BACT review. Second, we reviewed
information from the EPA's RBLC, including permits for which no GHG
BACT review was included. The subsections of this preamble that follow
describe each review and the key findings.
a. GHG Permitting Under Step 1 of the Tailoring Rule
    The main purpose of this analysis was to assess and summarize the
GHG permitting experience to date for ``anyway sources'' emitting GHGs
at or above the 75,000 tpy CO2e GHG threshold level, the
effective GHG permitting level for sources that were otherwise subject
to PSD permitting for conventional non-GHG pollutants under Step 1 of
the Tailoring Rule. The term ``anyway sources'' refers to sources that
trigger PSD permitting requirements ``anyway'' based on pollutants
other than GHGs, regardless of the amount of their project-related GHG
emissions. We focused on these ``anyway source'' permits since they are
the only GHG sources and projects that would potentially be subject to
GHG permitting following the UARG decision that effectively limited GHG
permitting to sources and projects that would otherwise be subject to
permitting based on emissions of pollutants other than GHGs. We did not
include in our review PSD permitting conducted under Step 2 of the
Tailoring Rule since Step 2 required PSD permits and GHG BACT review
for sources and modifications based solely on GHG emission increases.
Such sources do not trigger PSD after the UARG decision and subsequent
revisions to the EPA's regulations, including those proposed in this
rule.
    By analyzing the types of GHG emission units and sources subject to

GHG BACT review during the past four years, we developed a historical
profile of the source coverage and GHG BACT review process at the
75,000 tpy CO2e GHG permitting level. Looking at this
historical record, we can better assess to what extent the existing
75,000 tpy CO2e permitting level subjects significant GHG-
emitting sources to BACT review, and whether GHG BACT review at that
level yields emission reductions that were meaningful.
    For this analysis, we reviewed summary information on 200 PSD
permits issued during the 2011-2014 timeframe that contained GHG BACT
requirements after GHGs became a regulated NSR pollutant. We summarized
the characteristics of the sources and types of units that have been
subject to GHG BACT review. Some of the key findings from this review
are presented here; more details on this analysis are included in the
docket for this proposed rulemaking.\56\ Based on this review sample,
approximately 90 percent of all the PSD permits with GHG BACT limits
were issued to ``anyway sources,'' \57\ with the other 10 percent
issued to sources that were subject to PSD permitting only because of
their GHG emissions (and thus would not be captured at any SER level
because they are not ``anyway sources'').
---------------------------------------------------------------------------

    \56\ ``A Summary Analysis of the GHG Permitting Experience
between 2011 and 2014.'' Prepared by EPA Staff, March 2015.
    \57\ As discussed previously in Section V.D.1, the ``anyway
source'' permits with GHG BACT limits all involved energy-intensive
industries, emitting significant amounts of CO2 from the
burning of fossil fuels in various types of combustion units.
---------------------------------------------------------------------------

    The importance and contribution of the power generating sector to
GHG national emissions cannot be overstated when considering
opportunities for GHG reductions and identifying where there is clear,
non-trivial value in applying BACT review to obtain such reductions.
Power plants are responsible for a majority of the country's total
stationary source GHG emissions, approximately 66 percent of the
reported 2013 GHG emissions under the EPA's GHGRP.\58\ Since combustion
units, such as large gas turbines and steam boilers installed at power
plants, consistently have GHG emission increases well in excess of
75,000 tpy CO2e, a GHG SER at this level will ensure that
permitting authorities continue to apply GHG BACT review to the largest
and most prevalent GHG emission units in the power plant sector as part
of ``anyway sources'' permitting actions.
---------------------------------------------------------------------------

    \58\ 2013 GHGRP Overview Report, http://www.epa.gov/sites/production/files/2015-07/documents/ghgrp-overview-2013.pdf.
---------------------------------------------------------------------------

    A 75,000 tpy CO2e level also does not overlook other
significant units. In our review of GHG permitting at a variety of
``anyway sources'' besides power plants, we found that GHG emissions
for units subject to GHG BACT review were generally well above the
75,000 tpy CO2e threshold. This is because of the greater
level of GHG emissions associated with large fossil-fuel fired
combustion units, such as turbines and boilers. The addition of these
units was typically the triggering event that caused the need for a PSD
permit for pollutants other than GHGs. It was also evident from the
review that most newly constructed facilities (i.e., ``greenfield
facilities'' as opposed to modifications of existing major sources)
that obtain ``anyway source'' PSD permits will generally have GHG
emissions well in excess of a 75,000 tpy CO2e threshold
based on the cumulative, facility-wide total GHG emissions from all
emission points in the facility fence line.
    As part of this same analysis, we also performed a more detailed
review on a sample subset of 55 individual ``anyway source'' permits
that included GHG BACT limits and represented PSD permits for different
source category types. Key findings from these sample permit reviews
are summarized here with more details of the review included in the
docket for this proposed rulemaking.\59\ The source category types
represented by these 55 permits included the following: Power plants;
chemicals production facilities; oil and gas industry sources; metals
and mineral production facilities; pulp and paper production
facilities; ethanol production plants; and a municipal waste combustion
facility.
---------------------------------------------------------------------------

    \59\ ``A Summary Analysis of the GHG Permitting Experience
between 2011 and 2014.'' Prepared by EPA staff, March 2015.
---------------------------------------------------------------------------

    We found that the construction projects covered by these PSD
permits included at least one, and in most cases multiple, large
combustion units, such as large fossil fuel-fired turbines, boilers,
process heaters, or furnaces, along with associated stationary IC
engines for some facilities (generally as backup emergency generators
or for associated equipment such as pumps and compressors). The GHG
emission levels associated with these sample PSD projects were
consistently over 100,000 tpy CO2e, with many facilities,
particularly greenfield facilities, reporting much higher levels. The
principal fuels used in the combustion units were natural gas for
boilers, furnaces, and turbines and diesel or natural gas for large
stationary IC engines. There were limited cases of biomass fuel used,
principally in the pulp and paper sector. The emissions from these
larger combustion units were in most cases the principal cause for
these projects requiring PSD review for both non-GHG pollutants and
GHGs. Over 90 percent of the permitted activities within the sample of
reviewed permits involved combustion units of some type, primarily
fossil fuel-fired boilers, turbines, or stationary IC engines.
    Some permits for these combustion unit projects also included
ancillary, non-combustion related sources of GHGs for which GHG BACT
review was conducted. These sources consisted principally of fugitive
emission releases of CH4 from natural gas delivery,
processing or storage units, and SF6 releases from circuit
breaker equipment associated with power plants.\60\ There were isolated
examples of other non-combustion related sources at two chemical
production facilities: GHG emissions from a nitric acid production
process and CO2 from a CO2 liquefaction process.
These processes were both large GHG-emitting processes, emitting more
than 90,000 tpy CO2e.
---------------------------------------------------------------------------

    \60\ ``A Summary Analysis of the GHG Permitting Experience
between 2011 and 2014.'' Prepared by EPA staff, March 2015.
---------------------------------------------------------------------------

b. RBLC Permitting Information
    For this analysis, we reviewed information on PSD permits contained
in the RBLC to understand the types of non-GHG emission sources that
were subject to BACT review for other pollutants besides GHG but that
may also be important from a GHG emission perspective. Since the UARG
decision limited the scope of the PSD permitting program to ``anyway
sources,'' it is important to understand the types of sources that are
typically part of ``anyway sources'' PSD permitted projects and their
potential to emit GHGs. This analysis differed from our review of
historical GHG permitting data since the RBLC dataset also contains PSD
permits that did not contain GHG BACT limits, and thus we could
identify if there were other GHG emissions sources that could
potentially be subject to GHG BACT review at permitting threshold
levels below 75,000 tpy CO2e. A detailed report of this
analysis is included in the docket for this rulemaking.\61\
---------------------------------------------------------------------------

    \61\ ``A Summary Review of Recent PSD Permitting Activity for
``Anyway Source'' Categories and the Potential GHG-Emitting Units
and Processes within Those Categories.'' Prepared by EPA staff,
March 2015.

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

    We began our review of ``anyway source'' PSD permits by assessing
the types of emission units and sources that triggered PSD actions for
pollutants other than GHGs. We then identified which of the units would
most likely emit GHGs. We reviewed detailed process level information
from over 100 ``anyway source'' PSD permits issued in the last 4 years
for source categories likely to have some amount of GHG emissions.\62\
---------------------------------------------------------------------------

    \62\ ``A Summary Review of Recent PSD Permitting Activity for
``Anyway Source'' Categories and the Potential GHG-Emitting Units
and Processes within Those Categories.'' Prepared by EPA staff,
March 2015.
---------------------------------------------------------------------------

    We examined individual source category projects as represented in
the RBLC dataset to see if there was evidence of any consistency in the
type and/or size of combustion units across key source categories and
the extent to which they appear to be the primary emissions unit that
is installed or modified and triggers PSD for pollutants other than
GHGs. To get a representative sample across different source
categories, we reviewed permits from a variety of industrial
classifications, including potentially important GHG-emitting
categories such as metals production, chemical manufacturing, petroleum
refineries, the oil and gas industry, pulp and paper industries, and
waste industries.\63\ We did not include power plants in the RBLC
sample set we reviewed because we knew with a high level of certainty
that the PSD permitted projects for these facilities principally
involved very large combustion units, such as large gas turbines, with
GHG levels well in excess of the current 75,000 tpy CO2e
threshold. Therefore, these permits would not provide any additional
insight into the characterization of sources that obtained permits
because of pollutants other than GHGs for purposes of evaluating a
possible GHG SER option.
---------------------------------------------------------------------------

    \63\ ``A Summary Review of Recent PSD Permitting Activity for
``Anyway Source'' Categories and the Potential GHG-Emitting Units
and Processes within Those Categories.'' Prepared by EPA staff,
March 2015.
---------------------------------------------------------------------------

    Across the sampled industry categories, we found that ``anyway
sources'' triggered PSD for conventional pollutants primarily because
of the addition or modification of combustion units, such as turbines,
boilers, process heaters, furnaces, and stationary IC engines. For most
facilities, combustion units or associated combustion unit-related
emissions (e.g., flares, exhaust gas treatment systems) constituted the
majority of the overall processes for which BACT limits were required
for pollutants other than GHGs at any given facility. Most of the
larger combustion units covered by PSD permits were fueled principally
by either natural gas or process-related gas for industries (such as
petroleum refineries) where such gas is generated. Some permits also
included smaller, stationary engines (typically emergency generators or
fire pumps) principally fueled by either diesel or natural gas.
    From a sample of about 400 PSD permits contained in the RBLC
dataset for the years 2011 to 2014, we identified only 20 PSD permits
for modification projects \64\ from the RBLC data set that included
combustion units whose cumulative GHG emissions would likely not exceed
75,000 tpy CO2e based on their fuel input data. Although we
recognize that the RBLC dataset does not reflect a complete dataset of
permitting actions due to its voluntary participation and under-
reporting, we reasonably expect, based on the overall characteristics
of the other PSD permits we reviewed and the type of GHG source
categories affected under PSD, that there are a relatively low number
of ``anyway source'' PSD projects with GHG emissions likely to be less
than 75,000 tpy CO2e.
---------------------------------------------------------------------------

