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 11th Avenue 

Helena, MT 59601 

(406) 442-5768 

www.bison-eng.com 

November 5, 2007
CFAC BART Analysis 11/5/07 pg. ii 

Project #: CFA207819

TABLE OF CONTENTS 

1.0 INTRODUCTION............................................................................................... 1-1 

1.1 Summary ................................................................................................ 1-1 

1.2 Background and Purpose ....................................................................... 1-2 

1.3 Site Location and Description ................................................................. 1-3 

2.0 PROCESS DESCRIPTION ............................................................................... 2-1 

3.0 BART ANALYSIS: MODEL AND SOURCE SELECTION................................. 3-1 

3.1 Initial BART Emission Data..................................................................... 3-1 

3.2 Initial EPA/WRAP CFAC BART Emissions Summary............................. 3-1 

3.3 CFAC BART Emissions Summary.......................................................... 3-2 

3.4 CFAC BART Near Field Model Addition ................................................. 3-2 

3.5 CFAC BART Model Results Comparison................................................ 3-3 

3.6 SO2 Applicable Units Emissions ............................................................ 3-3 

3.7 NOX Applicable Units Emissions............................................................. 3-4 

3.8 PM10 Applicable Units Emissions ........................................................... 3-5 

4.0 BEST AVAILABLE RETROFIT TECHNOLOGY REVIEW................................. 4-1 

 4.1 Summary ................................................................................................ 4-1 

 4.1.1 Affected Units............................................................................... 4-2 

 4.1.2 Applicable Pollutants.................................................................... 4-3 

 4.2 BART Analysis Methodology .................................................................. 4-3 

 4.3 SO2 and PM10 BART Analysis for the Potlines (Primary and 

 Secondary Sources) ............................................................................... 4-4 

 4.3.1 Step 1 – Identify All Available SO2 Retrofit 

 Control Technologies ................................................................... 4-5 

 4.3.2 Step 2 – Eliminate Technically Infeasible SO2 Control Options.... 4-8 

 4.3.3 Step 3 – Evaluate Control Effectiveness of Remaining 

 Control Technologies ................................................................. 4-12 

 4.3.4 Step 4 – Evaluate Impacts and Document Results .................... 4-12 

 4.3.5 Step 5 – Evaluate Primary Controls Visibility Impacts................ 4-16 

 4.3.6 Step 5 – Evaluate Secondary Controls Visibility Impacts........... 4-16 

 4.3.7 Select SO2 BART ....................................................................... 4-16 

 4.4 BART Analysis for PM10 from the Potline Roof Vents........................... 4-17 

 4.4.1 Step 1 – Identify Available Particulate Control Technologies ..... 4-17 

 4.4.2 Step 2 – Eliminate Technically Infeasible PM10 

 Control Options .......................................................................... 4-18 

 4.4.3 Step 3 – Evaluate Control Effectiveness of Remaining 

 PM10 Control Technologies ........................................................ 4-19 

 4.4.4 Step 4 – Evaluate Impacts and Document Results .................... 4-19 

 4.4.5 Step 5 – Evaluate PM10 Visibility Impacts .................................. 4-21 

 4.4.6 Select Secondary Source PM10 BART ....................................... 4-21 

 4.5 Select Overall BART ............................................................................ 4-22 

 4.5.1 Summary of Impacts – Section E, Item 1................................... 4-22 
CFAC BART Analysis 11/5/07 pg. iii 

Project #: CFA207819

 4.5.2 Selecting a “Best” Alternative – Section E, Item 2...................... 4-31 

 4.5.3 Consideration of Affordability – 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 Emissions ...................................... 3-2 

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

Table 3-4: SO2 Sources Analyzed for BART............................................................ 3-4 

Table 3-5: PM10 Sources Analyzed for BART .......................................................... 3-5 

Table 4-1: Sources Analyzed for BART ................................................................... 4-3 

Table 4-2: Summary of SO2 Control Technology Efficiency................................... 4-12 

Table 4-3: Summary of Primary SO2 Emissions Cost and Visibility Impacts.......... 4-15 

Table 4-4: Summary of Secondary SO2 Emissions Cost and Visibility Impacts..... 4-16 

Table 4-5: Secondary Emissions (Potline Roof Vent) PM10 Control 

 Technology Effectiveness ..................................................................... 4-19 

Table 4-6 Summary of Secondary PM10 Emissions Cost and Visibility Impacts ... 4-21 

Table 4-7: Summary of Potential BART Scenarios ................................................ 4-24 

Table 4-8: Summary of SO2/PM10 Emissions Cost Analysis and 

 Visibility Impacts ................................................................................... 4-26 

Table 4-9: Potential BART Cost-Effectiveness Scenarios...................................... 4-28 

LIST OF TABLES 

Figure 4-1: Annualized Cost vs. Deciview 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 Analyses 
CFAC BART Analysis 11/5/07 pg. 1-1 

Project #: CFA207819

1.0 INTRODUCTION 

1.1. Summary 

Columbia Falls Aluminum Company, LLC (CFAC) is submitting a Best Available Retrofit 

Technology (BART) analysis to the U.S. Environmental Protection Agency Region VIII 

office (EPA). EPA submitted a letter dated June 22, 2007, to CFAC requiring the 

preparation of a BART analysis for their aluminum ore reduction plant located near 

Columbia Falls, Montana. The letter was received by CFAC on June 27, 2007. The 

letter notified CFAC that EPA 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 cause visibility degradation in a nearby Class I 

area (Glacier National Park). The notification 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 EPA will develop the analysis instead. 

CFAC chose to analyze the EPA modeling results and prepare a BART engineering 

analysis to submit to EPA. A copy of the EPA letter is included here as Appendix A. 

CFAC analyzed the existing emission units for specific BART eligibility2, and determined 

that there are nine sulfur dioxide (SO2) emission sources, three particulate matter 

(PM10) sources and zero nitrogen oxides (NOx) emission sources that must be 

addressed by a BART analysis. Table 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 constructed 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 subject 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 Department 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 Addressed by CFAC BART Analysis

PTE (Ton/year) 

Emission Unit 

SO2 PM10 NOx 

BART 

Analysis 

Performed 

(Yes or No) 

028 – Dry Alumina Scrubber #5 255 Nil1 Nil1 Yes 

029 – Dry Alumina Scrubber #6 255. Nil1 Nil1 Yes

030 – Dry Alumina Scrubber #7 255 Nil1 Nil1 Yes

031 – Dry Alumina Scrubber #8 255 Nil1 Nil1 Yes

032 – Dry Alumina Scrubber #9 255 Nil1 Nil1 Yes

033 – Dry Alumina Scrubber #10 255 Nil1 Nil1 Yes 

036 – Potline 3 Roof Vents 38.4 72.7 Nil1 Yes 

037 – Potline 4 Roof Vents 38.4 72.7 Nil1 Yes 

038 – Potline 5 Roof Vents 38.4 72.7 Nil1 Yes 

043 – Casting Furnaces #8 and #9 Nil1 Nil1 6.7 No

047 – Casting Pits #8 and #9 Nil1 14.9 Nil1 Yes 1

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

CFAC performed an SO2 BART analysis on Potlines 3, 4 and 5 with their associated dry 

alumina scrubbers (numbers 5-10) and roof vents. CFAC determined that there are no 

SO2 controls or process alterations that meet the definition of best available retrofit 

technology. See Section 4.3 of this report for the SO2 BART analysis. 

CFAC performed a PM10 BART analysis on the roof vents for Potlines 3, 4 and 5. CFAC 

determined that there are no PM10 controls or process alterations that meet the 

definition of best available retrofit technology. See Section 4.4 for the potline PM10

BART analysis. 

CFAC determined that there are no BART-eligible 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 Clean Air Act in 1977 to include a new Section 169A 

and 169B for the purpose of protecting visibility in certain scenic areas. The areas 

afforded this visibility protection are identified 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 document, EPA promulgated 40 CFR 51.308(e) which requires certain 

types of existing stationary sources to install best available retrofit technology (BART). 

The term BART is defined in §301 as follows: 

Best Available Retrofit Technology (BART) means an emission limitation based on the 

degree of reduction achievable through the application 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 available, the costs of compliance, the energy and non-air 

quality environmental impacts of compliance, any pollution control 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 reasonably be anticipated to result from the use of 

such technology. 

As noted in Section 1.1 above, EPA has identified the CFAC aluminum ore reduction 

plant as an ‘existing stationary facility’4

 that is subject to the BART requirements. EPA 

has further identified guidelines for identifying BART-eligible sources and suggested 

methodologies to be employed for conducting a BART analysis. These guidelines are 

codified in 40 CFR 51, Appendix Y. 

