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CERTIFIED MAIL

CERTIFICATION NUMBER 7006 2760 OOO5 5303 9375

RETURN RECEIPT REOUESTEI)

November 18, 2008

John Lyons, Director

Kentucky Division for Air Quality

200 Fair Oaks Lane

Frankfort, KY 40601

Re: Agreed Order entered into on October 20,2008

File No. DAQ-29458-039

Dear Mr. Lyons:

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Louisville Gas and Electric (LG&E) and the Kentucky Energy and Environment Cabinet entered

into an Agreed Order on Octob er 20,2008 (File No. DAQ-29458-039). As specified in

paragraph I of the order, LG&E is herein providing the Kentucky Division for Air Quality with

information identiffing emission rates utilized for the modeling conducted in conjunction with

LG&E's Septembet 24,2007 submittal of Mill Creek Station's Best Available Retrofit

Technology analysis. Additionally, this correspondence provides written explanation of the

infeasibility of incorporating a sulfur trioxide (SO:) emission limitation of 0.015 lb/mmBtu into

the Mill Creek Station Title V permit.

As described in the submitted analysis, for the purpose of SO: emission determination, all HzSO+

particles determined from the CALPUFF modeling were assumed to be SO: emissions. As

shown in "TableT-l CALPUFF Modeling Parameters" of the report, the baseline HzSO+ primary

particle information are in units of grams per second (g/s), 25.39 g/s and 27 .67 g/s for Mill Creek

Units 3 and 4, respectively. When input into the CALPUFF model, they were converted to

pounds per hour (lb/hr) values of 20L5 lb/hr and2l9.6lblhr for Mill Creek Units 3 and4,

respectively. In determining the effectiveness of sorbent injection technology, a stack exit

concentration of five (5) parts per million (ppm) SO: was used to evaluate the technology's

effect on visibility impacts. For input into the CALPUFF model, five (5) ppm SO3 eeuates to

HzSO+ emission rates of 64.3|blhr and76.5lblhr for Mill Creek Units 3 and 4, respectively.

These values are displayed in Appendix D on pages D-4 and D-5 of the previously submitted

analysis. The lb/hr values were the primary model input values utilized in our CALPUFF

modeling. As such, these are the values that are appropriate for incorporation into Mill Creek

Station's Title V permit.

For illustrative purposes only, the lbftr values were converted to lb/mmBtu values in TableT-4

of the Septemb er 24, 2007 submittal. While we apolo gize for the confusion which resulted from
including the value in our submittal, we wish to clarify that we never intended to suggest that it

is appropriate for inclusion as an emission limit in our permit.

The 0.015 lb/mmBtu value provided in Table 7-4 is based on the design heat input (i.e.,

maximum) value for the two units. However, in the course of normal utility operations, the units

operate at a wide range of heat inputs, some of which are substantially lower than the design heat

input value. Although the SO: mitigation system proposed by LG&E can meet the specified

lb/hr emissions values necessary to achieve BART, it is not capable of controlling HzSO+

emission to 0.015 lb/mmBtu at all heat input levels. Indeed, the measurement accuracy of HzSO+

emissions is questionable when operating at the level of lower heat inputs that would be

encountered in the course of normal operations.

Consequently, adding a 0.015 lb/mmBtu limit to the permit would place severe constraints on

our operational flexibility which could effectively preclude us from operating the unit at certain

heat inputs. This would have major financial implications for us. In conclusion, it is not

technically feasible for our proposed SO3 mitigation system to meet the 0.015 lb/mmBtu HzSO+

target at all operating loads and we do not believe that the value reflects BART for our units.

Therefore, if the Division desires to incorporate specific BART emission limits into the Title V

permit for Mill Creek, the appropriate values would be 64.3 and 7 6.5 lb/hr HzSO+ for Units 3 and

4 respectively. If you have any questions or require additional information, please contact me at

(502) 627-4621 or Jason Wilkerson at (502) 627-4043.

Respectfully,rh,{

Environmental Affairs

E.ON U.S.

Cc: Robin Thomerson, KDAQ