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KENTUCKY POWER COOPERATIVE

December 3, 2015

Via E-Mail and CertifiedMail

Sean Alteri, Director Division for Air Quality 200 Fair Oaks Lane, First Floor Frankfort, Kentucky 40601

RE: John Sherman Cooper Power Station (AI 3808) Burnside, Pulaski County, Kentucky 2010 1-Hour S02 NAAQS Designation Analysis CEMS DataProcessing

- Additional Information

Dear Mr. Alteri:

East Kentucky Power Cooperative, Inc. (EKPC) appreciated the opportunity to meet with representatives ofthe Kentucky Division for Air Quality (DAQ) onNovember 24, 2015 to discuss questions posed by the U.S. Environmental Protection Agency (EPA) Region 4 to DAQ regarding EKPC's September 2, 2015 Designation Analysis. As promised during the meeting, the enclosed attachment provides additional information regarding the CEMS dataprocessing for the designation modeling in response to the questions raised by EPA. EKPC understands that DAQ will forward this information to EPA and that DAQ will facilitate the scheduling ofa call among EKPC, DAQ and EPAto discuss the modeling and any remaining questions EPA may have. It

### is our understanding that the call is confirmed for 11 a.m. on December 9, 2015.

Ifyou have any questions regarding the enclosed information, please contact me at (859) 745-9244.

Enclosure

cc:

# t:~**~ ~~** **;lm, is**  Director ofEnvironmental Affairs

Kevin Davis- DAQ (w/enc.)(via email only) Jackie Quarles- DAQ (w/out enc.)(via email only) John West- OGC (w/out enc.)(via email only) Rick Shewekah- DAQ (w/out enc.)(via email only) Troy Lovell- EKPC (w/enc.) Louis Petrey- EKPC (w/enc.) John Colebrook- Trinity (w/out enc.) George Schewe- Trinity (w/out enc.)

4775 Lexington Road 40391 P.O. Box 707, Winchester Kentucky 40392-0707 Tel. (859) 744-4812 Fax: (859) 744-6008 http://www.ekpc.coop A Touchstone Energy" Cooperative

### Attachment 1 -Additional Information for EKPC Cooper Station Unit 1 and 2 CEMS Data Processing for S02 NAAQS Designation Modeling

East Kentucky Power Cooperative, Inc. (EKPC) in association with our air quality contractor, Trinity Consultants (Trinity), performed 1-hour S02 National AmbientAir Quality Standard (NAAQS) modeling for the John Sherman Cooper Power Station and submitted the report, SOz NAAQS DesignationAnalysisAirDispersion Modeling Report, to the Kentucky Division for Air Quality (KDAQ or Division) on September 2, 2015. This workwas undertaken in supportofthe Division's response to the March 20,2015 letterfrom the U.S. Environmental ProtectionAgency (U.S. EPA) to Commissioner Scott ofthe Kentucky Departmentfor Environmental Protection (KDEP) regarding designations ofareas currentlyunclassified with respectto the 2010 1-hour SOz NAAQS. The modeling results demonstrated that the area surroundingthe Cooper Station should be considered for designation as attainment ofthe 1-hour SOz NAAQS.

EKPC understands thatU.S. EPA Region 4 has questions abouthowthe Unit 2 continuous emissions monitoring system (CEMS) datawere used. Specifically, U.S. EPA Region 4 is seeking additional information regarding:

1. Observed discrepancies between the Unit 2 hourly SOz emissions data presentedin the Clean Air Markets Database (CAMD) versus the Unit 2-only CEMS data presented in column Cof 1. Unit 1 & 2 Emissions tab of the Cooper Station SOz NAAQS modeling inputparameter spreadsheet (refer to Excel® spreadsheetprovided with Appendix Cofthe modelingreport).
2. Differences betweenthe Unit 2 modeled emission rates in column Kofthe 1. Unit 1 & 2 Emissions tab and the Unit 2 raw CEMS data included in column C.

EKPC's response to these questions is provided.



