"

IN THE MATTER OF A PERMIT APPLICATION (AP-6042) FROM PACIFICORP FOR A

BEST AVAILABLE RETROFIT TECHNOLOGY (BART) PERMIT FOR THE NAUGHTON

POWER PLANT

DECISION

I. Introduction:

The Air Quality Division received a BART permit application from PacifiCorp for the three coalfired boilers that operate at their Naughton Power Plant in' Lincoln 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. The three boilers at the

Naughton plant have heat inputs between 1,850 and 3,700 MMBtu per hour, and were installed

between 1963 and 1971. Potential emissions from each boiler for two visibility impairing air

pollutants, nitrogen oxides (NO.) and sulfur dioxide (SOz), exceed 250 tpy and therefore the units

are eligible for-HARJ:'.

The Division conducted an analysis ofthe BART permit application for the Naughton plant, and

ptlblished on June 4, 2009 in the Kemmerer Gazette a public notice and notice of public hearing

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

Division's analysis were placed in the Lincoln County clerk's office in Kemmerer, Wyoming in

accordance with regulations. A 62-day public notice period ran from June 4, 2009 to August 4,

2009, and a public hearing was held on August 4, 2009 at 1 p.m. in the Lincoln County Library,

located at 519 Emerald Street in Kemmerer, Wyoming.

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

comment period: 1) a letter dated Jtlly 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 al.; 6) a letter received July 20~ 2009 from Joanna

Taylor; 7) a letter dated July 16,2009 from Andrew H. Salter; 8) a letter received July 20, 2009

. from Evelyn and Marvin Griffin; 9) a letter received July 23, 2009 from Mimi McMillen; 10) a

letter received July 24,2009 from William M. Anderson; 11) a letter received July 24, 2009 from

Rebekah Smith; 12) a letter dated July 24,2009 from Mike Shonsey; 13) a letter dated July 24,

2009 from Susie Mohrmann; 14) a letter dated July 28, 2009 from Janice H. Harris; 15) a letter

dated July 28, 2009 from M. Christensen; 16) a letter dated July 27, 200~ from Clint Morri~on;

17) a letter dated August 3, 2009 from Ann Fuller; 18) a letter dated August 3,' 2009 from Mary

Fenton; 19) 725 unsigned letters received under a signed cover letter dated July 28, 2009 from

Brad Mohrmann, Sierra Club Associate Regional Representative; and 20) 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 comll).ents 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 respons~ to

comments on the Regional Haze SIP. . .

n. Analysis of Comments from the USDA Forest Service:

ILl BART Conclusions for NOLControIs: SCR for Naughton - 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 the Jim Bridger and Naughton power

plants. The Forest Service applauds the proposal to install SCR at the four units at the Jim

Bridger plflntfor a long~terin strategY, but ·SeRs at Jiin·:aiiager should be Installed as13ART on

all units by 2015-2016.

. Response - The Division determined BART for NOx control at the Jim Bridger and Naughton

power plants 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. The BART

determination for NOx control on all four units at Jim Bridger included low NOx burners (LNB)

with overfire air (OFA). The BART determinations for NOx control at Naughton included

LNB/OFAon Units 1 and 2 and SCR on Unit 3. The Division's BART analyses provide the

basis for the BART determination for both plants.

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 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: Statusof,PoIlution Control P,ro.ieets·Under.takenbYPaciflCorp

S02 Scrubbers

New=N LNB Baghouse .SO./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 2010-N 2010 2010 Under

Construction

Huntington 1 Utah 2010- U 2010 2010 Permitted

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

Construction

Naught<m-i 'Wyoriang' 1bl1--N 2011 wi. Under

Construction

Hunter 2 Utah 2011- U 2011 2011 Permitted

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

Construction

Wyodak Wyoming 2011- U 2011 2011 Permitted

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 Permitted

Naughton 3 Wyoming 2013- U 2013 2013 Permitted

11.2 BART Conclusions.for SOLControls: WFGD -The Forest Service commented that, based on

their review ofthe five statutory factors for BART, wet flue gas desulfurization (WFGD) should

be BART for S02 control for all units at the Jim Bridger and Naughton power plants.