    \64\ ``List of Permits Identified in RACT/BACT/LAER
Clearinghouse that Likely Have Combustion-Related Emissions that are
less than 75,000 tpy CO2e''. Prepared by EPA Staff,
October 2015.
---------------------------------------------------------------------------

    We also found that where non-combustion processes were covered by a
PSD permit, the emissions from these processes principally consisted of
PM-related fugitive emissions, such as dust from material handling or
roads. There were also some specific industries, such as oil and gas
processing plants, refineries, chemical production plants and
landfills, where VOC emissions, often fugitive in nature, from piping,
pumps and storage tanks, were subject to BACT requirements. However, in
most of these cases there were large combustion units included in the
PSD-permitted project that appear to be the key source of the emissions
of a pollutant other than GHGs that exceed the applicable pollutant
significance level, and thus drive the requirement for a PSD
permit.\65\
---------------------------------------------------------------------------

    \65\ ``A Summary Review of Recent PSD Permitting Activity for
``Anyway Source'' Categories and the Potential GHG-Emitting Units
and Processes within Those Categories.'' Prepared by EPA staff,
March 2015.
---------------------------------------------------------------------------

    Working from our preliminary finding above regarding non-combustion
sources, we took a closer look at the extent to which combustion units
were the main component of PSD projects related to a particular source
category that has significant non-combustion GHG emissions, namely,
facilities in the oil and gas sector with CH4 emissions. The
oil and gas industry is well represented in PSD permitting, with the
third highest count of permits between 2011 and 2014, and is also the
second largest emitting industrial sector for non-combustion related
CH4 emissions.\66\ We were particularly interested in
understanding the contribution of combustion units in triggering PSD
``anyway'' at oil and gas sector facilities, and how this might
influence GHG permitting at a proposed GHG SER level.
---------------------------------------------------------------------------

    \66\ ``Inventory of U.S. Greenhouse Gas Emissions and Sinks:
1990-2013,'' Table ES-2. Document No. EPA 430-R-15-004. April 15,
2015. http://www.epa.gov/climatechange/ghgemissions/usinventoryreport.html.
---------------------------------------------------------------------------

    We found that, for projects subject to PSD in the oil and gas
industry, combustion units still dominate the GHG emission profile. We
examined a sample of 16 PSD permits issued between 2011 and 2015
associated with the oil and gas sector to determine whether PSD permits
in the industry are principally and routinely required due to projects
involving combustion units or if they are sometimes triggered by non-
combustion emissions units alone, and whether such non-combustion units
might also be sources of GHG emissions. A detailed summary of this
review of oil and gas sector PSD permits is provided in the docket for
this proposed rulemaking, from which the following key findings are
taken.\67\ In all the PSD permits that we evaluated for this oil and
gas sector review, combustion sources were the primary driver of PSD
applicability for the permitted new source or major modification. Based
on available emissions data within the permits, we did not find a PSD
permit that did not cover combustion units as the primary emitters of
PSD pollutants, including GHGs. Of the 13 permits for which GHG
emissions were provided or could be readily calculated, 12 of the
projects involved GHG emissions greater than 75,000 tpy
CO2e, with four of these over 500,000 tpy CO2e.
The one project with less than 75,000 tpy CO2e was a
modification project to increase flaring as a BACT control strategy for
VOCs. Of the 10 permit actions with adequate data to estimate GHG
emissions on a unit basis, combustion emissions accounted for more than
70 percent of GHG emissions in all cases, more than 80 percent in 8 of
the 10 cases, and more than 90 percent in 5 of the 10 cases.
---------------------------------------------------------------------------

    \67\ ``A Summary Review of Recent PSD Permitting Activity for
``Anyway Source'' Categories and the Potential GHG-Emitting Units
and Processes within Those Categories.'' Prepared by EPA staff,
March 2015.

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

3. GHG Emissions Levels for Combustion Units
    Once we had an understanding of the characteristics of ``anyway
source'' permitting actions specially, the prevalence of combustion
units as the primary GHG-emitting sources in these PSD permits based on
the permitting review described in Section V.D.2 of this preamble, we
then focused on identifying the level of GHG emissions associated with
the combustion units most likely to be part of future PSD-triggering
projects. From our review of ``anyway source'' PSD permits, we found
that most of the projects involved some combination of turbines,
boilers, process heaters/furnaces, and stationary IC engines.\68\ Most
of the units were either natural gas or diesel-fired, with a smaller
number of biomass-fueled units. Natural gas-fired units predominated in
the larger combustion categories of turbines and boilers. This finding
is consistent with the projections from the EPA's Boiler maximum
achievable control technology (MACT), which shows over 94 percent of
projected industrial boilers and process heaters to be natural gas-
fired units.\69\
---------------------------------------------------------------------------

    \68\ ``A Summary Review of Recent PSD Permitting Activity for
``Anyway Source'' Categories and the Potential GHG-Emitting Units
and Processes within Those Categories.'' Prepared by EPA staff,
March 2015.
    \69\ Memorandum from Eastern Research Group, Inc. to Brian
Shrager, EPA, ``Revised New Unit Analysis Industrial, Commercial,
and Institutional Boilers and Process Heaters National Emission
Standards for Hazardous Air Pollutants--Major Source,'' November
2011.
---------------------------------------------------------------------------

    In order to estimate the level of GHG emissions that correlated
with the type and size of combustion units that are most likely to
trigger PSD for ``anyway sources,'' we needed to equate GHG emissions
with those from an appropriate non-GHG pollutant SER that would trigger
PSD applicability. From our review of permit data, we identified that
the combustion units most often occurring in ``anyway sources'' PSD
permits were commonly triggering PSD for emissions of NOX.
We determined that the use of the NOX SER would be a
reasonable and appropriate value to use as the basis for estimating
equivalent GHG emissions associated with these ``anyway source''
combustion units. A full description of this analysis is provided in
the docket for this rulemaking.\70\
---------------------------------------------------------------------------

    \70\ ``Estimating Equivalent GHG Emissions Levels based on the
PSD NOX SER Value.'' Prepared by EPA staff, September
2015.
---------------------------------------------------------------------------

    The basic premise of this analysis was to identify a theoretical
minimum GHG emissions level that equates to the existing NOX
SER level (i.e., 40 tpy) for different combustion unit types. We could
then consider the merits, in the context of meeting the de minimis
principles, of aligning GHG BACT review on similar-sized combustion
unit projects that would be otherwise requesting PSD review for non-GHG
pollutants. From a theoretical standpoint alone, such an alignment
would optimize the emissions-reduction benefits available through the
BACT review process with a marginal increase in permitting burden
program-wide for both permitting authorities and sources (the
incremental increase in burden from the BACT review for an additional
pollutant).
    We identified NOX as the most appropriate surrogate
``anyway'' pollutant with which to compare the GHG emissions level.
NOX is commonly emitted in significant quantities from the
types of combustion units that are expected to be covered in most of
the future PSD permits. These are new electricity generation, large
natural gas and diesel-fired turbines, boilers, process heaters,
furnaces, and IC engines. We did not consider coal-fired units in
designing the surrogate analysis because projections of future boiler
and process heater units from the EPA's Boiler MACT (78 FR 7138,
January 31, 2013) and EGU NSPS (80 FR 64510, October 23, 2015)
rulemakings show little, if any, new coal-fired capacity as part of
projected new construction.\71\
---------------------------------------------------------------------------

    \71\ Memorandum from Eastern Research Group, Inc. to Brian
Shrager, EPA, ``Revised New Unit Analysis Industrial, Commercial,
and Institutional Boilers and Process Heaters National Emission
Standards for Hazardous Air Pollutants--Major Source,'' November
2011.
---------------------------------------------------------------------------

    We investigated the possibility of using alternative surrogate
pollutants for performing the equivalency analysis but found little
value in pursuing these other options. For various reasons, these other
pollutants did not correlate well with estimating equivalent GHG
emissions from the combustion unit sources that represent the largest
proportion of the sources that have been permitted for GHG. For
example, CO is not a good surrogate since its emissions are typically
inversely related to the amount of CO2 emitted from
combustion, the former representing more incomplete combustion
conditions and the latter more complete combustion. Also, since the CO
SER level is relatively high compared to other pollutants (100 tpy),
equating CO2 emissions to CO levels would result in a GHG
SER level well above 100,000 tpy, which would not adequately capture
significant projects that are otherwise subject to permitting for other
non-GHG combustion pollutants based on our knowledge of GHG permitting
for ``anyway sources'' that occurred under the GHG Tailoring Rule. PM
is also a combustion pollutant, but it is emitted in very small
quantities from natural gas units and PM often does not trigger PSD
review on its own. Therefore, as a surrogate, PM would not adequately
capture significant projects involving natural gas fired units, which
are anticipated to comprise a large proportion of future PSD permitted
units. Volatile organic compounds (VOCs) are emitted from a large
variety of processes, many of which do not involve combustion units or
have associated CO2 emissions, and therefore is not well
suited as the basis for developing a representative, surrogate GHG
level.
    Our equivalency analysis used the ratio of the emission factors of
GHG to NOX for each applicable unit type.\72\ The ratio was
then used to calculate the equivalent emissions of GHG, on a PTE)
basis, for a 40 tpy NOX emission level for each unit type.
The GHG-to-NOX ratio varied based on the unit types, which
was expected since the emission factors for NOX, and to a
lesser extent CO2, vary among the unit types and their
control configurations. The underlying emission factors used for the
surrogate analysis were selected to best represent the most likely
configurations for newly installed units at PSD permitted facilities.
---------------------------------------------------------------------------

    \72\ Estimating Equivalent GHG Emissions Levels based on the PSD
NOX SER Value.'' Prepared by EPA staff, September 2015.
---------------------------------------------------------------------------

