IN THE MATTER OF A PERMIT APPLICATION (AP-6043) FROMPACIFICORP FORA BEST AVAILABLE RETROFIT TECHNOLOGY (BART) PERMIT FOR THE WYODAK POWERPLANT DECISION 

### I. Introduction: The Air Quality Division received a BART permit application from PacifiCorp for the coal-fired boiler (Unit 1) that operates at their Wyodak Power Plant in Campbell County, Wyoming. Regulations governing the BART programhave been establishedby the U.S. EPA in 40 CFRPart 51

- Appendix Y. As stated in the regulations, a source is eligible for BART ifitbelongs within a particular group ofstationary source categories, was not in operationpriorto 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) perhourheat input are listed as an eligible source type. Unit 1 atthe Wyodakplanthas a heat input of 4,100 MMBtu per hour and was in existence on August 7, 1977. Potential emissions from each boiler for two visibility impairing air pollutants, nitrogen oxides (NOx) and sulfur dioxide (S02), exceed 250 tpy andtherefore the units are eligible for BART. The Division conducted an analysis ofthe BART permit application for the Wyodakplant and on June 4,2009, published in the Gillette News-Record 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 Campbell County Clerk's office in Gillette, Wyoming in accordance with regulations. A 63-day public notice period ran from June 4, 2009 to August 5, 2009, and a public hearing was held on August 5, 2009, at 6 p.m. in the George Amos Memorial Building, located at 412 South Gillette Avenue in Gillette, Wyoming. The Division received numerous comment letters on the proposed permit during the public comment period: 1) a letter dated July 21,2009 from the USDA Forest Service; 2) a letter dated August 3,2009 from EPA Region 8; 3) a letter dated August 4,2009 from PacifiCorp; 4) a letter dated August 4, 2009 from the National Park Service; 5) a letter dated August 4, 2009 from the Powder River Basin Resource Council, et aI.; 6) a letter dated August 5, 2009 from the Powder River Basin Resource Council; 7) a letter received July 20,2009 from Joanna Taylor; 8) a letter dated July 16, 2009 from Andrew H. Salter; 9) a letter received July 20,2009 from Evelyn and Marvin Griffin; 10) a letter received July 23, 2009 from Mimi McMillen; 11) a letter received July 24, 2009 from William M. Anderson; 12) a letter received July 24, 2009 from Rebekah Smith; 13) a letter dated July 24,2009 from Mike Shonsey; 14) a letter dated July 24,2009 from Susie Mohrmann; 15) a letter dated July 28,2009 from Janice H. Harris; 16) a letter dated July 28,2009 from M. Christensen; 17) a letter dated July 27,2009 from Clint Morrison; 18) a letter dated August 3,2009 from Ann Fuller; 19) a letter dated August 3, 2009 from Mary Fenton; 20) 725 unsigned letters received under a signed cover letter dated July 28, 2009 from Brad Mohrmann, Sierra Club Associate Regional Representative; and 21) 89 signatures received under a signed cover letter dated July 24, 2009 from Brad Mohrmann, Sierra Club Associate Regional Representative. Due to the number 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, PowderRiver 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 butthey are not included inthis document as no response is required.PacifiCorp Wyodak Power Plant DecisionDocument, BART PermitApplication, AP-6043 Page 2 of25 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 thatdealtwiththe State's BART analyses. The Division is also preparing a revised Wyoming State Implementation Plan (SIP) for Regional Haze, and has solicited comments on that SIP. Some comments have been received which were submitted as comments on the Regional Haze SIP, butwere principally directed at the Division's BART analyses. These comments will be addressed bythe Division as itprepares the response to comments onthe Regional Haze SIP. 

## n. Analysis ofComments from the USDAForest Service: ILl BART Conclusions for NO,LControls: SCR

- The Forest Service commented that based on their review ofthe five statutory BART factors, Selective Catalytic Reduction (SCR) should be BART for NOx control for all units at plants such as the Jim Bridger power plant. The Forest Service applauds the proposal to install SCR at the four units at the Jim Bridgerplant for a longterm strategy, but SCRs atJimBridger shouldbe installed as BART on allunits by 2015-2016. Response

- The Division determined BART for NOxcontrol at power plants in Wyoming 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 statutoryfactors intheir entirety. 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 BridgerUnit 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 ofWyoming's State Implementation Plan (SIP) for regional haze as well as PacifiCorp's construction plan for pollution control projects. The schedule for the installation of SCR controls at other plants is uncertain at this point due to the demands on PacifiCorp for compliance with BART and other regulatory programs. PacifiCorp operates 19 coal-fired units, 14 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 includedinPacifiCorp's constructionplanthrough 2014.PacifiCorp WyodakPowerPlant DecisionDocument, BARTPermitApplication, AP-6043 

### Page 3 of25

, '

..Table 1:·Status ofPQlhitio,nControlPro.iectslJndertakett by**Pa~ifiCorp** :
SOz Scrubbers New=N LNB Baghouse SOz/LNB PowerPlant 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 JimBridger4 Wyoming 2008- U 2008 n/a Completed JimBridger2 Wyoming 2009- U 2005 n/a Completed Dave Johnston 3 Wyoming 201O-N 2010 2010 Under Construction Huntington I Utah 2010 - U 2010 2010 Pennitted JimBridger 1 Wyoming 2010-U 2010 n/a Under Construction Naughton 2 Wyoming 2011-N 2011 n/a Under Construction Hunter2 Utah 2011-U 2011 2011 Pennitted JimBridger3 Wyoming 2011-U 2007 n/a Under Construction Wyodak Wyoming 2011-U 2011 2011 Pennitted 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 Pennitted Naughton 3 Wyoming 2013

- U 2013 2013 Pennitted 

### 11.2 N0;LStep 

### 5: Visibility Improvement Determination (Class I areas modeled)

- 

### The Forest Service commentedthat all Class I areas within 300 

### kIn ofa given source shouldbe 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 thatyield impacts above 0.5 dvjust beyond 300 

### kIn, those results should be considered also. Savage Run Wilderness Area should also be modeled and considered. Response

- 

### Only those Class I areas most likely to be impacted by sources 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 would not yield modeled impacts greater than those yielded by the Class I areas chosen for BART modeling. The modeling results for the Class I areas chosen for analysis allowed the Division to make an informed decision on the effect on visibility from the various BART control options. Additionally, EPA's Appendix Y BART guidance does notinclude anyrequirements for modeling distance. EPA's Appendix Y BART guidance does mention that "dollars per deciview" ($/dv) is a metric that could be used to evaluate the cost ofBART compliance, but by no means identifies $/dv as an essential or required metric. The Division considered capital cost, annual cost, costPacifiCorp WyodakPowerPlant Decision Document, BART PermitApplication, AP-6043 Page 4 of25 effectiveness, and incremental cost effectiveness in the cost evaluation ofeach 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 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 modeled value. Itcouldbe based onthe 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 orthe sum ofdeciview changes across multiple areas. The Division has found that $/dv values are often presented without explanation ofthe basis for the calculation. To avoid these confounding factors, the Division choseto evaluate and presentthe cost analyses andvisibility 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 notrequiredto include it in the BART modeling. 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. II.3 NO!..Step 5: Visibility Improvement Determination (significant impact)

- The Forest Service commentedthatit is incorrectto dismiss a control strategy on the basis thatthe modeledvisibility improvementis 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 WesternRegional AirPartnership (WRAP) region. IIA NOLControls: SCR

- The Forest Service commented that significant, cumulative visibility improvements modeled for SCRinstallations atthe Jim BridgerandNaughtonplants indicatethat 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 ofSCRshould not be a factor in the BART determinations and energy impacts from SCR should not be a factor becausethey have alreadybeen considered inthe cost analysis. Response

- The costs for SCR controls, as described in the Division's BART analyses, were deemed bythe 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/MMBtu, which would be achieved by tuning the existing LNB/OFA system. For Naughton Units 1 and 2, PacifiCorp proposed a BART limit for NOx of 0.26 Ib/MMBtu for each unit using new LNB/OFA. Visibility modeling showed that the NOxemission level proposed by PacifiCorp forPacifiCorp WyodakPowerPlant DecisionDocument, BART PermitApplication, AP-6043 Page 5 of25 Naughton Unit 3 provided less in terms of modeled visibility reductions from baseline as comparedto otherunits atthe two plants. Forexample, NaughtonUnits 1 and 2 showed a 72% to 73% reduction in the number ofdays 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 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 unitwith the 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 ofnon-air quality environmental impacts that ledthe Division to conclude thatLNB/OFA would be BART for NOx control at the Wyodak plant. 

### In comparison, modeled visibility impacts for Naughton Unit 3 were reduced to levels comparable to those yielded by LNB/OFA controls on Naughton Units 1 and 2 only through the addition ofSCR as BART on Naughton Unit 3. Potential energy losses and environmental impacts from the operation ofSCR were mentioned in the Division's BART analysis for all PacifiCorp plants, but were only part ofthe larger evaluations that considered all five statutory factors. 11.5 NO!...Controls: SCR Efficiencies

- The Forest Service commented that greater SCR control efficiencies shouldbe factored into the cost andvisibility analyses. Response

- The Division conducted a search ofthe EPA RACTIBACTILAER Clearinghouse (RBLC) to find NOx emission limits as BACT associated with SCR control in recently issued permits. Table 2 presents a summary ofthe Division's RBLC search. Two plants have limits of 0.05 Ib/MMBtuNOx with a 12-monthrolling average, which is significantly longerthan a 30-day averaging period. Because the 0.05 Ib/MMBtu limits are based on a 12-month averaging period, they are not comparable to the 30-day limits establishedbythe Division. Thetwo plants with 30- day averaging periods will be subjected to either a 0.08 Ib/MMBtu or 0.07 Ib/MMBtu limit, and the limits established by the Division meet these lower limits. A spreadsheet compiled by the National Park Service with a summary ofnationwide BART determinations shows thatboth units outside ofWyoming for which SCR is proposed as BART will be subjectto aNOxemission limit of0.07 Ib/MMBtu, and bothwill be based on a 30-day averagingperiod. The RBLC search showed two plants that will be subjectto 24-hourNOxlimits ofless than 0.07 Ib/MMBtu (0.067 Ib/MMBtu), 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 that the NOxemission limit of0.07 Ib/MMBtu (3D-day rolling average) that was evaluated for SCR control under BART is the most stringent control level likely to be achieved in aretrofit.PacifiCorp WyodakPowerPlant DecisionDocument, BARTPermitApplication, AP-6043 

### Page 6 of25

Table 2: SCR.PermitLimits from theRBLC .. Size of NOx PermitLimit(s) for Permit FacilitylLocation Source Source Description SCRControl Date JohnW. TurkPower 600MW 6,000 MMBtu/hrPC Boiler 1) 0.067 Ib/MMBtu Nov 2008 Plant!Arkansas (PRE 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) [SCR, BACT] WYGEN3/Wyoming 100MW 1,300 MMBtu/hr PC Boiler 0.05 Ib/MMBtu Feb 2007 (12-monthrolling)

[SCR,BACT] Jatan 

## -- PC Boiler 0.08 Ib/MMBtu Jan 2006 Station/Missouri (30-dayrolling) [SCR,BACT] Big Cajun II Power 675MW PC Boiler 0.07 Ib/MMBtu Aug 2005 PlantlLouisiana (annual average) [SCR, BACT] TS Power 200MW PC Boiler 0.067 Ib/MMBtu May 2005 Plant/Nevada (24-hourrolling) [SCR, BACT] OPPD

- Nebraska 

## -- -- 0.07Ib/MMBtu Mar2005 City (30-dayrolling) Station/Nebraska [SCR, BACT] Note: "••" mdicates thatthis value was notprovided m the RBLC 

### 11.6 SOLControls (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 inthe demonstration, i.e., are the existing controls needed to accomplish the "Better than BART" demonstration for Section 309? They also note thatthe 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 allowedbythe Regional Haze Rule. Part ofthe SIP submittal is a "Better than BART" demonstration, required by rule, which does not require that each and every unit demonstrate emission controls that are "Betterthan BART". The demonstration is aregional demonstration. The Division is aware than the 309 program only establishes milestones through 2018, and that following 2018 another strategy may be necessary to reduce visibility-impairing pollutants. Additional strategies will be addressed in future SIP revisions. II.? Visibility Impairment

- The Forest Service commented that because EPA BART guidelines state that 0.5 dv "contributes" to visibility impairment, and 1.0 dv "causes" visibility impairment, the discussion from Ronald Henry regarding perceptibility in the BART applications from PacifiCorp is irrelevant andused in an impropercontext.PacifiCorp WyodakPower Plant DecisionDocument, BART PermitApplication, AP-6043 

### Page 7 of25 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 used bythe Divisionto evaluate the relative benefit ofa given BART control option was the number ofdays yielding a modeled impact of0.5 dv ormore. ill. 

### Analysis ofComments from EPARegion 8: IlLI 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 (ThunderBasin = 

### 50-55 ppb, 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 for the 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 recent years (2007-2008) and all available data for 2009 for many ofthe stations that were used for inputto CALPUFF, including Thunder Basin, Jonah, Rocky Mountain National Park, Centennial, and Pinedale. Annual average values forthese stations ranged from 35 ppb to 49 ppb, with an overall average ofapproximately40 ppb. The Division is confident that the default background value of44 ppb was appropriate for the BART modeling, andthatthere is no need for additional analyses to explore alternate background concentrations. IlL2 Weight ofVisibility Modeling Results in BART Determinations

- EPA Region 8 commented that DEQ should provide an explanation ofhow modeled visibility improvements were weighed in making BART determinations. Response

- The Division's BART determinations were based on consideration of all five statutory factors, as required by EPA's Appendix Y BART guidance. The modeled visibility improvements for a given control strategy were one ofthe five factors that were considered. No single factor was weighted as being more 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 improvementthatwould be acceptable or significant. The Division used two metrics thatwere mentioned inthe EPA BART guidance, the 98th 

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

### to present the results ofthe BART visibility modeling. Also see the response to USDA Forest Service commentIIA.PacifiCorp WyodakPower Plant DecisionDocument, BART PermitApplication, AP-6043**Pag~** 80f25 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 applicationfor States to usefor the particularpurposes of this rule, to determine 

## if an individualsource is reasonably anticipatedto cause or contribute to impairment ofvisibility in Class I areas, and to predict the degree of visibility improvement which could reasonably be anticipated to resultfrom the use ofretrofit technology atan**individual~.** We encourage States to use it for thesepurposes." [emphasis added] IlIA Language from BART Determinations

- EPA Region 8 commented that the Division should clarify the statements of "3-year average visibility improvements". Are dv improvements calculated for each Class I area added together? 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 reported 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 other two 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. Regarding the sufficiency ofthe number ofmodeled Class I areas and the question of other Class I areas within 300 km, see response to USDA Forest Service commentII.2. ilLS NO:!...Controls

- EPA Region 8 commented that the most stringent emission control levels for NOx controls have not been evaluated, resulting in inflated calculated cost effectiveness values. Lower emission limits should be evaluated for selective non-catalytic reduction (SNCR) and SCR. Response

- The Division has analyzed the most stringent levels for SNCR and SCR, and does not agree that the cost effectiveness numbers have been inflated. See response to USDA Forest Service comment II.5. Furthermore, the Division has deemed the costs associated with all analyzed BART NOx control options, including SNCR and SCR, to be reasonable (see the conclusions listed under the section: NOx: EVALUATE IMPACTS AND DOCUMENT RESULTS in each ofthe five BARTApplicationAnalyses). ilL6 12-Month Average for N0x..- EPA Region 8 commented that there is no formula to calculate if the 12-month rolling emission limit has exceeded the permit condition. A permit condition to match condition 12.a.iiifrom 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 ofIblMMBtu and lb/hr. The ton per year limit is based on a calendaryear ratherthan a rolling average, andtherefore the formula associated withthe annual BART limitfor NOxatthe Laramie River Station is notrelevant.PacifiCorp WyodakPowerPlant DecisionDocument, BART PermitApplication, AP-6043 Page 9 of25 IlL7 PM Controls: Averaging Periods- EPA Region 8 commented that the BART conclusions and the permitconditions should include associated averaging periods for all PMlPMlO limits. Response

- The averaging periods for the PMlPMlO limits are dictated by the performance test requirements in the BART permits. Compliance with the Ib/MMBtu and lblhr PMlPMlO limits is based on the average ofthree I-hourtests per40 CFR 60.46. IlL8 PM Controls: Control Effectiveness

- EPA Region 8 commented that the Division should explain why 0.015 Ib/MMBtu for baghouse/fabric filter control effectiveness is acceptable, when 0.012 Ib/MMBtu has been approved by the Division for other permits and 0.010 Ib/MMBtu was approved for the Desert Rock project. The BART determinations should include analyses of electrostatic precipitators (ESPs) and baghouses at lower control levels. Response

- Recent Prevention ofSignificantDeterioration (PSD) permits issued by the Division did include PMlPMlO limits of0.012 Ib/MMBtu for fabric filter controls, but those limits (and PMlPMlO limits established for the Desert Rock Project in New Mexico) were determined through Best Available Control Technology (BACT) analyses for new sources. The BART process deals withretrofit 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 ofvisibility improvement, with predicted cumulative improvements across three Class I areas ofonly 0.03 to 0.1**~dv** for Units 1- 4. These results indicate that requiring more stringent control levels for a fabric filter would not provide significantvisibility improvement. As described on page 12 of the Division's BART analysis for the Wyodak plant, flue gas conditioning (FGC) was considered for enhancement ofthe existingESP on Unit 1. The existing ESP is well designed and provides adequate space and residence time for the flue gas particles to gain an electric charge and migrate to the collection plate. The application ofFGC was not expectedto significantly improve PMlPMlO removal efficiency. I1L9 PM Controls: Permit Exemption

- EPA Region 8 commented that Condition 5 in the proposed EGU BART permits contains an inappropriate exemption for startup. The exemption from the Ib/MMBtu PM limit during startup should be removed or it may be appropriate to analyze the needfor a startup BART limit. Response

- For each EGU subject to BART in Wyoming, only the BART limits for PMlPMlO that are expressed in Ib/MMBtu will not apply during startup. The BART limits for PMlPMlO that are expressed in lb/hr and tpy (as based on the Ib/MMBtu limits) will apply during all operatingperiods including startup. The Division considers the BART limits expressed in terms oflb/hr and tpy to be appropriate limits for startup. For the four units at the Jim Bridger plant, PacifiCorp calculated that the particulate emissions from the startup fuel (fuel oil) would be no greater than 10.9 lb/hr per unit, conservatively assuming that the ESP controls had zero control efficiency during the startup process. As a comparison, the BART limit that would apply for each unit during startup is 180 lblhr. Further, PacifiCorp has agreed to minimize startup emissions from the four units at the plant by placing the ESPs in service prior to the introduction of coal to the boilers, which isPacifiCorp WyodakPowerPlant DecisionDocument, BART PermitApplication, AP-6043 Page 10 of25 contrary to the manufacturer's recommendation to energize the ESP only after the unit is at full operating temperature and combustion offuel oil has ceased. Similarly for Unit 1 atWyodak, particulates are controlledby an ESP and startup is accomplished with fuel oil. The maximum emissions estimated for startup (8.9 Ib/hr) would be well below the BART limit 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 set at 193 Ib/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/hr BART limits. In the case ofthe Naughtonplant, particulate controls will include a mixture ofESPs (Units 1 and 2) and a fabric filter/baghouse (Unit 3). Natural gas is the startup fuel for each ofthese units, and particulate emissions during startup are expected to be well below the established Ib/hr BART limits. IlL10**SO~** Controls: Reasonable Progress

- EPA Region 8 commented that the Division must 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 onthe 20% worst days and improvement or at least no degradation on the 20% best days. Furthermore, the Regional Haze rule allows a state to take full credit for strategies implemented under 309 when addressing Class I Areas away from the Colorado Plateau (51.309(g)(4)(i)). IlL11 PM Control Level

- EPA Region 8 commentedthatbecause the Division recently issued a PSD permit for the Wyodak plant, it is inappropriate for the BART analysis options to be less protective than the permitted enforceable controls. Controls already permitted through PSD should be viewed as baseline forthe BART analysis. Response

- The permit limit for PMlPMlO emissions from the Wyodak plant established under the recent permit (MD-7487, issued 5/20/09) is 0.015 Ib/MMBtu, and the control technology is a fabric filter baghouse. The emission limit of0.015 Ib/MMBtu was confmned through the BART analysis thatwas conducted forthe facility. RecentPrevention ofSignificantDeterioration (PSD) permits issued by the Division did include PMlPMlO limits of0.012 Ib/MMBtu for fabric filter controls, but those limits were determined through Best Available Control Technology (BACT) analyses. The BART process deals with retrofit controls, andtherefore is not directly comparable to BACT determinations. The fabric filter controls added at Wyodak under MD-7487 were not subjectto BACT. 40 CFR 51.309(b)(7) states that "Base year means the year for which data for a source included within the program were used by the WRAP to calculate emissions as a starting point forPacifiCorp WyodakPowerPlant Decision Document, BARTPermitApplication, AP-6043 

### Page 11 of25 development ofthe milestone required by paragraph (d) (4) (i) ofthis section." Because the Western Regional Air Partnership (WRAP) used 2003 as the starting point fOf development of milestones for S02 emissions, the emission control configuration in place at a given facility in 2003 was considered by the Division to be the baseline configuration for BART. Additionally, the period for establishingthe baselinevisibility conditions underthe Regional Haze Rule is 2000 to 2004 [40 CFR 51.308(d)(2)]. The fabric filter configuration for the Wyodak plant that was permitted in May of 2009 was therefore considered a control strategy option rather than a baseline configuration. Additionally, visibility modeling conducted by the Division has shown that the addition of a fabric filter as an upgrade to an ESP provides very little in the way of modeled visibility improvement, and these results indicate that requiring more stringent control levels for a fabric filter would not provide significant visibility improvement. Also see response to EPA Region 8 commentIII.8. llI.12 NOLControls

- EPA Region 8 commented that the most stringent emission control levels have not been evaluated, resulting in inflated calculated cost effectiveness values. Lower emission limits should be evaluated for SNCR and SCR. A revised cost analysis should indicate that SCR is costeffective atWyodak. Response

- See response to USDA Forest Service comment ll.5 and EPA Region 8 comment lll5. IV. Analysis ofComments from PacifiCorp: 

### N.1 General Comments: Cost Metrics

- PacifiCorp commented that EPA's Appendix Y BART guidance states that a properBART evaluation should include "othercost-effectiveness measures (such as $/deciview)". Thus, any BART determination that is limited to use only cost effectiveness and incremental costeffectiveness 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 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 modeled value. It 

### could be based on the 98th 

### percentile value for anyone modeledyear or itcouldbe 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 commentedthat any BART determination requiring a sourceto install post-combustion controls like SCRor spendmorethan $1,500 perton ofNOx

### removedwouldbe contraryto EPAAppendixYBART guidance.PacifiCorp WyodakPower Plant DecisionDocument, BARTPermitApplication, AP-6043 Page 12 of25 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 current combustion controls and a somewhathigher cost level for a subset ofunits that would require advanced combustion controls such as rotating opposed fire air (ROFA). The EPA guidance does not attempt to 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 that the use ofSCR is appropriate. As stated previously, the Division established NOxemission limits for BART based on consideration ofall five statutory factors intheir entirety, as requiredby 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 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. IVA General Comments: Post-Combustion Controls

- PacifiCorp commented that EPA never contemplated the use of post-combustion controls to meet BART limits for tangentially-fired boilers, and that it is nearly impossible under Appendix Y guidance to show that anything other than combustion controls should be required as BART. Response

- See response to PacifiCorp commentIV.2. IV.5 General Comments: Visibility Improvement

- PacifiCorp commented that a BART determination that only relied on the 98th percentile, three-year average results from CALPUFF may betoo narrowto satisfy AppendixY. Response

- The Division did not rely solely on the three-year average ofthe 98th percentile CALPUFF results to evaluate the 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 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 in AppendixA).PacifiCorp WyodakPowerPlant Decision Document, BART PermitApplication, AP-6043 

### Page 13 of25 IV.6 General Comments: Modeling

- PacifiCorp commented that visibility modeling contains inherent bias or exaggeration because it assumes that a particular source will operate at its maximum capacity 100% ofthe time andthat each unitat afacility operates inthe sameway. 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 Wyodak. Additionally, the conclusions drawn from BART visibility modeling primarily involve comparisons between control scenarios for whichthe emissions are determined similarly. IV.7 General Comments: NO!-Emissions

- PacifiCorp commented that emissions ofNOx 

### during the 20% best and 20% worst days at Class I 

### areas in Wyoming are not a significant contributor to regional haze as compared to other emissions, and therefore the Division should consider this before requiring extremeNOx

### control measures such as SCR as BART. Response

- Forthe 20% worst days during the years 2000-2004 atthe BridgerWilderness Area, 6.21 % of the total visibility degradation was attributable to nitrates. Source apportionment modeling provided by the WRAP showedthat 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 BARTprocess. IV.8 Perceptibility

- PacifiCorp commented that credible studies indicate that only changes in visibility as high as 1.5-2.0 dv are perceptible to the human eye. The Division should consider this while drawing conclusions based on the results of the visibility modeling and before requiring extremeNOx 

### controlmeasures such as SCR. Response

- Seeresponse to USDA Forest Service commentn.7. IV.9 Presumptive BART for Wyodak

- PacifiCorp commentedthatthe Division correctly identified the presumptive BART limit of0.23 IblMMBtu for the Wyodakplant, butthey do not agree with the statement inthe Division's BART analysis thatthe limitis "notapplicable". Response

- The statement on page 6 ofthe Division's BART analysis that presumptive BART levels do not apply to Wyodak is based on the fact thatthe cumulative generating capacity ofthe facility is less than 750 MW. In 

### accordance withthe EPA's AppendixY guidance for BART, the presumptive NOx 

### levels apply to EGUs greater than 200 MW located at power plants with total capacity of750 MW or more. Because the Wyodak plant has a total capacity ofonly 335 MW, the presumptive limits do not strictly apply.PacifiCorp WyodakPowerPlant DecisionDocument, BART PermitApplication, AP-6043 

### Page 14 of25 V. Analysis ofComments from the NationalParkService: V.l NO!..Step 3: Evaluate Effectiveness ofRemaining Control Technologies (SCR capabilities)- The NPS commented that the Division underestimated the ability ofSCR to reduce emissions. The proposed NOx 

### limit for SCR (0.07 Ib/MMBtu) is not low enough. SCR can achieve greater reductions. NPS suggests 0.06 Ib/MMBtu for 30-day limit, 0.05 

### Ib/MMBtu or lower for an annual limit. Response

- Seeresponse to USDAForest Service commentII.5. V.2 NO!..Step 4: Evaluate Impacts and DocumentResults (SCR costs)

- The NPS commentedthat SCR costs were generally overestimated because the OAQPS Control CostManual was not used for costestimates. 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 estimatedcosts are reasonable and that costs alone wouldnotpreclude the use ofSCR. V.3 NOLStep 4: Evaluate Impacts and Document Results (incremental costs for SCR)

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

- Seeresponse to PacifiCorp commentN.l andNPS commentV.2. VA NO!..Step 4: Evaluate Impacts and DocumentResults (basis for costs)

- The NPS commented that costestimates shouldbe documentedby vendor orbythe EPA Control CostManual. Response

- Seeresponse to NPS commentV.2. V.S NOLStep 5: Visibility Improvement Determination (Class I Areas Modeled)

- The NPS commented that the Division should consider visibility impacts at all Class I areas within 300 kilometers (km) 

### ofa source. Response

- Seeresponse to USDAForest Service commentII.2. V.6 NO!..Step 5: Visibility ImprovementDetermination (incremental benefits ofSCR)

- TheNPS 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 improvemept resulting from acombination ofcontrol options shouldhave beenpresented. Response

- The incremental improvement in modeled visibility with the addition ofSCR 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 comment

### N.S.PacifiCorp Wyodak PowerPlant DecisionDocument, BART PermitApplication, AP-6043 Page 15 of25 V.? NOLStep 5: Visibility ImprovementDetermination (sulfuric acid mist emissions)

- The NPS commented thatthe 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 calculatedby PacifiCorp. Response

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

• 1.0% ofthe S02inthe boiler is convertedto S03

• An additional 1.0% ofthe S02is convertedto S03 in an SCRunit

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

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

• An SCRunithas 2.0 ppmvdNH3slip

• 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 S04 mist, 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 determined that the costs for SCRwere reasonable, yetrejected SCRfor BART control. DEQ should explain why and providethe costbenchmarks usedto 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 therange ofcontrol costs thatwere reasonable. V.I0 BART Conclusions for NOLControls: Non-Air Ouality Impacts

- The NPS commented that the Division mentioned non-air quality impacts as reasons to reject SCR for BART controls. RecentPSD permits issued by DEQ and requiring SCRdid notmention such impacts. Why were such impacts mentioned in these particular cases? SCR has been used at many facilities with minimal problems withtransport and storage ofammonia, whywouldthis be aparticularproblem for SCR as BART control? Response

- The Division's BART determinations for the Wyodak plant was 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 inthe Division's BART analysis,PacifiCorp WyodakPowerPlant DecisionDocument, BART Permit Application, AP-6043 Page 16 of25 but were only part of the larger evaluation that considered all five statutory factors in their entirety. V.11 BART Conclusions for NOLControls: Parasitic Power Loss

- The NPS commented that the Division mentioned parasitic power loss in association with the operation of OFA and SCR. Parasitic power loss associated with SCR has already been accounted for in the cost analysis for NOx and should not be "double-counted" by using it to draw conclusions for BART control unless itwould cause a power shortage. Response

- Seeresponse to NPS commentV.lO. V.12 BART Conclusions for N0x-Controls: Fly Ash Sales

- The NPS commented that the Division stated that the operation of SCR could impact the "salability" of fly ash. Evidence should be presented andthe economic impactquantified. Response

- Seeresponse to NPS commentV.1

## o. V.13 BART Conclusions for NO! Controls: 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 thatit assumes that PacifiCorp canproperly controlthe injectionrate. Response

- Seeresponse to NPS commentV.l

## o. V.14 BART Conclusions for NO!....Controls: SCR Installation

- The NPS commented that PacifiCorp states that SCRwouldtake 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 inhalfofthattime. 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 and Permit: 18-24 months 

## • Design: 9-12 months 

## • Procurement: 9-13 months 

## • Construct: 18-24 months 

## • Start, Tune, andTest 4-6 months 

## • Total (including overlap ofindividualtasks): 60-66 months V.15 BART Conclusions for PMlO Controls: Control Effectiveness

- The NPS commented that the Division should explain why 0.015 Ib/MMBtu was acceptable to the Division as a control effectiveness for a ESP/polishing fabric filter combination, when 0.012 Ib/MMBtu has been approved by the Division for other recent permits involving fabric filters and limits as low as 0.010 Ib/MMBtu have recently been approved for fabric filters (e.g., DesertRockProject). Response

- Seeresponse to EPA Region 8 commentIll.8.PacifiCorp WyodakPowerPlant DecisionDocument, BART PermitApplication, AP-6043 Page 17 of25 V.16 BART Conclusions for PMlO Controls: Fabric Filters

- NPS believes that PacifiCorp would not have agreed to install fabric filters unless it finds the option to be reasonable or is compelled to do so. DEQ should accept fabric filters as a reasonable BART alternative in the context ofthe PM reductions and associated costs, or state what it considers reasonable average and incremental costs for afabric filter. Response

- The Division concluded that the costs ofa fabric filter for Wyodak Unit 1 was not reasonable. However, as stated on page 36 of the Division's BART analysis for Wyodak:
"
...PacifiCorp is committedto installing this control device and has permittedthe installation ofa full-scale fabric filter on Unit 1 in a recently issued New Source Review construction permit. A full-scale fabric filter is the most stringent PMlPM10 control technology and therefore the Divisionwill accept it as BART." VI. Analysis ofComments from thePowderRiverBasin Resource Council: VI. 1 SCR as BART

- The Powder River Basin Resource Council commented that SCR is the best available retrofittechnology and shouldbe required as BART at all ofthe Wyoming powerplants under consideration. Response

- The Division determined BART for the control ofNOxemissions from power plants in Wyoming based on a full consideration ofall five statutory factors in their entirety, as required byEPA's AppendixY BART guidance. The BART guidance does not dictate that a state require the controltechnology withthe highestlevel ofcontrol in all cases. VII. Analysis ofComments from thePowderRiverBasin Resource Council, et aI.: VII. 1 Modeled Class I Areas

- The Powder River Basin Resource Council, et al. commented that all Class I areas within 300 km ofa given source shouldbe modeled forvisibility impacts. Response

- See response to USDA Forest Service comment 11.2. VII.2 SCR as BART

- The Powder River Basin Resource Council, et al. commented that SCR is BART and mustbe required for all units at all coal-firedpowerplants. Response

- See responses to USDAForest Service comments 11.1,11.4 and 11.5. VII.3 Section 309 Milestone Program

- The PowderRiverBasin Resource Council, et al. commented that DEQ should impose BART limits for S02 because participation in the Section 309 program only excuses DEQ from setting BART limits ifthe State's 309 SIP is approved by the EPA and if the 309 SIP demonstrates that emissions levels would result in greater visibility improvement than source-specific BART limits. Response

- The Regional Haze Rule allows the State ofWyoming to submit a 309 SIP in lieu of establishing BART limits for S02. The 309 SIP submittal includes a "Better than BART" demonstration. The entire submittal is currently undergoing EPA review and the State has no control over how long the EPA takes to review the SIP. The State, however, does not wait for EPA to complete its review before implementing a SIP. All of the 309 states have been participating in the 309 program, collecting S02 inventories, allowing independent audits ofthe information, comparing the regional totals to the milestones, and taking public comment on thePacifiCorp WyodakPowerPlant DecisionDocument, BART PermitApplication, AP-6043 Page 18 of25 regional figures and the comparisons with the milestone figures. The S02 levels have shown compliance with the milestones and continue to demonstrate declining S02 emissions levels. Also see responses to USDA Forest Service comment 11.6 andEPA comment

### ill. 10. VIlA SCR for Long-Term Strategy

- The Powder River Basin Resource Council, et al. commented that the BART limits for NOx determined by the Division for Wyodak meet presumptive BART, butfurther reductions are warranted to reduce Class 

### I impacts. The Division shouldrequire SCR underLong-Term Strategy. Response

- Seeresponse to USDAForest Service comment 11.1. VIII. Analysis ofComments from the Sierra Club and Citizens Associated with the Sierra Club: 

### Vill.l Air Quality Laws and Regulations

- The Sierra Club commented that it is important that air quality laws and regulations are strictly complied with to preserve park resources for present and future generations. Response

- The 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 CFR51.308(e)]

• Guidelinesfor BARTDeterminations Under the RegionalHaze Rule [AppendixY to part 51]

• Chapter 6, Section 9 ofthe Wyoming Air Quality Standards and Regulations (W AQSR), BestAvailable Retrofit Technology 

### Vill.2 Regional Haze Rule

- The Sierra Club commentedthatthe State ofWyoming can and should do moreto 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 ImplementationPlan (SIP) for regional haze. The SIP incorporates the emissions reductions associatedwiththe Long-Term Strategyfor regional haze. 

### Vill.3 Control of Emissions of Nitrogen Oxides

- The Sierra Club commented that the State of Wyoming shouldrequire the coal plants to install devices to reduce emissions ofnitrogen oxides. Response

- All ofthe Division's BART determinations for coal-firedpowerplants inthe State of Wyoming include pollution control equipmentthatwill substantiallyreduce emissions ofnitrogen oxides. VillA 20-Year Trend

- A commenter stated that the amount of air and water pollution has clearly escalated in the past 20 years, with little 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-impairingPacifiCorp WyodakPowerPlant Decision Document, BART PermitApplication, AP-6043 

### Page 19 of25 pollutants; nitrogen oxides (NOx), 

### particulate matter (pMIPMlO), 

### and sulfur dioxide (S02)' As an example, BART controls at the Jim Bridger plant will result in a total annual reduction in potential NOx

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

- The BART program is designed to assess Best Available Retrofit Technology on existing sources ofairpollution, includingthe existing powerplants inWyoming. 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 BARTprogram. VIII.6 Pollution Reduction from PowerPlants - A commenter statedthatWyoming 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 ensuringthat 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. VIII.? SCR Controls

- Several commenters stated that BART for NOx

### control should be SCR for all plants. Response

- Seeresponses to USDAForest Service comments II. 1 and 11.4. IX. 'Analysis ofPublic Comments: IX. 1 SCR Controls

- Several commenters stated that BART for NOx 

### control should be SCR for all plants. Response

- See responses to USDAForest Service comments 11.1 and 11.4.PacifiCorp WyodakPowerPlant DecisionDocument, BART PermitApplication, AP-6043 Page 20 of25 

### X. Decision: On the basis of comments received during the public comment period, an analysis of those comments, and representations made by PacifiCorp, the Department 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 WyodakPower Plant. 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.

# DavitJi~ Administrator Wyoming Air QualityDivision ohn

. Corra i ctor yomingDepartmentofEnvironmental Quality

### APPENDIXA VISIBILITYMODELINGRESULTS (Baseline vs. LNB and SCR)Figure 1 Modeled BART Impacts in Bridger Wilderness Area Naughton and Jim BridgerPowerPlants: 98th Percentile (delta-dv)

Nau U1 

### =Naughton Unit 1 (160 MW) Nau U2

### =Naughton Unit 2 (210 MW) Nau U3

### =Naughton Unit 3 (330 MW) JB U1 

### = Jim Bridger Unit 1 (530 MW) JB U2

### =Jim Bridger Unit 2 (530 MW) JB U3 =Jim Bridger Unit 3 (530 MW) JB U4

### = Jim Bridger Unit 4 (530 MW) [] Baseline

• LNB/OFA

• LNB/OFA + SCR



### > "9 III

..... Qj 

## e. 2.500

2.000

1.500

1.000

0.500

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

(Modeling results represent the three-year average using 2001-2003 meteorology)Figure 2 Modeled BART Impacts in Wind CaveNational Park Wyodak, Dave Johnston, and LaramieRiver Station PowerPlants: 98th Percentile (delta-dv)
Wyodak

### =335 MW DJ U3

### = DaveJohnston Unit 3 (230 MW) DJ U4

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

### =Laramie River Station Unit 1 (550 MW) LRS U2

### =Laramie River Station Unit 2 (550 MW) LRS U3

### =Laramie River Station Unit 3 (550 MW) ill Baseline
• LNBjOFA

• LNBjOFA

### +SCR



### >" 'C I III


### .... Qj 

## e. 2.500 ,...,---------------------------------

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

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

1.000

0.500

0.000 I t·._. Wyodak DJ U3 DJ U4 (Modeling results represent the three-year average using 2001-2003 meteorology) LRS Ul LRS U2 LRS U3Figure 3 Modeled BART Impacts in BridgerWilderness Area Naughton and Jim BridgerPowerPlants: #Days> 0.5 delta-dv

60

50

40

Vi 30 o :!!.. 20

10



### o Nau U1 

### =Naughton Unit 1 (160 MW) Nau U2 = Naughton Unit 2 (210 MW) Nau U3 = Naughton Unit 3 (330 MW) JB U1 

### = Jim Bridger Unit 1 (530 MW) JB U2 

### =Jim Bridger Unit 2 (530 MW) JB U3

### =Jim Bridger Unit 3 (530 MW) JB U4

### =Jim Bridger Unit 4 (530 MW) lJ Baseline

• LNB/OFA

• LNB/OFA 

### + SCR

Nau U1 Nau U2 Nau U3 JB U1 JB U2 JB U3 JB U4 (Modeling results represent the three-year average using 2001-2003 meteorology)Figure 4 Modeled BART Impacts in Wind CaveNational Park Wyodak, Dave Johnston, and Laramie River Station PowerPlants: # Days> 0.5 delta-dv
Wyodak = 335 MW DJ U3 = Dave Johnston Unit 3 (230 MW) DJ U4 = Dave Johnston Unit 4 (330 MW) 60

50

40

30

20

10



### o I**!""'.~** •.< LRS Ul 

### =Laramie River Station Unit 1 (550 MW) LRS U2 

### =Laramie River Station Unit 2 (550 MW) LRS U3 

### =Laramie River Station Unit 3 (550 MW) [] Baseline

• LNB/OFA

• LNB/OFA 

### + SCR

Wyodak DJ U3 DJ U4 (Modeling results represent the three-year average using 2001-2003 meteorology) LRS U1 LRS U2 LRS U3