"



### IN THE MATTER OF A PERMIT APPLICATION (AP-6042) FROM PACIFICORP FOR A BEST AVAILABLE RETROFIT TECHNOLOGY (BART) PERMIT FOR THE NAUGHTON POWERPLANT DECISION I. Introduction: The Air Quality Division received aBART permit application from PacifiCorp for the three coalfired boilers that operate at their Naughton Power Plant in' Lincoln County, Wyoming. Regulations governingthe BART program have been established by the

## u.s. EPA in 40 CFRPart 51

- Appendix Y. As stated inthe regulations, a source is eligible forBART ifitbelongs within a particular group ofstationary source categories, was not in operationpriorto August7, 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 eligiblefor-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 ofpublic hearing ofthe 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 Streetin 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) aletter received July 23, 2009 from Mimi McMillen; 10) a

letter received July 24,2009 from William M. Anderson; 11) a letterreceived 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 ofpublic 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 BasinResource 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 butthey are not included inthis document as no response is required.

AQD Naughton BART 001148'./ ..' PacifiCorp NaughtonPowerPlant DecisionDocument, BARTPermit Application, AP-6042 Page 2 of28 The Division received numerous comments that were descriptive ofenvironmental impacts other than the impacts from BART-eligible sources in Wyoming on Class I area visibility. The Division's responses are limitedto the comments thatdealtwith 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 bythe Division as itprepares the**respons~** to comments onthe Regional Haze SIP.

. . 

# n. Analysis ofComments from the USDAForest 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 ofall 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 NOxcontrol on all four units at Jim Bridger included low NOxburners (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 forthe BART determination for both plants. Regarding the installation ofadditional control equipment at the Jim Bridgerplant, PacifiCorp is required by the BART permitto install SCR on Jim BridgerUnit 3 in 2015 and Jim Bridger Unit 4 in 2016 as well as add-on NOxcontrol 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 forthe installation ofSCR 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 ofwhich are BART-eligible. Additional BART-eligible units are owned or partly owned in Arizona, Colorado, and Montana. Table 1 presents a summary ofthe pollution control projects that are included in PacifiCorp's construction planthrough 2014.

AQD Naughton BART 001149',,: PacifiCorpNaughton Power Plant DecisionDocument, BARTPermitApplication, AP-6042 Page 3 of28 .' '.

. 

### . . ''Table 1: Statusof,PoIlution ControlP,ro.ieets·Under.takenbYPaciflCorp S02Scrubbers New=N LNB Baghouse .SO./LNB PowerPlant Location Upgrade=U Installations Installations ProiectStatus Hunter 3 Utah Installed 2008 Installed Completed Huntington 2 Utah 2007-N 2007 2007 Completed Cholla4 Arizona 2008- U 2008 2008 Completed Jim Bridger4 Wyoming 2008-U 2008 n/a Completed Jim Bridger2 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 Hunter2 Utah 2011-U 2011 2011 Permitted Jim Bridger3 Wyoming 2011-U 2007 n/a Under Construction Wyodak Wyoming 2011-U 2011 2011 Permitted Dave Johnston4 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 BARTfor S02control for all units atthe Jim Bridgerand Naughton power plants. Response

- WFGD upgrades have already been (or are scheduled to be) installed on all units at the Jim Bridger plant. Forthe 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 withinthe TransportRegion 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 ofa given source should be modeled and the cost ofeach BART alternative divided by the sum ofthe deciview (dv) improvement at all impacted Class I areas. Ifmodeling exists for Class I areas that yield impacts above 0.5 dvjust beyond 300 km, those results should be considered also. Savage Run Wilderness Area should also be modeled and considered.

AQD Naughton BART 001150· .. .

.

