the PM BART controls for the AEP Flint Creek Power Plant, the Entergy
White Bluff Power Plant, and the No. 1 Power Boiler of the Domtar
Ashdown Mill before knowing what the SO2 and NOX
BART controls will be because the SO2 or NOX
controls determined to be BART may increase PM emissions or otherwise
affect the PM BART determination.
    Response: You cannot infer from the RHR that the disapproval of the
BART determination for one pollutant at a given source requires
disapproval of BART determinations for other pollutants at the same
source. Each BART analysis for an individual visibility impairing
pollutant is separate. As such, disapproval of the SO2 or
NOX BART determination does not affect the PM BART
determination even though SO2 and NOX are
precursors to PM. This is because when the BART determination is
conducted for PM, it is analyzed without taking in account whether BART
controls for SO2 or NOX are being adopted. As
such, EPA may take action on the BART determinations for
NOX, SO2, and PM for a given source in separate
rulemaking actions. In addition, EPA may approve the BART determination
for one pollutant for a given source while disapproving the BART
determination for one or more pollutants at the same source. Therefore,
EPA disagrees with the commenter that it cannot approve the PM BART
determinations for the Flint Creek Boiler No. 1, the White Bluff Units
1 and 2, and the Domtar Ashdown Mill Power Boiler No. 1, and disapprove
the SO2 and NOX BART determinations for these
sources without promulgating SO2 and NOX BART
determinations for these sources in the context of a FIP.
    As explained in our proposed rulemaking and elsewhere in this final
rulemaking, our disapproval begins a two year period after which if
Arkansas has not provided a new SIP revision and EPA has approved that
SIP revision correcting the deficiencies, EPA must promulgate a FIP. If
in conducting the BART analyses for NOX and SO2,
Arkansas, or EPA in the context of a FIP, determines that direct
emissions of PM will increase because of the implementation of certain
control technologies, the BART PM limit can be re-evaluated at that
time and balanced against the potential visibility improvements from
the reductions of the other pollutants.
    Comment: In the testimony for a permit proceeding, Entergy's
primary contractor for engineering and procurement of its BART controls
showed that PM emission rates much lower than 0.1 lb/MMBtu could be met
with either a wet scrubber or with a dry scrubber and a baghouse
installed at the Entergy White Bluff Units 1 and 2 (see Exhibits 12 and
16). Entergy's contractor indicated that if a dry scrubber and baghouse
were installed at White Bluff Units 1 and 2, the baghouse would be
designed to lower the PM emissions to 0.012 lb/MMBtu, giving an
advantage of the dry scrubber over the wet scrubber. Since the
selection of the SO2 scrubber (wet vs. dry) will have an
impact on the PM emissions rate that will be achievable at the White
Bluff units, EPA should not take any action on PM BART for White Bluff
until the SO2 controls to meet BART are known.
    Response: The comment points out that in the testimony for a permit
proceeding before the Arkansas Public Service Commission,\142\
Entergy's contractor indicated that if a dry scrubber and baghouse are
installed at the Entergy White Bluff Units 1 and 2, the baghouse would
be designed to lower the PM emissions to an emission rate of 0.012 lb/
MMBtu.\143\ However, it has also been brought to EPA's attention that
Entergy White Bluff has since canceled the proceeding before the
Arkansas Public Service Commission to obtain a declaratory order
approving the installation of those controls. Furthermore, the State
has not submitted to EPA a revision to the RH SIP EPA received on
September 23, 2008, August 3, 2010, and supplemented on September 7,
2011. As far as EPA is aware, the State has not adopted revisions to
the Arkansas RH SIP with respect to BART for SO2 for Entergy
White Bluff Units 1 and 2 based on the proceeding before the Arkansas
Public Service Commission. Therefore, what is before EPA is the
Arkansas RH SIP submitted to EPA on September 23, 2008 August 3, 2010,
and supplemented on September 7, 2011, which does not include
installation of a dry scrubber and baghouse for control of
SO2 at White Bluff Units 1 and 2. As explained elsewhere in
our response to comments, the RHR states that the BART determinations
are made on a individual pollutant specific basis and this analysis is
separate from the BART determinations for other pollutants at the same
source. Therefore, EPA disagrees that it should not take action on PM
BART for White Bluff Units 1 and 2 until the SO2 controls to
meet BART are known.
---------------------------------------------------------------------------

    \142\ The Arkansas Public Service Commission is an appointed
executive board in the Arkansas state government. The commission is
responsible for regulating the rates and services of Arkansas's
electricity, natural gas, water, phone, and pipeline safety
utilities.
    \143\ See Exhibit 12 to Sierra Club's comment letter to EPA,
found in the docket for this rulemaking action.
---------------------------------------------------------------------------

    Our approval of the limit for direct PM emissions was based on the
extremely low modeled visibility impact from these emissions. While
reductions in PM may occur from future controls necessary to meet
SO2 BART, these PM reductions are not necessary to meet BART
for PM.
    Comment: The EPA's BART Guidelines specify that BART should be
evaluated and defined for both PM10 and PM2.5
(see 40 CFR part 51, appendix Y, section IV.A.). However, with the
exception of the oil-firing scenario for Lake Catherine Unit 4, ADEQ
did not adopt BART limits for PM2.5, yet EPA did not
identify this as a deficiency. EPA must disapprove the PM/
PM10 BART limits in the Arkansas RH SIP along with
disapproving the RH SIP for the lack of BART limits for
PM2.5.
    Response: The BART Guidelines do not specify that states must make
BART determinations for PM2.5. The BART Guidelines provide
the following:

    ``You must look at SO2, NOX, and direct
particulate matter (PM) emissions in determining whether sources
cause or contribute to visibility impairment, including both
PM10 and PM2.5.'' \144\
---------------------------------------------------------------------------

    \144\ Appendix Y to Part 51, section III.A.2.

    This language in the BART Guidelines was meant to clarify that when
a state is making a BART determination as to whether a source is
subject to BART, the modeling evaluation to determine the source's
impact on visibility has to account for both PM10 and
PM2.5 emissions. There are several instances in which we
state in both the preamble to the RHR, and in the BART Guidelines that
PM10 may be used as indicator for PM2.5 in
determining whether a source is subject to BART. However, neither the
RHR nor the BART Guideline specify that states must set separate BART
limits for PM2.5. We have concluded that Arkansas's PM BART
determinations for the natural gas firing scenario for Entergy Lake
Catherine Unit 4; for the bituminous and sub-bituminous coal firing
scenarios for Entergy White Bluff Units 1 and 2; for the AEP Flint
Creek Boiler No. 1; and for the Domtar Ashdown Mill Power Boiler No. 1
are reasonable.
    Comment: The existing PM limit of 0.1 lbs/MMBtu in the AEP Flint
Creek Title V permit, which EPA proposed to approve as BART for PM, is
based on EPA's New Source Performance Standards (NSPS) for Fossil-Fuel
Fired Steam Generators that commenced construction after August 17,
1971 (40 CFR part 60, subpart D, Sec.  60.42(a)(1)).

This PM emission limit does not apply during periods of startup,
shutdown, and malfunction (SSM) (see 40 CFR 60.8(c)); only applies to
filterable PM emissions (see 40 CFR 60.46(b)(2) and EPA Method 5 in 40
CFR part 60, appendix A); and only applies during scenarios of firing
coal and tire-derived fuel at Flint Creek (see Title V permit for Flint
Creek, Permit No. 0276-AOP-R5, at 18 (Exhibit 3)). When the unit is
firing coal with leachate injection a PM10 emission limit of
778.4 lb/hr applies, which at maximum heat input capacity equates to
0.12 lb/MMBtu. Since the Title V permit directs Flint Creek to ask EPA
for a determination regarding the applicability of NSPS Subpart D
limits for oil-firing and coal-and-oil-firing scenarios, it is not
clear whether any PM emission limit applies to Flint Creek during oil-
firing and oil-and-coal-firing. EPA recently proposed to disapprove SSM
exemptions from BART limits in the Kansas RH SIP (see 76 FR 52604,
52617-18 and section 302(k) of the CAA). Because BART must reflect the
best system of continuous emission reduction, the BART limits must
apply at all times. The existing PM limit in the Flint Creek Title V
permit cannot satisfy BART because the existing PM limit in the Flint
Creek Title V permit does not apply during SSM, and there does not
appear to be a PM limit in the Flint Creek Title V permit during oil-
firing and oil- and coal-firing. A proper BART evaluation would have
shown that these limits do not reflect BART for Flint Creek's PM
emissions.
    Response: In our review of the Arkansas RH SIP, we evaluated the
determination by ADEQ that no additional PM controls are required at
the AEP Flint Creek Boiler No. 1. ADEQ's determination was based on the
pre-control modeling performed by ADEQ and on AEP SWEPCO's statement
that the PM visibility modeling did not ``trip the BART impact
threshold.'' We reviewed the pre-control modeling ADEQ performed using
the 24-hr actual maximum emissions from the baseline period. The
modeling results in Appendix 9.2B of the Arkansas RH SIP and presented
in Table 7-6 of Appendix A of the TSD\145\ indicate that PM contributes
less than 0.5% of the total visibility impacts from Flint Creek Boiler
No. 1 at all nearby Class I areas with the exception of Upper Buffalo.
PM contributions to visibility impacts at Upper Buffalo from Flint
Creek are less than 2% of the total visibility impairment at this Class
I area. On the most impacted day at Upper Buffalo, modeling the 24-hr
actual maximum emissions demonstrates that PM contributes only 0.07 dv
of the total 3.781 dv modeled visibility impact from the source.
Clearly, the most effective controls to address visibility impairment
from the source are those that would reduce emissions of visibility
impairing pollutants other than direct emissions of PM. In this action,
we are finalizing our proposal to disapprove Arkansas's NOX
and SO2 BART determinations for Flint Creek Boiler No. 1, as
ADEQ did not properly identify and evaluate NOX and
SO2 controls to address visibility impairment from the
source.
---------------------------------------------------------------------------

    \145\ These documents can be found in the docket associated with
our final rulemaking.
---------------------------------------------------------------------------

    As stated in our proposed rulemaking on the Arkansas RH SIP, we
found that the source's visibility impact from PM emissions alone is so
minimal such that the installation of any additional PM controls on the
source could only result in very small visibility benefit that would
not justify any upgrades to the existing controls. This is in keeping
with the BART Rule, which states the following:

    ``Consistent with the CAA and the implementing regulations,
States can adopt a more streamlined approach to making BART
determinations where appropriate. Although BART determinations are
based on the totality of circumstances in a given situation, such as
the distance of the source from a Class I area, the type and amount
of pollutant at issue, and the availability and cost of controls, it
is clear that in some situations, one or more factors will clearly
suggest an outcome. Thus, for example, a State need not undertake an
exhaustive analysis of a source's impact on visibility resulting
from relatively minor emissions of a pollutant where it is clear
that controls would be costly and any improvements in visibility
resulting from reductions in emissions of that pollutant would be
negligible. In a scenario, for example, where a source emits
thousands of tons of SO2 but less than one hundred tons
of NOX, the State could easily conclude that requiring
expensive controls to reduce NOX would not be
appropriate. In another situation, however, inexpensive
NOX controls might be available and a State might
reasonably conclude that NOX controls were justified as a
means to improve visibility despite the fact that the source emits
less than one hundred tons of the pollutant.'' \146\
---------------------------------------------------------------------------

    \146\ 70 FR 39116.

    Therefore, we agreed with the State that PM BART for Flint Creek
Boiler No. 1 is the existing PM emission limit (i.e. no additional
controls). The BART Rule provides that states may determine that for a
given source no additional control satisfies the BART requirement for a
particular pollutant.\147\ In our final approval of the Kansas RH SIP,
we approved the State's determination that no additional control (and
no new emission limit) for PM is BART for a number of sources.\148\ In
our final approval of the Oklahoma RH SIP, we also approved the State's
determination that no additional control (and no new emission limit)
for PM is BART for a number of sources.\149\ In the above cases, Kansas
and Oklahoma adopted no new PM emission limit for PM BART for
particular sources, and EPA approved this based on the low visibility
impact attributable to PM emissions. As such, it was not necessary for
Arkansas to establish a new PM emission limit for BART for Flint Creek
Boiler No. 1, as ``no additional controls'' satisfies PM BART in this
particular case. Since no additional controls satisfies BART for Flint
Creek Boiler No. 1, it is not problematic that the existing PM emission
limit that Arkansas adopted in Chapter 15 of APCEC Regulation No. 19 as
meeting PM BART for Flint Creek Boiler No. 1 (i.e. the EPA NSPS, and
also included in the Title V permit) does not apply on a continuous
basis and only applies to filterable PM emissions. We also clarify that
the distinction between our approval of an existing PM emission limit
adopted in Arkansas's Chapter 15 of APCEC Regulation No. 19 for Flint
Creek Boiler No. 1 that does not apply during SSM and our disapproval
of an exemption of SSM for BART in the Kansas RH SIP is that the BART
determinations that would have exempted SSM in the Kansas RH SIP were
not based upon the minimal visibility impact from a particular
pollutant. Therefore, we are finalizing our proposed approval of
Arkansas determination that PM BART is the existing PM emission limit
in Chapter 15 of APCEC Regulation No. 19 for Flint Creek Boiler No. 1.
---------------------------------------------------------------------------

    \147\ 70 FR 39116.
    \148\ 76 FR 52604 and 76 FR 80754.
    \149\ 76 FR 16168 and 76 FR 81728.
---------------------------------------------------------------------------

    That being said, we note that the 0.1 lb/MMBtu existing PM emission
limit (for Flint Creek Boiler No. 1) in Chapter 15 of APCEC Regulation
No. 19, which is based on EPA's NSPS standards (40 CFR part 60, subpart
D, Sec.  60.42(a)(1)), applies during the following firing scenarios:
coal firing; coal and tire derived fuel (TDF) firing; and during coal
firing with leachate injection.\150\ We are finalizing our proposed
approval of PM BART for the AEP Flint Creek Boiler No. 1.
---------------------------------------------------------------------------

    \150\ See section IV, specific conditions 3.a., 8.a., and 17.b
of the ADEQ Operating Air Permit for AEP-Flint Creek Power Plant
(Permit No. 0276-AOP-R5). This permit can be viewed at http://www.adeq.state.ar.us/ftproot/pub/WebDatabases/PermitsOnline/Air/0276-AOP-R5.pdf.
---------------------------------------------------------------------------

    Comment: The existing PM limit of 0.1 lbs/MMBtu in the Entergy
White

Bluff Title V permit, which EPA proposed to approve as BART for PM, is
based on EPA's NSPS for Fossil-Fuel Fired Steam Generators that
commenced construction after August 17, 1971 (40 CFR part 60, subpart
D, Sec.  60.42(a)(1)). This PM emission limit does not apply during SSM
(see 40 CFR 60.8(c)), and only applies to filterable PM emissions (see
40 CFR 60.46(b)(2) and EPA Method 5 in 40 CFR part 60, appendix A).
Since the Title V permit directs White Bluff to ask EPA for a
determination regarding the applicability of NSPS Subpart D limits
during fuel oil-firing and biodiesel firing during startup, shutdown
and malfunction, it is not clear whether any PM emission limit applies
to White Bluff for these scenarios. EPA recently proposed to disapprove
SSM exemptions from BART limits in the Kansas RH SIP (see 76 FR 52604,
52617-18 and section 302(k) of the CAA). Because BART must reflect the
best system of continuous emission reduction, the BART limits must
apply at all times. The existing PM limit in the White Bluff Title V
permit cannot satisfy BART because this limit does not apply during
SSM, and there does not appear to be a PM limit in the White Bluff
Title V permit during fuel oil-firing and bio-diesel firing. The
existing PM limit in the White Bluff Title V permit cannot satisfy BART
because it does not apply during all periods of operation of the unit.
    Response: First, we disagree that we are approving the White Bluff
Title V permit as BART for PM. We are approving the part of the Chapter
15 of APCEC Regulation No. 19 that applies to the Entergy White Bluff
Units 1 and 2 as BART for PM. We agree that the part of the submitted
rule that applies to the two White Bluff units is based on EPA's NSPS
for Fossil-Fuel Fired Steam Generators that commenced construction
after August 17, 1971 (40 CFR part 60, subpart D, Sec.  60.42(a)(1)).
Secondly, in our review of the Arkansas RH SIP, we evaluated the
determination by ADEQ that no additional PM controls are required at
the Entergy White Bluff Units 1 and 2. We reviewed the data submitted
by ADEQ, including pre-control modeling in Appendix 9.2B of the
Arkansas RH SIP, to evaluate the State's determination that the
majority of visibility-causing emissions are due to emissions of
NOX and SO2, and that no additional PM controls
are warranted. The modeling results in Appendix 9.2B of the Arkansas RH
SIP and presented in Table 7-7 of Appendix A of the TSD, indicate that
PM contributes less than 0.4% of the total visibility impacts at all
nearby Class I areas. On the most impacted day at Caney Creek, modeling
the 24-hr actual maximum emissions, PM contributes only 0.03 dv of the
more than 8 dv modeled visibility impact from the White Bluff Units 1
and 2. Clearly, the majority of visibility-causing emissions are due to
emissions of NOX and SO2 and the most effective
controls to address visibility impairment from the units are those that
would reduce emissions of NOX and SO2 rather than
direct emissions of PM. In this action, we are finalizing our proposal
to disapprove Arkansas's NOX and SO2 BART
determinations for White Bluff Units 1 and 2, as the State did not
properly evaluate and identify controls to address visibility
impairment from these units.
    As articulated in our proposed rulemaking on the Arkansas RH SIP,
we are finding that the source's visibility impact from PM emissions
alone is so minimal such that the installation of any additional PM
controls on the two units could only result in such small visibility
benefits that it could not justify any upgrades to the existing
controls. This is in keeping with the BART Rule, which states the
following:

    ``Consistent with the CAA and the implementing regulations,
States can adopt a more streamlined approach to making BART
determinations where appropriate. Although BART determinations are
based on the totality of circumstances in a given situation, such as
the distance of the source from a Class I area, the type and amount
of pollutant at issue, and the availability and cost of controls, it
is clear that in some situations, one or more factors will clearly
suggest an outcome. Thus, for example, a State need not undertake an
exhaustive analysis of a source's impact on visibility resulting
from relatively minor emissions of a pollutant where it is clear
that controls would be costly and any improvements in visibility
resulting from reductions in emissions of that pollutant would be
negligible. In a scenario, for example, where a source emits
thousands of tons of SO2 but less than one hundred tons
of NOX, the State could easily conclude that requiring
expensive controls to reduce NOX would not be
appropriate. In another situation, however, inexpensive
NOX controls might be available and a State might
reasonably conclude that NOX controls were justified as a
means to improve visibility despite the fact that the source emits
less than one hundred tons of the pollutant.'' \151\
---------------------------------------------------------------------------

    \151\ 70 FR 39116.

    Therefore, we agree with the State that PM BART for White Bluff
Units 1 and 2 is the existing PM emission limit in Chapter 15 of APCEC
Regulation No. 19 (i.e. no additional controls). The BART Rule provides
that states may determine that for a given source no additional control
satisfies the BART requirement for a particular pollutant.\152\ In such
cases, it is not necessary for a state to establish a new emission
limit when no additional control is BART. In our final approval of the
Kansas RH SIP, we approved the State's determination that no additional
control (and no new emission limit) for PM is BART for a number of
sources.\153\ In our final approval of the Oklahoma RH SIP, we also
approved the State's determination that no additional control (and no
new emission limit) for PM is BART for a number of sources.\154\ In the
above cases, Kansas and Oklahoma adopted no new PM emission limit for
PM BART for particular sources, and EPA approved this based on the low
visibility impact attributable to PM emissions. As such, it was not
necessary for Arkansas to establish a new PM emission limit for BART
for White Bluff Units 1 and 2, as ``no additional controls'' satisfies
PM BART in this particular case. As explained above, the distinction
between our approval in the Arkansas RH SIP of an existing PM emission
limit in Chapter 15 of APCEC Regulation No. 19 for White Bluff that
does not apply during SSM and our disapproval of an exemption of SSM
for BART in the Kansas RH SIP is that the BART determinations that
would have exempted SSM in the Kansas RH SIP were not based upon the
minimal visibility impact from a particular pollutant. Since no
additional controls satisfies BART for White Bluff Units 1 and 2, it is
not problematic that the existing PM emission limit that Arkansas
adopted for PM BART for Units 1 and 2 does not apply on a continuous
basis and only applies to filterable PM emissions. Therefore, we are
finalizing our proposed approval of Arkansas determination that PM BART
is the existing PM emission limit in Chapter 15 of APCEC Regulation No.
19 for White Bluff Units 1 and 2.
---------------------------------------------------------------------------

    \152\ 70 FR 39116.
    \153\ 76 FR 52604 and 76 FR 80754.
    \154\ 76 FR 16168 and 76 FR 81728.
---------------------------------------------------------------------------

    Comment: The technology available for control of the pollutant in
question is the first factor that must be evaluated in a BART analysis.
The most effective PM control technology is a fabric filter baghouse.
ESPs can achieve control efficiencies of 99% or better, and baghouses
can achieve PM control efficiencies as high as 99.9% or even higher.
Baghouses have been installed since the 1970's and are the PM control
technology of choice for new coal-fired EGUs. Several recent PSD
permits have been issued with best available control technology (BACT)
limits at 0.010 lb/

MMBtu, based on installation of a fabric filter baghouse. Matt Haber,
EPA Region 9's BACT expert and current Deputy Director of the Air
Division, concluded in 2002 that BACT for filterable PM at two existing
PC boilers firing Powder River Basin coal and equipped with a baghouse
was 0.006 lb/MMBtu based on a 3-hour average and monitored via EPA
Method 5 and continuously using triboelectric broken bag detectors.
Even though AEP Flint Creek and Entergy White Bluff are subject to
BART, and not BACT, after evaluating the achievable emission rates with
a new baghouse at these units, there is no reason why Flint Creek and
White Bluff could not achieve PM emission rates similar to those of a
new unit with a baghouse. Particularly since White Bluff will be
installing new baghouses at the two units. Even these BACT limits fail
to reflect the low levels of filterable PM emissions that can be
achieved with fabric filter baghouses. As early as May 2004, at least
147 performance tests measured filterable PM/PM10 at less
than 0.010 lb/MMBtu and 82 recorded PM/PM10 emissions less
than 0.005 lb/MMBtu using fabric filter baghouses. The lowest reported
PM/PM10 emission rate was 0.0004 lb/MMBtu. Other states have
made PM BART determinations that are much lower than ADEQ's proposed
limit of 0.1 lb/MMBtu, based on use of a baghouse. South Dakota adopted
and EPA recently approved a PM BART emission limit of 0.012 lb/MMBtu
for the Big Stone Power Plant, a 600 MW power plant burning Powder
River Basin coal, and with an existing baghouse. Even though Big Stone
is located 431 km from the nearest Class I area, EPA did not exempt the
plant from PM BART as EPA has proposed for Flint Creek.
    Response: EPA agrees that baghouses have very high PM control
efficiency capabilities. However, as articulated in our proposed
rulemaking and further explained in our response to comments, due to
the low visibility impact from the AEP Flint Creek Boiler No. 1 and the
Entergy White Bluff Units 1 and 2 attributable to PM, we agree with
Arkansas that the existing PM emission limit adopted for these sources
in Chapter 15 of APCEC Regulation No. 19 satisfies BART for these
units. As explained elsewhere in our response to comments, this is
consistent with the BART Rule and EPA's action on other states' RH
SIPs. We are finalizing our proposed approval of the existing PM
emission limit as PM BART for the AEP Flint Creek Boiler No. 1 and
Entergy White Bluff Units 1 and 2.
    With regard to the comment that White Bluff will be installing
baghouses on Units 1 and 2, EPA is aware that Entergy White Bluff has
canceled the proceeding before the Arkansas Public Service Commission
to obtain a declaratory order approving the installation of these
controls. Furthermore, as explained elsewhere in our response to other
comments, the Arkansas RH SIP that is before EPA to act on does not
include installation of a dry scrubber and baghouse for control of
SO2 and PM emissions at White Bluff Units 1 and 2.
Therefore, EPA disagrees that it should disapprove the PM BART
determination for White Bluff Units 1 and 2 because the source may be
considering installing these controls.
    Comment: Coal-fired boilers with hot-side ESPs, including the
Navajo Power Plant Units, are meeting PM emission rates much lower than
0.1 lb/MMBtu. Even if EPA finds that it is acceptable to not evaluate
additional control technologies for PM10 at AEP Flint Creek,
the PM10 BART limit for Flint Creek must reflect the
technology determined to represent BART. The 0.1 lb/MMBtu PM emission
limit of Subpart D of the NSPS does not. Because the existing PM
emission limit of 0.1 lb/MMBtu is much higher than the maximum 24-hour
average PM10 levels emitted by Flint Creek, the existing
limit fails to reflect the best system of continuous emission reduction
as required by the definition of BART in 40 CFR 51.302. There will be
less incentive to properly operate and maintain the PM control
equipment if the PM BART limit is unreasonably high.
    Response: As articulated in our proposed rulemaking and further
explained in earlier response to comments, due to the low visibility
impact from the AEP Flint Creek Boiler No. 1 attributable to PM, we
agree with Arkansas that the existing PM emission limit in Chapter 15
of APCEC Regulation No. 19 satisfies BART for this unit. EPA agrees
with Arkansas that requiring the source to install and operate
additional PM controls on this unit (including any upgrades to the
existing PM controls) would not be justified because of the low
visibility benefit that would result. As explained elsewhere in our
response to comments, this is consistent with the BART Rule and EPA's
action on other states' RH SIPs. We are finalizing our proposed
approval of the existing PM emission limit in as PM BART for the AEP
Flint Creek Boiler No. 1.
    Comment: Even if it was determined that the existing ESPs represent
BART for the White Bluff Units 1 and 2, the existing PM emissions
limits fail to reflect BART. According to ADEQ, the maximum 24-hour
actual PM10 emission rates at White Bluff Units 1 and 2 are
much lower than the emissions allowed by the existing PM limit in the
White Bluff Title V permit. At an emission rate of 0.1 lbs/MMBtu, while
firing coal and a maximum allowable heat input capacity of 8,700 lbs/
MMBtu, the maximum pound per hour emission rate would be 879 lb/hr.
However, ADEQ modeled Entergy White Bluff's highest-24 hour actual
PM10 emission rate as 15.592 grams per second for Unit 1 and
16.653 grams per second for Unit 2, which equate to 123.7 lb/hr and
132.2 lb/hr, respectively. Assuming the highest actual PM10
emission rate occurred during the time of maximum heat input capacity,
the maximum 24-hour actual PM10 emission rate modeled
equates to 0.027 lb/MMBtu. In 2010, PM stack testing at White Bluff
Units 1 and 2 showed the units were emitting filterable PM and total PM
at rates much lower than ADEQ's PM BART limit of 0.1 lb/MMBtu, which
under Subpart D of the NSPS only applies to filterable PM (see Exhibits
14 and 15). With the installation of a scrubber and NOX
controls to meet BART, the condensable PM emissions will be even lower
than the 2010 stack testing results show. Even if EPA finds it
acceptable to not evaluate additional control technologies for PM at
White Bluff Units 1 and 2, the PM BART limit for the units must reflect
the technology determined to represent BART, which in this case it does
not. Because the existing PM emission limit of 0.1 lb/MMBtu is much
higher than the maximum 24-hour average PM10 levels emitted
by White Bluff, the existing limit fails to reflect the best system of
continuous emission reduction as required by the definition of BART in
40 CFR 51.302. There will be less incentive to properly operate and
maintain the PM control equipment if the PM BART limit is unreasonably
high.
    Response: As articulated in our proposed rulemaking and further
explained in our previous response to comments, due to the low
visibility impact from the Entergy White Bluff Units 1 and 2
attributable to PM, we agree with Arkansas that the existing PM
emission limit adopted in Chapter 15 of APCEC Regulation No. 19
satisfies BART for these units. EPA agrees with Arkansas that requiring
the source to install and operate additional PM controls on these units
(including any upgrades to the existing PM controls) is not justified
based on the small visibility benefit. As explained elsewhere in our
response to comments, this is consistent with the BART Rule and EPA's
action on other states' RH

SIPs. We are finalizing our proposed approval of the existing PM
emission limit as PM BART for White Bluff Units 1 and 2.
    Comment: Other states have made PM BART determinations that are
much lower than ADEQ's proposed limit of 0.1 lb/MMBtu for White Bluff
Units 1 and 2. South Dakota adopted and EPA recently approved a PM BART
emission limit of 0.012 lb/MMBtu for the Big Stone Power Plant, a 600
MW power plant burning Powder River Basin coal, and with an existing
baghouse. Even though Big Stone is located 431 km from the nearest
Class I area, neither South Dakota nor EPA exempt the plant from PM
BART as EPA has proposed for White Bluff. In Big Stone's case, South
Dakota and EPA are following the Federal regulations regarding BART,
which requires that sources that are subject to BART obtain BART limits
for ``each pollutant emitted by'' the BART-eligible source (see 40 CFR
51.301 and Appendix Y, section IV.A). The State of Wyoming has also
adopted PM BART determinations for several EGUs that are lower than 0.1
lb/MMBtu, including 0.042 lb/MMBtu for Naughton Unit 1; 0.054 lb/MMBtu
for Naughton Unit 2; 0.015 lb/MMBtu for Naughton Unit 3, Dave Johnson
Units 3 and 4, and Wyodak; and 0.03 lb/MMBtu for Jim Bridger Units 1-4.
    Response: The EPA agrees that other states have adopted PM emission
limits more stringent than those adopted by Arkansas for PM BART.
However, as articulated in our proposed rulemaking and further
explained in our response to comments, due to the low visibility impact
from White Bluff Units 1 and 2 attributable to PM, we agree with
Arkansas that the existing PM emission limit in Chapter 15 of APCEC
Regulation No.19 satisfies BART for these units. EPA agrees with
Arkansas that requiring the source to install and operate additional PM
controls on these units (including any upgrades to the existing PM
controls) is not justified based on the small visibility benefit. Such
was not the case with regard to the visibility impact due to direct PM
emissions from the sources in other states referenced in the comment.
As explained elsewhere in our response to comments, this is consistent
with the BART Rule and EPA's action on other states' RH SIPs. We are
finalizing our proposed approval of the existing PM emission limit as
PM BART for Entergy White Bluff Units 1 and 2.
    Comment: The EPA proposed to approve Entergy's determination that
PM BART for the natural gas firing scenario is the existing PM limit
for Lake Catherine Unit 4, or 45.0 lb/hr (76 FR 64204). EPA identifies
the PM emission limit as 45.0 lb/hr, but the permit identifies the
PM10 limit as 44.5 lb/hr (see Exhibit 21). EPA cannot
approve the existing PM limit as meeting BART for Lake Catherine Unit 4
for the natural gas firing scenario because Lake Catherine's Title V
permit does not include provisions to ensure the enforceability of the
PM limit. There are no requirements in the permit for testing to
determine compliance with this limit. The permit states that Condition
9, which is a requirement to install and maintain O2
monitors and to maintain a positive O2 reading when the
boilers are operating, is to be used for compliance with the
PM10 and PM limits of the permit for Lake Catherine Unit 4
(see Exhibit 21). It is not clear how this will ensure compliance with
the numerical PM10 emission limit of 44.5 lb/hr. The
provisions of Condition 9 appear to be operational standards, and if
ADEQ was relying on the O2 monitoring provision to meet BART
for PM, the State would need to show that the operational standard will
ensure equivalent results to the lb/hr emission limit assumed for BART
(see 40 CFR 51.308(e)(1)(iii)). EPA cannot justify its approval of the
unenforceable PM/PM10 limit for Lake Catherine Unit 4 based
on its statement that PM emissions are expected to be very low from
natural gas firing. Once a unit is determined to be subject to BART, it
must make a determination of BART for each pollutant emitted by the
unit.
    Response: In our review of the Arkansas RH SIP, we evaluated the
determination by ADEQ that PM emissions from Entergy's Lake Catherine
Unit 4 are inherently very low when burning natural gas and that as a
result, no additional PM controls are required for the natural gas
firing scenario. We agree with the State's conclusion, based on its
modeling results, that the visibility impact of this unit from direct
PM emissions alone is minimal. We note that the modeling results
submitted by Arkansas in Appendix 9.2B of the Arkansas RH SIP indicate
that under natural gas firing conditions, NOX contributes
over 99.9% of Lake Catherine Unit 4's total visibility impacts at all
nearby Class I areas on the most impacted days. Based on the State's
modeling results, the visibility impact of this unit from direct PM
emissions alone is so minimal such that the requirement of any
additional PM controls on this unit would only achieve minimal
visibility benefit and would not be justified. It is clear that the
most effective controls to address visibility impairment from the
source during natural gas firing are those that would reduce emissions
of NOX. Given these conclusions, we proposed to find that
the State reasonably concluded that BART for PM for the natural gas
firing scenario is the existing PM emission limit for Unit 4 in Chapter
15 of APCEC Regulation No. 19. This is consistent with the BART Rule,
which states the following:

    ``Consistent with the CAA and the implementing regulations,
States can adopt a more streamlined approach to making BART
determinations where appropriate. Although BART determinations are
based on the totality of circumstances in a given situation, such as
the distance of the source from a Class I area, the type and amount
of pollutant at issue, and the availability and cost of controls, it
is clear that in some situations, one or more factors will clearly
suggest an outcome. Thus, for example, a State need not undertake an
exhaustive analysis of a source's impact on visibility resulting
from relatively minor emissions of a pollutant where it is clear
that controls would be costly and any improvements in visibility
resulting from reductions in emissions of that pollutant would be
negligible. In a scenario, for example, where a source emits
thousands of tons of SO2 but less than one hundred tons
of NOX, the State could easily conclude that requiring
expensive controls to reduce NOX would not be
appropriate.'' \155\
---------------------------------------------------------------------------

    \155\ 70 FR 39116.

    Based on our analysis of the data submitted by ADEQ in the Arkansas
RH SIP, and our agreement that PM emissions from burning natural gas
are inherently very low, we agree with the State that PM BART for Lake
Catherine Unit 4 is the existing PM emission limit in Chapter 15 of
APCEC Regulation No. 19 (i.e. no additional controls). The BART Rule
provides that states may determine that for a given source no
additional control satisfies the BART requirement for a particular
pollutant.\156\ In such cases, it is not necessary for a state to
establish a new emission limit when no additional control is BART. In
our final approval of the Kansas RH SIP, we approved the State's
determination that no additional control (and no new emission limit)
for PM is BART for a number of sources.\157\ In our final approval of
the Oklahoma RH SIP, we also approved the State's determination that no
additional control (and no new emission limit) for PM is BART for a
number of sources.\158\ In the above cases, Kansas and Oklahoma adopted
no new PM emission limit for PM BART for particular sources, and EPA
approved this based on the low visibility impact attributable to PM
emissions. Arkansas adopted the

existing PM emission limit from the facility's existing permit as BART
for Lake Catherine Unit 4, which is consistent with the finding that
``no additional controls'' is sufficient to satisfy PM BART in this
particular case. With regard to the commenter's concerns about the
enforceability of the limit, because of the extremely low visibility
impact of direct PM emissions from this source and the inherently low
emissions of PM from natural gas combustion, the practical
enforceability of this limit is not critical to our approval. We also
note that NOX contributes over 99.9% of Lake Catherine Unit
4's total visibility impacts at all nearby Class I areas on the most
impacted days. Therefore, we are finalizing our proposed approval of
Arkansas's determination that PM BART is the existing PM emission limit
in Chapter 15 of APCEC Regulation No. 19 for the Entergy Lake Catherine
Unit 4.
---------------------------------------------------------------------------

    \156\ 70 FR 39116.
    \157\ 76 FR 52604 and 76 FR 80754.
    \158\ 76 FR 16168 and 76 FR 81728.
---------------------------------------------------------------------------

    A review of the emissions based on AP-42 emissions factors
substantiates that the PM emissions from natural gas combustion are
inherently low. Table 1.4-2 of EPA's AP-42 Compilation of Air Pollutant
Emission Factors \159\ indicates the total PM (i.e. condensable plus
filterable PM) emission factor from combustion of natural gas is 7.6
lb/10\6\ standard cubic feet, which is equivalent to an emission rate
of 0.0074 lb/MMBtu.\160\ A unit's maximum emission rate for a given
pollutant can be calculated by using the following standard equation:
---------------------------------------------------------------------------

    \159\ Compilation of Air Pollutant Emission Factors, Volume I:
Stationary Point and Area Sources, AP-42, 5th Edition, January 1995.
    \160\ EPA's AP-42 emission factors are based on an average
natural gas higher heating value of 1,020 Btu/standard cubic foot.
As explained under Table 1.4-2 of EPA's AP-42 emission factors, to
convert from 1b/10\6\ standard cubic feet to lb/MMBtu, divide by
1,020. Based on this calculation, the 7.6 lb/10\6\ standard cubic
feet emission factor from combustion of natural gas is equivalent to
an emission rate of 0.0074 lb/MMBtu.

Pollutant mass emission rate (lb/hr) = Pollutant emission rate (lb/
---------------------------------------------------------------------------
MMBtu) x Unit heat input rate (MMBtu/hr)

    Accordingly, Appendix 9.1A of the Arkansas RH SIP indicates that
the Lake Catherine Unit 4 has a heat input rate of 5,850 MMBtu/hr.
Based on Unit 4's heat input rate and the 0.0074 lb/MMBtu PM emission
rate from natural gas combustion, the unit's maximum mass emission rate
for PM is 43.29 lb/hr. This is actually slightly lower than the
existing PM emission limit for Entergy Lake Catherine Unit 4 as of
October 15, 2007 (i.e. 45 lb/hr).
    With regard to the comment that the Entergy Whit Bluff Title V
permit identifies the PM10 limit as 44.5 lb/hr, EPA is
approving the part of Chapter 15 of APCEC Regulation No. 19 \161\ that
establishes PM BART for the natural gas firing scenario for Entergy
Lake Catherine Unit 4. The Title V permit that was in effect at the
time of the State's adoption of Chapter 15, Regulation 19, which is
Permit No. 1717-AOP-R4, required Unit 4 to meet a PM emission limit of
45 lb/hr. The Title V permit referenced by the commenter is Permit No.
1717-AOP-R5, and appears to contain revisions to several emission
limits, including the PM emission limit for Unit 4. However, EPA can
act only upon what is submitted to it by a state as a SIP revision.
Arkansas submitted Chapter 15, Regulation 19 as part of its RH SIP
revision. The State's submitted RH Rule adopts the existing PM emission
limit as of October 15, 2007 (i.e. 45 lb/hr) as the PM BART emission
limit.
---------------------------------------------------------------------------

    \161\ The Arkansas RH SIP was originally submitted to EPA on
September 23, 2008. We received a revision to the RH SIP on August
3, 2010, and a supplemental submittal on September 27, 2011. The
revisions to Chapter 15 of APCEC Regulation 19 that we are referring
to were submitted to us in the August 3, 2010 RH SIP revisions.
---------------------------------------------------------------------------

    The EPA is finalizing its approval of the existing PM emission
limit as meeting PM BART for Entergy Lake Catherine Unit 4 for the
natural gas firing scenario.
4. Comments on the Capacity Factor Used in the State's BART Analyses
for Entergy Lake Catherine and White Bluff
    Comment: The EPA was incorrect in its assessment of Entergy's Lake
Catherine BART determination that Entergy's Lake Catherine Unit 4
assumption of a 10% capacity unit needs to be supported by an
enforceable limit. A 10% capacity factor for Catherine Unit 4 is a
conservative assumption as demonstrated by the following table:

                                                      Lake Catherine Unit 4 Annual Capacity Factor
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                2011 (1/1-11/
      2003              2004             2005             2006             2007             2008             2009             2010             31)
--------------------------------------------------------------------------------------------------------------------------------------------------------
         10.4               3.2              4.2              0.5              0.7              2.7              3.0              3.1              2.5
--------------------------------------------------------------------------------------------------------------------------------------------------------

    This is consistent with the BART Guidelines because the baseline
emissions rate represents a realistic depiction of anticipated annual
emissions for the source and actual emissions for existing sources
subject to BART should be based from a baseline period by the state.
The BART Guidelines provide that only if future operating parameters
differ from past practices and they have a deciding effect in the BART
determination, then these parameters need to be enforceable limits.
Consistent with the BART Guidelines, annual emissions for Entergy Lake
Catherine Unit 4 were estimated based on the continuation of past
practice of using 10% capacity for future emissions. Therefore, an
enforceable permit limitation is not required for a 10% capacity use of
Entergy Lake Catherine Unit 4.
    Response: The EPA agrees that in our proposed rulemaking on the
Arkansas RH SIP we made an error in our calculation of the capacity
factor for recent years for Entergy Lake Catherine Unit 4. Based on
certain statements made in the BART analysis for Lake Catherine, to the
effect that in the future the unit was expected to be dispatched
approximately 10% of the time only, we were under the impression that
the source had factored into their cost analysis that the unit would
only be operating 10% of the time when the unit has historically
operated at considerably more than 10% of the time. Based on the
information provided by the commenter, we agree that the source has
historically operated at less than a 10% capacity factor. We also agree
that the BART Guidelines provide that for the purpose of calculating
the cost of controls, the state may calculate baseline emissions based
upon continuation of past practice.\162\
---------------------------------------------------------------------------

    \162\ Appendix Y to Part 51, section IV.4.
---------------------------------------------------------------------------

    However, our finding that the State did not properly document the
cost analysis for NOX controls for the fuel and gas firing
scenarios and SO2 and PM controls for the fuel oil firing
scenario for Lake Catherine Unit 4 has not changed, as the proper
documentation necessary to allow us to make an informed and proper
evaluation of the BART analysis was not included in the SIP, as the
BART Guidelines require. As explained in our proposed rulemaking, the
RH SIP includes the results of a

computerized model the source used to calculate the costs associated
with each NOX control technology for both the natural gas
and fuel oil firing scenarios. However, the SIP includes no detailed
breakdown of the costs. The only explanation of the computerized model
is a paragraph in Appendix 9.3B, which points out that inputs that went
into the model were based on inputs derived from the EPRI document
entitled ``Retrofit NOX Control Guidelines for Gas and Oil
Fired Boilers,'' \163\ which were further analyzed to reflect
performance expected for Lake Catherine Unit 4, as according to the
source ``each specific boiler will perform differently due to the
unique characteristics of that boiler.'' \164\ The BART Guidelines
provide that states should include documentation for any additional
information used for the cost calculations, including any information
supplied by vendors that affects your assumptions regarding purchased
equipment costs, equipment life, and other elements of the
calculation.\165\ This was not done in the Arkansas RH SIP.
---------------------------------------------------------------------------

    \163\ EPRI document entitled ``Retrofit NOX Control
Guidelines for Gas and Fired Boilers,'' Version 2, June 1997.
    \164\ See Appendix 9.3B of the RH SIP.
    \165\ Appendix Y to Part 51, section IV.4.
---------------------------------------------------------------------------

    Furthermore, as noted in our proposed rulemaking on the Arkansas RH
SIP, the State did not properly consider NOX post-combustion
controls in the BART analysis for natural gas firing and fuel oil
firing. As pointed out by another comment, the State eliminated post-
combustion controls from consideration because they were found to be
not cost-effective and the State eliminated two NOX control
options (for natural gas firing) involving a combination of combustion
controls because of their incremental cost-effectiveness. Based on the
information provided from the source's computerized model, the cost-
effectiveness of a combination of combustion controls and SNCR is
$3,378/NOX ton removed for the natural gas firing scenario
and $3,440/NOX ton removed for the fuel oil firing scenario.
This is not an unreasonably high cost-effectiveness value, and
depending on the visibility impact of these controls and the
consideration of any of the other statutory factors, the State may find
that these controls are BART. In light of Entergy Lake Catherine's pre-
control visibility impact of 6.607 dv and post-control visibility
impact of 3.671 dv at Caney Creek for the fuel oil firing scenario,
which is based on the BART controls adopted by the State in Chapter 15,
Regulation 19 (i.e. for NOX BART this consists of boiler
tuning, boiler modifications, and burners out of service), we believe
that it is possible that NOX and SO2 controls
more stringent than those adopted by the State, including post-
combustion controls, would be cost-effective and help reduce the
visibility impact of the source at Arkansas and Missouri Class I areas.
Therefore, the State should have evaluated both the cost-effectiveness
and the incremental cost-effectiveness in addition to the visibility
impact of post-combustion controls and each of the other control
options considered at each potentially affected Class I area before
eliminating any given control option. It appears that the source and
the State may have only considered the incremental cost-effectiveness
of controls in eliminating post-combustion controls and all other
controls more stringent than the controls adopted by the State for
NOX BART. The BART Guidelines provide that average cost-
effectiveness (reported by the source to be $1,701/ton NOX
removed and $3,757/ton NOX removed for the two sets of
combination of controls mentioned above for the natural gas firing
scenario), in addition to the visibility impacts at each potentially
affected Class I area, should also be taken into consideration before a
BART determination is made.
    In addition, as articulated in our proposed rulemaking on the
Arkansas RH SIP, the State did not consider SO2 post-
combustion controls in the BART analysis for fuel oil firing.
Furthermore, as noted in our proposed rulemaking, the use of a wet
scrubber system that controls both SO2 and PM emissions may
prove to be cost-effective and provide for substantial visibility
improvement. As explained elsewhere in our response to comments, in
light of Entergy Lake Catherine's pre-control visibility impact of
6.607 dv and post-control visibility impact of 3.671 dv at Caney Creek
for the fuel oil firing scenario,\166\ we believe that it is possible
that NOX, SO2, and PM controls more stringent
than those adopted by the State in Chapter 15 of APCEC Regulation No.
19, including post-combustion controls, would be cost-effective and
help reduce the visibility impact of the source at Arkansas and
Missouri Class I areas.
---------------------------------------------------------------------------

    \166\ See Tables 9.4f and 9.4e of the Arkansas RH SIP. The pre-
and post-control visibility impact reported is the maximum
[Delta]dv. The post-control visibility impact is the visibility
impact resulting from the BART controls adopted by the State.
---------------------------------------------------------------------------

    Therefore, we are finalizing our proposed disapproval of BART for
the Entergy Lake Catherine Unit 4 for NOX for both the
natural gas and fuel oil firing scenarios, and SO2 and PM
for the fuel oil firing scenario.
    Comment: The EPA was incorrect in criticizing the cost-analysis
conducted for Entergy's White Bluff Units 1 and 2 because the source
assumed 85% utilization of the units without an enforceable limit when
the EPA believes that the units are capable of utilization of 100%
capacity factor. Utilization of 85% capacity factor for these units is
a conservative assumption, as demonstrated by the following table:

                                                              White Bluff Capacity Factors
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                2011 (1/1-11/
                              Unit                                  2003     2004     2005     2006     2007     2008     2009     2010         31)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1...............................................................     75.3     73.4     63.1     55.1     81.3     78.2     71.1     82.5            60.7
2...............................................................     58.7     74.4     63.0     74.8     54.3     71.5     74.6     65.5            71.9
--------------------------------------------------------------------------------------------------------------------------------------------------------

    This is consistent with the BART Guidelines because the baseline
emissions rate represents a realistic depiction of anticipated annual
emissions for the source and actual emissions for existing sources
subject to BART should be based from a baseline period by the state.
The Guidelines provide that only if future operating parameters differ
from past practices and they have a deciding effect in the BART
determination, then these parameters need to be enforceable limits.
Consistent with the Guidelines, annual emissions from Entergy White
Bluff Units 1 and 2 were estimated based on the continuation of past
practice of using 85% capacity for future emissions. Therefore, an
enforceable permit limitation is not

required for an 85% capacity use of Entergy White Bluff Units 1 and 2.
    Response: The EPA agrees that in our proposed rulemaking on the
Arkansas RH SIP we made an error in our calculation of the capacity
factor for recent years for Entergy White Bluff Units 1 and 2. Based on
certain statements made in the BART analysis for White Bluff, to the
effect that in the future the unit was expected to be dispatched
approximately 85% of the time only, we were under the impression that
the source had factored into their cost analysis that the unit would
only be operating 85% of the time when the unit has historically
operated at more than this. Based on the information provided the
commenter, we agree that the source has historically operated at
slightly less than an 85% capacity factor. We also agree that the BART
Guidelines provide that for the purpose of calculating the cost of
controls, the state may calculate baseline emissions based upon
continuation of past practice.\167\
---------------------------------------------------------------------------

    \167\ Appendix Y to Part 51, section IV.4.
---------------------------------------------------------------------------

    However, our finding that the State did not properly document the
cost analysis for NOX and SO2 controls for both
the bituminous and sub-bituminous coal firing scenarios for White Bluff
Units 1 and 2 has not changed. As articulated in our proposed
rulemaking, the proper documentation necessary to allow an informed and
proper evaluation of the BART analysis was not included in the SIP, as
the BART Guidelines require. As pointed out in another comment, the
annual cost estimates of NOX combustion controls in the BART
analysis for White Bluff Units 1 and 2 are significantly higher than
those of similar controls at comparable facilities. The State must
provide documentation of its cost calculations and a reasonably
detailed breakdown of the costs. The State must also document the
reason for any unusually high costs, which may require a higher level
of detail in cost breakdown. Furthermore, the State did not properly
consider the available controls and cost of controls because it did not
evaluate SO2 and NOX controls that can achieve
emission limits more stringent than the presumptive emission limits. As
articulated in more detail in our proposed rulemaking, some of the
control technologies evaluated by the State for SO2 are
capable of achieving a higher control efficiency than that evaluated by
the State, and there are NOX control technologies capable of
achieving a more stringent limit than the presumptive limit. Because
such controls have been found to be cost-effective at similar
facilities, the State must evaluate the costs and visibility impact of
these controls before making a BART determination. Moreover, as
articulated in our proposed rulemaking and in previous response to
comments, the RHR, BART Guidelines, and CAA require that states
consider the controls available, including the most stringent control
technology, as well as the maximum level of control achievable by each
technology.
    Therefore, we are finalizing our proposed disapproval of the
NOX and SO2 BART determinations for the Entergy
White Bluff Units 1 and 2 for both the bituminous and sub-bituminous
coal firing scenarios.
5. Comments on the State's Cost Evaluations
    Comment: The ``cost of compliance'' is a BART consideration factor
that should be properly left to the states and EPA cannot void a
state's cost assessment on the grounds that EPA would have used a
different analysis or would have reached a different conclusion if it
had primary jurisdiction.
    Response: The EPA agrees that the BART Rule provides states with
some flexibility in how they calculate and consider costs.\168\
However, our grounds for disapproving Arkansas's NOX BART
determinations (natural gas and fuel oil firing conditions) and
SO2 BART determination (fuel oil firing conditions) for
Entergy Lake Catherine Unit 4 and the NOX and SO2
BART determinations (bituminous and sub-bituminous coal firing
conditions) for Entergy White Bluff Units 1 and 2, as articulated in
our proposal, are not based on EPA arriving at a different BART
determination. Our disapproval of the above BART determinations is
based in part on the fact that the State did not provide the proper
documentation, as required by the BART Guidelines.\169\ The BART
Guidelines provide that states must develop estimates of capital and
annual costs and document the basis for equipment cost estimates either
with data supplied by a vendor (i.e. budget estimates or bids) or by a
referenced source (such as the OAQPS Control Cost Manual).\170\ The
BART Guidelines also provide that cost estimates should be based on the
OAQPS Control Cost Manual, where possible, to maintain and improve
consistency, and that states should include documentation for any
additional information used in cost calculation. The State did not
satisfy this requirement in the above BART determinations because the
State provided no documentation, breakdown, or any sufficiently
detailed supporting information for its cost analyses. Without the
documentation, neither we nor the public have the basis to verify the
validity of either the cost estimates or Entergy's BART determination
based on the cost estimation. As pointed out in another comment, the
annual cost estimates of NOX combustion controls in the
State's BART analysis for White Bluff Units 1 and 2 are significantly
higher than those of similar controls at comparable facilities. In
summary, our disapproval for these BART determinations is based (among
other reasons) on the fact that the proper documentation necessary to
allow us to make an informed and proper evaluation of the BART analysis
was not included in the SIP, as the BART Guidelines require.
---------------------------------------------------------------------------

    \168\ 70 FR 39127.
    \169\ Appendix Y to Part 51, section IV.4.
    \170\ Appendix Y to Part 51, section IV.4.
---------------------------------------------------------------------------

    Comment: The EPA claims that Arkansas's BART determinations should
be disapproved because they rely on cost estimates that are not
adequately documented or that lack sufficiently detailed supporting
information (76 FR 64206), yet EPA fails to provide any specific
discussion in the proposed rule's preamble of the purported
shortcomings in the state's cost information and fails to describe the
type or degree of documentation it believes is mandated. In other
similar RH SIP rulemakings, EPA has described a level of cost estimate
documentation that is of such an extensive and detailed nature that it
cannot be reasonably deemed an appropriate requirement of a BART cost
assessment (76 FR 52388, 52396).
    Response: The EPA disagrees that our proposed rulemaking did not
provide any specific discussion on the type or degree of documentation
needed in a state's cost evaluation. Our proposed rulemaking and the
TSD for our proposed rulemaking both specify that the basis for
equipment cost estimates should be documented either with data supplied
by an equipment vendor or by a referenced source, such as the OAQPS
Control Cost Manual. Our proposed rulemaking also specified that for
the SO2 BART analysis for fuel oil firing for Entergy Lake
Catherine Unit 4, the State should clearly indicate the quantity of
fuel oil consumption on which the State's annual cost calculation is
based. However, the BART Guidelines set specific requirements regarding
this matter. The BART Guidelines provide that states should base their
cost estimates on the OAQPS Control Cost Manual, where possible, and
that the level of detail in the Cost Control

Manual addresses most control technologies in sufficient detail for a
BART analysis. In general, a state should include a reasonably detailed
line by line breakdown of the cost estimates, and document the vendor
and/or referenced source. However, as explained in the BART Guidelines,
where unusual costs due to site-specific design or other conditions are
factored into the cost calculation, this should also be documented
properly. For cases involving unusual costs, such as was the case at
the San Juan Generating Station in New Mexico,\171\ which was subject
to a FIP for BART controls (which the comment references), a higher
level of detail in documentation may be necessary. Furthermore, the
State is encouraged to work with EPA to determine the appropriate level
of detail needed for any future BART analyses to be submitted to EPA as
SIP revisions.
---------------------------------------------------------------------------

    \171\ 76 FR 52388.
---------------------------------------------------------------------------

    Comment: The EPA found that Entergy's cost evaluation for BART for
NOX and SO2 for White Bluff Units 1 and 2 was
deficient because the company assumed 85% utilization of the two units
when they are not subject to any federally enforceable limit on
utilization, and the units are capable of 100% utilization. We agree
with EPA's concerns that by assuming 85% utilization of the White Bluff
units under the proposed NOX and SO2 BART limits,
Entergy underestimated the tons of NOX and SO2
emissions that would be reduced and overestimated the costs per ton of
pollutant removed for the combustion controls evaluated. The EPA also
found that the cost analysis is inadequate because Entergy did not take
into account the achievable emissions reductions with the control
technologies evaluated. We agree with EPA's finding that Entergy did
not adequately evaluate the cost-effectiveness of controls in the
NOX and SO2 BART analyses for White Bluff Units 1
and 2.
    Response: Based on comments received during the public comment
period, it has come to our attention that we made an error in the
calculation of the capacity factors for White Bluff Units 1 and 2.
Based on the information provided, we agree that the source has
historically operated at a slightly less than 85% capacity factor. The
BART Guidelines provide that for the purpose of calculating the cost of
controls, the state may calculate baseline emissions based upon
continuation of past practice.\172\ However, our finding that the State
did not properly document the cost analysis for NOX and
SO2 controls for White Bluff Units 1 and 2 has not changed,
as the proper documentation necessary to allow us to make an informed
and proper evaluation of the BART analysis was not included in the SIP,
as the BART Guidelines require. As pointed out in another comment, the
annual cost estimates of NOX combustion controls in the BART
analysis for White Bluff Units 1 and 2 are significantly higher than
those of similar controls at comparable facilities. In addition, the
State did not properly consider the available controls and cost of
controls because it did not evaluate SO2 and NOX
controls to achieve emissions limits more stringent than the
presumptive emission limits. As articulated in more detail in our
proposed rulemaking, some of the control technologies evaluated by the
State for SO2 are capable of achieving a higher control
efficiency than that evaluated by the State, and there are
NOX control technologies capable of achieving a more
stringent limit than the presumptive limit. Because such controls have
been found to be cost-effective at similar facilities, the State must
evaluate the costs and visibility impact of these controls in making a
BART determination. Furthermore, as articulated in our proposed
rulemaking and in previous response to comments, the RHR, BART
Guidelines, and CAA require that states consider the most stringent
control technology, as well as the maximum level of control achievable
by each technology.
---------------------------------------------------------------------------

    \172\ Appendix Y to Part 51, section IV.4.
---------------------------------------------------------------------------

    Comment: Comparing Entergy's stated costs for SO2
controls with those found in other companies' SO2 BART
evaluations, it appears that Entergy has overstated the costs of
SO2 controls. Entergy assumes much higher cost numbers for
SO2 controls in its revised 2008 BART analysis for White
Bluff than in its 2006 BART analysis (see Exhibit 11). The
SO2 control cost numbers in Entergy's revised 2008 BART
analysis for White Bluff are much higher than the cost numbers in other
plants' SO2 BART analyses (see Exhibit 17). Even though
Entergy's revised 2008 BART analysis for White Bluff is not before EPA
for approval, these comments are being provided now in case the revised
2008 BART analysis is eventually submitted to EPA. EPA should require
that Entergy's cost-effectiveness calculations are based on the
emission reductions achievable with the controls being evaluated and
that Entergy's cost-analysis is well-documented, sound, and that the
documentation and details be made publicly available.
    Response: The EPA agrees that the 2008 BART analysis for Entergy
White Bluff is not before EPA to take action on. As far as EPA is
aware, the State has not revised the RH SIP to include Entergy White
Bluff's revised analysis. As such, it is unclear whether the State
plans to submit it to EPA in the future as a SIP revision. However, we
do agree that the cost numbers in the 2008 analysis are considerably
higher than those in the 2006 BART analysis that is before EPA to take
action on. Consistent with the action we are taking on the Arkansas RH
SIP in this rulemaking, if the State submits the revised 2008 BART
analysis to EPA in the future in the context of an official RH SIP
revision, the State must provide documentation of its cost calculations
and a reasonably detailed breakdown of the costs. The State will also
have to document the reason for any unusually high costs, which may
require a higher level of detail in cost breakdown. If the State
anticipates submitting a revised BART analysis for White Bluff or any
other source to EPA as a SIP revision, EPA encourages the State to work
with us to resolve any uncertainties it may have with regard to the
level of detail needed in the cost analysis. Consistent with the action
we are taking on the Arkansas RH SIP in this rulemaking, we agree that
the State must ensure that its BART analyses evaluate the most
stringent emission limit achievable by each control considered, and
that the cost-analysis be well-documented, sound, and that the
documentation and all other relevant details are made publicly
available.
    Comment: It appears that the annual cost estimates of
NOX combustion controls in Entergy's December 2006 BART
analysis for the Entergy White Bluff Units 1 and 2 are very high ($5.2
million for Unit 1 and $5.3 million for Unit 2) compared to the cost
estimates for similar controls at other coal-fired EGUs, such as those
at the Boardman Power Plant (617 MW, $3.7 million), the Four Corners
Power Plant (790 MW, $3.0 million), and the Sherburne County Power
Plant (690 MW, $2.2 million) (see Exhibit 19). Since neither Entergy
nor ADEQ have provided the specific details that went into these cost
estimates, it is difficult to discern why Entergy's cost estimates are
much higher.
    Response: The EPA agrees with the comment that the cost estimates
Arkansas provided in the cost evaluation of NOX combustion
controls in the 2006 Entergy White Bluff BART analysis are considerably
higher than the cost estimates for similar controls at the other coal
fired EGUs. The EPA notes that the Entergy White Bluff Units 1 and 2
have a slightly greater generating capacity (850 MW each), but because
of the lack of detail in Entergy White Bluff's cost calculations, it is
not

clear what issues are attributing to the wide difference in the
annualized cost estimates. As explained in our proposed rulemaking, the
State must provide proper documentation of all cost calculations, and a
reasonably detailed breakdown in costs. In cases where the State finds
that cost of controls are unusually high, especially in comparison to
the cost of the same controls at other similar sources, the State must
provide a more detailed breakdown of costs, as provided in the BART
Guidelines.\173\
---------------------------------------------------------------------------

    \173\ Appendix Y to Part 51, section IV.4.
---------------------------------------------------------------------------

    Comment: The EPA was incorrect in its assessment of Entergy's Lake
Catherine Unit 4 BART determination that Entergy provided no
documentation or detailed breakdown of cost. Entergy only included the
expected capital cost and any impacts the control technology will have
on the unit heat rate in the cost estimate, which is a conservative
cost estimate of the cost of each control technology. Entergy's methods
of calculations are described in the Appendix of the Determination
Report. This approach is supported by EPA's BART Guidelines. In
addition, by incorporating the costs provided by Entergy in the RH SIP
Arkansas supports Entergy's cost analysis.
    Response: The comment appears to be in contradiction with what was
documented in Arkansas's RH SIP. In Appendix 9.3B of the Arkansas RH
SIP, Entergy states that a computerized model was used to evaluate
electrical generating unit performance and the capital and operation
and maintenance cost associated with each identified control
technology. As such, the State should provide proper documentation of
the equipment costs with data supplied by an equipment vendor or by a
referenced source, and include a reasonably detailed breakdown of all
cost estimates. The Appendix to the Determination Report referenced in
the comment appears to be ``Appendix A: Cost and Emissions Estimates
for NOX and SO2 Control Options.'' \174\ This
document contains the total annual cost (with no breakdown), the cost-
effectiveness and the incremental cost-effectiveness calculated by
Entergy of the controls considered in the BART analysis, along with
formulas that were used by the source in calculating costs (i.e. total
capital requirement, levelized control cost, etc.). But the actual
calculations or numbers that went into these formulas are not included.
As explained in our response to other comments, this approach is not
supported by the BART Guidelines. We also note that the State's support
for a particular cost analysis alone is not grounds for EPA approval.
The EPA must evaluate the details of a cost analysis and determine
whether it meets the RH requirements and BART Guidelines before we can
consider it in approving or disapproving a BART determination.
---------------------------------------------------------------------------

    \174\ See ``BART Analysis for Lake Catherine Plant- Unit 4,''
prepared by Robert Paine, dated December 2006 (Appendix 9.3A of the
Arkansas RH SIP).
---------------------------------------------------------------------------

    Comment: Entergy demonstrated that post-combustion NOX
controls for Lake Catherine Unit 4 are not economically viable. Thus,
EPA should not have disapproved Lake Catherine Unit 4's BART
determination on the grounds that post-combustion controls were not
evaluated. ADEQ noted that in the BART analysis for Lake Catherine
facility Entergy used a computerized model that evaluated EGU
performance and the cost associated with each identified technology.
Entergy's analysis started with the most economical control technology
and then conducted a stepped approach where the next economical control
was analyzed. The analysis continued with a combination of all
identified control technologies. Entergy reported the combination of
control technologies until that combination was no longer cost
effective. This is consistent with the BART Guidelines which provide
that in the BART review, one or more of the available control options
may be eliminated from consideration if it is demonstrated to be
technically infeasible or to have unacceptable energy, cost, or non-air
quality environmental impacts on a case by case basis. The incremental
NOX control cost of $41,739/ton (option 5) and $10,101/ton
(option 4) shown in the Lake Catherine BART analysis do not pass the
cost test as described in the BART Guidelines. This is consistent with
the BART Guidelines, which provide that installation of current
combustion control technology is cost-effective and should be
considered in determining BART for oil- and gas-fired sources.
    Response: As noted in our proposed rulemaking, we agree that the RH
SIP includes the results of a computerized model the source used to
calculate the costs associated with each technology. However, the SIP
includes no detailed breakdown of the costs. The only explanation of
the model is a paragraph in Appendix 9.3B, which points out that inputs
that went into the model were based on inputs derived from the EPRI
document entitled ``Retrofit NOX Control Guidelines for Gas
and Oil Fired Boilers,'' \175\ which were further analyzed to reflect
performance expected for Lake Catherine Unit 4, as ``each specific
boiler will perform differently due to the unique characteristics of
that boiler.'' \176\ The BART Guidelines provide that States should
include documentation for any additional information used for the cost
calculations, including any information supplied by vendors that
affects the assumptions regarding purchased equipment costs, equipment
life, and other elements of the calculation.\177\ We find that this
documentation was not provided by Arkansas.
---------------------------------------------------------------------------

    \175\ EPRI document entitled ``Retrofit NOX Control
Guidelines for Gas and Fired Boilers,'' Version 2, June 1997.
    \176\ See Appendix 9.3B of the RH SIP.
    \177\ Appendix Y to Part 51, section IV.4.
---------------------------------------------------------------------------

    The comment states that post-combustion controls were eliminated
from consideration because they were found to be not cost-effective.
Based on the information provided from the Entergy's computer model,
the cost-effectiveness of a combination of combustion controls and SNCR
is $3,378/NOX ton removed. Again, the issue of documentation
aside, we find that Arkansas should have evaluated the visibility
impact of this and each of the other control options considered at each
potentially affected Class I area before eliminating any given control
option. The comment also notes that some control options, including
options 4 and 5 that are each a combination of combustion controls,
were eliminated from consideration based on their incremental cost-
effectiveness. However, the BART Guidelines provide that the average
cost-effectiveness (which was reported by the source to be $1,701/ton
for option 4 and $3,757/ton for option 5), in addition to the
visibility impacts from the installation of controls at each
potentially affected Class I area, should also be taken into
consideration before a BART determination is made. Based on average
cost effectiveness, these options should not be eliminated from
consideration. As the BART Guidelines explain, cost effectiveness
cannot be assessed without an analysis of the projected visibility
benefit. This holds true even for control options evaluated on the
basis of their incremental cost effectiveness. In the preamble to the
BART Rule, in response to comments that modeling should not be included
as part of a BART review, EPA supported its decision to include
modeling by stating that CAA section 169(g)(2) clearly requires an
evaluation of the expected degree of improvement

in visibility from BART Controls.\178\ The BART Rule also states the
following:
---------------------------------------------------------------------------

    \178\ 70 FR 39129.

    ``We believe that modeling, which provides model concentration
estimates that are readily converted to deciviews, is the most
efficient way to determine expected visibility improvement.'' \179\
---------------------------------------------------------------------------

    \179\ 70 FR 39129.

    Furthermore, in the preamble to the BART Rule, in response to
---------------------------------------------------------------------------
comments received, we stated the following:

    ``We agree with commenters who asserted that the method for
assessing BART controls for existing sources should consider all of
the statutory factors.'' \180\
---------------------------------------------------------------------------

    \180\ 70 FR 39130.

    Therefore, Arkansas must evaluate all five statutory factors before
eliminating a given control option, especially if there are no unusual
circumstances that would make it clear that a particular control option
should be eliminated before all five statutory factors are considered.
With regard to the comment that the BART Guidelines provide that
installation of current combustion control technology is cost-effective
and should be considered in determining BART for oil- and gas-fired
sources, we note the context of that statement is with regard to
whether we believed a presumptive emission limit was appropriate for
oil and gas fired EGUs.\181\ It was not intended to limit the
consideration for BART of possible post-combustion control options.
---------------------------------------------------------------------------

    \181\ Appendix Y to Part 51, section IV.E.5.
---------------------------------------------------------------------------

    Comment: Arkansas's failure to consider the actual costs of
compliance for its BART determination is reflected by the APCEC
rulemaking record for the Arkansas RH SIP. No actual costs of
compliance with presumptive limits for the White Bluff and Flint Creek
facilities are provided. The petition to initiate rulemaking before the
APCEC contains no information about the costs to install the required
control technology at these two plants nor does it identify or contain
any explanation of the five BART factors that the APCEC is supposed to
consider under the CAA. The financial documentation filed in support of
the petition contains no indication of the actual costs of compliance.
The documentation suggests that the financial impact of the rule to the
citizens and ratepayers of Arkansas would be zero. Thus, Arkansas
should not have adopted EPA's presumptive limits for the Entergy White
Bluff Units 1 and 2 and AEP Flint Creek Boiler 1 without first
determining whether the assumptions underlying those presumptive
emission limits, including the costs of compliance, were still valid
and reasonable.
    Response: EPA notes that the APCEC is the State's rulemaking body
for environmental regulations. EPA agrees that the rulemaking record
for the Arkansas RH SIP lacks sufficient information to support the
State's BART determinations for the two facilities. As reflected in our
proposed rulemaking and in our previous response to comments, the State
should have conducted a proper evaluation of the five statutory factors
before adopting the NOX and SO2 presumptive
limits for BART for Entergy White Bluff Units 1 and 2 and Flint Creek
Boiler 1.
6. Comments on the August 2008 Revised BART Analysis for White Bluff
    Comment: The EPA's evaluation of the BART submittal for Entergy
White Bluff Units 1 and 2 is based on a December 2006 BART analysis
submitted by Entergy Arkansas Inc., and included in the Arkansas RH SIP
in Appendix 9.3A. Entergy subsequently submitted a revised BART
analysis to ADEQ for White Bluff on August 8, 2008 (see Exhibit 11),
stating that this revised document should supersede the Entergy's
original December 2006 BART determination for White Bluff. It does not
appear that ADEQ ever adopted the revised BART analysis as part of the
Arkansas RH SIP, but in 2009 ADEQ did propose to issue a Title V permit
for White Bluff that proposed to incorporate the control equipment
proposed by Entergy in its revised 2008 BART analysis to meet BART.
These controls differed from the controls assumed to meet BART in
Entergy's 2006 BART analysis. Specifically, the 2006 BART analysis
proposed to install wet scrubbers to achieve the SO2
presumptive limit of 0.15 lb/MMBtu and no additional controls for PM,
while the revised 2008 BART analysis proposed to install dry scrubbers
and baghouses to meet the SO2 presumptive limit of 0.15 lb/
MMBtu and no additional controls for PM. Although ADEQ never issued the
permit it proposed in 2009, it appears that Entergy may intend to
change its planned controls to meet BART. The EPA's proposal does not
mention Entergy's revised 2008 BART analysis because it has not yet
been adopted by Arkansas as a SIP revision, and it is therefore not
before EPA to approve or disapprove. However, as EPA acts on the
Arkansas RH SIP, it must consider that Entergy may be installing a
baghouse as part of its SO2 controls. Since a baghouse is
more effective at controlling PM emissions than an ESP, EPA should not
act on the state's proposed PM BART limit until it has a complete and
approvable suite of BART controls that it is acting on or otherwise
promulgating as a FIP.
    Response: The EPA agrees that the December 2006 White Bluff BART
analysis is what was included in Appendix 9.3A of the Arkansas RH SIP
received by EPA on September 23, 2008. As such, that is the BART
analysis that is before EPA to take action on. EPA does not have the
authority to take action on a SIP revision that has never been
officially submitted by the State. As the comment notes, the controls
assumed to meet BART in Entergy's 2008 revised BART analysis differ
from those in the 2006 BART analysis that was submitted to EPA as part
of the Arkansas RH SIP. However, since to the best of EPA's knowledge,
the State has never officially adopted the 2008 revised BART analysis
as a revision to the Arkansas RH SIP and since the State never issued
the permit that proposed to install the controls in the 2008 revised
BART analysis, it is not clear if the State is even considering
submitting such a revised SIP to EPA. As such, EPA can only review what
has been submitted to it by Arkansas. Therefore, we are basing our
decision upon Arkansas's submitted RH SIP and our review of comments.
As articulated in our proposed rulemaking and elsewhere in our response
to comments, we find that the current permit limit (i.e. no additional
controls) is PM BART for Entergy White Bluff Units 1 and 2 for both
bituminous and sub-bituminous coal firing scenarios.
    Comment: The EPA cannot propose to disapprove the BART
determination for SO2 for the Entergy White Bluff Units 1
and 2 because the EPA did not evaluate the most recent and more
detailed BART analysis conducted for Entergy's White Bluff facility
when making its decision. The EPA's proposal references the 2006 BART
analysis as the basis for EPA's decision on Arkansas's White Bluff BART
determinations and not the 2008 revised BART analysis. The 2008 revised
BART analysis considered additional non-air quality environmental
impacts and provided a detailed BART five factor analysis. The 2008
revised BART report was evaluated by ADEQ and provided to EPA. Even
though EPA did not consider the 2008 revised BART analysis in its
proposed rulemaking, it agreed with its findings in a 2009 letter to
ADEQ staff that installation of dry scrubber technology is BART for the
White Bluff facility. The EPA's lack of consideration of the most
current and accurate BART analysis and determination for the White
Bluff facility makes EPA's

proposed rule regarding the White Bluff facility inaccurate and
arbitrary.
    Response: The EPA notes that the December 2006 White Bluff BART
analysis is the BART analysis that was included in Appendix 9.3A of the
Arkansas RH SIP received by EPA on September 23, 2008. As such, the
December 2006 White Bluff BART analysis is what is before EPA to take
action on. The EPA does not have the authority to take action on a SIP
revision that has never been officially submitted by the State. The EPA
is aware that in a letter dated August 8, 2008, sent by Entergy to
ADEQ, the source requests that the 2008 revised BART analysis supersede
the 2006 BART analysis.\182\ The EPA notes that the CAA places the
authority and duty to submit SIPs on the states. Under the RH
regulations, it is the State who is authorized to make BART
determinations for inclusion in the RH SIP submitted to EPA. As such,
even if a source submits a revised BART analysis to the State and
requests that the revised version supersede the one currently in the RH
SIP, EPA is not authorized to take action on the revision if the State
does not adopt the revised version as a revision to the RH SIP, allow
the FLM to review the proposed RH SIP revision at least 60 days prior
to holding any public hearing, undergo reasonable notice and public
hearing, and submit the revision to EPA in the context of an official
SIP submission. This did not happen.
---------------------------------------------------------------------------

    \182\ Letter from Mark C. Bowles, Arkansas Environmental Support
Manager, to Mike Bates, Air Division Chief, ADEQ, dated August 8,
2008. Please see the docket for this rulemaking for a copy of this
letter.
---------------------------------------------------------------------------

    While EPA did provide comments in a letter dated November 25, 2009,
to the State on the 2008 revised BART analysis for White Bluff, this
was done in the context of EPA's review of a draft Title V/Prevention
of Significant Deterioration (PSD) permit for White Bluff.\183\ Since
the draft Title V permit proposed by the State proposed to incorporate
the control equipment proposed by Entergy in the 2008 revised BART
analysis for White Bluff, the 2008 BART analysis was provided as an
attachment to the proposed permit. Our review of the draft Title V
permit did not involve a full review of the 2008 BART analysis, as we
were only reviewing that BART analysis in the context of providing
comments to the State on the draft Title V permit. In the comment
letter EPA sent to the State, we did note that we agreed that dry
scrubber technology is generally considered BART, but we also noted
that we did not agree that the SO2 emission limit proposed
by the source is reflective of the control efficiency this control
technology is capable of achieving, and that we did not agree that this
SO2 emission limit of 0.15 lb/MMBtu is BART. Our superficial
review of the 2008 revised BART analysis also revealed that many of the
same flaws we identified in our proposed rulemaking for the 2006 White
Bluff BART analysis are also found in the 2008 White Bluff analysis.
Furthermore, the draft Title V permit that proposed to incorporate the
control equipment proposed by Entergy in the 2008 revised White Bluff
BART analysis was never issued by the State.
---------------------------------------------------------------------------

    \183\ Letter from Jeff Robinson, Air Permits Chief, EPA Region
6, to Tom Rheaume, Permits Branch Manager, ADEQ, dated November 25,
2009.
---------------------------------------------------------------------------

    We disagree that our rulemaking regarding White Bluff Units 1 and 2
is inaccurate and arbitrary because the EPA did not rely on the 2008
revised White Bluff BART analysis, as the 2008 revised White Bluff BART
analysis is not before EPA to take action on.
7. Other Comments Related to BART
    Comment: The EPA's proposed disapproval of BART for the Entergy
White Bluff auxiliary boiler is legally incorrect because the unit is
not BART eligible. The EPA disapproved ADEQ's BART determination that
BART for the White Bluff auxiliary boiler is a restriction to operate
no more than 4360 hours annually. However, the White Bluff auxiliary
boiler has only a heat input capacity of 183 MMBtu/hr, which is less
than the BART-eligible threshold of 250 MMBtu/hr. The BART Guidelines
supports this finding that units which are located at a steam electric
plant, but which themselves are not in any of the 26 BART source
categories, such as the White Bluff auxiliary boiler, should not be
considered BART-eligible. Further, the Guidelines state that for
fossil-fuel boilers more than 250 MMBtu/hour heat input, this category
includes only those boilers that are individually greater than 250
MMBtu/hour heat input.
    Response: The EPA agrees that the Auxiliary Boiler (SN-05) at the
Entergy White Bluff Plant does not fall into ``Category 2'' (i.e.
fossil-fuel boilers of more than 250 million BTU/hr heat input) under
the BART Guidelines. However, as noted in our proposed rulemaking, it
does fall into ``Category 1'' (i.e. steam electric plants of more than
250 million BTU/hr heat input) under the BART Guidelines. The BART
Guidelines state the following regarding the BART eligibility of steam
electric plants of more than 250 MMBTU/hr heat input:

    ``Because the category refers to `plants,' we interpret this
category title to mean that boiler capacities should be aggregated
to determine whether the 250 million BTU/hr threshold is reached.
This definition includes only those plants that generate electricity
for sale.'' \184\
---------------------------------------------------------------------------

    \184\ Appendix Y to Part 51, section II.A.

    The BART Guidelines also provide the following example to help
states determine whether a boiler at a steam electric plant of more
than 250 MMBtu/hr heat input falls into ``Category 1'' (i.e. steam
electric plants of more than 250 million BTU/hr heat input) under the
---------------------------------------------------------------------------
BART Guidelines:

    ``Example: A stationary source includes a steam electric plant
with three 100 million BTU/hr boilers. Because the aggregate
capacity exceeds 250 million BTU/hr for the `plant,' these boilers
would be identified in Step 2.'' \185\
---------------------------------------------------------------------------

    \185\ Appendix Y to Part 51, section II.A.

    Therefore, even though the Auxiliary Boiler (SN-05) at the Entergy
White Bluff Plant is individually only 183 MMBtu/hr, since it is
located at a plant where the aggregate capacity exceeds 250 MMBtu/hr,
the Auxiliary Boiler is BART eligible and, as explained in our proposed
rulemaking, subject to BART. As such, our proposed disapproval of BART
for the auxiliary boiler is consistent with the BART Guidelines and is
legally correct. For the reasons articulated in our proposed
rulemaking, we are finalizing our proposed disapproval of BART for the
Auxiliary Boiler (SN-05) at the Entergy White Bluff plant.
    Comment: The EPA has not demonstrated in its proposed partial
disapproval of Arkansas RH SIP that post-combustion controls are cost-
effective. The EPA has also not demonstrated that Arkansas's reliance
on presumptive limits without analyzing post-combustion controls abused
its authority to determine the appropriateness of the selected BART
technologies.
    Response: The BART Guidelines provide that in identifying all
options, you must identify the most stringent option as well as a
reasonable set of options for analysis.\186\ The RHR also provides that
in establishing source specific BART emission limits, the State should
identify and consider in the BART analysis the maximum level of
emission reduction that has been achieved in other recent retrofits at
existing sources in the source category.\187\ The visibility
regulations define BART as ``an emission limitation based on the degree
of reduction achievable through the application of the best system of
continuous emission

reduction.'' Since recent retrofits at existing sources provide a good
indication of the current ``best system'' for controlling emissions,
these controls must be considered in the BART analysis. As explained in
our proposed rulemaking, post-combustion controls for NOX,
SO2, and PM have been demonstrated to be technically
feasible and cost-effective controls at fossil fuel fired EGUs that are
similar to those that are subject to BART in Arkansas. As articulated
in our proposed rulemaking (and also discussed elsewhere in our
response to comments), EPA is also aware of at least one type of
NOX post-combustion control (SNCR) that has been
demonstrated to be technically feasible for a power boiler at a kraft
pulp mill with similar design specifications as Domtar Ashdown Mill
Power Boilers No. 1 and 2. Therefore, states must consider post-
combustion controls in their BART analyses for NOX,
SO2, and PM if such controls have been recently installed as
retrofits at existing sources in the source category.
---------------------------------------------------------------------------

    \186\ Appendix Y to Part 51, section IV.D.
    \187\ 64 FR 35740.
---------------------------------------------------------------------------

    Furthermore, our disapproval of some of Arkansas's BART
determinations where the State did not consider post-combustion
controls, is not based on a demonstration by EPA that post-combustion
controls are cost-effective at any of Arkansas's subject to BART
sources. Instead, it is based on our finding that some of the State's
BART analyses did not satisfy the RHR and applicable EPA guidance. We
did not perform a source specific BART analysis to determine if post-
combustion controls are cost-effective at Arkansas's subject to BART
sources nor are we required to perform such an analysis in reviewing a
SIP revision. As explained in our response to other comments and as
required by CAA section 169A(g)(2) and 40 CFR 51.308(e)(1)(ii)(A), it
is the State's responsibility to conduct a five factor BART analysis
that satisfies the RHR and BART Rule using the NOX and
SO2 presumptive emission limits as a starting point in the
BART analysis. In addition, as explained above, states must consider
post-combustion controls in their BART analyses for NOX,
SO2, and PM if such controls are technically feasible. It is
EPA's responsibility to review the adequacy of this analysis.
    Comment: The EPA's proposed disapproval is inconsistent with EPA's
guidance and regulations concerning visibility protection causing
regulatory uncertainty among the EGU industry. The EPA's proposed
disapproval action should be withdrawn in favor of approval of the
Arkansas RH SIP.
    Response: Because the comment is not specific about what aspect of
our proposed disapproval is believed to be inconsistent with EPA
guidance and RH regulations, it is not possible for EPA to address in
this response any specific concerns. Several similar comments raised
very specific concerns. Our responses to these can be found elsewhere
in our responses to comments. As articulated in our proposed rulemaking
and further explained in our responses to other comments, EPA's partial
approval and partial disapproval of the Arkansas RH SIP is consistent
with the CAA, the RHR, BART Rule, and EPA guidance. Since our
rulemaking is consistent with the above, we disagree that it causes
regulatory uncertainty among the EGU industry.
    Comment: Arkansas's BART determinations are consistent with the
BART Guidelines and EPA should defer to the state's decision. Instead
of deferring to the state's judgment about the necessary measures to
implement BART within its borders, EPA proposed to substitute its
judgment concerning what constitutes BART and what constitutes an
acceptable LTS for making reasonable progress toward the national goal.
    Response: The EPA disagrees that all of Arkansas's BART
determinations satisfy the CAA, the RHR, BART Rule, and EPA guidance.
For some BART determinations, Arkansas adopted NOX and
SO2 presumptive limits without conducting a source-specific
analysis of appropriate levels of control when those sources have the
capability of more stringent controls. This is in contradiction with
the RHR and the BART Guidelines. We have determined that Arkansas's
failure to conduct the BART analysis despite the evidence that the BART
analysis might result in adoption of a different emissions limit was
significant enough to result in BART determinations that were
unreasoned and unjustified. Accordingly, those BART determinations,
that adopted presumptive limits without conducting any additional BART
analysis when information exists that may affect the BART
determination, are not approvable. For some BART determinations,
Arkansas did not perform a full BART analysis by not considering one or
more factors it is required to consider in determining whether retrofit
control should be required. We have determined that not considering one
or more BART factors by Arkansas in its BART determinations, when it is
demonstrable that this lack of analysis could alter the BART
determination, is unreasoned and unsupportable. Thus, those BART
determinations, which lack the consideration of one or more BART
factors when it can be demonstrated that lack of consideration of the
BART factor has the potential to alter the BART determination, are not
approvable. We are also disapproving Arkansas's LTS because it does not
satisfy the requirements under 40 CFR 51.308(d)(3) by relying on BART
determinations that are inconsistent with the CAA and the RHR as
detailed in our BART disapproval actions.\188\ As explained in our
response to other comments, EPA agrees that States have broad authority
and flexibility under the RHR. Furthermore, we are not substituting our
judgment and forcing Arkansas to adopt any specific BART determination.
Rather, we are disapproving portions of Arkansas's RH SIP that address
BART, the LTS, and the RPGs because the State omitted critical analyses
and made flawed assumptions that may compromise any decisions that
arise from it. In doing so, the State did not satisfy the requirements
of the CAA, RHR, and the BART Rule. The state could submit and EPA
would approve RH SIP revisions that reached identical determinations as
the current SIP submittal if Arkansas's analyses in reaching those
determinations are consistent with the CAA, RHR, and BART Rule.
---------------------------------------------------------------------------

    \188\ 76 FR at 64186, at 64187.
---------------------------------------------------------------------------

    Comment: Because of the limited ability to combust fuel oil on a
short-term basis for the Domtar Ashdown Mill Power Boiler No.1, a
higher SO2 emission rate was proposed of 1.12 lb/MMBtu even
though the average long-term emissions are low. The EPA is incorrect in
stating that there is a mismatch between ADEQ's high BART
SO2 emission limit and the emission needs of the Domtar
Power Boiler No.1 when you take into account the actual operation of
and the fuels used by the boiler.
    Response: As articulated in our proposed rulemaking, as part of its
BART analysis, the State should have conducted a fuel inventory for
Domtar Power Boiler No. 1 and investigated sources of potential sulfur
emissions. If the source believes that burning fuel oil on a relatively
long-term basis is the primary source of high SO2 emissions
from Domtar Power Boiler No. 1, the State should consider in its BART
analysis establishing a limit on the sulfur content of the fuel oil
burned at the boiler and/or lowering the limit of fuel oil usage. In
addition, if the boiler operator wishes to burn fuel oil on a long-term
basis and this is the primary source of SO2 emissions from
the boiler, the State should evaluate SO2 post-

combustion controls in its BART analysis. A proper BART evaluation of
SO2 controls may demonstrate that the installation and
operation of an SO2 scrubber is cost-effective and would
result in significant visibility improvement.
    Comment: With regard to the evaluation of upgrades to the existing
scrubber at Domtar's Power Boiler No. 2, multiple scrubber upgrades
were considered including the addition of a spray tower and/or a third
scrubber. Preliminary estimates of capital costs for the third scrubber
exceed $10 million not taking into account the expenses of installing
the technology in a limited space. Considering Arkansas's progress
towards the overall goal of the RH program, such costs are clearly not
justified.
    Response: As articulated in our proposed rulemaking, the BART
Guidelines provide that if a state determines that a source has
controls already in place that are the most stringent controls
available and that all possible improvements to any control devices
have been made, it may take a streamlined approach for the BART
analysis for this source. Since the source has an existing wet scrubber
for control of SO2 emissions, Arkansas has elected to take
this streamlined approach for Power Boiler No.2. As explained in our
proposed rulemaking, we agree that SO2 post-combustion
controls are typically the most stringent technology available for
control of SO2. However, we disagree that a BART emission
limit of 1.2 lb/MMBtu for SO2 is reflective of the most
stringent controls available. Further, the State has not provided
sufficient documentation of the upgrades considered for the existing
wet scrubber. In addition, based on the information available, it also
appears that the State has not considered all possible improvements to
the scrubber. As articulated in our proposed rulemaking, the BART
Guidelines state that there are numerous scrubber enhancements
available to upgrade the average removal efficiencies of all types of
existing scrubber systems, including increasing a scrubber system's
reliability (and conversely decreasing its downtime) by way of
optimizing operational procedures, improving maintenance practices,
adjusting scrubber chemistry, and increasing auxiliary equipment
redundancy.\189\ The BART Guidelines also provide the following
detailed list of potential scrubber upgrades that have been proven in
the industry as cost-effective means to increase overall SO2
removal of wet systems:
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    \189\ Appendix Y to Part 51, section IV.E.4.
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     Elimination of Bypass Reheat
     Installation of Liquid Distribution Rings
     Installation of Perforated Trays
     Use of Organic Acid Additives
     Improve or Upgrade Scrubber Auxiliary System Equipment
     Redesign Spray Header or Nozzle Configuration
    Based on the limited information that has been provided to EPA, it
does not appear that the State has evaluated all possible improvements
to the existing wet scrubber at Domtar Ashdown Mill Power Boiler No. 2.
Therefore, the State must either consider all possible improvements to
the existing wet scrubber (including proper documentation of these) or
conduct a full five factor BART analysis that satisfies the
requirements of the RHR and the BART Rule for Power Boiler No. 2. EPA
is finalizing our proposed disapproval of the State's SO2
BART determination for the Domtar Power Boiler No. 2.
    Comment: The EPA should not question if the proposed SO2
BART limit of 1.2 lb/MMBtu represents 90% control for Domtar's Power
Boiler No. 2. The 90% control value has never been confirmed via
testing. Rather this control efficiency was estimated based on a
comparison of the actual maximum daily emissions measured via CEMS and
the uncontrolled emission rate predicted by EPA's AP-42 data. It may be
overestimated, but the percent control value is somewhat irrelevant due
to the BART limit on a lb/MMBtu basis.
    Response: As articulated in our proposed rulemaking, we agree that
SO2 post-combustion controls are typically the most
stringent technology available for control of SO2. However,
we disagree that a BART emission limit of 1.2 lb/MMBtu for
SO2 is necessarily reflective of the most stringent controls
available. Since Arkansas has elected to take the streamlined approach
for the SO2 BART analysis for this source, it must ensure
that the source has controls already in place that are the most
stringent controls available and that all possible improvements to any
control devices have been made. This has not been done. Since the State
is relying on the fact that the source has the most stringent controls
in place to take a streamlined approach to the BART analysis, we
disagree that the control efficiency of the existing wet scrubber is
irrelevant. As explained elsewhere in our response to comments, the
State must either ensure it has the most stringent controls in place
and consider all possible improvements to the existing wet scrubber
(including proper documentation of these) or conduct a five factor BART
analysis that satisfies the requirements of the RHR and the BART Rule
for Domtar Power Boiler No. 2. EPA is finalizing our proposed
disapproval of the State's SO2 BART determination for
Domtar's Power Boiler No. 2.
    Comment: Since EPA is proposing to partially approve and partially
disapprove portions of the Arkansas SIP, EPA should clarify that the
compliance dates are all based on the same final approval date of the
entire SIP. Compliance should be five years after final approval by
EPA.
    Response: The EPA disagrees that compliance with the BART
requirements is contingent upon full approval of the entire Arkansas RH
SIP. 40 CFR 51.308(e)(iv) requires subject to BART sources to install
and operate BART as expeditiously as practicable, but in no event later
than 5 years after the approval of the implementation plan revision.
Therefore, in the event of a partial approval of the RH SIP, those
sources whose BART determinations for a particular pollutant have been
approved by EPA are required to install BART as expeditiously as
practicable, but in no event later than 5 years after the partial
approval of the BART determination. The RH regulatory language in no
way conditions the BART compliance dates on EPA's full approval of the
entire RH SIP.
    Comment: Arkansas did a proper BART evaluation for Entergy Lake
Catherine Unit 4 and White Bluff Units 1 and 2 when it adopted the
presumptive limits. Arkansas did the BART five factor analyses, which
is consistent with the BART Guidelines. EPA's proposed disapproval of
Arkansas's NOX and SO2 BART determinations for
Entergy's White Bluff and Lake Catherine facilities is based on EPA's
incorrect evaluation of Arkansas's BART analyses and prioritizes EPA's
disagreements with Arkansas concerning available technologies and the
associated costs of compliance over the visibility protection program's
fundamental purpose of remedying visibility impairment by 2064, which
the Arkansas's RH SIP achieves. The EPA's disapproval for Arkansas's
BART determinations for Entergy Lake Catherine and White Bluff
facilities is a disagreement with the results of the BART determination
as to the appropriate level of control for the Lake Catherine and White
Bluff facilities. Accordingly, EPA should withdraw its proposed partial
disapproval and approve the existing Arkansas RH SIP.

    Response: As explained in our proposed rulemaking,\190\ we disagree
that Arkansas did a proper five factor BART evaluation for
NOX and SO2 BART when it adopted the presumptive
limits for White Bluff Units 1 and 2, and we also disagree that
Arkansas did a proper five factor BART evaluation for NOX
BART (natural gas and fuel oil firing) and SO2 and PM BART
(fuel oil firing) for Lake Catherine Unit 4. We do note that in our
proposed rulemaking on the Arkansas RH SIP, we proposed to find that
Arkansas did not appropriately consider the costs of controls when they
assumed a 10% capacity factor for Lake Catherine Unit 4 and an 85%
capacity factor for White Bluff Units 1 and 2. Based on comments
received during the public comment period, we have found that we made
an error in proposed rulemaking in our calculation of the historical
capacity factors for these units. We agree that assuming a 10% capacity
factor for Lake Catherine and an 85% capacity factor for White Bluff
Units 1 and 2 in the calculation of emissions reductions achieved and
cost of controls is appropriate and in accordance with the BART
Guidelines (see our response to similar comments for a more detailed
explanation).
---------------------------------------------------------------------------

    \190\ EPA notes that in our proposed rulemaking on the Arkansas
RH SIP, we proposed to find that Arkansas did not appropriately
consider the costs of controls when they assumed a 10% capacity
factor for Lake Catherine Unit 4 and an 85% capacity factor for
White Bluff Units 1 and 2. Based on comments received during the
public comment period, we have found that we made an error in
proposed rulemaking in our calculation of the historical capacity
factors for these units. We agree that assuming a 10% capacity
factor for Lake Catherine and an 85% capacity factor for White Bluff
Units 1 and 2 in the calculation of emissions reductions achieved
and cost of controls is appropriate and in accordance with the BART
Guidelines (see our response to other comments in our response to
comments for a more detailed explanation). However, we still find
that Arkansas did not appropriately consider a number of factors (as
articulated in our proposed rulemaking and explained elsewhere in
our response to comments) in its five factor BART analysis for
NOX BART (natural gas and fuel oil firing), and
SO2 and PM (fuel oil firing) BART for Lake Catherine Unit
4, and for NOX and SO2 BART (bituminous and
sub-bituminous coal firing) for White Bluff Units 1 and 2.
Therefore, we are finalizing our disapproval of BART for the
aforementioned pollutants and units.
---------------------------------------------------------------------------

    However, we still find that Arkansas did not appropriately consider
a number of factors (as articulated in our proposed rulemaking and
explained elsewhere in our response to comments) in its five-factor
BART analysis for NOX BART (natural gas and fuel oil
firing), and SO2 and PM (fuel oil firing) BART for Lake
Catherine Unit 4, and for NOX and SO2 BART
(bituminous and sub-bituminous coal firing) for White Bluff Units 1 and
2. The State's BART analyses for Lake Catherine Unit 4 and White Bluff
Units 1 and 2 for the aforementioned pollutants do not satisfy all the
requirements of the RHR and BART Guidelines. As such, our disapproval
of the BART determinations for Lake Catherine Unit 4 and White Bluff
Units 1 and 2 is not based on our disagreement with the results of the
BART determination as to the appropriate level of control for the Lake
Catherine and White Bluff facilities. Instead, our disapproval is based
on our finding that Arkansas's BART analyses for these units and
pollutants do not satisfy all the requirements of the RHR and BART
Guidelines. The State omitted critical analyses and made flawed
assumptions that compromise the resulting BART determinations. As such,
until a proper five-factor BART analysis is conducted for these
pollutants that satisfies all the statutory and regulatory RH
requirements and adheres to the applicable guidelines, it will not be
possible to know whether the level of control adopted by the State or a
different level of control is BART for these units and pollutants. The
state could submit and EPA would approve RH SIP revisions that reached
identical determinations as the current SIP submittal if Arkansas's
analysis in reaching those determinations is consistent with the RHR
and applicable EPA Guidance. As explained elsewhere in our response to
comments, even if the CENRAP's modeling shows that the State is
expected to meet the URP for the first implementation period ending in
2018 and is projected to meet the natural visibility goal by 2064 if
the same level of visibility improvement expected to take place during
the first implementation is achieved for every remaining implementation
period, the State of Arkansas has not satisfied all its BART
requirements. We are finalizing our disapproval of BART for
NOX (natural gas firing and fuel oil firing) and
SO2 and PM (fuel oil firing) for Lake Catherine Unit 4 and
BART for NOX and SO2 (bituminous and sub-
bituminous coal firing) for White Bluff Units 1 and 2.
    Comment: It appears that EPA agrees with the State's approach of
developing BART determinations for each fuel-burning scenario for
subject to BART units that are permitted to burn more than one type of
fuel. Setting separate, individual BART limits for each fuel type that
a source is physically capable of burning and permitted to burn is a
generally reasonable approach to addressing multi-fuel units. Other
approaches may also be reasonable if chosen by the State, so long as
they do not amount to a redefinition of the source, as would occur if
use of a particular fuel-type, otherwise permitted, were prohibited or
made infeasible as a result of the imposition of a BART limit.
    Response: The EPA generally agrees with the State's approach of
developing BART determinations for each fuel burning scenario for
subject to BART sources that are permitted to burn more than one type
of fuel, as was done for Entergy Lake Catherine Unit 4 and Entergy
White Bluff Units 1 and 2. There is nothing in the RHR or the BART
Guidelines prohibiting a State from doing so. Although the BART
Guidelines provide that we do not consider BART as a requirement to
redesign the source when considering available control
alternatives,\191\ we do note that if a State considers it appropriate,
it may consider a fuel switch (i.e. switch from burning fuel oil to
natural gas), which does not necessarily constitute a redesign of the
source, as one of the options in the BART analysis for a particular
source. This was done by the State of Kansas, which determined that a
switch from fuel oil to natural gas satisfied the BART requirements for
SO2 and NOX for Westar Energy Gordon Evans Unit 2
(the unit can burn both fuel oil and natural gas).\192\ The EPA
approved Kansas' aforementioned BART determination.
---------------------------------------------------------------------------

    \191\ Appendix Y to Part 51, section IV.D.1.
    \192\ 76 FR 52604 and 76 FR 80754.
---------------------------------------------------------------------------

    Comment: As stated by EPA in its proposed action on the Arkansas RH
SIP, neither AEP nor ADEQ performed a five-factor BART analysis for
Flint Creek Boiler No. 1 (76 FR 64203). The company commented that
since it was proposing to meet the presumptive BART limits for
SO2 and NOX, it did not need to undertake a five-
factor BART analysis. This does not constitute a proper BART analysis,
and EPA was right in proposing disapproval of Arkansas's SO2
and NOX BART requirements for Flint Creek. The presumptive
limits in EPA's BART Guidelines do not exempt a source from a five-
factor BART analysis. If ADEQ or AEP-SWEPCO had performed a five-factor
analysis for Flint Creek, the BART limits would likely have been lower
than 0.15 lbs/MMBtu for SO2 and 0.23 lbs/MMBtu for
NOX.
    Response: As explained elsewhere in this final rulemaking, we are
finalizing our proposed disapproval of BART for NOX and
SO2 for Flint Creek Boiler No. 1 because the State did not
conduct a five factor BART analysis for the source.
    Comment: The SO2 and NOX emission limits for
Flint Creek Boiler No. 1 do not reflect the best system of continuous

SO2 and NOX emission reduction and EPA cannot
find that these emission limits satisfy the legal BART requirements
without a five-factor BART analysis. The proposed SO2 BART
limit of 0.15 lbs/MMBtu for Flint Creek reflects only 67% removal from
the uncontrolled 2010 average annual SO2 emission rate of
0.46 lbs/MMBtu. The best system of continuous SO2 emission
reductions is a wet scrubber, which can achieve 95-99% removal. The
next best system of continuous SO2 emissions reductions is a
dry scrubber, which can achieve 90-95% SO2 removal. EPA
recently proposed and finalized as a FIP the installation of dry
scrubbers as BART at six coal-fired EGUs in Oklahoma to achieve the
SO2 BART emission limit of 0.6 lbs/MMBtu on a 30-day rolling
average basis. The Oklahoma units are all similar to Flint Creek in
size and coal type. This provides evidence that had a proper five
factor BART analysis been done for Flint Creek, the SO2 BART
limit would have been lower than 0.15 lb/MMBtu. Similarly, a five-
factor analysis for NOX at Flint Creek would have required
the evaluation of SCR and SNCR, which can achieve NOX
emission limits lower than 0.23 lbs/MMBtu. If SCR had been evaluated as
BART for NOX, emissions would have been 78% lower, providing
significant benefits to the State's Class I areas. NOX BART
emission limits as low as 0.5 lb/MMBtu have been promulgated (76 FR
52390, 52439).
    Response: The EPA agrees that we cannot approve the State's BART
determinations for SO2 and NOX for Flint Creek
Boiler No. 1 because the State adopted presumptive limits as meeting
BART for the source without conducting a BART five-factor analysis. The
EPA also believes that a proper evaluation of the five statutory
factors is likely to demonstrate that emission limits lower than the
NOX and SO2 presumptive emission limits are BART
for Flint Creek Boiler No. 1. We are finalizing our proposed
disapproval of the State's BART determinations for SO2 and
NOX for Flint Creek Boiler No. 1.
    With regard to the comment that a wet scrubber is the ``best system
of continuous emissions reductions'' for SO2 and a dry
scrubber is the next ``best system of continuous emissions reductions''
for SO2, we note that 40 CFR 51.308(e)(1)(ii)(B) directs
States to identify the ``best system of continuous emissions control
technology'' taking into account ``the technology available, the costs
of compliance, the energy and non-air quality environmental impacts of
compliance, any pollution control equipment in use at the source, and
the remaining useful life of the source.'' Therefore, while we agree
that a wet scrubber and a dry scrubber are generally the two most
stringent control technologies available for control of SO2
emissions and have been found to be BART for many sources, we disagree
that a wet scrubber or a dry scrubber will necessarily be BART in every
case.
    Comment: The EPA's proposal is correct that the White Bluff BART
analyses for SO2 and NOX in the Arkansas RH SIP
are incomplete and inadequate because the company only evaluated
options to comply with the presumptive BART limits rather than
evaluating emission limits reflective of the best system of continuous
emission reduction at White Bluff Units 1 and 2. In Entergy's 2006 BART
analysis, which is part of the Arkansas RH SIP, the company did not
explain why it proposed a 0.15 lb/MMBtu SO2 emission limit
for either a wet scrubber or a dry scrubber, when the higher control
efficiency associated with a wet scrubber would result in the ability
to meet a lower SO2 emission limit. Also, the proposed
SO2 BART limit of 0.15 lb/MMBtu only reflects approximately
80% control from the base case SO2 emission rates, and not
the 95% and 92% control efficiency capable of being achieved by a wet
and dry scrubber, respectively. Entergy's 2006 BART analysis did note
that the resulting SO2 emission limit from either control
technology would ``depend on the future coal sulfur content'' (see
Appendix 9.3 of Arkansas RH SIP). Entergy's revised 2008 BART analysis,
which has not been adopted by Arkansas or submitted to EPA as a RH SIP
revision, elaborated on this, explaining that 2 lb/MMBtu SO2
is assumed as the highest coal sulfur content for dry scrubbing and 3
lb/MMBtu is assumed for wet scrubbing. Taking into account Entergy's
projected future coal sulfur content (which varies depending on the
control technology used) and Entergy's claimed percent removal
efficiencies for the control technologies considered, the resulting
emission limit just happens to equal EPA's presumptive BART limit for
SO2 of 0.15 lb/MMBtu. White Bluff is not authorized to burn
coal of unlimited sulfur or ash content, and the higher uncontrolled
coal sulfur content that Entergy assumed in its December 2006 BART
analysis (as well as in its revised 2008 BART analysis) is prohibited
from being utilized at the White Bluff units under the terms of the
White Bluff permit. It would be virtually impossible for White Bluff to
comply with Permit Condition IV.6 in its Title V permit and burn coal
with uncontrolled SO2 emissions at the inlet to the scrubber
of 2 lb/MMBtu, much less 3 lb/MMBtu. The future uncontrolled
SO2 emission rate must not be raised above the level of
uncontrolled SO2 emissions/coal sulfur content authorized by
the White Bluff permit and EPA must make clear that the assumed
uncontrolled SO2 emission rate cannot be improperly inflated
in proposing a BART emission limitation. EPA has commented on the BART
determinations of the Wisconsin Department of Natural Resources as well
as other states that BART cannot be based on characteristics of coal
that might be burned in the future (see Exhibit 18). Instead, it is to
be based on the fuel characteristics during the base case. If Entergy
plans to burn higher sulfur coal in the future as compared to that
utilized in the base case, that must be made clear in the BART analysis
because sulfur content of coal should be considered in determining
whether it is most beneficial to install a wet scrubber or a dry
scrubber.
    Response: The EPA agrees that in its SO2 BART analysis
for White Bluff Units 1 and 2, the State did not explain why it
proposed a 0.15 lb/MMBtu SO2 emission limit for either a wet
scrubber or a dry scrubber, when the higher control efficiency
associated with a wet scrubber would result in the ability to meet a
lower SO2 emission limit. EPA also agrees that the State's
proposed SO2 BART limit of 0.15 lb/MMBtu only reflects
approximately 80% control from the base case SO2 emission
rates, and not the 95% and 92% control efficiency capable of being
achieved in many cases by a wet and dry scrubber, respectively. EPA
also agrees that the BART Guidelines provide that BART must be based on
the fuel characteristics during the base case. If a source projects
that future operating parameters (i.e. limited hours of operation or
capacity utilization, type of fuel, raw materials or product mix or
type) will differ from past practice, resulting in greater (or less)