# BEST AVAILABLE RETROFIT TECHNOLOGY (BART) ANALYSIS

Columbia Falls Aluminum Company, LLC

Prepared for:



### Columbia Falls Aluminum Company, LLC 2000 Aluminum Drive Columbia Falls, MT 59912

Prepared by:



### Bison Engineering, Inc. 1400 11 th 

### Avenue Helena, MT 59601 (406) 442-5768 www.bison-eng.com

November 5, 2007CFAC BART Analysis 11/5/07 pg. ii Project #: CFA207819 

## TABLE OF CONTENTS

1.0 INTRODUC TION............................................................................................... 1-1 1.1 Summa ry ................................................................................................ 1-1 1.2 Background and Purpose ....................................................................... 1-2 1.3 Site Location and Descriptio n ................................................................. 1-3

2.0 PROCESS D ESCRIPTION ............................................................................... 2-1

3.0 BART ANALYSIS: MODEL AND SOURCE SEL ECTION................................. 3-1 3.1 Initial BART Em ission Da ta..................................................................... 3-1 3.2 Initial EPA/WRAP CFAC BA RT Emissions Summary............................. 3-1 3.3 CFAC BART Emi ssions Summa ry.......................................................... 3-2 3.4 CFAC BART Near Fi eld Model Ad dition ................................................. 3-2 3.5 CFAC BART Model Re sults Compar ison................................................ 3-3 3.6 SO 2 Applicable Units Emissions ............................................................ 3-3 3.7 NO X Applicable Unit s Emissi ons............................................................. 3-4 3.8 PM 10 Applicable Units Emissions ........................................................... 3-5

4.0 BEST AVAILABLE RETROFIT TECHNOLOGY REVIEW................................. 4-1 4.1 Summa ry ................................................................................................ 4-1 4.1.1 Affect ed Units ............................................................................... 4-2 4.1.2 Applicable Pollutant s.................................................................... 4-3 4.2 BART Analysi s Methodol ogy .................................................................. 4-3 4.3 SO 2 and PM 10 BART Analysis for the Potlines (Primary and Secondary Sources) ............................................................................... 4-4 4.3.1 Step 1 – Ident ify All Available SO 2 Retrofit Control Te chnologie s ................................................................... 4-5 4.3.2 Step 2 – Eliminate Technically Infeasible SO 2 Control Options.... 4-8 4.3.3 Step 3 – Evaluate Cont rol Effectiveness of Remaining Control Tec hnologies ................................................................. 4-12 4.3.4 Step 4 – Evaluate Impacts and Document Re sults .................... 4-12 4.3.5 Step 5 – Evaluate Primary Controls Visibilit y Impacts................ 4-16 4.3.6 Step 5 – Evaluate Secondary Co ntrols Visibility Impacts........... 4-16 4.3.7 Select SO 2 BART ....................................................................... 4-16 4.4 BART Analysis for PM 10 from the Potline Roof Vents........................... 4-17 4.4.1 Step 1 – Identify Available Pa rticulate Control Technologies ..... 4-17 4.4.2 Step 2 – Eliminate Technically Infeasible PM 10 Control Options .......................................................................... 4-18 4.4.3 Step 3 – Evaluate Cont rol Effectiveness of Remaining PM 10 Control Techno logies ........................................................ 4-19 4.4.4 Step 4 – Evaluate Impacts and Document Re sults .................... 4-19 4.4.5 Step 5 – Evaluate PM 10 Visibility Impacts .................................. 4-21 4.4.6 Select Secondary Source PM 10 BART ....................................... 4-21 4.5 Select Over all BART ............................................................................ 4-22 4.5.1 Summary of Impacts – Section E, Item 1................................... 4-22CFAC BART Analysis 11/5/07 pg. iii Project #: CFA207819 4.5.2 Selecting a “Best” Alter native – Section E, Item 2...................... 4-31 4.5.3 Consideration of Affordabi lity – Section E, Item 3 ...................... 4-32



## LIST OF TABLES

Table 1-1: Sources Addressed by CFAC BART Analysis ........................................ 1-2 Table 3-1: Initial EPA/WRAP CFAC BART Emissions Summary............................. 3-1 Table 3-2: CFAC BART Modeled Sources and Em issions ...................................... 3-2 Table 3-3: CFAC BART Model Results Com parison ................................................ 3-3 Table 3-4: SO 2 Sources Analyze d for BAR T............................................................ 3-4 Table 3-5: PM 10 Sources Analyz ed for BAR T .......................................................... 3-5 Table 4-1: Sources A nalyzed for BART ................................................................... 4-3 Table 4-2: Summary of SO 2 Control Technology Efficien cy................................... 4-12 Table 4-3: Summary of Primary SO 2 Emissions Cost and Visi bility Impacts.......... 4-15 Table 4-4: Summary of Secondary SO 2 Emissions Cost and Visibility Impacts..... 4-16 Table 4-5: Secondary Emissi ons (Potline Roof Vent) PM 10 Control Technology Effe ctiveness ..................................................................... 4-19 Table 4-6 Summary of Secondary PM 10 Emissions Cost and Visibility Impacts ... 4-21 Table 4-7: Summary of Pot ential BART Sce narios ................................................ 4-24 Table 4-8: Summary of SO 2 /PM 10 Emissions Cost Analysis and Visibility Impacts ................................................................................... 4-26 Table 4-9: Potential BART Co st-Effectiveness Sc enarios...................................... 4-28



## LIST OF TABLES

Figure 4-1: Annualized Cost vs. Decivi ew Improvement by Scenario ..................... 4-27 Figure 4-2: Annualized Cost vs. Deciview Improvement – 3 Scenarios .................. 4-30



## APPENDICES

Appendix A: EPA Letter to CFAC of June 22, 2007 Appendix B: Visibility Impacts Modeling Appendix C: BART Cost AnalysesCFAC BART Analysis 11/5/07 pg. 1-1 Project #: CFA207819 

## 1.0 INTRODUCTION

1.1. Summary

Columbia Falls Aluminum Comp any, LLC (CFAC) is submitting a Best Available Retrofit Technology (BART) analysis to the U.S. Environmental Prot ection Agency Region VIII office (EPA). EPA submitted a letter dated June 22, 2007, to CFAC requiring the preparation of a BART analysis for their al uminum ore reduction plant located near Columbia Falls, Montana. The letter was received by CFAC on June 27, 2007. The letter notified CFAC that EP A had [through Western Regional Air Partnership (WRAP)] completed visibility modeling and determined that CFAC was a BART-eligible source due to the possibility that CFAC could caus e visibility degradation in a nearby Class I area (Glacier National Park). The notific ation requested CFAC to submit a BART analysis within 90 days of the June letter. 1 The letter also noted that if CFAC chooses not to perform an engineering analysis, then EP A will develop the analysis instead. CFAC chose to analyze t he EPA modeling results and pr epare a BART engineering analysis to submit to EPA. A copy of the EPA letter is included here as Appendix A.

CFAC analyzed the existi ng emission units for spec ific BART eligibility 2 , and determined that there are nine sulfur dioxide (SO 2 ) emission sources, three particulate matter (PM 10 ) sources and zero nitrogen oxides (NOx ) emission sources that must be addressed by a BART analysis. Tabl e 1-1 lists those sources.

1 An extension to November 5, 2007, was granted by Laurel Dygowski of EPA in response to CFAC’s August 15, 2007 request for extension.
2 The BART program is only applicable to facilities that (in general) were constr ucted or reconstructed between 1962 and 1977. For CFAC this would only include those units generally associated with Potlines 3, 4 and 5. The remainder of the facility is not subjec t to BART since it fails to meet the definition of an “existing stationary facility” per 40 CFR 51.301. The identification of Potlines 3, 4 and 5 was generally determined through correspondence with the Montana De partment of Environmental Quality (DEQ) prior to the June 19, 2006, letter to EPA from DEQ on the Regional Haze program (see EPA June 22, 2007, letter included here as Appendix A). The selection of these units is also confirmed via EPA’s choice of emitting units for modeling purposes pursuant to their June 22, 2007 letter.CFAC BART Analysis 11/5/07 pg. 1-2 Project #: CFA207819 

### Table 1-1: Sources Addre ssed by CFAC BART Analysis

PTE (Ton/year)

Emission Unit SO 2 PM 10 NO x BART Analysis Performed (Yes or No)

028 – Dry Alumina Scrubber #5 255 Nil 1 Nil 1 Yes
029 – Dry Alumina Scrubber #6 255. Nil 1 Nil 1 Yes

030 – Dry Alumina Scrubber #7 255 Nil 1 Nil 1 Yes

031 – Dry Alumina Scrubber #8 255 Nil 1 Nil 1 Yes

032 – Dry Alumina Scrubber #9 255 Nil 1 Nil 1 Yes

033 – Dry Alumina Scrubber #10 255 Nil 1 Nil 1 Yes

036 – Potline 3 Roof Vents 38.4 72.7 Nil 1 Yes
037 – Potline 4 Roof Vents 38.4 72.7 Nil 1 Yes
038 – Potline 5 Roof Vents 38.4 72.7 Nil 1 Yes 043 – Casting Furnaces #8 and #9 Nil 1 Nil 1 6.7 No 047 – Casting Pits #8 and #9 Nil 1 14.9 Nil 1 Yes

1 Nil means that emissions of this pollutant from this emitting unit are un-quantifiably small and we re not considered further.

CFAC performed an SO 2 BART analysis on Potlines 3, 4 and 5 with their associated dry alumina scrubbers (numbers 5-10) and roof vents. CFAC det ermined that there are no SO 2 controls or process alterations that meet the definition of best available retrofit technology. See Section 4.3 of this report for the SO 2 BART analysis.

CFAC performed a PM 10 BART analysis on the roof vents for Potlines 3, 4 and 5. CFAC determined that there are no PM 10 controls or process alterations that meet the definition of best available retrofit technology. See Se ction 4.4 for the potline PM 10 BART analysis.

CFAC determined that there are no BART-eligib le sources of NOx at their plant. See Section 3.3 of this report for the detailed discussion of NOx BART eligibility.

The remainder of this report details all of the BART steps and analyses performed for the CFAC facility.



### 1.2. Background and Purpose

Congress amended the Federal Cl ean Air Act in 1977 to incl ude a new Section 169A and 169B for the purpose of protecting visibi lity in certain scenic areas. The areas afforded this visibility protection are ident ified as “Mandatory Class I Federal Areas.” 3

3 These areas are identified in 40 CFR 81.401 et seq . Those areas within Montana and Wyoming are found in §417 and §436, respectively.CFAC BART Analysis 11/5/07 pg. 1-3 Project #: CFA207819 The rules EPA promulgated to implement these sections of the Act are generally found in 40 CFR 51, Subpart P.

Specific to this doc ument, EPA promulgated 40 CFR 51.308(e) which requires certain types of existing stationary sources to instal l best available retrof it technology (BART). The term BART is defined in §301 as follows:

Best Available Retrofit Technology (BART) means an em ission limitation based on the degree of reduction achievable through the applicati on of the best system of continuous emission reduction for each pollutant which is emitted by an existing stationary plant. The emission limitation must be established, on a case-by-case basis, taking into consideration the technology av ailable, the costs of compli ance, the energy and non-air quality environmental impacts of compliance, any pollution co ntrol equipment in use or in existence at the source, the remaining useful life of the source, and the degree of improvement in visibility which may reasonabl y be anticipated to result from the use of such technology

. As noted in Section 1.1 above, EPA has ident ified the CFAC aluminum ore reduction plant as an ‘existing stationary facility’ 4 that is subject to the BART requirements. EPA has further identifi ed guidelines for ident ifying BART-eligible sources and suggested methodologies to be employed for conducting a BART analysis. Th ese guidelines are codified in 40 CFR 51, Appendix Y.

It is the purpose of this document to fulf ill the requirements for conducting a BART analysis for the CFAC plant. The remainder of this document conducts a BART analysis for each unit and pollutant subject to the regulation [40 CFR 51.308(3)]. The methodologies and guidelines found in 40 CF R 51, Appendix Y were used to develop this BART document.



### 1.3. Site Location and Description

The CFAC plant is located in Columbia Falls in Section 3, Townsh ip 30 North, Range 20 West, Flathead County, Mont ana, with approximate UTM coordinates of Zone 11, Easting 712.2 km, and No rthing 5,363.8 km. The elevati on is approximately 3,108 feet above sea level. Maps of the CFAC plant are on file with the Montana Department of Environmental Quality (MDEQ). Site descripti on information is also on file with MDEQ. Copies of the maps and descripti ons are available upon request.

4 As defined in 40 CFR 51.301.CFAC BART Analysis 11/5/07 pg. 2-1 Project #: CFA207819 

## 2.0 PROCESS DESCRIPTION

CFAC operates five Vertical Stud Soderberg potlines at the Columbia Falls plant. Each potline has 120 individual cells that produce aluminum by the Hall- Heroult process.

The Hall-Heroult process consists of passing an electric current through aluminum oxide ore, or alumina (Al 2 O 3 ), dissolved in molten cryolite. The reduction process is accomplished in a Vertical Stud Soderberg style pot. Soderberg technology describes the type of consumable carbon anode used in the process. CFAC Soderberg pots (cells) have 60-ton anodes (positive el ectrode) and 100-ton cathodes (negative electrode). The electrolytic reduction of alum inum oxide is repres ented by the following reactions:

Al 2 O 3 + 11⁄2C → 2Al + 1 1⁄2 CO 2 ↑
2Al 2 O 3 + 6C → 4Al + 6CO ↑

The cells or “pots” are housed in buildings call ed potrooms. Tw o potrooms are connected electrically in series to form one pot line. At CFAC there are ten potrooms that comprise the five potlines. Al umina is fed into a molten ba th of cryolite and heated to about 1740°F (949°C). Through the electrochemical process, electricity passes from the anode to the cathode, causing the aluminum to be reduced. The aluminum metal is siphoned from the pot every 48 hours and transported to t he casting department, where it is cast into ingots of various sizes, s hapes and alloys. Each pot is tapped every other day, which results in a pot operational cycle of 48 hours.CFAC BART Analysis 11/5/07 pg. 3-1 Project #: CFA207819 

## 3.0 BART ANALYSIS: MODEL AND SOURCE SELECTION

3.1 Initial BART Emission Data

In a series of letters, MDEQ requested that CFAC submit a list of the BART-eligible sources at the plant and s upply sulfur dioxide (SO 2 ), nitrogen oxides (NO x ), and particulate matter less than 10 microns (PM 10 ) emission data for the BART-eligible sources. CFAC concluded 18 emitting units (as provided in the Title V permit) from the plant qualify as BART-eligible . The emission data requested was for annual potential to emit (PTE) and the highest 24 -hour emission rates occurring during the three year period of 2001, 2002, and 2003. The plant wa s not operating at 100% capacity during this time period, therefore; the highest 24-hour emission rates occurring during 1999, when the plant was in operating at 100% were supplied to DEQ, EPA, and WRAP for this analysis.



### 3.2 Initial EPA/WRAP CFAC BART Emissions Summary

For purposes of BART applicability determi nation only, EPA had WRAP perform the modeling (via the University of California Riverside) for the initial BART applicability determination. The WRAP model included 14 of the 18 identif ied BART eligible emitting units in the initial BART applicability determination. Table 3-1 summarizes the 14 sources of SO 2 and NO X and PM 10 emissions that were included in the EPA/WRAP BART applicability determination.



### Table 3-1: Initial EPA/WRAP BART Modeled Sources and Emissions

Modeled Emissions (lbs/hr) Modeled Emitting Units SO 2 PM 10 NOx

004 - East Alumina Elevator 0.00 0.08 0.00

005 - East Alumina Unloader 0.00 0.08 0.00 006 - East Alumina Conveyor Storage 0.00 0.08 0.00 019 - Therminol Oil Heating System 0.00 0.00 0.00

020 - East Plant Alumina Transfer 0.00 0.05 0.00

021 - East Plant Alumina Transfer 0.00 0.05 0.00 028 – Dry Alumina Scrubber #5 58.22 0.09 0.00 029 – Dry Alumina Scrubber #6 58.22 0.09 0.00 030 – Dry Alumina Scrubber #7 58.22 0.09 0.00 031 – Dry Alumina Scrubber #8 58.22 0.09 0.00 032 – Dry Alumina Scrubber #9 58.22 0.09 0.00 033 – Dry Alumina Scrubber #10 58.22 0.09 0.00 043 - Casting Furnace #8 & 9 0.01 1.08 1.52 047 - Casting Pits #8 & 9 0.00 3.39 0.00
Note: To convert lbs/hr to tons/yr, multiply by 4.38. Ex ample: 58.22 lbs/hr x 8760 hrs/yr / 2000 lbs/ton = 255 tons/yrCFAC BART Analysis 11/5/07 pg. 3-2 Project #: CFA207819 

### 3.3 CFAC BART Emissions Summary

CFAC, with the assistance of Bison Engineer ing, reviewed the initial EPA/WRAP BART applicability determination. The WRAP model included six potline point sources (dry alumina scrubber stacks) as six volume s ources, and did not incl ude the potline roof vents at all. As a result of this review, 17 of the 18 initial BART eligible sources were included in all subsequent m odeling analyses. Emitting Un it EU049 (Sheet ingot saw) was not included in any model ing analysis because there ar e no emissions associated with it. The additional three s ources included in the CFAC models are the potline roof vents. The 17 sources SO 2 , NO X , and PM 10 emissions that were included in the regional scale and near field modeling analyses performed by CFAC are listed in Table 3-2.



### Table 3-2: CFAC BART Modeled Sources and Emissions

Modeled Emissions (lbs/hr) Modeled Emitting Units SO 2 PM 10 NOx

004 - East Alumina Elevator 0.00 0.08 0.00

005 - East Alumina Unloader 0.00 0.08 0.00 006 - East Alumina Conveyor Storage 0.00 0.08 0.00 019 - Therminol Oil Heating System 0.00 0.00 0.00

020 - East Plant Alumina Transfer 0.00 0.05 0.00

021 - East Plant Alumina Transfer 0.00 0.05 0.00 028 – Dry Alumina Scrubber #5 58.22 0.09 0.00 029 – Dry Alumina Scrubber #6 58.22 0.09 0.00 030 – Dry Alumina Scrubber #7 58.22 0.09 0.00 031 – Dry Alumina Scrubber #8 58.22 0.09 0.00 032 – Dry Alumina Scrubber #9 58.22 0.09 0.00 033 – Dry Alumina Scrubber #10 58.22 0.09 0.00

036 - Potline #3 Roof Vents 8.76 16.60 0.00

037 - Potline #4 Roof Vents 8.76 16.60 0.00

038 - Potline #5 Roof Vents 8.76 16.60 0.00 043 - Casting Furnace #8 & 9 0.01 1.08 1.52 047 - Casting Pits #8 & 9 0.00 3.39 0.00
049 - Sheet Ingot Saw (Not Modeled) 0.00 0.00 0.00
Note: To convert lbs/hr to tons/yr, multiply by 4.38. Ex ample: 58.22 lbs/hr x 8760 hrs/yr / 2000 lbs/ton = 255 tons/yr



### 3.4 CFAC BART Near Fi eld Model Addition

A near field model was develop ed to address the potential CFAC visibility impacts on the nearby receptors located in Glacie r National Park (GNP). The WRAP BART applicability determination recognized the di fference of modeled impacts for the long range receptors (>50km) and the near field receptors (<50km) by listing CFAC’s potential visibility impacts in GNP for both receptors at gr eater than 50 km and less thanCFAC BART Analysis 11/5/07 pg. 3-3 Project #: CFA207819 50 km from the plant. The complex terrain in the area surrounding CFAC is better represented by a refined model analysis. The near field modeling domain reduces the CALMET grid spacing from 6 km to 1 km and significant ly improves the terrain resolution over the regional scale modeling domain. Given the short distance (<10 km) between CFAC and the nearest National Park Service generated receptors for Glacier National Park, the development of this refined CALPUFF modeling analysis is appropriate for this BART analysis.



### 3.5 CFAC BART Model Results Comparison

The two different source emission summari es detailed in Tables 3-1 and 3-2 above were used in the modeling analysis for the CFAC BART applicability determination. The EPA applicability det ermination used an incomplete em ission inventory to perform the regional scale CALPU FF modeling analysis to conc lude BART is applicable to CFAC. The complete emission inventory in Table 3-2 was used in both the regional scale CALPUFF model analysis to com pare to the EPA/WR AP applicability determination; and the near field modeling analys is for Glacier National Park and the subsequent cost/benefit analysis. Please s ee Appendix B for a complete modeling discussion.

A comparison of the 98 th percentile visibility impacts for the three different CALPUFF models is presented in Table 3-3 below.



### Table 3-3: CFAC BART Model Results Comparison

Modeled Visibility Impacts (98 th percentile)

Modeled Emitting Units 2001 (Deciview change) 2002 (Deciview change) 2003 (Deciview change) 3 year Average (Deciview change)
EPA/WRAP Regional Sc ale Visibility 3.13 4.54 3.40 3.69 CFAC/Bison Regional Scale Visibility 4.56 6.29 4.89 5.25 CFAC/Bison Near Field Visibility 4.43 2.94 4.28 3.88

This table shows that the visi bility impacts were greater in the CFAC regional model when the additional 3 potline r oof vent emission units were added to the sources from the EPA/WRAP model. The table also shows t hat the CFAC near field model, with the same emission sources as the CFAC regional model, shows substantially lower visibility impacts than the CFAC regiona l model. CFAC believes the near field model is a more refined and representative model for predict ing close (<10 km) visibility impacts than either the EPA/WRAP or CFAC regional model.



### 3.6 SO 2 

### Applicable Units Emissions

Potlines 3, 4, and 5 each consist of two potrooms. Each potr oom is equipped with an emission collection system to route pot emissions to a bank of six dry aluminaCFAC BART Analysis 11/5/07 pg. 3-4 Project #: CFA207819 scrubbers intended to capture fluoride, hydr ocarbon and particulate emissions. The emissions from these scrubber s are considered primary em issions by CFAC. These scrubbers are assumed to be i neffective for controlling SO 2 emissions. The emission unit numbers for each alumina scrubber are EU028 through EU033. By calculation, the scrubbers each emit 255 tons of SO 2 per year and are analyzed in this BART analysis. Furthermore, Potlines 3 through 5 each also have dual roof vents, EU036, EU037, and EU038, respectively, that by calcul ation, each emit 38.4 tons of SO 2 per year. The emissions from the potline roof vents are considered secondary emissions by CFAC. The roof vents will also be analyzed in this BART analysis.

Table 3-4 provides a summary of the nine SO 2 -emitting units subject to further BART analysis. The table also shows the current emissions control associated with those units.



### Table 3-4: SO 2 

### Sources Analyzed for BART

Source Current SO 2 Source Control Current SO 2 Emissions (tpy) 028 - Dry Alumina Scrubber #5 None 255.0 029 - Dry Alumina Scrubber #6 None 255.0 030 - Dry Alumina Scrubber #7 None 255.0 031 - Dry Alumina Scrubber #8 None 255.0 032 - Dry Alumina Scrubber #9 None 255.0 033 - Dry Alumina Scrubber #10 None 255.0 036 – Potline 3 Roof Vents (Secondary) None 38.4 037 – Potline 4 Roof Vents (Secondary) None 38.4 038 – Potline 5 Roof Vents (Secondary) None 38.4



### 3.7 NO
x 

### Applicable Units Emissions

The CFAC plant emits a total of 6.7 tons of NOx per year from natural gas combustion that primarily occurs in casting fu rnaces. Under 40 CFR 51, Appendix Y, EPA established a de minimis level for emission units and pollutants that constitute BART eligibility. Appen dix Y explains de minimislevels of emission for pollutants at BARTeligible sources:

“.........De Minimis values should be identified with the purpose of exluding only those emissions so mi nimal that they are unlikely to contribute to regional haze. Any de mi nimis values that you adopt must not be higher than the PSD applic ability levels: 40 tons/yr for SO 2 and NOx and 15 tons/yr for PM 10 . These de minimis levels may only be applied on a plant-wide basis.”

CFAC’s plant-wide NO x emissions of 6.7 tons per year are well below the PSD applicability level of 40 tons per year ; therefore, they are categorized as de minimis and are not analyzed further.CFAC BART Analysis 11/5/07 pg. 3-5 Project #: CFA207819 

### 3.8 PM 10 

### Applicable Units Emissions

Potlines 3, 4, and 5 each consist of two potrooms. Each potr oom is equipped with an emission collection system to route pot emissions to a bank of six dry alumina scrubbers intended to capture fluoride, hydr ocarbon and particulate emissions. These scrubbers incorporate high efficiency bag houses as part of the design and are considered 99%+ effect ive at capturing PM 10 emissions. The em ission unit numbers for each alumina scrubber are EU 028 through EU033. These are considered primary sources by CFAC.

Although the six dry alumina scrubbers are eligible for BART analysis, CFAC believes that the current PM 10 control is already the best po ssible at 99+% control and further improvement could not be practically accomplished. The current PM 10 emission rates are so low that visibility impacts from these sources are negligible, and further reductions could not improve upon t hat. Therefore, the primary PM 10 emission sources from the potlines have not been analyzed for BART.

Potlines 3, 4, and 5 each hav e dual roof vents. The emi ssion unit numbers for the roof vents are EU036, EU037, and EU 038. As shown in Table 3-2, each roof vent emits 72.7 tons/year of PM 10 ; therefore, the roof vents warrant further analysis for BART.

EU47, Casting Pits #8 and #9, have an estimated PM 10 emission rate of 14.9 tons per year. This is a relatively small source , and through the modeling performed, it was determined that this source, even with 100% PM 10 control efficiency, had a negligible impact on visibility. Therefore any control implemented on the source could not produce a significant visibility improvement. Theref ore, EU47 was not analyzed further in this BART analysis.

Table 3-5 provides a summary of the three emitting units eligib le for further BART analysis. The table also shows the current emissions control associated with those units.



### Table 3-5: PM 10 

### Sources Analyzed for BART

Source Current Source Control Current PM 10 Emissions (tpy) 036 – Potline 3 Roof Vents (Secondary) None 72.7 037 – Potline 4 Roof Vents (Secondary) None 72.7 038 – Potline 5 Roof Vents (Secondary) None 72.7CFAC BART Analysis 11/5/07 pg. 4-1 Project #: CFA207819 

## 4.0 BEST AVAILABLE RETROFIT TECHNOLOGY REVIEW

The Clean Air Act (CAA), in section 169(a)(2), requires that State Implementation Plans (SIPs) for visibility protection must apply BART to certain large emitting sources. BART is required for s ources that meet all of the following criteria:

1. The source is in one of 26 s pecific listed source categories; 5

2. The source was in existence as of August 1977, but was not in operation in August of 1962; 6

3. The facility has the potent ial to emit 250 tons per year of any visibility-impairing pollutant; and

4. The BART-eligible source emits an air pollutant that “may reasonably be anticipated to cause or contribute to any impairment of visibilit y in any mandatory Class I federal area, . . .” 7

Appendix Y further explains how to identify sources subject to BART:

“Once you have determined that your s ource or sources are subject to BART, you must conduct a visibility improvement determination for the source(s) as part of the BART determination. When making this determination, we believe you have flexibility in setting absolute thresholds, target levels of improvement, or de minimis levels since the deciview improvement must be weighed among the five factors, and you are free to determine the weight and significance to be assigned to each factor.”



### 4.1 Summary

The CAA, section 169(a)(2) requ ires that SIPs for visibility protection must apply BART to certain large emitting sources. EPA iden tified CFAC as a possible BART-eligible source because it is a Primary Aluminum Ore Reduction Plant, which is one of the 26 BART source categories under 40 CFR Part 51.301 under the definition of “Existing stationary source.” The CFAC plant has emitting units t hat meet the time frames specified in item 2 above. In addition, the entire complex has a potential to emit greater than 250 tons per year.

EPA has completed initial visibility modelin g through the WRAP program. As a result of those investigations, EPA has determined that CFAC is subject to a BART analysis in

5 The 26 source categories are found in the definition of “Existin g stationary facility” found in 40 CFR 51.301.
6 The terms “in existence” and “in operation” are defined in 40 CFR 51.301.

7 40 CFR 51.308(e).CFAC BART Analysis 11/5/07 pg. 4-2 Project #: CFA207819 accordance with the BART prov isions of 40 CFR 51.308. The EPA documentation of this requirement and conclusion is found in a letter from EPA Region VIII dated June 22, 2007, addressed to Mr. Steve Wright of CFAC. A copy of that letter and conclusion is found in Appendix A of this document.

In accordance with the June 22, 2007, le tter, CFAC has conducted a BART analysis using EPA-recommended methodologies and dispersion modeling recommendations found in 40 CFR 51, A ppendix Y, more specif ically the CALPUFF dispersion model, to assist with the proposed BART determination. The purpose of the modeling analysis is to determine the visibility improvement ex pected at Class I areas from the potential BART control technology applied to the source . The modeling analysis is found in Appendix B of this document.

4.1.1 Affected Units

There are a total of 18 emitting units at the CFAC plant that have been identified as potentially “BART–eligible.” These units have received that designation since they meet the definition of BART-eligible since they were “in existence” 8 as of August 1977, but not “in operation” 9 in August of 1962 and havin g (collectively) the potential to emit 250 tons per year of an air pollutant that could cause visibility degradation in a Class I area (applicable pollutants are listed in Section 4.1.2 below). S ee Table 3-1 for a list of the 18 potential BART-eligible emitting units.

Nine of the potential BART-eligible source s have the potential to cause visibility impairment, and a detailed BART engineeri ng analysis has been performed on these sources. These sources are potlines 3, 4 and 5 with their asso ciated dry alumina scrubbers and roof vents. The other nine units have very low emission rates and were not analyzed for BART by CFAC. Table 4-1 lis ts the emissions units analyzed for BART by CFAC.