It is the purpose of this document to fulfill 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 CFR 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, Township 30 North, Range 20 

West, Flathead County, Montana, with approximate UTM coordinates of Zone 11, 

Easting 712.2 km, and Northing 5,363.8 km. The elevation 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 description information is also on file with MDEQ. 

Copies of the maps and descriptions 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 (Al2O3), 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 electrode) and 100-ton cathodes (negative 

electrode). The electrolytic reduction of aluminum oxide is represented by the following 

reactions: 

Al2O3 + 11⁄2C → 2Al + 11⁄2 CO2 ↑

2Al2O3 + 6C → 4Al + 6CO ↑ 

The cells or “pots” are housed in buildings called potrooms. Two potrooms are 

connected electrically in series to form one potline. At CFAC there are ten potrooms that 

comprise the five potlines. Alumina is fed into a molten bath 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 the casting department, where 

it is cast into ingots of various sizes, shapes 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 supply sulfur dioxide (SO2), nitrogen oxides (NOx), and 

particulate matter less than 10 microns (PM10) 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 was 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 determination 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 identified BART eligible emitting 

units in the initial BART applicability determination. Table 3-1 summarizes the 14 

sources of SO2 and NOX and PM10 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 SO2 PM10 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. Example: 58.22 lbs/hr x 8760 hrs/yr / 2000 lbs/ton = 255 tons/yr 
CFAC BART Analysis 11/5/07 pg. 3-2 

Project #: CFA207819

3.3 CFAC BART Emissions Summary 

CFAC, with the assistance of Bison Engineering, reviewed the initial EPA/WRAP BART 

applicability determination. The WRAP model included six potline point sources (dry 

alumina scrubber stacks) as six volume sources, and did not include 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 modeling analyses. Emitting Unit EU049 (Sheet ingot saw) 

was not included in any modeling analysis because there are no emissions associated 

with it. The additional three sources included in the CFAC models are the potline roof 

vents. The 17 sources SO2, NOX, and PM10 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 SO2 PM10 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. Example: 58.22 lbs/hr x 8760 hrs/yr / 2000 lbs/ton = 255 tons/yr 

3.4 CFAC BART Near Field Model Addition 

A near field model was developed to address the potential CFAC visibility impacts on 

the nearby receptors located in Glacier National Park (GNP). The WRAP BART 

applicability determination recognized the difference 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 greater than 50 km and less than 
CFAC 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 significantly 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 summaries detailed in Tables 3-1 and 3-2 above 

were used in the modeling analysis for the CFAC BART applicability determination. 

The EPA applicability determination used an incomplete emission inventory to perform 

the regional scale CALPUFF modeling analysis to conclude BART is applicable to 

CFAC. The complete emission inventory in Table 3-2 was used in both the regional 

scale CALPUFF model analysis to compare to the EPA/WRAP applicability 

determination; and the near field modeling analysis for Glacier National Park and the 

subsequent cost/benefit analysis. Please see Appendix B for a complete modeling 

discussion. 

A comparison of the 98th 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 (98th percentile) 

Modeled Emitting Units 

2001 

(Deciview 

change) 

2002 

(Deciview 

change) 

2003 

(Deciview 

change) 

3 year 

Average 

(Deciview 

change) 

EPA/WRAP Regional Scale 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 visibility impacts were greater in the CFAC regional model 

when the additional 3 potline roof vent emission units were added to the sources from 

the EPA/WRAP model. The table also shows that the CFAC near field model, with the 

same emission sources as the CFAC regional model, shows substantially lower visibility 

impacts than the CFAC regional model. CFAC believes the near field model is a more 

refined and representative model for predicting close (<10 km) visibility impacts than 

either the EPA/WRAP or CFAC regional model. 

3.6 SO2 Applicable Units Emissions 

Potlines 3, 4, and 5 each consist of two potrooms. Each potroom is equipped with an 

emission collection system to route pot emissions to a bank of six dry alumina 
CFAC BART Analysis 11/5/07 pg. 3-4 

Project #: CFA207819

scrubbers intended to capture fluoride, hydrocarbon and particulate emissions. The 

emissions from these scrubbers are considered primary emissions by CFAC. These 

scrubbers are assumed to be ineffective for controlling SO2 emissions. The emission 

unit numbers for each alumina scrubber are EU028 through EU033. By calculation, the 

scrubbers each emit 255 tons of SO2 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 calculation, each emit 38.4 tons of SO2 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 SO2-emitting units subject to further BART 

analysis. The table also shows the current emissions control associated with those 

units. 

Table 3-4: SO2 Sources Analyzed for BART 

Source 

Current SO2 Source 

Control 

Current SO2

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 NOx 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 furnaces. Under 40 CFR 51, Appendix Y, EPA 

established a de minimis level for emission units and pollutants that constitute BART 

eligibility. Appendix Y explains de minimis levels of emission for pollutants at BARTeligible sources: 

“.........De Minimis values should be identified with the purpose of 

exluding only those emissions so minimal that they are unlikely to 

contribute to regional haze. Any de minimis values that you adopt must 

not be higher than the PSD applicability levels: 40 tons/yr for SO2 and 

NOx and 15 tons/yr for PM10. These de minimis levels may only be applied 

on a plant-wide basis.” 

CFAC’s plant-wide NOx 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 PM10 Applicable Units Emissions 

Potlines 3, 4, and 5 each consist of two potrooms. Each potroom is equipped with an 

emission collection system to route pot emissions to a bank of six dry alumina 

scrubbers intended to capture fluoride, hydrocarbon and particulate emissions. These 

scrubbers incorporate high efficiency baghouses as part of the design and are 

considered 99%+ effective at capturing PM10 emissions. The emission unit numbers for 

each alumina scrubber are EU028 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 PM10 control is already the best possible at 99+% control and further 

improvement could not be practically accomplished. The current PM10 emission rates 

are so low that visibility impacts from these sources are negligible, and further 

reductions could not improve upon that. Therefore, the primary PM10 emission sources 

from the potlines have not been analyzed for BART. 

Potlines 3, 4, and 5 each have dual roof vents. The emission unit numbers for the roof 

vents are EU036, EU037, and EU038. As shown in Table 3-2, each roof vent emits 72.7 

tons/year of PM10; therefore, the roof vents warrant further analysis for BART. 

EU47, Casting Pits #8 and #9, have an estimated PM10 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% PM10 control efficiency, had a negligible 

impact on visibility. Therefore any control implemented on the source could not produce 

a significant visibility improvement. Therefore, EU47 was not analyzed further in this 

BART analysis. 

Table 3-5 provides a summary of the three emitting units eligible for further BART 

analysis. The table also shows the current emissions control associated with those 

units. 

Table 3-5: PM10 Sources Analyzed for BART 

Source Current Source Control 

Current PM10

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 72.7 
CFAC 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 sources that meet all of the following criteria: 

1. The source is in one of 26 specific 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 potential 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 visibility 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 source 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) requires that SIPs for visibility protection must apply BART 

to certain large emitting sources. EPA identified 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 that 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 modeling 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 “Existing 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 provisions 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, letter, CFAC has conducted a BART analysis 

using EPA-recommended methodologies and dispersion modeling recommendations 

found in 40 CFR 51, Appendix Y, more specifically the CALPUFF dispersion model, to 

assist with the proposed BART determination. The purpose of the modeling analysis is 

to determine the visibility improvement expected 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 having (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). See Table 3-1 for a list of the 

18 potential BART-eligible emitting units. 

Nine of the potential BART-eligible sources have the potential to cause visibility 

impairment, and a detailed BART engineering analysis has been performed on these 

sources. These sources are potlines 3, 4 and 5 with their associated 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 lists 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 SO2 PM10 NOx SO2 PM10 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 analyzed in this BART analysis are: 

y Sulfur dioxide (SO2), and 

y Particulate matter less than 10 microns (PM10). 

PM10 is used as an indicator for particulate matter. As emissions of PM10 include the 

components of PM2.5 as a subset, there is no need to have separate 250-ton thresholds 

for PM10 and PM2.5.

4.2 BART Analysis Methodology 

In general terms, EPA has identified a methodology for conducting a BART analysis that 

is similar to the Best Available Control Technology analyses conducted under the PSD 

permitting program (40 CFR 51.166 and elsewhere). For BART, the methodology is 

more refined to include pollutants related to visibility impairment and to include an 

analysis of the impacts the proposed technology has on the visibility directly. 

The BART methodology is a case-by-case procedure. The BART methodology chosen 

for this analysis follows the guidelines established by EPA in 40 CFR 51, Appendix Y. 

