DSI...............              90          13,277      34,841,379           2,624           3,151
                                                      SDA...............            92.4          13,632      29,445,018           2,160         -15,201
                                                      Wet FGD...........            94.9          14,005      29,786,106           2,127             914
Harrington......................  061B..............  DSI...............              50           2,477       9,187,608           3,710
                                                      DSI...............              80           3,962      16,073,779           4,057           4,637
                                                      SDA...............            90.2           4,466      17,455,679           3,909           2,742
                                  062B..............  DSI...............              50           2,455       6,524,937           2,658
                                                      DSI...............          * 88.9           4,364      11,981,111           2,746           2,858
                                                      SDA...............            88.9           4,364      18,240,127           4,180             N/A
J T Deely.......................  1.................  DSI...............              50           3,072       8,854,319           2,883

                                                      DSI...............              90           5,529      18,071,878           3,269           3,752
                                                      SDA...............            91.3           5,609      21,689,526           3,867          45,221
                                                      Wet FGD...........            94.2           5,787      22,555,395           3,898           4,864
                                  2.................  DSI...............              50           3,222       9,865,798           3,062
                                                      DSI...............              90           5,800      20,229,233           3,488           4,020
                                                      SDA...............            91.3           5,884      21,812,518           3,707          18,849
                                                      Wet FGD...........            94.2           6,070      22,530,901           3,712           3,862
Welsh...........................  1.................  DSI...............              50           3,343       8,963,761           3,469
                                                      DSI...............          * 87.2           5,832      23,090,408           3,960           5,676
                                                      SDA...............            87.2           5,832      22,697,048           3,892             N/A
                                                      Wet FGD...........            91.5           6,116      23,998,161           3,924           4,581
W.A. Parish.....................  5.................  DSI...............              50           6,712      15,002,337           2,235
                                                      DSI...............              90          12,081      30,865,711           2,555           2,955
                                                      SDA...............            92.1          12,364      31,195,787           2,523           1,166
                                                      Wet FGD...........            94.7          12,717      30,735,030           2,417          -1,305
                                  6.................  DSI...............              50           7,525      16,014,988           2,128  ..............
                                  ..................  DSI...............              90          13,545      33,302,528           2,459           2,872
                                                      SDA...............            92.1          13,862      32,758,784           2,363          -1,715
                                                      Wet FGD...........            94.7          14,258      32,215,226           2,259          -1,373
--------------------------------------------------------------------------------------------------------------------------------------------------------
* DSI control level limited to that of SDA.

b. Impact Analysis Part 1: Cost of Compliance for Scrubber Upgrades

    In our BART FIP TSD, we analyze those units listed in Table 7 with
an existing SO2 scrubber in order to determine if cost-
effective scrubber upgrades are available. Of our subject-to-BART
units, Martin Lake Units 1, 2, 3; Monticello Unit 3, and Fayette Units
1 and 2 are currently equipped with wet FGDs. Of these, all but the
Fayette units were analyzed for scrubber upgrades in our Texas-Oklahoma
FIP. For all but the Fayette units, we propose to adopt the total
annualized cost calculations used to make the cost-effectiveness
calculations in our Texas-Oklahoma FIP in this action. We acknowledge
that these costs could change slightly, due to changes in the costs of
various materials and services. However, these costs were calculated in
2013 dollars. Escalating them to 2015 dollars would result in a
reduction in cost, which we conservatively do not take into
consideration.\88\
---------------------------------------------------------------------------

    \88\ The CEPCI for 2013 is 567.3 and that for 2015 is 556.3.
Therefore, the costs would be multiplied by a factor of 556.8/567.3,
which is approximately 0.98.
---------------------------------------------------------------------------

    In our Texas-Oklahoma FIP action, after responding to comments we
revised our proposed cost-effectiveness basis from where all scrubber
upgrades were less than $600/ton, to where all scrubber upgrades ranged
from between $368/ton to $910/ton.\89\ As with our Texas-Oklahoma FIP,
we are limited in what information we can include in this section,
because we used information that was claimed as CBI. This information
was submitted in response to our Section 114(a) requests. The following
summary is based on information not claimed as CBI.
---------------------------------------------------------------------------

    \89\ 81 FR 318.
---------------------------------------------------------------------------

     The absorber system had either already been upgraded to
perform at an SO2 removal efficiency of at least 95%, or it
could be upgraded to perform at that level using proven equipment and
techniques.
     The SO2 scrubber bypass could be eliminated,
and the additional flue gas could be treated by the absorber system
with at least a 95% removal efficiency.
     Additional modifications necessary to eliminate the
bypass, such as adding fan capacity, upgrading the electrical
distribution system, and conversion to a wet stack could be performed
using proven equipment and techniques.
     The additional SO2 emission reductions
resulting from the scrubber upgrade are substantial, ranging from 68%
to 89% reduction from the current emission levels, and are cost-
effective.
    We now update these calculations for 2011-2015 data.\90\ The
revised scrubber upgrade results for Martin Lake Units 1, 2, and 3; and
Monticello Unit 3 are presented below in Table 11:
---------------------------------------------------------------------------

    \90\ See Coal vs CEM data 2011-2015.xlsx.

                              Table 11--Summary of Updated Scrubber Upgrade Results
----------------------------------------------------------------------------------------------------------------
                                                  2011-2015 3-yr
                                                     avg. SO2      SO2 emissions   SO2 emissions   SO2 emission
                                                     emissions    at 95% control   reduction due    rate at 95%
                      Unit                        (eliminate max      (tons)        to scrubber   control  (lbs/
                                                     and min)                     upgrade (tons)      MMBtu)
                                                      (tons)
----------------------------------------------------------------------------------------------------------------
Monticello 3....................................           8,136           1,180           6,956            0.05
Martin Lake 1...................................          19,040           3,208          15,832            0.12
Martin Lake 2...................................          17,973           3,393          14,580            0.12
Martin Lake 3...................................          16,113           2,591          13,522            0.11
                                                 ---------------------------------------------------------------
    Total SO2 Removed...........................                                          50,890
----------------------------------------------------------------------------------------------------------------

    As we note above, we updated the cost-effectiveness for each of
these units. Because those calculations depended on information claimed
by the companies as CBI we cannot present it here, except to note that
in all cases, the cost-effectiveness was $1,156/ton or less. We invite
the facilities listed above to make arrangements with us to view our
complete updated cost analysis for their units.
    The Fayette Units 1 and 2 are currently equipped with high
performing wet FGDs. Both units have demonstrated the ability to
maintain a SO2 30 BOD average below 0.04 lbs/MMBtu for years
at a time.\91\ As we discuss above, we evaluate BART demonstrating that
retrofit wet FGDs should be evaluated at 98% control not to go below
0.04 lbs/MMBtu. Because the Fayette units are performing below this
level, we propose that no scrubber upgrades are necessary. We propose
to find that the Fayette Units 1 and 2 maintain a 30 Boiler Operating
Day rolling average SO2 emission rate of 0.04 lbs/MMBtu
based on the actual emissions data we present above. We believe that
based on its demonstrated ability to maintain an emission rate below
this value on a 30 BOD basis, it can consistently achieve this emission
level.
---------------------------------------------------------------------------

    \91\ See our BART FIP TSD for graphs of this data.
---------------------------------------------------------------------------

c. Impact Analysis Part 1: Cost of Compliance for Gas Units That Burn
Oil
    As we noted in Section III.C.1.b, a number of the units we proposed
in Table 9 as being subject to BART primarily fire gas, but have
occasionally fired fuel oil in the past as reported by the EIA. These
units are limited by their permits to burning oil with a sulfur content
of no more than 0.7% sulfur by weight. We proposed to consider both a
reduction in fuel oil sulfur and SO2 scrubbers as potential
BART controls. Below we consider the cost of these potential controls.
Reduction in Fuel Oil Sulfur
    In order to determine the cost of these facilities switching to
lower sulfur content fuel oils, we sent the Graham, Newman, Stryker
Creek, and the Wilkes facilities Section 114 letters requesting certain
information.\92\ We received very limited information in response to
one of our questions concerning the present cost of the historic fuel
oil burned, and the cost of various lower sulfur replacement fuel oils.
Because of this, we were unable to compile facility-specific
information on the cost of switching to lower sulfur fuel oils.
Consequently, we considered the best available information by
consulting more general information from the EIA, which reports the
prices for various refinery petroleum products on a monthly and annual
basis. Below is a summary of various distillate and residual fuel oil
products for 2001 to 2015, averaged across the U.S.\93\
---------------------------------------------------------------------------

    \92\ Copies of these letters and the facilities' responses are
in our docket. We inadvertently did not send the O W Sommers a
letter.
    \93\ EIA Refiner Petroleum Product Prices by Sales Type,
available here: http://www.eia.gov/dnav/pet/pet_pri_refoth_dcu_nus_a.htm; http://www.eia.gov/dnav/pet/pet_pri_spt_s1_a.htm.

                                             Table 12--Selected EIA Reported Annual Refiner Petroleum Prices
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                U.S. no. 4
                                                                       West Texas         U.S. no. 2 diesel    U.S. no. 2 fuel oil       distillate
                              Date                                 intermediate  crude    wholesale/resale      wholesale/resale      wholesale/resale
                                                                      oil--Cushing        price by refiners     price by refiners     price by refiners
                                                                    Oklahoma ($/bbl)         ($/gallon)            ($/gallon)            ($/gallon)
--------------------------------------------------------------------------------------------------------------------------------------------------------
2015............................................................                 48.66                 1.667                 1.565                 1.215
2014............................................................                 93.17                 2.812                 2.741                 2.333
2013............................................................                 97.98                 3.028                 2.966                 2.767
2012............................................................                 94.05                 3.109                 3.031
2011............................................................                 94.88                 3.034                 2.907                 2.801
2010............................................................                 79.48                 2.214                 2.147
2009............................................................                 61.95                 1.713                 1.657                 1.561
2008............................................................                 99.67                 2.994                 2.745                 2.157
2007............................................................                 72.34                 2.203                 2.072                 1.551
2006............................................................                 66.05                 2.012                 1.834                 1.395
2005............................................................                 56.64                 1.737                 1.623                 1.377
2004............................................................                 41.51                 1.187                 1.125                 1.033
2003............................................................                 31.08                 0.883                 0.881                 0.793
2002............................................................                 26.18                 0.724                 0.694                 0.663
2001............................................................                 25.98                 0.784                 0.756                 0.697
2000............................................................                 30.38                 0.898                 0.886                 0.778
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Lacking facility-specific pricing information, for the purposes of
calculating the cost of compliance, we make the following assumptions:
     No. 4 distillate is the type of fuel oil currently
available that most closely approximates the types of fuel oil that
were historically burned by the facilities. It is available in a range
of sulfur up to the facilities' permitted maximum of 0.7% sulfur by
weight or 7,000 ppm. We will use the cost of this fuel oil in
constructing ``business as usual'' scenarios of the annual cost of fuel
oil.
     No. 2 fuel oil is available at approximately 3,000 ppm,
which roughly corresponds to the sulfur level present in No. 2 fuel oil
prior to our implementation of the Ultra-Low-Sulfur Diesel (ULSD)
regulations.\94\ We will use the cost of this fuel oil in constructing
a ``medium control'' annual cost of fuel oil.
---------------------------------------------------------------------------

    \94\ 69 FR 39073: ``Both high sulfur No. 2-D and No. 2 fuel oil
must contain no more than 5000 ppm sulfur,131 and currently [as of
the date of our final rule, 6/29/04] averages 3000 ppm nationwide.''
---------------------------------------------------------------------------

     No. 2 diesel fuel corresponds to ULSD, with a sulfur
content of 15 ppm. We will use the cost of this fuel oil in
constructing a ``high control'' annual cost of fuel oil.
    Having identified a reasonable set of historical and lower sulfur
fuel oils, we turned to the matter of establishing SO2
baselines. We would expect that regardless of the baseline selected, a
cost-effectiveness calculation that simply depended on differing fuel
oil costs and the resulting reductions in SO2, would result
in the same value. In other words, the cost-effectiveness in $/ton is
independent of the SO2 baseline, since in this case, it is
calculated on a unit basis--the increased cost in burning a unit of
fuel divided by the increased reduction in the resulting

SO2. While the above is true, reported data for these units
does not match this expectation. This can be illustrated by examining
selected EIA and emissions data for the Graham Unit 2:

                 Table 13--Graham Unit 2 Example Discordance in Fuel Oil Burned and Reported SO2
----------------------------------------------------------------------------------------------------------------
                                                                   Quantity fuel   Reported SO2    Reported EIA
                        Date (month/year)                           oil burned       for month    sulfur content
                                                                      (bbls)          (tons)          (wt %)
----------------------------------------------------------------------------------------------------------------
Mar-02..........................................................           9,800          21.614            0.65
Feb-03..........................................................           8,400          90.389            0.66
Jun-12..........................................................          18,177           0.064            0.50
Jul-12..........................................................           5,657            0.07            0.50
----------------------------------------------------------------------------------------------------------------

    As can be seen from the above table, even though the reported
sulfur content of the fuel oil in March 2002 and February 2003 was
approximately the same, and the quantity burned was fairly close, the
reported SO2 emissions were significantly different.
Similarly, although the amount of fuel oil burned in June 2012 was more
than three times that burned in July 2012 (at the same sulfur content),
the reported SO2 emissions in June 2012 were less than that
in July 2012. Also, although the fuel oil sulfur content in the 2012
examples was only slightly less than that in the 2002/2003 examples,
and the amount of fuel oil burned was the same order of magnitude, the
resulting reported SO2 emissions in 2012 were three orders
of magnitude less than that in 2002/2003. We conclude that either the
values for the EIA fuel quantities, the EIA fuel oil sulfur contents,
and/or the reported SO2 emissions are in error. Further
examination of the CAMD emissions data for Graham and Stryker revealed
that the data contained a large amount of substitute data for
SO2 emissions and heat input during periods when the units
burned fuel oil.
    As a consequence of this discordance between the type and amount of
fuel oil burned and the reported SO2 emissions, we cannot
rely on historical SO2 emissions to construct a baseline,
because a barrel of fuel oil with a given sulfur content does not
result in a consistent reported SO2 value over time.
Instead, we will conduct our cost-effectiveness analysis on the basis
of unit values of 1,000 barrels, using the following assumptions:
     Fuel oil costs will be based on the 2015 U.S. average
prices as reported in Table 12 for No. 4 distillate at 0.7 wt. % (the
permitted maximum for all units) as the current business as usual fuel,
No. 2 fuel oil at 0.3 wt. % as the moderate control option, and No. 2
diesel at 0.0015% as the high control option.
     The emission factor for calculating the tons of sulfur
emitted by the three fuel oils are taken from AP 42, Compilation of Air
Pollutant Emissions Factors.\95\
---------------------------------------------------------------------------

    \95\ The emission factor (lb/10\3\ gal) used is 150 x S, where S
= weight % sulfur, taken from AP 42, Fifth Edition, Volume 1,
Chapter 1: External Sources, Section 1.3, Fuel Oil Combustion,
available here: https://www3.epa.gov/ttn/chief/ap42/ch01/index.html.
Boilers >100 Million Btu/hr, No. 4 oil fired.
---------------------------------------------------------------------------

    Below is the result of that calculation:

                       Table 14--Cost Effectiveness of Switching to Lower Sulfur Fuel Oils
----------------------------------------------------------------------------------------------------------------
                                                                                Cost
                                                  Cost for 1,000   Tons reduced    effectiveness    Incremental
                Level of control                      barrels        for 1,000       for 1,000         cost-
                                                   baseline  ($/      barrels      barrels  ($/    effectiveness
                                                        yr)                            ton)           ($/ton)
----------------------------------------------------------------------------------------------------------------
Business as usual (No. 4 distillate $1.215/gal).         $51,030             N/A             N/A  ..............
Moderate control (No. 2 fuel oil $1.565/gal)....          65,730            1.26          11,218  ..............
High control (ULSD $1.667/gal)..................          70,014            2.20           8,627          -2,756
----------------------------------------------------------------------------------------------------------------

    We suspect our price information for ULSD may be high, as the
Wilkes facility indicated in its reply to our Section 114 request that
its 8/12/16 contract for oil was for ULSD, which had an index price of
$1.423/gallon. Assuming this price and retaining the same price for our
business as usual No. 4 distillate fuel oil of $1.215/gallon, results
in a cost-effectiveness of $3,970/ton--a significant improvement in
cost-effectiveness. We invite the affected facilities to provide site-
specific information for delivery of ULSD.
Scrubber Retrofits
    Elsewhere in our proposal, we conclude that certain types of wet
scrubbers were technically feasible as potential control options for
gas boilers that occasionally burn oil, similar to the ones under BART
review here. Were we to calculate the cost-effectiveness of a wet FGD,
similar to those under consideration for the coal units undergoing BART
review, we could expect that the capital and operating costs would be
on the same order, as displayed in Table 10. It is a straightforward
exercise to demonstrate that the installation of such a scrubber on any
of the gas-fired units that occasionally burn oil would result in a
very high cost-effectiveness value.
    For instance, taking the smallest total annualized wet FGD cost in
Table 10, corresponding to the Harrington Unit 0161B (approximately the
same size as the Graham Unit 2), results in a value of $19,145,500.
Assuming a 98% reduction from a baseline equal to the largest annual
SO2 emissions from any of the gas units, 1,287 tons/year
(Graham Unit 2, 2001), results in a SO2 reduction of 1,261
tons/year. The cost-effectiveness is then $15,183/ton, which is very
high for a SO2 scrubber. In addition, the annual
SO2 values for Graham Unit 2 from 2002 to 2015, and the
annual SO2 values for the remaining units, have always been
an order of magnitude less than the 2001 Graham Unit 2 value. Although
we have not modeled the visibility benefit of

installing SO2 scrubbers on these units, the visibility
benefit from scrubbers is estimated to be slightly less than the amount
of benefit estimated from switching to ULSD.\96\
---------------------------------------------------------------------------

    \96\ For example, switching from 0.7% sulfur fuel oil to ULSD at
0.0015% sulfur results in a reduction in sulfur emissions of 99.8%
compared to an estimated 98% reduction due to the use of a scrubber.
---------------------------------------------------------------------------

4. Impact Analysis Parts 2, 3, and 4: Energy and Non-air Quality
Environmental Impacts, and Remaining Useful Life
    Regarding the analysis of energy impacts, the BART Guidelines
advise, ``You should examine the energy requirements of the control
technology and determine whether the use of that technology results in
energy penalties or benefits.'' \97\ As discussed above in our cost
analyses for DSI, SDA, and wet FGD, our cost model allows for the
inclusion or exclusion of the cost of the additional auxiliary power
required for the pollution controls we considered to be included in the
variable operating costs. We chose to include this additional auxiliary
power in all cases. Consequently, we believe that any energy impacts of
compliance have been adequately considered in our analyses.
---------------------------------------------------------------------------

    \97\ 70 FR 39103, 39168 (July 6, 2005), [40 CFR part 51, App.
Y.].
---------------------------------------------------------------------------

    Regarding the analysis of non-air quality environmental impacts,
the BART Guidelines advise: \98\
---------------------------------------------------------------------------

    \98\ 70 FR at 39169 (July 6, 2005), [40 CFR part 51, App. Y.].

    Such environmental impacts include solid or hazardous waste
generation and discharges of polluted water from a control device.
You should identify any significant or unusual environmental impacts
associated with a control alternative that have the potential to
affect the selection or elimination of a control alternative. Some
control technologies may have potentially significant secondary
environmental impacts. Scrubber effluent, for example, may affect
water quality and land use. Alternatively, water availability may
affect the feasibility and costs of wet scrubbers. Other examples of
secondary environmental impacts could include hazardous waste
discharges, such as spent catalysts or contaminated carbon.
Generally, these types of environmental concerns become important
when sensitive site-specific receptors exist or when the incremental
emissions reductions potential of the more stringent control is only
marginally greater than the next most-effective option. However, the
fact that a control device creates liquid and solid waste that must
be disposed of does not necessarily argue against selection of that
technology as BART, particularly if the control device has been
applied to similar facilities elsewhere and the solid or liquid
waste is similar to those other applications. On the other hand,
where you or the source owner can show that unusual circumstances at
the proposed facility create greater problems than experienced
elsewhere, this may provide a basis for the elimination of that
---------------------------------------------------------------------------
control alternative as BART.

    The SO2 control technologies we considered in our
analysis--DSI and scrubbers--are in wide use in the coal-fired
electricity generation industry. Both technologies add spent reagent to
the waste stream already generated by the facilities we analyzed, but
do not present any unusual environmental impacts. As discussed below in
our cost analyses for DSI and SDA SO2 scrubbers, our cost
model includes waste disposal costs in the variable operating costs.
Consequently, we believe that with one possible exception, any non-air
quality environmental impacts have been adequately considered in our
analyses. We are aware that the Harrington facility has instituted a
water recycling program and obtains some of its water from the City of
Amarillo.\99\ Due to potential non-air quality concerns, we limit our
SO2 control analysis for Harrington to DSI and dry
scrubbers.
---------------------------------------------------------------------------

    \99\ http://www.powermag.com/xcel-energys-harrington-generating-station-earns-powder-river-basin-coal-users-group-award/.
---------------------------------------------------------------------------

    Regarding the remaining useful life, the BART Guidelines advise:
\100\
---------------------------------------------------------------------------

    \100\ 70 FR 39103, 39169, [40 CFR part 51, App. Y.].

    You may decide to treat the requirement to consider the source's
``remaining useful life'' of the source for BART determinations as
one element of the overall cost analysis. The ``remaining useful
life'' of a source, if it represents a relatively short time period,
may affect the annualized costs of retrofit controls. For example,
the methods for calculating annualized costs in EPA's OAQPS Control
Cost Manual require the use of a specified time period for
amortization that varies based upon the type of control. If the
remaining useful life will clearly exceed this time period, the
remaining useful life has essentially no effect on control costs and
on the BART determination process. Where the remaining useful life
is less than the time period for amortizing costs, you should use
---------------------------------------------------------------------------
this shorter time period in your cost calculations.

    We are unaware that any of the facilities we have analyzed for BART
have entered into an enforceable document to shut down the applicable
units earlier than what would occur under our assumed 30-year
operational life.\101\ As we stated in our Oklahoma FIP,\102\ we noted
that scrubber vendors indicate that the lifetime of a scrubber is equal
to the lifetime of the boiler, which might easily be well over 60
years. We identified specific scrubbers installed between 1975 and 1985
that were still in operation. Because a DSI system is relatively simple
and reliable, we have no reason to conclude that its service life would
be any less than what we typically use for scrubber cost analyses.
Because none of the facilities involved have entered into enforceable
documents to shut down the applicable units earlier, we will continue
to use a 30-year equipment life for DSI, scrubber retrofits, and
scrubber upgrades, as we believe that is proper.
---------------------------------------------------------------------------

    \101\ We received a November 21, 2016 letter from the source
owner regarding Parish Units 5 & 6. The letter, now added to the
docket, explains the units have natural gas firing capabilities and
expresses interest in obtaining flexibility to avoid BART or
obtaining multiple options for complying with BART. While we
acknowledge this interest, the letter does not provide or commit to
any specifics in furtherance of the BART analysis that EPA is now
required to conduct under the BART Guidelines.
    \102\ Response to Technical Comments for Sections E. through H.
of the Federal Register Notice for the Oklahoma Regional Haze and
Visibility Transport Federal Implementation Plan, Docket No. EPA-
R06-OAR-2010-0190, 12/13/2011. See discussion beginning on page 36.
---------------------------------------------------------------------------

5. Step 5: Evaluate Visibility Impacts
    Please see the BART Modeling TSD, where we describe in detail the
various modeling runs we conducted, our methodology and selection of
emission rates, modeling results, and final modeling analysis that we
used to evaluate the benefits of the proposed controls and their
associated emission decreases on visibility impairment values. Below we
present a summary of our analysis and our proposed findings regarding
the estimated visibility benefits of emission reductions based on the
CALPUFF and/or CAMx modeling results.
a. Visibility Benefits of DSI, SDA, and Wet FGD for Coal-Fired Units
    We evaluated the visibility benefits of DSI, for the twelve units
depicted in Tables 15 and 16 below that currently have no
SO2 control. We evaluated all the units using the control
levels we employed in our control cost analyses. In summary, we
evaluated these units at a DSI SO2 control level of 50%,
which we believe is likely achievable for any unit. At the lower
performance level we assumed, we conclude that the corresponding
visibility benefits from DSI in most cases would be close to half of
the benefits from scrubbers resulting in the visibility benefits from
scrubber retrofits being much more beneficial. We also evaluated the
visibility benefits for scrubber retrofits (wet FGD and SDA) for these
same units, assuming the same control levels corresponding to SDA and
wet FGD that we used in our control cost analyses. For those sources
that are within 300 to 400 km of a Class

I area, we utilized CALPUFF and CAMx modeling to assess the visibility
benefit of potential controls. For the remaining coal-fired sources (J
T Deely, Coleto Creek, Fayette and W A Parish), only CAMx modeling was
utilized as these sources are located at much greater distances to the
nearest Class I areas. In evaluating the impacts and benefits of
potential controls, we utilized a number of metrics, including change
in deciviews and number of days impacted over 0.5 dv and 1.0 dv.
Consistent with the BART Guidelines, the visibility impacts and
benefits modeled in CALPUFF and CAMx are calculated as the change in
deciviews compared against natural visibility conditions.\103\ We note
that the high control scenario modeling for Fayette units 1 and 2
demonstrate the benefit from existing high performing controls. As
discussed elsewhere, we found that for these units no additional
controls or upgrades were necessary. For a full discussion of our
review of all the modeling results, and factors that we considered in
evaluating and weighing all the results, see our BART Modeling TSD.
Below, we present a summary of some of those visibility benefits at the
Class I areas most impacted by each source:
---------------------------------------------------------------------------

    \103\ 40 CFR 51 Appendix Y, IV.D.5: ``Calculate the model
results for each receptor as the change in deciviews compared
against natural visibility conditions.''

                                   Table 15--Visibility Benefit of Retrofit Controls: Coal-Fired Units (CAMx Modeling)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Visibility impact            Visibility benefit
                                                                                -----------------------------------------------------------
          Facility name              Emission unit       Class I area           Metric                                                DSI        WFGD
                                                                                Baseline    DSI (50%)  WFGD (98%)    benefit     benefit
--------------------------------------------------------------------------------------------------------------------------------------------------------
Big Brown.......................  Source (Unit 1 and  WIMO..............  Max dv............       4.017       2.249       0.474       1.768       3.542
                                   2).
                                                                          Days >0.5 dv......          65          33           0          32          65
                                                                          Days >1.0 dv......          33          13           0          20          33
                                                      CACR..............  Max dv............       3.775       2.539       0.787       1.236       2.988
                                                                          Days >0.5 dv......          91          62           4          29          87
                                                                          Days >1.0 dv......          57          21           0          36          57
                                  Unit 1............  WIMO..............  Max dv............       2.154       1.168       0.245       0.986       1.909
                                                                          Days >0.5 dv......          33          13           0          20          33
                                                                          Days >1.0 dv......          12           1           0          11          12
                                                      CACR..............  Max dv............       2.016       1.327       0.409       0.688       1.606
                                                                          Days >0.5 dv......          58          22           0          36          58
                                                                          Days >1.0 dv......          17           4           0          13          17
                                  Unit 2............  WIMO..............  Max dv............       2.175       1.181       0.235       0.994       1.940
                                                                          Days >0.5 dv......          34          13           0          21          34
                                                                          Days >1.0 dv......          12           1           0          11          12
                                                      CACR..............  Max dv............       2.033       1.338       0.391       0.695       1.642
                                                                          Days >0.5 dv......          58          23           0          35          58
                                                                          Days >1.0 dv......          17           4           0          13          17
Monticello......................  Source (Unit 1, 2   CACR..............  Max dv............      10.498       6.121       2.079       4.377       8.419
                                   and 3).
                                                                          Days >0.5 dv......         152         107          28          45         124
                                                                          Days >1.0 dv......         111          54           8          57         103
                                                      WIMO..............  Max dv............       5.736       2.769       0.774       2.968       4.962
                                                                          Days >0.5 dv......          67          35           4          32          63
                                                                          Days >1.0 dv......          40          14           0          26          40
                                  Unit 1............  CACR..............  Max dv............       4.516       3.123       0.733       1.393       3.783
                                                                          Days >0.5 dv......          79          43           3          36          76
                                                                          Days >1.0 dv......          32          16           0          16          32
                                                      WIMO..............  Max dv............       2.241       1.290       0.252       0.951       1.989
                                                                          Days >0.5 dv......          30          10           0          20          30
                                                                          Days >1.0 dv......           8           2           0           6           8
                                  Unit 2............  CACR..............  Max dv............       4.487       3.065       0.563       1.422       3.924
                                                                          Days >0.5 dv......          78          42           1          36          77
                                                                          Days >1.0 dv......          30          13           0          17          30
                                                      WIMO..............  Max dv............       2.189       1.252       0.186       0.937       2.003
                                                                          Days >0.5 dv......          30          10           0          20          30
                                                                          Days >1.0 dv......           6           2           0           4           6
Coleto Creek....................  Source (Unit 1)...  WIMO..............  Max dv............       0.845       0.526       0.176       0.318       0.668
                                                                          Days >0.5 dv......           9           1           0           8           9
                                                                          Days >1.0 dv......           0           0           0           0           0
                                                      CACR..............  Max dv............       0.791       0.458       0.186       0.333       0.606
                                                                          Days >0.5 dv......           5           0           0           5           5
                                                                          Days >1.0 dv......           0           0           0           0           0
Harrington \1\..................  Source (Unit 061B   SACR..............  Max dv............       5.288       4.287       3.235       1.001       2.053
                                   & 062B).
                                                                          Days >0.5 dv......          13           7           3           6          10
                                                                          Days >1.0 dv......           5           1           1           4           4
                                                      WIMO..............  Max dv............       4.928       4.362       3.798       0.565       1.130
                                                                          Days >0.5 dv......          15          11           6           4           9
                                                                          Days >1.0 dv......           6           5           4           1           2
                                  Unit 061B.........  SACR..............  Max dv............       2.908       2.322       1.738       0.586       1.170
                                                                          Days >0.5 dv......           5           1           1           4           4
                                                                          Days >1.0 dv......           1           1           1           0           0
                                                      WIMO..............  Max dv............       2.708       2.382       2.065       0.326       0.643
                                                                          Days >0.5 dv......           6           5           4           1           2
                                                                          Days >1.0 dv......           4           2           1           2           3
                                  Unit 062B.........  SACR..............  Max dv............       2.998       2.373       1.719       0.625       1.279
                                                                          Days >0.5 dv......           5           1           1           4           4
                                                                          Days >1.0 dv......           1           1           1           0           0
                                                      WIMO..............  Max dv............       2.770       2.407       2.046       0.363       0.723
                                                                          Days >0.5 dv......           6           5           4           1           2
                                                                          Days >1.0 dv......           4           1           1           3           3

J T Deely.......................  Source (Sommers     WIMO..............  Max dv............       1.513       0.939       0.814       0.574       0.699
                                   1&2, J T Deely
                                   1&2).
                                                                          Days >0.5 dv......          47           8           1          39          46
                                                                          Days >1.0 dv......           6           0           0           6           6
                                                      CACR..............  Max dv............       1.423       1.155       0.905       0.268       0.518
                                                                          Days >0.5 dv......           7           3           2           4           5
                                                                          Days >1.0 dv......           2           1           0           1           2
                                  J T Deely 1.......  WIMO..............  Max dv............       0.757       0.449       0.270       0.307       0.487
                                                                          Days >0.5 dv......           4           0           0           4           4
                                                                          Days >1.0 dv......           0           0           0           0           0
                                                      BIBE..............  Max dv............       0.652       0.373       0.069       0.279       0.583
                                                                          Days >0.5 dv......           2           0           0           2           2
                                                                          Days >1.0 dv......           0           0           0           0           0
                                  J T Deely 2.......  WIMO..............  Max dv............       0.632       0.387       0.334       0.245       0.298
                                                                          Days >0.5 dv......           3           0           0           3           3
                                                                          Days >1.0 dv......           0           0           0           0           0
                                                      CACR..............  Max dv............       0.604       0.490       0.387       0.114       0.217
                                                                          Days >0.5 dv......           2           0           0           2           2
                                                                          Days >1.0 dv......           0           0           0           0           0
W.A. Parish.....................  Source (WAP 4, 5,   CACR..............  Max dv............       3.177       2.032       0.511       1.145       2.665
                                   & 6).
                                                                          Days >0.5 dv......          54          26           1          28          53
                                                                          Days >1.0 dv......          22           9           0          13          22
                                                      UPBU..............  Max dv............       1.994       1.215       0.234       0.779       1.760
                                                                          Days >0.5 dv......          34          14           0          20          34
                                                                          Days >1.0 dv......           9           1           0           8           9
                                  WAP 5.............  CACR..............  Max dv............       1.698       1.052       0.180       0.646       1.518
                                                                          Days >0.5 dv......          22           9           0          13          22
                                                                          Days >1.0 dv......           8           1           0           7           8
                                                      UPBU..............  Max dv............       1.038       0.613       0.094       0.424       0.943
                                                                          Days >0.5 dv......          11           1           0          10          11
                                                                          Days >1.0 dv......           1           0           0           1           1
                                  WAP 6.............  CACR..............  Max dv............       1.648       1.018       0.156       0.630       1.492
                                                                          Days >0.5 dv......          22           8           0          14          22
                                                                          Days >1.0 dv......           6           1           0           5           6
                                                      UPBU..............  Max dv............       1.003       0.591       0.081       0.412       0.922
                                                                          Days >0.5 dv......           9           1           0           8           9
                                                                          Days >1.0 dv......           1           0           0           1           1
Welsh \2\.......................  Source (Unit 1 &    CACR..............  Max dv............       4.576  ..........       0.822  ..........       3.754
                                   2).
                                                                          Days >0.5 dv......          92  ..........           3  ..........          89
                                                                          Days >1.0 dv......          39  ..........           0  ..........          39
                                                      MING..............  Max dv............       2.544  ..........       0.570  ..........       1.973
                                                                          Days >0.5 dv......           9  ..........           1  ..........           8
                                                                          Days >1.0 dv......           3  ..........           0  ..........           3
                                  Unit 1............  CACR..............  Max dv............       2.343       1.659       0.822       0.684       1.521
                                                                          Days >0.5 dv......          37          18           3          19          34
                                                                          Days >1.0 dv......           8           3           0           5           8
                                                      MING..............  Max dv............       1.150       0.886       0.570       0.264       0.579
                                                                          Days >0.5 dv......           2           1           1           1           1
                                                                          Days >1.0 dv......           1           0           0           1           1
Fayette \2\.....................  Source (Unit 1 &    CACR..............  Max dv............       1.894  ..........       0.903  ..........       0.991
                                   2).
                                                                          Days >0.5 dv......          26  ..........           2  ..........          24
                                                                          Days >1.0 dv......           9  ..........           0  ..........           9
                                                      WIMO..............  Max dv............       1.175  ..........       0.580  ..........       0.595
                                                                          Days >0.5 dv......          19  ..........           1  ..........          18
                                                                          Days >1.0 dv......           2  ..........           0  ..........           2
                                  Unit 1............  CACR..............  Max dv............       1.002  ..........       0.480  ..........       0.522
                                                                          Days >0.5 dv......           9  ..........           0  ..........           9
                                                                          Days >1.0 dv......           1  ..........           0  ..........           1
                                                      WIMO..............  Max dv............       0.609  ..........       0.306  ..........       0.302
                                                                          Days >0.5 dv......           2  ..........           0  ..........           2
                                                                          Days >1.0 dv......           0  ..........           0  ..........           0
                                  Unit 2............  CACR..............  Max dv............       0.974  ..........       0.441  ..........       0.534
                                                                          Days >0.5 dv......           9  ..........           0  ..........           9
                                                                          Days >1.0 dv......           0  ..........           0  ..........           0
                                                      WIMO..............  Max dv............       0.598  ..........       0.282  ..........       0.316
                                                                          Days >0.5 dv......           2  ..........           0  ..........           2
                                                                          Days >1.0 dv......           0  ..........           0  ..........           0
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Harrington high control scenario for both units is SDA at 95% reduction.
\2\ Welsh Unit 2 and Fayette Units 1 & 2 were not modeled at DSI level control. Welsh Unit 2 has shut down and Fayette units have WFGD (wet FGD)
  installed. Welsh source-wide modeling for high control includes a unit 2 shutdown.

                                 Table 16--Visibility Benefit of Retrofit Controls: Coal-Fired Units (CALPUFF Modeling)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Visibility impact               Visibility benefit
                                                                                ----------------------------------------------------------------
         Facility name            Emission unit       Class I area          Metric                                                               WFGD
                                                                                Baseline    DSI (50%)    WFGD (98%)  DSI benefit    benefit
--------------------------------------------------------------------------------------------------------------------------------------------------------
Big Brown.....................  Source (Units 1    WIMO.............  Max dv...........         4.27         2.54         0.43         1.73         3.83
                                 and 2).
                                                                      Days >0.5 dv Avg.        67.33        43.33         2.67        24.00        64.67
                                                                      Days >1.0 dv Avg.        42.00        21.00         1.00           21        41.00
                                                   CACR.............  Max dv...........         4.03         2.41         0.47         1.62         3.55
                                                                      Days >0.5 dv Avg.        91.67        64.33         4.67        27.33        87.00
                                                                      Days >1.0 dv Avg.        60.33        30.00         0.00        30.33        60.33
Monticello \1\................  Source (Unit 1, 2  CACR.............  Max dv...........         6.57         3.68         1.70         2.89         4.87
                                 and 3).
                                                                      Days >0.5 dv Avg.       143.67       115.00        62.33        28.67        81.33
                                                                      Days >1.0 dv Avg.       113.00        66.33        23.67        46.67        89.33
                                                   UPBU \4\.........  Max dv...........         3.45         1.77         0.77         1.68         2.68
                                                                      Days >0.5 dv Avg.       103.00        61.00        13.67        42.00        89.33
                                                                      Days >1.0 dv Avg.        39.33        16.67         2.67        22.67        36.67
                                                   WIMO.............  Max dv...........         3.23         1.60         0.54         1.63         2.70
                                                                      Days >0.5 dv Avg.        60.00        34.67         6.00        25.33        54.00
                                                                      Days >1.0 dv Avg.        39.33        16.67         0.67        22.67        38.67
Harrington \2\................  Source (Units      SACR.............  Max dv...........         1.06         0.86         0.61         0.20         0.45
                                 061B & 062B).
                                                                      Days >0.5 dv Avg.        21.00        15.33         6.33         5.67        14.67
                                                                      Days >1.0 dv Avg.         6.67         3.00         0.67         3.67         6.00
                                                   WIMO.............  Max dv...........         1.29         0.97         0.55         0.32         0.74
                                                                      Days >0.5 dv Avg.        26.00        15.33         8.67        10.67        17.33
                                                                      Days >1.0 dv Avg.         9.00         4.67         1.33         4.33         7.67
Welsh \3\.....................  Source (Unit 1)..  CACR.............  Max dv...........         1.44         1.12         0.72         0.32         0.72
                                                                      Days >0.5 dv Avg.        50.33        32.67        12.33        17.67           38
                                                                      Days >1.0 dv Avg.        15.33         8.00         2.33         7.33        13.00
                                                   UPBU.............  Max dv...........         0.76         0.49         0.22         0.27         0.54
                                                                      Days >0.5 dv Avg.        12.00         4.67         0.33         7.33        11.67
                                                                      Days >1.0 dv Avg.         0.67         0.00         0.00         0.67         0.67
                                                   WIMO.............  Max dv...........         0.56         0.33         0.15         0.23         0.41
                                                                      Days >0.5 dv Avg.         7.33         2.67         0.33         4.67         7.00
                                                                      Days >1.0 dv Avg.         1.33         0.33         0.00         1.00         1.33
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Monticello's controlled level is a combination of scrubber upgrades and scrubber install in the facility impact modeling with CALPUFF.
\2\ Harrington high control scenario for both units is SDA at 95% reduction.
\3\ Welsh Unit 2 and Fayette Units 1 & 2 were not modeled at DSI level control. Welsh Unit 2 has shut down and Fayette units have WFGD installed. Welsh
  source-wide modeling for high control includes a unit 2 shutdown.
\4\ UPBU = Upper Buffalo Wilderness Area.

b. Visibility Benefits of Scrubber Upgrades for Coal-Fired Units
    We also modeled the visibility benefits of those same units for
which we conducted control cost analysis for upgrading their existing
scrubbers. We assumed the same 95% control level we used in our control
cost analyses. We also modeled a lower level control at 90%. The
visibility benefits from these scrubber upgrades are quantified
specifically in our BART Modeling TSD. Below, we present a summary of
the del-dv visibility benefits and reduction in number of days
impacted.

                                   Table 17--Visibility Benefit of Scrubber Upgrades: Coal-Fired Units (CAMx Modeling)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Visibility impact               Visibility benefit
                                                                                ----------------------------------------------------------------
         Facility name            Emission unit       Class I area          Metric                       (90%)        (95%)        (90%)        (95%)
                                                                                Baseline     control      control      benefit      benefit
--------------------------------------------------------------------------------------------------------------------------------------------------------
Martin Lake...................  Source (Unit 1, 2  CACR.............  Max dv...........        6.651        4.491        4.321        2.159        2.329
                                 & 3).
                                                                      Days >0.5 dv.....          141           75           56           66           85
                                                                      Days >1.0 dv.....           99           31           16           68           83
                                                   UPBU.............  Max dv...........        5.803        2.669        2.528        3.134        3.275
                                                                      Days >0.5 dv.....           99           39           22           60           77
                                                                      Days >1.0 dv.....           67           11            7           56           60
                                Unit 1...........  CACR.............  Max dv...........        2.633        1.550        1.468        1.083        1.165
                                                                      Days >0.5 dv.....           71           17            6           54           65
                                                                      Days >1.0 dv.....           26            3            1           23           25
                                                   UPBU.............  Max dv...........        2.254        0.867        0.805        1.387        1.449
                                                                      Days >0.5 dv.....           44            6            3           38           41
                                                                      Days >1.0 dv.....           10            0            0           10           10
                                Unit 2...........  CACR.............  Max dv...........        2.466        1.882        1.811        0.585        0.655
                                                                      Days >0.5 dv.....           68           18            9           50           59
                                                                      Days >1.0 dv.....           26            3            1           23           25
                                                   UPBU.............  Max dv...........        2.189        1.077        1.025        1.112        1.164
                                                                      Days >0.5 dv.....           40            6            5           34           35
                                                                      Days >1.0 dv.....           10            1            1            9            9
                                Unit 3...........  CACR.............  Max dv...........        2.755        1.682        1.609        1.074        1.146
                                                                      Days >0.5 dv.....           76           15            6           61           70
                                                                      Days >1.0 dv.....           29            2            1           27           28
                                                   UPBU.............  Max dv...........        2.368        0.942        0.890        1.425        1.478
                                                                      Days >0.5 dv.....           46            6            4           40           42

                                                                      Days >1.0 dv.....           13            0            0           13           13
Monticello....................  Source (Unit 1, 2  CACR.............  Max dv...........       10.498        6.121        2.079        4.377        8.419
                                 and 3).
                                                                      Days >0.5 dv.....          152          107           28           45          124
                                                                      Days >1.0 dv.....          111           54            8           57          103
                                                   WIMO.............  Max dv...........        5.736        2.769        0.774        2.968        4.962
                                                                      Days >0.5 dv.....           67           35            4           32           63
                                                                      Days >1.0 dv.....           40           14            0           26           40
                                Unit 3...........  CACR.............  Max dv...........        4.632        0.905        0.914        3.728        3.719
                                                                      Days >0.5 dv.....           79            5            5           74           74
                                                                      Days >1.0 dv.....           32            0            0           32           32
                                                   WIMO.............  Max dv...........        2.282        0.462        0.364        1.820        1.918
                                                                      Days >0.5 dv.....           31            0            0           31           31
                                                                      Days >1.0 dv.....            7            0            0            7            7
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                 Table 18--Visibility Benefit of Scrubber Upgrades: Coal-Fired Units (CALPUFF Modeling)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Visibility impact               Visibility benefit
                                                                                ----------------------------------------------------------------
         Facility name            Emission unit       Class I area          Metric                                                               WFGD
                                                                                Baseline    DSI (50%)    WFGD (98%)  DSI benefit    benefit
--------------------------------------------------------------------------------------------------------------------------------------------------------
Martin Lake                     Source (Units 1,   CACR.............  Max dv...........         4.46         2.27         1.86         2.18         2.60
                                 2 & 3).
                                                                      Days >0.5 dv Avg.       129.67        77.33        63.00        52.33        66.67
                                                                      Days >1.0 dv Avg.        91.33        32.67        22.33        58.67        69.00
                                                   UPBU.............  Max dv...........         2.73         1.10         0.85         1.63         1.88
                                                                      Days >0.5 dv Avg.        81.67        30.33        18.67        51.33        63.00
                                                                      Days >1.0 dv Avg.        46.67         7.33         3.67        39.33        43.00
Monticello \1\................  Source (Unit 1, 2  CACR.............  Max dv...........         6.57         3.68         1.70         2.89         4.87
                                 and 3).
                                                                      Days >0.5 dv Avg.       143.67          115        62.33        28.67        81.33
                                                                      Days >1.0 dv Avg.          113        66.33        23.67        46.67        89.33
                                                   UPBU.............  Max dv...........         3.45         1.77        0.765         1.68         2.68
                                                                      Days >0.5 dv Avg.          103           61        13.67           42        89.33
                                                                      Days >1.0 dv Avg.        39.33        16.67         2.67        22.67        36.67
                                                   WIMO.............  Max dv...........         3.23         1.60         0.54         1.63         2.70
                                                                      Days >0.5 dv Avg.           60        34.67            6        25.33           54
                                                                      Days >1.0 dv Avg.        39.33        16.67         0.67        22.67        38.67
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Monticello's controlled level is a combination of scrubber upgrade on Unit 3 and scrubber retrofits on Units 1 and 2 in the facility impact modeling
  with CALPUFF.

c. Visibility Benefits of Fuel Oil Switching for Gas/Fuel Oil-Fired
Units
    We also modeled the visibility benefits of those gas/fuel oil-fired
units for which we conducted control cost analysis for switching to
lower sulfur fuels. We evaluated the visibility benefits of switching
to fuel oils corresponding to ultra-low sulfur diesel at 0.0015% sulfur
by weight and 0.3% sulfur by weight as we evaluated in our control cost
analyses. The visibility benefits from these fuel switches are
quantified specifically in our BART Modeling TSD. Below, we present a
summary of the del-dv visibility benefits.

                              Table 19--Visibility Benefits From Lower Sulfur Fuel
----------------------------------------------------------------------------------------------------------------
                                                           Baseline
                                                       visibility impact                      Visibility benefit
          Facility name              Emission unit     from source (most  Visibility benefit   of 0.0015% S fuel
                                                       impacted Class I   of 0.3% S fuel oil          oil
                                                             area)
----------------------------------------------------------------------------------------------------------------
Stryker                           ST2...............  CALPUFF 0.65% S:    CALPUFF (0.3% S):   CALPUFF: 0.522 dv
                                                       0.786 dv @ CACR     0.263 dv @ CACR     @ CACR (Facility)
                                                       (Facility).         (Facility).
Graham                            Unit 2............  CALPUFF 0.69% S:    CALPUFF (0.3% S):   CALPUFF: 0.851 dv
                                                       1.228 dv @ WIMO     0.465 dv @ WIMO     @ WIMO (Facility)
                                                       (Facility).         (Facility.
Wilkes                            Units 1, 2, 3.....  CALPUFF 0.43% S:    CALPUFF (0.1% S):   CALPUFF: 0.037 dv
                                                       0.698 dv @ CACR     0.029 dv @ CACR     @ CACR (Facility)
                                                       (Facility).         (Facility).
Newman \1\                        Unit 2............  N/A...............  N/A...............  N/A
                                  Unit 3............  N/A...............  N/A...............  N/A
                                  Unit 4............  N/A...............  N/A...............  N/A
Calaveras                         Sommers...........  CAMx: 1.513 dv @    0.004 dv @ CACR...  0.008 dv @ CACR
                                  Unit 1............   WIMO (Source);
                                                       0.106 dv @ CACR
                                                       (Unit).

                                  Sommers...........  CAMx: 1.513 dv @    0.023 @ CACR......  0.047 @ CACR
                                  Unit 2............   WIMO (Source);
                                                       0.180 dv @ CACR
                                                       (Unit).
----------------------------------------------------------------------------------------------------------------
\1\ Newman is on the edge of the CALMET and CALPUFF modeling grids for the database that were used in this
  action. Since the facility was near the edge, emissions of the facility's impacts could not be adequately
  modeled since some of the plumes could have gone out of the grid and not be adequately assessed if they come
  back into the grid and transport to impact a Class I area.

6. BART Analysis for PM
    In our recent Texas-Oklahoma FIP, we initially proposed to approve
Texas' determination that no PM BART controls were appropriate for its
EGUs, based on a screening analysis of the visibility impacts from just
PM emissions and the premise that EGU SO2 and NOX
were covered separately by participation in CSAPR (allowing
consideration of PM emissions in isolation). Because of the CSAPR
remand and resulting uncertainty regarding SO2 and
NOX BART for EGUs, we decided not to finalize our proposed
approval of Texas' PM BART determination.\104\ For reasons earlier
stated we are proposing to disapprove the SIP determination regarding
PM BART for EGUs. Following from that proposed disapproval, we are
proposing a PM BART FIP for those Texas EGUs that are subject to BART.
---------------------------------------------------------------------------

    \104\ 81 FR 302 (January 5, 2016).
---------------------------------------------------------------------------

    The BART Guidelines permit us to conduct a streamlined analysis of
PM BART in two key ways. First, the Guidelines allow a streamlined
analysis for PM sources subject to MACT standards. Unless there are new
technologies subsequent to the MACT standards which would lead to cost-
effective increases in the level of control, the Guidelines state it is
permissible to rely on MACT standards for purposes of BART.\105\
---------------------------------------------------------------------------

    \105\ 70 FR 39163-39164.
---------------------------------------------------------------------------

    Second, with respect to gas-fired units, which have inherently low
emissions of PM (as well as SO2), the Regional Haze Rule did
not specifically envision new or additional controls or emissions
reductions from the PM BART requirement. The BART guidelines preclude
us from stating that PM emissions are de minimis when plant-wide
emissions exceed 15 tons per years. While we must assign PM BART
determinations to the gas-firing units, there are no practical add-on
controls to consider for setting a more stringent PM BART emissions
limit. The Guidelines state that if the most stringent controls are
made federally enforceable for BART, then the otherwise required
analyses leading up to the BART determination can be skipped.\106\
---------------------------------------------------------------------------

    \106\ 70 FR 39165 (``. . . you may skip the remaining analyses
in this section, including the visibility analysis . . .'')
---------------------------------------------------------------------------

    With this background, we are providing our evaluation along with
some supplementary information on the BART sources as divided into two
categories: coal-fired EGUs, and gas-fired EGUs.
BART Analysis for PM for Coal-Fired Units
    All of the coal-fired EGUs that are subject to BART are currently
equipped with either Electrostatic Precipitators (ESPs) or baghouses,
or both, as can be seen from Table 20:

                       Table 20--Current PM Controls for Coal-Fired Units Subject to BART
----------------------------------------------------------------------------------------------------------------
                                                      Fuel type
         Facility name               Unit ID          (primary)        SO2 control(s)         PM control(s)
----------------------------------------------------------------------------------------------------------------
Big Brown......................               1  Coal..............  ..................  Baghouse +
                                                                                Electrostatic
                                                                                Precipitator.
Big Brown......................               2  Coal..............  ..................  Baghouse +
                                                                                Electrostatic
                                                                                Precipitator.
Coleto Creek...................               1  Coal..............  ..................  Baghouse.
Harrington Station.............            061B  Coal..............  ..................  Electrostatic
                                                                                Precipitator.
Harrington Station.............            062B  Coal..............  ..................  Baghouse.
J T Deely......................               1  Coal..............  ..................  Baghouse.
J T Deely......................               2  Coal..............  ..................  Baghouse.
Martin Lake....................               1  Coal..............  Wet Limestone.....  Electrostatic
                                                                                Precipitator.
Martin Lake....................               2  Coal..............  Wet Limestone.....  Electrostatic
                                                                                Precipitator.
Martin Lake....................               3  Coal..............  Wet Limestone.....  Electrostatic
                                                                                Precipitator.
Monticello.....................               1  Coal..............  ..................  Baghouse +
                                                                                Electrostatic
                                                                                Precipitator.
Monticello.....................               2  Coal..............  ..................  Baghouse +
                                                                                Electrostatic
                                                                                Precipitator.
Monticello.....................               3  Coal..............  Wet Limestone.....  Electrostatic
                                                                                Precipitator.
Fayette........................               1  Coal..............  Wet Limestone.....  Electrostatic
                                                                                Precipitator.
Fayette........................               2  Coal..............  Wet Limestone.....  Electrostatic
                                                                                Precipitator.
W A Parish.....................            WAP5  Coal..............  ..................  Baghouse.
W A Parish.....................            WAP6  Coal..............  ..................  Baghouse.
Welsh Power Plant..............               1  Coal..............  ..................  Baghouse (Began Nov 15,
                                                                                2015) + Electrostatic
                                                                                Precipitator.
----------------------------------------------------------------------------------------------------------------

    As an initial matter, we examine the control efficiencies of both
baghouses and ESPs. We consider a baghouse, widely reported to be
capable of 99.9% control of PM, to be the maximum level control for PM
and so the units equipped with a baghouse will not be further analyzed
for PM BART. The remaining units are fitted with ESPs.
    The particulate matter control efficiency of ESPs varies somewhat
with

the design, the resistivity of the particulate matter, and the
maintenance of the ESP. We do not have any information on the control
level efficiency of any of the ESPs for the units in question. However,
reported control efficiencies for well-maintained ESPs typically range
from greater than 99% to 99.9%.\107\ We consider this pertinent in
concluding that the potential additional particulate control that a
baghouse can offer over an ESP is relatively minimal.\108\ In other
words, if we did obtain control information specific to the ESP units
in question, we do not believe that additional information would lead
us to a different conclusion.
---------------------------------------------------------------------------

    \107\ EPA, ``Air Pollution Control Technology Fact Sheet: Dry
Electrostatic Precipitator (ESP)--Wire Plate Type,'' EPA-452/F-03-
028. Grieco, G., ``Particulate Matter Control for Coal-fired
Generating Units: Separating Perception from Fact,'' apcmag.net,
February, 2012. Moretti, A. L.; Jones, C. S., ``Advanced Emissions
Control Technologies for Coal-Fired Power Plants, Babcox and Wilcox
Technical Paper BR-1886, Presented at Power-Gen Asia, Bangkok,
Thailand, October 3-5, 2012.
    \108\ We do not discount the potential health benefits this
additional control can have for ambient PM. However, the regional
haze program is only concerned with improving the visibility at
Class I areas.
---------------------------------------------------------------------------

    Nevertheless, w`e will examine the potential cost of retrofitting a
typical 500 MW coal fired unit with a baghouse. Using our baghouse cost
algorithms, as employed in version 5.13 of our IPM model,\109\ and
assuming a conservative air to cloth ratio of 6.0, results in a capital
engineering and construction cost of $77,428,000.\110\ Applied to the
subject units, this cost assumes a retrofit factor of 1.0, and does not
consider the demolition of the existing ESP, should it be required in
order to make space for the baghouse.
---------------------------------------------------------------------------

    \109\ IPM Model--Updates to Cost and Performance for APC
Technologies, Particulate Control Cost Development Methodology,
Final March 2013, Project 12847-002, Systems Research and
Applications Corporation, Prepared by Sargent & Lundy. Documentation
for v.5.13: Chapter 5: Emission Control Technologies, Attachment 5-
7: PM Cost Methodology, downloaded from: https://www.epa.gov/sites/production/files/2015-08/documents/attachment_5-7_pm_cost_methodology.pdf.
    \110\ Id. See page 9.
---------------------------------------------------------------------------

    We do not calculate the cost-effectiveness resulting from replacing
an ESP with a baghouse. However, we expect that the tons of additional
PM removed by a baghouse over an ESP to be very small, which would
result in a very high cost-effectiveness figure. Also, we do not model
the visibility benefit of replacing an ESP with a baghouse. However,
our visibility impact modeling indicates that the baseline PM emissions
of these units are very small, so we expect that the visibility
improvement from replacing an ESP with a baghouse to be a small
fraction of that. For instance, our CAMx baseline modeling shows that
on a source-wide level, impacts from PM emissions on the maximum
impacted days from each source at each Class I area was 3% of the total
visibility impairment or less (calculated as percent of total
extinction due to the source). Therefore additional PM controls are
anticipated to result in very little visibility benefit on the maximum
impacted days. Similarly, our CALPUFF modeling indicates that
visibility impairment from PM is also a small fraction (typically only
a few percent) of the total visibility impairment due to each source.
    Adding to the above discussion, we are tasked to assign the
enforceable emission limitations that constitute PM BART. We believe a
stringent control level that would be met with existing or otherwise-
required controls is a filterable PM limit of 0.03 lb/MMBtu for each of
the coal-fired units subject to BART. We note that the Mercury and Air
Toxics (MATS) Rule establishes an emission standard of 0.03 lb/MMBtu
filterable PM (as a surrogate for toxic non-mercury metals) as
representing Maximum Achievable Control Technology (MACT) for coal-
fired EGUs.\111\ This standard derives from the average emission
limitation achieved by the best performing 12 percent of existing coal-
fired EGUs, as based upon test data used in developing the MATS Rule.
We are not familiar with any new technologies subsequent to this
standard that could lead to any cost effective increases in the level
of control; thus, consistent with the BART Guidelines, we are proposing
to rely on this limit for purposes of PM BART for all of the coal-fired
units as part of our FIP. We understand the coal-fired units covered by
this proposal to be subject to MATS, but to the extent the units may be
following alternate limits that differ from the surrogate PM limits
found in MATS, we welcome comments on different, appropriately
stringent limits reflective of current control capabilities.\112\
Because we anticipate that any limit we assign should be achieved by
current control capabilities, we propose that compliance can be met at
the effective date of the rule. To address periods of startups and
shutdowns, we are further proposing that PM BART for these units will
additionally be met by following the work practice standards specified
in 40 CFR part 63, subpart UUUUU, Table 3, and using the relevant
definitions in 63.10042. We are proposing that the demonstration of
compliance can be satisfied by the methods for demonstrating compliance
with filterable PM limits that are specified in 40 CFR part 63, subpart
UUUUU, Table 7. However, we would give consideration to commenter-
submitted requests for alternate or additional methods of demonstrating
compliance.
---------------------------------------------------------------------------

    \111\ 77 FR 9304, 9450, 9458 (February 16, 2012) (codified at 40
CFR 60.42 Da(a), 60.50 Da(b)(1)); 40 CFR part 63 Subpart UUUUU--
National Emission Standards for Hazardous Air Pollutants: Coal- and
Oil-Fired Electric Utility Steam Generating Units.
    \112\ The various limits are provided at 40 CFR part 63, subpart
UUUUU, Table 2 (``Emission Limits for Existing EGUs'').
---------------------------------------------------------------------------

BART Analysis for PM for Gas-Fired Units
    We note that PM emissions for the gas-only fired units that are
subject to BART are inherently low.\113\ We therefore conclude that PM
emissions from natural gas firing is so minimal that the installation
of any additional PM controls on the unit would likely achieve very low
emissions reductions and have minimal visibility benefits. As there are
no appropriate add-on controls and the status quo reflects the most
stringent controls, we are proposing to make the requirement to burn
pipeline natural gas federally enforceable. We note that in addition to
satisfying PM BART, this limitation will also serve to satisfy
SO2 BART for these gas-fired units, as well as the fuel-oil
units when they fire natural gas. We are proposing that PM and
SO2 BART for gas fired-units will limit fuel to pipeline
natural gas, as defined at 40 CFR 72.2.
---------------------------------------------------------------------------

    \113\ AP 42, Fifth Edition, Volume 1, Chapter 1: External
Sources, Section 1.4, Natural Gas Combustion, available here:
https://www3.epa.gov/ttn/chief/ap42/ch01/final/c01s04.pdf.
---------------------------------------------------------------------------

    The available PM controls for gas units that also burn fuel oil are
the same for the coal-fired units. We would expect similar costs for
installing a baghouse on a typical gas-fired boiler that occasionally
burns fuel oil. Again, our visibility impact modeling indicates that
the baseline PM emissions of these units are very small, so we expect
that the visibility improvement from the installation of a baghouse to
be a small fraction on the order of 1-3% of the visibility impacts from
the facility. We are confident that the cost of retrofitting the
subject units with a baghouse would be extremely high compared to the
visibility benefit for any of the units currently fitted with an ESP.
We conclude that the cost of a baghouse does not justify the minimal
expected improvement in visibility for these units. Accordingly, we are
proposing that the fuel content limits for oil burning that we propose
to meet SO2 BART will also satisfy PM BART.

    Lastly, should our assumptions regarding the frequency and type of
fuel oil burned in these units significantly change, we expect that
Texas will address such a change appropriately in its SIP, which we
will review in the next planning period.

D. How, if at all, do issues of ``Grid Reliability'' relate to the
proposed BART determinations?

    On July 15, 2016, a preliminary order of the Fifth Circuit Court of
Appeals took the view that EPA's Texas-Oklahoma FIP (81 FR 295, January
5, 2016) gave a ``truncated discussion of grid reliability'' and
additionally stated that ``the agency may not have fulfilled its
statutory obligation to consider the energy impacts of the FIP.'' The
Court's preliminary ruling made particular reference to ``the explicit
directive in the [CAA] that implementation plans `take[ ] into
consideration . . . the energy . . . impacts of compliance,' 42 U.S.C.
7491(g)(1).'' \114\ Because the BART requirement at issue in this
proposal has similar language on energy impacts of compliance appearing
at 42 U.S.C. 7491(g)(2), we wish to provide a clear explanation on how
grid-related considerations for EGUs could bear on this proposal.
---------------------------------------------------------------------------

    \114\ EPA Guidance on this statutory language specifically
explains that energy impacts are a matter of whether ``energy
requirements associated with a control technology result in energy
penalties.'' U.S. EPA, Office of Air Quality Planning and Standards,
``Guidance for Setting Reasonable Progress Goals under the Regional
Haze Program,'' (June 1, 2007 rev), at Page 5-2.
---------------------------------------------------------------------------

    First, the BART factor for energy impacts of compliance does not
call for the examination of grid reliability considerations from
alleged plans to shut down or retire a unit rather than comply with a
more stringent emission limit or limits. The language instead calls for
consideration of energy impacts from complying by installing retrofit
controls on a source that continues in operation. In this regard, our
proposal follows the required BART Guidelines for EGUs.\115\ The
Guidelines explain that the energy impacts factor relates to the
penalties and benefits that may be associated with the assessment of a
control option, e.g., whether (for power penalties) the operation of
add-on control technology subtracts from the productive yield of
electricity from an EGU (what is sometimes termed an auxiliary or
parasitic load).\116\ It is also useful to note that the statutory
text, while using the word ``energy,'' can apply to sources that do not
produce energy or electricity. Thus, the statutory text regarding
``energy impacts'' of compliance with BART is not confined to the power
generating industry and does not dictate that we study grid reliability
issues.
---------------------------------------------------------------------------

    \115\ The promulgation of the Guidelines was required by 42
U.S.C. 7491(b)(1). Adherence to the Guidelines is mandatory for
fossil-fuel fired generating power plants having total generating
capacities ``in excess of 750 megawatts.''
    \116\ Other CAA provisions requiring consideration of ``energy
impacts'' or ``energy requirements of the control technology'' are
understood similarly. See, e.g., CAA section 169 (the 1977 ``best
available control technology'' requirement with consideration of
``energy . . . impacts''); see also CAA section 108 (``energy
requirements . . . of the emission control technology; ``energy . .
. impact of such processes, procedures, and methods [to reduce or
control air pollution''); section 111 (``taking into account . . .
energy requirements'' of an emission limitation), etc.
---------------------------------------------------------------------------

    We have considered whether this topic has any separate relevance to
our proposal. Various court filings, news accounts, and industry market
reports suggest that some source operators for some Texas BART units
may be contemplating unit retirements. The BART Guidelines directly
address such scenarios under the ``remaining useful life'' factor:
``there may be situations where a source operator intends to shut down
a source . . . . but wishes to retain the flexibility to continue
operating beyond that date in the event, for example, the market
conditions change.'' \117\ The Guidelines advise that a source that is
willing to assure a permanent stop in operations with a federally- or
State-enforceable restriction preventing further operation may obtain a
short remaining useful life for BART analysis purposes that could then
factor in the overall cost analysis.\118\ As the Guidelines state,
``Where the remaining useful life is less the than the time period for
amortizing costs, you should use this shorter period in your cost
calculations.'' \119\ We have no information on enforceable
restrictions of this type for any of the units that we propose to be
subject to BART. Absent that, we must assume that controls installed on
the BART units will experience their full useful life. Affected sources
are free to submit information as part of their comments containing
appropriate enforceable documentation of shorter remaining useful
lives.
---------------------------------------------------------------------------

    \117\ Id. at 39169-39170.
    \118\ Similar to calculating a mortgage, remaining useful life
is used in our cost-effectiveness analysis to calculate the annual
cost of a particular control. The longer the remaining useful life,
the smaller the total annualized cost, and the more cost-effective
the control.
    \119\ Id. at 39169.
---------------------------------------------------------------------------

    We note, however, that the Guidelines recognize there may be cases
where the installation of controls, even when cost-effective, would
``affect the viability of continued plant operations.'' \120\ Under the
Guidelines, where there are ``unusual circumstances,'' we are permitted
to take into consideration ``the conditions of the plant and the
economic effects of requiring the use of a control technology.'' \121\
If the effects are judged to have a ``severe impact,'' those effects
can be considered in the selection process. In such cases, the
Guidelines counsel that any determinations be made with an economic
analysis with sufficient detail for public review on the ``specific
economic effects, parameters, and reasoning.'' \122\ It is recognized,
by the language of the Guidelines, that any such review process may
entail the use of sensitive business information that may be
confidential. The ADDRESSES section of this proposal explains how to
submit confidential information with comments, and when claims of
confidential business information, or CBI, are asserted with respect to
any information that is submitted, the EPA regulations at 40 CFR part
2, subpart B-Confidentiality Business Information apply to protect it.
All of that said, the Guidelines also advise that we may ``consider
whether other competing plants in the same industry have been required
to install BART controls if this information is available.'' \123\
Because Texas EGUs are among the last to have SO2 BART
determinations, this information is available. It is indeed the case
that other similar EGUs have been required to install the same types of
SO2 BART controls that we are proposing as very cost
effective.\124\
---------------------------------------------------------------------------

    \120\ 70 FR 39103, 39171 (July 6, 2005), [40 CFR part 51, App.
Y].
    \121\ Id.
    \122\ 70 FR at 39171.
    \123\ Id.
    \124\ See for instance, the EIA information we present elsewhere
in this notice in which we summarize the hundreds of scrubber
installations that have been performed on similar EGUs.
---------------------------------------------------------------------------

    We have considered the state of available information on whether
the proposed controls could affect the viability of continued plant
operations. On this point, we note that we are proposing BART
determinations for several units where SO2 control
requirements were separately promulgated as part of the Texas-Oklahoma
FIP. These under-controlled EGU sources are: Big Brown 1 and 2;
Monticello 1, 2 and 3; Martin Lake 1, 2 and 3; and Coleto Creek 1. In
litigation over the reasonable progress FIP, various declarations were
filed on the issues of alleged forced closures and alleged reliability
impacts. These declarations have been compiled and added to the docket
for this rulemaking.

By our review, these declarations do not appropriately inform or
substantiate source-specific allegations of ``unusual circumstances''
that may have a severe impact on plant operations, because they do not
offer any site-specific information.\125\ Thus, we are unable to
conclude that the proposed cost-effective BART controls would severely
impact plant operations. Generalized claims of possible retirements and
discussions on attributes of the market design of the Electric
Reliability Council of Texas (ERCOT) cannot inform the statutorily
required, source-specific BART determinations.
---------------------------------------------------------------------------

    \125\ Certain statements in declarations from representatives of
both Luminant and Coleto Creek, who are the source owners of these
facilities, cited compliance planning efforts that would be
consistent with continued plant operations.
---------------------------------------------------------------------------

    As a predicate to studying effects on transmission or reliability
as ``unusual circumstances,'' we would require site-specific
information from any source that would wish for us to potentially
consider ``affordability of controls,'' under the terms specified in
the Guidelines. Source owners may submit information, including
information claimed to be CBI, for our assessment and consideration to
potentially support an economic analysis that might be used in the BART
selection process. As suggested by the Guidelines, the information
necessary to inform our judgment would likely entail source-specific
information on ``product prices, the market share, and the
profitability of the source.'' Consideration of such information does
not dictate what will be selected as a ``best'' alternative under the
Guidelines, but it will substantiate the likelihood of a retirement
scenario that would then give the parameters for: A non-conjectural
examination of grid reliability issues; judging the significance or
insignificance of such issues; and assessing whether such issues could
be avoided through appropriate transmission planning. In sum, unless we
are able to substantiate an ``affordability of controls'' problem for
any particular unit and substantiate that a particular unit retirement
would not be happening anyway at about the same time, alleged grid
reliability impacts are speculative and are not able to inform these
required BART determinations. As a final note, we acknowledge Executive
Order 13211 (``Actions Concerning Regulations That Significantly Affect
Energy Supply, Distribution, and Use''). In cases where it does apply,
agencies are ordered to prepare a Statement of Energy Effects for
submission to the Administrator of the Office of Information and
Regulatory Affairs (OIRA), Office of Management and Budget. This EGU
BART proposal is not considered a significant regulatory action under
Executive Order 12866, so the proposed action cannot be a ``significant
energy action'' for purposes of Executive Order 13211 on that basis.
This proposed action has also not been designated a significant energy
action by the Administrator of OIRA, so Executive Order 13211 could not
apply under that separate basis. With this proposal, there are no
anticipated adverse effects on energy supply, distribution, or use that
are meaningful or distinguishable from any other scenario where an EGU
is expected to install cost-effective pollution controls required by
the CAA.

IV. Our Weighing of the Five BART Factors

    Below we present our reasoning for proposing our BART
determinations for 29 EGUs in Texas, based on our analysis and weighing
of the Five BART Factors: (1) Proposed SO2 and PM BART
determinations for 12 coal-fired units with no SO2 controls,
(2) proposed BART SO2 and PM BART determinations for 6 coal-
fired units with existing scrubbers, (3) proposed SO2 and PM
BART determinations 7 gas-fired units that occasionally burn fuel oil,
and (4) proposed PM BART determinations for 4 gas-fired units.
    In previous sections of this proposal, we have described how we
assessed the five BART factors. In no case do we see any instance in
which our assessment of energy impacts is a determining factor in
assessing BART.\126\ Also, in no case do we see any instance in which
our assessment of the remaining useful life is a determining factor in
assessing BART. Should a facility indicate in comments to us that the
remaining useful life is less than the 30 years we have assumed in our
control cost analyses, and is willing to enter into an enforceable
document to that effect, we will adjust our cost-effectiveness
calculation accordingly in making our final decision. In two cases,
Harrington units 061B and 062B, we have limited our SO2
control analysis for Harrington to DSI and dry scrubbers due to
potential non-air quality concerns. In all other instances, we conclude
that the cost of compliance, and the visibility benefits of controls
are the controlling BART factors in our weighing of the five BART
factors.
---------------------------------------------------------------------------

    \126\ In addition to our assessment of energy impacts, also see
our discussion in Section III.D concerning our conclusion that
energy impact considerations do not relate to potential electrical
grid reliability issues.
---------------------------------------------------------------------------

    In considering cost-effectiveness and visibility benefit, we do not
eliminate any controls based solely on the magnitude of the cost-
effectiveness value, nor do we use cost-effectiveness as the primary
determining factor. Rather, we compare the cost-effectiveness to the
anticipated visibility benefit, and we take note of any additional
considerations.\127\ Also, in judging the visibility benefit we do not
simply examine the highest value for a given Class I area, or a group
of Class I areas, but we also consider the cumulative visibility
benefit for all affected Class I areas, the number of days in a
calendar year in which we see significant improvements, and other
factors.\128\
---------------------------------------------------------------------------

    \127\ For instance, as we discuss later in Section IV.C why we
believe that there are certain mitigating factors that should be
considered when assessing BART for the gas-fired units that
occasionally burn fuel oil.
    \128\ See for example 70 39130: ``comparison thresholds can be
used in a number of ways in evaluating visibility improvement (e.g.
the number of days or hours that the threshold was exceeded, a
single threshold for determining whether a change in impacts is
significant, a threshold representing an x percent change in
improvement, etc.).''
---------------------------------------------------------------------------

    First, we note that all of the sources addressed in our proposed
BART determinations have already been shown to cause or contribute to
visibility impairment at a Class I area as a condition of being
subject-to-BART as part of the BART screening analysis. This analysis
eliminated any BART-eligible source that emits lower amounts of
visibility impacting pollutants, or otherwise impacts any Class I area
at less than 0.5 deciviews. In fact, all of the individual units that
we are proposing for BART controls exceed 0.5 deciviews on a unit
basis, with most exceeding 1.0 deciview impact on a unit basis. As a
consequence, all of the units we are proposing for BART controls are
among the largest emitters of visibility impacting pollutants in Texas.
A number of these units (i.e., Big Brown, Martin Lake, Monticello, and
Coleto Creek) were previously determined by us to require the same type
and level of controls under the reasonable progress and long-term
strategy provisions of the Regional Haze Rule that we are proposing
here.\129\
---------------------------------------------------------------------------

    \129\ See our recent Texas-Oklahoma FIP, 81 FR 321.
---------------------------------------------------------------------------

    Second, not discounting our approach of considering both cost-
effectiveness and visibility benefit in unison, the cost-effectiveness
of all of the controls that form the basis of our proposed BART
determinations are within a range found to be acceptable in other
cases.\130\ As we

stated in the BART Rule, ``[a] reasonable range would be a range that
is consistent with the range of cost effectiveness values used in other
similar permit decisions over a period of time.'' \131\
---------------------------------------------------------------------------

    \130\ See for instance 79 FR 5048 (January 30, 2014): Jim
Bridger BART determination of LNB/SOFA + SCR on Units 1-4; 77 FR
18070 (March 26, 2012): EPA proposed approval of Colorado's BART
determination of SCR for Hayden Unit 2, later finalized at 77 FR
76871 (December 31, 2012).
    \131\ 70 FR 39168 (July 6, 2005).
---------------------------------------------------------------------------

A. SO2 BART for Coal-fired Units With No SO2
Controls

    As we have discussed in this proposal and in our TSD, we have
assumed two DSI control levels corresponding to 50% control and either
a maximum of 80% or 90% control, depending on the particulate matter
control device in use.\132\ We did this to address the BART Guidelines
directive that in evaluating technically feasible alternatives we ``(1)
[ensure we] express the degree of control using a metric that ensures
an ``apples to apples'' comparison of emissions performance levels
among options, and (2) [give] appropriate treatment and consideration
of control techniques that can operate over a wide range of emission
performance levels.'' \133\ In most cases, the cost-effectiveness of
the higher control level of DSI was higher than either SDA or wet FGD.
This was not the case for Monticello Unit 2; Harrington Unit 062B; and
J T Deely Units 1 and 2.
---------------------------------------------------------------------------

    \132\ Note for Harrington Unit 062B and Welsh 1, we further
limited the maximum DSI control level to that of our calculated SDA
control level.
    \133\ 70 FR 39166 (July 6, 2005).
---------------------------------------------------------------------------

    However, these maximum DSI control levels are theoretical and we
believe that any DSI control level above 50% must be confirmed by
onsite testing before we could propose a BART control based on it. As
is evident in comparing the 50% control level to the higher control
level, the cost-effectiveness of DSI worsens (higher $/ton) as the
control level increases, and the certainty of any unit attaining that
control level decreases. We therefore regard the cost-effectiveness
values of the maximum DSI control levels as being useful in a basic
comparison of cost-effectiveness between DSI and scrubbers, but we
place much less weight on these values. We therefore conclude that
given the uncertainty concerning the maximum control level of DSI, the
greater control efficiency and resulting visibility benefit offered by
scrubbers overrides any possible advantage DSI may hold in cost-
effectiveness. Should the affected facilities provide site-specific
information to us in their comments that conflicts with this
assumption, we will incorporate it into our final decision on
SO2 BART and potentially re-evaluate DSI.
    As we indicate elsewhere in our proposal, both SDA and wet FGD are
mature technologies that are in wide use throughout the United States.
We are not aware of any unusual circumstances that exist for any of the
sources that would serve to indicate they should not be viewed
similarly to these hundreds of previous scrubber retrofits. In
comparing wet FGD versus SDA we note that in a number of cases the
cost-effectiveness of wet FGD is lower than the cost-effectiveness of
SDA. In the remaining cases, we conclude that the incremental cost-
effectiveness of wet FGD over SDA, which we review in Section III.C.3.a
is reasonable, and the improved control and visibility benefit offered
by wet FGD overrides the small penalty in cost-effectiveness FGD has in
comparison to SDA. We propose that with the exception of the Harrington
units, SO2 BART for all other coal-fired units should be
based on the wet FGD control levels we have used in our BART analyses.
We propose that SO2 BART for the Harrington units should be
based on the SDA control levels we have used in our BART analyses.
Below we discuss our consideration of the cost-effectiveness and
anticipated visibility benefits of controls. See section III.C.5 for
additional information on the anticipated visibility benefits from each
level of control modeled. See the BART Modeling TSD for a complete
summary of our visibility benefit analysis of controls, including
modeled benefits and impacts at all Class I areas included in the
modeling analyses and additional metrics considered in the assessment
of visibility benefits.
    CAMx model results shown in the tables below summarize the benefits
from the recommended controls at the two Class I areas most impacted by
the source or unit in the baseline modeling. The benefit is calculated
as the difference between the maximum impact modeled for the baseline
and the maximum impact level modeled under the control scenario. Also
summarized are the cumulative benefit and the number of days impacted
over 0.5 and 1.0 dv. Cumulative benefit is calculated as the difference
in the maximum visibility impacts from the baseline and control
scenario summed across the 15 Class I areas included in the CAMx
modeling. The baseline total cumulative number of days over 0.5 (1.0)
dv is calculated as the sum of the number of modeled days at each of
the 15 Class I area impacted over the threshold in the baseline
modeling. The reduction in number of days is calculated as the sum of
the number of days over the chosen threshold across the 15 Class I
areas included in the CAMx modeling for the baseline scenario
subtracted by the number of days over the threshold for the control
scenario. The CALPUFF cumulative model results only consider those
Class I areas within the typical range of CALPUFF and not all 15 Class
I areas included in the CAMx modeling.
1. Big Brown 1 & 2
    In reviewing the Big Brown units, we conclude that the installation
of wet FGD will result in very significant visibility benefits. We
summarize some of these visibility benefits in the tables below:

                          Table 21--Wet FGD Visibility Benefits at Big Brown (CALPUFF)
----------------------------------------------------------------------------------------------------------------
                                                                       Total        Cumulative      Cumulative
                                  Improvement at  Improvement at    cumulative     reduction in    reduction in
             Source                   Wichita       Caney Creek     visibility    number of days  number of days
                                     Mountains         (dv)        benefit  (dv)   above 0.5  dv   above 1.0  dv
                                       (dv)                             \1\             \2\             \2\
----------------------------------------------------------------------------------------------------------------
Big Brown Units 1 & 2...........            3.83            3.55            7.38          151.67          101.33
----------------------------------------------------------------------------------------------------------------
\1\ Cumulative benefit is calculated as the difference in the maximum visibility impacts from the baseline and
  control scenario runs summed across the following Class I areas: Caney Creek and Wichita Mountains.
\2\ Using the three years (2001-2003) of CALPUFF modeling results an annual average of the number of days
  reduced was calculated. The Reduction in number of days is calculated as the sum of the number of days over
  the chosen threshold across the following Class I areas for the baseline scenario subtracted by the number of
  days over the threshold for the control scenario: Caney Creek and Wichita Mountains.

    In evaluating Big Brown, we note there are two Class I areas within
the typical range that CALPUFF has been used for assessing visibility
impacts. Using the three years of 2001-2003 CALPUFF modeling results,
we assessed the annual average number of days when the facility impacts
were greater than 0.5 del-dv at each of the Class I areas and then
summed this value for each of the Class I areas to yield an annual
average cumulative value for total number of days impacts were above
0.5 del-dv at all Class I areas within typical CALPUFF range. The
reduction in the number of days (annual average) was calculated as the
cumulative value of the number of days over the 0.5 del-dv threshold
across the Class I areas for the baseline scenario subtracted by the
cumulative number of days over the threshold for the control scenario.
For the two Class I areas that are within the range that CALPUFF is
typically used, the 2001-2003 CALPUFF modeling results indicate that
wet FGD on both units will eliminate 151.6 days annually (3 year
average) when the facility has impacts greater than 0.5 delta deciview.
The same analysis was also calculated using a 1.0 del-dv threshold and
is reported in the table above. DSI operated at 50% control results in
approximately half of the visibility benefits in terms of dv benefits
at the most impacted Class I areas and about 1/3rd to half the
cumulative benefits over the class I areas included in the modeling
analysis.

                            Table 22--Wet FGD Visibility Benefits at Big Brown (CAMx)
----------------------------------------------------------------------------------------------------------------
                                                                       Total      Baseline total
                                  Improvement at  Improvement at    cumulative      cumulative     Reduction in
              Unit                    Wichita       Caney Creek     visibility    number of days  number of days
                                     Mountains         (dv)           benefit      over 0.5/1.0    above 0.5/1.0
                                       (dv)                           (dv)\1\         dv \2\          dv \3\
----------------------------------------------------------------------------------------------------------------
Big Brown 1.....................           1.909           1.606          12.728          174/44          174/44
Big Brown 2.....................           1.940           1.642          12.924          175/45          175/45
Source..........................           3.542           2.988          24.274         372/170         362/170
----------------------------------------------------------------------------------------------------------------
\1\ Cumulative benefit is calculated as the difference in the maximum visibility impacts from the baseline and
  control scenario runs summed across 15 Class I areas included in the CAMx modeling.
\2\ Baseline Total Cumulative number of days over 0.5 (1.0) dv is calculated as the sum of the number of modeled
  days at each of the 15 Class I area impacted over the threshold.
\3\ Reduction in number of days is calculated as the sum of the number of days over the chosen threshold across
  the 15 Class I areas included in the CAMx modeling for the baseline scenario subtracted by the number of days
  over the threshold for the control scenario.

    CAMx modeling results indicate that wet FGD will eliminate all days
impacted over 1dv at all Class I areas on a unit and source-wide basis,
and eliminate all but 10 days across the impacted Class I areas where
the source-wide impacts exceeds 0.5 dv. At the most impacted Class I
area, wet FGD will on each unit result in visibility improvements of
1.9 dv on the most impacted day. DSI operated at 50% control results in
approximately half of the wet FGD visibility benefits at the most
impacted Class I areas and half of the cumulative benefits over the 15
class I areas included in the CAMx modeling.
    We also conclude that wet FGD is very cost-effective for both units
at less than $1,200/ton and more cost-effective than DSI. Based on this
consideration of the BART factors, we propose that SO2 BART
for Big Brown Units 1 and 2 should be based on the installation of wet
FGD at an emission limit of 0.04 lbs/MMBtu based on a 30 BOD.
2. Monticello 1 & 2
    Similar to the Big Brown units, the installation of wet FGD at
Monticello Units 1 and 2 will result in very significant visibility
benefits. We summarize some of these visibility benefits in the tables
below:

                          Table 23--Wet FGD Visibility Benefits at Monticello (CALPUFF)
----------------------------------------------------------------------------------------------------------------
                                                                       Total      Baseline total    Cumulative
                                  Improvement at  Improvement at    cumulative      cumulative     reduction in
             Source                 Caney Creek       Wichita       visibility    number of days  number of days
                                       (dv)          Mountains     benefit  (dv)   over  0.5/1.0   above 1.0  dv
                                                       (dv)             \1\           dv \2\            \2\
----------------------------------------------------------------------------------------------------------------
Monticello Units 1, 2 & 3.......            4.87            2.70           10.25          224.67          164.67
----------------------------------------------------------------------------------------------------------------
\1\ Cumulative benefit is calculated as the difference in the maximum visibility impacts from the baseline and
  control scenario runs summed across the following Class I areas: Caney Creek, Wichita Mountains, and Upper
  Buffalo.
\2\ Using the three years (2001-2003) of CALPUFF modeling results an annual average of the number of days
  reduced was calculated. The Reduction in number of days is calculated as the sum of the number of days over
  the chosen threshold across the following Class I areas for the baseline scenario subtracted by the number of
  days over the threshold for the control scenario: Caney Creek, Wichita Mountains, and Upper Buffalo.

    In evaluating Monticello, we note there are three Class I areas
within the typical range that CALPUFF has been used for assessing
visibility impacts. Using the three years of 2001-2003 CALPUFF modeling
results we assessed the annual average number of days when the facility
impacts were greater than 0.5 del-dv at each of the Class I areas and
then summed this value for each of the Class I areas to yield an annual
average cumulative value for total number of days impacts were above
0.5 del-dv at all Class I areas within typical CALPUFF range. The
reduction in the number of days (annual average) was calculated as the
cumulative value of the number of days over the 0.5 del-dv threshold
across the Class I areas for the baseline scenario subtracted by the
cumulative number of days over the threshold for the control scenario.
For the three Class I areas that are within the range that CALPUFF is
typically used, the 2001-2003 CALPUFF modeling results indicate wet FGD
on both units will eliminate 224.6

days annually (3 year average) when the facility has impacts greater
than 0.5 delta deciview. The same analysis was also calculated using a
1.0 del-dv threshold and is reported in the table above. DSI operated