    We estimated the following GHG emissions based on our equivalency
analysis. For natural gas-fired turbines, the range was 50,346 to
425,655 tpy CO2e, with an average of 186,537 tpy
CO2e across configurations. For large (greater than 100
MMBtu/hr) natural gas boiler/process heaters/furnaces, the range was
34,302 to 63,188 tpy CO2e, with an average of 48,504 tpy
CO2e across configurations. For small (less than 100 MMBtu/
hr) natural gas boilers/process heaters/furnaces, the range was 48,023
to 150,072 tpy CO2e, with an average of 98,047 tpy
CO2e across configurations. The resulting equivalency level
for GHGs was greater for the smaller boiler category since the ratio of
GHG to NOX in the emission rate was greater; in other words,
for the small boiler category, each ton of NOX emissions
correlated with more tons of GHG emissions than for the large boiler
category. For biomass boilers, the result was 78,210 tpy
CO2e based on average factor for wood residue, including
bark and wet wood. For large (greater than 500 horsepower (HP)) natural
gas-fired stationary IC engines, the result was

19,000 tpy CO2e. For large (greater than 750 HP) diesel-
fired stationary IC engines, the result was 17,529 tpy CO2e.
The average result across all ranges and units was 98,333 tpy
CO2e.\73\
---------------------------------------------------------------------------

    \73\ ``Estimating Equivalent GHG Emissions Levels based on the
PSD NOX SER Value.'' Prepared by EPA staff, September
2015
---------------------------------------------------------------------------

    It is important to note that the levels of GHG equivalency shown
earlier provide an approximate measure of the theoretical minimum level
of GHG emissions that could be associated with adding a particular type
of combustion unit with emissions that just exceed the NOX
SER level of 40 tpy. This does not necessarily mean that applying BACT
for GHGs to projects of a certain size would yield greater than a de
minimis benefit. This analysis is simply another data point to inform
the identification of a SER level for GHGs where the confluence of
``anyway source'' PSD projects and GHG reduction benefits is
meaningful. The equivalent GHG emissions level represents emissions
from a theoretical project that adds a combustion unit(s) that emits
just over 40 tpy NOX. However, based on what we saw in our
review of ``anyway source'' permits described in Section V.D.2 of this
preamble, the likelihood of such a project is not high because, in
cases where the NOX emission increase is close to the
NOX SER level, and where it is considered a practical
operating condition for the unit involved (such as smaller units), the
applicant very often accepts PTE limits to avoid triggering PSD at all.
    Also, as we have seen in our review of actual permits, it is more
likely that a PSD-permitted project would have NOX emissions
well in excess of the 40 tpy NOX SER level, due to the
addition of multiple combustion units or the sheer size of the unit
itself, such as a power plant turbine or steam-generating unit. In
these more typical PSD scenarios, GHG emissions would be multiple times
higher than the values shown earlier. Although our review of actual
samples of PSD permits revealed few cases where projects involving
these units would have GHG emissions just above these equivalent
NOX SER equivalent levels, these equivalency levels have
value in helping us understand and establish a marker point for the
theoretical minimum level of GHG emissions that would be associated
with particular unit types. It is also useful to look at the results
above in light of the type of unit involved. As shown earlier,
stationary IC engines have an equivalent GHG emission ratio below the
30,000 tpy CO2e level. Most of these IC engines units
typically show up in one of two ways in ``anyway source'' PSD permits:
(1) As associated equipment (e.g., emergency backup generator or fire
pump engine) where there is a large combustion unit such as a turbine
or boiler that is principally responsible for triggering the permitting
action; or (2) in multiple-unit configuration generator sets (e.g., 10
or more large IC engines linked together for electricity production).
Unlike the addition or modification of a large turbine unit where a
single unit can trigger a PSD action, it is a much less common scenario
where a single IC engine would be the triggering event for a PSD permit
since such units generally consume much less fuel and generate much
lower emissions, non-GHG or GHG, than larger boiler and turbine units.
    Our reviews and analyses to this point have clearly identified the
importance of combustion units as both a triggering event for ``anyway
source'' permitting actions for conventional pollutants and also as a
critical GHG emission component of these projects. The next section in
this preamble describes our review of non-combustion related GHG
emission sources, and how they may also contribute to GHG emissions for
certain PSD projects associated with certain source categories.
4. Non-Combustion Related GHG Emissions
    We conducted an additional evaluation to identify any GHG source
categories that we might not have identified in our review of
permitting activity described in earlier sections of this preamble. We
were particularly focused on process-related, GHG-emitting units which
could potentially be subject to the GHG BACT requirement at de minimis
levels below 75,000 tpy CO2e. Our review of PSD permits
issued to date with GHG limits had shown a very small percentage of PSD
permits and GHG BACT reviews that have been triggered based principally
on non-combustion units or processes. We wanted to better understand
the types and sizes of GHG-emitting units and processes that might
possibly fall into non-combustion source categories to ensure that we
did not miss potential non-trivial reductions at the proposed GHG SER
level.
    One category we looked at specifically was landfills. Municipal
waste landfills are important non-combustion, CH4-emitting
sources, and are the third largest contributing source category to
national CH4 emissions behind enteric fermentation and
natural gas systems.\74\ A landfill project can trigger PSD
applicability as an ``anyway source'' if its increased emissions exceed
the PSD SER level of 50 tpy for NMOC, the applicable NSR regulated
pollutant for municipal waste landfills. A landfill emitting just over
50 tpy NMOC would emit just over 190,000 tpy of CH4 on a
CO2e basis, well in excess of the current 75,000 tpy
CO2e GHG permitting level.\75\ Thus, there is high
confidence that any landfill project exceeding the PSD SER level for
NMOC will likely exceed any GHG SER option below this 190,000 tpy
CO2e level.
---------------------------------------------------------------------------

    \74\ ``Inventory of U.S. Greenhouse Gas Emissions and Sinks:
1990-2013,'' Table ES-2. Document No. EPA 430-R-15-004. April 15,
2015. http://www3.epa.gov/climatechange/ghgemissions/usinventoryreport.html.
    \75\ Memorandum from H. Ward, EPA/SPPD, to J. Mangino, EPA/AQPD,
re: Methane to NMOC ratio at landfills. June 17, 2014.
---------------------------------------------------------------------------

    We analyzed other source categories with significant non-combustion
related GHG emissions based on the EPA's national GHG inventory.\76\
The inventory included source categories with facilities that had a
likelihood of triggering PSD based on our review of past permits.
Unlike landfills, these categories do not have a source-specific,
regulated NSR pollutant that can be equated with GHG emissions and
compared to a GHG SER option. The categories we looked at included
cement production, glass production, nitric acid production,
electronics manufacturing, petroleum refineries, natural gas systems,
underground coal mines and industrial wastewater treatment. For this
effort, we analyzed GHG emissions data for these source categories that
were submitted under the GHGRP. A technical support document describing
the analysis and results is provided in the docket.\77\ In the
following discussion, we summarize the analysis and some of our key
findings.
---------------------------------------------------------------------------

    \76\ ``Inventory of U.S. Greenhouse Gas Emissions and Sinks:
1990-2013,'' Table ES-2. EPA 430-R-15-004. April 15, 2015. http://www3.epa.gov/climatechange/ghgemissions/usinventoryreport.html.
    \77\ Memorandum from T. Parise and S. Edgerton, EC/R
Incorporated, to J. Montanez and J. Mangino, EPA, ``Analysis of
Greenhouse Gas Emissions Data Collected Under Selected Subparts of
the Greenhouse Gas Reporting Rule,'' September 30, 2015.
---------------------------------------------------------------------------

    For this analysis, we characterized GHG emissions at the unit level
where available (for some categories only facility level data were
available) and compared these emissions to various actual emissions-
based thresholds (50,000 tpy CO2e, 37,500 tpy
CO2e, 25,000 tpy CO2e, and 12,500 tpy
CO2e) to provide an indication of the magnitude of emissions
above each

threshold in the reporting population. We used actual emissions because
that is the form in which emissions data are submitted under the GHGRP.
We selected the actuals-based thresholds to represent possible PTE-
based levels if one were to assume something less than 100 percent
capacity utilization. For example, at a 50 percent utilization rate, a
37,500 tpy CO2e actuals-based level equates to a 75,000 tpy
CO2e PTE-based level and a 25,000 tpy CO2e
actuals-based level equates to a 50,000 tpy CO2e PTE-based
level. Utilization rates can vary from site to site, and across and
within industry types, but we believe the actuals-based thresholds we
chose for the analysis provide a good representation of the possible
range of equivalent PTE CO2e emissions levels.
    Our non-combustion unit analysis across all the source categories
in the analysis showed a consistent profile of a high percentage of GHG
emissions associated with a relatively small percentage of high-
emitting units and facilities. Also, the variation in the amount of
total GHG emissions covered across the analysis thresholds was not
great. Across all categories, this varied from 95 percent of GHG
emissions at the 12,500 tpy CO2e actuals-based threshold to
88 percent of GHG emissions at the 50,000 tpy CO2e actuals-
based threshold. We found that for a number of the source categories
there are particular subcategories of processes or units that are
responsible for a majority of the non-combustion related GHG emissions.
Also, within those particular subcategories there tend to be a
relatively small percentages of large emitting units that are
responsible for most of those emissions. A summary of all the source
category analyses is provided in the supporting technical document
included in the docket for this rulemaking.\78\
---------------------------------------------------------------------------

    \78\ Memorandum from T. Parise and S. Edgerton, EC/R
Incorporated, to J. Montanez and J. Mangino, EPA, ``Analysis of
Greenhouse Gas Emissions Data Collected Under Selected Subparts of
the Greenhouse Gas Reporting Rule,'' September 30, 2015.
---------------------------------------------------------------------------

