a Z KENTUCKY POWER COOPERATIVE 

December 3, 2015 

Via E-Mail and Certified Mail 

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 Data Processing - Additional Information 

Dear Mr. Alteri: 

East Kentucky Power Cooperative, Inc. (EKPC) appreciated the opportunity to meet with 

representatives of the Kentucky Division for Air Quality (DAQ) on November 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 data processing 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 of a call 

among EKPC, DAQ and EPA to 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. 

If you have any questions regarding the enclosed information, please contact me at (859) 

745-9244. 

Enclosure 

cc: 

~~

t:~;lm,~ is Director of Environmental 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 Ambient Air Quality Standard (NAAQS) modeling for the John Sherman 

Cooper Power Station and submitted the report, SOz NAAQS Designation Analysis Air Dispersion Modeling Report, 

to the Kentucky Division for Air Quality (KDAQ or Division) on September 2, 2015. This work was undertaken in 

support of the Division's response to the March 20,2015 letter from the U.S. Environmental Protection Agency 

(U.S. EPA) to Commissioner Scott of the Kentucky Department for Environmental Protection (KDEP) regarding 

designations of areas currently unclassified with respect to the 2010 1-hour SOz NAAQS. The modeling results 

demonstrated that the area surrounding the Cooper Station should be considered for designation as attainment 

of the 1-hour SOz NAAQS. 

EKPC understands that U.S. EPA Region 4 has questions about how the Unit 2 continuous emissions monitoring 

system (CEMS) data were used. Specifically, U.S. EPA Region 4 is seeking additional information regarding: 

1. Observed discrepancies between the Unit 2 hourly SOz emissions data presented in the Clean Air Markets 

Database (CAMD) versus the Unit 2-only CEMS data presented in column C of 1. Unit 1 & 2 Emissions tab of 

the Cooper Station SOz NAAQS modeling input parameter spreadsheet (refer to Excel® spreadsheet provided 

with Appendix C of the modeling report). 

2. Differences between the Unit 2 modeled emission rates in column K of the 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 direct measurement of Cooper Station Unit 2 SOz 

emissions (Unit 2 CEMS) as a result of the dry flue gas desulfurization (DFGD) environmental controls before 

entering the 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 of the 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 

of the point where the exhaust streams from each unit merge ).1 CAMD uses each unit's heat input rate to 

prorate the combined Unit 1 and 2 CEMS emissions data to the individual units. This approach ignores the 

impact the DFGD has on Unit 2 emissions, and thus, incorrectly assigns uncontrolled Unit 1 emissions to the 

controlled Unit 2. A CAMD sample calculation is provided below for the first hour in the 3-year modeling period 

(i.e., 7/1/12 Hour 0) which demonstrates this proration by heat input 

CAMD Input Data 

Combined Unit 1 and 2 SOz Emission Rate Measured by CEMS: 969.1lb/hr 

Reported Unit 1 Heat Input Rate: 494.7 MMBtujhr 

Reported Unit 2 Heat Input Rate: 1,362.5 MMBtu/hr 

1 Although the Unit 2 CEMS data is not reported to CAMD, it is reported on a semiannual basis to U.S. EPA as mandated by 

Paragraph 126 of EKPC's Consent Decree. 
Cooper Station CEMS Data Processing for SOz NAAQS Modeling 

December 2, 2015 

Total Unit 1 and 2 Heat Input Rate: 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/hr for Unit 1 & 2 = 

258.138lb S02 /hr for 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 /hr for Unit 2 

As shown in the Appendix C model input parameter spreadsheet, the Unit 2-only CEMS measured an actual Unit 

2 SOz emission rate of 76.1lb SOz/hr for that hour. This shows that prorating emissions by heat input is not 

necessarily correct 

EKPC understands that U.S. EPA Region 4 specifically questioned the discrepancy for 12/10/12 at Hour 8 when 

the CAMD Unit 2 SOz emission rate was set to a non-zero value (based on the stack CEMS heat input proration 

technique shown above) whereas the modeled emission rate derived from the Unit 2 only CEMS was set to zero. 

This discrepancy is due to the use of a default value of 1 MW in the CAMD data during startup prior to syncing up 

the boiler's steam output with the steam turbine. As shown in Table 1, Unit 2 initiated a startup sequence on 

12/09/12 at Hour 14 (refer to first non-zero Unit 2 operational flag). For the next 20 hours of the startup (from 

12/9/12 Hour 14 to 12/10/12 Hour 9 and including the 12/10/12 Hour 8 mentioned by U.S. EPA), Unit 2 

operated at a 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 

of power generation during this timeframe, Unit 2 was not actually generating power. The heat input rate 

assigned to Unit 2 during this timeframe produces a CAMD Unit 2 SOz emission rate of approximately 20 lb/hr 

based on the simplistic heat input rate scaling approach discussed previously. The Unit 2 only CEMS readings 

for this startup event showed actual SOz emissions rates below 2lb/hr (where most values were below the 

detection limit of the analyzer and appropriately logged as 0 lb/hr) until Unit 2 was synced to the steam turbine 

and the heat input rate began to ramp up (refer to 12/10/12 Hour 10). 

Understanding the basis of the 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 of Unit 2 Startup Event in CAMD Dataset 

CAMD CAMD CAMD CAMDUnit2 CAMD CAMD 

Combined S02 Unit 1 Heat Unit 1 Gross S02 Derived Unit 2 Heat Unit 2 Gross 

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 0 
Cooper 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 of the modeling report, EKPC performed two types of data substitution on the raw 

Unit 2 SOz CEMS data to create the modeled emission rates for Unit 2. First, a limited number of missing or outof-control (OOC) data periods (flagged with "TRUE" in column D of the 1. Unit 1 & 2 Emissions tab in the model 

input parameter spreadsheet) were filled in based on a linear interpolation technique using the two surrounding 

hours of good data (detailed examples given in the September 2, 2015 modeling report, Section 3.7.2).2 While 

EKPC is not aware of any specific questions or concerns from U.S. EPA or KDAQ regarding this filling technique, 

EKPC does understand that KDAQ would like more information about the specific time periods when this filling 

approach for missing/DOC data was implemented. To fulfill this request, EKPC has added a 4. Unit 2 CEMS 

Completeness tab to the revised Appendix C modeling file input parameter spreadsheet This data completeness 

review tab provides a summary of missing/DOC data periods. For each calendar year within the selected 

modeling period and for the 3-year period overall, a missing/DOC hour count is provided along with a count of 

missing data periods based 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 lasting for 4 or more hours is provided to demonstrate that 

none of the missing/DOC data periods were sustained for long periods of Unit 2 operating time. As a further 

step to highlight missing/DOC data periods, EKPC has also added light green shading to identify the surrounding 

hours of good data in the 1. Unit 1 & 2 Emissions tab used in the interpolation technique and light orange shading 

to identify the missing/DOC hours flagged with a 'TRUE" value in column D. 

The second type of data substitution used for the Unit 2 modeled emission rate derivation involves setting nonzero S02 emission rates indicated by the CEMS during non-operational periods of Unit 2 to zero as SOz emissions 

from Unit 2 are not possible when the unit is not running. The CEMS instrumentation is located in the Unit 2 

duct branch downstream of the DFGD but upstream of the combined stack. This CEMS could measure a nonzero SOz emission rate during non-operational periods of Unit 2 for various reasons, but this anomalous CEMS 

data would never reflect the actual S02 emissions profile of Unit 2 when it is not operating. Therefore, EKPC has 

flagged each instance when this type of CEMS data issue arises with light yellow 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 of Unit 2 include "backflow" of Unit 1 emissions from the combined stack into the Unit 2 

duct branch, daily calibrations of the CEMS analyzer, concentration drift of the 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 of these 

situations may result in some minimal emissions being reported at the Unit 2 CEMS, none of them are valid, nonzero emissions because the unit is not operating. 

2 40 CFR Part 75.33 refers to a procedure for data that is 95 percent complete overall and less than 24 hourly values 

consecutive whereby the "average" value of the last good value and the next good value is used for all hours. This was 

judged to either over or underestimate the SOz emissions and the interpolation method used instead based on good 

engineering judgement.