Hereafter these guidelines will be referred to as either the “Appendix Y Guideline” or 

simply “Appendix Y.” Appendix Y suggests that the case-by-case BART analysis should 

follow the five steps below (Section 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 all10 available retrofit control technologies; 

 Step 2 - Eliminate technically 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 released in significant quantities. BART for 

SO2 and PM10 emissions from the potlines, essentially the only source of these 

compounds, will be addressed first. 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 Appendix Y, CFAC reviewed the New Source Performance Standards 

(NSPS) Subpart S for primary aluminum reduction plants to determine if any control 

technologies or emission restrictions were applicable to new facilities. This review 

showed that NSPS for primary aluminum reduction plants applies only to fluoride 

emissions and opacity. 

To facilitate the following BART determinations, CFAC queried the EPA RACT-BACTLAER Clearinghouse (RBLC) database for listings of pollutant emission limits and 

required control technologies at other aluminum production facilities across the country. 

The information generated by these queries serves as a helpful guideline to indicate 

expected emission rate ranges and control technologies that may have been 

successfully applied at facilities similar to the CFAC plant. 

4.3 SO2 and PM10 BART Analysis for the Potlines (Primary and Secondary 

Sources) 

For the purposes of this BART analysis, CFAC has chosen to analyze SO2 and PM10

simultaneously. Although the primary and secondary sources can have independent 

controls, they are all part of the same source (the potlines), and most of the control 

options intertwine SO2 and PM10 control. Therefore, any visibility improvements have 

been modeled using both the SO2 and PM10 reductions achieved by the same control 

system. 

SO2 emissions in the CFAC electrolytic reduction plant are generated by oxidation of 

sulfur-bearing coke and pitch used in the manufacture of aluminum. The contract 

specifications for sulfur content (% by wt) of the anode raw materials are shown below: 

 

10 Appendix Y notes that the term “all” refers to identifying the most stringent option and a reasonable set 

of options for analysis that reflect a comprehensive list of options. It is not necessary (according to 

Appendix Y) to list all permutations of available 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 consumption of sulfur-bearing carbon anodes 

accounts almost all of the SO2 released in the process. 

It is assumed that 100% of the sulfur present in the raw anode materials is converted to 

SO2. CFAC estimates that 93% of the primary pot exhaust gas, which contains the SO2, 

is collected by exhaust hoods and ducted to the dry alumina scrubbers. Secondary pot 

gases, the 7% of pot exhaust gases not collected by the exhaust hoods, are mixed with 

ambient potroom air and discharged through the roof vents. This secondary emission 

source has a very large volume with a very low concentration of SO2. 

4.3.1 Identify All Available SO2 Retrofit Control Technologies – 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 limits and the control 

technologies approved to achieve those limits. Another source of information regarding 

potentially applicable SO2 control technology for aluminum manufacturing is EPA’s AP42 for Primary Aluminum Production (Chapter 12, Section 1). Finally, CFAC has used 

an independent engineering company with considerable aluminum plant experience to 

identify and judge applicability of potential control strategies. The following were 

identified as potentially applicable for controlling SO2 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 SO2 scrubber; 

(v) Dual alkali Na/Ca process wet SO2 scrubber; 

(vi) Roof vent spray chamber SO2 controls. 

Process note pertaining to all candidate primary SO2 removal processes: 

The most prevalent FGD processes involve removing SO2 from combustion exhaust 

streams such as those typically found in large coal-fired generation stations burning 

high sulfur (1-3%) coal. SO2 removal processes in these installations have two 

characteristics quite different from those in the primary and secondary gases from 

electrolytic aluminum reduction plants: 

• Higher concentrations of SO2 (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/mass discharge rates for primary and 

secondary emission sources, CFAC estimates the following emission source gas 

conditions: 

Typical SO2 Emissions from Dry Alumina Scrubbers and Roof Monitors

Emission Source 

Volume 

(ACFM) 

SO2 

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 SO2 concentrations in aluminum process flue gases (especially in 

the secondary gases) are much lower than those for standard fossil fuel flue gas. 

Control Technology Description: 

(i) Proper Design and Operation

The CFAC facility has been in operation since the 1950s and has followed the 

advancements in aluminum reduction technology. CFAC believes the current operation 

has efficiencies and operational procedures that are similar to other plants in the US. 

CFAC believes the facility has proper design and operation procedures. 

(ii) Process Alterations – Reducing Primary and Secondary Emissions

1. Improved Reduction Process (Anode) Efficiencies

The aluminum oxide reduction process consumes anode carbon to form 

CO2 along with some CO. Any CO produced represents sub-optimal 

oxidation of carbon which corresponds to increased carbon consumption; 

therefore, SO2 emissions. A process modification which increased the 

CO2/CO ratio would have the effect of reducing SO2 emissions. 

 2. Improved Pot Line Fume Collection Efficiency

CFAC estimates overall fume collection efficiency at 93%. Therefore, 93% 

of the SO2 emissions are currently ducted to the dry alumina scrubber. 

This serves as a collection method of SO2, which could be routed to an 

effective SO2 scrubber. Since 7% of the SO2 escapes collection and is 

vented through the roof vents, the total potential for SO2 emission 

reduction to be achieved by 100% collection is 7% of the 1645 tpy of SO2
CFAC BART Analysis 11/5/07 pg. 4-7

Project #: CFA207819

generated, or approximately 115 tons. This assumes 100% SO2 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 percent sulfur than is currently used. 

By reducing the amount of sulfur in the coke and pitch used in the 

process, the generation of SO2 is reduced proportionally. 

(iii) Dry Sorption/Spray Dry Process Applied to the Primary Sources

The term Spray Dryer Absorber (SDA) here refers to those technologies that inject a 

dry, semi-dry or semi-wet alkaline 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 SO2 emissions. An SDA could be applied to 

the gas stream currently ducted to the dry alumina scrubbers. 

The resulting reactants (along with process particulates and spent reagent) are 

removed as dry solids. The simplicity of this process makes it attractive in 

boiler/furnace retrofit applications because, in most applications, baghouse/ESP 

collection/disposal mechanisms are already in place. SO2 removal efficiencies are 

generally limited to ~70%. Optimum SO2 reductions using limestone require significant 

excess reactants (75%) and very finely ground reagents. The flue stream is cooled by 

evaporation of the injected slurry and the SO2 removal reaction takes place on the 

surface of the finely divided solid alkali at temperatures between 350oF and 1000oF. 

(iv) Single Alkali Wet SO2 Scrubber Applied to the Primary Sources

A wet SO2 scrubber is one that uses an aqueous chemical system. These systems have 

been successfully employed in various industries to remove SO2 from concentrated 

exhaust streams. These systems 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 SO2-laden gas enters at the bottom 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, caustic soda/soda ash or a mixture of slaked 

lime and alkaline fly ash, although many other sorbent processes exist. Absorption of 

SO2 is accomplished by the contact between the gas and the reagent slurry. The sulfur 

oxides react with the sorbent, forming a wet mixture of alkali (sodium or calcium) sulfite 

and sulfate. 

The slurry combines with the SO2-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 SO2, the waste reacted sludge is disposed of, 

recycled or regenerated, or, in some cases, 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 process, feed stock reagents are not regenerated or 

recovered and reaction by-products (sodium sulfates) are typically of little commercial 

value and must ultimately be treated as controlled landfill material. This process 

achieves good efficiencies at temperatures between 200-1000oF, particularly with 

caustic soda. 

(v) Dual Alkali Wet SO2 Scrubber Applied to the Primary Sources

The Dual Alkali process has not been as widely accepted in boiler/furnace applications 

as the limestone/lime slurry processes, but has the process advantage of separating the 

SO2 absorption and sulfite/sulfate 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 precipitation stage and are recirculated to the primary scrubbers. More process steps are required, but removal 

efficiencies over 90% can be obtained with sodium based reagents even at lower flue 

gas temperatures (200-300oF). 

(vi) Roof Vent SO2 Controls Applied to the Secondary Sources

CFAC has investigated the use of spray chamber type roof vent controls. This system 

consists of roof-mounted water spray chambers (no other reactants used) to capture 

and remove SO2 and PM10 from the roof vent exhaust stream. Parallel systems of 

multiple 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. SO2 is readily absorbed in the 

airborne liquid droplets and particulate is captured by impingement. Efficiencies of 50% 

for both SO2 and particulate have been reported. 

4.3.2 Eliminate Technically Infeasible SO2 Control Options – Step 2 

This section discusses the feasibility or infeasibility of each technology identified in 

Section 4.3.1 above. The decision regarding whether a particular technology was 

deemed “technically feasible” was based on discussions found in 40 CFR 51, Appendix 

Y. Appendix Y describes guidelines for BART 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 technologies 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 describe 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 through 
CFAC BART Analysis 11/5/07 pg. 4-9

Project #: CFA207819

commercial channels. In the alternative, the technology is “available” within the common 

sense meaning of that term. 