# :
PacifiCorpNaughton PowerPlant DecisionDocument, BART PermitApplication, AP-6042 

### Page 4 of28 Response

- Only those Class I areas most likely to be impacted by sources subjectto 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 ofless 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 notinclude 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 ofBART 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 ofeach proposed BART contrqloption, The Division chose notto use a hybrid metric such as $/dv primarilybecause of the lack of historical precedent regarding reasonable/acceptable levels for such a metric. Additionally, the use ofa 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 orthe 98th 

### percentile modeledvalue. 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 ofdeciview changes across multiple areas. The Division has fOlmd that $/dv values are often presented without explanation ofthe basis for the calculation. To avoid these confounding factors, the Division choseto evaluate and presentthe costanalyses 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-designatedClass I area, the Division was notrequiredto include itinthe BARTmodeling. Additionally, the Division did not include' Savage Run in any ofits 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 ofSavage Run, the Division anticipates similar improvements in visibility from the analyzed emissionreductions. IIA NO!.-Step 5: Visibility ImprovementDetermination (significant impact)

- The Forest Service commented that it is incorrectto 

### dismiss a control strategy on the basis thatthe modeled visibility improvement is notperceptible or significant. Response

- The Division used 0.5 dv as the threshold level to exempt a source from BART orto deem modeled impacts as insignificant. EPA's Regional Haze Regulations and Guidelinesfor BestAvailable 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.

AQD Naughton BART 001151PacifiCorp Naughton PowerPlant DecisionDocument, BARTPermitApplication, AP-6042 

### Page 5 of28 II.S Five FactorAnalysis for BART Selection: Coal Composition

- The Forest Service commented that PacifiCorp's analysis ofcoal composition is flawed and it does not meet the requirement for ademonstration ofwhy presumptive limits cannot bereached. Response

- Although the BART emission limits forNOx

### 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 ofall 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 notrequired 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 statutoryfactors before making aBART determination. II.6 

### N!1: Controls:. SCR

- The Forest Service commented that significant, cumulative visibility improvements modeledfor SCRinstallations atthe JimBridger 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 otherNaughton units and all Jim Bridgerunits are similar. Also, environmental degradation from the operation ofSCR should not be afactor in the BART determinations and energy impacts from SCR should notbe a factor becausethey have alreadybeen considered in the costanalysis. Response

- The costs for SCR controls, as described in the Division's BART analyses, were deemed by the Divisionto be reasonable for all units atthe Jim Bridger andNaughton plants, but the Division's BART determinations for the two plants were based on consideration ofall 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/OF

### A. 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 otherunits atthe two plants. Forexample, NaughtonUnits I and 2 showeda 72% to 73% reduction in the number ofdays with predicted impacts of0.5 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 ofthe 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 unitwiththe exception ofNaughton Unit 3 (1.4 dv). The predicted number ofdays 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

AQD Naughton BART 001152PacifiCorpNaughtonPowerPlant Decision**Documen~,** BARTPermitApplication, AP-6042 Page 60f28 ,environmental impacts that led the Division to conclude thatLNB/OFA would be BART for NOx control at the Jim Bridgerplant 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 costand 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 ofthe Division's RBLC search. Two plants have limits of 0.05 Ib/MMBtu NOxwith a 12-monthrolling average, which is significantly longerthan a 3D-day averagjng ,period. B,ecause the 0.05 IbJMMBtu lilIlits are basedon a 12-month ayeraging period, they are not comparableto the 3D-day limits establishedby 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 ofnationwide BART determinations shows that both units outside ofWyoming for which SCR is proposed as BART will be subject to a NOxemission limit of0.07 Ib/MMBtu, andboth will bebased on a 3D-day averaging period. The RBLC search showed two plants that will be subject to**24~hour** NOxlimits ofless than 0.07 IblMMBtu (0.067 IbIMMBtu), butthese limits are for newly constructed plants which have been engineered to meet these levels. BART

# will require the retrofit ofsignificant controls at plants that were not designed to meet these lower levels. Based on the Division's evaluation, the Division is satisfied thatthe NOxemission limit of0.07 IblMMBtu**(30~day** rolling average) that· was evaluated for SCR control under BART is the most stringent control level likely to be achieved in aretrofit.

AQD Naughton BART 001153·_-5\ '.,.,
PacifiCorp NaughtonPowerPlant Decision Document, BARTPermitApplication, AP-6042 Page 7 of28

" : ' 

### . -, 

## .. -, .'., :. -", 

# .. :. " 

### "**".;~:** 

### ,Table

## 2: 'SCR**~ermitLimits** 

## tram the RBLC
" " i Size of NO. Permit Limit(s) for Permit FacilitvlLocation Source Source Description SCRControl Date John W. TurkPower 600MW 6,000 MMBtu/hrPC Boiler I) 0.067Ib/MMBtu Nov 2008 Plant/Arkansas (pRB Coal) (24-hrrolling) 2) 0.05 Ib/MMBtu (12-monthrolling)

