### IN THE MATTER OF A PERMIT APPLICATION (AP-6041) FROM PACIFICORP FOR A BEST AVAILABLE RETROFIT TECHNOLOGY (BART) PERMIT FOR THE DAVE JOHNSTONPOWERPLANT DECISION I. Introduction: The Air Quality Division received a BART permit application from PacifiCorp for two coal-fired boilers (Units 3 and 4) that operate at their Dave Johnston Power Plant in Converse County, Wyoming. Regulations governing the BART program have been established by the U.S. EPA in 40 CFR Part 51

- Appendix Y. As stated in the regulations, a source is eligible for BART ifit belongs within a particular group ofstationary source categories, was not in operation prior to August 7, 1962, was in existence on August 7, 1977, and has the potential to emit 250 tons per year (tpy) ormore ofany visibility impairing airpollutant. Fossil fuel boilers with more than 250 million Btu (MMBtu) per hour heat input are listed as an eligible source type. Units 3 and 4 commenced service in 1964 and 1972, respectively. Potential emissions from each boilerfor two visibility impairing airpollutants, 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 Dave Johnston plant and published inthe Douglas Budget apublic notice ofproposed approval ofthe BART permit on June 3, 2009. At the time ofthe June 3, 2009 publication, a copy ofthe Dave Johnston BART application and the Division's analysis were placed in the office ofthe Converse County clerk in accordance with regulations. Due to an error in the initial public notice, a revised public notice was published on August 5, 2009 and the public comment period was extended to September 4, 2009. An initial public hearing was held on August 5, 2009 and a continuation ofthat hearing was held on September 4, 2009 following the extension ofthe public comment period. Both public hearings were held atthe Council Chambers in City Hall, located at 101 North 4th Streetin Douglas, 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 al.; 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 Griffm; 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. The Division also received a letter after the close ofthe public notice period from the Colorado Department ofPublic Health and Environment (letter dated September 14, 2009) in support ofthe Division's BART determinations for the Dave Johnson and Jim Bridger powerplants.PacifiCorp Dave Johnston PowerPlant DecisionDocument, BART PennitApplication, AP-6041 Page 2 of25 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 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 notincluded inthis document as no response is required. 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. II. Analysis ofComments from the USDA Forest Service: ILl BART Conclusions for NO! Controls: 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 Bridger plant for a longterm strategy, but SCRs atJim Bridger shouldbe installed as BART on all units 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 statutory factors intheir entirety. Regarding the installation ofadditional control equipment atplants such as 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 NOx control on Units 1 and 2 no later than 2023. The schedule for installation is based onthe incorporation ofSCRadd-on control onthese units under the long-term strategy component ofWyoming's State Implementation Plan (SIP) for regional haze as well as PacifiCorp's construction plan for pollution control projects. The schedule forthe 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 controlprojects that are included inPacifiCorp's constructionplan through 2014.PacifiCorp Dave JohnstonPowerPlant Decision Document, BART PermitApplication, AP-6041 

### Page 3 of25

'fable 1: Status of Pollution Contr()IP
..**o.iect~Undertakenby** PacifiCorp SOz Scrubbers New=N LNB Baghouse SOz/LNB PowerPlant Location Upgrade=U Installations Installations Project Status 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 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 Permitted JimBridger 3 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 

### II.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 Dave Johnston PowerPlant Decision Document, BART PermitApplication, AP-6041 

### 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 modeledvalue. It

### couldbe 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 or the 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 Divisionwas notrequired to include it inthe 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 invisibility from the analyzed emissionreductions. ITJ 

### NO!..Step 5: Visibility ImprovementDetermination (significant impact)

- The Forest Service commentedthat 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 WesternRegional AirPartnership (WRAP) region. ITA 

### NOLControls: SCR

- The Forest Service commented that significant, cumulative visibility improvements modeled for SCRinstallations atthe Jim BridgerandNaughton 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 a factor in the BART determinations and energy impacts from SCR should notbe 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 by the Division to 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 0037 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 thatthe NOx