Commercially available is further discussed in the Appendix Y Guideline as having 

attained either stage (5) or (6) of the following 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 Guideline 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 Guideline, infeasible technologies are rejected where appropriate. 

Those technologies deemed infeasible are no longer discussed in further sections of 

this BART analysis. 

(i) Proper Design and Operation

Proper design and operation is clearly feasible 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 last 50 years have reduced the carbon 

consumption from approximately 0.7 lb of carbon per pound of Al in the 

1950s to present levels of approximately 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. Significant process improvements over 

the current efficiency, while highly desirable, are very difficult to achieve 

and must be categorized as technically 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 analysis. No further discussion of this 

technology will be presented. 

 2. Improved Pot Line Fume Collection Efficiency

The current overall efficiency of the fume collection system at CFAC is 

estimated at 93%. CFAC believes that the design of the current exhaust 

hoods is typical of the industry in the US. CFAC is not aware of exhaust 

hoods with newer design or better capture efficiencies for vertical stud 

soderberg aluminum reduction facilities. CFAC believes that added 

exhaust hood capture efficiency would be experimental in nature and 

could only come at the expense of access to the pots for normal 

operations and interference with 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, most smelters use a petroleum coke 

with approximately 2.5% sulfur 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 possible. 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 the 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, although low in sulfur, is not the best 

petroleum coke for aluminum production. To improve anode operation, 

which would reduce anode carbon use 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 content of 0.7%. CFAC is not aware of 

any pitch available with a lower sulfur content. 

Conclusion: Using a coke with a lower sulfur content is considered feasible for 

purposes of Step 2 in this BART analysis. Using a pitch with a lower 

sulfur content is not considered feasible 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 Process Applied to the Primary Sources

The “Dry Sorbent” and “Spray Dry” processes are primarily designed for treatment of 

high-temperature, high-sulfur content combustion flue gases such as those found in 
CFAC 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 temperature 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 scrubber exit (260°F and 100-

300 ppm of SO2) are too cool and too dilute for these “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 350oF. 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 analysis. No further discussion of this 

technology will be presented. 

(iv) Single Alkali Wet SO2 Scrubber Applied to the Primary Sources

The single alkali “throw-away” processes 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 compounds is more than offset by their higher 

materials cost coupled with their one-pass consumption. In the case of the sodiumbased processes, disposal of the soluble sulfate waste products may pose groundwater 

leaching issues. The calcium-based systems require tight process control to prevent 

scaling problems in flues and scrubbers. Sodium-based systems operate with less 

scaling and freeze at a lower temperature than simple slurries such as lime or 

limestone. All of the wet scrubber designs suffer from freezing issues when operated in 

a northerly climate with the cold temperatures normally found at the CFAC facility in 

wintertime. In fact, EPA considered this 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 SO2 Scrubber Applied to the Primary Sources

The Dual Alkali process also facilitates the precipitation 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. All of the wet scrubber designs 

suffer from freezing issues when operated in a northerly climate with the cold 

temperatures normally found at the CFAC facility in wintertime. 

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

BART analysis. 

(vi) Roof Vent SO2 Controls Applied to the Secondary Sources

Aluminum industry installations have successfully used spray chambers to capture 

fugitive pot line gases. One process reviewed used a water spray (no reagents) to 
CFAC BART Analysis 11/5/07 pg. 4-12

Project #: CFA207819

achieve ~50% removal of SO2 and ~50% removal of total particulates. An advantage of 

this process over cloth filter baghouses is that this process not only removes particulate 

fluorides, but gaseous fluoride as well. Operation of this wet scrubber may be limited to 

non-winter months. It is anticipated 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 Remaining Control Technologies – Step 3 

Of the alternative SO2 control technologies identified above, proper potline design and 

operation, a process alteration (coke sulfur content reduction), single alkali wet SO2

scrubbers, dual alkali wet SO2 scrubbers, and roof vent SO2 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 control effectiveness of the remaining control 

technologies. 

Table 4-2: Summary of SO2 Control Technology Efficiency

Control Option Efficiency (%) 

Dual Alkali Wet SO2 Scrubber 90% on primary sources 

Single Alkali Wet SO2 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 direct 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 was 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 greater than the cost of the currently used 1.5% sulfur 
CFAC 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/short ton = $7,079,680/year. 

Coke Sulfur Content Reduction Energy Impacts

CFAC is not aware of any indirect or direct energy impacts associated with using low 

sulfur coke. 

(b) Single Alkali Wet SO2 Scrubber Impacts 

Single Alkali Wet SO2 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 problems in flues and scrubbers. The highest 

SO2 recovery rates are obtained with sodium-based processes; however, in a single 

pass process, feed stock reagents 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 facilities. The impacts of these effects have not 

been studied. 

Single Alkali Wet SO2 Scrubber Economic Impacts

CFAC has calculated the cost-effectiveness for employing a single alkali wet SO2

scrubber for SO2 control, with the results presented in Table 4-3 below. CFAC has 

utilized the EPA’s Air Pollution Cost Control Manual to estimate costs of SO2 scrubber 

control. The manual provides the EPA’s recommended methodology for estimating the 

costs for add-on control technology. To calculate the cost-effectiveness of a control 

technology in dollars per ton ($/ton), the following factors are used: 

Cost-effectiveness ($/ton) = [(total capital investment x capital recovery factor 

{CRF}) + Direct Annual Cost + Indirect Annual Cost]/(tons SO2 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) = multiplier 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 baseline of proper design and operation. Details of the 

single alkali wet SO2 scrubber cost analysis can be found in Appendix C. 

Single Alkali Wet SO2 Scrubber Energy Impacts

EPA Publication EPA-542/F-03-034 states that modern wet scrubber designs result in 

an energy penalty of less than 1% of the total plant energy consumption. This is a minor 

energy impact which is only further considered in the economic analysis. 

(c) Dual Alkali Wet SO2 Scrubber Impacts 

Dual Alkali Wet SO2 Scrubber Environmental Impacts

The dual alkali process facilitates the precipitation 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 alkali 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 SO2 Scrubber Economic Impacts

CFAC has calculated the cost-effectiveness for employing a dual pass alkali wet SO2

scrubber for SO2 control, with the results presented in Table 4-3 below. CFAC has 

utilized the EPA’s Air Pollution Cost Control Manual to estimate costs of the dual pass 

system.

Dual Alkali Wet SO2 Scrubber Energy Impacts

EPA Publication EPA-542/F-03-034 states that modern wet scrubber designs result in 

an energy penalty of less than 1% of the total plant energy consumption. This is a minor 

energy impact which is only further considered in the economic analysis. 

(d) Roof Vent SO2 Control Impacts 

Roof Vent Control: Water Spray Chamber Environmental Impacts

This system acts as a simplified wet scrubber, 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 SO2 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 typically of little commercial value and must 

be landfilled. In the case of this sodium-based process, disposal of the soluble sulfate 

waste products, either on-site or in a landfill 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 water 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 

SO2 control, with the results presented in Table 4-4 below. CFAC has utilized EPA’s Air 

Pollution Cost Control methodology to estimate 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 states that modern wet scrubber designs result in 

an energy penalty of less than 1% of the total plant energy consumption. This is a minor 

energy impact which is only further considered 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 years used to calculate the annualized costs. 

Primary Sources 

There are two separate sources of SO2 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 feasible controls for the primary SO2-emitting sources. 

Table 4-3: Summary of Primary SO2 Emissions Cost and Visibility Impacts 

Glacier Nat'l Park 

Control Option 

Capital 

 Cost 

Annualized 

Costa

Efficiency 

(%) 

SO2

Emitted

(tpy) 

SO2

Removed 

(tpy) 

Costb

($/ton) 

SO2

Impact 

(deciview) 

Deciviews 

Removed 

(24 hr - ∆) 

Cost 

($/dc) 

Dual Alkali 

Wet SO2

Scrubber $50,581,438 $12,142,136 90% 153 1,377 $8,817 2.605 1.279 $9,490,987 

Single Alkali 

Wet SO2

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 ton x 44,248 tpy 

(1999 production) = $7,079,680/yr. 

b

Note: The cost per ton of SO2 removed from coke sulfur content reduction is calculated from using the facility-wide SO2 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 SO2-emitting sources. 