    Overall, this analysis gave us an indication of the relative size
of emissions from GHG- emitting processes and units in some key non-
combustion related GHG source categories. Our analysis showed that,
even when not including direct combustion emissions from these sources
and isolating only the non-combustion related GHG-emitting units or
processes, a high percentage of GHG emissions would be covered at the
current GHG permitting threshold level of 75,000 tpy CO2e on
PTE basis. Most PSD projects involving sources in these non-combustion
categories, such as refineries and cement production facilities, would
also likely include combustion units with substantial associated GHG
emissions. This would increase the overall GHG emissions from such
projects.
5. Potential BACT Techniques Applicable to GHG Emission Sources
    To evaluate the value obtained through the BACT review process, we
looked at the emission reduction potential of control techniques that
might be considered as BACT for a particular type of unit/process. The
following section describes the most common BACT techniques available
for reducing GHG emissions from units that have been, and will continue
to be, part of ``anyway source'' PSD projects.
    Under the CAA and applicable regulations, a PSD permit must contain
emissions limitations based on application of BACT for each regulated
NSR pollutant. CAA section 165(a)(4); 40 CFR 52.21(j). An analysis of
BACT for GHGs should be conducted in the same manner as for any other
PSD regulated pollutant. The CAA and corresponding implementing
regulations require that a permitting authority conduct a BACT analysis
on a case-by-case basis. The permitting authority must evaluate the
amount of emissions reductions that each available emissions-reducing
technology or technique would achieve, as well as the energy,
environmental and economic impacts and other costs associated with each
technology or technique. Based on this assessment, the permitting
authority must establish a numeric emissions limitation that reflects
the maximum degree of reduction achievable for each pollutant subject
to BACT through the application of the selected technology or
technique. However, if the permitting authority determines that
technical or economic limitations on the application of a measurement
methodology would make a numerical emissions standard infeasible for
one or more pollutants, it may establish design, equipment, work
practices or operational standards to satisfy the BACT requirement. 40
CFR 52.21(b)(12).
    One overarching challenge to analyzing GHG emissions-reduction
potential is the inherent difficulty in predicting the specific makeup
of new construction and modification projects that will trigger PSD in
general. Another challenge is that the BACT control requirement is
determined on a case-by-case basis, based on site-specific factors at
the source in question. Thus, even if we could roughly predict what
sources are likely to be subject to PSD and required to get a permit,
it is still challenging to calculate the emission reductions associated
with application of BACT to GHG emissions from a particular source.
    The emissions-reduction benefits that may result from the
application of BACT can vary widely, depending on the specific
configuration of the project and source, and the results of the case-
specific BACT review. Thus, the variation in project composition and
case-specific BACT review not only affects the ability to generate
``typical'' emissions increases and reductions from BACT, but, in turn,
also severely hinders any ability to relate this to health or
environmental benefits. Further complicating the ability to quantify
the benefit of BACT is that the emission reductions would have to be
measured from some alternative baseline, i.e., what the facility would
have emitted absent the application of the BACT technique selected
through the review process. After predicting the project components
subject to BACT review, establishing what the alternative baseline
would have been absent application of a BACT technique requires
specific information about each facility site, the source's development
options and what the potential emissions would have been absent
application of BACT. The alternative future baseline scenarios for any
given facility can vary based on the planned operations and practices.
Thus, it is difficult to project a future project's PTE level with any
specificity within or across industries.
    In light of these challenges, we focused on the possible GHG
control techniques that could apply to GHG-emitting units/processes
that other parts of our analysis indicated would most likely be subject
to GHG BACT review at ``anyway sources.'' This review informed our
consideration of the meaningfulness of the GHG BACT review for units
and sources that might be covered at various GHG SER levels.
    Recognizing that larger combustion units will likely be the most
predominant GHG emission source type at ``anyway source'' PSD projects,
one finding from this review was that energy efficiency measures are
currently the most common BACT strategy for these units. In addition,
we found that larger combustion units provide the best opportunity for
achieving GHG reductions through case-by-case BACT review. Sources with
small combustion units or other sources of GHGs provide limited
opportunities for achieving additional GHG reductions through the BACT
review.

    The sections that follow discuss the most common types of BACT
techniques that have been evaluated through GHG BACT review at ``anyway
sources'' and implemented by sources that obtained permits. These are
not intended to represent every possible category of BACT for GHGs but
reflect the techniques most commonly evaluated and applied across a
variety of ``anyway sources.'' In specialized cases, there are unique
GHG control techniques available for industry-specific processes that
emit GHGs, such as those that can be implemented at nitric acid plants
to reduce nitrous oxide emissions from the ammonia oxidation step.
However, based on our review of permitting data at ``anyway sources''
and considering the nature of units emitting GHGs below 75,000 tons per
year, we expect for the near to medium term that energy efficiency
measures will continue to be the most predominant GHG BACT mitigation
strategy applicable to ``anyway sources'' that increase emissions of
GHGs by less than 75,000 tons per year (on a CO2e basis).
Therefore, the emissions-reduction achievable with this technique at
sources that have the potential to emit less than 75,000 tons per year
was an important consideration in developing our proposed GHG SER.
a. Energy Efficiency Measures
    While energy efficiency measures can reduce emissions of all
combustion-related pollutants, they are particularly important for GHGs
for two reasons: (1) GHG emissions from combustion sources
(particularly CO2) make up a large majority of the GHG
inventory from the industrial facilities most often subject to PSD
permitting; and (2) the use of add-on controls to reduce GHG emissions
is expected, for the foreseeable future, to be a viable BACT option at
a only small set of the largest GHG emission sources. To date, most GHG
BACT determinations for combustion sources have relied on some
combination of energy efficiency measures. Therefore, it is important
to consider the implementation, effectiveness and value of energy
efficiency measures as applied through the BACT process to combustion
sources that may trigger the GHG BACT requirement at different GHG SER
option levels. The following is a description of efficiency improvement
measures that have been applied to industrial combustion units.
    The EPA has identified a number of energy efficiency measures, many
of which have been utilized to date to satisfy GHG BACT requirements in
actual PSD permits. These procedures include: \79\
---------------------------------------------------------------------------

    \79\ ``Available and Emerging Technologies for Reducing
Greenhouse Gas Emissions from Industrial, Commercial, and
Institutional Boilers,'' Office of Air Quality Planning and
Standards, EPA. October 2010. http://www.epa.gov/nsr/ghgdocs/iciboilers.pdf.
---------------------------------------------------------------------------

     High efficiency burners.
     Combustion and boiler performance optimization.
     Combustion system instrumentation and controls.
     Air preheat and economizers.
     Turbulators for firetube boilers.
     Boiler insulation.
     Minimization of air infiltration.
     Boiler blowdown heat exchanger.
     Condensate return system.
     Refractory material selection.
     Minimization of gas-side heat transfer surface deposits.
     Steam line maintenance.
    In many cases, the impacts of these measures were highly site-
specific and the benefits varied based on the site-specific
configuration and operational conditions of the unit. These measures
were typically associated with a GHG emission limit, steam generation
rate or required maximum fueling rate for the combustion units
involved. For most of these measures, site-specific conditions and
economic variables must be addressed to determine whether they would be
technically and economically viable. Also, the absolute benefits for
any given facility or project undergoing PSD BACT review will depend on
the relative improvement over some baseline unit efficiency that might
have been used absent the GHG BACT review process.
    To give some perspective on the potential benefits of these
measures, a new natural gas-fired industrial boiler unit will generally
have a baseline thermal efficiency in the 82 to 85 percent range.\80\
Implementing a mix of the additional measures above, it is possible to
obtain thermal efficiencies close to 90 percent.\81\ Thus, looking at
the difference between the baseline efficiency of a new boiler unit and
a maximum efficiency around 90 percent, we can identify a maximum GHG
reduction potential of approximately 7 percent.
---------------------------------------------------------------------------

    \80\ ``Evaluating Efficiency and Compliance Options for Large
Industrial Boilers in California's Changing Local and State
Regulatory Environment,'' 2009 ACEEE Summer Study on Energy
Efficiency in Industry.
    \81\ ``Climate Leaders GHG Offset Protocol: Industrial Boiler
Efficiency (Industrial Boiler Applications),'' EPA, Climate
Protection Partnerships Division, August 2008, Version 1.
---------------------------------------------------------------------------

    In evaluating the value of BACT review, it is also helpful to look
at the type and size of combustion unit involved. Industrial boilers,
process heaters and furnaces of the size typically seen as part of
``anyway source'' projects (e.g., greater than 50 MMBtu/hr heat input
rating) are not generally purchased as an ``off-the-shelf'' item. These
units can be site-designed in a way that enables consideration and
incorporation of a combination of the measures shown earlier. The BACT
review is particularly valuable for these types of units as it is based
on case-by-case review of technology implementation and cost
considerations. Manufacturers have models that they can construct based
on the specifications provided by a facility design engineer. To
achieve the desired performance, the engineer will specify the desired
design output capacity, steam pressure and/or temperature requirements,
and emission thresholds that the boiler unit must meet. The design
engineer can then provide the project-specific boiler specifications to
the boiler manufacturer who will then apply the correctly sized boiler
components to its boiler plan and engineered specifications before
running a computer model to estimate the resulting operational
characteristics, including thermal efficiency and emissions of the
resulting boiler.\82\
---------------------------------------------------------------------------

    \82\ ``Boiler Efficiency Projects-Development of Issues Papers
for GHG Reduction Project Types: Boiler Efficiency Projects,''
Prepared for the California Climate Action Registry, January 7,
2009. http://www.climateactionreserve.org/wp-content/uploads/2009/03/future-protocol-development_boiler-efficiency.pdf.
---------------------------------------------------------------------------

    Smaller combustion units, such as smaller industrial and commercial
size boilers and stationary IC engines, are typically purchased ``off
the shelf'' and meet manufacturer's efficiency standards. Minimum
efficiency requirements for these boilers are mandated to manufacturers
by the federal government (U.S. Department of Energy (DOE) and the
EPA), and some states have minimum efficiency requirements for boilers
that are allowed to be sold in the market. Stationary IC engines that
are part of ``anyway source'' PSD projects typically have to meet NSPS
requirements for non-GHG pollutants, which in many cases form the basis
for the BACT requirement for those, resulting in purchase decisions
that include newer, highly-efficient engines that are low-emitters for
all combustion pollutants, including GHGs. The range in performance
efficiency across manufacturers for these new engines is typically
within a couple of percentage points.
    Beyond small differences in efficiencies between manufacturers and
model types, the ability to achieve

additional GHG reductions at these smaller ``off-the-shelf'' type
units, whether they are small boilers or IC engines, is difficult for a
couple of reasons. First, implementing a number of the efficiency
measures described previously requires site-specific design and
construction criteria, more typically associated with larger scale
projects where these measures can be part of unit design and
manufacture. Second, ``off-the-shelf'' units typically cannot be
substantially modified or tampered with in order to be guaranteed to
meet their certified performance standards. Many of the energy
efficiency measures described previously involve significant additions
and/or modifications to the basic unit, which also may not be
technically or economically viable for smaller unit applications.
b. Carbon Capture and Storage
    For the purposes of the initial step of a BACT analysis for GHGs,
the EPA classifies CCS as an add-on pollution control technology that
is ``available'' for facilities emitting CO2 in large
amounts, including fossil fuel-fired power plants and industrial
facilities with high-purity CO2 streams (e.g., hydrogen
production, ammonia production, natural gas processing, ethanol
production, ethylene oxide production, cement production and iron and
steel manufacturing).\83\ CCS is a promising technology with the
potential for substantially reducing CO2 emissions. In
October 2015, EPA issued a final NSPS\84\ for new fossil-fueled power
plants. The EPA found that a highly efficient supercritical boiler
implementing partial CCS is the Best System of Emission Reduction
(BSER) for newly constructed steam generating units.\85\ The final NSPS
requires that newly constructed steam generating EGUs meet an emission
standard consistent with the implementation of a CCS system capturing
less than 30 percent of the CO2 emissions from the
plant.\86\ This level of control is referred to as ``partial CCS.''\87\
For units subject to this standard, this NSPS standard sets the minimum
requirements for a BACT emission limit. 42 U.S.C. 7479(3) (``In no
event shall application of [BACT] result in emissions of any pollutants
which will exceed the emissions allowed by any applicable standard
established pursuant to section 7411 or 7412 . . .''). However, a PSD
BACT analysis is a case-by-case analysis that considers several factors
before determining the ``maximum degree of reduction'' that is
achievable for a particular source. In the context of some PSD permit
applications, such as those that predate the October 2015 NSPS or those
for other types of sources, CCS has not been selected as BACT because
it was not found to be technically feasible or the costs of CCS have
made the application of the technology economically unachievable.\88\
CCS is most likely to be a viable BACT candidate for projects involving
very large CO2 emission sources that already trigger GHG
BACT review at the current 75,000 tpy CO2e GHG permitting
level. CCS technologies may not be technically feasible or economically
achievable for lower emitting stationary sources--i.e., those below the
75,000 tpy CO2e GHG threshold--and for sources that emit
CO2 in a dilute emission stream.
---------------------------------------------------------------------------

    \83\ ``PSD and Title V Permitting Guidance for Greenhouse
Gases,'' EPA, Office of Air Quality Planning and Standards, Research
Triangle Park, NC, EPA-457/B-11-001, p. 32, March 2011.
    \84\ Final Rulemaking titled ``Standards of Performance for
Greenhouse Gas Emissions from New Stationary Sources: Electric
Utility Generating Units'' (80 FR 64513, October 23, 2015).
    \85\ For newly constructed intermediate and baseload stationary
combustion turbines, the final NSPS requires meeting an emission
standard consistent with the performance of modern, efficient
Natural Gas Combined Cycle (NGCC) technology.
    \86\ EPA Fact Sheet on Carbon Dioxide Capture and Sequestration,
http://www3.epa.gov/climatechange/ccs/.
    \87\ ``Partial CCS'' is the implementation of CCS technology to
capture only a portion of the CO2 emission from a
stationary source--typically some amount less than 90 percent of the
CO2 and often by treating only a portion of the sources
emission stream. ``Full CCS'' is the capture of more than 90 percent
of the sources CO2--typically accomplished by treating
the sources entire emission stream.
    \88\ However, this was not always the outcome in PSD permits
that pre-date the October 2015 NSPS. For example, in November 2014,
the EPA issued a PSD permit for GHGs for the Nuevo Midstream, LLC--
Ramsey Gas Plant in Orla, Reeves County, Texas that assumes use of
partial CCS as BACT to capture 35 percent of the CO2
emissions from the Ramsey IV and VI plants amine still vents.
---------------------------------------------------------------------------

c. Gas Recovery and Utilization
    The collection and combustion or utilization of either industrial
process waste gas or biogas, both streams which can contain
CH4, is a GHG BACT control technique that has been required
as BACT in PSD permits addressing GHG emissions at oil and gas
production facilities, refineries, landfills, and chemical plants.
Flares are commonly used to control VOC emissions as part of ``anyway
source'' PSD permits for projects that include a process that produces
the waste gas emissions that must be controlled. Combustion of the
waste gas stream avoids simply venting the VOC emissions to the
atmosphere, and as described later in this preamble can also have a
beneficial impact on the CO2e emissions profile for the
sources. Flares are used extensively to dispose of: (1) Purged and
wasted products from refineries, (2) unrecoverable gases emerging with
oil from oil wells, (3) vented gases from blast furnaces, (4) unused
gases from coke ovens, and (5) gaseous wastes from chemical industries.
Id. From our review of ``anyway source'' PSD permitting activity for
these types of industries, these waste gas streams are usually
coincidental to a larger project component driving the PSD
applicability for the project. As an example, for an iron and steel
facility, the addition of a blast furnace would likely trigger
applicability for PSD for a number of criteria pollutants, and also
have significant GHG emissions in terms of direct combustion related
CO2 emissions (large blast furnace units typically will
exceed 75,000 tpy CO2e emissions). Associated with this
furnace unit, however, are likely to be off-gas streams, possibly
containing CH4 gas, which also then become subject to BACT
review as part of the overall project.
    A common method for minimizing emissions from flares is through
good combustion practices. When these waste gas streams are combusted
in either a flare or a thermal oxidizer, CH4 in the waste
gas stream is converted to CO2, typically at efficiency
levels greater than 96.5 percent.\89\ Since CO2 is a GHG
with less radiative force than CH4, this technique produces
a lower overall GHG emissions increase on a CO2e basis.
Assuming a combustion efficiency of 96.5 percent and CH4
being the principal GHG of concern in the waste gas stream, the
combustion process can result in reductions of CO2e
emissions of approximately 86 percent (assumes a GWP value of 25 for
CH4).
---------------------------------------------------------------------------

    \89\ AP-42, Fifth Edition, Volume I, Chapter 13: Miscellaneous
Sources, Section 13.5 ``Industrial Flares,'' EPA, April 2015. http://www.epa.gov/ttn/chief/ap42/ch13/final/C13S05_4-20-15.pdf.
---------------------------------------------------------------------------

    Utilization of process waste gas, which often can contain
CH4, for on-site energy or off-site sale and use can provide
additional GHG benefits beyond simply flaring. Like flaring, the
collection and utilization of the waste gas can serve as a BACT control
technique that effectively converts CH4 to CO2
through a combustion unit with the net benefits realized on a
CO2e emissions basis. In addition, utilization of the gas
has the potential to avoid additional GHG emissions associated with
supplemental on-site fossil-fuel usage.
    For example, at sites such as natural gas processing plants,
refineries, or at

other facilities where the collected waste gas can be used to fuel on-
site equipment or made available for sale or other uses, there may be
alternatives to simply flaring the gas. In addition, the on-site use of
the collected gas in lieu of additional fossil-fuel use can also lead
to a reduction in the facility's GHG emissions, although GHG emissions
from any off-site sale and use of the collected gas are completely
excluded from the seller facility's calculated GHG emissions.
    Another example where gas collection and utilization has
applications for GHG BACT is landfills, where large amounts of
CH4 gas generated through waste decomposition can, at
properly designed sites, be collected through biogas collection wells
and used to run IC engines or microturbines that produce energy for
onsite usage or sale to the electric grid. As mentioned earlier in
Section V.D.4 of this preamble, landfills that are subject to PSD
permitting for their NMOC emissions will likely have CH4
emissions well in excess of 75,000 tpy CO2e, such that BACT
strategies involving gas utilization and recovery may be found
applicable for both non-GHG and GHG emissions from the landfill.
d. Leak Detection and Repair Measures
    Leak detection and repair (LDAR) systems have been used as GHG BACT
controls for both fugitive CH4 losses and SF6
emission losses from electrical equipment. Typically, and as previously
described in more detail in the summary of our review of ``anyway
source'' permits in Section V.D.2 of this preamble, these fugitive
sources were associated with a PSD project that involved a larger
stationary source unit or process, such as combustion unit
installations at a power plant or a large gas or oil production/process
unit that contained associated fugitive release points, such as piping
or valves. The GHG reduction potential for LDAR systems can be highly
variable depending on the site-specific design and implementation
procedures. The EPA has identified VOC applications for LDAR systems
that can achieve VOC emissions reductions in the 45 to 70 percent range
for various equipment types (since CH4 would typically be
part of the same waste gas stream, these level of reductions in
fugitive VOC emissions would be expected for fugitive CH4
emissions as well).\90\ The emission sources for CH4 where
these methods are deployed are generally CH4 fugitive losses
from associated piping and natural gas delivery networks, or equipment
leaks at compressor or pumps that move natural gas product. These
sources tend to be most commonly encountered at PSD-triggering projects
involving the oil and gas sector, primarily in the production,
processing and transmission subsectors. However, anywhere combustion
units utilize natural gas as fuel, they can also have associated leaks
in the piping network associated with the unit configuration. In both
these general cases where LDAR has been selected as a BACT for GHG
emissions dominated by CH4, the fugitive CH4
losses have been ancillary to the main GHG emission points in the
project, typically a single or combination of large fossil fuel
combustion units. At all of the ``anyway source'' permits we have
reviewed that required LDAR as GHG BACT, combustion units triggered the
BACT requirement for conventional pollutants as well as GHGs
(principally CO2 from combustion). The fugitive
CH4 losses associated with the combustion unit projects were
included in the BACT review for the GHG emissions increases for the
project.
---------------------------------------------------------------------------

    \90\ ``Leak Detection and Repair: A Best Practices Guide.'' EPA-
305-D-07-001. EPA Office of Compliance, Office of Enforcement and
Compliance Assurance, October 2007.
---------------------------------------------------------------------------

    Another application of LDAR has been in the power plant sector. In
this sector, fugitive leaks of SF6 gas from ancillary
circuit breaker equipment associated with power plant projects have
been subject to GHG BACT review where the principle PSD-triggering
event involved the installation of power-generating combustion units.
SF6 is used as an electrical insulator and interrupter in
equipment that transmits and distributes electricity.\91\ Fugitive
emissions of SF6 can escape from gas-insulated substations
and switchgear through seals, especially from older equipment. The gas
can also be released during equipment manufacturing, installation,
servicing and disposal. The EPA estimates that where consistently
implemented in the power plant sector, applications of LDAR systems
could reduce SF6 emissions by 20 percent.\92\
---------------------------------------------------------------------------

    \91\ ``Inventory of U.S. Greenhouse Gas Emissions and Sinks:
1990-2013,'' Section 4.24. EPA 430-R-15-004. April 15, 2015. http://www3.epa.gov/climatechange/ghgemissions/usinventoryreport.html.
    \92\ SF6 Emissions Reduction Partnership for Electric
Power Systems, http://www3.epa.gov/highgwp/electricpower-sf6/basic.html.
---------------------------------------------------------------------------

6. Costs of GHG BACT Review
    We have estimated that it costs an individual source approximately
$24,000 to undergo GHG BACT review for a PSD modification project and
the associated title V permit revision costs to include those
requirements in the facility's title V permit.\93\ These costs include
preparing the permitting application, supporting analyses and various
other aspects of the review and submission of the permit application as
it pertains to GHGs. These estimates do not include what can be
significant additional costs for the GHG BACT control that is
ultimately adopted and implemented by the permitted facility since
BACT, and ultimately the costs, can vary from site to site based on
site specific factors that are difficult to predict with any
specificity or certainty in advance. We also estimate it costs the
permitting authority approximately $5,000 for regulatory review and
processing costs related to the GHG BACT review for a PSD modification
project and the associated title V revisions costs to include those
requirements in the facility's title V permit.
---------------------------------------------------------------------------

    \93\ Information related to the associated individual and
programmatic burden at the proposed GHG SER level is provided in
Section VI of this preamble.
---------------------------------------------------------------------------

E. Proposed GHG SER and Request for Comment

    After consideration of several factors, we are proposing to
establish a GHG SER of 75,000 tpy CO2e. Establishing a de
minimis exemption threshold requires both policy and legal judgments to
determine what constitutes a ``gain of trivial value'' and ``pointless
expenditure of effort.'' In an effort to identify an appropriate SER
for GHGs, we considered the approaches that the EPA has previously used
to identify de minimis levels for other pollutants in the PSD program,
but we have found that a new approach is needed for GHGs. To develop
this approach, we have considered the legal basis for establishing de
minimis exemptions under the D.C. Circuit's Alabama Power opinion and
the factors the Court called for the agency to consider. These include
the context in which a SER for GHGs would apply to determine only
whether BACT applies to the pollutant GHGs at a source that triggers
PSD based on other pollutant emissions. Other factors we considered are
the nature of the pollutant and the dangers caused by increases in that
pollutant, the nature and purposes of the regulatory program, the gains
achieved from regulating GHG emissions through the PSD program at or
below a certain level, and administrative and implementation burdens of
regulating at or below such levels. We developed findings relevant to
these factors through a four-part technical analysis of GHG-emitting

sources, PSD permitting information, and GHG emissions reduction
strategies likely to be considered in a BACT review for those sources.
    Based on all the information obtained from the various data reviews
and analyses summarized in Section V.D.1 of this preamble, taking into
account the factors mentioned previously, we are proposing a SER of
75,000 tpy CO2e for GHGs. The following discussion describes
how each of the key findings together led to and support our proposed
GHG SER value of 75,000 tpy CO2e.
    First, our actual, historical experience of GHG BACT reviews
occurring at a 75,000 tpy CO2e level for sources under Step
1 of the Tailoring Rule provided us valuable insight into the affected
sources and value of GHG BACT review at that permitting level. When
considered in the context of individual sources and the collective
population of sources subject to PSD, the degree of GHG reductions
achievable through application of GHG controls to new sources and
modifications that increase GHG emissions by more than 75,000 tpy
CO2e is meaningful, and thus has more than ``trivial''
value. The current 75,000 tpy CO2e threshold has resulted in
the PSD BACT requirement applying to GHGs in the vast majority of the
actual ``anyway source'' PSD permits covering the type of units for
which GHG BACT review would be expected to achieve meaningful emissions
reductions. We also found that the types of GHG sources that have been
addressed in those GHG BACT reviews represent the most important
industry sectors in terms of national GHG emissions contribution. These
include source categories such as power plants, refineries, chemical
production facilities, and oil and gas production sites. While most of
the GHG emissions from these sources, as well as the ``anyway source''
PSD triggering actions, are related to large, fossil-fueled combustion
units, our investigation into non-combustion sources also revealed that
the most important, non-combustion related GHG-emitting sources, such
as landfills, cement plants, refineries, and nitric acid plants, have
process emissions well in excess of the 75,000 tpy CO2e
level. In summary, based on information from previous permitting
decisions using the 75,000 tpy CO2e applicability level for
GHG BACT review at ``anyway sources,'' we did not see any sources
within major GHG source categories that were ``missing'' BACT limits
for GHGs in permits issued to ``anyway sources,'' which would have been
an indicator that there may be value in applying BACT to GHGs at a
lower SER.
    In addition to finding broad coverage of sources in the major GHG
emissions source categories using a 75,000 tpy CO2e
threshold, we found that the ``anyway source'' permitting experience
involving GHG BACT reviews to date since GHGs became subject to PSD has
not imposed unreasonable administrative and enforcement burdens. State
and local permitting authorities, as well as affected industries, have
successfully implemented PSD permitting for GHGs at a 75,000 tpy
CO2e threshold.
    Second, our investigation into ``anyway source'' PSD permits that
did not go through GHG BACT review under the Tailoring Rule Step 1
permitting level of 75,000 tpy CO2e revealed only a few
cases where a GHG SER level below 75,000 tpy CO2e may have
resulted in additional GHG BACT reviews. Considering the limited
additional cases where GHG BACT review could apply at a GHG SER below
75,000 tpy CO2e and the limited degree of emissions
reductions that might be achieved in each case, we propose to conclude
that the burdens of subjecting such projects to case-by-case BACT
review for GHGs would yield a gain of trivial or no value.
    Our review revealed only a handful of PSD modification projects on
a yearly basis nationwide that can be expected to increase GHG
emissions in the range from 30,000 to 75,000 tpy CO2e. Based
on our review of permitting data at ``anyway sources'' and considering
the nature of units emitting GHGs between these values, we expect for
the near to medium term that energy efficiency measures will continue
to be the most predominant GHG BACT mitigation strategy that could be
applicable to sources with the potential to emit between 30,000 and
75,000 tpy CO2e. At a project scale, if we were to consider
a single hypothetical, combustion-related project with a GHG emissions
increase of 74,999 tpy CO2e (just under the 75,000 tpy
CO2e proposed GHG SER level) and a maximum energy efficiency
gain through GHG BACT review of 7 percent described above, the maximum
marginal difference in GHG emissions that could result from applying
BACT to GHGs is approximately 5,500 tpy CO2e. Given the
limited number of projects expected in this 30,000 to 75,000 tpy
CO2e range and the limited amount of emissions reductions
that could theoretically be achieved at each source, from a
programmatic perspective, there is little to be gained in terms of
overall reduction in GHG emissions from applying GHG BACT review at a
GHG SER level below 75,000 tpy CO2e. Thus, we propose to
conclude that the burdens of regulation at a GHG SER level between
30,000 and 75,000 tpy CO2e would yield a gain of trivial or
no value from both a programmatic and individual project-level
perspective.
    For PSD modification projects that increase GHGs by less than
30,000 tpy CO2e, we found virtually no value in applying the
GHG BACT requirement. We found through both our equivalency analysis
and permitting reviews that these smaller emitting unit projects will
typically not qualify as ``anyway source'' projects by themselves. In
addition, we found that many smaller emissions units will often be
pulled into the GHG BACT analysis because they are ancillary units to a
larger combustion unit that emits well above 75,000 tpy
CO2e; examples include emission units such as flares,
thermal oxidizers, emergency generators, and fugitive emission leaks.
Since the types of units adding GHGs in amounts less than 30,000 tpy
CO2e would not likely trigger PSD at all or would already be
covered because of other changes occurring at the same time, lowering
the GHG threshold to 30,000 tpy CO2e would subject few, if
any, additional projects to the GHG BACT requirements. In cases where a
project theoretically could increase emissions of a pollutant besides
GHGs enough to trigger PSD, the project would involve emission units
such as IC engines. There is virtually no value obtained in conducting
a GHG BACT review of such a unit. We found that ``off-the-shelf''
combustion units, such as IC engines, are generally meeting
manufacturers' performance and efficiency compliance standards
established by DOE and the EPA for new units with only marginal
variations in efficiency ratings on newly purchased units. Also, we do
not expect that GHG BACT review for IC engines would produce any
reductions for GHGs beyond that resulting from the NSPS compliance
standards that already exist for these new units. Thus, the gain from
applying BACT to GHG emissions would yield a gain of virtually no value
and be a pointless expenditure of effort. This is even more apparent
when considered in light of the administrative burdens of conducting a
case-by-case BACT analysis for GHGs at such sources. Thus, the EPA is
not considering establishing a GHG SER level below 30,000 tpy
CO2e.
    We are soliciting comment on the extent to which our proposed GHG
SER level of 75,000 tpy CO2e reflects a level below which
the burdens of applying the BACT requirement to GHGs would ``yield a
gain of trivial or no value'' and

thus would be a ``pointless expenditure of effort'' when applied to all
of the affected units and sources. We are also soliciting comment on
whether a value between 30,000 and 75,000 tpy CO2e,
specifically such as 30,000 tpy or 45,000 tpy CO2e, would
better represent a de minimis threshold for applying the BACT
requirement to GHGs. We encourage commenters to consider the following
in submitting comments. Comments, arguments, and supporting data for a
specific GHG SER level other than 75,000 tpy CO2e should
identify a more appropriate level and explain why that specific level
would be better. Commenters are encouraged to provide information as to
the likely number and type of new or modified emission sources and
units that would trigger PSD and be subject to the GHG BACT requirement
at the suggested alternative GHG SER level. Comments should also
address what source categories would be affected, what types of control
technique would be considered in the GHG BACT review, the expected
degree of GHG reductions achievable from such control techniques, and
the anticipated burden to permitting authorities and sources of
conducting a BACT analysis at the specific alternative level.
    In soliciting comment for a SER between 30,000 and 75,000 tpy
CO2e, we recognize that sources and others in the public may
have access to information that is not available to the Agency and that
may inform an appropriate SER level. Therefore, we are specifically
soliciting comment on and requesting data for areas in our technical
analysis where commenters believe such information will provide support
for adjusting our applied assumptions. However, commenters should keep
in mind that the universe of future PSD permitting is constrained by
the U.S. Supreme Court's decision limiting the program to ``anyway
sources'' and modifications at ``anyway sources.'' The GHG BACT
requirement is potentially applicable only to sources and modifications
that would otherwise trigger PSD requirements based on emissions of
pollutants other than GHGs.
    We are proposing a GHG SER value based on the GHG metric of
CO2e, representing the single air pollutant defined as the
aggregate group of the six well-mixed greenhouse gases (CO2,
N2O, CH4, HFCs, PFCs and SF6). As
explained earlier, this aggregate pollutant is measured in terms of
``carbon dioxide equivalent'' or ``CO2e'' emissions, which
is a metric that allows all the compounds comprising GHGs to be
evaluated on an equivalent basis despite the fact that the different
compounds have different heat-trapping capacities. The GWP that has
been determined for each compound reflects its heat-trapping capacity
relative to CO2. The mass of emissions of a constituent
compound is multiplied by its GWP to determine the emissions in terms
of CO2e. A source's emissions of all compounds in terms of
CO2e are summed to determine the source's total GHG
emissions.\94\ This construct differs from other pollutant SERs based
solely on a mass basis; however, we believe, as we did in the Tailoring
Rule, that the CO2e metric is consistent with the definition
of the pollutant as defined in the Administrator's endangerment and
contribution findings regarding GHGs (74 FR 66496) and that by
incorporating the GWP values, best addresses the relevant environmental
endpoint, which is the radiative forcing of the GHGs emitted. We also
see no requirement for using a mass-based calculation method for the
GHG SER, such as we determined necessary in the Tailoring Rule. The
determination that a mass-based calculation method was a necessary
first step under the Tailoring rule was due to the statutory 100 and
250 tpy levels in the statutory definition of ``major emitting
facility.'' \95\ The SERs are based on EPA's inherent authority to
identify a de minimis level of GHG emissions for purposes of
determination applicability of the statutory BACT provisions of the
CAA. These provisions in the Act do not include a mass-based emissions
applicability threshold. In addition, the emissions thresholds in the
definition of major stationary source that influenced our reasoning in
the Tailoring rule are no longer applicable to GHGs in light of the
U.S. Supreme Court's decision in UARG.
---------------------------------------------------------------------------