### emission level proposed by PacifiCorp forPacifiCorp Dave Johnston PowerPlant Decision Document, BART PermitApplication, AP-604l Page 5 of25 Naughton Unit 3 provided less in terms of modeled visibility reductions from baseline as comparedto otherunits atthe two plants. Forexample, 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 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 ofnon-air quality environmental impacts that ledthe Division to conclude that LNB/OFA would be BART for NOx control at the Jim Bridger plant and for Units 1 and 2 at the Naughton Plant. Modeled visibility impacts for Naughton Unit 3 were reduced to levels comparable to those yielded by LNB/OFA controls on Naughton Units 1 and 2 only through the addition of SCR as BART on Naughton Unit 3. Potential energy losses and environmental impacts from the operation of SCR were mentioned in the Division's BART analysis for both the Naughton and Jim Bridger plants, but were only part ofthe larger evaluations thatconsidered all five statutory factors. U.5 N0:LControls: SCR Efficiencies _-:- The Forest Service commented that greater SCR control efficiencies shouldbe factored into the cost and visibility 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 IblMMBtu NOxwith a 12-monthrolling average, which is significantly longerthan a 30-day averaging period. Because the 0.05 IblMMBtu limits are based on a 12-month averaging period, they are not comparable to the 30-day limits established by the Division. Thetwo plants with 30- day averaging periods will be subjected to either a 0.08 IblMMBtu 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 of0.07IblMMBtu, and bothwill be based on a 30-day averaging period. The RBLC search showed two plants that will be subjectto 24-hourNOxlimits ofless than 0.07 IblMMBtu (0.067 IblMMBtu), 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 NOx emission 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.PacifiCorp Dave JohnstonPowerPlant DecisionDocument, BARTPennitApplication, AP-6041 Page 6 of25 ',' "" Table 2: 

### seR PermitLiinitsfromtbe,RBLC Size of NOx PermitLimit(s) for Permit Facilitv/Location Source SourceDescription SCR Control Date JohnW. TurkPower 600MW 6,000 MMBtuJhrPC Boiler 1) 0.067lblMMBtu Nov 2008 Plant!Arkansas (PRB Coal) (24-hrrolling) 2) 0.05 IblMMBtu (12-monthrolling)

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

[SCR, BACT] Iatan


### -- PC Boiler 0.08 Ib/MMBtu Jan2006 StationlMissouri (30-dayrolling) / [SCR,BACT] Big CajunII Power 675MW PC Boiler 0.071b1MMBtu Aug 2005 PlantILouisiana (annual average) [SCR,BACT] TS Power 200MW PC Boiler 0.067 lblMMBtu May 2005 PlantlNevada (24-hourrolling) [SCR,BACT] OPPD

- Nebraska



### -- 

## -- 0.07 lblMMBtu Mar2005 City (30-dayrolling) StationINebraska [SCR, BACT] Note: "••" mdlcates thatthiS value was not provided m the RBLC II.6 SOLControIs (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 thatwould have resulted from BART. Are the existing S02 controls in place at plants such as the Jim Bridger and Naughton plants at least equivalent to the control scenario used in the demonstration, Le., are the existing controls needed to accomplish the "Better than BART" demonstration for Section 309? They also note that the 309 program sunsets in 2018 and added S02 controls maybe needed forreasonable progress atthattime. Response

- The State ofWyoming submitted a 309 SIP as is allowed by the 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 "Better than BART". The demonstration is a regional demonstration. The Division is aware than the 309 program only establishes milestones through 2018, and that following 2018 another strategy may be necessary to reduce visibility-impairing pollutants. Additional strategies will be addressed in future SIP revisions. II.? Visibility Impairment

- The Forest Service commented that because EPA BART guidelines state that 0.5 dv "contributes" to visibility impairment, and 1.0 dv "causes" visibility impairment, the discussion from Ronald Henry regarding perceptibility in the BART applications from PacifiCorp is irrelevant andused in an improper context.PacifiCorp Dave Johnston PowerPlant DecisionDocument, BART PermitApplication, AP-6041 

### 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 Divisionhas 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 impactof0.5 dv ormore. ill. Analysis ofComments from EPA Region 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 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 recent years (2007-2008) and all available data for 2009 for many ofthe stations that were used for input to CALPUFF, including Thunder Basin, Jonah, Rocky Mountain National Park, Centennial, and Pinedale. Annual average values forthese 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, 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 inmaking 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 improvementthat would be acceptable or significant. The Division used two metrics that were 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 ildv), to present the results ofthe BART visibility modeling. Also see the response to USDA Forest Service comment ITA.PacifiCorp Dave JohnstonPowerPlant DecisionDocument, BARTPermitApplication, AP-6041 Page 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 theresults 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 useforthe 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 at !!!! individualsource. 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 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 ofone control optionto another. Regarding the sufficiency ofthe number ofmodeled Class I areas and the question ofother Class I areas within 300 

### km, see response to USDA Forest Service commentII.2. III.5 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). III.6 12-Month Average for NO.!..- EPA Region 8 commentedthat 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 shouldbe created. Response

- The BART limits for NOx emissions from the PacifiCorp plants include 30-day rolling limits interms ofIb/MMBtu and lb/hr. The ton peryear limit is based on a calendaryear ratherthan arolling average, andtherefore the formula associatedwiththe annual BART limitfor NOxatthe Laramie River Stationis notrelevant.PacifiCorp Dave Johnston Power Plant DecisionDocument, BARTPermit Application, AP-6041 Page 9 of25 IlL7 PM Controls: Averaging Periods- EPA Region 8 commented that the BART conchlsions 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 BARTpermits. Compliance with the lb/MMBtu and lb/hrPMlPMlO limits is based onthe 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 lb/MMBtu for baghouse/fabric filter control effectiveness is acceptable, when 0.012 lb/MMBtu has been approved by the Division for other permits and 0.010 lb/MMBtu was approved for the Desert Rock project. The BART determinations should include analyses of electrostatic precipitators (ESPs) andbaghouses at lowercontrol levels. Response

- Recent Prevention ofSignificantDeterioration (PSD) permits issued by the Division did include PMlPMlO limits of0.012 lb/MMBtu for fabric filter controls, but those limits (and PMlPMlO limits established for the Desert Rock Project in New Mexico) were determined through Best Available Control Technology (BACT) analyses for new sources. The BART process deals with retrofit controls on 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**~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 14 ofthe Division's BART analysis for Dave Johnston, ESP performance enhancements using FGC were considered for Unit 3, butthe application ofFGC is not expected to significantly improve PMlPMlO removal efficiency. PacifiCorp did not evaluate the application ofFGC on Unit4 because it is typically used to

### enha~ce the removal efficiency ofan existing, constrainedESP. IlL9 PM Controls: PermitExemption

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

- For each EGU subject to BART in Wyoming, only the BART limits for PMlPMlO that are expressed in lb/MMBtu will not apply during startup. The BART limits for PMlPMlO that are expressed in lb/hr and tpy (as based on the lb/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 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 isPacifiCorp Dave Johnston PowerPlant Decision Document, BARTPermitApplication, AP-6041 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 forUnit 1 atWyodak, particulates are controlledby an ESP and startup is accomplished with fuel oil. The maximum emissions estimated for startup (8.9 lblhr) would be well below the BART limit of7llblhr. The three units at LRS are also started on fuel oil and controlled with ESPs, and the particulate emissions during startup are expected to be well below the BART limits, which are set at 193 lb/hrto 198 lblhrforthe three units. Forunits with baghouse controls for particulate matter such as Dave Johnston Units 3 and 4, emissions from fuel oil during the startupprocess are also estimatedto be well belowthe allowable lblhrBART limits. 

### In the case ofthe Naughton plant, particulate controls will include a mixture ofESPs (Units 1 and 2) and a fabric filter/baghouse (Unit 3). Natural gas is the startup fuel for each ofthese units, and particulate emissions during startup are expected to be well below the established lblhr BART limits. IlL10 SOl Controls: Reasonable Progress

- EPA Region 8 commented that the Division must evaluate the visibility impacts ofS02controls and demonstrate reasonable progress for the Class I areas away from the Colorado Plateau. Response

- Wyoming, along with other 309 states in the WRAP region, evaluated the impact of the 309 program on all Class I areas in the west, even though the requirement by rule was to demonstrate improvement in Class I areas on the Colorado Plateau. The WRAP modeling for sulfates shows that all Class I areas in and around Wyoming sources are benefiting from the sulfur dioxide emission reductions instituted in the 309 program. Sulfate extinction levels show improvement on the 20% worst days and improvement or at leastno degradation onthe 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 (5l.309(g)(4)(i)). I1Ul PM Control (ESP vs. Baghollse)

- EPA Region 8 commented that the Division's statement in the BART analysis forthe Dave Johnston plantthat an ESP is an effective PM control device and commonly proposed for consideration in BACT analyses is not accurate. The currenttechnology most often usedto satisfyPMlPMlOBACT is afabric filter baghouse. Response

- The Division's BART determinations for Units 3 and 4 at the plant include new fabric filters for the control ofPMlPMlO emissions on both units. Any statements on the relative effectiveness of the existing control equipment at the plant made in the BART analyses are irrelevantbecause the chosenBART controls representthe most stringenttechnology. I1I.12 NO!...Control Efficiencies and Visibility Modeling

- EPA Region 8 commented that the most stringent emission control levels have not been evaluated for NOx control, resulting in inflated calculated cost effectiveness values. The State should also consider the large visibility improvementwith SCRinmaking a BART determination. 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 11.5. Furthermore, the Division has deemed the costs associated with all analyzed BART NOx control options, including SNCR and SCR, to be reasonable (see thePacifiCorp Dave JohnstonPowerPlant DecisionDocument, BART PermitApplication, AP-6041 Page 11 of25 conclusions listed under the section: NOx: EVALUATE IMPACTS AND DOCUMENT RESULTS in each ofthe five BARTApplicationAnalyses). For a discussion ofthe Division's consideration ofmodeledvisibility impacts, seethe response to USDA commentTIA. TILl3 Post-Control Scenario 3 vs. B

- EPA Region 8 commented that it was not clear how PostControl Scenario 3 differs from Post-Control Scenario B relative to the BART visibility modeling forthe Dave Johnston plant. Response

- The Division requested that PacifiCorp perform additional CALPUFF modeling (scenarios A and B) afterthe modeling for Post-Control Scenarios 1-4 had alreadybeen submitted to the Division. Post-Control Scenario B is nearly identical to Post-Control Scenario 3, with the exception ofa slight refinement to the estimate ofsulfate emissions. Total sulfate emissions for the older Post-Control Scenario 3 were 7.3 lb/hr, and the total sulfate emissions for Post-Control Scenario B were 7Alb/hr. The results for Scenario B were usedbythe Division as representative ofSCRforNOxcontrol. TI1.14 AveragingPeriod for NO!.-EPA Region 8 commentedthat an averaging period is missing from thetpyNOxlimitinthe BART determination forthe Dave Johnston plant. Response

- The BART limits forNOxemissions forthe Dave Johnston plant include 30-day rolling limits in terms ofIb/MMBtu and lblhr. The ton peryear limit is based on a calendaryear ratherthan arolling average. TILl5 Collateral Impacts

- EPA Region 8 commented that PacifiCorp and the Division state that the installation ofSNCR or SCRatplants such as the Jim Bridgerplantcould impactthe "saleability" offly ash and that SCR could create a "blue plume" ifthe ammonia injection rate is not well controlled. The fact that injection rates may not be well controlled should not be a reason to eliminate atechnology such as SNCRin amodern powerplant. Response

- The Division's BART determinations were based on consideration of the five statutory factors, including the cost of compliance 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, butwere only part ofthe larger evaluationthat considered all five statutory factors intheir entirety.PacifiCorp Dave JohnstonPowerPlant DecisionDocument, BARTPermitApplication, AP-6041 Page 12 of25 IV. Analysis ofComments from PacifiCorp: IV. 1 General Comments: Cost Metrics

- PacifiCorp commented that EPA's Appendix Y BART guidance states that a properBART evaluation should include "other cost-effectiveness measures (such as $/deciview)". Thus, any BART determination that is limited to use only cost effectiveness and incremental costeffectiveness maybe 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 itcould 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. IV.2 General Comments: CostEffectiveness

- PacifiCorp commentedthat any BART determination requiring a sourceto install post-combustion controls like SCR or spend morethan $1,500 perton ofNOxremovedwouldbe contraryto EPA AppendixY 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 somewhathigher costlevel for a subset ofunits that would require advanced combustion controls such as rotating opposedfire 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 statedpreviously, the Division established NOxemission limits for BART based on consideration ofall five statutory factors intheir entirety, as requiredbythe 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 forpowerplants 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.PacifiCorp DaveJohnstonPowerPlant DecisionDocument, BARTPermitApplication, AP-6041 Page 13 of25 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 shouldbe 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 maybetoo narrowto satisfyAppendixY. 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). 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 eachunit 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 Dave Johnston. Additionally, the conclusions drawn from BART visibility modeling primarily involve comparisons between control scenarios forwhichthe 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 at the BridgerWilderness 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 BARTprocess.PacifiCorp Dave Johnston PowerPlant DecisionDocument, BART PermitApplication, AP-6041 Page 14 of25 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 extremeNOxcontrol measures such as SCR. Response

- See response to USDA Forest Service comment 11.7. V. Analysis ofComments from the National Park Service: V.l NO!..-Step 3: Evaluate Effectiveness ofRemaining Control Technologies (SCR capabilities)- The NPS commented that the Division underestimated the ability of SCR to reduce emissions. The proposed NOx limit for SCR (0.07 Ib/MMBtu) is not low enough. SCR can achieve greater reductions. NPS suggests 0.06 IblMMBtu for 30-day limit, 0.05 Ib/MMBtu or lower for an annual limit. Response- See response to USDA Forest Service comment 11.5. 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 estimated costs are reasonable andthatcosts alone wouldnotpreclude the use ofSCR. V.3 N0;LStep 4: Evaluate Impacts and Document Results (incremental costs for SCR)

- The NPS commentedthatthe Division over-emphasizedthe 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. 1 andNPS commentV.2. VA NO!..-Step 4: Evaluate Impacts and DocumentResults (basis for costs)

- The NPS commented that costestimates shouldbe documented by vendor or by the EPA Control CostManual. Response

- See response to NPS commentV.2. V.5 N0;LStep 5: Visibility Improvement Determination (Class I Areas Modeled)

- The NPS commented that the Division should consider visibility impacts at all Class 1 areas within 300 kilometers (km) ofa source. Response

- See response to USDA Forest Service comment 11.2. V.6 NO!.-Step 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 shouldhave beenpresented.PacifiCorp DaveJohnstonPowerPlant DecisionDocument, BARTPermitApplication, AP-6041 Page 15 of25 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 111.2 and PacifiCorp's comment IV.5. V.? 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 SCR for the PacifiCorp coal-fired powerplants (as provided in a letter from PacifiCorp thatwas submittedto the Division on September 16, 2009):

• 1.0% ofthe S02in the 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 wetFGD 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 $/dvas an additional metric for evaluating BART controls. Response

- See response to PacifiCorp response IV.1. V.9 BART Conclusions for NOx Controls: Cost Benchmarks

- The NPS commented that the Division determined thatthe costs for SCRwere reasonable, yet rejected SCR for BART control. DEQ should explain why andprovide the 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 the range ofcontrol costs thatwere reasonable. V.10 BART Conclusions for NO!..Controls: Non-Air Quality Impacts

- The NPS commented that the Division mentioned non-air quality impacts as reasons to reject SCR for BART controls. RecentPSD permits issuedby 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 minimal problems withtransport and storage ofammonia, why wouldthis be a particularproblem for SCRas BART control?PacifiCorp Dave Johnston PowerPlant Decision Document, BART PermitApplication, AP-6041 

### Page 16 of25 Response

- Seeresponseto EPA Region 8 commentIIL15. V.U BART Conclusions for N0;LControls: 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 apower shortage. Response

- Seeresponse to EPA Region 8 commentIIL15. V.12 BART Conclusions for NOLControls: 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 impactquantified. Response

- Seeresponseto EPARegion 8 commentIIL15. V.13 BART Conclusions for NOLControls: 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 thatitassumes thatPacifiCorp can properly controlthe injectionrate. Response

- Seeresponseto EPARegion 8 commentill. 15
. V.14 BART Conclusions for NO! Controls: SCR Installation

- The NPS commented that PacifiCorp states that SCRwouldtake a minimum ofsixyears to plan and install. NPS states that MinnesotaPower 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 on the time neededto 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 lb/MMBtu was acceptable to the Division as a control effectiveness for a ESP/polishing fabric filter combination, when 0.012 lb/MMBtu has been approved by the Division for other recent permits involving fabric filters and limits as low as 0.010 lb/MMBtu have recentlybeen approved for fabric filters (e.g., DesertRockProject). Response

- Seeresponse to EPA Region 8 commentill.8. V.16 BART Conclusions for PM10 

### Controls: Fabric Filters

- NPS believes that PacifiCorp would not have agreed to install fabric filters unless it [mds the option to be reasonable or is compelled to do so. DEQ should accept fabric filters as areasonable BART alternative in the context ofthePacifiCorp Dave Johnston PowerPlant Decision Document, BART PermitApplication, AP-6041 Page 17 of25 PM reductions and associated costs, or state what itconsiders reasonable average and incremental costs for afabric filter. Response

- The Division concludedthatthe costs offabric filters for Dave Johnston Units 3 and 4 were notreasonable. However, as stated on page 48 ofthe Division's BART analysis for Dave Johnston: "PacifiCorp is committed to installing this control device and has permitted the installation ofa full-scale fabric filter (on) Unit 3 and Unit 4 in Air Quality PermitMD-5098. A full-scale fabric filter is the most stringent PMlPMlO control technology and therefore the Divisionwill accept it as BART." VI. Analysis ofComments from the PowderRiverBasin 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 Appendix Y BART guidance. The BART guidance does not dictatethat a state require the controltechnology withthe highestlevel ofcontrol in all cases. Vll. Analysis ofComments from the PowderRiverBasin Resource Council, et al.: VII. 1 Modeled Class I Areas

- The Powder River Basin Resource Council, et al. commented that all Class 1areas within 300 km ofa given source shouldbe modeled for visibility impacts. Response

- Seeresponse 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

- Seeresponses to USDAForest Service comments 11.1 and 1I.4. 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 settingBART 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 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 comment 11.6 and EPA commentIII. 10.PacifiCorp Dave Johnston PowerPlant DecisionDocument, BARTPermitApplication, AP-6041 Page 18 of25 

### VIlA SCR for Long-Term Strategy

- The Powder River Basin Resource Council, et al. commented that the BART limits for NOxdetermined by the Division for the two units at the Dave Johnston plant meet presumptive BART, but further reductions are warranted to reduce Class I impacts. The Division shouldrequire SCRto be installed underLong-Term Strategy. Response

- See responses to USDAForest Service comments 

### II. 1 and 

### 1104. VITI. Analysis ofComments from the Sierra Club and Citizens Associated with the Sierra Club: 

### VIlLI Air Quality Laws and Regulations

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

- The Division followed federal regulations and guidance as well as state regulations in assessing the BART applications and for making the BART determination for all sources eligible for BART in the State of Wyoming. The BART rules and guidance used by the Division included:

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

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

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

### Vill.2 Regional Haze Rule

- The SierraClub commentedthatthe 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 Implementation Plan (SIP) for regional haze. The SIP incorporates the emissions reductions associatedwiththe Long-Term Strategy forregionalhaze. 

### Vill.3 Control ofNitrogen Oxide Emissions

- The SierraClub commentedthatthe State ofWyoming shouldrequire the 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. 

### 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 regionalhaze 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 potentialNOxemissions ofapproximately 13,500tons peryear.PacifiCorp Dave JohnstonPowerPlant DecisionDocument, BARTPermitApplication, AP-6041 Page 19 of25 Vill.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 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 BARTprogram.

.Vill.6 Pollution Reduction from PowerPlants

- A commenter stated thatWyoming has an obligation to protect treasured public spaces by adhering to federal air quality laws. The State must reduce air pollutants from the old coal plants that are federally required to utilize the most advanced technical developments in ensuring that air pollution is minimized. Response

- The Division determined BART controls based on the five statutory factors developedby the EPA. Various control technologies were evaluated for each source subject to BART, including the "most advanced technical developments", but the ultimate BART determinations were made based on a full consideration of all five statutory factors in their entirety. Vill.7 SCR Controls

- Several commenters stated that BART for NOx control should be SCR for all plants. Response

- See responses to USDAForest Service comments II.l and 114. IX. Analysis ofPublic Comments: IX. 1 SCR Controls

- Several commenters stated that BART for NOx control should be SCR for all plants. Response

- Seeresponses to USDA Forest Service comments III and II.4.PacifiCorp DaveJohnstonPowerPlant DecisionDocument, BARTPermitApplication, AP-6041 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 Dave Johnston Power Plant. All ofthe conditions proposed in the Division's analysis will be included in the permit. No permit conditions required revision as a result ofthe public comment period. Datedthis 31stday ofDecember, 2009.

# Davf:!i~ Administrator Wyoming Air Quality Division 

# Jdv.**+-I-~=--~~-=:::::::~:::::** o V.Corra

. ector yoming Department ofEnvironmental Quality

### APPENDIX A VISIBILITYMODELING RESULTS (Baseline vs. LNB and SCR)Figure 1 Modeled BART Impacts in BridgerWilderness Area Naughton and Jim BridgerPowerPlants: 98th Percentile (delta-dv)

>' "9 ltI 

## .... (jj 

## e. 2.500

2.000

1.500

1.000

0.500

-

0.000 Nau Ul 

### =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) El Baseline

• LNB/OFA

• LNB/OFA + SCR

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)

### Figure2 Modeled BART Impacts inWind CaveNationalPark Wyodak, Dave Johnston, and LaramieRiver StationPowerPlants: 98th 

### Percentile (delta-dv)
rn Baseline

• LNB/OFA

• LNB/OFA

### +SCR LRS Ul

### =Laramie RiverStation Unit 1 (550 MW) LRS U2

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

### =Laramie River Station Unit 3(550 MW) Wyodak

### = 335 MW DJ U3

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

### = Dave Johnston Unit4 (330 MW)
2500 

# 1

2.000 .----------------------------------

0500

0.000 I be,s" 1.000 1.500 +1------1 

### '> "C I J!! Qj 

# e.

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

60

50

40

'iii' 30 c 

## ::.
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) EJ 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 LaramieRiver 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) 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) fill Baseline

• LNB/OFA

• LNB/OFA 

### + SCR 60 ...-,-------------------------------------------

50 +1----------,

40 +1-------- 

### j 30 

## .::.

20

10



## o I !f£ill'iItO' Wyodak DJ U3 DJ U4 (Modeling results represent the three-year average using 2001-2003 meteorology) LRS Ul LRS U2 LRS U3