Table 4-4: Summary of Secondary SO2 Emissions Cost and Visibility Impacts 

Glacier Nat'l Park 

Control 

Option 

Capital 

 Cost 

Annualized 

Cost 

Efficiency 

(%) 

SO2

Emitted

(tpy) 

SO2 

Removed 

(tpy) 

Cost 

($/ton) 

SO2

Impact 

(deciview) 

Deciviews 

Removed 

(24 hr - ∆) 

Cost 

($/dc) 

Roof Vent 

Spray 

Room SO2

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 ton x 44,248 tpy 

(1999 production) = $7,079,680/yr. 

b

Note: The cost per ton of SO2 removed from coke sulfur content reduction is calculated from using the facility-wide SO2 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 using the CALPUFF model to predict visibility impacts of 

the identified potentially applicable SO2 control technologies, using the 98th 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 using the CALPUFF model to predict visibility impacts of 

the identified potentially applicable SO2 control technologies, using the 98th percentile 

visibility result as recommended by EPA. The 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 Area. Details of the modeling are found in 

Appendix B of this document. 

4.3.7 Select SO2 BART 

The purpose of BART is to apply a control technology 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, efficiency and visibility improvement from any SO2

and PM10 controls is inter-related. Section 4.4 analyzes the control options for the 

secondary PM10 emissions. An analysis was performed using the combination of SO2
CFAC BART Analysis 11/5/07 pg. 4-17

Project #: CFA207819

primary and secondary controls in conjunction with PM10 secondary controls to 

determine an overall BART selection. The combination of SO2 and PM10 controls 

showed possible scenarios for visibility improvements. See Section 4.5 for the overall 

BART selection. 

4.4 BART Analysis for PM10 from the Potline Roof Vents 

4.4.1 Identify Available Particulate Control Technologies – Step 1 

EPA’s RBLC describes several permitted aluminum plants and lists their pollutant 

emission limits and the control technologies approved to achieve those limits. Another 

source of information regarding potentially applicable PM10 control technology for 

aluminum manufacturing is EPA’s AP-42 for Primary Aluminum Production (Chapter 12, 

Section 1). The PM10 emissions from the primary emitting sources are very small and 

had a negligible modeled impact on visibility; however, the PM10 emissions from the 

secondary emitting sources were predicted by the model to cause the most significant 

degradation to the visibility in Glacier National Park and are further analyzed below. 

The secondary particulate emissions are fugitive emissions released from the roof vents 

on the top of the potline buildings. There are several components to these fugitive 

particulate emissions. CFAC estimates a fraction (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, cryolite, aluminum 

fluoride, calcium fluoride, chiolite (Na5Al3F14), and ferric oxide. Fugitive dust is also 

generated by normal potline operations within the buildings, including particulate from 

materials handling and vehicle traffic. 

The following were identified as potentially applicable for controlling PM10 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 since the 1950s and has followed the 

advancements in aluminum reduction technology. CFAC believes the current operation 

has similar efficiencies and operational procedures to other plants in the US. Therefore, 

CFAC believes the facility has proper design and operation 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 series of baghouses. The air flow passes 
CFAC BART Analysis 11/5/07 pg. 4-18

Project #: CFA207819

through tightly woven or felted fabric, causing particulates in the flow to be 

collected on the fabric by sieving and other mechanisms. As particulate 

collects on the filter, collection 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 the use of spray chamber type roof vent controls. 

This system consists of roof-mounted water spray chambers (no other 

reactants used) to capture and remove SO2 and PM10 from the roof vent 

exhaust stream. Parallel systems of multiple 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. SO2 is readily 

absorbed in the airborne liquid droplets and particulate is captured by 

impingement. Efficiencies of 50% for both SO2 and particulate have been 

reported. 

4.4.2 Eliminate Technically Infeasible PM10 Control Options – Step 2 

(i) Proper Potline Design and Operation

Proper potline design and operation is considered baseline and is technically feasible. 

Conclusion: This technology is considered technically feasible for purposes of 

Step 2 in this BART analysis. 

(ii) Roof Vent Controls 

1. Although CFAC is not aware of an aluminum production facility which 

incorporates roof vent baghouse control, the technology is mature and 

there are no known technical challenges with this type of installation. 

Conclusion: This technology is considered technically feasible for purposes of 

Step 2 in this BART analysis. 

2. Aluminum industry installations have successfully used spray chambers to 

capture fugitive potline gases. One process reviewed used a water spray 

(no reagents) to achieve approximately 50% removal of SO2 and 

approximately 50% removal of total particulates. An advantage of this 

process over a cloth filter baghouse is that the process not only removes 

particulate fluorides, but gaseous fluoride as well. A disadvantage to the 

operation of this wet scrubber is that the wet roof scrubber 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 considered 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 PM10 Control Technologies – Step 3 

Of the alternative PM10 control technologies identified above, proper potline design and 

operation, roof vent baghouse control and roof vent water spray 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 control effectiveness of the remaining control 

technologies. 

Table 4-5: Secondary Emissions (Potline Roof Vent) PM10 

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 requirements; so environmental impacts would result from the 

generation of this additional electrical power. Also captured particulate would be 

disposed in a landfill and this may have 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 PM10 control, with the results presented in Table 4-6 below. CFAC has 

utilized the EPA’s Air Pollution Cost Control Manual to estimate the costs of PM10 

baghouse control. The manual provides the EPA’s recommended methodology for 

estimating the costs for add-on control technology. To calculate the cost-effectiveness 

of a control technology in dollars per ton ($/ton), the following factors are used: 

Cost-effectiveness ($/ton) = [(total capital investment x capital recovery factor 

{CRF}) + Direct Annual Cost + Indirect Annual Cost]/(tons PM10 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) = multiplier 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. Details 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 fans required to power the baghouses would 

consume approximately 7,500,000 kwh per year of electricity. This energy impact is only 

further considered in the economic analysis. 

(b) Roof Vent Control: Water Spray Chamber 

Roof Vent Control: Water Spray Chamber Environmental Impacts

This system acts as a simplified wet scrubber, 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 SO2 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 typically of little commercial value and must 

be landfilled. In the case of this sodium-based process, disposal of the soluble sulfate 

waste products, either on-site or in a landfill 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 demand 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 

PM10 control, with the results presented in Table 4-6 below. CFAC has utilized EPA’s Air 

Pollution Cost Control methodology to estimate 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 Spray Chamber Energy Impacts

EPA Publication EPA-542/F-03-034 states that modern wet scrubber designs result in 

an energy penalty of less than 1% of the total plant energy consumption. This is a minor 

energy impact which is only further considered 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 years used to calculate the annualized costs. 

Table 4-6 summarizes the cost analysis and visibility impacts for the remaining feasible 

controls for the secondary PM/PM10 emitting sources. 

Table 4-6: Summary of Secondary PM10 Emissions Cost 

and Visibility Impacts 

Glacier Nat'l Park 

Control Option 

Capital 

 Cost 

Annualized 

 Cost 

Efficiency 

(%) 

PM10

Emitteda

(tpy) 

PM10

Removed 

(tpy) 

Cost 

($/ton) 

PM10

Impact 

(deciview) 

Deciviews 

Removed 

(24 hr - ∆) 

Cost 

($/dc) 

Roof Vent PM10

Control: 

Baghouse $556,716,625 $104,151,834 99% 2.18 216 $482,587 2.359 1.525 $68,281,360

Roof Vent PM10 

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 SO2 and PM10 emissions; therefore, visibility impacts, improvements, and cost per deciview for the 

spray room include SO2 emissions. 

4.4.5 Evaluate PM10 Visibility Impacts – Step 5 

CFAC has performed modeling using the CALPUFF model to predict visibility impacts of 

the identified potentially applicable PM10 control technologies, using the 98th percentile 

visibility result as recommended by EPA. The 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 Area. Details of the modeling are found in 

Appendix B of this document. 

4.4.6 Select Secondary Source PM10 BART 

The purpose of BART is to apply a control technology 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, efficiency and visibility improvement from any SO2

and PM10 controls is inter-related. The previous section, Section 4.3, analyzes the 

control options for the primary and secondary SO2 emissions. An analysis was 

performed using the combination of SO2 primary and secondary controls in conjunction 
CFAC BART Analysis 11/5/07 pg. 4-22

Project #: CFA207819

with PM10 secondary controls to determine an overall BART selection. The combination 

of SO2 and PM10 controls showed possible scenarios for visibility improvements. See 

Section 4.5 for the overall BART selection. 

4.5 Select Overall BART 

Sections 4.3 and 4.4 have provided a framework for analyzing various control 

technologies, eliminating infeasible options, and evaluating control effectiveness, control 

impacts and visibility impacts. The analyses have been related to PM10 and SO2. Given 

that these previous sections have identified those available options and their relative 

impacts, it is the purpose of this section to consider 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 discussions found in the Appendix Y Guideline11. 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 labelled as: “How do I 

select the ‘best’ alternative using the results of Steps 1 through 5.” For our case, steps 

1 through 5 in the title refer to steps 1 through 5 found in the discussions in Sections 4.3 

and 4.4 above. 

There are a total of five discussion points found in Section E. For CFAC, only the first 

three are relative since the fourth and fifth points relate solely to utility boilers. The three 

remaining points for discussion regarding the selection of BART are:12

1. Summary of the impacts, 

2. Selecting a “best” alternative, 

3. Consideration of affordability (paraphrased). 

These three steps will be considered in concert with the SO2 and PM10 analysis in prior 

sections to select BART for this facility. As noted in earlier discussions, it was decided 

to include analyses of PM10 and SO2 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 and non-air impacts. However, for this to be 

useful, it is necessary to consider both the PM10 and SO2 emission strategies previously 

discussed in Sections 4.3 and 4.4 and to review impacts and costs associated with not 

only each pollutant separately, but as a combined analysis. To that end, Table 4-7 

below has been created that compares 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 SO2 and PM10, and secondary PM10 BART analysis offered 

many possible combinations of technologies for analysis. In order to simplify the BART 

selection process, the single pass wet SO2 scrubber has been removed from the 

following analysis. CFAC views the single pass and dual pass wet scrubbers as similar 

technologies. The single pass wet SO2 scrubber has the same control efficiency as a 

dual pass wet SO2 scrubber, has similar annualized costs, and poses greater potential 

environmental hazards. CFAC viewed the single pass system as redundant, and has 

only analyzed the dual pass wet SO2 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 the alumina scrubbers while the secondary sources 

represent the roof vent potline emissions. 

Primary Sources Secondary 

Sources 

 

Scenario

 

Description

SO2 

Emissions 

% 

Reduction 

PM10

Emissions % 

Reduction 

SO2 

Emissions 

% 

Reduction 

PM10

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 SO2 & PM 

Controls 

0% 0% 50% 50% 

Collect gases vented from 

roof vents and add a water 

spray scrubber that 

removes modest amounts 

of PM10 and SO2. 

2a 

Roof Vent Spray 

Chamber SO2 & PM 

Controls and Sulfur 

Reduction in Coke 

42% 0% 71% 50% Scenarios 1 and 2 

combined. 

3 Wet Scrubber SO2

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 SO2

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 SO2

Controls and Roof 

Vent Spray 

Chamber SO2 and 

PM Control 

90% 0% 50% 50% Combination of Scenarios 

2 and 3. 

5a 

Wet Scrubber SO2 

Controls, Roof Vent 

Spray Chamber 

SO2 and PM 

Control and Sulfur 

Reduction in Coke 

94% 0% 71% 50% Combination of Scenarios 

1 and 5. 

6 

Wet Scrubber SO2

Control and Roof 

Vent Baghouse 

90% 0% 0% 99% Combination of Scenarios 

3 and 4. 

6a 

Wet Scrubber SO2

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 visibility impacts, costs, cost-effectiveness, etc. 

Using the information already presented in Sections 4.3 and 4.4 along with the 

dispersion modeling results summarized in Appendix B, the following table provides the 

substantive comparative values. 
CFAC BART Analysis 11/5/07 

Project #: CFA207819

Table 4-8: Summary of SO2/PM10 Emissions Cost Analysis and Visibility Imp

Primary Sources Secondary Sources 

Scenario Description

SO2

% 

Removal 

PM10

% 

Removal 

SO2

% 

Removal 

PM10

% 

Removal 

Average 

(3 Years) of 98th

Percentile 

Deciview Impact 

Average 

(3 Years) of 

98th Percentile 

Improvement 

in Deciviews 

(24 hr - ∆)

Total SO2

Removed 

(Ton/yr)

Total PM10

Removed 

(Ton/yr)

Capital Cost 

($)

Annualized 

Cost 

($/year)

Effe

Baseline Existing Controls - - - - 3.884 0 - - - - 

1 Coke Sulfur Content Reduction 42% 0% 42% 0% 3.267 0.617 691 0 N/A $7,079,680 2 

Roof Vent Spray 

Chamber SO2 & PM 

Controls 

0% 0% 50% 50% 3.020 0.864 58 109 $33,476,076 $12,096,206 $

2a 

Roof Vent Spray 

Chamber SO2 & PM 

Controls and Sulfur 

Reduction in Coke 

42% 0% 71% 50% 2.326 1.558 724 109 $33,476,076 $19,175,886 

3 Wet Scrubber SO2 Controls 90% 0% 0% 0% 2.605 1.279 1377 0 $50,581,438 $12,142,136 

3a 

Wet Scrubber SO2

Controls and Sulfur 

Reduction in Coke 

94% 0% 42% 0% 2.477 1.407 1487 0 $50,581,438 $19,221,816 

4 Roof Vent Baghouse 0% 0% 0% 99% 2.359 1.525 0 216 $556,716,625 $104,151,834 

4a 

Roof Vent Baghouse 

and Sulfur Reduction 

in Coke 

42% 0% 42% 99% 1.497 2.387 691 216 $556,716,625 $111,231,514 $

5 

Wet Scrubber SO2

Controls and Roof 

Vent Spray Chamber 

SO2 and PM Control 

90% 0% 50% 50% 1.549 2.335 1435 109 $84,057,514 $24,238,341 

5a 

Wet Scrubber SO2 

Controls, Roof Vent 

Spray Chamber SO2

and PM Control and 

Sulfur Reduction in 

Coke 

94% 0% 71% 50% 1.461 2.423 1520 109 $84,057,514 $31,318,021 

6 

Wet Scrubber SO2

Control and Roof Vent 

Baghouse 

90% 0% 0% 99% 0.817 3.067 1377 216 $607,298,063 $116,293,969 

6a 

Wet Scrubber SO2

Control, Roof Vent 

Baghouse and Sulfur 

Reduction in Coke 

94% 0% 42% 99% 0.607 3.277 1487 216 $607,298,063 $123,373,649 
CFAC BART Analysis 11/5/07 pg. 4-27 

Project #: CFA207819

Given that there are numerous scenarios to consider along with numerous criteria 

(control effectiveness, deciview improvement, etc), it will be necessary to narrow the 

choices of potential BART technologies. One such method to begin the process of 

selecting a single BART choice will be to eliminate those scenarios that cost 

significantly more than competing alternative scenarios and provide no significant 

improvement in visibility. In other words, it would be appropriate to drop from further 

consideration any technology that provides similar 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 compared against the relative 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 8th 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

Average Change in Deciview 

Annualized Cost ($)

Baseline Scenario 3

Scenario 6

Scenario 5

Scenario 4

Scenario 2

Scenario 1

Scenario 5a

Scenario 4a

Scenario 3a

Scenario 2a

Scenario 6a
CFAC BART Analysis 11/5/07 pg. 4-28 

Project #: CFA207819

A review of Figure 4-1 reveals some startling 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 those four scenarios provide either no additional 

improvement or very little improvement over most of the other scenarios. In particular, 

Scenarios 4 and 4a provide no visibility improvement over scenarios 2a and 5a, while 

costing substantially more than these equally effective scenarios. 

The same general observation appears appropriate for Scenarios 6 and 6a. Both of 

these scenarios provide a modest improvement in modeled visibility, 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 improvements in visibility. 

For purposes of the continuing analysis, Scenarios 4, 4a, 6 and 6a are eliminated as 

BART. 

The next step is to compare the cost-effectiveness of the remaining control options in 

relation to emission reductions on an annualized 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 

SO2

Cost-Effectiveness 

($/ton) 

PM10 

Cost-Effectiveness 

($/ton) 

Baseline As configured - - 

1 Coke Sulfur Content Reduction $10,245 NA 

2 Roof Vent SO2 & PM Controls $210,057 $110,921 

2a Roof Vent SO2 & PM Controls and Sulfur 

Reduction in Coke $26,470 $183,546 

3 Wet Scrubber SO2 Controls $8,817 NA 

3a Wet Scrubber SO2 Controls and Sulfur 

Reduction in Coke $12,929 NA 

5 Wet Scrubber SO2 Controls and Roof 

Vent PM (and SO2) Control $16,894 $222,262 

5a 

Wet Scrubber SO2 Controls, Roof Vent 

PM (and SO2) 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 BACT analysis. BACT is, by definition, an 

analysis that is applicable to a “new” or “modified” facility. When a new facility installs air 

pollution control equipment, it must do so based on the ‘best’ controls at the time 

considering economic and other impacts. For BACT 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 history regarding the costs of equipment designed to control sulfur 

dioxide and particulates (the primary subject of this investigation). 

Again, although there are no bright-line values, it is generally understood that maximum 

acceptable control cost-effectiveness for these 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 highly 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 well 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 compare the annualized cost of these alternatives against the air 

quality benefit (improvement in visibility) on its own merit. Figure 4-1 provided such a 

comparison, but the information was used to compare scenarios among themselves, as 

opposed to modeled visibility impacts. 