[SCR,BACT] DryFork 385MW PC Boiler 0.05 Ib/MMBtu Oct2007 Station/Wyoming (12-monthrolling) rSCR,BACT] WYGEN3/Wyoming 100MW 1,300 MMBtulhr,PC Boiler 0.05 Ib/MMBtu Feb 2007 (12-monthrolling)

[SCR,BACT] Iatan 

# -- PC Boiler 0.08 Ib/MMBtu Jan 2006 StationlMissouri (30-dayrolling) [SCR, BACT] Big Cajun'II Power 675MW PC Boiler O.Q7lb/MMBtu Aug2005 Plant/Louisiana (annual average) [SCR,BACTl TS Power 200MW PC Boiler 0.067Ib/MMBtu

.May 2005 PlantlNevada (24-hourrolling) [SCR,BACT] OPPD

- Nebraska


### .

# - 

# - . O.Q7lb/MMBtu Mar2005 City (30-dayrolling) StationlNebraska [SCR,BACT] Note: "--" IndIcates thatthiS value was notprovIded In the RBLC II.8 Reasonable Progress Controls

- The Forest Service asked why Naughton Units 1 and 2 are not required to install SCRas part ofreasonable progress like otherPacifiCorp units. Response

- See response to Forest Service commentII.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 correctvalue, Response

- The application ofwet FGD on Unit 3 is anticipated to lower S02 emissions to 0.10 Ib/MMBtu, based on an average coal sulfur content of0.58% 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 notrelevantbecause BART limits for S02will notbe 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.

AQD Naughton BART 001154;_.-....
PacifiCorpNaughtonPowerPlant Decision Document, BARTPermitApplication, AP-6042 Page 8of28 ILI0 S07. Controls (Section 309)

- The Forest Service understands the role of Section 309 in exempting the State ofWyoming 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 equivalentto 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 atthattime. Response

- The State ofWyoming submitted a 309 SIP as is allowed by the Regional Haze Rule. Part ofthe SIP submittal is a "Betterthan 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 andused in an impr.opercontext.
. Response

- The Division did not attempt to endorse a particular threshold for ·human eye "perceptibility" since the level ofperceptibility has long been disputed. Instead, the Division has relied on EPA's AppendixY BART guidance, which suggests avalue of0.5 dv as the level that a source "contributes" to visibility impairment. One ofthe metrics usee). by the Divisionto evaluate the relative benefit ofa given BART control option was the number ofdays yielding a modeled impactof0.5 dv or more. . 

## m. Analysis ofComments from EPARegion 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 nearthe facilities (Thunder Basin = 50-55ppb, Jonah = 55-58 ppb). DEQ should provide an analysis ofhow higher ozone background concentrations would affectresults. 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 ofthe 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 forthe modelto usethe defaultbackground of44 ppb. Although the model did not use the default background value for the BART analyses, the Division calculated annual average concentrations for recentyears (2007-20.08) and all available data for 2009 for many ofthe stations that were used for input to CALPUFF, including Thunder

AQD Naughton BART 001155PacifiCorp Naughton PowerPlant Decision Document, BART Pennit Application, AP-6042 Page 9 of28 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 ofapproximately 40 ppb. The Division is confident that the default background value of44 ppb was appropriate for the BART modeling, and thatthere is no need for additional analyses to explore alternate background concentrations. III.2 Weight ofVisibility Modeling Results in BART Determinations

- EPA Region 8 commented 

### that DEQ should provide 8.1, 

### explanation ofhow 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 importantthan another, because the Division looked at all five statutory factors in their entirety. EPA guidance did not provide a quantification ofthe amount ofmodeled visibility improvementthat would be acceptable or significant. The Division used two metrics thatwere 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 additionto 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 CALPUFFis an appropriate applicationforStates to usefor the particularpurposes of this rule, to determine 

## ifan individualsource is reasonably anticipatedto cause or contribute to impairment ofvisibility in Class 

### 1 areas, and to predict the degree of visibility improvement which could reasonably be anticipated to resultfrom the use ofretrofit technology 

### ill. !!!!**individual~.** We encourage States to use it for thesepurposes." [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? Ifso, 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 ofdays above 0.5 dv predicted for a given year ofmeteorology was averaged with the similar result from the othertwo years ofmeteorology. 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 optionto another. Regardingthe sufficiency ofthe number ofmodeled Class I areas and the question ofother Class I areas within 300 