### 1. DISCREPANCIES BETWEEN UNIT 2 CAMD AND RAW CEMS DATA
A federally enforceable U.S. EPA Consent Decree requires the directmeasurement ofCooper Station Unit 2 SOz emissions (Unit 2 CEMS) as a resultofthe dryflue gas desulfurization (DFGD) environmental controls before enteringthe common stack. EPA CAMD data are collected, recorded, and reported from the common stack.

Unlike the Unit 2 raw CEMS data, which is directly measured downstream ofthe DFGD, the Unit 2 CAMD data is calculated from the combined Unit 1 and Unit 2 CEMS, which is located in the combined stack (i.e., downstream ofthe pointwherethe exhaust streams from each unitmerge ).1 CAMD uses each unit's heatinputrate to prorate the combined Unit 1 and 2 CEMS emissions data to the individual units. This approach ignores the impactthe DFGD has on Unit 2 emissions, and thus, incorrectly assigns uncontrolled Unit 1 emissions to the controlled Unit 2. A CAMD sample calculation is providedbelow for the first hourin the 3-yearmodelingperiod (i.e., 7/1/12 Hour 0) which demonstrates this prorationbyheatinput



### CAMD Input Data
Combined Unit 1 and 2 SOz Emission Rate Measured byCEMS: 969.1lb/hr Reported Unit 1 Heat Input Rate: 494.7 MMBtujhr Reported Unit2 Heat Input Rate: 1,362.5 MMBtu/hr

1 Although the Unit 2 CEMS data is notreported to CAMD, it is reported on a semiannualbasis to U.S. EPA as mandatedby

Paragraph 126 ofEKPC's Consent Decree.Cooper Station CEMS Data Processing for SOz NAAQS Modeling December 2, 2015

Total Unit 1 and 2 HeatInputRate: 1,857.2 MMBtujhr



### CAMD Output Data
CAMD Calculated Unit 1 SOz Emission Rate Page2

969.1lb SOz/hr for Unit 1 & 2 x 494.7 MMBtu/hr for Unit 1/1,857.2 MMBtu/hrfor Unit 1 & 2 

## = 258.138lb S02 /hrfor Unit 1 CAMD Calculated Unit 2 SOz Emission Rate

969.1lb SOz/hr for Unit 1 & 2 x 1,362.5 MMBtu/hr for Unit 2/1,857.2 MMBtu/hr for Unit 1 & 2 = 710.962 lb SOz /hrfor Unit 2

As shown in the Appendix Cmodel inputparameter spreadsheet,the Unit 2-only CEMS measured an actual Unit 2 SOz emission rate of76.1lb SOz/hr for thathour. This shows thatprorating emissions by heatinputis not necessarily correct

EKPC understands that U.S. EPA Region 4 specifically questioned the discrepancyfor 12/10/12 at Hour 8 when the CAMD Unit 2 SOz emission rate was setto a non-zero value (based on the stack CEMS heatinputproration technique shown above) whereasthe modeled emission rate derived from the Unit 2 only CEMS was setto zero. This discrepancyis due to the use ofa defaultvalue of 1 MW in the CAMD data during startup priorto syncingup the boiler's steam outputwith the steam turbine. As shown in Table 1, Unit 2 initiated a startup sequence on 12/09/12 at Hour 14 (referto first non-zero Unit 2 operational flag). Forthe next 20 hours ofthe startup (from 12/9/12 Hour 14to 12/10/12 Hour 9 and including the 12/10/12 Hour 8 mentionedby U.S. EPA), Unit 2 operated ata minimum firing rate with no power generation to warm up the boiler and to ensure all systems
were prepared to commence full load operation. Although the CAMD data for Unit 2 gross load indicates 1 MW ofpower generation duringthis timeframe, Unit 2 was notactually generatingpower. The heatinputrate assigned to Unit 2 duringthis timeframe produces a CAMD Unit 2 SOz emission rate ofapproximately 20 lb/hr based on the simplistic heatinputrate scaling approach discussed previously. The Unit 2 only CEMS readings for this startup event showed actual SOz emissions ratesbelow 2lb/hr (where mostvalues were belowthe detection limit ofthe analyzer and appropriatelylogged as 0 lb/hr) until Unit 2 was synced to the steam turbine and the heatinputratebegan to ramp up (refer to 12/10/12 Hour 10).
Understanding the basis ofthe individual unit SOz emissions data available from CAMD, EKPC relied on the accurate data from the Unit 2 CEMS for the SOz NAAQS modeling.Cooper Station CEMS Data Processing for SOz NAAQS Modeling December 2, 2015

Table 1. Example ofUnit2 Startup Eventin CAMD Dataset

CAMD CAMD CAMD CAMDUnit2 CAMD CAMD Combined S02 Unit 1Heat Unit 1Gross S02 Derived Unit 2Heat Unit 2Gross Emission Rate Input Rate Load Emission Rate Input Load Year Date Hour (lbhu) (MMBtwhr) (MW) (lbhlr) (MMBtuhlr) (MW)

2012 12/9/2012 11 1735.6 805.9 85 2012 12/9/2012 12 1734.6 819.2 85 2012 12/9/2012 13 1672.4 785.2 85 2012 1219/2012 14 1589.363 747.4 83 14.737 6.93 1 2012 1219/2012 15 1632.938 734.2 80 20.462 9.2 1 2012 1219/2012 16 1607.901 709.4 79 20.399 9 1 2012 12/9/2012 17 1724.616 751.9 85 20.184 8.8 1 2012 12/9/2012 18 1954.883 871.3 96 20.417 9.1 1 2012 12/9/2012 19 1993.063 877.7 97 20.437 9 1 2012 1219/2012 20 1991.277 897 97 20.423 9.2 1 2012 1219/2012 21 1696.719 763 82 20.681 9.3 1 2012 1219/2012 22 1501.932 686.4 73 20.568 9.4 1 2012 1219/2012 23 1468.861 685.6 73 20.139 9.4 1 2012 12/10/2012 0 1478.835 692.8 74 20.065 9.4 1 2012 12/10/2012 1 1487.441 686.2 74 20.159 9.3 1 2012 12/10/2012 2 1499.182 689.6 74 20.218 9.3 1 2012 12/10/2012 3 1510.021 689.1 74 20.379 9.3 1 2012 12/10/2012 4 1504.057 691 74 20.243 9.3 1 2012 12/10/2012 5 1491.782 682.2 74 20.118 9.2 1 2012 12/10/2012 6 1904.902 849.8 93 20.398 9.1 1 2012 12/10/2012 7 2079.271 928.4 100 20.829 9.3 1 2012 12/1012012 8 1553.485 707.7 76 20.415 9.3 1 2012 12110/2012 9 1518.15 700.7 75 20.15 9.3 1 2012 12/10/2012 10 1527.419 694.6 75 40.681 18.5 2 2012 12/10/2012 11 1865.789 792.9 75 845.711 359.4 34 2012 12/10/2012 12 1795.611 703.7 75 2226.589 872.6 93 2012 12/10/2012 13 927.157 682.1 75 1347.443 991.3 109 2012 12/10/2012 14 577.119 661.7 74 966.981 1108.7 124 2012 12/10/2012 15 548.201 665.3 74 962.999 1168.7 130 2012 12110/2012 16 726.83 827.3 94 1082.47 1232.1 140 2012 12/10/2012 17 700.167 885.5 103 1305.133 1650.6 192 2012 12/10/2012 18 654.374 873.7 101 1380.126 1842.7 213 2012 12/10/2012 19 395.154 649.1 75 1127.446 1852 214 2012 12/10/2012 20 224.604 456.8 53 902.596 1835.7 213 2012 12/10/2012 21 244.376 455.5 53 982.224 1830.8 213 2012 12/10/2012 22 296.522 565.6 67 942.778 1798.3 213 2012 12/10/2012 23 528.202 780 91 1236.398 1825.8 213 Page 3

Cooper Unit 2 EKPCCooper Modeled Unit2 Emission Rate Operational from Unit2- Flag OnlyCEMS (min) (lbhlr)