8 As defined by 40 CFR 51.301
9 Ibid.CFAC BART Analysis 11/5/07 pg. 4-3 Project #: CFA207819 

### Table 4-1: Sources Analyzed for BART

Emission Rates (lbs/hr) Detailed BART Analysis Performed? Modeled Emitting Units SO 2 PM 10 NOx SO 2 PM 10 NOx

028 - Dry Alumina Scrubber #5 58.22 0.09 0.00 Yes No No 029 - Dry Alumina Scrubber #6 58.22 0.09 0.00 Yes No No 030 - Dry Alumina Scrubber #7 58.22 0.09 0.00 Yes No No 031 - Dry Alumina Scrubber #8 58.22 0.09 0.00 Yes No No 032 - Dry Alumina Scrubber #9 58.22 0.09 0.00 Yes No No 033 - Dry Alumina Scrubber #10 58.22 0.09 0.00 Yes No No

036 - Potline 3 Roof Vents 8.76 16.60 0.00 Yes Yes No

037 - Potline 4 Roof Vents 8.76 16.60 0.00 Yes Yes No

038 - Potline 5 Roof Vents 8.76 16.60 0.00 Yes Yes No

4.1.2 Applicable Pollutants

The visibility-impairing pollutants anal yzed in this BART analysis are:

y Sulfur dioxide (SO 2 ), and

y Particulate matter less than 10 microns (PM 10 ).

PM 10 is used as an indicator for particu late matter. As emissions of PM 10 include the components of PM 2.5 as a subset, there is no need to have separate 250-ton thresholds for PM 10 and PM 2.5

. 

### 4.2 BART Analysis Methodology

In general terms, EPA has identified a metho dology for conducting a BART analysis that is similar to the Best Available Contro l Technology analyses conducted under the PSD permitting program (40 CFR 51.166 and elsew here). For BART, the methodology is more refined to include pollutants related to visibility impairment and to include an analysis of the impacts the proposed technol ogy has on the visibility directly.

The BART methodology is a case-by-case procedure. The BART methodology chosen for this analysis follows the guidelines est ablished by EPA in 40 CFR 51, Appendix Y. Hereafter these guidelines will be referred to as either the “App endix Y Guideline” or simply “Appendix Y.” Appendix Y suggests that the case-b y-case BART analysis should follow the five steps below (S ection IV.D of Appendix Y).CFAC BART Analysis 11/5/07 pg. 4-4 Project #: CFA207819 Case-by-Case Five Step BART Analysis:

Step 1 - Identify all 10 available retrofit control technologies; Step 2 - Eliminate techni cally infeasible options; Step 3 - Evaluate control effectiveness of remaining control technologies; Step 4 - Evaluate impacts and document the results; and Step 5 - Evaluate visibility impacts.

The following paragraphs will evaluate BART for each source or source group emitting any of the pollutants noted above as being re leased in significan t quantities. BART for SO 2 and PM 10 emissions from the potlines, ess entially the only source of these compounds, will be addressed fi rst. As stated in Section 3.3, no BART analysis will be performed for the plant- wide NOx emissions because they are below the de minimis threshold and are unlikely to contribute to regional haze.

As suggested by Ap pendix Y, CFAC reviewed the Ne w Source Performance Standards (NSPS) Subpart S for primary al uminum reduction plants to determine if any control technologies or emission restrictions were applicable to new facilities. This review showed that NSPS for primary aluminum r eduction plants applies only to fluoride emissions and opacity.

To facilitate the following BART determi nations, CFAC queried the EPA RACT-BACTLAER Clearinghouse (RBLC) database for listi ngs of pollutant em ission limits and required control technologies at other alum inum production facilities across the country. The information generated by these queries serv es as a helpful guideline to indicate expected emission rate ranges and cont rol technologies that may have been successfully applied at facilities similar to the CFAC plant.



### 4.3 SO 2 

### and PM 10 

### BART Analysis for the Pot lines (Primary and Secondary Sources)

For the purposes of this BART anal ysis, CFAC has chosen to analyze SO 2 and PM 10 simultaneously. Although the primary and secondary sources ca n have independent controls, they are all part of the same sour ce (the potlines), and most of the control options intertwine SO 2 and PM 10 control. Therefore, any vi sibility improvements have been modeled using both the SO 2 and PM 10 reductions achieved by the same control system.

SO 2 emissions in the CFAC el ectrolytic reduction plant are generated by oxidation of sulfur-bearing coke and pitch used in the manufacture of aluminum. The contract specifications for sulfur c ontent (% by wt) of the anode ra w materials are shown below:

10 Appendix Y notes that the term “all” refers to iden tifying the most stringent option and a reasonable set of options for analysis that reflect a comprehensiv e list of options. It is not necessary (according to Appendix Y) to list all permutations of avail able control levels for a given technology.CFAC BART Analysis 11/5/07 pg. 4-5 Project #: CFA207819 Material Analysis (1999) % by Wt Coke 1.5% Pitch 0.7%

Sacrificial anode carbon is consumed at an overall rate of about 0.54 – 0.58 pounds of carbon per pound of aluminum. This consum ption of sulfur-bearing carbon anodes accounts almost all of the SO 2 released in the process.

It is assumed that 100% of the sulfur present in the raw anode materials is converted to SO 2 . CFAC estimates that 93% of the primar y pot exhaust gas, which contains the SO 2 , is collected by exhaust hoods and ducted to the dry alumina scrubbers. Secondary pot gases, the 7% of pot exhaust gases not co llected by the exhaust hoods, are mixed with ambient potroom air and disc harged through the roof vents. This secondary emission source has a very large volume with a very low concentration of SO 2

.

4.3.1 Identify All Available SO 2 Retrofit Control T echnologies – Step 1

In accordance with Step 1 described in Section 4.2 above, CFAC has sought to identify all “available” retrofit technologies. To that end, EPA’s RBLC describes several permitted aluminum plants and lists their pollutant emission lim its and the control technologies approved to achiev e those limits. Another sour ce of information regarding potentially applicable SO 2 control technology for aluminum manufacturing is EPA’s AP42 for Primary Aluminum Produc tion (Chapter 12, Section 1). Finally, CFAC has used an independent engineeri ng company with considerable aluminum plant experience to identify and judge applicability of potential control strat egies. The following were identified as potentially app licable for controlling SO 2 from the potlines at CFAC:

(i) Proper design and operation (baseline); (ii) Process alterations; (iii) Dry sorption/spray dry processes; (iv) Single alkali process wet SO 2 scrubber; (v) Dual alkali Na/Ca process wet SO 2 scrubber; (vi) Roof vent spray chamber SO 2 controls.

Process note pertaining to all candidate primary SO 2 removal processes : The most prevalent FGD proc esses involve removing SO 2 from combustion exhaust streams such as those typi cally found in large coal-fir ed generation stations burning high sulfur (1-3%) coal. SO 2 removal processes in t hese installations have two characteristics quite different from thos e in the primary and secondary gases from electrolytic aluminum reduction plants:

• Higher concentrations of SO 2 (3000 ppm vs 300 ppm)

• Higher temperature reaction environments (up to 2500oF vs 250oF max)CFAC BART Analysis 11/5/07 pg. 4-6 Project #: CFA207819 Based on sulfur mass balance and volume/m ass discharge rates for primary and secondary emission sources, CFAC estima tes the following emission source gas conditions:

Typical SO 2 Emissions from Dry Alumina Scrubbers and Roof Monitors

Emission Source Volume (ACFM) SO 2 Concentration (ppmv) Temperature (deg. F) Primary Gas Emission Sources Potline 3 66,000 260 230 Potline 4 66,000 260 230 Potline 5 66,000 260 230 Secondary Gas Emission Sources Potline 3 6,080,000 <1.0 70 Potline 4 6,080,000 <1.0 70 Potline 5 6,080,000 <1.0 70

As shown, expected SO 2 concentrations in aluminum process flue gases (especially in the secondary gases) are much lower than t hose for standard fossil fuel flue gas.

Control Technology Description:

(i) Proper Design and Operation The CFAC facility has been in operation si nce the 1950s and has followed the advancements in aluminum reduction technol ogy. CFAC believes the current operation has efficiencies and operationa l procedures that are similar to other plants in the US. CFAC believes the facility has pr oper design and operat ion procedures.

(ii) Process Alterations – Reducin g Primary and Secondary Emissions

1. Improved Reduction Process (Anode) Efficiencies The aluminum oxide reduction proce ss consumes anode carbon to form CO 2 along with some CO. Any CO produced represents sub-optimal oxidation of carbon which corresponds to increased carbon consumption; therefore, SO 2 emissions. A process modification which increased the CO 2 /CO ratio would have the effect of reducing SO 2 emissions.

2. Improved Pot Line Fume Collection Efficiency CFAC estimates overall fume collection efficiency at 93%. Therefore, 93% of the SO 2 emissions are currently ducte d to the dry alumina scrubber. This serves as a collection method of SO 2 , which could be routed to an effective SO 2 scrubber. Since 7% of the SO 2 escapes collection and is vented through the roof vents, the total potential for SO 2 emission reduction to be achieved by 100% colle ction is 7% of the 1645 tpy of SO 2CFAC BART Analysis 11/5/07 pg. 4-7 Project #: CFA207819 generated, or approximat ely 115 tons. This assumes 100% SO 2 scrubbing efficiency.

3. Coke and Pitch Sulfur Content Reduction One method to reduce sulfur dioxide emissions is to use an anode petroleum coke and pitch with lower perce nt sulfur than is currently used. By reducing the amount of sulfur in the coke and pitch used in the process, the generation of SO 2 is reduced proportionally.

(iii) Dry Sorption/Spray Dry Proce ss Applied to the Primary Sources The term Spray Dryer Absorber (SDA) here refe rs to those technologies that inject a dry, semi-dry or semi-wet al kaline solution/suspension either directly into the boiler furnace combustion stream or into hot flue gas streams prior to baghouse filters and/or electrostatic precipitators (ESP) to control SO 2 emissions. An SDA could be applied to the gas stream currently duct ed to the dry alumina scrubbers.

The resulting reactants (along with proce ss particulates and spent reagent) are removed as dry solids. The simplicity of this process makes it attractive in boiler/furnace retrofit applications bec ause, in most applications, baghouse/ESP collection/disposal mechanisms are already in place. SO 2 removal efficiencies are generally limited to ~70%. Optimum SO 2 reductions using limestone require significant excess reactants (75%) and very finely ground r eagents. The flue stream is cooled by evaporation of the inje cted slurry and the SO 2 removal reaction takes place on the surface of the finely divided solid alkali at temperatures between 350oF and 1000oF.

(iv) Single Alkali Wet SO 2 Scrubber Applied to the Primary Sources A wet SO 2 scrubber is one that uses an aqueous chemical system. These systems have been successfully employed in various industries to remove SO 2 from concentrated exhaust streams. These system s use aqueous solutions or slurries as the contact and reaction media. A typical installation uses spray tower scrubbers to introduce a reagent slurry as atomized droplets through the spray nozzles at the top of, or in stages within, the scrubber. The SO 2 -laden gas enters at the botto m of the column and travels upward through the tower in a countercurrent flow, although horizontal spray towers which use a crosscurrent design also exist. In most cases the sorbent is an alkaline slurry, commonly limestone, slaked lime, caus tic soda/soda ash or a mixture of slaked lime and alkaline fly ash, alt hough many other sorbent processes exist. Absorption of SO 2 is accomplished by the contact betwe en the gas and the reagent slurry. The sulfur oxides react with the sorbent, forming a wet mi xture of alkali (sodium or calcium) sulfite and sulfate.

The slurry combines with the SO 2 -laden waste gas to form a waste slurry in the bottom of the scrubber. The sludge is removed from the scrubber and, depending upon the reagent or sorbent used to react with the SO 2 , the waste reacted sludge is disposed of, recycled or regenerated, or, in some ca ses, sold as a salable product.CFAC BART Analysis 11/5/07 pg. 4-8 Project #: CFA207819 The highest efficiencies are obtained with sodium-based processes; however, in a single pass sodium-based pr ocess, feed stock reagent s are not regenerated or recovered and reaction by-products (sodium su lfates) are typically of little commercial value and must ultimately be treated as c ontrolled landfill material. This process achieves good efficiencies at temperatures between 200-1000oF, particularly with caustic soda.

(v) Dual Alkali Wet SO 2 Scrubber Applied to the Primary Sources The Dual Alkali process has not been as widel y accepted in boiler/fu rnace applications as the limestone/lime slurry pr ocesses, but has the process advantage of separating the SO 2 absorption and sulfite/sulfat e precipitation operations. Dual Alkali systems utilize higher efficiency (albeit higher cost) sodium reactants in the first (absorber) stage and lower cost (calcium) reactants in the second (precipitation) stage. The relatively more expensive sodium reactants are regenerated during the precip itation stage and are recirculated to the primary scr ubbers. More process steps are required, but removal efficiencies over 90% can be obtained with s odium based reagents even at lower flue gas temperatures (200-300oF).

(vi) Roof Vent SO 2 Controls Applied to the Secondary Sources CFAC has investigated the us e of spray chamber type roof vent controls. This system consists of roof-mounted water spray chamber s (no other reactant s used) to capture and remove SO 2 and PM 10 from the roof vent exhaust stream. Parallel systems of multiple modules can be employed. The hi gh volume secondary exhaust streams are captured by dormer outlets in the roof, and inducted by low pressure, high volume fans through large chambers fitted wit h multiple spray bars. SO 2 is readily absorbed in the airborne liquid droplets and particulate is ca ptured by impingement. Efficiencies of 50% for both SO 2 and particulate have been reported.

4.3.2 Eliminate Technically Infeasible SO 2 Control Options – Step 2

This section discusses the feasibility or in feasibility of each technology identified in Section 4.3.1 above. The decision regardi ng whether a particular technology was deemed “technically feasible” was based on discussions found in 40 CFR 51, Appendix Y. Appendix Y describes guidelines for BA RT determinations under the regional haze rule.

The issue of feasibility is found in Section IV.2.STEP 2 of the Appendix Y Guideline. The Guideline states that control technolog ies are technically feasible if either:

“(1) they have been installed and operated successfully for the type of source under review under similar conditions, or

(2) the technology could be applied to the source under review.”

The Appendix Y Guideline goes on to descri be these circumstances further and discuss the meaning of “available” and “applicability” within the meaning of BART. As a general rule, “available” means that the owner of the facility may obtain the technology throughCFAC BART Analysis 11/5/07 pg. 4-9 Project #: CFA207819 commercial channels. In the alte rnative, the technology is “available” within the common sense meaning of that term.

Commercially available is further discuss ed in the Appendix Y Guideline as having attained either stage (5) or (6) of the followi ng stages of bringing a control technology to reality as a commercial product:

(1) Concept stage; (2) Research and patenting; (3) Bench scale or laboratory testing; (4) Pilot scale testing; (5) Licensing and commercial demonstration; and (6) Commercial sales. Also of note in the Appendix Y Guid eline is the following statement:

Similarly, we do not expect a source owner to conduct extended trials to learn how to apply a technology on a totally new and dissimilar source type. Consequently, you would not consider technologies in the pilot scale testing stages of development as “available” for purposes of BART review.

The reader is referred to further discussion in the Appendix Y Guideline on this matter.

Using the Appendix Y Gu ideline, infeasible technologie s are rejected where appropriate. Those technologies deemed inf easible are no longer discussed in further sections of this BART analysis.

(i) Proper Design and Operation Proper design and operation is clearly feas ible and serves as the baseline case.

Conclusion: Proper design and operation is considered feasible for purposes of Step 2 in this BART analysis.

(ii) Process Alterations

1. Improved Reduction Process (Anode) Efficiencies Engineering refinements over the la st 50 years have reduced the carbon consumption from approxim ately 0.7 lb of carbon per pound of Al in the 1950s to present levels of approximat ely 0.54 to 0.58 lb of carbon per pound of Al. The stoichiometric lower limit to the carbon consumption is approximately 0.33 lb of carbon per pound of Al, which implies that, at best, a 40% reduction is possible. Si gnificant process improvements over the current efficiency, while highly desir able, are very difficult to achieve and must be categorized as technicall y experimental at this point.CFAC BART Analysis 11/5/07 pg. 4-10 Project #: CFA207819 Conclusion: This process alteration is considered technically infeasible for purposes of Step 2 in this BART anal ysis. No further di scussion of this technology will be presented.

2. Improved Pot Line Fume Collection Efficiency The current overall efficiency of the fume collection syst em at CFAC is estimated at 93%. CFAC believes that the design of the current exhaust hoods is typical of the industry in t he US. CFAC is not aware of exhaust hoods with newer design or better capture efficiencies for vertical stud soderberg aluminum reduction facilit ies. CFAC believes that added exhaust hood capture efficiency woul d be experimental in nature and could only come at the expense of access to the pots for normal operations and interference wit h the existing process.

Conclusion: This technology is considered technically infeasible for purposes of Step 2 in this BART analysis. No further discussion of this technology will be presented.

3. Coke Sulfur Content Reduction In the aluminum smelting industry, mo st smelters use a petroleum coke with approximately 2.5% su lfur content. CFAC believes this is the norm worldwide. CFAC has used 1.5% sulfur coke for many years to keep sulfur dioxide emissions as low as po ssible. CFAC has a contractual coke percent sulfur limit of 1.5% with its supplier. To CFAC’s knowledge, the 1.5% sulfur coke used by CFAC is t he lowest sulfur content coke available from United States sources. There may be petroleum cokes offered from overseas sources that have lower sulfur content.

CFAC’s 1.5% sulfur petroleum coke, al though low in sulfur, is not the best petroleum coke for aluminum produc tion. To improve anode operation, which would reduce anode carbon us e and the resulting carbon monoxide and carbon dioxide emissions, CFAC would need to switch to a higher sulfur coke.

CFAC uses a pitch with a sulfur cont ent of 0.7%. CFAC is not aware of any pitch available with a lower sulfur content.

Conclusion: Using a coke with a lower sulf ur content is considered feasible for purposes of Step 2 in this BART anal ysis. Using a pitch with a lower sulfur content is not considered feas ible for purposes of Step 2 in this BART analysis. All further discussion of this technology will refer to reduced coke sulfur content only.

(iii) Dry Sorption/Spray Dry Proce ss Applied to the Primary Sources The “Dry Sorbent” and “Spray Dry” processe s are primarily designed for treatment of high-temperature, high-sulfur content com bustion flue gases such as those found inCFAC BART Analysis 11/5/07 pg. 4-11 Project #: CFA207819 large power generation stations. In these applications, the most efficient alkali sulfate formation takes place at temperatures between 1000 - 2000°F and in spray dry systems the flue gas must be cooled to a temperatur e of 10°C to 15°C (20°F to 35°F) below saturation temperature to avoid wet solids deposition and plugging on the downstream particulate device. The reaction conditions at the pot-line scrubbe r exit (260°F and 100- 300 ppm of SO 2 ) are too cool and too dilute for t hese “dry” processes to be considered effective. To apply the Spray Dry process to the CFAC primary emissions, the exhaust stream would have to be significantly pre- heated to at least 350o F. This option would also require retrofitting the existing process with a particulate control device such as a baghouse or electrostatic precipitator.

Conclusion: This process alteration is considered technically infeasible for purposes of Step 2 in this BART anal ysis. No further di scussion of this technology will be presented.

(iv) Single Alkali Wet SO 2 Scrubber Applied to the Primary Sources The single alkali “throw-away” proce sses involve non-recoverable use of the calcium/sodium reagents. In the case of caustic soda and/or soda ash, the higher inherent reaction efficiency of the sodium co mpounds is more than offset by their higher materials cost coupled with their one-pass cons umption. In the case of the sodiumbased processes, disposal of the soluble sulfate waste products may pose groundwater leaching issues. The calcium-based systems r equire tight process control to prevent scaling problems in flues and scrubbers. Sodium-based syst ems operate with less scaling and freeze at a lower temperature than simple sl urries such as lime or limestone. All of the wet scr ubber designs suffer from free zing issues when operated in a northerly climate with the cold temperatures normally f ound at the CFAC facility in wintertime. In fact, EPA considered th is when developing the NESHAP for Primary Aluminum Reduction Plants (40 CFR 63 Subpart LL), Basis and Purpose document.

Conclusion: This technology is considered feasible for purposes of Step 2 in this BART analysis.

(v) Dual Alkali Wet SO 2 Scrubber Applied to the Primary Sources

The Dual Alkali process also facilitates the precipitation and settli ng or filtration of the calcium sulfates and recycles the caustic solu tion to the scrubber. This can significantly reduce makeup water and discharge requirement s. All of the we t scrubber designs suffer from freezing issues when operated in a northerly clim ate with the cold temperatures normally found at th e CFAC facility in wintertime.

Conclusion: This technology is considered feasible for purposes of Step 2 in this BART analysis.

(vi) Roof Vent SO 2 Controls Applied to the Secondary Sources Aluminum industry installati ons have successfully used spray chambers to capture fugitive pot line gases. One process re viewed used a water spray (no reagents) toCFAC BART Analysis 11/5/07 pg. 4-12 Project #: CFA207819 achieve ~50% removal of SO 2 and ~50% removal of total particulates. An advantage of this process over cloth filter baghouses is that this proce ss not only removes particulate fluorides, but gaseous fluoride as well. Oper ation of this wet scrubber may be limited to non-winter months. It is anticipat ed that the wet roof scrubber would not be operable in winter conditions due to freezing issues. For purposes of this analysis, year-round operation has been assumed.

Conclusion: This technology is considered feasible for purposes of Step 2 in this BART analysis.

4.3.3 Evaluate Control Effectiveness of Rema ining Control Technologies – Step 3

Of the alternative SO 2 control technologies identified above, proper potline design and operation, a process alteration (coke sulfur content reduction), single alkali wet SO 2 scrubbers, dual alkali wet SO 2 scrubbers, and roof vent SO 2 controls remain as technically feasible options. Proper design and operation is the baseline case for this analysis. The other listed control methods will be evaluated for their potential to improve upon this basis. Table 4-2 summarizes the cont rol effectiveness of the remaining control technologies.



### Table 4-2: Summary of SO 2 

### Control Technology Efficiency

Control Option Efficiency (%)

Dual Alkali Wet SO 2 Scrubber 90% on primary sources Single Alkali Wet SO 2 Scrubber 90% on primary sources Roof Vent Controls 50% on secondary sources Coke Sulfur Reduction 42% on both primary and secondary sources Baseline 0%

4.3.4 Evaluate Impacts and Document Results – Step 4

(a) Coke Sulfur Content Reduction Impacts

Coke Sulfur Content Reduction Environmental Impacts

CFAC is not aware of any indirect or dire ct environmental impacts associated with using low sulfur coke other than those associated with shipping this coke from outside the US to CFAC.

Coke Sulfur Content Reduction Economic Impacts

CFAC believes there may be petroleum cokes offered from overseas sources that have sulfur contents as low as 0. 5 to 0.75%. For the purposes of this study, and based on CFAC’s experience, a 0.75% sulfur coke wa s used as the basis for this analysis. The cost for this extremely low sulfur coke delivered from offshore sources would be approximately $160/short ton great er than the cost of the currently used 1.5% sulfurCFAC BART Analysis 11/5/07 pg. 4-13 Project #: CFA207819 coke. CFAC consumed approximately 44,248 short tons of anode coke in 1999, the highest year of production to occur recently. The increased cost for a 0.75% sulfur coke would be approximately 44,248 short ton/year x $160/shor t ton = $7,079,680/year.

Coke Sulfur Content Reduction Energy Impacts CFAC is not aware of any indirect or dire ct energy impacts associated with using low sulfur coke.

(b) Single Alkali Wet SO 2 Scrubber Impacts

Single Alkali Wet SO 2 Scrubber Environmental Impacts

In the case of the sodium-based processes, disposal of the soluble sulfate waste products may pose groundwater leaching issues. The calcium-based systems require tight process control to prevent scaling pr oblems in flues and scrubbers. The highest SO 2 recovery rates are obtained with sodium- based processes; however, in a single pass process, feed stock r eagents are not regenerated or recovered and reaction byproducts (sodium sulfates) are typically of little commercial value and must be treated as a leaching landfill material . This control option also puts greater demand on CFAC’s water supply and wastewater treatment facilit ies. The impacts of these effects have not been studied.

Single Alkali Wet SO 2 Scrubber Economic Impacts

CFAC has calculated the cost-effectiv eness for employing a single alkali wet SO 2 scrubber for SO 2 control, with the resu lts presented in Tabl e 4-3 below. CFAC has utilized the EPA’s Air Pollut ion Cost Control Manual to estimate costs of SO 2 scrubber control. The manual provides the EPA’s recommended methodology for estimating the costs for add-on control technology. To ca lculate the cost-effect iveness of a control technology in dollars per ton ($/to n), the following factors are used:

Cost-effectiveness ($/ton) = [(total capital investment x capital recovery factor {CRF}) + Direct Annual Cost + Indirect Annual Cost]/(tons SO 2 controlled)

Capital Recovery Cost = (total capital investment x CRF)

• Total capital investment = direct and indirect costs for purchasing and installing control equipment.

• Capital recovery factor (CRF) = mult iplier to determine the uniform end-ofyear payment necessary to repay an investment in n years with an interest rate of i.

o Control system life, n = 10 to 20 years, typically

o Interest rate, I = 7% recommended interest rate For this BART analysis, CRF = 10 years @ 7% = 0.142 Direct Annual Cost (utilities, labor, taxes) Indirect Annual Cost (overhead, insurance, taxes)CFAC BART Analysis 11/5/07 pg. 4-14 Project #: CFA207819 Table 4-3 summarizes the cost-effectiveness for each of the technically feasible control options, compared against a bas eline of proper design and op eration. Details of the single alkali wet SO 2 scrubber cost analysis can be found in Appendix C.

Single Alkali Wet SO 2 Scrubber Energy Impacts

EPA Publication EPA-542/F-03-034 st ates that modern wet scrubber designs result in an energy penalty of less than 1% of the total pl ant energy consumption. This is a minor energy impact which is only further c onsidered in the economic analysis.

(c) Dual Alkali Wet SO 2 Scrubber Impacts

Dual Alkali Wet SO 2 Scrubber Environmental Impacts

The dual alkali process facilitates the precipit ation and settling or filtration of the calcium sulfates and recycles the caustic solution to the scrubber. This can significantly reduce makeup water and discharge requirements over that of the single alka li system. This control option also puts greater demand on CFAC’s water supply and wastewater treatment facilities. The impacts of these effects have not been studied.

Dual Alkali Wet SO 2 Scrubber Economic Impacts

CFAC has calculated the cost-effectivene ss for employing a dual pass alkali wet SO 2 scrubber for SO 2 control, with the resu lts presented in Tabl e 4-3 below. CFAC has utilized the EPA’s Air Polluti on Cost Control Manual to esti mate costs of the dual pass system.

Dual Alkali Wet SO 2 Scrubber Energy Impacts

EPA Publication EPA-542/F-03-034 st ates that modern wet scrubber designs result in an energy penalty of less than 1% of the total pl ant energy consumption. This is a minor energy impact which is only further c onsidered in the economic analysis.

(d) Roof Vent SO 2 Control Impacts

Roof Vent Control: Water Spra y Chamber Environmental Impacts

This system acts as a simplified wet scrub ber, only without a reaction tower, and using only water (no reagent). Nevertheless, the environmental impacts of this system are similar to those of a si ngle pass wet scrubber. As SO 2 is collected by the system, it is converted through chemical process to sodium sulfate. Both the sodium sulfate and collected particulate matter are discharged to a settling pond through the blowdown water. Sodium hydroxide used to treat the settling pond is not regenerated or recovered. Reaction by-products (sodium sulfates) are ty pically of little commercial value and must be landfilled. In the case of this sodium-bas ed process, disposal of the soluble sulfate waste products, either on-site or in a landf ill may pose groundwater leaching issues.CFAC BART Analysis 11/5/07 pg. 4-15 Project #: CFA207819 CFAC estimates the total water consumption of this system at 700 gallons per minute (200 gpm blowdown plus 500 gpm evaporation rate during the summer). This control option puts a great demand on CFAC’s wate r supply. The impact of this water consumption rate has not been studied.

Roof Vent Control: Water Spray Chamber Economic Impacts

CFAC has calculated the cost-effectiveness of employing a water spray chamber for SO 2 control, with the results presented in Tabl e 4-4 below. CFAC has utilized EPA’s Air Pollution Cost Control methodology to esti mate costs of the water spray chamber. Details of the water spray chamber cost analysis can be found in Appendix C.

Roof Vent Control: Water Spray Chamber Energy Impacts

EPA Publication EPA-542/F-03-034 st ates that modern wet scrubber designs result in an energy penalty of less than 1% of the total pl ant energy consumption. This is a minor energy impact which is only further c onsidered in the economic analysis.

Alternatives Analysis Summary

For the purposes of this cost analysis, it has been assumed that the remaining life of all of the equipment is at least the 10 y ears used to calculate the annualized costs.

Primary Sources There are two separate sources of SO 2 emissions: primary and secondary. The primary sources include the six dry alumina scrubbers (EU28 through EU33) and the secondary sources are the potline roof vents (EU34 through EU38). Table 4-3 summarizes the cost analysis for the remaining feas ible controls for the primary SO 2 -emitting sources.



### Table 4-3: Summary of Primary SO 2 

### Emissions Cost and Visibility Impacts

Glacier Nat'l Park

Control Option Capital Cost Annualized Cost a Efficiency (%) SO 2 Emitted

(tpy) SO 2 Removed

(tpy) Cost b ($/ton) SO 2 Impact (deciview) Deciviews Removed (24 hr - ∆ ) Cost ($/dc)

Dual Alkali Wet SO 2 Scrubber $50,581,438 $12,142,136 90% 153 1,377 $8,817 2.605 1.279 $9,490,987 Single Alkali Wet SO 2 Scrubber $34,883,750 $9,422,298 90% 153 1,377 $6,842 2.605 1.279 $7,365,006 Coke Sulfur Content Reduction $0 $7,079,680 42% 887 643 $10,245 3.267 0.617 $11,480,562

Baseline $0 $0 0% 1,530 0 -- 3.884 0.00 --

a Note: The annualized cost for coke sulfur content reduction is calculated using the increased cost per anode coke $160/short to n x 44,248 tpy (1999 production) = $7,079,680/yr.

b Note: The cost per ton of SO 2 removed from coke sulfur content reduction is calculated from using the facility-wide SO 2 emissions of 1645 tpy (1530 tpy primary + 115 tpy secondary emissions).CFAC BART Analysis 11/5/07 pg. 4-16 Project #: CFA207819 Secondary Sources Table 4-4 summarizes the cost analysis for the remaining feasible controls for the secondary SO 2 -emitting sources.



### Table 4-4: Summary of Secondary SO 2 

### Emissions Cost and Visibility Impacts

Glacier Nat'l Park

Control Option Capital Cost Annualized Cost Efficiency (%) SO 2 Emitted

(tpy) SO 2 Removed

(tpy) Cost ($/ton) SO 2 Impact (deciview) Deciviews Removed (24 hr - ∆ ) Cost ($/dc)

Roof Vent Spray Room SO 2 Control $33,476,076 $12,096,206 50% 58 58 $210,057 3.020 0.864 $13,994,839 Coke Sulfur Content Reduction $0 $7,079,680 42% 67 48 $10,245 3.267 0.617 $11,480,562

Baseline $0 $0 0% 115 0 -- 3.884 0.00 --

a Note: The annualized cost for coke sulfur content reduction is calculated using the increased cost per anode coke $160/short to n x 44,248 tpy (1999 production) = $7,079,680/yr.

b Note: The cost per ton of SO 2 removed from coke sulfur content reduction is calculated from using the facility-wide SO 2 emissions of 1645 tpy (1530 tpy primary + 115 tpy secondary emissions).

4.3.5 Evaluate Primary Controls Visibility Impacts – Step 5

CFAC has performed modeling usi ng the CALPUFF model to pred ict visibility impacts of the identified potentia lly applicable SO 2 control technologies, using the 98 th percentile visibility result as recommended by EPA. The results of the modeling are shown in Table 4-3 above. The results are only presented for Glacier National Park receptors, as it is the closest and most impacted Class I Area. Details of the modeling are found in Appendix B of this document.

4.3.6 Evaluate Secondary Controls Visibility Impacts – Step 5

CFAC has performed modeling usi ng the CALPUFF model to pred ict visibility impacts of the identified potentia lly applicable SO 2 control technologies, using the 98 th percentile visibility result as recommended by EPA. T he results of the modeling are shown in Table 4-4 above. The results are only presented for Glacier National Park receptors, as it is the closest and most impacted Class I Ar ea. Details of the modeling are found in Appendix B of this document.

4.3.7 Select SO 2 BART

The purpose of BART is to apply a control technol ogy that would improve the visibility to a degree that would be beneficial to the area analyzed in a cost-effective manner. In the case of the CFAC facility, the cost, effi ciency and visibility impr ovement from any SO 2 and PM 10 controls is inter-related. Section 4.4 analyzes the control options for the secondary PM 10 emissions. An analysis was perfo rmed using the combination of SO 2CFAC BART Analysis 11/5/07 pg. 4-17 Project #: CFA207819 primary and secondary cont rols in conjunction with PM 10 secondary controls to determine an overall BART select ion. The combination of SO 2 and PM 10 controls showed possible scenarios for visibility improv ements. See Section 4.5 for the overall BART selection.



### 4.4 BART Analysis for PM 10 

### from the Potline Roof Vents

4.4.1 Identify Available Particulate Control Technologies – Step 1

EPA’s RBLC describes several permitted alum inum plants and lists their pollutant emission limits and the control technologies approved to achieve those limits. Another source of information regardi ng potentially applicable PM 10 control technology for aluminum manufacturing is EP A’s AP-42 for Primary Alumi num Production (Chapter 12, Section 1). The PM 10 emissions from the primary emi tting sources are very small and had a negligible modeled impact on visibility; however, the PM 10 emissions from the secondary emitting sources were predicted by the model to cause the most significant degradation to the visibility in Glacier Nati onal Park and are further analyzed below.

The secondary particulate emissions are fugiti ve emissions released from the roof vents on the top of the potli ne buildings. There are several components to these fugitive particulate emissions. CFAC estimates a frac tion (7%) of potline gases are not collected by the exhaust hoods and then routed to the dry alumina scrubbers. Emissions from reduction cells include alumina and carbon from anode dusting, cr yolite, aluminum fluoride, calcium fluoride, chiolite (Na 5 Al 3 F 14 ), and ferric oxide. Fugi tive dust is also generated by normal potline operations within the buildings, including particulate from materials handling and vehicle traffic.

The following were ident ified as potentia lly applicable fo r controlling PM 10 from the secondary emitting sources at the facility:

(i) Proper potline design and operation (baseline), (ii) Roof Vent Controls (Baghouses + Water Spray Chamber)

Control Technology Description:

(i) Proper Potline Design and Operation The CFAC facility has been in operation si nce the 1950s and has followed the advancements in aluminum reduction technol ogy. CFAC believes the current operation has similar efficiencies and operational procedures to other plants in the US. Therefore, CFAC believes the facility has pr oper design and operat ion procedures.

(ii) Roof Vent Controls

1. Fabric Filter Baghouse It would be possible to collect the air flow currently vented through the roof vents and direct the flow to a seri es of baghouses. The air flow passesCFAC BART Analysis 11/5/07 pg. 4-18 Project #: CFA207819 through tightly woven or felted fabric, c ausing particulates in the flow to be collected on the fabric by sieving and other mechanisms. As particulate collects on the filter, co llection efficiency increases while pressure drop through the system increases. Bags are intermittently cleaned by shaking the bag, pulsing air through the bag, or temporarily reversing the airflow direction.

2. Water Spray Chamber CFAC has investigated t he use of spray chamber ty pe roof vent controls. This system consists of roof-mount ed water spray chambers (no other reactants used) to capture and remove SO 2 and PM 10 from the roof vent exhaust stream. Parallel systems of mu ltiple modules can be employed. The high volume secondary exhaust streams are captured by dormer outlets in the roof, and inducted by low pressure, high volume fans through large chambers fitted with multiple spray bars. SO 2 is readily absorbed in the airborne liquid droplet s and particulate is captured by impingement. Efficiencies of 50% for both SO 2 and particulate have been reported.

4.4.2 Eliminate Technically Infeasible PM 10 Control Options – Step 2

(i) Proper Potline Design and Operation Proper potline design and oper ation is considered baseline an d is technically feasible.

Conclusion: This technology is consider ed technically feasible for purposes of Step 2 in this BART analysis.

(ii) Roof Vent Controls 1. Although CFAC is no t aware of an aluminum production facility which incorporates roof vent baghouse contro l, the technology is mature and there are no known technical challen ges with this type of installation.

Conclusion: This technology is consider ed technically feasible for purposes of Step 2 in this BART analysis.

2. Aluminum industry installations ha ve successfully used spray chambers to capture fugitive potline gases. One process reviewed used a water spray (no reagents) to achieve appro ximately 50% removal of SO 2 and approximately 50% removal of total parti culates. An advantage of this process over a cloth filt er baghouse is that the process not only removes particulate fluorides, but gaseous fluorid e as well. A disadvantage to the operation of this wet scrubber is that the wet roof scr ubber would probably not be operable in winter conditions due to freezing issues. For purposes of this analysis, year-round operation has been assumed.

Conclusion: This technology is consider ed technically feasible for purposes of Step 2 in this BART analysis.CFAC BART Analysis 11/5/07 pg. 4-19 Project #: CFA207819 4.4.3 Evaluate Control Effectiveness of Remaining PM 10 Control Technologies – Step 3

Of the alternative PM 10 control technologies identified above, proper potline design and operation, roof vent baghouse co ntrol and roof vent water sp ray chamber control remain as technically feasible options. Proper design and operation is the baseline case for this analysis. The other listed control methods will be evaluated for their potential to improve upon this basis. Table 4-5 summarizes the cont rol effectiveness of the remaining control technologies.



### Table 4-5: Secondary Emissions (Potline Roof Vent) PM 10 

### Control Technology Effectiveness

Control Option Efficiency (%) Roof Vent Baghouse Control 99% Roof Vent Water Spray Chamber Control 50%

Baseline 0%

4.4.4 Evaluate Impacts and Document Results – Step 4

(a) Roof Vent Control: Baghouse

Roof Vent Control: Baghouse Environmental Impacts

CFAC is not aware of any severe adverse environmental impacts of operation of a baghouse system. A baghouse system of this magnitude would greatly increase facility auxiliary electrical power r equirements; so environmental im pacts would result from the generation of this additional el ectrical power. Also captured particulate would be disposed in a landfill and this may hav e some local environmental impacts.

Roof Vent Control: Baghouse Economic Impacts

CFAC has calculated the cost-effectiveness for employing a series of very large baghouses for PM 10 control, with the results presented in Table 4-6 below. CFAC has utilized the EPA’s Air Pollution Cost Contro l Manual to estimate the costs of PM 10 baghouse control. The manual provides the EPA’s recommended methodology for estimating the costs for add-on control technolog y. To calculate the cost-effectiveness of a control technology in dollars per t on ($/ton), the followi ng factors are used:

Cost-effectiveness ($/ton) = [(total capital investment x capital recovery factor {CRF}) + Direct Annual Cost + Indirect Annual Cost]/(tons PM 10 controlled)

Capital Recovery Cost = (total capital investment x CRF)CFAC BART Analysis 11/5/07 pg. 4-20 Project #: CFA207819 • Total capital investment = direct and indirect costs for purchasing and installing control equipment.

• Capital recovery factor (CRF) = mult iplier to determine the uniform end-ofyear payment necessary to repay an investment in n years with an interest rate of i.

o Control system life, n = 10 to 20 years, typically

o Interest rate, I = 7% recommended interest rate For this BART analysis, CRF = 10 years @ 7% = 0.142 Direct Annual Cost (utilities, labor, taxes) Indirect Annual Cost (overhead, insurance, taxes)

Table 4-6 summarizes the cost-effectiveness for baghouse control, compared against a baseline of proper design and operation. De tails and the technical basis of the baghouse cost analysis can be found in Appendix C.

Roof Vent Control: Baghouse Energy Impacts

CFAC estimates that operation of the fa ns required to power the baghouses would consume approximately 7, 500,000 kwh per year of electricit y. This energy impact is only further considered in the economic analysis.

(b) Roof Vent Control: Water Spray Chamber

Roof Vent Control: Water Spra y Chamber Environmental Impacts

This system acts as a simplified wet scrub ber, only without a reaction tower, and using only water (no reagent). Nevertheless, the environmental impacts of this system are similar to those of a single pass wet scrubber, as SO 2 is collected by the system, it is converted through chemical process to sodium sulfate. Both the sodium sulfate and collected particulate matter are discharged to a settling pond through the blowdown water. Sodium hydroxide used to treat the settling pond is not regenerated or recovered. Reaction by-products (sodium sulfates) are ty pically of little commercial value and must be landfilled. In the case of this sodium-bas ed process, disposal of the soluble sulfate waste products, either on-site or in a landf ill may pose groundwater leaching issues.

CFAC estimates the total water consumption of this system at 700 gallons per minute (200 gpm blowdown plus 500 gpm evaporation rate during the summer). This control option puts a great dem and on CFAC’s water supply. The impacts of this water consumption rate have not been studied.

Roof Vent Control: Water Spray Chamber Economic Impacts

CFAC has calculated the cost-effectiveness of employing a water spray chamber for PM 10 control, with the results presented in T able 4-6 below. CFAC has utilized EPA’s Air Pollution Cost Control methodology to esti mate costs of the water spray chamber. Details of the water spray chamber cost analysis can be found in Appendix C.CFAC BART Analysis 11/5/07 pg. 4-21 Project #: CFA207819 Roof Vent Control: Water Sp ray Chamber Energy Impacts

EPA Publication EPA-542/F-03-034 st ates that modern wet scrubber designs result in an energy penalty of less than 1% of the total pl ant energy consumption. This is a minor energy impact which is only further c onsidered in the economic analysis.

Alternatives Analysis Summary

For the purposes of this cost analysis, it has been assumed that the remaining life of all of the equipment is at least the 10 y ears used to calculate the annualized costs.

Table 4-6 summarizes the cost analysis and visi bility impacts for the remaining feasible controls for the secondary PM/PM 10 emitting sources.



### Table 4-6: Summary of Secondary PM 10 

### Emissions Cost and Visibility Impacts

Glacier Nat'l Park

Control Option Capital Cost Annualized Cost Efficiency (%) PM 10 Emitted a

(tpy) PM 10 Removed

(tpy) Cost ($/ton) PM 10 Impact (deciview) Deciviews Removed (24 hr - ∆ ) Cost ($/dc)

Roof Vent PM 10 Control: Baghouse $556,716,625 $104,151,834 99% 2.18 216 $482,587 2.359 1.525 $68,281,360 Roof Vent PM 10 Control: Water Spray Chamber $33,476,076 $12,096,206 50% 109 109 $110,974 3.020 0.864 $13,994,839

Baseline $0 0% 218 0 -- 3.88 0.00 --

a Note: The spray chamber reduces both SO 2 and PM 10 emissions; therefore, visibility impacts, improvements, and cost per deciview for the spray room include SO 2 emissions.

4.4.5 Evaluate PM 10 Visibility Impacts – Step 5

CFAC has performed modeling usi ng the CALPUFF model to pred ict visibility impacts of the identified potent ially applicable PM 10 control technologies, using the 98 th percentile visibility result as recommended by EPA. T he results of the modeling are shown in Table 4-6 above. The results are only presented for Glacier National Park receptors, as it is the closest and most impacted Class I Ar ea. Details of the modeling are found in Appendix B of this document.

4.4.6 Select Secondary Source PM 10 BART

The purpose of BART is to apply a control technol ogy that would improve the visibility to a degree that would be beneficial to the area analyzed in a cost-effective manner. In the case of the CFAC facility, the cost, effi ciency and visibility impr ovement from any SO 2 and PM 10 controls is inter-related. The previous section, Section 4.3, analyzes the control options for the primary and secondary SO 2 emissions. An analysis was performed using the combination of SO 2 primary and secondary controls in conjunctionCFAC BART Analysis 11/5/07 pg. 4-22 Project #: CFA207819 with PM 10 secondary controls to determine an over all BART selection. The combination of SO 2 and PM 10 controls showed possible scenarios for visibility improvements. See Section 4.5 for the ov erall BART selection.



### 4.5 Select Overall BART

Sections 4.3 and 4.4 have provided a fr amework for analyzing various control technologies, eliminating inf easible options, and evaluating c ontrol effectiveness, control impacts and visibility impacts. The analyses have been related to PM 10 and SO 2 . Given that these previous sections have identified thos e available options and their relative impacts, it is the purpose of this section to cons ider all of the options in their entirety and select BART for this facility.

Similar to prior discussions, the methodology for selecting an appropriate BART will generally follow the di scussions found in the Appendix Y Guideline 11 . Much of that discussion is found in Section IV.E of the Guideline (also found on pages 39170 and 39171 of the July 6, 2005 Federal Register ). That discussion is l abelled as: “How do I select the ‘best’ alternative using the result s of Steps 1 through 5.” For our case, steps 1 through 5 in the title refer to steps 1 thr ough 5 found in the discussi ons in Sections 4.3 and 4.4 above.

There are a total of five discu ssion points found in Section E. For CFAC, only the first three are relative since the fourth and fifth poi nts relate solely to utility boilers. The three remaining points for discussion r egarding the selection of BART are: 12

1. Summary of the impacts, 2. Selecting a “best” alternative, 3. Consideration of a ffordability (paraphrased).

These three steps will be cons idered in concert with the SO 2 and PM 10 analysis in prior sections to select BART for this facility. As noted in earlier discussions, it was decided to include analyses of PM 10 and SO 2 together in this final section since both pollutants play a potential role in visibility analysis as well as in control technology considerations.

4.5.1 Summary of Impacts – Section E, Item 1

The Appendix Y Guideline suggests that a chart or charts be developed that displays, for comparison purposes, parameters such as emission rate, emission reductions (by control alternative), control costs and air an d non-air impacts. However, for this to be useful, it is necessary to consider both the PM 10 and SO 2 emission strategies previously discussed in Sections 4.3 and 4.4 and to revi ew impacts and costs associated with not only each pollutant separately, but as a co mbined analysis. To that end, Table 4-7 below has been created that com pares a number of reasonable scenarios that would be considered “feasible” prior to analysis of costs and benefits.

11 40 CFR 51, Appendix Y.
12 40 CFR 51, Appendix Y, Section E, Subsections 1 through 3.CFAC BART Analysis 11/5/07 pg. 4-23 Project #: CFA207819 The combined primary SO 2 and PM 10 , and secondary PM 10 BART analysis offered many possible combinations of technologies for analysis. In order to simplify the BART selection process, the single pass wet SO 2 scrubber has been removed from the following analysis. CFAC vi ews the single pass and dual pass wet scrubbers as similar technologies. The single pass wet SO 2 scrubber has the same co ntrol efficiency as a dual pass wet SO 2 scrubber, has similar annualized costs, and poses greater potential environmental hazards. CFAC viewed t he single pass system as redundant, and has only analyzed the dual pass wet SO 2 scrubber in the following sections.CFAC BART Analysis 11/5/07 pg. 4-24 Project #: CFA207819 

### Table 4-7: Summary of Potential BART Scenarios

Note: Primary sources are the emissions from t he alumina scrubbers while the secondary sources represent the roof vent potline emissions. Primary Sources Secondary Sources

Scenario Description SO 2 Emissions % Reduction PM 10 Emissions %

Reduction SO 2 Emissions % Reduction PM 10 Emissions % Reduction Explanation

Baseline Existing Controls - - - - As the facility is currently configured.

1 Coke Sulfur Content Reduction 42% 0% 42% 0% Purchase and use lowsulfur anode-grade petroleum coke.

2 Roof Vent Spray Chamber SO 2 & PM Controls 0% 0% 50% 50% Collect gases vented from roof vents and add a water spray scrubber that removes modest amounts of PM 10 and SO 2

.

2a Roof Vent Spray Chamber SO 2 & PM Controls and Sulfur Reduction in Coke 42% 0% 71% 50% Scenarios 1 and 2 combined.

3 Wet Scrubber SO 2 Controls 90% 0% 0% 0% Add a wet scrubber (single or dual alkali) to the flue gas following (or preceding) the current alumina scrubbers.

3a Wet Scrubber SO 2 Controls and Sulfur Reduction in Coke 94% 0% 42% 0% Combination of Scenarios 1 and 3.

4 Roof Vent Baghouse 0% 0% 0% 99% Collect gases vented from roof vents and baghouse control.

4a Roof Vent Baghouse and Sulfur Reduction in Coke 42% 0% 42% 99% Combination of Scenarios 1 and 4.

5 Wet Scrubber SO 2 Controls and Roof Vent Spray Chamber SO 2 and PM Control 90% 0% 50% 50% Combination of Scenarios 2 and 3.

5a Wet Scrubber SO 2 Controls, Roof Vent

Spray Chamber

SO 2 and PM Control and Sulfur Reduction in Coke 94% 0% 71% 50% Combination of Scenarios 1 and 5.

6 Wet Scrubber SO 2 Control and Roof Vent Baghouse 90% 0% 0% 99% Combination of Scenarios 3 and 4.

6a Wet Scrubber SO 2 Control, Roof Vent

Baghouse and Sulfur Reduction in Coke 94% 0% 42% 99% Combination of Scenarios 1 and 6.CFAC BART Analysis 11/5/07 pg. 4-25 Project #: CFA207819 Given that a generous set of scenarios has now been developed, it is appropriate to compare the various scenarios against visibilit y impacts, costs, cost-effectiveness, etc. Using the information already presented in Sections 4.3 and 4.4 along with the dispersion modeling results su mmarized in Appendix B, the following table provides the substantive comparative values.CFAC BART Analysis11/5/07 pg. 4-26Project #: CFA207819Table 4-8: Summary of SO2/PM10Emissions Cost Analysis and Visibility ImpactsPrimary Sources Secondary SourcesScenarioDescriptionSO2%RemovalPM10%RemovalSO2%RemovalPM10%RemovalAverage(3 Years) of 98thPercentileDeciview ImpactAverage(3 Years) of98thPercentileImprovementin Deciviews(24 hr -∆)Total SO2Removed(Ton/yr)Total PM10Removed(Ton/yr)Capital Cost($)AnnualizedCost($/year)SO2CostEffectiveness($/ton)PM10CostEffectiveness($/ton)Visibility CostEffectiveness($/deciview)Baseline Existing Controls - - - -3.8840--- - - - -1Coke Sulfur ContentReduction42%0%42%0%3.2670.6176910N/A$7,079,680$10,245NA$11,480,5622Roof Vent SprayChamber SO2& PMControls0% 0%50% 50% 3.0200.86458109$33,476,076 $12,096,206 $210,057 $110,921 $13,994,8392aRoof Vent SprayChamber SO2& PMControls and SulfurReduction in Coke42%0%71%50%2.3261.558724109$33,476,076$19,175,886$26,470$175,840$12,305,3813Wet Scrubber SO2Controls90%0% 0% 0%2.6051.27913770$50,581,438 $12,142,136 $8,817 NA $9,490,9873aWet Scrubber SO2Controls and SulfurReduction in Coke94%0%42%0%2.4771.40714870$50,581,438$19,221,816$12,929NA$13,664,7984 Roof Vent Baghouse 0% 0% 0%99% 2.3591.5250216$556,716,625 $104,151,834 NA $482,184 $68,281,3604aRoof Vent Baghouseand Sulfur Reductionin Coke42%0%42%99%1.4972.387691216$556,716,625$111,231,514$160,963$515,140$46,592,3685Wet Scrubber SO2Controls and RoofVent Spray ChamberSO2and PM Control90%0%50% 50% 1.5492.3351435109$84,057,514 $24,238,341 $16,894 $222,262 $10,381,9285aWet Scrubber SO2Controls, Roof VentSpray Chamber SO2and PM Control andSulfur Reduction inCoke94%0%71%50%1.4612.4231520109$84,057,514$31,318,021$20,602$287,182$12,925,3086Wet Scrubber SO2Control and Roof VentBaghouse90%0% 0%99% 0.8173.0671377216$607,298,063 $116,293,969 $84,446 $538,398 $37,917,8256aWet Scrubber SO2Control, Roof VentBaghouse and SulfurReduction in Coke94%0%42%99%0.6073.2771487216$607,298,063$123,373,649$82,984$571,374$37,652,182CFAC BART Analysis 11/5/07 pg. 4-27 Project #: CFA207819 Given that there are numer ous scenarios to consider along with numerous criteria (control effectiveness, deciview improvement, etc), it will be necessary to narrow the choices of potential BART technologies. O ne such method to begin the process of selecting a single BART choice will be to eliminate those scenarios that cost significantly more than competing alternat ive scenarios and provide no significant improvement in visibility. In other words, it would be appropriate to drop from further consideration any technology that provides sim ilar visibility improvement at substantially higher costs that competing technologies.

To make such a comparison, Figure 4-1 has been created. The figure shows relative annualized costs of the various scenarios com pared against the relati ve improvement in visibility (expressed on a peak 24-hour basis) for each scenario. Mathematically this is the equivalent of dividing the last column in Table 4-8 by the 8 th column in the table.



### Figure 4-1: Annualized Cost vs. Deciview Improvement by Scenario

Annualized Cost versus Deciview Improvement (24 hr - ∆ )

$0 $20,000,000 $40,000,000 $60,000,000 $80,000,000 $100,000,000 $120,000,000 $140,000,000

0 0.5 1 1.5 2 2.5 3 3.5

A

verage Change in DeciviewAnnualized Cost ($)

Baseline Scenario 3 Scenario 6

Scenario 5 Scenario 4

Scenario 2

Scenario 1 Scenario 5a Scenario 4a

Scenario 3a

Scenario 2a Scenario 6aCFAC BART Analysis 11/5/07 pg. 4-28 Project #: CFA207819 A review of Figure 4-1 reveals some startli ng differences between several scenarios. To begin, Scenarios 4, 4a, 6 and 6a are vastly more costly than all other options. Of particular interest, of course, is that thos e four scenarios provid e either no additional improvement or very little impr ovement over most of the ot her scenarios. In particular, Scenarios 4 and 4a provide no visibility impr ovement over scenarios 2a and 5a, while costing substantially more than these equally effective scenarios.

The same general observati on appears appropriate for Sc enarios 6 and 6a. Both of these scenarios provide a modest improvement in modeled visi bility, but appear to do so at an extraordinary cost. These scenarios are about six times more expensive than other scenarios (disregarding 4 and 4a) with only modest impr ovements in visibility.

For purposes of the continui ng analysis, Scenarios 4, 4a, 6 and 6a are eliminated as BART.

The next step is to compare the cost-effectiv eness of the remaining control options in relation to emission reductions on an annualiz ed cost basis. This comparison will help narrow the field of possibilities by eliminating those scenarios that are, by themselves or in comparison to each other, excessively expensive. Table 4-9 provides such a comparison.



### Table 4-9: Potential BART Cost-Effectiveness Scenarios

Scenario Description SO 2 Cost-Effectiveness ($/ton) PM 10 Cost-Effectiveness ($/ton)

Baseline As configured

- - 1 Coke Sulfur Content Reduction $10,245 NA 2 Roof Vent SO 2 & PM Controls $210,057 $110,921

2a Roof Vent SO 2 & PM Controls and Sulfur Reduction in Coke $26,470 $183,546

3 Wet Scrubber SO 2 Controls $8,817 NA

3a Wet Scrubber SO 2 Controls and Sulfur Reduction in Coke $12,929 NA

5 Wet Scrubber SO 2 Controls and Roof Vent PM (and SO 2 ) Control $16,894 $222,262

5a Wet Scrubber SO 2 Controls, Roof Vent PM (and SO 2 ) Control and Sulfur Reduction in Coke $20,602 $294,888

This table yields some interesting results. An obvious observation is that the $/ton costs are clearly excessive in all but perhaps two scenarios. This observation is based on what may be typically considered during a BAC T analysis. BACT is, by definition, an analysis that is applicable to a “new” or “modifi ed” facility. When a new facility installs air pollution control equipment, it must do so bas ed on the ‘best’ controls at the time considering economic and other impacts. For BAC T purposes, there is no “bright-line”CFAC BART Analysis 11/5/07 pg. 4-29 Project #: CFA207819 that distinguishes cost-effective costs from “non-cost-effective” costs. Nonetheless, there is considerable histor y regarding the costs of equipment designed to control sulfur dioxide and particulates (the primary subject of this investigation).

Again, although there are no bri ght-line values, it is generally understood that maximum acceptable control cost-effectiveness for thes e pollutants typically ranges from about $5,000 to $10,000 per ton. Table 4-9 demonstrates costs far in excess of this general range. For example, all of the options that involve the control of particulate emissions exceed $100,000 per ton. Further consideration of any of those options would clearly be outside of the intended scope of BART. If one were analyzing the appropriate BACT for a new facility, it is highl y likely that control costs in the $10,000+ range would be rejected. It is clear that one would also reject BART controls in the same or lower range. To that end, four of the above scenarios (2, 2a, 5 and 5a) exceed this guideline by factors ranging from 1.6 to 21. As a result, those scenarios are no longer in consideration for BART.

The only remaining scenarios deserving any further consideration are 1, 3 and 3a. It would be perfectly reasonable to reject these scenarios as we ll since they have BART cost-effectiveness values of about $9,000 to $13, 000 per ton. For sulfur dioxide, this cost is well above typical BACT costs. As a result, they should be rejected on this basis alone. Nonetheless, it has been decided to review these scenarios further. The next item of interest is to com pare the annualized cost of these alternativ es against the air quality benefit (improvement in visibility) on its own meri t. Figure 4-1 provided such a comparison, but the information was used to compare scenarios among themselves, as opposed to modeled visi bility impacts.

Figure 4-2 has been created to co mpare the modeled improvem ent in visibility against the cost of accomplishi ng that modeled result.CFAC BART Analysis 11/5/07 pg. 4-30 Project #: CFA207819 

### Figure 4-2: Annualized Cost vs. D eciview Improvement - 3 Scenarios

CFAC Annualized Cost versus Deciview Improvement (24 hr - ∆ ) (Remaining 3 Scenarios)

$0 $5,000,000 $10,000,000 $15,000,000 $20,000,000 $25,000,000

0.0 0.5 1.0 1.5 2.0 2.5 3.0

A verage Change in DeciviewAnnualized Cost ($)

Baseline Scenario 3

Scenario 1 Scenario 3a

This figure provides a better resolution of the cost of anticipated (modeled) visibility impacts from the three remaining scenarios. In all three cases, the anticipated visibility impact is minor. Scenario 1 improvement is less than 1 deciview. One deciview is a value that is only barely detectible by humans. Scenarios 3 and 3a are only slightly better. In addition, the m odeling improvements are only fo r one small area of Glacier National Park. The vast majority of the par k shows impacts from CFAC to be less than 0.5.

Of particular interest is the cost associat ed with the small model ed improvements. The costs range from about $7,000,000 per year to about $19,000,000 per year. Although there is no previously est ablished regulatory cost presumed to be excessive, it would only seem logical that the BART program did not contemplate these types of costs.CFAC BART Analysis 11/5/07 pg. 4-31 Project #: CFA207819 4.5.2 Selecting a “Best” Alternat ive – Section E, Item 2

The Appendix Y Guidelin e (Section E.2) suggests that t he next step is to evaluate the various control options. It furt her notes that regardless of t he order of the evaluation, the agency should always: 13

1. Display the options, 2. Identify the average and incremental costs, 3. Consider the energy and non-air quality impacts, 4. Consider the rema ining useful life, and 5. Consider the model ed visibility impacts.

For purposes of fulfilling thos e obligations, this document has analyzed the five steps above. Item 1 (display the options) is summa rized as Table 4-7. Those options are based on the detailed control technology revi ews and discussions found primarily in Sections 4.3 and 4.4.

Item 2 has also been discussed throughout the document but is summarized in Table 4- 8. Those costs were developed using general EPA guidelines as well as actual retrofit costs associated with this facility.

Item 3 has been discussed in a more general manner where necessary. Those impacts, while discussed, were not analyzed in any si gnificant manner since the results of other investigations (primarily Items 2, 4 and 5) have supplanted the need for detailed analyses. More detailed analyses can be provided if necessary.

Item 4 relates to the useful life of this fa cility. While the plant has been in existence since the 1950s, its future health and long-t erm outlook will depend on many local, state, national and internat ional parameters. Am ong the more pressing matters is the subject of future electrical supply at a reasonable cost. It is commonly understood that aluminum reduction plants use large am ounts of electricity as the underlying mechanism for creating the final product. The co st of electricity is the largest single expense in making aluminum. As it currently stands, the curr ent power contract for one potline of electricity is set to expire in 2011, the timeframe in which installation of BART controls would need to at leas t be initiated. Power for t he other two currently operating potlines is purchased on the open market. CF AC has every intention to continue operating the facility, but it can not guarantee this will be the case unless costs remain reasonable.

Item 5 has been analyzed in cons iderable detail. The details of the modeling itself are found in Appendix B. A summary of the modeling impacts ar e presented in Table 4-8. Modeled visibility changes were noted for each control technology scenario, along with various associated costs.

13 From: 70 FR 39170 and 39171.CFAC BART Analysis 11/5/07 pg. 4-32 Project #: CFA207819 The selection of BART is a culmination of a review of the summa rized data primarily found in Section 4.5.1 abov e. That analysis makes several clear points:

Modeling indicates that t he pollutant providing the most modeled visibility benefit is particulate matter.

Particulate matter reducti ons are extremely expensive in this case due to extremely large quantities of gas being handled and the need, in most cases, to first collect th ose gases for processing.

The cost of both particulate and sulfur dioxide controls is in the multi-million dollar range.

The cost-effectiveness ($ per ton of po llutant reduced) is very expensive on its face and in comparison to typical BACT costs of the same pollutants.

The cost-effectiveness for visibility impr ovement is in the multi-million dollar range. The estimates for even the most efficient scenarios start at about $10,000,000 per deciview.

Given the entire discussion above and throughout this document, it becomes quite clear that the only logical conclusion for BART at this facility is t he current plant configuration. The addition of more controls on this facility fo r the purposes of improving visibility is far in excess of any reasonable retrofit cost. This fa cility is unique in that the cost of control is inordinately high due to the physical desi gn characteristics of the plant. To control emissions from those pollutants for which t he model predicts visibility impacts would be especially costly due to the lar ge volumes and collection needs.

As a result, CFAC proposes that BART for this facility is its current configuration and operation.

4.5.3 Consideration of Affordability – Section E, Item 3

On a final note, the Appendix Y Guide line also notes that t he Agency is entitled to consider the affordability of controls. Th is may be considered regardless of the costeffectiveness of the alternatives (scenarios) that have been identifi ed. Specifically, the Guideline notes the following:

1. Even if the control technology is cost effective, there may be cases where the installation of controls would affect the viability of continued plant operations

. 2. There may be unusual circumst ances that justify taking into consideration the conditions of the plant and the economic effects of requiring the use of a given control technology. These effects would include effects on product prices, the market share, and profitability of the source . Where there are suchCFAC BART Analysis 11/5/07 pg. 4-33 Project #: CFA207819 unusual circumstances that are judged to affect plant operations, you may take into consideration the conditions of the plant and the economic effects of requiring the use of a control technology . Where these effects are judged to have a severe impact on plant operations you may consider them in the selection process, but you may wish to provide an economic analysis that demonstrates, in sufficient detail for public review, the specific economic effects, par ameters, and reasoning. . . .”

CFAC believes that this deserves consideration for this facility. CFAC is a producer of commodity grade aluminum ingot. The rev enue CFAC receives is determined by the daily trading prices of al uminum on the London Metal Exchang e. CFAC has no control over the revenue received for its product. CFAC’s competition is global and any increase in CFAC’s operating costs will furt her weaken its compet itiveness in the world market.

The aluminum industry in the Pacific Nort hwest has been in decli ne for the past eight years due to the poor economic position of the region’s alumin um reduction facilities. In 1999, there were ten aluminum reduction fa cilities operating in Washington, Oregon and Montana. Currently, t here are only three of these fac ilities still operating, most at reduced capacity. Of the shutdo wn facilities, most have been torn down and will never resume operation. The profit ability of aluminum smelting in the Pacific Northwest is marginal due to the region’s lack of availa ble power at a reasonable cost for aluminum reduction.

Any requirement to implement any of the pollution control strategies described in this document will greatly increas e CFAC’s operating costs and probably result in the shutdown of the facility.

## APPENDIX A: EPA LETTER TO CFAC

## APPENDIX B: VISIBILITY IMPACTS MODELINGCFAC BART Analysis pg. B-1 Appendix B 

## 1.0 VISIBILITY IMPACTS

1.1 Introduction and Summary

CFAC has concurred with the init ial EPA BART analysis that the Columbia Falls facility is a BART-eligible source. The following sect ions detail the modelin g analysis that Bison performed on behalf of CFAC to comply with t he intent of 40 CFR 51, Appendix Y. This document describes the methodol ogies and results of the re gional scale and near field model analyses.

In conducting the initial regional scale and the near field BART modeling analyses, Bison closely followed the Montana Department of Environmental Quality’s (MDEQ) modeling protocol for regi onal modeling in support of the BART progr am, entitled State of Montana Draft CALPUFF BART Modeling Protocol For Federal Mandatory Class I Areas, September 2006 Draft (“Montana BART protocol”). The anal ysis also relied on guidance in the Interagency Workgroup on Air Quality Modeling (IWAQM) Phase 2 Summary Report for Modelin g Long Range Transport Impacts (EPA, 1998), and the Federal Land Managers’ Air Qual ity Related Values Workgr oup (FLAG) Phase I Report, December 2000 (“FLAG document”).

The BART modeling analysis spec ifically requires demonstrations of impacts to visibility at surrounding mandatory federal Class I ar eas. The mandatory federal Class I areas evaluated on a regional scale are:

• Glacier National Park,

• Bob Marshall Wilderness Area,

• Mission Mountain Wilderness Area, and

• Cabinet Wilderness Area.

The additional near field BART modeling analysis focused on Glacier National Park and provides the basis for this BART analysis. This near field model was developed to address the potential visibility impacts from CFAC emissions on the nearby receptors located in Glacier National Park. Given the short distance (<10 km) between CFAC and the nearest National Park Service (NPS)-gener ated receptors for Glacier National Park, the development of this refined CA LMET grid was deemed appropriate.

Visibility Impacts: The visibility impacts analysis began with the predicted emissions from the BART-eligible sources located at t he Columbia Falls facility. Regional scale modeling was completed to co nfirm that CFAC had potentia l modeled visibility impacts greater than 0.5 deciview at the surrounding Class I areas. The near field modeling analysis of Glacier National Park focused on the Class I area where CFAC could have the most visibility impacts. These near fi eld impacts were developed to establish a visibility baseline to analyze what effects, if any, different control technologies or operating practices had on visibili ty at Glacier National Park.CFAC BART Analysis pg. B-2 Appendix B The visibility impacts analyses in cluded the appropriate potential NO x , SO 2 , and PM 10 emissions from the sources modeled since all three pollut ants contribute to visibility impairment.



### 1.2 Model Selection

Selection of the appropriate di spersion model for assessing visibility impacts in Class I areas is typically based on the distance from the emitting source to the Class I area. Appendix W in 40 CFR Part 51 recommends different models for different applications and identifies appropriate models for short- and long-range impacts.

Since EPA has already established CALPUFF for the visibility analysis, the CALPUFF model was used in the present analyses of Class I visibility impacts for both the regional and near field modeling analyses.

CALPUFF is a non-steady-state Lagrangian dispersion model that simulates pollutant releases as a continuous series of “puffs.” It includes algorithms for building downwash, pollutant removal due to wet scavenging a nd dry deposition, chemical transformation, and plume fumigation. It is supported by two primary sub-programs, CALMET and CALPOST. CALMET is used in refined analyse s to create three-dim ensional wind fields based on multiple sources of geophysical and meteorological data. The output of the CALPUFF model consists of binary dat a files with information on pollutant concentrations, wet and dry flux rates, and visibility parameters. CALPOST processes these data based on specified input parameters, and reports calculated impact values.

The present CALPUFF analysis utilized the most current version of the following primary programs and pre- and post-processors obt ained from the CALPUFF developer, Atmospheric Studies Group (ASG) at:

http://www.src.com/calpuff/calpuff1.htm

. Geophysical Data Processors

• TERREL (Version 3.311, Level 030709)

• CTGCOMP

• CTGPROC (Version 2.42, Level 030709)

• MAKEGEO (Version 2.22, Level 030709)

Meteorological Preprocessors

• SMERGE (Version 5.31a, Level 040706)

• PXTRACT

• PMERGE (Version 5.31, Level 030528)

• READ62 (Version 5.52, Level 040716)

Main Models

• CALMET (Version 6.211, Level 060414)

• CALPUFF (Version 6.112, Level 060412)CFAC BART Analysis pg. B-3 Appendix B Postprocessors

• CALPOST (Version 6.131, Level 060410)

• PRTMET

• CALSUM

• POSTUTIL

The version and level identifie rs for the major modules used for this project are identified above. Electronic ex ecutable files for the primar y modules and the primary electronic input and output files associated wit h this analysis are available upon request.



### 1.3 Modeling Domain

The regional modeling domain was defined to follow t he Montana BART Pr otocol and is based on 6 kilometer (km) grid spacing with 180 grids in the easti ng direction and 95 grids in the northing direction. The r egional modeling domain is defined in a Lambert Conformal Conic (LCC) system. The LCC c oordinate system for this project has a projection origin at 44.25° N and 109.5° W and matching paral lels of latitude of 44.0° and 49.0° N. The coordinates of the southwest corner of the domain are 0.000 km easting and 0.000 km northing

. This varies from the WR AP modeling domain which defined matching parallels of lati tude of 45.0° and 49.0° N.

The near field modeling domai n follows the Montana BART Protocol and was developed with a 1 km grid spacing with 190 grids in the easting direction and 100 grids in the northing direction. The near field m odeling domain uses the same LCC system, projection origin, and matching parallels as used in the regional modeling domain. The coordinates of the southwes t corner of the dom ain are 187.278 km easting and 438.090 km northing

.



### 1.4 CALMET

CALMET, the meteorological preprocessor for CALPUFF, was used to compile and process land use data, terrain data, and me teorological data for use in the CALPUFF model program. The CALMET output files defined gridded fi elds of wind speed, wind direction, mixing heights, stab ilities, micrometeorological pa rameters, and precipitation – all parameters required for input to the CALPUFF dispersion model. The following sections provide a brief description of each of these data sets.

1.4.1 

### Land Use Data

CALMET uses specific land use data deve loped by the U.S. Geological Survey (USGS) 1 . The data files used for bot h the regional an d near field modeling analyses for this project were 1:250,000-scale files. Each land use cell, typically 200 meters square, is assigned a land use code. Using severa l data processing programs provided by ASG, the land use data were processed and comb ined with other geophysical data into a single data set for input to the CALMET model.

1 Available for download from the USGS Earth Re sources Observation and Science (EROS) web site.CFAC BART Analysis pg. B-4 Appendix B 1.4.2 

### Terrain Data

CALMET uses USGS Digital Elevation Models (DEMs) to determine the terrain elevation in the model domai n. The regional scale mode l used USGS 1:250k DEMs and the near field model used USGS 1:24K DEMs. The terrain data is preprocessed into a data set recognized by CALMET and used to help create the CALMET output file. Terrain data obtained from www.webmet.com we re used to create the appropriate files for CALMET.

1.4.3 

### Meteorological Data

CALMET output files repr esenting meteorological data for the 2001, 2002, and 2003 calendar years were prepared for the analysis in accordanc e with the Montana BART Protocol. Input meteorol ogical data cons isted of Mesoscale Model (MM5) meteorological data (processed by the CALMM5 utility program), observed hourly surface data, upper air rawinsonde dat a, and hourly precipitation data.

Mesoscale Model Data

The MM5 meteorological data for the 2001, 2002, and 2003 calend ar years obtained from the Western Regional Air Partnership (WRAP) are available at the following website: http://pah.cer t.ucr.edu/aqm/308/bart.shtml . These data are generated by Pennsylvania State University/National Cent er for Atmospheric Research mesoscale models. The mesoscale models are limited-area, nonhyd rostatic or hydrostatic, terrainfollowing sigma-coordinate models designed to simulate or predict mesoscale and regional-scale atmospheric ci rculation. The data are used as a basis for generating an “initial guess field” of multilayer wind vector s in CALMET. The meteorological data for all three years are in the CALMM5 utility pr ogram MM5 format. They reflect a spatial resolution of 36 km used in both modeling domains.

Surface Data

Hourly observed surface data for 2001, 2002, and 2003 were also obtained from the WRAP internet site. In accordance with t he Montana BART protocol, National Weather Service (NWS) hourly surface data for 39 st ations for 2001 and 36 stations for 2002 and 2003 were processed in CALMET for the regi onal modeling domain. The data files were provided in the SMERGE format and we re ready for input into CALMET.

Surface data from the followi ng locations were used for the CALMET regional modeling analysis:

• Badger Peak, MT (2001 only)

• Billings, MT

• Bismarck, ND

• Boise, ID

• Bozeman, MT

• Butte, MTCFAC BART Analysis pg. B-5 Appendix B • Casper, WY

• Coeur d’Alene, ID

• Cut Bank, MT

• Dickinson, ND

• Dillon, MT

• Estevan, SK

• Havre, MT

• Kalispell, MT

• Garfield Peak, MT (2001 only)

• Glacier National Park, MT

• Glasgow, MT

• Great Falls, MT

• Helena, MT

• Havre, MT

• Lander, WY

• Lewistown, MT

• Livingston, MT

• Medicine Hat, AB

• Miles City, MT

• Minot, ND

• Missoula, MT

• Morningstar, MT (2001 only)

• Peabody Coal, MT

• Pocatello, ID

• Rapid City, SD

• Rexburg, ID

• Riverton, WY

• Salmon, ID

• Sheridan, WY

• Spokane, WA

• Spring Creek Coal, MT

• Theodore Roosevelt National Park, ND

• Williston, ND

• Yellowstone National Park, WY

The CALMET near field modeling domain used onl y the Kalispell, MT and Cut Bank, MT surface data and included surface data from the CFAC onsite meteorolog ical station.

Upper Air Data

The Montana BART Protocol included the use of upper air data; however, the EPA BART Protocol specified that upper air dat a would not be used, and consequently the WRAP modeling omitted this data. Bison fo llowed the Montana m odeling protocol and included the upper air station data in the BART modeling analysis.CFAC BART Analysis pg. B-6 Appendix B Upper air rawinsonde data collected by sev en NWS stations were obtained from the rawinsonde data repository maintained by NOAA at http://raob.fsl.noaa.gov/. The data were obtained in the standard FSL data forma t for use in the CALMET system. The seven NWS upper air rawinsonde locations used for this project’s regional modeling domain are:

• Bismarck, ND

• Boise, ID

• Glasgow, MT

• Great Falls, MT

• Rapid City, SD

• Riverton, WY

• Spokane, WA

Great Falls, MT and Spokane, WA upper ai r rawinsonde data are the two upper air locations used in developing the near fi eld model for Glacier National Park.

Upper air data substitution and extrapolation were accomplished as needed according to ASG’s FAQ 2.3.4, which re commends temporal substitution (for example, substituting an afternoon sounding with the previous or succeeding afternoon so unding) or spatial substitution from a nearby location if s oundings are missing. For in-sounding values flagged by READ62, the data values were corrected using an in-house computer program (Fix6201.exe) developed for this pur pose. Nearly all of these flagged values were due to either (1) the pressure remaini ng constant or rising with height, or (2) the elevation remaining constant or decreasing with height. These were corrected by the inhouse program by changing the flagged values by a small amount so that the pressure decreased with height or the el evation increased with height as appropriate. For spatial substitutions, another in-house program (A djUa.exe) was used to adjust for the difference in elevation between the two lo cations. Temporal substitutions were accomplished manually using a text edit or. All raw and proce ssed data and data processing algorithms ar e available upon request.

Precipitation Data

The use of precipitation data was refer enced in the Montana and EPA BART Modeling Protocols. The WRAP modelin g omitted this precipitation data. Bison followed the modeling protocols and includ ed the precipitation station data in the BART modeling analysis.

Hourly precipitation data in NCDC’s TD-3240 format were obtained from the data set developed by MDEQ for their BA RT modeling analysis effort. All precipitation stations located within the CALMET regional sca le and near field modeling domains were extracted from the data set and were used in the CALMET analysi s. A total of 286 stations were selected for each of the th ree modeled years in the regional scale analysis and 14 stations were selected for t he near field model analysis. A complete list of precipitation stations used is available upon request.CFAC BART Analysis pg. B-7 Appendix B No precipitation data inter polation or substitution was required for this project.



### 1.5 Ozone

The ozone data provided on the WRAP websit e contained all the ozone sites in the United States and for the y ear 2002 the number of ozone sites exceeded the number of stations allowed in the CALPUFF model. Bison obtained ozone data for the following three ozone stations in the modeling domain:

• Yellowstone National Park

• Glacier National Park

• Theodore Roosevelt National Park



### 1.6 CALPUFF

CALPUFF applies mathematical algorithms to calculate po llutant concentrations at Class I receptors. CALPUFF r equires CALMET output files, source emissions, and receptor grids to model Class I impacts.

1.6.1 

### CALPUFF Parameters

CALPUFF was run in the refined mode using the MESOPUFF III chemical transformation scheme and dry and wet deposition calculations . Model settings were based on recommendations found in the M ontana BART protocol. The table below summarizes the model control file settings used for this analysis. Complete CALPUFF input files will be provided upon request.CFAC BART Analysis pg. B-8 Appendix B 

### CALPUFF Model Control File Settings
Model Parameter/Option Value Number of chemical species 9 Number of chemical species emitted 7 Vertical distribution near field Gaussian Terrain adjustment method Partial plume path adjustment Subgrid-scale complex terrain Not modeled Slug model Not used Transitional plume rise Yes Stack tip downwash Yes Vertical wind shear Yes Puff splitting Yes Chemical mechanism MESOPUFF II scheme Wet removal Yes Dry deposition Yes Dispersion coefficient method PG disp ersion coefficients for rural areas Partial plume penetration – elevated inversion Yes PDF used under convective conditions No CSPEC SO 2 , SO 4 , NO X , HNO 3 , NO 3 , SOA, EC, PMC, PMF Chemical parameters – dry gas deposition Default Size parameters – dry particle deposition Default Reference cuticle resistance (RCUTR) 30 s/cm Reference ground resistance (RGR) 10 s/cm Reference pollutant reactivity (REACTR) 8 Number of particle-size intervals (NINT) 9 Vegetation state in un-irrigated areas (IVEG) 1 Wet deposition parameters Default Ozone data input option 0 Background ozone concentration Ozo ne data: Yellowstone NP, Glacier NP, Theodore Roosevelt NP Background ammonia concentration (values specific to each Class I area analyzed) 1.22, 1.23, 1.6, 1.94, 2.29, 1.63, 1.65, 1.69, 0.98, 1.04, 1.37, 1.06 ppb SYTDEP 550 m MHFTSZ 0 JSUP 5 XSAMLEN 1.0 grid units MXNEW 99 MXSAM 99 Maximum mixing height 3,000 m Minimum mixing height 50 m NSPLIT 2 IRESPLIT Hour 17-22 = 1 ZISPLIT 100 m ROLDMAX 0.25
Notes: ppb = parts per billion s/cm = seconds per centimeterCFAC BART Analysis pg. B-9 Appendix B 1.6.2 

### Receptors

The Air Resources Division (ARD) of the Na tional Park Service (NPS) has developed a database of modeling receptors for all federal Class I areas in the United States. ARD has also developed a file conversion program to convert the data from latitude/longitude to either LCC or UTM coordinates. Receptor grids for each federally mandated Class I area of concern were develop ed using the ARD data files converted to the appropriate LCC coordinate system.

1.6.3 

### Modeled Sources - General

The visibility analyses included potential emi ssions for the CFAC BART-eligible sources and the projected emissi on reductions for the applicable pollutant controls. The BARTeligible sources that were in cluded in the analysis are:

• EU004 East Alumina Elevator,

• EU005 East Alumina Unloader,

• EU006 East Alumina Conveyor Storage,

• EU019 Therminol Oil Heating System,

• EU020 East Plant Alumina Transfer,

• EU021 East Plant Alumina Transfer,

• EU028 Dry Alumina Scrubber #5,

• EU029, Dry Alumina Scrubber #6,

• EU030, Dry Alumina Scrubber #7,

• EU031, Dry Alumina Scrubber #8,

• EU032, Dry Alumina Scrubber #9,

• EU033 Dry Alumina Scrubber #10,

• EU036 Potline #3 Roof Vents,

• EU037 Potline #4 Roof Vents,

• EU038 Potline #5 Roof Vents,

• EU043 Casting Furnaces #8 and 9, and

• EU047 Casting Pits #8 and #9.

1.6.4 

### Modeled Sources - Physical Parameters

The physical parameter for each of the s ources included in the models is based on CFAC’s emission inventory. This differs from the WRAP model inputs which included the six potline point sources incorrectly input as volume emission sources and did not include the potline roof vents. A complete source list and source parameters are included in Table 1 – attached at the end of this document.CFAC BART Analysis pg. B-10 Appendix B 1.6.5 

### Modeled Sources – Baseline Emission Rates

Class I visibility impacts dem onstrations were performed using the maximum actual emission rates for each modeled eligible s ource for 1999. These emission rates were obtained from CFAC’s current air permi ts and emission inventory analysis. The following table provides the emission rates used to demonstrate the BART impacts for regional haze:



### Baseline Modeled Emission Rates Emitting Unit Unit Description NOx (lb/hr) SO 2 (lb/hr) PM 10 (lb/hr) EU004 East Alumina El evator 0.00 0.00 0.08

EU005 East Alumina Un loader 0.00 0.00 0.08

EU006 East Alumina Conveyor Storage 0.00 0.00 0.08

EU019 Therminol Oil Heatin g System 0.00 0.00 0.00

EU020 East Plant Alumin a Transfer 0.00 0.00 0.05

EU021 East Plant Alumin a Transfer 0.00 0.00 0.05

EU028 Dry Alumina Scr ubber #5 0.00 58.22 0.09

EU029 Dry Alumina Scr ubber #6 0.00 58.22 0.09

EU030 Dry Alumina Scr ubber #7 0.00 58.22 0.09

EU031 Dry Alumina Scr ubber #8 0.00 58.22 0.09

EU032 Dry Alumina Scr ubber #9 0.00 58.22 0.09

EU033 Dry Alumina Scr ubber #10 0.00 58.22 0.09

EU036 Potline #3 Roof Vents 0.00 8.76 16.60

EU037 Potline #4 Roof Vents 0.00 8.76 16.60

EU038 Potline #5 Roof Vents 0.00 8.76 16.60

EU043 Casting Furnaces #8 and #9 - aluminum handling and natural gas combustion 1.52 0.01 1.08

EU047 Casting Pits #8 and #9 0.00 0.00 3.39CFAC BART Analysis pg. B-11 Appendix B To most accurately demonstrate the changes in visibility impacts at surrounding mandatory Class I areas, NO x , SO 2 , and PM 10 emission rates were calculated using 1999 production rates and entered into the CALPUFF models to establish a baseline case for comparison. CFAC’s current permit does not contain emission limits specific to these BART-eligible sources.

Particulate matter can be present in differ ent forms, or species, and each species can affect visibility to a differ ent degree. The speciation of PM 10 used in the BART modeling analysis assumed all t he primary source PM 10 emissions as PMF while the secondary source PM 10 emissions were split between PM F and PMC based on the particle distributions in AP-42, Table 12.1-2.

1.6.6 

### Modeled Sources – BART Control Options

The BART modeling analysis re quired that the baseline emi ssions be adjusted to reflect the predicted emission reductions for each pollutant. The following table shows the proposed scenarios used in this second step in the BART modeling analysis.CFAC BART Analysis pg. B-12 Appendix B 

### Summary of Potential BART Options

Note: Primary sources are the emissions from the alumina scrubbers while the secondary sources represent the roof vent potline emissions. Primary Sources Secondary Sources

Scenario Description SO 2 Emissions % Reduction PM 10 Emissions %

Reduction SO 2 Emissions % Reduction Scenario

Baseline Existing Controls - - - Baseline

1 Coke Sulfur Content Reduction 42% 0% 42% 1

2 Roof Vent Spray Chamber SO 2 & PM Controls 0% 0% 50% 2

2a Roof Vent Spray Chamber SO 2 & PM Controls and Sulfur Reduction in Coke 42% 0% 71% 2a

3 Wet Scrubber SO 2 Controls 90% 0% 0% 3

3a Wet Scrubber SO 2 Controls and Sulfur Reduction in Coke 94% 0% 42% 3a

4 Roof Vent Baghouse 0% 0% 0% 4

4a Roof Vent Baghouse and Sulfur Reduction in Coke 42% 0% 42% 4a

5 Wet Scrubber SO 2 Controls and Roof Vent Spray Chamber SO 2 and PM Control 90% 0% 50% 5

5a Wet Scrubber SO 2 Controls, Roof Vent Spray Chamber SO 2 and PM Control and Sulfur Reduction in Coke 94% 0% 71% 5a

6 Wet Scrubber SO 2 Control and Roof Vent Baghouse 90% 0% 0% 6

6a Wet Scrubber SO 2 Control, Roof Vent Baghouse and Sulfur Reduction in Coke 94% 0% 42% 6aCFAC BART Analysis pg. B-13 Appendix B 

### 1.7 CALPOST

Data generated by CALPUFF was entered into the CALPOST program to summarize peak Class I visibility impacts as required. For the visibility analysis, CALPOST used modeled sulfate, nitrate, and PM 10 concentration data to dete rmine the light-absorbing and light-scattering effects resulting from the project’s emissions. The method recommended and used for calculating light extinction was “Method 6: Compute extinction from speciated particulate matte r measurements.” The ba ckground extinction coefficients were calculated based on the annual relative humidity factors and data presented in Section 6.1 and Appendices C and D of t he Montana BART Protocol. Inputs to CALPOST for visibilit y processing are summarized in the following table. The attached CD-ROM contains t he CALPOST input files.



### CALPOST Visibility Control File Settings
CALPOST Parameter/Option Value Maximum relative humidity (RHMAX) 95% Included species Sulfate, nitrate, coarse particulate (as PM 10 ), and fine particulate (as PM 2.5 ) Coarse particulate extinction efficiency 0.6 (l/Mm per μg/m 3 ) Fine particulate extinction efficiency 1.0 (l/Mm per μg/m 3 ) Ammonium sulfate extinction efficiency 3.0 (l/Mm per μg/m 3 ) Ammonium nitrate extinction efficiency 3.0 (l/Mm per μg/m 3 ) Organic carbon extinction efficiency 4.0 (l/Mm per μg/m 3 ) Soil extinction efficiency 1.0 (l/Mm per μg/m 3 ) Elemental carbon extinction efficiency 10.0 (l/Mm per μg/m 3 ) Method used for background light extinction MVISBK = 6
Relative humidity From *.VIS Files Background extinction coefficients, SO 4 0.120 Background extinction coefficients, NO 3 0.100 Background extinction coefficients, PMC 3.006 Background extinction coefficients, OC 0.471 Background extinction coefficients, soil 0.501 Background extinction coefficients, EC 0.2 Extinction due to Rayleigh scattering 10.0
Notes: NO 3 = Nitrate



### 1.8 Modeling Results

1.8.1 

### Regional Haze (Visibility)

Impacts to natural background visibility, expressed in te rms of percentage change in 24-hour average background extinction ( Δ B ex ) were calculated by CALPOST. The guidelines also reference 40 CFR §51.301(a) in asserting t hat determinations must be made on a “...case-by-case basis taking into account the geographic extent, intensity, duration, frequency and time of vi sibility impairments....” The average 98 th percentile impact results are summarized in the following table.CFAC BART Analysis pg. B-14 Appendix B 

### Summary of BART Options and Visibility Impacts

Primary Sources Secondary Sources

Scenario Description SO 2 % Removal PM 10 % Removal SO 2 % Removal PM 10 % Removal Average (3 Years) of 98 th
Percentile Deciview Impact Average (3 Years) of 98 th Percentile Improvement in Deciviews (24 hr - ∆ ) Total SO 2 Removed (Ton/yr) Total PM 10 Removed (Ton/yr)

Baseline Existing Controls - - - - 3.884 0 - -

1 Coke Sulfur Content Reduction 42% 0% 42% 0% 3.267 0.617 $11,461 NA

2 Roof Vent Spray Chamber SO 2 & PM Controls 0% 0% 50% 50% 3.020 0.864 $210,057 $110,921

2a Roof Vent Spray Chamber SO 2 & PM Controls and Sulfur Reduction in Coke 42% 0% 71% 50% 2.326 1.558 $27,630 $183,546

3 Wet Scrubber SO 2 Controls 90% 0% 0% 0% 2.605 1.279 $8,817 NA

3a Wet Scrubber SO 2 Controls and Sulfur Reduction in Coke 94% 0% 42% 0% 2.477 1.407 $13,494 NA

4 Roof Vent Baghouse 0% 0% 0% 99% 2.359 1.525 NA $482,184

4a Roof Vent Baghouse and Sulfur Reduction in Coke 42% 0% 42% 99% 1.497 2.387 $162,179 $519,032

5 Wet Scrubber SO 2 Controls and Roof Vent Spray Chamber SO 2 and PM Control 90% 0% 50% 50% 1.549 2.335 $16,894 $222,262

5a Wet Scrubber SO 2 Controls, Roof Vent Spray Chamber SO 2 and PM Control and Sulfur Reduction in Coke 94% 0% 71% 50% 1.461 2.423 $21,155 $294,888

6 Wet Scrubber SO 2 Control and Roof Vent Baghouse 90% 0% 0% 99% 0.817 3.067 $84,446 $538,398

6a Wet Scrubber SO 2 Control, Roof Vent Baghouse and Sulfur Reduction in Coke 94% 0% 42% 99% 0.607 3.277 $83,549 $575,265

## APPENDIX C: BART COST ANALYSES