Figure 4-2 has been created to compare the modeled improvement in visibility against 

the cost of accomplishing that modeled result. 
CFAC BART Analysis 11/5/07 pg. 4-30 

Project #: CFA207819

Figure 4-2: Annualized Cost vs. Deciview 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

Average Change in Deciview 

Annualized 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 modeling improvements are only for one small area of Glacier 

National Park. The vast majority of the park shows impacts from CFAC to be less than 

0.5. 

Of particular interest is the cost associated with the small modeled improvements. The 

costs range from about $7,000,000 per year to about $19,000,000 per year. Although 

there is no previously established 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” Alternative – Section E, Item 2 

The Appendix Y Guideline (Section E.2) suggests that the next step is to evaluate the 

various control options. It further notes that regardless of the 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 remaining useful life, and 

5. Consider the modeled visibility impacts. 

For purposes of fulfilling those obligations, this document has analyzed the five steps 

above. Item 1 (display the options) is summarized as Table 4-7. Those options are 

based on the detailed control technology reviews 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 significant 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 facility. While the plant has been in existence 

since the 1950s, its future health and long-term outlook will depend on many local, 

state, national and international parameters. Among 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 amounts of electricity as the underlying 

mechanism for creating the final product. The cost of electricity is the largest single 

expense in making aluminum. As it currently stands, the current 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 least be initiated. Power for the other two currently operating 

potlines is purchased on the open market. CFAC 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 considerable detail. The details of the modeling itself are 

found in Appendix B. A summary of the modeling impacts are 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 summarized data primarily 

found in Section 4.5.1 above. That analysis makes several clear points: 

 Modeling indicates that the pollutant providing the most modeled visibility 

benefit is particulate matter. 

 Particulate matter reductions are extremely expensive in this case due to 

extremely large quantities of gas being handled and the need, in most 

cases, to first collect those 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 pollutant reduced) is very expensive on 

its face and in comparison to typical BACT costs of the same pollutants. 

 The cost-effectiveness for visibility improvement 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 the current plant configuration. 

The addition of more controls on this facility for the purposes of improving visibility is far 

in excess of any reasonable retrofit cost. This facility is unique in that the cost of control 

is inordinately high due to the physical design characteristics of the plant. To control 

emissions from those pollutants for which the model predicts visibility impacts would be 

especially costly due to the large 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 Guideline also notes that the Agency is entitled to 

consider the affordability of controls. This may be considered regardless of the costeffectiveness of the alternatives (scenarios) that have been identified. 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 circumstances 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 such 
CFAC 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, parameters, and reasoning. . . .” 

CFAC believes that this deserves consideration for this facility. CFAC is a producer of 

commodity grade aluminum ingot. The revenue CFAC receives is determined by the 

daily trading prices of aluminum on the London Metal Exchange. 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 further weaken its competitiveness in the world 

market. 

 

The aluminum industry in the Pacific Northwest has been in decline for the past eight 

years due to the poor economic position of the region’s aluminum reduction facilities. In 

1999, there were ten aluminum reduction facilities operating in Washington, Oregon and 

Montana. Currently, there are only three of these facilities still operating, most at 

reduced capacity. Of the shutdown facilities, most have been torn down and will never 

resume operation. The profitability of aluminum smelting in the Pacific Northwest is 

marginal due to the region’s lack of available power at a reasonable cost for aluminum 

reduction. 

Any requirement to implement any of the pollution control strategies described in this 

document will greatly increase CFAC’s operating costs and probably result in the 

shutdown of the facility. 
APPENDIX A: EPA LETTER TO CFAC 





APPENDIX B: VISIBILITY IMPACTS MODELING 
CFAC BART Analysis pg. B-1 

Appendix B 

1.0 VISIBILITY IMPACTS 

1.1 Introduction and Summary 

CFAC has concurred with the initial EPA BART analysis that the Columbia Falls facility 

is a BART-eligible source. The following sections detail the modeling analysis that Bison 

performed on behalf of CFAC to comply with the intent of 40 CFR 51, Appendix Y. This 

document describes the methodologies and results of the regional 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 regional modeling in support of the BART program, entitled State 

of Montana Draft CALPUFF BART Modeling Protocol For Federal Mandatory Class I 

Areas, September 2006 Draft (“Montana BART protocol”). The analysis also relied on 

guidance in the Interagency Workgroup on Air Quality Modeling (IWAQM) Phase 2 

Summary Report for Modeling Long Range Transport Impacts (EPA, 1998), and the 

Federal Land Managers’ Air Quality Related Values Workgroup (FLAG) Phase I Report, 

December 2000 (“FLAG document”). 

The BART modeling analysis specifically requires demonstrations of impacts to visibility 

at surrounding mandatory federal Class I areas. 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)-generated receptors for Glacier National Park, 

the development of this refined CALMET grid was deemed appropriate. 

Visibility Impacts: The visibility impacts analysis began with the predicted emissions 

from the BART-eligible sources located at the Columbia Falls facility. Regional scale 

modeling was completed to confirm that CFAC had potential 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 field impacts were developed to establish a 

visibility baseline to analyze what effects, if any, different control technologies or 

operating practices had on visibility at Glacier National Park. 
CFAC BART Analysis pg. B-2 

Appendix B 

The visibility impacts analyses included the appropriate potential NOx, SO2, and PM10

emissions from the sources modeled since all three pollutants contribute to visibility 

impairment. 

1.2 Model Selection 

Selection of the appropriate dispersion 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 and dry deposition, chemical transformation, 

and plume fumigation. It is supported by two primary sub-programs, CALMET and 

CALPOST. CALMET is used in refined analyses to create three-dimensional wind fields 

based on multiple sources of geophysical and meteorological data. The output of the 

CALPUFF model consists of binary data 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 obtained 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 identifiers for the major modules used for this project are 

identified above. Electronic executable files for the primary modules and the primary 

electronic input and output files associated with this analysis are available upon request. 

1.3 Modeling Domain 

The regional modeling domain was defined to follow the Montana BART Protocol and is 

based on 6 kilometer (km) grid spacing with 180 grids in the easting direction and 95 

grids in the northing direction. The regional modeling domain is defined in a Lambert 

Conformal Conic (LCC) system. The LCC coordinate system for this project has a 

projection origin at 44.25° N and 109.5° W and matching parallels 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 WRAP modeling domain which 

defined matching parallels of latitude of 45.0° and 49.0° N. 

The near field modeling domain 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 modeling domain uses the same LCC system, 

projection origin, and matching parallels as used in the regional modeling domain. The 

coordinates of the southwest corner of the domain 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 meteorological data for use in the CALPUFF 

model program. The CALMET output files defined gridded fields of wind speed, wind 

direction, mixing heights, stabilities, micrometeorological parameters, 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 developed by the U.S. Geological Survey 

(USGS)1. The data files used for both the regional and 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 several data processing programs provided by ASG, 

the land use data were processed and combined with other geophysical data into a 

single data set for input to the CALMET model. 

 

1

 Available for download from the USGS Earth Resources 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 domain. The regional scale model 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 were used to create the appropriate files 

for CALMET. 

1.4.3 Meteorological Data 

CALMET output files representing meteorological data for the 2001, 2002, and 2003 

calendar years were prepared for the analysis in accordance with the Montana BART 

Protocol. Input meteorological data consisted of Mesoscale Model (MM5) 

meteorological data (processed by the CALMM5 utility program), observed hourly 

surface data, upper air rawinsonde data, and hourly precipitation data. 

Mesoscale Model Data 

The MM5 meteorological data for the 2001, 2002, and 2003 calendar years obtained 

from the Western Regional Air Partnership (WRAP) are available at the following 

website: http://pah.cert.ucr.edu/aqm/308/bart.shtml. These data are generated by 

Pennsylvania State University/National Center for Atmospheric Research mesoscale 

models. The mesoscale models are limited-area, nonhydrostatic or hydrostatic, terrainfollowing sigma-coordinate models designed to simulate or predict mesoscale and 

regional-scale atmospheric circulation. The data are used as a basis for generating an 

“initial guess field” of multilayer wind vectors in CALMET. The meteorological data for all 

three years are in the CALMM5 utility program 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 the Montana BART protocol, National Weather 

Service (NWS) hourly surface data for 39 stations for 2001 and 36 stations for 2002 and 

2003 were processed in CALMET for the regional modeling domain. The data files were 

provided in the SMERGE format and were ready for input into CALMET. 

Surface data from the following locations were used for the CALMET regional modeling 

analysis: 

• Badger Peak, MT (2001 only) 

• Billings, MT 

• Bismarck, ND 

• Boise, ID 

• Bozeman, MT 

• Butte, MT 
CFAC 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 only the Kalispell, MT and Cut Bank, MT 

surface data and included surface data from the CFAC onsite meteorological station. 

Upper Air Data 

The Montana BART Protocol included the use of upper air data; however, the EPA 

BART Protocol specified that upper air data would not be used, and consequently the 

WRAP modeling omitted this data. Bison followed the Montana modeling 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 seven 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 format 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 air rawinsonde data are the two upper air 

locations used in developing the near field model for Glacier National Park. 

Upper air data substitution and extrapolation were accomplished as needed according 

to ASG’s FAQ 2.3.4, which recommends temporal substitution (for example, substituting 

an afternoon sounding with the previous or succeeding afternoon sounding) or spatial 

substitution from a nearby location if soundings 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 purpose. Nearly all of these flagged values 

were due to either (1) the pressure remaining 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 elevation increased with height as appropriate. For spatial 

substitutions, another in-house program (AdjUa.exe) was used to adjust for the 

difference in elevation between the two locations. Temporal substitutions were 

accomplished manually using a text editor. All raw and processed data and data 

processing algorithms are available upon request. 

Precipitation Data 

The use of precipitation data was referenced in the Montana and EPA BART Modeling 

Protocols. The WRAP modeling omitted this precipitation data. Bison followed the 

modeling protocols and included 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 BART modeling analysis effort. All precipitation stations 

located within the CALMET regional scale and near field modeling domains were 

extracted from the data set and were used in the CALMET analysis. A total of 286 

stations were selected for each of the three modeled years in the regional scale 

analysis and 14 stations were selected for the 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 interpolation or substitution was required for this project.

1.5 Ozone 

The ozone data provided on the WRAP website contained all the ozone sites in the 

United States and for the year 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 pollutant concentrations at 

Class I receptors. CALPUFF requires 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 Montana 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 dispersion coefficients for rural areas 

Partial plume penetration – elevated inversion Yes 

PDF used under convective conditions No 

CSPEC SO2, SO4, NOX, HNO3, NO3, 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 Ozone 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 centimeter 
CFAC BART Analysis pg. B-9 

Appendix B 

1.6.2 Receptors 

The Air Resources Division (ARD) of the National 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 developed using the ARD data files converted to the appropriate 

LCC coordinate system. 

1.6.3 Modeled Sources - General 

The visibility analyses included potential emissions for the CFAC BART-eligible sources 

and the projected emission reductions for the applicable pollutant controls. The BARTeligible sources that were included 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 sources 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 demonstrations were performed using the maximum actual 

emission rates for each modeled eligible source for 1999. These emission rates were 

obtained from CFAC’s current air permits 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) 

SO2

(lb/hr) 

PM10

(lb/hr) 

EU004 East Alumina Elevator 0.00 0.00 0.08 

EU005 East Alumina Unloader 0.00 0.00 0.08 

EU006 East Alumina Conveyor 

Storage 

0.00 0.00 0.08 

EU019 Therminol Oil Heating System 0.00 0.00 0.00 

EU020 East Plant Alumina Transfer 0.00 0.00 0.05 

EU021 East Plant Alumina Transfer 0.00 0.00 0.05 

EU028 Dry Alumina Scrubber #5 0.00 58.22 0.09 

EU029 Dry Alumina Scrubber #6 0.00 58.22 0.09 

EU030 Dry Alumina Scrubber #7 0.00 58.22 0.09 

EU031 Dry Alumina Scrubber #8 0.00 58.22 0.09 

EU032 Dry Alumina Scrubber #9 0.00 58.22 0.09 

EU033 Dry Alumina Scrubber #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 3.39 
CFAC BART Analysis pg. B-11 

Appendix B 

To most accurately demonstrate the changes in visibility impacts at surrounding 

mandatory Class I areas, NOx, SO2, and PM10 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 different forms, or species, and each species can 

affect visibility to a different degree. The speciation of PM10 used in the BART modeling 

analysis assumed all the primary source PM10 emissions as PMF while the secondary 

source PM10 emissions were split between PMF 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 required that the baseline emissions 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

SO2 

Emissions 

% 

Reduction 

PM10

Emissions % 

Reduction 

SO2 

Emissions 

% 

Reduction 

Scenario 

Baseline Existing Controls - - - Baseline 

1 Coke Sulfur 

Content Reduction 42% 0% 42% 1 

2 

Roof Vent Spray 

Chamber SO2 & PM 

Controls 

0% 0% 50% 2

2a 

Roof Vent Spray 

Chamber SO2 & PM 

Controls and Sulfur 

Reduction in Coke 

42% 0% 71% 2a

3 Wet Scrubber SO2

Controls 90% 0% 0% 3 

3a 

Wet Scrubber SO2

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 SO2

Controls and Roof 

Vent Spray 

Chamber SO2 and 

PM Control 

90% 0% 50% 5

5a 

Wet Scrubber SO2 

Controls, Roof Vent 

Spray Chamber 

SO2 and PM 

Control and Sulfur 

Reduction in Coke 

94% 0% 71% 5a

6 

Wet Scrubber SO2

Control and Roof 

Vent Baghouse 

90% 0% 0% 6

6a 

Wet Scrubber SO2

Control, Roof Vent 

Baghouse and 

Sulfur Reduction in 

Coke 

94% 0% 42% 6a 
CFAC 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 PM10 concentration data to determine 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 matter measurements.” The background extinction 

coefficients were calculated based on the annual relative humidity factors and data 

presented in Section 6.1 and Appendices C and D of the Montana BART Protocol. 

Inputs to CALPOST for visibility processing are summarized in the following table. The 

attached CD-ROM contains the CALPOST input files. 

CALPOST Visibility Control File Settings 

CALPOST Parameter/Option Value 

Maximum relative humidity (RHMAX) 95% 

Included species Sulfate, nitrate, coarse particulate (as PM10), and 

fine particulate (as PM2.5) 

Coarse particulate extinction efficiency 0.6 (l/Mm per μg/m3) 

Fine particulate extinction efficiency 1.0 (l/Mm per μg/m3) 

Ammonium sulfate extinction efficiency 3.0 (l/Mm per μg/m3) 

Ammonium nitrate extinction efficiency 3.0 (l/Mm per μg/m3) 

Organic carbon extinction efficiency 4.0 (l/Mm per μg/m3) 

Soil extinction efficiency 1.0 (l/Mm per μg/m3) 

Elemental carbon extinction efficiency 10.0 (l/Mm per μg/m3) 

Method used for background light 

extinction MVISBK = 6 

Relative humidity From *.VIS Files 

Background extinction coefficients, SO4 0.120 

Background extinction coefficients, NO3 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: 

NO3 = Nitrate 

1.8 Modeling Results 

1.8.1 Regional Haze (Visibility) 

Impacts to natural background visibility, expressed in terms of percentage change in 

24-hour average background extinction (ΔBex) were calculated by CALPOST. The 

guidelines also reference 40 CFR §51.301(a) in asserting that determinations must be 

made on a “...case-by-case basis taking into account the geographic extent, intensity, 

duration, frequency and time of visibility impairments....” The average 98th 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

SO2

% 

Removal 

PM10 

% 

Removal

SO2 

% 

Removal 

PM10 

% 

Removal 

Average 

(3 Years) of 

98th

Percentile 

Deciview 

Impact 

Average 

(3 Years) of 

98th Percentile 

Improvement 

in Deciviews 

(24 hr - ∆)

Total SO2

Removed 

(Ton/yr)

Total PM10

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 SO2 & 

PM Controls 

0% 0% 50% 50% 3.020 0.864 $210,057 $110,921 

2a 

Roof Vent Spray 

Chamber SO2 & 

PM Controls and 

Sulfur Reduction 

in Coke 

42% 0% 71% 50% 2.326 1.558 $27,630 $183,546 

3 Wet Scrubber 

SO2 Controls 90% 0% 0% 0% 2.605 1.279 $8,817 NA 

3a 

Wet Scrubber 

SO2 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 

SO2 Controls and 

Roof Vent Spray 

Chamber SO2

and PM Control 

90% 0% 50% 50% 1.549 2.335 $16,894 $222,262 

5a 

Wet Scrubber 

SO2 Controls, 

Roof Vent Spray 

Chamber SO2

and PM Control 

and Sulfur 

Reduction in 

Coke 

94% 0% 71% 50% 1.461 2.423 $21,155 $294,888 

6 

Wet Scrubber 

SO2 Control and 

Roof Vent 

Baghouse 

90% 0% 0% 99% 0.817 3.067 $84,446 $538,398 

6a 

Wet Scrubber 

SO2 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