Response - WFGD upgrades have already been (or are scheduled to be) installed on all units at

the Jim Bridger plant. For the Naughton plant, WFGD is scheduled to be installed on Units 1 and

2 and WFGD is scheduled to be upgraded for Unit 3. BART lim.its for S02 will not be set

because Wyoming is a §309 state participating in the Regional S02 Milestone and Backstop

Trading Program. §308(e)(2) provides states within the Transport Region addressed by the Grand

Canyon Visibility Transport Commission with the option to implement or require participation in

an emissions trading program or other alternative measure rather than to require sources subject

to BART to install, operate, and maintain additional control technology to meet an established

emission limit on a continuous basis.

11.3 NOLStep 5: Visibility Improvement Determination (Class I areas modeled) - The Forest

Service commented that all Class I areas within 300 km 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 km, those results should be considered also. Savage Run Wilderness Area should

also be modeled and considered.

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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 wQuld 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 qeciview" ($/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

contrqloption, 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 fOlmd 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 inthe 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.

IIA 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.

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II.S Five Factor Analysis for BART Selection: Coal Composition - The Forest Service commented

that PacifiCorp's analysis of coal composition is flawed and it does not meet the requirement for

a demonstration of why presumptive limits cannot be reached.

Response - Although the BART emission limits for NOx for Naughton Units I and 2 exceed the

presumptive BART limit for tangential-fired boilers burning sub-bituminous coal, PacifiCorp's

analysis of coal composition was not a factor in the Division's determination. The Division

established NOx emission limits for BART at the Naughton plant based on consideration of all

five statutory factors, as required by EPA's Appendix Y BART guidance. The Division

interpreted the presumptive emission levels for NOx. and S02 as recommended control levels

proposed by EPA after reviewing technical data related to BART. Requiring sources to meet

presumptive emission levels was not required as one ofthe five statutory factors. Conversely, the

Division did not automatically determine emission levels below presumptive levels to be BART,

but considered all five statutory factors before making a BART determination.

II.6 N!1: Controls:. SCR - The Forest Service commented that significant, cumulative visibility

improvements modeled for SCR installations at the Jim Bridger and Naughtori 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/.M:MBtu, 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

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 I 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

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

control at the Jim Bridger plant and for Units 1 and 2 at the Naughton Plant. Modeled visibility

impacts for Naughton Unit 3 were reduced to levels comparable to those yielded by LNB/OFA

controls on Naughton Units I 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 both the Naughton and Jim Bridger plants, but

were only part ofthe larger evaluations that considered all five statutory factors.

II.7 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 Clef,J.ringhouse

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

permits. Table 2 presents a summary of the 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 3D-day

averagjng ,period. B,ecause the 0.05 IbJMMBtu lilIlits are based on a 12-month ayeraging period,

they are not comparable to the 3D-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 IblMMBtu 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 3D-day averaging period.

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

IblMMBtu (0.067 IbIMMBtu), 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 IblMMBtu (30~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 ~ermitLimits tram the RBLC "

" i

Size of NO. Permit Limit(s) for Permit

FacilitvlLocation Source Source Description SCRControl Date

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

Plant/Arkansas (pRB 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)

rSCR,BACT]

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

(12-month rolling)

[SCR,BACT]

Iatan -- PC Boiler 0.08 Ib/MMBtu Jan 2006

StationlMissouri (30-day rolling)

[SCR, BACT]

Big Cajun'II Power 675MW PC Boiler O.Q7lb/MMBtu Aug 2005

Plant/Louisiana (annual average)

[SCR,BACTl

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

PlantlNevada (24-hour rolling)

[SCR,BACT]

OPPD - Nebraska .- -. O.Q7lb/MMBtu Mar 2005

City (30-day rolling)

StationlNebraska [SCR,BACT]

Note: "--" IndIcates that thiS value was not provIded In the RBLC

II.8 Reasonable Progress Controls - The Forest Service asked why Naughton Units 1 and 2 are not

required to install SCR as part ofreasonable progress like other PacifiCorp units.

Response - See response to Forest Service comment II.1.