### km, see response to USDA Forest Service cpmment IIJ.

AQD Naughton BART 001156PacifiCorpNaughtonPowerPlant ' DecisionDocument, BARTPermitApplication, AP-6042 Page 10 of28 IlLS NO!..Controls

- EPA Region 8 commented that the most stringent emission control levels for NOxcontrols 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 BARTApplicationAnalyses). m.6**12~Month** Average for NO

### c 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 LaramieRiver Station analysis should be created. Response

- The BART limits for NOx emissions from the PacifiCorp plants ,include 30-day rolling limits in terms ofIb/MMBtu**~d** lb/hr. The ton peryear limit is based on a calendaryear ratherthan arolling average, andtherefore the formula associated withthe annual BART limitfor NOxatthe LaramieRiver Station is notrelevant. IlL7 PM Controls: Averaging Periods- EPA Region 8 commented that the BART conclusions and the permitconditions 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 onthe average ofthree I-hourtests per40 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 -'RecentPrevention ofSignificantDeterioration (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 retrofitcontrols on existingunits, 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 ofvisibility improvement, with predicted cumulative improvements across three Class I areas ofonly 0.03 to 0.1 Lldv forUnits 1- 4. These results indicate that requiring more stringent control levels for a fabric filter would not provide significantvisibility 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. ForUnit 3, anew full-scale fabric filterwill be installed for BART control.

AQD Naughton BART 001157

## .,

.. PacifiCorpNaughtonPower Plant Decision Document, BARTPermitApplication, AP-6042 Page 11 of28 III.9 PM Controls: PermitExemption

- 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 operatingperiods including startup.
. The Division considers the BART limits expressed in terms ofIb/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 greaterthan 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 atWyodak, particulates are controlledby 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 of71 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 setat 193 lb/hrto 198 Ib/hrforthe 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/hrBART limits. In the case oftheNaughton 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 bewell 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 ofsulfuric acid (H2S04) mist. A control option should notbe considered as aBART option ifitwill result in an increase in visibility-reducing pollutants. Response

- The Division has already evaluatedthe impacts' ofFOC atthe Naughton plant as part ofthe 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 ofthe ESPs on Units 1 and 2. The permit application included a modeling evaluation ofthe impacts to Class I area visibility from the FOC, and the impacts were predictedto be insignificant.

AQD Naughton BART 001158PacifiCorpNaughtonPowerPlant DecisionDocument, BARTPermitApplication, AP-6042

. Page 12 of28 III. 11

.**SO~** Controls: Reasonable Progress

- EPA Region 8 commented that the Division must evaluatethe visibility impacts ofS02controls and demonstrate reasonable progress forthe 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 orat leastno degradation onthe 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 commentJIJ. 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 indicatethat SCRis costeffective atNaughton. Response

- See response to EPARegion 8 commentm.5. JII.l4 PM Controls: FGC

- EPA Region 8 commented that flue gas conditioning (FGC) willbe applied to Naughton Units I and 2 and decommissioned from Unit 3 upon installation ofafabric filter permitted under PSD. The application ofFGC prior to FGD upgrades will result in a significant increase in emissions ofsulfuric acid (H2 S04 ) mist. This collateral increase should be avoidedto maintain visibility improvements at Class I areas. Response

- Seeresponse to EPARegion 8 commentIII.IO. IV. Analysis ofComments 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 ofthe lack ofhistorical precedentregarding 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

AQD Naughton BART 001159PacifiCorpNaughtonPowerPlant pecisionDocument, BARTPermitApplication, AP-6042 Page 13 of28 highest modeled value in a given area orthe 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: CostEffectiveness

- PacifiCorp commented that any BART determination requiring a sourceto install post-combustion cQntrols like SCR or spend more than $1,500 perton ofNOxremoved would be contrary to EPA Appendix

### Y BART guidance. Response...:.. The EPA's Appendix

### Y guidance describes the EPA's selection ofpresumptive NOx limits for coal-fired EGUs, and provides approximate cost levels for meeting the presumptive limits with currentcombustion controls and a somewhathighercost level for a subset ofunits that would require advanced combustion controls such as rotating opposed fire air (ROFA). The EPA guidance does not attemptto establish costthresholds 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 thatthe use ofSCR is appropriate. As stated previously, the Division establishedNOxemission limits for BART based on consideration ofallfive statutory factors intheirentirety, as required bythe 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 powerplants greaterthan 750 MW. Response

- The Division followed EPA and State ofWyoming 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 otherfacilities. 