    \94\ See the accompanying proposed regulatory text to this
preamble at 40 CFR 51.666 (b)(31) and 40 CFR 52.21(b)(32) for
further details on the calculation of CO2e emissions.
    \95\ See 75 FR 31531 for background on why this step was needed
in Tailoring Rule.
---------------------------------------------------------------------------

    In addition to consistency with the Administrator's endangerment
and contribution findings, there are programmatic and policy advantages
to using the ``sum-of-six'' construct based on CO2e for
purposes of the GHG SER BACT review. One significant advantage to this
construct is that it allows more flexibility to sources for designing
and implementing control strategies that maximize reductions across
multiple GHGs. From a programmatic standpoint, the CO2e
metric facilitates permitting authorities' review and consideration of
the combined effect of the six individual GHGs when sources emit any
one or combination of the individual gases. Also, given that Congress
built in considerations of energy, environmental, and economic impacts
into the BACT requirement, we think that allowing consideration of
those factors across six gases will result in decisions that more
appropriately account for those impacts at the source. In summary, we
see no statutory requirement or programmatic advantages for considering
a GHG SER value that incorporates a mass-based component; however, we
welcome comments on whether such a need exists and how such a component
would function for GHG BACT applicability purposes.
    Lastly, we are also requesting any specific comments related to the
administrative and enforcement burdens associated with implementing GHG
BACT review at the proposed GHG SER level (75,000 tpy CO2e),
or at a suggested alternative GHG SER level. Due to the relatively
short history of applying the BACT requirement to GHGs (as compared to
PSD permitting overall), the limited experience in applying BACT to
GHGs permitting in some sectors, and the overall uncertainties in
predicting exact levels of future PSD activity, we solicit any comments
pertaining specifically to the administrative and programmatic burdens
associated with the proposed GHG SER and applying the BACT review
process to GHGs emitted at that level or at a suggested alternative
level. We also solicit comments from all parties, including the
regulated community and permitting authorities, as well as commenters
supporting an alternative threshold, as to the administrative and
enforcement burdens of establishing a de minimis threshold at the
suggested alternative level.

VI. What would be the economic impacts of the proposed rule?

    The main focus of the Economic Impact Analysis (EIA) is the cost
savings to permitting authorities and affected sources due to ``anyway
sources'' that are below the proposed de minimis GHG SER not having to
go through GHG BACT review. If not for provisions we are proposing to
remove in this proposal and that currently remain in the EPA's
definition of ``subject to regulation'' at this time, under the present
definition of ``significant'' in the PSD regulations, any GHG emissions
increase would require a newly constructed major source of another
regulated NSR pollutant, or a major modification at an existing
facility significantly increasing another pollutant, to undergo PSD GHG

BACT review.\96\ Therefore, the EIA includes estimated costs relative
to a ``no-action'' scenario where the current functioning GHG
permitting level of 75,000 tpy CO2e would no longer be
applicable and any increase in GHG emissions at sources otherwise
subject to PSD would trigger the requirement for a GHG BACT analysis.
The proposed rule would remove the requirement of conducting the GHG
BACT review, as well as the need to include the requirements resulting
from this GHG BACT review in a source's title V permit, for sources
with GHG emissions increases less than the proposed GHG SER. A summary
of the avoided costs relative to the ``no-action'' scenario for both
PSD and title V programs based on the proposed 75,000 tpy
CO2e GHG SER is described in the following paragraphs.
Details related to the EIA are documented in the report titled
``Economic Impact Analysis for Revisions to the Prevention of
Significant Deterioration and Title V Greenhouse Gas Permitting
Regulations and Establishment of a Significant Emissions Rate for
Greenhouse Gas Emissions Under the Prevention of Significant
Deterioration Program: Proposed Rule.'' This report is available in the
rulemaking docket.
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    \96\ Definition of ``significant,'' 40 CFR 51.166(b)(23)(ii) and
40 CFR 52.21(b)(23)(ii).
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    For affected sources, the avoided permitting cost or savings for
PSD permits is approximately $23,532 per permit (in 2014 dollars).
Total annual avoided cost program-wide is under $870,000 for sources
that would not have to go through GHG BACT review. State, local and
tribal permitting authorities are estimated to expend $4,400 per permit
to conduct a GHG BACT review in the context of reviewing a PSD permit
application for a source with GHG emissions in the applicable range.
Thus, annual savings for permitting authorities program-wide are less
than $165,000 at a 75,000 tpy CO2e GHG SER.
    We anticipate sources subject to title V will experience avoided
regulatory costs because they will not have to add requirements to
their title V permit resulting from a GHG BACT review. Avoided cost is
estimated at approximately $2,470 per permit for addressing GHG
requirements in a new permit, and $520 per permit for revising an
existing permit to include requirements related to a GHG BACT limit.
Total program-wide savings for title V permitting related to the
proposed GHG SER of 75,000 tpy CO2e is less than $20,000
dollars per year for sources. Regulatory cost avoided relative to no
GHG SER for state, local, and tribal permitting authorities is
estimated at $2,632 per permit for adding GHG requirements to a new
permit, and $504 per permit for revisions to existing permits. At the
proposed GHG SER of 75,000 tpy CO2e, title V program-wide
avoided costs for permitting authorities totals approximately $20,000
per year.
    Total annual regulatory cost avoided relative to no GHG SER for
sources for both PSD and title V programs together amounts to less than
$890,000 at the proposed 75,000 tpy CO2e GHG SER level.
Total annual avoided costs for permitting authorities for both PSD and
title V programs together is expected to be less than $185,000 at the
proposed 75,000 tpy CO2e GHG SER level. This rulemaking does
not impose economic impacts on any sources or permitting authorities,
but should instead be viewed as leading to savings for ``anyway
sources'' and permitting authorities. Because no businesses or
governmental entities are expected to incur positive costs as a result
of this rule, there is not a significant impact on a substantial number
of small entities. Because the savings are small and spread among many
sources, the market impacts of this rule will be minimal.

VII. How should state, local and tribal authorities adopt the
regulatory revisions included in this action?

    Consistent with the PSD regulations for SIP-approved programs at 40
CFR 51.166 and the title V regulations for title V program approvals at
40 CFR part 70, the EPA expects that many state, local and tribal
permitting authorities will amend their respective PSD and title V
permitting regulations and seek revisions of their SIPs, TIPs or title
V program approvals, as applicable, to incorporate (once finalized) the
regulatory changes consistent with those contained in this proposal.
    For PSD, 40 CFR part 51.166(a)(6)(i) states that ``any state
required to revise its implementation plan by reason of an amendment to
section [51.166]. . . shall adopt and submit such plan revision to the
Administrator for approval no later than three years after such
amendment is published in the Federal Register.'' Therefore, any
implementation plan that defines a source or modification as major
based solely on GHGs emissions will require a revision to conform to
the amendments to 40 CFR part 51.166 proposed in this rule. However,
states may elect not to incorporate a significant emissions rate for
GHGs into their program if they wish to apply BACT to GHGs at sources
emitting or increasing this pollutant by any amount.
    We request comment on what we described in our Preliminary Views
Memo as the ``most efficient and least burdensome way to accomplish
such revisions to state, [local], or tribal programs'' to meet the SIP
or TIP submittal requirements, as applicable.\97\ Furthermore, we ask
for comments on whether the Administrator should shorten the 3-year
time period required under 40 CFR part 51.166(a)(6) (and section
110(a)(1) of the CAA, to the extent applicable), for each state, or
local permitting authority to revise its SIP or TIP (or make a new
submission).
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    \97\ Next Steps and Preliminary Views on the Application of
Clean Air Act (CAA) Permitting Programs to Greenhouse Gases
Following the Supreme Court's Decision in UARG v. EPA, Memorandum
from Janet G. McCabe, Acting Assistant Administrator, Office of Air
and Radiation, and Cynthia Giles, Assistant Administrator, Office of
Enforcement and Compliance Assurance, U.S. EPA, to Regional
Administrators, p. 5, July 24, 2014.
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    For purposes of the title V program, 40 CFR part 70.4(a) states in
relevant part that: ``If part 70 is subsequently revised such that the
Administrator determines that it is necessary to require a change to an
approved State program, the required revisions to the program shall be
submitted within 12 months of the final changes to part 70 or within
such a period as authorized by the Administrator.'' Since we believe
that the changes being proposed, once finalized, may require changes to
many EPA-approved state title V programs, we also ask for comments on
the most efficient way to accomplish those title V program revisions
and what time period would be appropriate for those revisions.
    Furthermore, SIP revisions for the PSD program and revisions to
title V programs that still include the Step 2 provisions may be needed
if any permitting authorities prefer to retain under state law the
construction or operating permit requirements equivalent to the PSD and
title V permitting requirements for Step 2 sources that are no longer
approvable parts of a PSD or title V program under federal law. In the
Preliminary View Memo, we stated that ``we do not read the [UARG v EPA]
U.S. Supreme Court decision to preclude states from retaining
permitting requirements for sources of GHG emissions that apply
independently under state law even when those requirements are no
longer required under federal law'' \98\ and that

``similar to state-law construction permitting requirements, the [UARG
v EPA] U.S. Supreme Court decision does not preclude states from
continuing to require that certain types of sources obtain operating
permits meeting requirements that apply independently under state
law.'' \99\ Therefore, state, local, or tribal programs wishing to
retain construction or operating permit requirements equivalent to the
PSD and title V permitting requirements for Step 2 sources as a matter
of state, local or tribal law should consult with the EPA Regional
offices on how best to retain those requirements as appropriate, while
excluding them from the EPA-approved SIPs, TIPs or title V
programs.\100\
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    \98\ Next Steps and Preliminary Views on the Application of
Clean Air Act (CAA) Permitting Programs to Greenhouse Gases
Following the Supreme Court's Decision in UARG v. EPA, Memorandum
from Janet G. McCabe, Acting Assistant Administrator, Office of Air
and Radiation, and Cynthia Giles, Assistant Administrator, Office of
Enforcement and Compliance Assurance, U.S. EPA, to Regional
Administrators, p. 4, July 24, 2014.
    \99\ Id. at 5.
    \100\ As noted previously, while the UARG decision and the
Amended Judgment determined that the EPA may no longer require a
source to obtain a title V permit solely because it emits or has the
potential to emit GHGs above major source thresholds, the agency
does not read the UARG decision or the Amended Judgment to affect
other grounds on which a title V permit may be required or the
applicable requirements that must be addressed in title V permits.
Thus, as explained previously, the EPA's proposed revisions are not
intended to change the existing title V requirements in that regard
and the EPA would not expect proposed revisions to the EPA-approved
programs to change those requirements, either.
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    In cases where state, tribal or local air pollution control
agencies incorporate the federal regulations by reference or do not
have an approved SIP or TIP for the PSD program or a title V program
approval for the title V permitting requirements, the federal PSD
program at 40 CFR 52.21 and the title V program at 40 CFR part 71
apply, respectively. Therefore, the EPA anticipates that the revisions
included in this proposal will likely apply automatically to these
programs once finalized.