0 0 0 0 0 0 46 0.15 60 0 60 0 60 0 60 1.7 60 0 60 0 60 0 60 0 60 0 60 0 60 0 60 0 60 1.4 60 0 60 0 60 0 60 0 60 0 60 0 60 95.6 60 1410.6 60 2761.7 60 722.9 60 61.6 60 46.7 60 84.2 60 79.2 60 92.6 60 59.4 60 124.7 60 199.6 60 6.3 60 0Cooper Station CEMS Data Processing for SOz NAAQS Modeling December 2, 2015


### 2. UNIT 2 CEMS AND MODELED EMISSION RATE DIFFERENCES Page 4

As discussed in Section 3.7.2 ofthe modelingreport, EKPC performed two types ofdata substitution on the raw Unit 2 SOz CEMS data to create the modeled emission rates for Unit 2. First, a limited number ofmissing or outof-control (OOC) data periods (flagged with "TRUE" in column Dofthe 1. Unit 1 & 2 Emissions tab in the model inputparameter spreadsheet) were filled in based on a linear interpolation technique using the two surrounding hours ofgood data (detailed examples given in the September 2, 2015 modeling report, Section 3.7.2).2 While EKPC is not aware ofany specific questions or concerns from U.S. EPA or KDAQ regarding this filling technique, EKPC does understand that KDAQ would like more information aboutthe specific time periods when this filling approach for missing/DOC datawas implemented. To fulfill this request, EKPC has added a 4. Unit2 CEMS Completenesstab to the revised Appendix Cmodelingfile inputparameter spreadsheet This data completeness reviewtab provides a summaryofmissing/DOC data periods. For each calendaryearwithin the selected modeling period and for the 3-yearperiod overall, a missing/DOC hour countis provided along with a count of missing data periodsbased on duration for the 1-hour, 2-hour, 3-hour, and 4+-hour categories. The exact start time, end time, and duration for any data period lastingfor 4 ormore hours is provided to demonstrate that

none ofthe missing/DOC data periods were sustained for long periods ofUnit 2 operatingtime. As a further step to highlight missing/DOC data periods, EKPC has also added light green shadingto identifythe surrounding hours ofgood data in the 1. Unit 1 & 2 Emissions tab used in the interpolation technique and lightorange shading to identifythe missing/DOC hours flagged with a 'TRUE" value in column D.

The second type ofdata substitution used for the Unit 2 modeled emission rate derivation involves setting nonzero S0 2 emission rates indicated by the CEMS duringnon-operational periods ofUnit 2 to zero as SOz emissions from Unit 2 are notpossible when the unitis notrunning. The CEMS instrumentation is located in the Unit 2 ductbranch downstream ofthe DFGD butupstream ofthe combined stack. This CEMS could measure a nonzero SOz emission rate duringnon-operational periods ofUnit 2 for various reasons, butthis anomalous CEMS data would neverreflect the actual S02 emissions profile ofUnit 2 when itis not operating. Therefore, EKPC has flagged each instance when this type ofCEMS data issue arises with lightyellow shading in the 1. Unit 1 & 2 Emissions tab and has appropriately forced these non-zero SOz emission rates to be modeled as zero in the SOz NAAQS analysis. Possible explanations for non-zero SOz emissions readings from the Unit 2 CEMS during nonoperational periods ofUnit 2 include "backflow" ofUnit 1 emissions from the combined stackinto the Unit 2 ductbranch, daily calibrations ofthe CEMS analyzer, concentration drift ofthe Unit 2 CEMS analyzer from lack of exposure to stack gas flow, and CEMS maintenance activities when Unit 2 is offline. While some or all ofthese situations mayresultin some minimal emissions beingreported atthe Unit 2 CEMS, none ofthem are valid, nonzero emissions because the unitis not operating.

2 40 CFR Part75.33 refers to a procedure for data thatis 95 percentcomplete overall and less than 24hourlyvalues

consecutive wherebythe "average" value ofthe lastgood value and the next good value is used for all hours. This was judgedto either over orunderestimate the SOz emissions and the interpolation method used insteadbased on good engineeringjudgement.