Name: Craig R. Ecberg

Title: Manager, Air Resources Company: NRG Texas Power LLC Sign Date: 6/30/2010 Name: Mark Roach, P.E. Title: Technical Director, Source Group Company:Clean air Engineering, Inc. Sign Date: 6/30/2010 Permitted Facility Representative / Date Testing Company Representative / Date



### Utility Boiler MACT ICR Testing Unit 2 Limestone Generating Station Final Test Report for

/ / Based on information and belief formed after reasonable inquiry, I certify that the statements and information in this test report are true, accurate, and complete. I have reviewed all testing details and results in this test report and hereby certify that the test report is authentic and accurate.

Wednesday, February 23, 2011 Page 1 of 8Utility Boiler MACT ICR Testing Unit 2 Limestone Generating Station 6/30/2010 Facility Information: Limestone 9 miles north of Jewett, TX on FM 39

Jewett TX75846 Contact:Craig R. Eckberg Phone:713-795-6208 Fax: 713-795-7431 Email: craig.eckberg@nrgenergy.com Testing Company: Clean Air Engineering, Inc. 321 Century Plaza Drive Suite 130 Houston TX77073 Contact:Bart DeLatte Phone:281-443-6400 Fax: 281-443-1806 Email:bdelatte@clenaair.com

Air Permit Number: O75 Permitted Source ID/Name: LIM2 Unit 2 Permitted Maximum Process Rate: N/A Max. Normal Operation Process Rate: N/A Target Process Test Rate N/A

Description of the source (including control equipment). Please see the attachments for source or process flow diagram:

The following describes any modifications and/or deviations to the applicable test methods. If alternative methods were requested, see the attachments for documentation of request AND approval, including dates. Industry/SCC/NAIS221112

Sampling Location Information:

Test Parameter Information: AFS #:4828900010 FRS #:110034223668

SCC / Description10100202 External Combustion Boilers - Electric Generation - Bituminous/Subbituminous Coal - Pulverized Coal: Dry Bottom (Bituminous Coal)
The following state and federal regulations that apply to the proposed testing:

Location Round

Duct Diam. Distance from upstream dist. Distance from

downstream dist. Number of

Traverse Ports Equiv. Diam Min.Travers Points Rect. Duct Length /Width Stack Exit 357 960 4620 4 0 12 0 0

Target Parameter Test Method Number of

Test Runs Test Run

Duration Sample

Points Comments Location % H2O Method 1 - 4 3 120 0 Alt Method 320 Stack Exit Carbon Monoxide Method 10 3 120 0 Alt Method 320 Stack Exit Formaldehyde Method 0011 3 120 0 Alt Method 320 Stack Exit Total organic compounds

(TOC) as Propane Method 25A 3 120 0 Stack Exit

O2 Method 3A O2 3 120 0 Stack Exit Co2 Method 3A CO2 3 120 0 Stack Exit

Wednesday, February 23, 2011 Page 2 of 8Utility Boiler MACT ICR Testing Unit 2 Limestone Generating Station 6/30/2010 The following describes any modifications and/or deviations to the applicable test methods. If alternative methods were requested, see the attachments for documentation of request AND approval, including dates. The following compoundsw will be determined by US EPA Method 320: Formaldehyde, CO, Methane, Moisture. Described in protocol.

Wednesday, February 23, 2011 Page 3 of 8Utility Boiler MACT ICR Testing Unit 2 Limestone Generating Station 6/30/2010 Sampling / Stack Data Results Summary LocationStack Exit - Method 25A Average Run Number 1 2 3 Test Date 4/22/2010 4/22/2010 4/22/2010 Run Start Time 9:00:00 AM 11:55:00 AM 2:45:00 PM

Run Finish Time 11:15:00 AM2:10:00 PM 5:00:00 PM Carbon Dioxide, % 14.67 14.45 14.91 14.677 Oxygen, % 4.98 5.05 5.02 5.017 Dry Volumetric Flow Rate, dry scfm 1962000 1947000 19500001,953,000.00 0 F-Factor, dscfm/MMBtu @ %O2 10052 9787 9990 9,943.000 Moisture, % 19.02 19.12 19.26 19.133 Fuel Type Override Override Override Fw 11730 11484 11648 11,620.667 Fc 1910 0 1910 1,273.333

Wednesday, February 23, 2011 Page 4 of 8Utility Boiler MACT ICR Testing Unit 2 Limestone Generating Station 6/30/2010 Emissions Summary

Process Run Data Location: Stack Exit - Method 25A Compound: Total organic compounds (TOC) as Average Run 1 2 3 lb/mmBtuO2 0.00E+00 0.000 ppm 0.00E+00 0.000 ppm@7%O2 0.00E+00 0.000

Wednesday, February 23, 2011 Page 5 of 8Utility Boiler MACT ICR Testing Unit 2 Limestone Generating Station 6/30/2010 Process Run Data

