IN THE MATTER OF A PERMIT APPLICATION (AP-6044) FROM FMC WYOMING

CORPORATION FOR A ],lEST AVAILABLE RETROFIT TECHNOLOGY (BART) PERMIT

FOR THE GRANGER FACILITY

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 if it belongs within a particular

group of stationary source categories, was not in operation prior to August 7, 1962, was in existence on

August 7, 1977, and has the potential to emit 250 tons per year (tpy) or more of any visibility impairing

air pollutant. Fossil fuel boilers with more than 250 million Btu (MMBtu) per hour heat input are listed

as an eligible source type. 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 of public hearing of the proposed

intent to 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 at Western Wyoming

Community College, located at 2500 College Drive in Rock Springs, Wyoming.

To allow adequate opportunity for comment as specified under the Regional Haze Rule 40 CFR

51.308(i)(2), the public comment period was extended to October 20,2008.

The Division received three (3) comment letters on the proposed permit during the public comment

period: 1) a September 10,2008 letter from 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 comment period on November 7,2008 from the USDA Forest Service. The USDA Forest Service

comments were received after the close ofthe 69-day public notice period that ran from August 12, 2008

through October 20, 2008. As such, the Division cannot consider or respond 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 of Comments from the Wyoming Outdoor Council:

ILl Receptors Are Not Adequately Identified - The Wyoming Outdoor Council commented that

the Division's analysis did not adequately identify the receptors that were used to 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 in the NPS database are recommended by the Federal Land Managers (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 in the east-west direction and approximately 1.8 km in the
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Decision Document, BART Permit Application, AP-6044

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north-south direction. The receptor configurations that were used for Bridger Wilderness Area

(WA) and Fitzpatrick WA are shown in the figures below.

Figure 1

Rece tors for Brid er WA

Bridger Wilderness

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/Receptors
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Decision Document, BART Permit Application, AP-6044

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Figure 2

Receptors for Fitzpatrick WA

• • • • • • • • • • • • • • • • • • • • • •

• • • • • • • • • • • • • • • • • • • • + • • • • • •

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • + • • • • • • • •

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 Not Be Deemed A Per Se Does Not Contribute SituationThe Wyoming Outdoor Council commented that a modeled level of 0.5 dv should not be used as

a threshold below which visibility impacts are deemed to be insignificant.

Response - The Division is comfortable using 0.5 dv as the threshold level to exempt a source

from BART or to deem modeled impacts as insignificant. EPA's Regional Haze Regulations and

Guidelines for Best Available Retrofit Technology (BART) Determinations (Appendix Y to 40

CFR part 51), suggest that 0.5 dv can represent the level at which a source "contributes" to

visibility impairment. This is also consistent with the rules which are being applied by most

states in the 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 that the perceptibility threshold

is greater than 1.0 dv (from page 39120 ofAppendix Y to 40 CFR part 51).
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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% best visibility 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 of the EPA document Guidance for Estimating

Natural Visibility Conditions Under the Regional Haze Rule. The EPA guidance document

provides annual average values of natural 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 multiplied by the guidance table annual concentrations for each

species, the 20% best days concentrations for each species for that particular Class 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 light extinction is expressed as follows:

dv = 10 In (bexJI0) or bext = 10 exp (dv/lO)

where: bext= light extinction 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

set equal to a total extinction value of 12.17 Mm-I

. The relationship between total light extinction

and the individual components ofthe light extinction 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 represent background concentrations in Ilg/m3

• values in parenthesis represent scattering efficiencies

• f(RH) is the relative humidity adjustment factor (applied to hygroscopic species only)

• bray is light extinction 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 needed to convert the annual average natural

background concentrations to values representative of the 20% best days natural background.
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Solving for X provides a value of 0.376. Table 1 presents the annual average natural background

concentrations, the calculated scaling factor, and the calculated background concentrations for the

20% best days natural background for Bridger WA.

Table 1: Calculated Backl!round Components for Bride:er WA

Annual Average 20% Best Days

Natural Natural

Background for Calculated Background for

the West Region Scaling BridgerWA

Component (J12/m3

) Factor (J1e:/m3

)

Ammonium Sulfate 0.12 0.376 0.045

Ammonium Nitrate 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 of the 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 that were used for the two Class 1 areas

in question for this analysis are listed in Table 2 below.

ays aura ac '2roundAerosoI Concentrations (llg/m3)

Fitzpatrick

Aerosol WA&

Component Brid2erWA

Ammonium Sulfate 0.045

Ammonium Nitrate 0.038

Organic Carbon 0.178

Elemental Carbon 0.008

Soil 0.189

Coarse Mass 1.136

Table 2:20% Best D N t I B 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 in their October 17,2008 letter.

Response - Summing the 98th percentile modeled visibility impacts for separate facilities is not

an accurate portrayal of combined 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 are to be determined separately. As stated in the EPA's Appendix Y

to part 40 CFR 51 - Guidelinesfor BARTDeterminations Under the Regional Haze Rule, relative

to the use of the CALPUFF model for BART determinations, "We believe that CALPUFF is an

appropriate application for States to use for the particular purposes ofthis rule, to determine if

an individual source is reasonably anticipated to cause or contribute to impairment ofvisibility

in Class I areas, and to predict the degree of visibility improvement which could reasonably be
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anticipated to result from the use ofretrofit technology at an individual source. We encourage

States to use itfor these purposes."

ill. Analysis of Comments from EPA Region 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 - See response to wac Comment II.1.

IV. Decision:

On the basis of comments received during the public comment period, 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.

Dated this _17th _ day ofJuly, 2009.

o V. Corra

'rector

Wyoming Department ofEnvironmental Quality