### 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 shouldbe required as BART

.. Response

- Seeresponse 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 betoo narrowto satisfyAppendix

### Y. Response

- The Division did not rely solely on the three-year average ofthe 98th percentile CALPUFF results to evaluatethe expected visibility changes for the BART control options. The 98th percentile values and the number ofdays with predicted results above 0.5 dv were presented in the Division's BART analyses for each ofthree modeled years, for each' Class I area, and for

AQD Naughton BART 001160PacifiCorp NaughtonPowerPlant DecisionDocument, BARTPermitApplication, AP-6042 Page 14 of28 each control option. The three-year average ofthe 98th percentile results and the number ofdays 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 inAppendix 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 andthat each unit at afacility operates inthe 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 of24-hour periods ofmeteorology. 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 whichthe emissions are determined similarly. 

### N.? General Comments: NOLEmissions

- PacifiCorp commented that emissions ofNOx 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 extremeNOxcontrol measures such as SCRas BART. Response

- Forthe 20% worst days during the years 2000-2004 atthe 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 ofnitrates at the Bridger Wilderness Area and other Class 

### I areas warrants a full consideration ofprospective 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 extremeNOx 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 costfor 1 dv ofvisibility improvement is more than $15 million per year. If one considers that changes ofless than 1.5 dv are not perceptible to the human eye, the costper deciview reduction is notreasonable. Response

- See responses to PacifiCorp comment 

### N.l andUSDAForest Service comment 

### ILl I.

AciD Naughton BART 001161PacifiCorp Naughton PowerPlant DecisionDocument, BARTPermitApplication, AP-6042 Page 15 of28 IV.lO PresumptiveBART

- PacifiCorp commented thatthe Division's reference inthe BART analysis for the Naughton plant to a presumptive BART limit for NOxof0.15 lblMMBtu is not correct. For reasons stated in PacifiCorp's most recent submittals to the Division, primarily an argument regarding coal characteristics, the correctpresumptive BART limitforNaughton Units 1-2 is 0.28 IblMMBtu. Response

- Seeresponse to USDAForest Service comment U.s. IV.ll Reasonable Costs for SCR on Naughton Unit 3 - PacifiCorp commented thatthe calculated costs for SCRonNaughtonUnit 3 are notreasonable, accordingto EPA's AppendixY guidance. Response

- The EPA's Appendix Y guidance describes the EPA's selection ofpresumptiveNOx limits for coal-fired EGUs, and provides approximate cost levels for meeting the presumptive limits with currentcombustion controls and a somewhathighercost level for a subsetofunits that would require advanced combustion controls such as ROFA. The EPA guidance does not attempt to establish costthresholds that would be considered unreasonable for a given control technology, nor does itpresentthe approximate costs associated withthe 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 establishedNOxemission limits for BART atthe Naughtonpowerplantbased on consideration of all five statutoryfactors, as required bythe AppendixY guidance. IV.12 Incremental Costs for SCR on Naughton Unit 3

- PacifiCorp commented thatthe incremental costs per ton ofNOxreduction for SCR on Naughton Unit 3 shown in Table 10, page 15 ofthe Division's BART analysis is incorrect. The correct value is more than $4,000 perton ratherthan 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 ofthe 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 ofNOxreduction ($2,830/ton) and the incremental cost per ton ofNOxreduction ($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 andthe incremental costs for Unit 3 are lower compared to the other two units atthe 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 CostPerTon of Unit CostPerTon ofNOxReduction NOxReduction

1 $2,750 $8,089 2 $2,848 $7,852 3 $2,830 $4,049

AQD Naughton BART 001162PacifiCorpNaughtonPowerPlant Decision Document, BARTPermitApplication, AP-6042 Page 16 of28 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 costbenefitvalues for Boardman are more favorable for SCRinstallationthan for Naughton Unit 3. Response

- The Division determined BART for NOx control for Naughton Unit 3. based on consideration ofall 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, seeresponse to USDA Forest Service comment 11.6 andthe graphs in Appendix A. IV.14 PresumptiveBART for Naughton Unit 3 and LNB/OFAEmissions 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 ahigher calculatedBART limit of0.35 IbIMMBtu. Even ifthe 0.015 IblMMBtu presumptive limit is assumed to be correct, the requirements for SCR control at 0.07 Ib/MMBtu cannot bejustified 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 ofall five statutory factors, as required by EPA's Appendix Y BART guidance. PacifiCorp's analysis ofcoal composition and how it might affect the presumptive NOxlimit 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 visibilityreductions from baseline as comparedto otherBART-eligibleunits inthe state. For example, Naughton Units 1 and 2 showed a 72% to 73% reduction in the number ofdays 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 forNaughtonUnit 3 were reducedto levels comparable to those yielded by 

### LNB/OF A controls on Naughton Units I and 2 only through the' addition ofSCR 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.

AQD Naughton BART 001163.-)

PacifiCorpNaughtonPower Plant DecisionDocument, BART PermitApplication, AP-6042 

### Page 17 of28 V. Analysis ofComments from the NationalParkService: V.I NQ."Step 3: Evaluate Effectiveness ofRemaining Control Technologies (SCR capabilities)- The NPS commented that the Division underestimated the ability ofSCR 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

- Seeresponse to USDA Forest Service comment 11.7. V.2**~,** 

### Step 4: Evaluate Impacts and DocumentResults (SCR costs) .:. The NPS commented that SCR costs were generally overestimated because the OAQPS Control CostManual was not used for cost estimates.

. Response

- PacifiCorp developed cost estimates for SCR control using a combination ofthe 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 andthatcosts alone would notprecludethe use ofSCR. V.3 N0;LStep 4: Evaluate Impacts and Document Results (incremental costs for SCR)

- The NPS commented thatthe Division over-emphasized the incremental costs forthe addition ofSCR in the BART determinations. The Division should consider the average costs calculated for combustion controls plus SCR. Response

- See response to PacifiCorp commentIV.I andNPS commentV.2. VA NO, Step 4: Evaluate Impacts and DocumentResults (basis for costs)

- TheNPS commented thatcost estimates shouldbe documented by vendor orby the EPA Control CostManual. Response

- Seeresponse to NPS commentV.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) ofa source. Response

- See response to USDA Forest Service comment 11.3. V.6 NOLStep 5: Visibility ImprovementDetermination (incremental benefits ofSCR)

- The NPS commented that the Division placed too much emphasis on the incremental improvement in visibility that was predicted for the addition ofSCR. The total predicted visibility improvement resulting from a combination ofcontrol options should have been presented. Response

- The incremental improvement in modeled visibility with the addition of SCR was mentioned prominently in the summary ofthe Division's BART conclusions, but all visibility modeling results were considered. For more information on the presentation ofthe visibility modeling results in the Division's BART analyses, see the response to EPA Region 8 comment III.2 and PacifiCorp's commentIV.S.

AQD Naughton BART 001164,"
PacifiCorpNaughtonPowerPlant Decision Document, BARTPermitApplication, AP-6042 Page 18 of28 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 ofhow the sulfuric acid mist emissions were calculated by PacifiCorp. Response

- PacifiCorp's consultant, CH2M HILL, used the following methodology to calculate sulfate emissions for SCRfor the PacifiCorp coal-fired powerplants (as provided in a letter from PacifiCorp thatwas submitted tothe Division on September 16, 2009):

• 1.0% ofthe S02in the boiler is convertedto S03

• An additional 1.0% ofthe S02is converted to S03 in an SCRunit

• The S03 is convertedto H2 S04mist inthe flue gas
• 50% ofthe H2 S04mist is removed in a wetFGD unit

• 95% ofthe H2 S04mist is removed in a dry FGD unit

• An SCRunithas 2.0 ppmvdNH3 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 andbisulfate are removed 

### in a dry FGD unit

• Total sulfate emissions are made up ofH2 S04mist, ammonium sulfate and ammonium bisulfate V.8 BART Conclusions for NO!.-Controls: $/dv

- The NPS commentedthatthe 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 determinedthatthe costs for SCRwere reasonable, yet rejected SCR for BART control. DEQ should explain why and providethe costbenchmarks used to determine reasonable costs. Response

- The Division established NOxemission 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 optionsto determine the range ofcontrol costs thatwere 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 SCRdid not mention such impacts. Why were such impacts mentioned in these particular cases? SCR has been used at many facilities with niinimal problems withtransport and storage ofammonia, why wouldthis be aparticularproblem for SCRas BART control? Response

- The Division's BART determinations for the Naughton plant were based on consideration ofthe five statutory factors, including the cost ofcompliance and the energy and non-air quality environmental impacts ofcompliance. Potential energy losses and environmental impacts from the operation ofSNCR and SCRwere mentioned in the Division's BART analysis, butwere only part ofthe largerevaluation that considered all five statutory factors.