APCD Run Data Run Name Value UOM Comments Target Value 1 Bituminous Coal Burned 592.21 TPH 590 2 Bituminous Coal Burned 592.6 TPH 590 3 Bituminous Coal Burned 585.38 TPH 590 1 Average Heat Input 8735 mmBtu?hr 8600 2 Average Heat Input 8705 mmBtu?hr 8600 3 Average Heat Input 8666 mmBtu?hr 8600 1 Steam Output 61171000 lb steam/hr6100 2 Steam Output 61101000 lb steam/hr6100 3 Steam Output 60811000 lb steam/hr6100 1 Flue gas flow rate 2E+06 dscfm 2E+06 2 Flue gas flow rate 2E+06 dscfm 2E+06 3 Flue gas flow rate 2E+06 dscfm 2E+06 1 Unit Net Electric Generation 1956 MWh 1950 2 Unit Net Electric Generation 1947 MWh 1950 3 Unit Net Electric Generation 1939 MWh 1950 1 Flue Gas Oxygen Content 4.98 % 5 2 Flue Gas Oxygen Content 5.05 % 5 3 Flue Gas Oxygen Content 5.02 % 5 1 Flue Gas Carbon Dioxide Content 14.67 % 14 2 Flue Gas Carbon Dioxide Content 14.45 % 14 3 Flue Gas Carbon Dioxide Content 14.91 % 14 1 Flue Gas Moisture Content 19.02 % 18 2 Flue Gas Moisture Content 19.12 % 18 3 Flue Gas Moisture Content 19.26 % 18 1 Flue gas Temperature 150 Deg F 160 2 Flue gas Temperature 152 Deg F 160 3 Flue gas Temperature 153 Deg F 160 1 Unit Gross Electrical Output 912 MW 900 2 Unit Gross Electrical Output 909 MW 900 3 Unit Gross Electrical Output 906 MW 900

Run Name Value UOM Comments Target Value 1 LOW NOX BURNERS 0 0 Wednesday, February 23, 2011 Page 6 of 8Utility Boiler MACT ICR Testing Unit 2 Limestone Generating Station 6/30/2010

Process Lab Run Data 1 0 0 1 OVERFIRE AIR 0 0 1 SPRAY SCRUBBER 0 0 1 ELECTROSTATIC PRECIPITATOR 0 0

Run Name ValueUOM Comments 1 Fuel Higher Heating Value 10405Btu/lb 2 Fuel Higher Heating Value 10307Btu/lb 3 Fuel Higher Heating Value 10752Btu/lb 1 Fuel Moiture (Total) 29.98 % 2 Fuel Moiture (Total) 31.37 % 3 Fuel Moiture (Total) 31.17 % 1 Moisture as determined 13.18 % 2 Moisture as determined 13.62 % 3 Moisture as determined 13.81 % 1 Volatile Matter 41.55 % 2 Volatile Matter 42.58 % 3 Volatile Matter 43.68 % 1 Ash 17.8 % 2 Ash 14 % 3 Ash 13.23 % 1 Fixed Carbon 40.65 % 2 Fixed Carbon 43.42 % 3 Fixed Carbon 43.09 % 1 Carbon 62.79 % 2 Carbon 61.31 % 3 Carbon 64.3 % 1 Hydrogen 4.39 % 2 Hydrogen 4.09 % 3 Hydrogen 4.31 % 1 Nitrogen 1.15 % 2 Nitrogen 1.2 % 3 Nitrogen 1.22 % 1 Sulfur 0.86 % 2 Sulfur 1.08 % 3 Sulfur 0.68 % 1 Oxygen 13.01 % 2 Oxygen 18.32 % 3 Oxygen 16.26 %

Wednesday, February 23, 2011 Page 7 of 8Utility Boiler MACT ICR Testing Unit 2 Limestone Generating Station 6/30/2010 Sampling / Stack Data Results Detail LocationStack Exit - Method 25A Average Run Number 1 2 3 Test Date 4/22/2010 4/22/2010 4/22/2010 Run Start Time 9:00:00 AM11:55:00 AM 2:45:00 PM Run Finish Time 11:15:00 AM2:10:00 PM 5:00:00 PM Carbon Dioxide, % 14.67 14.45 14.91 14.677 Oxygen, % 4.98 5.05 5.02 5.017 Fuel Factor 1.09 1.1 1.07 Dry Volumetric Flow Rate, dry scfm 1962000 1947000 19500001,953,000.0 00 F-Factor, dscfm/MMBtu @ %O2 10052 9787 99909,943.000 Moisture, % 19.02 19.12 19.26 19.133 Analyzer Make JUM Jum JUM Analyzer Model 3-300A 3-300A 3-300A Analyzer Serial Number Operating Range 82.98 82.98 82.98 82.980 Operating Units ppm ppm ppm No. Readings/Avg. 60 60 60 60.000 Calibration Set 0 0 0 0.000 Calibration Pre Zero Cylinder ID Calibration Pre Zero Cylinder Instrument Response 0.119 0.268 0.035 0.141 Calibration Pre Zero Cylinder Bias 0 0.18 -0.1 0.027 Calibration Pre Zero Cylinder Drift 0 0 0 0.000 Calibration Pre High Cylinder ID Calibration Pre High Cylinder Instrument Response 25.427 25.251 25.731 25.470 Calibration Pre High Cylinder Bias 0 -0.21 0.37 0.053 Calibration Pre High Cylinder Drift 0 0 0 0.000 Calibration Post Zero Cylinder ID Calibration Post Zero Cylinder Instrument Response 0.268 0.035 0.196 0.166 Calibration Post Zero Cylinder Bias 0.18 -0.1 0.09 0.057 Calibration Post Zero Cylinder Drift 0.18 0.28 0.19 0.217 Calibration Post High Cylinder ID Calibration Post High Cylinder Instrument Response 25.251 25.731 25.775 25.586 Calibration Post High Cylinder Bias -0.21 0.37 0.42 0.193 Calibration Post High Cylinder Drift 0.21 0.58 0.05 0.280 Cavg -0.06 0.353 0.107 0.133 Cavg Units ppmvw ppmvw ppmvw Cgas 0 0.000 Cgas Units ppmvd ppmvd ppmvd Fuel Type Override Override Override Fw 11730 11484 1164811,620.667 Fc 1910 0 19101,273.333 Cgasw 0 0.000 Cgasw Units ppmvw ppmvw ppmvw

Wednesday, February 23, 2011 Page 8 of 8