in CSAPR and we have addressed our remand obligations for Phase 2
SO2 budgets by ending Texas EGU participation in CSAPR for
PM2.5 transport. We agree, however, that Texas sources can
continue NOX BART coverage under CSAPR and we are finalizing
a BART alternative for SO2 instead of establishing source-
specific SO2 BART determinations for units at those sources.
The BART alternative applies the CSAPR allowance allocations for
SO2 to all BART-eligible coal-fired EGUs, several additional
coal-fired EGUs, and several BART-eligible gas-fired and gas/fuel oil-
fired EGUs. In addition to being a sufficient alternative to BART, it
secures reductions consistent with visibility transport requirements
and is part of the long-term strategy to meet the reasonable progress
requirements of the Regional Haze Rule.
    Comment: EPA is now proposing to require stringent emission control
technology on units that have already met the BART obligations by
participation in the regional trading programs, CAIR, and its
replacement, CSAPR. In this proposal, EPA has effectively removed a
cost-effective compliance mechanism which has been in place for the
duration of the first planning period, with costs and reductions that
far exceed the regulatory obligation, with limited or no benefit to
visibility. Because it was only late last week that EPA made available
the technical documents that it claims would support its action and EPA
has yet to provide us with the specific modeling supporting the
proposal that we requested several weeks ago, We have not yet had an
opportunity to thoroughly evaluate EPA's technical justification for
the proposal.
    Response: Our proposal did not effectively remove CSAPR, and we
disagree with the comment's characterization of how and when CSAPR has
been ``in place.'' Regardless, we agree with the premise of the comment
that SO2 BART and NOX BART for Texas EGUs can be
addressed by the BART alternatives we rely on in our final action. We
also disagree that our proposal would have provided limited or no
benefit to visibility to the extent it suggests our final action is not
providing visibility benefits. Visibility benefits are being secured
and preserved into the future by the final FIP measures.
    Comment: Texas' SO2 emissions are below the levels that
EPA has found to be better-than-BART, and any reasonable assessment
would conclude that trends of anticipated emissions in Texas will
remain below those levels. EPA conducted two sensitivity analyses that
both demonstrate that revised CSAPR emission levels for Texas are
better-than-BART. We compared actual Texas EGU SO2 emissions
in 2015 and 2016 to the SO2 emission levels that EPA found
are better-than-BART. In both cases, Texas' actual emissions are well
below the budgets that EPA has determined are better-than-BART.
    Response: We are finalizing a BART alternative that applies the
CSAPR allowance allocations for SO2 to all BART-eligible
coal-fired EGUs, several additional coal-fired EGUs, and several BART-
eligible gas-fired and gas/fuel oil-fired EGUs. In addition to being a
sufficient alternative to BART, it secures reductions consistent with
visibility transport requirements and is part of the long-term strategy
to meet the reasonable progress requirements of the Regional Haze Rule.
To the extent, the comment suggests that current and anticipated
emissions alone are enough to satisfy requirements for BART or a BART
alternative, we disagree. As a fundamental matter, emissions reductions
must be enforceable to prevent undesired and unexpected increases in
future years. Pointing to ``trends''--i.e., unenforceable emissions
levels without legal requirements against future increases--does not
meet CAA requirements.
    Comment: EPA must promulgate or approve a BART alternative for
Texas, and must not finalize the unlawful and cost-prohibitive proposed
Texas BART FIP. EPA should not, and lawfully may not, finalize its
Proposed Texas BART FIP. The Proposed Texas BART FIP--like the
predecessor Reasonable Progress Rule that is stayed and was remanded by
the Fifth Circuit for reconsideration--is fundamentally flawed, cost-
prohibitive to implement, and contrary to reasoned decision-making. EPA
should address BART for Texas--not through federally-mandated specific
controls on individual units--but through one of several available BART
alternatives that will achieve equivalent or greater benefits at far
less costs, as demonstrated by EPA's own prior modeling and sensitivity
analyses.
    Among those available alternatives is EPA's original proposed BART
action for EGUs in Texas--reliance on Texas EGUs' participation in
CSAPR's annual SO2 and NOX trading Programs as
BART compliance. That alternative remains the most expeditious and
defensible path for finalizing a BART solution for Texas EGUs, and it
is fully supported by EPA's previous CSAPR better-than BART modeling
and sensitivity analyses. Indeed, EPA's only lawful path forward to
finalize a BART FIP for Texas by the current September 9, 2017 deadline
in EPA's consent decree with Sierra Club is to finalize a CSAPR-for-
BART FIP for Texas EGUs, as EPA signed in December 2014. For the many
reasons discussed in Section II of these comments, EPA would be acting
unlawfully were it to finalize the Proposed Texas BART FIP as issued in
December 2016.
    As an alternative to finalizing a CSAPR-for-BART FIP in September
2017, EPA could seek an extension of the consent decree deadline and
proceed to work cooperatively with the State of Texas and Texas EGU
operators to develop and propose for comment a different BART
alternative for Texas, as it has done in other states. Such an
alternative could, for example, establish SO2 emission caps
for Texas EGUs that are comparable to CSAPR budgets and would thus fall
squarely within EPA's previous CSAPR=BART demonstration and sensitivity
analyses for Texas. EPA has frequently worked with states and
stakeholders to develop workable BART alternatives for EGUs, and it
should do

the same here with Texas and Texas stakeholders, including Luminant.
    Promulgation of a CSAPR-for-BART FIP is EPA's only lawful option
for meeting the September 9, 2017 consent decree deadline. If EPA
believes that it must finalize a BART rule for Texas EGUs by September
2017, EPA's only valid legal option is to finalize its 2014 proposed
CSAPR-for-BART FIP. In that proposal, EPA specifically stated that it
was proposing ``a FIP to replace reliance on CAIR with reliance on the
trading programs of CSAPR as an alternative to BART for SO2
and NOX emissions from EGUs in the regional haze plan for
Texas.'' In support, EPA explained that it ``determined that [1] CSAPR
provides for greater reasonable progress towards the national goal than
would BART and [2] Texas is included in CSAPR for NOX and
SO2.'' The same is true today, and, indeed, recent emission
trends and EPA's sensitivity analyses for Texas confirm that CSAPR is
and remains better-then-BART for Texas EGUs. Texas remains in the CSAPR
annual programs for NOX and SO2, and EPA's
determination that CSAPR provides for greater reasonable progress than
the installation of BART remains scientifically sound. EPA has
determined that ``[CSAPR] achieves greater reasonable progress towards
the national goal of achieving natural visibility conditions than
source-specific BART.'' That conclusion remains valid today, and EPA
has not undertaken any action to revise or rescind that rulemaking. In
fact, the Eighth Circuit recently upheld EPA's conclusion that CSAPR is
better than BART, stating that ``EPA's explanation that the Transport
Rule is better than source-specific BART is rational.'' There is no
legal or technical barrier to EPA finalizing its original proposal of
CSAPR-for-BART for Texas EGUs, and, indeed, that is EPA's only lawful
current option if it were to meet the September 2017 deadline.
    EPA's consent decree with Sierra Club does not prevent EPA from
finalizing its original CSAPR-for-BART proposal in Texas. The consent
decree that EPA entered into with Sierra Club was revised in December
2015 to provide two alternative deadlines for issuing a final rule that
implements BART for Texas. First, the revised consent decree provides
that by ``[n]o later than December 9, 2016,'' EPA was to promulgate a
final BART FIP for Texas, unless EPA had approved Texas's SIP or
promulgated ``a partial SIP'' meeting the BART requirements under the
regional haze program. Alternatively, the December 2016 deadline would
be ``extended to September 9, 2017,'' if EPA signed a new proposed rule
for BART by December 9, 2016. EPA signed the Proposed Texas BART FIP on
December 9, 2016, thereby triggering the extension in the consent
decree.
    The consent decree, however, does not (and cannot) dictate the
substance of EPA's final BART rulemaking under the extended deadline of
September 9, 2017; the only prerequisite to invoking this extension is
the signing of a proposal by December 9, 2016. EPA is not bound by the
consent decree to finalize the terms of the current proposal or any
similar source-specific BART rule; in fact, established principles of
administrative law require EPA to remain open-minded during the
rulemaking process. The consent decree merely established deadlines for
EPA's pending course of action. Accordingly, for purposes of meeting
the upcoming deadline of September 9, 2017, EPA is not prohibited by
the consent decree from reverting to its 2014 proposal to finalize
CSAPR as a BART alternative for Texas EGUs.
    Response: We agree that the existence of the consent decree
deadline does not dictate the substance of our action to address Clean
Air Act requirements to meet the deadline. We disagree that our only
possible lawful action for meeting the deadline is to impose a FIP
based on CSAPR. 40 CFR 51.308(e) requires that states submit a SIP
containing emission limitations that represent BART for BART eligible
sources that may reasonably be anticipated to cause or contribute to
any impairment of visibility in any mandatory Class I Federal area.
Alternatively, 40 CFR 51.308(e) allows states to establish an emissions
trading program or other alternative as long as the trading program or
other alternative will achieve greater reasonable progress toward
natural visibility conditions than BART. Where a state has failed to
submit a SIP by the applicable deadline or has submitted a SIP that has
been disapproved by the EPA, the CAA authorizes and requires EPA to
promulgate a FIP that meets the requirements of the applicable federal
statutes and regulations. Thus, EPA has the authority to promulgate a
FIP containing emission limits that represent BART for BART eligible
sources that may reasonably be anticipated to cause or contribute to
any impairment of visibility in any mandatory Class I Federal area.
Alternatively, EPA may establish an emissions trading program or other
alternative which will achieve greater reasonable progress than BART.
We are meeting requirements with valid use of discretion where
appropriate to finalize NOX BART as proposed, and to
finalize a BART alternative with emission levels similar to CSAPR to
address SO2 BART. We are not able to revive the 2014
proposal to satisfy SO2 BART for Texas EGUs because remand
obligations have led to the removal of SO2 trading
requirements for Texas. We agree that this might have been a viable
solution, but Texas declined to submit a SIP to voluntarily participate
in CSAPR to fully preserve and accommodate this option.
    Comment: The Proposed Texas BART FIP is not only cost-prohibitive,
it is not necessary to achieve the goals of the Regional Haze Program
and satisfy the requirements of the CAA. EPA's own prior modeling and
analysis show that BART for these units is more than met by current
SO2 emission levels from Texas EGUs, and the stringent
additional limits in the Proposed Texas BART FIP are not necessary.
    EPA's sensitivity analyses for Texas's SO2 CSAPR budgets
and recent emission trends in Texas demonstrate that CSAPR remains
better-than-BART. EPA's sensitivity analyses definitively confirm that
EPA's determination that CSAPR is better-than-BART in Texas remains
scientifically sound. When EPA issued the final rule promulgating the
CSAPR-for-BART provision in June 2012, EPA confirmed that the upward
adjustments to Texas's budgets under CSAPR did not adversely impact
visibility conditions in nearby Class I areas. EPA initially calculated
visibility improvements for nearby Class I areas based on a
SO2 budget for Texas of 243,954 tons/year. Following EPA's
upward adjustments to the CSAPR budget due to errors in EPA's initial
calculation, EPA revised its visibility improvement estimates based on
a SO2 budget of 294,471 tons/year. EPA's methodology
demonstrates the expected visibility improvement as a result of
implementing the CSAPR is better-than-BART provision under the original
budget and the revised budget. Even with an SO2 budget of
nearly 300,000 tons for Texas, visibility at these Class I areas was
projected to improve (not degrade).
    Recent emissions data confirm EPA's prior determination--i.e., that
Texas's emissions are well below the threshold that was previously
determined to be better-than-BART. Implementation of CSAPR Phase 1
began in 2015, and implementation of Phase 2 began in 2017. For 2015
and 2016--during CSAPR Phase 1--Texas maintained its annual emissions
of SO2 and NOX well under the budgets established
by EPA. The state-wide budget for annual SO2 in Texas is
294,471 tons, and the state-

wide budget for annual NOX in Texas is 137,701 tons. These
same budgets will apply during Phase 2, and there is no expectation
that Texas EGUS will exceed these thresholds. In fact, EPA's own data
demonstrate that Texas has not exceeded, or even approached, its annual
allowance allocations for either SO2 or NOX
during Phase I of CSAPR. Emissions of SO2 from Texas EGUs
were 260,122 tons in 2015 and 244,233 tons in 2016. As for
NOX, emissions from Texas EGUs were 107,921 tons in 2015 and
106,625 tons in 2016. Once CSAPR became effective in Texas in 2015,
SO2 emissions from Luminant's coal-fired EGUs dropped
dramatically and have trended downward. There is no reason to believe,
and EPA presented no reason, that this trend will reverse--and
certainly not to a degree that Texas EGU SO2 emissions would
exceed CSAPR budgets or call into question EPA's CSAPR better-than-BART
demonstration.
    Texas has maintained its emissions well below the budgets
established by CSAPR. The record establishes that BART for these units
can be no more stringent than current emission levels, which are well
below CSAPR budgets. In 2012, EPA concluded that ``[CSAPR] achieves
greater reasonable progress towards the national goal of achieving
natural visibility conditions than source-specific BART.'' EPA
confirmed this determination in subsequent sensitivity analyses. So
long as Texas's emissions remain below the CSAPR budgets, the operation
of Texas EGUs in such a manner will continue to be better-than-BART.
    Thus, the Proposed Texas BART FIP is based on a fundamental flaw by
EPA--that BART for Texas EGUs must be ``more emission reductions than
projected under CAIR or CSAPR.'' To the contrary, because Texas validly
remains in the annual CSAPR programs for SO2 and
NOX combined with the fact that Texas EGU SO2
emissions are well below the annual allocations, EPA has no valid basis
to change course from its 2014 proposal to finalize CSAPR for BART in
Texas in order to impose more stringent source-specific BART controls.
EPA should proceed to finalize a FIP for Texas that approves CSAPR as a
BART alternative for Texas EGUs.
    Response: We agree that emissions similar to the CSAPR budgets
would be better than BART and can be justified as a BART alternative.
To the extent the comment suggests that merely pointing to current
emissions level can satisfy the requirements of a BART alternative, we
disagree. Those emissions levels must be made enforceable, and our
final action accomplishes that. NOX BART for EGUs is
addressed by continued participation in CSAPR program for ozone
transport. With regard to SO2, the BART alternative is
designed to achieve SO2 emission levels from Texas EGUs
similar to the SO2 emission levels that would have been
realized from the SO2 trading program under CSAPR. These
measures will assure Texas' recent reductions of SO2 and
NOX will be maintained and improved upon in the future.
    Comment: The D.C. Circuit's remand of CSAPR budgets does not create
``uncertainty'' that prevents EPA from finalizing CSAPR-for-BART for
Texas EGUs. EPA says that it did not finalize its initial CSAPR-for-
BART proposal for Texas EGUs because it noted some ``uncertainty
arising from the remand of Texas' CSAPR budgets'' by the D.C. Circuit.
EPA made that claim in the now-stayed January 2016 Reasonable Progress
Rule. That claim was wrong when it was made then, and it is clearly
wrong now. There is no ``uncertainty.'' The D.C. Circuit's remand does
not prevent EPA from finalizing CSAPR as an SO2 BART
alternative for Texas EGUs.
    First, EPA's claim that there is an ``absence of CSAPR coverage for
SO2'' in Texas following the D.C. Circuit's remand is simply
wrong. Texas EGUs are and have been regulated by a BART equivalent
trading program for the entirety of the first planning period to date--
first through CAIR and, after CAIR's replacement and up to the present
day, through CSAPR. Texas EGUs are presently subject to CSAPR's annual
SO2 and NOX programs under the budgets remanded
by the D.C. Circuit, which are budgets that EPA has confirmed as
better-than-BART. EPA's prior determination that CSAPR is better-than-
BART for all states, including Texas, is scientifically sound and
remains a binding part of EPA's regulations. EPA may properly respond
to the D.C. Circuit's remand by revising Texas's annual SO2
budget (as instructed by the D.C. Circuit) after it finalizes the
proposed CSAPR-for-BART FIP for Texas.
    Second, regardless of when EPA responds to the D.C. Circuit's
remand, EPA's own sensitivity analyses confirm that were EPA to
properly respond to the remand by increasing Texas's annual
SO2 budgets so they do not over-control as instructed by the
D.C. Circuit, those revised budgets would remain better-than-BART. EPA
established a multi-step methodology to analyze whether increases in
Texas's SO2 annual budgets would change EPA's CSAPR better-
than-BART determination (which remains part of EPA's binding
regulations). First, EPA's methodology for conducting a revised
sensitivity analysis requires the identification of the Class I areas
in and near Texas that that are most likely affected by Texas
emissions. Second, EPA's analysis then ``employ[s] [the] very
conservative'' assumption that ``all of the visibility improvement''
that EPA's CSAPR better-than-BART modeling predicted for these nine
areas as a result of all CSAPR reductions from all covered states is
``solely due to [reductions] from Texas.'' Third, with this
conservative assumption, EPA then ``proportionally reduce[s]'' the
modeled visibility improvements at these nine Class I areas based on
the corrected higher SO2 budget for Texas. For example, if,
in response to the D.C. Circuit's remand, EPA were to adjust Texas's
budget to 350,000 tons, CSAPR would still be better-than-BART for Texas
and other states. Such an adjustment would be equivalent to a 57%
reduction in the number of SO2 tons reduced compared to the
original Texas CSAPR reductions that were modeled for EPA's original
CSAPR better-than-BART modeling. EPA's methodology would thus reduce
the visibility benefit accordingly by multiplying the visibility
improvement at the Class I areas affected by Texas by a factor of 0.43.
Thus, for example, the visibility improvement at Wichita Mountains from
CSAPR, even after increasing Texas's budget to 350,000 tons, would be
0.688 deciview [1.6 deciview x 0.43 = 0.688]. This methodology could be
applied to other budgets as well. Visibility improvements at nine Class
I areas in or around Texas result from the application of EPA's
sensitivity analysis of a hypothetical adjustment of Texas's CSAPR
SO2 budget to 350,000 tons per year. Thus, EPA's own
modeling shows that visibility at these Class I areas is projected to
improve (not degrade) and that the BART requirements are met even if
the CSAPR budgets are increased.
    Response: We have completed our response to the CSAPR remand by
withdrawing Texas EGUs from CSAPR requirements for PM2.5
transport. We did not act to upward adjust Texas' SO2
budget. Whether that was a proper response to the remand or whether
upward adjustments would have preserved the analytic demonstration that
CSAPR is better than BART are not issues of concern with the present
finalized action. To the extent the comment asserts that CSAPR budgets
can be used to support a better than BART alternative, we agree with
the comment and this concept is part of the

BART alternative and weight of the evidence that we deem to justify it.
    Comment: The proposed rule is legally dependent on other pending
proposed rulemakings. EPA may not proceed with this action without
first finalizing other proposed rules under the CAA on which this
action is based.
    Since 2009, Texas EGUs have been subject to federal regulatory
programs that have resulted in substantial reductions in the
NOX and SO2 emissions that have been targeted by
EPA as contributing to interstate transport and haze. In compliance
with EPA rules and precedent, Texas relied on CAIR, and then its
replacement CSAPR as achieving reductions in haze precursors from EGUs
that are ``better than BART'' in its Texas Regional Haze SIP submittal.
In the unlawful proposed rule, EPA rejects its prior position that
Texas EGUs are exempt from BART due to participation in CSAPR. Yet,
Texas EGUs continue to this day to be subject to CSAPR requirements for
NOX and SO2. While EPA has proposed to withdraw
CSAPR SO2 requirements for Texas EGUs, it has not yet done
so and those EGUs remain subject to CSAPR allocations for both
NOX and SO2 under federal and state laws and
permits. Additionally, EPA's proposal to withdraw the CSAPR FIP with
respect to SO2 has been challenged in that rulemaking docket
as unlawful and not in accordance with the court decision remanding
that action to EPA.
    As a result, EPA may not proceed with the disapproval of Texas'
reliance on CSAPR as ``better than BART'' until such time that the
proposal is legally finalized in compliance with the Court decision
that remanded that rule to EPA. Once that rule is legally finalized,
then Texas should be given an opportunity to address whether and how
that affects the state's regional haze program before a FIP is
considered.
    Response: As was made clear by our proposal, we agree our rule is
dependent on other proposed and now finalized rulemakings. Nothing in
our proposal or final action prevents Texas from addressing the State's
regional haze program under its SIP planning authorities. Texas did not
request that we withhold our action to withdraw CSAPR SO2
requirements for Texas EGUs, and it did not submit comments to oppose
that action. We disagree that anything in the sequencing of actions
would allow us to suspend our FIP obligations when there is no SIP to
address the requirements.
    Comment: The effort to impose BART controls is the result of the
proposed withdrawal of Texas from the CSAPR Phase 2 or annual trading
program for SO2. Compliance with regional haze obligations
for BART-eligible facilities in Texas has depended on CAIR-equal BART
and CSAPR-equal BART and removing Texas from CSAPR results in
significant disruption and costs to planned future compliance for these
facilities. EPA seeks these excessive controls which will achieve
limited visibility benefits. EPA should take the proper approach and
follow the remand without vacatur of the D.C. Circuit, revise the
trading budgets and then finalize CSAPR as compliance strategy for BART
in lieu of this proposal.
    Response: We completed our response to the CSAPR remand in a
separate action and refer Commenter there. We are finalizing a BART
alternative for SO2 BART.

E. Comments on the Identification of BART-Eligible Sources

    Comment: We received comment from the owners of Coleto Creek
stating that in the Texas Regional Haze SIP, TCEQ determined that
Coleto Creek Unit 1 was not a BART-eligible source, based on its
interpretation and application of its SIP-approved regional haze rules
at 30 TAC Chapter 116, Subchapter M. In implementing its rules, TCEQ
prepared questionnaires that sought the information needed to render
its BART-eligibility determinations.\66\ As a result of this TCEQ-led
process, TCEQ determined that Coleto Creek Unit 1 was not BART-eligible
because it was not built, and did not commence operation, until 1980,
which is well after the August 7, 1977 applicability date. Coleto Creek
Unit 1 has reasonably relied on the state's eligibility determination
in evaluating its obligations under the Regional Haze Rule program.
EPA's decision to reject TCEQ's BART-eligibility determination for
Coleto Creek Unit 1 under 30 TAC 116.1500 is unsupported.
---------------------------------------------------------------------------

    \66\ See October 24, 2005 letter from Al Espinosa, Coleto Creek
Power Station, #TX187-0023-0001, Docket Item No. EPA-R06-OAR-2016-
0611-0023 at p. 6.
---------------------------------------------------------------------------

    Response: The commenter states that because Coleto Creek Unit 1 did
not commence operations until 1980, it should be determined to be not
BART-eligible, as was determined by the TCEQ. However, we believe the
TCEQ erred in not listing Coleto Creek Unit 1 as being BART-eligible.
The date test for BART-eligibility is whether the units was ``in
existence on August 7, 1977,'' and began operation after August 7,
1962. The BART rule defines as ``in existence on August 7, 1977'' as
follows (70 FR 39159):
    What does ``in existence on August 7, 1977'' mean?
    2. The regional haze rule defines ``in existence'' to mean that:
``the owner or operator has obtained all necessary preconstruction
approvals or permits required by Federal, State, or local air pollution
emissions and air quality laws or regulations and either has (1) begun,
or caused to begin, a continuous program of physical on-site
construction of the facility or (2) entered into binding agreements or
contractual obligations, which cannot be canceled or modified without
substantial loss to the owner or operator, to undertake a program of
construction of the facility to be completed in a reasonable time.'' 40
CFR 51.301.
    The owner of Coleto Creek Unit 1 provided information that onsite
construction began prior to August 7, 1977. Thus, Coleto Creek Unit 1
satisfies the above criteria as being ``in existence on August 7,
1977.'' Therefore, we disagree with the commenter and continue to find
that Coleto Creek Unit 1 is BART-eligible. The NOX BART
requirement for Coleto Creek is met by relying on CSAPR as an
alternative to EGU BART for NOX. The SO2 BART
requirement is met by the intrastate trading program FIP that we are
finalizing in this action and to which Coleto Creek will be subject.
The PM BART requirement is met by our determination that the visibility
impacts of PM emissions from Coleto Creek are too small to be
considered to cause or contribute to visibility impairment at any Class
I area and we determined the facility screens out and is not subject to
PM BART.

F. Comments on PM BART

    We previously proposed to disapprove the SIP's subject-to-BART
determinations for PM, on the grounds that the SIP had based these
determinations on reliance on a BART alternative for SO2 and
NOX and, as a result, considered only the contribution of PM
emissions to visibility impairment, and to adopt source-specific PM
emission limits to fill the SIP gap. In that context, we received
several comments related to PM BART issues. Now, however, we have
determined it is appropriate to adopt a BART alternative to address
SO2 and NOX and therefore find Texas' original
SIP was correct in considering only the contribution of PM emissions.
Considering only PM emissions, all sources considered in the Texas SIP
were demonstrated to screen out of the need for source specific PM BART
emission limits.
    Also, as explained above, we have identified additional sources as
BART-eligible that were not considered in the

2009 Texas Regional Haze SIP. As discussed elsewhere, we have
determined that the impact due to PM emissions from these additional
sources are also below the BART screen level. Thus, the SIP's
determination that none of the BART-eligible EGUs are subject-to-BART
for PM is correct and approvable. As a consequence, there is no SIP gap
needing to be filled by a FIP. Because we are approving EGU PM BART
screening determinations that result in no EGUs being subject to PM
BART analysis, comments supporting or alleging errors in the details of
our PM BART five-factor analysis and our proposed PM BART technology
selections and emission limits are not relevant. We address in this
section comments that are relevant to whether it is appropriate to
approve the portion of this 2009 SIP submission and EPA's analysis in
our proposal that determined that no PM emission limits for Texas EGUs
are needed to satisfy the BART requirement because the visibility
impacts of PM emissions from BART-eligible EGUs do not cause or
contribute to visibility impairment. The information in section III.A.
on the history of our proposals regarding the EGU PM BART element of
the 2009 Texas SIP submission and EPA's proposals is useful background
for understanding the comments and our responses on this topic.
    Although we are not finalizing the MATS-based PM limits proposed as
PM BART for the coal-fired EGUs, this regional haze action does not
affect the existing MATS requirements for these units. We are also not
finalizing the fuel oil sulfur percentage limits that we proposed for
gas/fuel oil-fired EGUs; the same limits in existing permits for these
sources are not affected by our action.
    Comments: AEP states that we provide no basis for not approving the
TCEQ's PM BART determination in 2016 or logical support for our
decision to proceed with modeling PM in the proposed Texas BART FIP.
AEP believes that when a state is provided statutory deference in
implementing the Regional Haze program, EPA must support its decision
for not approving the state's determination. While AEP also agrees that
current PM requirements for sources complying with MATS are sufficient
for meeting PM BART for Welsh Unit 1, it disagrees that PM BART is even
warranted at all or that EPA has provided adequate basis for declaring
that TCEQ's screening analysis is no longer reliable. AEP says that
buried in a footnote, EPA grasps at some claim of error that Texas' PM
BART determinations only looked at the impact of PM emissions on
visibility, that Texas can only take this approach when the BART
requirements of NOX and SO2 are satisfied, and
that Texas' error of not identifying several PM BART eligible sources
is grounds for disapproval. AEP believes this logic is unfounded and
the situation is created by EPA's piecemeal approach to rulemaking. AEP
agrees with EPA's conclusion that gas-fired units that occasionally
burn fuel oil should have no further control. AEP will limit burning
fuel oil with a sulfur content of 0.7% as currently required by its
permit. However, EPA has not provided sufficient reasons to be
addressing PM BART. EPA should finalize its earlier proposal to approve
Texas' determination that sources in Texas are not subject to PM BART.
    The Lower Colorado River Authority disagrees with the disapproval
of the Texas PM BART demonstration.
    The TCEQ and the Public Utilities Commission of Texas stated that
our reliance on language in a guidance memo \67\ to bar TCEQ from
conducting pollutant-specific modeling to determining BART eligibility
was incorrect. The TCEQ believes this memo did not state that the
TCEQ's pollutant-specific modeling is only appropriate when BART for
other pollutants is satisfied with a BART alternative such as the CAIR
or CSAPR. The TCEQ believes the memo states that such modeling may be
appropriate where an alternative program is used for other pollutants.
The TCEQ also believes we incorrectly claimed that its SIP acknowledges
PM-only modeling is inappropriate where an alternative to BART is not
employed.\68\
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    \67\ Regional Haze Regulations and Guidelines for Best Available
Retrofit Technology (BART) Determinations, Joseph Paisie, EPA
Geographic Strategies Group, July 19, 2006.
    \68\ Technical Support Document for the Texas Regional Haze BART
Federal Implementation Plan, BART FIP TSD, Docket ID No. EPA-R06-
OAR-2016-0611-004, page 26, footnote 39.
---------------------------------------------------------------------------

    The TCEQ states that our CAMx modeling supports the conclusions
from the screening modeling conducted by it that shows these same units
did not meet the 0.5 deciview (dv) threshold.\69\ Furthermore, the TCEQ
states that we found that for gas-fired units, PM emissions are
``inherently low,'' and that existing controls plus compliance with the
MATS filterable PM limit of 0.03 lb/MMBtu is already BART, further
supporting its conclusion that there are no significant visibility
impacts from PM emissions from these sources and BART controls for PM
are unnecessary. Thus, the TCEQ reasons, a FIP for PM BART is
unnecessary and the EPA should approve the screening modeling the TCEQ
conducted, as we proposed to do in January 2015.
---------------------------------------------------------------------------

    \69\ Id, at 82.
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    Luminant provided comments similar to those above. Luminant added
that it believes that Texas remains in CSAPR so there is no basis for
us to deviate from our prior proposal to approve Texas's PM BART
determination. Luminant also stated that our reliance on a Ninth
Circuit Court decision to support our rejection of pollutant-specific
BART screening is incorrect because the case in point relied upon the
BART de minimis exemption, which does not apply in this instance.
    Response: We are approving the EGU PM BART element of Texas's 2009
SIP submittal. Under the combination of reliance on the CSAPR ozone-
season NOX trading program to satisfy NOX BART
and reliance on the FIP's intrastate trading program for SO2
emissions to satisfy SO2 BART, it is appropriate for
determinations of whether a BART-eligible EGU is subject to BART for PM
to be based only on the visibility impact of the source's PM emissions.
It is not necessary for us to respond to the comments stating that a
PM-only analysis would be appropriate even if both SO2 and
NOX were not addressed by trading programs.
    In particular, TCEQ's comments are correct that the BART Guidelines
do not prohibit pollutant-specific screening. The July 19, 2006
guidance memo states that EPA does not generally recommend a pollutant-
specific screening approach, however, such a screening approach may be
appropriate for PM in certain situations. The memo provides the
situation of a state relying on CAIR for NOX and
SO2 BART as an example where pollutant-specific screening
for PM may be appropriate. We agree with TCEQ that the memo's intention
is not to limit PM-only analysis to SIPs that rely on CAIR. While we
disagree with TCEQ's position that a PM-only analysis is appropriate in
a situation involving source-specific SO2 BART emission
limits, the approaches promulgated here for SO2 and
NOX BART are BART alternatives and are similar to the CAIR
situation described in the memo. Therefore, we find that the pollutant
specific PM screening approach in TCEQ's original 2009 SIP submittal is
appropriate and demonstrates that the sources covered by the BART
alternative program for SO2 screen out of PM BART. For BART-
eligible EGU sources not participating in the BART alternative program
for SO2, all these sources screened out of BART for all
visibility impairing pollutants utilizing model plants and CALPUFF
modeling as described in our proposed rule and

BART Screening TSD. Therefore, we are approving the determination that
no Texas EGUs are required to have source-specific PM emission limits
in order for the BART requirement to be met. This approval is
consistent with our December 2014 proposal for PM BART, in which EPA
proposed to rely on Texas' CSAPR participation for SO2 and
NOX BART and to approve the SIP's determinations regarding
the need for PM emission limits. See 79 FR 74817, 74848 (January 13,
2015). We are also determining that other sources that EPA identified
in our December 2016 proposal as BART-eligible that were not identified
as BART eligible in TCEQ's 2009 Regional Haze SIP are also screened out
from PM BART.
    Comment: The Sierra Club states that we should finalize our
proposed disapproval of Texas's PM BART determinations, which assumed
that SO2 and NOX emissions contributing to PM
formation would be regulated under CSAPR, see 82 FR at 935. Following
the D.C. Circuit Court's remand of CSAPR, SO2 emissions from
Texas sources are no longer limited by CSAPR. The assumption underlying
Texas's PM BART determinations--that CSAPR would limit emissions of PM
precursors from Texas sources--is now inaccurate; therefore, reasons
the Sierra Club, we must disapprove the State's PM BART determinations.
    Response: We note that the D.C. Circuit Court remanded the budget
for Texas EGUs in the CSAPR trading program for SO2 without
vacatur, so the commenter's statement that Texas EGUs are no longer
limited by CSAPR was not true at the time the comment was offered. It
is true now as a result of our recent action to remove Texas EGUs from
the annual SO2 and NOX trading programs. However,
a large set of Texas EGUs will, under the final FIP, be subject to
CSAPR for ozone-season NOX and the intrastate trading
program FIP for SO2. For these EGUs, the BART guidelines and
our guidance allow for the subject-to-BART for PM determination to be
based on only the impacts of PM emissions on visibility. For the BART-
eligible EGUs that will not be required to participate in the FIP's
intrastate trading program, our analysis indicates that even when all
three pollutants are included in the modeling, all of these sources
affect visibility at surrounding Class I Areas by less than 0.5 dv,
thus screening out of being subject to PM BART.
    Comment: EPA in its previous rulemaking on the reasonable progress
measures for the Texas and Oklahoma regional haze plans initially
proposed to accept Texas' finding that no PM BART controls were
necessary for EGUs ``based on a screening analysis of the visibility
impacts from just PM emissions . . . .'' In its current Texas BART
rulemaking, EPA states that ``[i]n connection with changed
circumstances on how Texas EGUs are able to satisfy NOX and
SO2 BART, we are now proposing to disapprove the portion of
the Texas Regional Haze SIP that evaluated the PM BART requirements for
EGUs.'' The changed circumstances EPA refers to is the removal of Texas
sources from the SO2 caps of the CSAPR rule. Unless a source
is subject to a BART alternative or is otherwise determined to be
exempt from BART for a particular pollutant, EPA's regulations and BART
guidelines do not generally provide for exemptions from a five-factor
BART analysis for a specific pollutant. Under EPA's BART Guidelines and
the definition of BART, once a source has been determined to be subject
to BART, a five-factor BART analysis must be done for each pollutant
pursuant to 40 CFR part 51, 51.301 and Appendix Y, section IV.A. So,
EPA is correct that it must address BART for PM for the BART-subject
sources in Texas.
    Response: The premise in the comment that EGUs in Texas will not be
subject to a BART alternative for both NOX and
SO2 is incorrect, given the content of this final action.
    Comment: Coleto Creek Unit 1 should not be subject to any FIP
emission limits, because it should not be determined to be BART-
eligible.
    Response: Texas' 2009 SIP submission did not include Coleto Creek
Unit 1 as a BART-eligible source and consequently the SIP did not
present any analysis of whether it is subject-to-BART, while we are
determining in this action that Coleto Creek Unit 1 is BART-eligible.
However, we evaluated the available modeling and other analyses and we
have concluded that this information shows minimal impacts from PM from
this particular BART-eligible source. Modeled PM impacts from Coleto
Creek Unit 1 are expected to be much less than 0.32 delta deciviews
(see Section III.4).
    Comment: Requiring the Stryker and Graham units to switch to ultra-
low-sulfur diesel would significantly improve visibility. Requiring
this switching at Stryker would improve visibility by more than 0.5 dv
at Caney Creek, and switching to ultra-low-sulfur diesel at Graham
would improve visibility by 0.85 dv at Wichita Mountains.
    Response: Insofar as this is a comment on our proposed source-
specific FIP emission limits to address BART for PM, it is not
necessary for us to respond because we are approving the SIP and not
promulgating any such limits in this action. We note that the cited
visibility benefits of switching to low-sulfur fuel reflect assumed
reductions in both direct PM emissions and SO2 emissions
from these two sources. The Stryker and Graham units are both covered
by the intrastate trading program for SO2 and CSAPR for
NOX, so it is appropriate that the subject-to-BART
determination be made on the basis of the impacts of direct PM
emissions alone. Those impacts are less than 0.5 dv.
    Comment: Texas identified 126 sources as BART-eligible or
potentially BART eligible.
    Yet Texas ultimately concluded that no BART-eligible source is
subject to BART. Texas's determination is based in part on the
unsupported selection of 0.5 dv as the threshold for contribution to
visibility impairment. EPA must disapprove Texas's determination as to
the sources subject to BART. Texas adopted 0.5 dv as the threshold for
``contribution'' to visibility impairment. Texas provided no
justification for using a 0.5 dv threshold. There is no documentation
in the record as to how or why Texas selected this threshold, and there
is no legal support for such threshold. EPA's BART Guidelines do not
authorize states automatically to use a 0.5 dv contribution threshold.
Instead, the BART Guidelines state only that ``any threshold that you
use for determining whether a source `contributes' to visibility
impairment should not be higher than 0.5 deciviews. In the next
sentence, the Guidelines instruct each state that it ``should consider
the number of emissions sources affecting the Class I areas at issue
and the magnitude of the individual sources' impacts.'' There is no
evidence in the record that Texas ever conducted this analysis.
Furthermore, the Guidelines conclude that ``a larger number of sources
causing impacts in a Class I area may warrant a lower contribution
threshold.'' As Texas's list of 126 BART eligible sources indicates, a
large number of sources impact the Class I areas in Texas and in
neighboring states. Indeed, the subset of sources that screened out of
BART based on individual modeling have a combined, baseline impact of
nearly 10 deciviews. Thus, the situation in Texas is exactly what EPA
had in mind when it noted that a contribution threshold lower than 0.5
dv may be appropriate. Had Texas followed the BART Guidelines, it may
well have selected a threshold lower than 0.5 dv. Using a lower
contribution threshold would change Texas's conclusion as to which

sources are subject to BART because there are sources with a baseline
impact just below 0.5 deciviews. EPA has a statutory responsibility to
ensure that a SIP meets all applicable Clean Air Act requirements and
is supported by the record. Here, Texas's use of a 0.5 dv threshold has
two fatal flaws: It is not based on the analysis prescribed by the BART
Guidelines, and it is not supported by any analysis whatsoever in the
record. Therefore, EPA must disapprove Texas's conclusions that sources
are not subject to BART, where Texas screened out sources because of a
visibility impact below 0.5 deciviews.\70\
---------------------------------------------------------------------------

    \70\ This comment was submitted to a public docket (separate
from the docket established for this action), in response to our
December 2014 proposal (79 FR 74817, 74853-54 (Dec. 16, 2014)) to
approve the subject-to-BART determinations in Texas' 2009 SIP
submission and to disapprove the reasonable progress and some other
elements of that SIP submission. See Docket Item No. EPA-R06-OAR-
2014-0754-0067. We never took final action on PM BART, and did not
respond to the comment. We are responding to it today because of its
relevance to this final action.
---------------------------------------------------------------------------

    Response: EPA's BART Guidelines allow states conducting source-by-
source BART determinations to exempt sources with visibility impacts as
high as 0.5 dv. While we agree that a state may choose to use a lower
threshold, this should be based on consideration of not only the number
of sources, but the proximity to the Class I area and the potential
combined visibility impacts from a group of sources. States have the
discretion within the CAA, Regional Haze Rule, and BART Guidelines to
set an appropriate contribution threshold considering the number of
emissions sources affecting the Class I areas at issue and the
magnitude of the sources' impacts.

G. Comments on EPA's Source-Specific SO2 BART Cost Analyses

    Comment: We received a large number of comments from the EGU owners
covered under our proposal and environmental groups concerning various
aspects of the SO2 BART cost analyses we performed for the
coal-fired EGUs. These comments included both criticisms of and support
for our basic approach, the tools we used, and various individual
aspects of our cost analyses. We also received Confidential Business
Information (CBI) comments from the owner of one of the EGUs covering
the same areas.
    We also received comments from environmental groups stating that we
should have required the gas-fired units that occasionally burn fuel
oil to minimally switch to Ultra-Low-Sulfur Diesel (ULSD) in lieu of
our proposed BART determination that these units be limited to 0.7%
fuel oil by weight. These commenters argued that our estimate of the
price per gallon for ULSD was too high and that in any case, the total
annual cost to make the switch is very low. They also argue that
requiring the Stryker and Graham units to switch to ultra-low-sulfur
diesel would significantly improve visibility.
    Response: Due to the comments we received requesting a BART
alternative in lieu of source-specific EGU BART determinations, we are
finalizing a SO2 trading program as an alternative to
source-by-source BART. As a consequence, we believe that comments
concerning the SO2 BART cost analyses we performed on the
coal-fired EGUs and these gas-fired units that occasionally burn fuel
oil are no longer relevant. The trading program, by its nature,
provides sources with flexibility in meeting the requirements. As a
result, we expect compliance for sources to be extremely cost-
effective. The program addresses both BART eligible and non-BART
eligible EGUs. The combination addresses 89% of the emissions (based on
2016 annual emissions) that would have been addressed by CSAPR and, as
a result, EGU emissions in Texas will be similar to emission levels
anticipated in the CSAPR better than BART demonstration and will
achieve greater reasonable progress than BART.

H. Comments on EPA's Modeling

1. Modeling Related to Screening out BART-eligible sources based on
CALPUFF Modeling and Model Plant analysis
    Comment: We received comments stating that we used an outdated
version of CALPUFF and CALMET in our CALPUFF analyses and there are
more recent EPA approved versions of CALPUFF and CALMET. The commenter
indicated that there are more recent non-regulatory versions of CALPUFF
(such as version 6.4) that include a number of technological
improvements that could have been used. The commenter also indicated we
did not follow USDA Forest Service Guidance that recommend using
Mesocscale Model Interface Program (MMIF) for generating met fields for
CALPUFF.\71\ The commenter concluded that EPA's CALPUFF analysis was
less reliable because of these issues.
---------------------------------------------------------------------------

    \71\ USDA Forest Service, Guidance on the Use of the Mesoscale
Model Interface Program (MMIF) for Air Quality Related Values Long
Range Transport Modeling Assessments (Aug. 2016).
---------------------------------------------------------------------------

    Response: For those BART-eligible EGUs that are not covered by the
BART alternative for SO2, we are finalizing determinations
that those EGUs are not subject-to-BART for NOX,
SO2 and PM as proposed, based on the methodologies utilizing
model plants and CALPUFF modeling as described in our proposed rule and
BART Screening TSD. As mentioned in the BART screening TSD, we used
versions (CALPUFF v5.8.4 and an existing CALMET data set that utilized
CALMET v5.53a) that do not significantly differ from the current
regulatory versions of CALPUFF (v5.8.5) and CALMET (v5.8.5). The
current regulatory versions do include some additional bug fixes but
the bugs that were fixed are not expected to significantly change the
results for the modeling assessments we have done. The 2016 USDA Forest
Service Guidance was not released until August of 2016 and no BART
modeling was conducted by states and RPOs using MMIF. The USDA Forest
Service Guidance is more germane for future SIP developments and any
visibility analyses for other regulatory assessments in the future.
    In considering the comment that we should use a more recent version
of CALPUFF (6.4) or an earlier version 6.112, we considered the
regulatory status of CALPUFF for visibility analyses and what analyses
are needed to utilize an updated CALPUFF modeling system. The
requirements of 40 CFR 51.112 and 40 CFR part 51, Appendix W, Guideline
on Air Quality Models (GAQM) and the BART Guidelines which refers to
GAQM as the authority for using CALPUFF, provide the framework for
determining the appropriate model platforms and versions and inputs to
be used. Because of concern with CALPUFF's treatment of chemical
transformations, which affect AQRVs, EPA has not approved the chemistry
of CALPUFF's model as a ``preferred'' model. The use of the regulatory
version is approved for increment and NAAQS analysis of primary
pollutants only. Currently, CALPUFF Version 5.8, is subject to the
requirements of GAQM 3.0(b) and as a screening model, GAQM 4. CALPUFF
Versions 6.112 and 6.4 have not been approved by EPA for even this
limited purpose. The versions of CALPUFF, version 6.112 or 6.4, that
the commenter recommended could be used to provide modeling analyses of
BART eligible sources that have not gone through a full regulatory
review in accordance with 40 CFR part 51 Appendix W Section 3.2.2.
Furthermore, the currently available information does not support the
approval of these versions of the CALPUFF model for use in making BART
determinations. In addition, if these versions of the model

were acceptable for use, EPA would have to reconsider whether using the
98th percentile impact for determining impairment was appropriate.
Therefore, EPA does not believe the use of CALPUFF version 6.112 or 6.4
is appropriate for this rulemaking. We believe we have made the
appropriate choice in using CALPUFF version 5.8. For further
discussion, see our Modeling RTC and the response to comments in our
previous New Mexico Final FIP in 2011.\72\
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    \72\ 76 FR 52388, 52431-52434 (Aug. 22, 2011).
---------------------------------------------------------------------------

    Comment: We received a number of comments concerning the acceptable
distances/range for which CALPUFF modeling results should be used for
BART screening. A number of commenters indicated that EPA has
repeatedly stated that 300 km should be the maximum distance for
CALPUFF modeling results and even cited to some past actions (several
FIPs--Arkansas, Oklahoma, Montana, and New Mexico) where EPA has
indicated that 300 km was the general outer distance for CALPUFF.
Commenters also raised past promulgation of CALPUFF in 2003 and IWAQM
guidance/reports to support the claim that 300 km is the acceptable
outer range of CALPUFF. TCEQ commented we should not use CALPUFF for
distances beyond 400 km. Two commenters indicated that EPA had
inappropriately reported CALPUFF results for distances of 412 km and
436.1 km, well outside of 300 km. Another commenter indicated we
included some model plants at distances greater than 400 km in our
model plant screening analysis.
    Other commenters indicated that we should use the modeling results
from CALPUFF for BART screening at ranges much greater than 400 km.
They stated that CALPUFF over-predicts visibility impacts at distances
greater than 300 km; therefore, CALPUFF is an acceptable and
conservative tool for screening BART sources at large distances from
Class I areas. We received comments from several different companies
(NRG, LCRA, Coleto Creek, and Luminant) that provided contractor
(AECOM) analysis with opinions on the acceptable range of CALPUFF.
AECOM's report for LCRA included CALPUFF modeling results for 14 Class
I areas with distances out to more than 1000 km and asserted that TCEQ
and EPA had utilized CALPUFF previously in screening out sources from
being subject to a full BART analysis in the 2009 Texas regional haze
SIP submission, our 2014 proposal, and our 2015 final action. Some
comments were supportive of using CALPUFF results at distances of 400-
1000 + km,\73\ while others opposed using CALPUFF beyond 300 km if the
results did not screen a facility out of a full BART analysis.
---------------------------------------------------------------------------

    \73\ For example, see comment from Andrew Gray, Footnote 11,
``For example, Texas used CALPUFF to perform BART modeling for Alcoa
Inc, RN100221472 (nearest Class I area 490 km); Equistar Chemicals
LP, RN 100542281 (nearest Class I area 517 km); ExxonMobil,
RN102579307 and RN102450756 (nearest Class I areas 526 and 482 km,
respectively); and Invista, RN104392626 and RN102663671 (nearest
Class I areas 472 and 614 km, respectively). See February 25, 2009
Texas Regional Haze Plan, Chapter 9 at pages 9-9 through 9-14,
available at https://www.tceq.texas.gov/airquality/sip/bart/haze_sip.html. South Dakota used CALPUFF for Big Stone's BART
determination, including its impact on multiple Class I areas
further than 400 km away, including Isle Royale, which is more than
600 km away. See 76 FR 76656. Nebraska relied on CALPUFF modeling to
evaluate whether numerous power plants were subject to BART where
the ``Class I areas [were] located at distances of 300 to 600
kilometers or more from'' the sources. See Best Available Retrofit
Technology Dispersion Modeling Protocol for Selected Nebraska
Utilities, p. 3. EPA Docket ID No. EPA-R07-OAR-2012-0158-0008. EPA
has approved reliance on these models.''
---------------------------------------------------------------------------

    A number of commenters also raised concerns with the accuracy of
the CALPUFF model and several uncertainty issues related to the CALPUFF
model and results from the model. We also received the comment that
CALPUFF's regulatory status as a preferred model recently changed and
that this change raises a question of whether CALPUFF should have been
used for the Proposed Texas BART FIP.
    Response: As previously discussed and included in our record for
our proposal we did use direct CALPUFF modeling results of facilities
out to 432 km for some very large EGU facilities (very large emissions
from tall stacks). We also used CALPUFF for model plants for screening
of sources beyond 360 km to a Class I Area, but the actual distance to
a Class I Area was 360 km or less for each of the model plants used for
screening of sources. In our 2014 proposed action \74\ and the 2015
final action \75\ on Texas regional haze we approved the use of CALPUFF
to screen BART-eligible non-EGU sources at distances of 400 to 614 km
for some sources. In those actions, we weighed the modeling results
that were mostly well below 0.5 delta-dv with the potential uncertainty
of CALPUFF results at these greater distances outside the typical range
of CALPUFF in deciding how to use the results in screening of
facilities. We disagree with the comment that it was inappropriate to
rely on CALPUFF to screen BART-eligible EGU sources at ranges beyond
400 km and that it would not be consistent with our past approval of
the BART screening modeling included in the 2009 Texas Regional Haze
SIP of non-EGU BART sources.\76\
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    \74\ 79 FR 74818 (Dec. 16, 2014).
    \75\ 81 FR 296 (Jan. 5, 2016).
    \76\ We note that the Fifth Circuit Court of Appeals remanded
the rule in its entirety. See Texas v. EPA, 829 F.3d 405 (5th Cir.
2016).
---------------------------------------------------------------------------

    It has been asserted by the commenters that CALPUFF overestimates
visibility impacts at greater distances (greater than 300/400 km) and
therefore some commenters claimed that use of CALPUFF is conservative
and acceptable for screening BART sources. We disagree with this
comment. EPA has seen situations of both under-prediction and over-
prediction at these greater distances. EPA has indicated historically
that use of CALPUFF was generally acceptable at 300 km and for larger
emissions sources with elevated stacks. We and FLM representatives have
also allowed or supported the use of CALPUFF results beyond 400 km in
some cases other than the Texas actions as pointed out by
commenters.\77\ EPA has a higher confidence level with results within
300 km and when analysis of impacts at Class I areas within 300 km is
sufficient to inform decisions on BART screening and BART
determinations, we have often limited the use of CALPUFF results to
within 300 km as there are fewer questions about the suitability of the
results. However, that does not preclude the use of model results for
sources beyond the 300 km range with some additional consideration of
relevant issues such as stack height, size of emissions, etc. As one
commenter pointed out, EPA and FLM representatives have utilized
CALPUFF results in a number of different situations when the range was
between 300-450 km. The model plants utilized in our model plant
screening analysis were modeled at distances of 300-360 km from the
Class I area. In our model plant analysis, we found that in some
situations there was a difference in whether or not a source screened
out based on the distance between the model plant and the Class I area.
Some initial model plant runs were done at distances of 201-300 km from
a Class I Area and yielded higher Q/D ratios than the same model plant
evaluation with the same modeled visibility impact at 350-360 km (only
20% more than 300 km).\78\ This difference and the lower Q/

D modeling for the model plant located at a greater distance from the
Class I area indicated that using the model plant modeling at 300 km or
less was overly conservative when we are evaluating facilities at
distances of 360-600 km. Therefore, we chose the range that we thought
was appropriate in the context of the distances of the sources being
evaluated with that model plant. A distance of 300-360 km also fell
within a range for which we have evaluated CALPUFF results a number of
times and felt comfortable with using for large elevated point sources,
and in most cases the comparison of Q/D ratios of the facility to model
plant were not similar and the facility screened out with a significant
safety margin.\79\
---------------------------------------------------------------------------

    \77\ See comments from Andrew Gray, n 11 (which is listed in its
entirety earlier in this document) citing examples of modeled
impacts from sources at distances greater than 300 km in Texas,
Nebraska, and South Dakota.
    \78\ We did iterative modeling with the model plants to model
emissions at a level that would yield a value just under the
screening level of 0.5 del-dv, typically a value around 0.49 del-dv.
In these model distance sensitivity runs when we used the same
number of sources and stack parameters but varied the emissions to
yield 98th percentile max impacts of approximately 0.49 del-dv. We
found that model plants at 350-360 km range had lower resulting Q/Ds
than the same model plants at 300 km, thus sources more easily
screened out using model plants at 350-360 km.
    \79\ See our Screening of BART TSD.pdf (EPA-R06-OAR-2016-0611-
0005.pdf); most sources had Q/D values on the order 30-50% of the
critical Q/D from the model plant.
---------------------------------------------------------------------------

    We note that we also had direct CALPUFF screening of some coal-
fired plants out to 412 km with NOX, SO2, and PM
in our proposal. The impacts of these facilities in the proposal
screening modeling were typically very large and well above the 0.5
del-dv, so even considering that there are more uncertainties at
distances greater than 300 km the impacts were large enough that it was
clear that these facilities would have impacts above the threshold
based on impacts from the 3 pollutants.\80\ The BART Guidelines
indicate other models may be used on a case-by-case basis. CAMx is a
photochemical modeling platform with a full chemistry mechanism that is
also suited for assessing visibility impacts from single facilities/
sources at longer distances where CALPUFF is more uncertain (such as
distances much greater than 300 km). Texas and EPA have previously
approved the use of CAMx for determining source impacts for BART
screening purposes, and we also decided to supplement our CALPUFF
analysis for some large coal-fired sources with CAMx modeling. Our CAMx
modeling of these coal-fired sources in the proposal further supported
the magnitude of the assessed impacts were well above 0.5 del-dv
(NOX, SO2, and PM) for these facilities that fell
into the greater than 300 km range. We note that this screening
modeling for these coal-fired facilities directly modeled with CALPUFF
beyond 300 km and also modeled with CAMx is not pertinent to this final
action since these coal-fired sources are participating in the
SO2 trading program and we are not finalizing subject to
BART determinations for these sources.
---------------------------------------------------------------------------

    \80\ Id. For example, Big Brown was 404 km from WIMO and the
maximum impacts with NOX, SO2, and PM was
4.265 del-dv (over 8 times the 0.5 del-dv threshold).
---------------------------------------------------------------------------

    Due to the comments we received requesting a BART alternative in
lieu of source-specific EGU BART determinations, we are finalizing a
SO2 trading program as an alternative to source-by-source
BART. With the NOX BART coverage from CSAPR, all the BART-
eligible sources participating in the SO2 trading program
only have PM emissions that have to be assessed for screening and
potential subject to PM BART determinations. As discussed elsewhere, we
are approving the determination in the 2009 Texas Regional Haze SIP
that PM BART emission limits are not required for any Texas EGUs.
    We disagree with the commenter's characterization of uncertainties
raised that invalidate the CALPUFF modeling results. We respond to
comments raised briefly here and in our Modeling RTC. We have also
responded to a number of these issues in our past FIP actions.\81\
---------------------------------------------------------------------------

    \81\ For example, see Arkansas FIP, 81 FR 66332, 66355- 66413
(Sept. 27, 2016) and the Response to Comments, Docket No. EPA-R06-
OAR-2015-0189.
---------------------------------------------------------------------------

    In response to the court's 2002 finding in American Corn Growers
Ass'n. v. EPA \82\ that we failed to provide an option for BART
evaluations on an individual source-by-source basis, we had to identify
the appropriate analytical tools to estimate single-source visibility
impacts. The 2005 BART Guidelines recommended the use of CALPUFF for
assessing visibility (secondary chemical impacts) but noted that
CALPUFF's chemistry was fairly simple and the model has not been fully
tested for secondary formation and thus is not fully approved for
secondary-formed particulate. In the preamble of the final 2005 BART
guidelines, we identify CALPUFF as the best available tool for
analyzing the visibility effects of individual sources, but we also
recognized that it is a model that includes certain assumptions and
uncertainties.\83\ Evaluation of CALPUFF model performance for
dispersion (no chemistry) to case studies using inert tracers has been
performed.\84\ It was concluded from these case studies the CALPUFF
dispersion model had performed in a reasonable manner, and had no
apparent bias toward over or under prediction, so long as the transport
distance was limited to less than 300km.85 86 As discussed
above EPA has indicated historically that use of CALPUFF was generally
acceptable at 300 km and for larger emissions sources with elevated
stacks we and FLM representatives have also allowed or supported the
use of CALPUFF results beyond 400 km in some cases.
---------------------------------------------------------------------------

    \82\ Am. Corn Growers Ass'n v. EPA, 291 F.3d 1 (D.C. Cir. 2002).
    \83\ 70 FR 39104, 39121 (July 6, 2005).
    \84\ ``[M]ore recent series of comparisons has been completed
for a new model, CALPUFF (Section A.3). Several of these field
studies involved three-to-four hour releases of tracer gas sampled
along arcs of receptors at distances greater than 50km downwind. In
some cases, short-term concentration sampling was available, such
that the transport of the tracer puff as it passed the arc could be
monitored. Differences on the order of 10 to 20 degrees were found
between the location of the simulated and observed center of mass of
the tracer puff. Most of the simulated centerline concentration
maxima along each arc were within a factor of two of those
observed.'' 68 FR 18440, 18458 (April 15, 2003), 2003 Revisions to
Appendix W, Guideline on Air Quality Models.
    \85\ Interagency Workgroup on Air Quality Modeling (IWAQM) Phase
2 Summary Report and Recommendations for Modeling Long-Range
Transport Impacts. Publication No. EPA-454/R-98-019. Office of Air
Quality Planning & Standards, Research Triangle Park, NC. 1998.
    \86\ 68 FR 18440, 18458 (Apr. 15, 2003). (2003 Revisions to
Appendix W, Guideline on Air Quality Models).
---------------------------------------------------------------------------

    In promulgating the 2005 BART guidelines, we responded to comments
concerning the limitations and appropriateness of using CALPUFF.\87\ In
the 2005 BART Guidelines the selection of the 98th percentile value
rather than the maximum value was made to address concerns that the
maximum may be overly conservative and address concerns with CALPUFF's
limitations.\88\
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    \87\ 70 FR 39104, 39121 (July 6, 2005).
    \88\ Id., at 39121. ``Most important, the simplified chemistry
in the model tends to magnify the actual visibility effects of that
source. Because of these features and the uncertainties associated
with the model, we believe it is appropriate to use the 98th
percentile--a more robust approach that does not give undue weight
to the extreme tail of the distribution.''
---------------------------------------------------------------------------

    In the 2003 revisions to the Guideline on Air Quality Models,
CALPUFF was added as an approved model for long range transport of
primary pollutants. At that time, we considered approving CALPUFF for
assessing the impact from secondary pollutants but determined that it
was not appropriate in the context of a PSD review because the impact
results could be used as the sole determinant in denying a permit.\89\
However, the use of CALPUFF in the context of the Regional Haze rule
provides results that can be used in a relative manner and are only one
factor in the overall BART determination. We determined the visibility
results from CALPUFF could be used as one of the

five factors in a BART evaluation and the impacts should be utilized
somewhat in a relative sense because CALPUFF was not explicitly
approved for full chemistry calculations.\90\ We note that since the
BART Guidelines were finalized in 2005 there has been more modeling
with CALPUFF for BART and PSD primary impact purposes and the general
community has utilized CALPUFF in the 300-450 km range many times (a
number of examples were pointed out by a commenter) and EPA and FLM
representatives have weighed the additional potential uncertainties
with the magnitude of the modeled impacts in comparison to screening/
impact thresholds on a case-by-case basis in approving the use of
CALPUFF results at these extended ranges.
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    \89\ 68 FR 18440 (Apr. 15, 2003).
    \90\ 70 FR 39104, 39123-24 (July 6, 2005). ``We understand the
concerns of commenters that the chemistry modules of the CALPUFF
model are less advanced than some of the more recent atmospheric
chemistry simulations. To date, no other modeling applications with
updated chemistry have been approved by EPA to estimate single
source pollutant concentrations from long range transport,'' and in
discussion of using other models with more advanced chemistry, ``A
discussion of the use of alternative models is given in the
Guideline on Air Quality in appendix W, section 3.2.''
---------------------------------------------------------------------------

    We disagree with the commenter's general statement that there is an
acknowledged over-prediction of the CALPUFF model or an acknowledged
inaccuracy at low impact levels, and that the actual visibility impacts
from the BART sources are lower. The CALPUFF model can both under-
predict and over-predict visibility impacts when compared to predicted
visibility impacts from photochemical grid models. See our Modeling RTC
for more detailed response.\91\
---------------------------------------------------------------------------

    \91\ For example, see Comparison of Single-Source Air Quality
Assessment Techniques for Ozone, PM2.5, other Criteria
Pollutants and AQRVs, ENVIRON, September 2012; and Anderson, B., K.
Baker, R. Morris, C. Emery, A. Hawkins, E. Snyder ``Proof-of-Concept
Evaluation of Use of Photochemical Grid Model Source Apportionment
Techniques for Prevention of Significant Deterioration of Air
Quality Analysis Requirements'' Presentation for Community Modeling
and Analysis System (CMAS) 2010. Annual Conference, (October 11-15,
2010) can be found at http://www.cmascenter.org/conference/2010/agenda.cfm.
---------------------------------------------------------------------------

    CALPUFF visibility modeling, performed using the regulatory CALPUFF
model version and following all applicable guidance and EPA/FLM
recommendations, provides a consistent tool for comparison with the 0.5
dv subject-to-BART threshold. The CALPUFF model, as recommended in the
BART guidelines, has been used for almost every single-source BART
analysis in the country and has provided a consistent basis for
assessing the degree of visibility benefit anticipated from controls as
one of the factors under consideration in a five factor BART analysis.
Since almost all states have completed their BART analyses and have
either approved SIPs or FIPs in place, there is a large set of
available data on modeled visibility impacts and benefits for
comparison with, and this data illuminates how those model results were
utilized to screen out sources and as part of the five-factor analysis
in making BART control determinations.
    The regulatory status of CALPUFF was changed in the recent
revisions to the Guideline on Air Quality Models (GAQM) as far as the
classification of CALPUFF as a preferred model for transport of
pollutants for primary impacts, not impacts based on chemistry. The
recent GAQM changes do not alter the original status of CALPUFF as
discussed and approved for use in the 2005 BART guidelines. The GAQM
changes indicated that the change in model preferred status had no
impact on the use of CALPUFF for BART.\92\
---------------------------------------------------------------------------

    \92\ 82 FR 5182, 5196 (Jan. 17, 2017). ``As detailed in the
preamble of the proposed rule, it is important to note that the
EPA's final action to remove CALPUFF as a preferred appendix A model
in this Guideline does not affect its use under the FLM's guidance
regarding AQRV assessments (FLAG 2010) nor any previous use of this
model as part of regulatory modeling applications required under the
CAA. Similarly, this final action does not affect the EPA's
recommendation [See 70 FR 39104, 39122-23 (July 6, 2005)] that
states use CALPUFF to determine the applicability and level of best
available retrofit technology in regional haze implementation
plans.''
---------------------------------------------------------------------------

    Comment: We received comments stating that we used out-of-date and
unrealistic emissions for some units, which artificially inflate the
actual visibility impacts. The commenters state that the data used is
unrealistic due to the 2000-2004 time period selected and also due to
reporting errors to CAMD. Had more recent emissions been utilized in
the screening analysis, these units would have been determined to not
be subject to BART by the various screening methods applied by EPA.
Commenters also state that a common sense reading of the Clean Air Act,
BART regulations, and BART Guidelines indicate that the ``subject to
BART'' analysis should be based on the most recently available emission
data, which EPA's subject-to-BART analysis does not use. Furthermore,
the BART Guidelines do not specifically mandate the use of the 2000-
2004 emission rates. Although the BART Guidelines recommend that for
the purpose of screening BART-eligible sources, ``States use the 24-
hour average actual emission rate from the highest emitting day of the
metrological period modeled,'' the BART Guidelines do not state that
the time period analyzed must be restricted to 2000-2004. In fact, in
the context of analyzing cost effective control options, the BART
Guidelines recommend the use of emissions that are a ``realistic
depiction of anticipated annual emissions for the source.'' \4\ And
``[i]n the absence of enforceable limitations, you calculate baseline
emissions based upon continuation of past practice.'' \5\ EPA must also
use realistic emissions when determining whether a unit causes or
contributes to visibility impairment for BART. The use of 15-year old
NOX and SO2 data for purposes of evaluating this
threshold question is illogical and arbitrary and capricious.
    We also received comments that doubling the annual emissions of PM
was conservative and we should have potentially used maximum heat input
to estimate PM emission rates for subject to BART modeling. We also
received comments that the values we modeled based on CEM data may have
included emission rates during upset conditions, thus the emission
rates used may be larger than normal operations.
    Response: We note that, as discussed elsewhere, we are not making a
subject-to-BART determination for those sources covered by the
SO2 trading program. In our final rule, the relevant BART
requirement for these participating units will be encompassed by BART
alternatives for NOX and SO2 such that we do not
deem it necessary to finalize subject-to-BART findings for these EGUs.
In addition, we are approving the determination in the 2009 TX RH SIP
that none of these sources are subject to BART for PM. Therefore,
comments concerning the emissions utilized in our subject to BART
modeling for the sources participating in the SO2 trading
program are no longer relevant. For those BART-eligible EGUs that are
not covered by the BART alternative for SO2, we are
finalizing determinations that those EGUs are not subject-to-BART for
NOX, SO2 and PM as proposed, based on the
methodologies utilizing model plants and CALPUFF modeling as described
in our proposed rule and BART Screening TSD.
    We disagree with the commenter and believe using emissions from the
2000-2004 period is appropriate for determining if a source is subject
to BART. Our analysis for facilities followed the BART Guidelines and
was consistent with the BART analyses done for all BART-eligible
sources. The BART Guidelines recommend that for the

purpose of screening BART-eligible sources, ``States use the 24-hour
average actual emission rate from the highest emitting day of the
metrological period modeled'' unless this rate reflects periods start-
up, shutdown, or malfunction. The emissions estimates used in the
models are intended to reflect steady-state operating conditions during
periods of high capacity utilization. Consistent with this guidance, we
utilized the 24-hr maximum emission rate from the 2000-2004 baseline
period and modeled using 2001-2003 meteorological data. We based our
analysis on the CEM data from the baseline period 2000-2004 and removed
what looked like questionably high values that did not occur often as
they were potentially upset values. As discussed elsewhere we did
review sources to determine if they installed controls during the
baseline period and when that occurred we only looked at baseline
emission data post controls. We received general comments that the
values we used from CEM data might include upset values, but did not
receive comments that indicated the values used were specifically upset
values during the baseline period and should not be used. Facilities
did not give us specific information to justify that the emission rates
we used were not representative maximum 24-hour emission rates during
the 2000-2004 period, so EPA considers the emission rates used were
acceptable for the BART screening process.
    We are not aware of any newly installed controls or limitations on
emissions that have been put in place between the 2000-2004 baseline
period and now for any of the BART-eligible sources not participating
in the SO2 trading program that would affect the potential
visibility impact from the source. Furthermore, because all these
sources were shown to have visibility impacts less than the 0.5 dv
threshold using the maximum 24-hr actual emissions during the 2000-
2004, modeling of lower emissions due to any new controls or emissions
limits would also result in the same determination. We were also not
provided any specific information where additional emission reductions/
controls had been installed and resulted in a short-term (24-hour)
maximum emission rate significantly less than modeled at any of these
units.
    The overall concern of the commenters was that the emissions used
in the modeling resulted in some facilities being subject to a full
BART analysis, but, as discussed elsewhere, we are not finalizing
subject to BART determinations for the sources participating in the
SO2 trading program. For the sources not participating in
the trading program, they have been screened out with our baseline
emissions modeling, so underlying concerns about emissions being high/
non-representative would not result in any differences to the sources
being screened out from a full BART analysis.
    Comment: We received comments that stated that the proposed PM BART
demonstration by Texas only considered PM emissions because
SO2 and NOX emissions were to be controlled
through an alternative BART program, CAIR. Following the same type of
approach, EPA in this Proposed Rule finds that CSAPR for ozone season
NOX is better than BART. However, for the screen modeling
used in the development of this Proposed Rule, instead of setting the
NOX emission rate consistent with CSAPR, EPA uses the
maximum 24-hour NOX emission rates from the 2000-2004 time
period. EPA ignores the continued application of CSAPR ozone season
budgets that apply to EGUs in Texas. This methodology is inconsistent
with past practices and overestimates cumulative conditions and
facility impacts. Commenters also state that because NOX is
to be controlled by CSAPR, NOX related haze impacts should
not be considered in the screening analysis.
    Response: As discussed in our response to another comment, the
emission rates used in the modeling should reflect maximum 24-hour
emission rates from the baseline period. CSAPR for ozone season
NOX is a seasonal NOX budget but does not
effectively limit short-term emission rates such that a newer maximum
24-hour emission rate can be determined. Therefore, even if it were
appropriate to consider any potential reductions due to CSAPR, it is
not possible to accurately model any reductions/limits due to CSAPR on
a short term basis. Furthermore, emissions from a unit can vary greatly
over time as the CSAPR program allows sources to meet emission budgets
in a given year by using banked allowances from previous years or by
purchasing allowances from other sources within or outside of the State
allowing emissions from the source to exceed their annual allocation
level. We also note that we were not provided specific short-term
emission rate limits from commenters that were based on the
installation of new controls or other reductions that were permanent
reductions to short-term emission rates. Our proposal did assess if
emission controls were installed during the base period and we utilized
the maximum short-term emission rate from the base period after the
controls were installed where applicable. Regardless of this issue, the
underlying concern of the commenters was whether their facility
screened out of being subject to a full BART analysis. With CSAPR
coverage for NOX and the SO2 intrastate trading
program coverage for BART for all BART-eligible coal-fired EGUs, and
several BART-eligible gas-fired and gas/fuel oil-fired EGUs, all the
BART eligible units screen out of a full BART analysis for the
pollutants not covered by trading programs, thus the chief concern that
the modeling based on 2000-2004 maximum emissions and the inclusion of
NOX contributed to a determination that the source was
subject-to-BART, is no longer relevant.
    Concerning the inclusion of NOX emissions in the
screening analysis, EPA's position is that the modeling must include
both pollutants (NOX and SO2) since they both
compete for ammonia. If we modeled only SO2, all of it would
convert to ammonia sulfate (based on ammonia availability) and both
baseline screening impacts for SO2 and visibility benefits
from any control assessments would also be overestimated. The chemical
interaction between pollutants and background species can lead to
situations where the reduction of emissions of a pollutant can actually
lead to an increase or inaccurate assessment of the visibility
impairment, if both NOX and SO2 are not included
in CALPUFF modeling. Therefore, to fully assess the visibility benefit
anticipated from the use of controls, all pollutants should be modeled
together.
    BART screening modeling would also include the PM emissions. BART
screening is meant to be a conservative and inclusive test. We have
always considered combined NOX, SO2, and PM
impacts even if the facility had NOX coverage or stringent
NOX controls already installed. The BART guidelines state
``You must look at SO2, NOX, and direct
particulate matter (PM) emissions in determining whether sources cause
or contribute to visibility impairment'' unless emissions of these
pollutants from the source are less than de minimis.\93\ The BART
Guidelines then provide three modeling options to determine which
sources and pollutants need to be subject to BART: \94\ (1) Dispersion
modeling to ``determine an individual source's impact on visibility as
a result of its emissions of SO2, NOX and direct
PM emissions''; (2) model plants to exempt individual sources with
common characteristics as

described in our BART Screening TSD; and (3) cumulative modeling on a
pollutant by pollutant basis or for all visibility-impairing pollutants
to show that no source in the State is subject to BART. The BART
guidelines are clear that individual source modeling should evaluate
impacts from NOX, SO2 and PM in determining if a
source is subject to BART and the pollutant-specific analyses are
directed as an option to screen out the impacts of all BART sources in
the State for a specific pollutant such as VOC or PM (in the case of
EGUs covered by trading programs for NOX and
SO2). The BART Guidelines also state that in assessing the
visibility benefits of controls ``modeling should be conducted for
SO2, NOX, and direct PM emissions
(PM2.5 and/or PM10).'' \95\ In many cases a state
may have only a handful of sources and impacts from more linear species
(VOC or PM) may be so small that they make up a very small contribution
(on the order of a 0-2% of the NOX and SO2
impacts) to the visibility impacts at a Class I Area, therefore it may
be acceptable to screen out pollutants that have a minimal impact. This
is not the situation with NOX, SO2 and PM
emissions from EGUs in Texas where some EGUs' PM modeled impacts were
greater than 0.25 del-dv. EPA's 2006 memorandum on this is clear that
you have to model both (NOX and SO2) because of
technical and policy concerns, and also reiterated that pollutant
specific analysis was for the limited situation of addressing PM when a
large group of sources had BART coverage for the non-linear reacting
pollutants (NOX and SO2) through a BART
alternative.\96\ The BART Guidelines specifically indicate that
NOX, SO2 and PM should be modeled together when
modeling BART eligible units at one facility.\97\ This is similar to
the BART eligibility test contemplated in the BART guidelines where if
the emissions from the identified units at source exceed a potential to
emit of 250 tons per year for any single visibility-impairing
pollutant, the source is considered BART-eligible and may be subject to
a BART review for all visibility impairing pollutants.\98\
---------------------------------------------------------------------------

    \93\ 40 CFR part 51 Appendix Y, Section III.A.2.
    \94\ 40 CFR part 51 Appendix Y, Section III.A.3.
    \95\ 40 CFR part 51 Appendix Y, Section IV.D.5 (emphasis added).
    \96\ EPA Memorandum from Joseph W. Paisie OAQPS to Kay Prince
EPA Region 4, ``Regional Haze Regulations and Guidelines for Best
Available Retrofit Technology (BART) Determinations'', July 19,
2006.
    \97\ 40 CFR part 51 Appendix Y, Section III.A.3.
    \98\ See first example in 40 CFR part 51 Appendix Y, Section
II.A.4.
---------------------------------------------------------------------------

    As previously discussed the commenter's primary concern with regard
to the inclusion of NOX was that this may have contributed
to facilities not screening out from a full BART analysis. Because, in
the final rule, trading programs constitute BART alternatives for
NOX and SO2, the facilities that were proposed as
subject to BART now screen out for the pollutants not covered by a
trading program.
    Comment: We received a comment from TCEQ that EPA should screen out
the Newman facility based on CALPUFF modeling or use CAMx to
appropriately screen Newman and determine its visibility impacts. We
also received comments from the owner of Newman, EPEC, stating that the
PM and SO2 BART limits for those gas-fired units that
occasionally burn fuel oil, applicable to Newman 2 and 3, of a fuel oil
sulfur content of 0.7% is acceptable, and that Newman 4 is restricted
to burn only natural gas. EPEC has maintained on-site diesel fuel oil
with a lesser sulfur content as emergency backup fuel for testing for
preparedness purposes, and in the unlikely scenario of a natural gas
curtailment event or other situation that may compromise the steady
flow of the primary pipeline quality natural gas fuel supply. EPEC also
notes that these units are only permitted to operate 876 hours per
year.
    Response: Based upon the comments we received requesting a BART
alternative in lieu of source-specific EGU BART determinations, we are
finalizing a SO2 trading program as an alternative to
source-by-source BART. We are not finalizing subject-to-BART
determinations for BART eligible sources covered by the BART
alternative for SO2 and NOX. In our final rule,
the relevant BART requirement for these participating units, including
the BART-eligible Newman units, will be satisfied by BART alternatives
for NOX and SO2 such that we do not deem it
necessary to finalize subject-to-BART findings for these EGUs. In
addition, we are approving a determination that none of these sources
are subject to BART for PM. Therefore, we do not find it necessary to
respond to the merits of comments concerning screening modeling for
this source, because the outcome of that modeling is not dispositive to
the source's inclusion in the BART alternative or its allowance
thereunder. See discussion above for assessment of previous CAMx PM
screening (Texas 2009 RH SIP) where the Newman source was included in
Group 2 with a number of other sources and screened out from being
subject to BART for PM.
    Comment: We received comments that some of the stack parameters
were incorrect at facilities in our CALPUFF and CAMx modeling. New
stack height, diameter, velocity values were given for some units.
    Response: We reviewed the information provided and note that some
facilities gave contradicting data within their comments. For those
facilities for which we are relying on modeling to determine they are
not subject to BART, we have evaluated potential changes where we may
have had an inaccurate number in our proposal modeling. We have
determined that the impacts from changes to stack parameters would be
minimal and not change our current assessment and decisions.
2. Modeling Related to Whether Coal-Fired Sources Are Subject to BART
    Comment: We received comments on the CALPUFF and CAMx modeling
utilized to determine which coal-fired EGUs are subject to BART. These
included comments concerning emissions inputs, the metrics used, the
post-processing methodology, and the model performance.
    Response: Due to the comments we received requesting a BART
alternative in lieu of source-specific EGU BART determinations, we are
finalizing a SO2 trading program as an alternative to
source-by-source BART. This trading program includes participation of
all BART-eligible coal-fired EGUs such that we do not deem it necessary
to finalize subject-to-BART findings for these EGUs except for PM
emissions. As a consequence, we believe that it is not necessary to
respond to the merits of comments concerning modeled baseline
visibility impacts using CALPUFF or CAMx and determination of which
coal-fired sources are subject to BART. In this final action we are
approving the determination in the Texas RH SIP that all EGU sources
screen out of BART for PM. We are also finalizing the determination
that all BART-eligible EGUs not participating in the trading program
screen out of BART for NOX, SO2 and PM based on
upon CALPUFF modeling (direct source and Model Plant). We address all
comments pertinent to the use of CALPUFF (direct source and Model
Plant) for BART screening for these sources in other responses to
comments. We note that the comments expressing concerns about CALPUFF
modeling were associated with facilities that did not screen out from a
full subject to BART analysis. Since we have determined that no EGU
sources are now subject to BART and a source-specific BART control
analysis for pollutants not covered by a BART alternative, the

specific concerns raised by commenters about being determined to be
subject to a BART control analysis because of emissions inputs used,
metrics used, etc. are not relevant to this final action. See the
Modeling RTC document for the entirety of the modeling comments and our
responses.
    Comment: The 0.5 dv threshold used by EPA in its proposed
determinations based on CAMx modeling of what sources are subject to
BART is too low, given the uncertainties in the CAMx modeling methods
used to quantify the visibility impacts of sources.
    Response: In our proposed action, we utilized CAMx modeling to
evaluate visibility impacts from BART-eligible sources that include
BART eligible coal-fired EGUs. Due to the comments we received
requesting a BART alternative in lieu of source-specific EGU BART
determinations, we are finalizing a SO2 trading program as
an alternative to source-by-source BART. This trading program includes
participation of all BART-eligible coal-fired EGUs such that we do not
deem it necessary to finalize subject-to-BART findings for these
sources except for PM emissions.
    In this final action the only CAMx modeling we are relying upon is
CAMx modeling performed for TCEQ in screening of EGU emissions of PM
that was included in TCEQ's 2009 SIP. Our approval of the CAMx PM
screening of EGUs is based on the original CENRAP modeling datasets,
agreed modeling protocols and Texas' use of the 0.5 del-dv to screen
sources as agreed upon by TCEQ in 2007. Any potential concerns with
CAMx bias were considered in 2007 and TCEQ, EPA and FLM representatives
agreed to the approach of using 0.5 del-dv to screen groups of sources
using CAMx modeling. We note that the BART guidelines specifically
state that ``as a general matter, any threshold that you use for
determining whether a source ``contributes'' to visibility impairment
should not be higher than 0.5 deciviews.'' \99\ Furthermore, our action
on the PM BART determinations in the 2009 Texas SIP submittal would not
be any different had we used a higher threshold since all sources
screened out based on the use of the 0.5 dv threshold. Since we are not
relying on the CAMx modeling we had performed for our proposal, any
comments concerning the use of this modeling are not pertinent to this
final action and it is not necessary to respond to the merits of those
comments.
---------------------------------------------------------------------------

    \99\ 40 CFR part 51 Appendix Y, Section III.A.1.
---------------------------------------------------------------------------

3. Modeling Related to Visibility Benefit of Sources Subject-to-BART
    Comment: We received comments on the CALPUFF and CAMx modeling
utilized to estimate the visibility benefits of controls. These
included comments concerning the emissions inputs, the metrics used,
the post-processing methodology, and the model performance.
    Response: Based on the comments we received requesting a BART
alternative in lieu of source-specific EGU BART determinations, we are
finalizing a SO2 trading program as an alternative to
source-by-source BART. This trading program includes participation of
all BART-eligible coal-fired EGUs and a number of BART-eligible gas or
gas/fuel oil-fired EGUs. It also includes a number of non-BART eligible
EGUs. The combination of the source coverage for this program, the
total allocations for EGUs covered by the program, and recent and
foreseeable emissions from EGUs not covered by the program will result
in future EGU emissions in Texas that are similar to the SO2
emission levels forecast in the 2012 better-than-BART demonstration for
Texas EGU emissions assuming CSAPR participation. We are not finalizing
our evaluation of whether individual sources are subject to BART. As a
consequence, we believe that it is not necessary to respond to the
merits of comments concerning source-specific visibility benefits of
controls on these units, because we are not finalizing requirements
based on those controls.

I. Comments on Affordability and Grid Reliability

    Comment: We received comments from the State, EGU owners covered
under our proposal and environmental groups concerning whether our
proposal would cause EGUs to retire and thus cause grid reliability
issues. These comments included both criticisms of and support for our
proposed position. Texas, in particular, stated that recent ERCOT
studies have raised concerns that several units in Texas will no longer
be economically viable if required to install capital intensive
controls. They also indicated that EPA's IPM modeling supports this
conclusion. Texas believed that if units shutdown with little notice it
could cause reliability concerns.
    Response: EPA takes very seriously concerns about grid reliability.
We are finalizing a SO2 trading program as an alternative to
source-by-source BART. We believe the program we have designed will
help address reliability concerns because it does not require
installation of capital intensive controls and will provide much more
flexibility to sources than the source by source compliance we
proposed. In fact, aggregate emissions of the covered sources in 2016
were below the level called for by the trading program. In addition,
the supplemental allowance pool is expected to provide additional
flexibility to allow sources to run, if necessary, in an emergency. We
believe that it is not necessary to respond on the merits to specific
comments concerning the impacts to grid reliability related to the
requirements of the proposed source-specific controls, because we are
not finalizing those requirements.

V. SO[bdi2] Trading Program and Its Implications for Interstate
Visibility Transport, EGU BART, and Reasonable Progress

    The Regional Haze Rule provides each state with the flexibility to
adopt an allowance trading program or other alternative measure instead
of requiring source-specific BART controls, so long as the alternative
measure is demonstrated to achieve greater reasonable progress than
BART. As discussed in Section III.A.3 above, based principally on
comments submitted by the State of Texas during the comment period
urging us to consider as a BART alternative the concept of system-wide
emission caps using CSAPR allocations as part of an intrastate trading
program,\100\ we are acknowledging the State's preference and
exercising our authority to promulgate a BART alternative for
SO2 for certain Texas EGUs. The combination of the source
coverage for this program, the total allocations for EGUs covered by
the program, and recent and foreseeable emissions from EGUs not covered
by the program will result in future EGU emissions in Texas that are
similar to what was forecast in the 2012 better than BART demonstration
for Texas EGU emissions assuming CSAPR participation.
---------------------------------------------------------------------------

    \100\ See Docket Item No. EPA-R06-OAR-2016-0611-0070, p. 3.
---------------------------------------------------------------------------

A. Background on the CSAPR as an Alternative to BART Concept

    In 2012, the EPA amended the Regional Haze Rule to provide that
participation by a state's EGUs in a CSAPR trading program for a given
pollutant--qualifies as a BART alternative for those EGUs for that
pollutant.\101\ In promulgating this

CSAPR-better-than-BART rule (also referred to as ``Transport Rule as a
BART Alternative''), the EPA relied on an analytic demonstration based
on an air quality modeling study \102\ showing that CSAPR
implementation meets the Regional Haze Rule's criteria for a
demonstration of greater reasonable progress than BART. In the air
quality modeling study conducted for the 2012 analytic demonstration,
the EPA projected visibility conditions in affected Class I areas \103\
based on 2014 emissions projections for two control scenarios and on
the 2014 base case emissions projections.\104\ One control scenario
represents ``Nationwide BART'' and the other represents ``CSAPR + BART-
elsewhere.'' In the base case, neither BART controls nor the EGU
SO2 and NOX emissions reductions attributable to
CSAPR were reflected. To project emissions under CSAPR, the EPA assumed
that the geographic scope and state emissions budgets for CSAPR would
be implemented as finalized and amended in 2011 and 2012.\105\ The
results of that analytic demonstration based on this air quality
modeling passed the two-pronged test set forth at 40 CFR 51.308(e)(3).
The first prong ensures that the alternative program will not cause a
decline in visibility at any affected Class I area. The second prong
ensures that the alternative program results in improvements in average
visibility across all affected Class I areas as compared to adopting
source-specific BART. Together, these tests ensure that the alternative
program provides for greater visibility improvement than would source-
specific BART.
---------------------------------------------------------------------------

    \101\ 40 CFR 51.308(e)(4); see also generally 77 FR 33641 (June
7, 2012). Legal challenges to the CSAPR-better-than-BART rule from
conservation groups and other petitioners are pending. Utility Air
Regulatory Group v. EPA, No. 12-1342 (D.C. Cir. filed August 6,
2012).
    \102\ See Technical Support Document for Demonstration of the
Transport Rule as a BART Alternative, Docket ID No. EPA-HQ-OAR-2011-
0729-0014 (December 2011) (2011 CSAPR/BART Technical Support
Document), and memo entitled ``Sensitivity Analysis Accounting for
Increases in Texas and Georgia Transport Rule State Emissions
Budgets,'' Docket ID No. EPA-HQ-OAR-2011-0729-0323 (May 29, 2012),
both available in the docket for this action.
    \103\ The EPA identified two possible sets of ``affected Class I
areas'' to consider for purposes of the study and found that
implementation of CSAPR met the criteria for a BART alternative
whichever set was considered. See 77 FR 33641, 33650 (June 7, 2012).
    \104\ For additional detail on the 2014 base case, see the CSAPR
Final Rule Technical Support Document, available in the docket for
this action.
    \105\ CSAPR was amended three times in 2011 and 2012 to add five
states to the seasonal NOX program and to increase
certain state budgets. 76 FR 80760 (Dec. 27, 2011); 77 FR 10324
(Feb. 21, 2012); 77 FR 34830 (June 12, 2012). The CSAPR-better-than-
BART final rule reflected consideration of these changes to CSAPR.
---------------------------------------------------------------------------

    For purposes of the 2012 analytic demonstration that CSAPR as
finalized and amended in 2011 and 2012 provides for greater reasonable
progress than BART, the analysis included Texas EGUs as subject to
CSAPR for SO2 and annual NOX (as well as ozone-
season NOX). CSAPR's emissions limitations are defined in
terms of emissions ``budgets'' for the collective emissions from
affected EGUs in each covered state. Sources have the ability to
purchase allowances from sources outside of the state, so total
projected emissions for a state may, in some cases, exceed the state's
emission budget, but aggregate emissions from all sources in a state
should remain lower than or equal to the state's ``assurance level.''
The final emission budget under CSAPR for Texas was 294,471 tons per
year for SO2, including 14,430 tons of allowances available
in the new unit set aside.\106\ The State's ``assurance level'' under
CSAPR was 347,476 tons.\107\ Under CSAPR, the projected SO2
emissions from the affected Texas EGUs in the CSAPR + BART-elsewhere
scenario were 266,600 tons per year. In a 2012 sensitivity analysis
memo, EPA conducted a sensitivity analysis that confirmed that CSAPR
would remain better-than-BART if Texas EGU emissions increased to
approximately 317,100 tons.\108\
---------------------------------------------------------------------------

    \106\ Units that are subject to CSAPR but that do not receive
allowance allocations as existing units are eligible for a new unit
set aside (NUSA) allowance allocation. NUSA allowance allocations
are a batch of emissions allowances that are reserved for new units
that are regulated by the CSAPR, but weren't included in the final
rule allocations. The NUSA allowance allocations are removed from
the original pool of regional allowances, and divided up amongst the
new units, so as not to exceed the emissions cap set in the CSAPR.
Each calendar year, EPA issues three pairs of preliminary and final
notices of data availability (NODAs), which are determined and
recorded in two ``rounds'' and are published in the Federal
Register. In any year, if the NUSA for a given CSAPR state and
program does not have enough new units after completion of the 2nd
round, the remaining allowances are allocated to existing CSAPR-
affected units.
    \107\ See 40 CFR 97.710 for state SO2 Group 2 trading
budgets, new unit set-asides, Indian country new unit set-asides,
and variability limits.
    \108\ For the projected annual SO2 emissions from
Texas EGUs See Technical Support Document for Demonstration of the
Transport Rule as a BART Alternative, Docket ID No. EPA-HQ-OAR-2011-
0729-0014 (December 2011) (2011 CSAPR/BART Technical Support
Document), available in the docket for this action. at table 2-4.
Certain CSAPR budgets were increased after promulgation of the CSAPR
final rule (and the increases were addressed in the 2012 CSAPR/BART
sensitivity analysis memo. See memo entitled ``Sensitivity Analysis
Accounting for Increases in Texas and Georgia Transport Rule State
Emissions Budgets,'' Docket ID No. EPA-HQ-OAR-2011-0729-0323 (May
29, 2012), available in the docket for this action. The increase in
the Texas SO2 budget was 50,517 tons which, when added to
the Texas SO2 emissions projected in the CSAPR + BART-
elsewhere scenario of 266,600 tons, yields total potential
SO2 emissions from Texas EGUs of approximately 317,100
tons.
---------------------------------------------------------------------------

    As introduced in Section I.C, in the EPA's final response to the
D.C. Circuit's remand of certain CSAPR budgets, we finalized the
withdrawal of the requirements for Texas' EGUs to participate in the
annual SO2 and NOX trading programs and also
finalized our determination that the changes to the geographic scope of
the CSAPR trading programs resulting from the remand response do not
affect the continued validity of participation in CSAPR as a BART
alternative. This determination that CSAPR remains a viable BART
alternative despite changes in geographic scope resulting from EPA's
response to the CSAPR remand was based on a sensitivity analysis of the
2012 analytic demonstration used to support the original CSAPR as
better-than-BART rulemaking. A full explanation of the sensitivity
analysis is included in the remand response proposal and final
rule.\109\
---------------------------------------------------------------------------

    \109\ 81 FR 78954 (Nov. 10, 2016) and final action signed
September 21, 2017 available at regulations.gov in Docket No. EPA-
HQ-OAR-2016-0598.
---------------------------------------------------------------------------

B. Texas SO2 Trading Program

    Texas is no longer in the CSAPR program for annual SO2
emissions and accordingly cannot rely on CSAPR as a BART alternative
for SO2 under 51.308(e)(4).\110\ Therefore, informed by the
TCEQ comments, we are proceeding to address the SO2 BART
requirement for coal-fired, some gas-fired, and some gas/fuel oil-fired
units under a BART alternative, which we are justifying according to
the demonstration requirements under 51.308(e)(2).
---------------------------------------------------------------------------

    \110\ See final action signed September 21, 2017 available at
regulations.gov in Docket No. EPA-HQ-OAR-2016-0598.
---------------------------------------------------------------------------

1. Identification of Sources Participating in the Trading Program
    Under 51.308(e)(2), a State may opt to implement or require
participation in an emissions trading program or other alternative
measure rather than to require sources subject to BART to install,
operate, and maintain BART. Such an emissions trading program or other
alternative measure must achieve greater reasonable progress than would
be achieved through the installation and operation of BART. At the same
time, the Texas trading program should be designed so as not to
interfere with the validity of existing SIPs in other states that have
relied on reductions from sources in Texas. As discussed elsewhere, the
Texas trading program is designed to provide the measures that are
needed to address interstate visibility transport requirements for
several NAAQS and to be part of the long-term strategy needed to meet
the reasonable progress requirements of the

Regional Haze Rule.\111\ To meet all of these goals, the trading
program must not only be inclusive of all BART-eligible sources that
are treated as satisfying the BART requirements through participation
in a BART alternative, but must also include additional emission
sources such that the trading program as a whole can be shown to both
achieve greater reasonable progress than would be achieved through the
installation and operation of BART, and achieve the emission reductions
relied upon by other states during consultation and assumed by other
states in their own regional haze SIPs, including their reasonable
progress goals for their Class I areas.
---------------------------------------------------------------------------

    \111\ EPA is not determining at this time that this final action
fully resolves the EPA's outstanding obligations with respect to
reasonable progress that resulted from the Fifth Circuit's remand of
our reasonable progress FIP. We intend to take future action to
address the Fifth Circuit's remand.
---------------------------------------------------------------------------

    The identification of EGUs in the trading program necessarily
begins with the list of BART-eligible EGUs for which we intend to
address the BART requirements through a BART alternative. As discussed
elsewhere, we determined that several BART-eligible gas-fired and gas/
oil-fired EGUs are not subject-to-BART for NOX,
SO2, and PM, therefore those BART-eligible sources are not
included in the trading program. The table below lists those BART-
eligible EGUs identified for participation in the trading program.
---------------------------------------------------------------------------

    \112\ Dynegy purchased the Coleto Creek power plant from Engie
in February, 2017. Note that Coleto Creek may still be listed as
being owned by Engie in some of our supporting documentation which
was prepared before that sale.

    Table 4--BART-Eligible EGUs Participating in the Trading Program
------------------------------------------------------------------------
                  Facility                               Unit
------------------------------------------------------------------------
Big Brown (Luminant)........................  1.
Big Brown (Luminant)........................  2.
Coleto Creek (Dynegy \112\).................  1.
Fayette (LCRA)..............................  1.
Fayette (LCRA)..............................  2.
Graham (Luminant)...........................  2.
Harrington Station (Xcel)...................  061B.
Harrington Station (Xcel)...................  062B.
J T Deely (CPS Energy)......................  1.
J T Deely (CPS Energy)......................  2.
Martin Lake (Luminant)......................  1.
Martin Lake (Luminant)......................  2.
Martin Lake (Luminant)......................  3.
Monticello (Luminant).......................  1.
Monticello (Luminant).......................  2.
Monticello (Luminant).......................  3.
Newman (El Paso Electric)...................  2.
Newman (El Paso Electric)...................  3.
Newman (El Paso Electric)...................  4.
O W Sommers (CPS Energy)....................  1.
O W Sommers (CPS Energy)....................  2.
Stryker Creek (Luminant)....................  ST2.
WA Parish (NRG).............................  WAP4.
WA Parish (NRG).............................  WAP5.
WA Parish (NRG).............................  WAP6.
Welsh Power Plant (AEP).....................  1.
Welsh Power Plant (AEP).....................  2.
Wilkes Power Plant (AEP)....................  1.
Wilkes Power Plant (AEP)....................  2.
Wilkes Power Plant (AEP)....................  3.
------------------------------------------------------------------------

    For a BART alternative that includes an emissions trading program,
the applicability provisions must be designed to prevent any
significant potential shifting within the state of production and
emissions from sources in the program to sources outside the program.
Shifting would be logistically simplest among units in the same
facility, because they are under common management and have access to
the same transmission lines. In addition, since a coal-fired EGU to
which electricity production could shift would have a relatively high
SO2 emission rate (compared to a gas-fired EGU), such
shifting could also shift substantive amounts of SO2
emissions. To prevent any significant shifting of generation and
SO2 emissions from participating sources to non-
participating sources within the same facility, coal-fired EGUs that
are not BART-eligible but are co-located with BART-eligible EGUs have
been included in the program. While Fayette Unit 3, WA Parish Unit 8
(WAP8), and J K Spruce Units 1 and 2 were identified as coal-fired
units that are not BART-eligible but are co-located with BART-eligible
EGUs, these units have scrubbers installed to control SO2
emissions such that a shift in generation from the participating units
to these units would not result in a significant increase in emissions.
Fayette Unit 3 has a high performing scrubber similar to the scrubbers
on Fayette Units 1 and 2,\113\ and has a demonstrated ability to
maintain SO2 emissions at or below 0.04 lbs/MMBtu.\114\ We
find that any shifting of generation from the participating units at
the facility to Fayette Unit 3 would result in an insignificant shift
of emissions. The scrubber at Parish Unit 8 maintains an emission rate
four to five times lower than the emission rate of the other coal-fired
units at the facility (Parish Units 5, 6, and 7) that are
uncontrolled.\115\ Shifting of generation from the participating units
at the Parish facility to Parish Unit 8 would result in a decrease in
overall emissions from the source. Similarly, J K Spruce Units 1 and 2
have high performing scrubbers and emit at emission rates much lower
than the co-located BART-eligible coal-fired units (J T Deely Units 1
and 2).\116\ In addition, because these units not covered by the
program are on average better controlled for SO2 than the
covered sources and emit far less SO2 per unit of energy
produced, we conclude that in general, based on the current emission
rates of the EGUs, should a portion of electricity generation shift to
those units not covered by the program, the net result would be a
decrease in overall SO2 emissions, as these non-
participating units are on average much better controlled. Relative to
current emission levels, should participating units increase their
emissions rates and decrease generation to comply with their
allocation, emissions from non-participating units may see a small
increase. Therefore, we have not included Fayette Unit 3, WA Parish
Unit 8 (WAP8), and J K Spruce Units 1 and 2 in the trading program. The
table below lists those coal-fired units that are co-located with BART-
eligible units that have been identified for inclusion in the trading
program.
---------------------------------------------------------------------------

    \113\ See the BART FIP TSD, available in the docket for this
action (Document Id: EPA-R06-OAR-2016-0611-0004), for evaluation of
the performance of scrubbers on Fayette Units 1 and 2.
    \114\ The annual average emission rate for 2016 for this unit
was 0.01 lb/MMBtu.
    \115\ Parish Units 5 and 6 are coal-fired BART-eligible units.
Parish Unit 7 is not BART-eligible, but is a co-located coal-fired
EGU. Unlike Parish Unit 8, these three units do not have an
SO2 scrubber installed.
    \116\ The annual average emission rate for 2016 for J K Spruce
Units 1 and 2 was 0.03 lb/MMBtu and 0.01 lb/MMBtu, respectively. The
annual average emission rate for 2016 for J T Deely Units 1 and 2
was 0.52 lb/MMBtu and 0.51 lb/MMBtu, respectively.

     Table 5--Coal-Fired EGUs Co-Located With BART-Eligible EGUs and
                  Participating in the Trading Program
------------------------------------------------------------------------
                  Facility                               Unit
------------------------------------------------------------------------
Harrington Station (Xcel)...................  063B.
WA Parish (NRG).............................  WAP7.
Welsh Power Plant (AEP).....................  3.
------------------------------------------------------------------------

    In addition to these sources, we also evaluated other EGUs for
inclusion in the trading program based on their potential to impact
visibility at Class I areas. Addressing emissions from sources with the
largest potential to impact visibility is required to make progress
towards the goal of natural visibility conditions and to address
emissions that may otherwise interfere

with measures required to protect visibility in other states. EPA,
States, and RPOs have historically used a Q/D analysis to identify
those facilities that have the potential to impact visibility at a
Class I area based on their emissions and distance to the Class I area.
Where,
    1. Q is the annual emissions in tons per year (tpy), and
    2. D is the nearest distance to a Class I Area in kilometers (km).
    We used a Q/D value of 10 as a threshold for identification of
facilities that may impact air visibility at Class I areas and could be
included in the trading program in order to meet the goals of achieving
greater reasonable progress than BART and limiting visibility
transport. We selected this value of 10 based on guidance contained in
the BART Guidelines, which states:
    Based on our analyses, we believe that a State that has established
0.5 deciviews as a contribution threshold could reasonably exempt from
the BART review process sources that emit less than 500 tpy of
NOX or SO2 (or combined NOX and
SO2), as long as these sources are located more than 50
kilometers from any Class I area; and sources that emit less than 1000
tpy of NOX or SO2 (or combined NOX and
SO2) that are located more than 100 kilometers from any
Class I area.\117\
---------------------------------------------------------------------------

    \117\ See 40 CFR part 51, App. Y, Sec.  III (How to Identify
Sources ``Subject to BART'').
---------------------------------------------------------------------------

    The approach described above corresponds to a Q/D threshold of 10.
This approach has also been recommended by the Federal Land Managers'
Air Quality Related Values Work Group (FLAG) \118\ as an initial
screening test to determine if an analysis is required to evaluate the
potential impact of a new or modified source on air quality related
value (AQRV) at a Class I area. For this purpose, a Q/D value is
calculated using the combined annual emissions in tons per year of
(SO2, NOX, PM10, and sulfuric acid
mist (H2SO4) divided by the distance to the Class
I area in km. A Q/D value greater than 10 requires a Class I area AQRV
analysis.\119\
---------------------------------------------------------------------------

    \118\ Federal Land Managers' Air Quality Related Values Work
Group (FLAG), Phase I Report--Revised (2010) Natural Resource Report
NPS/NRPC/NRR--2010/232, October 2010. Available at http://www.nature.nps.gov/air/Pubs/pdf/flag/FLAG_2010.pdf.
    \119\ We also note that TCEQ utilized a Q/D threshold of 5 in
its analysis of reasonable progress sources in the 2009 Texas
Regional Haze SIP. See Appendix 10-1.
---------------------------------------------------------------------------

    We considered the results of an available Q/D analysis based on
2009 emissions to identify facilities that may impact air visibility at
Class I areas.\120\ The table below summarizes the results of that Q/D
analysis for EGU sources in Texas with a Q/D value greater than 10 with
respect to the nearest Class I area to the source.
---------------------------------------------------------------------------

    \120\ See the TX RH FIP TSD that accompanied our December 2014
Proposed action 79 FR 74818 (Dec 16, 2014) and 2009statesum_Q_D.xlsx
available in the docket for that action.

                  Table 6--Q/D Analysis for Texas EGUs
              [Q/D greater than 10, 2009 annual emissions]
------------------------------------------------------------------------
                        Facility                            Maximum Q/D
------------------------------------------------------------------------
H.W. Pirkey (AEP).......................................            35.8
Big Brown (Luminant)....................................           182.9
Sommers-Deely (CPS).....................................            56.9
Coleto Creek (Dynegy)...................................            46.0
Fayette (LCRA)..........................................            61.0
Gibbons Creek (TMPA)....................................            30.8
Harrington Station (XCEL)...............................           107.8
San Miguel..............................................            32.9
Limestone (NRG).........................................            85.1
Martin Lake (Luminant)..................................           367.4
Monticello (Luminant)...................................           425.4
Oklaunion (AEP).........................................            85.0
Sandow (Luminant).......................................            63.0
Tolk Station (XCEL).....................................           148.5
Twin Oaks...............................................            14.2
WA Parish (NRG).........................................            84.3
Welsh (AEP).............................................           230.1
------------------------------------------------------------------------

    Based on the above Q/D analysis, we identified additional coal-
fired EGUs for participation in the SO2 trading program due
to their emissions, proximity to Class I areas, and potential to impact
visibility at Class I areas. While Gibbons Creek is identified by the
Q/D analysis, the facility does not include any BART-eligible EGUs and
has installed very stringent controls such that current emissions are
approximately 1% of what they were in 2009.\121\ Therefore, we do not
consider Gibbons Creek to have significant potential to impact
visibility at any Class I area and do not include it in the trading
program. The Twin Oaks facility, consisting of two units, is also
identified as having a Q/D greater than 10. However, the Q/D for this
facility is significantly lower than that of the other facilities, the
facility does not include any BART-eligible EGUs, and the estimated Q/D
for an individual unit would be less than 10. We do not consider the
potential visibility impacts from these units to be significant
relative to the other coal-fired EGUs in Texas with Q/Ds much greater
than 10 and do not include it in the trading program. The Oklaunion
facility consists of one coal-fired unit that is not BART-eligible.
Annual emissions of SO2 in 2016 from this source were 1,530
tons, less than 1% of the total annual emissions for EGUs in the state.
We have determined that the most recent emissions from this facility
are small relative to other non-BART units included in the program and
we have not included Oklaunion in the trading program. Finally, San
Miguel is identified as having a Q/D greater than 10. The San Miguel
facility consists of one coal-fired unit that is not BART-eligible. In
our review of existing controls at the facility performed as part of
our action to address the remaining regional haze obligations for
Texas, we found that the San Miguel facility has upgraded its
SO2 scrubber system to perform at the highest level (94%
control efficiency) that can reasonably be expected based on the
extremely high sulfur content of the coal being burned, and the
technology currently available.\122\ Since completion of all scrubber
upgrades,\123\ emissions from the facility on a 30-day boiler operating
day \124\ rolling average basis have remained below 0.6 lb/MMBtu and
the 2016 annual average emission rate was 0.44 lb/MMBtu. Therefore, we
have determined that the facility is well controlled and have not
included San Miguel in the trading program. Other coal-fired EGUs in
Texas that are not included in the trading program either had Q/D
values less than 10 based on 2009 emissions or were not yet operating
in 2009. New units beginning operation after 2009 would be permitted
and constructed using emission control technology determined under
either BACT or LAER review, as applicable and we do not consider the
potential visibility impacts from these units to be significant