IN THE MATTER OF APERMIT APPLICATION (AP-6044) FROMFMC WYOMING CORPORATIONFORA ],lEST AVAILABLE RETROFIT TECHNOLOGY (BART) PERMIT FORTHE GRANGERFACILITY DECISION I. Introduction: The Air Quality Division received a BART permit application from FMC Wyoming Corporation for the two coal-fired boilers that operate at their Granger Facility in Sweetwater County, Wyoming. Regulations governing the BART program have been established by the U.S. EPA in 40 CFR Part 51

- Appendix Y. As stated in the regulations, a source is eligible for BART ifit belongs within a particular group ofstationary source categories, was not in operation prior to August 7, 1962, was in existence on August 7, 1977, and has the potential to emit 250 tons per year (tpy) or more ofany visibility impairing air pollutant. Fossil fuel boilers with more than 250 million Btu (MMBtu) per hour heat input are listed as an eligible source type. Potential emissions from the two 358.5 MMBtu/hr boilers at Granger (installed in 1976) for two visibility impairing air pollutants, nitrogen oxides (NOx) and sulfur dioxide (S02), exceed 250 tpy and therefore the units are eligible for BART. The Division conducted an analysis ofthe BART permit application and on August 12,2008, published in the Rock Springs Daily Rocket-Miner a public notice and notice ofpublic hearing ofthe proposed intentto issue BART determinations. Copies ofthe BART applications and the Division's analysis were placed in the Sweetwater County Clerk's office in Green River, Wyoming, in accordance with regulations. A 30-day public notice period ran from August 12, 2008, to September 11, 2008, and a public hearing was held on Thursday, September 11,2008, at 6 p.m. in Room 1302 atWestern Wyoming Community College, located at 2500 College Drive inRock Springs, Wyoming. To allow adequate opportunity for comment as specified under the Regional Haze Rule 40 CFR 51.308(i)(2), the public commentperiod was extendedto October20,2008. The Division received three (3) comment letters on the proposed permit during the public comment period: 1) a September 10,2008 letterfrom the Wyoming Outdoor Council; 2) an October 17,2008 letter with supplemental comments from the Wyoming Outdoor Council; and 3) an October 17, 2008 letter from EPA Region 8. The Division received one (1) comment letter on the proposed permit after the public commentperiod onNovember 7,2008 from the USDA Forest Service. The USDA Forest Service comments were received afterthe close ofthe 69-day public notice period thatran from August 12, 2008 through October 20, 2008. As such, the Division cannot consider orrespond to the comments in the final BART determination on this application. The comments and the Division's responses are presented on the following pages. II. Analysis ofComments from the Wyoming Outdoor Council: ILl Receptors Are Not Adequately Identified

- The Wyoming Outdoor Council commented that the Division's analysis did not adequately identifythe receptors thatwere usedto model visibility impacts at Class I areas. Response

- Latitude and longitude coordinates for Class I area receptors were taken from the National Park Service (NPS) 

### Class I Receptors database and converted to the appropriate Lambert Conformal Conic coordinates for input to the CALPUFF model. The Class I receptors contained inthe NPS database are recommended bythe FederalLandManagers (FLM) for use in long-range transport (e.g., CALPUFF) modeling of Class I areas. Receptor spacing for the modeled areas is approximately 1.3 km inthe east-west direction and approximately 1.8 km intheFMC Wyoming Corporation DecisionDocument, BARTPermitApplication, AP-6044 Page 2 of6 north-south direction. The receptor configurations that were used for Bridger Wilderness Area (WA) and FitzpatrickWA are shown in the figures below. Figure 1 Rece tors for Brid er WA

BridgerWilderness 684 Receptors USFS Boundary Source:

FS National Coverage file: NRIS· AlP group COlVallis.OR August 27.2003

Source: http://www.nature.nps.gov/air/Maps/ReceptorsFMC Wyoming Corporation DecisionDocument, BARTPermitApplication, AP-6044 Page 3 of6 Figure 2 Receptors for FitzpatrickWA



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• • • • + • • • • • • • • FlzpalrickWlderness 316 Receptors USFS Boundary Source:

FS National Coverage file: NRIS· AlP group Corvallis, OR hJgusl 27, 2003

Source: http://www.nature.nps.gov/air/Maps/Receptors/index.cfm II.2 Impacts Less Than 0.5 dv Should NotBeDeemed A Per SeDoes Not Contribute SituationThe Wyoming Outdoor Council commentedthat amodeled level of0.5 dv should notbe used as athresholdbelowwhichvisibility impacts are deemedto be insignificant. Response

- The Division is comfortable using 0.5 dv as the threshold level to exempt a source from BART orto deem modeled impacts as insignificant. EPA's RegionalHaze 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 WRAP region. Further, the Division believes that the 0.5 deciview threshold is a conservative value given that language in the Regional Haze Rule suggests that 1.0 dv is an appropriate perceptibility threshold and recent literature suggests thatthe perceptibility threshold is greaterthan 1.0 dv (frompage 39120 ofAppendixYto 40 CFRpart51).FMC Wyoming Corporation DecisionDocument, BART PermitApplication, AP-6044 Page 4 of6 11.3 

### Scaling Factors Used for Background Aerosol Concentrations Should be Explained And Justified

- The Wyoming Outdoor Council commented that the process of determining background aerosol concentrations for the 20% bestvisibility days was not explained in adequate detail. 

### Response

- Individual species concentrations corresponding to the 20% best days natural background were calculated for each Class I area by scaling back the annual average natural background concentrations given in Table 2-1 ofthe EPA document 

### Guidancefor Estimating Natural Visibility Conditions Under the Regional Haze Rule. The EPA guidance document provides annual average values ofnatural background for individual species, and total deciview values for the 20% best days for particular areas, but does not provide values for individual species for the 20% best days. Therefore, the Division developed separate scaling factors for each Class I area such that, when multipliedbythe guidance table annual concentrations for each species, the 20% bestdays concentrations for each species forthatparticularClass I area could be calculated. The scaling procedure is illustrated here for Bridger WA. From Appendix B in the EPA natural visibility guidance document, the total deciview value for the 20% best days at Bridger WA is 1.96 dv. To obtain the speciated background concentrations representative ofthe 20% best days, the deciview value (1.96 dv) was first converted to light extinction. The relationship between deciviews and lightextinction is expressed as follows: dv

### = 10 In (bexJI0) orbext

### = 10 exp (dv/lO) where: bext

### =lightextinction expressed in inverse megarneters 

### (Mm- I ). Using this relationship with the known deciview value of 1.96, one obtains an equivalent light extinction value of 12.17 

### Mm-I

. Next, the annual average natural visibility concentrations were setequalto atotal extinctionvalue of 12.17 

### Mm-I

. The relationship betweentotal lightextinction and the individual components ofthe lightextinction is as follows: bext 

### = (3)f(RH)[arnrnonium sulfate] 

### + (3)f(RH)[arnmonium nitrate] 

### + (0.6)[coarse mass] 

### + (4)[organic carbon] 

### +(l)[soil] 

### +(10)[elemental carbon] 

### +bray where:

• bracketed quantities representbackground concentrations in 

### Ilg/m3

• values in parenthesis represent scattering efficiencies

• f(RH) is the relative humidity adjustmentfactor (appliedto hygroscopic species only)

• bray is lightextinction due to Rayleigh scattering (10 

### Mm-I used for all Class I areas) Substituting the total light extinction for the 20% best days, the annual average natural background concentrations, the average f(RH) for Bridger WA, and including a coefficient for scaling, one obtains:

. 12.17 

### = (3)(2.1)[0.12]X

### + (3)(2.1)[0.I]X 

### + (0.6)[3.0]X 

### + (4)[0.47]X 

### + (1)[0.5]X 

### + (10)[0.02]X

### + 10 In the equation above, X represents a scaling factor neededto convertthe annual average natural background concentrations to values representative ofthe 20% best days natural background.FMC Wyoming Corporation DecisionDocument, BART PermitApplication, AP-6044 Page 5 of6 Solving for X provides a value of0.376. Table 1 presents the annual average natural background concentrations, the calculated scaling factor, and the calculatedbackground concentrations forthe 20% bestdays natural background for BridgerWA. Table 1: Calculated Backl!round Components for Bride:erWA Annual Average 20% BestDays Natural Natural Background for Calculated Background for the WestRegion Scaling BridgerWA Component (J12/m3) Factor (J1e:/m3) Ammonium Sulfate 0.12 0.376 0.045 AmmoniumNitrate 0.10 0.376 0.038 Organic Carbon 0.47 0.376 0.176 Elemental Carbon 0.02 0.376 0.008 Soil 0.50 0.376 0.188 Coarse Mass 3.00 0.376 1.127 Because ofthe geographical proximity and similar annual background visibility for the Bridger WA and Fitzpatrick WA, the scaled aerosol concentrations for the two areas were averaged. The 20% best days natural background aerosol concentrations thatwere used for the two Class 1 areas in questionforthis analysis are listed inTable 2 below. I C centrations (llg/m3) dA ays aura ac '2roun eroso on Fitzpatrick Aerosol WA& Component Brid2erWA Ammonium Sulfate 0.045 AmmoniumNitrate 0.038 Organic Carbon 0.178 Elemental Carbon 0.008 Soil 0.189 Coarse Mass 1.136 Table 2:20% BestD N t IB k

11.4 Combined Impacts from Three Trona Plants in Southwestern Wyoming

- The Wyoming Outdoor Council commented that the modeled impacts from three trona plants in southwestern Wyoming should be considered in combination rather than individually. Modeled results for individual facilities were summed in a table intheir October 17,2008 letter. Response

- Summing the 98th percentile modeled visibility impacts for separate facilities is not an accurate portrayal ofcombined impacts because the individual impacts may occur at different locations (receptors) and during different 24-hour time periods. Moreover, the visibility impacts from BART-eligible sources areto be determined separately. As stated inthe EPA's Appendix Y to part 40 CFR 51

- Guidelinesfor BARTDeterminations Under the RegionalHaze Rule, relative to the use ofthe CALPUFF model for BART determinations, "We believe that CALPUFF is an appropriate applicationfor States to usefor theparticularpurposes of this rule, to determine if an individual source is reasonably anticipated to cause or contribute to impairment of visibility in Class I areas, and topredict the degree of visibility improvement which couldreasonably beFMC Wyoming Corporation DecisionDocument, BART PermitApplication, AP-6044 Page 6 of6 anticipated to resultfrom the use ofretrofit technology at an individual source. We encourage States to use it for thesepurposes. " ill. Analysis ofComments from EPARegion 8: IILl Receptors Are Not Adequately Identified

- EPA Region 8 commented that the Division's analysis did not adequately identify the receptors that were used to model visibility impacts at Class I areas. Response

- Seeresponse to 

## wac Comment II.1. IV. Decision: On the basis ofcomments received during the public commentperiod, an analysis ofthose comments, and representations made by FMC Wyoming Corporation, the Department of Environmental Quality has determined that the two BART-eligible 358.5 MMBtu/hr gas fired boilers units at the FMC Wyoming Corporation Granger Facility are not "subject" to BART and no additional controls are required to address visibility impacts in Class I areas. Datedthis _17th

_ day ofJuly, 2009.

o V. Corra 'rector Wyoming Department ofEnvironmental Quality