AQD Naughton BART 001165/
PacifiCorp NaughtonPowerPlant Decision Document, BART PermitApplication, AP-60£l.2 Page 19 of28 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 itwould cause apower shortage. Response- Seeresponse 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" offly ash. Evidence should be presented andthe economic impact quantified. Response

- Seeresponse to NPS commentV.10. V.l3 BART Conclusions for NO,LControls: Ammonia Injection

- The NPS commented that the Division stated that SCR could create "blue plume" ifthe ammonia injection rate is not well controlled. NPS states that it assumes thatPacifiCorp can properly control the injection rate. Response

- Seeresponse to NPS commentV.1

### O. V.l4 BART Conclusions fo'r NO!' Controls: ,SCR Installation

- The NPS commented that PacifiCorp states that SCRwould take aminimum ofsixyears 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 halfofthattime. PacifiCorp should explainwhy so much extratime is needed. Response - A letter provided to the Division by PacifiCorp dated September 16,'2009,provided information onthe time needed to plan, design, and install SCR: '

• 'Develop andPermit: 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 ofindividualtasks): 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., DesertRockProject). Response

- See response to EPA Region 8 commentIII.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 areasonable BART alternative in the context ofthe PMreductions and associated costs, or statewhat it considers reasonable average and incremental costs for afabric filter.

AQD Naughton BART 001166PacifiCorp Naughton PowerPlant DecisionDocument, BARTPermitApplication, AP-6042 Page 20 of28 Response

- The Division concluded that the costs ofa 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 ofa 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 ofComments from the PowderRiverBasin 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 ofa 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 of0.15 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 atNSPS levels. This would require at least 0.11 Ib/MMBtu forNOx limits, but SCR should be required at 0.07 IbIMMBtu. "Response

- WAQSR Chapter 

### 6, §9(d)(i)(A) applies to the determination ofwhich 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 ofWyoming's Visibility SIP and visibility regulations to address reasonably attributable visibility impairment, neitherthe Federal Land Managers ofany Class 

### I areanorthe Division has certifiedthatvisibility 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 ofChapter 9, Section 

### 2 ofthe WAQSRare therefore notrelevantto the Division's BART analyses. VIA Section 309 Milestone Program

- The Powder RiverBasin 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

AQD Naughton BART 001167PacifiCorp NaughtonPowerPlant Decision Document, BART PermitApplication, 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 ofthe information, comparing the regional totals to the milestones, andtaking 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 USDAForest Service commentII.I0 and EPA commentIILII. 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 aminimum, a PM limit 0.015 Ib/MMBtu at theNaughton plantusing 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 stringentPM control. Response

- The Division established PMlPMlO emission limits for BART atthe 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, butthe BART guidance does not dictate that a state require the control technology with the highest level ofcontrol in all cases. Regarding the relevance of reasonably attributable visibility impairment, see response to Powder River Basin Resource Council, et al. commentVI.3. VII. Analysis ofComments 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 Divisionfollowed 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)]

• GuidelinesforBARTDeterminations Under the RegionalHaze Rule [Appendix Y to part 51]

• Chapter 6, Section 9 ofthe Wyoming Air Quality Standards and Regulations (W AQSR), BestAvailableRetrofit Technology VIL2 Regional Haze Rule

- The Sierra Club commented thatthe State ofWyoming can and should do more to protect airquality 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 ImplementationPlan (SIP) forregional haze. The SIP incorporates the emissions reductions associated withthe Long-Term Strategy forregional haze.

AQD Naughton BART 001168PacifiCorpNaughtonPowerPlant DecisionDocument, BARTPermitApplication, AP-6042 

### Page 22 of28 VII.3 Control ofNitrogen Oxide Emissions

- The SierraClub commented thatthe State ofWyoming should requirethe coal plants to install devices thatreduce nitrogen oxide emissions. Response

- All ofthe Division's BART determinations for coal-firedpowerplants inthe 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 relieffor citizens or for the health offorests and the environment. Response

- The Division's BART determinations and otherrequirements underthe 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 potentialNOx

### emissions ofapproximately 13,500tons peryear. VII.5 Wind Power - A commenter stated that Wyoming can readily replace aging coal-fired power plants with wind power to protectpublic health andto protect our national parks and wilderness areas. Response

- The BART program is designed to assess Best Available Retrofit Technology on existing sources ofair pollution, including the existing powerplants 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 ofthe power plants with an alternate source of energy is well beyondthe scope ofthe BART program. VII.6 Pollution Reduction from PowerPlants --'A commenter stated thatWyoming has an obligation to protecttreasured 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 airpollution is minimized. Response

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

- Seeresponses to USDAForest Service comments II.I and II.6.

AQD Naughton BART 001169PacifiCorpNaughtonPowerPlant DecisionDocument, BARTPermitApplication, Ap·6042 Page 23 of28 VIII. Analysis ofPublic 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 ofEnvironmental 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 PowerPlant. All ofthe conditions proposed in the Division's analysis will be included inthe permit. No permitconditions requiredrevision as aresultofthe public commentperiod. Datedthis 31stday ofDecember, 2009.

# Dav(!i~ Administrator WyomingAir QualityDivisiqn 

### hn

. Corra

. ctar yorningDepartment ofEnvironmental Quality

AQD Naughton BART 001170•.•t'



## APPENDIXA VISIBILITYMODELINGRESULTS (Baselinevs. LNB and SCR)

AQD Naughton BART 001171Figure 1 Modeled BART Impacts in BridgerWilderness Area Naughton and Jim BridgerPowerPlants: 98thPercentile (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--------------------------------------------------

}

J8 U4 J8 U3 J8 U2 J8 Ul Nau U3 Nau U2 Nau Ul (Modeling results representthethree-year average using 2001-2003 meteorology) 1··

0.000 0.500 2.000 I

# ~l**~,**

1.500

# u i**~··:·.I** kY:;j}}---------! 

# fZ

# J**r;~fi~fj** (jj**,~** . 

### ·'1 

## s [

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### i**.~:. ;~**  

### _



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### z ""0>

C <0 :::T 0" ::l to -l

### Figure2 Modeled BART Impacts in Wind CaveNational Park Wyodak, DaveJohnston, and LaramieRiver StationPowerPlants: 

### 98th Percentile (delta-dv)
Wyodak=335 MW DJ U3

### =DaveJohnston Unit3 (230 MW) DJ U4

### = DaveJohnston Unit4 (330 MW) LRS Ui

### =Laramie RiverStation Unit 1 (550 MWj LR5 U2=Laramie RiverStation Unit2 (550 MW) LRS U3 = Laramie RiverStation Unjt3(550 MW) i§ Baseline (I 

### LNBjOFA II LNBjOFA

### +SCR 2.500 ,,--------------------------------- 

## )

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

(Modelingresults representthe three-year average using2001-2003 meteorology) LRS U3 LRS U2 LRSUl DJ U4 DJU3 

# I

Wyodak 1.500**-1-----~**

0.500 1.000

0,000 

### "'> "li' III


### .... Qi 

## .e.

0»

. 00**~o** ---I 

### z 

## "'lll

C <0 ::r 8" ::::l OJ 

### » ;;0 -l___1

Figure 3 Modeled BARTImpacts in BridgerWilderness Area Naughton and JimBridgerPowerPlants: # 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 Unit4 (530 MW) 60 .,--------'------------------------------'------------

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

# !~~t:1**Lt~~'** 40 50**+I-~----_i**

(Modeling results representthe three-yearaverage using 2001-2003 meteorology) 20



### o 10 30 

# .. o :!!.



### 0» °D**~o**


### ...... z 

## "'"Ill

C cc ::::J" 

## o ::>

-IFigure 4 Modeled BARTImpacts inWind CaveNationalPark Wyodak, DaveJohnston, and LaramieRiverStationPowerPlants: #Days> 0.5 delta-dv
Wyodak= 335 MW OJ U3 = Dave Johnston Unit 3.(230 MW) OJ U4 = Dave Johnston Unit4 (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: