IN THE MATTER OF A PERMIT APPLICATION (AP-6043) FROM PACIFICORP FOR A

BEST AVAILABLE RETROFIT TECHNOLOGY (BART) PERMIT FOR THE WYODAK

POWER PLANT

DECISION

I. Introduction:

The Air Quality Division received a BART permit application from PacifiCorp for the coal-fired

boiler (Unit 1) that operates at their Wyodak Power Plant in Campbell County, Wyoming.

Regulations governing the BART program have been established by the U.S. EPA in 40 CFR Part

51 - Appendix Y. As stated in the regulations, a source is eligible for BART ifit belongs within a

particular group ofstationary source categories, was not in operation prior to August 7, 1962, was

in existence on August 7, 1977, and has the potential to emit 250 tons per year (tpy) or more of

any visibility impairing air pollutant. Fossil fuel boilers with more than 250 million Btu

(MMBtu) per hour heat input are listed as an eligible source type. Unit 1 at the Wyodak plant has

a heat input of 4,100 MMBtu per hour and was in existence on August 7, 1977. Potential

emissions from each boiler for two visibility impairing air pollutants, nitrogen oxides (NOx) and

sulfur dioxide (S02), exceed 250 tpy and therefore the units are eligible for BART.

The Division conducted an analysis ofthe BART permit application for the Wyodak plant and on

June 4,2009, published in the Gillette News-Record a public notice and notice of public hearing

ofthe proposed intent to issue BART determinations. Copies of the BART application and the

Division's analysis were placed in the Campbell County Clerk's office in Gillette, Wyoming in

accordance with regulations. A 63-day public notice period ran from June 4, 2009 to August 5,

2009, and a public hearing was held on August 5, 2009, at 6 p.m. in the George Amos Memorial

Building, located at 412 South Gillette Avenue in Gillette, Wyoming.

The Division received numerous comment letters on the proposed permit during the public

comment period: 1) a letter dated July 21,2009 from the USDA Forest Service; 2) a letter dated

August 3,2009 from EPA Region 8; 3) a letter dated August 4,2009 from PacifiCorp; 4) a letter

dated August 4, 2009 from the National Park Service; 5) a letter dated August 4, 2009 from the

Powder River Basin Resource Council, et aI.; 6) a letter dated August 5, 2009 from the Powder

River Basin Resource Council; 7) a letter received July 20,2009 from Joanna Taylor; 8) a letter

dated July 16, 2009 from Andrew H. Salter; 9) a letter received July 20,2009 from Evelyn and

Marvin Griffin; 10) a letter received July 23, 2009 from Mimi McMillen; 11) a letter received

July 24, 2009 from William M. Anderson; 12) a letter received July 24, 2009 from Rebekah

Smith; 13) a letter dated July 24,2009 from Mike Shonsey; 14) a letter dated July 24,2009 from

Susie Mohrmann; 15) a letter dated July 28,2009 from Janice H. Harris; 16) a letter dated July

28,2009 from M. Christensen; 17) a letter dated July 27,2009 from Clint Morrison; 18) a letter

dated August 3,2009 from Ann Fuller; 19) a letter dated August 3, 2009 from Mary Fenton; 20)

725 unsigned letters received under a signed cover letter dated July 28, 2009 from Brad

Mohrmann, Sierra Club Associate Regional Representative; and 21) 89 signatures received under

a signed cover letter dated July 24, 2009 from Brad Mohrmann, Sierra Club Associate Regional

Representative.

Due to the number of public comments with similar concerns, the Division grouped individual

comments and developed summary comments and responses. Comments from the EPA, Forest

Service, National Park Service, Powder River Basin Resource Council, et aI., and PacifiCorp are

addressed individually. The comments and responses are presented on the following pages. The

Division also received positive comments supporting this project. The Division appreciates these

comments but they are not included in this document as no response is required.
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The Division received numerous comments that were descriptive of environmental impacts other

than the impacts from BART-eligible sources in Wyoming on Class I area visibility. The

Division's responses are limited to the comments that dealt with the State's BART analyses.

The Division is also preparing a revised Wyoming State Implementation Plan (SIP) for Regional

Haze, and has solicited comments on that SIP. Some comments have been received which were

submitted as comments on the Regional Haze SIP, but were principally directed at the Division's

BART analyses. These comments will be addressed by the Division as it prepares the response to

comments on the Regional Haze SIP.

n. Analysis of Comments from the USDA Forest Service:

ILl BART Conclusions for NO,LControls: SCR - The Forest Service commented that based on

their review of the five statutory BART factors, Selective Catalytic Reduction (SCR) should be

BART for NOx control for all units at plants such as the Jim Bridger power plant. The Forest

Service applauds the proposal to install SCR at the four units at the Jim Bridger plant for a longterm strategy, but SCRs at Jim Bridger should be installed as BART on all units by 2015-2016.

Response - The Division determined BART for NOx control at power plants in Wyoming based

on consideration of all five statutory BART factors, as required by EPA's Appendix Y BART

guidance. No single factor was weighted as being more important than another, because the

Division looked at all five statutory factors in their entirety.

Regarding the installation of additional control equipment at the Jim Bridger plant, PacifiCorp is

required by the BART permit to install SCR on Jim Bridger Unit 3 in 2015 and Jim Bridger Unit

4 in 2016 as well as add-on NOx control on Units 1 and 2 no later than 2023. The schedule for

installation is based on the incorporation of SCR add-on control on these units under the longterm strategy component of Wyoming's State Implementation Plan (SIP) for regional haze as

well as PacifiCorp's construction plan for pollution control projects. The schedule for the

installation of SCR controls at other plants is uncertain at this point due to the demands on

PacifiCorp for compliance with BART and other regulatory programs. PacifiCorp operates 19

coal-fired units, 14 of which are BART-eligible. Additional BART-eligible units are owned or

partly owned in Arizona, Colorado, and Montana. Table 1 presents a summary of the pollution

control projects that are included in PacifiCorp's construction plan through 2014.
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, '

.. Table 1:·Status ofPQlhitio,nControl Pro.iectslJndertakett by Pa~ifiCorp :

SOz Scrubbers

New=N LNB Baghouse SOz/LNB

Power Plant Location Upgrade=U Installations Installations Proiect Status

Hunter 3 Utah Installed 2008 Installed Completed

Huntington 2 Utah 2007-N 2007 2007 Completed

Cholla4 Arizona 2008-U 2008 2008 Completed

Jim Bridger 4 Wyoming 2008- U 2008 n/a Completed

Jim Bridger 2 Wyoming 2009- U 2005 n/a Completed

Dave Johnston 3 Wyoming 201O-N 2010 2010 Under

Construction

Huntington I Utah 2010 - U 2010 2010 Pennitted

Jim Bridger 1 Wyoming 2010- U 2010 n/a Under

Construction

Naughton 2 Wyoming 2011-N 2011 n/a Under

Construction

Hunter 2 Utah 2011- U 2011 2011 Pennitted

Jim Bridger 3 Wyoming 2011- U 2007 n/a Under

Construction

Wyodak Wyoming 2011- U 2011 2011 Pennitted

Dave Johnston 4 Wyoming 2012-N 2009 2012 Under

Construction

Naughton 1 Wyoming 2012-N 2012 n/a Under

Construction

Hunter 1 Utah 2014- U 2014 2014 Pennitted

Naughton 3 Wyoming 2013 - U 2013 2013 Pennitted

11.2 N0;LStep 5: Visibility Improvement Determination (Class I areas modeled) - The Forest

Service commented that all Class I areas within 300 kIn of a given source should be modeled and

the cost of each BART alternative divided by the sum of the deciview (dv) improvement at all

impacted Class I areas. If modeling exists for Class I areas that yield impacts above 0.5 dv just

beyond 300 kIn, those results should be considered also. Savage Run Wilderness Area should

also be modeled and considered.

Response - Only those Class I areas most likely to be impacted by sources subject to BART at a

given facility were modeled, as determined by source/Class I area locations, distances to each

Class I area, and professional judgment considering meteorological and terrain factors. The

Division recognizes that more distant Class I areas may yield modeled impacts of some

magnitude, but the Division is also satisfied that Class I areas at a greater distance and in

directions of less frequent plume transport would not yield modeled impacts greater than those

yielded by the Class I areas chosen for BART modeling. The modeling results for the Class I

areas chosen for analysis allowed the Division to make an informed decision on the effect on

visibility from the various BART control options. Additionally, EPA's Appendix Y BART

guidance does not include any requirements for modeling distance.

EPA's Appendix Y BART guidance does mention that "dollars per deciview" ($/dv) is a metric

that could be used to evaluate the cost ofBART compliance, but by no means identifies $/dv as

an essential or required metric. The Division considered capital cost, annual cost, cost
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effectiveness, and incremental cost effectiveness in the cost evaluation of each proposed BART

control option. The Division chose not to use a hybrid metric such as $/dv primarily because of

the lack of historical precedent regarding reasonable/acceptable levels for such a metric.

Additionally, the use of a hybrid cost metric such as $/deciview can introduce uncertainty as to

how the value was calculated. The value of "/deciview" could be based on the highest modeled

value in a given area or the 98th percentile modeled value. It could be based on the 98th percentile

value for anyone modeled year or it could be an average for multiple years. It could even be

based on an average modeled value across an entire Class I area or the sum of deciview changes

across multiple areas. The Division has found that $/dv values are often presented without

explanation of the basis for the calculation. To avoid these confounding factors, the Division

chose to evaluate and present the cost analyses and visibility analyses separately.

EPA's Regional Haze Rule affects sources that may cause or contribute to visibility impairment

at any mandatory, federal Class I Area. Because Savage Run is a state-designated Class I area,

the Division was not required to include it in the BART modeling. Additionally, the Division did

not include Savage Run in any of its analyses for the State's Regional Haze Visibility SIP. For

BART, the Division did model the impacts at several mandatory Class I areas that are located in

the same general plume transport direction downwind of Savage Run, including Mt. Zirkel

Wilderness, Rawah Wilderness, and Rocky Mountain National Park. Based on the modeling

results for these Class I Areas in the proximity of Savage Run, the Division anticipates similar

improvements in visibility from the analyzed emission reductions.

II.3 NO!..Step 5: Visibility Improvement Determination (significant impact) - The Forest Service

commented that it is incorrect to dismiss a control strategy on the basis that the modeled visibility

improvement is not perceptible or significant.

Response - The Division used 0.5 dv as the threshold level to exempt a source from BART or to

deem modeled impacts as insignificant. EPA's Regional Haze Regulations and Guidelines for

Best Available Retrofit Technology (BART) Determinations (Appendix Y to 40 CFR part 51),

suggest that 0.5 dv can represent the level at which a source "contributes" to visibility

impairment. This is also consistent with the rules which are being applied by most states in the

Western Regional Air Partnership (WRAP) region.

IIA NOLControls: SCR - The Forest Service commented that significant, cumulative visibility

improvements modeled for SCR installations at the Jim Bridger and Naughton plants indicate that

SCR should be BART for all units at those two plants. The Forest Service questions why DEQ

chose SCR as BART only for Naughton Unit 3 when SCR costs for other Naughton units and all

Jim Bridger units are similar. Also, environmental degradation from the operation of SCR should

not be a factor in the BART determinations and energy impacts from SCR should not be a factor

because they have already been considered in the cost analysis.

Response - The costs for SCR controls, as described in the Division's BART analyses, were

deemed by the Division to be reasonable for all units at the Jim Bridger and Naughton plants, but

the Division's BART determinations for the two plants were based on consideration of all five

statutory BART factors, as required by EPA's Appendix Y BART guidance. PacifiCorp

proposed a BART limit for NOx emissions from Naughton Unit 3 of 0.37 Ib/MMBtu, which

would be achieved by tuning the existing LNB/OFA system. For Naughton Units 1 and 2,

PacifiCorp proposed a BART limit for NOx of 0.26 Ib/MMBtu for each unit using new

LNB/OFA. Visibility modeling showed that the NOx emission level proposed by PacifiCorp for
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Naughton Unit 3 provided less in terms of modeled visibility reductions from baseline as

compared to other units at the two plants. For example, Naughton Units 1 and 2 showed a 72% to

73% reduction in the number of days with predicted impacts of 0.5 dv or more at the nearest

Class I area (Bridger Wilderness) for LNB/OFA as compared to baseline. The reduction for

Naughton Unit 3 for LNB/OFA vs. baseline was only 31%. Appendix A includes graphs of the

modeled results at the Class I area that yielded the highest modeled impacts for the Jim Bridger

and Naughton plants (Bridger Wilderness) and the Class I area that yielded the highest modeled

impacts for the Wyodak, Dave Johnston, and Laramie River Station plants (Wind Cave National

Park). As shown in the graphs, the LNB/OFA option reduces the 98th percentile result to less

than 1.0 dv for every unit with the exception ofNaughton Unit 3 (1.4 dv). The predicted number

of days above 0.5 dv for the LNB/OFA option was 40 for Naughton Unit 3, and 16 or less for

each of the other twelve units. The Division determined that SCR would be required on

Naughton Unit 3 to bring about additional NOx emissions reductions and modeled visibility

improvement, and these factors differentiated the Naughton Unit 3 BART analysis from the

others.

It was the full consideration of all five statutory BART factors, principally the pronounced

visibility improvement for LNB/OFA as compared to baseline and the lack of non-air quality

environmental impacts that led the Division to conclude that LNB/OFA would be BART for NOx

control at the Wyodak plant. In comparison, modeled visibility impacts for Naughton Unit 3

were reduced to levels comparable to those yielded by LNB/OFA controls on Naughton Units 1

and 2 only through the addition of SCR as BART on Naughton Unit 3. Potential energy losses

and environmental impacts from the operation of SCR were mentioned in the Division's BART

analysis for all PacifiCorp plants, but were only part of the larger evaluations that considered all

five statutory factors.

11.5 NO!...Controls: SCR Efficiencies - The Forest Service commented that greater SCR control

efficiencies should be factored into the cost and visibility analyses.

Response - The Division conducted a search of the EPA RACTIBACTILAER Clearinghouse

(RBLC) to find NOx emission limits as BACT associated with SCR control in recently issued

permits. Table 2 presents a summary ofthe Division's RBLC search. Two plants have limits of

0.05 Ib/MMBtu NOx with a 12-month rolling average, which is significantly longer than a 30-day

averaging period. Because the 0.05 Ib/MMBtu limits are based on a 12-month averaging period,

they are not comparable to the 30-day limits established by the Division. The two plants with 30-

day averaging periods will be subjected to either a 0.08 Ib/MMBtu or 0.07 Ib/MMBtu limit, and

the limits established by the Division meet these lower limits. A spreadsheet compiled by the

National Park Service with a summary of nationwide BART determinations shows that both units

outside ofWyoming for which SCR is proposed as BART will be subject to a NOx emission limit

of 0.07 Ib/MMBtu, and both will be based on a 30-day averaging period.

The RBLC search showed two plants that will be subject to 24-hour NOx limits of less than 0.07

Ib/MMBtu (0.067 Ib/MMBtu), but these limits are for newly constructed plants which have been

engineered to meet these levels. BART will require the retrofit of significant controls at plants

that were not designed to meet these lower levels. Based on the Division's evaluation, the

Division is satisfied that the NOx emission limit of 0.07 Ib/MMBtu (3D-day rolling average) that

was evaluated for SCR control under BART is the most stringent control level likely to be

achieved in a retrofit.
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Table 2: SCR.PermitLimits from theRBLC ..

Size of NOx Permit Limit(s) for Permit

FacilitylLocation Source Source Description SCRControl Date

John W. Turk Power 600MW 6,000 MMBtu/hr PC Boiler 1) 0.067 Ib/MMBtu Nov 2008

Plant!Arkansas (PRE Coal) (24-hr rolling)

2) 0.05 Ib/MMBtu

(12-month rolling)

[SCR, BACT]

DryFork 385MW PC Boiler 0.05 Ib/MMBtu Oct 2007

Station/Wyoming (12-month rolling)

[SCR, BACT]

WYGEN3/Wyoming 100MW 1,300 MMBtu/hr PC Boiler 0.05 Ib/MMBtu Feb 2007

(12-month rolling)

[SCR,BACT]

Jatan -- PC Boiler 0.08 Ib/MMBtu Jan 2006

Station/Missouri (30-day rolling)

[SCR,BACT]

Big Cajun II Power 675MW PC Boiler 0.07 Ib/MMBtu Aug 2005

PlantlLouisiana (annual average)

[SCR, BACT]

TS Power 200MW PC Boiler 0.067 Ib/MMBtu May 2005

Plant/Nevada (24-hour rolling)

[SCR, BACT]

OPPD - Nebraska -- -- 0.07Ib/MMBtu Mar 2005

City (30-day rolling)

Station/Nebraska [SCR, BACT]

Note: "••" mdicates that this value was not provided m the RBLC

11.6 SOLControls (Section 309) - The Forest Service understands the role of Section 309 in

exempting the State of Wyoming from making BART determinations for S02 controls based on

the demonstration that the benefits from S02 emissions reductions under Section 309 exceed

those that would have resulted from BART. Are the existing S02 controls in place at the Jim

Bridger and Naughton plants at least equivalent to the control scenario used in the demonstration,

i.e., are the existing controls needed to accomplish the "Better than BART" demonstration for

Section 309? They also note that the 309 program sunsets in 2018 and added S02 controls may

be needed for reasonable progress at that time.

Response - The State ofWyoming submitted a 309 SIP as is allowed by the Regional Haze Rule.

Part of the SIP submittal is a "Better than BART" demonstration, required by rule, which does

not require that each and every unit demonstrate emission controls that are "Better than BART".

The demonstration is a regional demonstration. The Division is aware than the 309 program only

establishes milestones through 2018, and that following 2018 another strategy may be necessary

to reduce visibility-impairing pollutants. Additional strategies will be addressed in future SIP

revisions.

II.? Visibility Impairment - The Forest Service commented that because EPA BART guidelines

state that 0.5 dv "contributes" to visibility impairment, and 1.0 dv "causes" visibility impairment,

the discussion from Ronald Henry regarding perceptibility in the BART applications from

PacifiCorp is irrelevant and used in an improper context.
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Response - The Division did not attempt to endorse a particular threshold for human eye

"perceptibility" since the level of perceptibility has long been disputed. Instead, the Division has

relied on EPA's Appendix Y BART guidance, which suggests a value of 0.5 dv as the level that a

source "contributes" to visibility impairment. One ofthe metrics used by the Division to evaluate

the relative benefit of a given BART control option was the number of days yielding a modeled

impact of 0.5 dv or more.

ill. Analysis of Comments from EPA Region 8:

IlL I Background Ozone Concentration in CALPUFF - EPA Region 8 commented that the

Division's visibility modeling used 44 ppb as a background ozone concentration as the default

value for periods when measured data was missing. This value appears to be too low based on

the average annual concentrations at sites near the facilities (Thunder Basin = 50-55 ppb, Jonah =

55-58 ppb). DEQ should provide an analysis of how higher ozone background concentrations

would affect results.

Response - The default ozone background concentration is used by CALPUFF as a domain-wide

substitute for any hour for which all measured ozone concentrations are missing. For the

Division's visibility modeling for BART, hourly ozone concentrations measured at seven

monitoring stations spaced across the modeling domain were input to CALPUFF. A visual

inspection of the ozone files that were input to CALPUFF reveals that at least one valid ozone

observation was available for every hour of the modeled period (2001-2003), making it

unnecessary for the model to use the default background of44 ppb.

Although the model did not use the default background value for the BART analyses, the

Division calculated annual average concentrations for recent years (2007-2008) and all available

data for 2009 for many ofthe stations that were used for input to CALPUFF, including Thunder

Basin, Jonah, Rocky Mountain National Park, Centennial, and Pinedale. Annual average values

for these stations ranged from 35 ppb to 49 ppb, with an overall average of approximately 40 ppb.

The Division is confident that the default background value of 44 ppb was appropriate for the

BART modeling, and that there is no need for additional analyses to explore alternate background

concentrations.

IlL2 Weight of Visibility Modeling Results in BART Determinations - EPA Region 8 commented

that DEQ should provide an explanation of how modeled visibility improvements were weighed

in making BART determinations.

Response - The Division's BART determinations were based on consideration of all five

statutory factors, as required by EPA's Appendix Y BART guidance. The modeled visibility

improvements for a given control strategy were one ofthe five factors that were considered. No

single factor was weighted as being more important than another, because the Division looked at

all five statutory factors in their entirety. EPA guidance did not provide a quantification of the

amount ofmodeled visibility improvement that would be acceptable or significant. The Division

used two metrics that were mentioned in the EPA BART guidance, the 98th percentile result for a

given year and the level at which a source "contributes" to visibility degradation (0.5 ~dv), to

present the results of the BART visibility modeling. Also see the response to USDA Forest

Service comment IIA.
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III.3 Cumulative Modeled Impacts - EPA Region 8 commented that cumulative, modeled Class I

impacts from all units at a facility (or combined impacts from multiple facilities) should be

presented in addition to the results for individual units.

Response - The visibility impacts from BART-eligible sources are to be modeled separately. As

stated in the EPA's Appendix Y guidance, relative to the use ofthe CALPUFF model for BART

determinations, "We believe that CALPUFF is an appropriate application for States to use for the

particular purposes ofthis rule, to determine ifan individual source is reasonably anticipated to

cause or contribute to impairment of visibility in Class I areas, and to predict the degree of

visibility improvement which could reasonably be anticipated to result from the use ofretrofit

technology at an individual~. We encourage States to use itfor these purposes." [emphasis

added]

IlIA Language from BART Determinations - EPA Region 8 commented that the Division should

clarify the statements of "3-year average visibility improvements". Are dv improvements

calculated for each Class I area added together? If so, what is the meaning of the number? Are

three Class I areas sufficient to quantify cumulative impacts? Were all Class I areas within 300

km considered?

Response - To arrive at the "3-year average visibility improvements" that were reported in the

Division's BART analyses, the modeled 98th percentile dv change or the number of days above

0.5 dv predicted for a given year of meteorology was averaged with the similar result from the

other two years of meteorology. These 3-year average values were determined for each modeled

Class I area separately, and were devised to allow a straightforward, direct comparison of one

control option to another. Regarding the sufficiency ofthe number ofmodeled Class I areas

and the question of other Class I areas within 300 km, see response to USDA Forest Service

comment II.2.

ilLS NO:!...Controls - EPA Region 8 commented that the most stringent emission control levels for

NOx controls have not been evaluated, resulting in inflated calculated cost effectiveness values.

Lower emission limits should be evaluated for selective non-catalytic reduction (SNCR) and

SCR.

Response - The Division has analyzed the most stringent levels for SNCR and SCR, and does

not agree that the cost effectiveness numbers have been inflated. See response to USDA Forest

Service comment II.5. Furthermore, the Division has deemed the costs associated with all

analyzed BART NOx control options, including SNCR and SCR, to be reasonable (see the

conclusions listed under the section: NOx: EVALUATE IMPACTS AND DOCUMENT

RESULTS in each ofthe five BART Application Analyses).

ilL6 12-Month Average for N0x..- EPA Region 8 commented that there is no formula to calculate if

the 12-month rolling emission limit has exceeded the permit condition. A permit condition to

match condition 12.a.iii from the Laramie River Station analysis should be created.

Response - The BART limits for NOx emissions from the PacifiCorp plants include 30-day

rolling limits in terms of IblMMBtu and lb/hr. The ton per year limit is based on a calendar year

rather than a rolling average, and therefore the formula associated with the annual BART limit for

NOx at the Laramie River Station is not relevant.
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IlL7 PM Controls: Averaging Periods- EPA Region 8 commented that the BART conclusions and

the permit conditions should include associated averaging periods for all PMlPMlO limits.

Response - The averaging periods for the PMlPMlO limits are dictated by the performance test

requirements in the BART permits. Compliance with the Ib/MMBtu and lblhr PMlPMlO limits is

based on the average ofthree I-hour tests per 40 CFR 60.46.

IlL8 PM Controls: Control Effectiveness - EPA Region 8 commented that the Division should

explain why 0.015 Ib/MMBtu for baghouse/fabric filter control effectiveness is acceptable, when

0.012 Ib/MMBtu has been approved by the Division for other permits and 0.010 Ib/MMBtu was

approved for the Desert Rock project. The BART determinations should include analyses of

electrostatic precipitators (ESPs) and baghouses at lower control levels.

Response - Recent Prevention of Significant Deterioration (PSD) permits issued by the Division

did include PMlPMlO limits of 0.012 Ib/MMBtu for fabric filter controls, but those limits (and

PMlPMlO limits established for the Desert Rock Project in New Mexico) were determined

through Best Available Control Technology (BACT) analyses for new sources. The BART

process deals with retrofit controls on existing units, and therefore is not directly comparable to

BACT determinations. Additionally, visibility modeling described in the Division's BART

analysis for the Jim Bridger plant showed that the addition of a fabric filter to replace an

Electrostatic Precipitator (ESP) provided very little in the way of visibility improvement, with

predicted cumulative improvements across three Class I areas of only 0.03 to 0.1 ~dv for Units 1-

4. These results indicate that requiring more stringent control levels for a fabric filter would not

provide significant visibility improvement.

As described on page 12 of the Division's BART analysis for the Wyodak plant, flue gas

conditioning (FGC) was considered for enhancement ofthe existing ESP on Unit 1. The existing

ESP is well designed and provides adequate space and residence time for the flue gas particles to

gain an electric charge and migrate to the collection plate. The application of FGC was not

expected to significantly improve PMlPMlO removal efficiency.

I1L9 PM Controls: Permit Exemption - EPA Region 8 commented that Condition 5 in the proposed

EGU BART permits contains an inappropriate exemption for startup. The exemption from the

Ib/MMBtu PM limit during startup should be removed or it may be appropriate to analyze the

need for a startup BART limit.

Response - For each EGU subject to BART in Wyoming, only the BART limits for PMlPMlO

that are expressed in Ib/MMBtu will not apply during startup. The BART limits for PMlPMlO

that are expressed in lb/hr and tpy (as based on the Ib/MMBtu limits) will apply during all

operating periods including startup.

The Division considers the BART limits expressed in terms of lb/hr and tpy to be appropriate

limits for startup. For the four units at the Jim Bridger plant, PacifiCorp calculated that the

particulate emissions from the startup fuel (fuel oil) would be no greater than 10.9 lb/hr per unit,

conservatively assuming that the ESP controls had zero control efficiency during the startup

process. As a comparison, the BART limit that would apply for each unit during startup is 180

lblhr. Further, PacifiCorp has agreed to minimize startup emissions from the four units at the

plant by placing the ESPs in service prior to the introduction of coal to the boilers, which is
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Decision Document, BART Permit Application, AP-6043

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contrary to the manufacturer's recommendation to energize the ESP only after the unit is at full

operating temperature and combustion offuel oil has ceased.

Similarly for Unit 1 at Wyodak, particulates are controlled by an ESP and startup is accomplished

with fuel oil. The maximum emissions estimated for startup (8.9 Ib/hr) would be well below the

BART limit of 71 Ib/hr. The three units at LRS are also started on fuel oil and controlled with

ESPs, and the particulate emissions during startup are expected to be well below the BART

limits, which are set at 193 Ib/hr to 198 Ib/hr for the three units.

For units with baghouse controls for particulate matter such as Dave Johnston Units 3 and 4,

emissions from fuel oil during the startup process are also estimated to be well below the

allowable Ib/hr BART limits.

In the case ofthe Naughton plant, particulate controls will include a mixture ofESPs (Units 1 and

2) and a fabric filter/baghouse (Unit 3). Natural gas is the startup fuel for each ofthese units, and

particulate emissions during startup are expected to be well below the established Ib/hr BART

limits.

IlL10 SO~ Controls: Reasonable Progress - EPA Region 8 commented that the Division must

evaluate the visibility impacts of S02 controls and demonstrate reasonable progress for the Class I

areas away from the Colorado Plateau.

Response - Wyoming, along with other 309 states in the WRAP region, evaluated the impact of

the 309 program on all Class I areas in the west, even though the requirement by rule was to

demonstrate improvement in Class I areas on the Colorado Plateau. The WRAP modeling for

sulfates shows that all Class I areas in and around Wyoming sources are benefiting from the

sulfur dioxide emission reductions instituted in the 309 program. Sulfate extinction levels show

improvement on the 20% worst days and improvement or at least no degradation on the 20% best

days. Furthermore, the Regional Haze rule allows a state to take full credit for strategies

implemented under 309 when addressing Class I Areas away from the Colorado Plateau

(51.309(g)(4)(i)).

IlL11 PM Control Level - EPA Region 8 commented that because the Division recently issued a PSD

permit for the Wyodak plant, it is inappropriate for the BART analysis options to be less

protective than the permitted enforceable controls. Controls already permitted through PSD

should be viewed as baseline for the BART analysis.

Response - The permit limit for PMlPMlO emissions from the Wyodak plant established under

the recent permit (MD-7487, issued 5/20/09) is 0.015 Ib/MMBtu, and the control technology is a

fabric filter baghouse. The emission limit of 0.015 Ib/MMBtu was confmned through the BART

analysis that was conducted for the facility. Recent Prevention of Significant Deterioration (PSD)

permits issued by the Division did include PMlPMlO limits of 0.012 Ib/MMBtu for fabric filter

controls, but those limits were determined through Best Available Control Technology (BACT)

analyses. The BART process deals with retrofit controls, and therefore is not directly comparable

to BACT determinations. The fabric filter controls added at Wyodak under MD-7487 were not

subject to BACT.

40 CFR 51.309(b)(7) states that "Base year means the year for which data for a source included

within the program were used by the WRAP to calculate emissions as a starting point for
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development of the milestone required by paragraph (d) (4) (i) of this section." Because the

Western Regional Air Partnership (WRAP) used 2003 as the starting point fOf development of

milestones for S02 emissions, the emission control configuration in place at a given facility in

2003 was considered by the Division to be the baseline configuration for BART. Additionally,

the period for establishing the baseline visibility conditions under the Regional Haze Rule is 2000

to 2004 [40 CFR 51.308(d)(2)]. The fabric filter configuration for the Wyodak plant that was

permitted in May of 2009 was therefore considered a control strategy option rather than a

baseline configuration.

Additionally, visibility modeling conducted by the Division has shown that the addition of a

fabric filter as an upgrade to an ESP provides very little in the way of modeled visibility

improvement, and these results indicate that requiring more stringent control levels for a fabric

filter would not provide significant visibility improvement. Also see response to EPA Region 8

comment III.8.

llI.12 NOLControls - EPA Region 8 commented that the most stringent emission control levels have

not been evaluated, resulting in inflated calculated cost effectiveness values. Lower emission

limits should be evaluated for SNCR and SCR. A revised cost analysis should indicate that SCR

is cost effective at Wyodak.

Response - See response to USDA Forest Service comment ll.5 and EPA Region 8 comment

lll5.

IV. Analysis of Comments from PacifiCorp:

N.1 General Comments: Cost Metrics - PacifiCorp commented that EPA's Appendix Y BART

guidance states that a proper BART evaluation should include "other cost-effectiveness measures

(such as $/deciview)". Thus, any BART determination that is limited to use only cost

effectiveness and incremental cost effectiveness may be unacceptably narrow.

Response - EPA's Appendix Y BART guidance does mention that "dollars per deciview" ($/dv)

is a metric that could be used to evaluate the cost of BART compliance, but by no means

identifies $/dv as an essential or required metric. The Division considered capital cost, annual

cost, cost effectiveness, and incremental cost effectiveness in the cost evaluation of each

proposed BART control option. The Division chose not to use a hybrid metric such as $/dv

primarily because of the lack of historical precedent regarding reasonable/acceptable levels for

such a metric. Additionally, the use of a hybrid cost metric such as $/deciview can introduce

uncertainty as to how the value was calculated. The value of "/deciview" could be based on the

highest modeled value in a given area or the 98th percentile modeled value. It could be based on

the 98th percentile value for anyone modeled year or it could be an average for multiple years. It

could even be based on an average modeled value across an entire Class I area or the sum of

deciview changes across multiple areas. The Division has found that $/dv values are often

presented without explanation of the basis for the calculation. To avoid these confounding

factors, the Division chose to evaluate and present the cost analyses and visibility analyses

separately.

N.2 General Comments: Cost Effectiveness - PacifiCorp commented that any BART determination

requiring a source to install post-combustion controls like SCR or spend more than $1,500 per ton

ofNOx removed would be contrary to EPA Appendix Y BART guidance.
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Response - The EPA's Appendix Y guidance describes the EPA's selection of presumptive NOx

limits for coal-fired EGUs, and provides approximate cost levels for meeting the presumptive

limits with current combustion controls and a somewhat higher cost level for a subset of units that

would require advanced combustion controls such as rotating opposed fire air (ROFA). The EPA

guidance does not attempt to establish cost thresholds that would be considered unreasonable for

a given control technology, nor does it present the approximate costs associated with the

presumptive levels as absolute limits above which cost should be deemed unreasonable. The

guidance also states that states may in specific cases find that the use of SCR is appropriate. As

stated previously, the Division established NOx emission limits for BART based on consideration

of all five statutory factors in their entirety, as required by the Appendix Y guidance.

IV.3 General Comments: Power Plants More Than 750 MW - PacifiCorp commented that

Appendix Y indicates that states must follow Appendix Y guidelines in making BART

determinations on a source-by-source basis for 750 MW plants. Wyoming rules impose similar

requirements for power plants greater than 750 MW.

Response - The Division followed EPA and State of Wyoming rules for the BART analyses.

Specifically, the Division followed WAQSR Chapter 6, §9(c)(ii), which states that power plants

with generating capacities greater than seven hundred fifty megawatts shall comply with EPA

Appendix Y, and that Appendix Y should be used as guidance for preparing BART analyses for

all other facilities.

IVA General Comments: Post-Combustion Controls - PacifiCorp commented that EPA never

contemplated the use of post-combustion controls to meet BART limits for tangentially-fired

boilers, and that it is nearly impossible under Appendix Y guidance to show that anything other

than combustion controls should be required as BART.

Response - See response to PacifiCorp comment IV.2.

IV.5 General Comments: Visibility Improvement - PacifiCorp commented that a BART

determination that only relied on the 98th percentile, three-year average results from CALPUFF

may be too narrow to satisfy Appendix Y.

Response - The Division did not rely solely on the three-year average of the 98th percentile

CALPUFF results to evaluate the expected visibility changes for the BART control options. The

98th percentile values and the number of days with predicted results above 0.5 dv were presented

in the Division's BART analyses for each of three modeled years, for each Class I area, and for

each control option. The three-year average ofthe 98th percentile results and the number of days

above 0.5 dv were chosen for graphical representation and were mentioned prominently in the

Division's conclusions because they offered the clearest comparison of one control option to

another (see graphs in Appendix A).
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IV.6 General Comments: Modeling - PacifiCorp commented that visibility modeling contains

inherent bias or exaggeration because it assumes that a particular source will operate at its

maximum capacity 100% ofthe time and that each unit at a facility operates in the same way.

Response - The results from BART visibility modeling, as required by EPA guidance, are based

on daily (24-hour) averages. Reported results for a given control scenario, expressed in units of

deciviews, represent the predicted change in visibility as compared to natural background over

the course of 24-hour periods of meteorology. The modeled emission rates for a given unit at a

power plant should reflect the highest rate that could be achieved over a 24-hour period, and

therefore the assumption that a· given unit is operating at its maximum operating capacity is

appropriate for each unit at a base-load power plant such as Wyodak. Additionally, the

conclusions drawn from BART visibility modeling primarily involve comparisons between

control scenarios for which the emissions are determined similarly.

IV.7 General Comments: NO!-Emissions - PacifiCorp commented that emissions ofNOx during the

20% best and 20% worst days at Class I areas in Wyoming are not a significant contributor to

regional haze as compared to other emissions, and therefore the Division should consider this

before requiring extreme NOx control measures such as SCR as BART.

Response - For the 20% worst days during the years 2000-2004 at the Bridger Wilderness Area,

6.21% of the total visibility degradation was attributable to nitrates. Source apportionment

modeling provided by the WRAP showed that 19% ofthe nitrates come from Wyoming sources.

The Division recognizes that pollutants other than nitrates contribute more toward the total

visibility degradation at the Bridger Wilderness Area, but the Division has concluded that the

contribution from Wyoming sources toward the formation of nitrates at the Bridger Wilderness

Area and other Class I areas warrants a full consideration of prospective NOx controls under the

BART process.

IV.8 Perceptibility - PacifiCorp commented that credible studies indicate that only changes in

visibility as high as 1.5-2.0 dv are perceptible to the human eye. The Division should consider

this while drawing conclusions based on the results of the visibility modeling and before

requiring extreme NOx control measures such as SCR.

Response - See response to USDA Forest Service comment n.7.

IV.9 Presumptive BART for Wyodak - PacifiCorp commented that the Division correctly identified

the presumptive BART limit of 0.23 IblMMBtu for the Wyodak plant, but they do not agree with

the statement in the Division's BART analysis that the limit is "not applicable".

Response - The statement on page 6 of the Division's BART analysis that presumptive BART

levels do not apply to Wyodak is based on the fact that the cumulative generating capacity ofthe

facility is less than 750 MW. In accordance with the EPA's Appendix Y guidance for BART, the

presumptive NOx levels apply to EGUs greater than 200 MW located at power plants with total

capacity of 750 MW or more. Because the Wyodak plant has a total capacity of only 335 MW,

the presumptive limits do not strictly apply.
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V. Analysis of Comments from the National Park Service:

V.l NO!..Step 3: Evaluate Effectiveness ofRemaining Control Technologies (SCR capabilities)-

The NPS commented that the Division underestimated the ability of SCR to reduce emissions.

The proposed NOx limit for SCR (0.07 Ib/MMBtu) is not low enough. SCR can achieve greater

reductions. NPS suggests 0.06 Ib/MMBtu for 30-day limit, 0.05 Ib/MMBtu or lower for an

annual limit.

Response - See response to USDA Forest Service comment II.5.

V.2 NO!..Step 4: Evaluate Impacts and Document Results (SCR costs) - The NPS commented that

SCR costs were generally overestimated because the OAQPS Control Cost Manual was not used

for cost estimates.

Response - PacifiCorp developed cost estimates for SCR control using a combination of the

OAQPS Control Cost Manual, vendor-obtained price quotes, and a database developed by the

engineering firm Sargent & Lundy. The degree to which the SCR costs may have been

overestimated does not require further review because the Division has concluded that the

estimated costs are reasonable and that costs alone would not preclude the use of SCR.

V.3 NOLStep 4: Evaluate Impacts and Document Results (incremental costs for SCR) - The

NPS commented that the Division over-emphasized the incremental costs for the addition of SCR

in the BART determinations. The Division should consider the average costs calculated for

combustion controls plus SCR.

Response - See response to PacifiCorp comment N.l and NPS comment V.2.

VA NO!..Step 4: Evaluate Impacts and Document Results (basis for costs) - The NPS commented

that cost estimates should be documented by vendor or by the EPA Control Cost Manual.

Response - See response to NPS comment V.2.

V.S NOLStep 5: Visibility Improvement Determination (Class I Areas Modeled) - The NPS

commented that the Division should consider visibility impacts at all Class I areas within 300

kilometers (km) of a source.

Response - See response to USDA Forest Service comment II.2.

V.6 NO!..Step 5: Visibility Improvement Determination (incremental benefits of SCR) - The NPS

commented that the Division placed too much emphasis on the incremental improvement in

visibility that was predicted for the addition of SCR. The total predicted visibility improvemept

resulting from a combination of control options should have been presented.

Response - The incremental improvement in modeled visibility with the addition of SCR was

mentioned prominently in the summary of the Division's BART conclusions, but all visibility

modeling results were considered. For more information on the presentation of the visibility

modeling results in the Division's BART analyses, see the response to EPA Region 8 comment

III.2 and PacifiCorp's comment N.S.
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V.? NOLStep 5: Visibility Improvement Determination (sulfuric acid mist emissions) - The NPS

commented that the modeled sulfuric acid mist emissions increased for the SCR control scenario,

and the Division should provide a detailed explanation of how the sulfuric acid mist emissions

were calculated by PacifiCorp.

Response - PacifiCorp's consultant, CH2M HilL, used the following methodology to calculate

sulfate emissions for SCR for the PacifiCorp coal-fired power plants (as provided in a letter from

PacifiCorp that was submitted to the Division on September 16, 2009):

• 1.0% ofthe S02 in the boiler is converted to S03

• An additional 1.0% ofthe S02 is converted to S03 in an SCR unit

• The S03 is converted to H2S04 mist in the flue gas

• 50% ofthe H2S04 mist is removed in a wet FGD unit

• 95% ofthe H2S04 mist is removed in a dry FGD unit

• An SCR unit has 2.0 ppmvd NH3slip

• 50% of the NH3 slip is converted to ammonium sulfate and 50% is converted to

ammonium bisulfate

• 50% of the ammonium sulfate and bisulfate are removed in a wet FGD unit and 90% of

the ammonium sulfate and bisulfate are removed in a dry FGD unit

• Total sulfate emissions are made up of H2S04 mist, ammonium sulfate and ammonium

bisulfate

V.8 BART Conclusions for NO!..Controls: $/dv - The NPS commented that the Division should use

$/dv as an additional metric for evaluating BART controls.

Response - See response to PacifiCorp response IV.1.

V.9 BART Conclusions for NO" Controls: Cost Benchmarks - The NPS commented that the

Division determined that the costs for SCR were reasonable, yet rejected SCR for BART control.

DEQ should explain why and provide the cost benchmarks used to determine reasonable costs.

Response - The Division established NOx emission limits for BART based on consideration of

all five statutory factors (as required by EPA's Appendix Y BART guidance) and not merely

based on cost. The Division relied on past experience with BACT determinations for similar

sources/control options to determine the range of control costs that were reasonable.

V.I0 BART Conclusions for NOLControls: Non-Air Ouality Impacts - The NPS commented that

the Division mentioned non-air quality impacts as reasons to reject SCR for BART controls.

Recent PSD permits issued by DEQ and requiring SCR did not mention such impacts. Why were

such impacts mentioned in these particular cases? SCR has been used at many facilities with

minimal problems with transport and storage of ammonia, why would this be a particular problem

for SCR as BART control?

Response - The Division's BART determinations for the Wyodak plant was based on

consideration of the five statutory factors, including the cost of compliance and the energy and

non-air quality environmental impacts of compliance. Potential energy losses and environmental

impacts from the operation of SNCR and SCR were mentioned in the Division's BART analysis,
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but were only part of the larger evaluation that considered all five statutory factors in their

entirety.

V.11 BART Conclusions for NOLControls: Parasitic Power Loss - The NPS commented that the

Division mentioned parasitic power loss in association with the operation of OFA and SCR.

Parasitic power loss associated with SCR has already been accounted for in the cost analysis for

NOx and should not be "double-counted" by using it to draw conclusions for BART control

unless it would cause a power shortage.

Response - See response to NPS comment V.lO.

V.12 BART Conclusions for N0x-Controls: Fly Ash Sales - The NPS commented that the Division

stated that the operation of SCR could impact the "salability" of fly ash. Evidence should be

presented and the economic impact quantified.

Response - See response to NPS comment V.1 o.

V.13 BART Conclusions for NO! Controls: Ammonia Injection - The NPS commented that the

Division stated that SCR could create "blue plume" if the ammonia injection rate is not well

controlled. NPS states that it assumes that PacifiCorp can properly control the injection rate.

Response - See response to NPS comment V.lo.

V.14 BART Conclusions for NO!....Controls: SCR Installation - The NPS commented that

PacifiCorp states that SCR would take a minimum ofsix years to plan and install. NPS states that

Minnesota Power plans to install SCR, fabric filter, and a new chimney on the 330 MW Boswell

Unit #3 in half ofthat time. PacifiCorp should explain why so much extra time is needed.

Response - A letter provided to the Division by PacifiCorp dated September 16, 2009 provided

information on the time needed to plan, design, and install SCR:

• Develop and Permit: 18-24 months

• Design: 9-12 months

• Procurement: 9-13 months

• Construct: 18-24 months

• Start, Tune, and Test 4-6 months

• Total (including overlap ofindividual tasks): 60-66 months

V.15 BART Conclusions for PMlO Controls: Control Effectiveness - The NPS commented that the

Division should explain why 0.015 Ib/MMBtu was acceptable to the Division as a control

effectiveness for a ESP/polishing fabric filter combination, when 0.012 Ib/MMBtu has been

approved by the Division for other recent permits involving fabric filters and limits as low as

0.010 Ib/MMBtu have recently been approved for fabric filters (e.g., Desert Rock Project).

Response - See response to EPA Region 8 comment Ill.8.
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V.16 BART Conclusions for PMlO Controls: Fabric Filters - NPS believes that PacifiCorp would

not have agreed to install fabric filters unless it finds the option to be reasonable or is compelled

to do so. DEQ should accept fabric filters as a reasonable BART alternative in the context ofthe

PM reductions and associated costs, or state what it considers reasonable average and incremental

costs for a fabric filter.

Response - The Division concluded that the costs of a fabric filter for Wyodak Unit 1 was not

reasonable. However, as stated on page 36 of the Division's BART analysis for Wyodak:

" ...PacifiCorp is committed to installing this control device and has permitted the installation of a

full-scale fabric filter on Unit 1 in a recently issued New Source Review construction permit. A

full-scale fabric filter is the most stringent PMlPM10 control technology and therefore the

Division will accept it as BART."

VI. Analysis of Comments from the Powder River Basin Resource Council:

VI. 1 SCR as BART - The Powder River Basin Resource Council commented that SCR is the best

available retrofit technology and should be required as BART at all ofthe Wyoming power plants

under consideration.

Response - The Division determined BART for the control of NOx emissions from power plants

in Wyoming based on a full consideration of all five statutory factors in their entirety, as required

by EPA's Appendix Y BART guidance. The BART guidance does not dictate that a state require

the control technology with the highest level of control in all cases.

VII. Analysis of Comments from the Powder River Basin Resource Council, et aI.:

VII.1 Modeled Class I Areas - The Powder River Basin Resource Council, et al. commented that all

Class I areas within 300 km of a given source should be modeled for visibility impacts.

Response - See response to USDA Forest Service comment 11.2.

VII.2 SCR as BART - The Powder River Basin Resource Council, et al. commented that SCR is

BART and must be required for all units at all coal-fired power plants.

Response - See responses to USDA Forest Service comments 11.1,11.4 and 11.5.

VII.3 Section 309 Milestone Program - The Powder River Basin Resource Council, et al. commented

that DEQ should impose BART limits for S02 because participation in the Section 309 program

only excuses DEQ from setting BART limits ifthe State's 309 SIP is approved by the EPA and if

the 309 SIP demonstrates that emissions levels would result in greater visibility improvement

than source-specific BART limits.

Response - The Regional Haze Rule allows the State ofWyoming to submit a 309 SIP in lieu of

establishing BART limits for S02. The 309 SIP submittal includes a "Better than BART"

demonstration. The entire submittal is currently undergoing EPA review and the State has no

control over how long the EPA takes to review the SIP. The State, however, does not wait for

EPA to complete its review before implementing a SIP. All of the 309 states have been

participating in the 309 program, collecting S02 inventories, allowing independent audits of the

information, comparing the regional totals to the milestones, and taking public comment on the
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regional figures and the comparisons with the milestone figures. The S02 levels have shown

compliance with the milestones and continue to demonstrate declining S02 emissions levels.

Also see responses to USDA Forest Service comment 11.6 and EPA comment ill. 10.

VIlA SCR for Long-Term Strategy - The Powder River Basin Resource Council, et al. commented

that the BART limits for NOx determined by the Division for Wyodak meet presumptive BART,

but further reductions are warranted to reduce Class I impacts. The Division should require SCR

under Long-Term Strategy.

Response - See response to USDA Forest Service comment 11.1.

VIII. Analysis of Comments from the Sierra Club and Citizens Associated with the Sierra Club:

Vill.l Air Quality Laws and Regulations - The Sierra Club commented that it is important that air

quality laws and regulations are strictly complied with to preserve park resources for present and

future generations.

Response - The Division followed federal regulations and guidance as well as state regulations in

assessing the BART applications and for making the BART determination for all sources eligible

for BART in the State of Wyoming. The BART rules and guidance used by the Division

included:

• Section 308 ofthe Regional Haze Rule [40 CFR 51.308(e)]

• Guidelinesfor BARTDeterminations Under the Regional Haze Rule [Appendix Y to part

51]

• Chapter 6, Section 9 ofthe Wyoming Air Quality Standards and Regulations (WAQSR),

Best Available Retrofit Technology

Vill.2 Regional Haze Rule - The Sierra Club commented that the State ofWyoming can and should do

more to protect air quality as the Regional Haze Rule is implemented.

Response - The Division's BART determinations for Wyoming sources, as well as additional air

pollution controls that will be required to further reduce regional haze, will be addressed in the

Wyoming State Implementation Plan (SIP) for regional haze. The SIP incorporates the emissions

reductions associated with the Long-Term Strategy for regional haze.

Vill.3 Control of Emissions of Nitrogen Oxides - The Sierra Club commented that the State of

Wyoming should require the coal plants to install devices to reduce emissions ofnitrogen oxides.

Response - All ofthe Division's BART determinations for coal-fired power plants in the State of

Wyoming include pollution control equipment that will substantially reduce emissions ofnitrogen

oxides.

VillA 20-Year Trend - A commenter stated that the amount of air and water pollution has clearly

escalated in the past 20 years, with little relief for citizens or for the health of forests and the

environment.

Response - The Division's BART determinations and other requirements under the regional haze

program will result in large, state-wide emission reductions for three visibility-impairing
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pollutants; nitrogen oxides (NOx), particulate matter (pMIPMlO), and sulfur dioxide (S02)' As an

example, BART controls at the Jim Bridger plant will result in a total annual reduction in

potential NOx emissions of approximately 13,500 tons per year.

VIII.5 Wind Power - A commenter stated that Wyoming can readily replace aging coal-fired power

plants with wind power to protect public health and to protect our national parks and wilderness

areas.

Response - The BART program is designed to assess Best Available Retrofit Technology on

existing sources of air pollution, including the existing power plants in Wyoming. The Division's

BART determinations will result in significant reductions in air pollutants from several power

plants in Wyoming, but complete replacement of the power plants with an alternate source of

energy is well beyond the scope ofthe BART program.

VIII.6 Pollution Reduction from Power Plants - A commenter stated that Wyoming has an obligation

to protect treasured public spaces by adhering to federal air quality laws. The State must reduce

air pollutants from the old coal plants that are federally required to utilize the most advanced

technical developments in ensuring that air pollution is minimized.

Response - The Division determined BART controls based on the five statutory factors

developed by the EPA. Various control technologies were evaluated for each source subject to

BART, including the "most advanced technical developments", but the ultimate BART

determinations were made based on a full consideration of all five statutory factors in their

entirety.

VIII.? SCR Controls - Several commenters stated that BART for NOx control should be SCR for all

plants.

Response - See responses to USDA Forest Service comments II. 1 and 11.4.

IX. 'Analysis ofPublic Comments:

IX. 1 SCR Controls - Several commenters stated that BART for NOx control should be SCR for all

plants.

Response - See responses to USDA Forest Service comments 11.1 and 11.4.
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X. Decision:

On the basis of comments received during the public comment period, an analysis of those

comments, and representations made by PacifiCorp, the Department of Environmental Quality

has determined that the permit application filed by PacifiCorp complies with all applicable

Wyoming Air Quality Standards and Regulations and that a BART permit will be issued for the

Wyodak Power Plant. All of the conditions proposed in the Division's analysis will be included

in the permit. No permit conditions required revision as a result ofthe public comment period.

Dated this 31st day ofDecember, 2009.

Administrator

DavitJi~ Wyoming Air Quality Division

ohn . Corra

i ctor

yoming Department ofEnvironmental Quality
APPENDIX A

VISIBILITY MODELING RESULTS (Baseline vs. LNB and SCR)
Figure 1

Modeled BART Impacts in Bridger Wilderness Area

Naughton and Jim Bridger Power Plants: 98th Percentile (delta-dv)

Nau U1 =Naughton Unit 1 (160 MW)

Nau U2 =Naughton Unit 2 (210 MW)

Nau U3 =Naughton Unit 3 (330 MW)

JB U1 =Jim Bridger Unit 1 (530 MW)

JB U2 =Jim Bridger Unit 2 (530 MW)

JB U3 = Jim Bridger Unit 3 (530 MW)

JB U4 =Jim Bridger Unit 4 (530 MW)

[] Baseline

• LNB/OFA

• LNB/OFA + SCR

>

"9

III

.....

Qj

e.

2.500

2.000

1.500

1.000

0.500

0.000

Nau Ul Nau U2 Nau U3 JB Ul JB U2 JB U3 JB U4

(Modeling results represent the three-year average using 2001-2003 meteorology)
Figure 2

Modeled BART Impacts in Wind Cave National Park

Wyodak, Dave Johnston, and Laramie River Station Power Plants: 98th Percentile (delta-dv)

Wyodak =335 MW

DJ U3 =Dave Johnston Unit 3 (230 MW)

DJ U4 =Dave Johnston Unit 4 (330 MW)

LRS Ul=Laramie River Station Unit 1 (550 MW)

LRS U2 =Laramie River Station Unit 2 (550 MW)

LRS U3 =Laramie River Station Unit 3 (550 MW)

ill Baseline

• LNBjOFA

• LNBjOFA +SCR

>"

'C

I

III

....

Qj

e.

2.500 ,...,---------------------------------

2.000 +1--------------------------------

1.500 +1--------'

1.000

0.500

0.000 I t·._.

Wyodak DJ U3 DJ U4

(Modeling results represent the three-year average using 2001-2003 meteorology)

LRS Ul LRS U2 LRS U3
Figure 3

Modeled BART Impacts in Bridger Wilderness Area

Naughton and Jim Bridger Power Plants: # Days> 0.5 delta-dv

60

50

40

Vi

30

o

:!!..

20

10

o

Nau U1 =Naughton Unit 1 (160 MW)

Nau U2 = Naughton Unit 2 (210 MW)

Nau U3 = Naughton Unit 3 (330 MW)

JB U1 =Jim Bridger Unit 1 (530 MW)

JB U2 =Jim Bridger Unit 2 (530 MW)

JB U3 =Jim Bridger Unit 3 (530 MW)

JB U4 =Jim Bridger Unit 4 (530 MW)

lJ Baseline

• LNB/OFA

• LNB/OFA + SCR

Nau U1 Nau U2 Nau U3 JB U1 JB U2 JB U3 JB U4

(Modeling results represent the three-year average using 2001-2003 meteorology)
Figure 4

Modeled BART Impacts in Wind Cave National Park

Wyodak, Dave Johnston, and Laramie River Station Power Plants: # Days> 0.5 delta-dv

Wyodak = 335 MW

DJ U3 = Dave Johnston Unit 3 (230 MW)

DJ U4 = Dave Johnston Unit 4 (330 MW)

60

50

40

30

20

10

o I !""'.~ •.<

LRS Ul =Laramie River Station Unit 1 (550 MW)

LRS U2 =Laramie River Station Unit 2 (550 MW)

LRS U3 =Laramie River Station Unit 3 (550 MW)

[] Baseline

• LNB/OFA

• LNB/OFA + SCR

Wyodak DJ U3 DJ U4

(Modeling results represent the three-year average using 2001-2003 meteorology)

LRS U1 LRS U2 LRS U3