11.9 S0:LControls (cost effectiveness) - The Forest Service commented that performance for a wet

scrubber on Naughton Unit 3 was stated to be 0.10 Ib/MMBtti, but the cost effectiveness was

based on 0.15 IblMMBtu. Cost per ton for S02 reduction should be based on 0.10 Ib/MMBtu if

that is the correct value,

Response - The application of wet FGD on Unit 3 is anticipated to lower S02 emissions to 0.10

Ib/MMBtu, based on an average coal sulfur content of 0.58% by weight, and to 0.15 Ib/MMBtu,

based on an average coal sulfur content of 1.02% by weight. Because both low sulfur and high

sulfur coals are used to fuel the boilers at Naughton, 0.15 Ib/MMBtu was used as the basis for

cost effectiveness. The cost effectiveness is not relevant because BART limits for S02 will not be

set. Wyoming is a §309 state participating in the Regional S02 Milestone and Backstop Trading

Program. §308(e)(2) provides states with the option to implement or require participation in an

emissions trading program or other alternative measure rather than to require sources subject to

BART to install, operate, and maintain additional control technology to meet an established

emission limit on a continuous basis.

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ILI0 S07. Controls (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 3097 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, whiC;h 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.

lUI 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 impr.oper context. .

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 usee). 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. .

m. Analysis of Comments from EPA Region 8:

IlL1 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 = 50-55ppb, 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 of 44 ppb.

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

Division calculated annual average concentrations for recent years (2007-20.08) and all available

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

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Basin, Jonah, Rocky Mountain National Park, CentelU1.ial, 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.

III.2 Weight of Visibility Modeling Results in BART Determinations - EPA Region 8 commented

that DEQ should provide 8.1, explanation of how modeled visibility improvements 'vvere v/eighed

in making BART determinations.

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

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

improvements for a given control strategy were one ofthe five f!'lctors 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 ofthe

amount of modeled 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 .6.dv), to

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

Service comment n.6.

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 applicationfor States to use for the

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

cause or contribute to impairment of visibility in Class 1 areas, and to predict the degree of

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

technology ill. !!!! individual~. We encourage States to use itfor these purposes." [emphasis

added]

llIA 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 ofthe 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 repOlted 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 of modeled Class I areas

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

cpmment IIJ.

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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 Ir.7. 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).

m.6 12~Month Average for NOc EPA Region 8 commented that there is no formula to calculate if

the l2-month rolling emission limit has exceeded the permit condition. A permit condition to

match condition l2.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 Ib/MMBtu ~d 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.

IlL7 PM Controls: Averaging Periods- EPA Region 8 commented that the BART conclusions and

the permit conditions should include associated averaging periods for aU PMlPM10 limits.

Response - The averaging periods for the PM/PM1o limits are dictated by the performance test

requirements in the BART permits. Compliance with the IblMMBtu and lb/hr PM/PM10 limits is

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

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

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

0.012 Ib/MMBtu has been approved by the Division for other permits and 0.010 IblMMBtu 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 PM/PMIO limits of 0.012 Ib/MMBtu for fabric filter controls, but those limits (and

PM/PMlO 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 Lldv 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 17 of the Division's BART analysis for the Naughton plant, ESP

performance enhancements using FGC were considered for Units I and 2, and will be utilized for

BART control. For Unit 3, a new full-scale fabric filter will be installed for BART control.

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III.9 PM Controls: Permit Exemption - EPA Region 8 commented that Condition 5 in the proposed

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

IblMMBtll PM limit during startup should be removed or it may be appropriate to analyze the

need for a startup BART limit..

Response - For each EOU 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 Ib/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

lb/hr. 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

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 I at Wyodak, particulates are controlled by an ESP and startup is accomplished

with fuel oil. The maximum emissions estimated for startup (8.9 lb/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 lb/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 I 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 lb/hr BART

limits.

III.lO PM Controls: FGC - EPA Region 8 commented that flue gas conditioning (FOC) must be

applied only after FOD is installed or upgraded to avoid increases in the emissions of sulfuric

acid (H2S04) mist. A control option should not be considered as a BART option if it will result in

an increase in visibility-reducing pollutants.

Response - The Division has already evaluated the impacts' ofFOC at the Naughton plant as part

of the review ofPacifiCorp's permit application for permit MD-5156, which was issued on May

1,2009. Permit MD-5156 authorized FOC to enhance the performance of the ESPs on Units 1

and 2. The permit application included a modeling evaluation of the impacts to Class I area

visibility from the FOC, and the impacts were predicted to be insignificant.

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III. 11 .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 Haz~ 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)).

III.l2 CALPUFF Visibility Modeling: Other Class I Areas - EPA Region 8 commented that

visibility impacts at Flattops Wilderness Area in Colorado should have been modeled for the Jim

Bridger and Naughton plants.

Response - See response to USDA Forest Service comment JIJ.

JIL13 NOLControls - EPA Region 8 commented that the control efficiencies assumed for all NOx

technologies are underestimated, resulting in inflated calculated cost effectiveness values. A

revised analysis should indicate that SCR is cost effective at Naughton.

Response - See response to EPA Region 8 comment m.5.

JII.l4 PM Controls: FGC - EPA Region 8 commented that flue gas conditioning (FGC) will be

applied to Naughton Units I and 2 and decommissioned from Unit 3 upon installation of a fabric

filter permitted under PSD. The application of FGC prior to FGD upgrades will result in a

significant increase in emissions ofsulfuric acid (H2S04) mist. This collateral increase should be

avoided to maintain visibility improvements at Class I areas.

Response - See response to EPA Region 8 comment III.IO.

IV. Analysis of Comments from·PacifiCorp:

IV.l 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

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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 cQntrols like SCR or spend more than $1,500 per ton

ofNOx removed would be contrary to EPA Appendix Y BART guidance.

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.

NA 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 N .2.

N.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

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each control option. The three-year average of the 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).

N.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 Naughton. Additionally, the

conclusions drawn from BART visibility modeling primarily involve comparisons between

control scenarios for which the emissions are determined similarly.

N.? General Comments: NOLEmissions - PacifiCorp commented that emissions of NOx during the

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

regional haze as compar,ed 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% of the 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 proc~ss.

N.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 ILl I.

N.9 Cost Metrics for Naughton Unit 3 - PacifiCorp commented that it opposes the determination

that SCR is BART for NO. control, and that the Division should have considered other costbenefit metrics such as $/dv. Using $/dv, tbe cost for 1 dv of visibility improvement is more than

$15 million per year. If one considers that changes of less than 1.5 dv are not perceptible to the

human eye, the cost per deciview reduction is not reasonable.

Response - See responses to PacifiCorp comment N.l and USDA Forest Service comment ILl I.

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IV.lO Presumptive BART - PacifiCorp commented that the Division's reference in the BART analysis

for the Naughton plant to a presumptive BART limit for NOx of 0.15 lblMMBtu is not correct.

For reasons stated in PacifiCorp's most recent submittals to the Division, primarily an argument

regarding coal characteristics, the correct presumptive BART limit for Naughton Units 1-2 is 0.28

IblMMBtu.

Response - See response to USDA Forest Service comment U.s.

IV.ll Reasonable Costs for SCR on Naughton Unit 3 - PacifiCorp commented that the calculated

costs for SCR on Naughton Unit 3 are not reasonable, according to EPA's Appendix Y guidance.

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 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 NOxemission limits for BART at the Naughton power plant based on consideration of

all five statutory factors, as required by the Appendix Y guidance.

IV.12 Incremental Costs for SCR on Naughton Unit 3 - PacifiCorp commented that the incremental

costs per ton of NOx reduction for SCR on Naughton Unit 3 shown in Table 10, page 15 of the

Division's BART analysis is incorrect. The correct value is more than $4,000 per ton rather than

the value of $1,783 that is shown in Table 10. When considering the true incremental costs of

SCR, the Division's BART determination cannot stand.

Response - The incremental cost listed for SCR control in Table 10 of the Division's BART

analysis for Naughton Unit 3 was incorrect, and should have been listed as $4,049 per ton.

However, the Division concluded that the correct cost per ton ofNOx reduction ($2,830/ton) and

the incremental cost per ton of NOx reduction ($4,049) are both reasonable for SCR control on

Naughton Unit 3. Table 3 below presents a comparison ofthe costs associated with SCR control

for Naughton Units 1 through 3 which shows that the costs associated with all three units are

comparable and the incremental costs for Unit 3 are lower compared to the other two units at the

plant. Furthermore, costs for Units 1 and 2 were identified in the analysis as reasonable and the

costs for Unit 3 are within that range. The Division's error had no bearing on the BART

determination.

Table 3: Costs for 'SCR,'ControLon Na~l!hton Units111hroul!h3

Incremental Cost Per Ton of

Unit Cost Per Ton ofNOxReduction NOxReduction

1 $2,750 $8,089

2 $2,848 $7,852

3 $2,830 $4,049

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IV.13 Boardman, Oregon BART Determination - PacifiCorp commented that the state of Oregon

determined that SCR control was not appropriate for the Boardman Power Plant, yet the costbenefit values for Boardman are more favorable for SCR installation than for Naughton Unit 3.

Response - The Division determined BART for NOx control for Naughton Unit 3. based on

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

The costs for SCR controls, as described in the Division'~ BART analysis, were deemed by the

Division to be reasonable. Modeled visibility reductions from baseline for the LNB/OFA option

on Naughton Unit 3 were not nearly as pronounced as they were for other BART-eligible units in

the state. The Division determined that SCR would be required on Naughton Unit 3 to bring

about additional NO. emission reductions and additional modeled visibility improvement, and

these factors differentiated the Naughton Unit 3 analysis from the others. For additional details,

see response to USDA Forest Service comment 11.6 and the graphs in Appendix A.

IV.14 Presumptive BART for Naughton Unit 3 and LNB/OFA Emissions Compared to Units 1/2-

PacifiCorp commented that presumptive BART for NO. control on Naughton Uriit 3 is not 0.15

IblMMBtu as stated in the Division's BART analysis, but is 0.28 IblMMBtu. Sufficient

justification exists under Appendix Y to select a higher calculated BART limit of 0.35 IbIMMBtu.

Even if the 0.015 IblMMBtu presumptive limit is assumed to be correct, the requirements for

SCR control at 0.07 Ib/MMBtu cannot be justified as BART because it is so far below the EPA's

presumptive limit of 0.15 IblMMBtu. PacifiCorp also commented that the modeh~d deciview ,

reductions for Naughton Units 1 and 2 as compared to Unit 3 are interesting but not relevant in

making a BART deterrilination. The fact that Units 1 and 2 can achieve greater modeled

visibility improvements is only an indication that Unit 3 has already installed and achieved a

significantlevel ofNO.reductions.

Response - The Division determined BART for NO. control for Naughton Unit 3 based on

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

PacifiCorp's analysis of coal composition and how it might affect the presumptive NOx limit for

Naughton Unit 3 was not a factor in the Division's determination. The NOx emission level

proposed by PacifiCorp for Naughton Unit 3 using LNB/OFA provided less in the way of

modeled visibility reductions from baseline as compared to other BART-eligible units in the state.

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 Bridger Wilderness Area for LNB/OFA as

compared to baseline. The reduction for Naughton Unit 3 with LNB/OFA vs. baseline was only

31%. Modeled visibility impacts for Naughton Unit 3 were reduced to levels comparable to those

yielded by LNB/OFA controls on Naughton Units I and 2 only through the' addition of SCR on

Naughton Unit 3 (see graphs in Appendix A). A comparison between the modeled visibility for

Naughton Units 1 and 2 at the proposed level for LNB/OFA control (0.26 Ib/MMBtu) and the

proposed level for LNB/OFA control for Naughton Unit 3 (0.37 Ib/lY.lMBtu) is certainly relevant

for making a BART determination for Naughton Unit 3. Also see response to USDA Forest

Service comment 11.6.

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V. Analysis of Comments from the National Park Service:

V.I NQ."Step 3: Evaluate Effectiveness ofRemaining Control Technologies (SCR capabilities)-

The NPS commented that the Division underestimated the ability of SCR to redu~e emissions.

The proposed NO, limit for SCR (0.07 IbIMMBtu) is not low enough. SCR can achieve greater

reductions. NPS suggests 0.06 Ib/MMBtu for 30~day limit, 0.051b/MMBtl.l or: lower for an

annual limit.

Response - See response to USDA Forest Service comment 11.7.

V.2 ~, 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 N0;LStep 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 IV.I 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.5 NO, Step 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 11.3.

V.6 NOLStep 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 improvement

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 IV.S.

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V.7 NO;;..Step 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 H2S04mist in the flue gas

• 50% ofthe H2S04mist is removed in a wet FGD unit

• 95% ofthe H2S04mist is removed in a dry FGD unit

• An SCR unit has 2.0 ppmvd NH3 slip

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

ammonium bisulfate

• 50% ofthe 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.lO BART Conclusions for N0:t.Controls: Non-Air Quality 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

niinimal 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 Naughton plant were 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,

but were only part ofthe larger evaluation that considered all five statutory factors.

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V.l1 BART Conclusions for NO!..Controls: 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

NO. 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 commentV.10.

V.12 BART Conclusions for NO, 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.10.

V.l3 BART Conclusions for NO,LControls: 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.1 O.

V.l4 BART Conclusions fo'r 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 of individual tasks): 60-66 months

V.l5 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 1b/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 III.8.

V.l6 BART Conclusions for PM\o 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.

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Page 20 of28

Response - The Division concluded that the costs of a fabric filter for Naughton Unit 3 was not

reasonable. However, as stated on page 51 of the Division's BART analysis for Naughton:

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

full-scale fabric filter on Naughton Unit 3 in a recently issued New Source Review construction

permit. A full-scale fabric filter is the most stringent PM/PMIQ control technology and therefore

the Division will accept it as BART."

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

VLl 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 11.3.

VL2 Presumptive BART - The Powder River Basin Resource Council, et al. commented that DEQ

failed to impose the presumptive BART limit for NOx of 0.15 Ib/MMBtu for Naughton Units 1

and 2, applying the mistaken logic that the presumptive limits do not apply because Naughton's

cumulative capacity is less than 750 MW,

"Response - Seeresponse to USDA Forest Service comment II.5.

VI.3 Reasonably Attributable Visibility Impairment - The Powder River Basin Resource Council,

et al. commented that" because of the magnitude of modeled visibility impacts, DEQ should

certifY that Wyoming power plants are causing reasonably attributable visibility impairment, and

establish more stringent BART controls. A single SO)lrce that is responsible for a 1.0 deciview

change or more" should be considered to "cause" visibility impairment, according to WAQSR

Chapter 6, §9(d)(i)(A). Because ofthe reasonably attributable visibility impairment, BART must

be determined under WAQSR Chapter 9, §2(d)(ii) and 40 CFR §51.302(c)(4)(iii). These

regulations provide that BART is presumed to be at least at NSPS levels. This would require at

least 0.11 Ib/MMBtu for NOx limits, but SCR should be required at 0.07 IbIMMBtu.

"Response - WAQSR Chapter 6, §9(d)(i)(A) applies to the determination of which sources in

Wyoming are subject to BART under the regional haze program, and is not relevant to the

determination of reasonably attributable visibility impairment. Since adoption of Wyoming's

Visibility SIP and visibility regulations to address reasonably attributable visibility impairment,

neither the Federal Land Managers of any Class I area nor the Division has certified that visibility

impairment, attributable to a source or small group of sources, exists in any Wyoming Class I

area pursuant to provisions in Chapter 9, Section 2 ofthe WAQSR. The provisions of Chapter 9,

Section 2 ofthe WAQSRare therefore not relevant to the Division's BART analyses.

VIA 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 of Wyoming 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

AQD Naughton BART

001167
PacifiCorp Naughton Power Plant

Decision Document, BART Permit Application, AP-6042

Page 21 of28

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

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 II.I 0 and EPA comment IILII.

VI.5 BART Conclusions for PMJO Controls - The Powder River Basin Resource Council, et al.

commented that the Division should require PacifiCorp to meet, at a minimum, a PM limit 0.015

Ib/MMBtu at the Naughton plant using full baghouse or polishing baghouse because: 1) the plant

is causing reasonably attributable visibility impairment in at least two Class I areas, and 2)

because BART is supposed to be the "best system of continuous emission reduction" and the

Division's analysis identified fabric filters as the most stringent PM control.

Response - The Division established PMlPMlO emission limits for BART at the Naughton plant

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

guidance. Various control technologies were evaluated for each source subject to BART,

including the most advanced controls, but the BART guidance does not dictate that a state require

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

reasonably attributable visibility impairment, see response to Powder River Basin Resource

Council, et al. comment VI.3.

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

VILl 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 ~d

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 S1.308(e)]

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

51]

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

Best Available Retrofit Technology

VIL2 Regional Haze Rule - The Sierra Club commented that the State of Wyoming 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.

AQD Naughton BART

001168
PacifiCorp Naughton Power Plant

Decision Document, BART Permit Application, AP-6042

Page 22 of28

VII.3 Control of Nitrogen Oxide Emissions - The Sierra Club commented thatthe State ofWyoming

should require the coal plants to install devices that reduce nitrogen oxide emissions.

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 nitrogen oxide

emissions.

VIlA 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

pollutants; nitrogen oxides (NOx), particulate matter (PM/PMlO), 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.

VII.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 the State. 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.

VII.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.

VII.? 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. I and II.6.

AQD Naughton BART

001169
PacifiCorp Naughton Power Plant

Decision Document, BART Permit Application, Ap·6042

Page 23 of28

VIII. Analysis of Public Comments:

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

plants.

Response - See responses to USDA Forest Service comments ILl and 11.6.

IX. 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

Naughton Power Plant. All ofthe 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.

Dav(!i~ Administrator

Wyoming Air Quality Divisiqn

hn . Corra

. ctar

yorning Department ofEnvironmental Quality

AQD Naughton BART

001170
•.•t'

APPENDIX A

VISIBILITY MODELING RESULTS (Baseline vs. LNB and SCR)

AQD Naughton BART

001171
Figure 1

Modeled BART Impacts in Bridger Wilderness Area

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

f"i Baseline

Nau U1 = Naughton Unit 1 (160 MW)

Nau U2 = Naughton Unit 2 (210 MW)

Nau U3 = Naughton Unit 3 (330 MW)

JB Ul = 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)

.. LNBjOFA

II LNB/OFA+SCR

2.500 ..,.1--------------------------------------------------

}

Nau Ul Nau U2 Nau U3 J8 Ul J8 U2 J8 U3 J8 U4

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

1··

0.000

0.500

2.000 I ~l ~,

1.500ui~··:·.I kY:;j}}---------!

fZ J r;~fi~fj (jj ,~ . ·'1

s [... :~

1.000 i .~:. ;~ _

0»00

~o---J z ""0>C

<0

:::T

0"

::l

to

-l
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 Unit4 (330 MW)

LRS Ui=Laramie River Station Unit 1 (550 MWj

LR5 U2 =Laramie River Station Unit 2 (550 MW)

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

i§ Baseline

(I LNBjOFA

II LNBjOFA +SCR

2.500 ,,---------------------------------

)

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

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

DJU3 DJ U4 LRSUl LRS U2 LRS U3

I

Wyodak

1.500 -1-----~

0.500

1.000

0,000

"'>"li'

III

....

Qi

.e.

0» . 00

~o

---I z "'lllC

<0

::r

8"

::::l

OJ

»

;;0

-l
___1

Figure 3

Modeled BART Impacts in Bridger Wilderness Area

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

FJ Baseline

II LNB/OFA

II LNB/OFA + SCR

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)

60 .,--------'------------------------------'------------

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

!~~t:1

Lt~~'

40

50 +I-~----_i

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

20

o

10

30 ..

o

:!!.

0»

°D

~o

...... z "'"IllC

cc

::::J"

o::>

-I
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

OJ U3 = Dave Johnston Unit 3.(230 MW)

OJ U4 = Dave Johnston Unit 4 (330 MW)

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

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

LRS U3 = Laramie River Station Unit 3 (550 MWj

E! Baseline

II LNBjOFA

lIlI LNBjOFA + SCR

O~

°D

~o

--lz

(11",

C

<0

::!

o

:::J

60

50

40 +1--------

u;

>- 30

20

10

o I h·..':....

Wyodak DJ U3 DJ U4

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

LRS Ul LRS U2 LRS U3

j: