4APT-APB 

Mr. James P. Johnston 

Program Manager, Planning and Support Program 

Georgia Department of Natural Resources 

4244 International Parkway, Suite 120 

Atlanta, Georgia 30354 

Dear Mr. Johnston:

Thank you for the opportunity to review the proposed Best Available Retrofit 

Technology (BART) technology evaluation for the Georgia Power Company (GPC) – 

Plant Bowen dated February 2007. Enclosed are our draft comments on the GPC 

document. Enclosure 1 describes our comments on the control and cost analyses. 

Enclosure 2 details our comments on the modeling analysis. Enclosure 3 provides 

clarification to certain statements made in the GPC document. 

We appreciate your transmittal of this package for our consideration. If you have 

questions regarding this draft letter, please contact Stacy Harder of the Region 4 staff at 

(404) 562-9042. 

Sincerely, 

Kay T. Prince 

Chief 

Air Planning Branch 

Enclosures 
2

Enclosure 1: Control and Cost Analyses 

1. Capital Recovery Factor (CRF) Calculations: For the capital recovery cost factor 

calculations, it appears that an equipment life of 15 years and a seven percent 

interest rate of return is assumed for all the control options evaluated (pp.4-20, 4-

32). Where these assumptions differ from those in the EPA Air Pollution Control 

Cost Manual (Cost Manual) for the particular control technology, the document 

should provide justification. The Cost Manual notes on page 3-50 in Section 

3.4.2 of Chapter 3, “Electrostatic Precipitators,” (September 1999) of Section 6, 

“Particulate Matter Controls,” that, “For ESPs, the system lifetime varies from 5 

to 40 years, with 20 years being typical,” and much of the equipment at power 

plants is designed to last 40 years. The document should include further 

explanation for the assumed equipment life of 15 years. (To access the most 

current version of the Cost Manual, go to: 

http://www.epa.gov/ttncatc1/products.html#cccinfo.) 

2. Particulate matter emission limits associated with each control technology option 

considered are not included in the report. SCS should clarify the WESP capital 

and O&M costs of $115/kW and $0.47/MWh, respectively. The EPA WESP Air 

Pollution Control Technology Fact Sheet EPA-452/F-03-029 referenced in 

footnotes 38 and 43, indicates capital and O&M cost ranges of $40 to $200, and 

$6 to $10 per scfm, respectively ( EPA-452/F-03-029, 08/07/03, 

www.epa.gov/ttn/catc/dir1/fwespwpi.pdf). It may be useful to indicate any unit 

conversion calculations.

3. Provide documentation for the additional energy charges. There are

 assumptions presented involving both purchasing power and constructing 

 additional capacity without clearly documenting the basis for the 

 assumptions and why both charges apply. If the control equipment 

 requires power to operate and reduces the ability of the power plant to 

 generate power, costs associated with the power losses are appropriate. 

 However, given their magnitude, EPA would expect greater documentation of the 

 assumptions and why a combination of capacity increases and purchased 

 power are the lowest cost solution. 

4. The EPA Air Pollution Control Cost Manual suggests that an ESP system lifetime 

varies from 5 to 40 years, with 20 years being typical for capital recovery cost 

calculation purposes (Section 6 - Particulate Matter Controls, 3.4.2 Indirect 

Annual Costs, pg. 3-50). It is unclear from the BART Report whether or not the 

"juice can" cost effectiveness calculations are based on upgrading all or a few 

ESP transformer-rectifier sets. Footnote 32 mentions that "some" of the existing 

transformer-rectifier sets are already equipped with "juice can" technology. The 

technical and economic feasibility of the "juice can" ESP control technology 

option is well established since it is already utilized successfully at Plant Bowen. 

Visibility impacts do not override all other considerations in a BART analysis. 
3

Based on a review of the BART determination analysis for PM included in the 

attachment, additional consideration should be given to the "juice can" upgrade 

option for Plant Bowen ESP electrode systems. Cost effectiveness values for the 

Bowen ESP electrode system upgrade are consistent with those determined to be 

reasonable for TECO Big Bend Station PM control device upgrades. Modeling 

results indicate a six to nine percent reduction in both filterable PM10 and PM2.5

emissions (e.g., 72.0 TPY PM10 emissions total on pg. 4-16 ). It would also 

appear that some additional gas flow optimization may be feasible based on 

previous studies, operational data, and information from other similar units. 

5. When identifying all available retrofit control technologies, the “Guidelines for 

BART Determinations Under the Regional Haze Rule” (BART Guidelines) 

clarify that consideration should be given not only to add-on controls but also 

improvement in the performance of existing controls and P2. The analysis does 

not discuss the facility’s evaluation of any P2 options for the four BART-eligible 

units. 

6. On page 1-2 and at several other points, the report compares potential BART cost 

per ton controlled values for Plant Bowen to threshold values used in previous 

BACT determinations. The report indicates that costs above $10,000 per ton 

controlled are considered to be prohibitive. However, most past BACT 

determinations are conducted for new units and establish a cost/ton value for each 

control option that assumes an uncontrolled baseline. This is clearly not the case 

in this BART analysis since controls currently exist. It would be more 

appropriate to compare the cost per ton values to incremental costs in past BACT 

determinations. Incremental costs are quantified as a tool to evaluate the point 

where diminishing returns might be expected as several increasingly expensive 

options are compared. This point of diminishing returns is case-specific and can 

be significantly higher than $10,000/ton. 

7. On page 4-22 it is indicated that biannual PM stack tests from 2003-2005 were 

used to establish baseline emission rates. The data was then used to estimate tons 

reduced for each technology being evaluated. Since very limited data was 

available (two tests for three years), EPA recommends that an analysis be 

conducted to evaluate whether the stack test-measured emissions are likely to be 

representative of emissions during the rest of the period. Examples of possible 

information that should be evaluated are the electrical parameters of the ESP 

during the stack tests as compared to the rest of the operating year. This data 

should be readily available at the plant. If, for example, the overall secondary 

current to a particular ESP was significantly greater during the stack test than the 

rest of the year, it would be appropriate to adjust baseline emissions higher as 

well as the tonnages expected to be controlled by each technology option. 
4

Enclosure 2: Modeling Analysis 

1. Overall, the modeling procedures followed the VISTAS BART Modeling 

Protocol and are acceptable. 

2. Estimated PM emission reductions were modeled for two emission control 

scenarios. The results of the modeling indicate that the estimated visibility 

improvement at the Cohutta Class I area was low. On page 5-2 of Section 5.0, the 

GPC document states several reasons why a 0.2 deciview (dv) improvement in 

visibility at Cohutta is considered by the facility to be too small to merit the 

additional costs of using a wet ESP. References are made to “...the level that 

EPA considers to be detectable (approximately one deciview), and is also below 

the level (0.5 deciview) that EPA has recommended be used for visibility 

contribution analyses...” This statement appears to imply the controls are not 

considered to make enough of an improvement in visibility at the Cohutta 

Wilderness Area. We note; however, that there is no bright line for evaluating in 

the BART determination analysis the degree of visibility improvement that is 

considered significant enough to warrant BART controls. Rather, a State has 

flexibility in setting absolute thresholds and determining the weight and 

significance to be assigned to each BART factor. (See 70 FR 39170, 1st col., July 

6, 2005.) In addition, EPA suggests that GA EPD carefully evaluate the other 

four BART statutory factors in assessing the Wet ESP control option. Visibility 

improvement based on modeling results is only one of the factors that should be 

assessed in this decision. 

3. The modeling results presented in Appendix E of the report indicate that the 

primary contributor to the visibility impairment at the Cohutta Class I area is 

sulfate concentrations, which are the result of sulfuric acid emissions. Since SO2

emissions are not being modeled (because they will be addressed under the Clean 

Air Interstate Rule rule), potential controls for sulfuric acid emissions should be 

examined closely. Section 4.2 of the report (Pages 4-9 & 4-10) discusses the 

potential sulfuric acid controls. One control option that is considered feasible is 

sorbent (lime) injection. Section 4.4 indicates that lime injection has been shown 

to be an effective method for reducing flue gas SO3 and thus controlling sulfuric 

acid emissions. However, the report indicates that the addition of the lime adds to 

total PM10 emissions and therefore the total PM10 emissions reductions are low 

with this control option. Since the total PM10 emission reductions are low, the 

cost effectiveness for lime injection in $/ton is shown to be very expensive 

(Tables 4-15 thru 4-18). If this analysis considered the cost effectiveness of 

reducing sulfuric acid emissions (since sulfuric acid is the primary contributor to 

the visibility impairment), the conclusions may be different. EPA suggests that 

this option be reconsidered and that modeling of the lime injection control 

scenario be conducted to evaluate the visibility impacts. 

4. Page 2-5 of the Modeling Protocol contained in Appendix D of the report 

describes how the PM emissions were speciated into the coarse and fine fractions. 
5

The discussion references AP-42 Table 1-1.6. It is unclear how the values of 

55.6% coarse and 44.4% fine were calculated from the information in AP-42 

Table 1.1-6. It would be helpful if additional information describing the PM 

speciation procedures was provided. 

5. Section 4.4 of the Modeling Protocol contained in Appendix D of the report 

indicates that visibility impacts presented in the report were developed using the 

New IMPROVE equation as implemented in an external spreadsheet created by 

Dr. Ivar Tombach. The report provides very limited discussion of the rationale 

for using the New IMPROVE algorithm instead of the default IMPROVE 

algorithm that is contained in CALPOST. The report should provide additional 

justification for using the new algorithm. Sea salt is not an issue for the Cohutta 

Class I Area. The additional justification should focus on the why the new 

IMPROVE algorithm is preferred for this specific application. 

 

6. Page 3-3 of the report indicates that an external hard drive containing all the 

modeling files and data was provided with the report. EPA did not have access to 

this information and thus was unable to do a complete review. EPA suggests that 

GA EPD carefully evaluates the modeling files and data contained on this hard 

drive to ensure that the modeling was conducted as it was described in the report. 

7. The State has flexibility in determining how the five statutory BART factors 

should be addressed. EPA recommends that the modeling should be discussed for 

each control used in the determination. 
6

Enclosure 3: Text Clarifications 

Below is clarification to certain statements in the text. 

1. Factors Identified in Section IV.E. of the BART Guidelines: The first 

paragraph on page 5-1 of Section 5.0 states that the BART Guidelines 

“...indicate that, for each option, the emissions reduction, costs, energy and 

non-air quality environmental impacts, and modeled visibility improvement 

must be considered.” A footnote is provided to Section IV.E. of the BART 

Guidelines. EPA notes that the remaining useful life of the source is missing 

from the list of factors referenced on page 5-1. This factor is listed in the 

referenced Section IV.E. of the Guidelines (see page 70 FR 39170, 3rd

column).