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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 200FairOaks

Lane Frankfort,

KY 40601
Re: Agreed

Order entered into on October

20,2008 File No. DAQ-29458-039
Dear Mr. Lyons: K\feroF- 

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QUALTTY

Louisville Gas and Electric (LG&E) and the Kentucky Energy and Environment Cabinet entered into an AgreedOrderon 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 emissionratesutilized for the modeling conducted in conjunctionwith LG&E's Septembet

24,2007 submittal of Mill Creek Station's Best Available Retrofit Technologyanalysis. Additionally, this correspondence provideswritten explanation of the infeasibility of incorporating a sulfur trioxide (SO:) emissionlimitation of 0.015 lb/mmBtu into the Mill Creek Station Title V permit.
As described

in the submittedanalysis, for the purpose

of SO: emission

determination,

all HzSO+ particlesdetermined

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 gramsper 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 convertedto poundsper hour (lb/hr) valuesof 20L5 lb/hr and2l9.6lblhr for Mill Creek Units 3 and4, respectively. In determining the effectiveness

of sorbentinjection technology, a stackexit 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 CreekUnits 3 and4, respectively. These valuesare displayedin 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,theseare the values that are appropriatefor incorporation into Mill Creek Station'sTitle V permit.
For illustrative purposes only, the lbftr values were convertedto lb/mmBtu values in TableT-4 of the Septemb

er 24, 2007 submittal. While we apolo gize for the confusion which resulted fromincluding the value in our submittal, we wish to clarify that we never intendedto suggest that it is appropriate

for inclusion as an emissionlimit in our permit.
The 0.015 lb/mmBtu value provided in Table 7-4 is based on the designheat input (i.e., maximum) value for the two units. However, in the courseof normal utility operations, the units operateat a wide range of heat inputs, some of which are substantially lower than the design heat input value. Although the SO: mitigation systemproposedby LG&E can meet the specified lb/hr emissions

valuesnecessary

to achieveBART, 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 courseof 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 operatingthe unit at certain heat inputs. This would have major financial implications for us. In conclusion, it is not technicallyfeasible

for our proposed

SO3 mitigation system

to meetthe 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 emissionlimits into the Title V permit for Mill Creek, the appropriatevalues would be 64.3 and76.5 lb/hr HzSO+ for Units 3 and 4 respectively. If you have any questionsor require additional information, pleasecontact me at (502) 627-4621

or Jason Wilkersonat (502) 627-4043. 

### Respectfully, 

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Environmental Affairs E.ONU.S.
Cc: Robin Thomerson, KDAQ