VIII. Environmental Justice Considerations

    This action proposes certain revisions to the PSD and title V GHG
permitting regulations in response to the June 23, 2014, UARG v. EPA
U.S. Supreme Court decision and the April 10, 2015, Amended Judgment by
the D.C. Circuit in Coalition for Responsible Regulation v. EPA. To
comport with these decisions, the proposed revisions would ensure that
neither PSD nor title V rules require a source to obtain a permit
solely because the source emits or has the PTE GHGs above the
applicable thresholds. It also establishes a SER for GHGs that would
serve to determine when a source otherwise subject to PSD would be
required to conduct a BACT analysis for GHGs. Therefore, this proposed
action itself does not compel any specific changes to our permitting
public participation requirements nor does it finalize a particular
permit action that may affect the fair treatment and meaningful
involvement of all people. Rather, it ensures that the Coalition
Amended Judgment is implemented and makes clear in the EPA's PSD
regulations that sources are no longer required to submit a PSD permit
application if GHGs are the only pollutant that the sources emits above
the applicable major source thresholds or that will increase in major
amounts due to a modification of an existing major sources. Similarly,
this proposed rule clarifies in the EPA's title V regulations that a
source is not required to apply for title V permit solely because it
emits or has the PTE GHGs above the major source threshold.

IX. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive
Order 13563: Improving Regulation and Regulatory Review

    This action is a significant regulatory action that was submitted
to the Office of Management and Budget (OMB) for review because it
raises novel legal or policy issues. Any changes made in response to
OMB recommendations have been documented in the docket. The EPA
prepared an EIA of the potential costs and benefits associated with
this action, which is discussed in Section VI of this preamble. This
analysis, ``Economic Impact Analysis for the Revisions to the
Prevention of Significant Deterioration and Title V Greenhouse Gas
Permitting Regulations and Establishment of a Significant Emissions
Rate for Greenhouse Gas Emissions under the Prevention of Significant
Deterioration Program; Proposed Rule,'' is available in the rulemaking
docket.

B. Paperwork Reduction Act (PRA)

    This action does not impose any new information collection burden
under the PRA. The OMB has previously approved the information
collection activities contained in the existing regulations and has
assigned OMB control number 2060-0003 for the PSD program and OMB
control numbers 2060-0243 and 2060-0336 for the title V part 70 and
part 71 programs, respectively.
    This action does not impose an information collection burden
because it does not impose a new or revised information collection
burden for stationary sources of air pollution. Instead, the regulatory
revisions reduce the number of sources that may be subject to the PSD
and title V program due to the sources' GHG emissions. Specifically,
this proposed action revises several regulatory provisions under the
federal and state-specific PSD and title V regulations and establishes
a GHG SER for the PSD program.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic
impact on a substantial number of small entities under the RFA. In
making this determination, the impact of concern is any significant
adverse economic impact on small entities. An agency may certify that a
rule will not have a significant economic impact on a substantial
number of small entities if the rule relieves regulatory burden, has no
net burden or otherwise has a positive economic effect on the small
entities subject to the rule. This rule relieves regulatory burden
because it reduces the number of sources that may be subject to the PSD
and title V program due to the sources' GHG emissions. We have,
therefore, concluded that this action will relieve regulatory burden
for all directly regulated small entities.

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain an unfunded mandate of $100 million or
more as described in UMRA, 2 U.S.C. 1531-1538, and does not
significantly or uniquely affect small governments. The EPA expects
that many state, local and tribal permitting authorities will amend
their respective PSD and title V permitting regulations and seek
revisions of their SIPs, TIPs or title V program approvals, as
applicable, to incorporate, once finalized, the regulatory changes
consistent with those in this proposed action. This will result in a
small increase in burden to these entities. However, as discussed in
Section VI of this preamble, this proposed action is expected to result
in cost savings and an administrative burden reduction for permitting
authorities. We have therefore concluded that there are no unfunded
mandates greater than $100 million or any significant or unique effect
on small governments.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have
substantial direct effects on the states, on the relationship between
the national government and the states or on the

distribution of power and responsibilities among the various levels of
government.

F. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments

    This action does not have tribal implications, as specified in
Executive Order 13175. The proposed rule would not impose substantial
direct compliance costs on Indian tribal governments nor preempt tribal
law. There are no tribal agencies currently implementing the PSD
program under a tribal implementation plan under 40 CFR part 51.166 or
delegation of the federal PSD program at 40 CFR part 52.21. Only two
tribes are implementing the title V program, one through the approval
of its title V program under 40 CFR part 70 and one through a
delegation agreement under 40 CFR part 71. In addition and as explained
previously, this proposed action relieves regulatory burden because it
reduces the number of sources that may be subject to the PSD and title
V program due to the sources' GHG emissions. Specifically, this action
revises several regulatory provisions under the federal and state-
specific PSD and title V regulations and establishes a GHG SER for the
PSD program. If the current PSD GHG permitting level of 75,000 tpy
CO2e were to not be applicable, as described in the
Preliminary Views Memo, any increase in GHG emissions at sources
otherwise subject to PSD would trigger the requirement for a GHG BACT
analysis and thus increase the permitting costs and burden for both
permittees (including entities in tribal areas) and permitting
authorities (including any tribal agencies). Tribal programs may need
to make minor changes to their title V program approvals and their
implementing regulations, as applicable, to incorporate, once
finalized, the regulatory changes being proposed in this action.
Nevertheless, we expect the burden of undertaking those revisions to be
minimal as compared to the burden of applying and reviewing the permits
for GHG-emitting sources that would otherwise be subject to title V
program without the regulatory revisions included in this proposed
action. Thus, Executive Order 13175 does not apply to this action.

G. Executive Order 13045: Protection of Children From Environmental
Health Risks and Safety Risks

    The EPA interprets Executive Order 13045 as applying only to those
regulatory actions that concern environmental health or safety risks
that the EPA has reason to believe may disproportionately affect
children, per the definition of ``covered regulatory action'' in
section 2-202 of the Executive Order. This action is not subject to
Executive Order 13045 because it does not concern an environmental
health risk or safety risk.

H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution or Use

    This action is not a ``significant energy action'' because it is
not likely to have a significant adverse effect on the supply,
distribution or use of energy. Further, we have concluded that this
rule is not likely to have any adverse energy effects because to the
extent that this action would affect PSD and title V permit applicants
in the energy supply, distribution or use sectors, it would reduce the
permitting burden for such sectors.

I. National Technology Transfer and Advancement Act

    This rulemaking does not involve technical standards.

J. Executive Order 12898: Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Populations

    The EPA believes the human health or environmental risk addressed
by this action will not have potential disproportionately high and
adverse human health or environmental effects on minority, low-income
or indigenous populations. The results of this evaluation are contained
in Section VIII of this preamble titled, ``Environmental Justice
Considerations'' for this action.

K. Determination Under CAA Section 307(d)

    Pursuant to CAA 307(d)(1)(J) and 307(d)(1)(V), the Administrator
determines that this action is subject to the provisions of section
307(d). Section 307(d)(1)(J) provides that the provisions of section
307(d) apply to promulgation or revision of regulations under part C of
title I of the CAA (relating to PSD and protection of visibility), and
section 307(d)(1)(V) of the CAA provides that the provisions of section
307(d) apply to such other actions as the Administrator may determine.

X. Statutory Authority

    The statutory authority for this action is 42 U.S.C. 7401-7671q.

List of Subjects

40 CFR Part 51

    Environmental protection, Administrative practice and procedure,
Air pollution control, Carbon monoxide, Greenhouse gases,
Intergovernmental relations, Lead, Nitrogen dioxide, Ozone, Particulate
matter, Reporting and recordkeeping requirements, Sulfur oxides,
Transportation, Volatile organic compounds.

40 CFR Part 52

    Environmental protection, Air pollution control, Carbon monoxide,
Greenhouse gases, Intergovernmental relations, Lead, Nitrogen dioxide,
Ozone, Particulate matter, Reporting and recordkeeping requirements,
Sulfur oxides, Volatile organic compounds.

40 CFR Part 60

    Environmental protection, Administrative practice and procedure,
Air pollution control, Greenhouse gases, Intergovernmental relations,
Reporting and recordkeeping requirements.

40 CFR Part 70

    Environmental protection, Administrative practice and procedure,
Air pollution control, Greenhouse gases, Intergovernmental relations,
Reporting and recordkeeping requirements.

40 CFR Part 71

    Environmental protection, Administrative practice and procedure,
Air pollution control, Greenhouse gases, Reporting and recordkeeping
requirements.

    Dated: August 26, 2016.
Gina McCarthy,
Administrator.

    For the reasons stated in the preamble, title 40, Chapter I of the
Code of Federal Regulations is proposed to be amended as follows:

PART 51--REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF
IMPLEMENTATION PLANS

0
1. The authority citation for part 51 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

Subpart I--Review of New Sources and Modifications

0
2. Section 51.166 is amended by:
0
a. Revising paragraphs (b)(1)(i)(a) and (b);
0
b. Revising paragraph (b)(2)(i);
0
c. Revising paragraph (b)(23)(i);
0
d. Adding paragraph (b)(31); and
0
e. Revising paragraph (b)(48).

    The revisions and addition read as follows:

Sec.  51.166  Prevention of significant deterioration of air quality.

* * * * *
    (b) * * *
    (1) * * *
    (i) * * *
    (a) Any of the following stationary sources of air pollutants which
emits, or has the potential to emit, 100 tons per year or more of any
regulated NSR pollutant (except the pollutant greenhouse gases as
defined in paragraph (b)(31) of this section): Fossil fuel-fired steam